Ronny Neumann

Polyoxometalates for Catalytic Oxidation and Reduction

In the year 2000, it was discovered that the phosphovanadomolybdate, H₅PV₂Mo₁₀O₄₀, could very uniquely serve as an oxygen donor and that the reactivity could be explained by an electron transfer-oxygen transfer (ET-OT) mechanism wherein electrons are transferred from the organic substrate to the catalyst and oxygen is transferred from the polyoxometalate to the organic substrate. In this talk, it will be explained how the understanding of the mechanistic aspects of such reactions has led to ET-OT oxidation reactions that enable C-H, C-C and C-M bond activation and rather unusual oxidative transformations. Recent research allowing the conversion of carbohydrates such as cellulose to synthesis gas, water gas shift and selective oxygenation of toluene derivatives and even the electron transfer oxidation of benzene will be emphasized.

Polyoxometalates can also be used in conjunction with various metal-organic catalyst to yield so-called hybrid catalytic assemblies, where the polyoxometalate acts as an “electron shuttle”. For example, in this way polyoxometalates also can be used in electron transfer based transformations in the opposite sense, that is, to enable reductive transformations. Recent results in this context on the photoelectrochemical reduction of CO₂ to CO will be emphasized.