Selective Oxidation with Aqueous Hydrogen Peroxide by [PO4{WO(O2)2}4]3- Supported on Zinc-Modified Tin Dioxide

We prepared supported phosphorus-containing tetranuclear peroxotungstate ([PO4{WO(O-2)(2)}(4)](3-), denoted by PW4) catalysts by using zinc-modified SnO2 supports with different zinc contents [PW4-Zn(x)/SnO2, in which x denotes the zinc content (wt%)]. The supported catalysts, in particular PW4-Zn(0.8)/SnO2, could act as efficient and reusable heterogeneous catalysts for selective oxidation with aqueous H2O2 as the terminal oxidant. The catalytic performance of PW4-Zn(0.8)/SnO2 was much superior to those of the corresponding homogeneous analogue THA(3)PW4 (THA=tetra-n-hexylammonium) and the previously reported tungstate-based heterogeneous catalysts such as our W-Zn/SnO2. In the presence of PW4-Zn(0.8)/SnO2, various types of organic substrates such as alkenes, amines, silanes, and sulfides could be converted into the corresponding oxygenated products in high to excellent yields by using near-stoichiometric amounts of H2O2 with respect to the substrates (typically 1.2equiv.). The PW4 species interacting with highly dispersed Zn2+ species on SnO2 likely plays an important role in the present oxidation.