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Homogeneous H2-hydrogenation of imines catalyzed by Rh- and Ir-bis (tertiary phosphine) complexes Marcazzan, Paolo 2002

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HOMOGENEOUS H2-HYDROGENATION OF MINES CATALYZED BY Rh- AND Ir-BIS(TERTIARY PHOSPHINE) COMPLEXES by PAOLO MARCAZZAN Laurea, Universita' degli Studi di Bologna (Italy), 1996 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Chemistry) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August 2002 © 2002 Paolo Marcazzan In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of C^ffM Stl^Y The University of British Columbia Vancouver, Canada Date QcX^efe oi , £ o o V DE-6 (2/88) Abstract The coordination chemistry of several Rh and Ir precursors, containing monodentate tertiary phosphines (PR3, R = aryl), in the presence of N-donor ligands (imines and amines), and aspects of the resulting mechanistic implications in their use as catalysts for the homogeneous H2-hydrogenation of imines, were investigated. The reactivity of the Rli(I) and Ir(I) precursors [M(diene)(PR3)2]PF6 (1) under 1 atm H 2 was examined and several of the corresponding M(III)-bis(hydrido) complexes [M(H)2(PR3)2-(solv)?]PF6 (2) formed in MeOH and acetone were isolated and characterized. While for M = Rh, complexes 2 exhibit moderate and low stability in the solid state and in solution, respectively, toward reductive elimination of H2, when M = Ir the corresponding species 2 display no tendency to lose H2 neither in the solid state nor in solution. Consequently, upon loss of H 2 in solution ready formation of the corresponding c«-[M(PR3)2(solv)2]PF0 (3), characterized in situ for solv = MeOH, acetone, was observed only when M = Rh. The new Rh(I) dimeric complexes [Rh2(PR3)4][PF6]2 (R = Ph, 4a; p-tolyl, 4b), obtained by in vacuo removal of the coordinated solvent and hydrides from the corresponding 2, were isolated and characterized in both the solid state and in solution. The dimeric assembly observed in the solid state for complexes 4a and 4b is retained and as such observable only in CDCI3 and CD 2 C1 2 solutions; however, evidence for a change in hapticity of the bridging arenes from n 6 in the solid state to r|4 in solution is presented. When R = benzyl (Bz), the 1:1 (Rh:phosphine) dimer Rh2(PBz3)2-PF5 (4c) was obtained. In coordinating media, species 4a and 4b generate 2 equivalents of the corresponding 11 monomeric 3, and in either form provide useful precursors for an array of Rh(I) complexes. Several of the aryl imines investigated undergo ort/zo-metallation at both Rh and Ir centers. Several new M(III)-o-metallated complexes [M(H){RW=C(R")(o-C6H4)}-(PR3)2(solv)]PF6, with different combinations of R, R' and R", were isolated and/or characterized in situ for M = Ir and Rh (5-11). The Ir species display an inherent stability in all solvents, whereas some of the Rh analogues are fluxional in MeOH solution: solvent-exchange, discussed on the basis of variable temperature NMR studies, is proposed, and the implications of the kinetic lability of MeOH in catalytic hydrogenation reactions are discussed. The lack of suitable ortTzo-positions in the cyclic ketimine 6,7-dimethoxy-l-methyl-3,4-dihydro-isoquinoline (diq) results in the formation of cis-[Rh(PR3)2(diq)2]PF6 (R = Ph, 20a; 77-tolyl, 20b), the only bis-imine species observed in this work. Metal-catalyzed hydrolytic cleavage of some (liquid) imines with formation of the corresponding coordinated amine and free aldehyde or ketone was observed suggesting that the source of H 2 0 was the imine, although trace moisture in the solvent is not excluded. As a result, the new complexes [Ir(H){PhCH2A^=CH(o-C6H4)}(PPh3)2(NH2-CH2Ph)]PF6 (12*a), [Rh(H){PhCH2yV=C(Me)(o-C6H4)}(PPh3)2(NH2CH2Ph)]PF6 (18a) and cw-[Rh(PR3)2(PhCH2N=CHPh)(NH2CH2Ph)]PF6 (R = Ph, 14a; p-tolyl, 14b) were isolated (~ 15-30 % yield) and characterized. 5-11 12*a 14a Observation of the hydrolytic cleavage of the imines led to investigations on the reactivity of Rh precursors toward benzylamine. Depending on the conditions, the new complexes cw-[Rh(PPh3)2(PhCH2NH2)2]PF6 (15a) and cis,trans,cis-[Rh(R)2(??h3)2-iii ( N H 2 C H 2 P h ) 2 ] P F 6 (17a) w e r e i s o l a t e d a n d c h a r a c t e r i z e d , t h e i r s t r u c t u r e a n d s t a b i l i t y b e i n g s o l v e n t - d e p e n d e n t ; f o r e x a m p l e , i n a c e t o n e s o l u t i o n , b o t h 15a a n d 17a c o n v e r t i n t o [ R h ( P P h 3 ) 2 { N H 2 C H 2 ( r , 2 - C 6 H 5 ) } ] P F 6 ( 1 6 a ) . H o m o g e n e o u s c a t a l y t i c h y d r o g e n a t i o n o f s e v e r a l i m i n e s w a s a c h i e v e d w h e n u s i n g t h e R l i s y s t e m s i n M e O H . A m e c h a n i s t i c p r o p o s a l f o r t h e c a t a l y s i s i s f o r m u l a t e d b a s e d o n s t u d i e s c o n d u c t e d m o s t l y o n t h e i m i n e P h C H 2 N = C H P h : o c c u r r e n c e o f h y d r o l y s i s a n d f o r m a t i o n o f a m o n o - a m i n e - s o l v e n t o s p e c i e s a n d o f s p e c i e s 14a, a n d t h e i r i n v o l v e m e n t a n d r o l e i n t h e c a t a l y t i c c y c l e , a r e d i s c u s s e d i n p a r t i c u l a r . V a r i a b l e t e m p e r a t u r e m o n i t o r i n g o f s t o i c h i o m e t r i c h y d r o g e n a t i o n s w a s a l s o c a r r i e d o u t , a n d t h e i m p l i c a t i o n s o f f l u x i o n a l i t y o f t h e c o r r e s p o n d i n g o - m e t a l l a t e d s y s t e m s a r e d i s c u s s e d . C a t a l y s t p o i s o n i n g b y t h e h y d r o g e n a t i o n p r o d u c t , e x a m i n e d a n d e x c l u d e d f o r ( P h C H 2 ) 2 N H a n d P h C H 2 N H M e , w a s c o n c l u s i v e l y e s t a b l i s h e d f o r P h C H 2 N H P h : t h e n e w c o m p l e x [ R h { r ) 4 -( C 6 H 5 ) N H C H 2 P h } ( P P h 3 ) 2 ] P F 6 (21a), i s o l a t e d a n d f u l l y c h a r a c t e r i z e d , c o n t a i n s t h e a m i n e c o o r d i n a t e d t h r o u g h a p h e n y l r i n g , t h e h a p t i c i t y o f w h i c h v a r i e s f r o m t h e s o l i d t o s o l u t i o n s t a t e . O n l y o n e s u b s t r a t e ( P h C H = N P h ) w a s h y d r o g e n a t e d w h e n u s i n g t h e I r s y s t e m s . T h e h i g h e r s t a b i l i t y o f t h e I r v s . R h o - m e t a l l a t e d c o m p l e x e s e v e n i n M e O H r e s u l t s i n h e t e r o l y t i c c l e a v a g e o f H 2 a n d i n s e q u e s t r a t i o n o f t h e a c t i v e s i t e i n t h e f o r m o f n e u t r a l , i n s o l u b l e c o m p l e x e s s u c h a s [ I r ( H ) 2 { P h C H 2 7 V = C ( P h ) ( o - C 6 H 4 ) } ( P P h 3 ) 2 ] (22*a). 21a 22*a iv Table of Contents Abstract ii Table of Contents v List of Figures xi List of Tables xviii List of Symbols and Abbreviations xx Key to Numbered Complexes xxiii Acknowledgements . xxv Chapter 1 Catalytic Homogeneous H2-Hydrogenation 1 1.1. Catalytic Chemistry 1 1.2. Asymmetric Catalysis 2 1.3. Catalytic Asymmetric Reduction of Imines 3 1.3.1. Homogeneous H2-Hydrogenation 4 1.3.2. Hydrosilylation and Transfer Hydrogenation 7 1.4. Scope of the Thesis 9 1.5. References 10 Chapter 2 General Experimental Procedures 14 2.1. Materials 14 2.1.1. Solvents 14 2.1.2. Gases 14 2.1.3. Reagents 14 2.1.4. Imines and Amines 15 2.1.5. General Preparation of Aldimines and Ketimines 15 2.1.5.1. 'H NMR Data of Selected Aldimines and Ketimines 16 2.1.5.2. *H NMR Data of Selected Hydrogenation Products 17 2.2. Rh Precursors 18 2.2.1. Preparation of [Rh(COD)Cl]2 18 2.2.2. Preparation of [Rh(NBD)Cl]2 18 v 2.2.3. Preparation of [Rh(diene)(PR3)2]PF6 (1) 18 2.2.4. Preparation of [Rh(diene)(PPh2CH3)2]PF6 (Id) 19 2.3. Ir Precursors 20 2.3.1. Preparation of [Ir(COD)Cl]2 20 2.3.2. Preparation of [Ir(COD)(PR3)2]PF6 (1*) 20 2.4. Instrumental Methods 21 2.5. Hydrogenation Studies 22 2.6. References 23 Chapter 3 Rh and Ir Catalyst Precursors 24 3.1. Introduction 24 3.2. Rhodium Hydride Complexes 26 3.3. Synthesis of [Rh2(PR3)4][PF6]2 (4) 31 3.3.1. Solid State Characterization of [Rh2(PR3)4][PF6]2 (4) 33 3.3.2. Solution Behavior of [Rh2(PR3)4][PF6]2 (4) 38 3.3.3. In situ Reaction of [Rh2(PPh3)4][PF6]2 (4a) with Toluene 48 3.3.4. In situ Reaction of [Rh2(PPh3)4][PF6]2 (4a) with Ethylene 51 3.3.5. The Crystal Structure of Rh2(PBz3)2 (4c) 53 3.4. Iridium Hydride Complexes 57 3.4.1. The Crystal Structure of [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) 60 3.5. Experimental 63 3.5.1. Preparation of [Rh(H)2(PR3)2(acetone)2]PF6 (2) 63 3.5.2. In situ Characterization of [Rh(H)2(PPh2CH3)2(CD3OD)2]PF6 (2d') and [Rh(H)2{P(p-ClC6H4)3}2(CD3OD)2]PF6 (2e') 64 3.5.3. Preparation of [Rh(H)2(PBz3)2(CH3OH)2]PF6 (2c') 64 3.5.4. Preparation of [Rh2(PR3)4][PF6]2 (4) 65 3.5.5. Preparation of [Ir(H)2(PR3)2(acetone)2]PF6 (R = p-tolyl (2*b)) 65 3.5.6. In situ Characterization of [Ir(H)2(PR3)2(solv)2]PF6 (solv = acetone, R = Ph, 2*a; />FC 6H 4, 2*g; solv = CD 3OD, R = Ph, 2*a'; p-FC 6 H 4 , 2*g') 66 3.6. References 67 vi Chapter 4 Imines and Amines as N-Donor Ligands and Their Interaction with Rh and Ir Centers 70 4.1. Introduction 70 4.2. The Orr/iO-metallation Reaction 72 4.3. Ir Systems 73 4.3.1. The PhCH=NCH2Ph Ligand 73 4.3.2. The PhCH=NPh Ligand 82 4.4. Rh Systems 83 4.4.1. The PhCH=NCH2Ph and PhCH2NH2 Ligands 83 4.4.2. The PhC(Me)=NCH2Ph Ligand 104 4.4.3. The (Ph)2C=NCH2Ph Ligand 108 4.4.4. The (p-tolyl)C(Me)=NPh Ligand 109 4.4.5. The (diq) Ligand I l l 4.5. Experimental 115 4.5.1. Preparation of [Rh(H){PhCH2/V=CH(o-C6H4)} (PPh3)2-(acetone)]PF6 (5a) 115 4.5.2. In situ Characterization of [Rh(H){PhCH2A^=CH(o-C6H4)}-(P(/>tolyl)3)2(acetone-<f6)]PF6 (5b) 115 4.5.3. Preparation of [Rh(H){CH3/V=CH(o-C6H4)}(PPh3)2-(acetone)]PF6 (6a) 116 4.5.4. In situ Characterization of [Rh(H){RiV=CH(o-C6H4)}(PPh3)2-(acetone-<4)]PF6 (R = Ph, 7a; C 6 H U , 8a) 116 4.5.5. Preparation of [Rh(H){PhCH2/V=C(Me)(o-C6H4)}(PPh3)2-(acetone)]PF6 (9a) 117 4.5.6. In situ Characterization of [Rh(H){PhCH2/V=C(R)(oC6H4)}-(PPh3)2(CD3OD)]PF6 (R = Me 9a', Ph 10a') 117 4.5.7. Preparation of [Rh(H){PhyV=C(Me)(o-C7H7)}(PPh3)2-(acetone)]PF6 (11a) 118 4.5.8. In situ Characterization of [Rh(H) {PhCH2/V=CH(o-C6H4)}-(PPh3)2(NH2CH2Ph)]PF6 (12a) in CD2C12 118 4.5.9. Preparation of Gs-[Rh(PR3)2(PhCH2N=CHPh)(PhCH2NH2)]PF6 vii (R = Ph, 14a;p-tolyl, 14b) 119 4.5.10. Preparation of Cw-[Rh(PPh3)2(PhCH2NH2)2]PF6-0.5 MeOH (15a) 120 4.5.11. In situ Characterization of [Rh(PPh3)2{NH2CH2(r|2-C6H5)}]PF6 (16a) 120 4.5.12. Preparation of Cis,trans,cw-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (17a) 121 4.5.13. Preparation of Cw-[Rh(P(p-tolyl)3)2(diq)2]PF6 -H20 (20b) 121 4.5.14. Preparation of [h(H){PhCH2^=CH(o-C6H4)}(PPh3)2-(acetone)]PF6 (5*a) 122 4.5.15. Preparation of [h(H){PhCH27V=CH(o-C6H4)}(P0!7-tolyl)3)2-(acetone)]PF0 (5*b) 122 4.5.16. Preparation of [Ir(H){CH37vT=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (6*a) 123 4.5.17. In situ Characterization of [Ir(H){RA^=CH(o-C6H4)}(PPh3)2-(CD3OD)]PF6 (R = Ph, 7*a'; C 6 H M , 8*a') 123 4.5.18. Preparation of [Ir(H){PhyY=CH(o-C6H4)}(PPh3)2(H20)]PF6 (7*a") 124 4.5.19. In situ Characterization of [Ir(H){PhCH2/vr=C(Me)(o-C6H4)}-(PPh3)2(acetone-d6)]PF6 (9*a) 124 4.5.20. In situ Characterization of [h(H){PhCH2A^=C(Ph)(o-C6H4)}-(PPh3)2(CD3OD)]PF6 (10*a*) 125 4.5.21. Preparation of [h(H){PhCH2A^=CH(o-C6H4)}(PPh3)2-(PhCH2NH2)]PF6 (12*a) 125 4.6. References 126 Chapter 5 Homogeneous H2-Hydrogenation Studies 128 5.1. Introduction 128 5.2. Catalytic Homogeneous Hydrogenation at the Rh Center 130 5.2.1. The PhCH2N=CHPh/(PhCH2)2NH System 130 5.2.2. The PhCH=NMe/PhCH2NHMe System 143 vm 5.2.3. The PhCH=NPh/PhCH2NHPh System 145 5.2.4. The/?4olylC(Me)=NPlV/?4olylCH(Me)NHPh System 152 5.2.5. The (Ph)2C=NCH2Ph/(Ph)2CHNHCH2Ph System 153 5.2.6. The PhC(Me)=NCH2Ph/PhCH(Me)NHCH2Ph System 154 5.2.7. ThePhCH=NC6Hi1/PhCH2NHC6Hn System 155 5.2.8. The C 1 2 Hi 5 0 2 N/Ci 2 H , 6 0 2 NH {(diq)/(diq-(H)2)} System 156 5.3. Catalytic Homogeneous Hydrogenation at the Ir Center 158 5.3.1. The PhCH=NPh/PhCH2NHPh System 159 5.3.2. Other Substrates 161 5.4. Experimental 166 5.4.1. Preparation of [Rh{PhCH2NH(n4-C6H5)}(PPh3)2]PF6 (21a) 166 5.4.2. Preparation of [Ir(H)2{PhCH2Af=C(Ph)(o-C6H4)}(PPh3)2] (22*a) ....166 5.4.3. Preparation of [Ir(H)2{C6HiiiV=CH(o-C6H4)}(PPh3)2]-H20 (23*a)..167 5.4.4. NMR Characterization of [Ir(H)2{PhCH2A^=C(Me)(o-C6H4)}-(PPh3)2] (24*a) 167 5.5. References 168 Chapter 6 Summary and Indications for Further Work 170 6.1. General Conclusions 170 6.2. References 175 Structural Appendices Appendix Al Experimental Details for [Rh2(PPh3)4][PF6]2 (4a) 176 Appendix A2 Experimental Details for [Rh2(P/?-tolyl3)4][PF6]2 (4b) 184 Appendix A3 Experimental Details for Rh2(PBz3)2-PF5 (4c) 187 Appendix A4 Experimental Details for [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) 193 Appendix A5 Experimental Details for [Ir(H){PhCH2A^=CH(o-C6H4)}(PPh3)2-(acetone)]PF6 (5*a) 202 Appendix A6 Experimental Details for [Ir(H){PhCH2A^=CH(o-C6H4)}(PPh3)2-(NH2CH2Ph)]PF6 (12*a) 211 Appendix A7 Experimental Details for Gs4Rh(P7>toiyl3)2(PhCH2N=CHPh)-IX (NH2CH2Ph)]PF6 (14b) 220 Appendix A8 Experimental Details for G5-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (15a) 225 Appendix A9 Experimental Details for Q'5,?ra«5,cw-[Rh(H)2(PPh3)2-(NH2CH2Ph)2]PF6 (17a) 234 Appendix A10 Experimental Details for [Rh(H){PhCH2A^=C(Me)(o-C6H4)}(PPh3)2-(NH2CH2Ph)]PF6 (18a) 239 Appendix A l 1 Experimental Details for a5-[Rh(PPh3)2(diq)2]PF6 (20b) 248 Appendix A12 Experimental Details for [Rh{r|4-(C6H5)NHCH2Ph}(PPh3)2]PF6 (21a) 256 Appendix A13 Experimental Details for [Ir(H)2{PhCH2A^=C(Ph)(o-C6H4)}(PPh3)2] (22*a) : 262 x List of Figures Figure 1.1. Chiral phosphines in common use as ancillary ligands in homogeneous catalytic systems 5 Figure 1.2. Asymmetric synthesis of (5)-Metolachlor using Spindler's Ir-ferrocenylphosphine catalytic system 6 Figure 1.3. Pfaltz's Ir-phosphinoxazoline catalytic system 7 Figure 1.4. Buchwald's chiral a«s<3-titanocene catalyst 7 Figure 1.5. Noyori's Ru-diamine transfer-hydrogenation catalyst 9 Figure 3.1. Reaction scheme of [M(COD)(PR3)2]+ with H 2 (M = Rh 1, Ir 1*; R = Ph, a;p-tolyl, b; Bz, c; Ph2Me, d;p-ClC 6H 4, e;p-FC 6H 4, g) 24 Figure 3.2. High-field 'H NMR spectra (300 MHz, 298 K) of [Rh(H)2(PR3)2-(solv)2]PF6 (R = p-tolyl; solv = acetone, 2b; MeOH, 2b') 27 Figure 3.3. High-field ! H NMR spectrum (300 MHz, 298 K) of [Rh(H)2(PR3)2-(CD3OD)2]PF6 (R = p-tolyl, 2b') generated in-situ 28 Figure 3.4. General scheme for the reductive elimination of H 2 from species 2 30 Figure 3.5. Structural representation of the dication [Rh2(diphos)2]2+ 32 Figure 3.6. Structural representation of [(Me2SiC6H5)4Rh2H2] 32 Figure 3.7. ORTEP diagram for the dication [Rh2(PR3)4]2+ (R =p-tolyl, 4b) with 50% probability thermal ellipsoids 33 Figure 3.8. ORTEP diagram for the dication [Rh2(PR3)4]2+ (R = Ph, 4a) with 50% probability thermal ellipsoids 34 Figure 3.9. Representation of the deviation from planarity of the coordinated arene in [Rh2(PR3)4][PF6]2 (R = p-tolyl, 4b) (not to scale) 35 Figure 3.10. General scheme for possible distortion modes of coordinated arenes 36 Figure 3.11. 31P{'H} NMR spectrum (121 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = p-tolyl, 4b) in CD2C12 or CDC13 39 Figure 3.12. 3 1 P-'H HETCOR NMR spectrum (162 and 400 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = jp-tolyl, 4b) in CD2C12 (selected regions; the "extra" peaks indicated by arrows are not real but are due to scale enlargement) 40 xi Figure 3.13. 'H NMR spectrum (300 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = p-tolyl, 4b) in CD2C12 41 Figure 3.14. 'H{31P} NMR spectrum (300 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = p-tolyl, 4b) in CD2C12 41 Figure 3.15. 13C{'H} NMR spectrum (75 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = p-tolyl (4b)) in CD2C12 (p-C 6H 4CH 3 region) 42 Figure 3.16. 3,P{'H} NMR spectrum (121 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = Ph, 4a) in CD2C12 43 Figure 3.17. 31P{'H} NMR spectrum (121 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = Ph, 4a) in CDC13 43 Figure 3.18. *H NMR spectrum (300 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = Ph, 4a) in CD2C12 44 Figure 3.19. Proposed n4-coordination mode adopted by 4a and 4b in solution 45 Figure 3.20. 'H-'H EXSY NMR spectrum (400 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = Ph, 4a) in CD2C12 (selected regions) 46 Figure 3.21. 31P{'H} NMR spectrum (121 MHz, 298 K, CD3OD) of cw-[Rh(PPh3)2-(CD3OD)2]PF6 (3a*) 47 Figure 3.22. 31P{'H} NMR spectrum (121 MHz, 298 K) of the equilibrium mixture of cz's-[Rh(PPh3)2(acetone)2]PF<3 (3a) and I in acetone-J6 48 Figure 3.23. Reaction of cz's-[Rh(PPh3)2(acetone)2]PF6 (3a) with toluene in acetone-afe 48 Figure 3.24. 'H NMR spectrum (300 MHz, 298 K) of the equilibrium mixture of cis-[Rh(PPh3)2(acetone)2]PF6 (3a) and I in acetone-ci6 49 Figure 3.25. 31P{1H} NMR spectrum (121 MHz, 298 K) of the reaction product from [Rh2(PPh3)4][PF6]2 (4a) and toluene in CD2C12 50 Figure 3.26. 'H NMR spectrum (300 MHz, 298 K) of the reaction product from [Rh2(PPh3)4][PF6]2 (4a) and toluene in CD2C12 50 Figure 3.27. Differentiation of the olefinic H-atoms in (acac)Rh(C2H4)2 52 Figure 3.28. ORTEP diagram of Rh2(PR3)2 (R = Bz, 4c) with 50% probability thermal ellipsoids 54 xu Figure 3.29. ORTEP diagram of the monomeric unit of Rh2(PBz3)2-PF5 (4c) with the occluded PF5 molecule (50% probability thermal ellipsoids) 56 Figure 3.30. ORTEP diagram of the cation [Ir(H)2(PR3)2(acetone)2]+ (R = Ph, 2*a) with 50% probability thermal ellipsoids 60 Figure 4.1. Representation of a general intramolecular five-membered cyclometallated ring structure (X = donor atom) 72 Figure 4.2. Possible configurations of five-membered metallacycles of benzylideneamines 73 Figure 4.3. Proposed steps for the insertion-reaction mechanism 75 Figure 4.4. Proposed reaction steps for the formation of [Ir(H) {PhCH2JV=CH(o C6H4)}(PPh3)2(acetone)]PF6 (5*a) 75 Figure 4.5. ORTEP diagram of the cation [h(H){PhCH2Ar=CH(o-C6H4)}(PPh3)2-(acetone)]+ (5*a) with 50% probability thermal ellipsoids 76 Figure 4.6. ORTEP diagram of the cation [Ir(H){PhCH2A^=CH(o-C6H4)}(PPh3)2-(NH2CH2Ph)]+ (12*a) with 50% probability thermal ellipsoids 79 Figure 4.7. 3,P{'H} NMR spectrum (121 MHz, 298 K) of [Rh(H){PhCH27V=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in acetone-t/6 85 Figure 4.8. High-field *H NMR spectrum (300 MHz, 298 K) of [Rh(H){PhCH2-/vr=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in acetone-4 85 Figure 4.9. VT 31P{'H} (121 MHz) and 'H (300 MHz) NMR spectra of [Rh(H)-{PhCH27V=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD 3OD 86 Figure 4.10. 'H- 1 3 C (400-100 MHz, 298 K) HETCOR NMR spectrum (selected regions) of [Rh(H){PhCH2A^=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in C D 3 O D 88 Figure 4.11. ORTEP diagram of the complex cw-[Rh(Pp-tolyl3)2(PhCH27Vr=CHPh)-(NH2CH2Ph)]PF6 (14b) with 50% probability thermal ellipsoids 91 Figure 4.12. 3IP{'H} NMR spectrum (121 MHz, 298 K) of cw-[Rh(PR3)2(PhCH2-7Vr=CHPh)(NH2CH2Ph)]PF6 (R = p-tolyl, 14b) in CD2C12 93 Figure 4.13. 'H NMR spectrum (300 MHz, 298 K) of c/s-[Rh(PR3)2(PhCH2-/V=CHPh)(NH2CH2Ph)]PF6 (R = p-tolyl, 14b) in CD2C12 94 Figure 4.14. 'H- 1 3 C (400-100 MHz, 298 K) HETCOR NMR spectrum of cw-[Rh(PR3)2 xiii (PhCH2/V=CHPh)(NH2CH2Ph)]PF6 (R = p-tolyl, 14b) in CD2C12 95 Figure 4.15. Proposed coordination environments of cz'.s-[Rh(PR3)2(PhCH2iV=CH-Ph)(NH2CH2Ph)]PF6 (R = p-tolyl, 14b) in solution 95 Figure 4.16. Reaction scheme for the formation of cw-[Rh(PPh3)2(]SfH2CH2Ph)2]PF6 (15a) 96 Figure 4.17. ORTEP diagram of the cation cw-[Rh(PPh3)2(NH2CH2Ph)2]+ (15a) with 50% probability thermal ellipsoids 97 Figure 4.18. Reaction scheme for the formation of c/5,/ra«^,cz5-[RJi(H)2(PPh3)2(NH2-CH2Ph)2]PF6 (17a) in MeOH 99 Figure 4.19. ORTEP diagram of the cation cw,/raAZ5,cw-[Rh(H)2(PPh3)2(NH2CH2Ph)2]+ (17a) with 50% probability thermal ellipsoids 100 Figure 4.20. Proposed steps for the reaction between [Rh(H){PhCH2/V=CH(o-C6H4)}-(PPh3)2(acetone)]PF6 (5a) and PhCH2NH2 in acetone-<4 102 Figure 4.21. 31P{'H} NMR spectrum (121 MHz, 298 K) of the 1:1 in situ reaction between [Rh(H){PhCH2A^=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) and benzylamine in CD 3OD 102 Figure 4.22. ] H NMR spectrum (300 MHz, 298 K) of the 1:1 in situ reaction between [Rh(H){PhCH2^=CH(o-C5H4)}(PPh3)2(acetone)]PF6 (5a) and benzylamine in CD 3OD 103 Figure 4.23. Reaction scheme for the in situ formation of [Rh(H){PhCH2/V=C(Me)(o-C6H4)}(PPh3)2(CD3OD)]PF6 (9a') in CD 3OD 104 Figure 4.24. Proposed H-D exchange in CD 3OD at the CH 3 group of PhC(Me)=NCH2Ph in [Rh(H){PhCH27vr=C(Me)(o-C6H4)}(PPh3)2-(CD3OD)]PF6 (9a') 105 Figure 4.25. ORTEP diagram of the cation [Rh(H){PhCH2iV=C(Me)(o-C6H4)}(PPh3)2-(NH2CH2Ph)]+ (18a) with 50% probability thermal ellipsoids 105 Figure 4.26. Reaction scheme for the formation of [Rh(H){PhCH2/V=C(Me)(o-C6H4)} (PPh3)2(acetone)] PF6 (9a) 107 Figure 4.27. Reaction scheme for the in situ formation of [Rh(H) {PhCH2Ar=C(Ph)(o-C6H4)}(PPh3)2(CD3OD)]PF6 (10a') in CD 3OD 108 xiv Figure 4.28. Reaction scheme for the formation of [Rh(H){PhA/=C(Me)(o-(p-CH3C6H3))}(PPh3)2(acetone)]PF6 (11a) in acetone 109 Figure 4.29. Possible n6-arene coordination of (p-tolyl)C(Me)=NPh in the product formed from reaction with 3a' in CD 3OD 110 Figure 4.30. Possible resonance structures for RR'C=NAr imines I l l Figure 4.31. Representation of the two geometric isomers of cz's-[Rh(PR3)2(diq)2]PF6 (R = Ph, 20a; p-tolyl, 20b) in solution 112 Figure 4.32. ORTEP diagram of the cation cw-[Rh(PR3)2(diq)2]+ (R = /?-tolyl, 20b) with 50% probability thermal ellipsoids 113 Figure 5.1. Plot of % conv. vs. t for the hydrogenation of PhCH2N=CHPh (53 mM) catalyzed by [Rh(COD)(PPh3)2]PF6 (0.53 mM) in MeOH at 30 °C 131 Figure 5.2. Plot of [imine] vs. t for the hydrogenation of PhCH2N=CHPh (53 mM) catalyzed by [Rh(COD)(PPh3)2]PF6 (0.53 mM) in MeOH at 30 °C 132 Figure 5.3. Proposed reaction steps for the hydrogenation of PhCH2N=CHPh 133 Figure 5.4. The proposed mechanism by Longley et al. for the hydrogenation of aldimines by [Rh(COD)(PPh3)2]PF6 precursors in MeOH 135 Figure 5.5. VT 31P{'H} (121 MHz) and 'H (300 MHz) NMR spectra of the in situ H 2 -hydrogenation of [Rh(H){PhCH2yV=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD 3OD 137 Figure 5.6. VT 'H NMR (300 MHz) spectra (selected regions) of the in situ H 2 -hydrogenation of [Rh(H){PhCH2^=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD 3OD 138 Figure 5.7. VT 31P{'H} (121 MHz) and *H (300 MHz) NMR spectra (selected regions) of the reaction between ds-[Rh(Pp-tolyl3)2(solv)2]PF6 (3b') and (PhCH2)2NH (Rkamine 1:2) in CD 3OD 140 Figure 5.8. Proposed exchange at the Rh center of ds-[Rh(Pp-tolyl3)2(solv)2]PF6 (3b') in the presence of 2 (PhCH2)2NH in CD 3OD 141 Figure 5.9. VT 31P{'H} (121 MHz) and 'H (300 MHz) NMR spectra (selected regions) of the reaction between ds-[Rh(P/>tolyl3)2(solv)2]PF6 (3b') and (PhCH2)2NH (Rh:amine 1:1) in CD 3OD 142 xv Figure 5.10. Proposed reaction steps for the H2-hydrogenation of PhCH=NMe in MeOH 144 Figure 5.11. Plots of % conv. vs. t for the hydrogenation of PhCH2N=CHPh and PhN=CHPh (53 mM) catalyzed by la in MeOH (1 atm H 2 , 30 °C, Rh:imine= 1:100) 145 Figure 5.12. Formation of [Rh{r|4-(C6H5)NHCH2Ph}(PPh3)2]PF6 (21a) in MeOH ....146 Figure 5.13. ORTEP diagram of the cation [Rh{r|4-(C6H5)NHCH2Ph}(PPh3)2]+ (21a) with 50% probability thermal ellipsoids 147 Figure 5.14. Possible resonance structures for PhCH2NHPh 148 Figure 5.15. 3IP{'H} NMR spectrum (121 MHz, 298 K) of [Rh{r,6-(C6H5)NHCH2Ph}-(PPh3)2]PF6 (21a) in CD2C12 149 Figure 5.16. *H NMR spectrum (300 MHz, 298 K) of [M{n6-(C6H5)NHCH2Ph}-(PPh3)2]PF6 (21a) in CD2C12 149 Figure 5.17. 31P{]H} NMR spectrum (121 MHz, 298 K) of [Rh{T]6-(C6H5)NHCH2Ph}-(PPh3)2]PF6 (21a) in acetone-</6 • 150 Figure 5.18. 'H NMR spectrum (300 MHz, 298 K) of [Rln{n6-(C6H5)NHCH2Ph}-(PPh3)2]PF6 (21a) in acetone-<i6 150 Figure 5.19. 31P{'H} NMR spectrum (121 MHz, 298 K) of [Rh{n6-(C6H5)NHCH2Ph}-(PPh3)2]PF6 (21a) in CD3OD 151 Figure 5.20. Species formed by reaction of c«-[Rh(PPh 3) 2(soiv) 2]PF 0 (3a') and p-tolylC(Me)=NPh in CD 3OD 152 Figure 5.21. Fate of [Rh(H){PhCH2A^=C(Ph)(o-C6H4)}(PPh3)2(CD3OD)]PF6 (10a') upon exposure to 1 atm H 2 in CD3OD 154 Figure 5.22. Reaction conditions for the hydrogenation of PhC(Me)=NCH2Ph in MeOH 154 Figure 5.23. Possible dead-end pathway for 2a'/PhCH=NCy under H 2 in CD 3OD ....156 Figure 5.24. Reactivity scheme of the 2b'/diq system in CD 3OD under 1 atm H 2 157 Figure 5.25. 31P{'H} NMR spectrum (121 MHz, 298 K) of the in situ product from the 1:1 reaction between [Ir(H)2(PPh3)2(CD3OD)2]PF6 (2*a') and PhCH=NPh in CD 3OD 159 xvi Figure 5.26. 'H NMR spectrum (300 MHz, 298 K) of the in situ product from the 1:1 reaction between [k(H)2(PPh3)2(CD3OD)2]PF6 (2*a*) and PhCH=NPh in CD 3OD 160 Figure 5.27. Proposed steps for the 1:1 reaction of [Jj(H)2(PPh3)2(CD3OD)2]PF6 (2*a') with PhCH=NPh in CD 3OD 160 Figure 5.28. ORTEP diagram of [Ir(H)2{PhCH2A^=C(Ph)(o-C6H4)}(PPh3)2] (22*a) with 50% probability thermal ellipsoids 161 Figure 5.29. 31P{'H} NMR spectrum (121 MHz, 298 K) of [Ir(H)2{C6H„AA=CH(o-C6H4)}(PPh3)2] (23*a) in CD2C12 163 Figure 5.30. 'H NMR spectrum (300 MHz, 298 K) of [fr(H)2{C6HnA/=CH(o-C6H4)}(PPh3)2] (23*a) in CD2C12 163 Figure 5.31. Proposed reaction steps for the formation of [Ir(H)2{C6HnA^=CH(o-C6H4)}(PPh3)2] (23*a) in CD 3OD 164 Figure 6.1. Examples of chiral monodentate ligands for precursors 1 170 xvii List of Tables Table 3.1. Table 3.2. Table 3.3. Table 3.4. Table 3.5. Table 3.6. Table 4.1. Table 4.2. Table 4.3. Table 4.4. Table 4.5. Table 4.6. Selected N M R data for the [Rh(H)2(PR3)2(solv)2]PF6 (2) complexes under 1 atm H 2 29 3 1P{'H} N M R data for selected in situ czs-[Rh(PR 3) 2(solv) 2]PF 6 (3) complexes 30 Selected bond lengths for [Rh 2 (PR 3 ) 4 ] 2 + (R = p-tolyl, 4b; Ph, 4a) with estimated standard deviations in parentheses 35 Selected angles for [Rh 2 (PR 3 ) 4 ] 2 + (R = p-tolyl, 4b; Ph, 4a) with estimated standard deviations in parentheses 38 Selected bond distances and angles for Rh 2 (PR 3 ) 2 -PF 5 (R = Bz, 4c) with estimated standard deviations in parentheses 55 Selected bond distances and angles for [Ir(H)2(PR3)2(acetone)2]+ (R = Ph, 2*a) with estimated standard deviations in parentheses 61 Selected bond distances and angles for [Ir(H) {PhCH 2/V=CH(o-C6H4)}(PPh3)2(acetone)]+ (5*a) with estimated standard deviations in parentheses 77 Selected bond distances and angles for [Ir(H) {PhCH 2/V=CH(o-C 6 H 4 )}(PPh 3 )2(NH2CH 2 Ph)] + (12*a) with estimated standard deviations in parentheses 80 Selected bond distances and angles for cis-[Rh(?p-tolyl 3 ) 2 (PhCH 2 A^=CHPh)(NH 2 CH 2 Ph)] + (14b) with estimated standard deviations in parentheses 92 Selected bond distances and angles for a's-[RJi(PPh 3) 2(NH 2CH2Ph) 2] + (15a) with estimated standard deviations in parentheses 97 Selected bond distances and angles for a '5,<'ra«5,cr5-[Rh(H)2(PPh 3) 2(TSfH 2-CH2Ph)2]+ (17a) with estimated standard deviations in parentheses 100 Selected bond distances and angles for [Rh(H) {PhCH 2iV=C(Me)(o-C 6 H 4 )}(PPh 3 )2(NH2CH 2 Ph)] + (18a) with estimated standard deviations in parentheses 106 xvm Table 4.7. Selected bond distances and angles for c/c7-[Rh(PR3)2(diq)2]+ (R =/?-tolyl, 20b) with estimated standard deviations in parentheses 114 Table 5.1. Selected bond distances and angles for the cation [Rh{r|4-(C6H5)NHCH2Ph}(PPh3)2]+ (21a) with estimated standard deviations in parentheses 148 Table 5.2. Selected bond distances and angles for [Ir(H)2 {PhCH2A^=C(Ph)(o-C6H4)} -(PPh3)2] (22*a) with estimated standard deviations in parentheses 162 xix List of Symbols and Abbreviations acac acetylacetonate Ar argon, or aryl Anal. analysis atm atmosphere b broad bcpm 2-diphenylphosphinomethyl-4-dicyclohexylphosphino-1 -/-butoxy-carbonylpyrrolidine bdpp 2,4-bis(diphenylphosphino)pentane binap 2,2'-bis(diphenylphosphino)-1,1 '-binapthalene Bz benzyl Bu butyl Calcd. calculated cat. catalyst chiraphos 2,3-bis(diphenylphosphino)butane COD 1,5-cyclooctadiene conv. conversion COSY homonuclear correlation spectroscopy (NMR) Cp cyclopentadienyl anion Cy cyclohexyl cycphos 1 -cyclohexyl-1,2-bis(diphenylphosphino)ethane d day, or doublet (NMR) dd doublet of doublets dt doublet of triplets diop 2,3-0-isopropylidene-2,3-dihydroxy-l,4-bis(diphenylphosphino)butane dppb 1,4-bis(diphenylphosphino)butane dppe 1,2-bis(diphenylphosphino)ethane (diphos) diq 6,7-dimethoxy-l-methyl-3,4-dihydroisoquinoline duphos substituted l,2-bis(phospholano)benzene E German, entgegen (trans) xx e electron e.e. enantiomeric excess EI electron impact (MS) Et ethyl EXSY exchange NMR spectroscopy FAB fast atom bombardment (MS) FID flame ionization detector FT Fourier Transform GC gas chromatography J coupling constant (Hz) h hour HETCOR heteronuclear correlation NMR spectroscopy i iso IR infrared K Kelvin (T) L litre, or monodentate ligand M molar (mol L"1), or metal m multiplet, or medium intensity (IR), or milli m meta mccpm 2-diphenylphosphinomethyl-4-dicyclohexylphosphino-1 -methylamino-carbonylpyrrolidine Me methyl Mes mesityl min minute mol mole MS mass spectrometry n normal NBD bicyclo(2.2.1)hepta-2,5-diene NMR nuclear magnetic resonance OAc acetate o ortho xxi p pseudo p para P-P chelating diphosphine ppm parts per million Pr propyl psi pounds per square inch (pressure) q quartet R organic functional group R Latin, rectus (right) r.t. room temperature s second, or singlet (NMR), or strong intensity (IR) S Latin, sinister (left) solv solvent t time, or triplet (NMR) t tertiary T temperature td triplet of doublets TFA trifluoroacetic acid TON turnover number (mol product per mol catalyst) UV-vis ultraviolet-visible VT variable temperature w weak intensity (IR) xyliphos l-[2-(diphenylphosphino)ferrocenyl]ethyl-di(3,5-xylyl)phosphine Z German, ziisammen (cis) 5 chemical shift (ppm) n hapticity K ligating atom u bridging coordination mode, or micro v wavenumber (cm"1) [ ] concentration (mol L"1) { } broadband decoupled (NMR) xxn Key to Numbered Complexes [Rh(COD)(PPh3)2]PF6 (la) [Rh(COD)(Pp-tolyl3)2]PF6 (lb) [Rh(NBD)(PBz3)2]PF6 (lc) [Rh(COD)(PPh2CH3)2]PF6 (Id) [Rh(NBD)(P(p-ClC6H4)3)2]PF6 (le) [Ir(COD)(PPh3)2]PF6 (l*a) [Ir(COD)(Pp-tolyl3)2]PF6 (l*b) [Ir(COD)(P(/,-FC6H4)3)2]PF6 (l*g) [Rh(H)2(PPh3)2(acetone)2]PF6 (2a) [Rh(H)2(Pp-tolyl3)2(acetone)2]PF6 (2b) [Rh(H)2(PBz3)2(acetone)2]PF6 (2c) [Rh(H)2(PBz3)2(CH3OH)2]PF6 (2c') [Rh(H)2(PPh2CH3)2(CD3OD)2]PF6 (2d') [Rh(H)2{P(p-ClC6H4)3}2(CD3OD)2]PF6 (2e') [Ir(H)2(PPh3)2(acetone-(i6)2]PF6 (2*a) [Ir(H)2(PPh3)2(CD3OD)2]PF6 (2*a') [Ir(H)2(Pp-tolyl3)2(acetone)2]PF6 (2*b) [Ir(H)2(P(p-FC6H4)3)2(acetone-ci6)2]PF6 (2*g) [Ir(H)2(P(>-FC6H4)3)2(CD3OD)2]PF6 (2*g') c«-[Rh(PPh3)2(acetone-d6)2]PF6 (3a) m-[Rh(PPh3)2(CD3OD)2]PF6 (3a') cw-[Rh(Pp-tolyl3)2(acetone-(i6)2]PF6 (3b) c/5-[Rh(Pp-tolyl3)2(CD3OD)2]PF6 (3b') [Rh2(PPh3)4][PF6]2(4a) [Rh2(Pp-tolyl3)4][PF6]2 (4b) Rh2(PBz3)2.PF5 (4c) [Rh(H) {PhCH2A^=CH(o-C6H4)} (PPh3)2(acetone)]PF6 (5a) [Ir(H) {PhCH2/V=CH(o-C6H4)} (PPh3)2(acetone)]PF6 (5*a) [M(H){PhCH2Af=CH(o-C6H4)}(P(>-tolyl)3)2(acetone-li6)]PF6 (5b) xxiii [Ir(H) {PhCH2/V=CH(o-C6H4)}(P(>-tolyl)3)2(acetone)]PF6 (5*b) [Rh(H){CH3yV=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (6a) [Ir(H){CH3A^=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (6*a) [Rh(H) {PriyV=CH(o-C6H4)}(PPh3)2(acetone-rf6)]PF6 (7a) [Rh(H) {PhyV=CH(o-C6H4)} (P^-tolyl 3) 2(CD 3OD)]PF 6 (7b') [Ir(H){PbJV=CH(o-C6H4)}(PPh3)2(CD3OD)]PF6 (7*a') [Ir(H){Ph7V=CH(o-C6H4)}(PPh3)2(H20)]PF6 (7*a") [Rh(H) {Cy7V=CH(o-C6H4)} (PPh3)2(acetone-J6)]PF6 (8a) [Ir(H) {CyA^=CH(o-C6H4)} (PPh 3) 2(CD 3OD)]PF 6 (8*a') [Rh(H) {PhCH27V=C(Me)(o-C6H4)} (PPh3)2(acetone)]PF6 (9a) [Rh(H) {PhCH2A^=C(Me)(o-C6H4)} (PPh 3) 2(CD 3OD)]PF 6 (9a') [Ir(H){PhCH2yV=C(Me)(o-C6H4)}(PPh3)2(acetone-4)]PF6 (9*a) [Rh(H){PhCH2A^=C(Ph)(o-C6H4)}(PPh3)2(CD3OD)]PF6 (10a') [Ir(H){PhCH2/V=C(Ph)(o-C6H4)}(PPh3)2(CD3OD)]PF6 (10*a') [Rh(H){PhJV=C(Me)(o-(>-CH3C6H3))}(PPh3)2(acetone)]PF6 (11a) [P^(H){PhJV=C(Me)(o-(>-CH3C6H3))}(PPh3)2(CD3OD)]PF6 (11a') [Rh(H){PhCH2iV=CH(o-C6H4)}(PPh3)2(NH2CH2Ph)]PF6 (12a) [Ir(H){PhCH2^=CH(o-C6H4)}(PPh3)2(PhCH2NH2)]PF6 (12*a) cw-[Rh(PPh 3)2(PhCH2N=CHPh)(PhCH 2NH2)]PF6 (14a) cw-[Rh(Pp-tolyl3)2(PhCH2N=CHPh)(PhCH2NH2)]PF6 (14b) cw-[Rh(PPh 3)2(PhCH 2NH2)2]PF 6 (15a) [Rh(PPh3)2 {NH 2CH 2(ri 2-C 6H5)} ]PF 6 (16a) cw,fra/w,cw-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (17a) [Rh(H){PhCH 2A^=C(Me)(o-C 6H 4)}(PPh 3) 2(NH 2CH 2Ph)]PF 6 (18a) [PJi{ri^(C 6H 5)N=C(Me)(p-CH 3C 6H 3)}(PPh 3) 2]PF 6 (19a) c«-[Rh(PPh 3)2(diq) 2]PF 6 (20a) m-[Rh(P(p-tolyl)3)2(diq)2]PF6 (20b) [Rh{Ti 4-(C 6H 5)NHCH 2Ph}(PPh 3) 2]PF 6 (21a) [Ir(H)2 (PhCH27V=C(Ph)(o-C6H4)} (PPh3)2] (22*a) [rr(H) 2{C 6H, ,yV=CH(o-C6H4)}(PPh3)2] (23*a) [Ir(H)2{PhCH2yV=C(Me)(o-C6H4)}(PPh3)2] (24*a) XXIV Acknowledgements My sincere gratitude to my supervisor, Prof. Brian R. James, for his indispensable advice and patient guidance. This journey could not have reached thus far without the punctual and unfailingly acute insights of the elegant scientist and fine man he is. Among all past and present members of the group I have had the honour and pleasure to work with, I particularly thank Kapila, Craig, Nathan, Paul, David, Maria, Julio, Jo Ling, Elizabeth, Lynsey, Terrance and Erin, for according me their trust and talented experience. I thank Dr. Brian Patrick of this Department and Dr. Victor Young of the University of Minnesota for a superior job in determining the X-ray structures presented in this work. As well, efficiency and competence of all UBC Departmental services and staff are gratefully acknowledged. Special tributes go to Nadine and Lara, for the occasional "roof and couch" and a genuine friendship; to Cheyenne, Hopi and their families, for the privileged treatment they reserved for me during the past three years; to Liana, for the vividness of her numerous crafts; to Julia, for her many delightful ventures into my own language. Lastly, my profound indebtedness to my ineffable family, for their unconditional, incessant support: not a single minute ticked by without leaving inside resounding each one of their names, incorruptible depositaries of the little whole that am I. xxv "Dipagine bianche e' impossibile vivere" T.L. xxvi To my most precious, secretly treasured far away, past the ocean. xxvii Chapter 1 Chapter 1 CATALYTIC HOMOGENEOUS H 2-HYDROGENATION 1.1. Catalytic Chemistry The quest for achieving organic transformations mediated by transition metals in a catalytic fashion has encompassed an impressive amount of research efforts, from within both academic and industrial contexts, in what has grown into an area of vital importance to applied chemistry. Conciliation of profitable, viable processes with the impellent need to reduce their impact on the environment has often been provided by the intrinsic advantages of catalytic chemistry,1 either imparting significant improvements in the efficiency and selectivity of existing applications, or encouraging the search and the development of new, more efficient approaches. A negative balance is in many cases intrinsic to the "atom economy"2 of stoichiometric applications in terms of costs of starting materials as well as of treatment of undesired by-products and total waste generated. Development of large- as well as laboratory-scale productions revolving around a highly selective catalytic operating core has thus come into increasingly greater demand, especially in the industrial sector, bound to face emanation of ever more stringent environmental regulations from national and supranational bodies. Of the two common families of homogeneous and heterogeneous catalytic systems, and their underlying philosophies, the benefits that use of heterogeneous systems brings about still surpass those offered by their homogeneous counterparts, and justify from an economic standpoint their much wider distribution among industrially applied synthetic processes. Issues such as cost, durability, productivity and ease of recovery of a catalyst may prove strictly discriminating in evaluations of economic feasibility, and often dictate the choice of heterogeneous vs. homogeneous systems.3 Some of the advantages associated with the use of homogeneous systems, on the other hand, are unparalleled in any heterogeneous application. Tailoring of the active catalytic site, often achieved by choice and design of specific ancillary ligand sets,4,5 results in usually higher selectivity (chemo-, regio- and stereo-) and activity of these systems; milder operating conditions provide for potential energy savings and an easier access to 1 References on page 10 Chapter 1 spectroscopic techniques and to mechanistic studies.6'7 Several large-scale, industrial processes are based on homogeneous systems (e.g. Amoco for oxidation of p-xylene to terephthalic acid, Wacker for oxidation of ethylene and cyclohexene and Monsanto for carbonylation of MeOH); 3 however, the generally lower robustness of soluble transition metal complexes, the requirement of expensive starting materials for their assembly, and the more difficult separation from the reactants-products and recycling are still adverse to their wider application. To address and circumvent particularly the last two obstacles, much attention has thus been given to "heterogenization" methods such as support of metal complexes on insoluble materials,8 use of biphasic systems9"11 and phase transfer catalysis.12 Lower total yields (i.e. conversion x selectivity) in the desired product that often characterize heterogeneous processes, compared to homogeneous ones, can be enhanced relatively easily, also from a technical feasibility standpoint, through successive circulations of the reactants. Metalloenzyme systems (not discussed in this Introduction) might be classified as polymer-supported homogeneous catalysts. 1.2. Asymmetric Catalysis Enantiopure chiral molecules are of cardinal importance in industry, particularly to the agrochemical and pharmaceutical sectors, as indicated by worldwide sales in the chiral drug market alone that exceed $100 billion a year.13 Production of a single beneficial stereoisomer (eutomer) of a racemic mixture is not only desirable, in terms of process efficiency and waste reduction,4 but compulsory i f the issues posed by generation of the unwanted isomer (distomer) go beyond those of lower, or non-, reactivity to cross those of harmful toxicity. Development of synthetic strategies in order to perform catalytically asymmetric syntheses in enantioselective fashion is therefore a vibrant area of research. Natural occurrence of chiral derivatives, and the dependence on chiral recognition of several enzymatic cycles in many biological systems, demand the production of selectively targeted compounds, and neglect of safety, optical purity and efficiency issues can no longer be afforded by the industrial sectors involved. The renowned superior stereoselectivity achieved by chiral transition metal-based homogeneous systems14'15 has had the fine- and specialty-chemicals industries to often 2 References on page 10 Chapter 1 elect them as the most attractive and viable. Steadily growing demand for enantiopure fine chemicals has nurtured research efforts and has resulted in remarkable improvements in the area of applied homogeneous asymmetric catalysis. 1.3. Catalytic Asymmetric Reduction of Imines Development of homogeneous catalytic asymmetric reduction of unsaturated moieties promoted by transition metal-based systems has been the focus of a great deal of interest over the past decades, and has resulted in (and is still producing) some diverse and fascinating chemistry.15"17 In particular, homogeneous asymmetric hydrogenation of the imine C=N double bond has been at the forefront of research, because of the strategic importance of optically active amines to the pharmaceutical and agrochemical 18 20 industries. * Several strategies to this aim have been developed, based on different synthetic approaches ranging from reductive aminations to C-C bond-forming reactions.19 Asymmetric hydrogenation of imines catalyzed by transition metal complexes has been most extensively explored since first demonstrated by three groups independently in 1974-75. Boyle et al. demonstrated in 1974 the hydrogenation of the C=N double bond in folic acid using a chiral (Py)3RhCl3/PhC*H(Me)NHCHO/NaBH4 system;21 Scorrano et al. investigated the asymmetric hydrogenation of PhC(Me)=NCH2Ph catalyzed by the chiral 22 Rh complex [Rh(NBD)(diop)]C104, while Botteghi et al. reported the asymmetric hydrogenation of the ketoxime PhC(?-Bu)=NOH using the chiral Ru cluster 23 H4Ru4(CO)g[(-)-diop]2- Substantial improvements have been attained in recent years in tailoring new phosphorus ligand-based catalytic systems, with particular regard to the design of the ancillary ligand framework (Fig. 1.1), resulting in some impressive achievements in both catalyst activity and stereoselectivity. A brief survey of selected methodologies, namely homogeneous H2-hydrogenation, hydrosilylation and transfer hydrogenation, for enantioselective reduction of imines is provided in the following sub-sections. In most examples, however, because of forcing experimental conditions (particularly in terms of H2-pressure) and in situ formation of the catalyst, the advancement towards a more thorough understanding of the catalytic steps and of the nature of the intermediate species thereby involved has only marginally progressed. 3 References on page 10 Chapter 1 1.3.1. Homogeneous H2-hydrogenation Previous work at U B C has focused on Rh- and Ru-based systems containing chelating phosphines. For the Rh systems,24'25 the best results for the reduction of the acyclic imine PhCH2N=C(Me)(/>-C6H4OMe) (90% e.e.) were obtained using a catalyst formed in situ from [Rh(NBD)Cl]2 and the chiral diphosphine (+)-cycphos (Fig. 1.1) in the presence of added KI in toluene:MeOH (1:2) at 1000 psig H2 pressure. Collapse in enantioselectivity when using the corresponding preformed [Rh(NBD)(cycphos)]PF6 catalyst suggested an essential role for the halide, although such a co-catalyst was found to strongly inhibit the hydrogenation of the important industrial substrate MeOCH2C(Me)=N(o,o'-(Me)(Et)C6H3), possibly by preventing formation of a chelate species.25 In contrast with the reaction mechanism of the Rh-mediated hydrogenation of acyclic aldimines proposed by Longley et al.,26 whereby oxidative addition of H 2 to Rh(I) was suggested to be the first step, Becalski et al. suggested that coordination of the imine 27 N-atom to the Rh center was the first step of the reaction. In addition, as demonstrated by the successful hydrogenation of PhCH2N=C(Me)(p-C6H40Me), chelate formation was considered not essential for obtaining high chemical and optical yields. Work on Ru systems produced the best results when using the mixed-valence [RuCl(P-P)]2(u-CI)3 precursor (P-P = chiraphos); however a maximum of only 27% e.e. was achieved in the hydrogenation of PhCH2N=C(Me)Ph. Other Ru-based systems tested, containing chiral and achiral diphosphines, proved to be less effective especially toward enantioselection.29-32 Considerable other work on the development of catalytic systems based on Rh-and Ru-phosphine species has been carried out by other groups. For example, Bakos et a/.3 3"3 5 investigated the asymmetric hydrogenation of the acyclic ketimines PhC(R)=NR' (R, R' = alkyl, aryl) using in situ formed [Rjh(NBD)Cl]2/(P-P) catalysts, with a maximum 8 3 % e.e. being obtained for the hydrogenation (70 atm H 2 ) of PhC(Me)=NCH 2Ph when P-P = S.S-bdpp (Fig. 1.1). Bakos et al}6 and a D S M group37 reported up to 96% e.e. in the hydrogenation (70 atm H2) of the same ketimines using in situ formed [Rh(COD)Cl]2/sulphonated-bdpp catalysts in a two-phase system. Burk-ef a/. 3 8 ' 3 9 developed a highly enantioselective (up to 95% e.e.) hydrogenation (4 atm H2) of N -4 References on page 10 Chapter 1 acylhydrazone derivatives using a cationic Rh(I)-(i?,i?)-Et-duphos complex (Fig. 1.1). Oppolzer et alA0 reported excellent enantioselectivities (> 99% e.e.) in the hydrogenation (4 atm H 2 ) of N-arylsulfonyl imines using a Ru-binap/Et3N system (Fig. 1.1). (R)-cycphos (S,S)-chiraphos diop (Ar = Ph) mod-diop (Ar = p-MeO-m,m'-Me 2C 6H 2) bdpp (R = Ph) bcpm (R = 'BuO) (R)-binap m o d - b d P P mccpm (R = MeNH) (R = p-MeO-m,m'-Me 2C 6H 2) Figure 1.1. Chiral phosphines in common use as ancillary ligands in homogeneous catalytic systems. 5 References on page 10 Chapter 1 Ir-based systems have also been extensively investigated for H2-hydrogenation of imines. Osborn's group 4 1 , 4 2 and Spindler et al.42, independently reported moderate (up to 70% e.e.) enantioselectivities in the hydrogenation (~ 70 atm H 2 ) of MeOCH2C(Me)=N(o,o'-(CH3)2C6H3) using Ir(I)/(+)-diop systems. Spindler et al. also developed an improved version of the catalyst using a new chiral ferrocenyl-diphosphine ligand system44 (xyliphos, Fig. 1.1) in situ with [Ir(COD)Cl]2: comparable conditions (~ 80 atm H 2 ) and values of ~ 80% e.e. with a total TON of 106 in 36 h have led to industrial application of the method for the synthesis of the herbicide (SyMetolachlor (Fig. 1.2).45 More recent work from the same group on ligand optimization has increased to 87% the e.e. in the hydrogenation of the same substrate,46 while Zhang et al.47 have reported up to > 99% e.e. in the hydrogenation (1000 psig H 2 ) of (PhC(Me)=N(2,6-dimethyl-C6H3)) using a similar Ir(I)/(P-P) system (P-P = a l,l'-bisphosphanoferrocene). Achiwa's group48 Figure 1.2. Asymmetric synthesis of (•S)-Metolachlor using Spindler's Ir-ferrocenylphosphine catalytic system. achieved 81% e.e. in the hydrogenation (100 atm H2) ofa cyclic imine using an Ir(I)/(P-P) system (P-P = mod-diop, mod-bdpp, Fig. 1.1). When P-P = bcpm or mccpm (Fig. 1.1), 91% e.e. was obtained;49 these studies also revealed that a phthalimide was an highly effective cocatalyst for the hydrogenation of an isoquinoline derivative (93%> e.e. vs. ~ 30% in absence of imide). 5 0 Approaching the ligand design from a different perspective, Pfaltz's group51 tested a heterobifunctional P-N ligand within a phosphine-oxazolidine system, in the presence of the [Ir(COD)Cl]2 precursor (Fig. 1.3), and reported 89% e.e. for the hydrogenation (100 atm H 2 ) of PhC(Me)=NPh. 6 References on page JO Chapter 1 Figure 1.3. Pfaltz's Ir-phosphinoxazoline catalytic system. 52 55 Buchwald et al., ' in an even more radical departure, developed a phosphine-free, chiral attsa-titanocene system, similar to those more widely used in olefin polymerization (Fig. 1.4).56 High enantioselectivity (98% e.e.) for the hydrogenation (6-Figure 1.4. Buchwald's chiral aflsa-titanocene catalyst (X = F). 145 atm H2) of cyclic ketimines, while moderate to good values (43-85%) for acyclic substrates, were reported. These systems have since attracted much interest and optimization of their design is still under investigation.57 1.3.2. Hydrosilylation and Transfer Hydrogenation Since first reported by Kagan et al. in 1975,58 the second example of imine reduction via Rh-catalyzed hydrosilylation (with subsequent hydrolysis) was reported by Brunner et al. some 10 years later.59 Acyclic oximes were reduced by diphenylsilane in 7 References on page 10 Chapter 1 the presence of a [Rh(COD)Cl]2/((-)-diop) catalytic system, however in moderate yields (60%) and poor enantioselectivities (14%> e.e.) due to E-Z isomerization of the O-silylated oxime. Better results (84% yield, 64% e.e.) were obtained for a cyclic imine under the same conditions.60 On the other hand, an important modification on Buchwald's ansa-titanocene systems has rendered them attractive as hydrosilylation catalysts. Treatment of the bis-fluoride precursor with "BuLi in the presence of phenylsilane as the hydrogen source, to generate an active Ti(III)-hydride species, resulted in very high chemical (95-97%) and optical (92-98% e.e.) yields for the reduction of both cyclic and acyclic ketimines.61 Improvements in the catalytic recycle were also obtained by introducing a primary amine ('BuNH2) as a proton source to cleave to intermediate amido complex, and replacing phenylsilane with the more cost-effective polymethylhydrosiloxane as the hydride source.62 Ru-based systems have also gathered interest as catalysts for asymmetric reduction of imines via transfer hydrogenation. Use of stable organic molecules, less hazardous than H2 gas, as the hydrogen source has endorsed continuing interest and efforts in the development of this alternative approach. While initial studies on RuCl2(PPh3)3 using 2-propanol as the hydrogen source showed transfer hydrogenation to aldimines and ketimines,63'64 introduction of chiral diphosphines on dinuclear Ru2 species did not produce encouraging results.65'66 Recent years have, however, seen a dramatic reversal of this trend to which the most significant contribution has come from Noyori and co-workers.67 Again withdrawing from the more conventional resort of phosphine-based ligand systems, chiral 7V-tosylated 1,2-diamine ligands were reacted with [RuCl2(arene)2] (arene = benzene, /?-cymene) in the presence of a base to give mononuclear Ru-amine-amide precursors for highly enantio selective transfer hydrogenation catalysis (Fig. 1.5).68'69 With a 5:2 formic acid-triethylamine azeotropic mixture serving as the hydrogen source, a variety of cyclic imines were reduced in MeCN with excellent enantioselectivities (89-99% e.e.). The catalysis was proposed to take place via a six-membered cyclic transition state, stabilized by H-bond interactions between the C=N moiety and the NH 2 protons of the ligand without coordination of the substrate to the active Ru-monohydride site. The system also showed remarkable chemoselectivity whereby reduction only of the imine functionality was observed even 8 References on page 10 Chapter 1 when carrying out the reaction in acetone. Introduction and development of diamine-type ligands by Noyori and co-workers " have since revitalized interest and efforts in an area that is becoming one of the most promising routes towards homogeneous, enantioselective reduction of imines. Ar Figure 1.5. Noyori's Ru-diamine transfer-hydrogenation catalyst. 1.4. Scope of the Thesis This thesis work aims primarily at unveiling some of the mechanistic details involved in the homogeneous hydrogenation of imines catalyzed by Rh- and Ir-monodentate phosphine systems. Because of their mild operating conditions and thus relatively easy access to spectroscopic investigations, complexes of the general type [M(COD)(PR 3) 2]A (M = Rh 1, Ir 1*; R = aryl; A = monoanion) were chosen. [Chiral phosphines were not incorporated in the synthesis of these precursors, and thus investigations on potential chiral induction were not undertaken and questions of stereocontrolled synthesis were not addressed]. The solution behavior of complexes 1 under 1 atm H 2 and under inert (Ar) atmosphere, and the reactivity of the species thereby generated, are described in Chapter 3. Aspects of the coordination chemistry of several imine and amine substrates to the catalytic sites under Ar and under 1 atm H 2 are presented in Chapter 4. Some results on the homogeneous hydrogenation of a series of imines by Rh and Ir systems are discussed in Chapter 5. General experimental procedures are provided in Chapter 2, while a pertinent experimental section is included at the end of each individual Chapter. General conclusions and suggested directions for further investigations are given in Chapter 6. 9 References on page 10 Chapter 1 1.5. References (1) Gates, B. C. Catalytic Chemistry; John Wiley and Sons: New York, 1992. (2) Trost, B. M. Science 1991, 254, 1471. (3) Hagen, J. Industrial Catalysis: A Practical Approach; Wiley-VCH: Weinheim, 1999. (4) Knowles, W. S. Acc. Chem. Res. 1983, 16, 106. (5) van Leeuwen, P. W. N. M. In Rhodium Catalyzed Hydroformylation; van Leeuwen, P. W. N. M., Claver, C , Eds.; Kluwer Academic Publishers: Dordrecht, 2000. (6) Tolman, C. A.; Faller, J. W. In Homogeneous Catalysis with Metal Phosphine Complexes; Pignolet, L. H., Ed.; Plenum Press: New York, 1983. (7) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1987, Chapter 10. (8) Hartley, F. R. Supported Metal Complexes: A New Generation of Catalysts; Reidel, D. ed.; Kluwer Academic Publishers: Dordrecht, 1985. (9) Kuntz, E. G. CHEMTECH1987,17, 570. (10) Herrmann, W. A.; Kohlpaintner, C. W. Angew. Chem., Int. Ed. Engl. 1993, 32, 1524. (11) Rutherford, D.; Juliette, J. J. J.; Rocaboy, C ; Horvath, I. T.; Gladysz, J. A. Catal. Today 1998, 2^, 381. (12) Dehmlow, E. V.; Dehmlow, S. S. Phase Transfer Catalysis; VCH: Weinheim, 1993. (13) Stinson, S. C. Chem. Eng. News 2000, 55. (14) Parshall, G. W.; Ittel, S. D. Homogeneous Catalysis: The Applications and Chemistry of Catalysis by Soluble Transition Metal Complexes, 2nd ed.; John Wiley & Sons: New York, 1992. (15) Noyori, R. Asymmetric Catalysis in Organic Synthesis; John Wiley & Sons: New York, 1994. (16) Zassinovich, G.; Mestroni, G.; Gladiali, S. Chem. 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D.; James, B. R.; Kang, G.; Rettig, S. J. Inorg. Chem. 1991, 30, 5002. (28) Fogg, D. E.; James, B. R.; Kilner, M. Inorg. Chim. Acta 1994, 222, 85. (29) Thorburn, I. S.; Rettig, S. J.; James, B. R. J. Organomet. Chem. 1985, 296, 103. (30) James, B. R.; Pacheco, A.; Rettig, S. J.; Thorburn, I. S.; Ball, R. G.; Ibers, J. A. J. Mol. Catal. 1987, 41, 147. (31) Joshi, A. M.; MacFarlane, K. S.; James, B. R.; Frediani, P. Chem. Ind. 1993, 50, 497. (32) Fogg, D. E.; James, B. R. Inorg. Chem. 1995, 34, 2257. (33) Bakos, J.; Heil, B.; King, R. B.; Marko, L.; Takach, N. E.; Toros, S.; Vastag, S. J. Mol. Catal. 1984, 22, 283. (34) Bakos, J.; Toth, I.; Heil, B.; Marko, L. J. Organomet. Chem. 1985, 279, 23. (35) Bakos, J.; Toth, I.; Heil, B.; Szalontai, G.; Parkanyi, L.; Fiilop, V. J. Organomet. Chem. 1989,370, 263. (36) Bakos, J.; Orosz, A.; Heil, B.; Laghmari, M.; Lhoste, P.; Sinou, D. J. Chem. Soc, Chem. Commun. 1991, 1684. (37) Lensink, C ; de Vries, J. G. Tetrahedron: Asymmetry 1992, 3, 235. (38) Burk, M. J.; Feaster, J. E. J. Am. Chem. Soc. 1992,114, 6266. 11 References on page 10 Chapter 1 (39) Burk, M. J.; Martinez, J. P.; Feaster, J. E.; Cosford, N. Tetrahedron 1994, 50, 4399. (40) Oppolzer, W.; Wills, M.; Starkeman, C ; Bernardinelli, G. Tetrahedron Lett. 1990,57,4117. (41) Chan, Y. N. C ; Osborn, J. A. J. Am. Chem. Soc. 1990,112, 9400. (42) Chan, Y. N. C ; Meyer, D.; Osborn, J. A. J. Chem. Soc, Chem. Commun. 1990, 869. (43) Spindler, F.; Pugin, B.; Blaser, H.-U. Angew. Chem., Int. Ed. Engl. 1990, 29, 558. (44) Togni, A.; Breutel, C ; Schnyder, A.; Spindler, F.; Landert, H.; Tijani, A. J. Am. Chem. Soc. 1994,116, 4062. (45) Spindler, F.; Pugin, B.; Jalett, H.-P.; Buser, H.-P.; Pittelkow, U . ; Blaser, H.-U. Chem. Ind. 1996, 68, 153. (46) Spindler, F.; Blaser, H.-U.; Buser, H.-P.; Hausel, R.; Jalett, H.-P. J. Organomet. Chem. 2001, 621, 34. (47) Zhang, X.; Xiao, D. Angew. Chem., Int. Ed. Engl. 2001, 40, 3425. (48) Morimoto, T.; Nakajima, N.; Achiwa, K. Chem. Pharm. Bull. 1994, 42, 1951. (49) Morimoto, T.; Nakajima, N.; Achiwa, K. Synlett. 1995, 748. (50) Morimoto, T.; Achiwa, K. Tetrahedron: Asymmetry 1995, 6, 2661. (51) Schnider, P.; Kock, G.; Pretot, R.; Wang, G.; Bohnen, F. M.; Kriiger, C ; Pfaltz, A. Chem. Eur. J. 1997, 3, 887. (52) Willoughby, C. A.; Buchwald, S. L. J. Am. Chem. Soc. 1992,114, 7562. (53) Willoughby, C. A.; Buchwald, S. L. Org. Chem. 1993, 58, 7627. (54) Willoughby, C. A.; Buchwald, S. L. J. Am. Chem. Soc. 1994,116, 8952. (55) Willoughby, C. A.; Buchwald, S. L. J. Am. Chem. Soc. 1994,116, 11703. (56) Bohm, C. Angew. Chem., Int. Ed. Engl. 1993, 32, 232. (57) Ringwald, M.; Sturmer, R.; Brintzinger, H. H. J. Am. Chem. Soc. 1999, 121, 1524. (58) Kagan, H. B.; Langlois, N.; Dang, T.-P. J. Organomet. Chem. 1975, 90, 353. (59) Brunner, H.; Becker, R. Angew. Chem., Int. Ed. Engl. 1984, 23, 222. (60) Brunner, H.; Becker, R.; Mahboobi, S.; Wiegrebe, W. Angew. Chem., Int. Ed. Engl. 1985, 24, 995. 12 References on page 10 Chapter 1 (61) Verdaguer, X.; Lange, U. E. W.; Reding, M. T.; Buchwald, S. L. J. Am. Chem. Soc. 1996,118, 6784. (62) Verdaguer, X.; Lange, U. E. W.; Buchwald, S. L. Angew. Chem., Int. Ed. Engl. 1998, 37, 1103. (63) Grigg, R.; Mitchell, T. R. B.; Tongpenyai, N. Synthesis 1981, 442. (64) Wang, G.-Z.; Backvall, J.-E. J. Chem. Soc, Chem. Commun. 1992, 980. (65) Joshi, A. M. Ph.D. Dissertation, The University of British Columbia, 1990. (66) James, B. R.; Thorburn, I. S.; Joshi, A. M. Unpublished results. (67) Noyori, R.; Uematsu, N.; Fujii, A.; Hashiguchi, S.; Dcariya, T. / . Am. Chem. Soc. 1996, 118, 4916. (68) Hashiguchi, S.; Fujii, A.; Takehara, J.; Dcariya, T.; Noyori, R. J. Am. Chem. Soc. 1995, 117, 7562. (69) Fujii, A.; Hashiguchi, S.; Uematsu, N.; Dcariya, T.; Noyori, R. J. Am. Chem. Soc. 1996,118, 2521. (70) Doucet, H.; Ohkuma, T.; Murata, K.; Yokozawa, T.; Kozawa, M.; Katayama, E.; England, A. F.; Dcariya, T.; Noyori, R. Angew. Chem., Int. Ed. Engl. 1998, 1998, 1703. (71) Ohkuma, T.; Doucet, H.; Pham, T.; Mikami, K.; Korenaga, T.; Terada, M.; Noyori, R. J. Am. Chem. Soc 1998, 120, 1086. (72) Ohkuma, T.; Koizumi, M.; Doucet, H.; Pham, T.; Kozawa, M.; Murata, K.; Katayama, E.; Yokozawa, T.; Dcariya, T.; Noyori, R. J. Am. Chem. Soc 1998, 120, 13529. (73) Ohkuma, T.; Ishii, D.; Takeno, H.; Noyori, R. J. Am. Chem. Soc. 2000,122, 6510. (74) Mashima, K.; Abe, T.; Tani, K. Chem. Lett. 1998, 1199. (75) Mashima, K.; Abe, T.; Tani, K. Chem. Lett. 1998, 1201. (76) Murata, K.; Dcariya, T.; Noyori, R. J. Org. Chem. 1999, 64, 2186. (77) Abdur-Rashid, K.; Lough, A. J.; Morris, R. H. Organometallics 2000, 19, 2655. (78) Abdur-Rashid, K.; Lough, A. J.; Morris, R. H. Organometallics 2001, 20, 1047. (79) Casey, C. P.; Singer, S. W.; Powell, D. R.; Hayashi, R. K.; Kavana, M. J. Am. Chem. Soc. 2001,123, 1090. 13 References on page 10 Chapter 2 Chapter 2 GENERAL EXPERIMENTAL PROCEDURES 2.1. Materials 2.1.1. Solvents Solvents were purchased from Fisher Scientific or Aldrich and purified by standard techniques;' MeOH and EtOH were dried over Mg turnings/^  and distilled from the corresponding Mg alkoxide; acetone was distilled from K2CO3; CH2CI2 and CHCI3 were dried and distilled over CaH2; benzene and hexanes were distilled from Na; toluene and E12O were distilled from Na/benzophenone. The deuterated solvents CD 3OD, acetone-ii6, CD 2Cl2, CDCI3 were purchased from Cambridge Isotope Laboratories (CIL), dried according to the same procedure described for the non-deuterated solvents, and vacuum transferred into storage vessels or directly into NMR tubes equipped with J.Young PTFE valves. 2.1.2. Gases Purified Ar (99.997%) was purchased from Praxair, dried with CaS04 and activated molecular sieves (Fisher Scientific type 4 A) and further passed through P2O5. H 2 (Extra Dry, 99.9%) was also supplied by Praxair, passed through an Engelhard Deoxo catalytic hydrogen purifier to remove traces of O2 and through P2O5 to remove traces of H 2 0 . Prepurified N2 (NF, > 99.0%) was also purchased from Praxair and dried with CaS04 and activated molecular sieves (Fisher Scientific type 4 A). 2.1.3. Reagents RhCl3-3H20 and IrCl 3 -3^0 were supplied by Colonial Metals. The phosphines PPh3, P(p-tolyl)3, PPI.2CH3, P(p-C1C6H4)3 and (S)-(+)-neomentyldiphenylphosphine were purchased from Strem Chemicals, P(CH2C6H5)3 was purchased from Aldrich, and all were 14 References on page 23 Chapter 2 used as received. COD, norbornane and acetophenone and benzaldehyde were purchased from Aldrich, N B D and cyclooctane from Eastman, and KPF6 was purchased from Alfa; all these materials were used as received. 2.1.4. Imines and Amines The liquid imines N-benzylidenebenzylamine and N-benzylidenemethylamine, and amines benzylamine, dibenzylamine and N-methylbenzylamine were purchased from Aldrich, purified by distillation and stored under Ar; the solid amine N-phenylbenzylamine was purchased from Aldrich and used as received; the imines N-(a-methyl-benzylidene)benzylamine, N-benzylideneaniline, N-benzylidenecyclohexylamine, and N-(a-phenyl-benzylidene)benzylamine, were prepared by Dr. D. Fogg of this laboratory (see Section 2.1.5). The imine (p-tolyl)C(Me)=NPh was prepared by Dr. M . Ezhova of this laboratory. The cyclic ketimine 6,7-dimethoxy-l-methyl-3,4-dihydroisoquinoline was previously prepared in this laboratory from reaction of 3,4-(CH30)2CeH3CH2CH2NH2 with acetic anhydride according to a standard method. 2.1.5. General Preparation of N-benzylideneamines (PhCH=NR) and ketimines (PhC(R')=NR). The general approach3'4 for the synthesis of aldimines and ketimines, involving acid-catalyzed condensation of the carbonyl compound (aldehyde or ketone, respectively) with the amine under reflux, with azeotropic removal of the water formed, was found to be unnecessarily vigorous for the synthesis of the substrates employed in this work. Instead, these compounds were prepared by the method described by Fogg,5 by simple condensation of the corresponding amines and aldehydes. In a general procedure, addition of neat amine (1.05 equivalents) to the appropriate aldehyde or ketone (typically 50 mmol), and removal with a pipette of the (immiscible) water layer formed afforded the desired product in quantitative yield; the product was purified from residual water by addition of CeH6 (~ 40 mL) and azeotropic distillation of the solvent on a rotary evaporator. Products were then 15 References on page 23 Chapter 2 further purified by chromatography on neutral alumina (hexanes eluent). *H NMR (300 MHz) characterization data of selected substrates are reported below. 2.1.5.1. "H NMR Data of Selected Aldimines and Ketimines R = CH 2Ph 'H NMR (300 MHz, CD3OD): 8 4.80 (s, 2H, CH2), 7.2-7.8 (m, 10H, CeH5), 8.50 (s, 1H, CH=N). 'H NMR (300 MHz, acetone-^ ): 8 4.81 (s, 2H, CH2), 7.2-7.9 (m, 10H, Crfs), 8.50 (s, 1H, CH=N). R = Ph 'H NMR (300 MHz, CD3OD): 8 7.2-7.9 (m, 10H, C ^ s ) , 8.55 (s, 1H, Cf7=N). ! H NMR (300 MHz, acetone-<i6): 8 7.2-7.9 (m, 10H, C ^ s ) , 8.50 (s, 1H, CH=N). R = CgHii 'H NMR (300 MHz, CD3OD): 8 1.10-1.88 (m, 10H, C6(E.)HW), 3.12-3.22 (m, 1H, C6(/f)H,0), 7.3-7.8 (m, 5H, Cei/s), 8.30 (s, 1H, CH=N). ] H NMR (300 MHz, acetone-de): 8 1.15-1.90 (m, 10H, C6(H)/710), 3.10-3.27 (m, 1H, C6(#)H10), 7.3-7.8 (m, 10H, Cefls), 8.35 (s, 1H, CH=N). R = C H 3 'H NMR (300 MHz, CD3OD): 8 3.48 (s, 3H, CH3), 7.3-7.8 (m, 10H, C ^ s ) , 8.30 (s, 1H, C//=N). 'H NMR (300 MHz, acetone-Je): 5 3.43 (s, 3H, CH3), 7.2-7.9 (m, 10H, Crfs), 8-32 (s, 1H, C#=N). R' = Ph, R = CH 2Ph 'H NMR (300 MHz, CD3OD): 8 4.66 (s, 2H, CH2), 7.2-7.6 (m, 15H, C ^ ) - *H NMR (300 MHz, acetone-J6): 8 4.60 (s, 2H, CH2), 7.2-7.7 (m, 15H, C ^ s ) . 16 References on page 23 Chapter 2 R* = C H 3 , R = CH 2Ph 'H NMR (300 MHz, CD3OD): 6 4.75 (s, 2H, CH2), 7.2-7.8 (m, 10H, C(H5). "H NMR (300 MHz, acetone-c/s): 8 2.31 (s, 3H, CH3), 4.71 (s, 2H, CH2), 7.1-8.0 (m, 10H, Crfs). (p-CH3C6H4)C(CH3)=NPh 'H NMR (300 MHz, CD3OD): 5 2.31 (s, 3H, p-CH3C^U), 2.40 (s, 3H, C(C//3)=N), 6.8-7.8 (m, 9H, p-CH.3C(H5). 'H NMR (300 MHz, acetone-fife): 5 2.21 (s, 3H, p-CH2C6R4), 2.38 (s, 3H, (C(C7/3)=N), 6.7-7.9 (m, 9H,p-CR3CeH5). 2.1.5.2. 'H NMR Data of Selected Hydrogenation Products NH(Me)(CH2Ph) 'H NMR (300 MHz, CDC13): 5 2.0 (bs, 1H, Ni/), 2-40 (s, 3H, CH3), 3.75 (s, 2H, CH2), 7.2-7.4 (m, 5H, C(H5). NH(CH2Ph)2 'H NMR (300 MHz, CDC13): 5 1.8 (bs, 1H, N/f), 3.82 (s, 4H, CH2), 7.2-7.4 (m, 10H, CeH5). NH(C6Hn)(CH2Ph) 'H NMR (300 MHz, CDC13): 5 1.0-2.0 (m, 10H, CH2), 2.4-2.55 (m, 1H, CH), 3.80 (s, 2H, CH2), 1.2-1 A (m, 5H, Cffls). NH(Ph)(CH2Ph) 'H NMR (300 MHz, CDC13): 5 1.8 (bs, 1H, Nfl), 4.30 (s, 2H, CH2), 6.6-6.8 (m, 5H, NC^s) , 7.2-7.4 (m, 5H, CeHs). NH(CH2Ph)[C*H(Me)Ph] 'H NMR (300 MHz, CDC13): 5 1.38 (d, 3H, CH3, 3 J H H = 6.6), 1.63 (bs, 1H, N/J), 3.60, 3.67 (ABq, 2H, CH2, J= 13.2), 3.82 (q, 1H, C*H, V H H = 6.6), 7.21-7.39 (m, 10H, C ^ ) -17 References on page 23 Chapter 2 2.2. Rh precursors 2.2.1. Preparation of IRh(COD)Cl]2 This precursor was prepared according to a published procedure.6 To a stirred, dark red solution of RhCl3-3H20 (1.31 g, 0.0063 mol) in an H 20/EtOH mixture (2.5 + 12.5 mL) under Ar, COD was added (1.65 mL, 0.014 mol) via a syringe through a rubber septum. The mixture was then refluxed under stirring for 6 h, to afford an orange precipitate. After the mixture was cooled to r.t., the precipitate was collected by filtration, washed with cold EtOH (3x10 mL) to afford a yellow solid that was dried under vacuum. Yield: 1.16 g (75%). *H NMR (CDC13): 5 1.70 (m, 8H, CH2), 2.50 (m, 8H, CH2), 4.25 (s, 8H, =CH). Anal. Calcd for Ci6H24Cl2Rh2: C, 38.97; H, 4.91. Found: C, 38.71; H, 4.83. The characterization data agree with the reported literature.6'7 2.2.2. Preparation of [Rh(NBD)Cl]2 This precursor was prepared according to a published procedure.8 To a dark red solution of RhCl3-3H20 (0.70 g, 0.0033 mol) in a H20/EtOH mixture (1+9 mL) under Ar, NBD was added (2 mL, 0.019 mol) via a syringe through a rubber septum. The mixture was then stirred for 2 days at r.t., to afford a yellow precipitate. After 2 days, the precipitate was collected by filtration, washed with cold EtOH (3x5 mL) to afford a yellow solid that was dried under vacuum. Yield: 0.6 g (79%). 'H NMR (CDCI3): 5 1.50 (s, 4H, CH2), 4.18 (s, 4H, CH), 4.30 (m, 8H, =CH). Anal. Calcd for Ci4H,6Cl2Rh2: C, 36.64; H, 3.07. Found: C, 36.65; H, 2.97. The characterization data agree with the reported literature. 2.2.3. Preparation of [Rh(diene)(PR3)2]PF6 (1) These precursors were prepared according to a published procedure.9 In a general method, to a stirred orange solution of [Rh(diene)Cl]2 (~ 0.25 g, ~ 0.50 mmol) and KPF 6 (~ 0.26 g, ~ 1.40 mmol) in a CH2CI2/H2O mixture (3 + 3 mL), a solution of the appropriate phosphine PR3 (~ 1.00 g, ~ 3.90 mmol) in CH2CI2 (2 mL) was cannulated under Ar through a 18 References on page 23 Chapter 2 rubber septum. The mixture turned immediately bright red, and was stirred at r.t. for 40 min. The H2O layer was then removed and the organic phase further washed with H2O (3x5 mL), then concentrated to ca. 1 mL. The addition of Et20 (8 mL) afforded the precipitation of a yellow solid that was collected by filtration, washed with Et 2 0 (3x8 mL) and dried under vacuum. R = Ph; diene = COD (la): Yield: 0.73 g (90%). ^Pf'H} NMR (CDC1 3 ): 5 25.96 (d, JR h P= 145.2). 'H NMR (CDCI3): 5 2.05-2.33 (m, 8H, CH2 COD), 4.35 (s, 4H, =Ci¥COD), 7.0-7.35 (m, 30H, C(Ji5). Anal. Calcd for C44H 4 2F 6P 3Rh: C, 60.00; H, 4.81. Found: C, 60.21; H, 4.73. The characterization data agree with those in the literature.9 R =/?-tolyl; diene = COD (lb): Yield: 0.71 g (90%). 31P{'H} NMR (CDC1 3 ): 5 24.77 (d, J^?= 145.1). 'H NMR (CDCI3): 6 2.05-2.33 (m, 8H, CH2 COD), 2.19 (s, 18H, jp-C// 3C 6H 4), 4.35 (s, 4H, =CH COD), 7.0-7.35 (m, 24H, p-CK&eH*). Anal. Calcd for C5oH54F6P3Rh: C, 62.25; H, 5.64. Found: C, 61.97; H, 5.53. R = Bz; diene = NBD (lc): Yield: 0.35 g (85%). 31P{'H} NMR (CD2C12): 5 7.10 (d, JRhP= 155.7). ] H NMR (CD2C12): 5 1.30 (s, 2H, CH2 NBD), 2.88 (s, 12H, -Gf/ 2C 6H 5), 3.50 (s, 2H, CH NBD), 4.35 (s, 4H, =CH NBD), 7.10-7.45 (m, 30H, -CH2C6r/5)- Anal. Calcd for C49H5oF6P3Rh: C, 62.03; H, 5.31. Found: C, 62.04; H, 5.42. R = p-C\C6H4; diene = NBD (le): Yield: 0.20 g (65%). 31P{'H} NMR (CDCI3): 5 28.32 (d, JR h P= 157.1). 'H NMR (CDCI3): 6 1.40 (s, 2H, CH2 NBD), 4.05 (s, 2H, CH NBD), 4.50 (s, 4H, =CH NBD), 7.10-7.59 (m, 24H, p - C K ^ ) . Anal. Calcd for C 43H3 2Cl6F 6P 3Rh: C, 48.21; H, 3.01. Found: C, 48.18; H, 2.99. Complexes lb, lc and le were not synthesized before. 2.2.4. Preparation of [Rh(diene)(PPh2CH3)2]PF6 (Id) This precursor was prepared according to a published procedure.9 To a stirred solution of [Rh(diene)Cl]2 (~ 0.25 g, ~ 0.50 mmol) and KPF 6 (~ 0.26 g, ~ 1.40 mmol) in acetone (3 mL), a solution of PPI12CH3 (~ 0.42 g, ~ 2.10 mmol) in acetone (2 mL) was cannulated through a rubber septum under Ar. The resultant red suspension was stirred at r.t. for 30 min, then CH2C1 2 was added (4 mL), the inorganic salt removed by filtration and the limpid red filtrate concentrated to ca. 1 mL. The addition of Et 2 0 afforded an orange precipitate, which was collected by filtration, washed with Et 2 0 (3x8 mL) and dried under vacuum, diene = COD, Yield: 0.25 g (80%). 3IP{1H} NMR (CDC13): 5 15.04 (d, 7^= 19 References on page 23 Chapter 2 144.1). 'H NMR (CDCh): 5 1.50 (s, 6H, CH3), 2.10-2.50 (m, 8H, CH2 COD), 4.58 (s, 4H, =CH COD), 7.25-7.70 (m, 20H, C ^ ) . Anal. Calcd for C34H 3 8 F 6 P 3 Rh: C, 53.98; H, 5.06. Found: C, 53.90; H, 5.01. diene = NBD, Yield: 0.65 g (80%). 3]V{lH} NMR (CDCI3): 5 13.13 (d, JRW= 155.3). 'H NMR (CDC13): 5 1.45 (s, 2H, CH2 NBD), 1.51 (s, 6H, CH3), 4.00 (s, 2H, CH NBD), 4.60 (s, 4H, =CH NBD), 7.30-7.59 (m, 20H, CeH5). Anal. Calcd for C33H34F6P3Rh: C, 53.53; H, 4.63. Found: C, 53.76; H, 4.68. The NMR data of both diene complexes compare well with those reported for the analogous CIO4" salts.9 2.3. Ir precursors 2.3.1. Preparation of [Ir(COD)Cl]2 This precursor was prepared according to a published procedure.10 To a stirred, dark red solution of IrCl3-3H20 (0.80 g, 0.0027 mol) in a H20/z'-PrOH mixture (5+4 mL) under Ar, COD was added (1.20 mL, 0.0098 mol) via a syringe through a rubber septum. The mixture was left stirring at r.t. for 2 days, to afford an orange precipitate. The precipitate was collected by filtration, washed with cold EtOH (3x8 mL) to afford an orange-red solid that was dried under vacuum. Yield: 0.45 g (50%). ] H NMR (CDC13): 5 1.50 (m, 8H, CH2), 2.20 (m, 8H, CH2), 4.20 (s, 8H, =CH). Anal. Calcd for Ci 6H 2 4Cl 2Ir 2: C, 28.61; H, 3.60. Found: C, 28.66; H, 3.61. The characterization data agree with the reported literature.10'11 2.3.2. Preparation of [Ir(COD)(PR3)2]PF6 (1*) These precursors were prepared according to a published procedure.12'13 In a general method, to an orange suspension of [Ir(COD)Cl]2 (0.150 g, 0.23 mmol) and KPF 6 (0.173 g, 0.94 mmol) in MeOH (3 mL), a solution of the appropriate phosphine PR3 (~ 0.20 g, ~ 0.89 mmol) in MeOH (1 mL) was cannulated through a rubber septum under Ar. The resultant deep red suspension was stirred at r.t. overnight. The solvent was then removed under reduced pressure, the residue redissolved in CH2C12 (4 mL) and the inorganic salt removed by filtration. The limpid red filtrate was then concentrated to ca. 1 mL, and subsequent 20 References on page 23 Chapter 2 addition of E t 2 0 afforded a red precipitate, which was collected by filtration, washed with Et 2 0 ( 3 x 8 mL) and dried under vacuum. R = Ph (l*a), Yield: 0.40 g (90%). 3 1 P{'H} N M R (CDC13): 8 17.39 (s). ' H N M R (CDCI3): 5 1.90-2.30 (m, 8H, CH2 COD), 4.15 (s, 4H, =CH COD), 7.27-7.55 (m, 30H, Ceflj). Anal. Calcd for C44H42F6P3Ir: C, 54.49; H, 4.36. Found: C, 54.62; H, 4.26. The characterization data agree with those in the literature.12 R = p-tolyl (l*b), Yield: 0.57 g (90%). 3 1 P{'H} N M R (CDC13): 5 19.88 (s). ' H N M R (CDCI3): 5 1.88-2.20 (m, 8H, CH2 COD), 2.30 (s, 18H, p-CH3C6H.4), 4.05 (s, 4H, =CH COD), 7.00-7.20 (m, 24H, p - C H j C ^ ) . Anal. Calcd for C5oH54F6P3Ir: C, 56.97; H , 5.16. Found: C, 56.77; H, 5.20. Complex l*b was not synthesized before. R = />-FC6H4 (l*g), Yield: 0.35 g (70%). 3 1 P{ 1 H} N M R (CDCI3): 5 15.32 (s). ' H N M R (CDC13): 8 1.95-2.35 (m, 8H, CH2 COD), 4.19 (s, 4H, =C//COD), 7.00-7.55 (m, 24H,p-YCeH^). 1 9 F{'H} N M R (CDC13): 8 -29.93 (s, 6F,/>-FC 6 H 4 ) . Anal. Calcd for C 4 4 H3 6 Fi 2 P 3 Ir : C, 49.03; H, 3.37. Found: C, 49.15; H, 3.24. The 13 N M R data compare well with those reported for the analogous SbF6_ salt. 2.4. Instrumental Methods Nuclear magnetic resonance (NMR) spectra were recorded on Bruker AC-200E (200 MHz for ' H , 81.0 M H z for 3 1 P{ 1 H} and 188 MHz for ' ^ { ' H } ) , AV300 (300 MHz for ! H , 121.49 M H z for 3 I P { ' H } , 75.48 M H z for 1 3 C), AV400 (400 M H z for *H, 100.62 MHz for 1 3 C) or Varian XL300 (300 MHz for ' H , 121.42 MHz for 3 1 P{ 'H}) spectrometers. Residual solvent protons ('H), external 85% H 3 P 0 4 (^Pj 'H}) or external TFA ( ' ^{ 'H}) were used as references. Variable temperature N M R experiments were performed on the Bruker AV300 instrument. Temperature regulation of the probehead was calibrated using a calibration curve based on the chemical shift separation of the resonances in 4%> MeOH in CD 3 OD according to a standard method.14 A l l coupling constant J values are reported in Hertz. Gas chromatographic analyses were performed on a temperature-programmable Hewlett Packard 5890A instrument containing an HP 17 capillary column and equipped with a flame ionization detector (FID), using He as the carrier gas. Infrared spectra were recorded on an ATLI Mattson Genesis Series FTIR spectrophotometer (range 500 to 4000 cm"1): samples for 21 References on page 23 Chapter 2 analysis were made into KBr pellets. All IR bands are reported in wavenumbers (cm"1). Elemental analyses (C, H, N) were performed by Mr. P. Borda of this Department on a Carlo Erba Instruments EA 1108 CHN-0 analyzer: some samples were dried in an Abderhalden pistol over refluxing EtOH or H 2 0 prior to analysis to remove residual solvents. Mass spectra (EI or FAB) were obtained by Dr. G. Eigendorf and his staff of this Department. All X-ray crystal structures, with the exception of 4b, 14b and 22*a, were determined by Dr. B. O. Patrick and Dr. S. J. Rettig of this Department on a Rigaku/ADSC CCD area detector with graphite monochromated MoKa radiation; Dr. Rettig solved just the structure of 20b. The single crystal X-ray diffraction studies of 4b and 22*a were performed by Dr. V. G. Young, Jr., while that of 14b by Dr. M. Pink, of the X-Ray Crystallographic Laboratory at The University of Minnesota, on a Siemens SMART Platform CCD system (4b and 14b) and on a Bruker SMART System (22*a), with MoKa radiation. 2.5. Hydrogenation studies In a typical catalytic run, a three-neck flask was used in which the central neck was connected to the H 2 inlet, a small side neck, fitted with a half-hole rubber septum, served as the sampling as well as the injection port, and the third was used to charge the flask with solvent (MeOH, 10 mL) and catalyst precursor 1 (~ 0.005 mmol). After 1 was reacted with H 2 (1 atm) in a thermostated bath (30 °C) for 1 h to form 2 ([Rh(H)2(PR3)2(MeOH)2]PF6, Section 3.2) the substrate was injected (~ 0.50 mmol, 100:1) via a microsyringe and the reaction mixture sampled (5 uL) periodically, and conversions monitored by GC analysis. In some cases, conversions to the product were confirmed by *H NMR of the residue after solvent evaporation. 22 References on page 23 Chapter 2 2.6. References (1) Perrin, D. D.; Amarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals, 2nd ed.; Pergamon Press: Oxford, 1980. (2) Org. Synth. 1977, 56, 3. (3) Layer, W. R. Chem. Rev. 1963, 63, 489. (4) Juday, R.; Atkins, H. J. Am. Chem. Soc. 1955, 77, 4559. (5) Fogg, D. E. Ph.D. Dissertation, The University of British Columbia, 1994. (6) Chatt, J.; Venanzi, L. M. J. Chem. Soc. A 1957, 4735. (7) Giordano, G.; Crabtree, R. H. Inorg. Synth. 1979,19, 218. (8) Abel, E. W.; Bennett, M. A.; Wilkinson, G. J. Chem. Soc. A 1959, 3178. (9) Schrock, R. R.; Osborn, J. A. J. Am. Chem. Soc. 1971, 93, 2397. (10) Crabtree, R. H.; Morris, G. E. J. Organomet. Chem. 1977,135, 395. (11) Herde, J. L.; Lambert, J. C ; Senoff, C. V. Inorg. Synth. 1974,15, 18. (12) Haines, L. M.; Singleton, E. J. Chem. Soc, Dalton 1972, 1891. (13) Crabtree, R. H.; Parnell, C. P.; Uriarte, R. J. Organometallics 1987, 6, 696. (14) Braun, S.; Kalinowski, H.-O.; Berger, S. 100 and More Basic NMR Experiments: A Practical Course; VCH Publishers: New York, 1996. 23 References on page 23 Chapter 3 Chapter 3 Rh AND Ir CATALYST PRECURSORS 3.1. Introduction . Cationic complexes of the type [M(diene)(PR3)2]A (diene = COD, NBD; A = monoanion; M = Rh, 1; M = Ir, l*)1'2 have long been known to catalyze the homogeneous H2-hydrogenation of a variety of unsaturated, like C=C,3"6 C=0 7 and C=N 8 ' 9 moieties. These precursors operate under relatively mild conditions compared to analogous complexes containing chelating, bidentate phosphine ligands (see Section 1.3.1). When treated with molecular H 2 at ambient conditions, these precursors react in the appropriate solvent medium and, depending on the phosphine, usually show the stoichiometry of Fig. 3.1 (solvent = MeOH, acetone). The "resting state" of the active + A" P R 3 H„_ | i i 0 so lv ^rvT + alkane solvent H | ^ s o l v P R 3 2 Figure 3.1. Reaction of [M(COD)(PR 3) 2] + with H 2 (M = Rh 1, Ir 1*; R = Ph, a; p-tolyl, b; Bz, c; Ph 2Me, d; /?-ClC 6 H 4 , e;/>-FC6H4, g). catalytic species, formed in solution after complete saturation of the diene moiety and subsequent liberation of the corresponding alkane have occurred, is a six-coordinate, M(III)-dihydrido complex; the two phosphine ligands in 1 rearrange from a mutually cis to a trans geometry in 2. Geometrical constraints for the same chemistry to occur are inherent in the use of bidentate phosphine ligands possessing a "fixed" geometry, and hence such systems usually require more severe experimental conditions for any hydrogenation catalysis (see Section 1.3.1). The mild conditions under which these Rh-24 References on page 67 Chapter 3 and Ir-based systems 1 actively function as hydrogenation catalysts render them attractive for achieving the homogeneous riVhydrogenation of imines at ambient conditions. As well, a better understanding of the mechanistic fundamentals governing the process may be gained through an easier access to spectroscopic investigations. From both an industrial and academic perspective, the hydrogenation of C=N moieties is an important reaction, particularly for prochiral substrates that would generate chiral products in enantioselective fashion (see Sections 1.2 and 1.3). However, much less progress has been made in the elucidation of their mechanistic aspects, in contrast with the far greater extent to which they are understood for the hydrogenation of C=C and C=0 moieties. In this Chapter, the syntheses of a series of Rh and Ir catalyst precursors with different combinations of phosphines, diene and counterion are reported. The vast majority of this work was carried out on the two systems [M(COD)(PR3)2]PF6 (1) (R = Ph, /7-tolyl; M = Rh and Ir). 25 References on page 67 Chapter 3 3.2. Rhodium Hydride Complexes The Pvh(III) complexes [Rh(H)2(PR3)2(acetone)2]PF6 (2) were isolated for R = Ph (2a), /?-tolyl (2b), Bz (2c) and were characterized by 31P{'H} and ! H NMR spectroscopy (Table 3.1), elemental analysis and IR spectroscopy. Analogous complexes with PR3 = Ph2PMe (2d') and R = /?-ClC6H4 (2e') were formed in CD 3OD and characterized in situ by 3IP{'H} and 'H NMR spectroscopy. Isolation of the MeOH-solvated [Rh(H)2(PR3)2(MeOH)2]PF6 was possible only for R = Bz (2c'). In most cases, the expected 31P{1H} NMR doublet for each complex (when under 1 atm H2) is observed, due to coupling of the two equivalent 3 1P nuclei to 1 0 3Rh (/ = 1/2, 100%). The J R h P coupling constants (117-120) are within the range corresponding to a trans arrangement of the phosphine ligands, and are consistently smaller than those observed for compounds with cis phosphines ( J R h p > 130), as for instance in the case of compounds of type 1 (see below). The Rh-H IR stretching frequency (~ 2100 cm"1) is indicative of mutually cis hydride ligands;3 also, the recorded vc=o of the coordinated acetone is in agreement with previously reported data,10 and is characteristically lower in frequency compared to that of free acetone. The 'H NMR spectra of acetone-c/6 solutions of 2 show one doublet of triplets (for 2a, 8 -20.74, dt, J R m H = 25, V H P = 15), due to coupling of the hydrides to 1 0 3Rh and two equivalent 3 1P nuclei (Fig. 3.2, (a); see also Table 3.1). Literature data for a number of octahedral hydrido-phosphine complexes11 show that the 2JHP coupling constants (ca. 15 Hz) are consistent with two equivalent hydride ligands cis to a P-atom; values range from 80 to 150 Hz for hydride ligands trans to P.1 1 When recorded in CD 3OD, however, the high-field *H NMR signals for the two hydrides in 2b display further multiplicity; the signals were poorly resolved and therefore a complete characterization of the coupling pattern could not be established (Fig. 3.2, (b)). The spectra were recorded only at r.t.. Systems of this type are known to undergo rapid solvent exchange, due to the solvent molecules being trans to the hydrido ligands, which exert a strong rrans-labilizing effect; the exchange rate is also dependent upon the 1 9 nature of the tertiary phosphine ligand. The data in CD 3OD indicate that the two hydrides are chemically inequivalent, consistent with each being trans to a different solvent molecule. A competitive process for the metal center between the two solvents, as 26 References on page 67 Chapter 3 shown in Scheme 1, could account for the data. Complex 2a showed a behavior similar to that of 2b. (a) (b) J acetone-<i6 C D 3 O D Figure 3.2. High-field 'H NMR spectra (300 MHz, 298 K) of [Rh(H)2(PR3)2-(solv)2]PF6 (R = p-tolyl; solv = acetone, 2b; MeOH, 2b'). PR, H, Rh H PR PFR PR, PFK P R 3 ? n + pF 6 ^ O C M e 2 CD3OD H " „ I . . v O C M e 2 CD 3 OD H „ ( | ,>OCD3 O C M e 2 acetone H | O C D 3 acetone H | ^ O C D g PR3 D PR3 D Scheme 1. Solvent exchange of isolated complexes 2 in CD3OD solution. The corresponding signal in the 31P{'H} NMR spectrum of 2b (5 39.41, J R h P = 119) is the same as that observed for [Rh(H)2(P/?-tolyl3)2(CD3OD)2]+ generated in-situ from the precursor lb in CD 3OD under H 2 , and is different from that of 2b measured in acetone-^ (8 43.45, / Rhp = 117). However, for the in situ formed species 2b' the hydrides appear as one doublet of triplets (8 -22.30, dt, J R hH = 27, 2JHP = 16) with no further multiplicity, as expected (Fig. 3.3). The 31P{!H} NMR spectra in CD 3OD show that the acetone ligands of 2b are displaced, an apparent conflict with the ! H NMR evidence: it appears that the phosphines cis to the solvent ligands are not sensitive to the exchange process ongoing in the equatorial plane. VT NMR studies could elucidate this apparent 27 References on page 67 Chapter 3 discrepancy. H NMR studies for the exchange of one solvent molecule were previously carried out on the [Rh(H)2(PPh3)2(solv)2]+ system in CD2CI2, and showed that the most C D 3 O D Figure 3.3. High-field ] H NMR spectrum (300 MHz, 298 K) of [Rh(H)2(PR3)2-(CD3OD)2]PF6 (R = p-tolyl, 2b') generated in-situ. labile complexes contained coordinated acetone13 (i.e. 2a in this work). Reportedly, in the spectra recorded at 253 K after the addition of 1 equivalent of pyridine to the acetone species in CD2CI2, the hydride resonances consisted of two separate doublets of triplets due to C W - V H H coupling; at r.t the signals coalesced to give a doublet of triplets due to fast solvent exchange averaging the environment trans to the hydrido ligands. In this thesis work, the spectra observed at r.t. for 2a in acetone-^ are qualitatively similar (Fig. 3.2, (a)). However, MeOH appears to bind less strongly and is not capable of preventing acetone from re-coordination, thus giving rise to a chemically inequivalent environment trans to each hydride even at r.t. (Fig 3.2, (b)). A classification of the donor abilities of different solvents has been defined by a donor number (DN)/ The DN for MeOH is slightly higher than that of acetone (20 vs. 17), and the latter is therefore expected to be thermodynamically a somewhat poorer donor. The spectroscopic evidence obtained in this work implies that MeOH is probably also the more kinetically labile ligand (i.e. more rapidly exchanging), at least at a Rh(III) center in the presence of strongly £ra«s-directing H" ligands. No 31P{'H} NMR data were The DN measures the negative enthalpy of the reaction of solvents as Lewis bases toward a 17 specific Lewis acid center (SbCl5). Its general applicability has been questioned, particularly as being defined relative to a single acidic center. 28 References on page 67 Chapter 3 reported at all for the Rh systems.13 In this thesis work, the 3 1 P{ 1 H} N M R spectra at room temperature were solvent-dependent, and the doublet is slightly broader in acetone-fife (W>A = 17) than in CD3OD (w>/2 = 10). This observation is consistent with the MeOH systems being more labile, thus providing for the enhanced resolution of the 3 1 P{'H} N M R signal, and also accounts for the generally unattainable isolation of the MeOH complexes. The exception is with R = Bz, when [Rh(H)2(PBz3)2(MeOH)2]PF6 (2c') precipitated directly from solution; the hydride signals appear as a single doublet of triplets in CD 3 OD and in acetone-<i6, while the corresponding 3 1 P{'H} N M R spectra in the two solvents indicate that the MeOH ligands are fully displaced in acetone. Table 3.1. Selected N M R data for the [Rh(H) 2(PR 3) 2(solv) 2]PF 6 (2) complexes under 1 atm H 2 . 'H NMR (5)* 3 1P{'H} NMR (5)c Compound" acetone-<af6 C D 3 O D acetone-d6 C D 3 O D (2a) -20.74 (25, 15) -22.10 (m) 45.61 (117) 41.80 (120) (2b) -20.95 (26, 15) -22.25 (m) 43.45 (117) 39.41 (119) (2c) -22.39 (26, 15) -23.54 (26, 16) 31.49 (121, 13/ 32.92 (123, 13/ ( 2 d ' / - -22.60 (m) - 25.84(118) (2e') r f - -22.10 (24, 15) - 42.06(121) (2c-r -22.40 (26, 16) -23.63 (25, 15) 31.70 (122, 10) 32.83 (123) " Isolated solids where (solv) = acetone, unless stated otherwise. * High-field signal for Rh(H)2: doublet of triplets (/RI,H, VHp) unless stated otherwise. c Doublets at 293 K unless stated otherwise (JRhp). d Formed in-situ in CD 3OD at 293 K. e Isolated for (solv) = MeOH. 7 Doublet of triplets at 293 K (J R h P , 2JHP). The above observations directly relate to the marked solvent-dependence of these complexes with respect to homogeneous H2-hydrogenation catalysis (see Section 5.2). Hydrogenation of an imine substrate, when achieved, was observed to take place only in MeOH, with virtually no conversion when corresponding reactions were performed in acetone. This empirical evidence correlates with the observation that MeOH is the more labile solvent and provides easier access to the metal center for an incoming substrate. 29 References on page 67 Chapter 3 The isolated Rh-bis(hydrido) complexes, upon dissolution in MeOH or acetone under Ar, reductively eliminate H 2 (markedly slower in acetone) to form the solvated species m-[Rh(PR3)2(solv)2]PF6 (3) (Fig. 3.4), as detected by 3l¥{lK} NMR spectroscopy (see also Section 3.3.2). The reductive elimination goes to completion P R 3 PF 6 " | + P F 6 H " . I - > s o l v solvent R 3 p - - so lv ^ so lv PR .Rh ^ " R h + H 2 H | ^ s R 3 P ^ s o l v v 3 2 Figure 3.4. General scheme for the reductive elimination of H 2 from species 2. irreversibly (under Ar) over different timespans, depending on the nature of the phosphine and particularly the solvent. 31P{1H} and *H NMR data for species 3 are given in Table 3.2. The behavior is well known, and it has been reported that on treating the Table 3.2. 31P{'H} NMR data for selected in situ c«-[Rh(PR 3) 2(solv) 2]PF 6 (3) complexes. 3 ,P{'H} N M R (5)" Compound acetone-e?6 CD 3OD (3a) 54.20 (202) 57.02 (207) (3b) 52.66 (202) 55.15 (208) (3c) 37.42 (204) 38.33 (206) " Doublets at 293 K (JR h P). diene precursors 1 with H 2 (see Fig. 3.1) and depending on the nature of the phosphine, either 2 or 3 can be formed in MeOH solutions. When PR3 = Ph2PCH3, after initial formation of 2, the formation of 3 occurs spontaneously upon standing of the solution for 30 References on page 67 Chapter 3 18 20 min. In the presence of a chelating diphosphine such as 1,2-(diphenylphosphino)-ethane (dppe), the corresponding systems of type 1 consume 2 moles of H 2 and form 3 exclusively.19 In this thesis work, for the PPh3 derivative 2a, partial formation of 3a' was observed (by 31P{'H} NMR) to occur immediately upon dissolution of 2a in MeOH under Ar, and complete conversion to 3a' was evident after 18 h; these findings contrast 1 Q with literature data, where only trace 3a' was said to form. For the P(j9-tolyl)3 system in MeOH under Ar, 2b was still present even after 24 h (3b':2b ~ 5:1). In acetone-c/6 solutions under Ar, 2a and 2b underwent H 2 loss much more slowly, and in both cases these were still the major species detected even after 2 days. Under 1 atm H 2 , Rh-bis(hydrido) species 2 remained stable over 48 h. A 31P{'H} NMR investigation of a solution of 2b in the weakly coordinating CD2C12 showed elimination of H 2 , initially accompanied by the formation of a species which appears as a doublet in the 31P{'H} NMR (8 44.77 d, J R h p = 206). The identity of this species remains unknown. However, it is eventually fully converted to a product corresponding to an 8-line, AMX-type pattern (2 dd), which indicates a system containing two inequivalent phosphines. These systems were determined to possess the dimeric structure [Rh2(PR3)4][PF6]2 (4), and constitute a new class of compounds, presented and discussed in the next section. Of note, treatment of a general precursor 1 with H 2 in CD2C12 immediately affords 4 as the only product, and no high-field signals due to a hydride species were detected: this demonstrates that following saturation of the diene moiety, H 2 is not retained by the system because of the lack of coordinating ability of the solvent. 3.3. Synthesis of [Rh2(PR3)4][PF6]2 (4) A new class of versatile starting materials was obtained by removing solvent and H 2 from solutions of some of the Rh-bis(hydrido) complexes. The new species are dimeric, with each Rh center bonded to two P-atoms and linked, in the solid state, to an rf-arene moiety present on the phosphine ligands of the other Rh atom. The compounds have the general formulation [Rh2(PR3)4][PF6]2 and were isolated for R = p-tolyl (4b), Ph (4a) and characterized by 31P{'H} and *H NMR spectroscopy, elemental analysis and X-ray crystallography. Such 7c-arene bonding is not uncommon in Rh(I) complexes,20"24 and 31 References on page 67 Chapter 3 this class of compounds still attracts much interest. The only similar compound reported in the literature is that in which the phosphine ligand is dppe (= diphos); this complex was crystallized from C F 3 C H 2 O H as the solvated tetrafluoroborate salt [Pvh2(diphos)2][BF4]2-CF3CH20H (Fig. 3.5). 1 9 ' 2 7 The dication was successfully employed as a homogeneous catalyst in the hydrogenation of some olefinic substrates, including the prochiral methyl-(Z)-a-acetamidocinnamate,28 and some arenes.29 Figure 3.5. Structural representation of the dication [Rh2(diphos)2] . Another related example is the Rh(III)-hydrido dimer [(Me2SiC6H5)4Rh2H2]30 (Fig. 3.6) in which the alkylarylsilane ligands display a coordination mode remarkably similar to the one adopted by the phosphines in [Rh2(PR3)4]2+ (4): for each Rh, one silane ligand links the metals through a bridging phenyl group, while another is simply a -bonded to the Rh and not involved in any n6-bridging, in a fashion virtually identical to that observed in this work (see below). Figure 3.6. Structural representation of [(Me2SiC6H5)4Rh2H2]. 32 References on page 67 Chapter 3 The formation of the dinuclear species 4 containing monodentate tertiary phosphines is critically dependent on the nature of the phosphine ligands involved, and occurs only in the presence of tris-aryl, relatively electron-rich phosphines, with the aryl fragments either unsubstituted (PPh3) or containing electron-donating substituents (P(/> tolyl)3). In the presence of electron-withdrawing groups on the aryl moieties (p-F or p-Cl), the hydrogenation step did not go to completion, whereas with a reduced number of aryl groups available for bridging coordination (Ph2PCH3), the residue after removal of the solvent was insoluble in most deuterated solvents; the latter case conflicts somewhat with the literature dppe system in which each P-atom bears only two phenyl groups. 3.3.1. Solid State Characterization of [Rh2(PR3)4][PF6]2 (R = Ph 4a,/>-tolyl 4b) X-ray quality crystals of [Rh2(Pp-tolyl3)4][PF0]2 (4b) were grown from a CHCl3/hexanes solvent mixture, whereas [Rh2(PPh3)4][PF6]2 (4a) was isolated from a CH2Cl2/hexanes mixture by Dr. M. Ezhova of this laboratory. In both cases, the solid state structures show that the bridging arene moiety adopts an n6-coordination mode to the metal center (Figs. 3.7, 3.8). Both molecules are centrosymmetric and crystallize in Figure 3.7. ORTEP diagram for the dication [Rh2(PR3)4] (R = p-tolyl, 4b) with 50% probability thermal ellipsoids. C14 C35 33 References on page 67 Chapter 3 Figure 3.8. ORTEP diagram for the dication [Rh2(PR3)4]2+ (R = Ph, 4a) with 50% probability thermal ellipsoids. the PI space group. The distance between the two metal centers (4.4827(2) A for 4b and 4.5196(6) A for 4a) is well beyond the value expected for any significant Rh-Rh interaction (2.7-2.9 A).2 1 '2 2 For [Rh2(diphos)2]2+, the shorter Rh-Rh distance of 4.275 A likely arises from the presence of a chelating phosphine with its smaller bite angle (Pl-Rh-P2 ~ 84° vs. values of 93-95° for the PR3 systems), which brings the two metal centers closer. The distances Rhl-(C1A-C6A) between the metal and the ring C-atoms, as shown in Table 3.3, fall within the range reported for n6-arene interactions (average Rh-Carenc = 2.343(2) A for 4b and 2.337(5) A for 4a).21'22'31 The differences between each of these distances clearly shows that the n6-arene ring is somewhat distorted. The Rh(l)-C(nA) distances in 4b decrease in the order n = 4>5>1>2>3>6, with the result that Rh(l)-C(3A) and Rh(l)-C(6A) are ca. 0.1 A shorter than the average of the four remaining ones, consistent with a deviation from planarity towards a distorted boat conformation as shown in Fig. 3.9. Such distortions are not unusual and have been previously 34 References on page 67 Chapter 3 Figure 3.9. Representation of the deviation from planarity of the coordinated arene in [Rh2(PR3)4][PF6]2 (R = /?-tolyl, 4b) (not to scale). Table 3.3. Selected bond lengths for [Rh 2 (PR 3 ) 4 ] 2 + (R = p-tolyl, 4b; Ph, 4a) with estimated standard deviations in parentheses. Length (A) Bond 4b 4a Rh( l ) -Rh( lA) 4.4827(2) 4.5196(6) Rh(l)-P(l) 2.2673(6) 2.259(1) Rh(l)-P(2) 2.2688(6) 2.264(1) Rh(l)-C(1A) 2.379(2) 2.403(4) Rh(l)-C(2A) 2.338(2) 2.372(4) Rh(l)-C(3A) 2.278(2) 2.281(5) Rh(l)-C(4A) 2.404(2) 2.355(5) Rh(l)-C(5A) 2.381(2) 2.343(5) Rh(l)-C(6A) 2.276(2) 2.270(4) P( l ) -C( l ) 1.851(2) 1.843(5) C(1A)-C(2A) 1.411(3) 1.411(7) C(2A)-C(3A) 1.418(3) 1.422(7) C(3A)-C(4A) 1.418(4) 1.427(8) C(4A)-C(5A) 1.407(4) 1.397(8) C(5A)-C(6A) 1.411(3) 1.419(7) C(6A)-C(1A) 1.420(3) 1.417(7) 35 References on page 67 Chapter 3 20 22 24 26 32 30 6 observed ' ' " ' or inferred. Among the general n -arene-ML2 compounds, the bending of the distorted portion of the ring has been observed to occur both away from or towards the metal center.32 There are two possible limiting conformations, both with C2v symmetry: one (Fig. 3.10, (a)) has the plane containing M L 2 bisecting two C=C bonds of the ring (between arbitrarily labelled ortho and meta positions), with the two para C-atoms forming a vector normal to the plane and being bent away from the metal; the z (a) (b) Figure 3.10. General scheme for possible distortion modes of coordinated arenes. alternative conformation (Fig. 3.10, (b)) has the same ML2 plane bisecting the ring but containing the para positions, which now bend towards the metal.3 2 In complexes 4a and 4b, the conformation observed is of type (b), with the plane containing the Pl-Rh-P2 subunit bisecting the ring through C(3A) and C(6A), which bend towards the metal. Extensive theoretical modeling has been carried on metal-arene systems: the factors determining the deviation from planarity are thought to be mainly electronic, rather than steric, as the n6-arene-metal orbitals and the donor lone-pairs of L2 overlap.32 The HOMO of these combinations is mostly metal-<fyz and -d^ in character for (a) and (b), respectively, and is antibonding relative to a 7t-orbital of the arene, with a maximum antibonding interaction with the para C-atoms in conformation (a), and with the other four (0, ni) C-atoms in conformation (b). It is easy to see how a relative stabilization is achieved in each case by minimization of such an antibonding interaction through the indicated distortion: an alternative way to picture case (b) is to imagine the four C-atoms bending upwards, away from the metal. Structural characterization of the mononuclear Rh(I)-n6-arene complexes [(r16-C6H5CH2CH2CH2P,Pr2-K-P)Rh(C8H14)]+ (i), 2 6 [ ( T I 6 - C 6 H 5 -CH2CH2P'Pr2-K-P)Rh(C8H14)]+ (ii), 2 6 and [(r|6-jp-CH3C6H4)Rh{CH3(CH2)3P(C6H5)2}2]+ (iii) reveal conformation (b), the ring assuming a slightly distorted, inverse boat 36 References on page 67 Chapter 3 conformation with bow and stern (para C-atoms) pointing towards the Rh. Minimal distortion in (i) when compared to that in (ii) was attributed to the release of strain in the P-Rh-n6-arene cycle because of the presence of an extra C-atom in the phosphine "arm" directly bearing the coordinating phenyl group, and this may suggest that deviations from planarity can be more generally accounted for as a combination of electronic and steric factors. In examples of coordination of the tetraphenylborate anion to Rh through one arene moiety, the phenomenon is also observed; in [(diphos)Rh(n6-C6H5BPh3)]+ a (b)-like geometry was determined,24 with Rh-Carene distances virtually identical to those presented for 4a and 4b. An (a)-type conformation is observed in [{P(OMe)3}2Rh(n6-C6H5BPh3)]+, the bow and stern of the distorted boat pointing away from the metal.20 Extreme deviation from planarity involving two adjacent C-atoms of the ring has also been observed, where a shift of the ring off the metal-centroid axis is accompanied by a bending away from the metal of one C=C bond, leading to an n4-coordination mode. Again, the reasons for this behavior are thought to be mostly electronic in nature.32 In most rf-arene complexes, a significant distortion from planarity of the coordinating arene is reflected by differences in the Rh-Carene distances, with only four C-atoms bonding, and significant differences in the C-C bond lengths are observed. The C=C distance of the uncomplexed bond is significantly shorter than those of the n4-moiety, and is representative of a conventional C=C double bond.32'33 In the structurally characterized Rh(I) complex [(COD)Rh'-CoIII(TMPP-0)2]2+ with a phenyl ring ^-coordinated to Rh (TMPP = tris(2,4,6-trimethoxyphenyl)phosphine, TMPP-0 = [P(C6H2(OMe)3)2(C6H2-(OMe)20)]-),34 the six C-C distances are not significantly different from one another, this being inconsistent with a localized bonding picture. In the present work with 4a and 4b, the Rh-Carene distances are all within the expected bonding range for an n6-arene system and the differences within the ring C-C bond lengths are not significant (average C-C = 1.414(4) A in 4b, and 1.416(8) A in 4a, see Table 3.3). The angles defined by the each of the ring C-atoms, the Rh center and each P-atom, similar for 4a and 4b (Table 3.4), have very similar values for Pl-Rh-Carene and P2-Rh-Carene in each system. The Rh-P distances and Pl-Rh-P2 angles in both molecules are similar to those of other arene-bridged Rh(I) complexes containing monodentate tertiary phosphines.25'26 37 References on page 67 Chapter 3 Table 3.4. Selected angles for [Rh2(PR3)4] (R = p-tolyl, 4b; Ph, 4a) with estimated standard deviations in parentheses Angle (°) Bond 4b 4a Rh(l)-P(l] -C(l) 109.17(7) 109.8(1) P(l)-Rh(l] -P(2) 95.23(2) 93.67(4) P(l)-Rh(l] -C(1A) 107.67(5) 107.1(1) P(l)-Rh(l) -C(2A) 137.93(5) 135.8(1) P(l)-Rh(l} -C(3A) 169.89(6) 170.1(1) P(l)-Rh(l} -C(4A) 140.92(7) 144.1(1) P(l)-Rh(i; -C(5A) 110.35(6) 112.6(1) P(l)-Rh(i; -C(6A) 95.50(6) 96.2(1) P(2)-Rh(i: -C(1A) 142.21(6) 143.7(1) P(2)-Rh(i: >-C(2A) 110.36(6) 112.0(1) P(2)-Rh(i: -C(3A) 94.84(6) 95.2(1) P(2)-Rh(i: -C(4A) 106.29(6) 106.0(1) P(2)-Rh(i; >-C(5A) 135.98(6) 135.3(1) P(2)-Rh(i: l-C(6A) 168.68(6) 169.4(1) C(2A)-Rh( ;i)-C(4A) 63.29(8) 63.2(4) 3.3.2. Solution Behavior of [Rh2(PR3)4] [PF6]2 (R = Ph, 4a; /Molyl, 4b) The solution behavior of 4a and 4b is critically dependent on the solvent. In non-or weakly-coordinating media (CDC13, CD2C12) the dimeric assembly is thought to be retained, although the possibility of higher nuclearity species cannot be ruled out; the limited stability of 4a and 4b even in these solvents under Ar precluded any reliable solution data to examine this possibility. The expected 8-line pattern in the 31P{'fi} NMR 38 References on page 67 Chapter 3 spectrum of the dication 4b (an AMX, 2dd pattern) is sharp and well separated as shown i , , r - i i i i | i i i , i i i , , | i i , i i i , i i | i , i i i , i i i | i , i , | ppm 55 50 45 40 35 30 25 Figure 3.11. 31P{'H} NMR spectrum (121 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = p-tolyl, 4b) in CD2C12 or CDC13 (8 39.63 dd, J^v = 212.6,2JPP = 38; 43.09 dd, JRhP = 202.2, V p P = 38). in Fig. 3.11. The sensitivity of a Rh(I) n4-arene moiety to the nature of the solvent has been reported,34 and the bonding to the arene ring was also only observed in non-coordinating media (CD2C12 or CDCI3, the two solvent systems giving rise to virtually identical 31P{'H} and *H NMR spectra). By comparison with literature data for monomeric Rh(I) units containing monodentate phosphines (one of which is involved in n6-bridging),26 the observed chemical shift range and . / R n p values observed are in agreement with those reported for "bridging" phosphines. Correlations between the observed shifts and JR^P values with the number of methyl substituents on the bridging arene have also been proposed,25 whereby increased electron-donor ability of the arene leads to a linear increase in the J R h p value, in conjunction with more downfield shifts, although the effect trails off with increasing substitution of the arene, as structural and steric factors predominate over electronic ones.35 3 1 P- 1 H HETCOR NMR experiments (Fig. 3.12) allow for the assignment of the 8 39.63 upfield resonance of 4b to the "bridging" phosphine, and the 8 43.09 shift to the monodentate one (see below). The system contravenes the J-b correlation cited above, whereby the more downfield resonance is associated with the larger value of J ^ p , but the findings are in agreement with data for the [(n6:n1-C6H50(CH2)2PPh2)Rh(ri1-PhO(CH2)2PPh2)]+ system reported in the literature.36 The ] H NMR of 4b in CD2C12 shows upfield shifted resonances for the protons on the bridging aryl rings (Fig. 3.13), and their positions in the spectrum are comparable with those reported in similar systems (e.g. in [(n6-C7H7)Rh(CH3(CH2)3-39 References on page 67 Chapter 3 P(C 6 H 5 ) 2 )2] + ) . 2 5 It appears, however, that an asymmetric, n4-bridging mode is adopted in solution. One upfield doublet (5 5.99 d, V H H = 6.6) is assigned to n4-aryl m-protons, each PD" 7,2 7.0 6.8 6,6 Figure 3.12. 3 1 P- ] H HETCOR NMR spectrum (162 and 400 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = p-tolyl, 4b) in CD2C12 (selected regions; the "extra" peaks indicated by arrows are not real but are due to scale enlargement). of which is coupled to the o-proton through a three-bond coupling. A second triplet (8 6.60 t, V H H = 6.6) is attributed to o-protons: 'H{31P} NMR of the same CD2C12 solution (Fig. 3.14) shows that the multiplicity of this signal now collapses to a doublet, without change in chemical shift or 3J"H , implying that these protons are also coupled to 3 1P, although with such a small V H p value that the expected doublet of doublets in the coupled *H NMR spectrum appears as a pseudo-triplet. Careful analysis of the integration values (particularly in the 'H{31P} NMR spectrum) is indeed consistent with an n4-bound arene (see Fig. 3.14). It has previously been suggested on the basis of j H NMR data, for instance in the case of [(n4-COD)RhI(nn-C7H8)]+ (n = 4, 6),37 that such molecular cations may adopt either a 16- or 18-e configuration depending on the hapticity of the arene ring (n4 vs. r\6), which can vary from the one observed in the solid state. 40 References on page 67 Chapter 3 p-Mz i i i 1 1 i r ppm B 7 6 5 -1 3 2 Figure 3.13. 'H NMR spectrum (300 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = /7-tolyl, 4b) in CD2C12. 1 | I [ \ ] p POn 6 7 6 5 4 3 2 Figure 3.14. 'H{31P} NMR spectrum (300 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = p-tolyl, 4b) in CD2C12 (5 5.99 d, 3H, m-n4-C6#4CH3, V H H = 6.6; 6.60 d, 3H, o-n4-C6i/4CH3, V H H = 6.6; 6.80-7.30 m, 42H, C ^ C H ^ . 41 References on page 67 Chapter 3 In addition, the r.t. 1 3 C NMR spectrum of 4b in CD2C12 (Fig. 3.15) provides further evidence for the proposed asymmetry in the bridging coordination of the aryl moieties. Although not incontestably showing n4-coordination, detection of 4 resonances for the p-CR3 (8 18.95 s, 20.96 s, 21.06 s, 21.37 s) and for the ipso C-atoms (8 140.91 s, 141.77 s, 142.07 s, 144.40 s), each in an approximate 1:6:4:1 ratio, shows that these C-atoms on the bridging aryls experience different chemical environments, supporting a localized bonding picture between each Rh center with different bonds of each aryl. Several limiting structures can be envisioned for this type of coordination, and in opm ' 26 24 22 20 18 16 14 Figure 3.15. 13C{]H} NMR spectrum (75 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = p-tolyl, 4b) in CD2C12 (p-C 6H 4CH 3 region). principle an n6-mode for one of the rings is not excluded. The , 3 C NMR evidence is thus consistent with the two bridged aryl moieties being bonded differently. Characteristically25 upfield-shifted resonances for the o- and m-C of the bridging aryls are also detected (8 102.65, 103.32, 2 bs); however, the equivocal hapticities of these groups preclude a clear assignment for these resonances. The ] H resonances of the jr>CH3 groups appear as two resonances in a 1:5 ratio, corresponding to the "bridging" and monodentate phosphines, respectively. Each resonance displays a further splitting which disappears 31 SI upon P-decouphng, suggesting that an unusual long-range coupling to P may also be operative for these protons. The 2 doublets of doublets in the 31P{1H} NMR spectrum of the PPh3 analogue 4a partially overlap (Fig. 3.16), resulting in a spectrum that resembles an ABX pattern; this may suggest that the less electron-rich phenyl rings of PPh3 possess a somewhat 42 References on page 67 Chapter 3 diminished donor ability, which results in a less efficient bridging capacity compared to the /7-tolyl moiety (at least in solution). Again, based on 3 1 P-'H HETCOR NMR ' ' ' ' | ' • ' ' | ' ' ' ' | ' ' ' ' 1 ' ' ' ' 1 ' ' ' ' 1 ' ' '—^ 1 ' ' 1 1 1 ' ' 1 ' 1 r— DDm 55.0 52.5 50.0 47.5 45.0 42.5 40.0 37.5 35,0 Figure 3.16. 31P{'H} NMR spectrum (121 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = Ph, 4a) in CD2C12. experiments and comparisons with the reported literature,26 the more downfield resonance, which in this case is associated with the larger jRhp value, is assigned to the "bridging" phosphine (§ 47.47 dd, J^P = 210.9, 27 P P = 37), and the upfield one to the monodentate phosphine (8 45.46 dd, JKh? = 198.8, 2 J P P = 38). In addition, the downfield resonance clearly shows that each peak is further split into a doublet, with small P-H coupling ( 3JHp = 6.3), as well as a strong correlation in the -"P-'H HETCOR NMR with resonances in the more downfield aromatic region assigned to the ortho protons on the two phenyl rings of the bridging phosphine. The overlapping of the two sets of signals is even more pronounced in CDCI3, as shown in Fig. 3.17 (8 46.17 dd, j R h P = 201.0,2JPP = 36; 47.15 dd, J R h p = 215.0, J P P = 36), thus indicating a solvent dependence for the degree of overlap. Figure 3.17. 31P{'H} NMR spectrum (121 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = Ph, 4a) in CDC13. 43 References on page 67 Chapter 3 The corresponding 'H NMR spectrum of 4a in CD2C12 (Fig. 3.18) shows the typical upfield shifted resonances, similar to those reported for [(n6:^1-C6H50(CH2)2PPh2)Rh(r|1-PhO(CH2)2PPh2)]+.36 The most upfield resonance appears as a broad, poorly resolved triplet (5 4.90 pt, V H H ~ 6.0), and is attributed to ring-current effects on the p-H of the bridging arene.38 The sharp triplet (8 6.89 t, V H H = 6.0), integrating as 2:1 with the resonance at 8 4.90, is assigned to the meta protons. The five Ph protons would be expected to give rise to a set of three distinctive upfield-shifted resonances upon coordination of the Ph group to the Rh: the observation of only two suggests that the third set (hidden in the 8 7.0-7.8 region) is perhaps due to protons which, although part of the bridging ring, are not subjected to an upfield shift because they are likely bound to a C=C moiety not directly bonded to the metal. In addition, similar considerations on the integration of the entire spectrum perhaps provide additional evidence for the preference in solution for an n4-coordination mode, as observed in 4b. 'H{31P} NMR spectra showed a moderate increase in the resolution of the triplet at 8 4.90, while 31P-decoupling did not affect the triplet at 8 6.89. ' 1 ' • ' i I ' 1 I 1 I I PP" B 7 6 5 4 3 Figure 3.18. ! H NMR spectrum (300 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = Ph, 4a) in CD2C12 (8 4.90 pt, 2H, vf-p-CeHs, V H H = 6; 6.89 t, 4H, rf-m-Cffls, V H H = 6; 7.05-7.70 m, 54H, QZ/s). 44 References on page 67 Chapter 3 The same ' H NMR features are seen in CDCI3, except the sharp triplet is now more downfield (5 7.90 t, 3 J H H - 6.5) and the still poorly resolved p-R resonates further upfield (5 4 .34 pt, V H H ~ 6.5). The ' H NMR evidence seems to suggest that an n4-bridging mode exists in solution (Fig. 3.18); only three of the five protons on each bridging ring are shifted upfield (6F£ total, 2 H at 4 .90, 4 H at 6.89), the remaining two being hidden within the aromatic region (54 H total). Figure 3.19. Proposed r\ -coordination mode adopted by 4a and for 4b in solution. 31 1 The P { H} NMR spectra of 4a imply fluxional behavior in solution, likely due to exchange of bridging phenyl groups and an averaging of the n4- and n6-hapticities; each of the three aryl rings on the bridging phosphine may be exchanging with one another. The NMR spectra of 4a (with poorer donor Ph rings vs. the p-to\y\ rings of 4b) suggest that the process is sufficiently slow on the NMR-timescale and renders the time-averaged chemical environment experienced by the "bridging" and the monodentate phosphines less different (Scheme 2). In the case of the more electron rich p-tolyl fragment of 4b, the sharpness and separation of the 31P{'H} signals indicate that a similar exchange is not operative. Interaction of some of the H-atoms on the bridging arene with 3 IP is also clear in 4a and 4b: the detection of the P-H coupling in the 31P{'H} NMR of 4a may also be related to the intramolecular exchange. Variable temperature 31P{'H} NMR experiments on 4a in CDCI3 performed over the 300-223 K range did not increase the separation of the overlapping resonances with decreasing temperature: assuming a negligible entropic contribution for the exchange, the relative insensitivity to temperature 45 References on page 67 Chapter 3 implies that the system is also nearly thermoneutral. Similar VT experiments in the 300-330 K range revealed decomposition at T > 320 K, with no significant changes from the spectrum measured at 298 K. • & 2* P h 3 P Rh R h — P P h 3 TO 2+ P h 3 P - — R h R h — P P h 3 etc. TO Scheme 2. Proposed intramolecular exchange of the bridging arene rings in [Rh2-(PR3)4][PF6]2(R = Ph, 4a). A 'H-'ri EXSY NMR experiment (Fig. 3.20) produced weak evidence that an exchange process may be in place for 4a in CD2C12 solution; the data show a correlation CH 2 C1 2 5.2 5.0 4.B Figure 3.20. ' H - ' H EXSY NMR spectrum (400 MHz, 298 K) of [Rh2(PR3)4][PF6]2 (R = Ph, 4a) in CD2C12 (selected regions). 46 References on page 67 Chapter 3 between the upfield resonance of the p-R of the bridging ring with the non-bridging portion of the aromatic region. Optimization of the experimental conditions, particularly the choice of the appropriate mixing time ( T m ) , could lead to more conclusive results in terms of exchange cross-peaks, expected but not detected, for the 8 6.89 resonance of the bridging arene. In coordinating media (CD3OD, acetone-^ ) the dimeric assembly of 4a and 4b is lost in favour of the in situ formation of the cw-[Rh(PR3)2(solv)2]PFfi species (R = p-tolyl (3b), Ph (3a)), in which the two equivalent P-atoms give rise to a doublet in the 31P{'H} NMR spectrum as shown in Fig. 3.21. The solvated species provided extremely versatile precursors for further investigations. Attempts to isolate 3 were unsuccessful Figure 3.21. 3IP{'H} NMR spectrum (121 MHz, 298 K, CD3OD) of m-[Rh(PPh3)2-(CD3OD)2]PF6 (3a'). due to the lability of the coordinated solvent. The 31P{]H} doublet for 3a in acetone-J6 is much broader than that seen in CD3OD (see Fig. 3.22 and 3.21, respectively): the previously hypothesized slower exchange rate of the acetone molecules with respect to MeOH becomes dramatically evident, the trans arrangement of each phosphine to a solvent molecule rendering them sensitive to its nature and exchange ability. The corresponding *H NMR spectra in each solvent show only the PPh3 aromatic signals. The red solutions of cz's-[Rh(PR3)2(solv)2]PF6 prepared from [Rh2(PR3)4][PF6]2 in coordinating media readily react with 1 atm H 2 to afford the pale yellow solutions of the bis(hydrido) species 2 (see Section 3.2). When 2 is generated in-situ in CD3OD from [Rh2(PR3)4][PF6]2 rather than from [Rh(H)2(PR3)2(acetone)2]PF6 (i.e. in the absence of acetone), the high-field hydride signal appears as the expected doublet of triplets and does not show the 2 J H H coupling which arises in the presence of two different solvent ligands as shown previously (Section 3.2). 70 60 50 47 References on page 67 Chapter 3 3.3.3. In situ Reaction of [Rh2(PPh3)4][PF6]2 (4a) with Toluene Addition of toluene to an acetone-<4 solution of czs-[Rh(PPh3)2(acetone)2]PF6 (toluene:Rh = 2) shows that an equilibrium is established (Fig. 3.22) between 3a, which still remains the major component under these conditions, and a monomeric unit I in which toluene has coordinated in an n6-fashion and displaced both acetone ligands (Figs. 3.22 and 3.23). The 31P{'H} NMR spectrum for the 2:1 mixture, recorded after 15 min i 1 i 1 1 1 1 1 r ppm 65 60 55 50 45 40 35 30 25 Figure 3.22. 3'P{'H} NMR spectrum (121 MHz, 298 K) of the equilibrium mixture of c/s-[Rh(PPh3)2(acetone)2]PF6 (3a) and I in acetone-ofe. from the addition of toluene, shows the typically broad doublet due to 3a when the solvent is acetone (5 54.20 d, Jr<hp= 202.0), and a smaller, upfield, sharper doublet that is assigned to the n6-complex (5 45.15 d, jRhp = 207.7). The Rh(I) in I can be envisioned as a 5-coordinate, 18-e species; addition of excess toluene (10:1 molar ratio) gives quantitative formation of I. The reported isolation of Rh(I)-arene complexes such as [(n6-~ ~ ] + P F 6 -Ph 3 P . ^ O C M e 2 Ph 3 P OCMe 2 3a Figure 3.23. Reaction of cw-[Rh(PPh3)2(acetone)2]PF6 (3a) with toluene in acetone-ofe. 48 References on page 67 Chapter 3 C7H7)Rh(CH3(CH2)3P(C6H5)2)2]+or [(T16-C7H7)Rh(Ti2-dppp)]+,25 all required use of excess arene; attempts to isolate I were unsuccessful. The corresponding 'H NMR spectrum (Fig. 3 . 2 4 ) similarly shows formation of the n6-complex, identified by the upfield shifted acetone DD« 6 7 6 5 \ 3 2 Figure 3.24. 'H NMR spectrum (300 MHz, 298 K) of the equilibrium mixture of cis-[Rh(PPh3)2(acetone)2]PF6 (3a) and I in acetone-J6; for I: (5 2.25 s, C 6 H 5 C/ / 3 ; 5.60 d, VH H = 6.0, o-C(JH5CH3; 5.95 t, V H H = 6.0, m-C^CKy, 6.90 t, 2JHH= 6.0, p-CfJHsCRi). resonances, and the chemical shifts and the multiplicities are in good agreement with those reported for [(r|6-C7H7)Rh(CH3(CH2)3P(C6H5)2)2]+.25 After exposure of the 3a/I solution to 1 atm H 2 for 10 min, [Rh(H)2(PPh3)2(acetone)2]+ (2a) was formed in quantitative yield, with concomitant liberation of the labile toluene ligand; 2a is presumably formed from 3a. There is no hydrogenation of the arene (or the acetone) under 1 atm H2 conditions. Addition of 4 equivalents of toluene to a solution of [Rh2(PPh3)4][PF6]2 (4a) in CD2CI2 (toluene : Rh = 2) afforded solely the n6-complex I, as detected by 31P{'H} NMR spectroscopy (5 45.06 d, J R h P = 207.0) (Fig. 3.25). In the *H NMR spectrum, the resonances of I (5 2.20 s, 3H C 6H 5C7/ 3; 5.33 d, 3 J H H = 6.0, 2H o-CeHsCU^; 5.68 t, 3 J H H = 6.0, 2H m-C(JJsCrIy, 6.80 t, 3 7 H H = 6.0, 1H p-CbHsCH.?,) compare well with those reported 49 References on page 67 Chapter 3 for [(ri6-C7H7)Rh(CH3(CH2)3P(C6H5)2)2]+;25 free toluene was the only other species DPm 50 45 40 35~ Figure 3.25. 31P{'H} NMR spectrum (121 MHz, 298 K) of the reaction product from [Rh2(PPh3)4][PF6]2 (4a) and toluene in CD2C12. detected (Fig. 3.26). Furthermore, the complex was unaltered by exposure of the mixture to 1 atm H 2 for 1 h, showing that in the absence of a sufficiently coordinating solvent, a bis(hydrido) species is not formed (and the toluene ligand is not displaced). /?-CH3 free toluene Figure 3.26. *H NMR spectrum (300 MHz, 298 K) of the reaction product from [Rh2(PPh3)4][PF6]2 (4a) and toluene in CD2C12. 50 References on page 67 Chapter 3 3.3.4. In situ Reaction of [Rh2(PPh3)4][PF6]2 (4a) with Ethylene To investigate further the reactivity of the dinuclear species 4 toward small molecules, in-situ reactions with 1 atm ethylene were carried out at r.t. No reaction products could be isolated; however, the 31P{1H} NMR spectra of the reaction mixture containing [Rh2(PPh3)4][PF6]2 (4a) and ethylene in CDC13 revealed after 3 h the 8-line pattern corresponding to the starting material (8 42.33 dd, J R ^ = 202.8, 2JPP = 38; 37.82 dd, J R h p = 212.1, 2JPP = 38), a second 8-line set of lower intensity partially overlapping with the first one (8 41.55 dd, JRhP = 200.0, 2JPP = 38; 38.62 dd, J R h P = 214.1, 2JPP = 38), and a doublet further downfield (8 51.63 d, Jp^p = 192.0). These data imply that in such a medium the dinuclear species is less prone to fragmentation in the presence of C2H4 (vs. toluene), perhaps reflecting the difference in the coordinating ability of C 2 H 4 and toluene. The species giving rise to the single doublet has not been identified. The presence of a new 8-line pattern may be due to a species such as II (Scheme 4), where the C2H4 has bonded to the 16e, n4-bridged Rh(I) centers initially present in a solvent such as CDC13 (see Fig. 3.19); a vacant site for the C2H4 could become accessible if the non-coordinating arene portion is bent away from the metal. Scheme 4. Proposed coordination of C2H4 to [Rh2(PPh3)4][PF6]2 (4a). The 3,P{'H} NMR spectrum from the reaction of cw-[Rh(PPh3)2(acetone)2]PF6 (3a) with C2H4 (1 atm, r.t.) in acetone-^ after 3 h showed the signal corresponding to 2+ II 51 References on page 67 Chapter 3 unreacted 3a (5 54.30 d, JRUP - 201.0) and a second doublet of much lower intensity (5 33.65 d, JRhp = 123.2), likely due to the bis-ethylene product IV (Scheme 5), approximately in a 1:1 ratio. Two broad, unresolved regions centered around 8 58 and 20, respectively, were resolved at 223 K to reveal the presence of two doublets of doublets (5 19.53 dd, J R h P = 157.7, V P P = 38; 57.70 dd, = 178.5, 2JPP = 38) possibly corresponding to the monosubstitution product III (Scheme 5): the more downfield resonance, based on the chemical shift and / R h p values, is attributed to the P-atom trans to the solvent molecule, and the upfield one to the P-atom trans to ethylene. I C 2 H 4 P h 3 P ^ s o l v (- solv) P h 3 P ^ s o l v 3a P h 3 P . ^ s o l v p h 3 p ^ y III C 2 H 4 P h 3 P ^ ^ \ ^ ^ R h + solv p^p Y IV Scheme 5. Proposed reaction modes of C2H4 with 3a in acetone-<i6 at 298 K. The corresponding 'H NMR spectra remained virtually unchanged from 298-223 K, showing a singlet at 5 3.22 and two doublets (5 3.62, 3.85, 2JM = 8), which are attributed to IV. The observation is comparable with reported studies in which two sets of different protons were identified by VT 'H NMR analysis of another bis(ethylene) Rh(I), 16-e complex (Fig. 3.27, L-L = acac).39 Figure 3.27. Differentiation of the olefmic H-atoms in (acac)Rh(C2H4)2. One set is constituted by the "inner" protons (Hj) and the other by the "outer" (H0), and these were observed as a single resonance at r.t. (5 2.96) because of rapid 52 References on page 67 Chapter 3 rotation of the coordinated C2H4 about the Pvh-olefm axis, but at 213 K two separate doublets of doublets were seen. The C2H4 ligands in 16-e square planar, coordinatively unsaturated Rh(I) complexes undergo rapid exchange with free C 2 H 4 in solution even at 213 K, via a presumed associative mechanism involving an 18-e tris-alkene intermediate;39 the exchange was detected by 'H NMR where a single broad absorption (5 3.05) arose in the spectrum upon addition of excess ethylene, suggesting that the intermolecular exchange is faster than the rotation. Of note, in the coordinatively saturated (Cp)Rh(C2H4)2 the exchange between free and coordinated C2H4 was not observed even at 373 K . 3 9 The data for IV fit the model provided by the (acac)Rh(C2H4)2 system, although with the difference that for IV at r.t. partial resolution of the inequivalent protons of the bound olefin is achieved, indicating that the rotation is slower, possibly due to the steric hindrance of the PPI13 ligands. 3.3.5. The Crystal Structure of Rh2(PBz3)2 (4c) Treatment of an orange suspension of [Rh(COD){P(CH2C6H5)3}2]PF6 in MeOH with 1 atm H2 for 30 min at r.t. resulted in spontaneous precipitation of the white bis(hydrido) complex [Rh(H)2(PBz3)2(MeOH)2]PF6 (2c'). The isolated solid constitutes the only example of MeOH-solvated Rh(III) species obtained during this work, and none was found in the literature. However, evaporation of a solution of 2c' in acetone did not result in the formation of the expected [Rh2(PBz3)4]2+ dimer. Serendipitously, green, X-ray quality, crystals formed overnight from a CD2CI2 solution of 2c' in air. The structure was determined to be that of the neutral Rh(0) dimeric complex Rh 2(PBz 3) 2«PF 5 (4c) (cf. Section 3.3), containing one phosphine ligand per Rh, a bridging n6-benzyl ring and a metal-metal bond (Fig. 3.28). An occluded PF5 molecule (a gas at r.t.) was found in the lattice. The net reaction includes reduction of the Rh, loss of one F" ligand from the initial PF6" counterion, and loss of the hydride and one of the phosphine ligands. An entirely speculative proposal for the reactions involved (Scheme 6) contemplates an initial interaction of one F from the PF6- with one hydride ligand of 2c' to generate HF (not detected because of its known reactivity with glass) and a Rh(I) species, [RhH(PBz3)2(MeOH)]. One phosphine ligand could then undergo 02-oxidation and 53 References on page 67 Chapter 3 dissociate to generate a Rh(I)-hydrido complex. Finally, close proximity of two Rh(I)-H sites could lead to elimination of H 2 and formation of 4c. The presence of an extra CH 2 "spacer" in the benzylic arm of the phosphine likely confers C19* C19 Figure 3.28. ORTEP diagram of Rh2(PR3)2 (R = Bz, 4c) with 50% probability thermal ellipsoids. Scheme 6. Proposed reaction steps for the formation of Rh2(PBz3)2«PF5 (4c). 54 References on page 67 Chapter 3 additional flexibility to the system compared to that of the dimeric, non metal-metal bonded species 4a and 4b: the n6-bridgmg mode of the arylphosphine in 4c can be adopted with the two metal centers in much closer proximity without necessitating severe distortions. Unfortunately, the crystals were not isolated in sufficient yield for NMR and elemental analyses, and successive attempts to prepare the complex on a larger scale were unsuccessful. The PF5 in the lattice appears to be involved in some significant H-F interactions, as shown by the data given in Table 3.5 (see Fig. 3.29). Table 3.5. Selected bond distances and angles for Rh2(PR3)2'PF5 (R = Bz, 4c) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) Rh(l)-Rh(l*) 2.7104(9) Rh(l*)-Rh(l)-P(l) 89.40(4) Rh(l)-P(l) 2.251(2) P(l)-C(l)-C(2) 114.3(4) Rh(l)-C(2*) 2.259(5) Rh(l*)-Rh(l)-C(2) 93.0(1) Rh(l)-C(3*) 2.327(6) Rh(l*)-Rh(l)-C(3) 110.9(2) Rh(l)-C(4*) 2.330(6) Rh(l*)-Rh(l)-C(4) 143.6(2) Rh(l)-C(5*) 2.262(6) Rh(l*)-Rh(l)-C(5) 168.3(2) Rh(l)-C(6*) 2.322(5) Rh(l*)-Rh(l)-C(6) 134.2(2) Rh(l)-C(7*) 2.304(6) Rh(l*)-Rh(l)-C(7) 104.6(1) P(l)-C(l) 1.849(6) P(l)-C(l)-C(2) 114.3(4) P(l)-C(8) 1.847(6) P(l)-C(15)-C(16) 115.2(4) H(3)-F(3) 2.36 C(3)-Ff(3)-F(3) 176.0 H(19)-F(3) 2.36 C(19)-H(19)-F(3) 138.0 H(5)-F(2) 2.25 C(5)-H(5)-F(2) 169.4 P(l*)-Rh(l*)-C(2) 171.9(2) C(4)-Rh(l*)-C(6) 63.6(2) P(l*)-Rh(l*)-C(4) 109.8(2) P(l*)-Rh(l*)-C(6) 118.1(2) 55 References on page 67 Chapter 3 The overall geometry of the bimetallic core bears some resemblance to that of the well known Rh(I) "A-frame" precursor type complexes such as Rh2X2(u.-dppm)2 (X = halogen);40 these, however, contain bidentate phosphines bridging the two metals through the P-atoms and there is no metal-metal bond. The Rh-Rh distance in 4c is well within the range for significant metal-metal interactions.21'22'41 Slight differences in the distances Rh(l*)-C(2,5)* and Rh(l*)-C(3,4,6,7)* seem to indicate a distorsion of the ring from coplanarity: the ligands in the ML2 fragment are in this case one phosphine and one metal, and the overall conformation of the system is again of type (b) (see Fig. 3.10), with the plane containing ML2 bisecting the ring through C(2,5)*: the distortion again takes place with the ipso and para C pointing towards the metal, as shown by the shorter Rh(l*)-C(2,5)* distances, with the four noneclipsed C(3,4,6,7)* atoms oriented away from the metal. C19 Figure 3.29. ORTEP diagram of the monomeric unit of Rh2(PBz3)2'PF5 (4c) with the occluded PF5 molecule (50% probability thermal ellipsoids). 56 References on page 67 Chapter 3 3.4. Iridium Hydride Complexes The corresponding family of Ir-bis(hydrido) derivatives was studied (cf. Sections 3.1 and 3.2). In fact, the reactivity of the general precursors [Ir(COD)(PR3)2]PF6 (1*) toward H 2 is more facile, the discoloration of their initial deep red, acetone solutions, corresponding to the saturation of the diene and formation of the bis(hydrido) species [Ir(H)2(PR3)2(acetone)2]PF6 (2*) (R = Ph, 2*a; R = p-to\y\, 2*b; R = /?-FC 6H 4, 2*g), occurring rapidly. This observation (made previously)10 is consistent with the stronger Ir-H bond (vs. Rh-H)4 2'4 3 and the general relative stability of the two metals in the +3 oxidation state.14'44 Complex 2*b was isolated and characterized by 31P{'H} and *H NMR spectroscopy, IR and elemental analysis; 2*g was formed in-situ, in either acetone-tie, or CD 3OD and characterized by 31P{'H} and 'H NMR spectroscopy. Crystals of 2*a suitable for X-ray diffraction analysis were obtained (see Section 3 .4.1) and the structural data were comparable to those reported for the analogous BF4~ salt; 2*a was also characterized by 31P{'H} and 'H NMR spectroscopy. Spectroscopic characterization is in agreement with reported data. The position of the high-field Ir-H resonance in the 'H NMR depends on the nature of the trans ligand: when the trans ligand is PR3, H or C=C, a resonance at 8 - 1 0 to -15 is expected.45 The observed resonances are in the 8 -29 to - 30 region for the alcohol complexes and 8 -27 to -28 for the acetone complexes, indicating that phosphine and hydrido ligands must be mutually cis, and establishing a range of 8 -27 to - 30 for Ir(III) complexes with oxygen donor ligands trans to H . 4 6 In addition, analogous to the Rh systems (see Section 3.2), a typically cis 2 JPH coupling constant of 15-17 Hz is observed in all cases. The Ir systems in solution show a relatively higher stability (vs. Rh) toward the loss of H 2 : in neither MeOH nor acetone was loss of H 2 observed upon dissolution of 2*b, and consequently no formation of cis-[Ir(PR3)2(solv)2]+ was observed. Solvent exchange still occurs, but is not accompanied by the elimination of H 2 : this is evidenced by the 31P{'H} and 'H NMR spectra of 2*b in CD3OD under Ar which show a singlet and a broadened high-field triplet, respectively, indicating that only solvent scrambling is taking place, whereas in acetone-<4 the triplet is well resolved and sharp, as expected in the absence of a second, different solvent ligand. As observed in the Rh analogues (see Section 3.2), in both solvents the only singlet in the 57 References on page 67 Chapter 3 31P{'H} NMR corresponds to that of the bis(hydrido), as formed in-situ from the precursor 1 *b under H2, showing once more the relative insensitivity of the two mutually trans P to the nature of the cis solvento molecules and their possible involvement in an exchange process. Previous studies47 have reported an order of relative stability for the isolated complexes of type [Ir(H)2(PR3)2(solvl)2]BF4 when redissolved in CD2CI2 in the presence of controlled amounts of a second solvent solv2. The following trend was presented: H 2 0 = THF < ;-BuOH < z-PrOH < acetone < EtOH < MeOH < MeCN Replacement of solvl by solv2 was sometimes observed, sometimes the retention of solvl, or sometimes formation of mixed-solvento complexes, as indicated by the appearance of 2 JHH cis coupling of ~ 5 Hz in the high-field lH NMR spectra, particularly in the case of solvl = MeOH and solv2 = acetone, in line with the observations presented in this work for analogous Rh systems (Section 3.2). Of interest, MeOH-solvated species are easily isolable for the Ir systems and, according to the stability order shown above, are even more stable than the bis-acetone solvento complexes, in contrast with Rh systems. Again, in contrast to what is observed for the Rh analogues, treatment of 1* with H 2 (1 atm) in CH2CI2 did not generate a similar [fr^PRaW species, and the complexity of the spectroscopic (NMR) features did not allow for the identification of the species formed, suggesting that a very labile system is initially established under these conditions. The less labile [Ir(H)2(PR3)2(solv)2]+ (2*) complexes have been more thoroughly characterized generally than their Rh counterparts, reflecting the intrinsic stability of the former. Ir-bis(hydrido) complexes of the type 2* have been used previously as homogeneous catalysts for a variety of reactions, from hydrogenation of olefins to activation and dehydrogenation of alkanes,46"48 and these examples also show a marked solvent dependency and display quite different behaviour from that of their Rh analogues.46'47 More specifically, the catalytic hydrogenation activity of the Ir systems suffers strong inhibition in the presence of coordinating solvents (acetone, EtOH), whereas maximum efficiency was attained in poorly coordinating media (e.g. CH2C12), for both non-sterically hindered and hindered olefins. Coordination of the olefin (or 58 References on page 67 Chapter 3 diene), as the best available ligand, to 2* (with no loss of H2) was determined by VT ! H NMR experiments to be the first step in CH2CI2 at 193 K, and the bis-olefm species [Ir(H)2(olefin)2L2]+ was detected. Formation of the alkane was observed upon gradual warming of the solution. Similar tests in either non- or coordinating media (CH2CI2, acetone) using the related Rh systems (2) displayed lower activity and immediate liberation of H 2 upon coordination with diene (NBD, COD), even at low temperature, to afford the stable [Rh(diene)(PR3)2]+ complexes, implying that the mechanism could be substantially different for the two metals, namely the slow step in the Rh case likely involving oxidative addition of H2. It was suggested that in the weakly coordinating CH2CI2, no solvento complexes are formed, and that in the Ir case the olefin constitutes the best available ligand able to give rise to the 2:1 transient species that can at r.t. rapidly transfer H 2 intramolecularly and afford the products, as observed.47 For the Rh systems, in which no dihydrido-olefin intermediates were detected, there was practically no difference in activity in CH2CI2, EtOH or acetone46 Some insight in this regard is provided in this thesis work, as the [Rh(H)2(PR3)2(solv)2]+ species in EtOH or acetone interact with substrate with immediate loss of H2, while in CH2CI2 the relatively stable species [Rh2(PR3)4] is formed even under 1 atm H2: in each solvent, it is likely that the slow step for the hydrogenation of the substrate is the oxidative addition of H 2 . 59 References on page 67 Chapter 3 3.4.1. The Crystal Structure of [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) X-ray quality crystals of 2*a were obtained by slow evaporation of a CH2CI2 solution of 2*a layered with hexanes, and the structure was determined (Fig. 3.30). C22 Figure 3.30. ORTEP diagram of the cation [Ir(H)2(PR3)2(acetone)2]+ (R = Ph, 2*a) with 50% probability thermal ellipsoids. The BF4" salt was structurally characterized earlier by Crabtree and coworkers,49 and the cationic portion of the compound is identical to that obtained in this work: both molecules crystallize in the P2i/c space group and the metrical parameters (Table 3.6) are in excellent agreement. Solvento complexes of this type have been reported several times since 1963,50 initially sometimes formulated as [Ir(H)2(PPh3)2]+,51 although subsequent work established clearly the solvated nature of these species.10 Davies and Hartley52 have stated that the isolation of acetone complexes of the low-valent platinum metals is usually 60 References on page 67 Chapter 3 unsuccessful because the solvent is so weakly bound that even H 2 0 can usually displace it. For these Ir(III) systems, acetone is more strongly bound than water. Table 3.6. Selected bond distances and angles for [fr(H)2(PR3)2(acetone)2]+ (R = Ph, 2*a) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) Ir(D-P(l) 2.298(1) P(l)-Ir(l)-P(2) 171.95(4) Ir(l)-P(2) 2.309(1) P(l)-Ir(l)-0(1) 89.1(1) IrO)-O(l) 2.209(3) P(l)-Ir(l)-0(2) 101.9(1) Ir(l)-0(2) 2.203(3) P(2)-Ir(l)-0(1) 96.2(1) Ir(l)-H(l) 1.51(6) P(2)-Ir(l)-0(2) 85.2(1) Ir(l)-H(2) 1.50(7) 0(l)-Ir(l)-0(2) 77.3(1) 0(1)-C(37) 1.229(6) P( l ) -h( l ) -H(l ) 90(2) O(2)-C(40) 1.227(6) P(l)-Ir(l)-H(2) 87(3) C(37)-C(38) 1.483(8) P(2)-Ir(l)-H(l) 83(2) C(37)-C(39) 1.502(8) P(2)-Ir(l)-H(2) 87(3) C(40)-C(41) 1.480(8) 0(1)-Ir(l)-H(l) 102(2) C(40)-C(42) 1.489(8) 0(2)-Ir(l)-H(2) 102(3) h(l)-0(l)-C(37) 135.9(4) Ir(l)-O(2)-C(40) 136.2(3) The Ir-0 distances are long. The "expected" Ir-0 distance in an aquo complex is said to be 2.02 A,53 and the sp2 O of a ketone would be expected to give a slightly shorter distance. As reported by Crabtree,49 calculations have provided an estimate of ~ 1.96 A for the expected Ir-0 distance in the acetone bis(hydrido) complex. The h-0 distances in both the literature and this thesis work are thus about 9-10 % longer than the expected estimated length.49 These structural data reflect the significant trans-influence of the 61 References on page 67 Chapter 3 hydride ligands, and are consistent with the high reactivity of this general type of complexes. The C=0 bond lengths are similar to that of free acetone (1.20 A) , 5 4 and the o-bound acetone ligands contrast with the 7i-bound groups observed for electron-accepting ketones as in [Pt(PPh3)2{r|2-(CF3)2CO}].5 5 Also, the large Ir-O-C angles (Ir-Ol-C37 = 135.9(4)° and Ir-O2-C40 = 136.2(3)° in 2*a) suggest that the endo methyl groups of the acetone molecules (C38 and C42 in 2*a) may be subject to steric repulsion by the Ir(PR3)2 moiety: the expected distortion of the other angles involving these methyl groups is more pronounced for the BF 4 " salt,49 whereas in the case of 2*a the deviation from the C sp2 trigonal planar geometry is much less marked. The Pl-Ir-P2 angle of 171.95(4)° in 2*a (171.63(8)° in the BF 4 " salt) also indicates that the phosphine ligands are slightly bent away from the acetone groups and towards one another. 62 References on page 67 Chapter 3 3.5. Experimental 3.5.1. Preparation of [Rh(H)2(PR3)2(acetone)2]PF6 (R = Ph, 2a; /Molyl, 2b; Bz, 2c) An orange solution of [Rh(COD)(PR3)2]PF6 (in general, 0.100 g, ~ 0.1 mmol) in acetone (2 mL) was stirred under H 2 (1 atm) for 1 h. The resultant clear, pale yellow solution was then treated with Et 20 (4 mL), followed by addition of hexanes (6 mL) to afford a creamy-white precipitate. The product [Rh(H)2(PR3)2(acetone)2]PF6 was collected by filtration, washed with hexanes (3x5 mL) and stored under H 2 (1 atm). R = Ph (2a), Yield: 0.060 g (60 %). 31P{'H} NMR (acetone-4): 5 45.61 (d, JMP = 117.8). ! H NMR (acetone-rf6): 8-20.74 (dt, 2H, Wi(H)2, JRHH = 25, V H P = 15), 2.10 (s, 6H, C//3COCfY3), 7.20-7.90 (m, 30H, C^s). 31P{1H} NMR (CD3OD): 8 41.80 (d, JRHP = 120.6). 'H NMR (CD3OD): 8 -22.10 (2 dt, 2H, Rh(/f)2, JRM = 26, 2JHP = 15, 2JHH = 7), 2.15 (s, 6H, CH3COCHi), 6.90-8.10 (m, 30H, CfjHs). IR (KBr pellet): v 1668 (C=0, s), 2137 (Rh-H, m). Anal. Calcd for C 4 2 H 4 4 F 6 0 2 P 3 Rh: C, 56.64; H, 4.98. Found: C, 56.10; H, 4.93. Complex (2a) has been prepared before;13 however no NMR data in CD 3OD were reported. IR data compare well with those reported in the literature for the analogous bis-EtOH and mixed EtOH/acetone complexes.1 (2b) and (2c) have not been made previously. R = /7-tolyl (2b), Yield: 0.075 g (75%). 31P{'H} NMR (acetone-J6): 8 43.45 (d, JRHP = 117.2). 'H NMR (acetone-rf6): 8 -20.95 (dt, 2H, Rh(//)2, J^H = 26, 2JH P = 15), 2.10 (s, 6H, CH3COCH3), 2.34 (s, 36H, p-Ce^CH^), 7.19-7.46 (m, 42H, p-C6^4CH3). 31P{'H} NMR (CD3OD): 8 39.41 (d, = 119.1). 'H NMR (CD3OD): 8 -22.25 (2 dt, 2H, Rh(//)2, / R h H = 26, 2JH P = 15, 2JH H = 7), 2.15 (s, 6H, C// 3COC// 3), 2.37 (s, 18H,p-C6H4C//3), 7.20-7.45 (m, 24H, p-C^CRi). IR (KBr pellet): v 1669 (C=0, s), 2104 (Rh-H, m). Anal. Calcd for C 4 8 H 5 6 F 6 0 2 P 3 Rh: C, 59.14; H, 5.79. Found: C, 59.11; H, 5.77. Similarly, the analogous bis(deuteride) [Rh(D)2(Pp-tolyl3)2(acetone-ii6)2]PF6 (2b^ ) was prepared by the same method in acetone-*^  under 1 atm D 2 . Yield: 0.060 g (60 %). 31P{'H} NMR (acetone-^ ): 5 43.49 (d, J^P = 117). 'H NMR (acetone-rf6): 8 2.35 (s, 36H, p-C 6H 4C// 3), 7.25-7.35 (m, 42H, p-C^CRi). IR (KBr pellet): v 1665 (C=0, s), 1919 (Rh-D, m). Anal. Calcd for C48H7oF602P3Rh: C, 58.30; H, 7.13(5.79). Found: C, 58.49; H, 5.83. R = Bz (2c), Yield: 0.065 g (65%). 31P{'H} NMR (acetone-J6): 8 31.49 63 References on page 67 Chapter 3 (dt, JRHP = 117.8, VH P = 13). ] H NMR (acetone-«i6): 5 -22.39 (dt, 2H, Rh(#)2, J R h H = 26, VH P = 16), 2.10 (s, 6H, CH3COCH3), 2.70-3.30 (m, 12H, C// 2 C 6 H 5 ) , 6.60-7.80 (m, 30H, CeZ/s)- 31P{'H} NMR (CD3OD): S 35.92 (dt,/R h P = 123.2, VH P = 13). 'HNMR (CD3OD): 5 -23.54 (dt, 2H, Rh(#)2, J ^ H = 27, VH P = 16), 2.15 (s, 6H, C7/3COC7/3), 2.90-3.10 (m, 12H, C7/2C6H5), 6.30-7.70 (m, 30H, CeHs). IR (KBr pellet): v 1676 (C=0, s), 2148 (Rh-H, m). Anal. Calcd for C 48H56F 60 2P 3Rh: C, 59.14; H, 5.79. Found: C, 59.43; H, 5.65. 3.5.2. In situ Characterization of [Rh(H)2(PPh2CH3)2(CD3OD)2]PF6 (2d') and [Rh(H)2{P(p-ClC6H4)3}2(CD3OD)2]PF6 (2e') An NMR tube equipped with an air-tight JYOUNG PTFE valve was charged with the appropriate precursor (1) (0.015 g, 0.020 mmol, (Id); 0.015 g, 0.014 mmol, (le)), and the solvent (CD3OD, ~0.8 mL) was added by vacuum transfer to afford an orange suspension that was placed under H 2 (1 atm) for 30 min. The resultant clear, pale yellow solutions were then analyzed by 31P{'H} and 'H NMR spectroscopy. PR 3 = Ph 2PCH 3 (2d*), 31P{'H} NMR: 5 25.84 (d, J^p = 118.0). 'H NMR: 5 -22.60 (bm, 2H, Rh(#)2), 2.00 (s, 6H, CH3), 7.20-8.30 (m, 20H, CeHs). R = />-ClC6H4 (2e'), 31P{]H} NMR: 8 42.06 (d, J R h P = 121.2). 'H NMR: 5 -22.10 (dt, 2H, Rh(/f)2, JR^H = 24, 2JHP = 15), 7.50-8.15 (m, 24H,/7-ClC<^/4). 3.5.3. Preparation of [Rh(H)2(PBz3)2(CH3OH)2]PF6 (2c') An orange suspension of [Rh(COD)(PBz3)2]PF6 (0.100 g, 0.1 mmol) in MeOH (2 mL) was stirred under H 2 (1 atm) for 30 min, during which spontaneous precipitation ofa white solid occurred. The product was collected by filtration, washed with MeOH (2x3 mL) and hexanes (2x3 mL) and stored under H 2 (1 atm). Yield: 0.070 g (73%). 31P{1H} NMR (acetone-afe): 5 31.70 (dt, / R h P = 121.8, V H p = 10). 'H NMR (acetone-afe): 5-22.40 (dt, 2H, Rh(/f)2, J R h H = 26, 2 J H P = 16), 3.20 (s, 12H, CH2C6tt5), 3.40 (m, 6H, C7/3OH), 7.10-7.75 (m, 30H, CHzC^s). ^Pl'H} NMR (CD3OD): § 32.83 (d, JRHP = 123.4). 'H NMR (CD3OD): 6 -23.63 (dt, 2H, Rh(#)2, J^n = 25, 2J H P = 15), 3.10 (s, 12H, 64 References on page 67 Chapter 3 C / / 2 C 6 H 5 ) , 3.37 (s, 6H, C// 3 OH), 6.90-7.70 (m, 30H, CT^C^)- Anal. Calcd for C44H52F602P3Pvh: C, 57.28; H , 5.68. Found: C, 57.60; H, 5.33. Complex (2c') has not been previously prepared. 3.5.4. Preparation of [Rh 2 (PR 3 ) 4 ] [PF 6 ] 2 (R = Ph, 4a; / M o l y l , 4b) A yellow suspension of [Rh(COD)(PR 3) 2]PF 6 (0.100 g, -0.1 mmol) in MeOH (10 mL) was stirred under H 2 (1 atm) for 1 h. The resultant clear, pale yellow solution was then evaporated to dryness under reduced pressure, to afford a red-brown residue that was dried in vacuo. R = Ph (4a), Yield: 0.060 g (70%). 3 1P{'H} N M R (CD 2C1 2): 6 45.46 (dd, J R h P = 198.8, 2JPP = 38), 47.47 (dd, JKhP = 210.9, 2JPP = 36). lH N M R (CD 2C1 2): 8 4.90 (pt, 2H, rf-p-CeHs, 3JHH = 6), 6.89 (t, 4H, n ' - m - C ^ , V H H = 6.0), 7.05-7.70 (m, 54H, CeHs). 3 1P{'H} N M R (CD 3 OD, 3a'): 5 57.02 (d, J R h P = 206.8). *H N M R (CD 3 OD, 3a'): 5 7.11-7.81 (m, 30H, CeHs). Anal. Calcd for C 7 2 H 6 0 F 1 2 P 6 R h 2 : C, 55.98; H , 3.91. Found: C, 55.87; H , 3.88. R = / M o l y l (4b), Yield: 0.060 g (70%). 3 1P{'H} N M R (CD 2C1 2): 5 39.63 (dd, J R H P = 212.6, 2 J P P = 39), 43.09 (dd, = 202.2, V P P = 38). ] H N M R (CD 2C1 2): 5 2.15-2.25 (m, 6H, n 4 -^ -C 6 H 4 C/ / 3 ) , 2.31-2.45 (m, 30H, p-C6H4CH3), 5.99 (d, 3H, n4-m-C6/ / 4 CH 3 , VHH = 6.6), 6.60 (t, 3H, n 4 -o-Cei/ 4 CH 3 , V H H = 6.6) 6.80-7.30 (m, 42H, p-CeH4CU3). , 3 C{ 'H} N M R (CD 2C1 2): 5 18.95 (s, n V c 6 H 4 C H 3 ) , 20.96 (s, j p-C 6 H 4 CH 3 ) , 21.06 (s, p-CbH4CH2), 21.37 (s, n V C e ^ C H s ) , 102.65, 103.32 (2 bs, n 4 -o,m-C 6 H 4 CH 3 ), 122.70-133.92 (m, "free"- and n 4 -o,m-C 6 H 4 CH 3 ), 140.91 (s, ^ o - n 4 - C 6 H 4 C H 3 ) , 141.77 (s, ipso-CelUCRz), 142.07 (s, /pso-C 6H 4CH 3), 144.40 (s, r^o- r | 4 -C 6 H 4 CH 3 ) . 3 1P{ 1H} N M R (CD 3 OD, 3b'): 5 55.15 (d, JRHP = 207.7). ' H N M R (CD 3 OD, 3b'): 5 2.23-2.43 (m, 18H, /?-C 6 H 4 C// 3 ) , 6.89-7.60 (m, 24H, jp-C 6# 4CH 3). Anal. Calcd for C 8 4 H 8 4 F , 2 P 6 R h 2 : C, 58.89; H, 4.94. Found: C, 58.26; H, 4.97. A better analysis could not be obtained. 3.5.5. Preparation of [Ir(H) 2(PR 3) 2(acetone) 2]PF 6 (R = />-tolyl, 2*b) A red solution of [Ir(COD)(P(p-tolyl)3)2]PF6 (0.100 g, -0.1-0.13 mmol) in acetone (2 mL) was stirred under H 2 (1 atm) for 1 h. The resultant clear, pale yellow solution was then treated with E t 2 0 (2 mL), followed by addition of hexanes (8 mL) to 65 References on page 67 Chapter 3 afford a white precipitate. The product was collected by filtration, washed with hexanes ( 3 x 2 mL) and stored under H 2 (1 atm). Yield: 0.070 g (70%). 3 I P{ 'H} N M R (acetone-d6): 5 26.24 (s). ' H N M R (acetone-J6): 5 -27.92 (t, 2H, Ir(//)2, VH P = 16), 2.10 (s, 6H, C//3COC//3) , 2.38 (s, 18H,/?-C 6H 4C# 3), 7.25-7.40 (m, 24H,p-Ce^CHs). 3 1 P{ ! H} N M R ( C D 3 O D ) : 5 27.61 (s). ' H N M R (CD 3OD): 5 -29.82 (t, 2H, h(H)2, VH P = 16), 2.15 (s, 6H, C//3COC//3) , 2.35 (s, 18H, />-C 6H 4C// 3), 7.10-7.40 (m, 24H, p-CeHtCRs). IR (KBr pellet): v 1657 (C=0, s), 2243 (Ir-H, m). Anal. Calcd for C^HseFeO^Ir: C, 54.18; H, 5.30. Found: C, 54.24; H, 5.43. Complex (2*b) has not been prepared previously. The IR data are, however, very close to those recorded in CH 2 C1 2 for [Ir(H)2(PPh3)2-(acetone)2]BF4.46 3.5.6. In situ Characterization of [Ir(H)2(PR3)2(soIv)2]PF6 (solv = acetone, R = Ph, 2*a; />-FC6H4, 2*g; solv = CD 3 OD, R = Ph, 2*a'; />-FC6H4, 2*g ' ) An N M R tube equipped with an air-tight JYOUNG PTFE valve was charged with the appropriate precursor (1*) (0.015 g, 0.015 mmol, ( l *a ) ; 0.015 g, 0.014 mmol, ( l * g ) ) , and the solvent (~ 0.8 mL) was added by vacuum transfer to afford a red suspension (CD3OD) or solution (acetone-^) that was placed under H 2 (1 atm) for 30 min. The resultant clear, pale yellow solutions were then analyzed by 3 , P{ 1 H} and ] H N M R spectroscopy. R = Ph (2*a), 3 1 P{'H} N M R (acetone-^): 5 28.47 (s). ' H N M R (acetone-d6): 5 -27.70 (t, 2H, Ir(/f)2, 2JHP = 16), 2.10 (s, 6H, CH3COCH3), 7.20-7.70 (m, 30H, CfiiYj). R = Ph (2*a'), 3 1 P{'H} N M R (CD3OD): 5 27.13 (s). ' H N M R (CD 3OD): § -29.47 (t, 2H, I r ( / / ) 2 , 2 J H P = 17), 2.15 (s, 6H, C / / 3 COC/ / 3 ) , 7.30-7.65 (m, 30H, C ^ ) - Complex (2*a) has been prepared previously as the BF 4 " salt;46 however, no N M R data in acetone-de nor in CD 3 OD were reported. (2*g) has not been made before. R = />-FC6H4 (2*g), 3 1 P{'H} N M R (acetone-J6): 8 25.66 (s, 2P). ' H N M R (acetone-t/6): 5 -27.63 (t, 2H, lr(H)2, 2JHp = 15), 2.10 (s, 6H, CH3COCH3), 7.10-7.80 (m, 24H, p-¥C6H4). R = />-FC6H4 (2*g') s 3 1 P{'H} N M R (CD 3OD): § 24.68 (s, 2P). ] H N M R (CD 3OD): 5 -29.37 (t, 2H, lr(H)2,2JHP = 17), 2.15 (s, 6H, CH3COCH3), 7.20-7.70 (m, 24H, Jr>FC 6//4). 66 References on page 67 Chapter 3 3.6. References ( 1 ) Schrock, R. R.; Osborn, J. A. J. Am. Chem. Soc. 1971, 93, 2397. (2) Haines, L. M.; Singleton, E. J. Chem. 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Phosphorus-31 NMR Spectroscopy in Stereochemical Analysis; VCH Publishers: Deerfield Beach, FL, 1987. Singewald, E. T.; Shi, X.; Mirkin, C. A.; Schofer, S. J.; Stern, C. L. Organometallics 1996,15, 3062. Green, M.; Kuc, T. A. J. Chem. Soc, Dalton Trans. 1972, 832. Friebolin, H. Basic One- and Two-Dimensional NMR Spectroscopy; VCH: New York, 1991. Cramer, R. J. Am. Chem. Soc. 1964, 86, 211. Kubiak, C. P.; Eisenberg, R. J. Am. Chem. Soc. 1977, 99, 6129. Stobart, S. R.; Grundy, S. L.; Bailey, J. A. Organometallics 1990, 9, 536. Parshall, G. W. Acc. Chem. Res. 1970, 3, 179. 68 References on page 67 Chapter 3 (43) Parshall, G. W. Acc. Chem. Res. 1975, 8, 113. (44) Halpern, J. Acc. Chem. Res. 1970, 3, 386. (45) Green, J. C.; Green, M . L. H. In Comprehensive Inorganic Chemistry; Emelus, J. H. , Ed.; Pergamon Press: Oxford, 1973; Vol. 4. (46) Crabtree, R. H. ; Demou, P. C ; Eden, D.; Mihelcic, J. M . ; Parnell, C. A. ; Quirk, J. M . ; Morris, G. E. Am. Chem. Soc. 1982,104, 6994. (47) Crabtree, R. H. ; Mellea, M . F.; Mihelcic, J. M . ; Quirk, J. M . J. Am. Chem. Soc. 1982, 104, 107. (48) Crabtree, R. H. ; Parnell, C. P.; Uriarte, R. J. Organometallics 1987, 6, 696. (49) Crabtree, R. H . ; Hlatky, G. G.; Parnell, C. P.; Segmuller, B. E.; Uriarte, R. J. Inorg. Chem. 1984, 23, 354. (50) Angoletta, M . ; Araneo, A. Gazz. Chim. Ital. 1963, 93, 1343. (51) Malatesta, L.; Caglio, G.; Angoletta, M . J. Chem. Soc. 1965, 6974. (52) Davies, J. A.; Hartley, F. R. Chem. Rev. 1981, 81, 79. (53) Shustorvich, E. M . ; Porai-Koshits, M . A. ; Buslaev, Y . A . Coord. Chem. Rev. 1975, 17, 1. (54) Allen, P. W.; Bowen, H. J. M . ; Sutton, L. E.; Bastiansen, O. Trans. Faraday Soc. 1952, 48, 991. (55) Clarke, B.; Green, M . ; Osborn, R. B. L.; Stone, F. G. A . J. Chem. Soc. A 1968, 167. 69 References on page 67 Chapter 4 Chapter 4 IMINES AND AMINES AS N-DONOR LIGANDS AND THEIR INTERACTION WITH Rh AND Ir CENTERS 4.1. Introduction A fundamental understanding of the mechanistic features of catalytic homogeneous H2-hydrogenation of the imine C=N moiety remains far less developed than for the corresponding reductions of C=C and C=0 functionalities.1 The more forcing reaction conditions required for H2-hydrogenation of C=N, a direct consequence of the smaller enthalpic gain associated with H2-saturation of C=X moieties when X = N (or O) , (ca. -60 kJ mol"') relative to X = C (ca. -130 kJ mol"1),1 often preclude easily accessible investigative methods such as N M R and UV-vis spectroscopies. Catalytic systems based on transition metal complexes are briefly reviewed in Chapter 1. Among the two classes of Schiff base imines, aldimines and ketimines, the latter undergoes hydrogenation with greater difficulty, for reasons which, although possibly linked to increased steric hindrance in the ketimine (RC(R")=NR') versus aldimine (RCH=NR') substrates, still elude a satisfactory, quantitative rationale. The n 1 -binding mode generally adopted by substrates containing N - and O-donor atoms1"3 may also inhibit an H-atom transfer step in the catalytic cycle, which usually requires a shift to n 2 -coordination of the unsaturated moiety as usually observed in the case of olefins.4 Furthermore, competition for the metal center by the hydrogenated product may be greater when it contains a -NH donor versus the -OH group of alcohols or a saturated C center, and this may contribute to the more difficult hydrogenation of imines relative to ketones and olefins. The mild conditions under which the catalyst precursors [Rh(diene)(PR3)2]+ (1) homogeneously hydrogenate aldimine substrates5 render these systems ideally suited for studies aimed at reaching a more thorough knowledge of the mechanistic steps governing such processes. The coordination of ligands containing N -ft 7 donor groups to transition metals has been extensively explored, ' but only a few of these studies have been concerned with mechanistic details of Rh-catalyzed hydrogenation of • • 5,8-10 imines. 70 References on page 126 Chapter 4 In this Chapter, the results of investigations on the nature of the interaction between metal and several imine substrates are reported, and some common trends are presented. The majority of aldimines employed in this work belong to the general family of acyclic N-benzylideneamines (RCH=NR', R = aryl; R' = aryl, alkyl), while the ketimine substrates belong to that of the corresponding a-carbon methyl- and phenyl-substituted compounds (RC(R")=NR', R" = Me, Ph). In one case, a cyclic ketimine was investigated. 71 References on page 126 Chapter 4 4.2. The Ort/io-metallation Reaction Intramolecular activation of a C-H bond of an aryl group contained in a donor ligand of a transition metal complex has long been known for several metals (e.g. Pd, Pt, Ir, Rh)."" 1 3 In the majority of cases formation of a five-membered metallacycle is observed: first proposed in 1966 by Matsuda and coworkers for the interaction between tin and halosuccinic acid dialkyl esters,14 a five-membered ring structure theory has now been extended to the intramolecular organometallic interactions of various metal-ligand combinations. Activation of ortho C-H bonds at a metal center (ort/zo-metallation) tends to give rise to five-membered chelate ring structures owing to the favorable bond lengths and angles: the metal generally forms four-(square-planar), five-(bipyramidal) and six-octahedral) coordinate structures, and in each geometry the bond angle formed by the two bonds containing the metal within the ring is closer to 90° (than to 109° (sp3) or 120° (sp2)), as required in a five-membered metallacycle (Fig. 4.1).1 5 Figure 4.1. Representation of a general intramolecular five-membered cyclometallated ring structure (X = donor atom). Oz7zo-metallated compounds have been extensively reviewed and classified according to the ligand group: in particular, those containing N-donor type ligands form complexes almost exclusively containing a five-membered ring structure.15 The interactions of several benzylideneamine (RCH=NR') and ketimine (RC(R")=NR') substrates (R = aryl) with either [M(H)2(PR3)2(solv)2]PF6 (M = Rh, 2; Ir, 2*) or cis-[Rh(PR3)2(solv)2]PF6 (3) in CD3OD and acetone-J6 were investigated. The outcome of the reaction was found to depend on several variables, including metal, stoichiometry of metal and substrate, nature of substrate, solvent, and reaction time. In most cases, however, the first step involves a 1:1 (metal:substrate) coordination to form a six-coordinate M(III)-monohydrido complex containing an n1-imine ligand RC(R")=NR' (R" = H, Me, Ph) bound to the metal via the N atom and metallated at the ortho position of 72 References on page 126 Chapter 4 the R moiety giving rise to a five-membered metallacycle, in analogy to several examples reported in the literature.16'17 4.3. Ir Systems 4.3.1. The PhCH=NCH2Ph Ligand Reaction of [Ir(H)2(PPh3)2(solv)2]PF6 (solv = acetone, 2*a) with benzylidene-benzylamine (PhCH2N=CHPh:Ir = 1:1) in acetone at r.t. resulted in the formation of the ortAo-metallated complex [Ir(H){PhCH2AA-CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5*a), which was isolated and characterized by 3 1 P{'H} NMR, ' H N M R and IR spectroscopies, elemental analysis and X-ray crystallography (Fig. 4.5, see below). Complex 5*a represents the prototypical example of the type of compounds obtained in this work from analogous reactions between different combinations of metal and substrate. With the exception of the cyclic ketimine 6,7-dimethoxy-l-methyl-3,4-dihydroisoquinoline (see Section 4.4.5), acyclic substrates (aldimines and ketimines) react with bis(hydrido) species 2 or bis(solvated) 3 in the same fashion to form or^o-metallated complexes similar to 5*a. Of the two possible five-membered metallacycles that benzylideneamines can form, in which the C=N moiety either is or is not included in the ring (endo and exo respectively, Fig. 4.2), only the endocyclic compound was observed. endo exo 5*a Figure 4.2. Possible configurations of five-membered metallacycles of benzylideneamines (endo adopted in 5*a). 73 References on page 126 Chapter 4 These imine substrates exist as mixtures of EIZ geometrical isomers with respect to the stereochemistry about the C=N bond, with the E isomer generally observed as the thermodynamically favoured;18"20 from the E isomer both endo- and exocycles can be formed, whereas the Z isomer would be expected to lead to exclusive formation of exocyclic chelates. Formation of the endocycle (the only possibility for the E isomer), as observed in all the structurally characterized examples in this work, directly relates to the inherently higher thermodynamic stability of the E vs. Z geometry.21 Studies on the reactivity of substituted benzylidenebenzylamines with [Pt2Me4(yu-SMe2)2] have revealed a similar tendency to form an endocyclic chelate;22 even in the presence of a weaker C-X bond (X = CI, ~ 86 kcal/mol) at the ortho position of the benzylic fragment, activation of the ortho C-H bond (~ 112 kcal/mol) of the benzylidene fragment and exclusive formation of the endocycle were observed. Only when X = Br is the bond sufficiently 23 weak to impart a reversed behavior leading to formation of the exocycle from metallation of the benzylic fragment at the C-X ortho position. When X = H , however, in no case was activation of the benzylic fragment observed. The imine functionality thus appears to be quite important in determining the regiochemistry of the C-X bond activation, with formation of endocycles being generally preferred. It has been suggested that thermodynamic considerations such as restricted rotation about the C=N bond, and conjugation of the metallated aryl with the C=N bond (possible only in the endo form), may be critical factors in determining the structures of or^o-metallated derivatives (i.e. intramolecular over intermolecular activation).1 5 , 2 2 OtAo-metallation of imine and amine substrates at Pt(II) and Pd(II) centers are believed to proceed via a substitution reaction mechanism of the metal with the hydrogen of the C-H bond, with the hydrogen subsequently reductively eliminated in conjunction with a suitable leaving group on the metal. This results from the strong tendency of the heavier Group 10 metals to achieve four-coordinate, square-planar geometry, this type of reactivity being accounted for in part by the electrophilic character of the metal.11 van Baar and coworkers reported the reaction of benzylidenemethylamine with trans-[IrCl(N2)(PPh3)2], which resulted in the displacement of the N2 ligand and formation of an octahedral, six-coordinate orr/20-metallated complex resembling 5*a (Fig. 4.3).24 An alternate reaction pathway at the Ir(I) center invokes an insertion rather than a 74 References on page 126 Chapter 4 substitution reaction involving a H-atom.13 The nucleophilic character of the metal, enhanced by the use of basic phosphines as co-ligands,25 appears to be critical for ortho-metallation to occur at Ir(I) and Rh(I) centers; of interest, reaction of the same imine with [RhCl(CO)2]2 containing electron-withdrawing CO ligands did not produce the analogous or/Zzo-metallated complex, and exclusive formation of the a(N)-coordinate complex cis-[RhCl(CO)2(PhCH=Mvle)] was observed.13 It was speculated24 that the first step in the orrTzometallation involved a(N)-coordination of the imine ligand, which would bring an ortho C-H group close to the metal atom (Fig. 4.3). The basicity of the low-valent d8 Ir(I) and the extra charge density on the metal brought about by the N-donor ligand may then promote the second step, namely the oxidative addition of the ortho C-H group to the metal center (i.e. insertion of the metal across the C-H bond). Detection of a hydride ligand even when the reaction is performed in deuterated media has ruled out the solvent as the hydride source.1 3'2 4 Cl C H . ^ P P h 3 R I - > P P h 3 R [lrCI(N 2)(PPh 3) 2] + PhCH=NR —^-U- C I - ^ l r - - - N ^ * • H ^ ! r ~ - ~ N — C - N 2 P h 3 P ^ H _ c J P h 3 P (odho-C-H) Figure 4.3. Proposed steps for the insertion-reaction mechanism. In the formation of 5*a from 2*a in this work, an analogous mechanism may be in place, whereby the imine displaces a solvent ligand in the first step (Fig. 4.4), which is P P h 3 H + P F 6 n + PFa O C M e . H ' P F e H V I , - 0 C M e 2 acetone , - P P ^ L R H„._ I , - P P h 3 ^ l r M e 2 C O — p l r — - N C ^ ^ .,lr' HT I ^ O C M e 2 PhCH=NCH 2Ph P h 3 P ^ H QJ P^P I ^ N ' "Ph P P h 3 - H 2 {ortho-C-H) H 2*a 5*a Figure 4.4. Proposed reaction steps for the formation of [Ir(H) {PhCH2./V=CH(o-C 6H 4)} (PPh3)2(acetone)]PF6 (5*a). 75 References on page 126 Chapter 4 accompanied by reductive elimination of the hydride ligands as H 2 (detected in solution). Oxidative addition of the C-H bond to the Ir center would then lead to the product. Yellow crystals of 5*a suitable for X-ray diffraction analysis were obtained from slow evaporation of a CH2Cl2/hexanes solution of the complex; the compound crystallized in the P2]/n space group, with the Ir in a nearly octahedral environment (Fig. 4.5). Formation of the endocycle is evident from the structural data, and comparison between the N(l)-C(7) and N(l)-C(8) bond lengths of the imine ligand (Table 4.1) shows the N(l)-C(7) distance (included in the five-membered metallacycle) as a C=N double bond.21 C12 Figure 4.5. ORTEP diagram of the cation [fr(H){PhCH2Ar=CH(o-C6H4)}(PPh3)2-(acetone)]+ (5*a) with 50% probability thermal ellipsoids. 76 References on page 126 Chapter 4 Table 4.1. Selected bond distances and angles for [Ir(H){PhCH 2A=CH(o-C 6H 4)}-(PPh3)2(acetone)]+ (5*a) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) Ir(l)-P(l) 2.3161(8) P(l)-Ir(l)-P(2) 169.21(3) Ir(D-P(2) 2.3390(9) C(l)-Ir(l)-0(1) 171.7(1) h-O)-N(l) 2.153(3) P(l)-Ir(l)-0(1) 93.49(7) Ir(l)-C(l) 2.013(4) P(2)-Ir(l)-0(1) 92.69(7) l r ( l ) -0( l ) 2.203(2) P( l ) -h( l ) -N(l ) 93.00(8) Ir(l)-H(l) 1.48(3) P(2)-Ir(l)-N(l) 95.61(8) N(l)-C(7) 1.293(5) P( l ) -h( l ) -C( l ) 88.13(9) N(l)-C(8) 1.471(5) P(2)-Ir(l)-C(l) 87.04(9) C(15)-0(l) 1.227(5) N(l)-Ir( l)-C(l) 79.7(1) C(6)-C(7) 1.439(5) Ir(l)-0(1)-C(15) 134.6(3) C(8)-C(9) 1.511(5) Ir(l)-C(l)-C(6) 113.7(3) C(l)-C(6) 1.417(5) h(l)-N(l)-C(7) 112.7(2) C(l)-C(2) 1.398(5) C(l)-C(6)-C(7) 115.9(3) C(15)-C(16) 1.502(6) C(7)-N(l)-C(8) 121.0(3) The hydride ligand was refined isotropically. The phosphine ligands are mutually trans, with Ir-P distances in the expected range for Ir(III) octahedral complexes (see Section 3.4). The acetone ligand occupies the coordination site trans to the metallated o-C-atom. The Ir(l)-0(1) and the C(15)-0(l) distances are similar to those reported for complex 2*a, showing a C=0 distance in the coordinated acetone comparable to that of the free molecule, and an Ir(l)-0(1) distance longer than the one predicted by theoretical calculations; this was attributed to the strong trans influence exerted by the hydride ligands in 2*a.26 In complex 5*a a similarly strong zVans-labilizing effect can be 77 References on page 126 Chapter 4 attributed to the ortho C-atom. z / The C(l)-Ir(l)-N(l) angle (80°) of the metallacycle is smaller than expected (90°) for this type of five-membered ring geometry (see above). The solid state IR spectroscopic characterization of 5*a is consistent with literature data for the related [IrCl(H){MeA^=CH(o-C6H4)}(PPh3)2]+ complex.24 In particular, the Ir-H stretching frequency appears at 2211 cm"1, while the C=0 stretch of the coordinated acetone appears as an intense band at a characteristically lowered frequency (1651 cm"1) compared to that of the free molecule (1715 cm"1), consistent with 0-bonded acetone.28 The cyclometallated C=N moiety gives rise to a band, also usually decreased in frequency upon coordination,21 at 1607 cm"1 comparable in energy to that observed for the free imine ligand (1644 cm"1), consistent with a-bonding of the imine to the metal through the N lone pair rather than through n -coordination of the azomethine double bond.2 4 The r.t. 3 1 P { ' H } N M R spectrum in acetone-fife appears as a singlet (5 17.05 s). In the ' H N M R spectrum the hydride ligand appears as a triplet (8 -16.35 t, 2 JHP = 17) due to coupling to the two equivalent phosphines, and occurs downfield of the hydride ligands in 2*a ( 8 - 2 7 . 7 0 t, 2 J H p = 16, see Section 3.4). These observations are consistent with the low trans influence of the N-atom in 5*a. 2 9 The upfield shifted resonances corresponding to the aromatic protons of the ortAo-metallated ring are assigned by ' H - ' H COSY N M R experiments and on the basis of respective multiplicities and integration data. The resonance of the proton of the azomethine CH=N moiety is also shifted upfield to 8 7.67 upon coordination (cf. the free imine at 8 8.50). This is in agreement with literature data24 and consistent with retention of the n 1 -binding of the imine through the N-atom: n -coordination through the C=N is expected to cause a much larger (A8 ~ 2) upfield shift of this resonance.15 The analogous Ir(III) complexes [Ir(H){PhCH2Af=CH(o-C6H4)}(P^-tolyl3)2(acetone)]PF6 (5*b), [Ir(H){CH3A>=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (6*a) and [Ir(H){PhA^=CH(o-C6H4)}(PPh3)2(H20)]PF6 (7*a") were also isolated, whereas (7*a'), (8*a'), (9*a), and (10*a') (imine = PhCH=NPh, PhCH=NCy, PhC(Me)=NCH 2Ph, and (Ph) 2C=NCH 2Ph respectively) were characterized in situ by 3 1 P{'H} and ' H N M R spectroscopy (see Section 4.5). Isolation of MeOH-solvated species from reactions performed under the same conditions (Ir:imine = 1:1) in MeOH was not accomplished, but these species were identified in-situ and are fully formed in solution (see also Scheme 1 below). However, 78 References on page 126 Chapter 4 reaction of 2*a with excess imine (Ir:imine = 1:4) in MeOH led to the isolation of the o-metallated compound [Ir(H){PhCH2A/=CH(o-C6H4)}(PPh3)2(NH2CH2Ph)]PF6 (12*a), which in place of acetone contains the benzylamine ligand PI1CH2NH2 derived from hydrolysis of the imine. Benzaldehyde, the co-product from hydrolysis of the imine, was detected in the filtrate by *H N M R spectroscopy. X-ray quality crystals of 12*a were obtained by slow evaporation of a CH2Cl2/hexanes solution of the complex , and the structure is shown in Fig. 4.6. C37 Figure 4.6. ORTEP diagram of the cation [Ir(H){PhCH2A/=CH(o-C6H4)}(PPh3)2-(NH 2 CH 2 Ph)] + (12*a) with 50% probability thermal ellipsoids. Complex 12*a crystallizes in the P2)/n space group, with two CH2CI2 molecules present in the lattice. The hydride ligand was refined isotropically. The endo configuration of the metallacycle is again observed, and the coordination geometry at the 79 References on page 126 Chapter 4 Ir(III) center is essentially octahedral. Bond lengths and angles are comparable to those seen in 5*a (Table 4.2), including an Ir(l)-N(2) (amine) distance in 12*a that is virtually the same as the Ir(l)-0(1) (acetone) distance in 5*a. Table 4.2. Selected bond distances and angles for [h(H){PhCH 2A=CH(o-C 6H 4)}-(PPh3)2(NH 2CH 2Ph)]+ (12*a) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) h-(l)-PO) 2.331(1) P(l)-Ir(l)-P(2) 167.41(3) Ir(l)-P(2) 2.323(1) N(2)-Ir(l)-C(l) 175.0(1) Ir(l)-N(l) 2.167(3) P(l)-Ir(l)-N(l) 95.8(1) Ir(l)-N(2) 2.202(3) P(l)-Ir(l)-N(2) 92.2(1) Ir(l)-C(l) 2.041(4) P(2)-Ir(l)-N(l) 94.9(1) Ir(l)-H(50) 1.52(4) P(2)-Ir(l)-N(2) 93.2(1) N(l)-C(7) 1.282(5) P(l)-Ir(l)-C(l) 88.9(1) N(l)-C(8) 1.480(5) P(2)-Ir(l)-C(l) 86.7(1) N(2)-C(15) 1.495(5) N( l ) -h( l ) -C( l ) 78.6(1) C(8)-C(9) 1.505(5) N(l)-h(l)-N(2) 96.5(1) C(15)-C(16) 1.504(6) N(l)-C(7)-C(6) 117.9(4) C(6)-C(7) 1.450(5) N(l)-C(8)-C(9) 117.3(3) C(l)-C(6) 1.409(5) N(2)-C(15)-C(16) 110.9(4) C(l)-C(2) 1.413(5) h(l)-N(l)-C(7) 113.6(3) C(5)-C(6) 1.400(5) Ir(l)-N(l)-C(8) 124.9(2) The ER. data for 12*a are also similar to those for 5*a, except for the absence of the band due to coordinated acetone. The Ir-H stretch (2208 cm"1) appears as a medium-intensity band; medium-strong bands at 1605 and 3301 cm"1 are assigned to the C=N and N-H modes, respectively, each occurring at lower frequencies with respect to those of the free ligands (1644 and 3373 cm"1, respectively). The immediate 3 1 P{ 1 H} N M R spectrum 80 References on page 126 Chapter 4 of isolated 12*a in acetone-fife shows two resonances (5 15.57 d, JHP = 15, 12*a; 17.02 d, 2 J H p = 14, 5*a), of which 12*a is the major component (8:1 approximate ratio), indicating that in solution the benzylamine ligand is partially displaced by acetone. Accordingly, in the ' f i N M R spectrum, two high-field resonances corresponding to each complex (5 -17.42 t, V H p = 16.0, 12*a; -16.35 t, V H P = 17.1, 5*a) were detected. Upfield shifted resonances for the ort/zo-metallated ring of each complex, and signals due to free (8 1.28 s, P h C H 2 N / / 2 ; 4.47 s, PhC/ / 2 NH 2 ) and coordinated (8 2.80-2.92 m, PhC7/ 2 NH 2 and PhCH 2N/7 2 overlapping) benzylamine, were also identified. Free imine was not detected, indicating that o-metallation is retained, and no resonances downfield of 8 7.8 were detected. Integration of the signals of each complex confirms an approximate 12*a/5*a ratio of 8:1, but these spectra are time-dependent. The ratio of the two species increasingly favoured 5*a, which was the only species detected after 2 weeks at r.t.. On the other hand, 3 1 P{'H} and ' H N M R analysis of an in situ reaction of 5*a in acetone-^ with benzylamine (Ir:amine = 1:1) at r.t. showed immediate formation of 12*a as the largely dominant species in a mixture containing only traces of 5*a. In the weakly coordinating CD 2 C1 2 , however, reaction between 5*a and benzylamine (Ir:amine =1:1) resulted in the exclusive formation of 12*a. A more thorough N M R spectroscopic characterization (including ' H - , 3 C HETCOR and 1 3 C APT experiments) of isolated 12*a was therefore performed in CD 2 C1 2 solution, whereby no substitution products are formed due to the lack of coordinating ability of this solvent, and 12*a is the sole species present. A singlet at 8 15.04 is detected in the r.t. 3 1 P{'H} N M R spectrum. In the corresponding r.t. ' H N M R spectrum, the hydride resonance (8 -17.63 t, 2JHp = 17) and signals due to coordinated benzylamine (8 2.80 m, P h C / / 2 N H 2 and P h C H 2 N / / 2 overlapping) and benzylideneamine (8 5.05 s, PhC// 2N=CH(o-C 6H 4); 7.30 s, PhCH 2N=Cf7(o-C 6H 4)) were detected. Upfield-shifted resonances for the o-metallated ring are also present; a sharp resonance at 8 5.70 (d, 3JHH = 7), also present in the corresponding acetone-^ spectrum (8 5.72 d, VHH = 7), integrating for 2 protons, was characteristically observed during the course of this work for metal complexes (Ir and Rh, see below) containing the benzylamine moiety. On the basis of the ! H - 1 3 C HETCOR experiment, this resonance is attributed to aromatic protons of the benzylamine ligand, namely the ortho protons of the 81 References on page 126 Chapter 4 benzylic ring (each coupled to the neighboring meta). These protons thus appear to be strongly affected by coordination of the amine to the metal, and their possible involvement in a 7i-arene interaction with Ph groups of the PPh 3 ligands could account for the marked shift in the corresponding ' H N M R resonance. Formation of complexes containing the benzylamine ligand was observed only when using excess (with respect to metal) liquid imines such as PhCF£2N=CHPh in MeOH solvent. From similar reactions in acetone under the same conditions, 12*a was isolated as a minor product along with 5*a. The imine ligands that are liquid at r.t. likely contain traces of water; however, their hydrolysis appears to be metal-catalyzed, as shown by the stability of the neat imine PhCH2N=CHPh in MeOH. The water content of the solvent also appears to be critical, as the different findings for the reactions in acetone and MeOH indicate; however, despite attempts to rigorously dry and determine the H 2 0 content of the solvent, a clear assessment of its role has yet to be established. 4.3.2. The PhCH=NPh Ligand Reaction of 2*a with an excess of the crystalline benzylideneaniline PhN=CHPh in MeOH led to isolation of the ort/zo-metallated aquo-complex 7*a", analogous to 5*a (Scheme 1), whereas no product was isolated from a similar reaction in acetone, although the o-metallated species [Ir(H){PliA=CH(o-C6H4)}(PPh3)2(acetone-J6)]PF6 (7*a) was fully formed in situ. Compound 7*a" was isolated and characterized by 3 1 P{'H} and *H N M R spectroscopy, IR and elemental analysis. The V i r - H appears as a medium intensity band at 2192 cm"1, typical for complexes of this type. The coordinated C=N moiety absorbs at a lower frequency (1603 cm"1) compared to that of the free imine (1627 cm"1). Strong, broad bands in the far-IR region (3470, 3558, 3646 cm"1) are attributed to the coordinated H 2 0 . The 3 1 P{'H} N M R spectrum of 7*aM in acetone-^ shows a singlet at 5 17.31. The high-field hydride signal in the *H N M R spectrum in acetone-^ is the expected triplet (8 -16.95 t, J H p = 16). The para and one of the meta H-atoms of the orr/zo-metallated ring appear as triplets at § 6.54 and 8 6.85 with 3 J H H = 7 Hz. The expected doublets corresponding to the other meta and to ortho H-atoms partially overlap with the signals of the non-shifted aromatics, and their assignments remain equivocal. 82 References on page 126 Chapter 4 The resonance of the azomethine proton appears as a singlet (5 8.10), characteristically upfield compared to the free imine value (5 8.50). Comparison of data for 7*a", 5*a and 12*a suggests that 7*a" also adopts the endo geometry. PPh , ~TPF 6 H„ I ,OCMe 2 h r | ^ O C M e 2 P P h 3 2*a excess PhCH 2 N=CHPh (/) (- PhCHO) Ph NH, MeOH H + P F e H'„ I ^ P P n 3 P h 3 p N Ph H 12*a P h 3 P excess PhN=CHPh (s) O H 2 H,„ | „ P P h 3 P F B Ph H 7*a" Scheme 1. Reaction of different imines at Ir in MeOH. 4.4. Rh Systems 4.4.1. The PhCH=NCH2Ph and PhCH 2NH 2 Ligands Reaction of either [Rh(H)2(PPh3)2(acetone)2]PF6 (2a) or c«-[Rh(PPh 3) 2-(acetone)2]PF6 (3a) with PhCH 2N=CHPh (Rh:imine = 1:1) in acetone-4 at r.t. (Scheme 2) similarly afforded the Rh(III)-cyclometallated analogue [Rh(H) {PhCH2/V=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a), which was isolated and characterized by 3 1 P{'H} and ' H N M R spectroscopy, IR and elemental analysis. Detection of the hydride in the product after reaction of benzylidenebenzylamine with the analogous bis(deuteride) precursor 83 References on page 126 Chapter 4 [Rh(D)2(Pp-tolyl3)2(acetone-<i6)2]PF6 (2brf) (see Section 3.5.1) in acetone-rf6 excludes the starting bis(hydride) complex as the possible hydride source. The oxidative addition mechanism proposed for the Ir center is thus likely to apply similarly to the Rh systems. P h 3 P . P h 3 P ' P P h 3 H„ ( | ^ O C M e 2 J ^ R h ' " ' H | ^ O C M e ; , P P h 3 2a , O C M e ;Rh 3a ^OCMe P F K acetone 1 PhCH=NCH 2 Ph - H 2 "6 acetone 1 PhCH=NCH 2 Ph P h 3 P O C M e 2 H„_ | , . . P P h 3 " ^ R h " N Ph H 5a Scheme 2. Possible synthetic routes for the formation of [Rh(H) {PhCH2A=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a). Characterization data fully support the formulation of 5a, and display features similar to those of the Ir complex. The VRh-H in the IR spectrum (2096 cm"1) is at lower frequency compared to the Vir-H in 5*a, whereas the absorptions of the coordinated C=0 and C=N moieties (1660 and 1611 cm"1, respectively) occur essentially at the same frequencies as those observed in 5*a. The N M R data in acetone-^ are also consistent with the formulation. A doublet in the 3 1 P{'H} N M R spectrum (5 40.40, J R h P = 116.0, Fig. 4.7) is again indicative of the coupling of the phosphine ligands to 1 0 3 Rh, and the JRhp value of their mutually trans arrangement (see Section 3.2). The high-field hydride ' H N M R resonance (5 -12.85 pq, 2JHp ~ JRhH = 13) shows splitting due to coupling to two equivalent3 1P and one 1 0 3 R h nuclei, and appears as a pseudo-quartet from an overlapping doublet of triplets (Fig. 4.8). The lineshape of this resonance appears to be caused by a smaller difference in the 27HP and J RhH values for this type of complexes (10-16 Hz for 84 References on page 126 Chapter 4 ppm 50 45 40 35 30 Figure 4.7. 3 1 P{'H} N M R spectrum (121 MHz, 298 K) of [Rh(H){PhCH27V=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in acetone-fife. each), and other similar examples have been reported for such cationic Rh(PPh 3) 2-mono(hydride) moieties.30"34 Upfield shifted resonances in the ] H N M R spectrum for the Figure 4.8. High-field ] H N M R spectrum (300 MHz, 298 K) of [Rh(H){PhCH2-/V=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in acetone-fife. metallated ring and for the CH=N are also observed. Attempts to obtain X-ray quality crystals of the compound were unsuccessful (possibly, the acetone ligand is less strongly bound than in the Ir complex). The analogous Rh(ni) complexes [Rh(H) {CH3JV=CH(o-C6H4)}(PPh3)2(acetone)]PF5 (6a) and [Rh(H){PhCH2A^=C(Me)(o-C6H4)}(PPh3)2-(acetone)]PF6 (9a) were also isolated via 2a or 3a precursors, whereas (5b) (PR 3 = Pp-tolyl3) and (7a), (8a), (9a')> (10a') and (11a) (imine = PhCH=NPh, PhCH=NCy, PhC(Me)=NCH 2Ph, (Ph) 2C=NCH 2Ph and (p-tolyl)C(Me)=NPh, respectively) were characterized in situ (see Section 4.5). The solution behavior of 5a in acetone-ofe, 85 References on page 126 Chapter 4 however, differs markedly from that in CD3OD, in contrast with 5*a that exists as a single species in either solvent. Conversely, while present as a single species in acetone-l i e , 5a in C D 3 O D reveals a significantly different behavior, which was investigated by VT N M R experiments (Fig. 4.9, where i = free imine): C H 3 O H 1 1— 1 1 . . 1 . . . . 1 . . . . 1 1 1 1 1 1 1 1 r 60 55 50 4 5 4 0 p p r a 9 8 7 6 5 4 P P M 3 1 P{'H} T = 298 K ' H Figure 4.9. VT 3 1 P{'H} (121 MHz) and ] H (300 MHz) N M R spectra of [Rh(H)-{PhCH2/vr=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD 3 OD. The r.t. 3 1 P{'H} N M R spectrum of isolated 5a indicates the presence of several species, namely 5a (8 40.52 d, J R h p = 116), 3a' (§ 57.02 d, JRW = 207) and two broad, unresolved resonances centered at 8 ~ 46 and 8 - 5 5 likely due to a fluxional species. These resonances resolve at 253 K into an A M X , 8-line pattern (8 44.55 dd, J^p = 164, 2 J P P = 54; 54.74 dd, J R n p = 214, 2JPP = 54), indicative of a species containing two inequivalent phosphines (i.e. rearranged to a mutually cis position, each with a different trans ligand). Detection of free imine in the r.t. J H N M R spectrum indicates that 5a has 86 References on page 126 Chapter 4 undergone "reductive elimination" of this ligand, a premise confirmed by the presence of 3a' in the 3 I P{'H} N M R spectrum; the § 4.7-5.3 region, in which the benzylic protons of free and ort/jo-metallated imine appear (5 4.80 s and 4.99 s, respectively), is slightly broadened, suggesting that the imine ligand may be involved in or be within a fluxional environment. The ' H N M R spectrum recorded at 253 K shows improved resolution of this broad region into a pair of doublets (5 4.50 d, 5.35 d, 2 J H H = 6), indicating diastereotopic inequivalence of the benzylic protons, i.e. the imine is present within a non-symmetric complex. The r.t. ' H N M R spectrum also shows a downfield doublet (8 9.65 d, 3 J H H ~ 8) (observed only in traces in the spectrum of 5a in acetone-fife) that is not attributable to 3a' nor to free imine. The corresponding r.t. ' H - ^ C HETCOR N M R experiment revealed correlation of this signal with resonances in the region of the 1 3 C N M R spectrum corresponding to aromatic C H carbon atoms (8 132), which incidentally also correlate with the upfield, aromatic ! H resonances of the o-metallated ring (Fig. 4.10). Correlation in this region of the 1 3 C spectrum rules out the possibility that this resonance may originate from formation, and possibily coordination, of benzaldehyde, a product of imine hydrolysis. In a related example containing a coordinated benzaldehyde-derivative ([Ir(H)2(PPh3)2{r|2-(A^,0)-2-pyridinecarboxaldehyde}]BF4), formed by reaction of 2-pyridinecarboxaldehyde with [Ir(H)2(PPh3)2(acetone)2]BF4 at r.t. in C6H 6, a key feature is the *H N M R shift of the aldehydic proton (8 9.78, bs), involved in a long-range, 4-bond coupling with the two cis hydrides.35 A more plausible rationale for the 8 9.65 ! H N M R resonance observed for 5a in this work is perhaps that of involvement of the ortho protons of the imine Ph moiety in a 7i-arene interaction with Ph groups of the PPh 3 ligands, analogous to that observed for 12*a (see above). More explicit information on this point could be obtained from studies on Rh and Ir precursors containing tris-alkyl phosphines. 87 References on page 126 Chapter 4 Figure 4.10. ' H - I 3 C (400-100 MHz, 298 K) HETCOR N M R spectrum (selected regions) of [Rh(H){PhCH2A=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD 3 OD. The spectroscopic evidence shows that the Rh(III)-cyclometallated compound 5a is inherently more labile than the Ir analogue 5*a, and that MeOH is capable of reversing the orz^o-metallation process to afford an intermediate Rh(I) species containing one imine ligand and one MeOH ligand, each trans to one phosphine ligand in a low-temperature limit structure V (as identified from the J^n? values at 253 K , see below) as shown in Scheme 3. In an alternative picture, the ortho protons of the Ph ring (assuming free rotation of the Ph group) of the imine could be involved in an agostic interaction with the metal center (formally 5-coordinate at this stage), en route to formation of the ort/zo-metallated product, and where exchanging solvent molecules at one coordination site could account for the broadness of the 3 1 P{ 1 H} N M R resonances observed at r.t.. These "agostic" o-H-atoms are then considered responsible for the 8 9.65 ! H resonance, and slow rotation of the Ph group at low temperature accounts for the loss of resolution. 88 References on page 126 Chapter 4 Ph 3 P O C M e 2 | + P F 6 H,, | ,„PPh 3 ' ^Rh ' ' ^ N ^ P h D OCD H CD3OD P h 3 P . y-J^z ^ R h Ph3P ^OCD3 D PF, P h 3 P N ^ P h J ^ R h " P h 3 P ^ ^ O C D 3 D 5a 3a' Scheme 3. Proposed behavior of [M(H){PhCH2Ar=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD3OD. Prior to gathering ' H - 1 3 C HETCOR N M R evidence, an alternative, quite seductive rationalization for the behavior of 5a in CD3OD was formulated, in which the fluxionality was envisioned as resulting from a facile interconversion of n 1 and r\2 coordination modes of the CH=N moiety, possibly solvent assisted (Scheme 4). OCMe 2 l + P F6 H',. I , - P P h 3 C D 3 O D .Rh . — , P h 3 P " ^ I ^ N ^ P h 5a P h 3 P . ^ R h P h 3 P ^ ^ O C D 3 D 3a 1 O C D 3 C D 3 •Ph 3P / O - D ^ R h P h 3 P ^ "^N=<^ PF. Ph Ph H Ph 3 P . P h 3 P ' C D 3 :Rh Ph " P F . N H Ph Scheme 4. Alternative rationalization for N M R data for [Rh(H) {PhCH27V=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD3OD. 89 References on page 126 Chapter 4 In four-coordinate Pt(II) complexes containing a a(N)-bound imine like cis-[(CH3)2Pt{S(CH3)2}{PhCH2A^=CH(Mes)}] (Mes = mesityl),22 a prominent feature is the downfield ' H N M R shift (5 9.4-9.6) observed at r.t. for the iminic proton CH=N, the resonance appearing as a doublet due to three-bond coupling to 1 9 5Pt. By analogy, the proton of the azomethine moiety in the fluxional species described in this thesis work might have accounted for the downfield resonance at § 9.65. Broadening of this resonance at lower temperatures would then elude a satisfactory explanation, although some interaction of the iminic proton with the coordinated solvent within a Z-conformational structure formed via isomerization of the E isomer could be invoked, as shown in Scheme 4. However, absence of correlation of this resonance with the distinctively downfield (5 176) C-atom of the azomethine group rules out this alternative picture. Evidence for the formation of a mono-imine solvento complex similar to V was gathered when reacting the Rh(I) precursors 3a' and 3b' in CD3OD with PhCH=NMe and PhCH=NPh, respectively (Rh:imine = 1:2). The 3 1 P{'H} N M R spectrum of the in situ reaction between 3a' and PhCH=NMe does not indicate fluxionality of the system and the A M X , 8-line pattern is seen at r.t. (5 46 .42 dd, Jm? = 164, 2J?P = 54; 55.96 dd, JRh? = 216, 2Jpp = 53); the corresponding ' H N M R spectrum displays a broad resonance at 5 9.86, again likely due to the ortho protons of the imine Ph moiety. Fluxionality at r.t. was revealed, however, by 3 1 P{'H} N M R analysis of the in situ reaction mixture between 3b' and PhCH=NPh; the broad regions (5 ~ 45 and 53) resolved at 2 5 3 K, similarly to the behavior of V, into an A M X , 8-line pattern (8 45 .50 dd, J^p = 168, 2JPP = 54; 53 .16 dd, JRHP = 213 , l /pp = 54). In both imine systems, the J R n p values are comparable to those of V, and are indicative of one N - and one O-donor ligand each trans to a phosphine.10 The corresponding *H N M R spectra in the two temperature regimes show a resonance at 5 9.80 displaying a behavior similar to the one observed in the case of V: loss of resolution upon lowering of temperature is observed also in the PhCH=NPh case, suggesting that a fluxional process analogous to the one observed for V is established. Observation of the resonance at 8 9.60-9.80 in the *H N M R spectra (CD3OD) of in situ reaction mixtures containing the PhCH=NCH 2Ph, PhCH=NMe, P h C H = N C 6 H n and PhCH=NPh imines rules out the possibility that it may originate from the substituent on 90 References on page 126 Chapter 4 the N atom. The importance of the behavior displayed by 5a in C D 3 O D , however, rests on the fact that a Rh(I) species is obtained which, although as yet not unambiguously identified, renders the metal center available for oxidative addition and thus, upon admission of H 2 into the system, for entering into a catalytic cycle (as discussed in Section 5.2.1). Reaction of either Rh(I) precursor 2a', 2b' or 3a', 3b' with excess PhCH 2N=CHPh (Rh:imine = 1:4) in MeOH led to the isolation of the square-planar complex m-[Rh(PR 3) 2(PhCH 2A/=CHPh)(NH 2CH 2Ph)]PF 6 (R = Ph, 14a; p-tolyl, 14b) containing one imine moiety o-bound to the metal through the N atom (not ortho-metallated in the solid state) and one benzylamine fragment resulting from metal-catalyzed hydrolysis of the imine, as observed in the Ir complex 12*a. Complex 14b was isolated and characterized by 3 1 P{'H} and ' H N M R spectroscopies, IR, elemental analysis and X-ray crystallography; the structure is shown in Fig. 4.11. Figure 4.11. ORTEP diagram of the complex cw-[Rh(Pp-tolyl3)2(PhCH2A^=CHPh)-(NH 2CH 2Ph)]PF 6 (14b) with 50% probability thermal ellipsoids. 91 References on page 126 Chapter 4 X-ray quality crystals of 14b were obtained by slow evaporation of a CD3OD solution of the complex. The molecule crystallizes in the P2i/c space group; the geometry at the Rh(I) is essentially square-planar, and there is hydrogen-bonding between the anion and the cation. Selected structural parameters are listed in Table 4.3. The IR spectrum 31 1 reveals VC=N and VN-H of the coordinated imine and amine, respectively. The P{ H} NMR spectrum in CD3OD consists of an A M X , 8-line pattern due to inequivalence of the two phosphine ligands, fully resolved at r.t. with no indication of fluxionality. Based on the JRHP values (see data for 5a above and 16a below), the upfield resonance is assigned to the P-atom trans to the imine (8 45.06 dd, jRhp = 166, Vpp = 50), and the downfield one to the P-atom trans to the amine (8 48.20 dd, JRhp = 180, Vpp = 50). Table 4.3. Selected bond distances and angles for cz's-[Rh(P/?-tolyl3)2(PhCH2-Af=CHPh)(NH2CH 2Ph)] + (14b) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) Rh(l)-P(l) 2.2539(9) P(l)-Rh(l)-N(l) 172.47(8) Rh(l)-P(2) 2.2503(9) P(2)-Rh(l)-N(2) 176.26(10) Rh(l)-N(l) 2.128(3) P(l)-Rh(l)-P(2) 96.96(3) Rh(l)-N(2) 2.211(3) P(l)-Rh(l)-N(2) 86.34(9) N(l)-C(50) 1.494(5) P(2)-Rh(l)-N(l) 90.43(8) N(l)-C(43) 1.288(5) C(43)-N(l)-C(50) 116.2(3) N(2)-C(57) 1.487(5) C(50)-N(l)-Rh(l) 113.4(2) C(43)-C(44) 1.460(5) C(43)-N(l)-Rh(l) 130.3(3) C(57)-C(58) 1.519(5) C(57)-N(2)-Rh(l) 122.3(2) C(50)-C(51) 1.507(5) N(2)-C(57)-C(58) 111.8(3) No high-field resonances were detected in the ' H N M R spectrum in CD 3 OD, consistent with the solid state structure and with the intrinsic higher lability of the Rh vs. Ir systems that favour retention of ort/zo-metallation. However, ' H resonances at 8 9.81 (d, V H H = 7), similar to that at 8 9.65 detected for 5a in CD 3 OD, and at 8 6.02 (d, V H H = 92 References on page 126 Chapter 4 7), similar to that at 5 5.72 (d, 2JHH = 7) observed for 12*a in acetone-c/6, were detected in a roughly 1:1 ratio. The azomethine proton appears as a poorly resolved doublet, possibly because of coupling to Rh. Resonances indicating diastereotopic inequivalence of the benzylic protons of the imine (8 4.45 d, 1H, 2 J H H = 12; 5.15 d, 1H, 2 J H H = 12) and of the amine (5 2.46 d, 1H, 2JHH = 14; 2.61 d, 1H, 2JM = 14) were detected. A similar set of inequivalent resonances for the -NH2 group was not detected, likely because of H-exchange with the deuterated solvent. Circumvention of this problem and a more accurate N M R spectroscopic characterization were.again possible in CD2CI2. The 8-line pattern is detected in the r.t. 3 ! P{ 'H} N M R spectrum (5 45.15 dd, JRHP = 166, 2 J P P = 49; 48.20 dd, J R h P = 180, 2J P P = 49) as shown in Fig. 4.12. r 1 1 1 ' ' 1 1 1 1 1 i ' 1 ' 1 1 ' ' 1 ' '—'—r~~'—1—1—1—1—1—'—1—•—1—1—1—1— ppm 54 52 50 40 46 44 42 40 38 Figure 4.12. 3 1 P{ 1 H} N M R spectrum (121 MHz, 298 K ) o f cw-[Rh(PR 3) 2(PhCH 2-/V=CHPh)(NH 2CH 2Ph)]PF 6 (R = p-tolyl, 14b) in CD 2 C1 2 . In the corresponding ' H N M R spectrum, improved resolution of all the expected resonances, including those of the -NH2 group, is achieved (Fig. 4.13). In particular, the benzylic protons of the amine appear as two overlapping triplets of doublets (§ 2.52 td, 1H, V H H = 13, 2JHH = 4; 2.58 td, 1H, V H H = 13, 2JHH = 4), due to coupling to the - N H 2 protons and to each other, and similarly the - N H 2 protons, although less well resolved, appear as two somewhat broad and overlapping triplets (5 1.12 t, 1H, 3 J H H = 12; 1.24 t, 1H, 3 J H H = 12). The diastereotopically inequivalent benzylic protons of the imine are clearly seen as two doublets (8 4.38 d, 1H, 2JUH = 12; 5.15 d, 1H, 2JHH = 12) at virtually the same chemical shifts as those observed in CD 3 OD. The resonance for the azomethine proton (8 8.03) again appears as a broad doublet, however further multiplicity is clearly not resolved. The sharp resonances at 8 5.95 (d, J H H = 7) and 5 9.76 (d, JHH = 7) are similarly observed in this solvent. 93 References on page 126 Chapter 4 Figure 4.13. *H N M R spectrum (300 MHz, 298 K) of cw-[Rh(PR3)2(PhCH27V=CHPh)-(NH 2CH 2Ph)]PF 6 (R = p-\o\y\, 14b) in CD 2 C1 2 . Of interest, the ' H N M R spectroscopic features of 14b somehow encompass those of both the related Rh and Ir complexes 12a in CD 2 C1 2 (see below) and 12*a in acetone-d6, which display a similar resonance at around 5 6 but none downfield of 5 8, and of 5a in CD3OD, which conversely displays a downfield resonance around 5 9 but none at 5 6. In both cases, the ' H - 1 3 C HETCOR N M R experiments (see Figs. 4.10 and 4.14) show correlation of each of these resonances with aromatic protons. Ot/zo-metallation being retained and partially "reversed" in the Ir and Rh complexes, respectively, leads to assignment of the resonance at 5 ~ 6 to protons of the benzylic ring of the amine, and that at 5 ~ 9 to protons of the phenyl ring of the azomethine moiety after being "reductively eliminated" from o-metallation. Each resonance also appears as a doublet (VHH = 7 for both), and integrates for two protons. These observations suggest involvement of the ortho protons of the Ph and Bz moieties of the imine and the amine, respectively, each coupling to the neighboring meta-H, in an interaction with either the metal or, perhaps more likely, with Ph groups of the PPI13 ligands. Furthermore, in contrast with the data for 5a, the resonance for the azomethine H-atom of 14b is clearly detected in both 94 References on page 126 Chapter 4 C D 2 C I 2 and C D 3 O D , ruling further out involvement of the imine in an nVr|2-coordination shift. Plausible coordination environments for 14b in solution are shown in Fig. 4.15. Figure 4.14. ' H - 1 3 C (400-100 MHz, 298 K) HETCOR N M R spectrum of cis-[Rh(PR3)2(PhCH2/V=CHPh)(NH2CH2Ph)]PF6 (R = p-tolyl, 14b) in CD 2 C1 2 . Figure 4.15. Proposed coordination environments of ds-[Rh(PR3)2(PhCH2Af=CHPh)-(NH 2CH 2Ph)]PF 6 (R = p-tolyl, 14b) in solution. 95 References on page 126 Chapter 4 The 3 1 P{'H} and *H N M R characterization of 14a in CD 2 C1 2 virtually replicates that of 14b. The 3 1 P{'H} N M R 8-line pattern is detected at r.t. (8 46.94 dd, J R n P = 166, JPP = 49; 50.07 dd, J R h p = 180, J P p = 49), again with no indication of fluxionality. The corresponding r.t. ' H N M R spectrum displays features almost identical to those of 14b, except for the absence of the p-CH3 resonances. Resonances for the inequivalent benzylic protons of the amine (8 2.60 2 overlapping td, 2H, V H H = 13, 2 J H H = 4) and imine (8 4.40 2 2 d, 1H, JHH = 13; 5.12 d, 1H, 7HH = 13) moieties are detected, as well as those of the -N H 2 group (8 1.10 t, 1H, 3JHH = 11; 1.26 t, 1H, 3 J H H = 11) and of the azomethine proton (8 8.01 bd). Similarly to 14b, sharp resonances at 8 5.98 and 8 9.70 are present. The coordination modes illustrated in Fig. 4.15 are again favoured. Reaction of 3a' with benzylamine in MeOH (Rh:amine = 1:2) led to isolation of the bis-amine complex c/s-[Rh(PPh 3) 2(NH 2CH 2Ph) 2] + (15a) (Fig. 4.16). The complex was characterized by 3 I P{ 'H} and ! H N M R spectroscopy, elemental analysis and X-ray crystallography. I_I ^ P F " + P F " ? ' 6 Ph 1 6 P h 3 p \ / 0 M e 2 P h C H 2 N H 2 P h 3 P . , N H 2 — / . R h j ; R h P h 3 P ^ ^ O M e MeOH P h 3 P ^ ^ N H 2 -i H 3a' 15a Ph Figure 4.16. Reaction scheme for the formation of m-[Rh(PPh 3) 2(NH 2CH 2Ph) 2]PF 6 (15a). Formation of the bis-amine complex occurs from 3a' in MeOH or is observed in situ from 4a in C D 3 O D and CD 2 C1 2 . When using 2a' in MeOH, however, formation of 17a (see below) also occurs. Furthermore, no products could be isolated from similar reactions in acetone, where different chemistry is realized (see below). Indeed, X-ray quality crystals of 15a (Fig. 4.17) crystallized with 0.5 MeOH were obtained from slow evaporation of a MeOH solution of the isolated solid. Selected structural parameters are given in Table 4.4. 96 References on page 126 Chapter 4 C13 Figure 4.17. ORTEP diagram of the cation cw-[Rh(PPh3)2(NH2CH2Ph)2]+ (15a) with 50% probability thermal ellipsoids. Table 4.4. Selected bond distances and angles for cw-[Rh(PPh3)2(NH2CH2Ph)2]+ (15a) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) RhO)-P(l) 2.2067(8) P(l)-Rh(l)-N(l) 178.1(1) Rh(l)-P(2) 2.2481(8) P(2)-Rh(l)-N(2) 173.6(1) Rh(l)-N(l) 2.201(3) P(l)-Rh(l)-P(2) 93.87(3) Rh(l)-N(2) 2.147(3) P(l)-Rh(l)-N(2) 92.4(1) N(l)-C(37) 1.487(4) P(2)-Rh(l)-N(l) 87.7(1) N(2)-C(44) 1.475(6) C(37)-N(l)-Rh(l) 120.0(2) C(37)-C(38) 1.507(5) C(44)-N(2)-Rh(l) 119.9(3) C(44)-C(45) 1.510(6) N(l)-Rh(l)-N(2) 86.0(1) 97 References on page 126 Chapter 4 Of note, 15a could be observed as such by 3 1 P{ ] H} N M R only in C D 3 O D solution (5 52.21 d, y R h p = 176), whereas it rearranges in acetone-fife into the non-symmetric complex cw-[Rh(PPh3)2{/VH2CH2(Ti2-C6H5)}]PF6 (16a) (Scheme 5), described by an A M X , 8-line pattern in the 3 1 P{'H} N M R spectrum (8 47.46 dd, J^? = 167, VPP = 49; 52.44 dd, y R h P = 183, 2JPP = 49). Accordingly, the *H N M R spectrum of 16a, generated from a solution of 15a in acetone-fife, shows inequivalence of both sets of protons of the coordinated amine ligand (5 2.90, 3.16 2d, 2H, 2JHH = 12, P h C H 2 N / / 2 ; 4.50, 4.75 2d, 2H, VH H = 12, PhC/ / 2 NH 2 ) , free ligand (8 4.55 s, 2H, PhC# 2 NH 2 ) and upfield shifted resonances in the aromatic region (8 6.23 d, 1H, 2JHH = 8.5, <>n2-C6#5CH2NH2; 7.05 m, 2H, m, p-v\ -Ce^5CH 2 NH 2 ). In situ reactions at r.t. between 3a and benzylamine (Rh:amine = 1:2) confirmed the behavior in each solvent, giving rise to spectra virtually identical to those of isolated 15a in each solvent. Scheme 5. Different behavior of cw-[Rh(PPh 3) 2(NH 2CH 2Ph) 2]PF 6 (15a) in different The spectroscopic evidence is consistent with the existence of two limiting structures in the two solvents (Scheme 5), the fact being possibly related to the different coordination abilities of MeOH and acetone. The N M R data for 15a in acetone-fife thus provide further insight in terms of identifying some of the species observed or implied in the spectroscopic characterization of 14b and 5a in solution. Particularly, for 15a in acetone-fife (i.e. 16a) the 8 6.23 resonance appears to be due to an aromatic o-proton P h 3 P N H 2 16a solvents. 98 References on page 126 Chapter 4 involved in an n2-arene coordination. The assignment of the 5 6.0 *H resonance displayed by 14b in CD3OD to o-protons of the benzylamine is thus consistent with the data for 15a in acetone-^6- Of note, however, a corresponding upfleld-shifited resonance for the o-protons of 15a in CD3OD, observed for complexes 14, was not detected for 15a. Involvement of these protons in a 7c-arene interaction with the benzylic moiety of the coordinated imine, rather than with the aryl moieties of the phosphines, in species 14, not possible in 15a, could account for the discrepancy. In addition, reaction of 2a' with benzylamine (Rh:amine = 1:2) in MeOH gives formation of the complex cis, trans, cis -[Rh(H) 2(PPh3)2(NH2CH 2Ph)2]PF 6 (17a) (Fig. 4.18). H H + PF 6 " H OMe M e 6 s I ...PPh 3 2 P h C H 2 N H 2 ^ R h * P h 3 P ^ | MeOH H 2a" Ph I 1 N H 2 + PF H 2 N, ,PPh, ' Rh P h 3 P " ^ I X H H 17a Figure 4.18. Formation of cw,/ra«5,cw-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (17a) in MeOH. Two closely separated v R hH (2050, 2090 cm"1) and a broad band at 3336 cm"1, assigned to the N - H modes, are the most prominent features in the IR spectrum of isolated 17a. X-ray quality crystals of 17a were obtained by slow evaporation of a CH2Cl2/hexanes solvent mixture of the complex under Ar, and the structure is shown in Fig. 4.19. The complex crystallizes in the C2/c space group: one complete CH2CI2 molecule was found in the asymmetric unit, while at a second site lA molecule of CH2CI2 is disordered with % molecule of C6H ] 4 . Only the N - H hydrogen atoms were refined isotropically. The complex resides on two-fold rotation axis, and the geometry at the Rh(III) is somewhat distorted from octahedral. Selected bond distances and angles are given in Table 4.5. 99 References on page 126 Chapter 4 Figure 4.19. ORTEP diagram of the cation c«>a«s,cw-[Rh(H)2(PPh 3)2(NH 2CH2Ph) 2] + (17a) with 50% probability thermal ellipsoids. Table 4.5. Selected bond distances and angles for cis,trans,cis-[^{Yl)2(?V\\3)2-(NH 2 CH 2 Ph)2] + (17a) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) Rh(l)-P(l) 2.2931(10) P(l)-Rh(l)-N(l) 91.77(12) Rh(l)-P(l*) 2.2931(10) P(l*)-Rh(l)-N(l*) 91.77(12) Rh(l)-N(l) 2.238(3) P(l)-Rh(l)-P(l*) 165.64(5) Rh(l)-N(l*) 2.238(3) P(l)-Rh(l)-N(l*) 98.00(11) Rh(l)-H(l) 1.47(3) P(l*)-Rh(l)-N(l) 98.00(11) N(l)-C(l) 1.488(5) P(l)-Rh(l)-H(l) 88.1(14) C(l)-C(2) 1.515(6) N(l)-Rh(l)-H(l) 175.2(13) N(l)-H(27) 0.89(6) C(l) -N(l) -Rh(l ) 114.8(3) N(l)-H(28) 0.82(5) N(l)-Rh(l)-N(l*) 94.3(2) 100 References on page 126 Chapter 4 The 3 1 P{'H} doublet for 17a appears in the r.t. spectrum at 8 49.55 (JRhP = 116) in CD 2 C1 2 , and the ' H high-field resonance for the equivalent hydrides (8 -17.55 pq, J R h H ~ 2 2 JRH ~ JHP = 14) appears as a pseudo-quartet instead of the expected doublet of triplets (as with 5a, see above); the 8 value, downfield of that of the analogous bis-alcohol species 2a', is consistent with the presence of low trans-influence ligands (NH2 vs. OH) (see data for 5a above). Of note, a sharp ] H N M R resonance at 8 6.20 (d, V H H = 6, 4H) is also detected, similar to those observed in complexes 14 and 12*a, again indicating the sensitivity of the ortho protons of the benzyl ring to coordination to the metal. 17a is not fully stable in CD3OD under Ar, and undergoes reductive elimination of H2 to form 15a, with partial substitution of the amines by the solvent to form 2a', in an approximate ratio 17a:15a:2a' ~ 1:1:0.3. Upon exposure of this mixture to 1 atm H 2 , 15a is fully converted into 17a, with 2a' being the only other species detected. Interestingly, the 3 1 P{'H} and *H N M R spectra of isolated 17a in acetone-a^, virtually identical to those of isolated 15a in this solvent, display full conversion to the monoamine species 16a (see Scheme 5). The 3 1 P { ' H } N M R spectrum of the in situ reaction between 5a and benzylamine (Rh:amine = 1:1) in acetone-d6 at r.t. under Ar showed after 1 h partial formation of the amine-substituted or/Tzo-metallated complex 12a (8 42.27 d, JRhP = 114) analogous to the Ir-complex 12*a, while 5a and a non-symmetric complex, giving rise to the same pattern observed for 16a (8 47.46 d, / R h P = 167, 2J?? = 49; 52.44 d, 7R h P = 183, V P P = 49), were the major components of the reaction mixture. The corresponding ' H N M R displays signals corresponding to 5a, to 12a, to free imine and acetone, the same set of resonances observed for 16a and traces of a second non-symmetric unit similar to 14a. For this last species, low intensity resonances at 8 9.83 and 6.10 (2 d, 2Jun = 7) in fact indicate an intermediate amine-imine complex as described above (Fig. 4.15), and likely correspond to those observed at 8 9.81 and 6.0 for 14a in CD 3 OD. This implies that benzylamine coordinates to Rh initially to form 12a, which however eventually rearranges, via the bis-agostic form and subsequent displacement of the imine, into the preferred n2-amine complex 16a (Fig. 4.20), as evidenced in the solution behavior of 15a in acetone-^. Indeed, the acetone-^ spectra of 14a and of the in situ reaction mixture just described, as well as of in situ reaction mixtures of 3a and PhCH2N=CHPh (Rh:imine ~ 0.5; i f 101 References on page 126 Chapter 4 Rh:imine ~ 0.02, 5a and 14a form initially), are time-dependent, and all eventually evolve into that of the stable n2-amine complex. Figure 4.20. Proposed steps for the reaction between [Rh(H){PhCH27V=CH(o-C6H4)}-(PPh3)2(acetone)]PF6 (5a) and P h C H 2 N H 2 in acetone-^. In contrast to the study in acetone-^, the r.t. 3 1 P{'H} N M R spectrum of the in situ reaction of 5a with benzylamine (Rh:amine = 1:1) in C D 3 O D under Ar (Fig. 4.21) recorded after 1 h revealed formation of 12a (5 41.54 d, J R h P = 114), of 14a (5 46.90 dd, JRHP = 166, 2 y P P = 49; 50.10 d, J^v = 180, 2Jp P = 49), and of the bis-amine complex 15a (5 52.21 d,JRhP = 176). i ^ r 1 1 • 1 ' 1 ' 1 ' r ppm 60 55 50 45 10 35 30 Figure 4.21. 3 1 P{'H} N M R spectrum (121 MHz, 298 K) of the 1:1 in situ reaction between [Rh(H){PhCH2A^=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) and benzylamine in CD 3 OD (14a:15a:12a ~ 1:0.6:0.2). These data are consistent with the 3 1 P{ ] H} N M R spectra observed for 15a and 14a in CD 3 OD, and suggest that in this solvent, as opposed to acetone-^, interaction of 102 References on page 126 Chapter 4 benzylamine with 5a results in the formation of the two more stable complexes 14a and 15a. The corresponding *H N M R spectrum (Fig. 4.22, where i * and a* indicate free imine and amine, respectively) displays resonances due to 12a (e.g. 8 2.63 s, 2H, PhC7/ 2NH 2; 5.12 s, 2H, PhC// 2N=CH(o-C 6H 4)), to free imine (8 4.78 s, 2H, PhCH=NC// 2Ph; 8.50 s, 1H, PhC7/=NCH2Ph) and acetone (8 2.11 s), to 14a (8 2.50, 2.65 2 d, VH H = 14; 4.48, 5.18 2 d, 2JHH = 12; 6.0 d, 2Jm = 7; 8.21 bd; 9.81 bd) and 15a (8 3.50 s, 4H, PhC/ / 2 NH 2 ) . Resonances for the inequivalent protons of the amino group in 14a are again not detected in this solvent (see above). Figure 4.22. ' H N M R spectrum (300 MHz, 298 K) of the 1:1 in situ reaction between [Rh(H){PhCH2iV=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) and benzylamine in CD 3 OD. Of note, the observed r.t. spectra of in situ reactions between 3a' and PhCH=NCH 2Ph (Rh:imine < 1) in CD 3 OD are similar to those of 5a, but also time-dependent. The system rearranges faster than in acetone-^ and eventually, depending on the Rh:imine stoichiometry, affords a single species displaying spectra virtually identical to those of 14a (if Rh:imine « 1, 14a forms immediately and solely). When Rh:imine = 1, formation of only 5a and 14a occurs. The same in situ r.t. reaction between 5a and 103 References on page 126 Chapter 4 benzylamine in CD2CI2 (Rh:amine = 1 : 1 ) results in exclusive formation of complex 12a (5 42 .27 d, J R H P = 114). 4.4.2. The PhC(Me)=NCH2Ph Ligand The in situ reaction of 3a' with the ketimine PhC(Me)=NCH 2Ph (Rh:imine = 1:2) (in which the azomethine H-atom is replaced by a C H 3 group) was investigated in CD3OD by 3 1 P{'H} and ! H NMR. In contrast to the PhCH=NCH 2Ph system, no ' H resonances at 8 9.6-9.8 were detected, and the system was not fluxional, as shown by the sharp resonance in the r.t. 3 1 P{'H} N M R spectrum (8 40.23 d, J ^ P = 119): the J R h P value, and the distinctive high-field pseudo-quartet and upfield shifted resonances at 8 ~ 6-7 in the 'IT N M R spectrum identify this species as the ort/zo-metallation product [Rh(H){PhCH2^=C(Me)(0-C6H4)}(PPh3)2(CD3OD)]PF6 (9a') (Fig. 4 .23) . D ~~] + PF6 P h 3 P / O C D 3 2 PhC(Me)=NCH 2Ph ^ R h 1 P h 3 P ^ " " O C D 3 CD3OD D 3a' Figure 4.23. Reaction scheme for the in situ formation of [Rh(H){PhCH2Ar=C(Me)(o-C6H4)}(PPh3)2(CD3OD)]PF6 (9a') in CD 3 OD. Thus in this case, the ort/zo-metallated complex is stable, and solvent-exchange in conjunction with reductive elimination of the o-metallated Ph moiety as suggested for 5a are not taking place. The difference in the behavior of 5a and 9a' must be related to electronic effects of C H 3 vs. H . Signals due to excess free imine were detected. Interestingly, however, no ' H signals for the C H 3 group of the coordinated ligand were detected: an exchange process of these protons with the deuterated solvent, through tautomerization of the imine group (Fig. 4.24), could account for the lack of the C H 3 P h 3 P D O C D 3 H,,, I ^F>Ph 3 v. + PF R N Ph Me 9a' 104 References on page 126 Chapter 4 signals. Although mechanistic studies on the hydrogenation of PhC(Me)=NNH(CO)Ph and related imines, catalyzed by various Rh and Ir systems,1 have ruled out enamine intermediates, no o-metallated species were detected in these catalytic systems. Figure 4.24. Proposed H -D exchange in CD3OD at the CH3 group of PhC(Me)=NCH2Ph in [Rh(H){PhCH2^=C(Me)(o-C6H4)}(PPh3)2(CD30D)]PF6 (9a'). Complex 9a' seemed particularly stable even in CD3OD, but such a solution, upon standing for 2 days, spontaneously afforded X-ray quality crystals of the complex [Rh(H){PhCH27V=C(Me)(o-C6H4)}(NH2CH2Ph)(PPh3)2]PF6 (18a) (Fig. 4.25). Figure 4.25. ORTEP diagram of the cation [Rh(H){PhCH27V=C(Me)(o-C6H4)}(PPh3)2-(NH 2 CH 2 Ph)] + (18a) with 50% probability thermal ellipsoids. 105 References on page 126 Chapter 4 Complex 18a displays retention of ortrco-metallation, in contrast with the corresponding behavior of 12a (see Fig. 4.20) and of the isolated imine-amine complex 14a, but it similarly contains the benzylamine fragment formed from hydrolysis of the imine: this imine is also a liquid, supporting the hypothesis that the substrate is the source of H 2 0 . In addition, the immediate in situ N M R spectra of 9a' did not reveal occurrence of hydrolysis, i.e. no resonances due to benzylamine were seen, consistent with a stoichiometric imine:Rh ratio. Complex 18a was characterized only by X-ray crystallography and constitutes the only example in this thesis work of an ortho-metallated species at a Rh center for which a structural determination was achieved. Selected structural parameters are given in Table 4.6. The molecule crystallizes in the P2]/n space group and the endocyclic conformation solely is observed. Table 4.6. Selected bond distances and angles for [Rh(H) {PhCH27v=C(Me)(o-C6H 4)}(PPh3) 2(NH 2CH 2Ph)]+ (18a) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) Rh(l)-P(l) 2.3499(6) P(l)-Rh(l)-P(2) 169.30(2) Rh(l)-P(2) 2.3344(6) N(l)-Rh(l)-C(18) 178.55(9) Rh(l)-N(l) 2.224(2) P(l)-Rh(l)-N(l) 92.22(7) Rh(l)-N(2) 2.162(2) P(l)-Rh(l)-N(2) 97.08(5) Rh(l)-C(18) 1.999(2) P(2)-Rh(l)-N(l) 92.29(7) Rh(l)-H(54) 1.43(2) P(2)-Rh(l)-N(2) 91.49(5) N(2)-C(15) 1.288(3) P(l)-Rh(l)-C(18) 88.50(6) N(2)-C(8) 1.478(3) P(2)-Rh(l)-C(18) 86.79(6) N( l ) -C( l ) 1.509(4) N(2)-Rh(l)-C(18) 79.45(8) C(l)-C(2) 1.509(4) N(2)-C(15)-C(16) 124.9(2) C(15)-C(16) 1.511(3) N(2)-C(15)-C(17) 116.0(2) C(15)-C(17) 1.467(3) C(8)-N(2)-C(15) 121.0(2) C(8)-C(9) 1.512(3) N(2)-C(8)-C(9) 115.1(2) C(17)-C(18) 1.411(3) N(l)-C(l)-C(2) 114.3(2) 106 References on page 126 Chapter 4 The Pvh-P distances, significantly longer than those observed for the square-planar c/5-[Rh(Pp-tolyl3)2(PhCH=NCH 2Ph)(PhCH 2NH 2)]PF 6 (14b), and the Rh-N distances of the coordinated amine and imine groups are comparable to those determined for the Ir(III) analogue 12*a (see Fig. 4.6, Section 4.3.1). On the other hand, reaction of 3a with PhC(Me)=NCH 2Ph (Rh:imine = 1:2) in acetone led to isolation the corresponding or^o-metallated acetone-complex [Rh(H){PhCH27V=C(Me)(o-C6H4)}(PPh3)2(acetone)]PF6 (9a) analogous to 5a, further indicating that isolation of these species strongly depends on the lability of the coordinated solvent (Fig. 4.26). + P F B P h 3 P ^ O C M e 2 ^ R h P h 3 P ^ ^ O C M e 2 PhC(Me)=NCH 2Ph j acetone P h 3 P H +PF 6 O C M e 2 H " , | ^ P P h 3 " ^Rh " N Ph Me 3a 9a Figure 4.26. Reaction scheme for the formation of [Rh(H){PhCH27V=C(Me)(o-C6H4)}-(PPh3)2(acetone)]PF6 (9a). Complex 9a was characterized by 3 1 P{'H} NMR, ' H N M R and IR spectroscopies, but unfortunately a satisfactory elemental analysis could not be obtained. The complex in acetone-c?6 gives rise to a single resonance in the 3 1 P{'H} N M R spectrum (8 40.33 d, J^h? = 116.6). The high-field ' H hydride signal again appears as a pseudo-quartet (8 -12.42 pq, J\-\p ~ JRhH - 13) (cf. data for 5a), and upfield shifted resonances of the ort/zo-metallated ring protons were detected (8 6.50 t, P-(O-C(MA), VHH = V; 6.65 d, o-(o-C(yH4), 3 J H H = V; 6.85 m, m-(o-CeHd), VHH - 7). Of note, the resonance for the C H 3 group was in this instance detected (8 1.95, s), upfield compared to that of the free imine (8 2.35, s), further showing that the solvent is responsible for its absence in the ' H N M R spectrum of 9a' in CD 3 OD. The VR^ .H appears as a broad, weak band in the IR spectrum (2105 cm"1) and is in agreement with the values observed for similar Rh-o-metallated complexes (cf. 5a). 107 References on page 126 Chapter 4 The coordinated acetone gives rise to a strong absorption band at 1670 cm"1, again at lower frequency compared to that of the free molecule. A medium intensity absorption band (1600 cm"') is assigned to the C=N mode. 4.4.3. The (Ph) 2 C=NCH 2 Ph Ligand Similar in situ reactions of 3a' with the solid ketimine (Ph) 2C=NCH 2Ph (Rh:imine = 1:2) in CD3OD showed quantitative formation of the analogous ortAo-metallated product [Rh(H){PhCH2/V=(Ph)(o-C6H4)}(PPh3)2(CD3OD)]PF6 (10a') (Fig. 4.27). As with the PhC(Me)=NCH 2Ph system, no ' H resonances were detected at 5 9.6-9.8, and no fluxionality was detected in the r.t. 3 1 P{ 1 H} NMR. The complex is stable in CD 3 OD, as shown by the single sharp resonance in the 3 I P{'H} N M R spectrum (5 38.54 d, JRhP = 117.6). The high-field hydride *H resonance appears again as a pseudo-quartet (8-12.61 pq, J\\p ~ j R h H = 13); upfield shifted resonances due to the orr7?o-metallated ring were detected, in this instance however accompanied by a closely separated similar set which was assigned to the aromatic protons of the second Ph moiety on the azomethine C-atom. Excess free imine was detected, and in this instance formation of products containing the benzylamine moiety from hydrolysis was not observed even on a week-old sample. Analogous reactions in acetone-ri6 were not performed. P h 3 P . P h 3 P ' ; R h D ,OCD, ^ O C D 3 D H + P F e 2 ( P h ) 2 C = N C H 2 P h CD3OD P h 3 P H + p F 6 3a" 10a' Figure 4.27. Reaction scheme for the in situ formation of [Rh(H) {PhCH2A/=C(Ph)(o-C 6H4)}(PPh 3) 2(CD 3OD)]PF 6 (10a') in CD 3 OD. 108 References on page 126 Chapter 4 4.4.4. The (p-tolyl)C(Me)=NPh Ligand 31i P{ H} N M R analysis of the in situ reaction between 3a and (p-tolyl)C(Me)=NPh (Rh:imine = 1:2) in acetone-^ showed exclusive formation of the complex [Rh(H){PhiV=C(Me)(o-(p-CH3C6H3))}(PPh3)2(acetone)]PF6 (11a) (5 38.03 d, J R h P = 116.6) (Fig. 4.28). The corresponding ] H N M R showed resonances due only to 11a and free excess imine. Of note, similarly to what observed for complex 9a in acetone-J6, resonances of both C H 3 groups of the coordinated ligand were detected, shifted upfield compared to those of the free imine (5 2.20 s, C(CH3)=N; 2.38 s, p-C 6 H 4 C / / 3 ) . acetone P h 3 P ^ O C M e 2 (p-tolyl)C(Me)=NPh ^ R h *• P h 3 P " ^ O C M e 2 3a P h 3 P H 3 C OCMe , H,,_ I ^ P P h 3 " : R h " N Ph C H 3 11a Figure 4.28. Reaction scheme for the formation of [Rh(H){PhN=C(Me)(o-(p-CH3C6H3))}(PPh3)2(acetone)]PF6 (11a) in acetone. Complex 11a was isolated and characterized by 3 1 P{'H} N M R , 'ff N M R and IR spectroscopies, but as with 9a a satisfactory elemental analysis could not be obtained. In CD3OD, in situ formation of the corresponding ort/zo-metallated complex [Rh(H){Ph7V=C(Me)(o-(p-CH3C6H3))}(PPh3)2(CD3OD)]PF6 (11a') occurs (5 37.78 d, JRHP = 117.6); however there was a co-product. The second product is likely [Rh{n6-(C6H5)N=C(Me)(p-tolyl)}(PPh3)2]PF6 (19a) (Fig. 4.29), which gives rise to a single 3 1 P{'H} resonance (5 47 .42 d, j R h p = 211.4) and to a set of upfield-shifted resonances at 5 ~ 5-6 in the ' H N M R spectrum, distinct from that due to 11a'. Subsequent work (see Section 5.2.3) demonstrates that reaction of 3a' with benzylideneaniline PhCH=NPh (Rh:imine = 1:2) in MeOH under 1 atm H2 results in the formation of the complex 109 References on page 126 Chapter 4 isolated in the solid state as [Rh(r) 4-(C 6H 5)NHCH2Ph)(PPh3)2]PF 6 (21a). The spectroscopic features of 21a in CD 3 OD, showing that a change from n 4 to n 6 in the hapticity of the coordinated Ph moiety takes place in solution, are virtually identical to those observed for 19a, suggesting that this complex also contains an n6-coordinated phenyl moiety (Fig. 4.29). Similar behavior was not observed for the reaction of PhCH=NPh with 3a under Ar (Rh:imine = 1:2), which resulted in the in situ formation of the o-metallated complex [Rh(H)-{PhAr=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (7a). Common to the amine and imines discussed above is a direct link of the N-atom to the Ph group (without the - C H 2 - "spacer" group contained in other imines used in this work); this allows for the possibility of conjugation with the aromatic ring which would increase its electron-richness and tendency to act itself as a ligand. Interruption of this type of "communication" in the presence of a benzylic group would prevent the phenomenon. Figure 4.29. Possible n6-arene coordination of (/j-tolyl)C(Me)=NPh in the product formed from reaction with 3a' in CD 3 OD. Such conjugation could be further facilitated in (p-tolyl)C(Me)=NPh by the presence of electron-donating methyl groups assisting in stabilization a positive charge (Fig. 4.30). By the same token, the electron-donating C H 3 group could lead to n6-coordination of the p-tolyl moiety: this possibility, however, is ruled out by the presence of three upfield resonances in a 1:2:2 ratio (5 4.90 t, 1H, p-(r\b-C(Ji5), V H H = 7; 5.50 d, 2H, o-{tf-C(fls), VHH = 7; 5.95 t, 2H, m-^-CtJls), VHH - 7) indicating 3 sets of different protons as is possible only in the unsubstituted Ph moiety. C H 3 19a 110 References on page 126 Chapter 4 Figure 4.30. Possible resonance structures for RR'C=NAr imines. Two sets of singlets for the C H 3 groups in 11a' and 19a would be expected in the ' i i N M R spectrum of the above reaction mixture. One resonance due to the free imine C(C7/3)=N was detected (5 2.40 s), while a new, intense singlet (8 2.30) overlaps with the resonance (5 2.31 s) due to the p-CH3 of the free imine. What appears as an upfield-shifted set of two singlets was detected (5 1.61, 1.49, p-CH3 and C(Gf/3)=N, respectively), however with the 5 1.49 resonance of much lower intensity. A second set of singlets could not be detected under these conditions (Rh:imine = 1:2). In the ' H N M R of the analogous 1:1 reaction, signals due to free imine were not detected. The singlet at 5 2.30 is present with the set of two upfield singlets observed for the 2:1 mixture, in this instance however in the expected 1:1 ratio. From integration data these resonances correspond to 11a'. The 5 2.30 resonance could be due to the p-CH3 of the /?-tolyl-acetophenone formed from hydrolysis of the imine; however, the corresponding resonance for the acetyl protons is not detected. An H-D exchange similar to that proposed for PhC(Me)=NCH 2Ph in 9a' could account for this observation, as well as for the decreased intensity of the C(C// 3)=N resonance of 11a' in the ! H N M R of the 1:2 mixture. In an alternative rationalization, both CH3 groups in complex 19a could give resonances at 8 2.30; however, the integration for this resonance is too high for even two Me groups. 4.4.5. The (diq) Ligand The in situ r.t. reaction of the cyclic ketimine 6,7-dimethoxy-l-methyl-3,4-dihydroisoquinoline (diq) with 3a' in CD3OD (Rh:imine = 1:2) was investigated by N M R spectroscopy. Sole formation of the square-planar complex cw-[Rh(PPh3)2(diq)2]PF6 111 References on page 126 Chapter 4 (20a) was observed, existing, however, as two geometric isomers in a 5:1 approximate ratio (Fig. 4 .31) , each giving rise to a doublet in the 3 1 P{ 'H} N M R (5 4 6 . 1 4 d, JRHP = 171, major; 45.05 d, J R h p = 1 7 1 , minor). The corresponding complex 20b ( P R 3 = P(/?-tolyl)3) was previously isolated by Dr. K. Seneviratne of this laboratory and characterized by 3 I P { ' H } and ' H N M R spectroscopy, elemental analysis and X-ray crystallography. The 3 I P{ 'H} N M R spectrum of isolated 20b in CD 3 OD also shows two doublets (5 44 .52 d, JRW = 171, major; 43.31 d, JR^P = 172, minor) in a ~ 5:1 ratio, and the presence of two isomers in solution is confirmed by the } H N M R spectrum, in which the resonances due to each isomer are replicated in two sets in the same 5:1 ratio. Of interest, the ] H N M R resonance due to the C H 3 group on the iminic functionality is once more not detected in CD 3 OD, for solutions of either free imine or 20b, suggesting that the proposed exchange with C D 3 O D constitutes general behavior typical of methyl-substituted ketimines even in the absence of the metal. O M e anti Figure 4.31. Representation of the two geometric isomers of cz's-[Rh(PR3)2(diq)2]PF6 (R = Ph, 20a; /?-tolyl, 20b) in solution. Complex 20b constitutes the only example of a bis-imine complex encountered during the course of this work: notwithstanding the relative steric bulk of the imine, formation of 20b occurs likely because of the absence of C H bonds in ortho positions 112 References on page 126 Chapter 4 available for metallation. X-ray quality crystals of 20b were obtained by slow evaporation of a CF^Cyhexanes solvent mixture (Fig. 4.32). Figure 4.32. ORTEP diagram of the cation cw-[Rh(PR3)2(diq)2]+ (R = p-tolyl, 20b) with 50% probability thermal ellipsoids. The isolated crystals consisted of a single isomer in which the imine Me groups are anti with respect to the square plane, pointing "outwards" with respect to the symmetry plane that bisects the P-Rh-P and N-Rh-N angles, and likely correspond to the major isomer. Indeed, the observed doublet in the 3 1 P{ 1 H} N M R for each isomer indicates that the minor component must also be symmetrical, unequivocally determining its geometry as syn, with both Me groups pointing "inwards", a more sterically demanding, less populated state. The crystal structure of the analogous [Rh(diphos)(diq)2]BF4 complex has been obtained before10 but, of interest, the imines here adopt a syn arrangement. Complex 20b crystallizes in the P2j/c space group, C ( 2 3 ) C ( l l ) 113 References on page 126 Chapter 4 whereas the PI space group was found for the diphos analogue. Both molecules display a square-planar coordination environment at the metal. Selected structural parameters for 20b are given in Table 4.7. Table 4.7. Selected bond distances and angles for c«-[Rh(PR.3)2(diq)2]^ (R = p-tolyl, 20b) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) Rh(l)-PO) 2.2647(9) P(l)-Rh(l)-P(2) 95.81(3) Rh(l)-P(2) 2.2454(10) N(l)-Rh(l)-N(2) 81.34(10) Rh(l)-N(l) 2.129(3) P(l)-Rh(l)-N(l) 170.93(9) Rh(l)-N(2) 2.140(3) P(l)-Rh(l)-N(2) 90.53(7) N( l ) -C( l ) 1.287(4) P(2)-Rh(l)-N(l) 92.30(8) N(2)-C(13) 1.274(4) P(2)-Rh(l)-N(2) 173.64(7) N(l)-C(9) 1.495(4) C(l)-N(l)-Rh(l) 127.1(2) N(2)-C(21) 1.493(4) C(13)-N(2)-Rh(l) 128.1(3) The P(l)-Rh(l)-P(2) and N(l)-Rh(l)-N(2) angles in 20b (see Table 6) are larger or smaller, respectively, than those of the diphos analogue (84.9(1)° and 86.3(3)°). The presence of a chelating phosphine with a smaller bite angle perhaps provides a sufficiently larger N(l)-Rh(l)-N(2) angle for the syn imine ligands to minimize the steric repulsions between the methyl groups. The other geometrical parameters are comparable in the two structures. 114 References on page 126 Chapter 4 4.5. Experimental 4.5.1. Preparation of [Rh(H){PhCH2A=CH(0-C6H4)}(PPh3)2(acetone)]PF6 (5a) Method A: To a red solution of [Rh2(PPh3)4][PF6]2 (4a) (0.090 g, 0.058 mmol) in acetone (3 mL) the imine PhCH 2N=CHPh was added (22.0 uL, 0.116 mmol) under Ar and the mixture stirred for 2 h. The volume was then reduced to ~ 1 mL to afford spontaneous precipitation of a creamy-white solid that was collected by filtration, washed with Et 2 0 ( 3 x 4 mL) and dried in vacuo. Yield: 0.090 g (75%). 3 i P{ 'H} N M R (acetone-db): 5 40.40 (d, JRHP = 116.0). ' H N M R (acetone-^): 8 -12.85 (pq, 1H, Rh(#), JRHH ~ 2 J H P = 13), 2.10 (s, 6H, CH3COCH3), 5.25 (s, 2H, PhGr7 2N=CH(o-C 6H 4)), 6.52 (t, \R, p-(o-C6H4), V H H = 6.5), 6.72 (d, 1H, o-io-Ctft), V H H = 6.5), 6.95 (m, 2H, m - ^ - C ^ ) , VHH = 6.5), 7.01-7.79 (m, 35H, aromatics), 7.81 (s, 1H, PhCH 2N=Cr7(o-C 6H 4)). IR (KBr pellet): v 1660 ( C O , s), 1611, 1576 (C=N, m), 2096 (Rh-H, m). Anal. Calcd. for C 5 3 H 4 9 N O P 3 F 6 R h : C, 62.06; H, 4.81; N , 1.37. Found: C, 62.01; H , 4.92; N , 1.47. Method B: A n orange solution of [Rh(COD)(PPh 3) 2]PF 6 (la) (0.100 g, 0.113 mmol) in acetone (3 mL) was stirred under H 2 (1 atm) for 2 h. To the resultant pale yellow solution, the imine PhCH 2N=CHPh (21.4 uL, 0.113 mmol) was added under Ar and the mixture stirred for 2 h. After 2 h the volume was reduced to ~ 1 mL to afford spontaneous precipitation of a creamy-white solid that was collected by filtration, washed with E t 2 0 ( 3 x 4 mL) and dried in vacuo. Yield: 0.085 g (73%). 4.5.2. In situ Characterization of [Rh(H){PhCH2A=CH(o-C6H4)}(P07-tolyl)3)2-(acetone-rf6)]PF6 (5b) An N M R tube equipped with an air-tight J Y O U N G PTFE valve was charged with the precursor [Rh2(P/?-tolyl3)4][PF6]2 (4b) (0.014 g, 0.009 mmol) and the imine (1.4 uL, 0.036 mmol) and the solvent (~ 0.8 mL) was added via vacuum-transfer. The resulting red solution was then analyzed by 3 I P{'H} and *H N M R spectroscopy. 3 1 P{'H} N M R (acetone-4): 5 38.84 (d, 7 R l l P = 115.0). ' H N M R (acetone-J6): 5 -12.96 (pq, 1H, Rh(#), JR\)H ~ V H p = 13), 2.27 (m, 18H,p-CH 3 ) , 5.18 (s, 2H, PhCtf 2N=CH(o-C 6H 4)), 6.50 (t, 1H, 115 References on page 126 Chapter 4 p-(o-CbH4), V H H = 7), 6.63 (d, 1H, o-(o-C 6// 4), V H H = 7), 6.70 (d, 1H, m-io-C^), V H H = 7), 6.90-7.90 (m, 31H, ^ - ( o - C ^ ) and aromatics), 7.96 (s, 1H, C//=N). 4.5.3. Preparation of [Rh(H){CH3^=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (6a) To a red solution of [Rh2(PPh3)4][PF6]2 (4a) (0.075 g, 0.048 mmol) in acetone (2 mL), the imine CH 3 N=CHPh was added (12.0 uL, 0.097 mmol) under Ar and the mixture stirred for 2 h. After 2 h the volume was reduced to ~ 1 mL, followed by addition of Et 2 0 (4 mL) to afford the precipitation of a creamy-white solid that was collected by filtration, washed with E t 2 0 ( 3 x 3 mL) and dried in vacuo. Yield: 0.065 g (70%). ^P j 'H} N M R (acetone-d6): 5 42.10 (d, J R h P = 116). ' H N M R (acetone-d6): 5-12.58 (pq, 1H, Rh(#), J\m\ ~ V H P = 13.0), 2.10 (s, 6H, C / / 3 COC/ / 3 ) , 3.79 (s, 3H, C# 3N=CH(o-C 6H 4)), 6.54 (t, \H, p-(o-CbH4), V H H = 6.3), 6.83-7.00 (m, 3H, m.o-^-Ce^), V H H = 6.3), 7.15-7.70 (m, 30H, aromatics), 7.74 (s, 1H, CH 3N=Ci/(o-C 6H 4)). IR (KBr pellet): v 1618, 1578 (C=N, m), 1666 (C=0, s), 2101 (Ir-H, m). Anal. Calcd for C 4 7 H45NOP 3 F 6 Rh: C, 59.44; H, 4.78; N , 1.47. Found: C, 59.14; H , 4.89; N , 1.46. 4.5.4. In situ Characterization of [Rh(H){RA^=CH(o-C6H4)}(PPh3)2(acetone-rf6)]PF6 (R = Ph 7a, C 6 H U 8a) An N M R tube equipped with an air-tight JYOUNG PTFE valve was charged with the precursor [Rh 2(PPh 3) 4][PF 6] 2 (4a) (0.007 g, 0.005 mmol and 0.006 g, 0.004 mmol) and the imine (0.002 g, 0.01 mmol (R = Ph), and 1.3 uL, 0.008 mmol (R = Cy)) and the solvent (~ 0.8 mL) was added via vacuum-transfer. The resulting red solution was then analyzed by 3 1 P{'H} and ' H N M R spectroscopy. R = Ph (7a): 3 1 P{'H} N M R (acetone-db): 5 39.91 (d, JRhP = 115.6). ' H N M R (acetone-rf6): 5 -13.12 (dt, 1H, Rh(#), JRm = 16, 2JHP = 13), 6.40 (t, IK,p-ip-CeHt), VHH = 7), 6.65 (d, 1H, o-(o-CeH4), V H H = 7), 6.80 (m, 2H, m-ip-CeH*)), 7.20-7.70 (m, 35H, aromatics), 8.00 (s, 1H, CH=N). R = C 6 H„ (8a): 3 I P{'H} N M R (acetone-J6): 5 38.40 (d, JRhP = 116.6). ! H N M R (acetone-^): 5 -12.82 (pq, 1H, Rh(#), JRm ~ 2JHP = 13), 1.20-1.90 (m, 10H, C 6 (H)// 1 0 ) , 4.30 (pt, 1H, C6(H)KW, V H H = 10), 6.45 (t, 1H, p-(o-CeH4), V H H = 7), 6.52 (d, 1H, o-{o-CeH*), V H H = 116 References on page 126 Chapter 4 7), 6.95 (t, 1H, m-(o-C(Ji4), VHH = 7), 7.05-7.90 (m, 31H, m-(o-C(Ji4) and aromatics), 8.10 (s, 1H, C#=N). 4.5.5. Preparation of [Rh(H){PhCH2A=C(Me)(o-C6H4)}(PPh3)2(acetone)]PF6 (9a) The complex was prepared in a manner identical to that used for synthesis of 6a, but using 0.080 g (0.052 mmol) of [Rh2(PPh3)4][PF6]2 (4a) precursor and 22.0 uL (0.104 mmol) of the imine PhCH 2N=C(Me)Ph. Yield: 0.080 g (70%). ^ P l / H } N M R (acetone-d6): 8 40.33 (d, J R h P = 116.6). ' H N M R (acetone-rf6): 5 -12.42 (pq, 1H, Rh(#), J R h H ~ V H P = 13), 1.95 (s, 3H, C(C// 3)), 2.10 (s, 6H, C/Y 3COCV/ 3), 5.45 (s, 2H, PhC#2N=C(Me)(o-C 6 H 4 )) , 6.50 (t, 1H, p-io-CbH*), V H H = 7), 6.65 (d, 1H, o-{o-C(Ji4\ V H H = 7), 6.85 (m, 2H, m-(o-C6H4), 3 J H H = 7), 6.90-7.80 (m, 35H, aromatics). IR (KBr pellet): v 1670 ( O O , s), 1600, 1576 (C=N, m), 2105 (Rh-H, m). • 4.5.6. In situ Characterization of [Rh(H){PhCH2iV=C(R)(o-C6H4)}(PPh3)2-(CD3OD)]PF6 (R = Me 9a', Ph 10a') An N M R tube equipped with an air-tight JYOUNG PTFE valve was charged with the precursor [Rh2(PPh3)4][PF6]2 (4a) (0.011 g, 0.007 mmol and 0.014g, 0.014 g, 0.009 mmol) and the imine (6.0 uL, 0.028 mmol (R = Me), and 0.010 g, 0.036 mmol (R = Ph)) and the solvent (~ 0.8 mL) was added via vacuum-transfer. The resulting red solution was then analyzed by 3 1 P{'H} and ' H N M R spectroscopy. R = Me (9a'): 3 1 P{'H} N M R (CD 3OD): 8 40.23 (d, 7 R h P = 116.6). ' H N M R (CD 3OD): 8 -12.61 (pq, 1H, Rh(/f), -4hH ~ 2 7 H P = 13), 5.18 (s, 2H, PhC// 2N=C(Me)(o-C 6H 4)), 6.50 (2 t, 2H,p.m-io-CeH*), VHH = 7), 6.65 (d, 2H, o,m-{p-Q(fl4\ VHH = 7), 7.0-7.80 (m, 35H, aromatics). R = Ph (10a'): 3 1 P{'H} N M R (CD 3OD): 8 38.54 (d, J R h P = 117.6). * H N M R (CD 3OD): 8-12.61 (pq, 1H, Rh(//), ~ V H P = 13), 5.13 (s, 2H, PhC// 2N=C(Me)(o-C 6H 4)), 5.94 (d, 1H, o-(o-C ^ 4 ) , VHH = 6.5), 6.40 (t, 1H, p-(o-CeH4), VHH = 6.5), 6.45 (t, 1H, m-(o-CeH4), VHH = 6.5), 6.54 (d, 1H, m-ip-C^), V H H = 6.5), 7.0-7.75 (m, 40H, aromatics). 117 References on page 126 Chapter 4 4.5.7. Preparation of [Rh(H){Ph/V=C(Me)(o-(p-CH3C6H3))}(PPh3)2(acetone)]PF6 (11a) An orange solution of [Rh(COD)(PPh3)2]PF6 (la) (0.100 g, 0.110 mmol) in acetone (4 mL) was stirred under H 2 (1 atm) for 1 h. To the resultant pale yellow solution, a solution of the imine (0.025 g, 0.110 mmol) in acetone (1 mL) was cannulated under Ar and the mixture stirred for 1 h. The volume was then reduced to ~ 1 mL and Et 2 0 added (8 mL) to afford a light-orange solid that was collected by filtration, washed with hexanes (3 mL) and E t 2 0 ( 3 x 3 mL) and dried in vacuo. Yield: 0.057 g (50%). 3 I P{'H} N M R (acetone-J6): 5 38.03 (d, JRhP = 116.6). ' H N M R (acetone-rf6): 5-13.05 (pq, 1H, Rh(/f), JRm ~ 2JHP = 14), 1.69 (s, 3H, C(Gtf3)=N), 1.90 (s, 3H, p-CH3), 2.10 (s, 6H, CH3COCH3), 6.35 (s, 1H, m-(o-(p-CH3C6#3))), 6.59 (d, 2H, o,m-(o-(p-CH 3Cei/ 3)), 3 J H H = 7.5), 7.05-7.75 (m, 35H, aromatics). IR (KBr pellet): v 1672 (C=0, s), 1579 (C=N, m), 2123 (Rh-H, m). 4.5.8. In situ Characterization of [Rh(H){PhCH1/V=CH(o-C6H4)}(PPh3)2-(NH 2 CH 2 Ph)]PF 6 (12a) in CD 2 C1 2 An N M R tube equipped with an air-tight JYOUNG PTFE valve was charged with complex 5a (0.014 g, 0.009 mmol) and the amine (0.010 g, 0.036 mmol) and the solvent (~ 0.8 mL) was added via vacuum-transfer. The resulting orange solution was then analyzed by 3 I P{ 'H} and ' H N M R spectroscopy. 3 1 P{'H} N M R (CD 2C1 2): 5 41.77 (d, JRhP = 114). ' H N M R (CD 2C1 2): 5 -14.03 (pq, 1H, Rh(H), J R m ~ 2JHP = 13), 1.65 (bs, 2H, PhCH 2 N// 2 ) , 2.60 (m, 2H, PhC// 2 NH 2 ) , 5.00 (s, 2H, PhC// 2N=C(H)(o-C 6H 4)), 5.65 (d, 1H, o-(o-CbH4), V H H = 8), 6.60 (t, l H . ^ o - C ^ ) , 3^HH = 6.5), 6.70-6.85 (m, 3H, m,o-{p-CSHA)), 6.95-7.49 (m, 40H, aromatics), 7.53 (bs, 1H, PhCH 2N=C(#)(o-C 6H 4). 118 References on page 126 Chapter 4 4.5.9. Preparation of a s - [ R h ( P R 3 ) 2 ( P h C H 2 N = C H P h X P h C H 2 N H 2 ) ] P F 6 (R = Ph, 14a; /Moly l , 14b) A red solution of [Rh2(PR3)4][PF6]2 (4) (~ 0.07 g, 0.04 mmol) in MeOH (3 mL) was treated with an excess of PhCH 2N=CHPh (57.0 uL, 0.304 mmol) under Ar and the mixture stirred for 24 h, during which time spontaneous precipitation of a creamy-white solid occurred. The product was collected by filtration, washed with E t 2 0 ( 3 x 4 mL) and dried in vacuo. R = Ph (14a), Yield: 0.044 g ( 45% ) . 3 , P{ 'H} N M R (CD 2C1 2): 6 46.94 (dd, JKW = 166, 2 y P P = 49), 50.07 (dd, JKW = 180, 2 / P P = 49). ' H N M R (CD 2C1 2): 5 1.10 (t, 1H, PhCH 2 N/ / 2 , 3 J H H = 11), 1-26 (t, 1H, PhCH 2 N/ / 2 , V H H = 11), 2.60 (2 td, 2H, PhC# 2 NH 2 , V H H = 13, VHH = 4), 4.40 (d, 1H, PhC// 2N=CHPh, 2JHH = 13), 5.12 (d, 1H, PhC// 2N=CHPh, 2 J H H = 13), 5.98 (d, 2H, NH2CH2(o-C<si/5), V H H = 7), 6.95-7.90 (m, 41H, aromatics), 8.01 (bd, 1H, PhCH2N=CM>h, V R H H ~ 6), 9.70 (d, 2H, PhCH 2N=CH(o-CaHs), 3-/HH = 7). 3 1 P{'H} N M R (CD 3OD): 5 46.90 (dd, JRHP = 166 , 2 J P P = 49), 50.10 (dd, JRHP = 180, 2J Pp = 49). l H N M R (CD 3OD): 5 2.51 (d, 1H, P h C / / 2 N H 2 , 2 J M = 14), 2.69 (d, 1H, PhC/ / 2 NH 2 , 2 J H H = 14), 4.49 (d, 1H, PhC// 2N=CHPh, 2JHH = 12), 5.19 (d, 1H, PhC// 2N=CHPh, 2JHH = 12), 6.00 (d, 2H, NH 2 CH 2 (o-C6#5), V H H = 7), 7.00-7.90 (m, 41H, aromatics), 8.21 (bd, 1H, PhCH 2N=CtfPh, V R H H ~ 6), 9.81 (bd, 2H, PhCH 2N=CH(o-C6// 5), V H H ~ 7). IR (KBr pellet): v 1616 (C=N, m), 3313 (N-H, m). Anal. Calcd. for C 5 7H 5 2 N 2 P 3 F 6 Rh: C, 63.70; H , 4.88; N , 2.61. Found: C, 63.67; H , 4.69; N , 2.63. R = / M o l y l (14b), Yield: 0.047 g (50%). 3 1 P{'H} N M R (CD 2C1 2): § 45.15 (dd, J R h P = 166, 2J Pp = 49), 48.20 (dd, / R h P = 180, 2J P P = 49). ] H N M R (CD 2C1 2): 5 1.12 (t, 1H, PhCH 2 N/ / 2 , V H H = 12), 1.24 (t, 1H, PhCH 2 N/ / 2 , V H H = 12), 2.31 (s, 9 H , /?-C 6H 4C# 3), 2.33 (s, 9 H , p-C6H4CHi), 2.52 (td, 1H, PhC# 2 NH 2 , V H H = 13, VHH = 4), 2.58 (td, 1H, PhC/ / 2 NH 2 , 3J HH = 13, 2JHH = 4), 4.38 (d, 1H, PhC# 2N=CHPh, 2 J H H = 12), 5.15 (d, 1H, PhC# 2N=CHPh, VHH = 12), 5.95 (d, 2H, NH2CH 2 (o-C 6 //5), V H H = 7), 6.90-7.85 (m, 35H, aromatics), 8.03 (bd, 1H, PhCH 2N=C#Ph, VRHH = 6), 9.76 (d, 2H, PhCH 2N=CH(o-Cft//5), 3-/HH = 7). 3 1 P{'H} N M R (CD 3OD): 5 45.06 (dd, J R h P = 166, 2 J ? ? = 50), 48.20 (dd, J R h P = 180, 2 J P P = 50). ' H N M R (CD 3OD): 5 2.29 (s, 9 H , / ? -C 6 H 4 C// 3 ) , 2.31 (s, 9H , p-C 6 H 4 C / / 3 ) , 2.46 (d, 1H, P h C / / 2 N H 2 , 2JHH = 14), 2.61 (d, 1H, P h C # 2 N H 2 , 2 J M = 14), 4.45 (d, 1H, PhC# 2N=CHPh, 2JHH = 12), 5.15 (d, 1H, PhCtf 2N=CHPh, 2JHH = 12), 6.02 (d, 119 References on page 126 Chapter 4 2H, NH 2 CH 2 (o-C F > ( ¥5), V H H = 7), 6.90-7.88 (m, 35H, aromatics), 8.21 (bd, 1H, PhCH2N=CM>h, V R H H ~ 6), 9.81 (bd, 2H, PhCH 2N=CH(o-C6^ 5), V H H ~ 7). IR (KBr pellet): v 1601 (C=N, m), 3307 (N-H, m). Anal. Calcd. for C 6 3 H 6 4 N 2 P 3 F 6 R h : C, 65.29; H, 5.57; N , 2.42. Found: C, 65.26; H, 5.61; N , 2.43. 4.5.10. Preparation of Cw-[Rh(PPh3)2(PhCH2NH2)2]PF6.0.5 C H 3 O H (15a) To a red solution of [Rh 2(PPh 3) 4][PF 6] 2 (4a) (0.080 g, 0.052 mmol) in MeOH (4 mL), the amine (32.0 uL, 0.290 mmol) was added under Ar and the resultant bright yellow solution stirred for 2 h. The volume was then reduced to ~ 1 mL to afford precipitation of a yellow solid that was collected by filtration, washed with hexanes (3 mL) and E t 2 0 ( 3 x 3 mL) and dried in vacuo. Yield: 0.050 g (53%). 3 I P{ 'H} N M R (CD 3OD): 5 52.21 (d, JRhP = 176). ' H N M R (CD 3OD): 5 3.55 (s, 4H, PhC// 2 NH 2 ) , 7.15-7.75 (m, 40H, aromatics). Anal. Calcd. for C 5oH 4 8N 2P 3F 6Rh-(0.5 CH 3 OH): C, 60.48; H, 4.99; N , 2.79. Found: C, 60.27; H, 4.90; N , 2.80. 4.5.11. In situ Characterization of [Rh(PPh3)2{NH2CH2(ri2-C6H5)}]PF6 (16a) An N M R tube equipped with an air-tight JYOUNG PTFE valve was charged with the precursor [Rh 2(PPh 3) 4][PF 6] 2 (4a) (0.006 g, 0.004 mmol) and the amine (0.9 uL, 0.008 mmol), and the solvent (acetone-^, ~ 0.8 mL) was added via vacuum-transfer. The resulting yellow solution was then analyzed by 3 1 P{'H} and *H N M R spectroscopy. 3 I P{'H} N M R (acetone-de): §47.46 (dd, = 167, V P P = 49), 52.44 (dd, J^? = 183, V P P = 49). ' H N M R (acetone-^): 5 2.90 (d, 1H, PhCH 2 N/ / 2 , V H H = 12), 3.16 (d, 1H, PhCH 2 N/ / 2 , VHH = 12), 4.50 (d, 1H, PhC/ / 2 NH 2 , 2JHH = 12), 4.75 (d, 1H, PhC# 2 NH 2 , VHH = 12), 6.23 (d, 1H, (o-r| 2-C6# 5)CH 2NH 2, VHH = 8.5), 7.05 (m, 2H, (m, p-T)2-C 6 JrY 5)CH 2NH 2), 7.15-7.90 (m, 32H, m-^2-CeH5) and aromatics). 120 References on page 126 Chapter 4 4.5.12. Preparation of as,^flns,as-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (17a) A yellow suspension of [Rh(COD)(PPh3)2]PF6 (la) (0.100 g, 0.110 mmol) in MeOH (5 mL) was stirred under H 2 (1 atm) for 2 h. To the resultant pale yellow solution, the amine (27.0 uL, 0.250 mmol) was added under Ar. A white solid spontaneously precipitated after 10 min that was collected by filtration, washed with hexanes (3 mL) and Et 2 0 ( 3 x 3 mL) and dried in vacuo. Yield: 0.050 g (53%). 3 1 P{'H} N M R (CD 2C1 2): 8 49.55 (d, . / R n p =116). ' H N M R (CD 2C1 2): 8 -17.55 (pq, 2H, Rh(//) 2, JRhH ~ 2JHP = 14), 2.20 (m, 4H, PhCH 2NZ/ 2), 2.80 (m, 4H, PhC// 2 NH 2 ) , 6.20 (d, 4H, NH 2 CH 2 (o-C6^ 5 ) , V H H = 6), 6.95-7.60 (m, 36H, aromatics). IR (KBr pellet): v 2050, 2090 (Rh-H, m), 3336 (N-H, m). Anal. Calcd. for C 5oH5oN 2P 3F 6Rh: C, 60.74; H, 5.10; N , 2.83. Found: C, 60.38; H, 4.87; N , 2.78. 4.5.13. Preparation of Cw-[Rh(P(p-tolyl)3)2(diq)2]PF6.H20 (20b) A yellow suspension of [Rh(COD)(P(p-tolyl)3)2]PF6 (0.097 g, 0.100 mmol) in MeOH (6 mL) was stirred under H 2 (1 atm) for 1 h. To the resultant pale yellow solution, the imine (0.082 g, 0.400 mmol) was added under Ar, to afford after 1 min spontaneous precipitation of a yellow solid that was collected by filtration, washed with hexanes (3 mL) and Et 2 0 ( 3 x 3 mL) and dried in vacuo. Yield: 0.104 g (80%). 3 1 P{ ! H} N M R (CD 3OD): 8 44.52 (d, JRh? = 171, major isomer); 43.31 (d, /RHP = 172, minor isomer). ] H N M R (CD 3OD): 8 2.13 (m, 4H, 2CH2, major), 2.27 (s, 18H,;?-Gr73 minor), 2.31 (s, 18H, p-CH3 major), 2.35 (m, 4H, 2CH2, minor), 2.60 (s, 6H, 2 (C773)C=N minor), 2.75 (s, 6H, 2 (C// 3)C=N major), 3.77 (2d, 24H, 8GrY30, major and minor), 3.80 (m, 4H, 2Cr72, major), 6.64 (s, 2H, 2CH, major), 6.67 (s, 2H, 2CH minor), 6.70 (s, 2H, 2CH, major), 6.73 (s, 2H, 2CH, minor), 6.90-7.55 (m, 24H, aromatics). Anal. Calcd. for C 6 6 H7 2 N 2 0 4 P3F 6 Rh.(H 2 0): C, 61.69; H, 5.81; N , 2.37. Found: C, 61.68; H , 5.82; N , 2.26. 121 References on page 126 Chapter 4 4.5.14. Preparation of [Ir(H){PhCH2/V=CH(0-C6H4)}(PPh3)2(acetone)]PF6 (5*a) A red solution of [Ir(COD)(PPh3)2]PF6 (l*a) (0.100 g, 0.103 mmol) in acetone (3 mL) was stirred under H 2 (1 atm) for 1 h. To the resultant pale yellow solution, the imine PhCH 2N=CHPh (19.5 uL, 0.103 mmol) was added under Ar and the mixture stirred for 24 h. After 24 h the volume was reduced to ~ 1 mL to afford spontaneous precipitation of a creamy-white solid that was collected by filtration, washed with E t 2 0 ( 3 x 4 mL) and dried in vacuo. Yield: 0.090 g (78%). 3 1 P{'H} N M R (acetone-ofe): 5 17.02 (d, 2JH? = 14.1). ' H N M R (acetone-J6): 5 -16.35 (t, 1H, h(H), 2JHP = 17), 2.10 (s, 6H, C / / 3 COC/ / 3 ) , 5.22 (s, 2H, PhC# 2N=CH(o-C 6H 4)), 6.40 (t, 1H, p-(o-C(JlA), V H H = 6.5), 6.71 (d, 1H, o-(o-CaH*), V H H = 6.5), 6.86 (m, 2H, m-(o-C6#4), V H H = 6.5), 7.00-7.60 (m, 35H, aromatics), 7.67 (s, 1H, PhCH 2N=C//(o-Cei/ 4)). IR (KBr pellet): v 1651 (C=0, s), 1607, 1580 (C=N, m), 2211 (Ir-H, m). Anal. Calcd. for C 5 3 H 4 9 NOP 3 F 6 I r : C, 57.09; H , 4.43; N , 1.26. Found: C, 57.11; H, 4.46; N , 1.39. 4.5.15. Preparation of [Ir(H){PhCH2iV=CH(o-C6H4)}(P(p-toiyl)3)2(acetone)]PF6 (5*b) A red solution of [Ir(COD)(PPh3)2]PF6 (l*a) (0.085 g, 0.081 mmol) in acetone (2 mL) was stirred under H 2 (1 atm) for 1 h. To the resultant pale yellow solution, the imine PhCH 2N=CHPh (15.0 uL, 0.081 mmol) was added under Ar and the mixture stirred for 24 h. After 24 h the volume was reduced to ~ 1 mL, followed by addition of hexanes (2 mL) and E t 2 0 (2 mL) to afford the precipitation of a creamy-white solid that was collected by filtration, washed with E t 2 0 ( 3 x 2 mL) and dried in vacuo. Yield: 0.063 g (65%). 3 1 P{'H} N M R (acetone-J6): 5 15.20 (s). ] H N M R (acetone-^): 5-16.43 (t, 1H, Ir(//), V H P = 17), 2.10 (s, 6H, C// 3 COC# 3 ) , 2.30 (s, 18H, P/?-C 6H 4C# 3), 5.20 (s, 2H, PhC// 2N=CH(o-C 6H 4)), 6.40 (t, 1H, p-(o-C^), V H H = 6.5), 6.75-6.85 (m, 3H, o,m-{p-C6H4), V H H = 6.5), 6.89-7.48 (m, 29H, aromatics), 7.60 (s, 1H, PhCH2N=Gtf(o-C6#4)). IR (KBr pellet): v 1607, 1580 (C=N, m), 1651 (C=0, s), 2211 (Ir-H, m). Anal. Calcd. for C 5 9 H 6 i N O P 3 F 6 I r : C, 59.09; H, 5.13; N , 1.17. Found: C, 59.18; H , 5.07; N , 1.17. 122 References on page 126 Chapter 4 4.5.16. Preparation of [Ir(H){CH37V=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (6*a) A red solution of [Ir(COD)(PPh3)2]PF6 (l*a) (0.090 g, 0.093 mmol) in acetone (2 mL) was stirred under H 2 (1 atm) for 1 h. To the resultant pale yellow solution, the imine CH 3N=CHPh (11.0 uL, 0.093 mmol) was added under Ar and the mixture stirred for 24 h. After 24 h the volume was reduced to ~ 1 mL, to afford the spontaneous precipitation of a creamy-white solid that was collected by filtration, washed with E t 2 0 ( 3 x 3 mL) and dried in vacuo. Yield: 0.063 g (65%). 3 1 P{'H} N M R (acetone-4): 5 18.83 (s). ' H N M R (acetone-rf6): 8-16.01 (t, 1H, Ir(#), V H P = 16), 2.10 (s, 6H, C/f 3COC// 3), '3.79 (s, 3H, C / / 3 NOH(o-C 6 H 4 ) ) , 6.45 (t, 1H,p-(o-CeH A), V H H = 7.5), 6.82 (t, 1H, m-{o-C^HA), V H H = 7.5), 6.92-7.00 (2d, 2H, m.o-io-Cffli), VHH = 7.5), 7.15-7.60 (m, 30H, aromatics), 7.75 (s, 1H, CFf 3 NO//(o-C 6 H 4 ) ) . IR (KBr pellet): v 1612, 1580 (C=N, m), 1654 ( C O , s), 2189 (Ir-H, m). Anal. Calcd. for C 4 7 H 4 5 N O P 3 F 6 R h : C, 59.44; H , 4.78; N , 1.47. Found: C, 59.14; H, 4.89; N , 1.46. 4.5.17. In situ Characterization of [Ir(H){RA^=CH(o-C6H4)}(PPh3)2(CD3OD)]PF6 (R = Ph 7*a',C 6Hi, 8*a') An N M R tube equipped with an air-tight JYOUNG PTFE valve was charged with the precursor [Ir(COD)(PPh3)2]PF6 (l*a) (0.012 g, 0.012 mmol and 0.011 g, 0.011 mmol) and the solvent (-0.8 mL) was added via vacuum-transfer to afford a red suspension (CD 3OD) that was placed under H 2 (1 atm) for 30 min. The imine (0.005 g, 0.024 mmol (R = Ph) and 4.1 uL, 0.022 mmol (R = Cy)) was then added under Ar (glove-box), and 3 1 1 1 the resultant clear, yellow solution analyzed by P{ H} and H N M R spectroscopy. R = Ph (7*a'): 3 1 P{'H} N M R (CD 3OD): 8 17.80 (s). *H N M R (CD 3OD): 8-16.69 (t, 1H, lr{H), V H P = 17), 6.39 (t, 1H, p-(o-C(JiA), VHH = 7), 6.72 (d, 1H, o-{o-C<flA), V H H = 7), 6.80 (t, 1H, m-ip-CM), VHH = 7), 6.85 (d, 1H, m-io-C^), V H H = 7), 7.10-7.60 (m, 35H, aromatics), 7.80 (s, 1H, CH=N). R = C 6 H , , (8*a'): 3 1 P{'H} N M R (CD 3OD): 8 15.11 (d, V H P = 12). ' H N M R (CD 3OD): 8 -16.32 (t, 1H, Ji(H), V H P = 17), 1.0-1.9 (m, 10H, C 6(H)#, 0), 3.87 (m, 1H, C 6(#)H 1 0), 6.23 (t, 1 H , p - i o - C ^ ) , V H H = 7), 6.36 (d, 1H, 123 References on page 126 Chapter 4 o-{o-C6H4), VHH = 7), 6.83 (m, 2H, m-fa-Cftf*), V H H = 7), 7.10-7.75 (m, 30H, aromatics), 8.13 (s, 1H, CH=N). 4.5.18. Preparation of [Ir(H){PhA=CH(0-C6H4)}(PPh3)2(H2O)]PF6 (7*aM) A red suspension of [Ir(COD)(PPh3)2]PF6 (l*a) (0.080 g, 0.082 mmol) in MeOH (3 mL) was stirred under H 2 (1 atm) for 1 h. The resultant pale yellow solution was treated with an excess of PhN=CHPh (60 mg, 0.331 mmol) under Ar and the mixture stirred for 72 h. The mixture was then concentrated to ~ 1 mL and E t 2 0 added (4 mL) to afford an orange solid. The product was collected by filtration, washed with E t 2 0 ( 3 x 4 mL) and dried in vacuo. Yield: 0.070 g (73%). 3 1 P{'H} N M R (acetone-rf6): 6 17.31 (s). ' H N M R (acetone-4): 5 -16.95 (t, 1H, Ir(#), V H P = 16), 2.91 (s, 2H, H20), 6.54 (t, l H , p -(o-C 6// 4), VHH = 7), 6.85 (t, 1H, m-{o-C(JiA), V H H = 7), 7.05 (d, 2H, m, o-(o-CsH4), V H H ~ 8), 7.10-7.55 (m, 35H, aromatics), 8.10 (s, 1H, P h N O / ^ o - C ^ ) ) . IR (KBr pellet): v 2192 (Ir-H, m), 1582, 1534 (C=N, s), 3470, 3558, 3646 (H 2 0, s). Anal. Calcd. for C 49H43NOP 3F 6Ir: C, 55.46; H , 4.09; N , 1.32. Found: C, 55.53; H , 4.12; N , 1.45. 4.5.19. In situ Characterization of [Ir(H){PhCH2A=C(Me)(o-C6H4)}(PPh3)2(acetone-</6)]PF6 (9*a) An N M R tube equipped with an air-tight JYOUNG PTFE valve was charged with the precursor [Ir(COD)(PPh3)2]PF6 (l*a) (0.007 g, 0.007 mmol) and the solvent (~ 0.8 mL) was added via vacuum-transfer to afford a red solution (acetone-^) that was placed under H 2 (1 atm) for 30 min. The imine (3.0 uL, 0.014 mmol) was then added under Ar (glove-box), and the resultant clear, yellow solution analyzed by 3 1 P{'H} and ] H N M R spectroscopy. 3 1 P{'H} N M R (acetone-^): 8 16.72 (d, V H p = 8.5). *H N M R (acetone-d6): 6-15.97 (t, 1H, Ir(#), V H P = 17), 1.95 (s, 3H, C(C// 3)=N), 5.45 (s, 2H, PhC// 2N=C(Me)(o-C 6H 4)), 6.48 (t, 1H, ^ - ( o - C ^ ) , V H H = 7), 6.68 (t, 1H, m-(o-C(fl4), V H H = 7), 6.80 (d, 2H, m, o-(o-C(J-[4), V H H = 7), 7.10-7.50 (m, 35H, aromatics). 124 References on page 126 Chapter 4 4.5.20. In situ Characterization of [Ir(H){PhCH27V=C(Ph)(o-C6H4)}(PPh3)2-(CD3OD)]PF6 (10*a*) An N M R tube equipped with an air-tight JYOUNG PTFE valve was charged with the precursor [Ir(COD)(PPh3)2]PF6 (l*a) (0.008 g, 0.009 mmol) and the solvent (~ 0.8 mL) was added via vacuum-transfer to afford a red suspension (CD 3OD) that was placed under H 2 (1 atm) for 30 min. The imine (0.005 g, 0.018 mmol) was then added under Ar (glove-box), and the resultant clear, yellow solution analyzed by 3 1 P{'H} and ' H N M R spectroscopy. 3 I P{ 'H} N M R (CD 3OD): 5 16.71 (s). *H N M R (CD 3OD): 8 -15.78 (t, 1H, lr(H), V H P = 18), 5.20 (s, 2H, PhC// 2N=C(Ph)(o-C 6H 4)), 5.60 (t, 1H, p-(o-CeHA), V H H = 7), 5.85 (d, 2H, o, m-io-Celi*), V H H = 7), 6.35 (t, 1H, m-io-Ctf*), V H H = 7), 6.40 (d, 2H, o-C(C6H5), VHH = 7), 6.80 (pq, 3H, m, p-C(CeH5), V H H = 7), 7.00-7.60 (m, 35H, aromatics). 4.5.21. Preparation of [Ir(H){PhCH2^=CH(o-C6H4)}(PPh3)2(PhCH2NH2)]PF6 (12*a) A red suspension of [Ir(COD)(PPh3)2]PF6 (0.080 g, 0.082 mmol) in MeOH (3 mL) was stirred under H 2 (1 atm) for 1 h. The resultant pale yellow solution was treated with an excess of PhCH 2N=CHPh (60.0 uL, 0.330 mmol) under Ar and the mixture stirred for 24 h, during which time spontaneous precipitation of a creamy-white solid occurred. The product was collected by filtration, washed with E t 2 0 ( 3 x 4 mL) and dried in vacuo. Yield: 0.050 g (52%). 3 1 P{'H} N M R (CD 2C1 2): 5 15.04 (s). *H N M R (CD 2C1 2): 5 -17.63 (t, 1H, Ir(//), V H P = 17), 2.80 (m, 4H, PhCH 2 N# 2 and PhC/ / 2 NH 2 ) , 5.05 (s, 2H, PhC// 2N=CH(o-C 6H 4)), 5.70 (d, 1H, N H j O M o - C ^ s ) , VHH = 7), 6.55 (t, 1H, PhC//2N=CH(p-(o-C6 jf/4)), VHH = 6.5), 6.75-7.50 (m, 41H, aromatics), 7.30 (s, 1H, PhCH 2N=C//(o-C 6# 4)). IR (KBr pellet): v 2208 (Ir-H, m), 1605, 1576 (C=N, m), 3301 (N-H, m). Anal. Calcd. for C 5 7H 5 2 N 2 P 3 F 6 Ir : C, 58.80; H , 4.47; N , 2.40. Found: C, 58.89; H, 4.94; N , 2.32. 125 References on page 126 Chapter 4 4.6. References (1) James, B. R. Catalysis Today 1997, 37, 209. (2) Mestroni, G.; Camus, A. ; Zassinovich, G. Asp. Homog. Catal. 1981, 4, 71. (3) Schrock, R. R.; Osborn, J. A . J. Chem. Soc., Chem. Commun. 1970, 567. (4) Lewandos, G. S. In The Chemistry of the Metal-Carbon Bond; Hartley, F. R., Patai, S., Eds.; Wiley: New York, 1982; Vol. 1, Chapter 7. -(5) Longley, C. J.; Goodwin, T. J.; Wilkinson, G. Polyhedron 1986, 5, 1625. (6) Comprehensive Coordination Chemistry; Wilkinson, G.; Gillard, R. D.; McCleverty, J. A. , Eds.; Pergamon Press: Oxford, 1987; Vol . 2, p.23 and refs. therein. (7) Comprehensive Organometallic Chemistry; Wilkinson, G.; Stone, F. G. A. ; Abel, E. W., Eds.; Pergamon Press: Oxford, 1982; Vol . 3, p. 19 and refs. therein. (8) Fryzuk, M . D.; Piers, W. E. Organometallics 1990, 9, 986. (9) Cullen, W. R.; Fryzuk, M . D.; James, B. R.; Kutney, J. P.; Kang, G. J.; Herb, G.; Thorburn, I. S.; Spogliarich, R. J. Mol. Catal. 1990, 62, 243. (10) Becalski, A . G.; Cullen, W. R.; Fryzuk, M . D.; James, B. R.; Kang, G.; Rettig, S. J. Inorg. Chem. 1991, 30, 5002. (11) Parshall, G. W. Acc. Chem. Res. 1970, 3, 179. (12) Parshall, G. W. Acc. Chem. Res. 1975, 8, 113. (13) van Baar, J. F.; Vrieze, K. ; Stufkens, D. J. J. Organomet. Chem. 1975, 97, 461. (14) Matsuda, S.; Kikkawa, S.; Omae, I. Chem. Abstr. 1966, 65, 18612e. (15) Omae, I. Chem. Rev. 1979, 79(4), 287. (16) Hughes, R. P. In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A. , Abel, E. W., Eds.; Pergamon Press: Oxford, 1982; Vol . 5, p.277 and refs. therein. (17) Leigh, G. J.; Richards, R. L. In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A. , Abel, E. W., Eds.; Pergamon Press: Oxford, 1982; Vol. 5, p.541 and refs. therein. (18) McCarthy, C. G. In The Chemistry of the Carbon-Nitrogen Double Bond; Patai, S., Ed.; John Wiley & Sons: New York, 1970. 126 References on page 126 Chapter 4 (19) Naulet, N . ; Filleux, M . L. ; Martin, G. J.; Pornet, J. Org. Magn. Reson. 1975, 7, 326. (20) Kobayashi, M . ; Yoshida, M . ; Minato, H. J. Org. Chem. 1976, 41, 3322. (21) Calligaris, M . ; Randaccio, L. In Comprehensive Coordination Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A. , Eds.; Pergamon Press: Oxford, 1987; Vol. 2,p.715. (22) Crespo, M . ; Martinez, M . ; Sales, J.; Solans, X . ; Font-Bardia, M . Organometallics 1992, 11, 1288. (23) Benson, S. W. Thermochemical Kinetics; Wiley: New York, 1976. (24) van Baar, J. F.; Vrieze, K. ; Stufkens, D. J. J. Organomet. Chem. 1975, 85, 249. (25) Shriver, D. F. Acc. Chem. Res. 1970, 3, 231. (26) Crabtree, R. H. ; Hlatky, G. G.; Parnell, C. P.; Segmuller, B. E.; Uriarte, R. J. Inorg. Chem. 1984, 23, 354. (27) Appleton, T. G.; Clark, H. C ; Manzer, L. E. Coord. Chem. Rev. 1973,10, 335. (28) Shapley, J. R.; Schrock, R. R.; Osborn, J. A . Am. Chem. Soc. 1969, 91, 2816. (29) Kaesz, H. D.; Saillant, R. B. Chem. Rev. 1972, 72, 231. (30) Al-Najjar, I. M . ; El-Baih, F. E. M . ; Abu-Loha, F. M . ; Gomaa, Z. Trans. Met. Chem. 1994,19, 325. (31) Albinati, A. ; Auklin, C. G.; Gunazzoli, F.; Ruegg, H . ; Pregosin, P. S. Inorg. Chem. 1987, 26, 503. (32) Ghedini, M . ; Neve, F.; Lanfredi, A . M . M . ; Uguzzoli, F. Inorg. Chim. Acta 1988, 147, 243. (33) Bhayat, 1.1.; McWhinnie, W. R. J. Organomet. Chem. 1972, 46, 159. (34) Di Vaira, M . ; Peruzzini, M . ; Zanobini, F.; Stoppioni, P. Inorg. Chim. Acta 1983, 69, 37. (35) Crabtree-, R. H. ; Yao, W. Inorg. Chem. 1996, 35, 3007. (36) Burk, M . J.; Martinez, J. P.; Feaster, J. E.; Cosford, N . Tetrahedron 1994, 50, 4399. 127 References on page 126 Chapter 5 Chapter 5 HOMOGENEOUS H 2-HYDROGENATION STUDIES 5.1. Introduction Optically pure amino-derivatives (R'R"C*(H)-N(H)R), widely distributed in many biologically relevant molecules, are building-blocks of utmost importance in industry, especially as pharmaceuticals and agrochemicals.1'2 Many organic transformations aimed at obtaining chiral N-containing products in enantioselective fashion are still being approached at the stoichiometric level, using reducing agents like chiral boro- and aluminum-hydrides.3"5 Development of metal-mediated homogeneous systems able to perform these conversions catalytically has been of increasing interest over the past few decades and has resulted, in recent years, in significant improvements in the design and the performance of newly tailored catalytic systems.6 A variety of metal-ligand combinations, as well as of synthetic approaches, has come into play (see also Section 1.3), displaying varying degrees of scope and applicability. Systems capable of the most notable results in terms of enantioselectivity usually possess a quite elaborate ligand framework, very specifically assembled by choice of geometrically constrained structures, often containing one or more asymmetric centers or possessing geometrical chirality. Particularly, within the family of P-donor ancillary ligands, chelating diphosphines possessing either backbone chirality or chirogenic P-atoms have been the ligands of choice in the vast majority of complexes successfully utilized in various metal-mediated asymmetric hydrogenations. Much fewer are the examples of homogeneous catalytic systems for H2-hydrogenation containing monodentate ligands,7"11 particularly for their generally diminished ability to provide a rigid, sterically discriminating framework around the metal center. Recently, however, excellent results have been also reported for certain monodentate ligands.12"14 The generally more severe experimental conditions required by systems containing chelating diphosphines for imine hydrogenations, however, have been protracting the lack of mechanistic insight which thus remains highly sought for the hydrogenation reaction of the C=N double bond. Conversely, easier access to spectroscopic investigations can be gained using precursors 128 References on page 168 Chapter 5 containing monodentate phosphine ligands, due to milder reaction conditions usually sufficient to these systems. In this Chapter, the results of investigations on the potential of catalyst precursors 1 toward hydrogenation of a series of imine substrates are reported; introduction of chiral monodentate phosphine was however not attempted, and possible chiral inductions were not investigated. Preliminary observations and some general trends in achiral environments are presented, and their implications toward a somewhat improved understanding of the factors affecting and determining the reaction course are discussed. 129 References on page 168 Chapter 5 5.2. Catalytic Homogeneous Hydrogenation at the Rh Center Homogeneous hydrogenation of imines catalyzed at ambient conditions by the Rh(I) precursor [Rh(COD)(PPh3)2]PF6 (la) was found to be extremely solvent-, substrate- and product-dependent. Among the two solvents used (acetone and MeOH), conversion to the amine product was observed only in MeOH. Depending on the substrate, however, low to negligible conversions could be observed also in this solvent. Monitoring of the catalytic reactions was conducted either by GC analysis of the reaction mixture, sampled at several time intervals, or by ' H N M R spectroscopy. Spectroscopic investigations aimed at elucidating mechanistic details are however difficult under actual catalytic conditions and, particularly for ] H N M R spectroscopy, scarcely informative due to the large excess of substrate (Rh:imine ~ 1:100). In most cases, therefore, such in situ N M R analyses were carried out on samples scaled down to an approximately stoichiometric (up to a maximum four-fold excess substrate) Rh:imine ratio. 5.2.1. The PhCH2N=CHPh/(PhCH2)2NH System In a typical catalytic run (Rh:imine ~ 1:100), the model liquid imine most extensively used in this work, PhCH 2N=CHPh, undergoes saturation by H 2 in MeOH solution, in the presence of preformed 2a', at ambient conditions in 1 h to give quantitatively dibenzylamine, as shown in Scheme 1, whereas negligible conversion is observed in acetone solution under the same conditions. H H 1 | ...OMe ;RrT PhCH 2 N=CHPh (100:1) T P h , OMe i H 1 atm H 2, r.t., 1 h MeOH (> 98%) 2a' Scheme 1. Reaction conditions for the H2-hydrogenation of N-benzylidene-benzylamine. 130 References on page 168 Chapter 5 Previous work done in this laboratory on these systems has determined a first-order dependence of ratem a x on the substrate at low [imine], while saturation behavior (pseudo-zero order) was observed at higher [imine].14 A first-order dependence on both [Rh]r and [H2] was also found for these catalytic systems.14 In a typical plot of % conv. vs. t obtained in this thesis work (Fig. 5.1), an induction period is observed during the first ~ 5 min (300 s) of reaction, followed by a linear region up to about 90% conv. 100 -i • • • 90 80 70 = 60 c " o 50 u 40 a 30 a 20 10 • : 0 U^- , , , , , , , , 0 500 1000 1500 2000 2500 3000 3500 4000 t(s) Figure 5.1. Plot of % conv. vs. t for the hydrogenation of PhCH 2N=CHPh (58 mM) catalyzed by [Rh(COD)(PPh 3) 2]PF 6 (0.58 mM) in MeOH at 30 °C. At high [imine], as under initial conditions (typically ~ 58 mM), pseudo-zero order conditions in [imine] are established after the induction period, and the corresponding [imine] vs. t zero-order plot gives the expected linear correlation (Fig. 5.2); the linear dependence is obeyed in the 5-20 min region, which includes three half-lives for the system, but not within the first 5 min of reaction. The value for the maximum rate obtained from linear regression on the 5-20 min interval (3.9 x 10"5 M s"1 at 30 °C) is somewhat higher than that determined in previous studies carried out in this group on the same system (3.0 x 10"5 M s"1).14 Such deviation probably results from the effect of H20-content in the solvent on the reaction rate, also established by previous studies in this group.15 N M R investigations of the reaction of either 2a' or 3a' with excess PhCH 2N=CHPh (Rh:imine = 1:100) in CD 3 OD under Ar have shown that there is 131 References on page 168 Chapter 5 exclusive formation of the complex cw-[Rh(PPh3)2(PhCH2N=CHPh)(PhCH2NH2)]PF6 (14a) (see Section 4.4.1). 0.07 T — 3000 3500 4000 Figure 5.2. Plot of [imine] vs. t for the hydrogenation of PhCH 2N=CHPh (58 mM) catalyzed by [Rh(COD)(PPh 3) 2]PF 6 (0.58 mM) in MeOH at 30 °C. The mechanistic proposal formulated from the previous work 1 4 suggested an "unsaturate" route in which a Rh-bis(imine) complex was undergoing oxidative addition of H 2 in the rate-determining step, for which a k value was determined at 30 °C. 1 4 With the exception that it is the imine-amine complex 14a that is actually present and involved in the catalytic cycle, as can be inferred from the evidence gathered in this thesis work, a pre-equilibrium followed by a slow step remains consistent with the kinetic dependences and provides a plausible description of these catalytic systems (Fig. 5.3). The induction period observed in the catalytic mixture under H2 thus likely involves coordination of the imine substrate to 2a', to afford initially a species similar to complex V , possibly containing coordinated H2O brought about by the large excess imine subtrate; the imine within this species could then undergo metal-catalyzed hydrolytic cleavage to afford an amino-solvento complex: coordination of a second imine to this complex in the pre-equilibrium step would form 14a. The question of whether the hydrolysis involves attack from coordinated or "external" H 2 0 remains unanswered. Complex 14a can then undergo oxidative addition of H 2 , and rapidly eliminate the hydrogenated product. After 5 min, steady-state conditions in 14a are likely reached: in a Michaelis-Menten type analysis of 132 References on page 168 Chapter 5 the rate law, the large excess substrate would account for the observed zero-order dependence on the substrate. This mechanistic proposal is consistent with oxidative H H ~ 1 + P F e " Ph 3 P,„ | ^ O M e | X P P h 3 + PhCH 2 N=CHPh OMe H 2a1 Figure 5.3. Proposed reaction steps for the hydrogenation of PhCEbNOHPh. addition of H2 being the slow step, as well as with the strong influence of the solvent, which can be explained in terms of its kinetic lability within species V under stoichiometric conditions (see Section 4.4.1). On the stoichiometric scale, the isolated complexes 14a and 14b undergo immediate reaction upon exposure to 1 atm H2 in CD3OD, to give dibenzylamine and benzylamine quantitatively. After hydrogenation, 2a' H, P h 2 P N " " R h " P h C H O - MeOH P h 3 P * + H 2 0 *OMe O H 2 H . . W . I 133 References on page 168 Chapter 5 and 2b', respectively, are the only species detected by 3 1 P{ 1 H} N M R . Under these conditions (Rh:imine = 1:1, [Rh] = 0.53 mM, [H2] ~ 10"3 M), the value of k determined previously accounts for the complete conversion to products observed by the time the N M R spectra could be recorded (not earlier than 10 min after exposure to H 2 ) , in that this stoichiometric reaction occurs within seconds after exposure to H 2 . In complex 14a the low-valent, d9, Rh(I) center is readily available for interaction with suitable incoming ligands, such as the H-atoms of the H 2 molecule and the solvent. Under 1 atm H 2 , after induction, the fully formed 14a likely undergoes subsequent slow oxidative addition of H 2 , followed by a rapid H-transfer step to the coordinated imine and release of the hydrogenated product. The coordination mode of the imine in the hydrogen transfer step is unclear. The mechanistic implication of a necessary shift to n2-coordination of the imine for the H-transfer step to take place is largely modeled on the accepted mechanism of olefin hydrogenation.2'7'16 The stronger tendency of the O N moiety to donate through the N -atom lone-pair rather than through the 7i-system, thus preventing the shift in coordination, has been suggested as a primary reason behind the scarcity of homogeneous systems for the hydrogenation of imines at ambient conditions.2'7'1 7 The few examples in which imines display n2-coordination involve mostly early metals,1 8'1 9 although there is evidence for these species in R h 2 1 7 and Fe 3 2 0 systems. Recent studies on sequential insertions of CO and imines into Mn- and Ni-alkyl bonds, however, imply that in these 2 21 22 reactions the shift to n -coordination may not be necessary. ' A mechanistic proposal for the hydrogenation of aldimines catalyzed by type-1 [Rh(diene)(PR3)2]PF6 systems by Longley et al.,7 although not substantiated by experimental evidence, invoked a role for the coordinated solvent (MeOH) in assisting the nVry2 shift by involving the N-atom in a hydrogen-bond interaction (Fig. 5.4). This mechanistic proposal also implies that oxidative addition of H 2 occurs rapidly, and that the slow step is the coordination of the substrate. The mechanism as outlined is flawed in the formulation of the starting bis(hydrido) species, in which the two phosphines are known to be trans to one another (see Section 3.2). In addition, the first-order dependence on both [Rh]r and [H 2], and the pseudo-first to zero-order dependence on [imine] (determined later by the group here),14 134 References on page 168 Chapter 5 + PF 6 RCH=NR' - solv H - amine - solv ' H-transfer r + solv Figure 5.4. The mechanism proposed by Longley et al. for the hydrogenation of aldimines by [Rh(diene)(PR3)2]PF6 precursors in MeOH. favour an "unsaturate route" in which a rapidly formed Rh-imine complex reacts with H 2 in a slow step. Similar kinetic dependences have also been observed in some Rh/(P-P) systems previously studied in this department, thereby also suggesting an "unsaturate route" for the reaction pathway within chelated diphosphine systems.2 , 2 3'2 4 In all these examples, a solvent-assisted ^-coordination of the azomethine moiety is envisioned, and formation of an alkylamido, rather than aminoalkyl, complex is proposed as the more plausible outcome of the first H-transfer (see below). The evidence gathered in this thesis work has shown that coordination of the imine through the N-atom, with concomitant reductive elimination of H 2 and formation the or/^o-metallated species, is the first step of the reaction under stoichiometric conditions at least in an inert atmosphere. Sole formation of species 14a is observed under excess imine conditions under Ar. A different perspective is assumed here on the role of the solvent, namely on its capability of reversing the ort/jo-metallation as well as its coordinative lability within complex V, which can undergo oxidative addition of H 2 (see Scheme 2, page 139). The lack of experimental evidence does not allow for unequivocal characterization of the intermediate steps, particularly with regard to the H-135 References on page 168 Chapter 5 transfer. The strong tendency of the imine to maintain coordination through the N-atom is, however, evidenced by the behavior of the ort/zo-metallated species 5a in CD3OD (see also below). Assuming a stepwise occurrence of the H-transfer, a transient alkylamido species is postulated as the more likely also in this instance. The mutually trans and cis geometries of phosphines and hydrides, respectively, impose that one hydride be trans to the azomethine group, and thus unlikely to be transferred before rearranging cis to the imine (or alkylamido). This is consistent with a stepwise H-transfer and rules out the alternative possibility of a "concerted", simultaneous transfer of both H-atoms,25 perhaps through a multicentered transition state, in which differentiation between the two possible alkylamido vs. aminoalkyl intermediates would be meaningless. Formation of 14a from reaction of 2a' (or 3a') with excess imine in CD3OD under Ar, as under actual catalytic conditions, could proceed via initial ort/zo-metallation, which is however not fully retained in CD3OD (see also Section 4.4.1), and must allow for an extra reaction pathway for hydrolysis, as illustrated in Fig. 5.3. On the other hand, retention of ort/zo-metallation observed in acetone-cfe for 5a (see Section 4.4.1), and formation of cis-[Rh(PPh3)2{A /H2CH2(ri2-C6H5)}]PF6 (16a) from reaction in this solvent of 2a (or 3a) with excess imine, may be directly related to the negligible hydrogenation of the imine: a saturated coordination environment in 5a (with the more strongly bound acetone compared to MeOH) likely prevents H 2 from accessing the catalytic site. Acetone solutions of in situ formed 16a did not show any reactivity upon exposure to 1 atm H 2 : this observation, and the absence of conversion in the presence of imine, imply that this species is a catalytic dead-end. An alternative cycle based on a neutral Rh monohydride catalytic species, derived from deprotonation of the cationic 2a' by either imine or amine ligands, could in principle be formulated: however, studies to confirm this possibility (e.g. deliberate addition of a non-coordinating base like N('Pr)2Et), were not undertaken. On the stoichiometric scale, hydrogenation of 5a in C D 3 O D was monitored by VT 3 I P{'H} and ' H N M R : H 2 was admitted to an evacuated gas-tight N M R tube containing 5a in CD 3 OD at 233 K, followed by gradual warming of the sealed sample up to 300 K over 1 h (Fig. 5.5). Under these conditions (Rh:imine 1:1), formation of 14a is not 31 1 observed at any stage of the reaction. The P{ H} N M R spectrum at 233 K is virtually identical to that of 5a under Ar at this temperature, except for the presence here of the 136 References on page 168 Chapter 5 resonance corresponding to the Pvh-bis(hydrido) species 2a' (5 41.80 d, = 120), partially overlapping with the resonance due to 5a (5 40.52 d, jRhp = 116), likely formed by reaction of 3a' (otherwise detected in the spectrum of 5a under Ar) with H2. The 8-line pattern for type-V complex (5 45.80 dd, /RKP = 164, 2J ? ? = 54; 55.95 dd, J ^ P = 214, V p P = 54) is fully resolved. In the corresponding ' H N M R spectrum at 233 K, only T = 300 K T = 300 K 3a' T = 300 K T = 273 K ViW^ M^tf*^ VvAv•^ v^ ^ A 1 }J T = 243 K V . 1 [, 2a' 5a T = 233 K A_ _JL...._j. J Jl .... t = 24h J l L i t = 70' f *_Lo. l__ t = 60' J l h . I» I Jl t = 40' t = 20' MeOH \ J k acetone V t = 0 50 45 40 35 ppm 10 9 ) 1 6 5 4 3 2 ppm Figure 5.5. VT 3 1 P{'H} (121 MHz) and ' H (300 MHz) N M R spectra of the in situ H 2 -hydrogenation of [Rh(H){PhCH2A=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD 3 OD. traces of free imine are detected, whereas the major species in solution are the asymmetric complex V , 5a and 2a', as also indicated by the presence of the high-field 137 References on page 168 Chapter 5 hydride resonances due to each of these two species (Fig. 5.6, where i = free imine). Free acetone displaced from 5a is also detected. T = 300 K J 1 t = 24h T = 300 K J I t = 70' T = 300 K ... — i ^ i 1_ t = 60' T = 273 K T = 243 K T = 233 K MeOH _kJL MeOH _J 'I acetone " ' I " T 1 I I 5 1 3 2 1 DDm 5a A . A. 2a' t = 40' t = 20' — t = 0 Figure 5.6. VT *H N M R (300 MHz) spectra (selected regions) of the in situ H 2 -hydrogenation of [Rh(H){PhCH27V=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD 3 OD. At 243 K, the intensities of the free imine ! H N M R resonances increase, while those due to V are decreased in both spectra: it is possible that at this temperature the solvent exchange becomes fast enough to cause "labilization" of the Rh-N bond and full decoordination of imine to form 3a', which is rapidly converted into 2a' because of the still relatively abundant [H2] at this stage. Improved resolution for both hydride resonances, particularly for that of 2a' (S -22.10), is also observed. At 273 K, traces of the dibenzylamine product are present in the ' H N M R spectrum (8 3.79 bs, C7/2), but in the corresponding 3 1 P{'H} N M R there is no indication of a possible intermediate species containing hydride and substrate ligands (as just prior to the H-transfer step). A somewhat poorer resolution for the hydride resonance of 2a' (Fig. 5.6), however, may 138 References on page 168 Chapter 5 imply that competition of the substrate with the solvent for the catalytic site is occurring. This observation further supports the suggestion that oxidative addition may be the slow step, compared to coordination of the substrate, and that the subsequent H-transfer step is rapid. A speculative mechanistic proposal is shown in Scheme 2. Scheme 2. Proposed reaction cycle for the H2-hydrogenation of [Rh(H) {PhCH 2-A^=CH(o-C 6H4)}(PPh3) 2(acetone)]PF6 (5a) in CD 3 OD; under Ar, only the species 5a, V and 3a' are seen (see Section 4.4.1). The system at 273 K consists of 5a, V and 2a'. When the solution is warmed, dissociation of imine from V increases as does the amount of 2a'. Competition of the substrate with the solvent for the Rh could also be promoted, leading to re-coordination and loss of H 2 to form V (in a first step towards ortrco-metallation). In the presence of H 2 , species V, via a parallel pathway to that of solvent-exchange/substrate-dissociation, may undergo oxidative addition and start the catalytic cycle. In the spectra at 300 K recorded after 1 h, no free imine is detected, and from the 3 1 P{ 1 H} N M R data the species present in solution are 2a', 3a' and residual 5a. The ' H N M R spectrum shows a singlet 139 References on page 168 Chapter 5 corresponding to the benzylic protons of the amine product (5 3.79 s, CH2); however, the two doublets at 8 3.58 and 4.01 (2d, V H H = 12) indicate diastereotopic inequivalence of the same set of protons. After standing overnight at 300 K , the sample was further exposed to 1 atm H2 before the 3 1 P{'H} and ' H N M R spectra were recorded, thereby accounting for detection of only 2a' in the 3 1 P{'H} N M R spectrum. In the corresponding ' i i N M R spectrum, the doublets at S 3.58 and 5 4.01 were not observed: only an unidentified resonance at 5 1.05 and that of free amine product were detected. In order to ascertain the nature of the two doublets noted above, reaction between cw-[Rh(Pp-tolyl3)2(CD3OD)2]PF6 (3b') and dibenzylamine (Rh:amine 1:2) in CD 3 OD was investigated by VT 3 1 P{'H} and ' H N M R spectroscopies (Fig. 5.7). T = 300 K I ' " Y ^ f ^ v p V ^ Y V 1 ^ ^ — T = 273 K T = 243 K .1. MeOH amine WiyW>Y*VV^ ~^ MeOH _ J L _ 60 J.5 50 4 5 1 • ' 1 ' ' r~ 1 ' 1 1 ' ' ' ' 1 .5 5.0 1.5 4.0 3.5 p p m Figure 5.7. VT 3 I P{ 'H} (121 MHz) and ' H (300 MHz) N M R spectra (selected regions) of the reaction between cw-[Rh(P/?-tolyl3)2(solv)2]PF6 (3b') and (PhCH2)2NH (Rh:amine 1:2) in CD 3 OD. The temperature-dependence of the 3 1 P{'H} N M R spectra indicates that fluxional processes are occurring at the Rh at r.t., whereby a rapid (on the N M R time-scale) 140 References on page 168 Chapter 5 exchange process, likely involving solvent and amine ligands, causes the resonances to be averaged out into the baseline of the spectrum. On the other hand, the set of signals detected at and below 243 K (5 43.38 dd, JRh? = 169, V P P = 55; 58.15 dd, J R h P = 217, V P P = 55) is indicative of a four-coordinate Rh(I) species containing one amine and one solvent ligand each trans to one phosphine. It thus appears that only one amine coordinates at the Rh (Fig. 5.8). Resonances due to free ligand (5 3.79 s, CH2) are I PF 6 " | PF 6 -p-tolyl 3P ^ s o l v a m i n e p-tolyl 3P ^.solv ^ R h ^ " ^Rh Ph p-tolyl 3P % o l v p-tolyl 3P ^ N H — / ^ P h Figure 5.8. Proposed exchange at the Rh center of cz.s-[Rh(Pp-tolyl3)2(solv)2]PF6 (3b') in the presence of 2 (PhCH 2 ) 2 NH in CD 3 OD. detected at all temperatures in the ' H N M R spectrum. The two doublets at 8 3.58 and 4.01 (27HH = 12) indicate inequivalence of the benzylic protons as when the amine is within an asymmetric environment, pictured in a static low temperature limiting structure. Detection of broad peaks in the r.t. ^ P l ' H } N M R spectrum of 5a in CD 3 OD under Ar suggests that in this case one ligand, namely the imine, binds relatively more firmly to the metal center compared to dibenzylamine, a behavior possibly dictated by the difference in their respective steric bulk. Under the conditions here used (Rh:amine 1:2), however, it is likely that the equilibrium between 3b' and the mono-amine complex is shifted much towards the latter (3b' is not detected at any temperature), and that even at r.t. the dominant species is a rapidly exchanging amino-solvento complex (Fig. 5.8). Formation of analogous ort/zo-metallated species was not observed for the amine ligand, again possibly due to the increased hindrance around the N-atom and thus consistent with N-coordination being the first step for this type of reactivity (see Sections 4.3 and 4.4). The benzylic fragment of non- and substituted benzylamines is known to undergo ortho-metallation and several examples have been reported at a variety of metal centers;26"28 141 References on page 168 Chapter 5 however, no literature precedents for this type of activation of the dibenzylamine unit were found. In the analogous V T N M R investigation on the 1:1 (Rh:amine) mixture, detection of 3b' in the 3 1 P{'H} N M R spectra at all temperatures (Fig. 5.9) suggests that the exchange still occurs as in the 1:2 mixture, with here one half of amine molecules coordinating and the other half free. In a crude sense, the total amine molecules are therefore rapidly exchanging at approximately one half of the Rh centers in solution, the remaining number of Rh sites being present throughout as the bis-solvated 3b' (5 55.75 d, J R h P = 204). T = 3 00 K T = 273 K T = 243 K T = 223 K SO 55 50 4 5 4 0 , , p „ , — ~n 5 .5 5 . 0 4 . 5 4 . 0 3 . 5 Figure 5.9. VT 3 1 P{'H} (121 MHz) and ' H (300 MHz) N M R spectra (selected regions) of the reaction between czs-[Rh(P/?-tolyl3)2(solv)2]PF6 (3b') and (PhCH 2 ) 2 NH (Rh:aminel : l ) inCD 3 OD. These observations complement and are in agreement with the spectra obtained from VT N M R monitoring of the hydrogenation of 5a presented above. It can be inferred that the coordination ability of the product is in this instance limited compared to that of the substrate, and poisoning of the catalyst by the product is likely to be excluded. 142 References on page 168 Chapter 5 Catalytic hydrogenation of PhCH2N=CHPh in the presence of 40% mol excess dibenzylamine (amine/catalyst) did not result in a lower activity. The progressive decrease in intensity of the acetone resonance in the ' H N M R spectrum of the hydrogenation of 5a (Fig. 5.6) appears to relate directly to the growth of the resonance at 5 1.05. It does not result from a product of conversion of acetone under H2: the distinctive resonance patterns for 2-propanol or propane are not seen. An alternative possibility to account for the 5 1.05 singlet is that it results from metal-mediated formation of the ketal [(Me)2C(OCD3)2]. Formation of 14a in the presence of excess imine in MeOH is of general relevance also for other Rh precursors, as revealed by further in situ N M R investigations mimicking catalytic conditions. Addition of excess imine (Rh:imine = 1:50) to a CD3OD solution of either cw-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (15a) or cw,fra/w,cw-[Rh(H)2(PPh3)2-(NH2CH2Ph)2]PF6 (17a) resulted in displacement of one coordinated benzylamine (and reductive elimination of H2 from 17a) and formation of 14a. Exposure of these solutions to 1 atm H2 for 1 h afforded conversions of up to 80% to dibenzylamine. It therefore appears that, under catalytic conditions, occurrence of hydrolysis and consequent formation of benzylamine do not interfere with the catalytic cycle, which on the contrary is believed to revolve around species 14a, resulting from the pre-equilibrium between a benzylamine-solvento complex and the imine substrate. 5.2.2. The PhCH=NMe/PhCH2NHMe System The liquid N-methylbenzylideneamine undergoes hydrogenation catalyzed by la in MeOH with conversions > 98 % in 1 h. Monitoring of the reaction was conducted by ' H N M R spectroscopy of CD3OD samples of the reaction mixture residue after evaporation of the solvent. A suitable GC temperature-program to separate imine and amine, which display the same retention time, could not be optimized using the standard column effective for other imines. The results are in line with the above general considerations for PhCH 2N=CHPh, and with the observed stoichiometric reactivity of PhCH=NMe with 3a' in C D 3 O D previously discussed (see Section 4.4.1) where, in addition to ort/zo-metallation, this imine forms a mono-imine-solvento complex in MeOH 143 References on page 168 Chapter 5 (5 46.42 dd, J R h P = 164, 2 J P P = 54; 55.96 dd, = 216, V P P = 53, non-fluxional at r.t.) similar to complex V considered to be formed from 5a. The r.t. 3 1 P{'H} N M R spectrum of the in situ reaction of 3a' with excess imine (Rh:imine = 1:100) shows a single resonance (5 43.01 d, J R hp = 170), the J R h p value of which is indicative of a Rh(I)-bis(amine) species, and an A M X , 8-line pattern (8 45.03 dd, J^P = 168 , 2 J P P = 48; 49.46 dd, y R h p = 171, Vpp = 48) comparable to that observed for 14a. This suggests that hydrolysis occurs also for this imine and that the more basic methylamine product (compared to benzylamine) is probably more prone to coordination to the Rh so as to afford a bis-amine complex. In this instance, the pre-equilibrium may involve a bis-amine, rather than the amino-solvento complex proposed for the PhCH2N=CHPh case. Coordination of the imine again forms an imine-amine species analogous to 14a that is similarly acting as the active catalyst under hydrogenation conditions (Fig. 5.10). Figure 5.10. Proposed reaction steps for the H2-hydrogenation of PhCH=NMe in MeOH (cf. Fig. 5.3). No resonances were detected in the r.t. 3 1 P{ ! H} N M R spectrum of the reaction between 3a' and the hydrogenated product PhCH 2 NHMe in CD 3 OD under Ar (Rh:amine 144 References on page 168 Chapter 5 1:2), suggesting a behavior similar to that of dibenzylamine described above. Resolution of the spectra into an A M X , 8-line pattern, similar to that observed for the dibenzylamine case, occurs at 233 K (5 46.78 dd, JRHP = 169, V P P = 55; 57.15 dd, J^P = 216, 2 y P P = 55). This observation seems to indicate that the P h C ^ N H M e product does not interfere significantly with the course of the hydrogenation reaction. 5.2.3. The PhCH=NPh/PhCH 2 NHPh System Hydrogenation of the solid benzylideneaniline PhCH=NPh catalyzed by l a at ambient conditions proceeds up to only 4% conversion within the first hour (Fig. 5.11), and precipitation of a red solid (21a, see below) occurs after the first 5 min of reaction. An explanation for the marked difference in % conversion compared to that achieved for PhCH2N=CHPh (~ 100%) under the same conditions is unlikely ascribable to efficiency of the catalyst. The only structural difference in the two substrates is in the N-aryl substituent: Ph vs. Bz group, respectively. Furthermore, reaction of 3b' and PhCH=NPh (Rh:imine 1:2) under Ar in C D 3 O D showed formation of the ort/20-metallated product 7b' and the presence ofa fluxional species that could be identified at 253 K (5 45.50 dd, •/RhP = 168, 2 J P P = 54; 53.16 dd, J^p = 213, 2JPP = 54), analogous to V for 5a, thus suggesting for this imine a behavior similar to that observed for PhCH2N=CHPh. 100 90 80 70 > 60 c 0 0 50 5? 40 30 20 10 0 • PhCH2N=CHPh - PhN=CHPh 1000 2000 3000 4000 5000 6000 7000 t(s) 8000 Figure 5.11. Plots of % conv. vs. t for the hydrogenation of PhCH 2N=CHPh and PhN=CHPh (53 mM) catalyzed by l a in MeOH (1 atm H 2 , 30 °C, Rh:imine = 1:100). 145 References on page 168 Chapter 5 VT 3 1 P{'H} and ' H N M R monitoring of the hydrogenation of the ortho-metallated species 7b' generated in situ in C D 3 O D was carried out similarly to that performed on 5a described in Section 5.2.2. Complex 7b' behaved similarly to 5a up to 273 K, whereby a new resonance at 5 44.61 (d, = 211) was detected in the 3 1 P{'H} N M R spectrum. The r.t. reaction of 3a' with the corresponding hydrogenated product PhCH 2NHPh in MeOH under Ar (Rh:amine 1:2) led to isolation of the complex [Rh{n4-(C6H5)NHCH2Ph}(PPh3)2]PF6 (21a) containing an amine ligand bonded to the Rh through a 71-arene interaction (Fig. 5.12), the degree of hapticity of the coordinating ring being different for the solid state and solution samples. r p F6 I+PF, H . — N H P h 3 P ^ / O M e 2 P h C H , N H P h \ 7 P h Rh P h 3 P ^ OMe MeOH / \ 1 P h 3 P P P h 2 3a' 21a Figure 5.12. Formation of [Rh{n 4-(C 6H 5)NHCH 2Ph}(PPh 3) 2]PF 6 (21a) in MeOH. Complex 21a was characterized by 3 1 P{'H} and ' H N M R spectroscopy, IR, elemental analysis and X-ray crystallography. Characterization data for the corresponding solid formed and isolated from the catalytic mixture are virtually identical to those of 21a, showing indeed that hydrogenation of the imine has occurred, likely via a pathway similar to that proposed for 5a; however, production of the amine results in the formation of 21a, which accounts for the suppression of catalytic activity. X-ray quality crystals were obtained by slow evaporation of a CH2Cl2/hexanes solution of the complex (Fig. 5.13). The complex crystallizes in the P2i/c space group with 0.5 CH 2 C1 2 from the crystallization solvent mixture. Prominent features in the solid state structure are an unexpected preference for coordination through an aryl rather than the N H donor group, and the n 4 hapticity adopted by the coordinated ring. Although Rh(I)-7t-arene complexes are most common (see Section 3.3.1), those adopting n4-hapticities are rare. 146 References on page 168 Chapter 5 C34 Figure 5.13. ORTEP diagram of the cation [Rh{n4-(C6H5)NHCH2Ph}(PPh3)2]+ (21a) with 50% probability thermal ellipsoids. Selected structural parameters for 21a are given in Table 5.1. The shorter Rh(l)-C(n) (n = 39-42) distances indicate that the arene is coordinated through the C(39)-C(40) and C(41)-C(42) bonds, whereas the longer Rh(l)-C(37) and Rh(l)-C(38) distances indicate that the C(37)-C(38) bond is non-coordinating. The corresponding distances of the coordinating C-C bonds within the phenyl group do not, however, differ significantly from those of the non-coordinating C-C bonds. The absence of a CH2 "spacer" between the N H and the one Ph group in PhNHCH 2Ph is likely the source of the electronic and steric factors that dictate the preference for coordination through the arene: favoured conjugation between the N-atom and the Ph ring (Fig 5.14), and thus a tendency to coordinate through the latter, and increased steric demand around the N H group, may account for the unusual coordination of this amine. 147 References on page 168 Chapter 5 Figure 5.14. Possible resonance structures for PhCH 2 NHPh. Table 5.1. Selected bond distances and angles for the cation [Rh{n 4-(C 6H 5)NH-CH 2Ph}(PPh 3 )2] + (21a) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) RhO)-P(l) 2.2636(8) P(l)-Rh(l)-P(2) 94.98(3) Rh(l)-P(2) 2.2421(7) P(l)-Rh(l)-C(37) 105.30(7) Rh(l)-C(37) 2.524(3) P(l)-Rh(l)-C(38) 129.33(7) Rh(l)-C(38) 2.442(3) P(l)-Rh(l)-C(39) 163.24(9) Rh(l)-C(39) 2.288(3) P(l)-Rh(l)-C(40) 152.61(9) Rh(l)-C(40) 2.287(4) P(l)-Rh(l)-C(41) 118.75(9) Rh(l)-C(41) 2.310(4) P(l)-Rh(l)-C(42) 98.37(8) Rh(l)-C(42) 2.291(3) P(2)-Rh(l)-C(37) 144.30(7) N(l)-C(37) 1.354(4) P(2)-Rh(l)-C(38) 112.61(7) N(l)-C(43) 1.468(4) P(2)-Rh(l)-C(39) 94.09(7) C(43)-C(44) 1.574(9) P(2)-Rh(l)-C(40) 102.24(10) C(37)-C(38) 1.405(4) P(2)-Rh(l)-C(41) 131.75(9) C(38)-C(39) 1.388(4) P(2)-Rh(l)-C(42) 165.90(8) C(39)-C(40) 1.416(5) C(37)-N(l)-C(43) 124.0(3) C(40)-C(41) 1.392(5) C(37)-Rh(l)-C(38) 32.83(10) C(41)-C(42) 1.416(5) C(39)-Rh(l)-C(40) 36.06(13) C(42)-C(37) 1.430(5) C(41)-Rh(l)-C(42) 35.85(12) 148 References on page 168 Chapter 5 The complex was also generated in situ from reaction of [Rh2(PPh3)4][PF6]2 (4a) with PhCH 2 NHPh under Ar (Rh:amine 1:2) in CD 2 C1 2 . The corresponding 3 1 P{ ] H} spectrum (Fig. 5.15) shows that the complex is stable in non- or weakly coordinating media (CD 2C1 2), where one doublet is detected (8 46.61 d, / R hp = 211). 5? fiO AB 'If. AA 4? 40 Figure 5.15. 3 I P{ 'H} N M R spectrum (121 MHz, 298 K) of [Rh{n 6-(C 6H 5)NHCH 2Ph}-(PPh 3) 2]PF 6 (21a) in CD 2 C1 2 . The corresponding *H N M R spectrum further indicates that the n4-hapticity is not retained in solution, whereby rf-coordination is adopted. Detection of 3 upfield-shifted resonances in a 2:2:1 ratio (Fig. 5.16, i * = free imine) indicates equivalence of the two meta and the two ortho protons. In an ^-coordination, a set of 5 different resonances would be expected. Shifted resonances for the C H 2 and N H protons of the coordinated amine, mutually coupled, and free ligand are also detected in this solvent. Figure 5.16. *H N M R spectrum (300 MHz, 298 K) of [Rh{n 6-(C 6H 5)NHCH 2Ph}-(PPh 3) 2]PF 6 (21a) in CD 2 C1 2 . 149 References on page 168 Chapter 5 Conversely, as shown by the 3 1 P{'H} and *H N M R spectra of the corresponding acetone-d6 solutions, in coordinating media partial displacement of the amine from 21a (§ 46.76 d, J R h p = 211) by the solvent and formation of 3a (8 54.19 d, VRhp = 202) occur (Fig. 5.17), similarly to the behavior of the analogous Rh(I)-n6-toluene complex previously discussed (see Section 3.3.3). The corresponding ] H N M R spectrum shows resonances due to 21a (8 4.00 s, 2H, PhC// 2 NH(n 6 -C 6 H 5 ) ; 5.35 t, 1H, p-(x\6-C6^ 5 )NHCH 2 Ph, V H H = 7; 5.71 d, 2H, o-(n 6-C6// 5)NHCH 2Ph, V H H = 7; 6.09 t, 2H, m-Figure 5.17. 3 , P{ 'H} N M R spectrum (121 MHz, 298 K) of [Rh{n 6-(C 6H 5)NHCH 2Ph}-(PPh 3) 2]PF 6 (21a) in acetone-^-(r| 6-C 67/ 5)NHCH 2Ph, V H H = 7) and to free amine (8 4.33 s, 2H, PhGf/ 2NHPh) (Fig. 5.18, a* = free amine). Resonances for the N-H group are not detected, and the resonance of Figure 5.18. ' H N M R spectrum (300 MHz, 298 K) of [Rh{n 6-(C 6H 5)NHCH 2Ph}-(PPh 3) 2]PF 6 (21a) in acetone-J6. 21a 3a 150 References on page 168 Chapter 5 the CH2 group appears as a singlet. The ratio between 21a and 3a in solution is ~ 1:1. Complex 21a behaves similarly in CD 3 OD, with the exception that in this solvent it exists presumably as two different isomers (3:1 approximate ratio). The resonance due to 3a' (8 57.03 d, JRW = 207) and two closely separated doublets for each isomer of 21a (8 46.71 d, J R h P = 211; 47.45 d, J R h P = 212) are detected in the 3 I P{ 'H} N M R spectrum (Fig. 5.19); correspondingly, two sets of upfield-shifted resonances for aromatic protons (5 5.21 t, 1H, /?-(Ti 6-C6tf5)NHCH 2Ph major isomer, V H H = 7; 5.23 t, 1H, p-(r\6-C 6 / / 5 )NHCH 2 Ph minor isomer, V H H = 7; 5.51 d, 2H, o-(n 6-C6# 5)NHCH 2Ph major isomer, V H H = 7; 5.55 d, 2H, o - ( n 6 - C 6 # 5 ) N H C H 2 P h minor isomer, VHH = 7; 5.92 t, 2H, w-(n 6-C6# 5)NHCH 2Ph major isomer, V H H = 7; 6.02 t, 2H, m-(n 6-C6// 5)NHCH 2Ph minor isomer, VHH = 7), as well as two upfield-shifted singlets for the amine C H 2 protons of each isomer (8 3.33 s, 2H, PhCH 2 NH(n 6 -C 6 H 5 ) minor isomer; 3.81 s, 2H, PhC// 2 NH(n 6 -CeHs) major isomer) are present in the ' H N M R spectrum. The second isomer may involve coordination of the amine through the arene of the benzylic group: in this solvent, involvement of the N-atom in hydrogen-bonding with the MeOH molecules may reduce the extent of conjugation with the Ph ring and allow for limited coordination through the second arene moiety (Bz). In the presence of excess amine, however, 21a fully forms in situ as shown in Fig. 5.12 and is detected as the single species. 21a 3a' 50 Figure 5.19. 3 1 P{'H} N M R spectrum (121 MHz, 298 K) of [Rh{n 6-(C 6H 5)NHCH 2Ph}-(PPh 3) 2]PF 6 (21a) in CD 3 OD. In either acetone-^, CD 3 OD or CD 2 C1 2 , exposure of 21a to 1 atm H 2 did not result in hydrogenation of the coordinated arene. Free amine and 2a or 2a', or unreacted 21a, were the only species detected. Although these data indicate further lability of the 151 References on page 168 Chapter 5 coordinated amine in coordinating media under 1 atm H 2 at the stoichiometric level, formation of 21a as observed under catalytic conditions (whereby a relative excess amine with respect to Rh can be formed via hydrogenation of the corresponding imine) clearly shows that in this case the hydrogenation product PhCH 2 NHPh competes for the metal center significantly enough to suppress its catalytic activity. This likely relates directly to the poor results obtained in the catalytic hydrogenation of the precursor imine, in contrast with the more labile interaction exerted by amines such as (PhCH 2 ) 2 NH and PhCH 2 NHMe described earlier (see Sections 5.2.1 and 5.2.2). 5.2.4. The/MolyIC(Me)=NPh//;-tolylCH(Me)NHPh System Negligible conversion was achieved during the first hour of the catalytic hydrogenation of the solid ketimine />tolylC(Me)=NPh using the catalyst precursor l a . Longer reaction times did not result in appreciable improvements; indeed, significant decomposition of the substrate to p-Me-acetophenone was then observed by GC analysis. The reactivity of this imine with the precursor 3a varies in different solvents even in the absence of H 2 (see Section 4.4.4). Particularly, in CD 3 OD (Fig. 5.20) the ortho-C H 3 19a Figure 5.20. Species formed by reaction of c«-[M(PPh 3 ) 2 (solv) 2 ]PF 6 (3a') and p-tolylC(Me)=NPh in CD 3 OD. 152 References on page 168 Chapter 5 metallation product 11a', formed exclusively in acetone-^ and CD2CI2, is non-fluxional at r.t. and is accompanied by formation of a second species proposed as 19a, the 3 I P{'H} and ' H N M R spectra of which closely resemble those of 21a. For 19a, however, a single isomer was detected in the 3 1 P{'H} N M R spectrum, in contrast with the spectra of 21a in CD 3 OD. Inhibition of hydrogenation of /?-tolylC(Me)=NPh likely occurs because the imine gives rise to two different coordination modes to the metal, neither of which provides a catalytic pathway. NMR-scale in situ reactions of 3a and p-tolylC(Me)=NPh (Rh:imine 1:1) with 1 atm H 2 in acetone-^ for 1 h resulted in only partial formation of the o/t/zo-metallated complex 11a (the major species) and the bis(hydrido) species 2a. Similarly, reactions in CD3OD resulted in partial formation of 11a' and 2a', free imine also being detected. At the stoichiometric level (Rh:imine = 1:1), therefore, oxidative addition of H2 occurs in both solvents to give the corresponding 2, but 19a is not seen, consistent with the weaker 71-arene coordination mode compared to that of the ort/jo-metallated complex. In neither solvent were ' H N M R resonances due to the hydrogenation product detected. N M R investigations under catalytic, excess imine conditions were not carried out; the limited catalytic hydrogenation results, however, suggest a reactivity similar to that seen under stoichiometric conditions. 5.2.5. The (Ph)2C=NCH 2Ph/(Ph)2CHNHCH 2Ph System Negligible conversion was also observed in the hydrogenation of the solid ketimine (Ph)2C=NCH2Ph catalyzed by la in MeOH. Oz7zo-metallation of this substrate gives rise to the species 10a stable in both acetone and MeOH; the inability of MeOH to "reverse" the o-metallation (see Section 4.4.3), and the consequent absence in solution of any Rh(I) species suitable for oxidative addition, may in this case underlie the poor hydrogenation results. Indeed, the r.t. NMR-scale in situ reaction of 10a' (thus in a stoichiometric Rh:imine ratio) with 1 atm H 2 in CD3OD resulted only in partial displacement of the imine and formation of 2a' (Fig. 5.21). It is conceivable that under catalytic, excess imine conditions, 10a' is fully formed and that even the partial displacement of imine and oxidative addition of H 2 , observed on the stoichiometric scale, are prevented. 153 References on page 168 Chapter 5 D O C D 3 H<„ I , < P P h 3 " " R h " + PF p h 3 p < N Ph Ph H 2, 1 atm CD3OD H H + P p < H„_ | ^ P P h 3 ^ R h ' D (10a') + yr . ^ P h 3 P « ^ I ^ O C D O C D 3 D + imine 10a1 Figure 5.21. Fate of [Rh(H){PhCH2A^C(Ph)(o-C6H4)}(PPh3)2(CD3OD)]PF6 (10a') upon exposure to 1 atm H 2 in CD 3 OD. 5.2.6. The PhC(Me)=NCH 2 Ph/PhCH(Me)NHCH 2 Ph System Appreciable conversion (~ 40% from GC integration) under catalytic hydrogenation conditions was achieved for the liquid PhC(Me)= :NCH2Ph ketimine but only after 24 h (~ 4% after 1 h) (Fig. 5.22). The observed stability of the corresponding or^o-metallated product 9a' in MeOH (see Section 4.4.2) would suggest, as inferred for 10a' (Fig. 5.21), inertness of the system toward H2-hydrogenation. The discrepancy with the (Ph) 2C=NCH 2Ph case may be ascribed speculatively to the kinetics of the reverse of the ort/zo-metallation step, if this occurs slower than for 5a but faster than for 10a', although this was not studied. H ~ OMe • H,„ I ^ P P h 3 " " R h " + P F K P h 3 P N Ph Me 1 atm H 2, 24 h MeOH 9a' N H - C H 2 P h ( - 4 0 % conv.) Figure 5.22. Reaction conditions for the hydrogenation of PhC(Me)=NCH 2Ph in MeOH. 154 References on page 168 Chapter 5 Crystallization of compound [M(H){PhCH 2Ar=C(Me)(o-C 6H 4)}(NH 2CH 2Ph)-(PPh3)2]PF6 (18a), containing the benzylamine moiety, from a solution of 9a' would however support this proposal: i f hydrolysis of the substrate is metal-catalyzed, reverse of the ort/io-metallation in 9a', to allow for coordination of H 2 0 , must have occurred. The in situ reaction of 9a' with 1 atm H 2 in CD3OD resulted in the formation of 2a' and the amine product. Similarly to the imine C(CH3)=N resonance (see Section 4.4.2) in CD 3 OD, neither the amine CH(C//3)NH nor the C/ / (CH 3 )NH resonance was detected in the ] H N M R spectrum in this solvent, and only a singlet (upfield compared to that of the imine) in the benzylic CH2 region could be detected. No further evidence for the product could be gathered from such in situ experiments in CD 3 OD. On the other hand, when the residue of the reaction mixture carried out in MeOH was redissolved in acetone-^, the C//3, CH and CH2 resonances of the product, and their expected multiplicities (d, q and ABq, respectively), were detected. The percent conversion based on ' H N M R integration is in agreement with that derived from GC analysis (~ 40% after 24 h). 5.2.7. T h e P h C H = N C 6 H , , / P h C H 2 N H C 6 H „ System ' H N M R analysis in CD3OD of the residue of the catalytic hydrogenation of the liquid PhCH=NCy in MeOH after 1 h showed 72% conversion to the amine product. The partial fluxionality displayed by the corresponding orZ/zo-metallated species 8a' in MeOH, similarly to that of 5a, could again be invoked as the plausible rationale underlying the observed behavior. However, NMR-scale, in situ reaction of 3a' and PhCH=NCy (Rh:imine 1:2) with 1 atm H 2 in C D 3 O D resulted in the spontaneous precipitation of a brown solid for which full characterization is incomplete because of unsuccessful attempts to isolate the material on a larger scale. The ' H N M R spectrum of the supernatant C D 3 O D solution shows resonances for the amine product and residual imine. However, it has not been ascertained whether the precipitate forms from reaction of the amine product with the Rh (cf. reaction of 3a' with P h C H 2 N H 2 in MeOH, see Section 4.4.1) or whether it is an imine complex (see below). Evidence of two high-field resonances in the ' H N M R spectrum of the solid dissolved in acetone-a^ suggests a behavior analogous to that observed for most Ir systems (see Section 5.3.2), whereby a 155 References on page 168 Chapter 5 neutral complex is formed, thus sequestering the active site from the reaction medium (Fig. 5.23). H,, . P P h , Rh D C D 3 O D H, P h 3 P ' O C D , O C D 3 D 2a' P h C H = N C y P h 3 P - H , D O C D 3 I » P P h 3 R h " C y N H 8a' P F K H H „ , I , ^ P P h 3 " " R h " P h 3 P ' H I 22a Figure 5.23. Possible dead-end pathway for 2aVPhCH=NCy under F£2 in CD 3 OD. 5.2.8. The C , 2 H , 5 0 2 N / C 1 2 H , 6 0 2 N H {(diq)/(diq-(H)2)} System No conversion was observed in the hydrogenation of the solid, cyclic ketimine 6,7-dimethoxy-l-methyl-3,4-dihydroisoquinoline (diq) in MeOH in the presence of preformed 2a'. Because of the lack of suitable ortho positions in diq, formation of the stable Rh(I) square-planar bis-imine complex 20a was observed (see Section 4.4.5) from the reaction of in situ formed 2a' in CD3OD with stoichiometric imine (Rh:imine 1:2) at r.t. Isolation and full characterization were however carried out for the corresponding p-tolyl complex 20b. Both 20a and 20b are insoluble in MeOH and spontaneously precipitate as yellow solids. On the NMR-scale, in situ experiment that afforded 20a, analysis of the supernatant CD3OD layer by 3 1 P{'H} and ! H N M R spectroscopy after exposure of the mixture to 1 atm H 2 for lh did not reveal any conversion of the imine to the corresponding amine, while the precipitate, dried in vacuo and redissolved in CD 2 C1 2 , afforded a clear yellow solution of 20a (Fig. 5.24). Complex 20a exists as a mixture of isomers in CD 2 C1 2 solution, as indicated by the 3 1 P{'H} N M R spectrum (§ 44.77 d, J-RM? = 170, major isomer; 43.74 d, JRh? = 170, minor isomer). The complex was again detected unaltered after exposure to 1 atm H 2 at r.t. Of interest, hydrogenation of quinoline (Q) to 1,2,3,4-tetrahydroquinoline (THQ) catalyzed by [Rh(COD)(PPh 3) 2]PF 6 (la) in toluene at ~ 97° C and atmospheric H 2 -pressure has been reported, and the coordination chemistry involved in the reaction was 156 References on page 168 Chapter 5 investigated.9 Reaction of l a with Q in CH 2 C1 2 at r.t., under either N 2 or H 2 , resulted in displacement of one phosphine ligand from l a and in the formation of the known P F 6 " H H„ I ^ P P h ; OMe | + P F 6 R h D 3 CD3OD ^ ^ ^ R h / \d C D 3 O D P H 3 P ^ ^ O C D 3 2 imine P h 3 P ^ > 6 2a' 20a ° C ° 3 - H , - - U J M ^ U . . . 1h >*A^  *" / K r V / A -~ no reaction 1 atm H , 1 atm H 2 CD 2 CI 2 1h no reaction Figure 5.24. Reactivity scheme of the 2a'/diq system in C D 3 O D under 1 atm H 2 . [Rh(COD)(PPh3)(Q)]+,29 indicating that, under these conditions, phosphine-displacement occurs more rapidly than the reaction with hydrogen, yielding the above cation that is inert toward hydrogenation of COD. Displacement of both phosphines could be obtained from l a and Q in refluxing toluene, to afford [Rh(COD)(Q) 2]+, also previously characterized.30 Of interest, this bis-imine complex was isolated quantitatively from the catalytic runs and was thus proposed as an intermediate in the catalytic cycle.9 On the other hand, reaction of 2a (formed in situ in acetone solution) with Q yielded [Rh(PPh3)2(Q)2]+, similar to complex 20a obtained in this thesis work. In the literature example, this species is believed to be of no significance in the catalytic cycle, as the precursor l a and Q are brought into contact before exposure to H 2 . The cycle is proposed to proceed via formation of [Rh(COD)(Q) 2]+ followed by oxidative addition of H 2 : reversible H-transfer to afford partial hydrogenation of Q to 1,2-dihydroquinoline (DHQ) is proposed as the slow step. A second oxidative addition of H 2 and liberation of the saturated THQ was thought to follow in a rapid step. Of note, the COD moiety is maintained intact throughout. 157 References on page 168 Chapter 5 In previous work 2 4 carried out in this laboratory on the hydrogenation of diq catalyzed by [Rh(P-P)]+ systems in benzene/MeOH (1:1) at r.t. and ~ 1000 psig H 2 , hydrogenation of the substrate was achieved ( ~ 70% conv. after 18 h) only when using a preformed, type-1 catalyst precursor (diene = NBD; P-P = o^iS-chiraphos), whereas when the catalyst was formed in situ from [Rh(NBD)Cl]2 and the ligand (P-P = i?-cycphos), no conversion was achieved. The more forcing experimental conditions thereby required for the formation of a bis(hydrido) complex, dictated by the presence of a chelating phosphine, in conjunction with isolation of the bis-imine complex [Rh(diphos)(diq)2]BF4 analogous to 20a led to the proposal of an "unsaturate route" for the mechanism, i.e. coordination of the substrate, followed by oxidative addition of H2 in a rate-determining step. Higher temperature and pressure, respectively, were used in the above cited examples compared to those utilized in this thesis work. Furthermore, the ligand sets were also significantly different (COD and P-P, respectively) from the monodentate tertiary phosphine of this work. The inertness of 20a toward reaction with H2 in both CD3OD and CD2CI2 observed in this thesis work must be accounted for by a combination of the largely different experimental conditions (r.t. vs. ~ 97° C and 1 atm vs. ~ 1000 psig) and of electronic and steric effects arising from replacement of the COD or P-P moieties with monodentate phosphine ligands. 5.3. Catalytic Homogeneous Hydrogenation at the Ir Center The analogous Ir(I) precursor [Ir(COD)(PPh3)2]PF6 (l*a) showed a markedly lower efficiency, compared to that of the Rh(I) systems, toward the hydrogenation of the imines used in this work. In fact, catalytic hydrogenation was achieved only in a single instance, namely for N-benzylideneaniline PhCH=NPh. The generally higher stability displayed even in MeOH by the Ir(III) orz7?o-metallated species, compared to that of the Rh analogues, may relate to, and to some extent account for the observed lower catalytic activity. In addition, however, for all substrates except PhCH=NPh, immediate precipitation of a light-yellow solid was observed when imines were added to the MeOH solution of the precursor catalyst 2*a'; this peculiar behavior, of general relevance to the Ir-based systems, and its consequences are discussed in Section 5.3.2. 158 References on page 168 Chapter 5 5.3.1. The PhCH=NPh/PhCH2NHPh System In contrast with the Rh system (see Section 5.2.3), the Ir prescursor l*a afforded complete catalytic H2-hydrogenation of the solid benzylideneaniline dissolved in MeOH during the first hour. Although the correspondingly formed ort/zo-metallated 7*a' (Fig. 5.27, see also Section 4.3.1) did not display fluxionality in CD 3 OD, its exposure (in situ, NMR-scale) to 1 atm H 2 for 10 min at r.t. resulted in full conversion to the amine product and formation of the corresponding bis(hydrido) species 2*a\ Such an apparent conflict between relative stability of the ort/zo-metallated species and achievement of significant conversion was observed also for the Rh/PhC(Me)=NCH 2Ph system (see Section 5.2.2). Similar considerations of the kinetics of the ort/zo-metallation reaction could also be put forth as a possible rationalization for the Ir system. However, in marked contrast with the Rh system, in situ N M R experiments showed no interaction at r.t. between the PhCH 2NHPh product and the Ir in CD 3 OD. Whether generated in solution from hydrogenation of the substrate, or added as a pure reactant to a solution of 2*a' (Ir:amine 1:2), benzylphenylamine and 2*a' remained intact in solution. Reluctance of the product to coordinate to the Ir, i.e. to form a species analogous to 21a (see Section 5.2.3), could also account for the difference in hydrogenation of benzylideneaniline performed by the two metals. VT N M R monitoring of the hydrogenation of benzylideneaniline catalyzed by 2*a' was not carried out. Addition of PhCH=NPh to a solution of 2*a' (Ir:imine 1:1) in CD3OD under Ar showed only partial formation of the ort/zo-metallated species 7*a' by ""Pi'H} N M R spectroscopy (Fig. 5.25). This is the only instance in which ortho-metallation does not occur quantitatively at the Ir center under stoichiometric conditions, showing that 2*a' is more inert toward this substrate compared to other imines. By the same token, its formation may be favoured upon exposure of 7*a' to H 2 . 2*a' 7*a' DDI* 28 26 ~Ii ' 22 20 IB Figure 5.25. 3 I P{ 'H} N M R spectrum (121 MHz, 298 K) of the in situ product from the 1:1 reaction between [Ir(H) 2(PPh 3) 2(CD 3OD) 2]PF 6 (2*a?) and PhCH=NPh in CD3OD. 159 References on page 168 Chapter 5 In the corresponding ' H N M R spectrum resonances for 7*a', 2*a' and free amine (a*) were detected (Fig. 5.26). The only source of H2 in this in situ system is 2*a\ This suggests that coordination of the substrate to 2*a' is followed by two parallel reactions, of which H-transfer to give the amine product is faster compared to displacement of H 2 from 2*a' and subsequent formation of 7*a' (Fig. 5.27). From ' H N M R integration, two-thirds of the total imine are hydrogenated while one-third is contained in 7*a'. Detection MeOH Figure 5.26. ' H N M R spectrum (300 MHz, 298 K) of the in situ product from the 1:1 reaction between [Ir(H)2(PPh3)2(CD3OD)2]PF6 (2*af) and PhCH=NPh in CD 3 OD. of 2*a' in the 3 1 P{'H} N M R spectrum may be ascribed to the presence of excess H 2 in solution from the in situ preparation of 2*a' from l*a (cyclooctane is also detected). H " T P F 6 H«„ I , » P P h 3 C D 3 O D ^| r ^P ^ P h 3 P ^ I ^ O C D 3 PhCH=NPh O C D 3 D 2*a' Ph 3 P ,<PPh3 H — ^ l r ~ - N H + P F 6 R H - C D-OCD 3 H, H-transfer - amine 9 H + P F 6 OCD3 H, H V I , ^ P P h 3 .Ph P h 3 P ; i r : N 7*a" Figure 5.27. Proposed steps for the 1:1 reaction of [Ir(H) 2(PPh 3) 2(CD 3OD) 2]PF 6 (2*a') with PhCH=NPh in CD 3 OD. 160 References on page 168 Chapter 5 5.3.2. Other Substrates No hydrogenation of any other substrate tested in this work was achieved when using the Ir precursor l*a. Each system, on the other hand, behaved similarly under 1 atm H 2 for both catalytic and stoichiometric conditions (in terms of the Ir:imine ratio). Reactions of each imine with 2*a' in MeOH under 1 atm H 2 afforded immediate precipitation of a light-yellow solid, indicating a non-polar character for this species. N M R and GC analysis of the residue of the catalytic mixture, obtained after evaporation of the supernatant MeOH solution and redissolution in CD3OD, showed exclusively unreacted imine and no detectable amine. In addition, no resonances other than that for the PF6" counterion were detected in the 3 1 P{ ! H} N M R spectrum. The yellow precipitate spontaneously formed from reaction of 2*a' with (Ph) 2C=NCH 2Ph in MeOH under H 2 at r.t. (Inimine = 1:2), was isolated and characterized as [h(H)2{PhCH2A^=C(Ph)(o-C6H4)}-(PPh3)2] (22*a) by 3 1 P{ 'H} , ' H N M R and IR spectroscopies and X-ray crystallography. X-ray quality crystals were obtained by slow evaporation of a C H 2 C l 2 / M e O H solution of the complex; the structure is shown in Fig. 5.28. C54 Figure 5.28. ORTEP diagram of [h(H)2{PhCH2A=C(Ph)(o-C6H4)}(PPh3)2] (22*a) with 50% probability thermal ellipsoids. 161 References on page 168 Chapter 5 The complex crystallizes in the P2i/c space group. Several crystal specimens were surveyed: all were non-merohedral twins. As a result, in the structure refinement the hydride ligands were included in fixed positions (see Table 5.2). The molecular structure of 22*a resembles that of the ort/zo-metallated complexes discussed in Section 4.3.1. The imine undergoes ort/zo-metallation as previously observed, with formation of the endocycle preferred. In 22*a-type complexes however the coordinated solvent is replaced by a second hydride ligand. Bond lengths and angles are comparable with those of [Ir(H){PhCH2yV=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5*a) (see Table 4.1). Table 5.2. Selected bond distances and angles for [Ir(H)2{PhCH27V=C(Ph)(o-C6H4)}-(PPh3)2] (22*a) with estimated standard deviations in parentheses. Bond Length (A) Bond Angle (°) Ir(D-P(l) 2.2877(19) P(l)-Ir(l)-P(2) 165.30(7) Ir(l)-P(2) 2.2770(18) N(l)-Ir(l)-C(3) 77.5(3) Ir(l)-N(l) 2.142(6) P(l)-Ir(l)-N(l) 98.36(16) Ir(l)-C(3) 2.108(8) P(2)-Ir(l)-N(l) 96.05(17) Ir(l)-H(l,2) 1.603" P(2)-Ir(l)-C(3) 91.7(2) N( l ) -C( l ) 1.295(10) P(l)-Ir(l)-C(3) 88.6(2) N(l)-C(14) 1.486(9) C(l)-N(l)-Ir(l) 117.2(5) C(l)-C(2) 1.480(10) C(2)-C(3)-Ir(l) 113.2(5) C(l)-C(8) 1.485(10) N(l)-C(l)-C(2) 115.0(7) C(14)-C(15) 1.529(11) N(l)-C(l)-C(8) 124.2(7) C(2)-C(3) 1.402(11) N(l)-C(14)-C(15) 112.3(6) C(2)-C(7) 1.419(11) C(l)-N(l)-C(14) 120.1(6) " The two hydrides were restrained to the Ir-H bond distance = 1.603 A (The International Tables for Crystallography, Vol. C, Ed. A.J.C. Wilson, Pag. 731). Similar behavior was observed for other imine substrates utilized (PhCH 2N=CHPh, MeN=CHPh); however, isolation and characterization by N M R and IR spectroscopies and elemental analysis were carried out only for the analogous neutral 162 References on page 168 Chapter 5 complex [Ir(H)2{C6H,i/V=CH(o-C6H4)}(PPh3)2] (23*a) (for the imine PhCH=NCy), whereas [Ir(H)2{PhCH2^=C(Me)(o-C6H4)}(PPh3)2] (24*a) (for the imine PhC(Me)=NCH2Ph) was characterized solely by 3 1 P{'H} and ] H N M R spectroscopy (see Section 5.4.4). The 3 'P{ 'H} singlet of 23*a in CD 2 C1 2 (Fig. 5.29) indicates two equivalent phosphines, while the corresponding ! H N M R spectrum shows two high-field _ J DD* 50 40 30 20 ' 10 0 ' Ho" Figure 5.29. 3 I P{'H} N M R spectrum (121 MHz, 298 K) of [Ir(H) 2{C 6H,,A=CH(o-C&H4)}(PPh3)2] (23*a) in CD 2 C1 2 . hydride resonances, and upfield-shifted resonances for the ort/zo-metallated ring protons (Fig. 5.30). The set of upfield resonances for the o-metallated ring corresponds to three protons: the fourth resonance, likely hidden within the bulk aromatic region, was not CH.CI I J " U A A 1 . A AAAAV A . Figure 5.30. ' H N M R spectrum (300 MHz, 298 K) of [h(H)2{C6H1,7v r=CH(o-C6H4)}-(PPh3)2] (23*a) in CD 2 C1 2 . 163 References on page 168 Chapter 5 detected. The two hydrides resonances are triplets of doublets, due to coupling to two equivalent P-atoms and to one another (each resonance collapses into a doublet in the 'HI 3 ' ?} N M R spectrum); the lower field resonance at § -11 is typical for hydrides trans to the weakly-directing N-atom, whereas the more strongly-directing C-atom has been shown to impart a much larger upfield shift (see also Section 4.3.1). Two strong virH bands were detected at 2105 cm"1, assigned by comparison with data for [Ir(H){PhCH2-A^=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5*a), to the hydride trans to the N-atom, and at 1957 cm"1, assigned to the hydride trans to the C-atom. Formation of 23*a-type complexes may occur via initial orr7zo-metallation of the substrate, with concomitant loss of H2 from 2*a'. Subsequent heterolytic cleavage of H2 would result in the coordination of the second hydride ligand to give the neutral, insoluble complex and formation of HPF6 species that remains in the MeOH filtrate, where the PF 6" signal was detected in the 3 1 P{'H} N M R spectrum (Fig. 5.31). Figure 5.31. Proposed reaction steps for the formation of [Ir(H)2{C6HiiA'=CH(o-C6H4)}(PPh3)2] (23*a) in CD 3 OD. Heterolytic dihydrogen cleavage by a transition metal complex is well documented.31"36 Of relevance to the chemistry of Fig. 5.30, deprotonation of the Ir(III)-hydride-dihydrogen complex [h(H)(bq-H)(H2)(PPh3)2]BF4 (bq-H = 7,8-benzoquinoline) by base ('BuLi) has been reported to afford the neutral Ir(III)-bis(hydrido) species [h(H)2(bq-H)(PPh3)2].3 7 Subsequent incorporation of a basic pendant - N H 2 group in the benzoquinolinate ligand can internally fulfil the base function, when the hydride-dihydrogen complex is only formed en route to the final cationic dihydride [Ir(H)2(bq-164 References on page 168 Chapter 5 NH3)(PPh3)2]BF4, containing a - N H 3 + group formed by deprotonation of the H 2 ligand;3 8 this species was observed only in solution and, because of ready loss of H 2 in the solid state, full characterization was precluded. This conversion was reversible in that removal of H 2 by a stream of N 2 through the solution generated ([Ir(H)(bq-NH2)(H20)-(PPh 3) 2]BF 4); the stability of the dihydrogen species varied with the nature of the phosphine, and a change from PPh 3 to the more basic P JBU 3 resulted in formation of the more stable hydride-dihydrogen complex [fr(H)(bq-NH2)(H2)(PnBu3)2]BF4 (at least at 230 K). This was rationalized in terms of a decrease in acidity of the coordinated H 2 and a concomitant increase in basicity of the hydride ligands when utilizing more basic phosphines and, as a result, a proton from the initially present - N H 3 + is moved to a terminal hydride to form the H 2 complex. The neutral complexes isolated in this thesis work spontaneously precipitate from MeOH at r.t. as neutral bis(hydrido) species, and are stable toward loss of H 2 both in the solid state and in CD 2 C1 2 solution. Low temperature NMR investigations for possible detection of a similar Ir(H)(H2) species were not conducted, although by analogy with the literature, the presence of the less basic PPh 3 may determine exclusive formation of the dihydride complex. Of more relevance from the catalytic standpoint, formation of these species results in the active site being immediately sequestered from the reaction medium, and the potential for catalysis dissipated. 165 References on page 168 Chapter 5 5.4. Experimental 5.4.1. Preparation of [Rh{PhCH2NH(ti4-C6Hs)}(PPh3)2]PF6 (21a) To a red solution of [Rh2(PPh3)4][PF6]2 (0.130 g, 0.084 mmol) in MeOH (5 mL), a solution of the amine (0.031 g, 0.168 mmol) in MeOH (1 mL) was cannulated under Ar and the deep-red solution stirred for 2 h. The volume was then reduced to ~ 1 mL to afford precipitation of a red solid that was collected by filtration, washed with E t 2 0 (3 x 2 mL) and dried in vacuo. Yield: 0.060 g (75%). 3 1 P{'H} N M R (CD 2C1 2): 5 46.61 (d, J R H P = 211). ' H N M R (CD 2C1 2): 5 3.83 (d, 2H, PhC# 2 NH(n 6 -C 6 H 5 ) , V H H = 5), 4.08 (t, 1H, PhCH 2 N//( i i 6 -C 6 H 5 ) , VHH - 5), 5.09 (t, 1H, /?-(n 6-C6^ 5)NHCH 2Ph, VHH = 6), 5.42 (d, 2H, o-(n 6-C6// 5)NHCH 2Ph, VHH = 7), 5.94 (t, 2H, m-(n 6-C6# 5)NHCH 2Ph, VHH = 6), 7.15-7.70 (m, 35H, aromatics). IR (KBr pellet): v 1567 (C-N, m), 3388 (N-H, s). Anal. Calcd. for C49H 4 3 NP 3 F 6 Rh: C, 61.58; H, 4.54; N , 1.47. Found: C, 61.40; H , 4.54; N , 1.65. 5.4.2. Preparation of [Ir(H)2{PhCH27V=C(Ph)(o-C6H4)}(PPh3)2] (22*a) A red suspension of [Ir(COD)(PPh3)2]PF6 (0.070 g, 0.073 mmol) in MeOH (4 mL) was stirred under H2 (1 atm) for 1 h. To the resultant pale yellow solution, the imine PhCH 2N=C(Ph) 2 (0.040 g, 0.147 mmol) was added under H 2 to afford immediate precipitation of a yellow solid. The mixture was stirred under 1 atm H 2 for 1 h, then the solid was collected by filtration, washed with MeOH ( 3 x 3 mL) and dried in vacuo. Yield: 0.055 g (76%). 3 1 P{'H} N M R (CD 2C1 2): 5 23.55 (s). ' H N M R (CD 2C1 2): 5-18.78 (td, 1H, Ir(//), V H H = 5, V H P = 22), -11.00 (td, 1H, Ir(#), V H H = 5, V H P = 20), 4.16 (s, 2H, PhC// 2N=C(Ph)(o-C 6H 4)), 5.60 (t, m,p-{o-C(JH4), VHH = 7), 5.85 (d, 2H, o, m-(o-C6//4), VHH = 7), 6.35 (t, 1H, m-(o-Q(JtiA\ VHH = 7), 6.40 (d, 2H, o - C ( C ^ 5 ) , VHH = 7), 6.80 (pq, 3H, m, p-C(C(Ji5), V H H = 7), 7.00-7.60 (m, 35H, aromatics). IR (KBr pellet): v 1566 (C=N, m), 1993 (Ir-H, s), 2192 (Ir-H, s). 166 References on page 168 Chapter 5 5.4.3. Preparation of [Ir(H)2{C6Hi,/V=CH(o-C6H4)}(PPh3)2]-H20 (23*a) The procedure was exactly as that used for 22*a, but using 0.090 g (0.093 mmol) of the Ir(I) precursor, and the imine C 6Hi,N=CHPh (35.0 u.L, 0.187 mmol). Yield: 0.065 g (77%). 3 1 P{ 'H) N M R (CD 2C1 2): 8 23.30 (s). ' H N M R (CD 2C1 2): 8-19.38 (td, 1H, Ir(Y7), 2 y H H = 3, 2 J H P = 19), -11.40 (td, 1H, Ir(tt), 2Jm = 3, 2JHP = 18), 0.2-1.46 (m, 10H, C 6(H)7V, 0), 1.51 (s, 2H, H20), 2.73 (pt, 1H, C 6 (#)H 1 0 , V H H = 12), 6.31 (t, IH,p-io-CM), V H H = 7), 6.73 (t, 1H, m-io-CaH*), V H H = 7), 6.92 (d, 1H, m - f o - C ^ ) , 3 Jim = 7), 7.18-7.50 (m, 30H, aromatics, 1H, o-(o-CeH4)), 7.90 (s, 1H, CJ7=N). IR (KBr pellet): v 1592 (C=N, m), 1957 (Ir-H, s), 2105 (Ir-H, s). Anal. Calcd. for C49H48NP2Ir.(H20): C, 63.99; H, 5.42; N , 1.51. Found: C, 64.11; H, 5.34; N , 1.75. 5.4.4. NMR Characterization of [Ir(H)2{PhCH2/V=C(Me)(o-C6H4)}(PPh3)2] (24*a) The solid was isolated on an NMR-scale amount, according to the same procedure as that used for 22*a and 23*a. 3 1 P{'H} N M R (CD 2C1 2): 8 24.46 (s). ! H N M R (CD 2C1 2): 8 -19.02 (td, 1H, lr(H), 2JHH = 5, 2JH? = 21), -10.91 (td, 1H, h(H), 2JHH = 5, 2JHP = 19), I. 80 (s, 3H, C(C#3)=N), 4.39 (s, 2H, PhC//2N=C(Me)(o-C6H4)), 6.41 (t, 1H, p-(o-CtH4), VHH = 7), 6.73 (t, 1H, m-io-CeUt), 3JHH = 7), 6.81 (d, 2H, m, o-ip-Cffl*), 3Jm = 7), 7.00-7.65 (m, 35H, aromatics). 167 References on page 168 Chapter 5 5.5. References (1) Kobayashi, S.; Ishitani, H. Chem. Rev. 1999, 99, 1069. (2) James, B. R. Catalysis Today 1997, 37, 209. (3) Shimizu, M. ; Kamei, M . ; Fujisawa, T. Tetrahedron Lett. 1995, 36, 8607. (4) Cho, B. T.; Chun, Y . S. Tetrahedron: Asymmetry 1992, 3, 1583. (5) Srebnik, M . ; Ramachandran, P. V. Aldrichimica Acta 1987, 20, 3. (6) Noyori, R. Asymmetric Catalysis in Organic Synthesis; John Wiley & Sons: New York, 1994. (7) Longley, C. J.; Goodwin, T. J.; Wilkinson, G. Polyhedron 1986, 5, 1625. (8) Herrera, V. ; Munoz, B.; Landaeta, V. ; Canudas, N . J. Mol. Catal. A: Chemical 2001, 174, 141. (9) Sanchez-Delgado, R. A. ; Rondon, D.; Andriollo, A. ; Herrera, V . ; Martin, G.; Chaudret, B. Organometallics 1993, 12, 4291. (10) Herrera, V . ; Fuentes, A. ; Rosales, M . ; Sanchez-Delgado, R. A. ; Bianchini, C ; Meli, A.; Vizza, F. Organometallics 1997, 16, 2465. (11) Herrera, V. ; Munoz, B.; Landaeta, V. ; Canudas, N . J. Mol. Catal. A: Chemical 2001, 174, 141. (12) van den Berg, M . ; Minnaard, A. J.; Schudde, E. P.; van Esch, J.; de Vries, A. H. M . ; de Vries, J. G.; Feringa, B. L. J. Am. Chem. Soc. 2000,122, 11539. (13) Reetz, M . T.; Mehler, G. Angew. Chem., Int. Ed. 2000, 39, 3889. (14) Abu-Gnim, C ; James, B. R. Unpublished results . (15) Seneviratne, K. N . ; James, B. R. Unpublished results . (16) Lewandos, G. S. In The Chemistry of the Metal-Carbon Bond; Hartley, F. R., Patai, S., Eds.; Wiley: New York, 1982; Vol . 1, Chapter 7. (17) Fryzuk, M . D.; Piers, W. E. Organometallics 1990, 9, 986. (18) Chamberlain, L. R.; Steffey, B. D.; Rothwell, I. P.; Huffman, J. C. Polyhedron 1989, 8, 341. (19) Durfee, L. D.; Fanwick, P. E.; Rothwell, I. P.; Folting, K. ; Huffman, J. C. J. Am. Chem. Soc. 1987,109, 4720. (20) Andrews, M . A. ; Kaesz, H. D. J. Am. Chem. Soc. 1977, 99, 6763. 168 References on page 168 Chapter 5 Arndtsen, B. A. ; Davis, J. L. Organometallics 2000, 19, 4657. Arndtsen, B. A. ; Lafrance, D.; Davis, J. L.; Dhawan, R. Organometallics 2001, 20, 1128. Cullen, W. R.; Fryzuk, M . D.; James, B. R.; Kutney, J. P.; Kang, G. J.; Herb, G.; Thorburn, I. S.; Spogliarich, R. J. Mol. Catal. 1990, 62, 243. Becalski, A. G.; Cullen, W. R.; Fryzuk, M . D.; James, B. R.; Kang, G.; Rettig, S. J. Inorg. Chem. 1991, 30, 5002. Casey, C. P.; Singer, S. W.; Powell, D. R.; Hayashi, R. K. ; Kavana, M . Am. Chem. Soc. 2001,123, 1090. Cope, A. C ; Friedrich, E. C. J. Am. Chem. Soc. 1968, 90, 909. Omae, I. Chem. Rev. 1979, 79(4), 287. Manzer, L. E. J. Organomet. Chem. 1977, 135, C6. Uson, R.; Oro, L. A. ; Claver, C ; Garralda, M . A. J. Organomet. Chem. 1976, 105, 365. Uson, R.; Oro, L. A. ; Garralda, M . A. ; Claver, C ; Lahuerta, P. Transition Met. Chem. 1979, 4, 55. Huhmann-Vincent, J.; Scott, B. L.; Kubas, G. J. J. Am. Chem. Soc. 1998, 120, 6808. Schlaf, M . ; Lough, A . J.; Maltby, P. A. ; Morris, R. H . Organometallics 1996, 15, 2270. Smith, K. T.; Tilset, M . ; Kuhlman, R.; Caulton, K. G. J. Am. Chem. Soc. 1995, 117, 9473. Heinekey, D. M . ; W J , J. O. Chem. Rev. 1993, 93, 913. Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1992, 32, 789. Brothers, P. J. Progr. Inorg. Chem. 1981, 28, 1. Crabtree, R. H. ; Lavin, M . ; Bonneviot, L. Am. Chem. Soc. 1986,108, 4032. Lee, D.-H.; Patel, B. P.; Clot, E.; Eisenstein, O.; Crabtree, R. H . J. Chem. Soc, Chem. Commun. 1999, 297. 169 References on page 168 Chapter 6 Chapter 6 SUMMARY AND INDICATIONS FOR FURTHER WORK 6.1. General Conclusions Some of the mechanistic features involved in the homogeneous H2-hydrogenation of aldimines and ketimines catalyzed by Rh and Ir precursors [M(COD)(PR3)2]PF6 (R = aryl, 1) have been investigated in this thesis work. While some general trends have been unveiled, a comprehensive picture encompassing a general description of these systems remains still elusive, and recommendations for further work abound. In addition, incorporation of chiral monodentate ligands (Fig. 6.1) in the synthesis of precursors 1 may open these systems to studies on their yet only marginally explored1"4 potential for asymmetric syntheses. Figure 6.1. Examples of chiral monodentate ligands for precursors 1. A new family of Rh-dimers of general formula [Rh2(PR3)4][PF6]2 (R = p-\o\y\, 4b; Ph, 4a) has been discovered in this work, and their synthesis, characterization and reactivity are described; they provide a new class of useful starting materials, as such in non- and weakly coordinating media, or as cz's-[Rh(PR3)2(solv)2]PF6 (R = p-to\y\, 3b; Ph, 3a) in coordinating solvents. Isolation of these (4) species from C H 2 C 1 2 solutions needs to be achieved: fine-tuning of the experimental conditions and the consequent devising of a general synthetic protocol will provide a convenient alternative way of accessing these compounds. Further, selective N M R experiments are necessary to unambiguously establish the hapticity adopted in solution by the bridging arene moieties in 4, while optimization of the ' H - ' H E X S Y N M R parameters (xm) and implementation of the 170 References on page 175 Chapter 6 corresponding ^ P J ' H J - ^ P I ' H } and 3 1 P - ' H E X S Y N M R experiments may provide more conclusive evidence for the fluxionality proposed for the bridging rings in complex 4a (Section 3.3.2). Investigations of the reactivity of these species could be extended to a variety of other small molecules, particularly CO, H 2 S, N 2 0 and NO, and applications of the resulting chemistry are worthwhile considering. As well, a closer investigation of the different behavior observed upon treatment of complexes 1 containing the PJ3z3, Ph 2 PCH 3 , P(/7-C6H4X)3 (X = CI, F) ligands with H 2 is also worth pursuing. A viable synthetic route (possibly involving electrochemical reduction of Rh(I) or Rh(III) precursors) must be developed for obtaining in a reproducible fashion the neutral, dinuclear species Rh 2(PBz 3) 2-PF5 (4c) containing a Rh-Rh bond (Section 3.3.5), so that the reactivity of this metal-metal bond can be investigated. Experimental conditions to achieve complete hydrogenation of the diene moiety of complexes 1 containing electron-withdrawing phosphines in MeOH are needed (Sections 3.2 and 3.3), while the reactivity of 1 toward 1 atm H 2 in the weakly coordinating CH 2 C1 2 remains to be studied. Although quantitative hydrogenation of the COD moiety of Id (PR 3 = Ph 2 PCH 3 ) was not observed upon exposure to 1 atm H 2 in either MeOH or in CH 2 C1 2 , spontaneous formation of crystals was observed in the latter, ^  indicating a different type of reactivity (possibly involving the formation of a dimeric species related to either 4a/4b or 4c); X-ray analysis of the crystals will provide a useful insight. Orrco-metallation of several imine ligands (ArCR=NR', R = H , alkyl, aryl) bearing suitable ortho positions was observed at Rh and Ir centers, and several of the corresponding complexes were isolated and characterized (Sections 4.3 and 4.4). Sequential, selective deuteration at the ortho positions and at the azomethine functionality (CD=N) in the model imine PhCH 2N=CHPh, in conjunction with 1 3 C APT N M R experiments, should discriminate unambiguously on the nature of the 5 9.65 *H N M R resonance observed for the ort/zo-metallated Rh(III)-complex [Rh(H){PhCH2-N=CH(o-C6H4)}(PPh3)2(acetone)]PF6 (5a) in CD 3 OD (Section 4.4.1, and see below). The fluxionality displayed in this solvent by some of the Rh-systems needs more extensive investigation, and collection of data on other NMR-active nuclei present in these systems This observation was not included in the relevant portion of the text (Section 3.2). 171 References on page 175 Chapter 6 1 3 C , l 0 3 Rh), combined with selective one- and two-dimensional N M R experiments, is necessary. Evaluation of kinetic parameters associated with the proposed solvent-exchange should be carried out by extending the V T N M R studies to higher temperature regimes to reach coalescence. Implications of this phenomenon in the catalytic activity of the Rh-based systems will consequently become clearer. Correlations between the nature of the imine, the metal and the relative stability of the resulting ort/zo-metallated complexes in different solvents may be established, possibly by Hammett-type correlation studies. In addition, further studies are required to address and elucidate the chemistry involved in the hydrolytic cleavage observed for several of the imine substrates used, particularly with regard to ascertaining the role of the metal and to unequivocally identifying the source of the requisite H2O (imine or solvent). Isolation and characterization of the consequently formed imine-amine complexes, cz5-[Rh(PR3)2(Ph-CH2N=CHPh)(NH2CH2Ph)]PF6 (R = Ph, 14a; />tolyl, 14b) (Section 4.4.1), were carried out. Syntheses and spectroscopic characterization of the analogous 14 species containing tris-alkyl phosphine could elucidate whether the 5 9.81 (cf. 5 9.65 for 5a) and 6.02 ' H N M R resonances are in fact due to a 71-arene interaction of the o-protons with the phosphine aryl groups (Section 4.4.1). In this respect, detection of a resonance similar to that at § 6.02 (assigned to the amine o-protons in species 14) in the related species [Rh(H){PhCH2/V=CH(o-C6H4)}(PPh3)2(NH2CH2Ph)]PF6 (12a), [Ir(H) {PhCH2-/V=CH(o-C6H4)}(PPh3)2(NH2CH2Ph)]PF6 (12*a) and c/5,;ran5,cw-[Rh(H)2(PPh3)2(NH2CH2-Ph) 2]PF 6 (17a), but not in the bis-amine complex cw-[Rh(PPh3)2(NH2CH2Ph)2]PF6(15a), needs clarification. An alternative rationalization for the observed upfield shift, based on ring-current effects exerted on these o-protons by their proximity to the imine benzylic ring (in species 14 and 12) or to the phenyl groups of the trans phosphines (in 17a), is not excluded. In all cases but one (using PhCH=NPh with [Ir(COD)(PPh3)2]PF6 (l*a)), the catalytic hydrogenating activity of the Ir precursors was inhibited unexpectedly by sequestering of the metal as the orr/20-metallated, neutral Ir(III)-bis(hydrido) complexes represented by the structurally characterized [Ir(H)2{PhCH2A^=C(Ph)(o-C6H4)}(PPh3)2] (22*a) (Section 5.3.2). Conversely, the activity displayed by the corresponding Rh systems, with a fairly attractive scope and range of applicability, renders them still worth 172 References on page 175 Chapter 6 pursuing in terms of extension to future applications as well as, and perhaps mostly, mechanistic investigations. The marked solvent-dependency for catalytic activity is tentatively rationalized in terms of a pronounced kinetic lability of the coordinated MeOH, compared to that of acetone. Screening of the catalytic activity in different solvents could yield more informative data. VT N M R experiments on the stoichiometric systems under H 2 (Section 5.2.1), monitoring the system over longer periods at lower temperatures, could provide the still sought evidence for transient species, which could in turn assist in identifying the H-transfer steps. Conclusively established for benzylphenylamine (PhCH 2NHPh), whereby the complex [Rh{r| 4-(C 6H 5)NHCH 2Ph}-(PPh3) 2]PF 6 (21a) containing an amine moiety coordinated through a 7trarene was isolated and fully characterized (Section 5.2.3), and studied by V T N M R spectroscopy for (PhCH 2 ) 2 NH and for PhCH 2 NHMe (Sections 5.2.1 and 5.2.2), the nature of the interaction between the hydrogenated product and the active site needs to be ascertained for other imine substrates. In this regard, further studies on the reactivity of the appropriate Rh precursors with the corresponding amine ligands are needed. Although not a hydrogenation product, benzylamine, generated by hydrolysis of some of the imines, reacts with the Rh precursors in MeOH under Ar to afford either the bis-amine complex 15a or the related bis(hydrido) 17a (Section 4.4.1). Both 15a and 17a display an unusual solvent-dependency for their solution structure in acetone, where formation of the catalytically inactive [Rh(PPh3) 2{NH 2CH 2(rj 2-C 6H5)}]PF 6 (16a) occurs. Catalyst poisoning by production of this benzylamine ligand under catalytic hydrogenation conditions (i.e. in MeOH), however, does not seem applicable. On the contrary, if a mono-amine-solvento species is postulated in a pre-equilibrium with species 14, formation of benzylamine appears to be of relevance to the course of the reaction. Mechanistic investigations can be integrated with further kinetic analyses of these systems. The kinetic dependences on [Rh]T, [imine] and [H2] under catalytic conditions had been determined previously in this group,1'2 and a value for the second-order rate constant for a slow H2-oxidative addition step provided (at zero-order conditions in imine). Additional studies involving faster techniques (UV-vis, stopped-flow) on the stoichiometric scale, particularly the monitoring of the reaction of isolated 14a with H 2 and evaluation of the associated rate constant, could provide further evidence for the 173 References on page 175 Chapter 6 oxidative addition being the slow step; this would also provide evidence that 14, rather than the bis-imine complex proposed in the previous work,1'2 is the active species under catalytic conditions, at least in the substrate-independent linear region (Section 5.2.1). For some of the elementary steps and of the equilibria identified and presented in the course of this work (e.g. orrTzo-metallation to give 5a and its fluxional behavior in CD 3 OD), the associated kinetic and thermodynamic parameters remain to be determined. 174 References on page 175 Chapter 6 6.2. References (1) Abu-Gnim, C.; James, B. R. Unpublished results. (2) Seneviratne, K. N . ; James, B. R. Unpublished results. (3) Reetz, M . T.; Mehler, G. Angew. Chem., Int. Ed. 2000, 39, 3889. (4) van den Berg, M . ; Minnaard, A. J.; Schudde, E. P.; van Esch, J.; de Vries, A . H. M . ; de Vries, J. G.; Feringa, B. L. J. Am. Chem. Soc. 2000, 122, 11539. 175 References on page 175 [Rh2(PPh3)4][PF6]2 (4a) Appendix A l Experimental Details for [RhzCPPha^HPFgh (4a) II „ « £ 1 ° \% g..§i 3 1 ! f i i 1 &s 1 s a •g E 3 3 S I' ? ¥ i' § = g g g 8 ? 8 g S S a. .a 2 v. -a •§ =. s § * <U S 3 g 3 d 0 <* W I .1 I I l a I 'S 5 a "S •;i -a 5 I I i 1 1 3 s x 8 1 u s II II n II II II 0. rH ^ 8 S S o o o cn Q «: I 2 2 B. •a I 1 176 Appendix A1 [Rh2(PPh3)4][PF6]2 (4a) Table A l . l . Atomic Coordinates and B( eq 0 O) *-* 01 o co •—< CO 8 3 8 3 ^ co (o (o o OJ CO lO CO —i • <© —• co i o co ro CN s "9 o r-H CN CO lO LO CO CTl O •—« CN 3 LD r - 00 c n Q CN CN CN CN CN CN CN CN CO CO CO U O o o U U u o o O 8 3 S CO o 9 CN t-« s 8 a <N CO s s 9 9 S ?! 2 3 a a s s CO t r- CN o cn m O I t CO- to" u D Q 0 O o o o 177 Appendix A1 [Rh2(PPh3)4][PF6]2 (4a) Table A2 .1 . Atomic Coordinates and B e q (contd.) 3 S S S 2 S S 3 2 + s s lO CN C- CO CN CN CN CN CN CN K X 5f EE X x £ co cn 2 f: 3 SCO fH cn co CN .-• r-3 VO S3 5 2 3 CN 3) 3) £o 10 cn O) o r1 to a CN CO lO ID t-X X X X X X X X X X X x X X X X X 178 Appendix A1 [Rh2(PPh3)4][PF6]2 (4a) Table Al.2. Bond Lengths (A) « o o o o o o o « to O) 3 LO CO ro O O O O O o O n co R I 3 2 CO So 6T 1.598 1.597 1.417 1.427 1.419 1.382 1.355 1.388 § 3 3 £ & 0 G S O 3 X a s l i t i s 179 Appendix A1 Table A1.2. Bond Lengths (A) (contd.) [Rh2(PPh3)4][PF6]2 (4a) OO 01 00 00 CO oi 00 o> 00 00 o» d d d d d d d p .—. O CN TJ"<£) GO O CN rr <£> CO C? CN lO g C N T f ^ c O i ^ . ^ r H f ^ r ^ C N C N C N C N e ^ c O C O C Q C O _ o CN iO r- o CN CN <o CO Ol CO oo cs CN CN CN CO CO CO co CO CO U U U O O O <J O O o o o U O O O O CO at OO cn 00 CO CO CI 00 OT 00 Oi CO Ol 00 Ol 00 oo 01 CT) oo o> 00 Ol 00 Ol CO Ol CO Ol CO Oi CO Oi d d d d d d d d d d d d d d d d d d — _ CO Ol CO iO o> co m rt Ol CN CN CN CN CN CO CO CO K rc rc rc rc rc K m EC ffi rc rc rc rc rc oo CO <D CO o 3 8 CD CN tO Oi f* —< CN CN CN CN CO CO CO O O O O O O O U o u <J O O 180 Appendix Al [Rh2(PPh)4][PF6]2 (4a) Table A1.3. Bond Angles (°) « cs .—- TT .—. .—. .—. 10 .—. ,—. m - * i o i o i r a ^ ' i o i o i O ' * » n ^ o ^ ^ t ^ ^ o d R d ^ ^ c o ^ ^ ^ c o o i d d d o i d d c o d q o o o e o t - i - i »f ~H o> ~ j o r - c s e s i - « c s c s c s ^ c s c s c s c s 3 o i O i O > ' - ' < O i - ' r - - H t - t O > - i ( O r * » H r - i i - - « ^ H i - i i - - f i - - i > - H r - < i - 4 « - ' P .—, . . .—. .—. .—. .—. .—. -^^  . CN . , f-H —. CO fcO l ~ —« o ^ ( 0 * O i ~ | t o < O i - - ' c o ^ r c o i o ( 0 ' - - t i O r - t c j » ' - - « * - * < - H ^ - < i - - ' ^ - ' c s c « i rt fe fe fe fc O O O O O O O O O O O O O O ' O O O O O O n .—. ,—. ,—. ,—, .—. , — ^ . — — . ,—. o es co -<r to oo cn o o co co co ^ c^ <r^  ro <^ u u o o o o o o o o o o o o o o o o o o o CO CO* o o cs" cs" CN" CS ro" iO CO CO -— co" co" -* co* Co" to oo" oi oo i i 179.4 to 123.7 117.8 68.7( 75.7( 121.2 cs" 73.2( 119.7 oT 117.5 119.1 120.5 120.1 120.3 119.3 120.5 d CS 00 g ^ , - — . ^ - . , ~ . — , , — , . — , , - - , C N o CS 3 f c f c f c f e O O O O O O O O O O O O O O O O O O O O g « * . — . v ,—. , — . ,—, , .—. .—, ,—, ,—, i—1 to CO io i*~ oi oi 3 f c f c f c f c O O O O O O O O O O O O O O O O O O O O * f e f e f e f e 2 a . o 2 2 o 2 2 o 2 f c o o o f c o o o f c o ii2.6{i; 135.3(i; CA CN* CS CS cs" cs" o I0il ii2.6{i; CO 95.2( 135.3(i; s 74.1( 35.21 CO to 00 es to CO co (O to s 00* co - (O - m io CS to •f <o lO lO O O O u O CJ O U U O O O O o f- 00 ci oi oo oo ^ S S ^ S S S S S S S c S S S S f c f c fcCUfcfcfcfcfcfc rtfcfcfcfcfcfcoOuoouooSooSoofcua.fc _ _ es cs cs cs cs .— cs <v r- co C"". d d ^ ^ ^ ^ ^ C - ^ w c o ^ c o ' c o ' t o ' ^ E i C i w e i o ' CS CS CS CS CS cs cs (-4 q io Ol co co in co co io to (O CO R >d CO to t- CO to _ 3 ^ c s d d ^ ^ u ^ ^ * ^ ^ d t ^ M ^ c o c s < 0 . t j : ? < : 0 o i c o e o ^ W i ^ O t D c o c o i n c O i o w c o O ' - ^ o ^ ' - ' O o i o o i t - -~ ~ . ._ — ^ _ . •- i - I C O O l O O r - i P — — — . ^ . ^ . ^ . ^ . c o co oi *-> ~* « n ^ S c s C S ^ « C S V t O C O i O ( O i O V t O l O ' - « i - H i - i ^ C O C O c S ^ t o v rt fcOUQUOOUOOU O U U U O U O U O fe ST U fe fcfca.fcpL.a.fcp-.feCu E O f c f c f c f c f c f c f c 2 C C C C ^ ^ S C - ^ S i f l S S i j I C ^ j w C C C J i « « « « - - « « 0 0 0 0 0 0 0 2 2 0 2 2 0 ^ . ^ ! * ^ 181 Appendix A1 [Rh2(PPh3)4][PF6]2 (4a) Table A l .3. Bond Angles (°) (contd.) 3- J2. S O- 2 i - 2 . d. ^ *-• 1 - 1 "~" -~l 1 - 1 2 u u 2 U O O O O O O Q O O O O U f-H CN < S3 o £ u o S o o c3 o> —• u u vo to TJ- io io io Tj" m IO io tr CN CN r- C W C N ' ^ O O ' C K ' C ^ C O ' O ' Sw d p e o c n d Q u i Q c n d i - J C N C N - H ^ H C N C N C N C N - H C N - H I a a s & a a S o o o o u o co IO m co co CO CO O O O O O CM IO <£> CO o CN OO N CN CN CN CN CO CO CO CO CO to U U U o o u U u u u U CN CT) —^s LO Is-CN CN CN (3 N « CO CO 3 s o u &, o o O Ou O O <U>-*0—«cOCNr-t—l .OCNrH^]>rO S o o o o o o o o o o G o B r - < e o i o i n r , - o i ' - H r - * c o t o t ~ c n Q CN^  CN^  CN CS CN CN CO CO CO CO CO CO Q CI w w w ^ " CO CO CO C- o-182 Appendix A1 [Rh2(PPh3)4][PF6]2 (4a) Table A l .3. Bond Angles (°) (contd.) 119.9 120.1 120.0 119.5 119.9 120.5 119.4 119.9 108.7 108.7 109.5 109.1 109.1 108.7 108.8 109.5 CO C N CM CM CO CM CM CO CM CD CM o CO CN CO S UO CO lO CO co CO X x X X X X X X X a a a a X £ S 00 C N CM o CO CM CO CO CO in CO <o CO r -co CO co CO CO CO CO o CO CO o> CO o u O o <J u U O o o O O o o CM oo" CM CM CO CM CO TT CO CO £T CO uo to" I u u U O U O U O O G a O 0 o O a 119.9 119.9 120.1 120.0 119.5 119.9 120.5 119.4 119.9 108.7 108.7 109.1 i 109.5 108.7 108.8 CN CN CN WO CN co CN CN CO CN CH CN CN CO CN CO a CO CO CO CD CO B a S a a a a a a a a a a a a CN 00 CN n o CO CN CO CO CO N* CO «o CO co CO CO t-CO CO CO CO CO 8 o co OO CO o o o O o o O o o O o u u O y O o o o u C H CN o 5 o C a o 0 183 Appendix A1 [Rh2(Pp-tolyh)4][PF6]2 (4b) Appendix A2 Experimental Details for [Rh2(Pp-tolyl3)4][PF6]2 (4b) C r y s t a l Data E m p i r i c a l f o r m u l a C r y s t a l H a b i t , c o l o r C r y s t a l s i z e C r y s t a l s y s t e m S p a c e g r o u p Volume Z F o r m u l a w e i g h t D e n s i t y ( c a l c u l a t e d ) A b s o r p t i o n c o e f f i c i e n t F ( 0 0 0 ) C.,H„-F,P,Rh 4 5 4 8 6 3 I r r e g u l a r p l a t e , Red 0 . 2 5 x 0 . 2 0 x 0 . 2 0 mm T r i c l i n i c P I a - 1 3 . 2 4 3 4 ( 1 ) A b = 1 4 . 0 9 1 1 ( 2 ) A C - 1 4 . 2 6 6 4 ( 2 ) A 2 1 6 1 . 9 3 ( 5 ) A 3 2 8 9 8 . 6 5 1 . 3 8 0 Mg/m3 0 . 5 6 2 mm" 9 2 4 a • 1 0 9 . 7 9 6 ( 1 ) 0 - 1 1 1 . 9 7 4 ( 1 ) C 7 - 1 0 1 . 2 6 8 ( 1 ) ' Data C o l l e c t i o n D i f f r a c t o m e t e r W a v e l e n g t h T e m p e r a t u r e 6 r a n g e f o r d a t a c o l l e c t i o n I n d e x r a n g e s R e f l e c t i o n s c o l l e c t e d I n d e p e n d e n t r e f l e c t i o n s Siemens SMART P l a t f o r m CCD 0.71073 A 173(2) K 1.65 t o 25.03° -15 i h s 14, -16 s k x 15, 0 % I % 16 13273 7420 (R i n t 0 . 0 1 8 5 ) S o l u t i o n a n d R e f i n e m e n t S y s t e m u s e d S o l u t i o n R e f i n e m e n t method W e i g h t i n g scheme A b s o r p t i o n c o r r e c t i o n Max. a n d m i n . t r a n s m i s s i o n E x t i n c t i o n c o e f f i c i e n t D a t a / r e s t r a i n t s / p a r a m e t e r s R i n d i c e s ( I > 2 c ( I ) - 6729) R i n d i c e s ( a l l d a t a ) 2 G o o d n e s s - o f - f i t on F L a r g e s t d i f f . p e a k a n d h o l e SHELXTL-V5.0 D i r e c t methods 2 F u l l - m a t r i x l e a s t - s q u a r e s o n F w - [ f f 2 ( F 2 ) + ( A P ) 2 + ( B P ) ] ~ 1 , w h e r e P -2 2° (Fo +2Fc ) ) / 3 , A = 0.0409, a n d B = 1.9049 SADABS ( S h e l d r i c k , 1996) 1.000 a n d 0.929 0.0002(2) 7420 / 84 / 535 RI - 0.0292, W R 2 » 0.0721 RI • 0.0333, wR2 - 0.0740 1.033 0.445 and -0.437 eA"3 184 Appendix A2 [Rh2(Pp-tolyl3)4][PF6]2 (4b) Table A2.1. Atomic Coordinates and B, i n i n i n i n 1/1 00 CO CO CO CO CO CO CO CD CD n M fi r*i n O O O O O t- r- ri «j" ro i n co vo o en CJ M O *J3 O M M H H n 0*1 o co rn i f co o cn m n r - ri T co H H M f l M ID (N H r l o * H ID 1/1 CO i n ^ r - m o cn CD M T (N U) U l IN M CO CN cn r- T u> I N o - f i n i o U, In (n I H H H H H (H i I ri H H rH , u i i f i i n i r t i n w i f l i r i m O ) N ( N ( N I N I N l N ( 0 ( 0 H r l H r i H r i H C O C O I O O O O O O O O O H r o * i ' i o o ^ m i o u i r o * o m i n c n c N m c h m c o * © n u i o i © H ri ri H H Hi ri ri o ^ r * r a ^ r o m w v * D ^ ^ i ^ c n r ^ c n r o i n r o r - i n r ^ M \ ^ c o r - f o ^ r ^ ^ r i c N ^ ^ < n v t ^ r o w r - t H c n H r ^ i N C A r H t H f o i ^ o s c o u j i n y > c n o c n r i o c o O f O i n < ^ i n o ^ u i u > m r o ™ ri I rH CN fN CN I < f H ri IN ri H ri ri rinnnninin^yl^Utin^in^UiriHHHNnHCNCNnHr-lriHfNrN rivo^voujinojaor^uiromuninrir^cncnririvoTO ^ ^ r ^ r ^ < N v » r i ^ c » « r c o L n o u > o u ) c n c h i n c n c n i ^ < D ^ o o T f r ^ v o o c o c n r s m M f o i n r i r i ^ o ^ o > ^ i / , \ o < n i n i n u i i n i / , * o j c o t T > 0 ( f t c D H v o i o v o i j ) i i ) > D w ^ ^ r - o o r N f M ^ t p r ^ m c n t n r i M o r s f n c n r i r ^ r ^ o c o r ^ rimfomr-vcnyjLnnooro^uirir^ujor^cn o i i n ^ c o c n r i M H ^ ^ c D M r ^ o s r - v ^ r ^ c o u i r ^ r ^ ri l ri ri I ri ri H H H H N M M N W M M ^ L n W ^ V ^ N m i n i N r t H r i M r l C O V 185 Appendix A2 [Rh2(Pp-tolyh)4][PF6]2 Table A2.2. Bond Lengths (A) and Angles (°) <*i n * n H — i — n — rs — r* " rs n n v r» M ft M n * , « w ^ ^ r t n M M r t ? n N f l n n m M n N - \o — o — <-\ •— in — ww^.-— u - v u w v ai o _\ •——~- — _ - _ • . _ . - _ _ . _ , . . _ ^ „ ^ ^ „ - _ , l _ , ^ L , ^ . _ i i j . _ _ ! ? £ ' N : ^ r M £ M _ * : ^ H H O H W O O M ^ m ^ 0 ^ H r t m 0 r o l H H rH t H H H H r S r H r i H H H r t H H H H r t H H H H H H H H i H H H H H r* H r l o u u u u u u u O U U U ~ < J O U U U » I 0 . O . U O U U O U E J U U U U U U 6 U 1 ^ I fi€*> m MM MM'-'--"-' 1 ' - '- '-"— OI CU P< OI & Oi Oi U U O U U U O U O U U U O O U U O O U U U O U O U U U U U U U U U U U O U * C u U 4 l i , ( » * U , ( i . t i , ( i , & i U , ( i , f c [ i i t — -— f N r j — I N -o H ( - . - — • » j > a > - - ' " — — • •—• •— •—--- - - - CA co in - ,. _ _ _ _ _ _ _ _ _ _ - ) M r t « _ i m r t > f o m o » i f l r i i o f f l m m i i i i / i h a ) r i i o O M h V f i h n i O N O \ i i o i n m _ ) f f l ^r-r--^r~-o\_>vo-majrsOr^coHOrtOw™tni^ O r H r H r ^ w r ~ H ™ u > H ( _ > r ~ H H N r s r > i r 4 r s r s r s ™ o o H r H r s r 4 < N r s H tHiH H H ^ H H H H r 4 < H H H r l r ^ H f S r i r - 1 f H r - 4 < H < H r - t t H H r H < H r - l r - l f H H H 1C fN M H H » <r U > l £ i ( K [ a i ( i i ( i 4 ( i < ( - i [ i . WW W WW _—.^(*JO — , « ) r i O - - . « « M « m O l h O.— .<NU"IS*r-.-.-l«NrH — — — O l H H i N H r t n r i m M H r i N M M f N n N f O m r t M r N n v i 1 H r-4 rH .H r-i <J» — — — — — — — — D M - _ « _ - _ - » _ - — -_- _ - > _ . . _ . _ ^ , _ _ . _ — _ „ _ _ . , v ~ r o r - ~ y > ~ ^ ~ r H U U U U A U U U ~ ~ ^ U P j U U U U O « U U U U O * U U U i n { s r < i . £j_l — ~ - j q — j C i 5 ( J — i O U « i i i i i i i i i i — • c d W O U P i U K K ' 0t — , i , « m — „ „ „ ^ _ _ _ . r t „ m — - m ( _ , f _ , C_i U * ( » 4 f - , t _ . t - . — - — — -.—. i O r i M i n i f t h a i i j i — — — M i N ' f i n w m m H r . n u j - i D i r t o i i - . - . rs <N_ r-* rs cs rstNrsrsrN<»irnrnrororor*i'«* 1 —..—..—. .—. -—. rn ro m ro ro " " ' " " ----------- ' f o f o f i f o r o r o c i • I A m u> —* ( U U U U U U U U - U C J ( J U U U U C » O t O . O . O O U U U U U O _ ) U U U U U U - OtPi&PtOiACIiOi ' Oi Oi Oi Oi Oi Pi 0< U U U O U U U U U O U U U U U U U U U U O O O O O U U O O U U O U U U U f c ^ U , b i & < C i H f c f c f c U * U i b . & i b * ( i , ) is a) . to . o) ( irsrOfOfsrsnror . ^ ^ 0 ' f H ^ ^ ^ ^ H ^ ^ ^ O - N _ o ^ t o m N ( o « l » » l O ^ M O l ^ a ) ( ^ l » _ ( l l l ^ l a ) f f l I I N f l H r l N H r i r t H I r-4 H r-4 r-t H i • n u i f U ' O r t n i n u i i ( H H r H H H H H r H H i in Ul i H H H * — l/> f*l VO —' '—' WWClWrSWHWlAlTi I H H H ~ ^ ^ H H — . «^.Or4inujeom^.rsfO-iy)0\i-<(N\or-o\o — - - -S S 5 5 a O U U O U U U U O U U U O O O i U O U U O U U U C . U U O i O . O i O i O i O i Oi U CJ o u H H u> rs I ro r-t vo n H \o (s i O C J O i U U U U U U U U O i U — ^ - H H « <N I IO Ol _ H r l . . n u> o A ( i if r- Ci N ( - fS (S -I — — . 1 O U> f PvoaorHrsHOoocor~^H^ M a)H<Nr^_>f^focnHroo^voo» . r - n < l ) ^ ^ / ^ r N r t ^ ^ o O f l ) - 0 ^ ( l l o a ) H p | « l | I ) l ( O H ^ ^ l n > ^ < ^ l B H r • < o o ) ^ a l ( l ^ tt W W t . IN m m -. A » I N n o o H — -i r i O H H M r l N I I K - — — — ft f D.UUU ^ — — — — ^ r — — U O U U U - — t . . . . U U U U U O K K O U ' ' ' < ' U V H H H H — — .—, ,—. .—. ^ H (N Ul M D ^ ( - _ - V H r ( H n r t 1 l " l l i n ( 0 ( r i H H r ( H r t ( N M I „ „ ^_ _ S S S S f c f t U o U U U U t J U U U U U U 0 i P * U U U U ( - l U U U U U 0 i O i 0 i 0 i Q . 0 i • i/i <Ji O rs n v W WW WW WW H rt H - H ^ . « H - - H - - H WWWrsWi-t^WulWIW'*''* W , , , | — , , — , I •— .H »- «> H --" CO 5 5 5 I _ ! H S A ^ $ H H 2 H M . P.O.UUUU I t t i W i * i W iWW iWW — ' < i i « > H P I N f i - r l . r i N n H N n H H - t - i N . I O H O i O i f l . P i U a i U U D i U U D i U . U U U U U . U 186 Appendix Rh2(PBz3)2-PF5 (4c) Appendix A3 Experimental Details for Rh 2 (PBz 3 )2 'PF 5 (4c) 5 S § I 3 o X 1 II II H II fe ti Xl u fx » 8 8 i 5 o I I i j i I •I a 187 Appendix A3 Rh2(PBz3)rPF5 (4c) Table A3.1. Atomic Coordinates and B eq PQ <N (O UJ OO t-pg J*J OO « CN to to tO to to cn o CN 1/5 CN o »2! S IS u> 00 d 8 S « « S S fS f- U? trt Oi O *P tN m CO CN r-. O m C N ^ O C O C N t O ^ i c j c n ^ c N A o S c n c 4 ^ < d e N F - c 4 c N t - « r - t - t o i o - ^ i o - ^ t o rt" S-i l l S CO co $ r » 0 0 A ^ C N O » C N U 3 O O O O C 0 > - 4 i - i i - t < N i - l CN CN t-< Q Q B A n n w w w 00 to s CO .-I CM iM S 3 CN CN «£> 3 a to 05 s jo »o, CNT to W OS 3 3 CO CN? to" ST 00 CN r - © ui 1 1 S GO 1 8 d d d d d d d U* 00 0.7147 0.6498 0.5646 CO cn s d 0.4695 0.4751 0.4551 p p i ol ST 9 8 t-l CN 2-io 1752 142( 133( 1741 1399 i § d d d o d d d d d C - OO iS " i f CA o o -o CN O U o O O O O 188 Appendix A3 Rh2(PBz3)2.PF5 (4c) Table A3.1. Atomic Coordinates and B c q (contd.) 189 Appendix A3 Rh2(PBz3)2-PF5 (4c) Table A3.2. Bond Lengths (A) S 8 8 8 S © w © a o o C N C O 00 u i r - O i a * ^ « w g -« ^ <o C O Q —" T ^ * W " ^ 8 8 8 8 8 8 8 8 ^ to oo § — ^ - - s ^ . * — . k O 00 © 3 Q O O U O O O U 8 CN* S* «o* < o c o t * - « o o o » o » o » cn, S> ^ ^ M c« es c* s .—* (O —< O i ^ *—' ^ ^ ^-H CN CN CN CN 5 -s g S S s r s r s r s r u o o o o o o i O C O ^ C O < O l ~ ^ 0 0 0 0 C T > O > C D O ^ v ^ 1 1 1 I u 1 1 n i ii u C I CN CN CN •-« a c O O O f e f a W O O O O S 8 ^H" -^T ,—, , ,—, .—. -—. ,—- <G I*, eft • j i ' ^ ' ^ ' ^ ' t - * CN CN *-> 2- S S- C w ^ B a g a f c f e f e H r o o o w o o o 190 Appendix A3 Rh2(PBz3)2'PF5 (4c) Table A3.3. Bond Angles (°) ^ a ^ s a R •J rH Ol 00 O _^ O CN CN r-< -H C N q t , Ji, J _, J s o u u o o O o O O u w o o to O r- CM to P ^ » » .—* —. — .—. l_> co co o « u u o o o o o u o o o o o <£> j o ^ ^ — t o <_5 -<r to to r - r -S .—, —• /—. ,—, ,—, in ,_, _Q __ C_ Q M f ^ ^ r t ^ i O ^ r ^ t o ^ C N ^ S c s 6 j j j - C d . ^ C " ^ - ^ ^ S~ GO" 5' °J « d " » CN CO v w t o CN oj oo M ^ ^ a £ * 5 _ L _ _ , M cs ^ ^ ^ to w S" 1 5 5 3 ' E E E S S S 3 _ S _ § 2 ' £ S ^ ~ ^ ^ ' _ ' 2 ' CN I r-l CN CN CN - 0 L , O O _ O _ O _ O O O O O O a £ £ £ £ £ £ £ £ £ £ £ £ £ £ — — — — — — — — — -191 Appendix A3 Rh2(PBz3)2>PF5 Table A3.3. Bond Angles (°) (contd.) angle 109.0 108.6 131.1 120.2 119.6 122.0 119.6 121.0 130.4 119.7 106.5 109.2 108.1 CN t-118.6 120.4 120.9 121.2 119.8 atom CN a CN w H(3) J2-X H(4) JO EE tO JC H(6) r -a c -X 2. K a H(15) H(16) a H(18) H(19) & a CN a atom C(l) C(l) C(3) C(3) C(4) C(5) o (9)0 C(7) u C(8) ST o C(15) to* O o (81)0 (61)0 C(20) C(21) atom ST C(2) 1 «r Q C(3) i (9)0 to" O i co o ft. p(D C(16) a (81)0 (61)0 C(20) CN O C(20) angle 108.8 107.9 108.0 119.3 130.9 120.9 119.6 129.4 120.3 119.0 107.1 CO OO O 108.9 108.0 119.6 121.3 119.3 118.3 119.5 atom a a H(2) H{3) -? K B B H(6) CO X H(7) So ES {6)H H(16) H(16) H(17) co a 8T a c? CN a CN a atom C(l) C U co O C(4) *y U iO U C(6) C(6) r -O to U io U iO U r - ' O So" O (61)0 C(20) CN O atom P(l) CN" o C(2) i C(5) O i C(7) CN' U ST a ST S" o (91)0 o ''A o oV O CD O 192 Appendix [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) Appendix A4 Experimental Details for [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) o s I O O 51 O ) °? 10 oi °6 II II II II s s § s K-6 51 O (4 193 Appendix A4 [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) Table A4.1. Atomic Coordinates and B eq S S O O r H . H S 3 ID to to iO to to CI8C 1 1845 2787 2565 1422 o d d d d d d d d C N c O T f i O t O t — OOCTIO CN CO IO to CO 8 8 CN 3 lO CN CN CN CN CN CN CN CN CO CO CO CO U o u u o u u O o u O r H f* CN i-- ^ CN o -o CN ST CO "J1 to" CO* CN" CN •-5 r H •-* CN CN CN CN 1-1 r H CN CN CN to o O rt co oo OO cO 2 S S 8 ~H r— - H ro 00 CO IO CN s d d d d lO IO to to O r i r H 194 Appendix A4 [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) Table A4.1. Atomic Coordinates and B e q (contd.) cn lO cs lO u . lO CO oo to t~ -3 to ID «S cs* £T £T oT of O CO cs" CO cf to o> oi CO CM oi CO CO 0.0872(4) lO 116(4) u_ OO to co_ 0.0872(4) 0.050/ 116(4) *r lO ST 0.0872(4) 0.050/ o d Ol O cs d Ol d d CO d Ot d to 00 o* oT co" CO co CO V u O O U u 8 to OO t-to to o to ira Si CO "I* 1606 7607 o i oi oi oi 5 oi r— 00 CS g g CN 2494 2470 1961 d d d d d d d CO «_> r-S9 cO lO o r-CO iO UO lO CO o» to d o d o d d © o d m CO 00 cs o CO eO o CO o cO d d d d d d d 00 oT CO 5f X a K K 55* 195 Appendix A4 [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) Table A4.1. Atomic Coordinates and B e q (contd.) C c O C n O ^ C N C O - V i O l O r - c d c O O l Z x x x x x x x x x x x x x CN + 8 S 8 2 + 3 5 196 Appendix A4 [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) Table A4.2. Bond Lengths (A) 3 J _ , t , S _ . S ° , S _ . ^ ' M ' « ro co M -r uo u. i g „ ; _ ; _ ; , _ ; „ ; , _ ; ^ C ro in CO ir m h co co J_- J2, 3. 3 O O O O O O U g ro ro co to J J_ v S U O U O O O O S 2 _^ ^ ^ 2 ro -«r ro co uo ^ g ro ro ro ro ro TT TT rtOOOOOUO C O l - ^ C O i O ^ O C O ' g c N r O c O e O r o - < r - | " riUOUOOOO . «~ co _o io to" co to r ^ r ^ c o r ^ f ^ o o P ^ ^ 01 S" M ^ » M a 5 _f _? T*' tc O) oo o ^ ^ ^ o ^ ^ S T ^ ' t - ^ ' ^ So ie> i o r— C"- ccT i J O O c O C N e N O i O l C O C N C T i C O C Q O O T O m c o c N c o c o c o i o i o i O M c o c o c o e o c o c O M ^ C N C M H M M H ^ r ^ ^ M M . ^ . ^ ^ ^ ^ M ^ M r ^ r ^ ^ ^ f ^ 5 M w _. C S 0 1 co S , " ! 2 . - _ _ _ C . _ w ! , ! - 5 _ ^ ! i rt S T o u o u u T u T f e o o o o o o o o o o o o o o o o c - — — - « .—. —. .—. .—. .—. . — . ^ - . o c o t r t o o o c N i o t o o o Q ^ ^ r - C N c s r o r o r O £ ^ , ^ C H T f r - - c o - - ' - > - - ' - - " -^i CN CN CN CN CN « J i a fc a. ST fc fc o o o o o o o o o u u o o o o o . g c s C N « _ 3 C O » 0 » O y 3 C S « < 0 B SS _r- E_ _3 • — . ^ ^ C N ^ S ' C N ' C ^ ^ C ^ ^ C N ^ ^ O ^ C O * flfcOOOOfefcfeOOOOOOOOOOOOOOOO G __ __• "T" '—- -—• -~~ •—• • — . - — . . — . • - . • c o 10 t- oi H S io P O _1- C- w ~* C O c O ^ C O ^ r - i C O l O r - O l - H — ^-i CN CN CN CN rt ^3 £ fc fc fc fc fc fc O O O O O O O O U O O O U O O O 197 Appendix A4 [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) Table A4.2. Bond Lengths (A) (contd.) cn 3 (4 a ° 2 a S 8 § 0 0 o — o <0 - D - O I i 3. s, 3 a s K < m m S o u o 8 8 S a s s C ,—» .—. .—. .—. O CS T OO O CN CO OO Q CN tp op O CN T 1 I O " J R .—. .—. .—. ^ o CN i o r-- o c^ v r - o t c N ^ l o o o c h c n ' - i c - t c N 3" "2 * £ 0 0 0 0 0 0 0 0 o o o o o o o o o o o o o o o S S 3 s p —. ^ m ,H o »o r-- o> co to i-- Oi <—•**> io t- en to io S -H co io r- cn »-< -H — « >— o* C ! . £ i . J i £ ! . ' 2 . 2 . 2 . S J 3 - 2 . S - i rt X X X X X K X X X X X X X X X X X X X X « X X E ^ ^ ^ ^ ^ M t i o M ^ ' S ' i o W O CO m 00 OO 0> — —" CN -»r 0 •—i CN (o eft •-. " £ i J ^ £ i f J , f 2 - w 2 ' G - G . G . 2 ! - 2 . ^ - 2 ! . rtS'oOOOOO O O O O O O O O O O O O O O O O 198 Appendix A4 [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) Table A4.3. Bond Angles (°) CM CO CN ?T tN CN fo to IO 5 - IO angle 89.1( CM <£) O 117.1 103.4 103.0 117.5 105.8 102.8 90.2(: IO o> oi oo oi o> oo oo 135.9 CO 118.1' 120.7i 120.7i 118.41 119.31 119.41 atom 0(1) 0(1) 0(2) FT" U C(7) CO o O O O F(3) ST F(3) F(5) F(4) F(6) sr C(37) CN o C(6) C(4) C(6) • (8)0 c-T O C(10) atom -S £ ST cu P(l) P(2) c-T cu c 7 aT ST ST P(3) P(3) to" sr. sr P(3) CO CL O C(l) C(l) C(3) C(5) C(7) C(7) (6)0 atom ST ST o o O S' C(19) S3 ST uT ST sr s sr u . sr ST C(2) C(2) <3 ST (8)0 C(8) 3 171.95(4) 101.9(1) 85.2(1) 110.8(2) 116.6(2) 104.5(2) 112.3(2) 113.0(2) 104.1(2) 90.1(2) 179.3(2) 89.5(2) 90.2(2) 89.6(2) 90.3(2) 90.3(2) 90.8(2) 136.2(3) 123.2(4) 120.7(5) 119.1(5) 120.7(5) 122.3(4) 121.0(5) atom P(2) 0(2) 0(2) O C(13) C(13) C(19) C(31) C tN ST ST to sr F(4) F(6) sr sr F(6) u to O C(3) iO O •o O C(12) ST O atom 0 . a. a. a. a. • P(2) CL CL P(3) Cu CL CL CL CL O O o O O O O atom Cu o C(19) o . tL Lb a. o O o a. O 199 Appendix A4 [Ir(H)2(PPh3)2(acetone)2]PF6 (2*a) Table A 4 . 3 . Bond Angles (°) (contd.) H O - — • ^ to Oi Ot ^ & Ot Oi O Ol O* C3 Ot ^ O Ch a% tG <B CO S r - r ~ I ^ O ^ r H C N C N r H r ^ C ^ r H r H C > t r H C M C N CN > r H r - . r H . - i r H , _ i GO CO rH rH rn r - . — . r H r - r - l r H r H , H r H r - « r H r H r H . H r H . « H r H , H p . — .—. .—. .—. .—. .— » ,—, .—. .—. o *H es co m S * f ^ o o cn o *— CN g C N i e ^ J C N C N C O ^ ' O U J . ^ c O C ^ r H r H r - . ^ r H r ^ r ^ r H r - . H C ^ C N C N r i j X X > E X X E > n X X X X . E X X X X X X X X E X X X c .—, ^ c ? ^ CN" ^ in S" c^ « « i i i ^ O O O O U U U O O O O O O O U O O O U O 3 0 , 0 , 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 CN t O O t--; 00 OCT) IO rH CN rH IO O CN & o ~ oi o> o a* ao ci oi & o & r* r H C N C N > - > ' H C N - - l - - i e N r - . C N C N C N C N c N c O ' t f i o t o r — o o c n o g _ rH rH CN CO_ "Tj" IO CO r- 00 Ol rH ^ - W ^ — ' 3 Z _ _ _ . O -H CN lO ( O r ~ C O O ^ « ^ l O < O 0 0 O > » H rH „ rH rH t-H r-i -HCN O O U O O O O O O O O O O O O O O O O e OH PH S rH rH CN CO rH O C N t O ^ t O O O O l C N - ^ i O i O CO CO CO CO CO CO CO " 3, 5, O O O O O O O O O O O O O o u o o o u o O O E c N T r c o t o o o o ^ c N i f t o p Q _ _| rH rH rH CN CN CN CN CN CO g r H C O C O U O t - W O l r H C O W r t ^ O r H ^ C O ^ § O O O O O U U O O O U O O O O U O U J ^ S S I H ^ S ^ C N ' S S S g Z Z r-o rH rH CN CN CNCNCOCNCN CN CO tO CO £T_ C*^  ^  ^ 3_ o o o o o u o o o o o o o o o u o u o o o p o c N c o ^ t o T O e n o c N T f - i o i o c o c s r H g ™ _ H r H W r H r H r H e N C N C N C N C N C N C O C 0 C O CO, CO_ CO_ ^ ^  % O O O O U O O O O O O O U O O O O O O O O O O 3 O O f c O O O t C o O O O ^ O O O O O O o 200 Appendix A4 [Ir(H)2(PPh3)2(acetone)2]PF6 (2*, Table A4.3. Bond Angles (°) (contd.) _0> Ol CN to rO Ol OO M c o d d o i o S - ^ " . oi < -< < CQ CQ CQ 10 in 10 Tf *r TP CJ CJ CJ cj CJ CJ CJ to r- 00 Oi o Ol co iO to 00 S Oi Ol Ol i-> Ol CM CN Ol OJ Ol Ol CO co CO CO CO tO CO CO CO T U CJ CJ CJ CJ CJ CJ CJ CJ O CJ o c j CJ O U c j u U CJ CJ u u U CN CO Tf r- co r— t- to o o O) o o Ol CN to O CO CO CO CO CO CO eO rr CJ c j u U O CJ c j c j c j CJ CJ CJ x c j CJ X CJ CJ X U O X CJ CJ a > « O O O r - " t f o o o i O t o c N r ~ t 0 ^ ^ c O r t ^ i f t M W C O ^ « c o C N ^ d a i c ^ c i c o o o d o i o c o p c o C C N ^ r t ^ ^ ^ ' - i ^ C N f - l C N O O O ' - ^ O ^ ^ ' ^ O O O O ' - i CJ o> Cl o> CM Ol Ol V CO CO co CJ CJ CJ CJ CJ CJ CJ O CJ CJ r- s s o CO 3 to t- CO to r~ O Ol o o Ol CO CO CO to CO CO CO to ro CO CO CO T CJ O cj CJ CJ t j O U c j CJ CJ O X X CJ X X CJ X X CJ X X O 201 Appendix [Ir(H)(PPh})2{BzN=CH(o-C6H4)}(acetone)]PF6(5*a) Appendix A5 Experimental Details for [Ir(H)(PPh3)2{BzA^=CH(o-C6H4)}(acetone)]PF6 (5*a) •a c < s s S _ s ci 11 c p on 7309 -d 37530 : 10205 i-polariz tion factors: TotaJ: Unique Lorent: Absorp (trans. •VI" i 1 $ % 7 | S g I _ I S _ w „ S3 a a a I a 1 i 1 1 { j * a; « a rt T 3 "0 d o I ^ o CJ -s a f F, I>3 !S a 1 tc 3 •a persioi A ¥ s s C o •8 u c A c ci 0 "8 £ .5 a E a 5 .2 8 n g 5 c tc s i •— o w 1 a 8 •a 8? c .2 1 •if E 3 s 6 o > s -o •a C/l O 3 •a E s o a 6 d CC 2 o o s "5 .s < cd O V. o 12 «2 o ^ "3 ^ | 3 S 3 j >o ui a ^ - N <" tl II II II CJ CJ oo Q <: I S3 8 S ue o. O n) S & B 5 •g & o SI i 6 « 202 Appendix A 5 [Ir(H)(PPhi)2{BzN=CH(o-C6H4)}(acetone)]PF6(5*a) Table A5.1. Atomic Coordinates and B e q ^ co n 7989: J OO CO r - t o a o O t T CN ii i I d o c a d d d d c S _ u cj o r S CO d r-t CM T -—- -—-O CJ» OQ 00 Ol CO o C-203 Appendix A5 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(acetone)]PF6(5*a) Table A5.1. Atomic Coordinates and B e q (contd.) CN CN CN IO tO 3 v - H ^ C O « ( O t ^ ^ ^ ^ C N C N C N C O - H T r t O r H l ^ r ^ C Q c N C N C N O M < N ^ ^ ^ ^ T r T r e > i M e o c N e ^ f ^ > - - l - - « ( O C 7 i C O O C N C N C N L O C O O C N O i O c o v t o ^ r - ^ c ^ r o c o c N Q r H o o i O ' O o ^ T T C O C N O - — ' O O O O T r i O k O - ^ C N . — i 9 a s S ^ S r H O o P S c Q ^ C ^ S ^ t o S o i O 0 * 5 * i 0 t > - i / l i / 5 e o i 0 0 ) r — C N O t O o O O ^ c q r ^ t - r ^ t O i ^ t ^ i ^ Q O c T i c S o f i c n 0) , — . ^ C O I ^ O D C ^ ( ^ C 7 > C O t ^ » ^ C n ^ ^ C T > ^ N N r H r H r - . 0 r-< - •—- -—- — w - «—- -—- -—- ,—i i—i to °o co f- »o iO w •—• r - r i c o t O O r H C N O ' Q " * — - CO CO t - f - CO cn T r c O C ^ o q C N ^ C N c O r H t O C N M CN CN CN H rH i CN CN CN * «—« CN CN CN CN C> H CN CN rH CN •—' CO •—- C7* CQ r—« CO >—' § s t— t o CO r- o> t o i™* CN 00 cn o CN CO •n* >o t o 00 cn o rH CN CO , v to CO CO T TJ- lO IO rH CN CO t o r-O o O O O O U O U o O O U O O EG EC S S 204 Appendix A5 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(acetone)]PF6(5*a) Table A5.1. Atomic Coordinates and B e q (contd.) 8 S s § § o o o o o o d o o o o o 0 §, s rt X X + 205 Appendix A5 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(acetone)]PF6 (5*a) Table A5.2. Bond Lengths (A) $ <o" (O^  IO* t~- to lO* t-^  S* l/? i - ^ to" 5 <xf to "X in" r - c^T to cn ot « 10 s ^ M r ^ o o i c o a o > r - - r ^ o ) o o e p m c o c O T r r o c o c o c o c o c o c o c o c o CO OJ CO CO CO CO co cO -r rp m m »o o cj CJ CJ CJ CJ u CJ cj CJ U CJ o cs to CO o CM t o CO o cs CO CO CO CO CO •3" T lO LO U J J J J CJ CJ CJ CJ CJ CJ CJ O l O t O t O t o u O l — l O l O t O l O i O t — 5 m c ^ o C T ^ i ^ n N C 3 f t o t ) 5 ' J ; o o i i ^ c i c o t - - c 7 i o o o o c j > o o o o i/> CO co co co co co co co co co CO cs r— oo o CO to oi O cs CO CO CO CO CO -r lO LO CJ CJ O CJ CJ CJ O CJ CJ CJ O CJ o cO o Ol cs CO lO 00 O) cO co cO cO CO CO lO o CJ u o o CJ CJ O CJ U CJ CJ o ^, C Cs" CO* IO w CO* to to Ol 2 "0" r- co cs CS CO CS Ol cs c-cs Ol cs CJ Pu U, tu, CJ o CJ CJ CJ O O CJ CJ CJ CJ CJ o CJ CJ CJ ! CO CO CO CO cs o cs CS cs S CO oo o> 00 iO tO *# to" O f* co t o Ol o cs IO to 00 o cs CO •<r cs to h - CS CO CS cs cs cs cs 0. O CJ CJ O O [K U* Ch CJ CJ CJ CJ CJ CJ CJ CJ CJ CJ O CJ O CJ CJ C S C S C 0 C O C 0 ' - , ' - < O ) ' « J , « D 0 > ' - ' CS iO 00 Ol ~H cs IO cs cs fl M J ,i! a a . c u c u i i « e u ^ C J U C J U C j O CJ U O CJ CJ O O U 206 Appendix A5 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(acetone)]PF6(5*a) Table A5.2. Bond Lengths (A) (contd.) o P CO 3 o S 8 Ol Q o> O d .-1 CO r- 01 •-< CO CO CO CO m co o CO lO O CN CN CN CN CO CO CO CO LO VO u o o <_> o o O U U U u O O O O O U O o U O E 5f g « o CN CO r - p CN IO o CN •>* t— cn f-H *o cn _ o CN CN CN CN CN CO CO CO CO td u U O O O o u O U u u u O O o u U U 207 Appendix A5 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(acetone)]PF6(5*a) Table A5.3. Bond Angles (°) t II i iliSSIiifSIS! l i l S I I i i i & l I I 1 I ! 1 I I I § § 111 s i § § § § I § i § § § § i § § § § § i § § § i § § i § i § i § i I & I § I I I | | S | § | 3 § | § S I § § S | | 1 co Jo* *0 CO o* io CN —• oi d — CN o S S § 2. §, £1 rt o u o o o o 117.8(3) 118.9(3) 120.7(4) 120.4(4) 119.7(3) 118.6(3) C(19) C(23) C(21) C(23) I I 1 I C(20) C(22) I I g § I 1 P(l) C(25) TT to" ^T" ^ ^r" ^ rH M oi cri co oi d •H rH CN to n *5> co 5 O O O U o f O <£> CO C? CO co co cO "f U U U U U PT —* f^ " ST CO CN CO CO CO U CU o u u r- Oi CO — — *- CN C-J CN CN . — C - T —. ro* C+ to ro ^  ~T *a ~. ™. ™. ^. m to c* * vo ci °. °. ~. ol oi ™ <a ai t*: o o 5 ^ S ^ S O T ^ 0 0 ^ 0 0 5 ? o o ^ o t - c ^ r o c N C N - H c ^ c N TO CTj OO C^  C^  t1^ H rH —H rH H^ O* Ol Ol H^ Cift H^ CO rH p4 r, rH B « « r t r S ^ ? ' ? O c T « « „ r t ^ r t ^ „ „ u 5 ' r t « « ^ , ^ O Zj, O w w w w £i- J2- ^  ^ ^ f t O ' O C O l O ^ l O C O ' H O O C N I O ' r t D S o u 2 ?- u o o u o u u f c u T u r i . C ' u r u r i ^ o o u 1 1 g g 1 g g g g 1 1 g 1 1 I g g g § f g § § ? § § £ 5 £ g g g g I 1 1 g § 5 angle 169.21(3) IISIIIIIII 90.0(2) 179.3(2) 90.0(2) 90.5(2) 89.8(2) 89.7(2) 89.5(2) I 112.7(2) 121.0(3) 121.1(3) 119.5(4) I g N(l) 0(1) C(l) C(l) C(18) C(30) C(30) C(36) C(48) C(48) g g g g g g g g I I 1 I I f f f f g g g g g g P(3) P(3) P(3) g g g g g 1 1 1 C(2) C(4) I g g g g | g f § § § § g g g g g g g g I & I I § 208 Appendix A5 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(acetone)]PF6(5-ka) Table A5.3. Bond Angles (°) (contd.) s s g o t"3 IO IO IO 1- 1^  <n o CM - o cj cj cj o o u o o o o o u O o CJ cj CJ CJ CJ CJ to" ST ST o 10 IO 00 o o CM o C cj o o 0 o 5? c u o o o o o c 5f c o X U c J 209 Appendix A5 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(acetone)]PF6(5*i Table A5.3. Bond Angles (°) (contd.) _«J o> o -»r O CN" CO U CJ CJ rt cj cj o fO ' T t~— IO 2 ^ 2 3-E co I O <J3 cn o <-> CN CO m to 0 0 cn o CN CO CN CN CN CN CN CN cO co CO CO cO co CO CO CO CO a EC X EE X X X X X X X X X X X X X X X X X X X X CN CO i o t o r - 0 0 O) CM £2 - r i - OO cn o to IO to o CN CN CN CN CN CN CN CO CO c$ CO CO CO CO CO LO CJ J J J CJ J J J J CJ J O J J J CJ CJ CJ CJ O U u CJ O CO CM O r - oo cn 0 0 CN CO iO 0 0 cn o o rr IO to t-~ to o CM CM CN CN CM CM CM CO CO CO cO CO CO CO rr lO iO CJ J CJ CJ CJ CJ CJ CJ CJ CJ CJ J O U U U O O CJ CJ CJ CJ O O J U C N C O C M C N p c O C O p O O t O ^ C O ^ C O C O t O ' O C ^ C C M M r ^ r - C N - ^ C N C M M C N C M r - . r t « - - . C M r - « « C M C N C M ^ - - i C N CO IO to r - 3 o — i CN CO lO CO h- OO o o CN CO to to CM CM CM CM CN CN CO CO CO CO CO CO CO co CO CO rr • r X X X X X X X X X X X X X X X X X X X X X X X X CN CO uO to oo cn CM CO »»• LO r - OO cn o eo iO to cn o CM CN CM CN CM CM CN CO CO CO CO CO co co co T rr i o u u U u u CJ CJ CJ CJ CJ CJ CJ U CJ CJ CJ CJ u CJ U U u CJ CJ CO T LO <0 J— o CM co Q to 00 cn to CN CO lO CM 0 0 Ch CN - H CM CM CM CM CM CO CO CO CO cO CO co CO CO CO CJ CJ J J CJ cj CJ CJ CJ CJ CJ u CJ U CJ O CJ CJ CJ u O CJ CJ CJ 210 Appendix flr(H)(PPh3)2{BzN=CH(o-C6H4)}(NH2CH2Ph)]PF6 (12*a) Appendix A6 Experimental Details for [Ir(H)(PPh3)2{BzA^=CH(o-C6H4)}(NH2CH2Ph)]PF6 (12*a) s 8 £ » ~ - I + ol | S g S 2 „ k s| U 1 3 ~ ** If | j g s 8 I | '* S g ? - a S „ - a S o 2 -5 S cd ta u-j ? S ^ S i 5 O 13 « 2 1 .8 . .1 1 1 * 9 I 2 ^ r 8 § <*' - 3 .a (£ is | a <" s s « s H ; s > - 2 - 0 > c ' 2 - ? ' s -1 I I S s Q o II II II 2 * a o o o to Q 3 3 3 211 Appendix A6 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(NH2CH2Ph)]PF6(12*a) Table A6.1. Atomic Coordinates and B eq cr> .—. ^ (71 •—. -—- -—. C7> 01 - -—• •—- iO 3 >— o» - 8 g CN h-— K CN O O — r~l CN CN r i o o p o S o -t o - H OO E S 8 O r-t CN CO to C— CO O l o CN CO «o to 00 Ol o CN o> CN CN CN CN CN CN CN CN CN CO CO CO O G O O O O O U U O U O o O o o O u u U O U U -< ™ m w w to CO CO W5 CO CO CO to IO to cn co ' -a-CN CO to d d d d 212 Appendix A6 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(NH2CH2P Table A6.1. Atomic Coordinates and Beq (contd.) « ° ? o ^ - r ~ . w t q c N r ^ c o c o c o o o c n c o r o o o o O i o ^ i o p cn CN C5 t- rr CO »o 9 d d d d d C N t Q C h C O C O i * C O r - > t - - l O O C O C O l O O O l O C O ' - ' r - . C O O t O t - H O O CO p 00 iO IO »o U O I- - r O) *-< I O o —• O O rr u} CO I-I TT co co r— cs S S S 2 CO »o t~ OO cn o CN CO IO <o r- 00 cn o CN CO iO to CO CO CO CO co rt CO -0* iO iO IO iO lO IO lO U . CJ CJ CJ U CJ O U CJ CJ CJ CJ O CJ CJ CJ CJ U U CJ CJ CJ CJ U 213 Appendix A6 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(NH2CH2Ph)]PF6(12*a) Table A6.1. Atomic Coordinates and B c q (contd.) 214 Appendix A6 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(NH2CH2Ph)JPF6 (12*a) Table A6.2. Bond Lengths (A) s w p t g i O i p e n o o o o c j > i o o . g c O r f r t M C O e o H ^ f O M c O C O c O ^ e O c O P t o c n o c N t o i o o c t r - ' c s T t ' h . oo" o" ?^ S" O f ^ f ^ ^ ^ M W C O ^ rf rf rj- r> ,o IO LO —« CO U 6 S FT S O O o o CJ o O o CTl CO <S" ST S3 CJ C o o o CJ o o « r— i-i CU CN o u 215 Appendix A6 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(NH2CH2Ph)]PF6(12-ka) Table A6.2. Bond Lengths (A) (contd.) -o o o o I §. a s ri £C X X p r- oo C7> o S, i2, "2, * O O <J g 00 rH CO g T m to X X K E O 00 CT> § 12. 12, »2, * u u o CN CN ffl JC CO "—• rH CN CN CN CN Q ^ C N ^ < £ } C O i ^ f ^ r H r H r ^ C N C > ) C N C N C N C O ? O C O C ^ 3 w a x b T K M f f i a x K W K W a W K E W X W X K K X ^ ^ CO lO 00 u o u u o o o o o o o y o o u u u u u o u u u 216 Appendix A6 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(NH2CH2Ph)]PF6(12i'a) Table A6.3. Bond Angles (°) to to to <o CO *»• HO >o tO CO CO oT crT CM oT oT co- CO JC JC JC to to oT CN JC co o" CO to to uS d CN CO OJ d C N CN CN OJ CN d CN cri C N CN CN oi d CM CM CN d oi d CN E o to O CN o CN to to C N CO co O CO CN CO CN CO Ol CO to co CO co CO I O « U U O U CJ O O U U CJ CJ CJ CJ CJ CJ CJ U CJ U CJ CJ CJ CJ E o to r- cn cn CO I O to cn CN CN CN CO CN to CN r-C N oo CN CO CO CO CO co cn CO o « U O CJ O cj U (J CJ U U CJ u U CJ O CJ U CJ CJ CJ CJ O CJ CJ E o co o o CN CN" LO tO OO to CN CM CN 00 CN o CO OO CN •V co •o co tr CO CN" CO o 'Z. U O U u U CJ O CJ CU CJ CJ CJ a. U CJ CJ CU O CJ CJ CU N - CO iO to h- CO iO CO CO -Si r- CO CO p Ol to CN to to ri uo I Q vO CO tO tN to r-hfl CM CN CN d CN C N Oi d CN d OO od d CN od d CN d CN od od d CN oi oi cd d C N d CN d om • O cn* co co CN cn CN CO CN r-CN CN CN co CO CO CO CO CO o> CO CO Ol ro O O CJ CJ cj o U O CJ O u U CJ o o CJ J U CJ CJ o O CJ CJ om tc? CO* oT o (O to oo o CN CN CN CN CN TI" CN to CN 00 CN OO CN o CO CN co CO CO to co o <0 O CJ U O O CJ u U CJ CJ CJ U CJ CJ CJ CJ CJ J CJ CJ CJ CJ CJ U om LO CO cn o> tO t- cn CO CO CN IO CN Ol CN Ol CN co _ iO <n CO CO CN (0 CJ CJ U cj CJ U CJ o CJ 0, CJ CJ CJ cu CJ CJ CJ CU CJ J CJ CU M ^ p C N U O ^ ^ Q ^ ^ ^ - ^ C N C O t O ^ r ^ C O ^ ^ ^ g 5 S S S S t " 5 9 ^ ° ° t ' f f i O O l O O O > r J c N C N « « C J > C O O » O l r H ^ r H ^ r H r H - H r H 0 0 O > C 0 c S O ) 0 0 r 1 atom u CM CN 7. CJ C(28) C(28) co CD <o U CN iO CJ to uT IO" uT CO uT I O Lu to uT £ * uT u CO* U CM CJ o O o E o cr ^7 - CN* co CO CO CO co" co* CO cr cr cr ^. ST ST ST CU CU Cu CU oT oT ST cu Cu u O C E 2 CU cu CN* CU 7. CN* f C J U CN o o* u to TT CJ Lu tu CN uT CM tu CO* uT « Lu o CN? c ? O O co „ CN CN CN" CM CN CM* co" "5) (O C N ' CN Ol of Oi r-to 00 ( O o 00 to cO IO I O o n oi 00 i CN oi to oi r-to s CO o> 5T oi 00 •T od of 1* CN 2 c? CN to Ci E o CN" CN CN CN CO o CM I O CN IO CM* —. <o* to* iO IO o" CO* to to1 « cu C u O O u CJ uT Lu uT uT uT Lu Lu uT O U U O o E 3 - — .^ CN" CN* CN CO* to" CO* to* CO* CO* to cr CN CN « ST ST cu Cu of CU oT ST Cu Cu cu Cu z u c E o CT CN CN 5 CN" CN cr O =. cr cr CN* CN* cO T tO C-? % cu sr CU CU 5f O CJ uT uT uT lu uT O o 217 Appendix A6 [Ir(H)(PPhi)2{BzN^CH(o-C6H4)}(NH2CH2Ph)]PF6(12-ka) Table A 6 . 3 . Bond Angles (°) (contd.) — ^ ^ ^ - ^ . t t m ^ o i o t ^ O i n > i ^ c i a t o t D - + -tr 10 cn oo ^ r- oo o i 2 , i 2 - d ' £ ! . G . 3 - i 2 . i £ . S . t - S 0 , 2 ! - d . c l . ' ~ ' •"" H H « M CS flXXXXXXXXXXXXXXXXXXXXXXEX « S ' i O O O O O O O U O O o o o o o o o o o o o o C N c o - f c o ^ t o i D r ^ o o o i O c s c o O CS CN^  l-H CS CO TT t— —1 01 . Ifi 3 oT *f o O O O ^ T T O X O O U U O X . O O O O O O O O w C i ^ C I - c A c r i d d r - I C i O t ^ t - . - * . - i C N C S C S p o o c s i — c n c o m ^ r r o o T r o c s r -o i o > o o c n c ^ c © C T i c 7 » o c n o i d o i ^ « C S C N — 0 0 0 — < CN r-i CS — p o o o - ~ - . - - - x . — , , — . , — . 0 ~— CN ro co »r 10 <o 0 u o i o » o > - < c s c o ' r r i o f - - r ^ o o c f ) ' - * ^ - i _ „< ^  _ _ « X X X X X x x x x x x x x x x x x x x x i—i CN Q . ^ - s ^ ~ « ^ ^ . ^ , o — cs co rr to 10 «o r- oo cn <ET r-"" co" « i i i o o o o o o o o o o o o o o o o o o o o o P . — -—- -—• -—. . . , ~ . .—. v .—. . o «-H cs --^  -—^  co co co 01 o o Tf-O — ^ — ^ ^ ^ ^ < O r - H C n C T « ^ r - c n C ^ " ^ ^ ^ C N C N C N C N rt Cu £T O O O O O O O O O O O O O ^ U X O O O O O O to —« s p e s T rr ~H co o o r-^ * rr" S" S* CT" Q r r r r r r i O r r v O i O i o i O i O i o 3-£ 0 0 0 0 0 0 0 0 0 0 0 0 £ « c o i O O c ^ o i ' - i c s c o i o r - C f > O ^ T T f i t ' r r r j ' i O i O i O i O i O i O « O O O O O O O O O O O O g O C S O ^ . < 0 0 0 ( 0 ^ - x C S r i ' c s S ? O 2, CN rf Tf -"T CS iO lO lO rtOOOC^OOOCuOOOO CN .-• R i O C O i 0 1 ^ > - t C J l < - H < O I ^ > O t * - JCT O r r r r r r r r L O r r i O L O i O v O t o J j ^ 3 O O U O O O O O O O O O P O C N r r i O t O O O O C N C N r r C O O O g r / r r r j - T T ^ r r f i O i O i O L O i O l O * o o o o o o o o o o o o c - n « c O r t t - r~ oi —, co co m 1? Q w w S - 0 * 3 ^ , 2 , ^ i n 1 0 >o rtOOOoTo O 0 0 . 0 0 0 0 218 Appendix A6 [Ir(H)(PPh3)2{BzN=CH(o-C6H4)}(NH2CH^ Table A6.3. Bond Angles (°) (contd.) o o o o o a> to oo M oi Oi p c o f t O t O r ^ o O o o o o i O rtOOOOOOOO o u £ rf 10 t o r- <0 ? N " lo" rtOOOOOO o o o v ^ & t~t tn QQ o\ o & 10 o> ao oo ^ a ^ to a o* t*- to M o c n c r t o S c S o i d o S r o o i d o S tO (O 8 3 CN 3 IO to 00 Oi CN CO lO 00 Ol o w CO CN CN CN CO CO CO CO CO CO CO rf *r •o IO iO O O O o o O o O U O O O O O O O o o o o O O O O »o CN CO Ol o CO rr lO t o rf O f~i CN CO o to 00 Ol t o CN CN CN CN CN CO CO CN CO CO co CO CO rf rf rf rf r f rf rf rf rf •O O o O O O o o o o o O O O O O O o O O O o o O O CN •—< w—> s s rf IO to Ol o CN cO IO t o r - cc Ol CN CO to r-. 93 Ol O CN cs CN CN CN CO CO CO CO CO CO CO CO ro rf rf r f Tf rf rf rf IO O O O O O O O O O O O O O O o O o o o o o O o O IO to CN CN r» to O CN CN CO co CN CO CO CO CN CO t o CO CO 00 CO Ol CO CO CO CN rf CO rf r f t o rf co rf Oi rf s IO o lO O O O O O o o O O O O o O O O o o O o O o O O O 219 Appendix A6 cis-[Rh(Pp-tolyl3)2(PhCH2N=CHPh)(NH2CH2Ph)]PF6 (14b) Appendix A7 Experimental Details for Cis-[Rh(P/>-tolyl3)2(PhCH2N=CHPh)(NH2CH2Ph)]PF6 (14b) Table 1. C r y s t a l data, data c o l l e c t i o n , and s o l u t i o n and refinement f o r 99019. C r y s t a l Data E m p i r i c a l formula C r y s t a l Habit, c o l o r C r y s t a l s i z e C r y s t a l system Space group Volume Z Formula weight Density ( c a l c u l a t e d ! A b sorption c o e f f i c i e n t F(OOC) c o l o r l e s s , p l a t l e t 0.8 x 0.4 x 0.1 mm Monoclinic C2/c a » 31.3817(2) A b - 7.3386(1) A 0 c « 24.7439(4) A 5350.95(12) A3 8 558.63 1.387 Mg/m3 0.24 9 mir."1 2336 .= 90.000(1) 110.113(1)' » 90.000(1)' Data C o l l e c t i o n DiffT a c t o m e t e r Wavelength Temperature 6 range f o r data c o l l e c t i o n Index ranges R e f l e c t i o n s c o l l e c t e d Independent r e f l e c t i o n s Siemens SKA?.? Platform CCD 0.71073 A 173(2) K 1.38 t c 25.10° -37 s .t s 35, -8 s k s 8, -29 s f s 29 16115 4724 (R. . = 0.0537) S o l u t i o n and Refinement System used S o l u t i o n Refinement method Weighting scheme Abs o r p t i o n c o r r e c t i o n Max. and min. t r a n s m i s s i o n E x t i n c t i o n c o e f f i c i e n t Data / r e s t r a i n t s / parameters R i n d i c e s (I» 2 t J(I) - 3945) R i n d i c e s ( a l l data) 2 G o o d n e s s - o f - f i t on F Largest d i f f . peak and hole SHELXTL-VS.0 D i r e c t methods F u l l - m a t r i x l e a s t - s q u a r e s on F -1 [o 2 ( F 2 ) * ( A P ) 2 <Fo 2+2Fc 2))/3, •(BP)) A - 0.0614, Sadabs 1.000000 and 0.441572 0. 0012 (2) 4714 / 0 / 448 Rl = 0.0373, wR2 » 0.1033 Rl = 0.04Se, wR2 = 0.1078 1. 061 0.378 and -0.464 e A " 3 where P = and B . 1.0565 220 Appendix A 7 cis-[Rh(Pp-tolyh)2(PhCH2N=CHPh)(NH2CH2Ph)]PF6(14b) Table A7.1. Atomic Coordinates and B, eq I r-t H i—I r-t • I rH ri ri r l ri I r o o O N a ) c o i f l i n y ) ' » n r i ^ r i ' i > n H < i | o > o g i / l i ^ m O > 0 0 , f ' H ^ O ^ l N l T i l / I O t i / 1 0 » f i T i ( h l f l f - l uiiflvfl*or*my)>o'o*flt ,'>o>c>or" oo co co co co a> i i n f rt r j IN M i r l IN 1*1 O » N t T M O i f M M M W f t r - h CTIM'OS H m i f l w o r i H r - r i o i a j < i « n m r - o 3 c o o H H U \ T r- v f f l u i o i i n i / i O H i n c ^ c o i ' i H f - i a f ' i O H v cooomo%a\cooor^r^i^u>i/.iAii>r^>x)u)u>UJiov£> r\ T T ^ T f ro o i/i »H ro r- rim(f\or'iilrico(Jii»i<j'Oo)fnri o o v o r i O r - t i H m r - riUiinNr,«)r,(NHii.ini(i (M I H I H H rO CO "» T V T CO I I I rH rH I r | ri r l r l H H i i n n M IN * IN i ri rt ri ff , H lA U l/l O I >r i f T " f 1 H r t r l r l M H I N M P J D r l H r t ' N O I I N M H n rs H n r l . I (N (N H IN r ) I IN IN IN r l [N JI (-j r i t 0\ i n • JJ o m VD r i - i N *r <*i N" u i i n • CO U) VO VU ' ' r j O ^ O N ' l J i I ^ r ^ U l H r O a t U J W N ^ r ^ O r ^ r O ^ O ^ v f f ^ O r O O r S i C i r i n n u i i u u v o r - a i r i r i ' f h r - ' i ' r i r i r i i i J r - u i i n ' f ' j H i i r a i 7 o i i n { < O O H n v r t M ^ i f l O i / , U ( r . i B m a i o o i r n o I H r i n r l M n i f l t N I N I N i N i N I N i N i N 14 IN H f l I rto\nu,iicou]corconiiu)i>a)r.i-o a i a ) ^ i A N i N i n u ) O r i i i i r i i / i o n a > i > < u -r •*> •-> H f s ^ n H f N u i ' j ' i N u . t D h ^ O N r a o . c o ' T M r h i e r- •tj - L r f,'j ' i v > i i ' N ' N ,r - u>ij3r- r > i e \ o i n i o m u i i CO T CJ H) Ul i I OJ CN U\ I (4 a fi ro (N ' » UJ • ! I~ r l i IN IN CN IN IN (N (N CN IN fl tN Ol fN IN f-l (1 I IN Ol ' f i I f uj N" l ~ rt <i\ \- ui N* I 1 a» f* rO Ul CO IN T rH 00 «p r I Ol T I" r-t „ , ^ O U ) O n O ' * l H r t O f f l ( I I I / l ' l ( r j l N ( N r - U\ (D CI I s 1)1 "f o r i i ) i N . 4 n y M ' i ' f O u 9 i n o > N i n r i i , h O o . a 3 o ^ r n c i f \ i o ) i N O i m l n l / l l i ^ u ) l f l u ) m o ^ o \ o ^ l » o ^ ^ ^ ^ c o ^ ^ ^ o ^ o u ) y ) y ) ^ • i n rH U) •» ID M M 1*1 M I I M II 11 II I •/ M1 f n m n i i ro T ro ro i ro 0\ in N1 o *n IN f— IN r** i ^ ro to rH U3 ro tx> CU H> ui o IN JI o> (> IM O> I o ^ v o o o ^ c o u O H c o r o r ^ r o a i r O r H N ' O U j M r - i 1/1 ui i~ vi in ' r o H n r i co i h l ! 1 r * ^ C O l N I , 1 0 I I ) 7 H 0 1 > l l r l C O r l l f l 0 1 0 3 H 111 CO IN I'l IM f l f lh m I I I TT ^  in V ^ in ro rN I M IN fN CO fN H CO r l rl I ri r l > 1 i l IN CO I i O 00 r» .Jl N" CN i u> <r vo r a i n IN i to i d o «j< n r» I iH IN 1 IN r l I 0 , i l > O M 1 ' 0 « ) 0 * > 1 ' O r H l j r > 0 IW)OUlCOlfHN(*l'J"*ll'IHH ' J 1 0 i f - F H f H o r - U J r o i n o r - O i r , r - a > , H ( N h ( N H 1 r l f 1 ( N n r i d n —. — — — — —. — — — — — o rH IN IO f "I Ni I~ U) ill O r I ^ H r ^ n r t l N M V U l « ) H l N r i l N n ' f l n ^ ^ m 0 1 ^ l ^ l r l ^ l ^ l l l r M ^ l r i « l N K f t f t f t l i . l i . k r , f c l i , Z 2 U U U U U U U U U U U U U U 221 Appendix A 7 cis-[Rh(Pp-tolyh)2(PhCH2N=CHPh)(NH2CH2Ph)]PF6(14b) Table A7.2. Bond Lengths (A) I rH rH O O O O 01 — r-i n m H i c m i n i n i n u i I o o o o co . i o VQ c. n • f i / i a j P n C h O r i r t • r u i i n i n i n i n i / i i n u i i n i j j u i u i i o w U C J O C j O O U O O O U U t J U ' J i - r o — ui CTI rs r- co lrll*lUlOi*t/*IMrtr'lO\ u\ u\ O IN m « i <r 7 >n i/i in in i U X K U U U O U P ; X O U O O U X U U U U U O U O O U U U O O U U . ' ! l ^ ' C C ' , ' t f t n " L n i n i o ' ' 1 L n m m >o I D ui in m ui i,, ui in in u m m in to u. u. ui in in --.ui r i n n m h n r - n v - r - i g i o i n o .H in ci CM m O H c o t o .-< in r- o ^ rs in oo u> — ^ ' rHaivfroininiomchrMCft<hmcoojina>OOT i N r ^ c D r a c o i n i n t n ^ m r O r O r n r ^ M fN ( I r l rt O i I H rH O O rH , IrlrlOOrlrlrHl l O O i H r H r H r H r H O O , I r i r i r t O O O O r H O O r i O O O l I O O O - HI - — — m n — — — — — ^ a ~ — -m-fTminmrHr-iarNOiNiNmuii. i * i i * i r i r i ( * i r . ' r ' i r i i , i i i ' r i ' ' r - f ' ™ - - -- — *C. - r i n n ri f w r- ai «i u o IM H i Ol rH O ^ — — . —. — — — [tl ro O ( H r l .1 . H H .1 .1 r-l .1 n I N <» I N M N </ \u in M n -f in w) ui r- ii r i ••• _ _ _ _ _ _ _ _ _ _ „ !"_ ~ r" ~ __ ~ "T_ *"* — — — — O i i u n n n u i h io ih o , i n n <f m io i - ai in u n N M t U I in in I B r- a > i n o i N n r i g i i i . i i } ^ i ui u i r-t VII ui i i I N m et -r ,m m u> oi m n oi H QI in o i*«n>ohcoro^iftininiNi/ii»iooiniiiiiiniuiDjiuiin . i i n m i w a i i n i n i n r i ^ i f i M m m i n o i m f l i v m c h i / i i n i J i ^ i u> UJ I i r H H M r t r t r t r t r t r t O r t O O r t O O O r H O O . O O O r t O O r t O O O i O O rH O I O n O O r H Q O O O H r H H i ~ ,-. ,( O -. it, l.) .-. . " — — — — —. ffl — — O if r i N 1 I 1 O lO l~ r l ul r l r l (•! I H I N i n - t f J - « « r l h t - - . « *C(,J riHHiHHNHHIN rt i l n (N I " - H H n i n r i t H v u i i N i N ' N r i h i n r r ' m a i - - - ' - - ' — — ._.,.. _ _ ._ _ _ _ _ _ _ _ _ _ _ _ _ . „ * * u z z u: £ u u K u x « o * * * o « * v ? ? : ' ; v « v ^ ,: ^ v ^ ^ ^ ^ K u ^ ^ ° w ^ w ° ° u u u K K ° u u ° ° - .M: o ui — — — — m ~ i i n m i . i r ' O j o i O r i r i M i ' u i i i i f a ) i c i f i i ' i n i ' i i ' i V ' j ' t i f v u ' V f ' t I IN IN ri IN I V l/l f f CO (Jl r l r l i tfo:CwPv.l^O,p«0,:_;:_;;_;uUUUUUOUUOOU 222 Appendix A 7 cis-[Rh(Pp-tolyl3)2(PhCH2N=CHPh)(NH2CH2Ph)JPF6 Table A7.3. Bond Angles (°) IN <r r- IN rt Cl Ol CO i 1 n N rt N r i v 10 r~ in in in ( • m N 00 IN O (N i n n n n i N f N f O N , ( N c i ( N ( N n < i / i m m o < r i D i n i i O ) a ) i o H i n i n i / i i m rf <N H m r- ci . cn o oi Ui d cn rt H at <n u> H < H M H O O O I N n H H H M i rtrlrlHrlHrlHHHHHi , i oi oi ni o> •» • ai o\ ( CNHOOOfNfNrtHr CJ — — CJ — (J n O W W - - l>. U. . (0 O H « ~ ~ ^ « M U i u . . . ... „ m U m in in ui ui Ii, ui ui >f> ID r-- r- r-t cn m o i-t ^  CN — IN T * to m IN co m M — d O H H u i m u \ 7 i / i i n n n i ' i c i n u m M HHr i r iNHHr^ N N " N n t N n r j (M(N(NrNMr i - (NO(Mr t i T^M ( v m n n - ' - — m _ „ ' i i i i j r - m i D i i i o o r i H f i M r i n T i ' i i n i i i h P - c o c o i N m o o H M M n v v u i i n i i ^ O U U O O O O U O U i U O U U U U U U U U U i U O O U U U U U (J o o V V V V V ^ )^ CD *H n ^ n * >fl ^ N in in 2 o oi M n -r r i o> () « S !n In in f/i U O U C J U O U O O U • ** "r *r rr N" v I U U I) u u u u L * u u u u u u u o u K O U u u u o u u u u u u ; u u u o u t j u u u o o ; i : a : u : u ; u : u a ; a ; u u u u o o u u u u 3 ; 3 : K L ) u u u o u u u IINniNW1T*INiN ClClfNVCNVN"fNO»r*l el (1 f| ' T ifl r- O n i ; r i n i n i n O i j i n M ) n o o t j i f i n i / i i n r - i N i D l O i o c i i o r i ^ i n m m c f i r ' O c i i r i m r i n i n i t i i i i m m r f f l m IMfMMCNfN'-if-tOOOrHfNrl(NHrNCNiHr*OOOf-Hrlrt I r< >H >-4 r4 r-( r-t r-« ri r-1 i-H H H H H r-t H ri r-t r-l r( <-1 tl rl .1 i in n m ri ui m H m u\ h U J C N O r- n r- r- ui in ui IN i iu oi , i in u> ft oi m o o\ ui r- o oi o oi o\ ui oi to i Cl Ul O f O ID 1 O H r< H H ri M r l (N H O Q D r l I rH " H H H , ( | 1 , H r i H r t H H H r l H r i r l r l N" CO IN N- fN ( IN « r n ui i d. x u x u u ac PG , m o — r a u in o — ci iii I>I in u. \u ~, u i ^ ~ — . —•. .—• •—• •—• »< co co —. . - m m fl m hi m ui m m m . . — ( Q U f N i M O i n — MLn-j'Cor~-ujr-ai(NfN'Jr —. o o ,H m H M >r m n 11 HI ^ m n 11 m M n — c o r - t D O f N O i O r H i N f S N ' — in »<v in r- to i - r-l " " N I \ N N I N N N N O I I N — '— M M rt n M M ii i l n n — — ro -. f,, r l ^ ^ ^  ^ vr --- <-l T f <f *r vr «r v in t i i i^i^u)Oio^o .Hrs | {NCNriMs*s* in iot^ ^ ^ ^ ^ ^ ^ ^ ^ ^ " " ^ ^ j ^ ^ ^ ^ f j j ^ ^ ^ ^ ^ r ^ r s r n r ^ u u u u u u u u u ^ i o u o u o o u o u o i i O I J U U U U O U O L J V V U V O V V Y V V U U O U D r ' v / j t o o i o t i i o i c o H H ^ c i ' f r i i n i o w r ' i c i n r a t o IN H H H iH fN r1HrifNINlN(NfHIN(NN(NMNnlNI-l O U U U U O U U U K X U U U U U t J U l J L t i J X ' X U O U U U U U O O U X X U X U X X X X X L t U U U U t J U U U t j U X i Z L t U U L i U U U • -— CN — — CN — -• to — r-t r- — cn < i> oi m (N O o ir v i ii v r- M o i i IN -» •» ) H f IN I 1 IN IN I i oi m m i * IN n o n o in m in in ID i I CD 01 Ol OJ Ol i ._ — — x: • — - 44 J : "> T N- . 1 . t U> tO " J ft. n. n. u « JI u « (i', — — —- u t • • < I ' tli I I I IM u. u, lu lu lu lu I ~ : ! 1J! >• ... O - i cn . , o, ft, fi. ft. n, ft. •~ . - - • — PI U I" i-l O) »- H r l — •— X ' ; r i .1 rs <*i n i - m H to r- r- — —- on — u u 3; o —• X X i ( - — — — — — w o, u ~- x ' i i • P : • • -. (i. o u (J x u a; w K • • 1 x > — — — — • — — s> -| i 1 • 1 1 i ~. r-4 H IS m *f *p ,-i I — — -~ —. r- CO Ol -~ O H r t rt rl rt H r-i — < ; ri 14 rs f i N- >r m m u r> r- - — 01 »s *— — — " H " — u • ^ u u u u u u (j — U U 1 < W U O U U U U (J U U (J 1 1 1 U L 1 1 1 1 t U i ' - • - (H r I (N -"4 2 ft l* li I n ' U N <f >r m m in ci in 1*1 r\ «p m ci vp in M ^ r- r\ H m 01 I.. I.. U . l i , O U O U : « U t J O U U O U ( J O U O W U O U U U U U U U U O W O I ' N ' n n f n M m n f r i f f i N m n »»i i m r H m m i n i n i N H i o a i H H ^ n i n i n i n i n o i io in 01 IN r i m H ui 0 1 - - r f ^ o c o m m o i N u i t J i i ' - r- o\ o ui o . ( u i m o i o i o i r ^ o t i i r i o i r i H O I O I O I O I O I O J ) r- co 01 o ri o o 1 1 in to 1- 01 r- r- cu ca n IN CI HI .1 ri ri I\) H 11 01 H ri O O O H M fi N ri n n ri .-i o ci O ri r-i rH H H r-l H rH ri rl • 4 i-l rH.tricirHHr'iHHrHrHrHriHr-lrHriHrHrHrH'-ii-ir-ifH - . it; |I1 —. -~ - O - f n i N d f H H O IN cs .-I co — . i 11 IN - ^ ~ - - -—- — cj cj . - ^ ^ . - ^ . ^ . r- r- * ^ . m ri • — — — — 3; X '— •-• — w •— — .— j ; i i m -f r i .-t m MJ ID j ; ,L; ~- - r i .1 H i i in M u m 10 r- - - r i - - K U U a: X X • • U 2 ft- (»• u — xi u (J m pi u: :i: - -• •-• -* - •-• — — — — x x u — x o • — — • 1 . > 1 u n> 1 1 • M< u. u. ii. u, (J. u. (J. . . 1 1 u n. :« u x u u K x K 1 • > ft. < 1 — — — — — " ^ s- — — —.^.^.1 1 — — 1 . .- .1 . 1 1 - 1 - . m O r i n O l r l » r i r l l / l rl r l rl rt - . -•- n ri H -•. - • — .-. .' I I-J IN H • - r. .-. „ — f~ r CD - Ol O H . i rH rl r l H - w ri — — — — M M — - — i i i i ci m 11 in n n -•• ••• - n ri i i c i rn <r in in m r —• to-— <H ' ~ — (j O "-" ^J^^U. — — (1.(1.11, — — — X V. X 'A • — — v.- o U U — U — U O U U U U " ' U o: it in 1 a o. 1 1 i u . f t . o . o . o . f t . f t . a . 1 • • i i j t j u u u u u t j u u i • i U i u > t 1 > > • -~ — 1 1 1 1 — 1 1 — 1 1 1 1 t 1 1 1 — — - --^ — 1 — 1 — —• —. —. ti ft — — Ul., ^UlUJIil ,.. » , n f-' ri rl . . '•. «•  — *s ,^ >s «( «( PI — 0 ~ r i l N H M O I r i f f v y ) r-t rs IN rH co co rs 0 i i in IN IN in m 01 10 .H >f ui ui is ci s* n in s* u> in r~ r- w H cn H H in rs r i rs rH H t-i 1£ Z u u U u it o i . . I.. (., 11, li, u ii. u. u u n; iii U u u u u u u u U U K K U U u O U U U U U (J 3: X U 223 Appendix cis-[Rh(Pp-tolyh)2(PhCH2N=CHPh)(NH2CH2Ph)]PF6 (14b) Table A7.3. Bond Angles (°) (contd.) i i f l H O i i r i f r i o i c i i o o i r t r ' i r t i A i f i O O O r i r i i n H m o r- riOfAOHdimoaiOfriHomooooriiii N H r i O O I M M H N O I r i r K N r l H O O P I M r t r N I N O I M n H r H r H r i r i r H r H H M r S r t r S H H t H t M t H H H r H H f H r t in CQ ^ m < W IA o n I N n rt u i H K u i r - o o\ C J CN i i I J u i n o o — i n i n i n m u i i / i t n i n m r - r - — ui>oiniJjiiivu\ouiu) — — i n m X . ^ . - ^ - - u i u i a ; " " — — —' 0 a: — — i U U K S U K K U B ' u u a x u a x u x 1 i KX - i i i i K X ~ ' • i o i t n - N ^ u i r i i N M r i v • f i d u i i o ^ - ^ i ' i a i d o i O r t H H n n • r ^ o o — u i i / i u i i / i u i i / i u i u i u i r r - — J J I U I U I M J I U O H J U I I I I — — m ui u - — ' w - w s - m m u - - — — _ —. ^ u u — — i C J U U O O U U U C J — ~ i U U U O CJ O U CJ C) i i CJ L» — i i t i U Cl — . . • t i i i i I I co v r- —. o rs H n v v i i ^ f i A H - — r- cn oo o r i o IN H n to 7VHHiiiLninmi/iiflinuii/iinMMi«muiuiii)«M)toio , J i u u z z x u u u u o u u u o z i a w u u o u u u i j u u i ri f T n w • M fN N 1/1 O Ol O O Ol M B l IN 1 V [~ *JT I 1*1 H Ol ' ro n s" IN >f rl f< f rl I iffllNrttNullO.-IOOoJHI IN . o o i m o m o o i o i I N H H I N H M r i r l i-tr^i-iriHHi-tt-il^inmofJiooooioi i i I H H ri (N H IN H IN H (N . I IrtrlHrti-trir-irHrHHrl ^ [U ~ ~ ~ ~ —- — < ca — — — — — — — ~ — in 01 >^OOW)OININmN*U>UlljD — r-r-rnr-OlOlOrlfOINm < r ^ i i i n i n i J i i n u i i n i i i u i i n i n i n a ) i n i n u > i n i f l i n u i i v i o u i i i i *XP4 — X S C U U X O K X O X X ^ - W W U U X U W P S O W ^ U U 2 C O C J U U U O U U C J U K U U U U U U O U O U U 224 Appendix A 7 cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (15a) Appendix A8 Experimental Details for Cw-[Rh(PPh3)2(NH 2CH 2Pli) 2]PF 6 (15a) 2 s J 1 J I j f I | s E * & g | § ._ o ii _ •_ •s I 1 -a 8 I i 5 1 | S I } j 1 I M 1 J a J i J J s B Q _ _ 1 225 Appendix A8 cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (15a) Table A8.1. Atomic Coordinates and B, eq 2, —* " to" tr> 2 S 8 CN* CN* CO O. UO cn CO CO CD d O 8 S t-H IO « o o 5? CO !? uO 2" co" ST U U u Cr CN co IO CO CN"" to" CN CN CN CN o O u u u o u u CN-r—I « CM g _ 2 g S CN co* 2 § CO g s t. f t S >i CN s n d d d d o o _ CN ^* CO* CO s CO* CO i— CN CO VO to s § 8 -0.03 CN o TO d d d -0.03 d d r-lr-.CN 3 8 •J? CO d d ! 5 s s a « o. o. - <; < — — 226 Appendix A8 cis-[Rh(PPh3)2(NH2CH2Ph)2JPF6(15a) Table A8.1. Atomic Coordinates and B e q (contd.) 2 8 CN O 3 s Ol CO o o r - r - t o co o ? •o CO CM CN © O d o d d s 8 8 9 >, 3 3 a 8 o d d d CN "0 oo I O CN r- CN o r-, d d d d Q I O tO [Vi 3 x x x 2.96(8) 2 (I) (l) z« S 2.96(8) UO CN O o 4.0 5.3 4.2 4.31 4.01 3.4! CO vj-8 S 8 8 8 2 a a s 2 9 9 8 3 5? £ s s 3. to ~ 227 Appendix A8 cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6(15a) Table A8.1. Atomic Coordinates and B e q (contd.) o o o o o o o c p o o o o o o o o o o © o o o o o o o d o o > < S £ 2 8 6 = S 3 S g 8 3 _ _ S I S S 3 g _ § 8 _ o o d o o d d o d o o _ 2 . _ _ _ i _ J . _ n J2, <y5 ",f ''»' •* •* f *T "*4« K « x x x x x x x x x x x x x x x x x x x x x x x 228 Appendix A8 cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (15a) Table A8.2. Bond Lengths (A) S o t O C N C N C O r - —• Ol to I -, j C O » — 0 0 > r - O r — l O h - r - o p i g c o c o c o c o c o i o c o c o c o c o c o t- Oi CN CN CN CO u o o to oo 00 o CN >o to oo CN CN CO CO CO CO CO o o o O U O O o U O u ^ y i o ^ i o t o i o t o c o ^ t o r - r - r - -S ^ ' I ^ C N ' ^ O U ^ ' C O ' I O t o o ^ T o o o ^ O C Q C 7 ) C J i r - - C J l C J ) 0 0 t ' - ' — ' C 7 » t ^ O T t/> ^ CO CO CO CO CO CO CO CO IO CO CO CO 3 S t n t N ^ t c t o w S r t t o t o ^ ^ t O M c o ^ r t r t o r t - t r - ^ c o c o o o o o S 8 S •-I r- tO § s s s 3 ft. z u s (IS CO tN o CN 00 t o 00 N* tN tN tN O (J U <J O o o O n a2 a ! a . ft. CO *f CN CT (O1 lO o O U U o CO m CN u U O U U a 229 Appendix A8 cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (15a) Table A8.2. Bond Lengths (A) (contd.) i s -a I I 1 I h i c ST CT o 3, ^ S E X rt u u J ! I i i § i i i I § _ i I i i i I _ § 1 1 I i S I | | | | § | | § 1 | | § § § § I | | § | | | | | I I I § § § § I I I I I I 1 ! ! ! | I I I I I ! I S i I I i i i i 2 i i i I 1 i i i i I S i _ I I 1 1111 § 11111111111111111111 I I I I § § § I I 11 I I § I 1 I I I I I ! I I I 230 Appendix A8 cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6(15a) Table A8.3. Bond Angles (°) CO CO CN CO CO CO CN CO CO o 1-4 CNJ i f CO uo CO CN T s 8 oi 8 CO CN oS CN CN od d CN CN •* OO <0 00 o CN ^p CN CN CN CN 8 s OO CN O CO CN CO CD CO TJ1 co CO s n o CN CN IO o tO cj u CJ CJ O O o cj cj o u U cj o CJ CJ u o O CJ o u CJ CJ «-« CO CO uo r- Oi CN CN tO CN r~ CN co CO CO CO iO CO n 3 CJ) CO 3 CO tO tO a O O O O O O O O O O O O O O O U O U O O O O O O P o — . i 1 <o — o o ~— <° °o •—. .> * r .— t - oo O co E —. rH oo u_ r- r- CN a CO CN o CO f-CN CN CD CN ID CO CO CO to CO to ot CO CO CO f CO to CJ CJ CJ O O U CJ CJ cj CJ CJ cj CJ O CJ CJ U CJ CJ u CJ U CJ O C N C 0 - W ( O 0 0 C _ . O CN CN tO CN to CN CO CN o CO CO CN CO CO CO CO 00 CO 00 CO o T CN T C J C J O C J C J C J C J C J o O O u o o CJ CJ CJ o o CJ CJ u CJ u _ 2; S C u •< _ — — _ _r _ c u- 2 a. o _ 5 89.3(3) to" CO r~ r--112.31 101.81 126.51 110.01 08*66 89.3(3) co CO CO CN 5T CO of oS d o> CO d CN CN CN CN s - _ - ~ S 5 5 oT 231 Appendix A8 Table A8.3. Bond Angles (°) (contd.) f 1 I 108(4) 103(4) 116(4) 119.2 120.0 120.4 119.6 § i i § 1 1 I 1 I I 1 1 1 I I I I ! 1 1 1 I 1 1 cf I § I § § § 1 1 1 1 I I I & g B B § § § § angle 107.4 1 1 I 1 I 1 120.0 120.2 119.6 119.5 119.8 119.7 I 1 I I I I I 1 1 1 I H I I 1 I I 1 I I I I 1 (6)0 (8) 0 (9) 0 (S)O I I ! 1 1 I I § 5 & f § & I cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6(15a) 1 i 1 U9.8 119.6 120.5 119.7 1 i 1 1 I I 1 H(23) H(24) 1 I 1 I I I ! I § ! 1 I § 5 o s i l l I I 1 I i i i i i I i I I 1 I 1 I I I ! I I H(22) H(23) ! § I ? 2 S £ o o o o 1 § C(22) C(23) ! I I C(15) C(16) C(17) C(18) s I V LO „ , , , o oT ci? s e 2. 2. M cri oj ° 9 "* °) *R 5 S § S! cS> S g S5" o p m PQ « O A iO CO CO « u u uT uT uT u. g P a B ffl « u u ST ST cu ST | § * ^ -^ 5 ^ « u u C" ST p P c h o T m c o ' m c a 5 to m irj co S U U U tC b, p i o ^ S o o ' f f l f f l C Q C Q o 2. 2. 12, 2, 2, ^ 3. B S £ — ^ o 2, 3. -^r *» io to 232 Appendix A8 cis-[Rh(PPhi)2(NH2CH2Ph)2]PF6(15a) Table A8.3. Bond Angles (°) (contd.) p oO 0> — -< £ TJ- Tf 10 in £ X X X 33 O X to p Oi oi 3 3 LO to cj o O o c j o ST ST o " lO c j o X X 8 8 CN rH _l oo Cn O CN CO 3 iO to r~ i- l- cn o CN CO >T (O C- CO cn CM CN CN CN cO co CO co CO CO co co CO -tf -* CJ CJ u cj O O U O u CJ U CJ CJ U CJ (J cj CJ u U CJ O CJ U uo to r- 00 m CN CO T CO lO o CN CO CN >o to QO CN CN CN CN CO CO CO CO CO CO CO CN U CJ J CJ U O O J J O CJ X O O cj O CJ V. u CJ CJ CJ CJ C3 Oi Oi 00 Ol Q I-H CN CN CO CO X X X X CN to CN CN oo CN Oi CN O CN CO CO 3 T CO lO CO CO CO co CO CO o 3 CN T CO T T T T 5 to r - •0 U U CJ o o CJ CJ o CJ CJ O U CJ O CJ CJ CJ CJ CJ CJ CJ CJ CJ CJ 233 Appendix A8 cis,trans,cis-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (17a) Appendix A9 Experimental Details for as,fra«s,m-[Rh(H)2(PPh3)2(NH2CH2Pli)2]PF6 (17a) co 3 a B 0, *^  *^  e £ S g CT. to CN 2 cn II II II II rt X) u <U § _ s t •a _ a 5 3 3 234 Appendix A9 cis,trans,cis-[Rh(H)2(PPhs)2(NH2CH2Ph)2]PF6 (17a) Table A9.1. Atomic Coordinates and B, X y z U(eq) Rh(l) 0 2793(1) 2500 27(1) C l ( l ) -3251(2) 4715(1) 1531(1) 120(1) Cl(2) -3810(2) 5731(1) 2348(2) 132(1) P(l) -966(1) 2662(1) 1470(1) 27(1) P(3) 0 5320(1) 2500 61(1) F ( l ) 654(12) 5736(10) 2981(13) 288(17) F(2) -608(13) 4840(7) 2826(17) 270(17) F(3) -678(8) 5276(11) 1829(4) 167(9) F(4) -761(9) 4842(8) 2266(11) 155(8) F(5) 683(7) 5780(4) 2219(6) 87(3) F(6) -632(12) 5277(16) 3098(7) 305(19) N(l) -1023(3) 3486(2) 2866(2) 34(1) C( l ) -1594(3) 3275(2) 3434(2) 38(1) C(2) -2363(3) 3730(2) 3603(2) 37 (1) C(3) -2152(4) 4167(3) 4099(3) 61(2) C(4) -2849(5) 4592(3) 4235(4) 78(2) C(5) -3766(4) 4578(3) 3876(4) 67(2) C(6) -3995 (4) 4133(2) 3390(3) 54(1) C(7) -3294(3) 3708 (2) 3255(2) 42 (1) C(8) -2270(3) 2653(2) 1587(2) 30(1) C(9) -2933(3) 3054(2) 1248(2) 36(1) CUO) -3924(3) 3019(2) 1342(2) 43(1) C ( l l ) -4251(3) 2582(2) 1766(2) 40(1) C(12) -3602(3) 2182(2) 2118(2) 40(1) C(13) -2613(3) 2216(2) 2032(2) 35(1) C(14) -804(3) 1959(2) 990(2) 31(1) C(15) -1586(3) 1640(2) 657(2) 38(1) C(16) -1447(4) 1127(2) 265 (2) 43(1) C(17) -512(4) 935(2) 188(3) 49(1) C(18) 277(4) 1246(2) 518(3) 50(1) C(19) 130(3) 1750(2) 917(3) 45(1) C(20) -877(3) 3251(2) 804(2) 29(1) C(21) -767(3) 3121(2) 112(2) 34(1) C(22) -679(3) 3586(2) -365(2) 43(1) C(23) -717(3) 4186(2) -162(3) 44(1) C(24) -836(3) 4326(2) 528(3) 40(1) C(25) -908(3) 3862(2) 1005(2) 34(1) C(26) -2910(5) 5207(3) 2219(5) 85(2) Cl(42) -3033(8) 2429(5) 4751(6) 111(3) C(42) -3066(10) 1878(7) 4028(8) 19(3) C(43) -3089(13) 1492(9) 3960(10) 177(7) C(44) -3186(8) 2013(5) 4241(6) 75(3) C(45) -2519(8) 2256(4) 4794(5) 69(2) 235 Appendix A9 cis,trans,cis-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (17a) Table A9.2. Bond Lengths (A) and Angles (°) — - O — O — O O — — — O — O — O — O O O O C N f N — o o o — o o — o o c o o i ^ o t n o o c n c o a - o y D O f o O ' * o o o o — — o o o o r - o o r H O O r ^ L n c o i n i ^ u n i n c o m c o u n r ^ u O c i i i n r o r o O i r o O i r o C 7 i O i r o r o r n C J i r O O i r O C J * r o C T » < J \ C T » C T i r ^ n f i r H O t r i r H r - m o e o i n ' . O O r H r H r H O r O H O H O O O O r t r l r . O O r l O O U X O X U X X U U O X O X U X U X X X X I I ( J X X X C J X X C J X X r - v D o _ r - c n c o ( T \ r I I I I I I 1 (N f. -u ) l o ^ ^ a ) o o ^ o O H H N M n f ^ * ^ u 1 v o * T ; T J ^ ^ ^ n ^ l , o ' f ^ | T J ' l r l l H H r l H r l H r i N r l l \ M ( . N N N N N < N r l l N ' - w ' l l ' f V ' ) l ' f ' < l l ' ) l ' l 1 ' * * H H rl H H — — I — I t — I I — o — r-t — H •» i n t n t* * m O O O J O T H — — — — — —- — " M f l — £ „ „ m [ n i n i / i [ n S - q S i I — I — — I — ~ i oi I — —.pui — fefe—.fefe rofO**fcro<fcvO**i rofeferoroferofeio fe fe -• c2 — c2 _2 — c2t2 — r i — rH — P 4 f t n t l . n m f t i T > r n O . C i ( r n r S j q i j c j i i - C i i flOiP. - fe ~ fe i l —- • •—• — * i i — I 1 *t | Ht 1t I « % | | | *fc * | *fc I I =t»= I I 4* •* I riHHHHHrlHWr^HrlWHCON^^'t^'firi'J'flllinfffl'U ro fe e fe ro U U U U U U U U U U U O C J O U U O U O O O U U U U U U U U U O O Z a - 5 - 3 - 3 f e S S f e f e O U U U U O f e f e f e f e f e f e f e f e f e P 7 f W ' l ' i ro • — to r- »J T ^ < f ' •— ri rt m — —• *— — — — — — — — — mm ro CN ro scororo — coowi/iu>oocoo^o^crtcf»OOroror--r--— — — 1 ro (N ro ro -—• — UD t-- to co cn co I s- v j m i s r* y . 10 vo io V D _ 1 — O O — — •—' O — • o — o — o o — —• •— o — O — O — O O — — — O — ^ t n o o m i x i ^ o v o o c A O c o o o ^ r o r - o r - o c N O r H O O v o r - t N o m w _ _ L i ^ i n w i n » i n i n M O c n i r t v o i i i _ _ i ( j i w riricN(N^r^r-coco<»u^ . O O r l r H r H O r H O r I O O rl rl r O r l O r l O r O O r l r l r lONr -i ro i n cn i n K 2 fe fe x O O jo vo — —.it. * * =» *t « m r H W l N ^ ^ U I U l r O r O V O V O f N C N H r l r O U ^ ^ W V U U f e f e f e f e f e f e f e f e f e f e f e f e f e U . f e f e f e H tN -I I I I I I I I I t I - o o H r i M N p i V f m m Xi-C-q-CrCrHM — — — " ^ ^ — — — — — — — CI 2£22.-iuufefefefefefefefefefefefe 236 Appendix A9 cis, trans,cis-fRh(H)2(PPh3)2(NH2CH2Ph)2J'PF6 (17a) Table A9.2. Bond Angles (°) (contd.) i i v M« in in in L JOOOOCDOllOiM'a'ailBlOhMOiNINV -a- P I P I v ^ m m f in u )VD\DCOr^ VDr~r>fOCOCOfN01CftOOOr^  J c r \ c n a i m r ^ c o o o o a i r j i O o i o \ c n a o c ^ l O O O O O H n r N t N H r i N H H H M N r t M M O I H H H N H r N H H N H H M HHHHrlHHHHHriHHHHrlHHrlHHHriHrlriHHHHHHHHHHHHHHHH 1 r l r l r l r l r '~~ r " C " —- o — I N H H c i N o i — m — o i — — ^ i f t u i i n i o t o c o r ^ r ^ i ^ o o a ) - q i o \ ^ ^ r T ^ S S — — —• -OlHOHHHHHHtOHrOHHHHriHrtHrlrlrlHriHHHH — H r- fN CO fN CN — O, tt, m PQ H — — — — — , , — — ^ „ ^ M ^ H O - m ' ~ - - H - - - - ^ - ' - - H - - ' - - - - ' ~ — S i I as i i U K K K X i o u o ^ x a ^ x t t u K \a \ > ~ l — — l l t i I — l i i I I I I I i I i I l i i i i i i I — I i — o o — r*r4tHCic*<vmr^~^^^inintf\io<oyor'r~r*a3aitBa\a\ — — H-r*H« — — — — rl — — — — — — — — — — — — CO 0>rtHOHHHrlHrlr(HrlHHrirlrlHrlHriHrlHrlrIHHH fa,r*i-H — r-< ri H H H H - • CN I N rN c i P I c i T » ^ ^ t n i n i n v o t o i o p - r - r ~ - c D o o — o i o i — — — ,-(— — — — - •— •— ^  — — — — — — — — — — — w _ _ w * I I — I — — I I I I I — I I I I I I I I I I I I I I I I I I I I — I I — — — I — , ,— — I — — — — — — — — — — — — — — — — — — — ri — rHp- — — — — — < — — — — — — — — — — — — — — — rr, — — Oriri — o o N H r i m i N i N — i n i r t r j i \ o \ j D T * r ~ r ^ i n u > t o c o r j i c ^ i ^ c c m r r t H W r I'UJCNfNOlJDOir-'-O-il'CNfN* IN * IN in o — r - o ^ m r i o i i n c N -H r - in r I f i n i n H H i / i r i a o r - c T i i m a i f N P - w i n i n o i i n i l i n i N i A O r ^ i N o c o r n c o c h r ^1 liHO fN tt <t f — i — I I — — I — I I 1 —- —- I —- • I — i — — i — i I — t I — — I — I | — | — i I — I | — | — — i i — — — — i l — — i ( — [l, — [H — — pL.pL,— pL, — fjt, [14 — U, pL, — pL, pL| — [n — — pL, p ^ U , — pM — — pL,— pL,— pL,p4~pL,— — pL,— pL,&,, .0,(1,0,0, — — ft, [l, O, J&, — — ( u p c o . t P I i ro P I i i P I i P I P I P I i I ro l P I P I i m l i ro I P I P I i P I P I i I P I l pi P I l P I i P I l i n i n r o I M I I H H l I l l P I P I i I t I m m i i i rOfcPiP,&PlPifcPiO<D^ftp>p^ C i l r i f t H H f t P ( H f t H H r t f t P . H r i i r t H f t r t t l ( n 1 r t f t H r t P i H H f t f t H A I # I # * I t ** I * <• <* I I I * I 4* I I <fc I « 1 tt tt I I tt I tt tt I tt 1 tt I I tt I tt tt I tt t I tt tt I I I 1 * * 1 I I I tt tt I I 1 i n i r i p i r o ' j ' ^ i / i i n r o p i t o ^ ^ i n i n f o p i i o ^ * * ^ 237 Appendix A9 cis,trans,cis-fRh(H)2(PPh3)2(NH2CH2Ph)2JPF6 (17a) Table A9.2. Bond Angles (°) (contd.) C(14) -C (19) -H(19) 119 5 C(21)-C(20)-C<25) 118 2(4) C ( 2 1 ) - C ( 2 0 ) - P ( l ) 123 4(3) C ( 2 5 ) - C ( 2 0 ) - P ( l ) 118 4(3) C (20 ) -C (21 ) -C (22 ) 120 8(4) C (20) -C (21) -H(21) 119 6 C (22) -C (21) -H(21) 119 6 C (23 ) -C (22 ) -C (21 ) 120 4(4) C(23)-C(22)-H<22) 119 S C (21) -C (22) -H(22) 119 8 C (22 ) -C (23 ) -C (24 ) 119 7(4) C (22) -C(23) -H(23) 120 1 C (24) -C (23) -H(23) 120 1 C (25) -C (24) -C (23) 119 7(4) C (25) -C (24) -H(24) 120 1 C(23)-C(24)-H{24) 120 1 C (24 ) -C (25 ) -C (20 ) 121 0(4) C (24) -C (25) -H(25) 119 5 C (20) -C (25) -H(25) 119 5 C1 (2 ) -C (26 ) -C1 (1 ) 112 5(4) C1(2)-C(26)-H{26A) 109 1 C1(1) -C(26) -H(26A) 109 1 C1(2) -C(26) -H(26B) 109 1 C1(1) -C(26) -H(26B) 109 1 H(26A)-C(26)-H(26B) 107 8 C1(42)#2-C1(42)-C(42) 120 0(11) C (44 ) -C(43)-H(43A) 109 5 C(44) -C(43) -H(43B) 109 5 H(43A)-C(43)-H(43B) 109 5 C(44) -C(43) -H(43C) 109 5 H(43A)-C(43)-H(43C) 109 5 H(43B)-C(43)-H(43C) 109 5 C(43)-C(44)-C(45> 124 1(13) C(43) -C(44) -H(44A) 106 3 C(45) -C (44 ) -H(44A) 106 3 C(43) -C(44) -H(44B) 106 3 C(45) -C(44) -H(44B) 106 3 H (44A ) -C(44)-H(44B) 106 4 C (45 )#2-C(45)-C(44) 136 5(13) C(45)#2--C(45)-H(45A) 103 0 C ( 4 4 ) -C(45) -H(45A) 103 0 C (45)#2-C(45)-H(45B) 103 0 C (44 ) -C(45)-H(45B) 103 0 H(45A)-C(45)-H(45B) 105 1 Symmetry t r a n s f o r m a t i o n s used to generate e q u i v a l e n t atoms• #1 - x , y , - z + l / 2 #2 - x - l / 2 , - y + l / 2 , - z + l 238 Appendix A9 [Rh(H)(PPh3)2{BzN=C(Me)(o-C6H4)}(NH2CH2Ph)]PF6 (18a) Appendix A10 xperimental Details for [Rh(H)(PPh3)2{BzA^=C(Me)(o-C6H4)}(NH2CH2Ph)]PF6 (18a) ° £ H ° ° «> !2 _§ 5. Q CN o c _ 8 ~ S. .9 » " s ^ & « &. "3 .sr l l | _ i o " o -° h S 3 sr _> g 1 2 3 S 3 * 6S •a a 2 a o G S 3 a I 3 s 1 S s t "3 o a cC a 3 1 X II n II II M M ^ Q O O O Q < •a bO 2 8 8 - •a ° I " 1 -< * a O rd 8 3 o 239 Appendix A10 [Rh(H)(PPh3)2{BzN=C(Me)(o-C6H4)}(NH2CH2Ph)]PF6(18a) Table A10.1. Atomic Coordinates and B eq 3 B 8 B £ 3 5 CM O CS co CS to CS rH 8 8 cs o s s O 9 9 d d CN r-. r l r-< rH CN CS r l r-l —I 31 § 1 co 3 S 3 S 8 3 8 8 5" G. 2. CN Ol (O cn co g to rS O d 9 I 8 Jo 2 . J2 S 2 8 8 S 3 3 c? CN cs" cs s to 8 s IO CS d CS d cs d d I 5 S a S 3 B a. ft, o. „ ^ -i: IO ^ £ ^ uT C o o a ~ o JT 240 Appendix A10 [Rh(H)(PPh3)2{BzN=C(Me)(o-C6H4)}(NH2CH2Ph)]PF6 (18a) Table A10.1. Atomic Coordinates and B e q (contd.) 241 Appendix A10 [Rh(H)(PPhi)2{BzN=C(Me)(o-C6H4)}(NH2CH2Ph)]PF6(18a) Table A10.1. Atomic Coordinates and B e q (contd.) 8 U T r - v i a o o t N o o i o c n . - . t © c f > ^ c N « . - < o i o , r > C lO "fl* Cl CN 00 OO (0 CO fflNcincsrinrtCNH *• ^ N s s 3 § 2 § 1 o d o d o s to tN + 8 a to" CN f * 1 ^ 0 « — ( N r - r O O - — • !o r O O i O t p t N i O i O C O h - 2£ M 3 ^ S c N c o S e N « « "q d d d d d d d d d '3 CN to g ig B I 8 S 2 g o d d © + —. to X t > » > » 5 < 0 ^ 8 2 i O ? " co \n _ _ _ _ _ _ _ _ _ _ _ _ _ II J! 1 i "i I ! ! I I ? I I 1 I I ! I I I 1 I I 1 1 • 111! S! 1113! 11! I!! 111111! -1 1111 I 11 I!!11111 I I I 1 I I 11 - i i i i i i i i i i i i i i i i i i i i i i f i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I I I I 242 Appendix AlO [Rh(H)(PPhi)2{BzN=C(Me)(o-C6H4)}(NH2CH2Ph)]PF6 (18a) Table Al 0.2. Bond Lengths (A) s s CN r - —• ^ co ? CN 3 CO CO CO 8 CO C7> CO CN CO V oo at V uO UO tO O c j O U o O u CJ O O CJ O O o CJ CJ *o CN o CO CN CO tO CO IO CO s CN r- o tO CO lO iO to CJ c j CJ CJ CJ CJ CJ o O CJ CJ CJ CJ CJ CJ O IO 00 CN o 00 o to 5 to CN o CN oo to CN CN co CO CO iO IO iO C J C J u O C J U U C J C J C J C J C J C J U C J cj uO t-- 8 co m to to at — cO CN CN co CO CO CO CO 1" U 5 tO to c j C J C J c j O C J C J u c j u C J C J O C J U C J O 8 S-2 S s -w C N t » m t O ' H r ~ l O t C - O r - « r - " ( p S r ^ r ^ o o o o ^ c n t o o o o o r - t r ^ c n C N l T l O r O C O C O C O C O C O l O ' O ' C O a c c ~ <3 5 tC to icT at tO S oo CN IO o CO to 00 CTI CN 1" CN 3 O U . C J o C J o C J C J o C J C J C J O C J o C J C J C J . , CO CO" co S" CN CN _ CN ST o CN to r-- 00 o CN CO CN CN OH a. a. O o V. O C J C J C J C J o o C J C J O C J C J C J — « SI f< IT* t*J VJ «"J V t-J Oi -t at t~~ C T i O c o t-- <o oi oo oi H oo cs r - - r ^ < 3 ' J-' S C N C > r O C O C O C O C 7 > C D O O C O r - C O C O r ^ C 7 > r - t ~ t O Q C ^ O T t O O O C O i O u ^ t O t O i O C N C O t O C O i O C O f O t O ^ - * r^  CC oT 3 —. io" _^ rr CN r - CN o CN CO CN CN (O to CO to Ol * - CN CN CN CN ft. 2 O CJ u o u* u O CJ u CJ CJ CJ o o CJ o o CJ CJ CJ ^ ^ 2" |—^  CN_ CN O C O C O C N ^ - H C N C N C O iO 00 O) n r- —« £ 3 S f c f e t t o T ^ o ^ ^ . 0 0 0 0 0 0 0 0 0 243 Appendix A10 [Rh(H)(PPh3)2{BzN=C(MeXo-C6H4)}(NH2CH2Ph)]PF6 (18a) Table A l 0.2. Bond Lengths (A) (contd.) 1 1 1 1 g X 8 8 3 o u o J i 1 s f i l l t i l l 1 I s 1 i I 1 § 1 I i I I I if 1 I I 1 I i g 2 i I 1 I I | E | | | | § | | § I | | § | | & | § | | | I I § § § § § I I I I I I I I I I I I I I ! ! l I i I t I i% I % t ^ % ^  i % % 2 I n ^ ^ ^ t il % 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 S I I § § § § I I I I § I I § I § I H I I I ! I 244 Appendix AlO [Rh(H)(PPh3)2{BzN=C(Me)(o-C6H4)}(NH2CH2Ph)JPF6(18a) Table A10.3. Bond Angles (°) OO •CC cn 0 ID 00 to 00 .5(3} O t— « <o CO fN a 06 8 8 -NT CN oi si N * 1- ci oi Oi d CN d CN co CN d CN oi 8 d CN d CM CN V) o CN 10 CN 1 - 01 CN co CN r- CO CO CO CO a r-co O) CO Oi CO C J C J 0 O u C J C J O O C J C J O O U u U u O U 0 u C J 0 0 CO uO iO r - 00 00 0 CN CO V to 00 cn 0 CN LO to 0 CTl CN CN CN CN CN CO CO <o CO CO CO C J O O O C J O C J O O C J O C J U U U U C J C J U 0 U U U U s~ O O CM CN" to Oi t- co CN R CO « co to cO U o O u U Z U O C J O O OL, C J C J 0 0 0 C 5T U C J C J *r —• CO co r - oo CN Ol O CN 00 to 00 0 CTl CN CN CN CN CN CN CO O O O C J O C J O O C J O C J C J O O C J C J C J 8 S S o u o o o o o o o o o u o u o o o o o o o o o o p —. — —. K CN OO Ol a u z o o 8 8 8 3 f^ " — (I (1 8 100.8( 103.0( oi 107.6( 101.7( ? oi 6 S S 8 -< CN O Z s ^ s 2 a 2. 8 ST aT 2 z 2 u c2 o u 5 S z o 0 o •a 3 —N — 0> S £. S ST eg g» cn LO ufj — — -S g CN CO* CO CO to p oq 00 CN d CN 00 2 0 ~ - — 00 § " a c s. 3 Oh Z Z O CO ~ " 5 £ •NT «0 £ !*, " 2 , ^ fc uT 2 CJ CJ o o 245 Appendix AlO [Rh(H)(PPh3)2{BzN^C(Me)(o-C6H4)}(NH2CH2Ph)]PF6(18a) Table A10.3. Bond Angles (°) (contd.) 9 $ uo 10 .—• oo oo oi d c?t ~* cri oo co CTJ c» c» d c» cn gi oi oi oi r ~ O C ^ » Q O O ^ C N ^ i ^ ^ O o a ^ r H C J « « C > O O r ~ c — „ — _ _ _ o o — <M co 10 <o 00 00 cn o 5 10 uo -< d 2. — 2- 2 t - S S - S - d c c - c n ^ . ^ - w ^ - c i c i C i -« x x x x x x x x x X x x x x x x x x x x x x x x C rH —. , _^ O rH CN CO T IO <0 tO Oi 3 2 2 z Z Z O O O O O O O O U U O O U Q r ~ * a. *-=. 2 u — , — — . ^ - O - H CM co -*r ro io r-- 00 o d - d M co^  10 <N ci ^ H -1 «-i c i d — d- £i X X o o o u o u ^ o . x o o o u u o X X u 0> Oi CO O CN CN i 0 i 0 C 0 " 0 O ' - ' O - - < ( 0 0 0 i f r - 0 0 i O i 0 i O ^ w ^ ^ a i ^ a o c o o i d d c n r ^ o i w g b 9 S O O C $ S S ^ 2 S ^ ^ H ^ H ^ ' - ' 2 S ^ ^ * 2 ^ ^ Q io ^ • r ' c r f C T ' r r ' r ' C C " ' —• CN co •N* 10 co r- 01 cr. o C N C N C O C O - ^ ' i O C O r — 0 0 O ) 3 X X X X X X X X X X X X X X X X X X X X X X X W a _ —i . . — . - ^ .— . O — CN CO T tO tO <£> Oi P ——. <» •— .— —- — —, — O ^H" CN iO iO I— 00 jjj rH rH rH r- CN CO T l O l O I - O C N Ol Ol -H rH rH ^  C!. w C -^% aT £f u 2 o £f o x u U O O U ^ U O O O C J U C J U X O <7i >n uo --i E i o c o m » o c N c y > r H r H o o i o f ~ r * Q ^ V ^ ^ I O V I O U O U O J O ^ J O , JO^ to U O U U U U O C J U U U O a ^ rH to r-. C S C N C N C N C N C N W C N C N W C N _ C O <u ao ^? ~*r tO O co -« oq —j ^ r ^ ^ d d ' » r o 6 d ' ' B C N C D V ' O O O C N O C N T r C O O O O < q a ^ < T > . 4 < * ! > u O t O i A i O k O i O u ? 3 o o u u u u u o u o o u t d U U O O U U O O O C J U O G CN CN — . 0 0 0 0 0 — . V ^ r f D 3 C N , V ' f l , ^ C N * l , ' * > O C N l O i O > 0 246 Appendix A10 [Rh(H)(PPh3)2{BzN=C(Me)(o-C6H4)J(NH2CH2Ph)JPF6 (18a) Table A10.3. Bond Angles (°) (contd.) jl; C- CN p lO C- — Ol O CO " t i o i d d o i o i d o i d o i E L O ~ c o r ~ o o a i O ' - . C N r O 3 X X X X X X X X X q S T o ^ t ^ v i o t o ^ ^ c i o * O O Q U U U O U C J G O ^-H* CS* »-< .n CO r- CO >~~ rtOOOOUOOUU 8 2 oo oi Q CS CO If •*>• X a x X X X X Ol © r i CN TT CO r~ OO N* H LO iO Jb tO •A lO m O u o O U O O U U Ol Q • H CN CO CO 1— oo Ol o f— CN CO iO to r~ CO Oi cs CS es cs cs CO CO CO cO cO CO cO CO CO *»• "<r *r X X X X X X X X X X X X X X X X X X X X X X X X o CM TT lO to i~- CO o cs CO to CO *0* o i o e s c o T j - t o t o c o CS CN cs CO CO CO CO CO CO O O u o O U U O O U U O U U V o O O O O O O O O —• CS »-i •o to CS i -es oo CS CN —• cs CO CO co CO CO co to r-co oo CO Ol CO o at CO 3 3 •* O O O O o o o O O U O U U U O U u o o o O o CO to o o (O CO 00 cs 00 Ol 00 oo r-. »n CO DO LO r-oi d es d es oi d cs d cs oi Oi oi d es oi o i o i d CS oi d es Cn oi o i 8 oi Oi o i CS cs CO cs TT CS cs to cs ir-es OO cs Ol cs o co co CS CO CO CO -r CO m CO to CO r-co co" Ol CO O cs CO T X X X X X X X X X X X X X X X X X X X X X X X X 8 cs cs tO CS CO cs t-CN CO CO CO CO CO T CO to CO CO Of? CO Oi CO es CO •*r LO to " M " OO U O O O O U o O O O O O O O O O O o O U O U U O Ol o r- CO m to co" oi" cT CN Oi m tO CO tO es CO cs cs CS cs cs CS CS CO CO CO CS co CO CO cO cO T O O O O O O U O O O U O O o O O O O o O O O o o 247 Appendix AlO cis-[Rh(Pp-tolyh)2(diq)2]PF6 (20b) Appendix A l l Experimental Details for as-[Rh(P/?-toIyl 3)2(diq) 2]PF 6 (20b) E D.04' II % ~ i. CO o S 11° Total: 59749 Unique: 164J a ^ . 12 o c o a g.-tSc 3 5 1 S S • 1 , 1 , £ I S 5 | £ « £ | I ? „ 1 - 1 1 M I U H ! 1 M 1 i3 5 t 5 t 2 3 " i . < z z ( S g 2 a ' «** rt I II " O 2 fc E o •3 t! u 5 248 Appendix Al I cis-[Rh(Pp-tolyh)2(diq)2]PF6 (20b) 249 Appendix Al 1 cis-[Rh(Pp-tolyl3)2(diq)2]PF6(20b) Table A l l . l . Atomic Coordinates and B e q (contd.) i - !C lO OJ —-o —; 3 S3 =? 9 § a o o o o oo gi O <—i CN f •o CO So oT o CM rO to" p 00 bi 3' U CJ CJ CJ o c j O o CJ CJ o CJ U CJ u CJ U u U 250 Appendix All cis-[Rh(Pp-tolyl3)2(diq)2]PF6 (20b) Table A l l . l . Atomic Coordinates and B e q (contd.) S CO CN o I- CN cn oo op r— CTI o r-t t-t oo co io co o •*r i-> o cn - r io 00 oo CN io to 01 co - H co cn co co co —. o •-• o CO CO CN CO CO CO to I O cO CO CO 1- aO CO CO O) CO o CI T iO to t - 00 cn Cos) iO •o !o X X X X X X X X X X X X X X X X X X X X X X X X r. 00 to I'-' 00 C71 (01) (12) CO » B P3 ac s B 251 Appendix Al J cis-[Rh(Pp-tolyl3)2(diq)2]PF6 (20b) Table A l l . l . Atomic Coordinates and B e q (contd.) atom X >' z H(54) -0.1961 0.1502 0.2093 2.8 H(55) -0.0981 0.2061 0.2897 2.4 H(56) -0.2349 0.0608 0.1310 4.6 H(57) -0.1663 0.0457 0.0916 4 6 H(58) -0.1808 -0.0134 0.1420 4.6 H(59) 0.0318 0.0246 0.3351 3.0 H(G0) 0.0465 •0.0708 0.4090 3.4 H(61) 0.1635 0.0720 0.5436 3.4 H(62) 0.1458 0.1684 0.4699 3.0 H(63) 0.0618 -0.0887 0.5338 5.4 H(64) 0.1485 -0.1111 0.5181 5.4 H(65) 0.1458 -0.0515 0.5712 5.4 H(66) 0.1130 0.3383 0.3724 2.0 H(67) 0.0552 0.4235 0.4307 3.5 H(68) -0.1096 0.2683 0.4613 3.3 H(69) -0.0544 0.1815 0.4010 2.8 H(70) -0.0197 0.4235 0.5273 7.5 H(71) -0.0880 0.4508 0.4685 7.5 H(72) -0.1080 0.3833 0.5099 7.5 B,, - ; - V ( t ; n ( a a - ) ' + V-n(bb'f + Uizicc')7 + 2Vnaa'bb'cos-f+ 2U\3aa'cc' c o s / 3 + lUizbb'cc' cos a ) 252 Appendix Al 1 cis-[Rh(Pp-tolyh)2(diq)2]PF6 (20b) Table A11.2. Bond Lengths (A) <j 10 iO to to 5 " l o ? « K 3 oi oi oo Q m TJ- CO CO iO :a rt rt rt rt Ol n rt O CM CO oo CN CO 3 CO CO CO co SS 3 o 'O tO oo iO IO iO Cn « iO to CN to to io to c j u CJ CJ CJ CJ CJ CJ O O CJ CJ o CJ CJ U U CJ CJ CJ CJ O E o iO OO CN CO IO to Ol CN' O I- Ol o co iO to o CN Ot CN CN CO CO CO CO co T iO >o •o to U CJ J O CJ u u J CJ CJ U CJ CJ CJ CJ CJ CJ O U CJ CJ CJ " ?} z* CN Ol 8 s o tO Ol o h- IO 00 o CO 'J' « Ol CN •o i- QO 'O CO to CN CN CM CN CO co CO to T IO N* iO tO lO iO to to IO J J U CJ J CJ J u c j U CJ CJ c j u U CJ O U O O O CJ Ol uo tO CN CS 00 CN Ol CN CN CO T CO iO Ol CO CO o CN CO to OQ ST CO •o iO to Ol cO to to CJ CJ o CJ CJ CJ CJ CJ CJ CJ u CJ CJ CJ u c j CJ CJ CJ U u c j rt o —. to LO CD CJ O O CJ CJ CJ Ol CJ CJ 5 ST lO rt O V. c j U O U i o O o 253 Appendix Al 1 cis-[Rh(Pp-tolyl3)2(diq)2]PF6 (20b) Table A l 1.3. Bond Angles (°) b O O O ^ O O l C N C O I - - - - - < C J l * T C 7 > „ . _ , — — . ^ CN iO O l iO I N OO Ol O —. CO O GO •— O CO I - >o Q rr lO TJ- CO CO CO 00 CN _t •-. t-» C C ' w w S t i ^ S G . " — rtOOUUUO U u o u t j u o o u u u . o U O O O U C_> co •o en co IO t- co Ol O iO CN m cs [It, CS Ol cs CO cs' CO 3 O C J O O C J O C J C J o , C J C J O C J U C J O C J C J C J C J C J C J u „ „ , CO _ -o I-" ' T Si CO to Si CO w C J O O u C J C J if. C J U O U O U < J C U U C J u O OH C J u CO CO CO co CO T" CO 3. V CO CO i" to CO Ol » ' T *T - H CO <o iO o co* <q "X to cT cs to CO CN crT d cs cs CO iri CS cs CO o co CN oi 22 d >o 2 oi oi CN CN 2 oi d CN oci CS cs CN K c s o i t o r - t o c i o t o o o o CO CS CS CO CS CO co 3 O O U O O O O ^ O O U U U U O L f U U V U O U U U •o to t- i - oi oi lO.to coco o CN CS " CS CN CS CO CO CO. ^r co" to T CO — . co o O C J o C J C J C J X. C J O C J O O C J C J C J S. C U lO I- Ol " CN P ^ ^ s n. a si 3 z z z 1 £ £ £ -~ H CN z z z o £ —. CD — r~ CN ~ XS & o £ z u co 3 8 S CO — — *—i P-H CN tO — — H H CO 5 £ £ £ C o £ £ C 254 Appendix All cis-[Rh(Pp-tolyl3)2(diq)2]PF6 (20b) Table A11.3. Bond Angles (°) (contd.) rH OJ r*H t—4 CN CN CM rH rH CN CNJ CN CN rt CN 04 CM CN rH CN Oi CN 3 U O CJ CJ CJ U O U U U O U C J ( j U U O O U U C J O G « O C O O . O > r H C N r O I O O « « O l O f O C O ' O l O I - O O C M C O ' q ' K c O c O C O r O ^ J i ' N , ' ' » ' V , " q , ' ^ , , * r i O ' O i O i O i O i O l O ( 0 ( 0 « O u i > P iO — > 0 O rt" CN I - I- «) Ol .— T T 'O 5*—.—' >^  CN CO Q f O c O r t * r » I ' ^ l ' * 3 ' O I T ' * r M , ' ' * J ' < N t O i O > O i O C N « 0 ( 0 < 0 ( 0 SW c o o i d c N d ^ " d d > o - H C « r H d c n r H r H C N C N C N C N r H C N C N C N C N r - . 0 * 0 < r H C N r H C N C N C N C N ^ C N C N Q C O C O C O V ' W V ^ ^ I O >tr I O O I O I O I O I O "O O CO to CO »0 ni u o o u o o o o o u o o o CJ CJ CJ CJ CJ O CJ CJ O CJ S u ? ' 5 r - C ' > O C N 0 * ' ^ " C D I - - 0 1 C 7 > - H C 0 ^ , C 0 l 0 0 0 O r H c 0 C 0 ' 0 9 2^- 13- C2. ^ ^ ^.'*T ^ "J" iO iO iO .O iO iO <o CO to <o <o rt u o u o u cj o u cj C J U C J C J rj U O U O U U C J C J O ' O ^ G, C O r - i C O - ^ f c O C N ' r T f i O - ^ ' C N ' O i O i O i r t C N ' O ' O t O l O 255 Appendix Al 1 [Rh {rf-(C6H5)NHCH2Ph}(PPh3)2]PF6 (21a) Appendix A12 Experimental Details for [Rh{Ti4-(C6H5)NHCH2Ph}(PPli3)2]PF6 (21a) s 2" • c S.5 • - r, - - rt " ^ S r a * o Q U O T 3 P O <T>*£0CO < Q ; S OI OI V i > h - » S 2 O Q> 2 UJ 5 X z 5 < < < o « —- •< a) r>- s p „ 5""~" a> o - ' ro ro t ul ro ro oo ) oo <o 0 ro " *" »- V 256 Appendix Al2 fRh{r]4-(C6H5)NHCH2Ph}(PPh3)2JPF6(21a) £ £ U Ii. CNI o • i n II * 5 is CO o a: 5 <5? £ OJ ;s ^_ e o 5 .S Q. £-o O 257 Appendix Al2 [Rh{rt4-(C6H5)NHCH2Ph}(PPh3)2]PF6(21a) 258 Appendix Al2 [Rh{ri4-(C6H5)NHCH2Ph}(PPh3)2]PF6(21 Table A12 .2 . Bond Lengths (A) (-. .o o IN <V> O O r-l tTl r-1 ui cu o o o o o o o m in m fO — cr. cu (Jl ,^ !• C) <n Ol . ui a u r i J i - • o • • • • o o o o o o m -x. ( J I J U I ) u u u • i/l U H O uO iO H ' i i n i O i n i / i i n i u i i i i i i i i i v I J to L n o c o i / ) * O i ' ) i o * r o i « j ' ' r r i c o i o < . f i cl n n i*t M n o M n c i n m r i n 11 i'i ro (1 ( | V |TI <r \0 I ' n f i r - I ~ i~- PI V J l ui ui . 4 O cTi O CT\ O O CJ ai o ai ai o O m tJi .-i c l ul w </l w v i i i id J l v in «• v i / u f i v v i/i • l a i o i o i d f j i o i o i o i t n v o O O in Q * w O in i n m a i o i o i c i i C A O i o i i n a i u i o ^ a i o i O l O i f J i o ^ ' O O O O O O O O C") O O O O O O O O O O O O O O O O O O C J O O O . i IN OD i * i/l SJ r- I v >n vl> f- c o O r - t C s i c l «r >H (-i ,1 H i i c-i H (N IN <M IN IM N IM : x x x X X x x x X x x :c: 7 U U U U U U U U S U U ^ I ( I U U O U O U U U U U U U U O U O U U U U O U (J u u ; -O «T ,n IN <N i l IN L I IN I I i • IN M IN IN IN IN ' ) i£> VO VJ Vi) \t> 'H <N r 1 LT> . i i n i / l i / i a l i r i i A v v i / l i • m oi oi • c o o m o i m H n : f l ; i 3 : < < i ; < m i t i H i ( n i n i H I N I ' ) i n f ' W v ' - 7 f l l - r l r t c N f O < f i / 1 1 0 l \ l ' l r l H I N W I 1 1 ' i a. tu u u i) u u u u u u <J u u u. u. i^ . u u. u. u. u. u. i>. i • OJ Ol O IN 1*1 s- ill N IU Ol O H N N- V iO Ol Ol iA * r- r W in Ol ' 1 IN CN 11 I I 1*1 I'l f i <0 '1 -J1 CO f i -* V *J" • * *»" " N- ^ T *J- N* *J- < I u U U U IJ ( I U U U IJ U U O U O (J U U U U U U O U U IH ) U ! r t . . .-i ,-t i-i H r i »j; < «; *c iu m ui i JZ c J : j , ' r; c. xz xz CN CN IN to n IO f i «*i co m n m i a ^ i t f o C t f i x ' t f i X t t l O j p ^ i ,ij ni i - ui oi >-i . i fN i*i T ui r- r- in oi o r-i n ro v N- vr m >fi vD M> i - i - a* -J- « " ^ I i'i i r , ,NI (\J N M I ' ) n in r i n I'l «r v w » J -r w - i >f <r >r J v I'I c l M . a. a Z Ir*. U U U U O U U U U U U U U C J U O O O O O U U U U t , U O U U I J O 259 Appendix Table Al2.3. Bond Angles (°) [Rh{t14-(C6H5)NHCH2Ph}(PPhs)2JPF6(21a) U U U U <-> O U U (J U U U U ( > O U U U O U ( u u u u u u n l l) U O U U !-> U U U ci LII 1-1 1/1 ii i-l vr sr in Jl W r r- «r T x' u ij o u u u o u tj u u u u u o U (j (J u i I ) (J ( J U O U U U 1 ' U ' v£> I U U U U U I U U U U U U I J O O U O U (J U IJ U CJ U U U (J : • I— 00 CD OO CH Ul <J1 O O O •'! .-I.I (M (nnf^flM^M 'T'r'JV^-J'TiDvUlOiiiJi i: J U O U U O O U O O U l J O C J O U U U U O t () U U (J (' U I (1 <J CJ CJ U U U O (J U U U U U CJ O (J O CJ U (J (J (J IJ : 11 n: « m it u u o u u u u u u o (J O u cj u • i u u u u (J u o it u o u u u U u <J u u fe u fe b u t., i., u. i>. u b b b b j ^ ou u i U J r • CD r- f o w n IN M T f i * O O r- in «i ' I , i .1 .1 , l .1 H <N IN IN CM IN IN IN IM 'N M ''1 IN M (Ml I U Ij U U U U U U U U U U U U U U U U U U U 1 < ft, < rC < 't I rl Ol IN M l \ N IN I1! Ii II M I'l M 4 a, cu a. ft, ft. n. a. ou u. u. a. n. : a* . J ; .r. in . a. a. a. n. (J t; i l) u U U () U U U U O U l , . ,1 M iMn.n «; < < • r~ I! J ! n n N v Jl ri H , I ri .-i ) ( j o r : o : B : t j u u u - u . u . u . u . u . c » , c <r •< < « i U l ) u u u o ui o --i I N oi in vu r- to >' i J I N ( N i i ( N ( N I N r l ( N I N I N I N I N ( N ,"N . - a. u u cj u (J o a. cu u u u u u rc. i r-l HJ c m IN i 1 O i-l CN r- 00 Ot O r i I N CO Ol O r l I N Ji O <•< tN O •-< CM .-• I N I N Oi Ot f J U CJ U O O (J CJ IJ U (J U U U O (> CJ U CJ CJ U CJ U (J LI I - U. I I HI [ft til (Q I o , a . a , i i . O u t ^ i v . a . a . ( i . i i ,n m m m m ui t i o r i in m m ifi »1 (ii ul Ul ul fli id Hi P» <n f i ci ro n n I ' I n ^ if «J> • •! • • < i r i . H • i I N T I N CN C*> ci c i — l O U CJ CJ O CJ L> U O U 1>, U. In U, U. U. bi [•< in I». U. u u c j u u a . f u o ( J u u u o - u u , t j t . ) C i < 260 Appendix A12 [Rh{714-(C6H5)NHCH2Ph}(PPh3)2JPF6(21a) Table A12.3. Bond Angles (°) (contd.) o tTi r- cu a) ••• ' J l O u> m m m m ro ca m m m m ai m i - !-• oi to iO ui iii cn ui u u u i i u u o y u o in m iii ni m m U o o t j u u u u (.J u cu oi rH o o u> o -a- a> o OOOCOOCOr-lO 11 r- , . H ol n O H IN .1: *i; CQ < jo ro m ^ «7 ^ --r •sr «r >^  vi- vr X x x x a; x :i: x x x i i i i i i i i i • ( j U O O U t J U U O U I I I I 1 I I I I I cu -era , H ,_ -r -J- i i T « [ i ( J U Z 7. U U K U U 261 Appendix Al2 [Ir(H)2{PhCH2N=C(Ph)(o-CJI4)}(PPh3)2] (22*a) Appendix A13 erimental Details for [Ir(H)2{PhCH2A^=C(Ph)(o-C6H4)}(PPh3)2] (22*a) Identification code Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions Volume Z Density (calculated) Absorption coefficient F(000) Crystal habil and color Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Observed Reflections Compleleness lo Iheta = 25.21° Absorption correction Max, and min. transmission Refinement method Dala / restraints / parameters Goodness-of-fit on F 2 Final R indices [I>2sigma(I)] R indices (all dala) Largest diff. peak and hole 01353bbb CJSH48 I rNP ; 989.09 173(2)K 0.71073 A Monoclinic P2,/c a = 20.533(3) A a= 90°. b= 12.0437(19) A P= 117.526(3)°. c = 20.404(3) A y = 90°. 4474.7(12) A5 4 1.468 Mg/mJ 3.094 mm'1 1992 Yellow, Plate 0.22 x 0.20 x 0.07 mm3 2.00 to 25.21°. -24>h>21,-14>k> 14, 0> 1 > 24 48200 7877 [R(int) = 0.0682] 6640 97.5% Multiscan 1.000000 and 0.773411 Full-matrix least-squares on F 2 7877/2/551 1.098 Rl =0.0430, wR2 = 0.1278 Rl. = 0.0533,wR2 = 0.1360 2.082 and -2.524 e.A"5 262 Appendix Al3 [Ir(H)2{PhCH2N=C(Ph)(o-C6H4)}(PPh3)2J (22*a) Table A13.1. Atomic Coordinates and B eq M fS M (N (N M <N fN (N fN fN CN fN CN CN CN CN CN CO m <n m m <n m «n m m vi co CN co m ro ro fN >© r - O oo 00 rO 00 in O vO " S O\ O V fl tj ifi ft rt V -« N M - M m if in in — oo in r» m CN ro — CN m m o § in m in —• ON — tn — oo — r— m O C N r o O i \ 0 0 > t O C S f N C O C O C N t N C N -* oo m CN 3 G *t >n m in m •* oo ro <n 5" O* in CN* w-l ro O N* CN Oi r— ON — 06 CN 0\ CN co so so m \o so O — c N m ^ r ' n ' O r - o o ON O — CN ro *r r O r o r o r o f n m c o c i r O f N f O ^ j - ' i j ' T j - T t ' i -U U O U U U U U U C u U O U U U U r — o o o o — C N c o T t m » o ^ t ^ ^ r m i n i n i n u i i n i n U U O U U O U O U O <N fN fN in O ^ >n co CN CN CN CO (N fN CO CN CN CN CN S N S * & tN CO CN CN — in o * fN CN CN OO iO (N m »o m >n CN oo m »o fN CN CO — N3 oo m oo ro CN in CN 3 3 0 0 OO CN C— —• O oo r-_ CN. NJJ oo CN CN CN fN _ _ sO CN ro oo m r - oo oo oo © 00 3 o «n >n m co CN oo CN 0\ in o oo to CN co CN in ON - H t m co CO CN OO OO v© m m m m • 5 Z U U U U U C J C J U S u O U U V CJ u u oo o o —. — CN CJ U CJ 263 Appendix Al3 [Ir(H)2{PhCH2N=C(Ph)(o-C6H4)}(PPh3)2] (22*a) Table A13.2. Bond Lengths (A) Cj UO i n *o M oo o> O — 0 s q c g q c •*r u-i P- r - oi ON 0 G G 0 S 0 3 oo m c j c j o u c j c j c j r o W Oi m " ro ro ro u u u c j c j c j c j c j cj !9-C40 I0-C41 U-C42 12-C43 13-C44 15-C46 CJ 0 U CJ O 0 u u u u u u o u u ^ w O r - w OO OO OO tN CN ON fN OO CN OO <N OO I— •—• — Q f l «-) sO CO 1 I S ? B cj £ G CJ a 6 u cj 4 IT) o cj — ( N r o m o o r - o o o o o r N r o ^ r C S = 2 G g G 5 g q c g g g g g g q q q q O O U C J U U U O U O C J U U O E E E O C J U U 264 Appendix A13 [Ir(H)2{PhCH2N=C(Ph)(o-C6H4)}(PPhi)2] (22*a) Table A13.3. Bond Angles (°) > O i n o o o o o a o o r - r - * O i O o o o o D o r - r i O) ^ ^ ^5 i~~ if ot (5 IN r- TJ — d d r N o b o i r s r ^ i n - o — 6 d c?i -ft. CJ CJ CJ S t 5 " b> V V V u u u u u u m m m **o rs rs ^ "i "i U £ ft, O U U CJ m m m m u u u cy u u M j > t < r S r o ^ t m ^ t — • i n « n m m i n i n i n » n C J C J C J C J C J C J C J U m rs rs 5 „ Z - - - cj cj y u a J= i 3, £ E E E E E G a. o. (J o* o\ d> 0 0 $ ro rs CJ CJ 5 5 U U U U U U U C J C J U C J C J C J U C J U 3 o O ro r— iO «o 00 00 00 oo 00 ro ro rs 5C rs — oo X Co OS rn in" o» in ro oo ro P •n 2T ci oo in oi u-i oi d d d d d oi d oi d ai Oi oi d oi d CO Oi — d o oi d rs rs O O ON — — rs rs rs rs rs rs rs rs rs u u u u vo r~ oo oi U U U CJ ro — 0 0 G E u u o cj <J 0 c rs ro rs m iO in oo O a, a. U — — — r s r n , d - ' j - ) i O r - r - r - - o o r n r ^ r o — o > o r s — ^ f o ^ — r s r s o o r -G G u G G G O G O a G G o G G G ft. ft. ft, ft. G 0 os 6 G 0 0 G U u u a. CJ u u CJ CJ U U CJ u u 3 3 (J u cj u o o u * » s m r- r- r- r-rs r*; O m of OO in O) Ol •o rs ro iO Oi m ro oi co d oi od d rs 00 oi rs rs rs rs rs rs t ~ — o — C J C J C J n U U L ) •o 2 E E o . a . E O i 2 U U U O O O O i A U C J ( J U O u 2 ° < i - - " 4 - - -V S s i s i S i S Z j o ^ C G G O G G ^ 5 6 G 5 o 2 K 6 6 o S S G G b D 5 5 G o i 265 Appendix Al3 

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