The role of protons in cyclohexene oxidation with H2O2 catalysed by Ti(IV)-monosubstituted Keggin polyoxometalate

Heteropolyacid H5PTiW11O40 and its acid sodium salts Na5 − nHnPTiW11O40 (n = 2-4) catalyse efficiently cyclohexene oxidation by aqueous H2O2 in acetonitrile via heterolytic oxygen-transfer mechanism to yield trans-cyclohexane-1,2-diol. The diprotonated peroxotitanium species [H2PTi(O2)W11O39]3− is suggested as an active intermediate responsible for this reaction.