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The syntheses and reactions of carbonyl(phosphine)(thiolator)ruthenium(II) complexes Jessop, Philip Gregory 1991

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THE SYNTHESES AND REACTIONS OF CARBONYL(PHOSPHINE)(TmOLATO)RUTHENIlM(n) COMPLEXES By PHILIP GREGORY JESSOP B.Sc, The University of Waterloo, 1986 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Chemistry) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA February 1991 © Philip Gregory Jessop, 1991 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 Chemistry  The University of British Columbia Vancouver, Canada Date 22 April iggi  DE-6 (2/88) ABSTRACT The chemistry of homogeneous transition metal systems offer parallels to the reactions on the surfaces of industrial hydrodesulphurization catalysts. The reactions of several ruthenium complexes with sulphur-containing reagents are described, with an emphasis on the kinetics and mechanisms thereof. The complex Ru(CO)2(PPh3)3 (2), for example, reacts quickly with thiols and disulphides, producing cc/-RuH(SR)(CO)2(PPh3)2 (9) and ccf-Ru(SR)2(CO)2(PPh3)2 (14), respectively, although 2 fails to react with unstrained thioethers. Reactions of the related complex Ru(CO)2(PPh3)(dpm) (dpm=Ph2PCH2PPh2) are complicated by the lability of all of the three different ligands. The two dihydrides ccf-RuH2(CO)2(PPh3)2 (3) and RuH2(dpm)2, as a cis/trans mixture (7), react with thiols to produce the hydrido-thiolato complexes 9 and RuH(SR)(dpm)2 (13). respectively. The mechanisms appear to depend on the basicity of the hydride ligands; the more basic dihydride, 7, is probably protonated by the thiol, giving an unobserved molecular hydrogen intermediate, while 3 reacts by slow reductive elimination of H2- The same rate constant, rate law, and activation parameters are found for the reaction of 3 with thiols, CO or PPI13. The reaction of 3_ with RSSR produces mostly 9_, with small amounts of 14-The complete characterization of several members of the series 9 and 14 is described, including the crystal structure of the p-thiocresolate example of each. The reactions of 9 with other thiols, P(C6H4pCH3)3, CO, RSSR, HCl, PPI13, and H2, are also reported. The first three of these reactions share the same rate law and rate constant, the common rate determining step probably being initial loss of PPI13. Some equilibrium constants for the exchange reactions of 9_d (R=CH2CH3) with other thiols were tetermined, the Keq values increasing with the acidity of the uicorning thiol. The mercapto hydrogens of 9a and 14a (R=H) exchange with the acidic deuterons of added CD3OD. The hydridic and ortho-phenyl hydrogens exchange more slowly, presumably by intramolecular processes. Complex 14b (R=C6H4pCH3) is unstable in the presence of light, exchanges phosphines rapidly with added P(C6H4pCH3)3, exchanges thiolate groups with added thiols, and is converted by high pressures of H2 to a mixture of 9J> and 2. Intermediates proposed for the mechanism of the thiol exchange reactions of 9 and 14 contain two or three thiolate groups sharing a proton. A related complex, [Ru((X))2(PPh3)(uSEt)2(^3SEt)Na(THF)]2, which contains three thiolate groups on a ruthenium centre sharing a sodium cation, was isolated from the reaction of ccf-RuCl2(CO)2(PPh3)2 with sodium ethanethiolate. In acetone, 9b and 14b can be formed cleanly from ccr-RuHCl(CO)2(PPh3)2 and ccr-RuCl2(CO)2(PPh3)2, respectively, by reaction with p-thiocresolate. Complex 3 or cheaper analogues could be used as catalysts for the reduction of disulphides by H2, or as recyclable reagents for the non-oxidative extraction of thiols from thiol-containing mixtures such as oil fractions. The chemistry described above will help to guide future researchers to systems that more closely parallel the processes occurring on the surfaces of industrial hydrodesulphurization catalysts. to my family V TABLE OF CONTENTS Abstract ii List of Tables x List of Figures xiiList of Abbreviations xxii Numerical Key to Ruthenium Complexes xxviAcknowledgements xxix 1 INTRODUCTION 1 1.1 Sulphur 2 1.1.1 History and applications 2 1.1.2 Natural occurrence 4 1.1.3 Nomenclature of sulphur compounds 7 1.2 The extraction of sulphur from fossil fuels 8 1.2.1 Reasons for sulphur extraction1.2.2 Sulphur extraction from petroleum 11 1.3 Reactions of sulphur-containing organics with transition metal complexes 22 1.3.1 Reactions involving S-H bond cleavage 23 1.3.2 Reactions involving S-S bond cleavage 7 1.3.3 Reactions involving S-C bond cleavage 31 2. GENERAL EXPERIMENTAL PROCEDURES 34 2.1 Materials 32.2 Equipment and techniques 35 vi 2.2.1 Reaction conditions 35 2.2.2 Spectroscopy and chromatography 36 2.2.3 Kinetic measurements 38 2.2.4 Data handling for kinetic experiments 41 2.3 Syntheses of the precursor complexes 45 2.3.1 ccr-RuCl2(CO)2(PPh3)22.3.2 Ru(CO)2(PPh3)3 46 2.3.3 ccr-RuH2(CO)2(PPh3)2 8 2.3.4 ccr-RuH(Q)((X))2(PPh3)2 49 2.3.5 cis- and rran5-RuCl2(dpm)2 50 2.3.6 cis- and rra/w-RuH2(dpm)2 2 2.3.7 An attempted new synthesis of RuH2(dpm)2: the synthesis of trans-RuH(r|iBH4)(dpm)2 53 3. THE REACTIONS OF RUTHENIUM COMPLEXES WITH THIOLS 63 3.1 The reaction of Ru(CO)2(PPh3)3 with H2S and thiols 63 3.2 The characterization of RuH(ER)(CO)2(PPh3)2 64 3.3 The reaction of RuH2(CO)2(PPh3)2 with H2S and thiols 77 3.4 The reaction of RuH2(dpm)2 with H2S and thiols 89 3.5 The thiol exchange reactions of ccf-RuH(SR)(CO)2(PPh3)2 103 3.6 The slower reaction of RuH(SR)(CO)2(PPh3)2 with H2S and thiols 110 3.7 The reaction of RuH(SH)(dpm)2 with H2S 115 3.8 The thiol exchange reactions of ccr-Ru(SR)2(CO)2(PPh3)2 119 3.9 The reactions of other carbonyl(phosphine)ruthenium(0) complexes with H2S and thiols 133 vii 3.10 Experimental details 138 4. REACTIONS OF CARBONYL (PHOSPHINE) RUTHENIUM COMPLEXES WITH DISULPHIDES, THIOETHERS, AND RELATED REAGENTS 152 4.1 The reactions of Ru(CO)2(PPh3)3 with disulphides 152 4.2 The characterization of ccr-Ru(SR)2(CO)2(PPh3)2 158 4.3 The reaction of ccr-RuH2(CO)2(PPh3)2 (3) with disulphides 168 4.4 The reaction of ccf-RuH(SR)(CO)20?Ph3)2 with disulphides 170 4.5 The reactions of carbonyl (phosphine) ruthenium complexes with strained cyclic thioethers 174.6 The non-reactions of carbonyl (phosphine) ruthenium complexes with unstrained thioethers 172 4.7 The reactions of carbonyl (phosphine) ruthenium complexes with other neutral sulphur-containing reagents 172 4.8 Experimental details 173 5. THE METATHESIS REACTIONS OF CHLORORUTHENIUM COMPLEXES WITH THIOLATE SALTS 180 5.1 Introduction 185.2 The reactions of ccf-RuCl2(CO)20?Ph3)2 with sodium thiolates 182 5.3 TTie characterization of [Ru(SEt)3(CO)2(PPh3)Na(THF)]2 188 5.4 The reactions of other ruthenium chloro complexes with sodium thiolates 212 5.5 Experimental details 213 viii 6. THE REACTIONS OF THIOLATO RUTHENIUM(II) COMPLEXES WITH NON-SULPHUR-CONTAINING REAGENTS 218 6.1 The reactions of ccr-RuH(SR)(CO)2(PPh3)2 (9) 218 6.1.1 P(C6H4pCH3)3 216.1.2 CO 227 6.1.3 PPh3 233 6.1.4 H2 4 6.1.5 Acids 236.1.6 CD3OD 5 6.2 The reactions of ccr-Ru(SR)2(CO)2(PPh3)2 (14) 239 6.2.1 Light 236.2.2 P(C6H4/>CH3)3 245 6.2.3 H2 249 6.2.4 CD3OD6.3 Experimental details 253 7. GENERAL CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE RESEARCH 259 7.1 Potential applications for the complexes in sulphur chemistry 259 7.2 Parallels to surface chemistry 260 7.3 Conclusions 262 7.4 Recommendations for future research 264 8. REFERENCES 266 ix APPENDIX 1 Summary of crystallographic data 282 APPENDIX 2 Atomic coordinates for ca-RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b) 284 APPENDIX 3 Atomic coordinates for ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) 288 APPENDIX 4 Atomic coordinates for [(CO)2(PPh3)Ru(SEt)3Na(THF)]2 (21) 294 APPENDIX 5 Kinetic data 29X LIST OF TABLES 1.1 Estimated concentrations of selected sulphur compounds identified in Was son, Texas, crude oil 5 1.2 Nomenclature of compounds containing sulphur, carbon and hydrogen 9 1.3 Canadian nationwide emissions of sulphur oxides, in 1972 12 2.1 Fragments detected in the FAB/mass spectrum of RuH(BH4)(dpm)2 55 2.2 lH NMR data for ira/w-RuH(X)(dpm)2 53.1 3lp{ lH} and lH NMR data for ccf-RuH(ER)(CO)2(PPh3)2 complexes in Cf5D6 at 20°C and 300 MHz 67 3.2 FT-IR data for ccf-RuH03R)(CO)20?Ph3)2 complexes in Nujol, HCB, or CH2CI2 at room temperature 67 3.3 Selected bond lengths (A) with estimated standard deviations in parentheses, for RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b) 73 3.4 Selected bond angles (°) with estimated standard deviations in parentheses, for RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b) 73 3.5 3lp{ lH) and lH NMR data for RuH(SEt)(CO)2L2 73.6 Kinetic data for the reaction ofRuH2(CO)20?Ph3)2 (3J with various reagents in C6D6 at 26oC 85 3.7 NMR data for Ru(X)(Y)(dpm)2 complexes 96 3.8 Published pKa values for selected thiols in aqueous solution 106 4.1 NMR spectroscopic data for complexes of the series ccr-Ru(SR)(SR')(CO)2(PPh3)2 159 4.2 Selected bond lengths (A) for ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) 166 xi 4.3 Selected bond angles (°) for ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) 166 4.4 Selected bond lengths (A) for ccf-Ru(SH)2(CO)2(PPh3)2 (14a) 167 4.5 Selected bond angles (o) for ccr-Ru(SH)2(CO)2(PPh3)2 (14g) 167 5.1 Fragments detected in the FAB-Mass spectrum of ccr-RuCl(SEt)(CO)2(PPh3)2 187 5.2 NMR and m spectral (lata for Ru(X)(SEt)(CO)2(PPh3)2 187 5.3 Fragments detected in the FAB-Mass spectrum of [(CO)2(PPh3)Ru(SOT2CH3)3NaOHF)]2 197 5.4 Selected bond lengths (A) for 21 201 5.5 Selected bond angles (o) for 21A2.1 Final atomic coordinates (fractional) and B(eq) (9b) 284 A2.2 Calculated hydrogen coordinates and B(iso) (9b) 286 A3.1 Final atomic coordinates (fractional) and B(eq) (14b) 288 A3.2 Calculated hydrogen coordinates and B(iso) (14b) 291 A4.1 Final atomic coordinates (fractional) and B(eq) (21) 294 A4.2 Calculated hydrogen coordinates and B(iso) (21) 296 A5.1 The reaction of cc/-RuH2(CO)20?Ph3)2 (2) with p-thiocresol 298 A5.2 The reaction of ccr-RuH2(CO)20?Ph3)2 (2) with ethanethiol 298 A5.3 The reaction of cc/-RuH2(CO)2(PPh3)2 (2) with carbon monoxide 299 A5.4 The reaction of ccr-RuH2(CO)2(PPh3)2 (3) with triphenyl phosphine 299 A5.5 The reaction of ccr-RuH(SCH2CH3)(CO)2(PPh3)2 (9d) with thiophenol at 22°C 299 A5.6 The reaction of ccf-Ru(SH)2(CO)2(PPh3)2 (14a) with thiophenol at 25°C 300 A5.7 The reaction of Ru(CO)2(PPh3)3 (2) with p-tolyl disulphide (RSSR) at 25°C 300 xii A5.8 The reaction of c^RuH(SR)(CO)2(PPh3)2 (2) with P(C6H4pCH3)3 (L') at 45°C 300 A5.9 The reaction of ccr-RuH(SR)(CO)2(PPh3)2 (9) with 1 arm carbon monoxide 301 xiii LIST OF FIGURES 1.1 The spirit of sulphur 3 1.2 The dependence of sulphur content of three crude oUs on the fraction (hstilled 5 1.3 An overview of a petroleum refinery, emphasizing the placement of desulphurization units 13 1.4 Hydroprocessor flow plan 4 1.5 The dependence of the HDS activity of the transition metal sulphides on their heat of formation 16 1.6 Transition metal complexes exhibiting different modes of thiophene coordination 18 1.7 The Lipsch-Schuit mechanism for thiophene HDS 20 1.8 The Angelici mechanism for thiophene HDS 1 2.1 Anaerobic UV/vis. cell 37 2.2 Constant pressure gas uptake apparatus 39 2.3 FAB mass spectrum of RuH(BH4)(dpm)2 in p-nitrobenzyl alcohol 56 2.4 lH NMR spectrum of RuH(BH4)(dpm)2 under H2 at 20OC, 300 MHz 57 2.5 lH NMR (300 MHz) spectra of RuH(BH4)(dpm)2 in C6D5CD3 below ambient temperatures 59 2.6 FT-IR spectra of HCB mulls of a) RuH(BH4)(dpm)2 and b) RuD(BD4)(dpm)2 (88% deuteration) 61 3.1 lH NMR spectrum of ccr-RuH(SEt)(CO)2(PPh3)2 (9d) in Cf5D6 at 20°C and 300 MHz 65 3.2 lH NMR spectrum of ccf-RuH(SCH2Ph)(CO)2(PPh3)2 (2e) in C6D6 at 20°C and 300 MHz 6 3.3 FT-IR spectrum of cct-RuH(SR)(CO)2(PPh3)2 (9) in HCB where a) R=Me and xiv b) R=Ph. 69 3.4 13C{ lH} NMR spectrum of ccr-RuH(SEt)(CO)2(PPh3)2 (9d) in CD2CI2 at20°Cand75MHz 71 3.5 X-ray crystallographic structure of c^RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b) 72 3.6 Stereo-view of the structure of c^RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b) 72 3.7 Relationship between the 3 lp NMR chemical shift and the Ru-P bond length of thiolato-phosphine ruthenium complexes 75 3.8 The UV/vis. spectra of ccr-RuH(ER)(CO)2(PPh3)2 in THF at room temperature, where ER = SC6H4/7CH3 (9b), SCH3 (9c), or SeC6H5 (9h). The spectra of Ru(CO)2(PPh3)3 (2) and RuH2(CO)2(PPh3)2 (3) are included for comparison 75 3.9 lH NMR spectra acquired during the reaction of ccr-RuH2(CO)2(PPh3)2 (3) with H2S in C6D6 78 3.10 Plot absorbance at 400 nm versus time during the reaction of c«-RuH2(CX))20?Ph3)2 (2) with ethanethiol in THF at 26°C 80 3.11 logarithmic plot of absorbance at 400 nm for the reaction of ccr-RuH2(CO)2(PPh3)2 (2) with ethanethiol in THF at 26°C 80 3.12 Dependence of the pseudo-first order rate constant on the concentration of ccr-RuH2(CX))20?Ph3)2 (3) for the reaction with ethanethiol in THF at 26°C 81 3.13 Dependence of the pseudo-fast order rate constant on the thiol concentration for the reaction of ccf-RuH2(CO)2(PPh3)2 (2) with ethanethiol in THF at 26°C 81 3.14 logarithmic plot of absorbance at 400 nm versus time for the reaction of crt-RuH2(CO)2CPPh3)2 (2) and p-thiocresol in THF at 26°C 82 3.15 Dependence of the pseudo-first order rate constant on the concentration of ccr-RuH2(CO)2(PPh3)2 (2) for the reaction with p-thiocresol in THF at 26°C 83 3.16 Dependence of the pseudo-first order rate constant on thiol concentration for the reaction of ccf-RuH2(CO)2(PPh3)2 (3) with p-thiocresol in THF at 26°C 83 3.17 Eyring plot for the reactions of ccf-RuH2(CO)20?Ph3)2 (2) with several reagents XV 3.18 logarithmic plot of absorbance at 350 nm versus time for the pseudo-fust order reaction of ccf-RuH2(CO)2(PPh3)2 (2) with CO in THF at 26°C 87 3.19 logarithmic plot of absorbance at 400 nm versus time for the pseudo-rust order reaction of ccr-RuH2(CO)2(PPh3)2 and PPh3 in THF at 26°C 87 3.20 a) lH NMR spectra (hydride region) for the reaction of cis- and tra/w-RuH2(dpm)2 with H2S in C6D6 at 25°C and 300 MHz 91 b) lH NMR spectra (methylene region) for the reaction of cis- and jrans-RuH2(dpm)2 with H2S in C6D6 at 25°C and 300 MHz 92 3.21 lH NMR spectra (hydride region) for the reaction of RuH2(dpm)2 with PhCH2SH in C6D6 at 25°C 93 3.22 lH NMR spectrum (300 MHz) of a sample of RuH(SPh)(dpm)2 prepared in situ from RuH2(dpm)2 and thiophenol in C6D6 94 3.23 a) 31p{ lH) NMR spectrum of a sample of RuH(SPh)(dpm)2 (13) prepared in situ from RuH2(dpm)2 and thiophenol in toluene-d8 b) Simulated spectrum for cis-13b 95 3.24 Time dependence of concentrations during the reaction of RuH2(dpm)2 with thiophenol in C6D6 at 25°C 98 3.25 Time dependence of the concentration of cw-RuH2(dpm)2 (cis-7) in the reaction with thiols in C(p6 at 25°C 98 3.26 The lH NMR spectrum (hydride region) acquired during the reaction of RuH2(dpm)2 with p-toluenesulphonic acid 101 3.27 lH NMR spectra acquired during the reaction of ccr-RuH(SEt)(CO)2(PPh3)2 with thiophenol in C6D6 at 22°C 105 3.28 Time dependence of concentrations during the reaction of ccf-RuH2(CO)2(PPh3)2 with PhSH and EtSH in C6D6 at 36°C 106 3.29 logarithmic plot of concentrations versus time for the pseudo-fust order reaction of ccr-RuH(SEt)(CO)20?Ph3)2 and PhSH in C6D6 at 22°C 108 xvi 3.30 Dependence of the pseudo-first order rate constant on [PhSH] for the reaction with ccr-RuH(SEt)(CO)2(PPh3)2 in C6D6 at 22°C 108 3.31 lH NMR spectra (hydride region) acquired during the reaction of ccr-RuH(SH)(CO)2(PPh3)2 (2a) with H2S in C6D6 at 60°C 112 3.32 a) lH NMR spectra Oiydride region) acquired during the reaction of RuH(SH)(dpm)2 (12a) with H2S in C6D6 at 60°C 116 b) lH NMR spectra (methylene region) acquired during the reaction of RuH(SH)(dpm)2 (12a) with H2S in C6D6 at 60°C 117 3.33 logarithmic plot of concentration of »rflns-RuH(SH)(dpm)2 (13a) during the reaction of that compound with H2S at 60°C in CgDg 118 3.34 The 31p{ lH} NMR spectrum of Ru(SH)2(dpm)2 (15) in C6D6 118 3.35 31p{ IH} NMR spectra acquired during the reaction of ccr-Ru(SH)2(CO)2(PPh3)2 (14a) with PhSH at 25°C in QsD6 121 3.36 UV/vis. spectra acquired at 1 min intervals during the reaction of ccf-Ru(SH)2(CO)2(PPh3)2 (14a) with PhSH at 25°C in THF 122 3.37 Time dependence of the concentrations of species detected by 31p{ lH} NMR during the reaction of ccr-Ru(SH)2(CO)2(PPh3)2 (14a) with PhSH at 25°C in CgDfi a) at 77 mM PhSH 123 b) at 690 mM PhSHc) at 1700 mM PhSH 124 d) at 2900 mM PhSHe) at810mMPhSHand470mMPPh3 125 3.38 The log plot of the concentration of ccr-Ru(SH)2(CX))2(PPh3)2 (14a) during its reaction with thiophenol in C<>D6 at 25°C 125 3.39 The dependence on [PhSH] of the observed initial rate constant for the loss of ccr-Ru(SH)2(CO)2(PPh3)2 (14a) during the reaction with PhSH at several xvii concentrations of added PPI13 126 3.40 Phosphine dependence of the inverse of the observed initial rate constant for the loss of ccr-Ru(SH)2(CO)2(PPh3)2 (14a) during the reaction with PhSH at several [PhSH] 126 3.41 Thiol dependence of the calculated rate constant kj} for the second step of the reaction of ccr-Ru(SH)2(CX))2(PPh3)2 with thiophenol at 25°C in CgDg 130 3.42 lH NMR spectrum Oiydride region) of the products of the reaction of Ru(CO)2(dpm)(PPh3) with ethanethiol 136 3.43 31p{ lH) NMR spectrum of the products of the reaction of Ru(CO)2(dpm)(PPh3) with ethanethiol 137 4.1 The logarithmic dependence of the concentration of Ru(CO)2tTPh3)3 (2, [2]o = 7.5 mM) during its reaction with p-tolyl disulphide in C6D6 at 18°C with or without a free-radical trap 153 4.2 The UV/visible absorption spectrum of a solution of Ru(CO)2(PPh3)3 and p-tolyl disulphide in THF at 26°C 155 4.3 The dependence on [2] of the initial rate of the reaction Ru(CO)2Q?Ph3)3 (2) with p-tolyl disulphide in THF at 26°C 156 4.4 a) The dependence on [RSSR] of the initial rate of the reaction of Ru(CO)2(PPh3)3 (2) with p-tolyl disulphide in THF at 26°C b) Plot of l/(initial rate) against 1/TRSSR] for the same reaction 157 4.5 lH NMR spectrum of ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (9b), in C6D6 161 4.6 FT-IR spectrum of ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 in HCB 162 4.7 a) The structure of ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) b) A stereoscopic view of the same structure 164 4.8 The structure of ccr-Ru(SH)2(CO)2(PPh3)2 165 xviii 5.1 a) !H NMR spectrum of ccr-RuCl(SEt)(CO)2(PPh3)2 b) Expanded region of the lH NMR spectrum of a sample of ccr-Ru(SEt)2(CO)2(PPh3)2 containing 20% ccr-RuCl(SEt)(CO)2(PPh3)2 184 5.2 a) The FT-IR spectrum of ccf-RuCl(SEt)(CO)20?Ph3)2 in Nujol mull b) Carbonyl region of the FT-IR spectrum of a sample of cct-Ru(SEt)2(CO)20?Ph3)2 containing 20% of ccf-RuCl(SEt)(CO)2(PPh3)2 in a Nujol mull 185 5.3 The FAB-Mass spectrum of ccr-RuCl(SEt)(CO)2(PPh3)2 in ap-nitrobenzyl alcohol matrix 186 5.4 The lH NMR spectrum of a C6D6 solution of [(CO)2(PPh3)Ru(SC^2CH3)3Na(THF)]2 at 20°C 189 5.5 The lH COSY NMR plot for a C6D6 solution of [(CO)2(PPh3)Ru(SCH2CH3)3Na(THF)]2 190 5.6 The methylene region of lH NMR spectra of a C(>D6 solution of [(CO)2(PPh3)Ru(SCH2CH3)3Na(THF)]2 191 5.7 Simulated lH NMR spectra of a) the CH2a protons, and b) the CH2b protons of [(CO)2(PPh3)Ru(SCH2CH3)3Na(THF)]2 193 5.8 The FT-IR spectrum of [(<X»)2(PPh3)Ru(SCH2CH3)3Na(THF)]2 in Nujol 194 5.9 The FAB-Mass spectrum of [(CO)2(PPh3)Ru(SCH2CH3)3Na(THF)]2 in a p-nitrobenzyl alcohol matrix 196 5.10 The structure of one half of a molecule of [(CO)2(PPh3)Ru(SOT2CH3)3Na(THF)]2 198 5.11 The structure of [((X>)2(PPh3)Ru(SCH2CH3)3Na(THF)]2 199 5.12 Stereoscopic view of the structure of [(CX))2(PPh3)Ru(SCH2CH3)3Na(TrIF)]2 200 5.13 a) 13C solid state (CP/MAS) NMR spectrum of [(CO)2(PPh3)Ru(SCH2CH3)3Na(TrIF)]2 xix b) 13C solid state (CP/MAS) NQS NMR spectrum of [(CO)2(PPh3)Ru(SCH2CH3)3Na(THF)]2 203 5.14 13C{ lH} NMR spectrum of [Ru(CO)2(PPh3)Ru(SEt)3Na(THF)]2 in C6D6 at 20°C 204 5.15 13C APT NMR spectrum of [Ru(C»)2(PPh3)Ru(SEt)3Na(THF)]2 in C6D6 at 20°C 205 5.16 The Heteronuclear Correlation (13C/1H) NMR plot for [Ru(<X))2(PPh3)Ru(u5Et)2(WSEt)Na(THF)]2 in CgDg 206 5.17 The lH [Ru(CO)2(PPh3)Ru(^SEt)2(^3SEt)Na(THF)]2 in toluene-d8 at -78°C 210 6.1 3 lp { IH } NMR spectra acquired during the reaction of cct-RuH(SCH2Ph)(CO)2(PPh3)2 (2e) with P(C6H4pCH3)3 in C6D6 at 45°C 220 6.2 lH NMR spectra acquired during the reaction of cct-RuH(SCH2Ph)(CO)2(PPh3)2 (2§) with P(C6H4pCH3)3 in C6D6 at 45°C 221 6.3 Time dependence of the concentrations of observed complexes during the reaction of ccr-RuH(SCH2Ph)(CO)2(PPh3)2 (9e) with P(C6H4pCH3)3 inC6D6at45°C 222 6.4 Log plot of [9e] during the reaction of ccr-RuH(SCH2Ph)(CO)20?Ph3)2 (9e) with P(C6H4pCH3)3 in C6D6 at 45°C 222 6.5 The dependence of d\\2e\ld\ on [22el during the reaction of cct-RuH(SCH2Ph)(CO)2(PPh3)2 (Se) with P(C6H4pCH3)3 in C6D6 at 45°C 225 6.6 Time dependence of the concentration of observed complexes during the reaction of ccf-RuH(SCH2Ph)(CO)2(PPh3)2 (9e) with P(C6H4pCH3)3 in the presence of PPI13 in C6D6 at 45°C 226 6.7 Time dependence of Qi and Q2 during the reaction of cct-RuH(SCH2Ph)(CO)2(PPh3)2 (9e) with P(C6H4pCH3)3 in the presence of PPh3 in C6D6 at 45°C 226 XX 6.8 UV/vis. spectra acquired every 900 s during the reaction of cct-RuH(SEt)(CO)2(PPh3)2andCOmTHFat26°C 228 6.9 Log plot of absorbance versus time for the reaction of cct-RuH(SEt)(CO)2(PPh3)2 (?d) and CO in THF at 26.5°C 229 6.10 Eyring plot for the reactions of ccf-RuH(SR)(CO)20?Ph3)2 (9J with CO in THF 231 6.11 lH NMR spectrum acquired 30 min after the start of the reaction of ccr-RuH(SC6H5)(CO)2(PPh3)2 (9j) with excess HBF4/H2O in C6D6 at room temperature 236 6.12 The time dependence of the intensity of the lH NMR signals due to ccr-RuH(SH)(CO)2(PPh3)2 in 4% v/v CD3OD/C6D6 at 19°C 237 6.13 The log plot of the intensity of the lH NMR signals due to cct-RuH(SH)(CO)2(PPh3)2 in 4% v/v CD3OD/C6D6 at 19°C 237 6.14 UV/vis. absorbance spectra of a THF solution of cct-Ru(SC6H4pCH3)2(CO)2(PPh3)2 at 25°C being irradiated at 430 nm 240 6.15 FAB Mass spectrum of the solid residue from a THF solution of cct-Ru(SC6H4/)CH3)2(CO)2(PPh3)2 irradiated for 90 min under a Hanovia lamp 241 6.16 a) Observed isotopic pattern for the fragment m/z =1149±4 b) The predicted isotopic pattterns for four possible formulations for the fragment 242 6.17 31p{ lH} NMR spectra acquired during the reaction of cct-Ru(SH)2(CO)2(PPh3)2 (14a) with P(C6H4pCH3)3 in C6D6 at 25°C 246 6.18 lH NMR spectra acquired during the reaction of cct-Ru(SH)2(CO)2(PPh3)2 (14a) with P((*H4/>CH3)3 in C6D6 at 25°C 247 6.19 The time dependence of the concentrations of the observed complexes during the reaction of ccf-Ru(SH)2(CO)2(PPh3)2 (14a) with P(C6H4pCH3)3 inC6D6at25°C 248 6.20 lH NMR spectrum of a C6D6 solution of the product from the reaction xxi of a THF solution of c^Ru(SC6H4pOT3)2(CO)2(PPh3)2 with H2 250 6.21 31p{ lH} NMR spectrum of CoT>6 solution of the product from the reaction of a THF solution of ccr-Ru(SC6H4pCH3)2(CO)20?Ph3)2 withH2 251 6.22 The time dependence of the intensity of the iH NMR signals due to ccr-Ru(SH)2(CO)2(PPh3)2 in 4% v/v CD3OD/C6D6 at 25°C 252 xxii LIST OF ABBREVIATIONS A = absorbance A°o = absorbance after infinite reaction time alkyl/polym. = polymerization unit APT = attached proton test (13c NMR pulse sequence) AT = acquisition time during an FT-NMR pulse sequence atm. = atmosphere(s) atm. disL = atmospheric pressure distillation tower (Fig. 1.3) Beq = isotropic equivalent thermal parameters B, Biso = isotropic thermal parameters BDH = British Drug Houses Chemicals Ltd. bipy = 2,2'-bipyridyl br. = broad Bu = butyl DUS4 = l,2-bis((3,5-di-tert-butyl-2-mercapto-phenyl)thio)ethanato(2-) Bz = benzyl (CH2C6H5) c = cis C = a constant calcd. = calculated ccc = cis, cis, cis cct = cis, cis, trans CDE = cyclododecene CDT = 1,5,9-cyclodecatriene COD = 1,5-cyclooctadiene COSY = Homonuclear Correlated Spectroscopy (FT-NMR experiment) xxiii COT = 1,3,5-cyclooctatriene Cp = cyclopentadienyl CP/MAS = cross-polarization/magic angle spinning (13c solid state NMR technique) etc = = cis, trans, cis 8 = bending mode (IR) or chemical shift (NMR) d = doublet (NMR) or bond distance D = deuterium D1.D2 = delay times in an FT-NMR pulse sequence DBU = l,8-diazabicyclo-[5,4,0]-undec-7-ene DEA = diethanolamine deC4 = unit for the separation of C-4 hydrocarbons def = deformation dippp = 13-ow(diisopropylphenylphosphino)propane dma = = N,N-dimethylacetamide dmdppe = - 1 -dmiethylphosphmo-2-diphenylphosphinoe thane dmpe = = l^-ow(dimethylphosphino)ethane dmso = = dimethylsulphoxide dpm = = W5(diphenylphosphino)methane dppe = = l^-ow(diphenylphosphino)ethane dq = doublet of quartets dt = doublet of triplets e = molar extinction coefficient Elem. Anal. = elemental analysis est. = estimated Et = ethyl F(000) = electrons per unit cell FAB/MS = fast-atom bombardment mass spectroscopy xxiv FT = Fourier transform GC = gas chromatograph(y) gof = goodness of fit indicator h = hour AH$ = enthalpy of activation Hb = bridging hydrogen atom HCB = hexachloro-1,3-butadiene HDN = hydrodenitrogenation HDO = hydrodeoxygenation HDS - hydrodesulphurization HETCOR = heteronuclear correlation (FT-NMR experiment) Ht = terminal hydride ligand H2TPP = tetraphenylporphyrin I = intensity IR = infra-red (spectroscopy) IUPAC = International Union of Pure and Applied Chemistry J = coupling constant (NMR) Keq = equilibrium constant KMS = Kezdy-Mangelsdorf-Swinbourne method £obs = observed pseudo-first order rate constant / = path length (spectroscopy) L = ligand (usually PPh3 in this work) (i = absorption coefficient m- = meta-M = metal, or unit of molarity MCB = Matheson, Coleman and Bell m/z = mass to charge ratio xxv Me = methyl Merox = mercaptan oxidation process min = minutes mol = moles or molecular MSD = Merck, Sharp and Dohme multi. = multiplet n = order of the rate dependence on free ligand concentration NMR = nuclear magnetic resonance nOe = nuclear Overhauser effect o- = ortho-p- = para-Pl, P2 = duration of pulses in an FT-NMR pulse sequence Ph = phenyl PPh3 = triphenylphosphine ppm = parts per million ppth = parts per thousand Py = -2-C5H4N q = quartet Q = quotient (defined in Section 6.1.1) qn = quintet p = density R = alkyl or aryl group, or rate of change of absorbance (dA/dt) R, Rw = agreement factors (defined on page 283) rearr. = rearrangement RNA = ribonucleic acid s = singlet AS$ = entropy of activation xxvi 6 = Bragg angle t = trans t = triplet T = constant delay time or temperature Tl = longitudinal relaxation time THF = tetrahydrofuran THT = tetrahydrothiophene TMS = tetramethylsilane tol = p-tolyl (-C6H4PCH3) ttt = trans, trans, trans UV/vis. = ultra-violet or visible absorption (spectroscopy) V = volume (of the unit cell) v/v = concentration by volume vac. dist = vacuum distillation tower (Fig. 1.3) v = frequency or stretching mode (IR) VD/VH = isotopic shift HfQ.5 = peak width at half-height wt. = weight Z = formulas per unit cell xxvii NUMERICAL KEY TO THE RUTHENIUM COMPLEXES 1 ccr-RuCl2(CO)2(PPh3)2 2 Ru(CO)2(PPh3)3 3 ca-RuH2(CO)2(PPh3)2 4 ccr-RuH(Cl)(CO)2(PPh3)2 5 cw-RuCl2(dpm)2 6 /ran5-RuCl2(dpm)2 7 cis- or fra/w-RuH2(dpm)2 8 fra/w-RuH(BH4)(dpm)2 9 ccr-RuH(ER)(CO)2(PPh3)2a 10 Ru(CO)3(PPh3)2 11 ccr-RuH(ER)(CO)2(PPh2Py)2a 12 cc/-RuH(ER)(CO)2{P(C6H4pCH3)3}2a 13 cis- or irans-RuHQ3R)(dpm)2 a R = H (trans only) b C6H5 c CH2C6H5 14 ccf-Ru(SR)2(CO)2(PPh3)2a 15 cis- or rra/w-Ru(SH)2(dpm)2 16 Ru(CO)2(PPh3)(dpm) 17 isomer of RuH(SCH2CH3)(CO)(PPh3)(dpm) 18 isomer of RuH(SCH2CH3)(CO)(PPh3)(dpm) 19 c«-RuS2(CO)2(PPh3)2 20 ccr-RuCl(SCH2CH3)(CO)2(PPh3)2 21 [Ru(CO)2(PPh3)(SEt)3Na(THF)]2 22 ca-RuH(SR)(CO)2(PPh3)0?{ C6H4pCH3} 3)a xx viii 23 ccr-Ru(SR)2(CO)2(PPh3)(P{C6H4pCH3}3)a 24 ccf-Ru(SR)2(CO)2(P{C6H4pCH3)3)2a a Complexes 9.11.12,14. and 22 through 24 are further identified by one of the following letters, which indicate the thiolate or selenolate group (ER). In the case of complexes 14 with two different thiolate ligands, two such initials are shown in the abbreviation. f SC6H40CH3 g SC6H4mCH3 h SeC6H5 i SC6H5 j SC6F5 a SH b SC6H4/7CH3 c SCH3 d SCH2CH3 e SCH2C6H5 xxix ACKNOWLEDGEMENTS I offer my sincerest thanks to the following people for the assistance they have provided me during my studies and the preparation of this thesis: my supervisor, Dr. Brian R. James, and the members of his research group, for their guidance and input; Dr. Chung-Li Lee of the Pulp and Paper Research Institute of Canada, who started the project, for his continuing support and advice; three undergraduate researchers, Mr. Marc Prystay (the PPh2Py systems), Miss Kavita Khajuria (the light sensitivity of ccr-Ru(SR)2(CO)2(PPh3)2), and Miss Golnar Rastar (the reaction of cis- and trans-RuH2(dpm)2 with H2S); Dr. S. Rettig, for the X-ray crystallography; Mr. P. Borda, for the elemental analyses; the technical and adnunistrative staff of the chemistry department; several employees of Imperial Oil Ltd. for useful discussions and help with Figure 1.3; Johnson-Matthey for a loan of ruthenium trichloride; the National Sciences and Engineering Research Council and the University of British Columbia for funding; and my wife for her patience and help in preparing the figures and list of references. 1 1. INTRODUCTION The mechanism of the hydrodesulphurization (HDS) of sulphur-containing organics in fuel remains a mystery, even after decades of research. Even the kinetics of the reaction, outside of the adsorption and desorption steps, are not understood. Analogies to the reactions of homogeneous complexes can lead to greater understanding of heterogeneous catalysts. Such analogies are central to a mechanism proposed recently! for thiophene HDS. Although such research has emphasized thiophenes because of their resistance to desulphurization, three decades of related research into the coordination chemistry of thiols, thioethers, disulphides, and other sulphur compounds have identified many modes of coordination in, and reactions of, their complexes. The kinetics of the formation and subsequent reactions of such complexes have been largely ignored. It is the purpose of the research described in this thesis to assist in this regard. Two ruthenium complexes, RuH2(CO)2(PPh3)2 and Ru(CO)2(PPh3)3, were chosen because of the high HDS activity of ruthenium sulphide (Fig. 1.6), and because of the ease by which the two complexes and their reaction products could be identified by IR and NMR spectroscopies. The reactions of these and related complexes with thiols, disulphides, thioethers, thiophenes and sulphur itself were to be observed and monitored kinetically if possible. In addition, the products and their properties and reactivities were further subjects for study. Finally, the effect of ligand choice on reactivity and rate was to be examined. This first chapter reviews the applications, natural occurrence, and nomenclature of sulphur compounds, the industrial use of HDS, some theories on the mechanism of the reaction, and the coordination chemistry of simple sulphur-containing compounds. 1.1 SULPHUR 2 1.1.1 History and Applications Sulphur (Fig. 1.1) can be both beneficial and harmful, according to popular belief. Sulphurous hot springs have long been used as healing baths. This, along with the natural fumigating action of sulphurous vapours, led to myths about sulphur's medicinal properties. Pliny the Elder, in his "Natural History" (c. 77 A.D.), reported the use of sulphur for medicine, fumigation, and religious ceremonies.3 However, the production of sulphur from the gases of volcanoes and fumaroles naturally suggested an association with hell and the centre of the earth. Apollonius of Tyana (AD 17-97) believed that "volcanoes are caused by a mixture of bitumen and sulphur in the earth, which smokes by its own nature."^ The connection of volcanoes, "brimstone" (probably sulphur), and hell is a common theme in the Bible (Gen. 19:24, Rev. 14:9-11; 20:10; 21:8). The presence of sulphur within the earth, according to the alchemical sulphur-mercury theory of metals, was essential for the natural production of gold.3 Although our understanding of sulphur and its compounds has increased, the element still retains its two-sided nature. Much of the recent research into sulphur chemistry has been aimed at sulphur removal, rather than the practical applications of its compounds. Large amounts of sulphur are removed from natural gas, petroleum, and coal-based fuels, not for the price the sulphur will fetch, but to prevent catalyst fouling, pipe corrosion, and environmental damage. The production of sulphur as waste from fuel processing has the result of keeping down the price of sulphur, and consequently the price of sulphuric acid. In fact, 80% of sulphur is converted to sulphuric acid, which is used as a reagent in the production of phosphate fertilizers, synthetic fibres (Rayon, Nylon 6), white pigments, and steel pickling.5 U.S. production of sulphuric acid in 1988 (86 x 109 lb) was larger than for any other chemical. Other sulphur chemicals used industrially are hydrogen sulphites and sulphates (pulping processes), sulphites (tanning, sugar refining, etc.), sodium Fig. 1.1 The Spirit of Sulphur? 4 thiosulphate (photography), sulphur dioxide and carbon disulphide (solvents), sulphur hexafluoride (transformer oil), xanthates (fungicides), thiokols (plastics), and several compounds used in the treatment of rubber.5 1.1.2 Natural Occurrence Sulphur occurs as the native element, as well as in organic and inorganic compounds. Sulphur is mined or extracted by the Frasch process as the native element at a number of sites, such as Sicily and Louisiana. It is also "recovered as a byproduct in smelting sulfide ores, from sour natural gas, and from pyrite."6 The United States, with its reserves of elemental sulphur, relies on the Frasch process. Canada, on the other hand, obtains 85% of its sulphur from the desulphurization of natural gas7 The sulphur-containing minerals, other than sulphur itself, are sulphides (e.g. pyrite FeS2), sulpharsenides (e.g. cobaltite (Co,Fe)AsS), sulphosalts (e.g. tetrahedrite CU12S04S13) and sulphates (e.g. gypsum CaS04).6 Sulphur-containing organics, hydrogen sulphide, and even elemental sulphur8 are found in petroleum. The sources of these compounds are the sulphur compounds in the original biological matter, and the biogenic reduction of sulphate minerals to hydrogen sulphide, followed by reactions with components of petroleum.8 The type of functional group and the concentration of the sulphur compound depend on the fraction of petroleum studied. "Sulfur in the lower-boiling straight-run distillates is mainly in the form of mercaptans, sulfides, and disulfides, whereas thermally-cracked distillates contain the more refractory thiophene type, in addition to the thiophenols that occur in catalytically cracked distillates.'^ A thorough study by the U. S. Bureau of Mines described the relationship between sulphur content (weight percent) and boiling point of the fuel fraction (Fig. 1.2), and identified 200 individual sulphur compounds contained in 5 CRUDE OIL DISTILLED, weight-percent Fig. 1.2 The dependence of sulphur content of three crude oils on the fraction distilled.8 Table 1.1 Estimated Concentrations of Selected Sulphur Compounds Identified in Wasson, Texas, crude oil.a Name b.p. (QQ ppm bv wt. methanethiol 5.9 24.0 ethanethiol 35.0 53.0 2-thiapropane 37.4 8.8 2-propanethiol 52.6 19.9 2-thiabutane 66.7 22.2 2-butanethiol 85.0 38.6 2-pentanethiol 112.4 14 2.3- dithiapentaneb 133. (est) 2-methylthiacyclopentane 133.2 23 2-hexanethiol 138.9 8 /ra/w-2,5-dimethylthia-cyclopentane 142.0 142.0 25 cw-2,5-dimethylthiacyclopentane 142.3 4 2-methylthiacyclohexane 153.0 29 cyclohexanethiol 158.7 12 2- methylbenzo[b]thiophene 243. (est) 24.8 3- methylbenzo[b]thiophene 246. (est) 9.5 2.4- dimethylbenzo[b]thiophene - 9.4 2.5- and/or 2.7-dimethvlbenzo-rblthiophene 10.1 a) Ref. 8 b) Tentative identification only. four crude oils (Table l.l).^ Although thiophene itself is low boiling, heterocyclic compounds such as thiophene are usually more common in the heavier fractions of oil because of their ability to form hydrogen bonds. 10 Coal contains up to 10 wt % sulphur, consisting of sulphate sulphur (sulphates of iron, calcium, and others, less than 0.1 wt %), pyritic sulphur (pyrite and marcasite, up to 8.0 wt %), and organic sulphur (thiols, sulphides, and thiophenes, up to 6.0 wt %).! 1-3 The first two classes of sulphur compounds can be extracted by washing and gravity separation. Of the organic sulphur in bituminous coal, thiols make up 10-30%, sulphites 5-27%, and thiophenes 40-70%. 13 These compounds, especially the thiophenes, are difficult to remove. Conventional coal-cleaning processes, such as leaching, have had only mediocre success. The only effective technique is conversion to coal-derived liquids, followed by hydrodesulphurization (Section 1.2.2). 14 A wide variety of sulphur-containing chemicals is found in biology. Sulphur minerals are oxidized by weathering to sulphates, which are required by most plants and some micro-organisms. Plants convert these sulphates to the amino acids L-cystine, L-cysteine, and L-methionine, which are required, with the vitamins thiamine and biotin, by the higher animals. These organic sulphur compounds are "largely degraded to hydrogen sulfide as a result of microbial action on plants and animals after their death." 15 The classes of sulphur-containing compounds, a few examples, and the materials in which they have been found are the following: a) Thiols: 3-methyl-l-butanethiol (skunk),16 ergothioneine (cereal grains), glutathione (widespread), transfer RNA (bacteria), a variety of enzymes, and the amino acids L-cysteine and homocysteine. b) Disulphides: the amino acids cystine and homocystine, lipoic acid (widespread), thiamine disulfide, and several antibiotics.17 7 c) Sulphides: pheromones, the amino acid methionine, vitamins thiamine and biotin, the penicillin and cephalosporin classes of antibiotics.17 and many of the odoriferous volatiles in foods, such as kahweofuran (coffee). d) Thiophenes: more than ISO thiophene derivatives isolated from Compositae and fungi. 18 e) Thioesters: the thioesters of the two thiols Coenzyme A and acyl carrier protein "are involved in the functioning of oxidoreductases, transferases, hydrolases, ligases, lyases, and isomerases."17 f) Coordination Compounds: The sulphur-containing ligands found in metalloproteins are S2- and the residues of the amino acids cysteine and methionine. Methionine-coordinated metal ions can be found in some cytochromes c (heme Fe atoms)19 and in blue copper proteins such as azurin and plastocyanin.20 Cysteine-bound metal ions are found in metallothioneins (Cd),21 liver alcohol dehydrogenase (Zn),22 rubredoxin (Fe),23 azurin and plastocyanin (Cu),20 and zinc fingers such as those in the yeast protein ADR 1.24 Ferredoxins contain sulphide-bridged iron atoms bound to cysteine or other ligands.25-7 The structure of the FeMo cofactor of nitrogenase is not known, but estimates of the stoichiometry of its tniolate-bound core are in the range IMo, 6-8Fe, 6-9S.25.28-9 1.1 J Nomenclature of Sulphur Compounds The nomenclature of sulphur chemistry was invented by the devil. If one omits for the moment the difference between "sulphur" (British) and "sulfur" (American), and ascribes the thiol vs. mercaptan problem to the vagaries of a nomenclature system built around historical labels, one is still faced with a bewildering array of systematic and trivial names. An extreme example is the word "sulphide", which means a binary 8 metal/sulphur compound to a geochemist, a thioether complex to a coordination chemist, an S2- ion to an inorganic chemist, a thiol to some biochemists, 17 and either a thioether or a thiolate salt to an organic chemist IUPAC confusingly allows its use for thioethers, thiolate salts and S2- ligands.30 Table 1.2 presents a summary of the terms used to refer to compounds or ligands which contain only sulphur, carbon, hydrogen, and/or metal atoms. In the following work, the terms thiol, thioether, thiolate anion, and disulphide are used to refer to the organic species RSH, RSR, RS-, and RSSR. The term sulphide is reserved for complexes containing the ligand S2-. The "ph" spelling is used, except in direct quotes from sources that use the other convention. 1.2 THE EXTRACTION OF SULPHUR FROM FOSSIL FUELS 1.2.1 Reasons for Sulphur Extraction The deleterious effects of high-sulphur-content fossil fuels are catalyst fouling, corrosion of pipes and reactor vessels, undesirable properties of the fuel products, and air pollution during processing or after combustion. As the world reserves of low-sulphur fuels are consumed and the demands of environmental legislation and the public become more stringent the use of desulphurization will increase. 1.2.1.1 Catalyst Fouling Noble metal catalysts in the catalytic reformer,33 some hydrocracking units,9 and the butadiene hydrogenator section of the alkylation unit of the refinery are poisoned by sulphur-containing compounds. It is the poisoning of the reformer catalyst which is the economic incentive for hydrodesulphurization. Table 12 Nomenclature of Compounds Containing Sulphur, Carbon and Hydrogen Formula Name Notes Reference RSH alkanethiol suffix 30 RSH alkyl hydrosulfide 5 32,30 RSH thio(alcohol) trivial 30 RSH alkyl mercaptan outdated 30 RSH mercapto- prefix biochemistry 30 RSH sulfide 17 RSSH alkyl hydrodisulfide 32,30 RSSH alkyldisulfane 1 30 RSSH alkylpersulflde 32 RSR dialkyl sulfide 4,5 30 RSR dialkyl thioether outdated 30 RSR alkylthio- prefix 30 RSR thia- prefix, 6 30 RSR thio- trivial 30 RSR epithio- prefix, 2 30 RSSR dialkyl disulfide 5 30 RSSR dialkyldisulfane 1 30 RSSR dithiodi- prefix, 3 30 RSSR disulfanediyldi- prefix, 1,3 30 RSSR epidithio- prefix, 2 30 RSSR alkyldisulfanyl- prefix, 1 30 RS- alkylsulfanyl free radical 30 RS- alkanesulfenyl free radical 30 RS- alkylthio free radical 30 RS+ alkylsulfanyl cation 30 RS+ alkanesulfenyl cation 30 RS+ alkylsulfanyh'um cation 30 RS+ alkanesulfenylium cation 30 R3S+ trialkylsulfonium cation, suffix 30 R3S+ S2- dialkylsulfonio- cation, prefix 30 sulfide anion 31 S2- thio ligand 31 S2 - disulfide anion 31 S2 - disulfide ligand 31 HS- hydrogensulfide anion 31 HS- mercapto- ligand 31 RS- alkane thiolate suffix, anion 31 RS- alkyl sulfide anion 30 RS- sulfido- anion, prefix 30 RS- alkylthio- ligand 31 RS- alkanethiolato- ligand 31 Notes: 1. S-S chain is straight, not branched. 2. S atom bridges two carbons already in a ring. 3. Identical R groups. 4. Compounds of the formula RS(CH2)nSR' have been referred to as disulphides.1J0 5. Radicofunctional nomenclature. 6. For use when an S atom replaces a CH2 group in the parent formula. 10 1.2.1.2 Corrosion Corrosion in the refinery due to sulphur compounds occurs at high temperatures or pressures. Regions where these conditions exist, such as pipe still heaters, fractionators, and reactors, are prone to iron oxide and iron sulphide scale formation. At low temperatures, acid attack by HCl, H2S, or CO2 in condensates is the principal cause of corrosion.34 1.2.1.3 Undesirable Properties of Fuel Products Fuel products high in hydrogen sulphide, thiols, and volatile sulphides have distinctly unpleasant odours. This problem is rectified by either extraction of the sulphur, or conversion of the thiols to the non-volatile disulphides, which are often allowed to remain in the fuel product9 The stability of fuel products is compromised if H2S, disulphides, or polysulphides are present The last two species "actively promote the formation of sludges."35 Sulphur compounds are removed from kerosenes to decrease smoke formation.36 The effectiveness of alkyl-lead anti-knock agents is inhibited by thiols and disulphides.37 However, since the use of alkyl-lead compounds is dirninishing, this inhibition is no longer a justification for desulphurization. 1.2.1.4 Air Pollution The bulk of anthropogenic emissions of sulphur gases in the U.S. are of sulphur dioxide.38 Although industrial emissions of hydrogen sulphide are in sufficient quantities to cause concern, they represent only 1% of the total anthropogenic sulphur emissions in Canada.39 The gaseous products of fossil fuel combustion contain sulphur dioxide and sulphur trioxide in ratios of between 40:1 and 80:1.14 Fuel combustion in 11 stationary sources, such as heating systems in buildings, and power generating stations, is responsible for greater emissions than combustion by mobile sources such as transportion vehicles (Table 1.3). In the United States, where coal combustion plays a greater role in power generation, the stationary source emissions are significantly greater than in Canada ' Stack gases of fluid catalytic crackers are a major source of sulphur oxides. These emissions can be reduced by scrubbing of the gases, or hydrotreating of the cracker feedstock.41 Once emitted, S02 is oxidized in the atmosphere to SO3 in a reaction catalyzed by metallic oxide particulates. Sulphur trioxide reacts with water or particulates to form sulphuric acid or sulphates, respectively. Both products cause reduced visibility, corrosion of materials, and acid rain. The observed useful life of galvanized sheet steel at 65% humidity and 13 g/m3 SO2 (rural setting) is 30-35 years. At 1040 g/m3 SO2 (heavily industrial setting), the useful life is reduced to 3-5 years.42 The effects of sulphur oxides on the environment are more difficult to measure, but the serious consequences of large scale damage are sufficient to keep the subject under intense scientific and political scrutiny. 1.2.2 Sulphur Extraction from Petroleum The removal of organic sulphur from petroleum is accomplished by amine treatment, caustic treatment, molecular sieve adsorption, or catalytic hydrotreating.43 The last mentioned process is the most effective at removing sulphur and therefore is used to treat feedstocks of the catalytic reformer, and refinery product streams which need to be particularly low in sulphur. The placement of desulphurization units within a simplified refinery flow-plan is shown in Fig. 1.3. Hydrotreating (Fig. 1.4) involves passing the feed over catalysts of nickel, cobalt or molybdenum oxides on alumina, under high 12 Table 1.3 Canadian Nationwide Emissions of Sulphur Oxides, in 1980a Emissions Percent Source (x iff kg SQ2) of Total COMBUSTION IN VEHICLES marine 60 1.4 diesel 39 0.9 gasoline 19 0.5 railroad 3 0.1 aircraft 2 0.1 subtotal 123 2.9 STATIONARY SOURCES power generation by utilities 696 16.5 residential, commercial and industrial 556 13.2 fuel wood 2 0.1 subtotal 1,255 29.8 INDUSTRIAL PROCESSES Cu, Ni production 1,723 40.9 natural gas processing 348 8.3 Fe production 219 5.2 other metals 167 4.0 tar sands operations 136 3.2 pulping 104 2.5 petroleum production/refining 100 2.4 other 38 0.9 subtotal 2,837 67.3 solid waste incineration 3 0.1 TOTAL a Adapted from reference 39b. 4,218 100.0 C1-200 c r u • d LIGHT ENDS SEPARATION C1-C2 DEA TREATS* C3 ATER C4 C5-200 MEROX TREATER op A T M D I S T 650+ "F 200-350°F MEROX TREATER HYTJROTREATER CATALYTIC REFORMER deC4 350-500°? 500-700°F HYDROCRACKER deC4 V A C D I S T 500-700°F 700-1050 OF 1050+ °F M WDROTREATER *\ HYDROTREATER \-FRACTION-ATOR T Lubes/Specialties -fW COKER U Coke FRACTION-ATOR CATALYTIC CRACKER Refinery Fuel Gas c2L deC2,C4 f C4 FRACTION-ATOR Roffnofy Fuel Gas -*> Propane -*» Butane ALKYL/ POLYM B L E N D E R B L E N D E R *\ HYDROTREATER \-• Gasoline Diesel Stove oil Jot Fuel BLENDER Heavy Fuel OH -•> Asphaft Fig. 1.3 An overview of a petroleum refinery, emphasizing the placement of desulphurization units. Abbreviations are defined in the list of abbreviations. 14 Stan y-Makeup H3 Recycle H, I Furnace Purge lo fuel gas H,S Fresh leed Heat-exchange • lection Liquid/gas-separation section Naphtha l > Product stripper Desulfurized product Fig. 1.4 Flow plan for a naphtha hydrotreater.45 15 pressures of hydrogen. If the temperature is kept below 300°C, only the thiols are converted to H2S, and the process is called hydrosweetening.44 Naphtha (catalytic reformer feedstock) hydrotreating usually occurs at catalyst bed temperatures of up to 370OC.43 At these temperatures, the following reactions take place: a) Hydrodesulphurization (HDS) CxHyS + 2H2 > CxHy+2 + H2S 1.1 b) Hydrodenitrogenation (HDN) c) Hydrodeoxygenation (HDO) d) Hydrogenation of olefins and some aromatics e) Hydrocracking46 RCH2CH2R' + H2 —> RCH3 + R'CH3 1.2 After conversion, the products are separated; hydrogen is recycled; and H2S is converted to sulphur in a Claus plant. The HDS catalysts are usually M0O3, with CoO as a promoter, deposited from an ammonia solution onto a high surface area alurnina support. The oxides are converted to sulphides by presulphiding the catalyst with H2/H2S mixtures.46 Heavy metals in the feed poison the HDS catalyst, but this is preferable to poisoning of the expensive reformer catalyst. The sulphides of Ru, Os, Rh, and Ir are far more efficient HDS catalysts than those of either Co or Mo, possibly because of the intermediate heats of formation of the noble metal sulphides (Fig. 1.5).47-9 However, the success of catalysts containing both Co and Mo, and the cost of the noble metal catalysts, prohibit their use industrially. The mechanism of the hydrodesulphurization reaction is not known. Thiophene is the model substrate of choice, because it is the parent molecule of the least easily desulphurized class of molecules. The hydrocarbon products of the reaction of thiophene with 1 atm of hydrogen, over cobalt molybdate on alumina at 2880C, are butadiene (2%), 16 T—i—i—i—i—r-r-i—i—r AH FORMATION (kcal/molt of mtUl) Fig. L5 The dependence of the HDS activity of the transition metal sulphides on their heat of formation (DBT = dibenzothiophene).47 Mixtures of metal sulphides are shown as filled squares at the average of the heats of formation of the individual sulphides. The commercial catalyst is shown as a hollow circle. 17 1-butene (48%), os-2-butene (20%), ira/u-2-butene (24%), and butane (6%).50 Central to the debate over the mechanism are the mode of coordination of thiophene to the surface and the nature of the first step in the reaction pathway. Studies of thiophene adsorption onto clean or sulphided surfaces of various metals found examples of S-bound perpendicular, S-bound tilted, and rj5-bound thiophenes.* IR studies on molybdenum sulphide catalysts showed evidence for thiophenes coordinated by one (n2 or r\3) or two (T|4 or T|5) double bonds.^l Perpendicular binding through the S atom is preferred in molybdenum sulphide anion vacancies, according to quantum chemical extended Hiickel theory studies.52 Coordination complex analogues for four of these binding modes have been reported (Fig. 1.6)303 It is likely that the mode of binding on surfaces varies depending on the adsorbed species. One study53 of thiophenes and thianthrenes adsorbed on commercial C0M0/AI2O3 catalysts at normal operating conditions divided the molecules into those concentrating their electron density at the sulphur, and those having their electron density delocalized over an extensive Tt system. The former group would bind by the sulphur atom. The latter group, especially if steric hindrance existed around the sulphur, would bind in the manner of a Tt complex. This is consistent with observations in coordination chemistry: benzothiophene and dibenzothiophene, which fall in the latter group, bind to metal atoms by the benzene, not thiopene, ring.54-6 Angelicil used parallels with coordination chemistry to argue in favour of T|5 coordinated thiophenes in HDS. He argued that a) T|5 coordination is stronger and more activating than the nl coordination, and that b) product distributions of exchange reactions of D2 with thiophene bound to HDS catalyst surfaces are very similar to those of exchange reactions of CD3OD with Ru((^)(T|5-tniophene)+. After adsorption, what is the first step in the HDS of thiophene; desulphurization to butadiene followed by hydrogenation, or hydrogenation to di- or tetrahydrothiophene followed by desulphurization? Studies by Desikan and Amberg63 suggest the former, 18 a) T]l<oor<lination*7'58 + Fig. 1.6 Transition metal complexes exhibiting different modes of thiophene coordination. 19 because the HDS of tetrahydrothiophene gives a different product distribution than the HDS of thiophene. However, results with benzothiophene64 and the presence of tetrahydrothiophene in thiophene HDS effluent^ suggest that both pathways are being followed simultaneously. It is likely that two kinds of sites exist One type, responsible for desulphurization, is poisoned by H2S, thiophene, pyridine and NH3. The other, weakly electrophilic site, responsible for hydrogenation, is poisoned only by NH3 or alkali.63 The Lipsch-Schuit mechanism^ proposes T]l-coordination of the thiophene, followed by H atom donation from an OH or SH group to the a carbon, causing C-S bond cleavage. This would be repeated, liberating butadiene. The sulphur atom would then be removed from the surface by hydrogenation (Fig. 1.7). This mechanism has been criticized for its use of S-bound thiophene species67-8, and because the hydrogenation of the sulphide on the surface would be rate limiting.69 Kolboe70 proposed intramolecular B-elimination of H2S from thiophene, which would produce adsorbed diacetylene. This is supported by IR detection of an acetylene on the surface of the catalyst0^ but would require unstable benzyne species if it were the pathway of reaction of benzothiophenes.46,67 Mechanisms involving Ti2- or ^-coordination of the thiophene have since been proposed.67,71 Angelicil has developed a mechanism (Fig. 1.8) based on observed reactions of thiophene coordination complexes, including the donation by hydride complexes of H- to bound thiophene complexes (reaction 1.3),68,72 the protonation of the allyl sulphide intermediate (reaction 1.4)68, and the elimination of butadiene from Fe(CO)4(2,5-dihydrothiophene) (reaction 1 J).l»73 H Mn(CO)3+ MtCO^ - Fe(CO)4 or W(CO)5 (ref. 68) Mn(CO)3 Fig. 1.7 The Lipsch-Schuit meciianism for thiophene HDS.^6 21 Fig. 1.8 The Angelici mechanism for thiophene HDS.l 22 H + HCl H Mn(CO)8Cl 1.4 (CO)4Fe(n1-2,5-DHT) —* CH2=CHCH=CH2 + "(CO)4FeS" 1.5 The mechanism assumes that hydride species would be available on the surface of the catalyst "as a result of dissociative adsorption of H2." 1 The mechanism does not satisfy the concerns of Gellman et al.69, about the slow rate of hydrogenation of .sulphide species on the surface. More recently, Wang and Angelici55 have used analogies from coordination chemistry to study the more difficult problem of the mechanism of the HDS of dibenzothiophene. 1.3 REACTIONS OF SULPHUR-CONTAINING ORGANICS WITH TRANSITION METAL COMPLEXES The reactions which occur on the surface of the HDS catalyst involve thiols, sulphides and disulphides. Their reactivity is affected by meir cc<>rdination to me surface. These reactivity changes are most easily studied in the chemistry of the analogous homogeneous systems. The coordination of sulphur compounds to transition metal centres is usually, but not always, followed by S-H, S-S or S-C bond cleavage. Despite the fact that, of the three groups, the S-H bonds have the greatest bond dissociation energies (83-91 kcal/mol) 74 23 they are the most easily cleaved because of their ionic character. Thiols are acidic ih aqueous solution, with pKa's of 6.6,7.0 and 10.7 for aryl thiols, hydrogen sulphide and alkyl thiols, respectively (Table 3.8). The S-S bonds of di- and poly-sulphides are also easily cleaved, having a bond strength of 66 kcal/mol (for HSSH)75 Sulphur-carbon bonds (61-77 kcal/mol),74 on the other hand, are rarely cleaved. Coordinated thioethers (M-SR2) are more common than organometallic thiolato complexes (M(R)(SR)} that result from oxidative addition of thioethers to metal centres. The following sections describe reactions with transition metal complexes in which S-H, S-S or S-C bonds have been cleaved. 1.3.1 Reactions Involving S-H Bond Cleavage Oxidative addition of thiols has been known since the early 1960's, for example, with Vaska's compound. H Ph3P—Ir PPh3 OC^| a 1.6 (refs. 76-80) Similar reactions are: Pt(PPh3)n + H2S —> Pt(PPh3)2(SH2) —> Pt(PPh3)2H(SH) 1.7 n=2 or 3 (refs. 81-2) »ra/tf-Mo(dppe)2(N2)2 + RSH —> Mo(dppe)2(H)(SR) + 2N2 1.8 dppe = Ph2PCH2CH2PPh2 (refs. 83-5) Ru(CO)2(PPh3)3 + RSH —*> crt-RuH(SR)(CO)2(PPh3)2 + PPh3 R = H, Et, C6H4pCH3 (ref. 86) 1.9 24 Reaction 1.9 will be more fully described in Sections 3.1 and 3.2 of this work. Examples of H2S or thiol coordination without cleavage of the S-H bond, such as that in equation 1.7, are rare, although that type of structure is proposed to be the intermediate in all such reactions. A few observed compounds of this type are Fe(RSH)(CO)4,87 rRu(NH3)50HSEt)]2+,88 (PhCH2SH)^ [CpRu(PPh3)2(H2S)]+,°0 and possibly Fe(TPP)(PhSH)(SPh) t^2TPP^traphenylporphyrin).°l Oxidative addition of thiols is often followed by dimerization, because thiolate ligands have a tendency to adopt bridging positions.0^ 2MCl(PPh3)3 + 2RSH —> rMH(Cl)(PPh3)2]2(RSR)2 + 2PPh3 1.10 M=Rh or Ir (refs. 93-4) 2R11H2P4 + 4H2S —> P3Ru(LtSH)3Ru(SH)P2 + 3P + 4H2 1-H P=PPhMe2 (ref. 95) 2Fe(CO)4L + 2RSH -> (O0)3Fe(LuSR)2Fe(O0)3 + 2CO + H2 + 2L 1.12 L=COorH2(refs. 96-7) The hydrido-thiolato products of the oxidative addition may react with excess thiol in a second step. RuH(SH)(CO)2(PPh3)2 + H2S —> Ru(SH)2(CO)2(PPh3)2 + H2 1.13 (ref. 86) MoH(SR)(dppe)2 + RSH —> Mo(SR)2(dppe)2 + H2 1.14 (refs. 83-5) This type of reaction can be inhibited by the use of bulky thiols, or the use of exactly one equivalent of thiol in the initial reaction. This problem of subsequent reaction, along 25 with the tendencies of these complexes either to dimerize or eliminate thiol, restricts the number of well-characterised hydride thiolato complexes. The kinetics of the oxidative addition reaction are rarely studied. The reaction of trfl/ts-Mo(dppe)2(N2)2 with /i-propyl or phenyl thiol (reaction 1.8 followed by reaction 1.14) was monitored by UV.84 The rate had a first-order dependence on the concentration of the complex, and zero to first-order dependence on the thiol concentration. The proposed mechanism (Scheme 1.1) included two unobserved species [MoH(SR)(dppe)2] and [MoH2(SR)2(dppe)2], modelled after the known complexes [MoH(tpbt)(dppe)2] (tpbt = 2,4,6-iPr3C6H2S-) and [MoH2Cl2(dppe)2]. Addition of thiols across a metal-metal bond produces a bridging thiolate and either a bridging hydride, (CO)4 /**\ 1.15 Ru3(CO)12 + EtSH - (CO)3Ru^H*^Ru(CXD)3 + 2 CO s Et (refs. 98-9) a terminal hydride, I I H Pt Pt CO + MeSH PP = dpm (ref. 100) or no hydride ligand. PhSH ^ [Cp*RuCl2]2 > [Cp*Ru(LtSPh)3RuCp*]Cl + (3HC1?) 1.17 Cp* = r\5.Q5Ue5 (ref. 101) 1.16 26 Scheme 1.1 The proposed mechanism for the reaction of <rons-Mo(dppe)2(N2)2 with thiols (adapted from ref. 84). ( ( N2 No N, SR Mo SR ) -H, RS N, Mo r ) RS :MO RSH RSH J ( N, Mo RS H ) fast -N, H RS Mo 27 Similarly, one or both of the S-H bonds in H2S may be cleaved, and one or both of the hydrogens eliminated. I I X Pd—Pd—X +H2S • X = Cl,Br, PP = dpm(refs. 102-5) 2+ Pt P O 1 u8o Pt 7\. + H2S PP = dpm (ref. 106) P P I I X Pd—S Pd— X + H2 P. P H Pt Pt 1.18 + H+ + CO 1.19 During the conversion of H2S to elemental sulphur, the production of hydrogen gas in a process based on this type of chemistry would be preferable to the production of water as found in modem Claus plants. 1.3.2 Reactions Involving S-S Bond Cleavage Oxidative addition of disulphides involves cleavage of S-S bonds, forming two terminal thiolate ligands, M(PPh3)2(N3)2 + RSSR —• M(SR)2(PPh3)2 + 3N2 R = Me,BuorPh; M = Pd or Pt (ref. 95) 28 or forming a thiolate-bridged structure. 3Fe(CO)5 + 3PhSSPh -> (CO)3Fe(LtSPh)3Fe(LiSPh)3Fe(CX>)3 Ul (refs. 107-9) The intermediate in disulphide oxidative addition reactions may be a disulphide coordinated by one or two sulphur atoms to the metal. This is usually not observed; but such compounds have been isolated. [CpFe(a))2(THF)]BF4 + PhSSPh - OC«^FC ? (refs. 110-2) ^ ^Ph °° S BF4" + THF 122 Reactions of disulphides with metal hydrides produce a thiolate complex and one equivalent of liberated thiol. [FeH(CO)5]- + RSSR —> [Fe(SR)(CO)4]- + RSH 1.23 (ref. 113) RuH2(PPh3)4 + MeSSMe -> RuH(SMe)(PPh3) + (PPh3? + MeSH?) 1.24 (ref. 114) Addition of disulphides across metal-metal bonds leads to thiolate-bridged structures, either directly or through a monomeric thiolate complex. P^P P^P I I ^ci cu I ,sNI .a ^;W=WC + PhSSPh ^w=wc 125 Cl^ I I ^Cl ci^ I ss' I ^Cl p p n p P P = dpm (ref. 115) 29 [Ru(CO)2Cp]2 + RSSR -» Ru(SR)(Cp)(CO)2 + [Ru(Cp)(CO)0iSR)]2 R = Ph, Me or CH2Ph (ref. 116) 1.26 M2(CO)io + RSSR -> 2M(SR)(CO)5 -> M2(CO)8(uSR)2 121 R = Me, n-Bu, sec-Bu, f-Bu, Ph; M=Re, Mn (ref. 117) The first steps in reaction 121 were photolytic cleavage of the dimer to form M(CO)5-, followed by RS group transfer from RSSR. Pseu^fo-first-order kinetics showed that the rate decreased with the bulk of the alkyl group of the disulphide, although diphenyl disulphide reacted more quickly than the dialkyl disulphide due to either its weaker S-S bond or "the electron accepting capability of the phenyl group" which would favourably affect the rate of the donation of an electron from M(CO)5- to the disulphide. 117 The reactions of elemental sulphur with transition metal complexes also involve S-S bond cleavage. Sulphur has been widely used as an S atom donor, along with ethylene and propylene sulphides, and alkyl trisulphides. The products are mononuclear, M(CO)2(PPh3)3 + 3/8S8 M(CO)2(PPh3)2S2 + (SPPh3?) 1.28 M = Os,Ru(ref. 118) dinuclear, 2CpRuP2Cl + 1/4S8 + 2Ag+ -> [CpP2Ru(uS>2RuQpP2]2+ + 2AgCl P = PPh3; Cp=C5H5 or CsH4Me (refs. 119 and 120) \29 30 or polynuclear inorganic sulphides. Pt(PPh3)2,3 + S8 -> [PtS(PPh3)2]n 1.30 (ref. 82) The resulting sulphur bridge in dinuclear complexes can be unsupported and of several atoms. [RuCp(CO)2]2 + 5/8S8-^[RuCp(CO)2]20AS5) 1.31 (ref. 121) Metal hydrides react with sulphur to yield mercapto complexes, some of which react further to give inorganic sulphido complexes. Sg [Cp*2ZrH(Ldi)]2 + S8-^Cp*2Zr(SH)2-~>Cp*2ZrS5 1.32 Cp* =T|5-C5H4fBu (ref-122-3) RuH2(PPh3)4 + 1/4 S8 —» RuH(SH)(PPh3)3 + SPPh3 1.33 (ref. 18) Pt(SH)2(PPh3)2 + 3/8 S8 —> PtS4(PPh3)2 + H2S 1.34 (ref. 124) There are even reports of the sequential insertion of sulphur into the M-C bonds of metal alkyl complexes. Cp(NO)WR2 + 1/4 S8 -> Cp(NO)W(SR)2 R=CH2SiMe3 (refs. 125-6) 1.35 31 1.3 J Reactions Involving S-C Bond Cleavage The Pd2X2(dpm)2 dimers which extracted sulphur from hydrogen sulphide (reaction 1.18) failed to extract sulphur from thiols or sulphides,103 because of the greater resistance to cleavage of S-C bonds compared to S-H and S-S bonds. The same reason can be given for the stability of metal thioether complexes relative to their thiol or disulphide cousins. Examples of stable ruthenium thioether complexes include [Ru(NH3)5L]2+ (L=Me2S, tetrahydrothiophene (THT), thiophene),88,127 cis- and rrflw-[Ru(bipy)2L2]2+ (bipy=2,2,-bipyridyl, L=MeSPh, phenothiazine, l,4-dithiane),128 [CpRu(PPh3)2L]+ (L=THT, ethylene sulphide),129 mer-[RuCl3L3] (L=Me2S, Et2S, PhSMe, THT, etc.),130-2 and [RuCl3(Et2S)2]2-131 In addition, a large number of transition metal crown thioether complexes have been reported. 133 Stoichiometric sulphur extraction from thiols and thioethers is known (see also Jang «fa/.).134 P P = dpm (ref. 135) Cl H 4 atm Ha p |/Sv| p Ta2Cl6(SMe2)3 • Q>Ta-H-Ta^) + CH3CH3 H Cl PP = iPr2P(CH2)3PiPr2(dippp) (ref. 136) 32 A reaction similar to 1.37, but involving sulphur atom abstraction from PhSSPh has been reported.308 Oxidative addition reactions of thioethers involving cleavage of only one S-C bond (especially an allyl-S bond) are far more common than reactions involving cleavage of 2 S-C bonds. CH2=CHCH2SAr + RhH(PPh3)4 —> l/2[Rh(PPh3)2(u.SAr)]2 + 2PPh3 + CH2=CHCH3 1 Ar = Ph, PhMe etc. (ref. 137) CH2=CHCH2SPh + 2PdL2 L-Pd-Pd-L + 2L I.39 L = P(C6Hl 1)3 (refs. 138-40) ^ 2Fe(CO)5 + 2RSR —> (CO)3Fe(LiSR)2Fe(CO)3 + 400 + R-R 1.40 R = Me, Et, cyclopentyl, Ph (ref. 96) "NiL2" + ArSAr —> iran$-Ni(SAr)(Ar)L2 1.41 {in-situ) L=PEt3 or P(nBu)3 (refs. 141-2) Strained-ring thioethers such as ethylene and propylene sulphides are a special case. Although coordinated ethylene sulphide exists 129 in the complex [CpRu(PPh3)2(SC2H4)]+, it more typically donates the sulphur atom, liberating ethylene. FeH2(CO)4 + • [Fe(SH)2(CO)4] —> Fe2S2(CO)6 + Fe3S2(CO)9 1.42 (ref. 143) 5 Thiophenes are another special case. A few of their transition metal complexes have been mentioned (section 1.22). Examples of reactions in which one or both of the S-C bonds of a thiophene group have been cleaved by reaction with transition metal complexes are shown below. 33 2Ni(bipy)(C0D) • l^J-yj ^J-\ /) S Ni bipy Ni(bipy)2+ ^Jf^/) (ref. 144) 2Fc(00)5 + gT^Cm ( + "S" + 4CO) R(CX»3 (ref. 145) (ref. 146) 34 2. GENERAL EXPERIMENTAL PROCEDURES The materials, the general techniques common to most of the experiments, and the syntheses of the non-sulphur-containing ruthenium complexes, are described in this chapter. Details of individual experiments can be found in the last section of each subsequent chapter. 2.1 MATERIALS All of the ruthenium complexes were synthesized from RuCl3-3H20, supplied by Johnson Matthey. Thiophene, benzyl trisulphide, benzene selenol, triphenyl phosphine sulphide, and the thiols, sulphides, and disulphides were supplied by Aldrich. Diphenyl sulphide was purified before use by mixing 1:1 with acetone, adding a concentrated acetone solution of KMn04 until it stayed purple, filtering and fractionally distilling under vacuum. Elemental analysis and NMR spectroscopy showed the thioether to be pure. Other chemicals used were benzophenone (BDH), dpm (Aldrich), fluoboric acid (MCB), sodium borohydride (BDH), sodium tetraphenylboron (Fisher), tetrafluoroboric acid diethyl ether complex (Aldrich), triphenyl phosphine (BDH), tris-p-tolyl phosphine (Strem) and sodium methylate (Fisher). Sodium ethyl and p-tolyl thiolates were synthesized by the reaction of the thiol with an excess of sodium in undistiUed diethyl ether under N2. After 1 h, unreacted sodium was removed with tweezers and the white suspension filtered. The salt was dried under vacuum overnight and stored under N2 or Ar. Na/Hg amalgam was prepared by dissolving Na slivers into Hg under Ar until the solution solidified. Then extra Hg was added until the solution could be easily stirred, Tetra-n-butyl ammonium tetrafluoroborate was synthesised by Mr. A. Pacheco of this research lab, from the reaction of tetra-n-butyl ammonium hydroxide with tetrafluoroboric acid, followed by recrystallization (twice) from ethyl acetate and n-pentane. The solvents, analytical or glass distilled grade, were dried by refiuxing for several days over clrying agents under N2, and distilling from the drying agent immediately before use. 35 Tetrahydrofuran or "THF" (supplied by BDH), toluene (Omnisolve), benzene (BDH), diethyl ether (BDH), and hexanes (BDH) were dried over sodium and benzophenone. Pentane was dried over phosphorus pentoxide. Acetone was dried over K2OO3. Methanol (BDH, glass distilled) was dried over magnesium turnings treated with iodine. N,N-cumethylacetamide (BDH) to be used in the synthesis of RuH(Cl)(CO)2(PPh3)2 was not distilled, but only degassed by repeated freeze/thaw cycles under hydrogen. C6Df> CD2CI2. CD3OD, D2O, C6D5CD3, (CD3)2CO, and THF-d8 were supplied by Cambridge or MSD Isotopes. All of these, except CD3OD and D2O, were received as ampoules, and transferred to storage vessels and thence to the NMR sample tubes under an inert gas (N2 or Ar). CD3OD and D2O were received in bottles and were not stored under anaerobic conditions. Gases (N2, Ar, H2,02, CO, H2S, HCl, and MeSH) were used as received from Matheson. The thiols and thiolate salts are extremely smelly, and all of the sulphur-containing organics are extremely toxic. Hydrogen sulphide and methanethiol must be handled with particular care because of the fatal consequences of accidental exposure to these gases. Selenium-containing compounds such as benzene selenol are even more toxic than their sulphur-containing analogues. 2.2 EQUIPMENT AND TECHNIQUES 2.2.1 Reaction Conditions Except where noted, synthetic scale reactions were performed in THF at room temperature and under one atmosphere of an inert gas (either N2 or Ar), using standard Schlenk tube techniques. NMR scale in situ experiments were performed in the following manner. Into a wide-mouth Schlenk tube was placed a 5 mm glass NMR tube containing a known weight of the solid reagents, or the unknown to be characterized. After evacuation of the Schlenk tube, the gas was admitted. The cap to the Schlenk tube was removed, with the gas flow sufficiently high to 36 prevent the entry of air. The solvent, usually C5D5, was pipetted into the NMR tube, which was sealed with a septumn flushed with an inert gas. The liquid reagent was then injected through the septum to start the reaction. 2.2.2 Spectroscopy and Chromatography All NMR spectra were acquired at 19°C and using a Varian XL-300 at 300 MHz (lH) or 121 MHz (31P nuclei) unless otherwise stated. Other NMR spectrometers used were a Bruker AC-200, a Bruker WH-400 for special experiments requiring greater field strength, and a Bruker AMX-500 for 31p-decoupled lH spectra. Solid state 13c NMR spectra were acquired using a Bruker MSL-400 operated by Dr. L. Randall; the spectrometer contained zirconium spinners and a standard MAS probe tuned to 100.6 MHz. The solid state spectra were obtained with adamantane as external reference, and reported with respect to TMS. Solution NMR chemical shifts were measured with respect to TMS in C6D6 for lH and 13c, triphenyl phosphine in C6D6 for 31p, and BF3:(C2H5)20 in 1:1 C6D6:(C2H5)20 for 1 lB nuclei, all as external references. The 31p chemical shifts, however, are reported here with respect to 85% H3PO4 aqueous solution which shows a resonance, in the XL-300 at room temperature (20°C), at 6.05 or 5.46 ppm downfield of PPh3 in C6D6 or CD2CI2, respectively. The deuterium lock signal was the solvent itself. All of the 31p and 13c spectra were lH broad-band decoupled. The chemical shift of triphenylphosphine in C6D6 with respect to aqueous 85% H3PO4 was determined by acquiring the 31p spectrum of a 10 mm NMR tube containing the former solution, with a 5 mm NMR tube containing the latter solution held inside it by plastic O-rings. The chemical shift of PPh3 has been reported previously. 147 UV/vis spectra were measured taken in specially designed 1 cm or 1 mm quartz or glass cells 0?ig. 2.1) sealed under the desired gas. The spectrometer, a Perkin Elmer 552A, contained an electronically temperature controlled cell holder accurate to ±0.2°C. 38 Infrared spectra of Nujol or hexacMoro-1,3-butadiene mulls, or THF, toluene, or CH2CI2 solutions were taken in a Nicolet 5DX FTIR internally calibrated with a He/Ne laser. Fast Atom Bombardment Mass Spectra (FAB-MS) were acquired by Ms. C. Beaulieu of this department, using an AEI MS 9 mass spectrometer with a 6 kV ion source, a 7-8 kV, 1 mA xenon gun, and a 10 s/decade scan rate. The samples were contained in a p-nitrobenzyl alcohol matrix. The theoretical isotope patterns were predicted using the simulation program PEEKS-1982.148 The experimental conditions of the X-ray crystallography experiments will be described in the sections which detail their results. The conductivity of solutions was measured with a Yellow Springs Instrument Co. 3403 Cell (with a cell constant of 1 cm-1) and a Serf ass Conductivity Bridge Model RCM 15B1. Organic products were separated in a Hewlett Packard HP S890A gas chromatograph with a 15 m OV101 column at 30°C with helium carrier gas, a split/splitless injector, and a flame ionization detector. The injection volume of liquids was 0.1 jlL, Hydrogen gas was detected qualitatively with a 10 ft molecular sieve column and a thermal conductivity detector. Quantitative measurement of gas production was achieved using a constant pressure gas-uptake apparatus, described in section 2.2.3. Microanalyses were performed by Mr. P. Borda of this department. 2.23 Kinetic Measurements The reaction rates were monitored by one or more of three methods; UV/vis. spectroscopy, NMR spectroscopy, and gas-uptake measurements. Times were recorded from an electronic stopwatch during the NMR experiments, and from a Lab-Chron 1400 timer during uptake and UV/vis. experiments. The constant pressure gas-uptake apparatus (Fig. 2.2) has been briefly described in the literature 149,150. This equipment can be used to measure the rate of gas-uptake or evolution at Fig. 2.2 Constant pressure gas uptake apparatus. The following parts are labelled: A reaction flask, B hook, C stopcock, D stopcock, E fine valve, F two-way valve to a gas cylinder, G agitating motor and mechanism, H temperature-controlled oil bath, J n-dibutyl phthalate manometer, K mercury manometer. 40 constant gas pressure. A solution of the required concentration of reagent (thiol or phosphine) was placed in reaction flask A, and a glass bucket containing the ruthenium complex was suspended from a hook inserted through sidearm B. A ground glass joint sealed the hook to the flask while allowing the hook to be rotated to drop the bucket The flask was attached to coiled glass tubing, which in turn was attached via valve C to valve D. With the needle valve E closed, the solution was degassed three times by freezing, evacuating, and adding 400 torr of the desired gas (usually N2 or Ar) through valve F. Then the coils and valve C (closed) were reattached to valve D, and the reaction flask was clamped to a shaker mechanism G and immersed in the oil bath H at the reaction temperature (±0.05°C). After 20 min of temperature equilibration, the section of the system between C and F was evacuated and filled to 400 torr. Then valve C was opened, the system set to the final reaction pressure, the bucket dropped, and the timer and shaker started. As gas evolved, the height of the liquid (n-dibutyl phthalate) in the left column of manometer J decreased. Gas was withdrawn slowly through needle valve E to restore the balance in manometer J. The resulting dip in the mercury manometer K was measured by a Precision Tool Vernier Microscope Type 2158. Both manometers were suspended in a water bath at 25°C. Calibration permitted the conversion of mercury height measurements to millimoles of gas produced. The monitoring of reaction kinetics by FT-NMR spectroscopy requires the assumption that the areas under the peaks in the spectra are proportional to the concentrations of the respective nuclei. This is true only if 1) all of the peaks to be compared are due to protons with identical Ti values (and identical nOe effects for 31p NMR), or 2) the time between pulses is greater than five times the longest Ti value of the relevant nuclei. 151-2 The time between pulses was 1.364 s and 0.750 s for the IH and 31p{ IH} NMR experiments respectively. Because the Ti values of most of the nuclei involved were greater than l/5th of these times, condition 2 was not satisfied for most of the experiments described herein. The 41 error involved is small, however, if the Tj values of the reactants and products are almost identical. This occurs in a series of related complexes if the varying group does not significantly affect the magnetic environment around the nucleus being measured. For example, it was shown that the ratios of concentrations in mixtures of complexes of the type ccr-RuH(SR)(CO)2(PPh3)2 can be accurately measured by 31p{ lH} or lH NMR. Thus, a known C6D6 solution of ccr-RuH(SCH3)(CO)2(PPh3)2 and ccr-RuH(SC6H4-p-CH3)(CX))2(PPh3)2 containing 55% of the latter, was analyzed by comparing the intensities of the hydride triplets, the methyl singlets, and the 31p{ lH} singlets. The results (58%, 57% and 60%, respectively), show that the accuracy is sufficient for kinetic experiments. The error is greater when comparing complexes with greater differences in structure, or when comparing complexes and free ligands. In particular, free triphenylphosphine in solution has a very large Ti value of 26 s.153 2.2.4 Data Handling for Kinetic Experiments Many of the reactions in coordination chemistry are of the type M + L —> P where M, L, and P are a metal complex, a reagent, and a product, respectively. If the reaction rate is first order with respect to [M] and nth order with respect to [L], dt and if [L] > 10 [M] (pseudo-first order conditions), then the rate law can be simplified. -d\M\ = *[M][L]n Eqn. 2.1 -JM1 = *obs[M] dt where *obs = *[L]n Eqn. 2.2 The integrated rate law can be expressed in terms of [M], 42, ln[M\t = ln\M\0 - *obst Eqn. 2.3 or in terms of a measurable quantity A (hereafter referred to as absorbance) such as JR or UV/vis. absorbance, if one assumes that L does not absorb, A©° is the final absorbance, [M]«> is zero (the reaction goes to completion), and Cm and Cp are proportionality constants for the absorbances of M and P (ie. for UV/vis., C = e»/, where e is the extinction coefficient and / is the path length). At = Cm[M]t + Cp[P]t At - Aoo = CmtMlt + Cp[P]t - CmtMJoo - Cp[P]°<> = CmtMJt + Cp([M]0 - [M]t) - Cp[M]0 = (Cm-Cp)[M]t A0-Aoo=(Cm-Cp)[M]0 Inserting these expressions into the integrated rate law (Eqn. 2.3), one obtains the final expression. //i(At - Aoo) = /W(AQ - Aoo). jfcobst Eqn. 2.4 A plot of /n(At-Aoo) or /n[M]t versus time is referred to as a pseudo-first order log plot, and is linear if the reaction is pseudo-first order. The slope of the line is equal to -Jtobs-There are at least six methods for the calculation of kobs- The first three use the pseudo-first order plot, but differ in the way that A~ is determined. The error involved in the determination of Aoo is the weakest point of these methods. These three methods are: 1. Waiting for five or more half lives, and directly measuring Aoo, 2. Calculating Aoo from [M]Q and the Cp of an independently synthesized and characterized sample of the product, 3. Optimizing the straightness (correlation coefficient) of the pseudo-first order log plot by varying the value of Aoo. The value of A«> which gives the straightest line should be similar to that determined by methods 1 or 2. 43 The other three methods calculate JfcODS direcdy, and thereby avoid the problem of error in Aoo. These methods are based on two series of absorbance readings at times t\, t2, etc., and at times ti + T, t2 + T, etc., where T is a constant delay time. Applying equation 2.4, one obtains (A~-At) = (Aoo-Ao)e-tobst Eqn. 2.5 and (Aoo-At+T) = (Aoo-A0)e-tobs(t+T) Eqn. 2.6 Subtracting these equations, one obtainsl54 (At+T - At) = (Aoo - AQXI - e-*obs-T)e-tobs-t /»(At+T - At) = /*{(Aoo. AQXI - e-*°bs T)}. ^ Eqn 2j The application of these methods, however, can place undue weight on the less accurate late data points. Ordinary or weighted least squares linear regression can lead to a bias. 155 The type of linear regression which should be used is therefore a concern, as is the choice of T.155 These methods for calculating itobs are: 4. The Guggenheim method, 154,156 in which a plot of /n(At+T - At) versus time has a slope of -*obs (Eqn. 2.7), 5. The Kezdy-Mangelsdorf-Swinbourne (KMS) method,154-5,157-9 in which a plot of At versus At+T has a slope of e^obsT, At = A~(l - e*obs T) + At+T e*obs T Eqn. 2.8 and 6. The R/R method,160 in which jfcobs is determined from the average value of Rt/Rt+T« The rates are determined from the tangents to the plot of the time dependence of [M]. Rt/Rt+T = e&>bs T Eqn. 2.9 where 44 Rt = (dNa\\ = (AD - Aoo)(-jt)e-*obst Eqn. 2.10 Equation 2.8 is obtained by dividing equation 2.5 by equation 2.6, and rearranging. 154 Equation 2.10 can be derived from equation 2.4 by rearranging to equation 2.11 and then taking the derivative. 160 In order to compare these six methods, kobs was calculated using each method, from the UV/vis. absorbance data for the reaction of cc/-RuH2(CD)2(PPh3)2 (1.0 mM) with ethanethiol (94.5 mM) at 26°C in THF to give ca-RuH(SEt)(CO)2(PPh3)2 (see section 3.3 and Fig. 3.10). The values of ifcobs. obtained from the absorbance data at 400 nm taken up to 3400 s after the reaction started, and using a delay time (T) of 1600 s, are 7.01,7.63,6.73,6.61,6.58, and 6.50 x 10-4 s-l calculated by methods 1 through 6, respectively. The first two methods are the least accurate because they rely heavily on the accuracy of a single point, A°°. The differences (3 %) between the other four are considered to be of the same order as the experimental error. Method 3 was used to calculate the A°° and kQ\yS values reported in this thesis. Rate constants from multiple experiments are quoted with 90 % confidence limits, calculated with the use of t-factors.154 Plots of *obs versus [M] are linear and horizontal for all reactions pseudo-first order in [M]. Plots of Aobs versus [L] should be linear and horizontal (n=0), linear through the origin (n=l), or curved (0<n<l or n>l). AT = (AQ - A~)e-*obs-t + A~ Eqn. 2.11 45 2.3 SYNTHESES OF THE PRECURSOR COMPLEXES Throughout the equations in section 2.3, the abbreviation "L" will be used for triphenyl phosphine. 2.3.1 cc/-RuCl2(CO)2(PPh3)2 The cct isomer of this complex (1) has been synthesized through a variety of routes: 161-2 MeOH CO RuCl3 + 6L > RuCl2Ln > RuCl2(CO)2L2 2.1 reflux n = 3,4 (refs. 163-4) 140°C RuCl3 + L + CDT + H2 + CO > RuCl2(CO)2L2 + CDE 2.2 CDT = 1,5,9-cyclododecatriene, CDE = cyclododecene (ref. 165) 1. MeOH 2L RuCl3 + CO > Ru(THF)(CO)3Cl2 —> RuCl2(CO)2L2 2.3 2. THF (ref. 166) L Ru3(CO)9L3 + Cl2 -»[Rua2(CO)2L]2 —> RuCl2(CO)2L2 2.4 (ref. 167) Other methods give other isomers of the complex, often the yellow ttt isomerl61 which can be converted by heating in solution 168-9 or in the solid state 170 to the white cct isomer. Although the cis positions of the carbonyls are evident from the two stretching bands in the IR spectrum, it requires 13c NMR to prove the cct geometry. The substituted, o- and m- carbons of the phenyl groups appear in that spectrum as triplets, 165 a phenomenon characteristic of complexes with trans txiphenylphosphine ligands. 171 No X-ray crystallographic structure has been reported of this complex. 46 The method used in this work, based upon reaction 2.1, was used previously in this laboratory. 172 The complex RuCl3.xH20 (3 g, 10 mmol) was dissolved in reagent methanol (400 mL) under air, and the solution refluxed for IS min. To the cooled solution was added triphenylphosphine (20 g, 76 mmol), and the mixture was refluxed for 1 h; the resulting dark brown suspension was filtered and washed with methanol (150 mL). The RuCl2Q?Ph3)3 thus isolated was dissolved in CH2CI2 (300 mL) under N2. The flask was flushed with CO and the solution stirred overnight. The resulting yellow solution was concentrated by vacuum distillation of half of the solvent A pale yellow precipitate appeared. Methanol (40 mL) was added to encourage the precipitation. The white product was collected by filtration and dried over 24 h under vacuum. The yield was 6 g, or 80%. IR (Nujol) 2057,1994 cm-1 v(CO); IR (CH2C12) 2059,1996 cm-1 v(CO); 31p{ lH} NMR (C6D6) 8 15.65 ppm (s). The IR frequencies are within the range of reported values.165 2.3.2 Ru(CO)2(PPh3)3 The direct reaction of phosphines with Ru(CO)5 does not proceed past the disubstituted product 173 Other methods are used for the synthesis of Ru(CO)2(PPh3)3 (2). MeCN MeO-RuHCl(CO)L3 > [RuH(CO)(MeCN)2L2]+ > Ru(CO)2L3 + MeOH + MeCN 2.5 Ag+ (ref. 173) -CO L Ru(CO)3L2 + ArN2+ > [Ru(N2Ar)(CO)2P2]+ • Ru(CO)2L3 2.6 -N2Ar+ (ref. 174) RuHCl(CO)2L2 + L + DBU Ru(CO)2L3 + DBUHC1 DBU = l,8-diazabicyclo-[5,4,0]-undec-7-ene (ref. 175) 2.7 47 Another method17** used Ru(PPh3)4(MeCN>2 generated by the electrochemical reduction of RuCl2(PPh3)4 in acetonitrile. 2e- CO RuCl2l4 + 2MeCN >RuL4(MeCN)2 >Ru(CO)2L3 2.8 -2C1-A method which appears obvious in hindsight is the reaction of ccr-RuH2(CO)2(PPh3)2 (Section 2.3.3) with PPh3 RuH2(CO)2L2 + L—> Ru(CO)2L3 + H2 2.9 which has not yet been reported, although the reverse reaction was observed as long ago as 1972.173 The details and kinetics of reaction 2.9 are described in Section 3.3. The method used in the present work was only reported fairly recently. Na/Hg RuCl2(CO)2L2 + L + 2Na > Ru(CO)2L3 + 2NaCl 2.10 (ref. 172) Samples of ccr-RuCl2(CO)2(PPh3)2 (2 g, 2.6 mmol) and PPh3 (1.4 g, 5.2 mmol) were dissolved in distilled and dried THF (400 mL) under an inert gas. Sodium/mercury amalgam (15 to 20 mL) was added, and the mixture stirred for 2 to 3 days. The suspension was allowed to settle, and the supernatant solution was transferred to a separate flask and filtered through diatomaceous earth. The orange filtrate was reduced in volume to 100 mL by vacuum distillation. Addition of hexanes (140 mL) induced the formation of a deep yellow precipitate, which was collected by filtration and dried under vacuum overnight The yields were 60 to 80%. Elem. Anal. Calcd. for RUP3O2C56H45: C, 71.3; H, 4.8. Found: C, 71.0; H, 4.8. IR (Nujol) 1902 cm-1 v(CO); 31p{ lH} NMR (C6D6) 5 49.26 ppm (s); UV/vis. (THF) Xmax 345 nm (e=17,000 M-l cm-1). The v(CO) stretch falls within the range of reported values for this complex. 173-4,177 The geometry of this 5-coordinate complex is believed to be trigonal bipyramidal. The single carbonyl stretching band in the IR spectrum indicates trans and therefore axial carbonyls. The 48 single peak in the 31p{ IH} NMR spectrum indicates equivalent and therefore equatorial phosphines. 2.33 cc/-RuH2(CO)2(PPh3)2 Although in the present work cc/-RuH2(CO)20?Ph3)2 (2) was prepared from Ru(CO)2(PPh3)3 (2), as indicated in equation 2.11, Ru(CO)2L3 + H2 > RuH2(CO)2L2 + L 2.11 (ref. 173,177) complex 3_ was knownl78 (equation 2.12) well before 2 was first synthesized. 173 120 atm Ru(CO)3L2 + H2 > RuH2(CO)2L2 + CO 2.12 130°C (ref. 178) H3PO4 L Ru3(CO) 12 + Na/NH3 > RuH2(CO)4 > RuH2(CO)2L2 2.13 (ref. 179) NaBH4 [Ru(N2Ar)(CO)2L2]BF4 > RuH2(CO)2L2 2.14 ethanol (ref. 174) Ru(CO)2(PPh3)3 (1.2 g, 1.2 mmol) was dissolved in THF (50 mL) under H2 (1 atm) and stirred for 30 min The yellow colour faded, but reintensified when the volume of the solvent was reduced by vacuum distillation. Hydrogen was reintroduced. After the yellow colour had faded again, hexanes (40 mL) were added to induce precipitation. The suspension was filtered and the white product dried in a vacuum at room temperature for several days; yield 95%. Elem. Anal. Calcd. for C38H32O2P2RU: C, 66.8; H, 4.7. Found: C, 67.1; 4.8. IR (Nujol) 2012,1977 cm-1 v(CO); 1880,1825 cm-1 v(Ru-H); IR (CH2CI2) 2017,1977 cm-1 v(CO); IR (THF) 2019, 1981 cm-1 v(CO); 31p{ lH} NMR (C6D6) 8 56.29 ppm (s). JH NMR (CgDg) 8 -6.34 (t, 2H, 49 JPH=23.4 Hz, Ru-H), 7.05 (multi, 18H, m-,p-Ph), 7.90 ppm (multi, 12H, o-Ph). The UV/vis. absorbance was negligible between 625 and 350 nm, rising steeply at lower wavelengths. The IR frequencies, hydride chemical shift, and the 2jpn value are close to the reported values. 174 The white product has two carbonyl stretching bands in the IR spectrum, indicating cis carbonyls (C2V symmetry). The complex contains magnetically equivalent hydride ligands and magnetically equivalent phosphorus atoms, as indicated by the high field triplet in the lH NMR spectrum. Therefore two structures are possible; cct and tec. L'Epplattenier and Calderazzol78 favoured the former, but presented no evidence. Because the lH NMR signal of the o-phenyl protons is separated from that of the m- and p-phenyl signals by greater than 0.5 ppm, a phenomenon associated with trans phosphines 180, then the observed isomer is believed to be ccr-RuH2(CO)2(PPh3)2. 2.3.4 ccr-RuH(CI)(CO)2(PPh3)2 The complex RuH(Cl)(CO)2(PPh3)2 (4) has been synthesised from RuHCl(CO)(PPh3)3 and, in the method used here, from RuCl20?Ph3)3. RuHCl(CO)L3 + CO—> RuHCl(CO)2L2 + L 2.15 (Ref. 175) dma 1:1 H2/CO RUCI2L3 + H2 > R11HCIL3 RuHCl(CO)2L2 + RuCl2(CO)2L2 2.16 -HCl (dma = N,N-dimethylacetamide, ref. 164,181) RuCl20?Ph3)3 (0.40 g, 0.42 mol) was dissolved in 10 mL of degassed dma under H2 (1 atm), giving a red-brown solution. After 30 min, the hydrogen atmosphere was replaced with CO (1 atm). The solution turned yellow within 5 min. After another 30 min, the solvent volume was reduced by vacuum distillation, and methanol (20 mL) added The resulting white precipitate was filtered and dried under vacuum. The yield was 40%. 31p{ IH} NMR (C6D6) 8 38.43 ppm 50 (s). *H NMR (CgDg) 8 -3.86 ppm (t, JPH=19.2 Hz, Ru-H), 7.04 (multi, m- andp-phenyl), 7.99 (multi, o-phenyl). The NMR data match those reported by Dekleval82 for ccr-RuH(a)(CO)2(PPh3)2, synthesized from RuH(Cl)(PPh3)3 in CH2CI2 under CO. The wide difference in chemical shifts between the m-lp- and the o-phenyl signals indicates the presence of trans phosphine ligands; the structure is therefore cct. Joshi and James 183 reached the same conclusion based on the 13c NMR spectrum of a sample of 4 formed by hydrogenolysis of a norbomenolyl derivative. In the lH NMR spectrum of 4, the ratio of the peak areas of the hydride versus the phenyl proton signals is 1:21, although 1:30 is the theoretical value. The difference is caused by the longer Ti values of the phenyl protons, which do not allow for complete relaxation between pulses. The same effect is observed in an analytically pure sample of the similar complex cct-RuH(SEt)(CO)2(PPh3)2 (Chapter 3), for which the hydride.phenyl peak area ratio is also 1:21 under the same NMR conditions. As noted, the second step of the synthesis involved exposure of the solution to CO and not the 1:1 H2/CO mixture recommended earlier.164 The use of CO alone is reportedl64 to give fcc-RuCl2(CO)2Q?Ph3)2. However, in our hands, the pure CO treatment reproducibly gave pure ccf-RuHCl(CO)2(PPh3)2; the reason for the differing results is not known. 2.3 J cis- and fra/zs-RuCr2(dpm)2 The cis (5) and trans (6) isomers of the complex RuCl2(dpm)2 can be differentiated by lH and 31p{ lH} NMR spectroscopy. The ratio of isomers depends on the synthetic method. Those reported to produce the trans isomer are: ethanol RuCl3 + 2dpm > RuCl2(dpm)2 2.17 reflux (ref. 184) SI 1. ethanol, reflux RuCl3 + CO » RuCl2(dpm)2 2.18 2. C6H5, reflux, dpm (ref. 185) RUCI2L3 + 2dpm —> RuCl2(dpm)2 + 3L3 (ref. 186) 2.19 The reactions reported to form the cis isomer are: dpm RuCl3 + L' —> L'3Ru(uCl)3RuL'3 L'=PEt2Ph (ref. 184) » RuCl2(dpm)2 2.20 toluene RuCl2(dmso)4 + 2dpm 80°C » RuCl2(dpm)2 + 4dmso 2.21 (ref. 187) Although no X-ray crystal structure of either isomer has been reported, that of the related complex iranj-RuCl20?h2PCH2AsPh2)2 has been described by Balch et al. 188 A sample of 5 was kindly donated by Dr. C.-L. Lee, who had prepared it by the method of Chaudret et a/.187a; A solution of RuCl3-3H20 (2 g, 8 mmol) in dmso (30 mL) was refluxed for 30 min, during which time it turned yellow/orange. After reduction of the volume to 10 mL, and addition of a large excess of acetone, a yellow precipitate of cw-RuCl2(dmso)4 formed. This was collected by filtration and dried under vacuum. A refiuxing 100 mL toluene solution of this product (1 g, 2 mmol) and dpm (1.6 g, 4.2 mmol) turned bright yellow over 2 h. The solution was then allowed to cool, and diethyl ether (100 mL) was added. Filtration afforded a yellow product 31p{ lH) NMR (C6D6) -0.44 ppm (t), -26.72 ppm (t). Similar 31p{ lH} NMR shifts and coupling constant have been reported. 187 A mixture of £ and 6 was also synthesized and donated by Dr. C.-L. Lee; RuCl3-3H20 (3 g, 10 mmol) in methanol (250 mL) was refluxed for 2 h, with hydrogen gas bubbling through the solvent The resulting solution was transferred into a boiling mixture of methanol, dpm (9.2 g, 52 24 mmol), and 37% aqueous formaldehyde (7 mL). Refiuxing was continued for another hour, after which the solution was cooled to room temperature and filtered. The yellow compound was reprecipitated twice from CH2a2/petroleum ether. 31p{ IH} (CD2CI2) 5 -0.35 (t, Jpp=35.9 Hz, 5), -8.03 (s, 6J, -26.38 ppm (t, JPP=35.9 Hz, 5). The integration showed that 70% of the mixture was the trans isomer 6_. The 31p{ lH} NMR chemical shift of 6 in CH2CI2 is -6.9 ppm,186 relative to P(OMe)3 at 141 ppm downfield of 85% H3PO4. 2.3.6 RuH2(dpm)2 Difficulties encountered in the synthesis of RuH2(dpm)2 (7) have no doubt restricted its use in experimental chemistry. The complex cannot be formed by the reactions of dpm with RuH20?Ph3)4, or LiAlH4 with RuCl2(dpm)2 (5 or 6J, which instead form RuH2(dpm)(PPh3)2l87 and RuHCl(dpm)2,189 respectively. The reaction of NaBH4 with 5 produced mostly RuH(TllBH4)(dpm)2 with some Ru(T|lBH4)2(dpm)2 (Section 2.3.7). The only successful method to date requires the preparation of the air-sensitive compound Ru(COD)(CX)T) (CX)D=l,5-cyclooctadiene, CX)T=l,3,5-cyclooctatriene). COD dpm H2 RuCl3 > Ru(COD)(COT) > Ru(COD)(dpm)2 > RuH2(dpm)2 2.22 Zn (ref. 187,190) A 20 mL ethanol solution of COD (17 mL, 140 mmol) and RuCl3-3H20 (0.7 g, 2.7 mmol) was refluxed under argon for 20 min. Zn dust (6 g), activated by washing with water, 2% HCl, EtOH, and dry Et20, was added. The resulting mixture was refluxed for 45 min, filtered, and dried to a gelatinous residue by overnight evaporation under vacuum. The solubles from this residue were extracted by washing with pentane (100 mL), and passing the resulting solution through a 20 cm neutral alumina column (Brockmann Activity U 80-200 mesh). The volume of the yellow filtrate was reduced to 5 mL by vacuum transfer. The solution was cooled in a dry 53 ice/acetone bath overnight, resulting in the formation of yellow crystals.191 A 20 mL toluene solution of dpm (640 mg, 1.7 mmol) was added to the product After overnight exposure to H2, the solution was reduced in volume by vacuum transfer of most of the solvent, and hexanes (20 mL) were added to encourage the formation of the yellow precipitate, which was collected by filtration. 191 The overall yield is typically low (10-40%), and attempts by Dr. C.-L. Lee to perform increased-scale syntheses resulted in lower, not higher yields. Characterization of cis- and tanu-RuH2(dpin)2: Elem. Anal. Calcd, for R11P4C50H46: C, 68.9; H, 5.3. Found: C, 68.9; H, 5.2. lH NMR (C6D6)191 8 -7.58 (dq, 2JtransPH = 73 Hz, 2JcisPH = 18 H*. RuH of cw-isomer), -4.80 (qn, 2JCJSPH = 19 Hz, RuH of fra/w-isomer), 4.10 (multi, CH2 of cis-isomer), 4.63 (multi, CH2 of rra/w-isomer), 4.81 ppm (multi, CH2 of ris-isomer). 31p{lH} NMR (C6D6)!91 8 14.06 (t 2JcisPP = 19-3 ^ «$-isomer), 9.11 (s, tfww-isomer), 0.57 ppm (t 2JcisPP = 18.8 Hz). Similar lH NMR data has been reported.47 The product is always formed as a 1:4 mixture of the trans and cis isomers. 187 Although this was the synthetic method used by G. Rastar and the present author to prepare samples for the present study, the reaction of NaBH4 with 5 was investigated as a possible alternate route (Section 2.3.7). 2.3.7 An Attempted New Synthesis of RuH2(dpm)2: The Synthesis of trans-RuH(r]lBH4)(dpm)2 Hydrogen was bubbled through a suspension of m-RuCl2(dpm)2 (0.5 g, 0.5 mmol) in benzene (30 mL) and methanol (50 mL) for 10 min. Fresh sodium borohydride (2 g, 50 mmol) was added in 3 portions over 5 min. Hydrogen was bubbled through the resulting mixture for 1 h, after which methanol (100 mL) was added. The white product isolated by filtration was washed with methanol (20 mL) and dried under vacuum at room temperature. The yield was 0.45 g. The spectroscopic analysis of the product is consistent with RuH(r|lBH4)(dpm)2 (8), 54 although the presence of some Ru(TjlBH4)2(dpm)2 is suggested by the FAB/MS data. Reprecipitation from methanol/benzene resulted in partial conversion to RuH2(dpm)2. As a result, the elemental analysis was of an unpurified sample. RuCl2(dpm)2 + 2NaBH4 —> RuH(BH4)(dpm)2 + 2NaQ + "BH3" 2.23 Elem. Analccalcd. for C50H49BP4RU: C, 67.8; rL5.6. Found: C, 65.2; H, 5.5. FT-IR (Nujol or HCB): 2397 cm-1 (v(B-Ht), VD/VH = 0.755); 2346 (v(B-Ht), 0.754); 1788 (v(B-Hb) or v(Ru-Ht), 0.732); 1069 cm-1 (8(BH3), 0.723); *H NMR (C6D6,20°C) 5 -10.60 (qn, IH, 2JPH = 19.5 Hz, Ru-H), -1.05 (br, 4H, BH4), 4.53 (dt, 2H, 2jHaHb = 14 Hz, 2jPH = 3 Hz, CHa (methylene)), 4.97 (dt, 2H, 2jHaHb = 14 Hz, 2jPH = 4 Hz, CHb (methylene)), 6.88 (multi, 12H, m-/p-Ph), 7.07 (multi, 12H, m-/p-?h), 7.46 (s, 8H, o-Ph), 7.71 ppm (s,8H,o-Ph); lH NMR (C6D5CD3, -89°C) 5 -10.5 (br, RuH), -9.0 (br, Ru-Hb-B); *H NMR Tl values (C6D5CD3,20°C) 0.36 s (BH4), 0.56 s (RuH), (C^CD^ -58°C) 0.26 s (BH4), 0.35 s (RuH); 31p{ lH} NMR (C6D6,20°C) 8 2.43 ppm (s); 1 *B NMR (C6D6.20°C) 8 -2 (br, major), 46 (br, minor), -46 ppm (br, minor); FAB/MS (p-nitrobenzylalcohol) m/e 1036 {RuH(BH4)(dpm)2-02NC6H4CH20H}; 1008 {RuH(BH4)(dpm)2.02NC6H4}; 900 {Ru(BH4)2(dpm)2}; 885 {RuH(BH4)(dpm)2); 869 {Ru(dpm)2}; 501 (RuH(BH4)(dpm)}; plus 20 other fragments (Table 2.1, Fig. 2.3). The lH NMR spectrum of the product 0?ig. 2.4) resembles that of trans-[RuH(T|2H2)(dppe)2]BF4,192 which has a broad peak at -4.6 ppm QH2) and a quintet at -10.0 ppm (JpH=16 Hz) in acetone-d6. However, the Tl measurements and the microanalysis, which showed the virtual absence of chlorine, eliminate the possibihty of the product being trans-[RuH(r|2H2)(dpm)2]Cl. Further, the THF and the benzene solutions of the product do not conduct at room temperature. 55 Table 2.1 Fragments detected in the FAB/mass spectrum of Ru(H)(BH4)(dpm)2 Observed m/z Expected m/z Fragment Allocation 1036 1038 RuH(BH4)(dpm)2 + O2NC6H4CH2OH 1008 1007 RuH(BH4)(dpm)2 + O2NC6H4 900 900 Ru(BH4)2(dpm)2 885 885 RuH(BH4)(dpm)2 869 869 Ru(dpm)2 791 792 Ru(dpm)(PPh2CH2PPh) 717 715 Ru(dpm)(PPh2CH2P) 685 684 Ru(dpm)(PPh2CH2) 669 670 Ru(dpm)(PPh2) 607 607 Ru(dpm)(PPhCH2) 593 593 Ru(dpm)(PPh) 531 530 Ru(dpm)(PCH2) 515 516 Ru(dpm)(P) 501 501 RuH(BH4)(dpm) 485 485 Ru(dpm) 468 468 Ru(BH4)(PPh2CH2PPh)(PCH2) 439 439 Ru(PPh2CH2PPh)(P) 417 407 408 Ru(PPh2CH2PPh) 393 394 Ru(PPh2)(PPh) 363 362 Ru(PPh2CH2PPh)(P) 331 331 Ru(PPh2CH2P) 315 317 Ru(PPh)2 285 285 Ru(PPhCH2P)(P) 285 286 Ru(PPh2) 253 254 RufPPhCH^ TABLE 22 lH NMR DATA FOR *ra/w-RuH(X)(dpm)2a X H* Hb Ht _JPHb JHaHh JPT-Tt solvent ref. H 4.6 4.6 -4.8 n.a. n.a. n.a. 18.9 C6D6 b H - - -4.7 n.a. n.a. n.a. 19.7 CD2CI2 187 SH 4.5 5.2 -9.5 3 - 16 19 C6D6 c SPh 4.3 4.8 -10.9 3.3 - 13.8 19.9 C6D6 c SBz 4.4 5.2 -10.2 32 - 13.5 20.0 C6D6 c BH4 4.5 5.0 -10.6 3.1 4.2 14.2 19.5 C6D6 d Cl - - -14.1 - - - 19.7 CD2CI2 187 H2O 4.6 5.2 -18.8 3.5 3.5 11.5 19.1 (CD3)2CO 187 CO 5.4 5.4 - - - - - CD^OD 185 a n.a. = not applicable Ha, Hb = methylene protons Ht = terminal hydride Coupling constants and chemical shift in Hz and ppm, respectively b Section 2.3.6 of this work c Section 3.4 of this work d* Section 2.3.7 of this work —I— 500 —i— 550 —i— 600 Fig. 2.3 FAB mass spectrum of RuH(BH4)(dpm)2 in /Miitrobenzyl alcohol. , I I I f I I i i i I I I i i . , • . i , i I . i i ; i i i t I . . i . 1 i . i • I i i I i i i | i i • • i » i ; i i . i | ! i i . | i i i t ; i i i i l i i i i | i i i i | i iji 8 6 4 2 0 -1 -4 -6 4* -lOppm Fig. 2.4 lH NMR spectrum of RuH(BH4)(dpm)2 under H2 at 20<>C, 300 MHz a) full spectrum (solvent = C6D6) b) phenyl region (C6D6) c) methylene region (C6D5CD3) 58 The methylene region of the *H NMR spectrum contains an ABX2 pattern, consistent with a /ra/tf-Ru(X)(Y)(dpm)2 structure, and the coupling constants and chemical shifts are comparable to those in similar complexes (Table 2.2). In the phenyl region, two multiplets are observed for the o-phenyl protons, and two for the m- and p-phenyl protons, compared to only one of each type for £. The complexes of the formula /ra/ts-RuX2(dpm)2 are of D4h symmetry, and have equivalent phenyl groups. In contrast, fra/ts-RuX(Y)(dpm)2 complexes (Qv) such as 8 have phenyl groups in two different environments; four in the hemisphere of the X, and four in the hemisphere of the Y ligand. The linewidth of the broad peak in the iH NMR spectrum increases as the temperature decreases, while the terminal hydride remains at -10.5 ppm, although the quintet pattern is not resolved at lower temperatures Q?ig. 2.5). At -79°C, the broad peak is barely visible, and a new broad peak at -9.0 ppm appears. These changes are believed to result from the slowing down of the exchange between the BHt (terminal) hydrogens and the hydrogen(s) bridging the Ru and B atoms, the new peak being due to the bridging hydrogen. At -89°C the integral of that peak has increased to half that of the quintet at higher field. At even lower temperatures, where the peak would be better resolved, the area should be equal to that of the quintet, assurning VIBH4 coordination. The peak for the terminal borohydride hydrogen atoms, if it were close to that of B2H6 (8 = 4 ppm),193a,194 woui(j be obscured by the solvent The slowing of the exchange has been observed in only a few borohydride complexes. 193 The lH NMR spectrum of a toluene-dg solution of the complex changed irreversibly at temperatures greater than 50°C; the principal product was 7. RuH(BH4)(dpm)2 —> RuH2(dpm)2 + "BH3" 2.24 8 7 The complex fra/w-RuD(BD4)(dpm)2 was synthesized from 5 and NaBD4 under H2. The lH NMR spectrum of this product indicates 88% deuteration at the hydride and borohydride positions. This suggests that H2 played no role in the reaction, and indeed later experiments 59 I'i''i'ii'|iiii 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 11 i i i i i i 0 -2-4-6 -8 -10 PPM Fig. 2.5 *H NMR (300 MHz) spectra of RuH(BH4)(dpm)2 in C6D5CD3 below ambient temperatures. 60 showed that N2 was as effective in the synthesis. The pattern at 4.97 ppm due to one of the methylene protons has changed to a triplet at 4.93 ppm (JpH=4.3 Hz). Including this triplet, the ratio of the multiples at 4.9 and 45 ppm has changed from 1:1 in RuH(BH4)(dpm)2 to 1:0.5 in RuD(BD4)(dpm)2. Therefore monodeuteration at the methylene site has occurred, giving a complex of the ligand Ph2PCHDPPh2. The H-D coupling is not resolved. The 1 IB NMR spectra of & or the borodeuteride contain a very broad singlet (wo.5=3000 Hz) at -2 ppm, and two equally broad minor peaks which are present in varying intensities of up to 25 % in different samples. None of the peaks have been positively identified, although the fact that three peaks were observed suggests that none of the samples are pure. No changes in the spectrum were observed down to -80°C or with broad band *H decoupling. Very few 1 *B NMR spectra of transition metal borohydride complexes have been reported; for example, the spectrum of IrH2(Tl2BH4)(PBut2Me)2 consists of a singlet at 13.1 ppm (wo.5=350 Hz) in C^Dg.195 The IR spectra of borohydride complexes are characteristic for the bonding mode of the BH4-ligand. 193b, 196 Four structures have been considered M—H—B -..„, H M M-H,(ft,...-B—H M+BH/ ^H \r H ^H^ i n m rv The IR spectrum of fi and its deuteride (Fig. 2.6) are most consistent with structure L Structures UJ and rV have v(B-Ht) bands at 2450-2600 and 2200-2300 cm-1, respectively, 195 which are not observed in the spectrum of fi. Structure II requires a bridge stretching band at 1300-1500 cm-1, but no peak appears in this region of the spectrum of fi which does not appear in that of RuD(BD4)(dpm)2. However, Marks and Kolbl°5 predicted that for structure I two bands, v(M-Hb) and v(B-Hb), would be observed in the region of 1650-2150 cm-1. Based on this, the one band at 1788 cm-1 in the spectrum of 8 is more consistent with structure H However, Holah et 0/.196 took the absence of a band at 1900-2000 cm-1, as found here, to be indicative of structure I rather than II, and this suggests mat structure I is the correct assignment The IR results are 61 Fig. 2.6 FT-IR spectra of HCB mulls of a) RuH(BH4)(dpm)2 and b) RuD(BD4)(dpm)2 (88 % deuteration). The peaks due to HCB are marked with asterisks. 62 therefore somewhat ambiguous, but structure II, a 20 electron, seven-coordinate species, is considered unlikely. The monodentate borohydride complex FeHQHBH3)(dmpe)2, which has been structurally characterized as type I, has IR bands (cm-1) at 2340 (v(B-Ht)), 2030 (v(Fe-Hb), v(B-Hb)), 1788 (v(Fe-Ht) and 1045 (BH3 def.).197 Ruthenium borohydride complexes which have been reported include RuH(BH4)0?R3)3 (PR3=PPh3,198-200 pph2Me,201 PPhMe2,202 or RUH(TI2BH4)(CO)(PR3)2 (PR3=PPh3,200 p/Pr3, PMe(*Bu)2204), RuH(BH4)(CX))2(PCy3)2200. CpRu(BH4)0?R3)2 (Cp=C5H5 or CsMes, R=Ph,205 Me, Et, Cy206), and Ru3(CO)9(H)(BH4)207. Although RuH(BH4)(dpm)2 reacts with Lewis bases such as thiophene and amines to form RuH2(dpm)2, this route is not of higher yield or greater reliability than the preparation of the latter complex from Ru(COD)(COT). Note added in proof: Bianchini et al.302 have very recently reported the synthesis of RuH(TilBH4)(PP3) from RuCl2(PP3) andNaBlLi (PP3 = P{CH2CH2PPh7}3). The variable temperature lH NMR spectra of the complex bear a strong resemblance to those of RuHOl lBH4)(dpm)2. 63 3. THE REACTIONS OF RUTHENIUM COMPLEXES WITH THIOLS 3.1 THE REACTION OF Ru(CO)2(PPh3)3 WITH H2S AND THIOLS The RuO complex Ru(CO)2(PPh3)3 (2) reacts rapidly at room temperature with a variety of ligands, including H2, C2H4, PhCCPh, 02,!73 and C0.177 A possible mechanism, based on the reported kinetics for the reactions with H2 and CO is: 172 *1 Ru(CO)2(PPh3)3 <== Ru(CO)2(PPh3)2 + PPI13 3. la 2 k-i *2 Ru(CO)2(PPh3)2 + X —> RuX(CO)2(PPh3)2 3.1b 3 or 10 -_dm= JhJbf21IXl di Jfc-i[PPh3]+*2[L] where X= CO or H2 and RuX(CO)2(PPh3)2 = Ru(CO)3(PPh3)2 (IQ) or RuH2(CO)2(PPh3)2 (3J The rate of reaction shows an inverse dependence on [PPI13]. In the absence of added PPI13, the rate is independent of [X], suggesting that under these conditions the second term in the denominator of the rate law is significantly greater than the first, and that the overall rate is determined by the rate of PPI13 loss for both the H2 and CO substitution reactions.172 The oxidative addition reaction of 2 with H2S, examined earlier in this laboratory,86 Ru(CO)2(PPh3)3 + H2S —» RuH(SH)(CO)2(PPh3)2 + PPh3 3.2 2 9a is complete after 2 h at -35°C in THF. The product is isolated in 95% yield by addition of hexanes.86 This reaction and the corresponding reactions with thiols (briefly examined in an earlier report from this laboratory)86 and selenols 64 Ru(CO)2(PPh^)3 + REH —> RuH(ER)(CO)2(PPh3)2 + PPh3 3.3 ER = 9a SH, fe SC6H4/7CH3, £ SCH3, d SCH2CH3, £ SCH2C6H5, f SC6H40CH3, g SC6H4mCH3, h SeC6H5, i SC6H5, or j SC6F5 are complete within minutes at room temperature, and form a series of products with the formula RuH(ER)(CO)2(PPh3)2 (9), the characterization of which is described in the following section. Complex 2 failed to react with ethanol (85 mM) in THF. Alcohols are structurally similar to thiols, but are much less acidic (pKa's 3.5 to 5.5 units higher). We shall see in Section 3.5 that the more acidic thiols bind more strongly in these systems than the less acidic thiols. 3.2 THE CHARACTERIZATION OF RuH(ER)(CO)2(PPh3)2 Analytically pure samples of several of the title complexes (9a, c-h) have been isolated. The carbon analyses of 9b and 9j were 1% low. In addition, 9j was isolated but not purified, and samples of RuH(SCH2CH3)(CO)2(PPh2Py)2 (lid) (where PY-2-C5H4N) and RuH(SCH2CH3)(CO)2(P(C6H4£»CH3)3)2 (12d) were prepared in situ in C6l>6 in order to make comparisons with their NMR spectra. The lH NMR spectra of 9 (Figs. 3.1 and 3.2, and Table 3.1) contain a high field triplet due to the hydride ligand, split by two equivalent phosphines. The coupling constant 2jPjj is within the range 19.5 to 20.5 Hz in C6D6. comparable to those of other complexes with phosphines cis to hydride ligands, such as mer-RuH2(CO)(PPh3)3 (cis 2JpH=16,29,30 Hz, trans 2JPH=74 Hz),208 65 m-j)-Ph o-Ph CH2 8 Ru-H JU 1 I I T | 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 | | I | I I I I | I I I I | I I I I | I | I | 8 6 4 2 0 -2 -4ppm Fig. 3.2 lH NMR spectrum of ccf-RuH(SCH2Ph)(CO)2(PPh3)2 (2fi) in C6D6 at 20OC and 300 MHz. 67 Table 3.1 31P{1H} and *H NMR Data for cc/.RuH(ER)(CO)2(PPh3)2 Complexes in C6D6 at 20OC and 300 MHz. 9 ER 3 lPa Ru-Hb 2JPH CH3 Other 9a SH 42.01 -4.79 20.1 - -3.00 (t, 3JPH=4.9, 3JHH=3, SH) 9c SCH3 37.14 -4.68 20.5 1.04 -9d SCH2CH3 37.25 -4.67 20.4 0.77 1.28(q,3jHH=7.4,CH2) 9e SCH2C6H5 37.09 -4.63 20.3 - 2.53 (s, CH2) 9i SC6H5 37.26 -4.32 19.5 - -9) SC6F5 38.45 -4.31 19.5 - -9b SC6H4/7CH3 37.43 -4.33 19.5 2.04 -H SC6H4mCH3 37.39 -4.36 19.5 1.93 -9f SC6H40CH3 36.55 -4.23 19.5 2.19 -9h SeC*Hs 36,98 -4.75 19,8 - -a singlet. b triplet, except for that of 9_a, which is a doublet of triplets (3JHH = 3 Hz). Table 3.2 FT-IR Data for cc/-RuH(ER)(CO)2(PPh3>2 Complexes in Nujol, HCB, or CH2CI2 at room temperature.^ 9 ER Nujol v(CO) vfRuH) HCB v(CO) vfRuH) CH2Cl2D vfCO) 9a SH 2029,1984 1901 2035,1979 9c SCH3 2021,1970 1899 2023,1971 1902 9d SCH2CH3 2025,1964 1925 2029,1971 9e SCH2C6H5 2019,1981 b 9i SC6H5 2030,1981 1920 9b SC6H4PCH3 2021,1987 1900 2021,1987 1900 2033,1975 9g SC6H4mCH3 2026,1983 1906 2035,1975 9f SC6H40CH3 2025,1991 1900 2035,1977 9h SeC*Hs 2027.1978 1919 a All frequencies in units of cm-1. b v(RuH) not detected. 68 CO PPh3 Ph3P/,""-Ru^XPPh3 Ru *^ PhjP^ | >Ni OC^ | >>SH H PPh3 wtfr-RuH2(CO)(PPh3)3 ccr-RuH2(CO)2(PPh3)2 ccr-RuH2(CO)2(PPh3)2 (cis 2jpn=23.4 Hz, Section 2.3.3), and others. 178,187 The 31p{ lH} NMR spectra of 9_ consist of a sharp singlet, indicating equivalent phosphines and a lack of rapid exchange with free phosphine. The IR spectra of 9_ in Nujol mull (Fig. 3.3) include two carbonyl stretch bands of unequal intensity, one in the range 2019 to 2030 and the other in the range 1964 to 1991 cm-1, and a single v(Ru-H) stretch at 1899 to 1925 cm-1; the exact frequencies are listed in Table 3.2. In CH2CI2 solution, the v(CO) bands appear at 2035 and 1979 (ER=SH) or 2029 and 1971 cm-1 (ER=SC2H5), and the v0lu-H) band is not detected. The presence of two carbonyl bands in the IR spectra indicates that the carbonyls have cw positions in both solid state and in solution. There are two possibilities for the structure of 2 in solution, given that the phosphine ligands are equivalent and cis to the hydride ligand, and the carbonyl ligands are mutually cis: H PPh3 OGNL ^PPH3 0C8NL>*H OC^ I ^PPh, OC^ I >%ER ER PPh3 tec cct The relative positions of the phosphines were determined by lH and 13C{ lH} NMR spectroscopy. If the two PPh3 ligands are trans, the 13C{ lH} NMR signal of the phosphorus-bound carbons should be a triplet, and the chemical shift difference between the o- and the m-lp-phenyl signals in the lH NMR spectrum should be greater than 0.5 ppm. Conversely, if the two PPh3 ligands are cis, then the 13C NMR signal should be a doublet,171 while the lH NMR 90OO S200 2SOO 2000 1700 1400 1 IOO 800 SDO 200 wavenumbers (cm-1) Fig. 33 a) The FT-IR spectrum of ccf-RuH(SMe)(CO)2(PPri3)2 (5s) In HCB. The peaks due to HCB are marked with asterisks, b) The carbonyl region of the corresponding spectrum of c<*-RuH(SPh)(CO)2(PPh3)2 (50. 70 chemical shift difference should be less than 0.5 ppm. 180 jhe *3C spectrum (Fig. 3.4) of RuH(SC2H5)(CO)2(PPh3)2 in CD2CI2 shows triplets at 135.6 (t, I Jcp+JcP* I =23-3' P"C). 134.6 (t, I Jcp+JcP' I =5-9» °-PH)>128-2 (t. I JCP+JCP' I =4-4» M"PH)» 8X1(1 13(U PPm (s» P-ph)-The lH NMR chemical shift difference between the o- and m-/p-phenyl signals of complexes 9ja.-j in C6D6 is 0.9 ppm. These observations show that the phosphine ligands are trans, and therefore that 9_ exists as the cct isomer in solution. The solid state structure of 9Jb was investigated by X-ray crystallography, and was shown to be the cct isomer (Figs. 3.5 and 3.6 and Tables 3.3 and 3.4).209 No other monomelic ruthenium hydrido thiolato complex has been crystallographically characterized, although the structure of a triruthenium complex has been reported.98 Some deviations from the octahedral geometry at the metal are due to the four ligands cis to the hydride ligand crowding the hydride. The P-Ru-P bond angle is 172.6o, and the C(l)-Ru-S bond angle is 167.2o. The Ru-S bond length (2.458 A) is similar to that for the thiolate ligand (2.453 A) trans to a carbonyl in the complex Ru(pyS)2(CO)2(PPh3)2 (pyS=o-SC5H4N).210,211 Shorter RuH-S bonds (2.406 to 2.429 A) exist in thiolate ligands trans to weaker Tt acceptors than CO, such as phosphine or thiolate groups,210-12 although an apparent exception is (PhMe2P)3Ru(LiSH)3Ru(PMe2Ph)2(SH) with a terminal Ru-S (trans to a bridging SH ligand) bond length of 2.44 A.213 The MD-S-C bond angle is large (113.6°) in 9b, as it is in other complexes with thiolates trans to carbonyls, such as Fe(SPh)2(CO)2(dppe) (112.4 to 114.90)214 Smaller angles (107.7 to 109.6O) are found in complexes with thiolates trans to phosphine or thiolate ligands.210-2,214 The length (1.875 A) of the Ru-C bond trans to the thiolate ligand in 9b is slightly shorter than that found in Ru(pyS)2(CO)2(PPh3) (1.895 A),2H possibly because of the intramolecular interactions which exist in the pyridyl complex. The Ru-C bond trans to hydride is 1.945 A in 9Jb, (cf. 1.970 A in [RuH(H20)(CO)2(PPh3)2]+),215 longer than that trans to the thiolate because of the strong trans influence of hydride ligands.216 The aquo complex shows o-Ph P-Ph m-Ph P-C 1111 11' 111111111111I;1111111111111111111111111111 n 11111111111111111111111111111|iM 136 135 134 133 132 131 130 129 128 ppm CH2 CD2CI2 _JL_ CH3 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 ' T I I I I I I | I I I I I I 140 120 100 80 60 ' 1 1 1 I 1 1 1 1 I 1 1 1 1 I 40 20 ppm Fig. 3.4 13C{lH) NMR spectrum of ccl-RuH(SEt)(CO)2(PPh3)2 (9d) in CD2CI2 at 20OC and 75 MHz, as provided by Dr. C.-L. Lee. Inset shows an expansion of the phenyl region. 72 Fig. 3.6 Stereo-view of the structure of cc/-RuH(SC6H4pCH3KCO)2(PPh3)2 (9b). Hydrogen atoms (other than hydride) omitted for clarity. 73 Table 33 Selected bond lengths (A) with estimated standard deviations in parentheses, for RuH(SC6H4pCH3)(CO)2(PPh3)2 (26). atom atom distance Ru H(l) 1.58 (3) Ru C(l) 1.875 (3) Ru C(2) 1.945 (3) Ru P(D 2.361 (1) Ru P(2) 2.381 (1) Ru S 2.458 (1) S C(39) 1.769 (3) Pd) C(3) 1.828 m atom atom distance P(l) C(9) 1.835 (3) P(l) C(15) 1.836 (2) P(2) C(21) 1.825 (3) P(2) C(33) 1.834 (3) P(2) C(27) 1.837 (3) O(l) C(l) 1.136 (3) 0(2) C(2) 1.135 (3} Table 3.4 Selected bond angles (°) with estimated standard deviations in parentheses, for RuH(SC6H4pCH3)(CO)2(PPh3)2 (2b). atom atom atom angle atom atom atom angle H(l) Ru C(l) 81(1) C(39) S Ru 113.6(1) HQ) Ru C(2) 176(1) C(3) P(D C(9) 105.4 (1) H(l) Ru P(D 87(1) C(3) P(D C(15) 102.3 (1) H(l) Ru P(2) 88 (1) C(3) P(D Ru 117.53(9) H(l) Ru S 87 (1) C(9) P(D C(15) 101.1 (1) C(l) Ru C(2) 96.0 (1) C(9) P(D Ru 111.35 (8) C(l) Ru P(D 92.80 (9) C(15) P(D Ru 117.30 (8) C(l) Ru P(2) 91.59 (9) C(21) P(2) C(33) 103.3 (1) C(l) Ru S 167.2 (1) C(21) P(2) C(27) 104.4 (1) C(2) Ru P(l) 93.79 (8) C(21) P(2) Ru 115.49(8) C(2) Ru P(2) 91.64 (8) C(33) P(2) C(27) 101.2 (1) C(2) Ru S 96.7 (1) C(33) P(2) Ru 113.98 (8) P(D Ru P(2) 172.63 (3) C(27) P(2) Ru 116.71 (9) P(D P(2) Ru S 84.04 (4) 0(1) C(l) Ru 174.3 (3) Ru s 90.39 (4) 0(2) C(2) Ru 173.4 (3) Table 33 31p{lH} and lH NMR Data for RuH(SEt)(CO)2L2. L! 8 5 RuH 2LP Qi? CH3 3IHH_ Ptol3(12) 35.17 -4.52 20.2 1.46 086 12 PPh3(9d) 37.25 -4.67 20.4 1.28 0.77 7.3 PPh?Pv(ll) 39.76 -4.06 20.7 0.97 0.79 7.2 aPh=C6H5 tol=C6H4pCH3 Py=-2-C5HsN 74 inequivalent Ru-P bond lengths that result from crystal packing effects The Ru.p DOn(i lengths in 9b are essentially equivalent, and match closely those in related complexes 215,217 The Ru-H bond length in 9Jj is slightly shorter (1.58 A) than those found in [RuH(H20)(CO)2(PPh3)2]+ (1.7 A),215 RuH(Cl)(PPh3)3 (1.7 A),218a and trans-RuH(Cl)(diop)2 (1.65 A)218b (diop = 4,5-bis(((hphenylphosphmo)me%l)-2,2-dimethyl-1,3-dioxolane). The effects of changes in the ER group on the NMR spectra of these complexes correlate with differences in electron-withdrawing ability and steric bulk. The chemical shift (8) of the hydride ligand (Table 3.1) decreases as the thiolate ligand is changed in the order: SC6H40CH3 > SAryl » SAlkyl > SeC6H5 > SH -4.23 -4.33±0.03 -4.65±0.03 -4.75 -4.79 This order is consistent with an electronic effect, and is almost the same as that observed for the acidic protons of the free thiols themselves in the same solvent, C6D6. ArylSH > CH3C6H40SH » AlkylSH = C6H5SeH > H2S 3.1±0.1 2.92 1.2±0.2 1.19 0.20 The coupling constant 2JPH (Table 3.1) is less variable than the chemical shift, having values of 19.5 (SAryl), 19.8 (SePh), 20.1 (SH) and 20.4 ± 0.1 Hz (SAlkyl). The chemical shift and the coupling constant provide a reliable indication of the nature of the R group in complexes of the formula RuH(SR)(CO)2(PPh3)2-The chemical shift of the 3 lp {lH} NMR singlet varies in a different order, with the ER = SH and SC6H40CH3 positions completely reversed compared to the previous sequence, SH » SC6F5 > SAryl > SAlkyl > SeC6H5 > SC6H40CH3 42.01 38.45 37.35±0.9 37.1410.11 36.98 36.55 presumably because of the steric effect of these ER groups on the Ru-P distance. The 31p chemical shift of ccr-RuX(Y)(CO)2(PPh3)2 complexes depends strongly and inversely on the Ru-P bond length, which in turn depends on the bulk of the X and Y ligands (Fig 3.7). This 75 25 31p NMR Chemical shift (ppm) Fig. 3.7 Relationship between the 31P NMR chemical shift and the Ru-P bond length of thiolato-phosphine ruthenium complexes (•). The line is that fitted by Dekleval82 to data for triarylphosphine ruthenium complexes (o). wavelength (nm) Fig. 3.8 The UV/vis. spectra of cc/-RuH(ER)(CO)2(PPh3)2 (2) in THF at room temperature, where ER = SC6H4/>CH3 (9_b), SCH3 (2c), or SeC*Hs (2b) The spectra of Ru(CO)2(PPh3)3 (2J and RuH2(CO)2(PPh3)2 (3) are included for comparison. 76 correlation was reported for a series of ruthenium hydrido, chloro, and/or acetato phosphine complexes. 182 The bond lengths and chemical shifts of the four thiolato complexes 9_b, 14a, 14b (Section 4.2), and 21 (Section 5.3) fit the reported correlation well. As has been observed for RuH(Cl)(CO)2(PPh3)2 with the dichloro- and dihydrido- analogues (1 and 3J.182 the 31p chemical shift of RuH(SR)(CO)2(PPh3)2 (42.01 for 2a) is within a few ppm of the average (38.35) of the chemical shifts of Ru(SR)2(CO)2(PPh3)2 (20.40 for R=H, Section 4.2) and RuH2(CO)2(PPh3)2 (56.29 ppm). The effect of changes in the phosphine ligand of RuH(SCH2CH3)(CO)20°R3)2 on the lH NMR spectra is summarized in Table 3.5. The three complexes 9d, 11, and 12 have similar spectra, presumably because PPI13, PPh2Py, and P(C6H4pCH3)3 are similar in nature. There is no apparent trend in v(Ru-H) in the IR spectra in Nujol. The symmetric v(CO) band is randomly scattered within a narrow 11 cm-1 range, while the asymmetric v(CO) band varies over a wider 27 cm-1 range, in the following order for RuH(X)(CO)20:>Ph3)2 in Nujol (the range of v(CO) values observed for CH2CI2 solutions of 9 is much narrower): X = SPhoMe > SPhpMe > SH = SPhmMe > SPh = asym. v(CO) 1991 1987 1984 1983 1981 SCH2Ph = Br164 > SePh > H > SMe » SEt 1981 1980 1978 1975 1970 1964 The rc backbonding from Ru to the CO n* antibonding orbitals, which lowers the v(CO), is seen to be stronger in alkyl vs. aryl thiolato complexes; the difference is attributed to the TC-acceptor ability of the aromatic rings. The UV/visible spectra of these complexes (Fig 3.8) contain a strong absorbance near 400 nm, which is most probably due to a thiolate ligand-to-metal charge transfer.219 The extinction coefficient and A-max are somewhat higher in the spectra of the aryl vs. alkyl thiolate complexes. The Xmax is particularly high in the selenolate complex. 77 ER , , =SeC6H5>SC6H4pCT3 = SC^5>>SCH2C6H5>SCH3>SC2H5 eCM'W1) = 1900 1900 1900 1300 1100 1000 XmaxCnm) = 411 398 397 393 395 396 The small and unpredictable effect of changes in the R group on the charge transfer bands of thiolato complexes has been observed previously in studies of /ra^-Tc(SR)2(dmpe)2n+ (n=0,l)220a and MoL4n" (L=dithio acid or 1,1-dithiolate ligand, n=2,3,4).220b Reported complexes similar in structure to 9_ include the following Ir79 and Os221 complexes. PPh3 PPh3 Cl CO, NvER PPh3 OC^ ;Os •SeSeMe PPh3 where E = S, Se; R = H, C3H7, C4H9, C6H5 33 THE REACTION OF RuH2(CO)20?Ph3)2 WITH H2S AND THIOLS As was shown in the previous report from these laboratories,86 the dihydride complex ccr-RuH2(CO)20?Ph3)2 (2) reacts with H2S or thiols at room temperature, giving complete conversion to RuH(SR)(CO)2(PPh3)2 (9_, R = H, alkyl or aryl) within 2 h. RuH2(CO)2(PPh3)2 + RSH —> RuH(SR)(CO)2(PPh3)2 + H2 3.4 2 9. The H2 produced in this reaction was qualitatively detected by gas chromatography and quantitatively measured in a gas-uptake experiment After 50 min at 30°C, the gas production due to reaction 3.4 had slowed to a value of 1.2 equivalents/Ru. 78 r 9_(RuSH) 2 (RuH) 2 (RuH) b) r 14_(RuSH) r e) r r i 1--2 —i IIII 1 i i -3-4-5-6 ppm Fig. 3.9 lH NMR spectra acquired during the reaction of cc/-RuH2(CO)2(PPh3)2 (2,10 mM) with H2S (1 arm.) in C6D6-a) after 2 to 9 minutes at 250C b) after 34 to 39 minutes at 25<>C c) after raising the temperature to 50©C. 79 The reaction of 2 with excess H2S was monitored by *H NMR spectroscopy (Fig. 3.9). The pseudo-first order log plot is linear for 3 half-lives, and the observed rate constant (at 25.0°C in C6D6) is 5.7x10-4 s-l. The rate of the reaction with ethanethiol in THF was monitored by the change in absorption at 400 nm in the visible spectrum (Fig. 3.10). Because the spectra of 2 and 9_ do not cross (Fig. 3.8), no isosbestic points are observed. If the reaction occurs under pseudo-first order conditions (large excess of EtSH), the log plot (Fig. 3.11) is linear for 4 half-lives. Shaking the vessel between absorbance measurements has no effect on the rate. Over the range 0.36 to 2.86 mM 3 at 95 mM EtSH and 260C, the rate constant is invariant (Fig. 3.12), which shows that the rate is first order with respect to [3J. The observed rate constant does not vary with changes in the thiol concentration. At 1 mM 3 the observed rate constant is essentially unchanged (Fig. 3.13) even though the thiol concentration was changed from 45 to 190 mM. The rate of reaction is therefore independent of [EtSH]. The value of the rate constant at 26©C is 6.7(±0.2) x IO-4 s"1 (average of 11 results). Corresponding results were obtained in the reaction with p-thiocresol. The reaction is again pseudo-first order (Fig. 3.14), with the average rate constant slightly lower, at 6.2 (±0.4) x 10"4 s"l (average of 11 results). Again, the observed rate constant is independent of the concentration of 2 (Fig 3.15) over the range of 0.045 to 0.96 mM 3 at 95 mM thiocresol, and independent of [CH3PC6H4SH] (Fig 3.16) over the range 9.5 to 110 mM at 0.93 mM 3. The rate law for both systems is therefore -JIM = k[32 dt which implies that the first and rate determining step of the mechanism is loss of H2. *1,-H2 *2,RSH RuH2(CO)2(PPh3)2 Ru(CO)2(PPh3)2 , RuH(SR)(CO)2(PPh3)2 M.H2 *-2,-RSH 80 5000 Timed) Fig. 3.10 Plot of absorbance at 400 nm versus time during the reaction of ccf-RuH2(CO)2(PPh3)2 (2, 10 mM) with ethanethiol (95 mM) in THF at 26<>C. 5000 Timed) Fig. 3.11 Logarithmic plot of absorbance at 400 nm vs. time for the reaction of ccf.RuH2(CO)2(PPh3)2 (2,1.0 mM) with ethanethiol (95 mM) in THF at 26oC. 81 [3J(mM) Fig. 3.12 Dependence of the pseudo-first order rate constant on the concentration of ccf-RuH2(CO)2(PPh3)2 (3J for the reaction with ethanethiol (95 mM) in THF at 26°C. Bars indicate estimated error (8 %) on individual measurements of k. 5? fEtSH] (mM) Fig. 3.13 Dependence of the pseudo-first order rate constant on the thiol concentration for the reaction of cc/-RuH2(CO)2(PPh3)2 (2» 1.0 mM) with ethanethiol in THF at 260C Bars indicate estimated error (8 %) on individual measurements of k. 82 1 .5-| , , , 1 ' 1 ' 0 2000 4000 6000 8000 time(s) Fig. 3.14 Logarithmic plot of absorbance at 400 nm vs. time for the reaction of cc<-RuH2(CO)2(PPh3)2 (3,1.0 mM) and p-thiocresol (91 mM) in THF at 26<>C. 83 8 2-1-OT • 1 • i • i • 1 • 0.0 0.2 0.4 0.6 0.8 1.0 [3J(mM) Fig. 3.15 Dependence of the pseudo-first order rate constant on the concentration of cci-RuH2(CO)2(PPh3)2 (3J for the reaction with p-thiocresol (92 mM) in THF at 260C. Bars indicate estimated error (8 %) on individual measurements of k. T 5-I *• * 3-2-4 1-0 1 'i • i » i i i i i i 0 20 40 60 80 100 120 [CH3C6H4PSH] (mM) Fig. 3.16 Dependence of the pseudo-first order rate constant on thiol concentration for the reaction of ccf-RuH2(CO)2(PPh3)2 (i 0.93 mM) with p-thiocresol in THF at 260C. Bars indicate estimated error (8 %) on individual measurements of k. 84 The unobserved intermediate "Ru(CO)20?Ph3)2" has been previously invoked to explain the mechanism of the reaction of Ru(CO)2(PPh3)3 with a variety of ligands. 173 The full rate law for this mechanism is: -Jill = frrRSHiffcir3i + *.9r<m - *.2[9j dt *-l[H2]+*2[RSH] If one assumes that &-l[H2]1S much less than it2[RSH] when RSH is present in excess, then this rate law simplifies to zam = *1[3] dt consistent with the observed data. The rate of the reaction with 95 mM EtSH is unchanged if one substitutes the argon atmosphere with H2 (1 atm). This allows us to put a lower limit on the ratio of kxlk.\. The concentration of H2 in benzene can be calculated from published data222 to be 14.4 mM under these conditions. If ifc2[RSH] » *-i[H2], *hen *2/*-l » 0.15. However, under 24 atm of H2, the reaction is reversed, in that the dihydride can be formed from 9 in the absence of free thiol (Chapter 6). The temperature dependence of the rate 0?ig 3.17) allows the calculation of AH| and ASt values (Table 3.6), which do not differ significantly between the reactions with ethanethiol and p-thiocresol. The essentially zero AS$ value is consistent with an activated complex similar in structure to Ru(n2H2)(CO)20?Ph3)2. A small but positive AS is expected for the change from a "static metal dihydride" to a rotor-like «2-H2 complex.223 The AH± values (90 kJ mol"1) for the reactions of 3_ are approximately what one would predict for the cleavage of two Ru-H bonds (about 250 kJ mol-leach)224 and the formation of an H2 molecule (H-H bond = 436 kJ mol-l).225 This again is consistent with an activated complex similar in structure to Ru(/i2H2)(CO)2(PPh3)2, assuming that the decrease in the H-H bond energy of the latter, 85 -10 -11--12--13' -14' • p-thiocresol ethanethiol O CO 3.05 ' l 3.10 —r~ 3.15 —I— 3.20 —| 1 1—i 1 • 3.25 330 335 3.40 i/rao'V1) Fig. 3.17 Eyring Plot for the Reactions of ccf-RuH2(CO)2(Pph3)2 (2) with several reagents (Table 3.6). Table 3.6 Kinetic Data for the Reactions of RuH2(CO)2(PPh3)2 (2) with Various Reagents in CfiDfi at 26°C.a Reagent Ws-1) AH± AS±. AG±_ CH3C6H4PSH 6.2(±0.6)xl0-4 96W) 10 (±30) 92ttl7) CH3CH2SH 6.7(±0.4)xl0-4 84 (±8) -30 (±30) 92 (±17) CO 6.5(±0.2)xl0-4 92 (±8) -20 (±30) 96 (±17) PPh3 6.4(±0,7)xl0-4 : -a The units for the activation parameters are kJ mol-1 for AHi and AG± , and J K"1 mol'l for AS±. 86 compared to free H2, is exacdy matched by the R11-H2 bond energy. Chinn and Heinekey223 reported that for the isomerization of rra/w-[RuH2(Cp)(dmdppe)]+ to fRu(n2H2)(C^)(dmdppe)]+(dmdppe - Me2PCH2CH2PPh2), ^ ^7 H<^_>Ph2 Ph2P^ ^/ the thermochemical data are AS = 19±1 J mol"1 K"1 and AH = 3.910.3 kJ mol"1. The activation parameters (AS± = -7.8 eu or -33 J mol'1 K"1 and AH± = 17.6 kcal mol-1 or 73.7 kJ mol-1) were also reported in Fig. 1 of their article, but were mislabelled as being for the reverse reaction. The AH± value is similar to that observed in the present system, suggesting that the activated complex in the present system has a structure intermediate between the cw-dihydride and the molecular hydrogen complexes. The reactions of ccr-RuH2(CO)20?Ph3)2 with non-protonating reagents provide useful comparisons (Table 3.6). The reaction with 00, RuH2(CO)2(PPh3)2 + CO—> Ru(CO)3(PPh3)2 + H2 3.5 2 m monitored by the change in absorbance at 350 nm, is pseudo-fast order (Fig. 3.18) with an observed rate constant independent of [3J. The rate constant (at 41°C and 1 atm of CO) is 4.1 (±0.4) x 10"3 s"1 (average of 2 results) at 1 mM of the complex, and 4.0 x 10"3 s"1 (single result) at 0.25 mM. At 0.09 atm of CO and 1 mM 3_, the rate decreases by only 5%. The rate constant was measured at several temperatures (Fig. 3.17), and corrected to 26<>C, is 6.1 x 10-4 g-l. Measurement of the kinetics of the reaction with PPh3 RuH2(CO)2(PPh3)2 + PPh3 —> Ru(CO)2(PPh3)3 + H2 3.6 1 87 •ST • 1 • 1 • 1 > 1 ' 0 1000 2000 S000 4000 5000 time(s) Fig. 3.18 Logarithmic plot of absorbance at 350 nm vs. time for the reaction of «*RuH2(CO)2(PPh3)2 (2, LI x 10-3 M) with CO (1 atm) in THF at 260C. i o-8 < -1-—, 1 1 1 1000 2000 3000 time (s) Fig. 3.19 Logarithmic plot of absorbance at 400 nm vs. time for the reaction of cc/-RuH2(CO)2(PPh3)2 (2,6 x 10-4 M) and PPh3 (0.38 M) in THF at 260C. 88 presented some technical difficulties. When monitored by UV/visible spectroscopy under N2 at 26°C and 400 nm, the reaction did not go to completion unless the cell was stirred or shaken between absorbance measurements. Monitoring the reaction by measuring the gas production in the "gas-uptake" apparatus was tried, because the apparatus allows for shaking. The amount of gas produced (1.0 equivalents/Ru) and the 31p{ lH} NMR spectra showed the reaction to be complete after 3 days. However, the pseudo-Gist order log plots of gas evolution were not linear. These problems probably resulted from the back reaction, which is rapid at this temperature under 1 atm of H2 (in the absence of added phosphine), and may be significant under the conditions used for reaction 3.6 if the diffusion of the H2 product into the gas phase is slow. If this is the case, and if the rate law is similar to that for thiols, then M[H2] is °f me same magnitude as Jfc2[PPh3] after the generation of some H2, and therefore k-\ must be one to two orders of magnitude larger than kl (assuming [H2] = 1/2 [3Jo = 0.5 mM, [PPh3] = 60 mM). Therefore, the rate of the reaction of the intermediate, Ru(CO)2(PPh3)2, with EtSH is one or more magnitudes faster than the reaction of the same intermediate with PPI13. Under conditions designed to guarantee that £-l[H2] is much less than &2[PPh3], namely [PPh3]/[3] greater than 130 and vigorous shaking between absorbance measurements to ensure H2 removal, the pseudo-fast order log plot is linear for 3 half-lives Q?ig. 3.19). At 0.33 mM of the dihydride, and 50 mM PPh3, the rate constant is 6.4 (±0.7) x 10"4 s"1 (average of 3 experiments), and at 375 mM PPI13, the rate constant was 6.5 x 10-4 s_l (single experiment). Therefore, the observed rate law and suggested mechanism for the reactions with CO and PPh3 correspond to those for the thiol reactions. As predicted by the mechanism, the observed pseudo-first order rate constant k is independent of the concentration or nature of the added reagent, and corresponds to k\. Of the three products of these reactions, only one, Ru(CO)2(PPh3)3, can be converted back into 3_ by the application of 1 atm of H2 to its solution (in the absence of free phosphine). 177 The other two, RuH(SR)(CO)2(PPh3)2 (Section 6.1.4) and Ru(CO)3(PPh3)2,178 require 89 elevated pressures for conversion back to 3_. RuH2(CO)2(PPh3)2 failed to react with methanol (247 mM) in THF within 1 h. 3.4 THE REACTION OF RuH2(dpm)2 WITH H2S AND THIOLS The mixture of cis- and *ra/w-RuH2(dpm)2 (7) reacts too quickly with H2S (reaction 3.7, R=H) at room temperature to monitor the course of the reaction accurately by NMR spectroscopy. 191 RuH2(dpm)2 + RSH —> RuH(SR)(dpm)2 + H2 3.7 7 13 dpm = Ph2PCH2PPh2 R = 13aH,b C6H5, £ CH2C6H5 The product of the reaction with H2S is exclusively rra/w-RuH(SH)(dpm)2 (Fig. 3.20). Reaction 3.7 (R = Ph, CH2Ph) produces 1:5 mixtures of cis- and rra/w-RuH(SR)(dpm)2. These complexes are easily identified by their characteristic lH and 31p{ lH} NMR spectra (Figs. 3.21 through 3.23, and Table 3.7). The hydride region of the lH NMR spectrum contains quintets for the fra/is-complexes and AX2YZ (doublet of doublet of triplet) patterns for the cis complexes. The 2jtransPH couplings are 90 to 100 Hz, while the 2jcispn coupling constants are 16 to 23 Hz, typical values for such constants.208 The 31p{ lH} NMR spectrum (Fig. 3.23) contains a strong singlet for the major product, trans-13, and four weak multiplets for cis-13, corresponding to the four different phosphine atoms in the molecule. The following assignments for cw-RuH(SPh)(dpm)2 in toluene-d8 are consistent with the NMR spectra, but have not been confirmed by decoupling experiments. The 2jcispp values are assumed to be negative, following a generalization suggested by Baker and Field226 that this is usually the case (an opposing view has been expressed by Bookham et al.)221 90 8H = -629 ppm 8PC =-15.86 ppm /^|d 5Pa = 4.44 ppm 8Pd =-15.96 ppm PbV I 8Pb = 7.67 ppm I ^SPh JPaPb = -20 Hz JPbPc = -24 Hz t 1 JPaPc = -26Hz JpbPd = -51Hz *» JPaPd = 330 Hz Jpcpd = -24 Hz JpbH = 24.1 Hz JpcH = 91.5 Hz JPaH = JPdH = 16.3 Hz The reaction with thiophenol (Fig. 3.24) is an order of magnitude faster at 25°C than that with a-toluenethiol (Hg. 3.25). There is too much scatter in the data to conclude that the rate of loss of cw-RuH2(dpm)2 is pseudo-first order. However, it is clear that the rate depended strongly on the thiol concentration (Fig. 3.25). A mechanism consistent with a dependence on the nature and concentration of thiol is the following, in which the cis- and *r<vtj-RuH2(dpm)2 reactants are treated as one species. RSH • Kl ' RS" + H* 38 RuH2(dpm)2 + H+ =====^ [RuH0H2)(dpm)2]+ ^ " [RuH(dpm)2l+ SR" fast RuH(SR)(dpm)2 Assuming a steady state condition for the unobserved molecular hydrogen species [RuH(fl2H2)(clpm)2]+, and assuming that Ki is small, the rate law for this mechanism is: dI3L3J= *7foKll/2mrRSHll/2 dt *-2 + *3 However, the mechanism is incomplete because of the question of the nature of the equilibrium between cis- and rra/ts-RuH2(dpm)2 at room temperature. According to Chaudret et 91 After 8 min Fig. 3.20 a) *H NMR spectra (hydride region) for the reaction of cis- and trans-RuH2(dpm)2 (11 mM) with H2S in C6D6 at 250C and 300 MHz.191 Fig. 3.20 b) lH NMR spectra (methylene region) for the reaction of cis- and trans-RuH2(dpm)2 (11 mM) with H2S in CoT>6 at 25©C and 300 MHz.191 93 cis-1 i r 1 1 1 1 1 1 -4-6-8 -10 ppm Fig. 3.21 lH NMR spectra (hydride region) for the reaction of RuH2(dpm)2 (4.1 mM) with PhCH2SH (280 mM) in C6T>6 at 25.0OC. H2 H2 rWKA J trans-\3b trans-l3b 11111111II1111II111111111111 II 11 4.5 4.4 4.3 ppm PhSH Julr i i i i i | i i i i j cis-1 unknown 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 i i | ; i i i | i i i -6 -7 -8 -9 -10 ppm i 111111111111111111111111111 8 6 11111'i»'''11'111111111111111111111111 11111111111111111111111111111111111111111111 4 2 0 -2 -4 -6 -8 -10 ppm -12 Fig. 3.22 lH NMR spectrum (300 MHz) of a sample of RuH(SPh)(dpm)2 prepared in situ from RuH2(dpm)2 and thiophenol in C6D6, with expanded views of the hydride region and part of the methylene region. 1 1 1 1 1 I 1 ' 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I I 1 1 1 1 15 10 5 0 -5 -10 -15 ppm Fig. 3.23 a) 31p{lH} NMR spectrum (expanded vertical scale) of a sample of RuH(SPh)(dpm)2 (13b) prepared in situ from RuH2(dpm)2 and thiophenol in toluene-dft. b) Simulated spectrum for ds-13_b. 96 Table 3.7 NMR Data for Ru(X)(Y)(dpm)2 Complexes in C6D6 solution.a a) trans isomers XY 31P Ru-Hb 2jpH PCH')P SH (H)2C J 9.11 -4.80 18.9 4.63 H(SH)d 0.39 -9.46 19 4.56,5.23 -3.55 (br) H(SPh)e -2.06 -10.86 19.9 4.27,4.78 H(SBz)d -1.68 -10.16 20.0 4.44,5.19 -3.73ft3jPH=5.7) (SH)?, -7.05 - 540 b) cis isomers XY 3JLP 2jpp Ru-Hf 2JPH PCH9P SH (H)2C 14.06 28T -7.53 7277718.3 4.10,3.81 -0.57 29.6 H(SPh)d v.i. v.i. -6.29 92,24,16 n.r. -H(SBz)d n.r. n.r. -7.17 101 ns. -(SH)2 -5.93 28.5 - - 4.62,5.10 -1.92 -22.65 26.5 a Bz=CH2C6H5, nj.=not resolved, v.i.=vide infra (the 31p{ lH} NMR spectrum of cis-RuH(SPh)(dpm)2 is described in Section 3.4). b quintets. c The NMR spectra of RuH2(dpm)2 have been reported previously. 187 cw-RuH(SH)(dpm)2 was not observed, d prepared in situ. e prepared in situ in toluene-dg. fddt. 97 a/.,18' the cisitrans ratio of a prepared sample in solution is constant over a wide range of temperatures, which suggests that the isomerization reaction is very slow or nonexistent. However, they concluded that there was a temperature-independent equilibrium between the isomers because the reactions with HBF4/H2O and CH2CI2 gave only the trans isomers of the products [RuH(H20)(dpm)2]+ and RuH(Cl)(dpm)2, respectively. In general, complexes of the type MH2(PR3)4 and MH2L2 (L=chelating diphosphine) are stereochemically non-rigid. 228 Although the trans-MH2L>2 complexes can be generated in situ,229 via deprotonation of the molecular H2 species, trans [MH(/t2H2)L2]+—> trans MH2L2 + H+ 3.9 M = Ru, Fe, L = dppe the subsequent isomerization to the cis complexes is rapid at room temperature. It is therefore believed that cis- and trans-7 are in equilibrium at room temperature, and one or both of them react with the proton from the thiol to form [RuH(/j2H2)(dpm)2]+. During the reaction with thiol, the ratio of cisitrans 7 does not change over time, even as the concentrations of each decline. This ratio is 6.7 (±1): 1 (average of 11 measurements), somewhat higher than the ratio observed in the absence of thiol. This could be caused by a situation wherein the reaction of trans-7 with H+ is faster than both the reaction of cis-7 with H+ and the isomerization of cis-7_ to trans-7. The ratio of the isomers of the product is constant during the reaction (Fig. 3.24) and up to 4 h after reaction 3.7 was complete. The two isomers of RuH(SR)(dpm)2 are possibly being formed independently by parallel reactions, or as a single isomer, the other isomer being produced by a rapid equilibrium between the isomers. The latter possibility is less likely, because other than the dihydrides, most six-cc>c>rdinate compounds are non-fluxional.228 The proposed mechanism has to take into account the possible equihbrium between the isomers of the dihydride 7. Scheme 3.1 shows the suggested mechanism. After a study of the related reaction, 98 1 1000 2000 3000 Time(s) • cis-7 • trans-13b • cis-13b O unknown Fig. 3.24 Time dependence of concentrations during the reaction of RuH2(dpm)2 (4.6 mM) with thiophenol (70 mM) in C6D6 at 25oC. Dashed line shows an extrapolation to the concentration of cis-1 in a solution of 7 in Q>D6-.a u i i 1000 2000 3000 4000 Hme(s) 5000 6000 7000 B 69mMBzSH • 150mMBzSH • 280mMBzSH • 570mMBzSH • 850mMBzSH D 70 mM PhSH Fig. 3.25 Time dependence of the concentration of c»-RuH2(dpm)2 (cis-7) in the reaction with thiols in CgD6 at 250C and [7]0 = 4.2 mM. 99 FeH2(dmpe)2 + RSH —> FeH(SR)(dmpe)2 + H2 3.10 dmpe=TCH3)2PCH2CH2P(CH3)2 Boyd et a/.230 proposed a mechanism analogous to that in Scheme 3.1 because they observed the intermediate rra/w-[PeH(n2H2)(dmpe)2]+ during the reactions with thiols230 and alcohols,231 and because the hydride ligands of FeH2(dmpe)2 exchanged with added D2 in the presence of alkanethiols. FeH2(dmpe)2 + REH^=^ [FeH(/i2H2)(dmpe)2]+ + RE- 3.11 E = O, S (ref. 230) In the present ruthenium system, [RuH(n2H2)(dpm)2]+ is not detected, although a minor intermediate is observed, which reaches a maximum concentration (in the reaction with thiophenol) of 12% after 0.5 half-lives 0?igs. 3.22 and 3.24). This unknown species appears in lower concentrations in the reaction with a-toluenethiol, but not at all in the reaction with H2S. The species also appears in the lH spectrum of a mixture of RuH2(dpm)2 and p-toluenesulphonic acid Q?ig. 3.26). It is seen in each case as a quintet (8 -9.6 ppm, 2JPJJ=19.3 Hz in toluene-d8) in the hydride region of the lH NMR spectrum, indicative of a complex of the type *ra/ts-RuH(X)(dpm)2. The unknown is not fra/w-[RuH(H20)(dpm)2]+, because this complex resonates at a higher field. 187 There was no peak in the lH NMR spectrum consistent with a molecular hydrogen ligand, even at lower temperatures, suggesting that the unknown is not rrfl«j-[RuH(/i2H2)(dpm)2]+. An inversion-recovery experiment was designed which produces a spectrum with positive peaks for all of the protons which have Ti relaxation times less than 60 ms. Most molecular hydrogen complexes have Ti's of less than 100 ms at high field Strengths, unless exchange is occurring with a terminal hydride ligand,232-3 and indeed such ruthenium complexes have particularly low Ti values.232,234 No positive peak was observed within the range 8 +10 to -10 ppm, when a spectrum was acquired with this pulse sequence during a reaction of RuH2(dpm)2 with PhSH. Thus, there is no direct evidence for the presence of [RuH(n2H2)(dpm)2]+. It is possible, however, that the /i2H2 peak is not observed 100 Scheme 3.1 Proposed mechanism for the reaction of RuH2(dpm)2 with thiols, based on that proposed by Boyd et al.229 H p^ ^P H trans -Z H -p cis -2 P H ^- P cw -13. IT SR SR-R*H f2 /PX I .^p\ H -Ho [RuH(PP)2]+ SR" t SR /PV I ^Px H trans -13. cis-7 trans-7 V 11111111111111111111111111111111111 n 1111111111111111111111 m 111111111 -4-5-6-7-8-9 PPM-10 A 1 1 r 10 ~» 1 • i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 r 5 0-5 -10 -15 I 1 r -20 PPM Fig. 3.26 The iH NMR spectrum (hydride region) acquired during the reaction of RuH2(dpm)2 (7.9 mM) with /Moluenesulphonic acid (200 mM). The products have not been identified. 102 because it is broad, or that the unknown complex is [RuH(dpm)2]+, in analogy to the intermediate proposed by Boyd et a/.230 The difference in the mechanisms for the reactions of RuH2(dpm)2 (2) and RuH2(CO)2(PPh3)2 (3J with thiols is believed to result from the more basic hydride ligands of the former complex. Thus, the hydride ligands of both cis- and trans-7 exchange with 4% CD3OD in QP6 in 10 min at room temperature, while the intensity of the hydride signals in the lH NMR spectrum of 3_ under the same conditions does not decrease significantly even after 2 h. The exchange reaction of 7 with CD3OD probably proceeds by an equilibrium analogous to reaction 3.11. The acidity of n^Hi complexes is decreased by increased electron density at the metal centre.229,235 Such complexes containing electron-withdrawing ancillary ligands, such as [Ru(n5C5(CH3)5)(/i2H2)(CO)2]+ (pK$= -5)236 are much more acidic than complexes containing electron-donating ligands such as [Ru(n5C5H5)(n2H2)(dpm)]+ (pKa=7.1).235 Complex 3_ is probably insufficiently basic to be protonated by a thiol. Why is the trans isomer of RuH(X)(dpm)2 observed exclusively (X=SH and BH4 in this work, H20+187 and CU87), or predorninandy (X=SPh and SBz), but RuH2(dpm)2 is predominantly cist This tendency of RuH(X)(dpm)2 to exist solely or predorninandy as a trans complex has been noted previously.237 Of the complexes of this type, it is likely that only RuH2(dpm)2 is fluxional in solution at room temperature, although the process is slow on the NMR time-scale. Its geometry therefore depends on thermodynamic factors such as steric interactions between PPh2 groups (favouring trans), and the rrwts-influence of the hydride ligands (favouring cis geometry). Obviously, the latter effect is stronger, of the 12 dihydrido phosphine ruthenium complexes studied by Meakin et al.P-1% nine are exclusively cis in solution, and the other three are predominantly cis. The remaining RuX(Y)(dpm)2 complexes, with the possible exception of RuH(BH4)(dpm)2, are probably geometrically rigid. The factors which determine the observed geometry are therefore kinetic rather than thermodynamic, and depend on the mechanism of the formation reaction. The preponderance of trans products is 103 Scheme 3 J, A partial mechanism for the formation of RuX(Y)(dpm)2 complexes. + X + r Pn ok (p>R»^P) favoured geometry Y-X | "*P Y trans -product disfavoured geometry Y cu -product consistent with mechanisms involving 5-coordinate square-pyramidal [RuX(dpm)2]+ intermediates. Of the two possible geometries for such intermediates, that with 4 rather than 3 equatorial phosphines is sterically favoured The trans product is therefore expected to be the major product (Scheme 3.2), unless Y or X is large. If X is large, then the other intermediate will be favoured, and a cis product obtained. If Y is large, then the reaction yielding the trans-product will be slower than the reaction yielding the os-product. 3.5 THE THIOL EXCHANGE REACTIONS OF cc/-RuH(SR)(CO)2(PPh3)2 The tide complexes (9J exchange with added thiols. RuH(SR)(CO)2(PPh3)2 + R'SH ^ RuH(SR')(CO)2(PPh3)2 + RSH 3.12 104 For example, the reaction of c^RuH(SEt)(CO)2(PPh3)2 (9d) with thiophenol generates cct-RuH(SPh)(CO)2(PPh3)2 (9i) and free ethanethiol; both products are detected by lH NMR spectroscopy (Fig. 3.27). The reaction of ccf-RuH2(CO)20?Ph3)2 (2) with a mixture of 5 equivalents each of ethanethiol and thiophenol initially produces a mixture of 9j and 9jl, but the final product is almost exclusively °jL The reactions of 2 with various binary mixtures of thiols were monitored by !H and/or 31p{ lH) NMR spectroscopy in Cf5D6 at 5(X>C (Fig. 3.28) to determine the equilibrium constants for reaction 3.12. The observed equilibrium constants (±10%) are 2.2 (R/R'=C6H4pCH3/C6H5), 71 (CH2CH3/C6H5), and 8.4 (CH2CH3/CH2C6H5). To confirm that equilibrium had been reached, the equilibrium between 9± and 9_d (R/R'=CH2CH3/C6H5) was approached from the "other side" by adding EtSH to a solution of 9i. After one hour, no further reaction was detected. Although equilibrium may not have been reached in this experiment, the Kobs value calculated from the results (83) serves as an upper limit for Keq. Comparisons of the thermodynamic stability of complexes of the formula ccr-RuH(SR)(CO)20?Ph3)2 (9) can be more easily made if the equilibrium constants are recalculated as Keq values for reaction 3.12 where R=Et. Keq = rRuH(SR")(CO)2(PPh3)2lfEtSH1 [RuH(SEt)(CO)2(PPh3)2i[R SH] These Keq values decrease in the following order: R' = C6H5 > C6H4PCH3 > CH2C6H5 > CH2CH3 Keq = 71 32 8.4 1 It is clear that the thermodynamic stability of 9 depends on the nature of the thiolate group, the aryl thiolato complexes being more stable than the alkyl thiolato complexes. This order of stability is similar to the order of acidity of the free thiols in aqueous solution, C6H5SH s CH3C5H4PSH > C6H5CH2SH > CH3CH2SH 105 ^AJO -42 -4A -4*6 -4.8 -SiOppm via 127 lH NMR 8Dectra acquired during the reaction of S»S(5Et)(W2?S& (8 mM) with thiophenol (1500 mM) in C6D6 at 22<>C. 106 Tune (s) Fig. 3.28 Time dependence of concentrations during the reaction of ccf-RuH2(CO)2(PPh3)2 (9.9 mM) with PhSH (1.6 M) and EtSH (2.5 M) in C6D6 at 36<>C. Table 3.8 Published pK^ Values for Selected Thiols in Aqueous Solution. Thiol pK» TfOQ Ref. H2S 7.0 25 238 7.0 25 239 7.04 18 240 7.06 25 241 7.24 25 242 CH3SH 10.70 25 243 CH3CH2SH 9.61 25 245 10.50 20 244 10.60 25 242 10.61 25 243 10.9 25 239 (CH3)2CHSH 10.86 25 243 C6H5CH2SH 9.4 25 239 10.7 25 243 C6H5SH 6.43 25 245 6.5 25 239 7.78 20 244 7.8 a 246 8.3 25 242 CH3C6H40SH 6.64 25 243 CH3C6H4mSH 6.58 25 243 CH3C6H4/7SH 6.52 25 243 C6FS5H 2.68 25 245 * not available. 107 although the published values of the pKa's of thiols show some variation; the value for thiophenol in particular varies widely (Table 3.8). The most stable complexes in the series 9 are those with the least basic thiolate ligands. The reason for this trend is not known. The same type of relationship between the acidity of a free thiol and its tendency to replace a thiolate ligand was observed by Que et al.,247 during studies of the thiol exchange reactions of an iron tetramer. [Fe4S4(SR)4]2- + nR'SH ^ [Fe4S4(SR)4-n(SR')n]2- + nRSH 3.13 (refs. 247-8) They noted that acidity is not the only factor involved. For example, sulphur ligands such as ethanethiolate bind much more strongly than oxygen ligands such as p-cresolate, despite the fact that the two reagents are equally basic. The pseudo-first order rate constant for the forward step of the reaction of 9d with thiophenol (reaction 3.12, R=Et, R'=Ph) in CfjD6 at 22(±1)°C is essentially independent of [9dJ. The rate constant is 1.9 x 10-4 s-1 at 1.8 mM 9d (single result) and 2.0(±0.2) x 10*4 s_1 at 9 mM (average of 4 results). The pseudo-first order log plot of \9d\ is linear for 3 half-lives (Fig. 3.29). The rate is also independent of the thiophenol concentration (Fig. 3.30) over the range 0.12 M to 3.4 M. -d\9d\ = *[9d] dt The rate constants and rate law are identical for the reactions of 9 with R'SH (reaction 3.12), with CO (Section 6.1.2), and with P(Q)H4pCH3)3 (Section 6.1.1). The mechanisms for all three of these reactions are thought to begin with elimination of PPh3, followed by coordination of R'SH, CO, or P(C6H4pCH3)3, respectively. If this is the case, then the mechanism for reaction 3.12 may be that in Scheme 3.3. The expected rate law, assuming that the back reactions with rate constants k-2 and £-3 are negligible, and reaction step &4 is rapid, is 108 T • r 2000 4000 T • r 6000 8000 time (s) 10000 12000 Fig. 3.29 Logarithmic plot of the concentration of 9_d versus time during the reaction of ccf-RuH(SEt)(CO)2(PPh3)2 (9d, 8.5 mM) and PhSH (1.5 M) in C6D6 at 22<>C. «9 6 1 2 [PhSH] (M) Fig. 3.30 Dependence of the pseudo-first order rate constant on [PhSH] for the reaction with cc/-RuH(SEt)(CO)2(PPh3)2 (9 mM) in C6D6 at 220C. Bars indicate estimated error (10 %) on individual measurements of Jr. 109 Scheme 3.3 The proposed mechanism for the reaction of RuH(SR)(CO)2(PPh3)2 (9J with R'SH. PPh, CO//,,..J ...uSR *i. -Pph3 CO/,, «SR k2> R'SH ^ CO/,,, 'Ru — ** Ru OCT" I "*H PPh3 OCT" ' PPh, H PPh, ' ...*SR k.2, -R'SH cor^i ^H PPh, PPh3 CO/,,... I ..uvSR' .Ru^ CO*^ | ^H PPh3 *-3 RSH rearr, *3 -RSH rearr. *4,PPh3 CO/,, ,vvSR' • .Ru^ kA, -PPh3 CO^ | ^H PPh3 110 rate= JbjfcoTCirR'SHl it-llPPh3]+it2[R'SH] or, if M[PPh3] « *2[R'SH], rate = *i[9J as observed. If PPh3 were added in sufficiendy high concentrations, then a decrease in the rate would be observed. In fact, only a small decrease in the rate constant (2.1x10-3,1.7x10-3, and 1.8x10-3 s-1 (±10%) at [PPh3]=0,260, and 660 mM, respectively) is observed for the reaction of 9_c (R=Me, [9Jo=6 mM) with PhSH (80 mM) in C6D6, monitored by NMR spectroscopy at 40OC. This result suggests that k-\ « *2. The thiol proton in the proposed intermediate [RuH(SR)(RSH)(CO)2(PPh3)] may be equally bonded to the two sulphur atoms, in the same way as the sodium atom in the complex [Ru(CX))2(PPh3)(|iSEt)2(|X3SEt)Na(THF)]2 (Section 5.2) is shared by three sulphurs on the same ruthenium centre. Similar sharing of a proton by a thiolate and a chloride ligand on the same metal centre is observed in the complex Ru(HCl)(buS4)(PPh3) (buS42- = l,2-Ms((3,5-di-rerr-butyl-2-mercapto-phenyl)thio)ethanato(2-)).249 The structure of this complex is shown in Section 7.2. 3.6 THE SLOWER REACTION OF RuH(SR)(CO)2(PPh3)2 WITH H2S AND THIOLS The reactions of free R'SH with RuH(SR)(CO)2(PPh3)2 (9) result in substitution, by R'S-, of either the thiolate ligand (reaction 3.12), or the hydride ligand (reaction 3.14). The latter reaction, which is significantly slower, forms a fcw-thiolato complex (14, Section 4.2). RuH(SR)(CO)2(PPh3)2 + RSH —> Ru(SR)2(CO)2(PPh3)2 + H2 3.14 2 14 The new complex 14 can therefore be prepared in one "pot," via 9, from the reaction of Ru(CO)2(PPh3)3 (2) or RuH2(CO)2(PPh3)2 (3) with thiols. For example, 2 reacts with excess Ill PhSH in THF at room temperature to produce RuH(SPh)(CO>2(PPh3)2 within 5 min (100% conversion, reaction 3.3), and Ru(SPh)2(CO)2(PPh3)2 after 3 days (46%, reaction 3.14). Because of the extremely slow rate of reaction 3.14 and the further reaction of 14 (R*H) under conditions of heat or light (Chapter 6), reaction 3.14 was not successfully monitored kinetically or used as the synthetic route to 14 (except for R=H). As Chapter 4 describes, the reaction of disulphides with Ru(CO)2Q?Ph3)3 is the preparative route of choice for 14 flt=aryl), The characterization of 14 is therefore described in that chapter. The reaction of 3 with acetic acid250 RuH2(CO)2(PPh3)2 + 2HOAc ^ Ru(OAc)2(CO)2(PPh3)2 + 2H2 3.15 probably proceeds via RuH(OAc)(CO)2(PPh3)2, if the chemistry is analogous to that observed with thiols. However, there was no mention, in the report, of any attempt to detect or isolate the acetatoOiydrido)-intermediate, which has since been observed in the present work (Chapter 2). Reaction 3.14 0*=H) was followed by NMR spectroscopy at 60«C (Fig. 3.31). The starting material, RuH(SH)(CO)2(PPh3)2 (9a). is easily generated in-situ by the reaction of 3 with excess H2S at 60°C for 3 min. The 9_a thus generated reacts with H2S more slowly. After 40 min (almost 2 half-lives), free PPI13 is observed, indicating some decomposition or side-reaction is occurring. Up to this point, the reaction has a half-life of approximately 1400 s, assuming pseudo-fust order behaviour. For comparison, reaction 3.4 (which forms 9_ from RuH2(CO)2(PPh3)2 and H2S or RSH) has a half-life of 24 s at this temperature in THF (calculated by extrapolation of data acquired between 26 and 46°C). Although these preliminary data do not include the dependence of the rate on [H2S], it is possible to speculate on the mechanism of reaction 3.14. Reductive elimination of thiol from RuH(SR)(CO)2Q?Ph3)2 cannot be the first step, as this would subsequently lead to the re formation of the starting material (i.e. no reaction would occur). The first steps of three possible mechanisms are protonation of the hydride (Scheme 3.4), elimination of PPI13 (Scheme 3.5), or (less likely) elimination of CO. 112 after 5-9 min -\ —f 11-15 min 20-24 min I V 14a (RuSH) A 9ja_(RuSH) 2a (RuH) -A. r 1. 1 1 1 1 1 1 1 T •2 -3 -4 -5 ppm Fig. 3.31 lH NMR spectra acquired during the reaction of cc/-RuH(SH)(CO)2(PPh3)2 (2a) with H2S in C6D6 at 60OC. 113 Scheme 3.4 A mechanism for the reaction of RuH(SR)(CO)2(PPh3)2 (2) with RSH, in which the first step is protonation of the hydride. PPh3 CO//,,..J ..,«SR *i.H* Ru_ * ccr^ | kA, -H+ PPh3 £ PPh3 CO//,,. I ...rtSR oof^r^H I H PPh3 *2> k-2* ^2 PPh3 CO//,,.. I ..,»\SR CO^ PPh, *3 RS' PPh3 CO//„..J ..,»\SR -Ru_. ccr^ j ^SR PPh3 14 Scheme 3.5 A possible mechanism for the reaction of RuH(SR)(CO)2(PPh3)2 (2) with RSH, in which the first step is dissociation of PPh3 from the complex. PPh3 CO//,,..J .„uSR CO^RU-H PPh3 1 PPh3 *i. -P% CO,,,. ...«SR *2>RSH CO-f-H PPh3 t.2» RSH PPh3 CO//,, ..J ...uSR CO^I^SR PPh3 R CO//,, Ru^l ccr^ j ^H PPh3 *3 H2 rearr. *3 -H2 rearr. *4> PPh3 CO// ,v\SR Ru^< JU -PPh3 CO^ j "^SR PPh3 14 114 The first of these mechanisms involves the formation of a molecular hydrogen complex, [Ru(fl2H2)(SR)(CO)2(PPh3)2]+. Two types of experiments to detect this complex or the chloro analogue were performed. a) The reactions of acids such as alcohols,251 HBF4/Et20,192,236 and H2C(S02CF3)2252 have been used to protonate hydrides to form molecular hydrogen complexes. Attempts at the protonation of RuH(SCoH4/>CH3)(CO)2(PPh3)2 by HBF4/ET.2O, HBF4/H2O or HCl(aqueous) failed to produce evidence of a molecular hydrogen complex (Section 6.1.5). b) Metathesis reactions of transition metal chloro-complexes with NaBPh4 under H2 gas have also been used to generate molecular hydrogen complexes.253 A mixture of RuCl2(CO)2(PPh3)2 and NaBPh4 in acetone under H2 was passed through diatomaceous earth after reacting at room temperature for 90 min, and a white solid was precipitated by removal of some of the solvent under vacuum. The 31p{ lH} NMR spectrum shows that the only phosphorus-containing compound in the recovered solid was RuCl2(CO)2(PPh3)2. The failure to produce a «2H2 complex may result from the insufficient basicity of the hydride ligand of 2. As described in Section 3.4, the presence of carbonyl ligands gready decreases the basicity of hydrido-complexes. The intermediate n2H2 complex shown in Scheme 3.4 is therefore unlikely. The mechanisms which involve initial loss of CO or PPI13 do not require a n?H2 complex as an intermediate. Because the phosphine ligands of 9 are known to be labile (Section 6.1.1), the latter mechanism (Scheme 3.5) is considered more likely. It involves the same initial steps and the same intermediate, [RuH(SR)03.SH)(CO)2Q?Ph3)], which were proposed for the reaction of 9 with R'SH (reaction 3.12, Scheme 3.3). The intermediate therefore represents the branching point of the two reactions. If thiol is eliminated (which is statistically favoured), then the product will be 2; if H2 is eliminated, then the product will be Ru(SR)2(CO)2(PPh3)2 (M). 115 3.7 THE REACTION OF RuH(SH)(dpm)2 WITH H2S The tide complex (13) probably undergoes thiol exchange reactions in a manner similar to reaction 3.12, although experiments to confirm this were not performed. The title complex also reacts with H2S and presumably other thiols to produce a frfr-thiolate complex (15_, cf. reaction 3.14). RuH(SH)(dpm)2 + H2S —> Ru(SH)2(dpm)2 + H2 3.16 13a 15 The reaction of fra/w-RuH(SH)(dpm)2 (13a) with H2S was monitored by NMR spectroscopy (Fig. 3.32). A C6D6 solution of RuH2(dpm)2 (7.4 mM) under H2S (1 atm) reacts within 3 min at 60°C to form 13a. which reacts more slowly (T1/2 = 20 min) to form a 1:1.8 mixture of cis-and trans-15. The H2 produced in the reaction was detected by lH NMR spectroscopy. The rate of disappearance of the hydride signal of 13a is pseudo-fast order, with a log plot linear over more than 3 half-lives Q7ig. 3.33). The rate dependence on [H2S] was not determined. The lH NMR spectrum of 15. in C6D6 (Pig- 3.32) contains two signals at -1.92 and -3.74 ppm for the cis and trans isomers, respectively. The former signal is a complicated multiplet, but the latter is a simple quintet (3JPH=5.6 Hz) due to the cis coupling of the SH group of trans-15 to four equivalent phosphorus atoms. The methylene signal of the trans complex appears at 5.10 ppm, while the cis complex has two methylene multiplets: one at 4.62 and the other under the peak at 5.10 ppm. The 31p{ lH} NMR spectrum of the cis/trans mixture (Fig. 3.34) contains a singlet (trans-15) at -7.05 ppm, and two triplets (os-15) at -5.93 (2jpp=28.5 Hz) and -22.65 ppm (2jpp=26.5 Hz). As previously mentioned, six-<xx)rdinate complexes are generally not fluxional. Although iron(II) and ruthenium(II) phosphine dihydrides have been found to be exceptions,228 there is no reason to suppose that 15. is fluxional. In fact, the observation of a different cis:trans ratio (2:1) in the filtrate from reaction 3.16254 shows that the isomerization reactions between the isomers of 15 are slow at room temperature. 116 after 3 -10 min trans-15a (RuSH) trans-13& (RuSH) / \ cis-lSa (RuSH) 11-19 min f 98-120 min r 1 trans-U& (RuH) -i I l T 1 j 1 1 1 1 r -3 -5 •11 ppm Fig. 3.32 a) lH NMR spectra (hydride region) acquired during the reaction of RuH(SH)(dpm)2 (13a, 7.4 mM) with H2S in C6D6 at 60.0OC. 117 5.5 53 ' 5A 4\9 ' 477 ' 4^5 ' 4.3 ppm Fig. 3.32 b) *H NMR spectra (methylene region) acquired during the reaction of RuH(SH)(dpm)2 (12& 7.4 mM) with H2S in C6D6 at 60.0OC. 118 •5 Time (min.) Fig. 3.33 Logarithmic plot of concentration of f7wis-RuH(SH)(dpm)2 (13a) during the reaction of that compound (7.4 mM) with H2S (1 atm) at 60.0<>C in C6D6-trans-l3a -i 1 r 8 PPM trans-lS_ A cis-15_ os-15_ 1 1 1 1 1 1 1 1 1 1 1 1 -6 -2e Fig. 3.34 The 31p{lH} NMR spectrum of Ru(SH)2(dpm)2 (15) in QsD6 (5 with reference to PPI13 in C6D6) 119 The reaction of flww-RuH(BH4)(dpm)2 (Section 2.3.7,0.4 g) with H2S (1 atm) in THF (30 mL) over 5 days at room temperature254 produces a similar mixture of cis- and trans-15 (cis: trans = 1:2, yield = 80%). RuH(BH4)(dpm)2 + 2H2S —> Ru(SH)2(dpm)2 + 2H2 + "BH3" 3.17 3.8 THE THIOL EXCHANGE REACTIONS OF ccf-Ru(SR)2(CO)2(PPh3)2 The title compound (14) reacts with added thiols to exchange the thiolate groups, in a reaction reminiscent of that with ccf-RuH(SR)(CO)2(PPh3)2 (reaction 3.12). Ru(SR)2(CO)2L2 + nR'SH ^ Ru(SR)2-n(SR')n(CO)2L2 + nRSH 3.18 L = PPh3 n= 1,2 For example, the reaction of ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b. 6 mM) in C6E>6 with H2S (1 atm) at room temperature is complete within 5 min, giving pure ccr-Ru(SH)2(CO)2(PPh3)2 (14a). However, the reaction of 14b (6 mM) with excess EtSH at room temperature produces equilibrium mixtures of the 14b. ccr-Ru(SCH2CH3)(SC6H4pCH3)(CO)2(PPh3)2 Q4bd), and ccr-Ru(SCH2CH3)2(CO)2(PPh3)2 (14d) within 20 min, after which the ratio is unchanging (monitored for a further 50 min). The 14b:14bd:14d ratio is 24:52:24 or 10:45:45 after the addition of 260 or 960 mM EtSH, respectively. The p-thiocresol produced in the reaction is clearly detected in the lH NMR spectrum. From three experiments of this type, rough estimates of the two equilibrium constants were calculated. Kl= rRu(SEt)(Stol)(CO)o(PPh3)2l ftolSHl [Ru(Stol)2(CO)2(PPlr^2lTEtSl5 K2= rRu(SEt)2(CO)2(PPh3)2l TtolSHI [Ru(SEt)tStol)(OC^(Pft [EtSH] where Et = CH2CH3 and tol = C6H4/7CH3 120 At 20°C, these constants were 4 x IO"2 and 1 x 10"2 (±25%), respectively. The Ru(SH)2(CO)2(PPh3)2 complex (14a. 5.7 mM) reacts with p-thiocresol (220 mM) in C6D6 (1 mL) at 210C to produce Ru(SH)(SCoH4pCH3)(CO)2(PPh3)2 (14ab) (56% conversion) and Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) (10%) after 140 min. The reaction of 14a with thiophenol is similar (Fig. 3.35 and 3.37). However, with 1500 equivalents of ethanethiol, no reaction is observed even after several hours. This is probably a result of the greater binding strength of the more acidic thiols such as H2S and the aryl thiols (Section 3.5). The mixed products of the reactions of 14a with thiols are detected by 31p{ lH} and lH NMR spectroscopy 0?ig. 3.35 and Table 4.1 on page 159). The reaction of 14a (0.70 mM) with thiophenol (2.0 mM) can also be followed by UV (Fig. 3.36). Isosbestic points are observed for the first 10 min at 367 nm (e = 2100) and 386 nm (e = 1830), because only Ru(SPh)2(CO)2(PPh3)2 (14i) is produced in the first 10 to 20 min, with no trace (NMR evidence) of Ru(SH)(SPh)(CO)20?Ph3)2 (14aj). The rate constant at 25<>C is 2.3 x 10-3 s-1, significantly higher than the result in C6D6 (4.2 x 10-4 s-1, see below). The rate of the same reaction of 14a with PhSH was also monitored by 31p{ lH} NMR spectroscopy at 25.0OC. At low [PhSH], the monosubstituted product (14ai) is produced more quickly and in greater amounts than the disubstituted product (14i. Fig. 3.37a). The reaction does not proceed to completion presumably because an equilibrium is attained. Since H2S is very soluble in benzene255, a significant amount of the H2S produced in the reaction must remain in solution. At high [PhSH], the rate of loss of 14a is pseudo-fast order (Fig. 3.37c,d). The log plot (Fig. 3.38) is linear for 2.5 half-lives, with a pseudo-fast order rate constant of 4.0 x IO-4 s-1. Because first order behaviour is not observed over the full range of thiol concentrations tested, the initial rate method was adopted for the kinetic study. The rate constant was calculated from the initial rate of loss of 14a as determined from the 31p{ lH} NMR spectra. This rate constant is independent of [PhSH] (77 to 1700 mM), although it decreases slighdy at very high concentrations of thiol (Fig. 3.39). The average value is 4.2 (±0.3) x 10~4 s"1 (average of 5 results). If extra PPh3 is added, the rate decreases and becomes dependent on [PhSH] (Fig. 121 after 2-8 min Ua IM 141 20-26 min 99-112 min 28 ' 26 r 24 ^ "I 1 1 I 1 -r 22 20 8 16 ppm Fig. 3.35 31p{lH} NMR spectra acquired during the reaction of «*-Ru(SH)2(CO)2(PPh3)2 (14& 9.4 mM) with PhSH (700 mM) at 25©C in C6D6. Chemical shift shown with respect to PPh3 in C6D6< i—i 1 i 1 1 IIII 1 1 1—7—1 r 1 1 1 1 * r t 325 340 360 380 400 420 440 460 480 500 520 nm wavelength Fig. 3.36 UV/vis. spectra acquired at 1 min intervals during the reaction of cc/-Ru(SH)2(CO)2(PPh3)2 (14ft, 0.70 mM) with PhSH (2.0 M) at 25©C in THF. 123 O 14a • 14ai • 14i Time (6) Fig. 3.37 Time dependence of the concentrations of species detected by 31p{lH} NMR during the reaction of cct-Ru(SH)2(CO)2(PPh3)2 (14a, 6 mM) with PhSH at 250C in C6D6. a) at 77 mM PhSH • 14a • 14ai • 14i 0 1000 2000 3000 4000 Time(s) b) at 690 mM PhSH 124 d 14a • 14ai • 14i 0 1000 2000 3000 4000 5000 Time (8) c) at 1700 mM PhSH O 14a • 14ai • 14i 4000 Time(s) d) at 2900 mM PhSH 125 D 14a • 14ai • 14i 0 1000 2000 3000 4000 5000 6000 Time(s) e) at 810 mM PhSH and 470 mM PPh3 -5.0 -7.0 H 1 1 » 1 • 1 1 1 ' 1 0 1000 2000 3000 4000 5000 Time(s) Fig. 338 The log plot of the concentration of ccf-Ru(SH)2(CO)2(PPh3)2 (14a) during its reaction (53 mM Ru) with thiophenol (1.7 M) in C6D6 at 25°C. 126 o 09 • 0mMPPh3 • 230mMPPh3 • 470mMPPh3 Fig. 3.39 The dependence on [PhSH] of the observed initial rate constant for the loss of cc/-Ru(SH)2(CO)2(PPh3)2 (14a) during the reaction with PhSH at several concentrations of added PPI13. Bars indicate estimated error (10 %) on individual measurements of k. 10000 8000 -6000 " 4000 -2000 • 67 mM PhSH O 770 mM PhSH [PPh3] (mM) Fig. 3.40 Phosphine dependence of the inverse of the observed initial rate constant for the loss of cc/-Ru(SH)2(CO)2(PPh3)2 (14a, 6 mM) during the reaction with PhSH at several [PhSH]. The lines are drawn from a fixed point at [PPh3]=0 mM based on data from experiments with no added phosphine. 127 Scheme 3.6 The proposed mechanism for the first step of the reaction of Ru(SH)2(CO)2(PPh3)2 (14a) with PhSH. PPh3 CO//„..J ...rtSH ccr^ | ^SH PPh3 14a ^ -P XT CO//,,..„ ...nSH *2phSH .Ru ccr^ | ^SH PPh3 PPh3 CO/„...J ...uSPh CO*^ | ^SH PPh, PPhq phvH CO/,„..J ..avSH .Ru_ 1 ^SH PPh, -H,S rearrangement CO//, ,«SPh .Ru_ ccr^ | ^SH PPh3 14ai 128 3.39). A mechanism consistent with these observations is shown in Scheme 3.6. The proton in the intermediate complex Ru(SH)2(PhSH)(CO)2(PPh3) probably is shared by all three thiolate groups, rather than being simply attached to one of them. This kind of intermediate was discussed in Section 3.5. The rate law predicted by the mechanism in Scheme 3.6, assuming that k-2 is negligible, is: -riri4al = JhJbrPhSHiri4a1 dt Jd[PPh3]+*2[PhSH] Under pseudo-fhst order conditions, [PhSH] is essentially constant during the reaction. PPh3 is neither produced nor consumed in the reaction and [PPI13] is therefore constant. Thus the observed initial rate constant ifcobs is given by *-l[PPh3]+*2[PhSH] or _!_ = *-nPPlrtl + J_ *obs *l*2[PhSH] k\ A plot of 1/kobs against [PPI13] should be a straight line with a slope inversely proportional to [PhSH]. Although there is considerable scatter in the data, this is perhaps the case (Fig. 3.40). The slope of the line drawn through the data for 67 mM PhSH is 14000, giving a value for k-i/ki of 0.4. The slope for 770 mM PhSH is 1800, giving a value for it l/*2 of 0.6. The average value is 0.5. During the reaction of 14a with low [PhSH], 14ai is produced at a higher initial rate than 14i. It was initially supposed that 14ai may be an intermediate in the formation of 14i. The reaction equations would therefore be the following. *A Ru(SH)2(CO)2(PPh3)2 + PhSH -*> Ru(SH)(SPh)(CO)2(PPh3)2 + H2S 14a 14ai 129 Ru(SH)(SPh)(CO)2(PPh3)2 + PhSH —> Ru(SPh)2(CO)2(PPh3)2 + H2S 14ai 14i However, at high [PhSH] (Fig. 3.37c,d), 14J is observed first, and the appearance of 14ai is considerably delayed. The rate constant for the second step was calculated, assuming that a) the first substitution reaction is first order with respect to (14a] and independent of [PhSH], b) the second substitution reaction is first order with respect to [14ail and nth order with respect to [PhSH], and c) n and [PhSH] are constant with respect to time. The rate equations, based on these assumptions, are: -</T14a1 = fcAfl4al <ffl4il = jtaTMaMfPhSHin = Jtari4ai1 dt dt where *B = *B'[PhSH]n. The integrated rate laws for this type of system are known.256 14a —» 14ai—» 14i [14a1t = exp(-*At) [14a]0 [14ailt = ^A(exp(-/:At)-exp(-£Rt)l [14a]0 *B-*A [14ilt = 1 + fcBexp(-fcAMAexp(-fcBtl [14a]0 *A-*B The value of JkA is already known (JtA -k\= 4.2 x 10-4 s-1). For each experiment, the plots of the observed and predicted concentrations of Ru(SH)2(CO)2(PPh3)2 (14a), Ru(SH)(SPh)(CO)2(PPh3)2 (IM), and Ru(SPh)2(CO)2(PPh3)2 Q4J) were compared for several values of JkB- The best value for kB was taken to be that which produced the best fit of the predicted concentration curve (calculated using the above equations) to the observed curve in the 130 Fig. 3.41 Thiol dependence of the calculated rate constant *B for the second step of the reaction of ccf-Ru(SH)2(CO)2(PPb3)2 with thiophenol at 25<>C in C6D6. Solid line assumes a first-order dependence at all [PhSH]. Dashed line shows an incorrect interpretation of the rate dependency. 131 initial rate region (the first two data points, Fig. 3.37). It is tempting to interpret the plot of the [PhSH] dependence of the Jfcp, values (Fig. 3.41) as showing n to be 0 at low thiol concentrations, and 1 at high thiol concentrations. The error on each point, although difficult to estimate, is probably too large for this interpretation, and the sloping line for a supposed first-order dependence on [PhSH] (dotted line in Fig. 3.41) should extrapolate back to the origin, which it fails to do. It is clear, however, that the value of kB depends on [PhSH]. This indicates that either i) the reaction of 14ai with PhSH is dependent on [PhSH], and is sufficiently fast at high [PhSH] that 14ai is not observed, or ii) 14ai is not an intermediate in the formation of 14J under these conditions. The first possibility is counter-intuitive, because one would expect that the mechanism of the reaction of 14ai with PhSH would correspond to that of 14a with PhSH. A mechanism consistent with the second possibility and with the mechanism proposed for the loss of 14a (Scheme 3.6) is shown in Scheme 3.7. Arcording to this mechanism, the unobserved five-coordinate complex [Ru(SH)(SPh)(CO)2(PPh3)] is an intermediate for which PPh3 and PhSH compete to form 14ai (directly) and 141 (via other intermediates), respectively. This accounts for the observation that high [PhSH] favours early formation of 14J (Figs. 3;37b,c,d), while added PPh3 increases the initial rate of formation of 14ai at the expense of 14i (Fig. 3.37e). With this mechanism, we can now interpret the observed dependence of kB on [PhSH] (Fig. 3.41). At very low [PhSH], kB should be independent of [PhSH], because in this region, the pathway via 14ai is predominant The value of kB in this range should therefore equal that of k-4. As mentioned earlier, the flattened region at low [PhSH] in Fig. 3.41 is believed to result from scatter in the data, although it is interesting that the lowest observed value of kB (4 x 10-4 s-1) is very close to the value of k\ (3.8 x 10-4 s-1). Because 14a and 14ai are so similar, the values of k-4 and kl are expected to be similar. At higher [PhSH], the other pathway should be predominant That is, 14j is formed without 14ai having been an intermediate. The value of *B/[PhSH] in this region (3 x 10-3 M-l s-1) is presumably that of ks. 132 Scheme 3.7 The proposed mechanism for the reaction of Ru(SH)2(CO)2(PPh3)2 (Jia) with PhSH. PPh, PhvH CO//,,.. I .„«SH *i> -PPh3 CO//„._ ...uSH *2» PhSH ^ CO/,,,..J ..,*SH ccr^ I ^*SH it.,, pph3 ccr^ i ^ SH £.2,-PhSH CO^ | ^*SH PPh, Ma PPh3 CO//,,.. J ...»\SPh Ru CO*" | ^SPh PPh3 PPh, -PPh, PPh, PPh, *-3 H2S rearr PPh3 CO//„..J ..,»vSPh .Ru^ CO*" | "*SH PPh3 Mai *3 -H2S rearr. *4,PPh3 CO// uSPh • .Ru^ kA, -PPh3 CO*" | ^SH PPh3 -PhSH k5 PhSH rearr. a CO// uSPh *6."H2S CO//,,.. I ..,»\SPh Ru Ru CO*" | ^SPh k.6, H2S co*" i ^SH PPh, rearr- PPh, HI 0 133 As we have seen, if one assumes that k_2 is negligible, then one can calculate that it_i/it2 is approximately 0.5. This leads one to speculate about the value of &4/&5. Both ratios are concerned with competing reactions of PPh3 and PhSH for a five-coordinate intermediate. If k^lks were also approximately 0.5, or even if k4 and its were of the same magnitude, then under the conditions of excess added thiol and no added phosphine, &5[PhSH] would be far greater than &4[PPh3], and therefore no 14ai would have been observed in the initial rate region. That the initial rate of production of 14ai is significant at 77 mM PhSH (Fig. 3.37a) suggests that htfks is much larger than Jt-i/Jt2 or that it-5 is larger than it-2- It is difficult to explain why k4/k5 should be larger than Jk- l/Jfe2, but it is clear why Jt-5 should be larger than it-2- For statistical and steric reasons, the thiol which is ejected from Ru(SPh)(SH)(PhSH)(CO)2(PPh3) is more likely to be PhSH (k-5) than H2S (*6). The corresponding complex Ru(SH)2(PhSH)(CO)2(PPh3) is more likely, for statistical reasons, to elirninate H2S (it3) than PhSH (it-2). Also, the steric crowding which might encourage elirriination of PhSH from Ru(SPh)(SH)(PhSH)(CO)2(PPh3) is weaker in Ru(SH)2(PhSH)(CO)2(PPh3). These arguments suggest that it-5 should be larger than it-2. Why does ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) react more quickly with thiols than does ccr-Ru(SH)2(CO)2(PPh3)2 (14a) ? The rate deterrnining step in Scheme 3.5 and 3.6 is dissociation of PPh3 from the complex. It is possible that the bulky thiolate groups in 14b labilize the phosphine. This is supported by the observation (Section 6.2.2) that the phosphine-exchange reaction of 14b with P(C6H4pCH3)3 proceeds more quickly than that of 14a. 3.9 THE REACTIONS OF OTHER CARBONYL(PHOSPHINE)RUTHENIUM(0) COMPLEXES WITH H2S AND THIOLS The bisphosphine tricarbonyl complex Ru(CO)3Q?Ph3)2, (10), is much less reactive than Ru(CO)2(PPh3)3 (2). After 3 h in refiuxing THF under H2S, only 6% of a sample of 10 had 134 been converted to ccr-RuH(SH)(CX))2(PPb3)2, of which half had reacted further (reaction 3.14) to produce cct-Ru(SH)2(CX))2(PPh3)2.254 Ru(CO)3(PPh3)2 + H2S -> RuH(SH)(CO)2(PPh3)2 + CO 3.19 The only related reactions which have been reported previously are the reaction of Ru(CO)3(PPh3)2 with pyridine-2-thiol, producing Ru(pyS)2(00)(PPh3),211 and reaction 3.20: M(CO)30?Ph3)2 + 2HX~>MX2(OO)2(PPh3)2 + CX) + H2 3.20 M=Os, X=Q, Br, I (ref. 257a) M=Ru,X=Cl, Br (ref. 257b), OCOR (ref. 257b,c,d) A mechanism proposed257a for this reaction (Scheme 3.8) was supported by the isolation of complexes of the formula [OsX(CO)30?Ph3)2]X (X=Br, I, l3)257a and OsH(Cl)(CO)2(PPh3)2.257e The mechanism of reaction 3.19 may parallel that in Scheme 3.8. Scheme 3.8 A mechanism proposed by CoUman and Roper257a for the reaction of Os(CO)30?Ph3)2 with HX (X=CI, Br, I). OO, PPh, oc—os CO PPh, PPh, ,0s i\\X ^x PPh3 H* HX -H, PPh, 0O« vCO Os ^H PPh3 CO PPh, OO/ Os 135 Samples of the complex Ru((X))20?Pb3)(dpm) (16). kindly supplied by Dr. C.-L. Lee, react with thiols to form mixtures of thiolate complexes (Figs. 3.42 and 3.43). The major product has not been identified. Three identified minor products of the reaction with ethanethiol in THF are cc/-RuH(SCH2CH3)(CO)2(PPh3)2 (M) and two isomers of RuH(SCH2CH3)(CO)(PPh3)(dpm), one (12) containing a 2JtransPH coupling, and the other (18) containing only ^JcisPH couplings. These three products are detected in the hydride region of the *H NMR spectrum. The integrals of the hydride signals are in a ratio 2d:17:18 of 120:2.3:1. The peaks due to 16 and 9_d_ comprise 28% and 13% of the 3*P{ lH) NMR signal, respectively. It is not clear which peaks in the 31p{ lH) NMR spectrum correspond to12 and lfi. Possible structures for these isomers are shown below. The detection of 17. 18, and 2d shows that loss of a carbonyl ligand and exchange of the phosphine ligands are significant reactions. The existence of three labile ligands on the starting complex 16 make this system too complicated to be amenable to a full study of its reactivity and kinetics. Results obtained in the reaction of 16 with H2 are summarized in the experimental section at the end of this chapter. The products of the reaction include trace amounts of ccr-RuH2(CO)2(PPh3)2, and several unidentified species. ^PPh2 PPh3 II 1£ Fig. 3.42 lH NMR spectrum (hydride region) of the products of the reaction of Ru(CO)2(dpm)(PPh3) with ethanethiol. 1 ' ' M '' ' 1 | • • • i i' '' • 'i' »»»i»i' ' r' 1 i' ' ' H '''' i ' ' ' ' i • • ' • i • '|' ' • n i 111 11 11 i | 11111111111 111; t 50 40 30 20 10 0 -10 -20 -30 ppm Fig. 3.43 31p{lH) NMR spectrum of the products of the reaction of Ru(CO)2(dpm)(PPh3) with ethanethiol. The signals due to unreacted starting material are indicated with asterisks. 138 3.10 EXPERIMENTAL DETAILS The reaction of Ru(CO)2(PPh3)3 with hydrogen sulphide, thiols and selenols over several hours: Complex Ru(CO)2(PPh3)3 (2) (400 mg, 0.4 mmol) in THF (50 mL) was reacted with a) gaseous H2S (1 atm) at -35°oC for 2 h,86 b) under gaseous MeSH (1 atm) at room temperature for 3 h, c) with excess (e.g. 8 equivalents) dissolved thiol at room temperature for 3 h, or d) with one equivalent of phenyl selenol for 1.5 h at room temperature. The product was precipitated by reduction of the solvent volume by vacuum distillation followed by addition of 100 mL hexanes, producing 40-95% yields of a) a pale tan powder, or b.c.d) a yellow powder, which analyzed for RuH(ER)(CO)2(PPh3)2 (2). The same products can be similarly prepared from the reactions of ccr-RuH2(CO)2(PPh3)2 with H2S or thiols. Elem. Anal.: 9a (ER=SH) Calcd. for C38H32O2P2RUS: C, 63.8; H, 4.5; S, 4.5. Found: C, 63.8; H, 4.7; S, 4.6. 9b_ (ER=SC6H4pCH3) Calcd. for C45H38O2P2RUS: C, 67.1; H, 4.8; S, 4.0. Found: C, 66.1; H, 4.8; S.4.3 9SL (ER=SCH3) Calcd. for C39H34O2P2RUS: C, 64.2; H, 4.7; S, 4.4. Found: C, 63.9; H, 4.8; S, 4.4. 9d (ER=SCH2CH3) Calcd. for C40H36O2P2RUS: C, 64.6; H, 4.9; S, 4.3. Found: C, 64.8; H, 5.1; S,4.5. 9e (ER=SCH2C6H5) Calcd. for C45H38O2P2RUS: C, 67.1; H, 4.8; S, 4.0. Found: C, 67.0; H, 4.9; S, 4.3. 9f (ER=SC6H4oCH3) Calcd. for C45H38O2P2RUS: C, 67.1; H, 4.8; S, 4.0. Found: C, 66.7; H, 4.8; S, 4.3. 2g (ER=SC6H4mCH3) Calcd. for C45H38O2P2RUS: C, 67.1; H, 4.8; S, 4.0. Found: C, 66.7; H, 4.3; S, 3.5. 9Jh (ER=SeC6H5) Calcd. for C44H3602P2RuSe: C, 63.0; H, 4.3. Found: C, 63.3; H, 4.6. 139 9j (ER=SC6H5) Calcd. for C^^gC^RuS: C, 66.7; H, 4.6. Found: C, 65.8; H, 4.8. The NMR and IR spectra of these complexes are described and shown in Section 3.2 and summarized in Tables 3.1,3.2, and 3.5. A sample of 9j (ER=Q)F5) was obtained, as confirmed by NMR spectroscopy, but an elemental analysis was not performed. The cct-RuD(SC6H5)(CO)2(PPh3)2 complex was synthesized from 2 and PhSD. Samples of cct-RuH(SCH2CH3)(CO)2(PR3)2 (PR3=PPh2Py, or P(C6H4/?CH3)3) were prepared in a similar manner from the corresponding m's-phosphine complexes, Ru(CO)2(PPh2Py)3 and Ru(CO)2(P(C6H4pCH3))3. The latter precursor was supplied by Dr. C.-L. Lee. The former precursor, Ru(CO)2(PPh2Py)3 was prepared by Mr. M Prystay, from [RuCl2(CO)3]2 and PPh2Py, followed by sodium amalgam reduction of the resulting ccr-RuCl2(CO)2(PPh2Py)2.258 The non-reaction of Ru(CO)2(PPh3)3 with ethanol: Ru(CO)2(PPh3)3 (12 mg, 13 Hmol) and ethanol (50 uL, 0.9 mmol) failed to react within 2 days in 10 mL THF at room temperature. The solvents were removed by vacuum distillation, and the unreacted solid, redissolved in C$D6, was identified by 31p{ lH} NMR spectroscopy. The X-ray crystallographic analysis of ccf-RuH(SC6H4pCH3)(CO)2(PPh3)2: Crystals of 9b suitable for X-ray crystallography were prepared by diffusion of hexanes into a saturated solution of the complex in THF, under Ar. The crystallographic data were acquired and analysed by Dr. S. J. Rettig of this department. The final unit-cell parameters were obtained by least-squares on the setting angles for 25 reflections with 28 = 31.1-35.6°. The intensities of three standard reflections, measured every 200 reflections throughout the data collection, were essentially constant. The data were processed259a and corrected for Lorentz and polarization effects and absorption (empirical, based on azimuthal scans for four reflections). 140 The structure analysis was initiated in the centrosymmetric space group PI, the choice being confirmed by the subsequent successful solution and refinement of the structure. The structure was solved by conventional heavy atom methods, the coordinates of the Ru, P, and S atoms being determined from the Patterson functions and those of the remaining non-hydrogen atoms from subsequent difference Fourier syntheses. All non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were fixed in idealized positions (dC-H = 0.98 A, BH = 1.2 Bbonded atom), except for the metal hydride which was refined with an isotropic thermal parameter. Neutral atom scattering factors and anomalous dispersion corrections for the non-hydrogen atoms were taken from the International Tables for X-Ray Crystallography 259b Final atomic coordinates and equivalent isotropic thermal parameters [Beq = 4/3ZiLjbij(aiaj)], bond lengths, and bond angles appear in Appendix 2, and Tables 3.3 and 3.4, respectively. Other crystallographic data for this structure and the other structures described in this work are presented in Appendix 1.209 The reaction of ccf-RuH2(CO)2(PPh3)2 (3) with thiols: The preparation of 9 from 3 was carried out in the same manner as described for the synthesis from 2 (see above), except that reaction times of 3 to 4 h were required. To confirm the production of H2 from the reaction, p-thiocresol (50 mg, 0.2 mmol) was added to a 1 mL saturated solution of 3 in THF in an NMR tube. After 2 h, and again after 25 h, 0.2 mL samples of the vapour phase were injected onto a molecular sieve column. A strong H2 peak was observed each time. The amount of H2 produced was determined by following the reaction between 3 (35 Hmol) and PhSH (290 (imol) in a constant pressure uptake apparatus at 30°C. After 50 min, the gas evolution measured had levelled off and corresponded to 40 jimoles of gas. The reaction of 3 with H2S was also monitored by lH NMR spectroscopy. A sample of 3 (4.17 mg, 10.3 mM) was dissolved in C6D6 (0.6 mL) under Ar in an NMR tube and 141 the Ar atmosphere was promptly replaced by flushing H2S through syringe needles inserted into the septum seal of the NMR tube. The sample tube was inserted into the NMR probe, which was maintained at 25.0°C. Successive spectra were acquired at a rate of one every 6 min, with every third being of the 31p rather than iH region of the NMR spectrum, in order to confirm that no products other than 9_a_ were forming. The concentrations of 2 and 9_a were calculated from the metal hydride signals in the lH NMR spectra. The reaction of cc*-RuH2(CO)2(PPb3)2 (2) with CO: The reaction of 3. (0.25 to 1.1 mM) with CO (1 atm) in THF was monitored at 350 nm, where the product Ru(CO)3(RPh3)2 (10, e=930 M"1 cm'1) absorbs more strongly than 2 (£=70 M"1 cm"1). The results at 41°C are described on page 86. Reactions at 25°C under N2 with sufficient CO injected through a septum to give a CO partial pressure of 0.09 atm had virtually the same first order rate constant (5.4 x 10-4 s-1) as reactions under a full atmosphere of CO (5.6 x 10-4 s-1). The 31p NMR chemical shift of the product (55.1 ppm) was identical to that reported by Dekleva,182 after correction for the different reference (all of the 31p NMR chemical shifts in Dekleva's work are exactly 1.5 ppm downfield of those observed in the present study, presumably because of a difference in the reference point). The reaction of cc/-RuH2(CO)20?Ph3)2 (2) with PPI13: The reaction of 2 (0.34 mM) with PPh3 (47 to 380 mM) in THF was monitored at 25°C and 400 nm, where the product 2 (E—6000 M"* cm"*) absorbs much more strongly than 2 (e=40 M"l cm"1). The plots of /n(A«»-A) versus time are linear for experiments with ratios of [PPh3]:[3J of 130 or greater. To insure proper mixing, particularly for the H2 co-product, the cell was quickly inverted four times between each measurement, or approximately every 25 seconds. Pseudo-first order kinetics were also observed if Ar was bubbled through the cell between measurements. The identity of the Ru product of the reaction, 142 Ru(CO)2(PPh3)3 (2), was confirmed by comparing the 31p{ NMR spectrum of the product to that of a C6j)6 solution of a known sample of 2 (Section 2.3.2). The non-reaction of cc/-RuH2(CO)2(PPh3)2 (2) with methanol: MeOH (70 ul, mmol) and 2 (8 mg, 12 umol) in THF (7 mL) failed to react within an hour. The solvents were removed by vacuum distillation, and the starting material was identified by its 3lp{ lH} and lH NMR spectra. The reaction of cc/-RuH2(CO)2(PPh3)2 (3) with acetic acid: Acetic acid (50 uL, 870 umol) and 2 (23 mg, 34 umol) were mixed in THF (10 mL) for 24 h at room temperature, during which no colour appeared. The volatiles were then removed by evacuation. The lH and 31p{ lH} NMR spectra of the residue redissolved in C6D6 showed signals for a major product consistent with ccf-RuH(OAc)(CO)2(PPh3)2-lH NMR (C6D6) 5 -3.68 ppm (t, IH, 2JPH = 19.0 Hz, Ru-H), 1.40 ppm (s, 3H, CH3); 31P{ lH} (C6D6) 8 45.24 ppm. These data match closely those found by Dekleva182 for ccf-RuH(OCOPh)(CO)2(PPh3)2 (JH NMR (C6D6) 8 -3.52 ppm (t, 2JPH = 20 Hz, Ru-H); 31p{ lH} (C6D6) corrected 8 44.8 ppm). The acetate made in the present study was not purified or analysed, and contained 10 % each (measured by 31p NMR) of ccr-RuH2(CO)2(PPh3)2, Ru(CO)3(PPh3)2, and an unknown (singlet at 44.63 ppm). The reaction of cis- and /rans-RuH2(dpm)2 (7) with thiols: A sample of 7 (6.0 mg, 6.9 umol) was dissolved in C5D5 (0.5 mL) in an NMR tube under Ar, and the tube was capped with a septum. The gas phase of the NMR tube was then flushed with H2S. The progress of the reaction was followed by NMR spectroscopy. The lH and 31p{ lH) spectra after 45 min showed almost complete conversion to a new complex, believed to be tfww-RuH(SH)(dpm)2 (13a). lH NMR (C6D6) 8 -9.46 (qn, 2JPH = 19 Hz, Ru-H), 143 *3.55 (br, Ru-SH), 4.54 (dt, 2JHH - 16 Hz, 2JPH = 3 Hz, CH^ 5.21 ppm (multi, CH2); 31P{ lH} NMR (C6D6) 8 0.40 ppm (s). The corresponding reaction of 7 with thiols was monitored by dissolving 7 (6.0 mg, 6.9 umol) in CgDg or toluene-dg (0.5 mL) in an NMR tube under Ar, and capping the tube with a septum. After an NMR spectrum of this sample had been acquired and the temperature of the probe had reached a steady 25°C, PhSH (4 uL, 70 mM) or PhCH2SH (5 to 60 uL, 70 to 850 mM) was injected through the septum. The progress of the reaction was followed by NMR spectroscopy. Three products were observed. Two of these, trans-md as-RuH(SR)(dpm)2 (13) could be identified from their NMR spectra. *ra/w-RuH(SPh)(dpm)2 (/r«iw-12b): lH NMR (toluene-d8) 8 -10.86 (qn, IH, 2JPH = 19.9 Hz, Ru-H), 4.27 (dt, 2H, 2JHH = 13.8 Hz, 2JPH = 3.3, CH2), and 4.78 (multi, 2H, CH2); 31p{ lH} NMR 5 -2.06 ppm (s). «s-RuH(SPh)(dpm)2 (cfr-13b); lH NMR (toluene-d8) 8 -6.29 ppm (ddt, 2JtransPH = 91.5 Hz, 2JcisPH = 24.1,16.3 Hz, Ru-H). The 31p{ lH} NMR spectrum of the toluene-d8 solution of this product is described in Section 3.4 and shown in Fig. 3.23. *ra/«-RuH(SCH2Ph)(dpm)2 (trans-Uc): lH NMR (C6D6) 8 -10.16 (qn, 2JPH = 20.0 Hz, Ru-H), 4.44 (dt, 2JHH = 13.5 Hz, 2jPH = 3.2, CH2), and 5.19 (multi, CH2); 31p{lH} NMR 8 -1.68 ppm (s). cw-RuH(SCH2Ph)(dpm)2 (cw-13e): lH NMR (C6D6) 8 -7.17 ppm (d of q, 2JtransPH = 97 Hz, 2JcisPH = 20 Hz, Ru-H). The peaks for this complex were not resolved in the 31p{ lH} NMR spectrum of the toluene-dg solution of the cis- and trans-13c mixture. Unknown minor product: lH NMR (C6D6) 8 -9.41 ppm (qn, 2JPH = 19.4 Hz, Ru-H); 31P{ lH} NMR (C6D6) 8 0.20 ppm (s). *H NMR (toluene-d8) 8 -9.66 ppm (qn, 2JPH = 19.2 Hz, Ru-H); 31p{ lH} NMR (toluene-d8) 8 0.15 ppm (s). This unknown product, in the reaction with PhSH, reached a maximum of up to 12 % and thereafter declined. In the reaction with PhCH2SH, the same product was observed, although at lower and more constant concentrations. The structure of this product remains unassigned. 144 An inversion-recovery NMR experiment with the following pulse sequence PI P2 Dl D2 AT where Dl = 1.00 s delay time D2 = 60 ms delay time PI = 0.092 ms = 180O pulse P2 = 0.046 ms = 90o pulse AT = 1.36 s acquisition time shows a positive peak for protons with Ti values of less than 60 ms. During a reaction of 7 (2.3 mg, 4.5 mM) and PhSH (4 uL, 70 mM) in CgDg (0.6 mL) at 20°C, spectra were acquired using this pulse sequence. Only negative peaks were observed. The reaction of cis- and /rans-RuH2(dpm)2 (2) with p-toluenesulphonic acid: Complex 7 (5.0 mg, 5.7 umol) and/>-toluenesulphonic acid (28 mg, 150 umol) reacted in deuterated toluene (0.7 mL) at room temperature to form several products within a few minutes. A major product, a minor product, and unreacted as- and fra/w-RuH2(dpm)2 were evident in the lH and 31p{ lH} NMR spectra. The major product was possibly RuH(S03C6H4pCH3)(dpm)2. *H NMR (toluene-d8) 8 -19.40 ppm (qn, 2JPH = 19.7 Hz, Ru-H), 4.39 (multi, CH2), and 5.40 (multi, CH2); 31p{ lH} NMR (toluene-d8) 8 -3.00 ppm (s). The minor product had the same NMR spectra as the unknown product observed in the reaction with thiols. lH NMR (toluene-dg) 8 -9.56 ppm (qn, 2JPH = 19.2 Hz, Ru-H); 31p{ lH) NMR (toluene-d8) 8 0.20 ppm (s). The reactions of cis- and //wns-RuH2(dpm)2 (7) and cc/-RuH2(CO)20?Ph3)2 (3) with deuterated methanol: A C6D6 solution of each of 7 and 3 (4 mM) was prepared under Ar, and a lH NMR spectrum of the sample acquired while the probe temperature equilibrated to 25°C. Enough CD3OD was then injected to make a 4% v/v CD3OD/C6D6 mixture. The decay in intensity of the peaks in the lH NMR spectrum 145 was then observed with successive acquisitions using constant experimental parameters. The results are summarized in Section 3.4. The reactions of cc/-RuH2(CO)2(PPh3)2 (3) with binary mixtures of thiols: Complex 2 (6.3 mg, 9.2 umol), PhSH (4.7 pL, 9.2 umol) and EtSH (3.4 uL, 9.2 umol) were stirred in THF (7 mL) overnight at room temperature. The solvent was removed by evaporation under vacuum, and the residual solid redissolved in Qpfr *H and 31p{ lH} NMR spectra showed that the product was ccf-RuH(SPh)(CO)2(PPh3)2 (9jj. This experiment was repeated ([3J = 10 mM, [EtSH] = 2.3 mM, [PhSH] = 1.62 mM) in an NMR tube to allow in situ monitoring of the reaction by lH NMR spectroscopy at 35.5°C. Complex 2 was consumed, producing both 9i and ccr-RuH(SEt)(CO)2(PPh3)2 (9d), the latter reaching a maximum of 32% and thereafter decreasing. After 50 min, no trace of 2 remained. After 100 min, the yield of 9j was 98%, the remainder being 9d. Several such reactions were performed, with several different mixtures of thiols. The concentrations of thiols were chosen so as to produce a fairly even mixture of thiolate products, that is, the major product was not over 80% of the mixture. The reaction of ccf-RuH(SEt)(CO)20?Ph3)2 (9d) with thiophenol: Complex 9d (1.8 or 8.4 mM) and PhSH (0.12 to 3.4 M) were dissolved in C6D6 (0.7 mL) in an NMR tube. lH NMR spectra were acquired every 8-20 min, for about 3 half-lives (190 min). Concentrations were calculated from the integration of the hydride signals. The observed rate constant, Jfcbbs. was determined from the plot of //i[9d] vs. time, which was linear (Fig. 3.29). One equivalent of free EtSH was detected by lH NMR spectroscopy. The reaction over 3 days of Ru(CO)20?Ph3)3 (2) with thiophenol: Complex 2 (86 mg, 91 umol) and PhSH (190 uL, 1.3 mmol) were left for 3 days at room temperature in THF solution (10 mL). The solvent was then removed by vacuum distillation, and the orange 146 oily residue redissolved in C5D5. The 31p{ IH} NMR spectrum shows that the product mixture contained (other than free PPI13): ccr-RuH(SPh)(CO)2(PPh3)2 (9j,37.26 ppm, 40% of 31p signal), ccr-Ru(SPh)2(CO)20?Ph3)2 (141, 10.73 ppm, 55%), and an unknown (23.88 ppm, 5%). None of the starting complex (2) remained. The same experiment, but with 300 mg of complex 2 and 0.5 mL PhSH, resulted in 90% conversion (based on 31p NMR signal integration) to 141.254 A similar experiment with m-thiocresol (0.3 mL, 2.5 mmol) gave only 55% conversion to the to-thiolato complex 14g. the other product being the mono-thiolato derivative 9JJ. No signal for 2 was detected in the 31p{ lH} NMR spectrum.254 The overnight reaction of Ru(CO)20?Ph3)3 with H2S: Ru(CO)2(PPh3)3 (400 mg, 0.42 mmol) under H2S (1 atm) in THF (20 mL), was stirred overnight at room temperature. The volume of solvent was reduced to 10 mL by vacuum transfer, and hexanes (150 mL) were added to induce precipitation. The isolated product had a 31p{ lH} NMR spectrum identical to that of a sample of cc/-Ru(SH)2(CO)2(PPh3)2 synthesised from ccr-RuH2(CO)2(PPh3)2 and H2S (see below).254 The overnight reaction of ccf-RuH2(CO)20?Ph3)2 (2) with H2S: Complex 3 (400 mg, 0.6 mmol) in THF (30 mL) was exposed to H2S overnight at room temperature. The solution was then reduced in volume by vacuum transfer, a solid, precipitated by addition of hexanes (150 mL), was filtered off and collected as a yellow powder (76% yield).254 The identity of the product, ccr-Ru(SH)2(CO)20?Ph3)2, was determined from the NMR spectra, the analysis, and the X-ray crystal structure (Section 4.2). Elem. Anal. Calcd. for C38H32O2P2RUS2: C, 61.0 H, 4.3 S, 8.6. Found: C, 60.4 H, 4.5 S, 8.7. lH NMR (C6D6) 8 -1.93 ppm (t, 3JpH = 6.8, Ru-SH), 6.95 (multi, m-/p-Ph), 8.15 (multi, o-Ph); 31p{ lH} NMR (C6D6) 8 20.45 ppm (s). For more complete details of the characterization, refer to Section 4.2. 147 Kinetic monitoring of the reaction of cc/-RuH(SH)(CO)2(PPh3)2 (2a) with H2S: Complex 9_a was generated in situ from the reaction of 3_ with H2S at 60°C. The concentrations of 2a and the final product ccf-Ru(SH)2(CO)2(PPh3)2 (14a) were calculated from their respective SH peak integrals. The experiment was stopped at the stage when PPI13 was detected in the 31p{ lH} NMR spectrum, which occurred after 40-50 min at 60°C. The non-reaction of cc/-RuCl2(CO)20?Ph3)2 (1) with NaBPh4: Complex 1 (0.109 g, 145 umol) and NaBPh4 (50 mg, 146 umol) were mixed in acetone (25 mL, distilled, freeze-thaw degassed three times under H2) under H2 (1 atm) at room temperature. After 90 min, the suspension was filtered through diatomaceous earth. The volume of the clear and colourless filtrate was reduced to 5 mL by vacuum distillation. The white precipitate thus formed was filtered and redissolved in C6D6- The 31p{ lH} NMR spectrum showed that this material was unreacted ccf-RuCl2(CO)2(PPh3)2. The reaction of tams-RuH(SH)(dpm)2 (13a) with H2S: Complex 13a was generated in situ by dissolving trans- and cis- RuH2(dpm)2 (L 4.3 mg, 7.4 mM) in C6D6 (0.5 mL) in an NMR tube under Ar, capping the tube with a septum, and flushing the gas phase of the NMR tube with H2S. The tube was then placed into the NMR probe, which was maintained at 60°C. Successive spectra were acquired at a rate of one every 10 min, with every fourth being of the 31p rather than lH region of the NMR spectrum. The lH NMR spectrum after 100 min showed almost complete conversion to a 1:1.8 mixture of cis- and /ra/tf-Ru(SH)2(dpm)2 (cis- and trans-15). /rans-Ru(SH)2(dpm)2 (trans-15): *H NMR (C6D6) 5 -3.73 ppm (t, 3JpH = 5.7 Hz, SH), 5.10 ppm (unresolved multi, CH2); 31p{ lH) NMR (C6D6) 5 -7.05 ppm (s). 148 cfr-Ru(SH)2(dpm)2 (m-15J: *H NMR (CgDg) 8 -1.92 ppm (s, SH), 4.62 ppm (unresolved multi, CH2), 5.10 ppm (unresolved multi, CH2); 31P{ !H} NMR (C&D6) 8 -5.93 ppm (t, 2jPP = 28.5 Hz), -22.65 ppm (t, 2jPP = 28.4 Hz). Cis- and trans-\S_ were isolated254 from the reaction of 7 (300 mg, 0.34 mmol) with H2S (saturated solution) in THF (30 mL) after 24 h at room temperature. The yellow precipitate thus formed was collected by filtration. Elem. Anal.: Calcd. for C50H46P4RUS2: C, 64.2; H, 5.0. Found: C, 63.6; H, 5.0. The precipitate contained only 5% of the trans isomer, while the solid precipitated from the filtrate contained 33% of the trans isomer. The reaction of /rans-RuH(BH4)(dpm)2 with H2S, using similar methods, produced a 1:2 mixture of cis- and /ra/ts-15.254 The reaction of cc/-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) with H2S: Complex 14b (3 mg, 3.3 nmol) was dissolved in CgDg (0.5 mL) and exposed to H2S at room temperature. The complex had been converted entirely to ccf-Ru(SH)2(CO)2(PPh3)2 by the time the first 31p{ lH} NMR spectrum had been acquired, within 5 min after the start of the reaction. The reaction of cc/-Ru(SC6H4pCH3)2(CO)20?Ph3)2 (14b) with ethanethiol: A saturated C6D6 solution of 14b was prepared in an NMR tube under Ar, the tube being capped with a septum. EtSH (24 uL, 0.32 mmol) was injected through the septum, and the tube was placed into the NMR probe at 20°C. Successive spectra were acquired at a rate of one every 6 min, with every third being of the lH rather than 31p region of the NMR spectrum. The 31p{ lH) NMR spectra after 26 min no longer changed. The solution contained 75% 14b and 25% cc/-Ru(SC2H5)(SC6H4pCH3)(CO)2(PPh3)2 (14bd). based on the 31p NMR integration. After 70 min, more EtSH (77 ul, 1.0 mmol) was added, which shifted the equilibrium. After 200 min, the product mixture was 11% 149 14b (8 10.90 ppm), 44% 14bd (11.00 ppm), and 45% ccr-Ru(SC2H5)2(CO)2(PPh3)2 (144 11.18 ppm). This experiment was repeated three times, but with 6 mM of the starting complex and three different concentrations of ethanethiol (260 to 1530 mM). Approximate Keq values at 20°C (Section 3.8) were calculated from the lH NMR spectra: Kj = 4(±1.4) x IO-2, K2 = 1(±0.2) x IO"2. The reaction of cc/-Ru(SH)2(CO)20?Ph3)2 (14a) with thiols: p-Thiocresol (2.8 mg, 0.223 M) and 14a (4.2 mg, 5.7 mM) were dissolved in C6T>6 (1 mL) in an NMR tube under Ar. Successive 31p{ lH} NMR spectra were acquired at 21°C, each taking 11 min. By 2 h, the concentrations of the complexes had converged to 34% 14a. 56% cc/-Ru(SH)(SC6H4pCH3)(CO)2(PPh3)2 (14ab) and 10% cc/-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b). A sample of 14a (4 mg, 7 mM) was dissolved in Q5D6 (0.8 mL) in an NMR tube under Ar, and PhSH (6 to 180 uL, 7.7 x 10"2 M to 2.0 M) was injected, before the start of monitoring by 31p{ lH} NMR spectroscopy at 21°C. The results of these experiments are described in detail in Section 3.8. Ethanethiol (0.25 mL, 3.3 mmol) and 14a (3 mg, 4.0 umol) were dissolved in CgDg and the reaction monitored in situ by 31p{ lH) NMR spectroscopy at room temperature. By 20 min, no change had been observed in the spectra. The reaction of Ru(CO)30?Ph3)2 (10) with H2S: The precursor complex 10 was supplied by Dr. C.-L. Lee, who prepared it by the reaction of Ru(CO)2(PPh3)3 with CD. 177 A refiuxing THF (40 mL) solution of 10 (600 mg, 0.85 mmol), after being under H2S (1 atm) for 3 h, was evaporated to dryness, the reaction giving 5-10% conversion to ccr-RuH(SH)(CO)2(PPh3)2 (9a) and 14a, as determined by 31p NMR spectroscopy, the remainder being unreacted starting material.254 150 The reaction of Ru(CO)2(dpm)(PPh3) (16) with thiols: The precursor complex, 16, was supplied by Dr. C.-L. Lee, who prepared it by the reaction of Ru(CO)2(PPh3)3 with dpm (synthesis and characterization, including the crystaUographicaUy-deterrnined structure of the l,l-bis(diphenylphosphino)ethane (dpm-Me) analogue, to be published). Ethanethiol (98 uL, 1.3 mmol) and 16. (16 mg, 19 umol) were stirred in THF (5 mL) for 5 h at room temperature, after which the volatiles were removed by vacuum distillation. The hydride region of the lH NMR spectrum of the residue in C6D6 contained three patterns at 8 -4.65 (t, 2JPH = 19.8 Hz, RuH of 2d), -8.09 (ddd, ^transPH = 107,2JcisPH = 20.1,13.8 Hz, RuH of 17), -8.55 ppm (ddd, 2JcisPH = 21.7,20.1,16.3 Hz, RuH of 18). The 31p{ lH} NMR spectrum contained a large number of unidentified peaks, in addition to those for 16 and 9d. The relative intensities of the peaks mentioned above are described in Section 3.9 Thiophenol (10 uL, 97 umol) and 16 (7 mg, 9.0 umol) were dissolved in CgDg. After 10 min, two singlets in the 31p{ lH} NMR spectrum were observed, in addition to the peaks for the starting complex. The largest, at 15% of the integral, was of an unknown complex (at -9.67 ppm), while the smallest, barely detectable by 31p( lH} NMR spectroscopy, was ccr-RuH(SPh)(CO)2(PPh3)2 (2L 37 ppm). The identity of this latter product was confirmed by the lH NMR spectrum, which shows a triplet at -4.54 ppm (2JPH = 19.8 Hz). No other hydride signal was observed. The reaction of Ru(CO)2(dpm)(PPh3) (16) with H2: A sample of Ru(CO)2(dpm)(PPh3) (7.4 mg, 9 umol) was stirred in THF (5 mL) under H2 for two days at room temperature. Hexanes were added to the light brown solution to induce precipitation of a product which was collected by filtration. The 31p{ lH} NMR spectrum (C6D6) contained many peaks, all unidentified. The metal-hydride region of the lH NMR spectrum contained four weak patterns, at 8 -5.30 (m, unidentified), -6.33 151 (t, 2JPH = 23.3 Hz, ccr-RuH2(CO)2(PPh3)2), -8.43 (ddd, 2JcisPH = 22.1,14.1, and 4.0 Hz, unidentified), and -8.14 ppm (ddd, 2jcisPH = 21.8,13.6, and 4.1 Hz, unidentified). 152 4. REACTIONS OF CARBONYL (PHOSPHINE) RUTHENIUM COMPLEXES WITH  DISULPHIDES. THIOETHERS. AND RELATED REAGENTS 4.1 THE REACTIONS OF Ru(CO)2(PPh3)3 WITH DISULPHIDES The reaction of 2 with p-tolyl disulphide (equation 4.1, R = C6H4PCH3), Ru(CO)2(PPh3)3 + RSSR —> Ru(SR)2(CO)2(PPh3)2 + PPh3 4.1 2 14 briefly mentioned in a previous publication from this laboratory,86 proceeds cleanly in THF, giving an isolable product, 14b (R=C6H4/?CH3). The same product is detected by 31p{ lH} NMR spectroscopy after the reactions of p-tolyl disulphide with ccr-RuH(SEt)(CO)2(PPh3)2 (9d. Section 4.4), and p-thiocresol with ccr-RuH2(CO)2(PPh3)2 (3, Section 3.6). Both 14b and the related complex ccf-Ru(SH)2(CO)2(PPh3)2 (14a) have been fully characterized (Section 4.2). Other examples of ccf-Ru(SR)2(CO)2(PPh3)2 complexes have been synthesized in this laboratory (Section 4.2) and other isomers have since been reported in the literature.260 The reaction of 2 (7.5 mM) with p-tolyl disulphide (210 mM) at 18°C in CgDg, monitored by 31p{ lH} NMR (Fig. 4.1), has a pseudo-first order rate constant of 1.2 x 10-3 s-1 and a half-life of 560 s (9.4 min). In the presence of a large amount of 1,1-dicyclopropylethylene (2.1 M), a thiyl-radical trap,261 the reaction rate is unchanged, suggesting that the reaction mechanism does not involve free radicals. After the reaction of 2 with p-tolyl disulphide in the presence of added phosphine, ccf-RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b) and Ph3PO are observed in addition to 14b. This may be due to a side-reaction involving trace water.262 RSSR + Ph3P + H20 2RSH + Ph3PO 4.2 153 2000 Time (s) A i THP iftoarithmic deoendence of the concentration of Ru(CO)2(PPh3)3 (2» J2Jo=7'?.. ^Kffl™/^^ PM mM) to C«D6 at 18* wtth or without a thiyl radical trap (M-dicyclopropylthyleiie). 154 The reaction of 2 with p-tolyl disulphide in THF, monitored by UV at 26°C, has an isosbestic point at 426 nm (Fig. 4.2), which decays because of a subsequent reaction which results in a UV spectrum having no maximum between 350 and 550 nm. This subsequent reaction, which is an order of magnitude slower than reaction 4.1, will be more fully described in Section 6.2.1. Because the subsequent reaction has an isosbestic at 395 nm, this wavelength was chosen for the collection of absorbance data for the measurement of the initial rate of reaction 4.1. This rate, calculated from the absorbances and the e values of isolated samples of 2 and 14b. increases with [2], although the scatter in the data is greater than expected (Fig. 4.3). The dependence of the observed initial rate on [RSSR] is first order at low [RSSR] (< 4 mM), decreasing to zero order at high [RSSR] (Fig. 4.4a). This is qualitatively consistent with the following mechanism. k\ -L k2 RSSR Ru(CO)2(PPh3)3 ^ ' " Ru(CO)2(PPh3)2 v ' ^ Ru(SR)2(CO)2(PPh3)2 2 *-i,L 14 4T141 = Jfciib.r2irRSSR1 dt Jti[L] + *2[RSSR] The observed initial rate constant at high [RSSR] (kobs - 7 x 10-3 s-1) should correspond to k\. The same constant can be calculated from the plot of the inverse of the rate equation (Fig. 4.4b). However, the value of k\ determined from the reaction of Ru(CO)2(PPh3)3 with CD is 4 x 10-2 s-1 (single experiment at 1.0 mM 2 and 1 atm CO in THF at 26°C). The reason for this discrepancy is not known. Reaction 4.1 is not sufficiendy clean for accurate kinetic data. The. proposed mechanism should therefore be considered as tentative. The initial concentration of PPh3 must be less than 0.05 mM because the concentration of PPh3 in solutions of Ru(CO)2(PPh3)3 is not detectable by 31p NMR. Thus, it is possible to place a lower limit of 80 on the value of k-\/k2, although the exact value cannot be determined because the conventional method 172 requires addition of excess PPh3, which causes a side reaction to occur. Values of k-\/k2 have been (ietermined for the corresponding mechanisms of the reactions of 2 with CO and H2 (0.043 and 0.15, respectively, at 24°C in dma).172 The 155 I l i i f l i i 1 1—-i \—i 1 1 i—i • i '—'— 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490 500 510 520 530 540 550 nm wavelength Fig. 4.2 The UV/visible absorption spectrum of a solution of Ru(CO)2(PPh3)3 (0.60 mM) and p-tolyldisulphide (8.2 mM) in THF at 260C a) after 70 s, b) 190 s, c) 320 s, d) 460 s, e) 620 s, f) 990 s, g) 1440 s, and thereafter every 600 s. 156 [2] (mM) Fig. 4.3 The dependence on [2] of the initial rate of the reaction Ru(CO)20?Ph3)3 (2) with /^tolyldisulphide (8 mM) in THF at 260C. 157 b) 1.8-r 1.6-1.4-1.2-=1 1.0-on • B 0.8-l/ra • l/ra 0.6-0.4-02-soo 1/TRSSR] (M-l) Fig. 4.4 a) The dependence on [RSSR] of the initial rate of the reaction of Ru(CO)2(PPh3)3 (2,034 mM) with /?-tolyl disulphide in THF at 26<>C, showing the line which corresponds to the best-fit straight line in Fig. 4.4b. b) Plot of l/(initial rate) against 1/[RSSR] for the same reaction, including the best-fit straight line. 158 reaction of the unobserved intermediate Ru(CO)2(PPh3)2 with p-tolyl disulphide is therefore three orders of magnitude slower than with CO or H2, if one neglects the effect of solvent. The reaction of 2 with ethyl disulphide is neither as fast nor as clean as that with p-tolyl disulphide, producing ccr-RuH(SEt)(CO)2(PPh3)2 (2c, 6 % by 3 lp NMR) and ccf-Ru(SEt)2(CO)2(PPh3)2 (14c, 12 %) after 110 min at room temperature in C6D6. The rate of the k2 step in the reaction with EtSSEt must be even slower than the rate with p-tolyl disulphide, as expected for the oxidative addition of a weaker Lewis acid. 4.2 THE CHARACTERIZATION OF ccf-Ru(SR)2(CO)2(PPh3)2 The complex ccf-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) was synthesized from Ru(CO)2(PPh3)3 (2) and p-tolyl disulphide (Section 4.1), while ccr-Ru(SH)2(CO)2(PPh3)2 (14a) was synthesized from 2 or ccr-RuH2(CO)2(PPh3)2 (3) and H2S (Sections 3.1 and 3.3). Both 14a and 14b have been fully characterized, and analyze correcdy. The structures of both have been determined by X-ray crystallography. In addition, several other members of the series ccr-Ru(SR)2(CO)2(PPh3)2 (Table 4.1) have been observed in situ by lH and 31p{ lH) NMR spectroscopy during the reactions of 14a or 14b with R'SH (reaction 3.18) or the reactions of ccf-RuH2(CO)2(PPh3)2 (3) with binary mixtures of thiols in large excess (reaction 4.3, cf. sections 3.5, 3.6). 45°C RuH2(CO)2(PPh3)2 + (2-n)RSH + nR'SH—> Ru(SR)2-n(SR')n(CO)2(PPh3)2 + 2H2 4.3 3_ 14 The 31p NMR chemical shift of 14 depends very little on the nature of the thiolate group, with the exceptions of complexes containing the -SH and -SC6F5 ligands, which have signals significantly further downfield (Table 4.1). The observed spectra show that the 31p chemical 159 Table 4.1 NMR Spectroscopic Data for Complexes of the Series cct-Ru(SR)(SR')(CO)2(PPh3)2a R R' 31p 5 obs.b 31p 8 calc.c 20.40e 21.47 16.62f 16.17 16.56f 16.07 18.30g 18.25 14.42g 14.46 11.25e 11.21 n.oof 11.04 10.90e 10.87 JHNMRd  -1.93 (t, 3JPH=6.8, SH) -1.82 (t, 3jPH=7.1,SH) -1.82 (t, 3jPH=7.3, SH) 1.16(t,3jHH=7.4,CH3) 1.97(q,3jHH=7.4,CH2) 6.54 (d, 3JHH=8.1, o-Ph) 6.86 (d, 3jRH=8.2, m-Ph) 2.03 (s,CH3) 14a 14ab 14ai 14j 14ij 14d 14bd 14b 14bi  14i H H H C6F5 C6F5 CH2CH3 CH2CH3 C6H4PCH3 H C6H4/7CH3 C6H5 C6F5 C6H5 CH2CH3 C6H4/7CH3 C6H4PCH3 C6H4PCH3 _C6H5 C6H5 C6H5. 10.78g 10.69g 10.77 10.67 a C6D6 solutions at room temperature. b observed chemical shift (ppm), with reference to 85 % H3PO4 in H2O. c calculated from the empirical equation presented in Section 4.2. d ppm, with reference to TMS in C6D6- Coupling constants are given in Hz. Data are for the protons of the thiolate ligands only, e isolated sample. f generated in situ via reaction 3.18. g generated in situ via reaction 4.3. 160 shift (8) of ccr-Ru(SR)(SR')(CO)20?Ph3)2 in CgDg at room temperature is roughly predicted by the following simple additivity rule. 8 = 10.67 ppm + X(R) + X(R') where R= H > C6F5 > CH2CH3 > C6H4PCH3 > C6H5 X= 5.4 3.79 0.27 0.10 0.00 ppm The error is ±0.06 ppm except for the complexes containing the -SH ligand. The chemical shifts of 14 in CD2CI2 are 21.91 (R=H), 11.43 (R=Ph), 11.39 (R=C£H4/?CH3), and 11.77 ppm (R=C6H4mCH3), not significandy different from those in C6D6- The 31p chemical shifts in CDCI3 of the ca-Ru(SR)2(CO)2(PPh3)2 complexes isolated by Catala et a/.260b were reported relative to P(OMe)3. After conversion to shifts relative to 85 % H3PO4 (assuming that the signal of P(OMe)3 appears at 141 ppm263), the reported shifts of these complexes are 22.8 (R=Me), 39.6 (rBu), 26.6 (C6F4H), and 29.4 ppm (C6F5,14j). It is not known why the chemical shift reported by Catala et al. for 14j and that in the present study differ by more than 10 ppm. The spread of the chemical shifts are similar in the two studies. The difference between the chemical shifts of ccf-Ru(SR)2(CO)2(PPh3)2 (R=Me and C6F5) in CDCI3 is 6.6 ppm 260b very similar to the difference Q^=Et vs. C6F5) of 7.05 ppm in C6D6 found in the present study. The lH NMR test described in Section 2.3.3, applied to the spectra of 14a and 14b (Fig. 4.5), proves that the PPh3 ligands of those complexes are in trans positions. The mercapto signals of 14a are triplets, 1.07 ppm downfield of the same signal in ccf-RuH(SH)(CO)2(PPh3)2 (9a). The methyl signal of 14b is at the same chemical shift (2.03 ppm) as its hydrido-thiolato analogue ?b. The FT-IR spectra of 14 (Fig. 4.6) contain two strong v(CO) bands at 2046 and 1981 cm-1 (14a)126 or at 2028 and 1968 cm-1 (R=14b)254, suggesting that both complexes contain cis-carbonyls, and therefore that both are cct isomers in solution. The cct isomer is the most stable of the isomers of ccf-RuCl2(CO)2(PR3)2.169 m-/?-PPh3 o-PPh3 1II|IIII|IIII|IIII|IHI|IIII|IIII|IIII|IIII|IMI|IIM|UII|IIII|IIII|IIII|IIII|" 8.0 7.8 7.6 7.4 7.2 7.0 6.8 6.6 ppm Li SPhCH3 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 | l l I I I l I I l | i i I I I I I i I | I I r I | l I I l ) l l l i | T I t I | I I I I | I l l I | i r 8 7 6 5 4 3 2 1 Oppm Fig. 4.5 lH NMR spectrum of ccf-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (2b>, In C6D6, with an expanded view of the phenyl region. 3BOO 3200 2BOO 2000 1700 1 AOO 1 1 OO BOO SOO wavenumbers (cm-1) Xau^^ in HCB. The 163 The UV/vis spectrum of 14 contains a maximum at 371 (e = 2460,14a) or 430 nm (e = 3040 M-l cm-1,14b). which causes the yellow colour. The absorption is probably caused by the same ligand-to-metal charge transfer which caused the similar band in the spectrum of ccf-RuH(SR)(CO)2(PPh3)2 (Section 3.2). The solid state X-ray crystal structure of 14b (Fig. 4.7) was investigated by Dr. S. Rettig,209 and can be compared to the previously solved structure of a crystal of 14a (Fig. 4.8) synthesized in this lab.264 Both were shown to be of cct geometry. Bond lengths, bond angles, and other crystallographic data are listed in Tables 4.2 through 4.5 and Appendices 1 and 3. Related complexes for which X-ray crystal structures have been reported include ccc-Os(SC6F5)2(CD)2(PEt2Ph)2260d and ccf-Ru(OCOPh)2(CO)2(PPh3)2.257d The observed deviations from octahedral geometry around the Ru centre of 14b are due to the PPh3 groups crowding the carbonyls in order to avoid the bulky thiolate ligands. The carbonyls therefore are slighdy further apart (91.6°), and the thiolates closer together (83.05°) than expected for octahedral geometry. This effect is not observed in 14a (angles: C-Ru-C 89.1°, S-Ru-S 92.2°)264 because the mercapto ligands are considerably less bulky than the thiolates in 14b. The proximity of the S atoms in 14b (3.26 A) but not 14a (3.56 A)264 is probably caused by the bulky p-tolyl groups which point away from each other. The S atoms are not so close together as to indicate S-S attractive interactions, which have been reported for some cw-thiolate complexes. "S-S contacts are invariably shorter when the sulphur lone pairs (assuming approximate sp3 hybridizations) are oriented so as to allow overlap, resulting in an interaction which would normally be considered repulsive."265 Visual inspection of the structure of 14b shows that the thiolate ligands are oriented so as to allow almost no lone pair overlap. In both complexes, and in ccc-Fe(SPh)2(CO)2(dppe) (dppe = l,2-bis{diphenylphosphino}ethane, S-S distance is 3.23 A),214 the S-S interatomic distance is considerably longer than observed for S-S bonds such as in ccr-Os(ri2S2Me)(CO)2(PPh3)2 (2.022 A).118 The lengths of the Ru-S, Ru-C, and C-0 bonds of 14a, 14b, and ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b, Section 3.2) are similar. The S-C bond lengths of 164 MrJgSIVTomsSid the THF molecule omitted for dantj,. Fig. 4.8 The structure of Ru(SH)2(CO)2(PPh3)2.264 Hydrogen atoms are omitted for clarity. 166 Table 4.2 Selected bond lengths (A) with estimated standard deviations in parentheses, for ccf-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) .209 atom atom distance atom atom distance Ru C(2) 1.863 (8) P(D C(9) 1.814(8) Ru C(l) 1.900 (8) P(l) C(15) 1.838 (8) Ru P(l) 2.444 (2) P(D C(3) 1.841 (7) Ru P(2) 2.449 (2) P(2) C(33) 1.826 (7) Ru S(2) 2.450 (2) P(2) C(27) 1.833 (7) Ru S(l) 2.470 (2) P(2) C(21) 1.841 (7) S(D C(39) 1.788 (7) 0(1) C(l) 1.129(7) S(2) C(46) 1.778 m 0(2) C(2) 1.148 (8) Table 4.3 Selected bond angles (o) with estimated standard deviations in parentheses, for cc/-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b).209 atom atom atom angle atom atom atom angle C(2) Ru C(l) 91.6 (3) C(46) S(2) Ru 113.6 (2) C(2) Ru P(D 86.8 (2) C(9) P(D C(15) 103.2 (4) C(2) Ru P(2) 94.8 (2) C(9) P(D C(3) 106.3 (3) C(2) Ru S(2) 178.1 (2) C(9) P(l) Ru 107.0 (2) C(2) Ru S(l) 95.9 (2) C(15) P(D C(3) 98.4 (3) C(l) Ru P(l) 88.3 (2) C(15) P(l) Ru 119.3 (3) C(l) Ru P(2) 90.1 (2) C(3) P(D Ru 120.7 (2) C(l) Ru S(2) 89.4 (2) C(33) P(2) C(27) 103.1(3) C(l) Ru S(D 172.3 (2) C(33) P(2) C(21) 101.9 (3) P(D Ru P(2) 177.8 (1) C(33) P(2) Ru • 114.3 (3) P(l) Ru S(2) 91.62 (8) C(27) P(2) C(21) ' 103.5(3) P(D Ru S(l) 90.64 (8) C(27) P(2) Ru 113.0(2) P(2) Ru S(2) 86.87 (8) C(21) P(2) Ru 119.1 (2) P(2) Ru S(l) 90.74 (8) O(l) C(l) Ru 176.7 (6) S(2) Ru S(l) 83.05 (7) 0(2) C(2) Ru 174.2 (7) C(39) S(D Ru 113.0 (2) 167 Table 4.4 Selected bond lengths (A) with estimated standard deviations in parentheses, for cc/-Ru(SH)2(CO)2(PPh3)2 (14al.264 atom atom distance Ru P(2) 2.418 (2) Ru S(2) 2.470(2) Ru C(2) 1.891 (7) S(2) H(2) 1.2 (1) P(l) C(21) 1.846 (8) P(2) C(41) 1.835(7) P(2) C(51) 1.836 (9) C(l) 0(1) 1.12(1) atom atom distance Ru P(D 2.411(1) Ru S(l) 2.472 (2) Ru C(l) 1.891 (8) S(l) H(l) 1.0 (2) P(D C(ll) 1.846 (6) P(D C(31) 1.832 (6) P(2) C(41) 1.835 (7) P(2) C(61) 1.841 (4) C(2) 0(2) 1.12(1) Table 4.5 Selected bond angles (o) with estimated standard deviations in parentheses, for cc/-Ru(SH)2(C0)2(PPh3)2 (14a).264 atom atom atom angle P(l) Ru P(2) 175.57(7) P(l) Ru S(2) 85.4(1) P(l) Ru C(2) 92.0(1) P(2) Ru S(2) 90.5(1) P(2) Ru C(2) 92.1(1) S(l) Ru C(l) 175.6(2) S(2) Ru C(l) 91.8(2) C(l) Ru C(2) 89.1(2) Ru S(2) H(2) 99(14) Ru P(l) C(21) 120.3(1) C(ll) P(l) C(21) 99.7(3) C(21) P(l) C(31) 102.8(3) Ru P(2) C(51) 117.1(2) C(41) P(2) C(51) 106.3(3) C(51) P(2) C(61) 101.1(3) Ru C(2) Q(2) 178.1(9) atom atom atom angle P(D Ru S(l) 91.0(1) P(l) Ru C(l) 91.2 (2) P(2) Ru S(l) 87.5 (1) P(2) Ru C(l) 90.6 (2) S(l) Ru S(2) 92.2 (1) S(l) Ru C(2) 86.9 (2) S(2) Ru C(2) 177.3 (1) Ru S(l) H(l) 84 (12) Ru P(D C(ll) 117.1 (1) Ru P(D C(31) 109.9 (1) C(ll) P(D C(31) 105.1 (3) Ru P(2) C(41) 108.5 (3) Ru P(2) C(61) 120.0 (3) C(41) P(2) C(61) 102.0 (3) Ru C(l) 0(1) 176.8 (7) 168 14b (1.778 and 1.788 A) are slighdy longer than that found in 9b (1.769 A), possibly because of the steric effect of the thiolate ligands in 14b. The protons of the mercapto ligands of 14a were located, although the errors in the bond lengths and angles are high.264 The Ru-P bond lengths of the complexes increase with the increasing bulk of the ligands, in the following order: RuH(SR)(CO)2(PPh3)2 < Ru(SH)2(CO)2(PPh3)2 < Ru(SR)2(CO)2(PPh3)2 9b 14a 14b. As discussed in Section 3.2, an increase in Ru-P bond length has the effect of decreasing the 31p chemical shift (Fig. 3.7). The results here support the speculation (Section 3.2) that the changes in the 31p NMR chemical shift of 9 and 14 with changes in the thiolate group are due to steric effects. 4.3 THE REACTION OF ccf-RuH2(CO)2(PPh3)2 (3) WITH DISULPHIDES As mentioned in a communication from this laboratory,126 3 reacts with organic disulphides to produce the hydrido-thiolato complex, 2RuH2(CO)2(PPh3)2 + RSSR -> 2RuH(SR)(CO)2(PPh3)2 + H2 4A 3 9_ R = CH3, CH2CH3, CH2C6H5, C6H4PCH3 rather than the Ws-thiolato complex 14 that one might expect from a mechanism involving reductive elimination of H2 (cf. reaction 3.4) followed by oxidative addition of RSSR (cf. reaction 4.1). It was suggested by the authors of the reportl26 that the reaction involves two steps. RuH2(CO)2(PPh3)2 + RSSR -> RuH(SR)(CO)2(PPh3)2 + HSR 4.5 169 RuH2(CO)2(PPh3)2 + RSH RuH(SR)(CO)2(PPh3)2 + H2 3.4 The evidence for this was the detection of RSH (0.02 mmol) after a 5 h reaction of a THF solution (40 mL) of the dihydride (0.41 mmol) and p-tolyl disulphide (0.41 mmol). 126,266 Although the suggested sequence of reactions is reasonable, it is not unequivocal that the detection of a small amount of thiol is evidence for reaction 4.5; the thiol could instead have been produced by reaction 4.6 (see below). The reaction of 3_ with an 18-fold excess of p-tolyl disulphide in C6D6 was monitored by NMR at 45°C. After 1 h, the conversion to 9b was 84 %. If the reaction is monitored at room temperature, a small amount Oess than 11 %) of 14b is observed while the reaction to 9b proceeds. No p-thiocresol was detected in the lH NMR spectrum during this time, possibly because reaction 3.4 is faster than reaction 4.4; the concentration of thiol never reaches a level sufficient for detection. The production of the Ws-thiolate complex 14b is evidence for reaction 4.6 (to be described in Section 4.4), although a small amount of this product could have been produced by reaction 4.7, for which no independent evidence exists. The rate of reaction 4.4, monitored by either NMR or UV/vis spectroscopy is neither reproducible nor pseudo-fixst order, not surprising considering that reactions 3.4,4.5,4.6 and possibly 4.7 are all occurring in the same solution. No isosbestic points are observed because the UV/vis spectra of 3 and 9b do not have cross-over points. The mechanism of reaction 4.4 was not determined. RuH(SR)(CO)2(PPh3)2 + RSSR -> Ru(SR)2(CO)2(PPh3)2 + RSH 9 14 4.6 RuH2(CO)2(PPh3)2 + RSSR -> Ru(SR)2(CO)2(PPh3)2 + H2 3 14 4.7 170 4.4 THE REACTION OF cc/-RuH(SR)(CO)2(PPh3)2 WITH DISULPHIDES The reaction of ccf-RuH(SMe)(CO)2(PPh3)2 (9c) with p-tolyl disulphide in C6D6 was monitored by lH and 31p{ lH} NMR at 45°C. The complex is cleanly converted to ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b). The reaction has a half-life of 8.3 min (at [9c]=17 mM, [RSSR] =250 mM), assuming pseudo-fust order behaviour. RuH(SR)(CO)2(PPh3)2 + R'SSR' -> RuH(SR')(CO)2(PPh3)2 + RSSR' 4.8 The complex ccf-RuH(SEt)(CO)2(PPh3)2 (9d) reacts with p-tolyl disulphide in THF for two days at room temperature, resulting in complete conversion to ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) and the photolysis products thereof (Section 6.2.1). RuH(SR)(CO)2(PPh3)2 + R'SSR' ~> Ru(SR')2(CO)2(PPh3)2 + RSH 4.9 9 14 Reaction 4.8 is probably the first step in reaction 4.9. 4.5 THE REACTIONS OF CARBONYL (PHOSPHINE) RUTHENIUM COMPLEXES WITH STRAINED CYCLIC THIOETHERS The strained cyclic thioethers ethylene and propylene sulphide, otherwise known as thiirane and methylthiirane, are commonly-used sulphur transfer agents and rarely coordinate. 129 Propylene sulphide, for example, reacts overnight with ccr-RuH2(CO)2Q?Ph3)2 (3, reaction 4.10) or Ru(CO)2(PPh3)3 (2, reaction 4.11), or for 3 days with ccf-Ru(SH)2(CO)2(PPh3)2 (14a. reaction 4.12) at room temperature in THF to produce ccf-RuS2(CO)2(PPh3)2 (19)254 a complex which has been reported previously! 18a (Section 4.7). The production of propene, H2, and H2S in these reactions has not been experimentally confirmed. 171 RuH2((X>)2(PPh3)2 + 2CH2-CHCH3 RuS2(CXD)2(PPh3)2 + 2012=01013 + H2 12 4.10 Ru(CX))2(PPh3)3 + 3CH2-01CH3 1 V RuS2((X>)2(PPh3)2 + 3012=01013 + SPPh3 4.11 12 Ru(SH)2(CO)2(PPh3)2 + CHrCHCH2 1 14a xs7 „ RuS2(CX))20?Ph3)2 + 012=010l3 + H2S 12 4.12 The production of SPPI13 in reaction 4.11 (identified by 31p{ lH} NMR spectroscopy) suggests the possibility of reaction 4.13, but propylene sulphide and PPI13 in C6P6 fail to react within 12 h at room temperature. Oxidation of the phosphine to the phosphine sulphide must therefore involve the ruthenium complex. In the present work, reaction 4.10 (using a large excess of thioether) was monitored by 31p{ lH) NMR spectroscopy at 21°C, and initially two sulphureontaining complexes were observed, 19 (22 % of the 31p NMR signal after 10 min) and ccr-RuH(SR)(CO)2(PPh3)2 (2,10 %, R unknown). After 160 rnin, the signals due to these species had increased to 53 % and 29 %, respectively, while SPPh3 started to appear (12 % of the 31p NMR signal). After 7 days, the sole product detected in the 3 lp NMR spectrum was SPPI13. The rate of loss of 3_, as measured by 31p NMR spectroscopy, was not pseudo-fast order. The initial rate constant was calculated from the concentrations of 3 and 2 (determined from the 31p NMR peak integration) assuming the initial rate is first order in [31. The value of this rate constant (6.0 x 10-4 s-l at 21°C) is similar to that of the reaction of 3_ with thiols (Section 3.3), and is therefore consistent with a mechanism involving reductive elimination of H2 as the first and rate detemining step. Similar Oi2-Oiai3 + PPh3 • a*2=CHCH3 + SPPh3 4.13 172 31p{ *H) NMR experiments monitoring the reaction of 2 with propylene sulphide showed that reaction 4.11 is complete after 3 min at 25°C in CgDg. 4.6 THE NON-REACTIONS OF CARBONYL (PHOSPHINE) RUTHENIUM COMPLEXES WITH UNSTRAINED THIOETHERS The two complexes Ru(CO)2(PPh3)3 (2)254 and ccr-RuH2(CO)2(PPh3)2 (3) fail to react with thioethers such as MeSMe, PhSPh, and dibenzothiophene. Ru(CO)2(PPh3)3 + RSR —> no reaction 4.14 RuH2(CO)2(PPh3)2 + RSR —> no reaction 4.15 A 35-fold excess of freshly distilled thiophene reacts with 3_ at room temperature to produce ccr-RuH(SR)(CO)2(PPh3)2 (2% conversion, R=unknown alkyl group) after three days. This reaction is probably due to a trace (0.5ppth, calculated from the extent of conversion of 3 to 9) of thiol which was not removed by the distillation. At least four C4-thiols have boiling points267 within 20o of that of thiophene. 4.7 THE REACTIONS OF CARBONYL(PHOSPHINE)RUTHENIUM COMPLEXES WITH OTHER NEUTRAL SULPHUR-CONTAINING REAGENTS The reaction of Ru(CO)2(PPh3)3 (2) with elemental sulphur in benzene has been reported, although the fate of the extra phosphine ligand was not mentioned. 118a Ru(CO)2(PPh3)3 + 3/8S8 -> RuS2(CO)2(PPh3)2 + (SPPI13?) 4.16 2 19 173 The same product complex (19J is observed, along with SPPlty after the reaction of sulphur with ccr-Ru(SH)2(CO)2(PPh3)2.254 Dibenzyl trisulphide has been used to oxidize bridging thiolate groups to sulphides.268 The trisulphide reacts with ^Ru(S(^6H4p(H3)2(CO)2G?Ph3)2 (14b) relatively quickly at room temperature, giving SPPh3 and a host of minor products (<3 % each) after 40 min. The trisulphide reacts with 2 or 2 more slowly, producing SPPh3, and two unknowns with 31p NMR singlets with chemical shifts (34.67 and 31.34 ppm in C6D6) different from those of any of the related complexes that have been previously isolated, such as ccf-Ru(SR)2(CO)2(PPh3)2 (R=rl or CH2Ph), ccr-RuH(SR)(CX))2(PPh3)2, or ccr-RuS2(CO)2(PPh3)2. The desulphurization of trisulphides by triphenyl phosphine, giving disulphides and SPPI13, has been reported.269 4.8 EXPERIMENTAL DETAILS The reaction of Ru(CO)20?Ph3)3 (2) with p-tolyl disulphide: Complex 2 (140 mg, 0.15 mmol) and the disulphide (91 mg, 0.36 mmol) were dissolved in THF (20 mL) in a Schlenk tube wrapped with foil in darkness at room temperature. The solution remained orange throughout the reaction. After 4.5 h, the volume of the solution was reduced to 5 mL by vacuum distillation, and hexanes (60 mL) were added to induce precipitation. The collected yellow solid was ccr-Ru(SC6H4pCH3)2(CO)20?Ph3)2 (14b. 85 % yield). Elem. Anal. Calcd. for C52H44O2P2RUS2: C, 67.3; H, 4.8; S, 6.9. Found: C, 67.3; H, 4.7; S, 6.8. UV/vis max (0.25 mM in THF) 430 nm (e 3000 M"1 cm'1); FT-IR (Nujol) 2028,1968 cm"1 (v(C=0)); (HCB) : 2029,1971 cm-1; IH NMR (C6D6) 8 2.03 (s, 6H, CH3), 6.54 (d, 4H, Sjjjji = 8.1 Hz, SC5H4), 6.86 (d, 4H, 3JHH = 8.2 Hz, SC6H4), 6.99 (m, 18H, p-,m-PPh3), 7.95 ppm (m, 12H, 0-PPI13); 13C{ lH} NMR (C6D6) 20.90 ppm (s, CH3); 31p{ lH} NMR (C6D6) 10.95 ppm (s). A crystal of 14b suitable for X-ray crystallography was prepared by diffusion of hexanes into a concentrated THF solution under Ar in darkness. The collection and analysis of the 174 crystallographic data were performed by Dr. S. J. Rettig of this department.209 The final unit-cell parameters were obtained by least-squares on the setting angles for 25 reflections with 28 = 10.0-16.0°. The intensities of three standard reflections, measured every 200 reflections throughout the data collection, were essentially constant The data were processed259a and corrected for Lorentz and polarization effects, and absorption (empirical, based on azimuthal scans for four reflections).209 The structure analysis was initiated in the centresymrnetric space group PI, the choice being confirmed by the subsequent successful solution and refinement of the structure. The structure was solved by conventional heavy atom methods, the coordinates of the Ru, P, and S atoms being determined from the Patterson functions and those of the remaining non-hydrogen atoms from subsequent difference Fourier syntheses. The asymmetric unit contains one tetrahydrofuran solvate molecule in addition to the complex molecule. All non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were fixed in idealized positions (dC-H = 0.98 A, BH =1.2 Bbonded atom). Neutral atom scattering factors and anomalous dispersion corrections for the non-hydrogen atoms were taken from the International Tables for X-Ray Crystallography.259b Final atomic coordinates and equivalent isotropic thermal parameters [Beq = 4/3Zi2^jbij(ajaj)], bond lengths, and bond angles209 appear in Appendix 3, and Tables 4.2 and 4.3 respectively. Other crystallographic data for this structure and the other structures described in this work are presented in Appendix 1.209 The reaction of Ru(CO)20?Ph3)3 (2) with ethyl disulphide: A sample of 2 (3.3 mg, 7.1 mM) was dissolved in Q5D6 (0.46 mL) in an NMR tube at room temperature under Ar, and EtSSEt (36 uL, 592 mM) was added to start the reaction. After 30 min, ccr-RuH(SEt)(CO)2(PPh3)2 (9ji, 4 % conversion), ccf-Ru(SEt)2(CO)2(PPh3)2 (14d. 6 %), and PPI13 were detected by 31p{ lH} NMR spectroscopy. After 110 minutes, these conversions had increased to 6 and 12 %, respectively. 175 Monitoring the reaction of Ru(CO)2(PPh3)3 (2) with p-tolyl disulphide by 31P{1H} NMR spectroscopy: a) without added PPh3: Complex 2 (4.2 mg, 7.5 mM) and p-tolyl disulphide (31.7 mg, 210 mM) were dissolved in Cep6 (0.46 mL) in an NMR tube at 18<>C under Ar. After 30 min, ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b. 91 % conversion) and PPh3 were observed. After 60 min, the conversion had increased to 99 %. The pseudo-fust order log plot was linear, with some scatter (Fig. 4.1); the rate constant was 1.2 x 10-3 s-1. b) with added PPh3: Complex 2 (2.7 mg, 4.1 mM), p-tolyl disulphide (15.7 mg, 91 mM), and PPh3 (23.7 mg, 130 mM) were dissolved in C6D6 (0.70 mL) in an NMR tube at 26<>C under Ar. After 30 min, ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b, 6 % conversion), 14b (8 %), and OPPh3 (5 % of the 3lp NMR signal) were observed, in addition to the signals for the starting materials. After 30 min at 50°C, these conversions had increased to 41,45, and 10 %, for 9b. 14b. and OPPh3 respectively (the integration of the signal for OPPh3 cannot be assumed to accurately represent the concentration of that species,because of its large Tl value). c) with added 1,1-dicyclopropyIethyIene: Complex 2 (4.6 mg, 7.3 mM), and p-tolyl disulphide (31.8 mg, 200 mM) were dissolved in a mixture of C6D6 (0.49 mL) and 1,1-dicyclopropylethylene (0.13 mL, 2.1 M) in an NMR tube at 180C under Ar. After 5,14, and 28 min, 14b (40, 67, and 87 % conversion) and PPh3 were observed. The pseudo-fust order log plot was linear (Fig. 4.1), with more scatter than observed without the free radical trap; the rate constant was 1.1 x 10-3 s-1. The reaction of ccr-RuH2(CO)2(PPh3)2 (3) with mixtures of thiols: Complex 3 (4.6 mg, 8.4 mM) and p-thiocresol (24.4 mg, 246 mM) were dissolved in C6D6 under Ar in an NMR tube, which was capped with a septum. Thiophenol (20 uL, 244 mM) was injected through the septum. After 400 min at 210C, the products were ccr-RuH(SC6H5)(CO)2(PPh3)2 (31P{ lH} NMR 8 37.24 ppm, 46 %), ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (37.42 ppm, 21 %), ccf-Ru(SC6H5)2(CO)2(PPh3)2 (!0.69 ppm, 12 %), ccr-Ru(SC6H5)(SC6H4pCH3)(CO)2(PPh3)2 176 (10.78 ppm, 15 %), and ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (10.90 ppm, 6 %). Experiments with other mixtures of thiols were performed in a similar manner. The reaction of cc/-RuH2(CO)2(PPh3)2 (3) with p-tolyl disulphide: a) 210C: Complex 3_ (1.7 mg, 3.9 mM) and p-tolyl disulphide (20 mg, 130 mM) were dissolved in C(p6 (0.63 mL) in an NMR tube under Ar. The reaction was monitored by 31p{ lH} NMR spectroscopy, with the temperature of the sample being maintained at 21±1°C. After 40 min, 4 h, and 14 h, the species detected were 3 (55,38, and 10 %), ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (42,57, and 74 %), and ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (3,5, and 11 %). b) 45»C: Complex 3 (3.5 mg, 7.3 mM) and p-tolyl disulphide (23 mg, 130 mM) were dissolved in C(p6 (0.69 mL) in an NMR tube under Ar. The reaction was monitored by 31P{ lH} NMR spectroscopy, with the temperature of the sample being maintained at 45°C. After 30 min and 1 h, the species detected were 3 (33 and 16 %), and ccf-RuH(SC6H4pCH3)(CO)2(PPh3)2 (67 and 84 %). The reaction of cc/-RuH(SR)(CO)20?Ph3)2 with p-tolyl disulphide: a) over minutes: A sample of ccf-RuH(SMe)(CO)2(PPh3)2 (9c, 8.0 mg, 17 mM) and p-tolyl disulphide (39 mg, 250 mM) were dissolved in C(>D6 (0.65 mL) in an NMR tube under Ar. The reaction was monitored by lH and 31p{ lH} NMR spectroscopy at 45°C. After 12 and 55 min, the species detected were unreacted 9c (66 and 10 % of the hydride region of the lH NMR spectrum) and ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (34 and 90 %). Only four spectra were acquired, not enough to confirm that the rate of loss of 9c was first order. However, assuming pseudo-first order behaviour, the observed rate constant was 1.4 x 10-3 s-1, corresponding to a half-life of 8.3 min. b) over days: A sample of ccr-RuH(SEt)(CO)2(PPh3)2 (14 mg, 19 umol) and p-tolyl disulphide (123 mg, 500 umol) were dissolved in THF (10 mL) in a Schlenk tube under Ar. The yellow 177 solution turned to a more orange colour over 2 days at room temperature. The solvent was removed by vacuum filtration, and the residue was redissolved in C6D6- The 31p{ lH} NMR spectrum revealed the presence of c^Ru(SC6H4pCH3)2(CD)2(PPh3)2 (14b. 38 % of the signal), PPh3 (15 %), and unknown species which generated nine signals (<7 % each), most of which are also observed when solutions of c^Ru(SQ)H4pCH3)2(CO)2(PPh3)2 are irradiated with 430 nm light (Section 6.2.1). The reaction of cc*-RuH2(CO)20?Ph3)2 (2) with propylene sulphide: A sample of 3 (3.6 mg, 12 mM) was dissolved in a mixture of CD2CI2 (0.44 mL) and propylene sulphide (0.10 mL, 2.9 M) in an NMR tube under Ar. The reaction was monitored by 31p{ lH} NMR at room temperature (210Q. The species detected after 10 min, 38 min, 160 min, and 7 days were 3 (64, 39,7, and 0 % of the signal), ccr-RuS2(CO)2(PPh3)2 (22,31,53, and 0%), an unknown complex with 31p and lH NMR signals sirnilar to those of ccr-RuH(SR)(CO)2(PPh3)2 (10, 25,29, and 0 %), and SPPI13 (0,4,12, and 100 %). The chemical shifts of these four species were 56.19, 39.35,38.36, and 42.86 ppm, respectively. The hydride region of the lH NMR spectrum contained triplets at -6.3 and -3.8 ppm, consistent with the presence of unreacted 3 and ccr-RuH(SR)(CO)20?Ph3)2. Sirnilar results were obtained when C6D6 was used as the solvent The reaction of Ru(CO)20?Ph3)3 (2) with propylene sulphide: Propylene sulphide (50 uL, 1.1 M) was added to a solution of 2 (2.4 mg, 4.5 mM) in C6E>6 (0.57 mL) at room temperature. A 31p{ lH} NMR spectrum acquired three minutes later detected three species; SPPh3 (8 41.97 ppm, 30 % of signal), ccr-RuS2(CO)2(PPh3)2 (39.76 ppm, 30 %), and an unknown complex (37.07 ppm, 40 %) with 31p and lH NMR signals consistent with ccf-RuH(SR)(CX))2(PPh3)2 (lH NMR 8 -4.77 ppm, t, 2JPJJ = 20.4 Hz, R unknown but probably alkyl based on the *H NMR data). 178 The non-reaction of cc/-RuH2(CO)2(PPh3)2 (3J with unstrained thioethers: a) PhSPh: A sample of 3 (110 mg, 7.9 mM) was dissolved in a mixture of THF (20 mL) and PhSPh (0.6 mL, 180 mM) and the solution was stirred for 2 days under Ar at room temperature. The volume of the solvent was reduced to 10 mL by vacuum distillation and hexanes (30 mL) were added to the remainder to induce precipitation. The off-white solid collected by filtration was shown by 31p{ lH} NMR spectroscopy to be unreacted 3. b) MeSMe:254 A sample of 3 (400 mg, 14.6 mM) was dissolved in a mixture of THF (40 mL) and MeSMe (0.5 mL, 170 mM) and the solution was stirred for a day at room temperature under N2- The solvent was removed by vacuum distillation. 31p{ lH} NMR spectroscopy of the residue in C6D6 showed the presence of unreacted 3 and a small amount of ccr-Ru02(CD)2(PPh3)2 (identified by comparison of the 31p NMR chemical shift to that reported by Dekleval82). c) thiophene: A sample of 3 (140 mg, 10 mM) was dissolved in a mixture of THF (20 mL) and thiophene (0.8 mL, 500 mM) and the solution was stirred for 3 days under Ar at room temperature. The volume of the solution was reduced to 5 mL by vacuum distillation and hexanes (20 mL) were added to the remainder to induce precipitation. The off-white solid collected by filtration was shown by 31p{ lH) NMR spectroscopy (C6D6) to be 3 (98 %) and ccr-RuH(SR)(CO)2(PPh3)2 (9,2 %, R unknown). The lH NMR spectrum contained a weak triplet at -4.6 ppm (9), in addition to the triplet at -6.3 due to the dihydride (3). d) dibenzothiophene: A sample of 3 (20 mg, 2.8 mM) and dibenzothiophene (154 mg, 84 mM) were dissolved in THF (10 mL) and the solution was left for four days under Ar at room temperature. The solvent was then removed by vacuum distillation, leaving a residue of 3 (identified by 31p{lH} NMR spectroscopy). The reactions of Ru(CO)2(PPh3)3 and crf-RuH2(CO)2(PPh3)2 with di benzyl trisulphide: Ru(CO)2(PPh3)3 (150 mg, 7.9 mM) and dibenzyl trisulphide (286 mg, 51 mM) were dissolved in THF (20 mL) and the solution was stirred for 1 day. The volume of the solution was reduced 179 to 10 mL by vacuum distillation and hexanes (20 mL) were added to the remainder to induce precipitation of a yellow solid. This product was isolated by filtration and washed with hexanes (20 mL). The 31p{ lH} NMR spectrum (C6D6) of the product contained three peaks at 42.08 ppm (SPPh3,10 % of integral), 34.67 ppm (unknown, 20 %), and 31.34 ppm (unknown, 70 %). The filtrate was dried by vacuum distillation. The 31p{ lH) NMR spectrum (C6D6) of the residue contained the same three peaks but with different intensities (73,25, and 2 %, respectively). The reaction of the trisulphide with cc/-RuH2(CD)2(PPh3)2 gave similar results. The reaction of cc/-Ru(SC6H4pCH3)2(CO)20?Ph3)2 (14b) with di benzyl trisulphide: a sample of 14b (160 mg, 1.8 mM) and dibenzyl trisulphide (286 mg, 11.6 mM) were dissolved in THF (20 mL) under Ar in a darkened room. After 40 min, the solvent was removed by vacuum distillation. The 31p{ lH} NMR spectrum (C6D6) of the yellow residue redissolved in C6D6 showed that the major phosphoras-containing product was SPPI13. Thirteen other signals were observed, although the integration of each of these peaks was less than 3 % of the total. 180 5 THE METATHESIS REACTIONS OF CHLORORUTHENIUM  COMPLEXES WITH THIOLATE SALTS 5.1 INTRODUCTION The metathesis reactions of transition metal chlorides with thiolate salts are common synthetic routes for the preparation of thiolate complexes. The driving force for the reaction is the precipitation of an insoluble salt (e.g. NaCl) or the formation of a volatile product (e.g. Me3SiCl). The following reactions illustrate the variety of thiolate salts that have been used. CpRu(PPh3)2Cl + MSR -» CpRu(PPh3)2(SR) + MCI 5.1 M=Li; R=H, nPr, »Pr, C6H4PCH3 (ref. 270) M=Na; R=H (refs. 90,271) C0X42- + 4T1SR —> Co(SR)42" + 4T1X 5.2 X = halide ion (ref. 272) [Cp*RuCl2]2 + 2Me3SiSR —> [Cp*ClRu0xSR)]2 + 2Me3SiCl 5.3 R=Et, iPr (ref. 101) 3NbCl5 + 5 (Al(SPh)3.Et20) —> 3Nb(SPh)5 + 5 AICI3 + 3Et20 5.4 (refs. 265,273) Other commonly used reagents include the potassium, lead(H) and mercury(II) thiolate salts.265 An alternative method involves addition of a base and a thiol to the solution of the chloro-transition metal complex. NEt3 RuCl2(CO)2L2 + pySH > Ru(pyS)2(CO)L + Ru(pyS)2(CO)2L 5.5 -HNE13C1 (L = PPh3,ref.211) Metathesis is also used in the following related reaction with alcohols. RuCl2(CO)2(PPh3)2 + 0-CoCl4(OH)2 + 2KOH —> ccr-Ru(Ti2o2C6Cl4)(CO)2(PPh3)2 + (2KC1 + 2H20) 5.6 (ref. 274,275) Catala et al. have reported260,276 the metathesis reactions of several (chloro)-phosphine ruthenium complexes with thiolate salts. The thiolato (phosphine) products react with CO to 181 produce isomers of Ru(SR)2(CO)2(PPh3)2. Although the authors report results with several lead thiolates and four different phosphines, only the results with PPh3 (L) and Pb(SC6F5)2 are summarized below. Pb(SR)2 CO RUCI2L3 -*» Ru(SR)2L2 —> rcc-Ru(SR)2(CO)2L2 5.7 acetone Pb(SR)2 RUCI2L3 > Ru(SR)3L2 acetone Pb(SR)2 CO RuCl3L2(solv) > Ru(SR)3L2 —> ccf-Ru(SR)2(CO)2L2 5.9 Zn solv = CH3OH or CH3NO2 Pb(SR)2 CO mer-RuCl3L3 > Ru(SR)3L2 —> ccc-Ru(SR)2(CO)2L2 Zn It is not clear in reference 276 whether reactions 5.7 and 5.8 occur under different conditions or whether both products are observed simultaneously. In addition, the same group260b report the metathesis reaction of rcc-RuCl2(CO)2(PPh3)2 to form the same isomer of the to-thiolate complex. rcc-RuCl2(CO)2L2 + Pb(SR)2 —> rcc-Ru(SR)2(CO)2L2 + PbCl2 5.11 Metathesis reactions followed or preceded by carbonylation reactions are viable alternatives to the reactions of Ru(CO)2(PPh3)3 with thiols or disulphides for the synthesis of ccf-Ru(S Aryl)2(CO)2(PPh3)2. For the alkyl analogues, metathesis reactions appear to be the only successful route. 5.8 5.10 182 5.2 THE REACTIONS OF cct-RuCl2(CO)2(PPh3)2 WITH SODIUM THIOLATES The metathesis reaction of ccf-RuO2(C0)2(PPh3)2 (1) with sodium p-thiocresolate proceeds cleanly in acetone, the pure product being identified by comparing its lH and 31p{ lH} NMR spectra with those of a sample prepared from Ru(CO)2(PPh3)3 and p-tolyl disulphide. ccr-RuCl2(CO)2(PPh3)2 + 2NaSR —> ccr-Ru(SR)2(CO)2(PPh3)2 + 2NaCl 5.12 1 14 The metathesis reaction of 1 with sodium ethanethiolate in acetone produces the desired complex, ccf-Ru(SEt)2(CO)2(PPh3)2 (14d), but isolation and reprecipitation of this product were plagued by the formation of intractable oils. The same reaction in THF generates 14d and two new products ccr-RuCl(SEt)(CO)2(PPh3)2 (20) and [Ru(SEt)3(CO)2(PPh3)Na(THF)]2 (21) in varying ratios depending on the amount and freshness of thiolate used. If two equivalents are used, less than 10 % conversion to 20 is observed. If a large excess of thiolate is used, the exclusive product is 21. At intermediate concentrations of thiolate, mixtures of 14d. 20, and 21 are observed. It is likely that reactions 5.14 through 5.16 occur consecutively. RuCl2(CO)2(PPh3)2 + NaSEt -» RuCl(SEt)(CO)2(PPh3)2 + NaCl 5.14 1 20 RuCl(SEt)(CO)2(PPh3)2 + NaSEt —> Ru(SEt)2(CO)2(PPh3)2 + NaCl 5.15 20 14d 2Ru(SEt)2(CO)2(PPh3)2 + 2NaSEt + 2THF —» [Ru(SEt)3(CO)2(PPh3)Na(THF)]2 + 2PPh3 5.16 14d 21 The lability of the phosphine Ugands of ccf-Ru(SR)2(CO)2(PPh3)2 (H) has already been demonstrated (Section 3.8). Reaction 5.16 may simply proceed by elimination of PPh3 followed by coordination of a third thiolate ligand. The full characterization of 21 is described in Section 5.3. The two other products ccf-RuCl(SEt)(CO)2(PPh3)2 (20) and ccr-Ru(SEt)2(CO)2(PPh3)2 (14d) have virtually identical solubility, and have not been successfully separated. However, .183 samples in which one or the other was predominant were obtained by reacting RuCl2(CO)2(PPh3)2 (1) with different concentrations of thiolate. A sample of c^RuCl(SEt)(CO)20?Ph3)2 (2fi) containing only 2 % of 14d (estimated by NMR spectroscopy) was characterized. The integration of the lH NMR spectrum (Fig. 5.1a) shows that the ligands PPh3 and SEt are present in a 2:1 ratio. The chemical shift difference between the o- and the m-/p-phenyl signals is 1.2 ppm, clearly indicating trans phosphines. The 31p{ lH} NMR signal of 20. is a singlet at 14.54 ppm, intermediate in position between those of ccr-RuCl2(CO)2(PPh3)2 (L 15.66 ppm) and ccr-Ru(SEt)2(CO)2(PPh3)2 (J4d, 11.27 ppm). Two v(CO) stretching bands in the infrared spectrum of 20 (Fig. 5.2a) indicate cis carbonyls. Therefore, the geometry of the complex is the same as that of the starting material. PPh3 oa | ^ci OCT | ^SEt PPfa3 The FAB-Mass spectrum of 20 (Fig. 5.3 and Table 5.1) contains the molecular peak and several identifiable fragments. The carbon analysis is low. A sample of Ru(SEt)2(CO)2(PPh3)2 (14d) containing 20 % of 20 was characterized. The integration of the iH NMR spectrum Q?ig. 5.1b) shows that the ligands PPI13 and SEt are present in a 1:1 ratio. The chemical shift difference between the o- and the m-/p-phenyl signals is 1.2 ppm, indicating trans phosphines. The 31P{ lH) NMR signal of 14d (Table 5.2) is at 11.18 ppm, slightly higher than those of the Ws-(aryl thiolato) derivatives such as 14b (Section 4.2). The same signal is observed after the reactions of Ru(CO)2(PPh3)3 with excess ethanethiol or ethyl disulphide, and the reaction of ccr-Ru(SC6H4pCH3)2(CXD)2(PPh3)2 (14b) with ethanethiol (see Chapters 3 and 4). The infrared spectrum of the mixture of 14d and 20 contains two v(CO) bands due to 14d (Fig. 5.2b), indicating cis carbonyls. The structure is again cct. 184 CH2 a) o-Ph C6D5H \ j i " 1111111111111111111111111) 111) j in 111111111111111111 20 1.8 1.6 1.4 12 1.0 ppm m-p-Vh CH3 CH2 JL 1 • 1 1 • 1 1 1 1 1 1 1 1 1 • 1 1 ' • 1 • 1 ' ' 1 • 1 1 1 1 1 1 11 11 1 ' 11 ' 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm I 1 1 1 1 1 1 9.0 8.0 Fig. 5.1 a) 1H NMR spectrum (200 MHz, C6D6 solution) of ccf-RuCl(SEt)(CO)2(PPh3)2. The signals for THF are indicated by asterisks. b) Expanded region of the lH NMR spectrum (300 MHz, C6D6 solution) of a sample of cc/-Ru(SEt)2(CO)2(PPh3)2 containing 20% of cc/-RuCl(SEt)(CO)2(PPh3)2. a) v(CO)Sym v(CO)aSym b) HCCOsym v^asym 3800 3200 2800 2QDO -+-1700 -+- -+-1 400 1 IOO BOO SOO 2000 wavenumbers (cm-1) Fig. 5.2 a) The FT-IR spectrum of cc/-RuCI(SEt)(CO)2(PPh3)2 in a Nujol mull. The signals for Nujol are indicated by asterisks. b) Carbonyl region of the FT-IR spectrum of a sample of ccf-Ru(SEt)2(CO)2(PPh3)2 containing 20% of cc/-RuCl(SEt)(CO)2(PPh3)2, in a Nujol mull. Fig. 53 The FAB-Mass spectrum of ccf-RuCl(SEt)(CO)2(PPh3)2 in a /r-nitrobenzyl alcohol matrix. The peaks due to the matrix are indicated by asterisks. 187 Table 5.1 Fragments Detected in the FAB-Mass Spectrum of cc/-RuCl(SEt)(CO)2(PPh3)2 m/z Allocation Fragmentation 778 RuCl(SEt)(CO)2(PPh3)2 M 750 RuCl(SEt)(00)(PPh3)2 M-CO 722 RuCl(SEt)(PPh3)2 M-200 689 RuCl(CO)(PPh3)2 M-CO-SEt 654 Ru(CO)(PPh3)2 M-CO-SEt-Cl 625 Ru(PPh3)2 M-2CO-SEt-Cl 547 Ru(PPh3)(PPh2) M-2CO-SEt-Cl-Ph 423 Ru(SEt)(PPh3) M-2CX)-Cl-PPh3 396 RuCl(PPh3)a M-2CX)-SEt-PPh3 363 RufPPh^ M-2CO-SEt-Cl-PPhi a Fragment has a predicted m/z two units above that observed. All others have predicted values within one unit of those observed. Table 5.2 NMRa and IRb Spectral Data for Ru(X)(SEt)(CO)2(PPh3)2-31PNMR lH NMR „ sym. asym. X 8PPh3 SCH2 8CH3 Iw yfCQ) v(CC0 He 37.25 1.28 0.77 7.4 Hz 2025 cm-1 1964 cm-1 Cl 14.54 1.92 1.13 7.4 2042 1987 SEt 11.18 1.97 1.16 7.4 2022 1963 SPhpMed 11.00 - - : a Q)D6 solutions at room temperature using a 300 MHz spectrometer, b Nujol mulls, c Section 3.2 d* Section 3.8 188 The spectroscopic data for the series ccf-Ru(X)(SEf)(CO)2(PPh3)2 are summarized in Table 5.2. The lH NMR shifts of the ethyl group in ccf-RuH(SEt)(CO)2(PPh3)2 are at significandy higher field than those in the other complexes because H- is not as electron withdrawing as Cl-orSR-. 5.3 THE CHARACTERIZATION OF [Ru(SEt)3(CO)2(PPh3)Na(THF)]2 The 31p{ lH} NMR signal of the tide complex (21) is a singlet (wi/2 = 8 Hz at 18°C in toluene-d8), which broadens at lower temperatures (w\/2 = 29 Hz at -58°C, 120 Hz at -78°C; all data at 121 MHz). In C6P6, the peak is asymmetric, which suggests the possibility of two peaks and therefore two environments for the P atoms in the complex. The lH NMR spectrum (Figs. 5.4 and 5.6a) is complicated, and can only be assigned with the help of a COSY experiment (Fig. 5.5) or selective homonuclear decoupling exeriments (Fig. 5.6). The CH3 region contains two triplets at 1.40 and 1.59 ppm (in C6D6) in a ratio of 2:1. There are therefore two different kinds of ethyl group, which will be referred to as (a) and (b) respectively. The CH3 peak of Et(a) coincides with one of the two resonances of THF, which is present in the sample. The ratio of the ligands PPh3 : THF : Et(a): Et(b) is 1:1:2:1, based on the integration. The methylene region is quite complicated, due to overlapping signals, second order spectra, and inequivalence of gerninal methylene protons. Irradiation of the CH3 resonances simplifies the signals to two AB patterns. The two doublets for CH2(a) evident in Fig. 5.6c are at 2.72 and 2.95 ppm. The 2JHH coupling constant in Et(a) is 9.0 Hz. The AB pattern for CH2(b) is second order, so that only the two central peaks of the pattern are observed (Fig. 5.6b). A simple AB pattern consists of four lines, of which the outer two are short and of equal intensity, and the inner two are tall and of equal intensity. The ratio of the intensities of the outside peaks relative to those of the inside peaks can be calculated using the following formulae.277 o-Ph J m-p-Ph THF CH2a + CH2b CH2a THF + CH3a CH3b 00 1 ppm Fig. 5.4 The iH NMR spectrum (400 MHz) of a C6D6 solution of [(CO)2(PPh3)Ru(SCH2CH3)3Na(THF)]2 at 20oC. 190 r 1X1 il + 3.6 32 2.8 2.4 2.0 1.6 1.2 ppm Fig. 5.5 The iH COSY NMR plot (400 MHz) for a C6D6 solution of [(CO)2(PPh3)Ru(SCH2CH3)3Na(THF)]2. 3 ppm Fig. 5.6 The methylene region of lH NMR spectra of a CrfD* solution of I(CO)2(PPh3)Ru(SCH2CH3)3Na(THF)]2 at 400 MHz, with a) no decoupling, b) selective decoupling at 1.59 ppm (CH3b), or c) selective decoupling at 1.40 ppm (CH3a and THF). 192 UAH « Uzl I(A2) D + J Al A2B1 B2 D = ((vA-vB)2 + J2)1/2 VA2 = 1/2 (VA + VB - J + D) VBI = 1/2(VA + VB+J-D) Assuming that J is again 9 Hz, and taking 2.976 and 2.987 ppm as the positions of the two central peaks (vA2 and VB l), then the relative intensities of the outside peaks compared to the inside peaks is calculated to be 16%; the outside peaks are therefore too small to be detected in the selective decoupling experiment or in the cross-sections of the COSY. The methylene region of the lH NMR spectrum (300 MHz) of 21 in Cf5E>6 was accurately simulated (Fig. 5.7) using the following data: CH3(a): 1.41 ppm, t, 3JHH = 7.6 Hz CH3(b): 1.59ppm,t, 3jHH = 7.3Hz CH2(a): 2.708 ppm, d of q, 2JHH = 9.0 Hz, 3JHH = 7.4 Hz 2.962 ppm, d of q, 2JHH = 9.0 Hz, 3JHH = 7.4 Hz CH2(b): 2.953 ppm, d of q, 2JHH = 9.0 Hz, 3JHH = 7.3 Hz 2.987 ppm, d of q, 2JHH = 9.0 Hz, 3JHH = 7.4 Hz The peak positions in the simulated spectra match those in the observed spectrum within 0.005 ppm. The infrared spectrum of 21 in Nujol (Fig. 5.8) contains two v(CO) bands at 2014 and 1952 cm-1, suggesting cis carbonyls. In solution, the equivalent thiolates must be those trans to the carbonyls (assuming &fac arrangement of thiolates), and are assigned to the Et(a) signals in the NMR spectra. The observations described to this point are consistent with any structure containing Ru(SEt)3(CO)2(PPh3) units. The compound does not conduct in THF solution (up to 1 mM), whereas tetrabutylammonium iodide, a 1:1 electrolyte, has a conductivity of lMho at 0.2 mM in THF. The ruthenium could not have been oxidized to the paramagnetic trivalent state, because the peaks in the lH NMR spectrum would have been broadened and shifted. Therefore the complex must contain one bound extraneous counter-ion per Ru atom. The elemental 193 Fig. 5.7 Simulated 1H NMR spectra (300 MHz) of a) the CH2a protons, and b) the CH2b protons of [(CO)2(PPh3)Ru(SCH2CH3)3Na(THF)]2. The peak positions match within 0.005 ppm of those in the observed spectrum (c) of the same complex in C6D6. The CH2a and CH2b protons are identified with the letters "A" and "B", respectively. -I r-ZOOO 1700 1400 wavenumbers (cm-1) 1 IOO Fig 5.8 The FT-IR spectrum of [(CO)2(PPh3)Ru(ixSEt)2(u3SEt)Na(THF)]2 In Nujol. The peaks for Nujol are indicated by asterisks. 195 analysis and FAB-MS (Fig. 5.9 and Table 5.3) are consistent with, and the X-ray structure confirms, the formula [(PPh3)(CO)2Ru(u2SEt)2(U3SEt)Na(THF)]2 (21). The FAB Mass Spectrum of 21 (Fig. 5.9) contains many peaks assignable to fragments of this molecule (Table 5.3). The peak corresponding to the highest m/e value is that of the dimer minus one THF moiety. The X-ray structure of 21 is shown in figures 5.10 to 5.12. The bond lengths, angles, and other data are listed in tables 5.4,5.5, and Appendix B, respectively. The structure contains a crystographically imposed centre of symmetry, and thus only one half of the atoms are labelled in Figures 5.11 and 5.12. Each sodium atom is bound to three thiolate ligands of one Ru(SEt)3(CO)2(PPh3) fragment, one thiolate of the other fragment, and a THF molecule. The sodium atoms therefore have a coordination number of five, the sixth site being blocked by a phenyl group of the phosphine ligand. The coordination geometry at the Na is a distorted square pyramid. The cis S-Na-S angles are 71 or 72°, except those involving S2*, because the sodium atom is shifted towards the empty site away from the centre of the square pyramid. The cis S-Na-0 angles are all greater than 90° because the THF is leaning towards the empty sixth site. The Na-S bond lengths (Nal-Sl, Nal-S3, and Nal*-S3) are 2.82 to 2.84 A, comparable to the length of the same bond in NaSMe (2.8 A).278 The Nal-S2 bond is slighdy longer (3.0 A) than the others, and can be classed as secondary bridging.92 There are three types of thiolates present; one (Si) trans to the phosphine and doubly bridging, one (S3) trans to a carbonyl and doubly bridging, and one (S2) trans to a carbonyl and triply bridging. The Ru-S bond lengths for the thiolate ligands (SEt(a)) trans to carbonyls (2.474,2.467 A) are virtually identical to those in the structures described in previous chapters. The Ru-S and the S-C bond lengths for the thiolate ligand (SEt(b)) trans to the phosphine (2.434 and 1.746 A, respectively) are somewhat shorter than in the SEt(a) ligands because of the trans influence of the phosphine ligand. The Ru-S bond length of a similar thiolate ligand in Ru(pyS)2(CO)2(PPh3) is comparable (2.42 A).210 The S-C(sp3) bond lengths of 21 are longer Fig. 5.9 The FAB-Mass spectrum of [(CO)2(PPh3)Ru(uSEt)2(tX3SEt)Na(THF)]2 in a p-nitrobenzyl alcohol matrix. 197 Table 53 Fragments Detected in the FAB-Mass Spectrum of [(PPh3)(CO)2Ru(u2SEt)2(u3SEt)Na(THF)]2 m/z Allocation Fragmentation 1326 1289 1269 1147 1088 1022 964 829 765 737 646 587 557 529 451 423 363 319 285 263 241 Ru2(SEt)6(CX))40?Ph3)2Na2(THF)a Ru2(SEt)6(CO)2(PPh3)2Na2(THF) Ru2(SEt)4(CXD)2(PPh3)2Na2(THF) Ru2(SEt)40?Ph3)2Na2(THF)a Ru2(SEt)4(CO)(PPh3)2Na Ru2(SEt)6(PPh3)Na2(THF)2 Ru2(SEt)6(CO)3(PPh3)Na2a Ru2(SEt)4(PPh3)Na2(THF) Ru2(SEt)5(CX3)4Na2(THF) Ru(SEt)(CX))2(PPh3)NaCrrIF)2 Ru(SEt)(CO)(PPh3) Ru(SEt)(PPh3) Ru(PPh3) Ru(SEt)2Na(THF) Ru(SEt)3 PPh3 Rp(SEt)(CO)?Na M-THF M-2CO-THF M-2SEt-2CO-THF M-2SEt-4CO-THF M-2SEt-3CX)-Na-2THF M-4CX>PPh3 M-CX)-PPh3-2THF M-2SEt-4CO-PPh3-THF M-SEt-2PPh3-THF M-Ru-5SEt-2CXD-PPh3-Na M-Ru-5SEt-3CX)-PPh3-2Na-2THF M-Ru-5SEt-4CX)-PPh3-2Na-2THF M-Ru-6SEt-4CO-PPh3-2Na-2THF M-Ru-4SEt-4CX)-2PPh3-Na-THF M-Ru-3SEt-4CX>2PPh3-2Na-2THF M-2Ru-6SEt-4CO-PPh3-2Na-2THF M-Ru-5SEt-3CO-2PPh^-Na-2THF a Indicated fragments have a predicted m/z value two or three units below those observed. All others have predicted values within one unit of those observed. Fie. 5.10 The structure of one half of a molecule of [(CO)2(PPh3)Ru^Et)2(wSEt)Na(THF)]2. Fig. 5.11 The structure of [(CO)2(PPh3)Ru(uSEt)2(p.3SEt)Na(THF)]2. Hydrogen atoms omitted for clarity. 200 Fig. 5.12 Stereoscopic view of the structure of [(CO)2(PPh3)Ru(uSEt)2(rx3SEt)Na(THF)]2. Hydrogen atoms omitted for clarity. 201 Table 5.4 Selected bond lengths (A) with estimated standard deviations in parentheses for 21.209 atom atom distance atom atom distance Ru(l) S(l) 2.434(2) S(2) C(21) 1.819(5) Ru(l) S(2) 2.474(1) S(3) Na(l) 2.821(2) Ru(l) S(3) 2.467(1) S(3) C(23) 1.825(5) Ru(l) P(D 2.375(1) P(D C(l) 1.839(4) Ru(l) C(25) 1.865(5) P(D C(7) 1.834(4) Ru(l) C(26) 1.877(5) P(D C(13) 1.840(4) S(l) Na(l) 2.824(2) Na(l) 0(3) 2.365(5) S(l) C(19) 1.746(7) 0(1) C(25) 1.144(5) S(2) Na(l) Nam* 3.019(2) 0(2) C(26) 1.146(5) S(2) 2.839(2) * denotes symmetry operation: 1-x, -y, -z. Table 5.5 Selected bond angles (o) with estimated standard deviations in parentheses, for 21.209 atom atom atom angle atom atom atom angle S(l) RuQ) S(2) 88.46(5) RuQ) S(3) Na(l) 85.91(6) S(l) Ru(l) S(3) 84.60(5) RuQ) S(3) C(23) 109.4(2) S(l) Ru(l) P(l) 170.79(5) Na(l) S(3) C(23) 109.3(2) S(D Ru(l) C(25) 84.6(1) Ru(l) P(D C(l) 114.2(1) S(l) Ru(l) C(26) 93.4(1) Ru(l) P(D C(7) 112.3(1) S(2) Ru(l) S(3) 88.47(5) Ru(l) P(D C(13) 120.6(1) S(2) Ru(l) P(D 90.33(5) C(l) P(l) C(7) 104.8(2) S(2) Ru(l) C(25) 173.0(1) C(l) P(D C(13) 102.6(2) S(2) Ru(l) C(26) 89.2(1) C(7) P(D C(13) 100.4(2) S(3) Ru(l) P(D 86.25(5) S(l) Na(l) S(2) 71.64(6) S(3) Ru(D C(25) 91.6(2) S(l) Na(l) S(D* 157.14(9) S(3) Ru(l) C(26) 176.9(1) S(l) Na(l) S(3) 71.50(6) P(D Ru(l) C(25) 96.6(1) S(l) Na(l) 0(3) 95.3(1) P(l) Ru(D C(26) 95.7(1) S(2) Na(l) S(2)* 85.79(7) C(25) Ru(l) C(26) 90.5(2) S(2) Na(l) S(3) 72.25(6) Ru(l) SQ) Na(l) 86.45(6) S(2) Na(l) 0(3) 166.9(1) Ru(D S(l) C(19) 114.0(3) S(2)* Na(l) S(3) 105.59(8) Na(l) S(l) C(19) 147.9(3) S(2)* Na(l) 0(3) 107.3(1) Ru(l) S(2) Na(l) 81.57(5) S(3) Na(l) 0(3) 104.2(1) Ru(l) S(2) Na(l)* 145.88(6) Na(l) 0(3) C(27) 129.1(5) Ru(D S(2) C(21) 110.1(2) Na(l) 0(3) C(30) 123.0(5) Na(l) S(2) Na(l)* 94.21(7) C(27) 0(3) C(30) 106.2(6) Na(l) S(2) C(21) 103.7(2) Ru(D C(25) O(l) 173.8(4) Nam* S(2) C(21) 103.8(2) Ru(l) Q26) 0(2) 176.8(5) * denotes symmetry operation: 1-x, -y, -z. 202 than the S-C(sp2) bond lengths for the structures of c^RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b) and ccf-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) described in Chapters 3 and 4. The Ru-C and C-O bond lengths of 21 are comparable to those in carbonyls trans to thiolates in 9b, 14b. and 14a (Chapter 4). The Ru-P bond length is 2.375 A, slighdy shorter that in the other complexes, probably because the trans influence of thiolates is weaker than that of phosphines. The CP/MAS (cross-polarized, magic angle spinning) solid-state 13C NMR spectrum of 21 (Fig. 5.13a) contains two strong peaks for the THF molecule (68.2 and 25.6 ppm), one of which partly obscures the methylene region. Two peaks are observed on either side of the THF peak, at 26.9 and 24.6 ppm. However, three peaks are expected, because there are three different ethyl groups in the solid state structure. It is possible that the third peak is obscured by the THF resonance. The methyl region clearly contains three signals, as expected. An NQS (Non-Quaternary Suppression) solid state 13c NMR experiment was performed to confirm the identification of the three high field peaks as methyl peaks (Fig. 5.13b). In such an experiment, strongly dipolar-coupled nuclei such as CH or CH2 carbons are suppressed, while quaternary carbons and carbons in rapidly moving groups (e.g. CH3 groups) are detected.279 The three high field peaks due to CH3 groups are detected, in addition to the strong THF peak at 25.5 ppm. From the latter observation, one can conclude that the J3 carbons of the THF ligand are mobile, as suggested by the size of their thermal ellipsoids (Fig. 5.11). The THF ligand is therefore "wagging." The peaks were assigned by analogy to the solution 13C{ lH} NMR spectrum (see below). The solution 13C{ lH) NMR spectrum of 21 (Fig. 5.14) was assigned with the help of an APT (Attached Proton Test) experiment (Fig. 5.15) and a HETCOR (13C/1H NMR Heteronuclear Correlation) experiment Q7ig. 5.16). The HETCOR plot allows direct correlation of the 13C{ lH} NMR signals with the assigned peaks of the lH NMR spectrum. The methylene region of the 13C{ lH} NMR spectrum again contains resonances due to the THF molecule, at 67.8 and 25.7 ppm. Also in the methylene region are a larger peak at 25.2 ppm and a smaller 203 a) THF T" 60 40 20 ppm b) 20 ppm Fig. 5.13 a) 13C solid state (CP/MAS) NMR spectrum of [(CO)2(PPh3)Ru(uSEt)2^3SEt)Na(THF)]2. b) 13c solid state (CP/MAS) NQS NMR spectrum of [(CO)2(PPh3)Ru(uSEt)2(u3SEt)Na(THF)]2. 204 CH3a C6D6< CH2, i J. :L 20 26 24 22 p-Ph o-Ph CO PC f JUL/ m-Ph • 11111111111111111111111111111111111 • 11 •' • i • i• 11 • i •11' 136 134 132 130 128 126 THF , I 1111111111111111111111111111111II11II11II< 11111111' 11'' I' 11' • • I • I' 11 •''' 111 •' I'''' 111' •,.•.•I.••• I 200 180 160 140 120 100 80 60 40 20 0 ppm Fig. 5.14 13C{1H} NMR spectrum of [Ru(CO)2(PPh3)Ru(SEt)3Na(THF)]2 in C6D6 at 20°C and 75 MHz. CH2a o-Ph Fig. 5.15 13C APT NMR spectrum of [Ru(CO)2(PPh3)Ru(SEt)3Na(THF)]2 in C6D6 at 20OC and 75 MHz. 206 CH3a THF CH3b -1.5 -2.0 ppm Fig. 5.16 The Heteronuclear Correlation (13C/1H) NMR plot for PRu(CO)2(PPh3)Ru(uSEt)2(>3SEt)Na(THF)]2 in C6D6 at 125 MHz. Points along the line defined by 13c 8 = 23.5 ppm are believed to be artifacts. 207 peak at 26.6 ppm representing CH2(a) and CH2(b), respectively. The fact that only two such peaks are detected supports the conclusion from the lH NMR spectral data that the two Et(a) groups are equivalent in solution on the NMR time-scale. The methyl region of the solution 13C{ lH} NMR spectrum contains a tall peak for the CH3(a) groups, again confirming their equivalence. However, the small signal for the CH3O)) groups appears split in the 13C{ lH} and APT spectra at 75 MHz, but not in the 13C{ lH} NMR spectrum at 125 MHz. The reason for this splitting is not known. The lH NMR spectrum is unequivocal in demonstrating that there is only one type of CH3(b) group in the solution. The 13c{ lH) NMR spectral assignments for the phenyl region are based on the assumption that the Jpc coupling constant decreases in the order P-bound, o-, m-, p-phenyl carbons. The lack of conductivity in solution indicates that the sodium atoms do not dissociate from the complex. The solution NMR spectra of 21 do not reveal whether the complex exists as a dimer or monomer in solution. It is neither sufficiently stable for a determination of the molecular weight by the Signer method,280 nor sufficiendy soluble for a solvent freezing-point depression experiment. However, we know that the structure is not identical to that of the solid state because the Et(a) groups are equivalent in solution and not in the solid state. For the two Et(a) groups attached to S2 and S3 to be chemically equivalent, as observed in the solution spectra, a mirror plane would have to exist between them. Because the positions of Et(b), THF and the Na atoms are not on this plane, these three groups must be in rapid motion across it to create such a mirror plane. In other words, the following motions must occur rapidly on the NMR time-scale. 1) Inversion at the chiral sulphur atom Si would bring EtO?) across the rnirror plane. Inversion at S2 or S3 is not required, nor is it likely because it would bring the Et(a) groups into collision with the phenyl rings of the phosphine. 2) Rapid back-and-forth motion of Nal* between S2 and S3, and Nal between S2* and S3*. If the complex were a monomer in solution, then symmetry would only require that the Nal-S2 and Nal-S3 bonds be equivalent. 208 3) Rapid motion of the THF molecule between the sites trans to S2 and S^. If the complex were a dimer in solution, this motion would not be possible without dissociation of the THF ligand because of hindrance from the phenyl rings. This motion would also have to occur simultaneously with motion 2, so that the site to which the THF is travelling would no longer be blocked by a phenyl group. Alternatively, the two THF ligands could be completely dissociated from the sodium atoms in solution. The lH and 13C{ lH} NMR chemical shifts of the THF protons and carbons are not significandy different from those of THF alone in Ct>D6. This is consistent with but not proof of THF dissociation. The situation is made more complicated by the fact that the methylene protons of CH2(b) (Cl9) are not equivalent. If the nnrror plane exists, then these protons should be equivalent Therefore inversion at Si (motion 1) is probably not occurring rapidly on the NMR time-scale. It is not clear whether or not motions 2 and 3 are occurring. However, it seems unlikely that the Et(a) protons could appear to be equivalent without at least motion 2 being rapid on the NMR time-scale. Studies on the effect of the R group on the rate of the anti to syn isomerization of [Fe(CO)3(u.SR)]2 (equation 5.17) R 5.17 anti syn (Fe = Fe(CO)3, ref. 281-3) have shown that bulkier and aromatic thiolates invert more quickly. The rate constant for the conversion of the anti to the syn isomer, in toluene solution at 35°C, range from 1.1 x 10"^ s~* (R=Me)281 or 2.4 x 10-4 s-1 (R=Ph) to 0.6 s-1 (R=tBu)282 0r higher283 for very bulky groups. The ethyl derivative undergoes this net inversion process only marginally faster than the methyl derivative.281 The mechanism is probably via Fe-S bond cleavage. Although the thiolates in 209 [0:>Ph3)(CO)2Ru(SEt)3Na(THF)]2 (21) and [Fe(CO)3(p.SEt)]2 are not in identical environments, it seems reasonable that the inversion process in 21 is not rapid on the NMR time-scale. The variable temperature lH NMR spectra of 21 shed little light on the problem of motion within the, molecule. At temperatures greater than 60°C, changes in the appearance of the spectrum are rapid and irreversible. The signals due to THF (1.4 to 1.6 ppm) and an unknown complex presumably resulting from the decomposition of 21 (2.15 ppm) become more intense relative to the peaks of the dimer, which become amorphous. The lH NMR spectrum is not restored to its original appearance after the solution is cooled to 20°C, and only PPh3 can be detected in the 31P{ lH} NMR spectrum. The lH NMR spectrum of a fresh sample at -78°C shows the peaks of 21 (but not those of THF or toluene-d7) to be gready broadened (Fig. 5.17). This effect may result from a slowing of internal motions within the dimer. Spectra at even lower temperatures would be required to confirm this, although toluene-d8 has too high a freezing point (-93°C) to be used in such experiments. The only other compound containing [RuX3(CO)2(PPh3)]- fragments (X=halide or pseudo-halide), which has been mentioned in the literature, is [Rul3(CO)2(PPh3)][PPh3Me]. Rul2(CO)2(PPh3)2 + Mel —> [Rul3(CO)2(PPh3)][PPh3Me] 5.18 (ref. 284) The related anions [RuX3(CO)3]- (X=C1, Br, 1)285,286 and [RuCl3(CO)(PPh3)2]-287 have also been reported. The structure of 21 is unique in that the two Ru centres are connected to each other by a network of six bridging thiolate ligands and two sodium atoms; four thiolates (SI, S3, SI*, and S3*) bridge one Ru and one Na, while two thiolates (S2 and S2*) triply bridge one Ru and two Na atoms. Such triple bridging of thiolates between transition metal and alkali metal ions is unprecedented. The recently reported anionic species [Na{Ru(CO)2(Se4)2}2]3" contains Se atoms (of Se42_ ligands) bridging Ru and Na atoms,288 while examples of alkyl thiolate ligands bridging three Ru atoms are known.289 More generally, there are few examples of transition Fig. 5.17 The lH NMR spectrum of IRu(CO)2(PPh3)Ru(uSEt)2(ri3SEt)Na(THF)]2 hi toluene-d8 at -78<>C 211 metal complexes containing alkali metal cations "trapped" via bridging thiolate ligands: (C5Me5)2Lu(uSteu)2Li(THF)2,290-1 [Li(dme)]4[U(edt)4] (dme = 1,2-dimethoxyethane, edt = l,2-ethylenedithiolate),292 and (SC6H4/3CH3)3Nb(^C6H4pCH3)3Na(Trn7)3.293 There are many more examples of trapped alkali metal cations in alkoxide chemistry, particularly as by products of metathesis reactions using alkoxide salts; these have been described in reviews of "double metal alkoxides" (complexes containing alkoxide ligands bridging two different metals).294 Double metal thiolates have not been reviewed. No previous Na/Ru double metal alkoxide or thiolate is known to us. Perhaps the mostly closely parallel alkoxide complex is Li2Ti2(OiPr)io, the structure of which has recently been deternrined.295 RO Li OR / /\ \ (ROVTi OR RO Ti(OR)2 \ \/ / RO Li OR Organic complexes containing alkali metal cations trapped by sulphur atoms are rare. Almost all of the reports covering crown thioether metal complexes deal exclusively with transition metals.296 No X-ray structure of a appears to have been reported. Comparisons between sodium crown-thioether complexes and 21, which represents an "inorganic crown thioether," will have to wait for the completion of the crystal structure of an example of a sodium crown-thioether complex. In the vast literature of the oxygen-containing crown ether ligands, there is, of course, an abundance of structures of sodium complexes.297-300 212 5.4 THE REACTIONS OF OTHER RUTHENIUM CHLORO COMPLEXES WITH SODIUM THIOLATES The reaction of a RuCl3/PPh3 mixture with excess NaSEt under CO in refiuxing MeOH produces a rnixture of 10 to 20% each of cc/-RuCl2(CO)2(PPh3)2 (D, ccr-RuCl(SEt)(CO)2(PPh3)2 (20), ccf-Ru(SEt)2(CO)2(PPh3)2 (14d), and a product with the same 31p chemical shift as [Q?Ph3)(CO)2Ru(SEt)3Na(THF)]2, plus smaller amounts of several unidentified products. This experiment was attempted because of a report of the synthesis of ccr-Ru(SC6F5)2(CO)2(PMePh2)2 direcdy from RuCl3 260b With optirnization of conditions, this method perhaps could provide a short-cut to the synthesis of these thiolato (carbonyl) phosphine complexes. The complex ccr-RuH(Cl)(CO)2(PPh3)2 reacts with one equivalent of NaSC6H5pCH3 in acetone to give 56% conversion to ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2. RuH(Cl)(CO)2(PPh3)2 + NaSR —> RuH(SR)(CO)2(PPh3)2 + NaCl 5.19 4 9 If excess thiolate is used, 90% conversion to ccf-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) is observed. The reactions of Ru(CO)2(PPh3)3 and ccf-RuH2(CO)20?Ph3)2 with thiols are the preferred synthetic routes to 9 because in these reactions the formation of the Ws-thiolate product is easier to control. A mixture of cis- and rra/w-RuCl2(dpm)2 (5 and 6) does not react with NaSEt. The role of the bulky phenyl rings of RuH(Cl)(dppe)2 (dppe=Ph2PCH2CH2PPh2) has been cited to explain its non-reaction with LLA1H4.189 However, cw-RuCl2(dpm)2 reacts easily with NaBH4 (Chapter 2), possibly because the BH4- anion is considerably smaller than AIH4- and SEt-. 213 5.5 EXPERIMENTAL DETAILS The reaction of ccf-RuCl2(CO)2(PPh3)2 (1) with NaSC6H4pCH3: A white acetone (40 mL) suspension of 1 (140 mg, 0.18 mmol) and the thiolate salt (56 mg, 0.38 mmol) under CO (1 atm) turned yellow within one minute at room temperature. The suspension was filtered, after being stirred overnight. The solid was discarded and the volume of the yellow filtrate was reduced to 10 mL by vacuum distillation. MeOH (approx. 30 mL) was added to encourage precipitation. The solid product collected by filtration was pure ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b). according to the 31p{ lH} and lH NMR spectra, which are identical to those of a known sample of that complex prepared from Ru(CO)2(PPh3)3 and the disulphide (Sections 4.1 and 4.2). The reaction of cc/-RuCl2(CO)2(TPh3)2 (1) and NaSEt in acetone: A white acetone (20 mL) suspension of 1 (450 mg, 0.60 mmol) and the thiolate salt (120 mg, 1.4 mmol) under CO (1 atm) turned yellow within one minute at room temperature. The suspension was stirred overnight and then filtered through diatomaceous earth. The volume of the yellow filtrate was reduced to 5 mL by vacuum distillation. MeOH (30 mL) was added to encourage precipitation, and the vessel left for 2 h at 0°C. During this time, a yellow precipitate formed. The suspension was filtered. The collected solid product was a mixture of ccf-Ru(SC2H5)2(CO)20?Ph3)2 (14d) and PPI13 according to the 31p{ lH} NMR spectrum of the C6D6 solution of this product. All attempts at purifying this complex, or repeating the reaction, resulted in yellow or brown oils which contained the same product The reaction of ccf-RuCl2(CO)2(PPh3)2 (1) and NaSEt in THF: A yellow THF (100 mL) suspension of 1 (520 mg, 0.70 mmol) and the thiolate salt (1.4 g, 17 mmol) under Ar was stirred for 1 h at room temperature, filtered, and the solid discarded. The yellow filtrate was evaporated to dryness. The products from two such reactions were dissolved together in THF (10 mL). The volume of the solution was reduced to 3 mL by vacuum distillation, and hexanes (15 mL) were 214 added to induce precipitation. The suspension was filtered and the collected yellow solid was washed with 15 mL of cooled hexanes. The overall yield was 53%. The NMR spectra show the product to be pure [(PPh3)(<X>)2Ru(SEt)3Na(THF)]2 (21). If only 2-3 equivalents of NaSEt were used, significant amounts of 1 remained after several hours. By using intermediate amounts of NaSEt and 15 min reaction times, mixtures of ccr-RuCl(SEt)(CO)2(PPh3)2 (20) and ccr-Ru(SEt)2(CX))2(PPh3)2 (14d) were obtained. Characterization of ccf-RuCl(SEt)(CO)2(TPb3)2 (2JL containing 2% 14d based on the 31p{ lH} NMR spectrum): Elem. Anal.: Calcd. for C40H35CIO2P2RUS: C, 61.7; H, 4.5. Found: C, 60.6; H, 4.6. lH NMR (C6D6,300 MHz) 8 1.13 (t, 3H, 3JHH = 7.4 Hz, CH3), 1.92 (q, 2H, 3JHH = 7.3 Hz, CH2), 7.0 (multi, 18H, m-/p-Ph), 8.25 ppm (multi, 12H, o-Ph); 31p{ lH} NMR (C6D6,121 MHz) 8 14.54 ppm (s); IR (Nujol) 2042,1988 cm"1 (v(CO)). Characterization of ccr-Ru(SEt)2(CO)2(TPh3)2 (14d. containing 20 % of 20 based on the 31p{ lH} NMR spectrum, listing resonances due to the major component only): lH NMR (C6D6,300 MHz) 8 1.16 (t, 6H, 3JHH = 7.4 Hz, CH3), 1.97 (q, 4H, 3JHH = 7.4 Hz, CH2), 7.04 (multi, 18H,ro-/p-Ph), 8.22 (multi, 12H,o-Ph); 31p{lH} NMR (C6D6,121 MHz) 8 11.18 ppm (s); IR (Nujol) 2022,1963 cm-1 (v(CO)). Characterization of [(PPh3)(CO)2Ru(MSEt)2(U3SEt)Na(THF)]2 (21): Elem. Anal.: Calcd. for C60H76Na2O6P2Ru2S6: C, 51.6; H, 5.5; S, 13.8. Found: C, 51.7; H, 5.5; S, 14.1. iH NMR (C6D6) 8 1.41 (t, 12H, 3JHH = 7.6 Hz, CH3(a)), 1.41 (multi, 8H, p-CH2 of THF), 1.59 (t, 6H, 3JHH = 7.3 Hz, CH3(b)), 2.71 (d of q, 8H, 2JHH = 9.0, 3JHH = 7.3 Hz, CH2(a)), 2.95 (d of q, 8H, 2JHH = 9.0, 3JHH = 7.5 Hz, CH2(a)), 2^97 (d of q, 4H, 2JHH = 9.0,3JHH = 7.3 Hz, CH2(b)), 2.98 (d of q, 4H, 2JHH = 9.0, 3JHH = 7.5 Hz, CH2(b)), 3.57 ppm (multi, 8H, a-CH2 of THF), 7.06 (multi, 6H, p-Ph), 7.15 (t, 12H, 3JHH = 7.0, m-Ph), 7.96 ppm (t, 12H, 3JRH = 8.8 Hz, o-Ph); 13C{ lH} NMR (C6D6,75 MHz) 8 20.73 (CH3(b)), 20.89 (CH3(a)), 25.16 (CH2(a)), 25.71 (B-C of THF), 26.62 (CH2(b)), 67.85 (a-C of THF), 128.16 (p-Ph), 130.22 (m-Ph), 134.50 (d, Jpc=9.4 Hz, o-Ph), 135.28 (d, Jpc=41.9 Hz, P-C), 197.48 ppm (CO); 31p{ lH} NMR 215 (C6D6,121 MHz) 8 25.05 ppm (s); IR (Nujol) 2014,1952 cm"1 (v(CO)). Solutions of 21 (up to 1 mM) in THF had no detectable conductance at room temperature under argon. A crystal of [(PPh3)(CO)2Ru(u.2SEt)2(^3SEt)Na(THF)]2 (21) suitable for X-ray crystallography was prepared by diffusion of hexanes into a concentrated THF solution under Ar in darkness. The structure analysis was performed by Dr. S. J. Rettig.209 The final unit-cell parameters were obtained by least-squares on the setting angles for 25 reflections with 20 = 20.0-26.5°. The intensities of three standard reflections, measured every 200 reflections throughout the data collection, decayed uniformly by 12%. The data were processed259a and corrected for Lorentz and polarization effects, decay, and absorption (empirical, based on azimuthal scans for four reflections).209 The structure analysis was initiated in the centrosymmetric space group PI, the choice being confirmed by the subsequent successful solution and refinement of the structure. The structure was solved by conventional heavy atom methods, the coordinates of the Ru, P, and S atoms being determined from the Patterson functions and those of the remaining non-hydrogen atoms from subsequent difference Fourier syntheses. The complex has crystallographically imposed symmetry. All non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were fixed in idealized positions (dC-H = 0.98 A, BH = 1.2 Bbonded atom)-Neutral atom scattering factors and anomalous dispersion corrections for the non-hydrogen atoms were taken from the International Tables for X-Ray Crystallography.259b Final atomic coordinates and equivalent isotropic thermal parameters [Beq = 4/3Zi2^bij(aiaj)], bond lengths, and bond angles appear in Appendix 4, and Tables 5.4 and 5.5 respectively. Other crystallographic data for this structure and the other structures described in this work are presented in Appendix 1.209 The reaction of RuCl3 with PPI13 and NaSEt: RuCl3 (300 mg, 0.96 mmol) and PPh3 (1.43 g, 5.4 mmol) were allowed to react in refiuxing MeOH (30 mL) under N2 for 15 min. During this time, the solution turned from brown to dark green. After the solution had cooled, NaSEt (155 216 mg, 1.8 mmol) was added, and CD introduced. The brown colour returned immediately, but again slowly changed to dark green. After 30 min, the volatiles were removed by vacuum distillation, leaving a yellow/brown unpurified product The 31p{ lH) NMR spectrum (C6l>6) shows that this product contained, in addition to PPh3, ccf-RuCl2(CO)2(PPh3)2 (1,20 % of 31p NMR signal excluding that of free PPI13), ccr-RuCl(SEt)(CO)2(PPh3)2 (20,7 %), cct-Ru(SEt)2(CO)2(PPh3)2 (14d. 19 %), a product having the same chemical shift as [(PPh3)(CO)2Ru(SEt)3Na(THF)]2 (16 %), and several unknowns at lower concentrations. The reaction of cc*-RuH(Cl)(CO)2(PPh3)2 (4) and NaSC6H4pCH3: Complex 1 (72 mg, 0.10 mol) and the thiolate salt (18 mg, 0.12 mmol) reacted very quickly in acetone (20 mL) at room temperature under Ar, the white solution turning yellow within minutes. After 2 h, the volatiles were removed by vacuum distillation, leaving a yellow powder. This unpurified product was dried overnight, and then redissolved in C6D6- The 31p{ lH} NMR spectrum (121 MHz) shows that the product mixture contained unreacted 4 (20 % of 31p NMR signal), ccf-RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b, 60 %), ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (Mb, 10 %), and small (<5 %) amounts of PPh3, Ru(CO)2(PPh3)3 (2), and Ru(CO)3(PPh3)2 (10). The lH NMR spectrum confirms the identification of the major product and the starting material. The overnight reaction of 4 with three equivalents of NaSC6H4pCH3 produced a mixture of 14b (90%) and 9b (10%). The attempted reaction of tams-RuCl2(dpm)2 (6) with NaSEt: Complex 6 (140 mg, 0.15 mmol) failed to react with NaSEt (120 mg, 1.6 mmol) in acetone (25 mL) at room temperature. After one day, the suspension was washed through diatomaceous earth with THF (20 mL). The volume of the filtrate was reduced to 6 mL, and hexanes (20 mL) were added to induce precipitation. The collected yellow powder was unreacted starting material (identification by 217 31P{ lH) NMR spectroscopy).301 The same result was obtained from a sirnilar experiment with NaSC6H4pCH3. 218 6. THE REACTIONS OF THIOLATO RUTHENIUM(II) COMPLEXES WITH NON-SULPHUR-CONTAINING REAGENTS Comparisons between the reactions described in this chapter and those of the preceding chapters allow for greater insight into the mechanisms of the reactions and the conditions under which Ru-S bonds may be broken. The latter information is required before a catalytic cycle for desulphurization can be designed. 6.1 THE REACTIONS OF cc/-RuH(SR)(CO)2(PPh3)2 (9) 6.1.1 P(C6H4pCH3)3 The complex ccf-RuH(SR)(CO)2(PPh3)2 (9) reacts with P(C6H4pCH3)3 to produce a complex (22) of a structure sirnilar to that of 9 but containing inequivalent phosphines (lH and 31p{ lH} NMR spectral evidence). This product reacts further to produce a third complex (12). again of a structure similar to 9, but containing equivalent phosphines. Based on the similarity of the NMR spectra of these complexes with those of the PPh3 analogues, it is believed that the structures are ccr-RuH(SR)(CO)2(PPh3)(P(C6H4pCH3)3) (22) and ccr-RuH(SR)(CO)2(P(C6H4pCH3)3)2 (12). The ethyl derivative of the latter (12d) has been independendy synthesized via the reaction of Ru(CO)2(P(C6H4pCH3)3)3 with ethanethiol (Sections 3.1 and 3.2). The sequence of reactions between 9e and P(C6H4pCH3)3 is the following: RuH(SR)(CO)2L2 + L' —> RuH(SR)(CO)2LL' + L 6.1 9 22 RuH(SR)(CO)2LL' + L' —> RuH(SR)(CO)2L'2 + L 6.2 22 12 219 L=PPh3, L'=P(C6H4pCH3)3, R=CH2C6H5, C5H4pCH3 The reaction of 9e (R=CH2C6H5) with P(C6H4pCH3)3 (L') was followed by 31p{ lH) and lH NMR spectroscopy (Figs. 6.1 to 6.3) in C6D6 at 45°C under pseudo-Gist order conditions (large excess of L'). The rate of loss of 9_e is pseudo-Gist order, the log plot being linear for at least 3 half-lives (Fig. 6.4) and has an observed rate constant of 1.1 (±0.1) x 10"3 s"l (average of 5 results, at [9e] = 11 mM). The rate constant for the corresponding reaction of ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (26) is 7.0 x 10-4 s-l (single experiment). The observed rate constant (for 9_e) is independent of the concentration of L' (94 to 502 mM, at [9_e] = 11 mM) or 9e (ifcobs = 1.2 x 10-3 s-1 at [9e] = 2.65 mM and 130 mM L'). The rate law is simply: -dJM = k\\M where k\ = 1.1 x 10-3 s-l. dt It therefore seems likely that the first step of reaction 6.1 is the rate deterrnining dissociation of the phosphine L (Scheme 6.1), although other less likely mechanisms are possible, such as initial reductive elimination of thiol. The rate law for the loss of 9_e, assuming a steady state for RuH(SR)(CO)2L (in Scheme 6.1), is the following: -rf[9el = *l[9ej- *-irL1(fcir9e1 +fc-?f221) dt *2[L'] + M[L] That reaction 6.1 goes to completion implies that the rate of the k-2 reaction is negligible (i.e. £-2[22] «rU[9e]), and thus if one assumes that M[L] « *2[L'] then the second term in the rate law is insignificant. This assumption appears to be valid during at least the first two half-lives if L' is present in large excess; this accounts for the observed pseudo-Gist order behaviour. Reaction 6.2 must be significantly faster than reaction 6.1, because complex 22 never appears in large amounts (Fig. 6.3). The rate law for the proposed mechanism of reaction 6.2 (Scheme 6.1) is the following: 220 after 5 min 26 min 49 min 2e 4 22e PPh3 P(C«H4(>CH3)3 40 30 20 10 Oppm Fig. 6.1 31p{lH} NMR spectra acquired during the reaction of cc/-Ru(SCH2Ph)(CO)20?Ph3)2 (2& 11 mM) with P(C6H4pCH3)3 (94 mM) in C6D6 at 450C. Chemical shift scale is relative to PPh3 in Q>D6. 221 i 1 1 1 1 1 i -4.4 -4.5 -4.6 -4.7 ppm Fig. 6.2 lH NMR spectra (hydride region) acquired during the reaction of cc/-RuH(SCH2Ph)(CO)2(PPh3)2 (Ss» 11 mM) with P(C*H4pCH3)3 (94 mM) in C6D6 at 45©C. 222 100 80 H 60 H 40 H 20 H • 2fi a 12e 4000 Fic 6.3 Time dependence of the concentrations of observed complexes during the reaction of cc/-RuH(SCH2Ph)(CO)2(PPh3)2 (2& 12 mM) with P(C6H4pCH3)3 (120 mM) in C6D6 at 450C. -4 Time(s) Fig. 6.4 Log plot of [9e] during the reaction of cc/-RuH(SCH2Ph)(CO)2(PPh3)2 (9e, 12 mM) with P(C6H4pCH3)3 (120 mM) in C6l>6 at 450Q 223 Scheme 6.1 A proposed mechanism for the reaction of RuH(SR)(CO)2(PPh3)2 with P(C6H4pCH3)3 (L=PPh3 L'=P(C6H4pCH3)3). RuH(SR)(CO)2L2 1 RuH(SR)(CO)2L'2 12 *i,-L k.uh k4, V RuH(SR)(CO)2L -L' ky, L' 22 RuH(SR)(CO)2LU *3,-L RuH(SR)(CO)2L* 224 dim = k^SL'm^ + k-^lltt - *-4[12] dx k4[L'] + Jk-3[L] This rate law simplifies if one assumes that Jt4[L'] » *-3[L] in the presence of excess L\ dU21 = *3[22] dt The value of ks could then be determined by plotting d\12\/dt vs. [22]. The values of d\12Vdt are easily determined from the tangents to the plot of [12] against time (Fig. 6.3). The resulting plot should be a straight line of positive slope ks, if the assumption of a negligible back reaction (£-3[L]) is correct. In fact, a decreasing trend is observed (Fig. 6.5), suggesting that the k-S\L] back reaction is significant. Because all back-reactions are negligible at the start of the reaction, an approximate value of ks can be obtained from the y-intercept of this plot. The value thus obtained (0.01 s-1) shows that ks is an order of magnitude greater than kl. If PPh3 (L, 100 mM) is added to the reaction of 9e (11 mM) with P(C6H4pCH3)3 (L\ 110 mM) at 45°C in CgDg, a mixture of three complexes, 9,22, and 12 is obtained (Fig. 6.6). Because reaction 6.1 does not go to completion, the back reaction must be significant under these conditions. It is not surprising, therefore, thatpseudo-fkst order behaviour is not observed. The fact that the initial rate is unchanged suggests that k-i/k2 « 1. p-Tolyl phosphine (L'), more basic than PPI13, may labilize the phosphine trans to it by increasing the electron density at the metal centre, thereby promoting formation of the activated complex en route from 22 to 12. The observation that ks is greater than kl suggests that reaction 6.2 may reach an equilibrium before reaction 6.1. This can be checked by plotting Qi and Q2 against time for the experiment described above, in which both L and L' were present in excess, where:. Ql = f22]rL1 [9][L'] 225 0.012 [22e] (mM) Fig. 6.5 The dependence of d[12ej/<ft on f22e1 during the reaction of ^-R"H(SCH2Ph)(CO)2(PPh3)2 (2fc 12 mM) with P(C6H4pCH3)3 (120 mM) in C6D6 at 226 100 I e 1 4000 Fig. 6.6 Time dependence of the concentrations of observed complexes during the reaction of cc/-RuH(SCH2Ph)(CO)2(PPh3)2 (9g, 11 mM) with P(C6H4pCH3)3 (110 mM) in the presence of PPh3 (100 mM) in C6D6 at 45©C. a 1000 • Qi # 02 i • 2000 3000 4000 time (s) Fig. 6J Time dependence of Qi and Q2 (defined in Section 6.1.1) during the reaction of RuH(SCHjPh)(CO)2(PPh3)2 (Se, 11 mM) with P(QsH4pCH3)3 (110 mM) in the presence of PPh3 (100 mM) in C6D6 at 450C. 227 Q2 = mirLi [22][L'] In fact, Ql varies over time (Fig. 6.7), while Q2 settles quickly to a value of approximately 1.2. The equilibrium constants for reactions 6.1 and 6.2 are thus Ki>4 and K2=1.2. The rate of the exchange reaction of 2 with thiols (Section 3.5) RuH(SR)(CO)2(PPh3)2 + R'SH —> RuH(SR')(CO)2(PPh3)2 + RSH 3.15 has the same simplified rate law and rate constant (1.0 x 10-3 s-1 at 45°C in R=CH2C6H5, R'=C6H5) as reaction 6.1, suggesting that the rate determining steps of the two reactions are the same. 6.1.2 CO The reactions of several complexes of the series ccf-RuH(SR)(CO)2(PPh3)2 (2) with CO (1 atm) to give Ru(CO)3(PPh3)2 RuH(SR)(CO)2(PPh3)2 + CO —> Ru(CO)3(PPh3)2 + RSH 6.3 9 IQ in THF at several temperatures was monitored by UV/vis. spectroscopy Q7ig. 6.8). Under pseudo-first order conditions (1 atm CO) the pseudo-first order log plot is linear for 3 half-lives (Fig. 6.9). The observed rate constant is independent of the pressure of CO (760 to 6 torr for R=Et, at 26°C)), but is dependent on the choice of thiolate group. The rate law and rate constants (all at 55°C) are as follows. -dm = *[9J dt I 1 1 1 1 1 1 340 360 380 400 420 440 460 nm Fig. 6.8 UV/vis. spectra acquired every 900 s during the reaction of ccf-RuH(SEt)(CO)2(PPh3)2 (0.9 mM) and CO (1 atm) in THF at 26©C. 229 4 < 8000 Fig. 6.9 Logarithmic plot of absorbance at 400 nm versus time for the reaction of cc/-RuH(SEt)(CO)2(PPh3)2 (?e, 0.9 mM) and CO (1 atm) in THF at 26 JoC. 230 R: CH2CH3 > CH3 > CH2Ph > Cott^Ct^ > CgHs k: 1.2x10-2 7.1x10-3 2.2x10-3 9.3x10-4 5.5x10-4 s-l The temperature dependence of these rate constants has also been determined 0?ig. 6.10). Because the-rate law and rate constant of the reaction of 9_d with CO (reaction 6.3, R=Et) extrapolated to 22°C (1.8 x 10"4 s"1) are the same (within the experimental error) as those for the reaction of 9d with PhSH (reaction 3.12, Section 3.5) at the same temperature (1.9 x 10-4 s-1), then the two reactions most likely proceed by analogous mechanisms. As explained in Sections 6.1.1 and 3.5, these mechanisms probably involve loss of a phosphine ligand as the first step. The subsequent steps of the mechanism of reaction 6.3 are co-ordination of CO and elimination of thiol, but the order in which they occur is not known. The path which leads to a 3-cc>ordinate species (elimination of thiol before coordination of CO) seems less likely. The proposed mechanism is shown in Scheme 6.2. Attempts to test the effect of a large excess of PPh3 on the rate of reaction 6.3 were hindered by the occurrence of a side reaction of 9 with PPh3 (Section 6.1.3). The enthalpies of activation are 120±20 kJ/mol for 9b (R=C6H4pCH3) and 100+10 U mol-1 for 9d (R=C?Hs). consistent with the suggestion (Section 6.1.1) that increased electron density at the metal centre increases the rate of reaction by stabilizing the activated complex {RuH(SR)(CO)20?Ph3))1:- Ethanethiolate, a more basic ligand than thiophenolate, would increase the electron density. The large error inherent in the calculation of the entropy of activation (40±40 and 20±25 J mol"1 K"1 for 9b and 9d, respectively) precludes any conclusion about the possible effect of the nature of the thiolate group on AS$. However, it is clear that the entropy of activation is positive, as expected for a dissociative mechanism. The enthalpy term is mainly responsible for the difference in rates between the reactions of 8b (R=C6H4pCH3) and 8d (CH2CH3) at this temperature. It has now been established that reactions 6.1,6.3, and 3.15 all proceed via the same rate determining step, suggested to be the initial dissociation of PPh3 from the Ru centre. Further 231 • R • p-tolyl • R - benzyl • R = ethyl 1/T(10-3K-1) Fie. 6.10 Eyring plot for the reactions of cd-RuH(SR)(CO)2(PPh3)2 (2) with CO (1 arm) in THF, where R=Q>H4pCH3 (2bJ, CH2C6H5 (2e), or CH2CH3 (9d). 232 Scheme 6.2 A proposed mechanism for the reaction of RuH(SR)(CO)2(PPh3)2 with CO (L = PPh3). RuH(SR)(CO)2L2 Ru(CO)3L2 in *i,-L *.i,L £4, L RuH(SR)(CO)2L *.2, -CO *2,CO RuH(SR)(CO)3L *_3, RSH *3, -RSH Ru(CO)3L 233 evidence for this is the magnitude of the effect on the rate of reaction 6.1 when the phosphine trans to the dissociating ligand has p-methyl substituents; the rate is increased ten-fold. This strong an effect is consistent with a trans effect, rather than a cis effect That is, if the rate determining step were initial reductive elimination of thiol, then the effect of a change in the phosphine in the cis position would not be as large as that observed. The evidence, therefore, supports a rate deterniining step of PPh3 dissociation. However, cct-RuH(SC6H4pCH3)(CO)2(PPh3)2 reacts 1.7 times faster with CO than does cct-RuH(SC6H5)(CO)2(PPh3)2. If the rate-deterrnining step were initial dissociation of PPI13, then this would constitute a ris-effect. It is not possible to evaluate whether 1.7 is a reasonable value because the magnitudes of the cw-effects of thiolate ligands on the rate of eurnination of phosphines have not been previously reported. If the first and rate-deterrnining step is reductive elimination of thiol, then a large rate difference is expected. The argument for initial phosphine loss is considered stronger because the trans-effect of the phosphine is more pronounced, and because the mechanisms of the reactions of 9 are expected to be analogous to those of 14. In the latter system (Section 3.8 and 6.2.2), the evidence for initial phosphine loss includes kinetic measurements of the inhibition by added PPh3 of the reaction of 14 with thiols. Reaction 6.3 is the reverse of reaction 3.19 (Section 3.9), the kinetics and mechanism of which are not known. 6.1.3 PPh3 A large excess of PPh3 in THF at room temperature converts ccr-RuH(SEt)(CO)2(PPh3)2 (9d) to Ru(CO)2(PPh3)3 (2,26 % conversion after 4 h, 100 % after 4 days). RuH(SR)(CO)2(PPh3)2 + PPh3 ===== Ru(CO)2(PPh3)3 + RSH 6.4 9 2 234 The slow rate of this reaction shows that the rate determirring step is not the same as that of reactions 6.1,6.3, and 3.12. This result is not suprising because initial dissociation of a phosphine from the metal centre is an unlikely step in a reaction which has a net increase in the number of coordinated phosphines. The generation of thiol in this reaction was not confirmed. The reaction is the reverse of reaction 3.3 (section 3.1). 6.1.4 H2 The complex ccr-RuH(SMe)(CO)2(PPh3)2 (9c), dissolved in THF and subjected to 60 atm of H2 for 25 h at room temperature is largely converted to ccr-RuH2(CD)20?Ph3)2 (3). RuH(SR)(CO)2(PPh3)2 + H2 ^== RuH2(CO)2(PPh3)2 + RSH 6.5 9 3 The generation of thiol in this reaction was not confirmed. The reverse reaction (reaction 3.4) proceeds even under 1 atm of H2 (Section 3.3). Because reaction 3.4 is the reverse of reaction 6.5, the latter is believed to proceed via reductive elimination of thiol followed by oxidative addition of H2-6.1.5 Acids The complex ccr-RuH(SCH2C6H5)(CO)2(PPh3)2 (9e, 8.6 mol) was dissolved in a heterogeneous mixture of C6D6 (0.6 mL) and aqueous concentrated HCl (0.05 mL, 0.6 mmol). After 10 min at room temperature, 84 % conversion to ccf-RuH(Cl)(CO)2(PPh3)2 (4) was observed. RuH(SR)(CO)2(PPh3)2 + HCl -> RuH(Cl)(CO)2(PPh3)2 + RSH 6.6 9 4 235 This reaction parallels reaction 3.12 (Section 3.5) in that HCl acts in the same manner as a thiol. As shown in Section 3.5, the most acidic thiols react preferentially, and thus the high reactivity of HCl seems reasonable. Reaction 6.6 is highly favourable, and the reverse reaction would require a very large excess of thiol (or in a more practical sense an excess of NaSR, cf. Section 5.4). The products of the reaction of ccr-RuH(SC6H5)(CO)2(PPh3)2 (3.3 nmol) in C^Dg (0.6 mL) with HBF4/H2O (50 \\L, 300 umol) at room temperature have not been identified. However, the *H (Fig. 6.11) and 31p{ lH} NMR spectra are consistent with a major product of the formula ccr-RuH(X)(CO)2(PPh3)2 (where X is unknown). A broad peak at 1.5 ppm in the lH NMR spectrum has the correct integral and chemical shift215 for the aquo ligand of ccr-[RuH(H20)(CO)2(PPh3)2]+, suggesting that this is the major product. The same product is not observed when HBF4/Et20 is used as the protonating agent Instead, a large number of unassigned peaks is observed in the 31p{ lH) NMR spectrum. 6.1.6 CD3OD The hydrido and mercapto hydrogen atoms of ccf-RuH(SH)(CO)2(PPh3)2 (9a) undergo deuterium exchange with 4% v/v CD3OD in C6D6 (Fig. 6.12). D+ RuH(SH)(CO)2(PPh3)2 —> RuH(SD)(CO)2(PPh3)2 + RuD(SD)(CO)2(PPh3)2 6.7 The first-order rate constants, at 19°C, are 4.1 x 10"^ and 2.9 x 10"^ s"*, respectively Q?ig. 6.13). Of the two hydrogens, the mercapto hydrogen exchanges more rapidly, suggesting that it is exchanging intermolecularly with the D+ ions in the solution, possibly with the following mechanism: Fig. 6.11 lH NMR spectrum acquired 30 min after the start of the reaction of cc/-RuH(SC6H5)(CO)2(PPh3)2 (9i, 5.6 mM) with excess HBF4/H20 (50 uL) in CgD6 at room temperature. 237 0 I i i i i i i i i i i • i • i 0 5000 10000 15000 tirne(s) ?f B'S/SS^SV6 fiE!ln?ence of the tot"18"* 0) of the lH NMR signals due to cc/-RuH(SH)(CO)2(PPh3)2 (4.4 mM) in 4% v/v CD3OD/C6D6 at 19oc7 Fig. 6.13 The log plot of the Intensity of the *H NMR signals due to ccr-RuH(SH)(CO)2(PPh3)2 (4.4 mM) in 4% v/v CD3OD/C6D6 at 190C. 238 Ru^ + D+ - Ru Ru^ + H* SH SD SH The mercapto hydrogens of ccr-Ru(SH)2(CO)2(PPh3)2 (148) also exchange with 4% CD3OD in CD2CI2 (Section 6.2.4), showing that the exchange does not require a hydride cis to the mercapto group. The hydrido hydrogen of 9_a is either exchanging intermolecularly or intramolecularly. The intermolecular exchange process is unlikely, because ccf-RuH2(CXD)2(PPh3)2 shows no exchange in 4% CD3OD in C6D6 even after 2 h (Section 3.4). The intramolecular exchange could take place in the following manner: RU Ru-S^ Ru \ SH \ SD " SH Osakada et a/.304 have reported on the H/D exchange of the hydrido and mercapto hydrogens of RuH(SH)(PPh3)3 with 4% CD3OD in CD2CI2. It appears from Figure 2 of their report that the rate of the exchange of the hydrido hydrogen is faster than that of the mercapto hydrogen. However, the authors of the report concluded the reverse, and therefore, that the mercapto hydrogen alone was exchanging with the CD3OD, and the deuteration at the hydridic site was via intramolecular exchange. They cited the lack of H/D exchange of the complexes RuH(SPh)(PPh3)3 and RuH(Cl)(PPh3)3, and the observation of mtramolecular exchange in PtH(SH)(PPh3)2 by Ugo et a/.82 The conclusions in the RuH(SH)(PPh3)3 system are therefore analogous to those in the ccr-RuH(SH)(CO)2(PPh3)2 system. The lH NMR spectral data (Fig. 6.12) also show a slight decrease in the intensity of the o-phenyl proton signal, a phenomenon not observed with the m- and p-phenyl signals. The mechanism by which o-hydrogen exchange could occur is not known for this system. 239 6.2 THE REACTIONS OF cc/-Ru(SR)2(CO)2(PPh3)2 (14) All of the observations of the reactivity of these bis-thiolate complexes (14) toward H2, thiols, and phosphines suggest that the reactivity of 14 and associated mechanisms are similar to those of the hydrido-thiolato complexes (9J. The lability of the phosphines in 14 has already been noted (Sections 3.8 and 5.2). A major difference in reactivity between species of types 9 and 14 is the instability of solutions of 14 (but not 14a) in solution. 6.2.1 Light Tetrahydrofuran solutions of ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) under Ar, when exposed to light at 430 nm in the UV/vis. spectrometer exhibit a changing spectrum with an isosbestic point at 395±2 nm (Fig. 6.14). Unfortunately, the products have not been identified unambiguously, with the exception of PPh3. The presence of added water or 02 (1 atm) had no effect on the spectral changes, including the isosbestic wavelength. Two samples of 14b (4.4 mM in Q>D6) hi NMR tubes at room temperature were analyzed by 31p{ lH} NMR spectroscopy after 8 h of darkness for one sample and 8 h under a Hanovia UV lamp for the other. Both samples were exposed to room light immediately before and during the NMR spectrum acquisition. The amount of unreacted starting material remaining in the former "dark" sample (70 %) compared to the latter (2 %) shows that the reaction being observed is promoted by exposure to light. In attempts to identify the products of this reaction, a FAB mass spectrum was acquired of the solid product obtained from one such reaction using a THF solution under a Hanovia lamp for 90 minutes Q7ig. 6.15). The strong peak at m/z = 1149 (±5) must represent a fragment containing at least two Ru atoms, unless it is Ru(PPh3)4. The match between the observed and predicted isotopic patterns is poor for RuO?Ph3)4, but fair for two Ru2 and one Ru3 complexes (Fig. 6.16). i 1 1 1 IIIII r 350 370 390 410 430 450 470 490 510 530 550 nm Fig. 6.14 UV/vis. absorbance spectra of a THF solution of cc/-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (032 mM) at 25oC being irradiated at 430 nm (between spectral acquisitions), after a) 50, b) 300, c) 600, d) 1,200, e) 2,100, f) 3,300, g) 5,400, h) 8,000, i) 13,000 and j) 240,000 s. 520 560 600 640 680 720 760 800 840 880 920 960 1000 1040 1080 1120 1160 1200 1300 1560 1600 m/z Fig. 6.15 FAB Mass Spectrum of the solid residue from a THF solution of cc/-Ru(SC6H4pCH3)2(CO)2(PPh3)2 irradiated for 90 min under a Hanovia lamp. 242 a) Observed isotopic pattern b) Ru3(O0)2(PPh3)3 , 120 100 H 80 60 40-20 0 llll Ru2(CO)2(PPh3)2(SC^H4pCH3)3 120-100' 80> eo - 1 40 • ll 1 20- ...Illl Ru2(00)3(SC6H4pCH3)7 Ru(PPh3)4 1» -100' 80-to- 1 ll 40 • ll III 20 • 0- ...ill o<-«n*«iON«aO''M»<riii«Naao w««««««««ta<eieiDioiotDie«>ii><B •Nn«aos>ao-Nn*««Nsao Fig. 6.16 a) Observed isotopic pattern for the fragment m/z = 1149±5, and b) the predicted isotopic patterns for four possible formulations for the fragment 243 If the suggested fragmentation trees (shown in Scheme 6.3) are correct, then the most likely formula for the fragment at m/z = 1149 (Ru2(SC&H4pCH3)3(CO)2(PPh3)2) suggests that the unfragmented molecule could be Ru2(SC^H4pCH3)4(CO)3(PPh3)2 (m/z = 1300). sS„ *SR OC— Ru — S —Ru — CO OC^ \^ \pph3 R If this were the case, however, then the suggested connections in Scheme 6.3 between the peak at 1300 and the peaks at 1562 and 1591 would have to be incorrect. The suggested triply thiolate-bridged complex would have two singlet peaks in the 31p{ lH} NMR spectrum and three v(CO) bands in the IR spectrum. The 31p{ lH} NMR spectrum of the sample submitted for the FAB/mass spectroscopy contains several peaks, including two at 32.84 and 42.84 ppm of roughly equal intensity. The same two peaks were observed in the 31p{ lH} NMR spectra of isolated product mixtures from many similar reactions. The IR spectrum contains three v(CO) bands at frequencies (2034,1977, and 1941) different from those of ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (2028,1968 cm-1). it is not certain whether the three v(CO) bands are due to the same complex which gives rise to the NMR and FAB/MS signals already discussed. Precedents for the triply-bridged type of complex include [(PMe2Ph)3Ru(uSMe)3Ru(PMe2Ph)3]+305 and [(CO)3Fe(pSMe)3Fe(CO)3]+,306 while several of the series L3Ru(|i.Cl)3Ru(Q)L2234,307 have been reported. In addition, [(CO)2(PPh3)Ru0xSEt)3Na(THF)]2 (described in Section 5.3) has a similar structure and is formed via a similar ccr-Ru(SR)2(CO)2(PPh3)2 precursor (14d). In summary, the products of the light-induced decomposition reaction of ccf-Ru(SR)2(CO)2(PPh3)2 cannot be identified with certainty, beyond the fact that at least one of them contains two or more Ru atoms. A possible formulation for one of the products is suggested. 244 Scheme 63 Suggested fragmentation trees for the FAB mass spectrum of the products from the light-induced decomposition of cct .Ru(SC6H4pCH3)2(CO)2(PPh3)2 (HhJ. 1591 -CO 1562 -PPh3 1300 -SR 1176 -CO 1149 968 -OO, PPh3 -CO, PPh3 -C7H7+ 619- 711 -C7H/ 526 877 -SR 755 -PPh3 487 449 245 6.2.2 P(C6H4PCH3)3 The complex c^Ru(SH)2(CO)2(PPh3)2 (14a) reacts with P(C6H4pCH3)3 in C6D6 at 25°C to produce two previously unknown complexes of structures similar to 14a. the NMR data (Figs. 6.17 and 6.18) being consistent with the following reactions (L=PPh3, L'=P(C6H4pCH3)3, all complexes cct): Ru(SH)2(CO)2L2 + L' —> Ru(SH)2(CO)2LL' + L 6.8 14a 23a Ru(SH)2(CO)2LL' + L' —> Ru(SH)2(CO)2L'2 + L 6.9 23a 24a The rates of these sequential reactions were followed by lH NMR spectroscopy (Figs. 6.18 and 6.19). The observed concentrations match exactly those predicted for the system k\ k2 A —> B —> C for over 4 half-lives of the first reaction (with kl = 6 x 10-4 and k2 = 5 x 10-4 s-1 at 25°C). This shows that in contrast to the mechanism of the reaction of the phosphine with a hydrido-thiolato analogue described in Section 6.1.1 (reactions 6.1 and 6.2), the rates of the reverse reactions shown in equations 6.8 and 6.9 are negligible for at least four half-lives. The complex ccr-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) reacts much more quickly than 14a with L', giving complete conversion to a new product of structure similar to 24a by the time the first NMR spectrum can be taken, 3 minutes after the start of the reaction. The new complex is presumably cc^Ru(SC^H4pa^3)2(CK))2{P(C6H4pCH3)3}2 (24b). The difference in rates suggests that the phosphines of 14b must be considerably more labile than those of 14a. This is consistent with the difference in rates of the reactions of 14a and 14b with thiols (Section 3.8). Fig. 6.17 31p{lH) NMR spectra acquired during the reaction of cc/-Ru(SH)2(CO)2(PPh3)2 (14a, 8.3 mM) with P(C6H4pCH3)3 (230 mM) in C6D6 at 250C. Chemical shift scale is relative to PPn3 in C$D6« after 9 min Fig. 6.18 lH NMR spectra acquired during the reaction of cc/-Ru(SH)2(CO)2(PPh3)2 (14a, 8.3 mM) with P(C6H4pCH3)3 (230 mM) in C6D6 at 25©C. 248 B 14a B 24a time (s) Fig. 6.19 The time dependence of the concentrations of the observed complexes during the reaction of crt-Ru(SH)2(CO)2(PPh3)2 (14& 8.3 mM) with P(C6H4pCH3)3 (230 mM) in C6D6 at 250C. 249 6J2.3 H2 A toluene solution of cc/-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) was exposed to 24 atm of H2 at room temperature for 100 min. The lH and 31p{ lR} NMR spectra of the isolated product mixture in C6D6 (Figs. 6.20 and 6.21) showed that the solution contained unreacted 14b (20 % of the 31p NMR signal), the major product ccr-RuH(SC6H4pCH3)(CX))2(PPh3)2 (9b, 45 %), ccr-RuH2(CX))2(PPh3)2 (3,1 %), and several unknowns. The hydride region of the lH NMR spectrum contained, in addition to the expected peaks for 9b and 3, a triplet at -10.19 ppm (2JPH=15.9 Hz) and a doublet of doublets at -6.40 ppm (2JtransPH=96.9,2JcisPH=28.2 Hz). Complexes which could give rise to the latter pattern are ccc- or crc-RuH(SR)(CO)2(PPh3)2-Neither of these isomers have been observed, although ccc-Ru(SC6F5)2(CO)2(PPh3)2 is known.260b Ru(SR)2(CO)2(PPh3)2 + H2 —> RuH(SR)(CO)2(PPh3)2 + RuH2(CO)2(PPh3)2 + others 6.10 Attempts to detect or isolate the organic products of the reaction were not made, except for the observation that the singlet (3.02 ppm) in the lH NMR spectrum which corresponds to the mercapto proton of p-thiocresol is very small indeed (Fig. 6.20), suggesting that the thiol is not the major organic product. 6.2.4 CD3OD The mercapto hydrogens of ccr-Ru(SH)2(CO)2(PPh3)2 (14a) exchanged with 4% CD3OD in CD2CI2 (Fig. 6.22), probably by the same mechanism as that proposed for reaction 6.7. Ru(SH)2(CO)2(PPh3)2 + 2CD3OD Ru(SD)2(CO)2(PPh3)2 + 2CD3OH 6.11 a) p-thiocresol IA V b) J 9b i J II . ^ )iiii;iiiiii)ii|im|iiiMiiii|iiii)ini|iiii|iiii|iiii|nii|ini| -4 -5 -6 -7 -8 -9 -10 PPM i _U .11. 1 M ' ' 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 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 i I I i I I ) i I 11 i i I I i i i i I 8 6 4 2 0 -2 -4 -6 -8 -lOppm Fig. 6.20 a) *H NMR spectrum of a C6D6 solution of the product from the reaction of a THF solution of cc/-Ru(SC6H4pCH3)2(CO)2(PPh3)2 with H2 (24 arm). b) Expanded view of the hydride region of the same spectrum. 251 2b 2 PPh3 I I I ) I I I I I I I I I | I 60 50 i i i i i i i i i i i i i i i | i i i i i i i i i | ' 40 30 20 i i i i i i I i i i i i i i i i i»i > i i 1 10 Oppm Fig. 6.21 31p{lH} NMR spectrum of a C6D6 solution of the product from the reaction of a THF solution of crt-Ru(SC6H4pCH3)2(CO)2(PPh3)2 with H2 (24 atm). Chemical shift scale is shown relative to PPh3 in Q&D6. 252 0 I i i i i i i i i i i i i i i i i i 0 1000 2000 3000 time(s) Fig. 6.22 The time dependence of the intensity (I) of the iH NMR signals due to cc/-Ru(SH)2(CO)2(PPh3)2 (3.3 mM) in 4% v/v CD3OD/C6D6 at 25oC. 253 Once again, a significant decrease in the intensity of the signal for the o-phenyl proton was observed, although the mechanism by which such an exchange may occur is not known. 6.3 EXPERIMENTAL DETAILS The reaction of cc/-RuH(SR)(CO)2(PPh3)2 with P(C6H4pCH3)3: The reagents were placed in an NMR tube within a wide-mouth Schlenk tube. The latter tube was evacuated and Ar introduced at 1 atm. C6D6 (0.6 mL) was added into the NMR tube, which was then sealed with a septum. The tube was inserted into the pre-warmed NMR probe (45°C), at which point the reaction was considered to have started. The change in reaction was monitored by lH NMR spectroscopy, with the assumption that the Ti's of the hydride ligands on the complexes observed were the same (Section 2.2.3). The products were not isolated, but were identified by comparison of their lH and 31p{ lH) NMR spectra with those of the corresponding starting complex. ccNRuH(SCH2C6H4)(CO)2(PPh3){P(C6H4pCH3)3}: lH NMR (C6D6) 5 -4.58 ppm (t, 2JPH = 20.3 Hz, RuH); 31p{ lH) NMR (C6D6) 8 36.49, 35.83 ppm (both single peaks, considered to be the centre two peaks of an AB pattern with the two oudying peaks unobserved, 2Jpp unknown). cc/-RuH(SCH2C6H4)(CO)2{P(C6H4pCH3)3}2: lH NMR (C6D6) 8 -4.53 ppm (t, 2JPH = 20.2 Hz, RuH); 31p{ lH) NMR (C6D6) 8 35.17 ppm (s). cc/-RuH(SC6H4pCH3)(CO)2(PPh3){P(C6H4pCH3)3>: not detected cc/-RuH(SC6H4pCH3)(CO)2{P(C6H4pCH3)3}2: *H NMR (C6D6) 8 -4.22 ppm (t, 2JPH = 19.7 Hz, RuH); 31p{ lH} NMR (C6D6) 8 35.09 ppm (s). The reaction of ccf-RuH(SCH2CH3)(CO)2(PPh3)2 (9d) with PPhy The complex (6.7 mg, 1.3 mM) and PPh3 (270 mg, 150 mM) were dissolved in THF (7 mL). After 4 h at room 254 temperature, the solvent was removed by vacuum distillation, and the residue redis solved in C6D6. The 31p{ lH} NMR spectrum contained signals for Ru(CO)2(PPh3)3 (2, 30 % of the 31p signal excluding the free PPh3 or its oxide), the starting materials, and a small amount of OPPI13. The conversion to 2 was calculated to be 26 %, using correction factors determined from the 31p{ lH} NMR spectrum of a known mixture of 2 and ccf-RuH(SR)(CO)2(PPh3)2. The 31p{ lH} NMR spectrum of the residue from a similar reaction ([9d] = 2.2 mM, [PPh3] = 78 mM) of 4 days duration contained no signal for 9d. Conversion to 2 was therefore complete. The reaction of cct-RuH(SCH3)(CO)2(PPh3)2 (9c) with H2: A solution of 9c (8 mg, 2.3 mM) in THF (5 mL) was exposed to H2 (60 atm) for 25 h in a glass-lined steel vessel. After depressurization, the solution was transferred by syringe into an Ar-filled Schlenk tube through a septum. The volatiles were removed by vacuum distillation, and the solid residue redissolved in C6D6. The 31p{ lH} NMR spectrum contained signals for ccf-RuH2(CO)2(PPh3)2 (5 56.33 ppm, 86 % of the total signal), unreacted 9c (37.05 ppm, 5 %), Ru(CO)2(PPh3)3 (49.25,2 %), and ccr-Ru02(CO)2(PPh3)2 (33.93 ppm, 8 %). The reaction of cc/-RuH(SCH2C6Hs)(CO)20?Ph3)2 (9e) with HCl: Complex 9e (6.9 mg. 8.6 mol) was dissolved in a heterogeneous mixture of C6D6 (0.6 mL) and aqueous concentrated HCl (0.05 mL, 0.6 mmol). The reaction was monitored by 31p{ lH} and lH NMR spectroscopies. After 10 min at room temperature, the 31p{ lH} NMR spectrum of the solution showed the presence of ccf-RuH(Cl)(CO)2(PPh3)2 (38.43 ppm, 84 % of the total signal), unreacted 9e (37.09 ppm, 5 %), and an unknown (38.76 ppm, 11%). A lH NMR spectrum was acquired from 15 to 48 min after the start of the reaction. In addition to the triplet for ccr-RuH(Cl)(CO)2(PPh3)2 (6 -3.86 ppm, 2JPH = 19.1 Hz, 76 % of the integral of the hydride region), two other triplets of unidentified species were observed, at 8 -5.25 ppm (^Jpjj = 16.7 Hz, 7 %) and -13.31 ppm (2JpH = 15.4 ppm, 16 %). The triplet of the starting complex was not observed at this time. 255 The reaction of cc/-RuH(SC6H5)(CO)2(PPh3)2 (9i) with HBF4: A heterogeneous mixture of aqueous HBF4 (50 uL, 48 wt. %, 300 |imol) and a 0.6 mL C5D6 solution of cc?-RuH(SC6H5)(CO)2(PPh3)2 (3.3 \unol) was prepared under argon at room temperature. The 31p{ lH} NMR spectrum acquired after 20 min showed singlets for unreacted 9j (37.19 ppm, 25 %) and an unidentified product (41.71 ppm, 75 %). The lH NMR spectrum (Fig. 6.11) acquired after 30 min contained three triplets, for 91 (-4.33 ppm, 2jpjj = 19.3 Hz, 27 %), the major product (-3.83 ppm, 2jpn = 18.3 Hz, 68 %), and a second unknown (-3.98 ppm, 2JPH = 17.6 Hz, 5 %). A broad peak at 1.5 ppm in the lH NMR spectrum has the correct integral and chemical shift215 for the aquo ligand of ccr-[RuH(H20)(CO)2(PPh3)2]+, suggesting that this could be the major product The reaction of ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b, 9.2 umol) with HBF4/TX2O (0.2 mL, 1 mmol) in toluene-d8 (0.6 mL) at 1°C was monitored by NMR spectroscopy. After 4 min, the 31p{ lH} NMR spectrum showed singlets at 38.6 ppm (unassigned, 63% of the integration), 37.8 ppm (9b. 15%) and 18.9 ppm (unassigned, 18%), in addition to a large number of very small unassigned peaks. After 30 min, the integrals of the three major peaks had changed to 26,10, and 46%, respectively, while the size of the smaller peaks had increased. The hydride region of the lH NMR spectrum contains an unassigned triplet at -5.1 ppm. The reaction of cc/-RuH(SH)(CO)2(PPh3)2 with CD3OD: Complex 9a (2.1 mg, 4.4 mM) was dissolved in C6D6 (0.66 mL) under Ar in a septum-sealed NMR tube. CD3OD (26 uL) was injected to start the reaction. Successive lH NMR spectra, acquired every 7-10 min, showed a decrease in the signals of the o-phenyl (7.91 ppm), mercapto (-3.01 ppm) and hydrido (-4.83 ppm) hydrogens. The temperature was maintained at 19°C. The results are further described in section 6.1.6. 256 The light-induced reaction of c^Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b): Complex 14b (18 mg, 0.32 mM) was dissolved in THF (6 mL) in a quartz cell under Ar. A UV/vis. spectrum Q?ig. 6.14) was acquired after 50,290,610,1200,2100,3300,5400,8000,13,000, and 240,000 s, the absorbance at 430 nm being monitored continuously until 15,000 s, except during spectral acquisition (100 s per acquisition). The temperature was maintained at 25.5°C. The rate of change in absorbance decreased over time, but was not first- or second-order. An isosbestic point was observed at 393 nm. The spectrum acquired after 240,000 s showed a departure from the isosbestic. The solvent was removed from the sample by vacuum distillation, and the residue was redissolved in C6D6 for analysis by NMR. Five unassigned peaks were present, at 24.22, 24.23, 32.82, 32.87, and 42.88 ppm, each with approximately 20 % of the total integral. A similar experiment with only 4 h reaction time produced a 31p{ lH} NMR spectrum with peaks for unreacted 14b (60 %), RPh3 (6 %), and unknowns at 23.60 (9%), 24.16 (12 %, possibly ORPh3), 34.31 (5 %), and 34.82 ppm (6 %). A sample of ccf-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b. 63 g, 4.5 mM) was dissolved in THF (15 mL) in a Pyrex Schlenk tube under Ar. The tube was held 15 cm from a Hanovia lamp for 90 min without cooling the sample solution, during which time the yellow/orange solution turned orange/red. The temperature of the solution did not increase significandy above room temperature. The volatiles were then removed by vacuum distillation, and some of the residue redissolved in QjDfr The 31p{ lH} NMR spectrum contained signals for unreacted 14b (30 %), PPh3 (8 %), and unknowns at 13.90 (28 %), 24.18 (5 %), 32.84 (11 %), and 42.84 ppm (16 %). The FT-IR spectrum of the crushed residue in Nujol contained three v(CO) bands, at 2034,1977, and 1941 cm-1. The residue was submitted for FAB/MS. The reaction of ccf-Ru(SH)2(CO)2(PPh3)2 (14a) with P(C6H4pCH3)3: Complex 14a (2.8 mg, 8.3 mM) and P(C6H4pCH3)3 (31.8 mg, 230 mM) were placed in an NMR tube within a wide-mouth Schlenk tube. The latter tube was evacuated and Ar introduced. Q>D6 (0'46 mL) was added to the NMR tube, which was then sealed with a septum and cooled 257 in liquid N2. After being transported to the NMR room, the tube was warmed to the melting point of benzene, and inserted into the pre-warmed NMR probe (25°C). At this point the reaction was considered to have started. The change in reaction was monitored by lH NMR spectroscopy, with the assumption that the Ti's of the mercapto hydrogens on the three reactant and product complexes were the same (Section 2.2.3). The products were not isolated, but were identified by comparison of their lH and 31p{ lH} NMR spectra with those of the starting complex 14a. cc/-Ru(SH)2(CO)2(PPh3){P(C6H4pCH3)3> (23a): lH NMR (C6P6) 8-1.90 ppm (t, 3JPH = 6.9 Hz, SH); 31p{ lH} NMR (C6D6) 8 19.70,19.87 ppm (both single peaks, considered to be the centre two peaks of an AB pattern with the two outlying peaks unobserved, 2jPP unknown). cc/-Ru(SH)2(CO)2{P(C6H4pCH3)3}2 (24a): lH NMR (C6D6) 8 -1.85 ppm (t, 3JPH = 7.1 Hz, SH); 31P{ lH} NMR (C6D6) 8 19.18 ppm (s). The reaction of ccf-Ru(SC6H4pCH3)2(CO)20?Ph3)2 (14b) with P(C6H4pCH3)3: The method described above was adopted for studying the title reaction. However, the reaction was complete by the time the first 31P{ lH} NMR spectrum was acquired (3 min). Only three peaks were observed; those of P(C6H4pCH3)3, PPh3 (-6.05 ppm), and the product (9.93 ppm). The last mentioned is 1 ppm upfield of the position of the starting material, and therefore probably results from the ccr-Ru(SC6H4pCH3)2(CO)2{P(C6H4pCH3)3}2 complex (24b). The reaction of ccf-Ru(SC6H4pCH3)2(CO)20PPh3)2 (14b) with H2: A toluene solution (50 mL) of 14b (42 mg, 0.90 mM) was exposed to H2 (24 atm) at room temperature for 100 min in a glass-lined steel vessel. After depressurization, the solution was transferred by syringe into an Ar-filled Schlenk tube through a septum. After the volatiles were removed, the solid products were redissolved in C6D6 and analyzed by lH and 31p{ lH} NMR spectroscopies. The spectra indicated the presence of 14b (20 % of the 31p NMR signal), ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b, 45 %), ccr-RuH2(CO)2(PPh3)2 (3,1 %), and several 258 unknowns. The hydride region of the *H NMR spectrum contained triplets at -4.33 (9b.  2JPH=19.7,71 %), -6.33 (3, 2JPH=23.4,4 %), and at -10.19 ppm (unknown, 2jPH=i5.o Hz, 8 %) and a doublet of doublets at -6.40 ppm (unknown, 2JtransPH=96.9,2JcisPH=28.2 Hz, 17 %). The reaction of cc/-Ru(SH)2(CO)20?Ph3)2 (14a) with CD3OD: Complex 14a (2.1 mg, 3.3 mM) was dissolved in C6D6 (0.85 mL) under Ar in a septum-sealed NMR tube. CD3OD (34 uL) was injected to start the reaction. Successive *H NMR spectra, acquired every 6 min, showed a rapid decrease in the intensity of the mercapto (-1.97 ppm) hydrogen signal, and a slower decrease in the intensity of the o-phenyl signal. The temperature was maintained at 25°C. 259 7. GENERAL CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE RESEARCH 7.1 Potential Applications for the Complexes in Sulphur Chemistry The dihydride complex ccf-RuH2(CO)2(PPh3)2 is not a likely catalyst for hydrodesulphurization (HDS) because none of its reactions with sulphur containing compounds, other than propylene sulphide, resulted in S-C bond cleavage. As discussed previously (Section 1.3), S-C bonds, especially those found in thiophenes, are more difficult to cleave than S-H and S-S bonds. The mechanism for such a S-C bond cleavage reaction with thioethers would almost certainly involve a thioether complex as an intermediate. In general, thioether transition metal complexes are unstable, usually with respect to dissociation of the thioether from the metal rather than decomposition via C-S bond cleavage. The ccr-RuH2(CO)2(PPh3)2 complex is a potential catalyst for disulphide reduction (reaction 7.1) because reactions 4.4 and 6.5 together constitute a catalytic cycle for this reaction. 2RuH2(CO)2(PPh3)2 + RSSR -> 2RuH(SR)(CO)2(PPh3)2 + H2 4.4 RuH(SR)(CO)2(PPh3)2 + H2 RuH2(CO)2(PPh3)2 + RSH 6.5 Ru RSSR + H2 —> 2RSH 7.1 Problems which could be encountered include significant back reactions (reverse of reactions 4.4 and 6.5) under conditions of excess H2 and thiol, and loss of the catalyst via production of ccf-Ru(SR)2(CO)2(PPh3)2 (reactions 4.7 and 4.9) and its subsequent decomposition (Section 6.2.1). Reduction of disulphides to thiols is practiced in organic chemistry as the last step in the synthesis of thiols, if the direct synthesis of the thiol gives lower yields or is less safe than synthesis via the disulphide. In addition, unstable thiols are often stored as the disulphide.309 260 Stoichiometric methods for the reduction of disulphides have been reviewed.30^ The reduction of disulphides by o-methylbenzaldehyde and methanol is catalyzed by S^'-tetramethylene-bridged 4-methylthiazolium bromide.310 Thioredoxin and thioredoxin reductase together catalyse the reduction of disulphides in mammalian cells.311 The reverse reaction, oxidation of thiols to disulphides, is catalyzed by several transition metal complexes.312,313 A potential non-catalytic application of the chemistry described in this thesis is the non-oxidative extraction of thiols from petroleum. Such a process would require two steps; extraction of the thiols by passing the oil fraction over a supported transition metal complex such as a derivative of ccf-RuH2(CO)20?Ph3)2, followed by regeneration of the same complex from the thiolate, ccr-RuH(SR)(CO)2(PPh3)2, by applying high pressures of hydrogen. Obviously, any complex containing either Ru or PPh3 would be too expensive for such an application. However, similar applications 0x)th oxidative and non-oxidative) for unsupported iron carbonyls have been suggested,314 although cost remains a problem even in the iron system. Leaching of a supported transition metal catalyst, or incomplete separation of an unsupported catalyst, would also create problems of heavy-metal contamination of the fuel product.314 7.2 Parallels to Surface Chemistry The hydrido thiolato complex ccf-RuH(SR)(CO)2(PPh3)2 has parallels in the chemistry of thiols on transition metal surfaces. In most cases of thiol adsorption to such surfaces, cleavage of the S-H bond occurs and thiolato species are detected.315-9 The fate of the hydrogen atom is rarely reported. However, after H2S adsorption on a Ru(l 10) surface, rnixtures of H2S, SH, S, and H species are detected, depending on the coverage.320 Examples of adsorption of thiols on the surface without S-H bond cleavage are reported to exist at low temperatures.317,319 The instability of S-bonded thiols is also recognized in transition metal solution chemistry. No such M-S(H)R species was directly observed in the present work. 261 A related type of complex, in which two or possibly three thiolate ligands share a proton, is proposed as an intermediate in the thiol exchange reactions of ccf-RuH(SR)(CO)2(PPh3)2 and ccr-Ru(SR)2(CXD)2(PPh3)2 (reactions 3.12 and 3.18). PPh3 oc< |UN*SR RS—H' The type of bonding illustrated above may exist on the surface of HDS catalysts. The formation of such species on the surface would be associated with adsorption or liberation of 1/2 to 2/3 of the hydrogen from the adsorbed thiol. Isolated metal complexes with structures containing H+ or other cations trapped by thiolate groups are [Ru((X>)2(PPh3)(uSEt)2(p3SEt)Na(TrIF)]2 (Section 5.2) and Ru(ClH)(buS4)(PPh3) (bus42- = l,2-ow((3,5-di-rm-butyl-2-mercapto-phenyl)thio)ethanato,249 the latter being shown below. 262 7.3 Conclusions One of the phosphine ligands of Ru(CO)2(PPh3)3 (2) is quickly displaced by thiols and disulphides, producing species of the type ccr-RuH(SR)(CO)2(PPh3)2 (2) and ccr-Ru(SR)2(CO)2(PPh3)2 (14), respectively. The kinetics of the disulphide reaction are consistent with a two-step mechanism involving elimination of PPI13 followed by oxidative addition of RSSR. Similar mechanisms have been proposed in earlier studies of the related reactions of 2 with CO and H2.172 Complex 2 fails to react with unstrained thioethers. Reactions of the related complex Ru(CO)2(PPh3)(dpm) (16, dpm = bis(mphenylphosphino)methane) are complicated by the lability of all of the three different ligands. Reactions of this complex with thiols produce mixtures of thiolate complexes. The two dihydrides ccf-RuH2(CO)2(PPh3)2 (3) and RuH2(dpm)2, as a cisltrans mixture (7), react with thiols to produce the hydrido-thiolato complexes ccf-RuH(SR)(CO)2(PPh3)2 (2) and RuH(SR)(dpm)2 (13). respectively. The mechanism appears to depend on the basicity of the hydride ligands; the more basic dihydride, 7, is probably protonated by the thiol, giving an unobserved molecular hydrogen intermediate. The reaction rate depends on the acidity and concentration of the thiol. The less basic dihydride, 3, reacts by slow reductive ehmination of H2 followed by rapid oxidative addition of thiol, the rate being independent of the nature or concentration of the thiol. The same rate constant, rate law, and activation parameters are found for the reaction of 3 with thiols, CO or PPI13. The reaction of 3 with RSSR produces mostly 9, with small amounts of 14 that increase with time. The mechanism of the reaction with RSSR was not determined. The hydrido-thiolato complexes ccf-RuH(SR)(CO)2(PPh3)2 (9) are well characterized for a variety of R groups. The related complex ccf-RuH(SePh)(CO)2(PPh3)2 was also synthesized. The reactions of 2 with other thiols, P(C6H4pCH3)3, CO, RSSR, HCl, PPI13, and H2, are also reported. The first three of these reactions share the same rate law and rate constant, the common rate deterrmning step probably being initial loss of PPI13. The rate constant depends 263 strongly on the choice of thiolate group, with the complexes containing the more basic thiolate groups reacting faster. The entropy and enthalpy of activation for the reaction of 9b (R=C6H4pCH3) with CO are higher than those for the same reaction of 2d (R=CH2CH3), although the error in the entropy values is large. The difference in enthalpy is mainly responsible for the difference in rate. Some equilibrium constants for the exchange reactions of 9_d (R=CH2CH3) with other thiols were determined, the Keq values increasing with the acidity of the mcorning thiol. The reactions of c^Ru(SC&H4pOrl3)2(CO)2(PPh3)2 (14b) are complicated by the extreme lability of the phosphine ligands. The complex in solution is unstable in the presence of light, exchanges phosphines rapidly with added P(C6H4pCH3)3, exchanges thiolate groups with added thiols, and is converted by high pressures of H2 to a rnixture of 9b and 3. The X-ray crystallographic structures of ccr-RuH(SC6H4pCH3)(CO)2(PPh3)2 (9b) and cct-Ru(SC6H4pCH3)2(CO)2(PPh3)2 (14b) show that the Ru-P bond lengths in 14b are longer, consistent with the higher lability of the phosphines of that complex. The phosphine ligands of Ru(SH)2(CO)2(PPh3)2 (14a) on the other hand are less labile, and the Ru-P bond lengths shorter, than in 14b. Complex 14a is stable in solution in the presence of light, and exchanges phosphines more slowly with added P(C6H4pCH3)3. The mercapto hydrogens of 9a (R=H) and 14a exchange with the acidic deuterons of added CD3OD. The hydridic and ortho-phenyl hydrogens exchange more slowly, presumably by intramolecular processes. Intermediates proposed for the mechanism of the thiol exchange reactions of 9 and 14 contain two or three thiolate groups sharing a proton. A related complex, containing three thiolate groups on a ruthenium centre sharing a sodium cation, was isolated and fully characterized. In the solid state, this |TRu(CO)2(PPh3)(p;SEt)2(M-3SEt)Na(THF)]2 complex exists in dimeric form, and is formed as a by-product from the synthesis of 14d (R=Et) from ccf-RuCl2(CO)2(PPh3)2 and sodium ethanethiolate. In acetone, 9_b and 14b can be formed cleanly from 264 ccf-RuHCl(CO)2(PPh3)2 and m-RuCl2(CO)2(PPh3)2, respectively, by reaction with ethanethiolate. Complex 3_ could be used as a catalyst for the reduction of disulphides by H2, or as a recyclable reagent for the non-oxidative extraction of thiols from tWol-containing mixtures such as oil fractions. However, the cost of RuCl3 and PPh3 is too high to allow such direct applications. The chemistry described above will help instead to guide future researchers to related complexes with higher activity and lower costs, and systems that more closely parallel the processes occurring on the surfaces of industrial HDS catalysts. 7.4 Recommendations for Future Research As has been suggested recentiy by another group,90 the redox chemistry of ccf-RuH(SH)(CO)2(PPh3)2. cc*-Ru(SH)2(CO)2(PPh3)2 and «*-RuS2(CO)2(PPh3)2 should be investigated. Initial experiments during the present research, but not otherwise reported here, show that high pressures of H2 (24 atm) over CH2CI2 solutions of ccr-RuS2(CO)2(PPh3)2 for 2 h at room temperature do not cause formation of ccf-RuH2(CO)2(PPh3)2 or cc/-Ru(SH)2(CO)2(PPh3)2. However, such reactions may possibly be achieved in the presence of acid, because of the ease of electrophilic attack on the S2^- ligand. 118,221,321-2 Research should focus on complexes which are capable of cleaving unstrained S-C bonds. The most likely candidates are bimetallic complexes containing at least one transition metal which bonds strongly with sulphur. One such complex, (CO)3Mo(uH)2(dpm)2Ru(CO)2323 has some similarities to the complexes described in the present work. However, for closer parallels to industrial HDS catalysts, a Co/Mo bimetallic complex should be used. 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Chem., 21,2853 (1988). 282 APPENDIX 1; SUMMARY OF CRYSTALLOGRAPHIC DATA compound 9J> 14b-THF 21 formula CgH^C^PjRuS C56HJ203P2RuS2 CjoH-gNaaOgPjF fw 804.86 928.06 1395.68 color, habit yellow, irregular yellow, prism yellow, prism crystal size, mm 0.30x0.35x0.50 0.15x0.22x0.46 0.10x0.15x0.35 crystal system triclinic triclinic triclinic space group PI Pi Pi a, A 12.340(4) 13.173(3) 12.189(3) b,A 14.948(3) 19.766(4) 13.124(3) c.A 10.684(4) 9.770(4) 12.032(4) a, deg 90.05(3) 98.26(2) 99.70(2) P. deg 99.27(3) 91.24(3) 110.61(2) Y. deg 86.84(3) 78.31(2) 67.95(2) V.A3 1942(1) 2465(1) 1668.4(8) Z 2 2 1 Pca/c.g/an3 1.38 1.25 1.39 F(000) 826 956 720 KMo^.cm"1 5.63 4.91 7.27 transmission factors 0.947-1.00 0.926-1.00 0.946-1.00 scan type (0-26 (0-29 (0-26 scan range, deg in (0 1.31+0.35 tan 6 1.16+0.35 tan 0 1.26+0.35 tan 0 scan speed, deg/min 32 32 16 data collected +h, tk, tJ lit, ±y +fa. ±A, ±/ 26ma» deg 60 50 55 283 cryst decay negligible negligible 12.0% total no. of reflections 11794 9129 7986 no. of unique reflections 11310 8713 7627 Emerge 0.022 0.074 0.040 no. of reflcns with / > 3o(/) 7174 3597 4252 no. of variables 464 577 352 0.032 0.041 0.039 Rw 0.037 0.043 0.043 gof 1.28 1.17 1.43 max A/o (final cycle) 0.14 0.06 0.02 residua] density e/A3 0.55 0.54 0.84 (near Ru) a Temperature 294 K, Rigaku AFC6S diffractometer. Mo X» radiation (X - 0.71069 A), graphite monochromator, takeoff angle 6.0°, aperture 6.0 x 6.0 mm at a distance of 285 mm from the crystal, stationary background counts at each end of the scan (scan/background time ratio 2:1), a2(F2) - [^(C* 45)+ (pF2)2]/!^)2 (5 - scan rate, C- scan count, B - normalized background count, p - 0.035 for 1,0.040 for 2, and 0.030 for 3), function minimized 2w(|F0|-|Fcl)2 where w - 4F02/o2(F02), R - IIIFoHFdlWol. *w - oH^^o!2)1'2. and gof - rZ(|F0|-IFcD^m-n)]m. Values given for R, Rw, and gof are based on those reflections with / 23o(/). 284 APPENDIX 2: ATOMIC COORDINATES FOR  cc/-RuH(SC^HipCH^(CO)?fPPh^h(9b) Table A2.1 Final atomic coordinates (fractional) and B(eq). atom X y z B(eq) Ru 0 .39625(2) 0 .23433(1) 0 .36310(2) 2.663(7) S 0 .30451(6) 0 .28651(5) 0 .15245(6) 4.10(3) Pd) 0 .21506(5) 0 .22674(4) 0 .40562(5) 2.80(2) P(2) 0 .57093(5) 0 .25962(4) 0 .30634(6) 2.89(2) 0(1) 0 .4931(2) 0 .2198(2) 0 .6397(2) 6.4(1) 0(2) 0 .4235(2) 0 .0331(2) 0 .3080(3) 7.2(1) C(l) 0 .4578(2) 0 .2206(2) 0 .5347(3) 4.0(1) C(2) 0 .4098(2) 0 .1080(2) 0 .3212(3) 4.1(1) C(3) 0 .1218(2) 0 .3258(2) 0 .3689(2) 3.3(1) C(4) 0 .1576(2) 0 . 4095(2) 0 .4061(3) 4.6(1) C(5) 0 .0893(3) 0 .4860(2) 0 .3786(3) 5.8(2) C(6) -0 .0150(3) 0 .4796(2) 0 .3142(3) 5.7(2) C(7) -0 .0512(3) 0 .3979(2) 0 .2761(3) 5.2(2) C(8) 0 .0166(2) 0 .3206(2) 0 .3025(3) 4.3(1) C(9) 0 .2141(2) 0 .2017(2) 0 .5736(2) 3.4(1) C(10) 0 .1798(3) 0 .2634(2) 0 .6568(3) 5.2(1) C(ll) 0 .1915.4) 0 .2409(3) 0 .7859(3) 7.5(2) C(12) 0 .2354(4) 0 .1593(3) 0 .8294(3) 7.1(2) C(13) 0 .2689(3) 0 .0976(3) 0 .7477(3) 5.8(2) C(14) 0 .2595(2) 0 .1183(2) 0 .6206(3) 4.5(1) C(15) 0 .1332(2) 0 .1371(2) 0 .3287(2) 2.97(9) C(16) 0 .0491(2) 0 .1047(2) 0 .3843(2) 3.6(1) C(17) -0 .0176(2) 0 .0407(2) 0 .3233(3) 4.2(1) C(18) 0 .0003(2) 0 .0078(2) 0 .2084(3) 4.4(1) C(19) 0 .0836(2) 0 .0391(2) 0 .1526(3) 4.5(1) C(20) 0 .1499(2) 0 .1038(2) 0 .2119(2) 3.7(1) 285 Table A2.1 (contA atom X y z B(eq) C(21) 0 .5932(2) 0. 3756(2) 0 .2689(2) 3 .2(1) C(22) 0 .5912(2) 0. 4398(2) 0 .3638(3) 4 .1(1) C(23) 0 .6022(3) 0. 5293(2) 0 .3375(3) 5 .3(1) C(24) 0 .6153(3) 0. 5558(2) 0 .2174(4) 5 .8(2) C(25) 0 .6170(3) 0. 4934(2) 0 .1246(3) 5 .5(2) C(26) 0 .6069(2) 0. 4032(2) 0 .1495(3) 4 .2(1) C(27) 0 .6091(2) 0. 1954(2) 0 .1718(2) 3 .5(1) C(28) 0 .7179(2) 0. 1726(2) 0 .1651(3) 4 .5(1) C(29) 0 .7471(3) 0. 1263(2) 0 .0624(3) 5 .3(2) COO) 0 .6689(3) 0. 1019(3) -0 .0343(3) 6 .1(2) C(31) 0 .5628(3) 0. 1239(4) -0 .0291(4) 9 .3(3) C(32) 0 .5318(3) 0. 1698(3) 0 .0737(4) 7 .6(2) C(33) 0 .6875(2) 0. 2290(2) 0 .4309(2) 3 .1(1) C(34) 0 .7742(2) 0. 2838(2) 0 .4650(3) 4 .1(1) C(35) 0 .8616(2) 0. 2563(2) 0 .5575(3) 5 .0(1) C(36) 0 .8636(2) 0. 3755(2) 0 .6177(3) 4 .9(1) C(37) 0 .7784(3) 0. 1196(2) 0 .5830(3) 4 .8(1) C(38) 0 .6909(2) 0. 1465(2) 0 .4907(3) 4 .1(1) C(39) 0 .2654(2) 0. 4023(2) 0 .1460(2) 3 .6(1) C(40) 0 .3239(2) 0. 4682(2) 0 .2124(3) 4 .6(1) C(41) 0 .2911(3) 0. 5577(2) 0 .1958(3) 5 .3(2) C(42) 0 .1987(3) 0. 5857(2) 0 .1115(3) 5 .4(2) C(43) 0 .1404(3) 0. 5200(2) 0 .0443(3) 5 .4(2) C(44) 0 .1715(2) 0. 4300(2) 0 .0611(3) 4 .5(1) C(45) 0 .1629(4) 0. 6837(3) 0 .0915(4) 8 .2(2) H(l) 0 .390(2) 0. :36(2) 0 .405(3) 5 .4(7) 286 Table A2.2 Calculated hydrogen coordinates and B(iso). atom J X y z B(iso] H(2) 0.2323 0.4146 0.4525 5.5 H(3) 0.1158 0.5447 0.4053 6.9 H(4) -0.0636 0.5336 0.2955 6.9 H(5) -0.1259 0.3936 0.2294 6.3 H(6) -0.0103 0.2623 0.2740 5.1 H(7) 0.1477 0.3223 0.6261 6.2 H(8) 0.1675 0.2846 0.8456 9.0 H(9) 0.2432 0.1447 0.9199 8.5 H(10) 0.2995 0.0385 0.7793 7.0 H(ll) 0.2850 0.0741 0.5626 5.4 H(12) 0.0365 0.1271 0.4673 4.3 H(13) -0.0777 0.0189 0.3628 5.1 H(14) -0.0463 -0.0379 0.1660 5.2 H(15) 0.0964 0.0156 0.0702 5.4 H(16) 0.2089 0.1260 0.1710 4.5 H(17) 0.5818 0.4215 0.4493 5.0 H(18) 0.6007 0.5739 0.4045 6.4 H(19) 0.6234 0.6190 0.1990 7.0 H(20) 0.6255 0.5123 0.0391 6.6 H(21) 0.6095 0.3591 0.0820 5.1 H(22) 0.7753 0.1894 0.2341 5.4 H(23) 0.8249 0.1109 0.0592 6.4 H(24) 0.6897 0.0687 -0.1067 7.3 H(25) 0.5062 0.1073 -0.0992 11.2 H(26) 0.4537 0.1840 0.0761 9.1 H(27) 0.7737 0.3423 0.4234 4.9 287 Table A2.2 (cont.) atom X y z B(iso H(28) 0.9229 0.2953 0.5801 6.0 H(29) 0.9247 . 0.1573 0.6848 5.8 H(30) 0.7800 0.0608 0.6241 5.7 H(31) 0.6306 0.1067 0.4673 5.0 H(32) 0.3903 0.4509 0.2728 5.6 H(33) 0.3345 0.6025 0.2451 6.3 H(34) 0.0750 0.5377 -0.0173 6.5 H(35) 0.1271 0.3852 0.0130 5.4 H(36) 0.0973 0.6971 0.1306 9.8 H(37) 0.2223 0.7205 0.1305 9.8 H(38) 0.1458 0.6969 0.0004 9.8 APPENDIX 3; ATOMIC COORDINATES FOR  cc/-Ru(SCnH4pCH^?fCObfPPh^b(14b) Table A3.1 Final atomic coordinates (fractional) and B(eq). atom X y z B(eq) Ru 0 .13050(5) 0 .21874(4) 0. 32473(7) 2.66(3) S(l) 0 .1587(2) 0 .2929(1) 0. 1517(2) 3.6(1) S(2) 0 .1947(2) 0 .1238(1) 0. 1380(2) 3.7(1) Pd) 0 .3056(2) 0 .2177(1) 0. 4135(2) 3.0(1) P(2) -0 .0436(1) 0 .2150(1) 0. 2351(2) 3.0(1) 0(1) 0 .1126(4) 0 .1136(3) 0. 5150(5) 4.7(3) 0(2) 0 .0592(5) 0 .3329(3) 0. 5611(6) 5.8(4) 0(3) 0 .468(2) 0 .4670(8) 0. 171(1) 17(1) C(l) 0 .1182(5) 0 .1515(4) 0. 4409(7) 2.8(4) C(2) 0 .0858(6) 0 .2920( 4 ) 0. 4664(8) 3.7(4) C(3) 0 .4197(6) 0 .1805(4) 0. 3016(7) 3.1(4) C(4) 0 .5130(6) 0 .1487(4) 0. 3539(8) 4.0(4 ) C(5) 0 .5985(6) 0 .1260(4) 0. 269(1) 4.4(5) C(6) 0 .5928(7) 0 .1344(5) 0. 132(1) 5.3(5) C(7) 0 .4999(7) 0 .1665(5) 0. 0802(8) 5.7(5) C(8) 0 .4141(6) 0 .1897(4) 0. 1632(8) 4.0(4) C(9) 0 .3199(5) 0 .1696(4) 0. 5599(7) 3.3(4) C(10) 0 .2799(6) 0 .2019(5) 0. 6875(8) 4.5(5) C(ll) 0 .2801(7) 0 .1658(6) 0. 7988(8) 5.3(6) C(12) 0 .3212(7) 0 .0952(6) 0. 781(1) 5.6(6) C(13) 0 .3582(7) 0 .0613(5) 0. 656(1) 5.5(6) C(14) 0 .3578(6) 0 .0981(4) 0. 5434(8) 4.2(5) C(15) 0 .3422(5) 0 .3006(4) 0. 4846(8) 3.5(4) C(16) 0 .3114(6) 0 .3580(5) 0. 4167(9) 4.9(5) C(17) 0 .3456(8) 0 .4199(4) 0. 462(1) 6.1(6) 289 Table A3.1 (cont.) atom X y z B(eq) C(18) 0 .4094(7) 0 .4233(5) 0 .576(1) 6.0(6) C(19) 0 .4409(7) 0 .3663(5) 0 .641(1) 5.3(5) C{20) 0 .4077(6) 0 .3058(4) 0 .5967(8) 4.3(5) C(21) -0 .0744(6) 0 .2335(4) 0 .0578(7) 3.5(4) C(22) -0 .0051(6) 0 .2043(4) -0 .0495(8) 4.2(5) C(23) -0 .0286(8) 0 .2187(5) -0 .1814(9) 5.7(6) C(24) -0 .1201(9) 0 .2626(6) -0 .210(1) 6.6(7) C(25) -0 .1890(7) 0 .2895(5) -0 .104(1) 6.4(6) C(26) -0 .1681(7) 0 .2761(4) 0 .0285(9) 4.9(5) C(27) -0 .0793(5) 0 .1302(4) 0 .2372(7) 3.0(4) C(28) -0 .0908(5) 0 .1079(4) 0 .3650(7) 3.1(4) C(29) -0 .1096(6) 0 .0423(4) 0 .3712(8) 3.8(4) C(30) -0 .1175(6) -0 .0024(4) 0 .2516(9) 4.3(5) C(31) -0 .1109(6) 0 .0202(4) 0 .1263(8) 3.9(4) C(32) -0 .0910(6) 0 .0858(4) 0 .1178(7) 3.7(4) C(33) -0 .1476(6) 0 .2759(4) 0 .3352(7) 3.4(4) C(34) -0 .1390(6) 0 .3446(4) 0 .3693(9) 4.7(5) C(35) -0 .2148(7) 0 .3936(4) 0 .447(1) 6.3(6) C(36) -0 .3008(7) 0 .3731(5) 0 .489(1) 6.5(6) C(37) -0 .3127(7) 0 .3065(5) 0 .452(1) 6.4(6) C(38) -0 .2367(6) 0 .2580(4) 0 .3773(9) 4.6(5) C(39) 0 .0664(5) 0 .3736(4) 0 .1657(8) 3.4(4) C(40) 0 .0598(6) 0 .4250(4) 0 .2810(8) 4.2(5) C(41) -0 .0121(7) 0 .4859(4) 0 .2860(9) 4.7(5) C(42) -0 .0824(7) 0 .4i?83(4) 0 .180(1) 4.8(5) C(43) -0 .0731(7) 0 .4 f86(5) 0 .0676(9) 5.2(5) 290 Table A3.1 (cant.) atom X y z B(eq) C(44) -0. 0002(7) 0 .3862(4) 0.0576(8) 4.4(5) C(45) -0. 1646(8) 0 .5640(5) 0.187(1) 7.6(7) C(46) 0. 2398(5) 0 .0419(4) 0.1963(7) 3.1(4) C(47) 0. 1718(6) 0 .0026(4) 0.2349(8) 3.8(4) C(48) 0. 2081(7) -0 .0649(4) 0.2640(7) 4.5(5) C(49) 0. 3116(8) -0 .0948(4) 0.2585(9) 4.9(5) C(50) 0. 3789(7) -0 .0552(5) 0.224(1) 5.9(5) C(51) 0. 3448(6) 0 .0120(4) 0.1916(8) 4.5(5) C(52) 0. 3501(9) -0 .1673(5) 0.289(1) 8.1(7) C(53) 0. 551(2) 0 .409(2) 0.149(3) 21(2) C(54) 0. 523(2) 0 .357(1) 0.069(4) 25(3) C(55) 0. 418(2) 0 .369(1) 0.050(2) 16(2) C(56) 0. 389(2) 0 .442(2) 0.084(3) 18(2) 291 Table A3.2 Calculated hydrogen coordinates and B(iso). atom X y z B(iS0 H(l) 0.5181 0.1423 0.4517 4.8 H(2) 0.6643 0.1036 0.3066 5.3 H(3) 0.6539 0.1180 0.0715 6.3 H(4) 0.4953 0.1727 -0.0176 6.8 H(5) 0.3488 0.2127 0.1253 4.8 H(6) 0.2505 0.2521 0.6997 5.4 H(7) 0.2514 0.1900 0.8886 6.3 H(8) 0.3239 0.0692 0.8597 6.7 H(9) 0.3852 0.0108 0.6437 6.6 H(10) 0.3844 0.0733 0.4531 5.0 H(ll) 0.2656 0.3553 0.3366 5.9 H(12) 0.3243 0.4606 0.4137 7.3 H(13) 0.4323 0.4669 0.6091 7.2 H(14) 0.4874 0.3688 0.7205 6.3 H(15) 0.4308 0.2653 0.6451 5.2 H(16) 0.0606 0.1734 -0.0315 5.0 H(17) . 0.0205 0.1974 -0.2569 6.8 H(18) -0.1349 0.2741 -0.3037 8.0 H(19) -0.2553 0.31,92 -0.1235 7.7 H(20) -0.2189 0.2963 0.1026 5.9 H(21) -0.0854 0.1393 0.4508 3.7 H(22) -0.1173 0.0274 0.4612 4.5 H(23) -0.1279 -0.0498 0.2558 5.2 H(24) -0.1204 -0.0106 0.0411 4.6 H(25) -0.0852 0.1005 0.0271 4.4 292 Table A3.2(contJ atom X y z B(iso) H(26) -0.0778 0.3594 0.3381 5.7 H(27) -0.2067 0.4421 0.4707 7.6 H(28) -0.3539 0.4066 0.5458 7.8 H(29) -0.3760 0.2927 0.4786 7.7 H(30) -0.2461 0.2098 0.3537 5.5 H(31) 0.1069 0.4174 0.3588 5.1 H(32) -0.0140 0.5218 0.3668 5.7 H(33) -0.1198 0.4569 -0.0104 6.2 H(34) 0.0036 0.3516 -0.0258 5.3 H(35) -0.2293 0.5559 0.2231 9.1 H(36) -0.1764 0.5769 0.0937 9.1 H{37) -0.1417 0.6018 0.2476 9.1 H(38) 0.0974 0.0227 0.2418 4.6 H(39) 0.1583 -0.0918 0.2891 5.4 H(40) 0.4534 -0.0748 0.2215 7.0 H(41) 0.3951 0.0384 0.1656 5.4 H(42) 0.3270 -0.2005 0.2171 9.7 H(43) 0.4261 -0.1770 0.2921 9.7 H(44) 0.3226 -0.1720 0.3791 9.7 H(45) 0.6089 0.4225 0.1040 24.7 H(46) 0.5749 0.3944 0.2381 24.7 H(47) 0.5576 0.3497 -0.0205 29.9 H(48) 0.5427 0.3145 0.1133 29.9 H(49) 0.4014 0.3545 -0.0471 19.4 H(50) 0.3837 0.3453 0.1102 19.4 293 Tnhle A3.2 (cont.) atom x y z B(iso) H(51) 0.3224 0.4548 0.1348 21.2 H(52) 0.3818 0.4648 0.0003 21.2 294 APPENDIX 4! ATOMIC COORDINATES FOR  f(CO)?.(PPh^?.Ru(SEt)^Na(THFil7(21) Table A4.1 Final atomic coordinates (fractional) and B(eq). atom X y z Ru(l) 0.56768(4) 0.18197(3) 0.28424(3) 3.26(2) S(l) 0.7506(1) 0.0165(1) 0.3369(1) 6.05(8) S(2) 0.4531(1) 0.0666(1) 0.1457(1) 4.04(6) S(3) 0.6480(1) 0.1922(1) 0.1263(1) 4.12(6) Pd) 0.3992(1) 0.34358(8) 0.2063(1) 3.15(6) Na(l) 0.6960(2) -0.0365(2) 0.0905(2) 5.0(1) 0(1) 0.7373(4) 0.2883(3) 0.4683(3) 7.3(2) 0(2) 0.4763(4) 0.1566(3) 0.4777(3) 7.2(3) 0(3) 0.9066(4) -0.1109(4) 0.0945(4) 8.9(3) C(l) 0.4439(4) 0.4662(3) 0.2257(4) 3.2(2) C(2) 0.4975(4) 0.5018(4) 0.3398(4) 3.9(2) C(3) 0.5348(5) 0.5925(4) 0.3598(4) 4.9(3) C(4) 0.5178(5) 0.6478(4) 0.2649(5) 5.4(3) C(5) 0.4661(5) 0.6135(4) 0.1512(5) 5.5(3) C(6) 0.4279(4) 0.5225(4) 0.1305(4) 4.0(2) C(7) 0.2778(4) 0.3828(4) 0.2776(4) 3.6(2) C(8) 0.2392(4) 0.4810(4) 0.3404(4) 4.2(3) C(9) 0.1514(5) 0.4991(5) 0.3966(5) 5.8(3) C(10) 0.1005(5) 0.4206(6) 0.3879(5) 6.4(4) Cdl) 0.1359(5) 0.3232(5) 0.3245(6) 6.3(4) C(12) 0.2237(5) 0.3051(4) 0.2698(5) 5.0(3) C(13) 0.3039(4) 0.3465(3) 0.0488(4) 3.4(2) C(14) 0.1887(4) 0.4310(4) 0.0119(4) 4.5(3) C(15) 0.1163(5) 0.4402(4) -0.1058(5) 5.5(3) 295 Table A4.1 (cont.) atom X y 2 C(16) 0.1583(5) 0.3618(5) -0.1884(4) 5.4(3) C{17) 0.2704(5) 0.2781(4) -0.1549(4) 4.6(3) C(18) 0.3441(4) 0.2704(3) -0.0366(4) 3.7(2) C(19) 0.7885(7) •0.0265(7) 0.4795(7) 10.9(6) C(20) 0.9046(8) -0.1152(8) 0.5161(8) 12.9(7) C(21) 0.4517(6) -0.0382(4) 0.2263(5) 6.3(4) C(22) 0.3365(7) -0.0278(7) 0.2348(8) 11.3(6) C(23) 0.7955(5) 0.2173(5) 0.1933(5) 6.0(3) C(24) 0.7799(6) 0.3372(6) 0.2072(7) 8.6(5) C(25) 0.6699(5) 0.2530(4) 0.3947(4) 4.6(3) C(26) 0.5076(5) 0.1663(4) 0.4019(4) 4.6(3) C(27) 0.9580(8) -0.1873(9) 0.0214(8) 11.4(7) C(28) 1.087(1) -0.242(1) 0.090(1) 18(1) C(29) 1.106(1) -0.203(1) 0.205(1) 15(1) C(30) 1.005(1) -0.101(1) 0.194(1) 17(1) 296 Table A4.2 Calculated hydrogen coordinates and B(iso). atom X y z Bls, H(l) 0.5093 0.4621 0.4075 4.6 H(2) 0.5729 0.6169 0.4411 5.9 H(3) 0.5431 0.7127 0.2786 6.5 H(4) 0.4558 0.6530 0.0840 6.6 H(5) 0.3899 0.4985 0.0491 4.8 H(6) 0.2743 0.5383 0.3452 5.1 H(7) 0.1261 0.5681 0.4424 6.9 H(8) 0.0380 0.4336 0.4272 7.7 H(9) 0.0988 0.2671 0.3183 7.6 H(10) 0.2485 0.2358 0.2243 6.0 H(ll) 0.1587 0.4849 0.0711 5.4 H{12) 0.0368 0.5008 -0.1308 6.6 H(13) 0.1068 0.3666 -0.2722 6.5 H(14) 0.2985 0.2235 -0.2145 5.5 H(15) 0.4250 0.2111 -0.0131 4.4 H(16) 0.7927 0.0365 0.5355 13.0 H(17) 0.7219 -0.0502 0.4811 13.0 H(18) 0.9197 -0.1324 0.5994 15.5 H(19) 0.9010 -0.1803 0.4652 15.5 H(20) 0.9725 -0.0936 0.5159 15.5 H(21) 0.4826 -0.1096 6.1865 7.6 H(22) 0.5088 -0.0369 0.3073 7.6 H(23) 0.3039 0.0425 0.2757 13.6 H(24) 0.2777 -0.0302 0.1549 13.6 297 T»hle A4.2 (cont.) atom X y z Bis< H(25) 0.3470 -0.0884 0.2797 13.6 H(26) 0.8364 0.1859 0.2720 7.2 H{27) 0.8485 0.1B09 0.1428 7.2 H(28) 0.8619 0.3456 0.2428 10.3 H(29) 0.7391 0.3698 0.1291 10.3 H(30) 0.7284 0.3745 0.2589 10.3 H(31) 0.9543 -0.1525 -0.0465 13.7 H(32) 0.9139 -0.2403 -0.0074 13.7 H(33) 1.1424 -0.2276 0.0572 21.0 H(34) 1.1040 -0.3217 0.0864 21.0 H(35) 1.1867 -0.1916 0.2391 18.2 H(36) 1.1016 -0.2524 0.2550 18.2 •H(37) 0.9790 -0.0842 0.2650 20.4 H(38) 1.0311 -0.0420 0.1835 20.4 298 APPENDIX S: KINETIC DATA Table A5.1 The reaction of cc/-RuH2(CO)2(PPh3)2 (3J with p-thiocresol (reaction 3.4, page 77) r31 (mM) TRSHl (mM) T(oC) Jfcr.hQ (s-1) 0.88 9.5 26 6.4 x 10-4 0.95 10 26 5.7 x 10-4 0.95 11 26 6.1 x 10-4 0.93 26 26 6.4 x 10-4 0.96 91 26 6.7 x 10-4 0.91 110 26 7.3 x 10-4 0.045 94 26 6.4 x 10-4 0.073 87 26 6.0 x 10-4 0.23 91 26 6.1 x 10-4 0.59 91 26 6.2 x 10-4 0.98 92 35 1.8 x 10-3 0.93 80 42 4.5 x 10-3 0.97 94 42 4.5 x 10-3 Table A5.2 The reaction of cc/-RuH2(CO)2(TPb3)2 (2) with ethanethiol (reaction 3.4, page 77) r31 (mM) rRSHl (mM) T(oC) knhi (s-1) 1.0 45 26 6.4 x 10-4 1.0 91 26 6.7 x 10-4 1.0 95 26 6.7 x 10-4 1.0 95 26 7.3 x 10-4 1.0 95 26 6.5 x 10-4 1.0 190 26 7.1 x 10-4 1.0 190 26 5.9 x 10-4 0.36 95 26 7.5 x 10-4 0.39 95 26 6.3 x 10-4 2.9 95 26 6.7 x 10-4 1.0 95 36 1.9 x 10-3 1.1 95 37 2.8 x 10-3 1.0 95 47 6.0 x 10-3 1.0 190 47 5.7 x 10-3 1.5 95 47 6.0 x 10-3 299 Table A5J The reaction of cc/-RuH2(CO)20?Pb3)2 (2) with carbon monoxide (reaction 3.5, page 86) i31 fmM) Poo (atm) T(oC) *'nhS (s-1) 1.0 0.09 25 5.4 x 10-4 1.0 1 25 5.7 x 10-4 1.1 1 25 5.7 x 10-4 1.0 1 34 1.8 x 10-3 1.0 1 41 4.1 x 10-3 1.0 1 41 4.1 x 10-3 0.25 1 41 4.0 x 10-3 1.1 1 51 1.1 x 10-2 Table A5.4 The reaction of cc/-RuH2(CO)20?Ph3)2 (2) with triphenyl phosphine (reaction 3.6, page 86) • 31 (mM) rPPml (mM) T(oQ knh* (s-D 033 5l 26 6.0 x 10-4 0.31 0 5 6.6x10-0.36 47 25 6.5x10-4 0.55 3_80_ i 6.5 x 10-4 Table A5.5 The reaction of cc/-RuH(SCH2CH3)(CO)2(PPh3)2 ©dj with thiophenol at 220C (reaction 3.12, page 103) f9dl (mM) rPhSHI (mM) *nhc (s-1) 8.2 120 1.7 xKH 9.7 550 1.8x10-4 8.5 1500 1.9x10-9.5 3400 2.0 x 10-4 L8 12QQ 1.9 x 10-4 300 Table A5.6 The reaction of cc/-Ru(SH)2(CO)2(PPh3)2 (14a) with thiophenol at 25°C (reaction 3.18, page 119) ri4al (mM) TPhSHl (mM) IPPh^l (mM) knhsi (S-l) kn (s-1) 6.2 69 0 4.7 x 10-4 4 x 10-4 7.8 77 0 4.2 x 10-4 4 x 10-4 6.2 330 0 4.0 x 10-4 3 x 10-4 5.1 690 0 4.4 x 10-4 lx 10-3 9.4 700 0 3.8 x 10-4 5x10-4 5.3 1700 0 3.9 x 10-4 5x10-3 4.8 2800 0 3.4 x 10-4 5.3 2900 0 3.2 x 10-4 1x10-2 5.7 770 23 3.1 x 10-4 3x10-3 5.4 750 240 3.6 x 10-4 3x10-3 6.5 66 220 2.5 x 10-4 3x10-4 6.2 66 325 1.3 x 10-4 4 x 10-4 6.3 64 460 1.1 x 10-4 4 x 10-4 6.1 67 490 1.1 x 10-4 5.9 810 470 3.1 x 10-4 2 x 10-3 Table A5.7 The reaction of Ru(CO)2(PPh3)3 (2) with p-tolyl disulphide (RSSR) at 25<>C (reaction 4.1, page 152) T21 (mM) TRSSR1 (mM) initial rate (M s-1) 0.34 2.1 6.4 x 10-7 0.31 2.1 6.1 x 10-7 0.33 6.0 1.0 x 10-6 0.35 7.8 1.5 x 10-6 0.33 8.8 1.1 x 10-6 0.36 17 2.0 x 10-6 0.34 30. 2.1 x 10-6 0.35 51 2.0 x 10-6 0.083 8.0 1.3 x 10-7 0.19 8.1 3.0 x 10-7 0.72 7.9 2.3 x 10-6 1.3 7.8 2.0 x 10-6 1.3 7.9 2.5 x 10-6 Table A5.8 The reaction of ccf-RuH(SR)(CO)2(PPh3)2 (9) with P(C6H4pCH3)3 (L') at 450C (reactions 6.1 and 6.2, page 218) E [91 (mM) fL'1 (mM) tobsMl -CH2Ph 2.7 130 1.2 xlO^ -CH2Ph 11 94 1.0x10-3 -CH2Ph 2 120 1.1x10--CH2Ph 10. 150 1.2x10-3 -CH2Ph 11 300 1.3x10--CH2Pn 1 500 1.0x10-3 -CfHApCH* 12 260 7.0 x 10-4 301 Table A5.9 The reaction of cc/-RuH(SR)(CO)2(PPh3)2 (9) with 1 atm carbon monoxide (reaction 6.3, page 227) R T91 (mM) T(oQ knh* (Vi) -CH3 0.87 55 7.0x10-3 -CH3 1.0 55 7.2x10-3 -CH2CH3 0.88 26 3.2x10-4 -CH2CH3 0.92 35 1.2x10-3 -CH2CH3 0.89 55 1.2x10-2 -CH2Ph 0.79 45 6.1 x 10-4 -CH2Ph 0.74 55 2.2x10-3 -C6H5 0.53 55 5.5 x 10-4 -C6H4PCH3 0.86 45 2.3 x 10-4 -C6H4/7CH3 1.0 55 9.3 x 10-4 1.0 60 1.6 x 10-3 

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