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An investigation into the synthesis and catalytic hydrogenation activity of rhodium - stannous - chloride… Thackray, David Carden 1983

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AN INVESTIGATION INTO THE SYNTHESIS AND CATALYTIC HYDROGENATION ACTIVITY OF RHODIUM - STANNOUS -CHLORIDE COMPLEXES By DAVID CARDEN THACKRAY B.Sc. Concordia U n i v e r s i t y , 1978 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Chemistry We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA September, 1983 ©David Carden Thackray, 1983 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e head o f my department o r by h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 Wesbrook P l a c e V ancouver, Canada V6T 1W5 Date 3E-6 (2/79) i i ABSTRACT RhCl 3 ;3H 20 i n 3M HC1 or ethanol was t r e a t e d with various amounts of SnCl 2;2H 20 and R4NC1 (R = Me, Et) or [Et^N ] [ S n C l ^ ] . K i n e t i c products obtained i n c l u d e [ R h C l 2 ( S n C 1 3 ) 4 ] 3 " and the new complex [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 ~ . At longer r e a c t i o n times [ R h C l ( S n C l 3 ) 5 ] 3 " , [ R h C l 3 ( S n C l 3 ) 3 ] 3 " and [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] a m o n g s t other uncharacterised complexes, were found. The r e l a t i v e proportions of the'complexes formed were dependent on the use of aerobic or anaerobic c o n d i t i o n s , temperature, r e a c t i o n time, p r e c i p i t a n t and l i g h t . The products were c h a r a c t e r i s e d using UV-VIS andc i n f r a r e d spectroscopy and where p o s s i b l e by elemental a n a l y s i s , conductance and t i n Mossbauer spectroscopy. Based on the v a r i a b i l i t y of product mixture under d i f f e r e n t s y n t h e t i c c o n d i t i o n s , a Rh(I) c a t a l y s e d s u b s t i t u t i o n a t Rh(III ) centres i s b e l i e v e d to a f f o r d the i n i t i a l R h(III) a n i o n i c complexes. Other Rh(I) products form v i a reduction of Rh(III) to Rh(I) by S n ( I I ) . Thermodynamic products r e s u l t from slow e q u i l i b r a t i o n of the i n i t i a l product mixture. The a n i o n i c products obtained were found to be l i g h t - s e n s i t i v e i n s o l u t i o n . A p r e l i m i n a r y study of s i m i l a r complexes, formed i n s i t u , as c a t a l y s t precursors f o r the hydrogenation of fumaric and maleic acids was undertaken. In 3M HC1 (or 3M DC1/D20) at 80°C and under 450 mmHg of H 2 (or D 2) the most c a t a l y t i c a l l y a c t i v e systems were those c o n t a i n i n g S i i ( I I ) and Rh(II I ) with a t e n - f o l d excess of o l e f i n over R h ( I I I ) . An increase to t h i r t y - f o l d excess o f o l e f i n markedly decreased a c t i v i t y although a c t i v i t y was independent o f the i i i presence of S n ( I I ) . A s t o i c h i o m e t r i c r e d u c t i o n by S n ( I I ) , or rhodium-tin c h l o r i d e complexes plus two protons, was found to compete with the c a t a l y t i c processes. Deuterium scrambling was observed f o r both c a t a l y t i c and s t o i c h i o m e t r i c systems. In the absence of Rh, t h i s suggested the intermediacy of t i n hydrides formed v i a B - e l i m i n a t i o n of t i n - a l k y l i ntermediates. As a working hypothesis, a conventional c a t a l y t i c mechanism i s proposed t o operate v i a a 'hydride r o u t e 1 i n v o l v i n g rhodium mono-hydrides formed by h e t e r o l y t i c s p l i t t i n g of H 2 (or D 2). Evidence a l s o suggests that s t o i c h i o m e t r i c reduction of the o l e f i n by a r h o d i u m ( I ) - t i n c h l o r i d e complex r e s u l t i n g i n o x i d a t i o n of Rh(I) t o R h ( I I I ) may be coupled to the hydrogen r e d u c t i o n o f R h ( I I I ) t o Rh(I) i n the most a c t i v e hydrogenation system. i v Table of Contents Page ABSTRACT i i LIST OF TABLES v i i i LIST OF FIGURES x ABBREVIATIONS x v i i ACKNOWLEDGEMENTS xx CHAPTER I. INTRODUCTION 1 1.1 Mechanisms of o l e f i n hydrogenation 3 1.1.1 A c t i v a t i o n of hydrogen 6 1.1.2 A c t i v a t i o n of substrate and hydrogen t r a n s f e r 9 1.2 Role of t r i c h l o r o s t a n n a t e ( I I ) i n c a t a l y s i s 17 1.3 Aim of t h i s work 20 CHAPTER I I EXPERIMENTAL METHODS 21 2.1 M a t e r i a l s 21 2.1.1 Solvents 21 2.1.2 Gases 21 2.1.3 O l e f i n i c substrates 22 2.1.4 Other m a t e r i a l s 22 2.1.5 Rhodium complexes 22 2.1.5.1 Preparation of f a c - [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] 23 2.1.5.2 Preparation of [ M e 4 N J 3 [ R h C l 2 ( S n C l 3 ) 4 ] • H 20 26 V Page 2.1.5.3 Preparation of [Me 4NJ 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] ( E t 4 N C l ) 0 > 5 2 7 2.1.6 Other s y n t h e t i c experiments discussed i n Chapter I I I 33 2.1.6.1 Trapping experiments using [ E t ^ j " LSnCl 3 ] 34 2.1.6.2 Reaction between [ R h 2 C l 2 ( C 0 T ) 4 ] and [ E t 4 N ] [ S n C l 3 l 36 2.2 Techniques 37 2.2.1 I n f r a r e d spectroscopy 37 2.2.2 E l e c t r o n i c spectroscopy 38 2.2.3 NMR spectroscopy 40 2.2.4 Mossbauer spectroscopy 41 2.2.5 C o n d u c t i v i t y measurements 41 2.2.6 Gas chromatography 41 2.2.7 Mass spectrometry 42 2.2.8 Gas Uptake measurements 42 2.2.9 Determination of Fe reduction e q u i v a l e n t s 45 2.2.10 Elemental a n a l y s i s 45 2.3 Computational techniques 46 CHAPTER I I I . RESULTS (PART I).THE SYNTHESIS OF VARIOUS TIN-CONTAINING RHODIUM COMPLEXES 3.1 I n t r o d u c t i o n 4 8 3.2 The nature o f [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 " 48 3.3 E f f e c t o f v a r i a t i o n of some parameters on the s y n t h e t i c 53 methods used i n 3M HC1 57 v i Page 3.3.1 P r e c i p i t a n t s i z e 56 3.3.2 Anaerobic vs. aerobic c o n d i t i o n s 61 3.3.3 V a r i a t i o n of Sn(II):Rh(111) r a t i o , and temperature 66 3.3.4 The e f f e c t of ambient l i g h t 77 3.4 Attempts to prepare s a l t s of [ R h 2 C l 2 ( S n C l 3 ) 4 ] 4 ~ 80 3.5 1 1 9 S n FT NMR experiments 93 3.6 Discussion 104 3.6.1 K i n e t i c products 105 3.6.2 Subsequent r e a c t i o n products 108 CHAPTER IV. RESULTS (PART I I ) . REACTIONS OF THE COMPLEXES 113 4.1 I n t r o d u c t i o n 113 4.2 SnCl 2(CH 3CN) 117 4.3 F a c - [ R h C l 3 ( S n C l 3 ) 3 ] 3 " and t r a n s - [ R h C l ' 2 ( S n C l 3 ) 4 J 3 " 117 4.4 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 " 126 4.5 Conclusion 131 CHAPTER V. RESULTS (PART I I I ) . HYDR0GENATI0N OF MALEIC AND FUMARIC ACIDS 133 5.1 I n t r o d u c t i o n 133 5.2 Stoichiometry and k i n e t i c s a t low [MA] 134 5.3 Deuteration s t u d i e s a t low [ o l e f i n ] 139 5.4 Stoichiometry and k i n e t i c s a t high [MA] 142 5.5 Reduction i n the absence of H 9 147 v i i Page 5.6 Discussion ^4 CHAPTER VI. GENERAL CONCLUSIONS 161 REFERENCES 1 6 4 APPENDIX A 1 ? 5 APPENDIX B APPENDIX C v i i i LIST OF TABLES Table Page 2.1 S o l u t i o n UV-VIS data f o r [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] : 2.2 S o l u t i o n VIS data f o r the Rh(II I ) stock s o l u t i o n 45 3.1 Far-IR absorption frequencies (cm~^) reported f o r [ R 4 N ] 4 [ R h 2 X 2 ( S n C l 3 ) 4 ] 49 3.2 Mossbauer data f o r various rtiodium-tin c h l o r i d e complexes 54 3.3 Far-IR data reported f o r Group V H I - t i n ( I I ) c h l o r i d e complexes , 57 3.4 P a r t i a l elemental analyses f o r products obtained from [ R h C l 3 ( S n C l 3 ) 3 ] synthesis using Et^NCl-HgO p r e c i p i t a n t .. 61 3.5 P a r t i a l elemental a n a l y s i s f o r [ R h C l 3 ( S n C l 3 ) 3 ] ~ s a l t s 67 3.6 P a r t i a l elemental a n a l y s i s of y e l l o w p r e c i p i t a t e from ethanol ( E t 4 N + s a l t ) 85 3.7 P a r t i a l elemental a n a l y s i s of brown p r e c i p i t a t e from ethanol ( E t 4 N + s a l t ) 87 119 3.8 Sn FT NMR c h a r a c t e r i s t i c s of various rhodium-tin complexes.. 94 119 3.9 Sn FT NMR c h a r a c t e r i s t i c s o f rhodium-tin complexes observed i n 3M DC1/D20 s o l u t i o n with Sn/Rh = 3 98 4.1 P s e u d o - f i r s t order r a t e s of decomposition o f [ M e 4 N ] 3 ~ [ R h C l 2 ( S n C l 3 ) 4 ] - H 2 0 i n CH3CN 126 4.2 P s e u d o - f i r s t order rates of decomposition o f [ E t 4 N ] 3 ~ [ R h ( S n C l 3 ) ( S n C l 4 ) ] - ( E t 4 N C l ) 0 g i n CH-jCN ,.. 131 i x Table Page 5.1 K i n e t i c data at 80°C f o r the Rh/Sn/hyMA system i n 3M HC1 135 5.2 K i n e t i c data a t 80°C f o r the Rh/Sn/H 2(D 2)/olefin system i n 3M DC1/D20 139 5.3 K i n e t i c and spectroscopic data f o r the Rh/Sn/H2/MA system i n 3M HC1 144 5.4 Extent of reduction of MA to SA at various times with net o x i d a t i o n of Sn(II) to Sn(IV) i n 3M HC1 148 5.5 Extent of reduction of MA or FA to SA at various times with net o x i d a t i o n of Sn(II) to Sn(IV) i n 3M DC1/D20 152 5.6 Comparison of rates of H 2 uptake f o r various c a t a l y t i c systems f o r the hydrogenation of MA at 80°C 155 X 1IST OF FIGURES Figure Page 2.1 Far-IR spectrum of f a c - [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] compared to t h a t reported i n r e f . 91 24 2.2 3M HC1 s o l u t i o n UV-VIS spectrum of [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] compared to that reported i n r e f . 91 25 2.3 CH3CN s o l u t i o n UV-VIS spectra of [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] without added c h l o r i d e and w i t h a 10-fol d excess o f Et 4NCl-H 20 26 2.4 Far-IR spectrum of [M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] - H g O compared to t h a t reported i n r e f . 91 28 2.5 I n i t i a l CH3CN s o l u t i o n UV-VIS spectrum o f . [ M e 4 N ] 3 -[ R h C l 2 ( S n C l 3 ) ] -H20 29 2.6 Mossbauer spectrum of [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] - H 2 0 at 77°K 30 2.7 Far-IR spectrum of u n r e c r y s t a l l i z e d [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 -( S n C l 3 ) ] • ( E t ^ N C l ) Q 5 compared to th a t a f t e r r e c r y s t a l l - i i z a t i o n from CH3CN 32 2.8 I n i t i a l CH3CN s o l u t i o n UV-VIS spectrum of [ E t 4 N ] 3 -[ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] - ( E t 4 N C l ) 0 5 33 2.9 Mossbauer spectrum of [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] -• ( E t 4 N C l ) 0 5 a t 77°C 35 2.10 Anaerobic s p e c t r a l c e l l 39 2.11 Uptake f l a s k (25 mL) 44 3.1 The molecular s t r u c t u r e of [ R h f S n C l ^ f S n C l y , ) ] 5 " 50 x i Figure Page 3.2 D i s t r i b u t i o n of rhodium complexes i n 3M HC1 s o l u t i o n as a f u n c t i o n of mole r a t i o of t o t a l coordinated t i n to t o t a l rhodium 52 3.3 3M HC1 s o l u t i o n UV-VIS spectra of , [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] and [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] 55 3.4 I n i t i a l CH3CN s o l u t i o n UV-VIS spectra of (a) [Me 4N] 3-[ R h C l 3 ( S n C l 3 ) 3 ] and (b) that obtained using E t 4 N + 59 3.5 Far-IR spectra of (a) [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] and (b) of the product obtained using E t 4 N + 60 3.6 I n i t i a l CHgCN s o l u t i o n UV-VIS spectra o f (a) [Me 4N] 3-[ R h C l 2 ( S n C l 3 ) 4 ] with (b) that o f the product obtained using E t 4 N + and (c) the r e s u l t a n t spectrum a f t e r s u b t r a c t i o n of that of [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 _ 62 3.7 Far-IR spectra of (a) [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 J and (b) of the product obtained using E t 4 N + compared to (c) [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] - ( E t 4 N C l ) n 5 spectrum 63 3.8 Far-IR spectra of (a) [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] and the! ; i s o l a t e d products of the anaerobic synthesis using (b) Me 4N + and (c) E t 4 N + 64 3.9 I n i t i a l CH3CN s o l u t i o n UV-VIS spectrum of the product obtained using E t 4 N + i n the synthesis of [Me 4N] 3~ [ R h C l 3 ( S n C l 3 ) 3 ] under anaerobic c o n d i t i o n s 65 3.10 Comparison o f (a) r e s u l t a n t spectrum a f t e r the sub-t r a c t i o n of 0.38 x f i g . 2.8 ( [ R h C l ( S n C l 3 ) 5 J 3 ~ ) from f i g . 3.9 with (b) [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] spectrum 66 x i i F i g u r e Page 3.11 IR s p e c t r a o f (a) t h e p r o d u c t i s o l a t e d , u s i n g E t 4 N + , o f t h e s y n t h e s i s f o r [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] under a n a e r o b i c c o n d i t i o n s , u s i n g S n ( I I ) / R h ( I I I ) = 5, and (b) the same p r o d u c t s e v e r a l months l a t e r 68 3.12 F a r - I R spectrum o f (a) t h e i s o l a t e d p r o d u c t o f th e s y n t h e s i s f o r [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] under a n a e r o b i c c o n d i t i o n s and u s i n g S n ( I I ) / R h ( I I I ) = 5, compared t o (b) [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] spectrum, 69 3.13 I n i t i a l CH 3CN s o l u t i o n s p e c t r a o f t h e p r o d u c t s i s o l a t e d u s i n g ( a ) the s y n t h e s i s o f [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] w i t h E t 4 N + , a n a e r o b i c c o n d i t i o n s and S n ( 1 1 ) / R h ( I I I ) = 90 5 and (b) t h e p r o d u c t o f t h e l i t e r a t u r e s y n t h e s i s o f [ M e 4 N ] 3 [ R h C l ( S n C l 3 ) 5 ] 70 119 3.14 The 37.336 MHz 1 3 S n FT NMR s p e c t r u m o f t h e p r o d u c t 90 i s o l a t e d u s i n g the l i t e r a t u r e s y n t h e s i s o f [ M e 4 N ] 3 [ R h C l ( S n C l 3 ) 5 ] 72 3.15 IR s p e c t r a o f the (a) f i r s t p r e c i p i t a t e and ( b ) s e c o n d p r e c i p i t a t e i s o l a t e d u s i n g [ E t 4 N ] [ S n C l 3 ] 74 3.16 The i n i t i a l CH 3CN s o l u t i o n UV-VIS s p e c t r a o f (a) t h e f i r s t p r e c i p i t a t e and (b) second p r e c i p i t a t e u s i n g [ E t 4 N ] [ S n C l 3 ] compared t o ( c ) f i g . 3.6a 75 3.17 F a r - I R s p e c t r a o f t h e (a) f i r s t and (b) second p r e c i p i t a t e s i s o l a t e d u s i n g [ E t 4 N ] [ S n C l 3 ] compared t o f i g . 3.7b '76 xi i i Figure Page 3.18 Far-IR spectra of the product isolated from the trapping experiments in the dark 78 3.19 Initial CH^ CN solution spectrum of the product isolated from the trapping experiments in the dark 79 3.20 Initial CH3CN solution UV-VIS spectra of products 10 3 isolated using the reported synthesis of [Me^ N]^ -[Rh2Cl2(SnCl3)4] 81 3.21 IR spectrum of the product isolated using the 103 reported synthesis of [Me4N]4[Rh2Cl2(SnCl3)4] 82 3.22 Far-IR spectra of (a) the product isolated using 103 , the reported synthesis of [Me4N]4[Rh2Cl2(SnCl3)4] but under anaerobic conditions compared to (b) fig. 3.12a 83 3.23 Initial CH3CN solution UV-VIS spectra of the isolated 103 _ products using the reported synthesis of [Me4NJ4-[Rh2Cl2(SnCl3)4] but under anaerobic conditions in ethanol 84 3.24 Far-IR spectra of the products isolated using the 10 3 reported synthesis of [Me4N]4[Rh2Cl2(SnCl3)4] but under anaerobic conditions in ethanol 86 3.25 Far-IR spectrum of the isolated product of the reaction between RhCl3'3H20 and SnCl2-2H20 in the presence of excess Li Cl in ethanol 89 3.26 Initial CH3CN solution spectrum of the isolated product of the reaction between RhCl3-3H20 and SnCl2'2H20 in the presence of excess Li Cl in ethanol 90 x i v Figure Page 3.27 Far-IR spectra of (a) the purple product of the r e a c t i o n o f [ R h 2 C l 2 ( C 0 T ) 4 ] with [ E t 4 N ] [ S n C l 3 J a n d (b) the same product a f t e r a i r o x i d a t i o n 91 3.28 I n i t i a l CH3CN s o l u t i o n UV-VIS spectrum of the purple product of the r e a c t i o n of [ R h 2 C l 2 ( C 0 T ) 4 ] with [ E t 4 N ] [ S n C l 3 ] 92 119 3.29 Sn FT NMR spectra of 3M HC1 s o l u t i o n s c o n t a i n i n g various r a t i o s of Sn(II) and Rh(II I ) c h l o r i d e s 95 3.30 The 29.88 MHz 1 1 9 S n FT NMR spectrum of a 3M DC1/D20 s o l u t i o n c o n t a i n i n g a S n ( I I ) / R h ( I I I ) r a t i o of 3, under Ar 96 119 3.31 The 29.88 MHz 3Sn FT NMR spectrum of an ethanol i c s o l u t i o n (15% acetone-dg) c o n t a i n i n g a 1:3:3 r a t i o of R h ( I I I ) , Sn(II) and L i C l under Ar 97 3.32 P l o t of I ^ , 4 . „ n i - + ^ / I „ , • vs. the number of coordinated s a t e l l i t e main 1 1 9 S n and 1 1 7 S n n u c l e i (n) 99 3.33 Comparison of observed and synthesized resonances f o r [RhCl(SnCl3)5] as observed i n ethanol/acetone-dg s o l u t i o n 102 4.1 P a r t i a l molecular o r b i t a l diagram f o r an octahedral d^ complex showing LMCT t r a n s i t i o n s 114 XV Figure Page 4.2 Solution UV-VIS spectra of [Me 4 N] 3 [ RhC l 3 ( SnC l 3) 3l in 3M HC1 showing progressive changes due to exposure to room i l luminat ion 116 4.3 CH3CN solut ion spectra of SnCl 2(CH 3CN) (a) and of (b) a s im i l a r solut ion during a i r oxidation 118 4.4 CH3CN solut ion UV-VIS spectra of [Me 4 N] 3 [RhCl 3 ( SnCl 3 ) 3 ] : (a) f i n a l spectrum in the absence of added E t^C l - r ^O and (b) with 8.7-fold excess of Et^Cl-h^O, compared with the i n i t i a l spectrum in 3M HC1 119 4.5 CH3CN solut ion UV-VIS spectra of [Me 4 N] 3 [RhCl 2 (SnCl 3 ) 4 ]-•H20 (a) in absence of added Et 4 NCl-H 2 0, (b) with a 12-fold excess and (c) a 23-fold excess of the sa l t 121 4.6 Comparison of CH3CN so l tu t ion UV-VIS spectra of [Me 4 N] 3 [RhCl 3 (SnCl 3 ) 3 ] and (b) [Me 4 N] 3 [RhCl 2 (SnCl 3 ) 4 ]-•H20 in the absence of Et^NCl-HgO; (c) and (d) are with a 8.7-fold excess and a 12-fold excess of .Et 4NCl-H 20 respect ively 122 4.7 Plots of absorbance at 420 nm vs time for the decomposition of trans-[Me 4 N] 3 [RhCl 2 (SnCl 3 ) 4 ]-H 2 0 in CH3CN 125 4.8 CH3CN solut ion UV-VIS spectra of [Et 4 N] 3 [Rh(SnCl 3 ) 4 -(SnC l 4 ) ] - ( E t 4 NCl )Q 5 a f te r decomposition in the presence of various amounts of added sa l t s 128 x v i Figure Page 5.1 H 2 uptakes f o r the Rh/Sn/h^/MA system i n the l i g h t and dark i n 3M HC1 s o l u t i o n at 80°C 136 5.2 Acetone-dg s o l u t i o n 80 MHz *H NMR spectrum of the ether evaporate from the hydrogenation of MA at low [MA] and a Sn/Rh r a t i o of 3 137 5.3 UV-VIS spectra of uptake s o l u t i o n s 138 5.4 400 MHz H^ NMR spectrum of the deuterated products from the hydrogenation of MA (expanded SA methylene region) 141 5.5 H 2 uptakes f o r the Rh/H2/MA system and Rh/Sn/H2/MA system a t high [ o l e f i n ] i n 3M HC1 at 80°C 143 5.6 *H NMR monitoring of the reduction of FA by Sn(II) i n the presence of Sn(IV), i n 3M DC1/D20 149 5.7 Expansion of SA methylene region of the *H NMR spectrum (400 MHz) of the same sample r e f e r r e d to i n f i g u r e 5.6 150 5.8 Comparison of the changes i n absorbance and *H NMR w i t h time f o r the reduction of FA by the Rh/Sn/DCl/D 20 system 153 x v i i ABBREVIATIONS The f o l l o w i n g l i s t o f a b b r e v i a t i o n s , most of which are commonly adopted i n chemical l i t e r a t u r e , w i l l be employed i n t h i s t h e s i s . A absorbance Ag " at time = zero A " " " = ' i n f i n i t y ' A , , A , " : observed value, c a l c u l a t e d value obs! c a l c . aq. aqueous br,s broad and strong Bu t t e r t i a r y butyl c a l c . c a l c u l a t e d c a t . c a t a l y s t [ ] Q concentration at time = zero COD cyclooctadiene COT cyclooctene 6 chemical s h i f t DMA N,N-dimethylacetamide DMSO dimethyl s u l f o x i d e diphos 1 ,2-diphenylphosphinoethane dipy 2 , 2'-dipyridyl E non-metal atom e e x t i n c t i o n c o e f f i c i e n t eq'n. equation Et ethyl en ethylenediamine f i g . f i g u r e x v i i i FT F o u r i e r Transform F.I.D. Free Induction Decay FA fumaric a c i d I s p i n or i n t e n s i t y IR I n f r a r e d I.S. Isomer S h i f t J c o u p l i n g constant In natural l o g a r i t h m * wavelength * v " at maximum absorbance m medium MA maleic a c i d MLA malic a c i d Me methyl M Molar or metal atom M.O. molecular o r b i t a l vi- chemical formula p r e f i x f o r a b r i d g i n g atom v frequency nbd norbornadiene NMR nuclear magnetic resonance PPhg triphenylphosphine PMePh 2 methyldiphenylphosphine press. pressure py p y r i d i n e Q.S. Quadrupole S p l i t t i n g x i x R a l k y l r e l . r e l a t i v e r c o r r e l a t i o n c o e f f i c i e n t s strong sec. s e c t i o n sh shoulder S/N s i g n a l to noise r a t i o sol 'n s o l u t i o n SA s u c c i n i c a c i d *<> time zero \ h a l f - l i f e UV-VIS u l t r a v i o l e t - v i s i b l e XSn o r xSn mole f r a c t i o n of Sn w weak XX ACKNOWLEDGEMENTS I wish to thank Professor B. R. James f o r h i s encouragement and h e l p f u l d i s c u s s i o n s throughout the course of t h i s work. I would a l s o l i k e to express my g r a t i t u d e to the members of the NMR 119 department f o r t h e i r guidance during the Sn FT NMR experiments, to Dr. J . Sams and L. S a l l o s f o r the t i n Mosstrauer measurements and to the members of the group who made the l a s t few years so enjoyable. CHAPTER I INTRODUCTION Synthesis of organics using s o l u b l e t r a n s i t i o n metal c a t a l y s t s i s i n d u s t r i a l l y important. Recent production i n the U.S. i s over 10,000,000 tons /annum!. Although not la r g e r e l a t i v e to heterogeneously c a t a l y s e d production, i t i s of r e l a t i v e l y high d o l l a r value*. P r i n c i p a l processes and key t r a n s i t i o n metals i n c l u d e hydroformyation (Co, Rh), c a r b o n y l a t i o n (Co, Rh), hydrocarbon o x i d a t i o n (Co, V, Cu, Mn, Pd, Mo), polymerization (Cu, Co, Mn, Zn, T i , Sb, N i , V), o l e f i n / d i e n e r e a c t i o n s ( N i , Rh, T i , Cu), hydrogenation 1 2 3 (Rh, Ni) and, a d d i t i o n of HCN (Ni) ' ' . Cobalt-based processes are most common i n terms of numbers and tonnage. Rhodium i s dominant among second-row t r a n s i t i o n - m e t a l s . The most important processes are the Wacker (hydrocarbon o x i d a t i o n , eq'n 1.1), v i n y l acetate (hydrocarbon o x i d a t i o n , eq'n:1.2), Oxo (hy d r o f o r m y l a t i o n , eq'n 1.3), methanol c a r b o n y l a t i o n (eq'n 1.4) and 5 Z i e g l e r - N a t t a p o l y m e r i z a t i o n (eq'n 1.5) . C 2H 4 + h 0 2 PdCl 2/CuCl 2(aq) (1.1) C2H 4 + %°2 + C H 3 C 0 2 H PdCl 2/CuCl 2(aq) > CH 3C0 2CH=CH 2 + H 20 (1.2) RCH=CH2 + CO + H 2 HCo(CO). (organic sol'n) ,CH0 » RCH9CH9CH0 + RCH (1.3) ) 2 2 -CH3 R h C l ( C 0 ) ( P P h 3 ) 2 (organic sol'n) -2-RhCl(CO)(PPhJ,/CH,I promoter CH3OH + CO — - > CH 3C02H (1.4) aqueous or organic s o l u t i o n — T i C l - ( s ) + A1(C9H,)„C1 C 2 H 4 T-1-. . \ \ . > V n ( C 2 H 4 ) ( 1 . 5 A ) suspension i n organic s o l u t i o n C 3H 6 • > l / n ( C 3 H 6 ) n (1.5b) 3 Despite a vast l i t e r a t u r e , hydrogenation i s not as important on an 2 i n d u s t r i a l s c a l e as other processes, except f o r the synthesis of o p t i c a l l y 3 1 + 6 a c t i v e amino acid s ' ' using a rhodium c a t a l y s t w i t h c h i r a l phosphine lig a n d s (eq'n 1.6). £0~H c h i r a l * / C 0 2 H y C 0 2 H R C H < > R CH 2CH > RCH.CH 6 ) 12 'NHCOR c a t . , H 2 d ^NHCOR 2 S|\|H, As i n d i c a t e d by the equations above, reactants i n c l u d e small molecules such as CO, H 2, 0 2 and o l e f i n s combined i n a g a s - l i q u i d process. Conditions are m i l d , t y p i c a l l y a t 70-150*C and ^  20 atm., p o t e n t i a l l y l e a d i n g to greater 6 s e l e c t i v i t y . For i n d u s t r i a l c a t a l y t i c processes, p r a c t i c a l ranges o f temperature and pressure are g e n e r a l l y 20-500*C and up to hundreds of 2 atmospheres , so homogeneous systems can a l s o o f f e r savings i n energy c o s t s . While no a p r i o r i g u i d e l i n e s f o r choosing between heterogeneous and homogeneous c a t a l y t i c processes e x i s t , s e l e c t i v i t y , thermal c o n t r o l and e f f e c t i v e u t i l i z a t i o n of c a t a l y t i c s i t e s are u s u a l l y advantageous i n homogeneous systems. On the other hand, c a t a l y s t expense, product s e p a r a t i o n , c a t a l y s t l o s s , -3-2 3 6 c o r r o s i o n ahd mass-transfer problems are o f t e n disadvantageous ' ' . This t h e s i s i s concerned w i t h homogeneous c a t a l y t i c hydrogenation o f unsaturated d i c a r b o x y l i c a c i d s using r h o d i u m - t i n ( I I ) c h l o r i d e c a t a l y s t 2 precursors. While no u n i f i e d theory of c a t a l y s i s e x i s t s , some c a t a l y t i c hydrogenation r e a c t i o n pathways have been f i r m l y e s t a b l i s h e d . The e s s e n t i a l steps (see below) are a c t i v a t i o n of and s u b s t r a t e , hydrogen t r a n s f e r to o l e f i n and re l e a s e of the reduced product. The hydrogen t r a n s f e r and product release steps are u s u a l l y s t e r e o s p e c i f i c , r e s u l t i n g i n o v e r a l l c i s - a d d i t i o n of H 2 t o the s u b s t r a t e . 7 1.1 Mechanisms of o l e f i n hydrogenation The t r a n s i t i o n - m e t a l centre plays a key r o l e i n mediating the a d d i t i o n of H 2 to an o l e f i n . Concerted c i s - a d d i t i o n to double bonds i s symmetry forbidden i n the ground-state ( f i g . 1 . 1 ) , although thermodynamically favour-8 9 -able * . Step-wise a d d i t i o n o f H atoms i s unfavourable since homolytic — O* <*® L U M 0 (g ^ HOMO C=C H H Figure 1.1 Symmetry forbidden a d d i t i o n of hydrogen to a C=C bond. -4-10 cleavage of H 2 i s a high energy process (<\420 KJ/mole(aq.)) . A t r a n s i t i o n --metal can have f i l l e d d - o r b i t a l s of s u i t a b l e symmetry to i n t e r a c t w i t h the a* o r b i t a l ( or p o s s i b l y u n f i l l e d ones to accept e l e c t r o n - d e n s i t y from the H 2 a o r b i t a l ) ( f i g . 1.2). Transfer of e l e c t r o n - d e n s i t y from d- to a* o r b i t a l s d e s t a b i l i z e s the H-H bond lea d i n g to formation of a dihydrido-metal complex ( v i a I ) or a monohydrido-metal complex i f p o l a r i z a t i o n of the H-H bond ( i . e . M"-H---H , v i a I I ) occurs during cleavage. H e t e r o l y t i c cleavage i n the I II III Figure 1.2 P o s s i b l e o r b i t a l i n t e r a c t i o n s between H 2 and a t r a n s i t i o n - m e t a l centre. absence of metal i s more favourable (^155 KJ/mole (aq.)) than homolytic cleavage, and base c a t a l y s e d hydrogenation of aromatic ketones v i a hydride n attack and susequent protonation has been reported but not s i m i l a r reduction of C=C. Although a d i h y d r i d e i s of the c o r r e c t symmetry, d i r e c t e i s - a d d i t i o n 3 has not been proven . S u p e r f i c i a l l y s i m i l a r c i s - a d d i t i o n s to o l e f i n s are known f o r c i s dioxo- and d i n i t r o s y l - c o m p l e x e s which are considered to be -5-analogous to 1,3 d i p o l a r a d d i t i o n s . [CpCo(N0)] 2 + 2N0 > 2[CpCo(N0) 2] (1.7) ^1 ^2 N [CpCo(N0) 2] t Y > CpCo( X K 3 K4 0 oh R 2 (1.8) R/i R 3 The metal centre a l s o appears to be e s s e n t i a l f o r a c t i v a t i o n during the H t r a n s f e r s t e p . Ordinary i s o l a t e d double bonds are unreactive to 13-15 n u c l e o p h i l i c a t t a c k ( i . e . H or M-H), but coordinated o l e f i n s o f t e n are 16 8 r e a c t i v e . The reasons are not obvious but f o r d Pt complexes c o o r d i n a t i o n of H and o l e f i n i n a c i s - c o p l a n a r arrangement ( 1 ) , optimal f o r i n s e r t i o n , : '\ M - - c (I) removes unfavourable r e p u l s i o n between f i l l e d o l e f i n and hydride o r b i t a l s by 15 mixing these with o l e f i n TT* and metal d - o r b i t a l s . The r e p u l s i o n then occurs with an empty d o r b i t a l . The r e s u l t s do not n e c e s s a r i l y bear extension to other metals, but do i n d i c a t e another expected r o l e of a t r a n s i t i o n metal i n hydrogenation. The f o l l o w i n g s e c t i o n s present a b r i e f overview of e x p e r i m e n t a l l y derived observations regarding c a t a l y t i c hydrogenation. The examples used p r i n c i p a l l y i n v o l v e mononuclear Rh-based systems with monoene s u b s t r a t e s . More complete d i c u s s i o n s , i n c l u d i n g polynuclear complexes and polyene s u b s t r a t e s , are found i n recent reviews and books ' - 6 -1.1.1 A c t i v a t i o n of hydrogen Both h e t e r o l y t i c and homolytic cleavage of H 2 have been found to occur. Homolytic cleavage i s favoured f o r low o x i d a t i o n s t a t e , e l e c t r o n - r i c h metal-centres that are c o o r d i n a t i v e l y unsaturated; h e t e r o l y s i s i s favoured f o r higher o x i d a t i o n s t a t e , l a b i l e metal centres i n the presence of a proton sink ( u s u a l l y added base). Pol a r media s t a b i l i z e the p o l a r i z e d t r a n s i t i o n -s t a t e of the l a t t e r and p o s s i b l y the released proton as w e l l , i f b a s i c or hydrogen-bonding. Formation of a h y d r i d i c species i s not synonymous w i t h c a t a l y s i s s i n c e f o r k i n e t i c or thermodynamic reasons some are c a t a l y t i c a l l y 17 i n a c t i v e . ( i ) H e t e r o l y t i c cleavage The process i n v o l v e s l i g a n d replacement with no change i n formal o x i d a t i o n s t a t e (eq'n. 1.9, 1.10). A vacant s i t e or p r i o r l i g a n d d i s s o c i a t i o n M H X + H 2 v N M H H + H + + C l " (1.9) [ R h C l g ] 3 " + H 2 > [ R h H C l 5 ] 3 " + H + + C l " (1.10) may be re q u i r e d . The proton produced i s s t a b i l i z e d by added'lbase (often N E t 3 ) , so l v e n t or by i n t e r a c t i o n with the l i g a n d 'X', p o s s i b l y v i a a four-centre 18 t r a n s i t i o n - s t a t e (2) . The same net h e t e r o l y t i c s p l i t t i n g of H 2 could r e s u l t H---H i i i i i > M X (2) from an i n i t i a l o x i d a t i v e a d d i t i o n followed by re d u c t i v e e l i m i n a t i o n of HC1, 19 20 p o s s i b l y base a s s i s t e d (1.11-1.13) ' . The i n i t i a l o x i d a t i v e a d d i t i o n i s 21 l e s s l i k e l y f o r R h ( I I I ) but i s p o s s i b l e f o r Ru(II) (e.g. RuH A(PPh,) Q formation) . -7-M°X + H 2 X M H H 2 > M°H + HX (1.11) RhClL 3 + H 2 RhH 2ClL 3 b a s e > RhHl_3 + base-HCl (1.12) R h L 2 S 2 + + H 2 R h H 2 L 2 S 2 + b a s e > RhHL 2S 2 + base-H + (1.13) (L= t e r t i a r y phosphine, S= sol v e n t ) Hydrogenolysis of coordinated hydrocarbon ligands i s f o r m a l l y s i m i l a r (eq'n. 22 1.14) , probably v i a o x i d a t i v e a d d i t i o n of H 2 followed by re d u c t i v e e l i m i n -H 2 R-Rh(PPhJ^ \ > HRh(PPhJ~ + R-H (1.14) J J 0 C, 90 atm. J <> -a t i o n of R-H. The r e v e r s i b i l i t y of equation 1.9 can be a useful c h a r a c t e r i s t i c . K i n e t i c evidence i n conjunction w ithH 2~D 20 (or D 2~solvent) exchange provided 23 evidence of non-detectable mono-hydrides i n a number of systems Proton e l i m i n a t i o n from a mono-hydride sometimes leads to an a c t i v e hydrogenation system. This i s e x e m p l i f i e d by Rh(III) systems where two-equi v a l e n t reduction to Rh(I) occurs (eq'n. 1.15). The Rh(I) formed u s u a l l y R h I H H v V Rh 1 + H + (1.15) enters the c a t a l y t i c c y c l e i v i a substrate a c t i v a t i o n p r i o r to H 2 a c t i v a t i o n . 2k I n i t i a l steps such as these have been proposed f o r a number of systems i n c l u d i n g c h l o r o r h o d a t e ( I I I ) / D M A 2 5 , c i s - R h C l 3 ( E t 2 S ) 3 / D M A 2 6 and RhCl 3(DMS0) 3/ 27 DMSO . Chl o r o r h o d a t e ( I I I ) i n 3M HC1 was a l s o reduced i n the presence of o l e f i n to form a R h ( I ) - o l e f i n complex, which u n l i k e the analogous DMA system, was not 28 c a t a l y t i c a l l y a c t i v e . ( i i ) Homolytic cleavage O x i d a t i v e a d d i t i o n o f H 2 to mono-nuclear metal centres i s commonly 29 observed . Coordination number and formal o x i d a t i o n s t a t e increase by two -8-(eq n. 1.16, 1.17) . A d d i t i o n i s c i s , trans d i h y d r i d e s u s u a l l y r e s u l t i n g M 1 + H 2 M I H H 2 (1.16) t r a n s - I r X ( C 0 ) ( P R 3 ) 2 + H 2 I r H 2 X ( C 0 ) ( P R 3 ) 2 (1.17) from subsequent r e a c t i o n s such as c i s - t r a n s rearrangements (e.g. MH2L^ (M= 31 Fe, Ru ) ). Low o x i d a t i o n s t a t e , high metal b a s i c i t y and c o o r d i n a t i v e 32 unsaturation promote o x i d a t i v e a d d i t i o n , although a d d i t i o n o f H 2 to a saturated metal centre with concomitant l o s s of l i g a n d i s w e l l known( eq'n 33 1.18) . Note t h a t a d d i t i o n of hydrogen has been considered r e d u c t i v e f o r [ l r ( C O ) 2 ( P P h 2 M e ) 3 ] + + H 2 > [ l r H 2 ( C 0 ) ( P P h 2 M e ) 3 ] + CO (1.18) [ l r ( C 0 D ) L 2 ] and [ir(COD)] . This i l l u s t r a t e s the sometimes equivocable nature of o x i d a t i o n s t a t e formalism i n r e l a t i o n to metal hydrides which are perceived as becoming l e s s h y d r i d i c and more covalent or a c i d i c i n nature on 3 5 , 36 passing from the e a r l y to l a t e t r a n s i t i o n metal hydrides A d d i t i o n across two metal centres u s u a l l y r e s u l t s i n an increase of 37 formal o x i d a t i o n s t a t e and c o o r d i n a t i o n number of one (eq'n. 1.19-1.21) ... . ( M L n ) 2 + H 2 r = i 2MHLn (1.19) 2MLn + H 2 2MHLn (1.20) : 2 C o n ( C N ) 5 3 " (or C o 2 ( C N ) 1 0 6 " ) + H 2 ^ = ± 2 C o n i H ( C N ) 5 3 " (1.21) Dinuclear complexes are known to form hydrides w i t h one H bound to each r t 38 metal ( [ l r H ( y - S B u t ) ( C O ) ( P P h 3 ) ] 2 ) or add H ? to only one metal ( [ ( P h 3 P ) 2 R h ( -3 9 y - C l ) 2 R h H 2 ( P P h 3 ) 2 ] ) . -9-1.1.2 A c t i v a t i o n of substrate and hydrogen t r a n s f e r C a t a l y t i c c y c l e s where the metal hydride has been preformed and o l e f i n subsequently coordinated have been termed the 'hydride' route. On the other hand o l e f i n binding followed by hydrogen a c t i v a t i o n has been c a l l e d the 'unsaturate' route . Coordinative unsaturation i s e s s e n t i a l to c a t a l y s i s . As a c o o r d i n a t i n g ki l i g a n d , s o l v e n t can a c t as a weakly c o o r d i n a t i n g ( l a b i l e ) l i g a n d f a c i l i t a t i n g u n s a t u r a t i o n . Solvent can a l s o compete with s u b s t r a t e f o r vacant metal s i t e s , e s p e c i a l l y with weakly binding simple terminal o l e f i n s (e.g. s o l v e n t = aromatic hi hydrocarbon) . Other complications i n c l u d e s i d e - r e a c t i o n s such as between a l c o h o l s and added base (a common combination) to form a l k o x i d e s . As a r e s u l t , e l u c i d a t i o n of a complete mechanism can be a complex problem. In the f o l l o w i n g d i s c u s s i o n these f a c t o r s should be borne i n mind, although the t o p i c w i l l not be expanded f u r t h e r . ( i ) Monohydride c a t a l y s t s Proposed n o n - f r e e - r a d i c a l mechanistic pathways i n v o l v i n g mono-hydride c a t a l y s t s are o u t l i n e d i n scheme 1.1. The unsaturate route goes v i a s t e p ( a ) , e x e m p l i f i e d by the c h l o r o - r u t h e n a t e ( I I ) c a t a l y s e d hydrogenation of a,6 unsat-u r a t e d c a r b o x y l i c a c i d s . On the b a s i s of k i n e t i c , deuterium t r a c e r and exchange st u d i e s the mechanism i s proposed to go v i a the 'acd' pathway . The hydride route i s suggested f o r [KUHCI ( P P h 3 ) 3 ] and fRhH(CO)(PPh 3) 3] v i a 'beef, and f o r t r i c h l o r o s t a n n a t e ( I I ) complexes of P t ( I I ) v i a 'bed' . . The i n s e r t i o n of o l e f i n i n t o the metal hydride bond (or hydride migration to o l e f i n ) i s b e l i e v e d to be f a c i l e and s t e r e o s p e c i f i c a l l y c i s , the 4-centre 3 15 t r a n s i t i o n - s t a t e (1) r e q u i r i n g copjlanar arrangement ' . The r e v e r s i b i l i t y - 1 0 -MH M 2 or 2M Scheme 1.1 Mechanistic pathways for mono-hydride catalysts of the steps 'be' and 'ac' provide an explanation for olefin isomerization in the absence of H2, and isotope exchange between metal hydride and alkene hydrogens, and also with solvent and/or W^. These are commonly observed reactions of mono-hydride catalysts. The metal-alkyl (3) intermediate has not been directly observed under catalytic conditions. The product release step (d,g or e-f) must occur with retention of configuration when overall cis addition of H2 to substrate is observed. For example,hydrogenation of fumaric and maleic acids catalysed, by chloro-ruthenate(II)/D2 yielded(±)-dideuterosuccinic acid with the former, while meso-2,3-dideutero succinic acid was obtained with the latter (via step d, 4 3 protonolysis) . Observation of non-stereospecific addition of D2 to (Z)-and (E)-cinnamic acid catalysed by Pt(II)/SnCl3~ complexes has been ascribed to isomerization via equilibration of rotamers of (3) and the reversibility -11-46 of step c . Hydrogenolysis v i a steps e and f represents net h e t e r o l y t i c s p l i t t i n g of H,,. The hydrogen t r a n s f e r step f i s considered to be f a s t and : the d i h y d r i d o a l k y l complex (4) has not been d i r e c t l y observed. B i n u c l e a r r e d u c t i v e e l i m i n a t i o n (step g) has been proposed f o r [CoH(CN) 5] 3" 1 + 7, [ R u H C l ( P P h 3 ) 2 ] 2 ' t 8 and [CoH(C0) 4] " systems, among o t h e r s 5 0 . I t o f f e r s an a l t e r n a t e pathway when o x i d a t i v e a d d i t i o n of H 2 to (3) i s unfavourable. F r e e - r a d i c a l pathways have been proposed f o r hydrogenation of p o l y c y c l i c 51 aromatic hydrocarbons c a t a l y s e d by [CoH(C0) 4J . Hydrogenation of some a ,e-unsaturated a c i d s , e s t e r s and n i t r i l e s c a t a l y s e d by [CoH(CN)^] may a l s o 52 r II 3 i n v o l v e H-atom t r a n s f e r . The hydride was formulated as [Co (CN)g(-H)] . Net c i s a d d i t i o n of H 2 was u s u a l l y observed, i n d i c a t i n g that recombination of organic r a d i c a l w i t h Co w i t h i n a solvent cage i s f a s t e r than r o t a t i o n about the a,e C-C bond. Two-electron reduction of substrate and a d d i t i o n of two protons to form the saturated product has been noted i n the absence of H 2. The mechanisms proposed are b a s i c a l l y two:(i) protonation a t metal followed by o x i d a t i v e hydride t r a n s f e r and p r o t o n o l y s i s to release the product, and ( i i ) c o o r d i n a t i o n of s u b s t r a t e followed by e l e c t r o n t r a n s f e r and protonation of the r e s u l t a n t carbanion and then p r o t o n o l y s i s . S t o i c h i o m e t r i c reductions probably v i a ( i i ) 53 54 55 are w e l l known f o r C r ( I I ) and V ( I I ) s a l t s among others . Pathway ( i ) i s a v a i l i a b l e to the more a c i d i c metal hydrides ( c f . reverse of eq'n. 1.15), such as [Rh( d i p y ) 2 J . For c a t a l y s i s a s a c r i f i c i a l reducing agent such as Zn/HCl, borohydride, CO or an electroc h e m i c a l process would be re q u i r e d . Strangely enough H 2 has not been f i r m l y e s t a b l i s h e d as a reductant i n any -12-57 c a t a l y t i c r e duction of an organic substrate ( i i ) Dihydride c a t a l y s t s E s s e n t i a l mechanistic pathways proposed f o r d i h y d r i d e c a t a l y s t s are summarized i n scheme 1.2. The hydride route goes v i a step 'a' and the MH2 + (7) Al + H 2 , b (5) M -I •I H H M + 4—4* T I ^ HM H (6) M T (8) I J Scheme 1.2. Mechanistic pathways f o r d i h y d r i d e c a t a l y s t s . unsaturate route v i a step 'b'. Dihydride formation and o l e f i n binding are u s u a l l y r a p i d l y e s t a b l i s h e d e q u i l i b r i a . L i k e the monohydride systems o v e r a l l c i s - a d d i t i o n of H 2 to o l e f i n r e s u l t s from the coplanar migratory i n s e r t i o n (step 'c') followed by r e d u c t i v e e l i m i n a t i o n with r e t e n t i o n of c o n f i g u r a t i o n 58 at the metal bonded carbon ( s t e p ' d 1 ) . The a l k y l - h y d r i d e (6) and hydrido-alkene (5) species have r a r e l y been observed. The cis , c i s - c o m p l e x [ I r H 2 ( C 0 D ) ( P M e P h 2 ) 2 ] + forms cyclooctane and d i h y d r i d e v i a c y c l e 'cdfb' on warming from -40°C under W^. In the absence of H 2, the r e l e a s e of H 2 to form [ l r ( C 0 D ) ( P M e P h 2 ) 2 ] + o c c u r s 5 9 . An a l k y l - h y d r i d e complex has been observed a t low temperature (see below). Unlike monohydride systems, l i t t l e hydrogen i s o t o p i c scrambling or -13-o l e f i n isomerization i s observed for eas i l y reduced substrates. Step d in th is case must be faster than alkyl-hydride formation which i s consistent with the d i f f i c u l t y of observing ( 6 ) . Two "dihydr ide" ca t a l y t i c systems are well understood in the sense that k ine t i c and equi l ibr ium parameters for each step in the proposed mechanisms have been measured. Hydrogenation of cyclohexene with RhCl(PPh^)3 60 (Wilkinson's cata lyst ) i s p r i n c i pa l l y v ia the hydride path 'acde' . In contrast hydrogenation of mono-olefins with Rh(diphos)S 2 + appears to operate 61 63 via the unsaturate route ' b c d f ' . Preference for unsaturate vs. hydride route for these cata lyst precursors appears to be in part due to avoidance of less thermodynamically stable configurations where the hydride l igand i s 62 63 • + trans to phosphine ' . For example, [Rh(diphos)(nbd)] reacts with 2 moles of H^  to form norbornane and solvated Rh(diphos) + , whereas the PPh^ analogue 63 reacts with 3 moles of H 2 forming a cis-hydride and saturated product . However, related Rh(Ph 2 P(CH 2 ) n PPh 2 ) 2 + species do form dihydrides with the 64 trans configurat ion . Preference can be a f fected, of course, by the \ re l a t i ve binding strength of the o l e f i n to species (7) and ( 8 ) . In general, species that form metal under H 2 in the absence of o l e f i n must go v ia the unsaturate route. That route i s usual ly proposed i f the dihydride (7) i s undetectable. I f one i s detectable or i so lab le , the hydride route i s generally proposed, or both routes i f o l e f i n and H 2 are found to coordinate separately (e.g. RhCl (PPh 3 ) 3 , see below). Scheme 1.3 i l l u s t r a t e s the mechanism proposed for the RhCHPPh-jJ-j catalysed hydrogenation of cyclohexene. The boxed part corresponds to the hydride route of scheme 1.2. None of the species within the box are observable -14-L. C l . | ,H 'Rh* . Rh. 04) [RhCI(H)L3(CH2CH3)] L = phosphine ["1 = site of unsaturation Scheme 1.3 Mechanism of R h C l ( R P h 3 ) 3 - c a t a l y s e d hydrogenation of cyclohexene. under c a t a l y t i c c o n d i t i o n s . The 14-electron bisphosphine complex (9) was proposed on k i n e t i c grounds and i s 10 4 times more r e a c t i v e towards H 2 than the t r i s p h o s p h i n e complex (10). Thus the solvated d i h y d r i d e (11) i s more r e a d i l y formed v i a (9) than v i a the i s o l a b l e species (10) and (12). Less -15-efficient catalytic cycles based on the observed species (13) and (14) have 65 been reported . In addition, evidence indicates that with styrene a further pathway involving species with two coordinated styrenes exists Scheme 1.4 illustrates the proposed mechanism for Rh(diphos)S2+ (S= MeOH)-catalysed hydrogenation of methyl (Z)- -acetamidocinnamate. From 0-50°C the reaction with was rate-determining, however, at -78°C the reductive - 1 31 13 elimination step stopped and species (15) was detectable by H, P, C 15 6 3 and N NMR . The molecular structure of the olefin complex (16) and Ph H + Scheme 1.4 Mechanism of Rh(diphos)S2+ (S= MeOH)-catalysed hydrogenation. -16-+ 5 5 Rh(diphos)S 2 have been c r y s t a l l o g r a p h i c a l l y determined . A d i h y d r o - o l e f i n complex ( i . e . (5)) has not been detected because the i n s e r t i o n step i s very f a s t , probably due to the migrating hydrides p o s i t i o n trans to phosphine. The R h ( d i p h o s ) S 2 + c a t a l y s t system i s of s p e c i a l i n t e r e s t because r e l a t e d c a t a l y s t s c o n t a i n i n g c h i r a l d e r i v a t i v e s of diphos (e.g. (R,R)-bappe (formerly dipamp) (17) or (S,S)-chiraphos (18)) are very e f f e c t i v e f o r the H\l ^ H Ph,P PPhi (18) asymmetric hydrogenation of p r o c h i r a l alkenes to give o p t i c a l l y a c t i v e amino , 6 a c i d s (eq n. 1.22) . The high e n a n t i o s e l e c t i v i t y i s u s u a l l y a s c r i b e d to RCH=C(NHC0CH3)C00H > RCH2C*H(NHC0CH3)C00H —> RCH2C*H(NH2)C00H (1.22) prefered binding of the p r o c h i r a l a l k e n i c s ubstrate c o n t r o l l e d by the o r i e n t a t i o n of the four phenyl groups of the c h i r a l diphosphine. However, f o r bappe and chiraphos systems the product was found to r e s u l t from r e a c t i o n H Ph, P P H Ph2 119) -17-66 of H2 with the minor diastereomer of (16) . Control of the asymmetric induction is subtle, small changes in ligand or substrate structure affecting 6 the enantiomeric excess of the product . A small bias in regioselectivity of HD addition to (Z)-a-acetamidocinnamic acid catalysed by Rh(diop)$2+ 67 (diop= (19)) has also been noted . 1.2 Role of chlorostannate(II) in catalysis. The SnCl^" ligand has been usually regarded as an ancillary 7r-acceptor ligand °. Commonly SnCl2*2H2n or SnC^anhydr.) is added as cocatalyst to a catalyst precursor with a metal chloride bond (eq'n. 1.23), into which SnC^ PtCl2(PR3)2 -^-2-> PtCl(SnCl3)(PR3)2 (1.23) 68 69 _ inserts ' . In the presence of Cl , SnCl3 can be formed (eq'n. 1.24) and SnCl2 + Cl" SnCl3" (1.24) 70 71 and coordinate ' . Additionally, molten tetraalkylammonium salts of SnCl3 have been used as the media for hydrogenation of monoenes and dienes by Pt 72 salts . The electronic nature of SnCl3" has been considered to be important 73 7k kO 70* 75 764 in a number of hydroformylation , carbonylation , hydrogenation ' ' ' 69 and isomerization systems using Pt(II) and Pd(II) catalysts. Little work has been reported on rhodium-based systems (see below). The systems tend to be much less active or selective without the addition of stannous chloride. The SnCl3~ ligand has been generally considered as a weaka-donor . 69 76.110 (<C0, PF3) and strong u-acceptor (>C0, PF3) . Its strong trans effect was considered to activate Pt(II) and Pd(II) centres towards nucleophilic -18-s u b s t i t u t i o n . I t has a l s o been suggested that c o o r d i n a t i o n of H" and o l e f i n was enhanced by reduction of the charge a t the metal centre due to TT-acceptance 77 by SnCl-j" . This f a c t o r a l s o s t a b i l i z e s against reduction to metal or low 7Sd 77 78 o x i d a t i o n s t a t e ' ' . On the other hand, c o o r d i n a t i o n of SnCl^ has been 79 80 suggested to make M-H bonds more h y d r i d i c ( i . e . Sn-M-H) ' i n nature, which i s i n accord w i t h the reducing power of t i n ( I I ) Examination of the s t o i c h i o m e t r i c c a r b o n y l a t i o n of phenylplatinum(II) complexes promoted by S n C ^ i n d i c a t e d that SnCl^" was a c t i n g as a good l e a v i n g 81 group of moderate n u c l e o p h i l i c i t y . The key step i n v o l v e d attack by S n C l 3 to form a 5-coordinate intermediate from which i n s e r t i o n occurred (scheme 1.5) CUSn P Scheme 1.5 Carbonylation of phenylplatinum(II), I t was noted that I " , and to a l e s s e r extent Br", which are b e t t e r nucleophiles and worse l e a v i n g groups promoted the r e a c t i o n l e s s e f f e c t i v e l y . A s i m i l a r -19-promotion of inser t ion v ia a 5-coordinate intermediate was proposed for the SnCl^" catalysed inser t ion of C 2 H 4 into trans-PtHClL^ ( L= phosphine) to form t rans-Pt (C 2 H 5 )C lL 2 8 2 . Recent invest igat ion of the precata ly t i c and ca ta l y t i c chemistry of c i s- PtCl 2 (L ) (PR 3 ) /SnCl 2-2H 20 and Pt 2 (y-Cl ) 2 C1 2 ( PR 3 ) 2 /SnCl 2 '2H 2 0 (L= PR 3, CO, th ioether , amine; R= a r y l , a l ky l ) o l e f i n hydrogenation and hydroformylation 83 systems reveals a r i ch solut ion chemistry involv ing stannous chlor ide . The stannous chlor ide acts both as an anc i l l a r y l igand as well as d i s p r o p o r t i o n a t e to form SnCl 3 ~ and ca t ion ic hydrates. Simple inser t ion was observed in CH^Cl 2 so lu t ion , but d i s p r o p o r t i o n a t e occurs in acetone leading to formation of a mixture of anionic and neutral Pt complexes, e lec t roneut ra l i t y being maintained by the cat ion ic t i n hydrates. The role of stannous chlor ide was not l im i ted to a spec i f i c intervent ion at a key step, but was proposed to be the promotion of the multicomponent system. Most components of the mixture were shown to be essent ia l to the ca t a l y s i s . Examples of a redox role for Sn in ca t a l y t i c systems are rare . In some cases where both Sn(II) and Sn(IV) cocatalysts are e f fec t i ve (e.g. 1,5-69 cyclooctadiene isomerization with P tC l 2 ( P Ph 3 ) 2 ) , the p o s s i b i l i t y should be considered. A water-gas-shift cata lyst system composed of K 2 PtCl 4 /SnCl 4 *5H 2 0 in HCl/H0Ac/H20 under CO and ethylene or propylene i s believed to involve a Sn(II)/Sn(IV) couple . The o l e f i n was hydrogenated but H 2 added to the . system was not consumed. Thus a hydride formed in a water-gas-shift cycle was believed to react with the o l e f i n , followed by protonation to release alkane (scheme 1.6). The water-gas-shift cycle had been previously reported to depend on the in teract ion of a Sn(II)/Sn(IV) couple with a cycle involv ing -20-Pt-H C0 2 /H + f-^ CO/H2O Pt <—7 H Pt- ' C2H6 Scheme 1.6 Hydrogenation of C 2 H 4 catalysed by K 2 PtCl 4 /SnCl 4 -2H 2 0/C0. 0 TT TV 8 5 P t V t ^ / P t ^ (eq'ns. 1.25, 1.26) . CO + H20 + S n C l 6 2 " Pt species^, C 0 2 + 2H + + SnCl^' + 3C1" (1.25) 2H+ + SnCl 3 - + 3CT P t s P e c i e s > ^ + SnClg 2- (1.26) 1.3 Aim of th is work The aim was to prepare a Rh-SnCl 3 cata lyst precursor complex and examine i t s o l e f i n hydrogenation a c t i v i t y . Addit ion of stannous chlor ide to platinum(II) chlor ide systems in the ear ly 1960s was found to give an act ive 76*1 ethylene hydrogenation system . Shortly afterwards ethanol solut ions of [RhCl(SnCU) 9 ] 4_: ' 3 ' 2 J 2 were reported to be act ive for the hydrogenation of 86 87' 88 hex-l-ene and n-heptaldehyde . L i t t l e further work has been reported ' , so further invest igat ion was f e l t to be warranted. Add i t i ona l l y , the absence of t e r t i a r y group VA ligands is noteworthy in view of the abundance of studies involv ing Rh complexes containing these ligands . -21-CHAPTER II  EXPERIMENTAL METHODS 2.1 Materials 2.1.1 Solvents Spectral or ana ly t ica l grade organic solvents were obtained from MCB, Mal1 inckrodt, Eastman or Fisher Chemical. Solvents were dr ied under Ar before use, as described below. The dried solvents were handled under flowing Ar and stored under Ar ( s l i g h t l y greater than 1 atmosphere). A c e t o n i t r i l e , diethyl ether and dichloromethane were d i s t i l l e d from CaHr,. Acetone was dried over molecular sieves (Fisher type 4 A ) . N i t ro-methane was d i s t i l l e d from P 2 0 5 . Ethanol (95-100%) was predried over BaO before d i s t i l l a t i o n from magnesium ethoxide. Aqueous HC1 solut ions were made up from reagent grade (A.C.S.) concentrated HCl from AMACHEM. Deuterated solvents were used without further p u r i f i c a t i o n . D 20 (99.7 atom %) and CD3CN (99 atom %) were obtained from Merck, Sharp and Dohme Canada Ltd. DC1 (38% in D 2 0; 99 atom %) and (CD 3 ) 2 N0 2 (99 atom %) were from Stohler Isotope Chemicals. CDC13 and (CD 3 ) 2 C0 (99.8 atom %) were from A ld r i ch Chemical Co. The 38% DC1 was d i lu ted to 3M with D 20 before use. 2.1 .2 . Gases Pur i f i ed oxygen, argon, carbon dioxide and nitrogen were obtained from Canada Liquid A i r L td . , or from Union Carbide Canada L t d . , and were used without further p u r i f i c a t i o n . Hydrogen, carbon monoxide and lecture bott les -22-of methane were from Matheson Gas Co. ("research grade") or Union Carbide Canada Ltd. ( "spec ia l ty gas" ) . Hydrogen was passed through an Engelhard Deoxo ca t a l y t i c p u r i f i e r to remove traces of oxygen, and then through a drying column containing calcium chlor ide and P2O5 to remove H2O. 2.1.3 O l e f i n i c Substrates C P . grade ethylene was obtained from Matheson Gas Co. and used without further p u r i f i c a t i o n . Maleic and fumaric acids were reagent grade from Mal l inckrodt and were r e c r y s t a l l i z ed from H2O before use. 2.1.4 Other materials The tetraalkylammonium chlorides were obtained from Eastman. Tetra-phenyl-rarsonium chlor ide was from K & K Laboratories Inc. Stannous ch lor ide , stannic chlor ide and l i th ium chlor ide were reagent grade from Fisher Chemical 89 Co. The [Et 4 N][SnCl 3 ] was prepared by the l i t e r a tu re method . A l l t in ( I I ) compounds were stored under anhydrous conditions in an argon atmosphere. 2.1.5. Rhodium Complexes The rhodium was obtained as RhCl 3-3H 20 (41.87% Rh) from Johnson, Matthey L td . The rhodium(I) complex Rh 2Cl 2 (C0T) 4 was a g i f t from Dr. D. Mahajan. Standard Schlenk techniques were employed for synthetic procedures under anaerobic condi t ions. Schlenkware wrapped in black e l e c t r i c a l tape was used in procedures requir ing absence of l i g h t . The iso lated products of -23-reactions were stored under anhydrous conditions to prevent hydrolysis by 90 atmospheric moisture . 2.1.5.1 Preparation of fac-[Me 4 N] 3 [RhCl 3 (SnCl 3 ) 3 ] 91 The method of Kimura was used . Under aerobic and ambient l i g h t conditions 0.15 g RhCl 3-3H 20 (0.61 mmole) was dissolved in 35 mL 3MHC1. To th is so lut ion was added 0.386 g SnCl 2-2H 20 (1.7 mmole). The solut ion was s t i r r ed for 70 min at 90°C. The resultant dark red-orange solut ion was stored for 20 - 24 h at -5°C. Careful addit ion of Me4NCl un t i l no further prec ip i ta t ion occurred y ie lded a reddish orange powder that was washed successively with 5 mL 3MHC1 (containing a few mg of Me 4NCl), 3MHC1 and dry ethanol. The prec ip i ta te was then dried in vacuo. Y ie ld was ^60%. The product i s insoluble in non-polar solvents but i s s l i g h t l y soluble in 3MHC1 and ethanol , moderately soluble in CH3CN, (CH 3) 2C0 and CH 3N0 2 , and very soluble in DMSO and DMA, where i t probably decomposes as judged by the resultant weakly coloured so lu t ions . Solutions of the complex are l i gh t sens i t i ve . Elemental analysis (% found (ca lc . ) ) for c i 2 H 3 6 C 1 1 2 N 3 R n S n 3 w a s c 1 2 - 9 0 (13.02), H 3.30(3.28), Cl 38.60(38.43), N 3.72(3.80) and Rh 9.70(9.30). Far-IR (Nujol m u l l , Csl plates) has bands (v(M-Cl)) at 362, 336, 321, 303(sh), 275 cm" 1 ( f i g . 2 . 1 ) . Solut ion UV-VIS spectra has X m a x (e, M 'W 1 ) i n 3M HC1 at 424 nm (4360), 304 nm (29500) and 257 nm (15400), ( f ig. 2.2) . In CH3CN the spectrum ( f i g . 2.3) depends on whether there i s excess C l " present or not , but the resul tant spectrum s t ab i l i z ed within minutes in both cases (see also chapter IV). -24-Figure 2.1 Far-IR spectrum ( N u j o l , Csl p l a t e s ) of f a c - [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] ( ) compared to that reported i n r e f . 9 l ( ) ( r e f . 91, f i g . 1-(2A); resampled d i g i t a l l y and scaled to match the a b s i s s a ). -25-Figure 2.2 3MHC1 s o l u t i o n UV-VIS spectrum o f [Me 4N] 3[RhC1 3(SnCl3)3] ( ) compared to that reported i n r e f . 91( ) ( r e f . 9 1 , f i g . 2-(2A); see note f i g . 2.1). -26-20 UJ o z gioH o (/> CD < 0-0-200 ~" "—I—•— — i — i — i | i—r-300 400 W A V E L E N G T H ( N M ) — I 500 Figure 2.3 CH^CN solut ion UV-VIS spectra of [Me 4 N] 3 [RhCl 3 (SnCl 3 ) 3 ] (6.04 x 10~ 4M, 0.1 cm c e l l ) ( ) without added chlor ide and with a 10-fold excess of Et 4NCl-H 20 ( -). 2.1.5.2 Preparation of [Me 4N] 3[RhCl 2(SnCl 3) 4]-h^O 91 The method of Kimura was used at ha l f-sca le . Under aerobic and ambient l i g h t condi t ions, 0.19 g RhCl 3-3H 20 (0.77 mmole) was dissolved in 12.5 mL of 3MHC1 at 90°C. Addit ion of 0.33 g. Me4NCl. (3.0 mmole) and 0.49 g -27-SnClg*2H2O (2.1 mmole) i n s t a n t l y y i e l d e d an orange p r e c i p i t a t e . The suspension was heated f o r two hours at 90°C w i t h constant s t i r r i n g . A f t e r f i l t e r i n g hot, the p r e c i p i t a t e was washed s u c c e s s i v e l y w i t h small amounts of 3MHC1 con t a i n i n g Me^NCl, 3MHC1 and dry ethanol. The orange powder (50% y i e l d ) was d r i e d i n vacuo. The s o l u b i l i t i e s and r e a c t i v i t i e s towards solvent are s i m i l a r to those of [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] . S o l u t i o n s o f the complex are a l s o l i g h t s e n s i t i v e . A d d i t i o n a l l y , one t i n l i g a n d d i s s o c i a t e s i n s o l u t i o n (see Chapter IV); however, the r a t e i s slow enough i n CH,CN (t, ^1450s) to allow the use of i n i t i a l s p e c t r a f o r c h a r a c t e r i z a t i o n . The complex i s considered to be the trans isomer. A trans arrangement of c h l o r i d e and S n C l 3 " gives r i s e tov(M-Cl) at 375cm"1 i n f a c - [ R h C l 3 ( S n C l 3 ) 3 ] 3 " r i 3 - 9 1 and | _ R h C l 4 ( S n C l , which i s absent in.the t e t r a k i s complex (see below). Elemental a n a l y s i s (% found ( c a l c . ) ) f o r C-^H-^Cl-|^ORhSn^ was C 10".58(10.96), H 2.90(2.74), Cl 38.00(37.82) N 3.04(3.20) and Rh 7.76(7.84). The far - I R ( N u j o l , C s l p l a t e s ) has bands (v(M-Cl)) at 363(sh), 326 and 287(sh) c m " 1 . ( f i g . 2.4), The CH3CN s o l u t i o n UV-VIS spectrum i s shown i n f i g u r e 2.5. In 3M HC1 s o l u t i o n the spectrum was unstable i n l i g h t and dark, but was s i m i l a r to t h a t reported i n reference 91 . The Mossbauer spectrum (77°K; f i g . 2.6) gave I.S. ( r e l . to BaSn0 3) = 1.68 ±.06 mm/s and Q.S. = 1.80 ± .03 mm/s. 2.1.5.3 Preparation of [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] - ( E t 4 N C l ) Q g This procedure was done under anaerobic c o n d i t i o n s and i n the dark, up to the stage at which the s o l i d s were drying i n vacuo. -28-Figure 2.4 Far-IR spectrum ( N u j o l , Csl p l a t e s ) o f [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] - h ^ O ( ) compared to t h a t reported i n r e f . 91 ( -) ( r e f . 91, f i g . l - ( 3 ) ; see note f i g . 2.1). -29-20* W A V E L E N G T H ( N M ) Figure 2.5 I n i t i a l CH3CN s o l u t i o n UV-VIS spectrum o f [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] -H^ O (5.13 x 10~ 4M, 0.1 cm c e l l ) . A s o l u t i o n o f 0.125 g RhCl 3-3H 20 (0.47 mmole) i n 25 mL 3MHC1 was heated to 60°C and 0.860 g [ E t 4 N ] [ S n C l 3 ] (2.42 mmole) was c a r e f u l l y added, with s t i r r i n g , i n the dark; the temperature was then r a i s e d to 90°C f o r 1 h. A f t e r c o o l i n g to room temperature the s o l u t i o n was f i l t e r e d and the y e l l o w -orange p r e c i p i t a t e washed with dry ethanol and d r i e d i n vacuo (75% y i e l d ) . -30-The f i l t r a t e was c o l o u r l e s s pr very pale coloured. R e c r y s t a l l i z a t i o n from warm, dry deaerated CH3CN i n the absence of l i g h t y i e l d e d a darker orange m i c r o c r y s t a l 1 i n e product i n l e s s than 30% y i e l d . Further r e c r y s t a l l i z a t i o n gave a very low y i e l d o f small n e e d l e - l i k e c r y s t a l s u n s u i t a b l e f o r c r y s t a l l o g r a p h i c determination. The complex i s l e s s s o l u b l e than the Rh(III) complexes described i n 0-25 T -1-00-1 , , , , ,— , , , , , , -5 -4 -3 -2 -1 0 1 2 3 4 5 VELOCITY (MM/SEC) Figure 2.6 Mossbauer spectrum o f [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] - H 2 0 at 77°K. - 3 1 -the preceeding two sect ions , but shows a s imi la r pattern of s o l u b i l i t i e s and r e a c t i v i t i e s . It is stable in the so l i d state i f stored in the absence of l i gh t under anhydrous conditions and can be handled in a i r for short periods without noticable change. In solut ion the complex i s very l i g h t sens i t ive while in the dark i t decomposes to give free SnCl 3~ and a mixture of Rh(III) and Rh(I) species (see Chapter 4 ) . In CH3CN the process has a t t 2-6000 sec in the dark, so the i n i t i a l spectrum i s usable to character ize the complex, while in 3MHC1 the decomposition reaction i s quite f a s t . Elemental analysis (% found (calc) ) for C 28 H 20 C 1 16 5N3 5 R h S n 5 w a s C 19."55(1 9.35), H 4.20(4.03), Cl 34.14(33.74), N 2.80(2.82) and Rh 5.96(5.93) for the unrecrys ta l l ized sample. For a r e c r y s t a l l i z ed sample the analysis was C 20.45, H 4.60, Cl 34.91 and N 3.43. The far-IR (Nujo l , Csl plates) for the unrecrys ta l l ized sample has bands at 348, 332(sh), 327, 315 and 307(sh) c m - 1 and for a recrysta l1 ized sample at 355, 332(sh), 327, 318(sh) and 306 (sh) ( f i g . 2.7) . The UV-VIS spectrum for a CH3CN solut ion of the recrysta l-l i z e d (or r ec rys ta l l i zed ) product i s shown in f igure 2.8. Pertinent data for th is and for other solvents are summarized in table 2 .1 . The Mossbauer spectrum (77°K; f i g . 2.9) was an asymmetric doublet I.S. (rel . to BaSn03) = 1.79 (±.03) mm/s and 0-S. = 1.84 (±.02) mm/s. Conductance in nitromethane ( in absence of l i g h t and a i r ) increased with t ime; the i n i t i a l value of A M was 249 ohm"1 mo l " 1 cm2 (1.2 x 10" 3 M, 25°C). After decomposition in acid 3+ solut ion in the presence of Fe , under argon, the complex yie lded 10.1 3 + 2 + reducing equivalents (Fe —*Fe ) per mole of rhodium as determined by 4+ t i t r a t i o n with Ce . -32-100 w UJ o z < I-t s o 5 (0 z < cc 400 — I — 350 — I — 300 WAVENUMBER (CM-1) 250 Figure 2.7 Far-IR spectrum ( N u j o l , C sl p l a t e s ) o f u n r e c r y s t a l l i z e d [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] . [ B t 4 N C l ] 0 g ( ) compared to that a f t e r r e c r y s t a l 1 i z a t i o n from CH.CN ( •). -33-2 0 CM UJ U z o tn eo < 00 ' 200 • I i i i 300 1 —I—r -400 W A V E L E N G T H ( N M ) — t 500 Figure 2.8 I n i t i a l CH3CN s o l u t i o n UV-VIS spectrum o f [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 -( S n C l 4 ) ] - [ E t 4 N C l ] 0 5 (1.93 x 10' 5M, 0.5 cm c e l l ) . 2.1.6 Other s y n t h e t i c experiments discussed i n chapter I I I . Several o f the experiments were simple v a r i a t i o n s on the procedures described i n the preceding s e c t i o n s and deserve no f u r t h e r comment here. The exceptions are described below. -34-2.1.6.1 Trapping experiments using [ E t 4 N ] [ S n C l 3 ] Method A: A l l manipulations were performed a n a e r o b i c a l l y under ambient l i g h t i n g c o n d i t i o n s . To a s o l u t i o n o f 0.0618 g. RhCl 3• 3H 20 (0.24 mmole) i n 15 mL 3MHC1, a t 40°C, was added 0.152 g [ E t 4 N ] [ S n C l 3 ] (0.43 mmole) with s t i r r i n g . A yellow-orange p r e c i p i t a t e formed immediately. The p r e c i p i t a t e was f i l t e r e d o f f , washed twice with 5 mL 3MHC1 then E t 2 0 and d r i e d i n vacuo. The CH3CN s o l u t i o n UV-VIS and I.R. spectra were s i m i l a r to those o f [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] - H 2 0 , correc t e d f o r replacement o f Me 4N + by E t 4 N + . The p a r t i a l elemental a n a l y s i s f o r C 24Hg 2Cl-| 4N 30RhSn 4 was (% found ( c a l c ) ) C 19.38 (19.43), H 4.18 (4.18) and N 2.85 (2.83). Y i e l d was 0.067 g (42%). S o l u t i o n UV-VIS data f o r [ E t 4 N ] 3IRhCSnCl 3) 4(.SnCl 4) J ( E t 4 N C l ) Q Solvent Wnm> ^ a p p r o x ^ c m _ 1 ) ) CH3CN 379 (81500) 277 (57800) 3MHC1 373 ( a ) (CH 3) 2C0 382 ( a ) (CH 3) 2S0 386 ( a ) (CH 3) 2NC(0)CH 3 385 ( a ) a. not estimated due to decomposition -35-0-251 at 77°K. Method B: A l l manipulations were performed a n a e r o b i c a l l y under ambient l i g h t i n g c o n d i t i o n s at 40°C. To a s o l u t i o n o f 0.189 g. RhCl 3-3H 20 (0.72 mmole) i n 30 mL of 3M HC1 was added dropwise a s o l u t i o n of 0.809 g [ E t 4 N ] [ S n C l 3 ] (2.28 mmole) d i s s o l v e d ^1.5 mL o f 3M HC1. A yellow-orange p r e c i p i t a t e formed as the t i n s o l u t i o n was added. The p r e c i p i t a t e was f i l t e r e d o f f , washed twice with 3MHC1 then E t 2 0 , and then d r i e d i n vacuo. -36-Further p r e c i p i t a t i o n was observed i n the f i l t r a t e and a f t e r standing overnight (^ 12 h) an orange p r e c i p i t a t e was i s o l a t e d i n the same manner as the f i r s t . Y i e l d o f the f i r s t p r e c i p i t a t e was 0.176 g and of the second 0.256 g . Method C: The procedure as described i n method B was modified by excluding l i g h t and lowering the temperature to ambient. The [Et^NlLSnCl^] reagent was added e i t h e r as a s o l i d or i n concentrated s o l u t i o n . The e f f e c t of the m o d i f i c a t i o n i s discussed i n sec. 3.3.4 . 2.1.6.2 Reaction between [Rh 2Cl 2(C 0 T ) 4 ] and [Et^N][SnCl^] A l l manipulations were performed a n a e r o b i c a l l y . Method A: To a s o l u t i o n of 0.10 g [Rh 2Cl 2 (C0T) 4 ] (0.14 mmole) i n 5 mL CH2C1 was added,in the dark w i t h s t i r r i n g , a s o l u t i o n o f 0.248 g [Et 4N][SnCl3 ] (0.56 mmole) i n 10 mL acetone at room temperature. The r e s u l t a n t purple-black p r e c i p i t a t e was f i l t e r e d o f f , washed with CH 2C1 2 u n t i l the washings were c o l o u r l e s s and d r i e d i n vacuo. The purple s o l i d had a b r i t t l e g l a s s -l i k e t e x t u r e and gave purple CH3CN s o l u t i o n s that faded to pale yellow-brown with time. The s o l i d s a l s o changed colour w i t h time, under anaerobic or aerobi c c o n d i t i o n s , to orange-brown. Method B: A s o l u t i o n o f 0.10 g [Rh 2Cl 2 (C0T) 4 ] (0.14 mmole) i n 10 mL CH 2C1 2 was cooled to -23°C by a d r y - i c e / C C l 4 bath. A s o l u t i o n o f 0.198 g [ E t 4 N ] -[SnCl-j] (0.56 mmole) was added sl o w l y from a dropping-funnel . The a d d i t i o n took ^40 min. I n i t i a l l y , an o l i v e coloured suspension formed which became dark purple a f t e r ^15 min o f a d d i t i o n . The f i n a l purple suspension was -37-allowed to s e t t l e and the y e l l o w supernatant s o l u t i o n siphoned o f f . The s l u r r y was washed with f r e s h c o l d CH 2C1 2 which was a l s o siphoned o f f . The s o l i d s that were on the sides of the glassware, not i n contact w i t h s o l v e n t , were o l i v e or greenish-yellow-brown i n colour while the 'wet' s o l i d s were purple. A sample o f the purple m a t e r i a l was q u i c k l y t r a n s f e r r e d i n t o CH3CN, g i v i n g a purple s o l u t i o n t h a t q u i c k l y faded to pale yellow-brown. The f l a s k c o n t a i n i n g the product was t r a n s f e r r e d to a vacuum l i n e . As the sample warmed to room temperature the purple c o l o u r faded to brown-purple ( c o l o u r faded r a d i a l l y inward). The purple colour could be r e s t o r e d by c o o l i n g the f l a s k b r i e f l y w i t h l i q u i d n i t r o g e n . The dry s o l i d s were very a i r s e n s i t i v e , d i s c o l o u r i n g immediately upon exposure to the atmosphere and becoming orange w i t h i n a few hours. The orange m a t e r i a l was not thermochromic. 2.2 Techniques. 2.2.1 I n f r a r e d Spectroscopy I n f r a r e d s p e c t r a were recorded over the range 4000 - 250 cm"1 on a Perkin Elmer model 457 or 598 g r a t i n g spectrophotometer. S o l i d samples were run as Nujol mulls between Csl p l a t e s held i n a clamp type c e l l holder (WILKS 531Q). M u l l i n g and c e l l assembly were done under a nitrogen atmos-phere, i n a glove bag. S o l u t i o n samples were run i n 0.1 cm pathlength c a v i t y c e l l s w i t h CaF 2 windows. The c e l l s were purged with argon or carbon monoxide ( i n a fumehood) where a p p r o p r i a t e . C a l i b r a t i o n of s p e c t r a was -38-against a polystyrene f i l m r eference. 2.2.2 E l e c t r o n i c Spectroscopy Spectra were recorded over the range 700 - 200 nm on e i t h e r a Cary Model 17 or a Perkin Elmer Model 552A spectrophotometer f i t t e d w i t h thermo-s t a t t e d c e l l h o l d e r s . Conventional c e l l s were used under aerobic c o n d i t i o n s while f o r anaerobic experiments s p e c i a l s p e c t r a l c e l l s o f the type i l l u s t r a t e d i n f i g u r e 2.10 were used. L i g h t - s e n s i t i v e s o l u t i o n s were a l s o handled i n t h i s type o f c e l l but a l l exposed surfaces (except ground glass and quartz c e l l ) were wrapped with black e l e c t r i c a l tape. A s l i p - o f f cover, made o f tape, was used to cover the quartz c e l l and was removed at the spectrophoto-meter under a black c l o t h draped over the c e l l compartment. In a t y p i c a l anaerobic experiment,a weighed amount o f s o l i d complex was placed i n the quartz c e l l . Solvent was p i p e t t e d i n t o the side arm f l a s k and then degassed by three freeze-pump-thaw c y c l e s . The s o l v e n t and s o l i d were then mixed u n t i l a homogeneous s o l u t i o n was achieved. For experiments where the r e s u l t a n t s o l u t i o n was 1 i g h t - s e n s i t i v e , t h e freeze-pump-thaw degassing c y c l e s were done before completely wrapping the sidearm f l a s k with tape to avoid s h a t t e r i n g the p l a s t i c tape at low temperature. S o l i d - s t a t e spectra were run by soaking a small piece of f i l t e r paper i n a Nujol mull of the complex to be examined. The paper was mounted on the face o f a conventional c e l l . To p a r t i a l l y compensate f o r l i g h t s c a t t e r i n g a Nujol blank was used as reference. Al t e r n a t i v e l y , a s o l u t i o n was evapora-ted ( i n vacuo) and the spectrum o f the c o a t i n g on the c e l l w a l l s taken. -39-HIGH VACUUM T E F L O N STOPCOCK B14 CONE & C A P SIDEARM F L A S K (-10 MLS) « B14 S O C K E T 3 C M V_7 QUARTZ C E L L Figure 2.10 Anaerobic s p e c t r a l c e l l -40-2.2.3 NMR spectroscopy NMR spectra were run on a Bruker WP-80, Bruker WP-400 or Varian XL-100 spectrometers in the Fourier Transform Mode using tetramethylsi lane (TMS) as standard. 119 Sn FTNMR spectra were recorded at 29.88 MH3 using a Bruker WP-80 spectrometer equipped with a 10 mm variable temperature probe. Some spectra were recorded, courtesy of Dr. C. Lassigne, at 37.336 MHz on a modified XL-100 spectrometer located at Simon Fraser Un ivers i ty . This machine used 92 a home bu i l t 22 mm probe. A l l spectra were run at ambient temperature (^27°C). Tetramethylstannane (TMT) was used as an external standard, with upf ie ld sh i f t s being taken as negative. Typica l ly , a sweep width of 10 KHz to 20 KHz was employed. Depending on the concentration and time ava i lab le 6K to 300K scans would be accumulated. To quant i ta t i ve ly observe t in( IV) species a delay between pulses of 4-5 sec was employed; for some t in ( I I ) species, up to 2 sec delay was needed although usual ly no delay was employed. A persistent problem, when using the Bruker machine, was a severely r o l l i n g baseline caused by signal breakthrough at sweep-widths of more than a few thousand Hz. Reducing the sweep-width reduced the e f f e c t , but increased the time needed to scan a reasonable range of chemical s h i f t s ( t yp i ca l l y + 100** -1000 ppm) which add i t iona l l y led to complications with folded-in s i gna l s . A sometimes necessary but unsat isfactory ' f i x ' was to drop the f i r s t four data points from the F.I.D. However, t h i s led to d i f f i c u l t i e s in phasing the spectrum a f t e r Fourier transformation of the F.I.D. Spectrum simulation was performed using UBC PANIC and UBC ADD programs, as modified by Dr. 0. Chan (see also Appendices B and C). - 4 1 -2.2.4 Mossbauer Spectroscopy Tin Mossbauer measurements and c a l c u l a t i o n s were performed by L. S a l l o s and Dr. J . Sams o f t h i s department. The measurements were made at l i q u i d - n i t r o g e n temperatures on s o l i d samples which had been sealed i n polyethylene containers under an atmosphere o f nitrogen i n a glove-bag. Isomer s h i f t s are quoted r e l a t i v e to BaSnC^. 2.2.5 C o n d u c t i v i t y measurements C o n d u c t i v i t y measurements of nitromethane s o l u t i o n s were done at room temperature under an argon atmosphere us i n g a Thomas Serfass c o n d u c t i -v i t y bridge and eel 1 . 2.2.6 Gas Chromatography A Carle Model 311 a n a l y t i c a l gas chromatograph with t h e r m i s t o r detectors was used to analyse gas mixtures. A 12 foot long 1/8" diameter s t a i n l e s s s t e e l column packed with Porapak Type Q (Waters A s s o c i a t e s , Inc.) was used. Typi c a l machine parameters used f o r a 0.5 mL sample were: 15 -20 psi He" c a r r i e r gas and a column temperature o f 30°C with no i n l e t heating The order o f r e t e n t i o n times f o r s e l e c t e d gases and vapours was found to be: H 20 >> C 2H 4 » C0 2 > CH 4 > CO, N 2, Ar, 0 2 > H 2 f o r example, the r e t e n t i o n time f o r H 2 was t y p i c a l l y 3.2 min (30°C, 20 psi He) and 15.5 min f o r C0 2 (30°C, 20 p s i He). The detector s e n s i t i v i t y towards H 2 was much lower than f o r the other gases, being 0.045 times that -42-of C0 2 . The s ens i t i v i t y , towards other gases and vapours was not quant i -t a t i ve l y determined but was comparable to C 0 2 . Methane was used as an internal standard. Typ ica l l y a 0.5 mL sample was withdrawn from the gas phase over the reaction,through a septum, using a Precis ion Sampling Corp. Pressure-Lok gas syr inge. The syringe needle was purged with 0.05 mL of the sample just before in jec t ion onto the column. 2.2.7 Mass spectrometry Analysis of gas samples by mass spectrometry was performed by J . Nip and Dr. 6. Eigendorf of th i s department using a Varian Mat CH4-B insrument f i t t e d with a gas sample i n l e t . I t was noted that because of the large internal volume of the machine, th is method was less sens i t i ve than the gas chromatograph for low concentrat ions, espec ia l l y for the detection of H 2 • 2.2.8 Gas Uptake measurements A constant pressure gas-uptake apparatus was used in k ine t i c and stoichiometr ic s tud ies . The procedure and apparatus are extensively 94 described elsewhere For experiments where l i gh t-sens i t i ve compounds were used^the reaction f lask was wrapped in black e l e c t r i c a l tape except for areas that would be immersed in the thermostat o i l (which removes the tape ! ) . These areas were care fu l l y wrapped in f o i l instead. Sample preparation was s im i l a r to that in reference 28.. Typ i ca l l y , -43-3-5 mL of 0.01M R h ( I I I ) stock s o l u t i o n (see below) was p i p e t t e d i n t o an uptake f l a s k ( f i g . 2.11) c o n t a i n i n g an appropriate amount of maleic or fumaric a c i d . The f l a s k atmosphere was purged w i t h argon and a small g l a s s bucket c o n t a i n i n g a weighed amount of S n C ^ ^ r ^ O was c a r e f u l l y mounted i n the f l a s k on a r o t a t a b l e hook. A f t e r a t t a c h i n g the f l a s k to a vaccuum l i n e , the s o l u t i o n was degassed by 3 freeze-pump-thaw c y c l e s . A f t e r warming the f l a s k to room temperature the bucket of SnCl2*2^0 was dropped i n t o the s o l u t i o n by r o t a t i n g the hook. The s o l u t i o n was thoroughly mixed and H 2 ( a t 90 mmHg pressure) i n t r o d u c e d w i t h o u t a g i t a t i o n of the s o l u t i o n . The f l a s k was then t r a n s f e r r e d to the thermostated bath o f the uptake apparatus and connected to the uptake apparatus. The sample was thermally e q u i l i b r a t e d f o r about 15 min without a g i t a t i o n (to minimize d i f f u s i o n i n t o the s o l u t i o n a t t h i s p o i n t ) . The H2 pressure was then r a i s e d to 450 mmHg and a g i t a t i o n s t a r t e d . The uptake of H2 by the c a t a l y s t s o l u t i o n was monitored manometrically as described 9 4 elsewhere . The concentration of H ? i n 3M HC1 at 80°C and 450 mmHg p a r t i a l pressure -4 2 8 i s 3.60 x 10 M .No c o r r e c t i o n f o r d i f f e r e n c e s i n s o l u b i l i t y between H 2 and D 2 was made. In H 20 the l a t t e r can be as much as 1.07 times more s o l u b l e than H 2 " A f t e r completion of an uptake the organic products were e x t r a c t e d from aqueous s o l u t i o n w i t h ether (5 x ^ 5 mL p o r t i o n s ) . The e x t r a c t s were d r i e d over anhydrous MgSO^ before s o l v e n t removal on a roto-vac and drying i n vacuo. The e f f i c i e n c i e s of e x t r a c t i o n f o r the various d i c a r b o x y l i c acids used were s i m i l a r except f o r malic a c i d which was 1/5 of the others. -44-Th e p r e c a t a l y t i c Rh(III) species i n 3M HC1 s o l u t i o n , i n the absence of SnCl 2-2H 20, was p r i n c i p a l l y R h C l 5 ( H 2 0 ) 2 " , with minor amounts of [ R h C l 4 ( H 2 0 ) 2 ] "5 28 and R h C l g . At 60°C the r e l a t i v e r a t i o s of the t e t r a c h l o r o - , pentachloro-96 and hexachloro-species a t e q u i l i b r i u m have been estimated to be 5:84:12 In the present i n v e s t i g a t i o n the stock R h ( I I I ) i n 3M HC1 or 3M DC1/D20 stock s o l u t i o n was heated a t 80°C f o r a week before use. The v i s i b l e s p e c t r a l data are summarized i n t a b l e 2.2 along w i t h comparative l i t e r a t u r e data. A d d i t i o n of maleic or fumaric a c i d to the stock s o l u t i o n d i d not cause any change i n the s p e c t r a , thus r u l i n g out formation of R h - o l e f i n complexes. The e f f e c t of adding stannous c h l o r i d e i s discussed i n chapter I I I . • TO UPTAKE MANOMETERS Figure 2.11 Uptake f l a s k ( 2 5 mL) -45-Table 2.2 Solution Vis data for the Rh(III) stock solut ion solut ion A i m a x ( nm) fe ( M ' W 1 ) ) *2m a x(nm) ( E (M _ 1cm" '*)) re f . stock Rh(III) s o l ' n 400 (113) 506 (106) th is work d i t to 404 (67) 511 (74) 28 R h C l 4 ( H 20) 2" 385 (54) 488 (72) 95 (c is ) (trans) 381 (102) " (68) ^  487 (90) 96 96 R h C l 5 ( H 20) 2" 402 (73) 507 (73) 95 R h C l 3 ~ 6 404 (104) 507 (105) 96 411 (94) 518 (112) 95 413 (82) 517 (111) 96 2.2.9 Determination o f F e J + reduction equivalents About 100 mg of the complex to be analysed was oxid ized with a large (10-fold) excess of Fe(NH^)(S0^)2•12H20 in 3MHC1-1MH2S04 so lut ion at 90°C for 2+ 5% h under an argon atmosphere. The amount of Fe formed was determined 98 by potentiometric t i t r a t i o n with a 0.1M cerium ammonium su l fa te so lut ion A Fisher Accumet pH Meter Model 140 with a combination glass/platinum electrode was used. 2.2.10 Elemental analys is Elemental analyses for C, H, N and Cl were performed by Mr. P. Borda of th i s department. Analysis for rhodium was done co lo r ime t r i c a l l y by -46-99 r e a c t i o n with excess stannous c h l o r i d e i n aqueous HC1 , which was a l s o 100 used as a q u a l i t a t i v e t e s t f o r rhodium. A c a c o t h e l i n e s o l u t i o n , which i s a r e v e r s i b l e redox i n d i c a t o r f o r most t i n ( I I ) r e a c t i o n s , was used as a q u a l i t a t i v e t e s t f o r free t i n ( I I ) c h l o r i d e i n s o l u t i o n . On r e a c t i o n w i t h t i n ( I I ) a colour change from yellow to v i o l e t was observed. 2.3 Computational Techniques In several instances a n a l y s i s was f a c i l i t a t e d by use of the computing f a c i l i t i e s o f the UBC Computer Center. Some UV-VIS spec t r a acquired on the Cary 17 spectrophotometer were d i g i t i z e d using the Talos CYBERGRAPH d i g i t i z i n g t a b l e under c o n t r o l o f the program *DIGIT described i n the UBC DIGITIZER manual. The d i g i t a l data were then used to analyse the spectra of mixtures by simple curve s u b t r a c t i o n (see experiments described i n Chapters 3 and 4 ) . I n t e r p o l a t i o n routines described i n UBC TSPLINE were used i n simple FORTRAN IV programs to generate the curves to be sub t r a c t e d . The r e s u l t s were d i s p l a y e d on a Te k t r o n i x 4010 s e r i e s Storage Scope and/or p l o t t e d on a Houston Complot p l o t t e r using p l o t t i n g r outines described i n UBC PLOT. A d d i t i o n a l l y , f i g u r e s 1 and 2 from reference 91 were d i g i t i z e d and r e p l o t t e d to c o r r e c t the s c a l e f o r d i r e c t comparison to spec t r a obtained on the Per k i n Elmer 598 and Cary 17 spectrophotometers. No i n t e r p o l a t i o n was performed i n these cases. For a n a l y s i s of some k i n e t i c data a program was w r i t t e n i n FORTRAN IV (see Appendix A f o r l i s t i n g and d e s c r i p t i o n o f use). The program f a c i l i t a t e s f i r s t - o r d e r a n a l y s i s and manipulation o f data obtained i n absorbance u n i t s . -47-Three kinds o f f i r s t - o r d e r a n a l y s i s were i n c l u d e d : ln(A-A r a] vs. t , 101 101 102 Guggenhiem's method and the Kezdy-Swinbourne method ' . The l a t t e r was als o used to c a l c u l a t e by e x t r a p o l a t i o n a value of A m that could then be used in a ln(A-A ) vs. t c a l c u l a t i o n . An estimate o f the o v e r a l l order could be * CO 101 a l s o obtained using an approximate d i f f e r e n t i a l method . Curve f i t t i n g was by the least-squares method; the 'goodness of f i t ' measure was Pearson's Moment. To check the f i t a t a b l e o f r e s i d u a l s ( A Q ^ - A ^ ^ ) could be p r i n t e d . The s i z e s and signs o f th*e r e s i d u a l s would then fje examined f o r systematic skewing or obviously i n c o r r e c t l y entered data p o i n t s . The program has a l i m i t e d c a p a b i l i t y to handle d a t a n o t i n absorbance u n i t s , i n which case data s c a l i n g may be r e q u i r e d . -48-CHAPTER I I I  RESULTS (PART I) THE SYNTHESIS OF VARIOUS TIN CONTAINING RHODIUM COMPLEXES 3.1 I n t r o d u c t i o n . The i n i t i a l goal of t h i s p r o j e c t was to prepare s a l t s o f the rhodium(I) dimer [ R h 2 C l 2 ( S n C l 3 ) 4 ] 4 ~ . Treatment o f 3M HC1 o r e t h a n o l i c s o l u t i o n s of rhodium t r i c h l o r i d e t r i h y d r a t e w i t h a 2h f o l d excess of 103 SnCl 2*2H 20 at room temperature was reported to y i e l d the s a l t upon a d d i t i o n of a l e s s than 2 - f o l d excess of M +C1"(M + = Me„N +, Ph PH +). The 4 3 orange product was s a i d t o be s t a b l e i n a i r and r e c r y s t a l l i z a b l e from a 101+ 10:1 ethanol-3M HC1 mixture, i n 85% y i e l d . Jobs Method experiments showed that the complex was f u l l y formed at a Sn(11)/Rh(III) r a t i o of 3. Consonant w i t h t h i s , the o v e r a l l r e a c t i o n was formulated as: 2RhCl 3 + 6 S n C l 3 " 105 A f a r - I R study on t h i s dimer and the bromo-analogue r e s u l t e d i n s p e c t r a l assignments c o n s i s t e n t with the proposed s t r u c t u r e (Table 3-1). Several 106 Mossbauer s t u d i e s have a l s o included the chloro-dimer i n t h e i r scope. However, more recent workers dispute the i s o l a t i o n o f t h i s complex (see below). Using higher Sn(11)/Rh(III) r a t i o s rhodium(I) monomers with Sn:Rh s t o i -c h i o m e t r i c s of 4 and 5 have been obtained from 3M HC1 s o l u t i o n using s i m i l a r Cl-Sn Cl SnCl, 3 \ / \ / 3 Rh Rh / \ / \ C l 3 S n Cl S n C l 3 + 2SnCi; (3-1) -49-Table 3.1 Far-IR absorption frequencies (cm ) reported f o r [ R 4 N ] 4 [ R h 2 X 2 ( S n C l 3 ) 4 ] ( r e f . 105)* X v(SnX 3) v(Rh-y-X) v(Rh-Sn) Me Cl 363.0 336.1 288.2 266.9 209.8 Et Cl 360.8 333.8 288.4 271.6 208.6 Et Br 271 .1 260.4 197.5 175.8 217.1 Nujol mull ** Broad, asymmetric and not always resolved procedures. When Sn(11)/Rh(111) was equal to f i v e , [ M e 4 N ] 4 [ R h ( S n C l 3 ) 5 ] was 107 i s o l a t e d . With a l a r g e excess of SnCI 2-2H 20(Sn(11)/Rh (111)=200) the impure 108 109 s a l t , [ Me 3(PhCH 2)N] 3[Rh(SnCl 3) 4]-2[Me 3(PhCH 2)N]SnCl 3-SnCl 2 ' was obtained. The l a t t e r species i s of i n t e r e s t s i n c e the UV-VIS spectrum o f the i n i t i a l 98 s o l u t i o n i s the same as that reported f o r the s o l u t i o n species i n the spectrophotometry determination of rhodium using stannous c h l o r i d e . A rhodium(I) species w i t h f i v e t i n l i g a n d s was i d e n t i f i e d , i n s i t u , by 119 1 1 0 SnFTNMR , as being the p r i n c i p l e rhodium-tin complex i n 3MHC1 s o l u t i o n where the S n ( I I ) / R h ( I I I ) r a t i o was between 5 and 7. From s i m i l a r s o l u t i o n s , 5- 9 1 R h ( S n C l 3 ) 4 ( S n C l 4 ) was i s o l a t e d i n high y i e l d by p r e c i p i t a t i o n with the 3+ 3+ h i g h l y charged ca t i o n s M(NH 3) g (M=Ir,Rh) or Rh(en) 3 . The v i o l e t or brown--50-red c r y s t a l l i n e products were found to contain a l so one molecule of free 4- i l l 3 + SnClg per rhodium(I) complex. A c r ys ta l determination o f the Rh(NH 3 ) g s a l t revealed the geometry o f the rhodium(I) complex as tbp at rhodium and d i s to r t ed tbp at the unique t i n ( I I ) , with the equator ia l planes perpendicular ( f i gure 3-1). The complex is approximately s p h e r i c a l . The ch lo r ine atoms are arranged as a symmetr ical ly d i s to r t ed , 16 vertex, tetracapped truncated tet rahedron. This arrangement is comparable to the carbonyl arrangement in 112 0Sg(CO)-|2 •) a n d probably represents the most favourable way of packing the ch lor ides in space constra ined by the bonding requirements of the tbp RhSn^ u n i t . Use of tetraalkyl-ammonium, -phosphonium or -arsonium ch lor ides 91 as p rec ip i t an t resu l ted in the nearly quant i t a t i ve i s o l a t i o n o f a diamagne-t i c complex with the empir ical formula (R 4 E ) 3 [RhSngCl^ ] (E=N,P,As). The in f ra red spectrum of th is complex contains bands at 1940 cm - 1 and 600 c m - 1 Figure 3.1 The molecular s t ruc ture o f [ Rh ( SnC l 3 ) 4 ( SnC l 4 ) ] 5 ~ ( a f t e r ref. 111). -51-(sometimes s p l i t ) , which were shown to be ne i ther due to a hydrido- or N 2 -conta in ing complex. The complex was unstable at room temperature i n the s o l i d 3+ s t a t e . The Fe reduct ion equiva lent of the complex decreased over a few weeks, from 11.2 to 8.70 equivalents with no change in the r a t i o o f Rh:Sn :C l . Concurrent ly , the bands at 1940 cm" 1 and 600 cm" 1 d isappeared. 4- 91 Regarding sa l t s of [ R h 2 C l 2 ( S n C l 3 ) 4 ] , the same author found that for Sn(II)/Rh(III) r a t i o s of 3 or l e s s , under aerobic cond i t i ons , in 3MHC1 so lu t i on only rhodium(III) species were obta ined. The se r i es o f te t raa l kyl- i : ammonium sa l t s of [ R h C l g _ n ( S n C l 3 ) n ] ~ (4>n>l) was synthesized and charac te r i-3+ zed by f u l l elemental a n a l y s i s , IR, UV-VIS, magnetic s u s c e p t i b i l i t y and Fe reduct ion equiva lent weights. By monitoring the progress o f react ions where Sn(11)/Rh(III) equals 3, for vary ing time periods and at se lec ted temperatures from -13°C to +100°C, i t was determined that [ R h C l 2 ( S n C l 3 ) 4 ] 3 " was the precursor to [ R h C l 3 ( S n C l 3 ) 3 ] , the thermodynamically more s tab le complex. 90 An analogous conc lus ion was reached by other workers who independently prepared, under anaerobic cond i t i ons , the se r i es where 5^n^3 fo r both the bromo- and chloro-analogues. Sa l ts o f [RhC l ( SnC l 3 ) g ] ~ were always p r e c i p i -ta tab le from f r e sh l y prepared 3MHC1 so lu t ions where the Sn(II)/Rh(III) r a t i o was between 2 and 4. Complexes where n<4 were bel ieved to form by a slow coproport ionat ion with unreacted rhodium(III) ha l i des . This phenomenon had 107 been prev ious ly proposed in a b r i e f report , as being general f o r Rh(I I I ) , Ru(I I ) , 0s(I I ) and Pt(IV) react ions with stannous hal ides and Sn(aca\c) 2 in aqueous a c i d . 119 1 1 0 A Sn FT NMR study of species formed in s i t u , under aerobic c o n -d i t i o n s , in 3MHC1 so lu t ion confirmed the existence o f predominantly rhodium(III) -52-t i n - c o n t a i n i n g complexes f o r S n ( I I ) / R h ( I I I ) r a t i o s o f 4 or l e s s ( f i g u r e 3-2). As mentioned above, only at higher r a t i o s was a rhodium(I) species with f i v e t i n l igands predominant. From the beginning of our experimental work, the rhodium(I) dimer proved e l u s i v e (probably n o n - e x i s t e n t ) . Our r e s u l t s are c o n s i s t e n t with the 90 91 H O f i n d i n g s of other workers ' ' (reviewed above), whose data f i r s t came to our a t t e n t i o n i n l a t e 1980. Somewhat s e r e n d i p i t o u s l y , the range of experiments undertaken i n the present work overlaps with both the aerobic 0 1 2 3 4 5 Figure 3.2 D i s t r i b u t i o n of rhodium complexes i n 3MHC1 s o l u t i o n as a f u n c t i o n of mole r a t i o o f t o t a l coordinated t i n to t o t a l rhodium. a: [ R h C l 5 ( S n C l 3 ) ] 3 ~ , b: [ R h C l ^ S n C ^ ^ ] 3 " , c: [ R h C l 3 ( S n C l 3 ) 3 ] 3 " , 2-d: uncharacterized RhClII) s p e c i e s , e: [ R h C ^ S n C l ^ ] ~, f: [ R h C l ( S n C l 3 ) 5 ] 3 " and g: [ R h ( S n C l 3 ) 5 J 3 ~ . ( a f t e r r e f . 110). -53-and anaerobic work described i n the l i t e r a t u r e . In a d d i t i o n to product v a r i a t i o n w i t h the Sn(II) to Rh(III) r a t i o and temperature, we f i n d e f f e c t s due to the s i z e o f t h e ' c a t i o n , use of aerobic vs. anaerobic c o n d i t i o n s , and l i g h t . These are discussed i n the f o l l o w i n g s e c t i o n s . The complexes i s o l a t e d i n t h i s s t u d y , with one exc e p t i o n , have been p r e v i o u s l y described i n the l i t e r a t u r e . The nature of t h i s new complex i s considered i n the next s e c t i o n . 3.2 The nature of [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 ~ Formally, t h i s complex can be regarded as a rhodium(I) adduct of S n C l 4 . The s t r u c t u r a l assignment i s t e n t a t i v e , being based i n part upon s p e c t r a l data and i n part upon mechanistic grounds. I t i s a k i n e t i c product probably a r i s i n g from trapping o f a rhodium(I) intermediate by t i n ( I V ) c h l o r i d e , both being formed i n s i t u from the reduction o f a rhodium(III) chloro species by S n C l 3 ~ (see f o l l o w i n g s e c t i o n s ) . I t has the same con-90 3_ s t i t u t i o n as the known rhodium(III) complex [ R h C l ( S n C l 3 ) 5 ] • Although 3+ elemental a n a l y s i s , conductance and Fe reduction equivalents (sec.2.1.5.3) 119 are c o n s i s t e n t of course with the Rh(III) complex f o r m u l a t i o n , the Sn Mossbauer, IR and UV-VIS s p e c t r a l data are not. 90 Mossbauer data from t h i s work and reference are summarized i n Table 3.2. Although the data sets are d i s c o r d a n t , the d i f f e r e n c e between the I.S. of the [ R h C l ( S n C l 3 ) 5 ] 3 ~ and [ R h ( . S n C l 3 ) 4 ( S n C l 4 ) ] 3 ~ s a l t s i s apparent when taken r e l a t i v e to that o f [ R 4 N ] 3 [ R h C l 2 ( . S n C l 3 ) 4 ] . The far-IR spectrum 90 -1 o f [ M e 3 N ] 3 [ R h C l ( S n C l 3 ) 5 ] contains a broad strong v'(SnCl) band at 330 cm and a weak v(RhCl) band a t 275 cm"1. This l a t t e r band i s missing from the -54-Table 3.2 Mossbauer data f o r various rhodium-tin c h l o r i d e complexes r e f I.S Q.S. [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] - H 2 0 1.68(±.06) 1.80(±.03) t h i s work [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] 1 .85(±.05) 1.83(±.05) 90 [ E t 4 N ] 3 [ R h ( . S n C l 3 ) 4 ( S n . C l 4 ) ] . ( E t 4 N C l ) 0 1.79(±.04) 1 .84(±.01) t h i s work [Me 4N] 3[RhCl(SnCl 3) 5] 1.83(±.05) 1.83(±.05) 90 spectra o f the u n r e c r y s t a l l i z e d and r e c r y s t a l l i z e d samples o f the E t 4 N + s a l t of [ R h ( S n C l 3 ) 4 ( S n C l 4 ] ( f i g u r e 2.7 ), which i s c o n s i s t e n t w i t h the absence _ • 91 o f a c h l o r i d e l i g a n d trans to S n C l 3 i n t h i s complex . The changes due to r e c r y s t a l l i z a t i o n are problematic and w i l l be b r i e f l y addressed below. The CH3CN s o l u t i o n UV-VIS spectrum ( f i g . 2.8 ) i s d i s t i n c t i v e and q u i t e u n l i k e that f o r [ R h C l 3 ( S n C l 3 ) 3 J 3 _ and [ R h C l 2 ( S n C l 3 ) 4 ] 3 " i n CH3CN s o l u t i o n ( f i g u r e s 2.3 and 2.5 ) or i n 3M HC1 ( f i g u r e 3.3). The band at ^  380 nm i s a l s o seen i n f r e s h DMSO, 3MHC1 or (CH 3) 2C0 s o l u t i o n s , although the complex i s unstable i n these solvents (see a l s o Chapter I V ) . We b e l i e v e the 8 10 d i s t i n c t i v e spectrum a r i s e s from the d -d metal-metal i n t e r a c t i o n i m p l i c i t 3 i n the complex's formulation as [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] " which i s rhodium(I) with four S n C l 3 " ligands and one S n C l 4 l i g a n d . Q u a l i t a t i v e l y , the spectrum — r • - 113 resembles t h a t of a rhodium(I) complex such as |Rh(CNC 2H 5) 4 J C10 4 U'n CH3CN s o l u t i o n : X m : i v nm ( e , M^cm" 1): 435(260), 380(8400), 333(3450, s h ) , 308(24350), max 11 3e 282 (2100, sh) ) . The band a t 380 nm f o r our complex obeyed Beers Law over -55-the c o n c e n t r a t i o n range 2.5x10 M to 3.0X10 M i n CH3CN ( i n the dark). Upon r e c r y s t a l l i z a t i o n changes were observed i n the f a r - I R spectrum, as noted above. A d d i t i o n a l l y , the elemental a n a l y s i s f o r C, H and N changed (see s e c t i o n 2.1.5.3). The elemental formula changed from CgH 2 QN ( i e . Et^N +) to C 7HjgN which suggests p a r t i a l replacement of Et^NCl by CH^CN. There was no change i n the s o l u t i o n spectra upon r e c r y s t a l l i z a t i o n ( w i t h i n experimental u n c e r t a i n t i e s ) . I t i s probable that the changes seen by f a r - I R are a s s o c i a -i 1 1 1 200 300 400 500 W A V E L E N G T H ( N M ) Figure 3.3 3MHC1 s o l u t i o n UV-VIS spectra of [Me 4N] 3 [ R h C l 2 ( S n C l 3 ) 4 ] ( ) (10°C, [SnCl 2-2H 20] = 0.2M) arid [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 4 ] (10°C) (----) ( r e f . 91 ( f i g . 2 - ( l ) and 2-(2A) r e s p e c t i v e l y ) ; see note ( f i g . 2.1). -56-ted with the replacement o f l a t t i c e Et^NCl by CH3CN. Almost a l l the reported far-IR s p e c t r a o f Group VIII metal c h l o r i d e - t i n c h l o r i d e complexes e x h i b i t a weak band i n the 345-365 cm"1 region (see t a b l e s 3.1 and 3.3). Only i n the case o f the reported [ R 4 N ] 4 [ R h 2 C l 2 ( S n C l 3 ) 4 ] complexes was the o r i g i n o f t h i s 105 weak band d i r e c t l y considered , the conclusion being t h a t i t was not a v(SnCl) or v(Rh-y-Cl) band. 3.3 E f f e c t o f v a r i a t i o n o f some parameters on the s y n t h e t i c methods used i n 3M HC1. 3.3.1 P r e c i p i t a n t s i z e . Only impure products were obtained when Me^NCl was s u b s t i t u t e d by Et^NCl as p r e c i p i t a n t i n the procedures f o r s y n t h e s i s i n g [ R 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] (sec. 2.1.5.1) and [ R 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] - H 2 0 (sec.2.1.5.2). These l i t e r a t u r e methods are reported to give pure products f o r Me 4N +, Et 3 N H + , and E t 4 N + i n the former case and f o r Me 4N + i n the l a t t e r one. Using Et 4NCl i n the procedure described f o r [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] r e s u l t e d i n a s o l i d that showed ( i n comparison to the Me 4N + species) small d i f f e r e n c e s i n the s o l u t i o n ( f i g u r e 3.4) and s o l i d s t a t e ( f i g u r e 3.5) s p e c t r a . These d i f f e r e n c e s are too small to i n d i c a t e what the c o p r e c i p i t a t e d species might be, but the elemental a n a l y s i s f o r C, H, N (Table 3.4) i s lower than expected. This would i n d i c a t e the presence o f a species w i t h a higher t i n to rhodium s t o i c h i o m e t r y (eg. [ E t 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] ) . Differences i n the i s o l a t e d products from the [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] procedure when using Me 4NCl or Et 4NCl are very n o t i c e a b l e . In p a r t i c u l a r , the CH3CN s o l u t i o n Table 3.3 FAR-IR DATA reported for Group VHI-tin(II) chloride complexes Complex v(M-Cl) ref. [RuCl(SnCl3)5][Me4N]4 [OsCl(SnCl3)5nMe4N 14 [RhCl5(SnCl3)]:[Me4N]3 367 [RhCl 4(SnCl 3) 2]Cs 3 364(w) cis-[RhCl 4(SnCl 3) 2] [ M e ^ trans-[RhCl4(SnCl3)2] [Me4N]3 [RhCl3(SnCl3)3][Me4N]3 [RhCl2(SnCl3)4][Me4N]3 360(sh) [RhCl(SnCl3)5][Me4N]3 [ lr 2Cl 6(SnCl 3) 4][Me 4NJ 4 [ IrCl 3(SnCl 3) 3][Et 4N] 3 368 354 354 358(w) 358(w) 327 325(sh) 340 320 327 344(s) 348(w) 332(s) 348(w) 332(s) 312 314 310 323(s) 310(s) 295 295 290 254 212 310(s) 310(s) 337(s) 322(s) 303(sh) 345(sh) 335(s) 330(bs) 330 332 318(bs) 326(s) 287(sh) 270 200 249 269(w) 208 273(m) 254(w) 205 254(w) 205 273(m) 208 279(m) 270(ra) 210 208 325(s) 310(sh) 284(w) 328 315 312 275(w) 274 210 210 196 Table 3.3 (continued) Complex v(M-Cl) {IrCl(SnCl 3) 5][Et 4N 13 330 316 304 272 196 9 tPd(SnCl3)5] [Et 4Nl 3 328 308 300 198 9 [PdCl 2(SnCl 3) 2][Et 4N] 2 328 300 192 9 [Pt(SnCl 3) 5][Et 4N] 3 338 316 209 h 337 e 337 1 [PtCl 2(SnCl 3) 2][Et 4N] 2 356 339 317 290 278 9 352 337 306 280 f [Ph4As]2 337(s) 320(bs) 289(s) 202 h [PtCl 2(SnCl 3) 2][Et 4N] 2 336 314 294 275 9 [Ph 4Asl 2 340(s) 335(w) 325(s) 209 h a ref. 114 : KBr and Polyethylene pellets b ref. 92 : Nujol mull c ref. 91 : Nujol mull d ref. 90 : Polyethylene discs e ref. 115 : Nujol mull f ref. 106b: not stated g ref. 80 : Polyethylene and KBr pellets h ref. 116 : Nujol mull on polystyrene i ref. 105 : Nujol mull -59-20-, i ; 1 1 ill 2 0 0 300 400 500 WAVELENGTH (NM) Figure 3.4 I n i t i a l CH3CN s o l u t i o n UV-VIS spectra of (a) [Me 4N] 3[RhCl 3 ( S n C l 3 ) 3 ] ( ) , [ ] = 0.550 g /L (4.97 x 10~4M) and (b) that obtained using E t ^ N + ( ), [ ] = 0.672 gm/L. (pathlength = 0.1 cm; dotted l i n e = b a s e l i n e ) . spectrum o f the t e t r a e t h y l d e r i v a t i v e ( f i g u r e 3.6a) looks l i k e the sum of those o f [ R h C l 2 ( S n C l 3 ) 4 and [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 " . Proceeding on t h i s assumption, the spectrum of the l a t t e r was subtracted ( s e c t i o n 2.3 ) from t h a t of the mixture i n order to estimate the st o i c h i o m e t r y . The d i f f e -rence spectrum (figure3.6b) r e v e a l s that other species are present a l s o Figure 3.5 Far-IR spectra ( N u j o l , Csl p l a t e s ) o f (a) [Me 4N] 3[RhCl 3(SnCl3 ) 3 ] ( ) and (b) of the product obtained using E t d N + ( ). -61-Table 3.4 P a r t i a l elemental analyses f o r products obtained from [ R h C T 3 ( S n C l 3 ) 3 J 3 _ synthesis using Et.NCl-H ?0 p r e c i p i t a n t C H W % c a t i o n Expected: [Et 4N ^ [ R h C l ^ S n C l ^ 22 .60 4.71 3 .30 30.61 [ E t 4 N l 3 [ R h C l 2 ( S n C l 3 ) ] 19 .67 4.10 2 .87 26.64 Found: [ E t 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 J " 19 .99 4.20 2 .93 27.12 ( v i z . the band at ^ 370 nm). From the s u b t r a c t i o n procedure the r a t i o of [ R h C l 2 ( S n C l 3 ) 4 ] 3 " to [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 _ was estimated to be 1.2(±0.2). The new species seen i n the d i f f e r e n c e spectrum was not f u r t h e r characte-r i z e d . The f a r - I R spectra ( f i g . 3.7) are a l s o c o n s i s t e n t with the presence of a mixture. 3.3.2 Anaerobic vs. a e r o b i c c o n d i t i o n s . Performing a l l manipulations i n an argon atmosphere had a n o t i c e a b l e e f f e c t on the products obtained when using the procedure f o r preparing [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 L In the f a r - I R spectrum ( f i g . 3.8) a broad band a t 330 cm"1 has replaced the three band s t r u c t u r e seen i n the pure Me 4N + s a l t ( f i g . 2.1 ), although the shape o f t h i s band and the band at 275 cm - 1 i n d i -cate i t i s present. The s o l u t i o n spectrum ( f i g . 9) resembles t h a t observed f o r [ R h C l 2 ( S n C l 3 ) 4 ] ~ ( f i g . 2.5 ). In f a c t , v i s u a l comparison of the 3-r e s u l t a n t spectrum from the s u b t r a c t i o n o f that o f [RhCl,(SnCl,),] I -62-i n d i c a t e s only ^ 40% of the l a t t e r species i s present ( f i g . 3 . 1 0 ) . Consistent with the c o p r e c i p i t a t i o n of s a l t s w i t h higher Sn:Rh r a t i o s was an observed decrease i n % c a t i o n , by elemental a n a l y s i s (Table 3.5), o f 4.3% and 1.7% 2-0« W A V E L E N G T H ( N M ) Figure 3.6 I n i t i a l CH3CN s o l u t i o n UV-VIS spectra o f (a) [Me 4N] 3[RhCl 2(Sn-C l 3 ) 4 ] (- ), [ ] Q = 0.665 gm/L (5.13 x 10"4M) with (b) t h a t o f the product obtained using E t 4 N + ( ) [ ] = 0.658 gm/L and (c) the r e s u l t a n t spectrum a f t e r s u b t r a c t i o n of t h a t of [ R h ( S n C l 3 ) 4 ( S n C l 4 ] 3 ' ( ). (pathlength = 0.1 cm; dotted l i n e = b a s e l i n e f o r (a) and ( b ) . -63-100-j 0 I i i i i I i i i i I i i i i I 400 350 300 250 W A V E N U M B E R (CM-1) Figure 3.7 Far-IR spectra ( N u j o l , Csl p l a t e s ) o f (a) [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] ( ) and (b) of the product obtained using E t 4 N + ( ) compared with [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] . ( E t 4 N C l ) 0 g spectrum (• •)• -64-Figure 3.8 Far-IR spectra ( N u j o l , Csl pl a t e s ) of (a) [Me 4N] 3[RhCl 3(SnCl3 ) 3 ] ( -) and the i s o l a t e d products o f the anaerobic syn t h e s i s using (b) Me 4N + C ) and (c) E t 4 N + ( ). -65-2 0 , 200 300 400 500 W A V E L E N G T H ( N M ) Figure 3.9 I n i t i a l CH3CN solut ion UV-VIS spectrum of the product obtained using E t 4 N + in the synthesis of [Me 4 N] 3 [RhCl 3 (SnCl 3 ) 3 ] under anaerobic condi t ions, [ ] = 0.670 g /L (path length = 0.1 cm; dotted l ine = base l ine ) . for the te t raethy l- and tetramethyl-ammonium s a l t s , respectively. No analogous experiments were performed using the procedure used for synthesis of [Me.N] , [RhCl ? (SnCU) J (but see sec. 3.3.3). -66-3.3.3 Variation of Sn(11):Rh( III) ratio,and temperature. The synthetic procedure for [Me4N]3[RhCl3(SnCl3)3] was modified by using Et^ NCI in place of Me^ NCl, anaerobic conditions and increasing the 3 Sn(II)/Rh(III) ratio to 5. Initially, it was expected that [RhCl(SnCl3)g] 9 0 would be the major product ; however, a complex mixture was obtained instead. ooH I 1 1 , 200 300 400 500 W A V E L E N G T H ( N M ) Figure 3.10 Comparison of (a) resultant spectrum after the subtraction of 0.38 x fig. 2.8 ([RhCl3(SnCl3)3]3") from fig. 3.9 ( ) with '(b) [Me4N]3[RhCl2(SnCl3)4] spectrum (fig. 2.5) (•-—). -67-Table 3.5 P a r t i a l elemental a n a l y s i s f o r [RhCl 3 ( S n C l 3 ) 3 J 3 - sal t s Complex C H N % c a t i o n Expected: [Me^[RhCl 3(SnCl 3 ) 3 ](J_) 13.02 3.28 3.80 20.10 [ E t 4 N J 3 [ R h C l 3 ( S n C l 3 ) 3 J ( 2 ) 22.60 4.71 3.30 30.61 Found: "1" 11 .79 3.01 3.63 18.43 112 H 19.52 3.97 2.81 26.30 The elemental a n a l y s i s f o r the c a t i o n (C,H,N) was ^ 25%. This i s higher than the 23.59% c a t i o n expected f o r [ E t 4 N ] 3 [ R h C l ( S n C l 3 ) 5 ] but 1.3% lower than the comparable experiment where Sn(11)/Rh(III) was 3 ( t a b l e 3.5, sec.3.3.2). The s o l i d s t a t e IR spectrum ( f i g . 3.11a) of the y e l l o w product 91 was s i m i l a r to that of [ E t 4 N ] 3 [ R h S n 5 C l l 5 ] (% c a t i o n = 24.09%) . Also c o n s i s t e n t w i t h such a species was the observed disappearance of the bands at 1923 cm - 1 and 600 cm"1 over a period of several months ( f i g . 3.11b), while the region below 400 cm"''" remained e s s e n t i a l l y unchanged. The lack of bands at 275 cm"1 or at 273 cm"1 and 254cm" 1 i n d i c a t e s the absence of [ R h C l 3 ( S n C l 3 ) 3 ] 3 " or [ R h C l 4 ( S n C l 3 ) 2 ] 3 " as major p r o d u c t s 9 1 . The 400-250 cm"1 region i s s i m i l a r to t h a t o f [ R h C l 2 ( S n C l 3 ) 4 ] 3 " ( f i g . 3.12 ). The CH3CN UV-VIS s o l u t i o n spectrum ( f i g . 3.13) i s comparable to that of [RhCl 2(SnCl3)4.]^ ( v i z . bands at 290 nm and 428 nm), however there c l e a r l y are features which d i f f e r e n t i a t e the two. No s o l u t i o n spectra have been reported f o r e i t h e r 3 3 the [ R h S n R C l l R ] " or [ R h C l ( S n C l ^ ) R ] " species. Attempts to synthesize cn co Figure 3.11 IR spectra (Nujol , Csl plates) o f (a) the product i s o l a t e d , using Et^N"1", of the synthesis f o r [Me 4N] 3 [ R h C l 3 ( S n C l 3 ) 3 ] under anaerobic c o n d i t i o n s , using S n ( I I ) / R h ( I I I ) = 5, and (b) the same product several months l a t e r . -69-100-1 Figure 3.12 Far-IR spectrum ( N u j o l , Csl p l a t e s ) of (a) the i s o l a t e d product o f the synthesis f o r [Me^N] 3i [ R h C l 3 l ( S n C l 3 ) 3 ] under anaerobic c o n d i t i o n s and using Sn(11)/Rh(III) = 5 ( ), compared to (b) [Me 4N] 3 [ R h C l 2 ( S n C T 3 ) 4 ] spectrum (-—-). -70-2-0-, o z < §•10 o co 03 < 00-200 300 4 0 0 W A V E L E N G T H ( N M ) 500 Figure 3.13 I n i t i a l CH3CN s o l u t i o n spectra of the products i s o l a t e d using (a) the synthesis of [Me 4N] 3 [ R h C l 3 ( S n C l 3 ) 3 ] with E t 4 N + , anaerobic c o n d i t i o n s and S n ( I I ) / R h ( I I I ) = 5 ( ) and (b) 90 the product of the l i t e r a t u r e s y n t h e s i s of [Me 4N] 3 [ R h C l ( S n C l 3 ) 5 ] ( - — - ) • -71-90 [ M e 4 N ] 3 [ R h C l ( S n C l 3 ) 5 ] using the l i t e r a t u r e method f a i l e d to give a pure 117 product . This method i s s i m i l a r to ours, the d i f f e r e n c e being that the S n ( I I ) : R h ( I I I ) r a t i o i s 7.5 w i t h only 30 minutes heating at ^90°C rat h e r 119 than 60 minutes. The Sn FT NMR spectrum of the y e l l o w product obtained from t h i s source ( f i g . 3.14) reveals t h i s complex to be the major product ( m u l t i p l e t : 6 = -113.7 ppm,f 1J'^ Q 3 n g i = 556 Hz). Other products o Rh- Sn 1 observed are [ R h C l 2 ( S n C l 3 ) 4 ] (<5 = -219.8 ppm ( d o u b l e t ) , J 1 0 3 l i g o i Rh- Sn 586 Hz) and [ R h C l 3 ( S n C l 3 ) 3 r " (6 = 310.9 ppm (doublet) A J = 722 Hz). These assignments are based on the data i n ref. 110. The weak doublet at 6 = -50 ppm ( : j = 528 Hz) i s believed to be due to [Rh(H.,0)(SnCl,),] 3~ (see Sec. 3.5 ), w h i l e t h a t at 6 = -268.3 ppm ( 1 J i n , 1 1 Q = 678 Hz) i s I U J R h - i ySn unassigned. Some decomposition was evident over the duration o f the NMR experiment ( M 8 h ). The dark red-brown colour o f the concentrated s o l u t i o n faded to a paler yellow-orange and [ M e 4 N ] 2 [ S n C l g ] p r e c i p i t a t e d out. The decomposition pathway i s not known, but [ E t 4 N ] [ S n C l 3 ] was found to react with CH 3N0 2 producing p a r t i a l l y s o l u b l e [ E t 4 N ] 2 [ S n C l g ] plus a very s o l u b l e y e l l o w complex. Since a main thermal pathway o f decomposition (see Chap. 4) o f R h ( I I I ) - S n ( I I ) complexes i s v i a d i s s o c i a t i o n o f S n C l 3 ~ , i t i s probable that the Sn(IV) p r e c i p i t a t e o r i g i n a t e s from t h i s d i s s o c i a t i o n and subsequent r e a c t i o n with the s o l v e n t . This would r a t i o n a l i z e the presence of [ R h C l 3 ( S n C l 3 ) 3 ] i n s o l u t i o n . The IR o f the y e l l o w rhodium s a l t was nearly i d e n t i c a l to that i s o l a t e d by us ( i e . f i g . 3.11a). The only point of departure was the lack o f s p l i t t i n g i n the band at 600 cm" 1, which 91 i s c o n s i s t e n t with the presence o f [Me 4N] 3[RhSn gCl-| g] ( i . e . s u b s t i t u t i o n o f Me^ N"1" c a t i o n f o r E t ^ N + c a t i o n i n the s y n t h e s i s ) . Comparison of the CH3CN -113.7 I I I -219.8 -268.3 -310.9 67 ppm Figure 3.14 The 37.336 MHz 1 1 9 S n FTNMR spectrum o f the product i s o l a t e d using the l i t e r a t u r e ' 0 synthesis of [ M e 4 N ] 3 [ R h C l ( S n C l 3 ) 5 ] . (ambient temperature i n CD 3N0 2; run on XL-100 (12 mm OD tube): 25 KHz sweep widt h , 130K scans). -73-s o l u t i o n UV-VIS spectra ( f i g . 3.13a and b) i n d i c a t e s that there i s a greater d i f f e r e n c e between the two products than does the IR s p e c t r a . In p a r t i c u l a r , the r e l a t i v e amount of [RhCl2(SnCl3)4] appears t o be l e s s i n the product from the l i t e r a t u r e procedure (see sec. 3.6 f o r f u r t h e r d i s c u s s i o n ) . Despite of the u n c e r t a i n t y i n the i d e n t i f i c a t i o n o f a l l i s o l a t e d products, i t i s evident that i n c r e a s i n g the Sn(II):Rh(111) r a t i o from 3 to 5 or more, under s i m i l a r c o n d i t i o n s , r e s u l t s i n an increase i n the t i n to rhodium r a t i o i n the products i s o l a t e d . The e f f e c t s on the k i n e t i c products of the r e a c t i o n between Rh(I I I ) c h l o r i d e s and Sn(II) c h l o r i d e are d i f f e r e n t . These experiments are analogous to the synthesis of [ M e ^ ^ R h C l ^ S n C l ^ ] - H 2 0 (s e c . 2.1.5.2) i n that the t i n reagent and p r e c i p i t a n t are introduced together as [ E t ^ N H S n C ^ ] . The p r e c i p i t a t e s were i s o l a t e d when p r e c i p i t a t i o n appeared complete, u s u a l l y w i t h i n 5 or 10 minutes of m i x i n g , under anaerobic condi-t i o n s . In a l l cases discussed i n t h i s s e c t i o n , p r e c i p i t a t i o n occurred while t h i s reagent was being added as a s o l i d (or i n concentrated s o l u t i o n i n 3M HC1). At room temperature using a Sn(11)/Rh(III) r a t i o o f 1.8, and [ R h ( I I I ) ] = 0.017M, [ E t 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] was i s o l a t e d i n 78% y i e l d (% Cation ( c a l c . ) = 26.36 (26.44); IR given i n f i g . 2.4; UV-VIS i n f i g . 2.5) At 40°C using a Sn(11)/Rh(111) r a t i o of 3, and [ R h ( I I I ) ] = 0.056 M, an impure yellow-orange product was obtained. The IR spectrum ( f i g . 3.15a) al s o resembles that of [ E t 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] ; however, from the UV-VIS of the CH3CN s o l u t i o n ( f i g . 3.16a) the product was determined t o be a mixture of [ R h C l 2 ( S n C l 3 ) 4 ] 3 " and [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 ~ s a l t s in a r a t i o o f 4.4 to 1. I n t e r e s t i n g l y , slow p r e c i p i t a t i o n continued f o r ^12 h . The IR spectrum of -74-t h i s orange s o l i d ( f i g . 3.15b, 3.17b) d i f f e r s from that of the y e l l o w -orange one ( f i g . 3.15a, 3.17a). The CH3CN s o l u t i o n UV-VIS spectrum ( f i g . 3.16b) i s comparable to that of f i g . 3.6b ( f i g . 3.16c), which i s of the product obtained using the Et^N + m o d i f i c a t i o n of the synthesis of [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] (see sec. 3.3.1). In a d d i t i o n , the fa r - I R of the orange product i s s i m i l a r to that of the same product ( f i g . 17b, c ) . The amount of product obtained i n the f i r s t and second p r e c i p i t a t e s was 176 mg and 256 mg, r e s p e c t i v e l y . Using the estimated compositions of the ye l l o w -orange and orange p r e c i p i t a t e s discussed above, the composition of the material aggregated over ^12 h a t 40°C i s comparable to that aggregated Figure 3.15 IR spectra ( N u j o l , C sl p l a t e s ) of the (a) f i r s t p r e c i p i t a t e and (b) second p r e c i p i t a t e i s o l a t e d using [Et.NJLSnCl-]. -75-Figure 3.16 I n i t i a l CH3CN s o l u t i o n UV-VIS spectra of the (a) f i r s t ( •) and (b) second ( ) p r e c i p i t a t e s i s o l a t e d using [ E t 4 N ] [ S n C l 3 ] compared to (c) f i g . 3,6a (• •). 100-i 400 T 1 1 1 1 r 350 300 WAVENUMBER (CM-0 250 Figure 3.17 Far-IR spectra ( N u j o l , C s l p l a t e s ) of the (a) f i r s t ( ) and (b) second ( ) p r e c i p i t a t e s i s o l a t e d using [ E t ^ N ] -[ S n C l 3 ] compared to (c) f i g . 3.7b (• •). -77-over 2 h at 90°C. 3.3.4 The e f f e c t o f ambient l i g h t . A few t r i a l syntheses were performed i n the dark using previous expe-riments w i t h [Et 4N][SnCT 3] (considered above) f o r temporal estimates. A l l glassware was completely wrapped i n black p l a s t i c e l e c t r i c a l tape and mani-pu l a t i o n s of s o l i d s were done with overhead l i g h t s o f f . This had a n o t i c e -able e f f e c t on the products obtained from these procedures. When [ E t 4 N ] [ S n C l 3 ] ( s o l i d ) was added a t a Sn( I I)/Rh( I I I ) r a t i o o f 3, at room temperature, mixtures were obtained whose IR and UV-VIS spectra were s i m i l a r to those formed using the procedures a t 40°C i n the l i g h t . However, the UV-VIS spectra i n d i c a t e d that r e l a t i v e proportions of [ R h C ^ S n C l ^ ] to [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] i n the f i r s t c o l l e c t e d p r e c i p i t a t e dropped from 4.4:1 ( l i g h t ) to 1.7:1 ( d a r k ) . A l s o , i n the second p r e c i p i t a t e [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] was roughly twice as abundant as i n the previous ( l i g h t ) case. S u r p r i s i n g l y , when a concentrated s o l u t i o n of [ E t 4 N ] [ S n C l 3 ] ( i n 3MHC1) was added i n s t e a d , only a t r i v i a l amount o f p r e c i p i t a t e was obtained from the f i r s t f i l t r a t i o n i n c o n t r a s t to the few hundred m i l l i g r a m s p r e v i o u s l y obtained. A f t e r 5 days, f i l t r a t i o n y i e l d e d reasonably pure [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] as revealed by the f a r IR ( f i g . 3.18) and UV-VIS spectra ( f i g . 3.19). The shoulders seen i n the l a t t e r at ^ 270 and 290 nm are probably due to SnC^tCH-jCN) a r i s i n g from s o l v o l y s i s o f the rhodium complex (see sec. 4.2 ). As observed i n the previous s e c t i o n , the rate of formation of s a l t s o f [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 ' i s increased a t 90°C. At t h i s temperature and with a S n ( I I ) / R h ( I I I ) r a t i o o f 5, e x c e l l e n t y i e l d s of [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] - [ E t 4 N C l ] 0 5 were obtained (see sec. 2.1.5.3). Figure 3.18 Far-IR spectra ( N u j o l , Csl p l a t e s ) of the product i s o l a t e d from the t r a p p i n g experiment i n the dark. -79-Figure 3.19 I n i t i a l CH3CN s o l u t i o n UV-VIS spectrum o f the product i s o l a t e d from the trapping experiment i n the dark. -80-3.4 Attempts to prepare s a l t s o f [ R h 2 C l 2 ( S n C l 3 ) 4 ] 4 ~ . The p r e p a r a t i v e procedure i s o u t l i n e d i n s e c t i o n 3.1. Most o f the experiments were undertaken at a 1/6th reduced s c a l e , although using concen-1 0 3 , 1 0 4 t r a t i o n s reported i n the l i t e r a t u r e 7 . The l i t e r a t u r e r e p o rts were vague about the r e a c t i o n time; i n the present experiments the a d d i t i o n o f p r e c i p i -t a n t occurred about 20 minutes a f t e r the a d d i t i o n of SnCl 2-2H 20. Mixtures were obtained o n l y . None of the s p e c t r a l data could be c o r r e l a t e d s p e c i f i -103 c a l l y with reported data f o r the rhodium(I) dimer. Some components o f these 2- 3-mixtures were i d e n t i f i a b l e as s a l t s o f [ R h C l 2 ( S n C l 3 ) 4 ] , [RhCl(SnCl3)5] . [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 _ and [ R h S n 5 C l | 5 ] 3 " (see below). Other uncharacterized species were a l s o present. In a d d i t i o n to stu d i e s under aerobic c o n d i t i o n s , anaerobic experiments using 3MHC1 and ethanol as solvent were c a r r i e d out. Since the des i r e d product was not obtained, d i r e c t l i g a n d exchange was t r i e d , by a d d i t i o n of s t o i c h i o m e t r i c amounts o f [Et 4N][SnCl.j] i n acetone to a CH 2C1 2 s o l u t i o n of [ R h 2 C l 2 ( C 0 T ) 4 ] . This y i e l d e d a complex mixture of compounds h i g h l y s e n s i t i v e to a i r and moisture, which could only be incompletely charac-t e r i z e d (see below). Under aerobic c o n d i t i o n s and using 3MHC1 as s o l v e n t , an orange or yellow-orange product was obtained. The i n i t i a l CH3CN s o l u t i o n UV-VIS spectrum ( f i g . 3.20a) i s s i m i l a r to that of the product obtained with a S n ( I I ) : Rh(III) r a t i o of 5 ( f i g . 3.13 ). Under anaerobic c o n d i t i o n s the product was more ye l l o w (sometimes with a greenish t i n g e ) . A f t e r exposure to a i r f o r about a day, i t became orange. The y e l l o w product i s l e s s s t a b l e i n CH3CN s o l u t i o n than t h a t i s o l a t e d under aerobic c o n d i t i o n s . Changes i n the s o l u t i o n UV-VIS spectrum were observed during scanning ( v i z : f i g . 3.20b, breaks in,curve at -81-2 0 UJ o z < CQ B - 1 0 o V) CO < A 00-J f 2 0 0 I " 1— 3 0 0 4 0 0 W A V E L E N G T H ( N M ) — I 5 0 0 Figure 3.20 I n i t i a l CH3CN s o l u t i o n UV-VIS spectra o f products i s o l a t e d using 103 the reported s y n t h e s i s of [Me 4N] 4 [ R h 2 C l 2 ( S n C l 3 ) 4 ] : (a) i s o l a t e d under aerobic c o n d i t i o n s , ( ), (b) under anaerobic c o n d i t i o n s ( ) and\'c) the dotted l i n e i s f i g u r e 3.13a f o r comparison. -82-A = 2.0; A = 350 nm when sca l e s were changed). Nevertheless, [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] ~ i s c l e a r l y a component o f the mixture. Following storage o f the s o l i d f o r a few weeks under dry aerobic or anaerobic condi-t i o n s , i t s s o l u t i o n spectrum was more l i k e t h a t o f t h e p r o d u c t i s o l a t e d at a higher Sn(11)/Rh(111) r a t i o ( f i g . 3.20c). The IR and far-IR spectra ( f i g . 3.21 and f i g . 3.22) were s i m i l a r to those obtained from the products a t the higher r a t i o . A y e l l o w product was al s o obtained from ethanol s o l u t i o n , under anaerobic c o n d i t i o n s . The amount of product increased t h r e e - f o l d i n the absence o f l i g h t ('dark' product). The CH3CN s o l u t i o n UV-VIS spectra ( f i g . 3.23a,b) d i f f e r from those o f the products i s o l a t e d from 3MHC1 ( f i g . 3.23c,d). The band a t 380 nm, due to [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 ~ , i s now 3 _ l e s s prominent and there i s 1 i t t l e evidence f o r [ R h C l ( S n C l 3 ) 4 ] ( e s p e c i a l l y i n the 'dark' product). Instead, there i s a new band at ^ 328 nm ( a l s o seen i n 3MHC1 (317 nm), and CHgClg (332 nm)), which i s most prominent f o r the 'dark' product. This peak decreased i n i n t e n s i t y at a much slower r a t e than -83-Figure 3.22 Far-IR spectra ( N u j o l , Csl p l a t e s ) o f (a) the product i s o l a t e d 103 using the reported synthesis o f [Me 4N] 4 [ R h 2 C l 2 ( S n C l 3 ) 4 ] but under anaerobic c o n d i t i o n s ( ) and (b) f i g u r e 3.12a( V -84-Figure 3.23 I n i t i a l CHgCN s o l u t i o n UV-VIS spectra o f the products i s o l a t e d using the reported s y n t h e s i s 1 0 3 o f [Me 4N] 4 [Rh 2Cl 2(SnCl3 ) 4 ] but under anaerobic c o n d i t i o n s i n et h a n o l : (a) i s o l a t e d i n the l i g h t (- •) (b) i s o l a t e d i n the dark ( -). Figures 3.20a, c are o v e r l a i d as (c) (- ) and (d) ( -) r e s p e c t i v e l y . -85-the 380 nm peak (see Chap. 4 and sec.2.1.5). The band i s probably one of the absorbances o f [R h C l ( S n C l 3 ) g ] , which was i d e n t i f i e d as one of the more 119 s t a b l e major species i n an i n s i t u Sn FTNMR experiment (sec. 3.5 ). This assignment i s c o n s i s t e n t with the observations made with respect to the UV-VIS and NMR experiments where the S n ( I I ) / R h ( I I I ) was 5 or greater (sec. 3.3.3). The elemental a n a l y s i s f o r the Et ^ N + c a t i o n ( t a b l e 3.6; C,H,N a n a l y s i s ) was c l o s e to that expected f o r the p e n t a k i s - t r i c h l o r o s t a n n a t o ( I I ) s p e c i e s , although low o v e r a l l . I t i s d i f f i c u l t to assess the d i f f e r e n c e s a r i s i n g from the presence or absence o f l i g h t . The elemental a n a l y s i s f o r the c a t i o n , the s o l u t i o n spectra, and the fa r - I R ( f i g . 3.24), are not very d i f f e r e n t f o r the ' l i g h t ' and 'dark' products, which suggests s i m i l a r compositions. A d d i t i o n o f a f u r t h e r two equivalents of p r e c i p i t a n t to each f i l t r a t e , a f t e r i s o l a t i o n of the i n i t i a l p r e c i p i t a t e s , y i e l d e d brown or orange-brown p r e c i p i t a t e s . The y i e l d i n the presence of l i g h t was 2-3 f o l d greater than the corresponding i n i t i a l Table 3.6 P a r t i a l elemental a n a l y s i s o f yellow p r e c i p i t a t e from ethanol ( E t 4 N + s a l t ) C H N % c a t i o n Product i s o l a t e d i n dark: 16.75 3.62 2.51 22.88 In l i g h t : 16.94 3.62 2.56 23.12 Expected f o r [Et 4N] 3[RhCl ( S n C l 3 ) 5 ] 17.42 3.63 2.54 23.58 -86-100-i WAVENUMBER (CM-1) Figure 3.24 Far-IR spectra ( N u j o l , Csl p l a t e s ) o f the products i s o l a t e d 1 03 using the reported synthesis o f [Me 4N] 4 [ R h 2 C l 2 ( S n C l 3 ) 4 ] but under anaerobic c o n d i t i o n s i n e t h a n o l : (a) i s o l a t e d i n the l i g h t ( ) , (b) i s o l a t e d i n the dark ( ). -87-p r e c i p i t a t e but the elemental a n a l y s i s f o r C, H and N ( t a b l e 3.7) was con-s i d e r a b l y higher and the e m p i r i c a l formula derived was not that o f E t ^ N + . In the absence of l i g h t the amount of p r e c i p i t a t e was about 1/10 t h a t of the corresponding i n i t i a l p r e c i p i t a t e . The elemental a n a l y s i s was c o r r e c t f o r E t ^ N + but higher than p r e v i o u s l y . Probably ambient l i g h t l e v e l s are promoting s o l v o l y s i s o f the rhodium-tin complexes y i e l d i n g compounds w i t h lower Sn:Rh r a t i o s and c o n t a i n i n g s o l v e n t . However, no new bands i n the IR due to coordinated ethanol could be observed. The experiments discussed above a r e , i n a sense, intermediate between those i n which the k i n e t i c products were i s o l a t e d ( i . e . using [ E t 4 N ] [ S n C l 3 ] or simultaneous a d d i t i o n of SnCl2-2H 20 and p r e c i p i t a n t ) , and those i n which a longer period of e q u i l i b r a t i o n was used ( i . e . s y n t h e s i s of [ R h C l 3 ( S n C l 3 ) 3 ] s a l t s ) . I t should be noted t h a t products i s o l a t e d from 3MHC1 using the room temperature procedures based on the reported [ R f ^ C l p ^ S n C l g ) ^ 4 " s y n t h e s i s are s i m i l a r to those i s o l a t e d under the more rigorous c o n d i t i o n based on the Table 3.7 P a r t i a l elemental a n a l y s i s of brown p r e c i p i t a t e from ethanol ( E t 4 N + s a l t ) C H N % c a t i o n Empirical formula Product i s o l a t e d i n dark: 22.00 4.69 3.37 30.06 c s H 2 0 N i n l i g h t : 32.85 5.80 2.98 - C^H^N -88-synthesis o f [ R h C l 3 ( S n C l 3 ) 3 ] J ~ . The s u b s t i t u t i o n o f ethanol as solvent re-s u i t e d i n a much higher proportion o f [RhCl ( S n C l 3 ) g ] than seen i n the products i s o l a t e d from 3MHC1 . This a l t e r n a t i o n i n product mixture was ?at l e a s t p a r t i a l l y , due t o the change i n c h l o r i d e c o n c e n t r a t i o n . The f o l l o w i n g experiment was i l l u s t r a t i v e : a 1:3:^15 mixture o f RhCl 3-3H 20, SnCl 2-2H 20 and L i Cl was s t i r r e d f o r a few minutes i n dry ethanol under argon before a %3 f o l d excess o f Et 4NCl was added. The f a r IR ( f i g . 3.25) and CH^CN s o l u t i o n UV-VIS ( f i g . 3.26) spectra o f the d u l l orange product are s i m i l a r to those of products i s o l a t e d from 3MHC1 under s i m i l a r c o n d i t i o n s using [ E t 4 N ] [ S n C l 3 ] (sec. 3.3.3). The p r i n c i p l e components o f the product are [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 " and probably [ R h C l 2 ( S n C l 3 ) 4 ] 3 ~ . Since the l i t e r a t u r e methods (or r e l a t e d ones) d i d not y i e l d 2 [ R h C l 2 ( S n C l 3 ) 4 ] " s a l t s , the r e a c t i o n between [ R h 2 C l 2 ( C 0 T ) 4 ] and S n C l 3 " was examined. A deep p u r p l e , a i r and moisture s e n s i t i v e p r e c i p i t a t e was obtained, upon a d d i t i o n o f a deaerated acetone s o l u t i o n of [ E t 4 N ] [ S n C l 3 ] to a deaerated CH 2C1 2 s o l u t i o n of [ R h 2 C l 2 ( C 0 T ) , under argon i n the dark (Sn(II)/Rh(I) r a t i o was 2.5). The product decomposed i n a few days to a brown m a t e r i a l whose i n f r a r e d contained bands due to water (3500 cm - 1 and 1600cm" 1 ) . The source of the water was u n c e r t a i n , since the same r e s u l t s were obtained with a d i f f e r e n t batch of acetone d r i e d over molecular s i e v e s . I t i s po s s i b l e that t r a c e s of H 20 remained i n the solvent or were adsorbed on the s o l i d reagents which had been weighed at i n a i r . The purple product showed a strong asymmetric v(M-Cl) band at ^285 cm - 1 i n the f a r - I R ( f i g . 3.27a). Exposed to a i r , the s a l t turned brown w i t h i n hours. In a d d i t i o n to bands i n the IR i n d i c a t i v e of coordinated and/or absorbed water, the v(MCl) o f -89-100-r UJ o z < 5 z < DC I -400 —1 « 1 • 1 | — 350 300 WAVENUMBER (CM-1) 250 Figure 3.25 Far-IR spectrum of the i s o l a t e d product o f the r e a c t i o n between RhCl 3 • 3H2O and S n C ^ ^ r ^ O i n the presence o f excess Li Cl i n et h a n o l . Figure 3.26 I n i t i a l CH3CN s o l u t i o n spectrum o f the i s o l a t e d product o f the r e a c t i o n between RhCl 3-3H 20 and SnCl 2-2H 20 i n the presence o f excess L i C l i n e t h a n o l . - 9 1 -the brown compound ( f i g . 3.27b) i s s h i f t e d by about 15 cm"1 to higher wavenum-ber than i n the purple compound. This s h i f t would be c o n s i s t e n t with formal o x i d a t i o n of Rh(I) to R h ( I I I ) , leading to a reduction of e l e c t r o n - d e n s i t y on 115 the t i n and thus to a higher v(SnCl) . C o m p l e x e s o f t h e t y p e R h ( d i o l e f i n ) ( L ) 3 S n C l 3 (L = phosphine, a r s i n e or s t i b i n e ) have two or three i l l 8 overlapping v(SnCl) bands j u s t below and around 300 cm . These s h i f t 600 400 250 WAVENUMBER (CM-1) Figure 3.27 Far-IR spectra ( N u j o l , Csl p l a t e s ) of (a) the purple product o f the r e a c t i o n of [ R h 2 C l 2 ( C O T ) 4 ] with [ E t 4 N ] [ S n C l 3 ] ( ) and (b) the same product a f t e r a i r o x i d a t i o n ( ). -92-1-oH o i i i 1 r 300 400 500 600 700 WAVELENGTH(NM) Figure 3.28 I n i t i a l CH3CN solut ion UV-VIS spectrum of the purple product of the reaction of [Rh 2 Cl 2 (C0T) 4 ] with [Et 4 N][SnCl 3 ] (lower l i n e ) . Upper l i ne is of a second sample at higher scale expansion. 118 to higher wavenumber as L becomes less basic . Only bands assignable to E t 4 N + and M-Cl were observed, while.no COT appears to be present in the purple product. The purple product was probably a rhodium(I) stannous chlor ide complex. Elemental analysis was not obtained pr ior to decomposition. The i n i t i a l CH3CN UV-VIS spectrum ( f i g . 3.28 ) i s s im i l a r ( in the v i s i b l e region) to that of [Rh(SnCl 3 ) 4 (SnCl 4 ) ] 5 ~ in 3M HC1 solut ion (sec. 3.1). In the dark the purple colour fades, quickly becoming yel low. If th is yellow solut ion i s evaporated under vacuum and the residue taken back up in CH,CN, a purple so lut ion i s obtained. This behaviour i s consistent with -93-r e v e r s i b l e s o l v o l y s i s o f a l a b i l e rhodium(l) center. Although some rhodium(I) complex has been i s o l a t e d i n low y i e l d , i t was l i k e l y t o have been the monomeric pentakis t i n species.In an attempt to slow down the formation of complexes with a higher Sn:Rh r a t i o , the sy n t h e t i c procedure was repeated at -23°C, when a mixed deep purple and greenish/yellow-brown p r e c i p i t a t e however was obtained. When allowed to warm to room temperature the product l o s t i t s deep purple c o l o u r a -t i o n . This m a t e r i a l was h i g h l y a i r s e n s i t i v e , d i s c o l o u r i n g r a p i d l y on exposure to a i r and becoming b r i g h t orange w i t h i n a few hours. The i n i t i a l CHgCN s o l u t i o n UV-VIS spectrum o f t h e o r a n g e o x i d a t i o n p r o d u c t i s that of [ R h C l 3 ( S n C l 3 ) 3 ] 3 - ( f i g . 2.3 ). Part o f the unoxidized product may co n t a i n a R h ( S n C l 3 ) 3 s t r u c t u r a l u n i t . When the f l a s k c o n t a i n i n g the unoxidized m a t e r i a l under an argon atmosphere was b r i e f l y cooled by l i q u i d n i t r o g e n , the purple c o l o u r a t i o n was r e s t o r e d . This colour change was r e v e r s -i b l e ; several cool/warm: c y c l e s were completed with no apparent decay. On o x i d a t i o n , the thermochromic behaviour was not observed. While t h i s system was i n t e r e s t i n g , i t was not i n v e s t i g a t e d f u r t h e r . 119 3.5 Sn FT NMR experiments . Anaerobic 3MDC1/D20 and ethanol/acetone-dg (7:1 v / v ) s o l u t i o n s with a Sn:Rh r a t i o o f 3 were examined. The e t h a n o l i c s o l u t i o n a d d i t i o n a l l y con-ta i n e d 3 eq u i v a l e n t s o f L i Cl r e l a t i v e to rhodium. The rhodium concentration was 0.5M, which i s an order o f magnitude greater than i n the s y n t h e t i c expe-riments. Comparable data i n 3MHC1 under aerobic c o n d i t i o n s (Table 3.8 and f i g . 3.29) have been p u b l i s h e d 1 1 0 ( s e e a l s o sec. 3.3.3, f i g . 3.14). Tin-119 ( I = h , natural abundance 8.68%) FT NMR spectroscopy i s po-Table 3.8 Sn FT NMR characteristics of various rhodium-tin complexes (after ref. 110) (in 3M HC1 solution unless otherwise indicated) Structure assignment oxidation number of rhodium number of coordinated tin ligands 6/ppm V 0 3 R h - 1 1 9 S n ) ' H 2 2 j < 1 1 9 S n - 1 1 7 S n > / H Z 1 [RhCl 5(SnCl 3)] 3" III 1 -991.6 864 none -932.4a 860a nonea -914.l b 850b noneb 2 [RhCl 4(SnCl 3) 2] 3" III 2 -654.4 796 N.R. -637.0a 791a 3056a -626.0b 780b ' 3091b 3 [RhCl 3(SnCl 3) 3] 3" III 3 -411.1 718 2804 -395.4b 708b 2840b 4 d III 2 -281.4 664 5 [RhCl 2(SnCl 3) 4] 3" III 4 -204.3 590 2158 6 [RhCl(SnCl 3) 5] 3" III 5 -100.5 547 1952c 7 [Rh(SnCl 3) 5] 4" . I 5 8.5 806 3634 a: concentrated residue after separation of [Me 4N] 3[RhCl 3(SnCl 3) 3], b: 12M HC1 solution, c: HMPA solution, d: not assigned. -95-110 t e n t i a l l y u s e f u l i n c h a r a c t e r i z i n g rhodium c h l o r i d e - t i n c h l o r i d e complexes . Coordination to rhodium r e s u l t s i n a doublet due to s p i n - s p i n coupling w i t h 103 Rh ( I = h , nat u r a l abundance 100%). Complexes c o n t a i n i n g more than one t i n l i g a n d show coupling to ^ S n (I = 1/2, nat u r a l abundance 7.61%) and/or 115 Sn (il - h' » n a t u r a l abundance 0.35%) at s u f f i c i e n t l y high S/N. Usu a l l y the l a t t e r i s not observable. With one ex c e p t i o n , patterns observed i n 3MDC1 ( f i g . 3.30, t a b l e 3.9) and e t h a n o l i c s o l u t i o n ( f i g . 3.31, t a b l e 3.10) can be matched to those reported i n the l i t e r a t u r e (see above), on the basis o f the chemical s h i f t and 1 J - i - Ig data. The new resonance patte r n observed i s t h a t centered " Sn-103Rh -200 -600 -800 8/ppm 119 Figure 3.29 Sn FTNMR spectra o f 3NHC1 s o l u t i o n s c o n t a i n i n g various r a t i o s o f Sn(II) and Rh(III) c h l o r i d e s ( a f t e r r e f . 110). Accompanying data are i n t a b l e 3.8. -96-o ' — — -500 - 5 0 0 5 / p p m Figure 3.30 The 29.88 MHz , Sn FTNMR spectrum o f a 3M DCl/DpO s o l u t i o n c o n t a i n i n g a Sn(11)/Rh(III) r a t i o of 3, under argon. (Ambient temperature, run on WP-80 (10 mm O.D. tube); upper segment: 20 KHz sweep w i d t h , 20.88..K scans (pulse delay 2.0s, pulse width 7.0, 6.0 Hz l i n e broadening), lower segment: 20 KHz sweep w i d t h , 16.82 K scans (pulse delay 5.0 s, pulse width 7.0, 6.0 Hz l i n e broadening)). -97--r o T T -200 119, I -400 S/PPm Figure 3.31 .The 29.88 MHz M 3 S n FTNMR spectrum o f an e t h a n o l i c s o l u t i o n (15% acetone-dg) c o n t a i n i n g a 1:3:3 r a t i o o f R h ( I I I ) , Sn(II) and L i C l under argon. (Ambient temperature, run on WP-80 (10 mm O.D. tube); 20 KHz sweep w i d t h , 13.240 K scans (pulse delay 4.5 s, pulse width 7.0, 6.0 Hz l i n e broadening); a d d i t i o n a l l y , f i r s t 4 data points were removed from the f . i . d . to smooth the b a s e l i n e ) . at (5 = -50 ppm (^119sn-103Rh = 526Hz) i n e t h a n o l i c s o l u t i o n , which appears 3-as a s i x l i n e m u l t i p l e t overlapping those due to [ R h C l ( S n C l ^ g ] 0 - at 6 = -112 ppm. With reference to f i g . 3.14 ( CD-jNOg s o l u t i o n ) , the same c e n t r a l doublet can be noted at <5 = -52 ppm ("^ng^ 103R n = 526Hz). The number of t i n atoms (n) coordinated to the rhodium center can be estimated from the r a t i o o f the i n t e n s i t y o f s a t e l l i t e peaks, due to 1 1 9 S n - ^ S n c o u p l i n g , to the i n t e n s i t y o f doublets due t o species contain-119 ing only one Sn n u c l e i . For the simplest case where a l l the t i n atoms 119 Table 3.9 Sn FT NMR characteristics of rhodium-tin complexes observed in 3M DC1/D-0 solution with Sn/Rh =3 Z Structure assignment oxidation number of number of coordinated rhodium tin ligands 6/ppm l j ( 1 0 3 R h - 1 1 9 S n ) / H z 2 J ( 1 1 9 S n _ 1 1 7 ^ / H z 'Sn)' [RhCl 3(SnCl 3) 3] 3" as #4 table 3.8 [RhCl 2(SnCl 3) 4] 3" n.o.: not observed III III III 3 2 4 -415.7 -282.7 -209.6 718 664 600 2838 n.o. n.o. 119 Table 3.10 Sn NMR characteristics of rhodium-tin complexes observed in ethanol/acetone-d6 solution containing Sn/Rh = 3 Structure assignment oxidation number of rhodium number of coordinated tin liqands 6/ppm 1 j ( 1 0 3 Rh- 1 1 9 Sn )/ H z 2 j ( 1 0 9 Sn- 1 1 7 Sn ) / H z [RhCl 4(SnCl 3) 2] 3-[RhCl 3(SnCl 3) 3] 3" [RhCl(SnCl 3) 5] 3" [Rh(H 20)(SnCl 3) 5] 3" III III III III 2 3 5 5 -600 a -425 -112 -50 > 740 a 737 556 526 n.o. n.o. b. 1689 dinated Sn(IV) species are at -460 p.p.m. b: see text for assignments and discussion, n.o.: not observed. p.p.m. Note that similarity "folded-in" signals due to uncoor--99-are m a g n e t i c a l l y equivalent (or are undergoing r a p i d exchange on the NMR time s c a l e ) combinatorial a n a l y s i s can be used t o c a l c u l a t e the 1 s a t e l 1 i t e ^ I m a i n p e a k ( I s / I m ) r a t i o i n the expected s e x t u p l e t pattern ( f o r n > 2) (see Appendix B). Figure 3.32 i s a p l o t o f I s/T as a fu n c t i o n o f n. In 3MHC1 s o l u t i o n a t ambient temperature, the observation o f only one kind o f s a t e l l i t e pattern ( i . e . a s e x t u p l e t ) can be a t t r i b u t e d to f a s t i n t r a m o l e c u l a r no scrambling of the t i n l i g a n d s on the NMR time s c a l e . Assuming t h i s to be the case i n e t h a n o l i c s o l u t i o n f o r the s e x t u p l e t at 6 = -50 ppm, the number 20.0H c E <0 10.0 0> 0.0 Figure 3.32 P l o t of ^ a t e n ^ / I ^ i n vs. the number of coordinated 1 1 9 S n and 1 1 7 S n n u c l e i (n) (see Appendix B). -100-of t i n l i g a n d s per rhodium i s 5 ( l s / I m ( o b s ) = 14.4%). The formal o x i d a t i o n s t a t e o f the rhodium i s probably ( I I I ) and not ( I ) , by analogy t o the trend reported f o r 5 and ^ 103Rh_119s n a s a f u n c t i o n o f n, f o r Rh(III) and Ru(II) n o 1 complexes . As n increases,6 becomes more p o s i t i v e and J i 0 3 R n 119sn decreases. A l t e r n a t i v e l y the S n ( I I ) : Sn(IV); Rh mass balance could be computed s i n c e only one species i s unknown. Due to time l i m i t a t i o n s , the data were not accumulated, although a f o l d e d - i n si g n a l a s s o c i a t e d with Sn(IV) species i s observed at about 6 = -465 ppm. The new p e n t a k i s ( t r i c h l o r o s t a n n a t o ( I I ) ) rhodium(III) complex may be [Rh(H,,0)(.SnCl3)gJ ". The constancy o f 6 and ^103Rh-H9sn i n ^ w 0 d i f f e r e n t s olvent systems and the downfield s h i f t r e l a t i v e to [ R h C l ( S n C l j ) ^ ] " i n d i c a t e replacement o f C l " by a l e s s e l e c t r o -A r> 92 negative 1 igand(e.g. [RuCl(Sn.Cl 3) 5] vs. [Ru(.CH 3CN)(SnCl3) 5] i n CD3NO3 ) t h a t i s not the s o l v e n t media. Since the concentration o f H 20 i n the et h a n o l i c s o l u t i o n i s comparable to the c h l o r i d e concentration and i s much greater than i n dry CD 3N0 2 , water i s the probable candidate. The resonance pattern f o r [RhCl(SnCl3)5] " deserves comment. In 110 3MHC1 a s e x t u p l e t was observed , but i n CD3N02 ( f i g . 3.14) and ethanol/ acetone-dg (7:1 v / v ; f i g . 3.31) the more complicated pattern suggests non-f l u x i o n a l behaviour. I f the molecule i s assumed to be r i g i d and, i f 115 coupling due to Snand to molecules c o n t a i n i n g 3 spin a c t i v e t i n atoms are assumed to be unobservable because o f the S/N, then a 28 l i n e pattern i s expected. The pattern i s the weighted sum o f two AX, four AMX and the AB parts o f one ABX pattern (see Appendix B f o r d e t a i l s ) . The t r a n s - 1 1 ^ S n - 1 1 ^ S n couplings are expected to be an order of magnitude greater than the c i s -110,119.120,121, couplings 1 ( i e . ^ 20,000Hz vs. ^2,000 Hz), and not r e a d i l y \ -Un-observed i n f i g . 3.31, because o f the r e l a t i v e l y narrow sweep width of 20,000 Hz. The spectrum i l l u s t r a t e d i n f i g . 3.14 i s s u f f i c i e n t l y wide but no trans couplings can be noted. A s i m u l a t i o n o f the c e n t r a l pattern o f resonances was attempted. Fewer than the expected 24 l i n e s were observed i n CD 3N0 2 ( f i g . 3.14) and ethanol/acetone ( f i g . 3.31), although r e l a t i v e i n t e n s i t i e s and the number of l i n e s were the same. A simulated spectrum was 122 generated using UBC PANIC and UBC ADD under the assumption that the d i f f e r e n c e i n chemical s h i f t s f o r the a x i a l and e q u a t o r i a l t i n s i s small enough so that the AX patterns merge due to the magnitudes of the peak width and d i g i t a l r e s o l u t i o n . A d d i t i o n a l l y , the c i s - c o u p l i n g constants were se l e c t e d so t h a t the l o w - f i e l d s a t e l l i t e s n e a r l y merge. The parameters used are l i s t e d on Appendix C. Comparison o f the c a l c u l a t e d and observed spectrum in ethanol/acetone-dg. reveals a mismatch on the high f i e l d s ide ( f i g . 3.33). In p a r t i c u l a r , there i s no correspondence between the c a l c u l a t e d pattern o f 119 couplings with a x i a l Sn and the observed p a t t e r n . The i m p l i c a t i o n i s that some exchange process i s s t i l l being observed. V a r i a b l e temperature e x p e r i -ments were not undertaken to i n v e s t i g a t e t h i s point f u r t h e r . Of .primary i n t e r e s t are comparisons that can be drawn between the i n s i t u NMR experiments and corresponding s y n t h e t i c s t u d i e s o f the complexes [ R h 2 C l 2 ( S n C l 3 ) 4 ] 3 " ( s e c . 3.4) and [ R h C 1 3 ( . S n C l 3 ) 3 ] 3 ~ (sec. 3.3.1,2). The i s o l a t e d products have been shown to be rhodium(III) or rhodium(I) complexes with four or more t i n ligands rather than the reported rhodium(I) dimer. The species observed i n the NMR experiments were shown to be s t a b l e f o r at l e a s t 48 h by c o l l e c t i n g a second spectrum i n each case. Very l i t t l e change was noted. However, over longer periods (1-2 weeks) considerable change was noted; only uncoordinated Sn(IV) c h l o r i d e s (^6 = -640 ppm) were - 1 0 2 -observed. The d i s t r i b u t i o n of species i n ethanol/acetone-dg s o l u t i o n i s i n reasonable agreement with the s y n t h e t i c r e s u l t s . The pentakis ( t r i c h l o r o -stannato)rhodium(III) complexes appear to be f a i r l y s t a b l e i n s o l u t i o n , although the presence of a minor amount o f [RhCl^(SnCl3) 33 p o s s i b l y r e s u l t e d from p a r t i a l decomposition (see sec. 3.3.3). The a d d i t i o n o f three equivalents of L i C l i n the NMR experiment represents the c h l o r i d e introduced w i t h the simulation Figure 3.33 Comparison of observed (29.88 MHz) and synthesized resonances f o r [ R h C l ( S n C l 3 ) " as observed i n ethanol/acetone-dg s o l u t i o n (note: trans couplings not shown due to s c a l e ) . -103-p r e c i p i t a n t i n the s y n t h e t i c procedure. The correspondence between the two experiments suggests that the c h l o r i d e ion concentration i s important to the outcome of the synth e s i s (see a l s o sec. 3.4). In c o n t r a s t both the anaerobic experiment i n 3M DC1/D20 ( f i g . 3.31), n o and the reported aerobic experiment i n 3M HCl/r^O ( f i g . 3.30; Sn/Rh = 3 ) , i n d i c a t e that [RhCl^(.SnCI3)3!] i s the major species i n s o l u t i o n . This i s c o n s i s t e n t with the [ R h C l 3 ( S n C l 3 ) 3 J s y n t h e s i s under aerobic c o n d i t i o n s using Me 4N + as the p r e c i p i t a t i n g c a t i o n . I t i s , however, i n c o n s i s t e n t with + 3-the r e s u l t s using Et 4N and/or anaerobic c o n d i t i o n s where [ R h C ^ C S n C l . ^ ] was the major or s i g n i f i c a n t product. This complex has been shown to 3- 91 decompose to [ R h C l 3 ( S n C l 3 ) 3 ] i n 3M HC1 (see a l s o chap. 4 ) , which could account f o r the present s i t u a t i o n . On the other hand, weak resonances due to [ R h C l 2 ( S n C l 3 ) 4 ] " are observable at -209.6 ppm ( f i g . 3.31) and the s y n t h e t i c product d i s t r i b u t i o n may a r i s e from p r e f e r e n t i a l p r e c i p i t a t i o n of 3 the l e s s s o l u b l e [ R h C l 2 ( . S n C l 3 ) 4 ] ~ s a l t which could be in e q u i l i b r i u m w i t h 3_ [RhCl 3(SnCl3 )3 ] i n s o l u t i o n . There i s , however, an i n t e r e s t i n g d i f f e r e n c e i n composition between the aerobic and anaerobic NMR experiments. In the , . 110 l a t t e r no m u l t i p i e t i s seen at +8.5 ppm due to a rhodium(I) complex , but there i s a r e l a t i v e l y greater amount o f free Sn(IV) i n r e l a t i o n to [ R h C l 3 ( S n C l 3 ) 3 ] 3 " (^20 - 25%) than i n the aerobic case (^8%). Presumably, e i t h e r more o x i d a t i o n o f Sn(II) to Sn(IV) ( i e : reduction o f Rh(III) to Rh(I)) occurs under anaerobic c o n d i t i o n s than under aerobic c o n d i t i o n s , or l e s s coordinated t i n i s ' v i s i b l e ' as a r e s u l t o f exchange processes. The l a t t e r 3-i s more l i k e l y s i n c e the [RhCl2(SnCl3)4] resonances are reported to be tempe-110 r a t u r e dependent -104-3.6 Discussion A n i o n i c rhodium(III) products were i s o l a t e d under most conditions using RhCl 3'3H 20 as s t a r t i n g m a t e r i a l . The complexes were not the r e s u l t o f a i r o x i d a t i o n of rhodium(I) complexes since both anaerobic and aerobic c o n d i t i o n s were i n v o l v e d . Trapping experiments i n 3M HC1 at or near ambient temperature revealed that [ R h C l 2 ( S n C l 3 ) 4 ] was formed p r i n c i p a l l y during the i n i t i a l stages o f r e a c t i o n , whereas the new complex [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] was formed g r a d u a l l y . A d d i t i o n a l l y , the p r e v i o u s l y reported observation 3- 3 91 that [ R h C l 3 ( S n C l 3 ) 3 ] i s not a precursor to [ R h C l 2 ( S n C l 3 ) 4 J i s corroborated. T h i s , and the l a t t e r ' s r a p i d formation would tend to r u l e out 3- 12 3 uncatalysed ' c l a s s i c a l ' stepwise formation o f [ R h C l 2 ( S n C l 3 ) 4 ] by sub-s t i t u t i o n or i n s e r t i o n processes. Based on the pattern of r e s u l t s presented i n the preceding s e c t i o n s , p r e l i m i n a r y concepts about the r e a c t i o n mechanism can be formulated. I t should be recognized that information i s l i m i t e d , s i n c e only the S n C l 3 ~ c o n t a i n i n g complexes were i s o l a t e d ( i n moderate to good y i e l d s with respect to t i n ) . The y i e l d based on rhodium was often small when the i s o l a t e d complexes contained Sn:Rh r a t i o s i n excess of the experimentally used r a t i o were obtained. The probable mechanism i n v o l v e d competition between the expected • 9 1 1 0 9 ' s t r a i g h t - f o r w a r d ' reduction of Rh(III) by Sn(II) ' , and s u b s t i t u t i o n of Rh(III) complexes c a t a l y s e d by Rh(I). S i m i l a r c a t a l y s i s by a lower valence species i s i m p l i c a t e d i n the CO reduction o f Rh(III) h a l i d e s i n aqueous h a l o - a c i d , and i n the formation of [ R h ( p y ) 4 C l 2 ] from [Rh(H 20)Cl,.]"" and 125 p y r i d i n e i n e t h a n o l i c s o l u t i o n . The mechanisms are b e l i e v e d to be -105-analogous to the c l a s s i c example of s u b s t i t u t i o n at Pt(IV) c a t a l y s e d by 126 P t ( I I ) complexes , where the presence o f four-coordinate P t ( I I ) , o r reducing agents capable of reducing Pt(IV) to P t ( I I ) , produced a marked increase i n r a t e s . 3.6.1 K i n e t i c products To the best o f our knowledge,details o f the reduction: Rh(III) + Sn(II) = Rh(I) + Sn(IV) (3.2) have not been i n v e s t i g a t e d but i t i s probably analogous to the known r a p i d 127 reduction o f Pt(IV) to P t ( I I ) by S n ( I I ) . In 3MHC1 the p r i n c i p l e reductant was SnCl^", and the reduction was more r a p i d than formation of 1:1 complexes between P t ( I I ) and S n ( I I ) . At low [ C l ~ ] , the rate was slower due to forma-t i o n o f l e s s a c t i v e d i - and mono-chloro Sn(II) species: [ S n C l ] + + C l " ^ = ^ S n C l 2 (3.3) S n C l 2 + C l " F=* [ S n C l 3 ] " (3.4) The e l e c t r o n t r a n s f e r was b e l i e v e d to be innersphere v i a the t r a n s i t i o n 3- ¥ s t a t e ( [ C l g P t . . . C l . . .SnCl 3] ~ ) T . In order to accommodate our s y n t h e t i c observations, the subsequent r e a c t i o n of Rh(I) w i t h SnCl^" must occur at a rate comparable to or - greater than the reduction step (see below). A second -106-3-presumption i s that [RhCl g _ n ( S n C l 3 ) n ] complexes are not as r e a d i l y reduced by SnCl2~ as n i n c r e a s e s . This i s reasonable s i n c e the d e s c r i p t i o n o f these complexes as f o r m a l l y Rh(III), i n the same sense perhaps as RhCl 5(H 20) , may be i n a p p r o p r i a t e given the reducing nature of the S n C l 3 ~ l i g a n d . The ii Rh(111)/Rh(I) formalism i s used here, bearing t h i s i n mind. The data on the k i n e t i c products are c o n s i s t e n t w i t h the f o l l o w i n g mechanism. ( I t should be noted that the composition of the "RhCl 3-3H 20" 96 s o l u t i o n i s i n d e f i n i t e , although i t s exact composition i s not c r u c i a l to the d i s c u s s i o n ) . L i s C l " or r^O. [ L 5 R h n i C l ] n - + [ S n C l 3 ] - — ^ R h ^ f - t S n C l 4 + L (3.5) m f a s t T 0 _ [RhL 4.] m" + 4 [ S n C l 3 r v = ^ [ R h x ( S n C l 3 ) 4 ] 3 - + 4L P" (3.6) [ R h ^ S n C l ^ ] 3 ^ + S n C l 4 — > [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 " (3.7) Y m" + [ R h ( S n C l 3 ) 4 ] 3 " + [L R h C l ] n _ ^[Y-Rh(SnCl 3) 4-"Cl---RhL 5] ( 3 + m + n )-J [ Y - R h ( S n C l 3 ) 4 C l ] ( 2 + n ) _ [ R h L 4 ] m _ + L (3.8) I f Y = H 20 then a subsequent step could be 3.9, although t h i s could be a R h C l ( H 2 0 ) ( S n C l 3 ) 4 2 " + C T F = ^ R h C l 2 ( S n C l 3 ) 4 3 ' (3.9) i ^ 128 slow step i f unassisted -107-r i l r Intermediates s i m i l a r to the c h l o r i d e bridged Rh /Rh species i n 129 ; step 3.8 are commonly involved i n inner-sphere redox processes , although high charge makes t h e i r chemical l i f e t i m e s h o r t . A f t e r a two-electron t r a n s f e r (Rh(I)—»Rh(III)) w i t h i n the intermediate, decomposition occurs v i a cleavage; of the newly l a b i l e RhCl)-yCl bond. D i r e c t observation o f analogous hali.de bridged d 6 - d 8 complexes i s l i m i t e d t o an I r ( I l / I r ( I I I ) d i m e r 3 0 , formed by a s s o c i a t i o n of (ICH 3C 6H 4)NH 2)Ir(.C0) 2Cl and t ( C H 3 C 6 H 4 ) N H 2 ) I r C C 0 ) 2 C l I 2 i n CH 2C1 2, having one of two p o s s i b l e s t r u c t u r e s : Cl CO Cl CO CCH 3C 6H 4)NH, CO ( C H 3 C 6 H 4 ) N H ^ I r \ CO 0C 0C ,C1 NH 2(C 6H 4CH 3) Cl 0C \ \ I r N NH 2(C 6H 4CH 3). C 0 II The newly formed Rh(I) species (equation 3.8) can react with, f r e e S n C l 3 ~ (equation 3.6) to complete a c a t a l y t i c c y c l e . The s e l e c t i v i t y towards high c o o r d i n a t i o n numbers o f S n C l 3 " r e s u l t s i n a scavenging e f f e c t with respect to the reductant. The k i n e t i c products, [RhCl ?(SnCl^) 41 3~ -108-and [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] ~, are not s t a b l e i n s o l u t i o n , and the products i s o l a t e d a t longer r e a c t i o n times r e f l e c t t h i s . The observed photo-enhancement o f the formation of [ R h C l 2 ( S n C l 3 ) 4 ] 3 ~ i s not i n c o n s i s t e n t with the postulated mechanism, and indeed, i t might be construed as i n d i r e c t support. Such photo-induced e l e c t r o n t r a n s f e r r e a c t i o n s 131 are known . For example [ ( N H 3 ) 5 C o I n N C R u n ( C N ) 5 r 5NH 3 + C o 1 ^ + [ R u 1 1 1 ^ ) ^ " (3. .10) 132 i s e f f e c t e d by i r r a d i a t i o n a t 375 nm . A l t e r n a t e l y , photo-induced s u b — 13 3 p s t i t u t i o n of the aquo-ligand i n [ R h C l ( H 2 0 ) ( S n C l 3 ) 4 ] by C l " could be important, although i n 3MHC1 exposure of t h i s complex to d a y l i g h t appears to cause a net replacement of S n C l 3 ~ by C l " (see Chapter 4 ) . 3.6.2 Subsequent r e a c t i o n products The net e f f e c t of competition ( r e d u c t i o n vs. s u b s t i t u t i o n ) on the products i s o l a t e d i s i n t r i c a t e l y dependent upon s t a r t i n g c o n d i t i o n s and r e a c t i o n time. I n i t i a l l y the f r e e S n C l 3 ~ i s r a p i d l y consumed by the combined a c t i o n of the c a t a l y s e d s u b s t i t u t i o n r e a c t i o n forming rhodium(III) t r i c h l o r o s t a n n a t o complexes and the formation of rhodium(I) t r i c h l o r o s t a n n a t o complexes, havingi t i n to rhodium s t o i c h i o m e t r i c s of 4 or 5. I f the t o t a l t i n to rhodium r a t i o i s low (= 3 ) , then R h ( I I I ) and Rh(I) complexes which do not c o n t a i n t i n w i l l a l s o e x i s t i n s o l u t i o n . At higher S n ( I I ) / Rh(III) r a t i o s (> 5), fewer R h ( I I I ) or non-tin c o n t a i n i n g R h ( I I I ) complexes w i l l be present by v i r t u e of the greater amount of reductant/1igand. -109-The presence of unreacted Rh(III) w i l l be important under anaerobic c o n d i t i o n s . Attempts at s y n t h e s i z i n g [ R h C l 3 ( S n C l 3 ) 3 ] ~ under these c o n d i t i o n s '3)4" i3-wa 91 3 r e s u l t e d i n i s o l a t i o n o f [RhClpOSnCl.,).] " as major product. Under ;aerobic conditions, however, [ R h C l 3 ( S n C l 3 ) 3 ] " s the major product. The t e t r a k i s - stannato complex i s unstable i n s o l u t i o n (sec. 4.3), y i e l d i n g t r i s - s t a n n a t o species and free S n C l 3 ~ as major products. + C 1 " [ R h C l 3 ( S n C l 3 ) 3 ] 3 " + S n C l 3 ' (3.11a) [ R h C l 2 ( S n C l 3 ) 4 ] 3 " ^ v e n ^ [ R h C l 2 ( s o l v e n t ) ( S n C l 3 ) 3 ] 2 " + S n C l 3 " (3.11b) These s u b s t i t u t i o n processes are a c c e l e r a t e d by l i g h t (see 4.1 ) and i t i s l i k e l y t h a t under c o n d i t i o n s of a low o v e r a l l Sn/Rh r a t i o , the f r e e S n C l 3 ~ thus formed (eq'ns 3.11a, b) reenters the c a t a l y s e d s u b s t i t u t i o n 3 c y c l e . In t h i s way [ R h C l 2 ( S n C l 3 ) 4 ] " i s p a r t i a l l y r e p l e n i s h e d . The f a t e of 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] , the other major k i n e t i c product, must a l s o be accounted f o r . With a p p l i c a t i o n of heat p r i o r to i s o l a t i o n of products ( i . e . the non-trapping experiments) the complex was not e v i d e n t , although i t could be trapped out as the s a l t during formation. At Sn(11)/Rh(III) = 5, the complex was obtained i n high y i e l d i n t h i s way, but at longer r e a c t i o n times [ R h C l ( S n C l 3 ) 5 ] 3 " was the major product with [ R h C l 2 ( S n C l 3 ) 4 ] 3 ' and 3 _ [RhSn 5Cl-| 5] ~ a l s o i s o l a t e d . S i m i l a r mixtures were obtained under mi l d e r c o n d i t i o n s i n the anaerobic " [ R h 2 C l 2 ( S n C l 3 ) 4 ] 4 " " syntheses. A f t e r -^ 20 min -110-r e a c t i o n the Rh(I) complex was s t i l l found with [RhCl CSnCl3) 5] , [ R h S n 5 C l 1 5 ] 3 " and the expected [ R h C l 2 ( S n C l 3 ) 4 ] 3 - product. Probably a net rearrangement i s occuring to y i e l d a f o r m a l l y R h ( I I I ) complex from [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 " . [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 _ > [ R h C l ( S n C l 3 ) 5 ] 3 " (3.12) As i n the case o f [RhCl 2(SnCl3 ) ^ ] , the Rh(II I ) complex could decompose v i a 3 C l " 7. [ R h C l ( S n C l 3 ) 5 ] > [ R h C l 2 ( . S n C l 3 ) 4 ] - + S n C l 3 " (3.13) I n t e r e s t i n g l y , the l i m i t e d data on the decomposition of [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] to R h ( I I I ) complexes i n CH3CN i n d i c a t e that the r a t e o f decomposition i s not a f f e c t e d by a i r ( s e c . 4.4 ). This suggests that the s h i f t i n product d i s t r i b u t i o n under aerobic c o n d i t i o n s noted above f o r the synthesis of 3-[RhCl 3(SnCl3)3] i s due to o x i d a t i o n o f S n C l 3 ~ and Rh(I) intermediates formed v i a r e a c t i o n such as 3.6. The i s o l a t i o n of [RhSn^Cl-j53 ~ i n some of the experiments was taken as i n d i c a t i v e of the presence o f [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] i n s o l u t i o n ' Several p l a u s i b l e routes to t h i s complex can be proposed (note t h a t o 134 " S n C l 3 " + C l " " could be replaced by " S n C l / " " ) [ R h C l ( S n C l 3 ) 5 ] 3 " + S n C l 3 " + C l " — > [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 5 " + S n C l 4 (3.14a) t [ R h ( S n C l 3 ) 4 ] 3 " + S n C l 3 " + C l " v = * [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 5 " (3.14b) -111-[ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 " + S n C l 3 " + C l " —=> [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 5 ~ + S n C l 4 (3.14c) I t i s not p o s s i b l e to d i s t i n g u i s h between these a l t e r n a t i v e s w i t h any confidence. However, the observations a t Sn:Rh r a t i o s > 5 (sec. 3.3.3) tend to r u l e out r e a c t i o n 3.14a, at l e a s t at higher temperature when 3— [ R h C l ( S n C l 3 ) 5 ] i s favoured. On the, other hand, both the Rh(I) complex 3-and [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] are sl o w l y formed at ambient temperatures ( r e f . , 91 and sec. 3.3.3). A l s o t h e i r composition d i f f e r s by only two e l e c t r o n s ; thus r e a c t i o n 3.14c i s most probable. When the sol v e n t system was changed from 3MHC1 to ethanol, a s h i f t i n product d i s t r i b u t i o n was observed which apparently r e s u l t s from the decrease i n [ C l ~ ] . This was r e f l e c t e d i n the decrease i n C l " content of the R h ( I I I ) 3 product; i . e . p r o p o r t i o n a l l y more [R h C l ( S n C l 3 ) g ] i s formed. More: s p e c i f i c a l l y , i f Y = sol v e n t i n the scheme shown i n 3.8 and r e a c t i o n 3.9 l i e s to the l e f t a t low [ C T ] , then [ R h C l ( s o l v e n t ) ( S n C l 3 ) 4 ] 2 " + S n C l 3 " — > [ R h C l ( S n C l 3 ) 5 ] 3 " (3.15) would be more favourable. A l t e r n a t i v e f a c t o r s could be an increase i n c o n t r i -bution from r e a c t i o n 3.8 when Y = SnCl,", or from [ R h ( S n C l 3 ) 4 ] 3 " + S n C l 3 " F = ± [ R h t S n C l ^ ] 4 " (3.16a) -112-[ R h ( S n C l 3 ) 5 ] 4 " + [ L 5 R h C l ] m " — ' • > I [ [ ( S n C l 3 ) 5 R h - . . C l - . - R h L 5 ] ( 4 ' K n ) - ] ^ [ R h C l ( S n C l 3 ) 5 ] 3 " [ R h L 4 ] m ~ + C l " ( 3 J 6 The e f f e c t o f reducing [ C l ] was observed a l s o i n the pronounced drop i n the y i e l d f o r the r e a c t i o n not protected from l i g h t . This was con-s i s t e n t w i t h photo-induced s u b s t i t u t i o n of solvent f o r coordinated C l ~ or SnCl 3 ~ j r e s u l t i n g i n much more s o l u b l e s o l v a t e d species (sec. 3.4 ). In 3MHC1 the same process could r e s u l t i n a s h i f t i n the product d i s t r i b u t i o n to species c o n t a i n i n g a lower Sn/Rh r a t i o . -113-CHAPTER IV  RESULTS (PART I I ) REACTIONS OF THE COMPLEXES 4.1 I n t r o d u c t i o n The UV-VIS s o l u t i o n spectra of t r a n s - [ R h C l 2 ( S n C l 3 ) 4 ] 3 " and [ R h ( S n C l 3 ) 4 -( S n C l 4 ) ] were important i n the e l u c i d a t i o n of the s y n t h e t i c "system". The s t a b i l i t y o f these complexes and [ R h C l 3 ( S n C l 3 ) 3 ] 3 " i n CH3CN and 3MHC1 w i l l be examined b r i e f l y in t h i s chapter. The st o i c h i o m e t r y of the sol v o -l y s i s r e a c t i o n i n CH3CN with respect to S n C l 3 ~ l o s s has been determined. Ad d i t -i o n a l e f f e c t s due to a d d i t i o n o f c h l o r i d e s a l t s andjto l i g h t are noted. In the context o f the use o f i n i t i a l s p e c t r a , mentioned above, a key element i s the time taken to obtain a spectrum r e l a t i v e to i t s r a t e o f change. In the present systems the complexes undergo s o l v o l y s i s and/or net l o s s of SnCl,, upon d i s s o l u t i o n i n CH3CN. The minimum time needed to acquire a spectrum, on the Cary 17 spectrophotometer, between 500 - 200 nm was ^ 200 s (45-60 s f o r d i s s o l v i n g the sample and mounting, plus ^150 s to scan 300 nm). Under c o n d i t i o n s comparable to those described i n the previous chapter ( i . e . ^ 25°C, ^5xlO" 4M complex concentration) l e s s than 10% change was observed i n the spectra of [ R h C l 2 ( S n C l 3 ) 4 ] 3 " and [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 " on t h i s 200 s time s c a l e . The UV-VIS spectra o f the Rh(III) complexes are c h a r a c t e r i z e d by intense bands (e>10 M cm ). Such high i n t e n s i t y i s u s u a l l y i n d i c a t i v e o f symmetry-allowed metal to l i g a n d (MLCT) or l i g a n d to metal (LMCT) charge 1 1 34 135 136 5 t r a n s f e r t r a n s i t i o n s ' ' • For a d octahedral t r a n s i t i o n - m e t a l complex with a,ir-donor c h l o r i d e l i g a n d s , two strong LMCT bands are expected: a high -114-energy t r a n s i t i o n o r i g i n a t i n g from the l a r g e l y Cl l o c a l i z e d a type MO ( a - L M C T ) and a lower energy one, als o Cl l o c a l i z e d , from a TT type MO ( T T - L M C T ) , both t e r m i n a t i n g on a Rh-centered empty M O (e.g. a*). 7T M M L 6 6 x L Figure 4.1 P a r t i a l molecular o r b i t a l diagram f o r an octahedral d 6 complex (L = Cl") showing LMCT t r a n s i t i o n s 1 3 6 . This simple p i c t u r e i s complicated by the presence o f the a-donor, ir-acceptor * SnCl2~1 igands. Charge t r a n s f e r from the occupied t ? (TT ) to the Sn 5d 1 37, 1 38 ._ - - 9 acceptor o r b i t a l s ( T : - M L C T ) would be expected to l i e at higher energy than 113 i s observable here ( i . e . >200 nm) , wh i l e the O.TT LMCT should occur a t lower energies than i n the absence o f S n C l 0 " because o f d e s t a b i l i z a t i o n o f the -115-l i g a n d based a,IT MOs by the more r e d u c i b l e SnCl3" l i g a n d . However, although both S n C l 3 ~ and C l ~ are weak o donors, the a energy l e v e l s may be s u f f i c i e n t l y 11 3b d i f f e r e n t to give r i s e to d i s t i n g u i s h a b l e L M C T bands . Nevertheless, the lower energy band at ^ 420 nm f o r [ R h C l 3 ( S n C l 3 ) 3 ] 3 ' ( f i g . 4.4 ( b ) : see sec. 4.3) and [ R h C l 2 ( S n C l 3 ) 4 ] ( f i g . 4.5) i s t e n t a t i v e l y assigned as TT-LMCT and the most intense band at <300 - 290 nm as a - M L C T . The exact s t r u c t u r e o f [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] i s not known but has been discussed p r e v i o s l y i n the context of i t s UV-VIS spectrum (sec. 3.2). In the work described i n the f o l l o w i n g s e c t i o n s , s o l u t i o n s c o n t a i n i n g Rh complexes were handled a n a e r o b i c a l l y , i n the dark and at 25°C, unless otherwise noted. The r e s u l t of exposure to l i g h t was dependent on s o l v e n t and c h l o r i d e c o n c e n t r a t i o n : the UV-VIS spectrum of a ^ 10~ 4M s o l u t i o n of [RhCl 3 ( S n C l 3 ) 3 ] 3 ~ i n 3M HC1 showed a decrease i n i n t e n s i t y and a s h i f t of the 305 nm band to ^ 315 nm ( f i g . 4.2). The higher wave! ength band ( 420 nm)did not s h i f t but decreased i n i n t e n s i t y . The o v e r a l l impression was that the t i n - c o n t a i n i n g complexes 3-were l o s i n g S n C l 3 i n a stepwise fashion s i n c e the spectrum o f [ R h C l 4 ( S n C l 3 ) 2 ] was noted during: t h e d e c a y p r o c e s s . In the absence of l i g h t no s p e c t r a l changes were observed. In 0.5M HC1 and CH3CN, the 305 nm peak d i d not s h i f t , but a general decrease i n i n t e n s i t y occurred. The f i n a l spectrum i n 0.5M HC1 had weak peaks a t ^ 500 nm, 386 nm, and a.more intense one at 203 nm. In CH3CN a continuum r e s u l t e d with higher energy bands obscured by SnCl 2(CH 3CN) absorbance (see sec. 4.2). The spectra of both [ R h C l 2 ( S n C l 3 ) 4 ] 3 ' and [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 ~ i n 3M HC1 s o l u t i o n i n the l i g h t r a p i d l y became l i k e t h a t of [ R h C l 3 ( S n C l 3 ) 3 ] J ~ and then followed a s i m i l a r decay. In CH3CN s o l u t i o n a continuum, as noted above, was observed. - 1 1 6 -3(H 0 - 1 1 7 -4.2 SnCl 2(CH 3CN) When SnCl 2-2H 20 o r [ S n C l 3 ] [ N E t 4 ] i s d i s s o l v e d i n dry CH3CN, several bands are observed i n the UV spectrum below 300 nm ( f i g . 4.3a). Upon shaking the s o l u t i o n w i t h a i r , the bands disappear l e a v i n g a shoulder at ^225 nm of much weaker i n t e n s i t y ( f i g . 4.3b). The changes are c o n s i s t e n t with formation of a S n C l 2 adduct with CH3CN and i t s subsequent o x i d a t i o n to 139 * * Sn(IV) . The UV bands are probably r e d - s h i f t e d TT-TT (^225 nm) and n - T r (270 and 290 nm) t r a n s i t i o n s of CH3CN , the auxochrome being SnCl,,. The s t o i c h i o m e t r y of the adduct was not determined but can be reasonably assumed t o be 1 :1 since many such adducts of the Lewis a c i d S n C l 2 137, li+l with N- and 0-donors are known . Beer's law was obeyed over the _3 range 0.7 - 1 .7x10 M. The c h a r a c t e r i s t i c shape and i n t e n s i t y were useful s i n c e 'free' S n ( I I ) was then r e a d i l y i d e n t i f i a b l e i n the s p e c t r o s c o p i c s t u d i e s described below. Estimates of i t s concentration were made by t r i a l and e r r o r curve s u b t r a c t i o n , using computer routines mentioned i n sec. 2.3, and these estimates are b e l i e v e d to be accurate to ±10% 4.3 F a c - [ R h C l 3 ( S n C l 3 ) 3 ] 3 " and t r a n s - [ R h C l 2 ( S n C l 3 ) 4 ] 3 " The spectrum of f a c - [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] i n dry CH3CN e x h i b i t e d r a p i d change f o r ^5 min and then remained unchanged f o r up to 13 h a f t e r that ( f i g . 4.4a). The change i n absorbance at 430 nm ( f i g . 4.4: i n s e t ) was zero-order f o r the most part w i t h a t t - 130s. In the presence o f an B J -'S f o l d excess of Et dNCl-HpO no changes were observed. Bands due to SnCl^CH^CN) -118-4 0 1 2-0 3 0 0 W A V E L E N G T H ( N M ) a ~r 3 0 0 W A V E L E N G T H ( N M ) Figure 4 3 CH3CN s o l u t i o n UV-VIS spectra o f SnCl 2(CH 3CN) (a) and of (b) a s i m i l a r s o l u t i o n during a i r o x i d a t i o n ( ) and a f t e r a i r o x i d a t i o n ( ) -119-.230 200 300 400 500 WAVELENGTH (NM) Figure 4.4 CH3CN solution UV-VIS spectra of [Me 4N] 3[RhCl 3(SnCl 3) 3]: (a) final spectrum in absence of added Et4NCl-H20 ( ) and (b) with 8.7-fold excess of Et4NCl-h^O ( -) . unchanged with time, compared to in i t ia l spectrum in 3M HC1 (— ). Inset is the change in absorbance at 430 nm vs. time for the CHjCN solution spectra ([ ] Q = 4.97 x 10"4M) in' the absence of added salt . -120-were not observed. The spectrum o f [ M e 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] ^ ,,0 a l s o e x h i b i t e d change, although slower than f o r the t r i s ( t r i c h l o r o s t a n n a t o ) c o m p l e x . A d d i t i o n a l l y , the spectrum o f SnCl 2(CH 3CN) grew i n at ^225 nm i n d i c a t i n g net d i s s o c i a t i o n of S n C l 2 , with an i s o s b e s t i c being observed at 248 nm ( f i g . 4.5a).The r e s u l -t a n t spectra were d i f f e r e n t when a 12-and 2 3 - f o l d excess of Et 4NCl-H 20 was added ( f i g . 4.5b,c), and only an 'approximate' i s o s b e s t i c was observed between 252 - 255 nm. The amount of SnCl 2(CH 3CN) estimated by spectrum s u b t r a c t i o n was n,l e q u i v a l e n t ; the estimates ranged from 0.9 to 1.3 as the added [ E t 4 N C l -H20] 1 was increased from zero. Some i r e p r o d u c i b i l i t y was observed: i n one run i n the absence of [Et^NCl'H 20] only 0.6 equ i v a l e n t s were found and i n another, with added [Et^NCl-H 20] , a s t a b l e spectrum d i d not r e s u l t a f t e r formation of 1 e q u i v a l e n t of SnCl 2(CH 3CN), i n t e n s i t y g r a d u a l l y decreasing across the spectrum (200 - 500 nm). However, most experiments were well-behaved and the spectra remained r e l a t i v e l y s t a b l e a f t e r formation of i / l e q u i v a l e n t of SnCl 2(CH 3CN). Comparison o f the r e s u l t a n t spectra of the complexes i n the presence o f comparable amounts of Et^NCl «H20 i n d i c a t e s that the major products are s i m i l a r ( f i g . 4.6). I t i s g e n e r a l l y not prudent to c h a r a c t e r i z e t r a n s i -t i o n metal complexes by e l e c t r o n i c spectra alone. However, attempts to i s o l a t e the products by p r e c i p i t a t i o n f a i l e d to give complexes whose spectra matched those before p r e c i p i t a t i o n . The o v e r a l l i n d i c a t i o n on the basis o f the s i m i l a r i t y and the formation of ^1 e q u i v a l e n t o f SnCl ?(CH ?CN) i s that the -121-60-1 _ 40 E o U i o Ul O u z o u — 20-| X u UJ cc < a a < IA rll A l \ °1-200 — I 1 — 300 400 W A V E L E N G T H ( N M ) — I 500 Figure 4.5 CH3CN solution UV-VIS spectra of [Me4N]3[RhCl2(SnCl3)4]-H20 (a) In absence of added Et4NC1-H20 ( ), (b) with a 12-fold, excess ( ) and (c) a 23-fold excess ( ) of the salt. The dotted line is the in i t ia l spectrum. -122-60-1 4 0 «? O *r K T E o Ul u LZ LL UJ O o z o o X Ul u i < OL Q. < o i 2 0 0 — I r-3 0 0 4 0 0 W A V E L E N G T H ( N M ) 5 0 0 Figure 4.6 Comparison of CH3CN solution UV-VIS spectra of (a) [Me 4N] 3[RhCl 3(SnCl 3) 3] (—•) and (b) [Me4N]3[RhCl2(SnCl3)4]-H20 ( •) in the absence of Et 4NCl-H 20; (c) ( ) and (d) ( ) with a 8.7-fold excess of Et4NCl -h^ O and with a 12-fold excess of Et4NCl-H20, respectively. -123-t e t r a k i s ( t r i c h l o r o s t a n n a t o ) c o m p l e x decomposes to give the t r i s ( t r i c h l o r o s t a n n a t o ) -complex. The dependence o f the product spectra on [Et^NCl-r^O] i s c o n s i s t e n t with replacement o f a, TT donor C l " by a donor, TT acceptor CH^CN. This would lead to s t a b i l i z a t i o n o f the ligand-based TT type MOs and r e s u l t i n a b l u e - s h i f t o f the TT-LMCT band, while the higher energy _a-LMCT band would be r e l a t i v e l y i n s e n s i t i v e to the s u b s t i t u t i o n . Scheme 4.1 i s c o n s i s t e n t with the observations. [ R h t l 2 ( S n C l 3 ) 4 J 3- "S n C 1? •SnCl +CH3CN [ R h C l 2 ( C H 3 C N ) ( S n C l 3 ) 3 ] 2 -CrLCN, +C1" , — J ± [ R h C l 3 ( S n C l 3 ) 3 ] J " - n C l " +nCH3CN +nCl -CH3CN •Cl , +CH3CN [ R h C l 2 _ n ( C H 3 C N ) n ( S n C l 3 ) 3 ] ( 2 " n ) ' 3-Scheme 4.1 Reaction of [ R h C l 2 ( S n C l 3 ) 4 ] with CH3CN. The t i n could be l o s t from [ R h C l 2 ( S n C l 3 ) 4 ] 3 " by d i s s o c i a t i o n of S n C l 3 " 109 (path b) or by " d e - i n s e r t i o n " (path c ) . The r a p i d r e a c t i o n of [RhCl 3(Sn-, _3_ 91 C 1 3 ) 3 J with iGHgCN i s c o n s i s t e n t with the previous observation that the f a c -complex r a p i d l y and r e v e r s i b l y exchanges the three C l " l i g a n d s f o r Br i n hydrobromic a c i d . This was be l i e v e d to be due to the strong trans e f f e c t of S n C l 3 " . Not s u r p r i s i n g l y , d i s s o l u t i o n of f a c - [ M e 4 N ] 3 [ R h C l 3 ( S n C l 3 ) 3 ] i n CH3CN with -124-excess Et^NCl'H 20 r e s u l t s i n a spectrum very s i m i l a r to that observed f o r a 3MHC1 s o l u t i o n ( f i g . 4.4). I n t e r e s t i n g l y the same i s not t r u e f o r [Me^N]-[ R h C l 2 ( S n C l 3 ) 4 ] - H 2 0 ; the: spectrum reported i n 3M HC1 s o l u t i o n i s clo s e to t h a t i n CH3CN a f t e r l o s i n g one equivalent of Sn ( f i g . 3.3 vs f i g . 4.5), implying a r a p i d l o s s of l i g a n d i n 3MHC1. The stereochemistry o f the r e a c t i o n . +CH,CN -t r a n s - [ R h C l 2 ( S n C l 3 ) 4 r f a c - [ R h C l 3 ( S n C l 3 ) 3 ] + SnCl 2(CH 3CN) (4.1) i s not expected on the basis of trans e f f e c t alone , an i n i t i a l l y formed mer-[ R h C l 3 ( S n C l 3 ) 3 ] 3 ~ complex), before l o s i n g one of the mutually trans S n C l 3 ~ 9 1 l i g a n d s , could have isomerised r a p i d l y to the more s t a b l e fac-isomer . The rate of decrease at 420 nm o f the CH3CN s o l u t i o n UV-VIS spectrum o f [ R h C l 2 ( S n C l 3 ) 4 ] 3 ~ increased with i n c r e a s i n g [Et^Cl-HgO] ( f i g . 4.7). Examination of the absorbance vs. time p l o t s revealed a small 's' shaped component at 6 - 7 t ^ s . At the highest [ E t ^ C l ' h ^ O ] shown i n f i g . 4.6,this occurs a f t e r 5000s. Good l n ( A - A j vs time p l o t s ( r > .9995 f o r i n i t i a l 12 pts.) covering > -4t^s were obtained f o r the data before the s-shaped component ( t . 4.1). 101,102 The values o f A^ were estimated using the method o f Kezdy-Swinbourne E x t r a p o l a t i o n ! to t Q gave c o n s i s t e n t A Q values from which e420nm w a s f o u n d t 0 be 16840 ±160 M _ 1 cm" 1. However, at the higher [Et 4NCl -H20] the c a l c u l a t e d f i t between 3000 - 6000 s underestimates the observed data. A b e t t e r f i t to t h i s region was obtained when the f i r s t two points were dropped from the ana-l y s i s , but the extapolated A n value was higher ( s o l i d l i n e , f i g . 4.7).; - 1 2 5 -.700-ft IU o z < CO cc o V) CO < .500 .300 •o--CL-.100-2000 4000 T I M E ( S ) 6000 8000 Figure 4.7 Plots of absorbance at 4 2 0 nm vs. time for the decomposition of trans-[Me 4 N] 3 [RhCl 2 (SnCl 3 ) 4 ]-H 20 in Crl^CN: ( O ) = run 1, ( • ) = run 2, ( ^ ) = run 3. Dashed l ines are f i r s t-order f i t s to the f i r s t 12 data points . So l id l ine : see tex t . Run #s refer to table 4.1j. The second ' s t e p ' , read i ly monitored at 4 2 0 nm, did not give marked spectral changes below 350 nm. Since th is step did not appear to be important in the estimation of SnCl2(CH3CN) and the overal l appearance of the spectrum af ter the f i r s t ' s t e p ' , i t was not investigated further . -126-Table 4.1 Pseudo-first order rates of decomposition of [Me4N]3[RhCl2(SnCl3)4] •H20 in CH3CN run [Rh(III)]0 [Et4NCl-H20]Q kobs K R (xl04),M (xl04),M (xloV1) (s) 1 4.27 0.00 4.79 1449 .9996 2 4.28 49.9 6.28 1104 .9998 3 4.27 99.9 10.6 654 .9996 Comparison of the of the initial 'step' with the estimate of the time required to acquire an initial spectrum indicates that only ^7% reaction would have occurred in the absence of added [Et^NCl'H20]. The dependence of the rate on the chloride concentration probably accounts for the lack of observation of [RhCl2(SnCl3)4]3" in 3M HC1. The limited data for the dependence of the rate on [Et^NCl-H20] suggest reaction via a chloride independent pathway and a chloride dependent pathway, i.e. ^ Q^s = k^  + k2fCl"] , which is indicative of substitution via associative type 142 processes involving both solvent and Cl as incoming nucleophiles 4.4 [Rh(SnCl3)4(SnCl4)]3~ The material used in these experiments was [Et4N]3[Rh(SnCl3)4(SnCl4)]— (Et4NCl)Q 5 recrystallized from CH3CN. The recrystal1ization results in replacement of an indeterminate amount of occluded Et4NCl (sec. 2.1.5.3). It was assumed that the molecular weight was that of the unrecrystallized -127-m a t e r i a l , which leads to a < 3 % e r r o r assuming t h a t at most h a l f the occluded s a l t was replaced and i s considered n e g l i g i b l e . The complex decomposes i n CH3CN more slowly than [RhCl 2(SnCl3)4] and, l i k e the l a t t e r complex,the product spectra vary with added Et^NCl-r^O ( f i g . 4.8). In the absence o f added Et 4NCl«H 20, ^2 eq u i v a l e n t s of SnCl 2(CH 3CN) were found by s u b t r a c t i o n o f the T a t t e r ' s spectrum. The estimate increased to ^3 e q u i v a l e n t s w i t h added c h l o r i d e s a l t . In both cases approximate! i s o s b e s t i c s were observed at %252, 270 and 335-344 nm. Use of Ph 4AsCl-H 20 i n place of Et^NCl-HgO d i d not a p p r e c i a b l y change the spectrum; n e i t h e r d i d a 200-f o l d excess of H 20 i n the absence of added c h l o r i d e s a l t . The complex was s l i g h t l y s o l u b l e i n 3M HC1, but decomposed r a p i d l y . The product spectrum had A m a x values of 314 and 424 nm w i t h an i n t e n s i t y r a t i o of 18.1 (e values could not be r e l i a b l y estimated) which i s c l o s e to that 3 91 reported f o r [ R h C l 4 ( S n C l 3 ) 2 ] : 320 nm and 432 nm i n a r a t i o of 18.8 . The d i f f e r e n c e was c o n s i s t e n t with the presence o f some [RhCl 3(SnCl3)3] In CH3CN s o l u t i o n w i t h % 9 - f o l d excess of c h l o r i d e s a l t , the p r i n c i p a l X m a x i s at ^315 nm and 3 equivalents o f SnCl 2(CH 3CN) were found, i m p l y i n g t h a t r e a c t i o n 4.2 occurs. [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 _ — > [ R h C l 4 ( S n C l 3 ) 2 ] 3 " + 3SnCl 2(CH 3CN) (4.2) However,the apparent e x t i n c t i o n c o e f f i c i e n t i n CHgCN at 315 nm i s M 4 % lower ^ i 1 9 1 than expected f o r [ R h C l 4 ( S n C l 3 ) 2 J " ( b a s e d on e - 37000 M~ cm i n 3MHC1) which means that the estimate of SnCl 2(CH 3CN) includes c o n t r i b u t i o n s from sources other than r e a c t i o n 4.2. The r e s u l t s f o r no added c h l o r i d e s a l t can be considered a s i m i l a r case. The spectrum resembles those seen i n the case of -128-o-<H 2 0 0 3 0 0 4 0 0 5 0 0 W A V E L E N G T H ( N M ) re 4.8 CHjCN solution UV-VIS spectra of [Et4N]3[Rh(SnCl 3 ) 4 (SnCl 4 ) ]-(Et^Cl ) Q S after decomposition in presence of various amounts of added chloride salts: (a) no added Et^NCl•HgO ( ), (b) 8.8-fold excess of Et4NCl-H20 ( ), (c) 8.8-fold excess of Ph4AsCl -H20 ( ) and (d) 12-fold excess of Et 4NCl-H 20( ). The dotted line is the in i t ia l spectrum (•indicates peaks due to Ph4As+ ; note that (c) and (d) are coincident at higher x ) . -129-[ R h C l 3 ( S n C l 3 ) 3 ] and [ R h C l 2 ( S n C l 3 ) 4 ] , and the 2 equiv a l e n t s observed matches the s t o i c h i o m e t r y of r e a c t i o n 4.3. [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 4 _ > [ R h C l 3 ( S n C l 3 ) 3 ] 3 " + 2SnCl 2(CH 3CN) (.4.3) Again, the apparent e x t i n c t i o n c o e f f i c i e n t s above 260 nm are low. The observations can be r a t i o n a l i z e d by noting that [ R h ( S n C l 3 ) 4 ~ ( S n C l 4 ) ] could decompose i n at l e a s t two ways. As noted i n sec. 3.6, 3 _ rearrangement to [ R h C l ( S n C l 3 ) 5 l followed by stepwise l o s s o f S n C l 3 ~ or S n C l 2 could occur (the "Rh(III) r o u t e " ) . The proposed rearrangement would involve a net C l + t r a n s f e r from S n C l 4 to Rh(I) v i a a h a l i d e bridged i n t e r -mediate such as : Cl ..Cl L 4 R h — S " ^ c , —> L 4 R h ^ / — > L 4 R h — C l * Sn Cl c< S » e f t ? Cl 143 Such bridges are known or have be proposed as intermediates i n h a l i d e exchange st u d i e s . A l t e r n a t i v e l y , the backward step of r e a c t i o n 3.7 could occur (the "Rh(I) r o u t e " ) : [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] 3 " > [ R h ( S n C l 3 ) 4 ] 3 " + S n C l 4 (4.4) foll o w e d by, [ R h ( S n C l 3 ) 4 ] 3 ' + nCH3CN [ R h ( C H 3 C N ) n ( S n C l 3 ) 4 _ n ] ^ 3 - n ^ + nS n C l 3 " (4.5) -130-or [ R h ( S n C l 3 ) 4 ] 3 " + n C l " ^ [ R h C l n ( S n C l 4 _ J 3 " + nS n C l 3 " (4.6) or [ R h ( S n C l 3 ) 4 ] 3 - + nCH3CN [ R h C l n ( S n C l 3 ) 4 _ n ] 3 " + nSnCl 2(CH 3CN) (4.7) In CH3CN these e q u i l i b r i a would tend to favour formation of SnCl 2(CH 3CN). E m p i r i c a l l y , assuming that the o v e r a l l i n t e n s i t y of bands due to rhodium(I) (and ( I I I ) ) complexes with S n C l 3 ~ was proportionate to the number of S n C l 3 ~ l i g a n d s , formation o f l a b i l e Rh(I) species would account f o r the decrease i n i apparent e x t i n c t i o n c o e f f i c i e n t s above ^260 nm without apparent decrease i n SnCl 2(CH 3CN). The change i n absorbance at 378 nm was found to f o l l o w f i r s t or p s e u d o - f i r s t order k i n e t i c s ( t a b l e 4.2). P l o t s o f l n ( A - A M ) vs. t gave good f i t s w i t h r > .9993 f o r 20 po i n t s covering a t l e a s t 70% r e a c t i o n , using estimates 101' of A^ c a l c u l a t e d by the Kezdy-Swinbourne method . By e x t r a p o l a t i o n t o tp an estimate o f e 3 7 g was c a l c u l a t e d to be 74210 ± 5745 cm~^ which agrees well w i t h a previous estimate (sec. 2.1.5.3). The agreement i n estimated e-values between runs 1 and 2 i n d i c a t e s t h a t [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] obeys Beers Law -4 -4 over the range 0.39x10 to 2.80x10 M. There was l i t t l e e f f e c t due to a i r on the. r a t e but the rates increased with added c h l o r i d e s a l t ( t a b l e 4.2). As noted i n the previous s e c t i o n , the form of the dependence, i . e . k Q U ( S = k j + k 2CCl ] , suggests an a s s o c i a t i v e type mechanism with solvent and C l " as incoming -131-Table 4.2 P s e u d o - f i r s t order rates of decomposition of [ E t 4 N ] 3 [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] • ( E t 4 N C l ) 0 5 i n CH3CN. run [Rh(I)]0 [ E t 4 N C l - H 2 0 J 0 kobs R (xl0 4M) (xl0 4M) (xloV1) (s) 1 2.80 0.00 1.12 6180 .9998 2 0.39 0.00 1.28 5451 .9998 3 2.50 22.0 1.65 4202 .9993 4 2.50 30.0 2.04 3395 .9997 5 2.90 22.0* 1.30 5317 .9998 6 2.90 200. * 0.95 7308 .9999 7 2.50 * 0.0 0.97 7149 .9999 Ph 4AsCl-H 20 ; 4 H 20 ; * a i r . n u c l e o p h i l e s . The data are l i m i t e d and some a d d i t i o n a l small e f f e c t of varying the c a t i o n i s i n d i c a t e d (run 3 vs. 5). 4.5 Corrclusion The p r i n c i p l e r e a c t i o n of t r a n s - [ R h C l 2 ( S n C l 3 ) 4 ] 3 " o r [ R h ( S n C l 3 ) 4 -3 ( S n C l 4 ) ] ~ i n f r e s h l y prepared CH3CN s o l u t i o n s i n the dark was found to in v o l v e a net l o s s o f S n C l 2 . The r a t e s , under c o n d i t i o n s s i m i l a r to those used i n the preceeding chapter, were slow enough f o r the use of i n i t i a l UV-VIS s o l u t i o n s p e c t r a i n c h a r a c t e r i z a t i o n . ' Less than 1% decomposition i s expected during a c q u i s i t i o n o f a 300 nm wide spectrum on the Cary 17'. -132-A l s o , although the r e a c t i o n s were followed only by UV-VIS, some i n t e r e s t i n g observations a r i s e concerning the formation of the Rh(III) products and t h e i r s t e reochemistry. I t i s w e l l known that S n C l 3 ~ has a strong trans i n f l u e n c e and e f f e c t ' . The s t a b i l i t y o f t h e f a c - c o m p l e x and r a p i d exchange o f l i g a n d s trans to S n C l 3 ~ a t t e s t s to t h i s . In GH^CN, t r a n s - [ R h C l 2 ~ 3- 3-(SnClq)^] " l o s e s S n C l 2 to give fac-[RhCl 3(SnCl 3 ) 3 ] " presumably with a concomittant i s o m e r i z a t i o n s t e p . The i n t e r e s t i n g point a r i s e s i n comparison 3 to the presumed " Rh( 111) r a t e " for'decomposition of [Rh(SnCl 3 ) 4 ( S n C l 4 ) ] . 3-In the presence o f added Cl some [ R h C l 4 ( S n C l 3 ) 2 ] i s formed,which i s d i f f i c u l t to r a t i o n a l i z e unless r e g i o s p e c i f i c r e a c t i o n s bypass t r a n s - [RhCl 2 — ( S n C l 3 ) 4 ] 3 _ and f a c - [ R h C l 3 ( S n C l 3 ) 3 ] 3 " products. A p o s s i b l e precedent i s 1 u 1+^ 1 i+ 5 the r e v e r s i b l e i n s e r t i o n o f SnX 2 i n t o f a c - F e ( C 0 ) 3 ( P P h 3 ) Y 2 (X,Y = h a l i d e s ) y i e l d i n g mer-Fe(C0) 3(PPh 3)Y(SnX 2Y), although i t has not been e s t a b l i s h e d i f the phosphine ends up trans to h a l i d e or not. -133-Chapter V RESULTS (PART I I I ) HYDROGENATION OF MALEIC AND FUMARIC ACIDS 5.1 I n t r o d u c t i o n The u l t i m a t e aim of the present work was to study c a t a l y s i s by Rh-Sn complexes. An i n s i t u approach was taken i n t h i s part r a t h e r than the intended one using defined p r e c a t a l y s t s , since an understanding of the s y n t h e t i c problem was reached l a t e i n the i n v e s t i g a t i o n . Red-orange s o l u t i o n s of RhCl 3-3H 20 and SnCl 2-2H 20 i n 3M HC1, a t 80°C, with an excess of fumaric (FA) or maleic a c i d (MA) were found to absorb H 2 (450 mmHg ) at conveniently measurable r a t e s . When a 1 0 - f o l d excess o f o l e f i n and S n ( I I ) / R h ( I I I ) r a t i o o f 3 or 6 was used, t o t a l uptakes corresponded to conversion of MA or FA to s u c c i n i c a c i d (SA) plus reduction o f Rh(III) to Rh(I). Hydration of o l e f i n to malic a c i d (MLA) was competitive with the metal-centered processes. In c o n t r a s t , a s i m i l a r system without the added SnCl 2-2H 20 was p r e v i o u s l y found to y i e l d a s t o i c h i o m e t r i c uptake corresponding 2 8 to the reduction of Rh(III) to Rh(I) only . Rh(III) + H 2 v Rh(III)H" Rh(.III)H~ + H + } Rh(I) + H + (5.2) (5.1) Rh(I) + MA f a s t i Rh(I)(MA) (5.3) -134-Reduction to Rh° was precluded by s t a b i l i z a t i o n o f Rh(.I) by MA (eqn. 5.3) as a yellow complex (353 nm ( e = 420 M"1 cm" 1), 425 nm (e = 180 M"1 cm"1) i n 28 3MHC1) of unknown s t o i c h i o m e t r y . The aim of the work presented i n t h i s chapter was to gain a p r e l i m i n a r y understanding o f the s t o i c h i o m e t r y and stereochemistry o f the modified system and thus mechanistic d e t a i l s . The hydrogenation was found to be very s e n s i t i v e to the o l e f i n concentration r e l a t i v e to th a t of rhodium. In the f o l l o w i n g d i s c u s s i o n s high [ o l e f i n ] r e f e r s to experiments where [ o l e f i n ] = 0.33M; and low [ o l e f i n ] = 0.1M. [ R h ] t o t a l w a s always 0.01M. 5.2 Stoichiometry and k i n e t i c s a t low [MAJ. In the presence of 6-and 3 - f o l d excesses o f SnCl 2-2H 20, uptakes were l i n e a r a t l e a s t to 6 H 2/Rh. Within experimental u n c e r t a i n t i e s no d i f f e r e n c e was observed i n rate between experiments i n the l i g h t and those with t o t a l e x c l u s i o n o f l i g h t ( t a b l e 5.1; f i g . 5.1). A t o t a l uptake of ^ 9.9 H2/Rh was observed with a 3-fo l d excess of SnCl 2'2H 20 and ^ 10.5 H2/Rh with a 6-fold excess. P r e c i p i t a t e d metal was present only near the end of the uptake. The r e s u l t a n t s o l u t i o n was f i l t e r e d and ex t r a c t e d with ether (see sec. 2.2.8). The IR of the white ether evaporate contained bands due to SA but none due to MA o r FA. The product mixture o f a run w i t h Sn/Rh = 3,stopped a t 5.6 H2/Rh uptake,was a l s o s t u d i e d . The organic products were worked up as above. The IR of the ether evaporate i n d i c a t e d a mixture of FA and SA; t h i s was -135-Table 5.1 K i n e t i c data at 80°C f o r the Rh/Sn/r^/MA system i n 3M HC1: H 2 press. = 450 mmHg; [ R h l t o t a 1 = 0.01M, |>1A] = 0.10M. [Sn] [ H 2 ] r a t e of uptake (M) (xl0 4M) ( x l 0 6 i M s _ 1 ) 0.03 3.60 1.7 0.03 3.60 1 .6* 0.06 * 3.60 - 2.8 i n the absence of l i g h t . confirmed by 80 MHz 'H NMR o f an acetone-dg s o l u t i o n which i n a d d i t i o n revealed the presence of a small amount of MA ( f i g . 5.2). Assuming SA to be formed only by hydrogenation, then the r e l a t i v e amounts of FA, MA and SA can be e s t i m a t e d f r o m NMR i n t e g r a t i o n s . A c c o r d i n g l y , b a s e d on i n i t i a l l y 10 equivalents of MA,there were 5.6 SA, 2,5 FA and 0.3 MA a f t e r an uptake o f 5.6 H 2/Rhleaving a ' r e s i d u a l ' o f 1.6 e q u i v a l e n t s . The t o t a l uptake, with a 3 - f o l d excess o f SnCl 2-2H 20,was. ^ 9.9 H2/Rh ins t e a d o f an expected uptake o f ^ 11 H2/Rh corresponding to hydrogenation of 10 equ i v a l e n t s of MA plus reduction o f Rh(III) to Rh(I). The discrepancy was smaller a t higher [ S n C l 2 * H 2 0 ] . Hydration o f MA or FA to MLA (sec. 5.4) and reduction by Sn(II) + 2H + (sec. 5.5) a l s o occur under these c o n d i t i o n s and could e x p l a i n the s h o r t - f a l l i n t o t a l uptake, which could p a r t i a l l y account f o r a d i f f e r e n c e of 1.6 H2/Rh at 5.6 H2/Rh uptake. However, ^ 1 equi v a l e n t i s s t i l l unaccounted f o r . This may be a t t r i b u t a b l e to the formation T 28 of the y e l l o w Rh (MA) complex reported p r e v i o u s l y since i t i s not e x t r a c t --136-able under these c o n d i t i o n s (sec. 5.4). The UV-VIS spectrum o f the uptake s o l u t i o n ( f i g . 5.3) had a A m a x at 428 nm (e = 1880 M"1 cm" 1). A d d i t i o n o f Et^NCl-r^O to s i m i l a r i l y prepared s o l u t i o n s gave orange p r e c i p i t a t e s whose IR contained bands a t t r i b u t a b l e p r i n c i p a l l y to [Et^NJgt R h C l 2 ( S n C T 3 ) 4 3 . Bands due to carboxylate or o l e f i n i c groups were not observed. The observations were 6 H Q UJ CC 4 O CO 03 < CM O X ^ 2 X t • 1 i - — '•• i 10 20 30 T I M E X 1 0 3 S Figure 5.1 H 2 uptakes f o r the Rh/Sn/H2/MA system i n the l i g h t ( 0 ) and dark (V) i n 3M HC1 s o l u t i o n a t 80 °C. [Rh] = 0.01M, [MA] = 0.10M and [Sn] = 0.03M. -137-6.80 6.43 2.60 5 ppm Figure 5.2 Acetone-dg s o l u t i o n 80 MHz H NMR spectrum of the ether evaporate from the hydrogenation of MA at low [MA] and a Sn/Rh r a t i o of 3. ( note: * = s o l v e n t , o = exchangable protons) c o n s i s t e n t with the presence of some Rh*(MA) but i n 3M DC1/D20 only *H resonances due to FA, MA, SA and HDO were observed a f t e r 10800 s of r e a c t i o n . Resonances due to coordinated o l e f i n could be obscured by HDO or exchange. Hydrogenation of a s o l u t i o n c o n t a i n i n g a 3 - f o l d excess o f SnCl 2-H 20 or SnCl 4'5H 20 but no o l e f i n r e s u l t e d i n r a p i d formation o f metal. With a 6-fo l d excess no metal was observed, and t o t a l uptakes of between 0.6 and 0.8 H2/Rh were then measured. A d d i t i o n of Et 4NCl-H 20 to the r e s u l t a n t dark red-orange/purple s o l u t i o n s ( A M N V = 470 nm (c = 3800 M"1 cm" 1)) y i e l d e d a pale-yellow p r e c i p i t a t e . A n a l y s i s f o r C, H and N 5and the IR spectrum, revealed -138-t h a t the p r e c i p i t a t e was p r i m a r i l y [Et 4N_] 3[RhSn,-Cl 1 5]. A d d i t i o n a l l y , the pal e -y e l l o w p r e c i p i t a t e gave a t r a n s i e n t purple CH^CN s o l u t i o n . These observations were a l l c o n s i s t e n t w i t h the reduced s o l u t i o n species being [RhCSnC^)^-(SnCl^)] . Presumably the l e s s than s t o i c h i o m e t r i c uptake was i n d i c a t i v e o f the p a r t i a l reduction of RhCHI) to Rh(I) by Sn(.II) p r i o r to reduction by H,,, which i s expected from the observations i n Chapter 3. The reason f o r metal formation a t the lower Sn/Rh r a t i o i s probably due to the presence o f non-t i n - c o n t a i n i n g Rh complexes, a l s o c o n s i s t e n t w i t h the previous o b s e r v a t i o n s . S u b s t i t u t i o n o f Sn(IV) f o r Sn(II) i n the hydrogenation experiments —i 1 1 1 l 400 500 600 W A V E L E N G T H ( N M ) Figure 5.3 UV-VIS spectra of uptake s o l u t i o n s . S o l i d l i n e i s MA/H2/HC1 system and the dashed l i n e i s the FA/D?/DC1 system( [ o l e f i n ] = 0.10M, [RhJ= 0.01M). -139-Table 5.2 K i n e t i c data at 80°C f o r the Rh/Sn/H 2(D 2)/olefin system i n 3M DC1/D20: H 2(D 2) press. = 450 mmHg; D*h]t t ^ = O.OlM.JSnl = 0.03M. UMA] [FA] [gas] r a t e of uptake (M) (M) ( x l 0 4 M ) ; ( x l O 6 Ms - 1) 0.10 - 3.60 1.1 0.10 - 3.60* 1.1 0.10 3.60* 1.3 * gas = D 2 with MA r e s u l t e d i n a s t o i c h i o m e t r i c uptake to form the y e l l o w Rh*(MA) compl ex. 5.3 Deuteration s t u d i e s at low [ o l e f i n ] Hydrogenation of MA at [Sn] = 0.03M was repeated i n 3M DC1/D20. , Uptakes using D 2 with both MA and FA were a l s o performed. The rates (R) were nearly i d e n t i c a l i n the deuterated s o l v e n t , the average R^/R^ value being 1.39 Ctables 5.1, 5.2). The re a c t i o n s were stopped a t uptakes of 4.9 to 6.9 H 2(D 2)/Rh, and the products were analysed as described i n sec. 5.2. The IRs of the ether evaporates contained bands due to FA and bands i n d i c a t i n g a mixture 146 of d i - and tetr a - d e u t e r a t e d isomers of SA . No s i n g l e isomer appeared to be predominant whether using MA or FA s u b s t r a t e s . I n c o r p o r a t i o n of deuterium i n t o SA was a l s o confirmed by H^ NMR. At 80 MHz or 100 MHz an asymmetric peak was observed a t ^ 2.4 ppm i n DMSO-dg, the p o s i t i o n expected f o r methylene resonances of SA. At 400 MHz t h i s was -140-resolved i n t o two p a r t s , s l i g h t l y u p f i e l d from undeuterated s u c c i n i c a c i d 1 p ( f i g . 5.4). The u p f i e l d s h i f t i n d i c a t e s t h a t replacement o f H by H was 1 2 s h i e l d i n g . The u p f i e l d s h i f t on replacement of H by H has been p r e v i o u s l y 14*. 147b noted i n deuterated styrenes and v i c i n a l groups . Increasing d e u t e r a t i o n was found to lead to i n c r e a s i n g u p f i e l d s h i f t , which i s assumed true here a l s o . The sharper low f i e l d peak was assigned as the c e n t r a l p o r t i o n o f the AB 2 (or ABB') pattern expected f o r mono-deutero SA. This approximates a HB-4 ^ » H A HBv, A A=COOH 148. t r i p l e t at J ^ g / A v ^ l (1:10:1 at J^g/Aw/*) , which i s be l i e v e d to be the case here. The more intense higher f i e l d peak was assigned to symmetrically d i s u b s t i t u t e d s p e c i e s , which were expected to be the p r i n c i p a l isomers. The unsymmetrically d i s u b s t i t u t e d and the t r i s u b s t i t u t e d species resonances overlap these but are probably minor. The r e l a t i v e amount of mono-deutero SA was smaller i n the MA/D2/DC1/D20 system than i n the MA/H2/DC1/D20 one. This i n d i c a t e d t h a t at l e a s t some of the H i n the product o r i g i n a t e d from the gas phase. Notably, some mono-deutero SA was present i n the MA/D2/DC1/D20 system; f o r FA/D2/DC1/D^O the proportion was higher. The ' a d d i t i o n a l ' H cannot s o l e l y r e s u l t from traces i n the DC1/D20 or from H 20 introduced with the hydrated s t a r t i n g m a t e r i a l s since these should be swamped by DC1/D20. Probably ' e - e l i m i n a t i o n from a l k y l 3 36 ' intermediates ' was the source. Some unsymmetrically d i s u b s t i t u t e d SA -141-SA ' 10Hz ' Figure 5.4 400 MHz *H NMR spectrum of the deuterated products from hydrogenation of MA (expanded SA methylene r e g i o n ) . S o l i d l i n e i s of product from MA/H2/DC1/D20 system. The dashed l i n e i s th a t from the MA/D2/DC1/D20 system. The SA methylene peak (dotted ) i s f o r reference. -142-would be expected, as w e l l as i s o m e r i z a t i o n of and deuterium i n c o r p o r a t i o n i n t o 0 V Rh-A D A ^ h - | | A A=COOH the s u b s t r a t e . Attempts to use the *H NMR i n t e g r a t i o n to estimate the product d i s t r i b u t i o n f o r the MA/D2/DC1/D20 system r e s u l t e d i n high estimates of the 'missing' component compared with the HC1/H20 system, even using c o r r e c t i o n s f o r the presence of mono-deutero SA. This would be expected i f deutero-FA or deutero-MA were present. S i m i l a r e r r o r s were seen f o r the FA/D2/DC1/D20 system but the e r r o r was p a r t i c u l a r l y high f o r the MA/H2/DC1/D20 one, c o n s i s t e n t w i t h the observed increase i n mono-deutero SA i n the l a t t e r . Although the former system showed more monodeutero-product than f o r the MA/D2/DC1/D20 system, the lower e r r o r could be due to the stronger complexing a b i l i t y of the i s o m e r i z a t i o n product (deutero-MA). Deuterium i s . o n l y s l o w l y incorporated i n t o SA i n 3MDC1/D20 at 80°C i n the absence o f metal c a t a l y s t s , so i s not considered to a f f e c t the above ob s e r v a t i o n s . 5.4 Stoichiometry and k i n e t i c s at high [MA] The H 2 uptakes a t [Sn(11)3 = 0.0, 0.03 and 0.06M were c h a r a c t e r i z e d by an i n i t i a l r a p i d uptake followed by a clos e to l i n e a r region of slower uptake ( f i g . 5.5). The i n i t i a l uptakes were e s s e n t i a l l y n o n - l i n e a r , the rat e s -143-decreasing somewhat with time. The rates of H 2 uptake f o r the l a t e r l i n e a r region were ca. 20% of those a t the lower [ o l e f i n ] ( t a b l e . 5.3). There was no marked' dependence of rate on [ S n ( I I ) ] . The red-orange s o l u t i o n s became y e l l o w approximately a t the end of the i n i t i a l region ( i n d i c a t e d i n f i g . 5.5 by y=»). 1 0 0 2 0 0 TIME x i c ' s Figure 5.5 H 2 uptakes f o r the Rh/H2/MA system and Rh/Sn/H2/MA system at high [ o l e f i n ] i n 3M HC1 at 80°C. [Rh]= 0.01M, [MA] = 0.33M. [Sn] = 0.0 ( O ) , 0.03 ( O ) , 0.06 ( ? ) . ( 'y=>': see t e x t ) -144-Table 5.3 K ine t i c and spectroscopic data fo r the Rh/Sn/hyMA system in 3M HC1: H ? press . = 450 mmHg, [Rh] = 0.01M, [MA] = 0.10M. [Sn] (M) rate of uptake ( x l 0 7 M s _ 1 ) quench time (x lO " 3 s ) xmax (nm) e (M 'W 1 ) 0.00 2.8 136 354 436 422 182 0.03 3.1 * 156 355 * 423 424 180 0.06 2.8 93 355 436 428 186 This colour change occurred at l a t e r times as [Sn] increased. The spectra of the yel low so lut ions were very s im i l a r to that reported for the yel low T 28 Rh (MA) complex ( table 5.3). Shor t l y a f t e r the co lour change, white p rec ip i t a t e formed, which was charac ter ized by IR and NMR as FA with a t race of SA. The so lub le organic products were extracted with ether as descr ibed above. Monitoring by UV-VIS revealed that the yel low complex was not extracted into the ether . The IR of the ether evaporates ind ica ted a mixture o f FA and SA, which was confirmed by *H NMR. A d d i t i o n a l l y , the resonances probably due to MLA were observed (see below) in acetone-dg so lu t ion at 6 = 4.82 ppm (t) and <S = 2.93 (m). An a l t e rna t i v e assignment could be chloro-SA however, i t s c h a r a c t e r i s t i c band at 674 cm - 1 was absent in the IR. Based on the p rec ip i t a t e y i e l d (33%) and the "'H NMR in tegra t ions -145-(c o r r e c t e d f o r i n e f f i c i e n t e x t r a c t i o n o f MLA - sec. 2.2.8), an attempt was made to determine the product d i s t r i b u t i o n f o r the case where [ S n ( I I ) ] = 0.03M. The assumption that SA was formed only by hydrogenation led to a la r g e proportion of "missing" s u b s t r a t e . An improved balance was obtained assuming the t o t a l SA was equal to the uptake (6.8) minus 1 ri^/Rh f o r reducing Rh(III) to Rh(I) plus 3 equivalents from d i r e c t reduction by Sn(II) + 2H + (sec. 5.5). The product d i s t r i b u t i o n from 33 equivalents o f MA was: 13.3 FA, 5.3 MLA and 8.8 SA. This l e f t 4.6 equivalents unaccounted f o r . Included i n t h i s q u a n t i t y would be the MA i n the unextracted .Rh*(MA) complex. The actu a l amount o f MLA was the l e a s t a c c u r a t e l y known, so some of the 4.6 equi-valents may be accountable as e r r o r i n determining the MLA. The high [MA] appeared to favour the formation of the s t a b l e Rh*(MA) complex. However, the e f f e c t i s s e n s i t i v e to the order of mixing reagents. Prehydrogenation o f a s o l u t i o n c o n t a i n i n g a 6-fold excess o f Sn(II) over Rh(III) before a d d i t i o n of MA, as described a t the end of sec. 5.2, l e d to a markedly d i f f e r e n t uptake. Within ^120s of a d d i t i o n of a 3 0 - f o l d excess of MA, the red-purple s o l u t i o n became red-orange. A l i n e a r uptake at a rate of 2.6 x 10"^ Ms~^ was observed. However, a f t e r an uptake o f only 6.5 H2/Rh the r a t e increased s l i g h t l y and the s o l u t i o n darkened to opaque red-brown. Metal was c l e a r l y v i s i b l e at 9.9 H2/Rh uptake, a s u r p r i s i n g observation. The timing of the metal p r e c i p i t a t i o n i s i n t e r e s t i n g . Metal was observed at ^ 3000s i n the experiment i n v o l v i n g prehydrogenation without o l e f i n ; t h i s time c o i n c i d e s approximately w i t h the t r a n s i t i o n to a slow l i n e a r uptake and yellow s o l u t i o n observed i n the other experiments at -146-high [MA]. In the l a t t e r experiments,1.5 - 7.5 equiv a l e n t s o f o l e f i n would have been consumed depending on the extent of reduction by Sn(II) + 2H +,and formation of Rh*(MA)and MLA. In the former, ^9 - 10 eq u i v a l e n t s would have been consumed p r i n c i p a l l y by hydrogenation. In the absence of Rh/Sn,the rat e constant f o r the disappearance o f MA due to i s o m e r i z a t i o n to FA 149 _5 _ i and hydration to MLA was estimated to be 5.1x10 s , assuming pseudo-f i r s t order decay. The estimate was based on product a n a l y s i s by NMR of the ether evaporate from ether e x t r a c t i o n o f a 0.33M MA s o l u t i o n i n 3M HC1 t h a t was heated a t 80°C f o r 86400s. At [ M A ] i n i t i a 1 o f 0.33M approximately 9 equi v a l e n t s are l e f t at 2800s and 4.5 equivalents MA at ^ 39000s. The correspondence between the two sets o f f i g u r e s suggests t h a t the behaviour of the Rh/Sn system a t high [MA] i s s t r o n g l y a f f e c t e d by d i f f e r e n c e s between MA And FA s u b s t r a t e s . The most obvious d i f f e r e n c e would be the stronger . • , . ^ . . . ^ ,-. . . . , 25 26 150,151 binding o f MA than FA to a rhodium complex ' ' . The cis-isomer (MA) i s l e s s s t e r i c a l l y demanding than the trans-isomer / x ' 1 5 2 ' (FA) when coordinated as a s i n g l e - f a c e d ir-acceptor l i g a n d ' . S t e r i c d i f f e -rences would a l s o be r e f l e c t e d i n r e l a t i v e r e a c t i v i t y towards Rh complexes, and i n an opposite sense when the o l e f i n i s a l e a v i n g group. I t i s d i f f i c u l t to assess e l e c t r o n i c d i f f e r e n c e s . The o l e f i n i c l i g a n d i n Fe(C0) 3(PPh 3) (methylmaleate) has the carboxylate groups o r i e n t e d perpendicular to each 152 other such that o n l y one group can conjugate to the double bond . S i m i l a r e f f e c t s w i t h MA c l e a r l y would be l e s s , but i t s T r-acceptor p r o p e r t i e s could be l e s s than those o f FA. The net e f f e c t o f the d i f f e r e n c e s i s observed i n the f a i l u r e o f FA to s t a b i l i z e Rh(I) a g a i n s t hydrogenation to metal i n DMA, 25 26 while MA does so ' . -147-Further d i s c u s s i o n on mechanistic inferences from the data a t high [MA] w i l l be deferred u n t i l sec. 5.6. 5.5 Reduction i n the absence o f H 2. So l u t i o n s of SnCl 2-2H 20 i n 3MHC1 at 80°C w i t h , and without, added RhCl 3-3H 20 or SnCl 4*5H 20 were found to reduce FA or MA to SA under an argon atmosphere. The concentration o f Sn(II) was t y p i c a l l y 0.055M and [ o l e f i n ] from 0.0099M to 0.0267M. When added,[Rh(III)] and [Sn(IV)] were 0.0091M. Organic products were ext r a c t e d w i t h ether as described i n sec. 5.2, and examined by IR and NMR. There were no n o t i c e a b l e d i f f e r e n c e s w i t h e x c l u s i o n of l i g h t from Rh-containing s o l u t i o n s . s The redu c t i o n of MA i n the presence of Sn(II) alone was slower than when Rh(III) was present ( t a b l e 5.4). The i n i t i a l dark red-orange c o l o u r of the Rh-containing s o l u t i o n s changed to l i g h t e r orange over the f i r s t 2500s, remaining e s s e n t i a l l y constant t h e r e a f t e r . A d d i t i o n of Et^NCl-H 20 to the orange s o l u t i o n s before e x t r a c t i o n w i t h ether y i e l d e d an orange or yellow-orange p r e c i p i t a t e . IR and CH^CN s o l u t i o n UV-VIS spectra showed the s o l i d to be predominantly [ E t 4 N ] 3 [ R h C l 2 ( S n C l 3 ) 4 ] . Y i e l d was ^65% assuming t h i s species only. Carboxylate or o l e f i n i c f u n c t i o n a l group absorbances were absent i n the IR. The , l o s s of s o l u t i o n colour i n the e a r l y part of the r e a c t i o n i s suggestive of a decrease i n the concentration of the Rh(I) species [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] b e l i e v e d to be present i n i t i a l l y i n s o l u t i o n under these c o n d i t i o n s (sec. 5.2). The f i n d i n g of Rh(III) and no Rh(I) complexes a f t e r r e a c t i o n was c o n s i s t e n t with the net reduction of the o l e f i n by Rh(I) with a concomitant o x i d a t i o n to R h ( I I I ) . This p o i n t w i l l be returned to l a t e r . -148-Table 5.4 Extent of reduction of MA to SA at various times with net o x i d a t i o n of S n(II) to Sn(IV) i n 3M HC1. a CSn(II)] [ R h ( I I I ) ] [MA] [SA] % conversion time (xl0 2M) (xl0 2M) (xl0 2M) (xl0 2M) (s) 5.55 - 1.98 0.13 6.5 8100 5.33 0.91 1.98 0.29 14.6 7200 5.30 0.91 1.98 0.34 17.1 10800 5.72 0.91 1.98 0.32 16.2 12300 From 1H NMR i n t e g r a t i o n , uncorrected f o r MLA. The reduction was als o examined i n 3M DCl/^O which o f f e r e d an oppor-t u n i t y to f o l l o w the formation of SA d i r e c t l y . For example, i n the absence of Rh the reduction of FA was followed ( f i g . 5.6). At 100 MHz a resonance*4 ppm u p f i e l d from FA was observed. Broader than the methylene resonance of SA, i t i n d i c a t e d d e u t e r a t i o n a t the methylene p o s i t i o n s . At 400 MHz t h i s resonance was resolved i n t o two peaks i d e n t i c a l i n r e l a t i v e p o s i t i o n s to those observed i n the hydrogenation experiments described i n sec. 5.3 ( i . e . f i g . 5.4). I t was notable t h a t the same pattern was observed i n the absence of Rh ( f i g . 5.7). Estimated conversions of MA/FA -»• SA i n 3M DCl/D^O are summarized i n Table 5.5. R e l a t i v e to the 3MHC1 system, values are overestimated due to the s i m p l i s t i c assumption t h a t only dideutero SA i s formed. Even so, com--149-(100 MHz) Figure 5.6 H NMR monitoring of the reduction of FA by Sn(II) i n the presence of Sn(IV), i n 3M DC1/D20. (run 2, t a b l e 5.5). -150-Figure 5.7 Expansion of SA methylene region of the lti NMR spectrum (400 MHz) of the same sample r e f e r r e d to i n f i g . 5.6.. -151-parisons w i t h i n the t a b l e are q u a l i t a t i v e l y v a l i d . Conversions are lower at comparable times i n the absence of Rh, as noted p r e v i o u s l y . There a l s o appears to be an e a r l y rapid reduction of the o l e f i n i c s u bstrate when Rh i s preent ( t a b l e 5.5). This seems to c o i n c i d e with the i n i t i a l c o l o u r change from red-purple to orange, i n the FA case. I n t e r e s t i n g l y , a f t e r complete re d u c t i o n of 1 equ i v a l e n t of FA the s o l u t i o n colour became dark red-orange and when a second eq u i v a l e n t of FA was added a colour change to l i g h t e r orange was observed with concomitant changes i n the *H NMR i n t e n s i t i e s ( f i g . 5.8). There was no darkening a f t e r complete reduction of FA nor was there any change on a d d i t i o n of a f u r t h e r e q u i v a l e n t . Monitoring by *H NMR revealed that the reduction s t i l l occurred but at a much slower r a t e . The o v e r a l l r e a c t i o n appears to be a net reduction by S n ( I I ) . SnCH) + 2H + + MA > S n ( I V ) + S A (5.5) Sn(II) + 2H + + FA >Sn(IV) + SA (5.6) In the presence o f Rh(II I ) and a s u f f i c i e n t excess of S n ( I I ) , reduction to some R h * ( S n C l 3 ) x species occurs, which i s apparently a more a c t i v e reductant f o r the o l e f i n s . At Sn(II)/Rh ^ 4 , such species are not important (see Chapter I I I ) . In the presence of s u f f i c i e n t excess of S n ( I I ) , or another reductant and S n ( I I ) , the r e a c t i o n would be considered c a t a l y t i c i n Rh. The s l i g h t l y lower conversions f o r MA vs. FA ( t a b l e 5.5) appear to be c o r r e l a t e d with the i n i t i a l l y l e s s purple colour of s o l u t i o n s c o n t a i n i n g MA, which i n d i c a t e s the presence of l e s s R h ^ S n C O . P o s s i b l y , MA i s i n h i b i t i n g the l a t t e r s formation by v i r t u e of strong binding to some Rh(I) p r e c u r s o r , and -152-Table 5.5 Extent of reduction of MA or FA to SA at various times w i t h net o x i d a t i o n of Sn(II) to S n ( I V ) i n 3M DC1/D20. [Rh(III)] [Sn(II)] [MA] [FA] [SA] a % conversion time (xl0 2M) (xl0 2M) (xl0 2M) (xl0 2M) (xl0 2M) (s) 0.91 5.33 1.98 - 0.44° 22 7200 0.85 d 43 18000 0.91 5.76 - 0.99 0.23 C 23 300 0.31 C 31 9300 0.00 b 5.46 - 2.76 0.47 C 17 11100 0.70 C 25 17040 a. uncorrected f o r MLA formation. b. i n presence of 0.90 M SnCl 4-5H 20. c. i n s i t u . d. ether evaporate. thus, i n s p i t e of i t s greater r e d u c i b i l i t y than FA J°, i n h i b i t i n g i t s own redu c t i o n . Another i n t e r e s t i n g f a c e t o f the reduction as judged by the isomeriza-t i o n and deuterium scrambling i s the i m p l i e d presence of hydride intermedia-tes even i n the absence o f H 2. Whether these are formed by d i r e c t protonation 153 at the metal,or by p r o t o n a t i o n o f reduced organic l i g a n d f o l l o w e d by 3 - e l i m i n a t i o n to form a Rh(III) h y d r i d o - o l e f i n complex, i s u n c l e a r . C e r t a i n l y the l a t t e r process i s i m p l i e d by the isotope scrambling. S i m i l a r scrambling was observed i n the absence of Rh. The data are very l i m i t e d , but the -153-.65 Iff * FA SA Figure 5.8 Comparison of the changes i n absorbance (x = 500nm) and !H NMR (100MHz) with time f o r the reduction of FA by the Rh/Sn/DCl/D 20 system. (Numbers above resonances are X $ A (or X p A ) values; t Q spectrum i s i n s t i representation). ck -154-mechanism l i k e l y i n v o l v e s Sn(IV) and s i m i l a r intermediates as presumed i n the case o f Rh. Complexes o f the type C l 2 S n [ C H 2 C H 2 C ( 0 ) X ] 2 and 151+15 5 Cl 3Sn[CH 2CH 2C(0)X] (X = 0R,NH2) are known » . I n t e r e s t i n g l y these are formed from the low temperature r e a c t i o n o f the appropriate a,e unsaturated 155 o l e f i n with Sn° and HC1 i n THF . These r e a c t i o n s were beli e v e d to go v i a C l 2 S n H 2 or Cl 3SnH intermediates that react w i t h the o l e f i n s . In the present work i f such complexes were formed, alkane release would r e s u l t by protono-l y s e s o f the Sn-C bond. Observation of mono-deutero SA suggests i n both the Rh and non-Rh systems that H +/D + exchange between s o l v e n t and hydride intermediates was slower than g - e l i m i n a t i o n and o l e f i n exchange. A l t e r n a t i -v e l y , an intermediate c o n t a i n i n g two organic moieties could be inv o l v e d i n the scrambling process. 5.6 Discussion M o d i f i c a t i o n o f the " i n a c t i v e " Rh/MA/H2/3MHC1 system by a d d i t i o n of SnCl 2«2H 20 r e s u l t e d i n c a t a l y t i c hydrogenation of MA and FA. The a c t i v i t y was comparable to other systems i n v o l v i n g d Ru and Rh precursor c a t a l y s t s under s i m i l a r c o n d i t i o n s (Table 5.6). The mechanisms are d i s p a r a t e . The Rh systems i n DMA are b e l i e v e d to p r i m a r i l y i n v o l v e Rh(III) d i h y d r i d e i n t e r -mediates formed by homolytic H 2 a c t i v a t i o n w i t h i n an "unsaturate route", although with R h C l 3 ( E t 2 S ) 3 a "hydride route" v i a a Rh(III) mono-hydride formed 2 6 h e t e r o l y t i c a l l y was a l s o evident . The Ru(II) system i n v o l v e d an "unsaturate 43 route" with h e t e r o l y t i c a c t i v a t i o n of H 2 by Ru(II) ( o l e f i n ) species . The present case i s more complicated. Besides reduction of o l e f i n i n v o l v i n g c a t a l y t i c hydrogenation, s t o i c h i o m e t r i c reduction i n v o l v i n g net o x i d a t i o n of -155-Table 5.6 Comparison of rates of H 2 uptake fo r various c a t a l y t i c systems fo r the hydrogenation of MA at 80 °C . [H21= 3 .60xlO" 4 M, [MA] = 0.1M [ ca ta l ys t ] = 0.01M. system solvent rate of uptake ( x l 0 6 M s _ 1 ) r e f . Rh/6Sn 3M HC1 2.6 th i s work RhCl 3 -3H 2 0 1.2M LiCl/DMA * ^ 4.7 25 " R u C l 2 " 3M HC1 ^ 8 + 43 R h C l 3 ( E t 2 S ) 3 DMA ^ 1.3* , 2 6 Estimated from data at CH21= 2.32x10 M and [Rh]= 0.01M; rate was 3 .0x lO~ 5 Ms _ 1 with the rate-law of - d ^ = k O ^ O C r ! ^ . dt * Estimated from rate at [Ru] = 0.0122M; corresponding rate-law as above. * Estimated from data at [H 2]= 2.32xlO" 3 M and [Rh]= 0.005M;same rate-law , rate = 4.25xlO" 6 Ms~ 1 . Sn(II) to Sn(IV) has been observed. The p r i n c i p l e mode of hydrogen a c t i v a t i on in the present case i s 28 bel ieved to be h e t e r o l y t i c . Compared to the t in- f ree system reported e a r l i e r , hydrogenation a c t i v i t y increased upon add i t ion of SnCl 2 -2H 2 0 ( i . e . S n C l 3 " in 3MHC1) and o l e f i n . The ir-acceptor nature o f both these l igands should P X JL promote nuc l eoph i l i c attack ( i . e . Rh + H H ) and decrease a c t i v i t y 156 towards ox ida t i ve add i t ion of H 2 . A lso the observed isotope scrambling and isomer izat ion i s more cons is tent with a mono-hydride intermediate ;(sec. 1.1.2) -156-Isomen"zation and isotope scrambling was observed f o r the "hydride route" v i a Rh(111)H f o r the R h C l 3 ( E t 2 S ) 3 system but not f o r the "unsaturate route" v i a 26-Rh (111)H 2 • Less c o n c l u s i v e i n the present case i s the f a c t that a c t i v i t y was greater f o r s o l u t i o n s w i t h a higher f r a c t i o n of t o t a l Rh present as R h ( I I I ) , which i s not as susceptable to o x i d a t i v e a d d i t i o n of H 2 as Rh(I). Although the l a s t item i s l e s s important as evidence towards hetero-l y t i c a c t i v a t i o n , i t does r e f l e c t one of the probable r o l e s of S n C l 3 ~ i n the c a t a l y s i s . The r e a c t i o n between Rh(III) and S n C l 3 ~ has already been shown (Chap. 3) to give mixtures of Rh(I) and Rh(III) t i n - c h l o r i d e complexes, h i g h l y coordinated with S n C l 3 ~ , and Rh complexes not c o n t a i n i n g S n C l 3 ~ . The r e l a t i v e amount of the l a t t e r was greater at lower Sn/Rh r a t i o . The i n i t i a l s o l u t i o n composition i n a l l hydrogenation experiments, except t h a t i n v o l v i n g prehydrogenation i n the absence of o l e f i n , was determined by modi-f i c a t i o n s induced by the presence of FA or MA. The composition would be impossible to determine i n any great d e t a i l , but some points are evident. Reduction to SA w i l l occur by r e a c t i o n w i t h Rh(I) species o f high Sn/Rh r a t i o , and w i t h free S n ( I I ) , presumably S n C l 3 " . A d d i t i o n a l l y , MA and FA should compete with S n C l 3 ~ at l a b i l e Rh(I) centers to form R h ( I ) ( o l e f i n ) type complexes. During hydrogenation the d i s t r i b u t i o n o f Rh complexes should change w i t h time due to the changes i n Sn(II) and o l e f i n concentra-t i o n s . At low [Sn], metal p r e c i p i t a t e d i n the absence of MA. In the presence of MA no metal formed u n t i l f u l l consumption o f MA, i n d i c a t i n g probable formation of Rh(I)(MA). However, with FA metal was not formed -157-e i t h e r , which i s c o n s i s t e n t w i t h isotope scrambling and concomittant i s o m e r i z a t i o n to MA. S o l u t i o n composition during hydrogenation as i n d i -cated by UV/VIS ( f i g . 5.3) was d i f f e r e n t f o r the two substrates, although no e f f e c t on the rat e of uptake was found. P o s s i b l e elements of the mechanism (mechanism A) which can q u a l i t a -t i v e l y e x p l a i n the observations are l i s t e d below (.Sn) nRh I H + H 2 — > ( S n ) n R h I H H " + H + (5.5) (Sn) R h I H H " + F A ^ ( S n ) n R h i n ( a l k y l ) ^ = i (Sn) R h I H H " + MA H + ( S n ) n R h i n + SA (5.6) ( S n ) n R h H I H " ( S n ) n R h ! + H + (5.7) (Sn) nRh J ^==h R h I + n S n ( I I ) (5.8) K" (Sn) nRh I + MA (Sn) n_-, Rh 1 (MA) + Sn(II) (5.9) ( S n ^ R h ^ M A ) v==^ Rh !(MA) + ( n - l ) S n ( I I ) (5.10) K" (Sn) Rh 1 + FA z=^=± ( S n ) n ^ Rh^FA) + Sn ( I I ) (5.11) n n-1 ( S n J ^ R ^ F A Rh X(FA) + ( n - l ) S n ( I I ) ( I D (5.12) -158-K1 Rh 1 + MA ^ m s Rh*(MA) (5.13) K 1 Rh 1 + FA N f N Rh !(FA) (5.14) ( S n ^ R h 1 + MA — ^ — > ( S n ) n R h I H ( a l k y l ) (5.15) H ( S n ^ R h 1 + FA — > ( S n ) n R h m ( a l k y l ) (5.16) H Sn(II) + MA — — > SA (5.17) Sn ( I I ) + FA 2 H > SA (5.18) The r a t e determining step i s l i k e l y to be 5.5, s i n c e no dependence of r a t e on s u b s t r a t e was seen at low [ o l e f i n ] . Constants such as K" , k and m m K*m are expected to be greater than K"^, k^ and , r e s p e c t i v e l y . At high [MA] the r e l a t i v e l y i n a c t i v e y e l l o w s o l u t i o n , probably c o n t a i n i n g Rh*(MA), i s u l t i m a t e l y favoured as S n ( I I ) i s 'burnt o f f by d i r e c t r e d u c t i o n o f o l e f i n , thus a d e c l i n i n g rate of uptake would be expected, and was observed. At high [Sn] formation o f Rh^MA) would be retarded. In the absence of Sn, c a t a l y t i c hydrogenation was observed at high [MA-]. Excluding the d i r e c t r e d u c t i o n s , a s i m i l a r mechanism (mechanism B) can be operative w i t h o l e f i n s u b s t i t u t e d f o r SnCl^" as the strong ir-acceptor. The necessary formation of R h ( I I I ) ( o l e f i n ) complexes could occur v i a Rh(I) c a l a l y z e d - s u b s t i t u t i o n at Rh(111 ) 9 as observed f o r SnCl^" and a l s o proposed -159-i n the R h C l 3 ( E t 2 S ) 3 / o l efin/H 2/DMA s y s t e m 2 6 . The increase i n i n i t i a l r a t e of uptake w i t h increased [MA] r e l a t i v e to the reported r a t e of the reported 28 s t o i c h i o m e t r i c uptake i s c o n s i s t e n t with t h i s i d e a . However, the independent i s o m e r i z a t i o n of MA to FA becomes important i n the present work. The e f f e c t of the independent i s o m e r i z a t i o n of MA was strongest when the s o l u t i o n w i t h Sn/Rh r a t i o of 6 was prehydrogenated before a d d i t i o n o f MA (high [MA]). U n l i k e the a l t e r n a t e procedure, l i t t l e R h(III) was present i n i t i a l l y . The s u r p r i s i n g premature p r e c i p i t a t i o n of metal during hydro-genation under these c o n d i t i o n s could be a s c r i b e d to p r e f e r e n t i a l reduction o f MA v i a the 'short cut' r e a c t i o n 5.15. This has two e f f e c t s . F i r s t , MA i s r a p i d l y consumed, i n c l u d i n g t h a t produced by i s o m e r i z a t i o n o f FA i n r e a c t i o n 5.6, but more im p o r t a n t l y Rh(I) i s apparently r e o x i d i z e d back to Rh(III) before formation of other Rh(_I) complexes that could lead to s t a b l e Rh(.I)(MA). Thus, when the more r e a c t i v e substrate i s consumed, the rate of r e o x i d a t i o n w i l l f a l l o f f and a l l o w more Rh(I) to form, but the [MA] would be too low to s t a b i l i z e a g a i n s t metal formation. A s i m i l a r r a t e of uptake was observed at low i n i t i a l [MA] and at a Sn/Rh r a t i o o f 6 I t appears that the choice of 10 equivalents o f o l e f i n f o r the low [ o l e f i n ] was a coincidence i n view of the observed metal formation. Since metal was not observed using FA as sub s t r a t e at low [ o l e f i n ] , i t must be assumed th a t the rat e of i s o m e r i z a t i o n to MA i s competitive with the formation o f Rh(I) complexes s u s c e p t i b l e to reduction to metal. However, the uptake i n t h i s case was not taken to the poi n t o f metal formation, so premature metal formation cannot be completely excluded. In c o n c l u s i o n , i t must be noted t h a t although a c a t a l y t i c hydrogenation - 1 6 0 -system f o r o l e f i n i c acids was generated by a d d i t i o n o f SnCl 2 "2^0 to Rh(III) at 80°C i n 3M HC1, the system i s a constrained one due to competing i s o m e r i -z a t i o n (e.g. MA to FA). C l e a r l y a broader range of c o n d i t i o n s needs to be examined w i t h an aim to reduce the e f f e c t o f i s o m e r i z a t i o n . Furthermore, the examination o f the e f f e c t of l i g h t on the system was cursory. From the 157 experiences i n Chapters 3 and 4 and elsewhere" , the lack o f i n f l u e n c e by l i g h t i s s u r p r i s i n g . Consideration o f product and isotope d i s t r i b u t i o n s , as w e l l as uptake rate, i s necessary f o r a f u l l e r statement on the e f f e c t o f l i g h t . -161-CHAPTER VI GENERAL CONCLUSIONS AND SUGGESTIONS FOR  FUTURE WORK The most s t r i k i n g f e a t u r e of the chemistry examined i n t h i s t h e s i s was the complexity engendered by the a d d i t i o n of stannous c h l o r i d e to the rhodium systems. However, while i n t e r e s t i n g and p o t e n t i a l l y important i n c a t a l y s i s , t h i s f e a t u r e made c h a r a c t e r i z a t i o n d i f f i c u l t . Treatment of s o l u t i o n s of "RhCl^•3H2O" with stannous c h l o r i d e followed by p r e c i p i t a t i o n with tetraalkylammonium c h l o r i d e s r e s u l t e d i n the i s o l a t i o n of various a n i o n i c rhodium-tin c h l o r i d e complexes. The v a r i a t i o n of the mixture of s y n t h e t i c products under various c o n d i t i o n s i n d i c a t e d Rh(I) c a t a l y s i s of s u b s t i t u t i o n a t Rh(II I ) centres was o c c u r r i n g . In p a r t i c u l a r the very r a p i d formation of [ R h C ^ S n C l ^ ] " (probably the tr a n s - isomer) was sup p o r t a t i v e of t h i s . Formation of a new Rh(I) complex, t e n t a t i v e l y c h a r a c t e r i z e d as [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] ~, formed v i a Sn(II) reduction of R h ( I I I ) , competed with the formation of Rh(II I ) products. The k i n e t i c products were not s t a b l e , and decomposed u l t i m a t e l y to thermodynamic products (e.g. [ R h C l 3 ( S n C l 3 ) 3 ] ). The nature of products not p r e c i p i t a b l e by tetraalkylammonium c h l o r i d e s was not determined. [ R h ( S n C l 3 ) 4 ( S n C l 4 ) ] may be s i m i l a r i n s t r u c t u r e to [ R h ( S n C l 3 ) 4 -5-( S n C l 4 ) ] (see f i g . 3.1); however, a molecular s t r u c t u r e determination i s r e q u i r e d . C l e a r l y the redox chemistry, and p o t e n t i a l r e l a t i o n s h i p 3+ wi t h l i g h t a c t i v a t i o n , of these 'e l e c t r o n r i c h ' (10 and 12 Fe reduction e q u i v a l e n t s , r e s p e c t i v e l y ) present a worthwhile avenue to pursue. For -162-example, i t might be p o s s i b l e to generate the t r i a n i o n e l e c t r o c h e m i c a l l y from the pentaanion. I t i s curious that so few 'simple' r h o d i u m - c h l o r i d e / t i n - c h l o r i d e complexes were i s o l a b le. Reaction between [Rh^Cl 2(C0T ) 4 1 and fEt^N][SnCl^1 d i d appear to y i e l d unstable and thermochromic Rh(I) complexes that were not f u l l y c h a r a c t e r i z a b l e . Although SnCl^", as a i r-acceptor l i g a n d , would be expected to form s t a b l e Rh(I) complexes (sec. 1.2), these complexes must be r e a d i l y o x i d i z e d (e.g. by Rh(III) i n 3M HC1). Perhaps the r e l a t i v e s t a b i l i t y of [ R h ( S n C l . j ) 4 ( S n C l 4 ) ] ^ ~ i s due to i t s nearly s p h e r i c a l outer arrangement of c h l o r i d e s b l o c k i n g o x i d i z i n g attack at Sn or Rh. Under hydrogenation c o n d i t i o n s , 3M HC1 s o l u t i o n s of RhCl^-Sri^O and SnC^^H^O c a t a l y s e d the reduction of fumaric and maleic acids to s u c c i n i c a c i d . Once again a complex system was observed. S t o i c h i o m e t r i c reduction of o l e f i n by Sn(II) and Rh(I) complexes was observed, protonation y i e l d i n g the reduced product. These r e a c t i o n s competed with c a t a l y t i c hydrogenation i n v o l v i n g Rh and H^. I s o t o p i c scrambling was found to have occurred i n the product suggesting a mono-hydride c a t a l y s t . On the basis of the l i m i t e d data, a "hydride-route" mechanism was proposed, with generation of hydride v i a h e t e r o l y t i c s p l i t t i n g o f H 2 at R h ( I I I ) . UV-Vis data i n d i c a t e t h a t the c a t a l y t i c s o l u t i o n s at lower [Sn] c o n t a i n a high c o n c e n t r a t i o n of Rh(III) complexes which presumably favours a Rh(III)-based c a t a l y t i c system. The r o l e of stannous c h l o r i d e may be n o n - s p e c i f i c , a c t i n g to promote formation of a complex 'soup' s i m i l a r to t h a t observed i n the s y n t h e t i c experiments. A d d i t i o n a l l y , some evidence points to c o u p l i n g between s t o i c h i o m e t r i c reduction of o l e f i n by a R h ( I ) - t i n c h l o r i d e complex and H ? reduction of -163-the r e s u l t a n t Rh(III) product to complete the c a t a l y t i c c y c l e . Confirmed examples of such a process are not known (sec. 1.1.2), so e l u c i d a t i o n of t h i s point would be u s e f u l . An o v e r a l l understanding o f the c a t a l y t i c system may be e l u s i v e given the complexity i n d i c a t e d here. I t i s not at a l l obvious how to approach the k i n e t i c problem. -164-REFERENCES G.W. P a r s h a l l , C a t a l . Rev. S c i . Eng. (1981), 23, 107. G. W. P a r s h a l l , 'Homogeneous C a t a l y s i s . The A p p l i c a t i o n s and Chemistry by Soluble T r a n s i t i o n Metal Complexes', W i l e y - I n t e r s c i e n c e , N.Y., 1980. C.N. 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B-276, B-281 and B-282. -175-Appendix A Two programs were w r i t t e n to f a c i l i t a t e k i n e t i c a n a l y s i s . The f i r s t i s a data storage program c a l l e d DSTORE.F, which i s used to i n t e r a c t i v e l y s t o r e data i n a format usable by the actu a l k i n e t i c a n a l y s i s program c a l l e d ALLKIN.F. ALLKIN.F has a rudimentry command language by which the user can c o n t r o l program flow. The program l i s t i n g s f o l l o w (sec. A l and A2), with imbedded comments t h a t e x p l a i n t h e i r o p e r a t i o n ; such statements are p r e f i x e d by ' C Note that there are 3 input streams to ALLKIN.F: (1) from a data f i l e f i l l e d using DSTORE.F, (2) from a t e r m i n a l , i n the same format as ( 1 ) , and (3). from a terminal as 'X,Y' p a i r s . Routes (1) and (2) are f o r data that can be described as a l i s t of 'Y' values with the 'X' values s p e c i f i e d by an i n i t i a l 'X' and an i n t e r v a l 'AX' (e.g. absorbance sampled at constant time i n t e r v a l s ) . Output d e f a u l t s to a terminal but 'hardcopy' can be generated on command v i a a temporary f i l e which can then be l i s t e d on an appropriate device. -176-Section A . l -177-cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c C PROGRAM DSTORE.F: STATEMENTS IN DSTORE.F C C OBJECTCODE IN DSTORE.O C C c C PURPOSE: STORAGE OF ABSORBANCE DATA IN F I L E C C ATTACHED TO UNIT 9 IN A FORMAT SUCH C C THAT 'ALLKIN' CAN RETRIEVE I T USING C C THE RUN-NUMBER CODE ('RNUM') VI A C C THE OPTION=1 DATA INPUT ROUTE OF C C 'ALLKIN'. C C C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC c DIMENSION A(30) INTEGER RNUM, LINE C C READ IN NUMBER OF STORED RUNS ALREADY IN F I L E ATTACHED TO C UNIT 9 ( 9=[FILENAME] ), THIS VALUE ('LINE') IS FOUND IN C THE FIRST 2 BYTES OF THE F I L E ( FORMAT 1 2 ) . C READ (9,50,END=30) L I N E LINE = L I N E * 1000 C C INPUT 'RNUM', NUMBER OF DATA POINTS ('NUM'; <31 VALUES), I N I T I A L C TIME 'TO', TIME INCREMENT ' T I ' . C 10 WRITE (6,60) CALL FREAD('SCARDS', '21:', RNUM, NUM, '2R:', TO, T I ) C C INPUT ABSORBANCE DATA AS A L I S T (SEPARATED BY COMMAS). C WRITE (6,70) CALL FREAD('SCARDS', 'R V:', A, 30, &20) C C INPUT A - I N F I N I T Y 'A8' C 20 WRITE (6,80) CALL FREAD('SCARDS', 'R:', A8) C EXECUTE STORAGE FIND (9 ' L I N E ) WRITE (9,90) RNUM, NUM, TO, T I , (A(I),I=1,NUM), A8 C C INPUT REQUEST TO RECYCLE TO ENTER ANOTHER RUN (YES=1,NO=0) C WRITE (6,100) CALL FREAD('SCARDS', ' I : ' , L ) I F ( L .EQ. 0) GO TO 30 LINE = L I N E + 1000 GO TO 10 30 WRITE (6,110) LINE = ( L I N E + 1000) / 1000 FIND (9'1000) WRITE (9,50) LINE -178-40 STOP 50 FORMAT (12) 60 FORMAT (1&ENTER RUN ID#.,NUMBER OF POINTS,TO,TI') 70 FORMAT (.' &ENTER DATA POINTS') 80 FORMAT ('&ENTER A-INFINITY') 90 FORMAT (15, 12, 2F11.4, 31F5.3) 100 FORMAT ('&ENTER MORE DATA') 110 FORMAT ('FINISHED') END -179-Section A.2 -180-ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc <- c C PROGRAM ALLKIN.F (STATEMENTS: DTHA:ALLKIN.F) C C (OBJECTCODE: DTHA:ALLKIN.O) C J c C INTERACTIVE PROGRAM TO FACILITATE FIRST-ORDER ANALYSIS C OF UV-VIS SPECTRAL DATA. ADDITIONALLY ROU INES FOR SIMPLE C REACTION ORDER DETERMINATION AND LINEAR LEAST-SQUARES FIT C C ARE INCLUDED. THE BASIC FLOW OF THE PROGRAM IS CONTROLLED C C INTERACTIVELY USING A TWO CHARACTER COMMAND 'LANGUAGE'. C C INITIALLY THE DATA SET IS INPUT FROM A SPECIAL F I L E , C C WHICH IS SET UP USING THE PROGRAM DTHA:DSTORE.0, OR DIRECTLY C C FROM A TERMINAL. THIS DATA IS MAINTAINED SEPARATELY FROM C C THE 'ACTIVE' COPY WHICH MAY BE MODIFIED BY THE USER. THUS C C BY ISSUING A RESTART COMMAND ('RS') THE PROGRAM CAN BE RE- C C INITIALIZED WITH THE ORIGINAL DATA AT ANY TIME. THE FIRST- C C ORDER ANALYSES AVAILIABLE ARE GUGGENHIEM, KEZDY-SWINBOURNE C C AND THE 'NORMAL' LEAST-SQUARES FIT TO THE INTEGRATED FORM C C OF A FIRST-ORDER RATE EQUATION FOR DATA WITH CONSTANT TIME C C INTERVALS. ONLY THE FIT TO THE INTEGRATED FORM IS AVAILIABLE C C IF VARIABLE TIME INTERVALS ARE INPUT. OUTPUT IS TO TERMINAL C C OR TO A TEMPORARY FILE ' - P I T ' FOR SUBSEQUENT PRINT-OUT. C C NOTE: NO PROTECTION IS PROVIDED AGAINST FATAL INTERRUPTS C C TERMINATING THE PROGRAM RESULTING IN LOSS OF INPUT C C DATA WHEN THE DATA IS INPUT FROM A TERMINAL. C 9 . C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC C DIMENSION X(30), Y(30) INTEGER RNUM, OPT INTEGER*2 CMDL(IO) /2HST, 2HRS, 2HOR, 2HDM, 2HFN, 2HFS, 2HFA, 1 2HNS, 2HDD, 2HLL/ INTEGER*2 CMD COMMON /MAIN1/ RNUM, NUM, A(30), A81, T(30) /MAIN2/ LTAG CALL FTNCMD('ASSIGN 3=~PIT;') C C *ENTRY POINT FOR NS COMMAND C 10 CALL FREAD(-1, 'PREFIX') C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC c C C INDICATE TYPE OF DATA TO BE INPUTED: 1: ABS. DATA FROM UNIT 9 C C AT CONSTANT TI C C 2: DITTO FROM TERMINAL C C 3: X,Y DATA PAIRS FROM C C TERMINAL C C , c C (NOTE: NO MORE THAN 30 DATA PAIRS CAN BE USED.) C c c c c ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c -181-WRITE (6,290) CALL FREAD('SCARDS' , ' I : ' , OPT) IF (OPT - 2) 20, 50, 90 C C INPUT DATA FROM UNIT 9 (0PT=1) C 20 WRITE (6,300) IP = 0 CALL FREAD('SCARDS' , ' I : ' , RNUM) FIND (9'1000) READ (9,310) LINE LT = LINE - 2 C DO 30 L = 1, LT READ (9,320) IDN IF (IDN .EQ. RNUM) GO TO 40 30 CONTINUE C WRITE (6,340) GO TO 270 40 IT « (L + 1) * 1000 READ (9*IT,330) NUM1, TO, T I , (Y(I),1=1,NUM1), A8 GO TO 70 C C INPUT DATA: CONSTANT TIME INTERVALS (T0=INITIAL TIME; TI=INCREMENT) C ALSO NEED A-INFINITY(OBS) (OPT=2) C 50 WRITE (6,350) CALL FREAD('SCARDS', ' 2 1 : ' , RNUM, NUM1, ' 2 R : ' , TO, TI) WRITE (6,360) CALL FREAD('SCARDS', ' R V : ' , Y, 30, &60) 60 WRITE (6,370) CALL FREAD('SCARDS', ' R : ' , A8) C C INITIALIZATION: 1: FILL A&T MATRICES C 2: FILL A81 ( I . E . A-INFINITY) C C *ENTRY POINT FOR RS COMMAND (DATA OPT .NE. 3) C 70 DO 80 IT = 1, NUM1 A(IT) = Y(IT) T(IT) = TO + TI * (IT - 1) 80 CONTINUE C A81 = A8 A8C = A8 NUM = NUM1 GO TO 130 C C INPUT DATA: FROM TERMINAL AS X,Y PAIRS (5<N<31) FOLLOWED BY C A-INFINITY (OPT=3) C 90 WRITE (6,380) CALL FREAD('SCARDS', ' 2 1 : ' , RNUM, NUM1) -182-C WRITE (6,280) C DO 100 IV = 1, NUM1 CALL FREAD('SCARDS', '2R:', X(IV), Y(IV)) 100 CONTINUE C C *ENTRY POINT FOR RS COMMAND (DATA OPT .EQ. 3) C 110 DO 120 IU = 1, NUM1 A(IU) = Y(IU) T(IU) = X(IU) 120 CONTINUE C NUM = NUM1 C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC C c C CHOOSE INITIAL OPTIONS IN PROGRAM FLOW C C C C ON PROMPTING (I.E. ":") THE FOLLOWING COMMANDS ARE VALID: C C C C DD : DISPLAY ACTIVE DATA TABLE C C DM : DATA MANIPULATOR/MODIFIER C C FA : GUGGENHIEM, KEZDY-SWINBOURNE & NORMAL C C FIRST-ORDER ANALYSIS USING "SWIN A-INFINITY" C C (DISABLED IF OPT=3) C C FN : NORMAL FIRST-ORDER ANALYSIS USING C C A-INFINITY(OBS) C C FS : FN USING "SWIN A-INFINITY" (DISABLED IF C C OPT=3) C C LL : LINEAR LEAST-SQUARES ANALYSIS OF (X,Y) C C NS : RESTART WITH NEW DATA SET C C OR : DIFFERENTIAL ANALYSIS FOR REACTION ORDER C C RS : RESTART WITH CURRENT DATA SET RE-INITIALIZED C C ST : STOP . C C C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC c 130 CALL FREAD(-2, 'PREFIX', ':') '< c C *SET LTAG=0 C LTAG = 0 140 CALL FREAD('SCARDS', 'S:', CMD, 2) C DO 150 L = 1, 10 IF (CMD .EQ. CMDL(L)) GO TO 160 150 CONTINUE C GO TO 140 160 GO TO (260, 250, 170, 180, 190, 210, 220, 10, 230, 240), L 170 CALL ORDERU140) 180 CALL DAMASSU140) -183-190 A8C = A81 200 CALL NORMAL(A8C, &140) 210 CALL SWIN(A8C, &200,OPT,& 140) 220 CALL GUGGE(&210,OPT,&140) 230 CALL DATA(A8C, 6140) 240 CALL LSQ(&140) 250 IF (OPT .EQ. 3) GO TO 110 GO TO 70 C C ***TERMINATION*** C 260 WRITE (6,390) 270 STOP C 280 FORMAT (' ENTER DATA PAIRS(X,Y);NOTE: X->T,Y->A', /) 290 FORMAT ('6ENTER DATA TYPE:(1,2 OR 3)') 300 FORMAT ('&IDENTIFY RUN FOR ANALYSIS') 310 FORMAT (12) 320 FORMAT (15) 330 FORMAT (5X, 12, 2F11.4, 31F5.3) 340 FORMAT (IX, /, ' RUN SPECIFIED NOT FOUND. RUN TERMINATED', /) 350 FORMAT ('&ENTER RUN ID#.,NUMBER OF POINTS,TO,TI') 360 FORMAT ('&ENTER DATA POINTS') 370 FORMAT ('&ENTER A-INFINITY') 380 FORMAT (' & ENTER RUN ID#, NUMBER OF DATA PAIRS (5<NUM1<31)') 390 FORMAT ('FINISHED') END -184-C ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c C SUBROUTINE ORDER: CALCULATES THE REACTION ORDER USING C C SIMPLE DIFFERENTIAL APPROXIMATION. C C c ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c SUBROUTINE ORDER(*) c DIMENSION X(30), Y(30) INTEGER RNUM INTEGER*2 LT /1HY/, LL COMMON /MAIN1/ RNUM, NUM, A(30), A81, T(30) /MAIN4/ SLP, YINT, 1 SESLP, SEYNT, CLS90, CLI90, R, N /MAIN2/ LTAG N = NUM - 1 C DO 10 I = 1, N D = A(I) - A(I + 1) AV=A81-(A(I)+A(I+1))/2.0 X(I) = ALOG(ABS(AV)) Y(I) = ALOG(ABS(D/(T(I + l) - T(l)))) 10 CONTINUE C CALL LLSQ(X, Y) C C OUTPUT TO TERMINAL C WRITE (6,20) RNUM, SLP, SESLP, R WRITE (6,30) C C HARDCOPY OPTION (UNIT 3) C CALL FREAD('SCARDS', 'S:', LL, 2) IF (LL .EQ. LT) WRITE (3,20) RNUM, SLP, SESLP, R C C *SET LTAG=3 C LTAG = 3 RETURN '1 C 20 FORMAT (' RUN ID=', 15, /, ' ', /, ' ORDER(S.E.)=', 1 F6.3, '( ', F8.5, ') R=', F9.5) 30 FORMAT ('^HARDCOPY(Y,N)1) END -185-C cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c C SUBROUTINE LLSQ: CALCULATES LINEAR LEAST-SQUARES FIT C C TO X,Y PAIRS PASSED FROM CALLING C C ROUTINES AS AN ARRAY. C c c cccccccccccccccccccccccccccccccccccccccecccccccccccccccccccccccccc c SUBROUTINE LLSQ(X, Y) c REAL X(30), P90(30), Y(30) DATA P90 /6.31, 2.92, 2.35, 2.13, 2.02, 1.94, 1.90, 1.86, 1.83, 1 1 .81 ,. 1 .80, 1 .78, 1 .77, 1 .76, 1 .75, 1 .75, 1 .74, 1 .73, 1 .73, 2 1.73, 1.73, 1.73, 1.73, 1.73, 1.71, 1.71, 1.71, 1.71, 1.71, 3 1.70/ COMMON /MAIN4/ SLP, YINT, SESLP, SEYNT, CLS90, CLI90, R, N C C INITIALIZATION C SY2 = 0.0 SX2 =0.0 SXY = 0.0 SY = 0.0 SX = 0.0 c DO 10 L = 1, N SY2 = SY2 + Y(L) ** 2 SX2 = SX2 + X(L) ** 2 SXY = SXY + X(L) * Y(L) SY = SY + Y(L) SX = SX + X(L) 10 CONTINUE C YM = SY / N XM = SX / N SYS = SY2 - N * (YM**2) SXS = SX2 - N * (XM**2) SSXY = SXY - N * XM * YM C LSQ SLP = SSXY / SXS YINT = YM - SLP * XM C STANDARD ERROR (SESLP: FOR SLOPE; SEYNT: FOR Y-INTERCEPT) DN = (N - 2) * SXS W = SYS - SLP * SSXY SESLP = SQRT(ABS(W/DN)) SEYNT = SQRT(ABS(W*((1/N + XM**2)/DN))) C CONFIDENCE LIMITS '90% LEVEL' (CLS90: FOR SLOPE; CLI90: INTER-C -CEPT) SI = N - 2 CLS90 = P90(SI) * SESLP CLI90 = P90(SI) * SEYNT C PEARSONS MOMENT CORELATION COEFFICIENT R1 = SQRT(ABS(N*SX2 - SX**2)) - 1 8 6 -R2 = SQRT(ABS(N*SY2 - SY**2)) R = (N*SXY - SX*SY) / (R1*R2) RETURN END -187-C ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c C SUBROUTINE GUGGE: FIRST-ORDER ANALYSIS BY GUGGENHIEM'S C C METHOD (CALLED BY 'FA') C C C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC C SUBROUTINE GUGGE(*,OPT,*) C REAL KOBS COMMON /MAIN1/ RNUM, NUM, A(30), A81, T(30) /MAIN4/ SLP, YINT, 1 SESLP, SEYNT, CLS90, CLI90, R, N /MAIN5/M(2), RATE(2), 2 RC(2) DIMENSION X(30) , Y(30) IF( OPT. EQ. 3 ) RETURN 2 N = NUM / 2 C DO 10 I = 1, N Y(I) = ALOG(ABS(A(l + N) - A(l))) X(I) = T(I) 10 CONTINUE C CALL LLSQ(X, Y) KOBS = SLP RATE(1) = KOBS RC(1) = R M( 1 ) = 1 RETURN 1 END -188-C ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c C SUBROUTINE SWIN: FIRST-ORDER ANALYSIS BY KEDZY- C C SWINBOURNE METHOD. ALSO CALCULATES C C A-INFINITY FOR USE BY 'NORMAL'. C C (CALLED BY 'FA' AND 'FS') C C C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC c SUBROUTINE SWIN(A8C,*,OPT,*) c REAL KOBS DIMENSION X(30), Y(30) COMMON /MAIN1/ RNUM, NUM, A(30), A81, T(30) /MAIN4/ SLP, YINT, 1 SESLP, SEYNT, CLS90, CLI90, R, N /MAIN5/ M(2), RATE(2), 2 RC(2) IF( OPT. EQ. 3) RETURN 2 N = NUM / 2 C DO 10 I = 1 , N X(I) = A(I + N) Y(I) = A(I) 10 CONTINUE C CALL LLSQ(X, Y) KOBS = ALOG(ABS(SLP)) / (T(N + 1) - T( 1 )) A8C = YINT / (1 - SLP) RATE(2) = KOBS RC(2) = R M(2) = 1 RETURN 1 END -189-C ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c C SUBROUTINE NORMAL: FIRST-ORDER ANALYSIS BY INTEGRATED C C FORM USING A-INFINITY(OBS) IF CALLED C C BY 'FN' OR A-INFINITY CALCULATED BY C C 'SWIN' IF CALLED BY 'FA' OR 'FS'. C C (CALLED BY 'FA','FS' AND 'FN') C C C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC C SUBROUTINE NORMAL(A8C,*) C INTEGER RNUM INTEGER*2 LT /1HY/, LL DIMENSION X(30), Y(30) COMMON /MAIN1/ RNUM, NUM, A(30), A8 1 , T(30) /MAIN4/ SLP, YINT, 1 SESLP, SEYNT, CLS90, CLI90, R, N /MAIN5/M(2), RATE(2), 2 RC(2) /MAIN2/ LTAG A8 = A8C N = NUM C DO 10 I = 1 , N X(I) = T(I) Y(I) = ALOG(ABS(A8 - A(l))) 10 CONTINUE C CALL LLSQ(X, Y) AO = A8 + EXP(YINT) DEL=A(N)-A(1) IF(DEL.GT.0.0)A0=A8-EXP(YINT) TH = ALOG(2.0) / ABS(SLP) C C OUTPUT ON TERMINAL C WRITE (6,40) RNUM IF (M(1) .EQ. 1) WRITE (6,50) RATE(1), RC(1) IF (M(2) .EQ. 1) WRITE (6,60) RATE(2), RC(2), A8 WRITE (6,70) SLP, R, AB, AO, TH WRITE (6,80) NUM WRITE (6,30) C C HARDCOPY OPTION (UNIT 3) C CALL FREAD('SCARDS', 'S:', LL, 2) IF (LL .NE. LT) GO TO 20 WRITE (3,40) RNUM IF (M(1) .EQ. 1) WRITE (3,50) RATE(1), RC(1) IF (M(2) .EQ. 1) WRITE (3,60) RATE(2), RC(2), A8 AO = A8 + EXP(YINT) DEL=A(N)-A(1) IF(DEL.GT.0.0)A0=A8-EXP(YINT) TH = ALOG(2.0) / ABS(SLP) WRITE (3,70) SLP, R, A8, AO, TH 20 C C C C 30 40 50 60 70 80 WRITE (3,80) NUM M( 1 ) = 0 . M(2) = 0 *SET LTAG=1 - 1 9 0 -1 1 2 LTAG = RETURN FORMAT FORMAT FORMAT FORMAT I FORMAT FORMAT END ' &HARDCOPY(Y,N)') ' RUN ID=', 15, /, GUGGE: K(OBS)=', SWIN NORM K(OBS)= E10.4, E10.4, ' , /) R=' A-INF (CALC)=', F6.3, /) K(OBS)=', E10.4, ' 3X, A-INF = ', F6.3, T-l/2=*, F11.4) 'NUMBER OF DATA PAIRS= R=' 12, /) F9.5, /) F9.5, /, F9.5, /, A-ZERO=' F6.3, /, -191-C ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c C SUBROUTINE DAMASS: DATA MANIPULATION ROUTINE. ALLOWS C C CORRECTION OF INPUT ERRORS OR C C MODIFICATION OF 'ACTIVE' VALUES FOR C C A-INFINITY, NUMBER OF DATA PAIRS OR C C DELETION OF OUTLIERS. THE ROUTINE C C USES IT'S OWN COMMAND LANGUAGE AND C C INPUT PROMPT ('>'). THE ORIGIONAL C C DATA SET IS NOT MODIFIED BY THIS C C ROUTINE. C C (CALLED BY 'DM') C C C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC c SUBROUTINE DAMASS(*) c INTEGER*2 CMDL(5) /2HNS, 2HDE, 2HA8, 2HST, 2HCP/ INTEGER*2 CMD REAL P(30) COMMON /MAIN1/ RNUM, NUM, A(30), A81, T(30) /MAIN2/ LTAG N = NUM CALL FREAD(-2, 'PREFIX', '>') C ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c C CHOOSE PROGRAM FLOW OPTIONS ON PROMPTING ('>'): C C NS {n}: (n<3l) RESETS NUM=n C C DE { k } { k' } {... : DELETES DATA PAIRS NUMBERED C C k, k' , . . . IN ASCENDING ORDER. ALSO RESETS C C NUM= NEW NUMBER OF DATA PAIRS. C C A8 {n.nnn}: ASSIGNS NEW VALUE TO A81 (A-INFINITY) C C CP {n} {nnnnn} {n.nnn}: REPLACES DATA PAIR n C C WITH WITH NEW VALUES OF T(n) A(n). C C ST : RETURN TO MAIN PROGRAM C c c c c ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c 10 ' CALL FREAD('SCARDS', 'S:', CMD, 2, 'RV:', P, 30, &20) 20 CONTINUE C DO 30 L = 1, 5 IF (CMD .EQ. CMDL(L)) GO TO 40 30 CONTINUE C GO TO 10 C C EXECUTE 'NS' C 40 IF (L .EQ. 1) NUM = P(1) C C EXECUTE 'A8' -192-C IF (L .EQ. 3) A81 = P(1) IF (L .EQ. 4) GO TO 90 IF (L .EQ. 5) GO TO 80 IF (L .NE. 2) GO TO 10 C C EXECUTE 'DE' C CALL FREAD(-2, 18, IVAL) KT = 0 IVAL = IVAL - 1 IF (IVAL .LE. 0) GO TO 70 C DO 60 K = 1, IVAL IPT = P(K) - KT C DO 50 J = IPT, N T(J) = T(J + 1) A(J) = A(J + 1 ) 50 CONTINUE C KT = KT + 1 60 CONTINUE C NUM = NUM - KT 70 WRITE (6,100) IVAL, NUM GO TO 10 C C EXECUTE 'CP' C 80 LP = P(1) T(LP) = P(2) A(LP) = P(3) GO TO 10 C C *SET LTAG=0 C 90. LTAG = 0 C C EXECUTE 'ST' C CALL FREAD(-2, 'PREFIX', ':') RETURN 1 C 100 FORMAT (3X, 12, ' POINTS DELETED; TOTAL NOW =', 12) END -193-C ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c C SUBROUTINE DATA: DATA TABULATION AND DISPLAY ROUTINE. C C LISTS 'ACTIVE' T, A AND A81 VALUES C C AS WELL AS A(CALC.) AND (A-A(CALC)) C C WHEN APROPRIATE. C C (CALLED BY 'DD') C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC C SUBROUTINE DATA(A8C,*) C INTEGER RNUM INTEGER*2 LT /1HY/, LL, LO /1HN/ COMMON /MAIN 1/ RNUM, NUM, A(30), A81, T(30) /MAIN4/ SLP, YINT, 1 SESLP, SEYNT, CLS90, CLI90, R, N /MAIN2/ LTAG LL = LO 10 IF (LL .EQ. LT) CALL FTNCMD('EQUATE 6=3;') WRITE (6,90) RNUM C C LTAG INDICATES LAST ACTIVE PROGRAM SEGMENT. C 0= DAMASS OR INITIALIZATION C 1= NORMAL C 2= LLSQ C 3= ZERO C IF (LTAG .EQ. 3) GO TO 50 WRITE (6,110) IF (LTAG .EQ. 0) WRITE (6,140) IF (LTAG .NE. 0) WRITE (6,120) C DO 40 I = 1, NUM IF (LTAG .EQ. 0) GO TO 30 C C LTAG=1 OR 2 C YC = SLP * T(I) + YINT DEL = A8C - A(1) IF (LTAG .EQ. 1 .AND. DEL .LT. 0.0) YC = A8C + EXP(YC) IF (LTAG .EQ. 1 .AND. DEL .GT. 0.0) YC = A8C - EXP(YC) 20 D = A(I) - YC WRITE (6,130) I, T(I), A(l), YC, D GO TO 40 C C LTAG=0 C 30 WRITE (6,180) I, T(I), A(I) 40 CONTINUE C WRITE (6,150) A8C WRITE (6,160) NUM GO TO 70 C c 50 WRITE (6,170) C DO 60 K = 1 , N D = A(K) - A(K+1) AV=A81-(A(K)+A(K+1))/2.0 X = ALOG(ABS(AV)) Y = ALOG(ABS(D/(T(K + -1 ) - T(K) ) ) ) YC = SLP * X + YINT DF = Y - YC WRITE (6,130) K, X, Y, YC, DF 60 CONTINUE C C HARDCOPY OPTION (UNIT 3) C 70 IF (LL .EQ. LT) GO TO 80 WRITE (6,100) CALL FREAD('SCARDS', 'S:', LL, 2) IF (LL .EQ. LT) GO TO 10 80 CALL FTNCMD('EQUATE 6=SPRINT;') RETURN 1 C 90 FORMAT (3X, ' RUN ID=', 15, /) 100 FORMAT ('&HARDCOPY(Y,N)') 110 FORMAT ('&', 2X, '#', T5, 'TIME(SEC)', T21, 'A(OBS)') 120 FORMAT (T7, 'A(CALC)', T20, 'DIFF', /) 130 FORMAT (1X, 12, 1X, F11.4, 3X, F9.4, 3X, F9.4, 3X, E9.2) 140 FORMAT (* .', /) 150 FORMAT (/, 3X, 'A~INFINITY=', F9.4) 160 FORMAT (3X, 'NUMBER OF DATA PAIRS=', 12, /) 170 FORMAT (2X, '#', T7, 'X(OBS)', T21, 'Y(OBS)', T33, 'Y(CALC)', 1 T46,'DIFF', /) 180 FORMAT (1X, 12, IX, F11.4, 3X, F9.4) END -195-C cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c C SUBROUTINE LSQ: SIMPLE LINEAR LEAST-SQUARES ANALYSIS C C ON ANY X,Y DATA PAIR SET. USUALLY C C DATA IS ENTERED VIA OPTION 3. C C (CALLED BY 'LL') C C C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC c SUBROUTINE LSQ(*) c INTEGER RNUM INTEGER*2 LT /1HY/, LL COMMON /MAIN1/ RNUM, NUM, A(30), A81, T(30) /MAIN4/ SLP, YINT 1 SESLP, SEYNT, CLS90, CLI90, R, N /MAIN2/ LTAG N = NUM C C *SET LTAG=2 C LTAG = 2 CALL LLSQ(T, A) C C OUTPUT ON TERMINAL C WRITE (6,20) RNUM, SLP, SESLP, CLS90 WRITE (6,30) YINT, SEYNT, CLI90 WRITE (6,40) R WRITE (6,10) NUM WRITE (6,50) C C HARDCOPY OPTION (UNIT 3) C CALL FREAD('SCARDS', 'S:', LL, 2) IF (LL .NE. LT) RETURN 1 WRITE (3,20) RNUM, SLP, SESLP, CLS90 WRITE (3,30) YINT, SEYNT, CLI90 WRITE (3,40) R RETURN .1 C 10 FORMAT (3X, 'NUMBER OF DATA PAIRS=', 12, /) 20 FORMAT (' RUN ID=', 15, /, ' ', /, ' SLOPE(S.E.)= 1 E10.4, '(', E10.5, ') CL90=', E10.5, /) 30 FORMAT (' Y-INT(S.E.)=', F6.3, '(' , F6.4, ') CL90=', F6.4, 40 FORMAT (' CORRELATION COEFF.(R)=', F9.5, //) 50 FORMAT ('^HARDCOPY(Y,N)') END -196-Appendix B 119 Estimation of intensities of Sn FT NMR resonance intensities  for [RhClg n(SnCU)n]3" complexes. B.1 As noted in section 3.5, the splitting patterns and the intensities 119 3-of Sn FT NMR resonances in the spectra of [RhClg_n(SnCl^) ] complexes are useful for determining the number of coordinated SnCl3~ ligands. The • 110 octahedral Rh complexes are considered to be fluxional in 3M HC1 , making the SnCl^" ligands magnetically equivalent. For complexes with more than one tin nuclei (n>2), a sextuplet pattern is expected due to coupling to ^Sn, assuming intensities of signals due to complexes with 3 or more spin active 115 nuclei, or Sn, to be negligible (see sec. 3.5). The problem of determining the coordination number from intensities has been addressed in ref. 110 where the measure used was the ratio of a satellite peak intensity to that of a main peak (ls/Im;csee fig. B.1). The method used was "simple statistics", which were not described and we have not been able to exactly duplicate. 158 In this work the ratios were calculated using combinatorial probabilities , as described below. The results are summarized in fig. 3.32; the values reported in ref. 110 lie slightly higher and follow a linear relation. The first section (B.2) concerns complexes with equivalent tin ligands, while the second deals with the special case of a rigid [RhCl(SnCl3)^3 complex, which was the subject of a simulation (sec. 3.5 and Appendix C). Table B.1 summarizes the natural abundance values used in the calculations. -197-Table B . l The nat u r a l abundances of various i s t o p e s o f t i n and r h o d i u m 1 5 9 B.2 B.2.1 For n =2: isotope s p i n abundance 1 0 3 R h 1/2 1.0000 1 1 9 S n (A) 1/2 0.0858 1 1 7 S n (B) 1/2 0.0761 1 1 5 S n •» 1/2 0.0035\ other Sn J (D) 0 i 0.8380 0.8345 J Case ( i ) . 1 x 1 1 9 S n P[(AOD) U ( D O A ) ] = 0.1438; i n t e n s i t y ( I) = 0.1438 Case ( i i ) . 2 x 1 1 9 S n PC(APlA) ] = 0.0074; I = 0.147 Case ( i i i ) . 1 x 1 1 9 S n , 1 x 1 1 7 S n P C ( A n B ) U ( B D A ) ] = 0.0131; I = 0.0131 I / I = 4.13% s m - 1 9 8 -B . 2 . 2 For n = 3 : Case ( i ) 1 x 1 1 9 S n P K A H D H D J U ( D n A f i D ) U ( D n D f l A ) ] = 0 . 1 8 0 8 ; I = 0 . 1 8 0 8 Case ( i i ) , 2 x l i y S n P [ ( A f l A n D ) U (ADDnA)U ( D P I A D A)T = 0 . 0 1 8 6 ; I = 0 . 0 3 7 0 Case ( i i i ) 1 x 1 1 9 S n , 1 x 1 A / S n 1 1 7 , I. P C(AD BflD) U (API D f l B j U (DR AH B)U (DTI B f l A ) U (B(~l Dfl A ) U (B D A f l D ) ] = 0 . 0 3 2 8 ; I = 0 . 0 3 2 8 I / I = 7 . 5 4 % s m B. 2 . 2 For n = 4 the values are s i m i l a r i l y c a l c u l a t e d : Case ( i ) 1 x 1 1 9 S n P = 0 . 2 0 2 ; I = 0 . 2 0 2 0 Case ( i i ) 2 x 1 1 9 S n P = 0 . 0 3 1 2 ; I = 0 . 0 6 2 4 Case ( i i i ) 1 x 1 1 9 S n , 1 x 1 1 7 S n P = 0 . 0 5 5 2 ; I = 0 . 0 5 5 2 I / I = 1 0 . 4 1 % s m B.2.4 For n = 5 : Case ( i ) Case ( i i ) 1 x 1 1 9 S n P = 0 . 2 1 1 5 ; I = 0 . 2 1 1 6 2 x 1 1 9 S n P = 0 . 0 4 3 0 ; I = 0 . 0 8 6 6 -199-Case ( i i i ) 1 x 1 1 9 S n , 1 x 1 1 7 S n P = 0.0760; I = 0.0768 s m B.3 In the case of a r i g i d octahedral n = 5 complex the d i s t r i b u t i o n of the isotopes was accounted f o r by apportioning the p r o b a b i l i t i e s (or 'weights') according to the number of p o s s i b l e arrangements of each combination. There are 1 a x i a l and 4 e q u i v a l e n t e q u a t o r i a l s i t e s : a Case ( i ) 1 x 1 1 9 S n 119 There are 5 arrangements, one of which has an a x i a l Sn. Thus there would be 2 doublets i n a 1:4 r a t i o . Case ( i i ) 2 x 1 1 9 S n 119 10 arrangements are po s s i b l e : - 4 w i t h Sn a x i a l 119 -4 with both Sn e q u a t o r i a l and c i s -2 with both 1 1 3 S n e q u a t o r i a l and trans The two l a t t e r arrangements give r i s e to a doublet at v of i n t e n s i t y = 6 and an ABX pattern of i n t e n s i t y = 4. -200-Case ( i i i ) Both 1 1 9 S n and 1 1 7 S n present 119 20 arrangements are p o s s i b l e : - 4 where Sn i s a x i a l - 4 where ** 7Sn i s a x i a l - 8 where both are e q u a t o r i a l and c i s - 4 where both are e q u a t o r i a l and trans The patterns are a l l AMX with the f i r s t one centered at v a 2 and the r e s t a t v. The j . coupling w i l l be an order e trans v * • . I , . 110,119-121 of magnitude greater than the c i s coupling ' Table B.2 sumarizes the patterns and weights used i n c a l c u l a t i n g a simulated spectrum f o r [ R h C l ( S n C l 3 ) 5 ] ~ . The simulated spectrum was assembled by s e q u e n t i a l l y s i m u l a t i n g the patte r n expected f o r a p a r t i c u l a r arrangement (using UBC PANIC) and then forming a l i n e a r combination of weighted amounts of these spectra (using UBC ADD). • b 1 a = J 1 0 3 R h - 1 1 9 S n b= 2j 1 1 9 S n - 1 1 7 S n Figure B . l Expected s e x t u p l e t p a t t e r n -201-Table B.2 Weights used f o r various arrangements of isotopes i n s i m u l a t i n g the 1 1 9 S n FT NMR spectrum of [RhCl(SnCl 3 ) 5 1 3 " . # of isotopes arrangement weight a t <"e> <"a' 1 x 1 1 9 S n e or a (AX) 0.1665 0.0416 no 2 x i i y S n c i s e,e (AX) 0.0510 c i s e,a (ABX) 0.0171 + 0.0171 1 x 1 1 9 S n + 1 1 7 c i s e,e (AMX) 0.0304 1 x l i X S n c i s e,a (AMX) 0.0152 0.0152 trans e,e (AMX) 0.0152 -202-Appendix C Values used in ca lcu la t ion of simulated spectrum of [RhCl (SnCl J c ] 3 " 3 o at a d i g i t a l resolut ion of 4.88 Hz/pt. 103 v{ Rh) = a r b i t r a r i l y large (1000000 Hz) v(U9Sn) = -2988 Hz e' *>( 1 1 9 SnJ = -2938 Hz a l j 119 103 = 5 5 6 H z 3 0 H z F W H H Sn - Rh e l j 1 1 9 , 103D h = " 5 3 2 H z 5 0 H z " Sn,- Rh a 2 J i ] q = 1918 Hz 30 Hz " l i y S n -117 e e Sn e 2 j i i i i n , = 1 8 3 2 h z " Sn - Sn, e a 2 , i c i s _ M n II 1 1 9 S n - 1 1 7 S n a e 2 jllL 119, = 2 0 1 3 Hz " " Sn - Sn e a 2 j 1 1 9 n S 119 * = 2 0 0 0 0 H z e e * Not included in simulat ion. 

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