UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Donor atom substitutions in amidophosphine ligands : early transition metal complexes of arsine and aryloxide… Carmichael, Christopher David 2005

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
831-ubc_2006-129794.pdf [ 15.25MB ]
Metadata
JSON: 831-1.0061127.json
JSON-LD: 831-1.0061127-ld.json
RDF/XML (Pretty): 831-1.0061127-rdf.xml
RDF/JSON: 831-1.0061127-rdf.json
Turtle: 831-1.0061127-turtle.txt
N-Triples: 831-1.0061127-rdf-ntriples.txt
Original Record: 831-1.0061127-source.json
Full Text
831-1.0061127-fulltext.txt
Citation
831-1.0061127.ris

Full Text

DONOR ATOM SUBSTITUTIONS IN AMIDOPHOSPHINE LIGANDS: EARLY TRANSITION METAL COMPLEXES OF ARSINE AND ARYLOXIDE CONTAINING LIGANDS by C H R I S T O P H E R D A V I D C A R M I C H A E L B.Sc. (Hons.), The University of Victoria (1998) A THESIS S U B M I T T E D IN P A R T I A L F U L F I L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F D O C T O R OF P H I L O S O P H Y in T H E F A C U L T Y OF G R A D U A T E S T U D I E S C H E M I S T R Y T H E U N I V E R S I T Y OF B R I T I S H C O L U M B I A October 2005 © Christopher David Carmichael 2005 ABSTRACT The effects of donor atom substitution in the amidophosphine ligands [P2N2] (where P h [ P 2 N 2 ] = PhP(CH2SiMe2NSiMe2CH2)2PPh) and p h [ N P N ] (where [NPN] = PhP(CH2SiMe2NPh)2 with both stronger and weaker donors is explored through early transition metal coordination chemistry. The diamidodiarsine macrocycle Ph[As2N2] (where ph[As2N2] = PhAs(CH2SiMe2NSiMe2CH2)2AsPh) can be synthesized as a 1,4-dioxane adduct of the dilithium salt, p h [As2N 2 ]Li 2 ( 1,4-dioxane). Reactions of the lithium salt with appropriate metal halides affords the complexes p h [ A s 2 N 2 ] Z r C l 2 , P h [ A s 2 N 2 ] T i C l 2 and (p h[As2N2]Y)2(u-Cl)2. The yttrium complex is the first structurally characterized complex containing an yttrium arsenic bond. Attempts to reduce the halide salts in the presence of dinitrogen lead to mixtures of products, and evidence points to the reduction of arsenic within the macrocycle. The chelating diamidoarsine p h [ N A s N ] (where p h [ N A s N ] = PhAs(CH2SiMe2NPh)2) can be synthesized as a T H F adduct of the lithium salt, P h [ N A s N ] L i 2 ( T H F ) 2 . Reaction of the lithium salt with T a M e 3 C l 2 affords the five-coordinate alkyl complex p h [ N A s N ] T a M e 3 . Hydrogenation of p h [NAsN]TaMe3 does not produce a hydride complex, but instead a modest yield of the protonated ligand precursor P h[NAsN]H2. Evidence suggests that p h [NAsN]H2 is produced through hydrogenation of tantalum-amide bonds. Density functional theory calculations carried out on the model complexes ' N A s N ' T a M e 3 and ( 'NAsN 'Ta ) 2 (u -H) 4 (where ' N A s N ' CH3As (CH2SiH 2 NCH3) 2 ) suggest that dissociation of the arsenic donor may play a role in the hydrogenation of the trimethyl complex. The bis(aryloxy)phosphine ligands R [OPO] (where R [ O P O ] = RP(3,5-( B u 2 C 6 H 2 0 ) 2 ) (R = Ph, 'Pr) are prepared as dimeric lithium salts ( R [ O P O ] L i 2 ) 2 ( T H F ) 4 , protonated ligand precursors R [ O P O ] H 2 , the dimeric potassium salt ( p h [ O P O ] K 2 ) 2 ( T H F ) 6 , and trimeric C P r [ O P O ] K 2 ) 3 ( T H F ) 3 . i i Reaction of [OPO] precursors with group 4 and 5 halides affords P h [ O P O ] M C l 2 ( T H F ) ( M = T i , Zr, H i ) and R [ O P O ] T a C l 3 . Direct alkylations of P h[OPO]TaCl3 produce only mixtures of products; however, the methyl complexes p h [ O P O ] T a M e C l 2 , P h [ O P O ] T a M e 2 C l and p h [ O P O ] T a M e 3 can be prepared by reaction of p h [OPO] precursors with TaMe3Cl2. Alkylation and reduction chemistry of the halide complexes is dominated by the formation of bis-ligand complexes, including p h[OPO]2Ti, likely a result of the reduced steric bulk that is inherent to these metal-ligand systems. Preliminary investigations suggest it may be possible to prepare dinitrogen complexes through reactions with hydrazine and substituted hydrazines, or through ligand exchange with the dinitrogen complex [TaCl3(THF)2]2(u.-N2). in TABLE OF CONTENTS A B S T R A C T T A B L E OF C O N T E N T S LIST OF T A B L E S LIST OF F I G U R E S G L O S S A R Y OF T E R M S A C K N O W L E D G E M E N T S D E D I C A T I O N S T A T E M E N T OF C O - A U T H O R S H I P Chapter One Mixed-donor multidentate ligands in early transition metal coordination chemistry 1.1. Introduction: defining the terminology 1 1.2. Mixed-donor ligands in the Fryzuk group 4 1.3. Dinitrogen coordination chemistry 7 1.4. Multidentate ligands in dinitrogen coordination chemistry 11 1.5. Ligand modification: the butterfly effect 17 1.6. Thesis scope and prospectus 19 1.7. References 21 Chapter Two Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors 2.1. Introduction 26 2.2. Synthesis of the P h [ A s 2 N 2 ] ligand 34 2.3. Coordination chemistry of p h [ A s 2 N 2 ] with zirconium 43 2.4. Coordination chemistry of p h [ A s 2 N 2 ] with titanium 51 2.5. Coordination chemistry of p h [ A s 2 N 2 ] with yttrium 54 2.6. Attempted synthesis of P h [ A s 2 N 2 ] tantalum complexes 57 iv i i iv v i i i x i i i xix xxiv xxv xxv i 2.7. Reduction chemistry of P h [ A s 2 N 2 ] complexes 58 2.8. Summary and conclusions 61 2.9. Experimental Section 62 2.9.1. General Considerations 62 2.9.2. Starting Materials and Reagents 63 2.9.3. Synthesis, Characterization and Reactivity of Complexes 64 2.10. References 69 Chapter Three Tantalum coordination chemistry supported by a diamido-arsine ligand 3.1. Introduction 75 3.2. Synthesis of the p h [ N A s N ] ligand 77 3.3. Synthesis of p h [ N A s N ] T a M e 3 83 3.4. Hydrogenation of P h [ N A s N ] T a M e 3 86 3.5. Density Functional Theory calculations 90 3.6. Summary and conclusions 109 3.7. Experimental Section 111 3.7.1. General Considerations 111 3.7.2. Starting Materials and Reagents 111 3.7.3. Synthesis, Characterization and Reactivity of Complexes 111 3.8. References 115 Chapter Four Synthesis of bis(aryloxy)phosphines as ligands for early transition metals 4.1. Introduction 122 4.2. Synthesis of R [ O P O ] L i 2 complexes 128 4.3. Synthesis of R [ O P O ] H 2 ligand precursors 139 4.4. Synthesis of R [ O P O ] K 2 complexes 142 4.5. Summary and conclusions 148 v 4.6. Experimental Section 149 4.6.1. General Considerations 149 4.6.2. Starting Materials and Reagents 149 4.6.3. Synthesis, Characterization and Reactivity o f Complexes 149 4.7. References 154 Chapter Five Early transition metal coordination chemistry supported by bis(aryloxy)phosphine ligands 5.1. Introduction 159 5.2. Coordination chemistry of R [OPO] with titanium 167 5.3. Coordination chemistry of p h [ O P O ] with zirconium, hafnium and yttrium 176 5.4. Coordination chemistry of R [OPO] with tantalum 177 5.5. Summary and conclusions 191 5.6. Experimental Section 193 5.6.1. General Considerations 193 5.6.2. Starting Materials and Reagents 193 5.6.3. Synthesis, Characterization and Reactivity of Complexes 193 5.7. References 200 Chapter Six Thesis summary and extensions: alternative routes to dinitrogen complexes 6.1. Thesis summary 206 6.2. Alternative routes to dinitrogen complexes: ligand exchange 207 6.3. Alternative routes to dinitrogen complexes: hydrazines 208 6.4. Experimental Section 216 6.4.1. General Considerations 216 6.4.2. Starting Materials and Reagents 216 6.4.3. Synthesis, Characterization and Reactivity of Complexes 216 6.5. References 217 v i Appendix A X-Ray crystal structure experimental information A.l. General Considerations 220 A. 2. References 222 A3. Tables of Crystallographic data 223 Appendix B Density Functional Theory calculation data B. l. General Considerations 232 B.2. References 232 B.3. Archival output summaries for model complexes 234 B.4. Z-matrices, input parameters and final coordinates 242 B.5. Gaussianisms 258 vi i LIST OF T A B L E S Chapter One Mixed-donor multidentate ligands in early transition metal coordination chemistry Table: Title: Page: Table 1.1. N - N bond lengths and stretching frequencies for some 10 simple molecules Chapter Two Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Table: Table 2.1. Table 2.2. Table 2.3. Table 2.4. Table 2.5. Table 2.6. Table 2.7. Title: Selected bond distances (A), intramolecular distances (A), and bond angles (°) for P h [As 2 N 2 ]L i 2 ( l ,4 -d ioxane) 2.1. Selected bond distances (A), intramolecular distances (A), and bond angles (°) for p h [ A s 2 N 2 ] L i 2 ( T H F ) 2 , 2.2. Selected bond distances (A) and bond angles (°) for p h [ A s 2 N 2 ] H 2 , 2.3. Selected bond distances (A), bond angles (°), and dihedral angles (°) for p h [ A s 2 N 2 ] Z r C l 2 , 2.4. Selected bond distances (A), bond angles (°), and dihedral angles (°) for P h [ A s 2 N 2 ] Z r I 2 , 2.5. Selected bond distances (A), intramolecular distances (A), and bond angles (°) for p h [ A s 2 N 2 ] T i C l 2 , 2.6. Selected bond lengths (A), bond angles (°), and dihedral angles (°) for ( p h [ A s 2 N 2 ] Y ) 2 ( u - C l ) 2 2.7. Page: 36 39 42 45 50 53 56 v i i i Chapter Three diamido Table: Table 3.1. Table 3.2. Table 3.3. Table 3.4. Table 3.5. Table 3.6. Table 3.7. Table 3.8. Table 3.9. Table 3.10. Tantalum coordination chemistry supported by a •arsine ligand Title: Selected bond distances (A) and bond angles (°) for P h [ N A s N ] L i 2 ( T H F ) 2 , 3.1. Selected bond distances (A) and bond angles (°) for P h [ N A s N ] H 2 , 3.2. Selected bond distances (A) and bond angles (°) for P h [ N A s N ] T a M e 3 , 3.3. Selected optimized bond distances (A) and bond angles (°) for ' N A s N ' L i 2 ( O M e 2 ) 2 , 3.4A. Selected optimized bond distances (A) and bond angles (°) for 'NAsN 'TaMe 3 , 3.5A. Selected optimized bond distances (A), bond angles (°), and dihedral angles (°) for ( ' N A s N ' T a ) 2 ( u - H ) 4 , 3.6A. Selected optimized bond distances (A) and bond angles (°) for ' N A s N ' L i 2 ( O M e 2 ) 2 , 3.4B. Selected optimized bond distances (A) and bond angles (°) for ' N A s N ' T a M e 3 , 3.5B. Selected optimized bond distances (A), bond angles (°), and dihedral angles (°) for ( ' N A s N ' T a ) 2 ( u - H ) 4 , 3.6B. Total energy (in kJ mol"1) for optimized compounds. Page: 79 82 85 93 93 94 96 98 101 102 Chapter Four Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Table: Title: Page: Table 4.1. Selected bond distances (A), bond angles (°), and dihedral angles (°) for ( p h [ O P O ] L i 2 ) 2 ( T H F ) 4 , 4.1. 130 ix Table 4.2. Table 4.3. Table 4.4. Table 4.5. Table 4.6. Table 4.7. Selected bond distances (A), bond angles (°), and dihedral angles (°) for [ ' P r [OP(=0)0]Li 2 (H 2 0)] 2 , 4.2-0. Selected bond distances (A), bond angles (°), and dihedral angles (°) for [ P h [ O P O ] L i 2 ( A r O L i ) ] 2 , 4.3. Selected bond distances (A), bond angles (°), and dihedral angles (°) for [ ' P r [OPO]Li 3 Cl(ArOLi ) ] (THF) 3 , 4 .4 . Selected bond distances (A), bond angles (°), and dihedral angles (°) for p h [ O P O ] H 2 4.5. Selected bond distances (A) and bond angles (°) for ( p h [ O P O ] K 2 ) 2 ( T H F ) 6 , 4.7. Selected bond distances (A) and bond angles (°) for ( , P r [ O P O ] K 2 ) 3 ( T H F ) 3 , 4.8. 133 136 138 141 144 146 Chapter Five Early transition metal coordination chemistry supported by bis(aryloxy)phosphine ligands Table: Title: Page: Table 5.1. Selected bond distances (A), bond angles (°), 169 and dihedral angles (°) for p h [OPO]TiC l 2 (py ) , 5.3. Table 5.2. Selected bond distances (A) and bond angles (°) 172 for p h [ O P O ] 2 T i , 5.4. Table 5.3. Selected bond distances (A), bond angles (°), 179 and dihedral angles (°) for ( P h [OPO]H 3 ) (TaCl 6 ) (5.10). Table 5.4. Selected bond distances (A) and bond angles (°) 181 for ( P h [OPO]TaCl 2 ) 2 (u -OH) 2 (5.11). Table 5.5. Selected bond distances (A) and bond angles ( ° ) 183 for ( , P r [OPO]TaCl 2 ) 2 (u-0) (5.12). x Table 5.6. Selected bond distances (A) and bond angles (°) 185 for P h [ O P 0 2 T a C l (5.13). Table 5.7. Selected bond distances (A), bond angles (°), 189 and dihedral angles (°) for P h [ O P O ] T a M e 2 C l (5.15). Chapter Six Thesis summary and extensions: alternative routes to dinitrogen complexes Table: Title: Page: Table 6.1. Selected bond distances (A), bond angles (°), 214 and dihedral angles (°) for p h [ O P O ] H 3 C l , 6.1. Appendix A X-Ray crystal structure experimental information Table: Title: Page: Table A- l . Crystallographic and Structure Refinement Data 223 for p h [ A s 2 N 2 ] L i 2 ( 1,4-dioxane) (2.1), p h [ A s 2 N 2 ] L i 2 ( T H F ) 2 (2.2), and p h [ A s 2 N 2 ] H 2 (2.3). Table A-2. Crystallographic and Structure Refinement Data 224 for p h [ A s 2 N 2 ] Z r C l 2 (2.4), P h [ A s 2 N 2 ] Z r I 2 (2.5), and p h [ A s 2 N 2 ] T i C l 2 (2.6). Table A-3. Crystallographic and Structure Refinement Data 225 for ( p h [ A s 2 N 2 ] Y ) 2 ( / / - C l ) 2 (2.7), p h [ N A s N ] L i 2 ( T H F ) 2 (3.1), and p h [ N A s N ] H 2 (3.2). Table A-4. Crystallographic and Structure Refinement Data 226 for P h [ N A s N ] T a M e 3 (3.3), ( P h [ O P O ] L i 2 ) 2 ( T H F ) 4 (4.1), and [ i P r [OP(=0)0 ]L i 2 (H 2 0) ] 2 (4.2-0). Table A-5. Crystallographic and Structure Refinement Data 227 for [ P h [ O P O ] L i 2 ( A r O L i ) ] 2 (4.3), [ i P r [ O P O ] L i 3 C l ( A r O L i ) ] ( T H F ) 3 (4.4), and P h [ O P O ] H 2 (4.5). xi Table A-6. Crystallographic and Structure Refinement Data 228 for ( p h [ O P O ] K 2 ) 2 ( T H F ) 6 (4.7), ( i P r [ O P O ] K 2 ) 3 ( T H F ) 3 (4.8), and p h [ O P O ] 2 T i (5.3). Table A-7. Crystallographic and Structure Refinement Data 229 for P h [ O P O ] 2 T i (5.4), ( p h [OPO]H 3 ) (TaCl 6 ) (5.10), and ( p h [OPO]TaCl 2 ) 2 (p -OH) 2 (5.11). Table A-8. Crystallographic and Structure Refinement Data 230 for ( , P r [OPO]TaCl 2 ) 2 (u-0) (5.12), p h [ O P O ] 2 T a C l (5.13), and p h [ O P O ] T a M e 2 C l (5.15). Table A-9. Crystallographic and Structure Refinement Data 231 for p h [ O P O ] H 3 C l (6.1). Appendix B Density Functional Theory calculation data Table: Title: Page: Table B-l. Method and z-matrix for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4A). 242 Table B-2. Method and z-matrix for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B). 243 Table B-3. Initial parameters for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4A), (3.4B). 244 Table B-4. Final atomic coordinates for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4A). 245 Table B-5. Final atomic coordinates for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B). 246 Table B-6. Method and z-matrix for ' N A s N ' T a M e 3 (3.5A). 247 Table B-7. Method and z-matrix for ' N A s N ' T a M e 3 (3.5B). 248 Table B-8. Initial parameters for ' N A s N ' T a M e 3 (3.5A) and (3.5B). 249 Table B-9. Final atomic coordinates for ' N A s N ' T a M e 3 (3.5A). 250 Table B-10. Final atomic coordinates for ' N A s N ' T a M e 3 (3.5B). 251 Table B- l l . Method and z-matrix for ( ' N A s N ' T a ) 2 ( u - H ) 4 (3.6A). 252 Table B-12. Method and z-matrix for ( ' N A s N ' T a ) 2 ( u - H ) 4 (3.6B). 253 Table B-13. Initial parameters for ( ' N A s N ' T a ) 2 ( u - H ) 4 (3.6A), (3.6B). 254 Table B-14. Final atomic coordinates for ( ' N A s N ' T a ) 2 ( p - H ) 4 (3.6A). 255 Table B-15. Final atomic coordinates for ( ' N A s N ' T a ) 2 ( u - H ) 4 (3.6B). 256 xi i LIST OF FIGURES Chapter One Mixed-donor multidentate ligands in early transition metal coordination chemistry Figure: Title: Page: Figure 1.1. George Orwell 1 Figure 1.2. Werner Heisenberg 2 Figure 1.3. Alfred Werner 2 Figure 1.4. Fritz Haber 8 Figure 1.5. Carl Bosch 8 Figure 1.6. Bonding modes for dinitrogen and one or two 11 transition metals. Activation of N 2 is implied by bond order. Figure 1.7. Arene bridged diamidophosphine ligands. 19 Chapter Two Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Figure: Title: Page: Figure 2.1. Binding modes of tetramethyldiarsine, 29 Me2As-AsMe2, and ligands derived from tetramethyldiarsine. Figure 2.2. Monodentate and bidentate arsenic ligands. 30 Figure 2.3. Arsenic containing macrocycles: (a) triarsine, 31 (b) methylcycloarsoxane (CrJ.3AsO)4, (c) benzazarsepine. Figure 2.4. Molecular structure (ORTEP) of 36 p h [As 2 N 2 ]Li 2 ( l ,4 -d ioxane) , 2.1. Ellipsoids are drawn at 50% probability. x i i i Figure 2.5. Molecular structure (ORTEP) of 39 P h [ A s 2 N 2 ] L i 2 ( T H F ) 2 , 2.2. Ellipsoids are drawn at 50% probability. Figure 2.6. Molecular structure (ORTEP) of p h [ A s 2 N 2 ] H 2 , 2.3. 42 Ellipsoids are drawn at 50% probability. Figure 2.7. Molecular structure (ORTEP) of p h [ A s 2 N 2 ] Z r C l 2 , 2 . 4 . 44 Ellipsoids are drawn at 50% probability; (a) top view, (b) side view. Si ly l methyl groups omitted for clarity, and only ipso carbons o f phenyl rings shown in (b). Figure 2.8. Molecular structure (ORTEP) of p h [ A s 2 N 2 ] Z r I 2 , 2.5. 49 Ellipsoids are drawn at 50% probability; (a) top view, (b) side view. Si ly l methyl groups omitted for clarity, and only ipso carbons of phenyl rings shown in (b). Figure 2.9. Molecular structure (ORTEP) of p h [ A s 2 N 2 ] T i C l 2 , 2.6. 52 Ellipsoids are drawn at 50% probability; (a) top view, (b) side view. Si ly l methyl groups omitted for clarity, and only ipso carbons of phenyl rings shown in (b). Figure 2.10. Molecular structure (ORTEP) of 55 ( P h [ A s 2 N 2 ] Y ) 2 ( u - C l ) 2 , 2.7. Ellipsoids are drawn at 50% probability. Chapter Three Tantalum coordination chemistry supported by a diamido-arsine ligand Figure: Title: Page: Figure 3.1. Bidentate and multidentate arsine ligands with 76 aromatic backbones: (a) diars (b) ptas (c) fars. Figure 3.2. Arsenic chelated phosphine oxide and 77 phosphoraminato ligands. xiv Figure 3.3. Figure 3.4. Figure 3.5. Figure 3.6. Figure 3.7. Figure 3.8. Figure 3.9. Figure 3.10. Figure 3.11. Figure 3.12. Figure 3.13. Figure 3.14. Figure 3.15. Molecular structure (ORTEP) of p h [ N A s N ] L i 2 ( T H F ) 2 , 3.1. Ellipsoids are drawn at 50% probability. Molecular structure (ORTEP) of P h [ N A s N ] H 2 , 3.2. Ellipsoids are drawn at 50% probability. Molecular structure (ORTEP) of P h [ N A s N ] T a M e 3 , 3.3. Ellipsoids are drawn at 50% probability. Simplified ' N A s N ' ligand model for D F T calculations. Calculated geometry for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B) with selected optimized bond distances (A). Values in brackets are experimental values for 3.1. Calculated geometry for ' N A s N ' T a M e 3 (3.5B) with selected optimized bond distances (A). Values in brackets are experimental values for 3.3. Calculated geometry for ( ' N A s N ' T a ) 2 ( u - H ) 4 (3.6B) with selected optimized bond distances (A). Depictions of the H O M O (left) and H O M O - 1 (right) for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B). Depictions of the L U M O (left) and L U M O + 1 (right) for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B). Depictions of the H O M O (top) and H O M O - 1 (bottom) for ' N A s N ' T a M e 3 (3.5B) together with simplified illustrations of the bonding. Depictions of the H O M O - 2 o f ' N A s N ' T a M e 3 (3.5B) together with a simplified illustrations of the bonding. Depictions of the L U M O (top) and L U M O + 1 (bottom) for ' N A s N ' T a M e 3 (3.5B) together with simplified illustrations of the bonding. Depictions of the H O M O (left) and H O M O - 1 (right) for ( 'NAsN 'Ta ) 2 (u -H) 4 (3.6B). xv Figure 3.16. Depictions of the L U M O (left) and L U M O + 1 (right) 109 for ('NAsN'Ta)2(u-H)4 (3.6B). Chapter Four transition Figure: Figure 4.1. Figure 4.2. Figure 4.3. Figure 4.4. Figure 4.5. Figure 4.6. Figure 4.7. Figure 4.8. Figure 4.9. Figure 4.10. Figure 4.11. Synthesis of bis(aryloxy)phosphines as ligands for early metals Title: Food industry antioxidants B H A and B H T . Monodentate aryloxides: (a) phenoxide, (a) 3,5-bistrifluoromethylphenoxide, (b) 2,4,6-tri-t-butylphenoxide, (d) 2,6-diisopropyl-phenoxide. Bidentate aryloxide ligands: (a) catechol, (b) 2-diphenylphosphinophenolate. A linked tridentate aryloxide ligand. A aryloxide macrocycle: calix[4]arene. Molecular structure (ORTEP) of ( P h [ O P O ] L i 2 ) 2 ( T H F ) 4 , 4.1. Ellipsoids are drawn at 50% probability. Diagram of [ , P r [OP(=0)0]L i 2 (H 2 0) ] 2 , 4.2-0. Molecular structure (ORTEP) of [ , P r [OP(=0)0 ]L i 2 (H 2 0) ] 2 , 4.2-0. Ellipsoids are drawn at 50% probability. Diagram of [ P h [ O P O ] L i 2 ( A r O L i ) ] 2 , 4.3. Molecular structure (ORTEP) o f [ p h [ O P O ] L i 2 ( A r O L i ) ] 2 , 4.3. Ellipsoids are drawn at 50% probability. Molecular structure (ORTEP) of [ , P r [OPO]L i 3 Cl (ArOLi ) ] (THF) 3 , 4.4. Ellipsoids are drawn at 50% probability. Page: 123 124 125 125 126 130 132 132 135 135 137 xvi Figure 4.12. Molecular structure (ORTEP) of p h [ O P O ] H 2 4.5. 141 Ellipsoids are drawn at 50% probability. Figure 4.13. Molecular structure (ORTEP) of 143 ( P h [ O P O ] K 2 ) 2 ( T H F ) 6 , 4.7. Ellipsoids are drawn at 50% probability. Carbon atoms of the T H F ligands removed for clarity. Figure 4.14. Molecular structure (ORTEP) of 145 ( ' P r [OPO]K 2 ) 3 (THF) 3 , 4.8. Ellipsoids are drawn at 50% probability. Carbon atoms of the T H F ligands and /-butyl groups removed for clarity. Chapter Five Early transition metal coordination chemistry supported by bis(aryloxy)phosphine ligands Figure: Title: Page: Figure 5.1. Molecular structure (ORTEP) of 169 P h [OPO]TiCl 2 (py) , 5.3; (a) side view, (b) top view. Ellipsoids are drawn at 50% probability. Figure 5.2. Molecular structure (ORTEP) of P h [ O P O ] 2 T i , 5.4. 172 Ellipsoids are drawn at 50% probability. Figure 5.3. Molecular structure (ORTEP) of 179 ( p h [OPO]H 3 ) (TaCl 6 ) , 5.10. Ellipsoids are drawn at 50% probability. Figure 5.4. Molecular structure (ORTEP) of 181 ( p h [OPO]TaCl 2 ) 2 (u -OH) 2 , 5.11. Ellipsoids are drawn at 50% probability. Figure 5.5. Molecular structure (ORTEP) of 183 ( , P r [OPO]TaCl 2 ) 2 (p-0) , 5.12. Ellipsoids are drawn at 50% probability. Figure 5.6. Molecular structure (ORTEP) of 185 xvi i ™[OPO] 2 TaCl, 5.13. Ellipsoids are drawn at 50% probability. Figure 5.7. Molecular structure (ORTEP) of 189 p h [ O P O ] T a M e 2 C l , 5.15; (a) side view, (b) top view. Ellipsoids are drawn at 50% probability. Chapter Six Thesis summary and extensions: alternative routes to dinitrogen complexes Figure: Title: Page: Figure 6.1. Common hydrazido ligand binding modes. 209 Figure 6.2. Titanium hydrazido complexes: 210 (a) [CpTiCl (u-NNPh 2 ) ] 2 ; (b) C p T i C l 2 ( r i 2 - N H N M e 2 ) . Figure 6.3. Tantalum hydrazido complexes: 211 (a) [Ta( r ) 2 -NMeNMe 2 ) (S 2 CNEt 2 )3] + ; (b) Cp 2 Ta(H)NNCPh 2 ) . Figure 6.4. Tantalum isodiazene complex: [TafT^CgHig^CLt]". 212 Figure 6.5. Molecular structure (ORTEP) of P h [ O P O ] H 3 C l , 6.1. 213 Ellipsoids are drawn at 50% probability. xvi i i GLOSSARY OF T E R M S The following abbreviations, most of which are commonly found in the chemistry literature, are used in this thesis: Term: Definition: R [PNP] N ( C H 2 S i M e 2 P R 2 ) 2 ligand R [ P 2 N 2 ] R P ( C H 2 S i M e 2 N S i M e 2 C H 2 ) 2 P R ligand R [ N P N ] R P ( C H 2 S i M e 2 N R ' ) 2 ligand P h [ A s 2 N 2 ] P h A s ( C H 2 S i M e 2 N S i M e 2 C H 2 ) 2 A s P h ligand p h [ N A s N ] P h A s ( C H 2 S i M e 2 N P h ) 2 ligand ' N A s N ' C H 3 A s ( C H 2 S i H 2 N C H 3 ) 2 model ligand R [OPO] R P ( 3 , 5 - ' B u 2 C 6 H 2 0 ) 2 ligand 0 (or deg) degrees in measure of angles °C degrees Celsius ' H proton {'H} proton decoupled 1 3 C carbon-13 7 L i lithium-7 31p phosphorus-31 { 3 1P} phosphorus-31 decoupled a, b, c unit cell dimensions; lengths (A) a, p ,y unit cell dimensions; angles (°) A Angstrom, 10"1 0 m Anal . Analysis A r general aryl group atm atmosphere B e q equivalent isotropic thermal parameter br broad xix C\, Ci, c 2 v Calcd. C C D cm cm"1 C O S Y Cp Cp*, Cp", C p t t Cy cf d dd ds D F T diox D M E d x y , d x z , d y z , d z 2 , dx2-y2 E E r Eex EI -MS equiv Et eV G g G C - M S gof h hv Schoenflies symmetry designations Calculated charge coupled device centimeters reciprocal centimeters correlated spectroscopy ( N M R ) cyclopentadienyl ligand (C5H5) substituted cyclopentadienyl ligands cyclohexyl group ^-electron configuration for a transition metal doublet doublet of doublets doublet of septets Density Functional Theory 1,4-dioxane 1,2-dimethoxyethane d orbitals of the appropriate symmetry total energy energy as related to electron density energy of correlated electron motion electron ionization mass spectrometry equivalent ethyl group, - C H 2 C H 3 electron volt Gauss grams gas chromatography/mass spectrometry goodness of fit hour photon xx Ha Hartrees H M D S O hexamethyldisiloxane H O M O highest occupied molecular orbital H O M O - n M O n orbitals lower in energy than the H O M O Hz Hertz, seconds"1 / nuclear spin 'Pr isopropyl group, -CH(CH3)2 IR infrared " i • M B n-bond scalar coupling constant between nuclei A and B k rate constant K degrees Kelv in K e q equilibrium constant kJ kilojoules L general ligand L n set of n general ligands L U M O lowest unoccupied molecular orbital L U M O + n M O n orbitals higher in energy than the L U M O M molar (mol L" 1 ) , or general metal M + parent ion m minute m- meta position on an aromatic ring mg milligrams Me methyl group, -CH3 m/e, m/z mass/charge ratio Mes mesityl group, -2,4,6-Me3C6H2 M H z Megahertz, one mil l ion Hertz M g A D P adenosine diphosphate, magnesium salt M g A T P adenosine triphosphate, magnesium salt mmol millimole M O molecular orbital xxi mol mole M S mass spectrometry n- normal (as in «-butyl) "Bu normal butyl group, -CH2CH2CH2CH3 N M R Nuclear Magnetic Resonance Np noepentyl group, -CH.2C(CH3)3 nm nanometers o- ortho position on an aromatic ring O R T E P Oak Ridge Thermal Ell ipsoid Plot or Program p- para position on an aromatic ring Ph phenyl group, - C 6 H 5 Pi inorganic phosphate, P O 4 " ppm parts per mil l ion py pyridine R, R ' general alkyl substiutents R, R w residual errors (X-ray crystallography) reflns reflections (X-ray crystallography) rt or r.t. room temperature S solvent or donor (or sulphur) s singlet silox siloxane group, -OSi( 'Bu) 3 T temperature, K or °C t triplet (1:2:1 unless otherwise specified) 'Bu tertiary butyl group, -C(CH3)3 T H F tetrahydrofuran T H T tetrahydrothiophene T M S trimethylsilyl group, - S i ( C H 3 ) 3 TJ(eq) equivalent isotropic displacement parameter V unit cell volume V S E P R valence-shell electron pair repulsion xx i i V T variable temperature X general halide Z asymmetric units per unit cell 5 chemical shift in ppm n," hapticity of order n X wavelength p n bridging n atoms p (Mo K a ) absorption coefficient (X-ray crystallography) p density p c a ] c calculated density (X-ray crystallography) a, it, § notations for bond type xxi i i A C K N O W L E D G E M E N T S No work of this magnitude is conducted in a vacuum, and I am indebted to the many people who have helped make this possible. The most thanks are due my supervisor, Professor M i k e Fryzuk; for granting me the freedom to choose my own project, the immense patience to watch me flail at it for a while, and great diligence in helping pick up the pieces. M y labmates, both past and present, have been excellent colleagues. There is not enough space to thank them all , but I would especially like to thank Bruce "-[]-" Mac Kay, for engaging some of my crazier ideas, and gleefully accepting my proposal to spend large chunks of every other weekend plowing through the local mud puddles of Pacific Spirit Park. I miss those days. I must also thank Mike "Noodles" Shaver for his lessons in D F T and navigating Gaussian 98. A n d I also thank Meghan Dureen, for discovering dozens o f new questions to answer. The U B C support staff has provided essential assistance in this undertaking. I am particularly grateful for the work of Brian Patrick in introducing me to the exquisite frustrations o f crystallography. To quote the master: "nothing ruins my day like modeling disordered solvent." I must also thank Dr. Nick Burlinson for his patient teaching of the nuances of N M R , and Brian Ditchburn for his glassblowing wizardry. The diligence of the mechanical shop and electronics personnel must be acknowledged, especially in dealing with fire-damaged gloveboxes. Through all this I have been supported indirectly, but no less importantly, by my parents and family, in somewhat bemused wonderment at the strange things a relation can get into I 'm sure. "Dinitrogen coordination, you say!" A n d last, but most certainly not least, I would be lost without my Cara. Without the untiring love and unwavering faith that I would emerge from this deep dark tunnel, I have doubts this would be finished. Thank you. xxiv DEDICATION "The time has come, " the Walrus said, "To talk of many things: Of shoes - and ships - and sealing-wax -Of cabbages - and kings -And why the sea is boiling hot -And whether pigs have wings." Lewis Carroll Through the Looking-Glass, and what Alice Found There For Cara, my wil low xxv S T A T E M E N T OF CO-AUTHORSHIP Chapters three, four, five and six were conducted in collaboration with Professor Michael D. Fryzuk, the research supervisor for this thesis, who assisted with identification and design of the research presented. Chapters four and five present several experiments initially conducted by Meghan A . Dureen, an undergraduate student in the Fryzuk laboratory, under the supervision of the thesis author. A l l other experimental research, data analysis and manuscript preparation were conducted by the thesis author. xxvi Chapter One Mixed-donor multidentate ligands in early transition metal coordination chemistry Introduction: defining the terminology Language is "the method of human communication, either spoken or written, consisting of the use of words in a structured and conventional way." 1 Words are bridges to other minds and permit the expression of complex thoughts and ideas. George Orwell (Figure 1.1) considered language "an instrument which we shape for our own purposes" necessary "for expressing and not for concealing or preventing thought."3 He decried the effects of cliche, bureaucratic euphemism, and academic jargon on literary styles, and ultimately on thought itself; and he exhorted those writers to let the "meaning choose the word, and not the other way around." Theodore Savory, a British biologist and expert in the history of science, wrote that science was "the natural enemy o f language."4 However, scientific knowledge exists because scientists are George Orwell writers and speakers, users and sharers of a language that is Page 1 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry constantly evolving. The global spread of scientific English has led to unprecedented international unity in science, a "modern Tower of Babel, recovering the ancient dream of a single language for the wisdom of the nations."5 A t the same time, the ever-increasing division of scientific disciplines creates the opposite impression, one of the Tower torn down and remade into a thousand images "by the power of jargon, dividing the disciplines by the arcanity of specialist speech."5 According to Werner Heisenberg (Figure 1.2),6 scientific knowledge "ultimately has to be based on ordinary language, because that is the only way in 7 R which we can be sure that we are dealing with reality." ' Thus it Figure 1 2 1S u s e ^ u ^ t o s P e n d a f e w minutes defining and illustrating the Werner Heisenberg terminology and jargon upon which this thesis depends so heavily. The most important term to discuss is expressed in the last two words of the title for this chapter, coordination chemistry. Coordination compounds have been known since the 1700s but it was not until the 1890s that their structure was adequately explained. The Swiss chemist Alfred Werner (Figure 1.3)9 proposed that transition metals have two types of valence, a primary valence for the formation of ionic bonds with oppositely charged ions and a secondary valence that binds molecules, 1 0 called ligands - from the Latin ligare meaning to bind. 1 1 The primary valence is now called the oxidation state, and the secondary valence is the coordination number. Thus Werner was able to show that the compound originally written as C o C l 3 - 6 N H 3 is actually [Co(NH 3 ) 6 ]Cl3 where the six ammine ligands are bound to the cobalt, and the three chlorides are counter ions. In compounds where a ligand is bound to two or more sites on a metal, it is termed multidentate, from the Latin dens or dentis meaning tooth. Bidentate ligands occupy two sites, from bidens meaning two teeth. Ligands occupying three sites are called tridentate, from tridens, and ligands occupying more sites are generally termed polydentate. Figure 1.3. Alfred Werner Page 2 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry Multidentate ligands are also referred to as chelating, a term that derives from the Greek chela, meaning claw, and referring to the caliper action of a crab or lobster c law. 1 2 The chelate effect refers to the enhanced stability of a complex containing chelate rings over a similar complex that contains none. Part of this stability can be expressed in terms of entropy, or disorder. If multiple monodentate ligands are bound to a metal center and the chelating ligand is free, there are two molecules; but i f the multidentate ligand is bound to the metal and the monodentate ligands are free, there are more discrete molecules, thus more disorder. Additionally, i f one arm of a chelating ligand is bound to a metal center, there is a far greater chance for additional arms of the ligand to bind in preference to a monodentate ligand due to the proximity of the free arm to the metal center. Even greater stability can be imparted to a coordination complex through the use of macrocyclic ligands. These ligands are rings that are at least nine-membered and incorporate at least three donor atoms. The macrocyclic effect refers to the enhanced stability of cyclic polydentate ligands versus a comparable linear ligand; it is due to movement of the arms in the open form compared to the lack of mobility for the closed macrocycle. When a transition metal forms a compound, it gives up electrons to other elements and becomes positively charged. For example, zirconium atoms (Zr) w i l l give up all four of its valence electrons in a reaction with chlorine gas (Cb) forming the compound Z r C U where the zirconium is in the +4 oxidation state, written Zr(IV). In the same manner, the other members of group 4, titanium and hafnium, form similar ions Ti(IV) and Hf(IV); group 5 metals such as tantalum wi l l give up five electrons and enter the +5 oxidation state, as Ta(V). While oxidation states are useful in explaining observed trends in the properties and reactions of complexes, it must be stressed that they are formalisms; calculations have shown that the actual charge on a metal center is much lower than the formal oxidation state would indicate. For instance, calculations on a formally Zr(IV) complex indicate the charge on zirconium is closer to one. 1 4 Stabilization of high oxidation states requires strong donor ligands capable of reducing the positive charge on the metal center. Oxides and amides are ligands that form strong a-bonds, but also can release electron density to the metal center through 71-bonding. L o w oxidation state Page 3 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry metals are stabilized by soft polarizable ligands capable of removing electron density from the metal through 7i-backbonding. Such 7r-acid ligands include C O , C N " , phosphines and arsines. Transition metals can be divided into hard and soft acids, while the ligands that bind to them can be divided into hard and soft bases. Early transition metals are generally considered hard acids, as they possess little electron density for back-donation and with a higher charge to size ratio they are less polarizable than soft-acid late transition metals. Ligands that bind via O, N , or the halides F and CI are considered hard bases, while ligands that bind through S, P, A s , or I are considered soft. Interactions of these acids and bases can be expressed through the hard-soft acid-base theory, 1 5" 1 7 which states that the most stable complexes generally result from hard acid-hard base and soft acid-soft base combinations. Thus, early transition metals w i l l be better stabilized by hard ligands, and late transition metals better stabilized by soft ligands. Incorporating different donors into a single ligand can further enhance the utility of chelation. In this manner, transition metal complexes can be stabilized over a range of oxidation states. Such mixed donor ligands often include hard N or O donors to stabilize high oxidation state hard metals with soft P or S donors to effectively stabilize soft metal 18 91 centers. Mixed donor multidentate ligands are used in several industrial processes. These ligands do have a serendipitous side effect. While they are able to stabilize metal centers over a range of oxidation states, they are never fully able to satisfy the ideal donor requirements of the metal. Thus, early transition metals supported by mixed-donor ligands can be electron deficient, or electrophilic, and late metals can be electron rich, or nucleophilic, potentially facilitating interesting chemical transformations at the metal center. 1.2. Mixed-donor ligands in the Fryzuk group Research in the Fryzuk laboratory has focused on the study of hybrid mixed-donor multidentate ligands that combine hard nitrogen donors, in the form of an amide Page 4 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry (NR2"), and soft phosphorus donors, in the form of phosphines (PR3). Historically, the first ligand design in the Fryzuk group to incorporate these disparate donors was the chelating, anionic amidodiphosphine ligand ('Pr2PCH2SiMe2)2N", abbreviated , P r [ P N P ] . 2 2 As anticipated, * P r[PNP] is well suited to bind low oxidation state late transition metals through the phosphine donors, and the chelate effect helps bind the amide; this is reversed for early transition metals and lanthanides that bind the amide donor strongly and the phosphine donors via the chelate effect.2 4 The ligand is available in good yield as an isolable lithiated precursor via reaction of the commercially available disilazane (ClCH2SiMe2)2NH with three equivalents of ' P r 2 P L i . Two equivalents of ' P r 2 P L i functionalize the chloromethyl sidearms via a metathesis reaction and the third equivalent deprotonates the amine, as shown in Equation 1.1. The major drawback to the use of [PNP] ligands is the propensity for phosphine dissociation. In several early transition metal complexes, one phosphine donor dissociates, resulting in a bidentate ligand with a pendant phosphine arm. 3 /Pr 2PLi THF (-2 LiCI) (-/Pr2PH) Me2 .Si (1.1) One tactic for limiting dissociation of the phosphine arms of [PNP] is to incorporate them into a macrocyclic array. This strategy led to the design and synthesis of the dianionic Ph[P2N2] macrocyclic ligand precursor (where Ph[P2N2] = PhP(CH2SiMe2NSiMe2CH2)2PPh2") by linking the phosphine donors with an additional equivalent of disilazane, as shown in Scheme 1.1.26 The stereochemical orientations possible at the two phosphine donors leads to the existence of both syn and anti isomers. The syn isomer can be prepared exclusively by judicious choice of solvent and temperature. Although macrocycle synthesis usually requires dilute conditions, 2 7 ' 2 8 the Page 5 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry synthesis of [P2N2] benefits from lithium templating, and thus the lithiated ligand precursor is easily prepared in good yield and purity without high dilution. Scheme 1.1 Addition of the second amido donor to the macrocyclic [P2N2] ligand set is not without consequence. The presence of an additional donor means that many transition metal complexes supported by this ligand are coordinatively and electronically saturated. This results in complexes with increased stability and diminished reactivity. One idea for rectifying this problem was to remove a phosphine donor and create a chelating ligand with two amido nitrogen donors and a single phosphine. Synthesis of the dianionic diamidophosphine ligand ph[NPN] (where [NPN] = ((PhNSiMe2CH2)2PPh2") is shown in Page 6 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry 29 Scheme 1.2. The lithium salt precursor is prepared by reaction of the silylated aniline C l C H 2 S i M e 2 N H P h with P h P H 2 in the presence of " B u L i . S c h e m e 1.2 While the evolution of these ligands is intriguing, their coordination to early transition elements and investigation of the resultant complexes is of great interest. A s it turns out these three donor sets [PNP], [P 2 N 2 ] and [NPN] have proven remarkably adept as ancillary ligands for coordination complexes that can activate molecular nitrogen. 1.3. Dinitrogen Coordination Chemistry Molecular nitrogen, or dinitrogen (N 2 ) , is one of the most important molecules in chemistry. A s the ultimate source for all nitrogen contained in l iving things and as the source of nitrogen used in industry, the efficient utilization of dinitrogen in the synthesis of nitrogen containing molecules remains an important focus of chemistry. 3 0" 4 0 A significant barrier to this is the fundamental inertness of dinitrogen. Despite the Page 7 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry importance of nitrogen for life, dinitrogen does not interact with l iving things directly; as a major component of the atmosphere, it flows in and out of the human respiratory system unaltered. Biological ly, dinitrogen is converted to chemically useful compounds, or ' f ixed ' , by a few species of bacteria using a process that reacts dinitrogen with protons and electrons in a nitrogenase metalloenzyme. 4 1 Industrially, only one commercially successful reaction utilizes dinitrogen as a feedstock. The Haber-Bosch process involves reaction of dinitrogen with three molecules of dihydrogen over an iron or ruthenium 4 2 catalyst to produce ammonia (Equation 1.2).43"46 The reaction is favorable under ambient conditions; however, high temperatures (400-550 °C) are necessary to give viable reaction rates, and at these elevated temperatures the gases must be compressed to 100-300 atm to favor the production of ammonia. For his work on this process, Fritz Haber (Figure 1.4) was awarded the 1918 Nobel Prize in chemistry, 4 7 and Carl Bosch (Figure 1.5) was similarly honored in 1931 for developing the high-pressure methods that made AO the industrial synthesis of ammonia feasible. Figure 1.4. Fritz Haber Figure 1.5. Car l Bosch N 2 (g ) + 3 H 2 ( g ) g a g , 2 N H 3 ( g ) 100-300 atm 400-550 °C (1.2) The inertness of dinitrogen stems from several properties of the molecule. It has a high ionization potential (1452.87 kJ mol"1) and a negative electron affinity (-173.67 kJ mol"1) making it difficult to ionize. The molecule has a high bond dissociation enthalpy (945 kJ mol" 1). However, the inertness of dinitrogen is not due to the strong triple bond; carbon monoxide is isoelectronic with dinitrogen and is a reactive molecule that undergoes a variety of transformations,4 9 yet has an even greater bond dissociation enthalpy (1076 kJ mol" 1). Dinitrogen has a low-energy highest occupied molecular orbital Page 8 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry or H O M O (-15.6 eV), and a high-energy lowest occupied molecular orbital or L U M O (7.3 eV). This combination gives dinitrogen a large H O M O - L U M O gap and makes electron transfer or Lewis acid-base reactions unfavorable. 5 0 Despite its inertness, dinitrogen does coordinate to transition metals. With the serendipitous discovery of [Ru(NH3)sN 2] 2 + in 1965 (Equation 1.3),5 1"5 4 it became apparent that dinitrogen could act as a ligand in a coordination complex. It should be noted that the dinitrogen moiety in this ruthenium complex is not derived from dinitrogen but from hydrazine. Due to the thermodynamic stability of dinitrogen it is common for nitrogen containing molecules, such as azide (N3"), to react by releasing N 2 . Dinitrogen complexes have been synthesized using a variety of sources for the N 2 fragment, including diazines ( R H N - N H R ) , 5 5 silylated hydrazines, 5 6 ' 5 7 nitrous oxide ( N 2 0 ) , 5 8 azides, 5 2 and several other more complex systems. 3 1 RuCI 3 -xH 2 0 N 2 H 4 - H 2 0 H 3 N " H 3 N * NHq ;Ru-NH, 12+ — N = CI, (1.3) While the synthesis of a dinitrogen complex was revolutionary, the dinitrogen unit was derived from hydrazine. The discovery of cobalt (I) dinitrogen complexes showed that transition metals could coordinate atmospheric N 2 d irect ly. 5 9 ' 6 0 Whether prepared from hydrazine or dinitrogen, the ruthenium and cobalt complexes, and a similar iridium complex, 6 1 share an important feature in their coordination o f dinitrogen. Measurement o f V N N stretching frequencies by IR showed strong absorptions at 2050-2100 cm" 1 indicative of a weakly activated N 2 unit. Dinitrogen is typically "activated" when coordinated to a transition metal, and the degree of activation can be measured by the V N N stretching frequency in the IR or Raman spectra and by the N - N internuclear distance determined crystallographically. These values can be loosely correlated to changes in bond order, and Table 1.1 summarizes some data on N - N triple, double and single bonds in representative simple molecules. Page 9 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry Activated dinitrogen units are often referred to as diazenido (N22") or hydrazido (N24") based on similarities to these compounds. The stretching frequencies of the coordinated dinitrogen complexes discussed above are slightly lower but still very close to that of free N2, thus these complexes are considered weakly activated dinitrogen complexes. A subsequent solid-state structure for the ruthenium complex showed the N2 fragment was bonded in an end-on fashion. 6 2 Table 1.1. N - N bond lengths and stretching frequencies for some simple molecules Compound: N - N bond length (A): VNN (cm"1) N 2 (g) 1.0975 2331 PhN=NPh 6 4 - 6 7 1.255 1442 H 2 N - N H 2 6 4 ' 6 8 ' 6 9 1.449 1111 The activation of coordinated N2 is affected by the metal-dinitrogen bonding mode, which can vary from metal to metal, the oxidation state of the metal, and the nature of the ancillary ligands in the complex. The weakly activated, end-on bonding mode found in [Ru(NH3) 5N2] 2 + is prevalent among late transition metal dinitrogen complexes. Strong activation is more characteristic of early transition metal complexes in higher oxidation states, and the coordinated N2 in these complexes can display a variety of bonding modes. Several bonding motifs for dinitrogen with one or two transition metals are shown in Figure 1.6. Page 10 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry Weak Activation Strong Activation End-on Mononuclear Side-on Mononuclear End-on Dinuclear Side-on Dinuclear Side-on End-on Dinuclear M N= =N M M N = N M M N M N M ^ N = (unknown) M N " V I N (unknown) M M M N M N M M N M N ' (unknown) Figure 1.6. Bonding modes for dinitrogen and one or two transition metals. Activation of N 2 is implied by bond order. 1.4. Multidentate ligands in dinitrogen coordination chemistry Because the discovery of [Ru(NH3)5N 2 ] 2 + was serendipitous it did not immediately lead to the widespread synthesis of such complexes, and successful synthetic strategies were developed empirically. Weakly activated complexes are sometimes available by substitution of a weakly coordinating ligand such as H2 with N 2 . 7 1 - 7 3 Such replacement reactions do depend on the metal center's affinity for N 2 , because there are examples of H2 displacing N 2 . 7 4 - 7 6 Page 11 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry Multidentate ligands have been extensively utilized as ancillary ligands for dinitrogen coordination. Zero-valent group 6 complexes were an important early class of such complex. These complexes were synthesized by reduction of metal salts in the presence of chelating phosphines and N 2 , as shown in Equation 1.4.77-79 This is an example of a common synthetic technique where a metal halide is reduced to give a low-valent intermediate that binds and activates N 2 , in the presence of an ancillary ligand. N MoCI4 + Na/Hg, N 2 .PR? (- NaCl) R 2 P--V R 2 N :Mo: N III N R 2 •P •P R 2 3 (1.4) A widely employed modification is the reduction of a metal halide complex that already includes the ancillary ligand; this has proven a versatile technique for the synthesis of early metal dinitrogen complexes containing amidophosphine ligands. Reduction of the amidodiphosphine complex (P r[PNP]ZrCl3 with Na/Hg amalgam under N 2 generates the side-on bridged dinitrogen complex (' P r[PNP]ZrCl) 2(p- r | 2 : T l 2 - N 2 ) RO (Equation 1.5). This complex can be formulated as having two Zr(IV) centers and a hydrazido, or N 2 4 - , ligand with a N - N bond length of 1.548 A . Page 12 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry 2 (1.5) M e 2 A s mentioned previously, the reactivity of early transition metal [PNP] complexes is plagued by phosphine dissociation and this led to development o f the macrocyclic [P 2 N 2 ] ligand. The complex p h [ P 2 N 2 ] Z r C l 2 is prepared by salt metathesis and reduced with KCg under N 2 to give the side-on dinitrogen complex ( P h [P 2 N 2 ]Zr ) 2 (p - r | 2 : n 2 -N 2 ) , as shown in Equation 1.6.81 Despite lower N 2 activation relative to the [PNP] complex ( N - N = 1.43 A ) , this complex reacts cleanly with hydrogen, producing a bridging N - N - H moiety and a bridging hydride. 8 2 (1.6) In the same manner, the d2 niobium complex p h [ P 2 N 2 ] N b C l can be prepared by salt metathesis. Reduction with K C g under N 2 yields a paramagnetic end-on dinitrogen complex rather than a side-on N 2 fragment (Equation 1.7).83 Alkylat ion of p h [ P 2 N 2 ] N b C l Page 13 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry with methylmagnesium chloride gives paramagnetic alkyl P h [ P 2 N 2 ] N b M e . This complex binds N 2 reversibly, giving a linear bimetallic dinitrogen complex. 8 4 P h [ P 2 N 2 ] V supports a 85 dinitrogen complex isostructural to the one shown in Equation 1.7. 2 (1.7) Similar low-valent chemistry is not available for the heavier group 5 metal tantalum, however, the complex p h [P 2 N2]TaMe3 can be synthesized by reaction of a ligand precursor with T a M e s C ^ . 8 6 Hydrogenation of P h [P2N2]TaMe3 generates the formally eight-coordinate dinuclear tetrahydride ( P h [P 2 N2]Ta) 2 (u . -H )4 , 8 7 which is surprisingly unreactive toward small molecules such as C O and ethylene. This was attributed to coordinative saturation and led to the development of the [NPN] ligand framework. Upon hydrogenation of the trialkyl complex, p h [ N P N ] T a M e 3 , the dark purple complex ( P h [NPN]Ta)2(p-H)4, a diamagnetic Ta(IV)-Ta(IV) complex with a metal-metal bond, is formed. This material gradually turns dark brown upon exposure to N 2 forming the side-on end-on dinitrogen complex ( P h [NPN]Ta) 2 (p -H) 2 (p - r | 1 : r i 2 -N 2 ) . 2 9 This chemistry is detailed in Scheme 1.3. This reaction is a rare example of an early transition metal complex eliminating hydride ligands as H 2 in dinitrogen complex formation. Page 14 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry Ph Ph Scheme 1.3 Multidentate ligands in dinitrogen coordination and activation are not limited to amidophosphines. Chelating amides like the beta-diketiminato, or nacnac, ligand have been used to synthesize dinitrogen complexes of iron. For example, Equation 1.8 shows the reduction of [(nacnac)FeCl] by potassium naphthalenide to form an end-on bound dinuclear N 2 complex. 8 8 Page 15 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry Equation 1.9 shows the formation of a heterodinuclear end-on bound N 2 complex supported by the chelating amido [N3N] 3" l igand. 8 9 The product has been used in further preparation of heterobimetallic dinitrogen complexes by salt metathesis with metal halides. 9 0 Cyclopentadienyl and substituted cyclopentadienyl ligands are very common in early transition metal chemistry. In another example of hydride elimination, The T i -Me bond of 6w-tetramethylcyclopentadienyl(methyl)titanium(III), [ ( C 5 M e 4 H ) 2 T i M e ] , reacts with H2 via hydrogenolysis to give a hydride. Two of these complexes react with N 2 with loss of H2 to form a linear bridging dinitrogen complex. 9 1 The substituted arcsa-bridged monomeric zirconocene dihydride reacts with N2 when a toluene solution is allowed to stand under an atmosphere of dinitrogen, forming the side-on bound dinitrogen complex shown in Equation 1.10. Page 16 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry 1.5. Ligand modification: the butterfly effect The butterfly effect is a term first coined by the meteorologist Edward Lorenz in 93 his attempts to describe the difficulty in predicting the behaviour of complex systems. Very small differences in the initial conditions of an experiment can lead to wildly different outcomes. Appl ied to coordination chemistry, the literature contains many examples where subtle changes to the ancillary ligand array have magnified effects on the coordination chemistry observed. The field of dinitrogen activation is no different; ligand design can influence not just the formation of N 2 complexes, but also the degree of activation and the bonding mode. One profound example of this can be found in a series of substituted cyclopentadienyl complexes of zirconium. The complex C p * 2 Z r C l 2 (Cp* = r | 5 - C 5 M e 5 ) is reduced with Na/Hg amalgam under N 2 to give the complex [Cp*Zr(r)'-N 2 ) ] 2 (p- r | 1 : r i 1 -N 2 ) , with three bound N 2 molecules (Scheme 1.4a).75 However, the reduction of the similar zirconocene (r | 5 -C 5 Me4H ) 2 ZrCl 2 with Na /Hg amalgam under N 2 produces ( ( r ) 5 -C 5 Me 4 H) 2 Zr) 2 (p- r | 2 : r | 2 -N 2 ) (Scheme 1.4b). 7 5 ' 9 4 A very subtle alteration to the ligand, the removal of a methyl group from Cp*, leads to a change in the dinitrogen coordination mode from end-on dinuclear to side-on dinuclear, and only one N 2 molecule is coordinated. Under similar reducing conditions, the related zirconocenes including C p " 2 Z r C l 2 and C p t t 2 Z r C l 2 (Cp" = n 5-C 5H3-l,3-(SiMe3) 2, Cp" = r i 5 -C 5 H3 - l , 3 - (CMe 3 ) 2 ) form paramagnetic Zr(III) complexes. 9 5 ' 9 6 Dinitrogen complexes supported by Cp" can be synthesized by the reaction of C p " 2 Z r C l 2 with ' B u L i and subsequent reductive Page 17 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry elimination of isobutene from a zirconocene isobutyl hydride complex to give (Cp"2Zr)2(n-n2:ri2-N2) (Scheme 1.4c);9 7 [Cp*Zr(n I-N 2)] 2(p-ri 1:ri 1-N2) can also be Q O prepared by this method. Scheme 1.4 Initial diversification of amidophosphine ligands [P 2 N 2 ] and [NPN] in the Fryzuk group focused on the alteration of functional groups attached to the amido and phosphine donors with varying degrees o f success. Reduction o f the cyclohexyl substituted C y [ P 2 N 2 ] Z r C l 2 under N 2 produces an intractable blue solid. Hydrogenation of the cyclohexyl substituted C y[NPN]TaMe3 and exposure to N 2 yields an analogous side-on Page 18 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry end-on dinitrogen complex (C y[NPN]Ta)2(p-H)2(p-r|1:ri2-N2); however, the reaction is considerably slower than the phenyl derivative. Attempts to utilize other modifications to the [NPN] ligand in dinitrogen coordination have failed. More recently, work has focused on altering the silylmethyl backbone of [NPN], with the synthesis of arene bridged diamidophosphines shown in Figure 1.7." Figure 1.7. Arene bridged diamidophosphine ligands. 1.6. Thesis scope and prospectus This introduction has featured examples of early transition metal complexes supported by several generations of amidophosphine ligands, and has explored some of their advantages and disadvantages in the coordination and functionalization of dinitrogen. Recent work with these ligands has explored the effect of altering the sterics and electronics through modification of functional groups attached to donor atoms, and through modification of the ligand backbone. This thesis further explores the effects of ligand modification in early transition metal dinitrogen coordination chemistry. This does not take the path of functional group modification, but investigates changes in chemistry through the more fundamental alteration of the nitrogen and phosphorus donors in [P2N2] and [NPN]. Page 19 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry Chapter two explores the chemistry of a system where the phosphorus donors have been substituted for the more moderate donor atom arsenic. Synthesis of the macrocyclic p h [ A s 2 N 2 ] L i 2 ligand precursor is detailed and early transition metal chemistry is explored. Even this subtle change of donor has pronounced changes in the chemistry of these early metal complexes; differences in the properties of phosphorus and arsenic open different reaction pathways for complexes supported by the p h [ A s 2 N 2 ] macrocycle. Chapter three explores the chemistry of tantalum complexes supported by the chelating diamidoarsine p h[NAsN] ligand. The synthesis of both the lithiated and protonated species is detailed and the chemistry of a tantalum alkyl with hydrogen is explored. The substitution of arsenic for phosphorus in this system opens a radically different reaction pathway for the hydrogenation of p h[NAsN]TaMe3, resulting in hydrogenation of Ta-N bonds. Chapter four takes the substitution chemistry in a different direction. Instead of exploring ligands with weaker donor arrays, it explores the synthesis of ligands and ligand precursors containing a stronger anionic oxygen donor together with a phosphine donor. The chemistry of bis(aryloxy)phosphines containing substituted aryl backbones is explored with the synthesis of lithium, potassium and protonated derivatives. Chapter five explores the early transition metal coordination chemistry of the bis(aryloxy)phosphines synthesized in chapter four. Substitution of the amide donor for a more strongly donating oxide facilitates the synthesis of a tantalum halide complex, something that proved impossible for the amidophosphine systems. However, the loss of steric bulk from the same substitution gives rise to detrimental ligand exchange reactions. Chapter six briefly explores alternative methods for the synthesis of dinitrogen complexes including ligand exchange and substituted hydrazines, utilizing the early metal complexes synthesized in previous chapters. Page 20 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry 1.7. References (1) Soanes, C , Ed. ; Oxford Dictionary of English, 2 n d ed.; Oxford University Press: Oxford, 2004. (2) Bowker, G . Inside George Orwell; Palgrave Macmil lan: N e w York, 2003. (3) Orwell , G . Politics and the English Language; Seeker and Warburg: London, 1998. (4) Savory, T. H . The Language of Science: Its growth, character and usage; Andre Deutch: London, 1953. (5) Montgomery, S. Science 2004, 303, 1333-1335. (6) Heisenberg, W . Nobel Lectures, Including Presentation Speeches and Laureates' Biographies; Elsevier Pub. Co. for the Nobel Foundation: Amsterdam, 1932. (7) Heisenberg, W. Physics and Philosophy: The Revolution in Modern Science; Harpar-Collins: New York, 1958. (8) Heisenberg, W . Encounters with Einstein and Other Essays on People, Places and Particles; reprint ed.; Princeton University Press: Princeton, 1989. (9) Werner, A . Nobel Lectures, Including Presentation Speeches and Laureates' Biographies; Elsevier Pub. Co. for the Nobel Foundation: Amsterdam, 1913. (10) Zumdahl, S. S. Chemistry; 2 n d ed.; D . C. Heath and Company: Lexington, Mass., 1989. (11) Brock, W . H . ; Jensen, K . A . ; Jorgensen, C . K . ; Kauffman, G . B . Polyhedron 1983, 2, 1-7. (12) Morgan, G . T.; Drew, H . D . K . J. Chem. Soc, Trans. 1920,117, 1456-1465. (13) Lindoy, L . F. The Chemistry of Macrocyclic Ligand Complexes; Cambridge University Press: Cambridge, 1989. (14) Basch, H . ; Musaev, D. G . ; Morokuma, K . J. Am. Chem. Soc. 1999, 121, 5754-5761. (15) Pearson, R. G . J. Chem. Ed. 1968, 45, 581-587. (16) Pearson, R. G . J. Chem. Ed. 1968, 45, 643-648. (17) Pearson, R. G . Coord. Chem. Rev. 1990,100, 403-425. Page 21 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry (18) Muller, U . ; Ke im , W. ; Kruger, C ; Betz, P. Angew. Chem. Int. Ed. 1989, 28, 1011-1013. Ke im, W. Angew. Chem. Int. Ed. 1990, 29, 235-244. Drent, E . ; Arnoldy, P.; Budzelaar, P. H . M . J. Organomet. Chem. 1993, 455, 247-253. Drent, E . ; Arnoldy, P.; Budzelaar, P. H . M . J. Organomet. Chem. 1994, 475, 57-63. Fryzuk, M . D . ; MacNei l , P. A . ; Rettig, S. J.; Secco, A . S.; Trotter, J. Organometallics 1982,1, 918-930. Fryzuk, M . D . Can. J. Chem. 1992, 70, 2839. Fryzuk, M . D . ; Haddad, T. S.; Berg, D . J. Coord. Chem. Rev. 1990, 99, 137-212. Fryzuk, M . D . ; Carter, A . ; Rettig, S. J . Organometallics 1992,11, 469-472. Fryzuk, M . D . ; Love, J. B . ; Rettig, S. J. Chem. Commun. 1996, 2783-2784. Caminade, A . M . ; Majoral, J. P. Chem. Rev. 1994, 94, 1183-1213. Coles, S. J.; Edwards, P. G . ; Fleming, J. S.; Hursthouse, M . B . ; Liyanange, S. S. Chem. Commun. 1996, 293-295. Fryzuk, M . D . ; Johnson, S. A . ; Patrick, B . O.; Albinati , A . ; Mason, S. A . ; Koetzle, T. F. J. Am. Chem. Soc. 2001,123, 3960-3973. Chatt, J . ; Dilworth, J. R. ; Richards, R. L . Chem. Rev. 1978, 78, 589-625. Hidai , M . ; Mizobe, Y . Chem. Rev. 1995, 95, 1115-1133. Gambarotta, S. J. Organomet. Chem. 1995, 500, 117-126. Bazhenova, T. A . ; Shilov, A . E . Coord. Chem. Rev. 1995,144, 69-145. Pickett, C . J. J. Biol. Inorg. Chem. 1996,1, 601-606. Hidai , M . Coord. Chem. Rev. 1999,185-186, 99-108. Fryzuk, M . D . ; Johnson, S. A . Coord. Chem. Rev. 2000, 200-202, 379-409. Hidai , M . ; Mizobe, Y . Pure Appl. Chem. 2001, 75, 261-265. Shaver, M . P.; Fryzuk, M . D. Adv. Synth. Catal. 2003, 345, 1061-1076. Kozak, C. M . ; Mountford, P. Angew. Chem. Int. Ed. 2004, 43, 1186-1189. MacKay , B . A . ; Fryzuk, M . D . Chem. Rev. 2004, 104, 385-402. Thorneley, R. N . F.; Lowe, D . J. J. Biol. Inorg. Chem. 1996,1, 576-580. Page 22 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry (42) Bielawa, H . ; Hinrichsen, O.; Birkner, A . ; Muhler, M . Angew. Chem. Int. Ed. 2001, 40, 1061-1063. (43) Ertl , G . In Catalytic Ammonia Synthesis; Jennings, J. R., Ed . ; Plenum Press: New York, 1991. (44) Postgate, J. Nitrogen Fixation; Cambridge Press: Cambridge, 1998. (45) A p p l , M . Ammonia; Wiley, V C H : Weinheim, 1999. (46) Schlogl, R. Angew. Chem. Int. Ed. 2003, 42, 2004-2008. (47) Haber, F. Nobel Lectures, Including Presentation Speeches and Laureates' Biographies; Elsevier Pub. Co. for the Nobel Foundation: Amsterdam, 1918. (48) Bosch, C . Nobel Lectures, Including Presentation Speeches and Laureates' Biographies; Eslevier Pub. Co. for the Nobel Foundation: Amsterdam, 1931. (49) Greenwood, N . N . ; Earnshaw, A . Chemistry of the Elements; 2 n d ed.; Butterworth-Hienemann: Oxford, 1997. (50) Alberty, R. A . J. Biol. Chem. 1994, 269, 7099-7102. (51) Al len , A . D . ; Senoff, C. V . Chem. Commun. (London) 1965, 621-622. (52) Al len , A . D. ; Bottomley, F.; Harris, R. D. ; Reinsalu, V . P.; Senoff, C. V . J. Am. Chem. Soc. 1967, 89, 5595-5599. (53) Chatt, J.; Nikolsky, A . B . ; Richards, R. L . ; Sanders, J. R.; Fergusson, J. E . ; Love, J. L . J. Chem. Soc. (A) 1970, 1479-1483. (54) Senoff, C. V . J. Chem. Ed. 1990, 67, 368-370. (55) Rocklage, S. M . ; Schrock, R. R. J. Am. Chem. Soc. 1982,104, 3077-3081. (56) Dilworth, J. R.; Harrison, S. J.; Henderson, R. A . ; Walton, D . R. M . J. Chem. Soc, Chem. Commun. 1984, 176-177. (57) Dilworth, J. R.; Henderson, R. A . ; Hi l l s , A . ; Hughes, D . L . ; Macdonald, C ; Stephens, A . N . ; Walton, D . R. M . J. Chem. Soc, Dalton Trans. 1990, 1077-1085. (58) Pell , S.; Mann, R. H . ; Taube, H . ; Armor, J. N . Inorg. Chem. 1974,13, 479-480. (59) Yamamoto, A . ; Kitazume, S,; Pu, L . S.; Ikeda, S. Chem. Commun. (London) 1967, 79-80. (60) Sacco, A . ; Rossi, M . Chem. Commun. (London) 1967, 316. (61) Collman, J. P.; Kang, J. W . J. Am. Chem. Soc. 1966, 88, 3459-3460. Page 23 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry Bottomley, F.; Nyburg, S. C. Acta Cryst. B 1968, 24, 1289-1293. Stoicheff, B . P. Canad. J. Phys. 1954, 82, 630-634. Sutton, L . E . Chemical Society Special Publications No. 11; Chemical Society: London, 1958. Brown, C . J . Acta Cryst. 1966, 21, 146-152. Mostad, A . ; Roemming, C. Acta Chem. Scand. 1971, 25, 3561-3568. Bouwstra, J. A . ; Schouten, A . ; Kroon, J. Acta Cryst. C. 1983, 3P, 1121-1123. Morino, Y . ; Iijima, T.; Murata, Y . Bull. Chem. Soc. Jpn. 1960, 33, 46-48. Col l in , R. L . ; Libscomb, W . N . Acta Cryst. 1951, 4, 10-14. Chatt, J.; Leigh, G . J. Chem. Soc. Rev. 1972,1, 121-144. Schlaf, M . ; Lough, A . J . ; Morris, R. H . Organometallics 1997,16, 1253-1259. Gao, Y . ; Holah, D . G . ; Hughes, A . N . ; Spivak, G . J.; Havighurst, M . D . ; Magnuson, V . R. Polyhedron 1998,17, 3881-3888. Tenorio, M . J.; Tenario, M . A . J. ; Puerta, M . C ; Valerga, P. Inorg. Chim. Acta 1997, 259, 77-S4. Hidai, M . ; Tominari, K . ; Uchida, Y . J. Am. Chem. Soc. 1972, 94, 110-114. Manriquez, J. M . ; Bercaw, J. E . J. Am. Chem. Soc. 1974, 96, 6229-6230. George, T. A . ; Tisdale, R. C. Inorg. Chem. 1988, 27, 2909-2912. George, T. A . ; Seibold, C. D . J. Am. Chem. Soc. 1972, 94, 6859-6860. George, T. A . ; Seibold, C. D . Inorg. Chem. 1973,12, 2544-2547. Day, V . W. ; George, T. A . ; Iske, S. D. A . J. Am. Chem. Soc. 1975, 97, 4127-4128. Fryzuk, M . D . ; Haddad, T. S.; Rettig, S. J. J. Am. Chem. Soc. 1990, 112, 8185-8186. Fryzuk, M . D . ; Love, J. B . ; Rettig, S. J.; Young, V . G . Science 1997, 275, 1445-1447. Basch, H . ; Musaev, D . G . ; Morokuma, K . ; Fryzuk, M . D . ; Love, J. B . ; Seidel, W. W.; Albinati , A . ; Koetzle, T. F.; Klooster, W . T.; Mason, S. A . ; Eckert, J. J. Am. Chem. Soc. 1999,121, 523-528. Fryzuk, M . D . ; Kozak, C. M . ; Bowdridge, M . R.; Patrick, B . O.; Rettig, S. J. J. Am. Chem. Soc. 2002,124, 8389-8397. Page 24 References begin on page 21. Chapter One: Mixed-donor multidentate ligands in early transition metal coordination chemistry (84) Fryzuk, M . D . ; Kozak, C. M . ; Patrick, B . O. Inorg. Chim. Acta 2003, 345, 53-62. (85) Bowdridge, M . R. M. Sc. thesis, University of British Columbia, 1998. (86) Fryzuk, M . D . ; Johnson, S. A . ; Rettig, S. J. Organometallics 1999, 18, 4059-4067. (87) Fryzuk, M . D . ; Johnson, S. A . ; Rettig, S. J. Organometallics 2000, 19, 3931-3941. (88) Smith, J. M . ; Lachicotte, R. J.; Pittard, K . A . ; Cundari, T. R.; Lukat-Rodgers, G . ; Rodgers, K . R.; Holland, P. L . J. Am. Chem. Soc. 2001,123, 9222-9223. (89) O'Donoghue, M . B . ; Davis, W. M . ; Schrock, R. R.; Reiff, W . M . Inorg. Chem. 1999, 38, 243-252. (90) O'Donoghue, M . B . ; Zanetti, N . C. ; Davis, W . M . ; Schrock, R. R. J. Am. Chem. Soc. 1997,119, 2753-2754. (91) de Wolf, J. M . ; Blaauw, R.; Meetsma, A . ; Teuben, J. H . ; Gyepes, R.; Varga, V . ; Mach, K . ; Veldman, N . ; Spek, A . L . Organometallics 1996,15, 4977-4983. (92) Chirik, P. J. ; Henling, L . M . ; Bercaw, J. E . Organometallics 2001, 20, 534-544. (93) Lorenz, E . N . J. Atmos. Sci. 1963, 20, 130-141. (94) Pool, J. A . ; Lobkovsky, E . ; Chirik, P. J. Nature 2004, 427, 527-530. (95) Urazowski, I. F. ; Ponomaryev, V . I.; Nifant'ev, I. E . ; Lemenovskii, D . A . J. Organomet. Chem. 1989, 368, 287-294. (96) Hitchcock, P. B . ; Lappert, M . F.; Lawless, G . A . ; Olivier, H . ; Ryan, E . J. J. Chem. Soc, Chem. Commun. 1992, 474-476. (97) Pool, J. A . ; Lobkovsky, E . ; Chirik, P. J. J. Am. Chem. Soc. 2003,125, 2241-2251. (98) Pool, J. A . ; Lobkovsky, E . ; Chirik, P. J. Organometallics 2003, 22, 2797-2805. (99) MacLachlan, E . A . ; Fryzuk, M . D. Organometallics 2005, 24, 1112-1118. Page 25 References begin on page 21. Chapter Two Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors* 2.1. Introduction O f all the elements of the periodic table, arsenic has perhaps the most fascinating historical connection to humanity. Arsenic minerals have been known since ancient times; in the fourth century B . C . , Aristotle made reference to a compound called sandarach, a deep red arsenic sulphide (AS4S4) now known as realgar (from the Arabic rahj al ghar meaning powder of the mine). Yel low orpiment (arsenic trisulphide, AS2S3) was used as a pigment in ancient Egypt, and later in China, for illuminating manuscripts and painting walls. The Romans knew arsenic as arsenicum, taken from the Greek word arsenikon, itself derived from the Arabic word for orpiment, az-zernikh, with roots in the * A version o f this chapter has been published. Carmichael, C . D.; Fryzuk, M . D. Dalton Trans. 2005, 452-459 Page 26 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Persian zerni-zar, meaning gold. The Greeks associated arsenikon with arsenikos, 1 2 meaning male, and it came to represent the power of arsenic as a poison. ' In the first century A . D . , Dioscorides described the use of arsenic as a poison in the court of the Roman Emperor Nero. In 15th-century France, it was known as poudre de succession, or inheritance powder. 3 ' 4 There has been much discussion whether the death of Napoleon Bonaparte was due to stomach cancer or arsenic poisoning. In the early 19 t h century it was known that wallpapers decorated with green arsenic pigments could cause death,3 especially i f present in damp rooms. Initially, these deaths were attributed to ingestion of particles from the wallpaper; however, in 1892 the Italian physician Bartolomeo Gosio demonstrated that certain fungi, growing in the presence o f arsenic compounds, released a volatile material that became known as "Gosio Gas", 5 later shown to be trimethylarsine (AsMe3). Napoleon could have ingested arsenic by this mechanism, 6 although the toxicity of trimethylarsine has recently been called an urban myth. Another conspiracy theory espouses the intentional poisoning of Napoleon by agents of the Bourbons. 7 Arsenic was a preferred poison because the symptoms were difficult to detect since they could mimic food poisoning and other common illnesses. A single large dose provoked violent abdominal cramping, vomiting and diarrhea, often quickly leading to death. Arsenic could also be given as a series of smaller doses, producing a more subtle form of chronic poisoning characterized by a loss of strength, confusion and paralysis. Detection was problematic: the hydrogen sulphide test - passing hydrogen sulphide through a solution containing arsenic to produce a yellow precipitate of arsenic trisulphide - was unreliable. In 1832, the English chemist James Marsh, furious at his futile turn as an expert witness in a poisoning case, set out to develop a better test for arsenic. The Marsh Test mixes finely divided zinc and sulphuric acid with the material suspected of containing arsenic. If arsenic is present, it is converted into arsine ( A s E y , a highly toxic and reactive gas that is then trapped in a glass tube.1 Heating the glass tube to 250 °C decomposes the arsine and the arsenic is deposited as a mirror on the inside of the flask. With such an accurate test for arsenic available to criminal investigators, the use of arsenic as a poison waned. Page 27 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Residents of Styria, a province of Austria, had a reputation for purposefully ingesting arsenic in the 19 t h century. These arsenic-eaters ingested arsenic to improve the complexion of skin and endurance at high altitudes.8 When news of this reached Victorian England, arsenic became so commonly used for medical treatment that it was dubbed the "therapeutic mule". 9 O f all these treatments the most famous is Fowler's Solution, a solution of potassium arsenite ( K H A S O 3 ) . In 1910 the German pharmacologist Paul Ehrlich introduced 3-amino-4-hydroxyphenylarsenic(I) (arsphenamine, salvarsan or Ehrlich606), the first effective treatment for syphilis, and the first modern targeted chemotherapeutic agent. Its structure was only recently determined to be a mixture o f a cyclic trimer and a cyclic pentamer. 1 0 Despite its long history as a poison, a preparation of arsenic trioxide has been developed for the treatment of acute promyelocytic leukemia, under the brand name Trisenox. 1 1 For centuries the toxicity of arsenic compounds led to their great use as insecticides and herbicides, particularly in the form of lead arsenate (Pb3(As04)2) and later calcium arsenate (Ca3(As04)2). The compounds copper acetoarsenite (Paris Green, Cu(C2H-302)2'3Cu(As02)2) and copper arsenite (Scheele's Green, CuHAsOs) found extensive use as pigments in wallpapers, cloth and tapestries, children's toys and 1 ~) amazingly even food. In the last century, chromated copper arsenate was used as a wood preservative. Arsenic has seen use in the manufacture of alloys, to improve the sphericity of lead shot and the hardness of lead in lead acid batteries. Arsenic is an important material in the semiconductor industry where gallium arsenide (GaAs) thin films are grown by metal vapour deposition techniques using volatile precursors such as 13 • arsine. These materials have favourable properties when compared to silicon based semiconductors, including lower power consumption, higher switching speed and higher electron mobility. These properties have made gallium arsenide based circuitry common in cell phones and computers. Gall ium arsenide is also a good emitter of light and is used in light-emitting diodes and lasers. The organometallic chemistry of arsenic began in 1757 when a French pharmacist-chemist, Louis-Claude Cadet de Gassicourt, mixed arsenic trioxide with potassium acetate and produced a fuming mixture with a penetrating odour of garlic. 1 4 Page 28 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors The identity of the fuming liquid remained unknown until the work of Robert Wilhelm Bunsen in 1837-1843. Different analyses produced the formulas C 4 H 1 2 A S 2 and C 4 H 1 2 A S 2 O . Bunsen, on the suggestion of the Swedish chemist Berzelius, chose the name kakodyl (cacodyl in English literature) for C 4 H 1 2 A S 2 , after the Greek words kakodes meaning evil smelling and hyle meaning matter, and thus C 4 H 1 2 A S 2 O became "cacodyl oxide". Bunsen did not attempt to establish the composition of the fuming liquid, but he synthesized many derivatives, including cacodyl chloride (Me2AsCl) and cacodyl cyanide (Me2AsCN). The fuming liquid is really a mixture of two components, the cacodyl dimer Me2As-AsMe2 or tetramethyldiarsine and the cacodyl oxide Me 2AsOAsMe2, whose ratios were not determined until the work of Valeur and Gaillot in the late 1920s. Derivatives of cacodyl such as dimethylarsinic acid (cacodylic acid, Me 2 As(=0)(OH)) have been used in various herbicides. More recently tetramethyldiarsine has been used as a ligand in transition-metal coordination chemistry, where it can bind in several different ways, as shown in Figure 2 .1 . 1 5 ' 1 6 The coordination chemistry of tetramethyldiarsine is no different than that of most arsine ligands in that the phosphorus analog, tetramethyldiphosphine is 17 18 known and its coordination chemistry is similar. ' Me ( O C ) 5 M * -Me M e 2 A s A s M e 2 M e 2 l _^ ft / / v , . A s — A s ( O C ) 4 M M ( C O ) 4 ( O C ) 4 M % — — / M ( C O ) 4 \ \ / A s M e Me M e 2 A s A s M e 2 M e 2 M = Cr, Mo, W Figure 2.1. Binding modes of tetramethyldiarsine, M e 2 A s - A s M e 2 , and ligands derived from tetramethyldiarsine. In Chapter 1, the strong o-donor and 7i-acceptor abilities, along with a convenient NMR-act ive nucleus, that make phosphine ancillary ligands ubiquitous throughout transition-metal coordination chemistry were discussed. Ligands of the next heaviest member of group 15 - arsenic - are much less common. Despite sharing similar Page 29 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors properties, arsenic ligands are known to be modest a-donors and 7i-acceptors. For N M R , 7 5 A s (I = 3/2) is not a useful nucleus due to its quadrupolar nature, 1 9 although it has been 20 used in examining the interactions between arsenic species and biological molecules. The majority of arsine chemistry has been limited to the late transition metals by the modest electron donating and accepting properties of arsenic, and there are many examples of adduct complexes containing monodentate trivalent arsines such as triphenylarsine (AsPh 3 ) , and bidentate chelating ligands such as diars (o-C6H.4(AsMe2)2), examples of which are shown in Figure 2.2. 2 1 ' 2 2 Figure 2.2. Monodentate and bidentate arsenic ligands. Macrocycles are also common in arsenic chemistry. Examples include 2,10-dimethyl-2,10-diarsa-6-phenylarsabicyclo[9.4.0]pentadeca-1 (11), 12,14-triene,2 3 (Figure 2.3a) and 2,3,4,5-tetrahydro-1-methyl-1,4-benzazarsepine2 4 (Figure 2.3c). There is also considerable literature on the family of alkylcycloarsoxanes (RAsO)„ and alkylcycloarsathianes (RAsS)„ (Figure 2.3b), ambidentate macrocyclic ligands that have the unusual ability to undergo ring expansion. Page 30 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors (a) Me A s - ^ P h Me / > 0 — A s I ! A s A s — 0 ^ / (b) Me -NH A s - A s H N -(c) Figure 2.3. Arsenic containing macrocycles: (a) triarsine, (b) methylcycloarsoxane (CH3AsO)4, (c) benzazarsepine. 26 Another cyclic arsine ligand is the metallomacrocycle shown in Equation 2 .1. In this system, the arsenic donors can bind additional transition metals, and the iridium centers have the ability to bind main group metals. ' P h 2 P ' / O C P h 2 P ..Br Ph v A s O C . A s Ph P P h 2 l r ' + M n + -. P P h , P h , P ' .Br P h 2 P Ph A s •M" \ . A s s Ph 1 n+ " P P h , Br.. P P h 2 (2.1) Although the majority of arsenic coordination chemistry has been limited to the late transition metals, there are examples of both monodentate and bidentate arsine ligands bound to early transition metals. Poor orbital overlap between arsenic and early Page 31 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors metals makes complexes with monodentate ligands unfavourable, and the chemistry is dominated by the chelating diarsine ligands. ' The different properties of arsenic and phosphorus also lead to changes in the reactivity of their complexes. A n excellent example is the difference in reactivity between Wilkinson's Catalyst ((Ph 3 P) 3 RhCl) and its arsenic analog ((Ph 3 As) 3 RhCl) . Wilkinson's Catalyst very effectively hydrogenates unsaturated substrates via the mechanism shown in Scheme 2.1 . 3 1 " 3 4 The essential steps are oxidative addition of dihydrogen to form a m-dihydride, coordination of the alkene followed by hydride-transfer, and finally, reductive elimination of the alkane. It has been shown that PPh 3 readily dissociates under catalytic conditions, and the inner catalytic cycle, involving a loosely coordinated solvent molecule, is approximately 1000 times faster than the outer cycle. B y contrast, the arsenic analog (Ph 3 As) 3 RhCl , is a very poor hydrogenation catalyst. 3 5 ' 3 6 It has been shown that under catalytic conditions the c/s-dihydride species does not transfer hydrogen to an unsaturated substrate. The lower a-donor strength of the arsenic ligands leave the rhodium metal center more electrophilic and thus less disposed to hydrogen transfer. Page 32 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Scheme 2.1 The relatively poor hydrogenation activity has been exploited in dehydrogenation catalysis where the related dimer complex [(Ph3As)2RhCl] 2 is a more capable dehydrogenation catalyst than the phosphine analog. 3 7 In hydroformylation catalysis, the arsenic complex (PhsAs^RhCl has comparable activity to Wilkinson's Catalyst. 3 8" 4 0 Wilkinson's Catalyst is an example of a system in which the arsenic analog displays much lower reactivity than the parent phosphine complex. This feature is commonly observed when comparing phosphine and arsine ligands. However, there are examples of complexes with organoarsine ligands displaying better reactivity than phosphine complexes. Triphenylarsine has been used effectively in palladium-catalyzed tandem Suzuki cross-coupling asymmetric Heck reactions between a C2-symmetric ditriflate and borane olefin. 4 1 The xantarsine ligand has shown increased activity, increased conversion, and reduced side-reaction products in the rhodium- and platinum/tin-catalyzed hydroformylation of olefins. 4 2 ' 4 3 Page 33 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors The possibility o f substituting arsenic for phosphorus in a macrocyclic ligand such as R[P2N2] and creating early transition-metal complexes capable of supporting interesting chemistry is compelling. In this chapter, the synthesis of the diamido-diarsine macrocycle, P h [ A s 2 N 2 ] (where A s 2 N 2 = PhAs(CH 2 SiMe 2 NSiMe 2 CH2)2AsPh) and its coordination chemistry with early transition metals is detailed. The results of attempts to prepare dinitrogen complexes stabilized by the p h [ A s 2 N 2 ] ligand system are also discussed. 2.2. Synthesis of the [As2N2] ligand Following the lithium template synthesis developed for the phosphine ligand p h [ P 2 N 2 ] L i 2 ( 1,4-dioxane),4 4 the synthesis of P h [As 2 N 2 ]L i 2 ( l ,4 -d ioxane) (2.1) is detailed in Scheme 2.2. Phenylarsine is synthesized in 72% yield by the reduction of phenylarsonic acid using zinc dust and hydrochloric acid . 4 5 Rigorous degassing of all aqueous solutions, and updating the procedure to take advantage of modern Schlenk techniques allows for a 20% increase in isolated yield over recent reports of the same preparation. 4 6 Reaction of two equivalents of L i A s H P h with the disilazane FPW(SiMe2CH2Cl)2 leads to formation of the intermediate diarsinosilazane HN(SiMe2CH2AsHPh)2 in virtually quantitative yield. Further reaction of the diarsinosilazane with another equivalent of HN(SiMe2CH2Cl)2 in the presence of four equivalents of " B u L i leads to a single product by ' H N M R spectroscopy. Addit ion of 1,4-dioxane to a concentrated toluene solution of the crude product gives 2.1 as a fine cream-coloured powder isolated in 67% yield by precipitation with hexanes. The product is sparingly soluble in hexanes, and the need to remove hexanes-soluble impurities from the product contributes to the modest yield. Page 34 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Zn dust Me, Me2 2.1 S = 1,4-dioxane Scheme 2.2 X-ray quality crystals of 2.1 were grown from a concentrated toluene solution at -40 °C. The solid-state molecular structure of 2.1 is presented in Figure 2.4; crystal data are given in Table A - l o f the Appendices, and selected bond distances and angles are collected in Table 2.1. The structure is a one-dimensional chain with 1,4-dioxane bridging the lithium atoms of adjacent molecules in a head-to-tail fashion. Both arsenic atoms are bound to a single lithium atom in a syn fashion, like that seen in syn-p h [ P 2 N 2 ] L i 2 ( T H F ) . 4 4 However, unlike ^ - p h [ P 2 N 2 ] L i 2 ( T H F ) in which the distances are equal by symmetry, the L i - A s distances in 2.1 differ by half an angstrom. The bond distance of 2.658(11) A between L i ( l ) and A s ( l ) agrees well with other literature L i - A s Page 35 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors distances. 4 7" 5 0 It is more difficult to describe the interaction between L i ( l ) and As(2) as a true bonding interaction; the distance of 3.162(10) A is significantly longer than the longest distance, 2.799 A, reported in the literature.5 1 This distance is, however, considerably shorter than the sum of the van der Waals radii for the two atoms (3.67 A) 5 2 and suggests that there is a weak interaction present in the solid state. 2.1. Ellipsoids are drawn at 50% probability. Table 2.1. Selected bond distances (A), intramolecular distances (A), and bond angles (°) for p h [As 2 N 2 ]L i 2 ( l ,4 -d ioxane) 2.1. Atom Atom Distance (A) Atom Atom Distance (A) L i ( l ) N ( l ) 2.186(13) Li(2) N ( l ) 1.982(17) L i ( l ) N(2) 2.106(14) Li(2) N(2) 2.029(15) L i ( l ) 0(1*) 2.080(13) Li(2) 0(2) 1.998(14) L i ( l ) A s ( l ) 2.658(11) L i ( l ) As(2) 3.162(10) Page 36 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) L i ( l ) N ( l ) Li(2) 74.8(5) L i ( l ) N(2) Li(2) 75.6(6) N ( l ) L i ( l ) N(2) 99.4(5) N ( l ) Li(2) N(2) 109.5(6) 0(1*) L i ( l ) N ( l ) 145.9(7) 0(2) Li(2) N(2) 130.4(9) C(13) A s ( l ) L i ( l ) 152.4(4) The solid-state structure of 2.1 discussed above does not persist in solution; its ' H N M R spectrum in ^-benzene is consistent with a C 2 v symmetric ligand environment, as it displays resonances due to only two types of silyl methyl protons, reflecting "top and bottom" asymmetry. The o-proton resonances of the arsine phenyl ring appear as a multiplet; the C H 2 ring proton signals appear as a pair of A B doublets. A singlet is observed for the dioxane protons at 8 3.45, shifted from free dioxane at 5 3.35 in de-benzene. The resonance integrates to one equivalent, and the dioxane is assumed to coordinate to the lithium not coordinated to arsenic. The observed symmetry suggests that P h [ A s 2 N 2 ] is fluxional in solution. Variable-temperature N M R experiments performed on 2.1 (290-190 K ) did not show any loss of symmetry through decoalescence of the phenyl, methylene or si lyl methyl resonances. Thus, it is not possible to distinguish between a solution structure with both arsenic donors coordinated to the lithium ions at all observed temperatures, or a structure in which the arsenic donors engage in an associative/dissociative process with L i ( l ) that is fast on the N M R timescale. The ' H and L i N M R spectra of 2.1 are both consistent with a symmetrical structure in solution identical to that proposed for the syn isomer of p h [ P 2 N 2 ] L i 2 ( T H F ) . 4 4 Unl ike the phosphine system where two different isomers can be isolated, no spectral evidence for anti-p h [As 2 N 2 ]Li 2 (d ioxane) is observed. Attempts to crystallize 2.1 from T H F result in displacement of dioxane and coordination of T H F , as shown in Equation 2.2. Removal of the solvents affords P h [ A s 2 N 2 ] L i 2 ( T H F ) 2 (2.2) as a colourless solid in 94% yield. Page 37 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors M e 2 M e 2 M e 2 M e 2 Ph' As Ph T H F S i SI M e 2 M e 2 S 2 = T H F As Ph (2.2) 2.2 1,4-dioxane X-ray quality crystals suitable for solid-state structure determination were grown by slow evaporation of a saturated T H F solution. The solid-state molecular structure of 2.2 is presented in Figure 2.5; crystal data are presented in Table A - l of the Appendices, and selected bond distances and angles are detailed in Table 2.2. The complex is monomeric in the solid-state with a T H F molecule bound to each lithium atom. The L i - N bond distances are not different from 2.1 indicating that the U 2 N 2 core is unchanged. The L i - 0 bond distances are shorter, suggesting a stronger interaction between the lithium atoms and donor solvent molecules. Only a single lithium-arsenic interaction is observed, and the L i ( l ) - A s ( l ) bond distance of 2.916(7) A is significantly longer than the distance observed in 2.1. The distance between the unbound arsenic and L i ( l ) of 3.470(7) A is also much longer than in 2.1. These longer distances can be attributed to the presence of stronger donor solvent molecules. The observation that a change in donors perturbs the L i - A s bond indicates that the interaction between lithium and arsenic is weaker than that of lithium and oxygen. Page 38 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Figure 2.5. Molecular structure (ORTEP) of ™[As 2N2]Li 2(THF)2, 2.2. Ellipsoids are drawn at 50% probability. Table 2.2. Selected bond distances (A), intramolecular distances (A), and bond angles (°) for p h [As 2 N2]Li 2 (THF)2 , 2.2. Atom Atom Distance (A) Atom Atom Distance (A) L i ( l ) N ( l ) 2.077(8) Li(2) N ( l ) 2.043(7) L i ( l ) N(2) 2.110(8) Li(2) N(2) 1.999(7) L i ( l ) 0(1) 1.935(8) Li(2) 0(2) 1.926(7) L i ( l ) A s ( l ) 2.916(7) L i ( l ) As(2) 3.470(7) Page 39 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) L i ( l ) N ( l ) Li(2) 74.8(3) L i ( l ) N(2) Li(2) 75.0(3) N ( l ) L i ( l ) N(2) 102.4(3) N ( l ) Li(2) N(2) 107.7(3) 0(1) L i ( l ) N ( l ) 122.9(4) 0(2) Li(2) N(2) 120.3(4) C(13) A s ( l ) L i ( l ) 166.0(2) The ' H N M R spectrum of 2.2 in ^-benzene is very similar to that of 2.1, with the same C 2 v symmetric ligand environment resulting in two si lyl methyl resonances and the methylene resonances appearing as a pair of A B doublets. Resonances due to the T H F protons are observed as distinct multiplets. The spectrum suggests that the presence of two donor solvent molecules does not influence the flexibility of the ligand. Attempts to probe the fluxionality through variable-temperature N M R experiments (290-190 K ) in d%-toluene did not show any decoalescence of the phenyl, methylene or silyl methyl resonances. If the *H N M R spectrum is obtained in Jg-THF, a distinct multiplet is observed for the resonances of only one T H F molecule, and it is assumed to coordinate to the lithium not bound to arsenic. Variable temperature ' H N M R experiments (290-200K) showed that the second T H F molecule is not bound or undergoes a rapid associative/dissociative process with the lithium at all observed temperatures. T H F is a strong donor solvent for the lithium ions, and it cannot be displaced by 1,4-dioxane or pyridine, and correlates to the shorter L i - 0 bond lengths in 2.2 compared to 2.1. Reaction of 2.1 with 2 equivalents of E t s N H C l produces the protonated ligand precursor p h [ A s 2 N 2 ] H 2 (2.3) as a pale yellow oi l in 91% isolated yield, as shown in Equation 2.3. lU N M R spectra show 2.3 adopts C 2 v symmetry, with two silylmethyl resonances and a pair of A B doublets for the methylene protons. Resonances for the amine protons are observed as a broad singlet at 0.62 ppm. Page 40 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors S = 1,4-dioxane The oi l solidifies over several weeks, producing colourless X-ray quality crystals of 2.3. The solid-state molecular structure is presented in Figure 2.6; crystal data are presented in Table A - l of the Appendices, and selected bond distances and angles are detailed in Table 2.3. The protons attached to nitrogen were found within the diffraction pattern and refined isotropically. Structurally, 2.3 assumes a twisted geometry that is very similar to the transition metal complexes discussed in later sections, and the arsine donors retain the syn displacement observed in the lithium salts. The planarity of the nitrogen = 360°) can be rationalized by derealization of the nitrogen lone pair into empty silicon d-orbitals, and this is reflected in short S i - N bond lengths. 5 3" 5 5 The acute angles about the central arsenic atom have also been observed in solid-state structures of other arsine molecules. 5 6" 5 8 Page 41 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Figure 2.6. Molecular structure (ORTEP) of P h [ A s 2 N 2 ] H 2 , 2.3. Ellipsoids are drawn at 50% probability. Table 2.3. Selected bond distances (A) and bond angles (°) for P h [ A s 2 N 2 ] H 2 , 2.3. Atom Atom Distance (A) Atom Atom Distance (A) N ( l ) S i ( l ) 1.736(6) A s ( l ) C(13) 1.951(7) N ( l ) Si(4) 1.734(7) As(2) C(19) 1.965(7) N(2) Si(2) 1.711(7) N ( l ) H(101) 0.743(18) N(2) Si(3) 1.728(7) N(2) H(102) 0.791(19) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) S i ( l ) N ( l ) Si(4) 137.5(5) Si(2) N(2) Si(3) 135.6(4) C ( l ) A s ( l ) C(2) 98.7(3) C(3) As(2) C(4) 98.4(3) C ( l ) A s ( l ) C(13) 98.6(3) C(3) As(2) C(19) 97.7(3) C(2) A s ( l ) C(13) 99.3(3) C(4) As(2) C(19) 102.1(3) Page 42 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors 2.3. Coordination chemistry ofPh[As2N2] and zirconium Reaction of 2.1 with Z r C l 4 ( T H F ) 2 or Z r C l 4 ( T H T ) 2 in refluxing toluene for 24h affords P h [ A s 2 N 2 ] Z r C l 2 (2.4) in 70% yield, as shown in Equation 2.4. A t such elevated temperatures the product decomposes over a period of days. Reactions performed at lower temperatures or for shorter periods of time do not go to completion. CI p i Z rC I 4 (THF) 2 \ / ZrCI 4 (THT) 2 ^ ^ A s ^ y r ^ A s ^ ( 2 4 ) toluene O^H<H>J^ A Si S i Si S i Me, M e 2 Me, M e 2 (- LiCI) 2 4 2 2 • P h S = 1,4-dioxane X-ray quality crystals of 2.4, containing one equivalent of co-crystallized solvent, were grown by slow evaporation of a saturated toluene solution. The solid-state molecular structure is presented in Figure 2.7; crystal data are presented in Table A - 2 of the Appendices, and selected bond distances and angles in Table 2.3. Structurally, 2.4 is a distorted trigonal prism, with the two trigonal planes described by C l ( l ) - A s ( l ) - N ( l ) and the crystallographically related plane C l ( l * ) - A s ( l * ) - N ( l * ) ; the chlorides are rotated out of the N( l ) -Zr ( l ) -N(2) plane by approximately 45°. The Z r - N and Z r - C l bond distances are comparable to those of p h [ P 2 N 2 ] Z r C l 2 and other similar zirconium complexes. 5 9 - 6 2 Very few complexes containing structurally characterized zirconium arsenic bonds are k n o w n , 3 0 ' 6 3 - 6 5 and the Zr -As bond length of 2.8812(4) A in 2.4 is in agreement with recently published zirconium diarsine complexes. 3 0 Page 43 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Figure 2.7. Molecular structure (ORTEP) of ™[As 2 N 2 ]ZrCl 2 , 2.4. Ellipsoids are drawn at 50% probability; (a) top view, (b) side view. S i ly l methyl groups omitted for clarity, and only ipso carbons of phenyl rings shown in (b). Page 44 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Table 2.4. Selected bond distances (A), bond angles (°), and dihedral angles (°) for P h [ A s 2 N 2 ] Z r C l 2 , 2.4. Atom Atom Distance (A) Atom Atom Distance (A) Zr ( l ) N ( l ) 2.098(2) Zr ( l ) N ( l * ) 2.098(2) Zr ( l ) A s ( l ) 2.8812(4) Zr ( l ) A s ( l * ) 2.8812(4) Zr ( l ) C l ( l ) 2.4810(7) Zr ( l ) C l ( l * ) 2.4810(7) Atom Atom Atom Angle (°) Atom Atom A t o m Angle (°) N ( l ) Z r ( l ) N ( l * ) 111.82(13) A s ( l ) Z r ( l ) A s ( l * ) 128.81(2) C l l Z r ( l ) C l ( l * ) 84.02(4) N ( l ) Z r ( l ) C l ( l ) 133.39(6) N ( l ) Z r ( l ) C l ( l * ) 98.39(6) Atom Atom Atom Atom Angle (°) A s ( l ) Z r ( l ) N ( l ) S i ( l ) -56.16(10) A s ( l * ) Z r ( l ) N ( l ) Si(2) -14.71(13) A direct result of the longer Zr-As interaction in 2.4 (2.88 A ) , as compared to the Zr-P distances in P h [ P 2 N 2 ] Z r C l 2 (2.694 A and 2.707 A ) , 5 9 is the position of the arsine phenyl rings; the angle between them is about 30° larger than any observed in the P | 1 [P 2 N 2 ] complexes of zirconium. Like p h [ P 2 N 2 ] Z r C l 2 , complex 2.4 displays a C 2 twist; however, due to the intrinsically longer Zr -As bond, the degree of twist is much more dramatic. A measure of the twist in the P h [ A s 2 N 2 ] macrocycle is given by the difference between the A s ( l ) - Z r ( l ) - N ( l ) - S i ( l ) dihedral angle o f - 5 6 . 1 6 ( 1 0 ) ° and the As ( l* ) -Zr ( l ) -N(l)-Si(2) dihedral angle of -14 .71(13)° . This difference of 41.45(3)° is large in comparison to the twist observed in p h [ P 2 N 2 ] Z r complexes like p h [ P 2 N 2 ] Z r C l 2 (27.8°) and p h [ P 2 N 2 ] Z r ( C H 2 P h ) 2 (12 .7°) , 5 9 comparable to the seven coordinate p h [ P 2 N 2 ] T a M e 3 (44 .8°) 6 6 and much larger than the untwisted p h [ P 2 N 2 ] N b C l (6 .8°) . 6 7 Page 45 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors The extreme Ci twist can be seen in the position of the chloride ligands. Because there is no electronic preference for the orbitals in a d° transition metal complex, the deviation from octahedral coordination about the zirconium centre is steric in nature. The chloride ligands may be rotated to reduce steric interactions with the si lyl methyl carbons, C(3) and C(3*) in Figure 2.3(a), that due to the extreme C2 twist are much closer to the metal centre than in PH[P2N2]Zr complexes. A s has been found for R[P2N2] complexes of the early transition elements, the metal is perched on, rather than nested in, the macrocycle. The As -Zr -As angle is 128.81(2)° and the N - Z r - N angle is 111.82(13)°, which differs from the binding of R[P2N2J to zirconium, for example, with P-Zr-P angles close to 180°, and N - Z r - N angles close to 90°. The distribution about the zirconium center is more closely reminiscent of a square pyramid and suggests that the metal center perches higher above the macrocycle than in early metal R[P2N2] complexes. Like complexes 2.1-2.3, 2.4 adopts a Civ structure in solution; its lK N M R spectrum in de-benzene shows resonances for the methylene protons as a pair o f A B doublets, and signals for the silyl methyl protons appear as two singlets. This indicates that the solution structure and solid-state structure differ, and that some fluxional process may be occuring on the N M R timescale. One possibility is that the complex undergoes a dynamic "rocking" motion of the disilylamido donors with a twisted structure at its two extremes and passes through a symmetrical intermediate, as shown in Scheme 2.3. If this occurs quickly on the N M R timescale, an averaged structure, equivalent to the symmetrical intermediate, is observed. Variable temperature N M R experiments performed on 2.4 (290-220 K ) in dg-toluene were not able to discern decoalescence of any resonances. The low solubility of 2.4 in toluene does not permit data collection at temperatures lower than 220 K . Page 46 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors CI CI CI c i Ph,. Zr> A s ' J\ „ : - A s (silylmethyl groups P h omitted for clarity) p h / P h P h ^ ^ s i xs r V s ^ ' S i CI CI \ As / •- As I'M ..Ph As Si S i S i S i M e 2 M e 2 M e 2 M e 2 Scheme 2.3 Work with hafnium complexes of [P2N2] has shown that the iodide complex can be a more reactive starting material than the chloride. 6 8 The synthesis of p h [As2N2 ]Z r I 2 (2.5) is outlined in Equation 2.5. Reaction of 2.4 with an excess (10 equiv) of iodotrimethylsilane produces the desired product as a pale yellow solid in 55% yield after washing with small amounts of benzene. ! H N M R spectra of these washings show a large number of silyl methyl resonances. If the reaction is conducted using a smaller excess (5 equiv) of iodotrimethylsilane, resonances of a new material, presumed to be due to the mixed iodide chloride species P h [ A s 2 N 2 J Z r ( I ) C l , can be observed in the ' H N M R spectrum. CI pi I J V V P h . ^ z r ^ ^ P h P h . ^ z ' r ^ ^ ^ P h As ' / '•- ^ A s (CH3)3Sil A s ^ / • ^ ~ ^ A s 4„W toiuene'-78°c <k^ *iv^  2.4 x£K*> HCH3)3Sicl) »Yw> (2.5) Page 47 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors i xjray quality crystals o f 2.5 were grown by slow evaporation o f a saturated T H F solution. The solid-state molecular structure is shown in Figure 2.8; crystal data are presented in Table A - 2 of the Appendices, and selected bond lengths and angles described in Table 2.4. Like 2.4, 2.5 is trigonal prismatic at the zirconium; the trigonal planes are described by I ( l ) -As ( l ) -N( l ) and I(2)-As(2)-N(2), and the iodides are rotated out o f the zirconium amido plane by about 45°. The Z r - N distances are comparable to those in 2.4; however, the Zr -As distances are shorter by approximately 0.05 A, suggesting that the iodide ligands make zirconium more electronegative and result in shorter Zr -As bonds. The Zr-I bonds are comparable to other zirconium diiodide complexes. 6 9 ' 7 0 The C 2 twist of 2.5 can be measured by comparing A s - Z r - N - S i torsion angles; the difference between the angles As ( l ) -Z r ( l ) -N( l ) -S i ( l ) and As(2)-Zr(l)-N(l)-Si(4) is 24.2°, significantly smaller than for 2.4. The As-Zr -As bite angle of 135.75(2)° and the N -Z r - N angle of 110.95(12)° suggest that in complex 2.5 the metal center is perched more closely to the macrocycle than in 2.4. In solution, 2.5 assumes C 2 v symmetry; resonances attributable to the methylene protons appear as a pair of A B doublets, and the silyl methyl proton resonances are a coincidental singlet in t/g-THF, or two singlets i f the spectrum is acquired in ^-benzene. Page 48 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Figure 2.8. Molecular structure (ORTEP) of ™[As 2 N 2 ]ZrI 2 , 2.5. Ellipsoids are drawn at 50% probability; (a) top view, (b) side view with silyl methyl groups omitted for clarity, and only ipso carbons of phenyl rings shown in (b). Page 49 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Table 2.5. Selected bond distances (A), bond angles (°), and dihedral angles (°) for p h [As 2 N 2 ]Zrl2, 2.5. Atom Atom Distance (A) Atom Atom Distance (A) Zr( l ) N ( l ) 2.112(3) Zr ( l ) N(2) 2.090(3) Zr ( l ) A s ( l ) 2.8326(5) Zr ( l ) As(2) 2.8719(5) Zr ( l ) I(D 2.8638(5) Zr ( l ) 1(2) 2.9265(4) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) N ( l ) Z r ( l ) N(2) 110.95(12) A s ( l ) Z r ( l ) As(2) 135.75(2) 1(1) Zr ( l ) 1(2) 83.888(13) N ( l ) Z r ( l ) 1(2) 140.02(9) N ( l ) Z r ( l ) 1(1) 102.45(8) Atom Atom Atom Atom Angle O A s ( l ) Z r ( l ) N ( l ) S i ( l ) 25.81(18) As(2) Z r ( l ) N ( l ) Si(4) 50.01(14) Reactions of 2.4 and 2.5 with various alkylating agents such as methyllithium or benzyl magnesium chloride result in decomposition. ' H N M R spectra of the isolated materials show many si lyl methyl environments, multiple methylene resonances, and several broad resonances. This evidence suggests that the ligand decomposes and potentially becomes separated from the metal centre. H o w this occurs is unknown, but it is possible that an open coordination site on zirconium; created by partial dissociation of one or both arsine donors, could promote complex decomposition. Page 50 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors 2.4. Coordination chemistry ofPh[As2N2] and titanium A n investigation of titanium coordination chemistry was prompted by the smaller size of titanium compared to zirconium and the possibilities derived from a greater size mismatch between the arsenic donors and the titanium centre. The synthesis of p h [ A s 2 N 2 ] T i C l 2 (2.6), is outlined in Equation 2.6, with the solution structure of 2.6 shown. Reaction of 2.1 with TiCl4(THF) 2 in toluene for five days produced the desired product as an orange solid in 84% yield. S = 1,4-dioxane X-ray quality crystals of 2.6, containing 2.5 equivalents of co-crystallized solvent, were grown from a saturated benzene solution. The solid-state molecular structure is shown in Figure 2.9; crystal data are presented in Table A - 2 of the Appendices, and selected bond lengths and angles described in Table 2.5. The titanium centre adopts a five-coordinate trigonal bipyramidal structure that includes only one titanium arsenic bond. Such a five-coordinate bonding motif has been observed before in the complex a ^ / - P h [ P 2 N 2 ] T i C l 2 7 1 and the four-coordinate complexes a « r / - P h [ P 2 N 2 ] M C l ( M = A l , Ga) . 7 2 In those cases, the second phosphine is unable to bind because the lone pair is oriented away from the metal centre. Complexes with only one coordinated neutral donor have not been observed in the s y « - p h [ P 2 N 2 ] or s y « - C y [ P 2 N 2 ] systems; however, the significant size difference and orbital mismatch between titanium and arsenic are likely reasons for the lack of coordination. Unlike complex 2.4, in which the Zr -As bonds are elongated, the single T i -As bond length in 2.6 agrees well with literature va lues . 2 9 ' 7 3 , 7 4 The T i - N and T i -75 78 C l bond distances also compare well to those of similar titanium complexes. Page 51 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Figure 2.9. Molecular structure (ORTEP) of ™[As2N 2 ]TiCl 2 , 2.6. Ellipsoids are drawn at 50% probability; (a) top view, (b) side view. Si ly l methyl groups omitted for clarity, and only ipso carbons of phenyl rings shown in (b). Page 52 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Table 2.6. Selected bond distances (A), intramolecular distances (A), and bond angles (°) for p h [ A s 2 N 2 ] T i C l 2 , 2.6. Atom Atom Distance (A) Atom Atom Distance (A) T i ( l ) T i ( l ) T i ( l ) N ( l ) A s ( l ) C l ( l ) 1.885(4) 2.6865(9) 2.3248(13) T i ( l ) T i ( l ) T i ( l ) N(2) As(2) Cl(2) 1.935(4) 4.186(1) 2.2960(13) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) N ( l ) C l ( l ) C(13) T i ( l ) N(2) T i ( l ) Cl(2) A s ( l ) T i ( l ) 111.04(15) 92.53(5) 134.74(16) N ( l ) N ( l ) T i ( l ) T i ( l ) C l ( l ) 110.44(11) Cl(2) 107.14(12) In solution, 2.6 assumes C 2 v symmetry; silylmethyl proton resonances appear as a coincidental singlet and the methylene resonances appear as a pair of A B doublets in the ' H N M R spectrum, indicating the complex is not five-coordinate in solution, but not indicating whether the complex is four-coordinate or six-coordinate. The absence of additional resonances in the spectrum indicates that slow ligand dissociation is not occurring, in contrast to similar six-coordinate and eight-coordinate arsine complexes of titanium. 2 9 Linewidths do not indicate fluxionality at room temperature, but the obvious differences between the solution and solid-state structures prompted a variable temperature ' H - N M R investigation of 2.6 from 290K-180K. Signal broadening and decoalescence occurs, indicating loss of symmetry or hindered rotation; however, no low temperature limiting spectrum was observed. If 2.6 is six-coordinate in solution, it is possible that the complex undergoes a fluxional process similar to that described for complex 2.4 above. Attempts to synthesize various [ A s 2 N 2 ] T i dialkyl complexes such methyl, benzyl and trimethylsilylmethyl from 2.6 resulted in unidentifiable products, likely via reduction to Ti(III). Page 53 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors 2.5. Coordination chemistry ofPh[As2N2] and yttrium Previous work in our group using yttrium and lanthanide metals with the Ph[P2N2] ligand has led to intriguing carbon-carbon bond formation upon reaction of the halide precursor ( [P 2N2]Y)2(p-Cl) 2 with aryllithium reagents. The biphenyldiide complex ( p h[P 2N 2]Y) 2{p-Ti 6:r) 6'-(C6H5)2} can be synthesized from the trimethylsilylmethyl complex, p h [ P 2 N 2 ] Y ( C H 2 S i M e 3 ) , and benzene or by direct reaction of ( P h [ P 2 N 2 ] Y ) 2 ( p - C l ) 2 with phenyllithium; the naphthalene and anthracene complexes can be synthesized by reduction of (Ph[P2N2]Y)2(p-Cl)2 with K C s in the presence of the appropriate arene. Equation 2.7 outlines the synthesis of the halide precursor (ph[As2N2]Y)2(p-Cl)2 (2.7). Reaction of 2.1 with Y C 1 3 ( T H F ) 3 in hot (100 °C) toluene produced 2.7 in 75% yield. Like 2.4, 2.7 is not stable at elevated temperatures. However, due to the increased solubility of Y C 1 3 ( T H F ) 3 in toluene, the reaction can be facilitated at a lower temperature, thereby reducing decomposition o f the product. M e 2 M e 2 M e 2 M e 2 'Si«vrSL ^ S i ^ s i . Y C I 3 ( T H F ) 3 A s ^ ^ V ^ - - A s . P h Y Ph / \ P n " '1^ CI p i (2-7) toluene V A P h ^ ^____^Y-^_ ^ / P h (-LICI) A s j\ A s S = 1,4-dioxane 2 7 ^ S i ^ S i > 3 i Si M e 2 M e 2 M e 2 M e 2 Crystals of 2.7 suitable for X-ray diffraction experiments were grown from a saturated hexanes solution. The solid-state molecular structure is shown in Figure 2.10; crystal data are presented in Table A-3 of the Appendices, and selected bond lengths and angles described in Table 2.6. Unlike the previously reported (P h[P2N2]Y)2(u-Cl)2 structure, in which the yttrium centres are structurally different, both yttrium centres in Page 54 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors 2.7 assume distorted trigonal prismatic geometries; the planes for Y ( l ) are described by Cl( l ) -As( l ) -N(2) and Cl(2)-N(l)-As(2). The Y - C l and Y - N bond lengths and the angles of the halide bridge core compare well with those of (Ph[P2N2]Y)2(p-Cl)2.80 Complex 2.7 82 is the first example of a coordination compound containing a Y - A s bond. The literature contains only five examples of complexes having arsenic coordinated to any group 3 or lanthanide metal, four complexes of samarium 8 3" 8 5 and one of lutetium. 8 6 A s expected, the bond lengths between the smaller yttrium and arsenic are shorter than known lanthanide arsenic bonds. Figure 2.10. Molecular structure (ORTEP) of C n[As2N 2]Y) 2(u-Cl)2, 2.7. Ellipsoids are drawn at 50% probability. Page 55 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Table 2.7. Selected bond lengths (A), bond angles (°), and dihedral angles (°) for ( p h [ A s 2 N 2 ] Y ) 2 ( u - C l ) 2 2.7. Atom Atom Distance (A) Atom Atom Distance (A) Y ( l ) N ( l ) 2.361(4) Y ( l ) N(2) 2.288(4) Y ( l ) A s ( l ) 2.9644(7) Y ( l ) As(2) 2.9591(7) Y(2) N(3) 2.320(4) Y(2) N(4) 2.283(4) Y(2) As(3) 2.9545(7) Y(2) As(4) 2.9968(7) Y ( l ) C l ( l ) 2.8119(13) Y ( l ) Cl(2) 2.7152(13) Y(2) C l ( l ) 2.7226(13) Y(2) Cl(2) 2.8135(13) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) C l ( l ) Y ( l ) Cl(2) 78.10(4) C l ( l ) Y(2) Cl(2) 77.95(4) C l ( l ) Y ( l ) As(2) 133.62(3) C l ( l ) Y(2) As(4) 85.00(3) C l ( l ) Y ( l ) N(2) 98.40(12) C l ( l ) Y(2) N(4) 146.28(11) Cl(2) Y ( l ) As(2) 83.27(3) Cl(2) Y(2) As(4) 124.61(3) Cl(2) Y ( l ) N(2) 142.82(12) Cl(2) Y(2) N(4) 95.05(11) A s ( l ) Y ( l ) As(2) 135.43(2) As(3) Y(2) As(4) 143.55(2) C l ( l ) Y ( l ) A s ( l ) 85.69(3) C l ( l ) Y(2) As(3) 124.86(3) C l ( l ) Y ( l ) N ( l ) 143.20(12) C l ( l ) Y(2) N(3) 97.27(11) Cl(2) Y ( l ) A s ( l ) 132.67(4) Cl(2) Y(2) As(3) 85.43(3) Cl(2) Y ( l ) N ( l ) 95.68(11) Cl(2) Y(2) N(3) 150.57(11) N ( l ) Y ( l ) N(2) 107.18(16) N(3) Y(2) N(4) 103.76(15) Atom Atom Atom Atom Angle (°) A s ( l ) Y ( l ) N ( l ) S i ( l ) -50.38(19) As(2) Y ( l ) N ( l ) Si(4) -17.9(2) As(3) Y(2) N(3) Si(5) -47.4(2) As(4) Y(2) N(3) Si(8) -13.0(2) Page 56 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors The degree of C 2 twist in the macrocyclic ligands of 2.7 is intermediate between 2.4 and 2.5; the difference between torsion angles about Y ( l ) is 32.2°, and the difference about Y(2) is 34.4°. A n examination of the As ( l ) -Y( l ) -As (2 ) angle, 135.43(2)°, and As(3)-Y(2)-As(4) angle, 143.55(2)°, show that the arsenic donors are more trans oriented than in 2.4 or 2.5; while the N ( l ) - Y ( l ) - N ( 2 ) angle, 107.18(16)°, and N(3)-Y(2)-N(4) angle, 103.76(15)°, indicate the amide donors are more cis disposed. The angles indicate that the metal center geometry in 2.7 most closely approaches the disphenoidal, or see-saw, geometry of the six-coordinate ph[As2N2] complexes. The angles also indicate that the yttrium centers of 2.7 are the most nested of the Ph[As2N2] complexes. In solution, the molecule behaves in a similar fashion to (Ph[P2N2]Y)2(p-Cl)2,80 Proton N M R spectra indicate that both ends of the molecule are equivalent, the flexibility of the Ph[As2N2] ligand framework allowing the complex to approximate Z>2d symmetry; all methylene resonances appear as a pair of A B doublets and resonances for the silylmethyl protons appear as two singlets. Reaction of 2.7 with various alkyl reagents such as M e s S i C F ^ L i produces a mixture of products from which the expected alkyl cannot be cleanly isolated. Attempts to produce and isolate a ;r-arene complex from 2.7 have not been successful. Reaction of 2.7 with KCg in the presence of anthracene yields intensely blue solutions; however, examination of the isolated solids by ' H N M R spectroscopy indicates that they consisted mostly of anthracene and unreacted 2.7. Small resonances, comprising less than 2% of the sample by integration, are observed that can be tentatively assigned to a biphenyldiide complex based upon the resonances observed for nP 2 N 2 ]Y) 2 {p-r | D : r | 0 -(C14H10)}. 2.6. Attempted synthesis ofPh[As2N2] tantalum complexes Several attempts to synthesize p h[As2N2]TaCi3 from TaCls have failed. For example, reaction of 2.1 with TaCls in toluene at elevated temperatures produces a colour change from bright yellow to a muted orange, but solution N M R analysis reveals a Page 57 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors variety of products. Attempts to separate these products via crystallization result in a colour change to dark brown and precipitation o f intractable solids. Attempts to utilize the protonated ligand 2.3 also did not yield ph[As2N2]TaCl3. Reaction with TaCls affords a bright yellow solid upon solvent removal. A *H N M R spectrum reveals several products, but unlike the Ph[P2N2] system where a simple adduct, (ph[P2N2]H2)TaCl5, is formed, the amine protons of 2.3 are absent from the spectrum. The adduct (Ph[P2N2]H2)TaCl5 decomposes over time; it is possible that a similar adduct o f P h [ A s 2 N 2 ] may rapidly decompose, preventing its isolation. It is also possible that the target complex, ph[As2N2]TaCi3, might rapidly decompose, i f it is formed at all . Particularly susceptible to decomposition are the S i - N bonds in the ph[As2N2] ligand. Reaction with a Ta-Cl bond can result in cleavage of a S i - N bond with the formation of a strong S i - C l bond and a strong imido Ta=N linkage. The ability o f tantalum chlorides to react with S i - N bonds has been used as a route to generate tantalum imide complexes. Reaction of 2.1 or 2.2 with pale yellow TaMesCb at -78°C immediately produces a dark red solution that rapidly turns dark brown upon warming. Examination of the isolated solids by ' H N M R spectroscopy reveals several products, none of which can be assigned to P h[As2N2]TaMe3. The large number o f silylmethyl resonances observed suggests ligand decomposition. Repeated attempts to synthesize and isolate Ph[As2N2]TaMe3 at low temperature have also failed. If the desired product is formed in these reactions, it is too unstable to isolate. 2.7. Reduction chemistry ofph[As2N2] complexes Chapter one introduced several methods for the synthesis of early transition metal dinitrogen complexes. Reduction of halide precursors in the presence of dinitrogen has proven a fruitful pathway in the Fryzuk group, particularly for Ph[P2N2] complexes, such as ( p h [P 2 N 2 ]Zr) 2 (p-n 2 : r i 2 -N2) 8 8 and ( P h[P 2N 2]Nb)2(p-ri I-N2). 8 9 These complexes are synthesized by reduction of chloride precursors using the strong alkali metal reducing Page 58 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors agent K C g . Synthesis of hafnium dinitrogen complexes has shown that a diiodide precursor can give coordinated dinitrogen complexes where reduction of a dichloride species fails to do so . 6 8 ' 9 0 If these reductions are performed in the absence of dinitrogen, phosphorus-phenyl activation occurs, giving rise to a highly activated arene bridged dimer. 9 1 Reduction pathways have also been used in the preparation of dinitrogen complexes of titanium, including the (P h[P2N2]Ti)2(p-ri1:r|1-N2) complex. Reaction of 2.4, 2.5 or 2.6 with two equivalents of K C g under dinitrogen does not produce the desired dinitrogen complexes. Reactions conducted under a variety of conditions produce pale hexanes-insoluble solids, in contrast to the intense blue-green of ( P h[P 2N 2]Zr) 2(u.-r) 2-N2). 8 8 Proton N M R spectra of the isolated materials shows many silyl methyl environments and multiple methylene resonances, evidence that suggests the ligand decomposes and potentially becomes separated from the metal centre. Reductions performed under argon produce a similar solid, and examination by ' H N M R spectroscopy shows only decomposition products; no products can be assigned to an activated arene bridged dimer. Reductions performed under argon using diphenylacetylene as a trap molecule produce only decomposition products and unreacted diphenylacetylene, suggesting that the decomposition pathway is intramolecular. Mass spectral analysis of the solids isolated from these reductions cannot locate any mass peak compatible with a dimeric complex. However, similarities in fragmentation patterns are evident. The most common fragment observed is the bis-dimethylsilylamide [N(SiMe2)2]+, unusual considering it is the S i - N bond that is responsible for the air and moisture sensitivity of the ligand. Many other fragments that retain the S i - N bond can be identified in the fragmentation patterns. However, no common fragments containing A s - C bonds can be assigned. The fragmentation patterns observed are not due to some inherent instability of the ligand, mass spectra can be obtained for all synthesized complexes, although 2.5 easily loses an iodide and the protonated ligand 2.3 loses a phenyl group. These results suggest that the cleavage of arsenic carbon bonds could be involved in decomposition of the complexes. The reduction of arsenic (III) to arsenic metal (E° = -0.608 V ) occurs at lower potential than the same reduction for phosphorus (E° = -0.87 V ) and both are significantly Page 59 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors easier to reduce than zirconium (E° = -1.45 V ) . 9 2 Potassium reducing agents are known to be strongly reducing, with potentials approaching that of free potassium metal (E° = -2.931 V ) . 9 2 It is possible that the larger difference in reduction potential between arsenic and zirconium contributes to decomposition. The reduction potential of arsenic may be sufficiently low that the potassium graphite directly reduces it. It is also possible that i f zirconium is reduced, it may quickly transfer the electron to arsenic before any intermolecular reactions can take place. With the possibility that K C g could reduce the arsenic atoms in the macrocycle, milder reducing agents were investigated. The T H F adduct of magnesium anthracene is a readily synthesized material with a reduction potential of approximately 2 V that has seen increasing use in organometallic chemistry as a reducing agent. 9 3 ' 9 4 Reaction of the halide complexes 2.4 or 2.5 with one or two equivalents of Mg(anthracene)(THF)3 under an atmosphere of dinitrogen produces olive green solids. Examination of these residues by ' H N M R spectroscopy indicates the presence of anthracene, varying amounts of the starting materials and what appear to be decomposition products. N o dinitrogen complex or other high molecular weight product can be detected by mass spectral analysis. Powdered magnesium (E° = -2.372 V ) 9 2 has been used in the reductive synthesis of titanium dinitrogen complexes. 9 5 Treatment of 2.6 with one or two equivalents of powdered magnesium produces an intensely red-brown solid. *H N M R and mass spectral analysis of the product indicate that multiple species are present, none of which are a dimeric dinitrogen complex. These experiments suggest that it may be impossible to cleanly reduce 2.4, 2.5, or 2.6. The lower reduction potential of arsenic relative to phosphorus in these ligand systems may contribute to decomposition by facilitating arsenic reduction. Page 60 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors 2.8. Summary and conclusions The macrocyclic ligand Ph[As2N2] can be synthesized from phenylarsine (PhAsH 2 ) and l,3-bis(chloromethyl)-l,l,3,3-tetramethyldisilazane in modest yield as a 1,4-dioxane adduct of the dilithium salt, p h [ A s 2 N 2 ] L i 2 ( 1,4-dioxane) (2.1). The coordinating solvent can be displaced by T H F , affording the T H F adduct P h [ A s 2 N 2 ] L i 2 ( T H F ) 2 (2.2). Reaction of either 2.1 or 2.2 with E t 3 N H C l yields the protonated ligand precursor p h [As 2 N 2 ]H2 (2.3). The lithium salt 2.1 has proven an excellent way to synthesize early transition-metal complexes via metathesis. Reactions with appropriate metal halides produces the complexes P h [As 2 N 2 ]ZrCl2 (2.4), p h [ A s 2 N 2 ] T i C l 2 (2.6) and ( P h [ A s 2 N 2 ] Y ) 2 ( p - C l ) 2 (2.7). A related iodide complex p h[As2N 2]ZrI 2 (2.5) can be prepared through the reaction of 2.4 with iodotrimethylsilane. The yttrium complex is the first structurally characterized complex containing an yttrium-arsenic bond. Attempts to produce coordinated dinitrogen complexes through the reduction of 2.4, 2.5 and 2.6 with K C g , activated magnesium and Mg(anthracene)(THF)3 result in decomposition of the parent complex. Analysis of the reaction products suggests that the ligand becomes separated from the metal center. This could be the result o f arsenic reduction within the macrocycle, resulting in the creation of an open coordination site on the metal centre through partial or complete dissociation of one or both arsine donors. Reactions between the metal halide complexes 2.4, 2.5, 2.6 and 2.7 and various alkylating agents have been unsuccessful for the synthesis of alkyl complexes. Instead, ligand decomposition is the major outcome. Every attempt to further react the halide complexes has resulted in ligand degradation. Such decomposition seriously limits the applications of this macrocycle in early transition-metal chemistry. Page 61 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors 2.9. Experimental Section 2.9.1 General Considerations Unless otherwise stated, all manipulations were performed under an atmosphere of dry oxygen-free dinitrogen or argon by means of standard Schlenk or glovebox techniques (Vacuum Atmospheres HE-553-2 glovebox equipped with a MO-40-2H purification system and a -40°C freezer). Anhydrous hexanes and toluene were purchased from Aldrich, sparged with dinitrogen, and further dried by passage through a tower of silica followed by passage through a tower of Ridox (or Q-5) catalyst prior to use. 9 6 Anhydrous pentane, benzene, tetrahydrofuran and diethyl ether were purchased from Aldrich, sparged with dinitrogen, and passed through an Innovative Technologies SPS-PureSolv-400-4 apparatus. Water was distilled and thoroughly degassed prior to use. A l l organic solvents were tested with addition of sodium benzophenone ketyl prior to use to ensure absence of oxygen and water. Alternatively, anhydrous diethyl ether was stored over sieves and distilled from sodium benzophenone ketyl under argon. Tetrahydrofuran was refluxed over CaH2 prior to distillation from sodium benzophenone ketyl under argon, and pentane was stored over sieves and distilled from sodium benzophenone ketyl solublized by tetraglyme under dry dinitrogen prior to storage over a potassium mirror. Nitrogen gas was dried and deoxygenated by passage through a column containing activated molecular sieves and M n O . Deuterated benzene was dried by refluxing with molten sodium/potassium alloy in a sealed vessel under partial pressure, then trap-to-trap distilled, and freeze-pump-thaw-degassed three times. Deuterated tetrahydrofuran and toluene were dried by refluxing with molten potassium metal or sodium-potassium alloy in a sealed vessel under vacuum, then trap-to-trap distilled, and freeze-pump-thaw-degassed three times. ' H , 3 1 P , ' H { 3 1 P } , 3 1 P { ' H } , l 3 C { ' H } , 7 L i { ' H } N M R spectra were recorded on either a Bruker A M X - 5 0 0 instrument operating at 500.13 M H z for ' H spectra, a Bruker A V A -400 instrument operating at 400.13 M H z for ! H spectra, or a Bruker A V A - 3 0 0 instrument Page 62 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors operating at 300.13 M H z for *H spectra. *H N M R spectra were referenced to residual protons in deuterated solvent as follows: C6D5H (51.\5), C4D7HO ( £ 3 . 5 8 ) , and C7D7H ( £ 2 . 0 9 ) with respect to tetramethylsilane at 8 0.0. 3 1 P N M R spectra were referenced to either external or internal P ( O M e ) 3 (8 141.0 with respect to 85% H3PO4 at 8 0.0). 1 3 C { ' H } N M R spectra were referenced to 1 3 C C 5 D 6 (8128.4). 7 L i { ! H } N M R spectra were referenced to external L i C l (0.3 M solution in M e O H at £ 0 . 0 ) . Elemental analyses were performed by M r . P. Borda and M r . M . Lakha and mass spectrometry (EI /MS on a Kratos M S 50 unless otherwise stated) by M r . M . Lapawa, all at the University of British Columbia, Department of Chemistry. Elemental analysis samples were prepared by placing finely ground crystalline material under vacuum for 24 h to remove co-crystallized solvent. Prior to submission the samples were sealed in small screw cap vials under nitrogen. For certain samples, it proved impossible to remove all co-crystalized solvent and this is accounted for in the calculated analysis (see complex 2.4). Extra care to employ glovebox or glovebag techniques was taken in the elemental analyses of air-sensitive compounds. 9 7 2.9.2. Start ing Mater ia ls and Reagents The compounds K C 8 , 9 8 T a M e 3 C l 2 , 9 9 Mg(anthracene)(THF) 3 , 1 0 0 Y C 1 3 ( T H F ) 3 , 1 0 1 T i C l 4 ( T H F ) 2 , 1 0 2 Z r C l 4 ( T H F ) 2 , 1 0 2 and Z r C l 4 ( T H T ) 2 , 1 0 3 were prepared according to literature procedures. Magnesium powder was activated using 1,2-dibromoethane. E t 3 N H C l was prepared by the reaction of triethylamine and aqueous hydrochloric acid, and recrystallized from ethanol. Phenylarsonic acid and 1.6M solutions of " B u L i in hexanes were purchased from Acros Chemicals and used as received. Iodotrimethylsilane was purchased from Aldr ich and used without further purification. A l l other reagents were obtained from a commercial source and purified by appropriate methods. 1 0 4 Page 63 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors 2.9.3 Synthesis, Characterization and Reactivity of Complexes Synthesis of Phenylarsine (PhAsH2). Phenylarsine was prepared according to the reaction published by Palmer and Adams. 4 5 To an ice-cooled mixture of Z n dust (60 g, 0.90 mol) and P h A s O ( O H ) 2 (30 g, 0.15 mol) in E t 2 0 (75 mL) and degassed H 2 0 (2 mL) was added degassed 12M HC1 (150 mL) dropwise over 3 h. After being stirred for 12 h, the solution was transferred to a Schlenk separatory funnel. The E t 2 0 layer was removed, and the aqueous solution was extracted with a further 50 m L E t 2 0 . The E t 2 0 extracts were combined and dried over CaSC>4. Removal of the E t 2 0 at 20 mm H g gave phenylarsine as a colourless liquid that was purified by vacuum distillation (20 mm Hg, 64-70 °C). Yie ld : 16.40 g (71%). Calc. M W : 154.61 g/mol. ' H N M R (200 M H z , C D C 1 3 , 25 °C): £ 7 . 4 0 (m, 2 H , o-Ph), 7.08 (m, 3H, m/p-?h), 3.50 (s, 2H , A s - / / ) . 4 6 Synthesis of [AsNAs] intermediate HN(SiMe2CH2AsHPh)2. To a solution of P h A s H 2 (14.06 g, 91.2 mmol) in E t 2 0 (150 mL ) was added a 1.6M solution of " B u L i in hexanes (57.0 m L , 91.2 mmol) dropwise at -78 °C. The solution was warmed to ambient temperature, stirred for 30 min, cooled to -78 °C and added dropwise to a solution of l,3-bis(chloromethyl)-l,l,3,3-tetramethyldisilazane (10.50 g, 45.6 mmol) in E t 2 0 at -78 °C. The resulting solution was warmed to ambient temperature, stirred 12 h then evaporated to dryness. The residue was extracted into toluene (50 mL) , filtered through Celite and the toluene was removed to yield H N ( S i M e 2 C H 2 A s H P h ) 2 as a yellow oil that was pure by ' H N M R spectroscopy. Yie ld : 20.67 g (97%). Calc. M W : 465.44 g/mol. ' H N M R (500 M H z , C 6 D 6 , 25 °C): £ 7 . 5 0 (dd, VHH = 1.5 Hz , 3JHH = 7.6 Hz , 4H , o-Ph), 7.09 (m, 6H, m/p-Ph), 3.79 (dd, 3 J m = 10.0 Hz . V H H = 5.3 H z , 2H , As-//), 1.06 (dd, 2JHH = 13.2 H z , VHH = 5.3 Hz , 2H , CH2), 0.81 (dd, 2JHH = 13.2 Hz , 3 J H H = 10.0 Hz , 2H, CH2), 0.23 (d, ' H , N / f ) , 0.11 (s, 12H, S i C / / 3 ) . Elemental analysis was not obtained. Page 64 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Synthesis of P h [As 2 N 2 ]L i 2 ( l , 4 -d ioxane ) (2.1). A solution of 1.6M " B u L i in hexanes (111.0 m L , 177.6 mmol) was added dropwise to a stirred solution of H N ( S i M e 2 C H 2 A s H P h ) 2 (20.67 g, 44.4 mmol) and 1,3-bis(chloromethyl)-l,l,3,3-tetramethyldisilazane (10.2 g, 44.4 mmol) in E t 2 0 (500 mL) at -78 °C. The solution was warmed to 25 °C, stirred for 12 h, and then evaporated to dryness. The resulting solid was extracted into toluene (100 mL) , the solution filtered through Celite, and the volume reduced to ca. 30 mL. 1,4-dioxane (4.01 g, 88.1 mmol) was added, and the solution reduced to a viscous o i l . Addit ion of hexanes (100 mL) precipitated a colourless solid that was collected and dried under vacuum. Yie ld : 21.33 g (67%). Calc. M W : 722.78 g mol" 1 . X-ray quality crystals of 2.1 were grown by cooling the concentrated toluene solution to -40 °C following addition of 1,4-dioxane. ' H N M R (500 M H z , C 6 D 6 , 25 °C): £ 7 . 5 5 (m, 4H, o-Ph), 7.14 (m, 6H, m/p-Ph), 3.45 (s, 8H, 1,4-dioxane), 1.12 ( A B d, V H H = 13.6 Hz , 4H , ring CH2), 1.04 ( A B d, V H H = 13.6 Hz , ring CH2), 0.40 (s, 12H, ring SiCrY 3 ) , 0.22 (s, 12H, ring SiCH3). 7 L i { ' H } N M R (194.4 M H z , C 6 D 6 , 25 °C) £ 0 . 3 6 (s), -1.48 (s). M S (EI) m/z, (%): 634, (100) [ M + - 1,4-dioxane]. Anal . Calcd. for C 2 8 H 5 0 A s 2 N 2 O 2 S i 4 L i 2 : C , 46.53; H , 6.97; N , 3.88. Found: C, 45.35; H , 7.08; N , 4.38. Repeated attempts to obtain satisfactory elemental analysis, even with use of added oxidant, were unsuccessful. Synthesis of r n [ A s 2 N 2 ] L i 2 ( T H F ) 2 (2.2). 2.1 (0.300 g, 0.42 mmol) was dissolved in T H F and left to stand for 48 h. Removal of the solvent under vacuum afforded 2.2 as a colourless powder. X-ray quality crystals were grown by evaporation of a saturated T H F solution at -40 °C. Y ie ld : 0.304 g (94%). Calc. M W : 778.88 g mol" 1 . ] H N M R (400 M H z , C 6 D 6 , 25 °C): £ 7 . 6 0 (m, 4 H , o-Ph), 7.07 (m, 6H, m/p-Ph), 3.65 (m, 8H, T H F - O C / / 2 C H 2 ) , 1.27 (m, 8H, T H F - O C H 2 C / / 2 ) , 1.08 ( A B d, V H H = 13.8 Hz , 4 H , ring CH2), 1.00 ( A B d, V H H = 13.8 Hz , ring CH2), 0.39 (s, 12H, ring SiCr7 3), 0.25 (s, 12H, ring SiCrY 3 ) . *H N M R (300 M H z , C 4 D 8 0 , 25 °C): £ 7 . 5 1 (m, 4H, o-Page 65 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors Ph), 7.24 (m, 6H, iw/p-Ph), 3.61 (m, 4H, T H F - O C / / 2 C H 2 ) , 1.77 (m, 4 H , T H F - O C H 2 C / / 2 ) , 0.95 ( A B d, 2 J H H = 13.8 Hz , 4 H , ring CH2), 0.89 ( A B d , 2 J H H = 13.8 Hz , ring CH2), 0.14 (s, 12H, ring S iC# 3 ) , 0.07 (s, 12H, ring S i C / / 3 ) . 7 L i { ' H } N M R (155.5 M H z , C 6 D 6 , 25 °C) 5 1.91 (s), 1.15 (s). M S (EI) m/z, (%): 634, (50) [ M + - 2THF] . Ana l . Calcd. for C 3 2 H 5 8 A s 2 N 2 0 2 S i 4 L i 2 : C , 49.35; H , 7.51; N , 3.60. Found: C , 50.94; H , 7.51; N , 4.34. Repeated attempts to obtain satisfactory elemental analysis, even with use of added oxidant, were unsuccessful. Synthesis of P h [ A s 2 N 2 ] H 2 (2.3). E t 2 0 (25 mL) was added to an intimate mixture of 2.1 (1.00 g, 1.38 mmol) and E t 3 N H C l (0.381 g, 2.76 mmol), and the resulting solution was stirred for 14 h. Removal of the solvent yielded an oily residue that was extracted into toluene (20 mL) and filtered through Celite. Removal of the solvent afforded 2.3 as a pale yellow oi l . Y ie ld : 0.78 g (91%). Calc. M W : 622.80 g mol" 1 . X-ray quality crystals of 2.3 were deposited from the oil over and extended period of time. ' H N M R (300 M H z , C 6 D 6 , 25 °C): £ 7 . 7 2 (m, 4H, o-Ph), 7.26 (m, 6H, w/p-Ph), 1.30 ( A B d, 2JHH = 13.3 Hz , ring CH2), 1.01 ( A B d, V H H = 13.3 Hz , ring CH2), 0.62 (br s, 2 H , NfY), 0.24 (s, 12H, ring S i C / / 3 ) , 0.20 (s, 12H, ring SiC7Y 3). M S (EI) m/z, (%): 622, (18) [ M + ] , 545 (100) [M+ - Ph]. Elemental analysis was not obtained. Synthesis of P h [ A s 2 N 2 ] Z r C l 2 (2.4). To an intimate mixture o f 2.1 (0.500 g, 0.69 mmol) and Z r C l 4 ( T H F ) 2 (0.29 g, 0.76 mmol) was added toluene (100 mL) . The solution was refluxed for 24 h, cooled to 50 °C and filtered through Celite. Removal of the solvent afforded a cream solid that was collected, washed with minimal hexanes and vacuum dried to obtain a colourless solid. Yie ld : 0.44g (70%). Calc. M W : 782.92 g mol" 1. X-ray quality crystals of 2.4 containing one equivalent of co-crystallised toluene were grown by evaporation of a toluene solution under vacuum without agitation. The synthesis o f 2.4 can also be performed using Z r C l 4 ( T H T ) 2 . *H Page 66 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors N M R (500 M H z , C 6 D 6 , 25 °C): £ 8 . 0 8 (dd, 4H , o-Ph), 7.10 (m, m/p-Ph), 1.20 ( A B d, 2 J H H = 13.1 Hz , 4H , ring CH2), 0.92 ( A B d, 2JHH = 13.1 Hz , 4 H , ring CH2), 0.38 (s, 12H, ring S i C / / 3 ) , 0.17 (s, 12H, ring S i C / / 3 ) . M S (EI) m/z, (%): 780, (40) [ M ] + . Anal . Calcd. for C24H42As2Cl2N 2Si4Zr0.75C 7H8: C, 41.23; H , 5.68; N , 3.30. Found: C, 41.67; H , 5.75; N , 3.44. Synthesis of P h [ A s 2 N 2 ] Z r l 2 (2.5). Iodotrimethylsilane (1.0 m L , 7.03 mmol) was added dropwise to a solution of 2.1 (0.582 g, 0.702 mmol) in toluene (100 mL) at -78 °C. The resulting solution was warmed to room temperature and stirred for 18h during which time a yellow colour developed. Removal of the solvent under vacuum produced a bright yellow solid. Washing the solid with benzene (-10 mL) gave 2.5 as a pale yellow solid. Y ie ld : 0.390 g (55%). Calc. M W : 965.82 g mol" 1. X-ray quality crystals of 2.5 were grown from a saturated T H F solution. ' H N M R (300 M H z , C 4 D 8 0 , 25 °C): £ 8 . 0 4 (m, 4H, o-Ph), 7.45 (m, m/p-?h), 1.53 ( A B d, 2 J H H = 13.1 Hz , 4 H , ring CH2), 1.38 ( A B d, 2JH  = 13.1 H z , 4 H , ring CH2), 0.39 (s, 24H, ring SiCfY 3 ). ! H N M R (300 M H z , C 6 D 6 , 25 °C): £ 8 . 1 2 (m, 4 H , o-Ph), 7.29 (m, m/p-Vh), 1.25 ( A B d, 2JHH = 13.1 H z , 4 H , ring CH2), 1.04 ( A B d, 2JHH = 13.1 H z , 4 H , ring CH2), 0.36 (s, 12H, ring S i C / / 3 ) , 0.24 (s, 12H, ring S iC# 3 ) . M S (EI) m/z, (%): 837, (30) [ M + -I]. Anal . Calcd. for C24H42As2l2N2Si4Zr: C, 29.85; H , 4.38; N , 2.90. Found: C, 29.46; H , 4.62; N , 3.03. Synthesis of P h[As 2N 2]TiCl 2 (2.6). A solution of 2.1 (1.08 g, 1.50 mmol) in toluene (10 mL) was added dropwise to a solution of TiCU(THF)2 (0.50 g, 1.50 mmol) in toluene (10 mL) . The resulting orange solution was stirred for five days followed by filtration through Celite. Removal of the solvent from the filtrate under vacuum afforded 2.6 as an orange solid. Yie ld : 0.99 g (84%). Calc. M W : 739.56 g mol" 1 . Dark orange x-ray quality crystals of 2.6 were grown Page 67 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors from a saturated benzene solution. ' H N M R (300 M H z , C 6 D 6 , 25 °C): £ 7 . 8 5 (dd, 4H , o-Ph), 7.23 (m, m/p-?h), 1.58 ( A B d, 2 J H H = 13.3 Hz , 4H , ring CH2), 1.06 ( A B d, 2JHH = 13.3 Hz , 4H , ring CH2), 0.68 (s, 12H, ring S i C / / 3 ) , 0.26 (s, 12H, ring S i C / / 3 ) . M S (EI) m/z, (%): 738, (35) [ M ] + . Ana l . Calcd. for C 2 4H42As2Cl 2 N 2 Si4Ti: C , 38.98; H , 5.72; N , 3.79. Found: C, 38.89; H , 5.91; N , 3.98. Synthesis of ( P h[As 2N 2]Y) 2(u.-CI) 2 (2.7). To an intimate mixture of 2.1 (2.00g, 2.77 mmol) and Y C 1 3 ( T H F ) 3 (1.14 g, 2.77 mmol) was added toluene (100 mL) . The solution was heated at 90 °C for 16 h followed by a hot (~50°C) filtration through Celite. Removal of the solvent afforded a yellow residue. Washing the residue with pentane gave a colourless solid that was collected and dried under vacuum. Yie ld : 1.54 g (75%). Calc. M W : 1491.30 g mol" 1 . X-ray quality crystals of 2.7 were grown by slow evaporation of a filtered hexanes solution. *H N M R (400 M H z , C 6 D 6 , 25 °C): £ 7 . 8 0 (m, 8H, o-Ph), 7.01 (m, 12H, mlp-?h), 1.47 ( A B d, 2JHn = 13.0 Hz , 8H, ring CH2), 1.10 ( A B d, 2JHH - 13.0 Hz , 8H, ring CH2), 0.38 (s, 24H, ring S iCf / 3 ) , 0.33 (s, 24H, ring S i C / / 3 ) . M S (EI) m/z, (%): 1488, (5) [ M ] + ; 744, (100) [ M + -[ A s 2 N 2 ] Y C l ] . Anal . Calcd. for C 48H84As4Cl2N4Si8Y 2: C , 38.68; H , 5.68; N , 3.76. Found: C, 39.18; H , 5.89; N , 3.74. Page 68 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors 2.10. References (1) Hammond, C. R. In CRC Handbook of Chemistry and Physics; 84 t h [Online] ed.; Lide, D . R., Ed. ; C R C Press: Boca Raton, F L , 2003. (2) Greenwood, N . N . ; Earnshaw, A . Chemistry of the Elements; 2 n d ed.; Butterworth-Hienemann: Oxford, 1997. (3) Cullen, W . R.; Bentley, R. J. Environ. Monit. 2005, 7, 11-15. (4) Bentley, R.; Chasteen, T. G . Chem. Educator 2002, 7, 51-60. (5) Gosio, B . Riv. Igiene Sanita Pubblica 1892, 3, 201. (6) Jones, D . New Scientist 1982, 101-104. (7) Weider, B . ; Hapgood, D . The Murder of Napoleon; Methuen: New York, 1982. (8) Wanklyn, J. A . Arsenic; Kegan Paul, Trench, Trubner & Co. Ltd. : London, 1901. (9) Haller, J. S. Pharm. Hist. 1975,17, 87-100. (10) Lloyd , N . C ; Morgan, H . W.; Nicholson, B . K . ; Ronimus, R. S. Angew. Chem. Int. Ed. 2005, 44, 941-944. (11) Cohen, M . H . ; Hirschfeld, S.; Flamm, H . S.; Ibrahim, A . ; Johnson, J. R.; O'Leary, J. J.; White, R. M . ; Will iams, G . A . ; Pazdur, R. Oncologist 2001, 6, 4-11. (12) Bartrip, P. W . J. Engl. Hist. Rev. 1994,109, 891-913. (13) Kuech, T. F. Mater. Sci. Rep. 1987, 2, 1-49. (14) Seyferth, D . Organometallics 2001, 20, 1488-1498. (15) Trenkle, A . ; Vahrenkamp, H . Chem. Ber. 1981,114, 1343-1365. (16) Hayter, R. C . Inorg. Chem. 1964, 3, 711-717. (17) Trenkle, A . ; Vahrenkamp, H . Chem. Ber. 1981,114, 1366-1381. (18) Basato, M . ; Brescacin, E . ; Tondello, E . ; Valle , G . Inorg. Chim. Acta 2001, 323, 147-151. (19) Harris, R. K . In NMR and the Periodic Table; Harris, R. K . , Mann, B . E. , Eds.; Academic Press: London, 1978, pp 379-382. (20) Geraldes, C. F. G . C ; Saraiva, M . E . J. Inorg. Biochem. 1992, 46, 99-108. Page 69 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors (21) Clifford, A . F. ; Mukherjee, A . K . Inorg. Chem. 1963, 2, 151-153. (22) Levason, W. ; McAul i f fe , C. A . Inorg. Chim. Acta 1974,11, 33-40. (23) Kyba, E . P.; Chou, S.-S. P. J. Am. Chem. Soc. 1980,102, 7012-7014. (24) Martin, J. W . L . ; Stephens, F. S.; Weerasuria, K . D . V . ; W i l d , S. B . J. Am. Chem. Soc. 1988,110, 4346-4356. (25) Sheldrick, W . S.; Muller , I. M . Coord. Chem. Rev. 1999, 182, 125-173. (26) Balch, A . L . ; Fossett, L . A . ; Ohmstead, M . M . ; Oram, D . E . ; Reedy Jr., P. E . J. Am. Chem. Soc. 1985,107, 5272-5274. (27) Balch, A . L . ; Nagle, J. K . ; Oram, D . E . ; Reedy Jr., P. E . J. Am. Chem. Soc. 1988, U0, 454-462. (28) Balch, A . L . ; Catalano, V . J. ; Chatfield, M . A . ; Nagle, J. K . ; Ohmstead, M . M . ; Reedy Jr., P. E . J. Am. Chem. Soc. 1991,113, 1252-1258. (29) Hart, R.; Levason, W. ; Patel, B . ; Reid, G . Eur. J. Inorg. Chem. 2001, 2927-2933. (30) Levason, W. ; Matthews, M . L . ; Patel, B . ; Reid, G . ; Webster, M . Dalton Trans. 2004, 20,3305-3312. (31) Osborn, J. A . ; Jardine, F. H . ; Young, J. F.; Wilkinson, G . J. Chem. Soc. (A) 1966, 1711-1733. (32) Jardine, F. H . ; Osborn, J. A . ; Wilkinson, G . J. Chem. Soc. (A) 1967, 1574-1578. (33) Montelatici, S.; Ent, A . v. d.; Osborn, J. A . ; Wilkinson, G . J. Chem. Soc. (A) 1968, 1054-1058. (34) Halpern, J.; Wong, C . S. J. Chem. Soc, Chem. Commun. 1973, 629-630. (35) Mague, J. T.; Wilkinson, G . J. Chem. Soc. (A) 1966, 1736-1740. (36) Hussey, A . S.; Takeuchi, Y . J. Org. Chem. 1970, 35, 643-647. (37) Mil le r , J. A . ; Knox, L . K . J. Chem. Soc, Chem. Commun. 1994, 1449-1450. (38) Carlock, J. T. Tetrahedron 1984, 40, 185-187. (39) Srivastava, V . K . ; Shukla, R. S.; Bajaj, H . C ; Jasra, R. V . Appl. Catal, A 2005, 252,31-38. (40) Srivastava, V . K . ; Sharma, S. K . ; Shukla, R. S.; Subrahmanyam, N . ; Jasra, R. V . Ind. Eng. Chem. Res. 2005, 44, 1764-1771. Page 70 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors (41) Kojima, A . ; Boden, C . D . J. ; Shibasaki, M . Tetrahedron Lett. 1997, 38, 3459-3460. (42) Veen, L . A . v. d.; Keeven, P. K . ; Kamer, P. C. J. ; Leeuwen, P. W . N . M . v. Chem. Commun. 2000, 333-334. (43) Veen, L . A . v. d.; Keeven, P. K . ; Kamer, P. C. J.; Leeuwen, P. W . N . M . v. J. Chem. Soc., Dalton Trans. 2000, 2105-2112. (44) Fryzuk, M . D . ; Love, J. B . ; Rettig, S. J. Chem. Commun. 1996, 2783-2784. (45) Palmer, C. S.; Adams, R. J. Am. Chem. Soc. 1922, 44, 1356-1382. (46) Beswick, M . A . ; Lawson, Y . G. ; Raithby, P. R.; Wood, J. A . ; Wright, D. S. J. Chem. Soc, Dalton Trans. 1999, 1921-1922. (47) Bashall, A . ; Bond, A . D . ; Hopkins, A . D. ; K i d d , S. J.; McPart l in, M . ; Steiner, A . ; Wolf, R.; Woods, A . D . ; Wright, D . S. J. Chem. Soc, Dalton Trans. 2002, 343-351. (48) Driess, M . ; Hoffmanns, U . ; Martin, S.; Merz, K . ; Pritzkow, H . Angew. Chem. Int. Ed. 1999, 38, 2733-2736. (49) Bashall, A . ; Beswick, M . A . ; Choi , N . ; Hopkins, A . D . ; K i d d , S. J. ; Lawson, Y . G. ; Mosquera, M . E . G . ; McPartlin, M . ; Raithby, P. R.; Wheatley, A . E . H . ; Wood, J. A . ; Wright, D . S. J. Chem. Soc, Dalton Trans. 2000, 479-486. (50) Bashall, A . ; Garcia, F. ; Hopkins, A . A . ; Wood, J. A . ; McPart l in, M . ; Woods, A . D . ; Wright, D . S. Dalton Trans. 2003, 1143-1147. (51) Driess, M . ; Kuntz, S.; Merz, K . ; Pritzkow, H . Chem. Eur. J. 1998, 4, 1628-1632. (52) Bondi, A . J. Phys. Chem. 1964, 68, 441-451. (53) Bartlett, R. A . ; Power, P. P. J. Am. Chem. Soc. 1987,109, 6509-6510. (54) Fooken, U . ; Khan, M . A . ; Wehmschulte, R. J. Inorg. Chem. 2001, 40, 1316-1322. (55) Ionkin, A . S.; Marshall, W . J. Organometallics 2003, 22, 4136-4144. (56) Cunninghame, R. G . ; Hanton, L . R.; Jensen, S. D. ; Robinson, B . H . ; Simpson, J. Organometallics 1987, 6, 1470-1479. (57) Kamepalli, S.; Carmalt, C. J.; Culp, R. D. ; Cowley, C. H . ; Jones, R. A . ; Norman, N . C. Inorg. Chem. 1996, 35, 6179-6183. Page 71 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors (58) Carlson, B . ; Phelan, G . D. ; Kaminsky, W. ; Dalton, L . ; Jiang, X . ; L i u , S.; Jen, A . K . - Y . J. Am. Chem. Soc. 2002,124, 14162-14172. (59) Fryzuk, M . D . ; Love, J. B . ; Rettig, S. J. Organometallics 1998,17, 846-853. (60) Schrock, R. R.; Seidel, S. W. ; Schrodi, Y . ; Davis, W . M . Organometallics 1999, 18, 428-437. (61) Fryzuk, M . D. ; Carter, A . ; Rettig, S. J. Organometallics 1992,11, 469-472. (62) Fryzuk, M . D . ; Haddad, T. S.; Berg, D . J. Coord. Chem. Rev. 1990, 99, 137-212. (63) Hey-Hawkins, E . ; Lindenberg, F. Organometallics 1994,13, 4643-4644. (64) Chen, L . ; Cotton, F. A . J. Cluster Sci. 1998, 9, 63-91. (65) Driess, M . ; Ackermann, FL; Aust, J.; Merz, K . ; Wullen, C . v. Angew. Chem. Int. Ed. 2002, 41, 450-453. (66) Fryzuk, M . D . ; Johnson, S. A . ; Rettig, S. J. Organometallics 1999, 18, 4059-4067. (67) Fryzuk, M . D . ; Kozak, C. M . ; Bowdridge, M . R.; Jin, W. ; Tung, D . ; Patrick, B . O.; Rettig, S. J. Organometallics 2001, 20, 3752-3761. (68) Fryzuk, M . D . ; Corkin, J. R.; Patrick, B . O. Can. J. Chem. 2003, 81, 1376-1387. (69) Hou, Z . ; Breen, T. L . ; Stephan, D . W . Organometallics 1993,12, 3158-3167. (70) King , W . A . ; Bella , S. D . ; Gulino, A . ; Lanza, G . ; Fragala, I. L . ; Stern, C . L . ; Marks, T. J. J. Am. Chem. Soc. 1999,121, 355-366. (71) Giesbrecht, G . R. PhD Thesis, University of British Columbia, 1998. (72) Fryzuk, M . D . ; Giesbrecht, G . R.; Rettig, S. J. Inorg. Chem. 1998, 37, 6928-6934. (73) Jones, R. A . ; Schwab, S. T.; Whittlesey, B . R. Polyhedron 1984, 3, 505-507. (74) Mercado, P.; D i M a i o , A . - J . ; Rheingold, A . L . Angew. Chem. Int. Ed. 1987, 26, 244-245. (75) Jimenez, G . ; Royo, P.; Cuenca, T.; Herdtweck, E . Organometallics 2002, 21, 2189-2195. (76) Shafir, A . ; Power, M . P.; Whitener, G . D . ; Arnold, J. Organometallics 2001, 20, 1365-1369. (77) Porter, R. M . ; Winston, S.; Danopoulos, A . A . ; Hursthouse, M . B . J. Chem. Soc, Dalton Trans. 2002, 3290-3299. Page 72 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors (78) Stephan, D . W. ; Stewart, J. C ; Guerin, F. ; Courtney, S.; Kickham, J.; Hollink, E . ; Beddie, C ; Hoskin, A . ; Graham, T.; Wei , P.; Spence, R. E . v. H . ; X u , W. ; Koch, L . ; Gao, X . ; Harrison, D . G . Organometallics 2003, 22, 1937-1947.. Fryzuk, M . D . ; Love, J. B . ; Rettig, S. J. J. Am. Chem. Soc. 1997,119, 9071-9072. Fryzuk, M . D . ; Jafarpour, L . ; Kerton, F. M . ; Love, J. B . ; Patrick, B . O.; Rettig, S. J. Organometallics 2001, 20, 1387-1396. Fryzuk, M . D . ; Jafarpour, L . ; Kerton, F. M . ; Love, J. B . ; Rettig, S. J. Angew. Chem. Int. Ed. 2000, 39, 767-770. A search of the Cambridge Crystallographic Data Center database, November 2004 update, did not return any complexes containing a Y - A s bond. Evans, W . J.; Leman, J . T.; Ziller, J . W. ; Khan, S. I. Inorg. Chem. 1996, 35, 4283-4291. Nief, F.; Ricard, L . J. Organomet. Chem. 1997, 529, 357-360. Nief, F.; Ricard, L . Organometallics 2001, 20, 3884-3890. Schumann, H . ; Palamidis, E . ; Loebel, J.; Pickardt, J. Organometallics 1988, 7, 1008-1010. Chao, Y . W. ; Wexler, P. A . ; Wigley, D . E . Inorg. Chem. 1989, 28, 3860-3868. Fryzuk, M . D . ; Love, J. B . ; Rettig, S. J.; Young, V . G . Science 1997, 275, 1445-1447. Fryzuk, M . D . ; Kozak, C. M . ; Bowdridge, M . R.; Patrick, B . O.; Rettig, S. J. J. Am. Chem. Soc. 2002,124, 8389-8397. Roddick, D . M . ; Fryzuk, M . D . ; Seidler, P. F.; Hillhouse, G . L . ; Bercaw, J. E . Organometallics 1985, 4, 97-104. Fryzuk, M . D . ; Kozak, C ; Mehrkhodavandi, P.; Morel lo, L . ; Patrick, B . O.; Rettig, S. J. J. Am. Chem. Soc. 2002,124, 516-517. Vanysek, P. In CRC Handbook of Chemistry and Physics; 84 [Online] ed.; Lide, D . R., Ed . ; C R C Press: Boca Raton, F L , 2003. Bogdanovic, B . Acc. Chem. Res. 1988, 21, 261-267. Protasiewicz, J. D . ; Bianconi, P. A . ; Will iams, I. D . ; L i u , S.; Rao, C . P.; Lippard, S. J. Inorg. Chem. 1992, 31, 4134-4142. Page 73 References begin on page 69. Chapter Two: Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors (95) Mull ins , S. M . ; Duncan, A . P.; Bergman, R. G . ; Arnold, J. Inorg. Chem. 2001, 40, 6952-6963. (96) Pangborn, A . B . ; Giardello, M . A . ; Grubbs, R. H . ; Rosen, R. K . ; Timmers, F. J. Organometallics 1996,15, 1518-1520. (97) Craig, J. M . ; Brimmer, S. P. Microchem. J. 1995, 52, 376-382. (98) Bergbreiter, D . E . ; Kil lough, J. M . J. Am. Chem. Soc. 1978,100, 2126-2134. (99) Schrock, R. R.; Sharp, P. R. J. Am. Chem. Soc. 1978,100, 2389-2399. (100) Bogdanovic, B . ; Liao, S.; Mynott, R.; Schlichte, K . ; Westeppe, U . Chem. Ber. 1984,117, 1378-1392. (101) Haan, K . H . D . ; Boer, J. L . d.; Teuben, J. H . ; Spek, A . L . ; Kojic-Prodic, B . ; Hays, G. R.; Huis, R. Organometallics 1986, 5, 1726-1733. (102) Manzer, L . E . Inorg. Synth. 1982, 21, 135-140. (103) Brand, H . ; Arnold, J. Organometallics 1993,12, 3655-3665. (104) Perrin, D . D . ; Amarego, W . L . F. Purification of Laboratory Chemicals; 3rd ed.; Butterworth-Heinemann: Oxford, 1994. Page 74 References begin on page 69. Chapter Three Tantalum coordination chemistry supported by a diamido-arsine ligand 3.1. Introduction Chapter two introduced arsenic as an element with a long and storied human history. Organoarsine chemistry was introduced with the coordination chemistry of tetramethyldiarsine (Me 2As-AsMe2), and the dominance of chelating diarsine ligands in early transition-metal coordination chemistry was briefly discussed. Chelating multidentate ligands have been extensively utilized in transition metal chemistry across the periodic table.1"4 The prevalence of these ligands is due to the chelate effect, in which coordination of a multidentate ligand is favored over coordination of several monodentate ligands. 5 Ubiquitous among bidentate arsines is the family o f ligands known collectively as 'diars', ( o - C e F L X A s R ^ ) , which has two organoarsine units ortho to each other on an aromatic ring. A variety of substituents are possible on the arsenic as a means of ft R • influencing the electronics and sterics of the ligand, including methyl, " shown in Figure 3.1a, ethyl , 9 ' 1 0 and phenyl ; 1 1 ' 1 2 the methyl derivative is by far the most commonly Page 75 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand utilized. A chiral version with one methyl and one phenyl substituent on each arsenic has been utilized in asymmetric catalysis. 1 3 ' 1 4 Related tridentate ligands, such as ptas (ptas = bis(2-(dimethylarsino)phenyl)phenylarsine), 1 5 ' 1 6 shown in Figure 3.1b, and quadridentate 17 ligands such as fars (fars = l,2-bis(diphenylarsinopropyl)methylarsinobenzene), shown in Figure 3.1c, have been synthesized. The diars ligands have been extensively used in late transition-metal coordination chemistry. However, as mentioned above, they are the most prevalent arsenic based ligand in early transition-metal chemistry, and complexes have been reported for each element of groups 4, 5 and 6 . 1 8 - 2 4 Figure 3.1. Bidentate and multidentate arsine ligands with aromatic backbones: (a) diars; (b) ptas; (c) fars. Chelating diarsines are also possible with non-aromatic backbones. Simple alkyl backbones have been utilized to link two diphenylarsine donors in ligands of the formula Ph2As(CH2)nAsPli2 (where n = 1-4). Late transition-metal complexes supported by these ligands are common, particularly of group 10 metals, 2 5" 2 8 although i f n = 1, bridging of the ligand is predominant. 2 9 ' 3 0 Only when n = 2 have simple adducts of early transition-18 metal halides been synthesized. Mixed-donor ligands containing arsenic have also been explored in the literature. For example, mixed-donor versions of diarsine type ligands, with aromatic or aliphatic backbones, have been synthesized with nitrogen, 3 1 ' 3 2 oxygen, 3 3 phosphorus, 3 4 ' 3 5 sulphur, 3 6 ' 3 7 and C p . 3 8 Phosphine oxide and phosphoraminato ligands, R3P=N", have been linked with arsenic in the complexes shown in Figure 3.2. 3 9 ' 4 0 The coordination chemistry Page 76 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand of the tridentate [AsNAs] ligand bis(2-(diphenylarsino)ethyl)benzylamine, and the binucleating A/,A/;A^W-tetrakis-[2-(diphenylarsino)ethyl]ethane-l,2-diamine have been investigated with ruthenium and copper.41'42 Ph--. ' P V A s \ / M =N Z_ PIT r Ph M = Rh , Ir F i g u r e 3.2. Arsenic chelated phosphine oxide and phosphoraminato ligands. In this chapter, the diamido-arsine ligand, [NAsN] (where NAsN = PhAs(CH2SiMe2NPh)2) is synthesized and its coordination chemistry with tantalum is detailed. The hydrogenation of a trialkyl complex is investigated, and in an attempt to understand the observed reactivity, density functional theory calculations on a series of model complexes are discussed. 3.2. Synthesis of the ™[NAsN] ligand The synthesis of Ph[NAsN]Li2(THF)2 (3.1) is shown in Equation 3.1. Based on the synthesis of ph[NPN]Li2(THF)2, addition of four equivalents of "BuLi to a mixture of two equivalents of PhNHSilv^CFkCl and one equivalent of PhAsH2 in diethyl ether leads to the formation of the crude product as a diethyl ether adduct. Addition of four equivalents of THF to a hexanes slurry of the crude product and subsequent precipitation affords 3.1 in 78% yield after washing with minimal hexanes to remove coloured impurities. Page 77 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Me2 Me2 Ph PhAsH 2 2 N H (3.1) CI 4 BuLi, 0 °C, E t 2 0 THF S = THF X-ray quality crystals of 3.1 were grown from a saturated T H F solution at -40 °C. X-ray diffraction studies determined the crystal to be a two-component twin; the two orientations of the lattice are related by a rotation of 7.77° normal to 0.03, -1.00, -1.39. The solid-state molecular structure of 3.1 is presented in Figure 3.3; crystallographic data is given in Table A-3 of the Appendices, and selected bond distances and angles are collected in Table 3.1. The structure contains a L i 2 N 2 core, similar to P h [ N P N ] L i 2 ( T H F ) 2 4 3 and macrocyclic complexes P h [ P 2 N 2 ] L i 2 ( 1,4-dioxane),4 4 p h [As 2 N 2 ]L i 2 ( l , 4 -d ioxane) (2.1) and p h [ A s 2 N 2 ] L i 2 ( T H F ) 2 (2.2); the bond distances and angles of the core agree well with these complexes. The L i ( l ) - A s ( l ) bond distance of 2.686(6) A agrees well with that of 2.1 and 2.2, and other similar molecules 4 5 - 4 7 Page 78 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Figure 3.3. Molecular structure (ORTEP) of ™[NAsN]Li 2 (THF) 2 , 3.1. Ellipsoids are drawn at 50% probability. Table 3.1. Selected bond distances (A) and bond angles (°) for p h [ N A s N ] L i 2 ( T H F ) 2 , 3.1. Atom Atom Distance (A) Atom Atom Distance (A) N ( l ) L i ( l ) 2.089(9) A s ( l ) L i ( l ) 2.686(8) N(2) L i ( l ) 2.045(9) 0(1) L i ( l ) 1.872(8) N ( l ) Li(2) 1.984(9) 0(2) Li(2) 1.880(9) N(2) Li(2) 2.020(9) Page 79 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) A s ( l ) L i ( l ) N ( l ) 92.5(3) 0(2) Li(2) N(2) 131.1(5) A s ( l ) L i ( l ) N(2) 95.0(3) L i ( l ) N ( l ) Li(2) 75.2(3) 0(1) L i ( l ) N ( l ) 128.4(4) L i ( l ) N(2) Li(2) 75.5(4) 0(1) L i ( l ) N(2) 120.3(4) The solid-state structure in 3.1 as discussed above is not retained in solution. The ambient temperature ' H N M R spectrum displays resonances due to only two types of silyl methyl protons and the CH2 ring proton signals appear as a pair of A B doublets. The 7 L i { ' H } spectrum is comprised of a narrow singlet, indicating that there is a single lithium environment in solution. Substituted variations of the p h [ N P N ] L i 2 complex with only one coordinated solvent donor generally possess a single environment in the 7 L i { ' H } N M R . 4 8 ' 4 9 A fluxional process that exchanges the lithium environments through migration of the phosphine and donor solvent from one lithium to another is postulated to explain this behaviour. Complex 3.1 is the first observation of a 7 L i { ' H } singlet in this ligand family with two coordinated solvent molecules. It is possible that a fluxional process involving arsenic migration can exchange the lithium environments, however, variable-temperature ' H N M R experiments performed on 3.1 (290-190 K ) did not show decoalescence of any resonances. Another possibility for the observed singlet is that arsenic may not be coordinated to the lithium ions in solution. The synthesis of the protonated ligand precursor p h [ N A s N ] H 2 (3.2) is outlined in Equation 3.2. Reaction of 3.1 with two equivalents of N E t 3 H C l affords 3.2 in 96% yield as a colourless oi l . Page 80 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Me 2 Allowing the oil to stand for several weeks produced X-ray quality crystals of 3.2. Crystallographic data is presented in Table A-3 of the Appendices, and selected bond lengths and angles are collected in Table 3.2. The asymmetric unit contains two independent molecules, one of which is shown in Figure 3.4. The hydrogen atoms bound to N ( l ) and N(2) can be located within the diffraction pattern and refined isotropically. Derealizat ion of the nitrogen lone pair into the aromatic ring is evidenced by the planarity around the nitrogen atoms = 360°). This is also reflected in the short C - N bonds (1.412(4) A and 1.401(4) A ) , 5 0 " 5 2 compared to non-conjugated alkyl amines, 5 3 ' 5 4 and indicates partial double bond character. The acute angles about the central arsenic atom are similar to the protonated ligand precursor Ph[As2N2]H2 (2.3). In solution, the silylamine arms are equivalent and the compound assumes C s symmetry with the silylmethyl proton resonances appearing as two singlets in the *H N M R spectrum, the signals due to methylene protons as a pair of A B doublets and the N H resonances as a broad singlet. Page 81 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Figure 3.4. Molecular structure (ORTEP) of ™[NAsN]H 2 , 3.2. Ellipsoids are drawn at 50% probability. Table 3.2. Selected bond distances (A) and bond angles (°) for P h [ N A s N ] H 2 , 3.2. Atom Atom Distance (A) Atom Atom Distance (A) N ( l ) S i ( l ) 1.747(3) Si(2) N(2) 1.741(3) N ( l ) C(13) 1.412(4) N(2) C(19) 1.401(4) A s ( l ) C ( l ) 1.997(3) N ( l ) H(91) . 0.745(5) A s ( l ) C(2) 1.990(3) N(2) H(92) 0.743(5) A s ( l ) C(7) 1.972(3) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) C ( l ) A s ( l ) C(2) 99.87(13) S i ( l ) N ( l ) C(13) 133.7(3) C ( l ) A s ( l ) C(7) 98.08(13) Si(2) N(2) C(19) 133.7(2) C(2) A s ( l ) C(7) 99.97(12) Page 82 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand 3.3. Synthesis ofph[NAsN]TaMe3 The synthesis of P h [ N A s N ] T a M e 3 (3.3) is given in Equation 3.3. Reaction of 3.1 with T a M e 3 C l 2 affords 3.3 as a pale yellow solid in 63% yield after washing with minimal pentane. The product is soluble in pentane, and the necessity of removing soluble coloured by-products contributes to the modest yield. Solutions of 3.3 are photochemically and thermally sensitive and appropriate precautions must be taken during the reaction; however, the isolated and dried solid can be stored for extended periods of time in the dark at -40 °C. (3.3) Crystals of 3.3 suitable for X-ray diffraction experiments were grown by slow evaporation of a concentrated benzene solution. The solid-state molecular structure of 3.3 is presented in Figure 3.5; crystallographic data is given in Table A - 4 o f the Appendices, and selected bond distances and angles are collected in Table 3.3. The most striking feature of the structure is that arsenic is not coordinated to tantalum (Ta--As = 4.55 A ) , which makes the tantalum five-coordinate. The geometry about the tantalum center is a distorted square pyramid with N ( l ) in the apical position, and the methyl groups are all cis disposed. There is a distinct lack of symmetry in the molecule; this can be observed in the phenyl amido groups and the phenyl group bound to arsenic. Comparing the bonding to the structurally characterized six-coordinate ph[NPN]TaMe3 complex, 4 3 the Ta-N and Ta-C bonds are, on average, slightly shorter, due to the five-coordinate nature of 3.3. The Ta-N distances are, however, not significantly different from other p h [ N P N ] T a complexes " and both Ta-N and Ta-C match those of similar literature complexes. Page 83 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Very few coordination complexes containing tantalum arsine interactions have been characterized in the solid state. There are two examples using the diars ligand (o-C 6 H 4 ( A s M e 2 ) 2 ) , 6 3 ' 6 4 and three examples of tantalum arsenic clusters. 6 5 ' 6 6 The absence of non-chelating examples suggests that interactions between arsenic and tantalum are weak and a stabilizing force is necessary for coordination. The fact that arsenic does not coordinate in 3.3, despite the chelating nature of the ligand, suggests that additional factors are involved. Figure 3.5. Molecular structure (ORTEP) of ™[NAsN]TaMe 3 , 3.3. Ellipsoids are drawn at 50% probability. Page 84 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Table 3.3. Selected bond distances (A), intramolecular distances (A), and bond angles (°) for p h [ N A s N ] T a M e 3 , 3.3. Atom Atom Distance (A) Atom Atom Distance (A) Ta(l) C ( l ) 2.189(2) Ta(l) N ( l ) 1.948(2) Ta(l) C(2) 2.223(2) Ta(l) N(2) 2.014(2) Ta(l) C(3) 2.176(2) Ta(l) A s ( l ) 4.550(2) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) C ( l ) Ta( l ) C(2) 77.53(11) N(2) Ta( l ) C ( l ) 87.39(8) C ( l ) Ta( l ) C(3) 126.43(10) N(2) Ta( l ) C(2) 149.72(8) C(2) Ta( l ) C(3) 78.71(11) N(2) Ta( l ) C(3) 89.88(8) N ( l ) Ta( l ) C ( l ) 117.20(8) N ( l ) Ta( l ) C(3) 113.44(9) N ( l ) Ta( l ) C(2) 98.83(9) N ( l ) Ta( l ) N(2) 111.44(7) The ambient temperature ' H N M R spectrum of 3.3 provides no evidence for the lack of symmetry observed in the solid-state molecular structure. The ligand approximates a C s environment with two silyl methyl resonances; the methylene resonances appear as a pair of A B doublets. A single resonance is observed for the three tantalum-bound methyl groups, indicating that some fluxional process must be exchanging the methyl groups in solution. If the complex is five-coordinate in solution and approximates the distorted square pyramid of the solid-state structure, the methyl groups can be made equivalent through the Berry pseudo rotation, shown in Equation 3.4. Ni" N 2 •Ta C 2 ^2, C 1 N 2 C 3 / I N-| T a . N-|—^-Ta 0.4) C 2 Page 85 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Variable-temperature ' H N M R experiments performed in Jg-toluene found that at 195 K , two resonances are observed for the tantalum bound methyl groups at £ 1 . 3 6 and 1.03, in a 2:1 ratio. A similar 2:1 ratio of methyl resonances has been observed at low temperature in the octahedral complex p h[NPN]TaMe3, but at significantly different shifts of £0 .40 and -0 .05 . 4 3 This was attributed to cis and trans conformation of the methyls in relation to the phosphine donor. The difference in the shift o f the methyl resonances is as pronounced in the room temperature spectra, where p h [NPN]TaMe3 has a doublet at £ 0 . 5 5 , due to phosphorus coupling, and the resonance in 3.3 is a singlet at £ 1.09. The low temperature *H N M R spectrum of p h[NPN]TaMe3 also shows hindered rotation of the amido phenyl groups; however, 3.3 shows no evidence of this, even at 185 K . There are significant differences in the chemical shifts of the methylene resonances of these two complexes, with p h [NPN]TaMe3 displaying two multiplets at 8 1.23 and 1.18, and 3.3 having A B doublets at £ 1 . 8 2 and 1.25. The spectral differences suggest that 3.3 may be five-coordinate in solution; lowering the temperature inhibits Berry pseudo rotation and results in the two methyl signals. However, a six-coordinate structure where the low temperature methyl signals are due to cis and trans conformations relative to the arsine donor cannot be definitively ruled out. Reaction o f 3.3 with donating solvents such as T H F , pyridine and P M e 3 does not produce solvent adduct complexes, which would be expected i f 3.3 was five coordinate in solution. This is not conclusive, however, because it is possible the arsine ligand, while not coordinated to the tantalum center, can still effectively block access to the open coordination site for a potential ligand. 3.4. Hydrogenation ofph[NAsN]TaMe3 Hydrogenation of 3.3 performed under one or four atmospheres of hydrogen in the absence of light does not afford the desired dinuclear tetrahydride ( p h[NAsN]Ta)2(p-H)4. When a diethyl ether solution of 3.3 is exposed to H 2 (4 atm), a subtle colour change Page 86 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand from pale yellow to pale tan is observed over 24 h and a colourless solid is deposited on the sides of the flask. In contrast, hydrogenation of p h[NPN]TaMe3 results in a deep purple-red solution and formation of the dinuclear tetrahydride. 4 3 Evaporation of the solvent leaves an oily brown residue and examination of the soluble material by ' H N M R spectroscopy indicates that a single material displaying two resonances in the silylmethyl region, a pair of doublets in the methylene region, and a broad resonance at £ 3 . 1 is the major product. The spectrum closely matches that of the protonated ligand P h [ N A s N ] H 2 (3.2). No resonances attributable to tantalum hydrides are observed, nor are resonances due to the starting material 3.3. A ' H N M R spectrum obtained in the presence of an internal standard (ferrocene) indicates a 33% yield of 3.2. Reaction of 3.3 with deuterium produces the same colour change and precipitate; however, a ' H N M R spectrum of the soluble material shows the broad resonance remains, although with significantly smaller integration relative to the methylene and silylmethyl resonances. Integration of the spectrum against an internal standard shows a 32% yield of deuterated 3.2 (D2-3.2). The trace amount of 3.2 is due to thermal decomposition of 3.3. A solution of 3.3 in benzene or T H F produces approximately 1% of 3.2, by integration, over the course of 24h at room temperature. Although the reaction of 3.3 with adventitious water cannot be completely ruled out, the degree of deuteration suggests the product is formed by reaction of 3.3 with H2/D2 exclusively. Hydrogenations performed under one atmosphere of hydrogen produce primarily unidentified products from which small amounts of 3.2 (<5%) can be identified, while deuterations produce similar small amounts of Z>2-3.2 and a trace of 3.2 from thermal decomposition of 3.3. Following the reaction by ' H N M R spectroscopy does not show any intermediates; the formation o f 3.2 is complete in the first 24-48 h o f the reaction, and no resonances attributable to tantalum hydrides are observed. Further reaction time leads to decomposition of the remaining 3.3. It is not known why the reaction stops producing 3.2, as dissolved hydrogen remains visible in the ' H N M R spectrum. Elemental analyses of the isolated materials, while not reproducible from reaction to reaction, are consistently low in carbon and hydrogen relative to the trimethyl complex 3.3, suggesting possible loss of methane. Methane gas can be detected in the headspace Page 87 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand of four atmosphere hydrogenations by G C - M S ; however, it could not be quantified due to limitations in the four-atmosphere apparatus. Methane was not detected in the one-atmosphere experiments, presumably because not enough methane is produced in such small-scale reactions to permit detection. Monitoring the hydrogenation reaction of 3.3 by ! H N M R spectroscopy does not reveal any hydride-containing intermediates. However, the detection of methane suggests that the hydrogenation of 3.3 begins with metathesis of Ta-C bonds producing methane and a tantalum hydride, as shown in Scheme 3.1. This mechanism has been postulated previously for the hydrogenation of p h [NPN]TaMe3; further hydrogenation results in the evolution of two additional equivalents of methane and the eventual formation of the dinuclear tetrahydride ( p h [NPN]Ta)2(p-H)4. The hydrogenation of 3.3 follows a different reaction pathway leading to the free ligand 3.2. It is possible that the amide could be removed from the metal center by reductive N - H formation followed by tantalum amine dissociation affording a Ta(III) dihydride species containing a dangling amine. However, the absence of intense colours in this reaction, typical of low valent tantalum complexes, suggests that any Ta(III) is present only as a transient species. It seems more probable that the mechanism parallels that of P h [NPN]TaMe3 with further metathesis of tantalum methyl bonds to produce a transient trihydride. A t this point, it is possible that a partially open coordination site permits coordination of an additional equivalent of H 2 , followed by hydrogenation of the Ta-N bonds, as shown in Scheme 3.1. This is supported by the H 2 pressure dependence of the reaction; suggesting that it may be necessary to force the H 2 into the tantalum coordination sphere, perhaps by fully displacing the arsenic donor. However, this steric argument is not supported by previous work with the macrocyclic P h [ P 2 N 2 ] ligand which has shown that a sterically congested seven-coordinate alkyl complex, p h[P2N2]TaMe3, can be cleanly hydrogenated to yield the dinuclear tetrahydride ( P h [P2N2]Ta) 2 (p -H)4.<Fryzuk, 2000 #383> Another possibility is the direct hydrogenation of Ta-N bonds in preference to the Ta-C bonds. The fact that Ta -N bonds are significantly stronger than Ta-C bonds, and the entropic driving force of methane elimination from Ta-C bond metathesis suggests that this would not be the preferred reaction. 6 7" 7 0 Page 88 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Scheme 3.1 Previous work in the Fryzuk group performed using ruthenium has shown that the R u - N bond can activate H2 to generate R u - H and N - H moieties, 7 1 including a system supported by the P h [ N P N ] l igand. 7 2 The hydrogenation of metal-amide bonds has also been implicated in the regeneration of the active catalytic species for the hydrogenation of ketones and imines via the metal-ligand bifunctional mechanism. 7 3" 7 5 However, this chemistry is virtually unknown for the early transition metals. There are examples of imide hydrogenation in substituted cyclopentadienyl titanium systems, 7 6 ' 7 7 a single report of vanadium amide bond hydrogenolysis, 7 8 and a molybdenum complex that formally adds molecular hydrogen across the S i - N bond of a diamido ligand via transfer of H from 70 a coordinated dihydrogen complex. Page 89 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand 3.5. Density Functional Theory calculations Calculations based on density functional theory (DFT) are an important tool in understanding the bonding and reactivity of inorganic coordination complexes. D F T calculations do not provide molecular orbital representations and energies in the manner of Hartree-Fock calculations; however, the Kohn-Sham orbitals derived from D F T are R1 R^ • similar to those derived from other more rigorous methods. " These orbitals have become important in the analysis of reactivity and structure because of the relationship between calculated orbital energies and the observed or spectroscopically determined molecular orbital energies. 8 1 However, it is critical to remember that the eigenvalues and energies derived from D F T calculations are essentially qualitative and for comparative use only. The appeal of D F T as a method for studying reactivity and bonding is its simplicity. The theory is based on the idea that the total energy, E , o f an electronic 84 system is determined by the electron density, p or E p . This was first suggested by Fermi and later proven by Kohn and Hohenberg. 8 5 Their proof showed that the energy of the system could be expressed as the energy of n non-interacting electrons and the term E e x , called the exchange-correlation hole function, that accounts for the correlated motion of the electrons. Electron density is attractive for calculations because it only depends on the Cartesian coordinates x, y, and z, unlike many particle wave functions which depend on 3JV or 4N variables. The calculation is simply the approximation of E e x . This level of theory is termed approximate density functional theory, and has fewer computational demands over traditional ah initio calculations. The literature contains many examples of theoretical investigations conducted on transition metal complexes, including reactivity studies. Comparative studies have been performed on the activation of methane C - H bonds via oxidative addition and a-bond metathesis in platinum and rhodium systems. ' Generally, a-bond metathesis reactions have been studied for high oxidation state early transition metals and lanthanides because oxidative addition is not possible. Investigations conducted on the reaction of C p 2 L n H Page 90 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand complexes with H - H , 8 9 and S i - H bonds, 9 0 have shown the reactions proceed via rj-bond metathesis. Similarly, D F T studies on zirconium systems have suggested that a variety of bond activation processes progress through the same mechanism. 9 1" 9 3 Many group 5 transition-metal complexes have been investigated by D F T , 9 4 ' 9 5 including a study of metal-metal bonding in the dinuclear complexes V2CI9 3 ", NbaClg 3" and Ta2Clc>3",96 and monomeric hydride complexes. 9 7 Previous work in the Fryzuk lab has studied [NPN] OR complexes of tantalum and niobium using D F T methods. However, there have been comparatively few published studies of arsenic ligands bound to transition metals. 9 9" 1 0 3 There are several reasons to undertake a D F T study of the [NAsN] complexes. First, can these complexes be effectively modeled using D F T and can they provide additional information on the bonding of arsenic to metal centers. Would a geometry optimization of 3.3 support a five-coordinate structure or a six-coordinate structure? Is the failure to synthesize the tetrahydride complex due to a problem in the reaction or is the complex simply unstable? Perhaps most importantly, studies on all complexes can be compared to previous D F T studies on similar [NPN] complexes. 9 8 Comparison of derived Kohn-Sham orbitals would hopefully provide information on the observed differences in reactivity between 3.3 and P h [NPN]TaMe3. It is puzzling that the complex p h [NPN]TaMe3 reacts with H2 to form the dinuclear tetrahydride, but the simple substitution of arsenic for phosphorus in the ancillary ligand leads to a different reactivity with H2. Geometry optimizations and D F T calculations were performed on the Gaussian 98 software package 1 0 4 using the B 3 L Y P hybrid functional. 1 0 5 Rather than using the [NAsN] ligand, a simplified version was desired to reduce calculation complexity. OR Previous studies of the [NPN] ligand used a simplified framework denoted ' N P N ' . A n arsenic version, ' N A s N ' (where ' N A s N ' = MeAs(CH2SiH 2NMe)2), is shown in Figure 3.6. This simplified ligand uses methyl groups on amide and neutral donors, and a secondary silane backbone instead of a bis(methyl)silyl backbone. Page 91 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Me replaces Ph • C H 3 S i H 2 replaces S i M e 2 Me replaces Ph Figure 3.6. Simplified ' N A s N ' ligand model for D F T calculations. Accurate calculations depend on the choice o f basis set. A basis set is the set of atomic orbitals built around the static nuclei. This basis set must be capable of describing the wave function well enough to give chemically useful data, but at the same time be solvable within reasonable computation time. Calculations conducted on the [NPN] ligand used the L A N L 2 D Z basis set. 1 0 6 The L A N L 2 D Z basis set is a primitive basis set and does not contain polarization or diffusion functions. While care must be taken in D F T calculations of systems with phosphines to incorporate the role of d-type functions in correlated wave functions to account for extra polarization, 1 0 7 the effect of phosphorus atom d-type functions on the calculated M - P bond lengths in diamidodiphosphine systems was studied systematically and found to have a negligible inf luence. 1 0 8 ' 1 0 9 Initial calculations were carried out on the model complexes 'NAsN'Li2(OMe2)2 (3.4), ' N A s N ' T a M e 3 (3.5), and ( 'NAsN 'Ta ) 2 (u -H) 4 (3.6) using the L A N L 2 D Z basis set so as to provide the most accurate comparison to previous [NPN] studies. Complete calculation details, z-matrices, initial parameters, and final coordinates are given in the Appendices. Selected optimized bond distances and bond angles are given in Table 3.4 (3.4A), Table 3.5 (3.5A) and Table 3.6 (3.6A), where the A designates the use of the L A N L 2 D Z basis set. Generally, geometries, bond distances and angles agree well with previous [NPN] studies indicating that the level of calculation employed can adequately model the interaction of arsenic with a metal center. Page 92 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Table 3.4. Selected optimized bond distances (A) and bond angles (°) for ' N A s N ' L i 2 ( 0 M e 2 ) 2 , 3.4A. Atom Atom Distance (A) Atom Atom Distance (A) N ( l ) L i ( l ) 1.999 A s ( l ) L i ( l ) 3.096 N(2) L i ( l ) 2.004 0(1) Li(2) 1.923 N ( l ) Li(2) 1.981 0(2) Li(2) 1.901 N(2) Li(2) 1.985 Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) N ( l ) L i ( l ) N(2) 104.86 A s ( l ) L i ( l ) N(2) 91.13 N ( l ) Li(2) N(2) 106.21 L i ( l ) N ( l ) Li(2) 73.21 A s ( l ) L i ( l ) N ( l ) 92.89 L i ( l ) N(2) Li(2) 73.01 Table 3.5. Selected optimized bond distances (A), intramolecular distances (A), and bond angles (°) for ' N A s N ' T a M e 3 , 3.5A. Atom Atom Distance (A) Atom A t o m Distance (A) Ta(l) A s ( l ) 4.638 Ta(l) C ( l ) 2.198 Ta(l) N ( l ) 1.967 Ta(l) C(2) 2.221 Ta(l) N(2) 2.017 Ta( l ) C(3) 2.194 Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) N ( l ) Ta( l ) A s ( l ) 54.72 C ( l ) Ta( l ) C(2) 79.51 N(2) Ta( l ) A s ( l ) 63.15 C ( l ) Ta( l ) C(2) 126.71 N ( l ) Ta( l ) N(2) 110.75 C(2) Ta( l ) C(3) 79.63 Page 93 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Table 3.6. Selected optimized bond distances (A), bond angles (°), and dihedral angles (°) for ( 'NAsN 'Ta ) 2 (u -H) 4 , 3.6A. Atom Atom Distance (A) Atom A t o m Distance (A) Ta(l ) H ( l ) 1.880 Ta(l) Ta(2) 2.657 Ta(2) H ( l ) 1.991 Ta(l) A s ( l ) 2.798 Ta(l) H(2) 2.081 Ta(2) As(2) 2.760 Ta(2) H(2) 1.841 Ta( l ) N ( l ) 2.039 Ta(l) H(3) 1.886 Ta( l ) N(2) 2.031 Ta(2) H(3) 2.151 Ta(2) N(3) 2.012 Ta(l) H(4) 2.637 Ta(2) N(4) 2.114 Ta(2) H(4) 1.785 Atom Atom Atom Angle (°) Atom Atom A t o m Angle (°) N ( l ) Ta( l ) N(2) 116.78 N(3) Ta(2) N(4) 100.73 N ( l ) Ta( l ) A s ( l ) 81.55 N(3) Ta(2) As(2) 73.68 N(2) Ta( l ) A s ( l ) 82.67 N(4) Ta(2) As(2) 88.10 Atom Atom Atom Atom Angle (°) A s ( l ) Ta( l ) Ta(2) As(2) -145.70 A s mentioned above, the L A N L 2 D Z basis set does not contain diffusion and polarization functions, and it is unable to account for the contribution of d orbitals in the bonding of atoms. Studies of phosphine ligand systems have shown the contribution of the d orbitals is minimal, but no similar studies exist for arsine ligands bound to transition metals. To better model the arsenic atom, calculations were performed on the model complexes ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B), ' N A s N ' T a M e 3 (3.5B), and ( ' N A s N ' T a ) 2 ( p - H ) 4 (3.6B) using the L A N L 2 D Z basis set augmented with diffusion and polarization functions for the arsenic atoms. 1 1 0 Recent results using the augmented L A N L 2 D Z basis Page 94 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand set (denoted L A N L 2 D Z p d ) have illustrated their utility in modeling arsenic ligands bonded to main group elements. 1 1 1 The model complex ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B) is depicted in Figure 3.7, and selected optimized bond lengths and bond angles are presented in Table 3.7. Comparing the bond distances and angles for 3.4B to the solid state structure of 3.1, the N2L12 core is more square in the model complex, with distances up to 0.1 A longer and angles closer to 90°, and the A s - L i bond distance is about 0.4 A longer in the model complex. The same differences of the N2L12 core distances and angles are observed when comparing 3.4B to the model complex ' N P N ' L i 2 ( O M e 2 ) 9 8 and the solid-state structures of p h [ N P N ] L i 2 ( T H F ) 2 , 4 3 and C y ' M e s [ N P N ] L i 2 ( T H F ) 4 9 with a cyclohexyl phosphine and the bulky mesityl amide. The values differ only slightly despite the fact that the model ' N P N ' complex and the cyclohexyl derivative only have a single solvent molecule. This suggests that the presence of the second solvent molecule in 3.1 does not greatly influence the structure of the ligand. Comparing values to those of 3.4A finds that, because the L A N L 2 D Z p d basis set only altered the basis set for the arsenic atom, bond distances and angles involving other atoms in the molecule are virtually identical. The arsenic to lithium distance is marginally longer in 3.4B. Page 95 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Figure 3.7. Calculated geometry for 'NAsN 'L i 2 (OMe 2 ) 2 (3.4B) with selected optimized bond distances (A). Values in brackets are experimental values for 3.1. Table 3.7. Selected optimized bond distances (A) and bond angles (°) for ' N A s N ' L i 2 ( O M e 2 ) 2 , 3.4B. Atom Atom Distance (A) Atom A t o m Distance (A) N ( l ) L i ( l ) 2.001 A s ( l ) L i ( l ) 3.074 N(2) L i ( l ) 2.005 0(1) Li(2) 1.923 N ( l ) Li(2) 1.980 0(2) Li(2) 1.900 N(2) Li(2) 1.985 Page 96 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) N ( l ) L i ( l ) N(2) 104.80 A s ( l ) L i ( l ) N(2) 90.86 N ( l ) Li(2) N(2) 106.34 L i ( l ) N ( l ) Li(2) 73.17 A s ( l ) L i ( l ) N ( l ) 92.62 L i ( l ) N(2) Li(2) 72.98 The model complex ' N A s N ' T a M e 3 (3.5B) is depicted in Figure 3.8, and selected optimized bond lengths and bond angles are presented in Table 3.8. The Ta-N and Ta-C bond distances and angles of model complex 3.5B compare very well with 3.3; they also compare well to the solid-state structures of p h [ N P N ] T a M e 3 4 3 and C y [ N P N ] T a M e 3 . 9 8 The Ta( l ) -As( l ) distance is 0.07 A longer in 3.5B than in 3.3, and marginally longer than in 3.5A. This reinforces the five-coordinate nature of 3.3 and indicates the lack of interaction between tantalum and arsenic is not a solid-state phenomenon. Comparing Ta-N and Ta-C bond distances and angles of the five-coordinate 3.3 and the six-coordinate ' N P N ' T a M e 3 reveals great similarity. This is surprising given the difference in coordination number and suggests that even in the six-coordinate [NPN] complexes, the interaction between the tantalum and phosphorus is weak, and the interaction has little influence on the geometry of the other ligands about the metal center. Page 97 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Figure 3.8. Calculated geometry for ' N A s N ' T a M e 3 (3.5B) with selected optimized bond distances (A). Values in brackets are experimental values for 3.3. Table 3.8. Selected optimized bond distances (A), intramolecular distances (A), and bond angles (°) for ' N A s N ' T a M e 3 , 3.5B. Atom Atom Distance (A) Atom Atom Distance (A) Ta(l) A s ( l ) 4.625 Ta(l) C ( l ) 2.194 Ta(l) N ( l ) 1.967 Ta( l ) C(2) 2.222 Ta(l) N(2) 2.018 Ta( l ) C(3) 2.198 Page 98 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) N ( l ) Ta( l ) A s ( l ) 54.53 C ( l ) Ta( l ) C(2) 79.63 N(2) Ta( l ) A s ( l ) 63.03 C ( l ) Ta( l ) C(2) 126.73 N ( l ) Ta( l ) N(2) 110.62 C(2) Ta( l ) C(3) 79.57 Ligand dissociation is not restricted to [NAsN]TaMe 3 . Hydrogenation of R [ N P N ] N b M e 3 (R = Ph, Cy) failed to produce a tetrahydride complex. 4 9 This was initially attributed to the thermal instability of the niobium trimethyl species. However, a D F T calculation on a model complex has shown that this may not be strictly correct. A no calculation on the model complex ' N P N ' N b M e 3 showed it to be five-coordinate, with a geometry virtually identical to 3.5B. The model complex ( 'NAsN'Ta) 2 (u . -H) 4 (3.6B) is depicted in Figure 3.9, and selected optimized bond lengths and bond angles are presented in Table 3.9. The bond distances and angles of 3.6B and ( 'NPN'Ta) 2 (u . -H) 4 , 9 8 are virtually identical; even the Ta-A s distances are only marginally longer than the Ta-P distances, in contrast to the trimethyl model complexes. The Ta-As distances compare well with literature values, 63,64,66 a n c j a r e m a r g m a U y shorter in 3.6B when compared to 3.6A. The convergence of 3.6A and 3.6B to rational structures suggests that the D F T method is an appropriate to model the hypothetical hydride complex ( p h [NAsN]Ta) 2 (p -H) 4 . Further, because the model complex does not dissociate in the calculation, it suggests that it is not some intrinsic instability in ( p h [NAsN]Ta) 2 (p -H) 4 that prevents its formation, but an alternate reaction pathway between 3.3 and H 2 . Significant differences between the model complexes 3.6B and ( 'NPN'Ta) 2 (p -H) 4 and the solid-state structure of ( P h [NPN]Ta) 2 (u.-H)4 arise when comparing the distances and angles of the T a 2 H 4 core. The hydrides have a very asymmetric distribution in the model complexes; there are two bridging hydrides and two terminal hydrides. The structure of ( p h [NPN]Ta) 2 (u.-H)4 does show a small asymmetric distribution; however, all four of the hydrides are bridging and Ta-H bond distances vary only marginally. The Ta-Ta distance in the structure is also shorter than for the model complexes, reflecting the Page 99 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand degree that the bridging hydrides support the Ta-Ta interaction. It is unknown what role this asymmetric binding could play in the reactivity of this complex; however, previous work could not rule out a solution structure of ( p h [NPN]Ta) 2 (p -H) 4 with bridging and terminal hydrides in rapid exchange. 4 3 Figure 3.9. Calculated geometry for ( ' N A s N T a ) 2 ( p - H ) 4 (3.6B) with selected optimized bond distances (A). Page 100 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Table 3.9. Selected optimized bond distances (A), intramolecular distances (A), bond angles (°), and dihedral angles (°) for ( 'NAsN'Ta) 2 (u-H)4 , 3.6B. Atom Atom Distance (A) Atom Atom Distance (A) Ta(l) H ( l ) 1.887 Ta(l) Ta(2) 2.672 Ta(2) H ( l ) 1.985 Ta( l ) A s ( l ) 2.754 Ta(l) H(2) 2.060 Ta(2) As(2) 2.722 Ta(2) H(2) 1.850 Ta(l) N ( l ) 2.040 Ta(l) H(3) 1.094 Ta( l ) N(2) 2.029 Ta(2) H(3) 2.123 Ta(2) N(3) 2.013 Ta(l) H(4) 2.724 Ta(2) N(4) 2.116 Ta(2) H(4) 1.784 Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) N ( l ) Ta( l ) N(2) 117.19 N(3) Ta(2) N(4) 99.99 N ( l ) Ta( l ) A s ( l ) 81.67 N(3) Ta(2) As(2) 88.56 N(2) Ta( l ) A s ( l ) 82.92 N(4) Ta(2) As(2) 73.43 Atom Atom Atom Atom Angle (°) A s ( l ) Ta( l ) Ta(2) As(2) -149.80 It is also useful to compare the total energies of the molecules from the two calculations. The total energies for all optimized compounds (in kJ mol" 1) are given in Table 3.10. In each case, the calculation utilizing the extended L A N L 2 D Z p d basis set is of lower energy. This is due to the larger number of parameters in the extended basis set calculations. The large energy differences between the complexes should not be considered accurate because the calculations do not take into account solvent and other intermolecular effects. However, the calculations do suggest that the trimethyl complex is the least stable of the model complexes, while the tetrahydride is the most stable. Page 101 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Table 3.10. Total energy (in kJ mol"1) for optimized compounds. L A N L 2 D Z Energy L A N L 2 D Z p d Energy ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4A) -1.704868 x l O 6 ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B) -1.704907 x l 0 b ' N A s N ' T a M e 3 (3.5A) -1.317315 x l O 6 ' N A s N ' T a M e 3 (3.5B) -1.317357 x l O6 ( 'NAsN 'Ta ) 2 (u -H ) 4 (3.6A) -2.012252 x l O 6 ( 'NAsN 'Ta ) 2 (u -H) 4 (3.6B) -2.012347 x l O6 The Kohn-Sham orbitals calculated following geometric optimizations of the model complexes offer insight into bonding and potential reactivity pathways. The isosurfaces of the H O M O and H O M O - 1 for the L A N L 2 D Z p d lithium salt calculation (3.4B) are shown in Figure 3.10. The orbitals are virtually isoenergetic and both show the essentially ionic interaction between lithium and the amides, with most density residing in p-type orbitals on the amide nitrogen atoms. This appears to qualitatively fit the reaction o f 3.1 with T a M e 3 C l 2 in that the initial step o f the metathesis is probably the interaction of a nitrogen lone pair with the tantalum center. Page 102 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Figure 3.10. Depictions of the H O M O (left) and H O M O - 1 (right) for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B). The isosurfaces of the L U M O and LUMO+1 for complex 3.4B are shown in Figure 3.11. These orbitals are primarily based on the donor solvent molecules. The diffuse contributions above and below the donor solvent molecules may represent a contribution from the oxygen lone pair that is not interacting with the lithium. The LUMO+1 also has a small contribution from the arsenic. Page 103 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Figure 3.11. Depictions of the L U M O (left) and L U M O + l (right) for ' N A s N ' L i 2 ( 0 M e 2 ) 2 (3.4B). The isosurfaces of the H O M O and H O M O - l , generated following geometric optimization of the L A N L 2 D Z p d 'NAsN 'TaMe3 calculation (3.5B), are shown in Figure 3.12, together with diagrams depicting the interactions. The orbitals are nearly isoenergetic with each other. The H O M O of 3.5B contains significant density in two Ta-Me a-bonding interactions and a rr-bonding interaction between tantalum and an amide lone pair. The H O M O - l isosurface depicts a strong a-bonding interaction between a d^-type orbital on tantalum and an orbital on a methyl carbon. There are also two weak anti-bonding interactions, one a and one n, with amide lone pairs. Both the H O M O and H O M O - l have similarities to the same orbitals of the model [NPN] complex ' N P N ' T a M e 3 9 8 in that both model complexes display Ta-C and T a - N interactions. However, the proximity of the phosphorus is seen in the H O M O of ' N P N ' T a M e 3 in the form of a Ta-P anti-bonding interaction. Other high-energy occupied orbitals, with the exception of the H O M O - 2 , contain additional Ta-Me and T a - N bonding interactions. Page 104 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Figure 3.12. Depictions of the H O M O (top) and H O M O - 1 (bottom) for 'NAsN'TaMe3 (3.5B) together with simplified illustrations of the bonding. The isosurface of the H O M O - 2 for complex 3.5B is shown in Figure 3.13, along with an illustration clarifying the orbital interactions. The H O M O - 2 shows high density on the arsenic donor, accompanied by A s - C bonding interactions with methyl and methylene substituents. It is clearly evident that the arsenic lone pair does not interact with the tantalum center. This is in contrast to the H O M O - 2 of ' N P N ' T a M e 3 where there is significant density associated with the tantalum and a weakly bonding Ta-P interaction is present.9 8 The H O M O - 2 of 3.5B is, however, virtually identical to that of the niobium model complex ' N P N ' N b M e 3 , a complex that, as mentioned earlier, exhibits phosphine dissociation. In summary, the high-energy occupied orbitals of 3.5B exhibit tantalum-methyl a-bonding interactions and 7i-bonding and anti-bonding tantalum-amide interactions, but no tantalum-arsenic interaction. Page 105 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand 0 A s . Figure 3.13. Depictions of the H O M O - 2 o f ' N A s N ' T a M e 3 (3.5B) together with a simplified illustrations of the bonding. The L U M O and L U M O + 1 orbitals for 3.5B are shown in Figure 3.14, together with diagrams depicting the interactions. The orbitals are primarily tantalum based empty d-type orbitals, with some non-bonding density present on a single amide donor. The L U M O s of the [NPN] model complexes ' N P N T a M e 3 and ' N P N ' N b M e 3 are also composed of empty d-type orbitals, and this has been linked to the susceptibility of these complexes to nucleophilic attack. The similarity of the L U M O s for these model complexes suggests that, from an electronic perspective, the reactivity o f these complexes toward nucleophiles is independent of the neutral donor and thus the parent complexes should display similar reactivity. This indicates that a partially open coordination site of complex 3.3 could play a role in the unusual Ta-N bond activation and not a difference in orbitals on the metal centers. In an attempt to gauge the reactivity of model complex 3.5B, the H O M O - L U M O can be calculated. The difference is 514 kJ/mol, significantly larger than the H O M O -L U M O gaps calculated for the model complexes ' N P N ' T a M e 3 (473 kJ/mol) and ' N P N ' N b M e 3 (468 kJ /mol) . 9 8 Typically, a larger H O M O - L U M O gap imparts greater stability to the complex; however, it is not known i f this value is due to relative stability of the H O M O or relative instability in the L U M O . The increased difference could also be due, in part, to the inclusion of diffusion and correlation functions to the basis set for arsenic. Additionally, since it is possible that the hydrogenation o f T a - N bonds follows Page 106 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand hydrogenation of Ta-C bonds, the H O M O - L U M O gaps o f any intermediate complexes could be a more accurate representation of the differences in the reaction pathway between 3.3 and p h [ N P N ] T a M e 3 in their reactions with H 2 . F igure 3.14. Depictions of the L U M O (top) and L U M O + 1 (bottom) for 'NAsN'TaMe3 (3.5B) together with simplified illustrations of the bonding. Isosurfaces of the H O M O and H O M O - 1 orbitals of the L A N L 2 D Z p d ( 'NAsN 'Ta ) 2 (u -H) 4 calculation (3.6B) are shown in Figure 3.15. The H O M O of 3.6B is the Ta-Ta bonding orbital with a small amount of density present on a single amide donor. There is very little contribution from the bridging hydride orbitals in the H O M O . The H O M O - 1 has bonding interactions between a d-type orbital on the metal center and Page 107 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand the hydride ligands, and significant density on a single amide donor. The asymmetry of hydride bonding is readily apparent. Bonding interactions involving the other tantalum and the hydrides occur at lower energies. The L U M O of 3.6B is composed primarily of a pair of empty d-type orbitals in a non-bonding 5 configuration, with some non-bonding density present on a pair of amide donors. The L U M O + 1 is composed of a pair of empty d-type orbitals of a-antibonding symmetry. Isosurfaces for these orbitals are shown in Figure 3.16. The frontier orbitals of 3.6B compare favorably with those o f the model complex ( 'NPN'Ta ) 2 (p -H ) 4 , and the absence of any Ta-As interactions in these orbitals, coupled with a similar absence of Ta-P interactions in the ( 'NPN 'Ta ) 2 (p -H ) 4 model complex, suggests that the hypothetical ( P h [NAsN]Ta) 2 (p -H) 4 and ( p h [NPN]Ta) 2 (p -H) 4 should display similar reactivity with N2. Figure 3.15. Depictions of the H O M O (left) and H O M O - l (right) for ( ' N A s N ' T a ) 2 ( p - H ) 4 (3.6B). Page 108 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Figure 3.16. Depictions of the L U M O (left) and L U M O + 1 (right) for ( ' N A s N ' T a ) 2 ( p - H ) 4 (3.6B). 3.6. Summary and conclusions The chelating diamido arsine ligand p h [ N A s N ] can be synthesized in 78% yield from phenylarsine (PhAsH 2 ) and P h N H S i ( M e 2 ) C H 2 C l as a T H F adduct of the lithium salt, P h [ N A s N ] L i 2 ( T H F ) 2 (3.1). The protonated ligand precursor, p h [ N A s N ] H 2 (3.2), can be synthesized in nearly quantitative yield by reaction of 3.1 with E t 3 N H C l . Reaction of 3.1 with T a M e 3 C l 2 at -78 °C yields the alkyl complex p h [ N A s N ] T a M e 3 (3.3) in 63% yield. The solid-state structure of 3.3 reveals a five-coordinate tantalum with no interaction between the arsenic donor and the metal center. Hydrogenation reactions performed under four atmospheres of hydrogen do not produce the anticipated dinuclear tetrahydride ( p h [NAsN]Ta) 2 (p-H)4 , but instead produce a modest yield of the diaminoarsine 3.2. The observation of methane suggests that the reaction may proceed through a metathesis mechanism, followed by hydrogenation of the tantalum amide bonds leading to the release of the ligand from the metal center as 3.2. Page 109 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Density functional theory calculations have been conducted on the model complexes ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4), ' N A s N ' T a M e 3 (3.5) and ( ' N A s N ' T a ) 2 ( p - H ) 4 (3.6) using the L A N L 2 D Z basis set, and an extended basis set for arsenic, L A N L 2 D Z p d , that contains additional diffusion and polarization functions. The convergence of the tetrahydride model complex 3.6 indicates that D F T is an appropriate technique to model the hypothetical tetrahydride complex ( p h [NAsN]Ta) 2 (p -H )4 . Calculations on the trimethyl model complex 3.5 reveal a five-coordinate complex very similar to the solid-state structure. Similarities in the frontier orbitals of the model complex 3.5 and p h[NPN]TaMe3 indicate that from an electronic perspective, similar reaction pathways should be available to both molecules. This suggests that dissociation of the arsenic donor may play a role in the hydrogenation of the trimethyl complex 3.3. Page 110 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand 3.7. Experimental Section 3.7.1 General Procedures Unless otherwise stated, general procedures were performed as in Section 2.9.1. 3.7.2 Starting Materials and Reagents The compound P h A s H 2 was prepared as in 2.9.3. P h N H S i ( M e 2 ) C H 2 C l , 5 5 and TaMe3Cl 2 1 1 2 were prepared according to literature procedures. TaCls was purchased from S T R E M and sublimed prior to use. Anhydrous Z n C l 2 was purchased from Aldr ich and dried by heating to reflux in excess S O C l 2 under an N 2 atmosphere. E t ^ N H C l was prepared by the reaction o f triethylamine and aqueous hydrochloric acid, and recrystallized from ethanol. High purity hydrogen gas was purchased from P R A X A I R and used as received. Deuterium gas was purchased from Cambridge Isotopes and used as received. 3.7.3 Synthesis, Characterization and Reactivity of Complexes Synthesis of [NAsN]Li2(THF)2 (3.1). To a solution o f P h A s H 2 (2.0 g, 13.0 mmol) and P h N H S i ( M e 2 ) C H 2 C l (5.2 g, 26.0 mmol) in E t 2 0 (100 mL) at 0 °C was added a 1.6M solution of " B u L i in hexanes (32.5 mL, 52.0 mmol) dropwise. The solution was warmed to ambient temperature, stirred for 2 h, and then evaporated to dryness. The residue was extracted into toluene (50 mL) , the solution filtered through Celite and the toluene removed. The colourless residue was slurried in hexanes (20 mL) , T H F was added (3.7 g, 52 mmol) and the solution cooled to -40 °C. The resultant microcrystalline solid was collected, rinsed with a small amount of hexanes to remove coloured impurities, and dried under vacuum. Yie ld : 6.50 g (78%). Calc. M W : 636.70 g mol" 1. X-ray quality crystals of 3.1 were grown from a saturated T H F solution at Page 111 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand -40 °C. 'H N M R (400 M H z , C 6 D 6 , 25 °C): <5 7.71 (d, V H H = 7.1 H z , 2 H , o-AsPh), 7.23 (m, 6H, m-AsPh and w-NPh), 7.15 (t, V H H = 7.3 Hz , 1H, j^-AsPh), 6.86 (d, 3 J H H = 7.9 Hz , 4H, o-NPh), 6.74 (t, 3JHH = 7.2 Hz , 2H,/?-NPh), 3.35 (m, 8H, T H F - O C t f 2 C H 2 ) , 1.27 ( A B d, 2 J H H = 13.7 Hz , 2 H , CH2), 1.20, A B d, 2JHH = 13.7 Hz , 2 H , CH2), 1.11 (s, 8H, T H F -O C H 2 C / / 2 ) , 0.49 (s, 6 H , S i C / / 3 ) , 0.42 (s, 6H, SiC77 3). *H N M R (500 M H z , c/ 8-THF), 25 °C): 6 7.59 (d, 3JHH = 7.3 Hz , 2 H , o-AsPh), 7.29 (t, VHH = 7.3 H z , 2 H , m-AsPh), 7.23 (t, VHH = 7.3 Hz , 1H, p-AsPh) , 6.85 (t, 3JHH = 7.8 Hz , 4 H , w-NPh) , 6.53 (d, 3JHH = 7.7 Hz , 4H, o-NPh), 6.33 (t, 3 J H H = 7.7 Hz , 2H,p -NPh) , 3.62 (m, 8H, T H F - O C f Y 2 C H 2 ) , 1.77 (m, 8H, T H F - O C H 2 C / f 2 ) , 1.15 ( A B d, 2 J H H =13.7 H z , 2 H , S i C / / 2 A s ) , 1.07 ( A B d, 2JHH = 13.7 Hz , 2 H SiCTfcAs), 0.15 (s, 6 H , SiC# 3 ) , 0.13 (s, 6 H , SiC7/ 3 ) . 7U{lU} N M R (155.5 M H z , C 6 D 6 , 25 °C) 5 -1.47 (s). M S (EI) m/z, (%): 492, (20) [ M - ( T H F ) 2 ] + ; 387 (45) [ M -N P h ( T H F ) 2 ] + . Ana l . Calcd. for C 3 2 H 4 7 A s N 2 0 2 S i 2 L i 2 : C , 60.36; H , 7.44; N , 4.40. Found: C, 60.00; H , 7.46; N , 4.73. Synthesis of [ N A s N ] H 2 (3.2). To an intimate mixture of 3.1 (1.0 g, 1.5 mmol) and E t 3 N H C l (0.43 g, 3.11 mmol) was added E t 2 0 (50 mL) . The solution was stirred for 12 h, and then evaporated to dryness. The residue was extracted into toluene (25 m L ) , the resulting solution was filtered through Celite, and the solvent removed under vacuum to yield a colourless o i l that solidified upon extended standing, producing X-ray quality crystals. Y ie ld : 0.69 g (96%). Calc. M W : 480.62 g mol" 1. ' H N M R (400 M H z , C 4 D 8 0 , 25 °C): 8 7.61 (m, 2 H , o-AsPh), 7.28 (m, 3H , w/p-AsPh), 6.98 (m, 4 H , w-NPh), 6.54 (m, 6 H , o/p-NPh), 4.22 (br s, 2H , NH), 1.24 ( A B d, VHH =13 .6 H z , 2 H , S i C / / 2 A s ) , 1.17 ( A B d, 2JHu =13 .6 H z , 2 H , S i C / / 2 A s ) , 0.17 (s, 6H , S i C H 3 ) , 0.07 (s, 6H, S iC# 3 ) . *H N M R (300 M H z , C 6 D 6 , 25 °C): 5 7.57 (m, 2H, A s P h o-H), 7.19 (m, 7H, AsPh mlp-H and N P h m-H), 6.82 (m, 2 H , NPhp-H), 6.58 (m, 4 H , N P h o-H), 3.09 (br s, 2 H , N / / ) , 1.13 ( A B d, 2JHH = 13.6 H z , 2H , S i C / / 2 A s ) , 1.02 ( A B d, 2JHH =13.6 Hz , 2H , S i C / / 2 A s ) , 0.23 (s, 6 H , S i C / / 3 ) , 0.18 (s, 6H, SiC# 3 ) . M S (EI) m/z, (%): 387, (55) [ M - N H P h ] + . Ana l . Calcd. for C 2 4 H 3 3 A s N 2 S i 2 : C , 59.98; H , 6.92; N , 5.83. Found: C , 60.14; H , 7.15; N , 6.06. Page 112 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand Synthesis of " [ N A s N l T a M e s (3.3). A solution o f TaMe3Cl2 (0.47 g, 1.57 mmol) in Et20 (10 mL) was added dropwise to a stirred solution of 3.1 (1.00 g, 1.57 mmol) in E t 2 0 (25 m L ) at -78 °C in the dark. The solution was stirred for 20 min at -78 °C, warmed to - 20 °C, and then evaporated to dryness. The residue was extracted into toluene (15 m L ) , the resulting solution was filtered through Celite, and the solvent removed under vacuum. The resulting solid was washed with a minimal amount of cold pentane to remove coloured impurities and further dried to give 3.3 as a pale yellow solid that was stored in the dark at -40 °C. Yie ld : 0.69 g (63%). Calc . M W : 704.66 g mol" 1 . Crystals o f 3.3 suitable for X - r a y diffraction experiments were grown by slow evaporation of a concentrated benzene solution. XW N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.62 (d, 3 J H H = 6.8 H z , 2 H , o-AsPh), 7.21 (m, 11H, m/p-AsPh and o/m-NPh), 7.03 (t, 3 J H H = 6.8 Hz , 2H,/?-NPh), 1.82 ( A B d, 2 J H H = 14.1 Hz , 2 H , S i C i / 2 A s ) , 1.25 ( A B d, 2JHH =14.1 Hz , 2 H , S i C # 2 A s ) , 1.24 (s, 9 H , TaCf7 3 ) , 0.37 (s, 6H, ring SiCf7 3 ) , 0.02 (s, 6H , ring S i C / / 3 ) . *H N M R (500 M H z , C 4 D 8 0 , 25 °C): 6 7.63 (d, VHH = 7.0 H z , 2 H , o-AsPh), 7.33 (m, 2 H , m-AsPh), 7.28 (m, 5H, / ? -AsPh and m-NPh), 7.16 (m, 2H,j9-NPh), 7.07 (d, 3 J H H = 7.3 Hz , 4 H , o-NPh), 1.87 ( A B d, 2 J H H = 14.2 Hz , 2H, S i C / / 2 A s ) , 1.40 ( A B d, 2JHH = 14.2 Hz , 2H , S i C / / 2 A s ) , 0.69 (s, 9H , T a C / / 3 ) , 0.27 (s, 6H, ring S iC# 3 ) , -0.02 (s, 6 H , ring S i C / / 3 ) . 1 3 C { ' H } N M R (75.4 M H z , C 6 D 6 , 25 °C): 6 144.8 (s, N P h i-Q, 141.4 (s, A s P h i-Q, 132.1 (s, A s P h o-Q, 129.9 (s, AsPhp-C), 129.5 (s, N P h p-C), 129.2 (s, A s P h m-C), 128.6 (s, N P h m-C), 126.1 (s, N P h o-C), 63.6 (s, TaCH 3 ) , 13.2 (s, S i C H 2 A s ) , 2.1 (s, S i C H 3 ) , 1.5 (s, S i C H 3 ) . M S (EI) m/z, (%): 689, (100) [ M - M e f , 673, (92) [ M - H M e 2 ] + . Anal . Calcd. for C 2 7H4oAsN 2 Si 2 Ta: C , 46.02; H , 5.72; N , 3.98. Found: C, 46.22; H , 5.62; N , 4.29. Reaction of P h [ N A s N ] T a M e 3 wi th H 2 . Hydrogen gas was admitted to a Kontes-valve-equipped thick-walled bomb fully immersed in liquid nitrogen containing a freeze-pump-thaw degassed solution of 3.3 (35 mg, 0.050 mmol) in E t 2 0 (10 mL) . The bomb was sealed and allowed to warm to room Page 113 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand temperature. The solution was stirred for 48h during which a colour change from pale yellow to pale tan was noted and a colourless precipitate was deposited on the side of the flask. Removal of the solvent under vacuum gave an oily brown residue. ' H N M R (300 M H z , C6D6, 25 °C) showed resonances attributable to 3.2 in 33% yield relative to an internal standard (ferrocene). Elemental analysis of the isolated material returned data indicating the solids were depleted in carbon and hydrogen relative to 3.3, a representative analysis found: C, 43.33; H , 5.20; N , 4.32. Deuteration experiments were conducted using the same procedure. Page 114 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand 3.8. References (1) McAul i f fe , C . A . In Comprehensive Coordination Chemistry; Wilkinson, G . , Gillard, R. D. , McCleverty, J. A . , Eds.; Pergamon Press, Oxford, 1987; V o l . 2, Chapter 14. (2) Minaham, D . M . A . ; H i l l , W . E . ; McAulif fe , C . A . Coord. Chem. Rev. 1984, 55, 31-54. (3) Butenschon, H . Chem. Rev. 2000,100, 1527-1564. (4) Gavrilova, A . L . ; Bosnich, B . Chem Rev. 2004,104, 349-383. (5) Martell , A . E . ; Hancock, R. D. ; Motekaitis, R. J. Coord. Chem. Rev. 1994, 133, 39-65. (6) Douglas, P. G . ; Feltham, R. D. ; Metzger, H . G . J. Am. Chem. Soc. 1971, 93, 84-90. (7) H i l l , A . M . ; Levason, W. ; Preece, S. R.; Webster, M . Polyhedron 1997, 16, 1307-1314. (8) Pensee, A . A . L . ; Bickley, J.; Higgins, S. J. J. Chem. Soc, Dalton Trans. 2002, 3241-3244. (9) Deutscher, R. L . ; Kepert, D . L . Inorg. Chem. 1970, 9, 2305-2310. (10) Braterman, P. S.; Wilson, V . A . ; Joshi, K . K . J. Organomet. Chem. 1971, 31, 123-129. (11) Brune, H . A . ; Klotzbuecher, R.; Schmidtberg, G . J. Organomet. Chem. 1989, 365, 389-401. (12) Levason, W. ; McAul i f fe , C . A . ; Sedgwick, R. D . J. Organomet. Chem. 1975, 84, 239-245. (13) Roberts, N . K . ; W i l d , S. B . Inorg. Chem. 1981, 20, 1892-1899. (14) Al len , D . G . ; W i l d , S. B . ; Wood, D . L . Organometallics 1986, 5, 1009-1015. (15) Fitzpatrick, M . G . ; Hanton, L . R.; McMorran, D . A . Inorg. Chem. 1995, 34, 4821-4827. Page 115 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand (16) Downard, A . J.; Bond, A . M . ; Clayton, A . J.; Hanton, L . R.; McMorran , D . A . Inorg. Chem. 1996, 35, 7684-7690. Bosnich, B . ; L o , S. T. D . ; Sullivan, E . A . Inorg. Chem. 1975,14, 2305-2310. Hart, R.; Levason, W. ; Patel, B . ; Reid, G . Eur. J. Inorg. Chem. 2001, 2927-2933. Levason, W. ; Matthews, M . L . ; Patel, B . ; Reid, G . ; Webster, M . Dalton Trans. 2004, 20,3305-3312. Ell is , J. E . ; Faltynek, R. A . ; Hentges, S. G . J. Am. Chem. Soc. 1977, 99, 626-627. Schrock, R. R.; Guggenberger, L . J.; English, A . D . J. Am. Chem. Soc. 1976, 98, 903-913. Hale, A . L . ; Levason, W. ; McCullough, F. P. Inorg. Chem. 1982, 21, 3570-3571. Alyea, E . C ; Ferguson, G . ; Somogyvari, A . Inorg. Chem. 1982, 21, 1372-1375. Drew, M . G . B . ; Wilkins , J. D . J. Organomet. Chem. 1974, 69, 271-278. Gray, L . R.; Gulliver, D . J.; Levason, W. ; Webster, M . J. Chem. Soc, Dalton Trans. 1983, 133-141. Davies, J. A . ; Hartley, F. R.; Murray, S. G . Inorg. Chem. 1980,19, 2299-2303. Dutta, R. L . ; Meek, D . W. ; Busch, D . H . Inorg. Chem. 1970, 9, 1215-1226. Song, L . - C ; Jin, G . - X . ; Zhang, W. X . ; Hu , Q . - M . Organometallics 2005, 24, 700-706. Colton, R.; McCormick , M . J. ; Pannan, C. D . Aust. J. Chem. 1978, 31, 1425-1438. Benner, L . S.; Balch, A . L . J. Am. Chem. Soc 1978,100, 6099-6106. Chiswell , B . ; Plowman, R. A . ; Verrall, K . Inorg. Chim. Acta 1971, 5, 579-589. Morris, T. L . ; Taylor, R. C. J. Chem. Soc, Dalton Trans. 1973, 175-179. Sindellari, L . ; Centurioni, P. Ann. Chim. 1966, 56, 379-385. Salem, G . ; W i l d , S. B . Inorg. Chem. 1984, 23, 2655-2663. Jarrett, P. S.; Dhubhghaill; Sadler, P. J. J. Chem. Soc, Dalton Trans. 1993, 1863-1870. (36) Abu-Surrah, A . S.; Lappalainen, K . ; Repo, T.; Kl inga, M . ; Leskela, M . ; Hodali, H . A . Polyhedron 2000,19, 1601-1605. Page 116 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand (37) Harbron, S. K . ; Higgins, S. J.; Hope, E . G . ; Kemmitt, T.; Levason, W . Inorg. Chim. Acta 1987,130, 42-41. (38) Doehring, A . ; Jensen, V . R.; Jolly, P. W. ; Thiel , W. ; Weber, J. C . Organometallics 2001, 20, 2234-2245. (39) Katti, K . V . ; Cavell , R. G . Organometallics 1989, 8, 2147-2153. (40) Katti, K . V . ; Cavell , R. G . Inorg. Chem. 1992, 31, 4231-4235. (41) Taqui Khan, M . M . ; Vijay Sen Reddy, V . Inorg. Chem. 1986, 25, 208-214. (42) Taqui Khan, M . M . ; Paul, P.; Venkatasubramanian, K . ; Purohit, S. J. Chem. Soc, Dalton Trans. 1991, 3405-3412. (43) Fryzuk, M . D . ; Johnson, S. A . ; Patrick, B . O.; Albinati , A . ; Mason, S. A . ; Koetzle, T. F. J. Am. Chem. Soc. 2001,123, 3960-3973. (44) Fryzuk, M . D . ; Love, J. B . ; Rettig, S. J. Organometallics 1998,17, 846-853. (45) Bashall, A . ; Bond, A . D . ; Hopkins, A . D. ; K idd , S. J.; McPart l in, M . ; Steiner, A . ; Wolf, R.; Woods, A . D . ; Wright, D . S. J. Chem. Soc, Dalton Trans. 2002, 343-351. (46) Driess, M . ; Hoffmanns, U . ; Martin, S.; Merz, K . ; Pritzkow, H . Angew. Chem. Int. Ed. 1999, 38, 2733-2736. (47) Bashall, A . ; Garcia, F.; Hopkins, A . A . ; Wood, J. A . ; McPart l in, M . ; Woods, A . D. ; Wright, D . S. Dalton Trans. 2003, 1143-1147. (48) Fryzuk, M . D . ; Shaver, M . P.; Patrick, B . O. Inorg. Chim. Acta 2003, 350, 293-298. (49) Shaver, M . P.; Thomson, R. K . ; Patrick, B . O.; Fryzuk, M . D . Can. J. Chem. 2003,57,1431-1437. (50) Weidenbruch, M . ; Olthoff, S.; Saak, W. ; Marsmann, H . Eur. J. Inorg. Chem. 1998, 1755-1758. (51) Deacon, G . B . ; Forsyth, C. M . ; Scott, N . M . J. Chem. Soc, Dalton Trans. 2001, 2494-2501. (52) Murugavel, R.; Palanisami, N . ; Butcher, R. J. J. Organomet. Chem. 2003, 675, 65-71. (53) Eichhorn, B . ; Noth, H . Z. Naturforsch. B: Chem. Sci. 2000, 55, 352-360. Page 117 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand (54) Westerhausen, M . ; Bol lwein, T.; Karaghhiosoff, K . ; Schneiderbauer, S.; Vogt, M . ; Noth, H . Organometallics 2002, 21, 906-911. (55) Fryzuk, M . D . ; Johnson, S. A . ; Rettig, S. J. J. Am. Chem. Soc. 1998, 120, 11024-11025. (56) Fryzuk, M . D . ; MacKay , B . A . ; Johnson, S. A . ; Patrick, B . O. Angew. Chem. Int. Ed. 2002, 41, 3709-3712. (57) Fryzuk, M . D . ; MacKay , B . A . ; Patrick, B . O. J. Am. Chem. Soc. 2003, 125, 3234-3235. (58) Pugh, S. M . ; Blake, A . J.; Gade, L . H . ; Mountford, P. Inorg. Chem. 2001, 40, 3992-4001. (59) Araujo, J. P.; Wicht, D . K . ; Jr., P. J. B . ; Schrock, R. R. Organometallics 2001, 20, 5682-5689. (60) Schmidt, J. A . R.; Chmura, S. A . ; Arnold, J. Organometallics 2001, 20, 1062-1064. (61) Schrock, R. R.; Lee, J.; Liang, L . - C . ; Davis, W. M . Inorg. Chim. Acta 1998, 270, 353-362. (62) Cook, K . S.; Piers, W. ; Rettig, S. J.; McDonald, R. Organometallics 2000, 19, 2243-2245. (63) Drew, M . G . B . ; Wolters, A . P.; Wilkins, J. D . Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1975, 31, 324-326. (64) Dewan, J. C ; Kepert, D . L . ; Raston, C. L . ; White, A . H . J. Chem. Soc, Dalton Trans. 1975,2031-2038. (65) Mast, K . ; Meiers, J.; Scherer, O. J.; Wolmershauser, G . Z. Anorg. Allg. Chem. 1999, 625, 70-74. (66) Mast, K . ; Scherer, O. J.; Wolmershauser, G . Z Anorg. Allg. Chem. 1999, 625, 1475-1478. (67) Adedeji, F. A . ; Cavell , K . J.; Cavell, S.; Connor, J. A . ; Pilcher, G . ; Skinner, H . A . ; Zafarani-Moattar, M . J. Chem. Soc, Faraday Trans. 1 1979, 603-613. (68) Luo, L . ; L i , L . ; Marks, T. J. J. Am. Chem. Soc 1997,119, 8574-8575. Page 118 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand (69) Kerr, J. A . In CRC Handbook of Chemistry and Physics; 84 [Online] ed.'; Lide, D . R., Ed. ; C R C Press: Boca Raton, F L , 2003. (70) Durgun, E . ; Ciraci , S. D . S.; Gulersen, O. J. Phys. Chem. B 2004,108, 575-582. (71) Fryzuk, M . D . ; Montgomery, C. D . ; Rettig, S. J. Organometallics 1991, 10, 467-473. (72) Fryzuk, M . D . ; Petrella, M . J.; Coffin, R. C ; Patrick, B . O. C. R. Chemie 2002, 5, 451-460. (73) Yamakawa, M . ; Ito, PL; Noyori , R. J. Am. Chem. Soc. 2000,122, 1466-1478. (74) Noyori , R.; Yamakawa, M . ; Hashiguchi, S. J. Org. Chem. 2001, 66, 7931-7944. (75) Abdur-Rashid, K . ; Faatz, M . ; Lough, A . J.; Morris, R. H . J. Am. Chem. Soc. 2001, 123, 7473-7474. (76) Poise, J. L . ; Andersen, R. A . ; Bergman, R. G . J. Am. Chem. Soc. 1998, 120, 13405-13414. (77) Hanna, T. E . ; Keresztes, I.; Lobkovsky, E . ; Bernskoetter, W . H . ; Chirik, P. J. Organometallics 2004, 23, 3448-3458. (78) Berno, P.; Gambarotta, S. Angew. Chem. Int. Ed. 1995, 34, 822-824. (79) Cameron, T. M . ; Ortiz, C . G . ; Ghiviriga, I.; Abboud, K . A . ; Boncella, J. M . J. Am. Chem. Soc. 2002,124, 922-923. (80) Ziegler, T. Chem Rev. 1991, 91, 651-667. (81) Stowasser, R.; Hoffmann, R. J. Am. Chem. Soc. 1999,121, 3414-3420. (82) DeKock, R. L . ; Baerends, E . J.; Hengelmolen, R. Organometallics 1984, 3, 289-292. (83) Bickelhaupt, F. M . ; Baerends, E . J.; Ravenek, W . Inorg. Chem. 1990, 29, 350-354. (84) Fermi, E . Z Phys. 1928, 48, 73. (85) Hohenberg, P.; Kohn, W . Phys. Rev. 1964,136, B864-B871. (86) N i u , S.; Ha l l , M . B . Chem. Rev. 2000,100, 353-403. (87) Gilbert, T. M . ; Hristov, I.; Ziegler, T. Organometallics 2001, 20, 1183-1189. (88) Hristov, I. H . ; Ziegler, T. Organometallics 2003, 22, 3513-3525. (89) Maron, L . ; Eisenstein, O. J. Am. Chem. Soc. 2001,123, 1036-1039. Page 119 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand (90) Perrin, L . ; Maron, L . ; Eisenstein, O. Inorg. Chem. 2002, 41, 4355-4362. (91) Hyla-Kryspin, I.; Gleiter, R. J. Mol. Catal. A: Chem. 2000,160, 115-124. (92) Watson, L . A . ; Yandulov, D . V . ; Caulton, K . G . J. Am. Chem. Soc. 2001, 123, 603-611. (93) Sakaki, S.; Takayama, T.; Sumimoto, M . ; Sugimoto, M . J. Am. Chem. Soc. 2004, 126, 3332-3348. (94) Veige, A . S.; Slaughter, L . M . ; Wolczanski, P. T.; Matsunaga, N . ; Decker, S. A . ; Cundari, T. R. J. Am. Chem. Soc. 2001,123, 6419-6420. (95) Daff, P. J.; Etienne, M . ; Donnadieu, B . ; Knottenbelt, S. Z . ; McGrady, J. E . J. Am. Chem. Soc. 2002,124, 3818-3819. (96) Stranger, R.; McGrady, J. E . ; Lovel l , T. Inorg. Chem. 1998, 37, 3802-3808. (97) L i u , D . ; Lam, K . ; L i n , Z . J. Organomet. Chem. 2003, 148-154. (98) Shaver, M . P., Ph.D. Thesis; University of British Columbia, 2004. (99) Kanematsu, N . ; Ebihara, M . ; Kawamura, T. Inorg. Chim. Acta 2001, 323, 96-104. (100) Galiano, L . ; Alcami , M . ; M o , O.; Yanez, M . ChemPhysChem 2003, 4, 72-78. (101) Matsubara, T. Organometallics 2003, 22, 4286-4296. (102) Machura, B . ; Jaworska, M . ; Kruszynski, R. Polyhedron 2004, 23, 2523-2531. (103) Guerraze, A . E . ; Anane, H . ; Serrar, C ; Es-sofi, A . ; Lamsabhi, A . M . ; Jarid, A . J. Mol. Struct. (Theochem) 2004, 709, 117-122. (104) Frisch, M . J . ; Trucks, G . W. ; Schlegel, H . B . ; Scuseria, G . E . ; Robb, M . A . ; Cheeseman, J. R.; Zakarzewski, V . G . ; Montgomery, J. A . ; Stratmann, R. E . ; Burant, J. C ; Dapprich, S.; Mi l l am , J. M . ; Daniels, A . D . ; Kudin , K . N . ; Strain, M . C ; Farkas, O.; Tomasi, J. ; Petersson, G . A . ; Ayala , P. Y . ; C u i , Q.; Morokuma, K . ; Mal ick, D . K . ; Rabuck, A . D . ; Raghavachari, K . ; Foresman, J. B . ; Cioslowski, J.; Ortiz, J. V . ; Stefanov, B . B . ; L u i , G . ; Liashenko, A . ; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L . ; Fox, D. J.; Kieth, T.; Al -Laham, M . A . ; Peng, C. Y . ; Nanayakkara, A . ; Gonzalez, C ; Challacombe, M . ; G i l l , P. M . W.; Johnson, B . G. ; Chen, W. ; Wong, M . W. ; Andres, J. L . ; Head-Gordon, M . ; Repogle, E . S.; Pople, J. A . ; Gaussian 98, revision a.9, Gaussian, Inc.: Pittsburgh, P A , 1998. (105) Becke, A . D . J. Chem. Phys. 1993, 98, 5648-5652. Page 120 References begin on page 115. Chapter Three: Tantalum coordination chemistry supported by a diamido-arsine ligand (106) Hay, P. J.; Wadt, W . R. J. Chem. Phys. 1985, 82, 270-283. (107) Magnusson, E . J. Am. Chem. Soc. 1993,115, 1051-1061. (108) Basch, H . ; Musaev, D . G . ; Morokuma, K . ; Fryzuk, M . D . ; Love, J. B . ; Seidel, W. W. ; Albinati , A . ; Koetzle, T. F.; Klooster, W. T.; Mason, S. A . ; Eckert, J. J. Am. Chem. Soc. 1999,121, 523-528. (109) Basch, H . ; Musaev, D . G . ; Morokuma, K . J. Am. Chem. Soc. 1999, 121, 5754-5761. (110) Check, C . E . ; Faust, T. O.; Bailey, J. M . ; Wright, B . J . ; Gilbert, T. M . ; Sunderlin, L . S . J . Phys. Chem. A 2001,105, 8111-8116. (111) Mahon, M . F.; Moldovan, N . L . ; Mol loy , K . C ; Muresan, A . ; Silaghi-Dumitrescu, I.; Silaghi-Dumitrescu, L . Dalton Trans. 2004, 4017-4021. (112) Schrock, R. R.; Sharp, P. R. J. Am. Chem. Soc. 1978,100, 2389-2399. Page 121 References begin on page 115. Chapter Four Synthesis of bis(aryloxy)phosphines as ligands for early transition metals 4.1. Introduction In chapter one the macrocyclic and chelating mixed-donor phosphorus amide ligands [P2N2] and [NPN] were discussed along with their early transition-metal coordination chemistry. Chapters two and three presented chemistry of more weakly donating ligands derived from the substitution of arsenic for phosphorus in the [P2N2] and [NPN] ligand systems, respectively. This chapter takes the substitution of [NPN] donor atoms in a different direction with the incorporation of a more strongly donating oxide in place of the amido nitrogen. Chapter one briefly mentioned recent work with [NPN] that has focused on alteration of the ligand backbone, with the synthesis of arene bridged ligands. 1 A major advantage of an arene-bridged [NPN] ligand is the removal of the water and oxygen sensitive S i - N linkage, potentially leading to the synthesis of oxygen and water stable transition metal coordination complexes. Unanticipated ligand rearrangements following addition of alkyl silanes to the complex (ph[NPN]Ta)2(|a-H)2(p-r)1:ri2-N2) have also Page 122 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals focused attention on the flexibility of the [NPN] framework, thus making the increased rigidity o f the arene linkage desirable. Incorporation o f an oxygen donor into an arene-bridged ligand system can be accomplished through the use of substituted phenoxides (generally called aryloxides) derived from phenol. Phenol, or carbolic acid (C6H5OH), is primarily a man-made compound, although it does exist in decaying organic matter. First isolated by Friedrich Ferdinand Runge through the distillation of coal tar,2 phenol is now largely produced by the cumene process, which makes acetone and phenol by oxidation of cumene (C6H5-CH(CH3)2), itself obtained from the Friedel-Crafts alkylation of benzene with propene. 3 ' 4 Phenol has antimicrobial properties and was used by Sir Joseph Lister in his pioneering antiseptic surgery. It is also used in the synthesis of pharmaceuticals, primarily aspirin, as well as its derivatives. The main use of phenol is in resins and plastics. When Dr. Leo Baekeland mixed phenol and formaldehyde under heat and pressure he synthesized the first truly synthetic plastic in the form of a chemically stable phenolic resin, which became known as Bakelite. 5 Substituted phenols are used commonly as antioxidants in a variety of applications. For example, the phenols B H A (a mixture of 3-r-butyl-4-hydroxyanisole and 2-/-butyl-4-hydroxyanisole) and B H T (3,5-di-/-butyl-4-hydroxytoluene) shown in Figure 4.1 are often added to food, food packaging and some cosmetic products to prevent the oxidation of fats.6'7 O' OH OH BHA BHT Figure 4.1. Food industry antioxidants B H A and B H T . Page 123 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals The coordination chemistry of aryloxide ligands has experienced rapid growth starting in the second half of the last century.8 Monodentate aryloxide ligands have been utilized extensively, particularly substituted aryloxides that possess substantial steric 9 13 bulk. Figure 4.2 shows several common monodentate aryloxide ligands. " (c) Figure 4.2. Monodentate aryloxides: (a) phenoxide, (b) 3,5-bistrifluoromethylphenoxide, (c) 2,4,6-tri-t-butylphenoxide, (d) 2,6-diisopropyl-phenoxide. A lka l i metal aryloxides, derived from deprotonation of substituted phenols, are an important group of compounds, primarily due to their ability to carboxylate activated C-H bonds. The reaction of sodium phenolate (CeFLjONa) with C O 2 leads to the formation of sodium salicylate (sodium o-hydroxybenzoate) in what is known as the Kolbe-Schmitt reaction. 1 4 This well known reaction is the starting point for the manufacture of many pigments, fertilizers and pharmaceuticals such as aspirin. Expansion of this chemistry to other alkali metals has shown a strong dependence on the cation involved. 1 5 Reaction of potassium phenolate with C O 2 produces a mixture of o- and /?-hydroxybenzoate. Linked aryloxide ligands are accessible through various synthetic methods. The strong ortho metallation directing effect of the phenol means that in linked aryloxide 16 18 ligands the aryloxide units are almost exclusively connected at the ortho positions. This has resulted in legions of orf/zo-substituted bidentate aryloxide ligands in the Page 124 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals 19 22 23 24 25 26 literature, including ligands containing phosphorus, " oxygen, ' sulphur, carbon, and tellurium. 2 7 Two common examples are shown in Figure 4.3. A variant diaryloxide ligand is the 2,2'-methylene-bis(phenoxide) ligand where two phenoxides are joined by a methylene bridge. 2 8 The introduction of substituents to the ortho positions of para-substituted phenols can be achieved by electrophilic aromatic substitution. Figure 4.3. Bidentate aryloxide ligands: (a) catecholate, (b) 2-dipheny lpho sphinophenolate. Multidentate linked aryloxide ligands bridged by methylene groups are synthesized by controlling the substitution pattern of the phenol in condensation reactions with phenols and formaldehyde. Control of ortho substituents on the phenol can give rise to the bidentate ligand mentioned above or tridentate ligands such as 2,6-bis(4-f-butyl-6-29 methylsalicyl)-4-/-butylphenoxide shown in Figure 4.4. Me fBu Me Figure 4.4. A linked tridentate aryloxide ligand. The condensation of para-substituted phenols with formaldehyde gives rise to the calix[«]arenes, an important class of macrocyclic ligands (Figure 4.5). " Calixarenes Page 125 References begin on page 154. Chapter Four: Synthesis ofbis(aryloxy)phosphines as ligands for early transition metals possess a unique molecular architecture with well-defined hydrophobic and hydrophilic regions that make these compounds excellent hosts for neutral and ionic species. Calixarenes have also been investigated as building blocks for supramolecular systems where calixarenes are coupled together or with other macrocycles. Industrially, calixarenes are used in a variety of processes, including stabilizing organic polymers, additives in instant adhesives, phase transfer agents and catalysis. A great deal of research continues to focus on the use of calixarenes for the separation of metal cations, particularly for the separation and recovery of radioactive nuclides. 3 4" 3 6 Figure 4.5. A aryloxide macrocycle: calix[4]arene. Alteration of the bridging moiety in linked aryloxides can be used to generate potentially tridentate mixed-donor ligands. This has led to a large family of ligands with arlyoxides. Ligands of this type with bridging phosphines are of particular interest due to the pairing of hard oxide and soft phosphine donors. The parent ligand bis(o-phenoxy)phenylphosphine has been reported, 4 2 ' 4 3 as have several containing phenoxides with substituents distributed around the aromatic rings. 4 4 " 4 6 A bulky bis(7-butyl) substituted version seemed a particularly interesting target due to its potential steric bulk. The ligand bis(3,5-r-butyl-2-phenoxy)phenylphosphine [OPO] was reported in 2000 by the Chaudhuri group and its synthesis is shown in Scheme 4 .1 . 4 7 Bromination of 2,4-di-r-butylphenol, then lithium-halogen exchange followed by coupling with such donors as nitrogen, 37,38 sulphur, 3 9 tellurium, 4 0 and selenium 4 1 bridging two Page 126 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals dichlorophenylphosphine and an aqueous work up gave the desired protonated ligand in very modest yield. Scheme 4.1 Limitations in the synthesis - the use of carbon tetrachloride chief among them -and the historical utility of lithium salt metathesis as a method for introducing ligands onto early transition metals necessitated modification of the synthetic scheme. This chapter presents the synthesis of the lithium salts ( p h[OPO]Li2)2(THF)4 (4.1) and ( ( P r [OPO]Li 2 )2(THF)4 (4.2), the protonated ligands p h [ O P O ] H 2 (4.5) and i P r [ O P O ] H 2 (4.6), and the potassium derivatives ( P h [ O P O ] K 2 ) 2 ( T H F ) 6 (4.7) and ( ' P r [OPO]K 2 ) 3 (THF)3 (4.8). Page 127 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals 4.2. Synthesis ofR[OPO]Li2 complexes Synthesis of the R [ O P O ] L i 2 ( T H F ) 2 complexes is shown in Scheme 4.2. Addition of «-bromosuccinimide (NBS) to a solution of the 2,4-di-r-butylphenol in acetonitrile affords the desired bromide as a colourless solid in 83% yield. The bromination reaction is performed under air, and the product dried under vacuum. Reaction of two equivalents of the bromophenol with R P C 1 2 (R = Ph, 'Pr) in the presence of " B u L i yields the crude product as a cream-coloured solid. Addition of excess T H F to a hexanes slurry of the crude product affords the T H F adducts ( p h [ O P O ] L i 2 ) 2 ( T H F ) 4 (4.1) and ( / P r [ O P O ] L i 2 ) 2 ( T H F ) 4 (4.2) as colourless solids, in 70% and 51% yield respectively. Scheme 4.2 Page 128 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals X-ray quality crystals of 4.1 containing three molecules of co-crystallized solvent were grown by slow evaporation of a saturated benzene solution. The solid-state molecular structure of 4.1 contains two independent but structurally similar molecular fragments in the asymmetric unit. One of these is presented in Figure 4.6, along with its crystallographically related fragment; crystallographic data is given in Table A - 4 of the Appendices, and selected bond distances and angles are collected in Table 4.1. The structure is dimeric with the two p h [OPO]Li2 fragments bound via L i - 0 bonds forming a ladder like structure composed of Li202 tetragons. Tetragons like these are very common in lithium oxide and phenoxide chemistry, 4 8" 5 1 although typically they form enclosed cubic or hexagonal structures. Each lithium is four-coordinate; L i ( l ) is bound by three [OPO] oxygens and P ( l ) , while Li(2) is to bound by two [OPO] oxygens and both T H F molecules. The L i - 0 and L i - P bond distances agree well with literature values. 5 2" 5 6 It is interesting to compare the structure of 4.1 to that of the p h [ N A s N ] lithium salt 3.1, where the bulkier and more flexible nature of the ligand prohibits dimerization, and a T H F donor is bound to each lithium, even though the complex has a similar Li2N2 core. Mass spectral analysis confirmed the dimeric nature of 4.1 with the observation of a mass peak corresponding to the dimer with loss of the T H F donors. In solution 4.1 displays C s symmetry, with resonances for the ^-butyl groups appearing as two distinct singlets in the ' H N M R spectrum. Page 129 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Figure 4.6. Molecular structure (ORTEP) of ( p t l [ O P O ] L i 2 ) 2 ( T H F ) 4 , 4.1. Ellipsoids are drawn at 50% probability. Table 4.1. Selected bond distances (A), bond angles (°), and dihedral angles (°) for ( p h [ O P O ] L i 2 ) 2 ( T H F ) 4 , 4.1. Atom Atom Distance (A) Atom Atom Distance (A) L i ( l ) P ( l ) 2.499(3) Li(2) 0(1) 1.936(3) L i ( l ) 0(1) 1.948(3) Li(2) 0(2) 2.148(3) L i ( l ) 0(2) 2.016(3) Li(2) 0(3) 1.981(3) L i ( l ) 0(2*) 1.890(3) Li(2) 0(4) 1.994(3) Page 130 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) P( l ) L i ( l ) 0(1) 79.76(10) 0(1) Li(2) 0(2) 93.91(13) P ( l ) L i ( l ) 0(2) 81.40(10) 0(1) Li(2) 0(4) 113.89(15) P ( l ) L i ( l ) 0(2*) 136.55(15) 0(1) Li(2) 0(3) 105.51(15) 0(1) L i ( l ) 0(2) 97.81(13) 0(2) Li(2) 0(3) 111.82(15) 0(1) L i ( l ) 0(2*) 142.18(16) 0(2) Li(2) 0(4) 123.16(15) 0(2) L i ( l ) 0(2*) 98.16(12) 0(3) Li(2) 0(4) 106.98(15) L i ( l ) 0(2) L i ( l * ) 81.84(12) L i ( l ) 0(2) Li(2) 76.48(12) L i ( l ) 0(1) Li(2) 83.23(13) Atom Atom Atom Atom Angle (°) L i ( l ) 0(2) L i ( l * ) 0(2*) 0.0 0(1) L i ( l ) 0(2) Li(2) -21.45(12) The isopropyl derivative 4.2 shows similar symmetry in solution, and a mass spectrum confirms a similar dimeric structure. A l l attempts to crystallize 4.2 failed to yield X-ray quality crystals. However, the presence of trace amounts of oxygen and water during the evaporation of a saturated benzene solution of 4.2 produced X-ray quality crystals of the related phosphine oxide complex [ , P r[OP(=0)0]Li2(H20)]2 (4.2-0), shown in Figure 4.7. Unlike 4.1, which can be exposed to air for several minutes in solution before phosphine oxidation is noticeable, 4.2 is very sensitive to oxygen, and oxidizes completely in minutes upon exposure to air. The solid-state molecular structure of 4.2-0 is presented in Figure 4.8; crystallographic data is presented in Table A-4 of the Appendices, and selected bond distances and angles in Table 4.2. Structurally, 4 .2-0 is a dimer, and the unit cell contains four equivalents of co-crystallized benzene. Severe disorder in the water molecule, 0(4), prohibits location of the attached protons. Like 4.1, the core of 4.2 is composed of Li202 tetragons, arranged in this structure not as a ladder but as corners of two half-cubes that share a face, a geometry that is rare in the literature. 4 9 ' 5 7 Each lithium is four-coordinate; the L i - 0 bond distances compare well with Page 131 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals that in 4.1 and the phosphorus oxygen double bond is reflected in the P - 0 bond distance of 1.52 A, which is toward the long end of the literature values. 5 8 ' 5 9 Figure 4.7. Diagram of f r [ O P ( = 0 ) 0 ] L i 2 ( H 2 0 ) ] 2 , 4.2-0. Figure 4.8. Molecular structure (ORTEP) of [ , P r [OP(=0)0 ]L i 2 (H 2 0) ] 2 , 4.2-0. Ellipsoids are drawn at 50% probability. Page 132 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Table 4.2. Selected bond distances (A), bond angles (°), and dihedral angles (°) for [ , P r [OP(=0)0 ]L i 2 (H 2 0) ] 2 , 4.2-0. Atom Atom Distance (A) Atom Atom Distance (A) L i ( l ) 0(1) 1.854(4) Li(2) 0(1) 1.916(4) L i ( l ) 0(2) 1.870(4) Li(2) 0(2*) 1.901(4) L i ( l ) 0(3) 1.975(4) Li(2) 0(3*) 2.026(5) L i ( l ) 0(3*) 1.991(4) Li(2) 0(4) 2.033(13) P( l ) 0(3) 1.5209(17) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) P ( l ) 0(3) L i ( l ) 119.04(15) L i ( l ) 0(1) Li(2) 85.3(2) P( l ) 0(3) L i ( l * ) 117.66(15) 0(1) Li(2) 0(3*) 93.3(2) P ( l ) 0(3) Li(2*) 154.24(17) Li(2) 0(3*) L i ( l ) 79.00(17) 0(3) P ( l ) C(13) 105.51(11) 0(3*) L i ( l ) 0(1) 96.37(19) L i ( l ) 0(3) L i ( l * ) 85.79(18) L i ( l ) 0(2) Li(2*) 85.56(19) 0(3) L i ( l * ) 0(3*) 94.21(18) 0(2) Li(2*) 0(3) 93.4(2) L i ( l * ) 0(3*) L i ( l ) 85.79(18) Li(2*) 0(3) L i ( l ) 79.60(17) 0(3*) L i ( l ) 0(3) 94.21(18) 0(3) L i ( l ) 0(2) 96.05(19) Atom Atom Atom Atom Angle (°) L i ( l ) 0(3) L i ( l * ) 0(3*) 0.0 0(1) L i ( l ) 0(3*) Li(2) 18.4(2) 0(2) L i ( l ) 0(3) Li(2*) 17.3(2) The modest yields for these lithium salt syntheses, particularly the isopropyl derivative, suggest that undesirable side products are formed during the reactions. For instance, in the synthesis of 4.1 leaving a concentrated toluene solution of the crude product, prior to the addition of T H F , to stand overnight deposits a small amount of Page 133 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals colourless crystals that have been characterized by X-ray crystallography as [ p h [OPO]Li2 (ArOLi)]2 (4.3), shown in Figure 4.9. The solid-state structure is presented in Figure 4.10; crystallographic data is given in Table A-5 of the Appendices, and selected bond distances and angles in Table 4.3. The complex is a dimer like the previous lithium salts, and the unit cell contains three molecules of co-crystallized toluene. Examination of the structure reveals two molecules of p h [ O P O ] L i 2 and two molecules of lithium 2,4-di-r-butylphenoxide arranged in a ladder o f five L i 2 0 2 tetragons. A s mentioned earlier, such tetragons are very common in lithium oxide chemistry, but the vast majority of such complexes with three or more tetragons form closed cubane or hexagonal structures, the open ' S ' shape of 4.3 is very rare. 6 0 The complex contains three distinct lithium coordination environments. L i ( l ) is four-coordinate, bound by two [OPO] oxygens, the A r O , and a phosphorus; while Li(2) is only two-coordinate. Li(3) is three-coordinate, bound by two [OPO] oxygens and the A r O . L i - 0 and L i - P distances agree well with other complexes in this chapter and with literature values. 5 2" 5 6 In solution 4.3 is the only lithium complex of [OPO] to display phosphorus lithium coupling, the P{ H} N M R spectrum is a 1:1:1:1 quartet with a ^ p y coupling of 107.1 Hz , a value on the large end of the 35-122 H z range observed for similar lithium phosphide complexes. 6 1" 6 3 Evaporation of the hexanes filtrate from the isolation of 4.1 yielded a residue that when examined by ' H and 31 1 P{ H} N M R spectroscopy showed several uncharacterized side-products in addition to 4.3. Page 134 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Figure 4.9. Diagram of [™[OPO]Li 2 (ArOLi)] 2 , 4.3. Figure 4.10. Molecular structure (ORTEP) of f h [ O P O ] L i 2 ( A r O L i ) ] 2 , 4.3. Ellipsoids are drawn at 50% probability. Page 135 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Table 4.3. Selected bond distances (A), bond angles (°), and dihedral angles (°) for [ p h [ O P O ] L i 2 ( A r O L i ) ] 2 , 4.3. Atom Atom Distance (A) Atom Atom Distance (A) L i ( l ) P ( l* ) 2.466(4) Li(3) 0(1) 1.897(5) L i ( l ) 0(1) 1.960(4) Li(3) 0(2*) 1.825(5) L i ( l ) 0(1*) 2.084(5) Li(3) 0(3*) 2.051(5) L i ( l ) 0(3) 1.883(5) Li(2) 0(3) 1.870(5) Li(2) 0(2) 1.849(5) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) P( l* ) L i ( l ) 0(1) 116.6(2) L i ( l ) 0(1*) Li(3*) 79.47(19) P( l*) L i ( l ) 0(1*) 81.09(14) 0(1*) Li(3*) 0(3) 98.7(2) P( l* ) L i ( l ) 0(3) 125.2(2) Li(3*) 0(3) L i ( l ) 80.64(19) L i ( l ) P ( l* ) C ( l ) 96.44(13) 0(3) L i ( l ) 0(1*) 98.0(2) 0(1) L i ( l ) 0(1*) 96.37(18) Li(2) 0(3) Li(3*) 79.7(2) L i ( l ) 0(1*) L i ( l * ) 116.6(2) 0(3) Li(3*) 0(2) 93.0(2) 0(1*) L i ( l * ) 0(1) 96.37(14) Li(3*) 0(2) Li(2) 86.4(2) L i ( l * ) 0(1) L i ( l ) 116.6(2) 0(2) Li(2) 0(3) 98.4(2) Atom Atom Atom Atom Angle (°) L i ( l ) 0(1) L i ( l * ) 0(1*) 0.0 0(3) L i ( l ) 0(1*) Li(3*) 14.0(2) Li(2) 0(3) Li(3*) 0(2) -11.7(2) Following the isolation of 4.2, concentration of the hexanes filtrate by slow evaporation deposited colourless crystals of X-ray quality. The solid-state structure of [ ' P r [ 0 P 0 ] L i 3 C l ( A r 0 L i ) ] ( T H F ) 3 (4.4) is shown in Figure 4.11, crystallographic data is given in Table A-5 of the Appendices, and selected bond distances and angles are Page 136 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals collected in Table 4.4. The structure reveals a cubane geometry containing one molecule of , P r [ O P O ] L i 2 , a molecule of lithium 2,4-di-r-butylphenoxide and lithium chloride. Cubane geometries are common in lithium oxide chemistry, 6 4 ' 6 5 although incorporation of a chloride in place of an oxygen is much less common, only three examples are known. 6 6 ' 6 7 Lithium chloride adducts, or 'ate' complexes, are very common in early transition metal and lanthanide chemistry; 6 8 the electron deficient nature of the metal center probably makes elimination of L i C l unfavorable. 6 9 ' 7 0 In complexes containing alkyloxide or aryloxide ligands retention of lithium chloride is partially driven by the oxophilic nature of l i th ium. 6 7 ' 7 1 Each lithium is four-coordinate, and L i - O , L i - P and L i - C l bond distances agree well with previous complexes in this chapter and with literature values. 5 2 " 5 5 ' 6 6 ' 6 7 Examination of the residue by ' H and 3 1 P { 1 H } N M R spectroscopy following evaporation of the remaining filtrate showed several additional materials in addition to 4.4. Because complexes 4.3 and 4.4 form capriciously during their respective syntheses, and the amount formed can vary considerably, no percentage yields were determined. Figure 4.11. Molecular structure (ORTEP) of [ , P r [ O P O ] L i 3 C l -(ArOLi)](THF)3, 4.4. Ellipsoids are drawn at 50% probability. Page 137 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Table 4.4. Selected bond distances (A), bond angles (°), and dihedral angles (°) for [ , P r [OPO]L i 3 Cl (ArOLi ) ] (THF) 3 , 4 . 4 . Atom Atom Distance (A) Atom Atom Distance (A) L i ( l ) 0(1) 2.027(4) Li(2) 0(1) 2.000(4) L i ( l ) 0(4) 1.933(5) Li(2) 0(2) 1.999(4) L i ( l ) C l ( l ) 2.445(5) Li(2) 0(3) 1.929(4) Li(3) 0(1) 1.999(3) Li(2) C l ( l ) 2.445(4) Li(3) 0(2) 1.810(5) Li(3) P ( l ) 2.340(5) Atom Atom Atom Angle (°) Atom Atom A t o m Angle (°) 0(1) Li(2) 0(2) 96.11(16) C l ( l ) Li(2) 0(2) 95.80(16) Li(2) 0(2) Li(3) 82.83(16) Li(2) 0(2) Li(2*) 92.5(2) 0(2) Li(3) 0(1) 102.61(18) L i ( l ) 0(1) Li(3) 82.99(15) Li(3) 0(1) Li(2) 78.28(18) 0(1) Li(3) 0(1*) 96.8(2) L i ( l ) 0(1) Li(2) 88.50(19) P ( l ) Li(3) 0(1) 86.40(15) 0(1) Li(2) C l ( l ) 100.15(15) P ( l ) Li(3) 0(2) 166.2(3) Li(2) C l ( l ) L i ( l ) 70.16(12) 0(4) L i ( l ) 0(1) 120.79(17) C l ( l ) L i ( l ) 0(1) 99.39(17) 0(4) L i ( l ) C l ( l ) 116.7(2) 0(3) Li(2) 0(1) 132.7(2) 0(3) Li(2) C l ( l ) 114.07(17) 0(3) Li(2) 0(2) 111.01(19) Atom Atom Atom Atom Angle (°) L i ( l ) 0(1) Li(3) 0(1*) 11.3(2) Li(3) 0(2) Li(2*) 0(1*) 3.2(2) C l ( l ) Li(2) 0(2) Li(2*) 15.2(2) In addition to the noted modest yields, the presence of lithium 2,4-di-r-butylphenoxide in both 4.3 and 4.4 suggests complications either with the lithiation of the Page 138 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals bromophenol, or the reaction of the dilithium phenolate with the dichlorophosphine. Although the bromophenol was dried prior to use, any water present would be expected to react quickly with B u L i and potentially lower the yield of the dilithium phenolate. Deprotonation of the acidic phenol proton by organolithium reagents is known to occur faster than lithium-halide exchange, 1 7 thus any deficiency in B u L i would likely result in the persistent presence of the monolithio intermediate. However, the absence of bromide in 4.3 or 4.4 suggests it is not incomplete reaction of the bromophenol that is giving rise to these impurities. A plausible explanation for the presence of lithiated phenol is reaction of the dilithium phenolate with adventitious water, as shown in Scheme 4.3. Scheme 4.3 4.3. Synthesis ofR[OPO]H2 ligand precursors Attempts to directly protonate the crude lithium salt in the manner of the Chaudhuri synthesis yield mixtures from which only small amounts of the protonated ligand can be isolated. A more fruitful synthesis of the protonated ligand precursors R [ O P O ] H 2 is outlined in Equation 4.1. Reaction of the lithium salt, 4.1 or 4.2, with four equivalents of E t 3 N H C l in diethyl ether gives the desired products, p h [ O P O ] H 2 (4.5) or , P r [ O P O ] H 2 (4.6), in 97% and 96% yields respectively. J H and 3l?{lH) N M R spectra of 4.5 are consistent with the literature values 4 7 The 3 1 P { ' H } N M R spectrum of 4.6 displays a singlet at £ - 6 1 . 6 , slightly upfield from that observed for 4.5, reflecting the more basic Page 139 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals nature of the alkyl phosphine. The ' H N M R spectrum of 4.6 contains two singlet resonances for the r-butyl groups, and a characteristic doublet of septets for the isopropyl methine proton coupled to both phosphorus and the methyl groups. Resonances for the methyl groups appear in a doublet of doublets pattern. (4.1) X-ray quality crystals of 4.5 containing three equivalents of co-crystallized solvent were grown by slow evaporation of a saturated benzene solution. The solid-state structure is presented in Figure 4.12, crystallographic data is given in Table A - 5 of the Appendices, and selected bond distances and angles are collected in Table 4.5. The unit cell parameters are identical to those reported for the related phosphine oxide compound. 4 7 This may seem surprising at first; however, the structure shows how the oxygen of a phosphine oxide could fit easily into the molecule without disturbing the structure. In addition, the phenolic hydrogens, which were located in the diffraction pattern and refined isotropically, are well positioned to engage in hydrogen bonding to a phosphine oxide. Phosphine/phosphine oxide systems with identical cell parameters are Page 140 References begin on page 154. Chapter Four: Synthesis ofbis(aryloxy)phosphines as ligands for early transition metals known, 7 2 and solid-state structures have been reported with partial oxidation of the phosphine - and thus fractional occupation in the crystal lattice. 7 3" 7 5 The phenol rings in 4.5 are not parallel, but twisted with respect to each other by 23°, a dihedral angle measured using carbon atoms attached to the phenol oxygen and the phosphorus in both rings. This method is used for all phenol ring dihedral angles of the [OPO] complexes. Figure 4.12. Molecular structure (ORTEP) of ™[OPO]H 2 4.5. Ellipsoids are drawn at 50% probability. Table 4.5. Selected bond distances (A), bond angles (°), and dihedral angles (°) for p h [ O P O ] H 2 4.5. Atom Atom Distance (A) Atom Atom Distance (A) P( l ) C ( l ) 1.828(2) 0(1) C(2) 1.375(2) P ( l ) C(7) 1.826(2) 0(2) C(8) 1.377(2) 0(1) H ( l ) 0.901(2) P ( l ) C(13) 1.824(2) 0(2) H(2) 0.950(2) Page 141 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) C ( l ) P ( l ) C(7) 102.31(9) C(2) 0(1) H ( l ) 107.04(10) C(7) P ( l ) C(13) 106.01(9) C(8) 0(2) H(2) 105.46(10) C ( l ) P ( l ) C(13) 107.03(10) Atoms Atoms Angle (°) Phenol ring Phenol ring -23.0 4.4. Synthesis ofR[OPO]K2 complexes The synthesis of the R [OPO] potassium derivatives is outlined in Equation 4.2. Reaction of the protonated ligands 4.5 or 4.6 with an excess of K H in T H F affords the products ( p h [ O P O ] K 2 ) 2 ( T H F ) 6 (4.7) and ( , P r [ O P O ] K 2 ) 3 ( T H F ) 3 (4.8) in 92.3% and 71.0% yield respectively. (4.2) Page 142 References begin on page 154. Chapter Four: Synthesis ofbis(aryloxy)phosphines as ligands for early transition metals X-ray quality crystals of 4.7 containing three molecules of co-crystallized solvent were grown by slow evaporation of a saturated T H F solution at —40 °C. The solid-state structure is presented in Figure 4.13; crystallographic data is given in Table A - 6 of the Appendices, and selected bond distances and angles in Table 4.7. Structurally, 4.7 is a symmetrical dimer with two crystallographically related fragments. Unlike the lithium complexes where the smaller size of lithium permits them to bridge the oxygens of a single [OPO] molecule in a L i 2 0 2 tetragon, the larger potassium ions in 4.7 bridge adjacent p h [ O P O ] molecules in K 2 0 2 tetragons - for example, K( l ) -0 ( l ) -K(2 ) -0 (2 ) . K ( l ) is six-coordinate and bound to two phosphorus atoms, while K(2) is five-coordinate, bound only to one phosphorus. Four T H F molecules are terminally bound to potassium ions and two are bridging potassium ions. Although the observed K - 0 bond distances in the structure of 4.7 vary by almost 0.4 A, they agree well with literature values. 7 6" 7 8 The 79 81 K - P bond distances also agree well with literature values. Figure 4.13. Molecular structure (ORTEP) of (™[OPO]K 2 ) 2 (THF) 6 , 4.7. Ellipsoids are drawn at 50% probability. Carbon atoms of the T H F ligands removed for clarity. Page 143 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Table 4.6. Selected bond distances (A) and bond angles (°) for ( p h [ O P O ] K 2 ) 2 ( T H F ) 6 , 4.7. Atom Atom Distance (A) Atom Atom Distance (A) K ( l ) 0(1) 2.690(6) K(2) 0(1) 2.591(6) K ( l ) 0(2) 2.673(6) K(2) 0(2) 2.551(6) K ( l ) 0(3) 2.913(7) K(2) 0(3*) 2.909(7) K ( l ) 0(5) 2.748(7) K(2) , 0(4) 2.667(8) K ( l ) P ( l ) 3.361(3) K(2) P ( l* ) 3.343(3) K ( l ) P ( l* ) 3.507(3) Atom Atom Atom Angle (°) Atom Atom A t o m Angle (°) P( l ) K ( l 0(1) 56.57(13) 0(1) K(2) 0(2) 89.04(19) P ( l ) K ( l 0(2) 137.15(15) 0(1) K(2) 0(3*) 77.76(19) P ( l ) K ( l 0(3) 88.29(14) 0(1) K(2) 0(4) 131.4(2) P ( l ) K ( l 0(5) 89.41(16) 0(1) K(2) P ( l* ) 98.29(14) P ( l ) K ( l P ( l* ) 106.25(7) 0(2) K(2) 0(3*) 141.29(19) 0(1) K ( l 0(2) 84.49(18) 0(2) K(2) 0(4) 106.4(2) 0(1) K ( l 0(3) 144.73(19) 0(2) K(2) P ( l* ) 57.00(14) 0(1) K ( l 0(5) 98.6(2) 0(3*) K(2) P ( l* ) 88.69(15) 0(1) K ( l P ( l* ) 92.58(14) K ( l ) P ( l ) K ( l * ) 73.75(7) 0(2) K ( l 0(3) 127.0(2) K ( l ) P ( l ) K(2*) 76.57(7) 0(2) K ( l 0(5) 115.8(2) K ( l ) 0(3) K(2*) 91.02(18) 0(2) K ( l P ( l* ) 53.88(14) K ( l ) 0(1) K(2) 88.18(18) 0(3) K ( l 0(5) 82.5(2) K ( l ) 0(2) K(2) 89.38(18) 0(3) K ( l P ( l* ) 94.93(15) K ( l ) P ( l* ) K(2) 64.84(6) Slow diffusion of hexanes into a benzene solution of 4.8 afforded X-ray quality crystals containing eight molecules of co-crystallized benzene and two molecules of co-crystallized hexane per unit cell. The solid-state structure of 4.8 is presented in Figure Page 144 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals 4.14, crystallographic data is given in Table A - 6 of the Appendices, and selected bond distances and angles are collected in Table 4.8. The molecule crystallizes as an asymmetric trimer, which shows some interesting structural features. A molecule of benzene is 71-bonded in a r | 6 fashion to a potassium atom, a motif that is quite common in * 82 84 potassium complexes. " What is more unusual is the observation of such a coordination in this system, considering the reaction was performed in T H F . 4.8 contains only a single molecule of T H F per , P r [ O P O ] , in contrast to 4.7 and the lithium salts, 4.1 and 4.2, that have two molecules of T H F per [OPO] ligand. Figure 4.14. Molecular structure (ORTEP) of C r [ O P O ] K 2 ) 3 ( T H F ) 3 , 4.8. Ellipsoids Eire drawn at 50% probability. Carbon atoms of the T H F ligands and ^-butyl groups removed for clarity. Page 145 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Table 4.7. Selected bond distances (A), intramolecular distances (A), and bond angles (°) for ( ' P r [ O P O ] K 2 ) 3 ( T H F ) 3 , 4.8. Atom Atom Distance (A) Atom Atom Distance (A) K ( l ) 0(1) 2.857(3) K(2) 0(2) 2.773(6) K ( l ) 0(2) 2.801(1) K(2) 0(3) 2.716(4) K ( l ) 0(4) 2.593(2) K(2) 0(5) 2.523(2) K ( l ) 0(6) 2.766(6) K(2) ' 0(6) 2.686(5) K ( l ) P ( l ) 3.187(9) K(2) P(3) 3.463(10) K(3) 0(3) 2.695(1) K(4) 0(5) 2.683(6) K(3) 0(4) 2.695(8) K(4) C(cent) 2.953(10) K(3) 0(6) 2.821(2) K(5) 0(2) 2.653(7) K(3) P(3) 3.466(2) K(5) 0(3) 2.669(5) K(6) 0(1) 2.421(8) K(5) P ( l ) 3.321(2) K(6) 0(4) 2.694(7) K(5) P(2) 3.282(8) K(6) P(2) 3.549(2) K(5) C(cent) 3.087(10) Atom Atom Atom Angle (°) Atom Atom A t o m Angle (°) 0(1) K ( l ) 0(2) 115.2(2) 0(4) K ( l ) 0(6) 88.8(2) 0(1) K ( l ) 0(6) 146.9(2) K ( l ) 0(6) K(3) 82.1(2) P ( l ) K ( l ) 0(2) 58.5(2) 0(6) K(3) 0(4) 85.6(2) P( l ) K ( l ) 0(6) 148.6(2) K(3) 0(4) K ( l ) 87.9(2) 0(2) K(2) 0(5) 137.1(2) K ( l ) 0(2) K(2) 82.1(2) 0(3) K(2) 0(5) 136.3(2) 0(2) K(2) 0(6) 93.0(2) 0(3) K(3) P(3) 100.5(2) K(2) 0(6) K ( l ) 84.3(2) P ( l ) K(5) P(2) 95.6(2) 0(6) K ( l ) 0(2) 90.7(2) 0(2) K(5) 0(3) 60.4(2) K(2) 0(3) K(3) 80.6(2) K ( l ) P ( l ) K(5) 72.4(2) 0(3) K(3) 0(6) 93.8(2) K(5) P(2) K(6) 96.0(2) K(3) 0(6) K(2) 78.9(2) Page 146 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Mass spectral analysis indicates that the trimeric form is persistent and not simply a solid-state phenomenon, so perhaps sterics prevents the coordination of additional molecules of T H F . This might explain why, for instance, K ( l ) or K(2) do not have coordinated T H F , but not why K(5) has an n, 6 benzene bound to it. Benzene should not displace T H F in this system, thus the presence of a bound benzene molecule remains a mystery. Furthermore, there is a second r\6 bound aromatic ring in this system, one of the phenol rings of a , P r [OPO] is 7r-bonded to a potassium ion, K(4). K - C bond distances in 83 85 86 these rc-bonded arenes agree well with literature values of similar complexes. ' ' There are several additional close contacts between aromatic carbon atoms of the , P r [OPO] ligands and potassium atoms. However, due to their positions and their relative orientation, no n overlap is possible and these are not considered bonds. For example, C(63) is the aromatic carbon bound to 0(5), which bridges K(2) and K(4); C(63) also has a close contact to K(4) of 3.066 A . Severe disorder of the T H F molecules is evidenced by the relatively large thermal ellipsoids of 0(7) and 0(8); the T H F associated with 0(10) is disordered over two positions in the lattice, only one of which is shown. The K - 0 and K -76 81 P bond distances agree well with 4.7 and literature values. N M R studies indicate complex 4.7 has a symmetric structure in solution with the /-butyl protons appearing as two distinct singlet resonances in the lH N M R spectra, and a singlet for the phosphorus nuclei in the 3 1 P { 1 H } N M R spectra. Mass spectral analysis indicates that the complex is dimeric in the bulk material. Thus, the complex must be somewhat flexible in solution to permit /-butyl group equivalence, although variable-temperature N M R experiments do not indicate any fluxional behaviour. N M R spectra of 4.8 in ^-benzene show a similar symmetrical structure in solution; however, this is more difficult to explain given the asymmetrical nature of the solid-state structure. A mass spectrum of 4.8 could not be obtained, presumably due to the high molecular weight of the trimer. One possible explanation for the symmetrical N M R spectra is that the trimer exists only in the solid state and it breaks up in solution forming monomeric species. However, the ' H N M R spectra indicate that the T H F donors exist in two different environments, with distinct multiplets attributable to one T H F , and Page 147 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals broad singlets attributable to two THFs . The distinct multiplets indicate that one T H F is strongly bound and not undergoing exchange. The broad singlets indicate two T H F molecules are undergoing exchange, or are not coordinated, which is unusual given the apparent lack of donors in the system, as evidenced by the coordinated benzene in the solid-state structure. Thus, 4.8 could exist as a mixture of monomer and dimer in solution. 4.5. Summary and conclusions A series of bis(aryloxy)phosphine ligands and ligand precursors for use as ancillary ligands on early transition metals have been synthesized. The dimeric lithium salts ( p h [ O P O ] L i 2 ) 2 ( T H F ) 4 (4.1) and ( , P r [ O P O ] L i 2 ) 2 ( T H F ) 4 (4.2) can be prepared by the reaction of 2-bromo-4,6-r-butylphenol with RPC1 2 (R = Ph, 'Pr) in the presence of " B u L i . Isolation of side-products incorporating lithium 2,4-di-r-butylphenoxide is indicative of problems with the lithium salt syntheses, perhaps caused by adventitious water in the reaction. The protonated ligand precursors p h [ O P O ] H 2 (4.5) and , P r [ O P O ] H 2 (4.6) are synthesized by reaction of the lithum salt with two equivalents of E t 3 N H C l in E t 2 0 . Reaction of the protonated ligands with excess K H in T H F affords the dimeric, ( p h [ O P O ] K 2 ) 2 ( T H F ) 6 (4.7), and trimeric, ( / P r [ O P O ] K 2 ) 3 ( T H F ) 3 (4.8), potassium derivatives. The dimeric and trimeric structures for the alkali metal complexes clearly show that the presence of bulky /-butyl groups on the aromatic backbone does not impose a high level of steric congestion on the metal centers. Page 148 References begin on page 154, Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals 4.6. Experimental Section 4.6.1 General Procedures Unless otherwise stated, general procedures were performed as in Section 2.9.1. 4.6.2 Materials The compounds 2,4-di-/-butylphenol and n-bromosuccinimide were purchased from A l d r i c h and used as r ece ived . Dichlorophenylphosphine (PhPCL.) and dichloroispropylphosphine ( 'PrPCb) were purchased from Strem Chemicals and used without further purification. Potassium hydride was purchased from Acros Chemicals and used as received. 4.6.3 Synthesis, Characterization and Reactivity of Complexes Synthesis of 2-bromo-4,6-di-f-butylphenol. rc-Bromosuccinimide (18.21g, 102.3 mmol) was added in portions to a solution of 2,4-di-r-butylphenol (20.10 g, 97.4 mmol) in C H 3 C N (300 mL) at 0 °C with stirring. The bright yellow solution was then warmed slowly to ambient temperature and the resulting orange solution stirred for 12 h. A saturated aqueous solution of sodium bisulphite (10 mL) was added. After stirring the solution for 10 m, evaporation of the solvent gave the product as a colourless solid. Yie ld 23.12 g (83%). Calc. M W : 285.22 g mof 1 . ' H N M R (300 M H z , C D C 1 3 , 25 °C): 7.22 (s, 1H, Ph), 7.18 (S, 1H, Ph), 5.58 (s, 1H, OH), 1.31 (s, 9H , o-PhC(C/ / 3 ) 3 ) , 1.21 (s, 9 H , p - P h C ( C r / 3 ) 3 . Page 149 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Synthesis of ( P h [ O P O ] L i 2 ) 2 ( T H F ) 4 (4.1). To a solution of the bromophenol (20.24g, 70.96 mmol) in E t 2 0 (150 mL) was added a 1.6M solution of B u L i in hexanes (95.0 m L , 152.0 mmol) dropwise at -78 °C, and the solution was returned to ambient temperature. After stirring for 1 h the solution was cooled to -78 °C and P h P C l 2 (4.8 m L , 35.4 mmol) was added dropwise by syringe and the solution was allowed to warm to ambient temperature slowly. After stirring for 8h, the solvent was removed under vacuum and the residue was extracted with toluene (100 mL), the solution filtered through Celite and then evaporated to dryness. The pale yellow residue was slurried in hexanes (50 mL) , T H F was added (10.30 g, 142 mmol) and the solution cooled to -40 °C. Over 24 h colourless microcrystals were deposited. These were collected, washed with minimal pentane and dried under vacuum. Y i e l d : 16.73 g (70%). Calc. M W : 1349.58 g mol" 1 . X-ray quality crystals of 4.1 containing three molecules of co-crystallized solvent were grown by slow evaporation of a saturated benzene solution. ' H N M R (500 M H z , C 6 D 6 , 25 °C): 6 7.53 (m, 10H, Ph), 7.06 (m, 8H, Ph), 3.29 (16, 8H, T H F - O C # 2 C H 2 ) , 1.60 (s, 36H, o-PhC(C// 3 ) 3 ) , 1-30 (s, 36H, /?-PhC(C# 3 ) 3 ) , 1.26 (s, 16H, T H F - O C H 2 C / / 2 ) . 3 1 P { ' H } N M R (202.4 M H z , C 6 D 6 , 25 °C): (5-37.56 (s). ^ { ' H } N M R (194.3 M H z , C 6 D 6 , 25 °C): 6-1.06 (br s). M S (EI) m/z, (%): 1060, (100) [ M - (THF) 4 ] + . Anal . Calcd. for C 8 4 H i 2 2 L i 4 0 8 P 2 - 2 C 6 H 6 : C , 76.57; H , 8.97. Found: C , 76.33; H , 9.05. Synthesis of ( , P r [ O P O ] L i 2 ) 2 ( T H F ) 4 (4.2). With the same procedure as described above for 4.1, the bromophenol (7.87 g, 27.59 mmol) was reacted with ' P r P C l 2 (2.00 g, 13.80 mmol). Y i e l d : 8.84 g (51%). Calc. M W : 1281.54 g mol" 1 . [ H N M R (300 M H z , C 6 D 6 , 25 °C): 8 7.72-7.46 (m, 8H, Ph), 3.06 (s, 16H, T H F - O C / / 2 C H 2 ) , 2.92 (m, 2 H , P - C / / ( C H 3 ) 2 ) , 1.64 (s, 36H, o -PhC(C/ / 3 ) 3 ) , 1.36 (s, 36H, />PhC(C/ / 3 ) 3 ) , 1.39 (d, V = 12.5 H z , 12H, P - C H ( C / / 3 ) 2 ) , 1.24 (s, 16H, T H F -O C H 2 C # 2 ) . 3 1 P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6-29.56 (s). 7 L i { ' H } N M R (194.3 Page 150 References begin on page 154. Chapter Four: Synthesis ofbis(aryloxy)phosphines as ligands for early transition metals M H z , C 6 D 6 , 25 °C): 6-0.72 (s, 2Li ) , -1.22 (s, 2Li ) . M S (EI) m/z, (%): 969, (100) [ M -(THF)4] + . Elemental analysis was not obtained. Isolation of [ P h [ O P O ] L i 2 ( A r O L i ) ] 2 (4.3). Prior to the addition of T H F in the synthesis of 4.1, a concentrated toluene solution of the crude product was allowed to stand overnight. Approximately 0.15 g of X-ray quality crystals of 4.3 were removed from the solution before continuing with the synthesis. Calc. M W : 1485.66 g mol" 1 . ' H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.63-7.03 (m, 24H, Ph), 1.46 (s, 18H, o -PhC(C/ / 3 ) 3 ) , 1-39 (s, 36H, o -PhC(C/ / 3 ) 3 ) , 1-34 (s, 36H, ^ - P h C ( C / / 3 ) 3 ) , 1.25 (s, 18H,;?-PhC(C// 3 ) 3 ) . 3 1 P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 8 -31.87 (q, lJPLi = 170.1 Hz) . 7 L i { ' H } N M R (155.5 M H z , C 6 D 6 , 25 °C): 6-1.13 (d, lJPLi = 170.1 Hz , O -L/P-O), -1.34 (s), -1.84 (s). M S (EI) m/z, (%): 1485, (34) [ M ] + . Elemental analysis was not obtained. Isolation of [ ' P r [ O P O ] L i 3 C l ( A r O L i ) ] ( T H F ) 3 (4.4). Fol lowing the isolation of 4.2 above, the hexanes filtrate was concentrated by slow evaporation over several days. Approximately 0.15 g of X-ray quality crystals of 4.4 were collected and dried under vacuum. Calc. M W : 967.53 g mol" 1. lH N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.61-7.46 (m, 6 H , Ph), 3.01 (s, T H F - O C / / 2 C H 2 ) , 2.96 (m, 2 H , P-Cf7(CH 3 ) 2 ) , 1.65 (s, 36H, o-PhC(C/ / 3 ) 3 ) , 1.53 (s, 18H, OPh-(C(C# 3 ) 3 ) 2 ) , 1.45 (s, 36H,p-PhC(C/7 3 ) 3 ) , 1.37 (d, 3 J = 12.5 Hz , 12H, P - C H ( C / / 3 ) 2 ) , 1.18 (s, T H F - O C H 2 C # 2 ) . 3 1 P { 1 H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6 -36.76 (s). ' L i ^ H } N M R (194.3 M H z , C 6 D 6 , 25 °C): 6 -0.72 (br s), -1.22 (s), -2.13 (br s), -2.45 (s). M S (EI) m/z, (%): 751, (55) [ M - ( T H F ) 3 ] + . Elemental analysis was not obtained. Page 151 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Synthesis of ™ [ O P O ] H 2 (4.5). To an intimate mixture of 4.1 (5.00 g, 7.41 mmol) and Et3NHCl (2.01g, 14.8 mmol) was added Et20 (150 mL) . The solution was stirred 12 h, and then the solvent was removed under vacuum. The residue was extracted into toluene (50 m L ) , the solution filtered filtered through celite and then evaporated to dryness. The colourless solid was washed with minimal pentane and dried under vacuum. Yie ld : 3.74 g, (97%). Calc. M W : 518.71 g/mol. X-ray quality crystals of 4.5 containing three equivalents of co-crystallized solvent were grown by slow evaporation of a saturated benzene solution. ' H N M R (500 M H z , C 6 D 6 , 25 °C): 6 7.64 ( d , V H H = 2.3 Hz , l H , p - P P h ) , 7.35 (m, 4 H , o/m-PPh), 7.23 (s, 2H , Ph), 7.02 (m, 2 H , Ph), 6.50 (d, V P H = 8.9 Hz , OH), 1.61, (s, 18H, o-PhC(Cr7 3 ) 3 ), 1.26 (s, 18H,p-PhC(Cr7 3 ) 3 ) . 3 1 P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 5-50.23 (s). [ H N M R (300 M H z , C 4 D 8 0 , 25 °C): 6 7.33 (d, V H H = 2.4 Hz , 2H , ?h-H), 7.27 (m, 7H, Vh-H), 6.84 (dd, V H H = 2.4 Hz , V P H = 5.5 Hz , 2H , OH), 1.42 (s, 18H, o-PhC(GrY 3 ) 3 ), 1.12 (s, \8R,p-PhC(Cf7 3 ) 3 ). 3 l P { 1 H } N M R (121.4 M H z , C 4 D 8 0 , 25 °C): 5-47.18 (s). Synthesis of / P R [ O P O ] H 2 (4.6). Following the procedure for 4.5, Et20 (150 mL) was added to an intimate mixture of E t 3 N H C l (1.95 g, 14.18 mmol) and 4.3 (4.54 g, 7.09 mmol). Y i e l d : 3.27 g (96%). Calc. M W : 484.69 g mol ' 1 . ! H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.58 (dd, 3 J P H = 4.5 Hz , 4 J H H = 2.2 Hz , 2H , o-OPh), 7.50 ( d , 4 J H H = 2.2 Hz , 2H , p-0?h), 7.00 (d, 4 J P H =11.2 Hz , OH), 2.88 (ds, V P H = 12.4 Hz , 3JHH = 6.9 Hz , 1H, P - C / / ( C H 3 ) 2 ) , 1.50, (s, 18H, o-PhC(C/ / 3 ) 3 ) , 1.29 (s, 18H, /?-PhC(C/ / 3 ) 3 ) , 0.92 (dd, 3 J P H = 18.2 Hz , 3 J H H = 6.9 H z , 6 H , P - C H ( C / / 3 ) 2 ) . 3 1 P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6-61.65 (s). M S (EI) m/z, (%): 484, (100) [ M ] + . Anal . Calcd. for C 3 i H 4 9 0 2 P : C, 76.82; H , 10.19. Found: C, 76.62; H , 9.96. Page 152 References begin on page 154. Chapter Four: Synthesis ofbis(aryloxy)phosphines as ligands for early transition metals Synthesis of (P h[OPO]K 2) 2(THF) 6 (4.7). Potassium hydride (1.16 g, 28.9 mmol) was added in portions over 30 m to a solution of 4.5 (5.00 g, 9.6 mmol) in T H F (100 mL) with stirring. The solution was then placed under partial vacuum until the evolution of hydrogen ceased, stirred 12 h under static partial vacuum, filtered through Celite and then evaporated to dryness. The resulting pale yellow residue was washed with minimal hexanes to give 4.7 as a colourless solid. Yie ld : 7.13 g (92%). Calc. M W : 1622.42 g mol" 1. X-ray quality crystals of 4.7 containing three equivalents of co-crystallized solvent were grown from a saturated T H F solution at -40 °C. ' H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.52-6.96 (m, 18H, Ph), 3.62 (m, 24H, T H F -O C / / 2 C H 2 ) , 1.64 (s, 36H, o-PhC(C/ / 3 ) 3 ) , L48 (m, 24H, T H F - O C H 2 C / / 2 ) , 1.33 (s, 36U,p-PhC(C/ / 3 ) 3 ) . ^ P ^ H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6-29.59 (s). M S (EI) m/z, (%): 1188, (6) [ M - ( T H F ) 6 ] + , 516, (80) [OPO] + . Anal . Calcd. for C 9 2 Hi 3 8K40ioP 2 -2C 4 H 8 0 : C, 67.99; H , 8.79. Found: C, 68.38; H , 8.65. Synthesis of ( , P r[OPO]K 2) 3(THF) 3 (4.8). Following the procedure for 4.7, K H (0.21 g, 5.19 mmol) was added to a solution of 4.6 (1.00 g, 2.017 mmol) in T H F (25 mL) . Yie ld : 0.93 g (71%). Calc. M W : 1898.94 g mol" 1. X-ray quality crystals of 4.8 containing two equivalents of co-crystallized solvent were grown from slow evaporation of a layer benzene/hexanes solution. *H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.15 (d, VHH = 2.6 Hz , 6H, Ph), 6.94 (d, 6H, V H H = 2.6 H z , Ph), 3.62 (m, 4H, T H F - O C # 2 C H 2 ) , 3.58 (s, 8H , T H F - O C / / 2 C H 2 ) , 2.28 (m, 3H, P - C # ( C H 3 ) 2 ) , 1.78 (m, 4H, T H F - O C H 2 C / / 2 ) , 1.73 (s, 8H, T H F - O C H 2 C / / 2 ) , 1.39 (s, 54H, o -PhC(C/ / 3 ) 3 ) , 1.21 (s, 54H,p-PhC(Ctf 3 ) 3 ) , 1.00 (dd, 3 J P H = 14.4 H z , V H H = 6.6 H z , 18H, P - C / / ( C H 3 ) 2 ) . 3 , P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6-37.41 (s). Anal . Calcd. for C i 0 5 H i 6 5 K 6 O 9 P 3 T / 3 C 6 H 6 : C, 67.43; H , 8.72. Found: C, 67.08; H , 8.61. Page 153 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals 4.7. References (1) MacLachlan, E . A . ; Fryzuk, M . D. Organometallics 2005, 24, 1112-1118. (2) Weinberg, B . A . ; Bealer, B . K . The World of Caffeine: The Science and Culture of the World's Most Popular Drug; Routledge: N e w York, 2001. (3) Panov, G . I. CATTECH2000, 7,18-31. (4) Hamada, R.; Shibata, Y . ; Nishiyama, S.; Tsuruya, S. Phys. Chem. Chem. Phys. 2003, 5, 956-965. (5) Sparke, P., Ed . The Plastics Age: From Bakelite to Beanbags and Beyond; Overlook Press: New York, 1993. (6) Will iams, G . M . ; Iatropoulos, M . J.; Whysner, J. Food Chem. Toxicol. 1999, 37, 1027-1038. (7) Lanigan, R. S.; Yamaric, T. A . Int. J. Toxicol. 2002, 21 (Suppl. 2), 19-94. (8) Malhotra, K . C. ; Martin, R. L . J. Organomet. Chem. 1982, 239, 159-187. (9) Buzzeo, M . C. ; Iqbal, A . H . ; Long, C. M . ; Mi l la r , D . ; Patel, S.; Pellow, M . A . ; Saddoughi, S. A . ; Smenton, A . L . ; Turner, J. F. C.; Wadhawan, J. D . ; Compton, R. G . ; Golen, J. A . ; Rheingold, A . L . ; Doerrer, L . H . Inorg. Chem. 2004, 43, 7709-7725. (10) Bartlett, R. A . ; Ell ison, J. J.; Power, P. P.; Shoner, S. C. Inorg. Chem. 1991, 30, 2888-2894. (11) Jones, R. A . ; Hefner, J. G . ; Wright, T. C. Polyhedron 1984, 3, 1121-1124. (12) Parkin, P. C.; Clark, J. R.; Viscigl io, V . M . ; Fanwick, P. E . ; Rothwell, I. P. Organometallics 1995,14, 3002-3013. (13) Mulford, D . R.; Clark, J. R.; Schweiger, S. W.; Fanwick, P. E . ; Rothwell, I. P. Organometallics 1999,18, 4448-4458. (14) Boullard, O.; Leblanc, H . ; Bresson, B . Ullmanns Encyclopedia of Industrial Chemistry; 5th ed.; V C H : Weinheim, Germany, 1993; V o l . A 2 3 . (15) Lindsey, A . S.; Jeskey, H . Chem. Rev. 1957, 57, 583-620. (16) Gilman, H . ; Morton Jr., J. W . Org. React. (N.Y.) 1954, 8, 258. (17) Posner, G . H . ; Canella, K . A . J. Am. Chem. Soc. 1985,107, 2571-2573. Page 154 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Kremer, T.; Junge, M . ; Schleyer, P. v. R. Organometallics 1996,15, 3345-3359. Willoughby, C . A . ; Duff Jr., R. R.; Davis, W . M . ; Buchwald, S. L . Organometallics 1996,15, 472-475. Heinicke, J.; Jux, U . ; Kadyrov, R.; He, M . Heteroatom Chem. 1997, 8, 383-395. Priya, S.; Balakrishna, M . S.; Mague, J. T. J. Organomet. Chem. 2004, 689, 3335-3349. Heinicke, J . ; Koehler, M . ; Peulecke, N . ; Kindermann, M . K . ; K e i m , W. ; Koeckerling, M . Organometallics 2005, 24, 344-352. Gramer, C. J.; Raymond, K . N . Inorg. Chem. 1997, 43, 6397-6402. Gigant, K . ; Rammal, A . ; Henry, M . J. Am. Chem. Soc. 2001,123, 11632-11637. Thomas, M . S.; Darkwa, J. Polyhedron 1998, 77, 1811-1815. Fujimura, O. J. Am. Chem. Soc. 1998,120, 10032-10039. Singh, A . K . ; Thomas, S.; Khandelwal, B . L . Polyhedron 1991,10, 2693-2697. Mulford, D . R.; Fanwick, P. E . ; Rothwell, I. P. Polyhedron 2000,19, 35-42. Matsuo, T.; Kawaguchi, H . Inorg. Chem. 2002, 41, 6090-6098. Vicens, J.; Bohmer, V . , Eds. Calixarenes. A Versatile Class of Macrocylic Compounds; Kluwer Academic Publishers: Dortrecht, The Netherlands, 1991. Neri , P.; Geraci, C. ; Piatelli, M . J. Org. Chem. 1995, 60, 4126-4135. Petrella, A . J. ; Raston, C. L . J. Organomet. Chem. 2004, 689, 4125-4136. Perrin, R.; Lamartine, R.; Perrin, M . Pure Appl. Chem. 1993, 65, 1549-1559. Shinkai, S.; Koreishi, H . ; Ueda, K . ; Arimura, T.; Manabe, O. J. Am. Chem. Soc. 1987,109, 6371-6376. Ungaro, R.; Casnati, A . ; Ugozzoli , F. ; Pochini, A . ; Dozol , J. F. ; H i l l , C. ; Rouquette, H . Angew. Chem. Int. Ed. 1994, 33, 1506-1509. Lumetta, G . J.; Rogers, R. D . ; Gopalan, A . S., Eds. Calixarenes for Separations; A C S Symposium Series 757, American Chemical Society: Washington, D .C . , 2000. Bruni, S.; Caneschi, A . ; Cariati, F.; Delfs, C ; Dei , A . ; Gatteschi, D . J. Am. Chem. Soc. 1994,116, 1388-1394. Page 155 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals Chaudhuri, P.; Hess, M . ; Weyermuller, T.; Wieghardt, K . Angew. Chem. Int. Ed. 1999,35,1095-1098. Natrajan, L . S.; Wilson, C ; Okuda, J.; Arnold, P. L . Eur. J. Inorg. Chem. 2004, 3724-3732. Nakayama, Y . ; Watanabe, K . ; Ueyama, N . ; Nakamura, A . ; Harada, A . ; Okuda, J. Organometallics 2000,19, 2498-2503. Paine, T. K . ; Weyermuller, T.; Slep, L . D . ; Neese, F.; B i l l , E . ; Bothe, E . ; Wieghardt, K . ; Chaudhuri, P. Inorg. Chem. 2004, 43, 7324-7338. Luo, H . ; Setyawati, I.; Rettig, S. J.; Orvig, C. Inorg. Chem. 1995, 34, 2287-2299. Cavell , R. G . ; Hilts, R. W. ; Luo, H . ; McDonald, R. Inorg. Chem. 1999, 38, 897-905. Yamamoto, Y . ; Han, X . - H . ; Nishimura, S.; Sugawara, K . ; Nezu, N . ; Tanase, T. Organometallics 2001, 20, 266-272. Coleman, K . S.; Fawcett, J.; Holloway, J. H . ; Hope, E . G . ; Nassar, R. J. Fluor. Chem. 2001,112, 185-189. Yamamoto, Y . ; Sugawara, K . ; Han, X . - H . J. Chem. Soc, Dalton Trans. 2002, 195-211. Siefert, R.; Weyermuller, T.; Chaudhuri, P. J. Chem. Soc, Dalton Trans. 2000, 4656-4663. Hursthouse, M . B . ; Hossain, M . A . ; Motevalli , M . ; Sanganee, M . ; Sullivan, A . C. J. Organomet. Chem. 1999, 381, 293-297. Khanjin, N . A . ; Menger, F. M . J. Org. Chem. 1997, 62, 8923-8927. Liddle, S. T.; Clegg, W . J. Chem. Soc, Dalton Trans. 2002, 3923-3924. Boss, S. R.; Haigh, R.; Linton, D . J.; Schooler, P.; Shields, G . P.; Wheatley, A . E . H . Dalton Trans. 2003, 1001-1008. Smith, G . D . ; Fanwick, P. E . ; Rothwell, I. P. Inorg. Chem. 1989, 28, 618-620. Clegg, W. ; Lamb, E . ; Liddle, S. T.; Snaith, R.; Wheatley, A . E . H . J. Organomet. Chem. 1999,573, 305-312. K o , B . -T . ; L i n , C . - C . J. Am. Chem. Soc. 2001,123, 7973-7977. Izod, K . ; O'Shaughnessy, P.; Clegg, W. Organometallics 2002, 21, 641-646. Page 156 References begin on page 154. Chapter Four: Synthesis of bis(aryloxy)phosphines as ligands for early transition metals (56) Fryzuk, M . D . ; Love, J. B . ; Rettig, S. J. Chem. Commun. 1996, 2783-2784. (57) Gueneau, E . D . ; Fromm, K . M . ; Goesmann, H . Chem.-Eur. J. 2003, 9, 509-514. (58) Clegg, W. ; Davies, R. P.; Dunbar, L . ; Feeder, N . ; Liddle, S. T.; Mulvey, R. E . ; Snaith, R.; Wheatley, A . E . H . Chem. Commun. 1999, 1401-1403. (59) Chivers, T.; Krahn, M . ; Schatte, G . ; Parvez, M . Inorg. Chem. 2003, 42, 3994-4005. (60) Bock, H . ; Heigel, E . ; Nagel, N . Z. Naturforsch. B: Chem. Sci. 2000, 55, 773-784. (61) Colquhoun, I. J.; McFarlane, H . C. E . ; McFarlane, W . J. Chem. Soc, Chem. Commun. 1982, 220-221. (62) Hitchcock, P. B . ; Lappert, M . F.; Power, P. P.; Smith, S. J . J. Chem. Soc, Chem. Commun. 1984, 1669-1670. (63) Barr, D . ; Doyle, M . J.; Mulvey, R. E . ; Raithby, P. R.; Reed, D . ; Snaith, R.; Wright, D . S. J. Chem. Soc, Chem. Commun. 1989, 318-319. (64) Boyle, T. J.; Pedrotty, D . M . ; Alam, T. M . ; V ick , S. C ; Rodriguez, M . A . Inorg. Chem. 2000, 39,5133-5146. (65) MacDougall , D . J.; Morris, J. J.; N o l l , B . C ; Henderson, K . W . Chem. Commun. 2005, 456-458. (66) Hyvarinen, K . ; Kl inga , M . ; Leskela, M . Polyhedron 1996,15, 2171-2177. (67) Pauls, J.; Neumuller, B . Z. Anorg. Allg. Chem. 2000, 626, 270-279. (68) Ihara, E . ; Yoshioka, S.; Furo, M . ; Katsura, K . ; Yasuda, H . ; Mohr i , S.; Kanehisa, N . ; K a i , Y . Organometallics 2001, 20, 1752-1761. (69) Boche, G . ; Schimeczek, M . ; Cioslowski, J.; Piskorz, P. Eur. J. Org. Chem. 1998, 1851-1860. (70) Muller , M . ; Bronstrup, M . ; Knopff, O.; Schulze, V . ; Hoffmann, R. W. Organometallics 2003, 22, 2931-2937. (71) Evans, W . J.; Shreeve, J. L . ; Broomhall-Dillard, R. N . R.; Ziller, J. W . J. Organomet. Chem. 1995, 501, 7-11. (72) Bennett, M . A . ; Cobley, C. J.; Rae, A . D . ; Wenger, E . ; Wi l l i s , A . C. Organometallics 2000,19, 1522-1533. (73) Hitchcock, P. B . ; Lee, T. H . ; Leigh, G . J. Dalton Trans. 2003, 2276-2279. Page 157 References begin on page 154. Chapter Four: Synthesis ofbis(aryloxy)phosphines as ligands for early transition metals (74) Atkinson, R. C ; Gibson, V . C ; Long, N . J.; White, A . J. P.; Will iams, D . J. Dalton Trans. 2004, 1823-1826. (75) Burger, S.; Therrien, B . ; Suss-Fink, G . Inorg. Chim. Acta 2004, 357, 1213-1218. (76) Brooker, S.; Edelmann, F. T.; Kottke, T.; Roesky, H . W. ; Sheldrick, G . M . ; Stalke, D . ; Whitmire, K . H . J. Chem. Soc, Chem. Commun. 1991, 144-146. (77) Evans, W . J.; Ansari, M . A . ; Ziller, J. W. ; Khan, S. I. J. Organomet. Chem. 1998, 553, 141-148. (78) Boyle, T. J.; Andrews, N . L . ; Rodriguez, M . A . ; Campana, C. ; Y i u , T. Inorg. Chem. 2003, 42,5357-5366. (79) Fermin, M . C. ; Ho, J.; Stephan, D . W . Organometallics 1995,14, 4247-4256. (80) Beswick, M . A . ; Hopkins, A . D. ; Kerr, L . C. ; Mosquera, M . E . G . ; Palmer, J. S.; Raithby, P. R.; Rothenberger, A . ; Stalke, D . ; Steiner, A . ; Wheatley, A . E . H . ; Wright, D . S. Chem. Commun. 1998, 1527-1528. (81) Wolf, R.; Schisler, A . ; Lonnecke, P.; Jones, C. ; Hey-Hawkins, E . Eur. J. Inorg. Chem. 2004, 3277-3286. (82) Hu, J.; Barbour, L . J.; Gokel , G . W . Chem. Commun. 2002, 1808-1809. (83) Forbes, G . C. ; Kennedy, A . R.; Mulvey, R. E . ; Roberts, B . A . ; Rowlings, R. B . Organometallics 2002, 27, 5115-5121. (84) Pu, L . ; Phillips, A . D . ; Richards, A . F.; Stender, M . ; Simons, R. S.; Olmstead, M . M . ; Power, P. P. J. Am. Chem. Soc. 2003,125, 11626-11636. (85) L i u , Y . ; Ballweg, D . ; Muller , T.; Guzei, I. A . ; Clark, R. W. ; West, R. J. Am. Chem. Soc 2002,124, 12174-12181. (86) Smith, J. M . ; Lachicotte, R. J.; Pittard, K . A . ; Cundari, T. R.; Lukat-Rodgers, G . ; Rodgers, K . R.; Holland, P. L . J. Am. Chem. Soc. 2001,123, 9222-9223. Page 158 References begin on page 154. Chapter Five Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands 5.1. Introduction The previous chapter explored the synthesis of several bis(aryloxy)phosphines, in their lithium, potassium and protonated forms. Chapter five explores the early transition-metal coordination chemistry of these phosphines, using the complexes prepared in the previous chapter as convenient starting materials. The chemistry of metal phenoxide complexes, where a metal atom replaces the proton of phenol, has experienced rapid growth, both in research and industrial applications since the middle of the last century. 1 ' 2 Metal phenoxides have been used in industry as antioxidants in paints and varnishes, as catalysts in the synthesis of phenolic resins, and as potent fungicides and antimicrobial agents. For example, alkylated lead and copper phenoxides are particularly effective fungicides and sodium polychlorophenoxide has been used as an insecticide in the treatment of wood. 1 Simple metal phenoxides can be prepared by a variety of routes. For very electropositive metals, such as the alkali metals and aluminum, direct reaction of the metal with phenol is possible. The reaction of Page 159 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands metal halides with phenols has been widely used for the synthesis of transition metal phenoxides. For example, addition of TiCL, to boiling phenol affords the homoleptic Ti (OPh) 4 ; 3 pentafluorophenol reacts at ambient temperature producing Ti(OC6Fs)4.4 A variety of group 5 and group 6 phenoxides, including Nb(OPh) 5 , Ta(OPh) 5 , W(OPh)6 and W(OPh)4Cl2 can be prepared by refluxing the appropriate metal halide with phenol in a solvent such as benzene or toluene. 5 ' 6 This continues to be the predominant method for 7 0 the synthesis o f both early and late transition-metal aryloxide complexes. " Reaction of transition metal amides with substituted phenols has been described as a cleaner method for the synthesis of mid to late transition-metal aryloxides. 1 0 For example, reaction of Mn[N(SiMe3)2]2 with HO(2,4,6-'Bu3C6rl2) cleanly produces the manganese aryloxide [Mn(0(2,4,6-'BuC6H2))2J2 (Equation 5.1). 1 1 This method has also been utilized in the preparation of the uranium aryloxide complexes U(0-2,6-R2C6H 3)3 (R = ' B u , ' P r ) . 1 2 \ / \/ 2 / N — M n - N ^ + 4 toluene (-4 HN(S iMe 3 ) 2 ) (5.1) O — Mn M n — O \ / O Page 160 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands For substituted phenols that are particularly acidic, reaction with a metal alkoxide can liberate the corresponding alcohol and afford the metal aryloxide complex. This has been utilized in the synthesis of Mo2(0-'Pr)2(OC6H3-2,6-Me2)4, a dimeric complex with 13 two bridging aryloxides and one alkyloxide on each molybdenum. Another commonly used synthetic method for the synthesis of metal phenoxides is the reaction of metal alkyls with phenol. For example, reaction of PhCu with phenol affords C u O P h . 1 4 The complex (2,6-Ph2C6H30)2Ti(CH3)2 can be synthesized by reaction of T i ( C H 3 ) 4 with the substituted phenol. 1 5 This method is also used for the preparation of alkali metal and alkali earth phenoxide complexes. In this manner, dimethylmagnesium can be reacted with phenol to give M g ( O P h ) 2 . 1 6 This particular methodology is applicable to a wide variety of substituted phenols, 1 7 ' 1 8 including multidentate chelating examples, 1 9 which can then be used as aryloxide transfer reagents with transition metal halides. Scheme 5.1 details the synthesis of (4-Me-2,6-'Bu2C6H20)2TiCl2 v ia the lithium salt [Li(OC6H2-4-Me-2,6-'Bu2)(OEt2)]2 2 0 ' 2 1 Aryloxide transfer reagents have been used to 22 23 prepare other early transition metal aryloxide complexes. ' Page 161 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands OH Scheme 5.1. The binding mode of aryloxides can be either linear or bent. When coordinated in a linear fashion, 7i-donation to the metal is possible and this often leads to lower coordination numbers at the metal center. Additionally, the oxygen atoms of aryloxide ligands have a propensity to bridge metal centers, rendering such complexes susceptible to dimerization, as Equation 5.1 and Scheme 5.1 demonstrate. A consequence of this is the ability for the aryloxide complexes to undergo ligand redistribution reactions. 2 4 ' 2 5 One method to minimize ligand redistribution is to use very bulky ligands, for example, an aryloxide with /-butyl groups in the ortho positions, that serve to encapsulate the metal center. The titanium complex in Scheme 5.1, for example, does not undergo ligand redistribution. A n alternative is to use chelating multidentate aryloxides, resulting in limited ligand mobility and reducing the ability of complexes to undergo ligand redistribution reactions. The use of multidentate chelating aryloxide ligands in early 26 transition metal and lanthanide chemistry has recently been reviewed. Page 162 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Historically, some of the earliest linked aryloxides investigated were 2,2'-methylene-bis(aryloxide) ligands and their complexes with t i tanium. 2 7 , 2 8 Synthesis of a representative titanium halide complex is shown in Equation 5.2. The halide complexes are highly active initiators for the ring-opening polymerization of e-caprolactone,2 9 and carbonates.3 0 However, they display only modest activity in traditional olefin polymerization reactions and this has been attributed to the rigid ligand structure that serves to effectively block a large segment of the coordination sphere. 3 1 ' 3 2 (5.2) Early transition-metal complexes supported by a variant ligand containing three linked aryloxide units have given rise to unique bridging hydride complexes. 3 3 ' 3 4 Reaction of a niobium halide dimer with LiBHEt3 in the presence o f dinitrogen affords a 35 complex where a molecule of dinitrogen has been cleaved (Equation 5.3). Page 163 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Substitution of the methylene linker can lead to tridentate linked aryloxide ligands with a non-oxygen central donor such as sulphur or phosphorus; chapter four details many of these linked ligands that have been synthesized in the literature. Early transition-metal complexes supported by these linked aryloxide ligands have proven important in the exploration of non-metallocene catalysts for the polymerization of olefins. ' Theoretical calculations have suggested that the presence of an additional donor lowers the barrier for olefin insertion into the metal-alkyl bond. 3 8 ' 3 9 In the absence of donating solvents, titanium chemistry of these ligands is dominated by the formation of dimeric complexes with bridging halides; monomeric species are accessible upon addition of a donor solvent (Scheme 5.2). The sulphur-linked ligand in Scheme 5.2 has also been used in the synthesis of monomeric and dimeric complexes of samarium (III). 4 0 ' 4 1 Page 164 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Rhenium and technetium complexes supported by the phosphorus-linked aryloxide ligand bis(o-phenoxy)phenylphosphine ([PO2]) have drawn interest for their potential use as radiopharmaceutical agents. 4 2 ' 4 3 For example, the rhenium complex (P02)ReCl(PPh3) can synthesized by reaction of the phenol, H 2(P02), with R e O C l 3 ( P P h 3 ) 2 (Equation 5.4). Bis-ligand complexes, such as (P0 2 ) (HP0 2 )ReO, are also available by reaction of two equivalents of the phenol, although one phenol of a (PO2) ligand remains protonated. 4 2 Page 165 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Addition of steric bulk to the aromatic backbone of phosphorus-linked aryloxide ligands does not appear to significantly reduce the propensity of these ligands to form complexes where two ligands are bound to the metal center. Bis(3,5-/-butyl-2-phenoxy)phenylphosphine [OPO] forms bis-ligand complexes with several transition metals, including cobalt and nickel; although again, in these complexes, one phenol arm of the ligand remains protonated. 4 4 Vanadium(IV) complexes supported by [OPO] can be synthesized by reaction of the protonated phenol with VCl3(THF)3 (Equation 5.5), 4 5 a short exposure to oxygen is necessary to oxidize the vanadium (III). Page 166 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands This chapter explores the early transition-metal coordination chemistry of the ligands bis(3,5-/-butyl-2-phenoxy)phenylphosphine, P h [ O P O ] , and bis(3,5-r-butyl-2-phenoxy)wo-propylphosphine, , P r [ O P O ] , utilizing ligand starting materials synthesized in chapter four. Attempts to synthesize coordinated dinitrogen complexes via hydrogenation of metal alkyls and reduction of halide complexes are also presented. 5.2. Coordination chemistry ofR[OPO] With titanium Synthesis of the titanium halide complexes R [ O P O ] T i C l 2 ( T H F ) is outlined in Equation 5.6. Reaction of the protonated ligand p h [ O P O ] H 2 (4.5) with T i C l 4 ( T H F ) 2 in toluene under reduced pressure affords P h [ O P O ] T i C l 2 ( T H F ) (5.1) as a red solid in 97% yield; the same reaction with , P r [ O P O ] H 2 (4.6) gives / P r [ O P O ] T i C l 2 ( T H F ) (5.2) as a dark red powder in 93% yield. The reactions are performed under a partial static vacuum to assist the removal of HC1 from the reaction mixture. If HC1 is not removed, impurities are formed and the final product is obtained in lower yield. Use of a base, such as triethylamine, to remove HC1 leads to the formation of by-products, and a lower yield of 5.1. (5.6) 1 "\ 1 1 The complexes have been characterized by H and P{ H} N M R spectroscopy, mass spectrometry and elemental analysis. Both complexes display a singlet resonance in the 3 1 P { ' H } N M R spectra, with 5.1 at 5 17.8 and 5.2 at £ 2 0 . 2 . The lH N M R spectra Page 167 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands show that the [OPO] ligand is symmetric, resulting in two singlets for the /-butyl protons. The T H F proton resonances are seen as two distinct multiplets in each complex. The isopropyl group in 5.2 displays a characteristic pattern of coupling to phosphorus, with a doublet of septets for the methine proton and a doublet of doublets for the methyl groups. Mass spectra of both complexes show mass peaks corresponding to [ M - T H F ] + . Despite repeated attempts from a variety of different solvent mixtures, X-ray quality crystals of 5.1 and 5.2 could not be obtained. However, exchange of the T H F solvent in 5.1 does afford a related complex that can be characterized crystallographically. Addit ion of an excess of pyridine to a toluene solution of 5.1 produces the pyridine adduct p h [ O P O ] T i C i 2 ( p y ) (5.3) as an orange-red solid in excellent yield. X-ray quality crystals containing 1.5 equivalents of co-crystallized solvent were grown from the slow evaporation of a concentrated benzene solution. The solid-state molecular structure is presented in Figure 5.1. Crystallographic data is given in Table A - 6 of the Appendices, and selected bond distances and angles are summarized in Table 5.1. The geometry about the titanium center is distorted octahedral, with the p h [ O P O ] ligand bound in a facial fashion. Figure 5.1 shows that, despite the bulky r-butyl groups, the P h [OPO] ligand provides very little steric bulk to the metal center; much of the steric bulk is, in fact, directed away from the metal center. The /-butyl groups facing away from the metal center are disordered within the crystal lattice, only one orientation of each /-butyl group is shown. The Ti -P bond distance is in agreement with other neutral phosphine titanium complexes. 4 6" 4 8 The T i - 0 and T i - C l bond distances also agree well with literature values. 4 9" 5 2 The chloride bound trans to the phosphine has a marginally shorter T i - C l bond distance than the equatorial chloride, reflecting the weaker electron donating power of the neutral phosphine relative to the anionic aryloxide. The preference for a trans bound halide is also seen in complex 5.16. The pyridine ligand is bound equatorially, making the complex formally C\ symmetric. The T i - N bond distance of 2.26 A agrees well with the many pyridine adducts of titanium in the literature. 5 3" 5 6 Page 168 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Figure 5.1. Molecular structure (ORTEP) of ™[OPO]TiCl 2 (py), 5.3; (a) side view, (b) top view. Ellipsoids are drawn at 50% probability. Table 5.1. Selected bond distances (A), bond angles (°), and dihedral angles (°) for p h [OPO]TiCl 2 (py) , 5.3. Atom Atom Distance (A) Atom Atom Distance (A) T i ( l ) P ( l ) 2.5918(8) T i ( l ) N ( l ) 2.258(2) T i ( l ) 0(1) 1.8540(16) T i ( l ) C l ( l ) 2.3570(8) ' T i ( l ) 0(2) 1.8800(16) T i ( l ) Cl(2) 2.2820(8) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) P ( l ) T i ( l ) N ( l ) 88.03(5) N ( l ) T i ( l ) 0(1) 161.38(7) P( l ) T i ( l ) 0(1) 73.81(5) N ( l ) T i ( l ) 0(2) 84.15(7) P( l ) T i ( l ) 0(2) 75.80(5) N ( l ) T i ( l ) C l ( l ) 84.82(6) P( l ) T i ( l ) C l ( l ) 86.29(3) N ( l ) T i ( l ) Cl(2) 95.53(6) P ( l ) T i ( l ) Cl(2) 171.50(3) C l ( l ) T i ( l ) 0(2) 159.23(6) Page 169 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Atoms Atoms Angle O Phenol ring Phenol ring -9.0 The ' H N M R spectrum of 5.3 indicates that, in solution, the molecule has a plane of symmetry passing through the T i - P bond of the P H [ O P O ] ligand. Thus, the /-butyl signals appear as a pair of singlets and the 3 1 P { ' H } N M R spectrum has only one resonance, a singlet at £ 2 0 . 8 6 . This is despite the equatorial coordination of the pyridine ligand, cis to the phosphine. It seems unlikely that the pyridine ligand would be cis to the phosphine in the solid-state and trans in solution, as it would place two good neutral a-donor ligands trans to each other. However, this does not explain the symmetrical N M R spectra. It is possible that the pyridine (and by extension the T H F of 5.1 and 5.2) is involved in an associative/dissociative process that is fast on the N M R timescale, resulting in an averaged spectrum. It is also possible, although more unlikely, that the /-butyls are so far from the equatorial ligands that they are able to approximate a symmetrical environment. In addition to mass peaks attributable to the loss of the donor solvent, mass spectra of complexes 5.1 and 5.2 have fragments at significantly higher mass that correspond to ions where two [ O P O ] ligands are bound to the titanium center. ' H and 3 I P { ' H } N M R spectra of the materials submitted show no resonances attributable to a bis-ligand complex, particularly the 3 1 P { 1 H } N M R where only a single resonance is observed. Therefore, the presence of such a bis-ligand complex must be due to some ligand redistribution reaction occurring in the mass spectrometer. The synthesis of bis-ligand complexes of cobalt and vanadium described in the introduction, combined with the isolation of dimeric and trimeric alkali metal complexes of [ O P O ] in chapter four indicates that, despite the bulky /-butyl groups on the aromatic backbone, [ O P O ] is not a sterically encumbering ligand. The ligand has so little steric bulk that the formation of bis-ligand complexes is possible even for a small transition metal such as titanium. The synthesis of b i s - [ O P O ] titanium complexes is outlined in Ph Equation 5.7. Reaction of two equivalents of the potassium salt ( [OPO]K2)2(THF)6 Page 170 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands (4.7) with T i C l 4 ( T H F ) 2 affords P h [ O P O ] 2 T i (5.4) as a yellow-orange solid in 85% yield. The isopropyl derivative , P r [ O P O ] 2 T i (5.5) can be synthesized in 81% yield by the analogous reaction of ( i P r [ O P O ] K 2 ) 3 ( T H F ) 3 (4.8) with T i C l 4 ( T H F ) 2 . Attempts to synthesize 5.4 by reaction of P h [ O P O ] H 2 (4.5) with T i C l 4 ( T H F ) 2 gives mixtures of 5.1 and 5.4. However, N M R spectra do not indicate the presence of a titanium species with a protonated ligand, as might be expected from the similar cobalt, rhodium and vanadium , . 4 4 45 chemistry. ' Dark orange crystals of 5.4 suitable for X-ray diffraction were grown by slow diffusion of hexamethyldisiloxane ( H M D S O ) into a benzene solution of 5.4, and contain one molecule of co-crystallized H M D S O per molecule of 5.4. The solid-state molecular structure is presented in Figure 5.2; crystallographic data is given in Table A - 7 of the Appendices, and selected bond distances and angles are collected in Table 5.2. The p h [ O P O ] ligands are facially coordinated to the metal center, leading to a distorted octahedral geometry about titanium. Without considering the orientation of the phenyl rings on phosphorus, the molecule is approximately C 2 symmetric through a 2-fold axis that bisects the P(l)-Ti( l ) -P(2) angle. The Ti-P and T i - 0 bond lengths agree well with 5.3 and literature values of similar complexes cited above. In solution, N M R spectra of 5.4 and 5.5 indicate the complexes have average C 2 symmetry, in agreement with the Page 171 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands 31 1 solid-state structure of 5.4. Each complex has a single resonance in the P{ H} N M R spectrum, and four singlets in the ' H N M R spectrum for the /-butyl protons. This has been observed in similar complexes of nickel and cobalt. 4 4 Figure 5.2. Molecular structure (ORTEP) of ™[OPO] 2 Ti, 5.4. Ellipsoids are drawn at 50% probability. Table 5.2. Selected bond distances (A) and bond angles (°) for p h [ O P O ] 2 T i , 5.4. Atom Atom Distance (A) Atom Atom Distance (A) T i ( l ) 0(1) 1.863(3) T i ( l ) P ( l ) 2.5852(11) T i ( l ) 0(2) 1.920(3) T i ( l ) P(2) 2.5307(12) T i ( l ) 0(3) 1.883(2) T i ( l ) 0(4) 1.925(3) Page 172 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) P ( l ) T i ( l ) P(2) 90.18(4) P(2) T i ( l ) 0(1) 162.97(9) P ( l ) T i ( l ) 0(1) 75.97(8) P(2) T i ( l ) 0(2) 88.86(9) P ( l ) T i ( l ) 0(2) 75.90(8) P(2) T i ( l ) 0(3) 75.36(8) P ( l ) T i ( l ) 0(3) 160.99(9) P(2) T i ( l ) 0(4) 77.12(8) P ( l ) T i ( l ) 0(4) 91.50(8) 0(2) T i ( l ) 0(4) 161.21(11) Reduction reactions of 5.1 and 5.2 in the presence of dinitrogen did not produce any identifiable dinitrogen complexes. For example, reaction of 5.1 with two equivalents of magnesium produced a dark brown solid. N o N M R spectra could be obtained, indicating the products are paramagnetic. Mass spectral analysis of the products indicates the presence of p h [ O P O ] i T i . Slow concentration of a benzene solution containing the products affords a small number of bright orange crystals, determined by X-ray diffraction and N M R spectroscopic experiments to be 5.4. It is possible that disproportionation of a putative p h [OPO]Ti(III) species produces the isolated crystals of 5.4; another possibility is reaction of adventitious oxygen with the paramagnetic material. A similar formation of 5.4 is observed in alkylation reactions. For example, attempts to synthesize the dibenzyl complex ph[OPO]Ti(CPi2Ph)2 produce 1,2-diphenylethane and several phosphorus-containing species, one of which is 5.4. Reaction of benzylmagnesium chloride with 5.1 in T H F at -40 °C, results in a dark brown solid. Examination of the solid by ' H N M R spectroscopy shows a few aromatic resonances and a singlet at £ 2 . 9 1 . N o 3 1 P { ! H } N M R spectrum could be obtained, indicating that any [OPO] containing species are paramagnetic. A mass spectrum of the isolated solid contains many mass peaks, including one with a mass of 182, and another for P h [ O P O ] 2 T i (5.4). The mass peak at 182 corresponds to 1,2-diphenylethane (PhCH2CH2Ph or bibenzyl). A ! H N M R spectrum of pure 1,2-diphenylethane in ^-benzene shows a singlet at £2 .84 . Slow concentration of the reaction mixture in benzene deposits crystals of 5.4. Performing the reaction while not allowing the solution to warm above -40 °C affords a brick red solid. N M R spectra obtained at -40 °C/232 K reveal several species, Page 173 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands indicating the reaction does not cleanly form the dibenzyl complex, or that it partially decomposes during isolation. Among other resonances, the *H N M R spectrum shows a singlet at 5 3.32 integrating to roughly four protons, and the major resonance in the 3 1 P { ' H } N M R spectrum is a singlet at 5 -6.49. These resonances could be due to a dibenzyl complex. They disappear over thirty minutes and the solution turns brown. N M R spectra of the brown solution are similar to those above as the only identifiable product is 1,2-diphenylethane. A ' H N M R spectrum obtained in the presence of an internal standard, ferrocene, indicates the yield of 1,2-diphenylethane is approximately 40%, on the assumption that the brick red solid is pure P h [ O P O ] T i ( C H 2 P h ) 2 . If the dark brown solid is exposed to atmospheric oxygen and water, an immediate colour change to bright orange is observed. A 3 1 P { 1 H } N M R spectrum reveals several phosphorus containing species, of which 5.4 composes approximately 30%, by integration. Transition metal benzyl bonds have been shown to be both thermally and 57 photolytically sensitive, and homolytic bond cleavage is the preferred reaction mode. Benzyl radicals have been observed in the irradiation of C p 2 Z r ( C H 2 P h ) 2 , 5 8 and in the reaction of C p 2 T i ( C H 2 P h ) C l with C C I 4 , 5 9 and benzyl radicals are known to combine in solution to form 1,2-diphenylethane.60 Photolysis of the tantalum aryloxide complex (ArO) 2 Ta(CH 2 Ph) 3 yields (ArO) 2 (PhCH 2 )Ta=CHPh. 6 1 Irradiation of the titanium complex ( s i lox) 2 Ti(CH 2 Ph) 2 (silox = 'Bu 3 SiO) in the presence of T H F yields the ring 1 1 6 2 opened complex [ ( s i l ox ) 2 Ti (OCH 2 (CH 2 ) 2 CH 2 ) ] 2 , among other products. Mechanistic work with the related zirconium complex, (s i lox) 2 Zr(CH 2 Ph) 2 , suggests that the initial step in the reaction is photolytically induced homolytic cleavage of the metal-benzyl bond, in preference to the reductive elimination of 1,2-diphenylethane. L o w valent titanium complexes have been used in the coupling of 2,2'-dialkoxystilbenes, 6 3 ketones, 6 4 and the dimerization of butadienes. 6 5 A variety of organic substrates, including benzyl, can be coupled using the titanium(II) species T i C l 2 ( T H F ) 2 . 6 6 It is possible that the formation of 1,2-diphenylethane from the putative P h [ O P O ] T i ( C H 2 P h ) 2 could be the result of reductive elimination. However, the dibenzyl has no obvious incentive to undergo reductive elimination, [OPO] is not a sterically crowding ligand, and Ti(II) is not an easily accessible oxidation state for titanium. A Page 174 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands more likely method o f reactivity is homolytic titanium-benzyl bond cleavage resulting in a titanium(III) species and a benzyl radical (Scheme 5.3). Coupling of the benzyl radicals leads to 1,2-diphenylethane, with subsequent ligand redistribution of Ph[OPO]Ti(CH2Ph) giving rise to p h[OPO]2Ti, among other materials. Because thermal sensitivity of the reaction has made characterization of the brick red solid difficult, the involvement of a monobenzyl complex such as P h[OPO]TiCl(CH.2Ph) in the formation of 1,2-diphenylethane cannot be ruled out. Scheme 5.3. Page 175 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands 5.3. Coordination chemistry ofPh[OPO] with zirconium and hafnium The synthesis of the complexes p h [ O P O ] Z r C l 2 ( T H F ) (5.6) and P h [ O P O ] H f C l 2 ( T H F ) (5.7) is outlined in Equation 5.8. Reaction of the potassium salt ( p h [ O P O ] K 2 ) 2 ( T H F ) 6 (4.7) with Z r C l 4 ( T H F ) 2 in T H F under reduced pressure affords 5.6 as a colourless solid in 96% yield; the same reaction with HfCl4(THF) 2 gives 5.7 in 52% yield. The modest yield of 5.7 is attributable to the presence of other reaction products that are removed by washing repeatedly with pentane. The potassium salts provide cleaner conversions than the protonated ligand precursors. (5.8) The complexes have been characterized by *H and 3 1 P { 1 H } N M R spectroscopy, 311 mass spectrometry and elemental analysis. The complexes display singlets in the P{ H} N M R spectrum, 5.6 at 6 -5 .3 , and 5.7 at 6-3.1. The ! H N M R spectra show two singlets for /-butyl resonances, and distinct multiplets for the T H F ligands. Mass spectra show the expected mass ions from the loss of T H F . Attempts to alkylate 5.6 or 5.7 with M e M g C l Page 176 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands among other alkylating agents, results in mixtures of products, from which the desired alkyl complex cannot be isolated. Reductions using K C g , M g , and Na /Hg in the presence of dinitrogen result in dark brown solids, similar to reductions of 5.1. Mass spectral analysis indicates the formation of p h[OPO]2Zr or p h[OPO]2Hf in these reactions. 5.4. Coordination chemistry ofR[OPO] with tantalum Synthesis of the tantalum chloride complexes p h[OPO]TaCl3 (5.8) and , P r [ O P O ] T a C l 3 (5.9) is outlined in Equation 5.9. Reaction of 4.5 with T a C l 5 in diethyl ether under reduced pressure affords 5.8 as a bright yellow solid in 92% yield. The isopropyl derivative is prepared in 82% yield by the analogous reaction of 4.6 with TaCls. The complexes have been characterized by ' H and 3 1 P { 1 H } N M R spectroscopy, mass spectrometry and elemental analysis. Both complexes have a single resonance in the 3 1 P { ' H } N M R spectrum, 5.8 at 5 33.5, 5.9 at 5 31.9. *H N M R spectra indicate the complexes are C s symmetric, with two resonances due to /-butyl protons; 5.9 also displays a diagnostic doublet of septets for the isopropyl methine proton and a doublet of doublets for the isopropyl methyl protons. (5.9) Attempts to crystallize 5.8 and 5.9 from a variety of solvents and solvent mixtures failed to yield X-ray quality crystals of either complex. However, several derivatives can be isolated from crystallization attempts through reactions with HC1 and adventitious Page 177 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands H 2 0 . For instance, in the synthesis of 5.8, filtration of the reaction mixture and slow concentration of the filtrate deposits a small number of X-ray quality yellow crystals. These crystals have been structurally characterized as the phosphonium salt ( P h[OPO]H 3)(TaCl6) (5.10). The solid-state molecular structure is presented in Figure 5.3. Crystallographic data is presented in Table A-7 of the Appendices, and selected bond distances and angles in Table 5.3. Hexachlorotantalate is quite common in tantalum halide chemistry, and the Ta-Cl bond lengths of 5.10 agree well with other similar structures,6 7"6 9 although this structure is somewhat unusual in that the Ta-Cl bond distances are not all equal, see Table 5.3. A similar triphenylphosphonium hexachlorotantalate is known, 7 0 and the phosphonium ion in 5.10 assumes a similar geometry. In contrast to the structure of the phosphine 4.5, the phenols in 5.10 are rotated by 146° with respect to each other. Although this particular geometry is not observed in other transition metal complexes of [OPO], this structure suggests it could exist, and that this or similar ligand geometries may be involved in the formation of the bis-[OPO] complexes discussed earlier, v ia disproportionation of bridged structures. The rotation of the phenol rings of the phosphonium is not driven by hydrogen bonding. None of the phenol or phosphonium protons are in appropriate positions for hydrogen bonding, t-butyl groups surround the hexachlorotantalate within the crystal lattice. Presumably, 5.10 is formed by reaction of three equivalents of HC1 with 5.8; however, attempts to produce this complex directly by bubbling HC1 through toluene solutions of 5.8 have only produced mixtures of products, one of which is p h [ O P O ] H 3 C l (6.1). Page 178 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Figure 5.3. Molecular structure (ORTEP) of ( p h [OPO]H 3 ) (TaCl 6 ) , 5.10. Ellipsoids are drawn at 50% probability. Table 5.3. Selected bond distances (A), bond angles (°), and dihedral angles (°) for ( p h [OPO]H 3 ) (TaCl 6 ) (5.10). Atom Atom Distance (A) Atom Atom Distance (A) Ta(l) C l ( l ) 2.3375(8) Ta(l) Cl(4) 2.3598(8) Ta(l) Cl(2) 2.3570(8) Ta(l) Cl(5) 2.3432(9) Ta(l) Cl(3) 2.3507(9) Ta( l ) Cl(6) 2.3657(8) P ( l ) C(6) 1.795(3) 0(1) C ( l ) 1.374(3) P ( l ) C(12) 1.791(3) 0(2) C(7) 1.374(3) P ( l ) C(13) 1.800(3) P ( l ) H(103) 1.288(4) 0(1) H(101) 0.719(5) 0(2) H(102) 0.757(5) Page 179 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) C l ( l ) Ta( l ) Cl(2) 90.29(3) Cl(2) Ta( l ) Cl(3) 89.25(4) C l ( l ) Ta( l ) Cl(3) 90.77(4) Cl(2) Ta( l ) Cl(4) 179.19(8) C l ( l ) Ta( l ) Cl(4) 89.30(3) Cl(2) Ta( l ) Cl(5) 90.00(4) C l ( l ) Ta( l ) Cl(5) 91.24(4) Cl(2) Ta( l ) Cl(6) 90.73(3) C l ( l ) Ta( l ) Cl(6) 178.91(3) Cl(3) Ta( l ) Cl(5) 177.86(4) C ( l ) 0(1) H(101) 111.60(4) C(7) 0(2) H(102) 110.27(4) Atoms Atoms Angle (°) Phenol ring Phenol ring -146.4 Slow concentration of a benzene solution of 5.8 deposited a small number of yellow X-ray quality crystals that have been structurally characterized as (ph[OPO]TaCl2)2(u-OH)2 (5.11). The solid-state molecular structure is presented in Figure 5.4; crystallographic data is given in Table A - 7 of the Appendices, and selected bond distances and angles are collected in Table 5.4. The structure is a bis-hydroxide bridged dimer composed of two crystallographically related fragments. The hydroxide protons can be located in the difference map and refined isotropically. Each tantalum is seven-coordinate in a distorted capped trigonal prismatic geometry where the phosphine is the capping moiety. The Ta -Cl bond distances compare well to those of 5.10 and similar complexes. The Ta-P bond distance also agrees well with those of [NPN] complexes of tantalum, 7 1" 7 3 and other literature complexes. 7 4" 7 6 The Ta-0 bond distances rji n o »7*1 *7Q of the [OPO] ligand agree well with other tantalum aryloxide complexes. ' " The bridging hydroxide Ta-0 bonds are approximately 0.1 A longer than the Ta-0 distances of the aryloxide, as expected due to the bridging nature of the hydroxide. However, no structurally characterized bridging. hydroxide complexes of tantalum exist in the literature. Terminal tantalum hydroxide complexes are known; ' however, the Ta -OH bond distances of 5.11 are significantly longer than in these complexes. Page 180 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Figure 5.4. Molecular structure (ORTEP) of O O P O ] T a C l 2 ) 2 ( u - O H ) 2 , 5.11. Ellipsoids are drawn at 50% probability. Table 5.4. Selected bond distances (A) and bond angles (°) for ( p h [OPO]TaCl 2 ) 2 (p -OH) 2 (5.11). Atom Atom Distance (A) Atom Atom Distance (A) Ta(l) P ( l ) 2.5875(19) Ta(l) 0(1) 2.010(5) Ta(l) C l ( l ) 2.363(2) Ta(l) 0(2) 1.915(6) Ta(l) Cl(2) 2.453(2) Ta(l) 0(3) 2.114(5) 0(3) H ( l ) 0.838(6) Ta(l) 0(3*) 2.061(6) Page 181 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Atom Atom Atom Angle (°) Atom Atom A t o m Angle (°) P ( l ) Ta( l ) C l ( l ) 86.74(7) 0(1) Ta( l ) . 0(2) 90.7(2) P ( l ) Ta( l ) Cl(2) 74.02(7) 0(2) Ta( l ) 0(3) 100.0(2) P ( l ) Ta( l ) 0(1) 72.70(16) 0(3) Ta( l ) 0(3*) 64.6(3) P ( l ) Ta( l ) 0(2) 74.24(16) 0(1) Ta( l ) 0(3*) 74.3(2) P( l ) Ta( l ) 0(3) 149.46(16) 0(1) Ta( l ) C l ( l ) 86.70(17) P( l ) Ta( l ) 0(3*) 144.28(16) 0(1) Ta( l ) Cl(2) 146.48(16) C l ( l ) Ta( l ) Cl(2) 87.58(8) 0(3) Ta( l ) C l ( l ) 94.63(18) Formation of 5.11 is probably by reaction of adventitious water with 5.8, affording HC1 and p h [ O P O ] T a C l 2 ( O H ) , which then dimerizes. Presumably, the controlled addition of one equivalent of H 2 0 to a solution of 5.8 would afford 5.11; however, this reaction has not been conducted, and the complex has not been further characterized. Slow concentration of a benzene solution containing the isopropyl derivative 5.9 deposited a small number of bright yellow crystals of X-ray quality that have been structurally characterized as ( ' P r [OPO]TaCl 2 ) 2 (p-0) (5.12). The solid-state molecular structure is presented in Figure 5.5; crystallographic data is given in Table A - 8 of the Appendices, and selected bond distances and angles are summarized in Table 5.5. Structurally, 5.12 is a bridging oxo complex composed of two crystallographically related fragments. Each tantalum is six-coordinate in a distorted octahedral geometry. The Ta-Cl bond distances are similar to 5.11 and other similar complexes. The Ta -0 bond distances are shorter than in 5.11, on average; the Ta-O of the bridging oxo agrees well with other bridging oxo complexes of tantalum. 8 3 ' 8 4 The Ta-P bond distance in 5.12 is significantly longer than in 5.11, despite the slightly more basic nature of the isopropyl phosphine. This is probably due to the change of geometry about the tantalum center in the two complexes; in 5.12 the phosphine is trans to the oxo, whereas in 5.11, the phosphine is not strictly trans to any ligand, although it is opposite the two hydroxide ligands. However, the Ta-P bond distance of 5.12 agrees well with the single reported isopropyl 85 phosphine complex of tantalum. Page 182 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Figure 5.5. Molecular structure (ORTEP) of ( ' " [OPO]TaCl 2 ) 2 (u-0) , 5.12. Ellipsoids are drawn at 50% probability. Table 5.5. Selected bond distances (A) and bond angles (°) for ( , P r [OPO]TaCl 2 ) 2 (u-0) (5.12). Atom Atom Distance (A) Atom Atom Distance (A) Ta(l) P ( l ) 2.6808(6) Ta(l) 0(1) 1.9184(18) Ta(l) C l ( l ) 2.3613(7) Ta(l) 0(2) 1.9170(18) Ta( l ) Cl(2) 2.3693(7) Ta(l) 0(3) 1.91294(10) Atom Atom Atom Angle (°) Atom Atom A t o m Angle (°) P ( l ) Ta( l ) C l ( l ) 89.49(2) 0(1) Ta( l ) 0(2) 91.64(8) P( l ) Ta( l ) Cl(2) 89.15(2) 0(1) Ta( l ) 0(3) 98.88(5) P( l ) Ta( l ) 0(1) 73.28(5) •0(1) Ta( l ) C l ( l ) 87.23(6) P( l ) Ta(l) 0(2) 72.25(5) 0(1) Ta( l ) Cl(2) 161.55(6) P( l ) Ta( l ) 0(3) 164.55(2) 0(2) Ta( l ) C l ( l ) 161.19(6) Page 183 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands The formation of 5.12 is likely by a pathway similar to that proposed for 5.11: reaction of adventitious water with the trichloride 5.9, which affords HC1 and , P r [OPO]TaCl 2 (OH) . Rather than dimerize, , P r [OPO]TaCl 2 (OH) reacts with another molecule of 5.9, forming the bridging oxo 5.12 and HC1. Presumably, the controlled addition of half an equivalent of H 2 0 to a solution of 5.9 would afford 5.12; however, this reaction has not been conducted, and the complex has not been further characterized. The synthesis of 5.8 and 5.9 is strongly linked to the dilution of the reaction mixture. For example, i f the synthesis of 5.8 is performed using only half the solvent volume, a second product is visible in the N M R spectra. This second complex is much more soluble and can be separated from 5.8 by washing the crude product with hexanes. X-ray quality crystals of this new material were grown by slow evaporation of the hexanes washings. The solid-state molecular structure o f p h [ O P O ] 2 T a C l (5.13) is presented in Figure 5.6; crystallographic data is given in Table A-8 of the Appendices, and selected bond distances and angles in Table 5.6. The complex has a distorted pentagonal bipyramidal geometry about tantalum. Ta-0 and T a - C l bond distances agree well with previously discussed [OPO] tantalum structures. The Ta-P bond distances are longer than for other [OPO] complexes of tantalum discussed previously, but remain well within literature values. ' ' The unit cell contains 1.5 equivalents of co-crystallized hexane per molecule of 5.13, and severe disorder of the solvent contributes to the higher residuals in this structure. Disorder in the co-crystallized solvent also contributes to disorder in the /-butyl groups pointing away from the tantalum center, disorder that could not be appropriately modeled, leading to the larger ellipsoids observed. Page 184 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Figure 5.6. Molecular structure (ORTEP) of ™[OPO] 2 TaCl, 5.13. Ellipsoids are drawn at 50% probability. Table 5.6. Selected bond distances (A) and bond angles (°) for p h [ O P 0 2 T a C l (5.13). Atom Atom Distance (A) Atom Atom Distance (A) Ta( l ) 0(1) 1.937(7) Ta(l) P ( l ) 2.719(3) Ta( l ) 0(2) 2.011(8) Ta(l) P(2) 2.662(3) Ta(l) 0(3) 1.931(7) Ta(l) C l ( l ) 2.432(3) Ta(l) 0(4) 2.034(7) Page 185 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Atom Atom Atom Angle (°) Atom Atom Atom Angle O C l ( l ) Ta( l ) P ( l ) 144.33(10) P ( l ) Ta( l ) P(2) 74.30(9) C l ( l ) Ta( l ) P(2) 140.93(10) P ( l ) Ta( l ) 0(1) 73.0(2) C l ( l ) Ta( l ) 0(1) 105.9(2) P ( l ) Ta( l ) 0(2) 68.5(2) C l ( l ) Ta(l) 0(2) 76.0(2) P ( l ) Ta( l ) 0(3) 83.9(2) C l ( l ) Ta( l ) 0(3) 99.6(2) P ( l ) Ta( l ) 0(4) 139.5(2) C l ( l ) Ta( l ) 0(4) 75.0(2) P(2) Ta( l ) 0(2) 140.7(2) 0(2) Ta( l ) 0(4) 150.1(3) 0(1) Ta( l ) 0(3) 154.2(3) Solution N M R spectra of 5.13 indicate that the solid-state structure is not retained in solution. A 3 1 P { 1 H ] N M R spectrum has a single resonance at 531.9, and the ' H N M R spectrum shows two singlets for the /-butyl protons. A change in geometry around the tantalum from pentagonal bipyramidal to capped trigonal prismatic would create a plane of symmetry through the molecule and make the two aryloxide arms of the [OPO] ligand equivalent. Such an interconversion is not sterically hindered, and many seven-coordinate 88 complexes are not stereochemical^ rigid. Attempts to directly synthesize 5.13 through reaction of two equivalents of the lithium salt 4.1 or the potassium salt 4.7 with TaCls result in mixtures of several different products, and only a small amount of 5.13 is formed. Reaction of two equivalents of 4.5 with TaCls lead to a mixture of 5.9 and 5.13 from which 5.13 can be isolated by extraction of the crude product into a small volume of hexanes. If the reactions are conducted with very small solvent volumes, a third product is observed, characterized by broad resonances in both the ' H and 3 1 P { ' H } N M R spectra. This material has not been isolated; however, it could be a complex with three p h [ O P O ] ligands bound to a single tantalum. One of the most important aspects relating to the synthesis of 5.8 and 5.9 is that they are tantalum halides supported by mixed-donor ligands, something that intense research with the amidophosphine ligands [P2N2] and [NPN] (and related amidoarsine ligands) has been unable to achieve. 7 1 With a tantalum halide species it is possible to Page 186 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands investigate reduction of the halide in the presence of dinitrogen, a technique that has proven useful in synthesizing dinitrogen complexes of group 4 metals supported by amidophosphine ligands. Reductions of 5.8 and 5.9 utilizing K C g , or Na /Hg in the presence of one or four atmospheres of dinitrogen result in dark brown solids that solution N M R spectral and mass spectral data indicate are composed of several different materials, none of which can be positively identified as a dinitrogen complex. It is possible that the lack of steric bulk around the metal center in these complexes opens alternative reactivity pathways for the reduced metal complex, potentially including the formation of metal-metal bonded species. 8 9 ' 9 0 Another route to dinitrogen complexes that has proven useful with [NPN] tantalum complexes is the hydrogenation of an alkyl l igand. 7 1 Reactions of 5.8 and 5.9 with alkylating agents such as ( P h C H 2 ) M g C l and C H 3 M g C l at -40 °C and -78 °C yield only mixtures of products, from which the desired alkyl cannot be cleanly isolated. However, in the absence tantalum halide complexes supported by [NPN] , work with that ligand turned to reaction of ligand precursors with tantalum alkyl halide materials, particularly T a M e 3 C l 2 . The synthesis of 5.8 has shown that phenols react with Ta -C l bonds, producing HC1 as the other product. This suggests that reaction of 4.5 with T a M e 3 C l 2 could yield the tantalum trimethyl complex, p h [ O P O ] T a M e 3 . Instead, addition of an ethereal solution of T a M e 3 C l 2 to 4.5 in E t 2 0 affords a pale yellow solid that solution N M R spectroscopy and mass spectrometry indicate is P h[OPO]TaMeCl2 (5.14) (Equation 5.10). This reaction indicates that the formation of methane is more favorable than formation of HC1. Further reactivity of 5.14 has not produced results to date. Attempts to create mixed alkyl species through reaction of 5.14 with ( P h C H 2 ) M g C l result in dark solids that are composed of several materials. A similar result is observed when 5.14 is reduced in the presence of dinitrogen. M u c h like the reduction of 5.13, reductions produce dark brown materials, from which no dinitrogen complexes could be identified. Hydrogenation of 5.14 under 4 atmospheres of hydrogen produces a mixture of products, and no resonances attributable to tantalum hydrides are observed. Page 187 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands CI (5.10) When a substoichiometric amount of 4.5 is reacted with TdMe^Ch an impurity is observed in solution N M R spectra that can be separated from 5.14 by crystallization. Slow evaporation of a benzene solution of the crude product deposits a few bright yellow crystals of X-ray quality. These have been structurally characterized as p h[OPO]TaMe2Cl (5.15). The solid-state molecular structure is presented in Figure 5.7; crystallographic data is given in Table A - 8 of the Appendices, and selected bond distances and angles are collected in Table 5.7. There is a distorted octahedral geometry about the tantalum center, similar to that of the titanium complex 5.3, and the symmetrical coordination, internal Ph bond distances and angles of the [OPO] ligand are also similar to 5.3. Ta-O, Ta-P and Ta-Cl bond distances compare well to those of similar complexes discussed previously. Ph The tantalum methyl bond distances are very similar to those of [NAsN]TaMe3 (3.3) and p h [ N P N ] T a M e 3 . 7 1 The synthesis of 5.15 is extremely sensitive and only partial characterization has been carried out at this time. The dimethyl complex has also been synthesized a single time using a substoichiometric amount of the lithium salt ( P h [ O P O ] L i 2 ) 2 ( T H F ) 4 (4.1). Page 188 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Figure 5.7. Molecular structure (ORTEP) of P h [ O P O ] T a M e 2 C l , 5.15, (a) side view, (b) top view. Ellipsoids are drawn at 50% probability. Table 5.7. Selected bond distances (A), bond angles (°), and dihedral angles (°) for p h [ O P O ] T a M e 2 C l (5.15). Atom Atom Distance (A) Atom Atom Distance (A) Ta(l) P ( l ) - 2.6331(13) Ta(l) 0(1) 1.939(3) Ta(l) C ( l ) 2.196(6) Ta(l) 0(2) 1.943(4) Ta(l) C(2) 2.179(5) Ta(l) C l ( l ) 2.300(2) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) P( l ) Ta( l ) C l ( l ) 172.35(6) C ( l ) Ta( l ) C(2) 82.8(2) P( l ) Ta( l ) C ( l ) 81.72(17) C ( l ) Ta( l ) 0(1) 86.82(19) P( l ) Ta( l ) C(2) 84.05(18) C ( l ) Ta( l ) 0(2) 152.5(2) P( l ) Ta( l ) 0(1) 72.30(10) C ( l ) Ta( l ) C l ( l ) 99.75(19) P ( l ) Ta( l ) 0(2) 72.58(10) 0(1) Ta( l ) C(2) 155.3(2) Page 189 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Atoms Atoms Angle (°) Phenol ring Phenol ring -0.5 Reactions between protonated [OPO] precursors and TaMesCb have not led to the tantalum trimethyl complex. Salt metathesis has proven productive and the synthesis of p h[OPO]TaMe3 (5.16) is outlined in Equation 5.11. The synthesis can also be carried out using the lithium salt 4.1; however, the potassium salt affords a cleaner transformation. In solution, 5.16 is highly symmetrical, the 3 1 P { 1 H } N M R spectrum displays a single resonance at 8 13.0, and the /-butyl protons appear as a pair of singlets in the ' H N M R spectrum. The methyl protons appear as a doublet with 37PH = 4.4 H z . The solid-state structure of 5.16 has not been determined to date; however a mass spectrum indicates the complex is monomeric. Thus, a structure similar to 5.15 would be expected. Reaction of 5.16 with four atmospheres of hydrogen results in the formation of a dark orange solid. N M R spectroscopy indicates this is composed of several different materials, and no resonances attributable to hydrides are observed. (5.11) Page 190 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands 5.5. Summary and Conclusions This chapter presents early transition-metal coordination chemistry of the [OPO] ligands synthesized in chapter four. Reaction of p h [ O P O ] H 2 (4.5) and , P r [ O P O ] H 2 (4.6) with T i C l 4 ( T H F ) 2 affords the titanium dichloride complexes p h [ O P O ] T i C l 2 ( T H F ) (5.1) and / P r [ O P O ] T i C l 2 ( T H F ) (5.2), respectively. Exchange of the T H F for pyridine in 5.1 leads to the formation of p h [OPO]TiCl 2 (py ) (5.3), a complex that is structurally characterized. Mass spectrometry of the titanium dichloride complexes indicated that ligand redistribution occurs with the formation of the bis-ligand complexes p h [ O P O ] 2 T i (5.4) and ' P r [ O P O ] 2 T i (5.5). Direct synthesis of the bis-ligand complexes is accomplished through reaction of TiCl4(THF) 2 with two equivalents of the potassium salts ( P h [ O P O ] K 2 ) 2 ( T H F ) 6 (4.7) and ( / P r [ O P O ] K 2 ) 3 ( T H F ) 3 (4.8), respectively. Formation of the bis-ligand complexes is extremely facile, 5.4 is observed as the primary product from reduction reactions and is also the primary [OPO] containing product observed in the decomposition of p h [ O P O ] T i ( C H 2 P h ) 2 . The decomposition of the benzyl species also produces a modest yield of 1,2-diphenylethane, and a mechanism involving homolytic titanium-benzyl bond breakage is proposed to account for its formation. The facile formation of the bis-ligand complex 5.4 is particularly surprising given the small size of titanium. However, a lack of steric bulk in the [OPO] ligand is thought to be a primary reason its formation is so prevalent in titanium [OPO] chemistry. Reaction of the potassium salt 4.7 with ZrCl4(THF) 2 and H f C l 4 ( T H F ) 2 leads to formation of p h [ O P O ] Z r C l 2 ( T H F ) (5.6) and p h [ O P O ] H f C l 2 ( T H F ) (5.7), respectively. Reductions of these complexes in the presence of dinitrogen form a mixture of several products, and mass spectral analysis indicates that the bis-ligand complexes p h [ O P O ] 2 Z r and p h [ O P O ] 2 H f are formed. The monomeric tantalum trichloride complexes can be synthesized by reaction of 4.5 or 4.6 with T a C l 5 , affording P h [ O P O ] T a C l 3 (5.8) and , P r [ O P O ] T a C l 3 (5.9) respectively. The bis-ligand complex p h [ O P O ] 2 T a C l can be synthesized by reaction of two equivalents of 4.5 with TaCls, and separated from 5.8 by its higher solubility in hexanes. Direct alkylations of 5.8 produce only mixtures of products. However, the Page 191 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands methyl complexes p h [ O P O ] T a M e C l 2 (5.14), P h [ O P O ] T a M e 2 C l (5.15) and p h [ O P O ] T a M e 3 (5.16) can be formed by reaction of 4.5 or 4.7 with TaMesC^ . In conclusion, the bis(aryloxide)phosphine ligand [OPO] can be used to prepare a range of early transition-metal complexes containing one or two ligands bound to the metal center. Reactivity of group 4 mono-ligand complexes is hampered by the propensity of these systems to form bis-ligand complexes. Further, the reactivity of all complexes is limited by the apparent availability of multiple reaction pathways in both alkylation and reduction reactions. A lack of steric bulk in the [OPO] ligands permits the formation of bis-ligand complexes and is thought to contribute to the uncontrollable reactivity of mono-ligand complexes. Page 192 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands 5.6. Experimental Section 5.6.1 General Procedures Unless otherwise stated, general procedures were performed as in Section 2.9.1. Selected complexes in this chapter do not have elemental analysis data due to difficulties with sample handling and the general air-sensitivity of these complexes. 5.6.2 Starting Materials and Reagents The complex HfCl4(THF)2 was prepared according to a literature procedure. 9 1 Pyridine was purified by distillation from C a H 2 . Hexamethyldisiloxane ( H M D S O ) was distilled from sodium benzophenone ketyl. 5.6.3 Synthesis, Characterization and Reactivity of Complexes Synthesis of P h[OPO]TiCI2(THF) (5.1). To an intimate mixture of p h [ O P O ] H 2 (4.5) (3.68 g, 7.10 mmol) and T i C l 4 ( T H F ) 2 (2.37 g, 7.10 mmol) was added toluene (250 mL) , and a colour change from bright yellow to dark red was observed. The solution was stirred for 12 h under reduced pressure, and then evaporated to dryness giving a red powder. The solid was washed with minimal pentane and then dried under vacuum yielding 5.1 as a red solid. Yie ld : 4.89 g (97%). Calc. M W : 707.57 g mol" 1. J H N M R (300 M H z , C 6 D 6 , 25 °C): 8 7.96 (dd, 3 J H H = 7.5 H z , 3J?H = 10.7 Hz , 2H , o-Ph), 7.56 (d, 3JHH = 1.9 Hz , 2H , />OPh), 7.45 (dd, 3JHH = 2.3 H z , VHH = 7.5 Hz , 2H , 77?-Ph), 7.20 (m, 3H, o-OPh and p-?h), 4.11 (m, 4 H , T H F - O C # 2 C H 2 ) , 1.68 (s, 18H, o-?hC(CH3)i), 1.21 (s, 18H,'p-PhC(C// 3)3), 1-06 (m, 4 H , THF-OCrfcC /fc). 3 1 P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 8 17.79 (s). M S (EI) m/z, (%): 634, (100) [ M - T H F ] + , Page 193 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands 1080 (10) [ p h [OPO] 2 Ti ] + . Ana l . Calcd. for C 3 8 H 5 3 C l 2 0 3 P T i : C , 64.50; H , 7.55. Found: C, 64.77; H , 7.68. Synthesis o f / P r [ O P O ] T i C l 2 ( T H F ) (5.2). With the same procedure outlined above for 5.1, , P r [ O P O ] H 2 (4.6) (0.200 g, 0.42 mmol) was reacted with T i C l 4 ( T H F ) 2 (0.139 g, 0.42 mmol), giving 5.2 as a dark red solid. Yie ld : 0.260 g (93%). Calc. M W : 673.56 g mol ' 1 . *H N M R (300 M H z , C 4 D g O , 25 °C): 5 7.27 (s, 2H,/>OPh), 7.17 (d, V P H = 6.4 Hz , 2H , o-OPh), 3.58 (s, 4 H , T H F - O C f 7 2 C H 2 ) , 3.34 (ds, 2 J P H = 6.8 Hz , 3 J H H = 6.8 Hz , 1H, P - C / f ( C H 3 ) 2 ) , 1.73 (s, 4 H , T H F - O C H 2 C / / 2 ) , 1.42 (dd, VPH = 15.0 H z , V H H = 6.8 H z , 6H , P - C H ( C / / 3 ) 2 ) , 1.38 (s, 18H, o-PhC(C# 3 ) 3 ) , 1.26 (s, 18H,/?-PhC(C# 3 ) 3 ) . 3 1 P { ' H } N M R (121.4 M H z , C 4 D 8 0 , 25 °C): 620.09 (s). M S (EI) m/z, (%): 600, (100) [ M - T H F ] + , 1013 (8) [ ' P r [OPO] 2 Ti] + . A n a l . Ca lcd . for C 3 5 H 5 5 C l 2 0 3 P T i : C , 62.41; H , 8.23. Found: C, 62.05; H , 8.09. Synthesis of P h [ O P O ] T i C l 2 ( p y ) (5.3). To a solution of 5.1 (0.110 g, 0.155 mmol) in toluene (10 mL) was added pyridine (50 u L , 3.87 mmol). The solution was stirred for 14 h and then evaporated to dryness giving 5.3 as an orange-red solid. Y i e l d : 0.099 g (90%). Calc. M W : 714.57 g mol" 1 . X-ray quality crystals of 5.3 containing two molecules of co-crystallized solvent were grown by slow evaporation of a concentrated benzene solution. ' H N M R (300 M H z , CeD^, 25 °C): 69.17 (br s, 2 H , o-Py), 7.81 (m, 2 H , o-Ph), 7.56 (s, 2H,/>OPh), 7.42 (m, 2 H , m-Ph), 7.10 (m, 3H , o-OPh and p-Ph), 6.58 (m, 1H, p-Py), 6.24 (m, 2 H , m-Py), 1.72 (s, 18H, o-PhC(C/ / 3 ) 3 ) , 1.19 (s, 18H, p - P h C ( C / / 3 ) 3 ) . 3 1 P { 1 H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6 24.86 (s). M S (EI) m/z, (%): 634, (100) [ M - pyridine]*. A n a l . Ca lcd . for C 3 9 H 5 0 C l 2 N O 3 P T i : C , 65.55; H , 7.05; N , 1.96. Found: C, 65.34; H , 6.97; N , 2.24. Page 194 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Synthesis of n [OPO] 2 T i (5.4). To a solution of T i C l 4 ( T H F ) 2 (0.100 g, 0.299 mmol) in toluene (5 m L ) was added a solution of ( p h [ O P O ] K 2 ) 2 ( T H F ) 6 (4.7) (0.443 g, 0.299 mol) in toluene (5 mL) by syringe, whereupon the solution quickly changed from yellow to orange. The solution was stirred for 12 h, filtered through Celite then evaporated to dryness. The residue was washed with minimal pentane and dried under vacuum affording 5.4 as a yellow-orange solid. Y ie ld : 0.275 g (85%). Calc. M W : 1081.25 g mol" 1. X-ray quality crystals were grown by slow diffusion of hexamethyldisiloxane ( H M D S O ) into a benzene solution of 5.4, and contained one molecule of co-crystallized H M D S O . lU N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.57-7.25 (m, 12H, Ph), 7.01 (m, 6H, Ph) 1.78 (s, 18H, o-PhC(C# 3 ) 3 ) , 1-64 (s, 18H, o-PhC(C# 3 ) 3 ) , 1.21 (s, 18H, /? -PhC(C# 3 ) 3 ) , 1.19 (s, 18H, /? -PhC(C# 3 ) 3 ) . 3l?{lH} N M R (121.4 M H z , C 4 D 6 , 25 °C): 6 20.69 (s). M S (EI) m/z, (%): 1080 (100) [ M ] + . Anal . Calcd. for C 6 8 H 9 0 O 4 P 2 T i : C, 75.54; H , 8.39. Found: C, 75.80; H , 8.43. Synthesis of'P r[OPO] 2Ti (5.5). With the same procedure outlined above for 5.4, ( i P r [ O P O ] K 2 ) 3 ( T H F ) 3 (4.8) (0.189 g, 0.100 mmol) was reacted with T i C l 4 ( T H F ) 2 (0.050 g, 0.150 mmol), giving 5.5 as an orange solid. Y i e l d : 0.123 g (81%). Calc. M W : 1013.22 g mol" 1 . *H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.52-7.25 (m, 8H, Ph), 2.92 (m, 2 H , P C / f ( C H 3 ) 2 ) , 1.79 (s, 18H, o-PhC(C/7 3 ) 3 ) , 1.58 (m, 3J= 11.3 Hz , 12H, P-CH(C/7 3 ) 2 ) , 1.55 (s, 18H, o-PhC(C# 3 ) 3 ) , 1.39 (s, 18H, />PhC(C/ / 3 ) 3 ) , 1.28 (s, 18H, />PhC(C# 3 ) 3 ) . 3 1 P { ' H } N M R (121.4 M H z , C 4 D 6 , 25 °C): 8 11.71 (s). M S (EI) m/z, (%): 1013 (100) [ M ] + . Elemental analysis was not obtained. Reaction of P h[OPO]TiCl 2(THF) (5.1) with PhCH 2MgCl. To a soluion of 5.1 (245 mg, 0.325 mmol) in T H F (10 m L ) at -40 °C was added a solution of benzylmagnesium chloride in E t 2 0 (0.35 m L , 0.35 mmol) dropwise from a Page 195 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands microsyringe. The resulting solution was stirred in the dark for 2 h at -40 °C and then evaporated to dryness. The residue was extracted with toluene (15 mL) at —40 °C, the solution filtered quickly through Celite, then evaporated to dryness, affording a brick red solid. Synthesis of P h [ O P O ] Z r C l 2 ( T H F ) (5.6). A solution of ( P h [ O P O ] K 2 ) 2 ( T H F ) 6 (4.7) (2.00 g, 1.20 mmol) in T H F (10 mL) was added dropwise to a solution of Z r C l 4 ( T H F ) 2 (0.93 g, 2.46 mmol) in T H F (10 mL) over a period of 2 m, during which a colourless ppt was observed. The solution was stirred 12 h and then the solvent was removed under vacuum. The colourless residue was extracted into toluene (10 mL) , the solution filtered through Celite and then evaporated to yield a pale yellow solid. The crude product was washed with minimal pentane then dried under vacuum giving 5.6 as a colourless solid. Yie ld : 1.94 g (96%). Calc. M W : 750.93 g mol" 1. ' H N M R (300 M H z , C 6 D 6 , 25 °C): 8 7.85 (m, 2H, o-Ph), 7.54 (m, 4 H , / > O P h and m-Ph), 7.19 (m, 3 H , o -OPh and p-?h), 3.90 (br s, 4 H , T H F - O C r Y 2 C H 2 ) , 1.66 (s, 18H, o-PhC(C/ / 3 ) 3 ) , 1.25 (s, \m,p-?hC(CHi)i), 1.13 (s, 4 H , T H F - O C H 2 C # 2 ) . M?{lH} N M R (121.4 M H z , C 6 D 6 , 25 °C): 5-5.34 (s). M S (EI) m/z, (%): 676, (100) [ M - T H F ] + , 1122 (6) [ p h [OPO] 2 Zr] + . Anal., Calcd. for C 3 8 H 5 3 C l 2 0 3 P Z r : C , 60.78; H , 7.11. Found: C, 60.92; H , 7.27. Synthesis of P h [ O P O ] H f C I 2 ( T H F ) (5.7). Following the same procedure outlined for 5.6 above, 4.7 (1.16 g, 0.71 mmol) was reacted with H f C l 4 ( T H F ) 2 (0.66 g, 1.44 mmol) yielding a pale yel low residue that was washed repeatedly with pentane and dried under vacuum affording 5.7 as a colourless solid. Yie ld : 0.68 g (52%). Calc. M W : 838.20 g mol" 1. ! H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.87 (m, 2 H , Ph), 7.59 (m, 4 H , Ph), 7.15 (m, 3H, Ph), 3.98 (m, 4 H , T H F - O C / / 2 C H 2 ) , I. 68 (s, 18H, o-PhC(C# 3 ) 3 ) , 1.26 (s, 18H, /?-PhC(Ctf 3 ) 3 ), 1.28 (m, 4 H , T H F - O C H 2 C / / 2 ) . Page 196 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands 3 1 P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6-3.12 (s). M S (EI) m/z, (%): 766, (100) [ M -T H F ] + , 1122 (8) [ p h [OPO] 2 HfJ + . Elemental analysis was not obtained. Synthesis of P h[OPO]TaCl 3 (5.8). To an intimate mixture of 4.5 (2.86 g, 3.86 mmol) and T a C l 5 (1.38 g, 3.86 mmol) was added toluene (100 mL) with stirring. The bright yel low solution was stirred for 12 h under reduced pressure during which time a yellow solid was deposited. Evaporation of the solvent and washing of the residue with hexanes gave 5.8 as a bright yel low solid. Yie ld : 2.86 g (92%). Calc. M W : 804.00 g mol" 1. ! H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.60 (m, 6 H , Ph), 7.05 (m, 3 H , Ph), 1.57, (s, 18H, o -PhC(C/ f 3 ) 3 ) , 1-16 (s, 18H, p-PhC(CfY 3 ) 3 ). 3 1 P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6 33.46 (s). M S (EI) m/z, (%): 802, (100) [ M ] + . Ana l . Calcd. for C 3 4 H 4 5 C l 3 0 2 P T a : C , 50.79; H , 5.64. Found: C , 50.90; H , 5.76. Synthesis of / P r[OPO]TaCl 3 (5.9). With the same procedure described above for 5.8, 4.6 (1.00 g, 2.07 mmol) was reacted with T a C l 5 (0.743 g, 2.07 mmol), giving 5.9 as a bright yellow solid. Y ie ld : 1.31 g (82%). Calc. M W : 769.98 g mol" 1. : H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.52 (m, 2 H , Ph), 7.21 (m, 2H , Ph), 3.03 (ds, 2 J m = 5.8 H z , 3JHH = 6.9 H z , 1H, P - C / / ( C H 3 ) 2 ) , 1.50 (s, 18H, o-PhC(C/ / 3 ) 3 ) , 1.35 (dd, 3 J P H = 19.2 H z , VHH = 6.9 Hz , 6H , P-CH(Cr7 3 ) 2 ) , 1.23 (s, 18H,/> PhC(C# 3 ) 3 ) . 3 1 P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6 31.88 (s). M S (EI) m/z, (%): 768, (100) [ M ] + . Elemental analysis was not obtained. Synthesis of P h[OPO]2TaCI (5.13). A solution of 4.5 (2.00 g, 3.87 mmol) in toluene (10 mL) was added dropwise to a suspension of T a C l 5 (0.693 g, 1.93 mmol) in toluene (10 mL) with stirring. The resulting yel low solution was stirred for 24 h then evaporated to dryness. The residue was Page 197 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands extracted into hexanes (5 m L ) , filtered through Celite and the solvent removed under vacuum. Analytically pure 5.13 was obtained by recrystallization from hexanes. Y ie ld : 1.09 g (45%). Calc . M W : 1249.79 g mol" 1 . X- ray quality crystals containing 1.5 equivalents of co-crystallized solvent were grown by slow evaporation of a saturated hexanes solution. J H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.70-7.04 (m, 18H, Ph), 1.49 (s, 36H, o-PhC(C/ / 3 ) 3 ) , 1-14 (s, 36H, p-?hC(CH3)3). 3i?{:R} N M R (121.4 M H z , C 6 D 6 , 25 °C): 6 37.85 (s). M S (EI) m/z, (%): 1249, (30) [ M ] + . Anal . Calcd. for C 68H9oC10 4P 2Ta: C, 65.35; H , 7.26. Found: C, 65.56; H , 7.43. Synthesis of P h [ O P O ] T a M e C l 2 (5.14). A solution of T a M e 3 C l 2 (0.12 g, 0.39 mmol) in E t 2 0 (10 mL) was added dropwise to a solution of 4.5 (0.20 g, 0.39 mmol) in E t 2 0 (50 mL) at -78 °C, and the resulting pale yellow solution was stirred at -78 °C for 1 h. Removal of the cold bath, slow warming for 40 m followed by removal of the solvent under vacuum gave a pale yellow residue that was washed with minimal pentane and dried under vacuum to give 5.14 as a pale yellow solid. Yie ld : 0.21 g (70%). Calc. M W : 783.58 g mol" 1. • H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.58 (m, 6H, Ph), 7.09 (m, 3H, Ph), 2.08 (d, V P H = 9.8 Hz , 3 H , T a - C / / 3 ) , 1.56 (s, 18H, PhC(C# 3 ) 3 ) , 1.23 (s, 6 H , PhC(C/Y 3 ) 3 ) , 1.19 (s, 12H, P h C ( C / / 3 ) 3 ) . 3 1 P { 1 H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 6 38.79 (s). M S (EI) m/z, (%): 782, (100) [ M ] + . Ana l . Calcd. for C 3 5 H 4 8 C l 2 0 2 P T a : C , 53.65; H , 6.17. Found: C, 53.87; H , 6.23. Synthesis of P h [ O P O ] T a M e 2 C l (5.15). Following the procedure outlined above for 5.14 above, 4.5 (0.076 g, 0.148 mmol), was reacted with T a M e 3 C l 2 (0.056 g, 0.188 mmol). Instead of evaporating the toluene solution to dryness it was concentrated to about half volume and allowed to slowly evaporate, affording 5.15 as several yel low crystals of X-ray quality. Y i e l d : not recorded. Calc. M W : 763.16 g mol" 1. ' H N M R (300 M H z , C 6 D 6 , 25 °C): 6 7.64 (m, 5H, Ph), 7.12 (m, 4H, Page 198 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands Ph), 1.56 (br s, 24H, Ta-C/ f 3 and o -PhC(C/ / 3 ) 3 ) , 1-22 (s, 18H, p - P h C ( C # 3 ) 3 ) . 3 1 P { 1 H } N M R (121.4 M H z , C 6 D 6 , 25 °C): 640.65 (s). Elemental analysis was not obtained. Synthesis of P H [ O P O ] T a M e 3 (5.16). A solution of T a M e 3 C l 2 (0.040 g, 0.135 mmol) in E t 2 0 (10 mL ) was added dropwise to a solution of 4.7 (0.100 g, 0.067 mmol) in E t 2 0 (50 mL ) at -78 °C, and the resulting pale solution was stirred at -78 °C for 1 h. Removal of the cold bath, slow warming for 40 m followed by removal of the solvent under vacuum gave a pale yellow solid. The residue was extracted into toluene (20 mL) , and the solution filtered through Celite. Evaporation of the solution produced a solid that was washed with minimal pentane and dried under vacuum to give 5.16 as an off white solid. Y ie ld : 0.068 g (68%). Calc. M W : 742.45 g mol" 1. ' H N M R (300 M H z , C 6 D 6 , 25 °C): 5 7.82 (m, l H , p - P P h ) , 7.65 (dd, 3JHH = 2.2 Hz , V P H = 6.1 Hz , 2 H , o-PPh), 7.58 (d, 3JHH = 2.2 Hz , 2H , /w-PPh), 7.11 (m, 4 H , Ph), 1.60 (s, 18H, o-PhC(C/ / 3 ) 3 ) , 1.53 (d, 3 J P H = 4.4 Hz , 9H , Ta-C / f t ) , 1.25 (s, 18H, jp-PhC(C//" 3) 3). 3 1 P { ' H } N M R (121.4 M H z , C 6 D 6 , 25 °C): <5 12.98 (s). 1 3 C { ' H } N M R (75.4 M H z , C 7 D 8 , 0 °C): d 166.2 (s, oPh i-C), 145.4 (d, ' j P C = 4.0 Hz , PPh i-C), 138.3 (d, V P C = 5.7 Hz , P-PhC(C/7 3 ) 3 i-C), 132.2 (s, PPh o-Q, 132.0 (s, PPh o-Q, 129.6-123.7 (Ph -Q, 63.5 (s, Ta-(CH 3 ) 3 ) , 35.3 (s, o -PhC(CH 3 ) 3 ) , 34.7 (s , />PhC(CH 3 ) 3 ) , 31.5 (s, o -PhC(CH 3 ) 3 ) , 29.6 (s,/> PhC(CH 3 ) 3 ) . M S (EI) m/z, (%): 742, (100) [ M ] + . Anal . Calcd. for C 3 7 H540 2 P T a : C, 59.83; H , 7.33. Found: C, 59.75; H , 7.45. Page 199 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands 5.7. References (1) Malhotra, K . C ; Martin, R. L . J. Organomet. Chem. 1982, 239, 159-187. (2) Bradley, D . C ; Mehrotra, R. C ; Rothwell, I. P.; Singh, A . Alkoxo and Aryloxo Derivatives of Metals; Academic Press: San Diego, C A , 2001. (3) Funk, V . PL; Rogler, F . Z Anorg. Chem. 1944, 252, 323-328. (4) Nayar, V . S. V . ; Peacock, R. D . J. Chem. Soc. 1964, 2827-2828. (5) Funk, V . PL; Baumann, W . Z Anorg. Chem. 1937, 231, 264-268. (6) Funk, V . PL; Mohaupt, G . Z Anorg. Chem. 1962, 315, 204-212. (7) Sartain, W . J.; Selegue, J. P. Organometallics 1989, 8, 2153-2158. (8) Anthis, J. W. ; Filippov, I.; Wigley, D . E . Inorg. Chem. 2004, 43, 716-724. (9) Snelgrove, J. L . ; Conrad, J. C ; Eelman, M . D . ; Moriarty, M . M . ; Yap, G . P. A . ; Fogg, D . E . Organometallics 2005, 24, 103-109. (.10) Sigel, G . A . ; Bartlett, R. A . ; Decker, D . ; Olmstead, M . M . ; Power, P. P. Inorg. Chem. mi, 26, 1773-1780. (11) Bartlett, R. A . ; Ell ison, J. J.; Power, P. P.; Shoner, S. C. Inorg. Chem. 1991, 30, 2888-2894. (12) Van Der Sluys, W . G . ; Burns, C . J.; Huffman, J. C ; Sattelberger, A . P. J. Am. Chem. Soc. 1988,110, 5924-5925. (13) Coffindaffer, T. W. ; Rothwell, I. P.; Huffman, J. C. Inorg. Chem. 1983, 22, 2906-2910. (14) Kawasi, T.; Hashimoto, H . Bull. Chem. Soc. Jpn. 1972, 45, 1499. (15) Chesnut, R. W. ; Durfee, L . D . ; Fanwick, P. E . ; Rothwell, I. P.; Folting, K . ; Huffman, J. C. Polyhedron 1987, 6, 2019-2026. (16) Ashby, E . C ; Goel, A . B . Inorg. Chem. 1979,18, 1306-1311. (17) Sartori, G . ; Casnati, G . ; B i g i , F. J. Org. Chem. 1990, 55, 4371-4377. Page 200 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands (18) Boyle, T. J.; Pedrotty, D . M . ; Alam, T. M . ; V i c k , S. C ; Rodriguez, M . A . Inorg. Chem. 2000, 39, 5133-5146. Liddle, S. T.; Clegg, W . J. Chem. Soc., Dalton Trans. 2002, 3923-3924. Cetinkaya, B . ; Gumrukcu, I.; Lappert, M . F.; Atwood, J. L . ; Shakir, R. J. Am. Chem. Soc. 1980,102, 2086-2088. Duff, A . W. ; Kamarudin, R. A . ; Lappert, M . F.; Norton, R. J. J. Chem. Soc, Dalton Trans. 1986, 489-498. Chamberlain, L . R.; Rothwell, I. P.; Huffman, J. C. Inorg. Chem. 1984, 23, 2575-2578. Rothwell, I. P. Polyhedron 1985, 4, 177-200. McKee , S. D . ; Burns, C. J.; Avens, L . R. Inorg. Chem. 1998, 37, 4040-4045. Giesbrecht, G . R.; Gordon, J. C ; Brady, J. T.; Clark, D . L . ; Keogh, D . W.; Michalczyk, R.; Scott, B . L . ; Watkin, J. G . Eur. J. Inorg. Chem. 2002, 723-731. Kawaguchi, H . ; Matsuo, T. J. Organomet. Chem. 2004, 689, 4228-4243. Floriani, C ; Corazza, F. ; Lesueur, W. ; Chies i -Vi l la , A . ; Gaustini, C . Angew. Chem. Int. Ed. 1989, 28, 66-67. Corazza, F.; Floriani, C ; Chiesi-Vil la , A . ; Gaustini, C. Inorg. Chem. 1991, 30, 145-148. Takeuchi, D . ; Nakamura, T.; Aida , T. Macromolecules 2000, 33, 725-729. Takeuchi, D . ; Aida , T.; Endo, T. Macromol. Chem. Phys. 2000, 201, 2267-2275. van der Linden, A . ; Schaverien, C. J. ; Meijboom, N . ; Ganter, C ; Orpen, A . G . J. Am. Chem. Soc. 1995,117, 3008-3021. Sernetz, F . G . ; Mulhaupt, R.; Fokken, S.; Okuda, J . Macromolecules 1997, 30, 1562-1569. Kawaguchi, H . ; Matsuo, T. J. Am. Chem. Soc. 2003,125, 14254-14255. Matsuo, T.; Kawaguchi, H . Organometallics 2003, 22, 5379-5381. Kawaguchi, H . ; Matsuo, T. Angew. Chem. Int. Ed. 2002, 41, 2792-2794. Fokken, S.; Spaniol, T. P.; Okuda, J.; Sernetz, F. G . ; Mulhaupt, R. Organometallics 1997,16, 4240-4242. Page 201 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands (37) Chan, M . C. W. ; Tarn, K . - H . ; Pui , Y . - L . ; Zhu, N . J. Chem. Soc., Dalton Trans. 2002, 3085-3087. (38) Froese, R. D . J. ; Musaev, D . G . ; Matsubara, T.; Morokuma, K . J. Am. Chem. Soc. 1997,779,7190-7196. (39) Froese, R. D . J. ; Musaev, D . G . ; Morokuma, K . Organometallics 1999, 18, 373-379. (40) Arnold, P. L . ; Natrajan, L . S.; Hal l , J. J.; Bi rd , S. J.; Wilson, C. J. Organomet. Chem. 2002, 647, 205-215. (41) Natrajan, L . S.; Ha l l , J. J.; Blake, A . J.; Wilson, C ; Arnold, P. L . J. Solid State Chem. 2003, 777,90-100. (42) Luo, H . ; Setyawati, I.; Rettig, S. J.; Orvig, C. Inorg. Chem. 1995, 34, 2287-2299. (43) Cavell , R. G . ; Hilts, R. W. ; Luo, H . ; McDonald, R. Inorg. Chem. 1999, 38, 897-905. (44) Siefert, R.; Weyermuller, T.; Chaudhuri, P. J. Chem. Soc, Dalton Trans. 2000, 4656-4663. (45) Paine, T. K . ; Weyermuller, T.; Slep, L . D . ; Neese, F . ; B i l l , E . ; Bothe, E . ; Wieghardt, K . ; Chaudhuri, P. Inorg. Chem. 2004, 43, 7324-7338. (46) Gomez, R.; Cuenca, T.; Royo, P.; Pellinghelli, M . A . ; Tiripicchio, A . Organometallics 1991,10, 1505-1510. (47) Hart, R.; Levason, W. ; Patel, B . ; Reid, G . Eur. J. Inorg. Chem. 2001, 2927-2933. (48) Basuli, F. ; Tomaszewski, J. ; Huffman, J. C ; Mindola , D . J. J. Am. Chem. Soc. 2003, 725, 10170-10171. (49) Larsen, A . O.; Taylor, R. A . ; White, P. S.; Gagne, M . R. Organometallics 1999, 75,5157-5162. (50) Aihara, H . ; Matsuo, T.; Kawaguchi, H . Chem. Commun. 2003, 2204-2205. (51) Reinartz, S.; Mason, A . F. ; Lobkovsky, E . B . ; Coates, G . W . Organometallics 2003, 22, 2542-2544. (52) Boyd, C . L . ; Toupance, T.; Tyrrell, B . R.; Ward, B . D . ; Wilson, C . R.; Cowley, A . R.; Mountford, P. Organometallics 2005, 24, 309-330. Page 202 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands (53) Latesky, S. L . ; M c M u l l e n , A . K . ; Rothwell, I. P.; Huffman, J. C. J. Am. Chem. Soc. 1985,707,5981-5987. (54) Hossain, M . A . ; Hursthouse, M . B . ; Mazid , M . A . ; Sullivan, A . C. J. Chem. Soc, Chem. Commun. 1988, 1305-1306. (55) Carmalt, C. J.; Newport, A . C ; Parkin, I. P.; White, A . J. P.; Will iams, D . J. J. Chem. Soc, Dalton Trans. 2002, 4055-4059. (56) Boyle, T. J.; Rodriguez, M . A . ; Alam, T. M . Dalton Trans. 2003, 4598-4603. (57) Pourreau, D . B . ; Geoffroy, G . L . Adv. Organomet. Chem. 1985, 24, 249-352. (58) Hudson, A . ; Lappert, M . F.; Pichon, R. J. Chem. Soc, Chem. Commun. 1983, 374-376. (59) Cardin, D . J.; Kel ly , J. M . ; Lawless, G . A . ; Trautman, R. J. J. Chem. Soc, Chem. Commun. 1982, 228-229. (60) Huang, R. L . ; Goh, S. H . ; Ong, S. H . A . The Chemistry of Free Radicals; Edward Arnold: London, 1974. (61) Chamberlain, L . R.; Rothwell, I. P. J. Chem. Soc, Dalton Trans. 1987, 163-167. (62) Covert, K . J.; Mayol , A . - R . ; Wolczanski, P. T. Inorg. Chim. Acta 1997, 263, 263-278. (63) Banerji, A . ; Nayak, S. K . J. Chem. Soc, Chem. Commun. 1991, 1432-1434. (64) Pons, J . - M . ; Santelli, M . J. Org. Chem. 1989, 54, 877-884. (65) Spencer, M . D . ; Wilson;.S. R.; Girolami, G . S. Organometallics 1997, 16, 3055-3067. (66) Eisch, J. J.; Shi, X . ; Lasota, J. Z. Naturforsch. B: Chem. Sci. 1995, 50, 342-350. (67) Solari, E . ; Floriani, C ; Chiesi -Vil la , A . ; R izzo l i , C . J. Chem. Soc, Chem. Commun. 1991, 841-843. (68) Dawson, D . Y . ; Brand, H . ; Arnold, J. J. Am. Chem. Soc. 1994, 776", 9797-9798. (69) Soria, D . B . ; Grundy, J.; Coles, M . P.; Hitchcock, P. B . Polyhedron 2003, 22, 2731-2737. (70) Ershova, M . M . ; Glushkova, M . A . ; Chumaevskii, N . A . ; Porai-Koshits, M . A . ; Buslaev, Y . A . ; Butman, L . A . ; Minaeva, N . A . ; Sadikov, G . G . Koord. Khim. 1981, 7, 556-567. Page 203 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands (71) Fryzuk, M . D . ; Johnson, S. A . ; Patrick, B . O.; Albinati , A . ; Mason, S. A . ; Koetzle, T. F. J. Am. Chem. Soc. 2001,123, 3960-3973. (72) Fryzuk, M . D . ; MacKay , B . A . ; Johnson, S. A . ; Patrick, B . O. Angew. Chem. Int. Ed. 2002, 41, 3709-3712. (73) Fryzuk, M . D . ; MacKay , B . A . ; Patrick, B . O. J. Am. Chem. Soc. 2003,125, 3234-3235. (74) Ankianiec, B . C ; Fanwick, P. E . ; Rothwell, I. P. J. Am. Chem. Soc. 1991, 113, 4710-4712. (75) Nikonov, G . I.; Kuzmina, L . G . ; Mountford, P.; Lemenovskii, D . A . Organometallics 1995, 14, 3588-3591. (76) Koeslag, M . A . D . ; Hunter, B . K . ; MacNei l , J. H . ; Roszak, A . W. ; Baird, M . C. Inorg. Chem. 1996, 35, 6937-6943. (77) Acho, J. A . ; Doerrer, L . H . ; Lippard, S. J. Inorg. Chem. 1995, 34, 2542-2556. (78) Son, A . J. R.; Schweiger, S. W.; Thorn, M . G . ; Moses, J. E . ; Fanwick, P. E . ; Rothwell, I. P. Dalton Trans. 2003, 1620-1627. (79) Thorn, M . G . ; Parker, J. R.; Fanwick, P. E . ; Rothwell, I. P. Organometallics 2003, 22, 4658-4664. (80) A search of the Cambridge Crystallographic Data Center database, November 2004 update, did not return any tantalum complexes containing a bridging hydroxide. (81) Gouzyr, A . I.; Wessel, H . ; Barnes, C. E . ; Roesky, H . W. ; Teichert, M . ; Uson, I. Inorg. Chem. 1997, 36, 3392-3393. (82) Blake Jr., R. E . ; Antonelli , D . M . ; Henling, L . M . ; Schaefer, W . P.; Hardcastle, K . I.; Bercaw, J. E . Organometallics 1998,17, 718-725. (83) Abbenhuis, H . C. L . ; Feiken, N . ; Grove, D . M . ; Jastrzebski, J. T. B . H . ; Kooijman, H . ; van der Sluis, P.; Smeets, W . J. J.; Spek, A . L . ; van Koten, G . J. Am. Chem. Soc. 1992,114, 9773-9781. (84) Schweiger, S. W. ; Til l ison, D . L . ; Thorn, M . G . ; Fanwick, P. E . ; Rothwell, I. P. J. Chem. Soc, Dalton Trans. 2001, 2401-2408. (85) Patow, R.; Fenske, D . Z Anorg. Allg. Chem. 2002, 628, 2790-2794. Page 204 References begin on page 200. Chapter Five: Early transition-metal coordination chemistry supported by bis(aryloxy)phosphine ligands (86) Hadi, G . A . A . ; Fromm, K . M . ; Blaurock, S.; Jelonek, S.; Hey-Hawkins, E . Polyhedron 1997,16, 721-731. (87) Schweiger, S. W. ; Freeman, E . E . ; Clark, J. R.; Potyen, M . C ; Fanwick, P. E. ; Rothwell, I. P. Inorg. Chim. Acta 2000, 307, 64-71. (88) Cotton, F. A . ; Wilkinson, G . Advanced Inorganic Chemistry; 5 ed.; John Wiley & Sons Inc.: N e w York, 1988. (89) Cotton, F. A . ; Diebold, M . P.; Roth, W. J. J. Am. Chem. Soc. 1987, 109, 5506-5514. (90) Scioly, A . J.; Leukens Jr., M . L . ; Wilson Jr., R. B . ; Huffman, J. C ; Sattelberger, A . P. Polyhedron 1987, 6, 741-757. (91) Manzer, L . E . Inorg. Synth. 1982, 21, 135-140. Page 205 References begin on page 200. Chapter Six Thesis summary and extensions: alternative routes to dinitrogen complexes 6.1. Thesis summary The preceding chapters of this thesis have explored donor atoms substitution in macrocyclic and chelating amidophosphine ligands and the effects o f these substitutions on the coordination chemistry of early transition metals, specifically in dinitrogen coordination reactions. Unfortunately, every attempt to use reductive processes to activate N 2 results in complicated mixtures of products. For example, with zirconium and titanium complexes supported by Ph[As2N2], evidence points to reduction of arsenic within the macrocycle. The combination of a chelating multidentate ligand, p h [ N A s N ] , and tantalum also did not lead to activation of N 2 . In this case, hydrogenation of the trimethyl complex P h[NAsN]TaMe3 leads to Ta-N hydrogenation and ultimately to the hydrogenated ligand p h [ N A s N ] H 2 . Finally, the bis(aryloxy)phosphine ligand sets R [OPO] (R = Ph, 'Pr) with group 4 and 5 metals undergo ligand redistribution reactions under reductive conditions, likely a result of the decreased steric bulk that is intrinsic to these Page 206 References begin on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes metal-ligand combinations. In this final chapter, some alternative routes to dinitrogen complexes are discussed, along with a few preliminary experiments that were attempted. 6.2. Alternative routes to dinitrogen complexes: ligand exchange The use of atmospheric N 2 in dinitrogen coordination reactions is desirable, as it is abundant, readily accessible and inexpensive. However, this is not the only route to coordinated dinitrogen complexes and chapter one briefly discussed other molecules that can give rise to the coordinated N 2 moiety. For example, the silylated hydrazine (Me3Si)2NN(SiMe3)2 reacts with TaCls to form the end-on dinitrogen complex [TaCl 3 (THF) 2 ] 2 (p -N 2 ) . 1 This complex can also be synthesized through a substitution reaction with P h C H = N N = C H P h as shown in Equation 6.1 2,3 HF 2 ^ T a CI ,..»CI ^ ^ C M e 3 HF P h C H = N N = C H P h -2 P h C H = C H C M e 3 C L , CI H F oCI T a H F ~N CI T a HF oCI <6-1> CI H F This dinitrogen complex has Ta-N and N - N bond distances that are consistent with a hydrazido (N 2 4") ligand. 4 ' 5 One of the more intriguing reactions that this complex undergoes is ligand exchange without displacement of the hydrazido fragment. Treatment of [TaCl3(THF) 2] 2(p-N 2) with an excess o f trimethylsilyl diethyldithiocarbamate, Me3SiS 2 CNEt 2 , gives the complex [Ta(S 2 CNEt 2 )3] 2 (p-N 2 ) . ' Other reactions have replaced the chloride ligands with /-butoxide, 3 the substituted phenoxide DIPP (DIPP = 2,6-'Pr 2-C 6 H 3 0 ) , 6 and a thiolate TIPT (TIPT = 2 ,4 ,6- 'Pr 3 -C 6 H 2 S) . 6 Extension of this ligand exchange reaction to more complex multidentate ligands is of interest, particularly for ligands where the synthesis of coordinated dinitrogen complexes using N 2 has proven Page 207 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes impossible. Synthesis of complexes in this manner would then allow an investigation of coordinated dinitrogen chemistry for ligand systems, such as the ligands studied in this thesis, that resist traditional synthetic methods. Preliminary ligand exchange reactions indicate that it may be possible to prepare dinitrogen complexes by non-traditional methods. Addit ion of a solution of P h [ O P O ] T a C l 3 (5.9) or ' P r [ O P O ] T a C l 3 (5.10) in T H F to a slurry o f [TaCl 3 (THF) 2 ] 2 (p -N 2 ) in T H F at ambient temperature results in the dissolution of solids over the course of an hour. N M R spectroscopy of the isolated solid indicates a variety of products are formed. Mass spectrometry indicates the complex ( R [OPO]TaCl) 2 (p-Cl ) 2 (p-NH) is formed in each reaction. The presence of bridging chlorides is speculative, but they are common in tantalum halide chemistry. 7" 9 Presumably this complex is formed by protonation of the N2 moiety by HC1 in a complex such as ( R [OPO]Ta(THF) 2 ) 2 (u-N 2 ) . The protonated arsine precursors ph[As2N2]H2 (2.3) and p h [NAsN]H2 (3.2) do not show significant reactivity with [TaCl 3 (THF) 2 ] 2 (p -N 2 ) . The lithiated arsines p h [ A s 2 N 2 ] L i 2 ( 1,4-dioxane) (2.1) and p h [NAsN ]Li2 (THF) 2 (3.1) do react at ambient temperature, however, like the [OPO] reactions, multiple products are formed. Future work in this area must focus on controlling the reactivity. 6.3. Alternative routes to dinitrogen complexes: hydrazines Hydrazine and substituted hydrazines can form other N - N bonded species in addition to coordinated dinitrogen complexes, and these have been extensively studied,1 0" 1 2 primarily because of their postulation as intermediates in the metal-mediated reduction of dinitrogen to ammonia by various nitrogenase enzymes. 1 3" 1 6 These metalloenzymes 1 n contain an iron-sulfur-molybdenum cofactor, or FeMoco, at their active site. Alternative nitrogenase enzymes using vanadium in place of iron or molybdenum are known, but are much less common. 1 8 In the nitrogenase reaction, dinitrogen is reduced and protonated at ambient temperature and pressure according to the reaction shown in Equation 6.2. The Page 208 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes mechanism of this reaction remains unknown, 1 9 the equation merely shows the limiting stoichiometry. N=N + 8 H + + 8 e" + 16 MgATP 2 N H 3 + H 2 + 16 M g A D P + 16 P, (6.2) The step-wise protonation of coordinated N 2 to N H 3 has been extensively studied via the protonation of W(0) and Mo(0) model complexes with phosphine and coordinated N 2 ligands. 11,20-22 Recently, the first catalytic reduction of dinitrogen to ammonia was 23-26 reported with a molybdenum N2 complex/ Hydrazido ligands can bind to transition metals through a variety of binding modes. 2 7" 2 9 The coordination is classified according to the charge carried by the hydrazido ligand. Common examples are hydrazide (1-) (NRNR2), hydrazide (2-) (NNR2) (where R signifies an organic group or H) , and the N24" o f the hydrazido dinitrogen moiety. The metal may be bound either to one (n,1) or both (r\2) hydrazido nitrogens; the ligand may also be terminal on a single metal center, or it may bridge two metal centers (p.2). Several common bonding modes are summarized in Figure 6.1. N ' M n1-hydrazido(1-) R« "N N ' \/ M n2-hydrazido(1-) Rv. ^R M n1-hydrazido(2-) R ^ . R N M" ^ " M u2:n1,ri1-hydrazido(2-) -N R M M u2:n2,r|1-hydrazido(2-) M ^ = N N = M u2:n.1,n,1-hydrazido(4-) Figure 6.1. Common hydrazido ligand binding modes. Page 209 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes While many hydrazido complexes have been synthesized and characterized for transition metals across the periodic table, examples of early transition metal hydrazido complexes are less common. For example, r)'-hydrazido(2-) complexes o f titanium are limited to the complexes (Me 3Si) 2N-N=TiCp2, 3 0 P h 2 N - N = T i ( T M T A A ) 3 1 (where T M T A A = tetramethyl-dibenzotetraaza[14]annulene) and porphyrin complexes R 2 N -N=Ti(TPP) 3 2 ' (where TPP = meso-tetra-p-tolylporphyrinato dianion). Related cyclopentadienyl complexes o f titanium have been synthesized bearing hydrazine derived ligands including the bridged system [CpTiCl(u.-NNPh 2 )] 2 shown in Figure 6.2(a), 3 3 ' 3 4 which contains a p 2:n 2 ,r | l-hydrazido(2-) and a p 2:ri 1,r | 1-hydrazido(2-) ligand. Similar complexes are known for zirconium. 3 5 The n 2 coordination mode is also commonly observed in titanium complexes containing hydrazido(l-) ligands. For example, reaction of C p T i C l 3 with M e 2 N N H 2 leads to the complex C p T i C l 2 ( n 2 - N r l N M e 2 ) , shown in Figure 6.2(b). 3 6 ' 3 7 Figure 6.2. Titanium hydrazido complexes: (a) [CpTiCl (p -NNPh 2 ) ] 2 ; (b) C p T i C l 2 ( n 2 - N H N M e 2 ) . There are several examples of 1,2-diphenylhydrazido(2-) (r) -azobenzene) complexes of T i , Zr, and Hf. For example, C p 2 T i ( C O ) 2 reacts cleanly with azobenzene losing C O and forming Cp 2 Ti( r ( 2 -PhNNPh) . 3 8 The zirconium analog can be prepared by reaction of l,2-dilithio-l,2-diphenylhydrazide with C p 2 Z r C l 2 . 3 9 ' 4 0 The free C p 2 Z r ( n 2 -Page 210 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes PhNNPh) is extremely reactive, readily adding an additional donor ligand such as T H F or P M e 3 . In tantalum hydrazido chemistry, a simple hydrazine adduct of a tantalum alkoxide, Ta(OMe)5(H2NNH2), has been reported. 4 1 However, group 5 hydrazido chemistry is generally less explored than that of group 4. The hydrazido(l-) complexes CpVCl2(NMeNMe2) and CpNbCl3(NMeNMe2) have been prepared by reaction o f C p V C h or CpNbCL- with lithiated hydrazides 4 2 A similar tantalum complex, [Ta(r| 2-NMeNMe2)(S2CNEt2)3]Br, shown in Figure 6.3(a), can be prepared by the reaction of TaBr2(S2CNEt2)3 with silylated hydrazines. 4 3 Tantallocene complexes with functionalized diazoalkane ligands, such as the complex Cp2Ta(H)(r| '-NNCPh 2) shown in Figure 6.3(b), are also known. 4 4 ' 4 5 Figure 6.3. Tantalum hydrazido complexes: (a) [Ta(n 2 -NMeNMe 2 ) (S 2 CNEt2 )3] + ; (b) Cp2Ta(H)(r]1-NNCPh2). Reaction of l-amino-2,2,6,6-tetramethylpiperidine with TaCls in the presence of E t 3 N / M e 3 S i C l gives the complex (Et3NH)[Ta(N2C9Hi8)2Cl4],46 shown in Figure 6.4(a). The T a - N - N moiety is formulated as isodiazene(O), a neutral isomer o f the hydrazido(2-) ligand, based on structural data and oxidation state arguments. Me NEt 2 Page 211 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes F i g u r e 6.4. Tantalum isodiazene complex: [TaCNaCgHis^CL;]". Hydrazine reacts readily with p h [ N A s N ] T a M e 3 (3.3) and P h [ O P O ] T a M e 3 (5.17) affording pale solids. N M R spectroscopy indicates that a single product is formed in each reaction. However, mass spectrometry and elemental analysis have not returned useful data on these complexes, presumably because of the sensitivity of metal-alkyl bonds and these complexes remain unidentified. Reactions of hydrazine with ' P r [ O P O ] T a C l 3 (5.9) suffer from the low solubility of the complex in common solvents, particularly at lower temperatures. This results in the reaction of multiple hydrazine equivalents with a single molecule of 5.9, and the isolation of product mixtures. Reaction of excess hydrazine with 5.9 also yields a mixture of products. However, slow concentration of a benzene solution containing the isolated material deposits several colourless crystals of X-ray quality. The deposited crystals have been structurally characterized as p h [ O P O ] H 3 C l (6.1). The solid-state molecular structure is presented in Figure 6.5; crystallographic data is presented in Table A - 9 of the Appendices, and selected bond distances and angles are detailed in Table 6.1. Each unit cell of the crystal contains two molecules of 6.1 in a hydrogen-bonded dimer, and 1.5 molecules of co-crystallized solvent. The p h [ O P O ] H 3 C l molecules face each other about an inversion center, with hydrogen bonding between phenolic protons and chlorides. Proton H(2) is shown bonding to the chloride C l ( l ) and H ( l ) is hydrogen-bonded to the chloride associated with the facing p h [ O P O ] H 3 + ; however, the association of one chloride with a particular p h [ O P O ] H 3 + molecule is arbitrary. The complex is very similar to p h [ O P O ] H 3 ) ( T a C l 6 ) (5.11), both are Page 212 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes phosphonium salts of [OPO], however, with different anions; 6.1 appears to be the first triphenylphosphonium salt reported with a simple halide anion. 4 7 Thus, bond distances are similar between the two complexes; however, 5.11 has no hydrogen bonding and this is reflected in the subtly longer C - 0 and O - H bonds in 6.1. Wi th no metal center to bind, the phenol rings are not parallel; although unlike 5.11, where they are rotated 146.4 °, the rings in 6.1 are rotated 87.3 °. Figure 6.5. Molecular structure (ORTEP) of P h [ O P O ] H 3 C l , 6.1. Ellipsoids are drawn at 50% probability. Page 213 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes Table 6.1. Selected bond distances (A), bond angles (°), and dihedral angles (°) for p h [ O P O ] H 3 C l , 6.1. Atom Atom Distance (A) Atom Atom Distance (A) P ( l ) C ( l ) 1.792(4) 0(1) C(2) 1.375(4) P( l ) C(7) 1.784(4) 0(2) C(8) • 1.384(4) P( l ) C(13) 1.776(4) 0(1) H ( l ) 1.014(2) P ( l ) H(3) 1.309(2) 0(2) H(2) 1.070(3) H(2) C l ( l ) 1.933(3) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) C ( l ) P ( l ) C(7) 107.60(17) C(2) 0(1) H ( l ) 114.74(18) C(7) P ( l ) C(13) 108.74(18) C(8) 0(2) H(2) 104.83(18) C ( l ) P ( l ) C(13) 110.38(17) C(7) P ( l ) H(3) 11.73(17) C ( l ) P ( l ) H(3) 109.71(17) C(13) P ( l ) H(3) 108.67(17) Atoms Atoms Angle (°) Phenol ring Phenol ring -87.3 A 3 l P { 1 H } N M R spectrum of the crystals taken in c?6-DMSO shows a single resonance at 37.8 ppm, in agreement with similar phosphonium sal ts . 4 8 , 4 9 However, i f the isolated crystals are dissolved in ^-benzene, a new resonance at -47 ppm can be observed in the ^ P l ' H } N M R spectrum, attributed to p h [ O P O ] H 2 (4.5) via loss of HC1. Phosphonium salts containing hydrohalic acids are known to dissociate under certain conditions, 5 0 and work with the bis(o-phenoxy)phenylphosphonium chloride has shown that the complex dissociates when dissolved in basic solvents such as pyridine 4 9 Formation of 6.1 l ikely involves reaction of one or more equivalents of hydrazine with 5.11, producing HC1 and a putative tantalum hydrazido species. Reaction o f multiple HC1 with additional 5.11 gives the observed products. Another possible mechanism is the Page 214 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes direct transfer of hydrazine protons to [OPO] in an intramolecular reaction. However, the pK.HA of phenol (18.0) 5 1 compared to the weaker acidity of hydrazine (-28-30) (see reference 52 and references therein for a discussion of hydrazine acidity) suggest that direct transfer of a proton would not be possible. The reaction of adventitious H 2 0 with 5.9 producing the required HC1 cannot be ruled out. In the absence of base, M e 2 N N H 2 does not react with 5.10. This is not unexpected considering the difficulty in reacting amines with Ta-Cl bonds discussed in chapter two. Addition of M e 2 N N H 2 to a solution of 5.10 containing triethylamine produces a mixture of products. Reaction of 1,2-diphenylhydrazine (PhHNNHPh) with 5.10 at ambient temperature also produces a mixture of products. Mass spectrometry indicates the complex ( / P r [0P0]TaCl) 2 (u--Cl)2(u-NH) is formed. Controlling the reactivity of [OPO] complexes with hydrazine and substituted hydrazines remains an important focus of ongoing work with these complexes. Page 215 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes 6.4. Experimental 6.4.1 General Procedures Unless otherwise stated, general procedures were performed as in Section 2.9.1. 6.4.2 Starting Materials and Reagents J6-DMSO was dried over C a H 2 and distilled. 6.4.3 Synthesis, Characterization and Reactivity of Complexes Synthesis of P h[OPO]H 3Cl (6.1). Addit ion o f hydrazine (98 p.L, 3.1 mmol) to a solution o f 5.9 (0.50 g, 0.62 mmol) in toluene (20 mL) produced a cream coloured solution. The solution was stirred for 12 h, and then evaporated to dryness. The residue was extracted with benzene (5 mL) and allowed to stand for 48 h producing colourless crystals. Y ie ld : not recorded. Calc. M W : 555.17 g mor'. 3l?{lU} N M R (121.4 M H z , C 6 D 6 , 25 °C): 6 -47.18 (s). 3 1 P { ' H } N M R (121.4 M H z , C 2 D 6 S O , 25 °C): 6 37.78 (s, IP). Ana l . Calcd. for C34H48CIO2P: C , 73.65; H , 8.71. Found: C, 73.82; H , 8.96. Page 216 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes 6.5. References (1) Dilworth, J. R.; Harrison, S. J.; Henderson, R. A . ; Walton, D . R. M . J. Chem. Soc., Chem. Commun. 1984, 176-177. (2) Turner, H . W. ; Fellman, J. D . ; Rocklage, S. M ; Schrock, R. R.; Churchill , M . R.; Wasserman, H . J. J. Am. Chem. Soc. 1980,102, 7809-7811. (3) Rocklage, S. M . ; Schrock, R. R. J. Am. Chem. Soc. 1982,104, 3077-3081. (4) Churchill , M . R.; Wasserman, H . J. Inorg. Chem. 1981, 20, 2899-2904. (5) Churchill , M . R.; Wasserman, H . J. Inorg. Chem. 1982, 21, 218-222. (6) Schrock, R. R.; Wesolek, M . ; L i u , A . H . ; Wallace, K . C ; Dewan, J. C. Inorg. Chem. 1988, 27, 2050-2054. (7) Chakravarty, A . R.; Cotton, F. A . ; Diebold, M . P.; Lewis, D . B . ; Roth, W . J. J. Am. Chem. Soc. 1986,108, 971-976. (8) Bradley, D . C ; Hursthouse, M . B . ; Howes, A . J.; Jelfs, A . N . d. M . ; Runnacles, J. D. ; Thornton-Pett, M . J. Chem. Soc, Dalton Trans. 1991, 841-847. (9) Chadeayne, A . R.; Wolczanski, P. T.; Lobkovsky, E . B . Inorg. Chem. 2004, 43, 3421-3432. (10) Dilworth, J. R. Coord. Chem. Rev. 1916, 21, 29-62. (11) Chatt, J.; Dilworth, J. R.; Richards, R. L . Chem. Rev. 1978, 78, 589-625. (12) Leigh, G . J. Acc. Chem. Res. 1992, 25, 177-181. (13) Burgess, B . K . Chem. Rev. 1990, 90, 1377-1406. (14) Dilworth, J. R.; Glenn, A . ' P . Biology and Biochemistry of Nirogen Fixation; Elsevier: Amsterdam, 1991. (15) Malinak, S. M . ; Coucouvanis, D . Prog. Inorg. Chem. 2001, 49, 599-662. (16) Einsle, O.; Tezcan, F. A . ; Andrade, S. L . A . ; Schmid, B . ; Yoshida, M . ; Howard, J. B . ; Rees, D . C. Science 2002, 297, 1696-1700. (17) Thorneley, R. N . F. ; Lowe, D . J. J. Biol. Inorg. Chem. 1996,1, 576-580. (18) Rehder, D . Coord. Chem. Rev. 1999,182, 297-322. (19) Pickett, C. J. J. Biol. Inorg. Chem. 1996,1, 601-606. (20) Hidai , M . ; Mizobe, Y . Chem. Rev. 1995, 95, 1115-1133. Page 217 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes (21) Hidai , M . Coord. Chem. Rev. 1999,185-186, 99-108. (22) Richards, R. h.'Coord. Chem. Rev. 1996,152, 83-97. (23) Yandulov, D . V . ; Schrock, R. R. J. Am. Chem. Soc. 2002,124, 6252-6253. (24) Yandulov, D . V . ; Schrock, R. R. Science 2003, 301, 76-78. (25) Ritleng, V . ; Yandulov, D . V . ; Weare, W. W.; Schrock, R. R.; Hock, A . S.; Davis, W . M . J. Am. Chem. Soc. 2004,126, 6150-6163. (26) Yandulov, D . V . ; Schrock, R. R. Inorg. Chem. 2005, 44, 1103-1117. (27) Nugent, W . A . ; Haymore, B . L . Coord. Chem. Rev. 1980, 31, 123-175. (28) Sutton, D . Chem. Rev. 1993, 93, 995-1022. (29) L i , Y . ; Shi, Y . ; Odom, A . L . J. Am. Chem. Soc. 2004,126, 1794-1803. (30) Wiberg, N . ; Haring, H . - W . ; Huttner, G . ; Friedrich, P. Chem. Ber. 1978, 111, 2708-2715. (31) Blake, A . J.; Mclnnes, J. M . ; Mountford, P.; Nikonov, G . I.; Swallow, D . ; Watkin, D. J. J. Chem. Soc, Dalton Trans. 1999, 379-391. (32) Thorman, J. L . ; Woo, L . K . Inorg. Chem. 2000, 39, 1301-1304. (33) Hughes, D . L . ; Latham, I. A . ; Leigh, G . J. J. Chem. Soc, Dalton Trans. 1986, 393-398. (34) Latham, I. A . ; Leigh, G . J. J. Chem. Soc, Dalton Trans. 1986, 398-401. (35) Walsh, P. J.; Carney, M . J.; Bergman, R. G . J. Am. Chem. Soc. 1991, 113, 6343-6345. (36) Dilworth, J. R.; Latham, I. A . ; Leigh, G . J.; Huttner, G . ; Jibril , I. J. Chem. Soc, Chem. Commun. 1983, 1368-1370. (37) Latham, I. A . ; Leigh, G . J.; Huttner, G . ; Jibril , I. J. Chem. Soc, Dalton Trans. 1986, 377-383. (38) Fochi, G . ; Floriani, C ; Bart, J. C ; Giunchi, G . J. Chem. Soc, Dalton Trans. 1983, 1515-1521. (39) Walsh, P. J.; Hollander, F. J.; Bergman, R. G . J. Am. Chem. Soc. 1990, 112, 894-896. (40) Walsh, P. J.; Hollander, F. J.; Bergman, R. G . J. Organomet. Chem. 1992, 428, 13-47. Page 218 References start on page 217. Chapter Six: Thesis summary and extensions: alternative routes to dinitrogen complexes (41) Hubert-Pfalzgraf, L . G . ; Riess, J. G . J. Chem. Soc., Dalton Trans. 1974, 585-588. (42) Jimenez-Tenorio, M . ; Leigh, G . J. Polyhedron 1989, 8, 1784-1785. (43) O'Flaherty, F. P.; Henderson, R. A . ; Hughes, D . L . J. Chem. Soc, Dalton Trans. 1990, 1087-1091. (44) Nikonov, G . I.; Putala, M . ; Zinin, A . I.; Kazennova, N . B . ; Lemenovskii, D . A . ; Batsanov, A . S.; Struchkov, Y . T. J. Organomet. Chem. 1993, 454, 87-90. (45) Lemenovskii, D . A . ; Putala, M . ; Nikonov, G . I.; Kazennova, N . B . ; Yufit , D . S.; Struchkov, Y . T. J. Organomet. Chem. 1993, 454, 123-131. (46) Danopoulos, A . A . ; Hay-Motherwell, R. S.; Wilkinson, G . ; Sweet, T. K . N . ; Hursthouse, M . B . Polyhedron 1997, 16, 1081-1088. (47) A search of the Cambridge Crystallographic Data Center database, November 2004 update, did not return any triphenylphosphonium halide complexes. (48) Tebby, J. C. In Phosphorus-31 NMR Spectroscopy in Stereochemical Analysis; Verkade, J . G . , Quin, L . D. , Eds.; V C H : Deerfield Beach, F L . , 1987, pp. 27. (49) Luo, H . ; Setyawati, I.; Rettig, S. J.; Orvig, C. Inorg. Chem. 1995, 34, 2287-2299. (50) Sheldon, J. C ; Tyree Jr., S. Y . J. Am. Chem. Soc 1958, 80, 2117-2120. (51) Bordwell , F. G . ; McCa l lum, R. J.; Olmstead, W . N . J. Org. Chem. 1984, 49, 1424-1427. (52) Zhao, Y . ; Bordwell , F. G . ; Cheng, J.-P.; Wang, D . J. Am. Chem. Soc. 1997, 119, 9125-9129. Page 219 References start on page 217. Appendix A: X-ray Crystal Structure Data Appendix A: X-ray crystal structure experimental information A. l. General Considerations In all cases, suitable crystals were selected and mounted on a glass fibre using Paratone-N oi l or an acceptable substitute and frozen to -100 °C. Measurements for structures 2.1, 2.2, 2.4, 2.5, 2.6, 2.7, 4.1, 4.2-0, 4.3, 4.5, 5.12, and 5.14 were made on a R igaku /ADSC C C D area detector with graphite monochromated M o - K a radiation. Data was processed using the d T R E K 1 module, part of the CrystalClear software package, version 1.3.6 SPO, 2 and corrected for Lorentz and polarization effects and absorption. Neutral atom scattering factors for all non-hydrogen atoms were taken from Cromer and Waber. Anomalous dispersion effects were included in F c a i c . 4 Measurements for structure 3.1 were made on a R igaku /ADSC C C D area detector with graphite monochromated M o - K a radiation. Data was determined to be a two component twin (components related by a rotation of 7.77° normal to 0.03, -1.00, -1.39) using the Twinsolve module of the CrystalClear software package, version 1.3.6 SPO. 2 Measurements for structures 2.3, 3.2, 3.3, 4.4, 4.7, 4.8, 5.3, 5.4, 5.11, 5.13, 5.16, and 6.1 were made on a Bruker X 8 area detector with monochromated M o - K a radiation, by Dr. B . O. Patrick. Data was processed and integrated using the Bruker S A I N T software package 5 and corrected for absorption effects using the multi-scan technique ( S A D A B S ) . 6 Neutral atom scattering factors for all non-hydrogen atoms were taken from Cromer and Waber. 3 Anomalous dispersion effects were included in F c a i c ; 4 the values for Af" and Af" were those o f Creagh and M c A u l e y . 7 The values for the mass attenuation coefficients are those of Creagh and Hubbell. Page 220 References located on page 222. Appendix A: X-ray Crystal Structure Data A l l structures were solved by direct methods using the programs SIR97 9 or SIR2002. 1 0 A l l non-hydrogen atoms were refined anisotropically by least squares procedures on F2 using S H E L X L - 9 7 . 1 1 Hydrogen atoms were included but not refined; their positional parameters were calculated with fixed C - H bond distances of 0.99 A for sp 2 C , 0.98 A for sp 3 C , and 0.95 A for aromatic sp C, with £/jso set to 1.2 times the £/ e q of the attached sp or sp 2 C and 1.5 times the Ueq values of the attached sp 3 C atom. Methyl hydrogen torsion angles were determined by electron density. Structure solution and 12 refinements were conducted using the W i n G X software package, version 1.64.05. Structural illustrations were created using ORTEP-III for Windows. Data files (.cif format) for indicated structures are available on-line at http://www.ccdc.cam.ac.uk/. C C D C Registry numbers are tabulated. Page 221 References located on page 222. Appendix A: X-ray Crystal Structure Data A.2. References (1) Pflugrath, J. W . Acta Cryst. 1999, D55, 1718-1725. (2) CrystalClear: A n Integrated Program for the Collection and Processing o f Area Detector Data, Rigaku Corporation, 2002-2004. (3) Cromer, D . T.; Waber, J. T. International Tables for X-ray Crystallography; Kynoch Press, 1974; V o l . V o l . IV. (4) Ibers, J. A . ; Hamilton, W. C. Acta Cryst. 1964,17, 781-782. (5) SAINT Software User Guide, Version 7.03A, Bruker Analytical X-ray Systems, Inc., Madison, WI , 1997-2003. (6) Sheldrick, G . M . S A D A B S , Version 2.05, Bruker Analytical X-ray Systems, Inc., Madison, WI, 2003. (7) Creagh, D . C ; McAuley , W . J. In Internaitional Tables for Crystallography; Wilson, A . J . C , Ed. ; Kluwer Academic Publishers: Boston, 1992; V o l . V o l . C , pp Table 4.2.6.8, pp 219-222. (8) Creagh, D . C ; Hubbell, J. H . In International Tables for Crystallography; Wilson, A . J. C , Ed. ; Kluwer Academic Publishers: Boston, 1992; V o l . V o l . C, pp Table 4.2.4.3, pp 200-206. (9) Altomare, A . ; Burla, M . C ; Cammali, G . ; Cascarano, M . ; Giacovazzo, C ; Guagliardi, A . ; Moliterni, A . G . G . ; Polidori, G . ; Spagna, A . J. Appl. Crystallogr. 1999,52,115-119. (10) Burla, M . C ; Camall i , M . ; Carrozzini, B . ; Cascarano, G . L . ; Polidori, G . ; Spagna, R. J. Appl. Crystallogr. 2003, 36, 1103. (11) Sheldrick, G . M . SHELX97: Programs for Crystal Structure Analysis (Release 97-2), University of Gottingen, Gottingen, Germany, 1998. (12) Farrugia, L . J. J. Appl. Crystallogr. 1999, 32, 837-838. (13) Farrugia, L . J. J. Appl. Crystallogr. 1997, 30, 565. Page 222 References located on page 222. Appendix A: X-ray Crystal Structure Data A.3. Tables of Crystallographic Data Table A - l . Crystallographic and Structure Refinement Data for p h [ A s 2 N 2 ] L i 2 ( 1,4-dioxane) (2.1), p h [ A s 2 N 2 ] L i 2 ( T H F ) 2 (2.2), and p h [ A s 2 N 2 ] H 2 (2.3). F h [ A s 2 N 2 ] L i 2 ( l , 4 -F h [ A s 2 N 2 ] L i 2 ( T H F ) 2 , P h [ A s 2 N 2 ] H 2 (2.3) dioxane), (2.1) (2.2) C C D C Registry 250322 - ~ Formula C28H5oAs2Li2N202Si4 C 3 2 H58As 2 N 2 Li 2 0 2 Si4 C24H44As2N2Si4 Fw 722.78 778.88 622.81 Colour, habit colourless, platelet colourless, irregular colourless, platelet Crystal size, mm 0 . 2 0 x 0 . 1 0 x 0 . 0 5 0.40 x 0.30 x 0.20 0.35 x 0.20 x 0.05 Crystal system Orthorhombic Monocl inic Monocl inic Space group P2,2 ,2 1 (no. 19) P2,/n (no. 14) P2/c (no. 13) a, A 9.3050(6) 17.5583(10) 15.049(3) b,A 17.8403(12) 10.7733(5) 10.3545(15) c,A 21.9501(15) 21.5084(11) 21.472(4) a , deg 90 90 90 P, deg 90 98.994(2) 107.236(6) y, deg 90 90 90 V , A 3 3643.8(3) 4018.5(4) 3195.7(10) z 4 4 4 T, ° C -100 ± 1 -100 ± 1 -100 ± 1 Pcalc, g/cm3 1.318 1.287 1.295 F(000) 1504 1632 1296 u(MoKcc), mm' 1 1.992 1.811 2.256 transmission factors 0 . 7 6 4 8 - 1.0000 0 .7825 - 1.0000 0 .7242-1 .0000 2 9 m a x , deg 55.74 55.74 49.62 total no. of re fins 33235 33448 22742 no. of unique reflns 7940 9059 5460 Emerge 0.0796 0.0447 0.1031 no. reflns with I > 2a(I) 6637 8271 3447 no. of variables 369 405 305 R (F 2 , all data) 0.0919 0.0739 0.1172 R W ( F 2 , all data) 0.1847 0.1633 0.1878 R ( F , I > 2 G ( I ) ) 0.0736 0.0664 0.0700 R w ( F , I > 2 o ( I ) ) 0.1695 0.1572 0.1598 gof 1.078 1.122 1.017 Page 223 References located on page 222. Appendix A: X-ray Crystal Structure Data Table A-2. Crystallographic and Structure Refinement Data for ™[As 2 N 2 ]ZrCl 2 (2.4), P h [ A s 2 N 2 ] Z r I 2 (2.5), and p h [ A s 2 N 2 ] T i C l 2 (2.6). P h [As 2 N 2 ]ZrCl 2 , (2.4) P h [As 2 N 2 ]ZrI 2 (2.5) P h [ A s 2 N 2 ] T i C l 2 (2.6) C C D C Registry 250323 250324 250325 Formula C24H42As2Cl2N2Si4Zr C 2 4 H 4 2 A s 2 I 2 N 2 S i 4Zr C 2 4 H 4 2 A s 2 C l 2 N 2 S i 4 T i •C7H8 •2.5CgH6 Fw 875.05 965.82 934.87 Colour, habit colourless, platelet colourless, irregular orange, irregular Crystal size, mm 0.30 x 0.20 x 0.05 0.25x0.10x0.05 0.3 x 0.2x0.1 Crystal system Monoclinic Monoclinic Monoclinic Space group C2/c(no. 15) C2/c(no. 15) P2,/a (no. 14) a, A 22.7484(17) 43.057(2) 17.8530(13) b,A 8.7492(6) 8.9499(3) 11.1792(7) cA 21.5246(18) 19.2595(11) 23.2490(17) a, deg 90 90 90 P, deg 113.146(2) 113.8957(15) 98.286(3) Y, deg 90 90 90 V , A 3 3939.2(5) 6785.7(6) 4591.7(6) Z 4 8 4 T, °C -100 ± 1 -100 ± 1 -100 ± 1 Peak, g/cm3 1.475 1.891 1.352 F(000) 1784 3744 1932 (j(MoKa), mm'1 2.227 4.239 1.866 transmission factors 0.7108- 1.0000 0.6830- 1.0000 0.7491 - 1.0000 2emax, deg 55.74 55.76 55.76 total no. of reflns 17016 29587 41258 no. of unique reflns 4353 7770 10510 R-merge 0.0346 0.0353 0.0670 no. reflns with I > 2a(I) 3858 7226 7809 no. of variables 215 324 459 R (F 2, all data) 0.0432 0.0386 0.0879 R W ( F 2 , all data) 0.0749 0.0905 0.1640 R(F,I>2a(I)) 0.0357 0.0354 0.0621 Rw(F,I>2o(I)) 0.0709 0.0883 0.1452 gof 1.153 1.085 1.044 Page 224 References located on page 222. Appendix A: X-ray Crystal Structure Data Table A - 3 . Crystallographic and Structure Refinement Data for ( [ A s 2 N 2 ] Y ) 2 ( / / - C l ) 2 (2.7), p h [ N A s N ] L i 2 ( T H F ) 2 (3.1), and P h [ N A s N ] H 2 (3.2). ( P h [As 2 N 2 ]Y) 2 (^i-Cl) 2 F h [NAsN]Li 2 (THF) 2 , P h [NAsN]H 2 , ( 3 . 2 ) ( 2 .7) ( 3 . 1 ) CCDC Registry 250326 ~ ~ Formula C 4 8H 8 4As4Cl 2 N 4 Si 8 Y 2 C 3 2 H 4 7 A s L i 2 N 2 0 2 S i 2 C 2 4 H 3 3 A s N 2 S i 2 Fw 1490.31 636.70 480.62 Colour, habit colourless, irregular colourless, irregular colourless, platelet Crystal size, mm 0.2x0.15x0.15 0.20x0.15x0.05 0.25 x 0.20 x 0.05 Crystal system Triclinic Triclinic Triclinic Space group P - l (no. 2) P - l (no. 2) P - l (no. 2) a, A 11.5406(9) 10.005(2) 9.8456(3) b, A 15.2243(11) 12.103(3) 11.7510(3) c,A 20.6305(14) 15.287(3) 23.8216(5) a, deg 94.8433(19) 83.135(14) 95.2940(10) P, deg 98.5004(19) 74.071(12) 96.1300(10) Y, deg 104.599(2) 73.759(14) 109.8230(10) V , A 3 3607.8(4) 1708.9(7) 2553.48(11) z 2 2 4 T, °C -100 ± 1 -100 ± 1 -100 ± 1 Peak, g/cm3 1.372 1.237 1.250 F(000) 1512 672 1008 u(MoKa), mm"1 3.659 1.094 1.437 transmission factors 0.8156- 1.0000 0.8372- 1.0000 0.7706- 1.0000 29 m a x , deg 53.46 55.74 49.94 total no. of reflns 30085 9247 53634 no. of unique reflns 13428 5564 8829 R-merge 0.0497 0.0774 0.0514 no. reflns with I > 2a(I) 11041 3618 6818 no. of variables 629 374 547 R (F 2, all data) 0.0668 0.0970 0.0569 R W ( F 2 , all data) 0.1331 0.1165 0.0933 R ( F , 1 > 2 G ( I ) ) 0.0530 0.0524 0.0374 R w (F, I >2G(I)) 0.1233 0.1042 0.0857 gof 1.098 0.949 1.017 Page 225 References located on page 222. Appendix A: X-ray Crystal Structure Data Table A - 4 . Crystallographic and Structure Refinement Data for [ N A s N ] T a M e 3 (3.3), ( P h [ O P O ] L i 2 ) 2 ( T H F ) 4 (4.1), and [ i P r[OP(=0)0]Li 2(H 20)] 2 (4.2-Q). ^[NAsNlTaMej , (3.3) ( P h [OPO]Li 2 ) 2 (THF) 4 (4.1) HpP(=0)0]Li 2 (H 2 0 ) 1 2 (4.2-0) CCDC Registry -- - ~ Formula C27H4oAsN2Si2Ta C84Hi22Li40gP2-3C6H6 C 6 2 H 9 8 L i 4 0 8 P 2 - 4 C 6 H 6 Fw 704.66 1583.84 1369.50 Colour, habit colourless, irregular colourless, irregular colourless, block Crystal size, mm 0.5x0.4x0.3 0.25x0.15x0.05 0.30x0.20x0.20 Crystal system Monoclinic Triclinic Monoclinic Space group P2,/a (no. 14) P- l (no. 2) P2!/c(no. 14) a, A 16.9447(3) 13.4016(13) 10.2530(11) b ,A 9.97240(10) 13.8466(17) 19.8120(16) c,A 17.9460(3) 27.718(3) 20.8950(19) a, deg 90 77.004(5) 90 P,deg 104.0290(10) 80.257(4) 102.419(3) y, deg 90 76.333(4) 90 V , A 3 2942.05(8) 4833.1(9) 4145.1(7) Z 4 2 2 T, °C -100 ± 1 -100 ± 1 -100 ± 1 p c a l c , g/cm3 1.591 1.088 1.097 F(000) 1400 1716 1480 u(MoKcc), mm' 1 4.951 0.097 0.104 transmission factors 0.3767- 1.0000 0.8956- 1.0000 0.8924- 1.0000 29 m a x , deg 55.74 56.0 53.4 total no. of reflns 41381 72152 23709 no. of unique reflns 7033 23119 8047 R-merge 0.0293 0.0318 0.0421 no. reflns with I > 2a(I) 6155 17228 6000 no. of variables 305 1057 475 R (F 2, all data) 0.0225 0.0765 0.1013 R W ( F 2 , all data) 0.0393 0.1466 0.2212 R (F, I >2a(I)) 0.0168 0.0533 0.0765 R w (F,I>2a(I)) 0.0355 0.1332 0.1980 gof 1.078 1.035 1.060 Page 226 References located on page 222. Appendix A: X-ray Crystal Structure Data Table A -5 . Crystallographic and Structure Refinement Data for [ F h [ O P O ] L i 2 ( A r O L i ) ] 2 (4.3), [ i P r [ O P O ] L i 3 C l ( A r O L i ) ] ( T H F ) 3 (4.4), and p h [ O P O ] H 2 (4.5). [ P h[OPO]Li 2(PhOLi)] 2 [ l P r[OPO]Li 3Cl(PhOLi)] F h [OPO]H 2 (4.5) (4J) (THF) 3 (4.4) C C D C Registry Formula C96Hi32Ll606P2-3C7Hg C 5 7 H 9 2 C l L i 4 0 6 P C 3 4 H 4 7 02P Fw 1747.97 968.55 518.69 Colour, habit colourless, irregular colourless, rod Colourless, irregular Crystal size, mm 0.50x0.20x0.20 0.35 x 0.25 x 0.10 0.40x0.30x0.20 Crystal system Triclinic Orthorhombic Monoclinic Space group P-l (no. 2) Pnma (no. 62) P2,/n (no. 14) a, A 12.9823(14) 17.7457(3) 10.130(4) b, A 15.5897(15) 18.2033(4) 21.406(12) c,A 16.1226(16) 18.3850(3) 14.296(8) a, deg 103.686(2) 90 90 P, deg 101.950(1) 90 96.889(18) y, deg 111.550(2) 90 90 v , A 3 2788.4(8) 5938.91(19) 3078.0(3) z 1 4 4 T, °C -100 ± 1 -100 ± 1 -100 ± 1 p c a l c , g/cm3 1.041 1.082 1.119 F(000) 946 2104 1128 u(MoKa), mm"' 0.088 0.135 0.116 transmission factors • 0.8895- 1.0000 0.9013-1.0000 0.8635- 1.0000 20max, deg 55.6 54.1 55.6 total no. of reflns 25238 130426 29449 no. of unique reflns 11572 6708 6927 R-merge 0.0526 0.0462 0.0510 no. reflns with I > 2a(I) 8470 5011 5475 no. of variables 653 389 385 R (F 2, all data) 0.1102 0.0756 0.0843 R W ( F 2 , all data) 0.2190 0.1670 0.1518 R ( F , I > 2 G ( I ) ) 0.0806 0.0526 0.0644 R W (F, I >2G(I)) 0.1942 0.1490 0.1371 gof 1.047 1.037 1.096 Page 227 References located on page 222. Appendix A: X-ray Crystal Structure Data Table A-6. Crystallographic and Structure Refinement Data for (™[OPO]K 2 ) 2 (THF) 6 (4.7), ( i P r [ O P O ] K 2 ) 3 ( T H F ) 3 (4.8), and P h [ O P O ] 2 T i (5.3). ( p h [ O P O ] K 2 ) 2 ( T H F ) 6 ( l P r [ O P O ] K 2 ) 3 ( T H F ) 3 P h [ O P O ] T i C l 2 ( p y ) (5.3) (4.7) (4.8) C C D C Registry ~ - -Formula C 9 2 H | 3 8 K 4 0 i o P 2 C105H165K6O9P3 C 3 9 H 5 0 C l 2 N O 3 P T i • 3 C 4 H 8 0 • 2 C 6 H 6 + 1 / 2 C 6 H I 4 T . 5 C 6 H 6 Fw 1838.68 2098.18 831.73 Colour, habit Colourless, irregular Colourless, prism Orange, platelet Crystal size, mm 0 . 1 0 x 0 . 1 0 x 0 . 1 0 0 . 2 5 x 0 . 2 0 x 0 . 1 5 0 . 2 5 x 0 . 1 5 x 0 . 0 5 Crystal system Tricl inic Monocl inic Tricl inic Space group P - l (no. 2) P2!/c (no. 14) P - l (no. 2) a, A 14.7955(11) 14.5758(5) 11.1411(3) b , A 15.0630(14) 17.5843(5) 12.1035(4) c,A 15.071(14) 52.6000(15) 18.9085(6) a, deg 77.520(2) 90 79.3110(10) P , deg 71.067(3) 92.9630(10) 85.7230(10) Y, deg 65.407(3) 90 68.1280(10) V , A 3 2876.4(4) 13463.6(8) 2325.11(12) Z 1 4 2 T , ° C -100+1 -100 ± 1 -100 ± 1 Peak, g/cm 3 1.061 1.035 1.188 F(000) 996 4540 882 u ( M o K a ) , mm"1 0.234 0.277 0.370 transmission factors 0 . 6 5 2 2 - 1.0000 0 .7866- 1.0000 0 . 8 4 4 3 - 1.0000 2 9 m a x , deg 46.4 54.1 50.5 total no. o f reflns 32080 136952 52208 no. of unique reflns 7374 23745 8255 Emerge 0.1487 0.0639 0.0780 no. reflns with I > 2a(I) 3369 14832 5235 no. of variables 589 1240 539 R (F 2 , all data) 0.2168 0.1252 0.0919 R W ( F 2 , all data) 0.3464 0.2636 0.1008 R ( F , I > 2 Q ( I ) ) 0.1033 0.0791 0.0424 R w ( F , I > 2 a ( I ) ) 0.2863 0.2326 0.0869 gof 1.039 1.053 1.020 Page 228 References located on page 222. Appendix A: X-ray Crystal Structure Data Table A - 7 . Crystallographic and Structure Refinement Data for p h [ O P O ] 2 T i (5.4), ( p h [OPO]H 3 ) (TaCl 6 ) (5.11), and ( P h [OPO]TaCl 2 ) 2 (p -OH) 2 (5.12). P h [ O P O ] 2 T i (5.4) (P h [ O P O ] H 3 ) ( T a C l 6 ) (5.11) ( p h [ O P O ] T a C l 2 ) 2 ( u -O H ) 2 (5.12) C C D C Registry -- ~ ~ Formula C68H90O4P2T1 • C 6 H 1 8 S i 2 0 C 3 4 H 4 8 C l 6 0 2 P T a - 2 C 7 H 8 C 6 8 H 9 2 C l 4 0 6 P 2 T a 2 • 4 C 6 H 6 Fw 1243.62 1097.61 1883.49 Colour, habit Irregular, red Colourless, tablet Yel low, irregular Crystal size, mm 0 . 2 0 x 0 . 1 0 x 0 . 1 0 0.35 x 0 . 2 0 x 0 . 1 0 0 . 2 5 x 0 . 1 5 x 0 . 0 5 Crystal system Monocl inic Monocl inic Tricl inic Space group P2, /n(no. 14) P2, /n(no. 14) P - l (no. 2) a, A 15.7525(5) 14.7171(2) 11.3234(11) b,A 19.6957(6) 24.1289(4) 13.9953(15) c,A 25.2114(9) 15.3353(3) 15.0988(14) a , deg 90 90 79.669(4) P, deg 99.0900(10) 106.3670(10) 84.919(5) y, deg 90 90 76.334(6) V ,A 3 7723.8(4) 5225.00(15) 2284.7(4) z 4 4 1 T , ° C -100 ± 1 -100 ± 1 -100 ± 1 p c a l c , g /cm 3 1.069 1.395 1.369 F(000) 2688 2232 960 u ( M o K a ) , mm' 1 0.227 2.475 2.594 transmission factors 0.8821 - 1.0000 0 .7604- 1.0000 0 . 7 2 4 6 - 1.0000 2 6 m a x , deg 50.1 55.6 51.1 total no. o f reflns 95088 74431 12092 no. o f unique reflns 13636 12340 7947 Emerge 0.0722 0.0421 0.0726 no. reflns with I > 2a(I) 8965 8922 6197 no. o f variables 769 523 494 R (F 2 , all data) 0.1163 0.0590 0.0825 R W ( F 2 , all data) 0.2150 0.0785 0.1443 R (F, I >2o(I)) 0.0727 0.0334 0.0575 R W ( F , I > 2 G ( I ) ) 0.1886 0.0721 0.1333 gof 1.042 1.043 1.030 Page 229 References located on page 222. Appendix A: X-ray Crystal Structure Data Table A - 8 . Crystallographic and Structure Refinement Data for ( , H r [OPO]TaCl 2 ) 2 (u-0) (5.13), p h [ O P O ] 2 T a C l (5.14), and P h[OPO]TaMe 2Cl'(5.16)1 ( , P r[OPO]TaCl 2) 2(u-0) P h [OPO] 2 TaCl (5.14) P h [OPO]TaMe 2 Cl (5.16) (5.13) CCDC Registry -- - --Formula C 6 2 H 9 4 C l 4 0 5 P 2 T a 2 C 6 8 H 9 0 C l O 4 P 2 T a C 3 6 H 5 l C 1 0 2 P T a •2C 6 H 6 •1.5C 6 H 1 4 Fw 1641.30 1379.00 763.14 Colour, habit Yellow, chip Yellow, platelet Yellow, block Crystal size, mm 0.25x0.15x0.05 0.40x0.30x0.10 0.40x0.25x0.15 Crystal system Monoclinic Monoclinic Monoclinic Space group P2,/n (no. 14) P2,/n (no. 14) P2,/n(no .14) a, A 12.9840(2) 17.564(2) 16.917(2) b,A 21.1870(4) 22.912(3) 10.239(2) c,A 14.9789(3) 20.412(2) 21.694(2) a, deg 90 90 90 P, deg 106.7520(10) 106.284(6) 109.36(2) Y, deg 90 90 90 v,A3 3945.70(12) 7884.8(16) 3545.2(9) z 4 4 4 T, °C -100 ± 1 -100 ± 1 -100 ± 1 Pcatc, g/cm3 1.381 1.162 1.430 F(000) 1668 2900 1552 u(MoKot), mm"1 2.991 1.511 3.249 transmission factors 0.7341 - 1.0000 0.6869- 1.0000 0.5679- 1.0000 28max, deg 53.1 51.7 55.6 total no. of reflns 95600 22901 31308 no. of unique reflns 9387 14569 7522 R-merge 0.0440 0.0796 0.0520 no. reflns with I > 2G(I) 7535 8554 6572 no. of variables 408 756 434 R (F 2, all data) 0.0387 0.1626 0.0539 R W ( F 2 , all data) 0.0614 0.2501 0.0971 R(F,I>2a(I)) 0.0252 0.0836 0.0447 R w (F,I>2a(I)) 0.0574 0.1936 0.0923 gof 1.042 1.082 1.159 Page 230 References located on page 222. Appendix A: X-ray Crystal Structure Data Table A-9. Crystallographic and Structure Refinement Data for p h [ O P O ] H 3 C l (6.1). [ 0 P 0 ] H 3 C 1 (6.1) C C D C Registry Formula C 3 4 H 4 8 C 1 0 2 P - 1 . 5 C 6 H F w 672.31 Colour, habit colourless, platelet Crystal size, mm 0.25 x 0 .10x0.05 Crystal system Tricl inic Space group P - l (no. 2) a, A 10.5058(4) b, A 13.5206(8) c,A 15.7841(8) a , deg 86.743(2) P ,deg 86.376(2) y, deg 69.029(2) V , A 3 2087.95(18) z 2 T , ° C -100 ± 1 Peak, g/cm3 1.069 F(000) 726 u(MoKoc), mm' 1 0.161 transmission factors 0 .8814 - 1.0000 2 6 m a x , deg 46.2 total no. o f reflns 28751 no. of unique reflns 5311 Emerge 0.1099 no. reflns with I > 2a(I) 3122 no. o f variables 479 R (F 2 , all data) 0.1325 R W ( F 2 , all data) 0.1630 R ( F , I > 2 a ( I ) ) 0.0636 R w ( F , I > 2 a ( I ) ) 0.1338 gof 1.003 Page 231 References located on page 222. Appendix B: Density functional theory calculation data A p p e n d i x B : D e n s i t y F u n c t i o n a l T h e o r y c a l c u l a t i o n d a t a B.l. General considerations Calculations were performed using the Gaussian98 suite of programs on either a dual 450MHz Pentium II workstation (CHOPIN) using G98RevA.9 , 1 or a dual 1.0 G H z Pentium III workstation ( M O Z A R T ) using G98RevA. 11.4,2 both running Red Hat Linux 8. Calculations were performed using the B 3 L Y P functional. 3 The basis functions and effective core potentials were those of the L A N L 2 D Z basis set.4 Additional calculations utilized the L A N L 2 D Z p d basis set augmented with polarization functions (p,d) developed for arsenic. 5. N o geometric constraints were set in the optimization of the complexes. Geometric illustrations were created using ORTEP-II I for Windows. 6 Orbital depictions were created using the Molden program. 7 B.2. References (1) Frisch, M . J.; Trucks, G . W. ; Schlegel, H . B . ; Scuseria, G . E.; Robb, M . A . ; Cheeseman, J. R.; Zakarzewski, V . G . ; Montgomery, J. A . ; Stratmann, R. E . ; Burant, J. C ; Dapprich, S.; Mi l l am , J. M. ; Daniels, A . D . ; Kudin , K . N . ; Strain, M. C ; Farkas, O.; Tomasi, J.; Petersson, G . A . ; Ayala , P. Y . ; Cu i , Q.; Morokuma, K. ; Mal ick , D . K . ; Rabuck, A . D . ; Raghavachari, K . ; Foresman, J. B . ; Cioslowski, J . ; Ortiz, J. V . ; Stefanov, B . B . ; Lui , G . ; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L . ; Fox, D. J.; Kieth, T.; Al -Laham, M . A . ; Peng, C. Y . ; Nanayakkara, A . ; Gonzalez, C ; Challacombe, M . ; G i l l , P. M . W.; Johnson, B . G. ; Page 232 References located on page 232. Appendix B: Density functional theory calculation data Chen, W. ; Wong, M . W.; Andres, J. L . ; Head-Gordon, M . ; Repogle, E . S.; Pople, J. A . ; Gaussian 98, revision a.9, Gaussian, Inc.: Pittsburgh, P A , 1998. (2) Frisch, M . J.; Trucks, G . W. ; Schlegel, H . B . ; Scuseria, G . E . ; Robb, M . A . ; Cheeseman, J. R.; Zakrzewski, J. A . ; Montgomery, J., J. A . ; Stratmann, R. E. ; Burant, J. C ; Dapprich, S.; Mi l l am , J. M . ; Daniels, A . D . ; Kudin , K . N . ; Strain, M . C ; Farkas, O.; Tomasi, J.; Barone, V . ; Cossi, M . ; Cammi, R.; Mennucci, B . ; Pomelli , C ; Adamo, C ; Clifford, S.; Ochterski, J.; Petersson, G . A . ; Ayala , P. Y . ; Cu i , Q.; Morokuma, K . ; Salvador, P.; Dannenberg, J. J.; Mal ick , D . K . ; Rabuck, A . D . ; Raghavachari, K . ; Foresman, J. B . ; Cioslowski, J . ; Ortiz, J. V . ; Baboul, A . G . ; Stefanov, B . B . ; L i u , G . ; Liashenko, A . ; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L . ; Fox, D . J.; Kieth, T.; Al -Laham, M . A . ; Peng, C. Y . ; Nanayakkara, A . ; Challacombe, M . ; G i l l , P. M . W. ; Johnson, B . ; Chen, W. ; Won, M . W. ; Andres, J. L . ; Gonzalez, C ; Head-Gordon, M . ; Repogle, E . S.; Pople, J. A . ; Gaussian 98, revision a. 11.4, Gaussian, Inc.: Pittsburgh, P A , 2001. (3) Becke, A . D . J. Chem. Phys. 1993, 98, 5648-5652. (4) Hay, P. J.; Wadt, W . R. J. Chem. Phys. 1985, 82, 270-283. (5) Check, C. E . ; Faust, T. O.; Bailey, J. M . ; Wright, B . J.; Gilbert, T. M . ; Sunderlin, L . S . J . Phys. Chem. A 2001,105, 8111-8116. (6) Farrugia, L . J. J. Appl. Crystallogr. 1997, 30, 565. (7) Schaftenaar, G . ; C A O S / C A M M Center: University of Nijmegen, Netherlands, 1991. Page 233 References located on page 232. Appendix B: Density functional theory calculation data B. 3. Archival output summaries for model complexes ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4A) l \ l \ G P N C - M O Z A R T \ F O p t \ R B 3 L Y P \ L A N L 2 D Z \ C 9 H 2 9 A s l L i 2 N 2 O 2 S i 2 \ C A R M \ 0 8 -Jun-2004\0\\# G F I N P U T B3 L Y P / L A N L 2 D Z O P T = ( M A X C Y = 2 0 0 ) S C F = ( M A X C Y = 5 1 2 ) IOP(6/7=3)\\nasnli2\\0,1 \ Li,-0.4754061815,1.5016427439,-1.284447605\N,-0.5790613596,1.6674378263, 0.687178222\Si,0.8568255365,1.6608233525,1.6897993862\C,2.055289972, 0.2565254212,1.2085138679\As,1.2408047604,-l. 5965833256,1.1769162091X C, 1.6216574356,-2.1213317094,-0.7281381925\Si,0.8165879729,-0.9832554218, -2.0436599118\N,-0.8036998555,-0.4125363633,-1.6979025841\Li,-1.313372377, -0.131955114,0.219668149\C,-1.609594504,2.6833670598,1.0488641966\ C,-1.940632798,-0.9762779396,-2.474071886\C,2.7593627053,-2.5814217636, 2.0364934904\O,-0.2555257504,2.9391180786,-2.5080823827\C,0.2373168352, 4.2482857876,-2.0900150062\C,-0.3419891576,2.759948896,-3.9535904584\ 0,-2.6798174253,-1.0100932013,1.2485718317\C,-2.7194851194,-0.6938813608, 2.6760474703\C,-3.1626392635,-2.3504987391,0.9347236265\H,1.6488523693, 2.9482228551,1.6424624831 \H,0.5544870065,1.4783277172,3.1600810265\ H , 2.5233764047,0.4502957731,0.2347745298\H,2.8654406558,0.2356249032, I. 9519029576\H,2.7114197076,-2.1405115003,-0.8828857257\H,1.2494250217, -3.1503733865,-0.8424895046\H,1.7451752939,0.2041229836,-2.1006345835\ H,0.9390922785,-1.6771998861,-3.3716879311\H,-2.0016022589,2.5741940712, 2.0822940527\H,-2.4831828952,2.606388876,0.3786217385\H,-1.2505716185, 3.7317985578,0.9759356688\H,-1.8092537687,-0.9020830624,-3.572107594\ H,-2.8703126835,-0.4321303833,-2.2360578742\H,-2.1428622025,-2.0482900567, -2.2691646266\H,3.7107417365,-2.3160639366,1.5596874003\H,2.5977804537, -3.6619139033,1.9409961751\H,2.8047620311,-2.3255655921,3.1020081427\ H,1.2484046546,4.4209334018,-2.4864485768\H,0.2648694064,4.2317782025, -0.9985925103\H,-0.4402153245,5.0410417245,-2.4385980954\H,0.6493231177, Page 234 References located on page 232. Appendix B: Density functional theory calculation data 2.8764835949,-4.4148225811\H,-1.0429739874,3.4874223218,-4.3879058037\ H,-0.7080086965,1.743605727,-4.1146772345\H,-3.7550966167,-0.7346361313, 3.0431898854\H,-2.321766914,0.3170764955,2.7788582179\H,-2.0897648451, -1.3973536169,3.2388792347\H,-4.2048195019,-2.4668456825,1.2658970022\ H , -2.5296107473,-3.1081606793,1.4190299982\H,-3.1047613507,-2.4587567344, -0.1502027535W Version=x86-Linux-G98RevA. 11.4\HF=-649.3500265\RMSD=6.452e-09\ RMSF=1.637e-05\Dipole=-0.9592694,0.2045721,-0.5343164\PG=C01 [X(C9H29As lL i2N202S i2 ) ] \ \@ ' N A s N ' T a M e 3 (3 .5A) l \ l \ G r N C - M O Z A R T \ F O p t \ R B 3 L Y P \ L A N L 2 D Z \ C 8 H 2 6 A s l N 2 S i 2 T a l \ C A R M \ 1 8 - J u n -2004\0\\# G F I N P U T B3 L Y P / L A N L 2 D Z OPT=(MAXCY=200) S C F = ( M A X C Y = 5 1 2 ) IOP(6/7=3)\\nasntame3-b\\0,l\ Ta,-1.4629005691,-0.3261383918,-0.4408938329\N,-l.1845765613,0.3243842773, I. 4484378836\Si,0.2377938965,0.1686271005,2.5256071792\C,1.8897559699, -0.2585583997,1.7059852298\As,2.7735706771,1.2231222857,0.6385486958\ N,0.2213729944,-1.0009021189,-1.2010233998\Si,1.4261472896,-0.0090036004, -2.0892325274\C,3.021558769,0.2173123423,-1.0935184185\C,4.6322837853, 0.9487692154,1.3370452674\C,-2.3429712035,0.9176198942,2.1911467929\ C,0.4794921943,-2.4776911069,-1.171505206\C,-2.7860440311,-1.848400125, 0.4326358248\C,-2.8461595767,-0.6839427151,-2.1419556184\C,-1.9990748, 1.7383612102,-0.9550569526\H,-0.0609426747,-0.8746501548,3.5570551891\ H , 0.3942115548,1.4572300804,3.2640854628\H,1.8016599441,-1.1480160332, I. 072921313\H,2.5838496149,-0.5171176724,2.5197892656\H,1.7191481528, -0.6968804462,-3.3787109865\H,0.8070838585,1.3120956675,-2.3502711693\ H , 3.7309851112,0.8029511492,-1.6980099875\H,3.4974405389,-0.7514935344, -0.8843357301\H,4.9222047377,-0.1081428052,1.2951205862\H,4.6815393078, I. 2953690328,2.3763353737\H,5.337332779,1.5397708513,0.7405851368\ Page 235 References located on page 232. Appendix B: Density functional theory calculation data H,-2.0957398128,1.9163226864,2.5823798491\H,-2.6485857054,0.2796189565, 3.036194417\H,-3.2125260895,1.0298846099,1.5338468661\H,1.4218669879, -2.7119979214,-0.654217736\H,0.5314818156,-2.8849754819,-2.191141088\ H,-0.324074379,-3.0070459583,-0.6439027936\H,-3.0441016239,-2.6399095223, -0.2850243955\H,-2.3254311993,-2.2985778456,1.3264437495\H,-3.731380862, -1.3761858897,0.7472373172\H,-2.5835099053,-0.0664974819,-3.0166071534\ H , -2.7777988923,-1.7441251975,-2.4456271033\H,-3.8994194224,-0.4815832863, -1.8943 578185\H,-3.0722131898,1.9186900579,-0.782414432\H,-1.4209328615, 2.4592962243,-0.3602258574\H,-l.8140368622,1.9211110853,-2.0238134654\\ Version=x86-Linux-G98RevA. 11.4\HF=-501.7389938\RMSD=6.895e-09\ RMSF=6.827e-06\Dipole=1.5109505,-0.5493233,0.349806\PG=C01 [X(C8H26As lN2Si2Ta l ) ] \ \@ ( 'NAsN'Ta)2(p-H) 4 (3.6A) l \ l \ G I N C - M O Z A R T \ F O p t \ R B 3 L Y P \ L A N L 2 D Z \ C 1 0 H 3 8 A s 2 N 4 S i 4 T a 2 \ C A R M \ 2 4 - J u l -2004\0\\# G F I N P U T B 3 L Y P / L A N L 2 D Z OPT=(MAXCY=200) S C F = ( M A X C Y = 5 1 2 ) IOP(6/7=3)\\nasntah4\\0,1\ Ta, 1.0744497841,0.280197117,0.7215755093\N, 1.2553815261 ,-0.6331736877, 2.5351953081\Si,2.7382129602,-0.5849423505,3.5346669852\C,4.207780502, -1.0513151871,2.4131119945\As,3.8012606931,-0.336450529,0.601272329\ N,1.7652451286,2.185144329,0.5834145906\Si,3.3855149202,2.7548094261, I. 1092142788\C,4.6871486445,1.4487947507,0.6318646775\C,4.9914492776, -1.3969266131,-0.5801262689\C,0.107560352,-1.3288754005,3.2094302791\ C,0.8982202108,3.3326945215,0.1367547943\H,3.0056699457,0.7559154244, 4.1304665672\H,2.6156391601,-1.5616732857,4.6541315836\H,5.1707547836, -0.674019225,2.7783897278\H,4.2762470851,-2.1447176212,2.337019855\ H , 3.4565459181,3.0125719336,2.5760080606\H,3.6863060342,4.0415590122, 0.4170448454\H,5.5496377131,1.4428087395,1.3097152579\H,5.0563526046, I. 6569048516,-0.3812154214\H,6.0279683888,-1.3443230864,-0.2287744109\ Page 236 References located on page 232. Appendix B: Density functional theory calculation data H,4.9285113245,-1.0040471873,-1.6007171316\H,4.6571452717,-2.4400472396, -0.5823481469\H,0.3334274053,-2.3915391015,3.3938425918\H,-0.7855726459, -1.2649225981,2.5870213594\H,-0.1282865557,-0.8554619374,4.1759923009\ H , 0.7307371548,4.0414828721,0.9637479747\H,-0.0733155264,2.9638222866, -0.1932154634\H, 1.3635066684,3.8817594461 ,-0.696627393\H,-0.5072247577, I. 2412168489,-1.1572518758\H,-0.7169662351,0.7587480499,1.0666134259\ H,0.9124508233,-0.425321039,-1.0137495798\H,-0.0890366617,-1.4265511103, 0.4678691458\Ta,-1.056031725,-0.398927729,-0.7141559102\N,-l.1013935812, -1.2411525 807,-2.5410191774\Si,-2.7440949498,-1.6224179286,-3.1841445017\ C,-3.9016787979,-0.1113847799,-2.9713299087\As,-3.342949572,0.9893738436, -1.3984483644\N,-2.6631772708,-1.4035154306,0.222273747\Si,-4.1389791405, -0.7994066046,0.9971426881\C,-4.7518697984,0.6791489216,-0.0416837787\ C,-3.6514252137,2.8410073757,-2.0190383706\C,0.0295860274,-1.573841715, -3.4576092385\C,-2.3851304695,-2.8509401788,0.5052033645\H,-2.6094994562, -1.9095007095,-4.6430012159\H,-3.3534813319,-2.8156828455,-2.5395324752\ H,-3.8354501245,0.5290454423,-3.8614162127\H,-4.9499536452,-0.4174661683, -2.8603104261\H,-3.9642258049,-0.3486457208,2.4131133917\H,-5.1728450826, -1.8780701999,1.0153520653\H,-4.8464940959,1.5877182571,0.5656612056\ H,-5.720473256,0.4858809967,-0.5171299579\H,-4.6813891646,2.9653783102, -2.3711081543\H,-2.9545304618,3.063733202,-2.8341816072\H,-3.4606844049, 3.5364789027,-1.1945760582\H,0.0581672993,-2.6507359001,-3.6884026731\ H,0.9761033906,-1.3022738717,-2.9826902424\H,-0.0480236563,-1.0278540308, -4.4107272016\H,-3.3134860732,-3.4454314749,0.4931387745\H,-1.893617473, -2.9981758219,1.4807378507\H,-1.7207879573,-3.2715832841,-0.2585407536\\ Version=x86-Linux-G98RevA. 11.4\HF=-766.4264327\RMSD=7.853e-09\ RMSF=2.910e-06\Dipole=0.419655,0.3257794,-0.8894007\PG=C01 [X(C 10H3 8 As2N4Si4Ta2)]\\@ ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4B) Page 237 References located on page 232. Appendix B: Density functional theory calculation data l \ l \ G I N C - M O Z A R T \ F O p t \ R B 3 L Y P \ G e n \ C 9 H 2 9 A s l L i 2 N 2 O 2 S i 2 \ C A R M \ 0 4 - M a r -2005\0\\# G F I N P U T B 3 L Y P / L A N L 2 D Z E X T R A B A S I S O P T = ( M A X C Y = 2 0 0 ) SCF=(MAXCY=512) IOP(6/7=3)\\nasnli2-b\\0,l\ Li,-0.4833883486,1.4946090581,-1.2762400652\N,-0.5822079633,1.6614359182, 0.693789387\Si,0.858639615,1.6582167975,1.6896091773\C,2.0625658464, 0.2637094254,1.1847209715\As, 1.2467007724,-1.572014885,1.1576950595\ C , l .6273171948,-2.1205629878,-0.7231362402\Si,0.8116643357,-0.9974236898, -2.0491094887\N,-0.8040692114,-0.4200343958,-1.6915488254\Li,-1.3110044082, -0.1430847528,0.2279419014\C,-1.61386054,2.674235524,1.0610972926\ C,-1.9463236733,-0.9735152434,-2.4678048236\C,2.7298596866,-2.5618628446, 2.0457923215\O,-0.2551688475,2.9318209155,-2.4978676466\C,0.2349515071, 4.2405633648,-2.0750904095\C,-0.3268383659,2.752478443,-3.944171189\ O,-2.6774977333,-1.0230172735,1.2555039215\C,-2.7211594963,-0.7059886692, 2.682524588\C,-3.1549199914,-2.3653275096,0.9416241552\H,1.6365584152, 2.9543246327,1.6478548717\H,0.5687705969,1.460111414,3.1604077282\ H , 2.5148794778,0.4666568765,0.2047370582\H,2.8831219487,0.2422654972, I. 9175294593\H,2.7167863041,-2.1449543842,-0.8839329907\H,1.2498307591, -3.1506236246,-0.8222205364\H, 1.7462313194,0.1834415485,-2.1362915938\ H,0.9130005696,-1.7107544483,-3.3683769306\H,-2.0109330728,2.5544966208, 2.0913555606\H,-2.4842271984,2.6048447704,0.3858687392\H,-1.2536388623, 3.7230736747,1.0009823976\H,-1.8201378527,-0.8898300384,-3.5656995599\ H,-2.8734414545,-0.4291755415,-2.2201891516\H,-2.1504875955,-2.0467673632, -2.2715744812\H,3.6937367097,-2.3218037816,1.5783130176\H,2.5484315454, -3.6418829696,1.9653886596\H,2.7639381299,-2.2898715244,3.109071165\ H,1.250543725,4.4115129843,-2.4605889901\H,0.2505562916,4.2246192435, -0.9834582801\H,-0.4375720936,5.0340272373,-2.4316298706\H,0.6691973854, 2.8684314213,-4.3952036983\H,-1.0229440711,3.4802567337,-4.3857154881\ H,-0.6917100256,1.736330648,-4.109036042\H,-3.7578507091,-0.7461857195, 3.046749741 l\H,-2.3233948573,0.304867675,2.7859995877\H,-2.0934720094, -1.4093547571,3.2478815807\H,-4.1977077622,-2.4846910743,1.269886321\ Page 238 References located on page 232. Appendix B: Density functional theory calculation data H. ,-2.5210395182,-3.1205375867,1.4287039316\H,-3.0935087634,-2.4746301904,-0.1429644478W Version=x86-Linux-G98RevA.11.4\HF=-649.3648478\PvMSD=3.051e-09\ RMSF=1.057e-05\Dipole=-0.9855961,0.22403,-0.5420615\PG-C01 [X(C9H29As 1 Li2N202Si2) ] \ \@ ' N A s N ' T a M e 3 (3.5B) l \ l \ G r N C - M O Z A R T \ F O p t \ R B 3 L Y P \ G e n \ C 8 H 2 6 A s l N 2 S i 2 T a l \ C A R M \ 0 4 - M a r -2005\0\\#P G F I N P U T B 3 L Y P / L A N L 2 D Z E X T R A B A S I S O P T = ( M A X C Y = 2 0 0 ) S C F = ( M A X C Y = 5 1 2 ) IOP(6/7=3)\\nasntame3-e\\0,l\ Ta,-1.4625448259,-0.3207320566,-0.4446064304\N,-l.1819085901,0.3303698488, I. 4443855763\Si,0.237473879,0.1697480271,2.5244206122\C,l.8914719768, -0.2699765013,1.7085074879\As,2.7682125067,l.1962274064,0.6445112136\ N,0.2224769081,-0.9969129707,-1.2018212514\Si,1.4350871201,-0.0062328542, -2.0805021271\C,3.0300587149,0.2069843575,-1.0760650315\C,4.6145748422, 0.9545551114,1.349391802\C,-2.335778444,0.9385835603,2.1820766172\ C,0.4743566977,-2.4749413043,-1.1795181174\C,-2.78920163,-1.8413153457, 0.4275468033\C,-2.84398873,-0.6749010075,-2.148999836\C,-1.9937984361, 1.7454222808,-0.9585313078\H,-0.0700646418,-0.867974355,3.5584955245\ H , 0.4027322441,1.4599523849,3.2585206384\H,1.8010488133,-1.165434938, I. 0830643718\H,2.5821593672,-0.5215332134,2.528310602\H,1.7280445594, -0.6884682587,-3.3727643377\H,0.8245324217,1.3199208959,-2.3351413975\ H , 3.7410661146,0.8001994588,-1.6730428745\H,3.5047946194,-0.7645179958, -0.8734000139\H,4.9241017313,-0.0980310036,1.3141450633\H,4.6517497394, I. 3088915739,2.3878656513\H,5.3125342275,1.5572297234,0.7539232006\ H,-2.0899157188,1.950546807,2.5385278496\H,-2.6275408866,0.325823321, 3.0503848374\H,-3.2140351191,1.0242582173,1.5324215568\H,1.4147229318, -2.7158585879,-0.6615002437\H,0.5269515101,-2.876872007,-2.2012513777\ H,-0.3323781079,-3.0038400008,-0.6563200669\H,-3.0487662429,-2.6308881954, Page 239 References located on page 232. Appendix B: Density functional theory calculation data -0.2918831657\H,-2.3291121876,-2.2939225768,1.3203753877\H,-3.7335757555, -1.3677708454,0.7431994524\H,-2.5809307685,-0.0562492425,-3.0226346338\ H , -2.7749678993,-1.7349395474,-2.4535877335\H,-3.8973943741,-0.4731354369, -1.9009508533\H,-3.0677972287,1.9272316007,-0.7930557254\H,1.4182349374, 2.4650693127,-0.359591672\H,-1.8009670013,1.9283711555,-2.0259702444\\ Version=x86-Linux-G98RevA. 11.4\HF=-501.7546793\RMSD=9.913e-09\ RMSF=6.183e-06\Dipole=1.4826514,-0.5711279,0.3383759\PG=C01 [X(C8H26As l N 2 S i 2 T a l )]\\@ ( 'NAsN'Ta) 2 (M-H)4 (3.6B) l \ l \GINC-CHOPIN\FOpt \RB3LYP\Gen\C10H38As2N4Si4Ta2\CAPJvl \05-Jun-2005\0\ \ # G F I N P U T B 3 L Y P / L A N L 2 D Z E X T R A B A S I S O P T = ( M A X C Y = 2 0 0 ) SCF=(MAXCY=512) IOP(6/7=3)\\nasntah4-d\\0,l\ Ta,1.0846915871,0.2967649372,0.7120715841\N,1.2187310433,-0.5849723323, 2.5462311551\Si,2.6885157841,-0.5452879278,3.5649597149\C,4.1630807678, -1.0404602429,2.4596090857\As,3.76415846,-0.3386703143,0.6543789224\ N , 1.787731284,2.1928782131,0.540980578 l\Si,3.4044000253,2.7463726 111, I. 0931701156\C,4.6888369539,1.4132828934,0.6377907334\C,4.9088684362, -1.4421390716,-0.5159433959\C,0.0492905796,-1.252768619,3.2105414434\ C,0.9462542083,3.3334189683,0.0338084315\H,2.9639155202,0.796760881, 4.1537752409\H,2.5383490262,-1.5102954424,4.6915421264\H,5.1302650184, -0.6724726119,2.8251240792\H,4.215654559,-2.1361217957,2.3918964295\ H , 3.4553949957,3.0061580213,2.5601660721\H,3.7321599567,4.0274200221, 0.4025635078\H,5.557978751,1.4062354992,1.3081514883\H,5.049746957, I. 5917151281,-0.3847235587\H,5.9535254946,-1.4086294127,-0.1826201873\ H,4.8385420492,-1.066774129,-1.5439401579\H,4.5492928898,-2.4778920157, -0.4950545526\H,0.2640176314,-2.3098336958,3.4359552845\H,-0.8262435863, -1.2046900404,2.5619210113\H,-0.2092890969,-0.7463231615,4.1543847317\ H,0.7549270088,4.0643632818,0.8358493773\H,-0.0151088474,2.9620373861, Page 240 References located on page 232. Appendix B: Density functional theory calculation data -0.3227955774\H,1.445885751,3.8573556839,-0.7958023652\H,-0.5655636533, 1.2517724653,-1.2334731346\H,-0.7346145886,0.780132732,0.9977932127\ H,0.9148156108,-0.3800324323,-1.0411095814\H,-0.0596798264,-1.3971268655, 0.4578818564\Ta,-1.0474490855,-0.3946947827,-0.7428003925\N,-l.109547774, -1.2245156824,-2.5758803793\Si,-2.7583164857,-1.5941493619,-3.2090082061\ C,-3.9212689539,-0.0933584392,-2.9345143902\As,-3.3324147132,0.9530522629, -1.3505690193\N,-2.6319103274,-1.442645245,0.1883987014\Si,-4.1125498858, -0.8808832342,0.9846763898\C,-4.7166650999,0.6472799941,0.0132533659\ C,-3.6082674106,2.8153638168,-1.918689551\C,0.0143683289,-1.5343642308, -3.508373549\C,-2.320642318,-2.8867349695,0.4497634477\H,-2.6405812936, -1.8380952327,-4.6770557137\H,-3.3557109404,-2.8075622073,-2.5913846934\ H,-3.8717143334,0.5735588701,-3.8069833246\H,-4.9669168875,-0.4067398027, -2.813006952\H,-3.9397191049,-0.5049768428,2.422778591\H,-5.1463247355, -1.9590606063,0.945454093\H,-4.7645220483,1.5387110699,0.6520028385\ H,-5.7027795717,0.4986453228,-0.4433913274\H,-4.6408742348,2.9723646035, -2.2536590241\H,-2.9163068723,3.0448902765,-2.7375196498\H,-3.3908479905, 3.4852684871,-1.0783313761\H,0.0454691005,-2.6069881132,-3.7585244202\ H,0.96394171,-1.2669781576,-3.0369690524\H,-0.0736363321,-0.9715251412, -4.4507204427\H,-3.2340266461,-3.5034950102,0.4235578329\H,-1.8301202009, -3.0354594295,1.4259100228\H,-1.6424021643,-3.2791076578,-0.3169228032\\ Version=x86-Linux-G98RevA.9\HF=-766.462458\RMSD=6.752e-09\ RMSF=3.335e-05\Dipole=0.355192,0.3186613,-0.8117876\PG=C01 [X(C 10H38 As2N4Si4Ta2)]\ \@ Page 241 References located on page 232. Appendix B: Density functional theory calculation data B.4. Z-matrices, initial parameters, and final coordinates Table B - l . Method and z-matrix for t N A s N , L i 2 ( O M e 2 ) 2 (3.4A). # GFINPUT B3LYP/LANL2DZ Opt=(maxcy=200) SCF=(maxcy=512) IOP(6/7=3) nasnli2-a 0 1 l i n 1 n l i l s i 2 s i n l 1 s i n l i l c 3 c s i l 2 c s i n l 1 c s i n l i l as 4 ascl 3 a s c s i l 2 ascsinl c 5 casl 4 easel 3 ca s c s i l s i 6 s i c l 5 sicas1 4 si c a s c l n 7 n s i l 6 n s i c l 5 nsicasl l i 8 l i n l 7 l i n s i l 6 l i n s i c l c 2 cnl 1 c n l i l 8 c n l i n l c 8 cn2 7 e n s i l 6 c n s i c l c 5 cas2 9 c a s l i l 2 c a s l i n l o 1 o l i l 2 o l i n l 9 o l i n l i l c 13 col 1 c o l i l 2 c o l i n l c 13 co2 1 coli2 2 colin2 o 9 ol i 2 8 olih2 1 o l i n l i 2 c 16 co3 9 co l i 3 8 colin3 c 16 co4 9 coli4 8 colin4 h 3 h s i l 2 hs i n l 1 h s i n l i l h 3 hsi2 2 hsin2 1 h s i n l i 2 h 4 hcl 3 h e s i l .2 hcsinl h 4 hc2 3 hcsi2 2 hcsin2 h 6 hc3 7 hcsi3 8 hcsin3 h 6 hc4 7 hcsi4 8 hcsin4 h 7 hsi3 8 hsin3 9 h s i n l i 3 h 7 hsi4 8 hsin4 9 hsin l i 4 h 10 hc5 2 hcnl 1 h c n l i l h 10 hc6 2 hcn2 1 hcnli2 h 10 hc7 2 hcn3 . 1 hcnli3 h 11 hc8 8 hcn4 9 hcnli4 h 11 hc9 8 hcn5 9 hcnli5 h 11 hclO 8 hcn6 9 hcnli6 h 12 h e l l 5 hcasl 9 h c a s l i l h 12 hcl2 5 hcas2 9 hcasli2 h 12 hcl3 5 hcas3 9 hcasli3 h 14 hcl4 13 hcol 1 h c o l i l h 14 hcl5 13 hco2 1 hcoli2 h 17 hc20 16 hco7 9 hcoli7 h 14 hcl6 13 hco3 1 hcoli3 h 17 hc21 16 hco8 9 hcoli8 h 15 hcl7 13 hco4 1 hcoli4 h 17 hc22 16 hco9 9 hcoli9 h 15 hcl8 13 hco5 1 hcoli5 h 18 hc23 16 hcolO 9 hcolilO h 15 hcl9 13 hco6 1 hcoli6 h 18 hc24 16 h c o l l 9 h c o l i l l h 18 hc25 16 hcol2 9 hc o l i l 2 Page 242 References located on page 232. Appendix B: Density functional theory calculation data Table B-2. Method and z-matrix for 'NAsN'Li2(OMe 2)2 (3.4B). # GFINPUT B3LYP/LANL2DZ Extrabasis Opt=(maxcy=200) SCF=(maxcy=512) IOP(6/7 =3) nasnli2 -b 0 1 l i n 1 n l i l s i 2 s i n l 1 s i n l i l c 3 c s i l 2 c s i n l 1 c s i n l i l as 4 ascl 3 ascsi1 2 ascsinl c 5 casl 4 easel 3 c a s c s i l s i 6 s i c l 5 s i c a s l 4 si c a s c l n 7 n s i l 6 n s i c l 5 nsicasl l i 8 l i n l 7 l i n s i l 6 l i n s i c l c 2 cnl 1 c n l i l 8 c n l i n l c 8 cn2 7 e n s i l 6 c n s i c l c 5 cas2 9 c a s l i l 2 c a s l i n l o 1 o l i l 2 o l i n l 9 o l i n l i l c 13 col 1 c o l i l 2 c o l i n l c 13 co2 1 coli2 2 colin2 o 9 ol i 2 8 olin2 1 o l i n l i 2 c 16 co3 9 co l i 3 8 colin3 c 16 co4 9 coli4 8 colin4 h 3 h s i l 2 h s i n l 1 h s i n l i l h 3 hsi2 2 hsin2 1 h s i n l i 2 h 4 hcl 3 h e s i l 2 hcsinl h 4 hc2 3 hcsi2 2 hcsin2 h 6 hc3 7 hcsi3 8 hcsin3 h 6 hc4 7 hcsi4 8 hcsin4 h 7 hsi3 8 hsin3 9 h s i n l i 3 h 7 hsi4 8 hsin4 9 hsin l i 4 h 10 hc5 2 hcnl 1 h c n l i l h 10 hc6 2 hcn2 1 hcnli2 h 10 hc7 2 hcn3 1 hcnli3 h 11 hc8 8 hcn4 9 hcnli4 h 11 hc9 8 hcn5 9 hcnli5 h 11 hclO 8 hcn6 9 hcnli6 h 12 h e l l 5 hcasl 9 h c a s l i l h 12 hcl2 5 hcas2 9 hcasli2 h 12 hcl3 5 hcas3 9 hcasli3 h 14 hcl4 13 hcol 1 h c o l i l h 14 hcl5 13 hco2 1 hcoli2 h 14 hcl6 13 hco3 1 hcoli3 h 18 hc24 16 h c o l l 9 h c o l i l l h 15 hcl7 13 hco4 1 hcoli4 h 18 hc25 16 hcol2 9 h c o l i l 2 h 15 hcl8 13 hco5 1 hcoli5 h 15 hcl9 13 hco6 1 hcoli6 As 0 h 17 hc20 16 hco7 9 hcoli7 SP 1 1.0 h 17 hc21 16 hco8 9 hcoli8 D 1 1.0 h 17 hc22 16 hco9 9 hcoli9 0.2660D-01 0.1000D+01 0.1000D+01 h 18 hc23 16 hcolO 9 hcolilO 0.2890D+00 0.1000D+01 0.1000D+01 Page 243 References located on page 232. Appendix B: Density functional theory calculation data Table B-3 . Initial parameters for t N A s N , L i 2 ( O M e 2 ) 2 (3.4A) and (3.4B). n l i l 2 . 044 c a s l i l 157 83 hcsin3 202. 9 s i n l 1. 704 o l i n l 130 92 hcsin4 85.5 c s i l 1. 894 c o l i l 129 79 h s i n l i 3 270 ascl 1. 979 coli2 120 52 h s i n l i 4 153. 8 casl 1. 961 olin2 128 48 h c n l i l 180 s i c l 1. 897 co l i 3 121 29 hcnli2 54.75 n s i l 1. 705 coli4 131 52 hcnli3 305.75 l i n l 2. 105 hs i n l 114 63 hcnli4 180 cnl 1. 407 hsin2 111 45 hcnli5 54 .75 cn2 1 394 h e s i l 108 14 hcnli6 305.75 cas2 1 957 hcsi2 108 13 h c a s l i l 180 o l i l 1 878 hcsi3 109 hcasli2 54 . 75 col 1 435 hcsi4 109 . 01 hcasli3 305.75 co2 1 435 hsin3 107 .23 h c o l i l 180 ol i 2 1 883 hsin4 114 .23 hcoli2 54 .75 co3 1 435 hcnl 109 . 5 hcoli3 305.75 co4 1 435 hcn2 109 . 5 hcoli4 180 h s i l 1 3 hcn3 109 . 5 hcoli5 54 . 75 hsi2 1 3 hcn4 109 . 5 hcoli6 305.75 hsi3 1 3 hcn5 109 .5 hcoli7 180 hsi4 1 3 hcn6 109 . 5 hcoli8 54 .75 hcl 0 98 hcasl 109 . 5 hcoli9 305.75 hc2 0 98 hcas2 109 . 5 hcolilO 180 hc3 0 98 hcas3 109 . 5 h c o l i l l 54 . 75 hc4 0 98 hcol 109 . 5 h c o l i l 2 305.75 hc5 0 98 hco2 109 . 5 hc6 0 98 hco3 109 . 5 hc7 0 98 hco4 109 . 5 hc8 0 98 hco5 109 .5 hc9 0 98 hco6 109 . 5 hclO 0 98 hco7 109 . 5 h e l l 0 98 hco8 109 .5 hcl2 0 98 hco9 109 . 5 hcl3 0 98 hcolO 109 .5 hcl4 0 98 h c o l l 109 .5 hcl5 0 98 hcol2 109 . 5 hcl6 0 98 c s i n l i l 299 . 8 hcl7 0 98 ascsinl 323 . 4 hcl8 0 98 c a s c s i l 119 . 7 hcl9 0 98 s i c a s c l 289 . 6 hc20 0 98 nsic a s l 324 .2 hc21 0 98 l i n s i c l 29. 2 hc22 • • 0 . 98 c n l i n l 233 . 1 V hc23 0 . 98 c n s i c l • 2 66 .7 hc24 0 . 98 c a s l i n l 118 .8 hc25 0 . 98 o l i n l i l 151 . 3 s i n l i l 124.13 c o l i n l 350 . 6 c s i n l 109.97 colin2 191 .7 a s c s i l 116.61 o l i n l i 2 128 easel 101. 3 colin3 206 . 1 s i c a s l 112 . 9 colin4 22. 4 n s i c l 112.98 h s i n l i l 57 . 8 l i n s i l 115.87 h s i n l i 2 182 c n l i l 95. 43 hcsinl 85. 4 ens i l 122.96 hcsin2 201 . 3 Page 244 References located on page 232. Appendix B: Density functional theory calculation data Table B-4. Final atomic coordinates for ' N A s N ' L i 2 ( O M e 2 ) 2 (3.4A). Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Y Z 1 3 0 -2 . 028104 0. 117549 0. 061041 2 7 0 -0. 925211 0. 893273 -1. 390655 3 14 0 -0. 041105 -0. 115616 -2 . 516515 4 6 0 0. 921212 -1. 501995 -1. 626624 5 33 0 2 . 162789 -0. 878883 -0. 154003 6 6 0 1. 420702 -1. 917515 1. 401695 7 14 0 -0. 408577 -1. 526718 1. 819986 8 7 0 -0. 898542 0. 150960 1. 693761 9 3 0 0. 014000 1. 297513 0. 326921 10 6 0 -1 640816 2 . 054253 -1. 994777 11 6 0 -1 157283 0. 915701 2. 943194 12 6 0 3 710098 -2 . 082644 -0 568241 13 8 0 -3 850389 -0. 401341 -0 087259 14 6 0 -4 491559 -0. 630233 -1 378810 15 6 0 -4 643205 -0. 821669 1 063323 16 8 0 1 094368 2 865935 0 591116 17 6 0 1 750629 3 408185 -0 598226 18 6 0 1 826725 3 118467 1 827314 19 1 0 -0 908770 -0 784200 -3 559155 20 1 0 0 974279 0 652478 -3 332277 21 1 0 0 239429 -2 256918 -1 214211 22 1 0 1 545309 -2 012344 -2 374592 23 1 0 1 523741 -2 993875 1 194988 24 1 0 2 062670 -1 679362 2 262927 25 1 0 -1 183375 -2 333761 0 808178 26 1 0 -0 702292 -2 139684 3 160967 27 1 0 -0 972254 2 763926 -2 526712 28 1 0 -2 155547 2 641975 -1 215071 29 1 0 -2 418050 1 766528 -2 734066 30 1 0 -1 884795 0 426300 3 621177 31 1 0 -1 577167 1 906976 2 702105 32 1 0 -0 252014 1 099257 3 558733 33 1 0 3 370866 -3 118009 -0 694019 34 1 0 4 438891 -2 039422 0 250102 35 1 0 4 197791 -1 746885 -1 491423 36 1 0 -4 699710 -1 700983 -1 518216 37 . 1 0 -3 784659 -0 288152 -2 137432 38 1 0 -5 426951 -0 056447 -1 448333 39 1 0 -4 . 853269 -1 899727 1 011561 40 1 0 -5 . 587436 -0 .259466 1 . 103114 41 1 0 -4 .039308 -0 .604258 1 . 947015 42 1 0 1 .836375 4 .501334 -0 .516877 43 1 0 1 .119396 3 .140939 -1 .447290 44 1 0 2 .745746 2 .958012 -0 .721868 45 1 0 1 .945760 4 .200291 1 . 984918 46 1 0 2 .813748 2 .634817 1 .792709 47 1 0 1 .232850 2 .689622 2 . 636968 Page 245 References located on page 232. Appendix B: Density functional theory calculation data Table B-5. Final atomic coordinates for 'NAsN 'L i 2 (OMe 2 )2 (3.4B). Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Y Z 1 3 0 -2. 018099 0. 139270 0. 064718 2 7 0 -0. 913456. 0. 902506 - -1. 389878 3 14 0 -0. 042778 -0. 119013 -2. 515100 4 6 0 0. 891009 -1. 522737 -1. 616990 5 33 0 2 . 127597 -0. 901860 -0. 160414 6 6 0 1. 414635 -1. 928518 1. 395529 7 14 0 -0. 408850 -1. 521315 1. 836013 8 7 0 -0. 885888 0. 159299 1. 695323 9 3 0 0. 036108 1. 297 335 0. 326774 10 6 0 -1. 617214 2 069980 -1. 995448 11 6 0 -1. 147247 0 932123 2. 939548 12 6 0 3. 683260 -2 072590 -0. 581817 13 8 0 -3 840751 -0 376144 -0. 084693 14 6 0 -4 482019 -0 598012 -1. 377487 15 6 0 -4 632526 -0 805198 1 063392 16 8 0 1 126538 2 858995 0 590684 17 6 0 1 782935 3 400232 -0 598856 18 6 0 1 864227 3 102802 1 825440 19 1 0 -0 921055 -0 767393 -3 561538 20 1 0 0 990291 0 629826 -3 326597 21 1 0 0 191803 -2 259930 -1 200096 22 1 0 1 506581 -2 050609 -2 360767 23 1 0 1 511128 -3 007738 1 197121 24 1 0 2 068640 -1 683622 2 247376 25 1 0 -1 202868 -2 340641 0 849251 26 1 0 -0 687787 -2 110271 3 190599 27 1 0 -0 939994 2 778254 -2 518092 28 1 0 -2 135858 2 657122 -1 217913 29 1 0 -2 389051 1 789535 -2 743146 30 1 0 -1 884731 0 453108 3 614055 31 1 0 -1 555220 1 926510 2 690715 32 1 0 -0 245017 1 109572 3 561281 33 1 0 3 364870 -3 116533 -0 700290 34 1 0 4 419238 -2 009399 0 230690 35 1 0 4 156285 -1 729238 -1 511364 36 1 0 -4 687706 -1 668314 -1 523794 37 1 0 -3 776327 -0 249275 -2 134150 38 1 0 -5 418841 -0 026074 -1 442637 39 1 0 -4 841333 -1 883108 1 004458 40 1 0 -5 577375 -0 244385 1 107367 41 1 0 -4 028604 -0 593090 1 948353 42 1 0 1 872783 4 .492993 -0 516353 43 1 0 1 149582 3 . 136319 -1 .447365 44 1 0 2 .776407 2 .946876 -0 724656 45 1 0 1 .990176 4 .183384 1 . 986342 46 1 0 2 .848377 2 .613622 1 .786146 47 1 0 1 .270431 2 . 674723 2 .635506 Page 246 References located on page 232. Appendix B: Density functional theory calculation data Table B-6. Method and z-matrix for ' N A s N ' T a M e 3 (3.5A). # GFINPUT B3LYP/LANL2DZ Opt=(maxcy=200) SCF=(maxcy=512) IOP(6/7=3) nasntame3-b 0 1 ta n 1 ntal s i 2 s i n l 1 s i n t a l c 3 c s i l 2 c s i n l 1 c s i n t a l as 4 ascl 3 a s c s i l 2 ascs i n l n 1 nta2 2 ntanl 3 nta n s i l s i 6 sin2 1 sinta2 2 sintanl c 7 csi2 6 csin2 1 csinta2 c 5 cas 1 1 castal 2 castanl c 2 cnl 3 en s i l 4 c n s i c l c 6 cn2 7 cnsi2 8 cnsic2 c 1 etal 5 ctaasl 9 ctaascl c 1 cta2 5 ctaas2 9 ctaasc2 c 1 cta3 5 ctaas3 •9 ctaasc3 h 3 h s i l 4 h s i c l 5 hsic a s l h 3 hsi2 4 hsic2 5 hsicas2 h 4 hcl 5 hcas 1 9 hcascl h 4 hc2 5 hcas2 9 hcasc2 h 7 hsi3 8 hsic3 5 hsicas3 h 7 hsi4 8 hsic4 5 hsicas4 h 8 hc3 5 hcas3 9 hcasc3 h 8 hc4 5 hcas4 9 hcasc4 h 9 hc5 5 hcas5 1 hcastal h 9 hc6 5 hcas 6 1 hcasta2 h 9 hc7 5 hcas7 1 hcasta3 h 10 hc8 2 hcnl 1 hcntal h 10 hc9 2 hcn2 1 hcnta2 h 10 hclO 2 hcn3 1 hcnta3 h 11 h e l l 6 hcn4 l ' hcnta4 h 11 hcl2 6 hcn5 1 hcnta5 h 11 hcl3 6 hcn6 1 hcnta6 h 12 hcl4 1 hctal 5 hctaasl h 12 hcl5 1 hcta2 5 hctaas2 h 12 hcl6 1 hcta3 5 hctaas3 h 13 hcl7 1 hcta4 5 hctaas4 h 13 hcl8 1 hcta5 5 hctaas5 h 13 hcl9 1 hcta6 5 hctaas6 h 14 hc20 1 hcta7 5 hctaas7 h 14 hc21 1 hcta8 5 hctaas8 h 14 hc22 1 hcta9 5 hctaas9 Page 247 References located on page 232. Appendix B: Density functional theory calculation data Table B-7. Method and input z-matrix for ' N A s N T a M e 3 (3.5B). #p GFINPUT B3LYP/LANL2DZ Extrabasis Opt=(maxcy=200) SCF=(maxcy=512) IOP(6/7=3) nasntame3-e 0 1 ta n 1 ntal s i 2 s i n l 1 s i n t a l c 3 c s i l 2 c s i n l 1 c s i n t a l as 4 ascl 3 a s c s i l 2 ascsinl n 1 nta2 2 ntanl 3 nt a n s i l s i 6 sin2 1 sinta2 2 sintanl c 7 csi2 6 csin2 1 csinta2 c 5 casl 1 castal 2 castanl c 2 cnl 3 e n s i l 4 cn s i c l c 6 cn2 7 cnsi2 8 cnsic2 c 1 etal 5 ctaasl 9 ctaascl c 1 cta2 5 ctaas2 9 ctaasc2 c 1 cta3 5 ctaas3 9 ctaasc3 h 3 h s i l 4 h s i c l 5 hsicasl h 3 hsi2 4 hsic2 5 hsicas2 h 4 hcl 5 hcasl 9 hcascl h 4 hc2 5 hcas2 9 hcasc2 h 7 hsi3 8 hsic3 5 hsicas3 h 7 hsi4 8 hsic4 5 hsicas4 h 8 hc3 5 hcas3 9 hcasc3 h 8 hc4 5 hcas4 9 hcasc4 h 9 hc5 5 hcas5 1 hcastal h 9 hc6 5 hcas6 1 hcasta2 h 9 hc7 5 hcas7 1 hcasta3 h 10 hc8 2 hcnl 1 hcntal h 10 hc9 2 hcn2 1 hcnta2 h 10 hclO 2 hcn3 1 hcnta3 h 11 h e l l 6 hcn4 1 hcnta4 h 11 hcl2 6 hcn5 1 hcnta5 h 11 hcl3 6 hcn6 1 hcnta6 h 12 hcl4 1 hctal 5 hctaasl h 12 hcl5 1 hcta2 5 hctaas2 h 12 hcl6 1 hcta3 5 hctaas3 h 13 hcl7 1 hcta4 5 hctaas4 h 13 hcl8 1 hcta5 5 hctaas5 h 13 hcl9 1 hcta6 5 hctaas6 h 14 hc20 1 hcta7 5 hctaas7 h 14 hc21 1 hcta8 5 hctaas8 h 14 hc22 1 hcta9 5 hctaas 9 As 0 SP 1 1.0 0.2660000000D-01 0.1000000000D+01 0.1000000000D+01 D 1 1.0 0.2890000000D+00 0.1000000000D+01 0.1000000000D+01 Page 248 References located on page 232. Appendix B: Density functional theory calculation data Table B-8. Initial parameters for ' N A s N T a M e 3 (3.5A) and (3.5B). ntal 2. 076 hsic3 113.28 s i n l 1. 698 hsic4 107.91 c s i l 1. 851 hcas3 109.94 ascl 1. 816 hcas4 108.66 nta2 2 . 002 hcas5 109. 5 sin2 1. 728 hcas6 109. 5 csi2 1. 838 hcas7 109. 5 casl 1. 816 hcnl 109.5 cnl 1. 391 hcn2 109. 5 cn2 1. 422 hcn3 109.5 etal 2 . 169 hcn4 109.5 cta2 2 . 207 hcn5 109.5 cta3 2 . 204 hcn6 109. 5 h s i l 1. 3 hctal 109.51 hsi2 1. 3 hcta2 110.18 hsi3 1. 3 hcta3 107.58 hsi4 1. 3 hcta4 111.06 hcl 0. 98 hcta5 109.17 hc2 0. 98 hcta6 108.25 hc3 0. 98 hcta7 109.58 hc4 0. 98 hcta8 109.47 hc5 0. 98 hcta9 110.13 hc6 0. 98 c s i n t a l 349.2 hc7 0. 98 ascsinl 45.2 hc8 0. 98 nta n s i l 50.8 hc9 0. 98 sintanl 247.8 hclO 0 98 csinta2 34 .7 h e l l 0 98 castanl 277 . 8 hcl2 0 98 c n s i c l 176. 3 hcl3 0 98 cnsic2 200.1 hcl4 0 98 ctaascl 241. 9 hcl5 0 98 ctaasc2 78 . 8 hcl6 0 98 ctaasc3 9.1 hcl7 0 98 hsicasl 165. 6 hcl8 0 98 hsicas2 286.3 hcl9 0 98 hcascl 206. 6 hc20 0 98 hcasc2 327 . 8 hc21 0 98 hsicas3 247.6 hc22 0 98 hsicas4 123.9 s i n t a l 124.22 hcasc3 314 . 6 c s i n l 105.16 hcasc4 75.3 a s c s i l ' 108.65 hcastal 180 ntanl 113.65 hcasta2 54 . 75 sinta2 134.58 hcasta3 305.25 csin2 101.98 hcntal 180 castal 131.13 hcnta2 54 .75 en s i l 108.99 hcnta3 305". 75 cnsi2 115 hcnta4 180 ctaasl 160.27 hcnta5 54 . 75 ctaas2 118.27 hcnta6 305.75 ctaas3 78 .13 hctaasl 256.8 h s i c l 108 .48 hctaas2 17 . 4 hsic2 111.91 hctaas3 136. 8 hcasl 109.98 hctaas4 352 hcas2 109.57 hctaas5 112 . 5 hctaas6 hctaas7 hctaas8 hctaas 9 233.3 158 . 8 279. 2 40.4 Page 249 References located on page 232. Appendix B: Density functional theory calculation data Table B-9. Final atomic coordinates for ' N A s N ' T a M e 3 (3.5A). Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Y Z 1 73 0 -1. 556791 -0. 118713 -0. 056056 2 7 0 -0. 764150 1. 736234 -0. 089355 3 14 0 0. 773594 2. 347371 0. 595882 4 6 0 2. 086790 1. 057388 1. 037138 5 33 0 3. 048138 0 . 183627 -0. 521156 6 7 0 -0. 256615 -1. 419916 0. 641292 7 14 0 0. 936383 -2. 323559 -0. 350901 8 6 0 2 . 708779 -1. 742090 -0 021495 9 6 0 4 . 898765 0. 300616 0 240076 10 6 0 -1. 584947 2. 868001 -0 628631 11 6 0 -0. 337516 -1 808498 2 087273 12 6 0 -2. 985126 0 675358 1 413758 13 6 0 -3 298733 -1 446636 -0 426592 14 6 0 -1 706111 0 025751 -2 240281 15 1 0 0 461510 3 142670 1 825378 16 1 0 1 361964 3 305859 -0 386683 17 1 0 1 674757 0 275114 1 683621 18 1 0 2 854100 1 582432 1 625746 19 1 0 0 800780 -3 770305 -0 018763 20 1 0 0 591486 -2 097195 -1 774449 21 1 0 3 395206 -2 350208 -0 630330 22 1 0 2 986158 -1 897015 1 031056 23 1 0 4 928427 -0 063349 1 274254 24 1 0 5 233264 1 344735 0 215404 25 1 0 5 583847 -0 297586 -0 372263 26 1 0 -1 045331 3 409016 -1 420914 27 1 0 -1 849792 • 3 586512 0 163928 28 1 0 -2 520947 2 499577 -1 063304 29 1 0 0 612173 -1 618834 2 609456 30 1 0 -0 585227 -2 874347 2 191413 31 1 0 -1 116483 -1 235160 2 .605726 32 1 0 -3 554133 -0 119747 1 .915910 33 1 0 -2 467442 1 .289297 2 .167946 34 1 0 -3 716382 1 .322844 0 .902243 35 1 0 -3 085441 -2 .186854 -1 . 215149 36 1 0 -3 . 533742 -2 .000422 0 .500214 37 1 0 -4 .207191 -0 .898586 -0 .719772 38 1 0 -2 .653587 0 .503355 -2 .537154 39 1 0 -0 .872659 0 .607537 -2 .658254 40 1 0 -1 .703897 -0 .979907 -2 . 685840 Page 250 References located on page 232. Appendix B: Density functional theory calculation data Table B-10. Final atomic coordinates for ' N A s N ' T a M e 3 (3.5B). Center Atomic Atomic Coordinates (Angstroms) Number Number ' Type X Y Z 1 73 0 -1. 556527 -0. 117291 -0. 055196 2 7 0 -0. 757509 1. 735125 -0. 088447 3 14 0 0. 781462 2. 343528 0. 595903 4 6 0 . 2. 093634 1. 049532 1. 041505 5 33 • 0 3. 036259 0 178288 -0. 508627 6 7 0 -0 255141 -1 420789 0. 635585 7 14 0 0 940309 -2 318395 -0. 358977 8 6 0 2 714017 -1 736564 -0 021750 9 6 0 4 887436 0 306334 0 213221 10 6 0 -1 571581 2 867659 -0 636335 11 6 0 -0 337934 -1 817770 2 079212 12 6 0 -2 979456 0 676882 1 420407 13 6 0 -3 301375 -1 443120 -0 424607 14 6 0 -1 710534 0 031610 -2 239104 15 1 0 0 470297 3 142920 1 822650 16 1 0 1 375366 3 296804 -0 388670 17 1 0 1 680813 0 273105 1 695678 18 1 0 2 864408 1 579699 1 622226 19 1 0 0 803548 -3 766792 -0 035471 20 1 0 0 599882 -2 083137 -1 782025 21 1 0 3 400935 -2 336494 -0 639849 22 1 0 2 992889 -1 900863 1 029678 23 1 0 4 942072 -0 057691 1 247381 24 1 0 5 214255 1 353920 0 179788 25 1 0 5 564320 -0 286571 -0 415460 26 1 0 -1 039894 3 380100 -1 452600 27 1 0 -1 807523 3 609310 0 143951 28 1 0 -2 523054 2 505371 -1 041516 29 1 0 0 611371 -1 631801 2 603529 30 1 0 -0 586284 -2 884112 2 176637 31 1 0 -1 116986 -1 246972 2 600324 32 1 0 -3 549332 -0 118809 1 920904 33 1 0 -2 458103 1 286629 2 175443 34 1 0 -3 710152 1 328210 0 912885 35 1 0 -3 092585 -2 . 180977 -1 216529 36 1 0 -3 532887 -1 .999367 0 501789 37 1 0 -4 210094 -0 .892031 -0 711716 38 1 0 -2 . 660233 0 . 505895 -2 534121 39 1 0 -0 . 879590 0 .616587 -2 . 657707 40 1 0 -1 .704962 -0 . 973803 -2 .685417 Page 251 References located on page 232. Appendix B: Density functional theory calculation data Table B - l 1. Method and z-matrix for ( 'NAsN'Ta) 2 (u-H)4 (3.6A). # GFINPUT B3LYP/LANL2DZ Opt=(maxcy= IOP(6/7=3) nasntah4-a 0 1 ta n 1 ntal s i 2 s i n l 1 s i n t a l c 3 c s i l 2 c s i n l 1 c s i n t a l as 4 ascl 3 a s c s i l 2 ascsinl n 1 nta2 2 ntanl 3 ntan s i l s i 6 sin2 1 sinta2 2 sintanl c 7 csi2 6 csin2 1 csinta2 c 5 casl 1 castal 2 castanl c 2 cnl 3 e n s i l 4 c n s i c l c 6 cn2 7 cnsi2 8 cnsic2 h 3 h s i l 4 h s i c l 5 hsicasl h 3 hsi2 4 hsic2 5 hsicas2 h 4 hcl 5 hcas 1 9 hcascl h 4 hc2 5 hcas2 9 hcasc2 h 7 hsi3 8 hsic3 5 hsicas3 h 7 hsi4 8 hsic4 5 hsicas4 h 8 hc3 5 hcas3 9 hc'asc3 h 8 hc4 5 hcas4 9 hcasc4 h 9 hc5 5 hcas5 1 hcastal h 9 hc6 5 hcas 6 1 hcasta2 h 9 hc7 5 hcas7 1 • hcasta3 h 10 hc8 2 hcnl 1 hcntal h 10 hc9 2 hcn2 1 hcnta2 h 10 hclO 2 hcn3 1 hcnta3 h 11 h e l l 6 hcn4 1 hcnta4 h 11 hcl2 6 hcn5 1 hcnta5 h 11 hcl3 6 hcn6 1 hcnta6 h 1 htal 2 htanl 3 htan s i l h 1 hta2 2 htan2 3 htansi2 h 1 hta3 2 htan3 3 htansi3 h 1 hta4 2 htan4 3 htansi4 ta 29 tahl 1 tahtal 2 tahtanl n 33 nta3 29 ntahl 1 ntahtal s i 34 sin3 33 sinta3 29 sintahl c 35 csi3 34 csin3 33 csinta3 as 36 asc2 35 ascsi2 34 ascsin2 n 33 nta4 34 ntan2 35 ntansi2 s i 38 sin4 33 sinta4 34 sintan2 c 39 csi4 38 csin4 33 csinta4 c 37 cas2 33 casta2 30 castahl c 34 cn3 35 cnsi3 36 cnsic3 c 38 cn4 39 cnsi4 40 cnsic4 h 35 hsi5 36 hsic5 37 hsicas5 h 35 hsi6 36 hsic6 37 hsicas6 SCF=(maxcy=512) h 36 hcl4 37 hcas8 41 hcasc5 h 36 hcl5 37 hcas9 41 hcasc6 h 39 hsi7 40 hsic7 37 hsicas7 h 39 hsi8 40 hcsi8 37 hsicas8 h 40 hcl6 37 hcaslO 41 hcasc7 h 40 hcl7 37 h c a s l l 41 hcasc8 h 41 hcl8 37 hcasl2 33 hcasta4 h 41 hcl9 37 hcasl3 33 hcasta5 h 41 hc20 37 hcasl4 33 hcasta6 h 42 hc21 34 hcn7 33 hcnta7 h 42 hc22 34 hcn8 33 hcnta8 h 42 hc23 34 hcn9 33 hcnta9 h 43 hc24 38 hcnlO 33 hcntalO h 43 hc25 38 hc n l l 33 hcntall h 43 hc26 38 hcnl2 33 hcntal2 Page 252 References located on page 232. Appendix B: Density functional theory calculation data Table B-12. Method and z-matrix for ( c N A s N , T a ) 2 ( | i - H ) 4 (3.6B). # GFINPUT B3LYP/LANL2DZ Extrabasis Opt=(maxcy=200) SCF=(maxcy=512) IOP(6/7=3) nasntah4-d 0 1 ta n 1 ntal s i 2 s i n l 1 s i n t a l c 3 c s i l 2 c s i n l 1 c s i n t a l as 4 ascl 3 a s c s i l 2 ascsinl n 1 nta2 2 ntanl 3 ntan s i l s i 6 sin2 1 sinta2 2 sintanl c 7 csi2 6 csin2 1 csinta2 c 5 casl 1 castal 2 castanl c 2 cnl 3 e n s i l 4 cn s i c l c 6 cn2 7 cnsi2 8 cnsic2 h 3 h s i l 4 h s i c l 5 hsicasl h 3 hsi2 4 hsic2 5 hsicas2 h 4 hcl 5 hcasl 9 hcascl h 4 hc2 5 hcas2 9 hcasc2 h 7 hsi3 8 hsic3 5 hsicas3 h 7 hsi4 8 hsic4 5 hsicas4 h 8 hc3 5 hcas3 9 hcasc3 h 8 hc4 5 hcas4 9 hcasc4 h 9 hc5 5 hcas5 1 hcastal h 9 hc6 5 hcas6 1 hcasta2 h 9 hc7 5 hcas7 1 hcasta3 h 10 hc8 2 hcnl 1 hcntal h 10 hc9 2 hcn2 1 hcnta2 h 36 hcl4 37 hcas8 41 hcasc5 h 10 hclO 2 hcn3 1 hcnta3 h 36 hcl5 37 hcas9 41 hcasc6 h 11 h e l l 6 hcn4 1 hcnta4 h 39 hsi7 40 hsic7 37 hsicas7 h 11 hcl2 6 hcn5 1 hcnta5 h 11 hcl3 6 hcn6 1 hcnta6 h 39 hsi8 40 hcsi8 37 hsicas8 h 1 htal 2 htanl 3 htansil h 40 hcl6 37 hcas10 41 hcasc7 h 1 hta2 2 htan2 3 htansi2 h 40 hcl7 37 hc a s l l 41 hcasc8 h 1 hta3 2 htan3 3 htansi3 h 41 hcl8 37 hcasl2 33 hcasta4 h 1 hta4 2 htan4 3 htansi4 h 41 hcl9 37 hcasl3 33 hcasta5 ta 29 tahl 1 tahtal 2 tahtanl h 41 hc20 37 hcasl4 33 hcasta6 n 33 nta3 29 ntahl 1 ntahtal h 42 hc21 34 hcn7 33 hcnta7 s i 34 sin3 33 sinta3 29 sintahl h 42 hc22 34 hcn8 33 hcnta8 c 35 csi3 34 csin3 33 csinta3 h 42 hc23 34 hcn9 33 hcnta9 as 36 asc2 35 ascsi2 34 ascsin2 h 43 hc24 38 hcnlO 33 hcntalO n 33 nta4 34 ntan2 35 ntansi2 h 43 hc25 38 hc n l l 33 hcntal1 s i 38 sin4 33 sinta4 34 sintan2 h 43 hc26 38 hcnl2 33 hcntal2 c 39 csi4 38 csin4 33 csinta4 c 37 cas2 33 casta2 30 castahl As 0 c 34 cn3 35 cnsi3 36 cnsic3 SP 1 1.0 c 38 •cn4 • 39 cnsi4 40 cnsic4 0. 2660D -01 0 1000D+01 0 . 1000D+01 h 35 hsi5 36 hsic5 37 hsicas5 D 1 1.0 h 35 hsi6 36 hsic6 37 hsicas6 0. 2890D+00 0 1000D+01 0 .1000D+01 * * * * Page 253 References located on page 232. Appendix B: Density functional theory calculation data Table B-13. Initial parameters for ( 'NAsN'Ta) 2 (u--H)4 (3.6A) and (3.6B). ntal 2 . 076 hc22 0. 98 hcasl2 109 . 5 hsicas8 214 . 1 s i n l 1. 75 hc23 0. 98 hcasl3 109 . 5 hcasc7 6.5 c s i l 1. 89 hc24 0. 98 hcasl4 109 .5 hcasc8 124 .7 ascl 1. 813 hc25 0. 98 hcn7 109 . 5 hcasta4 180 nta2 2. 102 hc26 0. 98 hcn8 109 . 5 hcasta5 54 . 75 sin2 1. 729 s i n t a l 118 . 7 hcn9 109 . 5 hcasta6 305 . 75 csi2 1. 882 c s i n l 104 . 9 hcnlO 109 . 5 hcnta7 180 casl 1. 823 a s c s i l 106. 79 hcnll 109 . 5 hcnta8 54 . 75 cnl 1. 431 ntanl 110. 89. hcnl2 109 . 5 hcnta9 305 .75 cn2 1. 425 sinta2 126. 23 c s i n t a l 314 . 1 hcntalO 180 h s i l 1. 3 csin2 105. 75 ascsinl 44 . 3 hcnt a l l 54 . 75 hsi2 1. 3 castal 123. 52 ntan s i l 304 .5 hcntal2 305 . 75 hcl 0. 98 e n s i l 112. 93 sintanl 94 . 3 hc2 0 . 98 cnsi2 118. 75 csinta2 332 . 6 hsi3 1. 3 h s i c l I l l . 16 castanl 129 . 4 hsi4 1. 3 hsic2 108. 02 c n s i c l 136 . 6 hc3 0. 98 hcasl 110. 36 cnsic2 155 .8 hc4 0. 98 hcas2 110. 36 hsicasl 284 . 9 hc5 0. 98 hsic3 108 . 47 hsicas2 165 hc6 0. 98 hsic4 107 . 11 hcascl 78 hc7 0 98 hcas3 109. 45 hcasc2 317 . 9 hc8 0 98 hcas4 109. 46 hsicas3 145 . 9 hc9 0 98 hcas5 109. 5 hsicas4 264 . 1 hclO 0 98 hcas 6 109. 5 hcasc3 235 . 3 h e l l 0 98 hcas7 109. 5 hcasc4 353 .5 hcl2 0 98 hcnl 109. 5 hcastal 180 hcl3 0 98 hcn2 109. 5 hcasta2 54 . 75 htal 2 002 hcn3 109. 5 hcasta3 305 . 75 hta2 1 819 hcn4 109. 5 hcntal 180 hta3 1 905 hcn5 109. 5 hcnta2 54 . 75 hta4 1 93 hcn6 109. 5 hcnta3 305 . 75 tahl 1 93 htanl 123. 79 hcnta4 180 nta3 2 076 htan2 79.06 hcnta5 54 . 75 sin3 1 75 htan3 156. 45 hcnta6 305 .75 csi3 1 89 htan4 98 . 58 htansil 211 . 1 asc2 1 813 tahtal 81.44 htansi2 172 . 4 nta4 2 102 ntahl 98 . 58 htansi3 100 . 6 sin4 1 729 sinta3 118. 7 htansi4 104 .8 ' csi4 1 882 csin3 104 . 9 tahtanl 253 . 6 cas2 1 823 ascsi2 106. 79 ntahtal 233 . 7 cn3 1 431 ntan2 110. 89 sintahl 255 . 2 cn4 1 425 sinta4 126. 23 csinta3 45. 9 hsi5 1 3 csin4 105 75 ascsin2 315 .2 hsi6 1 .3 casta2 123 52 ntansi2 55 . 5 hcl4 0 . 98 cnsi3 112 93 sintan2 265 . 2 hcl5 0 . 98 cnsi4 114 95 csinta4 27. 4 hsi7 0 . 98 hsic5 108 02 castahl 27 . 7 hsi8 0 . 98 hsic6 111 16 cnsic3 223 . 4 hcl6 0 . 98 hcas8 110 36 cnsic4 204 . 2 hcl7 0 . 98 hcas9 110 36 hsicas5 195 hcl8 0 . 98 hsic7 107 11 hsicas6 75. 1 hcl9 0 . 98 hcsi8 108 47 hcasc5 42. 1 . hc20 0 . 98 hcaslO 109 46 hcasc6 282 hc21 0 . 98 hc a s l l 109 45 hsicas7 95. 9 Page 254 References located on page 232. Appendix B: Density functional theory calculation data Table B-14. Final atomic coordinates for ( 'NAsN'Ta) 2 (u . -H) 4 (3.6A). Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Y Z 1 73 0 1. 281815 0. 079651 -0. 322847 2 7 0 2. 091366 1. 941078 -0. 512358 3 14 0 3. 843573 2 . 255352 -0. 688599 4 6 0 4 . 746970 1. 280564 0. 678398 5 33 0 3. 719242 -0. 398814 0 . 965659 6 7 0 1. 969021 -1. 350496 -1. 590734 7 14 0 3. 695444 -1. 742024 -1. 894754 8 6 0 4 . 644415 -1. 684441 -0. 244321 9 6 0 4 . 310055 -0. 987482 2 . 766011 10 6 0 1. 251836 3. 181686 -0. 622656 11 6 0 1. 060218 -2 . 130740 -2. 503645 12 1 0 4 . 389694 1. 831840 -2. 010265 13 1 0 4 . 104893 3. 715167 -0. 537331 14 1 0 5 795244 1. 064596 0. 438446 15 1 0 4 722363 1. 855522 1. 613719 16 1 0 4 334251 -0. 809263 -2 . 866789 17 1 0 3 778217 -3. 113669 -2. 475301 18 1 0 5 698562 -1 408600 -0 371166 19 1 0 4 609958 -2 674502 0 229540 20 1 0 5 403438 -1 040911 2 813416 21 1 0 3 883861 -1 973604 2 980125 22 1 0 3 944625 -0 275249 3 513707 23 1 0 1 473490 3 891170 0 190843 24 1 0 0 193668 2 921606 -0 580123 25 1 0 1 428253 3 693793 -1 582140 26 1 0 1 259149 -1 883000 -3 558823 27 1 0 0 017961 -1 890796 -2 291619 28 1 0 1 201291 -3 215005 -2 373424 29 1 0 -0 842727 -1 471455 -0 511624 30 1 0 -0 214092 0 550809 -1 370466 31 1 0 0 432579 -0 763687 1 127302 32 1 0 0 019588 1 227160 0 869236 33 73 0 -1 268370 -0 008434 0 418965 34 7 0 -2 052226 -0 871659 2 058856 35 14 0 -3 833968 -0 674605 2 268627 36 6 0 -4 739869 -1 093656 0 633925 37 33 0 -3 .565216 -0 718084 -0 939905 38 7 0 -2 .448399 1 741048 0 293034 39 14 0 -3 .482363 2 . 374117 -1 000605 40 6 0 -4 .364683 0 . 879842 -1 794065 41 6 0 -3 .987046 -2 .203526 -2 174554 42 6 0 -1 . 375943 -1 .677775 3 . 118456 43 6 0 -2 .161699 2 .739550 1 .376175 44 1 0 -4 .281561 -1 . 640856 3 . 314962 45 1 0 -4 .214643 0 . 690949 2 .717077 46 1 0 -4 . 983784 -2 .164598 0 .614422 47 1 0 -5 .681388 -0 .537357 0 .539236 Page 255 References located on page 232. Appendix B: Density functional theory calculation data 48 1 0 -2. 756844 3 124876 -2 072370 49 1 0 -4 . 487507 3 316638 -0 422622 50 1 0 -4 171544 0 822791 -2 872379 51 .. 1 0 -5 450277 0 904 685 -1 644186 52 1 0 -5 065140* -2 257869 ;-2 361654 53 1 0 -3 642817 -3 14'3787'" -1 730545 54 1 0 -3 459207 -2 048956 -3 121810 55 1 0 -1 495470 -1 218252 4 112606 56 .1 0 -0 306724 -1 7 4 3540 2 900194 57 1 0 -1. 781715 . -2 700159 3 169849 58 1 0 -3 054993 3 341630 1 610559 59 1 0 -1 343972 3 426706 1 104018 60 1 0 -1 862491 2 230284 2 299603 Table B-15. Final atomic coordinates for ( ' N A s N ' T a ) 2 ( p - H ) 4 (3.6B). Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Y Z 1 73 0 1 291307 0 074479 -0 314088 2 7 0 2 069068 1 954300 -0 458760 3 14 0 3 817618 2 299301 -0 611070 4 6 0 4 718366 1 289049 0 734063 5 33 0 3 697021 -0 391238 0 943805 6 7 0 1 987473 -1 319792 -1 614143 7 14 0 3 722351 -1 666828 -1 921799 8 6 0 4 648095 -1 649040 -0 255378 9 6 0 4 232151 -1 017242 2 738077 10 6 0 1 208431 3 181961 -0 542450 11 6 0 1 086325 -2 107072 -2 527522 12 1 0 4 379791 1 928960 -1 941654 13 1 0 4 055629 3 757413 -0 410481 14 1 0 5 772077 1 088224 0 502059 15 1 0 4 674161 1 832386 1 688345 16 1 0 4 351217 -0 685385 ' -2 851026 17 1 0 3 835250 -3 013504 -2 553594 18 1 0 5 706453 . -1 375152 -0 353886 19 1 0 4 596525 -2 648387 0 198799 20 1 0 5 324463 -1 078934 2 819229 21 1 0 3 793446 -2 005932 2 918775 22 1 0 3 846379 -0 319147 3 490646 23 1 0 1 428962 3 884859 0 27.7066 24 1 0 0 155068 2 903944 -0 490364 25 1 0 1 365386 3 708440 -1 497634 26 1 0 1 264080 -1 835594 -3 580545 27 1 0 0 041206 -1 899107 -2 295601 28 1 0 1 257860 -3 189248 -2 418588 29 1 0 -0 920719 -1 .494131 -0 572802 30 1 0 -0 243825 0 .553510 -1 333429 Page 256 References located on page 232. Appendix B: Density functional theory calculation data 31 1 0 0 417261 -0. 862545 1 071042 32 1 0 0 037018 1 152833 0 913667 33 73 0 -1 274824 -0 054528 0 420163 34 7 0 -2 089777 -0 999523 1 999870 35 14 0 -3 874286 -0 808725 2 187058 36 6 0 -4 747837 -1 095923 0 503429 37 33 0 -3 531000 -0 617966 -0 993726 38 7 0 -2 437560 1 712896 0 409828 39 14 0 -3 459142 2 447342 -0 838725 40 6 0 -4 297448 1 014019 -1 780389 41 6 0 -3 891210 -2 018966 -2 325832 42 6 0 -1 433856 -1 877237 3 013835 43 6 0 -2 137765 2 631728 1 557202 44 1 0 -4 347276 -1 848646 3 147986 45 1 0 -4 259455 0 521470 2 728294 46 1 0 -4 998477 -2 160966 0 397134 47 1 0 -5 682504 -0 524020 0 428091 48 1 0 -2 722230 3 306277 -1 817758 49 1 0 -4 491308 3 317429 -0 198195 50 1 0 -4 040908 1 027437 -2 847604 51 1 0 -5 390447 1 027068 -1 689720 52 1 0 -4 961507 -2 068319 -2 560693 53 1 0 -3 556331 -2 984169 -1 928072 54 1 0 -3 326107 -1 801905 -3 240046 55 1 0 -1 566840 -1 482450 4 033896 56 1 0 -0 361594 -1 934477 2 807961 57 1 0 -1 844406 -2 898771 2 992238 58 1 0 -3 026091 3 219700 1 840953 59 1 0 -1 318519 3 332067 1 324920 60 1 0 -1 833118 2 057985 2 440256 Page 257 References located on page 232. Appendix B: Density functional theory calculation data B.5. Gaussianisms Few things can duplicate the level of frustration derived from teaching oneself density functional theory applications using Gaussian 98. First, the endless trials in the creation of a stable z-matrix, followed by the inevitable wrangling with Gaussian 98 over things like syntax, often leading to profanity and the destruction of small objects. Then there are the endless weeks of waiting to see i f the structure has converged. Fortunately, Gaussian 98 rewards the successful convergence of a structure with a 'Gaussianism', a short quotation at the end of hundreds of pages of data from which one may garner great insight; or, as is more often the case, a moment of humour before the next optimization is started. Perhaps not coincidentally, similar frustrations may be derived from the writing -and reading - of a doctoral thesis. Therefore, all of the Gaussianisms observed during the course of this work are collected here, for posterity, insight and humour. GOD DOES NOT PLAY WITH DICE. — A. EINSTEIN EXPERIENCE IS THE FRUIT OF THE TREE OF ERRORS. THE LARGE PRINT GIVETH, AND THE SMALL PRINT TAKETH AWAY. — TOM WAITES JUST REMEMBER, WHEN YOU'RE OVER THE HILL, YOU BEGIN TO PICK UP SPEED. — CHARLES SCHULTZ BLACK HOLES SUCK. IT IS A QUALITY OF REVOLUTIONS NOT TO GO BY OLD LINES OR OLD LAWS, BUT TO BREAK UP BOTH, AND MAKE NEW ONES. -- A. LINCOLN (18.4 8) IF AT FIRST YOU DON'T SUCCEED, TRY, TRY AGAIN. THEN GIVE UP; THERE'S NO USE BEING A DAMN FOOL ABOUT IT. -- W. C. FIELDS Page 258 References located on page 232. Appendix B: Density functional theory calculation data THE MOST SERIOUS THREAT TO THE SURVIVAL OF MANKIND IS NOT NOW IGNORANCE IN THE TRADITIONAL SENSE, BUT A MORALLY NEUTRAL, AN INSENSITIVE OR INHIBITED HUMAN INTELLIGENCE. — MARGO JEFFERSON IN NEWSWEEK, SEPT. 2, 197 4 THE DIFFERENCE BETWEEN A NOOSE AND A HALO IS ONLY 12 INCHES. GETTING A SIMPLE ANSWER FROM A PROFESSOR IS LIKE GETTING A THIMBLE OF WATER FROM A FIRE HYDRANT. — PROF. LEN SHAPIRO, NDSU A GREAT MANY PEOPLE THINK THEY ARE THINKING WHEN THEY ARE MERELY REARRANGING THEIR PREJUDICES. — WILLIAM JAMES ...THOSE SCIENCES ARE VAIN AND FULL OF ERRORS WHICH ARE NOT BORN FROM EXPERIMENT, THE MOTHER OF CERTAINTY... -- LEONARDO DA VINCI, 1452-1519 THE WHOLE OF SCIENCE IS NOTHING MORE THAN A REFINEMENT OF EVERYDAY THINKING. — A. EINSTEIN WHEN I TOLD THE PEOPLE OF NORTHERN IRELAND THAT I WAS AN ATHEIST, A WOMAN IN THE AUDIENCE STOOD UP AND SAID, "YES, BUT IS IT THE GOD OF THE CATHOLICS OR THE GOD OF THE PROTESTANTS IN WHOM YOU DON'T BELIEVE?" -- QUENTIN CRISP NATURE WILL TELL YOU A DIRECT LIE IF SHE CAN. -- CHARLES DARWIN EVERYBODY IS IGNORANT, ONLY ON DIFFERENT SUBJECTS. — WILL ROGERS IT'S WHAT YOU LEARN AFTER YOU KNOW IT ALL THAT COUNTS. DO NOT POKE THE BEAR Page 259 References located on page 232. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            data-media="{[{embed.selectedMedia}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0061127/manifest

Comment

Related Items