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The synthesis of group 3 and group 4 metal amidate chloride complexes and titanium catalysts for olefin… Beard, James David 2005

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The Synthesis of Group 3 and Group 4 Metal Amidate Chloride Complexes and Titanium Catalysts for Olefin Hydroamination by James David Beard B.Sc. The University of Virginia, 2002 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 L M E N T OF T H E R E Q U I R E M E N T S FOR T H E D E G R E E OF M A S T E R OF SCIENCE in T H E F A C U L T Y OF G R A D U A T E STUDIES ( C H E M I S T R Y ) THE UNIVERSITY OF BRITISH C O L U M B I A February 2005 © James David Beard, 2005 Abstract The work presented in this thesis bridges the boundaries between what is considered traditional inorganic and organic chemistry. The uniting principle is a focus on synthesis. This manifests in the development of new synthetic strategies for preparing novel organometallic complexes, and in the investigation of the reactivity of these coordination compounds. The ultimate goal is the development of rationally designed, and well characterized metal complexes for use in new catalytic organic transformations. Two routes for the synthesis of amidate complexes from group 4 metal chlorides were developed. A variety of group 4 metal bis(amidate) dichloride complexes were synthesized and characterized. The structures of three titanium bis(amidate) dichlorides complexes were solved by X-ray crystallography. The first known homoleptic yttrium amidate complex was prepared and its structure was solved by X-ray crystallography. Investigations were made into the application of titanium bis(amidate) bis(amido) complexes for the synthesis of N-heterocyclic compounds. Several titanium catalysts for the intramolecular hydroamination of unactivated alkenes were discovered. A study was undertaken to elucidate the influence that steric and electronic factors in the amidate auxiliary ligand have on the activity of titanium bis(amidate) imido hydroamination catalysts. Finally, preliminary work was done on exploring the application of lanthanide chloride complexes toward new carbon-carbon bond forming reactions, and in the development of chiral amidate ligands for potential applications in asymmetric catalysis. 11 Table of Contents Abstract ii Table of Contents iii List of Figures v List of Tables vii List of Abbreviations viii Chapter 1 - Introduction 1 1.1 Group 4 Metallocene Catalysts 1 1.2 Group 4 Complexes with Non-Cyclopentadienyl ligands 3 1.3 Amidate Complexes of Metals 6 1.3.1 Amidate Complexes of Group 4 Metals and Lanthanides 9 1.4 Goals of the Thesis 12 1.5 References 13 Chapter 2 - Amidate Chloride Complexes of Group 3 and 4 Metals 16 2.1 Introduction 16 2.2 Proligand Design and Synthesis 19 2.3 Salt Metathesis Route 22 2.3.1 Titanium Complexes 25 2.3.2 Zirconium Complexes 31 2.3.3 Homoleptic Yttrium Amidate Complex 33 2.4 Chlorotrimethylsilyl Elimination Route 35 2.4.1 Silylated Amide Proligands 36 2.4.2 Metal Complexation - Titanium 39 i i i 2.4.3 Metal Complexation - Zirconium and Yttrium 43 2.5 Conclusion 44 2.6 Experimental Procedures 45 2.7 References 56 Chapter 3 - Catalytic Hydroamination 58 3.1 Introduction 58 3.2 Titanium bis(Amidate) bis(Amido) Complexes 65 3.3 Titanium Tetrakis(Amido) 68 3.4.1 Qualitative Screening of Complexes for Alkene Hydroamination 70 3.4.2 Rate Comparison of Most Active Catalysts 76 3.5 Conclusion 78 3.6 Experimental 79 3.7 References 86 Chapter 4 - Future Work and Summary 88 4.1 Introduction 88 4.2.1 Chiral Multidentate Ligand 88 4.2.2 Multidentate Ligands for Ln Complexation 90 4.3.1 C-C Bond Formation: 1,2-Addition of Zinc Reagents to Ketones 92 4.3.2 C-C Bond Formation: Olefin Polymerization 96 4.4 Summary 96 4.5 Experimental 99 4.6 References 100 Appendix - Crystallographic Data 105 iv List of Figures Figure 1-1. Group 4 Metallocene Precatalysts 2 Figure 1-2. N , 0 Chelating Complexes 3 Figure 1-3. Amidinate and Guanidinate Complexes 5 Figure 1-4. Bridging Amidate Dirhenium Complex 7 Figure 1-5. Bonding Motifs in Vanadium Amidate Complexes 8 Figure 1 -6. Diverse Bonding Motifs in Aluminum Amidate Complexes 9 Figure 1-7. Dysprosium Amidate Complex by Isocyanate Insertion 11 Figure 2-1. Selected Organometallic Complexes Derived From Metal Chlorides 17 Figure 2-2. Amide Proligands 20 Figure 2-3. Amidate Complexes via Salt Metathesis 24 Figure 2-4. T i [ p h ( 0 , N ) D i l P r P h ] 2 C l 2 (7) 25 Figure 2-5. T i [ t B u ( 0 , N ) D i M e P h ] 2 C l 2 (8) 27 Figure 2-6. T i [ t B (0 ,N) D i M e P h ] 2 (NMe 2 ) 2 (13) 29 Figure 2-7. Yttrium tr is[ t B u (0,N) D i M e P h ] (12) 34 Figure 2-8. Silylated Amide Proligands 37 Figure 2-9. bis(Amidate) Dichlorides Prepared by ClSiMe3 Elimination 39 Figure 2-10 T i [ P h ( 0 , N ) D i M e P h ] 2 C l 2 (10) 40 Figure 2-11. Titanium Chloride, Silylated Amide Metathesis 42 Figure 3-1. Imido Mechanism for Hydroamination of Alkynes 59 Figure 3-2. Proposed Mechanism for TiCL, Catalyzed Hydroamination of Alkene 61 Figure 3-3. Sigma-bond Metathesis Mechanism 62 v Figure 3-4. Lanthanide bis(Thiophosphinic Amidate) Precatalysts 63 Figure 3-5. Scandium "Nacnac" Precatalysts 64 Figure 3-6. Bis(amidate) Titanium Bis(amido) Precatalysts 65 Figure 3-7. Regioisomeric Products of Terminal Alkyne Hydroamination 66 Figure 3-8. N-2',6'-Diwopropylphenyl Perfluorophenylamide 66 Figure 3-9. Catalytic Intramolecular Alkene Hydroamination 67 Figure 3-10. Substrates for Intramolecular Alkene Hydroamination 68 Figure 3-11 Amide Proligands for Alkene Hydroamination Catalysts 71 Figure 3-12. Qualitative Ranking of Alkene Hydroamination Catalyst Activity 73 Figure 3-13. Quantitative Alkene Hydroamination Catalysts Activity Comparison 77 Figure 4-1. Silylated Amide Proligand with Additional Donor Group 92 Figure 4-2. Lewis Acid Catalyzed 1,2 Addition of Zinc Reagents to Ketones 95 vi List of Tables Table 1-1. Selected Bond Distances (A) for R e 2 [ M e ( 0 , N ) D i M e P l l ] 4 C l 2 7 Table 1-1. Selected Bond Distances (A) and Angles (°) for (Cp' 2 Dy[ N p (0,N) p h ] 2 ) 2 11 Table 2-1. Selected Bond Distances (A) and Angles (°) for 7 25 Table 2-2. Selected Bond Distances (A) and Angles (°) for 8 27 Table 2-3. Selected Bond Distances (A) and Angles (°) for 13 29 Table 2-4. Selected Bond Distances (A) and Angles (°) for 12 34 Table 2-5. Selected Bond Distances (A) and Angles (°) for 10 40 Table 3-1 Summary of Rate Comparison Data 77 Table A - l - Summary of Crystallographic Data for T i [ p h ( 0 , N ) D i i P r P h ] 2 C l 2 (7) 104 Table A - 2 - Bond Distances (A) and angles (°) for T i [ p h ( 0 , N ) D i i P r P h ] 2 C l 2 (7) 105 Table A -3 - Summary of Crystallographic Data for T i [ t B u ( 0 , N ) D i M e P h ] 2 C l 2 (8) 108 Table A -4 - Bond Distances (A) and angles (°) for Ti [ t B u (0 ,N) D i M e P h ] 2 Cl 2 (8) 109 Table A-5 - Summary of Crystallographic Data for T i [ t B u (0 ,N) D i M e P h ] 2 (NMe 2 ) 2 (13) 112 Table A-6 - Bond Distances (A) and angles (°) for T i [ t B u (0 ,N) D i M e P l l ] 2 (NMe 2 ) 2 (13) 113 Table A-7 - Summary of Crystallographic Data for Y [ t B u ( 0 , N ) D i M e P l l ] 3 (12) 115 Table A-8 - Bond Distances (A) and angles (°) for Y [ t B u ( 0 , N ) D i M e P h ] 3 (12) 116 Table A-9 - Summary of Crystallographic Data for T i [ p h ( 0 , N ) D i M e P h ] 2 C l 2 (10) 119 Table A-10 - Bond Distances (A) and angles (°) for T i [ p h ( 0 , N ) D i M e P h ] 2 C l 2 (10) 120 vii List of Symbols and Abbreviations A angstrom Ar aryl b broad Bu butyl °C degrees Celsius Calcd. calculated Cp cyclopentadienyl Cp' C5H4CH3 d doublet (NMR) or deuterated dd doublet of doublets (NMR) deg degree DiMePh 2' ,6' -di /soprophenyl DiiPrPh 2' ,6'-di/sopropy lphenyl DFT Density Functional Theory DMF N,N-dimethylformamide EI electron ionization Et ethyl g gram GC gas chromotograpy / iso h hours J coupling constant (Hz) mg milligram mL millilitre Ln lanthanide M molar (mol L"1) m multiplet Me methyl min minute mmol millimole M w molecular weight - weight average M w / M n polydispersity MS mass spectrometry M n molecular weight - number average N M R nuclear magnetic resonance P para Ph phenyl ppm parts per million Pr propyl RT room temperature s singlet (NMR) T temperature t triplet (NMR) t tertiary viii THF tetrahydrofuran vi. vide infra vs. vide supra V T variable temperature a Alpha 3 Delta (chemical shift) Note: A shorthand format for naming amidate metal complexes is used throughout this thesis. The amidate backbone is abbreviated as (0,N), and the substituents on the carbonyl and nitrogen of the amidate are labelled in superscript around the backbone. Eg. Titanium bis(N-2',6'-diisopropylphenyl(phenyl)amidate) dichloride would be written: T i [ p h (0 ,N) D i i P r ] 2 Cl 2 ix Acknowledgments I would like to give special thanks to Dr. Laurel L. Schafer for the support and guidance she lent me in the course of producing the work presented herein. I thank Dr. Brian Patrick for collecting X-ray crystallographic data, and for his assistance in solving the crystal structures reported in this thesis. I thank Dr. Martin E. Tanner, and Dr. Mark MacLachlan for sitting on my thesis committee. I extend thanks to all my colleagues in the Schafer group with whom I've had the pleasure of working. I would also like to specially thank Dr. Ming Hua X u and Dr. Lin Pu for the for the opportunities and education they gave me at the beginning of my research career. x Chapter 1 - Introduction 1.1 Group 4 Metallocene Catalysts Throughout the 1980s research into the organometallic chemistry of early transition metals predominantly focused on cyclopentadienyl and related metallocene complexes of group 4 metals. The impetus behind the development and study of these complexes lay in their application as polymerization catalysts for the production of polymeric materials such as polyethylene and polypropylene. Metallocenes were shown to have numerous advantages over older Zeigler-Natta polymerization systems. They offer well-defined, single site reactive centers, allowing for greater control over the polymerization process, and hence greater control over the molecular structure and properties of the generated polymer. In comparison with older systems, metallocenes also possess enhanced stability due to the electronic donation and steric protection provided to the metal center by the ligands. The increased stability of the catalytic species has proven particularly important since the discovery that methylaluminoxane (MAO), an extremely reactive cocatalyst, when used in conjunction with metallocenes produces highly active and long lasting olefin polymerization systems.1 The introduction of metallocene based polymerization catalysts into commercial use has transformed industrial polyolefin production. While traditional Zeigler-Natta systems are still widely used today, their importance is declining. Group 4 metallocene 1 catalysts such as dimethyltitanocene, and the related constrained-geometry catalyst are being incorporated into the current generation of olefin polymerization reactors. Me 2Sk / CI tBu Dimethyl Titanocene Constrained-Geometry Catalyst Figure 1-1. Group 4 Metallocene Precatalysts In the past ten years, metallocene catalysts have also attracted great interest from synthetic organic chemists. Group 4 metallocenes have been shown to have applications outside of polymerization in promoting such transformations as the reduction of imines, alkyne coupling/ hydroamination,4 hydrosilylation,33 dehydrosilylation,31' and carbonylation,6 to name only a few. Due to their diverse reactivity, further refinements of the metallocene family of catalysts remains an area of active research. Yet, despite the great attention that metallocenes have received, the scope for variation available with Cp type ligands remains limited, particularly in regards to introducing new functionality and geometries to these complexes. While there is still much chemistry to be explored with metallocene type catalysts, as is shown by recent work on the hydrogenation and cleavage of dinitrogen to produce ammonia using a zirconocene type complex with (/^-C^MesH)" ligands,7 the next generation of organometallic catalysts will likely be based upon non-cyclopentadienyl ligands. 1.2 Group 4 Complexes with Non-Cyclopentadienyl Ligands Since the early 1990s, many groups working on organometallic chemistry have o focused on developing new catalysts based upon non-metallocene ligand sets. Amongst non-cyclopentadienyl based metal complexes, there are several classes that pertain most directly to the work done in the Schafer Lab. These are complexes of mixed N,0 chelating ligands. amidinates, guanidinates, and amidates. One of the earliest reported N,0 chelating ligands used for generating complexes with group 4 metals is the bis-amido diphenyl ether ligand developed by the Schrock group (Fig. 1-2).9 The amido groups of this ligand form strong bonds with titanium (1.94 A), however the Ti-0 distance (2.4 A) is longer than a typical Ti-Odonor bond length (-2.15-2.20 A). 9 Cationic zirconium complexes derived from this ligand proved to be active catalysts for ethylene and 1-hexene polymerization. In comparison with metallocene based polymerization catalysts, these complexes exhibit reduced rates of termination by /^-elimination while retaining high activity. bis-Amido diphenyl ether Phenoxy-ketimine Figure 1-2. N,0 Chelating Complexes Another N,0 chelating ligand system that has received a great deal of attention in the literature is the phenoxy-ketimine ligands developed by Fujita and Coates. 1 0 The titanium bis(phenoxyketimine) dichloride complex illustrated in Fig. 1-2 was shown to be an excellent catalyst for ethylene polymerization. The activity of the complex (TOF = 20,000 min'atm"') was intermediate between M A O activated Cp 2 ZrCl 2 (18,600 min'atm"1) and C p 2 T i C l 2 (30,500 min'atm"1) under the same conditions. What is most distinctive about this catalyst is that it produces linear polyethylene with essentially zero branching. The polydispersity of the polymer produced is exceptionally narrow ( M w / M n = 1.13) and there is a linear relationship between the M n of the polymer produced, and the reaction time. These observations suggest a living polymerization catalyst. Living polymerization catalysts with high activity at room temperature are exceedingly rare, and ones which produce high molecular weight polyethylene with nearly perfect linearity were previously unknown. Amidinates (Fig. 1-3, A , B) are attractive non-Cp ligands for the reason that the steric bulk and electronic properties of the ligands are easily modified. These ligands have been explored for use with a wide variety of transition metals, however there are limited examples of their use with Group 4 metals. The Richeson group reported the synthesis of a series of bis(alkylamidinate) complexes of Ti , Zr, and Hf (Fig. 1-3, A). " These complexes were screened for polyethylene polymerization activity. The best performing catalysts were the titanium and zirconium bis(alkylamidinate) dichlorides with M A O as a cocatalyst, however their activities were substantially lower than those of metallocene systems. The catalysts produced polyethylene with high molecular weights, but very broad polydispersity ( M w / M n = 40-87). 4 >/. ^ 4-MePh K l Me Cy I Me2N /Pr C y - r T \ a k A N ' J N , P r - f Q - C I Me Cy 4-MePh M e 2 N , P r A B C Figure 1-3. Amidinate and Guanidinate Complexes Some unusual reactivity was observed by the Arnold group when a cyclohexane-linked benzamidinate titanium complex (Fig. 1-3, B) 1 2 was treated with H 2 . One equivalent of toluene was released in the reaction, and a novel ;/6-toluene complex was formed. The structure of the product was solved using X-ray crystallography and the arene was observed to have a puckered C 6 ring, revealing a strong cyclohexadiene-like character. Labelling studies suggest an intramolecular o-n rearrangement of an intermediate benzyl hydride species. Such unusual reactivity is indicative of the possibilities afforded by developing new and more refined ligand sets. Closely related to amidinate ligands are the guanidinates (Fig. 1-3, C)'.J, in which there is an amino substituent on the central carbon atom of the amidinate chelate, rather than an alkyl or aryl group. These ligands offer similar potential for steric and electronic tunability as the amidinate ligands. While guanidinates may be formally isoelectronic with amidinates, it is believed that donation from the lone pair of amino group into the chelate results in more electron rich metal complexes. The electron-rich nature of these ligands makes them especially suitable for facilitating redox chemistry. l j Titanium bis(guanidinate) imido complexes have also been shown to be active hydroamination catalysts.14 5 1.3 Amidate Complexes of Metals Amides are easily synthesized from a wide variety of commercially available starting materials, and their steric and electronic parameters may be easily modified by the appropriate selection of acyl chloride and amine starting materials (Scheme 1-1). The structural versatility, ease of synthesis, and stability of amide proligands exceeds that of the similar amidinates. The pKa of amide proligands is similar to that of cyclopentadiene. 0 0 II NEt 3 R ^ C I + N H 2 R ' x R ^ N H R ' C H 2 C I 2 , 0°C to R T Scheme 1-1 While published results on amidate complexes of the lanthanides, group 3, and group 4 metals are rare, there are numerous reports in the literature of amidate complexes of other transition metals.1:1 Generally, the motivation behind the syntheses of these complexes has been to either model protein-metal interactions or to compare the coordination chemistry of amidates with the analogous carboxylate complexes. There have been very few reports on the application of amidates as auxiliary ligands for controlling the reactivity of metal complexes. The Cotton group reported the synthesis and structural determination of four dirhenium complexes with bridging amidate ligands.16 Most of the dirhenium complexes reported were observed to assume the coordination isomer so that at each metal center, 6 the two oxygens are in a cis relationship to each other, and two nitrogens are also bonded cis to each other. This was compared with the coordination geometry of molybdenum amidate complexes previously reported by the group,17 which exhibit a similar tendency towards cis geometry, and contrasted with chromium amidate complexes which prefer a trans relationship.17 The dirhenium complex incorporating bulky 2"6'-dimethylphenyl methyl amidate ligands (Fig. 1-4) was found to assume the trans geometry. From this observation it was concluded that steric effects are the predominate factor in determining the coordination geometry of bridging amidate complexes, followed by the influence of whether the metal centers belong to the first or later transition series. Table 1-1. Selected Bond Distances (A) for Re 2 [ M e (0 ,N) D i M c P h ] 4 Cl 2 Bond Distances Re(l)-0(11) 2.023(5) R e ( l ) - N ( l l ) 2.117(8) C( l ) -0 (11) 1.296(8) C(l ) -N(21) 1.315(8) Figure 1-4. Bridging Amidate Dirhenium Complex1 6 A series of amidate complexes of ruthenium, osmium and iridium incorporating perfluroalkyl and perfluoroaryl groups were reported by the Robinson group in 1995.18 The amidate ligands in these complexes were found to bind to two metal centers in a 7 bridging fashion, in a similar manner to the complexes reported by Cotton. This bonding motif is in contrast to complexes formed with analogous carboxylate ligands, which tend to bind in a chelate manner to late transition metals. It was proposed that the difference in binding mode between carboxylate and amidate ligands with late transition metals can be attributed to differences in derealization energy between the two ligand types. The assumption is that the four-membered metallocycles formed by these ligands rely largely on derealization energy for their stability. It is argued that the charge in the asymmetric amidate would be less delocalized than in symmetrical carboxylate ligands, and would therefore disfavour chelation. Amidate complexes of vanadium have been shown to adopt several different bonding motifs (Fig. 1-5). 1 9 Chelating amidate complexes have not been reported, however, complexes in which the amidate binds in a monodentate manner through either the nitrogen (Fig. 1-5, A) or the oxygen (Fig. 1-5, B) have been observed. Any conclusions on the possibility of chelating vanadium amidate complexes would be Figure 1-5. Bonding Motifs in Vanadium Amidate Complexes19 premature, as the amidate ligands used in the complexes reported so far have possessed 8 structural features, such as a rigid aryl backbone combined with additional donor functionalities, that would likely disfavour the formation chelating amidate bonds. Spectroscopic studies have identified numerous ligand bonding motifs for aluminium amidate complexes (Fig. 1-6).20 The crystal structure of some of these complexes have also been solved. The observed coordination geometries include t Ph \ ^ Bu ( B u I Me T F Me Me x MeJBu N V ^ O Me -X | - lW V ? ~ A u i J ' > I M e 2 M e 2 A l ' AIMe 2 O' N ( M _ A I r\Jl \ .' /  I Ph N - A I - 0 \ V b ^ N P h - ^ A l ^ . Bu M e ' Me Me • ^ Y 'Bu ^ \ £ ph rr ;AU 0. Figure 1-6. Diverse Bonding Motifs in Aluminum Amidate Complexes 19 pentacoordinate dimeric complexes (Fig. 1-6, A), dinuclear monomeric chelates (Fig. 1-6, B), and eight (Fig. 1-5, C), and twelve membered rings (Fig. 1-6, D). While such complexes may have relevance to polymerization catalysis, no reports on the reactivity of these compounds has been made. 1.3.1 Amidate Complexes of Group 4 Metals and Lanthanides Given the great interest in developing non-Cp ligands for early transition metals, it is surprising that amidates have received so little attention in the literature. On paper, they seem to be ideal ligands, however, the synthesis of pure amidate complexes of early 9 transition metals and lanthanides is a non-trivial task. This is illustrated by the fact that previous to the work presented herein, there has been no report of the synthesis of pure amidate complexes using traditional salt metathesis techniques. In 1987, titanium amidate complexes were proposed as intermediates in the Cp2TiCb catalyzed rearrangement of Grignard reagents in reaction with isocyanates, however no evidence of the species was presented other than a mechanistic rationale for the observed products.21 In 1991, Rizvi reported the first syntheses of amidate amido complexes of early transition metals and homoleptic amidate complexes of some lanthanides in the Bulletin of the Chemical Society of Ethiopia.2 2 Unfortunately, this journal is not widely circulated, and it has so far proven impossible to obtain copies of the papers. In 1996, amidate complexes of group 4 metals were proposed as intermediates in titanium catalyzed living polymerization of isocyanates.2j The synthesis and complete structural characterization of mixed metallocene amidate complexes of samarium, dysprosium, and europium was reported by the Zhou Bu Cp'LnCI "BuLi, -30°C THF Cp'Ln"Bu(THF) PhNCO, -10°C Cp ' 2 Ln—N THF -THF Cp' = C 5 H 4 Me; Ln = Sm, Dy, Eu Bu' C p 2 L n—N 'Bu Scheme 1-2 10 group in 2001These complexes were prepared by an isocyanate insertion into a Ln-alkyl bond (Scheme 1-2). The mixed metallocene amidate dysprosium dimer, (Cp , 2Dy[ N p (0,N) | : > ' 1 ]2)2 (Fig. 1-7), is of particular interest in regard to the material presented in this thesis, due to the similar ionic radii of dysprosium and yttrium. Figure 1-7. Dysprosium Amidate Complex by Isocyanate Insertion It wasn't until 2001, that the Arnold group published the first deliberate synthesis of an early transition metal amidate complex to be found in accessible chemical literature.23 What has made the synthesis of group 4 amidate complexes readily accessible is the commercial availability of titanium and zirconium tetrakis(amido) complexes. Using a mild protonolysis route, titanium and zirconium amidate complexes may be made using amide proligands (Scheme 1-3). 11 NR 2 O I Q R1 1 JL R 2 Et20,-78°C to RT I / \T Ti(NR 2) 4 +2 R 1 ^ ^ N ' K • R 2 N—Ti ' : N y \ R R 2 Scheme 1-3 As of yet, the only reported attempt at using a titanium bis(amidate) complex for olefin polymerization revealed poor activity.23 However, titanium bis(amidate) bis(amido) complexes have proven to generate very active and highly selective alkyne hydroamination catalysts.26 The value of the modularity of this class of ligands has been established in that tunable activity and selectivity was observed by modifying the substituents on the carbonyl and nitrogen of the amide proligand. 1.4 Goals of the Thesis The development of amidate coordination chemistry for early transition metals and lanthanides, and the discovery of applications for these complexes in organic synthesis is an ongoing endeavour in the Schafer lab. The contributions to this field of research to be presented in this thesis are both in of these areas. Two new methods were developed for the preparation of previously troublesome bis(amidate) dichloride complexes of group 4 metals. One method was an improved salt metathesis reaction, and the other is based upon a metathesis reaction between group 4 metal chlorides and silylated amides. The salt metathesis methodology was used to prepare the first 12 homoleptic amidate complex of a lanthanoid to be fully structurally characterized. Work was also done in the area of catalysis. The first titanium based catalyst for the hydroamination of unactivated alkenes was discovered, and a study was made into how steric and electronic factors of the auxiliary amidate ligand influences the hydroamination activity of titanium bis(amidate) imido catalysts. 1.5 References 1. (a) H.H. Brintzinger, D. Fischer, R. Mulhaupt, B. Reiger, R . M . Waymouth, Angew. Chem. Int. Ed. Engl. 1995, 34, 1143-1170; (b)W. Kaminsky, J. Chem. Soc. Dalton Trans. 1998, 1413-1418. 2. H. G. Alt, K . Fottinger, W. Milius. J. Organomet. Chem. 1999, 572, 21-30. 3. Y.R. Dumond, E. Negishi, Tetrahedron, 2004, 60, 1345-1352. 4. I. Bytschkov, H. Siebeneicher, S. Doye, Eur. J. Org. Chem. 2003, 2888-2902. 5. (a) J.F. Harrod, Coord. Chem. Rev. 2000, 493-531; (b) A.D. Sadow, T.D. Tilley, Angew. Chem. Int. Ed. Engl. 2003, 42, 803-805. 6. F.A. Hicks, N . M . Kablaoui, S.L. Buchwald, J. Amer. Chem. Soc. 1999, 121. 5881-5898. 7. (a) J.A. Pool, E. Lobkovsky, P.J. Chirik, Organometallics, 2003, 22, 2797-2805; (b) J.A. Pool, E. Lobkovsky, P.J. Chirik, Nature, 2004, ¥27(6974), 527-530. 8. G.J.P. Brotovsek, V . C . Gibson, D.F. Wass, Angew. Chem. Int. Ed. Engl. 1999, 38, 428-447. 13 9. (a) R. Baumann, W.M. Davis, R.R. Schrock,./. Am. Chem. Soc, 1997, 119, 3830-3831; (b) L.C. Liang, R.R. Schrock, W . M . Davis, Organometallics, 2000, 19, 2526-2531. 10. (a) J. Saito, M . Mitani, J-I Mohri, Y . Yoshida, S. Matsui, S-i. Ishii, S-i. Kojoh, N . Kashiwa, T. Fuijita, Angew. Chem. Int. Ed. Engl. 2001, 40, 15, 2918-2920; (b) P.D. Hustad, J.Tian, G.W. Coates, J. Am. Chem. Soc., 2002, 124, 3614-3621. 11. A. Littke, N . Sleiman, C. Bensimon, D.S. Richeson, Organometallics, 1998, 17, 446-451. 12. J.R. Hagadorn, J. Arnold. Angew. Chem. Int. Ed. Engl, 1998, 57, 1729-1731. 13.S.M. Mullins, A.P. Duncan, R.G. Bergman, J. Arnold, Inorg. Chem. 2001, 40, 6952-6953. 14. T.G. Ong, G.P.A. Yap, D.S. Richeson, Organometallics, 2001, 21, 2839-2841. 15. (a) F. A. Cotton, W. H. Ilsely, W. Kaim, Inorg. Chem. 1980, 19(12), 3586-3589. (b) F. P. Intini, M . L. Lanfranchi, G. Natile, C. Pacifico, A. Tiripichhio, Inorg. Chem. 1996, 35, 1715-1717; (c) F. A . Cotton, L. M . Daniels, J. P. Donahue, C. Y . Liu, C. A. Murillo. Inorg. Chem. 2002, 41, 1354-1356. 16. F.A. Cotton, J. Liu, T. Ren, Polyhedron, 1994,13, 807-814. 17. A. Bino, F.A. Cotton, W.H. Ilsley, Inorg. Chem., 1979, 18. 3030. 18. S. D. Robinson, A . Shajpal, D.A. Tocher, J. Chem. Soc. Dalton. Trans., 1995, 3497-4502. 19. A.T. Vlahos, E.I. Tollis, C P . Raptapoulou, A.Tsohos, M.P. Sigalas, A . Terzis, T.A. Kabanos, Inorg. Chem., 2000, 39, 2977-2985. 14 20. B .H. Huang, T.L. Yu, Y . L . Huang, B.T. Ko, C.C. Lin , Inorg. Chem. 2002, 41, 2987-2994. 21. Y. Zhang, J. Jiang, Y. Chen, Tetrahedron Lett., 1987, 28, 3815-3816. 22. (a)S. S. A. Rizvi, Bulletin of the Chemical Society of Ethiopia, 1991, 5(1), 7-10; (b) S. S. A. Rizvi, Bulletin of the Chemical Society of Ethiopia 1992, 6(2), 115-118. 23. T.E. Patten, B . M . Novak, J. Am. Chem. Soc. 1996, 118, 1906-1916. 24. X . G . Zhou, L . B . Zhang, M . Zhu, R.F. Cai, L .H . Weng, Organometallics, 2001, 20, 5700-5706. 25. G.R. Giesbrecht, A. Shafir, J. Arnold, Inorg. Chem., 2001, 40, 6069-6072. 26. (a) C. L i , R.K. Thomson, B. Gillon, B. O. Patrick, L . L . Schafer, Chem. Commun, 2003, 2462-2463; (b) Z. Zhang, L . L . Schafer, Org. Lett., 2003, 5, 24, 4634-4736. 15 Chapter 2 - Amidate Chloride Complexes of Group 3 and 4 Metals 2.1 Introduction Work in the Schafer lab has focused on developing the chemistry of early-transition metal and lanthanide complexes incorporating ligands made from deprotonated amides. Our previously reported work in this area has been limited to bis(amidate) bis(amido) complexes of titanium and zirconium. 1 These compounds may be synthesized from the appropriate metal tetrakis(amido) starting material by protonolysis reactions (Scheme 1-3). This protocol has only been made practical in recent years with the introduction of commercially available amido starting materials. Unfortunately, these amido complexes are costly and are limited to only a few metals. Furthermore, the use of amidos as starting materials for further synthetic elaboration is limited due to the few efficient transformations available for the metal bound amido group. The efficient synthesis of amidate chloride complexes of early transition metals from metal chlorides has been a goal of the Schafer group since its inception. Metal chlorides of the early transition metals and lanthanides are readily available, low cost starting materials for the preparation of a great diversity of organometallic complexes, including alkoxides, alkyls, amidos, and alkynyls, to name a few (Fig. 2-1). A practical route to mixed amidate chloride complexes would provide access to a wide variety of related complexes and chemistry that is currently inaccessible by the established protonolysis method of amidate complexation. 16 L2M(OR)2 R U M V <l)Mg°'-MgCI 2 ^ \ * 2) RCCR R 2 NaNR2 -2 NaCI L2M(NR2)2 Figure 2-1. Selected Organometallic Complexes Derived From Metal Chlorides Given the ease of preparing organic amides and the potential for modification available to them, it is surprising that there has been so little mention in the literature of the use of amidates as auxiliary ligands. The first group 4 amidate complexes, known to be characterized, were reported by Arnold and coworkers.2 They published the synthesis of bis(amido) and dichloride derivatives of a titanium bis(amidate) complex. Arnold's titanium bis(amidate) bis(amido) complex yielded crystals suitable for X-ray diffraction, however, none of the three methods reported for the synthesis of a titanium bis(amidate) dichloride afforded pure products suitable for full characterization. The three reported routes to amidate chlorides presented by Arnold are outline in Scheme 2-1. In Arnold's report, a dilithio salt, made by deprotonation of the amide proligand with lithium bis-trimethylsilyl amide, was allowed to react with TiCUfTHF^ in THF. It proved impossible to separate the product of this reaction from other ligand containing impurities. In light of similar attempts at lithium salt metathesis in the Schafer group, it seems likely that these impurities are amide proligands, and "ate" complexes in which L i C l remains closely associated with the titanium amidate chloride complex. Secondly, a 2 NaOR -2 NaCI L2MCI2 2 RMgCI -MgCI2 L,MR, 17 V 2 eq LiN(SiMe3)2, THF, -15°C (N,0) 2Li 2 (THF)x -2 HN(SiMe3)2 2 eq. Ti(NR 2) 4 THF, -78°C 1 eq TiCI4(THF)2, THF, -78° C 4 HNR, [Ti(N,0)(NR2) 2eq. TiCI4(THF)2, Tol. 100°C 2)2\2 -2 eq. TiCI 2(NR 2) 2 | xs TMS-CJ, tol_ RT -4 TMS-NR 2 (N,0) = deprotonated ligand shown above •2 LiCI Scheme 2.1 disproportionation reaction between the titanium bis(amidate) bis(amido) complex and TiCl4(THF)2 was attempted for preparation of the amidate chloride complex. This reaction was presumably not very clean, and characterization of the red/brown solid obtained was not reported. • Finally, another method attempted by Arnold was the conversion of a titanium bis(amidate) bis(amido) complex into the dichloride by reacting it with excess chlorotrimethylsilane. This route yielded an oily red solid, the characterization of which was also not reported. It is doubtful that chlorotrimethylsilane 18 reacts exclusively with the amido ligand of the metal complex with good chemoselectivity to form amidate chloride complexes, and the oily nature of the observed product mixture is suggestive of silylated side products. Silylation of the amidate ligand is the most likely competing reaction. In fact, work in the Schafer group has shown that silylated amides, can be in certain instances useful proligands themselves (vi. 2.4.1). Consequently, of the three routes reported by Arnold, the lithium salt metathesis reaction was the most successful, but still did not afford satisfactorily pure products. 2.2 Proligand Design and Synthesis Amides are easily prepared, highly variable, N , 0 chelating proligands. They can be made in high yield from a wide variety of primary amines and acyl chlorides or carboxylic acids. With the appropriate choice of starting materials it is possible to tune the steric and electronic properties of the ligand. This allows for the synthesis of a wide range of amidate complexes, often with markedly different reactivity and selectivity in their catalytic behaviour.1 A general procedure for the synthesis of the amide proligand is presented in Scheme 2-2. A l l proligands were prepared by this procedure, unless otherwise noted. 0 0 A , NEt 3 A R CI + NH 2R' R NHR' CH 2 CI 2 . 0°C to RT Scheme 2-2 19 Starting from commercially available acyl chlorides and amines, a variety of amides were synthesized to allow for a comparison of metal bis(amidate) dichloride coordination chemistry. The proligands investigated for preparing metal bis(amidate) dichloride complexes to be reported in this thesis are shown in Fig. 2-2. 4 5 6 Figure 2-2. Amide Proligands The selection of proligands was made so as to provide a variety of [aryl, aryl] (1,3,5), [aryl, alkyl] (2,6), and [alkyl, alkyl] (4) functionalities. Ligands 1, 3, 5, and 6 have been used previously in bis(amidate) bis(amido) complexes in our group. Ligands 2, and 4 are new proligands and they represent the first amides with alkyl substituents on the acyl component to be used in bis(amidate) complexes. In general, sterically bulky substituents were chosen in order to favour the formation of monomeric complexes. Previous work in the group has shown that inadequate steric bulk on the nitrogen results in ill defined, oligomeric materials, which cannot be rigorously characterized.1 Amide 1 was chosen because its derivative titanium bis(amidate) bis(amido) complex has already been the focus of much study, and it is the 20 most commonly employed hydroamination catalyst within the group. Amide 3, a fluorinated analog of 1 was chosen so as to allow comparison between ligands having a strongly electron withdrawing group incorporated into the ligand set. A l l of the compounds in Fig. 2-2 were synthesized according to the method presented in Scheme 2-2. The isolated yield, after purification ranged from 70 to 85%. Most of the proligands were purified by recrystallization from EtOH/H?0, however 4, was purified by sublimation due to its high solubility. Al l amides purified by recrystallization were dried under vacuum for a minimum of 18 h before being used in further reactions. Proligands 1,3,5, and 6 are known compounds with previous use in the Schafer lab, and their synthesis was confirmed by 'H N M R spectroscopy. Amides 2, and 4 also appear in the literature/ however, they are new proligands for amidate complexes. These amides were characterized by ' H and l 3 C NMR spectroscopy, EI low resolution mass spectrometry, and elemental analysis. Each proligand has diagnostic 'H N M R signals that allow for amidate complexation reactions to be monitored by NMR spectroscopy. These are the doublets of the /sopropyl group, integrating in total to 12H, for amides incorporating the 2,6-diisopropylphenyl moiety: 1 (8 1.24 ppm), 3 (8 1.22 ppm); the singlet of the aryl methyl groups, integrating to 6H, for amides with a 2,6-dimethylpheny group: 2 (£2.26 ppm), 5 (£2.25 ppm); and the singlet, integrating to 9H, for /-butyl containing amides: 2 (8 1.32 ppm), 4 (8 1.05 ppm), and 6 (8 1.25 ppm). The proton on the nitrogen of the amide proligand also serves as a diagnostic peak, in that disappearance of this resonance is evidence for metal complexation. 21 2.3 Salt Metathesis Route Initial attempts to form amidate complexes via salt metathesis reactions were unsuccessful. A number of bases were tried for forming the amidate salt. Lithium salts prepared with «-butyl lithium were reacted with the metal chlorides, however pure amidate chloride complexes were not obtained. The products were powdery compounds, with good solubility in toluene, and moderate solubility in hexanes. Repeated attempts to recrystallize the product using a variety of mixtures of hydrocarbon and ethereal solvents failed to afford pure compounds. "Ate" complexes with closely bound lithium chloride salts are suspected to be intractable side products of this reaction. Neither sodium hydride nor potassium hydride yielded salts that were reactive towards the metal chlorides. Using metal hydrides, deprotonation of the proligand was slow in hydrocarbon and ethereal solvents. It is suspected that the reason why amidate ligands have been so overlooked in organometallic chemistry lies in the difficulty of preparing pure amidate complexes by traditional salt metathesis reactions. The attempted salt metathesis reactions presented by Arnold used lithium bis-trimethylsilylamide as a base for preparing the ligand salts. This reaction was perceived to be somewhat successful, however, pure products were not isolated. It was hypothesized that changing the base counter ion to sodium may improve the reaction, as the NaCI formed in the metathesis reaction would be less soluble in hydrocarbon solvents than L i C l , allowing for easier purification of the product, and perhaps avoid the formation of "ate" complexes.4 11 2equiv. rArA 2 N a N ( S i M e 3 ) 2 RJLti*> 1 equiv. M C I 4 _ H T H F , R T N a T o l u e n e , R T Scheme 2-3 When commercially available sodium bis-trimethylsilylamide was used to prepare the amidate salts, salt metathesis with group 3 and group 4 metal chlorides was successful. A general procedure for this reaction is outline in Scheme 2-3. The sodium amidate salt is generated by reacting the amide proligand with base in THF at room temperature using Schlenk techniques. After three to five hours, the solvent and hexamefhyldisilazane (b.p. 125°C) is removed under vacuum, and the reaction vessel is brought into the glovebox. The amidate salts were typically used without purification, however, the salt of 2 was sufficiently insoluble in hydrocarbon solvents that it could be washed to remove trace amounts of unreacted amide starting materials. As these compounds were used only as intermediates, without further purification, full characterization of the amidate salts was not undertaken. The subsequent salt metathesis reaction is performed by adding half an equivalent of metal chloride to the reaction vessel containing the amidate salt, followed by the addition of toluene. After the reaction mixture has been allowed to stir overnight, it is then filtered through Celite to remove sodium chloride. The filtrate is concentrated by removing the solvent under vacuum at 60°C without stirring, until a film forms on the surface of the solution. The concentrated solution is then allowed to cool slowly, and the product crystallizes over the course of several days. 23 This method proved to be very general, and a variety of amidate complexes were successfully prepared from group 3 and group 4 metal chlorides (Fig. 2-3). These include the titanium bis(amidate) dichloride complexes 7, 8, and 9 derived from proligands 1, 2, and 3 respectively; the zirconium bis(amidate) dichloride complexes 10, and 11 from proligands 1, and 4 respectively, and the homoleptic yttrium amidate complex from proligand 2. Cl R' CI R' R' C k , | C k , | D , / N ' - , | R'—N I R'—N I T ) CT I T> V ^ O V^ N U y y R' R R R 7- R=Ph, R'=2,6-DiiPrPh 10 - R=Ph, R'=2,6-DiiPrPh 12 - R=tBu,R'=2,6-DiMePh 8 - R=tBu, R' =2,6-DiMePh 11 - R=tBu, R'=Adamantyl 9 - R =C 6F 5, R'=2,6-DiiPrPh Figure 2-3. Amidate Complexes via Salt Metathesis The yields after crystallization were high, ranging from 60 to 90 %. A l l of the complexes were characterized by ' i f and l j C N M R spectroscopy. Additional characterization data was collected by mass spectrometry and/or elemental analysis. Each of the metal amidate complexes formed by salt metathesis reported here produced crystals suitable for X-ray crystallography, however, not all of the crystals could be mounted for full structural characterization. 24 2.3.1 Titanium Complexes T i [ p h O , N D i i P r P h ] 2 C l 2 (7) was prepared in good yield (68%) from proligand 1 by salt metathesis, forming deep orange red rectangular crystals. This complex crystallized with two inequivalent metal complexes, plus one molecule of toluene per unit cell. One of these complexes is depicted in Fig. 2-4. This titanium bis(amidate) dichloride complex is pseudo C 2 symmetric, and there are minor differences in the bond lengths and angles between the two ligands. It is likely that these distortions are a result of crystal packing. The Ti-0 oxygen bond (2.041(5) A) Table 2-1. Selected Bond Distances (A) and Angles (°) for 7 Bond Distances Ti-O(l) 2.041(5) Ti-N(l) 2.054(5) Ti-Cl(l) 2.243(2) 0(1)-C(1) 1.299(7) N(l)-C(l) 1.306(8) Bond Angles Ti(l)-N(l)-C(8) 140.6(4) 0(1)-C(1)-N(1) 111.6(5) Figure 2-4. Titanium Bis(Ar-2,6'-diwopropyIphenyl(phenyl)amidate) dichloride (7) of the amidate ligand is only slightly shorter than the Ti-N bond (2.054(5) A). Both the 25 Ti-0 and Ti-N bonds of the amidate chelate are longer than the bond length between an sp2 hybridized amido nitrogen and titanium (1.9 A) . 1 The C-0 (1.299(7) A) and C-N (1.306(8) A) bonds lengths of the amidate backbone are within error, which suggests significant delocalization. The Ti-O-C bond angle in the amidate backbone (92.9(4)°) is nearly equivalent to the Ti-N-C bond angle (92.0(4)°). In spite of this small bond angle, both the amidate nitrogen and oxygen are best described as being sp2 hybridized. Both the oxygen and nitrogen atoms of the amidate chelate may are 2e- donors in the a framework, with short Ti-O and Ti-N bond lengths indicating further donation through the n system. The Ti-Cl bonds (2.243(2) A ) are typical for related complexes and are unremarkable.3 The two di/Vsopropylphenyl groups on the nitrogens of the amidate ligands are oriented nearly perpendicular relative to each other which minimizes any steric interaction between the two groups. The ortho-diz'.sopropyl groups point back towards the metal centre, and provide effective steric protection of the metal coordination sphere and the nitrogen of the amidate ligand. A l l short contacts between atoms of the complex are greater than the sum of their combined Van der Waal radii, and thus there is no appreciable steric strain. Analysis of the ' H N M R spectrum shows there are two distinct doublets, each integrating to 12H, for the methyl protons of the isopropyl groups on the N-aryl ring, which suggests hindered rotation around the N - C a r y i bond. This observation is typical of all pure amidate complexes incorporating the Af-2',6'-di/.s'opropyl moiety. The methine protons of the isopropyl groups produce a broad resonance in the ' H N M R spectrum. 26 Further characterization data includes satisfactory elemental analysis, and low resolution EI mass spectrometry. The corresponding titanium bis(amidate) bis(amido) complex is known. This complex is rigorously C 2 symmetric. The Ti-N bond of the amido (1.899(2) A) is of a length that is consistent with multiple bond character, with significant n interaction between the orbital of the amido nitrogen and the d^-orbital of titanium.6 The amidate bonds are similar to Ti[ p h ( 0 , N ) D i i P r P h ] 2 C l 2 , however Ti[ P h (0 ,N) D i i P r P h ] 2 (NEt 2 ) 2 has longer Ti-0 (2.146(1) A), and Ti -N (2.156(1) A) bond lengths. The longer amidate bonds in the case of the titanium bis(amidate) bis(amido) complex may be attributed to the extra electron donation to the metal center provided by the lone pairs of the amido groups. The increase in bond length is not localized to the Ti-0 bonds which are trans to the amidos, but can be observed in both the Ti-0 and Ti-N bonds. This may be argued to be evidence of a high degree of derealization within the amidate backbone. Table 2-2. Selected Bond Distances (A) and Angles (°) for 8 Bond Distances T i - O ( l ) T i - N ( l ) T i - C l ( l ) 0(1)-C(1) N ( l ) - C ( l ) 2.017(3) 2.066(3) 2.246(1) 1.310(4) 1.310(5) Bond Angles T i ( l ) -N( l ) -C(6 ) 0(1)-C(1)-N(1) 139.6(5) 111.5(3) Figure 2-5. Titanium Bis(A/-2%6'-dimethylphenyl(f-butyl)amidate) dichloride (8) 27 Complex 8, the titanium bis(amidate) dichloride derived from proligand 2 was synthesized with excellent yield (88%) by using the general procedure described for salt metathesis. The structure of this complex was solved by X-ray crystallography. Ti[ l B u (0 ,N ) D ' M t . p n ]2Ci2 ^pjg 2_5) i s a distorted octahedral, pseudo C 2 symmetric complex. It assumes the same coordination isomer as complex 7 in the solid state, and the ' H N M R spectrum of redissolved crystals of the complex shows the existence of only one isomer in solution. The oxygens of the amidate ligand are in a cis relationship to each other and are trans to the chlorides. The nitrogens of the amidate are trans to each other. In comparison with complex 7, the Ti-0 (2.017(3) A) and Ti-N (2.066(3) A) bonds of the amidate chelate of complex 8 are longer and less equal in length. This suggests that complex 8 has more alkoxide character than complex 7. A possible rationale for the observed shortening of the Ti-0 bond in complex 8 over complex 7, may be attributed to the strong sigma donation to the carbonyl afforded by the /-butyl group in complex 8. Another possibility is that sterics play a significant role in influencing the bonding character of the amidate ligand. If steric congestion between the two substituents on the amidate chelate were an important influence on the bonding character of the ligand, then it may be expected that a more sterically demanding amidate would have a smaller O-C-N bond angle so as to provide greater separation between the bulky groups. The /-butyl group 8 is more sterically demanding than the phenyl group in 7, and the closest non-bonding contact between ligand substituents in 8 (3.007 A) is closer than 7 (3.061 A). However, the bond angle of the amidate chelate in 8 (111.6(5)°) is the same as in 28 complex 7 (111.5(3)°). While sterics effects may influence the bonding of the amidate, the data does not suggest a correlation between sterics and hybridization of the carbonyl carbon of the amidate chelate. T i [ t B u (0 ,N) D i M e P h ] 2 (NMe 2 ) 2 , 13, (Fig. 2-6) the titanium bis(amidate) bis(amido) complex corresponding to the dichloride complex 8, was synthesized by the established protonolysis methodology. T i [ t B u (0 ,N) D i M e P h ] 2 (NMe 2 ) 2 is a distorted octahedral, pseudo-C 2 symmetric complex. The amidate oxygens are in a cis configuration, and both are trans to an amido group as had been observed in the corresponding dichloride complex. In contrast to the dichloride complex 8, the Ti-0 (2.1258(11) A) and Ti-N (2.1268(12) A) bonds lengths of 13 are longer. It appears as if the trans influence of the amido ligands Table 2-3. Selected Bond Distances (A) and Angles (°) for 13 Bond Distances T i ( l ) - N ( l ) 2.1268(12) Ti ( l ) -0(1) 2.1258(11) C ( l ) - N ( l ) 1.3106(18) C( l ) -0 (1 ) 1.2979(18) Ti( l ) -N(3) 1.9144(13) Bond Angles 0(1)-C(1)-N(1) 112.79(13) Figure 2-6. Titanium Bis(Ar-2',6'-dimethylphenyl(^-butyl)amidate) Bis(dimethylamido) (13) 29 counteracts the preference of titanium to bond most strongly with oxygen. The C-0 (1.2979(18) A) and C-N (1.306(18) A ) bonds of the amidate backbone are within error, which suggests of a high degree of derealization throughout the O-C-N bonds. The ' H N M R spectrum suggests hindered rotation along the C - N a r y i bond of the amidate, and along the Ti-N bond of the amido groups. The aryl region exhibits a complicated mixture of peaks from £ 6.97-6.85 ppm which integrate in total to 3H. The predominate peak for the protons of the dimethyl groups on the aryl rings is at 8 2.40 ppm, however there is a second peak at £2.30 ppm. The ratio between the two peaks is 9:1, and their sum integrates to 6H. The major peak representative of the protons of the dimethylamido group is at £ 3.10 ppm, however there are several small peaks in the baseline which may represent minor isomers and free dimethylamine. The sum total of these peaks integrates to 6H. The ratio of the major isomer to the sum of the minor isomers is 5:1. The C N M R spectrum is noteworthy for its carbonyl carbon peak, which at £ 187.56 ppm is the most downfield shifted of any titanium bis(amidate) bis(amido) complex presented in this thesis. This is reflective of the strong bonding of the amidate ligand to titanium observed in this complex, which brings the carbonyl carbon closer to the strongly deshielding metal center. Several other titanium bis(amidate) dichloride complexes were synthesized using the salt metathesis methodology. Ti [ C f , F 5 (N,0) D i i P r P h ] 2 Cl2, 9, prepared from the perfluorophenyl A^-2',6'diisopropylphenyl amide 3 was made in high yield (77%) by salt metathesis. This complex was characterized by elemental analysis, ' H and 1 3 C NMR spectroscopy. In comparison with complex 7 (its non-fluorinated analogue) complex 9 has very similar 'H N M R and l j C N M R spectra. Both complexes show six distinct peaks 30 in the alkyl region of the l 3 C N M R spectrum, which suggests that there may be hindered rotation along both the N - C a r y i and Co r tho-C a r ),| bond. Another possibility would be that there is hindered rotation along just one of those bonds and that the complex exists as an asymmetrical dimer in solution. The aryl region of the spectrum for the two complexes are comparable, however the carbonyl carbon for complex 9 is shifted upfield 5 ppm relative to complex 7. This was somewhat surprising, as it was expected that the electron withdrawing perfluorophenyl group attached to the carbonyl in complex 9 would result in greater deshielding. A possible explanation for this observation would be that the perfluorophenyl groups of the amidate ligands in 9 contribute to generating a more ionic metal complex than 7. Such a trend has been observed in the titanium bis(amidate) bis(amido) complexes corresponding to 7 and 9. An increase in ionic character correlates with greater Ti-0 and Ti-N bond lengths, and this in turn would move the central carbon of the amidate metallocycle further away from the deshielding influence of the metal center. Elemental analysis confirmed the predicted percent composition of C, H, and N calculated for T i [ c « F j (0 , N ) D i i P r P h ] 2 C l 2 . 2.3.2 Zirconium Complexes The salt metathesis methodology was also applied to the preparation of zirconium bis(amidate) dichloride complexes. The coordination sphere of the zirconium metal center is much larger than that of titanium, and there was some question as to the ability of amidate ligands to provide sufficient steric protection to allow for the formation of stable zirconium bis(amidate) complexes. The synthesis of zirconium bis(amidate) 31 dichloride complexes is a particularly good test for this, as chlorides provide no appreciable steric protection or stabilizing multiple bond character, in comparison with the amido groups of previously prepared zirconium bis(amidate) bis(amido) complexes. Zirconium complexes are also of interest, because they tend to exhibit markedly different reactivity than analogous titanium complexes. This has been observed within the Schafer group in terms of hydroamination activity,1 and in the literature, particularly in regard to olefin polymerization activity.7 The zirconium bis(amidate) dichloride complex (10) made from proligand 1, analogous to the titanium complex 7, was synthesized by salt metathesis. Clear colorless crystals were isolated with excellent yield (74%). This complex was characterized by 'H 13 and C N M R spectroscopy, elemental analysis, and low resolution EI mass spectrometry. Mass spectrometry indicated the presence of the parent ion. The ' H and l 3 C N M R spectrums, follow a similar pattern as complex 7, but have double the peaks. This suggests that two coordination isomers exist in solution in nearly equal abundance. There are four sharp doublets corresponding to the methyl protons of the wopropyl groups at 8 1.56, 1.36, 1.02, and 0.89 ppm, and two sharp septets corresponding to the methine protons at 8 4.27 and 4.05 ppm. In the alkyl region of the 'H N M R spectrum there are some very small peaks suggestive of the presence in low abundance of other coordination isomers. The ] H N M R spectrum indicates the presence of one equivalent of bound THF with methylene protons at 8 4.43, and 1.26 ppm. (cf. 8 3.57, and 1.40 ppm for uncoordinated THF in C6D6). 8 Salt metathesis between ZrCl 4 and the sodium salt of proligand 4 produced complex 11 as a white powder in good yield (64%). This complex is highly soluble in 32 hydrocarbon solvents, making recrystallization impractical. Low resolution EI mass spectrometry indicates the presence of three major ions at 792, 709 and 135 m/z. The expected parent ion for the complex is 631 m/z. The peak for 792 m/z is consistent with the desired zirconium bis(amidate) dichloride complex with one equivalent of coordinated hexamethyldisilazane. 709 m/z corresponds to the loss of one trimethylsilyl group from the coordinated hexamethyldisilazane. 135 m/z is an adamantyl group. The l j C and 'H N M R spectrums are complex, but suggest the presence of two bound ligands with different chemical environments, and bound hexamethyldisilazane. The bound hexamethyldisilazane originates with the sodium bis(trimethylsilylamide) base used to form the sodium amidate salt. Redissolving the prepared amidate salt in toluene, and then pumping away the solvent to dryness may help to remove the amine. 2.3.3 Homoleptic Yttr ium Amidate Complex Another ongoing research project in the Schafer lab is development of homoleptic lanthanide amidate complexes suitable for luminescence applications. Previous attempts at the synthesis of these types of complexes employed the protonolysis methodology using yttrium tris(bis(trimethylsilyl)amide) as a starting material. So far, this route has met with limited success. A homoleptic yttrium amidate complex, with an additional amide donor ligand bound through the oxygen, has been prepared in this manner, and its structure solved by X-ray crystallography. A salt metathesis route to lanthanide amidate complexes is highly desirable due to the lower cost and greater availability of lanthanide chloride starting materials in comparison with lanthanide silylamides. The homoleptic yttrium amidate complex 12 was prepared in good yield (60%) from yttrium trichloride and proligand 2 via the salt metathesis protocol described above. 13 1 This complex was characterized by C and H N M R spectroscopy, low resolution EI mass spectrometry, and its structure was solved by X-ray crystallography (Fig. 2-7). Complex 12 is a rigorously C 2 symmetric dimer with a pair of amidate oxygens bridging Table 2-4. Selected Bond Distances (A) and Angles (°) for 12 Bond Distances Y ( l ) - 0 ( 1 ) Y ( l ) - 0 ( 2 ) Y ( l ) - 0 ( 3 ) Y ( l ) - N ( l ) Y( l ) -N(2 ) Y( l ) -N(3 ) Y ( l ) - 0 ( 1 ) (bridging) 0(1)-C(1) 0(2)-C(14) 0(3)-C(27) N ( l ) - C ( l ) N(2)-C(14) N(3)-C(27) Bond Angles 0(2)-C(14)-N(2) Figure 2-7. Yttrium Tris(A-2 V-dimethyphenyl(f-butyl)amidate) (12) Symmetrical Dimer, and Asymmetric unit 2.379(5) 2.256(5) 2.272(5) 2.475(6) 2.452(6) 2.492(6) 2.309(5) 1.333(9) 1.287(9) 1.282(9) 1.292(10) 1.298(10) 1.297(10) 114.7(7) 34 the metal centers. The crystallization of the complex as a dimer, is not surprising, and can be rationalized due to yttrium's very large coordination sphere, and strongly oxophilic nature. Despite crystallizing as a dimer, the low resolution EI MS spec of shows no evidence of the dimeric species. The ' H N M R spectrum shows one predominant set of /-butyl and dimethyl peaks, and numerous smaller peaks in the alkyl region. The l 3 C N M R also suggests the presence of numerous inequivalent amidate ligands. The region corresponding to the carbon of the amidate carbonyl has one predominant peak, and three other peaks of lesser intensity. It is likely that in solution there is an equilibrium of a monomeric species in which each of the amidate ligands are approximately equivalent and a symmetrical dimeric species, like the one observed in the solid state, in which the three amidate ligands are inequivalent. 2.4 Chlorotrimethylsilane Elimination Route While working on developing an effective route to amidate chlorides using salt metathesis, an alternate method was developed employing a chlorotrimethylsilane elimination reaction to form amidate complexes from metal chlorides (Scheme 2-4). This protocol utilizes what is essentially the reverse reaction of a commonly employed method of preparing metal chlorides by reacting either a metal amido or alkoxide complex with chlorotrimethylsilane (vs. Scheme 2-1).2 Further literature precedence for this method 35 o 1) NaN(SiMe 3) 2 THF, RT 2) 1.1 eq CISiMe3 Me 3 Si . O O R ^ ^ I \ T R ' -SiMe 3 i R' 0.5 equiv. MCI 4 Tol, RT ML 2 CI 2 + 2 CISiMe3 Scheme 2-4 exists in the report of the preparation of titanium amido benzamidinate dichloride complexes by tandem elimination of LiCl and chlorotrimethylsilane (Scheme 2-5).9 Ph Me 3Si—N 't; N N(Me)SiMe3 TiCI4(THF)2 - LiCl -CISiMe3 • Ph~vO. N—Ti M e 3 S K C | / >C| Scheme 2-5 2.4.1 Silylated Amide Proligands Silylated amides are known, but not widespread, in the literature. They have been prepared for use in volatilizing amides for gas chromatography10, as intermediates in the synthesis of beta-lactams", in nitrile synthesis12, and for use as highly active silylating agents.13 Some studies have been conducted on their physical organic characteristics, particularly for measuring their strength as silylating agents and for investigating their isomerization processes.14 Silylated amides are known to exist in equilibrium between N and O silylated forms, as well as cis and trans isomers. The populations of the different isomers is 36 dependant on the substituents at R and R' . For simplicity, the silylated amides used in the context of this thesis are illustrated in the N silylated form, which is, according to the literature, generally considered to be the lowest energy isomer.'3 The silylated amides prepared for amidate formation by chlorotrimethylsilane elimination (Fig. 2-8) were prepared from amides 2, 5, and 6. The use of an amide salt 14 15 16 Figure 2-8. Silylated Amide Proligands base was essential for product formation. Salt formation using sodium hydride, potassium hydride and «-butyl lithium were attempted, however none afforded a suitable nucleophile for reliable reactivity with chlorotrimethylsilane. L D A was the first base employed successfully, however both lithium dimethylamide and sodium bis(trimethylsilylamide) are equally effective, and because these are weighable, commercially available solids their use is preferable to LDA. The use of sodium bis(trimethylsilyl)amide as the base has an additional advantage in that the NaCl produced is much less soluble in organic solvents than L i C l . This precludes the need for distillation in order to isolate pure product, as simply dissolving the reaction mixture in hexanes and filtering through Celite is sufficient to remove NaCl. Proligand 14 is an oily liquid. The ' H N M R shows one broad peak at £0.09 ppm corresponding to the protons of the trimethylsilyl group. There are two small peaks at 8 37 0.53 ppm and £ 0.46 ppm, which may correspond to the trimethylsilyl group of other isomers, however the species with the resonance at £0.091 ppm predominates by a ratio of over 30:1. Proligand 15, a waxy solid, was prepared in good yield from amide 2 (78.3%). The ' H N M R spectrum of the crude silylated amide has two broad peaks corresponding to the trimethylsilyl groups of different isomers. One centered at £-0 .153 ppm and the other at £0.432 ppm. The relative integration of these two peaks is roughly 2:1 in favour of the more downfield resonance. There is one broad peak for the aryl dimethyl groups at £2.11 ppm. Proligand 16 is an oily liquid, which may be purified by vacuum distillation. Low temperature VT ' H N M R spectroscopy of the silylated amide shows three strong singlet peaks far upfield at £ 0.091, 0.041, and -0.066 ppm plus numerous small peaks, which correspond to the protons of the trimethylsilyl group of several isomers. The peaks at 0.091 and 0.041 coalesce at 70°C. The resonance at £-0.066 ppm broadens and covers several small peaks with negative chemical shifts, but remains independent from the trimethylsilyl peaks with a positive chemical shift. The ratio of the combined integrations of the 0.091 and 0.041 resonances (or the coalesced resonance at elevated temperature) and the integration of the peak at -0.066 and do not change, remaining roughly 7 : 1 . The results of this VT N M R study suggest interconversion of cis and trans isomers at high temperature, and a dynamic equilibrium between N and O silylated isomers even at lower temperatures. The ' H N M R spectrum of this compound at room temperature closely resembles the low temperature spectrum, with small changes in the relative population of the isomers. 38 2.4.2 Metal Complexation - Titanium Chlorotrimethylsilane elimination proved a viable method for synthesizing some group 4 bis(amidate) dichloride complexes. The complexes that were successfully prepared using this methodology are presented in Fig. 2-9. ci R' CI R' CU, | X,NN CU, | 0 \ N R'—NT 1 0 R ' — N I ^ 0 R R 8 - R=tBu, R' =2,6-DiMePh 18 - R=tBu, R'=2,6-DiMePh 17 - R =Ph, R'=2,6-DiMePh Figure 2-9. Bis(Amidate) Dichlorides Prepared by ClSiMe3 Elimination Two equivalents of 14 react with TiCUfTHF)? readily at room temperature in either toluene or benzene to afford T i [ l B u (0 ,N) D i M e P l l ] 2 Cl 2 . It is apparent from the ' H N M R spectrum of the crude product mixture that several coordination isomers initially form in relatively equal abundance. After heating the product mixture to 70°C in toluene, concentrating the solution, and then allowing it to cool to room temperature, crystalline material is produced in good yield (63%). The ' H N M R of the crystalline material gives a clean spectrum, identical with the spectrum of the same complex formed by salt metathesis, previously discussed. It exhibits only one isomer of the desired titanium bis(amidate) dichloride complex. This suggests that there is little kinetic preference for 39 formation of any particular coordination isomer of complex 8 using this method, however, a sufficiently deep thermodynamic well exists for the lowest energy geometric isomer and that further isomerization is not observed. Silylated amide 15 reacts with TiCUtTHF^ to form an isolable titanium amidate dichloride. This reaction was observed by ' H and 1 3 C N M R spectroscopy. While following the reaction by *H N M R it was observed that the two broad peaks corresponding to the protons of the trimethylsilyl group of the silylated amide quickly disappeared, and were replaced by as single peak at 5 0.19 ppm corresponding to the protons of chlorotrimethylsilane. There is a single peak (£2.56 ppm) for the six methyl protons, which suggests that one geometric isomer is formed preferentially. Crystals of this complex, suitable for X-ray crystallography, formed spontaneously in the benzene reaction mixture. The solved structure of the complex is illustrated in Fig. 2-10. Table 2-5. Selected Bond Distances (A) and Angles (°) for 10 Bond Distances T i ( l ) - N ( l ) T i ( l ) -0(1) C ( l ) - N ( l ) C( l ) -0 (1 ) T i ( l ) - C l ( l ) 2.0944(18) 2.0410(17) 1.318(3) 1.316(3) 2.2665(7) Bond Angles 0(1)-C(1)-N(1) 112.21(19) Figure 2-10 Titanium Bis(Ar-2'6'-dimethylphenyl(phenyl)amidate) dichloride (10) 40 The Ti-0 (2.0410(17) A) and Ti-N (2.0944(18) A) bond lengths in complex 10 are more disparate than in the similar titanium bis(amidate) dichloride complex 7 ( Ti-0 (2.041(5) A) and Ti-N (2.054(5) A). This indicates greater alkoxide character in complex 10. Ther C-0 (1.316(3) A ) , and C-N (1.318(3) A) bond lengths of the amidate backbone in 10 are longer than in 7 (cf. C-0 (1.299(7) A) and C-N (1.306(8) A)). The only difference between the amidate ligands of these two complexes is in the otho substituents of the N-aryl ring. This provides strong evidence that steric effects in the ligands influence the electronic character of the amidate bond chelate. Silylated amide 16 did not react with TiCl^THF)? to generate an amidate complex in isolable form. Examining the ' H N M R spectrum of the reaction mixture of 16 and TiCl 4 (THF) 2 after 24 h at room temperature shows a single THF peak at 8 3.57 ppm, corresponding to free THF in C6D 6, indicating that THF been displaced from the titanium coordination sphere. The peaks with negative chemical shifts disappear, and there is an emergence of three new strong resonances corresponding to /-butyl groups. Expanding the baseline of the spectrum in the alkyl region reveals the presence of many additional species in low concentrations. In the upfield region there are numerous peaks corresponding to the protons of the trimethylsilyl group. We propose that the silylated amide is acting as a neutral donor ligand, and that interactions with the metal center alter the equilibrium between N and O silylated forms. The question of why the proligand 16 was not effective in forming titanium bis(amidate) dichloride complexes may be explained by the fact, that in a closed system, amidate complexation by chlorotrimethylsilane elimination is a potentially reversible reaction. A proposed transition state is illustrated in Fig. 2-11. 41 Me 3 Si---CI A l l !'CI / ^ N - -Ti-CI / > 0 CI Figure 2-11. Titanium Chloride, Silylated Amide Metathesis The titanium bis(amidate) dichloride that would be made from proligand 16 is not known, despite multiple attempts at its synthesis by several methods, ie. chlorination of the amido with chlorotrimethylsilane, salt metathesis, and chlorotrimethylsilane elimination. However, the structure of the related titanium bis(amidate) bis(amido) complex has been solved by X-ray crystallography, and some insight into why proligand 16 is unsuitable for the chlorotrimethylsilane elimination reaction may be gained by examining this structure. Ti[ p h(0,N) t B u)2(NMe2)2 is a pseudo C2 symmetric, distorted octahedral complex. The oxygens of the amidate ligand are trans to each other, and the nitrogens of the amidate ligand are cis to each other and trans to the amido groups. The bonding of the amidate chelate is highly unequal with a strong Ti-0 (2.0423(13) A) bond and a much weaker Ti-N (2.2449(16) A) bond. The C - N (1.292(7) A ) and C-0 (1.314(2)A ) bonds in the amidate backbone are also of unequal length. These disparity suggests that the bonding of the amidate ligand has strong alkoxide character, and that there is little derealization throughout the amidate backbone. The /-butyl group on the nitrogen of the amidate projects away from the metal centre, and therefore provides little steric 42 protection of the metal center or of the nitrogen of the amidate. The /-butyl groups are also involved in non-bonding short contacts with the ipso and ortho carbons of the phenyl ring of the ligand, that are within the limits of their combined Van der Waal radii, and contribute to internal strain in the complex. 2.4.4 Metal Complexation - Zirconium and Yttrium The chlorotrimethylsilane elimination reaction with proligand 14 proved successful in reacting with ZrCl4(THF)2 to form zirconium bis(amidate) dichloride complexes. Recrystallization of the product mixture afforded clear colorless crystals in good yield (51%). The ' H N M R spectrum of the reaction mixture indicates the formation of three inequivalent sets of resonances for the aryl dimethyls and the /-butyl groups. There are also three inequivalent peaks suggestive of bound THF. The spectrum did not simplify after heating and recrystallization, as was the case with the titanium bis(amidate) dichloride complex, and even the ratios of the peak integrations remain unchanged. This suggests the energy barrier for interconversion between coordination isomers is small enough that that the N M R sample represents a dynamic equilibrium. Further support for facile isomerization of this zirconium bis(amidate) dichloride species comes from the fact that crystalline material, which presumably represents one coordination isomer of the complex in the solid state, showed an identical ' H N M R spectrum as the crude material when redissolved. Crystals of this complex suitable for X-ray were obtained, but were not solved. 43 Attempts to extend the chlorotrimethylsilane elimination route to yttrium (III) amidate chlorides were unsuccessful. Neither silylamide 14 nor 15 reacted with the yttrium chloride THF adduct to form amidate complexes. Neutral donor complexes of yttrium (III) chloride with two and three equivalents of 14 were isolated as powdery solids. Due to their low solubility and stability, the characterization of these compounds was problematic. 2.5 Conclusion Two new methods for preparing amidate complexes from the metal chlorides of early transition metals have been developed. The more general salt metathesis route is an irreversible reaction, and it is applicable for a wide range of amidate ligandspnd metal f chlorides. It has been shown that the proper choice of base, and counter-ion are crucial for successful salt metathesis. The chlorotrimethylsilane route is a reversible reaction, and it is only productive for some amidate ligands and metal chlorides. The investigation into the aspects of ligand structure that influence the equilibrium of the chlorotrimethylsilane elimination / amidate silylation reactions has highlighted several factors important for amidate complex stability. 44 2.6 Experimental Procedures 2.6.1 General Procedures Materials and Methods. A l l manipulations of air sensitive materials were performed with rigorous exclusion of oxygen and moisture in dry Schlenk-type glassware on a dual manifold Schlenk line interfaced to a high vacuum (10"6 Torr) pump or in a nitrogen filled gloved box. Reagent grade solvents were either distilled from sodium benzophenone ketyl (diethyl ether, THF) or purified by passage through activated alumina columns (toluene, hexanes, diethyl ether, THF) under N2. A l l deuterated solvents (CDCI3, C^De, CyDg) from Cambridge Isotope Laboratories or Aldrich. CeDe, and C7D8 used for N M R reactions were degassed by freeze-pump-thaw methods, and dried over 4 A molecular sieves. Reagents were purchased from commercial sources and used without further purification unless otherwise noted. A-2',6'-Di«opropylphenyl Phenyl amide, 1, l 6 a 7V-2',6'-Dimefhylphenyl /-butyl amide, 2, 3 a and A-Z-Butyl phenyl amide, 6,1 were prepared according to literature procedures. Physical and Analytical Measurements. A l l N M R spectra were collected on either a Bruker AV-300 or AV-400 spectrometer at ambient temperature, unless otherwise noted. Chemical shifts for 'H and , J C resonances are referred to internal solvent peaks and reported relative to SiMe4 (8 0.00). N M R spectra of air sensitive samples were collected in either Teflon sealed tubes, or screw top tubes fitted with septa. X-ray crystallographic analysis data was collected by Dr. Brian Patrick of the U B C Chemistry Department, using a Rigaku/ ADSC C C D area detector with graphite monochromated Mo-Ka 45 radiation. Elemental analysis were performed by Mr. Minaz Lakha of the UBC Chemistry Department, using a C A R L erba Elemental Analyzer E A 1108. The low resolution mass spectrometry, for all reported metal complexes was performed by Mr. Marshall Lapawa of the U B C Chemistry Department, on a Kratos MS-50, using an electron impact (70 eV) source. The low resolution mass spectrometry for all other reported compounds was collected using an Agilent 6890 Series GC system with a 5973 Mass Selective Detector, equipped with a 0.25-0.25 um HP-5 MS column and a FL/air flame ionization detector (FID). He was used as the carrier gas. Temperature sequence: 50 to 300°, 15°C/min. Synthesis of A^'^'-Di/sopropylphenyl perfluorophenyl amide (3). 1 7 To a 250 mL round bottomed flask equipped with a magnetic stirbar and charged with 2,6-di/sopropylaniline (4.5 mL, 24 mmol), triethylamine (3.6 mL, 26 mmol), and dry dichloromethane (50 mL), was added dropwise perfluorobenzoyl chloride (5.0 g, 22 mmol) at 0°C. The reaction mixture was allowed to stir and warm to room temperature overnight, and subsequently washed with 2M HCI and 1M NaOH. The solvent was then removed under reduced pressure. The crude amide was washed with petroleum ether and then recrystallized from EtOH/H 2 0. The crystals were collected and dried under vacuum (6.6 g). Yield 81%; *H N M R (300 M H z , CDC13) £7.36 (t, 1H, J=8.4 Hz), 7.21 (s, 1H), 7.08 (s, 1H), 3.17 (m, 2H), 1.22(d, 12H, J= 6.84 Hz). Synthesis of N-Adamantyl /-butyl Amide (4). 3 b To a 250 mL round bottomed flask equipped with a magnetic stirbar and charged with 1-Adamantyl amine (0.50 g, 3.3 mmol), triethylamine (0.50 mL, 3.6 mmol), and dry dichloromethane (50 mL), was added 46 dropwise pivaloyl chloride (0.41 mL, 3.3 mmol) at 0°C. The reaction mixture was allowed to stir and warm to room temperature overnight, and subsequently washed with 2M HC1 and 1M NaOH. The solvent was then removed under reduced pressure. The crude amide was washed with petroleum ether and then purified by sublimation (0.61 g). Yield 79%; ' H N M R (400 MHz, CDC13) £5.180 (s, 1H), 1.966 (m, 3H), 1.895 (m, 6H), 1.573 (m, 6H), 1.053 (s, 9H) ; l 3 C N M R (400 MHz, CDC1 3) £177.366, 51.074, 41.327, 38.728, 36.203, 30.025. 29.255, 27.481; MS(EI): m/z 235 (M), 178 (M -C(CH 3) 3), 150 (M -COC(CH 3 ) 3 ) 135 (M -HNCOC(CH 3 ) 3 ); Elemental analysis calcd. (%) for C 1 5 H 2 5 N O : C 76.55, H 10.71, N 5.95; Found: C 76.74, H 10.80, N 6.16. Synthesis of ./V-2',6'-Diniethylphenyl Phenyl amide (5) To a 500 mL round bottomed flask equipped with a stirbar and charged with 2,6-dimethylaniline (21.9 mL, 177 mmol), and 200 mL dichloromethane, benzoyl chloride (8.2 mL, 71 mmol) was added dropwise at 0°C. The reaction mixture was allowed to stir and warm to room temperature overnight, and subsequently washed with 2M HC1 and 1M NaOH. The solvent was then removed under reduced pressure. The crude amide was washed with petroleum ether and then recrystallized from E1OH/H2O. The crystals were collected and dried under vacuum to yield 9.5 g of 5 (59%); 'H N M R (300 MHz, CDC13) £7.89 (d, 2H, J= 8.6 Hz), 7.63 (s, br, 1H), 7.55 (t, 1H, J= 7.3 Hz), 7.46 (t, 1H, J= 7.1 Hz), 7.17-7.08 (m, 3H), 2.25 (s, 6H). Synthesis of Sodium 7V-2',6'-Di«opropylphenyl Phenyl amidate. Inside a glovebox, a 250 mL round-bottomed Schlenk flask, equipped with a stirbar, was charged with 47 amide 1 (3.32 g, 11.8 mmol), Sodium bis(trimethylsilylamide) (2.16 g, 11.8mmol), and 10 mL toluene. 20 mL THF was cannula transferred into the flask, and the reaction mixture was allowed to stir for three hours. The solvent was removed under reduced pressure, and the flask was brought back into the glovebox. Crude Sodium JV-2',6'-Di/.vopropylphenyl Phenyl amidate (THF) 15 was isolated and used without further purification (3.78 g ). Yield 78%; 'H N M R (400 MHz, C 6 D 6 ) 5 7.055 (m, 5H), 6.95 (m, 3H), 3.462 (m, 6H, THF), 2.182 (m, 2H), 1.33 (m, 6H, THF), 1.02 (d, 6H), 0.94 (d, 6H). Synthesis of Sodium /V-2',6'-Dimethylphenyl /-butyl amidate. Inside a glovebox, a 250mL round bottomed Schlenk was charged with amide 2 (3.001 g, 13.70 mmol) and sodium bis(trimethylsilylamide) (2.512 g, 13.70 mmol) and a stirbar. On the line, 100 mL THF was cannula transferred to the reaction vessel at room temperature. The solution was allowed to stir for 3 h at room temperature, and then the solvent was removed under reduced pressure. The product was then washed with 3 x 30 mL toluene and then all solvent was removed under vacuum (2.276 g). Yield 73%. General procedure for the preparation of amidate complexes by salt metathesis. Example: Synthesis of bis(Af-2',6'-di/s(?propylphenyl(phenyl)amidate)titanium-dichloride (7). Inside a glovebox, a 500 mL round bottomed Schlenk flask was charged with amide 1 (2.042 g, 7.262 mmol) and sodium bis(trimethylsilylamide) (1.330 g, 7.262 mmol) and a stirbar. To this, 100 mL THF was cannula transferred to the reaction vessel at room temperature. The solution was allowed to stir for 3 h at room temperature, and then the solvent was removed under reduced pressure. The flask was brought back 48 into the glovebox, and TiCl 4 (THF) 2 (1.212 g, 3.631 mmol) was added to the amidate salt, along with 100 mL toluene, and the reaction mixture was allowed to stir overnight. The red solution was then filtered over Celite to remove sodium chloride. In a 250 mL round bottomed Schlenk flask on a vacuum line, the toluene solution was heated to 70°C and solvent was removed under reduced pressure without stirring, until crystals began to form along the side of the flask. The flask was then closed to vacuum and allowed to cool to room temperature. The flask was brought back into the box, and the deep red crystalline product was dried on filter paper (1.670 g). Yield 68%; 'H N M R (400 MHz, C 6 D 6 ) 8 7.66 (d, 2H, J= 8.6 Hz), 7.18 (s, 3H), 6.88 (t, 1H, J= 6.4 Hz), 6.74 (t, 2H, .1= 8.0 Hz), 3.91 (s b, 2H), 6.1 (d, 6H, J= 5.1 Hz), 1.02 (d, 6H, .1= 4.6 Hz); l 3 C N M R (400 MHz, C 6 D 6 ) 8 182.5, 142.6, 142.3, 135.3, 133.1, 131.30, 129.6, 129.1, 125.7, 123.6, 123.6, 29.8, 28.1, 25.9, 24.7, 24.2, 23.0; MS(EI): m/z 678 (M); Elemental analysis calcd. (%) for C 4 1 . 5 H 5 2 C I 2 N 2 O 2 T 1 (Ti[ p l l (N,0) D i , P r P h ] 2 Cl2)2 + V2 C 7 H 8 ) : C 68.69, H 6.53, N 4.12; Found: C 68.60, H 6.94, N 4.25. Synthesis of bis(A^-2',6'-dimethylphenyl(/-butyl)amidate)titaniuni-dichloride (8). Method 1 Sodium iV-2',6'-dimethylphenyl /-butyl amidate was prepared from amide 2 (0.9934 g, 4.536 mmol) and sodium bis(trimethylsilylamide) (0.8362 g, 4.536 mmol) by the method described in the preparation of 7. The amidate salt was reacted with TiCl 4 (THF) 2 (0.7538 g, 2.268 mmol), and the orange red crystalline product was isolated by the method described in the preparation of 7 (1.051 g). Yield 88%; *H N M R (300 MHz, C 6 D 6 ) 8 7.40-7.25 (m, 2.2H), 2.36 (s, 6H), 1.17 (s, 9H); l 3 C N M R (400 MHz, C 6 D 6 ) 8 194.5, 49 144.7, 135.9, 132.2, 129.4, 128.0, 127.3, 125.8, 40.6, 29.1, 28.4, 27.3, 26.8, 25.7, 24.0, 22.0, 20.4, 19.2, 18.7, 17.6, 17.0. Method 2 General procedure for the preparation of amidate complexes by chlorotrimethylsilane elimination. Example: synthesis of bis(A/-2',6'-dimethylphenyl(/-butyl)amidate)titanium-dichloride (8). Inside a glovebox, a 25 mL Schlenk tube was charged with TiCl4(THF)2 (0.821 g , 2.46 mmol) and 10 mL toluene. Then amide 16 (1.364 g, 4.916 mmol) dissolved in 1.5 mL toluene was added to the TiCLt(THF)2 suspension all at once. The color of the reaction mixture turned immediately from a pale yellow to a orange red color and all of the TiCU(THF)2 went into solution. The reaction mixture was allowed to stir overnight. The solution was then filtered over Celite, and transferred into another 25 mL Schlenk tube. On a vacuum line, the toluene solution was heated to 70°C and solvent was removed under vacuum without stirring, until crystals began to form along the side of the tube. The tube was the closed to vacuum and allowed to cool to room temperature. The tube was brought back into the box, and the red-orange crystalline product was dried on filter paper (0.646 g). Yield 63%; 'H N M R (300 M H z , C 6 D 6 ) £7.40-7.25 (m, 2.2H), 2.36 (s, 6H), 1.17 (s, 9H); l 3 C N M R (400 MHz, C 6 D 6 ) 8 194.5, 144.7, 135.9, 132.2, 129.4, 128.0, 127.3, 125.8, 40.6, 29.1, 28.4, 27.3, 26.8, 25.7, 24.0, 22.0, 20.4, 19.2, 18/7, 17.6, 17.0. 50 Synthesis of bis(Af-2',6'-diwopropylphenyl(perfluorophenyl)amidate)titanium-dichioride (9). Sodium N-2\6'-di/.sopropylphenyl perfluorophenyl amidate was prepared from amide 3 (2.035 g, 5.398 mmol) and sodium bis(trimethylsilylamide) (0.9878 g, 5.398 mmol) by the method described in the preparation of 7. The amidate salt was reacted with TiCl4(THF)2 (0.9011 g, 2.699 mmol), and the dark maroon crystalline product was isolated by the method described in the preparation of 7 (1.7789 g). Yield 77%; ' H N M R (400 MHz, C 6 D 6 ) £7.01 (s, 3H), 3.71 (m, 2H), 1.57 (d, 6H), 1.124 (d, 6H); 1 3C N M R (400 MHz, C 6 D 6 ) £177.8, 145.9, 143.6, 142.5, 141.7, 139.6, 136.0, 130.4, 127.3, 125.5, 123.4, 107.2, 29.7, 28.8, 28.0, 27.0, 25.4, 23.8, 22.2; Elemental analysis calcd. (%) for CsgH^CbFmNjCbTi: C 53.10, H 3.99, N 3.26; Found: C 52.75, H 4.17, N 3.53. Synthesis of bis(A r-2 ,,6'-di«opropylphenyl(phenyl)amidate)zirconiuni-dichloride (10). Sodium AL2\6'-di/.sopropylphenyl phenyl amidate was prepared from amide 1 (2.0184 g, 7.178 mmol) and sodium bis(trimethylsilylamide) (1.3142 g, 7.178 mmol) by the method described in the preparation of 7. The amidate salt was reacted with ZrCU (0.8363 g, 3.589 mmol), and the translucent colorless crystalline product was isolated by the method described in the preparation of 7 (1.9222 g). Yield 74%; 'H N M R (400 MHz, C 6 D 6 ) 7.76 (d, 2H, J= 7.7Hz), 7.49 (d, 2H, J= 7.8Hz), 7.27 (s, 3H), 7.12 (s, 3H), 6.83 (t, 1H, J= 7.3Hz), 6.85 (t, 2H, J= 7.8Hz), 6.77 (t, 1H, J= 7.6Hz), 6.64(t, 2H, J= 7.8Hz), 4.43 (m, 4H, THF), 4.27 (m, 2H), 4.05 (m, 2H), 1.56 (d, 6H. J= 6.6Hz), 1.36 (d. 6H, J= 6.7Hz), 1.27 (m, 4H, THF), 1.02 (d. 6H, J= 6.8Hz), 0.889 (d, 6H, J= 6.8Hz); 1 3 C N M R (400 MHz, C 6 D 6 ) £181.1 , 179.8, 144.0, 143.1, 141.1, 139.3, 132.5, 131.7, 131.1, 51 131.0, 130.5, 130.2, 129.9, 129.5, 120.0, 129.6, 128.1, 127.9, 127.3, 126.6, 125.2, 75.0, 28.9, 28.7, 28.3, 27.9, 27.5, 26.5, 26.1, 25.8, 25.4, 25.2, 24.8, 24.7, 24.3, 24.2, 24.1, 23.7; MS(EI): m/z 722 (M); Elemental analysis calcd. (%) for C 3 8 H 4 4 C l 2 N 2 0 2 Z r : C 63.14, H 6.13, N 3.88; Found: C 62.86, H 6.53, N 4.28. Synthesis of bis(N-adamantyl (f-butyl)amidate)zirconium-dichIoride (HN(SiMe3)2) (11). Sodium N-adamantyl /-butyl amidate was prepared from amide 4 (0.7158g, 3.041 mmol) and sodium bis(trimethylsilylamide) (0.5569 g, 3.041 mmol) by the method described in the preparation of 7. The amidate salt was reacted with ZrCl 4(THF) 2 (0.5690 g, 1.5215 mmol), and the colorless powdery product was isolated by the method described in the preparation of 7 (0.6070 g). Yield 25%; 'H N M R (400 MHz, C 6 D 6 ) ; 2.47 (s, 2H), 2.31 (s, 2H), 2.185 (d, 4H), 2.05 (s b, 2H), 1.91 (s b," 2H), 1.86 (s b, 1H), 1.698 (d, 5H), 1.652 (s, 3H), 1.54 (s, 1H), 1.49 (m, 3H), 1,44 (s, 1H), 1.409 (s, 5H), 1.22 (s, 2.5H), 0.40 (s, 2H); 1 3 C N M R (400 MHz, C 6 D 6 ) 5 188.0, 162.6, 68.1, 54.9, 53.5, 48.0, 44.3, 41.8, 40.8, 40.7, 39.9, 37.3, 36.7, 36.4, 36.3, 35.7, 30.6, 30.2, 29.9, 29.4, 29.1, 27.9, 1.4. MS(EI): m/z 792 (M = Z r [ l B u ( 0 , N ) A d a m a n t > l ] 2 C l 2 (HN(SiMe3)), 709 (M-SiMe 3). Synthesis of tris(7V-2',6'-dimethylphenyl(/-butyl)amidate)yttrium (12). Sodium N-2',6'-dimethylphenyl /-butyl amidate was prepared from amide 2 (0.7953 g, 3.877 mmol) and sodium bis(trimethylsilylamide) (0.7098 g, 3.877 mmol) by the method described in the preparation of 7. The amidate salt was reacted with YC1 3 (0.2523 g, 1.292 mmol), and the colorless crystalline product was isolated by the method described in the preparation of 7 (0.460 g). Yield 60%; *H N M R (400 MHz, C 6 D 6 ) and l 3 C N M R (400 52 M H z , C 6 D 6 ) complicated; MS(EI): m/z 701 (M), 644 (M -C(CH 3 ) 3 ) , 497 (M - (-BuCON(DiMePh)). General procedure for the preparation of titanium bis(amidate) bis(amido) complexes. Example: Synthesis of bis(Ar-2',6'-dimethylphenyl(Nbutyl)amidate)titanium-bis(dimethylamido) (13). In a 250 mL round-bottomed Schlenk flask equipped with a stirbar, a solution of Ti(NMe2)4 (0.5115 g, 2.281 mmol) in 20 mL anhydrous ether was added to a suspension of amide 2 (0.9360 g, 4.563 mmol) in 50 mL anhydrous ether at -78°C under N 2 . The reaction was allowed to warm to room temperature and stir over night. The solvent was removed under reduced pressure, and the dark red residue was dissolved in anhydrous hexanes and filtered through Celite in the glovebox. The solvent was removed under vacuum, and the residue was redissolved in pentane, and the solvent was once more removed under vacuum to afford an orange-red powder which was used as a catalyst without further purification (1.0069 g). Yield 81%; ' H NMR.(300 MHz, C 6 D 6 ) S 6.97-6.85 (m, 3H), 3.02 (s, 1H), 2.32 (s, 6H), 1.09 (s. 9H); l 3 C N M R (300 MHz, C 6 D 6 ) £187.6, 144.9, 132.2, 127.9, 124.3,47.00,40.4,27.6, 19.1. Synthesis of N/O-Trimethylsilyl N-f-butyl phenyl amide (14). Inside a glovebox, a 100 mL Schlenk tube was charged with amide 6, (5.000 g, 37.0 mmol) and a stirbar. On a vacuum line, under Schlenk conditions, 50 mL dry THF was cannula transferred into the Schlenk tube, and the solution was cooled to -78°C. 1.3 equivalents L D A was added dropwise, and then the solution was allowed to warm to room temperature over the 53 course of several hours. The solution was then cooled to 0°C, and 1.3 equivalents chlorotrimethylsilane (6.1 mL, 48.1 mmol) was added and the reaction mixture was allow to warm to room temperature and stir overnight. The solvent was then removed under reduced pressure, and the reaction flask was brought into the glovebox. The oily product was dissolved in hexanes and filtered through Celite to remove lithium salts, and then the solvent was removed under reduced pressure to afford a clear oily liquid (8.1665 g). Yield 89%; ! H NMR (300 MHz, C 6 D 6 ) £7.69 (m, 2H), 7.06 (m, 3H), 1.508 (s, 9H), 0.03 (s, 8.3H), -0.05 (s, 0.6H). Synthesis of N/O-Trimethylsilyl A^'^'-dimethylphenyl phenyl amide (15). Inside a glovebox, a 100 mL Schlenk tube was charged with amide 5 (2.25 g, lO.Omml) and a stirbar. On a vacuum line, 30 ml THF was added by cannula transfer, and the solution was cooled to -78°C. 1.2 equivalents L D A was added by cannula transfer and the solution was allowed to warm to room temperature over several hours. The solution was then cooled to 0°C, and 1.2 equivalents chlorotrimethylsilane (1.52 mL, 12.0 mmol) was added dropwise, and the reaction mixture was allowed to warm to room temperature, and stir overnight. The solvent was removed under vacuum, and the Schlenk tube was brought back into the glovebox. The product was dissolved in hexanes and filtered through Celite, and then the solvent was removed under vacuum to afford a waxy solid (2.33 g). Yield 78%; ' H N M R (300 MHz, C 6 D 6 ) £8.23 (s b, 0.7H) 7.47 (s, b 1.1H), 6.96 (m b, 4.5), 2.11 (s b, 6H), 0.43 (s b, 5.4), -0.15 (s b, 3.5H); l 3 C N M R (300 MHz, C 6 D 6 ) £ 155.4, 146.3, 130.7, 128.7, 128.3, 123.0, 18.8, 1.4, 0.6. 54 Synthesis of N/O-Trimethylsilyl TV^'^'-dimethylphenyl f-butyl amide (16). Inside a glovebox, a 100 mL Schlenk tube was charged with Sodium A-2 ,,6'-dimethylphenyl /-butyl amidate (0.6625 g, 2.91 mmol) and a stirbar. On a vacuum line, under Schlenk conditions, 50 mL dry E12O was cannula transferred into the Schlenk tube. Chlorotrimethylsilane (0.44 mL, 3.49 mmol) was added at room temperature, and the reaction mixture was allowed to stir for 3 hours. The solvent was then removed under reduced pressure, and the reaction flask was brought into the glovebox. The salty, oily product was dissolved in hexanes and filtered through Celite to remove sodium chloride, and then the solvent was removed under reduced pressure to afford a clear oily liquid (0.8026 g). Yield 99%; ' H N M R (300 MHz, C 6 D 6 ) £7.34-7.04 (m, 3H), 2.33 (s, 6H), 1.44 (s,9H), 0.02 (s b, 9H). Synthesis of bis(/V-2\6'-dimethylphenyI(phenyl)amidate)titanium-dichloride (17). N/O-Trimethylsilyl A^'^'-Dimethylphenyl phenyl amide 15 (0.1000 g, 0.336 mmol) and TiCi4(THF)2 (0.0551 g, 0.168 mmol) were reacted according to the procedure outlined for 8, method 2, to afford a red crystalline solid (0.0678 g). Yield 71%; ' H N M R (300 MHz, C 6 D 6 ) 7.59 (d, 2H, J= 7.5Hz), 6.98 (s, 3H), 6.90 (t, 1H, J= 7.4Hz), 6.73 (t, 2H, J= 7.8Hz), 2.57 (s, 6H); l 3 C N M R (300 MHz, C 6 D 6 ) £182.0, 144.7, 134.2, 132.5, 129.2, 129.1, 128.9, 128.7, 127.4, 68.0, 25.8, 19.3, 18.8. Synthesis of bis(Ar-2',6'-dimethylphenyl(/-butyI)amidate)zirconium-dichloride (18). N/O-Trimethylsilyl N-2\6'-dimethylphenyl /-butyl amide 16 (0.2378 g, 1.159 mmol) and ZrCi4(THF)2 (0.2115 g, 0.5656 mmol) were reacted according to the procedure outlined 55 for 8, method 2, to yield a clear pale yellow crystalline solid (0.1856 g). Yield 51%; 'H N M R (300 MHz, C 6 D 6 ) 7.125-6.5 (m, 3H), 4.64 (m, 0.62 H, THF), 4.39 (b s, 0.54 H, THF), 4.13 (b,s,1.78H, THF), 3.74 (s,b, 1.1H, THF), 2.77 (s, 2.2H), 2.56 (s, 2.3 H), 2.42 (s, 1.5H), 1.36, (m, 2.5H, THF), 1.16 (s, 3.1H), 1.05 (s, 2.6H), 0.90 (s, 3.9 H). 2.7 References 1. C. L i , R.K. Thomson, B. Gillon, B. O. Patrick, L.L. Schafer, Chem. Commun, 2003, 2462-2463. 2. G.R. Giesbrecht, A . Shafir, J. Arnold, Inorg. Chem., 2001, 40, 6069-6072. 3. (a) F. El-Zahraa, S. El-Basil, M . El-Sayed, K. M . Ghoneim, M . Khalifa, Pharmazie, 1979, 34(1), 12-13. (b) R. D. Bach, J. W. Holubka, T. A . Taaffee, J. Org. Chem. 1979, 44(10), 1739-40. 4. G. Mund, D.Vidovic, , R.J. Batchelor, J.F. Britten, R.D.Sharma, C.H.W. Jones, D.B. Leznoff, Chem. Eur../., 2003, 9, 4757-4763. 5. A. Littke, N . Sleiman, C. Bensimon, D.S. Richeson, Organometallics, 1998, 17, 446-451. 6. R. K. Thomson, F. E. Zahariev, Z.Zhang, B. O. Patrick, Y. A. Wang, L. L Schafer, Submitted to J. Am. Chem. Soc. 7. J. Saito, M . Mitani, J-I Mohri, Y . Yoshida, S. Matsui, S-i. Ishii, S-i. Kojoh, N . Kashiwa, T. Fuijita, Angew. Chem. Int. Ed. Engl. 2001, 40, 15, 2918-2920 8. H. E. Gottlieb, V . Kotlyar, A . Nudelman,./. Org. Chem. 1997, 62(21), 7512-7515. 56 9. W.J. van Meerendonk, K. Schroder, E.A.C. Brussee, A. Meetsma, B . Hessen, J.H. Teuben, Eur. J. Inorg. Chem., 2003, 427-432. 10. A. J. Gee, L. A . Groen, M . E. Johnson, J. of Chromatography A, 1999, 859, 541-542. 11. G.S. Bisacchi, et al., Bioorg. Med Chem. Lett., 2004, 14, 2227-2231. 12. M . L. Hallensleben, Tetrahedron Lett., 1972, 20, 2051-2060. 13. J.F. Klebe, H. Finkbeiner, D. M . White, J. Amer. Chem. Soc. 1966, 88, 3390-3395. 14. A. R. Bassindale, T. B. Posner, J. Organomet. Chem., 1979,175, 2, 273-284. 15. (a) B.L. Feringa, J.F.G.A. Jansen, Tetrahedron Lett., 1986, 27, 507-508; (b) G. Courtois, L. Miginiac, Tetrahedron Lett... 1987, 28, 1659-1660; (c) P. Mamos, N . Klouras, Z. Anorg. Allg. Chem., 1991, 603, 89-94. 16. (a) N . De Kempe, R. Verhe, L. De Buyck, J. Chys, N . Schamp, Org. Prep. Proc. Int., 1978, 10, 139; (b) A. D. Nikolic, N . Perisic-Janjic, N . L. Kobilaraov, S. D. Petrovic,./. Mol. Struct., 1984, 114, 161. 17. Y . Hashimoto. Jpn. Koka Tokkyo Koho. 1998, 8. 57 Chapter 3 - Catalytic Hydroamination 3.1 Introduction Hydroamination, the formal addition of nitrogen and hydrogen across a carbon-carbon multiple bond is a highly desirable transformation for the synthesis of amines. In the past decade, numerous systems for catalytic hydroamination have been developed employing catalysts based upon early1 and late transition metals,2 the lanthanides,J alkali metals, 4 and even actinides." However, for the purposes of this thesis, a brief literature review will be restricted to early transition metals and lanthanides, in accordance with the research interests of the Schafer group. The majority of hydroamination catalyst systems reported in the literature are limited to alkynes and allenes. Catalysts based upon group 4 imido complexes have been widely studied for use with these substrates. The mechanism proposed by Doye and Bergman for titanocene imido catalyzed hydroamination of alkynes is the generally accepted mechanistic model (Fig. 3-1).6 In this mechanism, a precatalyst, such as dimethyltitanocene, is converted in the presence of primary amine into an imido complex, which is the active catalyst for hydroamination. The imido complex exists in equilibrium with both bridging imido dimers and bis(amido) complexes. Bulky ligands and/or amines shift the equilibrium in favour of the active imido species. In the next step, an alkyne or allene reacts with the imido in a [2+2]-cycloaddition reaction to form a four membered azametallocycle. A 58 protonolysis reaction between an amine substrate and the metallocycle breaks the metal carbon bond and forms an enamido complex. A second proton transfer results in the newly coordinated amido group being converted to an imido, regenerating the catalyst, and releasing the enamine product. Figure 3-1. Imido Cycloaddition Mechanism for Catalytic Hydroamination of Alkynes An investigation into the energetics of the different steps of this mechanism was performed by the Bergman group using DFT calculations.7 A monocyclopentadienyl imido complex [CpTi=NR(NHR)], which is believed to be the active species generated from Cp2TiMe2, was used as the model catalyst, and ammonia was the model amine. For ethyne and allene substrates it was determined that the transition state for the [2+2]-cycloaddition reaction had the highest energy level of any transformation in the catalytic 59 cycle (14.6 kJ mor ' a n d 40.3 kJ mol"1 respectively) and was therefore the rate determining step. The same approach was also used to analyze the potential for titanium imido catalysts to promote alkene hydroamination. Using ethene as a model substrate, it was found that the cycloaddition step had a high activation energy (31.4 kJ mol"1), but that the protonolysis step was even more unfavourable (82.9 kJ mol"1). It was concluded that in order to effect successful alkene hydroamination by this mechanism it would be necessary to stabilize the cycloaddition product intermediate relative to the imido complex resting state of the catalyst, and to increase the rate of the proton transfer step. Despite the demonstrated theoretical feasibility, there has not yet been a report in the literature of successful alkene hydroamination by a titanium imido catalyst. The Bergman group has since reported a cationic tantalum alkyl amido complex that promotes the addition of aniline to norbornene in poor yield. Ackermann, simultaneously reported the microwave assisted hydroamination of norbornene with aryl amines in moderate to good yield using TiCU as a precatalyst.9 A unique mechanism is proposed for the catalytic cycle in order to account for observed side products due to C-H activation (Fig. 3-2). According to this mechanism, a bis(amido) species, with unidentified auxiliary ligands, is in equilibrium with the imido complex, and with a four membered metallocycle derived from C-H activation of the aryl ring. Insertion of norbornene into the metallocycle is the chemoselective step, allowing for the generation of either hydroamination or C-C coupling products. Subsequent protonolysis releases the product and regenerates the catalyst. C-C coupling is the predominant pathway for aniline and 4-60 methylaniline, however hydroamination tends to be favoured with anilines containing electron withdrawing groups. A problem with the proposed mechanism is that L2Ti(NHPh)2 H N / L2Ti=NPh L 2Ti—NH 6 fo NHPh H 2NPh Figure 3-2. Proposed Mechanism for TiCI 4 Catalyzed Hydroamination of Alkenes 2,4,6-trimethyl aniline reacts with norbornene in the presence of TiCU to produce the hydroamination product in good yield. Due to the ortho methyl groups of the amine substrate, formation of the four membered metallocycle as a product aryl C -H activation would be impossible. In the least, it is clear that another reaction pathway must also be in effect, and that the understanding of this system is in an early stage. The most well established alkene hydroamination catalysts are lanthanide metallocenes. Since the early nineties, the Marks group has been studying the reactivity of these complexes.10 They are highly active for intramolecular hydroamination, 61 however intermolecular reactions are slow. These lanthanide metallocenes have been modified with chiral substituents to provide alkene hydroamination catalysts with moderate enantioselectivities (up to 74%)." The proposed mechanism for organolanthanide mediated hydroamination, supported by kinetic and DFT studies, is shown in Fig. 3-3. 1 2 L S M - E L ' R R Figure 3-3. c-Bond Metathesis Mechanism There are two steps in the cycle with significant energy barriers. The first is the alkene insertion to form a chair-like seven membered metallocyclic transition state. DFT calculations predict an activation energy of 49.8 kJ/mol for this step. This is in good accord with the experimentally derived value for the cyclization process (Fig. 3-3, /) of AH = 53.2 +/- 5.9 kJ/mol. The calculated energy level of cyclized product complex is 62 within the range of error of the product of alkene insertion, and so overall, the cyclization step is essentially thermoneutral. The second large energy barrier is for attaining the protonolysis transition state. An amine approaches the electrophilic metal center and undergoes a concerted sigma bond metathesis reaction with the M-CH2 bond of the cyclized intermediate (Fig. 3-3, ii). The transition state of this reaction has a calculated energy barrier of 53.6 kJ/mol, however, it is 17.6 kJ/mol lower than the energy barrier for olefin insertion and so it does not influence the overall kinetics. The protonolysis is exothermic (AH = -54 kJ/mol). The rate determining step for catalyst turnover is concluded to be olefin insertion. Lanthanide complexes incorporating non-Cp ligands have also been explored for alkene hydroamination activity. Livinghouse has reported catalysts for intramolecular alkene hydroamination based upon yttrium, neodymium and dysprosium amido, and bis(thiophosphinic amidate) ligands. i j These catalysts are believed to follow the mechanism proposed by Marks. An example of a bis(thiophosphinic amidate) complex that forms a highly active catalyst is shown in Fig. 3-4. These ligands are of particular interest in relation to work being done in the Schafer group as they contain four Figure 3-4. Lanthanide BisfThiophosphinic Amidate) Precatalysts 63 membered mixed donor metallocycles with a delocalized backbone, much like the amidate class of ligands that are the focus of our research. Complexes of this type exhibit high activity and good diastereoselectivity for the cyclization of secondary aminoalkenes. A direct comparison of alkene hydroamination activity between catalysts containing yttrium, and a lanthanide of similar covalent radius, dysprosium, have been made using this ligand type. It was shown that the yttrium complex was considerably more active than the dysprosium based catalyst. Interestingly, substitution of selenium for sulphur in the ligand resulted in a modest reduction of activity, however, substitution with oxygen resulted in complete loss of catalytic activity. Active group 3 alkene hydroamination catalysts are not limited to yttrium. Work done in the Schafer lab in collaboration with the Piers group, at the University of Calgary, has identified neutral and cationic scandium "Nacnac" complexes (Fig. 3-5) as highly active catalysts for the intramolecular hydroamination of alkynes and alkenes.14 Both the neutral and cationic catalysts have been shown to act according to the R'= Me, C H 3 B ( C 6 F 5 ) 3 Figure 3-5. Scandium " N a c n a c " Precatalysts 64 mechanism proposed by Marks. Cationic group 4 complexes can be considered to be isoelectronic with neutral group 3 complexes, and it can be expected that they would exhibit similar reactivity. The Scott group reported the first well characterized chiral cationic Zr amino-phenoxide complex that catalyzes the intramolecular addition of secondary amines to alkenes with good yields and high enantioselectivity (up to 84%). I ? Hultzsch followed up on this result and illustrated that cationic zirconocenes exhibit similar reactivity.16 These complexes are proposed to follow the same sigma bond metathesis mechanism presented by Marks. Evidence for this is the fact that primary amines are incompatible with the cationic group 4 catalysts, as these amines undergo deprotonation to form unreactive neutral imido complexes. 3.2 Titanium Bis(Amidate) Bis(Amido) Complexes Previous work on hydroamination in the Schafer group has focused on the use of titanium bis(amidate) bis(amido) complexes for alkyne and allene hydroamination.17 2 20: R=Ph R'=2,6-Di'PrPh 21: R=C 6 F 5 , R'= tBu Figure 3-6. Bis(Amidate) Titanium Bis(Amido) Precatalysts 65 Titanium is an attractive metal for catalyst design due to its low cost and low toxicity. A number of catalysts from the group have been previously reported in the literature, and of these, two in particular stand out (Fig. 3-6). Complex 20 is remarkable for its high activity for intermolecular alkyne hydroamination and its exceptional regioselectivity for anti-Markovnikov addition (Fig. 3-7).17 Complex 21 also possesses high catalytic activity, presumably due to the influence of the perfluorophenyl group of the ligand in generating a more electropositive metal 18 centre. NR' NR' •A Markovnikov Anti-Markovnikov Figure 3-7. Regioisomeric Products of Terminal Alkyne Hydroamination19 A great advantage of the amidate series of ligands is their modular nature. The character of the ligands can be tuned by selecting the appropriate acyl and amine components. In hopes of discovering a highly active and selective catalyst with potential for alkene hydroamination, a hybrid of 20 and 21 was synthesized, with perflourophenyl and di/sopropylphenyl groups on the ligand. The proligand for this complex is depicted in Fig. 3-8. F 3 Figure 3-8. A^'^'-Diwopropylphenyl Perfluorophenylamide 66 The titanium bis(amidate) bis(amido) complex made from this proligand proved active for intramolecular hydroamination of alkene 22 (Fig. 3-9) at 110°C in toluene. Unfortunately the yields for this reaction were low. The poor performance is believed to be due to catalyst decomposition. The moderate success in alkene hydroamination observed with the titanium bis(amidate) bis(amido) complex made from proligand 6 prompted a re-examination of complex 4 for alkene hydroamination. It was found that 4 did catalyze intramolecular hydroamination as outlined in Fig. 3-9, with complete conversion to the cyclic product within 24 h at 110°C in toluene. The discovery that titanium bis(amidate) bis(amido) complexes catalyze the intramolecular hydroamination of alkenes is important as it is the first observed hydroamination of unactivated alkenes to proceed with a titanium catalyst. The feasibility of this reaction has been predicted using computational methods,7 however, there has yet to be a report of experimental evidence for this transformation. Other early transition metal and lanthanide based catalysts for alkene hydroamination undergo a-bond metathesis reactions, ' and these catalysts require secondary amine substrates. The H 22 23 Figure 3-9. Catalytic Intramolecular Alkene Hydroamination 67 TiCLt catalyzed hydroamination of norbornene with primary aryl amines may also go through an imine intermediate, however this reaction both requires an activated alkene and high temperatures (135°C), 8 or microwave radiation9. 3.3 Titanium Tetrakis(Amido) Titanium (IV) tetrakis dimethyl amido, the starting material for the preparation of 20 and other titanium bis(amidate) bis(amido) complexes, has been reported as a viable catalyst for Markovnikov hydroamination of alkynes.20 This commercially available metal complex was tested for activity in the intramolecular hydroamination of alkene 22, and it was found to be a highly active catalyst for this reaction, with > 95% conversion to the cyclic product in less than 1 h at 110°C in toluene. Moderate activity was observed at lower temperatures with 45%o conversion after 3 h at 45 °C. In cooperation with other members of the Schafer group, additional substrates were screened to determine the scope of the catalyst. A number of these substrates are illustrated in Fig. 3-10. Ph Ph H 24 25 26 27 Figure 3-10. Substrates for Intramolecular Alkene Hydroamination 68 Alkeneamine 24 is the secondary amine analog of the alkene amine 22. This substrate did not undergo hydroamination, which suggests that the neutral titanium mediated hydroamination of alkenes does not proceed through a sigma bond metathesis mechanism, and supports the notion of a titanium imido catalytically active species. A co-worker observed that dimethyl substituted alkene amine 25 cyclized less readily than the diphenyl substrate, requiring over 24 hours to the reaction to go to completion. This result highlights the importance of the bulky geminal-substituted groups in promoting cyclization, and is an example of the Thorpe-Ingold effect. Restricted bond rotation directs the substrate to a favourable geometry for ring closure, and internal strain induced by the geminally substituted groups brings the energy level of the substrate closer to the energy level of the transition state.2la This type of effect has been observed to be particularly dramatic for the formation of five membered heterocycles that proceed via a chair-like transition state.21b The unsubstituted alkene amine 26 was not reactive, even at elevated temperatures. The vinyl ether substrate 27 was not reactive and caused decomposition of the catalyst. Intermolecular alkene hydroaminations with norbornene were not catalyzed by titanium tetrakis(dimethylamido). The importance of geminal substitutions in producing an active substrate is not surprising given the factors expected to encourage reactivity in titanium catalyzed hydroamination of alkenes as predicted by DFT calculations. One key aspect was stabilizing the metalloazacyclobutane intermediate relative to the catalyst resting state. This is effected by restricting the conformation of the substrate by means of the Thorpe-Ingold effect.21 69 3.4.1 Qualitative Screening of Titanium Bis(amidate) Bis(amido) Complexes for Alkene Hydroamination The catalytically active species for intramolecular hydroamination derived from tetrakis(dimethylamide) titanium exhibits relatively high activity in comparison with the catalysts derived from titanium bis(amidate) bis(amido) complexes reported thus far. There are, however, several reasons why it is a less desirable precatalyst for further study than the titanium bis(amidate) bis(amido) complexes. The only great advantage of titanium tetrakis(dimethylamido) is that it is commercially available. With titanium tetrakis(dimethylamido) as the precatalyst, it would be very difficult to determine what the actual catalytic species is, thus limiting mechanistic work of practical significance. Titanium tetrakis(dimethylamido) is a liquid, with a relatively low molecular weight, which makes it difficult to purify, handle, and measure, in comparison with the crystalline solid titanium bis(amidate) bis(amido) complexes. Most importantly, titanium tetrakis(dimethylamido) does not provide a suitable steric and electronic environment for controlling the selectivity of the hydroamination reaction. Undoubtedly, auxiliary compounds could be mixed in with the titanium tetrakis(amido) precatalyst in order to influence the reaction's selectivity, however, it is the goal of the Schafer group to develop well-defined organometallic complexes for use in catalysis, rather than in situ preparation of catalytically active mixtures. With this in mind, a study was undertaken to identify 70 titanium bis(amidate) bis(amido) precatalysts which afford catalyst activity that approaches the rates observed with titanium tetrakis(dimethylamido). An investigation into optimizing the activity of the titanium bis(amidate) imido catalyst by modifying the electronic properties of the ligands was performed using the internal alkene hydroamination of substrate 24 as a test reaction. The aryl rings of the carbonyl substituent on the amidate ligands were varied with different electron withdrawing and electron donating substituents in a manner analogous to the series of benzoic acid derivatives that produced the Hammett substituent constants.23 The set of ligands that were assessed is depicted in Fig. 3-11. In addition to the series of ligands with varying electronic properties, two proligands (5, 34) that were expected to provide Figure 3-11 Amide Proligands for Alkene Hydroamination Catalysts 71 complexes with differing coordination geometries and steric bulk were also included in the survey. The crude product of titanium bis(amidate) bis(amido) synthesis by protonolysis has been shown to be equally active as the purified complexes,17 and so crude materials were used in the screening process. Al l catalysts were tested at either approximately 5 to 8 mol % loading, and the reactions were carried out at 110°C in C 7 D 8 . A l l reactions were prepared on N M R tube scale and were run under identical reaction conditions. These experiments were repeated two to four times to create a reliable data set to permit ordering of the relative activity of the catalysts. The reaction progress was monitored by 'JT N M R spectroscopy, and percent conversion was measured by comparing diagnostic resonances for the starting material (£5.51 ppm, m, 1H) and the product (£2.42 ppm, dd, 1H). General trends between the activity of different catalysts in each run were observed. Unfortunately, the initial results with the same catalyst varied significantly between runs and so only qualitative comparisons could be made from this data. The most likely cause of the problem of reproducibility is inaccuracy in weighing out milligram quantities of the precatalyst, and small quantities of the oily substrate. Despite the inconsistencies between runs, enough side by side comparisons of the catalysts were made to provide a general ordering of the catalytic activity of these complexes. There was a clear division between ligands that afforded catalysts with higher activity, and those which were less active. However, within the groups of more active or less active catalysts there were some with very similar activity. The qualitative ranking for catalyst activity for complexes derived from these ligands is illustrated in Fig. 3-12. 72 Figure 3-12. Qualitative Ranking of Titanium Bis(amidate) Bis(amido) Precatalysts for Alkene Hydroamination Activity In the series with varying electronic properties, the complexes incorporating ligands with electron withdrawing substituents, 39, 40, and 41, produced catalysts with the greatest activity. We believe that ligands containing electron withdrawing groups render the metal center more electropositive. This would be expected to increase the rate of imido formation, olefin coordination, and favour the equilibrium of bound verses unbound substrate in a productive manner.18 It was hypothesized that a more electron rich aryl substituent would decrease the electropositivity of the metal center, and thereby reduce its reactivity. It was, therefore, 73 unexpected that the complexes with ligands containing n -donating substituents, 37 and 38, formed were more active catalysts than the one incorporating an unsubstituted phenyl group, 20. This suggests 7t-donation from the aryl ring does not have a significant influence on the titanium amidate bond. In the case of complexes 37 and 38, it is believed that the modest o-withdrawing nature of the amine and ether substituents of the ligands are the predominant electronic effects. In considering this, it would be expected that complex 36, bearing amidate ligands with three ether substituents, would produce a more active catalyst than 38 due to the greater net inductive effect, however this was not observed. A tendency toward catalyst decomposition in the case of 36, may explain its relatively low activity. Evidence for this lies in the observation that a white precipitate formed in the reaction mixtures containing this complex, soon after heating commenced. The observed order does not correspond precisely to predictions based upon standard Hammett o constants for relative acidity of benzoic acid derivatives. If there were cumulative effects from multiple substitutions, according to a constants for a trifluoromethyl group (om = 0.43, c p = 0.54)22 complex 39 would be expected to be more active than 40. That prediction is contrary to the observed results. The deviations from predicted results based upon Hammett constants may possibly result from experimental error. Nonetheless, it seems likely that there is only a loose correlation between the factors that increase the acidity of benzoic acids and those which increase the catalytic activity of titanium bis(amidate) bis(amido) complexes. The effects of n-donation from aryl substituents are likely to be more pronounced with benzoic acids, as a benzoic acid does not have steric constraints that disfavour effective n 74 overlap as is the case with titanium bis(amidate) bis(amido) complexes. Other aspects such as catalyst stability wil l also influence the reaction rate. A pleasantly surprising result was how much more active the catalyst derived from complex 42 was in comparison with 35. Complex 42 produced the most active catalyst by far, with an initial rate at least twice as great as the nearest competitor. Complex 35 is known to undergo facile interconversion between coordination isomers in solution at room temperature. It is possible that only one of these isomers produces a catalytically active species. Such interconversion would not be possible in 42, as its coordination geometry is constrained by the multidentate nature of the ligand. With unlinked amidate ligands, in order to enforce the geometry of what is assumed to be the active isomer, it is necessary to have a bulkier 2,6-diz.sopropyl aryl substituent on the nitrogen. In the case of the biphenyl ligand a less bulky substituent on the nitrogen may be used. Decreasing the size of the group on nitrogen increases substrate accessibility to the reactive metal centre, and this may account for the greater catalytic activity observed with 42. It should be noted, that characterization of the complex 42 is incomplete. Low resolution mass spectrometry indicates that the complex is monomeric, however the 'IT and , J C N M R spectrums of the complex are difficult to interpret. The complexity of the N M R spectra may be due to any of several possibilities including aggregate formation, diastereomeric interactions, and restricted bond rotation. Crystals suitable for X-ray crystallography have been successfully grown from benzene solution, however due to time constraints they have not been mounted. 75 3.4.2 Rate Comparison of Most Active Catalysts In order to get more quantitative results, another rate comparison was performed using the three most active catalysts. Standard solutions in C7D8 were made from the crude titanium bis(amidate) bis(amido) complexes 40, 41, and 42. By measuring larger quantities of precatalyst in order to make the standard solutions, the degree of error in weighing was reduced, and masses accurate to three significant figures were obtained. The preparation of standard solutions of known molarity was accomplished using volumetric flasks. By using precision micro-syringes to measure out volumes of standard solution, uniformity between samples was improved. Two samples were prepared with complex 40, and three for each of the complexes 41, and 42. These samples were run simultaneously at 110°C and the percent conversions were measured by ' H N M R spectroscopy at 30, 60 and 120 minutes. The results are shown in Fig. 3-13, and Table 3-1. The catalysts derived from the complexes 40 and 41 were close in activity. However, in all cases complex 41 afforded a more active catalyst. This was the predicted result according to the hypothesis that catalyst activity should be proportional to the o values of ligand substituents. The results relating to complex 40 were less precise than for the others. The catalyst made from this proligand had shown great variability in the initial screening reactions, and while the results of this experiment are in far greater accord, they suggest that this may not be a very "well behaved" catalyst. The influence of product inhibition was particularly apparent with the catalyst derived from 42. 76 Catalyst Activity Comparison 60 ] 50 ] 40 > 30 a U 20 10 20 4C 60 80 Time (minutes) IOC 120 >pCN(mean) i pCF3(mean) »DiPh(mean) 140 Figure 3-13. Percent Conversion vs. Time for the Most Active Hydroamination Catalysts Complex Mean Percent Conversion Catalyst Loading TON at 60 min 30 min 60 min 120 min 40 9.3 15.2 27.8 4.96 mol% 3.07 41 10.3 18.7 34.4 4.97 mol% 3.76 42 29.9 42.7 55.0 5.51 mol% 7.8 Table 3-1 Summary of Rate Comparison Data The secondary amine product is more nucleophilic than the primary amine substrate, and neutral coordination of the product to the metal center would be expected to hinder the approach of substrate to the L U M O of the metal complex and reduce catalyst turnover rate. 77 3.5 Conclusion The work here presented on the hydroamination of alkenes by titanium tetrakis(amido) and titanium bis(amidate) bis(amido) complexes represent the first known examples of the hydroamination of unactivated alkenes with primary amines using early transition metal based catalysts. Titanium tetrakis(dimethylamido) has been identified as a highly active, commercially available, precatalyst for the intramolecular hydroamination of 5-amino 4,4-diphenylpent-l-ene 22. 2 3 A series of experiments were undertaken to determine the effect of ligands with electron-withdrawing and electron-donating substituents on catalyst activity. It was determined that electron-withdrawing groups at the 4 position of the amidate ligand are most effective in increasing catalyst activity. It may be concluded that the effect that electron withdrawing substituents have on catalyst activity is transmitted primarily though the a-bond framework and that the influence of the 7r-system of the amidate ligand is negligible. Complex 42 has been identified as forming a highly active catalyst for intramolecular alkene hydroamination. The activity of 42 was much greater than any of the complexes formed with ligands incorporating electron-withdrawing groups. This suggests that steric accessibility and the complex's coordination geometry are of greater importance in influencing catalyst activity than the electronic properties of the amidate ligand. 7 8 3.6 Experimental 3.6.1 General Procedures As outlined in 2.6.1. Alkeneamine substrates were dried by distillation from Catb, and were stored in the glovebox over 4 A molecular sieves. Bis(A^-2', 6 '-di/sopropylphenyl(phenyl)amidate)titaniurn bis(diethylamido) 20, alkeneamines 22, 2 3 a b 24, 2 3 a 25, 2 3 b 25, 2 4 26, 2 4 and Bis(iV-26'-dimethylphenyl(phenyl)amidate)titanium-bis(dimethylamido) 352: i were prepared according to literature procedures. Alkeneamine 27 was purchased from Aldrich. Typical Conditions for Intramolecular Hydroamination of Alkenes Example: Synthesis of pyrrole 23. In a glovebox, an N M R tube was charged with 22 (20.3 mg, 0.085 mmol), 42 (5.5 mg, 0.007 mmol) and 1.5 mL C 7 D 8 . The tube was removed from the glovebox and heated at 100°C for 9 hours. > 95% conversion observed by ' H N M R ; ' H NMR (300 MHz, CDC13) £7.43-7.09 (m, 10H), 3.92 (d, 1H, J=15 Hz), 3.11 (d, 1H, J=12 Hz), 2.72 (m, 2H), 2.22 (dd, 1H), 1.66 (dd, 1H), 1.01 (d, 3H, J= 6 Hz). Synthesis of N-2'6'-di/5opropylphenyl 4-dimethylaminophenyl amide 28. A 250 mL round-bottomed flask, equipped with a stirbar, was charged with 2,6-dz.sopropylaninline (3.1 mL, 1.6 mmol), triethylamine (2.3 mL, 1.7 mmol), and 20 mL dichloromethane. The flask was cooled to 0°C and a slurry of 4-dimethylaminobenzoyl chloride in 10 mL dichloromethane was added in one portion. The reaction mixture was allowed to stir and warm to room temperature overnight, and subsequently washed with 2M HC1 and 1M NaOH. The solvent was then removed under reduced pressure. The crude amide was washed with petroleum ether and then recrystallized from EtOH/H20. The crystals were 79 collected and dried under vacuum (1.49 g). Yield of 34 %; ' H N M R (400 MHz, CDC13) £ 7.864 (d, 2H, J = 8.83 Hz), 7.361 (m, 2H), 7.235 (b, 1H), 6.733 (d, 2H, J= 8.84 Hz), 3.204 (m, 2H), 3.084 (s, 6H), 1.244 (d, 12, J=6.86 Hz) ; l 3 C N M R (400 MHz, CDC13) 8 166.6, 152.6, 146.52, 131.9, 128.7, 128.0, 123.3, 121.2, 111.2,40.1,28.7, 23.6; MS(EI): m/z 324 (M), 281 (M -CH(CH 3 ) 2 ) , 149 ( M -CONH(Di'PrPh)); Elemental analysis calcd. (%) for C 2 1 H 2 8 N 2 O : C 77.74, H 8.70, N 8.63; Found: C 77.81, H 8.89, N 8.69. Synthesis of N-2'6'-di/5opropylphenyl 4-trifluoromethylphenyl amide 29. 2,6-dmopropyllaniline (5.4 mL, 29 mmol), triethylamine ( 3.8 mL, 29 mmol), and 4-trifluoromethylbenzoyl chloride (5 g, 23.97 mmol) at 0°C were reacted and the product isolated according to the procedure outlined for the synthesis of 3 (4.54 g). Yield 54%; 'H N M R (400 MHz, CDC13) 8 8.004 (d, 2H, J= 8.13 Hz), 7.723 (d, 2H, J= 8.15 Hz), 7.511 (s, 1H), 7.408-7.357 (m, 1H), 7.234 (s, 1H), 3.111 (m, 2H), 1.220 (d, 12H, J= 6.86 Hz); 1 3 C N M R (400 MHz, CDC1 3) £165.7, 146.3, 137.7, 133.7, 130.7, 128.781, 127.7, 125.9, 125.8, 123.7, 29.0, 23.6 ; MS(EI): m/z 350 (M+l), 307 (M -C(CH3)3+1), 204 (M -pCF 3Ph+l) 173 (M -CONH(Di'PrPh)); Elemental analysis calcd. (%) for C 2 oH 2 2F 3 NO: C 68.75, H 6.35, N 4.01; Found: C 69.00, H 6.20, N 4.15. Synthesis of N-2'6'-di/5opropylphenyl 3,4,5-trimethoxyphenyI amide 30. 2,6-Di/Aopropylaniline (1.3 mL, 7.1 mmol), triethylamine (1.0 mL, 7.2 mmol), and benzoyl chloride (1.39 g, 6.04 mmol) were reacted, and the product isolated according to the procedure outlined for the synthesis of 3 (1.7685 g). Yield 78%>; ' H N M R (400 MHz, CDC13) £7.391-7.339 (m, 1H), 7.287 (s, 1H), 7.235 (s, 1H), 7.181, (s, 2H), 3.975 (s, 6H), 80 3.944 (s, 3H), 3.156 (m,. 2H), 1.258 (d, 12H, .1=6.87 Hz); l 3 C N M R (400 MHz, CDC13) 5 166.5 162.4, 153.4, 146.3, 141.4, 131.1, 130.0, 128.5, 123.6, 104.8, 60.9, 56.4, 28.9, 23.6; MS(EI): m/z 371 (M), 328 (M -CH(CH 3 ) 2 ) , 195 (M -CONH(Di'PrPh)); Elemental analysis calcd. (%) for C22H29NO4: C 71.13, H 7.87, N 3.77; Found: C 71.26, H 7.91, N 3.78. Synthesis of N-2'6'-di/'sopropylphenyl 4-cyanophenyl amide 31. 2,6-Di/i'opropylaniline (1.3 mL, 7.1 mmol), triethylamine (1.0 mL, 7.2 mmol), and 4-cyanobenzoyl chloride (l.OOg, 6.04 mmol) were reacted, and the product isolated according to the procedure outlined for the synthesis of 3 (0.7615 g). Yield 41%; ! H N M R (400 MHz, C D C 1 3 ) 8 7.941 (d, 2H, J= 8.09Hz), 7.684 (d, 3H, J= 8.26 Hz), 7.429-7.377 (m, 1H), 7.234 (s, 1H), 3.071 (m, 2H), 1.194 (d, 12H, J= 6.84Hz) ; , 3 C N M R (400 MHz, C D C I 3 ) 5 165.2, 146.3, 138.2, 132.6, 130.6, 128.9, 127.9, 123.7, 118.0, 115.3, 115.3, 29.0, 23.6; MS(EI): m/z 306 (M), 291 (M -N), 263 ( M -CH(CH 3 ) 2 ) ; Elemental analysis calcd. (%) for C 2 0 H 2 2 N 2 O : C 78.40, H 7.24, N 9.14; Found: C 78.26, H 7.48, N 9.21. Synthesis of N-2'6'-diwopropyIphenyl 4-methoxyphenyl amide 32. 2,6-Di/.9opropylaniline (6.1 mL, 32 mmol), triethylamine (4.9 mL, 35 mmol), and 4-methoxybenzoyl chloride (4.0 mL, 29 mmol) were reacted, and the product isolated according to the procedure outlined for the synthesis of 3 (5.6218 g). Yield 62%; 'H N M R (400 MHz, CDCI3) £7.896 (d, 2H, J= 8.75Hz), 7.422-7.342 (m, 2H), 7.235 (s, 1H), 6.973 (d, 2H, J= 8.73 Hz), 3.906 (s, 3H), 3.166 (m, 2H), 1.234 (d, 12H, J=6.85); l 3 C 81 N M R (400 MHz, CDCI3) £166.3, 162.4, 146.5, 131.5, 129.0, 128.3, 126.8, 123.5, 113.9. 55.5, 28.9, 23.6; MS(EI): m/z 311 (M), 368 (M -CH(CH 3 ) 2 ) , 135 (M -CONH(Di'PrPh)); Elemental analysis calcd. (%) for C20H25NO2: C 77.4, H 8.09, N 4.50; Found: C 77.16, H 8.16, N 4.68. Synthesis of N-2'6'-di/sopropylphenyl 3,5-trifluoromethylphenyl amide 33. 3,5-trifluoromethylbenzoyl chloride (5.0 g, 18 mmol), 2,6-di/sopropylaniline (3.8 mL, 20 mmol), and triethylamine (3.0 ml, 22 mmol) were reacted, and the product isolated according to the procedure outlined for the synthesis of 3 (5.214 g). Yield 69%; ! H N M R (400 MHz, C D C I 3 ) £8.367 (s, 1H), 8.089 (s, 1H), 7.448-7.354 (m, 2H), 7.234 (s, 1H), 3.078 (s, 1H), 1.231 (d, 12H. J=6.84) ; 1 3 C N M R (400 MHz, CDC13) £ 155.6, 146.2, 142.1, 136.6, 132.8, 132.3, 129.0, 127.4, 125.4, 123.8, 29.0, 23.6; MS(EI): m/z 417 (M), 374 (M -CH(CH 3 ) 2 ) , 241 (M -CONH(Di'PrPh)); Elemental analysis calcd. (%) for C 2 | H 2 | F 6 N O : C 60.43, H 5.07, N 3.36; Found: C 60.78, H 5.00, N 3.12. Synthesis of bisamide 34. 250 mL round-bottomed Schlenk flask equipped with a stirbar was charged with diphenic acid (0.727 g, 3.00 mmol), 30 mL dichloromethane, and three drops of anhydrous DMF. Oxalyl chloride (2.5 mL, 24 mmol) was added dropwise at room temperature. The reaction mixture was allowed to stir for eight hours, and then the solvent was removed under vacuum. 2,6-Dimethylaniline (0.80 mL, 6.5 mmol) and triethylamine (1.0 mL, 7.2 mmol) in 20 mL dichloromethane was cannula transferred into the flask, at -15°C. The reaction mixture was allowed to warm to room temperature and stir overnight, and subsequently washed with 2M HC1 and 1M NaOH. 82 The solvent was then removed under reduced pressure. The crude amide was washed with petroleum ether and then recrystallized from EtOH/fTO. The crystals were collected and dried under vacuum (0.6012 g). Yield 44%; ' H N M R (400 MHz, CDC1 3) 8 8.438 (m, 2H), 7.676 (m, 2H), 7.436 (m, 4H), 7.283 (m, 2H), 6.976 (m, 6H), 1.984 (s, 12H); l 3 C N M R (400 MHz, CDC13) £168.4, 139.1, 136.6, 135.4, 133.7, 130.0, 129.7, 128.1, 128.1, 127.4, 127.2, 18.4; MS(EI): m/z 448 (M), 328 (M- NH(DiMePh)); Elemental analysis calcd. (%) for C 3 0 H 2 8 N 2 O 2 : C 80.33, H 6.29, N 6.25; Found: C 80.00, H 6.39, N 6.44. Synthesis of Ti[ 3- 5 T r i M e O P h (0,N) l > i i P r P h] 2(NMe 2) 2 36. Ti(NMe 2 ) 4 (0.1516 g, 0.6762 mmol) and amide 30 (0.5020 g, 1.352 mmol), were reacted and isolated in the manner described for the synthesis of 13 (0.3528 g). Yield 60%; ' H N M R (400 MHz, C 6 D 6 ) 8 7.20 (s b 1H), 7.18 (s b, 12H), 7.132 (d b, 2H), 7.10 (s, 6H), 7.03 (s b, 3H), 3.861 (s, 2H), 3,78 (s, 8H), 5.76 (s b, 5H), 3.39 (s, 11H), 3.28 (s, 12H), 3.23 (s b 8H), 1.384 (d, 12H, J= 6.75Hz), 1.08 (d, 12H, J= 6.79Hz), 0.91 (t, 4H, J= 6.47Hz), 0.312 (s, 3H); l 3 C N M R (400 MHz, C 6 D 6 ) 8 176.6, 153.2 142.9, 142.3, 127.2, 125.7, 124.1, 108.3, 60.5/55.3, 50.5, 47.8, 31.9, 28.1, 24.8, 24.6, 23.0, 14.31, 1.4. Synthesis of Ti[ 4 " N M e 2 P h (0,N) D i i P r P h ] 2(NMe 2) 2 37. Ti(NMe 2 ) 4 (0.345 g, 1.54 mmol) and amide 28 (1.00 g, 3.08 mmol) were reacted and the orange red, powdery product was isolated in the manner described for the synthesis of 13 (0.9435 g). Yield 78%>; 'H N M R (400 MHz, C 6 D 6 ) 8 7.722 (d, 8H, J= 8.98 Hz), 7.275 (m, 11H), 6.165 (d, 5H, J= 9.10Hz), 6.123 (s, br, 2H), 3.854 (s, 8H), 3.384 (s, 10H), 2.262 (s, 10H), 2.228 (m, 12H), 83 1.421 (d, 12H, J= 6.71Hz), 1.151 (d, 12H J= 6.82Hz), 0.880 (t, 5H, J= 6.64Hz); 1 3C N M R (400 MHz, C 6 D 6 ) £ 177.29, 152.26, 143.70, 143.10, 132.17, 125.46, 123.92, 120.00, 110.67, 50.53, 47.92, 39.37, 31.95, 28,14, 24.94, 24.64, 23.03, 14.36. Synthesis of Ti[ 4 - M e O P h (0,N) B i i P r P h ] 2(NMe 2) 2 38. Ti(NMe 2 ) 4 (0.3643 g, 1.624 mmol) amide 32 (1.0121 g, 3.249 mmol), were reacted and the product isolated in the manner described for the synthesis of 13 (0.7810 g). Yield 64%; ' H N M R (400 MHz, C 6 D 6 ) £ 7.640 (d, 6H, J= 8.85Hz), 7.109-7.071 (m, b, 6H), 6.367 (d, 4H, J= 8.90 Hz). 6.266 (d, b, 3H), 3.719 (s, 3H), 3.649 (m, 4H), 3.268 (s, 10H), 2.973 (s, 6H), 2.923 (s, 5H), 2.119 (d, 2, J= 5.98Hz), 1.287 (d, 12H, J= 6.74Hz) 0.976 (d, 12H, J= 6.78Hz), 0.799 (t, 4H, J=6.90); l 3 C N M R (400 MHz, C 6 D 6 ) 8 176.7, 162.3, 142.8, 133.4, 131.3, 129.4, 126.8, 125.0, 124.7, 123.0, 114.4, 112.3, 57.5, 55.6, 53.7, 51.8, 48.7, 46.9, 44.9, 29.0, 27.3, 25.6, 23.9, 22.12. Synthesis of Ti[ 3< 5 C F 3 P h(0,N) , ) i i P r P h] 2(NMe 2) 2 39. Prepared from Ti(NMe 2 ) 4 (0.119 g, 0.532 mmol) and amide 33 (0.444 g, 1.06 mmol) in the manner described for the synthesis of 13 (0.3347 g). Yield 65%; 'H N M R (400 MHz, C 6 D 6 ) £7.61 (s, 9H), 6.69 (s, 5H), 6.650 (s, 5H), 6.63-6.61 (m, 6H), 3.209 (s, 7H), 2.984 (m, 4H), 2.77 (s, 7H), 1.77 (s b, 2H), 0.76 (d, 13H, J= 6.70Hz), 0.416 (t, 3H, .1= 6.66Hz), 0.37 (d, 8H, .1=6.80), -.184 (s, 3H); l 3 C N M R (400 MHz, C 6 D 6 ) £ 173.0, 142.1, 140.8, 134.6, 132.2, 131.9, 131.8, 131.6, 130.4 130.1, 127.0, 124.7, 124.6,50.5,47.5,31.9, 28.1,24.4, 24.0, 23.2, 14.3, 1.4. 84 Synthesis of T i [ 4 C N P h (0 ,N) D i i P r P h ] 2(NMe 2) 2 40. Ti(NMe 2 ) 4 (0.6420 g, 2.863 mmol) and amide 29 (2.000 g, 5.727 mmol), were reacted and the product isolated in the manner described for the synthesis of 13 (1.3947 g). Yield 65%; ' H N M R (400 MHz, C 6 D 6 ) £ 7.57 (d, 2H, J= 8.2Hz), 7.186-7.121 (m, 4H), 6.97 (d, 2H, J= 7.3 Hz), 3.471 (m, 2H), 3.241 (s, 6H), 1.26 (d, 6H, J= 6.8 Hz), 0.85 (d, 6H, J= 6.8 Hz) ; 1 3 C N M R (400 MHz, C 6 D 6 ) £175.5, 142.4, 141.6, 136.0, 133.1, 132.8, 130.4, 126.4, 125.1, 125.0, 124.3,47.6, 28.1,24.6, 24.2. Synthesis of Ti[ 4-C F>P h(0,N)D i i P r P h] 2(NMe 2) 2 41. Ti(NMe 2 ) 4 (0.1865 g, 0.8421 mmol) and amide 31 (0.5046 g, 1.648 mmol), were reacted and the product isolated in the manner described for the synthesis of 13 (0.4142 g). Yield 66%. ' H N M R (300 MHz, C 6 D 6 ) £7.43 (d, 2H, J= 8.7 Hz), 7.19-7.03 (m, 4H), 6.66 (d, 2H, J= 7.3 Hz), 3.42 (m, 2H), 3.27 (s, 6H), 1.27 (d, 6H, J= 6.7Hz), 0.86 (d, 6H, J= 6.8Hz); l 3 C N M R (300 MHz, C 6 D 6 ) £ 174.7, 142.2, 141.4, 135.9, 131.6, 130.2, 129.3, 126.4, 125.7, 124.3, 117.9, 115.3,47.6, 28.0, 24.5,24.2. Synthesis of Ti [ D i P h c n (0 ,N) 2 ( D i M c P h ) 2 ] (NMe 2) 2 42. Ti(NMe 2 ) 4 (0.152 g, 0.676 mmol) and amide 34 (0.303 g, 0.676 mmol), were reacted, and the products isolated, in the manner described for the synthesis of 13 (0.220 g). Yield 56%. N M R complicated. MS(EI): m/z 582 (M), 539 (M -NMe 2 ) , 494 (M -2 NMe 2 ) . 85 3.7 References 1. A . L . Odom, J. Chem. Soc. Dalton Trans., 2005, 225-233. 2. J.F. Hartwig, Pure Appl. Chem., 2004, 76, 507-516. 3. S. Hong, and T.J. Marks, Acc. Chem. Res., 2004, 37, 673-686. 4. A . Ates, C. Quinet. Eur. J. Org. Chem., 2003, 1623-1626. 5. (a) A . Haskel, T. Straub, M.S. Eisen, Organometallics, 1996, 15, 3773-3775; (b) B.D. Stubbert, C.L. Stern, T.J. Marks, Organometallics, 2003, 22, 3836-4838. 6. (a) J.S. Johnson, R.G. Bergman, J. Am. Chem. Soc. 2001, 123, 2923-2924; (b) B.D. Ward, A . Maisse-Francois, P. Mountford, L . H . Gade, Chem. Commun., 2004, 704-705. 7. B.F. Straub, R.G. Bergman, Angew. Chem. Int. Ed. Engl, 2001, 40, 24, 4632-4635. 8. L . L . Anderson, J. Arnold, R.G. Bergman. Org. Lett. 2004, 6, 15, 2519-2522. 9. L. Ackermann, L. Kaspar, C. Gschrei, Org. Lett. 2004, 6, 15, 2515-2518. 10. S. Hong, T.J. Marks, J. Am. Chem. Soc, 2002,124, 7886-7887. 11. J.S. Ryu, T.J. Marks, F.E. McDonald, J. Org. Chem., 2004, 69, 1038-1052. 12. A. Motta, G. Lanza, T.J. Marks, Organometallics, 2004, 23, 4097-4104. 13. Y . K . Kim, T. Livinghouse, Y . Horino. J. Am. Chem. Soc, 2003, 125, 9560-1961. 14. F. Lauterwasser, P.G. Hayes, S. Brase, W.E. Piers, L .L. Schafer. Organometallics, 2004, 23, 2234-2237. 15. P.D. Knight, I. Munslow, P.N. O'Shaughnessy, P. Scott. Chem. Commun., 2004. 894-895. 86 16. D.V. Gribkov, K.C. Hultzsch, Angew. Chem. Int. Ed. Engl. 2004, 43, 5542-5546. 17. Z. Zhang, L.L. Schafer, Org. Lett., 2003, 5, 24, 4634-4736. 18. C. Li, R.K. Thomson, B. Gillon, B. 0. Patrick, L. L. Schafer, Chem. Commun, 2003, 2462-2463. 19. IUPAC Compendium of Chemical Technology, 1994, 66, 1137. 20. Y. Shi, J.T. Ciszewski, A.L. Odom, Organometallics, 2001, 19, 3967-3969. 21. (a) D. St. C. Black, J. E. Doyle, Australian Journal of Chemistry, 1978, 31, 10, 2247-2257. (b) J. Kaneti, A. J. Kirby, A. H. Koedjikov, I. G. Pojarlieff Org. Biomol. Chem., 2004, 2, 1098-1103. 22. A.J. Gordon, R.A. Ford, The Chemist's Companion: A Handbook of Practical Data, Techniques, and References, Wiley: New York, 1972. ppl 45-155. 23. (a) D.E. Horning, J.M. Muchowski, Can. J. Chem., 1974, 52, 1321-1330; (b) N. De Kimpe, D. De Smaele, A. Hofkens, Y. Dejaegher, B. Kesteleyn, Tetrahedron, 1997,53,31, 10803-10816. 24. A. El Samii, K. M. Zakaria, M. I. Al Ashmawy, J. M. Mellor, J. Chem. Soc. Perkin Trans., 1988, 8, 2517-22. 25. R. K. Thomson, F. E. Zahariev, Z.Zhang, B. O. Patrick, Y. A. Wang, L. L Schafer, Submitted to J. Am. Chem. Soc. 87 Chapter 4 - Future Work and Summary 4.1 Introduction The results of the work presented thus far suggest a number of promising areas of related research. Further refinement of the ligand set in order to increase control over the coordination geometry of amidate metal complexes, and to improve the selectivity and reactivity these complexes, is one such area. The development of new synthetic applications for these complexes, particularly in the area of carbon-carbon bond forming reactions, is another. Some preliminary work has been done in regard to these projects, and while the results to be presented in this chapter are incomplete, they show promise worthy of continued attention. 4.2 Ligand Design 4.2.1 Chiral Multidentate Ligand The hydroamination of an alkene generates a tertiary carbon center, and thus there is the potential for asymmetric catalysis. This fact, together with the high activity of the hydroamination catalyst derived from the biphenyl bis(amidate) bis(amido) complex 42, suggests that a chiral biphenyl bis(amide) proligand should be prepared. The proposed synthesis o f this ligand is presented in Scheme 4-1. 88 The synthesis and resolution of the chiral diphenic acid is reported in the literature.1 This synthesis was carried out as far as the deprotection of the diacid, however, the amount of material obtained was deemed insufficient to make resolution with Brucine practical. The low yield of the diacid (20%) can be attributed almost entirely to a poor yield for the Ullman coupling of the methyl 2-iodo-3-methylbenzoate. NaOH H 2 0 reflux Scheme 4-1 Nontraditional reaction conditions were used for this step. Instead of the standard method of performing the reaction, using a copper powder catalyst in refluxing DMF, a modified procedure was used with THF as the solvent and an activated copper catalyst, prepared by reduction of a copper iodide phosphine complex. It is likely that performing 89 the reaction under standard conditions would improve the yield, and it would certainly make isolation of the products easier. Due to the high cost and low availability of 2-iodo-4-methylbenzoic acid, an attempt was made to prepare this compound on a large scale from ra-toluic acid according Scheme 4-21,3 to literature procedures (Scheme 4-2). However, due to difficulties encountered with the iodination step and time restrictions, this synthesis was not pursued further. 4.2.2 Multidentate Ligands for Ln Complexation Another aspect of ligand design which deserves further attention is the development of amidate ligands with additional donor functionalities. Lanthanides have a large ionic radius (0.8 - 0.9 A) 4 , and it is not unusual for a lanthanide to associate with up to twelve donor groups in order to fill its coordination sphere.4 Lanthanide complexes are often observed to form dimeric or oligomeric species in order to satisfy their need for donors, for example the dimeric tris(amidate) yttrium complex 12 reported in Chapter 2 (vs. Fig. 2-7). Dimeric and oligomeric species may be suitable for luminescence applications, however, for use in catalysis, discrete monomeric complexes would be preferable. 90 An amide proligand with an additional donor group 29, was prepared according to Scheme 4-3. It is expected that the oxygen of the ether group would coordinate to a lanthanide metal center and form an additional six membered chelate. This would have the benefit of providing additional stability to the ligand metal interaction, as well as to help satisfy the coordination environment of the lanthanide. The overall yield for the preparation of 44 (45%), is not optimized. This product was characterized by ' r l N M R spectroscopy and low resolution EI mass spectrometry. It should be noted that the only significant side product is the non-methylated benzylic alcohol. Use of a more active alkylating agent such as dimethylsulfate and increased reaction times would likely improve the yield. In addition, conversion of the alcohol side product to the ether would likely be trivial. MeO, 44 Scheme 4-3 MeO. 45 Figure 4-1. Silylated Amide Proligand with Additional Donor Group 91 The silylated amide 45 (Fig. 4-1) was prepared from 44 in hope that additional stability afforded by the six membered neutral donor chelate would be help to promote the formation of a yttrium amidate complex by the chlorotrimethylsilane elimination methodology. Amidate complexation by reaction of 45 with yttrium trichloride was not observed, and instead it is believed that neutral donor complexes were formed. Proligand 45 has steric bulk on only one side of the N-aryl ring, and it is possible that the nitrogen of the amidate ligand is too exposed to form an amidate chelate that would be resistant to silylation by chlorotrimethylsilane. Furthermore, the chlorotrimethylsilane elimination reaction with yttrium trichloride may not be favourable under any conditions. Nonetheless, the chelating donor group incorporated into this ligand is a promising functionality, and may be particularly useful in promoting the formation of monomeric amidate complexes of the lanthanides. 4.3 C-C Bond Formation 4.3.1 1,2-Addition of Zinc Reagents to Ketones Reactions that make new carbon-carbon bonds are of vital importance in organic synthesis, and catalytic reactions are of particular value due to their great efficiency. The development of new methodologies for selective catalytic carbon-carbon bond formation is one of the most difficult challenges facing synthetic chemists. One approach to generating carbon-carbon bonds that has received a great deal of attention in the past decade is the 1,2-addition of zinc reagents to carbonyls. On their own, zinc reagents react very slowly with aldehydes and not at all with ketones.3 The 92 lack of any appreciable background reaction allows for highly selective catalytic reactions. A well established method for enantioselective 1,2-addition reactions with aldehydes involves adding of a chiral amino alcohol ligand to the reaction mixture in catalytic amounts.6 Interactions between the ligand and the zinc reagent increase the nucleophilicity of the transfer group on zinc, and allow for enantioselective control over product formation. Another common technique is the use of titanium wopropoxide is a cocatalyst along with a chiral ligand.3 This tends to improve the reactivity and selectivity of 1,2-additions of zinc reagents to aldehydes. The titanium alkoxide acts as a Lewis acid activator of the carbonyl, and there is also some evidence to suggest that a titanium species may be the source for group transfer after transmetalation with the zinc reagent.7 A wide variety of ligand sets and catalysts have been reported in the literature for catalytic enantioselective 1,2-addition of zinc reagents to aldehydes, however, there are very few published methods of promoting the analogous reaction with ketones. A small number of successful catalysts have been developed for this reaction, and some of these afford good enantioselectivity.8 However, the best catalysts reported so far are still highly substrate specific, and so the development of an effective, general catalyst for promoting this reaction is highly desirable. Recently, a catalyst system employing titanium /sopropoxide along with a chiral alcohol ligand has been shown to be promote enantioselective 1,2-addition to aromatic ketones using zinc reagents.9 We hypothesized that lanthanide chlorides, may be even more effective than titanium alkoxides species in promoting this reaction due to their greater Lewis acidity. The ability of lanthanide chlorides to enhance the reactivity of 1,2-93 addition reactions had been previously established with CeCla / R L i systems, 1 0 however the extension of this concept to zinc reagents was yet to be explored. Initial experiments showed that stoichiometric amounts of the THF adduct of yttrium chloride would promote the addition of diethylzinc to benzophenone in good yield (85%), (Scheme 4-4). The product alcohol was identified by G C M S . Attempts to produce similar results with enolizable ketones such as acetophenone and 2-pentanone resulted in a mixture of oligomeric aldol products, as identified by GCMS. 0 ^ + Y r : i 3 r r H R , . D 1-1 equiv. E t ^ ^ OH kA k^. j 2) H 3 0 + I ^ 85% yield Scheme 4-4 This reaction was made catalytic by the addition of one equivalent of Figure 4-2. Lewis Acid Catalyzed 1,2 Addition of Zinc Reagents to Ketones 94 chlorotrimethylsilane (Fig. 4-2). The use of metal chlorides in conjunction with chlorotrimethylsilane for promoting 1,2-additions to carbonyls has an advantage over established metal alkoxide catalysts, in that the product alkoxide is simultaneously protected with a trimethylsilyl group. A ' H N M R study of diethyl zinc and Y C I 3 in benzene suggest that transmetalation of the ethyl group does not occur to any measurable extent. There was no discernible difference in chemical shift observed by ' H N M R in the ethyl groups in samples of diethylzinc in C6D6 with and without the addition of a Y C I 3 . The catalytic reaction does not suffer from the problem of substrate oligomerization when using acetophenone. The generality of the reaction, however, remains unknown, as only a few ketone substrates were screened. Unfortunately, an analogous reaction using cerium chloride instead of yttrium chloride was published while investigating this reaction." In order to make a significant improvement on the reported results, it would be necessary to make the reaction enantioselective. Introduction of a chiral ligand, such as the biphenyl bis(amidate) ligand outlined above, to form a chiral yttrium bis(amidate) monochloride complex may possibly prove useful in this endeavour. CISiMe 3, Et 2Zn O v ^ i c — 1 0 / OSiMe-, Ph- .A. YCI3 5 mol% Pri " P h PhMe, RT P h ' p h Ph Scheme 4-5 95 In similar work, the addition of phenylacetylene to benzophenone was observed using of Y C I 3 as a catalyst (Scheme 4-5). Propargyl alcohols are highly useful intermediates in the preparation of a wide variety of organic compounds. In the literature, there are very few reports of 1,2-additions of alkynyl zinc reagents to ketones. If this reaction proves to be useful for a wide variety of ketones, and can be made enantioselective, it would be a highly desirable transformation. 4.3.2 C-C Bond Formation: Olefin Polymerization There are many established systems for olefin polymerization based upon dichloride complexes of Group 4 metals activated by M A O . Before the work presented in this theses was done, there was no known means of preparing pure group 4 metal bis(amidate) dichloride complexes. While no experiments have been performed to test these complexes for olefin polymerization activity, investigation into this reactivity is a priority for future work. 4.4 Summary This thesis has presented a number of investigations into the coordination chemistry and reactivity of new group 3 and group 4 metal amidate complexes. Methods of synthesizing previously problematic group 4 metal bis(amidate) dichloride complexes were developed. The first known alkene hydroamination catalyst that is believed to proceed by a titanium imido [2+2] cycloaddition mechanism was discovered. A series of experiments were performed to elucidate the influence that electronic factors in auxiliary amidate ligands have on the activity of hydroamination catalysts derived from titanium 96 bis(amidate) bis(amido) complexes were performed, and a particularly active hydroamination catalyst based upon a multidentate biphenyl bis(amide) proligand was discovered. Some preliminary work was done that suggests that amidate chloride complexes of yttrium and the lanthanides would be promising catalysts for a number of carbon-carbon bond forming reactions. Two methods for the synthesis of amidate complexes from group 4 metal chlorides were developed. One of which represents the first salt metathesis methodology which affords amidate complexes of early transition metals in good yield and high purity. This method proved to be very general, and a number of titanium and zirconium dichloride complexes incorporating a range of [aryl,aryl], [alkyl,aryl] and [alkyl,alkyl] amidate ligands were prepared and characterized. These complexes represent the first group 4 amidate dichloride complexes to be fully characterized.lj The applicability of the salt metathesis route toward the synthesis of amidate complexes of the lanthanides has been established by using it to prepare the first homoleptic amidate complex of yttrium to be structurally characterized by X-ray crystallography. A second method of preparing amidate dichloride complexes of group 4 metals was developed which employed silylated amides as novel proligands. This route proved to be less general than the salt metathesis methodology, however, investigations into its limitations helped to elucidate several factors that contribute to the stability of amidate complexes in early transition metals. It was discovered that titanium tetrakis(amido) complexes are effective precatalysts for the intramolecular hydroamination of alkenes. By examining the range of substrate tolerance, and finding that only primary amines reacted productively, it was 97 concluded that the active catalyst most likely works according to the titanium imido [2+2] cycloaddition mechanism. This is the first known instance of an alkene hydroamination catalyst proceeding through this mechanism. Using intramolecular hydroamination of an alkene as the test reaction, a series of catalysts were screened in order to chart the influence of electronic factors in the amidate ligand on the reactivity of titanium bis(amidate) bis(amido) complexes. It was found that N-2'6'-diisopropylphenyl phenyl amidate ligands incorporating strongly electron withdrawing groups in the 4 position produced the most active complexes. It was determined that inductive effects through the sigma framework of the amidate ligand accounted for differences in reactivity observed. A comparison between the alkene hydroamination activity of complexes derived from a bis(A-2',6'-dimethylphenyl) biphenyl amide proligand 19, and the corresponding Af-2',6'-dimethylphenyl phenyl amide 5 suggest that the influence of coordination geometry and steric effects has an even greater influence on catalyst activity than electronic factors in the ligands. Initial steps have been made in the synthesis of more sophisticated amidate ligands, including a chiral multidentate amidate ligand, and amidates incorporating additional donor group functionalities. Finally, preliminary investigations into the reactivity of yttrium trichloride suggests that Ln bis(amidate) chloride complexes may be promising catalysts for promoting the 1,2 addition of zinc reagents to ketones. 98 4.5 Experimental 4.5.1 General Procedures As outlined in 2.6.1. Avanco silica gel 60 (240-400 mesh) was used for flash chromatography. Note: Although the reactions and products described herein do not meet publication standards, the experimental protocols attempted and basic characterization data have been included to facilitate future work in these areas. Synthesis of N-2'-acylphenyl /-butyl amide.14 2-aminoacetophenone (2.7 mL, 22 mmol), triethylamine (3.7 mL, 27 mmol), and pivaloyl chloride (2.7 mL, 22 mmol) were reacted, and the product isolated according to the procedure outlined for 3 (2.9 g). Yield 60%; ' H N M R (300 MHz, CDC13) 12.30 (s, b, 1H), 9.43 (d, 1H, J= 8.6 Hz), 7.34-7.24 (m, 2H), 6.72 (t, 1H, J= 7.0 Hz), 2.10 (s, 3H), 1.40 (s, 9H). Synthesis of amide 44. A solution of N-2'-acylphenyl /-butyl amide (5.14g, 23.5 mmol) in 40 mL THF / 2 mL DMF was cooled to -78°. Methyl lithium in E 2 0 (1.6M, 19 mL, 30.4 mmol) was added slowly to the solution. The reaction mixture was allowed to stir 18 h at -78°C and then methyl iodide (1.9 mL, 30.4 mmol) was added slowly to the solution. The reaction mixture was allowed to warm slowly to room temperature and stir for an additional 13 h. The solvent was removed under reduced pressure, and the residue was dissolved in 30 mL dichloromethane and washed with a liter of H?0 to remove DMF. Dichloromethane was removed under reduced pressure, and the crude product was purified by flash chromatography 20:1 Hexanes/EtOAc, 2 n d spot, (2.614 g). Yield 45%; 99 ' H N M R (300 MHz, CDC13) 10.08 (s, b, 1H), 9.34 (d, 1H, J= Hz), 7.31-6.92 (m, 3H), 2.84 (s, 3H), 1.41 (s, 6H), 1.37 (s, 9H). Synthesis of Silylated Amide 45. Inside a glovebox, a 100 mL Schlenk tube was charged with amide 44 (0.2614g, 1.048 mmol) and a stirbar. On a vacuum line, under Schlenk conditions, 50 mL dry THF was cannula transferred into the Schlenk tube, and the solution was cooled to -78°C. 1.3 equivalents L D A was added dropwise, and then the solution was allowed to warm to room temperature over the course of several hours. The solution was then cooled to 0°C, and chlorotrimethylsilane (0.17 mL, 1.4 mmol) was added and the reaction mixture was allow to warm to room temperature and stir overnight. The solvent was then removed under reduced pressure, and the reaction flask was brought into the glovebox. The oily product was dissolved in hexanes and filtered through Celite to remove lithium salts, and then the solvent was removed under reduced pressure to afford a clear oily liquid (0.2786 g). Yield 87%; 'H N M R (300 MHz, C 6 D 6 ) & 7.76 (d, 1H, J= 8.0 Hz), 7.30-6.90 (m, 3H), 3.29 (s, 3H), 1.80 (s, 6H), 1.40 (s, 9H), 0.02 (s, b, 9H). Typical Reaction Conditions for the 1,2 addition to Benzophenone. In a glovebox, a mixture of benzophenone (0.182, 1 mmol), and Y C l 3 ( T H F )3 5 (0.446 g 1 mmol) in 10 mL toluene was prepared in a 25 mL Schlenk tube. This was brought out of the box and allowed to stir at 60°C for three hours. Diethylzinc (1.5 mL, 1M in hexanes, 1.5 mmol) was then added under Schlenk conditions. The reaction mixture was allowed to stir overnight, and then quenched with 2M HCI. The organics were extracted with D C M , 100 dried, and run through a short plug of silica. The solvent was then removed under reduced pressure. Yield of 1,1-diphenylethanol from estimated from GC data 85%. 4.6 References 1. (a) S. Kanoh, H. Muramoto, N . Kobayashi, M . Motoi, H . Suda, Bull. Chem. Soc. Jpn., 1987, 60, 3659-3662; (b) M B . Andrus, D. Asgari, Tetrahedron, 2000, 56, 5775-5780. 2. F. O. Ginah, T.A. Donovan Jr., S. D. Suchan, D. R. Pfennig, G. W. Ebert. J. Org. Chem., 1990,55, 584-589. 3. G. B. Guise, W. D. Ollis, J. A. Peacock, J. S. Stephanatou, J. F. Fraser,./. Chem. Soc. Perkin Trans., 1982, 8, 1637-48. 4. F.A. Cotton, G. Wiljinson, C. A . Murillo, M . Bochmonn, Advanced Inorganic Chemistry 6,h Edition, 1999, 1110. 5. L. Pu, H.B. Yu, Chem. Rev., 2001, 101, 757-824. 6. (a) M . Kitamura, S. Suga, M . Niwa, R. Noyori, ./. Am. Chem. Soc, 1995, 117, 4832-4842; (b) M . Kitamura, m. Yamakawa, H. Oka, S. Suga, R. Noyori, Chem. Eur. J., 1996, 2, 1171-1181. 7. T. J. Davis, J. Balsells, P. J. Carroll, P. J. Walsh, Org. Lett., 2001, 3, 5, 699-702. 8. (a) P. I. Dosa, G. C. Fu, J. Amer. Chem. Soc, 1998, 120, 445-446; (b) D.J. Ramon, M . Yus, Tetrahedron, 1998, 54, 5651-5666; (c) E. F. DiMauro, M . C. Kozlowski, J. Amer. Chem. Soc, 2002, 124, 12668-12669; (d) C. Garcia, L. K . LaRochelle, P. J. Walsh, J. Amer. Chem. Soc, 2002,124, 10970-10971. 101 9. Y . Zhou, R. Wang, Z. Xu, W. Yan, L . Liu, Y. Kang, Z. Han, Org. Lett., 2004, 23, 4146-4149. 10. W.J. Evans, M . A . Ansari, J.D. Feldman, R.J. Doedens, J.W. Ziller,,/. Organomet. Chem., 1997, 157-162. U . S . Fischer, U . Groth, M . Jeske, T. Schtitz, Synlett, 2002, 11, 1922-1924. 12. (a) D. Tzalis, P. Knochel, Angew. Chem. Int. Ed. Engl, 1999, 48, 10, 1463-1465; (b) L. Tan, C-y. Chen, R. D. Tillyer, E. J. J. Grabowski, P. J. Reider, Angew. Chem. Int. Ed. Engl, 1999, 38, 5, 711-713; (c) N . K. Anand, E. M . Carreira, ./. Amer. Chem. Soc., 2001, 123, 9687-9688; (d) P. G. Cozzi, Angew. Chem. Int. Ed. Engl,2^3,, ¥2,2895-2898. 13. J. D. Beard, L. L. Schafer, Manuscript in preparation. 14. G.W. Gribble, F.P. Bousquet, Tetrahedron, 1971, 27, 3785-3794. 102 Appendix: Crystallographic Data 103 Table A - l - Summary of Crystallographic Data for T i [ P h (0 ,N ) D i i , > r P h ] 2 Cl 2 (7) empirical formula fw crystal system space group a (A) b (A) c(A) PC) V ( A 3 ) z p (calcd) ( g cm°) H (cm"1) radiation, X (A) temperature 2Qmax (°) no. observed reflections no. unique reflections no. of parameters residuals (refined on F~, all data): R l , wR2 residuals (refined on F, l>3a(I)) : R l , wR2 [(C30H28Cl2N 2O 2Ti)2C 7H 8] 1451.24 orthorhombic P b n 2 1 10.3501(2) 24.9023(6) 31.0070(8) 90.000(0) 7991.78(3) 4 1.21 3.83 0.71073 173(2) 50.0 97762 14115 891 0.083; 0.201 0.072; 0.196 104 Table A-2 - Bond Distances (A) and angles (°) for T i [ P h (0 ,N ) l ) i i P r P h ] 2 Cl 2 (7) T i l 01 2.041(5) T i l 02 2.049(5) T i l N l 2 . 054 (5) T i l N2 2.059(5) T i l C12 2.236(2) T i l C l l 2.243(2) T i l C20 2.456(6) T i l CI 2.473(6) T i 2 03 2.025 (4) T i 2 04 2.027 (5) T i 2 N4 2.069(5) T i 2 N3 2.088 (5) T i 2 C14 2.2334(19) T i 2 C13 2.2478(19) T i 2 C39 2.482(7) T i 2 C58 2.482(6) 04 C58 1.316(7) 02 C20 1.297 (7) 01 CI 1.299(7) N l CI 1.306(8) N l C8 1.435(8) 03 C39 1.313(7) N2 C20 1.326(9) N2 C27 1.451(8) N3 C39 1. 304 (8) N3 C46 1.433(8) C20 C21 1.480(9) N4 C58 1.323(8) N4 C65 1.420(8) C65 C70 1 382(9) C65 C66 1 391(10) C45 C44 1 363(11) C45 C40 1 382(10) C46 C51 1 398(9) C46 C47 1 397 (9) C27 C28 1 387(10) C27 C32 1 398 (10) C39 C40 1 475(9) C70 C69 1 370(9) C70 C71 1 544(9) C21 C26 1 398(10) C21 C22 1 397(10) C28 C29 1 414(9) C28 C33 1 496(10) CI C2 1 486(9) C48 C49 1 338(11) C48 C47 1 408(9) C51 C50 1 389(9) C51 C52 1 548 (10) C47 C55 1 515 (10) C2 C3 1.362(10) C2 C7 1.393(10) Bond Distances C8 C13 1 406(10) C8 C9 1. 418(11) C58 C59 1 .465(9) C50 C49 1 .400(11) C40 C41 1 .398(9) C67 C66 1 .391(10) C67 C68 1 .404(11) C22 C23 1 .377(10) C59 C64 1 .364(11) C59 C60 1 .405(10) C52 C54 1 .518(13) C52 C53 1 . 520(13) C60 C61 1 .387(10) C55 C57 1 .522(12) C55 C56 1 .528(11) C66 C74 1 .536(11) C32 C31 1 .408(10) C32 C36 1 .523(11) C41 C42 1 .387(10) C42 C43 1 .343(12) C36 C38 1 .483(12) C36 C37 1 .503(11) C3 C4 1. 420 (11) C64 C63 1 .417(12) C33 C35 1 .517(12) C33 C34 1 .536(12) C31 C30 1 .379(12) C26 C25 1 .401(11) C9 CIO 1 388(11) C9 C17 1 523(13) C7 C6 1. 376(12) C78 C83 1 .339(12) C78 C79 1 .361(13) C78 C77 1 .526(13) C25 C24 1 .367(12) C29 C30 1 .379(11) C44 C43 1 .422(12) C69 C68 1 .376(11) C61 C62 1 .351(13) C12 C13 1 .396(10) C12 C l l 1 .408(15) C71 C73 1 .519(13) C71 C72 1 .537(11) C13 C14 1 .520(13) C62 C63 1 .337(15) C74 C76 1 .513(17) C74 C75 1 .527 (14 ) C4 C5 1. 350(13) C l l CIO 1 .364(15) C23 C24 1 .371(12) C83 C82 1 .401(16) C6 C5 1. 432 (14) 105 C80 C81 1.374 (14) C80 C79 1.380 (12) C14 C15 1.452 (15) C14 C16 1.566(14) C81 C82 1.377(16) C18 C17 1.467(16) C17 C19 1.563(16) Bond Angles 01 T i l 02 83.8 (2) 01 T i l N l 63.48 (18) 02 T i l N l 89.5 (2) 01 T i l N2 94.2 (2) 02 T i l N2 64.3 (2) N l T i l N2 148.1(2) 01 T i l C12 156.23 (14) 02 T i l C12 95.05(15) N l T i l C12 92.81(15) N2 T i l C12 106.72(16) 01 T i l C l l 90.64(14) 02 T i l C l l 155.52 (14) N l T i l C l l 109.26(16) N2 T i l C l l 92.50(16) C12 T i l C l l 99.39(8) 01 T i l C20 85.8(2) 02 T i l C20 31.86(19) N l T i l C20 118.2(2) N2 T i l C20 32.7 (2) C12 T i l C20 105.65 (17) C l l T i l C20 124.13(16) 01 T i l CI 31.64(19) 02 T i l CI 85.3(2) N l T i l CI 31.9(2) N2 T i l CI 122.4 (2) C12 T i l CI 124.61(16) C l l T i l CI 102.22(16) C20 T i l CI 102.9(2) 03 T i2 04 88.2(2) 03 T i2 N4 91.19(18) 04 T i 2 N4 64.1 (2) 03 T i 2 N3 63.56(18) 04 T i2 N3 92.6 (2) N4 Ti2 N3 147.0(2) 03 T i2 C14 91.36(15) 04 T i2 C14 155.40(14) N4 Ti2 C14 91.31 (17) N3 Ti2 C14 109.16(16) 03 T i2 C13 157 .22 (12) 04 T i2 C13 91.38(16) N4 Ti2 C13 109.09(16) N3 T i 2 C13 93.72 (15) C14 Ti2 C13 98.22 (8) 03 T i2 C39 31.86(18) 04 T i2 C39 90.4(2) N4 Ti2 C39 120.4(2) N3 Ti2 C39 31.7 (2) C14 T i 2 C39 102.13(16) C13 T i 2 C39 125.40(16) 03 T i 2 C58 90.26(19) 04 T i 2 C58 31.94 (19) N4 T i 2 C58 32.2 (2) N3 T i 2 C58 121.6(2) C14 T i 2 C58 123.50(15) C13 T i 2 C58 101.35(16) C39 T i 2 C58 108.0(2) C58 04 T i 2 93.5(4) C20 02 T i l 91.6(4) CI 01 T i l 92.9(4) CI N l C8 126.2(5) CI N l T i l 92.0(4) C8 N l T i l 140.6(4) C39 03 T i 2 93.6(4) C20 N2 C27 124 .7(5) C20 N2 T i l 90.3(4) C27 N2 T i l 142.5(4) C39 N3 C46 127.7(5) C39 N3 T i 2 91.0(4) C46 N3 T i 2 140.4(4) 02 C20 N2 112.9(5) 02 C20 C21 118.0(6) N2 C20 C21 129.1(6) 02 C20 T i l 56.5(3) N2 C20 T i l 57.0(3) C21 C20 T i l 170.7(5) C58 N4 C65 129.4(5) C58 N4 T i 2 91.4(4) C65 N4 T i 2 139.0(4) C70 C65 C66 121.7(6) C70 C65 N4 120.5(6) C66 C65 N4 117.8(6) C44 C45 C40 120.7(6) C51 C46 C47 122.4(6) C51 C46 N3 118.9(6) C47 C46 N3 118.7(6) C28 C27 C32 124.1(6) C28 C27 N2 119.5(6) C32 C27 N2 116.2 (6) N3 C39 03 111.8(6) N3 C39 C40 130.3(6) 03 C39 C40 117.9(6) N3 C39 T i 2 57.3(3) 03 C39 T i 2 54.5(3) C40 C39 T i 2 172.3(5) 106 C69 C70 C65 118 . 6 (6) C43 C42 C41 121 .6(7) C69 C70 C71 120 . 2 (6) C38 C36 C37 109 .0(7) C65 C70 C71 121 • 2(6) C38 C36 C32 112 • 0(7) C26 C21 C22 118 • 7(6) C37 C36 C32 113 -6(7) C26 C21 C20 122 . 9 (6) C2 C3 C4 119.9 (7) C22 C21 C20 118 .3(6) C59 C64 C63 121 • 3(8) C27 C28 C29 116 . 8 (6) C28 C33 C35 109 • 8(7) C27 C28 C33 123 .9(6) C28 C33 C34 113 • 0(7) C29 C28 C33 119 .2(6) C35 C33 C34 112 • 1(8) 01 CI N l 111 .6(5) C30 C31 C32 120 .7(7) 01 CI C2 118 .9(6) C21 C26 C25 118 • 9(7) N l CI C2 129 .4 ( 6) CIO C9 C8 116.9 (8) 01 CI T i l 55 • 5(3) CIO C9 C17 119. 8 (8) N l CI T i l 56 .1 ( 3) C8 C9 C17 123.3(7) C2 CI T i l 172.9 (5) C6 C7 C2 119.6 (8) C49 C48 C47 122 .2(7) C83 C78 C79 120 • 7(9) C50 C51 C46 118 . 4 (6) C83 C78 C77 119 • 3(9) C50 C51 C52 118 . 4 (6) C79 C78 C77 120 .0(8) C46 C51 C52 123 . 2 (6) C24 C25 C26 121 .2(7) C46 C47 C48 116 • 4 (7) C30 C29 C28 120 • 5(7) C46 C47 C55 121 .9(6) C48 C49 C50 121 • 0(6) C48 C47 C55 121 . 6 (6) C45 C44 C43 120 • 0(7) C3 C2 C7 121 • 2(7) C70 C69 C68 121 .6(7) C3 C2 CI 116 .4(6) C29 C30 C31 121 • 1(7) C7 C2 CI 122 .5(6) C42 C43 C44 119 • 0(7) C13 C8 C9 121.3(6) C62 C61 C60 122 • 6(8) C13 C8 N l 119.6(6) C13 C12 C l l 118 .5(9) C9 C8 N l 119 • 1(6) C69 C68 C67 119 .7(6) 04 C58 N4 111.0(5) C73 C71 C72 112 • 1(7) 04 C58 C59 119. 9(6) C73 C71 C70 110 • 2(7) N4 C58 C59 129. 1(6) C72 C71 C70 110 • 9(6) 04 C58 T i 2 54.6(3) C12 C13 C8 119. 8 (8) N4 C58 T i 2 56.4(3) C12 C13 C14 120 .2(8) C59 C58 T i 2 174 . 3 (5) C8 C13 C14 120. 0(6) C51 C50 C49 119 . 5 (7) C63 C62 C61 119 .9(8) C45 C40 C41 119 . 0 (6) C76 C74 C75 109 • 2(8) C45 C40 C39 118 .8 (6) C76 C74 C66 108 .8(9) C41 C40 C39 122 . 0 (6) C75 C74 C66 111 • 8(7) C66 C67 C68 119 . 4 (7) C5 C4 C3 119.5(8) C23 C22 C21 121 . 0 (7) CIO C l l C12 120 • 9(8) C64 C59 C60 118 . 2 (7) C24 C23 C22 120 • 2(8) C64 C59 C58 118 .3 (7) C78 C83 C82 119 .8(10) C60 C59 C58 123 . 6 (7) C25 C24 C23 120 • 0(7) C54 C52 C53 112 . 0 (8) C l l CIO C9 122. 5(9) C54 C52 C51 112 . 6 (7) C7 C6 C5 119.1(8) C53 C52 C51 110 . 4 (7) C62 C63 C64 119 .6(9) C61 C60 C59 118 . 5 (8) C81 C80 C79 120 .3(10) C47 C55 C57 111 . 4 (6) C15 C14 C13 111 • 5(9) C47 C55 C56 115 .5 (6) C15 C14 C16 110 • 6(9) C57 C55 C56 111 . 5 (8) C13 C14 C16 111 • 0(9) C67 C66 C65 119 . 0 (6) C82 C81 C80 118 •7(10) C67 C66 C74 119 . 8 (7) C78 C79 C80 120 • 3(8) C65 C66 C74 121 . 1 (6) C4 C5 ce 120.6 (8) C27 C32 C31 116 . 7 (7) C81 C82 C83 120 .2(9) C27 C32 C36 122 . 6 (6) C18 C17 C9 112. 4 (8) C31 C32 C36 120 . 7 (6) C18 C17 C19 113 .0(10) C42 C41 C40 119 . 5 (7) C9 C17 C19 108. 6(10) 107 Table A -3 - Summary of Crysta l lographic Data for T i [ t B u ( 0 , N ) D i M e P h ] 2 C l 2 (8) empirical formula C 2 6 H 3 6 C l 2 N 2 0 2 T i fw 527.39 crystal system monoclinic space group P 21/n «(A) 11.805(1) b(A) 8.4510(4) c (A) 27.646(2) 98.928(3) V (A3) 2724.7(3) Z 4 p (calcd) ( g cm"3) 1.286 M (cm"1) 5.34 radiation, X (A) 0.71073 temperature 173(2) 26 m a x (°) 55.76 no. observed reflections 13555 no. unique reflections 5800 no. of parameters 299 residuals (refined on F 2 , all data): R l , wR2 0.097; 0.140 residuals (refined on F, I>3c(I)) : R l , wR2 0.040; 0.043 108 Table A-4 - Bond Distances (A) and angles (°) for Ti[ , B u(0,N) 1 ) i M e P h] 2Cl 2(8) Bond Distances T i (1) C l ( l ) 2.246(1) C 11) C 13) 1.507(5) T i (1) CI (2) 2.2 63(1) C 12) H 12C) 0 . 98 T i (1) 0(1) 2.017(3) C 12) H 12A) 0 . 98 T i (1) 0(2) 2.007(3) C 12) H 12B) 0 . 98 T i (1) N ( l ) 2.066(3) C 13) H 13B) 0. 99 T i (1) N(2) 2.076(3) C 13) H 13C) 0. 98 T i (1) C(1) 2.464 (4) C 13) H 13A) 0 . 98 T i (1) C (14) 2.470(4) C 14 ) C 15) 1.520(5) 0(1) C ( l ) 1.310(4) C 15) C 16) 1.530 (5) 0(2) C(14) 1.311(4) C 15) C 17) 1.537(5) N (1) C ( l ) 1.310(5) C 15) C 18) 1.532 (5) N (1) C(6) 1.431(4) C 16) H 16B) 0 . 98 N (2) C(14) 1.306(5) C 16) H 16C) 0 . 98 N (2) C(19) 1.436(4) C 16) H 16A) 0 . 99 C ( l ) C(2) 1.518(5) C 17) H 17A) 0 . 98 C (2) C(3) 1.538(5) C 17) H 17B) 0 . 98 C (2) C(4) 1.533(5) C 17) H 17C) 0 . 98 C (2) C(5) 1.524(5) C 18) H 18C) 0. 98 C (3) H(3C) 0.98 C 18) H 18A) 0. 97 C (3) H(3A) 0.98 C 18) H 18B) 0. 99 C (3) H(3B) 0.98 C 19) C 20) 1.387(5) C (4 ) H(4B) 0.98 C 19) C 24 ) 1.402(5) C (4 ) H(4C) 0.98 c 20) C 21) 1.394(5) C (4 ) H(4A) 0.98 c 20) C 25) 1.511(6) C (5) H(5A) 0.97 c 21) C 22) 1.382(6) C (5) H(5B) 0.98 c 21) H 21) 0 . 98 C (5) H(5C) 0.98 c 22) C 23) 1.375(6) C(6) C(7) 1.395(5) c 22) H 22) 0 . 97 C(6) C ( l l ) 1.393(5) c 23) C 24 ) 1.399 (5) C (7) C(8) 1.391(5) c 23) H 23) 0. 98 C (7) C(12) 1.511(5) c 24) C 26) 1.504(6) C (8) C(9) 1.377(5) c 25) H (25B) 0. 98 C (8) H(8) 0.98 c 25) H (25C) 0. 98 C (9) C(10) 1.387(6) c (25) H (25A) 0. 98 C (9) H(9) 0.98 c (26) H (26A) 0. 97 C (10) C ( l l ) 1.387(5) c (26) H (26B) 0. 98 C (10) H(10) 0.97 c (26) H (26C) 0 . 98 Bond Angles C l (1) T i (1) C l (2) 95.34 (5) C l (2) T i (1) 0(1) 155.32 (7) CI (1) T i (1) 0(1) 92.01(9) C l (2) T i (1) 0(2) 91.66(9) C l (1) T i (1) 0(2) 156.21 (8) C l (2) T i (1) N ( l ) 91.29(9) C l (1) T i (1) N ( l ) 109.63 (9) C l (2) T i (1) N(2) 108.36(9) C l (1) T i (1) N(2) 92.49(9) C l (2) T i (1) C ( l ) 123.25 (9) C l (1) T i ( l ) C ( l ) 100.6(1) C l (2) T i (1) C(14) 99.4 (1) C l (1) T i (1) C(14) 124 .23(9) 0(1) T i (1) 0(2) 91.0(1) 109 0(1) T i 1) N( l ) 64 . 1 (1) C 8) C(7) C(12) 120.5(4) 0(1) T i 1) N(2) 94 . 8 (1) C 7) C(8) C(9) 121.2(4) 0(1) T i 1) C ( l ) 32.1(1) C 7) C(8) H(8) 119.2 0(1) T i 1) C(14) 95.8(1) C 9) C(8) H(8) 119.6 0(2) T i 1) N( l ) 92 . 9 (1) C 8) C(9) C(10) 120.0(3) 0(2) T i 1) N(2) 63.7 (1) C 8) C(9) H(9) 120.8 0(2) T i 1) C ( l ) 94 . 4 (1) C 10) C(9) H(9) 119.2 0(2) T i 1) C(14) 32.0 (1) C 9) C(10) C ( l l ) 120.7(4) N( l ) T i 1) N(2) 149.1(1) C 9) C(10) H(10) 120.0 N( l ) T i 1) C ( l ) 32.1(1) C 11) C(10) H(10) 119.3 N( l ) T i 1) C(14) 123.3(1) C 6) C ( l l ) C(10) 118.4(4) N(2) T i 1) C (1) 124.7(1) C 6) C ( l l ) C(13) 120.6(3) N(2) T i 1) C(14) 31.9(1) C 10) C ( l l ) C(13) 121.0(3) C ( l ) T i 1) C(14) 114.5(1) C 7) C(12) H(12C) 109.1 T i (1) 0 1) C ( l ) 93.1 (2) C 7) C(12) H(12A) 109.8 T i (1) 0 2) C(14) 93.8 (2) C 7) C(12) H(12B) 109.4 T i (1) N 1) C ( l ) 90.9 (2) H 12C) C(12 ) H(12A) 109.5 T i (1) N 1) C(6) 139.5 (2) H 12C) C(12 ) H(12B) 109.4 C ( l ) N( l ) C(6) 129.6(3) H 12A) C(12) H(12B) 109.7 T i (1) N 2) C(14) 90.9 (2) C 11) C(13) H(13B) 109.5 T i (1) N 2) C(19) 138.9 (2) C 11) C(13) H(13C) 109.5 C(14) N 2) C(19) 129.9(3) C 11) 0(13) H(13A) 109.6 T i (1) C 1) 0(1) 54.8(2) H 13B) C(13) H(13C) 109.2 T i (1) C 1) N( l ) 57.0(2) H 13B) C(13 ) H(13A) 109.1 T i (1) C 1) C(2) 167.8 (3) H 13C) C(13) H(13A) 109.8 0 1) C ( l ) N( l ) 111.5(3) T i (1) C(14) 0(2) 54 • 2(2) 0 1) C (1) C(2) 116.9(3) T i (1) C(14) N(2) 57 • 2(2) N 1) C ( l ) C(2) 131.4(3) T i (1) C(14) C(15) 168.3(3) C 1) C(2) C(3) 105.3(3) 0 ( 2) C(14) N(2) 111 • 0(3) C 1) C (2) C(4) 108.0(3) 0 ( 2) C (14) C(15) 116.3(3) C 1) C(2) C(5) 114.8(3) N ( 2) C(14) C(15) 132.7(3) C 3) C(2) C(4) 109.6(3) c ( 14) C(15) C(16) 107.1(3) C 3) C(2) C(5) 109.5(3) C ( 14) C(15) C(17) 106.6(3) C 4) C(2) C(5) 109.5(3) C ( 14) C(15) C(18) 113.9(3) C 2) C(3) H (3C) 109.4 c ( 16) C(15) C(17) 109.9(3) C 2) C(3) H (3A) 109. 6 c ( 16) C(15) C(18) 109.5(3) C 2) C(3) H (3B) 109. 6 C ( 17) C(15) C(18) 109.6(3) H 3C) C(3) H (3A) 109.1 C ( 15) C(16) H(16B) 109.6 H 3C) C(3) H(3B) 109. 4 c ( 15) C(16) H(16C) 109. 7 H 3A) C(3) H(3B) 109.7 c ( 15) C(16) H(16A) 109. 3 C 2) C(4) H (4B) 109.1 H ( 16B) C(16) H(16C) 109.8 C 2) C(4) H (4C) 109. 6 H ( 16B) C (16) H(16A) 109.1 C 2) C(4) H (4A) 109. 6 H ( 16C) C(16) H(16A) 109.4 H 4B) C(4) H (4C) 109.3 C ( 15) C (17 ) H(17A) 109.3 H 4B) C(4) H (4A) 109.5 C ( 15) C(17) H(17B) 109.5 H 4C) C(4) H ( 4 A) 109.7 C ( 15) C(17) H(17C) 109.3 C 2) C(5) H (5A) 109.8 H ( 17A) C(17) H(17B) 109.9 C 2) C(5) H (5B) 108 . 8 H ( 17A) C(17) H(17C) 109.4 C 2) C(5) H (5C) 109.2 H ( 17B) C(17) H(17C) 109.4 H 5A) C(5) H (5B) 109. 8 C ( 15) C(18) H(18C) 109. 3 H 5A) C(5) H (5C) 110.0 C ( 15) C(18) H(18A) 109.7 H 5B) C(5) H (5C) 109.2 c ( 15) C(18) H(18B) 109.1 N 1) C(6) C(7) 118.3(3) H ( 18C) C(18) H(18A) 110 . 1 N 1) C(6) C ( l l ) 119.6(3) H ( 18C) C(18) H(18B) 109.2 C 7) C(6) C ( l l ) 121.9 (3) H ( 18A) C(18) H(18B) 109. 5 C 6) C(7) C(8) 117.9(4) N ( 2) C(19) C(20) 119.1(3) C 6) C(7) C(12) 121.7 (3) N ( 2) C(19) C(24) 118.2(3) 110 C (20) C (19) C (24) 122 4 (3) C (19) C (24 ) C(26) 120.9(3) C(19) C (20) C (21) 118 1 (4) C (23) C (24 ) C(26) 121.8(4) C(19) C (20) C (25) 121 1 (3) C (20) C (25) H(25B) 109.2 C(21) c (20) C (25) 120 8 (4) C (20) C(25) H(25C) 109.4 C (20) c (21) C (22) 120 6 (4) C (20) C (25) H(25A) 109.1 C (20) c (21) H (21) 119 5 H (25B) C (25) H(25C) 109.7 C (22) c (21) H (21) 119 8 H (25B) C (25) H(25A) 109.9 C(21) c (22) C (23) 120 5 (4) H (25C) C (25) H(25A) 109.5 C(21) c (22) H (22) 120 0 C (24) C(26) H(26A) 109. 6 C (23) c (22) H (22) 119 5 C (24) C (26) H(26B) 108 . 9 C (22) c (23) C (24) 121 0 (4) C (24) C(26) H(26C) 109.1 C (22) c (23) H (23) 120 0 H (2 6A) C (26) H(26B) 109.7 C (24 ) c (23) H (23) 119 0 H (26A) C (26) H(26C) 110. 1 C(19) c (24) C (23) 117 3 (4) H (26B) C (26) H(26C) 109.5 111 Table A-5 - Summary of Crystallographic Data for Ti[ t B u (0,Nr' M e P h ] 2 (NMe 2 ) 2 (13) empirical formula C 3 o H 4 8 N 4 0 2 T i fw 544.6 crystal system monoclinic space group P —1 21/n 1 a (A) 10.1241(3) b{k) 21.0826(5) c (A ) 15.2365(3) a (°) 90.000(0) PO 101.998(1) )' (°) 90.000(0) V ( A 3 ) 3181.07(7) Z ^ 4 p (calcd) ( g cm"3) 1.14 M (cm"1) 2.99 radiation, X (A) 0.71073 temperature 173(2) 20m ax (°) 55.8 no. observed reflections 69519 no., unique reflections 7529 no. of parameters 348 residuals (refined on F 2 , all data): R l , wR2 0.053; 0.109 residuals (refined on F , I>4o(I)) : R l , wR2 0.037; 0.101 112 Table A-6 - Bond Distances (A) and angles (°) for Ti[ t B u (0,N) D i M e P h ] 2 (NMe 2 ) 2 (13) Bond Distances T i l N4 1.9102(12) C6 C7 1 .406(2) T i l N3 1. 9144 (13) C16 C17 1.5300(19) T i l N2 2.1194(11) C l C2 1 .531 (2) T i l 01 2.1258(11) C17 C18 1.532(2) T i l N l 2.1268(12) C17 C19 1.532(2) T i l 02 2.1514(10) C17 C2 0 1.541(2) T i l C l 2.5478(15) C7 C8 1 .396 (2) T i l C16 2.5525(13) C7 C13 1.500(2) 01 C l 1.2979(18) C2 C3 1 .524 (2) 02 C16 1.2925(16) C2 C4 1 .532 (3) N2 C16 1.3144(18) C2 C5 1 .544(3) N2 C21 1.4197(17) C22 C23 1.394(2) N4 C14 1.445(2) C22 C28 1.505(2) N4 C15 1.453(2) C l l CIO 1.392(2) N3 C29 1.451(2) C l l C12 1.505(2) N3 C30 1.460(2) C8 C9 1 .383(3) N l C l 1.3106(18) C26 C25 1.399(3) N l C6 1.4219(17) C26 C27 1.501(3) C21 C26 1.402(2) C25 C24 1.366(3) C21 C22 1.404(2) C9 CIO 1.383(3) C6 C l l 1.404(2) C23 C24 1. 377(3) Bond Angles N4 T i l N3 97.56(6) 01 T i l C16 85.57 (4) N4 T i l N2 105.93(5) Nl T i l C16 118.75(5) N3 T i l N2 96.69(5) 02 T i l C16 30.40(4) N4 T i l 01 156.26 (5) C l T i l C16 102.34 (4) N3 T i l 01 92.96(5) C l 01 T i l 92.99 (8) N2 T i l 01 93.83 (4 ) C16 02 T i l 92.23 (8) N4 T i l N l 95.09(5) C16 N2 C21 131.61(11) N3 T i l N l 106.32(5) C16 N2 T i l 93.04 (8) N2 T i l N l 146.43(5) C21 N2 T i l 135.21 (9) Ol T i l N l 61.45 (4) C14 N4 C15 109.81(13) N4 T i l 02 95.38(5) C14 N4 T i l 124.36(10) N3 T i l 02 156.84(5) C15 N4 T i l 123.55 (10) N2 T i l 02 61.18 (4 ) C29 N3 C30 108.51(15) Ol T i l 02 82.54(4) C29 N3 T i l 123.69 (12) N l T i l 02 91.52 (4 ) C30 N3 T i l 126.13(12) N4 T i l C l 125.78 (5) C l N l C6 131.03(12) N3 T i l C l 102.46(5) C l N l T i l 92. 58(9) N2 T i l C l 120.75 (4) C6 Nl T i l 136.37(9) Ol T i l C l 30.58 (4) C26 C21 C22 120.82(14) N l T i l C l 30.92 (4) C26 C21 N2 120.11(13) 02 T i l C l 85.17 (4) C22 C21 N2 118.73(12) N4 T i l C16 104.59 (5) C l l C6 C7 121.57(13) N3 T i l C16 126.86 (5) C l l C6 N l 119.61(13) N2 T i l C16 30.94 (4) C7 C6 N l 118.53(13) 113 02 C16 N2 112.98 (12) 02 C16 C17 116.90(12) N2 C16 C17 130.04(12) 02 C16 T i l 57.38 (7) N2 C16 T i l 56.01 (7) C17 C16 T i l 169.62(10) 01 CI N l 112.79(13) 01 CI C2 116.74(13) N l CI C2 130.46(14) 01 CI T i l 56.43(7) N l CI T i l 56.50(7) C2 CI T i l 171.79(10) C16 C17 C18 107.87(12) C16 C17 C19 114.64 (12) C18 C17 C19 109.69(14) C16 C17 C20 105.88(12) C18 C17 C20 109.84(15) C19 C17 C20 108.81(13) C8 C7 C6 118.24(15) C8 C7 C13 120.98(15) C6 C7 C13 120.78 (13) C3 C2 CI 115.31(13) C3 C2 C4 109. 17 (14) CI C2 C4 107.08(16) C3 C2 C5 109.12 (18) CI C2 C5 105.97(13) C4 C2 C5 110.08(19) C23 C22 C21 118.55(16) C23 C22 C28 121.26(16) C21 C22 C28 120.18(14) CIO C l l C6 117.84(15) CIO C l l C12 121.24(15) C6 C l l C12 120.92 (14) C9 C8 C7 120.78(16) C25 C26 C21 117.94(16) C25 C26 C27 120.87(16) C21 C26 C27 121.19(15) C24 C25 C26 121.77(17) CIO C9 C8 120.06(16) C9 CIO C l l 121.46(16) C24 C23 C22 121.02(18) C25 C24 C23 119.90 (17) 114 Table A-7 - Summary of Crystallographic Data for Y[ t B u (0 ,N) D , M e P h ] 3 (12) empirical formula C 9 4 H 1 2 8 N 6 0 6 Y 2 fw 1615.9 crystal system triclinic space group p -1 " ( A ) 11.9579(3) b(A) 12.3269(3) c ( A ) 16.4452(4) «(°) 72.359(1) PC) 82.746(1) 67.121(1) V ( A J ) 2128.25(12) Z 1 p (calcd) ( g cm"3) 1.26 /"(cm"1) 1.413 radiation, X (A) 0.71073 temperature 173(2) 2e m a x ( ° ) 45.2 no. observed reflections 3 ] 989 no. unique reflections 5524 residuals (refined on F 2 , all data): R l ; wR2 0.118; 0.294 residuals (refined on F, i>3a(I)) : R l ; wR2 0.099; 0.266 115 Table A-8 - Bond Distances (A) and angles (°) for Y[ t B"(0,N) Bond Distances Y l 02 2.256(5) C20 C21 1 .391(12) Y l 03 2.272(5) C20 C26 1 .486(12) Y l 01 2.309(5) C33 C32 1 .385(12) Y l 01 2.379 (5) C33 C34 1 .390(13) Y l N2 2.452 (6) C33 C38 1 .505(13) Y l N l 2.475(6) C19 C24 1 .400(11) Y l N3 2.492(6) C6 C l l 1. 402(12) Y l C14 2.783 (8) C28 C30 1 .401(12) Y l C27 2.788 (8) C28 C29 1 .413 (17) Y l CI 2.876(8) C28 C31 1 .452 (17) Y l Y l 3.8444 (12) C24 C23 1 .370(12) 03 C27 1.282 (9) C24 C25 1 .471(13) 01 CI 1.333 (9) C16 C15 1 .519(12) 01 Y l 2.309 (5) C l l CIO 1 .408(13) 02 C14 1.287 (9) C l l C12 1 .500(13) Nl CI 1.292 (10) C36 C35 1 .369(15) Nl C6 1.417(10) C22 C21 1 .380(15) N3 C27 1.297(10) C22 C23 1 .408(15) N3 C32 1.419(10) CIO C9 1. 368(16) N2 C14 1.298 (10) C15 C17 1 .503(15) N2 C19 1.446(10) C15 C18 1 .520(16) C2 C3 1.521 (11) C9 C8 1 .359(16) C2 C4 1.527 (11) C34 C35 1 .367(15) C2 C5 1.529(11) C601 C602 1.261 (19) C2 CI 1.541 (11) C601 C600 1.44(2) C27 C28 1.566(11) C600 C602 1.33(2) C14 C15 1.528(12) C603 C602 1.5729 (17) C7 C8 1.382 (13) C602 C600 1.33(2) C7 C6 1.395(12) C701 C702 1.2984 (19) C7 C13 1.472(14) C701 C700 1.4 699 C37 C36 1.383(13) C700 C702 1.410(16) C37 C32 1.407(12) C702 C703 1.2026(13) C37 C39 1.491(13) C702 C700 1.410(16) C20 C19 1.387(11) Bond Angles 02 Y l 03 122.68(18) 01 Y l N l 114.04 (18) 02 Y l 01 85 . 95(17) 01 Y l N l 53.84(18) 03 Y l 01 85 . 35(18) N2 Y l N l 99.3(2) 02 Y l 01 113. 92(17) 02 Y l N3 148.87 (19) 03 Y l 01 115.53(17) 03 Y l N3 54.7(2) 01 Y l 01 69.82(18) 01 Y l N3 122.22 (19) 02 Y l N2 54.87(19) 01 Y l N3 90.16 (18) 03 Y l N2 88.6(2) N2 Y l N3 94.7(2) 01 Y l N2 127.46(19) N l Y l N3 91.5(2) 01 Y l N2 152 .9(2) 02 Y l C14 27.11(19) 02 Y l N l 87.81(19) 03 Y l C14 106.4 (2) 03 Y l N l 145.95(19) 01 Y l C14 106.75 (19) 116 01 Y l C14 137.24(19) 02 C14 N2 114 .7(7) N2 Y l C14 27.8(2) 02 C14 C15 115.2(7) Nl Y l C14 94.9(2) N2 C14 C15 130.1(7) N3 Y l C14 122.4 (2) 02 C14 Y l 53.0(3) 02 Y l C27 141.3(2) N2 C14 Y l 61 . 8 (4) 03 Y l C27 27.0(2) C15 C14 Y l 167.9(5) 01 Y l C27 104.7 (2) ' C8 C7 C6 118.8(9) 01 Y l C27 104.57(19) C8 C7 C13 119.6(9) N2 Y l C27 91.5(2) C6 C7 C13 121. 4 (8) Nl Y l C27 119.2 (2) C36 C37 C32 119.3(9) N3 Y l C27 27.7(2) C36 C37 C39 119.8(8) C14 Y l C27 117.0(2) C32 C37 C39 120.9(8) 02 Y l C l 103.43(19) C19 C20 C21 118.1(8) 03 Y l C l 133.57(19) C19 C20 C26 122.2(8) 01 Y l C l 93.42(18) C21 C20 C26 119.7(8) 01 Y l C l 27.35(19) C32 C33 C34 118.6(9) N2 Y l C l 126.0(2) C32 C33 C38 122.2(8) Nl Y l C l 26.6(2) C34 C33 C38 119.1(8) N3 Y l C l 89.0 (2) N l C l 01 113.8 (6) C14 Y l C l 118.2(2) N l C l C2 128.8(7) C27 Y l C l 112.7(2) 01 C l C2 117.3(6) 02 Y l Y l 102.03(12) N l C l Y l 59.1(4) 03 Y l Y l 102.59(13) 01 C l Y l 55.1(3) 01 Y l Y l 35.51(11) C2 C l Y l 168 .6(5) 01 Y l Y l 34.32 (11) C20 C19 C24 122.1(7) N2 Y l Y l 156.38(15) C20 C19 N2 119.3(7) Nl Y l Y l 83.09(14) C24 C19 N2 118.6(7) N3 Y l Y l 108.78(14) C7 C6 C l l 119.7(8) C14 Y l Y l 128.85(16) C7 C6 Nl 123.1 (8) C27 Y l Y l 107.95 (15) C l l C6 N l 116.9(7) C l Y l Y l 59.08(15) C33 C32 C37 119.9(8) C27 03 Y l 99.5(5) C33 C32 N3 120.8(7) C l 01 Y l 138 . 1 (4) C37 C32 N3 118.9(7) C l 01 Y l 97.6 (4) C30 C28 C29 108.8(14) Y l 01 Y l 110.18(18) C30 C28 C31 107.1(13) C14 02 Y l 99.9(4) C29 C28 C31 107.5(17) C l N l C6 127.6(6) C30 C28 C27 115.8(8) C l N l Y l 94.2(4) C29 C28 C27 107.3(8) C6 N l Y l 137.7(5) C31 C28 C27 110.1(8) C27 N3 C32 126.3 (7) C23 C24 C19 118.6(8) C27 N3 Y l 88.9(5) C23 C24 C25 119.2(8) C32 N3 Y l 144.5(5) C19 C24 C25 122.3(7) C14 N2 C19 128.5(6) C6 C l l CIO 118 .4(9) C14 N2 Y l 90.4 (4) C6 C l l C12 120.8(7) C19 N2 Y l 141.0(5) CIO C l l C12 120.8(9) C3 C2 C4 108.1(6) C35 C36 C37 120.8(10) C3 C2 C5 109.9(7) C21 C22 C23 119.7(9) C4 C2 C5 108.6(7) C9 CIO C l l 121.7 (10) C3 C2 C l 109.6(6) C17 C15 C16 108.3(8) C4 C2 C l 111.3(6) C17 C15 C18 109.9(10) C5 C2 C l 109.3(6) C16 C15 C18 108.2 (9) 03 C27 N3 116.8(7) C17 C15 C14 106.9(8) 03 C27 C28 114.4(7) C16 C15 C14 116.9(7) N3 C27 C2 8 128.7(7) C18 C15 C14 106.5(7) 03 C27 Y l 53.5(4) C8 C9 CIO 118.5(9) N3 C27 Y l 63.4 (4) C35 C34 C33 121.7(9) C28 C27 Y l 167.5(6) C9 C8 C7 122 .9(10) 1 1 7 C24 C23 C22 120.5 (9) C22 C21 C20 120.9(9) C34 C35 C36 119.6(9) C602 C601 C600 120.4(17) C602 C600 C601 117.5(17) C601 C602 C600 122.0(17) C601 C602 C603 128.6(12) C600 C602 C603 108.6(10) C702 C701 C700 116.02 (14) C702 C700 C701 111.8(10) C703 C702 C701 115.61 (9) C703 C702 C700 111.7 (8) C701 C702 C700 131.8 (8) 118 Table A -9 - Summary of Crystal lographic Data for T i | P h ( 0 , N ) D i M c P h ] 2 C I 2 (10) empirical formula C3oH2f(N202Cl2Ti fw 567.3 crystal system triclinic space group PI 21/c 1 a (A) 16.7170(3) b(A) 9.0217(2) c (A) 22.0902(5) «(°) 90.025(1) PC) 93.244(1) }'(°) 89.982(1) V(A3) 3326.21(2) Z 5 p (calcd) ( g cm"3) 1.42 H (cm"1) 5.544 radiation, X (A) 0.71073 temperature 173(2) 20™* (°) 59.6 no. observed reflections 45279 no. unique reflections 7762 no. of parameters 392 residuals (refined on F 2 , all data): R l ; wR2 0.081; 0.151 residuals (refined on F, I>3a(I)): R l ; wR2 0.050; 0.134 119 Table A-10 - Bond Distances (A) and angles (°) for T i [ P h ( 0 , N ) D i M c P h ] 2 C l 2 (10) Bond Distances T i l 02 2. 0388(15) T i l 01 2.0410(17) T i l N2 2.0735(18) T i l N l 2.0944(18) T i l C12 2.2642(8) T i l C l l 2.2665(7) T i l C16 2 .488 (2) T i l C l 2.489(2) 02 C16 1.317(3) 01 C l 1.316(3) N2 C16 1. 322(3) N2 C23 1.447(3) Nl C l 1.318(3) Nl C8 1.441(3) C8 C9 1.407(3) C8 C13 1.419(3) C l C2 1.495(3) C13 C12 1.398(3) C13 C14 1.514(3) C16 C17 1.486(3) C2 C3 1.404 (4) C2 C7 1.405(3) C28 C23 1.403(3) C28 C27 1.405(3) C28 C29 1.513(3) C17 C18 1 .391(3) C17 C22 1 .404(3) C12 C l l 1 .391(4) C24 C25 1 .404(3) C24 C23 1 .413(3) C24 C30 1 .520 (4 ) C9 CIO 1 409(3) C9 C15 1 509(3) C22 C21 1 .393 (4 ) C3 C4 1. 392(4) C7 C6 1. 405(4) C26 C27 1 .389(4) C26 C25 1 .392 (4) CIO C l l 1 .384 (4 ) C18 C19 1 .397 (4) C4 C5 1. 3 83(5) C19 C20 1 . 375(4) C21 C20 1 .377 (4) C5 C6 1. 395(5) C203 C204 1.303(5) C203 C200 1.340(5) C200 C201 1.370(6) C204 C205 1.387 (7) C201 C206 1.398 (7) C205 C206 1.433 (8) Bond Angles 02 02 01 02 T i l T i l T i l T i l 01 T i l N2 T i l 02 T i l 01 T i l N2 Nl 02 T i l T i l T i l 01 T i l N2 T i l Nl T i l C12 T i l 02 T i l 01 85.69 (7) N2 63.98(6) N2 97.07(7) N l 90.04 (7) Nl 63.82(7) N l 149.67 (7) C12 95.64(6) C12 155.50(5) C12 105.52(6) C12 91.70(6) C l l 154.34(5) C l l 90.97(5) C l l 91.31(5) C l l 111.25(6) C l l 97.77(3) C16 31.92 (7) 01 T i l C16 90.61(7) N2 T i l C16 32.09(7) Nl T i l C16 120.20 (7) C12 T i l C16 103. 44 (6) C l l T i l C16 122.94(6) 02 T i l C l 88.30(7) 01 T i l C l 31.86(7) N2 T i l C l 125.87 (7) Nl T i l C l 31.97(7) C12 T i l C l 123.64(6) C l l T i l C l 102.13(5) C16 T i l C l 108.30(7) C16 02 T i l 93.16 (12) C l 01 T i l 93.18(13) C16 N2 C23 129.49 (18) C16 N2 T i l 91.48(13) 120 C23 N2 T i l 138 .85(14) C l N l C8 127.50(18) C l N l T i l 90.74(13) C8 Nl T i l 139.79(15) C9 C8 C13 121.6(2) C9 C8 N l 119.09(19) C13 C8 Nl 119.13(19) 01 C l N l 112.21 (19) 01 C l C2 118.4 (2) Nl C l C2 129.4 (2) 01 C l T i l 54.96 (11) N l C l T i l 57.29(11) C2 C l T i l 173.27 (16) C12 C13 C8 117 . 8 (2) C12 C13 C14 120.5(2) C8 C13 C14 121.6(2) 02 C16 N2 111.28(19) 02 C16 C17 118.40(19) N2 C16 C17 130.3(2) 02 C16 T i l 54.92 (10) N2 C16 T i l 56.43(11) C17 C16 T i l 172.95(16) C3 C2 C7 120.7 (2) C3 C2 C l 121.5(2) C7 C2 C l 117.8(2) C23 C28 C27 117.4(2) C23 C28 C29 121.6(2) C27 C28 C29 121.0(2) C18 C17 C22 119.3(2) C18 C17 C16 123.6(2) C22 C17 C16 117.0(2) C l l C12 C13 121.5(2) C25 C24 C23 117.7(2) C25 C24 C30 120.8 (2) C23 C24 C30 121.5 (2) C28 C23 C24 122.4(2) C28 C23 N2 119.16(19) C24 C23 N2 118.3(2) C8 C9 CIO 117.9(2) C8 C9 C15 122.0(2) CIO C9 C15 120.1(2) C21 C22 C17 120.2 (2) C4 C3 C2 119.4(3) C2 C7 C6 118.5(3) C27 C26 C25 12010 (2) C26 C27 C28 121.5 (2) C l l CIO C9 121.2(2) CIO C l l C12 119.9(2) C26 C25 C24 121.0(2) C17 C18 C19 119.3(2) C5 C4 C3 120.6(3) C20 C19 C18 121.1 (3) C20 C21 C22 120.0(2) C19 C20 C21 120.1 (2) C4 C5 C6 120.2(3) C5 C6 C7 120.5(3) C204 C203 C200 122.3(4 C203 C200 C201 121.1(4 C203 C204 C205 120.2 (4 C200 C201 C206 120.0(4 C204 C205 C206 120.0(4 C201 C206 C205 116.2(4 121 

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