Metal–oxygen clusters, namely polyoxometalates (POMs), are anionic clusters of oxygen-bridged early transition metal cations in their highest oxidation states (configuration d0 or d1) with (heteropolyoxometalates) or without (isopolyoxometalates) heteroatoms (such as B, Al, Ge, Si, P and many more) [1-2]. Tetraethylammonium salt of a new Keggin-type 12-molybdovanadate nanocluster, [(C2H5)4N]4[VMo12O40] (1) was synthesized via reaction between sodium tungstate, ammonium vanadate and tetraethylammonium bromide in acidic medium. Compound 1 was characterized by X-ray crystallography and FT-IR and then applied as an efficient heterogeneous catalyst to oxidation of various organosulfides to sulfoxides with H2O2 at room temperature with 81–100% conversion and 60–99% selectivity. Nanocluster 1 was also shown to display excellent recyclability – it can be reused more than 10 times.
