Aerobic Oxidation Catalyzed By Polyoxometalates Associated To An Artificial Reductase At Room Temperature And In Water

Four polyoxometalates (POMs) were combined with an artificial reductase based on polyethyleneimine (PEI) and flavin mononucleotide (FMN) which is capable of delivering single electrons upon addition of nicotinamide adenine dinucleotide (NADH). The efficiency of this system for sulfoxidation reactions in water, at room temperature, under atmospheric pressure and with dioxygen as an oxidant was demonstrated, with yields up to 82% in sulfoxide. Mechanistic investigations allowed proposing two different catalytic pathways, depending on the nature of the POM. For the polyoxotungstates Na-12[(ZnW9O34)(2)WZn3(H2O)(2)]center dot 46H(2)O and Na7K7[{(PW9O34)Ni-3(OH)(H2O)(2)(Ale)}(2)Ni]center dot 34H(2)O (Ale = alendronate = [O3PC(O)(C3H6NH3)PO3](4-)), thein situproduction of H(2)O(2)by the artificial reductase that activates the POM was evidenced. Alternatively, for the polyoxomolybdates H-3[PMo12O40]center dot 14H(2)O and H-4[PMo11VO40]center dot 14H(2)O, the reduction of the POM by the artificial reductase, followed by the reductive activation of O-2, led to the sulfoxidation reaction.