A Highly Active Protortated Tetranuclear Peroxotungstate for Oxidation with Hydrogen Peroxide

摘要

Selective oxygen transfer to organic substrates with H2O2 as a terminal oxidant is important in industrial and synthetic chemistry because of the high content of active oxygen species in H2O2 and coproduction of only water. Therefore, a large number of complexes of titanium, vanadium, iron, manganese, tungsten, rhenium, and platinum have been developed for catalytic oxidation of various kinds of organic substrates with H2O2. Among these systems, selective oxidation by tungsten-based catalysts with H2O2 has been widely investigated because of their high reactivity for oxidation as well as an inherent poor activity for the decomposition of H2O2. While peroxotungstates, transition-metal-substituted polyoxotungstates, and lacunary polyoxotungstates efficiently catalyze H2O2-based selective oxidation of alkenes, alcohols, amines, sulfides, and silanes, these systems have some drawbacks: 1) use of an excess of H2O2 with respect to the substrates, 2) low turnover numbers (TONs), 3) limited substrate scope, and/or 4) requirement of microwave irradiation or additives. Therefore, developments of efficient tungsten-based catalysts for green oxidation with H2O2 applicable to a wide range of substrates are still in great demand.