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Formation and catalytic properties of some ruthenium (II) olefin complexes in solution. Louie, Judy Sok Beng 1968

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FORMATION AND CATALYTIC PRO?ERTIES OF SOME RUTHENIUM ( I I ) OLEFIN COMPLEXES IN SOLUTION by JUDY SOK BENG LOUIE B.Sc. (Hons), U n i v e r s i t y of B r i t i s h Columbia, 1966 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF • MASTER OF SCIENCE In the Department o f CHEMISTRY We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1968 In 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 a d v a n c e d d e g r e e 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 a nd S t u d y . I f u r t h e r a g r e e 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 b y t h e Head o f my D e p a r t m e n t o r b y h.iis 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 . D e p a r t m e n t o f C h e m i s t r y  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 V a n c o u v e r 8, C a n a d a D a t e A p r i l , 1968 ABSTRACT A k i n e t i c study of the complex formation between chlororuthenate ( I I ) species and the o l e f i n i c s u b s t r a t e s , 1,1 d i f l u o r o e t h y l e n e , f l u o r o e t h y l e n e and acrylamide i n aqueous h y d r o c h l o r i c a c i d s o l u t i o n has been c a r r i e d out. The k i n e t i c s were s t u d i e d e i t h e r by measurement of gas uptake or by f o l l o w -i n g s p e c t r o p h o t o m e t r i c a l l y at 680 my the disappearance of the blue Ru ( I I ) species at experimental c o n d i t i o n s i n which ruthenium, o l e f i n and c h l o r i d e concentrations were v a r i e d . A two step process i n v o l v i n g an i n i t i a l d i s s o c i a t i o n o f a c h l o r i d e l i g a n d seems l i k e l y f o r these systems, but a d e t a i l e d d i s c u s s i o n i s l i m i t ed by lack of i n f o r m a t i o n on the e q u i l i b r i a between chlororuthenate ( I I ) species i n s o l u t i o n . No evidence was obtained f o r hydrogenation by molecular hydrogen of the 1,1 d i f l u o r o e t h y l e n e or f l u o r o e t h y l e n e through a i r-complex formed w i t h the chlororuthenate ( I I ) s p e c i e s . C a t a l y t i c h y d r a t i o n of these o l e f i n s to a c e t i c a c i d and acetaldehyde r e s p e c t i v e l y was however observed, and a mechanism i s proposed to account f o r t h i s ; t h i s appears to be the f i r s t , r eport of a t r a n s i t i o n metal c a t a l y s e d h y d r a t i o n of o l e f i n s . Acrylamide was not hydrated but could be c a t a l y t i c a l l y hydrogenated t o propionamide; the k i n e t i c data f i t a w e l l e s t a b l i s h e d mechanism. S i m i l a r i t i e s between the hydrogenation and h y d r a t i o n processes are p o i n t e d out. TABLE OF CONTENTS CHAPTER • PAGE I. INTRODUCTION 1 (A) Object . 1 (B) Homogeneous Hydrogenation C a t a l y s t s 1 ( i ) Inorganic Substrates 2 ( i i ) O l e f i n i c and A c e t y l e n i c Substrates 3 (C) L i t e r a t u r e Reports Concerning Homogeneous C a t a l y s i s by Ruthenium Complexes 8 (D) Other Relevant L i t e r a t u r e Data on Ruthenium Chemistry . 9 I I . EXPERIMENTAL PROCEDURE 12 (A) M a t e r i a l s 12 (B) Apparatus f o r Constant Pressure Gas Uptake Measurements 15 (C) Spectrophotometric Measurements 19 (D) Separation and I d e n t i f i c a t i o n o f Organic Products . 22 (E) Spectra 2 2 I I I . RUTHENIUM ( I I ) - 1,1 DIFLUOROETHYLENE SYSTEM 24 (A) St o i c h i o m e t r y • 2 ^ (B) K i n e t i c s 2 7 (C) Hydrogenation Experiments 31 (D) D i s c u s s i o n 33 ( i ) I n i t i a l Rates and I n i t i a l Reactions 33 ( i i ) Subsequent Reactions A f t e r the I n i t i a l Complex Formation 41 IV. RUTHENIUM ( I I ) - FLUOROETHYLENE SYSTEM ' 48 i v CHAPTER PAGE V. RUTHENIUM ( I I ) - ACRYLAMIDE SYSTEM . 54 (A) Formation o f a Ru (II)-Acrylamide Complex 54 ( i ) S t c i c h i o m e t r y of the Reaction 54 ( i i ) K i n e t i c s 5 5 ( i i i ) D i scussion 57 (B) Homogeneous C a t a l y t i c Hydrogenation of the Acrylamide . 62 ( i ) K i n e t i c s 62 ( i i ) Mechanism 70 VI. GENERAL DISCUSSION AND RECOMMENDATIONS FOR FUTURE WORK 72 (A) C a t a l y t i c Hydration 72 (B) C a t a l y t i c Hydrogenation 76 (C) K i n e t i c s of Formation o f the Ru ( I I ) - O l e f i n Complexes.. 77 REFERENCES 81 LIST OF TABLES TABLE PAGE I,. E f f e c t o f V a r i a t i o n of [Ru**] and P a r t i a l Pressure o f 1,1 D i f l u o r o e t h y l e n e on the Rate of Reaction o f the Ru ( I I ) - 1 , 1 D i f l u o r o e t h y l e n e System . 28 I I . E f f e c t of Added [ T i 1 1 1 ] on the I n i t i a l Reaction Rate o f the Ru ( I I ) - 1 , 1 D i f l u o r o e t h y l e n e System 32 I I I . E f f e c t o f V a r i a t i o n o f [H +] and [Cl ~ ] on the I n i t i a l Reaction Rate of Ru ( I I ) - 1 , 1 D i f l u o r o e t h y l e n e System 32 IV. Temperature Dependence o f and k 3 o f the Ru ( I I ) -D i f l u o r o e t h y l e n e System • 40 V. Summary of K i n e t i c Data of Ru ( I I ) - F l u o r o e t h y l e n e System at Various Temperatures 50 VI. E f f e c t of V a r i a t i o n of [H +] and [ C I - ] on the I n i t i a l Rate o f Reaction o f Ru ( I I ) - F l u o r o e t h y l e n e System 50 V I I . Temperature Dependence o f k' and k 3 o f the Ru ( I I ) - F l u o r o -ethylene System 51 V I I I . Summary of K i n e t i c Data f o r Ru (II)-Acrylamide System at Varying Temperatures 60 IX. E f f e c t o f V a r i a t i o n of [ C I - ] and [H +] on the Reaction o f Ru ( I I ) with Acrylamide 60 X. Temperature Dependence o f k j and k 2 / k _ 1 of the Ru ( I I ) -Acrylamide System •••• 63 v i TABLE PAGE XI. E f f e c t of V a r i a t i o n of [Ru**], Acrylamide Concentration and Hydrogen Pressure i n . the Hydrogenation of Acrylamide 67 X I I . Temperature Dependence of Rate Constant i n the Hydrogenation o f Acrylamide ,. 67 + + X I I I . Comparison of k^, k 2 / k _ 1 , AHj and AS]/ f o r a s e r i e s of Reactions Between Various O l e f i n s and Chlororuthenate ( I I ) ... 78 LIST OF FIGURES FIGURE PAGE 1. Absorption Spectra of Ru ( I I I ) and Ru (IV) i n HC1 .... 13 2. Absorption Spectrum of Ru ( I I ) i n 3.0 M HC1 14 3. Apparatus f o r K i n e t i c Studies (Gas Uptake Measurement) ........ 16 4. Apparatus f o r the K i n e t i c Study of the Chlororuthenate ( I I ) -Acylamide 20 5. T y p i c a l Rate P l o t s f o r l , l D i f l u o r o e t h y l e n e Uptake i n the Ru ( I I ) - l , l D i f l u o r o e t h y l e n e System 25 6. Dependence o f Rate on the [R u 1 1 ] i n the Ru (II)-1,1 D i f l u o r o -ethylene System '• • 29 7. Disappearance of Ru ( I I ) during I n i t i a l Reaction 29 8. F i r s t Order Rate P l o t f o r the I n i t i a l Ru ( I I ) - 1 , l D i f l u o r o -ethylene Reaction 30 9. Dependence of Rate on the 1,1 D i f l u o r o e t h y l e n e Pressure i n the Ru (II)-1,1 D i f l u o r o e t h y l e n e System 30 10. Dependence of I n i t i a l Rate on the Added [ T i 1 1 1 ] i n the Ru ( I I ) - . 1,1 D i f l u o r o e t h y l e n e System 35 11. T y p i c a l P l o t o f ^  vs T r * -, 35 K L C 2 F 2 H 2 J 12. E f f e c t of [C l ~ ] on the I n i t i a l [ R u 1 1 ] 36 13. Dependence o f I n i t i a l Rate on [CI ] i n the Ru (II)-1,1-D i f l u o r o e t h y l e n e System 36 14. The Reduction o f Ru (IV) to Ru ( I I ) by T i ( I I I ) at Various m 1 1 1 1 39 v l i i FIGURE PAGE 15. Arrhenius P l o t f o r the Rate Constant, o f Ru ( I I ) - 1 , 1 -D i f l u o r o e t h y l e n e System 42 16. Arrhenius P l o t f o r the Rate Constant, k 3 of Ru ( I I ) - 1 , 1 -D i f l u o r o e t h y l e n e System 45 17. The I n f r a r e d Spectrum of the Inorganic Residue Obtained i n the Reaction Ru ( I I ) with 1,1 D i f l u o r o e t h y l e n e ... 47 18. Rate P l o t f o r the Reaction o f Ru ( I I ) w i t h Fluoroethylene 49 19. Dependence of Rate on the [Ru**] i n the Ru ( I I ) - F l u o r o e t h y l e n e System 52 20. Dependence o f Rate on Fluoroethylene Pressure at Various. Temperatures 52 21. E f f e c t o f Acrylamide on the Absorbance o f Ru ( I I ) S o l u t i o n at 680 mp 56 22. P l o t o f (T T + 1-) vs ^ 56 L £ A 1 23. Complexing o f a Ru ( I I ) S o l u t i o n by Acrylamide 58 24. F i r s t - O r d e r Rate P l o t f o r the Ru (II ) - A c r y l a m i d e Reaction 59 25. E f f e c t on the Rate Constant, k' of Varying the Acrylamide Concentration at Various Temperatures 61 26. T y p i c a l P l o t o f I_ v s ^ g ^ F f e f • 6 4 27. Arrhenius P l o t f o r the Rate Constant i n the Ru ( I I ) -Acrylamide System 64 28. T y p i c a l Rate P l o t f o r the Ru ( I I ) Catalysed Hydrogenation o f Acrylamide 65 29. Dependence o f Rate on [H 2] i n the Hydrogenation o f Acrylamide. 68 ix FIGURE PAGE 30. Dependence of Rate on [ R u 1 1 ] on the Hydrogenation o f Acrylamide. 68 31. Arrhenius P l o t f o r Rate Constant k i n the hydrogenation of Acrylamide 69 ACKNOWLEDGEMENT I would l i k e t o acknowledge my great debt t o Dr. B. R. James under whose p a t i e n t guidance t h i s research was performed. Valuable d i s c u s s i o n with my colleagues i s a l s o duly acknowledged. Sincere g r a t i t u d e i s due to my husband, L l o y d , whose cooperation and encouragement were a constant help throughout the work. CHAPTER I INTRODUCTION A. Object The work described i n t h i s t h e s i s i s p r i m a r i l y concerned w i t h a k i n e t i c study of the chemical r e a c t i o n and c a t a l y t i c p r o p e r t i e s of chlororuthenate ( I I ) species w i t h various o l e f i n i c s u bstrates i n a c i d aqueous s o l u t i o n . The i n t e r e s t i n the present work arose from the f a c t that ethylene and s u b s t i t u t e d ethylenes complexed r e a d i l y w i t h Ruthenium (I I ) c h l o r i d e i n s o l u t i o n , b u t , i n the presence of molecular hydrogen, c a t a l y t i c hydrogenation was observed only w i t h o l e f i n s i n which the double bond was a c t i v a t e d by the presence of an adjacent c a r b o x y l i c a c i d group e.g. m a l e i c , fumaric, a c r y l i c or c r o t o n i c a c i d s . * I t was of i n t e r e s t to i n v e s t i g a t e f u r t h e r the reason f o r t h i s , i n p a r t i c u l a r whether e l e c t r o n i c or s t e r i c e f f e c t s were important. By u s i n g other s u b s t i t u t e d o l e f i n s , e s p e c i a l l y fluoro'-deriva-t i v e s , i t was hoped to shed some l i g h t on t h i s matter. B. Homogeneous Hydrogenation C a t a l y s t s In recent y e a r s , a v a r i e t y of new c a t a l y t i c r e a c t i o n s c a t a l y z e d by t r a n s i t i o n metal complexes has been discovered and i n v e s t i g a t e d . Reviews 2 3 4 5 6 by Halpern, ' ' Bond, and Misano and Ogata have concerned themselves with a v a r i e t y of r e a c t i o n s , i n c l u d i n g homogeneous hydrogenations. The platinum group metal ions and t h e i r complexes were found to be e x c e p t i o n a l l y e f f e c t i v e f o r such c a t a l y t i c r e a c t i o n s , and r e c e n t l y , the c a t a l y t i c p r o p e r t i e s of 7 rhodium complexes i n s o l u t i o n have been reviewed by James. 2 Catalyzed hydrogen r e d u c t i o n of i n o r g a n i c and organic substrates w i l l f i r s t be considered g e n e r a l l y , and then f u r t h e r r e a c t i o n s c a t a l y z e d by ruthenium complexes w i l l be reviewed ( s e c t i o n C). i) Inorganic Substrates Chloro complexes of ruthenium ( I I I ) were found by Halpern and coworkers to c a t a l y s e homogeneously the r e d u c t i o n of i r o n ( I I I ) and ruthenium (IV) g by molecular hydrogen under m i l d c o n d i t i o n s . The mechanism was reported to i n v o l v e a rate determining h e t e r o l y t i c s p l i t t i n g of molecular hydrogen by the c a t a l y s t , w i t h r e s u l t i n g formation of an unstable metal hydride. This reacted i n a subsequent f a s t step w i t h the s u b s t r a t e : k l i n _ + Ru ( I I I ) + H 2 • Ru H + H (1) * k T ~ T T T - ' - fact + R u H +2Ru.(IV) > 3Ru ( I I I ) +H (2) T T T - fa<;t + or R u H + 2Fe ( I I I ) > Ru ( I I I ) + 2Fe ( I I ) + H (3) The r a t e law f o r e i t h e r s u b s t r a t e i s D i r e c t evidence f o r the h e t e r o l y t i c s p l i t t i n g mechanism i s provided by the ruthenium ( I I I ) c a t a l y s e d i s o t o p i c exchange between D2 and H 20 i n accord-9 ance w i t h equation (1). Complexes of copper ( 1 1 ) ^ , s i l v e r ( I ) * * , rhodium ( I I I ) * 2 ' * ^ , p a l l a d i u m ( I I ) * \ and cobalt (11)*^ c a t a l y s e the H 2 r e d u c t i o n of i n o r g a n i c substrates by a s i m i l a r h e t e r o l y t i c mechanism. Molecular hydrogen can a l s o undergo homolytic s p l i t t i n g i n the r a t e determining step. This i s demonstrated by the copper (I) c a t a l y s e d hydrogen reduction o f substrates such a copper ( I I ) or benzoquinone i n q u i n o l i n e s o l u t i o n . * ^ ' * ^ The rate law was found to be: ^ 1 = k [ H 2 ] [ C u ( T ) ] 2 dt which i s c o n s i s t e n t with the ra t e determining step 2Cu(I) + H 2 > 2Cu(I)H (4) In some cases, a given metal i o n , e.g. s i l v e r ( 1 ) * * may s p l i t H 2 e i t h e r h o m o l y t i c a l l y or h e t e r o l y t i c a l l y depending on such f a c t o r s as temperature and the b a s i c i t y o f the medium. i i ) O l e f i n i c and A c e t y l e n i c Substrates Among the metal complexes which a c t i v a t e hydrogen, only a few appear to be e f f e c t i v e c a t a l y s t s f o r the homogeneous hydrogenation o f o l e f i n i c 1 19 18 19 compounds. These i n c l u d e complexes o f ruthenium ( I I ) ' ' , platinum ( I I ) ,. cobalt ( I ) 2 0 , i r o n ( 0 ) 2 1 , rhodium ( I I I ) 7 , 2 2 , rhodium ( I ) 7 ' 1 3 , 2 2 , i r i d i u m ( I ) 2 3 " 2 5 and cob a l t ( I I ) 2 6 ' 2 7 . D e t a i l e d k i n e t i c s s t u d i e s have been reported f o r ruthenium ( I I ) * , 22 25 26 rhodium (I) , i r i d i u m (I) and cob a l t ( I I ) systems. I t i s of i n t e r e s t t t o d iscuss each of these as each d i f f e r s l i g h l y i n the proposed mechanisms. Ruthenium ( I I ) chloro complexes Halpem, Harrod and James* have reported that hydrogenation of s e v e r a l c a r b o x y l i c a c i d s , such as maleic and fumaric a c i d s , i s c a t a l y s e d by c h l o r o -ruthenate ( I I ) complexes i n aqueous a c i d s o l u t i o n . The ra t e law f o r the hydrogenation was found to be —Ir1 = k i [ H 2 ] [ R u H ( o l e f i n ) ] The mechanism i n v o l v e d the r a p i d formation of a 1:1 ruthenium ( I I ) -o l e f i n ir-complex, f o l l o w e d by a ra t e determining step i n v o l v i n g r e a c t i o n o f t h i s u-complex with H 2 . I t i s suggested that an intermediate hydride specie: undergoes rearrangement, the metal i o n and hydride i o n adding across the double bond. 1 / — Ru / | C +H2 (slow) H /I -> \ / H . rearrangement > 1 C — Ru' f a s t + SC =. C 's +H I y \ / I f Ru- + H-C- C-H < — — \ / F / \ — 1 -Ru C-C^H Scheme 1 Tracer s t u d i e s showed that c i s a d d i t i o n of K 2 occurred and that the added hydrogen comes from the s o l u t i o n . Simple o l e f i n s such as ethylene, although forming n-complexes w i t h ruthenium ( I I ) , were not hydrogenated. Ruthenium ( I I I ) c h l o r i d e s o l u t i o n s , which c a t a l y s e d the reduction o f i n o r g a n i c s u b s t r a t e s , d i d not c a t a l y s e the reduction of maleic a c i d ; a slow a u t o c a t a l y t i c H 2 uptake d i d r e s u l t , but t h i s was due t o the slow formation of the a c t i v e ruthenium ( I I ) species. Rhodium complexes Recently W i l k i n s o n and h i s coworkers have s t u d i e d e x t e n s i v e l y the hydrogenation o f o l e f i n s and acetylenes u s i n g a number of rhodium ( I I I ) and rhodium (I) complexes as c a t a l y s t s i n e t h a n o l , benzene or ethanol-benzene mixture and the a c t i v i t y o f RhCl(Ph3p)3 i n benzene s o l u t i o n has been reported 22 i n d e t a i l . The system i n v o l v e d the d i s s o c i a t i o n o f the complex i n s o l u t i o n 5 t o give a s o l v a t e d s p e c i e s , RhCl(Ph 3P) 2S (where S = s o l v e n t ) , which has a s i t e f o r c o o r d i n a t i o n of the o l e f i n or acetylene by displacement o f solvent. The benzene s o l u t i o n o f R h C l ( P h 3 P ) 3 i t s e l f takes up molecular hydrogen and t h i s hydride r a p i d l y reduces any o l e f i n present. The system i s summarized i n the f o l l o w i n g scheme: K i R h C l ( P h 3 P ) 2 ( S ) + H 2 H 2 RhCl (Ph 3P) 2 (S) K2 o l e f i n k o l e f i n k, R h C l ( P h 3 P ) 2 o l e f i n -rf—• RhCl ( P h 3 P ) 2 (S) + p a r a f f i n Ho Scheme 2 P a r a f f i n production i s thought t o occur s o l e l y by the k 1 path, the uncomplexed o l e f i n a t t a c k i n g the d i h y d r i d e at the vacant s i t e to give a t r a n s i t i o n s t a t e i n which both hydrogen and o l e f i n are bound to the metal. 13 In other recent s t u d i e s , i t has been found that s o l u t i o n s o f RhCl 3.3H 20 i n dimethylacetamide c o n t a i n i n g maleic a c i d take up molecular hydrogen to give the Rhodium (I) valence s t a t e , which r a p i d l y complexes with the o l e f i n present. This complex then undergoes f u r t h e r r e a c t i o n w i t h hydrogen produc-i n g the hydrogenated o l e f i n . The mechanism i s thought to be s i m i l a r to that reported f o r the futhenium ( I I ) c a t a l y s e d r e d u c t i o n of maleic a c i d i n aqueous a c i d c h l o r i d e s o l u t i o n (Scheme 1). I r i d i u m complexes: 23 24 25 Vaska and h i s group ' and workers i n t h i s l a b o r a t o r y have shown that complexes such as I r C O ( X ) ( P h 3 P ) 2 , where X = halogen, can act as homo-geneous c a t a l y s t s f o r the r e d u c t i o n o f o l e f i n i c compounds. A d e t a i l e d k i n e t i c study of the I r C O C l ( P h 3 P ) 2 c a t a l y s e d r e d u c t i o n o f maleic a c i d i n 25 dimethylacetamide s o l u t i o n s shows th a t the r e a c t i o n scheme i s analogous t o that i l l u s t r a t e d above f o r the R h C l ( P h 3 P ) 3 system (Scheme 2 ) . The a c t i v e c a t a l y s t i s the d i s s o c i a t e d species I r C O C l ( P h 3 P ) ( S ) . Production o f s u c c i n i c a c i d , however, i s thought to occur more l i k e l y v i a the k 2 path, w i t h attack of hydrogen on an o l e f i n i c complex. Cob a l t comp le xe s : Another c a t a l y s t f o r the homogeneous hydrogenation o f o l e f i n s and unsaturated substances (e.g. nitrobenzene, benzaldehyde) i n aqueous s o l u t i o n i s Co(CN)5 . O l e f i n i c bonds appear to be hydrogenated only i f a c t i v a t e d through c o n j u g a t i o n , e.g. butadiene, styrene. The hydrogenation of butadiene 26 to butenes has been s t u d i e d i n some d e t a i l by Kwiatek and coworkers and they proposed the f o l l o w i n g mechanism 2Co(CN)|" + H 2 - > 2HCo(CN)s" (5) HCo(CN)5 _ + C^Hg ^C l tH 7Co(CN)5 _ (6) o _ HCo(CN)|" 3_ C 4H 7CnrCN)5 ^ C^He + 2Co(CN)5 (7) -CN I +CN 1 butene CH 2 3_ // 9_ HCo(CN)5 3_ CH; Co(CN)^ —*• CH3CH=CHCH3 + 2Co(CN) 5 (8) XCH . , + / 2 butene CH 3 The CN"dependence e q u i l i b r i u m between the <r and ir a l l y l intermediate accounts f o r the observation that hydrogenation at high CN"concentration y i e l d s predominantly 1-butene and at low CN"concentration, predominantly t r a n s 2-butene. 7 Somewhat d i f f e r e n t behaviour was reported by Simandi and Nagy f o r the Co(CN)^ c a t a l y s e d hydrogenation of cinnamic a c i d . On the b a s i s of k i n e t i c observations the f o l l o w i n g mechanism i n v o l v i n g a r a d i c a l - a n i o n intermediate (HS) was proposed (S=C6H5CH2=CHCOO", HS=C5H£CH2CHCOO~; H 2S=C 5H 5CH 2CH 2C00~). 2 [ C o ( C N ) 5 ] 3 " + H 2 • 2[HCo(CN) 5]3" (9) [HCo(CN) 5] 3" + S > [ C o ( C N ) 5 ] 3 ~ + HS (10) [HCo(CN) 5] 3" + HS • [ C o ( C N ) 5 ] 3 " + H 2S ( H ) In each of the cases c i t e d , hydride species o f the t r a n s i t i o n metal c a t a l y s t s are i n d i c a t e d as r e a c t i o n i n t e r m e d i a t e s . Three routes have thus been found to give r i s e t o these i n t e r m e d i a t e s : (1) H e t e r o l y t i c s p l i t t i n g of H 2, e.g. R u 1 1 ( o l e f i n ) + H 2 — • R u H H ~ ( o l e f i n ) + H + (2) Homolytic s p l i t t i n g of H 2, e.g. 2 C o n ( C N ) 3 " + H 2 > 2HCo r i I(CN)^" (3) Formation of d i h y d r i d e , e.g. R h I C l ( P h 3 P ) 2 S + H 2 > H 2 R h I I I C l ( P h 3 P ) 2 H e t e r o l y t i c s p l i t t i n g i n v o l v e s e s s e n t i a l l y a s u b s t i t u t i o n process (replacement o f a c h l o r i d e l i g a n d by a hydride) without change i n the formal o x i d a t i o n number o f the metal. R e a c t i v i t y i s thus governed by f a c t o r s such as the s u b s t i t u t i o n l a b i l i t y o f the s t a r t i n g metal complex, the s t a b i l i t y and l a b i l i t y o f the hydride formed and the presence o f a base to s t a b i l i z e the r e l e a s e d proton. On the other hand, homolytic s p l i t t i n g and molecular 8 dihydride formation are accompanied by formal o x i d a t i o n o f the metal and r e a c t i v i t y a l s o depends on the s u s c e p t i b i l i t y of the metal to o x i d a t i o n . In general, the hydride intermediate formed must be s u f f i c i e n t l y s t a b l e , otherwise i t w i l l not be formed r e a d i l y , while i f i t s s t a b i l i t y i s too great, 2 i t s subsequent t r a n s f o r m a t i o n to the products w i l l be slow. C. L i t e r a t u r e Reports Concerning Homogeneous C a t a l y s i s by Ruthenium Complexes: A number o f other ruthenium complexes have been reported t o c a t a l y s e the hydrogen re d u c t i o n of o l e f i n s and a c e t y l e n e s , although these systems have not been s t u d i e d i n d e t a i l . l^Octene i n n-heptane s o l u t i o n i s homogeneously hydrogenated us i n g a c a t a l y s t mixture of Ruthenium ( I I I ) acetylacetonate and t r i i s o b u t y l 28 aluminum Both o l e f i n s and a c e t y l e n e s , such as hept-l-ene and hex-l-yne are r a p i d l y hydrogenated at 25° and 1 atm. H 2 by the complexes R u C l 2 ( P h 3 P ) ^ and 29 - o R u C l 2 ( P h 3 P ) 3 at about 10 M concentration i n benzene-ethanol (1:1)' s o l u t i o n . In contrast to the corresponding rhodium system (Scheme 2 ) , ethanol p l a y s an i n t i m a t e p a r t i n the mechanism; i n absence of such a co-17 s o l v e n t , hydrogenation i s exceedingly slow . Treatment of a concentrated s o l u t i o n o f the complex i n ethanol-benzene w i t h H 2 gives a hydrido complex RuClH(Ph 3P) 3. S o l u t i o n s of ruthenium c h l o r i d e i n dimethylformamide have al s o been reported t o c a t a l y s e hydrogenation o f cyclopentadiene The f i r s t case of a w e l l defined ruthenium complex, R u ( C O ) 3 ( P h 3 P ) 2 as 17 a hydroformylation c a t a l y s t has a l s o been reported Ruthenium ( I I ) c h l o r o complexes have al s o been found e f f e c t i v e c a t a l y s t s f o r promoting both i n t e r m o l e c u l a r and i n t r a m o l e c u l a r hydrogen atom t r a n s f e r r e a c t i o n s i n v o l v i n g a l l y l a l c o h o l , the r e a c t i o n l i k e l y proceeding through an intermediate u-complex . • In attempts t o hydrogenate acetylene using Ruthenium ( I I I ) c h l o r i d e '32 33 as a c a t a l y s t , Halpern, James and Kemp ' found.that the l a t t e r was an e f f e c t i v e c a t a l y s t f o r the h y d r a t i o n pf a c e t y l e n i c compounds. The mechanism proposed i n v o l v e d the rate determining i n i t i a l formation of an intermediate Tr-complex which subsequently rearranges t o add the metal i o n and a co-ordi n a t e d H2Q l i g a n d across the unsaturated bond, before decomposition to the h y d r a t i o n product and the s t a r t i n g Ruthenium ( I I I ) e.g. 1 I I I ' k 1 I -Ru—OHo + HCECH —£->-Ru —OHo • Ru — OH ' • 1 x + H+ - H II — •-Ru 1- 1 1 + C H 3 C H O (12) Ruthenium ( I I ) c h l o r i d e was a much l e s s e f f i c i e n t h y d r a t i o n c a t a l y s t f o r a c e t y l e n i c compounds. I n t r o d u c t i o n o f carbonyl l i g a n d s i n t o the chloro-33 ruthenate complexes was found t o decrease c a t a l y t i c a c t i v i t y g e n e r a l l y . A l c o h o l i c s o l u t i o n s of RuCl 3.3H 20 have been found to c a t a l y s e the 0 d i m e r i z a t i o n of a c r y l n i t r i l e under a hydrogen atmosphere and intermediate 34 ruthenium a c r y l n i t r i l e complexes have been i s o l a t e d . D. Other Relevant L i t e r a t u r e Data on Ruthenium Chemistry  Decarbonylation r e a c t i o n s : A number o f platin u m metal h a l i d e s have r e c e n t l y been shown t o decarbonylate a v a r i e t y of organic compounds i n c l u d i n g a l c o h o l s , aldehydes, e t h e r s , ketones and a c y l h a l i d e s w i t h the r e s u l t i n g formation o f metal 1 0 carbonyl complexes. Complexes of rhodium ( j ) ^ 5 , 3 6 , 3 7 , 3 8 ^ ^ Q ^ ^ ^ ( i H > >40 ^ . , T T , 4 1 , 3 3 + . 1 . , T T T . 3 9 , 4 2 , 4 0 . , T T T , 3 9 , 4 0 ruthenium ( I I ) , rutnenium ( I I I ) . , osmium ( I I I ) , osmium ( I V ) ^ ' ^ 3 , and i r i d i u m ( I I I ) ^ ' ^ have been found e f f e c t i v e . Very l i t t l e mechanistic s t u d i e s have been reported f o r these r e a c t i o n s . . A d e t a i l e d k i n e t i c study has been reported, however, f o r the decarbon-4 1 y l a t i o n o f formic a c i d by chlororuthenate ( I I ) complexes. The proposed mechanism i n v o l v e d an i n i t i a l S ^ l d i s s o c i a t i o n of a chlororuthenate (IT) complex II k l i i _ Ru C l > Ru C l . + C l ( 1 3 ) «—5 n - 1 •* • k _ i R u H C l + HCOOH * Z , > R u I 3 " ( C 0 ) ( 1 4 ) The f i r s t simple monoolefinic complexes o f ruthenium ( I I ) to be reported were the maleic a c i d and ethylene complexes discovered d u r i n g the c a t a l y t i c hydrogenation s t u d i e s . * Other ruthenium ( I I ) complexes such as d i o l e f i n i c 6 4 5 complexes w i t h norbornadine , the sandwich type complex with cyclopenta-4 6 4 7 diene (ruthenocene) , and a r e l a t e d d i i n d e n y l complex have also been reported. Reaction o f ruthenium ( I I I ) c h l o r i d e w i t h butadiene i n 2-methoxy 4 8 ethanol i s reported to give a complex R u C l 2 ( C u H 6 ) 3 [ d i c h l o r o (dodeca 2 , 6 , 1 0 -t r i e n e 1 , 1 2 d i y l ) ruthenium ( I V ) ] . The k i n e t i c s of the r e a c t i o n between ruthenium ( I I ) c h l o r i d e and ethylene i n aqueous a c i d c h l o r i d e medium have been s t u d i e d and a mechanism . • 4 9 s i m i l a r to that mentioned f o r the decarbonylation of formic a c i d was proposed I I k l I I Ru C l • Ru C l . + Cl ( 1 5 ) n «-—: n - 1 V J k - l R u I I C l n l + C 2 H i j > R u 1 1 ( C 2 H [ f ) C l n _ 1 ( 1 6 ) 11 Ruthenium ( I I I ) c h l o r o complexes si-owed no r e a c t i o n s w i t h ethylene i n 49 these a c i d c h l o r i d e s o l u t i o n s , although i t has r e c e n t l y been reported that i n the presence of c i t r i c a c i d , ruthenium ( I I I ) chloro complexes o x i d i s e ethylene to acetaldehyde. 5^ I t appears q u a l i t a t i v e l y that l i g a n d groups such as h a l i d e s , t e r t i a r y phosphines, CO, CN and SnCl3 are p a r t i c u l a r l y e f f e c t i v e i n a c t i v a t i n g 7 platin u m metal ions g e n e r a l l y , and a number of new ruthenium complexes c o n t a i n i n g these l i g a n d s , besides those already mentioned, have r e c e n t l y been described. The complexes prepared i n c l u d e : 51 52 51 33 The carbonyl Ru3(C0) 1 2 ' , the carbonyl h a l i d e species ' [Ru(CO) 3 C 1 2 ] 2 , [ R u ( C 0 ) 2 C l 2 ] n , [ R u ( C O ) C l 5 ] 2 ~ , [Ru(CO) (H 20) C l J 2 " and 2 -[Ru(CO) 2Cli+] ; a wide range d f complexes Ru ( C 0 ) 2 X 2 L 2 , where X = halogen 51 29 33 40 and L = n i t r o g e n donors , t e r t i a r y phosphines, a r s i n e s or s t i l b e n e s ' ' ' 51 53 54 53 . ' ' ; the complexes RUX3L3 and RuX 2(C0)L 3 where X = h a l i d e or SCN . . . _ .,. ' , . . 29,33,40,53 «..,,' «. 55 and L i s a t e r t i a r y phosphine, arsme , t r i h a l o g e n o s t a n n i t e , or p y r i d i n e 5 * * and the s p e c i e s 2 ^ [RuCli,.(CO)pyr] ; the complexes c o n t a i n i n g sulphur l i g a n d s 5 5 , Ru(S 2") 2(CO), R u ( S 2 " ) 2 ( C O ) 2 , [ R u ( S 2 " ) 2 ( C O ) 2 ] + , where S 2 " = R 2NCS 2~, and [Ru(C 6H 5S) 2(CO) 2]3; and a v a r i e t y o f dimeric and p o l y n u c l e a r co co 29 species such as L 3 R u 3 ( C O ) 9 , L 2Ru 2 (CO) 6 ,. R u 2 C l 3 ( S n C l 3 ) (CO) 2 L k , where L 52 56 i s a t e r t i a r y phosphine, [Ru(CO) 2(N0) 2] , and [ R u C l 2 ( C 0 ) d i e n e ] 2 . F i n a l l y the hydride complexes H^Ru^(CO) 1 2 5 7 , 5 8 ' and RuHX(C0)L 3 where X = 40 53 halogen and L i s a t e r t i a r y phosphine ' have been prepared. Some st u d i e s on the c a t a l y t i c a c t i v i t y f o r the a n i o n i c carbonyl h a l i d e complexes [Ru(CO) ( H 2 0 ) C l t t ] 2 ~ and [ R u ( C 0 ) 2 C l i f ] 2 " f o r hydrogenation and 33 h y d r a t i o n have been reported , but the p o t e n t i a l c a t a l y t i c p r o p e r t i e s o f the other complexes do not seem to have been i n v e s t i g a t e d . CHAPTER I I EXPERIMENTAL PROCEDURE A. M a t e r i a l s The ruthenium c h l o r i d e s o l u t i o n s used i n these s t u d i e s were made up by d i s s o l v i n g "specpure" ( N H j ^ R u ^ O ) C l 5 obtained from Johnson, Matthey Co. i n aqueous 3 M HC1. Although designated a ruthenium ( I I I ) compound, the r e s u l t i n g spectrum o f the s o l u t i o n (Figure 1) was very s i m i l a r to that reported f o r ruthenium (IV) i n HC1 s o l u t i o n s ' ^ a n d u n l i k e that reported f o r ruthenium ( I I I ) i n HC1 so l u t i o n * * ' ^ * . The ruthenium compound i s probably the hydroxy s a l t (NH^) 2Ru*^(0H)C I 5, s i n c e i t can be s t o i c h i o -8 m e t r i c a l l y reduced by H 2 i n s o l u t i o n t o produce ruthenium ( I I I ) . The ruthenium ( I I ) c h l o r i d e s o l u t i o n s were obtained from the ruthenium (IV)/HC1 s o l u t i o n s by treatment with an excess o f t i t a n i u m ( I I I ) c h l o r i d e s o l u t i o n . Such s o l u t i o n s o f ruthenium ( I I ) c h l o r i d e proved s t a b l e f o r periods o f up to s e v e r a l days when st o r e d under n i t r o g e n w i t h rigorous e x c l u s i o n o f oxygen. The spectrum o f the blue ruthenium ( I I ) s o l u t i o n s 62 63 corresponded t o that reported by Jorgensen and Rechnitz shown i n Figure 2. The t i t a n i u m ( I I I ) c h l o r i d e s o l u t i o n was obtained by d i s s o l v i n g 98.6% s o l i d t i t a n i u m t r i c h l o r i d e , from Alpha Inorganic Inc., i n 3.0 M HC1 under a n i t r o g e n atmosphere, t h i s was then q u i c k l y t r a n s f e r r e d to a glass v e s s e l , where i t could be st o r e d and dispensed under a n i t r o g e n atmosphere. The t i t a n i u m ( I I I ) was standardized s p e c t r o p h o t o m e t r i c a l l y as the c h l o r i d e 64 s o l u t i o n u s i n g the data of Hartman and S c h l a f e r (A 510 my,e 5 ) , and 6 max •H •M X 8000 I - R u l V i n 3.0 M HC1 I I - Ru I I I i n 5.0 M HC1 6000 c i a> •H o : H 0 ) O u c o 4000 2000 JL 300 400 wavelength my 500 Figure 1. Ab s o r p t i o n S p e c t r a of Ru*^ and Ru*** i n HC1 S o l u t i o n . 14 15 the c o n c e n t r a t i o n was found to be 1.8 M. Fluoroethylene and 1,1-difluoroethylene were obtained as research grade products from Matheson Co. P r e p u r i f i e d hydrogen and n i t r o g e n were obtained from Canadian L i q u i d A i r Co., the hydrogen was passed through a "deoxo" c a t a l y t i c p u r i f i e r to remove traces o f oxygen before use. C P . grade acrylamide from K § K Laboratories Inc. was r e c r y s t a l l i z e d from benzene s o l u t i o n , d r i e d i n vacuum, weighed and d i s s o l v e d i n 3 M HC1. Stock 3 M HC1 s o l u t i o n s were prepared by d i l u t i n g B.D.H. concentrated h y d r o c h l o r i c a c i d or C P . grade from the N i c h a l s Co. They were standardized against 1 M NaOH s o l u t i o n prepared from B.D.H. standard NaOH ampules. The concentrations o f the stock HC1 s o l u t i o n s were found to be 3.0 M. A l l other chemicals used were o f reagent grade. D i s t i l l e d water was used i n a l l experiments. B. Apparatus Used f o r the K i n e t i c Studies Using Gas Uptake Measurements  General: A technique i n v o l v i n g the measurement o f gas uptake at constant pressure was used f o r s t u d y i n g r e a c t i o n between chlororuthenate ( I I ) s o l u -t i o n s and the gaseous s u b s t r a t e s , f l u o r o e t h y l e n e and 1,1-d i f l u o r o e t h y l e n e . The c a t a l y s e d hydrogenation r e a c t i o n s of s o l i d substrates such as acrylamide was s t u d i e d s i m i l a r l y by f o l l o w i n g hydrogen uptake. The apparatus used f o r t h i s purpose i s shown d i a g r a m a t i c a l l y i n Figure 3. A glass s p r i n g c o i l arrangement (A') connected a c a p i l l a r y manometer D at tap C to the r e a c t i o n f l a s k A. This c o u l d be immersed and shaken, by means o f s u i t a b l e c o u p l i n g a i P , i n a s i l i c o n e o i l - b a t h B, which was thermo-s t a t e d at the r e a c t i o n temperature. The c a p i l l a r y manometer and a connected b u r e t t e E ( c o n t a i n i n g mercury) were housed i n a thermostated water-bavh at 25°C. A cathetometer was s i g h t e d on the mercury l e v e l i n the p r e c i s i o n t u b i n g N. The gas b u r e t t e was connected through the tap J and needle valve M t o the mercury manometer F which i n t u r n was j o i n e d to the pumping and the gas f i l l i n g s i d e of the apparatus. A l l q u i c k - f i t s shown are standard B7 or BIO t a p e r s . Thermostats: A f o u r l i t e r g l a s s beaker i n s u l a t e d by p o l y s t y r e n e foam on a l l s i d e s was used f o r the thermostated s i l i c o n e o i l - b a t h . This was enclosed by a wooden box w i t h a small c i r c u l a r hole f o r the observation of the c o l o r changes e t c . of the r e a c t i o n mixture. A f e r s p e x r e c t a n g u l a r tank was used f o r the water thermostat. A "Jumo" thermo r e g u l a t o r w i t h a "mere to mere" r e l a y c o n t r o l c i r c u i t , and h e a t i n g provided by a 25 watt elongated l i g h t bulb were used f o r the operation o f both thermostat u n i t s . With mechanical s t i r r i n g and the good i n s u l a t i o n , the temperature could be maintained w i t h i n ±0.05°. Procedure: The technique f o r a t y p i c a l r e a c t i o n between Ruthenium ( I I ) and d i f l u o r o -ethylene w i l l be d s c r i b e d . The r e a c t i o n f l a s k c o n t a i n i n g known amounts o f Ruthenium (IV) c h l o r i d e s o l u t i o n and t i t a n o u s c h l o r i d e s o l u t i o n (about 5 ml. t o t a l volume) was attached t o the gas h a n d l i n g side o f the apparatus at p o s i t i o n 0 through the s p i r a l t u b i n g arrangement. The r e a c t i o n mixture was degassed by a l t e r n a t e f r e e z i n g and thawing under vacuum. The r e a c t i o n v e s s e l was then f i l l e d to 18 some convenient pressure (1 atmosphere^ with 1,1-difluoroethylene at room temperature. The taps C and 0 were then closed and the r e a c t i o n v e s s e l complete w i t h the s p i r a l was moved and attached at H and P, the r e a c t i o n f l a s k b e i n g p l a c e d i n the o i l - b a t h . The r e s t o f the system beyond C, a f t e r b eing evacuated, was f i l l e d to about the pressure (up t o 1 atmosphere) with the d i f l u o r o e t h y l e n e . The tap C was then opened and the pressure i n the system adjusted t o the d e s i r e d r e a c t i o n pressure near 1 atmosphere and was measured. The shaker was then s t a r t e d , the taps K and L were closed and the t i m e r was s t a r t e d . A known pressure of gas was thus trapped i n the r i g h t limb of the c a p i l l a r y manometer and the gas uptake was i n d i c a t e d by the d i f f e r e n c e i n the o i l l e v e l s o f the manometer ( b u t y l phthalate whose vapour pressure at 25°C i s n e g l i g i b l e was used as the f i l l i n g l i q u i d . ) At s u i t a b l e time i n t e r v a l s , more gas was admitted i n t o the gas b u r e t t e through the needle valve t o maintain a constant pressure i n the r e a c t i o n f l a s k . The r i s e i n the mercury l e v e l thus produced was measured by the t r a v e l l i n g t e l e s c o p e . The volume of the gas taken up by the system could be c a l c u l a t e d from the known diameter of the gas b u r e t t e tube N, and expressed as moles per l i t e r of s o l u t i o n . The use of small volumes of s o l u t i o n w i t h an indented surface f o r the r e a c t i o n v e s s e l and r a p i d shaking r a t e s ensured the absence of p h y s i c a l c o n t r o l ( i . e . d i f f u s i o n ) f o r the gas uptake. The pressure o f the reactant gas was obtained by s u b t r a c t i n g the p a r t i a l pressure of the aqueous HCI s o l u t i o n s from the t o t a l pressure. The c o n c e n t r a t i o n o f the hydrogen i n the r e a c t i o n s o l u t i o n was c a l c u -l a t e d from s o l u b i l i t y data of S e i d e l l ^ 5 , c o r r e c t i n g f o r the e f f e c t o f HCI. 19 C. Spectrophotometric Measurements The k i n e t i c s of r e a c t i o n s i n v o l v i n g chlororuthenate ( I I ) species and s o l i d o l e f i n i c substrates have sometimes been s t u d i e d using spectrophoto-41 metric techniques i n the v i s i b l e r e g i o n . The r e a c t i o n s were followed by measuring the decrease i n the absorbance of the blue s o l u t i o n at 680 my where 2 - 62 ruthenium ( I I ) c h l o r i d e absorbs s t r o n g l y ( E 750, a t t r i b u t e d to RuCl^ ) These blue s o l u t i o n s are r e a d i l y o x i d i z e d i n a i r at room temperature to s o l u t i o n s c o n t a i n i n g Ru ( I I I ) , and hence the r e a c t i o n s were conducted under an atmosphere of pure n i t r o g e n . Apparatus The experimental apparatus i s shown i n Figure 4. The arrangement minimized any c o n c e n t r a t i o n changes i n . t h e s o l u t i o n due to evaporation o f s o l v e n t or uptake, o f HCI by the n i t r o g e n stream, as w e l l as keeping the atmosphere i n the r e a c t i o n v e s s e l oxygen-free. The r e a c t i o n s were s t u d i e d i n a 100 c c . f l a s k . The reactant s o l u t i o n s were added to the f l a s k . P r e p u r i f i e d n i t r o g e n was bubbled through a pre-s a t u r a t i n g tower (A) i n t o the r e a c t i o n v e s s e l (B), through the condenser (C), and f i n a l l y , out v i a the hypodermic needle (D) embedded i n a serum cap. The temperature o f the r e a c t i o n f l a s k was c o n t r o l l e d t o w i t h i n t0.05°C wi t h a thermostated s i l i c o n e o i l bath. Procedure Sampling Technique The technique and procedure f o r s t u d y i n g the r e a c t i o n between chl o r o -ruthenate ( I I ) and acrylamide i n 3 M HCI w i l l be described. I n i t i a l l y , the amounts of Ru (IV) c h l o r i d e s o l u t i o n and acrylamide s o l u t i o n r e q u i r e d to H J « Figure 4. Apparatus f o r the K i n e t i c Study of the Chlororuthenate (II)-Acrylamide Reaction. 21 obtain the d e s i r e d concentration of these reagents, were p i p e t t e d i n t o the r e a c t i o n v e s s e l and the volume of s o l u t i o n was made up to 59.5 ml by the a d d i t i o n o.c 3 M HC1. The condenser (C) with needle (D) i n place was then attached and a slow stream o f N 2 was introduced through the s i d e arm (E). The n i t r o g e n stream ensured r a p i d mixing. A f t e r thoroughly f l u s h i n g the system with n i t r o g e n , the si d e arm (F) was capped. The r e a c t i o n v e s s e l was then immersed i n t o the thermostated o i l bath. A f t e r a l l o w i n g ten minutes f o r thermal e q u i l i b r i u m 0.5 ml of T i ( I I I ) A w a s added from a 1 c.c. syringe through s i d e arm (F) . A ti m e r was s t a r t e d as t h e . T i ( I I I ) was introduced. Samples o f the r e a c t i o n mixture were withdrawn at p e r i o d i c i n t e r v a l s by means o f a N 2 - f l u s h e d 5 c.c. syringe (G) and t r a n s f e r r e d to a N 2 - f l u s h e d o p t i c a l c e l l (H) f i t t e d w i t h a.serum cap. An a d d i t i o n a l needle (I) was i n s e r t e d i n t o the c e l l during the t r a n s f e r o f s o l u t i o n t o allow n i t r o g e n i n the c e l l to be replaced by the s o l u t i o n . The c e l l was plac e d i n an ice-water bath f o r quenching the r e a c t i o n before measurement o f o p t i c a l d e n s i t y at room temperature. The time o f quenching was noted. The whole operation was performed r a p i d l y and readings.could be taken at two minute i n t e r v a l s . The s yringe and needle were r i n s e d w i t h water and acetone and l e f t to be d r i e d by a secondary n i t r o g e n stream ( J ) . Continuous Recording Technique A second technique was also used i n the k i n e t i c s t u d i e s . This i n v o l v e d p l a c i n g the reactant s o l u t i o n s d i r e c t l y i n t o the o p t i c a l c e l l (H) with serum cap and f l u s h i n g w i t h n i t r o g e n . The c e l l was then pl a c e d i n the spectr o -photometer compartment thermostated t o the d e s i r e d temperature ( w i t h i n *0..1°C) and allowed to reach thermal e q u i l i b r i u m (approximately two minutes). 22 The r e a c t i o n was s t a r t e d by i n t r o d u c i n g the r e q u i r e d small volume of T i ( I I I ) i n t o the o p t i c a l c e l l u s i n g a s y r i n g e . The absorption spectrum was recorded continuously at a f i x e d wavelength as a f u n c t i o n o f time. The above mentioned two techniques y i e l d e d e s s e n t i a l l y the same r e s u l t s and hence, the l a t t e r one,due t o i t s s i m p l i c i t y , w a s employed i n most of the spectrophotometric s t u d i e s . D. Separation and I d e n t i f i c a t i o n o f Organic Products Organic products of the c a t a l y t i c r e a c t i o n s were separated from the i n o r g a n i c components o f the r e a c t i o n by d i s t i l l a t i o n or s o l v e n t e x t r a c t i o n procedures, and were i d e n t i f i e d by standard techniques i n v o l v i n g gas chrom-atography, infrared,N.M.R. spectroscopy. The d e t a i l s o f i d e n t i f i c a t i o n w i l l be discussed i n the r e l e v a n t s e c t i o n of the r e s u l t s chapter. E. Spectra Absorption s p e c t r a were measured e i t h e r on Cary 14, Cary 11 r e c o r d i n g spectrophotometers or a P e r k i n Elmer 202 U.V. V i s i b l e Spectrophotometer u s i n g matched Beckman Standard S i l i c a C e l l s o f 1 cm. o p t i c a l path length. The spectrophotometers could be f i t t e d w i t h thermostated c e l l compartments when necessary (using a Haake Constant Temperature A c c e l e r a t o r 1 Model FSe) . The P e r k i n Elmer 202 model was f i t t e d w i t h various time d r i v e drum accessories f o r automatic r e c o r d i n g at a f i x e d wavelength. I n f r a r e d s p e c t r a were taken w i t h a P e r k i n Elmer model 21 Double Beam spectrophotometer u s i n g KBr d i s c s . Mass Spectrum was recorded on Associated E l e c t r i c a l I n d u s t r i e s MS9 mass spectrometer. Both Aerograph A 90/p3 and a Beckman Ge 2A gas chromatograph u n i t s were used f o r the a n a l y s i s of the organic r e a c t i o n products. 'H N.M.R. s p e c t r a were recorded on Varian HR 100 and A 60 n u c l e a r 23 magnetic resonance spectrometers.A 1 9 F N.M.R. spectrum was recorded or a Va r i a n HR 100 magnetic resonance spectrometer. CHAPTER I I I RUTHENIUM (I I ) - 1,1 DIFLUOROETHYLENE SYSTEM A. Stoichiometry Blue s o l u t i o n s o f ruthenium ( I I ) c h l o r i d e [abbreviated Ru ( I I ) ] i n 3 M HC1 were found to absorb 1,1 d i f l u o r o e t h y l e n e [abbreviated d i f l u o r o e t h y l e n e ] at conveniently measurable rates i n the temperature range 55°-70°. T y p i c a l r a t e p l o t s at 60° f o r three s o l u t i o n s c o n t a i n i n g d i f f e r e n t i n i t i a l [Ru**], namely: 0.48, 0.95 and 1.90 x 10~ 2 M are shown i n Figure 5 f o r the condi-t i o n s noted. From the i n i t i a l p a r t o f the graphs, i t can be seen that p r i m a r i l y the uptake shows a u t o - c a t a l y t i c behaviour, t h i s e f f e c t being more r e a d i l y observable w i t h the more d i l u t e Ru(II) s o l u t i o n s . The curve sub-sequently became l i n e a r , l i n e a r i t y s t a r t i n g w i t h gas uptake corresponding very roughly t o a 1:1 mole r a t i o , p o s s i b l y suggesting the i n i t i a l formation of a 1:1 TT-complex. The r a t e g e n e r a l l y became constant f o r a p e r i o d o f time 49 and then s l o w l y f e l l away. Un l i k e the ethylene and Ru ( I I ) system , no simple s t o i c h i o m e t r y i s observed i n the present' s t u d i e s . In the Ru ( I I ) -ethylene system, the t o t a l uptake o f ethylene corresponded t o the number of moles o f Ru ( I I ) i n i t i a l l y present. The k i n e t i c experiments were u s u a l l y followed over a p e r i o d of 3-5 hours. The i n i t i a l deep blue c o l o r g r a d u a l l y disappeared w i t h the uptake o f d i f l u o r o e t h y l e n e . The f i n a l s o l u t i o n s were dark green, the r e s u l t i n g absorption spectrum e x h i b i t i n g a c h a r a c t e r i s t i c peak at 680 my (Figure 2 ) ; hence, i t seems l i k e l y t h a t some i n i t i a l chlororuthenate ( I I ) i s s t i l l present i n the s o l u t i o n . This amount can be c a l c u l a t e d u s i n g Beer's law, and 25 o O *7 (1) o o 3 13 o [Ru 1 1 ] x. 102M - O - - 0.95 -a— i.9o Figure 5. 3 6 9 12 Time, sec x 10" 3 Typica l Rate P lo ts of Ru (I I)-1,1 Dif luoroethylene System (Pressure„ „ „ =630 mm of Hg, 3.0 HCI, 60°) L2«2-r2 26 the valuer obtained i n d i c a t e d that approximately up to 10% of the o r i g i n a l chlororuthevate ( I I ) was s t i l l present. A s o l u t i o n , a f t e r approximately 3 hours r e a c t i o n time, was o x i d i z e d on standing i n the a i r to chlororuthenate ( I I I ) species (Figure 1) and the r e s u l t i n g spectrum showed that the observed o p t i c a l d e n s i t y corresponded to the t o t a l i n i t i a l Ru (II) c o n c e n t r a t i o n present. A number of experiments were undertaken w i t h the purpose o f i s o l a t i n g the organic r e a c t i o n product formed from the d i f l u o r o e t h y l e n e . S o l u t i o n s i n i t i a l l y about 0.05 M i n [Ru 1*] were reacted w i t h the d i f l u o r o e t h y l e n e at 70° (1 atm. t o t a l pressure) f o r periods of up to 3 1/2 hours; a f t e r t h i s p e r i o d of time, the r e a c t i o n rate.was q u i t e small and the s o l u t i o n was now gra y i s h green. The aqueous d i s t i l l a t e was analyzed by vapour phase chromato-graphy and the only product detected was a c e t i c a c i d . Dinonyl p h t h a l a t e (temperature 130°, f i l a m e n t current 200 m.a.),50/80-Poropak Q (temperature 100°, f i l a m e n t current 200 m.a.) columns were used, e s p e c i a l l y the l a t t e r which e f f e c t i v e l y separated the dominant water c o n s t i t u e n t . (The t o t a l d i -f l u o r o e t h y l e n e absorbed was 0.17 M, and 0.11 M of the a c e t i c a c i d was formed.) An *H N.M.R. spectrum of the d i s t i l l a t e c o n s i s t e d of a s i n g l e t at ^  8.0 T which i s a l s o c o n s i s t e n t w i t h the presence o f an aqueous a c e t i c a c i d s o l u t i o n , and a broad peak about 5-6 T a t t r i b u t e d to water. The p-bromophenacyl e s t e r and p - n i t r o b e n z y l e s t e r d e r i v a t i v e s were al s o prepared and c h a r a c t e r i z e d by t h e i r melting p o i n t s . At the end.of a longer r e a c t i o n p e r i o d , an l 9 F N.M.R. spectrum of the d i s t i l l a t e was als o taken; no peaks were observed, suggesting that the F i s not present i n the organic product. The observed e t c h i n g o f the r e a c t i o n v e s s e l was an i n d i c a t i o n that HF was formed, and hence the F i s thought to f i n i s h up as HF. 27 A mass s p e c t r o s c o p i c a n a l y s i s o f a gas sample taken at the end o f an e x p e r i -ment i n d i c a t e d no mass peaks higher than that of the parent d i f l u o r o e t h y l e n e ; there was no evidence f o r the formation of dimers or higher s p e c i e s . B. K i n e t i c s The k i n e t i c s o f the r e a c t i o n have been i n v e s t i g a t e d i n the i n i t i a l region and i n the subsequent l i n e a r region o f the h i g h e r r a t e . Table I summarizes the r e s u l t s of experiments at v a r y i n g Ru ( I I ) and at v a r y i n g d i -f l u o r o e t h y l e n e c o n c e n t r a t i o n s . A s t r a i g h t l i n e was obtained on p l o t t i n g the i n i t i a l uptake ra t e against [Ru**], (Figure 6). The rates i n the l i n e a r r e g i o n , (Figure 6) however, show on l y an approximate f i r s t order dependence on Ru ( I I ) . Values o f the pseudo f i r s t order r a t e constant k' by the i n i t i a l r e a c t i o n were obtained by d i v i d -i n g the rate by the [Ru**], and are i n c l u d e d i n the t a b l e . The i n i t i a l rate was a l s o followed spec-trophotometrically by f o l l o w i n g the disappearance o f the 680 my peak of the blue RuCl^ species (Figure 7). The f i r s t order dependence on [Ru**] i s confirmed by the l i n e a r p l o t of l o g ab'sorbance against time (Figure 8), the slope of such p l o t gives k'=0.5 x 1 0 ~ 3 s e c - 1 which i s considered i n f a i r agreement with the values obtained from the gas uptake experiments (k'=0.33 x 1 0 - 3 s e c - 1 ) , t a k i n g i n t o account the d i f f e r e n c e i n [Ru**] used and the technique i n v o l v e d f o r the spectrophotometric measurements. The k i n e t i c dependence on the 1,1 d i f l u o r o e t h y l e n e concentration i s shown i n Figure 9, f o r data at 60°. I t i s seen that the dependence i s complex, both f o r i n i t i a l r e a c t i o n rate and f o r the rat e corresponding to the l i n e a r r e g i o n . At low o l e f i n c o n c e n t r a t i o n , the rat e shows f i r s t order dependence w i t h respect t o o l e f i n , whereas at higher o l e f i n concentration the order g r a d u a l l y decreases and f i n a l l y approaches zero. 28 Table I E f f e c t o f V a r i a t i o n o f [ R u 1 1 ] and P a r t i a l Pressure of 1,1 D i l f u o r o -ethylene on the Rate of Reaction of the Ru ( I I ) - 1 , 1 D i f l u o r o e t h y l e n e System C [ T i 1 1 1 ] a d d e d = 0-H M, t o t a l volume = 5.6 ml; 3 M HC1 60°) # Rates of.uptake [Ru ] P ,mm + [ C 2 F 2 H 2 ] x 10 5, M, s e c - 1 k ' ( i n i t i a l ) x 10 2,M L 2 H 2 h 2 x 1 Q 3 ^ M i n i t i a l l i n e a r x 10 3,sec" 1 0.48 630 1.17 0.13 0.21 0.27 0.95 630 1.17 0.28 0.32 . 0.29 1.90 630 1.17 0.53 0.58 0.28 0.95 320 0.60 0.20 0.27 0.21 0.95 165 0.31 0.16 0.18 . 0.17 0.95 120 0.22 0.15 - 0.16 0.95 71 0.13 0.08 - 0.09 The o l e f i n pressure represents t h e : t o t a l pressure less the p a r t i a l pressure o f 3 M HC'l at the r e a c t i o n temperature.70 t The s o l u b i l i t y o f 1,1 d i f l u o r o e t h y l e n e was obtained from a r a t i o using s o l u b i l i t y data of e t h y l e n e 7 * and data f o r 1,1 d i f l u o r o e t h y l e n e at 25°.72 . . . . 0.7 0.5 0.3 0.1 - - Q - - Linear rate —O— I n i t i a l r a t e 0.80 0.5 1.0 1.5 [ R u 1 1 ] x 102M the [ R u 1 1 ] Figure 6. Dependence of Rate on (Pressure,, „ .. = 630 mm. L2F2H2 60°) s _ \ \ N — 1 1 1 1000 2000 3000 0.60 0.40 h 0.20 Time, sec. " Figure 7. Disappearance of Ru ( I I ) During I n i t i a l Reaction ( [ R u 1 1 ] = 0.95 x l O " 3 M. Pressure^ „ _ =630 mm Hg. 60°) 30 o s -8 o 60 O o in O •a +-> &, in o OS -0.2 P -0.4 -0.6 -0.8 h F i gure 8. 1000 2000 3000 Time, sec. F i r s t order Rate P l o t f o r the Ru ( I I ) - 1 , 1 D i f l u o r o e t h y l e n e Reaction at 60°. (data from Figure 7) 0.4 0.3 0.2 h 0.1 100 300 Pressure., (mm) C 2 H 2 F 2 500 700 Figure 9. Dependence of Rate on the 1,1 D i f l u o r o e t h y l e n e Pressure II ([Ru ] = 0.95 x 10 - 2M: 60°) 31 Titaniam ( I I I ) [abbreviated T i ( I I I ) ] was used i n a l l these experiments to reduce the Ru (IV) t o Ru ( I I ) . The r a t e s were found to be u n a f f e c t e d by the [ T i * * * ] provided that i t s concentration was kept at about a ten f o l d excess over the i n i t i a l Ru (IV) concentration (Table I I , Figure 10). The dependence o f the i n i t i a l r a t e on the c o n c e n t r a t i o n o f H + and C l i s shown i n Table I I I . The concentration of H + was v a r i e d from 0.5 M to 3.0 M while the C l concentration was kept constant at 3.35 M by the addi-t i o n of L i C l . The?iCl concentration was v a r i e d from 3.35 t o 5.35 M; t e t r a -f l u o r o b o r a t e was sometimes added t o maintain a constant i o n i c s t r e n g t h . The [ C l - ] l i s t e d i n c l u d e s c o n t r i b u t i o n from the h y d r o c h l o r i c a c i d ,titanous t r i c h l o r i d e and l i t h i u m c h l o r i d e . An i n v e r s e dependence on both [H +] and [Cl ] i s apparent. In the absence of Ru ( I I ) , a c i d t i t a n o u s s o l u t i o n showed no r e a c t i v i t y toward d i f l u o r o e t h y l e n e under i d e n t i c a l experimental c o n d i t i o n s . C. Hydrogenation Experiment An experiment was performed to determine whether the R u * * - d i f l u o r o -cou'i ethylene complex Abe hydrogenated or whether the complex acted as a c a t a l y s t f o r the hydrogenation of the d i f l u o r o e t h y l e n e . A s o l u t i o n of 0.95 x 10" 2 M o f Ru ( I I ) i n 3 M HCI at 60°C was reacted f o r 3 hours w i t h 630 mm d i f l u o r o -ethylene pressure. At the end of the 3 hour p e r i o d , the r e a c t i o n f l a s k was removed from the thermostat and the remaining o l e f i n was pumped o f f at room temperature. About h a l f an atmosphere o f H 2 was introduced i n t o the system; no uptake of hydrogen occurred at 60°, and m e t a l l i c ruthenium was not observed i n s o l u t i o n . The t o t a l gas pressure was then r a i s e d t o 1 atmosphere by a d m i t t i n g d i f l u o r o e t h y l e n e i n t o the system. No appreciable 32 Table IT E f f e c t of [Ti 1*'''] added o n t n e I n i t i a l Reaction Rate o f the Ru ( I I ) -1,1 D i f l u o r o e t h y l e n e System at 60°C 3 M HC1 [R u 1 1 ] x 10 2,M [CI" ],M t o t a l volume,ml [ T i I 1 1 ] a d d e d x 10,M * PC 2F 2H£ mm f [ C 2 F 2 H 2 ] x 10 3, M I n i t i a l Rate of uptake x 10 5, M. s e c - 1 1.90 3. 18 5.3 0.56 630 1.17 0.29 0.95 3. 35 5.6 1.07 630 1.17 0.28 0.95 3. 18 5.3 0.56 630 1.17 0.23 0.95 3. 12 5.2 0.38 630 1.17 0.13 0.95 3. 12 5.2 0.38 320 0.60 0.10 * The o l e f i n pressure represents the t o t a l pressure l e s s the p a r t i a l pressure o f 3 M HC1 at the r e a c t i o n temperature.70 The s o l u b i l i t y o f 1,1 d i f l u o r o e t h y l e n e was obtained from a r a t i o using s o l u b i l i t y data o f et h y l e n e ? ! and data f o r 1,1 d i f l u o r o e t h y l e n e at 25°.72 Table I I I E f f e c t of V a r i a t i o n o f [H +] and [CI ] on the I n i t i a l Reaction Rate o f Ru ( I I ) - 1,1 D i f l u o r o e t h y l e n e System. ( [ R u 1 1 ] = 0.95 x l O " 2 M, [ T i I I I ] a d d e d =0.11 M, 60°) + - * [H ],M [CI ],M P ,mm I n i t i a l Rate o f L 2 2 2 Uptake x 10 5,M.sec" 1 3.0 3.35 630 0.28 1.5 3.35 630 0.42 0.5 3.35 630 "gas e v o l u t i o n " 3.0 3.35 120 0.15 3.0 4.35 120 * 0.08 3.0 5.35 120 0.06 3.0 3.35 120 0.13 a 3.0 4.35 120 0.11 b a a d d i t i o n of 2 M NaBF^. k A d d i t i o n c f 1 M NaBF^. 33 uptake was observed us i n g t h i s H 2 - d i f l u c r o e t h y l e n e mixture. Thus, Ru (I I ) i s not a c a t a l y s t f o r the H 2 r e d u c t i o n o f the double bond i n d i f l u o r o -ethylene. D. Di s c u s s i o n ( i ) I n i t i a l Rates and I n i t i a l Reactions The complex form o f the r a t e dependence on the o l e f i n c o n c e n t r a t i o n and the in v e r s e c h l o r i d e e f f e c t suggested t h a t complex formation between Ru ( I I ) and d i f l u o r o e t h y l e n e proceeds v i a a two step mechanism i n v o l v i n g an i n i t i a l S ^ l d i s s o c i a t i o n of the chlororuthenate ( I I ) species. Such k i n e t i c dependences had been observed p r e v i o u s l y f o r the Ru III)-ethylene system where 49 such a mechanism had been proposed. R u H C l > R u H C l . + Cl" (17) n r n-1 R u I I C l n + CF2=CH2 k 2 » Ru I I e i n_ 1(CF 2CH 2) (18) Assuming the steady s t a t e approximation f o r the intermediate Ru**Cl ^, the r a t e law becomes l r(CF 2CH 2) = ^ [ R ^ C l j r C F . C H , ] d t 2 2 k_i[Cl"] + k 2[CF 2CH 2] U y j At constant [Cl"] and [CF 2CH 2], ~^[CF 2CH 2] = k» [ R u H C l n ] (20) where k' = k j k 2 [CF2CH2]./{k_l [ C l ~ ] + k 2[CF 2CH 2]) (21) «. i l k _ i rci~ 1 k« ki k 1k 2[CF 2CH 2] 34 Thus, the observed f i r s t order dependence on [Ru**] i s c o n s i s t e n t w i t h the r e l a t i o n s h i p expressed i n equation (20). According t o equation (22), a p l o t of against [C F ^ C H ~ ] " ' A T A constant [Cl ] should be l i n e a r ; such a r e l a t i o n s h i p i s observed and i s shown i n Figure 11. From the slope and i n t e r c e p t of the p l o t , the value of k j and k ^ A - l at 60° can be c a l c u l a t e d ; the value o f k j f o r the d i s s o c i a t i v e step 3 was found to be 3.3 x l O ^ s e c " 1 , and k 2 / k _ 1 = 9.78 x 10 . Equation (19) sh ows that at low [ C F 2 C H 2 ] , the k _ ^ [ C l ] term i n the denominator w i l l predominate and the r e a c t i o n becomes f i r s t order i n o l e f i n . As the [CF 2CH 2] increases, the k 2 [ C F 2 C H 2 ] denominator term w i l l g r a d u a l l y predominate and the r e a c t i o n becomes zero order i n o l e f i n . Hence, at experiments u s i n g lower o l e f i n c o n c e n t r a t i o n s , an inv e r s e c h l o r i d e dependence should be observed, and the data are i n q u a l i t a t i v e agreement with t h i s . However, i t was a l s o found t h a t v a r y i n g the c h l o r i d e concentration a f f e c t s the d i s t r i b u t i o n o f ruthenium ( I I ) c h l o r o s p e c i e s . Evidence f o r t h i s i s suggested by the observation t h a t the absorbance at 680 my due to the blue 2 - -complex ( b e l i e v e d to be RuCl^ ) decreases somewhat as the C l conc e n t r a t i o n i s i n c r e a s e d from 3.0 M t o 6.0 M (Figure 12). This decrease p a r a l l e l s t o some extent the v a r i a t i o n of rat e s w i t h added c h l o r i d e c o n c e n t r a t i o n (Figure 13) and i n d i c a t e s that the v a r i a t i o n o f rate may r e s u l t to some extent from the presence o f d i f f e r e n t ruthenium ( I I ) chloro complexes i n s o l u t i o n . The most obvious i n t e r p r e t a t i o n of t h i s i s i n terms of a C l dependent e q u i l i b r i u m between various ruthenium ( I I ) c h l o r o complexes, hav-i n g d i f f e r e n t r e a c t i v i t i e s toward the o l e f i n , that of the blue ruthenium ( I I ) species exceeding those o f the other c h l o r o - c o m p l e x e s e . g . R u C l 2 + C l " > R u C l 3 " (23) 35 0.3 0.2 0.4 [ T i 1 1 1 ] ' a d d e d x 10, M . I I I . Figure 10. Dependence o f I n i t i a l Rate on the [Ti ] added 12 o 0 ) to CO I O X -• 1 o 1 1 1 Figure 11. ( [ R u 1 1 ] = 1 1 0 - 3 / [ C 2 H 2 F 2 ] , M"1 T y p i c a l P l o t of ±_ v s 0.95 x 10"2M, 60°, 3 M HC1) 0.19 0.18 0.17 o 3.4 [C1"],M 4.4 I I Figure 12. E f f e c t o f [ C l ~ ] on the i n i t i a l [Ru ] ( [ R u 1 1 ] = 0.95 x 10" 3 M. 25°) 5.4 1.5 1.2 0.9 U 0.6 h-0.3 h 4.35 3.35 [C1'],M Figure 13. Dependence of I n i t i a l Rate on [CI ] I I . 5.35 ( [ R u i X ] - 0.95 x 10" 2 M. P C 2 p 2 H 2 = 120 mm Hg. 60°) 37 R u C l 3 + C l " > RuCl,, 2" (24). RuClt^ 2" + C l " >• R u C l 5 3 " (25) U n f o r t u n a t e l y , i n the absence of q u a n t i t a t i v e i n f o r m a t i o n about these e q u i l i b r i a and o f the r e a c t i v i t i e s o f the various ruthenium ( I I ) c h l o r o complexes, a more d e t a i l e d i n t e r p r e t a t i o n of the C l dependence i s not p o s s i b l e . I t has long been considered that no s u i t a b l e i n e r t anion could be found which could be s u b s t i t u t e d f o r C l i n order t o keep the i o n i c s t r e n g t h constant i n the ruthenium ( I I ) system; ClO'^ , which i s commonly used f o r t h i s purpose,is r a p i d l y reduced by Ru ( I I ) . I t has r e c e n t l y been reported 67 that t e t r a f l u o r o b o r a t e does not complex and i s not reduced by Ru ( I I ) , but these s t u d i e s used concentrations of BF 4 of up t o only 2.6 x 10~ 2 M. In the present s t u d i e s , experiments at constant i o n i c s t r e n g t h were s t u d i e d by adding up to 2 M NaBF^ (Table I I I ) and changes i n the absorption at 680 my of up t o 15% were observed, i n d i c a t i n g that t e t r a f l u o r o b o r a t e does probably complex weakly w i t h Ru ( I I ) . The study of the dependence of the r a t e on the H + concentration was complicated at lower a c i d i t i e s (about 0.5 M) by the production of m e t a l l i c ruthenium. An i n v e r s e dependence of the r a t e on [H +] from 1.5-3.0 M was noted. A s i m i l a r inverse dependence was observed i n the Ru**-formic a c i d and i n the Ru ( I I ) - e t h y l e n e systems. I t may r e f l e c t some h y d r o l y t i c e q u i l i b r i a i n v o l v i n g chlororuthenate ( I I ) complexes, whose r e a c t i v i t y i s en~hanced through h y d r o l y s i s . Some i n d i c a t i o n o f such h y d r o l y t i c processes i s provided by the observation that at lower a c i d i t i e s (0.03 M to 0.3 M H + ) , 68 Chlororuthenate ( I I ) complexes are r e a d i l y o x i d i z e d by water to Ru ( I I I ) . 38 Ru (I I ) + H 20 > Ru ( I I I ) + OH" + 1/2H2 (26) The experiments at 0.5 M a c i d i t y (Table I I I ) i n d i c a t e d gas e v o l u t i o n which could r e s u l t from r e a c t i o n (26). The e f f e c t o f the t i t a n o u s concentration i s presumably concerned w i t h the e q u i l i b r i u m i n v o l v i n g the red u c t i o n o f Ru (IV) to Ru ( I I ) by T i ( I I I ) which can be expressed as f o l l o w s : Ru (IV) + 2Ti ( I I I ) ^ > Ru ( I I ) + 2Ti (IV) (27) Hence, at high t i t a n o u s c o n c e n t r a t i o n , more Ru (IV) should be reduced t o Ru ( I I ) , since the e q u i l i b r i u m tended to be s h i f t e d t o the r i g h t . From Figure 14, obtained from absorption measurements at 680 my, i t can be seen th a t only at high [ T i 1 1 1 ] used i s most o f the Ru (IV) reduced to Ru ( I I ) . This i s c o n s i s t e n t with the f i n d i n g that the [ T i 1 * ' 1 ] should be at l e a s t i n ten f o l d excess over the i n i t i a l Ru (IV) concentration t o give rates indepen-dent of [ T i * * * ] (Figure 10). . C a d y ^ has a l s o found t h a t an excess o f T i ( I I I ) was necessary to reduce Ru (IV) i n t r i f l u o r o a c e t i c a c i d , and 41 Halpern and Kemp used a s i m i l a r excess i n s t u d i e s of the chlororuthenate ( I I ) - f o r m i c a c i d system. The e f f e c t of the v a r i a t i o n o f temperature on the r a t e constant k 1 i s shown i n Table IV. In these experiments, the Ru ( I I ) concentration and the t o t a l pressure (1 atmosphere) were kept constant. Since the vapour pressure of 3 M HC1 v a r i e d s l i g h t l y at d i f f e r e n t temperatures, the p a r t i a l pressure of d i f l u o r o e t h y l e n e was obtained by s u b t r a c t i n g the vapour pressure o f 3 M HC1 from the t o t a l pressure. In a l l the temperature v a r i a t i o n experiments, q u i t e high p a r t i a l pressures ( i . e . 560-665 mm) o f d i f l u o r o e t h y l e n e pressure were used. Figure 9 shows that the rate o f uptake of d i f l u o r o e t h y l e n e i s not a f f e c t e d g r e a t l y by the v a r i a t i o n o f p a r t i a l pressure o f d i f l u o r o e t h y l e n e i n 39 40 Table IV Temperature Dependence o f k1 and k 3 of the Ru ( I I ) - 1,1 D i f l u o r o e t h y l e n e added Systems at 0.95 x 10"2 M [ R u 1 1 ] , 760 mm T o t a l Pressure, [ T i 1 1 1 ] d d e d = 0.11 M Temperature,°C k1 x 1 0 3 , s e c _ 1 k 3 x 10 3,sec" 1 55 0.13 0.26 , 60 0.31 0.39 65 0.57 0.70 69 0.96 0.96 41 t h i s range. Thus, equation (19) can be expressed as the l i m i t i n g form "g- t[CF 2CH 2] = k ^ R u 1 1 ^ ] (28) i . e . , k : % k 1 An Arrhenius p l o t was obtained by p l o t t i n g the l o g k 1 against I/T + as shown i n Figure 15, and the a c t i v a t i o n parameters were found to be Air ^ 29 k c a l , AS ^13 e.u. ( i i ) Subsequent Reactions A f t e r the I n i t i a l Complex Formation Subsequent r e a c t i o n s most l i k e l y t o take p l a c e are e i t h e r h y d r a t i o n or p o l y m e r i z a t i o n by which the d i f l u o r o e t h y l e n e i s consumed from the gas phase. Mass spectrum showed no evidence o f p o l y m e r i z a t i o n t a k i n g p l a c e . From the experimental r e s u l t s , c a t a l y t i c h y d r a t i o n of the o l e f i n s u b s t r a t e must take place (see A of t h i s chapter). The r e a c t i o n product would be formed from the ir-complex w i t h the l i b e r a t i o n of the R u C l n ^ sp e c i e s . R u I ] " C l n 1 [ C F 2 C H 2 ] ——Q> R U I I C L N i + hydrated product (29) Considering now the o v e r a l l r e a c t i o n s i n d i c a t e d by equation (17)(18) and (29), the r a t e of o l e f i n uptake at any stage can be expressed as f o l l o w s : " f t [ C F 2 C H 2 ] = k z t R u ^ C l ^ n C F z C H j , ] (30) Assuming a s t a t e l y s t a t e c o n c e n t r a t i o n o f Ru**Cl . • J n-1 k j t R u 1 1 ^ ] + k a l R ^ C l ^ C C F z C H z ) ] = k . i f R u 1 1 ^ [ C l ~ ] + k 2 [ R u 1 1 ^ ^ ] [CF 2CH 2] (31) 42 -2.0 -2.2 h -2.4 L o -2.6 h -2.8 U -3.0 r Figure 15. Arrhenius p l o t o f k j of Ru ( I I ) - 1 , 1 D i f l u o r o e t h y l e n e System. ( [ R u 1 1 ] = 0.95 x 1 0 - 2 M. 3 M HCI) 43 S u b s t i t u t i o n o f [Ru**Cl n_^] obtained from equation (31) i n t o equation (30) gives ^ - [ C F 2 C H 2 ] = k 2 r C F 2 C H 2 ] { k 1 [ R u I I C l n ] + k 3 [ R u 1 1 ^ ^ (CF 2CH 2) ]} ( 3 ? )  d t k _ 1 [ C l " ] + k 2 [ C F 2 C H 2 ] At constant [CI ] and [CF 2CH 2], t h i s becomes "^-[CF 2CH 2] - k'^kjERu11^] + k a R j ^ ^ ^ C C F z C H z ) } (33) where k" = k 2 [ C F 2 C H 2 ] / k _ 1 [ C l ~ ] + k 2 [ C F 2 C H 2 ] Equation (32) gives a complete d e s c r i p t i o n of the d i f l u o r o e t h y l e n e uptake i n c l u d i n g both the i n i t i a l and l i n e a r r e g i o n . I n i t i a l l y , the [ R u ^ C l j (CF 2CH 2) ] i s zero, and the equation reduces to equation (20). The d e t a i l e d d i s c u s s i o n of the i n i t i a l r a t e s have been presented i n the previous s e c t i o n of t h i s chapter. As the r e a c t i o n proceeds, the [Ru * * C l n ^(CF 2CH 2)] g r a d u a l l y increases. Equation (32) must be used i n order t o describe the system adequately. As observed p r e v i o u s l y , the i n i t i a l p o r t i o n o f the r a t e p l o t shows s l i g h t a u t o - c a t a l y t i c behaviour, hence, k 3 must be somewhat gre a t e r than k j . In the s e r i e s o f experiments which i n v o l v e d high o l e f i n c o n c e n t r a t i o n , the k _ i [ C l ] term becomes small as compared to k 2 [ C F 2 C H 2 ] , hence, the concentra-t i o n o f the blue Ru**Cl species w i l l a l s o be s m a l l . As the [Ru**Cl , n r n-1 (CF 2CH 2)] b u i l d s up, the i n i t i a l r a t e of uptake w i l l r a p i d l y increase and the o l e f i n uptake w i l l be given by the expression "^[CF 2CH 2] n, k a f R i ^ C l ^ C C F z C H z ) ] ' (34) 44 The abcve r e l a t i o n w i l l y i e l d a constant r a t e thus g i v i n g r i s e t o the l i n e a r region of the uptake p l o t . The R u I I C l n _ 1 ( C F 2 C H 2 ) ] £ [ R u I I ] i n i t i a l > thus, the r a t e of uptake of o l e f i n w i l l show an approximate f i r s t order k i n e t i c dependence on [Ru**], as shown i n Figure 6. The value of k 3 obtained from the slope of the p l o t i s roughly % 4 x l C T ^ s e c " 1 . We are thus s a y i n g that the r e a c t i o n mechanism f o r the l i n e a r region of the r a t e p l o t at higher o l e f i n . c o n c e n t r a t i o n can be w r i t t e n as TT f a s t TT p Ru CI + CF 2CH 2 > Ru C l n _ 1 ( C F 2 C H 2 ) (35) R u * * C l n 1(CF 2CH 2) + H 20 k 3 > R u * * C l n _ 1 + hydrated product (36) At the lower o l e f i n c o n c e n t r a t i o n , the k_![CI ] term which was neglected i n the previous d i s c u s s i o n f o r experiments at h i g h e r o l e f i n p r essure, be-comes more s i g n i f i c a n t , i n d i c a t i n g t h a t the [Ru**Cl n] i s l i k e l y to be higher f o r these experiments and equation (33) should be used f o r the r a t e of uptake. Using the l i n e a r rates from experiments at the high o l e f i n pressures over the temperature range 55-69°, approximate values o f k 3 were obtained by d i v i d i n g t h i s l i n e a r rate by the [Ru**]. Values of k 3 are given i n Table IV. An Arrhenius p l o t (Figure 16) y i e l d s the parameters AH ^ 2 1 k c a l and AS ^ -9.2 e.u. In a l l the systems which have been i n v e s t i g a t e d , the r a t e tends to f a l l o f f g r a d u a l l y a f t e r reaching the l i n e a r r e g i o n . S i m i l a r phenomena have 33 been observed i n the Ru ( I I I ) c a t a l y s e d h y d r a t i o n o f acetylene, where the decrease i n the r e a c t i o n r a t e was due t o the formation of Ru ( I I ) carbonyl species which are much le s s c a t a l y t i c a l l y a c t i v e . The i n f r a r e d spectrum of 45 2.90 3.00 103/T°(K) Figure 16. Arrhenius p l o t of k 3 of Ru ( I I ) - 1 / 1 D i f l u o r o e t h y l e n e System. ([Ru 1 1]'= 0.95 x l O " 2 M. 3 M HCI) 46 an i n o r g a n i c residue remaining from an experiment c a r r i e d out f o r a long p e r i o d was recorded as i s shown i n Figure 17; strong peaks are e x h i b i t e d at 1400 cm - 1 (assigned t o NH^*), 1620 cm 1 (assigned to H 20), a broad peak at 3100-3500 cm"1 (assigned to NH t t + and H 20), and tue other peaks at 1940 cm"1 and 2060 cm 1 might w e l l a r i s e from the CO s t r e t c h i n a Ru**(C0) complex II 33 and a CO s t r e t c h i n a Ru ( C 0 ) 2 species r e s p e c t i v e l y . 0.05 U o.io h 0.15 0.20 0.25 h 3300 3000 1600 1300 Figure 17. 2200 1900 wave number, cm - 1 The I n f r a r e d Spectrum o f an Inorganic Residue Obtained i n the Reaction o Ru ( I I ) w i t h 1,1 D i f l u o r o e t h y l e n e . (KBr P e l l e t ) CHAPTER IV RUTHENIUM ( I I ) - FLUOROETHYLENE SYSTEM S o l u t i o n s of chlororuthenate ( I I ) were found to absorb f l u o r o e t h y l e n e at conveniently measurable rates over the temperature range 50-60°. The ra t e p l o t s obtained were s i m i l a r to those of the R u * * - d i f l u o r o e t h y l e n e system but the i n i t i a l a u t o c a t a l y s i s region was more pronounced (Figure 18). The organic product of the r e a c t i o n was found t o be acetaldehyde (vapor phase chromatography at 100° u s i n g 50/80 Poropak Q). An *H N.M.R. spectrum of an aqueous d i s t i l l a t e from a r e a c t i o n c o n s i s t e d pf a doublet at 7.8 T and a quartet at 0.2 x. This was c o n s i s t e n t w i t h the presence o f acetaldehyde. 2,4-dinitrophenylhydrazone and semicarbazone d e r i v a t i v e s were a l s o prepared and c h a r a c t e r i z e d by m e l t i n g p o i n t s . The k i n e t i c s of t h i s system have been i n v e s t i g a t e d and analyzed g e n e r a l l y i n the same manner as d e s c r i b e d f o r the d i f l u o r o e t h y l e n e system i n Chapter IV, since the systems behaved very s i m i l a r l y . Tables V-VII summarize the r e s u l t s obtained f o r the f l u o r o e t h y l e n e system. A good f i r s t order dependence on the Ru ( I I ) concentration was obtained f o r both the i n i t i a l r a t e and the r a t e i n the l i n e a r region (Figure 19). I t should be noted that the Ru ( I I ) concentrations used were about ten times l e s s than those used i n the d i f l u o r o e t h y l e n e system. The v a r i a t i o n o f rates with o l e f i pressure are shown i n Figure 20. The r a t e dependence again shows between f i r s t order and zero order; at low o l e f i n p r essure, i t i s e s s e n t i a l l y f i r s t order and at high pressure, i s approximately zero order. The data f o r the o l e f i n dependence at the three temperatures d i d not [Ru ] x 10 3M 1 2 3 4 5 6 7 Time, sec x 10" 3 Figure 18. T y p i c a l Rate P l o t s f o r the Reaction o f Ru ( I I ) w i t h Fluoroethylene at 665 mm pressure of f l u o r o e t h y l e n e , 50°C. Table V Summary of K i n e t i c Data of Ru ( I I ) - F l u o r o e t h y l e n e System at Various Temperatures. (3 M HCI, T o t a l Volume = 5.6 ml, [ T i H I ] added = 0.06 M) Rates of uptake x 10 5, M.sec" 1 temperature, °C [Ru ] P ,mm I n i t i a l l i n e a r k 1 x 10 3,sec _ 1 x 10 3,M L 2 h h 3 ( i n i t i a l ) 50° 0.48 667 0.21 0.35 4.45 0.95 667 0.35 0.78 3.70 1.90 667 0.73 1.62 3,85 0.95 320 0.32 0.69 3.37 0.95 167 0.30 0.67 3.16 55° 0.95 662 0.98 1.48 10.3 0.95 320 0.79 1.08 8.35 0.95 167 0.43 0.78 4.55 60° 0.95 • 630 1.23 2.14 13.0 0.95 320 0.83 1.41 8.7 0.95 167 0.45 0.80 4.7 Table VI E f f e c t of V a r i a t i o n of [H +] and [ C l - ] on the I n i t i a l Rate of Reaction of Ru ( I I ) -Fluoroethylene System. At 0.95 x 1 0 - 3 M [R u 1 1 ] 55° [Ti i n . added = 0. 06 M [H +],M [C1~],M P„ _IT.mm I n i t i a l Rate C 2FH 3 of Uptake x 105, M s e c - 1 3.0 3.79 320 1.06 3.0 4.79 320 0.89 3.0 5.79 320 0.73 3.0 3.18 662 0.98 1.5 3.18 662 0.49 0.5 3.18 662 0.46 3.0 3.18 167 0.43 1.5 3.18 167 0.72 0.5 3.18 167 1.02 51 Table VII Temperature Dependence on k' and k 3 of the Ru ( I I ) - F l u o r o e t h y l e n e System at 0.95 x 1 0 - 3 M [R u 1 1 ] and 760 mm T o t a l Pressure. Temperature,°C k' x 10 3,sec 1 k 3 x 1 0 3 , s e c _ 1 50 3.7 8.2 55 10.3 15.6 60 13.0 22.5 52 o to LO o X rt §* O <D •t-> oj 1.6 1.2 0.8 0.4 ...£).... I n i t i a l Rate _ Q Linear Rate 0.2 - O ' 1.0 [ R u 1 1 ] x 103, M I I . 1.8 Figure 19. Dependence of Rate on the [Ru ] i n the Ru ( I I ) - F l u o r o e t h y l e n e System. ( T o t a l pressure: 760 mm Hg., 50°) o d) U •H t/> L O o X 0) g* O rt 2.0 1.6 1.2 0.8 0.4 o I n i t i a l Rate at 50° o—• A — I n i t i a l Rate at 55° I n i t i a l Rate at 60° • — •Linear Rate at 60° --/ > r 1 Co o i l 1 . 1 200 Pressure , L 2 FH 3 400 600 mm Figure 20. Dependence of Rate on Fluoroethylene Pressure at Various Tempera-ture . ( [ R u 1 1 ] = 0.95 x 10-3 M.) 53 give p a r t i c u l a r l y good l i n e a r p l o t s when p l o t t e d according t o equation 22 i n Chapter I I I , and r e l i a b l e values of k± obtained from the i n t e r c e p t could not be obtained. The k' values quoted (Table VII) w i l l then be somewhat lower than the true k j value. Assuming the s o l u b i l i t y o f f l u o r o e t h y l e n e to be the same as t h a t of d i f l u o r o e t h y l e n e , the value of k z / k ^ a t 60° f o r the f l u o r o e t h y l e n e system i s o f the order of 4 x 10 3. An Arrhenius p l o t u s i n g the k 1 values was again l i a b l e t o considerable s c a t t e r ; and the a c t i v a t i o n energy estimated i s about 28 t 4 k c a l . Values of k 3 were estimated as p r e v i o u s l y i n Chapter I I I and these are given i n Table V I I ; a q u i t e good Arrhenius p l o t was obtained and the a c t i v a t i o n parametersAH ^ 21 k c a l and AS ^ -5 e.u. were estimated. The C l ~ dependence f o r the i n i t i a l r a t e was s i m i l a r t o t h a t found i n the d i f l u o r o e t h y l e n e system (Table V I ) . I t was found that at high o l e f i n pressure, the i n i t i a l r a t e i n c r e a s e d w i t h i n c r e a s i n g a c i d i t y w h i l e at low o l e f i n p r essure, the r a t e showed an i n v e r s e dependence (Table V I ) . The. reason f o r t h i s i s not c l e a r . Experiments s i m i l a r t o those described i n the d i f l u o r o e t h y l e n e system were c a r r i e d out t o i n v e s t i g a t e the p o s s i b i l i t y o f a Ru ( I I ) c a t a l y s e d hydrogenation of f l u o r o e t h y l e n e . Again, s i m i l a r r e s u l t s were obtained and no such hydrogenation was observed. CHAPTER V RUTHENIUM ( I I ) - ACRYLAMIDE SYSTEM Reactions o f a f u r t h e r s u b s t i t u t e d ethylene, acrylamide (CH2CHC0NH2) wi t h the chlororuthenate ( I I ) s o l u t i o n s were i n v e s t i g a t e d . A. Formation o f a Ru ( I I ) - Acrylamide Complex ( i ) S toichiometry of the Reaction Blue s o l u t i o n s o f Ru ( I I ) i n 3 M HC1 were found t o complex with excess acrylamide at conveniently measurable rates i n the temperature range 35°-45°. As the r e a c t i o n progressed, the blue c o l o r faded completely and the maximum absorption at 680 my decreased. At s u f f i c i e n t l y low concentrations o f the added o l e f i n , i n the range of 10" 3 M, complex formation of acrylamide w i t h Ru ( I I ) a t t a i n e d a measurable e q u i l i b r i u m . The chemical e q u i l i b r i u m between Ru ( I I ) and acrylamide was achieved r a p i d l y by h e a t i n g the s o l u t i o n to 80° f o r a short time. Subsequently, the s o l u t i o n was cooled t*o room temperature and the extent o f complex formation determined by measuring the decrease i n absorb-ance at 680 my. The s t o i c h i o m e t r y of the r e a c t i o n was e s t a b l i s h e d by measuring the o p t i c a l d e n s i t y of a s e r i e s o f s o l u t i o n s w i t h a constant [Ru**] and v a r y i n g acrylamide concentrations (Figure 21). For a 1:1 Ru ( I I ) -acrylamide complex, i t can be shown that the f o l l o w i n g r e l a t i o n s h i p s h o l d : Ru** + CH2CHCONH2 K >' Ru**(CH2CHC0NH2) (37) K = [Ru**(CH 2CHC0NH 2)] = T M - [A] ( 3 g ) [Ru n][CH 2CHC0NH 2] [A]{T L - T M + [A]} 55 where T and T, = t o t a l metal and v o t a l o l e f i n used. M L I - e T [ A ] - — f * ( M ) A ~ B I = t o t a l absorbance. e = extinction c o e f f i c i e n t . S u b s t i t u t i n g equation (39) i n t o (38) T . + L i l = M _ 1 _ . EA ~ EB K 1 - £B TM £A ' EB For t h i s system e D = 0 and the r e l a t i o n s h i p reduces to D T T + 'L. = JL f A - (I - 1 ) (41) A K I M I EA A p l o t of T + — against Y~ 1 S shown i n Figure 22. The l i n e a r i t y i s L eA. 1 c o n s i s t e n t w i t h a 1:1 complex with K ^  6 x 10 3 M"1. ( i i ) K i n e t i c s > The k i n e t i c s of complex formation were followed by measuring c o n t i n -uously the decrease i n the Ru ( I I ) absorption at 680 mp'in the presence o f excess acrylamide, under a n i t r o g e n atmosphere. There i s no i n t e r f e r e n c e at t h i s wavelength from the Ru ( I I ) - a c r y l a m i d e complex, which absorbs i n a broad region around 250 my - 300 my (e ^ 300) and at 450 my (e ^ 130). There i s no i n d i c a t i o n of the presence of intermediate or by-products as shown by the s p e c t r a taken at various stages o f the r e a c t i o n . The only absorption observed was that of Ru (I I ) and the complex. When a Ru ( I I ) s o l u t i o n was allowed to stand i n s i m i l a r c o n d i t i o n s f o r 3 hours under n i t r o g e n atmosphere i n the absence of o l e f i n , there was no 56 o oo +-> rt CD o C rt •8 o w •§ rt +-> o •M 0 5 h 0.4 0.3 h 0.2 L 0.1 h 25 30 5 10 15 20 [CH2CHC0NH2] x 1 0 \ M Figure 21. E f f e c t of acrylamide on the absorbance of 1 x 10" 3 M Ru ( I I ) s o l u t i o n at 680 my, 3 M HCI, 25° o 24 L 20 h 16 U Figure 22. e A / I x 10" 3 I e A P l o t o f (T + — ) vs •=— according to Equation 41, A 1 57 decrease i n the absorption spectrum i n d i c a t i n g no d i s p r o p o r t i o n a t i o n or o x i d a t i o n . A t y p i c a l rate p l o t f o r the disappearance of the 680 my peak at 35° i s shown i n Figure 23. P l o t s of l o g absorbance versus time at constant acrylamide and HCI concentrations (Figure 24) gave good s t r a i g h t l i n e s f o r at l e a s t 80% of the r e a c t i o n time p r o v i n g that the r e a c t i o n was f i r s t order i n Ru ( I I ) at the concentrations used. The acrylamide c o n c e n t r a t i o n used i n a l l these experiments was always i n s u b s t a n t i a l excess over the Ru ( I I ) c o n c e n t r a t i o n and hence, i t s c o n c e n t r a t i o n remained e f f e c t i v e l y constant during the course of each experiment. A t e n f o l d excess of T i ( I I I ) over the Ru ( I I ) was again used t o o b t a i n the• maximum concentration o f the blue Ru ( I I ) s p e c i e s . The o v e r a l l r e a c t i o n r a t e can be w r i t t e n as ^ [ R u 1 1 (acrylamide)] = - d [ R u H ] / d t = k« [ R u 1 1 ] (42) Values of k' can be r e a d i l y estimated from the slope o f the l o g p l o t s . V a r i a t i o n of the i n i t i a l [ R u 1 1 ] from 0.35 x 10" 3 M t o 1.5 x 10" 3 M at 40° f u r t h e r confirmed that the r e a c t i o n was f i r s t order i n Ru ( I I ) (Table V I I I ) . V a r i a t i o n o f acrylamide c o n c e n t r a t i o n at the various temperatures showed that the r e a c t i o n was f i r s t order at low acrylamide concentration and tending t o zero order at higher acrylamide concentration (Figure 25, Table V I I I ) . An i n v e r s e dependence of k' on C l c o n c e n t r a t i o n was again observed; k' increased w i t h i n c r e a s i n g a c i d i t y (Table I X ) . ( i i i ) D i s c u s s i o n The observation of an inverse dependence of the r a t e on the [Cl ] along 58 rtui 089 souBqxosqv -0.2 j ! ! I ; i L 3 6 9 12 15 18 Time, sec x 10~ 2 Figure 24. F i r s t - o r d e r r a t e p l o t f o r the Ru ( I I ) - a c r y l a m i d e r e a c t i o n ( [ R u 1 1 ] = 1 x 10" 3M, [CH2CHC0NH2] =0.2 M, 3 M HC1, 35°) 60 Table V I I I Summary o f K i n e t i c Data f o r Ru (II)-Acrylamide System at Various Temperatures (3 M H C l , [ T i i n ] = 1.7 x 10" 2 M) Temperature, °C [ R u 1 1 ] x 10 3, M [CH2CHC 0NH 2], M k 1 x 10 3 , sec 1 35° 1.0 0.05 0.35 1.0 0.10 0.64 1.0 0.20 1.32 1.0 0.40 2.1-3 1.0 0.60 3.15 1.0 1.00 3.85 40° 0.35 0.10 0.99 1.0 0.10 1.04 1.5 0.10 -1.15 1.0 0.05 0.69 . 1.0 0.20 2.17 1.0 0.60 4.57 1.0 1.00 6.15 45° 1.0 0.05 1.24 1.0 0.10 2.12 1.0 0.20 3.72 1.0 0.40 5.95 1.0 1.00 10.10 Table IX E f f e c t o f V a r i a t i o n of [Cl ] and [H +] on the Reaction of Ru ( I I ) w i t h Acrylamide at 1 .0 x 10" 3 M Ruthenium ( I D Concentration and 0. 1 Acrylamide Concentration, 40°. [H +],M [C1"],M k 1 x 10 3, sec 1 3.0 3.05 1.04 3.0 4.05 0.83 3.0 5.05 0.48 1.5 3.05 0.72 0.5 3.05 0.30 61 2 4 6 8 10 12 [CH2CHC0NH2] x 10, M Figure 25. E f f e c t on the Rate Constant k' o f Varying the Acrylamide Concentra-t i o n at Various Temperatures. ( [ R u 1 1 ] = 1 x 10" 3M, 3 M HC1) 62 w i t h the observation that the r a t e tends to approach a l i m i t i n g value w i t h i n c r e a s i n g acrylamide concentration again suggested that formation of the Ru ( I I ) - a c r y l a m i d e complex proceeds through a two step d i s s o c i a t i o n mechanism. R u C 1 n RuC^.! + CI (43) R u C l n _ j + acrylamide ———> Ru**(acrylamide) (44) The observed k i n e t i c s were s i m i l a r to those found f o r the r e a c t i o n o f Ru ( I I ) w i t h d i f l u o r o e t h y l e n e and f l u o r o e t h y l e n e as described i n the previous chapters and the data have been t r e a t e d s i m i l a r l y . The values o f k^ and k z / ^ - l a t t n e three temperature s t u d i e d are o b t a i n -ed from the p l o t s of versus. r ^ CHCONH ] ' ( f i g u r e 26)and are shown i n Table X. A reasonable Arrhenius p l o t f o r k j ( F i g u r e 27)was obtained at the tempera-t u r e range s t u d i e d (35-45°). From t h i s , the a c t i v a t i o n energy f o r the d i s s o c i a t i v e step i s E a % 17.9 k c a l g i v i n g AH ^ 17 k c a l and AS ^ 12.4 e.u. B. Homogeneous C a t a l y t i c Hydrogenation of the Acrylamide ( i ) K i n e t i c s The 3 M HC1 s o l u t i o n s of the Ru**-acrylamide complex were subjected to hydrogen atmospheres and gas uptake was found t o occur at conveniently measurable r a t e s around 80°. Figure 28 shows t y p i c a l gas uptake p l o t s f o r the hydrogenation of acrylamide c a t a l y s e d by the Ru ( I I ) i n 3 M HC1 at 80°; i n the absence of Ru ( I I ) , there was no measurable gas uptake. The r a t e s were e s s e n t i a l l y l i n e a r f o r long periods>and t h i s constant r a t e o f uptake was measured f o r experiments i n which the c o n c e n t r a t i o n of Ru ( I I ) , / Table X Temperature Dependence of k1 and k 2 A - l o f t n e R u (II)-Acrylamide System at 3.0 M HCI. ( [ R u 1 1 ] = 1 x 10" 3 M.) Temperature, °C k 1 x 10 2, s e c " 1 k 2 A _ l 3 M 35 0. .71 3.03 40 1. .25 3.44 45 1. .70 4.77 J I 1— 0 5 10 15 20 I M"1 [CH2CHC0NH2] ' Figure 26. T y p i c a l P l o t of ~ vs -J-Q.; CKCONH 1 a t 3 5 ° 5 3 M H C 1 -1.8 -o \ -1.9 - N O -2.0 -2.1 1 i o \ 1 3.15 3.20 3.25 10 /T°, K _ 1 Figure 27. Arrhenius P l o t of k± f o r Ru.(II)-Acrylamide System ( [ R u 1 1 ] = 1 x 10"3M, 3 M HCI) 65 3.00 (M O 0 ) •p (M 2.5 2.0 1.5 1.0 0.5 500 1000 1500 2000 Time, sec Figure 28. T y p i c a l Rate P l o t f o r the Ru ( I I ) Catalysed Hydrogenation o f Acrylamide i n 3 M HC1, 80°C. ([Ru H]=0.72 x 10~2M, [CH2CHC0NH2]=6 x 10~ 2M, H 2 pressure = 450 mm of Hg.) 66 acrylamide and H 2 were varied (Table XI). The rate of reaction was independent of the concentration of the acrylamide provided that the lavter was sufficiently high so that complexing of the Ru (II) was substantially complete. The rates f e l l off toward the end of the reaction; an experiment •continued to the end point showed that the total hydrogen taken up accounted for complete reduction of acrylamide to propionamide (see below) and the final solution was again blue. Generally, the kinetic measurements were performed in the range of quite high acrylamide concentration so that rate was independent of the latter. It was found that the rate of reaction was f i r s t order in hydrogen (Figure 29) and in the Ru (II) concentration (Figure 30). Hence, the rate law can be expressed as -d[H 2]/dt = k[H 2][Ru 1 1] (45) and values of k are given in Table XI. At 80°, in 3 M HC1, the average value of k in this region of solution • composition was ^ 7.2 M _ 1sec - 1. The activation parameters determined from the temperature dependence of k over the range 60°-80° (Table XII) were: AH* ^ 10 kcal and A S * ^ -26 e.u. Figure (31). An experiment (Ru 1 1 = 0.05 M, acrylamide = 1.5 M, 1 atmosphere pressure of H2) was carried out to isolate the hydrogenation product. After a reaction period of 12 hours, the uptake of hydrogen was quite small. The organic product was obtained from the reaction solution by ether extraction. The yield was approximately 20% of the olefin used. The product, propion-amide, was analysed by I.R. spectrum, which showed peaks at 2900, 2800, 1650, 1425 cm-1, and 'H N.M.R. spectrum: t r i p l e t at 8.8 x, quartet at 7.6 x, 67 Table XI E f f e c t of V a r i a t i o n o f Ru ( I I ) and Acrylamide Concentrations, Hydrojen Pressure i n the Hydrogenation of Acrylamide at 80°C, 3 M HCI. [ R u » ] x 10 2,M [CH2CHC0NH2] x 10 2,M H 2 Pressure, mm [H 2] x 10h ,M Rate o f H 2 Uptake x 10 5,M.sec _ 1 M _ 1.sec 0.18 6.0 450 3.60 0.46 7.15 0.36 6.0 450 3.60 1.05 8.18 0.72 6.0 450 3.60 1.69 6.58 0.26 6.0 450 3.60 0.74 7.82 0.26 6.0 302 2.40 0.45 7.10 0.26 6.0 106 0.86 0.14 6.40 0.18 3.0 450 3.60 0.46 7.12 0.18 12.0 450 3.60 0.46 7.21 Table XII Temperature Dependence of Rate Constant i n the Hydrogenation o f 6.0 x l O " 2 M Acrylamide. ( [ R u H ] = 1.78 x 10" 3 M, 3 M HCI) Temperature, °C k, M" ' - 1sec 1 80 7. .15 70 4. .69 60 2. .76 70 doublet at 3.7 T . . ( i i ) Mechanism The k i n e t i c r e s u l t s and observation are very s i m i l a r t o those reported f o r the Ru ( I I ) c a t a l y s e d hydrogenation o f maleic a c i d i n 3 M HCI s o l u t i o n s and presumably the same p o s t u l a t e d mechanism a p p l i e s : H Ru — H iT H s c . H / I +H 1 / Ru -C / \ H C0NH2 (slow) k H H \ / H C = C y \ C0NH2 H f a s t C H C0NH2 - Ru — + C H C \ C0NH2 H +H -Ru^i1 ! C O N H , H H H . 1 / C-) / -Ru — C y \ / \ H C0NH2 • H H Scheme I I I This c l e a r l y accounts f o r the observed r a t e law and the l i n e a r hydrogenation r a t e s . The sequence of steps i s as f o l l o w s : (1) Formation of the Ru ( I I ) - o l e f i n n-complex, which i s s u f f i c i e n t l y r a p i d at 80° (see s e c t i o n A), as compared to the hydrogenation r e a c t i o n that e q u i l i b r a t i o n i s e f f e c t i v e l y achieved. (2) Rate determining h e t e r o l y t i c s p l i t t i n g o f H 2 by the Ru 1 1-acrylamide complex with the formation o f a metal-hydride complex. This seems to be a 71 common feature o f the mechanisms of many homogeneously c a t a l y s e d hydrogena-' « . • • « . ! , * j 1,8,9,12,14 t i o n r e a c t i o n s thus f a r examined. (3) The metal-hydride -rr-complex rearranges t o form a o - a l k y l complex by i n s e r t i o n o f the o l e f i n i n t o the metal-hydride bond. The term " i n s e r t i o n " i s used i n the broader sense, i m p l y i n g the entry o f an unsaturated molecule i n t o a me t a l - l i g a n d bond. The i n s e r t i o n r e a c t i o n i s f a i r l y general and extends to systems i n v o l v i n g the a d d i t i o n o f l i g a n d atoms other than hydrogen (e.g. carbon and oxygen c o n t a i n i n g groups) and to unsaturated molecules other than o l e f i n s (e.g. CO, acetylene, dienes, etc.) (4) The ruthenium a-complex i s then decomposed by a proton to the sat u r a t e d organic product with the l i b e r a t i o n o f Ru ( I I ) which again complexes r a p i d l y w i t h f u r t h e r o l e f i n . In the maleic a c i d system, deuterium isotope experiments showed th a t the hydrogen a d d i t i o n was c i s and that both hydrogen atoms o r i g i n a t e d from the s o l v e n t . Such s t u d i e s have not been c a r r i e d out i n the present work but i t seems l i k e l y that the acrylamide system would show s i m i l a r r e s u l t s . CHAPTER VI GENERAL DISCUSSION AND RE COMMENDATIONS FOR FUTURE WORK A. C a t a l y t i c Hydration The present s t u d i e s on the Ru ( I I ) - d i f l u o r o e t h y l e n e and f l u o r o e t h y l e n e systems have given r i s e to k i n e t i c r e s u l t s more complicated than was a n t i c i p a t e d , t h i s being due t o the subsequent rearrangement of the i n i t i a l l y formed ir-complex. The k i n e t i c s o f the gas uptake can be reasonably explained i n terms o f a c a t a l y t i c h y d r a t i o n through the intermediate u-complex. The hydr a t i o n products were a c e t i c a c i d from the d i f l u o r o e t h y l e n e , and acetalde-hyde from the f l u o r o e t h y l e n e . A f t e r formation o f the Tr-complex, the f o l l o w -i n g r e a c t i o n scheme seems p l a u s i b l e : F H(F) Ru C / \ H H OH -> — Ru F H(F) C / V H H (I) + H k 3 slow Ru ""C / \ H H H(F) — Ru-+ H 3C / I OH / C — F H(F) H HO F \ ' ^ H ( F ) 1 - '(-) — Ru C L J ' \ / \ H H ( I I I ) ( I I ) Scheme IV 73 ( I I I ) would be unstable and be expected to decompose to acetaldehyde or the a c e t i c a c i d : OH OH 0 H 3C-C-F - 2 > H3C-C-OH *-_H3C-C + H 20 (46) H H H +HF OH OH 0 ' 2HoO / ^ or HoC-C-F - 2 > H 3C-C-OH > H 3C-C + H 20 (47) F OH OH +2HF The steps i n v o l v e d i n the production o f species (I) t o ( I I I ) are o f a ra t h e r general type t h a t have been p o s t u l a t e d t o occur f o r a whole range of c a t a l y t i c r e a c t i o n s i n c l u d i n g hydrogenation, (see Chapter I , B) polymeriza-t i o n , o x i d a t i o n , and i s o m e r i z a t i o n o f o l e f i n s , and the hyd r a t i o n o f 2 3 73 acetylenes. ' ' Each system at some stage i n v o l v e s the " i n s e r t i o n " of the unsaturated compound between a metal l i g a n d bond. In the scheme above, the f l u o r o e t h y l e n e i s i n s e r t e d between the Ru-OH bond to produce the a a l k y l i ntermediate ( I I ) from an i n i t i a l ir-complex (I) . These r e a c t i o n s are most 74 l i k e l y l i g a n d m i g r a t i o n r e a c t i o n s although the term " i n s e r t i o n " r e a c t i o n i s i n common usage. In the present system, there w i l l be a n u c l e o p h i l i c attack by the coordinated OH at the C atom attached to the f l u o r i n e atom(s). The a intermediate ( I I ) i s f i n a l l y decomposed by e l e c t r o p h i l i c attack by a proton at. the C atom attached t o the metal; t h i s regenerates the hydrated product and Ru C l n _ ^ species which reacts r a p i d l y with f u r t h e r o l e f i n . The r e a c t i o n scheme i s s i m i l a r to one reported f o r the Ru ( I I I ) and 32 Ru ( I I ) c a t a l y s e d h y d r a t i o n of acetylenes where i t seemed that the water 74 molecule necessary for hydration was coordinated to the metal; in this system, the rate determining step involved formation of the ir-complex which then rapidly decomposed. In the present system, the i n i t i a l slower reaction involves Tr-complex formation but the subsequent decomposition is not rapid; the Ru (II) iT-complex persists in solution and i t s subsequent decomposition must involve a slow stage, determining the rate constant, k 3. In the Pd (II) 75 oxidation of ethylene, the i n i t i a l reaction scheme proposed is similar to that shown here; the rate determining step is thought to be the conversion of a ir-ethylene complex to the a S-hydroxy ethyl complex. A similar slow conversion could be involved here. It is interesting to note that the activation parameters for the k 3 step for both fluoroethylene systems are very similar to those reported for the Pd (II) system in perchloric acid solutions: AH* kcal 1,1 Difluoroethylene 21 Fluoroethylene 21 Pd/CzHi^system 19.8 The addition of water to the more reactive olefins, catalysed by acids 76 through carbonium ion intermediates, is well known and is the principal industrial source of lower alcohols. Catalytic hydration of olefin by transition metal complexes does not seem to have been reported before, 77 although Kemmitt and Nichols recently indicated that tetrafluoroethylene coordinated to Rh (I) might be hydrolysed by water An interesting and relevant report is one recently describing the synthesis of carboxylic acids from 1,1 dichloroethylene by reaction with AS e . u . -9 -5 -8.7 Reference Present work Present work 75 75 78 a l c o h o l s which can r e a d i l y give carbonium ions: R 2 _ cC +) + CH 2=CC1 2 • R 2 —C — CH 2 — I | \ R 3 R 3 C 1 H^O^/H^ R 2 _ c -CH 2-C R ; f (48) \ OH I t i s o f i n t e r e s t t o note the s i m i l a r i t y of the intermediate w i t h an i n t e r -mediate such as ( I I ) i n the present ruthenium c a t a l y s e d systems. A common feature f o r the c a t a l y t i c h y d r a t i o n r e a c t i o n s of o l e f i n s or acetylenes i s t h a t the rate tends t o f a l l o f f g r a d u a l l y a f t e r reaching the l i n e a r region and t h i s appears to be due t o the formation of ruthenium ( I I ) carbonyl species which are much l e s s c a t a l y t i c a l l y a c t i v e . The o r i g i n of the formation o f these ruthenium carbonyl complexes during the h y d r a t i o n r e a c t i o n s - 33 i s not known w i t h c e r t a i n t y . In the c a t a l y t i c h y d r a t i o n of acetylenes', the p r i n c i p a l h y d r a t i o n products were r u l e d out as precursors as they d i d not react w i t h R u ( I I I ) or Ru ( I I ) and the rates o f hy d r a t i o n were found to be unaff e c t e d by the a d d i t i o n of these products i n large excess. The study o f decarbonylation o f organic oxygen c o n t a i n i n g compounds ( a l c o h o l s , aldehydes, e t h e r s , etc.) by platinum metal complexes g e n e r a l l y i s c u r r e n t l y 36 79 a very a c t i v e research f i e l d and some mechanistic work has been done ' ; i t seems l i k e l y t hat such r e a c t i o n s go through unstable a c y l or aldehyde i n t e r m e d i a t e s . 76 There was no evidence f o r decomposition of the Ru ( I I ) - a c r y l a m i d e complex to h y d r a t i o n products; also no h y d r a t i o n had been observed f o r the other Ru ( I I ) complexes with ethylene, maleic, fumaric or a c r y l i c a c i d s * . The phenomenon i s thus f a r unique f o r a f l u o r i n e s u b s t i t u t e d ethylene; t h i s could r e f l e c t the very high e l e c t r o n e g a t i v i t y o f the F atom with the r e s u l t i n g nucleo-p h i l i c attack by OH i n the IT-complex (I) B. C a t a l y t i c Hydrogenation Acrylamide was c a t a l y t i c a l l y reduced by H 2 and the mechanism i s undoubt-edly the same as that p o s t u l a t e d f o r the Ru ( I I ) c a t a l y s e d hydrogenation of the o l e f i n i c unsaturated c a r b o x y l i c acids (Chapter I , B); the scheme i s s i m i l a r t o that shown i n (A) above f o r the h y d r a t i o n but w i t h OH replaced by H . The values of the rate constants and a c t i v a t i o n parameters f o r the r e a c t i o n o f H 2 w i t h the Ru ( I I ) - o l e f i n complexes, (the r a t e determining step) are summarized below, together w i t h the determined s t a b i l i t y constants of the complexes: O l e f i n k ( M _ 1 s e c _ 1 ) AH*(Kcal) AS*(e.u.) K (M~ 1) Reference maleic a c i d 2.3 14 -17 ^5 x 10 3 1 fumaric a c i d 3.6 17 - 8 ^2 x 10 3 1 acrylamide 7.2 10 -26 ^6 x 10 3 Present work (Rate data at 80°, K determined at 25°) No c l e a r trends emerge from t h i s l i m i t e d data but i t would be of i n t e r e s t to extend the s e r i e s u s i n g f u r t h e r s u b s t i t u t e d (and water s o l u b l e ) ethylenes. The ethylenes s u c c e s s f u l l y hydrogenated are a l l " a c t i v a t e d " i n t h a t they contain e l e c t r o n withdrawing groups adjacent t o the o l e f i n i c bond, 77 presumably g i v i n g e a s i e r n u c l e o p h i l i c attack by the hydride i o n . No evia°<nce was obtained f o r any c a t a l y t i c hydrogenation of the d i f l u o r o -ethylene N o r f l u o r o e t h y l e n e through the Ru ( I I ) - o l e f i n complex formed, and the Ru ( I I ) - o l e f i n complex was not reduced by molecular hydrogen to ruthenium metal. Hence, the Ru ( I I ) - d i f l u o r o e t h y l e n e and Ru ( I I ) - f l u o r o e t h y l e n e systems show somewhat intermediate behaviour to that observed f o r the Ru ( I I ) - a c r y l a m i d e system where the o l e f i n was homogeneously reduced, and the Ru ( I I ) - e t h y l e n e system where reduction to metal occurred. The f l u o r o -o l e f i n s thus s t a b i l i z e the Ru ( I I ) s u f f i c i e n t l y to prevent reduction t o the metal. The apparent n o n - a c t i v a t i o n of the o l e f i n i c bond f o r hydrogenation i s probably due to the f a c t that the hydrogenation step cannot compete. e f f e c t i v e l y w i t h the h y d r a t i o n process, i . e . the n u c l e o p h i l i c attack by OH r a t h e r than H predominates. Thus no d e f i n i t e conclusions regarding the a c t i v a t i o n by f l u o r o groups o f the o l e f i n i c bond f o r c a t a l y t i c hydrogenation can be drawn. Studies w i t h chorine s u b s t i t u t e d ethylenes would seem worthwhile. C. K i n e t i c s of Formation of the Ru ( I I ) - Q l e f i n Complexes The mechanism proposed f o r the complexing of the chlororuthenate ( I I ) w i t h d i f l u o r o e t h y l e n e , f l u o r o e t h y l e n e and acrylamide i s suggested by the k i n e t i c s t o be the same as that proposed by other workers f o r the complexing 49 w i t h ethylene i t s e l f . k, RuCl • RuCl . + CI (49) n <— n-1 1 k - l ko R u C l n + o l e f i n — > complex (50) The data f o r these Ru ( I I ) systems are summarized i n Table X I I I , together 78 Table X I I I + + Comparison of k l 5 k 2 / k _ 1 , AH and AS f o r a S e r i e s of Reactions Between Various O l e f i n s and Chlororuthenate ( I I ) . O l e f i n k'i x 1 0 3 s e c - 1 A H ^ K c a l As/e.u. k 2/k_! • Reference 1,1 d i f l u o r o e t h y l e n e 0.3 29 +13 9.7 x 10 3 present work f l u o r o e t h y l e n e ^13.0 "o28 M.2 x 10 3 present work acrylamide 7.1 17 -12 3 present work ethylene 3.4 23 - 4 6.5 x 10 3 (49) maleic a c i d 6.2 13.3 -29.2 27.8 (80) formic a c i d 1.0 23.5 - 5 33.0 (41) (measured i n 3 M HCI at 60°, except f o r acrylamide at 35°) 79 w i t h data f o r the maleic a c i d system, p r e s e n t l y being s t u d i e d i n t h i s 80 l a b o r a t o r y , and f o r a r e a c t i o n w i t h f o i m i c a c i d thought to occur by the T, • 41 same mechanism. On the simple scheme represented by equations 49 and 50, k 1 should be independent of the type and concentration of the o l e f i n s used while kz/k.^ r e f l e c t s the r e l a t i v e r e a c t i v i t i e s of the o l e f i n and Cl toward the Ru**Cl , n-1 i n t e r m e d i a t e . There are minor d i f f e r e n c e s i n concentrations of a c i d i t y , c h l o r i d e and added t i t a n o u s among these systems, but these v a r i a t i o n s are u n l i k e l y t o a f f e c t the r a t e constant to the degree of v a r i a t i o n shown i n the Table X I I I . The d i f f i c u l t y a r i s e s as t o what i s meant e x a c t l y by the RuCl term: s p e c t r a s t u d i e s have shown that the c h l o r i d e concentration does n a f f e c t the d i s t r i b u t i o n o f the chlororuthenate (II) species and there i s undoubtedly a mixture o f such•complexes i n i t i a l l y present. The blue peak at 680 my has been a t t r i b u t e d t o the RuCli+2 species which could be t e t r a -62 h e d r a l ; s u b s t i t u t i o n r e a c t i o n s of t e t r a h e d r a l species have been l i t t l e 81 s t u d i e d but an SXT1 d i s s o c i a t i o n from such a species seems r a t h e r u n l i k e l y . The maleic a c i d , formic a c i d and acrylamide systems have been followed by l o s s of the absorption at 680 my; the other three systems were st u d i e s by gas uptake techniques. C l e a r l y , the two techniques could give d i f f e r e n t r a t e data; a species not absorbing g r e a t l y at 680 my could s t i l l show r e a c t i v i t y toward the o l e f i n . The e q u i l i b r i a between the various chlororuthenate ( I I ) species would have to be e l u c i d a t e d before a more meaningful comparison of the k i values (and c h l o r i d e dependence) could be made. Because of these c o m p l i c a t i o n s , the observed ra t e constant k', and the derived r a t e constant k i must be considered as composite constants which may r e f l e c t c o n t r i b u t i o n s from more than one ruthenium ( I I ) complex. 80 The d i f l u o r o e t h y l e n e system does, however, seem anomalously d i f f e r e n t wi 82 i t s very slow, complex formation. 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