Reactions of Organic Disulfides and Gold(I) Complexes

Abstract

Gold-thiolate/disulfide exchange reactions of (p-SC6H4Cl)2 with Ph3PAu(SC6H4CH3) , dppm(AuSC6H4CH3)2, and dppe(AuSC6H4CH3)2 were investigated. The rate of reactivity of the gold-thiolate complexes with (p-SC6H4Cl)2 is: dppm(AuSC6H4CH3)2>> dppe(AuSC6H4CH3)2>Ph3PAu(SC6H4CH3). This order correlates with conductivity measurements and two ionic mechanisms have been evaluated. H1 NMR experiments demonstrate that in the reaction of dppm(AuSC6H4CH3)2 with (p-SC6H4Cl)2, the mixed disulfide, ClC6H4SSC6H4CH3, forms first, followed by the formation of (p-SC6H4CH3)2. The rate law is first order in (pp-SC6H4Cl)2 and partial order in dppm(AuSC6H4CH3)2. Results from electrochemical and chemical reactivity studies suggest that free thiolate is not involved in the gold-thiolate/disulfide exchange reaction. A more likely source of ions is the dissociation of a proton from the methylene backbone of the dppm ligand which has been shown to exchange with D2O. The implications of this are discussed in terms of a possible mechanism for the gold-thiolate/disulfide exchange reaction.