Oxidations in the H2O2/V^V/AcOH system. Evidence of vanadium(V) complexes with superoxide anion and singlet dioxygen molecule as ligands

Anthracene, its alkyl derivatives, and alkenes have been found to undergo oxidation by the VvH2O2AcOH catalytic system via a polar mechanism involving the transfer of singlet dioxygen from H2O2 to the unsaturated substrate molecule. The vanadium (V) complex with a singlet dioxygen molecule as ligand was suggested to be the only oxidant species active in the reaction. The Vv(O2•−) complex radical was detected as the only paramagnetic species in the system. Unusual acceleration of the styrene oxidation caused by the 2,6-di-tert-butyl-4-methylphenol additive (BHT) was observed and attributed to lowering the concentration of the Vv(O2•−) complex radical, which is assumed to be an active reductant toward the Vv complex with singlet dioxygen.