Homogeneous catalysis of the oxidation of thiols by metal ions

Abstract

The oxidation of thiols to disulphides is used as a model reaction to distinguish between different possible mechanisms of catalysis by metal complexes. Metal ions are shown to accept an electron from thiol anions either with or without the formation of a new chemical complex. Examination of a series of catalytically active complexes shows that an outer-sphere electron transfer is involved in only a few systems. The rates of electron transfer in such cases are found to be dependent on the electron-directing and geometric properties of the thiol. Comparison of these rates with the rates of overall oxidation shows that the electron transfer reaction is not rate-controlling.