Kinetics and Mechanism of Oxidation of Organic Sulphides and Olefins by a Molybdenum Peroxopolyoxoanion

Some standard aryl methyl sulphide and alkenes have been oxidized to sulphoxides and epoxides in chloroform by PCMP and MoO(O2)2HMPT, an anionic and neutral peroxo complex, respectively. Kinetic data reveal that PCMP is a more efficient oxidant than MoO(O2)2HMPT in sulphide oxidation whereas the opposite is true in alkene epoxidation. A possible pathway for the oxygen transfer step is suggested for these reactions. The different behavior of the two proxy complexes might be rationalized on the basis of the suggested mechanism and of a proposed structure of PCCMP, presumably an anionic, coordinately saturated, peroxo complex.