CoII-induced radical oxidations by peroxomolybdenum complexes

Abstract

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 (PlCO = 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 MoO₅PlCO, 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.