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Soluble and polymer-bound palladium and platinum complexes of ferrocene derivatives Han, Nam Fong 1986

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SOLUBLE AND POLYMER-BOUND PALLADIUM AND PLATINUM COMPLEXES OF FERROCENE DERIVATIVES By NAM FONG HAN B.Sc.  (Hons), University of Manitoba, 1982.  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES Department of Chemistry  We accept this thesis as conforming to the required standard  The University of British Columbia November (c)  1986  Nam Fong Han, 1986  In  presenting  degree freely  at  this  the  available  copying  of  department publication  of  in  partial  fulfilment  of  the  University  of  British  Columbia,  I  agree  for  this or  thesis  reference  thesis by  this  for  his thesis  and  study.  scholarly  or for  her  financial  Department  V6T Date  DE-6G/81)  Columbia  1Y3  (A-K. VAwdk,  further  purposes  Wfr.  gain  shall  that  agree  may  representatives.  permission.  T h e U n i v e r s i t y o f British 1956 Main Mall Vancouver, Canada  I  requirements  It not  be is  that  the  Library  permission  granted  by  understood be  for  allowed  an  advanced  shall for  the that  without  head  make  extensive of  copying my  it  my or  written  ii  ABSTRACT The preparation, characterization, and catalytic properties of some soluble and polymer-bound palladium and platinum complexes of ferrocene derivatives are described. Special emphasis has been placed on studies of the mixed "hard-soft" ligands such as PPFA and ISOPFA.  X  H, Y = Z = P P h  X  CHMeNMe , Y = P P h , Z = H  PPFA  X  CHMeNMe , Y -= P ( i - P r ) , Z = H  ISOPFA  X  CHMeNMe , Y = Z = P P h  BPPFA  2  BPPF  2  2  2  2  2  £  The soluble complexes (L-L)MC1 (L-L = BPPF, PPFA, ISOPFA, BPPFA; 2  M = Pd, Pt) and [(L-L)PdS ][C10 ] (L-L = BPPF, PPFA; S = DMF, py) have 2  4  2  been characterized by microanalyses, NMR and IR spectroscopic techniques. The cationic palladium(II) complex [(L-L)PdS ][C10 ] (L-L = PPFA, 2  4  2  S = DMF) is an effective catalyst precursor for the hydrogenation of simple olefins at 30°C and 1 atm pressure. The rate of styrene hydrogenation depends on the substrate concentration, catalyst concentration and the solvent. The results are consistent with a homogeneous catalytic system.  111  Platlnum(II) complexes ( L - L ) P t C l (L-L - (S.R)-PPFA, (S.R)2  ISOPFA) are e f f e c t i v e c a t a l y s t p r e c u r s o r s f o r the h y d r o s l l y l a t l o n o f aromatic ketones w i t h P h S 1 H . The complexes w i t h mixed " h a r d - s o f t " 2  2  U g a n d s are b e t t e r c a t a l y s t p r e c u r s o r s than those w i t h d l ( t e r t i a r y phosphlne) U g a n d s . Under the same c o n d i t i o n s the h y d r o s l l y l a t l o n o f f e r r o c e n y l ketones r e s u l t s 1n f u r t h e r r e d u c t i o n and a f f o r d s mainly the a l k y l f e r r o c e n e products. The s t a b l e carbonlum Ion FcC^HCH^ (Fc = Fe(C H )(C H )-) 5  5  5  4  1s reduced by P h S 1 H to FcCHgCHj 1n a thermal r e a c t i o n 2  2  which 1s c a t a l y z e d by the complex ( P P F A ) P t C l . The r e a c t i o n o f P h S 1 H 2  2  2  w i t h ( L - L ) P t C l (L-L « PPFA, ISOPFA) y i e l d s a s t a b l e platlnum(IV) 2  h y d r i d e , which e l i m i n a t e s Ph S1HCl 1n s o l u t i o n t o a f f o r d ( L - L ) P t H C l . 2  The m e c h a n i s t i c I m p l i c a t i o n s o f these o b s e r v a t i o n s a r e d i s c u s s e d . Polymers f u n c t i o n a l 1 z e d w i t h f e r r o c e n e and f e r r o c e n e d e r i v a t i v e s have been prepared. Mossbauer s p e c t r o s c o p i c techniques and microanalyses are used to c h a r a c t e r i z e these polymers and t h e i r p a l l a d i u m and platinum complexes. In a number o f cases these r e s u l t s are confirmed by the c r o s s 13  polarlzatlon/magic-angle spinning  C NMR s p e c t r o s c o p i c technique.  The palladium(II) and platlnum(II) d e r i v a t i v e s o f the f e r r o c e n y l amlne and -phosphlne c o n t a i n i n g polymers a r e e f f e c t i v e c a t a l y s t s f o r the hydrogenatlon and h y d r o s l l y l a t l o n o f o l e f i n s . A l l the c a t a l y s t s can be e a s i l y separated from the r e a c t i o n mixture and can be r e c y c l e d w i t h no l o s s o f a c t i v i t y . The pronounced e f f e c t o f the a t t a c h e d U g a n d 1n the p a l l a d i u m based polymers I n d i c a t e s t h a t f r e e metal 1s not Inv o l v e d . However, 1n the case o f platinum based c a t a l y s t s , I t 1s l i k e l y t h a t r e d u c t i o n t o platinum metal takes p l a c e .  iv  TABLE OF CONTENTS Page TITLE  1  ABSTRACT  i i  TABLE OF CONTENTS  iv  LIST OF TABLES  ix  LIST OF FIGURES  xii  ABBREVIATIONS  xiv  ACKNOWLEDGEMENTS  xvi  CHAPTER 1  INTRODUCTION  1  1.1  GENERAL ASPECTS OF FERROCENE DERIVATIVES  1  1.2  FERROCENYLPHOSPHIMES IN HOMOGENEOUS CATALYSIS  8  1.2.1  Hydrogenation  8  1.2.2  Hydrosilylation  11  1.2.3 G r i g n a r d C r o s s - c o u p l i n g  17  1.2.4  22  Other C a t a l y t i c Reactions  1.3 HOMOGENEOUS VERSUS HETEROGENEOUS CATALYSTS  24  1.4 GOALS OF THE PRESENT STUDY  27  CHAPTER 2 2.1  EXPERIMENTAL SECTION  28  GENERAL  28  2.1.1  Instrumentation  29  2.1.2  Hydrogenation Experiments  31  2.1.3  H y d r o s i l y l a t i o n Experiments  31  V  Page 2.2  SYNTHESES OF STARTING MATERIALS  33  2.2.1  Chlorodiisopropylphosphine  33  2.2.2  Di phenyl si lane  34  2.2.3  Acetyl ferrocene  34  2.2.4  Ferrocenylethanol  34  2.2.5  Ferrocenylethyl carbonium Tetrafluoroborate  35  2.2.6  Dilithioferrocene-TMEDA Adduct  35  2.2.7  U,H- Dimethyl ami nocyanomethylferrocene  35  2.2.8  N_, N-Dimethyl ami noethyl ferrocene, FA  36  2.2.9  (S)- and (R)-N,N-Dimethyl aminoethylferrocene,  2.3  (S)- and (R)-FA  36  2.2.10 Polystyrene Type Polymers  37  SYNTHESES OF FERROCENYLPHOSPHINES  38  2.3.1  1,1'-Bis(diphenylphosphino)ferrocene, BPPF  2.3.2  2- Di phenylphosphi no-1-(N,N-dimethy1aminoethyl)ferrocene,  2.3.3  PPFA  39  2- Diisopropylphosphino-l-(t^,N-dimethylaminoethyl)ferrocene,  2.3.4  38  ISOPFA  39  1' ,2-Bis(diphenylphosphino)-l-(N,N-dimethylaminoethyl)ferrocene,  BPPFA  ......  40  vi  Page 2.4  SYNTHESES OF PALLADIUM AND PLATINUM COMPLEXES OF FERROCENYLPHOSPHINES 2.4.1  Palladium Complexes (L-L)PdCl  2.4.2  Cationic Palladium Complexes [(L-L)PdS ][C10 ] 2  2.5  40  4  40  2  41  2  2.4.3  Platinum Complexes (L-L)PtCl  2.4.4  Platinum Complex (L-L)PtHCl  42  2  43  SYNTHESES OF POLYMER-BOUND FERROCENE DERIVATIVES. 2.5.1  Reaction of Lithioferrocene with BioBeads B, Polymer-I  2.5.2  44  Reaction of Lithioferrocene with Aldehydic Resin, Polymer-II  2.5.3  2.5.5  ....  45  Adduct with Aldehydic Resin, Polymer-IV . .  46  Reaction of Dilithioferrocene-TMEDA  Reaction of Lithium Derivative of FA with Bio-Beads B, Polymer-V  2.5.6  46  Reaction of Lithium Derivative of BPPF with Aldehydic Resin, Polymer-VII  2.5.8  46  Reaction of Lithium Derivative of FA with Aldehydic Resin, Polymer-VI  2.5.7  44  Reaction of Dilithioferrocene-TMEDA Adduct with Bio-Beads A, Polymer-III  2.5.4  44  47  Reaction of Lithium Derivative of PPFA with Aldehydic Resin, Polymer-VIII  47  vii  Page 2.5.9  Reaction o f L i t h i u m D e r i v a t i v e o f (S,R)PPFA w i t h A l d e h y d i c R e s i n , P o l y m e r - V I I I *  2.6  CHAPTER 3  ..  48  SYNTHESES OF PALLADIUM AND PLATINUM COMPLEXES OF POLYMER-BOUND FERROCENE DERIVATIVES  48  2.6.1  P a l l a d i u m Complexes  48  2.6.2  P l a t i n u m Complexes  49  CATIONIC PALLADIUM(II) COMPLEXES OF FERROCENYLPHOSPHINES  50  3.1  INTRODUCTION  50  3.2  RESULTS AND DISCUSSION  51  3.2.1  S y n t h e s i s and C h a r a c t e r i z a t i o n  51  3.2.2  Hydrogenation  62  3.3  Studies  SUMMARY  72  PLATINUM(II) COMPLEXES OF FERROCENYLPHOSPHINES  73  4.1  INTRODUCTION  73  4.2  RESULTS AND DISCUSSION  75  4.2.1  S y n t h e s i s and C h a r a c t e r i z a t i o n  75  4.2.2  Hydrosilylation Studies  84  CHAPTER 4  4.3 CHAPTER 5  SUMMARY  103  POLYMER-BOUND FERROCENE DERIVATIVES AND THEIR PALLADIUM AND PLATINUM COMPLEXES  105  5.1  INTRODUCTION  105  5.2  RESULTS AND DISCUSSION  107  5.2.1  S y n t h e s i s and C h a r a c t e r i z a t i o n  107  5.2.2  Hydrogenation  130  Studies  vi i i  Page  5.3 CHAPTER 6 6.1  5.2.3 H y d r o s i l y l a t i o n S t u d i e s  139  SUMMARY  154  GENERAL CONCLUSIONS AND PERSPECTIVES  155  SOLUBLE PALLADIUM(II) AND PLATINUM(II) COMPLEXES OF FERROCENYLPHOSPHINES  6.2  POLYMER-BOUND PALLADIUM AND PLATINUM COMPLEXES OF FERROCENE DERIVATIVES  REFERENCES  155  156 158  1x  LIST OF TABLES Table  Page  3.1  M i c r o a n a l y t i c a l r e s u l t s and m e l t i n g p o i n t s f o r (L-L) and ( L - L ) P d C l H and ^POH  53  2  3.2  }  } NMR data f o r (L-L) and ( L - L ) P d C l  3.3  M i c r o a n a l y t i c a l r e s u l t s and m e l t i n g p o i n t s f o r  ..  2  the c a t i o n i c p a l l a d i u m complexes 3.4  ^  and  3 1  60  P { H } NMR data f o r the c a t i o n i c 1  p a l l a d i u m complexes 3.5  61  C a t a l y t i c hydrogenation o f o l e f i n s c a t a l y z e d by c a t i o n i c p a l l a d i u m complexes I-V  -  3.6  63  E f f e c t o f EtgN i n the hydrogenation o f s t y r e n e c a t a l y z e d by complex IV  4.1  4.3  }  H and ^POH  76  2  } NMR data f o r ( L - L ) P t C l  H y d r o s i l y l a t i o n o f acetophenone (L-L)PtCl  4.4  Asymmetric h y d r o s i l y l a t i o n o f ketones with P h S i H 2  88  2  Ph SiH 2  c a t a l y z e d by ( ( S , R ) - P P F A ) P t C l  2  89  2  Asymmetric h y d r o s i l y l a t i o n o f butyrophenone 2  2  2  Asymmetric h y d r o s i l y l a t i o n o f ketones with  Ph SiH 4.7  c a t a l y z e d by 85  c a t a l y z e d by ( ( S , R ) - I S 0 P F A ) P t C l 4.6  77  2  2  c a t a l y z e d by ( ( S , R ) - P P F A ) P t C l 4.5  65  M i c r o a n a l y t i c a l r e s u l t s and m e l t i n g p o i n t s for (L-L)PtCl  4.2  54  2  with 90  M i c r o a n a l y t i c a l r e s u l t s and ^H NMR data f o r FcCH,R and FcCH(0H)R  92  X  Table 4.8  Page Microanalytical results for platinum hydride complexes  4.9  96  Physical and NMR data for platinum hydride complexes  5.1  99  Mossbauer parameters and microanalytical results for polymer-bound ferrocene derivatives  5.2  Mossbauer parameters for some ferrocene compounds  5.3  Mossbauer parameters and microanalytical results  116 ..  117  for palladium and platinum complexes of polymerbound ferrocene derivatives 5.4  Hydrogenation of olefins in benzene catalyzed by polymer-VIII-Pd  5.5  132  Hydrogenation of styrene catalyzed by polymerVHI-Pd  5.6  128  133  Hydrogenation of olefins catalyzed by polymerbound palladium complexes  134  5.7  Hydrogenation of 1-hexene in MeOH  135  5.8  Hydrogenation of olefins catalyzed by polymerbound platinum complexes  5.9  Hydrogenation of styrene catalyzed by polymerbound platinum complexes  5.10  137  138  Hydrosilylation of styrene with HSiCl^ catalyzed by polymer-bound palladium complexes  141  xi  Table 5.11  Page Microanalytical results for polymer-VIII and its palladium derivatives  143  5.12  Asymmetric hydrosilylation of styrene with HSiClg  5.13  Hydrosilylation of 1-hexene with HSiCl  5.14  Hydrosilylation of styrene with HSiClg catalyzed by  3  polymer-bound platinum complexes 5.15  145 148  149  Hydrosilylation of olefins with HSiClg catalyzed by soluble platinum complexes (L-LjPtC^  5.16  ..  151  Hydrosilylation of ketones with PhgSiHg catalyzed by polymer-VIII*-Pt  152  xii  LIST OF FIGURES Figure 1.1  Page Preparative routes to the chiral ferrocenylphosphine ligands  1.2  4  Two possible catalytic hydrogenation cycles for the dihydride catalysts: A, hydride route; B, olefin route  1.3  12  The proposed mechanism of hydrosilylation of olefins catalyzed by platinum complexes  1.4  15  The proposed mechanism of hydrosilylation of ketones catalyzed by rhodium complexes  1.5  16  Catalytic process of cross-coupling reaction catalyzed by nickel complexes  1.6  19  Proposed intermediate in Grignard cross-coupling reaction  21  3.1  32.3 MHz P { H } NMR spectrum of (BPPF)PdCl  3.2  32.3 MHz P { H } NMR spectrum of (BPPFA)PdCl  3.3  32.3 MHz P { H } NMR spectrum of (PPFA)PdCl , A;  31  56  1  2  31  57  ]  2  31  1  2  (IS0PFA)PdCl , B  58  2  3.4  Hydrogenation uptake curves for the hydrogenation of styrene catalyzed by cationic palladium complex IV at 30°C and 1 atm total pressure  3.5  67  Dependence of maximum hydrogenation rate on [styrene]  3.6  Dependence of maximum hydrogenation rate on [Pd]  68 ...  69  xiii  ure 3.7  Page Hydrogenation uptake curves for the hydrogenation of styrene; A, in the absence of Hg; B, same conditions as A with Hg added  70  4.1  121.4 MHz ^ P ^ H } NMR spectrum of (BPPF)PtCl  4.2  121.4 MHz  3 1  4.3  121.4 MHz  3 1  4.4  121.4 MHz  3 1  P { H } NMR spectrum of ((S,R)-PPFA)PtCl ]  2  2  80 81  P { H } NMR spectrum of ]  82  2  The crystal structure of ((S,R)-IS0PFA)PtCl  4.6  400 MHz ^H NMR spectrum (hydride region) of  2  (PPFA)PtCl (H)(SiHPh ) in CD^Cl solution 2  2  '83  97  2  NMR spectrum (hydride region) of  (IS0PFA)PtCl (H)(SiHPh ) in CD C1 solution 2  4.8  79  ]  4.5  400 MHz  ....  P { H } NMR spectrum of ((S,R)-BPPFA)PtCl  ((S,R)-IS0PFA)PtCl  4.7  2  2  2  100  2  Proposed mechanism for the hydrosilylation of ketones with Ph SiH catalyzed by (L-L)PtCl 2  2  2  102  5.1  Mossbauer spectrum of polymer-I  Ill  5.2  Mossbauer spectrum of BPPF  112  5.3  Mossbauer spectrum of PPFA  113  5.4  Mossbauer spectrum of IS0PFA  114  5.5  Mossbauer spectrum of BPPFA  115  5.6  1 3  C CP/MAS NMR spectrum of ferrocene, A; FA, B  118  5.7  1 3  C CP/MAS NMR spectrum of polymer-I  119  xiv ABBREVIATIONS  atm  atmosphere  bd  broad doublet  bm  broad m u l t i p l e t  BMPP  benzyl methyl phenylphosphine  bp  boiling point  BPPF  1,1'-bi s ( d i p h e n y l p h o s p h i n o ) f e r r o c e n e  BPPFA  1' ,2-bis(diphenylphosphino)-l-(f[,^-dimethylaminoethyl)ferrocene  bs  broad s i n g l e t  bt  broad t r i p l e t  Bu  butyl  cat  catalyst or catalyst precursor  COD  1,5-cyclooctadiene  CP  cross-polarization  DIOP  2,3-o-isopropylidene-2,3-dihydroxy-l,4-bis(diphenylphosphino)butane  DMF  N^N-dimethylformamide  DMSO  dimethyl s u l f o x i d e  dppe  bis(l,2-diphenylphosphino)ethane  e.e.  enantiomeric excess  Et  ethyl  FA  N_, N-d i methyl ami noethyl f e r r o c e n e  Fc GLC  Fe(C H )(C H )5  5  5  4  gas l i q u i d chromatography  XV  h  hour(s)  Hz  hertz  i-Pr  isopropyl  IR  infrared  ISOPFA  2-di i sopropylphosphi no-1-(N^N-dimethyl ami n o e t h y l ) f e r r o c e n e  m  multiplet  MAS  magic angle s p i n n i n g  MCPBA  m-chloroperbenzoic a c i d  Me  methyl  NBD  norbornadiene  n-Bu  n-butyl  NMR  n u c l e a r magnetic  Ph  phenyl  PPFA  2-diphenylphosphino-l-(N_,N-dimethylaminoethyl ) f e r r o c e n e  py  pyridine  q  quartet  s  singlet  t  triplet  t-Bu  tert-butyl  resonance  THF  tetrahydrofuran  TLC  thin layer  TMEDA  H»N»N.' ,N.'-tetramethylethylenediamine  TMS  chromatography  tetramethylsilane  xvi  ACKNOWLEDGEMENTS  I wish to express my s i n c e r e g r a t i t u d e to P r o f e s s o r W.R.  C u l l e n , my research s u p e r v i s o r , f o r h i s guidance and encouragement  during the course of t h i s work. I am much indebted to P r o f e s s o r s M.D.  Fryzuk, B.R. James and J.R. Sams f o r t h e i r suggestions and comments  on my work. I am very g r a t e f u l to the t e c h n i c a l s t a f f o f t h i s department, in p a r t i c u l a r Mr. P. Borda f o r h i s expert microanalyses, Dr. 0. Chan and h i s s t a f f members f o r a s s i s t a n c e during some NMR experiments,  and  Mrs. A. S a l l o s f o r r e c o r d i n g a l l the Mossbauer s p e c t r a . I a l s o want to thank a l l my l a b c o l l e a g u e s , i n p a r t i c u l a r Mr. C. Hampton, Mr. J . J . N i , Mr. E. Wickenheiser, Dr. I.R. B u t l e r and Mr. M.S.R. Cader f o r suggestions and a s s i s t a n c e during the p r e p a r a t i o n o f t h i s thes.is. My thanks are extended to the U n i v e r s i t y o f B r i t i s h Columbia and to the National Research Council of Canada f o r f i n a n c i a l  support.  To my parents and my w i f e , I express my g r e a t e s t thanks f o r t h e i r encouragement and u n f l a g g i n g f a i t h i n me and my work.  1  CHAPTER 1 INTRODUCTION  1.1  GENERAL ASPECTS OF FERROCENE DERIVATIVES  The discovery of ferrocene in 1951 [1], the first of the so-called "sandwich compounds", has played a major role in the development of transition metal organometallic chemistry.  There continues to be a large  number of papers and reviews published which are devoted to studies of ferrocene chemistry [2-6].  For example, an annual review of ferrocene in  1984 by Marr and Rockett [2] contains 211 references;  there are 233 and  199 references in the respective 1983 and 1982 reviews [3,4]. The observation that ferrocene behaves as an aromatic system [7] led to the preparation and investigation of many derivatives analogous to those of benzene [8].  In many ways, the chemistry of these two classes of  compounds is similar.  Thus, a number of potentially multidentate ligands  for use in metal complexes were prepared utilizing metalation reactions of ferrocene.  For example, the symmetrical l,l'-disubstituted ferrocenes 1_,  were synthesized by way of dilithiation of ferrocene followed by treatment of the product with halophosphine, haloarsine [9-11] or dialkyl disulfide [12].  2  l a E=P, R=Ph b E=P, R=t-Bu c E=P, R=i-Pr d E=P, R=Me e E=As, R-Me o r Ph f E=S, R=Me, i - P r , i - B u , Ph o r CH Ph £  Important differences between the chemistry of ferrocene derivatives and  benzenoid aromatic compounds arise when the stereochemistry of these  systems is considered. This is an area of great interest [13-17] due in part to the fact that ferrocene derivatives, 2, are chiral i f one ring bears two different substituents (X * Y) [13].  Thus these compounds are  optically active even if X and Y do not possess an asymmetric center. molecules are said to have a planar element of chirality [13,18,19].  Such The  preparation of these compounds is relatively easy, and provides access to a very wide variety of chiral ferrocene derivatives with either centers of chirality and/or planes of chirality [6,10,14,20-22].  Two descriptors for  configuration are necessary if both central and planar chirality are present [13-15].  In this thesis, the f i r s t descriptor "S", in compound  such as (S,R)-3_ refers to the configuration at the carbon atom of the -CHMeNMe group and the second "R", refers to the planar chirality. 2  3  An important event that instigated the efforts of several research groups [6,10,14,20-22] to study ferrocenylphosphines with planar chirality was a paper published by Ugi and coworkers in 1970 [15b].  These authors  reported that the optical resolution of N^N-dimethylaminoethylferrocene, FA, was particularly easy; both antipodes are obtained in high yield. Furthermore, the lithiation of the amine FA was found to proceed with high stereoselectivity as shown in Figure 1.1.  Thus by using the stereo-  selective lithiation of FA, chiral ferrocenylphosphines 4-5_ [6,10,20-23] were prepared.  A small amount of diastereomeric byproduct formed via the  minor lithio derivative, 3, was removed by simple recrystallization. When a diastereomeric product such as (R,R)-4a was required, it was prepared in quantity via the silylated ferrocene derivative, equation 1.1.  Ferrocenyl-  phosphines such as 7_ (or 4a with -CHMeNMe group replaced by CH CH ) and 2  2  3  its diphosphine analogue 8 (or 5a with -ChMeNMe group replaced by CH CH ) 2  were prepared from 4a and 5_a, respectively [21]. planar element of chirality.  2  3  These ligands have only a  In addition, optically active l-(dimethyl-  amino)methyl-2-(diphenylphosphino)ferrocene, £ , which is analogous to 4a  4  Nile,  n-BuLi  4  (S,R)-/(R,S)-3  :  n  ^ ~ ^  c  (S,S)-/ (R.R)-3  (1) n-BuLi ( i i ) n-BuLi/TMEDA (iii)  (S,R)-/(R,S)-5a b c d  F i g u r e 1.1  C1PR  X=H, X = H, X=H, X=PR  2  C l PR.  0  R=Ph R=i-Pr R=t-Bu , R=t-Bu  P r e p a r a t i v e routes t o t h e c h i r a l ligands.  ferrocenylphosphine  5  (R,R)-4a  (1.1)  6  (with CHMeNMe r e p l a c e d by CH NMe ) but lacks t h e carbon c e n t r a l c h i r a l i t y , 2  2  2  was prepared by o p t i c a l r e s o l u t i o n o f Its phosphlne s u l f 1 d e / d i b e n z o y l t a r t a r i c a c i d s a l t L21.24].  7  In summary, the ferrocenylphosphines have the following unique and significant features:  (i) Mono-, bis- and tris-phosphines can be prepared  from the same chiral source, simply by changing the lithiation procedure, Figure 1.1.  (ii) Aryl- and alkyl-phosphines can be synthesized by using  different halophosphines.  ( i i i ) Various kinds of functional groups such as  amino, alkoxyl or hydroxyl can be introduced into the side chain, e.g. -NMe group in 4_a is easily replaced by other -NR groups, 2  2  (iv)  the  They can  contain a planar element of chirality that does not racemize or epimerize under the usual reaction condition,  (v) The phosphine can have central  chirality and/or planar chirality; those lacking the central chirality can be prepared, e.g.  (S,R)-4_a, (R,R)-4_a and (R)-j3.  (vi) They can be isolated  and purified very readily because of their reasonable stability in air and orange color, making chromatographic separation easy. recrystal1ized.  They are also easily  (vii) Ferrocenylphosphine ligands with both P ("soft") and  N ("hard") atoms present such as 4_-5_, are particularly interesting since there is a continuing interest in ligand systems containing both "soft" and "hard" donor atoms [25-28], There are now numerous reports of metal complexes containing ferrocenylphosphines as chelating bidentate ligands [5,6].  Ferrocenyl-  phosphine complexes of group VIII metals have been the most widely studied and have been used as homogeneous catalysts for reactions such as hydrogenation, hydrosilylation and Grignard cross-coupling reactions.  The  following section will review briefly some of the interesting features of these reactions.  8  1.2 1.2.1  FERROCENYLPHOSPHINES IN HOMOGENEOUS CATALYSIS. Hydrogenation  Among all the transition metal complexes of ferrocenylphosphines, rhodium derivatives have been the most extensively studied [5,6].  The  crystal structure of the cationic rhodium(I) complex [(L-L)Rh(NBD)] , (L-L) +  = 4_a, shows that both N and P are bound to rhodium [29].  The same P-N  binding mode is found when (L-L) = 4b [30], 4c, be and 5d [23]. appears to use both P atoms to bind to rhodium [20,31].  Ligand 5a  Hence, it seems  that the nature of the groups attached to phosphorus exerts a considerable influence on the choice of binding mode. Cationic rhodium(I) complexes [(L-L)Rh(NBD)]  +  (L-L = ferrocenyl-  phosphine ligands) are very effective catalysts in the hydrogenation of amino acid precursors such as acylaminocinnamic acid, equation 1.2 [6,20,23).  The results for the acylaminocinnamic and acylaminoacrylic acid  reveal that the rates obtained with the tetraphenyl derivative, l a , are higher than those obtained with alkylphosphine derivative such as lb [11]. These trends are reversed in the reduction of sterically undemanding substrates such as itaconic acid, a-methylcinnamic acid, 1-octene and cyclohexene [11].  The presence of phenyl groups can result in lower rates,  for example, itaconic acid is only 21% hydrogenated in 72 h when using a catalyst derived f ran 4_a yet is 100% hydrogenated in 16 h using one derived from 4c [32].  9  H  ^N-C0CH  Ph. H  3  COOH  H  H  2  PhCHo-C?r!  ^N-C0CH  [Cat]*  3  COOH  (1.2)  Studies of rhodium complexes of 4c, 5c and 5d [23] indicate that, in the same solvent, the planar chirality of the ligands plays an important role in determining the configuration of the hydrogenated product; e.g.  the  hydrogenation of itaconic acid catalyzed by the complexes of (S,R)-4c, (S,R)-5_c and (S,S)-5d resulted in (S)-, (S)- and (R)-2-methylsuccinic acid, respectively, as the reduced product [23]. Ligand 5a gives products of the opposite absolute configuration when compared to ligand 4a [29,33].  Thus, (S,R)-5a leads to (S)-acylamino acids  while (S,R)-4a leads to (R)-isomers.  This reversal of product  configurations is also observed when using ligands 4a and 4c [32]. A higher optical yield is obtained in the hydrogenation of acylaminocinnamic acid when ligand 4a is replaced by 4c [32], whereas a lower optical yield resulted when the same substrate is hydrogenated under similar conditions using catalysts derived from 4a and 5_a by replacement of the -CH  3  group on the chiral center with -Ph or i-Pr groups [22].  A modified version of 5a with the -NMe group replaced by OH, JO, 2  has been used in the reduction of some prochiral carbonyl compounds [34]. The  -OH group in Jp_ is believed to be crucial for the high optical yields  10  (43-955.) achieved since much lower optical yields are obtained with (R,S)5a and (S)-8 which are both analogous to (R,S)-10_ but lack the -OH group [34].  10 Hence, steric and electronic effects of ligands, as well as the nature of other substituents on the ligand, seem to play a very important role in these catalyzed hydrogenation reactions and one of the advantages of using ligands based on the ferrocene skeleton is the ease with which these parameters can be varied. The mechanism of homogeneous hydrogenation of olefins catalyzed by rhodium complexes has been extensively studied [35-37].  The precise  mechanism may differ from system to system, but some common steps are present in most hydrogenation cycles: (i) Activation of hydrogen by formation of M-H bonds, (ii) activation of substrate by its coordination to metal, ( i i i ) hydride transfer from the central metal to the coordinated substrate, and (iv) product formation by reductive elimination.  These  basic steps may be combined in various ways in completing a catalytic cycle.  n  The majority of mononuclear and homogeneous olefin hydrogenation catalysts can be roughly classified as monohydride catalysts or dihydride catalysts [35].  The monohydride catalysts have been much less studied.  The catalytic mechanism of the dihydride class is thought to involve two possible routes namely the "hydride route" and the "olefin route", Figure 1.2.  Both routes may be simultaneously operative and both require vacant  coordination sites on the metal for addition of H and complexation of 2  substrate.  The active catalyst(s) is usually generated from the catalyst  precursor.  Wilkinson's earlier studies [38] and Halpern's stepwise kinetic  analysis [39] for the Wilkinson catalyst RhClL  3  (L = monodentate  phosphine), provide evidence for the "hydride route".  The mechanism of  hydrogenation of some olefins catalyzed by [(L-L)Rh(Diene)]+ (L-L = chelating di(tertiary phosphine) ligands; Diene = NBD or COD) is believed to proceed via the "olefin route" [40,41].  However, it must be emphasized  that these generalizations may not be always followed.  For example,  two research groups [42-44] independently found that catalyst precursors [(L-L)Rh(NBD)JC10 (L-L = chelating P-P or P-N di(tertiary phosphine) 4  ligands) produce metal hydrides when hydrogen is passed through solutions of the catalyst precursors.  These results indicate that some catalyst  precursors with chelating di(tertiary phosphines) as ligand could function via the hydride route.  1.2.2  Hydrosilylation The addition of Si-H bonds to olefins, acetylenes,  aldehydes, ana  Catalyst Precursor  I I  H H Figure 1.2  Two possible catalytic hydrogenation cycles for the dihydride catalysts. A : hydride route; B : olefin route.  13  ketones is catalyzed by many soluble transition metal complexes L45-49]. Rhodium, palladium and nickel complexes of ferrocenylphosphines have been used in homogeneous hydrosilylation of olefins and ketones L20.47J. .  (L-L) = I d , catalyzes not only the  The nickel complex (L-L)NiCl , 2  addition of silicon hydrides to olefins but also the interchange of hydrogen and chlorine on silicon [50].  Thus, the catalytic hydrosilylation  of trichlorosilane with 1-octene gave octyltrichlorosilane and octyldichlorosilane, both in 50% yield, equation 1.3.  C H CH=CH 6  1 3  2  +  HS1C1  •  3  C H 8  C  1 7  SiCl  8 17 H  3  S 1 H C 1  +  2  (1.3)  The palladium complex (L-L)PdCl » (L-L) = 4a, is a catalyst 2  precursor for the hydrosilylation of olefins such as styrene with trichlorosilane [51], equation 1.4.  If the ligand is optically active the  product is chiral and can be converted into an optically active alcohol or bromide via the potassium pentafluorosilicate derivatives, equation 1.4 L51.52].  The optical yields are only moderate (~50% e.e.).  14  0r^ + H S i c i Q r " 1  3  (14)  Rhodium complexes of chiral ligands such as 4a, 4d, 5a and 7_ are active catalyst precursors for the asymmetric hydrosilylation of ketones [47,53].  The asymmetric addition of trialkylsilanes and dialkylsilanes to  prochiral ketones readily takes place at ambient temperature.  It seems  that the extent of asymmetric induction depends strongly upon the structure of both the chiral phosphine ligands and the hydrosilanes employed.  The marked effect of the hydrosilanes on the stereoselectivity  is a very characteristic feature of the asymmetric hydrosilylation of ketones [54-56].  15  Figure 1.3  The proposed mechanism of hydrosilylation of olefins catalyzed by platinum complexes, M=Pt.  16  F i g u r e 1.4  The proposed mechanism o f h y d r o s i l y l a t i o n o f ketones c a t a l y z e d by rhodium complexes.  17  The mechanism of hydrosilylation of olefins and ketones is not well understood [35,47].  Plausible reaction schemes can be written which  rationalize the homogeneous results.  However, few kinetic data are  available on which to base a particular mechanism. In the case of olefins, Chalk and Harrod [57] proposed a scheme for the hydrosilylation catalyzed by platinum(II) complexes, Figure 1.3.  This  is analogous to that proposed for the rhodium(I)-catalyzed hydrogenation of olefins  (cf.  Section 1.2.1).  In the case of ketones, the basic features of the proposed mechanism of rhodium-catalyzed hydrosilylation are outlined in Figure 1.4 [45J. paths A and B have been invoked to account for the mechanism.  Both  Path A  involves the formation of an a-siloxyl alkyl-rhodium species [47] and an alkoxylrhodium complex is proposed in path B [58].  The latter path is  analogous to that rhodiumd)-catalyzed hydrogenation of ketones proposed by Schrock and Osborn [59] which involves an alkoxylrhodium intermediate.  1.2.3  Grignard Cross-coupling Grignard cross-coupling is a useful carbon-carbon bond forming  reaction, equation 1.5.  Hayashi and coworkers [20,60-63] found that  palladium and nickel complexes (L-L)MC1 (M = Ni or Pd; L-L = J a , (S,R)-4a, 2  (S,R)-5a, (R)-7_ or (S)-9_) catalyze a large number of cross-coupling reactions of Grignard reagents with organic halides.  For example, the  nickel- or palladium-catalyzed reaction of (l-phenylethyDmagnesium chloride and vinyl bromide, occurred smoothly at -20 to 0°C within several  18  hours to give optically active 3-phenyl-l-butene  in very high chemical  yields; in some cases optical yields up to 68% have been achieved [61]. The ferrocene planar chirality is found to be more important than the carbon central chirality and the dimethylamino group is necessary for the high stereoselectivity [61].  The stereoselectivity is not affected by  introduction of substituents onto the diphenylphosphino group of the ligand but is strongly affected by changing the steric bulkiness of the secondary amino group on the ferrocenylphosphine side chain [61].  RMgX  +  R'X'  R-R  1  +  MgXX'  (1.5) Kumada [60] has proposed a catalytic cycle for nickel-catalyzed cross-coupling reactions as shown in Figure 1.5.  Thus, a dihalo-  diphosphinenickel derivative a^ reacts with a Grignard reagent to form the intermediate diorganonickel complex b which is subsequently converted to the halo(organo)nickel  complex c_ by an organic halide.  Reaction of c_ with  the Grignard reagent then forms the new diorgano complex d^ from which the cross-coupling product f_ is released by the attack of the organic halide, possibly via the penta-coordinate intermediate  The original complex _c  is regenerated to complete the catalytic cycle.  An alternative scheme has  MgXX*  Figure 1.5  C a t a l y t i c process o f c r o s s - c o u p l i n g r e a c t i o n c a t a l y z e d by n i c k e l complexes, M=N1.  20  been proposed independently by Felkin and Swierczewski [63] and Corriu and coworkers [64].  These authors have suggested a mechanism involving  nickel(0) species. The catalytic cycle in Figure 1.5 seems to account for the results obtained using chiral ferrocenylphosphine ligands in the asymmetric Grignard cross-coupling reaction [20,61].  Thus, when a Grignard reagent  such as (1-phenylethyl)magnesium chloride approaches the  "active-catalyst"  analogous to c, Figure 1.5, the dimethylamino group in the ligand is believed to dissociate from the metal and coordinate with the magnesium atom in the Grignard reagent to form the intermediate shown in Figure 1.6 [20].  This coordination is considered to occur selectively with one of the  enantiomers of the racemic Grignard reagent.  The group bound to the  magnesium subsequently undergoes transmetallation to form the diorganometal intermediate such as e_, Figure 1.5.  The optical purity and configuration  of the coupling product are believed to be determined at this stage [20]. The asymmetric Grignard cross-coupling reaction can produce an optically active product even i f all the Grignard reagent is racemized, equation 1.6  [20],  R  1  R ~>C-R 2  R  4  3  optically active  (1.6)  21  M=Ni or Pd R =Me,  R =H  (S,R)-4a  R1=H,  R =Me  (R,R)-4a  R =H,  R =H  1  1  F i g u r e 1.6  2  2  2  (R)-9  Proposed intermediate i n Grignard cross-coupling reaction.  22  Honeychuk and coworkers L65] reported that palladium derivatives of the ferrocenyl thioether, Via, and ferrocenyl selenoether, effective Grignard cross-coupling catalysts.  Vlb, are  These authors have proposed a  mechanism similar to that shown in Figure 1.5 for the reaction.  b  E=Se  In nickel- and palladium-catalyzed cross-coupling reactions of alkyl Grignard and alkylzinc reagents with organic halides, the complex (L-L)PdCl , (L-L) = l a , was found to be by far the most active and 2  selective catalyst precursor L62J. in high yields. (L-L)PdCl  2  The cross-coupled products are obtained  The large P-Pd-P angle and small Cl-Pd-Cl angle in  (L-L = Ja) are thought to be responsible for the high efficiency  [62].  1.2.4  Other Catalytic Reactions The palladium complex lL-L)PdCl IL-L = Ja) is a catalyst precursor 2  23  for the hydroesterification, equation 1.7, and hydrocarboxylation, equation 1.8, of 3,3,3-trifluoropropene and pentafluorostyrene L66].  Under optimal  conditions either branched products or normal products were obtained in high yields with high regioselectivities.  For example,  3-(pentafluoro-  phenyDpropionic acid RCH CH C00H (R = C H ) was obtained in 93% yield with 2  995. regioselectivity  2  6  5  in the hydrocarboxylation of pentafluorostyrene  catalyzed by (L-L)PdCl  2  (L-L = Ja)-  The effect of stannous chloride on  these catalytic systems was also studied and in some cases found to give better activity and regioselectivity L66j.  [Cat] RCH=CH  2  + CO + R'OH  • RCH(C00R')CH RCH CH C00R' 2  3  +  2  R=CF o r C F ; 3  g  5  R'=Me, E t o r i - P r  (1.7)  [Cat] RCH=CH  2  + CO + H 0 2  •  RCH(C00H)CH RCH CH C00H 2  R=CF o r C F 3  6  3  +  2  5  (1.8)  The ferrocenylphosphine ligand Ja has also been used in the hydroformylation of olefins, equation 1.9 L&7J.  Thus in the ruthenium-catalyzed  24  homogeneous hydroformylation of 1-pentene, R = C H , equation 1.9, 3  the  7  ligand la induces higher normal-to-branched selectivities than PPh [67a]. 3  Unmh and coworkers [67c - 67f] reported that the derivatives of la containing electron-withdrawing substituent  on the Ph groups ( £ - C l , m-F,  _p_-CF ) give higher rates and higher normal-to-branched aldehyde ratios than 3  the ligand la in the rhodium-catalyzed hydroformylation of olefins.  [Cat] RCH=CH  2  + CO + H  RCH(CH0)CH  2  3  +  RCH CH CH0 2  2  (1.9)  1.3  HOMOGENEOUS VERSUS HETEROGENEOUS CATALYSTS  The advantages and disadvantages  of using homogeneous or hetero-  geneous catalysts can be briefly summarized under a number of headings [68]: (i)  Separation of the catalysts.  Heterogeneous catalysts are readily  separated from the products at the end of the reaction. homogeneous catalysts this is a major problem.  With  25  (ii)  Selectivity.  Homogeneous catalysts often have the advantage of  giving high selectivity under relatively mild operating conditions. Heterogeneous catalysts are often less active and less selective. The activity and selectivity of a homogeneous catalyst can be tailored by varying the solvent. (iii)  Solvent.  The range of suitable solvents for a homogeneous catalyst  is often limited by the solubility characteristics of the catalyst; this clearly presents no problem for a heterogeneous catalyst. (iv)  Efficiency.  Every molecule in a homogeneous catalyst is available  to participate in the reaction.  In the case of heterogeneous  catalysts only surface atoms or molecules may participate. (v)  Oxygen and moisture sensitivity.  Homogeneous catalysts are often  organometallic compounds and are more sensitive to oxygen and moisture than most heterogeneous catalysts. (vi)  Corrosion and plating out.  The use of some homogeneous catalysts on  a commercial scale has led to practical problems such as corrosion and plating out. An ideal catalyst would combine the advantages and simultaneously avoid the disadvantages of each catalyst.  One approach to this objective  is to attach soluble catalysts to insoluble supports such as polymers, s i l i c a , alumina and clay [68,69].  organic  The soluble catalyst attached  to an insoluble support takes on the properties of a heterogeneous species at a bulk level but the interactions taking place around the metal centre are probably very similar to those found in the soluble analog. Soluble catalysts which are attached to insoluble supports have been  26  studied extensively over nany years.  Such supported catalysts,  heteroge-  nized catalysts, have been employed for a variety of reactions such as hydrogenation, hydrosilylation and hyaroformylation L68j. As noted in previous sections, several organic reactions are known to be catalyzed by soluble transition metal complexes of ferrocenylphosphines and it seems that the ligands (chiral and achiral) play an important role.  In view of this it would be of interest to attach  ferrocene and its derivatives to inert materials and to develop the use of these materials and their metal derivatives as catalysts for heterogeneous reactions such as hydrogenation and hydrosilylation. There have been some studies concerned with supporting ferrocene derivatives on inert materials [69-72].  Ferrocenophanes such as J_2 and  other ferrocene derivatives have been attached to several types of electrodes for photovoltaic purposes [71J.  A number of workers L69.72J  have studied polymers prepared from substituted ferrocene monomers. However, no studies on polymer-bound catalysts derived from polymer supported ferrocene derivatives have been reported and research in this field could be f r u i t f u l .  R=C1, Me or Ph  12  27  1.4  GOALS OF THE PRESENT STUDY  The goals of the present study can be summarized as follows: (I)  The cationic palladium complexes [(L-L)PdS J  (L-L = chelating  2+  2  bidentate ligand; S = weakly coordinated solvent) are analogous to the cationic rhodium complexes L(L-L)Rh(NBD)] . +  These palladium  derivatives are essentially unstudied as hydrogenation catalysts [73].  Ferrocenylphosphines complexes of this type will be  synthesized and their catalytic activity will be examined. (II)  Platinum complexes of chiral ferrocenylphosphine (L-L)PtCl are 2  essentially unknown.  These complexes will be prepared and their  catalytic activity will be examined. (III) Polymer-bound catalysts derived from polymer supported ferrocene derivatives have not been explored.  Methods for attaching ferrocene  and its derivatives to polystyrene type polymers will be developed and the catalytic activity of the polymer-bound palladium and platinum complexes will be compared to those of their soluble counterparts.  28  CHAPTER 2 EXPERIMENTAL SECTION  2.1  GENERAL  All air-sensitive reagents and products were manipulated in a nitrogen atmosphere using standard Schlenk techniques. by standard methods [74].  Solvents were dried  In particular, hexane and diethyl ether were  refluxed over CaH ; THF was refluxed over sodium-benzophenone; MeOH and 2  EtOH were refluxed over magnesium and iodine; CH C1 and MeN0 were dried 2  over anhydrous CaS0  H  sieves;  2  2  (5gL ) for 24 h and then distilled onto molecular -1  DMF and DMSO were distilled in vacuo onto molecular sieves; py was  stored over KOH (5gL ) for 24 h and then freshly distilled prior to use. -1  All other solvents were either spectrophotometric grade or reagent grade and were used as received unless otherwise stated. The NajjPdCl^HjO and K PtCl 2  lt  salts were generously loaned by  Johnson Matthey Limited and were used as received.  The liquid olefins such  as styrene, o-methylstyrene, 1-hexene and cyclohexene (Aldrich Chemical Co.) were passed through a neutral alumina (Fisher Scientific Co.) column prior to use.  Acetophenone, butyrophenone and isobutyrophenone (Aldrich  Chemical Co.) were freshly d i s t i l l e d under vacuum prior to use. A l l other chemicals were either purchased or synthesized using literature methods described below, where appropriate.  29  2.1.1  Instrumentation (1) NMR spectra l  H NMR spectra were recorded on Bruker WP-80, Varian XL-100, Varian  XL-300 or Bruker WH-400 spectrometers operating at 80 MHz, 100 MHz, 300 MHz or 400 MHz, respectively.  Proton decoupled  31  P NMR spectra were recorded  on Bruker WP-80, Varian XL-100 or Varian XL-300 instruments operating at 32.3 MHz, 40.5 MHz or 121.4 MHz, respectively.  Chemical shifts to higher  frequency (lower shielding) of the standard are positive by convention; --H shifts are relative to external standard TMS (6 = 0 ppm) and are relative to 85i  H P0n 3  31  P shifts  with P(0Me) (6 = 141 ppm) used as an external 3  standard. The solid state  1 3  C NMR spectra were recorded on a Bruker CXP 200  MHz NMR spectrometer operating at 50.3 MHz.  The chemical shifts are  relative to TMS. ( i i ) GLC Either a Hewlett Packard 5880A gas chromatograph equipped with an carbowax column or 20% SE-30 column, or a Varian 6000 gas chromatograph equipped with 20% tricresylphosphate column was used for GLC separation. (iii)  Infrared spectra  Infrared spectra were recorded on a Perkin-Elmer 598 spectrophotometer.  Solid state spectra were obtained from Nujol mulls between NaCl or  Csl plates; KBr cells with path length 0.25 mm were used for solution samples. (iv)  Melting points  Melting points were determined using a Gallenkamp melting point  30  apparatus and are quoted without correction. (v)  Elemental analyses  Elemental analyses were performed by Mr. P. Borda of the University of British Columbia, Mrs. Ni of Wuhan University (China), and Canadian Microanalytical Services Ltd. (Vancouver). (vi) 57  Mossbauer spectra  F e Mossbauer spectra were obtained as described elsewhere [75].  Spectra were recorded at 77K and the radiation source was Rh matrix.  57  Co in a Cu or  The Doppler velocity scale was calibrated using a metallic iron  f o i l absorber, and isomer shifts are quoted relative to the centre of an iron f o i l spectrum. (vii)  Optical rotation measurements  A l l optical rotations were measured at the sodium-D line (589 nm) using a Perkin-Elmer 141 spectrometer at room temperature; length was one decimeter.  the cell path-  The specific rotation of any chiral product was  calculated using equation 2.1,  [a]J where [a]J  = a/A.c  = specific rotation at temperature T measured at the sodium-D line (589 nm)  a  = observed rotation (+) or (-).  A  = cell path length in decimeters  c  = concentration of solution in g/100 mL.  (2.1)  31  2.1.2  Hydrogenation Experiments All hydrogenation experiments were carried out using either method  (i) for homogeneous systems or (ii) for heterogeneous systems. (i)  A constant pressure gas-uptake apparatus was used as described  in detail elsewhere [43]. (ii)  General procedure.  The appropriate amount of heterogenized  catalyst was suspended in the solvent in a Carius tube.  The substrate was  added, the system evacuated, and hydrogen was introduced at one atmosphere. The tube was sealed with a Teflon valve and the mixture was kept at the appropriate temperature with stirring.  After the appropriate reaction time  the resin was filtered off in air, washed successively (3x) with acetone and diethyl ether and dried before reuse.  The hydrogenated products were  identified by their known H NM3 spectra or by GLC by comparing their l  retention times with those of known compounds. Other conditions for the hydrogenation experiments are given in the appropriate Tables.  2.1.3  Hydrosilylation Experiments (i)  Hydrosilylation of ketones  Typically, the catalyst precursor (1 mol %) was dissolved in CH C1 2  2  (3 mL) in a Carius tube, the ketone (5 mmol) and silane (5 or 10 mmol) were then added to the tube under nitrogen.  The tube was sealed using a Teflon  valve and heated as shown in the appropriate Tables.  After the appropriate  32  reaction time, the reaction mixture was added to 20 mL of acetone containing 4 mL of 10% aqueous HCl solution.  After 2 h at 20°C, the  organic phase was extracted with diethyl ether and dried over MgSO^. The diethyl ether was evaporated and the organic residue was distilled under vacuum to afford a mixture of ketone and alcohol.  These were identified by  GLC and H NMR spectra. X  When supported catalysts were used no solvent was needed and the resin was filtered off before the hydrolysis step.  Other experimental  conditions are given in the appropriate Tables. (ii)  Hydrosilylation of acetyl ferrocene and benzoyl ferrocene  The catalyst precursor (1 mol %), CH C1 2  2  (10 mL), acetylferrocene  (4  mmol) and diphenylsilane (8 mmol) were mixed in a Carius tube under nitrogen. ~ 24 h.  The tube was sealed as above and heated (60°C) with stirring for The reaction was monitored by TLC until there was no acetyl-  ferrocene remaining.  Diethyl ether (100 mL) was added to precipitate any  metal complexes and the solution was filtered and evaporated to leave a red-brown o i l .  Column chromatography on neutral alumina, with CHC1 as 3  eluant, revealed the presence of first ethyl ferrocene followed by ferrocenylethanol.  Analytical and H NMR data for these compounds are presented 1  in Table 4.7. In the case of benzoyl ferrocene, 2 mol% of the catalyst precursor was employed and the reaction mixture was heated for 67 h.  Only benzyl-  ferrocene was isolated as product after work-up using column chromatography. 4.7.  Analytical and H NMR data for the product are presented in Table l  33  (iii)  Hydrosilylation of olefins  The catalyst precursor (0.01 mol%), CH C1 (3 mL), olefin (25 mmol) 2  2  and trichlorosilane (30 mmol) were mixed in a Carius tube under nitrogen, sealed and heated (70°C) with stirring for 24 h.  The products were  identified by comparing the retention times on GLC with those of standard compounds. When supported catalysts were used no CH C1 was needed and the 2  2  resin was filtered off in air, washed with acetone and diethyl ether and dried before reuse.  The products were identified as above.  Other  experimental conditions are given in the appropriate Tables. When necessary the product 1-phenylethyltrichlorosilane was converted to the alcohol 1-phenylethanol  using the literature procedure  [51].  2.2  SYNTHESES OF STARTING MATERIALS  2.2.1  Chlorodiisopropylphosphine [76,77] This was prepared following the procedure used for chlorodi-tert-  butylphosphine [76] with slight modification. A Grignard solution of i-PrMgCl prepared from i-PrCl (78.5 g, 1 mol) and Mg turnings (24.3 g, 1 mol) in diethyl ether (800 mL) was added dropwise (2 h) through an addition funnel to a stirred diethyl ether solution (50 mL) of PCI  3  (55 g, 0.4 mol).  A white precipitate formed  during the addition and the reaction mixture was refluxed for another two hours.  The diethyl ether solution containing the product was separated  34  from the precipitate by filtration it through a medium porosity Schlenk f i l t e r into a flask under nitrogen.  The ether solvent was removed by  distillation at atmospheric pressure to leave a yellowish o i l . further purified by vacuum d i s t i l l a t i o n . air-sensitive,  This was  The product thus obtained was an  colorless liquid (28-35 g, 64-80%), b.p.  27°C (3 mm Hg)  ( l i t . [77] b.p. 69°C (33 mm Hg)).  2.2.2  Diphenylsilane  [78]  This was prepared from LiAlH^ (5.6 g, 0.15 mmol) and dichlorodiphenylsilane (50 g, 0.2 mol) in 500 mL of anhydrous diethyl ether solution.  After vacuum distillation the desired product was a colorless  liquid (30 g, 81%), b.p. 92°C (3 mm Hg) ( l i t .  2.2.3  Acetyl ferrocene  b.p.  75-76°C (0.5 mm Hg)).  [17]  This was prepared from ferrocene (46.5 g, 0.25 mol), acetyl chloride (22 g, 0.28 mol), and anhydrous aluminum chloride (33.5 g, 0.25 mol) in 400 mL of dry CH C1 solution. 2  2  The orange solid product obtained (51 g, 89%)  was recrystallized from hot hexane, m.p. 83-85°C ( l i t . m.p. 85-86°C).  2.2.4  Ferrocenylethanol  [17]  This was prepared from acetyl ferrocene (25 g, 0.11 mol) and LiAlH^ (2.2 g, 0.06 mol) in 800 mL of anhydrous diethyl ether solution.  The  yellow-orange solid product obtained (20 g, 80%) was recrystallized from n-heptane to give yellow-orange needles, m.p. 79°C ( l i t . m.p. 78-79°C).  35  2.2.5  Ferrocenylethylcarbonium Tetrafluoroborate 179] Ferrocenylethanol (0.23 g, 1 mmol) was dissolved in 2 nt of acetic  anhydride and 0.5 mL of a solution of fluoroboric acid in acetic anhydride (prepared by dissolving 1.5 mL of aqueous fluoroboric acid (42%) in 4 mL of acetic anhydride) was added and the solution was stirred for 5 minutes after which anhydrous diethyl ether (25 mL) was added to precipitate a dark solid.  This was filtered off by suction and carefully washed with  anhydrous diethyl ether.  The dark solid product was then used irrmediately  in other reactions.  1,1'-Dilithioferrocene-TMEDA Adduct [9,80]  2.2.6  , This was prepared from ferrocene,(4.65  g, 25 mmol), jn-BuLi (1.6 M,  37.5 mL, 60 mmol) and TMEDA (3.5 g, 30 mmol) in 50 mL hexane solution.  The  product was a fine orange pyrophoric powder (7 g, 89%) which could be stored for long periods under nitrogen at room temperature.  2.2.7  N^-Dimethylaminocyanomethylferrocene  [81]  To a stirred solution of sodium bisulfite (52 g, 0.5 mol) in 300 mL of water was added a solution of ferrocene carboxaldehyde (108 g, 0.5 mol) in 300 mL of MeOH.  The mixture was stirred for 10 minutes after which a  solution of dimethylamine (30 g, 0.7 mol) in 100 mL of 50% MeOH was added followed by a solution of sodium cyanide (24.5 g, 0.5 mol) in 100 mL of water.  The color changed from red to orange.  Diethyl Ether (500 mL) was  added and the reaction mixture was left to s t i r overnight after which it was extracted with ether (5 x 500 mL).  The combined ether extracts were  dried over anhydrous MgSO^, the solvent was removed under vacuum and the  36  product was obtained as golden plates (120 g, 90%).  2.2.8  N^N-Dimethylaminoethylferrocene, FA [81]. The Grignard reagent MeMgl was prepared from Mg (18 g, 0.74 mol) and  Mel (105 g, 0.74 mol).  To this Grignard reagent, a solution of  dimethylaminocyanomethylferrocene (100 g, 0.37 mol) in freshly distilled diethyl ether (500 mL) was added dropwise, through a pressure-equalizing dropping funnel. reddish orange.  The yellowish brown color of the aminonitrile changed to The reaction mixture was refluxed for 2h and stirred  overnight, and then slowly treated with aqueous NH^Cl at 0°C. The ether layer was separated and the aqueous layer extracted with ether (5 x 500 mL).  The combined ether solution was dried over anhydrous K C 0 , filtered, 2  and evaporated to give an amber oil (81 g, 85%).  3  Solid product could be  obtained by recrystallizing the amber oil from MeOH [82].  2.2.9  (S)- and (R)-N,N-Dimethylaminoethylferrocene, (S)- and (R)-FA [17] Racemic amine FA (77.1 g, 0.3 mol) and (R)-(+)-tartaric acid (45 g,  0.3 mol) were each dissolved in 150 mL of MeOH in 500 mL Erlenmeyer flasks. Both flasks were immersed in a water bath at 55°C for about 10 minutes to reach thermal equilibrium.  The tartaric acid solution was.then poured into  the FA solution while stirring.  A few (-)-seeding crystals were added.  (If no seeding crystals are available, the flask should be occasionally scratched with a glass rod to aid solid formation.)  The temperature of the  bath was then allowed to fall at a rate of 2 to 5 ° / h . Stirring was continued overnight and the precipitate of the (S)-(-)-amine tartarate was  37  collected by suction f i l t r a t i o n . use.  The mother liquor was set aside for later  The tartarate salt was added to 20% aqueous NaOH solution in a  separatory funnel and the amine extracted with CH C1 (4 x 100 mL). The 2  amine solution was dried over anhydrous K C0 2  3  2  and evaporated to give  optically active amine as a dark oil (29 g, 75%).  The amine thus obtained  (29 g, 0.11 mol) and (R)-(+)-tartaric acid (16.5 g, 0.11 mol) each dissolved in 50 mL of MeOH were mixed and seeded as above.  After slow  cooling followed by the work-up procedure as described above, optically active (S)-(-)-FA was obtained (22 g, 57%), [a]jp - 1 2 . 6 ° (C1.5, EtOH) ( l i t . [a]jp - 1 4 . 1 ° (C1.5, EtOH)). The mother liquor from the first crystallization was concentrated to about one-fourth of its original volume.  Diethyl ether was added slowly to  the solution until precipitation was complete.  The mixture was left at 0°C  overnight and the (R)-(+)-amine tartarate was collected.  This was  recrystallized by dissolving it in a minimum amount of hot water (70-80°C) and warm acetone (the ratio of acetone to water was 10:1).  The  recrystallization was repeated twice and optically active (R)-(+)-FA was obtained from the tartarate as described above for the (S)-(-)-isomer (20 9, 52%), [ a ] p + 12.5° ( C l . 5 , EtOH) ( l i t . [ a ] p + 14.1° (C1.5, EtOH)). 5  5  2.2.10 Polystyrene Type Polymers Chioromethylated cross-linked polystyrene was obtained from Bio-Rad laboratories as Bio-Beads S-Xl 200-400 mesh, 1.34 meq/g (Bio-Beads A) and 4.2 meq/g (Bio-Beads B).  The beads were washed successively  (3x) with  0.5 M NaOH, 0.5 M HCl, water, MeOH, and diethyl ether, and dried to constant weight under reduced pressure.  38  The polymeric aldehyde was prepared from Bio-Beads A by DMSO oxidation [83] as described next. Bio-Beads A (30 g) were stirred in 200 mL of DMSO with 12.5 g of NaHC0 for 6 h at 155°C. 3  The resin was then collected on a glass f i l t e r ,  washed with DMSO, hot water, and a 2:1 mixture of dioxane and water, then rinsed with dioxane, acetone, EtOH, CH C1 , and benzene. 2  2  A yield of 29 g  of cream colored aldehydic resin was obtained after drying at 100°C under vacuum for 10 h.  Anal. Found: C, 87.89; H, 7.24; 0, 4.73; C l , 0.0.  2.3  SYNTHESES OF FERROCENYLPHOSPHINES  2.3.1  l,l'-Bis(diphenylphosphino)ferrocene, BPPF [9] Ferrocene (20 g, 0.11 mol) was suspended in freshly distilled  ji-hexane (200 mL) in a Schlenk tube.  To this solution was added slowly a  mixture of TMEDA (27.9 g, 0.24 mol) and ji-BuLi (148 ml, 1.6 M, 0.24 mol) in hexane.  The solution was stirred for 6 h at room temperature under  nitrogen and then a solution of chlorodi phenyl phosphine (53 g, 0.24 mol) in hexane (20 mL) was added dropwise over a period of 20 minutes with constant stirring.  During this procedure the temperature of the solution rose.  The  reaction mixture was stirred overnight under nitrogen and then carefully quenched with 100 mL of distilled water at 0°C. The supernatant hexane layer was decanted from the brown solid.  The brown solid was washed  successively with EtOH (2 x 30 mL) and hexane (2 x 30 mL), then dissolved in hot benzene. turbid.  Hot hexane was slowly added until the solution became  The solution was then cooled to room temperature to give the  product as orange crystals (30.5 g, 50%).  39  2.3.2  2-Di phenyl phosphi no-1-(JN[,N^-di methyl ami noethyl )ferrocene, PPFA [21,84] Racemic FA (3 g, 11.7 mmol) was dissolved in freshly distilled  anhydrous diethyl ether (30 mL) in a 250 mL Schlenk tube.  To this solution  was added slowly a solution of _n-BuLi (8.8 mL, 1.6 M, 14 mmol) in hexane. The mixture was stirred at room temperature for 1.5 h and chlorodiphenylphosphine (3 g, 14 mmol) was then added slowly.  This reaction was  exothermic and the color turned to yellow with the precipitation of L i C l . The mixture was stirred overnight.  The reaction mixture was hydrolyzed  with water at 0°C, the organic layer was separated, dried over MgSO^, filtered and concentrated to afford a red brown oil which crystallized from EtOH to give the product (3.2 g, 61%) as orange brown crystals. The (S,R)-PPFA was prepared in the same manner, but replacing racemic FA by (S)-FA.  2.3.3  2-Di isopropyl phosphi no- 1-(N_,_N-dimethyl ami noethyl )ferrocene,  ISOPFA  [10] This was prepared by the same procedure used for PPFA from racemic FA (3 g, 11.7 mmol), ji-BuLi (8.8 mL, 1.6 M, 14 mmol) and chl orodi isopropylphosphine (2.1 g, 14 mmol).  The product (3.3 g, 75%), a red orange o i l ,  was analytically pure and could be recrystallized from EtOH gave 45% yield of orange brown crystals. The (S,R)-IS0PFA was prepared in the same manner, but replacing racemic FA by (S)-FA.  40  2.3.4  1 ,2-Bis (di phenyl phosphi no)-l-(N^-dimethyl ami noethyl )ferrocene, 1  BPPFA [21,84] Racemic FA (3g, 11.7 mmol) was dissolved in diethyl ether (30 mL) in a Schlenk tube.  To this solution was added slowly a solution of ji-BuLi  (8.8 mL, 1.6 M, 14 mmol) in hexane.  The mixture was stirred at room  temperature for 1.5 h and then a mixture of freshly distilled TMEDA (1.6 g, 14 mmol) and _n-BuLi (8.8 mL, 1.6 M, 14 mmol) in hexane was added and stirring was continued for a further 5h at room temperature.  Chloro-  diphenylphosphine (5.3 g, 24 mmol) was then added to the reaction mixture and the solution was stirred overnight.  The mixture was hydrolyzed with  water at 0°C, and the resulting organic layer was separated, dried over MgSOj^, filtered and concentrated to afford an oily residue which crystallized from EtOH to give pure BPPFA (3.7 g, 50%) as orange crystals. The (S.R)-BPFFA was prepared in the same manner, but replacing racemic FA by (S)-FA. Analytical, physical and NMR data for these ligands are presented in Tables 3.1 and 3.2.  2.4  SYNTHESES OF PALLADIUM AND PLATINUM COMPLEXES OF FERROCENYLPHOSPHINES  2.4.1  Palladium Complexes (L-L)PdCl (i)  2  [61,62]  L-L = BPPF  Dichlorobis(benzonitrile)palladium(II)  (0.58 g, 1.5 mmol) (prepared  from Na PdCl »4H 0 [85]) was suspended in 10 mL of benzene in a Schlenk 2  tube.  lt  2  BPPF (0.94 g, 1.7 mmol) in 10 mL of benzene was added to the stirred  solution.  The mixture was stirred overnight at room temperature under  41  nitrogen after which the precipitate was collected by f i l t r a t i o n , washed with benzene, and dried in vacuo to give a reddish orange solid (1.0 g, 91%).  The solid was recrystallized either from CHC1 , CH C1 or acetone, 3  (ii)  2  2  L-L = PPFA, ISOPFA, BPPFA  These complexes were prepared in the similar manner as described in (i),  replacing BPPF by PPFA, ISOPFA and BPPFA, respectively.  (PPFA)PdCl  2  was recrystallized from CH Cl /hexane, yield 94%; (ISOPFA)PdCl and 2  2  2  (BPPFA)PdCl were recrystall ized from CHC1 and were obtained in 75% and 2  95% yields,  3  respectively.  The analytical, physical and NMR data for (L-L)PdC1~ are given in Tables 3.1 and 3.2.  2.4.2  Cationic Palladium Complexes [(L-L)PdS ][C10 ] [86,87] 2  4  2  These complexes were prepared essentially using the procedure of Hartley and coworkers [86,87], but with some modifications as follows: All procedures were carried out in Schlenk type apparatus in a nitrogen atmosphere. (i)  L-L = BPPF, S = DMF  The complex (BPPF)PdCl  2  mixture of CH C1 2  2  (0.37 g, 0.5 mmol) was dissolved in a  (20 mL) and DMF (10 mL), AgClO^ (0.21 g, 1 mmol) in MeN0  2  (10 mL) was added with stirring.  After 3 h the precipitate was filtered  off and the solution taken to dryness in vacuo.  The residual oily solid  was extracted with CH C1 and the combined extracts were reduced to a small 2  volume in vacuo.  2  Dropwise addition of anhydrous diethyl ether precipitated  a solid which was isolated and purified by dissolving it in CH C1 followed 2  2  42  by reprecipitation with anhydrous diethyl ether.  After f i l t r a t i o n , the  dark brown solid was dried in vacuo at room temperature, yield 655.. (ii)  L-L = BPPF, S = py  The complex (BPPF)PdCl (0.37 g, 0.5 mmol) was dissolved in a 2  mixture of CH C1 (20 mL) and py (10 mL), AgCIO,, (0.21 g, 1 rrmol) in MeN0 2  2  2  (10 mL) was added with stirring. worked up as above.  The mixture was left stirring for 3 h and  The purple solid obtained was dried in vacuo at room  temperature, yield 55%. (iii)  L-L = BPPF, S  2  = (DMF, Cl)  This complex was prepared as in (i) except that 0.5 mmol of AgClO^ was used.  The product was a dark brown solid, yield 50-60%.  (iv) L-L = PFFA, S = DMF This complex was prepared as in ( i ) , replacing (BPPF)PdCl by 2  (PPFA)PdCl . 2  (v)  The product was a dark brown solid, yield 52%. L-L = PPFA, S = py  This complex was prepared as in ( i i ) , replacing (BPPF)PdCl by 2  (PPFA)PdCl . 2  The product was a purple solid, yield 55%.  Analytical, physical and NMR data for these palladium complexes are given in Tables 3.3 and 3.4.  2.4.3  Platinum Complexes (L-L)PtCl  2  [88]  These complexes were prepared according to literature methods [88] with some modifications as follows: (i)  L-L = BPPF  KjPtCl^ (0.42 g, 1 mmol) in 10 mL of water was treated with a  43  solution of BPPF (0.55 g, 1 mmol) in 20 mL of CH C1 . 2  2  The solution mixture  was stirred for about 3 h or until the aqueous phase became colorless.  The  organic phase was separated, dried over MgSO,^ and the solvent was reduced to a small volume. of diethyl ether.  The solid product was precipitated by dropwise addition The solid was isolated and recrystallized from  CH Cl /MeOH to give yellow crystals, yield 70%. 2  2  (ii)  L-L = (S.R)-PPFA, (S,R)-IS0PFA, (S,R)-BPPFA.  These complexes were prepared in a similar manner to that described above, replacing BPPF by (S,R)-PPFA, (S.R)-ISOPFA and (S,R)-BPPFA, respectively.  ((S,R)-PPFA)PtCl was recrystallized from CH C1 by precipi2  2  2  tation with diethyl ether as an orange solid, yield 63%; ((S.R)-ISOPFA)PtCI was recrystallized from CH Cl /EtOH as orange crystals, yield 47%; 2  2  2  and ((S,R)-BPPFA)PtCl was recrystallized from CHCl /hexane as orange 2  3  crystals, yield 66%. Analytical, physical and NMR data for these platinum complexes are given in Tables 4.1 and 4.2.  2.4.4  Platinum Complex (PPFA)PtHCl  [26]  This was prepared according to the procedures of Clark and coworkers [26] with modification. To a suspension of (PPFA)PtCl (0.4 g) in 15 mL of MeOH at 0°C was 2  added a MeOH solution of sodium borohydride (0.01 g/mL) also at 0°C. The mixture was stirred under nitrogen until the color changed to brown.  After  stirring for about another 10 minutes the mixture was acidified with methanol ic HCl and extracted with benzene (3 x 10 mL).  The benzene extract  44  was reduced in volume and ji-pentane was added to give a pale orange solid, yield 43%. Analytical, physical and NMR data for this complex are given in Tables 4.8 and 4.9.  2.5  SYNTHESES OF POLYMER-BOUND FERROCENE DERIVATIVES  2.5.1  Reaction of Lithioferrocene with Bio-Beads B, Polymer-I To a Schlenk tube was added ferrocene (2.0 g, 10.8 mmol) followed by  30 mL of anhydrous diethyl ether.  The well stirred solution was treated  with n-BuLi (6.8 mL, 1.6 M, 10.8 mmol) in hexane for about 3 h before the addition of 50 mL of THF followed by Bio-Beads B (1.34 g, 5.4 rrniol).  The  reaction mixture was left stirring for 4 days at room temperature under nitrogen and then hydrolyzed with deionized water.  The resin was collected  and washed successively (3x) with water, EtOH, acetone, THF, CH C1 , hexane 2  2  and diethyl ether, and dried under vacuum at 100°C to give polymer-I as a yellow brown resin.  2.5.2  Reaction of Lithioferrocene with Aldehydic Resin, Polymer-II Ferrocene (2 g, 10.8 rrniol) was suspended in anhydrous diethyl ether  (30 mL) and ji-BuLi (6.8 mL, 1.6 M, 10.8 mmol) in hexane was added with stirring.  After 2 h THF (30 mL) was added followed by aldehydic resin  g, 5.4 mmol).  (1.8  The mixture was left stirring for 4 days and treated as  described above to give polymer-11 as orange brown resin, (a)  Reaction of polymer-II with HBr, polymer-IIa  Polymer-II (1 g) was suspended in 30 mL benzene.  Gaseous HBr was  45  bubbled through the well stirred suspension until the color darkened becoming dark brown.  The mixture was filtered, washed and dried as  described in Section 2.5.1 to give polymer-IIa as a dark brown resin, (b)  Reaction of polymer-IIa with HNMe , polymer-IIb 2  Polymer-IIa (0.5 g) was suspended in benzene (30 mL).  Excess  aqueous HNMe (42%) was then added with stirring and the color of the resin 2  changed from dark brown to orange brown.  The mixture was stirred for 10  minutes after which 30 mL of H 0 was added. 2  Following f i l t r a t i o n , the  resin was treated as described in Section 2.5.1 to give polymer-IIb as an orange brown resin. Alternatively, polymer-IIb could be prepared from polymer-II as described next. Polymer-II (0.5 g) was suspended in benzene (30 mL). Gaseous HBr was bubbled through the well stirred solution until the color darkened. Excess aqueous HNMe was then added with stirring; 2  changed to orange brown.  the dark brown color  The mixture was hydrolyzed and treated as  described in Section 2.5.1.  2.5.3  Reaction of Di1ithioferrocene-TMEDA Adduct with Bio-Beads A, Polymer-I 11 Solid di1ithioferrocene-TMEDA adduct (1.40 g, 4.46 mmol) was  suspended in 50 mL hexane and 50 mL THF.  Bio-Beads A (6.66 g, 8.92 mmol)  were added with constant stirring and the mixture was treated as described in Section 2.5.1 to give polymer-III as a reddish brown resin.  46  2.5.4  Reaction of Dilithioferrocene-TMEDA Adduct with Aldehydic Resin, Polymer-IV Solid dilithioferrocene-TMEDA adduct (2.4 g, 7.5 mmol) was suspended  in 50 mL hexane and 50 mL THF.  Aldehydic resin (5 g, 15 mmol) was added  with constant stirring and the mixture was treated as described in Section 2.5.1 to give polymer-IV as an orange resin. (a)  Reaction of polymer-IV with HBr, polymer-IVa  This was prepared as for polymer-IIa from polymer-IV. (b)  Reaction of polymer-IVa with HNMe , polymer-IVb 2  This was prepared as for polymer-IIb from polymer-IVa.  2.5.5  Reaction of Lithium Derivative of FA with Bio-Beads B, Polymer-V Racemic FA (2.57 g, 10 mmol) was dissolved in anhydrous diethyl  ether (30 mL) in a Schlenk tube.  To this solution was added slowly a  solution of _n-BuLi (6.3 mL, 1.6 M, 10 mmol) in hexane.  The mixture was  stirred at room temperature for 1.5 h and THF (30 mL) was added followed by Bio-Beads B (2.38 g, 10 mmol).  The suspension was stirred for 4 days and  the mixture was treated as described in Section 2.5.1 to give polymer-V as a yellow brown resin.  2.5.6  Reaction of Lithium Derivative of FA with Aldehydic Resin, Polymer-V I This was prepared in a manner similar to that described in Section  2.5.5 from a solution of lithio-FA (prepared from 3.3 g, 12 mmol of FA and 7.5 mL, 12 mmol of ji-BuLi) and aldehyd ic resin (4 g, 12 mmol).  The same  47  work-up as described in Section 2.5.1  gave polymer-VI as a yellow brown  resin.  2.5.7  Reaction of Lithium Derivative of BPPF with Aldehydic Resin, Polymer-VII BPPF (4.4 g, 8 mmol) was dissolved in 100 mL of THF/hexane (1:1).  To this jn-BuLi (6 mL, 1.6 M, 9.6 mmol) was added and the mixture was stirred for 2 days before aldehydic resin (2.7 g, 8 mmol) was added.  The  mixture was further stirred for 4 days and treated as described-in section 2.5.1 to give polymer-VII as an orange resin. In a second experiment,  BPPF was dissolved in anhydrous diethyl  ether and the lithiation carried out with _n-BuLi/TMEDA as in Section 2.5.8, described next.  2.5.8  Reaction of Lithium Derivative of PPFA with Aldehydic Resin, Polymer-VIII PPFA (1.76 g, 4 mmol) was dissolved in anhydrous diethyl ether (50  mL).  To this solution was added slowly a solution of jn-BuLi (2.5 mL, 1.6  M, 4 mmol) in hexane.  The mixture was stirred at room temperature for 2 h  and then a mixture of TMEDA (0.5 g, 4 mmol) and n-BuLi (2.5 mL, 1.6 M, 4 mmol) in hexane was added.  The reaction mixture was left stirring for 2  days, after which 50 mL of THF was added followed by aldehydic resin g, 4 mmol).  (1.35  The mixture was further stirred for 4 days and treated as  described in Section 2.5.1  to give polymer-VIII as a brown resin.  48  2.5.9  Reaction of Lithium Derivative of (S,R)-PPFA with Aldehydic Resin, Polymer-VIII* This was prepared in a manner similar to that used for polymer-VIII,  but replacing PPFA by (S.R)-PPFA. Analytical and Mossbauer data for these polymers are given in Table 5.1.  2.6  SYNTHESES OF PALLADIUM AND PLATINUM COMPLEXES OF POLYMER-BOUND FERROCENE DERIVATIVES  2.6.1  Palladium Complexes (i)  Polymer-VI (1.9 g) was added to an acetone solution (30 mL) of  Na PdCl »4H 0 (220 mg, 0.6 mmol) with stirring. 2  H  2  and refluxed for 2 h. was filtered off,  The mixture was stirred  The orange brown palladium complex, polymer-VI-Pd  and washed successively (3x) with water, EtOH, acetone,  THF, CH C1 , hexane and diethyl ether, and dried at 100°C under vacuum. 2  2  (ii)  The orange brown palladium complex, polymer-VII-Pd, was  prepared analogously from polymer-VII (1 g) and Na PdCl »4H 0 (51 mg, 0.14 2  1+  2  mmol). (iii)  The orange brown palladium complex, polymer-VIII-Pd, was  prepared in the same manner from polymer-VIII (0.7 g) and Na PdC^»4H 0 (73 2  2  mg, 0.2 mmol). (iv)  The orange brown palladium complex, polymer-VIII*-Pd, was  prepared in the same manner from polymer-VIII (0.11  g, 0.3 mmol).  (1 g) and Na PdCl -4H 0 2  lt  2  49  2.6.2  Platinum Complexes (i)  Polymer-VI (1 g) was added to a CH Cl /water (1:1) 2  2  (30 mL) of KjPtCl^ (0.12 g, 0.3 mmol) with stirring. stirred and refluxed for 5 h.  solution  The mixture was  The brown black platinum complex,  polymer-VI-Pt was filtered off, washed, and dried as above. (ii)  The dark brown platinum complex, polymer-VII-Pt, was prepared  analogously from polymer-VII (1 g) and K PtCl 2  (iii)  1+  (42 mg, o.i mmol).  The dark brown platinum complex, polymer-VIII-Pt, was  prepared in the same manner from polymer-VIII (0.4 g) and K P t C ^ (42 mg, 2  0.1 mmol). (iv)  *  The brown platinum complex, polymer-VIII -Pt, was prepared in  * the same manner from polymer-VIII  (0.5 g) and K PtCl 2  lt  (63 mg, 0.15 mmol).  Analytical and Mossbauer data for these supported complexes are given in Table 5.3.  50  CHAPTER 3 CATIONIC PALLADIUM(II) COMPLEXES OF FERROCENYLPHOSPHINES  3.1  INTRODUCTION  Homogeneous hydrogenation catalysts comprising metal complexes of phosphines and arsines are well known [36,37]. rhodium(I) complexes [(L-DRhfNBDJJC^  Among these, cationic  have been the most extensively  studied; (L-L) is a bidentate ligand, usually a di(tertiary phosphine) and optically active when necessary [36,37,45].  Such cationic rhodium(I)  complexes of ferrocenylphosphines are effective catalyst precursors for the asymmetric hydrogenation of amino acid precursors (cf. Section 1.2.1). High optical yields are obtained.  Only limited success has been achieved  in attempts to use cationic derivatives of other group VIII metals as homogeneous hydrogenation catalyst precursors.  In particular, Hartley and  coworkers [73,86,87,89] have reported that both the mono-cation palladium(II) derivative [(dppe)PdCl(DMF)JCIO^ in DMF and the di-cation complex [(dppe)Pd(0CMe ) ][C10 ] 2  2  4  2  in CH Cl /0CMe promote the hydrogenation 2  2  2  of styrene to ethylbenzene at 30°C and 1 atm pressure.  Very high catalyst  to substrate ratios (1:5) are necessary for the mono-cation to achieve reduction.  The di-cation is better than the mono-cation with the same  ratio being 1:10.  The hydrogenation of styrene with the di-cation as  catalyst is quantitative but only 10% when the mono-cation is the catalyst.  51  Since cationic palladium(II) complexes of ferrocenylphosphines were unknown at the beginning of this study, it seemed worthwhile to prepare some and study their properties.  In this chapter the synthesis and charac-  terization of a number of neutral and cationic palladium(II) complexes will be presented.  The use of the cationic palladium(II) complexes in  catalyzing the hydrogenation of olefins will also be described.  3.2  RESULTS AND DISCUSSION  3.2.1. Synthesis and Characterization The palladium(II) complexes (L-L)PdCl  2  (L-L = BPPF, PPFA, ISOPFA and  BPPFA) were prepared using the simple ligand exchange reaction as shown in equation 3.1;  a slight excess of the appropriate ligand was used.  The  analytical, physical and NMR spectroscopic data of the products are summarized in Tables 3.1 and 3.2. The *H NMR spectrum of (BPPF)PdCl is similar to that of the free 2  ligand except for a slight line broadening accompanied by a small chemical shift change.  The P{ H} NMR spectrum of this complex, as expected, shows 31  1  only one phosphorus resonance, Figure 3.1. The H NMR data of (BPPFA)PdCl reveal that the -NMe group is not l  2  2  bound to palladium since only one NMe resonance is present, Table 3.2. 31  P{ H} NMR spectrum, Figure 3.2, shows two doublets, J 1  The  = 22.5 Hz, with  both resonances shifted down field from those of the free ligand.  Thus the  BPPFA ligand is bound to palladium through both phosphorus atoms as in the case of (BPPF)PdCl . 2  In the rhodium(I) complex, [(BPPFA)Rh(NBD)]C10^  [20,31], the BPPFA ligand is also P-P bound.  52  (PhCN) PdCl 2  +  2  L-L  •+>  (L-L)PdCl  +  2  2PhCN  (3.1)  M e O ^ N M e  =  L-L  PPh  2  PPh  2  BPPF  2  PPFA  X=H,  R=Ph  ISOPFA  X=H,  R=i-Pr  BPPFA  X = P R , R=Ph 2  A P-N binding mode is found in the rhodium(I) complex [(PPFA)Rh(NBD)]PF L 2 9 ] , i.e. 6  the metal. (L-L)PdCl  both the -PPh and -NMe group of PPFA are bound to 2  2  The same P-N binding mode is found in the palladium complex (L-L = PPFA or ISOPFA) since the H NMR data show two NMe 1  2  resonances at room temperature, Table 3.2.  The resonances of the -NMe  2  group are sharp for the (PPFA)PdCl complex but are broad in (ISOPFA)PdCl . 2  2  This broadening is probably associated with a conformational non-rigidity as found in the complex [(L-L)Rh(NBD)]C10 , where (L-L) is a ligand 4  analogous to PPFA with -P(t-Bu) replacing the -PPh group [23,32]. 2  2  The  53  Table 3.1  M i c r o a n a l y t i c a l r e s u l t s and m e l t i n g p o i n t s f o r (L-L) and ( L - L ) P d C l . 9  n mp( C) (decomp)  Compound BPPF PPFA ISOPFA BPPFA (BPPF)PdCl (PPFA)PdCl (IS0PFA)PdCl (BPPFA)PdCl 2  2  2  2  183 -185 135 -136 57-!59 118 -120 262.-265 170 -172 179 -181 216 -220  Calcd.(%) C 73.67 70.76 64.39 72.96 55.81 50.49 43.65 50.81  H 5.06 6.39 8.58 5.96 3.87 4.53 5.82 4.12  Found{%) N  C  3. 17 3. 75 2. 24  -  2. 26 2. 54 1. 52  a  a: C a l c u l a t e d v a l u e i s based on (L-L)PdCl .CHCl ?  73. 64 71. 26 64. 66 72. 57 55. 41 50. 00 43. 68 51. 17  H 4.90 6.44 8.61 5.98 3.95 4.77 5.84 4.54  N  2. 81 3. 47 2. 44  -  2. 04 2. 51 1. 61  54  Table 3.2 H and P { H } NMR data f o r (L-L) and ( L - L j P d C l * . ]  3 1  Compound  1  NMe  2  BPPF  -  PPFA  1.77(s)  31  Others  4.05, 4.30(2xbt, F e ( C H ) ) ; 7.31(m, Ph^) 1.22(d,J =7.2,CHMe); 3.95(s, F e ( C H ) ) ; 3.56-4.49(m, F e f C ^ ) & CHMe); 7.28-7.78(m, Phg) 0.81-1.51(m, CHMe & CHMeg); 2.09-2.22(m, CHMe ); 3.99(s, F e ( C H ) ) ; 3.93-4.25(m, F e f C ^ ) & CHMe) 1.22(d, J = 7 , CHMe); 3.45-4.45(m, ( C ^ F e t f ^ ) ) 6.87-7.76(m, f j ^ ) 4.18, 4.40(2xbs, F e ( C H ) ) ; 7.43, 8.00(2xm, 6H, 4H, Phg) 1.42(d, J = 7 . 2 , CHMe); 3.40-3.70(m, CHMe); 3.80(s, F e t C ^ ) ) ; 4.29-4.50(m, F e f C ^ ) ) ; 7.20-7.70, 8.10-8.40(2xm, Ph-) &  2.03(s)  2  HH  5  ISOPFA  4  p  -17.61(s) -22.02(s)  5  -5.34(s)  2  5  BPPFA  1.85(s)  (BPPF)PdCl  2  (PPFA)PdCl  2  2.78(s), 3.56(s)  5  HH  &  HH  4  2  -23.28(s), -17.27(s) b  33.54(s) 10.61 ( s )  T a b l e cont'd  55  Compound  NMe  (IS0PFA)PdCl  (BPPFA)PdCl  2  2  2  2.30(bs), 3.33(bs)  2.33(s)  31  Others  1.31-1.75(m, CHMe & CHMe_ ); 2.75, 2.84(2xm, CHMe ); 3.93-4.13(m, CHMe); 4.26(s, FejCgHg)); 4.33-4.64(m, F e t C ^ ) ) 1.31(d, J = 7 , CHMe); 2  p  37.26(s)  2  HH  3.43-3.65, 4.13-4.68 (m, ( C ^ F e f C ^ ) ) ; 5.49-5.76(m,CHMe); 6.91-8.55(m, Phu)  28.33 (d, J =22.5) 36.63 (d, J =22.5) pp  pp  a: A l l s p e c t r a were o b t a i n e d i n CDC1-. C o u p l i n g constants a r e i n Hz. b: The resonance f o r P atom a d j a c e n t t o the amine group i s a t lower frequency ( h i g h e r s h i e l d i n g ) . J  b  56  1  '  n  40  Figure 3.1  1  1  35  1  — ' — " — i — I — i — i — i — r 30  32.3MHz P{ H } NMR spectrum of (BPPF)PdCl. 31  1  -i—r  57  A ' ' ' ' Figure 3.2  i  J i  i  i  40  32.3MHz  31  I  35  i  i  i  "I  30  r  -1 1 1  I  25 P { H } NMR spectrum of (BPPFA)PdCl . 1  2  1  1 | 20  58  1  PPM  r Figure 3.3  I 35  40  i —  1  —I—I—t  — i — i — I — i — r 30  32.3MHz ^ P ^ H } NMR spectra of (PPFA)PdCl , A; (ISOPFA)PdCl , B. 2  59  31  P{ H} NMR spectra of (PPFA)PdCl and (IS0PFA)PdCl show the expected 1  2  2  single phosphorus resonance, Figure 3.3. The cationic palladium(II) complexes [(L-L)PdS ][C10j (L-L = BPPF 2  2  and PPFA), I-IV, were prepared as shown in equation 3.2.  (L-L)PdCl  9  c  2AgC10, — CH C1 /S 2  *  The analytical  C(L-L)PdS ][C10 ] 2  4  2  +  2AgCl  2  (3.2) (L-L) = BPPF or PPFA S « DMF or py  and spectroscopic data of the products, Tables 3.3 and 3.4, are in accord with their formulation.  The IR spectra of a l l four cationic complexes  exhibit a broad band at 1090 cm  -1  and a medium sharp band at 620 c m ; -1  these are unsplit and indicate that the perchlorate ions do not interact with the cation [91].  The complexes I and III show IR absorption bands at  1605 and 1220 cm" consistent with the presence of coordinated py [92a]. 1  The complexes II and IV show a strong relatively broad absorption at 1636 cm" consistent with direct coordination of DMF ligands to palladium 1  through their carbonyl oxygen atoms [92b].  The H NMR spectra of the l  complexes II and IV show two broad singlet resonances for the two Me groups in the DMF ligand; these resonances are sharp in the free DMF ligand [93a]. The proton resonances for the py ligand in the complexes I and III are broader than those for the free py ligand [93b].  The P{ H} NMR 31  1  Table 3.3 M i c r o a n a l y t i c a l r e s u l t s and melting points f o r the c a t i o n i c palladium complexes. mp(°C) (decomp)  C  Calcd.(%) H N  [(BPPF)Pd(py) ][C10 ] . I  194-196  51.92  3.76 2.75  [ ( B P P F ) P d ( D M F ) ] [ C 1 0 ] , II  155-159  47.76 4.21  [(PPFA)Pd(py) ][C10 ] . I l l  158-163  [ ( P P F A ) P d ( D M F ) ] [ C 1 0 ] . IV [(BPPF)PdCl(DMF)][C10 ]  Complex  2  4  2  2  2  4  4  2  2  2  4  2  A  ,V  C  3.98  2.66  2.71  47.27 4.23  2.55  47.78  4.23 4.64  47.35 4.34  5.00  144- 148  43.05  4.74 4.71  43.20 4.86  4.23  145- 148  49.13 4.31  49.77 4.22  1.79  Data a r e c a l c u l a t e d f o r the d i h y d r a t e .  1.55  51.24  Found(%) H N  a  61  T a b l e 3.4  'H and P { ' H } NMR data f o r the c a t i o n i c p a l l a d i u m complexes. 31  31  Complex  I  4.63, 4.80(2xbm, F e C C ^ ^ ) ;  3  p  32.84(s)  6.90-7.18, 7.20-7.45, 8.58-8.88(3xbm, N C ^ ) ; 7.48-8.03(m, Phg) II  3.08, 3.33(2xbs, NMe_ );  43.23(s)  2  4.65(bs, F e ( C H ) ) ; 5  4  2  7.38-8.15(bm, Ph^ & CHO) III  20.20(s)  1.83(bd, CHMe);  c  2.50, 3.43(2xbs, NMe ); 2  3.90(s, FetCgHg)); 3.93-4.90(m, F e f C ^ ) & CHMe); 6.75-7.08, 7.25-7.35, 8.15-8.73(3xbm, N C ^ ) ; 7.35-8.25(m, Phg) IV  19.20(s)  1.65(bd, CHMe);  d  2.53, 3.80(2xbs,NMe2); 2.95, 3.30(2xbs, CHONMe^); 3.98(s, F e f C ^ ) ) ; 4.30-4.88(m, FefCgHg) & CHMe); 7.30-8.01 (m, Ph^); 8.31-8.63(m, CHO)  a  b  C D C l , was s o l v e n t unless otherwise s t a t e d . C D C l . C H C 1 . b  C  0  0  0  0  DMF.  62  spectra of complexes I-IV  show the expected single phosphorus resonance,  Table 3.4. The complex [(BPPF)PdCl (DMF^CIC^, V, was prepared in a similar fashion; it seems to be isolable as the dihydrate. stable than complexes I-IV microanalytical results.  This complex is less  and it is difficult to obtain reproducible The instability of this complex may be due to the  partial formation of a chloride bridged species as found in the case of the complex [(dppe)PdCl(DMFJJCIO^ [87], equation 3.3.  2[(L-L)PdCl(DMF)]C10  Ett-L) Pd Cl ][Cl6 ]  4  2  (L-L) •= dppe or BPPF  +  2  2  4  2  2DMF  (3.3) 3.2.2  Hydrogenation Studies The five cationic palladium complexes I-V were examined with regard  to their ability to catalyze the hydrogenation of styrene in DMF solution at 30°C and 1 atm pressure, and all except I were effective, Table 3.5. The highest rate was achieved with complex IV, a derivative of the mixed "hard-soft" ligand PPFA.  The lower reactivity of complexes I,  II  and V  which contain the di (tertiary phosphine) BPPF, is consistent with the results of Hartley and coworkers as described in the Introduction Section 3.1) for the complex [(dppe)PdCl(DMF)]C10^.  (cf.  Judging by the present  results, Table 3.5, the ferrocene skeleton does seem to have a positive effect on the rate of hydrogenation of styrene.  63  T a b l e 3.5 C a t a l y t i c hydrogenation o f o l e f i n s by c a t i o n i c p a l l a d i u m complexes I-V . a  Complex  Olefin  Solvent  Time(h)  Product  Chem. Yield(2;)  b  I  styrene  DMF  24  no product  II  styrene  DMF  24  e t h y l benzene  53  III  styrene  DMF  24  ethylbenzene  78  IV  styrene  DMF  2.2  e t h y l benzene  100  V  styrene  DMF  24  e t h y l benzene  20  IV  styrene  DMSO  2.2  e t h y l benzene  56  IV  styrene  py  2.2  e t h y l benzene  22  IV  1-hexene  DMF  2.2  n-hexane  61  IV  cyclohexene  DMF  2.2  cyclohexane  40  IV  o-acylam1noc1 nnamic a c i d  DMF  24  no product  0  IV  styrene  DMF  2.2  e t h y l benzene  24  d  styrene  DMF  72  e t h y l benzene  10  C  0  a : [ o l e f i n ] = 4.36x10" M; [Pd] = 8.72xlO" M i n 5 mL o f s o l v e n t used; 30°C; 1 atm t o t a l pressure o f hydrogen. b : GLC y i e l d based on s t a r t i n g o l e f i n . c : In presence o f excess PPFA, [PPFA]/[Pd] = 5/1. d : Complex i s [(dppe)PdCl(DMF)]C10, V CPd3 = 4xlO" M; [ o l e f i n ] = 0.2M. 2  4  2  64  Clark and coworkers L27] also reported that mixed monodentate platinum system P t t D d ' j C ^ / S n C l g ^ H j O (L = PPh , L' = sulphides, amines) 3  are more effective catalyst for the hydrogenation of styrene to ethylbenzene than P t L C l or P t L ' C l system. 2  2  2  2  The effect is attributed to the  ability of the weaker ligand L' to function as a leaving group. The nature of the ligand S is also important since for (L-L) = BPPF the ease of reduction of styrene in the palladium-catalyzed system seems to be in the order of S  2  = (py) <(Cl,DMF)<(DMF) . The same order (py) <(DMF) 2  is found for complexes of PPFA.  2  2  2  Similar effects are probably responsible  for the lower rates of hydrogenation found for derivatives of PPFA when the solvent is changed from DMF to the more strongly coordinating DMSO or py L94],  Thus an equilibrium such as shown in equation 3.4 might be  responsible for ligand exchange on adding the catalyst precursor to the solution in solvents such as py or DMSO.  [(PPFA)Pd(DMF) ] 2  S = DMSO o r py (in excess)  2+  + S  1*.  [(PPFA)PdS ]  2+  2  + DMF 2  (3.4) When the reaction is carried out in DMF in the presence of excess PPFA the rate of styrene hydrogenation is lowered as well suggesting that the excess ligand is competing for sites on the metal.  Indeed the color  changes from brown to orange in the reaction solution during the  65  Table 3.6 E f f e c t o f Et^N i n the hydrogenation o f s t y r e n e c a t a l y z e d by complex I V . a  Et N/Pd 3  Observed r a t e x 10 , MS"  Enhancement'  0:1  1.51  1.00  5:1  2.58  1.71  10:1  2.42  1.60  20:1  2.64  1.75  »:1  2.08  1.38  a : [ s t y r e n e ] = 4.36xlO"*M; [ I V ] = 8.72x10" 71 30°C; 1 atm t o t a l p r e s s u r e o f hydrogen; 1 b : Observed r a t e i s the maximum s l o p e o f the c : Enhancement i s the r a t i o o f observed r a t e to t h a t w i t h no E t N added. 0  i n 5 mL o f DMF; h. gas uptake p l o t , w i t h EtgN added  66  hydrogenation in the presence of excess PPFA.  This change is not observed  in the absence of excess PPFA. Addition of the base triethylamine to the reaction mixture results in enhancement of the rate of catalyzed styrene hydrogenation, Table 3.6. This rate enhancement is diminished in the presence of a large excess of added base.  A common interpretation of the rate enhancing effect of base  on a reaction is that it encourages the heterolytic cleavage of hydrogen by metal species by mopping up protons [95].  However, it has recently been  demonstrated that the role of a base may be less innocent since some amines can react with group VIII derivatives forming M-C bonds [96]. The complex IV also catalyzes the hydrogenation of 1-hexene and cyclohexene in DMF solution, Table 3.5.  These reductions seem to be slower  than styrene, a not so unusual observation [97a].  A disappointing aspect  of the results is seen in the failure of the complex IV to catalyze the hydrogenation of a-acylaminocinnamic acid, Table 3.5, which seems to eliminate possible use of these systems for asymmetric hydrogenation. When the hydrogenation of a-acylaminocinnamic acid was carried out at 30°C and 100 psi of hydrogen for 24 h, the complex IV decomposed to palladium metal and no reduced organic product was obtained. Selected hydrogenation uptake curves for the hydrogenation of styrene catalyzed by complex IV are shown in Figure 3.4.  The reaction is  completed in a reasonable time when the [styrene]/[Pd] ratio is 100/1 and the solvent is DMF.  The maximum rate is lower when the ratio is decreased  although the reaction is essentially completed in much the same time (cf. curves A and B in Figure 3.4).  Curve C in Figure 3.4 shows the more  •12  Figure 3.4  1  1  I  I  4  6  8  10  Time x 10  , sec  Hydrogen uptake curves f o r the hydrogenation o f styrene c a t a l y z e d o  by A, B, C, #  #  c a t i o n i c palladium complex IV a t 30 C and 1 atm t o t a l p r e s s u r e . [ s t y r e n e ] = 8.72xlO" M, [Pd] = 8.72xlO' M. DMF (5 mL); [ s t y r e n e ] = 4.36xlO" M, [Pd] = 8.72xlO" M, DMF (5 mL); [ s t y r e n e ] = 4.36x10~ M, [Pd] = 8.72xlO" M, DMSO (5 mL). The s c a l e does not permit the d i s p l a y o f the i n i t i a l induction period observed i n these experiments. 2  4  2  2  4  4  Figure 3.5  Dependence of maximum hydrogenation rate on [styrene]: DMF (5 mL) at 30°C, 1 atm total pressure, [Pd] = 8.72xlO" M. 4  CO  [Pd]  x IO , M 3  Figure 3.6 Dependence o f maximum hydrogenation r a t e on [Pd]: DMF (5 mL) a t 30°C, 1 atm t o t a l pressure, [ s t y r e n e ] = 4.36xlO" M. 2  6  A  O  I 0  1 4  I 8  Time x IO" , 2  I 12  sec  Figure 3.7 Hydrogenation uptake curves f o r the hydrogenation o f s t y r e n e ; A, same c o n d i t i o n s as 1n Figure 3.4(A); B, same c o n d i t i o n s as A with Hg added.  71  sluggish uptake obtained in DMSO as solvent; the reaction is completed in about 27 h.  The f i r s t order rate dependence of the reaction on the  substrate, in DMF, is shown in Figure 3.5.  The rate dependence on the  palladium concentration is shown in Figure 3.6.  The data for Figure 3.6  seem to indicate an i n i t i a l f i r s t order dependence which drops off with increasing concentration. These results seem to be consistent with a homogeneous system. However, a rate dependence of the reaction on solvent, substrate and catalyst concentration is also found in some heterogeneous systems [97b]. As a test for homogeneity, the hydrogenation of styrene was performed in the presence of excess mercury [98].  The data are shown in Figure 3.7.  Some inhibition by mercury does occur (~ 16%) by comparison of maximum rate values.  However, the effect would be expected to be much greater if the  system were heterogeneous [98]. In the absence of substrate, complex IV absorbs slightly more than two moles of hydrogen per mole of palladium, a result which suggests metal hydride formation.  Initial oxidative addition of hydrogen to form a  palladium(IV)-hydride seems unlikely because a much higher ionization energy is needed to produce palladium(IV) than platinum(IV) species [99]. There is no H NMR evidence for i n i t i a l metal hydride formation in 1  CD C1 or CDC1 solution (It should be noted that these are not the 2  2  3  solvents used in the hydrogenation reaction).  Hence no hard evidence is  yet available to indicate a possible mechanism for the hydrogenation of styrene and indeed the superiority of the "hard-soft" ligand PPFA which could conceivably be acting as a "hinge" on the metal by dissociation of  72  the -NMe group [20,32]. 2  3.3  SUMMARY The significant finding of this study is that cationic homogeneous  hydrogenation catalyst precursors based on the relatively metal, palladium, can be prepared.  inexpensive  Although they reduce a narrower range  of substrates than their cationic rhodium(I) counterparts this may be a benefit in allowing greater selectivity.  The complex of the ferrocenyl-  phosphine ligand, PPFA, gives higher activities than those of di(tertiary phosphine) ligands such as dppe and BPPF; this is another example of the advantages of using mixed "hard-soft" ligand.  The palladium complexes of  ferrocenylphosphines such as (L-L)PdCl have been used by others in 2  catalyzing hydrosilylation (cf. Section 1.2.2) and Grignard cross-coupling (cf. Section 1.2.3) reactions; this is the f i r s t report of their use as hydrogenation catalyst precursors.  73  CHAPTER 4 PLATINUM(II) COMPLEXES OF FERROCENYLPHOSPHINES  4.1  INTRODUCTION  Rhodium(I) complexes of c h i r a l f e r r o c e n y l p h o s p h i n e ligands such as PPFA, BPPFA and t h e i r analogues a r e a c t i v e c a t a l y s t p r e c u r s o r s f o r the h y d r o s i l y l a t i o n o f ketones such as acetophenone, J a , equation 4.1.  R-C-CH + 3  R R SiH 1  2  [Cat] 2  H /H 0 +  H  R-d-CrL I  OH  2  la b  R=Ph R=Fc  3  3a R=Ph b R=Fc (4.1)  A combination of Rh(I)/MPFA (MPFA = (R.S)-PPFA with -PMe r e p l a c i n g t h e 2  -PPh group) a f f o r d s good r e s u l t s (52% e.e.) u s i n g a-napthylphenyls1lane 2  (2, R = Ph, R x  2  = a-naphthyl) [ 5 3 ] . R e c e n t l y Brunner and coworkers have  found that very good o p t i c a l y i e l d s f o r ketone h y d r o s i l y l a t l o n s (97%) are o b t a i n a b l e u s i n g rhodlum(I) d e r i v a t i v e s of "harder" (non-phosphine c o n t a i n i n g ) c h i r a l ligands such as 4 and 5_ [100-102].  74  Derivatives of other metals such as platinum have received l i t t l e attention. * [L P t C l ] 2  2  Kumada and coworkers [47,103] found that platinum(II) * (L  complexes  = chiral monodentate phosphine) catalyze the hydrosilylation  of a series of alkyl phenyl ketones to give optically active alkylphenylcarbinols in good chemical yields but low optical yields (18.6% maximum). Brunner and coworkers [102] report low optical yields from catalysts based on platinum(II) complexes of chelating amines such as 5. There are only a few reports concerning platinum(II) complexes of ferrocenylphosphines [12,104,105], but none on the synthesis and catalytic properties of platinum(II) complexes of chiral ferrocenyl phosphine ligands. The present study on the asymmetric hydrosilylation of ketones such as 1_ was initiated because of our interest in the catalytic activity of platinum(II) complexes of mixed "hard-soft" ligands such as PPFA, and  75  because of our desire to prepare chiral ferrocenylethanol, 3b.  Successful  use of metal complexes of ligands such as PPFA in this particular reaction would effectively enable the catalyst to breed its own chirality, an objective which has been achieved for the chiral ligand (R)-l,2-bis(diphenylphosphino)propane [106].  Such a route would be viable  because 3_b is easily transformed into ,N,Ni-dimethylaminoethylferrocene, FA [107,108], an amine which is an important precursor for the synthesis of chiral ligands such as (S.R)-PPFA and (S.R)-BPPFA (cf. Section 2.3).  4.2  RESULTS AND DISCUSSION  4.2.1  Synthesis and Characterization The  platinum(II) complexes (L-L)PtCl  2  (L-L = BPPF, (S.R)-PPFA,  (S,R)-IS0PFA and (S,R)-BPPFA) were prepared using equimolar quantities of K PtCl 2  1+  and the appropriate ligand as shown in equation 4.2.  analytical, physical and NMR  The  spectroscopic data for the complexes are  summarized in Tables 4.1 and 4.2.  K PtCl 2  4  + (L-L)  • (L-L)PtCl  2  + 2KC1  L-L = BPPF, (S.R)-PPFA, (S.R)-ISOPFA, (S,R)-BPPFA. (4.2)  76  Table 4.1  M i c r o a n a l y t i c a l r e s u l t s and m e l t i n g p o i n t s f o r (L-L)PtCl . 2  (L-L)  mp(°C) (decomp)  Calcd.(%) C H N  BPPF  158-161  49.77  3.44  0.0  (S.R)-PPFA  191-193  43.06  4.14  1.93  (S.R)-ISOPFA  195-197  37.59  5.01  (S.R)-BPPFA  187-189  50.20 4.29  Calculated value is based  Found[%) C H N  49.25  3.49  0.0  43.16  3.83  1.90  2.19  37.49  5.23  2.05  1.54  50.78 4.32  1.55  8  on ( L - L ) P t C l ~ . H 0 . 9  77  Table 4.2  }  H and ^POH  (L-L)  NMe_2  BPPF  } NMR data f o r ( L - L ) P t C l * .  Others  4.20, 4.43(2xbs, F e t f ^ ) ) ;  12.5(J = ptp  7.49, 7.94(2xm, 6H, 4H, Ph_ )  3765.9)  2  (S.R)-PPFA  2.97(s)  1.39(d, J = 7 . 2 , CHMe);  -11.89  3.77(s)  3.57-3.62(m, CHMe);  (J  HH  3.81(s, F e ( C H ) ) ; &  p t p  =  3981.9)  5  4.25, 4.47(2xbs, F e t C ^ ) ) ; 7.31- 7.57, 8.19-8.25(2xm, Ph_ ) 2  (S.R)-ISOPFA  2.45(bs)  1.26-1.70(m, C H M e & C H M e ) ;  3.45(bs)  2.68, 3.08(2xbm, CHMe );  2  9.51(J = ptp  3889.3)  2  3.96-4.20(m, CHMe); 4.25(s, F e f C ^ ) ; 4.32- 4.64(m, FefCgHg)) (S.R)-BPPFA  2.32(s)  1-31(d. J = 7 . 2 , CHMe);  15.49(d,  3.42-3.58, 4.11-4.63  J --3860.5,  (m, ( C ^ j F e t C ^ ) ) ;  J =8);  5.89-5.97(m, CHMe);  8.70(d,  7.00-8.53(m, Ph_ )  J =3720.3,  HH  2  ptp  pp  ptp  J =8)  b  p p  A l l s p e c t r a were o b t a i n e d i n CDC1,. C o u p l i n g c o n s t a n t s a r e i n Hz. The resonance f o r P atom a d j a c e n t t o the amine group i s a t lower frequency (higher s h i e l d i n g ) .  78  The H NMR spectrum of (BPPF)PtCl is similar to that of its l  2  palladium counterpart (cf. Section 3.2.1). (BPPF)PtCl is shown in Figure 4.1. 2  The P{ H} NMR spectrum of 31  1  This spectrum typically shows a single  resonance due to 66.2% of the phosphorus nuclei coordinated to platinum nuclei other than  1 9 5  P t , and a doublet from the remaining 33.8% of the  phosphorus nuclei coupled to  1 9 5  P t (I = 1/2).  Hence, one observes a  pseudotriplet with relative intensities of 1:4:1 with Jp p being the x  t  separation of the two outer lines.  In the case of (BPPF)PtCl , this value 2  is 3765.9 Hz. The H NMR spectrum of ((S,R)-BPPFA)PtCl is also similar to that of l  2  its palladium counterpart (cf. Section 3.2.1) which shows only a sharp singlet for the -NMe group, Table 4.2.  The P{ H} NMR spectrum, Figure 31  2  4.2, shows two doublet resonances, each with  1 9 5  1  P t satellites.  Thus for  the complex ((S,R)-BPFFA)PtCl both -PPh groups are coupled to platinum 2  2  and hence the ligand is bound through both phosphorus atoms as in its palladium counterpart (cf. Section 3.2.1). For ligands such as BPPFA where there is a choice of P-N or P-P binding the only exceptions to the P-P binding mode found to date are in rhodium(I) complexes of the ligand where -PPh groups are replaced by 2  -P(t-Bu)  groups [23].  2  A P-N binding mode is found in the palladium complex (L-L)PdCl (L-L 2  = PPFA or ISOPFA). (L-L)PtCl  The same binding mode is found in the platinum complex  (L-L = (S.R)-PPFA or (S.R)-ISOPFA) since the H NMR data also l  2  show two NMe resonances at room temperature, Table 4.2.  The  3765.9 Hz  —i—i—i—r—i—i—i—r—i—i—i—i—|—TTT—i—i—r—i—i—i—i—|—i—i—i—i—i—i—i—i—i—|—i—i—i—r—r—i—i—i 30  25  20  1  15  10  5  0  -5  ppm Figure 4.1  121.4  MHz ^ P ^ H } NMR spectrum of  (BPPF)PtCl . 2  8  Hz  3720.3 Hz 3860.5 Hz l  i  r—n—i 1 i— 1 i— 1I— r i— i r— i 1 i— 1—«—• r—n—i— *— i i— i — r * ~ i 1— i 1— —i—i—i—i—i—i—i—i—i—r 30 20 10  T—|—i—i—i—i—I—r-  1  0  -5  ppm 31n,l  Figure 4.2 121.4 MHz P{'H } NMR spectrum of ((S,R)-BPPFA)PtCl . J,  2  \  00 ro  3889.3 Hz  T — | — I — i — i — i — | — i — i — I — r —]—i—i—i—r ~~J—i—i—i—i—|—i—i—i—i—I—r 30  Figure 4.4  20  15  10  5  3U l 121.4 MHz P{'H } NMR spectrum of ((S,R)-ISOPFA)PtCl J,  r  2<  Figure 4.5  The crystal structure of ((S,R)-ISOPFA)PtCl [109]. 9  84  resonances of the -NMe groups are sharp for ((S,R)-PPFA)PtCl complex but 2  2  are broad in ((S,R)-IS0PFA)PtCl as in their palladium counterparts 2  Section 3.2.1).  The  3l  (cf.  NMR spectra for ((S,R)-PPFA)PtCl and  P{ H} l  2  ((S,R)-ISOPFA)PtCl show the expected single resonance with 2  1 9 5  Pt  satellites, Figures 4.3 and 4.4. In the solid state the complex ((S,R)-IS0PFA)PtCl , Figure 4.5, 2  is  chiral, with an S_ configuration for the amine-substituted C(ll) atom, and R configuration for the asymmetrically-substituted  ferrocene moiety [109] as  anticipated from the preparation procedure used [14,15a].  The platinum  atom has cis-square planar coordination, to two Cl atoms and the P and N atoms of the ferrocene ligand; the coordination shows a significant distortion towards tetrahedral geometry, with Cl-Pt-P and Cl-Pt-N trans angles of 169.7(1) and 1 7 1 . 8 ( 2 ) ° , respectively [109].  4.2.2  Hydrosilylation Studies A.  Reduction of aromatic ketones  The platinum(II) complexes (L-L)PtCl  2  (L-L = BPPF, (S.R)-PPFA,  (S.R)-ISOPFA and (S.R)-BPPFA) were examined with regard to their ability to catalyze the hydrosilylation of acetophenone in CH C1 solution, Table 4.3. 2  2  The monohydrosilanes such as HSiCl , HSiEt and HSi(0Bu) give very low 3  3  3  yields (~ 5%) of products under the conditions used in these studies. use of the dihydrosilane Ph SiH 2  2  The  in the catalyzed hydrosilylation of  aromatic ketones is well established [37d,45,47,56]; in the present work this dihydrosilane was used and found to be effective in terms of chemical  85  T a b l e 4.3  H y d r o s i l y l a t i o n o f acetophenone c a t a l y z e d by (L-L)PtCl . a  2  (L-L)  Silane  Chem. Y i e l d ( % )  (S.R)-PPFA  HS1C1  (S.R)-PPFA  HSiEt  (S.R)-PPFA  HSi(0Bu)  (S.R)-PPFA  Ph SiH  2  100  (S.R)-ISOPFA  Ph SiH  2  100  (S.R)-BPPFA  Ph SiH  2  0  BPPF  Ph S1H  2  0  c  Ph SiH  a  3  5  3  0  2  2  2  2  2  5  3  95  2  Ketone/Pt = 100/1; s i l a n e / k e t o n e = 2/1; C H C 1 (3 mL); temp, 60°C; time, 48 h. P r o d u c t i s p h e n y l e t h a n o l , GLC y i e l d . T h e complex i s (PPFA)PtHCl, 7a. 2  b  c  2  86  yield of the alcohol isolated after the necessary hydrolysis step. The P-N bound complexes,  ((S,R)-PPFA)PtCl and ((S.R-ISOPFA)PtCl » 2  are more active than the P-P bound complexes, (BPPF)PtCl . 2  2  ((S,R)-BPPFA)PtCl and 2  This may be a further instance of the efficacious combination  of "hard-soft" ligands with the appropriate metal L27,32,60], since complexes of the mixed "hard-soft" ligands are often employed in catalysis in the hope of creating a vacant site on the metal by dissociation of one end of the ligand.  A number of plausible reaction mechanisms have been  based on this concept, e.g. the asymmetric cross-coupling reaction studied by Kumada and coworkers L20,60], but there is l i t t l e direct experimental evidence supporting this phenomenon.  It does seem that the complex  '[(L-L)Rh(NBD)]C10\ (L-L = PPFA with -AsPh replacing the -PPh group) is 2  2  such an example L 3 2 ] , The hydrosilylation reaction of aromatic ketones with Ph SiH 2  2  catalyzed by ((S,R)-PPFA)PtCl and ((S,R)-IS0PFA)PtCl , equation 4.3, 2  0  2  OSIHPh  2  OH R  R=CH ;(CH2)2CH ; CH(CH ) 3  3  3  2  (4.3)  is  87  unsatisfactory in terms of the optical yield of the isolated alcohol, Table 4.4 to Table 4.6.  In general the best optical yields (e.g.  13.2% from  butyrophenone) are obtained at low temperature and low conversion.  The  same effect was noted by Kolb and Hetflejs [113] for the DI0P/Rh(I) catalyzed hydrosilylation of PhC0CMe . 3  The results in Table 4.5 show that  the configuration of the product is also temperature dependent; R or S alcohols are obtained from the reaction of acetophenone catalyzed by ((S,R)-IS0PFA)PtCl at 20°'or 60°C, respectively. 2  This may be due to a  change in the relative populations of ligand conformations with temperature [23].  As noted above the H NMR spectrum of ((S,R)-ISOPFA)PtCl l  2  indicates  that the complex is conformationally non-rigid in solution. The absolute configuration of the product from acetophenone  (20°C)  is S for the reaction catalyzed by ((S,R)-PPFA)PtCl , Table 4.4, but is R 2  when the ligand is (S,R)-IS0PFA, Table 4.5.  A similar reversal has been  noted in the asymmetric hydrogenation of prochiral olefins when the catalyst precursors are [(L-L)Rh(NBD)]C10  ltt  (L-L) = (S.R)-PPFA or  (S.R)-PPFA with -P(t-Bu) replacing the -PPh group [32]. 2  2  The addition of excess ligand to the reaction mixture, Table 4.6, increases the optical yield although it decreases the chemical yield.  This  may be because the addition discourages the dissociation of the ligand from the metal complex (vide supra) thereby ensuring that the ligand is bound in the chelate mode which would be more favored to induce asymmetry into the reaction product.  The lower yield could be due to the formation of  (L-L) Pt type complexes, X>1, with loss of catalytic activity.  The  A  presence of excess PPFA resulted in the same lowering of catalytic activity  Table 4.4 Asymmetric h y d r o s i l y l a t i o n o f ketones with Ph„SirL c a t a l y z e d by ( ( S , R ) - P P F A ) P t C l , . a  Ketone  Si lane/Ketone  Product  Yield(%)  b  Optical Y i e l d ( % )  C H C0CH  3  1:1  C H CH0HCH  3  85  3.8(S)  C H C0CH  3  2:1  CgH CHOHCH  3  100  4.2(S)  30  9.4(S)  52  7-KS)  6  6  5  5  6  5  5  C H C0(CH ) CH  3  1:1  C H CH0H(CH ) CH  C H C0(CH ) CH  3  2:1  C H CHOH(CH ) CH no product  6  6  5  5  2  2  2  2  CgH COCH(CH )  2  1:1  C H C0CH(CH )  2  2:l  5  6  3  5  3  6  6  d  5  2  5  2  2  2  3  0  C H CH0HCH(CH ) 6  3  5  3  27  2  c  — 1.2(S)  Ketone/Pt = 100/1; CH C1 (3 mL); temp, 20°C; time, 48 h. GLC y i e l d based on s t a r t i n g ketone. 0 p t i c a l y i e l d s are c a l c u l a t e d with respect to o p t i c a l l y pure 1-phenylethanol, [ a ] -52.5° (C2.27, CH C1 )[110]; n - p r o p y l p h e n y l c a r b i n o l , [ a ] -45.9°(C6.1, b e n z e n e ) [ l l l ] ; p h e n y l i s o p r o p y l c a r b i n o l , [ a ] -48.3°(C7, e t h e r ) [ 1 1 2 ] ; and c a l i b r a t e d f o r the o p t i c a l p u r i t y o f c h i r a l l i g a n d used (90%). C o n f i g u r a t i o n s a r e quoted 1n b r a c k e t s . R e a c t i o n time, 90 h.  a  b  2  2  c  D  2  2  n  n  Table 4.5 Asymmetric h y d r o s i l y l a t i o n o f ketones with P h S i r L c a t a l y z e d by ((S,R)-ISOPFA)PtCl, . a  9  Silane/Ketone  Ketone  Time(h)  Product  b  Optical Yield(%)  c  C H C0CH  3  2:1  60  48  CgH CH0HCH  3  100  1.2 (S)  C H C0CH  3  2:1  60  24  CgH CH0HCH  3  100  1.9 (S)  C H C0CH  3  2:1  20  48  CgH CH0HCH  3  100  1.2(R)  C H C0CH  3  2:1  20  24  CgH CH0HCH  3  29  3.9(R)  C H C0CH  3  1:1  20  45  CgH CH0HCH  3  69  4.2 (R)  6  6  6  6  6  5  5  5  5  5  5  5  5  5  5  C H C0(CH ) CH  3  2:1  20  66  CgH CH0H(CH ) CH  3  100  2.8 (S)  C H C0(CH ) CH  3  1:1  20  65  CgH CH0H(CH ) CH  3  21  3.0 (S)  C H C0(CH ) CH  3  1:1  60  48  CgH CH0H(CH ) CH  3  97  1.5 (S)  6  5  2  fi  6  5  5  2  2  2  2  2  5  5  5  2  2  2  2  2  2  CgH COCH(CH )  2  2:1  20  66  CgH CH0HCH(CH )  2  3  C H C0CH(CH )  2  1:1  60  68  CgH CH0HCH(CH )  2  100  5  6  a  Temp(°C)  Chem. Y1eld(%)  5  3  3  5  3  5  3  Ketone/Pt = 100/1; C H C 1 (3 mL); see Table 4.4 f o r footnotes b and c. N o t recorded. d  2  2  d 1.1 (S)  Table 4.6  Asymmetric h y d r o s i l y l a t i o n o f butyrophenone with Ph S1rL c a t a l y z e d by ( ( S , R ) - P P F A ) P t C l ~ . a  9  Temp(°C)  Si lane/Ketone  a  T1me(h)  Chem. Y 1 e 1 d ( % )  Optical Y1e1d(%)  b  2:1  20  48  52  7.1 (S)  2:1  20  70  86  7.2 (S)  1:1  20  48  30  9.4 (S)  1:1  20  48  10  12.6 (S)  1:1  4  93  10  13.2 (S)  1:1  4  93  29  9.1 (S)  1:1  60  48  98  1.6 (S)  d  e  c  Ketone/Pt = 100/1; C H C 1 (3 mL); see Table 4.4 f o r footnotes b and c. (S,R)-PPFA/((S,R)-PPFA)PtC1 d  2  2  =5/1. HC1/((S,R)-PPFA)PtCl = 10/1. e  2  2  91  in the hydrogenation of olefin catalyzed by [(PPFA)Pd(DMF) ] 2  2+  (cf. Section  3.2.2). In the presence of excess HCl, Table 4.6, the chemical yield is increased but the optical yield is decreased.  This may be because the  addition of HCl encourages the dissociation of the dimethylamino group of the ligand from the metal complex, thus generating more vacant sites on the metal and hence a faster rate of butyrophenone hydrosilylation is achieved. The lowering of optical yield may be due to the ligand not being bound in the favorable chelate mode for the asymmetric induction to take place.  B.  Reduction of ferrocenyl ketones In contrast with the results described for equation 4.3, when  acetylferrocene is heated with Ph SiH 2  2  in the presence of ((S.R)-PPFA)-  P t C l , ethylferrocene (60% yield) and ferrocenylethanol (18* yield) are 2  produced directly, no hydrolysis step is necessary, equation 4.4, Table 4.7.  Under the same conditions benzoylferrocene affords only  H F"c-C—R + P h S ! H 2  0  2  Fc-*fc-R OH  H +  Fc-C-R ^  R^CH,; Ph  (4.4)  Table 4.7  M i c r o a n a l y t i c a l r e s u l t s and 'H NMR data f o r FcCH R and FcCH(0H)R. 9  Calcd.(%) C H  Compound  Found(%) C H  ]  H NMR  a  -  FcCH R 2  R = Me  67.38  6.54  67.68  6.30  1 . 2 2 ( t , J = 7 , CH Me); HH  2  2.35(q,J =7, CHgMe); HH  4.21(s, F e ^ g H g ) ) ; 4.70-4.75(m, F e ( C H ) ) 5  R = Ph  73.97  5.80  73.58  5.91  4  3.75(s, CHg); 4.20(s, ( C g H ^ F e f C g H ^ ) ) ; 7.28(bs, Ph)  FcCH(0H)R R = Me  62.67  6.09  62.77  6.04  1.45(d, J = 7 , Me); 1.93(bs, OH); HH  4.21(s, ( C ^ F e f C ^ ) ) ; 4.25-4.75(m, CH)  a  A l l s p e c t r a were obtained i n CDC1,. Coupling constants a r e i n Hz.  93  benzylferrocene.  The minor product from acetylferrocene, S-ferrocenyl-  ethanol, is chiral but the optical yield is low (1.5*).  This result seems  to negate any hopes expressed in the Introduction (cf. Section 4.1) of producing this alcohol in useful optical yield via a catalyzed hydrosilylation reaction. Although reduction of ketones to hydrocarbons during homogeneous catalyzed hydrosilylation is not common, polymethylhydrosiloxane will reduce nitrobenzene and benzaldehyde to aniline and toluene in the presence of Pd/C [114].  respectively  Diethyl ether is obtained from the N i C l  2  catalyzed reaction of ethyl acetate with HSiEt [115]. 3  Stochiometric reductions of organic compounds by hydrosilanes are not unusual [116-119].  For example, Gilman and Diehl [116] showed that  benzophenone can be reduced to diphenylmethane by Ph SiH at high tempera2  ture (270°C). is unaffected.  2  Other diary1 ketones react similarly although acetophenone In the case of benzophenone this uncatalyzed reaction is  believed to proceed via a siloxy intermediate Ph CH0(SiHPh ) which can be 2  2  isolated when the ketone and silane are heated at slightly lower temperature [117]. Kazakova and coworkers [118] showed that treating stoichiometric amounts of acetylferrocene with HSiEt /CF C0 H also gave ethylferrocene. 3  3  2  All these reductions likely involve carbonium ion intermediates as does presumably the LiAlH^/AlC^ reduction of ferrocenyl ketones to the corresponding alkane [8].  Since one of the well established features of the  chemistry of ferrocene compounds is the stability of the a-ferrocenyl carbonium ion [8,79,120], it seems likely that it is this that accounts for  94  the different products formed by hydrosilylation of the ferrocenyl ketones. The hydrogenolysis could involve reaction of the carbonium ion FcC HR with Ph SiH . +  2  2  The carbonium ion could be formed either from  FcCHRO(SiHPh ), the expected hydrosilylation product, or from an inter2  mediate such as JO (vide infra) earlier in the catalytic cycle.  As a test,  the preformed a-ferrocenylethylcarbonium ion (cf. Section 2.2.5) was treated with Ph SiH 2  2  in CH C1 at 60°C. 2  2  The dark colour of the solution  gradually fades (~ 2 days) and ethylferrocene can be isolated from the solution following the same work-up as used for the hydrosilylation of acetylferrocene  (cf. Section 2.1.3).  When an identical reaction is carried  out in the presence of 1 mol % of ((S,R)-PPFA)PtCl , the colour change is 2  almost immediate (60°C, 10 minutes) and ethylferrocene is again produced. These results provide support for the suggestion that the catalyzed hydrogenolysis of the ferrocenyl ketones by Ph SiH proceeds via the 2  2  carbonium ion FcC HR and it should be noted that the reaction, which on +  this basis would involve the more stable ion (R = Ph), affords only the hydrocarbon product.  C.  Some alcohol is produced when R = Me.  Reaction of Ph SiH with (L-L)PtCl 2  2  2  The oxidative addition of HX to platinum(II) complexes such as [PtHY(PEt ) ] (X,Y = C l , Br, I) results in the formation of platinum(IV) 3  2  hydrides in solution L121,122].  Similarly, silanes, germanes and stannanes  add to (dppe)PtCl to give six-coordinated platinum(IV) hydrides [123]. 2  The isolation and characterization of these and related platinum(IV) deriva-  95  tives as solids is difficult and the products readily decompose to the much more stable platinum(II) species in solution [121-124]. In the present investigation it was found that reaction of excess Ph SiH with either (PPFA)PtCl or (IS0PFA)PtCl in CD C1 solution takes 2  2  2  2  2  2  place at ambient temperature as judged by the H NMR spectra of the l  mixtures. ces;  These spectra show a number of high field metal hydride resonan-  the absence of coupling to platinum shows that the species (uniden-  tified) are exchanging hydrides.  Addition of diethyl ether to the reaction  solution precipitates solids which, as judged by the microanalytical data, Table 4.8, are the oxidative addition products _6, equation 4.5.  (I) Ph S1H 2  (L-L)PtC1  2  (II) CD-C1, or CH-C1  I (111) 20 C, 2 days 1  c2  The  ?  (L-L)PtCl (H)(SiHPh ) ' * 2  2  (iv) Et0 2  L-L * PPFA, ISOPFA.  6a L-L - PPFA b L-L - ISOPFA  (L-L)PtClH  • Ph S1HCl 2  7a L-L « PPFA b L-L • ISOPFA (4.5)  product 6a is not stable in solution and the H NMR spectrum (hydride l  region), Figure 4.6, shows a doublet resonance with  1 9 5  P t satellites.  The  NMR data are essentially the same as those of (PPFA)PtHCl, 7a, which can be  Table 4.8  M i c r o a n a l y t i c a l r e s u l t s f o r platinum hydride complexes. Calcd.(%)  Complex  Found(%)  C  H  N  Cl  C  H  N  Cl  (PPFA)PtCl (H)(SiHPh )  51.20  4.49  1.57  7.95  50.43  4.79  1.76  7.18  (PPFA)PtClH  46.42  4.31  2.08  5.27  46.80  4.65  2.30  5.00  46.68  5.34  1.70  8.61  46.36  5.52  1.64  8.44  2  2  (ISOPFA)PtCl (H)(SiHPh ) 2  2  1  -16  1  1  1  1  -17  -18  -19  -20  1—  -21  ppm Figure 4.6  400 MHz H NMR spectrum (hydride r e g i o n ) o f ( P P F A ) P t C l ( H ) ( S i H P h ) 1n C D C 1 Impurities. }  2  2  2  2  solution.  98  independently synthesized from (PPFA)PtCl using the procedure of Clark and 2  coworkers [26] (cf. Section 2.4.4).  The magnitude of 0 2  indicates that the hydride is ci_s to phosphorus [121].  p H  , Table 4.9,  The P{ H} NMR 31  1  data, Table 4.9, indicate that 6a decomposes to 7a in solution in much the same manner as other isolated platinum(IV) hydride species [121-124]. The complex 6b also decomposes in CD C1 , Figure 4.7. 2  platinum(II) hydride resonances, each with  1 9 5  2  P t satellites are present (6  -19.25 and -22.80, Table 4.9) of relative intensity 2.5:1. values indicate that either species could be complex 2b, to phosphorus.  However, two  The 6 and J  with hydride cis  In this case independent synthesis of 7b was not success-  ful. The complexes (BPPF)PtCl and (BPPFA)PtCl do not react with Ph SiH 2  2  2  2  under the same conditions, again showing the difference in reactivities between P-P and P-N binding.  The lack of reactivity with the si lane is  probably associated with the much lower catalytic activity of these species and strongly suggests that the true catalyst for these hydrosilylation and hydrogenolysis reactions is either a platinum(IV) hydride or, more likely, a platinum(II) hydride.  Certainly we find that 7a is an effective  catalyst  for the hydrosilylation of acetophenone under the same conditions, Table 4.3.  D.  Mechanistic consideration The mechanism of the hydrosilylation of ketones catalyzed by metal  complexes is not well established [45,47,58,113] (cf. Section 1.2.2). Hetflejs and coworkers [113] studied the kinetics of hydrosilylation of  Table 4.9  Physical and NMR data for platinum hydride complexes. mp(°C)  Complex  Yleld(X)  (PPFA)PtCl (H)(S1HPh ), 6a 2  2  30  Color  yellow-  (decomp)  136-138  orange  NMR (CD C1 ) 2  ]  @  2  H : 6 -18.56,  J  -1344.  ptH  J -14; pH  ^ P ^ H > : 6 9.34, J (PPFA)PtClH » 7a  43  pale-  139-142  orange  ]  Jp »1341, J -14; tH  J 2  2  25  yellow  #  H : « -18.55,  31  (ISOPFA)PtCl (H)(S1HPh ), 6b  »4401  p t p  114-116  pH  P { H } : 6 9.69, 1  ptp  -4392  *H « -19.25, J  ptH  -1326.  J -14; pH  « -22.80, J , -1143. D  U  J -20 DU  These complexes give very complex H NMR spectra from 0-10 ppm which are not f u l l y I n t e r p r e t e d a t t h i s stage; only the hydride region 1s presented here. Coupling constants are i n Hz. The NMR data are the same as found f o r 7a, thus complex 6a 1s not present 1n s o l u t i o n .  14 Hz  1-  Figure 4.7  20 Hz  1326 Hz -19.25 ppm  -22.8  ppm  400 MHZ H NMR spectrum (hydride region) o f (IS0PFA)PtCl (H)(S1HPh ) 1n C D C 1 ]  2  2  2  2  solution.  101  PhC0CMe with Ph SiH 3  2  2  catalyzed by DI0P/Rh(I) and concluded that the  reaction must f i r s t involve the oxidative addition of the organosllicon hydride to the rhodium(l) species followed by the reaction of the ketone with the silyl-hydrido-rhodium(III) species in the rate determining step of the hydrosilylation.  In order to obtain the final product, pathways  involving intermediates of type 8 and 9. (M = Rh) need to be invoked  \l/  Si I M-0 — C - H I  H I  I C-0 I  M  8  and both have been proposed [45,47,58] (see also Figure 1.4).  Kumada and  coworkers [47] proposed an intermediate such as £ (M = Pt) for the r  *  hydrosilylation of prochiral ketones with MeCl SiH catalyzed by [L P t C l J 2  (L* = chiral phosphine such as (R)-(+)-BMPP).  2  2  (L-L)PtCI j  2  Ph SiH 2  2  (L-L)PtCI (H)(SiHPh ) 2  2  -Ph SiHCI 2  r  o ro  (L-L)PtCIH =C  0  I  (L-L)PtCI(H)(SiHPh ) ( O - C - H )  (L-L)PtCI(O-C-H)  2  I  10 F i g u r e 4.8  Ph SiH 2  I  2  Proposed mechanism f o r the h y d r o s i l y l a t i o n o f ketones w i t h P h S i H by ( L - L ) P t C l , (L-L) = (S.R)-PPFA or (S.R)-ISOPFA. 2  2  2  catalyzed  103  The present studies of the reaction of (L-L)PtCl (L-L = PPFA, 2  ISOPFA) with Ph SiH provide evidence that the oxidative addition of the 2  2  organosilicon hydride to platinum(II) species to afford a platinum(IV) hydride is the i n i t i a l step in the catalytic reaction.  In its  simplest  form a likely mechanism can be written as shown in Figure 4.8 which supports a mechanism based on 8 (M = Pt).  This could account for the low  optical yields since the asymmetric center is developed further away from the metal atom.  An intermediate such as JO could also lead to direct  alcohol formation as found for the acetylferrocene reaction and direct carbonium ion formation leading to hydrogenolysis of the ferrocenyl ketones.  4.3  SUMMARY  In summary, platinum(II) complexes of chiral  ferrocenylphosphines  are effective catalyst precursors for the hydrosilylation of aromatic ketones with Ph SiH . 2  2  Chemical yields of the alcohol obtained following  hydrolysis are high (100%) but optical yields are low (13.2% e.e.  max).  The complexes with mixed "hard-soft" ligands are better catalyst precursors than those with di(tertiary phosphine) ligands.  Under the same conditions  the hydrosilylation of ferrocenyl ketones results in further reduction and affords mainly the alkylferrocene products. FcC HCH +  3  is reduced by Ph SiH to FcCH CH 2  2  2  catalyzed by the complex (PPFA)PtCl .  3  The stable carbonium ion in a thermal reaction which is  The catalyst precursor (L-L)PtCl  2  2  (L-L = PPFA or ISOPFA) reacts with Ph SiH yields the stable platinum(IV) 2  2  104  hydride.  This eliminates Ph SiHCl in solution to afford (L-L)PtHCl. 2  105  CHAPTER 5 POLYMER-BOUND FERROCENE DERIVATIVES AND THEIR PALLADIUM AND PLATINUM COMPLEXES  5.1  INTRODUCTION  Extensive research has been devoted to attach transition metal complexes to inert supports such as organic polymers, s i l i c a , alumina and clays [35,68,69].  Most of the recent work has focused on the conversion of  soluble catalysts,  homogeneous catalysts,  into easily separated polymer-  bound catalysts, heterogenized catalysts, that maintain the important properties of the soluble complexes.  In the case of ferrocene derivatives  there have been some studies concerned with supporting them on inert materials [69-72] (cf. Section  1.3).  Heterogenized catalysts have been employed for a variety of reactions such as hydrogenation, hydrosilylation and hydroformylation [68], with hydrogenation being the most widely studied.  There are some reports  on the use of heterogenized catalysts in asymmetric synthesis [68,69,125]. Most of the asymmetric reactions studied to date concern olefin hydrogenation and in some cases optical yields of the reduced product up to 86% are obtained [125].  The asymmetric hydrogenation of ketones catalyzed  by supported chiral complexes has also been studied, e.g. ~76% optical yield was achieved in the hydrogenation of keto-pantolactone, J , catalyzed by a supported chiral rhodium complex, equation 5.1 [126].  106  (5.1)  The asymmetric hydrosilylation of several aromatic ketones, equation 5.2, is catalyzed by rhodium derivatives of the optically active d i (tertiary phosphine) DI0P supported on polystyrene [49,56].  In the case of  acetophenone (_3, R = Me), optical yields of 1-phenylethanol up to 58% are obtained using a-napthylphenylsilane (4, R = Ph, R = o-naphthyl) [56J. x  2  107  The same reaction has been studied using chiral rhodium(I) complexes bound to inorganic supports such as s i l i c a and glass as the catalysts [127], but the optical yields obtained are much lower (0.4 - 19.7%). The present study is concerned with developing methods for the attachment of substituted ferrocene derivatives to polystyrene type polymers.  The ultimate objective of this work is to develop the use of  these polymers and their metal complexes as catalysts for heterogeneous reactions such as hydrogenation and hydrosilylation, which are catalyzed homogeneously by metal derivatives of ligands based on a ferrocene backbone (cf. Section 1.2).  In this chapter, the synthesis and characterization of  polymer-bound ferrocene derivatives will be presented.  In addition  studies of hydrogenation and hydrosilylation using palladiumUI) and platinum(II) complexes of some of these polymers will be described.  5.2  5.2.1  RESULTS AND DISCUSSION  Synthesis and Characterization A.  Polymer-bound ferrocene derivatives  In view of the high reactivity and ease of preparation of l i t h i o ferrocenes [80,128], these were the reagents of choice in experiments involving the attachment of ferrocene and its derivatives to the crosslinked chloromethylated polystyrene and to the aldehydic polymer. The reactions of lithioferrocene, dilithioferrocene and lithium derivative of FA with the two polymers are shown in equations 5.3 and 5.4. Lithioferrocene reacts with chloromethylated polystyrene to give an  108  (5.3)  109  €K^O>-  CH0  Polymer-VI  (5.4)  no  iron containing product, polymer-I, equation 5 . 3 .  The Massbauer spectra  for polymer-I and ferrocenylphosphine ligands such as BPPF, PPFA, ISOPFA and BPPFA are shown in Figure 5.1 to Figure 5 . 5 , respectively.  These  spectra are clean and show the expected single doublet with the isomer shift (6) and quadrupole splitting (A) values, Table 5 . 1 , in the expected range for simple ferrocene derivatives, Table 5.2 [ 1 2 9 - 1 3 1 j . The solid state 5.6A [ 1 3 2 ] ,  1 3  C NMR spectrum of ferrocene is shown in Figure  The sharp resonance at 70.4 ppm is assigned to the ten  equivalent carbon atoms of ferrocene, since a chemical shift of 6 7 . 9 ppm is quoted for the solution spectrum of ferrocene [ 1 3 3 ] . solid state  1 3  Figure 5.6B shows the  C NMR spectrum of FA, which gives only two peaks at around 70  ppm [132] for the ferrocene ring carbon resonances.  The solution spectrum  of FA gives much better resolution; it shows six different resonances for the ferrocene ring carbon atoms. (C-CH ); 40.6 (N(CH ) ); 3  3  68.4 (CgHg)).  2  1 3  C NMR data for FA in CDC1 : 6 16.1 3  5 8 . 4 (CHCH ); 6 6 . 6 , 6 7 . 0 , 6 7 . 2 , 6 9 . 1 , 8 7 . 0 ( C c ^ ) ; 3  Thus l i t t l e useful structural information can be obtained  from the solid state  1 3  The solid state [132J.  (The  C NMR spectrum of FA. 1 3  C NMR spectrum of polymer-I is shown in Figure 5 . 7  There is a broad peak at around 70 ppm which confirms the loading  of a ferrocene derivative.  As noted above, no useful structural informa-  tion can be obtained from this spectrum. The use of THF as swelling agent was found to be essential in the reaction of lithioferrocene with chloromethylated polystyrene.  Only low  loadings were achieved in its absence [ 1 3 2 ] . The reaction of lithioferrocene with the aldehydic resin to produce  Figure 5.1  Mossbauer spectrum of polymer-I.  112  Figure 5.2  Mossbauer spectrum of BPPF.  113  Figure 5 . 3 Mossbauer spectrum of PPFA.  114  Figure 5.4  Mossbauer spectrum of ISOPFA.  115  -  3  -  2  -  1  0  1  2  3  4  Velocity (mms") 1  1gure 5.5  Mossbauer spectrum of BPPFA.  116  Table 5.1  Polymer  Mossbauer parameters and m i c r o a n a l y t i c a l r e s u l t s f o r polymer supported f e r r o c e n e d e r i v a t i v e s . Mossbauer(mms~^) 6 A  Analytical Found(%)  I  0.44  2.33  Fe(3.39); Cl(2.80)  II  0.53  2.39  Fe(1.30)  Ha  @  Br(0.93)  lib  (?  N(0.83)  III  0.54  2.40  Fe(5.07); Cl(1.72)  IV  0.54  2.39  Fe(4.40)  IVa  @  F e ( l . 4 7 ) ; Br(2.68)  IVb  <a  N(0.72);  Br(1.38)  V  0.53  2.45  F e ( l . 2 1 ) ; C l ( 3 . 1 1 ) ; N(0.54)  VI  0.53  2.42  Fe(2.83); Cl(O.O); N(0.75)  VII  weak  weak  Fe(0.30); P ( 0 . 2 0 )  VIII  0.53  2.37  Fe(1.50); N(0.33); P(0.88)  VIII*  0.55  2.25  Fe(1.50); N(0.40); P(0.94)  Not recorded. In the presence o f TMEDA, Fe(0.38); P(0.40).  #  117  Table 5.2 Mossbauer parameters f o r some f e r r o c e n e compounds.  Compound  Fc-H  6(mms~^)  A(mms"^)  Reference  0.48  2.40  [129]  0.54  2.27  [130]  BPPF  0.44  2.29  [131]  BPPF  0.50  2.31  @  PPFA  0.44  2.34  0  ISOPFA  0.49  2.41  BPPFA  0.52  2.35  Fc-C0CH  3  This work.  (P  118  F i g u r e 5.6  C CP/MAS NMR spectrum o f f e r r o c e n e , A; FA, B [132]. SSB denotes the s p i n n i n g s i d e bands; * denotes the s i d e bands due t o the ferrocene r i n g carbon atoms. The truncated s i g n a l a t around 89 ppm i s due t o the carbon atoms o f the D e l r i n s p i n n e r , polyoxymethylene [132].  1 3  119  T—i—j—i—II  200  l  |  I  150  I—i—I—|—i—i—i—l—|—I—I—I—I—j—i—i—r  100  50  0 ppm  Figure 5.7  , C  T CP/MAS NMR spectrum o f polymer-I [132].  SSB denotes the s p i n n i n g s i d e bands; ** denotes the s i d e bands due t o the broad aromatic peak a t around 130 ppm. The truncated s i g n a l a t around 89 ppm i s due to the carbon atoms o f the D e l r i n s p i n n e r , polyoxymethylene [132].  120  polymer-II, equation 5.4, was carried out under similar conditions to those used for polymer-I.  Although the procedure was not optimized, the  Mossbauer spectrum of polymer-II is essentially the same as that of polymer-I.  The Mossbauer parameters of polymer-II, 6 0.53 rrms" and A 1  2.39 rnns" , are in the expected range for simple ferrocene 1  Table 5.2,  derivatives,  indicating that bonding a ferrocenyl moiety via a -CH(OH) group  rather than a -CH group as in polymer-I has l i t t l e 2  effect.  Since the hydroxyl group in polymer-II is adjacent to the ferrocene moiety it was of interest to see if the polymer would behave like its soluble monomeric counterpart Fc-CH(0H)R in allowing easy displacement of -OH by other groups [107-108,134].  In particular the sequence shown in  equation 5.5 has been developed for the synthesis of the very useful amine FA [107,108]. Treating a suspension of polymer-II in benzene with gaseous HBr causes darkening of color as in the homogeneous reactions [107,108] and simple filtration affords polymer-IIa.  The analytical data, Table 5.1,  show that 0.93% of bromine is incorporated into polymer-IIa.  Although the  reaction conditions have not been optimized, it is clearly facile and the derivative should be useful for further elaboration.  Thus, in the present  work, it has been established that polymer-IIa readily reacts with HNMe  2  affording polymer-Ilb. Alternatively, polymer-II can be taken through to polymer-Ilb without isolating polymer-IIa as in its soluble monomeric counterpart, R = Me, equation 5.5 [107,108].  121  Polymer-IVb  (5.6)  122  The reaction of 1,1'-dilithioferrocene-TMEDA with chloromethylated polystyrene, under the same conditions used to prepare polymer-I, gives a very good loading of iron in the product, polymer-III, equation 5.3.  The  Mossbauer parameters of polymer-III, 6 0.54 rims" and A 2.40 rrms" , are 1  1  also in the expected range for simple ferrocene derivatives, Table 5.2. The solid state polymer-I;  1 3  C NMR spectrum of polymer-III is similar to that of  it shows a broad peak at around 70 ppm confirming the loading  of a ferrocene derivative [132]. The reaction of 1,1'-dilithioferrocene-TMEDA with the aldehydic resin also results in a polymeric material, polymer-IV, with a high iron content, Table 5.1.  The Mossbauer parameters of polymer-IV are almost  identical with those of polymer-II. Since polymer-IV is like polymer-II in having -OH groups, it reacts with HBr to give polymer-IVa, equation 5.6.  Polymer-IVa has a higher  bromine content than polymer-IIa reflecting the higher i n i t i a l loading. The dimethylamino derivative, polymer-IVb, can be prepared in the same manner as polymer-IIb.  The solid state  1 3  C NMR spectra of polymer-IV and  polymer-IVb also show a broad peak at around 70 ppm indicating the loading of a ferrocene derivative [132]. The amine FA can be resolved into its enantiomers [17] and the i n i t i a l lithiation to produce lithium derivative of FA is essentially stereospecific [15b], equation 5.7 (also see Figure 1.1), a new chiral center because of the planar chirality.  and introduces  This, in principal,  allows reactions in equations 5.3 and 5.4 to be carried out to produce  123  FA (5.7)  chiral polymers, although racemic FA was used in the present  investigation.  In order to encourage selective lithiation, TMEDA is not added with the jn-BuLi.  The microanalytical data indicate that the reactions proceed as  expected.  The Mossbauer parameters, Table 5.1, of polymer-V and  polymer-VI show that the attachment has taken place as anticipated. solid state  1 3  The  C NMR spectra of polymer-V and polymer-VI also show a broad  peak at around 70 ppm confirming the loading of a ferrocene derivative in these polymers L132J. The lithiation of BPPF with n-BuLi with or without TMEDA affords a mixture of metalated products which consist mainly of isomers of the hetero ring dilithiated species L135], equation 5.8, X = Y = 1 for L l . . , BPPF. XT-y  Isomers occur because although most ferrocene substituents direct lithium mainly to the "3" position, the -PPh group has an enhanced tendency to 2  124  BPPF  L1 BPPF X+Y  CHO  POLYMER-VII (5.8)  d i r e c t metal a t i o n t o the "2" p o s i t i o n [135], making i t more l i k e a few e x c l u s i v e l y " 2 " - d i r e c t i n g s u b s t i t u e n t s [15b], e.g. equation 5.7.  I t should  be noted that because of the presence of p l a n a r c h i r a l i t y i n d i s u b s t i t u t e d metallocene rings some of the isomers are a c t u a l l y diastereomers.  Because  of these p o s s i b i l i t i e s i t seems u n l i k e l y that a well defined polymer bound BPPF l i g a n d can be prepared v i a the l i t h i u m d e r i v a t i v e of BPPF, L i  BPPF, x+y  and the r e s u l t s of the present study bear t h i s out. Only low loadings of l i g a n d are obtained from r e a c t i o n of the lithium derivative L i  BPPF with the a l d e h y d i c r e s i n , equation 5.8, e i t h e r x+y  i n the presence or absence of TMEDA. The Mossbauer spectrum of polymer-VII  i s too weak f o r p r o c e s s i n g ; t h i s i s due most probably t o the  low i r o n content, Table 5.1. The "2" p o s i t i o n with respect t o the amine group i s the p r i n c i p a l s i t e of l i t h i a t i o n of the l i g a n d analogous t o PPFA, with -SiMe r e p l a c i n g 3  the -PPh group i n the absence of TMEDA [136]. Thus the r e a c t i o n of _n-BuLi 2  125  with PPFA affords the monolithiated derivative of PPFA, L1 PPFA, X = 1, Y x+y  = 0, equation 5.9.  However, in the present study no polymer-bound product  was obtained following the reaction of this monolithiated derivative with the aldehydic resin, presumably because of the steric hindrance on the "top" ring of PPFA. The lithiation of PPFA with two moles of n-BuLi/TMEDA results mainly 1n hetero ring dilithiation although again other metalated products are present [135,136]. equation 5.9,  The dilithiated product L1 PPFA, X = Y = 1, x+y  is also a mixture of isomers since lithiation can occur at  any of the remaining three position on the P-N substituted ring, the top ring, although the most likely position is adjacent to the amine group (vide supra).  PPh  2  PPh  (1) n - B u L i ( i i ) n-BuLi/ TMEDA  PPFA  L i X+Y PPFA  . POLYMER-VIII  (5.9)  2  126  The reaction of the lithium derivative Li .PPFA with the aldehydic X+y  resin affords polymer-VIII. satisfactory loading.  Microanalytical data, Table 5.1, show a  The Mossbauer spectrum is usually a clean doublet  similar to that of the unbound ferrocenylphosphine ligands as shown in Figure 5.2 to Figure 5.5.  Some preparations show two doublets in the  Mossbauer spectrum; the outer doublet with A 2.35 urns  -1  indicates the  presence of a bound ferrocene derivative while the inner doublet with its much smaller A 0.66 mms' , indicates the presence of traces of an Fe(III) 1  impurity.  The increase in isomer shift for polymer-VIII as compared to the  unbound PPFA ligand, Tables 5.1 and 5.2,  is probably an indication that  substitution is, as anticipated mainly on the "bottom" ring of PPFA, since the isomer shift for polymer-VIII, 6 0.53 mms , is almost the same as -1  that of the BPPFA ligand, 6 0.52 mms . -1  In order to prepare an optically active version of polymer-VIII, * polymer-VIII , racemic PPFA is replaced by (S.R)-PPFA. The Mossbauer  * parameters of the iron doublet observed for polymer-VIII , Table 5.1, compare well with the parameters from polymer-VIII.  These results give a  measure of the reproducibility of the experimental procedures used.  This  methodology was developed to encourage polymer attachment to the bottom ring of PPFA. The microanalytical data, Table 5.1, for polymer-VIII and * polymer-VIII also agree well, indicating comparable loadings.  127  B.  Palladium and platinum complexes of polymer-bound ferrocene derivatives  Polymer-VI, -VII, -VIII and -VIII* a l l react with Na PdCl^, 2  equation  5.10, with incorporation of Pd and Cl as judged from the microanalytical data, Table 5.3.  The Cl:Pd ratio in each is ca. 2.  Na PdCl 2  In polymer-VI-Pd the  4  Polymer-Y  • Polymer-Y-Pd  + 2NaCl  Y = VI, VII, VIII, VIII*  (5.10)  N:Pd ratio is 2.3:1  indicating that not a l l the nitrogen atoms are bound  even if the complex is of the (NR ) PdCl type. 3  2  2  The Mossbauer parameters  of polymer-VI-Pd, Table 5.3, are essentially unchanged as compared with those of polymer-VI, Table 5.1. Polymer-VII-Pd seems to have a considerable excess of Pd for a PdCl type complex since the P:Pd ratio is 1:1.7 even though the Cl:Pd ratio is much as expected.  These analytical results are reproducible and it is  difficult to account for them.  Perhaps in this case the side chain of the  polymer has become involved in binding the metal since the unbound ligand BPPF forms a chelate complex with PdCl of known and expected structure 2  [62,90].  2  128  Table 5.3  Mossbauer parameters and microanalytical results for palladium and platinum complexes of polymer supported ferrocene derivatives. Mbssbauer(imms"^)  Polymer  6  Analytical Found(%)  A  Vl-Pd  0.50  2.45  Pd(2.44); Cl(1.71); N(0.75)  Vl-Pt  0.53  2.44  Pt(3.81); Cl(1.25); N(0.84)  VH-Pd  @  P d ( l . l l ) ; Cl(0.87); P(0.20)  VH-Pt VHI-Pd  Pt(0.59); Cl(0.20); P(0.17) 0.53  2.39  Pd(1.36); Cl(1.20); N(0.29); P(0.57)  VHI-Pt  0.57  2.29  Pt(1.99); Cl(0.62); N(0.30); P(0.64)  VIII*-Pd  0.57  2.23  Pd(2.23); Cl(1.95); N(0.43); P(0.94)  VIII*-Pt  0.53  2.27  Pt(2.51); Cl(0.92); N(0.30); P(0.75)  Not recorded.  129  In polymer-VIII-Pd, the P:Pd ratio is 1.4:1, Table 5.3.  These data  are reasonable for a P-N bound PdCl complex (cf. Section 3.2.1). 2  This  * P-N mode of binding is also found in the polymer-VIII -Pd since the P:Pd ratio is also 1.4:1.  The Mossbauer parameters of polymer-VI11-Pd and  polymer-VIII -Pd, Table 5.3, are l i t t l e changed from those of polymer-VIII and polymer-VIII*, Table 5.1.  * The four polymers, polymer-VI, -VII, -VIII and -VIII , a l l react with K P t C l , equation 5.11, to give dark colored resins with incorporation 2  4  K PtCl 2  4  Polymer-Y  • Polymer-Y-Pt  + 2KC1  Y = VI, V I I , V I I I , V I I I *  (5.11)  of Pt and Cl as judged from the microanalytical data, Table 5.3.  In the  case of polymer-VI-Pt, the N:Pt ratio is 3:1 indicating that not a l l the nitrogen atoms bind to the metal as in poymer-VI-Pd. polymer-VI-Pt is ca. 2.  The Cl:Pt ratio in  The same ratio is found for the other three  supported platinum derivatives.  The Mossbauer parameters, Tables 5.1 and  5.3, are essentially unchanged in the series polymer-VI,  130  polymer-VI-Pd and polymer-VI-Pt, showing that no oxidation of the iron takes place during the metal binding reactions [137], The loading of BPPF is low in polymer-VII, thus a low percentage of Pt is found in polymer-VII-Pt.  The Mossbauer spectra of polymer-VII,  polymer-VII-Pd and Polymer-VI I-Pt are all too weak for processing and therefore are not useful.  The microanalytical data yield a 2:1 ratio for  P:Pt in polymer-VII-Pt, indicating a chelating structure as found for many metal derivatives of the unbound BPPF ligand [90,138]. In the case of polymer-VIII-Pt, the P:Pt ratio is again 2:1.  These  data suggest that the ligand is not using the -NMe group to bind to the 2  metal in these materials, even though the unsupported PPFA ligand is P-N bound in its platinum(II)  complexes (cf. Section 4.2.2).  The P-P mode of  binding in polymer-V 111-Pt is also maintained to some extent in the * polymer-VIII -Pt, since the P:Pt ratio is ~1.9:1. The Mossbauer  *  parameters of polymer-VI I I-Pt and polymer-VIII -Pt, Table 5.3, show very  *  l i t t l e difference from those of polymer-VIII and polymer-VIII , Table 5.1. 5.2.2  Hydrogenation Studies A.  Supported palladium complexes  There are many examples of studies of the catalytic properties of Pand N-bound supported catalysts [68],  but l i t t l e is known about the mixed  P-N donor systems such as polymer-VIII-Pd.  The results of a number of  olefin hydrogenation reactions employing polymer-VI-Pd, polymer-VII-Pd and polymer-VIII-Pd as catalysts are summarized in Table 5.4 to Table 5.7; all three are effective.  131  Styrene and a-methylstyrene are readily hydrogenated at 1 atm pressure and 60°C in benzene in the presence of polymer-VIII-Pd, whereas cyclohexene is hydrogenated at a slower rate, Table 5.4.  Under the same  conditions 1-hexene is both hydrogenated and isomerized; trans-2-hexene the major product.  is  The catalyst can be recycled without loss of activity  as is seen in runs 8-10, Table 5.4. The nature of the solvent is an important factor that can be varied in order to control the activity and selectivity of supported hydrogenation catalysts [68a].  The effect of solvent on styrene hydrogenation catalyzed  by polymer-VIII-Pd is summarized in Table 5.5.  The relative rate of  hydrogenation increases with the solvent polarity even though benzene is a better solvent for swelling polystyrene than is MeOH or EtOH [68a,139]. Low rates are obtained in halogenated solvents such as CHC1 and CH C1 , 3  2  2  Table 5.5. Table 5.6 shows the catalytic activities of the three polymers, polymer-VI-Pd, polymer-VII-Pd and polymer-VIII-Pd, with respect to olefin hydrogenation at 30°C in MeOH.  The P-N bound complex, polymer-VIII-Pd, is  clearly less active than the other two.  Since it seems that palladium(II)  derivatives of unidentate functionalized polymers are more active hydrogenation catalysts than derivatives of bidentate [140], this provides further indirect evidence for bidentate binding in polymer-VIII-Pd as described above (cf. Section 5.2.1).  It should be noted that homogeneous  catalytic systems involving [(L-L)PdS ] , (L-L) = PPFA a P-N bound ligand, 2+  2  S = DMF, show higher activity for olefin hydrogenation than the P-P bound complexes (cf. Section 3.2.2).  132  T a b l e 5.4  Hydrogenation o f o l e f i n s i n benzene c a t a l y z e d by polymer-VIII-Pd . a  Run  b  Olefin  Product  Yield(%)  1  styrene  e t h y l benzene  100  2  styrene  e t h y l benzene  100  3  styrene  e t h y l benzene  66  4  a-methylstyrene  •fsopropyl benzene  84  5  cyclohexene  cyclohexane  3  6  cyclohexene  cyclohexane  65  7  1-hexene  iv-hexane  10  trans-2-hexene  44  cis-2-hexene  19  8  styrene  e t h y l benzene  100  9  styrene  ethylbenzene  100  10  styrene  e t h y l benzene  100  c  d  [ o l e f i n ] = 0.25M; o l e f i n / P d • 100/1 u n l e s s otherwise s t a t e d ; benzene (1 mL); temp, 60°C; 1 atm t o t a l p r e s s u r e o f hydrogen; time, 2 h . Run 1, o l e f i n / P d = 50/1; runs 8-10 reused c a t a l y s t from run 1 f o r the 1 s t , 2nd and 3rd times r e s p e c t i v e l y ; run 3, o l e f i n / P d = 200/1. GLC y i e l d based on s t a r t i n g o l e f i n . T i m e , 20 h . a  b  C  d  133  Table 5.5  Hydrogenation o f s t y r e n e c a t a l y z e d by polymer-VIII-Pd . a  Run  Solvent  Yield(%)  1  hexane  59  2  benzene  66  3  THF  100  4  EtOH  100  5  MeOH  100  6  DMF  100  7  CHC1  8  CH C1  a  2  20  3  2  20  [ o l e f i n ] = 0.25M; s o l v e n t (1 mL); o l e f i n / P d = 200/1; temp, 60°C; 1 atm t o t a l p r e s s u r e o f hydrogen; time, 2 h.  b  b  GLC y i e l d based on s t a r t i n g o l e f i n .  134  T a b l e 5.6  Run  Hydrogenation o f o l e f i n s c a t a l y z e d by polymer-bound p a l l a d i u m complexes.  Polymer  Olefin  Product  Yield(%)  1  VHI-Pd  styrene  ethyl benzene  41  2  VH-Pd  styrene  ethyl benzene  100  3  Vl-Pd  styrene  ethyl benzene  99  4  VHI-Pd  a-methylstyrene  isopropylbenzene  17  5  VH-Pd  a-methylstyrene  isopropylbenzene  98  6  Vl-Pd  a-methylstyrene  isopropylbenzene  79  7  VHI-Pd  cyclohexene  cyclohexane  2  8  Vll-Pd  cyclohexene  cyclohexane  26  9  Vl-Pd  cyclohexene  cyclohexane  49  a  [ o l e f i n ] = 0.25M; MeOH (1 mL); o l e f i n / P d = 200/1; temp, 30°C; 1 atm t o t a l pressure o f hydrogen; time, 2 h.  b  GLC y i e l d based on s t a r t i n g o l e f i n .  b  135  Table 5.7  Polymer  Hydrogenation o f 1-hexene i n MeOH .  hexane  Product, Y i e l d ( % )b trans-2-hexene cis-2-hexene  VHI-Pd  28  8  4  VH-Pd  46  23  11  Vl-Pd  61  31  8  See Table 5.6 f o r footnotes a and b.  136  All the catalysts are active for 1-hexene hydrogenation and isomerization in MeOH, Table 5.7.  Again, polymer-VIII-Pd shows the lowest rate.  Under these conditions polymer-V 111-Pd affords more ji-hexane than trans-2hexene.  The reverse is true in benzene at 60°C, Table 5.4.  There also  appears to be less selectivity with respect to trans-2-hexene formation when polymer-VI-Pd and polymer-VII-Pd are the  catalysts.  After the completion of all the reactions, the supported complexes can be easily separated from the reaction mixture by f i l t r a t i o n .  There are  no obvious physical changes in the catalysts especially in the color which remains unchanged.  Other PdX complexes of supported N-donor ligands are 2  good hydrogenation and isomerization catalysts and the oxidation state of the palladium is believed to be unchanged [141].  On the other hand PdX  2  derivatives of supported unidentate phosphines seem to function as hydrogenation catalysts only after reduction to palladium(O) [142].  The cause  of this reduction has been ascribed to a lower P:Pd ratio in the polymer than that required, 2:1, in the unsupported system [142].  As mentioned  above the overall lower activity of polymer-VIII-Pd may be due to the bidentate nature of the supported P-N ligand in polymer-VIII.  B.  Supported platinum complexes  The supported platinum derivatives, polymer-VI-Pt, polymer-VII-Pt, and polymer-VIII-Pt are effective catalysts for the hydrogenation of olefins, Tables 5.8 and 5.9.  In the case of styrene and a-methylstyrene  the relative rates of hydrogenation are comparable to those of the supported palladium(II) counterparts, Table 5.6.  137  Table 5.8  Hydrogenation o f o l e f i n s c a t a l y z e d by polymer-bound platinum complexes . 3  Run  Polymer  Olefin  Product  Yield(%)  1  VHI-Pt  1-hexene  n-hexane  100  2  VH-Pt  1-hexene  _n-hexane  100  3  Vl-Pt  1-hexene  rv- hexane  100  4  VHI-Pt  styrene  ethyl benzene  81  5  Vll-Pt  styrene  ethyl benzene  100  6  Vl-Pt  styrene  ethyl benzene  100  7  VHI-Pt  o-methylstyrene  isopropylbenzene  37  8  Vll-Pt  a-methylstyrene  isopropylbenzene  85  9  Vl-Pt  a-methylstyrene  isopropylbenzene  47  10  VHI-Pt  cyclohexene  cyclohexane  68  11  Vll-Pt  cyclohexene  cyclohexane  100  12  Vl-Pt  cyclohexene  cyclohexane  97  a  [ o l e f i n ] = 0.25M; MeOH (1 mL); o l e f i n / P t = 200/1; temp, 30°C; 1 atm t o t a l p r e s s u r e o f hydrogen; time, 2 h.  b  GLC y i e l d based on s t a r t i n g o l e f i n .  b  138  Table 5.9 Hydrogenation o f styrene c a t a l y z e d by polymer-bound platinum complexes. 3  Run  Polymer  Solvent  1  VHI-Pt  hexane  11  2  VHI-Pt  benzene  40  3  VHI-Pt  THF  56  4  VHI-Pt  MeOH  81  5  recycle-run 4  MeOH  78  6  recycle-run 5  MeOH  79  7  Vl-Pt  hexane  15  8  Vl-Pt  benzene  59  9  Vl-Pt  THF  75  10  Vl-Pt  MeOH  See Table 5.8 f o r f o o t n o t e s a and b.  Yield(%)  100  b  139  The results obtained in 1-hexene and cyclohexene hydrogenation, Table 5.8, are quite different from those using their palladium counterparts, Table 5.6.  In the case of 1-hexene the only product isolated  is _n-hexane, whereas trans-2-hexene and cis-2-hexene are also obtained using their palladium counterparts.  The rate of hydrogenation of cyclo-  hexene is much lower using the supported palladium(II) complexes, Table 5.6, but it is higher using supported platinum derivatives, Table 5.8. The effect of solvent on styrene hydrogenation catalyzed by polymerVl-Pt and polymer-VIII-Pt is summarized, in Table 5.9.  The relative rate of  hydrogenation increases with the solvent polarity as is found for their palladium analogues, Table 5.5. In all the reactions, polymer-VI I I-Pt is less active than the other two supported platinum complexes. The supported complexes can be easily separated from the reaction mixture by f i l t r a t i o n .  The color of the supported complexes changes from  dark brown to greenish brown.  This physical change may indicate that the  oxidation state of the platinum is changed.  Perhaps this is an indication  of reduction to platinum metal (vide infra).  5.2.3  Hydrosilylation Studies A.  Hydrosilylation of styrene catalyzed by supported palladium complexes  Many group VIII metal complexes particularly those of the nickel triad homogeneously catalyze the hydrosilylation of styrene with trichlorosilane, equation 5.12.  The product is either 1-phenylethyl-  140  SiCI SiCI  a-adduct  (3-adduct (5.12)  trichlorosilane (a-adduct) or 2-phenylethyltrichlorosilane (p-adduct) or a mixture of the two [46,47],  Normally palladium(II) derivatives catalyze  the formation of predominantly the a-adduct; the p-adduct results from reactions catalyzed by other metal derivatives such as platinum(II) and nickel(II) [46,47]. Polymer-VII-Pd and polymer-VIII-Pd are effective  catalysts for the  hydrosilylation of styrene with trichlorosilane, Table 5.10.  As  anticipated, the a-adduct is the major product at 70-90°C with some p-adduct being formed at lower temperatures. effective  Polymer-VI-Pd is less  as a catalyst for the same reaction, although the a:p ratio is  s t i l l high.  Other examples are reported [143] where palladium derivatives  supported on 0-, N-, and CN-functionalized polymers show low activity as hydrosilylation catalysts.  The present results seem to be in line with the  report that phosphine ligands are necessary to produce homogeneous hydrosilylation catalysts from palladium(II) salts [144].  141  Table 5.10  H y d r o s i l y l a t i o n o f styrene with H S i C l , catalyzed by polymer-bound p a l l a d i u m complexes .  Temp(°C)  Time(h)  Adduct Yield(%)  Adduct Ratio  Run  Polymer  1  VHI-Pd  40  48  51  79:21  2  VHI-Pd  70  48  99  98:2  3  VHI-Pd  90  48  100  100:0  4  VHI-Pd  70  24  90  99:1  5  VHI-Pd  90  24  100  100:0  6  VH-Pd  70  48  100  95:5  7  recycle-run 6  70  48  100  96:4  8  recycle-run 7  70  48  100  100:0  9  recycle-run 8  70  48  100  100:0  10  Vl-Pd  70  48  38  96:4  11  Vl-Pd  90  24  59  92:8  a  0 1 e f i n , 5nmol; s l l a n e , 6mmol; o l e f i n / P d • 1000/1.  b  GLC y i e l d based on s t a r t i n g o l e f i n .  c  T h e r a t i o o f a-adduct t o B-adduct.  b  c  142  Palladium metal is reported [144] to be inactive as a catalyst for olefin hydrosilylation, therefore in the present investigation, presumably reduction to the metal can be eliminated as the origin of the catalytic effect. In the case of polymer-VII-Pd, this complex can be used at least four times without loss of activity, Table 5.10, and it is interesting to note that the regioselectivity  of the catalyst actually increases after the  f i r s t recycling, resulting in the formation of the a-adduct  exclusively.  When polymer-VII-Pd and polymer-VI11-Pd are recovered after use, their color is lighter.  In order to investigate this, polymer-VIII-Pd was  recovered by filtration after a reaction, carefully washed with acetone and diethyl ether, and dried at 100°C under vacuum.  The microanalytical data,  Table 5.11, reveal no significant change in palladium content, that leaching of the metal from the support is minimal.  indicating  (In some cases of  catalytic hydrosilylation, some loss of metal from the support has been observed [143b, 145]).  The microanalytical data, Table 5.11, do show an  increase in the chlorine content of the polymer and a decrease in the carbon content,  indicating that there probably is a reaction between the  palladium complex and trichlorosilane during the i n i t i a l catalyzed reaction [144,146].  The possibility of formation of new catalytic species following  air exposure during recycling should not be ignored [56], especially as optical yields are lowered progressively during recycling experiments, as will be described next.  143  Table 5.11  Polymer  M i c r o a n a l y t i c a l r e s u l t s f o r polymer-VIII and i t s palladium derivatives.  C  H  Found (%) N  P  Pd  VIII  82.58  7.00  0.33  0.0  0.88  VHI-Pd  81.74  7.00  0.29  1.20  0.57  1.36  77.70  6.90  0.15  2.00  0.57  1.11  VHI-Pd (recovered)  a  S e e a l s o T a b l e 5.1.  b  S e e a l s o T a b l e 5.3.  b  144  B.  Asymmetric hydrosilylation of styrene catalyzed by supported palladium complexes  Kumada and coworkers (.51] found that the palladium(II) complex of (R,S)-PPFA is a homogeneous catalyst for the hydrosilylation of styrene with trichlorosilane (cf. Section 1.2.2).  Since the same reaction is  catalyzed with high regioselectivity by polymer-VI11-Pd, it was of interest to establish the effectiveness of polymer-VIII*-Pd in this regard. The o-adduct from styrene can be converted to 1-phenylethanol using the sequence shown in equation 5.13, Table 5.12.  These reactions proceed  (5.13)  145  Table 5.12 Asymmetric h y d r o s i l y l a t i o n o f styrene with H S i C l , . a  Adduct Run  a  d  Polymer  Yield(%)  b  Adduct  Optical  Ratio  Yield(%)  0  1  VIII -Pd  100  100:0  15.2 (R)  2  recycle-run 1  100  100:0  8.5 (R)  3  recycle-run 2  100  100:0  8.0 (R)  d  0 1 e f i n , 25mmol; s i l a n e , 30mmol; o l e f i n / P d = 1000/1; temp, 70°C; time, 48 h; see Table 5.10 f o r f o o t n o t e s b and c. 0 p t i c a l y i e l d s a r e c a l c u l a t e d with r e s p e c t t o o p t i c a l l y pure 1-phenylethanol, [ a ] -52.5°(C2.27, C H C 1 ) [110]. C o n f i g u r a t i o n s are quoted i n b r a c k e t s . n  2  2  146  with retention and the alcohol isolated following the use of polymer-VIII Pd as catalyst is (R)-l-phenylethanol with an optical yield of 15.2%.  The  optical yield is less than the 52% obtained in the homogeneous system. This result is not unusual, since lower optical yields are normally found for hydrogenation [69] and hydrosilylation [56, 68a, 127] when heterogenized versions of homogeneous catalysts are used. The absolute configuration of product, (R), is the same as would be anticipated from the results of the homogeneous reaction [51].  However,  this is not always the case [127,147]. On recycling polymer-VIII*-Pd, Table 5.11, the same regioselectivity is found but the stereoselectivity decreases.  This provides further  evidence for catalyst modification during recycling as discussed previously.  Lower optical yields were also achieved in the second  hydrosilylation of ketones using a supported rhodium complex which was isolated by filtration in a i r , following the first hydrosilylation reaction [56]. The present results do indicate that the ligand plays an important part in the catalytic cycle and hence reduction of the complex to metal during the reaction seems unlikely.  Although the asymmetric hydrosily-  lation of ketones catalyzed by supported chiral complexes has been studied (cf. Section 5.1),  the present study is the first example of the asymmetric  hydrosilylation of olefin catalyzed by such complexes.  147  C.  Hydrosilylation of 1-hexene catalyzed by supported palladium complexes  Polymer-VII-Pd and polymer-VIII-Pd also catalyze the hydrosilylation of the unactivated olefin 1-hexene with trichlorosilane, equation 5.14, Table 5.13.  As is usually found, 1-trichlorosilylhexane, the terminal  + HS1CI  3  (5.14)  adduct, is the only product under the same conditions as developed for the hydrosilylation of styrene, Table 5.10.  Polymer-VI-Pd is inactive for the  same reaction and this may due to the lack of phosphine ligand in the support as described in the hydrosilylation of styrene (vide supra).  D.  Hydrosilylation of olefins catalyzed by supported platinum complexes and soluble (L-L)PtCl  2  complexes  Polymer-VI-Pt, polymer-VII-Pt and polymer-VIII-Pt are very effective catalysts for styrene hydrosilylation, Table 5.14.  In this regard it is  important to note that the olefin/metal ratio for the supported palladium-catalyzed reactions in Table 5.10 is 1000/1, whereas, the ratio used for the reaction in Table 5.14 is 10,000/1.  The products are the  p-adducts exclusively, which is a dramatic, but not unusual [47], demonstration of the effect of changing the central metal in a catalyst.  148  Table 5.13  H y d r o s i l y l a t i o n o f 1-hexene with  HSiCl*  Run  Polymer  Olefin/M  1  VHI-Pd  1,000  15  2  VH-Pd  1,000  26  3  Vl-Pd  1,000  0  4  VHI-Pt  10,000  95  5  Vll-Pt  10,000  95  6  Vl-Pt  10,000  94  Product Y i e l d ( % )  O l e f i n , 5mmol; s i l a n e , 6mmol; temp, 70°C; time, 24 h. GLC y i e l d based on s t a r t i n g o l e f i n .  b  149  T a b l e 5.14 H y d r o s i l y l a t i o n o f s t y r e n e with H S i C l - c a t a l y z e d a  by polymer-bound platinum complexes . Run  Polymer  Temp(°C)  Time(h)  3  Adduct Yield(%)  b  Adduct Ratio 0  VHI-Pt  70  24  97  0:100  VHI-Pt  70  24  96  0:100  3  Vlll-Pt  90  24  100  0:100  4  recycle-run 3  90  24  95  0:100  5  VH-Pt  70  24  96  0:100  6  Vl-Pt  70  24  99  0:100  1 2  a  d  0 1 e f i n , 5mmol; s i l a n e , 6mmol; o l e f i n / P t = 10,000/1; see Table 5.10 f o r f o o t n o t e s b and c.  ^ O l e f i n , lOmmol; s i l a n e , 5mmol.  150  The selectivity remains unchanged on recycling the catalyst, Table 5.14,  and it is also unaffected by changing the olefin/si lane ratio.  In  some hydrosilylation reactions, the selectivity changes with changing the olefin/si lane ratio L46]. In the hydrogenation studies (cf. Section 5.2.2), the color of the three supported platinum complexes changes from dark brown to greenish brown after use.  The same change is observed in the present study of  olefin hydrosilylation.  Perhaps this is an indication of reduction to  metal in each case and could account for the similarity of their catalytic activity;  Pt/C is a known hydrosilylation catalyst [148].  However, in  this connection, it is claimed that supported platinum(IV) derivatives [149] afford active platinum(II) catalysts for hydrosilylation.  Further  reduction to platinum metal is claimed to result in lower or even zero activity [149]. All three supported platinum complexes are also very effective catalysts for the hydrosilylation of 1-hexene, Table 5.13. the supported palladium-catalyzed reactions, only product obtained.  As is found in  1-trichlorosilylhexane  is the  Again, the supported platinum complexes are more  effective than their palladium counterparts. Soluble platinum(II) complexes (L-L)PtCl  2  (L-L = BPPF, PPFA, ISOPFA  and BPPFA) were also examined with regard to their ability to catalyze the hydrosilylation of olefins with trichlorosilane.  The results of styrene  and 1-hexene hydrosilylation are summarized in Table 5.15.  As found in the  hydrosilylation of ketones (cf. Section 4.2.2), the P-N bound complexes (L-L = PPFA and ISOPFA) are effective for the hydrosilylation of olefins  151  Table 5.15 H y d r o s i l y l a t i o n o f o l e f i n s with H S i C l c a t a l y z e d by s o l u b l e platinum complexes ( L - L ) P t C l . 3  a  9  Run  Olefin  (L-L)  Product  Yield(%)  1  styrene  BPPF  no product  0  2  styrene  BPPFA  no product  0  3  styrene  PPFA  2-phenyl e t h y l trichlorosilane  4  styrene  ISOPFA  100  2-phenylethyl trichlorosilane  100  5  1-hexene  BPPF  no product  0  6  1-hexene  BPPFA  no product  0  7  1-hexene  PPFA  1-trichlorosilylhexane  8  1-hexene  ISOPFA  100  1-trichlorosilylhexane  a  100  0 1 e f i n , 25mmol; s i l a n e , 30nmol; o l e f i n / P t = 10,000/1; C H C 1 2  temp, 70°C; time, 24 h. b  b  GLC y i e l d based on s t a r t i n g o l e f i n .  2  (3 mL);  152  Table 5.16  Hydrosilylation  o f ketones with P h S i H ?  *  ?  a  catalyzed  by polymer-VIII -Pt .  Ketone  Time(d)  Acetophenone  3  Acetophenone  2  Butyrophenone  6  Isobutyrophenone  6  d  Product  Chem. Yield(%)  b  Optical Yield(%)  phenylethanol  10  phenylethanol  95  0  phenylpropanol  6  e  no product  0  1.7 (S)  --  a  Ketone, lOmmol; s i l a n e , 20mmol; ketone/Pt = 1000/1; temp, 20°C.  b  GLC y i e l d based on s t a r t i n g  c  0 p t i c a l y i e l d s are c a l c u l a t e d with r e s p e c t to o p t i c a l l y pure 1-phenylethanol  d  ketone.  ( c f . T a b l e 5.12).  Temp, 70°C. Not enough sample f o r o p t i c a l r o t a t i o n measurement.  c  153  while the P-P bound complexes (L-L = BPPF and BPPFA) are not.  These  results show that the ligands must play an important part in the catalytic cycle to achieve the activity. In contrast to the soluble system, the three supported platinum complexes, regardless of ligands, give uniform reactivity on the hydrosilylation of olefins, Tables 5.13 and 5.14, which again suggests that platinum metal may be involved.  E.  Hydrosilylation of ketones catalyzed by supported platinum complexes  Since soluble platinum(II) complexes (L-L = (S,R)-PPFA and (S,R)ISOPFA) are effective catalyst precursors for the hydrosilylation of ketones (cf. Section 4.2.2), it was of interest to examine the activity of * polymer-VIII -Pt in this regard. In the present investigation, it was  * found that polymer-VIII -Pt is not very effective for the hydrosilylation of ketones with diphenylsilane under the conditions used, Table 5.16. In the case of acetophenone only a 10% yield of 1-phenylethanol obtained at 20°C after 3 days; the optical yield, 1.7%, is lower than that achieved using soluble ((S,R)-PPFA)PtCl  2  (cf. Section 4.2.2).  The absolute  configuration of the product, (S), is the same as that results from the use of soluble ((S,R)-PPFA)PtCl  2  (cf. Table 4.4).  When the reaction tempera-  ture is raised to 70°C the chemical yield is increased but the optical yield is decreased; a similar effect is noted for the soluble case. The supported complex can also be easily separated from the reaction mixture. olefins  The color of the complex is changed as in the hydrosilylation of (vide supra).  154  5.3  SUMMARY In summary, ferrocene and its derivatives can be easily supported on  polystyrene polymers. ferrocene derivatives;  The Mossbauer spectra confirm the loading of in some cases, solid state  show the loading but the resolution is poor.  1 3  C NMR spectra also  The palladium and platinum  derivatives of the ferrocenyl-amine and -phosphine containing polymers are effective hydrogenation catalysts for styrene, a-methyl styrene, cyclohexene and 1-hexene.  Double bond migration also occurs in the palladium-catalyzed  hydrogenation of 1-hexene.  The supported palladium and platinum complexes  are also effective catalysts for the hydrosilylation of olefins with trichlorosilane.  All catalysts can be easily separated from the reaction  mixture by simple filtration and can be reused without loss of activity. In the case of platinum based polymers it is likely that reduction to platinum metal takes place.  The pronounced effect of the attached ligand  in the palladium based catalysts indicates that free metal is not involved in these cases.  155  CHAPTER 6  GENERAL CONCLUSIONS AND PERSPECTIVES  6.1  SOLUBLE PALLADIUM(II) AND PLATINUM(II) COMPLEXES OF FERROCENYLPHOSPHINES  The preparation, characterization, and catalytic properties of soluble palladiumUI) and platinumdl) complexes of ferrocenylphosphines have been described.  Special emphasis has been placed on the studies of  the mixed "hard-soft" ligands such as PPFA, ISOPFA and BPPFA.  Both the P  and N atoms 1n PPFA and ISOPFA ligands are bound to the metals in these complexes, whereas the P-P binding mode is found when the ligand is BPPFA. Although the nature of the binding mode in rhodium(I) complexes of these ligands has been examined [6,43], it would be desirable to investigate this in other transition metals such as iridium, ruthenium and osmium. In the present study the P-N bound palladiumdl) and platinumdl) complexes are more effective catalyst precursors than the P-P bound counterparts for the hydrogenation and hydrosilylation reactions.  Soluble  palladiumUI) and platinumdl) complexes of chiral phosphine ligands have been reported to be effective catalyst precursors for asymmetric hydroesterification [150] and asymmetric hydroformylation [151] of olefins, respectively.  Thus it would be worth investigating these reactions using  the pal ladiumdl) and platinumdl) complexes of the chiral ferrocenylphosphine ligands, particularly those with mixed "hard-soft" ligand systems.  156  6.2  POLYMER-BOUND PALLADIUMUI) AND PLATINUM(II) COMPLEXES OF FERROCENE DERIVATIVES  Polymers functional!zed with ferrocene and ferrocene derivatives such as FA, BPPF, PPFA and (S.R)-PPFA have been prepared. The palladium(II) and platinum(II) complexes of some of these polymers have also been prepared.  These results are supported by microanalytical and  Mossbauer data, and, to some extent, solid state  1 3  C NMR data.  The exact  nature of the binding mode in these polymer-bound complexes is not known and this remains an area to be further investigated. the cross-polarization/magic angle spinning (CP/MAS)  In this connection, 3 1  P NMR spectroscopic  technique could be useful. The polymer-bound palladium(II) and platinum(II) complexes are effective, olefins.  reusable catalysts for the hydrogenation and hydrosilylation of In the case of the platinum based polymers, it is likely that  reduction to platinum metal takes place.  No free metal seems to be  involved in the catalytic reactions of the palladium counterparts. However, this is an area worth investigating using electron spectroscopy for chemical analysis (ESCA) or X-ray photoelectron spectroscopic (XPS) techniques. While the synthesis and catalytic properties of palladium(II) and platinum(II) complexes of polymer-bound ferrocene derivatives have been examined, other metal complexes s t i l l remain to be studied.  In particular,  the rhodium(I) complexes deserve future investigation since the soluble rhodium(I) complexes of chiral ferrocenylphosphines are active catalyst  157  precursors for the asymmetric hydrogenation and hydrosilylation of olefins and ketones (cf. Sections 1.2.1 and 1.2.2). 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Cullen and N.F. Han, "Polymer Supported Ferrocene Derivatives. Catalytic Hydrosilylation of Olefins by Supported Palladium and Platinum Complexes", J . Organometal. Chem., submitted. 4. W.R. Cullen and N.F. Han, "Synthesis and Catalytic Properties of Palladium and Platinum Complexes of Polymer Supported Ferrocenylphosphines", 69th. Canadian Chemical Conference, Saskatoon, Saskatchewan, IN-D3-5, 1986. 5.  I.R. Butler, W.R. Cullen, N.F. Han, and J . J . Ni, "The Design, Synthesis and Use of Ferrocenylphosphines in Metal Catalyzed Reaction", 68th. Canadian Chemical Conference, Kingston, Ontario, IN-F1-03, 1985.  6.  I.R. Butler, W.R. Cullen, N.F. Han, and T . J . Kim, "Metal Hydrides from Cationic Rhodium(I) Species", International Chemical Congress of Pasific Basin Societies, Honolulu, Hawaii, 07L05, 1984.  7. T.G. Appleton, I.R. Butler, W.R. Cullen, N.F. Han, and T . J . Kim, "NMR Spectra of Ferrocenylphosphines and Their Complexes with Platinum Metals", Royal Australian Chemical Institution Conference, Hobart, Tasmania, 1984. 8. W.R. Cullen, N.F. Han, and T . J . Kim, "Cationic Rhodium(I) and Palladium(II) Complexes as Catalyst  Precursors for Olefins Hydrogenation", Canadian American Chemical  Congress, Montreal, Quebec, INI-02,  1984.  

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