Co(II) Induced Radical Oxidation by Peroxomolybdenum Complexes

Peroxomolybdenum complexes, which are usually rather stable materials both in the solid state and in solution, may undergo a decomposition reaction yielding dioxygen when relatively small amounts of Co(acac)2 are added to their solution in dichloroethane. Such a reaction is greatly dependent on the nature of the coordination sphere of the metal. In the series of neutral and anionic peroxomolybdenum species examined, the anionic complex MoO5PICO (PICO = picolinate N-oxido anion) has been found to be more prone to decompose than the neutral ones. By contrast, electrochemical measurements indicate that the one-electron reduction of the neutral species occurs at less negative potentials than that of the anionic ones. Under the conditions which allow the decomposition of MoO5PICO, the concomitant oxidation of organic substrates, e.g. alkanes and alkenes, takes place. The product analyses confirm that the peroxomolybdenum complex is acting as a radical oxidant. The role of Co(II) not only in promoting the decomposition but also in taking part in a radical process is suggested by kinetic and electrochemical experiments.