Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Synthesis, characterization, and reactivity of ruthenium(II)-diphosphine complexes for catalytic homogeneous… MacFarlane, Kenneth Shawn 1995

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-ubc_1996-091252.pdf [ 14.15MB ]
Metadata
JSON: 831-1.0059566.json
JSON-LD: 831-1.0059566-ld.json
RDF/XML (Pretty): 831-1.0059566-rdf.xml
RDF/JSON: 831-1.0059566-rdf.json
Turtle: 831-1.0059566-turtle.txt
N-Triples: 831-1.0059566-rdf-ntriples.txt
Original Record: 831-1.0059566-source.json
Full Text
831-1.0059566-fulltext.txt
Citation
831-1.0059566.ris

Full Text

SYNTHESIS, CHARACTERIZATION, AND REACTIVITY OF RUTHENIUM(II)-DIPHOSPHINE COMPLEXES FOR CATALYTIC HOMOGENEOUS HYDROGENATION By KENNETH SHAWN M A C F A R L A N E B.Sc, University of British Columbia, 1986 M.Sc, University of British Columbia, 1990 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF T H E REQUIREMENTS FOR T H E DEGREE OF DOCTOR OF PHILOSOPHY in T H E F A C U L T Y OF G R A D U A T E STUDIES DEPARTMENT OF CHEMISTRY We accept this thesis as conforming to the required standard T H E UNIVERSITY OF BRITISH COLUMBIA September 1995 ® Kenneth S. MacFarlane, 1995 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of CH&MIS~TCf The University of British Columbia Vancouver, Canada Date N W . DE-6 (2/88) A B S T R A C T The syntheses and reactivities o f a group o f ruthenium(II) d iphosphine complexes were invest igated, w i t h interest spec i f ica l ly directed toward interactions w i t h s m a l l gas molecu les , as w e l l as toward catalyt ic ac t iv i ty for the homogeneous hydrogena t ion o f nitrites and imines . These potential catalyst precursors were a l l based on the " R u X 2 ( P -P ) " core (where P - P = chela t ing diphosphine and X = C l or B r ) . T h e u t i l i ty o f the f ive -coordinate complexes R u X 2 ( P - P ) ( P A r 3 ) ( A r = P h or /? - to ly l ) , w h i c h were prepared i n h igh y i e l d i n two steps f rom R U C I 3 X H 2 O , was investigated as a precursor to complexes o f the type " R u X 2 ( P - P ) " . These precursors reacted w i t h a w i d e range o f neutral , two-elect ron donor l igands ( L ) to g ive complexes o f the formula t ions R u 2 X 4 ( P - P ) 2 ( L ) and R u X 2 ( P - P ) ( L ) 2 - T h e s e sys tems w e r e m a i n l y i n v e s t i g a t e d w i t h the p r e c u r s o r R u C l 2 ( D P P B ) ( P P h 3 ) ( D P P B = P h 2 P ( C H 2 ^ P P h 2 ) , w h i c h was easier to prepare than the b romo analogue and less expensive than the ch i r a l B I N A P analogue (F igure 1), both o f w h i c h were investigated i n a l imi t ed way . F igure 1 Structure o f the ch i ra l diphosphine ( ^ ? ) - B I N A P . Standard spectroscopic methods, par t icular ly ! H and 3 1 P { ! H } N M R , were used ex tens ive ly to characterize (sometimes i n conjunct ion w i t h X - r a y crys ta l lography) a l l o f the Ru-phosphine species discussed i n this thesis. T h e f ive-coordinate R u C l 2 ( D P P B ) ( P P h 3 ) was characterized c rys ta l lograph ica l ly , and i n so lu t ion is i n e q u i l i b r i u m w i t h the d i ru thenium c o m p l e x [ R u C l ( D P P B ) ] 2 ( p - C l ) 2 (also wr i t t en as R u 2 C l 4 ( D P P B ) 2 ) . T h e RuBr2 (PPh3)3 c o m p l e x , was s h o w n by X - r a y i i crys ta l lography to be o f a geometry s i m i l a r to that o f both the p rev ious ly determined RuCl2(PPh3)3 complex and R u C l 2 ( D P P B ) ( P P h 3 ) . T h e geometry o f the three complexes is pseudo-octahedral , w i t h a weak agostic interaction at the s ixth coord ina t ion site between the R u a t o m and an ortho-hydrogen o f the P P h 3 l i g a n d . T h e r e a c t i v i t y o f R u C l 2 ( D P P B ) ( P P h 3 ) w i t h neutral two-electron l igands (L ) is summar ized i n F igu re 2. R u 2 C l 4 ( D P P B ) 2 ( L ) . R u 2 C l 4 ( D P P B ) 2 (1) F ^ O / Q F L , A , 1 h (2) hexanes R u C l 2 ( D P P B ) ( P P h 3 ) ( - P P h 3 ) NRo - R u C l 2 ( D P P B ) ( L ) 2 L ( - D P P B ) R u 2 C l 4 ( D P P B ) 3 [ H 2 N R 2 ] + [ R u 2 C l 5 ( D P P B ) 2 ] " F igu re 2 Summary o f the react ivi ty o f R u C l 2 ( D P P B ) ( P P h 3 ) w i t h neutral , two-elect ron donor l igands ( L ) . A synthet ical ly superior route to that prev ious ly used i n this laboratory to prepare R u 2 C l 4 ( D P P B ) 2 has been establ ished. T h i s new route f r o m R u C l 2 ( D P P B ) ( P P h 3 ) or R u C l 2 ( D P P B ) ( P ( p - t o l y l ) 3 ) (see F igure 2) also a l lows for the preparation o f the p rev ious ly u n k n o w n b r o m o - a n a l o g u e R u 2 B r 4 ( D P P B ) 2 f r o m R u B r 2 ( D P P B ) ( P P h 3 ) . R u C l 2 ( D P P B ) ( P P h 3 ) reacts w i t h an excess o f S-donor l igands ( L = D M S O , T M S O , D M S , and T H T ) to produce R u 2 C l 4 ( D P P B ) 2 ( L ) species, w h i l e the N - d o n o r l igands L (L-2 = 2NH3, 2py, b ipy , and phen) g ive mononuclear R u C l 2 ( D P P B ) ( L ) 2 species (F igure 2). These monoru then ium complexes can also be synthesized f rom the phosphine-br idged s p e c i e s [ R u C l 2 ( D P P B ) ] 2 ( u - D P P B ) (a l so w r i t t e n as R u 2 C l 4 ( D P P B ) 3 ) . Cis-R u C l 2 ( D P P B ) ( p h e n ) was characterized by X - r a y crystal lography. i i i T h e an ion ic species [ R u 2 C l 5 ( P - P ) 2 ] ~ is p roduced on r e f l u x i n g an excess o f tertiary amine and the R u C l 2 ( P - P ) ( P P h 3 ) complex (Figure 2), a l though the nature o f the r eac t i on , p a r t i c u l a r l y the f o r m a t i o n o f the d i a l k y l a m m o n i u m c a t i o n , i s not w e l l understood. Subsequently, other routes to Ru2X4(DPPB)2 ( X = Cl , B r , I) c o m p l e x e s were deve loped . A l l three can be prepared by the addi t ion o f two equiva len ts o f H X to R u ( D P P B ) ( r i 3 - M e - a l l y l ) 2 , s ince the a l l y l group i s protonated and c l e a v e d o f f as 2-methylpropene. T h e b romo analogue c o u l d not be prepared by the H 2 reduc t ion o f Ru2Br5(DPPB)2 (the establ ished me thodo logy for the ch lo ro analogue) because the precursor to this c o m p l e x , R u B r 3 ( P P h 3 ) 2 , c o u l d not be i so l a t ed free o f c h l o r i d e contamina t ion . Ru2Br4(DPPB)2, however , was successfu l ly i so la ted by metathesis o f Ru2CU(DPPB)2 w i t h M e 3 S i B r . T h e sol id-s ta te r eac t iv i t y o f the f ive -coord ina te c o m p l e x e s R u C l 2 ( P P h 3 ) 3 , RuCl2 (DPPB ) (PPh 3 ) , Ru2Cl4(DPPB) 2, and Ru2Cl4(DPPB) 3 w i t h C O and N H 3 was inves t iga ted . Of interest, these heterogeneous (sol id-gas) react ions y i e l d oc tahedra l complexes , sometimes v i a displacement o f phosphine l igands. Attempts to prepare the p r e v i o u s l y k n o w n but p o o r l y c h a r a c t e r i z e d R u ( B I N A P ) ( T i 3 - M e - a l l y l ) 2 resul ted i n the i s o l a t i o n o f a c r y s t a l , s h o w n by X - r a y d i f f r a c t i o n to be h a l f Ru((R)-BINAP)(T|3-Me-allylh and h a l f (R)-(+)-2,2'-b i s ( d i p h e n y l p h o s p h i n o y l ) - l , l ' - b i n a p h t h y l , c o - c r y s t a l l i z e d w i t h t w o d i s o r d e r e d deuterobenzene regions. X - r a y crystal lography established the structure o f [ (DMA)2H] + [ (PPh3)2 (H)Ru (p -Cl )2(p-H)Ru(H)(PPh3)2]~, the anion conta in ing both terminal and br idg ing hydr ides . In so lu t ion , the species is i n e q u i l i b r i u m w i t h the p rev ious ly k n o w n neutra l , m o l e c u l a r h y d r o g e n c o m p l e x [(r) 2 -H 2 )(PPh3)2Ru(p-Cl)2(p-H)Ru(H)(PPh3)2]-2DMA s o l v a t e ; a proton is thus transferred from the [(DMA)2H]+ cat ion to a terminal hydr ide o f the anion, thereby generating the T | 2 - H 2 moiety . iv S o m e o f the ruthenium(II) D P P B - c o n t a i n i n g complexes were effective catalysts for the hydrogenat ion o f the imines P h C H 2 N = C ( H ) P h and P h N = C ( H ) P h at h igh pressures o f H 2 (1000 psi) and at r oom temperature, w h i l e the trinuclear species [ R u ( H ) C l ( D P P B ) ] 3 was an effective catalyst for the hydrogenat ion o f benzoni t r i le at 1 atm H 2 pressure and 70 °C. v TABLE OF CONTENTS Page A B S T R A C T i i T A B L E O F C O N T E N T S v i T A B L E O F C O M P O U N D N U M B E R S x v i i L I S T O F T A B L E S x x i L I S T O F F I G U R E S x x i i i L I S T O F A B B R E V I A T I O N S x x v i i i A C K N O W L E D G E M E N T S x x x i i Chapter 1 Introduction 1 1.1 Homogeneous Cata lys is 1 1.1.1 A s y m m e t r i c Cata lys i s 4 1.2 Homogeneous Hydrogena t ion 6 1.2.1 A s y m m e t r i c Homogeneous Hydrogenat ion 8 1.3 Scope o f this Thes is 11 1.4 References 14 Chapter 2 Experimental Procedures 19 2.1 Ma te r i a l s 19 2.1.1 Solvents 19 2.1.2 Gases 20 2.1.3 Phosphines 20 2.1.3.1 Preparation o f Cl 2 P(C 5 H8)PCl2, trans-l,2-bis(dichlorophosphino)cyclopentane 21 2.1.3.2 Preparation o f ?ran^- l ,2 - (R2P)2C5Hg, where R = P h , C y 22 2.1.4 Substrates 22 2.1.5 Other Mater ia l s 23 v i 2.1.5.1 Preparation of copper(I) chloride, CuCl 24 2.1.5.2 Preparation of tetrameric chloro(triphenylphosphine)-copper(I), [CuCl(PPh 3)] 4 25 2.1.5.3 Preparation of dibutylammonium chloride, [H 2N(n-butyl) 2] +Cl- 25 2.1.5.4 Preparation of dioctylammonium chloride, [H 2N(tt-octyl) 2] +Cl- 26 2.2 Instrumentation 26 2.3 Catalytic Hydrogenation 29 2.3.1 Ambient Pressure Hydrogenations 29 2.3.2 High Pressure Hydrogenations 30 2.4 Analysis of Hydrogenation Products 32 2.4.1 Measurement of Conversion 32 2.4.2 N M R Characterization of Imines 33 2.4.2.1 PhN=C(H)Ph, iV-benzylideneaniline 33 2.4.2.2 PhCH2N=C(H)Ph,iV-benzylidenebenzylamine 33 2.4.2.3 PhCH 2N=C(Me)Ph, N-(l-methylbenzylidene)benzylamine 33 2.4.3 N M R Characterization of Reduction Products (Amines) 33 2.4.3.1 PhNHCH 2 Ph, JV-phenylbenzylamine 33 2.4.3.2 NH(CH 2 Ph) 2 , dibenzylamine 34 2.4.3.3 NH(CH 2Ph)(CH(Me)Ph), //-(l-methylbenzy^-iV-benzylamine 34 2.5 Synthesis and Characterization of Ruthenium Complexes 34 2.5.1 Ruthenium Precursors 34 2.5.1.1 Preparation of trichloro(A^^V-dimethyl-acetamide)bis(triphenylphosphine)ruthenium(IIf) AyV-dimethylacetamide solvate, RuCl3(PPh 3 ) 2 (DMA)DMA solvate (1) 34 2.5.1.2 Preparation of trichloro(A^N-dimethylacetamide)bis(tri-p-tolylphosphine)ruthenium(III) N,Af-dimethylacetamide solvate, RuCl3(P(p-tolyl)3) 2(DMA)DMAsolvate (2) 36 vii 2.5.1.3 Preparation o f tr ibromo(methanol)bis-(tr iphenylphosphine)ruthenium (III), R u B r 3 ( P P h 3 ) 2 ( M e O H ) (3) 36 2.5.1.4 Preparation o f chlorohydridotr is( t r iphenylphosphine)-ruthenium(II) A^^V-dimethylacetamide solvate, R u ( H ) C l ( P P h 3 ) 3 D M A solvate (4) 37 2.5.1.5 Preparation o f 1,5-cyclooctadieneruthenium(II) ch lor ide polymer , [ R u C l 2 ( C O D ) ] x (5) 37 2.5.1.6 Preparation o f R u ( C O D ) ( r i 3 - a l l y l ) 2 (6) 38 2.5.1.7 Preparation o f R u ( C O D ) ( r | 3 - M e - a l l y l ) 2 (7) 38 2.5.2 Preparation o f R u X 2 ( P A r 3 ) 3 ; X = C l , B r ; A r = P h , p - t o l y l 39 2.5.2.1 X = C l , A r = P h ; Preparation o f dichlorotr is( tr iphenylphosphine)ruthenium(II) , R u C l 2 ( P P h 3 ) 3 (8) 39 2.5.2.2 X = C l , A r = /7-tolyl; Preparation o f dichlorotris( tr i(p-tolylphosphine)ruthenium(II) , R u C l 2 ( P ^ - t o l y l ) 3 ) 3 (9) 40 2.5.2.3 X = B r , A r = P h ; Preparation o f dibromotris( tr iphenylphosphine)ruthenium(II) , R u B r 2 ( P P h 3 ) 3 (10) 41 2.5.3 M i x e d - P h o s p h i n e Complexes , R u X 2 ( P - P ) ( P ( A r ) 3 ) 42 2.5.3.1 X = C l , A r = P h , P - P = D P P B ; Preparat ion o f dichloro(bis(diphenylphosphino)butane)( tr iphenyl-phosphine)ruthenium(II), R u C l 2 ( D P P B ) ( P P h 3 ) (11) 42 2.5.3.2 X = C l , A r = p - t o l y l , P - P = D P P B ; Preparat ion o f dichloro(bis(diphenylphosphino)butane)(tr i( /?-tolyl)-phosphine)ruthenium(II), R u C l 2 ( D P P B ) ( P ( p - t o l y l ) 3 ) (12) 43 2.5.3.3 X = B r , A r = P h , P - P = D P P B ; Preparat ion o f dibromo(bis(diphenylphosphino)butane)( t r iphenyl-phosphine)ruthenium(II), R u B r 2 ( D P P B ) ( P P h 3 ) (13) 43 2.5.3.4 X = C l , A r = P h , P - P = D C Y P B ; Preparat ion o f d ichloro(bis(dicyclohexylphosphino)butane)( t r iphenyl-phosphine)ruthenium(II), R u C l 2 ( D C Y P B ) ( P P h 3 ) (14) 44 2.5.3.5 X = C l , A r = P h , P - P = ( f l ) -BINAP; Preparat ion o f dichloro((/?)-2,2 '-bis(diphenylphosphino)-1,1'-binaphthyl)(tr iphenylphosphine)ruthenium(II) , R u C l 2 ( ( / ? ) - B I N A P ) ( P P h 3 ) (15) 45 v i i i 2.5.4 Preparation o f [Ru2X5(PPh3)4]- or [ ( P P h 3 ) 2 X R u ( u - X ) 3 R u X ( P P h 3 ) 2 ] - C o m p l e x e s ; X = C l or H 45 2.5.4.1 X = C l ; [ (DMA) 2 H]+ [Ru2Cl5(PPh 3 )4 ] - or [ (DMA) 2 H]+ [ ( P P h 3 ) 2 C l R u ( u - C l ) 3 R u C l ( P P h 3 ) 2 ] - (16) .45 2.5.4.2 X = C l and H ; At tempted Preparation o f [PSH]+ [ R u 2 H 3 C l 2 ( P P h 3 ) 4 ] - or [PSH]+ [ ( P P h 3 ) 2 ( H ) R u ( p : - H ) ( ) i - C l ) 2 R u ( H ) ( P P h 3 ) 2 ] - Isolat ion o f [ (Ti2 -H 2 ) (PPh 3 ) 2 Ru(p : -H)(p . -Cl ) 2 Ru(H)(PPh 3 ) 2 ] (17) 46 2.5.4.3 X = C l and H ; [(DMA) 2H]+ [Ru 2 H 3 Cl 2 (PPh 3 ) 4 ] -or [(DMA) 2H]+ [(PPh3)2(H)Ru(p:-H)(p:-Cl)2Ru(H)(PPh3)2]- (18) 47 2.5.5 Synthesis of Diphosphine-Bridged Dinuclear Ruthenium(II) Complexes, [(P-P)X 2Ru(p: 2-(P-P))RuX 2(P-P)] or [ R u X 2 ( P - P ) L 5 ] 2 .49 2.5.5.1 X = C1, P-P = DPPB; [(DPPB)Cl 2Ru(p. 2-(DPPB))RuCl 2(DPPB)] or [RuCl 2 (DPPB)i . 5 ] 2 (19) 50 2.5.5.2 X = Br, P-P = DPPB; [(DPPB)Br 2Ru(U2-(DPPB))RuBr 2(DPPB)] or [RuBr 2 (DPPB)i . 5 ] 2 (20) .50 2.5.5.3 X = C l , P-P = D C Y P B ; [(DCYPB)Cl 2Ru(p: 2-(DCYPB))RuCl 2(DCYPB)] or [RuCl 2 (DCYPB)i . 5 ] 2 (21) 50 2.5.6 Dichloro-tri-u-chloro-bis(bidentate phosphine)-diruthenium(II, III) Complexes, [(P-P)ClRu(u-Cl) 3RuCl(P-P)] or Ru 2 Cl 5 (P -P ) 2 51 2.5.6.1 Preparation of Ru 2Cl5(DPPB) 2 (22) 51 2.5.6.2 Preparation of Ru 2 Cl 5 ((fl)-BINAP) 2 (23) 52 2.5.7 Dihalo-di-p:-halo-bis(bidentate phosphine)diruthenium(II) Complexes, [(P-P)XRu(p:-X)2RuX(P-P)] or R u 2 X 4 ( P - P ) 2 52 2.5.7.1 X = C1, P-P = DPPB; Preparation of Ru 2 Cl 4 (DPPB) 2 (24) 52 2.5.7.2 X = Br, P-P = DPPB; Preparation of Ru 2 Br 4 (DPPB) 2 (25) 54 ix 2.5.7.3 X = Cl, P - P = ( / ? ) - B I N A P ; Preparation o f R u 2 C l 4 ( ( t f ) - B I N A P ) 2 (26) 55 2.5.7.4 X = I, P - P = D P P B ; Preparation o f R u 2 l 4 ( D P P B ) 2 (27) 55 2.5.8 Chlorot r i (p-chloro)( l igand)bis( 1,4-bis(diphenylphosphino)-butane)diruthenium(II) C o m p l e x e s , (L)(DPPB)RU(LI-C1) 3 RUC1(DPPB)] or R u 2 C l 4 ( P - P ) 2 ( L ) 56 2.5.8.1 L = N E t 3 : [ (NEt 3 )(DPPB)Ru(p-Cl) 3 RuCl(DPPB)] (28) 56 2.5.8.2 L = py: [ (py)(DPPB)Ru(p -Cl) 3 RuCl (DPPB)] (29) 56 2.5.8.3 L = H N E t 2 : [ (HNEt 2 ) (DPPB )Ru (p -Cl) 3 RuCl (DPPB)] (30) 57 2.5.8.4 L = acetone: [ (acetone)(DPPB)Ru(p -Cl) 3 RuCl (DPPB)]acetone solvate (31) 57 2.5.8.5 L = acetophenone: [ ( a c e t o p h e n o n e ) ( D P P B ) R u ( p - C l ) 3 R u C l ( D P P B ) ] (32) 58 2.5.8.6 L = D M S O : [ (DMSO)(DPPB )Ru (p -Cl) 3 RuCl (DPPB)] (33) 58 2.5.8.7 L = D M S : [ (DMS)(DPPB)Ru(p -Cl ) 3 RuCl (DPPBYJ (34) 59 2.5.8.8 L = T M S O : [ (TMSO)(DPPB )Ru (p -Cl) 3 RuCl (DPPB)] (35) 60 2.5.8.9 L = T H T : [(THT)(DPPB)Ru(p-Cl) 3 RuCl(DPPB)] (36) 61 2.5.9 Preparation o f [Ru 2 Cls (DPPB) 2 ] - or [ ( D P P B ) C l R u ( p - C l ) 3 R u C l ( D P P B ) ] - C o m p l e x e s 62 2.5.9.1 [ H 2 N ( n - O c t ) 2 ] + [ R u 2 C l 5 ( D P P B ) 2 ] - or [ H 2 N ( n - O c t ) 2 ] + [(DPPB)ClRu(p-Cl) 3 RuCl(DPPB)]- (37) 62 2.5.9.2 [ H 2 N ( n - B u ) 2 ] + [ R u 2 C l 5 ( D P P B ) 2 ] - or [ H 2 N ( n - B u ) 2 ] + [ ( D P P B ) C l R u ( p - C l ) 3 R u C l ( D P P B ) ] - (38) 63 x 2.5.9.3 [DMAH]+ [Ru2Cl 5 (DPPB)2]- or [ D M A H ] + [(DPPB)ClRu(p:-Cl)3RuCl(DPPB)]- (39) 64 2.5.9.4 [H 2 N(n-Bu) 2 ] + [Ru 2Cl 5((/?)-BINAP)2]- or [H 2 N(n-Bu) 2 ] + [((/?)-BINAP)ClRu(u-Cl)3RuCl((/?)-BINAP)]- (40) 64 2.5.9.5 [HNEt3] +[Ru 2Cl 5(DPPB)2]- or [HNEt 3] +[(DPPB)ClRu(|l-Cl)3RuCl(DPPB)]- (41) .65 2.5.10 Synthesis of Chlorohydrido(bidentate phosphine)ruthenium(II) Trimers, [Ru(H)Cl(P-P)] 3 65 2.5.10.1 P-P = DPPB; [Ru(H)Cl(DPPB)] 3 (42) 66 2.5.11 Preparation of Ruthenium(II) Amine Complexes from RuCl2(PPh3)3 , RuCl 2(DPPB)(PPh 3), and [RuCl 2(DPPB)i. 5)] 2........67 2.5.11.1 Preparation of dichloro(bis(diphenylphosphino)butane)-bis(pyridine)ruthenium(II), RuCl 2(DPPB)(py) 2 (43) 67 2.5.11.2 Preparation of dichloro(bis(diphenylphosphino)butane)-bipyridylruthenium(II), RuCl 2(DPPB)(bipy) (44) 69 2.5.11.3 Preparation of dichloro(bis(diphenylphosphino)butane)-(1,10-phenanthroline)ruthenium(II), RuCl2(DPPB)(phen) (45) 70 2.5.11.4 Preparation of dichlorobis(pyridine)bis-(triphenylphosphine)ruthenium(II), RuCl 2(py)2(PPh 3) 2 (46) 72 2.5.12 Reactions of Five-Coordinate Ru(II) Complexes of the Type R u C l 2 ( P ) 3 and R i ^ C L ^ D P P B ^ with Small Gas Molecules 72 2.5.12.1 RuCl 2 (PPh 3 ) 3 with CO in the solid state 72 2.5.12.2 RuCl 2(P(p-tolyl) 3) 3 with CO in the solid state 73 2.5.12.3 RuCl 2(DPPB)(PPh 3) with CO in the solid state 74 2.5.12.4 Ru2CU(DPPB)2 with CO in the so l id state 75 2.5.12.5 RuCl 2 (PPh 3 ) 3 with N H 3 ; Preparation of diamminedichloro(triphenylphosphine)ruthenium(II), RuCl 2(NH 3)2(PPh 3)2 (50) 75 2.5.12.6 RuCl 2(DPPB)(PPh 3) with N H 3 ; Preparation of diamminedichloro(bis(diphenylphosphino)butane)-ruthenium(II), RuCl 2 (DPPB)(NH 3 ) 2 (51) 76 2.5.13 Preparation of ?rans-RuCl2(DPPCP)2 (52) 77 xi 2.5.14 React ions o f RuCl2(DPPB)(PPh 3) w i t h Che la t ing Phosphines ( P - P ) 78 2.5.14.1 P - P = D P P C P , f r ans -RuCl2 (DPPB) (DPPCP) (53) .78 2.5.14.2 P - P = D P P E , * r a / w - R u C l 2 ( D P P E ) 2 (54) 79 2.5.15 Preparation o f Ru(P-P)(Ti 3 -allyl) 2 C o m p l e x e s 79 2.5.15.1 P - P = D P P B , a l l y l = M e - a l l y l ; Preparation o f R u ( D P P B ) ( r i 3 - M e - a l l y l ) 2 (55) 79 2.5.15.2 P - P = D P P B , a l l y l = a l l y l ; At tempted preparation o f R u ( D P P B ) ( n . 3 - a l l y l ) 2 80 2.5.15.3 P - P = ( f l ) - B I N A P , a l l y l = M e - a l l y l ; Preparation o f R u ( ( f l ) - B I N A P ) ( n 3 - M e - a l l y l ) 2 (56) 81 2.6 References 82 Chapter 3 Synthesis and Reactivity of Five-Coordinate Ruthenium(II) Ditertiary Phosphine Complexes 85 3.1 Introduction 85 3.2 Synthesis and Character izat ion of R u 2 C l 5 ( P - P ) 2 , R u 2 C U ( P - P ) 2 » and [Ru(H)Cl(P-P)]3 C o m p l e x e s - A B r i e f R e v i e w 87 3.3 Routes into the B r o m i d e Ana logues and Rela ted Chemis t ry 93 3.3.1 Ruthenium(in) B r o m i d e Complexes , RuBr 3(PPh3)2 93 3.3.2 Ruthenium(II) B r o m i d e C o m p l e x e s 95 3.3.3 R u X 2 ( D P P B ) ( P A r 3 ) , where X = Cl or B r and Ar = P h or (p-tolyl) 97 3.3.3.1 M o l e c u l a r Structure o f R u B r 2 ( P P h 3 ) 3 (10) 100 3.3.3.2 M o l e c u l a r Structure o f R u C l 2 ( D P P B ) ( P P h 3 ) (11) 104 3.3.4 R u 2 X 4 ( D P P B ) 2 C o m p l e x e s 111 3.3.4.1 Preparation o f Ru2CU(DPPB)2 (24) and R u 2 B r 4 ( D P P B ) 2 (25) I l l 3.3.4.2 Preparation o f R u 2 X 4 ( D P P B ) 2 v i a R u ( D P P B ) ( T i 3 - M e - a l l y l ) 2 120 3.3.4.3 Preparation o f R u ( B I N A P ) ( r ( 3 - M e - a l l y l ) 2 (56) 124 x i i 3.3.4.4 Metathesis o f R u 2 C l 4 ( D P P B ) 2 by L i B r or M e 3 S i B r 130 3.4 Reac t ion o f Tert iary A m i n e s w i t h R u C l 2 ( P - P ) ( P P h 3 ) C o m p l e x e s 131 3.4.1 Synthesis and Character izat ion o f [ H 2 N ( n - R ) 2 ] + [ R u 2 C l 5 ( D P P B ) 2 ] - R .= B u (38), Oct (37) 135 3.4.2 Synthesis and Character izat ion o f [H 2 N(/T-BU)2] + [RU 2 C15((/?)-BINAP)2]- (40) 138 3.5 Reac t ion o f Sulfoxides and Thioethers w i t h R u C l 2 ( D P P B ) ( P P h 3 ) 138 3.6 Reac t ion o f Ace tone w i t h R u C l 2 ( D P P B ) ( P P h 3 ) (11) 146 3.7 Reac t ion o f Acetophenone w i t h R u 2 C l 4 ( D P P B ) 2 (24) 147 3.8 Synthesis and Character izat ion o f R u 2 X 4 ( P - P ) 3 C o m p l e x e s 148 3.9 Reac t ion o f One Equiva len t o f Diphosph ine ( P - P ) w i t h R u C l 2 ( D P P B ) ( P P h 3 ) (11) 150 3.9.1 P - P = D P P C P ; Synthesis and Character izat ion o f f r a n s - R u C l 2 ( D P P B ) ( D P P C P ) 150 3.9.2 P - P = D P P E ; Synthesis and Character izat ion o f f r a n £ - R u C l 2 ( D P P E ) 2 152 3.10 Reac t ion o f One Equiva len t o f Diphosphine ( P - P ) w i t h R u C l 2 ( P P h 3 ) 3 (8) : 153 3.10.1 P - P = D P P C P ; Synthesis and Character izat ion o f f r a n s - R u C l 2 ( D P P C P ) 2 154 3.11 S u m m a r y 156 3.12 References 157 Chapter 4 Activation of Dihydrogen by Five-Coordinate Ruthenium(II) Complexes Containing Chelating Ditertiary Phosphines 161 4.1 Introduction 161 4.2 A B r i e f R e v i e w o f M o l e c u l a r Hydrogen C o m p l e x e s and T h e i r Properties and Character izat ion 162 4.3 A Summary o f Relevant Research Prev ious ly D o n e i n this Labora to ry on the Interaction o f D ihyd rogen and Other S m a l l M o l e c u l e s w i t h Ru(II) Diphosph ine C o m p l e x e s 167 4.3.1 Interaction w i t h H 2 i n the Absence o f an A d d e d Base 167 4.3.2 Interaction w i t h H 2 i n the Presence o f an A d d e d Base 169 x i i i 4.3.3 Interaction of Other Molecules with Ru2CLi(DPPB)2 170 4.4 Reactivity of H 2 and Five-Coordinate Ruthenium(II) Diphosphine Complexes Investigated in This Thesis Work 170 4.4.1 Interaction with H 2 in the Absence of an Added Base 170 4.4.1.1 Reaction of RuCl2((/?)-BINAP)(PPh 3) 15 with H 2 in the Absence of an Added Base 174 4.4.2 Interaction with H 2 in the Presence of an Added Base 183 4.5 Reaction of Other Neutral Two-Electron Ligands with Five-Coordinate Ruthenium(II) Complexes 190 4.5.1 Reaction of Ru 2 CU(DPPB) 2 24 with Ethylene 190 4.5.2 Reaction of Ru 2 Cl4(DPPB) 2 24 with Styrene 192 4.5.3 Reaction of RuCl 2(DPPB)(PPh 3) 11 with N 2 193 4.5.4 Reaction of Ru2CLi(DPPB)2 24 with CO 193 4.5.5 Reaction of RuCl 2((/?)-BINAP)(PPh 3) 15 with N 2 194 4.6 Reaction of H 2 with Ru2Cl5(P-P)2 Complexes 195 4.6.1 P-P = DPPB 195 4.6.2 P-P = (fl)-BINAP 197 4.7 A Brief Review Of Ru(II)-Monodentate Phosphine Complexes Containing Molecular Hydrogen and Classical Hydride Ligands Synthesized in This Laboratory 202 4.7.1 X-ray Structure of [(DMA) 2H]+ [(PPh 3) 2(H)Ru(p-Cl) 2(p-H)Ru(H)(PPh 3) 2]- 203 4.7.2 N M R Spectroscopic Studies of [(DMA)2H]+ [(PPh 3) 2(H)Ru(p-Cl)2(p-H)Ru(H)(PPh 3) 2]- 18 207 4.8 Summary 213 4.9 References 214 Chapter 5 Reactions of Ruthenium(II) Phosphine Complexes with N-Donor Ligands 217 5.1 Introduction 217 5.2 Reactions with Pyridine 219 xiv 5.2.1 Reaction of Pyridine with RuCl2(DPPB)(PPh3) and Ru 2Cl4(DPPB) 3 219 5.2.2 Reaction of Pyridine with RuCl2(PPh3)3 ••••• 223 5.2.3 Reaction of Pyridine with Ru 2Cl4(DPPB) 2 224 5.3 Reactions with 2,2'-Bipyridine 228 5.3.1 Reaction of 2,2'-Bipyridine with RuCl2(DPPB)(PPh3) and Ru 2Cl4(DPPB) 3 228 5.3.2 Reaction of 2,2'-Bipyridine with R ^ C l ^ D P P B ^ 232 5.4 Reaction of 1,10-Phenanthroline with RuCl2(DPPB)(PPh3) and Ru 2Cl4(DPPB) 3 233 5.5 Reactions with NH3 241 5.5.1 Reaction of NH3 with RuCl2(DPPB)(PPh3), Ru 2Cl4(DPPB) 3, and Ru2CU(DPPB)2 241 5.5.2 Reaction of N H 3 with RuCl2(DPPB)(PPh3) in the Solid State 246 5.5.3 Observation of Some Dinuclear Ruthenium(II)-NH3 Containing Complexes 246 5.6 Summary 248 5.7 References 249 Chapter 6 Homogeneous Hydrogenation of Imines and Nitriles Using Ruthenium(II) Phosphine Complexes 250 6.1 Introduction 250 6.1.1 Homogeneous Hydrogenation of Imines 250 6.1.2 Homogeneous Hydrogenation of Nitriles 253 6.2 H 2 Hydrogenation Catalyzed by Ruthenium(II) Diphosphine-Containing Complexes 255 6.2.1 Benzonitrile Hydrogenation Catalyzed by [Ru(H)Cl(DPPB)]3 42, (and Observations on Catalytic Hydrogenation of Styrene) 255 6.2.1.1 Rate Measurements 256 6.2.2 H 2 Hydrogenation of Imines at High Pressure 264 6.3 Summary '.' 270 6.4 References 271 xv Chapter 7 Solid-State Reactivity of Five-Coordinate Ruthenium(II) Complexes Containing Phosphine Ligands 274 7.1 Introduction 274 7.2 Solid-State Reactivity of Five-Coordinate Ruthenium(II) Complexes with CO 275 7.2.1 Reaction of RuCl2(PPh3>3 and CO in the Solid State 276 7.2.2 Reaction of RuCl2(P(p-tolyl)3)3 and CO in the Solid State 277 7.2.3 Reaction of RuBr2(PPh3)3 and C O in the Solid State 277 7.2.4 Reaction of RuCl2(DPPB)(PPh 3) and C O in the Solid State 278 7.2.5 Reaction of Ru 2Cl4(DPPB) 2 and CO in the Solid State 279 7.3 Solid-State Reactivity of Five-Coordinate Ruthenium(II) Complexes with N H 3 283 7.4 Solid-state Reactivity of Five-Coordinate Ruthenium(II) Complexes with H 2 and H 2 S 284 7.5 Summary 285 7.6 References 286 Chapter 8 General Conclusions and Some Recommendations for Future Work 288 Appendices 294 I X-Ray Crystallographic Analysis of RuBr2(PPh3)3,10 295 II X-Ray Crystallographic Analysis of RuCl 2(DPPB)(PPh3), 11 303 IE X-Ray Crystallographic Analysis of [TMP]+[(DPPB)ClRu(u-Cl)3RuCl(DPPB)]- 311 IV X-Ray Crystallographic Analysis of Ru(BINAP)(r|3-Me-allyl)2 56 Co-Crystallized with (/?)-(+)-2,2'-bis(diphenylphosphinoyl)-l,l'-binaphthyl (BINAP(0)2) 315 V T\ Calculations 327 VI X-Ray Crystallographic Analysis of [(DMA)2H]+[(PPh3)2(H)Ru(|i-Cl)2(p:-H)Ru(H)(PPh3)2]- 18 331 VII X-Ray Crystallographic Analysis of cw-RuCl2(DPPB)(phen), 45 339 xvi T A B L E O F C O M P O U N D NUMBERS N u m b e r C o m p o u n d Al ternat ive Formula t ions 1 R u C l 3 ( P P h 3 ) 2 ( D M A ) - D M A 2 R u C l 3 ( P ( p - t o l y l ) 3 ) 2 ( D M A ) D M A 3 R u B r 3 ( P P h 3 ) 2 ( M e O H ) 4 R u ( H ) C l ( P P h 3 ) 3 ( D M A ) D M A 5 [ R u C l 2 ( C O D ) ] x 6 Ru(COD)(r | 3 -al lyl) 2 7 R u ( C O D ) ( T | 3 - M e - a U y l ) 2 8 R u C l 2 ( P P h 3 ) 3 9 R u C l 2 ( P ( p - t o l y l ) 3 ) 3 10 R u B r 2 ( P P h 3 ) 3 11 R u C l 2 ( D P P B ) ( P P h 3 ) 12 R u C l 2 ( D P P B ) ( P ( p - t o l y l ) 3 ) 13 R u B r 2 ( D P P B ) ( P P h 3 ) 14 R u C l 2 ( D C Y P B ) ( P P h 3 ) 15 RuCl 2 ((/?)-BrNAP)(PPh 3 ) 16 [ ( D M A ) 2 H ] + [ R u 2 C l 5 ( P P h 3 ) 4 ] - [ ( D M A ) 2 H ] + [ ( P P h 3 ) 2 C l R u ( p - C l ) 3 R u C l ( P P h 3 ) 2 ] -17 [ ( u 2 - H 2 ) ( P P h 3 ) 2 R u ( p - C l ) 2 ( p -H ) R u ( H ) ( P P h 3 ) 2 ] 18 [ ( D M A ) 2 H ] + [ R u H 3 C l 2 ( P P h 3 ) 4 ] - [ ( D M A ) 2 H ] + [ ( P P h 3 ) 2 ( H ) R u ( p - C l ) 2 ( p -H ) R u ( H ) ( P P h 3 ) 2 ] -19 R u 2 C l 4 ( D P P B ) 3 [ R u C l 2 ( D P P B ) i . 5 ] 2 or [ R u C l 2 ( D P P B ) ] 2 ( p - D P P B ) x v i i T A B L E O F C O M P O U N D NUMBERS (continued) N u m b e r C o m p o u n d Al te rna t ive Fo rmu la t i on 20 Ru2Br 4 (DPPB) 3 [ R u B r 2 ( D P P B ) i . 5 ] 2 or [ R u B r 2 ( D P P B ) ] 2 ( p - D P P B ) 21 Ru 2Cl4(DCYPB)3 [ R u C l 2 ( D C Y P B ) i . 5 ] 2 or [ R u C l 2 ( D C Y P B ) ] 2 ( p - D C Y P B ) 22 R u 2 C l 5 ( D P P B ) 2 [RuCl (DPPB)] 2 (p -Cl )3 or [ (DPPB )ClRu (p -Cl ) 3 RuCl (DPPB)] 23 Ru 2Cl 5((/?)-BINAP)2 [((/?)-BINAP)ClRu(p-Cl) 3RuCl(W-BINAP)j 24 R u 2 C l 4 ( D P P B ) 2 [ R u C l 2 ( D P P B ) ] 2 or [ R u C l ( D P P B ) ] 2 ( u - C l ) 2 25 R u 2 B r 4 ( D P P B ) 2 [ R u B r 2 ( D P P B ) ] 2 or [ R u B r ( D P P B ) ] 2 ( u - B r ) 2 26 Ru2Cl4((#)-BINAP)2 [RuCl2((/?)-BINAP)]2 or [RuCl((i?)-BINAP)] 2 (p-Cl) 2 27 Ru 2 l4 (DPPB) 2 [RuI 2 (DPPB)] 2 or [ R u I ( D P P B ) ] 2 ( u - I ) 2 28 R u 2 C l 4 ( D P P B ) 2 ( N E t 3 ) [ ( N E t 3 ) ( D P P B ) R u ( p - C l ) 3 R u C l ( D P P B ) ] 29 Ru 2 Cl4(DPPB) 2 (py) [(py)(DPPB)Ru(p-Cl) 3 RuCl(DPPB)] 30 R u 2 C l 4 ( D P P B ) 2 ( H N E t 2 ) [ ( H N E t 2 ) ( D P P B ) R u ( p - C l ) 3 R u C l ( D P P B ) ] 31 Ru 2 CU(DPPB) 2 (acetone) acetone [(acetone)(DPPB)Ru(p-Cl) 3 RuCl (DPPB)]ace tone 32 Ru 2Cl4(DPPB) 2(acetophenone) [(acetophenone)(DPPB)Ru(u-Cl) 3 RuCl (DPPB)] x v i i i T A B L E O F C O M P O U N D NUMBERS (continued) Number Compound Alternative Formulation 33 Ru 2CU(DPPB) 2(DMSO) [(DMSO)(DPPB)Ru(u-Cl)3RuCl(DPPB)] 34 Ru2Cl4(DPPB)2(DMS) [(DMS)(DPPB)Ru(u-Cl)3RuCl(DPPB)] 35 Ru 2CU(DPPB) 2(TMSO) [(TMSO)(DPPB)Ru(n-Cl)3RuCl(DPPB)] 36 Ru2Cl4(DPPB)2(THT) [(THT)(DPPB)Ru(u-Cl)3RuCl(DPPB)] 37 [H 2N(n-Oct) 2]+ [H2N(n-Oct)2]+ [Ru 2Cl 5(DPPB) 2]- [(DPPB)ClRu(u-Cl) 3RuCl(DPPB)]-38 [H2N(n-Bu)2]+ [H2N(n-Bu)2]+ [Ru 2Cl 5(DPPB) 2]- [(DPPB)ClRu(U-Cl)3RuCl(DPPB)]-39 [DMAHT+ [DMAH]+ [Ru 2Cl 5(DPPB) 2]- [(DPPB)ClRu(u-Cl) 3RuCl(DPPB)]-40 [H2N(n-Bu)2]+ [H2N(n-Bu)2]+[((/?)-BINAP))ClRu(p:-[Ru2Cl5((/?)-BINAP)2]- Cl)3RuCl((/?)-BINAP))]-41 [HNEt 3] +[Ru 2Cl 5(DPPB) 2]- [HNEt 3]+[(DPPB)ClRu(u-Cl) 3RuCl(DPPB)]-42 [Ru(H)Cl(DPPB)]3 43 RuCl2(DPPB)(py)2 44 RuCl2(DPPB)(bipy) 45 RuCl2(DPPB)(phen) 46 RuCl 2(py) 2(PPh 3) 2 47 ccf-RuCl 2(CO) 2(PPh 3) 2 48 ccf-RuCl2(CO)2(P0?-tolyl)3)2 49 RuCl 2(CO) 2(DPPB) 50 RuCl 2(NH 3)2(PPh 3) 2 xix T A B L E O F C O M P O U N D NUMBERS (continued) 51 RuCl2(DPPB)(NH 3)2 52 *rans-RuCl2(DPPCP)2 53 frans-RuCl2(DPPB)(DPPCP) 54 frans-RuCl2(DPPE)2 55 Ru(DPPB)(r|3-Me-allyl)2 56 Ru((/?)-BINAP)(r| 3-Me-allyl)2 X X LIST O F T A B L E S Tab le T i t l e Page 3.1 The 3 1 P { X H } N M R C h e m i c a l Shifts for the Poss ib le cis, cis, mms-Isomers o f R u X Y ( C O ) 2 ( P P h 3 ) 2 96 3.2 Selected B o n d Lengths (A) for R u B r 2 ( P P h 3 ) 3 10 103 3.3 Selected B o n d A n g l e s (°) for R u B r 2 ( P P h 3 ) 3 10 103 3.4 Selected B o n d Lengths (A) for R u C l 2 ( D P P B ) ( P P h 3 ) 11 104 3.5 Selected B o n d A n g l e s (°) for R u C l 2 ( D P P B ) ( P P h 3 ) 11 106 3.6 3 1 P { lU) N M R Da ta for R u X 2 ( P - P ) ( P A r 3 ) C o m p l e x e s 109 3.7 Selected B o n d Lengths (A) for [ R u 2 C l 5 ( D P P B ) 2 ] - 114 3.8 Selected B o n d A n g l e s (°) for [ R u 2 C l 5 ( D P P B ) 2 ] - 116 3.9 3 1 P { l U ) N M R Da ta for R u 2 X 4 ( P - P ) 2 C o m p l e x e s 119 3.10 Selected B o n d Lengths (A) for R u ( ( / ? ) - B I N A P ) ( t i 3 - M e - a l l y l ) 2 56 129 3.11 Selected B o n d A n g l e s (°) for R u ( ( i ? ) - B I N A P ) ( n 3 - M e - a l l y l ) 2 56 129 3.12 Selected B o n d Lengths (A) for (/?)-(+)-2,2 '-bis(diphenylphosphinoyl)-l,r-binaphthyl 130 3.13 Selected B o n d A n g l e s (°) for (7?)-(+)-2,2'-bis(diphenylphosphinoyl)-l,r43inaphthyl 130 3.14 3 1 P { ! H } N M R Data for [ c a t i o n ] + [ R u 2 C l 5 ( P - P ) 2 ] - C o m p l e x e s 136 3.15 3 1 P { ! H } N M R Data for the Dinuc lea r C o m p l e x e s [ ( L ) ( D P P B ) R u ( u - C l ) 3 R u C l ( D P P B ) ] 143 3.16 U V - V i s i b l e Da ta o f R u 2 C l 4 ( D P P B ) 2 ( L ) C o m p l e x e s 145 3.17 U V - V i s i b l e Spectroscopic Data o f R u 2 X 4 ( P - P ) 3 C o m p l e x e s 19, 20, and 21 i n C 6 H 6 149 3.18 3 1 P { i H } N M R Spectral Parameters U s e d to Obta in the S imula ted Spectrum o f f r a n s - R u C l 2 ( D P P B ) ( D P P C P ) 53 S h o w n i n F igure 3.27 152 4.1 3 ! P { lU} N M R Data for the Dinuc lea r C o m p l e x e s [ ( L ) ( D P P B ) R u ( p - C l ) 3 R u C l ( D P P B ) ] 173 x x i 4.2 Temperature Dependence of the *H NMR T\ Relaxation Time Data for the (TI 2 -H 2 ) Resonances Observed on Reaction of H 2 and RuCl2((/?)-BINAP)(PPh3) 176 4.3 3 1P{ !H} NMR Data for RuCl2((i?)-BINAP)(PPh3) 15 under an atmosphere of H 2 in C6D6 177 4.4 31p{ 1H} NMR Spectral Data of Ru(H)Cl(P-P)(PPh3) Complexes 184 4.5 3 1P{ *H} NMR Data for the Interaction of H 2 and Ru2Cl5((/?)-BINAP)2 23 in C 6 D 6 200 4.6 Selected Bond Lengths (A) for [(DMA)2H]+[(H)(PPh3)2Ru(p-Cl)2(u> H)Ru(PPh3)2(H)]- with Estimated Standard Deviations in Parentheses... 206 4.7 Selected Bond Angles (°) for [(DMA) 2H]+[(H)(PPh 3) 2Ru(p-Cl) 2(p-H)Ru(PPh3)2(H)]- 206 5.1 3 1P{ ^H] NMR Data for Some Mononuclear Complexes [RuCl2(DPPB)(L) 2] 220 5.2 UV-visible Spectroscopic and Molar Conductivity Data for RuCl2(DPPB)(N) 2 Complexes 222 5.3 3 1P{!H} NMR Data for Some Dinuclear Complexes, [(L)(DPPB)Ru(u-Cl)3RuCl(DPPB)] 225 5.4 3 1P{ !H} NMR Data of RuCl 2(DPPB)(N) 2 Complexes in C D 3 O D 230 5.5 Selected Bond Lengths (A) for ds-RuCi2(DPPB)(phen) 45 238 5.6 Selected Bond Angles (°) for m-RuCi2(DPPB)(phen) 45 239 6.1 Rate Data for the Hydrogenation of PhCN Using [Ru(H)Cl(DPPB)]3 42 as the Catalyst 258 6.2 Conversion Data for High-Pressure Hydrogenation of PhCH2N=C(H)Ph Using a Variety of Catalyst Precursors 265 6.3 Conversion Data for High-Pressure Hydrogenation of PhN=C(H)Ph Using a Variety of Catalyst Precursors 270 xxii LIST O F FIGURES Figure Title Page 1.1 M e c h a n i s m s of homogeneous hydrogenation o f alkenes ca ta lyzed by metal species without M - H bonds 7 1.2 M e c h a n i s m o f homogeneous hydrogenation o f alkenes cata lyzed by metal species containing an M - H bond 8 1.3 Selected ch i r a l diphosphines used i n asymmetr ic hydrogenat ion 10 2.1 Structure o f trans-1,2-bis(dichlorophosphino)cyclopentane ind ica t ing N M R assignments 21 2.2 Anae rob ic UV -v i s ib l e c e l l 27 2.3 Constant-pressure gas-uptake apparatus 29 3.1 F ive-coordinate ruthenium(II) complexes containing a diphosphine that have been reported to date 86 3.2 Reac t ion o f one equivalent o f diphosphine w i t h R u C l 3 ( P R 3 ) 2 87 3.3 Geomet ry o f the R u 2 C l 5 ( ( S , S ) - C H I R A P H O S ) 2 complex 88 3.4 Suggested geometry for Ru 2 Cl4 (P -P )2 complexes 88 3.5 Suggested geometry for the Ru2Cl4(BINAP)2 complex 89 3.6 Reac t ion pathway from R U C I 3 X H 2 O to R u 2 C l s ( P - P ) 2 and Ru2CU(P-P)2 complexes 89 3.7 Reac t ion o f R u 2 C l 4 ( P - P ) 2 wi th neutral l igand L to form Ru2CU(P-P)2(L) complexes 90 3.8 Geomet ry o f the Ru 2 CU(DPPB) 2 (DMSO) complex 91 3.9 Geomet ry o f the Ru2Cl4(PPh3)4(CS) complex 91 3.10 Synthesis o f [Ru(H)Cl(P-P)]3 f rom R u 2 C l 4 ( P - P ) 2 92 3.11 Geomet ry o f the [ R u ( H ) C l ( P - P ) ] 3 complexes 92 3.12 The structure o f ( S ) - B I P H E M P 97 3.13 The O R T E P plot o f R u B r 2 ( P P h 3 ) 3 10 102 3.14 The ORTEP p lot o f R u C l 2 ( D P P B ) ( P P h 3 ) 11 105 3.15 The 31p{ l H } N M R spectra o f RuCl 2 (DPPB)(P(p- to ly l )3 ) 12 i n C D 2 C 1 2 at: (a) 20 °C and (b) -66 °C 108 3.16 The O R T E P plot o f the anionic [ R u 2 C l 5 ( D P P B ) 2 ] - i n [ T M P ] + [ R u 2 C l 5 ( D P P B ) 2 ] - 115 x x i i i 3.17 3 1P{ lH] NMR spectrum of Ru2Br 4(DPPB)2 25 in CDCI3 118 3.18 3 1P{ lH) NMR spectrum of Ru(DPPB)(Ti3-Me-allyl)2 55 in CDCI3 with: (a) 1 equiv HC1, (b) 2 equiv HC1, and (c) 3 equiv HC1 122 3.19 Comparison of three routes to the dimer, Ru2CLi(DPPB)2 123 3.20 The ORTEP plot of Ru((/?)-BINAP)(r|3-Me-aliyl)2 56 125 3.21 The ORTEP plot of (/?)-(+)-2,2'-bis(diphenylphosphinoyl)-l,l'-binaphthyl (BINAP(0)2) 126 3.22 Possible structural isomers for Ru2Cl4(DPPB)2(L) complexes 134 3.23 3 1P{ !H} NMR spectra of: (a) [(DMSO)(DPPB)Ru(p-Cl)3RuCl(DPPB)] 33 in C6D 6 and (b) [(TMSO)(DPPB)Ru(p-Cl)3RuCl(DPPB)] 35 in C ^ 140 3.24 3 1P{ lU} NMR spectra of [(DMS)(DPPB)Ru(u-Cl)3RuCl(DPPB)] 34 in: (a) CDCI3 and (b) C 6 D 6 141 3.25 3 1P{!H} NMR spectra of [(THT)(DPPB)Ru(p-Cl)3RuCl(DPPB)] 36 in: (a) CDCI3 and (b) C 6 D 6 142 3.26 Structure of the two possible enantiomers of *rans-RuCl2(DPPB)(DPPCP) 53 150 3.27 3 1P{ !H} NMR spectra of ?ra^-RuCl2(DPPB)(DPPCP) 53 in CDCI3 151 3.28 Structure of the P - N chelating ligands PMA and PAN 154 3.29 Stereoisomers of frans-RuCl2(DPPCP)2 52 155 3.30 The 3 1P{ !H} NMR spectrum of the two diastereomers of *rans-RuCl2(DPPCP)2 52 in CDCI3 156 4.1 Some examples of molecular hydrogen complexes 164 4.2 Equilibrium between Ru2Cl4(DPPB)2 24 and Ru2Cl4(DPPB)2(r| 2-H2).... 168 4.3 Suggested geometry of the Ru20l 2-H 2)(H)2Cl2(DPPB)2 complex 169 4.4 Geometry of the two possible isomers of [(ri2-H2)(P-P)Ru(p-X)3RuX(P-P)] 172 4.5 ! H NMR spectrum of RuCl2((/?)-BINAP)(PPh3) 15 under an atmosphere of H2 in C6D6 175 4.6 Temperature dependence of T\ for the molecular hydrogen complexes produced on reaction of H2 and RuCl2((/?)-BINAP)(PPh3) 176 4.7 ! H NMR spectrum of RuCl2((/?)-BINAP)(PPh3) 15 under an atmosphere consisting of 400 torr each of D2 and H2 179 4.8 3 1P{ !H} NMR spectrum of RuCl2((/?)-BINAP)(PPh3) 15 under an atmosphere of H2 in C$>6 180 xxiv 4.9 lH{ 3 1 P } high-f ie ld N M R spectra o f the two isomers [ ( T | 2 - H 2 ) ( ( / ? ) - B I N A P ) R u ( m - C l ) 3 R u C l ( ( ^ ) - B I N A P ) ] i n C 6 D 6 w i t h selective phosphorus decoupl ing 182 4.10 3 1 p { l r l } N M R spectra o f R u ( H ) C l ( ( f l ) - B I N A P ) ( P P h 3 ) and H 2 produced i n situ f rom R u C l 2 ( ( / ? ) - B I N A P ) ( P P h 3 ) at r oom temperature 185 4.11 The geometry o f the two diastereomers o f R u ( H ) C l ( ( / ? ) - B I N A P ) ( P P h 3 ) 187 4.12 ! H N M R spectrum o f R u ( H ) C l ( ( i ? ) - B I N A P ) ( P P h 3 ) produced i n si tu f rom R u C l 2 ( ( / ? ) - B I N A P ) ( P P h 3 ) 15 187 4.13 3 1 P { ! H } N M R o f Ru2Cl4(DPPB)2 24 under an atmosphere o f ethylene i n C6D6 191 4.14 H2-reduct ion o f the mixed-valence complex R u 2 C l 5 ( D P P B ) 2 22 to g ive Ru2Cl4 (DPPB)2 24, w h i c h reacts revers ibly w i t h H2 to produce R u 2 C l 4 ( D P P B ) 2 ( T l 2 - H 2 ) 195 4.15 3 1 P { iH} N M R spectrum o f a C 6 D 6 solut ion o f R u 2 C l 5 ( ( / ? ) - B I N A P ) 2 23 after bubbl ing H2 through the solut ion for 1 h 198 4.16 3 1 P { ! H } N M R spectrum o f R u C l 2 ( ( / ? ) - B I N A P ) ( P P h 3 ) 15 i n C 6 D 6 199 4.17 The unique ruthenium complex characterized by C h a n and L a n e m a n produced by P - C cleavage of the B I N A P l igand 202 4.18 M o l e c u l a r structure o f [ ( D M A ) 2 H ] + [ ( P P h 3 ) 2 ( H ) R u ( | i - C l ) 2 ( ( i - H ) R u ( H ) ( P P h 3 ) 2 ] - 18 203 4.19 The O R T E P plot o f [ ( D M A ) 2 H ] + [(PPh 3 ) 2 (H)Ru(p:-Cl)2(M:-H)Ru(H)(PPh3)2]- 18 205 4.20 3 1 P { !H} N M R spectra of 18 i n C 7 D 8 209 4.21 i f f N M R spectra o f 18 i n C 7 D 8 210 4.22 E q u i l i b r i u m between [ (DMA )2H]+ [(PPh 3) 2(H)Ru((i-Cl)2(H-H)Ru(H)(PPh 3) 2]- 18 and [(Ti2-H 2)(PPh 3)2Ru(p:-Cl)2(p:-H)Ru(H)(PPh3)2] 17 211 4.23 M o l e c u l a r structure o f [ T M P ] + [ R u 2 C l 5 ( D P P B ) 2 ] - 212 5.1 T h e two possible geometries o f R u C l 2 (DPPB) (py )2 that w o u l d produce a singlet i n the 3 1 P { 1 H } N M R spectrum 221 5.2 Poss ib le geometries o f the species RuCl2(py)2(PPh3)2 223 5.3 The 3 1 P { ! H } N M R spectra o f R u 2 C l 4 ( D P P B ) 2 24 i n CDCI3 plus (a) one equiv o f py , (b) two equiv o f py , (c) four equiv o f py , and (d) 10 equiv o f p y 226 5.4 Proposed reaction pathway from R u 2 C l 4 ( D P P B ) 2 24 through R u 2 C U ( D P P B ) 2 ( p y ) 29 to f r a H S - R u C l 2 ( D P P B ) ( p y ) 2 43 227 5.5 lH N M R spectrum of c w - R u C l 2 ( D P P B ) ( b i p y ) 44 i n CDCI3 231 X X V 5.6 Poss ib le geometries o f " [RuCl(DPPB)(N-N)]+Cl-" w h i c h w o u l d account for the observed 3 1 P { lH} N M R data 232 5.7 The 3 1 P { 1U} N M R spectrum o f a red solut ion o f 44 produced i n situ by adding 0.5 equivalents o f b ipy to Ru2Ci4(DPPB)2 24 233 5.8 ! H N M R spectrum o f ds-RuCl 2(DPPB)(phen) 45 i n CDC1 3 235 5.9 The ORTEP plot o f c/s-RuCl2(DPPB)(phen) 45 237 5.10 Graph o f R u - P bond length versus 3 1 P { lH} N M R chemica l shift for a series o f Ru(II) complexes containing DPPB 240 5.11 The two possible structures o f RuCl2(DPPB)(NH 3 ) 2 , 51 241 5.12 The 3 1 P { lH} N M R spectrum of RuCl2 (DPPB ) ( 1 5 NH 3 )2 51 i n CDC1 3 . The sample was prepared i n si tu f rom ^ N l ^ C l , RuCl 2 (DPPB)(PPh 3 ) , and6MNaOH 243 5.13 Isomerizat ion o f Zrans-RuCl2(DPPB)(NH 3)2 51 i n CDC1 3 244 5.14 Poss ib le structures o f the type " R u C l 2 ( D P P B ) ( N H 3 ) x " w h i c h w o u l d exhib i t a singlet i n the 3 1 P { lH} N M R spectrum 245 5.15 Structure o f [ R u 2 C l 3 ( D P P B ) 2 ( R C N ) 2 ] + X - species, where R = M e or P h and X = P F 6 or Cl 245 5.16 Poss ib le doubly-chloro br idged (edge sharing) structures o f the formulat ion Ru2Cl4 (DPPB )2(NH 3 )2 w h i c h w o u l d exhib i t two A B patterns i n the 3 1 P { lH] N M R spectrum 247 6.1 T h e structure o f the grass herbicide M e t o l a c h l o r ® 250 6.2 Reduc t ive animat ion scheme to produce ch i ra l amines f rom proch i ra l ketones 252 6.3 syn-anti Isomerizat ion o f imines 253 6.4 T y p i c a l reuptake plots for the hydrogenat ion o f PhCN ca ta lyzed by [Ru(H)Cl(DPPB)] 3 42 i n D M A at 70 °C and 800 torr pressure o f H 2 257 6.5 (a) Rate plots for PhCN hydrogenat ion catalyzed by 42 i n D M A at 70 °C at various [Ru 3]T. [PhCN] = 20 m M , [H2] = 2.39 mM. (b) Dependence o f the m a x i m u m hydrogenation rate on [ R u 3 ] x 259 6.6 Dependence o f the m a x i m u m hydrogenation rate on [H2] at 70 "C 261 6.7 The structure o f the dinuclear product produced on addi t ion o f PhCN to a C 6 D 6 solut ion o f [Ru(H)Cl(DPPB)] 3 42 262 6.8 C o n v e r s i o n o f the imine P h C H 2 N = C ( H ) P h to d ibenzy lamine us ing Ru2CLi(DPPB)2 24 and Ru2Br 4 (DPPB) 2 25 as the catalysts 267 7.1 Poss ib le geometry o f the y e l l o w so l id isolated on i somer iza t ion o f the product mixture obtained on reaction o f RuCh(DPPB)(PPh 3 ) 11 and C O i n the so l id state 279 x x v i 7.2 3 1 P { lU} NMR spectrum o f the products produced on reaction o f R u 2 C l 4 ( D P P B ) 2 24 and CO i n the so l id state for 24 h 280 7.3 3 1 P { lU} N M R spectrum o f the products produced on react ion o f R u 2 C l 4 ( D P P B ) 2 24 and CO i n the so l id state for 14 days 281 7.4 M o l e c u l a r structure o f f ra ra . s -RuCl 2 (CO ) 2 (DPPB) and m - R u C l 2 ( C O ) 2 ( D P P B ) 282 x x v i i LIST O F ABBREVIATIONS A angstrom, 10"8 centimeter ABq AB quartet (NMR) Ar argon, aryl group atm atmosphere (1 atm = 760 mm Hg, 101.3 kPa, 14.696 psi) BDPP (2S,4S)-2,4-bis(diphenylphosphino)pentane BINAP (R)- or (5)-2,2'-bis(diphenylphosphino)-1,1 '-binaphthyl BINAP(0)2 (/?)-(+)-2,2'-bis(diphenylphosphinoyl)-1,1'-binaphthyl BIPHEMP (5)-2,2'-dimethyl-6,6'-bis(diphenylphosphino)biphenyl bipy 2,2'-bipyridine BPPF A 1,1 '-bis(diphenylphosphino)-2'-( 1 -AT,N-a-dimethylamino-ethyl)ferrocene br broad Bu butyl, C H 2 ( C H 2 ) 2 C H 3 c,c,c cis,cis,cis c,c,t cis,cis, trans 1 3 C{ XH} proton-decoupled carbon-13 (NMR) CHIRAPHOS 2,3-bis(diphenylphosphino)butane COD 1,5-cyclooctadiene CP/MAS cross polarization / magic angle spinning Cy cyclohexyl C YCPHOS 1 -cyclohexyl-1,2-bis(diphenylphosphino)ethane D configuration relative to D-glyceraldehyde d doublet (NMR), day(s) dd doublet of doublets DCYPB 1,4-bis(dicyclohexylphosphino)butane xxviii DCYPCP rac-(±)-l,2-bis(dicyclohexylphosphino)cyclopentane; Joshi of this laboratory previously abbreviated this DPCYCP DIOP (2R,3R) or (2S,3S)-0-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane DiPAMP 1,2-bis(orf^ o-anisylphenylphosphino)ethane DMA A^-dimethylacetamide, CH3C(0)N(CH3)2 DMF MN-dimethylformamide, CH(0)N(CH3)2 DMS dimethyl sulfide DMSO dimethyl sulfoxide DPPB 1,4-bis(diphenylphosphino)butane DPPCP rac-{±)-1,2-bis(diphenylphosphino)cyclopentane DPPE 1,2-bis(diphenylphosphino)ethane DPPH 1,6-bis(diphenylphosphino)hexane DPPM bis(diphenylphosphino)methane DPPN 1,5-bis(diphenylphosphino)pentane DPPP 1,3-bis(diphenylphosphino)propane e.e. enantiomeric excess eq equation FID flame-ionization detector (GC) FT Fourier transform h hour(s) !H{31P} phosphorus-decoupled proton-1 (NMR) Hz Hertz, cycles per second IR infra-red (spectroscopy) isoPF A 1 - [a-(dimethylamino)ethyl] -2-(diisopropylphosphino)ferrocene J coupling constant, in Hz L configuration relative to L-glyceraldehyde xxix L ligand; litre L-Dopa 3-(3,4-dihydroxyphenyl)-L-alanine M central metal atom in a complex; molarity, mols L 1 m multiplet (NMR); medium intensity (IR) max maximum min minute(s) m.p. melting point NORPHOS 2,3-bis(diphenylphosphino)-bicyclo[2.2. l]hept-5-ene NMR nuclear magnetic resonance (spectroscopy) N - N chelating N-donor ligand o ortho Oct octyl, CH2(CH2)6CH3 31P{!l-I} proton-decoupled phosphorus-31 (NMR) p para PAN l-(dimethylamino)-8-(diphenylphosphino)naphthalene Ph phenyl, C 6 H 5 phen 1,10-phenanthroline PHENOP the chiral aminophosphinephosphinite ligand:, Ph 2PN(Et)CH(CH 2Ph)CH 2OPPh 2 PMA o-diphenylphosphino-//,A^-dimethylaniline PROPHOS 1,2-bis(diphenylphosphino)propane PS proton sponge, l,8-bis(dimethylamino)naphthalene py pyridine P-P ditertiary phosphine q quartet R alkyl group (/?)- absolute configuration (Latin: rectus; right) xxx rac racemic (sy absolute configurat ion (Lat in : sinister; left) s singlet ( N M R ) , strong (IR) , seconds t triplet t- tertiary Ti longi tudina l relaxation t ime ( N M R ) temp temperature T H T tetrahydrothiophene T M P l , l , 3 - t r ime thy l -2 ,3 -d ihydrope r imid in ium cat ion T M S tetramethylsilane T M S O tetramethylene sulfoxide T O S S total suppression o f sidebands U V - v i s u l t raviole t -vis ible (spectroscopy) w weak intensity (IR) A heat 5 chemica l shift ( in ppm) e ext inct ion coefficient descriptor for hapticity X wavelength A M molar conduct iv i ty descriptor for b r idg ing V frequency ( c m - l ) * ch i ra l centre x x x i A C K N O W L E D G E M E N T S I w o u l d to thank P r o f e s s o r B r i a n James for h i s exper t g u i d a n c e and encouragement throughout the course o f this work . I am also indebted to past and present members o f the James' group for their fr iendship and support. I w o u l d especia l ly l i k e to thank M r . R i c h a r d Schutte, M r . C h r i s A lexande r , and D r . D e r y n F o g g for m a n y useful discussions, D r . A j e y Josh i for getting me started on this work , and D r . M . M y l v a g a n a m ( M y l ) and M r . G u y C l e n s m i t h for their help and advice. I a m grateful to D r . S teven Re t t ig o f the U B C C r y s t a l l o g r a p h i c Se rv i ce for performing the crystal lographic studies w h i c h appear i n this thesis. T h e help o f M r . Peter B o r d a and M r . Steve R a k o f the U B C M i c r o a n a l y t i c a l Serv ice and G l a s s b l o w i n g Shop, respec t ive ly , was m u c h appreciated. T h e other departmental serv ices , i n c l u d i n g the n u c l e a r m a g n e t i c resonance and mass spec t romet ry l abora to r ies , are g ra t e fu l ly acknowledged . I w o u l d espec ia l ly l i k e to thank m y wi fe C a r o l for her somewhat reluctant but excel lent edi t ing sk i l l s . I also owe a great deal o f thanks to m y sister J o d i , m y m o m and dad, and m y good friends, D o n and P a u l , for their support f rom start to end. F i n a l l y , I w o u l d l i k e to thank a l l those w h o had the good sense not to ask the seeming ly t imeless question, " A r e y o u done yet?" x x x i i C H A P T E R 1 INTRODUCTION 1.1 Homogeneous Catalysis Homogeneous catalysis is used ever-increasingly by chemists to synthesize both new compounds in an academic setting, and industrially important fine chemicals. Fine chemicals ranging in use from fragrances, flavours, and perfumes to pharmaceuticals, herbicides, and pesticides can be prepared by reactions using homogeneous catalysts. Widespread interest in homogeneous systems is evident from the many books that have been published on this subject in the last fifteen years (e.g., references 1-5). The reactions that have been catalyzed by transition metal complexes in solution include: hydrogenation, hydrosilylation, hydroformylation, hydrocyanation, epoxidation, polymerization of olefins, oxidation of hydrocarbons, oxidation of olefins to aldehydes and ketones, and carbonylation of alcohols. ' Interest in the use of homogeneous catalytic systems arose out of their possible economic advantages over the established heterogeneous systems. Energy savings are realized through the use of lower temperatures and pressures, as well as the higher activity and selectivity generally observed for homogeneous catalytic systems.5'6 The high selectivity of organic transformations offered by homogeneous systems is the result of a well-defined metal environment which is usually easily amenable to study by conventional spectroscopic and kinetic methods.7 Heterogeneous catalytic systems are much more difficult to study, although recent advances allow the spectroscopic examination of metal surfaces by methods such as in situ X-ray absorption8 or magic-angle spinning N M R . 9 The reactivity of a homogenous catalyst is much easier to modify than that of a heterogeneous catalyst, and can be achieved simply by changing the ligands at the metal centre.1 0 Although a Chapter 1 References: p 14 1 Chapter 1 homogeneous catalyst can be tai lored toward certain properties (e.g., aqueous so lub i l i ty ) , the ma tch ing o f a par t icular catalyst precursor w i t h a speci f ic substrate is s t i l l l a rge ly e m p i r i c a l . 1 1 O n the d o w n side, homogeneous catalysts are often expens ive t ransi t ion meta l c o m p l e x e s , and are f requent ly d i f f i c u l t to separate f r o m bo th the reactants and p r o d u c t s . 1 ' 6 T h e y may also be sensi t ive to d ioxygen and mois ture , and are the rma l ly sens i t ive . 6 T h e p rob lem o f separating the catalyst f rom the product can be ove rcome by either: (1) the use o f insoluble supports such as s i l i c a or c ross l inked polystyrene, to w h i c h the catalyst is attached; (2) the use o f a b iphasic system; or (3) the use o f a phase-transfer catalytic s y s t e m . 1 3 ' 1 4 Inso lub le -suppor ted catalysts are referred to as he te rogenized homogeneous catalysts, and offer the advantages o f heterogeneous catalysts i n be ing eas i ly separated f rom the product(s) , w h i l e retaining the h igh ac t iv i ty and select iv i ty o f a homogeneous s y s t e m . 6 B i p h a s i c systems take advantage o f homogeneous catalysts w h i c h are designed to 1 o be soluble i n a phase different to that o f the organic reactants and products. Ideal ly , the catalyst w o u l d be designed to be soluble i n an aqueous phase by the use o f l igands w i t h h i g h l y polar funct ional groups. Phase-transfer cata lys is also takes advantage o f two-phase m e d i a but e m p l o y s phase-transfer agents (e.g., quaternary a m m o n i u m or phosphon ium salts, c r o w n ethers, etc.) to transfer reactants across the interface between p h a s e s . 1 5 A b iphas ic sys tem uses no such agent. Recen t and future developments i n the area o f homogeneous ca ta lys is shou ld increase the for ty-odd indus t r ia l processes current ly us ing homogeneous systems. S o m e notable examples o f indust r ia l product ions us ing homogeneous catalysts i nc lude the W a c k e r and O x o processes, methanol carbonylat ion, o l igomer iza t ion o f dienes, some Zieg le r -Nat ta systems, and adiponitr i le syn thes i s . 2 ' 5 2 Chapter 1 References: p 14 Chapter 1 19 16 O n e emerg ing area i s the catalysis o f organic reactions i n aqueous med ia . ' T h e o n l y c o m m e r c i a l successes o f homogeneous catalysis i n aqueous m e d i a to date are the W a c k e r process for the ox ida t ion o f alkenes and the R u h r c h e m i e / R h o n e - P o u l e n c oxo process for the hydroformyla t ion o f propylene to butyraldehyde. ' Improvement i n the catalytic act ivi ty o f the above hydroformyla t ion has been achieved on t w o separate occasions since the reaction was first used c o m m e r c i a l l y i n 1984. T h e i m p r o v e d ac t iv i ty was achieved by changing the water-soluble phosphine l igands o n R h to n e w l y developed analogous phosphines . T h e ac t iv i ty is n o w about 100 times greater than the o r i g i n a l 12 catalyst. A no the r industr ia l appl icat ion o f homogeneous catalysts is the use o f asymmetr ic hydrogenat ion o f a prochi ra l olef in to produce the opt ica l ly active L - D o p a , w h i c h is used i n the treatment o f Parkinson 's disease. T h e catalyst system used for this a symmet r ic 1 n transformation is a rhodium(I) catalyst w i th a ch i ra l diphosphine l igand (eq 1.1). H s ^ C C ^ R C = C + f \ N H C O R 1) [ R h ( R 2 P - P R 2 ) ( S ) 2 ] + H 2 , S = M e O H H O O H 2 ) H 3 ( ) + (1.1) T h e sweetener A s p a r t a m e ™ , a m e t h y l ester o f a d ipept ide c o n s i s t i n g o f L -phenyla lan ine and L-aspart ic ac id , also rel ies on homogeneous c h i r a l catalysts for the 17 product ion o f the two amino ac id precursors. The chi ra l i ty o f these compounds p lays an important role i n determining their properties; for example , it was found that none o f the other three diastereomers o f . A s p a r t a m e are s w e e t . 1 8 H o w e v e r , i n the future, the p roduc t ion o f Aspar tame by asymmetr ic catalyt ic hydrogenat ion m a y be replaced by an economica l ly more favourable fermentation process commerc i a l i zed by A j i n o m o t o . 5 ' 1 9 3 Chapter 1 References: p 14 Chapter 1 1.1.1 Asymmetric Catalysis M o s t o f the w o r k i n asymmetr ic or enantioselective catalysis has been done i n the 1 -7 area o f hydrogenat ion (see Sec t ion 1.2.1). T h i s is probably a result o f the fact that the vast major i ty o f op t i ca l ly act ive compounds have a hydrogen atom at the asymmet r ic carbon a t o m . 2 0 T h i s area o f research, and asymmetr ic catalysis i n general , have become more important i n recent years, as the pharmaceut ical and ag rochemica l industr ies have 21 22 an increased need to produce enant iomer ica l ly (or s tereochemical ly) pure materials . ' C o m p a n i e s operat ing i n these industries have both economic and regulatory reasons for want ing to prepare s tereochemical ly pure materials o f both new and exis t ing products. F r o m a regulatory standpoint, the F D A ' s ch i ra l drug p o l i c y ' s t i l l a l l ows for the deve lopment o f drugs as racemic mixtures , but on a case by case basis i t is better to develop enant iomerical ly pure materials. E c o n o m i c a l l y , companies have a vested interest i n deve lop ing c h i r a l drugs, not 99 91 o n l y to m a i n t a i n marke t share, but to even tua l ly reduce manufac tu r ing costs . Manufac turers o f racemic drugs run the risk o f racemic switches by th i rd party f i rms , w h i c h i n the wors t case scenario (at least for the f i rm ho ld ing a patent for the racemate) c o u l d lead to the i ssu ing o f a separate patent for the enan t iomer ica l ly pure d r u g . 2 2 A racemic s w i t c h is the redevelopment o f an o lder c h i r a l drug current ly marke ted as a r acemic mix tu re to produce the act ive s ingle enantiomer. M a n u f a c t u r i n g costs i n the p roduc t ion o f a s ingle enant iomer over a racemic mix tu re , w h i l e i n i t i a l l y h igher , can even tua l ly result i n e c o n o m i c benefits as a result o f not c a r r y i n g 5 0 % unwan ted or unnecessary mater ia l (i .e., the inac t ive enant iomer or precursor) through the reac t ion 21 pathway. Sav ings can occur f rom the use o f smal ler amounts o f reagents and solvents and their associated disposal costs. U n t i l recent ly , enan t iomer i sm has been treated as a rather " spec i a l " type o f i somer i sm , probably because o f the d i f f icul ty i n d is t inguishing one enant iomer f rom the other (wi th the except ion o f their opposite interaction w i t h plane po la r i zed l i g h t ) . 2 4 O n e 4 Chapter 1 References: p 14 Chapter 1 enantiomer has therefore rarely been regarded as an impurity in the presence of the other. However, in biological systems, in which the local environment is largely chiral (L-amino acids, D-sugars, chiral recognition of receptors and enzymes), the two enantiomers should be treated as very different. New terminology that has arisen from concern over using racemic mixtures as pharmaceuticals include: chirotechnology, technologies combining chemistry and biology 22 25 to produce enantiomeric compounds and enantioselective processes; ' racemic 9 9 switches, see above; eutomer, the enantiomer (of the two in a racemic mixture) 99 96 responsible for the desired pharmaceutical effect, distomer, the inactive or unwanted 99 96 isomer in a racemic mixture, ' and eudismic ratio, the ratio of activity in any given 99 96 pharmacological property of the eutomer relative to that of the distomer. ' Ariens has been one of the most vocal critics against the use of racemic 11 pharmaceuticals. From the titles of his articles alone, one gains a feel for Ariens' thoughts on the use of racemic mixtures. Some of the titles include: (1) Racemic 27 Therapeutics-Problems all Along the Line; (2) Stereochemistry, a Basis for Sophisticated Nonsense in Pharmacokinetics and Clinical Pharmacology; (3) Bias in 20 Pharmacokinetics and Clinical Pharmacology; and (4) Stereoselectivity of Bioactive Xenobiotics. A Pre-Pasteur Attitude in Medicinal Chemistry, Pharmacokinetics and O f ) Clinical Pharmacology. The most frequently used example cautioning against the use of racemic pharmaceuticals is the case of thalidomide, used as a sleeping pill and remedy for morning sickness between 1957 and 1961. The result of using racemic thalidomide in the early stages of pregnancy was fetal deaths and congenital malformations in more than 31 33 8000 cases. The teratogenicity causing the high incidence of malformations is now attributed to the S-enantiomer, while the /?-isomer is believed to have the hypnotic and sedative properties that were originally desired.3 4 The validity of the above statement has been argued by some workers recently and they suggest that "this conclusion should be 5 Chapter 1 References: p 14 Chapter 1 accepted with caution." 3 5 ' 3 6 Also of importance is the recent evidence which suggests 37 that thalidomide racemizes rapidly under physiological conditions. Although there is now some dispute over whether the S-enantiomer alone is the teratogen, there is no argument that the racemate causes congenital malformations. Therefore, the case of thalidomide remains a good illustration of the potential dangers involved with using racemic drugs. 1.2 Homogeneous Hydrogenation Although reports of homogeneous hydrogenation date back as far as 1938 when Calvin reduced quinone using a copper acetate system, it is not until more recently that • 7 homogeneous hydrogenation began to be more thoroughly investigated. An increase in the intensity of research in homogeneous hydrogenation came as a direct result of the discovery by Wilkinson's group in 1965 of the highly active RhCl(PPh3)3 system for the hydrogenation of olefins. ' The literature in the area of homogeneous hydrogenation has become vast since the discovery of Wilkinson's catalyst. A number of comprehensive reviews, 4 0 " 4 3 specialized texts, 4 4 ' 4 5 chapters in books, 3 ' 4 ' 7 ' 4 6 and whole books 1 5 ' 4 7 are available on this subject. Initial studies on homogeneous hydrogenation had much of their interest directed toward the reduction of carbon-carbon double bonds. Until recently, comparatively few studies on the hydrogenation of ketones and imines appeared in the literature. 1 7 ' 4 8 The concentration of research in the area of reducing olefins has occurred for probably two reasons: (1) carbon-carbon double bonds are more easily reduced than carbon-oxygen double bonds; 4 9 and (2) the substrates are readily available and there is interest in using the corresponding products. The majority of our mechanistic understanding comes from the hydrogenation of olefins using rhodium-phosphine catalyst systems.15 There are two general mechanisms 6 Chapter 1 References: p 14 Chapter 1 o f homogeneous hydrogenat ion o f alkenes by metal complexes w h i c h i n i t i a l l y do not con ta in an M - H bond . T h e first is referred to as the unsaturate route, w h i c h i n v o l v e s in i t i a l coordinat ion o f the substrate fo l l owed by act ivat ion o f d ihydrogen by the resul t ing c o m p l e x . T h e second poss ib i l i ty , k n o w n as the hydr ide route, i n v o l v e s i n i t i a l ac t ivat ion o f m o l e c u l a r hydrogen , f o l l o w e d by coord ina t ion o f the substrate (F igure 1.1). T h e hydr ide route is thought to be the more general o f the two reaction p a t h w a y s . 1 5 Figure 1.1 M e c h a n i s m s o f homogeneous hydrogenation o f alkenes ca ta lyzed by meta l species without M - H bonds. I f the ca ta ly t ic species i n i t i a l l y contains an M - H bond , the pa thway s h o w n i n F igure 1.2 is thought to operate. F igures 1.1 and 1.2 are meant to illustrate s imple models , i nc lud ing the important steps for the homogeneous hydrogenat ion o f alkenes. H o w e v e r , the actual mechan i sms operating i n these systems are often more complex , as they frequently conta in more than one ac t ive meta l s p e c i e s . 1 5 F o r example , the ac t iva t ion o f d i h y d r o g e n by o x i d a t i v e addi t ion m a y actual ly inc lude a molecula r hydrogen complex as an in t e rmed ia t e . 5 0 There are many examples o f i so lable molecu la r hydrogen complexes i n the l i t e r a t u r e 5 0 s ince K u b a s ' d i scovery o f the first such s p e c i e s . 5 1 A br ief r ev iew o f this area w i l l be g iven i n Chapter 4. 7 Chapter 1 References: p 14 Chapter 1 Figure 1.2 M e c h a n i s m o f homogeneous hydrogenation o f alkenes cata lyzed by meta l species containing an M - H bond. 1.2.1 Asymmetric Homogeneous Hydrogenation A large number o f the successful c h i r a l catalysts consis t o f a t rans i t ion meta l c o m p l e x conta in ing a ch i r a l phosphine l igand (the transit ion meta l is usua l ly Ir, R h , R u , or O s ) . 1 5 A measure o f the success o f asymmetr ic systems is g iven by the enant iomeric excess (e.e.) (eq 1.2). e.e.(%) = ' r [ p 1 ] " [ r ^ ' x l O O (1.2) O v e r the past fifteen years there has been an enormous amount o f w o r k i n the f i e ld o f asymmetr ic homogeneous hydrogenation, w i t h numerous comprehensive rev iews appearing i n the literature. 1°.11.1547,19,20,43,52-62 T h e first ch i ra l phosphine l igands used i n asymmetr ic hydrogenat ions were ch i r a l at the phosphorus atom (e.g., P M e P r P h ) . H o w e v e r , on ly poor op t i ca l induc t ions were observed w i t h these systems. T h e next s ignif icant development i n the synthesis o f new c h i r a l phosphines came w i t h the preparation by Kagan ' s group o f the d iphosphine D I O P (Figure 1 . 3 ) . 1 7 ' 6 3 ' 6 4 T h i s phosphine, w h i l e conta in ing the centre o f ch i ra l i ty on a carbon atom i n the l i g a n d backbone, gave h igh opt ica l y ie lds w i t h p roch i r a l o lef ins . A l s o , the 8 Chapter 1 References: p 14 Chapter 1 starting mater ia l for the synthesis o f D I O P is tartaric ac id , and therefore, the ch i ra l i ty on 17 carbon arises f rom natural sources, mak ing the l igand relat ively cheap to prepare. T h e h i g h enant ioselect iv i t ies that were observed for R h c o m p l e x e s o f D I O P p rov ided the impetus for the development o f new diphosphine l igands w h i c h conta ined their ch i ra l i ty on carbon. Some o f the most notable diphosphines deve loped (see F igu re 1.3) are: D i P A M P (chi ra l at P ) , w h i c h i s used i n Monsan to ' s synthesis o f L - D o p a ; 6 5 P R O P H O S , prepared f rom lact ic ac id ; C H I R A P H O S , w h i c h has two asymmetr ic centres i n its b a c k b o n e ; 1 7 B P P F A , a ferrocene d e r i v a t i v e ; 1 7 C Y C P H O S , w h i c h i s effect ive for i m i n e h y d r o g e n a t i o n ; 6 6 and B D ^ A P , w h i c h is effective i n the hydrogenat ion o f ca rbony l -con ta in ing compounds . These are just a few i l lustrat ive examples o f the more than a CO thousand ch i ra l phosphines that have been used i n asymmetr ic catalysis . T h e catalysts or "precatalysts" are general ly prepared by two methods: either (1) i n s i tu, by adding one equivalent o f the chelat ing ditertiary phosphine l igand per m o l o f R h ; o r (2) by addi t ion o f a s o l i d c o m p l e x o f the type [Rh(diphosphine)(diene)] +BF4~, w h i c h already contains the ch i ra l l igand . M o n o p h o s p h i n e s general ly seem to g ive l o w e r op t i ca l y i e ld s than d iphosphine l igands , and it shou ld be pointed out that the rigidity o f the chelate ring fo rmed w i t h diphosphines seems to p lay a k e y role i n obtaining h igh enant iomeric excess. L i g a n d s that fo rm r i g i d f ive-membered chelate rings seem to be general ly more eff ic ient than those w h i c h form more f lexib le s ix - or seven-membered che l a t e s . 5 3 T h i s is thought to be manifested through a r i g i d ch i r a l array o f p h e n y l rings i n the f ive -membered chelates w h i c h a l l o w s a degree o f d i sc r imina t ion o f the p roch i ra l o l e f in ic faces i n the b i n d i n g step. The first prochira l substrates to be reduced wi th the highest enant iomeric excesses were funct ional ized olefins, w h i c h are be l ieved to b ind i n a bidentate fashion. Therefore, i t has been suggested that these substrates impose some rigidity on the sys tem, thereby 9 Chapter 1 References: p 14 Chapter 1 increasing the optical yield of the product.52 For example, some enamide substrates have been hydrogenated with up to 100% e.e. H y * PPh2 H DIOP (chiral at C) Q Q d* \ O M e O DiPAMP (chiral at P) PPh 2 PPh2 CHIRAPHOS (chiral at C) Me P p h 2 PROPHOS (chiral at C) H , Me ^ V ^ N ( M e ) 2 PPh, BPPFA (planar chirality and chiral at C) Ph2?. PPh. CYCPHOS (chiral atC) P P h 2 PPho BINAP (axial chirality or atropisomerism) Figure 1.3 Selected chiral diphosphines used in asymmetric hydrogenation; the symbol * represents a chiral centre. A probable mechanism for asymmetric hydrogenation of (Z)-a-acylamido-cinnamic acid derivatives has been suggested by the groups of Ffalpern and Brown. 7 A combination of kinetic, X-ray, and NMR techniques were used to elucidate the pathway. The mechanism shows, in contrast to what was previously believed, that the major 10 Chapter 1 References: p 14 Chapter 1 enantiomer obtained by asymmetric hydrogenation corresponds to the minor diastereomer of the catalyst-substrate adduct present in solution. Thus, the hydrogenation is kinetically controlled, with the major product originating from faster reaction of the minor diastereomer of the catalyst-substrate adduct wiuVH2. Other studies have shown that the H2 pressure and temperature dependences on the enantiomeric excess agree with 73 75 those predicted by Halpern's mechanism. At higher H2 pressures, the e.e. decreases due to the increased rate of H2 addition relative to the interconversion of major and minor diastereomers, while at lower temperatures, the e.e. is also observed to decrease. 1.3 Scope of this Thesis T h e w o r k i n this thesis is d i rec ted toward the prepara t ion o f po ten t ia l R u -d iphosph ine catalysts for homogeneous hydrogenat ion . Interest i n this labora tory has recen t ly been concentra ted o n e x a m i n i n g different routes to species w i t h a s i ng l e d iphosphine per R u centre. Routes to these types o f complexes arose f rom earl ier w o r k i n this laboratory on the R u H C l ( D I O P ) 2 - c a t a l y z e d asymmetr ic hydrogena t ion o f alkenes w h i c h indicated that " [ R u H C l ( D I O P ) ] " is the active catalytic s p e c i e s . 7 6 " 7 8 The re fo r e , po t en t i a l routes to R u spec ies c o n t a i n i n g a s i n g l e c h e l a t i n g d iphosphine ( P - P ) per metal were invest igated i n this laboratory. T h i s w o r k l e d to the d i s c o v e r y , by T h o r b u r n , o f a route to Ru(P-P) c o n t a i n i n g c o m p l e x e s o f the type [ R u C l ( P - P ) ] 2 ( p - C l ) 3 (or R u 2 C l 5 ( P - P ) 2 ) and [ R u C l ( P - P ) ] 2 ( p - C l ) 2 (or R u 2 C l 4 ( P - P ) 2 ) . 7 9 - 8 2 B y 1990, Jo sh i had extended these series o f complexes by substi tuting different c h i r a l and a c h i r a l d iphosph ines to i n c l u d e 12 such R u 2 C l 5 ( P - P ) 2 and 8 R u 2 C L | ( P -P ) 2 OO OA complexes . ' Chapte r 3 w i l l r ev i ew previous w o r k i n this area f rom this and other laboratories, and outl ine new routes to complexes o f the type R u 2 X 4 ( P - P ) 2 (X = C l , B r , and I) and R u 2 C l 4 ( P - P ) 2 ( L ) . M u c h o f the w o r k was done w i t h the ach i ra l d iphosphine l i gand Ph2P(CH2 )4PPh2 ( D P P B ) , w h i c h forms a seven-membered chelate on b i n d i n g to 11 Chapter 1 References: p 14 Chapter 1 the Ru centre. This diphosphine is a useful analogue to the expensive chiral phosphines BINAP and DIOP, which also form seven-membered chelates. As the complexes outlined in Chapter 3 were prepared as potential hydrogenation catalysts, their reactivity with dihydrogen was investigated. Chapter 4 details the reactivity of complexes of the type Ru2X4(P-P)2 and RuCl2(P-P)(PPh3) with H2 and other small gas molecules (i.e., N2, C H 2 = C H 2 ) . A brief review of the literature on molecular hydrogen complexes and the relevant Ru(r|2-H2) complexes is presented at the beginning of Chapter 4. A ruthenium complex formulated as Ru2CU (BINAP) 2 (NEt3) has been successively used as a catalyst for the asymmetric hydrogenation of several prochiral 1 1 R i^ substrates. ' ' ' Therefore, ruthenium species containing both a diphosphine and a basic nitrogen-containing ligand were investigated as potential catalysts for homogeneous hydrogenation. Chapter 5 describes the reaction of R u C l 2 ( P - P ) ( P P h 3 ) and [RuCl2(P-P)]2(P>P-P) (or Ru2Cl4(P-P)3) with nitrogen-containing ligands (NH3, pyridine, 2,2'-bipyridine, and 1,10-phenanthroline) to generate species of the type RuCl2(P-P)(N)2, where N is the N-donor ligand. Catalytic studies for the homogeneous hydrogenation of nitriles and imines are described in Chapter 6. The hydrogenation reactions were performed at both ambient and high pressures (1000 psi). The studies on imine hydrogenation were performed under conditions to allow comparison with work done in this laboratory by Fogg et a l . 8 7 ' 8 8 The activities of Br- and I-containing catalysts compared with that of the Cl analogues were of O Q special interest, considering earlier reports for some Rh systems. These systems showed that addition of iodide was beneficial in terms of increased enantiomeric excesses for the hydrogenation of prochiral imines. A brief review of the literature on homogeneous hydrogenation of imines will begin Chapter 6. 12 Chapter 1 References: p 14 Chapter 1 Chapter 7 outlines initial studies on some interesting solid state reactivity of five-coordinate complexes of the type R u C l 2 ( P R 3 ) 3 with C O and NH3. Related solution reactivity is also described and discussed. The experimental procedures used to prepare the materials used in the work described in Chapters 3-7 are given in Chapter 2. General conclusions and some recommendations for future work are found in Chapter 8. 13 Chapter 1 References: p 14 Chapter 1 1.4 References (1) Nakamura, A.; Tsutsui, M . Principles and Applications of Homogeneous Catalysis; Wiley-Interscience: New York, 1980. (2) Jennings, J. R. Selected Developments in Catalysis; Blackwell Scientific: Oxford, 1985; Vol. 12. (3) Dickson, R. S. Homogeneous Catalysis with Compounds of Rhodium and Iridium; D. Reidel: Dordrecht, 1985. (4) Masters, C. Homogeneous Transition-Metal Catalysis: A Gentle Art; Chapman and Hall: London, 1981. (5) Parshall, G.; Ittel, S. D. Homogeneous Catalysis: The Applications and Chemistry of Soluble Transition-Metal Complexes; 2nd ed.; Wiley: New York, 1992. (6) Hartley, F. R. Supported Metal Complexes; D. Reidel: Dordrecht, 1985; Chapter 1. (7) Collman, J. R; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1987; Chapter 10. (8) Moggridge, G. D.; Rayment, T.; Ormerod, R. M . ; Morris, M . A.; Lambert, R. M . Nature 1992, 358, 658. (9) Worthy, W. Chem. Eng. News 1991,69(19), 25. (10) Knowles, W. S. Acc. Chem. Res. 1983,16, 106. (11) Takaya, H.; Ohta, T.; Noyori, R. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.; V C H : Oxford, 1993, p 1. (12) Haggin, J. Chem. Eng. News 1994, 72(41), 28. (13) Alper, H. Adv. Organomet. Chem. 1981,19, 183. (14) Dehmlow, E. V.; Dehmlow, S. S. Phase Transfer Catalysis; 3rd ed.; V C H : New York, 1993. (15) Chaloner, P. A.; Esteruelas, M . A ; Joo, F.; Oro, L. A. Homogeneous Hydrogenation; Kluwer Academic: Dordrecht, 1994. (16) Herrmann, W. A ; Kohlpaintner, C. W. Angew. Chem., Int. Ed. Engl. 1993, 32, 1524. (17) Brunner, H. J. Organomet. Chem. 1986, 39, 300. (18) Hadata, M . ; Jancarik, J.; Graves, B.; Kim, S. H. J. Am. Chem. Soc. 1985,107, 4279. 14 Chapter 1 (19) Noyori, R. CHEMTECH 1992, 360. (20) Brunner, H. Synthesis 1988, 645. (21) Sheldon, R. Chem. Ind. (London) 1990, 212. (22) Stinson, S. C. Chem. Eng. News 1993, 71(39), 38. (23) Borman, S. Chem. Eng. News 1992, 70(24), 5. (24) Hyneck, M . ; Dent, J.; Hook, J. In Chirality in Drug Design and Synthesis; Brown, C , Ed.; Academic: London, 1990; Chapter 1. (25) Stinson, S. C. Chem. Eng. News 1994, 72(38), 38. (26) Testa, B. In Chirality and Biological Activity; Holmstedt, B., Frank, H. , Testa, B., Eds.; Alan R. Liss: New York, 1990, pp 15-32. (27) Ariens, E. J. In Chirality in Drug Design and Synthesis; Brown, C , Ed.; Academic: London, 1990; Chapter 2. (28) Ariens, E. J. Eur. J. Clin. Pharmacol. 1984, 26, 663. (29) Ariens, E . J.; Wuis, E. W. Clin. Pharmacol. Ther. 1987, 42, 361. (30) Ariens, E . J.; Wuis, E. W.; Veringa, E. J. Biochem. Pharmacol. 1988, 37, 9. (31) Taber's Cyclopedic Medical Dictionary; 17th ed.; Thomas, C. L . , Ed.; F. A. Davis: Philadelphia, 1993, p 1974. (32) The Columbia Encyclopedia; 5th ed.; Chernow, B. A , Vallasi, G. A., Eds.; Columbia University: Boston, 1993, p 2725. (33) Selinger, B. Chemistry in the Marketplace; 4th ed.; Harcourt Brace Jovanovich: Sydney, 1989, p 583. (34) Carey, J. Chem. Br. 1993, 29, 1053. (35) Hunt, J. R. Chem. Br. 1994, 30, 280. (36) De Camp, W. H. Chirality 1989,1, 2. (37) Testa, B.; Carrupt, P.-A.; Gal, J. Chirality 1993, 5, 105. (38) Koenig, K. E. In Catalysis of Organic Reactions; Kosak, J. R., Ed.; Marcel Dekker: New York, 1984, p 63. (39) Young, J. F.; Osborn, J. A ; Jardine, F. H.; Wilkinson, G. / . Chem. Soc, Chem. Commun. 1965, 131. (40) Brown, J. M . Angew. Chem., Int. Ed. Engl. 1987, 26, 190. (41) James, B. R. Adv. Organomet. Chem. 1979,17, 319. 15 Chapter 1 (42) James, B. R. In Comprehensive Organometallic Chemistry; Wilkinson, G. , Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, 1982; Vol. 8, Chapter 51. (43) Pino, P.; Consiglio, G. In Fundamental Research in Homogeneous Catalysis; Tsutsui, M . , Ed.; Plenum: New York, 1979; Vol. 3, p 519. (44) Freifelder, M . Practical Catalytic Hydrogenation; Wiley-Interscience: New York, 1971. (45) Rylander, P. N. Hydrogenation Methods; Academic: New York, 1985. (46) Chaloner, P. A. Handbook of Coordination Catalysis in Organic Chemistry; Butterworths: Toronto, 1986; Chapter 2. (47) James, B. R. Homogeneous Hydrogenation; Wiley: New York, 1973. (48) James, B. R. Chem. Ind. 1995, 62, 167. (49) Mestroni, G.; Camus, A.; Zassinovich, G. In Aspects of Homogeneous Catalysis; Ugo, R., Ed.; D. Reidel: Dordrecht, 1981; Vol. 4, p 71. (50) Jessop, P. G.; Morris, R. H. Coord. Chem. Rev. 1992,121, 155. (51) Kubas, G. J.; Ryan, R. R.; Swanson, B. I.; Vergamini, P. J.; Wasserman, H. J. / . Am. Chem. Soc. 1984,106, 451. (52) Caplar, V.; Comisso, G.; Sunjic, V. Synthesis 1981, 85. (53) Bosnich, B.; Fryzuk, M . D. In Topics in Inorganic and Organometallic Stereochemistry; Geoffrey, G., Ed.; Wiley: New York, 1981, p 119. (54) Valentine, D.; Scott, J. W. Synthesis 1978, 329. (55) Blystone, S. L. Chem. Rev. 1989, 89, 1663. (56) Noyori, R. Science 1990, 248, 1194. (57) Asymmetric Synthesis; Morrison, J. D., Ed.; Academic: New York, 1985; Vol. 5. (58) Brunner, H. In Advances in Catalysis Design; Graziani, M . , Rao, C. N. R., Eds.; World Scientific: London, 1993; Vol. II, p 245. (59) Arntz, D.; Schafer, A. In Metal Promoted Selectivity in Organic Synthesis; Noels, A. F., Graziani, M . , Hubert, A. J., Eds.; Kluwer Academic: Dordrecht, 1991, p 161. (60) Asymmetric Catalysis; Bosnich, B., Ed.; Martinus Nijhoff: Dordrecht, 1986. (61) Kagan, H. B. In Comprehensive Organometallic Chemistry; Wilkinson, G. , Stone, F. G. A , Abel, E. W., Eds.; Pergamon: Oxford, 1982; Vol. 8, Chapter 53. (62) Noyori, R. Asymmetric Catalysis in Organic Synthesis; Wiley-Interscience: New York, 1994. 16 Chapter 1 (63) Dang, T. P.; Kagan, H. B. / . Chem. Soc., Chem. Commun. 1971, 481. (64) Kagan, H. B.; Dang, T. P. J. Am, Chem Soc. 1972, 94, 6429. (65) Vineyard, B. D.; Knowles, W. S.; Sabacky, M . J.; Bachman, G. L . ; Weinkauff, D. J. J. Am. Chem. Soc. 1977, 99, 5946. (66) Kang, G.; Cullen, W. R.; Fryzuk, M . D.; James, B. R.; Kutney, J. P. J. Chem. Soc, Chem Commun. 1988, 1466. (67) Kitamura, M . ; Ohkuma, T.; Inoue, S.; Sayo, N.; Kumobayashi, H.; Akutagawa, S.; Ohta, T.; Takaya, H.; Noyori, R. / . Am. Chem. Soc. 1988,110, 629. (68) Halpern, J. Science 1982,217, 401. (69) Chan, A. S. C ; Pluth, J. J.; Halpern, J. J. Am. Chem. Soc. 1980,102, 5952. (70) Brown, J. M. ; Chaloner, P. A. J. Chem Soc, Chem. Commun. 1980, 344. (71) Alcock, N. W.; Brown, J. M. ; Derome, A. E.; Lucy, A. R. J. Chem. Soc, Chem. Commun. 1985, 575. (72) Brown, J. M. ; Chaloner, P. A.; Morris, G. A. J. Chem. Soc, Chem Commun. 1983, 664. (73) Ojima, I.; Kogure, T.; Yoda, N. Chem Lett. 1979, 495. (74) Ojima, I.; Kogure, T.; Yoda, N. / . Org. Chem. 1980,45,4728. (75) Sinou, D. Tetrahedron Lett. 1981, 22, 2987. (76) Wang, D. K. W. Ph.D. Thesis, The University of British Columbia, 1978. (77) James, B. R.; Wang, D. K. W. Can J. Chem. 1980, 58, 245. (78) James, B. R.; McMillan, R. S.; Morris, R. H.; Wang, D. K. W. Adv. Chem. Ser. 1978,167,122. (79) James, B. R.; Pacheco, A.; Rettig, S. J.; Thorburn, I. S.; Ball, R. G.; Ibers, J. A. J. Mol. Catal. 1987, 41, Ul. (80) James, B. R.; Joshi, A. M . ; Kvintovics, P.; Morris, R. H.; Thorburn, I. S. In Catalysis of Organic Reactions; Blackburn, D. W., Ed.; Marcel Dekker: New York, 1990; Chapter 2. (81) Thorburn, I. S. Ph.D. Thesis, The University of British Columbia, 1985. (82) Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chem. 1986, 25, 234. (83) Joshi, A. M . ; Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chim Acta 1992, 198, 283. (84) Joshi, A. M . Ph.D. Thesis, The University of British Columbia, 1990. 17 Chapter 1 (85) Noyori, R. Chem. Soc. Rev. 1989,18, 187. (86) Noyori, R. In Modern Synthetic Methods; Scheffold, R., Ed.; Springer-Verlag: Berlin, 1989, p 115. (87) Fogg, D. E.; James, B. R ; Kilner, M . Inorg. Chim. Acta 1994,222, 85. (88) Fogg, D. E. Ph.D. Thesis, The University of British Columbia, 1994. (89) Becalski, A. G.; Cullen, W. R.; Fryzuk, M . D.; James, B. R.; Kang, G.-J.; Rettig, S. J. Inorg. Chem. 1991, 30, 5002. 18 C H A P T E R 2 E X P E R I M E N T A L P R O C E D U R E S 2.1 Materials 2.1.1 Solvents Spectral- or analytical-grade solvents were obtained from M C B , BDH, Aldrich, Eastman, Fisher or Mallinckrodt Chemical Company. Benzene, toluene, hexanes and diethyl ether were refluxed with, and distilled from, sodium metal/benzophenone under an atmosphere of nitrogen. N,N-dimethylacetamide (DMA) was stirred with C a H 2 for at least 24 h, vacuum distilled at 35-40 °C, and stored under argon in the dark. Dichloromethane, acetone, methanol, ethanol and 2-propanol were distilled after refluxing with the appropriate drying agents (P2O5 or C a H 2 for C H 2 C 1 2 ; anhydrous K2CO3 for acetone; and Mg/I 2 for the alcohols).1 Dibromomethane was dried over molecular sieves prior to use. Nitromethane, used in conductivity studies, was distilled from C a C l 2 and stored under Ar. The solvent n-pentane was used as received. Al l solvents were deoxygenated prior to use. The deuterated solvents (CDCI3, C D 2 C 1 2 , C 6 D 6 , C 7 D 8 , ( C D 3 ) 2 C O , C D 3 C N , (CD 3 ) 2 SO, C D 3 O D , (CD 3 ) 2 CD(OD) and D 2 0 ) , used in NMR spectroscopy, were obtained from Merck Frosst Canada, Cambridge Isotope Laboratories (CIL), Isotec, and Aldrich. All deuterated solvents (with the exception of D 2 0) were dried if necessary over activated molecular sieves (Fisher: Type 4 A, 4-8 mesh), deoxygenated, and stored under argon. For the preparation of sealed NMR samples, C6D6 and C7D8 were dried over Na/benzophenone and stored under vacuum, while CDCI3 was stored under vacuum over C a H 2 . Samples that were particularly 0 2 - and/or moisture-sensitive were prepared by vacuum-transferring the above solvents into sealable NMR tubes which were previously filled with the solid sample. 19 Chapter 2 References: p 82 Chapter 2 2.1.2 Gases Purified Ar (Linde), N 2 (Linde), CO (CP.), 0 2 (U.S.P) and H 2 (Research, extra dry) were obtained from Union Carbide Canada; all except H 2 and Ar were used without further purification. Hydrogen was passed through an Engelhard Deoxo catalytic hydrogen purifier to remove traces of oxygen. Argon was passed through a drying column of CaS04. Anhydrous NH3 (Matheson) and H 2 S (Matheson) were used without further purification. Deuterium (CIL and Merck Frosst Canada) was used as supplied. Ethylene (Matheson) was used without further purification. 2.1.3 Phosphines The monodentate phosphines, PPI13 (BDH, Aldrich, or Strem) and P(p-tolyf)3 (Strem), were used as supplied. The bidentate phosphines, Ph 2 P(CH 2 ) n PPh 2 , where n=2, DPPE, and n=4, DPPB, were purchased from Strem and used without purification. The chiral phosphine, (fl)-BINAP, ((/?)-2,2'-bis(diphenylphosphino)-l,l'-binaphthyl) (Strem), was a gift from Dr. S. King (Merck Research Laboratories). The phosphines, rac-(±)-1,2-bis(diphenylphosphino)cyclopentane (DPPCP) and rac-(±)-l,2-bis(dicyclohexylphos-phino)cyclopentane (DCYPCP) were synthesized from the previously prepared rac-{±)-l,2-bis(dichlorophosphino)cyclopentane (Section 2.1.3.1) by a reported method, and used as such without resolution. l,4-Bis(dicyclohexylphosphino)butane (DCYPB) was prepared by Mr. D. Chau in this laboratory by a modified reported preparation3'4 from dicyclohexylphosphine, n-butyllithium, and 1,4-dibromobutane. The purity of all of the phosphines was ascertained by 3 1P{ lU} and lH NMR spectroscopy. 20 Chapter 2 References: p 82 Chapter 2 2.1.3.1 Preparation of Cl2P(CsH8)PCl2, <ra«s-l,2-bis(cUchlorophosphino)-cyclopentane2 T h e tit le bis(phosphine) was prepared w i t h M r . R . Schutte by m o d i f i c a t i o n o f a publ i shed procedure. Cyc lopen tene (205 m L , 2.33 m m o l ) , phosphorus t r i ch lo r ide (298 m L , 3.42 m o l ) , and y e l l o w phosphorus (25.45 g, 0.21 m o l P4) were added together i n a steel autoclave, w h i c h was sealed and the contents stirred at 220 °C for 69 h . T h e pressure reached a m a x i m u m of 27 atm after 3 h , and was 21 atm w h e n the autoclave contents were c o o l e d for w o r k - u p . T h e resul t ing da rk -b rown mix tu re was f i l te red through a B u c h n e r funnel under a blanket o f N2, created by passing gas through an inver ted funnel , to remove any sol ids . T h e b r o w n filtrate was col lec ted i n a round-bot tom f lask that was then attached to a vacuum dis t i l la t ion apparatus. F o u r fractions were co l lec ted . T h e first two fractions contained starting cyclopentene, cyclopentane, and PCI3 ( 3 1 P { 1 H } N M R ( C 6 D 6 , 20 °C): 8 = 219.0, s) . T h e th i rd f r ac t ion con ta ined d i c h l o r o p h o s p h i n o -cyclopentane, ( C 5 H g ) P C l 2 , co l lec ted at a st i l lhead temperature o f 80-92 °C at ~ 0.1 m m H g . T h e desired product , C l 2 P ( C 5 H g ) P C l 2 , was i so la ted i n the four th f rac t ion as a colour less l i q u i d at a st i l lhead temperature o f 100-108 °C at ~ 0.1 m m H g . Y i e l d : 174 g 31P{ l H } N M R ( C 6 D 6 , 20 °C): 5 = 190.0, s. l H N M R ( C 6 D 6 , 20 °C): 5 1.28 (2H, pentet, J = 7 Hz, Ha); 1.65 (4H, m , H b ) ; and 2.38 (2H, m , H c ) (Figure 2.1). Figure 2.1 Structure of trans-l,2-bis(dichlorophosphino)cyclopentane indicating NMR (52%). assignments. 21 Chapter 2 References: p 82 Chapter 2 The physical and spectroscopic data agree with those reported.2 The 3 1 P{ 1 H} NMR data have not previously been reported, but the chemical shift is in the expected region for a PRCI2 compound (cf. PCI3, see above). dichlorophosphinocyclopentane, (C5Hs)PCl2 3lp{lH} NMR ( C 6 D 6 , 20 °C): 5 = 193.6, s. 2.1.3.2 Preparation of /ra«s- l ,2-(R2P)2C5H 8 , where R = Ph, C y 2 The title racemic phosphines (DPPCP and DCYPCP) were prepared by addition of the appropriate Grignard reagent RMgBr to trans-1,2-(Cl2P)2C5H-8, as outlined in the literature. The spectroscopic data are shown below. DPPCP (R = Ph) 31p{ I H } NMR (CDCI3, 20 °C): 8 = -8.1, s. ! H NMR (CDCI3, 20 °C): 8 1.65 (2H, m, CH2 of cyclopentane), 1.90 (2H, m, CH2 of cyclopentane), 2.26 (2H, m, CH2 of cyclopentane), 2.75 (2H, m, CH of cyclopentane), 7.05-7.55 (20H, m, Ph). DCYPCP (R = Cy) 31p{ 1 H } NMR (CDCI3, 20 °C): 8 = 7.8, s. *H NMR (CDCI3 , 20 °C): 8 1.28 (18H, br s, 2H of CH2 of cyclopentane and 16H of Cy), 1.8 (32H, br m, 4H of cyclopentane and 28H of Cy), 2.49 (2H, br m, CH of cyclopentane). 2.1.4 Substrates Benzonitrile (Aldrich), used as a substrate in hydrogenation studies, was purified by stirring over K2CO3 for several hours before decanting onto anhydrous CaS04. The nitrile was collected by vacuum distillation and stored under argon. 22 Chapter 2 References: p 82 Chapter 2 The imines, used as hydrogenation substrates, were prepared by Dr. D. Fogg by condensation of the appropriate amine and ketone or aldehyde.5 The imines used were the ketimine, Ph(Me)C=NCH2Ph, and the aldimine, Ph(H)C=NCH2Ph. Both were used without further purification. The aldimine, N-benzylidene aniline (Ph(H)C=NPh), was synthesized by Dr. P. Kvintovics of this laboratory (visiting from the University of Veszprem, Hungary). Styrene (Aldrich) was purified by passing through a column of activated alumina (Fisher, neutral alumina, activity I, 80-200 mesh) to remove the inhibitor, 4-f-butylcatechol, and was stored under Ar in the refrigerator. Authentic samples of the hydrogenation products corresponding to the above mentioned substrates were purchased from Aldrich, and used as supplied for comparison. 2.1.5 Other Materials The amines, diethylamine (Eastman), di(n-butyl)amine (Mallinckrodt), tri(«-butyl)amine (Anachemia), benzylamine, dibenzylamine and tri(rc-octyl)amine (Aldrich), were used without further purification. Triethylamine (MCB) was purified before use by stirring over K O H (Fisher) and collecting the amine by distillation. Poly(4-vinylpyridine), 2% cross-linked (Reillex™ 402 Polymer) (Aldrich) was used as received. The heterocyclic compounds, pyridine (BDH), 2,2'-bipyridine (MCB), and 1,10-phenanthroline monohydrate (Fisher) were used as supplied. The salts N H 4 C I (BDH), N H 4 P F 6 (Ozark-Mahoning) and 1 5 N H 4 C 1 (MSD Isotopes) were used as supplied. The sulfoxides, DMSO (BDH) and tetramethylene sulfoxide, T M S O (Aldrich), were used as supplied. The sulfides, dimethyl sulfide, DMS (Aldrich) and tetrahydrothiophene, THT (Aldrich) were used as supplied. 1,5-Cyclooctadiene (COD) was either used as supplied by Aldrich, or passed through an activity I neutral alumina column prior to use. Cyclopentene and allylmagnesium bromide (1.0 M in diethyl ether) 23 Chapter 2 References: p 82 Chapter 2 were used as supplied by Aldrich. Acetophenone (MCB) was vacuum distilled from anhydrous CaSCU and stored under argon. 7erft'ary-butanol (BDH) was used without prior purification for the Evans method ' of measuring magnetic susceptibility (Section 2.5.6.1). Phosphorus trichloride (BDH) was refluxed under N 2 , and then collected by fractional distillation and stored under argon. Yellow phosphorus, P4, (Aldrich) and 30% H2O2 (BDH) were used in synthetic preparations without purification. Cul (Aldrich) was used as supplied, while Zn dust (Fisher) was activated prior to use. Zinc dust (7 g) was stirred with a 2% aq HC1 solution (12 mL) for 1 min, then the solution was decanted off, and a second portion of the acid added. The Zn was collected on a filter and washed with distilled H 2 O (3 x 10 mL), 95% EtOH (2 x 10 mL), and anhydrous diethyl ether (10 mL). The activated Zn was dried under vacuum and stored under A r . 1 LiBr (Fisher and MCB) was dried under vacuum at room temperature to remove any moisture before using it in halogen exchange reactions. The drying agents, anhydrous CaCl2 (Fisher, 4-20 mesh), CaH2 (Fisher or BDH), anhydrous K 2 C O 3 (Fisher), and anhydrous MgSCU (Fisher), were all used as supplied. Molecular sieves (4 A, 1/16", BDH) were activated prior to use by heating overnight under dynamic vacuum. The filter aid, Celite 545® (Fisher) was used as supplied. Neutral alumina (Fisher, Brockmann activity I, 80-200 mesh) was used as purchased or converted to activity Ul by adding 6% H 2 O by weight.8 2.1.5.1 Preparation of copper(I) chloride, CuCl CuCl was prepared from CuCl2-2H20 (Fisher) by a previously described method.9'1 0 A solution of Na 2S03 (10 g in 50 mL H2O) was slowly added to a green solution of CuCl2-2H20 (13.0 g, 0.0763 mol) in H 2 O (20 mL). The resulting suspension was added to a solution of Na2SQ3 (1 g) and concentrated HC1 (2 mL) in H2O (1 L). This 24 Chapter 2 References: p 82 Chapter 2 mixture was stirred, and then the white CuCl allowed to settle out. The supernatant was decanted, and the white solid was washed onto a sintered glass filter with an acidified Na 2 S03 solution (same concentration as above). The solid was then washed with glacial acetic acid (5 x 20 mL), ethanol (3 x 30 mL), and diethyl ether ( 6 x 1 5 mL). Care was taken to ensure that the solid was covered by a layer of liquid at all times. After the final washing, the white product was quickly transferred to a Schlenk tube and dried under vacuum. Yield: 5.8 g (77%). The copper (I) chloride was stored in the dark under an atmosphere of argon. 2.1.5.2 Preparation of tetrameric chloro(triphenylphosphine)copper(I), [CuCl(PPh 3 )]4 1 1 1 2 Triphenylphosphine (1.35 g, 5.14 mmol) and CuCl (0.53 g, 5.33 mmol) were refluxed in C6H6 (25 mL) for 18 h. The resulting cloudy, slightly-yellowish solution was filtered to produce a clear, colourless solution. The volume of this solution was reduced slightly at the pump until a white product precipitated; this was collected by vacuum filtration, washed with hexanes ( 4 x 5 mL), and dried under vacuum. Calculated for [CuCl(PPh 3)] 4, [ C i 8 H i 5 C l P C u ] 4 : C, 59.84; H, 4.18%. Found: C, 59.73; H , 4.30%. The paper outlining the above procedure reports the product as Cu2Cl2(PPh3)3;11 however, another paper reports that identical conditions give [CuCl(PPh3)] 4. 1 2 A subsequent paper by Costa et al. reports that repeated recrystallizations of [CuCl(PPh3)] 4 give Cu 2Cl2(PPh 3)3. 1 3 2.1.5.3 Preparation of dibutylammonium chloride, [H2N(/i-butyl)2]+Cl-A n excess of concentrated HC1 (10 mL, 0.12 mol) was added dropwise to a solution of di-n-butylamine (2.8 mL, 13 mmol) in EtOH (25 mL) at 0 °C. The clear, colourless reaction mixture was stirred at room temperature for 2 h, and then the solvent was removed with a rotary evaporator. The resulting white solid was dried at 78 °C under 25 Chapter 2 References: p 82 Chapter 2 vacuum. Yield: 2.1 g (97%). Calculated for [H2N(rc-butyl)2]+Cl- C 8 H 2 0 N C 1 : C, 57.99; H, 12.16; N, 8.45%. Found: C, 58.13; H, 12.29; N, 8.26%. ! H NMR (CDCI3, 20 °C): 8 0.93 (6H, t, J = 7.3 Hz, C H 2 C / / 3 ) , 1.4 (4H, sextet, J = 7.5 Hz, C H 2 C # 2 CH 2 ) , 1.9 (4H, pentet, / = 7.9 Hz, C H 3 C H 2 C / / 2 C H 2 N ) , 2.9 (4H, br m, C H 2 C t f 2 N H 2 ) , and 9.4 (2H, br s, NH2). 2.1.5.4 Preparation of dioctylammonium chloride, [H2N(/i-octyl)2]+Cl-An excess of concentrated HC1 (10 mL, 0.12 mol) was added dropwise to a solution of di-n-octylamine (3.6 mL, 12 mmol) in EtOH (25 mL) at 0 °C. The clear, colourless reaction mixture was stirred at room temperature for 2 h, and then the solvent was removed with a rotary evaporator. The resulting white solid was dried at 78 °C under vacuum. Yield: 3.3 g (98%). Calculated for [H 2 N(«-octyl ) 2 ]+Cl- , C i 6 H 3 6 N C l : C, 69.15; H, 13.06; N, 5.04%. Found: C, 69.34; H, 13.09; N, 4.95%. ! H NMR (CDC1 3, 20 °C): 8 0.87 (6H, t, J = 6.8 Hz, C H 2 C / 7 3 ) , 1.3 (20H, m, C H 3 ( C / / 2 ) 5 C H 2 ) , 1.9 (4H, pentet J = 7.5 Hz, C H 2 C / / 2 C H 2 N ) , 2.9 (4H, br m, C H 2 C # 2 N H 2 ) , and 9.5 (2H, br s, NH2). 2.2 Instrumentation Infrared spectra were recorded on a Nicolet 5DX FT-IR or ATI Mattson Genesis Series FTIR spectrophotometer as KBr pellets, or as Nujol mulls between KBr plates, unless specified otherwise. UV-visible spectra were recorded on a Hewlett Packard 8452A diode array spectrophotometer with a thermostatted cell compartment, using quartz spectral cells (path length = 1.0 cm). Spectra were usually recorded in anaerobic cells (Figure 2.2) under an atmosphere of argon. 26 Chapter 2 References: p 82 Chapter 2 100 mm Sidearm Flask optical path sidearm flask lcm $ V i e w f rom bot tom 100 mm Kontes tap B14 socket B14 cone z 360 mm i L 60 mm Quartz Cell - I 12 mm Figure 2.2 Anaerobic UV-visible cell. The solution nuclear magnetic resonance (NMR) spectra were recorded on a Bruker AC200 (200.1 MHz for ! H and 81.0 MHz for 31p), a Varian XL300 (300.0 MHz for l H and 121.4 MHz for 3lp) and a Bruker AMX500 (500.0 MHz for ! H and 202.5 27 Chapter 2 References: p 82 Chapter 2 M H z for 3 1 P ) FT-NMR spectrometer. The J H chemical shifts are reported relative to the external standard of tetramethylsilane (TMS) at 0.0 ppm, while those measured for 3 1 P { 1 H } N M R were externally referenced relative to trimethylphosphite, P(OMe)3 (Aldrich), (141.0 ppm relative to 85% H3PO4).14 A l l 3 1 P{!H} N M R chemical shifts are reported relative to 85% H3PO4, with downfield shifts taken as positive. Variable-temperature N M R spectra were measured on the Varian XL300 spectrometer. Gas chromatographic analyses were performed on a temperature-programmable Hewlett Packard 5890A instrument equipped with a thermal conductivity detector and a flame ionization detector, using helium as the carrier gas (flow rate ~ 40 mL/min). Gas uptakes were performed on a conventional constant-pressure, constant-temperature gas-uptake apparatus. A detailed procedure employed for gas-uptake measurements is described elsewhere, ' while a brief description is given in Section 2.3.1, along with a diagram of the apparatus (Figure 2.3). Mass spectrometry was done either by Electron Ionization (EI) or Fast Atom Bombardment (FAB). F A B was performed on an AEI MS 902 Mass Spectrometer with 3-nitrobenzylalcohol as the matrix, while EI was performed on a Kratos MS 50. Conductivity measurements were made using a Serfass Conductance Bridge Model RCM15B1 (Arthur H . Thomas Co. Ltd.) connected to a 3403 cell from the Yellow Springs Instrument Company. The cell constant was determined by measuring the resistance of an aqueous solution of KC1 (0.0100 M , a = 0.001413 ohm - 1 cm" 1 at 1 7 2 5 ° C ) . 1 ' The cell was thermostatted in a water-bath. Conductance was measured on solutions with concentrations on the order of 1 x 10"3 M . The solutions were prepared in air with dry solvents just prior to use. Elemental analyses were performed by Mr. P. Borda of this department. Single crystal X-ray diffraction studies were carried out by Dr. S. Rettig of the departmental crystallographic service. 28 Chapter 2 References: p 82 Chapter 2 2.3 Catalytic Hydrogenation 2.3.1 Ambient Pressure Hydrogenations A constant-pressure gas-uptake apparatus was used to study the rate of catalytic hydrogenation of benzonitrile at a H 2 pressure of one atmosphere, and a temperature of 70 °C. The apparatus (Figure 2.3) and procedure have been described. 1 5 ' 1 6 Degassed solvents were used in the H2-uptake experiments, and the solutions of nitrile and solvent were further degassed by three freeze-pump-thaw cycles while connected to the uptake assembly. No air was allowed into the system as the catalyst was added to the solution by the dropping of a suspended bucket containing the catalyst. to mercury manometer to mercury manometer 4 Figure 2.3 Constant-pressure gas-uptake apparatus with the key components lettered: (A) thermostatted and insulated oil bath, (B) dimpled reaction flask, (C) oil manometer, (D) mercury reservoir and burette. (1)—(12) label the Kontes valves and greased taps and are described in the text. 29 Chapter 2 References: p 82 Chapter 2 A typical hydrogenation reaction followed by gas uptake was performed in the following manner. A flexible spiral glass capillary was used to connect the uptake flask B containing the solvent, substrate, and catalyst to the stopcock labelled 7 in Figure 2.3. While connected to this position, the solution was freeze-pump-thaw degassed at least three times, and then filled to slightly less than the required operating pressure with hydrogen. The flask B and spiral, once stopcocks 1 and 7 were closed, were then moved to Kontes valve 2. The flask and contents were allowed to equilibrate to the oil-bath temperature (A) for 30 minutes, during which time Kontes valves 2, 3, 4, and 5, and needle valve 6 were open to allow evacuation of the burette portion of the apparatus. The apparatus was then filled with the desired H2-pressure, and stopcock 1 was opened. Kontes valve 3 was then closed to lock in the reference pressure in the small volume of the burette. Unlike previous designs of the uptake apparatus, which used greased stopcocks at positions 2, 3, 4, and 5, significant pressure changes were observed in the oil levels as Kontes valve 3 was closed, thus decreasing the volume. Therefore, an additional step of re-levelling the oil in the burette by increasing the H2-pressure slightly with Kontes valve 10 was necessary. At this point, the H2-pressure could be recorded from the mercury manometer. Kontes valve 4 was then closed to isolate the Hg burette, and an initial reading was made from the Hg burette with the aid of a Precision Tool Vernier Microscope Type 2158. Needle valve 6 was then closed and the reaction started by dropping the bucket containing the catalyst. The progress of the catalytic reaction was followed by introducing hydrogen through needle valve 6 in order to level the oil burette, and by reading the Hg level. 2.3.2 High Pressure Hydrogenations Reactions at H2 pressures of up to 1000 psi (68 atm, 6.895 MPa) for hydrogenation of imines were performed in a machined-steel autoclave equipped with glass liners. The autoclave was topped with a high-pressure regulator which was 30 Chapter 2 References: p 82 Chapter 2 connected to an H 2 cylinder with flexible-steel hosing. Mixing of the hydrogenation reactions was achieved with the use of a magnetic stirrer. Conversion results were found by previous workers in the laboratory J ' ° to be dependent on the method of assembly of the autoclave (see below). Therefore, a standard procedure was developed and followed to ensure reproducible results in terms of rate of conversion. This procedure is described in the following paragraph. The empty autoclave was connected through the regulator on the H 2 cylinder to a vacuum line, then the autoclave was evacuated and filled with N 2 . The glass liner containing the catalytic solution was then placed in the autoclave under a stream of N 2 . The catalyst, imine substrate, and deoxygenated dry MeOH solvent had been previously placed in the glass liner under a flow of Ar. The head of the autoclave was screwed onto the assembly and tightened with a wrench. With the stirrer off, the solution was evacuated and flushed with N 2 three times, and finally evacuated again. The autoclave was then pressurized to 400 psi (2.7 MPa) H 2 and evacuated. This was repeated three times and the autoclave finally pressurized to 1000 psi (6.895 MPa) or any other desired pressure. The pressure was locked into the vessel with a needle valve and the stirrer started. The entire procedure, from the point of adding the solvent to the glass liner, to locking-in the final pressure, took just three minutes on average. This approach gave consistent results to within 3% or less from trial to trial. The source of the inconsistent results before the adoption of this procedure was found by previous workers to be due to the presence of trace dioxygen. 5 ' 1 8 A second autoclave, acquired toward the end of this thesis, was used on a couple of occasions. This autoclave featured sampling capabilities via a liquid sampling valve and dip tube, which allowed the hydrogenation to be easily followed by gas chromatography. Pressures of up to 1000 psi H 2 could be used with this stainless steel 50 mL autoclave, which was purchased from Parr Instrument Co. (4590 Bench Top Micro 31 Chapter 2 References: p 82 Chapter 2 Reactor) and equipped with a glass liner and temperature controller (Parr 4843 Series 942). Stirring was overhead by use of a magnetic drive. 2.4 Analysis of Hydrogenation Products 2.4.1 Measurement of Conversion Conversions of imine to amine in the case of the imines, PhN=C(H)Ph and PhCH.2N=C(H)Ph, were easily determined by removal of the MeOH solvent with a rotary evaporator, dissolution and dilution of the residue in CDCI3, and *H NMR spectroscopic analysis. In the cases where iV-phenylbenzylamine was the product, the integrations of the amine methylene and imine methyne were compared, while if dibenzylamine was the product, the integrations of methylenes of both amine and imine were used. Conversions of the ketimine, PhCH2N=C(Me)Ph, to amine were also determined by *H NMR spectroscopy, but were best performed in C 6 D 6 , as the imine appears to exist solely as the anti isomer in this solvent; only one methylene, attributed to the anrf-isomer, is apparent in C6E>6, instead of the two singlets observed in CDCI3 (in a ratio of ca. 9:1).5 Conversions of the imines PhCH2N=C(H)Ph and PhN=C(H)Ph to the corresponding amines could also be determined by gas chromatography using a HP-20M (Carbowax 20M) column (25 m x 0.2 mm x 0.2 p,m film thickness). The following conditions affected separation: initial temp 140 °C; initial time 2 min, rate 20 °C/min, final temp 220 °C, final time 20 min, FID detector temp 220 °C, and injector temp 220 °C. The above conditions were also effective for the identification of products from PhCN hydrogenation. The remaining PhCN, benzylamine, and dibenzylamine were separated; however, another possible product, PhCH2N=C(H)Ph, had the same retention time as benzylamine. The use of an OV-101 capillary column (25 m) allowed the imine PhCH2N=C(H)Ph to be distinguished from benzylamine using isothermal (140 °C) conditions. 32 Chapter 2 References: p 82 Chapter 2 2.4.2 NMR Characterization of Imines iff NMR spectroscopic data for the imines used as substrates in catalytic hydrogenation are given below. 2.4.2.1 PhN=C(H)Ph, W-benzylideneaniline ! H NMR (CDCI3, 20 °C): 8 7.2-7.5 (8H, m, Ph), 7.8-8.0 (2H, m, Ph), 8.46 (IH, s, CH). The data show only the presence of one isomer, presumably the anft'-configuration.5 2.4.2.2 PhCH2N=C(H)Ph, W-benzylidene benzylamine l H NMR (CDCI3, 20 °C): 8 4.83 (2H, s, CH2), 7.22-7.45 (8H, m, Ph), 7.74-7.82 (2H, m, PhC), 8.39 (IH, s, CH). The data show only the presence of one isomer, presumably the anri-configuration.5 2.4.2.3 PhCH2N=C(Me)Ph, iV-(l-niethylbenzyIidene)benzylamine l H NMR (CDCI3, 20 °C): 8 2.3-2.4 (3H total, both s, syn and anti CH3, respectively), 4.8 and 4.4 (2H total, both s, anti and syn CH2, respectively; 93% anti), 7.3-7.6 (8H, m, Ph), 7.9-8.0 (2H, m, Ph). ! H NMR ( C 6 D 6 , 20 °C): 8 1.74 (3H, s, anti C//3), 4.48 (2H, s, anti CH2), 7.1-7.33 (6H, m, Ph), 7.5-7.6 (2H, d, Ph), 7.85-7.95 (2H, m, Ph). 2.4.3 NMR Characterization of Reduction Products (Amines) *H NMR spectroscopic data for the amine products obtained from catalytic hydrogenation studies are given below. 2.4.3.1 PhNHCH 2Ph, W-phenylbenzylamine l H NMR (CDCI3, 20 °C): 8 1.8 (IH, br s, NH), 4.3 (2H, s, CH2), 6.6-6.8 (5H, m, NPh), 7.2-7.4 (5H, m, Ph). 33 Chapter 2 References: p 82 Chapter 2 2.4.3.2 NH(CH2Ph)2, dibenzylamine l H NMR (CDCI3, 20 °C): 8 1.8 (1H, br s, Nfl), 3.82 (4H, s, CH2), 1.2-1 A (10H, m, Ph). 2.4.3.3 NH(CH2Ph)(C*H(Me)Ph), AMl-methylbenzyl)-W-benzylamine l H NMR (CDCI3, 20 °C): 8 1.38 (3H, d, / = 6.6 Hz, C//3), 1.63 (1H, br s, NH), 3.60, 3.67 (2H, ABq, / = 13.2 Hz, CH2), 3.82 (1H, q, J = 6.6 Hz, CH), 7.21-7.39 (10H, m, Ph). l H NMR ( C 6 D 6 , 20 °C): 8 1.17 (3H, d, J = 6.6 Hz, C# 3 ) , 1.20 (1H, br s, NH), 3.43, 3.55 (2H, ABq, J = 13.2 Hz, CH2), 3.59 (1H, q, J = 6.5 Hz, CH), 6.88-7.51 (10H, m, Ph). 2.5 Synthesis and Characterization of Ruthenium Complexes The ruthenium was obtained on loan from Johnson Matthey Ltd. and Colonial Metals Inc. as RUCI3XH2O; depending upon the batch, the ruthenium content varied from 41.5 to 43.96%. All synthetic reactions, unless stated otherwise, were carried out in deoxygenated solvents under an atmosphere of argon, employing Schlenk techniques,19 as many of the ruthenium complexes prepared in the course of this work were susceptible to oxidation on exposure to air, especially in solution. 2.5.1 Ruthenium Precursors 2.5.1.1 Preparation of trichloro(A/,A/-dimethylacetamide)bis-(triphenylphosphine)ruthenium(III) A^A'-dimethylacetamide solvate, RuCl3(PPh3)2(DMA)DMAsolvate ( l ) 2 0 2 4 The title Ru(III) complex was synthesized by stirring a solution of RUCI3XH2O (2.0 g, 8.7 mmol) in D M A (30 mL) with two equivalents of PPI13 (4.58 g, 17.5 mmol) for indicates chiral centre 34 Chapter 2 References: p 82 Chapter 2 24 h at room temperature. If the reaction was performed in MeOH instead of D M A , as done originally,20 the product is RuCl3(PPh3)2(MeOH) where the sixth ligand is MeOH instead of D M A . The green solid was collected on a sintered glass filter by vacuum filtration, washed with a small amount of D M A (< 5 mL) and hexanes (2x5 mL), and vacuum dried. Yield: 5.5 g (73%). Calculated for C44H48N2CI3O2P2RU: C , 58.32; H , 5.34; N, 3.09; Cl , 11.74%. Found: C, 58.13; H, 5.21; N, 3.00; Cl , 11.73%. IR (Nujol, Csl plates, cm - 1): V(c=0) at 1634 (m, uncoordinated DMA); V(c=0) at 1598 (m, coordinated DMA). The physical and spectroscopic data for this complex agree with those 91 90 reported. The yield of this preparation could be improved (by 5-10%) by performing a second synthesis using the filtrate saved from the first reaction. The Ru(IU) product is somewhat soluble in D M A , and ideally the solution should be concentrated prior to filtration in order to improve the yield of the product. However, the high boiling point of D M A (165 °C) makes this difficult. RuCl3(PPh3)2(DMA)0.5 H 2 0 The title complex 1 was inadvertently prepared without a D M A solvate in this work by washing the green product RuCl3(PPh3)2(DMA)DMA solvate with EtOH (2 x 10 mL). The solid was light brown in colour. Yield: 5.1 g (72%, starting with the same amount of materials as shown above). Calculated for RuCl3(PPh3)2(DMA)0.5 H2O, C40H40NCI3O2P2RU: C, 58.01; H, 4.87; N, 1.69%. Found: C, 57.92; H, 4.86; N, 1.67%. IR (Nujol, Csl plates, cm"1): V(c=o) at 1601 (m, coordinated DMA). The IR spectrum showed the presence of H2O, but this was not conclusive as the IR spectra of other materials not requiring H2O solvates (based on elemental analysis) also show bands indicating the presence of H2O. 35 Chapter 2 References: p 82 Chapter 2 2.5.1.2 Preparation of trichloro(A^A^-dimethylacetamide)bis(tri-p-toIylphosphine)ruthenium(III) N,jV-dimethylacetamide solvate, RuCl3(P(>-tolyl)3)2(DMA)DMAsolvate (2) 2 1' 2 2 T h i s Ru(III ) c o m p l e x was prepared i n the same manner as its PPI13 analogue, except that two equivalents o f P(/?-tolyl)3 (5.3 g , 17.4 m m o l ) were used. Y i e l d o f the green s o l i d : 5.8 g (67%). C a l c u l a t e d for C 5 o H 6 0 N 2 C l 3 0 2 P 2 R u : C , 60.64; H , 6.11; N , 2.83; C l , 10.74%. F o u n d : C , 60.32; H , 6.11; N , 2.80; C l , 10.79%. I R (Nu jo l , C s l plates, c m - 1 ) : V(c=0) a t 1646 (m, uncoordinated D M A ) ; V(c=0) a t 1600 (m, coordinated D M A ) . T h e p h y s i c a l and spec t roscop ic data for this c o m p l e x agree w i t h those r e p o r t e d . 2 1 ' 2 2 2.5.1.3 Preparation of tribromo(methanol)bis(triphenylphosphine)-ruthenium(ffl), RuBr3(PPh3)2(MeOH) (3)2 0'2 3 A n attempt to prepare the ti t le c o m p l e x made u s ing the m e t h o d g i v e n by 20 Stephenson and W i l k i n s o n . A solut ion o f RUCI3XH2O (0.52 g , 2.3 m m o l ) and L i B r (3.4 g, 39 m m o l ; ~ 6 equiv / C l ) i n methanol (100 m L ) was stirred at r o o m temperature for 24 h . T r ipheny lphosph ine (1.1 g, 4.4 m m o l ; 2 equ iv / R u ) was then added to the s o l u t i o n and s t i r r ing con t inued . D u r i n g the next t w o days , a r e d d i s h - b r o w n s o l i d precipitated. The s o l i d was col lected by vacuum fi l t rat ion, washed w i t h methanol (3x10 m L ) and hexanes (6 x 10 m L ) , and dr ied under vacuum. Y i e l d : 1.3 g (64%). C a l c u l a t e d for C 3 7 H 3 4 B r 3 O P 2 R u : C , 49.52; H , 3.82; B r , 26.71%. F o u n d : C , 57.57; H , 4.16; B r , 20.49%. Repeated attempts to prepare this c o m p l e x resulted i n s i m i l a r m i c r o a n a l y t i c a l data. The U V - v i s spectroscopic and phys ica l data (m.p.) d i d not agree w i t h the literature values. ' These data are discussed i n Chapter 3, Sect ion 3.3.1. T h e synthesis o f the bromo-Ru(III ) complex , R u B r 3 ( P P h 3 ) 2 ( D M A ) D M A solvate also proved diff icul t . These diff icult ies are addressed i n Sect ion 3.3.1. 36 Chapter 2 References: p 82 Chapter 2 2.5.1.4 Preparation of chlorohydridotris(triphenylphosphine)ruthenium(II) N,N-dimethylacetamide solvate, Ru(H)Cl(PPh3) 3DMA solvate ( 4 ) 2 3 2 5 2 8 N, N-Dimethylacetamide (20 mL) was pipetted into a Schlenk tube containing RuCl2(PPh3)3 (1.00 g, 1.04 mmol). The resulting brown solution was immediately degassed and placed under an atmosphere of H 2 . After 15 minutes, the solution began turning a bright reddish-purple colour. The solution was stirred for another 18 h at room temperature. The red-violet solid that precipitated was collected on a Schlenk filter, washed with D M A (5 mL) and hexanes ( 2 x 5 mL), and finally dried under vacuum. Yield: 0.82 g (78%). Calculated for C 5 8 H 5 5 N C I O P 3 R U : C, 68.87; H , 5.48; N, 1.38%. Found: C, 68.70; H, 5.31; N, 1.50%. The physical and spectroscopic data for this complex agree with those reported in the literature. 2 3 , 2 5" 2 7 2.5.1.5 Preparation of l,5-cyclooctadieneruthenium(II) chloride polymer, [RuCl2(COD)]x (5)2 9'3 0 Ruthenium trichloride ( R U C I 3 X H 2 O ; 1.03 g, 4.23 mmol based on Ru content) was dissolved in degassed ethanol (40 mL). The clear, dark-orange solution was stirred with 1,5-cyclooctadiene (5.0 mL) for five days at room temperature. A brown solid precipitated from the solution, and was collected on a sintered glass filter, washed with ethanol (3 x 10 mL), and dried under vacuum. Yield: 0.87 g (74%). Calculated for [ C 8 H i 2 C i 2 R u ] x : C, 34.30; H, 4.32%. Found: C, 34.55; H, 4.48%. The physical data for this polymer agree with those reported in the literature;25 however, the yield was significandy better than the reported 30-40%. A new preparation that reports improved yields (99%) has been published recently. This new preparation was followed as described below. Ruthenium trichloride ( R U C I 3 X H 2 O ; 2.0 g, 8.3 mmol based on Ru content) was dissolved in 95% ethanol (80 mL), and 1,5-cyclooctadiene (7.5 mL, 61 mmol) was added to the resulting solution. This mixture was heated at reflux for 3 days, at which point very little colour was left in 37 Chapter 2 References: p 82 Chapter 2 solution, the brown product having precipitated. The brown solid was collected by vacuum filtration, washed with ethanol (2 x 30 mL), and dried under vacuum. Yield: 2.0 g (86%). 2.5.1.6 Preparation of Ru(COD)(ri3-allyl)2 (6) 3 1 ' 3 2 Allylmagnesium bromide (6.5 mL of 1.0 M in diethyl ether, 6.5 mmol) was added slowly to [RuCl2(COD)]x (0.52 g, 1.8 mmol) in diethyl ether (30 mL). The brown suspension of the Ru starting material immediately became a pale yellow solution upon addition of the Grignard reagent. The solution was stirred at room temperature for 24 h, hydrolyzed with H2O (30 mL), and the ether layer separated from the water layer. The ether washings (3 x 40 mL) were combined, dried over anhydrous CaCl2, and pumped to dryness to give a dark gum, which was taken up in n-pentane (5 mL) and passed through a neutral alumina column (Activity III, 15 x 2.5 cm). n-Pentane (50 mL) was used to elute the product as a faintly yellow solution. The solvent was removed at the pump to give an off-white, waxy product. Yield: 0.30 g (56%). ! H NMR ( C 6 D 6 , 20 °C): 5 -0.09 (2H, d, J = 10 Hz, anti H of allyl), 1.38 (2H, m, CH of COD), 1.72 (2H, d, J = 12 Hz, anti H of allyl), 1.6-2.0 (4H, m, CH2 of COD), 2.64 (2H, d, / = 12 Hz, anti H of allyl), 2.8-3.0 (4H, m, CH2 of COD), 3.1-3.4 (2H, m, central H of allyl), 3.71 (2H, dd, J = 2 and 8 Hz, syn H of allyl), 4.03 (2H, m, CH of COD). The physical and spectroscopic data for this complex agree with those reported in the literature.3 1 , 3 2 2.5.1.7 Preparation of Ru(COD)(Ti 3-Me-allyl) 2 (7) 3 0 ' 3 2 This material was prepared by Mr. Z. Liu of this department with minor modifications to a procedure outlined by Genet et a l . 3 0 The Grignard reagent, 2-methylallylmagnesium chloride, was found to be fairly insoluble in diethyl ether, and therefore THF was used as the solvent. The Grignard reagent (2 M , 6 mL, 12 mmol; prepared from Mg and 3-chloro-2-methylpropene in THF) was added to a suspension of 10 Chapter 2 References: p 82 Chapter 2 [RuCl2(C0D)] x (0.28 g, 1.0 mmol) in Et20 (10 mL) / T H F (15 mL), and the mixture stirred at room temperature for 10 min. The excess Grignard reagent was precipitated from solution by adding more diethyl ether, and the suspension was filtered through Celite. The filtrate was hydrolyzed in ice-water and the mixture extracted with diethyl ether (2 x 20 mL). The organic layer was dried over MgS04, concentrated, filtered through a short column of neutral alumina ( 5 x 5 cm), and evaporated to dryness. Reprecipitation from a mixture of methanol and petroleum ether gave pure material. Yield: 0.27 g (80%). Calculated for Ru(COD)(n3-Me-alryl)2, C i 6 H 2 6Ru: C, 60.16; H , 8.20%. Found: C, 59.93; H, 8.31%. m.p. = 80-85 °C; lit. m.p. = 80-85 °C. ! H NMR ( C 6 D 6 , 20 °C): 8 0.20 (2H, s, anti H of Me-allyl), 1.08-1.26 (2H, m, CH of COD), 1.45-1.70 (4H, m, CH2 of C O D ) , 1.56 (2H, s, syn H of Me-allyl), 1.70 (6H, s, C#3 of Me-allyl), 2.64-3.00 (4H, CH2 of C O D ) , 2.88 (2H, s, anti H of Me-allyl), 3.52 (2H, d, J = 2 Hz, syn H of Me-allyl), 3.98 (2H, dd, J = 5, 9 Hz, CH- of C O D ) . ^ C p H } NMR ( C 6 D 6 , 20 °C): 8 24.74 ( C H 3 of Me-allyl), 26.26 and 38.34 (CH 3C(CH 2)2), 51.22 and 51.68 ( C H 2 of C O D ) , 70.63 and 88.22 (CH- of C O D ) , 111.49 (CH 3 -C (CH 2 ) 2 ) . The physical and spectroscopic data for this complex agree with those reported in the literature.30'32 2.5.2 Preparation of RuX 2(PAr 3) 3; X = Cl, Br; Ar = Ph, /7-tolyl 2.5.2.1 X = C1, Ar = Ph; Preparation of dichlorotris(triphenylphosphine)-ruthenium(II), RuCl2(PPh3)3 (8) 2 0' 3 3' 3 4 The Ru(II) material was prepared by refluxing a methanol solution (300 mL) of RuCl 3 3 H 2 0 (1.95 g, 8.23 mmol) and PPh 3 (12.6 g, 4.82 mmol) under Ar for 3 h 2 0 ' 3 3 ' 3 4 The dark-brown solid was collected by vacuum filtration, washed with methanol (7 x 20 mL) and diethyl ether (3 x 20 mL) to remove the remaining PPh 3 , and dried under 39 Chapter 2 References: p 82 Chapter 2 vacuum. Y i e l d : 7.3 g (93%). Ca lcu la ted for C54H45CI2P3RU: C, 67.64; H , 4.73%. F o u n d : C, 67.66; H , 4.73%. 3 1 p { l H } N M R ( C D C I 3 , -60 °C): 5 A = 76.1 ( I P , 2 7 A X = unresolved) , 5x = 24.7 (2P, 2 J A X = unresolved) . A l s o , observed are 8 = -6.6 (free PPh3) and 8 A = 60.1, 8 B = 52.4, 2 7 A B = 41.1 Hz (Ru2Cl4(PPh3)4)-T h e phys ica l and spectroscopic data for this complex agree w i t h those reported i n the l i t e r a t u r e . 2 0 ' 3 3 ' 3 4 2.5.2.2 X = Cl, Ar = j?-tolyl; Preparation of dichlorotris(tri-/»-tolyl-phosphine)ruthenium(n), RuCl2(P(p-tolyl)3)3 (9)35 3 7 T h e t i t l e c o m p o u n d was prepared a c c o r d i n g to the m e t h o d d e s c r i b e d 35 37 previous ly , w i t h some m i n o r modi f ica t ions . R u t h e n i u m t r i ch lo r ide ( R U C I 3 X H 2 O ; 1.03 g, 4.33 m m o l ) was ref luxed i n methanol (200 m L ) for fifteen minutes . T h e dark-orange so lu t ion was coo led , excess t r i -p- to ly lphosphine (5.55 g , 18.2 m m o l ) added, and re f l ux ing cont inued for another three hours. A dark-purple s o l i d precipi ta ted f rom the so lu t ion , and after being coo led the solut ion was col lec ted on a sintered glass f i l ter . T h e s o l i d was washed thoroughly w i t h methanol (8 x 10 m L ) and d ie thyl ether (5 x 10 m L ) to remove any excess phosphine, and dried under vacuum. Y i e l d : 3.97 g (87%). Ca l cu l a t ed for C 6 3 H 6 3 C i 2 P 3 R u : C, 69.74; H , 5.85%. Found : C, 69.67; H , 5.80%. 3 1 p { l H } N M R ( C 6 D 6 , 20 °C): 8 = 42.8 (br s); ( C 7 D 8 , -65 °C) : 8 A = 77.6 ( I P , 2JAX = unresolved), 83 = 28.4 (2P, 2 7 A X = unresolved). A l s o , observed are 8= -9.6 (free P (p- to ly l ) 3 ) and 8 A = 60.6, 8 B = 53.7, 2 7 A B = 42.7 H z (Ru2CU(P(p-tolyl) 3 ) 4 ) . T h e phys i ca l and spectroscopic data for this complex agree w i t h those reported i n the literature. 40 Chapter 2 References: p 82 Chapter 2 2.5.2.3 X = Br, Ar = Ph; Preparation of dibromotris(triphenylphosphine)-ruthenium(II), RuBr2(PPh3)3 (10)2 0'2 3'3 5 T h i s ruthenium(II) m o n o m e r was synthesized i n m u c h the same manner as the ch lo ro analogue (Sect ion 2.5.2.1), except that L i B r (10.7 g, 123 m m o l , 30 equ iv / R u or 10 equ iv / Cl) was re f luxed w i t h R U C I 3 X H 2 O (1.0 g , 4.1 m m o l ) i n M e O H (250 m L ) before the addi t ion o f the P P h 3 . T h e orange solut ion was ref luxed for 30 m i n , c o o l e d to r o o m temperature, and PPh3 (6.0 g , 23 m m o l ) was added under a f l o w o f argon. T h e reddish-purple so lu t ion was ref luxed for 3 h , then coo led , and the b r o w n product that precipitated was col lec ted by vacuum fi l trat ion. Excess t r iphenylphosphine was r emoved by wash ing w i t h M e O H (6 x 30 m L ) and die thyl ether (3 x 10 m L ) . T h e b r o w n s o l i d was dr ied under v a c u u m . Y i e l d : 4.1 g (95%). C a l c u l a t e d for C 5 4 H 4 5 B r 2 P 3 R u : C , 61.90; H, 4.33; B r , 15.25%. F o u n d : C, 61.79; H, 4.26; B r , 15.11%. 3 1 P{!H} N M R ( C 7 D 8 , -79 °C): 6 A = 78.2 ( I P , 2 j A X = unresolved) , 5 X = 24.1 (2P, 2JAX = unresolved) . A l s o , observed are 8 = -6.6 (free PPI13) and 8 A = 59.0, 8B = 51.0, 2JAB = unresolved (Ru2Br4(PPh3)4). T h e phys i ca l and spectroscopic data for this complex agree w i t h those reported i n the l i t e r a t u r e . 2 0 ' 2 3 , 3 5 Dark-orange crystals o f 10 were i sola ted f rom a filtrate i n the preparat ion o f R u B r 2 ( D P P B ) ( P P h 3 ) (Sect ion 2.5.3.3). T h e so lu t ion consis ted o f C H 2 B r 2 / e thano l / hexanes (~ 1:12:4), plus a large amount o f PPI13 f rom the substitution o f R u B r 2 ( P P h 3 ) 3 by D P P B . T h e O R T E P plot, as w e l l as selected bond lengths and angles o f this c o m p l e x , are shown i n Sect ion 3.3.3.1, w h i l e the fu l l experimental parameters and details are g iven i n A p p e n d i x I. 41 Chapter 2 References: p 82 Chapter 2 2.5.3 Mixed-Phosphine Complexes, RuX2(P-P)(P(Ar)3) 2.5.3.1 X = Cl, Ar = Ph, P-P = DPPB; Preparation of dichloro-(bis(diphenylphosphino)butane)(triphenylphosphine)ruthenium(II), RuCl2(DPPB)(PPh3) ( l l ) 2 2 3 8 3 9 The title complex was prepared by addition of a CH2CI2 (20 mL) solution of DPPB (0.89 g, 2.09 mmol) to a C H 2 C 1 2 (15 mL) solution of RuCl 2(PPh 3) 3 (2.0 g, 2.09 mmol) at room temperature. The dark-orange solution of the starting ruthenium complex turned green immediately upon addition of the phosphine. The reaction mixture was stirred for 2 h, and then concentrated to ~ 10 mL by removal of the solvent under dynamic vacuum. Ethanol (80 mL) was added to precipitate the green product, which was collected by vacuum filtration, washed with ethanol (3 x 20 mL) and hexanes (3 x 20 mL) to remove PPh 3 , and dried under vacuum. Small amounts of the bridged-phosphine complex [RuCl2(DPPB)i 5]2 have sometimes been reported to be present in the 00 on product. ' In any case, this dinuclear complex can easily be removed by filtration prior to the concentration step, as it is quite insoluble in CH2CI2 (discussed in Section 3.3.3). Yield: 1.8 g (97%). Calculated for RuCl2(DPPB)(PPh3), C4 6 H4 3 Cl2P 3 Ru: C, 64.19; H , 5.04%. Found: C, 64.34; H, 5.16%. 3 1P{ 1H} NMR: see Chapter 3, Table 3.6. The physical and spectroscopic data for this complex agree with those reported in the literature. 2 2' 3 8' 3 9 Green crystals of 11 were isolated from a C7D8 solution containing approximately 14 equivalents of added PPh 3 . The crystals grew over several months by slow evaporation of C7D8 in a N2 glove-box. The results of an X-ray crystallographic study are given in Chapter 3. The ORTEP plot, as well as selected bond lengths and angles of this complex, are shown in Section 3.3.3.2, while the full experimental parameters and details are given in Appendix II. 42 Chapter 2 References: p 82 Chapter 2 2.5.3.2 X = Cl, Ar = p-tolyl, P-P = DPPB; Preparation of dichloro-(bis(d^phenylphosphino)butane)(tri-/>-tolylphosphine)ruthenium(II), RuCl2(DPPB)(P(p-tolyl)3) (12) This preparation was performed in the same manner as for the PPI13 analogue (Section 2.5.3.1). RuCl2(P(p-toiyl)3)3 (1.0 g, 0.92 mmol) was dissolved in CH2CI2 (20 mL), then DPPB (0.39 g, 0.92 mmol) was added under a flow of Ar, and the reaction mixture was stirred at room temperature for 2 h. The initially orange solution changed to dark green upon addition of the phosphine. In this preparation, unlike the above preparation, some bridged-phosphine complex was present. Therefore, some insoluble green complex (i.e., [RuCi2(DPPB)i_5]2) was removed by vacuum filtration (0.08 g or about 10% of the ruthenium). The green filtrate was then reduced in volume to ~ 5 mL, and ethanol (40 mL) was added to precipitate the green product. The complex was isolated by vacuum filtration, washed with ethanol (2 x 10 mL) and hexanes (3 x 10 mL), and dried under vacuum. Yield: 0.83 g (76%). Calculated for RuCl2(DPPB)(P(/?-tolyl)3), C 4 9 H 4 9 C l 2 P 3 R u : C, 65.19; H, 5.47; Cl , 7.85%. Found: C, 64.91; H, 5.36; Cl , 7.65%. 3 1P{ !H} NMR: see Chapter 3, Table 3.6. l H NMR ( C 6 D 6 , 20 °C): 8 1.38 (4H, br m, P C H 2 C # 2 of DPPB), 2.02 (9H, s, C # 3 of p-tolyl), 2.92 (4H, br m, PCtf 2 of DPPB), 6.65-7.95 (32H, m, 20H of Ph of DPPB and 12H of PhofP(p-tolyl)3). 2.5.3.3 X = Br, Ar = Ph, P-P = DPPB; Preparation of dibromo-(bis(diphenylphosphino)butane)(triphenylphosphine)ruthenium(II), RuBr2(DPPB)(PPh3) (13) This bromo analogue was prepared in much the same manner as the chloro derivative, the only difference being that the reaction was performed in methylene bromide and on a smaller scale. RuBr2(PPh3)3 (0.52 g, 0.49 mmol) and DPPB (0.20 g, 0.48 mmol) were dissolved in CH2Br2 (10 mL) and the mixture was stirred for 2 h at room temperature. The originally deep-red solution changed to a yellow-orange colour 43 Chapter 2 References: p 82 Chapter 2 over the course of the reaction. The reaction mixture was reduced to ~ 5 mL in volume and ethanol (40 mL) was added to precipitate the product. An olive solid was collected by vacuum filtration, washed with ethanol (2 x 10 mL) and hexanes (2 x 10 mL), and finally dried under vacuum. Yield: 0.45 g (97%). Calculated for RuBr 2 (DPPB)(PPh 3 ) , C 4 6 H 4 3 B r 2 P 3 R u : C, 58.18; H, 4.56; Br, 16.83%. Found: C, 58.04; H, 4.64; Br, 16.76%. ^Pl^H} NMR: see Chapter 3, Table 3.6. 2.5.3.4 X = Cl, Ar = Ph, P-P = DCYPB; Preparation of dichloro-(bis(dicyclohexylphosphino)butane)(triphenylphosphine)ruthenium(II), RuCl2(DCYPB)(PPh3) (14) An attempt to prepare the title complex was made using the same method employed for the DPPB mixed-phosphine analogues 11-13. The starting complex RuCl2(PPh3)3 (0.26 g, 0.27 mmol) and DCYPB (0.12 g, 0.26 mmol) were dissolved in C H 2 C 1 2 (10 mL) to give a dark-green solution. The dark-green colour was thought to be due to the formation of the desired RuCl2(DCYPB)(PPh3) complex. However, attempts to isolate the material by adding ethanol (30 mL) after stirring the green solution for 2 h at room temperature resulted in an immediate colour change to orange-brown. Repeated attempts to isolate the green solid from a variety of solvent pairs were unsuccessful. A red solid was eventually precipitated by the addition of methanol (10 mL) to a C H 2 C 1 2 solution (5 mL) of the above mixture. The solid was collected by vacuum filtration, washed with methanol ( 3 x 2 mL), and dried under vacuum. Calculated for Ru 2 CU(DCYPB) 2 -CH 2 Cl 2 , C, 51.47; H, 8.03%. Found: C, 51.26; H, 8.23%. The red solid was quite insoluble in CDCI3, CD 2 C1 2 , and C^Ds, making 3 1 P{ 1 H} NMR spectroscopy impossible. A subsequent in situ experiment was performed on a C H 2 C 1 2 solution of a 1:1 mixture of RuCl2(PPh)3 and DCYPB. The low-temperature 3 1P{!H} NMR data of the resulting solution (see Chapter 3, Table 3.6) indicated the presence of the desired RuCl2(DCYPB)(PPh3). However, within 24 h, the NMR solution had become orange. In 44 Chapter 2 References: p 82 Chapter 2 fact, after several weeks, red crystals deposited from the solution. However, an attempt at an X-ray diffraction study proved unsuccessful as the crystals did not diffract. 2.5.3.5 X = Cl, Ar = Ph, P-P = (fl)-BINAP; Preparation of dichloro((/f)-2,2'-bis(diphenylphosphino)-l,l'-binaphthyl)(triphenylphosphine)-ruthenium(II), RuCl2((fl)-BINAP)(PPh3) (15) 2 2 , 3 9 , 4 0 The title complex was prepared by a method similar to the one developed in this laboratory, except on a larger scale 2 2 , 3 9 A C H 2 C 1 2 solution (35 mL) of RuCl 2(PPh 3) 3 (1.0 g, 1.05 mmol) and (/?)-BINAP (0.65 g, 1.05 mmol) was stirred at room temperature for 24 h. The resulting orange-red solution was concentrated at the pump to ~ 15 mL, and diethyl ether (60 mL) added to precipitate the product. The orange-brown solid was collected by vacuum filtration, washed with diethyl ether (3 x 10 mL) and hexanes (3 x 10 mL), and dried under vacuum. Yield: 0.99 g (89%). Calculated for C6 2H4 7Cl 2P3Ru: C, 70.46; H, 4.48%. Found: C, 69.95; H, 4.54%. 3 1P{!H} NMR: see Chapter 3, Table 3.6. The physical and spectroscopic data agree with those repor ted . 2 2 , 3 9 , 4 0 One notable exception is that the colour of the product isolated by Mezzetti et a l . 4 0 was dark green, as opposed to the orange-brown solid obtained by the above preparation. However, the dark-green product obtained by Mezzetti et al. was isolated from toluene / ethanol, as opposed to the solvents used above, and the same dark-green colour is seen for other five-coordinate Ru(II) complexes (i.e., RuCl2(DPPB)(PPh3) and RuCl 2 (DIOP)(PPh 3 )) 2 2 , 3 8 2.5.4 Preparation of [Ru2X5(PPh3)4]- or [(PPh3)2XRu(u-X)3RuX(PPh3)2]-Complexes; X = Cl or H 2.5.4.1 X = Cl; [(DMA)2H]+ [Ru2Cl5(PPh3)4]- or [(DMA)2H]+ [(PPh3)2ClRu(p> Cl)3RuCl(PPh3)2]- (16) The ionic, title complex was prepared by modification of a route reported 3 5 , 4 1 , 4 2 for the neutral dimer, [Ru2Cl4(PPh3)4]. This ionic species has been observed previously 45 Chapter 2 References: p 82 Chapter 2 in solution but never isolated. 2 4 ' 3 5 ' 4 2 As in the preparation of the neutral dimeric complex, RuCl3(PPh3)2DMADMA (0.19 g, 0.21 mmol) was stirred under an atmosphere of H 2 in D M A (10 mL) for 5 days. The green suspension/solution of the Ru(III) starting complex became a deep-red solution after ~ 30 min of stirring at room temperature under H 2 . In the original preparation of the neutral complex, the solution was reduced in volume to ~ 5 mL, and MeOH (75 mL) was added to "break up" the ionic species that exists in solution. The neutral species was then isolated as an orange solid. In the case of this preparation, where the ionic Ru complex was the desired product, the solution was reduced in volume to ~ 5 mL, and diethyl ether (20 mL) was added to precipitate an orange solid. Precipitation of the product was slow. Therefore, after the addition of diethyl ether, the solution had to be left stirring overnight under H 2 for any solid to appear. The orange product was collected by vacuum filtration, washed with diethyl ether (3x5 mL), and dried under vacuum. Yield: 0.13 g (78%). Calculated for [(DMA)2H]+ [Ru2Cl5(PPh3)4]-, C 8 0 H 7 9 N 2 C I 5 O 2 P 4 R U 2 : C, 59.91; H , 4.96; N, 1.75; Cl , 11.05%. Found: C, 59.64; H, 5.00; N, 1.70; Cl , 10.90%. 31p{lH} NMR (C 7 D 8 ): 5 44.6, s from -85 to 20 °C. *H NMR ( C 7 D 8 , -40 °C): 8 2.02 (6H, br s, Ctf 3 of DMA), 2.25 (6H, br s CH3 of DMA), 2.68 (6H, br s, C / / 3 of DMA), 6.8-7.9 (60H, m, Ph of PPh 3), 8.0 (1H, br s , (DMA) 2//+). 2.5.4.2 X = Cl and H; Attempted Preparation of [PSH]+ [Ru2H 3Cl2(PPh 3)4]- or [PSH]+[(PPh3)2(H)Ru(p.H)(p-Cl)2Ru(H)(PPh3)2]-Isolation of [(n2.H2)(PPh3)2Ru(p-H)(p-Cl)2Ru(H)(PPh3)2] (17) An excess of Proton Sponge (0.20 g, 0.93 mmol) and [(DMA)2H ]+ [Ru2Cl5(PPh3)4]~ (0.38 g, 0.24 mmol) were dissolved in C6H6 (5 mL) to give a deep red-brown solution. This solution was placed under an atmosphere of H2 and stirred at room temperature for two days. The reaction mixture slowly became deep red in colour. The solution was washed through a layer of Celite with benzene ( 4 x 5 mL) to remove 46 Chapter 2 References: p 82 Chapter 2 PSH+C1 -, reduced in volume to ~ 5 mL, and diethyl ether (30 mL) was added to precipitate a red solid. The product was collected by vacuum filtration, washed with diethyl ether (3x5 mL), and dried under vacuum. Yield: 0.27 g (84%). Calculated for [PSH]+ [(PPh3)2(H)Ru(p-H)(p-Cl)2Ru(H)(PPh3)2]-, C86H82N2CI2P4RU: C , 67.05; H , 5.36; N, 1.82; Cl , 4.60%. Found: C, 65.80; H , 5.05; N, 0.00%. Calculated for [(T\2-H2)(PPh3)2Ru(p-H)(p-Cl)2Ru(H)(PPh3)2], C72H64CI2P4RU2: C , 65.21; H , 4.86; N, 0.00%. The product isolated is not the desired ionic complex, but rather the previously prepared molecular hydrogen complex. 2 4 ' 3 5 ' 4 1 ' 4 3 Although the above elemental analysis is approximately 0.6% high in carbon, it is the best that has been reported. 4 1' 4 3 The red product is reasonably difficult to handle because it turns brown on exposure to air. This may explain the elemental analysis being somewhat lower in carbon and hydrogen than the expected values. 31p{lH} NMR ( C 6 D 6 , 20 °C): 8 = 71.1 (br s), 45.9 (br s). ! H NMR ( C 6 D 6 , 20 °C): 8 -12.8 (4H, br s, r | 2 -# 2 , \i-H, terminal-//; all exchanging), 6.6-7.8 (60H, m, Ph of PPh3). 2.5.4.3 X = C l and H ; [(DMA) 2H]+ [Ru2H 3Cl2(PPh3) 4]- or [(DMA)2H]+ [(PPh3)2(H)Ru(p-H)(p-Cl)2Ru(H)(PPh3)2]- (18) A deep-red solution containing both a pink solid and a large dark-red crystal (see below) was left by a previous worker, Dr. A. Joshi, and was worked up in the following manner. The deep-red solution and pink solid were removed from the crystal by transferring them to a sintered glass filter via a cannula under a flow of Ar. The pink solid was washed with diethyl ether (3x5 mL) and dried under vacuum. Yield: 0.25 g. The pink solid proved to be [DMAH]+[Ru2Ci5(DPPB)2]-. The microanalytical and spectroscopic data for this complex are given in Section 2.5.9.3. 47 Chapter 2 References: p 82 Chapter 2 The starting materials used by Joshi for this reaction were thought to be RuCl3(PPh3)2(DMA)DMA solvate and one equiv of DPPB in D M A . The presence of D M A as the solvent was confirmed by *H NMR. Considering the nature of both the products and Ru(III) starting complex, it seems likely that the reaction was performed under an atmosphere of H2. The large, red crystal was submitted to Dr. S. Rettig of this department for X-ray diffraction analysis. A small crystal, cleaved from the large isolated crystal, was used for the crystallographic study. The red crystal proved to be [(DMA)2H]+[(PPh3)2(H)Ru(p-H)(p-Cl)2Ru(H)(PPh3)2]-. The ORTEP plot, as well as selected bond lengths and angles of this complex, are shown in Section 4.7.1, while the full experimental parameters and details are given in Appendix VI. Calculated for [(DMA)2H]+[(PPh3)2(H)Ru(p-H)(u-Cl) 2Ru(H)(PPh 3) 2]-, C80H82N2CI2O2P4RU2: C, 64.04; H, 5.51; N, 1.87; C l , 4.73%. Found: C, 64.08; H, 5.44; N, 1.79; Cl , 4.50%. IR (KBr, cm-1): v ( C = 0) at 1647; v 2114,1975, 1902, 1825 (all broad and weak). 31p{lH} NMR ( C 7 D 8 , 20 °C): 8 = 71.3 (br s), 46.3 (br s); ( C 7 D 8 , -89 °C): 8 A , B , C , D = 79.6, 63.8, 62.5, 30.2 plus 8 A = 71.9, 8 B = 68.7, 2 7 A B = 44.2 Hz. The A B C D spin system corresponds to that observed for [(r|2-H2)(PPh3)2Ru(u.-H)(p-Cl)2Ru(H)(PPh 3 ) 2 ] , 2 4 ' 3 5 ' 4 1 ' 4 3 while the AB pattern, which accounts for < 15% of the integration, must correspond to the title ionic complex. At 20 °C, the AB pattern is observed at 8 A = 56.8, 8B = 54.7, 2 / A B ~ 30 Hz. ! H NMR ( C 7 D 8 , 20 °C): 8 -12.8 (4H, br s, exchanging hydrides), 1.8 (6H, s, C//3 of DMA), 2.3 (6H, s, CH3 of DMA), 2.7 (6H, s, C//3 of DMA), 6.6-8.1 (60H, m, Ph of PPh3). ! H NMR ( C 7 D 8 , -89 °C): 8 -8.7 (1H, br d, 2Jm = 66.9 Hz,p-//), -12.6 (1H, br s, r\2-H2), -17.3 (1H, br s, terminal-tf) plus -14.9 (t, 2Jm = 31.1 Hz), -17.7 (br s). The first three resonances are those of [(Ti2-H2)(PPh3)2Ru(p-H)(p-Cl)2Ru(H)(PPh3)2], while the 48 Chapter 2 References: p 82 Chapter 2 r e m a i n i n g t w o resonances m u s t b e l o n g to [ ( D M A ) 2 H ] + [ ( P P h 3 ) 2 ( H ) R u ( ( i - H ) ( ( i -C l ) 2 R u ( H ) ( P P h 3 ) 2 ] - . A t t empt s to measure the U V - v i s spectrum of 18 i n D M A or C6H-6 were not successful , as the dark-red crystals d i s so lved to g ive green-black solu t ions , i nd i ca t ing ox ida t ion o f the complex . C h a u et a l . have also observed these green-black solut ions for R u ( I I ) spec ies i n the presence o f 0 2 4 ' 4 4 C o n d u c t i v i t y measurements were a lso imposs ib le , as no anaerobic c e l l was available. T h e a b o v e i o n i c c o m p l e x h a d b e e n p r e v i o u s l y p r e p a r e d f r o m R u C l 3 ( P P h 3 > 2 ( D M A ) D M A solvate i n D M A solvent i n this laboratory; the product was incor rec t ly formulated as the neutral Ru(III) c lass ica l hydr ide species, [(PPh3)2(H)Ru(p> H ) ( u - C l ) 2 R u ( H ) 2 ( P P h 3 ) 2 ] - 2 D M A s o l v a t e . 2 4 ' 3 5 W h e n the complex is prepared i n a solvent other than D M A (i.e., C7H.8) i n the presence o f Proton Sponge, the T | 2 -H.2 species 17 is i s o l a t e d . 4 3 ' 4 5 Th i s complex w i l l be described and discussed i n detai l i n Chapter 4. 2.5.5 Synthesis of Diphosphine-Bridged Dinuclear Ruthenium(II) Complexes, [(P-P)X2Ru(pi2-(P-P))RuX2(P-P)] or [RuX 2(P-P)i. 5] 2; X = Cl, Br; P-P = DPPB, DCYPB Severa l d iphosphine-br idged , d inuclear ru thenium c o m p l e x e s have p r e v i o u s l y b e e n s y n t h e s i z e d : [ R u C l 2 ( D P P B ) i . 5 ] 2 , 2 2 ' 4 6 [ R u C l 2 ( D I O P ) i . 5 ] 2 2 3 , 4 7 [ R u C l 2 ( D P P N ) i . 5 ] 2 2 2 and [ R u C l 2 ( D P P H ) L 5 ] 2 . 2 2 In a t yp ica l procedure, R u C l 2 ( P P h 3 ) 3 (0.10 g, 0.10 m m o l ) was stirred w i t h two equivalents o f a diphosphine i n C 6 H 6 (25 m L ) for 1 h at r o o m temperature under argon. T h e resul t ing dark-green solut ion was reduced i n v o l u m e to ~ 5 m L , and hexanes (20 m L ) were added to precipitate a green s o l i d . T h e green product was col lec ted by f i l t ra t ion, washed w i t h hexanes (4 x 10 m L ) , and dr ied under v a c u u m . A l l o f these diphosphine-br idged complexes are essent ia l ly inso lub le i n mos t non-a romat ic solvents , and o n l y spa r ing ly so lub le i n a romat ic so lven t s . T h e in so lub i l i t y o f 19, 20, and 21 (see be low) prevented the measurement o f either the lH or 49 Chapter 2 References: p 82 Chapter 2 3 1 p { l H } N M R spectra. These br idged species are also occas iona l ly isola ted as a side-product i n the preparation o f R u X 2 ( P - P ) ( P A r 3 ) species (Sect ion 2.5.3). 2.5.5.1 X = Cl, P-P = DPPB; [(DPPB)Cl2Ru(p2(DPPB))RuCl2(DPPB)] or [RuCl 2(DPPB)L 5] 2 (19)22'46 T h e above procedure was fo l l owed , except o n twice the scale. A CfjH-6 solu t ion o f RuCl2(PPh 3) 3 (0.20 g , 0.21 m m o l ) and D P P B (0.18 g, 0.42 m m o l ) was used. Y i e l d o f the green s o l i d : 0.15 g (89%). C a l c u l a t e d for [RuCl 2 (DPPB)i . 5 ] 2 , C84H84CI4P6RU2: C , 62.15; H , 5.22%. F o u n d : C, 61.86; H , 5.38%. U V - v i s ( C 6 H 6 ) : V a x (nm), E m a x ( M " 1 c m " 1 ) = 340, 4520; 450, 3950; 684, 1320. T h e phys ica l and spectroscopic data for this complex agree w i t h those reported i n the l i t e r a t u r e . 2 2 ' 4 6 2.5.5.2 X = Br, P-P = DPPB; [(DPPB)Br2Ru(p2-(DPPB))RuBr2(DPPB)] or [RuBr2(DPPB)i.5]2 (20) T h e general procedure ou t l ined for the ch lo ro -ana logue was f o l l o w e d u s ing R u B r 2 ( P P h 3 ) 3 (0.10 g, 0.095 m m o l ) and DPPB (0.081 g, 0.19 m m o l ) . Y i e l d o f the mustard s o l i d : 0.053 g (61%). Ca lcu la t ed for [RuBr2 (DPPB ) i .5] 2 , C 8 4 H 8 4 B r 4 P 6 R u 2 : C, 56.01; H , 4.70; B r , 17.74%. Found : C, 56.27; H , 4.58; B r , 17.52%. U V - v i s (C6H6): Xmax (nm), e m a x (MA c m " 1 ) = 364, 2580; 466, 3620; 710, 1170. 2.5.5.3 X = Cl, P-P = DCYPB; [(DCYPB)Cl2Ru(p2-(DCYPB))RuCl2(DCYPB)] or [RuCl 2(DCYPB)i. 5] 2 (21) The general procedure out l ined i n Sect ion 2.5.5 was f o l l o w e d us ing RuCl2(PPh 3) 3 (0.18 g , 0.19 m m o l ) and D C Y P B (0.18 g, 0.40 m m o l ) . Y i e l d o f the green s o l i d : 0.13 g (77%). C a l c u l a t e d for [ R u C l 2 ( D C Y P B ) i. 5]2, C 8 4 H i 5 6 C l 4 P 6 R u 2 : C , 59.49; H , 9.27; C l , 8.36%. F o u n d : C, 59.40; H , 9.33; Cl , 8.08%. U V - v i s (C6H 6): V a x (nm), emax ( M " 1 cm-1) = 340, 5080; 384, 3870 (sh); 682, 1940. 50 Chapter 2 References: p 82 Chapter 2 2.5.6 Dichloro-tri-p>chloro-bis(bidentate phosphine)diruthenium(n, HI) Complexes, [(P-P)ClRu(u-Cl)3RuCl(P-P)] or R u 2 C l 5 ( P - P ) 2 2 1 , 2 2 ' 3 9 , 4 8 A hexanes suspension (160 m L ) o f R u C l 3 ( P A r 3 ) 2 ( D M A ) D M A solvate (1.5 g), where A r = p h e n y l or p - t o l y l , and one equivalent o f the appropriate d iphosphine was ref luxed under a s l o w f l o w o f argon for 24 h . T h e red-brown so l ids that resulted were co l l ec t ed b y v a c u u m f i l t ra t ion and washed thoroughly w i t h hexanes (8 x 20 m L ) to remove any PPI13. T h e crude products were then reprecipitated by wash ing through the frit w i t h CH2CI2 (25 m L ) , concentrating the CH2CI2 so lu t ion to ~ 5 m L , and then adding d ie thy l ether (40 m L ) . Y i e l d s o f the R u 2 n ' i n C l 5 ( P - P ) 2 complexes were typ i ca l ly 70-85%. 2.5.6.1 Preparation of Ru 2Cl 5(DPPB) 2 (22)21 2 2 3 9 4 8 T h e above general procedure was f o l l o w e d w i t h R u C l 3 ( P P h 3 ) 2 ( D M A ) D M A solvate (1.7 g, 1.9 m m o l ) and D P P B (0.82 g, 1.9 m m o l ) . Y i e l d o f the b r i ck - r ed s o l i d : 0.99 g (85%). Ca lcu la t ed for R u 2 C l 5 ( D P P B ) 2 , C 5 6 H 5 6 C l 5 P 4 R u 2 : C , 54.58; H , 4.58; Cl , 14.38%. F o u n d : C , 54.60; H , 4.52; C l , 14.50%. T h e Evans method (CDCI3) gives %moi = 1.82 x 10 - 3 cgsu; Heff = 2.05 U . B / R u 2 , a 2% f -butanol so lu t ion i n CDCI3 be ing used for this measurement . T h i s m e t h o d i s desc r ibed i n the l i t e ra tu re ; 6 however , one shou ld note that the equa t ion o r i g i n a l l y d e s c r i b e d b y E v a n s i s fo r a c o n v e n t i o n a l magnet w h e r e the m a g n e t i c f i e l d i s perpendicular to the long axis o f the N M R tube. T h e magnets used i n the spectrometers i n this department are superconduct ing, w i t h the po la r i z ing magnet ic f i e ld a long the l o n g axis o f the N M R tube. Therefore, the first term o f the equat ion o r i g i n a l l y descr ibed by E v a n s must be m u l t i p l i e d by -2 to obtain % f rom the measured data and even tua l ly calculate p, eff. T h e negative s ign be ing necessary as the shift observed w i t h the use o f a superconduting magnet is downf ie ld w h i l e that o f a convent iona l magnet i s upf ie ld . T h i s is described i n more detail i n the l i terature. 7 T h e phys i ca l and spectroscopic data for this complex agree w i t h those reported i n the l i t e r a t u r e . 2 1 , 2 2 , 4 8 51 Chapter 2 References: p 82 Chapter 2 2.5.6.2 Preparation of Ru2Cl5((/0-BINAP)2 (23)5'22'39 T h e above general procedure was fo l lowed w i t h R u C l 3 ( P ( p - t o l y l ) 3 ) 2 ( D M A ) D M A solvate (0.67 g, 0.68 m m o l ) and ( t f ) -BINAP (0.44 g, 0.71 m m o l ) . Y i e l d o f the red-brown s o l i d : 0.43 g (76%). Ca l cu l a t ed for R u 2 C l 5 ( ( / ? ) - B I N A P ) 2 H 2 0 , C 8 8 H 6 6 C I 5 O P 4 R U 2 : C, 64.34; H, 4.05%. F o u n d : C, 64.35; H , 4.29%. A solvate o f D M A instead o f H 2 0 has also been repor ted. 5 T h e phys ica l and spectroscopic data for this complex agree w i t h those reported i n the l i t e r a t u r e . 2 2 ' 3 9 2.5.7 Dihalo-di-p>halo-bis(bidentate phosphine)diruthenium(II) Complexes, [(P-P)XRu(u-X)2RuX(P-P)] or Ru2X4(P-P)2; X = Cl, Br, I; P-P = DPPB, BINAP T h e c h l o r o de r iva t ive , Ru2Cl4 (P -P )2 , was prepared by ei ther a p r e v i o u s l y repor ted route f rom Ru2Cl5 (P -P )2 , or by a new route f rom the m i x e d phosph ine complexes , R u C l 2 ( D P P B ) ( P A r 3 ) , where A r = pheny l or p-io\y\. T h e b r o m o analogue, Ru2Br 4 (P-P )2 , was prepared f rom RuBr 2 (DPPB ) (PPh 3 ) , or f rom R u 2 C l 4 ( D P P B ) 2 , by metathesis w i t h M e 3 S i B r . A l s o , the R u 2 X 4 ( D P P B ) 2 species ( X = Cl , B r , or I) c o u l d be prepared i n s i tu by the react ion o f H X w i t h Ru(DPPB)(r) 3-Me-allyl)2. T h e synthetic preparations for a l l three compounds are out l ined be low. T h e dinuclear complexes were stored i n Sch lenk tubes under A r because the species are quite air-sensi t ive even i n the s o l i d state. On exposure to air, the orange-brown complexes became dark green over periods o f hours to days i n the so l id state, and wi th in minutes i n solut ion. 2.5.7.1 X = Cl, P-P = DPPB; Preparation of Ru 2CI 4(DPPB) 2 (24) Method 1 T h e ru thenium (II, II) d inuclear c o m p l e x was prepared by H 2 reduc t ion o f the cor responding ruthenium(II , III) dinuclear c o m p l e x . T y p i c a l l y , Ru2Cl5(DPPB)2 (1.0 g , 0.81 m m o l ) was suspended i n D M A (20 m L ) i n a large S c h l e n k tube under an 52 Chapter 2 References: p 82 Chapter 2 atmosphere of H2, and the reaction mixture was stirred at room temperature. After 1 h, the solution was clear orange. To ensure complete reduction of the mixed-valence starting material, the Schlenk tube was refilled with H2 after 18 h, and the mixture was stirred for another 6 h. The volume of the solution was then reduced to ~ 5 mL, and methanol (40 mL) was added to precipitate an orange-brown solid. The solid was collected by vacuum filtration, washed with methanol (2x5 mL) and diethyl ether (2x5 mL), and dried under vacuum. Yield: 0.71 g (73%). Method 2 Alternatively, compound 24 could be prepared by a new method from RuCl2(DPPB)(PPh3) or RuCl2(DPPB)(P(/Molyl)3). A benzene solution (5 mL) of RuCl2(DPPB)(PPh3) (0.19 g, 0.22 mmol) with added H2O (5 mL) was refluxed under argon. The dark-green two-layer mixture became orange after 1 h. The mixture was cooled, the C6H6 layer transferred via a cannula to a Schlenk tube, and the H2O layer washed several times with C6Hg ( 2 x 2 mL). The washings were added to the second Schlenk tube, the solution was reduced in volume to ~ 5 mL, and hexanes (30 mL) were added to precipitate a bright-orange solid. This solid was collected by vacuum filtration, washed with MeOH (2x5 mL) and hexanes (5x5 mL), and dried under vacuum. Yield: 0.099 g (75%). Calculated for Ru 2Cl4(DPPB) 2, C56H56CI4P4RU2: C, 56.20; H , 4.72%. Found: C, 56.20; H, 4.78%. The orange solid turned brown after drying under vacuum at 78 °C for 24 h. Other workers from this laboratory have noted that the product is hygroscopic. 5' 2 1' 2 2' 3 9 In this case, the calculated values are for Ru2Cl4(DPPB)2-H20, C5 6H5 6Cl4P 4Ru2-H20: C, 55.36; H, 4.81%. Found: C, 55.43; H, 4.89%.5 Subsequently, the procedure was shortened somewhat by adding hexanes (5 mL) directly to the two-phase mixture to precipitate the orange solid. The product was then simply collected by vacuum filtration and washed as above. 31P{ lH} NMR ( C 6 D 6 , 20 °C): 8 A = 64.7, 5 B = 55.6, 2 / A B = 47.3 Hz. (CDCI3, 20 °C): 5 A = 63.5, 8 B = 54.3, 2 / A B = 46.9 Hz. 53 Chapter 2 References: p 82 Chapter 2 (CD 2 C1 2 , 20 °C): 8 A = 64.2, 8 B = 56.0, 2JAB = 46.8 Hz. ( C 7 D 8 , 20 °C): 8 A = 64.7, 8 B = 55.5, 2 7 AB = 46.9 Hz. The spectroscopic data agree with those for the dimer isolated by the alternative preparation from Ru2Cl5(DPPB)2 described above. 2 1 ' 2 2 ' 3 9 Method 3 Finally, the tide complex could be prepared conveniently in situ from the reaction of HC1 with Ru(DPPB)(T|3-Me-allyl)2. To a C 6 D 6 or C D C I 3 N M R solution of Ru(DPPB)(ri3-Me-allyl)2 (0.6 mL, ~ 55 mM) was added 2.2 equiv of HC1 (0.26 mL of a 0.239 M MeOH solution) at room temperature. The initially yellow solution immediately became orange on addition of HC1. After several minutes, the solution had become red. A 31p{lH} NMR spectrum showed an AB quartet corresponding to 24 and a broad singlet at 57.6 ppm in C^D^. No starting material was evident (see Section 3.3.4.2). 2.5.7.2 X = Br, P-P = DPPB; Preparation of Ru 2Br 4(DPPB) 2 (25) Method 1 The title complex was prepared by the same method as for the above chloro dimer, but using RuBr2(DPPB)(PPh3)3 (0.20 g, 0.21 mmol) as the starting material. An orange-brown solid was isolated. Yield: 0.12 g (86%). Calculated for Ru 2 Br 4 (DPPB) 2 -3H 2 0, C 5 6H5 6Br 4P 4Ru2-3H20: C, 47.07; H, 4.37%. Found: C, 47.02; H , 4.20%. 31p{lH} NMR ( C 6 D 6 , 20 °C): 8 A = 66.4, 8 B = 56.8, 2/ AB = 43.7 Hz. ( C 7 D 8 , 20 °C): 8 A = 66.7, 8 B = 57.0, 2 7 AB = 45.2 Hz. Method 2 Alternatively, the complex 25 could be prepared by metathesis of the analogous chloride dimer 24. To a C 6 H 6 solution (5 mL) of Ru2Cl 4(DPPB) 2 (81 mg, 0.068 mmol) was added Me3SiBr (200 uL, 1.52 mmol) under a flow of Ar. The originally pale-orange solution became dark orange in colour on addition of Me3SiBr. After being stirred for 54 Chapter 2 References: p 82 Chapter 2 18 h at r o o m temperature, the result ing red-brown solut ion was pumped to dryness. The b r o w n s o l i d was washed w i t h hexanes ( 2 x 5 m L ) and dr ied under v a c u u m . Y i e l d : 0.050 g (54%). T h e spectroscopic data were the same as those recorded for the s o l i d i so la ted by method 1. 2.5.7.3 X = Cl , P-P = (J?)-BINAP; Preparation of Ru2Cl4(W-BINAP)2 ( 2 6 )5,22,39 A m i x t u r e o f R u 2 C l 5 ( ( / ? ) - B I N A P ) 2 H 2 0 (0.19 g , 0.12 m m o l ) and poly(4-v i n y l p y r i d i n e ) (0.86 g, 70 monomer equivalents) was stirred i n Crfi^ (15 m L ) under an atmosphere o f H2 for 24 h . T h e orange-red suspension was f i l tered to remove poly(4-v i n y l p y r i d i n e ) hydrochlor ide , washed w i t h C 6 H 6 (2x4 m L ) , and the filtrate reduced i n v o l u m e to ~ 1 m L . Hexanes (20 m L ) were added to precipitate an orange-brown s o l i d , w h i c h was co l lec ted by vacuum fi l t rat ion, washed w i t h hexanes (3x5 m L ) , and dr ied u n d e r v a c u u m . Y i e l d : 0.18 g (78%). C a l c u l a t e d f o r R u 2 C U ( ( t f ) - B I N A P ) 2 C88H64CI4P4R112: C, 66.50; H , 4.06; Cl, 8.92%. Found : C, 66.45; H , 4.11; Cl , 6.22%. 31P{ l H } N M R ( C 6 D 6 , 20 °C): 8 A = 75.6, 5 B = 72.3, 2JAB = 44.3 H z ; 8 = 51.4, s. l H N M R ( C 6 D 6 , 20 °C, hydr ide region): 8 -14.0 (t, 2 / H P = 29.9 H z ) . T h e A B quartet accounts for -70% o f the total integrat ion. T h e 3 1P{ XH} N M R data and ch lo r ide analysis (see Sec t ion 4.6.2) do not agree w i t h the data de termined prev ious ly for the complex Ru 2 CLi(W -BINAP) 2 2 2 , 3 9 2.5.7.4 X = I, P-P = DPPB; Preparation of Ru2l4(DPPB)2 (27) T o a CDCI3 N M R solut ion o f R u ( D P P B ) ( r i 3 - M e - a l l y l ) 2 (~ 47 m M ) was added 2.2 equ iv o f HI (0.17 m L o f a 0.302 M M e O H solut ion) at r o o m temperature. T h e i n i t i a l y e l l o w so lu t ion became a red-b rown suspension o n add i t ion o f HI. T h e r e d - b r o w n product was not very soluble i n CDCI3 / M e O H ; however , a 3 1 P { ! H } N M R spectrum c o u l d be recorded. T h e complex 27 was even less soluble i n C6D6. 55 Chapter 2 References: p 82 Chapter 2 31p{ lH} NMR (CDCI3 / MeOH, 20 °C): 6 A = 70.1, 8 B = 55.6, 2 J = 39.9 Hz. 2.5.8 Chlorotri(p:-chloro)(ligand)bis(l,4-bis(diphenylphosphino)butane)-diruthenium(n) Complexes, [(L)(DPPB)Ru(p>Cl)3RuCl(DPPB)] or Ru2Cl4(P-P)2(L) 2.5.8.1 L = NEt 3: [(NEt3)(DPPB)Ru(p-Cl)3RuCl(DPPB)] (28)22 3 9 The title compound was prepared by stirring RuCl2(DPPB)(PPti3) (0.50 g, 0.59 mmol) with an excess of NEt3 (5.0 mL, 35.9 mmol) in benzene (25 mL) for 48 h at room temperature. The initially green solution slowly changed to an orange-brown solution. The work-up consisted of reducing the volume to ~ 5 mL at the pump, followed by the addition of hexanes (40 mL) to precipitate an orange solid. The solid was collected on a filter, washed with ethanol (2 x 10 mL) and hexanes (2 x 10 mL), and dried under vacuum. Yield: 0.25 g (65%). Calculated for [(NEt3)(DPPB)Ru(p-Cl)3RuCl(DPPB)], C 6 2 H 7 1 N C I 4 P 4 R U 2 : C, 57.37; H, 5.51; N, 1.08%. Found: C, 56.78; H, 5.38; N, 0.97%. 31p{lH} NMR (CDCI3, 20 °C): 48.9, s. ! H NMR (CDCI3, 20 °C): 5 1.09 (9H, br m, C# 3 CH 2 N) , 1.30 (4H, br m, CH2 of DPPB), 1.69 (4H, br m, CH2 of DPPB), 2.16 (4H, br m, CH2 of DPPB), 3.00 (4H, br m, CH2 of DPPB), 3.18 (6H, br m, C H 3 C / / 2 N ) , 6.80-7.95 (40H, m, Ph of DPPB). The physical and spectroscopic data for this complex agree with those reported. 2 2' 3 9 2.5.8.2 L = py: [(py)(DPPB)Ru(p-Cl)3RuCl(DPPB)] (29) The title complex was prepared in situ by the addition of one equivalent of pyridine (0.5 uL, 6 umol) to a CDCI3 solution (0.6 mL) of Ru2CU(DPPB)2 (7.58 mg, 6 pmol). The initially clear-orange solution became darker upon the addition of py. 31P{1H} NMR ( C D C I 3 , 20 °C): 8 A = 54.3, 8 B = 45.0, 2JAB = 36.4 Hz, 8 C = 52.6, 5 D = 51.6, 2 7 C D = 42.7 Hz. 56 Chapter 2 References: p 82 Chapter 2 IH NMR (CDCI3, 20 °C): 6 1.2-3.1 (15H, m, CH2 of DPPB), 3.98 (IH, m, CH of C H 2 of DPPB), 6.33-8.67 (45H, m, 40H of Ph of DPPB and 5H of py). 2.5.8.3 L = HNEt 2: [(HNEt2)(DPPB)Ru(u^Cl)3RuCl(DPPB)] (30) Diethylamine (5 mL) was added to a green suspension of RuCl2(DPPB)(PPh3) (0.20 g, 0.23 mmol) in C^H^ (5 mL). The resulting mixture was refluxed for 2 h. Hexanes (30 mL) were added to the cooled orange solution to precipitate the orange-brown product. The solid was collected by vacuum filtration, washed with hexanes, and dried under vacuum. Yield: 0.06 g (40%). Calculated for [(HNEt2)(DPPB)Ru(u-Cl)3RuCl(DPPB)], C6oH67NCl4P4Ru2: C, 56.74; H, 5.32; N, 1.10%. Found: C, 56.65; H, 5.96; N, 1.46%. 3lp{lH} NMR (CDCI3, 20 °C): 848.9, s. ! H NMR (CDCI3, 20 °C): 8 1.31 (6H, t, J = 10.3 Hz, C//3 of HNEt 2), 1.40 (4H, br m, CH2 of DPPB), 1.72 (4H, br m, CH2 of DPPB), 2.15 (4H, br m CH2 of DPPB), 2.90 (4H, br m, CH2 of DPPB), 2.95 (4H, q, J = 10.3 Hz, CH2 of HNEt 2), 6.8-7.8 (40H, m, Ph of DPPB), 8.0 (IH, br s, #NEt 2). 2.5.8.4 L = acetone: [(acetone)(DPPB)Ru(p:-Cl)3RuCl(DPPB)]acetone solvate ( 3 1 ) 2 1 , 2 2 3 9 The title complex was prepared by modifying a preparation previously employed in this laboratory. 2 1 , 2 2 ' 3 9 A suspension of Ru2Cl4(DPPB)2 (0.20 g, 0.17 mmol) in acetone (10 mL) was stirred at room temperature for 24 h. The orange solid was collected by vacuum filtration, washed with diethyl ether ( 2 x 5 mL), and dried under vacuum. Yield: 0.18 g (82%). Care must be taken in degassing the solvents prior to use because the starting complex reacts with both 0 2 and N 2 . 31P{1H} NMR (C6D6, 20 °C): 8A = 53.7, 8B = 51.3, ^JAB = 42.7 Hz; 8c = 50.8, 8B = 49.6, 2 / A B = 38.5 Hz. 57 Chapter 2 References: p 82 Chapter 2 The physical and spectroscopic data for this complex agree with those reported in the literature. 2 1' 2 2' 3 9 2.5.8.5 L = acetophenone: [(acetophenone)(DPPB)Ru(p-Cl)3RuCl(DPPB)] (32) The dinuclear complex Ru2CU(DPPB)2 (83 mg, 0.069 mmol) was dissolved in CH2CI2 (5 mL) and acetophenone (5 mL). The dark-orange solution was stirred at room temperature for 4 h, and then diethyl ether (30 mL) and hexanes (10 mL) were added to precipitate a dark-orange solid. The solid was collected by vacuum filtration, washed with hexanes ( 6 x 3 mL), and dried under vacuum. Yield: 48 mg (52%). Calculated for [(acetophenone)(DPPB)Ru(u-Cl)3RuCl(DPPB)], C 6 4 H 6 4 C l 4 0 P 4 R u 2 : C, 58.37; H , 4.90%. Found: C, 57.58; H, 4.84%. IR (KBr pellet, cm"1): V(c=0) at 1679 (s); (CH 2 C1 2 solution, cm'1): V(c=0) at 1683 (s). 31p{lH} NMR (OA}, 20 °C): 8 A = 53.7, S B = 52.7, 2 7AB = 43.9 Hz; 5c = 52.1, 5 D = 47.5, 2 /CD = 37.4 Hz. *H NMR ( C 6 D 6 , 20 °C): 8 2.04 (C//3 of acetophenone). UV-vis ( C 6 H 6 ) : Xmax (nm), e m a x (M-l cm-1) = 364, 3320; 484 (sh), 815; (CH2CI2): 366, 3300; 484 (sh), 690. 2.5.8.6 L = DMSO: [(DMSO)(DPPB)Ru(p-Cl)3RuCl(DPPB)] (33) An excess of DMSO (170 pL, 2.3 mmol) was added to a dark-green suspension of RuCl 2(DPPB)(PPh 3) (0.18 g, 0.21 mmol) in C 6 H6 (5 mL). The originally green mixture became bright orange after refluxing for 1 h under argon. The solution was cooled, and hexanes (30 mL) added to precipitate a yellow-orange solid. This solid was collected on a sintered glass filter, washed with hexanes (5x5 mL) to remove PPh 3 , and dried under vacuum. Yield: 0.12 g (87%). Calculated for [(DMSO)(DPPB)Ru(p-Cl)3RuCl(DPPB)], C58H62CI4OP4RU2S: C, 54.64; H, 4.90%. Found: C, 54.45; H, 5.10%. IR (Nujol, cm-1): v ( S =o) at 1090 (s, S-bonded DMSO). 58 Chapter 2 References: p 82 Chapter 2 31P{ lH} NMR (C 6 D 6 , 20 °C): 8 A = 53.9, 5 B = 52.9, 2 7 A B = 43.8 Hz; 8 C = 42.5, 8 D = 33.7, 2JCD = 29.6 Hz. (CDCI3, 20 °C): 8 A = 54.2, SB = 51.2, 2 / A B = 42.8 Hz; 8 C = 42.2, 8 D = 29.5, 2 7 C D = 30.2 Hz. !H NMR (CDCI3, 20 °C): 8 0.65-2.32 (21H, m, 15H of CH2 of DPPB and 6H of CH3 of DMSO), 3.50 (IH, br m, CH of C H 2 DPPB), 6.78 (3H, m, Ph of DPPB), 6.94-7.96 (34H, m, Ph of DPPB), 8.47 (3H, m, Ph of DPPB). (C 6 D 6 , 20 °C): 8 0.50-2.50 (16H, m, 10H of CH2 of DPPB and 6H of C# 3 of DMSO), 2.74 (IH, m, CH of C H 2 DPPB), 3.29 (3H, m, CH2 DPPB), 3.51 (2H, m, CH2 of DPPB), 6.67 (4H, t, J = 6.9 Hz, Ph of DPPB), 6.80 (16H, m, Ph of DPPB), 7.34 (3H, t, J = 8.3 Hz, Ph of DPPB), 7.47 (5H, br m, Ph of DPPB), 7.61 (2H, t, / = 6.8 Hz, Ph of DPPB), 7.74 (2H, t, J = 8.0 Hz, Ph of DPPB), 8.07 (4H, pseudo q, J = 8.9 Hz, Ph of DPPB), 8.18 (2H, t, 7 = 8.3 Hz, Ph of DPPB), 8.67 (2H, t, J = 8.0 Hz, Ph of DPPB). UV-vis (C 6H 6): ? i m a x (nm), e m a x (M-l cm-1) = 378, 3010; 470 (sh), 590; (CH2C12): 376, 2900; 470 (sh), 650; (C 7H 8): 378, 3010; 472 (sh), 610. This compound has been prepared previously from a different starting material (cw-RuCl2(DMSO)4).22'39 The above IR and 31P{!H} NMR spectroscopic data agree with those reported in the literature.22'39 The UV-visible and *H NMR data have not been reported before. 2.5.8.7 L = DMS: [(DMS)(DPPB)Ru(p:-Cl)3RuCl(DPPB)] (34) An excess of dimethyl sulfide (106 uL, 1.44 mmol) was added to a dark-green suspension of RuCl2(DPPB)(PPh3) (0.17 g, 0.20 mmol) in C 6 H 6 (5 mL). The resulting mixture was stirred at room temperature (in a sealed Schlenk tube because of the smell and volatility of DMS) under an atmosphere of Ar for 4 h; the syntheses of the other sulfide and sulfoxide analogues were performed at reflux temperatures under a slow flow of Ar (Sections 2.5.8.6, 2.5.8.8, and 2.5.8.9). An orange-brown product was precipitated 59 Chapter 2 References: p 82 Chapter 2 by the addition of hexanes (30 mL). This solid was collected by vacuum filtration, washed with hexanes ( 5 x 5 mL), and dried under vacuum. Yield: 0.11 g (87%). Calculated for [(DMS)(DPPB)Ru(p-Cl)3RuCl(DPPB)] , C 5 8 H 6 2 Cl4P4Ru 2 S: C, 55.33; H, 4.96; Cl , 11.26; S, 2.55%. Found: C, 55.48; H, 4.88; Cl , 11.11; S, 2.57%. 31p{lH} NMR (CDCI3, 20 °C): 8 A ) B = 51.3, unresolved AB pattern; 8 C = 48.2, 5 D = 46.0, 2JCD = 35.6 Hz. ( C 6 D 6 , 20 °C): 8 A = 52.5, 8 B = 51.8, 2 / A B = 44.1 Hz; 8 C = 48.6, 8 D = 46.2, 2 /CD = 35.3 Hz. ! H NMR (CDCI3, 20 °C): 8 0.82-2.75 (20H, m, 14H of CH2 of DPPB and 6H of CH3 of DMS), 3.13 (1H, m, CH of C H 2 DPPB), 3.70 (1H, br m, CH of C H 2 DPPB), 6.65-7.80 (35H, m, Ph of DPPB), 8.04 (2H, t, J = 7.8, Ph of DPPB), 8.33 (3H, m, Ph of DPPB). ( C 6 D 6 , 20 °C): 8 0.52-2.75 (20H, m, 14H of CH2 of DPPB and 6H of C#3 of DMS), 3.35 (1H, br m, CH of C H 2 DPPB), 4.12 (1H, br m, CH of C H 2 DPPB), 6.68-7.85 (32H, m, Ph of DPPB), 8.15 (4H, m, Ph of DPPB), 8.70 (4H, m, Ph of DPPB). UV-vis ( C 6 H 6 ) : ? i m a x (nm), e m a x (M"l cnr*) = 374, 3780; 460 (sh), 730; (CH 2C1 2): 372, 3470; 460 (sh), 660. 2.5.8.8 L = T M S O : [(TMSO)(DPPB)Ru(u-CI)3RuCI(DPPB)] (35) The title product was synthesized in the same manner as the DMSO analogue (Section 2.5.8.6). An excess of tetramethylene sulfoxide (TMSO, 210 pL, 2.32 mmol) was added to a dark-green suspension of RuCl2(DPPB)(PPh3) (0.190 g, 0.221 mmol) in C6H6 (5 mL). The originally green mixture became bright orange after refluxing for 1.5 h under argon. The solution was cooled, and hexanes (30 mL) added to precipitate a pale-orange solid. The solid was collected on a sintered glass filter, washed with hexanes (5 x 5 mL) to remove PPI13, and dried under vacuum. Yield: 0.11 g (70%). Calculated for 60 Chapter 2 References: p 82 Chapter 2 [(TMSO)(DPPB)Ru(u-Cl)3RuCl(DPPB)] , C60H64CI4OP4RU2S: C, 55.39; H, 4.96; Cl , 10.90; S, 2.46%. Found: C, 55.11; H, 5.20; Cl , 10.71; S, 2.60%. IR (Nujol or KBr pellet, cm"1): v(S=0) at 1093 (s, S-bonded TMSO). 31P{ lH} NMR ( C 6 D 6 , 20 °C): 8 A = 55.1, 8 B = 52.2, 2 / A B = 42.8 Hz; 8 C = 44.2, 8 D = 29.1, 2JCD= 29.0 Hz. (CDCI3, 20 °C): 8 A = 54.7, 8 B = 50.8, 2 7 A B = 41.1 Hz; 8 C = 43.4, 8 D = 26.3, 2 / C D = 27.8 Hz. IH NMR (CDCI3, 20 °C): 8 0.65-3.10 (20H, m, 12H of CH2 of DPPB and 8H of CH2 of TMSO), 3.26 (3H, br m, CH2 DPPB), 3.73 (IH, br m, CH of C H 2 DPPB), 6.61 (3H, br m, Ph of DPPB), 7.00-8.12 (35H, m, Ph of DPPB), 8.51 (2H, br m, Ph of DPPB). ( C 6 D 6 , 20 °C): 8 0.30 (23H, m, 15H of CH2 of DPPB and 8H of CH2 of TMSO), 3.82 (IH, br m, CH of C H 2 DPPB), 6.6-8.48 (39H, m, Ph of DPPB), 8.74 (IH, brm, Ph of DPPB). UV-vis ( C 6 H 6 ) : XmSLX (nm), e m a x ( M _ 1 cm-l) = 376, 2470; 460 (sh), 830; (CH2CI2): 374, 2410; 460 (sh), 600. 2.5.8.9 L = T H T : [(THT)(DPPB)Ru(u-Cl) 3RuCl(DPPB)] (36) The title product was synthesized in the same manner as the DMSO analogue (Section 2.5.8.6). An excess of tetrahydrothiophene (THT, 180 uL, 2.0 mmol) was added to a dark-green suspension of RuCl2(DPPB)(PPh3) (0.18 g, 0.21 mmol) in C 6 H 6 (5 mL). The originally green mixture became bright orange after refluxing for 1 h under argon. The solution was cooled and hexanes (30 mL) added to precipitate a orange-brown solid. The solid was collected on a sintered glass filter, washed with hexanes ( 5 x 5 mL) to remove PPI13, and dried under vacuum. Yield: 0.12 g (90%). Calculated for [(THT)(DPPB)Ru(u-Cl)3RuCl(DPPB)] , C 6 0H64Cl4P 4Ru2S: C, 56.08; H , 5.02. Found: C, 56.61; H, 5.13%. 61 Chapter 2 References: p 82 Chapter 2 The elemental analysis was found to be slightly high in carbon, probably as a result of using unpurified THT, which is known to commonly contain impurities. Reprecipitation of this material did not improve the elemental analysis. 31p{lH} NMR (CDCI3, 20 °C): 8 A = 51.9, 8 B = 51.2, 2/^ = 43.2 Hz; 8 C = 49.1, 8 D = 46.7, 2 / C D = 36.1 Hz. ( C 6 D 6 , 20 °C): 8 A , B = 52.3, unresolved A B pattern; 8c = 49.5, 8 D = 47.1, 2/ C D = 36.1 Hz. l H NMR (CDCI3, 20 °C): 8 0.85-2.90 (22H, m, 14H of CH2 of DPPB and 8H of CH2 of THT), 3.20 (1H, br m, CH of C H 2 DPPB), 3.69 (1H, br m, CH of C H 2 DPPB), 6.78-7.75 (35H, m, Ph of DPPB), 8.07 (2H, t, J = 8.8, Ph of DPPB), 8.30 (3H, m, Ph of DPPB). ( C 6 D 6 , 20 °C): 8 0.50-2.75 (22H, m, 14H of CH2 of DPPB and 8H of CH2 of THT), 3.39 (1H, br m, CH of C H 2 DPPB), 4.10 (1H, br m, CH of C H 2 DPPB), 6.72-7.80 (32H, m, Ph of DPPB), 8.20 (4H, br m, Ph of DPPB), 8.65 (4H, br m, Ph of DPPB). UV-vis ( C 6 H 6 ) : Xmax (nm), e m a x (M-l cm-l) = 374, 3700; 460 (sh), 605; (CH 2C1 2): 372, 3200; 460 (sh), 440. 2.5.9 Preparation of [Ru2Ci5(DPPB)2]- or [(DPPB)ClRu(p-Cl)3RuCl(DPPB)]-Complexes 2.5.9.1 [H 2N(/i-Oct) 2]+ [Ru2Cl5(DPPB)2]- or [H2N(#t-Oct)2]+ [(DPPB)ClRu(p-Cl)3RuCl(DPPB)]- (37) An excess of tri-n-octylamine (5 mL, 11 mmol) was added to a dark-green suspension of RuCl2(DPPB)(PPh3) (0.19 g, 0.22 mmol) in C 6 H 6 (5 mL). After the solution was refluxed for 16 h under a slow flow of Ar, the volume of the orange suspension was reduced to ~ 5 mL, and hexanes (30 mL) were added to precipitate more product. The orange product was collected by vacuum filtration, washed with ethanol (2 x 5 mL) and hexanes (5x5 mL), and dried under vacuum. Yield: 0.063 g (40%, based on cry Chapter 2 References: p 82 Chapter 2 Ru content). Calculated for [H 2N(n-Oct) 2]+ [Ru 2Cl 5(DPPB) 2]- C 7 2 H 9 2 N C l 5 P 4 R u 2 : C, 58.64; H, 6.29; N, 0.95; Cl , 12.02%. Found: C, 58.55; H, 6.17; N, 0.90; Cl , 12.20%. 31p{lH} NMR (CDC1 3, 20 °C): 8 = 48.9, s. ( C 6 D 6 , 20 °C): 8 = 49.2, s. ! H NMR (CDCI3, 20 °C): 8 = 0.97 (6H, t, J = 8.8 Hz, - C H 2 C # 3 ) , 1.40 (24H, m, 20H for -CH 2 (C# 2 ) 5 CH3 and 4H for CH2 of DPPB), 1.70 (8H, m, 4 each of CH2 of DPPB and H 2 N C H 2 C / / 2 C H 2 - ) , 2.15 (4H, br m, CH2 of DPPB), 2.90 (4H, m, H 2 N C / / 2 C H 2 - ) , 2.95 (4H, br m, CH2 of DPPB), 6.9-7.6 (40H, m, Ph of DPPB), 7.9 (2H, brs ,#N 2 CH 2 - ) . UV-vis (CH 2C1 2): W (nm), emax (M"1 cm"1) = 316, 5080; 374, 3190; 486, 590. 2.5.9.2 [H2N(/i-Bu)2]+ [Ru2CI5(DPPB)2]- or [H 2N(n-Bu) 2]+ [(DPPB)CIRu(u-Cl)3RuCl(DPPB)]- (38) The title complex was prepared in exactly the same manner as the octyl analogue, except that tri-n-butylamine (5 mL, 21 mmol) was added to RuCl2(DPPB)(PPh3) (0.19 g, 0.22 mmol) in C6H6 (5 mL). The isolated product was orange like the octyl analogue. Yield: 0.070 g (44%, based on Ru content). Calculated for [ H 2 N (n-Bu)2]+ [Ru 2Cl 5(DPPB) 2]-, C64H 76NCl 5P4Ru 2: C, 56.41; H, 5.62; N, 1.03; Cl , 13.01%. Found: C, 56.47; H, 5.59; N, 0.98; Cl , 13.29%. 3 1P{!H} NMR (CDCI3, 20 °C): 8 = 48.8, s. (CD 2 Cl 2 , -98 °C):8 = 48.8, s. ! H N M R (CDCI3, 20 °C): 8 = 0.97 (6H, t, - C H 2 C / / 3 ) , 1.35 (4H, m, - C H 2 C / / 2 C H 3 ) , 1.40 (4H, m, CH2 of DPPB), 1.65 (4H, m, H 2 N C H 2 C / / 2 C H 2 - ) , 1.75 (4H, br m, CH2 of DPPB), 2.15 (4H, br m, CH2 of DPPB), 2.90 (4H, m, H 2 N C i / 2 C H 2 - ) , 2.95 (4H, br m, CH2 of DPPB), 6.9-7.6 (40H, m, Ph of DPPB), 7.9 (2H, br s, # N 2 C H 2 - ) . UV-vis (C 7 H 8 ) : Xmax (nm), e m a x ( M _ 1 cm"1) = 372, 3300; 484, 590; (CH 2C1 2): 316, 5330; 374, 3250; 484, 590. 63 Chapter 2 References: p 82 Chapter 2 2.5.9.3 [DMAH]+ [Ru2Cl5(DPPB)2]- or [DMAH]+ [(DPPB)ClRu(p-Cl)3RuCl(DPPB)]- (39) A pink solid isolated from a reaction mixture left by a previous worker in this laboratory, Dr. A. Joshi, proved to be the title complex (see Section 2.5.4.3). As outlined in Section 2.5.4.3, the reaction mixture most probably contained RuCl3(PPh3)2(DMA)DMA solvate and 1 equiv of DPPB in D M A under an atmosphere of H 2 . Yield: 0.25 g. Calculated for [DMAH]+ [(DPPB)ClRu(p-Cl)3RuCl(DPPB)]-, C60H66NCI5OP4RU2: C, 54.58; H, 5.04; N, 1.06; Cl, 13.42%. Found: C, 54.96; H, 5.06; N, 0.90; Cl , 13.47%. IR (KBr, cm-1): V(c=o> between 1623-1652 (br, m). 3ip{ lH} NMR (CDCI3, 20 °C): 8 = 48.9, s. ( C 6 D 6 , 20 °C):S = 49.2, s. ! H NMR (CDC1 3, 20 °C): 8 = 1.58 (4H, br m, CH2 of DPPB), 1.65 (4H, br m, CH2 of DPPB), 2.05 (3H, s, C//3 of DMA), 2.15 (2H, br m, CH2 of DPPB), 2.55 (4H, br m, CH2 of DPPB), 2.88 (2H, br m, CH2 of DPPB), 2.90 (3H, s, C H 3 of DMA), 3.00 (3H, s, C H 3 of DMA), 6.7-7.6 (40H, m, Ph of DPPB), 8.2 (1H, br s, DMA// ) . UV-vis (CH 2C1 2): W (nm), E m a x (M" 1 cm"1) = 316, 5990; 374, 3770; 480, 880. The title complex has previously been prepared in this laboratory by another route. 2 1' 4 9 The Ru starting material in this case was Ru2Cl5(DPPB)2, and the reaction was performed in D M A solvent under an atmosphere of H2. 2.5.9.4 [H2N(/i-Bu)2]+ [Ru2Cl5((K)-BINAP)2]- or [H2N(/i-Bu)2]+ [((/?)-BINAP)ClRu(u-CI)3RuCl((rt)-BINAP)]- (40) An excess of tri-n-butylamine (5 mL, 21 mmol) was added to an orange suspension of RuCl2((/?)-BINAP)(PPh3) (0.13 g, 0.12 mmol) in C 6 H 6 (5 mL). After the solution was refluxed for 20 h under a slow flow of Ar, the volume of the orange solution was reduced to ~ 5 mL, and hexanes (10 mL) were added to precipitate the product. The orange solid was collected by vacuum filtration, washed with hexanes (4x5 mL), and 64 Chapter 2 References: p 82 Chapter 2 dried under vacuum. Yield: 0.080 g (70%, based on Ru content). Calculated for [H2N(n-Bu) 2 ] + [Ru 2Cl 5((/?)-BINAP) 2]--2H 20, C 9 6H88NCl50 2 P 4 Ru 2 : C, 64.38; H, 4.95; N, 0.78%. Found: C, 64.24; H, 4.78; N, 0.68%. 31p{lH} NMR (CDCI3, 20 °C): 5 A = 55.1, 5 B = 51.6, 2 / A B = 37.6 Hz. ( C 6 D 6 , 20 °C): 8 A = 54.9, 5 B = 51.9, 2 / A B = 38.5 Hz. l H NMR (CDCI3, 20 °C): 8 1.05 (6H, t, J = 8.8 Hz, - C H 2 C i / 3 ) , 1.45 (4H, m, - C H 2 C / / 2 C H 3 ) , 1.87 (4H, m, N C H 2 C H 2 C H 2 - ) , 2.40 (IH, br m, H 2 NC#2CH 2 - ) , 2.95 (2H, br m, H 2 N C H 2 C H 2 - ) , 3.25 (IH, br m, H2NC//2CH2-) , 6.1-8.1 (64H, m, aromatic protons of BINAP), 8.5 (2H, br s, //2NCH2-). H2O was observed at 1.5 ppm. UV-vis (CH 2C1 2): Xmax, e m a x ( M _ 1 cm"1) = 334 (sh), 13700; 400 (sh), 4700. The UV-visible spectrum is relatively featureless. 2.5.9.5 [HNEt3] + [Ru 2 Cl5(DPPB)2]- or [HNEt3]+[(DPPB)CIRu(u-Cl)3RuCl(DPPB)]- (41) The title complex was isolated as an orange solid, a by-product in the preparation of the trinuclear species [Ru(H)Cl(DPPB)]3 (Section 2.5.10.1). Yield: 0.13 g (24%). Calculated for [HNEt3] +[Ru2Cl 5(DPPB) 2]-, C 6 2 H 7 2 N C I 5 P 4 R U 2 : C , 55.80; H , 5.44; N, 1.05; Cl , 13.28%. Found: C, 55.73; H, 5.49; N, 0.97; Cl , 12.95%. 31p{lH} NMR (CDCI3, 20 °C): 49.0, s. l H NMR (CDCI3, 20 °C): 8 1.05 (9H, br m, C / /3 of H N E 1 3 ) , 1.36 (4H, br m, CH2 of DPPB), 1.72 (4H, br m CH2 of DPPB), 2.15 (4H, br m, CH2 of DPPB), 3.01 (4H, br m, CH2 of DPPB), 3.15 (6H, br m CH3 of HNEt 3), 6.8-7.7 (40H, m, Ph of DPPB), 7.85 (IH, t , . / = 9 H z , / / N E t 3 ) . 2.5.10 Synthesis of Chlorohydrido(bidentate phosphine)ruthenium(n) Trimers, [Ru(H)Cl(P-P)]3 The title triruthenium-chlorohydrido complexes containing DPPB and S,S-CHIRAPHOS were first isolated in low yields (5-10%) by Thorburn in this laboratory.49 65 Chapter 2 References: p 82 Chapter 2 11 The yield of these reactions was improved (to 50%) by Joshi by changing the order of addition of the reagents H2 and NEt3. Originally, triethylamine was added to the diruthenium starting material Ru2Cl4(DPPB)2, followed by the addition of dihydrogen. 2.5.10.1 P-P = DPPB; [Ru(H)Cl(DPPB)] 3 (42)2 2 4 9 Method 1 A benzene solution (30 mL) of Ru2Cl4(DPPB)2 (0.49 g, 0.41 mmol) was stirred under an atmosphere of H2 for 1 h at room temperature. Triethylamine (deoxygenated, 0.11 mL, 0.86 mmol) was then added via a syringe under a blanket of H2. The orange-red suspension/solution was stirred under H2 for 36 h at room temperature, with the Schlenk tube being refilled with dihydrogen after the first 18 h. The NEt3-HCl produced was collected by vacuum filtration on a bed of Celite, washed with CgH.6 (5 mL), and the red-brown filtrate was reduced in volume to ~ 10 mL. Hexanes (15 mL) was added to precipitate an orange solid [HNEt3]+[Ru2Cl5(DPPB)2]~ (Section 2.5.9.5), which was collected by filtration, washed with a 1:1 mixture of benzene/hexanes (10 mL), and finally washed with hexanes ( 2 x 5 mL). The hexanes washes were not added to the filtrate as were the 1:1 mixture of C^Ha I hexanes washings. The filtrate was then reduced in volume to ~ 5 mL, followed by addition of hexanes (15 mL) to precipitate a brown solid. The brown product, [Ru(H)Cl(DPPB)]3, was collected by vacuum filtration, washed with hexanes ( 2 x 5 mL), and dried under vacuum. Yield of the triruthenium species, [Ru(H)Cl(DPPB)]3: 0.25 g (54%). Calculated for C g ^ g y C ^ R u : C, 59.63; H , 5.18; Cl, 6.29%. Found: C, 59.65; H, 5.36; Cl, 6.23%. 3lP{lH} NMR ( C 6 D 6 , 20 °C): 8 A = 71.7, 5 B = 48.3, 8 C = 68.9, 8 D = 61.6, 8 E = 59.5, 8F = 57.3. Al l resonances show unresolved c/s-coupling constants. The six resonances have been paired previously into AB quartets on the basis of line-shape49 and selective phosphorus decoupled-proton NMR studies.22 Figure 3.11 (Section 3.2) shows the molecular structure of [Ru(H)Cl(DPPB)]3. 66 Chapter 2 References: p 82 Chapter 2 *H NMR ( C 6 D 6 , 20 °C, hydride region): 5-21.9 (1H, t, 2 J P H = 32.1 Hz, terminal hydride coupled to P A and Pn), -21.1 (1H, m, bridging hydride coupled to P A , PB> ?E> and Pp), -17.7 (1H, t, 2 7 P H = 32.1 Hz, terminal hydride coupled to Pc and PD); see Figure 3.11 for phosphorus assignment. T\ measurements in C 6 D 6 (300 MHz, 20.0 °C): 5 -21.9 (275 ± 10 ms), -21.1 (390 ± 20 ms), -17.7 (390 + 10 ms). Mass spectrum (FAB, matrix: 3-nitrobenzylalcohol) [m/z]: 1692+4 [M+H]+. Method 2 An alternative route to the title triruthenium complex 42 was from Ru2Cl4(DPPB)2(NEt3). Ru2Cl4(DPPB)2(NEt3) (0.33 g, 0.25 mmol) was added to a C 6 H 6 solution (10 mL) which had been presaturated with H 2 . One equivalent of NEt3 (35 pL, 0.25 mmol) was then added to the resulting orange suspension. The reaction mixture which was contained in a glass liner was placed in an autoclave and pressurized to 1000 psi with H 2 . The contents were stirred at room temperature for 4 days. The resulting orange-brown solution was handled under Ar following the work-up outlined above. Yield: 0.11 g (40%). The spectroscopic data were as given above. The physical and spectroscopic data for this complex agree with those reported in the literature.22'49 The T\ data have not been measured previously. 2.5.11 Preparation of Ruthenium(II) Amine Complexes from RuCl 2(PPh3)3, RuCl2(DPPB)(PPh3), and [RuCl2(DPPB)1.5)]2 2.5.11.1 Preparation of dichloro(bis(di pheny lphosphino)butane)-bis(pyridine)ruthenium(II), RuCl2(DPPB)(py)2 (43) Method 1 An excess of pyridine (190 pL, 2.3 mmol) was added to a dark-green suspension of RuCl2(DPPB)(PPh3) (0.18 g, 0.21 mmol) in Q H 6 (5 mL). The solution became orange 67 Chapter 2 References: p 82 Chapter 2 after refluxing for 1.5 h under a slow flow of Ar. The solution was cooled, and hexanes (30 mL) added to precipitate a mustard-coloured solid. The solid was collected on a sintered glass filter, washed with hexanes (5x5 mL) to remove PPh3, and dried under vacuum. Yield: 0.13 g (82%). Solvated benzene could be removed from the solid by heating under vacuum in a Abderhalden drying apparatus at 78 °C, after the solid was finely divided in a mortar and pestle. Calculated for RuCl2(DPPB)(py)2, C38H38N2CI2P2RU: C, 60.32; H , 5.06; N, 3.70; Cl, 9.37%. Found: C, 50.94; H, 5.10; N, 3.53; Cl, 9.20%. 31p{lH}NMR ( C 6 D 6 , 2 0 ° C ) : 5 = 41.5,s. (CDCI3, 20 °C): 8 = 40.4, s. (CD 2C1 2 ,20 °C):8 = 40.4, s. ! H NMR ( C 6 D 6 , 20 °C): 8 1.63 (4H, br m, P C H 2 C / / 2 C / / 2 of DPPB), 3.15 (4H, br m, PC#2(CH 2 )2C// 2 P of DPPB), 6.17 (4H, t, J = 7.9 Hz, meta-py), 6.55 (2H, t, J = 7.9 Hz, para-py), 6.94 (12H, m, meta- and para-Ph protons of DPPB), 7.92 (8H, m, ortho-Ph protons of DPPB), and 9.40 (4H, d, J = 5.3 Hz, ortho-py). (CDCI3, 20 °C): 8 1.67 (4H, br m, P C H 2 C / / 2 C / / 2 of DPPB), 3.03 (4H, br m, PC#2(CH 2)2C# 2P of DPPB), 6.64 (4H, br m, meta-py), 6.95-7.20 (12H, m, meta-and para-Ph protons of DPPB), 7.22 (2H, br m, para-py), 7.61 (8H, m, ortho-Ph of DPPB), 8.85 (4H, br m, ortho-py). UV-vis (CH 2C1 2): X m a x (nm), e m a x (M"l cm-1) = 462, 430; 672, 90; ( C 6 H 6 ) = 458,492; 678,96. Conductivity data in MeOH and CH3NO2 are given in Table 5.2 (Section 5.2). Method 2 The title complex was also prepared from a different Ru starting material, [RuCl2(DPPB)i.5]2, following a synthetic procedure by Batista et a l . 5 0 , 5 1 To a CH2CI2 suspension (10 mL) of [RuCl2(DPPB)i.5]2 (0.28 g, 0.17 mmol) was added an excess of pyridine (140 pL, 1.7 mmol). The resulting mustard-coloured mixture was stirred at room 68 Chapter 2 References: p 82 Chapter 2 temperature for 4 h. The solution was then reduced to 1-2 mL at the pump, and diethyl ether (15 mL) added to precipitate the mustard product. The solid was collected by vacuum filtration, washed with diethyl ether (6x5 mL), and dried under vacuum. Yield: 0.23 g (87%). The physical and spectroscopic data are the same as those determined for the product isolated from the other preparation outlined above. 2.5.11.2 Preparation of dichloro(bis(diphenylphosphino)butane)-bipyridylruthenium(n), RuCl2(DPPB)(bipy) (44) Method 1 An excess of 2,2'-bipyridine (0.36 g, 2.3 mmol) was added to a dark-green suspension of RuCl2(DPPB)(PPh3) (0.20 g, 0.23 mmol) in C 6 H 6 (5 mL). The mixture immediately turned a cloudy red colour. The solution was refluxed for 1 h under a flow of Ar. The solution was cooled, and hexanes (15 mL) added to precipitate more red solid. The solid was collected on a sintered glass filter, washed with hexanes ( 5 x 5 mL) to remove PPI13, and dried under vacuum. Yield: 0.16 g (92%). Calculated for RuCl2(DPPB)(bipy), C38H36N2CI2P2R11: C, 60.48; H , 4.81; N, 3.71; Cl , 9.40%. Found: C, 60.57; H, 4.68; N, 3.60; Cl, 9.22%. 31p{lH} NMR (CDCI3, 20 °C): 5 A = 43.5, 8 B = 29.8, 2 / A B = 32.9 Hz for the cis isomer and 8 = 32.6, s for the trans isomer. The ratio of cis to trans is approximately 1:1. ! H NMR of trans-44 (CDCI3, 20 °C): 8 1.82 (4H, br m, CH2 of DPPB), 2.77 (4H, br m, CH2 of DPPB), 6.67 (2H, m, H 4 > 4 - of bipy), 7.13 (2H, m, H 5 ) 5 ' of bipy), 7.18-7.50 (12H, m, meta- and para-Ph of DPPB), 7.77 (8H, m, ortho-Ph of DPPB), 7.95 (2H, d, J = 8.8 Hz, H3;3- of bipy), 8.60 (2H, d, J = 4 Hz, H6,6' of bipy). ! H NMR of cw-44 (CDCI3, 20 °C): see Figure 5.5 (Section 5.3.1). UV-vis (CH 2C1 2): W (nm), emax (M" 1 cm-1) = 300,12300; 346 (sh), 2600; 458, 2200; (MeOH) = 292, 15400; 436, 2600. Conductivity data in MeOH and CH3NO2 are given in Table 5.2 (Section 5.2). 69 Chapter 2 References: p 82 Chapter 2 Method 2 The title complex was also prepared from a different Ru starting material, [RuCl2(DPPB)i.5]2, following a synthetic procedure by Batista et a l . 5 0 ' 5 1 An excess of 2,2-bipyridine (0.11 g, 0.70 mmol) was added to a CH2CI2 suspension (10 mL) of [RuCl2(DPPB)i.5]2 (0.26 g, 0.16 mmol). The initially green suspension, after being stirred at room temperature for 1.5 h, slowly changed to a chocolate-brown colour over a period of 1.5 h. After 4 h, the resulting red solution was reduced to 1-2 mL in volume at the pump, and diethyl ether (15 mL) was added to precipitate a brown solid, which was collected by vacuum filtration, washed with diethyl ether ( 6 x 5 mL), and dried under vacuum. Yield: 0.23 g (94%). The physical and spectroscopic data are the same as those determined for the product isolated from the above preparation using the starting material RuCl2(DPPB)(PPh3). 2.5.11.3 Preparation of dichloro(bis(diphenylphosphino)butane)(l,10-phenanthroline)ruthenium(n), RuCl2(DPPB)(phen) (45) Method 1 An excess of 1,10-phenanthroline monohydrate (0.48 g, 2.42 mmol) was added to a dark-green suspension of RuCl2(DPPB)(PPh 3) 3 (0.20 g, 0.23 mmol) in C 6 H 6 (5 mL). The mixture, which immediately turned a cloudy red colour, was stirred at room temperature for 1 h. The resulting red suspension was pumped to dryness, the red residue dissolved in CH2CI2 (3 mL), and EtOH (40 mL) added to precipitate the red product. The solid was collected by vacuum filtration, washed with ethanol ( 4 x 5 mL), and dried under vacuum. Yield: 0.14 g (77%). Calculated for R u C l 2 ( D P P B ) ( p h e n ) , C 4 o H 3 6 N 2 C l 2 P 2 R u : C, 61.70; H, 4.66; N, 3.60; Cl, 9.11%. Found: C, 61.63; H, 4.83; N, 3.60; Cl , 9.00%. 31p{lH} NMR (CDC13, 20 °C): 5 A = 45.1, 5 B = 29.6, 2 / A B = 33.7 Hz. l H NMR of cis-45 (CDC1 3, 20 °C): 5 1.25 ( I H , m, CH of C H 2 of DPPB), 1.74 ( I H , m, CH of C H 2 of DPPB), 1.90-2.37 (3H, m, CH of C H 2 of DPPB), 2.55 ( I H , m, CH 70 Chapter 2 References: p 82 Chapter 2 of C H 2 of DPPB), 3.26 (1H, q, CH of C H 2 of DPPB), 4.02 (1H, m, CH of C H 2 of DPPB), 6.23-10.05 (28H, m, 20 H of Ph of DPPB and 8H of phen). A COSY spectrum in CDCI3 did not allow complete assignment of the aromatic region. The *H NMR spectrum of c/*-45 in CDCI3 is shown in Figure 5.8 (Section 5.4). UV-vis (CH 2C1 2): V a x (nm), e m a x (M"1 cm-1) = 272, 13500; 438, 3900; (MeOH) = 270, 26800; 416, 4300. Conductivity data in MeOH and CH3N0 2 are given in Table 5.2 (Section 5.2). Orange crystals were isolated from an orange MeOH / C H 2 C 1 2 (largely MeOH) solution which had been stored for two months in a fridge. The crystals which were suitable for X-ray diffraction studies showed ds-RuCl2(DPPB)(phen) geometry. The ORTEP plot, as well as selected bond lengths and angles of this complex, are shown in Chapter 5, while the full experimental details and parameters are given in Appendix VII. Method 2 The title complex was also prepared from a different Ru starting material, [RuCl2(DPPB)i.5]2. An excess of 1,10-phenanthroline monohydrate (0.31 g, 1.57 mmol) and [RuCl 2(DPPB)i.5] 2 (0.28 g, 0.17 mmol) were stirred at room temperature in C H 2 C 1 2 (10 mL). The initially green suspension became cloudy red-brown over a period of 1 h. After 4 h, the clear-red solution was reduced to 1-2 mL in volume at the pump, and diethyl ether (15 mL) added to precipitate the product. The red-brown solid was collected by vacuum filtration, and washed with diethyl ether (6x5 mL). To completely remove the excess phenanthroline, the red-brown solid was washed through the filter with C H 2 C 1 2 (5x5 mL), reduced in volume to 1-2 mL, and hexanes (10 mL) were added to precipitate the product. The solid, after isolation by filtration, was washed with ethanol (5 x 2 mL) and hexanes (4x5 mL), and dried under vacuum. Yield: 0.19 g (71%). 31p{lH} NMR (CDCI3, 20 °C): 8 A = 45.1, 5 B = 29.6, 2 7 A B = 33.7 Hz (cis isomer, ~ 70%), plus 6 = 32.5, s (trans isomer, -30%). 71 Chapter 2 References: p 82 Chapter 2 2.5.11.4 Preparation of dichlorobis(pyridine)bis(triphenylphosphine)-ruthenium(II), RuCl 2(py)2(PPh3)2 (46)52 Pyridine (50 pL, 0.62 mmol) was added to a suspension of RuCl2(PPh3)3 (0.20 g, 0.21 mmol). The mixture was refluxed for 3 h. The yellow solid was collected by vacuum filtration, washed with ethanol (4x5 mL), and dried under vacuum. Yield: 0.16 g (88%). Calculated for RuCl2(py)2(PPh3)2, C46H40N2CI2P2RU: C, 64.63; H , 4.72; N, 3.28%. Found: C, 64.52; H, 4.21; N, 2.54%. 31p{lH} NMR (CDCI3, 20 °C): 8 27.7, s (sparingly soluble). l H NMR (CDCI3, 20 °C): 8 6.55 (4H, t, / = 4.5 Hz, meta-py), 6.87-7.56 (32H, m, 30H of Ph of PPh 3 and 2H of para-py), 8.81 (4H, d, J = 4.5 Hz, ortho-py). 52 The complex has been prepared previously, but the NMR spectroscopic data has not been reported. The elemental analysis data are somewhat low in H and N. This may be due to the presence of a small amount of Ru2Cl4(PPh3)4(py); for analogous species see Section 5.2.3. 2.5.12 Reactions of Five-Coordinate Ru(II) Complexes of the Type RuCl2(P)3 and Ru 2Cl 4(DPPB) 2 with Small Gas Molecules 2.5.12.1 RuCl2(PPh3)3 with CO in the solid state Solid RuCi2(PPh3)3 (0.3237 g, 3.376 x 10-4 mol) was stirred in a vial which was placed in a large Schlenk tube (~ 190 mL in volume) under 1 atm of CO. Over a period of 1 week, the brown starting complex slowly became yellow in colour. Yield: 0.3413 g (99.63% based on RuCl2(CO)2(PPh3)2 + PPh 3; 100% should be 0.3426 g). Calculated for RuCl2(CO)2(PPh 3) 2 + PPh 3, C56H45CI2O2P3RU: C, 66.27; H, 4.47; Cl , 6.97%. Found: C, 66.58; H, 4.56; Cl, 7.38%. IR (Nujol, KBr plates; or KBr pellet, cm"1): v ( C=0) at 1944 (br, s), 1978 (br, s), 1993 (br, s) 2041 (s), 2056 (s). 72 Chapter 2 References: p 82 Chapter 2 cis,cis,trans (ccO-RuCl2(CO)2(PPh3)2 (47) The yellow solid (~ 100 mg) obtained above was dissolved in C H C I 3 (5 mL) to give a yellow solution. The solution was stirred at room temperature for 1 h, at which point the solution was almost colourless. Ethanol (20 mL) was added to this solution to precipitate a white solid. The product was collected by vacuum filtration, washed with ethanol ( 3 x 5 mL), and dried under vacuum. The white solid was reprecipitated from CH2CI2 (5 mL) and methanol (20 mL) to give an analytically pure product. Yield: -70 mg (-70%). Calculated for RuCl2(CO)2(PPh3)2, C38H30CI2O2P2RU: C, 60.65; H , 4.02%. Found: C, 60.68; H, 4.04%. IR (Nujol, KBr plates, cm"1): v ( o o ) at 1997 (s) and 2060 (s); (CHCI3 soln, NaCl cell, cm"1): 1994 (s) and 2057 (s). 31 P {1 H }NMR (CDC1 3, 20 °C): 8 = 17.0, s. (CD 2 C1 2 , 20 °C):8 = 21.6, s. ! H NMR (CDC1 3, 20 °C): 8 7.40 (18H, m, ortho- and para-Ph) and 7.98 (12H, m, meta-Ph). The physical and spectroscopic data for this complex agree with those reported in the literature. 3 5' 5 3' 5 4 2.5.12.2 RuCb(P(p-tolyl)3)3 with C O in the solid state Solid RuCl2(P0>tolyl)3)3 (0.3306 g, 3.047 x 10"4 mol) was stirred in a vial which was placed in a large Schlenk tube (~ 190 mL in volume) under 1 atm of CO. Over several hours, the purple starting complex slowly became yellow in colour . The mixture was left stirring for 24 h, and then the product was weighed. Yield: 0.3478 g (100.0% based on RuCl2(CO)2(P(p-tolyl)3)2 + P(p-tolyl)3; 100% should be 0.3477 g). Calculated for RuCl2(CO)2(P(p-tolyl)3)2 + P(p-tolyl)3, C 6 5H 6 3Cl 2 02P3Ru: C, 68.41; H , 5.56%. Found: C, 68.32; H, 5.59%. IR (KBr pellet, cm-1): v (C=0) at 1944 (br, s), 1986 (br, s), and 2049 (s). 73 Chapter 2 References: p 82 Chapter 2 ccc- (70%) and cc?-RuCl2(CO)2(P(p-tolyl)3)2 (30%) (48) The above yellow solid (~ 100 mg) was stirred in CHCI3 (5 mL) for 1 h at room temperature, and the originally yellow solution slowly faded to give an almost colourless solution. The volume of this solution was reduced at the pump to ~ 3 mL, and ethanol (20 mL) added to precipitate the product. The off-white solid was collected by vacuum filtration, washed with ethanol (3x5 mL), and dried under vacuum. The off-white solid was reprecipitated from CH2CI2 (5 mL) and methanol (25 mL) to give an analytically pure product. Calculated for RuCl2(CO)2(P0?-tolyl)3)2, C44H42CI2O2P2RU: C, 63.16; H, 5.06%. Found: C, 62.90; H, 5.06%. IR (Nujol, KBr plates, cm'1): V(c=o) at (1997 (s), 2061 (s); ccMsomer) and (1969 (s), 2033 (s); ccc-isomer); (CHCI3 soln, NaCl cell, cm"1): 1992 (s) and 2055 (s); cct-isomer. 3lp{lH} NMR (CDCI3, 20 °C): 5 = 15.5, s; ccMsomer. ! H NMR (CDCI3, 20 °C): 5 2.35 (18H, s, para-Me), 7.19 (12H, d, J = 10 Hz, meta-Ph), 7.82 (12H, d of d, J = 10 Hz and 3 / H P = 5 Hz, ortho-Ph); ccMsomer. In CHCI3, the ccc-isomer was not observed as it has isomerized to the ccMsomer. 2.5.12.3 RuCl 2(DPPB)(PPh 3) with C O in the solid state This reaction was performed in the same manner as for the above mondentate triarylphosphine-containing analogues. Solid RuCl2(DPPB)(PPh3) (0.05984 g, 6.952 x 10 - 5 mol) was stirred in a vial which was placed in a large Schlenk tube under C O (1 atm). In this case, the dark-green solid became lighter as the reaction proceeded and finally (48 h) became tan. Yield: 0.06205 g (100.4% based on RuCl2(CO)(DPPB)(PPh3); 100% should be 0.06179 g). Calculated for RuCl2(CO)(DPPB)(PPh3), C47H43CI2OP3RU: C, 63.52; H, 4.88; Cl , 7.98%. Found: C, 63.35; H, 4.92; Cl , 7.70%. For RuCl2(CO)2(DPPB) + PPI13 (97.36%; 100% should be 0.06373 g). Calculated for C48H43CI2O2P3RU: C, 62.89; H, 4.73; Cl , 7.73%. 74 Chapter 2 References: p 82 Chapter 2 I R ( K B r pellet, c m - 1 ) : v (c=0) at 1944 (br, s), 2000 (br, s), and 2070 (s). Sect ion 7.2.4 discusses the possible products. 2.5.12.4 Ru2Cl4(DPPB)2 with CO in the solid state S o l i d R u 2 C l 4 ( D P P B ) 2 was left s t irr ing for 6 days under an atmosphere o f C O i n a large Sch lenk tube. The orange starting complex s l o w l y became l ighter i n co lou r over the 6 days , w h e n the atmosphere o f CO was removed under v a c u u m . T h e s o l i d was then d i s so lved i n C D C I 3 . I R (CDCI3 so ln , N a C l c e l l , c m " 1 ) : v ( C =0 ) at 1972 ( R U 2 C J 4 ( D P P B ) 2 ( C O ) ) ; 2024 and 2077 ( ? r a / M - R u C l 2 ( C O ) 2 ( D P P B ) ) . ^ P ^ H } N M R ( C D C I 3 , 20 °C): 5 a , B = 53.4, 2 / A B = unresolved; 8 C = 46.6, 5 D = 34.7; 2 / C D = 29.7 Hz (Ru 2 Ci4 (DPPB ) 2 (CO)) and 8 = 8.1, s ( f r a n s - R u C l 2 ( C O ) 2 ( D P P B ) 49) plus some remaining starting dimer R u 2 C L i . ( D P P B ) 2 at 8 A = 63.5, 8B = 54.3, 2 / A B = 46.9 Hz. I f the starting R u 2 C l 4 ( D P P B ) 2 complex was stirred for longer periods under CO, o n l y f r a n s - R u C l 2 ( C O ) 2 ( D P P B ) 49 and d s - R u C l 2 ( C O ) 2 ( D P P B ) ( 8 A = 32.8, 8 B = 6.9, 2JAB = 31.9 Hz) were evident by 3 1 P{ 1 H} N M R spectroscopy. There was ~ 42% cis-i somer and 58% o f the trans-isomer present i n C D C I 3 . The I R ( C D C I 3 so ln , N a C l ce l l ) o f c w - R u C l 2 ( C O ) 2 ( D P P B ) showed v (c=0) at 2001 and 2009 c m " 1 . 2.5.12.5 RuCl2(PPh3)3 with N H 3 ; Preparation of diamminedichloro(triphenylphosphine)ruthenium(II), RuCl 2(NH 3) 2(PPh 3) 2 (50) A n h y d r o u s NH3 was added v i a a smal l T e f l o n tube to a Schlenk tube con ta in ing a C 6 H 6 (5 m L ) solut ion o f R u C l 2 ( P P h 3 ) 3 (0.23 g , 0.24 m m o l ) . T h e a m m o n i a was f lushed over the so lu t ion for severa l minutes , then the S c h l e n k tube sealed, and the so lu t ion stirred at room temperature for 2 h . T h e cream-coloured so l id that precipi tated dur ing the react ion was co l lec ted by v a c u u m f i l t ra t ion, washed w i t h CfjHg ( 3 x 5 m L ) , and d r i ed 75 Chapter 2 References: p 82 Chapter 2 under vacuum. Yield: 0.13 g (77%). Calculated for RuCl2(NH3)2(PPh3)20.5 C 6 H 6 , C39H39N2CI2P2RU: C, 60.86; H, 5.11; N, 3.64%. Found: C, 61.10; H, 5.11; N, 3.74%. 31p{lH} NMR (CDCI3, 20 °C): 5 = 45.6, s. lH NMR (CDCI3, 20 °C): 5 2.15 (6H, s, Ntf 3), 6.95-7.62 (30H, m, Ph of PPh3); C6H6 solvate was observed as a singlet at 7.36. 2.5.12.6 RuCl2(DPPB)(PPh3) with N H 3 ; Preparation of diamminedichloro(bis(diphenylphosphino)butane)ruthenium(II), RuCl2(DPPB)(NH3)2 (51) Method 1 Anhydrous NH3 was added via a small Teflon tube to a Schlenk tube containing a C6H6 (5 mL) suspension of RuCl2(DPPB)(PPh3) (0.20 g, 0.23 mmol). The ammonia was flushed over the solution for several minutes, then the Schlenk tube sealed, and the solution stirred at room temperature for 24 h. The tan solid that precipitated during the reaction was collected by vacuum filtration, washed with hexanes (3x5 mL), and dried under vacuum. Yield: 0.12 g (82%). Calculated for RuCl2(DPPB)(NH 3) 21.5 C 6 H 6 , C37H43N2CI2P2R11: C, 59.27; H, 5.78; N, 3.74%. Found: C, 59.08; H, 5.76; N, 3.81%. 3 1P{!H} NMR (CDCI3, 20 °C): 5 = 46.7, s. *H NMR (CDCI3, 20 °C): 6 1.62 (4H, br m, CH2 of DPPB), 2.03 (6H, s, Ntf 3), 2.90 (4H, br m, CH2 of DPPB), 7.23-7.75 (20H, m, Ph of DPPB); C 6 H 6 solvate was observed as a singlet at 7.36. Conductivity data in MeOH and CH3NO2 are given in Table 5.2 (Section 5.2). Method 2 An alternative preparation is from [RuCl2(DPPB)i.5]2. Anhydrous NH3 was bubbled through a green suspension of [RuCl2(DPPB)i.5]2 (0.24 g, 0.15 mmol) in CH2CI2 (10 mL) for 2-3 min, and the mixture stirred at room temperature. After 5 h, the volume of the blue-green solution was reduced to ~ 2-3 mL, and diethyl ether (15 mL) added to precipitate the product. The tan solid was collected by vacuum filtration, washed 76 Chapter 2 References: p 82 Chapter 2 with diethyl ether (4x5 mL) and hexanes (5 mL), and dried under vacuum. Yield: 0.16 g (86%). The spectroscopic data were the same as those recorded for the solid isolated in Method 1. Method 3 A third method of preparation for compound 51 was from either RuCl2(DPPB)(PPh3) or Ru2Ci4(DPPB)2. Anhydrous ammonia was bubbled through a CDCI3 solution (~ 10 mM) of RuCl 2(DPPB)(PPh 3) or Ru2CLi(DPPB)2 for 2 min. An immediate colour change from the green (RuCl 2 (DPPB)(PPh 3 ) ) or orange (Ru2CL;(DPPB)2) to blue-green occurred on addition of N H 3 . The X H and 3 1P{!H} NMR spectroscopic data were as given above. Method 4 A vial containing RuCl2(DPPB)(PPh3) (0.04041 g, 4.695 x 10~5 mol) and a stir-bar were weighed and placed in a large-mouthed Schlenk tube. The tube was evacuated and anhydrous N H 3 added. The starting green solid immediately became brown. The solid was left stirring under an atmosphere for 24 h, and then the product was weighed. Yield: 0.04278 g (101.8% based on RuCl 2 (DPPB)(NH 3 ) 2 + PPh 3 ; 100% should be 0.04201 g). The solution spectroscopic data agree with those for the solid isolated from the reactions in solution (Methods 1-3). 2.5.13 Preparation of <rans-RuCl2(DPPCP)2 (52) Method 1 The complex fra/u-RuCl 2(DPPCP) 2 was isolated in an attempt to synthesize a mixed-phosphine complex of the formula RuCl2(DPPCP)(PPh3). The racemic phosphine, DPPCP (0.12 g, 0.26 mmol), and RuCl 2(PPh 3) 3 (0.26 g, 0.27 mmol) were dissolved in C H 2 C 1 2 (10 mL) and the solution stirred at room temperature. After two hours, the brown suspension was concentrated to about 5 mL at the pump. Ethanol (10 mL) was added to 77 Chapter 2 References: p 82 Chapter 2 precipitate a beige solid, which was collected by vacuum filtration, washed with ethanol (2x5 mL), and dried under vacuum. Yield: 0.050 g (36% based on the amount of starting phosphine). Method 2 Alternatively, the title complex could be prepared from RuCl 3 xH20 (0.25 g, 1.0 mmol; 41.50% Ru) and DPPCP (0.93 g, 2.1 mmol) in ethanol (25 mL). The resulting dark-orange reaction mixture was refluxed for 5 h. A light-coloured solid, which precipitated during the reaction, was collected by vacuum filtration, then washed with ethanol (10 mL), and dried under vacuum. Yield: 0.72 g (67%). Calculated for C58H56CI2P4RU: C, 66.41; H, 5.38; Cl, 6.76%. Found: C, 66.16; H, 5.36; Cl 7.03%. 31p{lH} NMR (CDCI3, 20 °C): 8 = 22.8 and 23.3, s; see Section 3.10.1 for assignment and discussion. ! H NMR (CDCI3 20 °C): 5 0.55 (2H, br m, CH2 of DPPCP), 1.30 (4H, br m, CH2 of DPPCP), 1.62 (4H, br m, CH2 of DPPCP), 1.83 (2H, br m, CH2 of DPPCP), 3.55 (4H, br m, CH of DPPCP), 6.80-7.90 (40H, m, Ph of DPPCP). 2.5.14 Reactions of RuCl2(DPPB)(PPh3) with Chelating Phosphines (P-P); Formation of RuCl2(DPPB)(P-P) 2.5.14.1 P-P = DPPCP, fra/w-RuCl2(DPPB)(DPPCP) (53) One equivalent of the bidentate phosphine, r a c-1,2-bis(diphenylphosphino)cyclopentane (DPPCP) (0.12 g, 0.28 mmol) was added to RuCl2(DPPB)(PPh3) (0.22 g, 0.25 mmol) in C 6 H 6 (30 mL). The initially green solution was stirred at room temperature for 1 h over which time it turned orange-brown in colour. The solution was then reduced in volume to ~ 5 mL, and hexanes (35 mL) were added to precipitate a beige solid, which was collected on a sintered glass filter, washed with hexanes ( 3 x 5 mL), and dried under vacuum. Yield: 0.19 g (73%). Calculated for C57H56CI2P4RU: C, 66.02; H, 5.44; Cl, 6.84%. Found: C, 66.23; H, 5.60; Cl, 7.00%. 78 Chapter 2 References: p '82 Chapter 2 3 1P{!H} NMR (CDCI3, 20 °C): a complicated second-order AA'BB' pattern is observed (Figure 3.27), and this will be discussed later in Section 3.9. l H NMR (CDCI3 20 °C): 8 0.65 (2H, br m, CH2 of DPPCP), 1.32 (4H, br m, CH2 of DPPB), 2.12 (2H, br m, CH2 of DPPCP), 2.19 (2H, br m, CH2 of DPPCP), 2.25 (2H, br m, CH2 of DPPB), 2.69 (2H, br m, CH2 of DPPB), 3.45 (2H, br m, CH of DPPCP), 6.42-8.02 (40H, m, Ph of DPPB and DPPCP). 2.5.14.2 P-P = DPPE, *ra#is-RuCl2(DPPE)2 (54) One equivalent of DPPE (0.98 g, 0.25 mmol) and RuCl2(DPPB)(PPh3) (0.24 g, 0.28 mmol) were dissolved in C^H^ (30 mL). After being stirred at room temperature for 2 h, the solution was concentrated to ~ 5 mL at the pump, and hexanes (35 mL) were added to precipitate the product. The pale yellow-green solid was collected by vacuum filtration, washed with hexanes (3x5 mL), and dried under vacuum. Yield: 0.10 g (40% based on Ru). 3 1P{!H} NMR (CDCI3, 20 °C): 45.0, s. ! H NMR (CDC1 3, 20 °C): 8 2.72 (8H t, J = 7.4 Hz, CH2 of DPPE), 6.80-7.42 (40H,m,PhofDPPE). The physical and spectroscopic data for this complex agree with those reported in the literature. ' ' This compound, previously prepared from RuCl 3 xH20, RuCl 2(PPh 3)3, J O and Ru 2CU(C6H 6)2, J was recently characterized by crystallography. 2.5.15 Preparation of Ru(P-P)(ri3-allyl)2 Complexes 2.5.15.1 P-P = DPPB, allyl = Me-allyl; Preparation of Ru(DPPB)(T|3-Me-allyl)2 (55) The title complex was prepared from Ru(COD)(Me-allyl)2 using a modified preparation of that used by Genet et al. for the synthesis of complexes of the type Ru(P-P)(Me-allyl)2, containing a wide variety of chiral phosphines. 3 0' 5 7' 5 8 One equivalent of 79 Chapter 2 References: p 82 Chapter 2 DPPB (0.13 g, 0.31 mmol) and Ru(C0D)(Me-allyl)2 (0.10 g, 0.31 mmol) were dissolved in CH2CI2 (1 mL) and heated in a Schlenk tube to 40 °C under a flow of Ar. The colourless solution slowly became yellow. After the reaction mixture was heated for 18 h, the solvent was removed under vacuum. The yellow solid was transferred onto a filter, washed with hexanes (4 x 2 mL) and diethyl ether (2x2 mL), and dried under vacuum. Yield: 0.15 g (76%). Calculated for Ru(DPPB)(Me-allyl)2, C3 6H42P2Ru: C, 67.80; H , 6.64%. Found: C, 67.52; H, 6.64 %. 31p{lH}NMR ( C 6 D 6 , 20 °C): 44.2, s. (CDC1 3,20 °C):44 .1 , s . l H NMR ( C 6 D 6 , 20 °C): 8 1.09 (2H, AB quartet, CH of Me-allyl), 1.43 (2H, s, CH of Me-allyl), 1.49 (2H, s, CH of Me-allyl), 1.55 (2H, br m, CH2 of DPPB), 1.70 (2H, br m, CH2 of DPPB), 2.10 (6H, s, CH3 of Me-allyl), 2.19 (2H, br m, CH2 of DPPB), 2.52 (2H, s, CH of Me-allyl), 2.59 (2H, br m, CH2 of DPPB), 6.85-7.37 (16H, m, ortho- and meta-Ph of DPPB), 7.86 (4H, t, J = 8.8 Hz, para-Ph of DPPB). 2.5.15.2 P-P = DPPB, allyl = allyl; Attempted Preparation of Ru(DPPB)(r(3-allyl)2 One equivalent of DPPB (0.37 g, 0.87 mmol) and Ru(COD)(T|3-allyl)2 (0.26 g, 0.89 mmol) were refluxed in benzene / hexanes (5 mL / 10 mL) for 5 h. The yellow solution was cooled to room temperature, and an aliquot taken for a 31p{lH} NMR spectrum. The spectrum in CDCI3 showed only the presence of free DPPB. Therefore, no reaction had taken place. This synthesis was not pursued further, as Ru(COD)(r|3-Me-allyl)2 proved to be a much better starting material for the synthesis of Ru(P-P)(r|3-allyl)2 type species. As in the case of Ru(DPPB)(r|3-Me-allyl)2, the synthesis of the title complex was attempted by modifying a procedure published by Genet et al. for complexes of the type Ru(P-P)(r(3-allyl)2 containing chiral diphosphines.58 80 Chapter 2 References: p 82 Chapter 2 2.5.15.3 P-P = (fl)-BINAP, allyl = Me-allyl; Preparation of Ru((/?)-BINAP)(Ti3-Me-allyl)2 (56) The title complex was synthesized by modifying a procedure reported by Genet et a l 30,57 Q n e e q u i v a i e n t 0 f (#)-BINAP (0.15 g, 0.24 mmol) and Ru(COD)(ri3-Me-allyl)2 (0.078 g, 0.24 mmol) were refluxed in C7H.8 (2 mL) for 4 h. The resulting orange-brown solution was reduced to dryness at the pump, and the dark-orange residue was placed on a filter and washed with hexanes (4x2 mL). The bright-orange washings were reduced to dryness at the pump. The brown solid remaining on the filter was dried under vacuum. 3lp{ lH} NMR (C6D 6, 20 °C) of the dark-orange residue: 5 = 42.1, s, plus another singlet resonance at 8 = -15.0 indicating some free BINAP. 31p{lH} NMR ( C 6 D 6 , 20 °C) of the brown solid: 8 = 42.1, s, plus two other singlet resonances at 8 = -15.0 (free BINAP) and 8 = 26.6 (BINAP(0)2). An orange crystal suitable for X-ray diffraction studies was deposited from a C 6 D 6 solution which showed singlets for BINAP, BINAP(0) 2 , and Ru(BINAP)(r|3-Me-allyl)2 in the 31p{If!} NMR spectrum. The crystal was deposited from the NMR solution over a period of several weeks, over which time the NMR solution had changed from orange to dark green in colour. The solution of the X-ray diffraction data showed the unit cell of the crystal to be composed of half of a Ru((/?)-BINAP)(r|3-Me-allyl)2 molecule and half of a (7?)-(+)-2,2'-bis(diphenylphosphinoyl)-l,r-binaphthyl molecule, co-crystallized with two disordered deuterobenzene regions (see Section 3.3.4.3 for discussion and Appendix IV for complete experimental details and parameters). The 31p{ Iff} NMR data are in agreement with those previously reported in the literature, although no assignments were given. 3 0' 5 7 81 Chapter 2 References: p 82 Chapter 2 2.6 References (1) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals; 2nd ed.; Pergamon: Oxford, 1980. (2) Allen, D. L.; Gibson, V. C ; Green, M . L. H.; Skinner, J. F.; Bashkin, J.; Grebenik, P. D. J. Chem. Soc, Chem. Commun. 1983, 895. (3) Priemer, H. Ph.D. Thesis, der Ruhr-Universitat Bochum, 1987. (4) Chau, D. E. K.-Y. M.Sc. Thesis, The University of British Columbia, 1992. (5) Fogg, D. Ph.D. Thesis, The University of British Columbia, 1994. (6) Evans, D. F. J. Chem Soc. 1959, 2003. (7) Live, D. H.; Chan, S. I. Anal. Chem. 1970, 42, 791. (8) Gordon, A. J.; Ford, R. A. In The Chemist's Companion: A handbook of practical data, techniques and references; Wiley: New York, 1972, p 374. (9) Jolly, W. L. In Synthetic Inorganic Chemistry; Prentice-Hall: Englewood Cliffs, N.J., 1960, p 142. (10) Keller, R. N.; Wycoff, H. D. Inorg. Synth. 1946, 2, 1. (11) Costa, G.; Pellizer, G.; Rubessa, F. J. Inorg. Nucl. Chem. 1964, 26, 961. (12) Glockling, F.; Hooton, K. A. J. Chem. Soc. 1962, 2658. (13) Costa, G.; Reisenhofer, E.; Stefani, L. J. Inorg. Nucl. Chem. 1965, 27, 2581. (14) Dixon, K. R. In Multinuclear NMR; Mason, J., Ed.; Plenum: New York, 1987; Chapter 13. (15) James, B. R.; Rempel, G. L. Disc. Faraday Soc. 1968,46, 48. (16) James, B. R.; Rempel, G. L. Can. J. Chem. 1966,44, 233. (17) Lind, J. E. , Jr.; Zwolenik, J. J.; Fuoss, R. M . J. Am. Chem. Soc 1959, 81, 1557. (18) Fogg, D. E.; James, B. R.; Kilner, M . Inorg. Chim. Acta 1994,222, 85. (19) Shriver, D. F.; Drezdon, M . A. The Manipulation of Air-Sensitive Compounds; 2nd ed.; Wiley: New York, 1986. (20) Stephenson, T. A.; Wilkinson, G. J. Inorg. Nucl. Chem. 1966,28, 945. (21) Thorburn, I. S. Ph.D. Thesis, The University of British Columbia, 1985. (22) Joshi, A. M . Ph.D. Thesis, The University of British Columbia, 1990. 82 Chapter 2 (23) Wang, D. K. W. Ph.D. Thesis, The University of British Columbia, 1978. (24) Dekleva, T. W.; Thorburn, I. S.; James, B. R. Inorg. Chim. Acta 1985,100, 49. (25) Markham, L. D. Ph.D. Thesis, The University of British Columbia, 1973. (26) Skapski, A. C ; Troughton, P. G. H. J. Chem. Soc, Chem. Commun. 1968, 1230. (27) Hallman, P. S.; McGarvey, B. R.; Wilkinson, G. J. Chem. Soc. (A) 1968, 3143. (28) Markham, L. D.; James, B. R. J. Catal. 1972, 27, 442. (29) Bennett, M . A ; Wilkinson, G. Chem. Ind. (London) 1959, 1516. (30) Genet, J. P.; Pinel, C ; Ratovelomanana-Vidal, V.; Mallart, S.; Pfister, X.; Cano De Andrade, M . C ; Laffitte, J. A. Tetrahedron: Asymmetry 1994, 5, 665. (31) Schrock, R. R ; Johnson, B. F. G.; Lewis, J. J. Chem. Soc, Dalton Trans. 1974, 951. (32) Powell, J.; Shaw, B. L . J. Chem. Soc. (A) 1968, 159. (33) Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth. 1970,12, 237. (34) Hoffman, P. R.; Caulton, K. G. J. Am. Chem. Soc. 1975, 97, 4221. (35) Dekleva, T. W. Ph.D. Thesis, The University of British Columbia, 1983. (36) Knoth, W. H. J. Am. Chem. Soc. 1972, 94, 104. (37) Armit, P. W.; Sime, W. J.; Stephenson, T. A.; Scott, L . J. Organomet. Chem. 1978,161, 391. (38) Jung, C. W.; Garrou, P. E.; Hoffman, P. R.; Caulton, K. G. Inorg. Chem, 1984, 23, 726. (39) Joshi, A. M . ; Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chim. Acta 1992, 198, 283. (40) Mezzetti, A.; Costella, L. ; Del Zotto, A.; Rigo, P.; Consiglio, G. Gazz. Chim. Ital. 1993,123, 155. (41) Hampton, C. R. S. M . Ph.D. Thesis, The University of British Columbia, 1989. (42) James, B. R.; Thompson, L . K.; Wang, D. K. W. Inorg. Chim. Acta 1978, 29, L237. (43) Hampton, C. R. S. M . ; Butler, I. R.; Cullen, W. R.; James, B. R.; Charland, J.-P.; Simpson, J. Inorg. Chem 1992, 31, 5509. (44) Chau, D. E. K.-Y.; James, B. R. Inorg. Chim. Acta in press. (45) Hampton, C ; Dekleva, T. W.; James, B. R ; Cullen, W. R. Inorg. Chim. Acta 1988,145, 165. 83 Chapter 2 (46) Bressan, M. ; Rigo, P. Inorg. Chem. 1975,14, 2286. (47) James, B. R.; McMillan, R. S.; Morris, R. H.; Wang, D. K. W. Adv. Chem. Ser. 1978,167, 122. (48) Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chem. 1986, 25, 234. (49) James, B. R ; Pacheco, A.; Rettig, S. J.; Thorburn, I. S.; Ball, R. G.; Ibers, J. A. J. Mol. Catal. 1987, 41, 147. (50) Batista, A. A ; Queiroz, S. L. ; Oliva, G.; Santos, R. H. A.; Gambardella, M . T. d. P. 5th Int. Conf. Chemistry of Platinum Metals, St. Andrews, UK; 1993; Abstract A40. (51) Batista, A. A ; Queiroz, S. L.; Oliva, G.; Gambardella, M . T. d. P.; Santos, R. H. A., personal communication. (52) Gilbert, J. D.; Wilkinson, G. J. Chem. Soc. (A) 1969, 1749. (53) Krassowski, D. W.; Nelson, J. H.; Brower, K. R ; Havenstein, D.; Jacobson, R. A. Inorg. Chem. 1988,27, 4294. (54) Batista, A. A ; Zukerman-Schpector, J.; Porcu, O. M . ; Queiroz, S. L. ; Araujo, M . P.; Oliva, G.; Souza, D. H. F. Polyhedron 1994,13, 689. (55) Mason, R.; Meek, D. W.; Scollary, G. R. Inorg. Chim. Acta 1976,16, LI 1. (56) Polam, J. R.; Porter, L. C. J. Coord. Chem. 1993, 29, 109. (57) Genet, J. P.; Pinel, C ; Mallart, S.; Juge, S.; Thorimbert, S.; Laffitte, J. A. Tetrahedron: Asymmetry 1991, 2, 555. (58) Genet, J. P.; Mallart, S.; Pinel, C ; Juge, S.; Laffitte, J. A. Tetrahedron: Asymmetry 1991,2, 43. 84 CHAPTER 3 SYNTHESIS AND REACTIVITY OF FIVE-COORDINATE RUTHENIUM(II) DITERTIARY PHOSPHINE COMPLEXES 3.1 Introduction Interest in ruthenium(II) complexes containing a ditertiary phosphine ligand as catalysts for homogeneous hydrogenation began in the late 1970s.1 The success of rhodium complexes containing chiral bidentate phosphines as catalysts for enantioselective hydrogenation of prochiral unsaturated substrates is evident from several commercial processes employing these systems as catalysts, as well as numerous publications in this area. Enantioselectivities of up to 100% e.e. have been achieved with rhodium catalysts for various substrates. Researchers have been actively studying the effect of substituting other transition metals for Rh in these chiral ligand systems. Ruthenium is of particular interest, due to its effectiveness as an achiral hydrogenation catalyst for terminal alkenes (cf. Ru(H)Cl(PPh3)3 vs. RhCl(PPh3)3),3"5 and because it is relatively inexpensive. Ruthenium has developed a rich coordination and organometallic chemistry over the years. Reports on the synthesis, properties, reactivity, and catalytic applications of ruthenium complexes containing tertiary phosphine ligands are numerous.6"11 Recently, the success of ruthenium-chiral phosphine complexes for asymmetric hydrogenation 1 ? (especially Ru-BINAP systems) has stimulated increased interest in the synthesis, reactivity, and catalytic activity of ditertiary phosphine ruthenium complexes. The chemistry that will be discussed in this chapter is the result of several observations of coordinatively unsaturated species in a catalytic environment. Coordinative unsaturation is thought to be necessary at some stage of a catalytic cycle for a complex to act as an effective catalyst. In this laboratory, mechanistic studies on ?rans-Ru(H)Cl(DIOP)2, which was shown to be a "catalyst" for the asymmetric Chapter 3 References: p 157 85 Chapter 3 hydrogenation of prochiral olefinic carboxylic acids, revealed the active catalyst to be ["Ru(H)Cl(DIOP)"]. 1 , 1 4' 1 5 More recently, a catalytic system for the enantioselective hydrogenation of similar alkenes using frans-Ru(H)Cl(BINAP)2 as the catalyst precursor shows the probable active catalytic species to be ["Ru(H)Cl(BINAP)"].16 The above two examples show that coordinatively unsaturated complexes are important for an active catalytic species. Similar fra«5 ,-Ru(H)Cl(P-P)2 complexes, where P-P is CHIRAPHOS or Ph2P(CFJ.2)nPPh2 with n = 1-3, exhibit little activity as catalysts for alkene hydrogenation, possibly because the phosphines are bound to the metal centre too -I c -in IQ strongly to allow an unsaturated, and thereby active, complex to be formed. ' ' The synthetic methodology discussed in this chapter is an ongoing study to develop preparative routes to coordinatively unsaturated ruthenium complexes containing a single, chelating ditertiary phosphine per metal centre. The five-coordinate ruthenium(II) complexes containing such a diphosphine that have been reported to date are shown in Figure 3.1. P kNx\Cl P _ p = D I O P or Ph2P(CH2)nPPh2 where n = 4, DPPB; 5, DPPN; 6, DPPH *V I > a Ru C l ^ ^ P P h , P—P = DPPB, DIOP, BINAP, or BIPHEMP Cl R u _ ^ R u , 'CT ^ C l P—P = DPPP, DPPB, DPPN, BINAP*, CHIRAPHOS, or BDPP * of different geometry, see Figure 3.5 Figure 3.1 Five-coordinate ruthenium(II) complexes containing a diphosphine that have been reported to date. 1 5' 1 7' 1 9" 2 6 86 Chapter 3 References: p 157 Chapter 3 3.2 Synthesis and Characterization of Ru2Cl5(P-P)2, Ru2Cl4(P-P)2, and [Ru(H)Cl(P-P)b Complexes-A Brief Review T h e route to R u 2 C l 5 ( P - P ) 2 , and subsequent reduc t ion to R u 2 C i 4 ( P - P ) 2 , were rye deve loped i n this laboratory by Thorbu rn et a l . , ' w h o also deve loped a l o w - y i e l d route (10%) f rom Ru2CU(P-P)2 to the tr inuclear species [ R u ( H ) C l ( P - P ) ] 3 , where P - P = D P P B or C H I R A P H O S . 2 6 J o s h i et a l . then ex tended the range o f R u 2 C l s ( P - P ) 2 and Ru2CU(P-P)2 22 23 c o m p l e x e s to i nc lude other c h i r a l and ach i ra l b is (phosphines) . ' T h e y i e l d o f the 22 t r i ruthenium c o m p l e x [ R u ( H ) C l ( P - P ) ] 3 was improved to 5 0 % by Joshi . S o m e analogous R u chemis t ry i n v o l v i n g monodentate phosphines was k n o w n before T h o r b u r n started his w o r k . T h e species Ru2CL|.(PR3)4> w h i c h is a monodentate analogue o f R u 2 C l 4 ( P - P ) 2 , cou ld be prepared by reduction o f R u C i 3 ( P R 3 ) 2 . 2 7 ' 2 8 A n attempt to prepare R u C l 3 ( P - P ) complexes by phosphine displacement w i t h i n R u C l 3 ( P R 3 ) 2 species l ed to the i so la t ion o f the fo rma l ly mixed-va lence d inuclear R u 1 1 ' 1 1 1 compounds , Ru2Cl s (P -P )2 (Figure 3.2) 2 3 ' 2 5 ' 2 9 2 R u 2 C l 5 ( P — P ) 2 + 0 = P R 3 . „ „ , / r m , . „ hexanes, reflux 4 R u C l 3 ( P R 3 ) 2 + 4 P — P T T _ + i V 5 ' 1 trace H 2 0 7 P R 3 + 2 H C 1 R = phenyl , p - t o l y l P — P = D P P P , D P P B , D I O P , C H I R A P H O S , or N O R P H O S F igure 3.2 Reac t ion o f one equivalent o f diphosphine w i t h R u C l 3 ( P R 3 ) 2 . J o s h i et a l . subsequently extended this series o f mixed-va lence c o m p l e x e s to i n c l u d e : D P P N , D P P H , D P P C P , D C Y P C P , B D P P , B I N A P , and P H E N O P . 2 2 ' 2 3 87 Chapter 3 References: p 157 Chapter 3 An X-ray diffraction analysis of Ru2Cl5(CHIRAPHOS)2 showed the complex to be a highly symmetric trichloro-bridged species with irregular octahedral geometry around each ruthenium centre (Figure 3.3). ' P - P = ( S , S ) - C H I R A P H O S Figure 3.3 Geomet ry o f the R u 2 C l 5 ( ( S , S ) - C H I R A P H O S ) 2 c o m p l e x . T h e reduct ion o f these mixed-va lence R u 2 C l 5 ( P - P ) 2 complexes w i t h H2 i n the presence o f a base gave the target "RuCl2(P-P)" species as d i c h l o r o - b r i d g e d d imers (Figure 3.4) . 2 5 ' 2 9 P—P = DPPP, DPPB, DIOP, or CHIRAPHOS Figure 3.4 Suggested geometry for Ru2Cl4(P-P)2 complexes. Joshi extended the series of Ru2CU(P-P)2 complexes to include: DPPN, (R)- and (S)-BINAP, and (S,S)-BDPP 2 2 ' 2 3 The BINAP species Ru2Cl4(BINAP)2 is thought to differ slightly in geometry from the other dimers based on 3 1P{!H} NMR spectral evidence (Figure 3 . 5 ) 2 2 ' 2 3 88 Chapter 3 References: p 157 Chapter 3 Cl C L C l Ru ***//cl^*" '""//p. P—P = (/?)- and (S)-BINAP Figure 3.5 Suggested geometry for the R ^ C L ^ B I N A P ^ complex. The preparative chemistry leading from RUCI3XH2O to Ru2Cl5(P-P)2, and subsequently to Ru2Cl4(P-P)2, is shown in Figure 3.6. R u C l 3 x H 2 0 + 2PR3 D M A 24 h, 25 °C RuCl 3(PR 3) 2(DMA) D M A solvate 50-70% D M A = A^N-dimethylacetamide R = phenyl or p-tolyl P-P (1 equiv / Ru111) hexanes, reflux 24 h 1 atm H 2 , 16 h, 25 °C Ru 2 Cl 4 (P-P) 2 40-85% — Ru 2 Cl 5 (P-P) 2 45-85% baseHCl base base = D M A for achiral diphosphines and polyvinylpyridine for chiral diphosphines Figure 3.6 Reaction pathway from RUCI3-XH2O to Ru2Cl5(P-P)2 and Ru2Cl4(P-P)2 complexes. It is interesting to note that Thorburn was unable to prepare Ru2Cl5(DPPE)2-25 This was unexpected, as the CHIRAPHOS analogue was prepared by this route, and DPPE and CHIRAPHOS both form five-membered chelate rings upon binding to the metal centre. DPPE differs from CHIRAPHOS only in having hydrogens in place of 89 Chapter 3 References: p 157 Chapter 3 methy l groups i n the carbon backbone. Recent ly , some pre l iminary experiments by F o g g 30 produced some R u 2 C l 5 ( D P P E ) 2 . In these studies, the reac t ion was pe r fo rmed i n CH2CI2 at r o o m temperature instead o f a re f luxing procedure i n hexanes. H o w e v e r , the R u 2 C l 5 ( D P P E ) 2 was not separated from some ? r a / « - R u C l 2 ( D P P E ) 2 , w h i c h was the sole 25 product ident i f ied by Thorburn when this reaction was performed i n hexanes. T h e neut ra l d i r u t h e n i u m c o m p l e x e s R u 2 C l 4 ( P - P ) 2 were i n i t i a l l y f o u n d b y Thorbu rn , and extended later by Josh i and F o g g , to react w i t h a var ie ty o f neutral two-electron donors (Figure 3.7) . 2 2 > 2 3 > 2 5 > 3 0 P -A ^Y'>w > R V ^ = , P A ^ R u \ ^ R U ^ ! « P D B PI I ^ c r ^ c i t_pf >• *A P-P = DPPB L = DMA, CO, Me2CO, Me2SO, MeCN, PhCN, N 2 , or H 2 Figure 3.7 Reaction of Ru2Cl4(P-P)2 with neutral ligand L to form Ru2CU(P-P)2(L) complexes. Forma t ion o f the t r ip ly-ch loro-br idged products was eas i ly assessed by 3 1 P { 1 H } N M R spec t roscopy, as these products gave spectra cons i s t i ng o f t w o A B quartets corresponding to the two ends o f the dinuclear complex . Occas iona l ly , some species gave 3 1 P { lH} N M R spectra w h i c h d id not consist o f the two A B patterns (e.g., for L = N E t 3 ) , and the s inglet observed i n the phosphorus N M R spectra was thought to be due to an exchange process (see Sect ion 3.4 for details). Some o f the R u 2 C l 4 ( P - P ) ( L ) species were observed i n s i tu, w h i l e others were isolated as s o l i d s . 2 2 ' 2 3 ' 2 5 ' 3 0 T h e isola ted R u 2 C l 4 ( P -P )2 (L) species inc lude : L = C O , Me2CO, Me2SO,.NEt3, M e C N , and P h C N . It shou ld be noted that not a l l o f the R u 2 C L ; ( P - P ) 2 ( L ) species were formed di rec t ly f rom R u 2 C l 4 ( P -P)2- Some o f the complexes were prepared from R u C l 2 ( P - P ) ( P P h 3 ) (see Sec t ion 3.3.3). 90 Chapter 3 References: p 157 Chapter 3 A n X - r a y crys ta l structure determinat ion o f R u 2 C l 4 ( D P P B ) 2 ( D M S O ) , p roduced by the add i t ion o f one equivalent o f D P P B to cz ' s -RuCl2(DMSO)4, revea led that the 22 23 geometry around each R u centre is irregular octahedral (Figure 3.8). ' 0 = s \ / p - ) p j n i i ^ R u - ^ R u ^ i i u / p C p ^ Cl ^ C l P-P = DPPB Figure 3.8 Geomet ry o f the R u 2 C U ( D P P B ) 2 ( D M S O ) complex . C o m p a r i s o n o f this geometry w i t h that seen for R u 2 C l 5 ( C H I R A P H O S ) 2 (F igure 3.3) shows one s t r ik ing difference. U n l i k e the h igh ly symmetr ica l C H I R A P H O S complex , the p o s i t i o n i n g o f the d iphosphines i n the D P P B c o m p l e x is u n s y m m e t r i c a l : one o f the 99 9^ octahedra has been rotated by 120° around the R u - R u vector. ' T h e analogous th iocarbonyl complex Ru2Cl4(PPh3)4(CS) reported by Fraser and r G o u l d also shows a s i m i l a r unsymmet r i ca l arrangement o f the PPI13 l i gands (F igure 3.9).31 P h 3 P » » ^ R u \ ^ R u ^ » « P P h i P h , P ^ Cl ^ C l Figure 3.9 Geomet ry o f the Ru2CU(PPh 3 )4(CS) complex . T h e tr i ruthenium species [ R u ( H ) C l ( P - P ) ] 3 synthesized by T h o r b u r n was i n i t i a l l y obta ined o n l y i n l o w y i e ld s (10%) f rom R u 2 C l 4 ( P - P ) 2 (F igure 3.10).26 T h e 3 1 P { ! H } N M R spectrum o f this [ R u ( H ) C l ( D P P B ) ] 3 complex first suggested a nuclear i ty o f greater than t w o , and this w a s c o n f i r m e d b y an X - r a y s tructure d e t e r m i n a t i o n o f the 91 Chapter 3 References: p 157 Chapter 3 CHIRAPHOS complex (Figure 3.II). 2 6 The placement of the hydrides is based on selective 1 H{ 3 1 P} NMR studies,22 as well as on the X-ray crystallography-determined framework. Ru 2 Cl 4 (P-P) 2 ( l ) 2 N E t 3 , C 6 H 6 (2) H 2 , 24 h, 25 °C route (a) route (b) (1) H 2 , C 6 H 6 , 1 h, 25 °C (2) 2NEt 3 ,23h • [Ru(H)Cl(P-P)]3 5-10% + [HNEt 3 ] + [Ru 2 Cl 4 (P-P) 2 r + NEt 3 H + Cl" [Ru(H)Cl(P-P)]3 50% + [HNEt 3] + [Ru2Cl5(P-P)2]~ + N E t 3 H + C r Figure 3.10 Synthesis of [Ru(H)Cl(P-P)]3 from Ru2CU(P-P)2, where P-P = DPPB, DIOP or CHIRAPHOS; (a) original synthetic method;26 (b) improved 22 synthesis developed by Joshi. Figure 3.11 Geometry of the [Ru(H)Cl(P-P)]3 complexes (based on the X-ray structure of the CHIRAPHOS derivative26 and phosphorus-decoupled proton NMR studies) 22 92 Chapter 3 References: p 157 Chapter 3 Joshi improved the synthesis of the trinuclear species, [Ru(H)Cl(P-P)]3, to 50% 22 by reversing the order of the addition of base and H.2 (Figure 3.10). The amine-containing co-product in the DPPB system was originally thought by Thorburn and Joshi to be the neutral Ru2CU(DPPB)2(NEt3) complex as judged by comparison of the 3 1P{!H} NMR spectrum with that of an authentic sample (Section 2.5.8.1). Also, the *H NMR spectrum showed the presence of amine. However, elemental analysis of the orange solid in this work showed that the complex is actually the ionic complex [HNEt3]+[Ru 2Cl 5(DPPB)2]- (Section 2.5.9.5). The 3 1P{!H} and lH NMR are essentially the same as those observed earlier by Thorburn and Joshi, but the 3 1 P{ 1 H} NMR spectroscopic studies are uninformative in distinguishing between the neutral and ionic complexes. The addition of one equivalent of NEt3-HCl to Ru2Cl4(DPPB) 2 in C D C I 3 produced an orange solution, which after 2 h at room temperature gave a singlet in the 3 1P{!H} NMR spectrum, strongly suggesting [HNEt3]+[Ru2Cl5(DPPB)2]~ formation. 3.3 Routes into the Bromide Analogues and Related Chemistry 3.3.1 Ruthenium(III) Bromide Complexes, RuBr3(PPh3)2 The logical entry point into the bromide analogues of the "RuCl(P-P)" species was to follow the route outlined in Figure 3.6 by first synthesizing the known complex RuBr 3(PPh 3) 2 (i.e., RuBr 3(PPh 3) 2(MeOH)) from R u C l 3 x H 2 0 , LiBr, and P P h 3 . 3 2 Unfortunately, there were many problems associated with this route (outlined below). Several sets of conditions were tried in attempting to prepare pure RuBr 3(PPh 3)2(DMA)DMA solvate or RuBr3(PPh 3) 2(MeOH). One such method is outlined in detail (Section 2.5.1.3). Various other conditions were attempted, and are summarized in equations 3.1-3.4. M e O H R u C l 3 x H 2 0 + xsLiBr + 2PPh3 » RuBr 3(PPh 3) 2(MeOH) (3.1) 93 Chapter 3 References: p 157 Chapter 3 R u C l 3 x H 2 0 + xs LiBr + 2PPh 3 D M A RuBr 3(PPh 3) 2(DMA)-DMA solvate (3.2) R u B r 3 x H 2 0 + 2PPh 3 MeOH RuBr3(PPh3)2(MeOH) (3.3) RuBr 3 xH 2 0+ 2PPh 3 D M A RuBr 3(PPh 3) 2(DMA)-DMA solvate (3.4) None of the above methods resulted in analytically pure material. A careful potentiometric titration^ of the red-brown solid isolated following the chemistry of equation 3.1 showed an inflection in the titration curve for the halide analysis, indicating the presence of chloride. aa Other workers have had similar difficulties in preparing RuBr3(PPh3)2(MeOH) and RuCl3(PPh3)2(MeOH). 3 4 ' 3 5 These workers obtained solids which were thought to be Ru 1 1 species34 or mixtures of Ru 1 1 (e.g., RuCl2(PPh3)3) and Ru 1 1 1 species. In this thesis work, the isolated solid was also probably a mixture of R u 1 1 and R u m species, the diamagnetic species being observed in the *H NMR spectrum. An additional difficulty was that the solid contained some residual chloride (potentiometric titration). The RuBr3-xH20 starting material (eqs 3.3-3.4) was found to be ineffective for preparing either Ru 1 1 1 or Ru 1 1 (described in Section 3.3.2) phosphine complexes. The difficulty in using this material is probably due to its limited solubility in MeOH. If, however, the "RuBr3" is produced in situ from RUCI3XH2O and LiBr, the material seems to be more soluble. Therefore, in equation 3.1, stoichiometric quantities of PPI13 are thought to react with "RuBr3(MeOH)3."3 3 The potentiometric titration was performed carefully by Mr. P. Borda of this department using small additions of 0.02 N silver nitrate. The inflection between the titrated chloride and bromide curves showed the presence of both halides. 94 Chapter 3 References: p 157 Chapter 3 O n the other hand, the syntheses o f R u C l 3 ( P A r 3 ) 2 ( D M A ) D M A solvate (where A r = PPI13 or P(p- tolyl)3) are straightforward, and these complexes have been prepared i n 99 9c M this w o r k (Sections 2.5.1.1 and 2.5.1.2), as w e l l as by numerous other workers . ' S o m e typ ica l analyt ica l results for the red-brown s o l i d i sola ted i n the attempted preparations o f R u B r 3 ( P P h 3 ) 2 include: (1) for equat ion 3.1, the best results obtained for R u B r 3 ( P P h 3 ) 2 ( M e O H ) [calculated: C , 49.52; H , 3.82%. F o u n d : C, 54.77; H , 3.97%], may be compared w i t h the values expected for R u B r 2 ( P P h 3 ) 3 [C, 61.90; H , 4.33%]. (2) for equation 3.4, calculated for R u B r 3 ( P P h 3 ) 2 ( D M A ) D M A solvate: C, 50.84; H , 4.65; N, 2.69%. F o u n d : C, 54.29; H , 4.23; N, 1.37%. 90 01 D e k l e v a ' s a n a l y t i c a l results were also ve ry h i g h (>10%) i n ca rbon , ' J J and w e r e indica t ive o f the presence o f RuBr2(PPh3)3. Therefore , attempts to isolate materials o f the compos i t i on RuBr3(PPh3)2 were f ina l ly abandoned i n favour o f a ruthenium(II) precursor. 3.3.2 Ruthenium(II) Bromide Complexes; RuBr 2(PPh3) 3 (10) T h e c o m p l e x RuBr2(PPh3)3 10 has been p rev ious ly reported i n the li terature 15 33 and has also been prepared i n this laboratory. ' T w o routes to 10 were attempted i n this present thesis w o r k (eqs 3.5-3.6). R u C l 3 x H 2 0 + xs LiBr + 6PPh3 M e Q H > A » R u Br 2 (PPh 3 ) 3 (3.5) R u B r 3 x H 2 0 + 6PPh3 M e Q H ' A > . R u B r 2 ( P P h 3 ) 3 (3.6) Equation 3.5 provided pure material on occasion, although quite often the isolated solid still contained chloride. The purity of this material (at least in terms of the presence or absence of chloride) could be ascertained by reaction of the isolated solid with C O in 95 Chapter 3 References: p 157 Chapter 3 CDCI3 (eq 3.7).33 The 3 1 P { ! H } NMR data for the products of the reaction with C O are shown in Table 3.1. C D C L RuXY(PPh 3) 3 + C O ^ ccf-RuXY(CO)2(PPh3)2 + PPh 3 (3.7) X, Y = Br or Cl Tab le 3.1 T h e 3 1 P { ! H } N M R C h e m i c a l Shifts (121.42 M H z , 20 °C) for the Poss ib le cis, cis, frans-Isomers o f R u X Y ( C O ) 2 ( P P h 3 ) 2 Complex Chemical Shift, 8 CDCI3 C 6 D 6 ccf-RuCl2(CO)2(PPh3)2 17.0a 17.0b cc;-RuBr 2(CO)2(PPh3)2 13.1a 13.3b cc?-RuBrCl(CO)2(PPh3)2 14.8a 15.0b (a) this work; (b) from Dekleva's Ph.D. Thesis. Therefore, the absence o f a resonance at 14.8 p p m i n the 3 1 P { 1 H } N M R spectrum (i.e., no cc? -RuBrCl (CO)2 (PPh3)2 is present) is indica t ive o f pure RuBr2(PPh3)3 . A d d i t i o n o f an excess o f pyr id ine to a sample o f "RuBr2(PPh3)3" was also useful i n determining the presence o f chlor ide impur i ty (Section 5.2). T h e species R u B r 3 - x H 2 0 was ineffective as a starting mater ial for the preparat ion o f R u B r 2 ( P P h 3 ) 3 (eq 3.6), as i t was i n prepar ing RuBr3(PPh3)2 c o m p l e x e s . T h i s is probably because o f the l imi t ed so lubi l i ty o f R u B r 3 XH2O i n M e O H . Other workers have experienced di f f icul ty i n comple te ly substi tuting B r for C l i n preparations o f RuBr2(PPh3)3 (eq 3.5).3 6 E v e n though pure mater ia l , free o f ch lo r ide , 96 Chapter 3 References: p 157 Chapter 3 could be isolated on occasion, this method was inconsistent, and therefore not a good route into "RuBr2(P-P)" chemistry. The results of an X-ray diffraction study of RuBr2(PPh3)3 will be presented in Section 3.3.3. 3.3.3 RuX 2 (DPPB)(PAr 3 ), where X = Cl or Br and A r = Ph or (p-tolyl) The mixed-phosphine complexes RuCl2(P-P)(PPh3), where P-P = D P P B 2 1 or DIOP, ' have been known for several years, and were synthesized by a simple phosphine exchange reaction (eq 3.8). More recently, the corresponding mixed-phosphine complexes of BINAP (see Figure 1.3)22"24 and (S)-BIPHEMP (Figure 3.12)2 4 have been prepared. P P — D P P R D T O P RuCl 2(PPh 3) 3 + P-P ' » RuCl2(P-P)(PPh3) + 2PPh3 (3.8) (S)-BIPHEMP Figure 3.12 The structure of (S)-BIPHEMP. The mixed-phosphine complexes are viewed as synthetically useful intermediates, largely because the following equilibrium (eq 3.9) is known to exist in solution (see below). 97 Chapter 3 References: p 157 Chapter 3 2RuCl2(P-P)(PPh3) .. Ru 2Cl 4(P-P) 2 + 2PPh3 (3.9) Therefore, if the correct set of conditions were discovered, it may be possible to isolate the species "RuCl2(P-P)" (i.e., Ru2CU(P-P)2 or Ru2CU(P-P)2(L), where L is a neutral two-electron donor). Joshi of this laboratory had, in fact, synthesized Ru2CLi(P-P) 2 (NEt 3 ) , Ru 2Cl 4(P-P)2(CO), and Ru 2Cl 4(P-P)2(HN(n-Bu^) from RuCl 2(DPPB)-(PPI13), although the formulation of the last mentioned complex remains in question, and will be discussed in Section 3.4. ' Ideally, the so-called naked dimer Ru2CLi(DPPB)2 24 could be isolated to allow maximum flexibility in terms of preparing additional species such as [Ru(H)Cl(DPPB)]3. Therefore, several different mixed-phosphine complexes were prepared in this work. Although the preparation of the mixed-phosphine complex was straightforward, occasionally the desired product had to be separated from the phosphine-bridged by-product, Ru2CU(DPPB)3 19 (or [RuCl2(DPPB)i.5]2). This minor complication has been 91 93 reported in the literature. The bridged-phosphine species are insoluble in CH2CI2, and can be separated from the mixed-phosphine complexes by washing the latter through a filter with CH2CI2, leaving the former behind. In the course of this work, it was noted in repeated preparations of RuCl2(DPPB)(PPh3) that varying amounts of 19 were present (ranging from 0-43% based on DPPB). This was correlated with the purity of the RuCl2(PPh3)3 8 starting material. If excess PPI13 was present in 8 (elemental analysis showed high C and H), then the bridged-phosphine complex was observed. However, if 8 was free of phosphine impurity, then no 19 was observed. Investigations into the origins of these observations included experiments in which free PPh3 was added to the reaction mixture, and in which the "so-called tetrakis(phosphine) complex RuCl2(PPh3)4" was used as the starting material. 98 Chapter 3 References: p 157 Chapter 3 A reaction mixture containing PPh3 (0.5 equivalents per Ru, an amount which corresponded to the amount of PPI13 present in an impure sample of 8), pure RuCl2(PPh 3)3, and DPPB produced only the mixed-phosphine complex 11. This was somewhat surprising, considering that 8 contaminated by PPI13 always gave some 19. In this experiment, the methylene chloride solvent was added to the three solids, 8, PPI13, and DPPB. The formation of increased amounts of the bridged-phosphine complex appears to require the PPh3 'impurity' to be somehow associated with the starting ruthenium complex. Therefore, a more informative experiment may have been to stir 8 and PPh3 in solution for several hours before adding DPPB. Excess phosphine would affect the position of the known equilibrium (eq 3.10). ' An alternative approach was to prepare RuCl2(PPh3)4 ' and observe the effect of using this starting material on the ratio of mixed-phosphine to bridged-phosphine complexes. Equations 3.11 and 3.12 illustrate the published preparations for RuCl2(PPh3)3 and RuCl2(PPh3)4, respectively. The ratio of starting materials and concentrations are identical, as are the other reaction conditions, with the exception of temperature and reaction time. Other workers have argued that RuCl2(PPh3)4 should be formulated as RuCl2(PPh3)3-PPh3, where the fourth PPI13 is not coordinated, but is in the lattice framework. The arguments are based on NMR evidence, as well as on the similarity of the colours of the two species. Hoffman and Caulton suggest that the supposed six-coordinate complex, isolated as a brown solid, should be yellow or colourless if it is in fact six-coordinate, as is observed for other six-coordinate Ru(II) phosphine-containing compounds. 2RuCl2(PPh3)3 i= Ru 2Cl 4(PPh 3) 4 + 2PPh3 (3.10) R u C l 3 x H 2 0 + 6PPh3 MeOH, A • RuCl 2(PPh 3) 3 (3.11) N 2 , 3 h 99 Chapter 3 References: p 157 Chapter 3 MeOH, 25 °C R u C l 3 x H 2 0 + 6PPh3 — - — - 7 ^ RuCl 2(PPh 3) 4 (3.12) One attempt in this thesis work at preparing RuCl2(PPh3)4 following the literature procedure37 resulted in the isolation of a brown solid which analyzed as RuCi2(PPh3)3. Calculated for RuCl 2(PPh 3)3: C, 67.64; H, 4.73%. Found: C, 67.56; H , 4.78%. The calculated values for the tetrakis species, RuCl2(PPh3)4 are: C, 70.82; H , 4.95%. Therefore, the effect of a fourth phosphine on the distribution of products could not be investigated. Although nothing can be concluded about the nature of the role of P P h 3 from these studies, one can at least use reaction conditions to avoid the production of the bridged-phosphine complex in the synthesis of the mixed-phosphine complex. The reaction conditions necessary to avoid the formation of the bridged complex include the use of: (1) pure R u C l 2 ( P P h 3 ) 3 , free of uncoordinated PPh3 , and (2) addition of exactly one equivalent of the bis(phosphine). If these conditions are employed, the R u X 2 ( P -P)(PAr3) species can be isolated in high yield (95%). Interestingly, it is possible to prepare the six-coordinate ruthenium(II) antimony analogue, RuCl2(SbPh 3)4. An X-ray crystallographic study shows that the Ru-Sb bond lengths (average: 2.63 A)38 are significantly longer than the Ru-P bond lengths found in five-coordinate ruthenium(II) phosphine complexes (2.17-2.42 A, see Sections 3.3.3.1 and 3.3.3.2). 3.3.3.1 Molecular Structure of RuBr2(PPli3)3 (10) During the course of these studies, a dark-orange crystal was isolated from the filtrate ( C H 2 B r 2 / EtOH / hexanes in ca. 1:6:2 ratio) of a preparation of R u B r 2 ( D P P B ) ( P P h 3 ) . This single-crystal X-ray diffraction study showed the molecular structure to be RuBr 2 (PPh3)3, the starting complex. The presence of free PPI13 in the 100 Chapter 3 References: p 157 Chapter 3 filtrate, resulting from the displacement of PPh 3 by DPPB in the starting complex, probably aided the crystallization of the product by affecting the position of the equilibrium between 10 and RU2B r 4(PPh 3) 4 (cf. eq 3.10). 3 3 The ORTEP plot of RuBr2(PPh3)3 10 is shown in Figure 3.13; the molecular structure corresponds to that found for RuCl2(PPh3)3 8 by La Placa and Ibers.39 The geometry of 10 around the Ru centre is distorted square pyramidal, with the sixth coordination site of an octahedron blocked by an ortho-H (H(5)) of a PPh 3 (P(l)). The Ru(l)-H(5) distance is 2.68 A. Blocking of the sixth coordination site is also observed for both RuCl 2(PPh 3) 3tand RuCl2(DPPB)(PPh3) (see Section 3.3.3.2 for the ORTEP plot and discussion of the DPPB complex). Hoffman and Caulton have discussed the preference of square pyramidal over trigonal bipyramidal geometries for five-coordinate Ru(II) complexes. Selected bond lengths and angles for RuBr2(PPh3)3 10 are given in Tables 3.2 and 3.3, respectively. The structural parameters and experimental details are given in Appendix I. T Several authors (references i, ii, and iii listed below) have indicated that this compound is the first example of an agostic C - H a metal interaction. The interaction in this case would be weak, as the M -H distance is quite long (2.59 A). (i) Perera, S. D.; Shaw, B. L. / . Chem. Comm., Chem. Commun. 1994,1201. (ii) Crabtree, R. H. Agnew. Chem., Int. Ed. Engl. 1993, 32, 789. (iii) Brookhart, M.; Green, M. L. H. J. Organomet. Chem., 1983,250, 395. 101 Chapter 3 References: p 157 Chapter 3 Figure 3.13 The ORTEP plot of RuBr2(PPh3)3 10. Thermal ellipsoids for non-hydrogen atoms are drawn at 33% probability. 102 Chapter 3 References: p 157 Chapter 3 Tab le 3.2 Selected B o n d Lengths (A) for RuBr2(PPh3)3 10 w i t h Es t imated Standard Devia t ions i n Parentheses Bond Length (A) Bond Length (A) Ru(l>—Br(l) 2.515(1) Ru(l)—Br(2) 2.526(1) Ru(l ) -P( l ) 2.423(2) Ru(l)-P(2) 2.389(2) Ru(l)-P(3) 2.227(2) P ( l ) - C ( l ) 1.834(7) P(l)-C(7) 1.844(7) P(l)-C(13) 1.839(7) P(2)—C(19) 1.843(7) P(2)—C(25) 1.857(7) P(2)—C(31) 1.837(7) P(3)—C(37) 1.849(7) P(3)—C(43) 1.834(7) P(3)—C(49) 1.846(7) Ru(l)—H(5) 2.68* non-bonded contact Tab le 3.3 Selected B o n d A n g l e s (°) for R u B r 2 ( P P h 3 ) 3 10 w i t h Es t imated Standard Devia t ions i n Parentheses Bonds Angles (°) Bonds Angles (°) Br(l)--Ru(l)--Br(2) 155.64(4) Br(l)--Ru(l)-- P ( D 82.19(5) Br(l)--Ru(l)--P(2) 84.31(5) Br(l)--Ru(l)--P(3) 110.39(5) Br(2)--Ru(l)--P(l) 93.04(5) Br(2)--Ru(l)--P(2) 91.34(5) Br(2)--Ru(l)-P(3) 93.96(5) P(l)—Ru(l)- -P(2) 156.43(7) P(l)- -Ru(l)--P(3) 101.28(7) P(2)--Ru(l)--P(3) 101.50(7) Br(l)--Ru(l)--H(5) 83.2 Br(2)--Ru(l)--H(5) 72.9 P( l ) - -Ru(l)--H(5) 68.3 P(2)--Ru(l)--H(5) 91.0 P(3)--Ru(l)--H(5) 162.2 103 Chapter 3 References: p 157 Chapter 3 3.3.3.2 Molecular Structure of RuCl2(DPPB)(PPh3) (11) The solid-state structure of RuCl2(DPPB)(PPh3) 11 was suggested by Joshi to be square pyramidal. His comparison of the solid-state (CP/MAS) and low-temperature solution 3 1 P{ 1 H} NMR spectra of 11 with the spectra of RuCi2(PPh3)3 8 showed 22 similarities that were thought to indicate a similar solid-state structure. An X-ray 22 crystallographic study of 11 in this present work confirmed this suggestion. Green crystals were isolated from an NMR solution comprised of 11 and 14 equivalents of PPh3 in C7D8, which was left under an atmosphere of N2 in a glove-box for several months. The molecular structure corresponded to those found for 8 and 10 (Figure 3.13). The ORTEP of RuCl2(DPPB)(PPh3) 11 is shown in Figure 3.14. The geometry of 11 around the Ru centre is distorted square pyramidal, with the sixth coordination site of an octahedron blocked by an ortho-U (H(29)) of a PPh3 (P(3)). The Ru(l)-H(29) distance is 2.69 A. Selected bond lengths and angles for RuCl2(DPPB)(PPh3) 11 are given in Tables 3.4 and 3.5, respectively. The structural parameters and experimental details are given in Appendix II. Table 3.4 Selected Bond Lengths (A) for RuCl2(DPPB)(PPh3) 11 with Estimated Standard Deviations in Parentheses Bond Length (A) Bond Length (A) Ru(l)—Cl(l) 2.3796(8) Ru(l)—Cl(2) 2.4047(9) Ru(l ) -P( l ) 2.3346(9) Ru(l)-P(2) 2.2029(9) Ru(l)-P(3) 2.3786(9) P ( l ) - C ( l ) 1.836(4) P(l)-C(5) 1.820(4) P ( l ) - C ( l l ) 1.826(4) P(2)-C(4) 1.849(3) P(2)—C(17) 1.842(3) P(2)—C(23) 1.834(3) P(3)—C(29) 1.824(3) P(3)—C(35) 1.844(3) P(3)—C(41) 1.834(3) Ru(l)—H(29) 2.69* * non-bonded contact 104 Chapter 3 References: p 157 Chapter 3 C 3 C 2 Figure 3.14 The ORTEP plot of RuCl 2pPPB)(PPh 3) 11. Thermal ellipsoids for non-hydrogen atoms are drawn at 33% probability (some of the phenyl carbons have been omitted for clarity). 105 Chapter 3 References: p 157 Chapter 3 Table 3.5 Selected Bond Angles (°) for RuCl2(DPPB)(PPh 3) 11 with Estimated Standard Deviations in Parentheses Bonds Angles (°) Bonds Angles O Cl(l)—Ru(l)—Cl(2) 158.75(3) Cl(l)—Ru(l)--P( l ) 88.61(3) Cl ( l ) -Ru( l ) -P(2) 109.76(3) Cl(l)—Ru(l)--P(3) 85.82(3) Cl(2)—Ru(l)—P(l) 87.06(3) Cl(2)—Ru(l)--P(2) 91.42(3) Cl(2)—Ru(l)—P(3) 91.87(3) P( l ) -Ru( l ) --P(2) 97.01(3) P(l)—Ru(l)—P(3) 161.78(3) P(2)-Ru(l)--P(3) 101.20(3) Cl(l)—Ru(l)—H(29) 81.2 Cl(2)—Ru(l)--H(29) 78.2 P(l)—Ru(l)—H(29) 92.6 P(2) -Ru( l ) - -H(29) 165.5 P(3)—Ru(l)—H(29) 69.4 The metal centres of RuBr2 (PPh 3 ) 3 10 and RuCl2 (DPPB)(PPh 3 ) 11 are best described as being near the centre of gravity of a distorted square pyramid composed of trans P atoms and trans C l atoms in the base, with a third P atom at the apex. The main differences in the structures of RuCl2 (PPh 3 ) 3 8, 10, and 11 are probably due to the chelating DPPB ligand in 11. The Ru metal centre in each of 8,10, and 11 is found above the mean plane created by the two halides and two basal phosphorus atoms, the Ru atom being observed 0.456, 0.518, and 0.404 A above the basal plane, respectively. In all three complexes, the apical Ru-P distances (2.20-2.23 A) are shorter than the basal Ru-P distances (2.34-2.42 A). Also, the Ru-P distances of the phosphine groups involved in the agostic hydrogen interaction (i.e., ortho-W of a phenyl group) are longer than the other basal Ru-P bond lengths. Other five-coordinate ruthenium(II) phosphine complexes for which X-ray structural data have been determined include RuCl2(PMA)(P(/7-tolyl) 3 ) 4 0 ' 4 1 and 106 Chapter 3 References: p 157 Chapter 3 RuCl2(isoPFA)(PPh3) 4 2 ' 4 3 which both contain P - N chelates (PMA is shown in Figure 3.28, Section 3.10). Interestingly, the latter complex has an ortho-H of a PPI13 blocking the sixth coordination site of an octahedron while the former complex does not. RuCl2(PMA)(P(p-tolyl)3) is known to coordinate a range of small molecules including 0 2 , CO, H 2 0 , H 2 S, S0 2 , and M e O H . 4 0 ' 4 1 The analogous mixed-phosphine complexes RuCl2(DPPB)(P(p-tolyl)3) 12, RuBr 2(DPPB)(PPh 3) 13, and RuCl2((/?)-BINAP)(PPh3) 15 prepared in this work are believed to have the same geometry around Ru as in 11, based on low temperature 3 1 P{ 1 H} NMR studies. Table 3.6 summarizes the room- and low temperature 3 1P{!H} NMR spectral data; those for 12 in CD2CI2 are shown in Figure 3.15. The dynamic process observed in the room temperature 3 1P{!H} NMR spectrum of 12 (and the other mixed-phosphine complexes) is due to intramolecular exchange of the DPPB (or other diphosphine) nuclei on the NMR timescale as observed for 11 by 21 Jung et al. The rate of PPh3 dissociation is too slow to be responsible for the fluxional process observed at room temperature (the linewidth of the PPI13 was essentially invariant over the temperature range -66-+20 °C). The A B X pattern observed in the low temperature 3 1 P{lH} NMR spectrum (see Figure 3.15 and Table 3.6) is consistent with the structure determined by X-ray crystallography for the PPI13 analogue. The spectrum is consistent with two cis- and one trans-phosphorus-phosphorus interactions. The trans 2Jpp coupling constants are known to be much greater in magnitude than cis 2Jpp coupling constants.44 107 Chapter 3 References: p 157 Chapter 3 (a) O II P(p-tolyl) 3 24 12 P(p-tolyl)3 DPPB(0) 2 0 (b) 12 12 12 24 P(p-tolyl)3 L 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 J 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 100 80 60 40 20 0 PPM -2C Figure 3.15 The ^P^H} NMR spectra (121.42 MHz) of RuCl2(DPPB)(P(p-tolyl)3) 12 in CD 2 C1 2 at: (a) 20 °C and (b) -66 °C. 24 = Ru2Cl4(DPPB)2. 108 Chapter 3 References: p 157 Chapter 3 Table 3.6 3 1 P{ l H} NMR Data (121.42 MHz)(a) for RuX2(P-P)(PAr3) Complexes Complex Solvent Temp C O Chemical Shift, 8 2/pp, (Hz) RuCl2(DPPB)(PPh3) 11 C 6 D 6 C 7 D 8 20 20 5 A =25.7 6 A = 26.7 140(b) 142(W C 7 D 8 -70 5 A = 28.4 8 B = 36.2 5 X = 86.1 2 J A X - unresolved 2 / B X = 37.7 2/^=297.5 CH 2Cl 2(c) -75 5 A = 26.3 8 B = 35.2 5 X = 83.2 2 / A X = -22.6 2 / B X = -37.5 2 / A B = 302.4 RuCl2(DPPB)(P(p-tolyl)3) 12 C 6 D 6 C D 2 C 1 2 20 20 8 A = 25.5 8 A = 24.5 141(b) 141(b) C D 2 C 1 2 -66 5 A = 25.9 8 B = 36.6 8 X = 83.9 2 J A X = unresolved 2 - / B X = -35.7 2 / A B = 303.2 CDC1 3 -58 8 A = 24.7 8B = 34.9 S X = 84.4 2 7 A X = unresolved 2 ^ B X = -35.9 2 J A E = 303.7 RuBr2(DPPB)(PPh3) 13 C 6 D 6 C D 2 C 1 2 20 20 8 A = 27.6 8 A = 27:3 135(b) 145(b) C D 2 C 1 2 -66 8 A = 29.3 8 B = 37.5 8 X = 86.8 2 7 A X = unresolved 2 ^ B X = -35.8 27AE = 300.4 109 Chapter 3 References: p 157 Chapter 3 Table 3.6 (continued) Complex Solvent Temp Chemical Shift, 2Jpp, (Hz) (°C) § RuCl2((S)-BINAP)(PPh3) CD 2 Cl 2 ( d ) 20 8A=19.0 151(b) CD 2 Cl 2 ( d ) -60 RuCl2(DIOP)(PPh3)(e) C 7 D 8 © -60 RuCl2((S)-BfPHEMP)(PPh3)(e) CD 2 Cl 2 ( d ) 20 8 A = 22.6 8 B = 26.4 8 X = 87.4 8 A =17.3 8 B = 32.7 8 X = 66.6 8 A = 20.1 2 / A X = 23.2 2 / B X = 39.6 27AB = 327.5 2 / A X = 24 2 / B X = 41 27AB = 310 151(b) CD 2Cl 2(d) -60 8 A 8 B 8x 21.0 :29.2 84.7 2 7 A X = 21.9 2 / B X = 41.5 27AB = 323.4 RuCl 2(DCYPB)(PPh 3) CD 2C1 2(8) -50 14 CD 2Cl 2(g) -70 8 A = 19.5 8 A 5B 8 X : 17.1 = 24.1 88.0 133(b) 2 J A X = unresolved 2JBX = unresolved 2 / A B = 303.7 (a) Spectrometer frequency used for the values measured in this work, (b) Triplet-like, three-line pattern; J value indicates line spacing. The 8 B of the A B 2 pattern observed at 20 °C appears as a very broad resonance between 50-60 ppm in all cases (an example is shown in Figure 3.15(a)) (c) Jung et a l . 2 1 (d) Mezzetti et al. (e) Included for completeness, (f) Wang 1 5 (g) Prepared in situ from RuCl 2 (PPh 3 ) 3 and DCYPB. 2 4 110 Chapter 3 References: p 157 Chapter 3 3.3.4 Ru2X4(DPPB>2 Complexes 3.3.4.1 Preparation of Ru 2Cl4(DPPB) 2 (24) and Ru 2Br 4(DPPB) 2 (25) T h e route p r ev ious ly e m p l o y e d to prepare the Ru2Cl4(DPPB)2 24 c o m p l e x i s out l ined i n F igure 3.6, and is shown to be v i a the H 2 - r e d u c t i o n o f Ru2Cl5(DPPB)2 22. T h e i n a b i l i t y i n this w o r k to prepare pure RuBr3(PPh3)2 c o m p l e x e s prevented the p repa ra t ion o f R u 2 B r5(DPPB)2 c o m p l e x e s . T h e r e f o r e , an a l t e rna t i ve route to R u 2 B r 4 ( D P P B ) 2 25 was necessary. G e n e r a l l y , routes to the ch lo r ide analogues were investigated before the more diff icul t bromide chemistry was attempted. E q u a t i o n 3.9 shows the e q u i l i b r i u m between the m i x e d - p h o s p h i n e c o m p l e x R u X 2 ( P - P ) ( P P h 3 ) and R u 2 X 4 ( P - P ) 2 , w h i c h suggests that the m i x e d - p h o s p h i n e complexes are good i n situ sources o f R u 2 X 4 ( P - P ) 2 . It w o u l d be useful , however , to be able to remove the P P h 3 , fo rc ing the equ i l i b r i um to the right, and a l l o w i n g the i so la t ion o f R u 2 X 4 ( P - P ) 2 . It w o u l d be interes t ing to attempt reverse osmos i s as a m e t h o d o f i so l a t i ng R u 2 C l 4 ( D P P B ) 2 - In reverse osmosis , a dissociable complex is forced against a se lect ively permeable membrane under pressure. T h e meta l species is retained by the membrane , w h i l e the dissociated l i gand (i.e., P P h 3 ) and the solvent diffuse through the membrane. Gosse r et a l . have made use o f this method to isolate Ru2Cl 4 (PPh3)4(N2) f rom solut ions o f RuCl2(PPh3)4, when N2 was used as the pressurizing g a s . 4 5 Other methods o f r e m o v i n g t r ipheny lphosph ine have been at tempted. J o s h i attempted to remove the PPI13 f rom RuCl2 (DPPB ) (PPh 3 ) by adding M e l to produce the quaternary phosphonium salt, P M e P h 3 + I . T h i s method resulted i n the fo rmat ion o f a species, w h e n 10 equivalents o f M e l were used, that showed an A B quartet (8A = 71.1, 8B = 56.6, 2 7 A B = 40.0 H z ) i n the 3 1 P { ! H } N M R s p e c t r u m . 2 2 Joshi suggested this species to be dinuclear , but d i d not suggest a structure because the 3 1 P { ! H } spectrum d i d not cor respond to that k n o w n for 24. In this present thesis w o r k , Ru2l4(DPPB)2 27 was prepared f rom R u ( D P P B ) ( r | 3 - M e - a l l y l ) 2 55 and H I , and the 3 1 P { ! H } N M R data (Table 111 Chapter 3 References: p 157 Chapter 3 3.9, later i n this section) for this complex agree w i t h those observed by Josh i . Therefore, the species observed on add i t ion o f 10 equivalents o f M e l to the m i x e d - p h o s p h i n e c o m p l e x is actual ly 27. H o w e v e r , an i n situ 3 1 P { 1 H } N M R experiment performed by Josh i et a l . 2 3 w i t h the add i t ion o f 100 equivalents o f M e l to RuCl2 (DPPB ) (PPh3) (instead o f 10 equ iv ) , showed two A B quartets (8A = 52.6, 8B = 51.7, 2 / A B = 43.4 H z ; 8c = 48.6, 8 D = 41.8, 2JCD = 36.7 H z ) w h i c h were attributed to R u 2 C U ( D P P B ) 2 ( M e I ) ; i n v i e w o f the n o w es tab l i shed fo rma t ion o f 27, this M e l adduct s h o u l d perhaps be r e fo rmu la t ed as R u 2 l 4 ( D P P B ) 2 ( M e I ) . C u ( I ) hal ides are k n o w n to react w i t h P P h 3 to f o r m c o m p l e x e s o f the type C u X ( P P h 3 ) 2 , C u X ( P P h 3 ) 3 , C u 2 X 2 ( P P h 3 ) 3 , and [ C u X ( P P h 3 ) ] 4 . 4 6 Therefore , attempts were made i n the course o f this w o r k to remove P P h 3 us ing CuCl or Cul. T h e use o f Cul, al though effective i n r emov ing P P h 3 f rom the R u C l 2 ( P - P ) ( P P h 3 ) c o m p l e x , resulted i n compl ica t ions because o f hal ide exchange. F o r example , R u C l 2 ( D P P B ) ( P P h 3 ) was found to g i v e a m i x t u r e o f c h l o r o and i o d o Ru(I I ) c o m p l e x e s , as w e l l as Cu2X2(PPh 3 ) 3 s p e c i e s . 4 6 Other Cu ( I ) -phosph ine spec ies ( l i s t ed above ) m a y be present , bu t C u 2 X 2 ( P P h 3 ) 3 species are thought to predominate i n solut ion 4 6 T h e use o f 10 equivalents o f CuCl was effective for the r e m o v a l o f P P h 3 f rom R u C l 2 ( D P P B ) ( P P h 3 ) i n C 6 H 6 so lu t ion . T h e product o f this reac t ion , howeve r , was a mix ture o f Cu + [Ru2Cl5 (P -P )2 ]~ and CuCl-phosphine complex(es) . The addi t ion o f CuCl to the dark-green suspension o f R u C l 2 ( D P P B ) ( P P h 3 ) produced an immedia te change to a dark-orange co lour . T h e so lu t ion was stirred at r oom temperature for 1 h . T h e excess cuprous chlor ide was then removed by f i l ter ing the solut ion through a layer o f Celite, and an orange s o l i d was obtained by concentrating the benzene solu t ion and adding hexanes. A l t h o u g h 3 1 P { 1 H } N M R spectroscopy has been used to show the c o m p l e x i t y o f the so lu t ion behaviour o f these CuX -PPh3 species, due to the l a b i l i t y o f the phosphine 112 Chapter 3 References: p 157 Chapter 3 l igands i n these copper(I) complexes , no 3 1 P { 1 H } N M R data for specif ic complexes have been r e p o r t e d . 4 6 ' 4 7 T h e 3 1 P { 1 H } N M R spectrum o f the orange s o l i d i n C 6 D 6 showed a s ingle t for C u + [ R u 2 C l 5 ( P - P ) 2 ] ~ at 53.5 p p m , and two broad resonances at 51 and -1.9 p p m for the C u C l - P P h 3 c o m p l e x formed. These broad resonances were con f i rmed as be long ing to a C u ( I ) - P P h 3 c o m p l e x through the prepara t ion o f such a C u - p h o s p h i n e c o m p l e x . A AO preparation was f o l l o w e d w h i c h reportedly gave Cu2Cl2(PPh3)3. In fact, the whi te s o l i d isolated by this procedure gave an elemental analysis w h i c h agreed w i t h the format ion o f another k n o w n c o m p l e x , C u C l ( P P h 3 ) (see Sec t ion 2.1.5.2),49 w h i c h has been s h o w n subsequently i n the literature by X - r a y crystal lography to be the tetramer, [CuCl(PPh3)]4, a c u b a n e - l i k e a r rangement o f coppe r and c h l o r i n e a t o m s . 5 0 T h e w h i t e s o l i d [CuCl (PPh3) ]4 gave a 3 1 P { 1 H } N M R spectrum showing the broad resonances at 51 and -1.9 p p m conf i rming that these are associated w i t h CuCl-PPh3 species. [CuCl(PPh3)]4 is k n o w n to d e c o m p o s e , u p o n repea ted r e c r y s t a l l i z a t i o n s f r o m C6H-6 , to g i v e C u 2 C l 2 ( P P h 3 ) 3 . 5 1 L i p p a r d and M a y e r l e made use o f vapour pressure o s m o m e t r y to investigate the dominant C u C l - p h o s p h i n e complex i n s o l u t i o n . 4 6 T h e anion [Ru2Cl5(DPPB)2] - has been isolated prev ious ly i n this laboratory w i t h both a D M A H and T M P ca t ion ( l , l , 3 - t r ime thy l -2 ,3 -d ihydrope r imid in ium, see F i g u r e 4.22, S e c t i o n 4.7.2 fo r s t ruc tu re ) , and an X - r a y s t r u c t u r e - d e t e r m i n a t i o n o f [TMP]+[Ru2Cl5(DPPB ) 2 ] - -2Me2CO -2H20 revealed the m o l e c u l a r structure s h o w n i n 52 53 F i g u r e 3.16. ' T h e molecu la r structure o f the unusual T M P ca t ion , generated f rom P r o t o n Sponge by net hyd r ide loss f r o m one m e t h y l g roup , has been p u b l i s h e d 52 previous ly , but X - r a y c r y s t a l l o g r a p h i c data fo r the a n i o n i c [ R u 2 C i 5 ( D P P B ) 2 ] _ determined b y T h o r b u r n et a l . have not appeared elsewhere, and w i l l be inc luded here for reference purposes. Selected bond lengths and angles for [ R u 2 C l 5 ( D P P B ) 2 ] ~ are g iven i n Tables 3.7 and 3.8, respectively. The structural parameters and exper imental details are g i v e n i n A p p e n d i x III. The 3 1 P { 1 H } N M R spectrum o f [ T M P ] + [ R u 2 C l 5 ( D P P B ) 2 ] - i s 113 Chapter 3 References: p 157 Chapter 3 reported to show a singlet at 53.6 p p m i n CD2CI2, w h i c h is the same as that observed when C u is the cat ion (see above). T h e i o n i c nature o f the C u product was further c o n f i r m e d by reac t ing one equivalent o f C u C l w i th Ru2CU(DPPB)2 i n CDCI3. T h e 3 1 P { ! H } N M R spectrum o f the orange so lu t ion after one week at r o o m temperature showed a s ingle t at 48.3 p p m ind ica t ing format ion o f C u + [ R u 2 C i 5 ( D P P B ) 2 ] - . T h e react ion was s l o w i n this so lvent p r o b a b l y because o f the l i m i t e d s o l u b i l i t y o f C u C l i n C D C I 3 . T h e A B pattern characteris t ic o f the starting d inuclear c o m p l e x was a lmost comple t e ly gone after one week. A s i m i l a r i on ic species, [ D M A H ] + [ R u 2 C i 5 ( D P P B ) 2 ] ~ , is k n o w n to be the species p roduced i n the H2-reduction o f R u 2 C l 5 ( D P P B ) 2 (see F igu re 3.6). T h i s i o n i c species i s not i so la ted i n this preparat ion because the c o m p l e x is b roken up by the add i t ion o f M e O H to generate the desired Ru2CU(DPPB)2 complex and D M A H C 1 . T h e r e m o v a l o f PPI13 by the add i t ion o f C u C l thus is a p r o m i s i n g route. T h e condi t ions for remova l o f the C u C l - P P h 3 complex f rom the ion ic ruthenium species, and subsequent break-up o f the ion ic complex to g ive Ru2Ci4(DPPB)2, were not invest igated further because a more straightforward route to this complex was discovered. Tab le 3.7 Selected B o n d Lengths (A) for [ R u 2 C l 5 ( D P P B ) 2 ] - w i t h Es t imated Standard Devia t ions i n Parentheses B o n d Leng th (A) B o n d L e n g t h (A) Ru—Cl(l ) 2.4269(10) C( l ) -C(2) 1.551(7) Ru—Cl(2) 2.4968(10) C(2)-C(3) 1.531(7) Ru—Cl(3) 2.4136(10) C(3)-C(4) 1.511(6) Ru—P(l) 2.2650(12) P (U -CQ) 1.858(4) Ru—P(2) 2.2642(10) P(2)-C(4) 1.841(4) 114 Chapter 3 References: p 157 Chapter 3 Figure 3.16 The ORTEP plot of the anionic [Ru2Cls(DPPB)2]- in [TMP] + [Ru 2Cl 5(DPPB)2]-. 115 Chapter 3 References: p 157 Chapter 3 Table 3.8 Selected Bond Angles (°) for [Ru2Cl5(DPPB)2]- with Estimated Standard Deviations in Parentheses Bond Angles (°) Bond Angles O Cl(l)--Ru—Cl(2) 78.85(3) Cl(3)—Ru—P(l) 88.12(4) Cl(l)--Ru—Cl(3) 167.71(3) Cl(3)—Ru—P(2) 86.67(4) Cl(l> —Ru—P(l) 97.50(3) Cl(3)—Ru—Cl(2)' 90.02(4) Cl(l> —Ru—P(2) 103.41(3) P(l)—Ru—P(2) 96.74(4) Cl(l)--Ru—Cl(2)' 78.77(3) P(l)—Ru—Cl(2)' 93.52(4) Cl(2)--Ru—Cl(3) 94.16(4) P(2)—Ru—Cl(2)' 169.10(4) Cl(2> —Ru—P(l) 172.04(4) Ru—Cl(l)—Ru' 87.77(5) Cl(2> —Ru—P(2) 91.01(4) Ru—Cl(2)—Ru' 84.64(3) Cl(2)--Ru—Cl(2)' 78.87(4) Ru—P(l)—C(l) 118.8(2) Ru— P(2)_C(4) 117.16(15) Refluxing RuCl2(DPPB)(PPh3) or RuCl2(DPPB)(P(/?-tolyl)3) in a 1:1 mixture of C6H6 / H2O, subsequently removing the H2O layer, and adding hexanes produced in high yield an orange solid (Section 2.5.7.1) that proved to be Ru2CU(DPPB)2 24. Alternatively, hexanes could be added directly to the two-phase system to precipitate 24. The mechanism of PPh 3 (or P(p-tolyl)3) removal is not understood, but H2O is known to be essential for the isolation of 24. In the absence of H 2 0 , when the mixed-phosphine complex was refluxed in benzene in order to shift the equilibrium 3.9 to the right, the reaction mixture retained the green colour of the starting five-coordinate complex. On addition of H2O, the reaction mixture quickly became orange, indicating formation of the dimer. In situ N M R experiments in C 6 D 6 / D2O showed that PPh 3 , for example, had not been oxidized to phosphine oxide. The mixed-phosphine complex was also refluxed in a 1:1 benzene / 116 Chapter 3 References: p 157 Chapter 3 hexanes so lu t ion i n an attempt to select ively precipitate the d imer as i t was formed, but this also d i d not result i n isola t ion o f pure dimer. T h e idea o f adding H 2 O to the mixed-phosph ine c o m p l e x i n order to produce Ru2Cl4(DPPB)2 came f rom no t ing that the e lementa l ana lys i s o f 24 de te rmined b y 22 23 25 3D previous workers showed the presence o f a mo le o f H2O. ' J^J'Dyj It is poss ib le that i n the solid-state the H2O is actual ly coordinated (i.e., R u 2 C l 4 ( D P P B ) 2 ( H 2 0 ) ) . In so lu t ion , the ^ P p H } N M R spectrum shows o n l y a s ing le A B pattern for 24, w h i l e t w o A B quartets w o u l d be expected i f the H 2 O remained coordinated i n so lu t ion . T o date, our group has been unable to isolate crystals o f Ru2CLi(P-P)2 w h i c h are suitable for X - r a y diffract ion studies, where P-P is any o f the eight different phosphines used (Sect ion 3.2). A solid-state C P / M A S 3 1 P{ i f f } N M R study o f the dimer , ana lyz ing for a m o l e o f H2O, might provide insight into the nature o f the water molecule (i.e., whether it is coordinated or solvated) . In fact, on one occas ion dur ing this w o r k the d i m e r was heated overnight (78 °C) under v a c u u m before submiss ion for elemental analysis . T h e c o l o u r o f the s o l i d changed f rom orange to b r o w n dur ing the heating per iod, and elemental analysis showed the c o m p l e x to be 24 wi thout H2O solvate (see Sect ion 2.5.7.1 for mic ro -ana ly t i ca l data). T h e b r o m o a n a l o g u e , R u 2 B r 4 ( D P P B ) 2 25, w a s a l so p r e p a r e d f r o m R u B r 2 ( D P P B ) ( P P h 3 ) i n the same manner (using H2O) as desc r ibed above (Sec t ion 2.5.7.2). T h e 3 1P{!H} N M R spectrum o f 25 is shown i n F igure 3.17. A d d i t i o n o f R u 2 C l 4 ( D P P B ) 2 to an N M R sample o f R u 2 B r 4 ( D P P B ) 2 i n CDCI3 resulted i n halide-exchange as evidenced by loss o f the A B quartet for 25 i n the 3 1P{ lH} N M R spectrum and appearance o f two mul t ip le - l ine patterns centred at 55 and 65 p p m . These c o m p l i c a t e d patterns are ind ica t ive o f the fo rmat ion o f [ R u B r 2 - x C l x ( D P P B ) ] 2 species. N o hal ide exchange is evident between 25 and the chlor inated solvents CD2CI2 or CDCI3. 117 Chapter 3 References: p 157 Chapter 3 | i I I I | i I I I | I I I I [ i I I I | I I I I | i I- I I | I I i i | i i i i | 80 7b 70 65 60 55 50 45 PPM 40 Figure 3.17 3 1 P{*H} N M R spectrum (121.42 MHz, 20 °C) of Ru2Br4(DPPB)2 25 in C 6 D 6 . This "aqueous" route, although very useful for the preparation of 24 and 25 is probably not a general one for the preparation of dimers containing other chelating phosphines. Using this method, a single attempt at preparing Ru2CU((/?)-BINAP)2 26 from RuCl2(BINAP)(PPh3) 15 gave material which by 3 1 P { 1 H } N M R spectroscopy did not appear to be the dimer. Interestingly, Joshi et al. did not observe a mole of H2O when the dimers of DIOP, CHIRAPHOS, and BINAP were submitted for micro-analysis. 2 2 ' 2 3 The 3 1 P { lH} N M R data for the dimers isolated in this thesis work are given in Table 3.9. 118 Chapter 3 References: p 157 Chapter 3 Table 3.9 3 1P{ !H} NMR Data (121.42 MHz, 20 °C) for Ru2X4(P-P)2 Complexes Complex Solvent Chemical Shift, 8 2Jpp, (Hz) Ru 2Cl4(DPPB) 2 24 Ru 2 Br4(DPPB) 2 25 Ru2Li(DPPB)2 27 Ru2Cl4((/?)-BINAP)2(c) 26 C 6 D 6 8 A = 64.7, 8 B = 55.6(a) 4 7 3 C D C 1 3 8 A = 63.5, 8 B = 54.3 46.9 C D 2 C 1 2 8 A = 64.2, 8 B = 56.0 46.8 C 7 D 8 8 A = 64.7, 8 B = 55.5 46.9 C 6 D 6 8 A = 66.4, 8 B = 56.8 43.7 CDCI3 8 A = 65.2, 8 B = 55.6 44.3 C D 2 C 1 2 8 A = 66.0, SB = 57.3 44.6 C 7 D 8 8 A = 66.7, 8 B = 57.0 45.2 C D C ^ ) 8 A = 70.1,8B =55.6 39.9 C 6 D 6 8 A = 76.4, S B = 6.4(a) 4 1 o 8 C = 59.6, 8 D = 58.9 41.0 (a) The chemical shifts differ somewhat from those given in the literature2 2'2 3 due to the method of referencing (Joshi referenced 3 1 P{ 1 H} NMR spectra with respect to external PPI13 and took this as -6 ppm relative to 85% H 3P04, regardless of solvent; while in this work, the spectra were referenced with external P(OMe)3 dissolved in the solvent of interest). (b) Small amounts of MeOH, used to add HI, are present. (c) Observed in solution from RuCl2((/?)-BINAP)(PPh3). 119 Chapter 3 References: p 157 Chapter 3 3.3.4.2 Preparation of Ru 2 X 4 (DPPB) 2 via Ru(DPPB)(n.3-Me-allyI)2 (X = C l , Br, I) Genet and co-workers have reported routes to chiral Ru(P-P)(T|3-anyl) 2 complexes, where allyl = allyl, or M e - a l l y l . 5 4 " 5 6 These are prepared from Ru(COD)(allyl)2 species and are used in situ as homogeneous hydrogenation catalysts for the asymmetric reduction of fi-keto esters, a , P-unsaturated acids, and allylic alcohols. 5 7' 5 8 The general preparative procedure involves refluxing a 1:1 mixture of diphosphine and Ru(COD)(allyl)2 in hexanes. For some of the chiral phosphines, higher temperatures were required, and therefore the reaction mixture was refluxed in toluene.54 The isolated Ru(P-P)(allyl)2 species are then reacted with HC1 and HBr to give in situ Ru2X4(P-P)2 complexes. However, no attempts were made to isolate any of these dimeric complexes, as the interests of Genet and co-workers concentrate on the organic 57 58 syntheses using these in situ catalytic systems. ' Therefore, in this thesis work, a preparation of Ru(P-P)(r|3-Me-allyl)2 containing the achiral DPPB ligand was undertaken. Refluxing DPPB and Ru(COD)(r|3-Me-allyl)2 7 in hexanes using the procedure outlined for the chiral phosphine analogues prepared by Genet et al. did not prove effective. However, if the solvent was changed to CH2CI2, a yellow solid analyzing as Ru(DPPB)(r|3-Me-allyi)2 55 was obtained. The 31p{ lH} NMR spectrum of this yellow solid in C^D^ showed a singlet at 44.2 ppm. A similar reaction between Ru(COD)(r(3-allyl)2 6 and DPPB was attempted in both hexanes and a hexanes / benzene mixture, but did not produce the desired Ru(DPPB)(n3-allyl)2. This reaction was not pursued in C H 2 C 1 2 , as Ru(COD)(r|3-Me-allyl)2 was a better starting material than the allyl analogue, which was a waxy solid and therefore more difficult to handle (Section 2.5.1.6). Reaction of 55 with two equivalents of dilute methanolic solutions of H X produced the corresponding Ru2X4(DPPB)2 complexes (X = Cl , Br, and I). This was 120 Chapter 3 References: p 157 Chapter 3 demonstrated by 3 1 P{ 1 H} NMR spectroscopy, as the singlet corresponding to 55 at 44.2 ppm decreased in intensity on addition of HX, while the AJ3 pattern corresponding to the appropriate dimer became apparent (Table 3.9). Equation 3.13 illustrates this reaction, in which the Me-allyl group is presumably removed by protonation as 2-methylpropene. The 3 1 P{ 1 H} NMR spectra corresponding to addition of one, two, and three equivalents of HC1 (in MeOH) to a CDCI3 solution of Ru(DPPB)(n3-Me-allyl)2 are shown in Figure 3.18. 2Ru(DPPB)(Me-allyl)2 + 4HX ^ Ru 2 X 4 (DPPB) 2 + 4(CH 3 ) 2 C=CH 2 (3.13) The peak at 57 ppm is known to be due to interaction of Ru2Cl4(DPPB)2 24 with HC1, but the nature of the complex formed remains undetermined. This resonance was substantiated as an interaction with HC1 by adding HC1 (in MeOH) directly to a C^D^ solution of 24. An interesting possibility is that the proton could be attached to a chloro ligand (i.e., the species could be an r^-HCl adduct; such species have been formulated within Pt(U) systems).59 Interestingly, the addition of NEt3-HCl to Ru(DPPB)(ri3-Me-allyl)2 55 in CDCI3 gave a resonance at 48.9 ppm due to Ru2Cl4(DPPB)2(NEt3) 28, the BINAP analogue of which is a very active asymmetric homogeneous hydrogenation catalyst.60 In essence, the Me-allyl group is protonated, causing its dissociation from the Ru centre, followed by dimerization of the remaining Ru fragment. The resulting 24 reacts with NEt3 to give 28. 121 Chapter 3 References: p 157 Chapter 3 Figure 3.18 3 1 P { lH} N M R spectra (121.42 M H z , 20 °C) o f Ru(DPPB ) (T i3 -Me-a l ly l ) 2 55 i n CDCI3 wi th : (a) 1 equiv HC1, (b) 2 equiv HC1, and (c) 3 equ iv HC1. 24 = R u 2 C l 4 ( D P P B ) 2 . 122 Chapter 3 References: p 157 Chapter 3 T h e various routes to R u 2 C l 4 ( D P P B ) 2 24 n o w avai lable are shown i n F igure 3.19. R u C l 3 x H 2 0 route ( a ) / 24 h / 3 h route (b) route (c) 3 days RuCl 3 (PPh 3 ) 2 DMADMA 73% R ^ p p ^ 9 3 % 24 h 2h [RuCl 2(COD)] x 86% 10 m i n R u ( C O D ) ( r i 3 - M e - a l l y l ) 2 80% R u 2 C l 5 ( D P P B ) 2 85% R u C l 2 ( D P P B ) ( P P h 3 ) 97% | 1 8 h R u ( D P P B ) ( r i 3 - M e - a l l y l ) 2 76% 24 h 1 h 73% R u 2 C l 4 ( D P P B ) 2 100% 75% 5 m i n i n situ F igu re 3.19 C o m p a r i s o n o f three routes to the dimer, R u 2 C l 4 ( D P P B ) 2 - T h e ove ra l l y ie lds o f d imer by these routes are: (a) 45%, (b) 68%, and (c) 52%. Y i e l d s o f the i nd iv idua l steps are indicated beside the complexes . Route (b) through the mixed-phosphine c o m p l e x is the most desirable o f the three routes because each o f the steps has a short reaction t ime and is h igh y i e l d . Rou te (a) i s somewhat less desirable, as the ove ra l l y i e l d (45%) is s ign i f i can t ly l o w e r than that o f route (b) (68%). A l s o , route (a) has longer reaction times and does not a l l o w access to the b romide analogues, as do both routes (b) and (c). The ma in drawbacks to route (c) are the l o n g react ion t ime required i n the first step, and the add i t iona l step that is needed, as compared to routes (a) and (b). H o w e v e r , the preparation o f Ru(DPPB)(T] 3 -Me-allyl)2 55 through route (c) m a y be desirable i n cer tain cases because i t a l l o w s for the i n s i tu generat ion o f the a i r -sensi t ive R u 2 C l 4 ( D P P B ) 2 wi thou t con tamina t ion b y PPI13. T h e d inuc lear c o m p l e x can also be generated i n situ f rom R u C l 2 ( D P P B ) ( P P h 3 ) (route (b)); however , the presence o f PPI13 i n catalytic hydrogenat ion applicat ions is detr imental (see Chapter 7). A l t h o u g h F igure 3.19 gives o n l y an ind ica t ion o f the react ion t ime, and does 123 Chapter 3 References: p 157 Chapter 3 not take into account the time required in the work-up and isolation of each species, it is still representative of the advantages and disadvantages of each step. Al l the steps illustrated take approximately an equal amount of time for work-up, except for the step in route (c) from [RuCl2(COD)]x to Ru(COD)(T)3-Me-allyl)2, which requires a somewhat more tedious work-up. 3.3.4.3 Preparation of Ru(BINAP)(T|3-Me-allyl)2 (56) The preparation of the title complex has been reported by Genet et al . ; 5 6 however, no micro-analytical data were given and the 3 1P{ NMR data5 4 (singlets at 40,27, and -15) are "ambiguous". In this work, difficulty was encountered in isolating pure Ru((/?)-BINAP)(Me-allyl)2 56; however, the three 3 1P{!H} NMR resonances could be assigned confidently to 56, (^)-(+)-2,2'-bis(diphenylphosphinoyl)-l,r-binaphthyl (BINAP(0)2), and free BINAP, respectively. An authentic sample of BINAP(0)2 was prepared by the H2O2 oxidation of BINAP in C6l>6, and addition of the oxide to a solution of the Ru complex in C6D6 increased the intensity of the 26.6 ppm resonance. An orange crystal of 56 was isolated from a C6D6 NMR solution. An X-ray diffraction analysis of this crystal showed the desired Me-allyl complex to be co-crystallized with (/?)-(+)-2,2'-bis(diphenylphosphinoyl)-l,l'-binaphthyl and two C6D6 molecules. Figure 3.20 shows the ORTEP plot of Ru(BINAP)(Ti 3-Me-allyl) 2 56, while Figure 3.21 shows the ORTEP plot of (/?)-(+)-2,2'-bis(diphenylphosphinoyl)-l,r-binaphthyl (BINAP(0)2). Selected bond lengths and angles for Ru((/?)-BINAP)(r|3-Me-allyl)2 56 are given in Tables 3.10 and 3.11, respectively, while those for (i?)-(+)-2,2'-bis(diphenyl-phosphinoyl)-l,l'-binaphthyl are given in Tables 3.12 and 3.13. The experimental parameters and experimental details for both are given in Appendix IV. 124 Chapter 3 References: p 157 Chapter 3 C26 Figure 3.20 The ORTEP plot of Ru((/?)-BINAP)(r|3-Me-allyl)2 56. Thermal ellipsoids for non-hydrogen atoms are drawn at 33% probability (some of the phenyl carbons have been omitted for clarity). A C2 axis rotates the labelled half of the molecule into the non-labelled half (e.g., P(l) reflects into P(l)'). 125 Chapter 3 References: p 157 Chapter 3 ire 3.21 The ORTEP plot of (/?)-(+)-2,2'-bis(diphenylphosphinoyl)-1,1 '-binaphthyl (BINAP(0>2). Thermal ellipsoids for non-hydrogen atoms are drawn at 33% probability. A C2 axis rotates the labelled half of the molecule into the non-labelled half (e.g., P(2) reflects into P(2)'). 126 Chapter 3 References: p 157 Chapter 3 The ORTEP of 56 (Figure 3.20) shows the complex to be chiral at the metal centre (A), and therefore one of the two possible diastereomers has crystallized (i.e., A, R; where the first designation is the metal centre, and the second is the chirality of the diphosphine). The geometry around the Ru centre of 56 can be described as strongly distorted tetrahedral, the tetrahedron being defined by the two phosphorus atoms and the two central carbons of the planar T|3-Me-alryl ligands. Distortions from tetrahedral are caused by the rigid chelating BINAP ligand (i.e., the P(l)-Ru-P(l)' angle is 91.92°). An X-ray diffraction study of Ru(PPh3)2(r|3-allyl)2 showed the Ru to be tetrahedrally coordinated, the P-Ru-P bond being 109 .9° . 6 1 The Ru-P bond distance of 2.342(4) A is identical (within experimental error) to that observed in 56. Two other X-ray diffraction studies have been reported on complexes of the type Ru(P-P)(r|3-Me-allyl)2, where P-P = (S,S)-DIOP and (S,S)-CHJRAPHOS. 5 4 These structures were described as distorted octahedral, but are in fact very similar to the molecular structure of 56. For example, the P-Ru-P bond angles are 96.8° (DIOP) and 84.96° (CHIRAPHOS), which are significantly smaller than the 109.9° seen for the monodentate PPI13 analogue. The preparation of species 56 was originally attempted by the same procedure as that found effective in the synthesis of Ru(DPPB)(ri3-Me-allyl)2 55 (i.e., in CH2CI2). However, the use of CH2CI2 as solvent was ineffective, as only the starting materials were isolated on work-up of the reaction. Therefore, the reaction was performed in refluxing toluene according to the procedure employed by Genet and co-workers.5 4'5 8 An X-ray diffraction study has previously been performed on a 1:1:1:1 complex of (5)-(-)-BINAP(0)2, (l/?)-(-)-camphorsulfonic acid, acetic acid, and ethyl acetate.62 The molecular structures of BINAP(0)2 determined in this work, and those determined by Takaya et al. were significantly different, probably a result of the two crystals crystallizing in different space groups (PI and in this work, 1422 ), as well as the hydrogen-bonding interactions between the phosphine oxide and the camphorsulfonic and 127 Chapter 3 References: p 157 Chapter 3 acetic acid groups. For example, the P(2)-0(l) bond length of 1.478 A observed in this work is significantly shorter than one of the two P-0 bond lengths of 1.506 and 1.483 A observed by Takaya et al. The 1.506 A P -0 bond length may be lengthened by the observed hydrogen-bonding interaction of the oxygen atom with camphorsulfonic acid. Although hydrogen-bonding of the oxygen atom of the other P-0 group with acetic acid is observed, this P-0 bond length is within the experimental error of that observed in this work. Also of note is the angle between the least-squares planes of the two naphthyl rings, which in this work was 79.3°, while in the work of Takaya et al. it was 90.3°. Attempts to prepare Ru2Cl4(BINAP)2 2 6 by adding HC1 (in MeOH) to the isolated solid containing Ru(BINAP)(r| 3-Me-allyl)2 and phosphine dioxide gave a ^ P ^ H } NMR spectrum which did not include resonances corresponding to those 22 9 3 reported for 26. ' The spectrum does not correspond to that recorded for any Ru(II)-BINAP species previously prepared in this laboratory (i.e., Ru2Ci4(BINAP)2) 2 2' 2 3. The spectrum showed resonances for BINAP and BINAP(0)2, which are present in the starting material, as well as numerous new overlapping resonances between 50-70 ppm (which are probably AB quartets, but are impossible to assign because of the large number of overlapping peaks). The resonance at 42.1 ppm for Ru(BINAP)(r|3-Me-allyl)2 56 was completely gone. 128 Chapter 3 References: p 157 Chapter 3 Table 3.10 Selected Bond Lengths (A) for Ru((/?)-BINAP)(r|3-Me-allyl)2 56 with Estimated Standard Deviations in Parentheses Bond Length (A) Bond Length (A) Ru(l ) -P( l ) 2.339(1) C( l ) -C(2) 1.387(6) Ru(l)—C(24) 2.178(5) C(2)—C(2)' 1.524(8) Ru(l)—C(23) 2.228(4) C(23)—C(24) 1.403(7) Ru(l)—C(25) 2.240(5) C(24)—C(25) 1.388(8) Ru(l)—A* 1.96 C(24)—C(26) 1.529(8) P( l ) -C ( l ) 1.845(5) * A refers to the unweighted centroid of the three coordinated carbon atoms of the methylallyl ligand. Table 3.11 Selected Bond Angles (°) for Ru((i?)-BINAP)(T|3-Me-allyl)2 56 with Estimated Standard Deviations in Parentheses Bond Angles (°) Bond Angles (°) P ( l ) -Ru( l ) -P( l ) ' 91.92(6) P(l)—Ru(l)—C(23) 86.8(2) P(l)—Ru(l)—C(23)' 97.1(1) P(l)—Ru(l)—C(24) 119.2(2) P(l)—Ru(l)—C(24)' 111.4(2) P(l)—Ru(l)—C(25) 152.2(2) P(l)—Ru(l)—C(25)' 89.1(2) P(l)—Ru(l)—A* 119.8 P(l)—Ru(l)—A' * 100.2 C(23)—Ru(l)—C(23)' 174.4(3) C(23)—Ru(l)—C(24) 37.1(2) C(23)—Ru(l)—C(24)' 137.6(2) C(23)—Ru(l)—C(25) 65.6(2) C(23)—Ru(l)—C(25)' 110.7(2) C(24)—Ru(l)—C(25)' 92.1(2) C(24)—Ru(l)—C(24)' 104.4(3) A—Ru(l)—A' * 122.0 C(24)—Ru(l)—C(25) 36.6(2) C(l)—C(2)—C(2)' 119.7(3) C(25)—Ru(l)—C(25)' 102.7(3) P(1)_C(1)_C(2) 123.9(4) Ru(l)—P(l)-C(l) 109.3(1) * A and A' refers to the unweighted centroid of the three coordinated carbon atoms of the methylallyl ligand. 129 Chapter 3 References: p 157 Chapter 3 Table 3.12 Selected B o n d Lengths (A) for (i?)-(+)-2,2 '-bis(diphenylphosphinoyl)-l ,r-binaphthyl w i t h Est imated Standard Devia t ions i n Parentheses B o n d Leng th (A) B o n d L e n g t h (A) P(2)—0(1) 1.478(4) P(2)—C(27) 1.795(6) P(2)—C(37) 1.811(6) P(2)—C(43) 1.807(6) C(28)—C(28)" 1.504(10) C(27)—C(28) 1.380(7) Tab le 3.13 Selected B o n d A n g l e s (°) for (/?)-(+)-2,2 '-bis(diphenylphosphinoyl)-l,l '-b inaphthyl w i t h Est imated Standard Devia t ions i n Parentheses B o n d A n g l e s (°) B o n d A n g l e s (°) O(l)—P(2)—C(37) 111.4(3) 0(1)—P(2)—C(27) 117.1(3) C(27)—P(2)—C(37) 104.9(3) 0(1)—P(2)—C(43) 110.6(3) C(37)—P(2)—C(43) 106.1(3) C(27)—P(2)—C(43) 106.0(3) P(2)—C(27)—C(28) 122.8(4) C(27)—C(28)—C(28)" 119.8(5) 3.3.4.4 Metathesis of Ru 2Cl4(DPPB) 2 by LiBr or Me3SiBr An alternative route into " R u B r 2 ( P - P ) " chemistry i n v o l v e d substi tut ion o f B r for C l d i rect ly o n the dimer. Th i s was accompl i shed most effect ively by the use o f M e 3 S i B r , w h i c h had been reported as synthet ical ly useful by Andersen i n the preparation o f some hafn ium s p e c i e s . 6 3 In i t ia l i n situ 3 1 P { lH} N M R studies showed M e 3 S i B r to be effective i n preparing R u 2 B r 4 ( D P P B ) 2 25 f rom R u 2 C U ( D P P B ) 2 24 in C 6 D 6 (eq 3.14); an excess o f M e 3 S i B r was used to dr ive the reaction to comple t ion . T h e chlorot r imethyls i lane product (b.p. 57 °C) can eas i ly be removed at the pump, as can the rema in ing excess M e 3 S i B r (b.p. 79 ° C ) . T h i s reac t ion was sca led up and p roved to be ef fec t ive i n p repa r ing R u 2 B r 4 ( D P P B ) 2 (Sect ion 2.5.7.2). 130 Chapter 3 References: p 157 Chapter 3 Ru 2Cl 4(DPPB) 2 + 4Me 3SiBr C ^ 6 - Ru 2Br 4(DPPB) 2 + 4Me 3SiCl (3.14) Al te rna t i ve ly , the addi t ion o f excess L i B r to 24 i n C6H6 c o u l d be used to effect subst i tut ion o f Cl for B r . H o w e v e r , the isolated product showed a s inglet at 51.0 p p m ( C 6 D 6 ) i n the 3 1 P { 1 H } N M R s p e c t r u m , and i s the re fore t h o u g h t to be Li +[Ru2Br5(DPPB)2]~. N o attempt was made to isolate the neutral d i m e r 25 f rom this ion ic species, as the other methods ment ioned earl ier were more convenient routes to 25. An i n s i tu 3 1 P { 1 H } N M R expe r imen t o f a CH2CI2 s o l u t i o n o f L i B r added to Ru2Cl4(DPPB)2 (wi th C 6 D 6 added to a l l o w the spectrometer f requency to be l o c k e d ) i n i t i a l l y s h o w e d many ove r l app ing AB quartets at 8 ~ 55 and ~ 65, i n d i c a t i n g the presence o f Ru2Cl4-xBrx(DPPB)2 complexes (n = 0-4), p lus a singlet at 50 p p m for the i o n i c species. Precedence for the format ion o f these ion ic species w i t h addi t ion o f L i C l to the analogous Ru2CU(PPh3)4 complex has been shown earlier by D e k l e v a (eq 3.15). Interest ingly, the addi t ion o f Ru2CU(DPPB)2 to a so lu t ion o f Ru2Br4 (DPPB) 2 produced m i x e d - h a l i d e d i ru then ium species, as ev idenced by the m a n y A B quartets observed i n the 3 1 P { *H} N M R spectrum. Ru 2Cl 4(PPh 3) 4 + LiCl , Li +[Ru 2Cl 5(PPh 3) 4]- (3.15) Section 3.4 w i l l discuss ongoing amine chemistry i n v o l v i n g these ionic species. R e c a l l also that an X - ray crystal lographic structure (Figure 3.16) has been determined for [TMP]+[Ru 2 Cl5(DPPB)2]- (Section 3.3.4.1).52 3.4 Reaction of Tertiary Amines with RuCl 2(P-P)(PPh 3) Complexes N o y o r i , Takaya , and co-workers have reported on enantioselective hydrogenat ions c a t a l y z e d by R u ( I I ) - B I N A P c o m p l e x e s , 6 4 " 6 6 and they have noted that a d inuc l ea r c o m p l e x formulated R u 2 C L ; ( B I N A P ) 2 ( N E t 3 ) is a h i g h l y effective catalyst precursor for 131 Chapter 3 References: p 157 Chapter 3 the asymmetric reduction of functionalized substrates, including ketones. ' This complex was prepared from the Ru(II) starting material, [RuCl2 (COD)] x , as outlined in equation 3 . 1 6 . 1 6 ' 6 7 C 7 H 8 , A [RuCl 2(COD)] x + BINAP + xs NEt 3 — »• Ru 2Cl 4(BINAP) 2(NEt 3) (3.16) 3 h However, King and DiMichele recently discovered that on repeating the above preparation, an ionic complex [H2NEt2]+[Ru2Ci5(BINAP)2]~ was isolated,69 rather than the originally reported neutral species Ru2CLi(BINAP)2(NEt3). The one difference between the reaction conditions of King and DiMichele and 70 those of Ikariya and co-workers was the reaction temperature. The former performed the reaction in a sealed vessel at 140 °C, while Ikariya and co-workers16 ran the reaction in refluxing toluene ( -110 °C). The complex was originally formulated as the neutral species on the basis of elemental analysis and 3 1 P{ 1 H} NMR spectroscopy ( 8 A = 56, S B = 51; 2 J A B = 35 Hz, the solvent was not reported);67 however, no indication was given as to whether the elemental analysis data included Cl , or whether it was just the routine C, H, N analysis. Chlorine analysis is thought to be key in distinguishing between the neutral and ionic species and this will become evident from the discussion below. Although King and co-workers report no elemental analysis data for the ionic complex, the spectroscopic data, coupled with results from this work, provide strong evidence for their formulation.6 9'7 0 Work in this thesis and by other workers in this laboratory clearly illustrates the existence of both neutral and ionic ruthenium(II) amine complexes of the type described above. The majority of the work in this laboratory has been done with the achiral DPPB containing complexes. Joshi performed the following reactions, involving tertiary amines, starting from either RuCl2(DPPB)(PPh 3) or Ru2Cl4(DPPB) 2 (eqs 3 . 1 7 - 3 . 2 0 ) . 2 2 ' 2 3 132 Chapter 3 References: p 157 Chapter 3 Ru 2Cl 4(DPPB) 2 + xsNEt 3 ^C^f** Ru 2Cl 4(DPPB) 2(NEt 3) (3.17) 25 L , o n C H Ru 2Cl 4(DPPB) 2 + xsHN(n-Bu)2 f 6 » Ru 2Cl 4(DPPB) 2(HN(n-Bu) 2) (3.18) 25 C, 6 h CgHg / hexanes RuCl2(DPPB)(PPh3) + xsN(n-Bu)3 ( 1 : 4 ) —^Ru 2 Cl 4 (DPPB) 2 (HN(n-Bu) 2 ) (3.19) reflux, 3 h C PL-RuCl2(DPPB)(PPh3) + xs NEt 3 o g * * » Ru 2Cl 4(DPPB) 2(NEt 3) (3.20) Reactions 3.17 and 3.18 are in fact known to give products of the formulation suggested by Joshi. The neutral complex Ru2Cl4(DPPB)2(NEt3) analyzed well for four chlorides. The 3 1 P{lH} NMR solution data do not distinguish between the neutral and anionic Ru-amine complexes, as both appear as singlets at ~ 49 ppm. While a singlet is expected for the anionic complex based on the structure (see Figure 4.22, Section 4.7.2), two AB quartets would be expected for a static neutral complex like that illustrated in Figure 3.22, structure A (or the enantiomer A') (L = NEt 3), or two singlets for structure B. The singlet observed for the neutral amine species has been rationalized in terms of a rapid reversible dissociation of the amine and recoordination to either Ru centre, which results in scrambling of all four P atoms, which are therefore equivalent on the NMR-9 9 9 3 timescale. ' This singlet appears at 49 ppm (CDCI3) at room temperature, and has been observed unchanged as low as -98 °C in this thesis work. 133 Chapter 3 References: p 157 Chapter 3 Figure 3.22 Possible structural isomers for Ru2Cl4(DPPB)2(L) complexes. T h e patterns ment ioned above for the 3 1 P { N M R spectra assume no c o u p l i n g through the ch lo r ide br idges , and indeed no through-br idge P - P c o u p l i n g has been obse rved for any o f the Ru2CLi(DPPB)2(L) c o m p l e x e s s tud ied to date. H o w e v e r , t h rough-br idge P - P c o u p l i n g has been observed for the monodenta te phosph ine -conta in ing species (PPh 3 ) 2 (H)Ru(p : -H) (p . -C l )2Ru ( T i 2 -H2) (PPh3) . 2 8 ' 7 1 Solid-state CP/MAS (TOSS) 3 1 p { l H } N M R data for R u 2 C l 4 ( D P P B ) 2 ( N E t 3 ) show four resonances (56.4, 54.1, 47.1, and 40.7; l ine broadening, coi/2 -162 H z , causes each o f these signals to appear as singlets rather doublets), w h i c h i m p l y structure A, where L = 72 N E t 3 . It is diff icul t to te l l f rom the l ine shape w h i c h pairs o f resonances be long together (AB quartet). The same structural arrangement has been demonstrated by crys ta l lography 99 93 for L = DMSO (F igure 3.8). ' Interestingly, the average c h e m i c a l shifts o f the four resonances observed for Ru 2 Cl4 (DPPB)2 (NEt3 ) i n the C P / M A S (TOSS) 3 1 p { l H ] N M R spectrum is 49.6 p p m , w h i l e that observed for the c o m p l e x i n solu t ion is a singlet at 49.4 p p m ( C 6 D 6 ) . T h e s o l i d - s t a t e C P / M A S (TOSS) 3 1 p { l H } N M R s p e c t r u m o f R u 2 C l 4 ( D P P B ) 2 ( C O ) 7 2 is a s i m i l a r to that o f R u 2 C l 4 ( D P P B ) 2 ( N E t 3 ) . 7 2 T h e L = C O 134 Chapter 3 References: p 157 Chapter 3 c o m p l e x (Figure 3.22, structure A ) also appears i n the C P / M A S (TOSS) 3 1 P { ! H } NMR spectrum as four resonances ( 8 A = 53.4, 8B = 49.1, 8 B = 44.8, 8 D = 29.0; l ine broadening, coi/2 ~ 405 H z ) , 7 2 w h i l e the solut ion 3 1 P { ! H } N M R spectrum o f R u 2 C l 4 ( D P P B ) 2 ( C O ) 23 reveals 'the expected' two A B quartets. 3.4.1 Synthesis and Characterization of [H2N(«-R)2] +[Ru2Cl5(DPPB)2]-, R = w-Bu (38), n-Oct (37) T h e title c o m p l e x w i t h R = B u 38, o r ig ina l ly thought to be the neutral c o m p l e x R u 2 C l 4 ( D P P B ) 2 ( H N ( n - B u ) 2 ) , 2 2 ' 2 3 has been found i n this w o r k , at least by the h igher temperature route (eq 3.19), to be [H2N(n-Bu)2] +[Ru2Ci5(DPPB)2]- T h e 3 1 P { ! H } N M R spect rum (a s ingle t at ~ 49 ppm) does not d i s t ingu ish between the neutra l and i o n i c species. T h e ch lor ine analysis (Sect ion 2.5.9.2) was ind ica t ive o f the i o n i c species. A n X - r a y crys ta l lographic o f the anion has been performed i n the past (see F i g u r e 3.16 for 52 53 the O R T E P plot) , ' and the chemica l shift for this species is i n the 49 p p m region as found for [ H 2 N ( n - B u ) 2 ] + [ R u 2 C l 5 ( D P P B ) 2 ] - (Table 3.14). T h e react ion o f t r i (n-butyl)amine w i t h the mixed-phosph ine c o m p l e x (eq 3.19) was o r i g i n a l l y repeated i n this w o r k i n an attempt to determine the fate o f the m i s s i n g a l k y l group. H o w e v e r , i so l a t i on o f [ H 2 N ( n - B u ) 2 ] + [Ru2Cl5(DPPB)2]~ resu l ted i n a second p rob lem: not on ly d i d the fate o f the organic fragment need to be accounted for, but so d i d the requirement that a ch lor ine-def ic ien t R u species must also be f o r m e d (eq 3.21). C He 2.5RuCl2(DPPB)(PPh3) + N R 3 - ^ ^ • [ H 2 N R 2 ] + [ R u 2 C l 5 ( D P P B ) 2 r + 0.5Ru? + R'? (3.21) 135 Chapter 3 References: p 157 Chapter 3 Table 3.14 3 1P{!H} NMR Data (121.42 MHz)(a> for [cation]+[Ru2Cl5(P-P)2r Complexes Cation P-P Solvent Chemical Shift, 8 TMP0>) DPPB C D 2 C 1 2 53.6, s D M A H 39 DPPB CDC1 3 48.9, s C 6 D 6 49.2, s HNEt 3 41 DPPB CDCI3 49.0, s H 2N(n-Bu) 2 38 DPPB C D C 1 3 48.8, s C D 2 C 1 2 48.8, s(c) H 2N(n-Oct) 2 37 DPPB CDCI3 48.9, s C 6 D 6 49.2, s Cu DPPB CDCI3 48.3, s . H 2NEt 2( d> BINAP C D 2 C 1 2 5 A = 56.5, 8 B = 52.3; 2JPP = 38.0(e) H 2N(n-Bu) 2 40 BINAP C 6 D 6 5 A = 54.9,8B =51.9; 2 /pp = 38.5(e) CDCI3 5 A = 55.1,8B =51.6; 27pP = 37.6(e) (a) Spectrometer frequency for the values measured in this work at 20 °C; s = singlet. (b) Refs 18,52. (c) Measured at -98 °C. (d) Ref69. (e) 27pp coupling in Hz. 136 Chapter 3 References: p 157 Chapter 3 In s i tu studies p r o v i d e d l i t t le ins igh t into the nature o f the other products . A second crop o f orange so l id was isolated from the reaction (illustrated by eq 3.21 where R = n - B u ) by r emov ing the solvent so that on ly excess amine remained. T h e 3 1 P { 1 H } N M R spectrum o f the isolated second crop showed singlets at 44.9,49.2,49.6, and 50.0 p p m , as w e l l as one at 48.8 p p m for the ion ic species 38 (CDCI3). T h e first c rop conta ined on ly 38, as evidenced by a single resonance at 48.8 ppm. N o n e o f the other resonances can be ass igned , a l though the peak at 44.9 p p m m a y b e l o n g to the b i s (amine) r u then ium m o n o m e r , R u C l 2 ( D P P B ) ( a m i n e ) 2 . T h i s type o f c o m p l e x was isola ted by F o g g o f this l abora tory o n reac t ion o f R u C l 2 (DPPB ) (PPh3) and b e n z y l a m i n e i n C6H6 at r o o m temperature: the isolated complex gave a singlet i n the 3 1 P { 1 H } N M R spectrum at 45.7 (CDC1 3 ). 7 3 No o rgan ic c o m p o u n d s c o u l d be iden t i f i ed f r o m the * H N M R spec t rum. Resonances were not observed between 3.2 and 6.8, and on this basis alkenes are ru led out as possible products. At tempts^were made to determine the co-product(s) o f the [ R u 2 C l 5 ( D P P B ) 2 ] _ i o n i c s p e c i e s b y / s w i t c h i n g to a r e a c t i o n b e t w e e n t r i ( n - o c t y l ) a m i n e a n d RuCl2(DPPB)(PPh3) (Sect ion 2.5.9.1). T h i s was i n the hope that any organic fragments p roduced w o u l d be less vo la t i l e than i n the bu ty lamine case. Unfor tuna te ly , no th ing further c o u l d be deduced about the nature o f these products f r o m i n s i tu N M R experiments . T h e m a i n source o f problems i n these i n situ studies was that o n l y a s m a l l excess o f amine (2 equiv) c o u l d be used i n order to ensure that the al iphat ic region o f the N M R spectrum was not swamped by free amine signals. U n d e r these condi t ions , the react ion was s l o w to reach comple t i on . E v e n after heat ing the C6D6 so lu t ion for t w o days, the reaction was on ly approximately 50% complete. T o conf i rm the identity o f the [H.2NR2] + [Ru2Ci5(DPPB)2]- species 37 or 38, D2O was added to the sample, and the peaks at 7.9 p p m disappeared f rom the spectrum. T h i s ind ica ted that the resonance indeed be longed to the exchangeable NH2 protons o f the 137 Chapter 3 References: p 157 Chapter 3 cat ion. Furthermore, the methylene protons adjacent to the N atom o f the a l k y l a m m o n i u m cat ions were c o u p l e d to the two protons o n ni t rogen (see Sec t ions 2 .5.9.1-2.5.9.2) . A d d i t i o n o f the appropriate salt (i.e., d ibu ty l - or d i o c t y l a m m o n i u m chlor ide) to an N M R sample o f the i o n i c R u species 38 or 37, r e spec t ive ly , showed that the m e t h y l and methylene resonances o f the a m m o n i u m cations coalesce w i t h those o f the added salt. Interestingly, the NCH2C//2 resonance i n the [ H 2 N ( n - B u ) 2 ] + shifted f rom 1.65 to 1.85 on addi t ion o f [ H 2 N ( n - B u ) 2 ] + C l -3.4.2 Synthesis and Characterization of [H2N(/i-Bu)2]+[Ru2Cl5((/?)-BINAP)2]- (40) T h e tit le c o m p l e x was prepared by the same method used to prepare the i o n i c D P P B analogues 37 and 38. T h e 3 1 P { lH} N M R data agree w i t h those reported by K i n g and D i M i c h e l e 6 9 for [ H 2 N E t 2 ] + [ R u 2 C l 5 ( ( / ? ) - B I N A P ) 2 ] - and are shown i n Tab le 3.14. 3.5 Reaction of Sulfoxides and Thioethers with RuCl2(DPPB)(PPh3) Josh i et a l . have prepared the complexes R u 2 C l 4 ( D P P B ) 2 ( L ) , where L = C O and N E t 3 f rom R u C l 2 ( D P P B ) ( P P h 3 ) . 2 2 ' 2 3 H o w e v e r , R U 2 C J 4 ( D P P B ) 2 ( D M S O ) 33 was prepared f rom ds-RuCl2(DMSO)4. ' F o g g o f this laboratory extended the series o f c o m p l e x e s p repared f r o m R u C l 2 ( D P P B ) ( P P h 3 ) to i n c l u d e L = M e C N 3 0 and 73 H 2 N C H 2 P h . Other such dinuclear Ru2CU (DPPB)2(L) species were prepared d i rec t ly from the air-sensitive d imer R u 2 C L i ( D P P B ) 2 2 2 ' 2 5 ' 3 0 T h e react ion o f DMSO w i t h RuCl2(DPPB)(PPh3) 11 was undertaken to examine the range o f u t i l i ty o f 11 as a starting mater ial for the preparation o f Ru2Cl4(DPPB)2(L) species. A n excess o f DMSO reacted wi th 11 to g ive 33 i n 87% y i e l d (Sect ion 2.5.8.6). T h i s reaction is m u c h cleaner than the one performed by Josh i us ing RuCl2(DMSO)4 , this requir ing the remova l o f side-products Ru2Cl4(DPPB)2 24 and R u 2 C L i (DPPB)3 19 before i so la t ion o f the p r o d u c t . 2 2 ' 2 3 A n X - r a y crys ta l lographic study o f the c o m p l e x w i t h L = DMSO showed that the DMSO was S -bonded to r u t h e n i u m , 2 2 ' 2 3 and the I R spect rum showed an S = 0 bond stretch at 1090 c m - 1 , w h i c h is i n the range reported for S -bonded 138 Chapter 3 References: p 157 Chapter 3 sulfoxides (1060-1130 cm - 1) in other ruthenium complexes, Vso for an O-bonded sulfoxide is generally observed at a lower wavenumber: between 920-980 cm-*. 7 4 Interestingly, it was not possible to prepare 33 from 19 by adding excess DMSO (10 equiv). Chapter 5 discusses the chemistry of reactions of ammonia, py, bipy, and phen with both 11 and 19, where the use of either starting material gives the same product: RuCi2(DPPB)(N) 2 ( N = a donor N-atom). The reaction of 19 with DMSO was attempted at both room and reflux temperatures, but only the starting material was isolated on work-up. A reaction of 11 with TMSO was undertaken to see if the reactivity was similar to that of D M S O . The addition of an excess of T M S O did in fact give Ru2Cl4(DPPB)2(TMSO) 35 (Section 2.5.8.8), again with S-bonded sulfoxide (v S o = 1093 cm-1). The analogous thioethers, DMS and THT, react with RuCl2(DPPB)(PPh3) to give similar products: Ru 2Cl4(DPPB) 2(L) where L = DMS 34, or T H T 36 (Section 2.5.8.7 and 2.5.8.9, respectively). Therefore, the use of the mixed-phosphine starting material is quite general for the preparation of R ^ C l ^ D P P B ^ L ) species where L is a reasonably bulky ligand (see Chapter 5). The 3 1P{ lH} NMR spectra of the four complexes (L = DMSO, TMSO, DMS, and THT) are shown in Figures 3.23-3.25, while the data are compiled in Table 3.15. 139 Chapter 3 References: p 157 Chapter 3 | i I I I | i . I l I | I I I I | i I l I | i I I l | i I l I | 1 I l l | I I I I | 60 55 50 45 4C 35 30 25 PPM 20 Figure 3.23 3 1P{ *H} NMR spectra (121.42 MHz, 20 °C) of: (a) [(DMSO)(DPPB)Ru(p-Cl)3RuCl(DPPB)] 33 in and (b) [(TMSO)(DPPB)Ru(p-Cl)3RuCl(DPPB)] 35 in CDC1 3 . 140 Chapter 3 References: p 157 Chapter 3 (a) l l I l I l l l l j I I I I I I I I I | l l 1 l I l l l l | l l l l I i l l I 1 l I I I | I I I I | l I l l | I l l l | 54 52 50 48 46 44 PPM Figure 3.24 3lp{lH} NMR spectra (121.42 MHz, 20 °C) of [(DMS)(DPPB)Ru(p:-Cl)3RuCl(DPPB)] 34 in: (a) CDC1 3 and (b) C 6 D 6 . Chapter 3References: p 157 Chapter 3 (a) I l l I l I I l M | l l II 1 l l l l | I 1 l l I l ) I l | 1 l l l I I l I l | l i l l I I I l l 1 l I l l | l I ) l | 54 52 50 48 46 44 PPM Figure 3.25 ^P{lH) NMR spectra (121.42 MHz, 20 °C) of [(THT)(DPPB)Ru(p-Cl)3RuCl(DPPB)] 36 in: (a) CDC1 3 and (b) C 6 D 6 . Chapter 3 References: p 157 Chapter 3 Table 3.15 3 1 P{ 1 H} NMR Data (121.42 MHz, 20 °C) for the Dinuclear Complexes [(L)(DPPB)Ru(^-Cl)3RuCl(DPPB)](a) Complex Solvent Chemical Shift, 8 2/ p p , (Hz) L = DMS, Me2S CDC1 3 5 A , B = 51.3(b) 34 8 C = 48.2, 8 D = 46.0 35.6 C 6 D 6 8 A = 52.5, 8 B =51.8 44.1 8 C = 48.6, 8 D = 46.2 35.3 DMSO, Me2SO CDC1 3 8 A = 54.2,8B =51.2 42.8 33 8 C = 42.2, 8 D = 29.5 30.2 C 6 D 6 8 A = 53.9, 8 B = 52.9 43.8 8 C = 42.5, 8 D = 33.7 29.6 THT, C 4 H 8 S CDC1 3 8 A = 51.9, 8 B =51.2 43.2 36 8 C = 49.1, S D = 46.7 36.1 C 6 D 6 8 A , B = 52.3(b) — 8 C = 49.5, 8 D = 47.1 36.1 T M ^ O , C 4 H 8 S O CDC1 3 8 A = 54.7, 8 B = 50.8 41.1 35 8 C = 43.4, 8 D = 26.3 27.8 C 6 D 6 8 A = 55.1,8B =52.2 42.8 8 C = 44.2, 8 D = 29.1 29.0 acetophenone 32 C 6 D 6 8 A = 53.7,8B = 52.7 43.9 C 6 H 5 C ( 0 ) C H 3 8 C = 52.1, 8 D = 47.5 37.4 acetone 31 C 6 D 6 8 A = 53.7,8B =51.3 42.7 C H 3 C ( 0 ) C H 3 8 C = 50.8, 8 D = 49.6 38.5 (a) Several other complexes of this type are listed in Tables 4.1 and 5.3. (b) Indicates unresolved AB pattern. 143 Chapter 3 References: p 157 Chapter 3 The spectra of the L = DMS complex 34 in C 6 D 6 (Fig. 3.24b) and the L = T H T complex 36 in CDCI3 (Fig. 3.25a) are well resolved into two AB quartets, but show strong second-order effects where the downfield resonance appears as a singlet. This is the case when the spectrum of 34 is run in CDCI3 (Fig. 3.24a) and that of 36 is run in C6D6 (Fig. 3.25b). The difference in the appearance of this downfield signal in different solvents may be due to changes in the extent of thermal motion permitted by the solvent cage. Alternatively, the greater difference in the chemical shift between the two halves of the A B pattern in C6D6 (34) or CDCI3 (36) may prevent averaging of the signals. It is interesting that the spectra of complexes 34 and 36 are resolved in the "opposite" solvents. These second-order effects have been previously observed for Ru2Cl4(DPPB) 2(PhCN) in C D 2 C I 2 by Fogg of this laboratory.30 If the solution of the nitrile complex is cooled to -40 °C, the singlet observed in the 3 1 P{ 1 H} NMR spectrum 30 begins to resolve into a tight AB pattern. The UV-visible spectra of the Ru2Cl4(DPPB)2(L) complexes (where L = DMSO, TMSO, DMS, and THT), although given previously with the preparation of each complex in Chapter 2, are shown in Table 3.16 to allow easy comparison. 144 Chapter 3 References: p 157 Chapter 3 Table 3.16 UV-Visible Data of Ru2Cl4(DPPB)2(L) Complexes Complex Solvent ^max (nm) Emax (M" 1 cm-1) L = DMSO C 6 H 6 378 3010(a> 33 470 (sh) 590 C H 2 C 1 2 376 2900 470 (sh) 650 C 7 H 8 378 3010 472 (sh) 610 TMSO C 6 H 6 376 2470 35 460 (sh) 830 C H 2 C 1 2 374 2410 460 (sh) 600 DMS C 6 H 6 374 3780 34 460 (sh) 730 C H 2 C 1 2 372 3470 460 (sh) 660 THT C6H-6 374 3700 36 460 (sh) 605 CH2CI2 372 3200 460 (sh) 440 acetophenone C 6 H 6 364 3320 32 484 (sh) 815 CH2CI2 366 3300 484 (sh) 690 (a) Complex 33 in C^H^ obeyed Beer's law over the concentration range 2.2-8.6 x 10"4 M . 145 Chapter 3 References: p 157 Chapter 3 3.6 Reaction of Acetone with RuCl2(DPPB)(PPh3) (11) The complex Ru2Cl4(DPPB)2(acetone> acetone 31 can be isolated by reaction of Ru2Cl4(DPPB)2 24 with an excess of acetone in methylene chloride. ' In this thesis work, stirring a suspension of 24 in acetone produced 31 (i.e., no CH-2C12 is necessary, Section 2.5.8.4). The 3 1 P{ 1 H} NMR spectrum of 31 in C6D6 shows resonances for 24 as 22 well as 31, indicating an equilibrium. In other words, acetone is not as strongly bound to ruthenium as the sulfoxide or thioether ligands (see Figures 3.22-3.24 where no resonances for Ru2CU(DPPB)2 are evident). In fact, efforts in this work to prepare 31 from RuCl2(DPPB)(PPh3) 11 by adding an excess of acetone to a refluxing benzene solution failed. Likewise, refluxing 11 in acetone or EtOH did not result in any reaction. This was somewhat surprising, as Dekleva had reported the preparation of the PPh3 analogue Ru2Cl4(PPh3)4(acetone)acetone by refluxing RuCl2(PPh3)3 8 in acetone.33 In contrast, the refluxing of 8 in EtOH has been reported to produce [RuCl2(PPh3)2]2.36'76 The inability to produce the acetone-coordinated dinuclear complex from 11 perhaps may be rationalized by comparing the donor number (DN) 7 7 of acetone with those of DMSO and H 2 0 (recall that 24 was isolated when 11 was reacted with H2O, Section 3.3.4.1). The DN of acetone is 17.0, while those of DMSO and H2O are 29.8 and 18.0, respectively. Acetone may not coordinate strongly enough to ruthenium to shift the equilibrium to the right (eq 3.9, Section 3.3.3). This is evident from the 3 1P{!H} NMR spectrum of Ru2CU(DPPB)2(acetone)-acetone recorded by Joshi, 2 2 which showed the presence of a significant amount of 24. At the higher reaction temperatures used, the equilibrium shown in Figure 3.7, Section 3.2 may be shifted to the left, making the isolation of the acetone adduct impossible. The preparation of the acetone complex from RuCl2(DPPB)(PPh3) was also attempted in CH2CI2 at room temperature. None of the desired product could be isolated 146 Chapter 3 References: p 157 Chapter 3 i n this l o w e r temperature react ion. The react ion was also attempted i n CgH^ at r o o m temperature, and again no product cou ld be isolated. H o w e v e r , an i n situ react ion of RuCl2 (DPPB) (PPh3) and excess acetone (~ 200 equ iv) i n C6D6 d i d show format ion o f a s m a l l amount o f Ru2CLi(DPPB)2(acetone) complex , as judged b y 3 1 P { 1 H } NMR spectroscopy. Resonances were observed for free P P h 3 (-5.4 p p m ) , R u C l 2 ( D P P B ) ( P P h 3 ) 11 ( t r i p l e t - l i k e pa t te rn at 25.7 p p m ) , R u 2 C l 4 ( D P P B ) 2 24 (see Tab le 3.9), and Ru2Cl 4 (DPPB)2(acetone) 31 (see T a b l e 3.15). T h e ra t io o f naked d i m e r 24 to 31 obse rved i n the 3 1 P { 1 H } N M R spec t rum i s approximate ly 4:1. H o w e v e r , the ratio observed by Josh i when isolated 31 was d i s so lved i n C6D 6 was 1:7 (i.e., 24 : 31).22 3.7 Reaction of Acetophenone with Ru2Cl4(DPPB)2 (24) Acetophenone reacts w i t h Ru2CLi(DPPB)2 24 i n CH2CI2 at r o o m temperature to produce Ru2Cl 4 (DPPB)2(ace tophenone) , 32. The 3 1 P { 1 H } N M R spec t rum o f 32 is s imi l a r to that o f the acetone complex , Ru2CU(DPPB)2(acetone) acetone solvate 31 ' (see Tab le 3.13 for the N M R data). Interestingly, the elemental analysis and I R spectrum show that 32 is not solvated by a mole o f ketone, as it is i n 31. A s ingle C=0 stretch for coordinated ketone is observed at 1679 c m - 1 i n the s o l i d state, and 1683 c n r 1 i n CH2CI2 so lu t ion . T h e C H I R A P H O S analogue, Ru2CU(CHIRAPHOS)2 (ace tone ) also has o n l y a coordinated acetone. The UV -v i s ib l e data for 32 are l is ted i n Tab le 3.16. T h e 3 1 P { 1 H } N M R spectrum o f 32 i n C 6 D 6 shows naked d i m e r as w e l l as c o m p l e x 32, indica t ing that acetophenone is not strongly coordinated, as observed i n the acetone complex 31 (Sect ion 3.6). A w i d e range o f R u 2 C l 4 ( D P P B ) 2 ( L ) complexes has been prepared by Josh i et a l , and i n a l l o f them (with the except ion o f L = amine derivatives, see Sect ion 3.4), the four phosphorus n u c l e i are c h e m i c a l l y and magnet ica l ly i n e q u i v a l e n t . 2 3 T h e 3 1 P { 1 H } N M R spectra t yp i ca l ly show two independent AB patterns o f equal integral intensity, consistent 147 Chapter 3 References: p 157 Chapter 3 w i t h the unsymmet r i ca l , t r ich loro-br idged d inuclear structure A s h o w n i n F i g u r e 3.22, 22 23 and c o n f i r m e d for the L = D M S O c o m p l e x by X - r a y c r y s t a l l o g r a p h y . ' A characterist ic pattern is observed, consis t ing o f one tight A B quartet near 52 p p m , and a second, more w i d e l y separated A B quartet at higher f i e ld (the c h e m i c a l shift o f w h i c h 93 25 var ies cons ide rab ly depending on the nature o f L ) . ' T h e latter resonance, par t ly because o f this dependence, is assigned to the 'L -end ' o f the c o m p l e x . T h e invar iance o f the d o w n f i e l d s ignal is attributed to the stabil i ty o f the geometr ica l env i ronment o f the ( P - P ) C l R u ( p - C l ) 3 unit. T h e conformat ion o f this end o f the c o m p l e x is l ocked , as l o n g as the t r iple-chlor ide bridge remains intact, and is to a large extent independent o f the nature o f the l i gand w h i c h is coordinated to the other ruthenium atom. S u c h d i scuss ion appl ies to the new complexes synthesized i n this thesis work (where L = D M S , T H T , T M S O , and acetophenone). 3.8 Synthesis and Characterization of Ru2X4(P-P)3 Complexes T h e br idged-phosphine species, ( P - P ) X 2 R u ( p - P - P ) R u X 2 ( P - P ) are prepared by react ing two equivalents o f d iphosphine w i t h R u X 2 ( P A r 3 ) 3 complexes (Sec t ion 2.5.5). T h e f ive -coo rd ina t e , d inuc l ea r ru then ium c o m p l e x e s o f this type that have been synthes ized p rev ious ly are s h o w n i n F igure 3.1. T h e c o m p l e x R u 2 C L i ( D P P B ) 3 19 has also been prepared by adding one equivalent o f D P P B to R u 2 C l 4 ( D P P B ) 2 24, 2 5 and is occas iona l ly observed as a side-product i n the preparation o f R u C l 2 ( D P P B ) ( P P h 3 ) 11 (Sect ion 3.3.3). Despi te the general i n so lub i l i t y o f these phosphine-br idged species, they have been found to be useful precursors for the preparation o f R u C l 2 ( P - P ) ( N ) 2 species, where N is a N - d o n o r l igand (see Chapter 5). T h e f ive-coordinate c o m p l e x 19 is k n o w n to react w i t h C O i n the solid-state to produce Ru2 (CO)2Cl4 (DPPB)3 . 1 9 T h i s was repeated i n this w o r k , and l e d to the 148 Chapter 3 References: p 157 Chapter 3 discovery of solid-state reactivity of C O with other five-coordinate complexes of the type RuCl2(PAr 3) 3, RuCl2(DPPB)(PAr3), and Ru2CU(DPPB)2 (see Chapter 7). The UV-visible spectroscopic data for complexes 19,20, and 21, although given previously with the preparation of each complex in Chapter 2, are shown in Table 3.17 to allow easy comparison. Table 3.17 UV-Visible Spectroscopic Data of Ru 2X 4(P-P)3 Complexes 19, 20, and 21 in C 6 H 6 Complex ^max (nm) Emax (M- 1 cm"1) Ru 2Cl4(DPPB) 3 19 340 4520 450 3950 684 1320 Ru 2 Br 4 (DPPB) 3 20 364 2580 466 3620 710 1170 Ru 2Cl4(DCYPB) 3 21 340 5080 384 (sh) 3870 682 1940 The addition of an atmosphere of CO to a C6H.6 solution of Ru 2Br 4(DPPB)3 20 resulted in the originally yellow solution immediately becoming colourless, with the U V -visible bands of 20 at 364,466, and 710 all disappearing. This presumably is the result of the formation of Ru 2(CO) 2Br 4(DPPB)3, as has been previously reported for the chloro-analogue (see above). 149 Chapter 3 References: p 157 Chapter 3 Despite the utility of Ru2CU(P-P)3 complexes in preparing RuCl2(P-P)(N)2 complexes, the bridged-phosphine species did not react with DMSO (Section 3.5). An excess of DMSO was added to a CH2CI2 solution of 19, and the resulting mixture was stirred at room temperature. However, no reaction was observed after stirring for 24 h. In addition, a reaction of excess H 2 O with a refluxing solution of 19 was attempted in the same manner as illustrated for the preparation of Ru2CU(DPPB)2 from RuCl2 (DPPB)(PPh3) (Section 3.3.4.1). However, on refluxing the resulting green suspension for three hours, no reaction was observed. 3.9 Reaction of One Equivalent of Diphosphine (P-P) with RuCl2(DPPB)(PPh 3) (11) 3.9.1 P-P = DPPCP; Synthesis and Characterization of trans-RuCI2(DPPB)(DPPCP) (53) The addition of one equivalent of racemic DPPCP to a Ceii6 solution of RuCl2(DPPB)(PPh3) 11 at room temperature produced the six-coordinate complex trans-RuCl 2(DPPB)(DPPCP) 53 (Section 2.5.14.1 and Figure 3.26). The 31p{lH} N M R spectrum of this complex was a complicated second-order AA'BB' pattern, as shown in Figure 3.27, along with a simulated spectrum. The chemical shift and coupling constant values used for the simulation are listed in Table 3.18. (S,S) mirror (R,R) Figure 3.26 Structure of the two possible enantiomers of frans-RuC^DPPB)(DPPCP) 53. 150 Chapter 3 References: p 157 Chapter 3 151 Chapter 3 References: p 157 Chapter 3 Joshi has prepared the analogous tams-RuCl2(DPPB)(DPPM) complex in a similar manner.22 The 3 1 P{ 1 H} NMR spectrum of this complex was also a complicated second-order pattern. The higher field pattern centred at 7.1 ppm in Figure 3.27 is assigned to the P-atoms of the five-membered chelate DPPCP, while the lower field pattern centred at 16.5 ppm is assigned to those of the seven-membered chelate DPPB. This is in keeping with the reported relative deshielding of phosphorus nuclei in five- and seven-membered chelates. 2 1' 2 5' 4 4' 7 8 For comparison, the DPPM phosphorus nuclei in the four-membered chelate of fra«s-RuCl2(DPPB)(DPPM) are centred at -24.2 ppm in the ^ P ^ H } NMR spectrum, while those of the seven-membered chelate appear at 17.1 99 AA 7R ppm. Four-membered chelates are known to be highly shielded. ' Table 3.18 3 1 P{ 1 H} NMR Spectral Parameters^) Used to Obtain the Simulated Spectrum of frans-RuCl2(DPPB)(DPPCP) 53 Shown in Figure 3.27 Spectral Parameter Value*) Spectral Parameter Value*) 8 A , 8a- (DPPB) 16.5 ppm 8 B , 8B' (DPPCP) 7.1 ppm 2 7 A ' B 313.8 Hz 2 7 A B ' 312.1 Hz 2JAA' 32.0 Hz 2 7 B B " 34.8 Hz 2JA'B' ( o r 2 7 A B ) -39.6 Hz 2 / A B (or 2 7 A ' B ' ) -39.1 Hz (a) Obtained using the program NMR" Version 1.0 by Calleo Scientific Software Publishers on a Macintosh computer, assuming an AA'BB' spin system. (b) The coupling constants 2 / A B ' and 2 7 A ' B are due to frans-disposed phosphines, while the remaining coupling constants arise from mutually cw-phosphines. Signs ° f 2Jcis are reported relative to one another while the 2Jtrans are positive. 3.9.2 P-P = DPPE; Synthesis and Characterization of <ra /« -RuCl 2 (DPPE) 2 The addition of one equivalent of DPPE to a C6H6 solution of RuCl2(DPPB)(PPh3) at room temperature produced the six-coordinate complex trans-152 Chapter 3 References: p 157 Chapter 3 RuCl2(DPPE)2 54 (Section 2.5.14.2). Unlike the case where DPPCP or DPPM were used as the diphosphines, DPPE displaced both the triphenylphosphine and DPPB from the Ru centre. Schutte of this laboratory has recently displaced triphenylphosphine from 11 with some pyridyl phosphines PPh3_ x py x to produce six-coordinate complexes of the type *rans-RuCl2(DPPB)(PPh3_ xpy x) where py = 2-pyridyl and x = 1, 2, and 3 . 7 9 Complex 54 has been prepared previously by refluxing R U C I 3 X H 2 O and 2.5 equivalents of DPPE in E t O H . 2 1 In this thesis work, the 3 1 P{ 1 H} NMR spectrum of 54 was a singlet in C D C I 3 at 45.0 ppm, which is in agreement with the literature data. 3.10 Reaction of One Equivalent of Diphosphine (P-P) with RuCl2 (PPh 3 ) 3 (8) Jung et al. have shown that the mixed-phosphine complex RuCl2 (DPPB ) (PPh3) 11 is produced on reaction of one equivalent of DPPB with RuCl2 (PPh3)3 8.2 1 This research group here at UBC has shown that it is possible to prepare the DIOP and BINAP analogues in the same manner (Section 3.3.3). All of the above mentioned diphosphines form seven-membered chelates on coordination to ruthenium. However, Jung et al. have shown that if diphosphines with smaller carbon backbones (DPPM, DPPE, and DPPP) are used, species of the type RuCl2 (P-P )2 are isolated, instead of the desired R u C i 2 ( P -PXPPI13) complexes, and this was attributed to the smaller chelate bite angle of DPPM, 21 DPPE, and DPPP, this angle results in the coordination sphere around ruthenium being less sterically crowded, and allows a second diphosphine to displace P P h 3 to form the 21 coordinatively saturated products. Interestingly, Mudalige of this laboratory was able to synthesize the P - N analogues, RuCl2(P-N)(PAr3) using the P M A and P A N ligands (Figure 3.28) via a similar displacement reaction of PPI13 from 8. 4 1 Both P M A (chelate ring size of 5) and P A N (chelate ring size of 6) produce the five-coordinate Ru complexes, while the diphosphines with same length carbon backbone (i.e., DPPE and DPPP, respectively) do 153 Chapter 3 References: p 157 Chapter 3 not react with 8 to give RuCl2(P-P)(PAr3) complexes. Therefore, electronic as well as steric factors must be playing an important role. PMA PAN Figure 3.28 Structure of the P-N chelating ligands PMA and PAN. 3.10.1 P-P = DPPCP; Synthesis and Characterization of trans-RuCl2(DPPCP)2 (52) The addition of one equivalent of racemic DPPCP to a CH2CI2 of RuCl2(PPh3)g 8 in an attempt to prepare RuCl2(DPPCP)(PPh3) resulted in the formation of trans-RuCl2(DPPCP)2 52 (Section 2.5.13), which was subsequently prepared directly from RUCI3XH2O in refluxing ethanol by the addition of two equivalents of DPPCP (Section 2.5.13). The diphosphine DPPCP has the same length carbon-backbone as DPPE, which was also observed to form the frans-RuCl2(P-P)2 product (Section 3.9.2). Initially, solution 3 1P{lH} NMR studies on the solid isolated from the reaction of 8 and DPPCP showed a singlet at 22.8 ppm, indicating a single product; however, orange crystals isolated from the filtrate gave a singlet at 23.3 ppm in CDCI3. Subsequently, both resonances were observed in the solution 3 1 P{lH} NMR spectrum of the solid isolated from the reaction of RUCI3XH2O with DPPCP. The two singlets presumably result from the use of the racemic DPPCP, which produces two diastereomers of 52 (Figure 3.29). 154 Chapter 3 References: p 157 Chapter 3 Cl enantiomers Figure 3.29 Stereoisomers of trans-RuCl2(DPPCP)2 52, where P represents the PPh2 group. The 3 1P{!H} NMR spectrum of the two diastereomers of 52 is shown in Figure 3.30. Based on a purely statistical approach, 50% of each diastereomer would be expected. However, the NMR spectrum shows an approximately 2:1 ratio of one diastereomer to the other. The difference in solubility of the two diastereomers observed on isolation of the products from the reaction of 8 and DPPCP presumably gives rise to the different ratios of diastereomers. Nothing can be deduced from the ratio of diastereomers observed (i.e., whether or not one diastereomer is kinetically or thermodynamically favoured over the other). Also, if the 3 1P{!H} NMR spectrum of the solid is measured in C6D6, the two resonances appear at 23.7 and 23.8 ppm, with the peak intensities reversed from those observed in Figure 3.30. This may indicate differing solubility of the two diastereomers, although another more likely possibility is that the resonance for the major diastereomer in CDCI3 has shifted more than that of the minor diastereomer on changing solvents. 155 Chapter 3 References: p 157 Chapter 3 oo o oo CM CN I D CN) CM J VTTT 50 TJTTTT-|TTTTTTrrTTTTTTTTTT^ 40 30 20 10 0 PPM Figure 3.30 The 3 1P{ !H} NMR spectrum (121.42 MHz, 20 °C) of the two diastereomers of *rans-RuCl2(DPPCP)2 52 in CDC1 3 . 3.11 Summary The five-coordinate complex RuCl2(DPPJ3)(PPh3) was found to be a versatile starting complex for the synthesis of Ru2Cl4(DPPB)2 and Ru2Ci4(DPPB)2(L) complexes, where L = DMSO, DMS, TMSO, THT, and acetophenone. During this work, it was necessary to find routes to the bromo-analogue Ru2Br4(DPPB)2, as this complex was needed for later studies as a catalyst for imine hydrogenation (Chapter 6). Both RuBr2(PPh3)3 and RuCl2(DPPB)(PPh3) were characterized in the solid state by X-ray crystallography, and were shown to be of pseudo-octahedral geometry, with a weak agostic interaction between the Ru centre and an ortho-hydrogen of the PPI13 ligand. 156 Chapter 3 References: p 157 Chapter 3 3.12 References (1) James, B. R.; McMillan, R. S.; Morris, R. H.; Wang, D. K. W. Adv. Chem. Ser. 1978,167,122. (2) Parshall, G.; Ittel, S. D. Homogeneous Catalysis: The Applications and Chemistry of Soluble Transition-Metal Complexes; 2nd ed.; Wiley: New York, 1992. (3) Jardine, F. H. Prog. Inorg. Chem 1984, 31, 265. (4) Collman, J. P.; Hegedus, L. S.; Norton, J. R ; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1987, p 545. (5) Chaloner, P. A.; Esteruelas, M . A.; Joo, F.; Oro, L. A. Homogeneous Hydrogenation; Kluwer Academic: Dordrecht, 1994. (6) Schroder, M. ; Stephenson, T. A. In Comprehensive Coordination Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon: Oxford, 1987; Vol. 4, Chapter 45. (7) Bruce, M . I. In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, 1982; Vol. 4, p 651. (8) Seddon, E. A.; Seddon, K. R. The Chemistry of Ruthenium; Elsevier: Amsterdam, 1984. (9) Jardine, F. H. Prog. Inorg. Chem. 1984, 31, 265. (10) Keister, J. B. J. Organomet. Chem. 1987, 318, 297. (11) Shapley, P. A. J. Organomet. Chem. 1987, 318, 409. (12) Noyori, R. Asymmetric Catalysis in Organic Synthesis; Wiley-Interscience: New York, 1994. (13) Henrici-Olive, G.; Olive, S. Angew. Chem., Int. Ed. Engl. 1971,10, 105. (14) James, B. R.; Wang, D. K. W. Can. J. Chem. 1980, 58, 245. (15) Wang, D. K. W. Ph.D. Thesis, The University of British Columbia, 1978. (16) Kawano, H.; Ikariya, T.; Ishii, Y.; Saburi, M . ; Yoshikawa, S.; Uchida, Y.; Kumobayashi, H. J. Chem. Soc, Perkin Trans. 11989, 1571. (17) James, B. R.; Wang, D. K. W. Inorg. Chim. Acta 1976,19, L17. (18) Thorburn, I. S.; James, B. R., unpublished results. (19) Bressan, M. ; Rigo, P. Inorg. Chem. 1975,14, 2286. 157 Chapter 3 (20) Joshi, A. M . ; Batista, A. A.; James, B. R., unpublished results. (21) Jung, C. W.; Garrou, P. E.; Hoffman, P. R.; Caulton, K. G. Inorg. Chem. 1984, 23, 726. (22) Joshi, A. M . Ph.D. Thesis, The University of British Columbia, 1990. (23) Joshi, A. M . ; Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chim. Acta 1992, 198, 283. (24) Mezzetti, A ; Costella, L.; Del Zotto, A ; Rigo, P.; Consiglio, G. Gazz. Chim. Ital. 1993,123, 155. (25) Thorburn, I. S. Ph.D. Thesis, The University of British Columbia, 1985. (26) James, B. R.; Pacheco, A.; Rettig, S. J.; Thorburn, I. S.; Ball, R. G.; Ibers, J. A. J. Mol. Catal. 1987,41, 147. (27) James, B. R.; Thompson, L. K.; Wang, D. K. W. Inorg. Chim. Acta 1978, 29, L237. (28) Dekleva, T. W.; Thorburn, I. S.; James, B. R. Inorg. Chim. Acta 1985,100, 49. (29) Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chem. 1986,25, 234. (30) Fogg, D. Ph.D. Thesis, The University of British Columbia, 1994. (31) Fraser, A. J. F.; Gould, R. O. J. Chem. Soc, Dalton Trans. 1974, 1139. (32) Stephenson, T. A ; Wilkinson, G. J. Inorg. Nucl. Chem. 1966,28, 945. (33) Dekleva, T. W. Ph.D. Thesis, The University of British Columbia, 1983. (34) Ruiz-Ramirez, L. ; Stephenson, T. A.; Switkes, E. S. J. Chem Soc, Dalton Trans. 1973, 1770. (35) Pez, G. P.; Grey, R. A.; Corsi, J. J. Am. Chem Soc. 1981,103,7528. (36) Hoffman, P. R.; Caulton, K. G. J. Am Chem. Soc. 1975, 97, 4221. (37) Hallman, P. S.; Stephenson, T. A ; Wilkinson, G. Inorg. Synth. 1970,12, 237. (38) Champness, N. R.; Levason, W.; Webster, M . Inorg. Chim. Acta 1993,208, 189. (39) La Placa, S. J.; Ibers, J. A. Inorg. Chem. 1965, 4, 778. (40) Mudalige, D. C ; Rettig, S. J.; James, B. R.; Cullen, W. R. / . Chem. Soc, Chem. Commun. 1993, 830. (41) Mudalige, D. C. Ph.D. Thesis, The University of British Columbia, 1994. (42) Hampton, C. R. S. M . ; Butler, I. R.; Cullen, W. R.; James, B. R.; Charland, J.-P.; Simpson, J. Inorg. Chem 1992, 31, 5509. 158 Chapter 3 (43) Hampton, C. R. S. M . Ph.D. Thesis, The University of British Columbia, 1989. (44) Dixon, K. R. In Multinuclear NMR; Mason, J., Ed.; Plenum: New York, 1987; Chapter 13. (45) Gosser, L. W.; Knoth, W. H.; Parshall, G. W. J. Am. Chem. Soc. 1973, 95, 3436. (46) Lippard, S. J.; Mayerle, J. J. Inorg. Chem. 1972,11, 753. (47) Muetterties, E. L. ; Alegranti, C. W. J. Am. Chem. Soc. 1970, 92, 4114. (48) Costa, G.; Pellizer, G.; Rubessa, F. / . Inorg. Nucl. Chem. 1964, 26, 961. (49) Glockling, F.; Hooton, K. A. J. Chem. Soc. 1962, 2658. (50) Churchill, M . R.; Kalra, K. L. Inorg. Chem. 1974,13, 1065. (51) Costa, G.; Reisenhofer, E.; Stefani, L. J. Inorg. Nucl. Chem. 1965,27, 2581. (52) Gamage, S. N.; Morris, R. H.; Rettig, S. J.; Thackray, D. C ; Thorburn, I. S.; James, B. R. J. Chem. Soc, Chem. Commun. 1987, 894. (53) Thorburn, I. S.; Rettig, S. J.; James, B. R., unpublished results. (54) Genet, J. P.; Pinel, C ; Ratovelomanana-Vidal, V.; Mallart, S.; Pfister, X.; Cano De Andrade, M . C ; Laffitte, J. A. Tetrahedron: Asymmetry 1994, 5, 665. (55) Genet, J. P.; Pinel, C ; Mallart, S.; Juge, S.; Cailhol, N.; Laffitte, J. A. Tetrahedron Lett. 1992, 33, 5343. (56) Genet, J. P.; Mallart, S.; Pinel, C ; Juge, S.; Laffitte, J. A. Tetrahedron: Asymmetry 1991,2, 43. (57) Genet, J. P.; Pinel, C ; Ratovelomanana-Vidal, V.; Mallart, S.; Pfister, X.; Bischoff, L.; Cano De Andrade, M . C ; Darses, S.; Galopin, C ; Laffitte, J. A. Tetrahedron: Asymmetry 1994, 5, 675. (58) Genet, J. P.; Pinel, C ; Mallart, S.; Juge, S.; Thorimbert, S.; Laffitte, J. A. Tetrahedron: Asymmetry 1991,2, 555. (59) Kuhlman, R.; Rothfuss, H.; Gusev, D.; Streib, W. E.; Caulton, K. G. Abstracts of Papers, 209th American Chemical Society National Meeting, Anaheim, CA; American Chemical Society: Washington, DC, 1995; Abstract INOR 497. (60) Noyori, R. Asymmetric Catalysis in Organic Synthesis; Wiley-Interscience: New York, 1994. (61) Smith, A. E. Inorg. Chem, 1972,11, 2306. (62) Takaya, H.; Mashima, K.; Koyano, K.; Yagi, M. ; Kumobayashi, H.; Taketomi, T.; Akutagawa, S.; Noyori, R. J. Org. Chem. 1986,51, 629. (63) Andersen, R. A. Inorg. Nucl. Chem. Lett. 1980,16, 31. 159 Chapter 3 (64) Noyori, R. Chem. Soc. Rev. 1989,18, 187. (65) Noyori, R. Science 1990,248, 1194. (66) Noyori, R.; Takaya, H. Acc. Chem. Res. 1990,23, 345. (67) Ikariya, T.; Ishii, Y.; Kawano, H.; Arai, T.; Saburi, M . ; Yoshikawa, S.; Akutagawa, S. J. Chem. Soc, Chem. Commun. 1985, 922. (68) Noyori, R.; Ohkuma, T.; Kitamura, M. ; Takaya, H.; Sayo, N.; Kumobayashi, H.; Akutagawa, S. J. Am Chem Soc. 1987,109, 5856. (69) King, S. A ; DiMichele, L. Chem. Ind. (Dekker) 1994, 62, 157. (70) King, S. A.; Thompson, A. S.; King, A. O.; Verhoeven, T. R. J. Org. Chem. 1992, 57, 6689. (71) Hampton, C ; Dekleva, T. W.; James, B. R.; Cullen, W. R. Inorg. Chim Acta 1988,145, 165. (72) Joshi, A. M.; James, B. R., unpublished results. (73) Fogg, D. E.; James, B. R. Inorg. Chem 1995, 34, 2557. (74) Bora, T.; Singh, M . M . Transition Met. Chem. 1978, 3, 27. (75) Pacheco, A.; Rettig, S. J.; James, B. R. Inorg. Chem. 1995, 34, 3477. (76) Caulton, K. G. J. Am. Chem Soc. 1974, 96, 3005. (77) Huheey, J. E. Inorganic Chemistry, Principles of Structure and Reactivity; 3rd ed.; Harper & Row: New York, 1983, p 340. (78) Garrou, P. E. Chem. Rev. 1981, 81, 229. (79) Schutte, R. P., unpublished results. 160 CHAPTER 4 ACTIVATION OF DIHYDROGEN BY FIVE-COORDINATE RUTHENIUM(II) COMPLEXES CONTAINING CHELATING DITERTIARY PHOSPHINES 4.1 Introduction Previous work in this laboratory has demonstrated the ability of Ru(II) five-coordinate complexes containing one chelating ditertiary phosphine ligand per Ru to react with dihydrogen to generate both classical hydride species1 and molecular hydrogen species.1"5 Generally, classical hydride complexes containing the moiety "Run(H)Cl" have been isolated as the products when a dichloro Ru(II) starting complex is reacted with H2 in the presence of an added base, while the molecular hydrogen complexes "Ru(H2)Cl2" are obtained in the absence of an added base. Our interest in the reactivity of "RuCl2(P-P)" species with H2 grew out of their successful use as hydrogenation catalysts. ' Hydride complexes and their molecular hydrogen relatives are possible intermediates in catalytic hydrogenation cycles. Some of the early work done in this area involved the generation of Ru(H)Cl(PR3)3 species by reacting RuCl2(PR3)3 with H2 in the presence of an appropriate base (eq 4.1).7 Work from this group has shown the importance of the appropriate choice of base in determining the nature of the Ru species formed (eqs 4.2 o in and 4.3). The highly nucleophilic character of the strongly basic trialkylamines, such as NEt3, can sometimes lead to complications through the coordination and/or dehydrogenation and/or dealkylation of the amines.11 NEt3 ' RuCl2(PR3)3 + H 2 : —— *~ Ru(H)Cl(PR3)3 + Et 3NH +Cl~ (4.1) 161 Chapter 4 References: p 214 Chapter 4 2 R u C l 3 ( P R 3 ) 2 + H 2 D M A [ R u C l 2 ( P R 3 ) 2 J 2 + 2 D M A H + C 1 (4.2) H 2 / Pro ton Sponge C 7 H 8 2 R u C l 3 ( P R 3 ) 2 + 4 H 2 Pro ton Sponge [ ( T l 2 - H 2 ) ( P R 3 ) 2 R u ( p - H ) ( p - C l ) 2 R u ( H ) ( P R 3 ) 2 ] + 4 P S H + C r (4.3) D M A T h e present study focuses on the react ivi ty o f Ru(II) species con ta in ing a s ingle di ter t iary phosphine w i t h H.2, i n both the presence and absence o f an added base. T h o r b u r n first s tudied the react iv i ty o f R u 2 C l 5 ( D P P B ) 2 and Ru2CU(DPPB)2 w i t h H2 under a variety o f c o n d i t i o n s . 1 ' 6 T h e reaction o f either o f the above complexes w i t h H2 i n the presence o f added Pro ton Sponge gave the t r ip ly -ch lo ro -b r idged d inuc lea r an ion ic species [ R u 2 C l 5 ( D P P B ) 2 ] - P S H + as the major isolable product (60-65%). 4.2 A Brief Review of Molecular Hydrogen Complexes and Their Properties and Characterization A comprehens ive r ev i ew by Jessop and M o r r i s o f t rans i t ion meta l d i h y d r o g e n 19 complexes appeared i n the literature i n 1992. T w o other, even more recent, r ev iews w h i c h deal extensively w i t h the coordinat ion chemistry o f molecu la r hydrogen have also appeared i n the l i t e r a t u r e . 1 3 ' 1 4 Therefore, on ly a br ie f r ev iew o f the type o f complexes con t a in ing the H2 l i g a n d and the character iza t ion methods o f these species w i l l be discussed here. Trans i t ion metal hydr ide format ion by oxida t ive addi t ion o f d ihydrogen at a meta l centre has been proposed to occur by a mechanism i n v o l v i n g the in i t i a l coord ina t ion o f a hydrogen molecu le , f o l l o w e d by cleavage ( i nvo lv ing addi t ion o f two electrons) into two hydr ide l i g a n d s . 1 5 ' 1 6 In 1976, A s h w o r t h and Single ton proposed that neutral d ihydrogen occupies a coordinat ion site i n the complexes [RuH4(PPh3)3J and [ R u H 3 ( D P P E ) 2 ] + , w i t h 162 Chapter 4 References: p 214 Chapter 4 little weakening of the H - H bond. 1 7 This was based on their observation that both complexes reacted with N2, PPI13, and NH3 via the initial loss of dihydrogen, which paralleled the chemistry seen for reversibly bonded molecular dioxygen compounds; however, it should be noted that the reversible 02-carriers often exhibit the nature of coordinated peroxide. Also, in the classical reversible binding of H2 by Vaska's compound, IrCl(CO)(PPh3)2, the H2 is bound as two classical hydrides, and so Ashworth 17 and Singleton's proposal was extremely speculative at best. Judging from IR spectroscopic evidence and the extreme lability of the "hydrogen ligand", Kubas suggested in 1980 that the bonding of hydrogen "may be novel" in the complexes MH2(CO)3(PCy3)2 (M = Mo, W ) . 1 9 Direct evidence of this "novel" binding of H-2 came from Kubas et al. in 1983 when X-ray and neutron diffraction studies of W(CO)3(PPr'3)2(ri2-H2) showed a side-on (r|2-) bonded H 2 l igand. 2 0 ' 2 1 The H - H separation of the r|2-bound dihydrogen was found to be 0.75(16) A by X-ray analysis, and 0.84 A by neutron diffraction analysis.22 This is in comparison with the 0.74 A found in free H2. Other evidence of this newly discovered mode of H2 binding came from the * H N M R spectrum of the HD isotopomer of the tungsten complex (i.e., W(CO) 3(PPr' 3) 2(HD)), which showed a 1:1:1 triplet with V H D = 33.5 H z . 1 6 ' 2 2 ' 2 3 The large HD coupling constant observed is on the order of magnitude for that seen in free gaseous HD ( ^ H D = 43.2 H z ) 2 4 which clearly indicates a somewhat reduced H - D bond order. On the other hand, the coupling constant seen between H/D in hydride-deuteride complexes is typically < 2 H z . 1 6 Numerous reports of molecular hydrogen complexes immediately followed these first reports by Kubas et al. In fact, by the end of 1991, more than 300 papers had been published in this area of research.12 To date, more than 90 structural types are known. Coordination of dihydrogen to many of the transition metals is now known, the ligand environment of the majority of these complexes contain phosphorus donors, although in some cases C O (rather than a P donor) is present as a ligand. 2 5 More recently, a few 163 Chapter 4 References: p 214 Chapter 4 examples of molecular hydrogen complexes in a nitrogen donor environment have been reported. Workers from this department have reported a dihydrogen complex with a P -N ligand system, where the P - N ligand is PMA (Figure 3.28, Section 3.10) and the complex is RuCl2(P-N)(P(p-tolyl)3)(r|2-H2).26'27 The initial reports by Kubas showing r| 2-H2 binding were followed quickly by reported syntheses of [Ir(H)(r|2-H2)(bq)(PPh3)2]+ (Figure 4.1, bq = 7,8-benzoquinolate) by Crabtree and L a v i n , 2 8 ' 2 9 and [ M ( H ) ( T I 2 - H 2 ) ( D P P E ) 2 ] + (Figure 4.1, M = Fe, Ru) by Morris et al. The latter report showed that the prediction by Ashworth and Singleton was, in fact, correct. PR 3 O C ' / / , . . i . . ^ C O O C ^ M ^ H P R 3 H C///„. J „ ^ P P h 3 ^ II'^. IT P h 3 P ^ ^ H H + H j H + H M = Mo, W R = Pr\ Cy C - N = 7,8-benzoquinolinate M = Fe, Ru P-P = DPPE Figure 4.1 Some examples of molecular hydrogen complexes. Several complexes originally thought to be polyhydrides have now been reformulated as molecular hydrogen complexes. For example, the complex [RuFf4(PPh3)3] is now recognized to be [Ru(H)2(r | 2 -H2)(PPh3)3], 3 1 while the dinuclear complex [Ru(H)2Cl(PPh3)2]2 is now reformulated as [(ii2-H2)(PPh3)2Ru(p>H)(p:-C l ) 2 R u ( H ) ( P P h 3 ) 2 ] 9 ' 1 0 ' 3 2 Generally, ! H NMR spectroscopy is the most useful method for characterizing molecular hydrogen complexes, and for distinguishing them from classical hydride species. The most direct evidence is structure determination by either neutron or X-ray diffraction studies. Unfortunately, suitable crystals for these types of studies are difficult 164 Chapter 4 References: p 214 Chapter 4 to grow. Also, because of the limited number of research institutions which have neutron-12 scattering and diffraction facilities, only four single-crystal studies have been reported. Vibrational spectroscopy (IR, Raman) is of limited use, particularly for non-carbonyl complexes, because the v(H-2) bands are often too weak to be observed.33 Measurement of the T\ relaxation time of the *H NMR upfield resonances is perhaps the most useful and readily available method for distinguishing molecular hydrogen and classical hydride species. The T\ criterion was introduced by Crabtree et 34 35 3(S al. ' and refined by Morris and co-workers. If a minimum T\ value is determined to be less than 40 ms at 250 MHz, then the complex is likely to contain the r| 2-H2 ligand. 1 4 A classical hydride resonance will exhibit a T\ relaxation value significantly larger than 100 ms . 1 2 ' 1 4 ' 3 5 Large apparent J couplings between protons in transition-metal trihydrides have been observed, and have been explained in terms of exchange couplings between protons, which are a manifestation of quantum mechanical motion in the hydrides. 3 7 The couplings are not magnetic in origin; in fact, there are examples in which the couplings are larger than those reported for molecular hydrogen.37 The T\ method relies on the fact that the two hydrogen atoms in an r| 2-H2 ligand are close to one another, in which case dipole-dipole or spin-lattice relaxation will dominate the modes of NMR relaxation in solution. The two protons for a classical dihydride will be greater than 1.6 A apart, and therefore exhibit a much longer T\ value. The rate of spin-lattice relaxation, R(DD), is related to the internuclear distance by equation 4.4: 165 Chapter 4 References: p 214 Chapter 4 R ( D D ) = { 7 1 ( D D ) r =0.3y = (2*) ( r H H ) 6 { i + U ^ + l + (4.4) where, x c rotational correlation time (s rad - 1) = 0.62/co at 0(min); 9 = temperature (K) co Larmor frequency (rad s _ 1); Co = 2TCV where v is the spectrometer frequency h Planck's constant (6.626 x l O " 3 4 J s) rnH H - H internuclear distance (cm for cgs units). The relevant units and conversion factors for both cgs and SI systems are shown in Appendix V. It is necessary to include another term in equation 4.4 if SI units are used. The right-hand side of the equation must be multiplied by (\io/4n)2, where p 0 is the permeability of a vacuum. If cgs units are employed and the T\ measurement is performed on a 300 MHz spectrometer, equation 4.4 reduces to equation 4.5, as shown below. If the T\ experiment is performed on a 300 MHz spectrometer, and SI units (and metres converted to angstroms) are used, then equation 4.6 is employed. Y gyromagnetic ratio ( for 1 H , y= 2.675 x 10 - 4 rad G _ 1 s - 1 ) Pv(DD) = { ^ ( D D ) } " 1 = 1.291xl0-46 cm 6 s^r^) ,-6 (4-5) R ( D D ) = { ^ ( D D ) } " 1 = 129.1 A 6 s ^ ) - 6 (4.6) 166 Chapter 4 References: p 214 Chapter 4 The values for the H - H internuclear distance of a r|2-H-2 moiety range from 0.8-1.0 A,1 2 while free dihydrogen gas has an H - H bond length of 0.74 A. 1 5 ' 1 6 The values obtained for the H - H distance from equations 4.4-4.6 were found to be systematically longer than the distances determined by crystallography. Morris et al. suggested multiplying the internuclear distance determined from equations 4.4-4.6 by a correction factor C (0.794).36 The source of the discrepancy (and the need for the correction factor) is the fast rotation of the r i 2 -H2 ligand as compared to the complex as a whole, which results in less efficient relaxation and longer T\ values. 3 5' 3 6 If the r | 2 - H 2 ligand were rotating slowly, then no correction factor would be necessary.35'36 Several reports have advised caution in the use of T\ measurements in the characterization of molecular hydrogen complexes. ' The existence of an equilibrium between a dihydrogen complex and the corresponding dihydride complex in solution has been demonstrated for some complexes (eq 4.7). This observation supports the notion that dihydride complexes are produced by oxidative addition of an initially formed T| 2 -H2 complex. 1 2 ' 1 5 ' 1 6 ' 3 3 ' 3 5 4.3 A Summary of Relevant Research Previously Done in this Laboratory on the Interaction of Dihydrogen and Other Small Molecules with Ru(II) Diphosphine Complexes 4.3.1 Interaction with H2 in the Absence of an Added Base Joshi et al. discovered that the dinuclear complex Ru2CU(DPPB)2 24 reacts with H2 (1 atm) in benzene or toluene, in the absence of an added base, to produce the molecular hydrogen complex [(r) 2-H2)(DPPB)Ru(p>Cl)3RuCl(DPPB)].2'3 The dihydrogen complex, which is in rapid, reversible equilibrium with the Ru2Ci4(DPPB)2 H H (4.7) 167 Chapter 4 References: p 214 Chapter 4 starting complex (Figure 4.2), was characterized in solution by lH and 3 1P{!H} NMR 2 3 spectroscopy. ' [RuCl(DPPB)(p-Cl)]2 + H 2 „ [(ri2-H2)(DPPB)Ru(p-Cl)3RuCl(DPPB)] Figure 4.2 Equilibrium between Ru2Cl4(DPPB)2 24 and Ru2CU(DPPB)2(r|2-H2). A *H NMR spectrum showed the T | 2 -H2 resonance as a broad peak at -11.0 ppm, with a T\ minimum in C 7 D 8 of 12 ± 1 ms at 276 K (300 MHz). If this value is entered in equation 4.6, the H - H internuclear distance of 1.08 A is obtained.2'3 When a correction factor C is applied (0.794 is suggested by Morris and co-workers ), the H - H internuclear distance was found to be 0.86 ± 0.02 A. Crabtree and Hamilton have described the correction factor and its use. ' ' When a C6D6 solution of the Ru2CU(DPPB)2 species was placed in a mixture of H2 (1.2 atm) and D2 (1.8 atm) at 20 °C, an T | 2 - H D isotopomer was observed in the NMR spectrum. Therefore, the dinuclear ruthenium complex must catalyze isotope exchange between H2 and D2. The *H NMR resonance was then observed at -11.0 ppm as a 1:1:1 triplet ( ^ H D = 29.4 Hz) of 1:2:1 triplets (cis, 2 / H P = 7.5 Hz). 2 ' 3 The 3 1P{ 1H} NMR spectra indicate that the equilibrium represented in Figure 4.2 shows about 35% conversion to the r| 2-H2 complex at 1 atm and 20 °C in C7D8. This was originally incorrectly reported as a 60% conversion.2'3 However, Chau has shown by P—P = DPPB 168 Chapter 4 References: p 214 Chapter 4 3 1 P{ 1 H} NMR spectroscopy that, in CH2CI2, the constant K for the equilibrium is 1400 M - 1 at 25 ° C . 4 ' 5 ' 4 3 This corresponds to ca. 80% conversion of 24 to the molecular hydrogen complex. Therefore, the extent of conversion to the molecular hydrogen complex is probably dependent on the conditions used (especially the solvent). 4.3.2 Interaction with H2 in the Presence of an Added Base Thorburn et al. found that Ru2CU(DPPB)2 reacted with H2 in the presence of two equivalents of NEt3 to produce a trinuclear complex [Ru(H)Cl(DPPB)]3 in low yield.1 Section 3.2 reviewed this work, as well as subsequent improvements made to the preparation by Joshi. Joshi investigated the interaction of H2 with [Ru(H)Cl(DPPB)]3 in C7D8 by NMR spectroscopy.2 A broad resonance was observed in the *H NMR spectrum at -13.1 ppm, with a T\ of 24 ms at 293 K (300 MHz). When the solution was cooled, this resonance decoalesced to show three broad signals at -7, -13 and -18 ppm at 220 K. The above data, coupled with the 3 1P{ 1H} NMR spectrum, were consistent with the structure shown in Figure 4.3, which contains a terminal and bridging hydride, as well as a r | 2-H2 moiety; such dinuclear species are well characterized within other phosphine or chelating phosphine-amine donor systems.4 4'4 5 P-P = DPPB Figure 4.3 Suggested geometry of the Ru2(T|2-H2)(H)2Cl2(DPPB)2 complex. 169 Chapter 4 References: p 214 Chapter 4 4.3.3 Interaction of Other Molecules with Ru2Cl4(DPPB) 2 Josh i also investigated the react ivi ty o f CO and N2 w i t h Ru2CU(DPPB)2 24.2'3'4 6 In CgDg, c o m p l e x 24 was found to form an a-N2 complex under an atmosphere o f N2 at 20 °C. 3 1 P { 1 H } N M R spectroscopy indicated ca. 70% convers ion to Ru2Cl4(DPPB)2(a-N2) under the above condi t ions . T h e analogous C O c o m p l e x , Ru2Cl4(DPPB)2(CO), c o u l d not be prepared by direct add i t ion o f carbon m o n o x i d e to 24; however , i t c o u l d be prepared f r o m 24 by decarbonyla t ion o f formaldehyde, acetaldehyde, benzaldehyde, or Mo(CO)6- 2 ' 4 6 D i r e c t a d d i t i o n o f C O to 24 was thought to g i v e a c o m p l e x i s o m e r i c m i x t u r e o f RuCl2(DPPB)(CO)2 and " R u C l 2 ( D P P B ) ( C O ) " c o m p l e x e s . 2 4.4 Reactivity of H 2 and Five-Coordinate Ruthenium(II) Diphosphine Complexes Investigated in This Thesis Work 4.4.1 Interaction with H 2 in the Absence of an Added Base T h e molecu la r hydrogen c o m p l e x Ru2Cl4(DPPB)2(T | 2-H2) c o u l d be prepared b y the react ion o f R u C l 2 ( D P P B ) ( P P h 3 ) 11 w i t h H2 i n C6D6- T h e reac t iv i ty o f 11 occurs through the equ i l i b r ium established wi th 24 by PPI13 d issocia t ion (eq 3.9, Sec t ion 3.3.3). A 3 1 P { 1 H } N M R spectrum o f 11 under an atmosphere o f H2 i n C6D6 s h o w e d 11, 24, R u 2 C l 4 ( D P P B ) 2 ( r | 2 - H 2 ) , and free PPh3. Integration o f the spectrum ind ica ted ca . 28% c o n v e r s i o n o f 24 to R ^ C ^ D P P B ^ O l 2 - ! ! ^ ) ( ignor ing the s ign i f i can t amounts o f 11 present). T h i s is s imi l a r to the 35% convers ion observed p rev ious ly by direct interact ion o f H2 and 24 (Sec t ion 4.3.1). N M R spectroscopy showed the molecu la r hydrogen resonance as a broad peak at -11.0 p p m , as observed p r e v i o u s l y . 2 ' 3 N o direct react ion o f the f ive-coordinate 11 w i t h H 2 was evident f rom either the ! H or 3 1 P { l H } N M R spectra. A C6D6 so lu t ion o f Ru 2 Cl4(DPPB)2(acetone)-acetone solvate 31 (0.02 M ) was placed under an atmosphere o f H2. Af te r the orange solut ion was stirred for 20 h at r o o m 170 Chapter 4 References: p 214 Chapter 4 temperature, a 3 1 P { l H } N M R spectrum was recorded. T h e 3 1 P { 1 H } N M R spec t rum s h o w e d a comple te loss o f the two A B quartets b e l o n g i n g to 31 (Tab le 3.15). T h e spectrum indicated that on ly 24 (Table 3.9) and R u 2 C l 4 ( D P P B ) 2 ( r | 2 - H 2 ) (Table 4.1) were present. Integration indicated ca. 33% o f the ruthenium to be i n the fo rm o f the molecu la r h y d r o g e n c o m p l e x , a va lue again ve ry s i m i l a r to the p r e v i o u s l y obse rved one for c o n v e r s i o n o f 24 to the molecu la r hydrogen c o m p l e x (Sec t ion 4.3.1). T h e lH N M R spectrum again showed the molecula r hydrogen resonance as a broad peak at -11.0 p p m . Unfor tuna te ly , the methylene protons o f D P P B obscured the a l ipha t ic r e g i o n o f the spectrum, m a k i n g it diff icul t to te l l whether the acetone was s i m p l y dissociated f rom the c o m p l e x , or had actual ly been hydrogenated to produce i sopropanol . A c e t o n e i s k n o w n by 3 1 P { lH} N M R spectroscopy to dissociate f rom 31, as evidenced by the presence o f 24 i n solut ions o f 31 (Sect ion 3.6). Interestingly, the reaction o f R u 2 C L i ( D P P B ) 2 ( D M S O ) 33 w i t h H2 i n C5D6 d i d not produce any mo lecu la r hydrogen complex . I n fact, the 3 1 P { 1 H } N M R spect rum o f 33 remained unchanged. T h i s non-react iv i ty m a y exp la in the poor ca ta ly t ic ac t iv i ty o f 33 observed for the hydrogena t ion o f imines (Chapter 6). A s s h o w n b y 3 1 P { 1 H } N M R spectroscopy, c o m p l e x 33 does not dissociate D M S O i n so lu t ion , u n l i k e c o m p l e x 31 w h i c h dissociates acetone. A n atmosphere o f H2 was also added to a 0.02 M D M A so lu t ion o f 24, w i t h a coup le drops o f C 6 D 6 be ing added to a l l o w the spectrometer to be l o c k e d . In D M A , c o m p l e x 24 is k n o w n to produce R u 2 C L i ( D P P B ) 2 ( D M A ) , 2 ' 4 6 w h i l e the interact ion o f H 2 w i t h th is species was o f interest, as a k i n e t i c and mechan i s t i c s tudy o n styrene hyd rogena t i on by 24 has been per formed i n D M A . 4 3 3 1 P { lH} N M R spec t roscop ic studies under the condi t ions described above showed on ly R u 2 C l 4 ( D P P B ) 2 ( D M A ) (the 3 1 P { 1 H } N M R data for this and other R u 2 C L ; (DPPB ) 2 (L ) complexes are l i s ted i n T a b l e 4.1) and o n l y a s m a l l amount o f R u 2 C U ( D P P B ) 2 ( r i 2 - H 2 ) . Reference 43 descr ibes this catalyt ic react ivi ty i n greater detail . 171 Chapter 4 References: p 214 Chapter 4 Dihydrogen also reacts with the bromo analogue Ru2Br4(DPPB)2 25. When a C6D6 solution of 25 was placed under an atmosphere of H2 for 24 h, the resulting NMR spectrum showed a broad resonance at -13.0 ppm. A T\ measurement at 20.1 °C on a 300 MHz spectrometer indicated that the product was a molecular hydrogen complex (7i = 24.0 ± 1 ms). Two other T\ measurements at 13.0 °C (21.8 ms) and 5.0 °C (20.7 ms) showed theTi min to lie below 5.0 °C. Unfortunately, the melting point of C6D6 is 5.0 °C, and therefore no T\ measurements could be attempted below this temperature. Note that the T\ minimum value for the chloro system is at 3 °C (Section 4.3.1). Several attempts were made to observe this molecular hydrogen complex, presumably Ru2Br4(DPPB)2Cn2-H2) in solvents with lower melting points (CD2CI2 and C7D8); however, surprisingly no resonances upfield of TMS were observed in these solvents. A 3 1 P{ 1 H} NMR spectrum of the C5H6 solution showed the A B pattern of the starting 25 (Section 3.3.4.1) and two broad singlets presumably belonging to Ru 2Br 4(DPPB) 2(Ti 2-H2) (5 = 63.4 and 39.7). These data suggest the likelihood of the geometry shown in Figure 4.4, structure B, which is different from that of the C l analogue of structure A. A B Figure 4.4 Geomet ry o f the two possible isomers o f [ ( r | 2 - H 2 ) ( P - P ) R u ( p . - X ) 3 R u X ( P -P ) l , where P - P = D P P B or ( i ? ) - B I N A P and X = C l or B r . 172 Chapter 4 References: p 214 Chapter 4 Table 4.1 3 1P{ !H} NMR Data (121.42 MHz, 20 °C) for the Dinuclear Complexes [(L)(DPPB)Ru(p-Cl)3RuCl(DPPB)] L(Complex) Solvent Chemical Shift, 8 2 7 P P , (Hz) (Tl 2 -H 2 ) C 6 D 6 6 A = 54.4, 6 B = 39.0 33.3 6 C = 53.8, 8 D = 53.3 46.6 (Tl 2 -H 2 ) CD 2C1 2 6 A = 54.6, 8B =39.1 33.9 8 C = 53.1, 8 D = 52.4 44.8 (o-N2) C 6 D 6 8 A - 55.3, 5B = 53.6 44.3 8 C = 47.2, 8 D = 37.5 32.1 CO C 6 D 6 8 A = 54.5, 8 B = 54.0 44.0 8 C = 47.5, 8 D = 33.8 29.7 CO CDCI3 8A, B = 53.8 46.0 8 C = 46.4, 8 D = 34.6 29.9 CO C D 2 C 1 2 8 A = 53.4 8 B = 52.8 44.6 5 C = 47.3, 8 D = 34.5 29.6 C2H4 C 6 D 6 8 A = 54.4, 8 B = 53.8 44.1 8 C = 46.8, 8 D = 35.6 34.7 D M A D M A / C 6 D 6 8 A = 52.5, 8B =51.2 43.5 5 C = 52.0, 8 D = 49.9 40.2 The 3 1P{!H} NMR resonances of the bromo-ruthenium complexes studied in this work are consistently broader than those of the corresponding chloro analogues. This is probably a result of the larger electric quadrupole moment of Br compared with that of Cl, and leads to peak broadening of any nearby nuclei. The 3 1P{!H} NMR spectra of the bromo-ruthenium complexes studied in this work were often more difficult to interpret 173 Chapter 4 References: p 214 Chapter 4 than those o f the c h l o r o analogues because o f loss o f c o u p l i n g i n f o r m a t i o n due to broadening o f the peaks. Another factor affecting the resolution o f the 3 1 P { lU) N M R spectra is the l i m i t e d so lub i l i ty o f the b romo analogues i n the N M R solvents c o m m o n l y used. 4.4.1.1 Reaction of RuCl2((fl)-BINAP)(PPh3) 15 with H 2 in the Absence of an Added Base The mixed-phosphine complex RuCl2 ( ( f l ) -BINAP)(PPh3) 15 reacts w i t h H2 i n the absence o f an added base to g ive species w h i c h show two broad resonances i n the hydr ide r eg ion o f the * H N M R spectrum (Figure 4.5). These were inves t igated to determine whether they were c lass ica l or r | 2 - H 2 protons. Inversion-recovery experiments were used to determine the T\ m i n i m u m . T h e T\ data over the temperature range o f 252-335 K are l is ted i n Tab le 4.2, w h i l e a plot o f T\ versus temperature is shown i n F igure 4.6. T h e T\ m i n i m u m values (measured on a 300 M H z spectrometer) o f the t w o resonances at -8.8 and -9.6 p p m were 11 and 9 ms , respect ive ly . B o t h occur red at a temperature o f 32 °C , w h i c h is re la t ive ly h i g h . T\ values o f this magni tude suggest mo lecu la r hydrogen species (see Sec t ion 4.2). I f the values are substituted into equat ion 4.6, the H - H internuclear distances for the r | 2 - H 2 moie ty are determined to be 1.06 A and 1.03 A for the -8.8 and -9.6 p p m resonances, respect ively . I f the cor rec t ion factor C suggested by M o r r i s and co-workers (0.794)36 is appl ied, the H - H internuclear distances are found to be 0.84 ± 0.02 and 0.86 ± 0.06 A. T h e errors are determined f rom the va lue g iven i n Tab le 4.2 for the particular T\ used. T h e H - H internuclear distance is s imi l a r to that determined by Josh i o f 0.86 ± 0.02 A for ( n 2 - H 2 ) ( D P P B ) R u ( i i - C l ) 3 R u C l ( D P P B ) , w h i c h corresponds to a T\ m i n i m u m 9 ^ o f 12 ms at 4 °C. ' T h e b o n d dis tance is s i m i l a r to that de t e rmined by X - r a y crys ta l lography o f 0.80(6) A for a related diruthenium species (see Sec t ion 4.5.1, i s o P F A c o m p l e x ) . 4 4 ' 4 5 174 Chapter 4 References: p 214 r i 2 - H 2 Chapter 4 Table 4.2 Temperature Dependence of the X H NMR T\ Relaxation Time Data<a) (300 MHz, C7D8) for the (TI 2 -H 2 ) Resonances Observed on Reaction of H2 and RuCl2((/?)-BINAP)(PPh3) Temperature T\ (ms) (K) -8.8 ppm resonance -9.6 ppm resonance 335 19 ± 2 2 1 ± 2 325 17 ± 2 2 0 ± 2 315 13 ± 3 17 ± 2 306 11 ± 2 9 ± 4 294 15 ± 4 14 ± 4 273 17 + 2 14 ±2 252 22 ± 6 17 ± 6 (a) T\ data were obtained by the inversion-recovery method using the conventional 180°-t-90° pulse sequence. • 7\ (-8.8 ppm) O 7\ (-9.6 ppm) 275 300 325 Temperature (K) 350 Figure 4.6 Temperature dependence of T\ for the molecular hydrogen complexes produced on reaction of H 2 and RuCl2((fl)-BINAP)(PPh3). Measured at 300 MHz in C7D8. 176 Chapter 4 References: p 214 Chapter 4 T h e ruthenium species catalyze isotope exchange between H2 and D2 i n solut ion. T h e starting c o m p l e x R u C l 2 ( ( / ? ) - B I N A P ) ( P P h 3 ) or the corresponding d inuc lea r species (see equ i l i b r i um i n equation 3.9) reversibly binds H2. Therefore, a solut ion o f RuCi2((7?)-B I N A P ) ( P P h 3 ) i n C 6 D 6 under an atmosphere o f H2 was evacuated to r emove H2 and placed under 400 torr each o f H2 and D2. Af t e r two days under the isotopic mix ture , the r | 2 - H D iso topomers were observed (F igure 4.7), thus c o n f i r m i n g the exis tence o f the molecu la r hydrogen species. The two upf ie ld resonances are observed as 1:1:1 triplets o f 1:2:1 triplets, w i t h coup l ing constants: V H D = 28.4 H z and cis, 2 / H P = 7.6 H z for the -8.8 p p m resonance, and ^ H D = 29.4 H z and cis, 2 7 H P = 6.6 H z for the -9.6 p p m resonance. Some smal ler coup l ing is also evident i n the -9.6 p p m resonance. Josh i also observed the r | 2 - H D isotopomer for the related D P P B system (Sect ion 4.3.1).2'3 T h e asymmetry o f the r | 2 - H D resonances shown i n Figure 4.7 is due to the under ly ing r | 2 - H 2 i sotopomer , w h i c h c o u l d be avoided i n s imi la r experiments i n the future by us ing 600 torr o f D2 and 200 torr o f H2 i n order to decrease the amount o f the T ) 2 - H 2 i sotopomer. T h e presence o f the r j 2 -D2 i sotopomer is not important, as on ly the * H N M R spectrum is recorded. A 3 1 P { lH} N M R spectrum o f R u C l 2 ( ( K ) - B I N A P ) ( P P h 3 ) under an atmosphere o f H2 i n C^D^ (Figure 4.8) shows three A B spin systems (two be long to one c o m p o u n d and one to another). Tab le 4.3 l ists the c h e m i c a l shifts and c o u p l i n g constants o f the two compounds . Table 4.3 3 1P{ lU) NMR Data (202.5 MHz, 20 °C) for RuCl2((/?)-BINAP)(PPh3) 15 under an atmosphere of H2 in C6D6 Complex Chemical Shift, 5 2Jpp, (Hz) (Ti2-H2)((/?)-BINAP)Ru(p:-Cl)3RuCl((/?)-BINAP) 5 A = 60.2, 5 B = 57.6 30.4 5c = 57.8, 5 D = 53.3 41.5 another isomer 5 A = 56.9, S B = 56.5 24.0 177 Chapter 4 References: p 214 Chapter 4 Efforts were made to define further the nature of the molecular hydrogen complexes, in particular to determine if the T| 2 -H2 species were mono- or diruthenium in nature. Equilibrium between 15 and the diruthenium species Ru 2Cl4(W-BINAP)2 (eq 3.9) could allow formation of either mono- or diruthenium molecular hydrogen complexes. Joshi et al. have observed the r i 2 -H2 diruthenium complex where DPPB is the diphosphine (Section 4.3.1), while Mezzetti and co-workers have observed a similar AO molecular dihydrogen complex where the diphosphine is BIPHEMP (the chemical shifts and coupling constants correspond to entry 1, Table 4.3). Excess PPI13 (10 equiv) was added to a C6H6 solution of RuCl2((/?)-BINAP)(PPh3) (~ 0.02 M) to force the equilibrium of equation 3.9 to the left. After the solution was left for 3 h to reach equilibrium, an atmosphere of H2 was added. After a further 3 h, *H and 3 1P{!H} NMR showed only resonances corresponding to free PPh3, RuCl2((/?)-BINAP)(PPh3) 15, and Ru(H)Cl((/?)-BINAP)(PPh3) (described in Section 4.4.2). No r| 2 -H2 resonances were evident in the *H NMR. These results, although complicated by the formation of Ru(H)Cl((/?)-BINAP)(PPh3), suggest that both molecular hydrogen complexes observed are "diruthenium" in nature. The fact that some Ru(H)Cl((/?)-BINAP)(PPh3) was formed suggests that the excess PPh3 added is sufficiently basic to abstract HC1, which may cloud the above conclusion. Figure 4.4 shows the geometries of two possible molecular hydrogen complexes formulated [(ri2-H2)((/?)-BINAP)Ru(p-Cl)3RuCl((/?)-BINAP)]. Structure A corresponds to the first entry in Table 4.3, which has been shown by selective !H{ 3 1 P} N M R spectroscopy to correspond to the r| 2 -H2 resonance at -8.8 ppm. Two AB patterns are expected in the 3 1 P{!H} NMR for a compound of structure A; the 2 / A B coupling constant of 30.4 Hz suggests that the phosphorus chemical shifts 8 A , B belong to the r | 2 -H2 end of the dinuclear complex (see Section 5.2.3 for discussion of [(L)(DPPB)Ru(p-Cl)3RuCl(DPPB)] 3 1P{!H} NMR chemical shifts and coupling constants). Broadband phosphorus decoupling at 57.7 ppm in the 3 1 P NMR while monitoring the *H NMR 178 Chapter 4 References: p 214 Chapter 4 179 Chapter 4 References: p214 Chapter 4 Chapter 4 spectrum showed complete loss of HP coupling in both r | 2 -HD resonances (Figure 4.9). Selective irradiation at either 57.3 or 60.2 ppm reduced the coupling of the ri 2 -HD resonance at -8.8 ppm from the 1:2:1 triplet ( 2 / H P ) to a doublet (both peaks are still split into 1:1:1 triplets by coupling to deuterium, ^ H D ) - This further confirmed that the 8 A , B shifts were associated with the end of the dinuclear complex containing the r | 2 -HD ligand. Selective irradiation at 53.3 ppm (i.e., 5 D of entry 1, Table 4.3) produced no visible change in the *H NMR spectrum. This fits the assignment, as 5 D is at the Cl-end of the dinuclear complex where phosphorus coupling to T ) 2 -HD is not observed. Further selective irradiations of the other 3 1 P resonances were hampered by the close proximity of the peaks to one another (56.5-57.8 ppm region). Unfortunately, this made the assignment of the exact geometry of the T | 2 - H 2 resonance at -9.6 ppm more difficult. Structure B, Figure 4.4 would be expected to give two singlets in the 3 1P{lH} NMR spectrum, one for each end of the dinuclear complex, when the diphosphine is achiral. If a chiral diphosphine is used, the singlets may each be split into A B patterns. Therefore, the 3 1P{ lH} NMR spectrum would be expected to show two AB patterns for a geometry like that shown in structure B. However, the 3 1 P{lH} NMR data (Table 4.3, entry 2) reveal only a single AB quartet. Second-order effects could explain this observation, as the outside resonances of the two A B quartets could be lost in the baseline, or buried under the other resonances in this region. If strong second-order effects are operating, then two "doublets" would be expected. In this case, the coupling constant listed in Table 4.3, entry 2 would actually be the line spacing of the inner two peaks of the second-order AB quartet. 181 Chapter 4 References: p 214 Chapter 4 I 1 r — i 1 1 1 1 1 1 1 1 1 1 1 1 ( 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ppm - 8 . 5 - 9 . 0 - 9 . 5 -10.0 -10 .5 Figure 4.9 !H{ 31P} high-field NMR spectra of the two isomers [(r|2-H2)((/?)-BINAP)-Ru(p-Cl)3RuCl((/?)-BINAP)] in C 6 D 6 (500 MHz for lH, 202.5 MHz for 3 1 P , 20 °C) with selective phosphorus decoupling at: (a) 60.2, (b) 57.3, (c) 53.3; (d) broadband at 57.7 ppm; the larger 1:1:1 ] 7 H D coupling remains unchanged as expected. 182 Chapter 4 References: p 214 Chapter 4 4.4.2 Interaction with H2 in the Presence of an Added Base The mixed-phosphine complexes, RuCl2(P-P)(PPh3), where P-P = DPPB or BINAP, were found to react with H2 in the presence of NEt3 to give products of the formulation Ru(H)Cl(P-P)(PPh3). For example, NEt3 (100 | iL, 50 equiv) was added to an orange solution of RuCl2((/?)-BINAP)(PPh3) in CH2CI2 / CD2CI2 (~ lO" 2 M). The system was evacuated, and an atmosphere of H2 was added. The solution became red over a period of 1 h. A 3 1 P{ ! H} NMR spectrum (Figure 4.10) showed the product to be Ru(H)Cl((/?)-BINAPXPPI13); the chemical shift and coupling constant data for two overlapping A B X patterns are listed in Table 4.4, and indicate the presence of two diastereomers. The Ru(H)Cl(P-P)(PPh3) products are chiral at the metal, and contain the (^-stereoisomer of the chiral diphosphine BINAP. Figure 4.11 shows the two diastereomers observed in solution. Mezzetti et al. have observed similar chemistry with BIPHEMP, which is an AQ analogous ligand to BINAP (Section 3.3.3). Interestingly, the A B X patterns in the case of BIPHEMP were broad at room temperature, and it was necessary to cool the solution AQ to 0 °C to resolve the resonances. The dynamic process thought to be responsible for AQ the broadness of the peaks is the interconversion of the diastereomers. As this dynamic process is observed for the achiral DPPB analogue where only one stereoisomer is present (see later in this section), the process responsible for the broadness is thought to be intramolecular exchange of the phosphorus atoms of the diphosphine (Section 3.3.3.2). However, for Ru(H)Cl((/?)-BINAP)(PPh3), the A B X patterns were resolved at 20 °C (Figures 4.10). The hydride proton was observed in the *H NMR spectrum (Figure 4.12) at -22.5 ppm as a doublet of triplets. The splitting is a result of coupling to the axial phosphorus (i.e., doublet, 2/HP(X) = 36.3 Hz) and two equatorial phosphorus atoms (i.e., triplet, 2^HP(A,B) = 22.7 Hz). 183 Chapter 4 References: p 214 Chapter 4 Mezzetti et al. isolated Ru(H)Cl((S)-BIPHEMP)(PPh3) as a red solid, but further characterization was impossible, as the compound was extremely air-sensitive, even in AO the solid state. No attempts were made in this work to isolate Ru(H)Cl((/?)-BINAP)(PPh3). Table 4.4 3 1P{!H} NMR Spectral Data (121. 42 MHz, CD 2 C1 2 ) of Ru(H)Cl(P-P)(PPh3) Complexes Complex Temp Chemical Shift, 8 2 / p p ? ( H Z ) e g P-P = DPPB Ru(H)Cl(DPPB)(PPh3) 20 8 = 42.6 127(a)>(b) -90 8A = 39.0 2 /AX = unresolved 8B = 45.0 2JBX = unresolved 8 A = 92.3 2 7 a b = m i P-P = (fl)-BINAP Ru(H)Cl((/?)-BINAP)(PPh3) 20 8 A = 90.3, 90.1 2 /AX = 39.4, 36.9 8 B = 45.0,44.9 2jBX = 20.9,18.8 S X = 36.0, 35.9 2 j A B = 3Q2.4, 303,0 (a) triplet-like pattern; J value indicates line spacing. (b) solvent is CH2CI2 with a couple of drops of added CD2CI2. 184 Chapter 4 References: p 214 PPhs unknown ^ ^ ^ ^ ^ ^ I 1 1 1 1 I I I I I I I I ' I I I I I I I I I I 1~T 8 0 6 0 4 0 2 0 0 P P M Figure 4.10 3 1 P { J H } N M R spectra (121. 42 MHz, C H 2 C 1 2 / CD 2 C1 2 ) of Ru(H)Cl((/?)-BINAP)(PPh3) produced in situ from RuCl2((/?)-BINAP)(PPh3) and H 2 at room temperature; (a) full sweep width and (b) expanded regions (see next page); • indicates resonances belonging to one diastereomer. Chapter 4 Chapter 4 mirror P-P = BINAP Figure 4.11 The geometry of the two diastereomers of Ru(H)Cl((/?)-BINAP)(PPh3). - 2 1 . 0 I I I I | i i i i | M M | i i i - 2 1 . 2 - 2 1 . 4 I I I [ I I I I | i i I I | i I I I |TT I I [ i i I I | II I I | I I I I | i - 2 1 . 6 - 2 1 . S - 2 2 . 0 - 2 2 . 2 P P M Figure 4.12 ! H NMR spectrum (121. 42 MHz, CD 2 C1 2 , 20 °C) of Ru(H)Cl((/?)-Bn\AP)(PPh 3) produced in situ from RuCl2((tf)-BINAP)(PPh3) 15. The analogous DPPB chemistry was somewhat more complicated. Triethylamine (100 pL, 30 equiv) was added to a green solution of RuCl2(DPPB)(PPh3) 11 (0.05 M) in C D 2 C 1 2 . The solution (still green) was evacuated and placed under an atmosphere of H 2 . Within 1 h, the reaction solution had become orange-red. A 3 1 P{ 1 H} NMR spectrum of the above solution at 20 °C showed starting 11, free PPh 3, and a singlet resonance at 50.0 ppm thought to be due to [HNEt 3]+[Ru 2Cl 5(DPPB) 2]- 41 (Table 3.14). It also showed a. triplet-like pattern at 42.6 with a line-spacing of 127 Hz (Table 4.4), indicating an exchange process on the NMR-timescale. When the solution was cooled to -90 °C, the 187 Chapter 4 References: p 214 Chapter 4 spectrum was resolved into an A B X pattern (Table 4.4), indicating a meridional arrangement of phosphorus atoms; the coupling constant 2/AB indicates two phosphorus atoms trans-disposed to one another, while the other two coupling constants which are unresolved because of broadness, indicate cw-disposed phosphorus atoms. The product is therefore assigned as Ru(H)Cl(DPPB)(PPh3), and the geometry is thought to be square-pyramidal, as shown for the BINAP analogue in Figure 4.11. The singlet at 50.0 ppm due to [HNEt3]+[Ru2Cl5(DPPB)2]~ 41 remains unchanged at -90 °C; under these reaction conditions, 41 could be produced by the reaction of Ru2Cl4(DPPB)2 24 and NEt3-HCl, which is produced by the reaction of 11, H2 and NEt3. Complex 24 is produced in situ by PPh3 dissociation from 11 (eq 3.9). Triethylamine hydrochloride was shown to react with 24 to produce 41 in this work (Section 3.2). A 3 1P{ 1H} NMR spectrum recorded several days later showed only Ru(H)Cl(DPPB)(PPh3), 41, and free PPh3, while the starting complex 11 was gone. A if! NMR spectrum of the above sample recorded at room temperature showed a quartet upfield of TMS at -20.7 ppm (27HP = 28.8 Hz). The two middle peaks of the quartet were quite broad, and seemed to show some smaller couplings. This is probably a result of intramolecular exchange of the DPPB phosphorus atoms observed at room temperature in the phosphorus spectrum (see Section 3.3.3.2). Based on the structure (Figure 4.11), a doublet of triplets (1 axial and 2 equatorial phosphorus atoms) would be expected, as is observed for the BINAP analogue when no exchange process was involved. In fact, at -90 °C, a six-line pattern resembling the doublet of triplets seen for the BINAP analogue was observed (Figure 4.12); however, excessive noise in this spectrum made complete assignment of the coupling constants impossible. Joshi had previously attempted to prepare Ru(H)Cl(DPPB)(PPh3) from RuCl2(DPPB)(PPh3) 11 in D M A , but found by gas-uptake measurements that only ~ 0.20 mole equivalents of H2 were used per Ru . 2 The 3 1P{ *H} NMR spectrum of this solution was complicated, showing none of the A B X pattern observed in this work. Joshi also 188 Chapter 4 References: p 214 Chapter 4 attempted the react ion o f 11 w i t h H.2 i n the presence o f P ro ton Sponge (1.1 equ iv) . In fact, this react ion d id result i n observation o f the same t r iple t - l ike pattern at 42.6 p p m i n the 3 1 P { i H } N M R spectrum that was observed i n this w o r k (Table 4.4). T h i s was one o f severa l products observed i n the react ion . Jo sh i d i d not rea l ize that the t r i p l e t - l i ke resonance was the result o f an exchange process. In the presence o f Pro ton Sponge, other hydr ide species (and poss ib ly molecula r hydrogen species) were observed by * H N M R spec t roscopy. 2 T h e importance o f the choice o f base (i.e., N E t 3 vs. D M A or P ro ton Sponge) i n determining the product(s) is i l lustrated by this thesis w o r k and Joshi 's work . Jo sh i noted the e x t r e m e a i r - s e n s i t i v i t y o f the r ed s o l u t i o n s p r o d u c e d b y i n t e r a c t i o n o f R u C l 2 ( D P P B ) ( P P h 3 ) w i t h H 2 i n the presence o f a base. T h i s was also noted by M e z z e t t i 48 et a l . for the B I P H E M P analogue, and i n this thesis w o r k i n attempts to isolate a product f rom a red so lu t ion produced on reaction o f R u C i 2 ( D P P B ) ( P ( p - t o l y l ) 3 ) 12 w i t h H 2 i n the presence o f NE13 (1 equiv) i n C^i^. One attempt was made to observe the bromo analogue o f the t r i ru thenium species (i.e., [ R u ( H ) B r ( D P P B ) ] 3 ) by 3 1 P { ! H } N M R spectroscopy. T r i e thy lamine (6 p i , 2 equiv) was added to a C 6 D 6 suspension o f R u 2 B r 4 ( D P P B ) 2 (28 m g i n 1 m L C 6 D g ) , and the resu l t ing b r o w n suspens ion was left s t i r r ing under an a tmosphere o f H 2 for 24 h . Unfortunately , the l imi ted so lubi l i ty o f the complex(es) resulted i n ! H and 3 1 P { ^H} N M R spectra w h i c h were very noisy and imposs ib le to interpret. In order to determine i f the B r chemis t ry paral lels the C l chemist ry i n the format ion o f a t r inuclear species under these cond i t ions , a larger-scale react ion needs to be attempted, where the product c o u l d be i so la ted and d i s s o l v e d i n a better so lvent (perhaps C D 2 C I 2 or C H 2 B r 2 ) for N M R spectroscopic investigations. 189 Chapter 4 References: p 214 Chapter 4 4.5 Reaction of Other Neutral Two-Electron Ligands with Five-Coordinate Ruthenium(II) Complexes 4.5.1 Reaction of Ru2Cl4(DPPB) 2 24 with Ethylene A C g D g so lu t ion o f R u 2 C l 4 ( D P P B ) 2 24 was p l aced under an a tmosphere o f e thylene for 2 h . A 3 1 P { 1 H } N M R spectrum o f the sample s h o w e d an e q u i l i b r i u m mix tu re o f 24 (an AB pattern) and the ethylene adduct Ru2Cl4(DPPB)2(u. 2-ethylene) (2 A B patterns). F igure 4.13 shows the 3 1 P { 1 H } N M R spectrum, w h i l e Tab le 4.1 l ists the N M R data. T h e reaction w i t h ethylene is reversible; i f the atmosphere o f ethylene is replaced w i t h argon, the resonances o f the e thylene adduct disappear. U n d e r the c o n d i t i o n s e m p l o y e d (i.e., 1 atm ethylene, 20 °C, ~ 10 - 2 M Ru2), the equ i l i b r i um is ca . 85% to the ethylene adduct side. 190 Chapter 4 References: p 214 (a) (a) 7 0 6 5 6 0 5 5 5 0 4 5 4 0 3 5 P P M 3 0 Figure 4.13 3 1P{ lH) NMR spectrum of Ru2CLi(DPPB)2 24 under an atmosphere of ethylene in C6D6 (121.42 MHz, 20 °C); (a) = Ru2CU(DPPB)2(Ti2-ethylene). Chapter 4 4.5.2 Reaction of Ru 2Cl4(DPPB) 2 24 with Styrene Styrene (100 pL, ~ 100 equiv) was added to a C6D 6 solution of Ru2Cl4(DPPB)2 24 at room temperature. After 0.5 h at room temperature, a 3 1P{!H} NMR spectrum of the orange solution showed only starting Ru2CU(DPPB)2 to be present. Another experiment with 10 equivalents of styrene and 2 h reaction time also showed no styrene adduct by 3 1 P{ 1 H} NMR spectroscopy. These results were somewhat surprising, considering that ethylene readily coordinates to 24 to produce a triply-chloro bridged adduct (Section 4.5.1). The phenyl group of styrene must provide sufficient steric bulk to force the equilibrium between 24 and any possible styrene adduct far to the side of 24. Styrene hydrogenation is catalyzed by 24 at 30 °C and 1 atm of H-2 in D M A , and the kinetics of this process have been investigated in some detail.4 3 The mechanism is thought to occur by a hydride route, whereby 24 initially reacts with H2 to form Ru2Cl4(DPPB)2(r|2-H2); in some later step, styrene perhaps coordinates, and subsequendy hydrogen transfer produces ethylbenzene.43 However, other possibilities considered43 include direct hydrogen transfer to non-coordinated styrene, which has been demonstrated for hydrogenation of oc-methylstyrene with MnH(CO)s a s the catalyst,49 and cannot be ruled out as a possibility in this case. The process would involve stepwise H-atom transfers via styryl radical intermediates.49 Of note, pairwise H2 transfer from the molecular hydrogen complex Ru(r|2-H2)(H)2(PPh3)3 to styrene has been demonstrated by the PHIP technique (para-hydrogen induced polarization).50 Interestingly, Ru2Ci5(DPPB)2 was also found to be an effective catalyst precursor for the hydrogenation of styrene.51 The rate of hydrogenation to ethylbenzene, under identical conditions described above for 24, is somewhat slower (28% of the initial rate). The active species is presumably formed via 24, produced in situ by H2 reduction of Ru2Cl5(DPPB)2, and the HC1 formed in the reduction process (Figure 4.14). Addition of one mole equivalent of HC1 gas to a system catalyzed by 24 produced a hydrogenation 192 Chapter 4 References: p 214 Chapter 4 rate comparable to that o f R u 2 C l 5 ( D P P B ) 2 system. T h e nature o f the catalyst remains to be elucidated (see Sect ion 4.6.1). 4.5.3 Reaction of RuCl2(DPPB)(PPh3) 11 with N 2 A C 6 D 6 so lu t ion o f R u C l 2 ( D P P B ) ( P P h 3 ) 11 (0.04 M ) was p l aced under an a tmosphere o f N2 for 5 h at r oom temperature, and a 3 1 P { 1 H } N M R spectrum was recorded. T h e spectrum showed 11, 24, R u 2 C l 4 ( D P P B ) 2 ( r i 1 - N 2 ) , and free P P h 3 . T h e N M R data (Table 4.1) for the two sets o f A B patterns (designated A B C D ) are the same as those o b s e r v e d fo r R ^ C l ^ D P P B ^ C n 1 - ^ ) p r e p a r e d b y d i r e c t r e a c t i o n o f R u 2 C l 4 ( D P P B ) 2 w i t h N 2 2 , 3 , 4 6 when ca. 70% convers ion to RU2CJ4(DPPB) 2 (TI 1 -N2 ) was observed under the condit ions employed for the above reaction (i.e., 1 a tm N2, 20 °C). In this thesis w o r k , N2 reacted w i t h 24, w h i c h was produced i n si tu b y PPI13 d issoc ia t ion f rom 11 (eq 3.9), and the R ^ C L ^ D P P B ^ O l 1 - ^ ) complex accounted for ca . 45% o f the integral intensity when compared w i t h the amount o f 24 present (i.e., the large amount o f 11 present was ignored) . N o direct reac t iv i ty between 11 and N 2 was observed , and therefore the e q u i l i b r i u m between 11 and 24 i s responsible for the observed reac t iv i ty (eq3.9). I R spectroscopy on a CH2CI2 so lu t ion o f 11 under an N2 a tmosphere showed a V ( N = N ) at 2170 c m - 1 , w h i c h agrees w i t h that observed for R ^ C L K D P P B ^ C n 1 - ^ ) prepared direct ly from 24. 4.5.4 Reaction of Ru 2Cl4(DPPB) 2 24 with CO T h e species R u 2 C U ( D P P B ) 2 ( C O ) , whose 3 1 P { 1 H } N M R spectral data are s h o w n i n Tab le 4.1, has been observed on several occasions i n the current work . A s discussed i n S e c t i o n 4.3.3, R u 2 C L i ( D P P B ) 2 ( C O ) had been i so la ted f r o m the d e c a r b o n y l a t i o n o f aldehydes by R u 2 C L i (DPPB)2 24.2'46 193 Chapter 4 References: p 214 Chapter 4 In the present w o r k , Ru2Cl4(DPPB)2(CO) was obse rved i n s o l u t i o n u p o n d i s so lv ing the so l id produced by the reaction o f CO w i th 24 i n the s o l i d state (see Chapter 7 for details). S ign i f ican t amounts o f Ru2Cl4(DPPB)2(CO) were also observed i n a sample o f 24, w h i c h had been prepared f rom R u 2 C l 5 ( D P P B ) 2 22 i n D M A (Sect ion 2.5.7.1). T h i s species is presumably produced by decarbonylat ion o f D M A by 24. The sample had been left i n D M A so lu t ion for severa l weeks . It s hou ld be noted that D M F i s k n o w n to CO decompose i n the presence o f ac id ic or basic materials to g ive d imethy lamine and CO, and i t i s therefore conce ivab le that D M A , i n the presence o f t ransi t ion meta l species, decomposes i n the same manner, and that the CO generated reacts w i t h 24. Small amounts o f Ru2Cl4(DPPB)2(CO) were observed on one occas ion w h e n 24 was prepared i n s i tu by the add i t ion o f HC1 ( in MeOH) to a C D C I 3 so lu t ion o f 24 (Sec t i on 2.5.7.1). I n this case, Ru2Cl4(DPPB)2(CO) was p r e s u m a b l y p r o d u c e d b y decarbonyla t ion o f phosgene COCI2, w h i c h i s k n o w n to be one o f the p h o t o c h e m i c a l decomposi t ion products o f ch loroform. 4.5.5 Reaction of RuCI2((/?)-BINAP)(PPh3) 15 with N 2 A C 6 D 6 so lu t ion o f RuCl 2 ((/?)-BINAP)(PPh 3 ) 15 (0.03 M) was p laced under an atmosphere o f N2 for 24 h at r o o m temperature, and a 3 1 P{!H} N M R spec t rum was recorded . T h e spectrum showed s m a l l amounts o f several new A B patterns some o f w h i c h m a y c o r r e s p o n d to a R u 2 C l 4 ( ( / ? ) - B I N A P ) 2 ( r i 1 - N 2 ) c o m p l e x , as p r e v i o u s l y observed for the D P P B analogue. In this B I N A P case, the spec t rum is d i f f i c u l t to interpret comple te ly because o f l o w convers ions to the " T | 1 - N 2 c o m p l e x " and addi t iona l resonances w h i c h m a y indicate the presence o f more than one isomer . Nonetheless , the appearance o f addi t ional resonances i n the 3 1 P{!H} N M R spectrum w h e n 15 is p laced under an atmosphere o f N2 indicate that a react ion is occur r ing . When the spectrum i s recorded under an atmosphere o f Ar, these addi t ional resonances are not observed. 194 Chapter 4 References: p 214 Chapter 4 N o attempts were made to observe the V ( N = N ) i n the I R spectrum due to the l o w convers ions to " r i 1 - N 2 products." 4.6 Reaction of H 2 with Ru 2 Cl5(P-P) 2 Complexes 4.6.1 P-P = DPPB Bubbling U2 gas through a C 6 D 6 or C D 2 C I 2 so lu t ion o f R u 2 C i 5 ( D P P B ) 2 22 resul ted i n the fo rmat ion o f R u 2 C l 4 ( D P P B ) 2 24 and R u 2 C l 4 ( D P P B ) 2 ( r i 2 - H 2 ) (F igure 4.14).53 I n C 6 D 6 so lu t ion , i t was necessary to bubb le H2 th rough an N M R sample (~ 1 m L , ~ 10"2 M ) for about 1 h . In CD2CI2 so lu t ion , under o therwise i d e n t i c a l condi t ions , bubb l ing H2 for ~ 15 m i n was sufficient to reduce comple t e ly the starting R u 2 C l 5 ( D P P B ) 2 complex . Civ. . ^-P .** ^ C l Ru-..,, C l . Cf 22 2 n 2 S ^ P 24 ^ + HCl j Cl + H , C 1 \ l H M ,t-Ru Figure 4.14 H2-reduct ion o f the mixed-valence complex Ru2Cl5(DPPB)2 22 to g ive Ru2Cl4(DPPB) 2 24, w h i c h reacts revers ibly w i t h H2 to produce R u 2 C l 4 ( D P P B ) 2 ( T i 2 - H 2 ) ; where P - P = P h 2 P ( C H 2 ) 4 P P h 2 . Previously, the presence of an added base was thought necessary to reduce R U 2 n , lIIci 5 (DPPB)2 22 to Ru2 n> nCl4(DPPB)2 24, because the starting complex was 195 Chapter 4 References: p 214 Chapter 4 reduced o n l y i n the basic so lvent D M A ; or i n C 6 H 6 or C7H8 w i t h the add i t i on o f p o l y v i n y l p y r i d i n e . 2 ' 6 ' 4 6 H o w e v e r , c lear ly complex 24 can be prepared i n the absence o f a base i f hydrogen is bubbled through a so lu t ion o f 22; p resumably because the HC1 generated is r emoved f rom solu t ion by the stream o f H2 gas. Indeed, w h e n the react ion was attempted i n a c losed H2 atmosphere i n a large S c h l e n k tube, the reduc t ion was incomple te , even after 24 h . V i s u a l inspect ion was effective i n determining the extent o f the react ion, as the starting suspension o f 22 was deep red, w h i l e the reduced products were orange. A l t h o u g h the reaction was s l o w to proceed wi thout the bubb l ing procedure, some reduct ion was evident i n the 3 1 P { 1 H } N M R spectrum o f the resul t ing so lu t ion i n C 6 D 6 . It should be noted that the product formed on reaction o f 24 w i t h HC1 (see be low) is also red and insoluble i n C 6 D 6 , and it is therefore di f f icul t to defini tely ident ify the red so l id as either starting 22 or the product formed on reaction w i t h HC1. Reac t ions o f either gaseous or aqueous HC1 (as a me thano l i c so lu t ion) w i t h Ru2Cl4(DPPB)2 24 have been attempted. B o t h reactions resulted i n a red s o l i d w h i c h was largely insoluble i n C^D^. Nonetheless, when HC1 was bubbled through a C6D6 solut ion o f 24 for 10 m i n , the result ing suspension showed remain ing 24, plus a ve ry broad peak at 48.8 p p m i n the 3 1 P { 1 H } N M R spectrum. T h e product is perhaps the i o n i c c o m p l e x " H + [ R u 2 C l 5 ( D P P B ) 2 ] ~ " ; the anion has been observed and isolated p rev ious ly w i t h other cat ions (Sect ion 3.4.1), but the formula t ion w i t h a 'free proton' is p robably not real is t ic . A n interesting poss ib i l i ty is that the proton c o u l d be attached to a ch loro l i g a n d (i.e., the species c o u l d be an r ^ - H C l adduct; such species have been formula ted w i t h i n Pt(II) s y s t e m s ) . 5 4 D e k l e v a has noted somewhat s imi l a r react ivi ty o f [ ( r| 2 -H2 ) (PPh3)2Ru( | i -Cl)2 ( j i -H ) R u ( H ) ( P P h 3 ) 2 ] and HC1, w h i c h produced " H + [ R u 2 C l 5 ( P P h 3 ) 4 ] - " and H 2 . 5 5 W h e n a methanol ic solut ion o f HC1 was added to 24 i n C 6 D 6 , the 3 1 P { X H } N M R spectrum showed a broad singlet at 57 ppm (see Sec t ion 3.3.4.2). T h e presence o f the polar solvent M e O H may effect the c h e m i c a l shift (49 vs . 57 ppm) . T h e product o f this 196 Chapter 4 References: p 214 Chapter 4 HC1 reaction needs to be isolated arid further characterized, especially in terms of determining the nature of the cation in C6D6. A reaction between gaseous HC1 and 24 in CD2CI2 was performed with Abu-Gnim of this laboratory to give the red product which was more soluble than in C6D6; the in situ 3 1 P{ lH) NMR spectrum showed a broad singlet at 48.8 ppm, as was observed in C 6 D 6 . Red crystals were isolated on one occasion from a solution produced by the addition of 3 equivalents of HC1 (methanolic solution) to Ru(DPPB)(r|3-Me-allyl)2. This reaction is known to produce 24, plus another species that gives a singlet at 57 ppm in the 3 1 P { 1 H ) NMR spectrum (Section 3.3.4.2). Unfortunately, X-ray diffraction studies were unsuccessful, as the crystals did not diffract. 4.6.2 P - P = ( f l ) -BINAP As for the DPPB analogue (Section 4.6.1), dihydrogen gas was bubbled through a C 6 D 6 solution of Ru2Cl 5((/?)-BINAP) 2 23 (~10-2 M) for 1 h . Over the bubbling period, the solution changed from red-brown to orange. A 3 1 P{ 1 H} NMR spectrum of the above solution shows at least three products (Figure 4.15). Two of the ruthenium(II)-BINAP-containing products are thought to be dinuclear, based on the observed A B C D spin system (i.e., two AB quartets). The third product, a singlet at 13.2 ppm, is probably mononuclear. Unfortunately, none of the 3 1 P{ 1 H} NMR resonances (Table 4.5) correspond to those observed for Ru2CU((R)-B I N A P ) 2 . 4 6 The 3 1P{!H} NMR spectrum reported for isolated Ru2CU((^)-BINAP)2 4 6 corresponds to that observed in this work by dissociation of PPh3 from RuCl2((/?)-BINAP ) ( P P h 3 ) (eq 3.9). For comparative purposes, Figure 4.16 shows the room temperature 3 1 P{ 1 H} NMR spectra of RuCl2((/?)-BINAP)(PPh3) (and in situ produced Ru2Cl4((/?)-BINAP)2). 197 Chapter 4 References: p 214 (3) (2) ]~n—i i | i—i r~~i | i 40: 2 0 P P M 10 Figure 4.15 3 1 P{ lU] NMR spectrum (121.42 MHz, 20 °C) of a CeD6 solution of Ru2Ci5((/?)-BINAP)2 23 after bubbling H 2 through the solution for 1 h. Table 4.5 lists the data for species numbered (1M3) on this spectrum. Chapter 4 Chapter 4 References: p 214 Chapter 4 T h e o n l y resonance observed upf ie ld o f T M S i n the * H N M R spectrum was a triplet at -3.7 p p m (2/HP = 19.4 H z ) , ind ica t ing the presence o f a c lass ica l hydr ide . N o broad resonances i nd i ca t ing the poss ib le presence o f mo lecu la r hyd rogen resonances were evident. T h e reduct ion o f Ru2Cl5((7?)-BINAP)2 by H2 was undertaken i n the hope of obse rv ing both Ru2CU((#)-BINAP)2 and R u 2 C l 4 ( ( / ? ) - B I N A P ) 2 ( r | 2 - H 2 ) , as had been prev ious ly observed for the D P P B analogue (Sect ion 4.6.1). Unfortunately , the exact nature o f the complexes present c o u l d not be determined, and the 3 1 P { lH] N M R data are l isted i n Tab le 4.5 for reference by future workers . Table 4.5 3 1 P { IH} NMR Data (121.42 MHz, 20 °C) for the Interaction of H 2 and Ru2Cl5((/?)-BINAP)2 23 in C 6 D 6 Species Chemical Shift, 8 2 / P P (Hz) 1 8 A = 58.9, 8 B =54.1 42.1 8 C = 49.3, 8 D = 48.5 27.2 2 8 A = 58.6, 8 B = 57.2 40.3 8 C = 45.2 8 D = 40.9 25.6 3 13.2, s s = singlet. W h e n the bubb l ing o f H2 through the above orange so lu t ion was cont inued for a further 1 h , the 3 1 P { 1 H } N M R spectrum showed o n l y a s ingle A B pattern (8A = 47.5, 8 B = 46.4, 2/AB = 30.3 H z ) . A g a i n , this species is thought to be a dinuclear R u ( I I ) - B I N A P -c o n t a i n i n g species , but b e y o n d this , the structure is u n k n o w n . T h e 3 1 P { 1 H } N M R spec t rum does no t c o r r e s p o n d to the resonances p r e v i o u s l y obse rved for ei ther Ru 2 Cl4 (BINAP)2 or Ru 2 CU (BINAP)2 (Tl 2 -H2) . Two attempts were made to prepare and isolate Ru2CLi((/?)-BINAP)2 26 f rom the mixed-va lence d imer R u 2 C l 5 ( ( / ? ) - B I N A P ) 2 23 by a procedure used p rev ious ly b y this 200 Chapter 4 References: p 214 Chapter 4 research group (Section 2.5.7.3 outlines the procedure). 2' 4 6' 5 6 The published procedure involves stirring Ru2Cl5((/?)-BINAP)2 23 under an atmosphere of H.2 in CgH-6 with poly(4-vinylpyridine) (70 equiv) for 24 h. However, on both occasions in this thesis work, the isolated orange-brown solid showed spectroscopic and microanalytical data different from those which had been previously determined. The C and H microanalytical data (C, 66.45; H, 4.11%) fit well for the Ru2CU((fl)-BINAP)2 formulation (C, 66.50; H, 4.06%); however, the Cl analysis was very low (6.22 vs. 8.92%). The 3 1 P{ 1 H} NMR spectrum showed two species to be present. The first, accounting for ~ 70% of the total integral intensity, was an AB pattern (8A = 75.6, 8B = 72.3, 2JAB = 44.3 Hz), while the second was a singlet (8 = 51.4); neither of these species has been observed before. The *H NMR spectrum showed a hydride signal at 8 = -14.0 (t, 2 /HP = 29.9 Hz), the coupling constant and splitting multiplicity indicating a hydride cis to two phosphorus atoms; however, the chemical shift and peak multiplicity do not 57 correspond to those reported for Ru(H)Cl(BINAP)2, the presence of which would explain the low chloride analysis. No attempts were made to separate or further characterize these reduction products, as the key goal was to isolate pure 26, which was needed to allow for direct comparison with the molecular hydrogen complexes produced in situ by the interaction of H 2 with RuCl2((tf)-BINAP)(PPh3) (Section 4.4.4.1). It should be noted that Chan and Laneman have isolated and characterized a decomposition product of a Ru-BINAP species.5 8 On attempting to improve the preparation of the catalyst Ru(BINAP)(OAc)2, Chan and Laneman isolated a unique Ru complex in which the BINAP ligand had undergone P-C cleavage via oxidative addition of the naphthyl-phosphorus bond to the ruthenium centre. This was followed by hydrolysis to give the unusual Ru complex, the structure of which has been determined by X-ray crystallography (Figure 4.17).58 201 Chapter 4 References: p 214 Chapter 4 Figure 4.17 The unique ruthenium complex characterized by Chan and Laneman produced by P-C cleavage of the BINAP ligand. 4.7 A Brief Review of Ru(n)-Monodentate Phosphine Complexes Containing Molecular Hydrogen and Classical Hydride Ligands Synthesized in This Laboratory In 1985, Dekleva et al. reported the chloride-bridged, dimeric ruthenium complexes [RuH2Cl(PR3)2J2 , where PR3 was either PPI13 or P(p-tolyf)3.9 The structures of the above species were based on a partial single-crystal X-ray diffraction study of the P(/>-tolyl)3 complex, as well as on 3 1P{ 1H} and *H NMR spectroscopic data. Three of the hydrides were reported as terminal, while the fourth was reported as bridging.9 The ruthenium was thought to be in oxidation state III, with a Ru-Ru bond explaining the diamagnetism. However, Hampton et al. re-investigated these systems three years later, and determined by T\ measurements that the above complexes should be reformulated as [(PR3)2(H)Ru(p:-H)(p:-Cl)2Ru(ri 2-H2)(PR3)2]. 1 0 The ruthenium was now formally Ru(II), and the complex contained one r | 2 - H 2 moiety. The heavy atom skeleton of the P P h 3 analogue, as determined by X-ray crystallography, has also been reported, and again no hydrides were located.45 This work was further extended by Hampton et al. to include other Ru(II) molecular hydrogen and hydrido derivatives. 3 2' 4 4' 4 5 The structure of [(r|2-H2)(isoPFA)Ru(p:-Cl)2(p:-H)Ru(H)(PPh3)2] is reported, as is the classical hydride complex Ru(H)Cl(PPh3)(isoPFA), where isoPFA is the ferrocene-based ligand (TJ-C 5 H 5 ) F e ( T i - C 5 H 3 ( C H M e N M e 2 ) P ( / - P r ) 2 - l , 2 ) . 3 2 ' 4 4 ' 4 5 202 Chapter 4 References: p 214 Chapter 4 The species containing the classical hydride ligand (i.e., Ru(H)Cl(PPh3)(isoPFA)) was synthesized by reaction of H2 with RuCl2(PPh3)(isoPFA) in the presence of an added base 32,45 4.7.1 X-ray Structure of [(DMA) 2H]+[(PPh 3)2(H)Ru(p-Cl)2(p-H)Ru(H)(PPh3) 2]-A dark-red prism isolated from a D M A solution of RuCl 3 (PPh3 ) 2 (DMA)DMA solvate and one equivalent of DPPB left under H2 for an extended period was proved by X-ray single-crystal crystallography to be [(DMA)2H]+[(PPh3)2(H)Ru(p-Cl)2(p-H)Ru(H)(PPh3)2]_ 18 (Section 2.5.4.3). The molecular structure of 18 is shown in Figure 4.18. Figure 4.19 shows the ORTEP plot, while Tables 4.6 and 4.7 list selected bond lengths and angles of 18, respectively. Appendix VI gives the full experimental parameters and details. [(DMA) 2H] + H . Ph3put»»'"; Ph3p Ru H Cl .PPh, Ru ^'""»/pph 3 'H Figure 4.18 Molecular structure of [(DMA)2H]+[(PPh3)2(H)Ru(p-Cl)2(p-H)Ru(H)(PPh3)2]- 18. The ORTEP plot of 18 shows the dinuclear ruthenium anion (C2). The dinuclear anion contains two terminal and one bridging hydride. The cation [(DMA)2H] + , which was disordered, has been observed previously, and has been studied by X-ray and neutron diffraction.59 The two D M A molecules are bridged by a hydrogen bond. 5 9 The Ru(l)-H(l) (bridging hydride) bond length of 1.72(3) A observed in 18 is of the same order as that observed for one side of the unsymmetrical hydride bridge in [(n2-203 Chapter 4 References: p 214 Chapter 4 H 2 )( isoPFA)Ru(p:-Cl)2(p : -H)Ru(H)(PPh3)2] (1.71(4) A ) . 4 4 H o w e v e r , the R u - H b o n d length on the other side o f the br idge (1.49(4) A ) 4 4 for the above mo lecu l a r hydrogen c o m p l e x is s ign i f i can t ly shorter than that observed i n 18. T h e Ru(l)-H(2) ( te rminal hydr ide) bond length o f 1.59(3) A is o f the order o f the R u - t e r m i n a l H distance (1.50(4) A) for the above molecula r hydrogen c o m p l e x . 4 4 T h e heavy a tom skele ton for [(PR3)2(Ti2-H2)Ru(p.-Cl)2(M:-H)Ru(H)(PR3)2] 17, where R = P h or /? - to ly l , has been determined by X - ray c rys ta l lography; however , the loca t ion o f the hydrogen atoms was not e s t a b l i s h e d . 9 ' 1 0 ' 3 2 ' 4 5 In the case o f 18 and the molecu la r hydrogen complex containing the i s o P F A l igand (see a b o v e ) , 4 4 the locat ions o f the hydr ide and molecu la r hydrogen l igands have been determined. T h e R u - R u bond length o f 2.8251(5) A determined for 18 is essential ly ident ica l to that de termined for [(Ti2-H2)(PPh3) 2Ru(p:-Cl)2(p:-H)Ru(H)(PPh3)2] o f 2.83 A. T h e above values are c lose to the m i d d l e o f the range general ly found for a R u - R u s ing le bond : 2.632 to 3.034 A . . 3 2 ' 4 5 T h e R u ( l ) - C l ( l ) - R u ( l ) * (69.20(3)°) and C l ( l ) - R u ( l ) -C l ( l ) * (81.58(4)°) bond angles o f 18 are also indicat ive o f a R u - R u s ingle b o n d . 6 0 Co t ton and Torralba have characterized a series o f Ru(II,II) and Ru(UI, I I I ) complexes w i t h face-shar ing b ioc tahedra o f the general f o r m u l a [Ru2Cl3(PR3)6][X], [Ru2Ci5(PR 3)4], and [Ru2Cl6(PR3)4] , respectively, and have demonstrated that longer R u - R u distances (3.28-3.44 A) result i n enlarged R u - C l b - R u angles (82.9-87.9°) and contracted C l b - R u - C l b angles (77.2-80.9°), where C l b is a br idging chlor ide 6 0 204 Chapter 4 References: p 214 Chapter 4 C 1 3 * Figure 4.19 The ORTEP plot of [(DMA)2H]+[(PPh3)2(H)Ru(p-Cl)2(p-H)Ru(H)-(PPh3)2] _ 18. Thermal ellipsoids for non-hydrogen atoms are drawn at 33% probability (some of the phenyl carbons have been omitted for clarity). 205 Chapter 4 References: p 214 Chapter 4 Table 4.6 Selected B o n d Lengths (A) for [ ( D M A ) 2 H ] + [ ( H ) ( P P h 3 ) 2 R u ( ^ - C l ) 2 ( p > H ) R u ( P P h 3 ) 2 ( H ) ] _ w i t h Est imated Standard Devia t ions i n Parentheses Bond Length (A) Bond Length (A) Ru(l)—Ru(l)* 2.8251(5) Ru(l)—Cl(l) 2.510(1) Ru(l)—Cl(l)* 2.4649(9) Ru(l ) -P( l ) 2.2576(9) Ru(l)—P(2) 2.3483(9) P(D-C(1) 1.850(3) P(D-C(7) 1.844(3) P(l)-C(13) 1.839(3) P(2)—C(19) 1.842(4) P(2)—C(25) 1.845(3) P(2)—C(31) 1.842(3) 0(1)—C(37) 1.174(8) N(l)—C(37) 1.108(10) N(l)—C(39) 1.370(8) N(l)—C(40) 1.630(9) Ru(l)—H(2) 1.59(3) Ru(l)—H(l) 1.72(3) * refers to the symmetry operation: -x, y, 1/2--z Table 4.7 Selected Bond Angles (°) for [(DMA)2H]+[(H)(PPh3)2Ru(p-Cl)2(p-H)Ru(PPh3)2(H)]_ with Estimated Standard Deviations in Parentheses Bonds Angles O Bonds AnglesO Ru(l)*—Ru(l)—Cl(l) 54.65(2) Ru(l)*—Ru(l)—Cl(l)* 56.15(2) Ru(l)*—Ru(l)—P(l) 109.64(2) Ru(l)*—Ru(l)—P(2) 145.07(2) Cl(l)—Ru(l)—Cl(l)* 81.58(4) C l ( l ) - R u ( l ) - P ( l ) 96.74(3) Cl(l)—Ru(l)—P(2) 107.71(3) Cl(l)*—Ru(l)—P(l) 163.57(3) Cl(l)*—Ru(l)—P(2) 94.24(3) P( l ) -Ru(l ) -P(2) 101.79(3) Ru(l)—Cl(l)—Ru(l)* 69.20(3) Ru(l)*—Ru(l)—H(2) 109.1(9) Ru(l)*—Ru(l)—H(l) 35(1) Cl(l)—Ru(l)—H(2) 163.8(9) Cl(l)—Ru(l)—H(l) 79.1(9) Cl(l)*—Ru(l)—H(2) 88.8(9) Cl(l)*—Ru(l)—H(l) 80.4(9) P( l ) -Ru( l ) -H(2) 88.8(9) P(l)—Ru(l)—H(l) 83.2(10) P(2)-Ru(l)-H(2) 85.9(9) P(2)—Ru(l)—H(l) 170.8(2) H(l)—Ru(l)—H(2) 86(1) * refers to the symmetry operation: -x, y, 1/2--z 206 Chapter 4 References: p 214 Chapter 4 A.l.2 N M R Spectroscopic Studies of [(DMA)2H]+[(PPh3)2(H)Ru(p:-CI)2(p:-H)Ru(H)(PPh3)2]- 18 3 1 P{ 1 H} and *H NMR spectroscopic studies of C7D8 solutions of the dark-red crystal of 18 show spectra almost identical to those of the neutral molecular hydrogen complex [(ri2-H2)(PPh3)2Ru(p:-H)(p,-Cl)2Ru(H)(PPh3)2 ] 17, thus demonstrating conversion of 18 to 17 in the deuterated toluene. 3 1P{ 1H} NMR spectra of 18 in CDCI3 at 20 °C and -89 °C are shown in Figure 4.20. The two broad singlets observed at 20 °C at 71.3 and 46.3 ppm give an A B C D spin system at -89 °C, which corresponds exactly to that previously observed for [(r|2-H2)(PPh3)2Ru(p:-H)(p:-Cl)2Ru(H)(PPh3)2].9'32'45'55 No coupling constants could be obtained for the A B C D spin system observed at low temperature, as the resonances are broad and unresolved. Dekleva et al. have previously reported the coupling constants, 2JAB and 2/cD> from a 32.4 MHz spectrum.9 The 3 1 P{ !H} NMR spectra shown in Figure 4.20 also show a very small amount of an AB pattern (8A = 56.8, 8B = 54.7, 27AB = 30 Hz), which is thought to be due to 18. The ! H NMR spectra of 18 in C 7 D 8 at 20 °C and -79 °C are shown in Figure 4.21. The hydride at 20 °C shows a single broad resonance at -12.8 ppm. Cooling the above sample to -79 °C resolves the hydride and molecular hydrogen resonances. The bridging hydride is observed at -8.7 as a broad doublet, the r| 2 -H2 ligand at -12.6 as a broad singlet, and the terminal hydride at -17.3 ppm as a broad singlet. Again, these *H resonances have been previously observed for [(r|2-H2)(PPh3)2Ru(ji-H)(p:-Cl) 2 Ru(H)(PPh 3 ) 2 ] . 9 ' 3 2 ' 4 5 ' 5 5 The two other resonances of lower intensity observed at -14.9 (t, 2 7 P H = 31.1 Hz) and -17.7 ppm (br s) are attributed to 18. The lH N M R resonance for the cation [(DMA)2H]+ in the complex [(DMA)2H]+[AuCi4]- has been reported at -17.45 ppm. 5 9 Therefore, the -17.7 ppm resonance is assigned to the hydrogen-bonded proton of the cation, while the triplet at -14.9 is assigned to the terminal-hydrides. A third resonance expected for the bridging hydride may be buried under the broad resonances of 17. Hampton et al. have explained 207 Chapter 4 References: p 214 Chapter 4 the exchange processes involved which account for the room- and low-temperature spectra observed for 17.32>45 An alternative assignment of the -17.7 ppm peak is possible as the resonance for the [(DMA)2//] + may be expected to be observed in the 10-12 ppm region as has been observed for [DMA//]+Cl~.+ Assignment of the protons of the ionic complex 18 are difficult as the equilibrium between 17 and 18 favours neutral complex 17. Attempts to measure the UV-visible spectrum and conductivity of 18 were unsuccessful. When some of the dark-red crystal was dissolved in either C6H6 or D M A , the solution became green-black, indicating oxidation of 18, although care was taken to avoid the presence of oxygen. This behaviour contrasts with that of the stable orange-red C7D8 solutions observed in the NMR studies described above. Compound 18 (or 17) may be sensitive to trace oxygen in the solvent (despite attempts to deoxygenate the solvents) at the lower concentrations used for UV-visible studies compared to those used in the NMR spectroscopic studies. Similar O2 oxidation of ruthenium(II) complexes has been observed by other workers in the research group; the green products were thought to be Ru(IJJ) species.4'5 t see Benedetti, E . ; Di Blasio, B.; Baine, P. /. Chem. Soc, Perkin II1980, 500. Chapter 4 References: p 214 208 Chapter 4 (a) 17 17 18 18 TT 17 | I I I I | I t M | I II I | i I I I j I I I I | ! I I I | I I I I | ! I I I | I I I I 70 60 50 40 30 PPM Figure 4.20 3 1P{ *H} NMR spectra (121.42 MHz) of 18 in C 7 D 8 at: (a) 20 °C and (b) -89 °C. 17 = [(Ti2-H2)(PPh3)2Ru(p-H)(p-Cl)2Ru(H)(PPh3)2]. 209 Chapter 4 References: p 214 Chapter 4 (a) 17 exchanging p,-H, terminal, and T] 2-H2 I I I I | , I I I | I I I I j ! I I I | I I I I | I I I I | I I I I | I I I I | I I I I | i I I I | I I I I | I I I I | -8 -10 -12 -14 -16 - I S P p M Figure 4.21 * H N M R spectra (upfield region, 300 M H z ) of 18 in C 7 D 8 at: (a) 20 °C and (b) -79 "C. 17 = [(Tl2-H2)(PPh3)2Ru(n-H)(p.-Cl)2Ru(H)(PPh3)2]. The spectral and X-ray structural data taken together demonstrate the existence of an equilibrium between 18 and the molecular hydrogen complex 17 (Figure 4.22). 210 Chapter 4 References: p 214 Chapter 4 H 3 C / N C H 3 H 3 C C O O C / C H 3 L .PPhq .... Ru > R u C " " " P P h q P h , P ^ Cl H H Ph 3p«»>»^ L3 : Ffc>C N NCHq 18 H H 2DMA + p h p ^ ^ . ^ R u P h 3 P ^ x s C 1 / x Cl .PPh„ 'Ru^i / / / /pph 3 17 Figure 4.22 Equilibrium between [(DMA)2H]+[(PPh3)2(H)Ru(ii-Cl)2(ii-H)Ru(H)-(PPh 3) 2]- 18 and [(Ti2-H2)(PPh3)2Ru(p:-Cl)2(M:-H)Ru(H)(PPh3)2] 17. The T\ measurements on 17 and the P(p-tolyl)3 analogue leave little doubt that 17 is in fact a molecular hydrogen complex . 1 0 ' 3 2 ' 4 5 Also, the heavy atom skeleton determined for 1745 did not contain a C2, as was seen for 18 (Section 4.5.2). Efforts were made to develop a controlled synthetic route to the ionic complex 18, as the crystal was isolated fortuitously after a long period of time from a reaction mixture which included the "superfluous" diphosphine DPPB (Section 2.5.4.3). Two reaction pathways to form complex 17 are shown in equations 4.2 and 4.3 (Section 4.1); one involves direct preparation from a Ru(III) starting complex (eq 4.3), while the other requires the initial preparation of a Ru(II) dinuclear species (eq 4.2). The pathway shown in equation 4.2 via Ru 2Cl4(PPh3)4 was attempted, except that the work-up was changed in the hope of isolating the "ionic analogues" of the neutral species shown in equations 211 Chapter 4 References: p 214 Chapter 4 A.l and 4.3. T h e first step was successful, i n that reduct ion o f R u C l 3 ( P P h 3 ) 2 D M A D M A solvate by H 2 i n D M A gave [ ( D M A ) 2 H ] + [ R u 2 C l 5 ( P P h 3 ) 4 ] - 16 (Sec t ion 2.5.4.1). T h e syn thes i s w a s the same as that used p r e v i o u s l y to i so la te the neu t r a l spec ies Ru 2 Cl4(PPh3)4; however , i n this case, the work -up was changed by subst i tut ing d i e thy l ether for M e O H i n order to precipitate the product (Sect ion 2.5.4.1). ' ' C o m p l e x 16 has p r e v i o u s l y been obse rved i n s o l u t i o n by 3 1 P { l H } N M R s p e c t r o s c o p y . 9 ' 5 5 T h e i so la ted orange s o l i d i n C7D8 gave a s ingle t at 44.6 ove r the temperature range o f -85 to 20 °C , suggesting a structure s imi l a r to that s h o w n by X - r a y crys ta l lographic studies for the D P P B analogue [ T M P ] + [ R u 2 C i 5 ( D P P B ) 2 ] - (Figure 3.16, Sect ion 3.3.4.1), except w i t h PPh3 occupy ing the D P P B posi t ions; F igu re 4.23 shows the molecu la r structure. F igure 4.23 M o l e c u l a r structure o f [ T M P ] + [ R u 2 C l 5 ( D P P B ) 2 ] - , where P - P = P h 2 P ( C H 2 ) 4 P P h 2 . T h e second step i n the synthesis o f 18 (or at least the P ro ton Sponge analogue, [PSH]+[ (PPh 3 )2 (H)Ru(p -Cl )2 (p-H)Ru(H)(PPh3)2] - ) is the reaction o f 16 w i t h H 2 i n the presence o f P ro ton Sponge i n C^H^. H o w e v e r , under w o r k - u p cond i t ions i den t i c a l to those used for the i so la t ion o f the ion ic complex 16, on ly the neutral mo lecu la r hydrogen c o m p l e x [ (Ti2 -H2)(PPh3)2Ru(p -Cl )2(p-H)Ru(H)(PPh 3 ) 2 ] 17 w a s i s o l a t e d ( S e c t i o n 2.5.4.2). The 31p{lH} and lH N M R spectra i n C 6 D 6 agree w i t h those o b s e r v e d 9 ' 3 2 ' 4 5 ' 5 5 prev ious ly for 17, as w e l l as w i t h the resonances shown i n F igu re 4.20 and 4.21, where 17 was produced i n solut ion f rom the equ i l ib r ium wi th 18 (Figure 4.22). 212 Chapter 4 References: p 214 Chapter 4 The neutral complex 17 has also been reported as a bis(DMA) solvate when the complex was prepared from RuCl3(PPh3)2DMA D M A via equation 4.3 and isolated from D M A solvent.9'55 The preparation described above and in Section 2.5.4.2 results in the isolation of DMA-free 17. In view of the determination of the X-ray crystal of 18 in this work, as well as the existence of the equilibrium shown in Figure 4.21, the solvated species [(ri2-H2)(PPh3)2Ru(p-Cl)2(p-H)Ru(H)(PPh3)2]-2DMA should be re-formulated, at least in the solid state, as [(DMA)2H]+[(PPh3)2(H)Ru(p-Cl)2(p-H)Ru(H)(PPh3)2]- 18. The solid isolated by Dekleva from D M A was red in colour, as was the crystal analyzed in this thesis work. The equilibrium between ionic 18 and neutral 17 shown in Figure 4.22 amounts to protonation of the anionic polyhydride complex by the acidic cation to produce the T}2-H.2 complex 17. Jessop and Morris list protonation of a hydride complex as a common method of preparing dihydrogen complexes, but there are no previous examples involving a 'proton transfer' within an ionic precursor like 18. Essentially, formation of 18 from 17 is the reverse of intramolecular heterolytic cleavage of a molecular hydrogen 12 complex. Several examples of an equilibrium mixture of M(H2) and M(H)2 have been 12 observed. 4.8 Summary The complex RuGl2(BINAP)(PPh3) reacted reversibly with H2 to give two molecular hydrogen complexes which were studied in solution by NMR spectroscopy. The products were shown by a combination of NMR spectroscopic techniques to be [(r|2-H2)(BINAP)Ru(p-Cl)3RuCl(BINAP)]. In the presence of base, RuCl 2(BINAP)(PPh 3) reacted with H2 to give two diastereomers of Ru(H)Cl(BINAP)(PPh3). The complex [(DMA)2H]+[(PPh3)2(H)Ru(p-Cl)2(p-H)Ru(H)(PPh3)2]-, which was characterized in the solid state by X-ray crystallography, was shown to be in equilibrium with the molecular hydrogen complex [(T|2-H)(PPh3)2Ru(p-Ci)2(p-H)Ru(H)(PPh3)2] in solution. 213 Chapter 4 References: p 214 Chapter 4 4.9 References (1) James, B. R.; Pacheco, A.; Rettig, S. J.; Thorburn, I. S.; Ball, R. G.; Ibers, J. A. J. Mol. Catal. 1987,47,147. (2) Joshi, A. M . Ph.D. Thesis, The University of British Columbia, 1990. (3) Joshi, A. M. ; James, B. R. J. Chem. Soc, Chem. Commun. 1989, 1785. (4) Chau, D. E. K.-Y.; James, B. R. Inorg. Chim. Acta, in press. (5) Chau, D. E. K.-Y. M.Sc. Thesis, The University of British Columbia, 1992. (6) Thorburn, I. S. Ph.D. Thesis, The University of British Columbia, 1985. (7) Hallman, P. S.; McGarvey, B. R.; Wilkinson, G. J. Chem. Soc. (A) 1968, 3143. (8) James, B. R.; Thompson, L. K.; Wang, D. K. W. Inorg. Chim. Acta 1978, 29, L237. (9) Dekleva, T. W.; Thorburn, I. S.; James, B. R. Inorg. Chim. Acta 1985,100, 49. (10) Hampton, C ; Dekleva, T. W.; James, B. R.; Cullen, W. R. Inorg. Chim. Acta 1988,145, 165. (11) McCrindle, R.; Ferguson, G.; Arsenault, J.; McAlees, A. J. J. Chem. Soc, Chem. Commun. 1983, 571. (12) Jessop, P. G.; Morris, R. H. Coord. Chem Rev. 1992,121, 155. (13) Heinekey, D. M. ; Oldham, W. J. Jr. Chem. Rev. 1993, 93, 913. (14) Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 789. (15) Kubas, G. J. Comments Inorg. Chem. 1988, 7, 17; and references therein. (16) Kubas, G. J. Acc Chem. Res. 1988, 21, 120. (17) Ashworth, T. V.; Singleton, E. J. Chem. Soc, Chem Commun. 1976, 705. (18) Knoth, W. H. J. Am. Chem. Soc. 1972, 94, 104. (19) Kubas, G. J. J. Chem. Soc, Chem. Commun. 1980, 61. (20) Chem. Eng. News 1983, 61(13), 4. (21) Kubas, G. J.; Ryan, R. R.; Vergamini, P. J.; Wasserman, H. J. Abstracts of Papers, 185th National Meeting of the American Chemical Society, Seattle, WA; American Chemical Society: Washington, DC, 1983; Abstract INOR229. (22) Kubas, G. J.; Ryan, R. R.; Swanson, B. I.; Vergamini, P. J.; Wasserman, H. J. J. Am. Chem. Soc 1984,106, 451. 214 Chapter 4 (23) Kubas, G. J.; Unkefer, C. J.; Swanson, B. I.; Fukushima, E. J. Am, Chem. Soc. 1986,108,7000. (24) Nageswara Rao, B. D.; Anders, L. R. Phys. Rev. 1965,140, A l 12. (25) Moreno, B.; Sabo-Etienne, S.; Chaudret, B.; Rodriquez-Fernandez, A.; Jalon, F.; Trofimenko, S. J. Am. Chem. Soc. 1994,116, 2635. (26) Mudalige, D. C ; Rettig, S. J.; James, B. R.; Cullen, W. R. J. Chem. Soc, Chem. Commun. 1993, 830. (27) Mudalige, D. C. Ph.D. Thesis, The University of British Columbia, 1994. (28) Crabtree, R. H.; Lavin, M . J. Chem Soc, Chem. Commun. 1985, 794. (29) Crabtree, R. H.; Lavin, M . J. Chem. Soc, Chem. Commun. 1985, 1661. (30) Morris, R. H.; Sawyer, J. F.; Shiralian, M . ; Zubkowski, J. D. J. Am. Chem. Soc. 1985,107, 5581. (31) Crabtree, R. H.; Hamilton, D. G. J. Am Chem. Soc. 1986,108, 3124. (32) Hampton, C. Ph.D. Thesis, The University of British Columbia, 1989. (33) Crabtree, R. H.; Hamilton, D. G. Adv. Organomet. Chem. 1988, 28, 299. (34) Crabtree, R. H.; Lavin, M. ; Bonnevoit, L. J. Am. Chem. Soc 1986,108, 4032. (35) Crabtree, R. H. Acc. Chem. Res. 1990,23, 95. (36) Bautista, M . T.; Earl, K. A.; Maltby, P. A.; Morris, R. H.; Schweitzer, C. T.; Sella, A. J. Am Chem. Soc. 1988,110, 7031. (37) Zilm, K. W.; Heinekey, D. M. ; Millar, J. M. ; Payne, N. G.; Neshyba, S. P.; Duchamp, J. C ; Szczyrba, J. / . Am. Chem. Soc 1990,112,920. (38) Antoniutti, S.; Albetin, G.; Amendola, P.; Bordignon, E. J. Chem. Soc, Chem. Commun. 1989, 229. (39) Cotton, F. A ; Luck, R. L. Inorg. Chem. 1989,28, 6. (40) Desrosiers, P. J.; Cai, L. ; Lin, Z.; Richards, R.; Halpern, J. J. Am. Chem. Soc. 1991,113, 4173. (41) Cotton, F. A.; Luck, R. L.; Root, D. R ; Walton, R. A. Inorg. Chem. 1990, 29, 43. (42) Hamilton, D. G.; Crabtree, R. H. / . Am. Chem. Soc 1988,110, 4126. (43) Joshi, A. M. ; MacFarlane, K. S.; James, B. R. J. Organomet. Chem. 1995, 488, 161. (44) Hampton, C ; Cullen, W. R.; James, B. R ; Charland, J.-P. J. Am. Chem. Soc. 1988,110, 6918. 215 Chapter 4 (45) Hampton, C. R. S. M . ; Butler, I. R.; Cullen, W. R.; James, B. R ; Charland, J.-P.; Simpson, J. Inorg. Chem. 1992, 31, 5509. (46) Joshi, A. M . ; Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chim. Acta 1992, 198, 283. (47) Sanders, J. K. M. ; Hunter, B. K. Modern NMR Spectoscopy: A Guide for Chemists; Oxford University Press: Oxford, 1987, pp 61-65. (48) Mezzetti, A.; Costella, L. ; Zotto, A. D.; Rigo, P.; Consiglio, G. Gazz. Chim. Ital. 1993,123, 155. (49) Sweany, R. L.; Halpern, J. J. Am Chem. Soc. 1977, 99, 8335. (50) Kirss, R. U.; Eisenschmid, T. C ; Eisenberg, R. J. Am. Chem, Soc. 1988,110, 8564. (51) Cyr, P. W. B.Sc. Thesis, The University of British Columbia, 1995. (52) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals; 2nd ed.; Pergamon: Oxford, 1980. (53) Abu-Gnim, C ; MacFarlane, K. S.; James, B. R , unpublished results. (54) Kuhlman, R.; Rothfuss, H.; Gusev, D.; Streib, W. E.; Caulton, K. G. Abstracts of Papers, 209th American Chemical Society National Meeting, Anaheim, CA; American Chemical Society: Washington, DC, 1995; Abstract INOR 497. (55) Dekleva, T. W. Ph.D. Thesis, The University of British Columbia, 1983. (56) Fogg, D. E. Ph.D. Thesis, The University of British Columbia, 1994. (57) Ikariya, T.; Ishii, Y.; Kawano, H.; Arai, T.; Saburi, M . ; Yoshikawa, S.; Akutagawa, S. / . Chem. Soc, Chem. Commun. 1985,922. (58) Chan, A. C. S.; Laneman, S. Inorg. Chim. Acta 1994,223, 165. (59) Hussain, M . S.; Schlemper, E. O. J. Chem. Soc, Dalton Trans. 1980, 750. (60) Cotton, F. A.; Torralba, R. C. Inorg. Chem. 1991,30, 2196. 216 C H A P T E R 5 REACTIONS O F RUTHENIUM(II) PHOSPHINE C O M P L E X E S W I T H N-DONOR LIGANDS 5.1 Introduction T h e c l a s s i ca l coord ina t ion chemis t ry o f ru thenium (II) monodentate phosphine c o m p l e x e s was e x a m i n e d i n some deta i l i n the late 1960s and 1970s but s t ructural assignments o f products were general ly tentative. 1 Par t icu lar ly relevant to the chemis t ry presented i n this chapter is the reaction o f R u X 2 ( P P h 3 ) 3 complexes w i t h pyr id ine , 2,2 '-b ipy r id ine , 1,10-phenanthroline, and ammonia . G i l b e r t and W i l k i n s o n reacted py r id ine w i t h RuCl2(PPh3)3 i n acetone to give c,c,*-RuCl2(py)2(PPh3)2-2 T h e tentative structural assignment was based on the observation o f two R u - C l stretching frequencies i n the far-I R . R e a c t i o n o f RuBr2 (PPh3)3 w i t h neat py r id ine produced R u B r 2 ( p y ) 3 ( P P h 3 ) , w h i l e w i t h longer react ion times, trans-RuBr2(py)4 was isolated. T h e ch lo ro-ana logue was isolated as a mixture o f mms-RuCl2(py)3(PPh3) and ? rans -RuCl2(py) 4 . T h e species R u X 2 ( P P h 3 ) 2 ( N - N ) , [ R u X ( P P h 3 ) ( N - N ) 2 ] X , and [ R u 2 X 2 ( P P h 3 ) 4 ( N -N ) ] X 2 have a l l been isolated f rom the reaction o f RuX2(PPh3)3 w i t h N - N l igands, where N - N is 2 ,2 ' -b ipyr id ine or 1,10-phenanthroline, and X = C l or B r . 3 Ba t i s t a et a l . have r e p o r t e d r u t h e n i u m ( I I ) c o m p l e x e s o f the f o r m u l a t i o n s R u C l 2 ( P P h 3 ) 2 ( N ) 2 , [ R u C l ( P P h 3 ) ( N ) 4 ] C l , and [ R u C l ( D P P B ) ( N ) 3 ] C l , where N is an i m i d a z o l e l i g a n d ( imidazo le or iV-me thy l imidazo l e ) . 4 C e n i n i et a l . have s h o w n that p r imary amines react w i t h R u C l 2 ( P P h 3 ) 3 to g i v e RuCl2 (PPh3)2 (RNH2)2 c o m p l e x e s . 5 I n pa r t i cu la r , they have s h o w n that b u b b l i n g a m m o n i a through a solu t ion o f RuCl2(PPh3)3 produces R u C l 2 ( N H 3 ) 2 ( P P h 3 ) 2 . 5 H o w e v e r , the stereochemistry o f the pr imary amine and ammine complexes has not been assigned. 217 Chapter 5 References: p 249 Chapter 5 None of the amine/ammine complexes mentioned above have been structurally characterized by X-ray analysis. The chemistry described in this chapter employs diphosphines instead of PPI13, thereby limiting the number of isomers available, as the phosphorus atoms of the chelate must be cis. Therefore, of the three possible geometries available for complexes of the type RuCl2(L)2(P-P), one (c,c,c) can be distinguished from the other two (t,c,c and c,t,c) by 3 1 P{ 1 H} NMR spectroscopy. In particular, this chapter examines the reactions of five-coordinate Ru(II)-diphosphine complexes with the N-donor ligands, pyridine, 2,2'-bipyridine, 1,10-phenanthroline, and ammonia. The chemistry described here was performed under similar reaction conditions to those described in Chapter 3, in which different S- or O-donor ligands produced diruthenium products. For example, the reaction of RuCl2(DPPB)(PPh 3) with S-donors (DMSO, TMSO, DMS, and THT) produced the species Ru2Cl4(DPPB)2(L). However, attempts to prepare the diruthenium pyridine analogue (i.e., Ru2CLi(DPPB)2(py)) resulted in different reactivity, and formation of a monoruthenium species (e.g., RuCl2(DPPB)(py)2). Later attempts under different conditions using Ru2Cl4(DPPB)2 as precursor did allow observation of Ru2Cl4(DPPB)2(py) in solution. Similar monoruthenium species have been observed previously in this laboratory on reaction of RuCl2(DPPB)(PPh3) 11 with C O , 6 R C N , 7 and R N H 2 . 7 Reaction with C O produces an isomeric mixture of RuCl2(X>PPB)(CO)2 and some "RuCl2(DPPB)(CO)" monocarbonyl complexes;6 reaction with benzonitrile produces RuCl2(DPPB)(PhCN)2,7 and similarly PhCH2NH2 gives RuCl2(DPPB)(PhCH2NH2)2,8 although, in these cases, the diruthenium species Ru2CLi(DPPB)2(L) could be isolated if different reaction conditions were employed. ' As mentioned above, the reactions of RuCl2(PPh3)3 with N H 3 5 and pyridine3 to give products of the formula RuCl2(L)2(PPh3)2 have appeared previously in the 218 Chapter 5 References: p 249 Chapter 5 literature, but as no 3 1 P{ 1 H} NMR data were reported in these studies. These reactions were repeated in this thesis work to allow comparison between the 3 1P{!H} NMR data of the DPPB and PPI13 analogues. 5.2 Reactions with Pyridine 5.2.1 Reaction of Pyridine with RuCl2(DPPB)(PPh3) and Ru 2Cl 4(DPPB) 3 The reaction of excess pyridine with either of the mixed- or bridged-phosphine complexes (i.e., RuCl2(DPPB)(PPti3) 11 and Ru2CU(DPPB)3 19) results in the formation of ?ra/zs-RuCl2(DPPB)(py)2 43 species (see Section 2.5.11.1). Originally, this reaction was performed in an attempt to prepare Ru2CLi(DPPB)2(py) 29 (see Figure 5.4, Section 5.2.3). The reaction conditions using 11 were the same as those used to prepare the Ru2CLi(DPPB)2(L) (where L = DMSO, TMSO, DMS, and THT) species. In all cases, an excess of L was refluxed with a C6H6 suspension of RuCl2(DPPB)(PPh3). However, in the case of pyridine, this produced a monomeric Ru species. The overall reaction can be written as a simple phosphine displacement (eq 5.1). C 6 H 6 , reflux RuCl2(DPPB)(PPh3) + xsL • RuCl 2(DPPB)(L) 2 + PPh 3 (5.1) The isolated RuCl2(DPPB)(py)2 species gave a singlet at 40.4 ppm in the 3 1 P{ 1 H} NMR spectrum (Table 5.1), indicating that the P-atoms were equivalent and ruling out the presence of the all-czs isomer. Unfortunately, the 3 1 P{ 1 H} NMR data do not distinguish between the trans-Cl and trans-py species (Figure 5.1). Other workers, one of whom (Batista) was a visiting scientist in this laboratory, have independently prepared the same RuCl2(DPPB)(py)2 complex from Ru2CLi(DPPB)3, the species isolated by their route giving the same singlet in the 3 1P{ lH] NMR spectrum. An X-ray crystallographic study of 43 by these workers proved the structure to be that of the isomer with trans chloro ligands.9'1 0 Their preparative method was repeated in this work to 219 Chapter 5 References: p 249 Chapter 5 ensure that the complexes isolated by the two procedures were in fact the same isomer (Section 2.5.11.1). The reaction proceeds by displacement of a molecule of DPPB from the dinuclear starting complex 19, which breaks the bridge between the two metals (eq 5.2). The displaced DPPB was observed by 3 1 P{ 1 H} NMR spectroscopy as a singlet at -17 ppm when in situ reactions were performed. Table 5.1 3 1P{!H} NMR Data (121.42 MHz, 20 °C) for Some Mononuclear Complexes [RuCl2(DPPB)(L)2] Complex Solvent Chemical Shift, 8(a) 2 Jpp, (Hz) 1 = py ?ra/w-RuCl2(DPPB)(py)2 43 (L) 2 = bipy ds-RuCl2(DPPB)(bipy) 44 fran^-RuCl2(DPPB)(bipy) (LV^ = phen m-RuCl2(DPPB)(phen) 45 *rans-RuCl2(DPPB)(phen) L = NEh fran5-RuCl 2(DPPB)(NH3) 2 51 C 6 D 6 5 = 41.5, s CDC1 3 5 = 40.4, s C D 2 C 1 2 5 = 40.4, s CDCI3 5 A = 43.5, 5 B = 29.8 CDCI3 5 = 32.6, s CDCI3 5 A = 45.1,5B =29.6 CDCI3 5 =32.5, s CDCI3 5 = 46.7, s 32.9 33.7 (a) s = singlet 220 Chapter 5 References: p 249 Chapter 5 Cl py P///"... I .,»^py I ...**xC1 . R u _ ^ R u rpy Cl py r C l Figure 5.1 The two possible geometries of RuCl2(DPPB)(py)2 that would produce a singlet in the 31p{lH} NMR spectrum, where P-P = Ph 2P(CH 2)4PPh 2. CH 2 C1 2 , room temp Ru 2Cl 4(DPPB) 3 + xs L • 2RuCl2(DPPB)(L)2 + DPPB (5.2) The UV-visible spectroscopic and molar conductivity data for trans-RuCl2(DPPB)(py)2 43 are shown in Table 5.2. The complex shows molar conductivity values below the normal range in both MeOH and CH3N0 2 , where A M values for 1:1 electrolytes are 80-115 and 75-95 ohm - 1 m o l - 1 cm 2 , respectively;11 the low value measured for the conductivity presumably indicates partial dissociation of chloride from the neutral species. The molar conductivity of 43 in CH3N0 2 increased with time, finally stabilizing after 3 h at 37.5 ohm - 1 m o l - 1 cm 2 , when the colour of the solution had changed from orange to purple. The nature of the purple species has yet to be elucidated. The bromo analogue of 43 was prepared in situ from both RuBr2(DPPB)(PPh3) and Ru2Br4(DPPB)3 by adding 10 equivalents of pyridine. The resulting orange solution showed a singlet at 39.3 ppm in the 31P{lH} NMR spectrum for a presumed trans-RuBr2(DPPB)(py)2 species. A small amount of chloride impurity in the starting material results in the observation of a trace singlet at 39.8 ppm attributed to trans-RuBrCl(DPPB)(py)2. Of note, the resonance for the bromo analogue is observed further upfield than for that of RuBrCl(DPPB)(py) 2, which in turn is further upfield than that of RuCl2(DPPB)(py)2 (40.4 ppm). This same trend in chemical shift is observed for the RuXY(CO) 2(PPh 3) 2 complexes (Table 3.1, Section 3.3.2), where X, Y = Br or Cl . 221 Chapter 5 References: p 249 Chapter 5 Table 5.2 UV-visible Spectroscopic and Molar Conductivity Data for RuCl2(DPPB)(N)2 Complexes, where N represents an N-donor ligand Complex Solvent ^max £max A M (nm) (M- 1 cm"1) (ohm - 1 mol"1 cm 2) /rans-RuCl2(DPPB)(py)2 C H 2 C 1 2 462 430 43 672 90 MeOH 258 342 374 (sh) 7990 4040 3030 39.3 C 6 H 6 458 678 492 96 -C H 3 N O 2 37.5 cis- and trans- CH2CI2 300 12300 RuCl2(DPPB)(bipy) 346 (sh) 2600 (50% of each) 44 458 2200 MeOH 292 436 15400 2600 59.1 C H 3 N O 2 56.5 ds-RuCl2(DPPB)(phen) CH2CI2 272 13500 45 438 3900 MeOH 270 416 26800 4300 74.9 C H 3 N O 2 69.2 trans- CH2CI2 260 5500 RuCl 2(DPPB)(NH3)2 51 314 (sh) 1400 MeOH 236 330 (sh) 4490 840 84.5 C H 3 N O 2 19.9 222 Chapter 5 References: p 249 Chapter 5 Also, a presumed frans-RuCl2((^,/?)-DIOP)(py)2 was prepared in situ by addition of 10 equivalents of pyridine to a green solution of Ru2CU(DIOP)3 in C D C I 3 . The resulting orange solution gave a singlet at 31.5 ppm in the 3 1 P{ 1 H} NMR spectrum, indicating the formation of the product. Another singlet at -23.4 ppm indicated the presence of free DIOP (cf. eq 5.2). 5.2.2 Reaction of Pyridine with RuCl2(PPh3)3 The previously known complex formulated c,c,?-RuCl2(py)2(PPh3)2 was prepared from RuCl2(PPh3)3 in acetone as outlined in Section 2.5.11.4. The stereochemistry of this complex was assigned as the c,c, ^-isomer based on Ru-Cl stretching frequencies (all possible geometries are illustrated in Figure 5.2). The isolated yellow solid is only sparingly soluble in CHCI3, C6H6, and acetone. P//> ci Rui C l c,c,c r N Cl P/A .Ru" Cl t,c,c r N Cl'//,„. Cl N Ru, N c,t,c C 1 in,,,.. I rt*\\N I ^ N N 1 r C l c,c,t t,t,t Figure 5.2 Possible geometries of the species RuCl2(py)2(PPh3)2, where P = PPI13 and N = pyridine. The 3 1 P{ 1 H} NMR spectrum of the yellow solid in CDCI3 showed a singlet at 27.7 ppm, consistent with the c,c>isomer. However, all the isomers shown in Figure 5.2 223 Chapter 5 References: p 249 Chapter 5 w o u l d be expected to g ive singlets, except the c,c,c-isomer, w h i c h shou ld be observed as an A B pattern. A reaction between RuCl2(PPh3)3 and pyr id ine (10 equiv) i n re f lux ing C6H-6 was also attempted i n this work . H o w e v e r , the y e l l o w s o l i d isola ted by this reac t ion gave a 3 1 P { 1 H } N M R spectrum i n CDCI3 w h i c h showed singlets at 27.7 and 51.9 p p m . T h e resonance at 27.7 p p m is as seen for the material isolated f rom the acetone react ion (i.e., the presumed c,c,£-RuCl2(py)2(PPh3)2), and the other resonance at 51.9 p p m is thought to be due to ? ran5-RuCl2 (py )3 (PPh3) . T h e X H N M R spec t rum (CDCI3) supports this assignment, as a 2:1 ratio o f ortho-py protons (doublets) are observed at 8.9 and 9.0 p p m for two sets o f inequivalent pyr id ine l igands. 5.2.3 Reaction of Pyridine with Ru 2Cl4(DPPB) 2 T h e addi t ion o f excess pyr id ine to RuCl2(DPPB)(PPh 3 ) 11 or R u 2 C U ( D P P B ) 3 19 produced fr*ans-RuCl2(DPPB)(py)2 43 (see Tab le s 5.1 and 5.2). E a r l i e r attempts to prepare Ru2Cl4(DPPB)2(py) i n s i tu by add ing ~ 5 equiva len ts o f p y r i d i n e to 11 i n CD2CI2 so lu t ion also produced on ly 43. E v e n i f an N M R tube conta in ing the reactants was s l o w l y w a r m e d (from l i q u i d N2 temperature) to -65 °C i n the NMR probe, no Ru2CU(DPPB)2(py) was observed. H o w e v e r , the desired d i ru thenium c o m p l e x Ru2CU(DPPB)2(py) 29 c o u l d be prepared i n s i tu by adding one equivalent o f py to Ru2CLi(DPPB)2 i n C D C I 3 so lu t ion (see S e c t i o n 2.5.8.2). T h e 3 1 P { 1 H } NMR spect rum o f the resu l t ing o r a n g e - b r o w n solut ion is shown i n F igure 5.3, and the spectral data are l is ted i n T a b l e 5.3. T h e two A B patterns observed are characterist ic o f complexes o f the type Ru2Cl4 (DPPB)2 (L) (see Sec t ion 3.5). T h i s is on ly the second observation o f such a dinuclear species that exhibi t s a chemica l shift for the L - e n d o f the complex further downf ie ld than the Cl-end (the other is R u 2 C l 4 ( D P P B ) 2 ( r | 2 - H 2 ) , Chapter 4). As discussed in Sec t ion 3.5, the c h e m i c a l shifts (8A and 8B) o f the phosphorus atoms o n the Cl-end o f the d inuc lea r c o m p l e x e s are 224 Chapter 5 References: p 249 Chapter 5 usually found with a coupling constant of 2 7 A B = 41^15 Hz in the 52 ppm region, while the chemical shifts (8c and 8D ) of the L-end are found upfield of the Cl-end, with the 2 / C D ranging from 28-40 Hz. In this case, where L = py, one phosphorus chemical shift of the py-end at 8 A = 54.3 ppm is found downfield of the phosphorus chemical shifts of the Cl-end. The coupling constants, 2 / A B and 2 7 C D (note that the A B and C D designations are reversed in this case by convention), are within the ranges listed above for complexes of this type. Table 5.3 3 1P{ !H} NMR Data (121.42 MHz, 20 °C) for Some Dinuclear Complexes, [(L)(DPPB)Ru(p-Cl)3RuCl(DPPB)] L(Complex) Solvent Chemical Shift, 8 2 J P P , (Hz) pyridine (py) CDC1 3 8 A = 54.3, 8 B = 45.0 36.4 29 8 C = 52.6 8 D = 51.6 42.7 ammonia, NH 3( a) CDC1 3 8 A = 55.6, 8 B =51.0 39.1 8 C = 52.6, 8 D = 51.9 43.7 ammonia, NH3(b) CDC1 3 8 A = 59.0, 8 B = 53.7 34.5 8 C = 58.5, 8 D = 56.7 39.8 (a) Sample formed by heating fran.s-RuCl2(DPPB)(NH3)2 51 under vacuum (see Section 5.5.3). (b) The complex is more likely of formulation Ru2CU(DPPB)2(NH3)2 (see Section 5.5.3). Figure 5.3 shows a series of 3 1P{ *H} NMR spectra which illustrate the effect of adding more pyridine to 29 produced in situ. Upon addition of a second equivalent of pyridine to Ru2Ci4(DPPB)2 ((b) in Figure 5.3), the 8c, 8 D phosphorus resonances become a broad multiplet. The 8 A , 5 B phosphorus resonances of 29 remain unchanged. As the 8c, 8 D resonances belong to the Cl-end of 29, the second equivalent of py is thought to coordinate to this end of the dinuclear complex en route to the monomeric ?ra«5-RuCl2(DPPB)(py)2 (observed as a singlet at 40.4 in spectra (b)-(d)). Figure 5.4 illustrates a possible route from Ru2CU(DPPB)2 to Ru2CLt(DPPB)2(py), and eventually to ?rans-RuCl2(DPPB)(py)2. 225 Chapter 5 References: p 249 Chapter 5 (d) 1—i—i f~~i i i—r—j i i—i—i—|—i—i—i—i—|—r i—i—i—|—i—i—m—|—ri 65 60 55 50 45 40 PPM Figure 5.3 The 3 1P{ lH} NMR spectra (121.42 MHz, 20 *C) of Ru 2Cl4(DPPB) 2 24 in CDCI3 plus (a) one equiv of py, (b) two equiv of py, (c) four equiv of py, and (d) 10 equiv of py. 43 = fran.y-RuCl2(DPPB)(py)2. 226 Chapter 5 References: p 249 Chapter 5 Figure 5.4 Proposed reaction pathway from Ru2CU(DPPB)2 24 through Ru2Cl4(DPPB)2(py) 29 to *rans-RuCl2(DPPB)(py)2 43, where P-P = Ph 2 P(CH 2 ) 4 PPh 2 . 227 Chapter 5 References: p 249 Chapter 5 The addition of one equivalent of py to 29 is thought to break one of the three chloro-bridges, thereby producing any of the doubly-chloro bridged species illustrated in Figure 5.4. This intermediate isomer(s), which is not observed by 3 1 P{ 1 H} NMR, is thought to be in rapid equilibrium with 29 on the NMR timescale. Thus, the phosphorus resonances at the py-end, after adding one more equiv of py (i.e., total of two equiv), appear as they do in the spectrum of 29 (spectrum (a), Figure 5.3), while the resonances assigned to the Cl-end are affected by the exchange process (spectrum (b), Figure 5.3). The addition of another two equivalents of pyridine breaks up the doubly-chloro -bridged intermediate to give complete conversion to tazns-RuCl2(DPPB)(py)2. This step is fast, as indicated by the 3 1P{ 1H} NMR spectra, which were recorded immediately after the addition of pyridine. Eventually, by adding pyridine to RuCl2(DPPB)(PPh3) 11, the correct conditions to observe 29 in solution were found. The experiment was performed in CDCI3 by adding 0.5 equivalents of pyridine to 11. Three minutes after the addition of py, the two A B quartets of 29 were observed in the 3 1P{ NMR spectrum (Table 5.3). A singlet at 40.4 ppm, indicating the presence of ?rans-RuCl2(DPPB)(py)2, decreased in intensity relative to 29 as the reaction proceeded. 5.3 Reactions with 2,2'-Bipyridine 5.3.1 Reaction of 2,2'-Bipyridine with RuCl2(DPPB)(PPh3) and Ru2Cl4(DPPB)3 The 2,2'-bipyridine analogue of the pyridine species 43 was also prepared from either RuCl2(DPPB)(PPh 3) or Ru 2Ci4(DPPB)3 (Section 2.5.11.2). In both of these preparations, an approximately 10-fold excess of bipy was added to the starting Ru compound. Unlike the pyridine case, where only ?rans-RuCl2(DPPB)(py)2 was observed with no ris-isomer present, both isomers were observed with bipy. The route from RuCl2(DPPB)(PPh3), performed in refluxing C6H6, produced an approximately 50:50 mixture of cis- and fra«5-RuCl2(DPPB)(bipy) 44 (Tables 5.1 and 5.2). However, the route from Ru2CLi(DPPB)3, performed at room temperature in 228 Chapter 5 References: p 249 Chapter 5 CH2CI2, produced largely frans-RuCl2(DPPB)(bipy) (>70%), as evidenced by the singlet at 32.6 ppm in the 3 1P{ XH} NMR spectrum. In fact, the frans-RuCl2(DPPB)(bipy) isomer is the kinetic product in either method of preparation, while cis-44 is the thermodynamic product. Heating a C^H^ solution of the two isomers for 18 h at reflux results in a 3 1 P{ 1 H} NMR spectrum showing only the AB quartet of cis-44. Likewise, a 3 1 P{ 1 H} NMR spectrum of a largely trans-44 C D C I 3 solution showed almost complete isomerization to cis-44 after one week at room temperature. Table 5.1 lists the 3 1P{ 1H} NMR data recorded for both cis- and trans-44. The *H NMR spectrum of c/s-RuCl2(DPPB)(bipy) in CDCI3, which is more complex than the spectrum of the trans-isomer (Section 2.5.11.2) because of the lower symmetry of the cis-geometry, is shown in Figure 5.5. Both the aliphatic and aromatic regions are quite complicated and no attempt was made to completely assign all the protons. The relative integrations of the aliphatic (8H) and phenyl regions (28H) agree with the formulation of 44. An X-ray crystallographic study of cis-44 has been performed by Batista et a l . , 9 ' 1 0 and is discussed in Section 5.4. The UV-visible spectroscopic and molar conductivity data are given in Table 5.2. Complex 44 undergoes ionic dissociation in MeOH ( A M = 59.1 ohm - 1 m o l - 1 cm 2 ; cf. A M = 80-115 ohm - 1 mo l - 1 cm 2 for a 1:1 electrolyte11). The A M value obtained for 44 may be due either to incomplete C l - dissociation from the neutral complex or to low mobility of the ions in solution. Similar molar conductivity values have been observed in this laboratory for other ruthenium(II) species; for example, ds-RuCl2(PPh3)(PN3) in MeOH has a molar conductivity of 67.4 ohm - 1 mo l - 1 c m 2 . 1 2 In fact, a 3 1 P{ 1 H} NMR spectrum recorded in CD3OD showed some of the neutral trans-44 as a singlet at 39.0 ppm. The mixture of cis- and trans-44 was not very soluble in CD3OD, and therefore, the 3 1 P{ 1 H} NMR spectra recorded showed poor signal-to-noise ratios. However, two AB quartets, presumably corresponding to ionic 229 Chapter 5 References: p 249 Chapter 5 species (see the conductivity in MeOH) were observed, along with the singlet discussed above (Table 5.4). The two AB patterns observed in the 3 1 P{ 1 H} NMR spectrum indicate the presence of two isomers in deuterated methanol. There are a number of possible pairs of geometric isomers which would give an AB pattern for each member of the pair (Figure 5.6). It is difficult to predict which of the geometries is present in solution from either the 3 1P{ lU} NMR or molar conductivity data. In nitromethane, the molar conductivity of RuCi2(DPPB)(bipy) increased over time, finally stabilizing after 18 h at 56.5 ohm - 1 m o l - 1 cm 2 , again somewhat below the values of 75-95 shown by 1:1 electrolytes.11 Table 5.4 3 1P{ *H} NMR Data of RuCi2(DPPB)(N) 2 Complexes in C D 3 O D , where N represents an N-donor ligand Complex Chemical Shift, 8 % of total integration 2 7 P P (Hz) cis- and trans- 8 A = 54.7, 8 B = 42.9 45 38.7 RuCl 2(DPPB)(bipy) 44 S A = 52.0, 8 B = 47.9 25 35.5 8 = 39.0 30 — cw-RuCl2(DPPB)(phen) 8A = 54.0,'8B =43.0 50 38.0 45 8 A = 52.2, 8 B = 48.7 50 34.6 230 Chapter 5 References: p 249 Chapter 5 Chapter 5 References: p 249 Chapter 5 P/A 'to,, MeO' H RiC Cl ^1 .'Ru' Cl OMe H N ; R U " J R U . | ^cr 2 + -Ru Cl ) p ~T -Ru N Figure 5.6 Possible geometries of "[RuCl(DPPB)(N-N)]+Cl-" which would account for the observed 3 1 P { lH} N M R data, where N - N = bipy or phen, and P-P = DPPB. 5.3.2 Reaction of 2,2'-Bipyridine with Ru 2Cl4(DPPB) 2 The addition of 0.5 equivalents of 2,2'-bipyridine to Ru2CU(DPPB)2 24 in CDCI3 did not produce a dinuclear species of the type Ru2Cl4(DPPB)2(L), as was produced with the addition of one equivalent of pyridine to 24 (Section 5.2.3). The 3 1 P { ! H } N M R spectrum of the red solution produced by the addition of 0.5 equiv of bipy to 24 showed only starting Ru2Cl4(DPPB)2, as well as the mononuclear cis- and trans-RuCl 2(DPPB)(bipy) 44 (Figure 5.7). The difference in reactivity observed on the addition of bipy and pyridine is a result of the chelating ability of the former. Unlike the pyridine case, where the Ru2CU(DPPB)2(py) species could be observed in solution, reaction of bipy with 24 232 Chapter 5 References: p 249 Chapter 5 probably results in the initial T|1-coordination of bipy to give the non-detected Ru2Cl4(DPPB)2(ri1-bipy), followed by rapid chelation of the bipy ligand to break-up any triply-chloro-bridged intermediate and produce cis- and frans-RuCl2(DPPB)(bipy). The ratio of cis- to trans-44 observed after 1 h at room temperature in C D C I 3 is ~ 30:70 (Figure 5.7). 1 1 1 : 1 I I I 1 I I I I , I I I I 1 60 55 50 45 l l i 70 65 40 I j I I I I j 30 P P M 2 5 Figure 5.7 The 3 1P{ lH} NMR spectrum (CDCI3, 20 °C) of a red solution of 44 produced in situ by adding 0.5 equivalents of bipy to Ru2CLi(DPPB)2 24. 5.4 Reaction of 1,10-Phenanthroline with RuCl2(DPPB)(PPh3) and Ru 2 Cl 4 (DPPB) 3 The 1,10-phenanthroline analogue of the py and bipy species 43 and 44 was also prepared from either RuCl2(DPPB)(PPh3) or Ru2CLi(DPPB)3 (Section 2.5.11.3). In both preparations, an approximately 10-fold excess of phen was added to the starting Ru compound. Unlike the bipy system, where 50% of trans-44 was isolated, almost no trans-233 Chapter 5 References: p 249 Chapter 5 R u C l 2 ( D P P B ) ( p h e n ) 45 (<2%) was observed w h e n the product was prepared f r o m R u C l 2 ( D P P B ) ( P P h 3 ) . The c o m p l e x was isolated almost ent i re ly as the d s - i s o m e r f rom 11. H o w e v e r , f rom R u 2 C l 4 ( D P P B ) 3 , a mixture o f cis- and f r ans -RuCl2 (DPPB) (phen ) was iso la ted (~ 70:30). A g a i n , as observed for R u C l 2 ( D P P B ) ( b i p y ) , the c / s - i somer i s the t h e r m o d y n a m i c product . T h e higher temperature route f rom R u C l 2 ( D P P B ) ( P P h 3 ) ( in ref luxing benzene) gives the d s - i s o m e r almost exc lus ive ly . T h e 3 1 P { 1 H } N M R spectral data for cis- and r r ans - R u C l 2 (DPPB) (phen ) 45 are g iven i n T a b l e 5.1. T h e X H N M R spectrum o f 45 i n CDCI3 is s h o w n i n F i g u r e 5.8; the assignments o f the al iphatic region are g iven i n Sect ion 2.5.11.3 but the aromatic reg ion c o u l d not be assigned despite attempts to do so using a l H - ! H C O S Y spectrum. Tab le 5.2 l ists the U V - v i s i b l e spectroscopic and molar conduct iv i ty data. In M e O H and C H 3 N O 2 , cis-45 undergoes C l - d i s s o c i a t i o n to g i v e a 1:1 electrolyte, as indicated by the observed A M values o f 74.9 and 69.2 o h m - 1 m o l - 1 c m 2 , respect ively; again values are s l ight ly be low those expected for complete d issoc ia t ion for s imple e l ec t ro ly t e s . 1 1 T h e molar conduct iv i ty o f cis-45 i n C H 3 N O 2 increased over t ime, reaching the noted value after ~ 24 h , and the co lour o f the solut ion changed f rom orange to y e l l o w dur ing the measurement per iod . In M e O H , the A M va lue i n i t i a l l y recorded remained invariant w i t h t ime. 234 Chapter 5 References: p 249 Chapter 5 Chapter 5 A 3 1 P{ ! H} NMR spectrum of cis-45 in C D 3 O D showed two AB quartets (Table 5.4), the values of the chemical shifts and coupling constants being very similar to those observed for RuCl2(DPPB)(bipy). However, in this case, no singlet was observed, which may explain the larger molar conductivity value observed for 45 than for 44 in MeOH (74.9 vs. 59.1 ohm - 1 m o l - 1 cm 2), because the singlet is thought to be due to neutral RuCl2(DPPB)(bipy). Possible ionic geometries which could account for the recorded data are shown in Figure 5.6. Another explanation for the lower molar conductivity and observed singlet in the 3 1P{ iH} NMR spectrum for RuCl2(DPPB)(bipy) may be due to the fact that a mixture of cis- and trans-44 were used for the measurements, while only the m-isomer of 45 was used. It is possible that the trans-isomer does not appreciably ionize in MeOH because, for example, the molar conductivity measured for ?nms-RuCi2(DPPB)(py)2 is much lower than 44 or 45. An orange crystal of 45 was isolated from a CH2CI2 / methanol solution, and an X-ray diffraction analysis showed the complex to be ds-RuCi2(DPPB)(phen). Figure 5.9 shows the ORTEP plot, while selected bond lengths and angles are given in Tables 5.5 and 5.6, respectively. Complete experimental parameters and details are given in Appendix VII. The geometry of cis-45 is slightly distorted from octahedral. The distortions are probably due to the presence of the chelating DPPB and chelating phenanthroline. For example, the P(l)—Ru(l)—P(2) angle is 93.89°, while the N(l)—Ru(l)—N(2) angle is 78.2°. The limited chelate bite size of the rigid planar phenanthroline ligand constrains the N(l)—Ru(l)—N(2) angle to less than 90°. The ORTEP plot arbitrarily shows the A-enantiomer of the two that are present in the monoclinic centrosymmetric space group P2i/c. 236 Chapter 5 References: p 249 Chapter 5 Figure 5.9 The ORTEP plot of cw-RuCl2(DPPB)(phen) 45. Thermal ellipsoids for non-hydrogen atoms are drawn at 33% probability (some of the phenyl carbons have been omitted for clarity). 237 Chapter 5 References: p 249 Chapter 5 The metal-ligand bond lengths show a trans influence phenomenon. The Ru(l)—N(l) bond length of 2.092(3), trans to Cl", is shorter than the Ru—N(2) bond length of 2.117(4), trans to P. This is as expected, because PR3 has a stronger trans influence than C l - . Likewise, the Ru(l)—Cl(2) bond length of 2.417(1), trans to N, is shorter than the Ru—Cl(l) bond length of 2.491(1), trans to P. Again, this is as expected, because PR3 is higher in the trans-directing series than py. However, the trans influence is not obeyed for the two Ru—P bonds. The Ru(l)—P(l) bond length of 2.286(1), trans to C l - is shorter than the Ru—P(2) bond length of 2.322(1), trans to N. This is the reverse of that predicted by the trans-directing series (i.e., C l - has a stronger trans influence than py). The breakdown in the trans-influence series may be due to the fact that the series was established for monodentate ligands such as py and PPh3, while in this case, the more complex bidentate ligands are present. Also, C l - and py are adjacent in the trans-directing series, and therefore may not be that different in their trans-influencing properties. Table 5.5 Selected Bond Lengths (A) for cw-RuCl2(DPPB)(phen) 45 with Estimated Standard Deviations in Parentheses Bond Length (A) Bond Length (A) Ru(l)—Cl(l) 2.491(1) Ru(l)—Cl(2) 2.417(1) Ru(l ) -P( l ) 2.286(1) Ru(l)-P(2) 2.322(1) Ru(l)—N(l) 2.092(3) Ru(l)—N(2) 2.117(4) P ( l ) - C ( l ) 1.837(4) P( 2)_C(4) 1.831(4) P(l)-C(5) 1.839(4) P ( l ) - C ( l l ) 1.828(5) P(2)—C(23) 1.852(4) P(2)—C(17) 1.835(4) N(2)—C(34) 1.319(6) N(2)—C(38) 1.357(6) N(l)—C(29) 1.326(6) N(l)—C(33) 1.365(5) 238 Chapter 5 References: p 249 Chapter 5 Table 5.6 Selected Bond Angles (°) for ds-RuCl2(DPPB)(phen) 45 with Estimated Standard Deviations in Parentheses Bond Angles (°) Bond Angles (°) Cl(D--Ru(l)—Cl(2) 92.46(4) Cl(l)--Ru(l ) - -P(l) 174.20(4) Cl(l)--Ru(l)--P(2) 91.86(4) Cl(l)--Ru(l ) - -N(l) 84.57(9) Cl(D--Ru(l)--N(2) 83.16(10) Cl(2)--Ru(l ) - -P(l) 88.42(4) Cl(2)--Ru(l)--P(2) 88.60(4) Cl(2)--Ru(l ) - -N(l) 167.4(1) Cl(2)--Ru(l)--N(2) 89.3(1) P(D--Ru(l ) - -P(2) 93.89(4) P(D--Ru(l)--N(l) 93.34(9) P(D--Ru(l ) - -N(2) 91.12(10) P(2)- -Ru(l)--N(l) 103.7(1) P(2)- -Ru(l ) - -N(2) 174.5(1) N(l) - -Ru(l)--N(2) 78.2(1) During the course of this work, it was learned that both fra/i5-RuCl2(DPPB)(py)2 and aVRuCl2 (DPPB)(bipy) had been prepared independently from a different Ru precursor and characterized structurally by other workers. 9' 1 0 The structure of cis-RuCl2(DPPB)(bipy) 44 is very similar, in terms of bond lengths and angles, to that observed for c/*-RuCl2(DPPB)(phen) 45 in this work. For 44, the bond lengths10 for Ru—P (2.279 and 2.331 A), Ru—N (2.088 and 2.097 A), and Ru—Cl (2.484 and 2.428 A) are almost identical to those observed for 45. The /rans-influence series is obeyed for the Ru—Cl bond lengths, and reversed, as above, for the Ru—P bond lengths. The two Ru—N bond lengths in 44 are essentially identical. A plot of the Ru-P bond lengths for Ru(II)(DPPB)-containing complexes versus their 3 1 P{tH} NMR chemical shift data is shown in Figure 5.10. The phosphorus chemical shifts are seen to exhibit an inverse dependence on Ru-P bond length, and similar trends have been observed for ruthenium(II) complexes containing PPh3, 1 3 ' 1 4 P(p-tolyl)3,1 5 and the P-N ligand P M A 1 5 (Section 3.10, Figure 3.28). 239 Chapter 5 References: p 249 Chapter 5 c 0 m a. 1 3 oi 2.45 2.4-•5 2.35-a 2.25 -1 0 0 3 1P{ lH} NMR Chemical Shift Figure 5.10 Graph of Ru-P bond length versus 3 1P{ !H} NMR chemical shift for a series of Ru(JJ) complexes containing DPPB. (a) RuCl2(DPPB)(PPh3)tw, (b) ds-RuCl2(DPPB)(phen)tw, (c) c /s-RuCl 2(DPPB)(bipy) 9 , 1 0 (d) frans-RuCl2(DPPB)(py)2,9'1 0 (e) R ^ C L t f D P P B ^ D M S O ) , 6 ' 1 6 (f) RuCl2(nbd)(DPPB),1 7 (g) [Ru(DPPB)(MeCN) 4][PF 6] 2, 7 (h) [RuCl(DPPB)(C 7D8)] +PF 6- 1 8 31p{lH} NMR data in CD 2 C1 2 (a, f-h) or CDCI3 (b-e); tw = this work. The three X-ray structural studies performed in this work on ruthenium (II) complexes containing the ligand PPh3 show Ru-P bond lengths and 3 1 P{ 1 H} NMR chemical shifts which agree with the trend observed by Dekleva 1 4 and Jessop et a l . 1 3 The data which fit this trend are for RuBr2(PPh3)3 (Chapter 3), RuCl2(DPPB)(PPh3) (Chapter 3), and [(DMA)2H]+[(PPh3)2(H)Ru(p-H)(p-Cl)2Ru(H)(PPh3)2]- (Chapter 4). Of note, the negative slope (-2.91 x 10 - 3 A ppm - 1) of the graph shown in Figure 5.10 for the DPPB systems is identical to that of the plot for the PPh3 systems;13 240 Chapter 5 References: p 249 Chapter 5 however, the intercepts are somewhat different (2.423 A for the DPPB system and 2.465 A for the PPI13 system). 5.5 Reactions with N H 3 5.5.1 Reaction of N H 3 with RuCl2(DPPB)(PPh3), Ru 2Cl 4(DPPB) 3, and Ru 2Cl4(DPPB) 2 The reactions of both gaseous NH3 and aqueous NH3 were investigated with a variety of ruthenium(II)-phosphine complexes. The reaction of excess NH3 with either RuCl2 ( D P P B ) ( P P h 3 ) or Ru2Cl4(DPPB)3 in solution produced isolable RuCl2(DPPB)(NH3)2 51 (Section 2.5.12.6). This species was also prepared in situ by bubbling NH3 through a CDCI3 solution of Ru2Cl4(DPPB)2. The UV-visible spectroscopic and molar conductivity data for 51 are listed in Table 5.2 (Section 5.2). The molar conductivity value of 84.5 ohm - 1 m o l - 1 cm 2 indicates that 51 is a 1:1 conductor in MeOH, while the value of 19.9 ohm - 1 m o l - 1 c m 2 in nitromethane is below the normal range for a 1:1 conductor in this solvent (see Section 5.2 for the ranges reported in the literature). Two possible isomers (Figure 5.11) could fit the observed 3 1 P{ 1 H} and X H NMR spectral data. The singlet observed in the 3 1P{ lH} NMR spectrum (Table 5.1) indicated a structure with equivalent phosphorus nuclei, while the fact that only two groups of protons (8 1.62 and 2.90, CDCI3) were observed for the methylenes of DPPB (Section 2.5.12.6) also indicated a structure having a mirror plane bisecting the diphosphine. Figure 5.11 T h e two possible structures o f RuCl2(DPPB)(NH3)2, 51, where P - P = P h 2 P ( C H 2 ) 4 P P h 2 . 241 Chapter 5 References: p 249 Chapter 5 In order to distinguish between the two possible geometries (i.e., trans-Cl (A) or trans-NHi (B)), an NMR spectral study was undertaken on the 1 5 N analogue of 51 prepared in situ (the nuclear spin of 1 5 N is 1/2). A CDCI3 solution (0.6 mL, ~ 40 mM) of RuCl2(DPPB)(PPh3) 11 was transferred with a cannula to an NMR tube containing 1 5 NH4C1 (~ 20 mg, 0.37 mmol) and a NaOH solution (0.5 mL, 6 M). The two-phase system was mixed, giving a blue-green solution. The 1 5 NH3 produced in situ reacted with the starting Ru complex to give a compound of the type RuCl2(DPPB)(15NH.3)2. A similar two-phase system was prepared with 1 4NH4C1 to prove that the same complex was produced as had been isolated with NH3 gas (Section 2.5.12.6); the characteristic singlet at 46.7 ppm was observed in the 3 1 P{ 1 H} NMR spectrum. Surprisingly, good 3 1 P{ 1 H} NMR spectra (Figure 5.12) could be recorded from these two-phase systems, as the more dense CDCI3 layer was in the region of the receiver coils of the NMR spectrometer, while the lighter H 2 O layer was above the receiver coils. Structure A, Figure 5.11 would be expected to show an A A ' X X ' pattern in the •^Pl1!!} NMR spectrum, while structure B would show an A2X2 pattern. Therefore, a triplet should be observed in the case of structure B, while a doublet of doublets should arise from structure A. In fact, a doublet of doublets centred at 46.7 ppm is observed in the 3 1 P{ 1 H} NMR spectrum. The observed coupling constants are 2Jpp = 21.8 and 2 /pN = 9.5 Hz, indicating that structure A (i.e., ?ra«s-RuCl2(DPPB)(1 5NH3)2) is the isomer observed. This is consistent with the molecular structure determined by X-ray crystallography for frans-RuCl2(DPPB)(py)2 43 by Batista et al. (Section 5.2.1).9'10 When a CDCI3 NMR solution of 51 is left at room temperature, other isomers begin to appear in the 3 1P{!H} NMR spectrum. A singlet at 50.7 ppm becomes apparent within 30 min (Figure 5.13), and the 1 5N-analogue of 51 slowly generates the corresponding 15N-analogue as a doublet of doublets centred at 50.7 ppm (27pp = 20.5 and 2 / P N = 8.1 Hz; Figure 5.12). This resonance is thought to be due to an ionic complex 242 Chapter 5 References: p 249 Chapter 5 of tfie type [RuCl(DPPB)( 1 5NH3)2]+Cl- produced by Cl" dissociation from the neutral complex 51. [ 1111111111ii111111111111111111 i 11111111111 M 111111i11111111111111111111111111111 5 5 52 5 1 50 49 45 47 46 PPM 45 Figure 5.12 The 31p{lH} NMR spectrum (121.42MHz, 20 °C) of RuCl2(DPPB)( 1 5NH3)2 51 in CDCI3. The sample was prepared in situ from ^NFUCl , RuCl2(DPPB)(PPh3), and 6 M NaOH. Under conditions of excess NH3, the only two resonances observed in the 3 1 P{ 1 H} NMR spectrum are at 46.7 and 50.7 ppm (discussed above). However, when isolated rrans-RuCl2(DPPB)(NH3)2 is dissolved in CDCI3 and the solution left at room temperature, other species, besides those giving the 46.7 and 50.7 ppm resonances, are observed (Figure 5.13). An AB quartet at 8 A = 59.5, 8 B = 44.4, 2 JAB = 38.8 Hz is indicative of the isomerization of fran.s-RuCl2(DPPB)(NH3)2 to the all-a's complex, while a singlet generated at 54.7 ppm could be assigned to any of the structures shown in Figure 5.14. 243 Chapter 5 References: p 249 Chapter 5 (c) c,c,c-RuCl2(DPPB)(NH3) 2 ccc-RuCl2(DPPB)(N]-r3) 2 (b) rRuCl(DPPB)(NH3)2] +C1-unknown (a) 51 J W inijiiiiji 64 rrr 52 50 4S 46 44 42 PPM. 6. : i i i | i i i i j ; l l l | m l | l l 60 5B 56 54 Figure 5.13 Isomerization of frfln5-RuCl2(DPPB)(NH3)2 51 in GDCI3 (121.42 MHz, 20 °C); (a) 10 rain, (b) 45 min, and (c) 2.5 h after dissolution. 244 Chapter 5 References: p 249 Chapter 5 N N N N Cl C D Figure 5.14 Poss ib le structures o f the type " R u C l 2 ( D P P B ) ( N H 3 ) x " w h i c h w o u l d exhib i t a singlet i n the 3 1 P{ 1 H} N M R spectrum, where P - P = Ph2P(CH2)4PPh2 and N = N H 3 . A c o m p l e x s imi l a r to B (Figure 5.14) has been p rev ious ly i sola ted as the P F 6 ~ salt, where N is a ni t r i le (i.e., M e C N or P h C N ) . The i somer isolated i n this case has the structure s h o w n i n F igu re 5.15, and gives rise to an A B pattern i n the 3 1 P { 1 H } N M R spectrum, as opposed to the singlet expected for structure B . Structure A is favoured over the other three possible geometries shown i n F igure 5.14, as no free NH3 i s observed i n the N M R (0.4-0.6 p p m region) , and the format ion o f structures B - D f r o m trans-R u C l 2 ( D P P B ) ( N H . 3 ) 2 a l l require the loss o f a mole o f NH3 per R u . RCN p B | i n « R U Cl Cl Ru " M i n i p^ NCR Figure 5.15 Structure of [Ru 2Cl3(DPPB) 2(RCN)2] +X- species, where R = Me or Ph and X = P F 6 orCl. 245 Chapter 5 References: p 249 Chapter 5 5.5.2 Reaction of NH 3 with RuCl2(DPPB)(PPh3) in the Solid State T h e mixed-phosphine c o m p l e x RuCl2 (DPPB ) (PPh3) 11 (or Ru2CU(DPPB)2 24) reac t s w i t h t w o m o l e s o f N H 3 (per R u ) i n the s o l i d state to g i v e trans-RuCl2 (DPPB ) (NH 3 )2 and a m o l e o f P P h 3 (Sec t i on 2.5.12.6). T h e a d d i t i o n o f an atmosphere o f a m m o n i a to 11 results i n an immedia te c o l o u r change f r o m green to b r o w n . T h e N H 3 atmosphere was then removed , the isolated b r o w n s o l i d d i s so lved i n C D C I 3 , and the ^Pf 1!!} N M R spectrum recorded, showing resonances for free PPI13 at -5.5 p p m , and f r a n s - R u C l 2 ( D P P B ) ( N H 3 ) 2 51 at 46.7 ppm. T h e solid-state react ion gives the iden t i ca l p roduct to that i so la ted w h e n the react ion is performed i n so lu t ion . S i m i l a r solid-state react iv i ty o f these f ive-coordinate Ru(II) complexes w i t h CO is also observed and is discussed i n Chapter 7. T h e reac t ion o f NH3 gas w i t h s o l i d R u 2 C l 4 ( D P P B ) 3 19 also p roduced 51 as evidenced by a 3 1 P { ! H } N M R spectrum o f a CDCI3 solut ion o f the isolated b r o w n so l id . A l s o observed i n the 3 1 P { N M R spectrum was a singlet at -16.2 p p m , ind ica t ing the presence o f free D P P B w h i c h is d isplaced f rom 19 on reaction w i t h NH3 (equation 5.2 i l lustrates the react ion where L = NH3 and no solvent is present). A s m a l l amount of another as yet unidentif ied product was evident as a resonance at 20.6 p p m . 5.5.3 Observation of Some Dinuclear Ruthenium(II)-NH3 Containing Complexes On heating a s o l i d sample o f frYMs-RuCl2(DPPB)(NH3)2 51 at 100 °C for several days under v a c u u m , the c o l o u r changed f rom tan to dark b r o w n . A 3 1 P{ 1 H} N M R spectrum o f this sample i n C D C I 3 showed two A B quartets (first N H 3 entry i n T a b l e 5.3, Sec t ion 5.2.3) i nd ica t ing the presence o f R u 2 C l 4 ( D P P B ) 2 ( N H . 3 ) , as the c h e m i c a l shifts and coup l ing constants observed are s imi la r to those observed for Ru2Cl4(DPPB)2(py) 29 (Table 5.3). T h e Ru2CLi (DPPB)2 ( N H 3 ) c o m p l e x was also observed i n the two-phase s y s t e m ( N H 4 C I i n aqueous N a O H and C D C I 3 ) u sed to p r o d u c e trans-RuCl 2 (DPPB ) ( N H 3 )2 i n situ (Sect ion 5.5.1). Thus , i f a RuCl2(DPPB)(PPh 3) so lu t ion was 246 Chapter 5 References: p 249 Chapter 5 transferred onto a solution of NH4CI in aqueous NaOH and a 3 1 P{ 1 H} NMR spectrum recorded without mixing the sample, the two AB quartets corresponding to the complex Ru2CU(DPPB)2(NH3) were observed. Also, observed were signals for free PPI13, RuCl2(DPPB)(PPh3), and Ru2CLi(DPPB)2 produced by phosphine dissociation and dimerization processes. On one occasion, stirring the two phase mixture for 1 day before recording a 3 1 P{ 1 H} NMR spectrum resulted in observation of two different A B quartets (second NH3 entry in Table 5.3). The two AB quartets again suggest a dinuclear formulation (possible structures are shown in Figure 5.16) perhaps with two coordinated NH3 ligands (i.e., Ru2Cl4(DPPB)2(NH3)2). The dinuclear species would have to be doubly-chloro bridged (edge sharing), as opposed to the first two entries in Table 5.3 which are triply-chloro bridged (face sharing). Figure 5.16 Poss ib le doubly-chloro br idged (edge sharing) structures o f the formula t ion Ru2Cl4(DPPB)2(NFJ.3)2 w h i c h w o u l d exhibi t two AB patterns i n the 3 1 P { lH} N M R spectrum, where P - P = P h 2 P ( C H 2 ) 4 P P h 2 . 247 Chapter 5 References: p 249 Chapter 5 T h e 2Jpp c o u p l i n g constants observed for the three entries i n T a b l e 5.3 g ive further suppor t for the first t w o entr ies be ing t r i p l y - c h l o r o b r i d g e d d i r u t h e n i u m complexes o f the type (L)(DPPB)Ru(p-Cl)3RuCl(DPPB). One c o u p l i n g constant o f the pai r observed is ~ 43 H z w h i c h is i n the range observed for the Cl-end o f these dinuclear complexes (see Sect ion 3.5 and 5.2.3). 5.6 Summary T h e c o m p l e x RuCl2 (DPPB ) (PPh3) reacts w i t h an excess o f the n i t rogen-c o n t a i n i n g l i g a n d s . N H 3 , p y , b i p y , and phen to g i v e species o f the f o r m u l a t i o n RuCl2(DPPB)(L)2. These complexes have been characterized i n so lu t ion by U V - v i s i b l e and N M R spectroscopy, as w e l l as by conduct iv i ty . T h e monodentate ni t rogen l igands py and N H 3 gave products o f the / r a n s - R u C i 2 ( D P P B ) ( L ) 2 geometry, w h i l e