Copper(ii)-containing tungstotellurates(vi): syntheses, structures and their catalytic performances in selective oxidation of thioethers

Abstract

We report the syntheses and structures of two new copper(II)-containing tungstotellurates(VI) Na₁₂[Te^VI₂W₈O₃₈Cu₂(H₂O)₂]·7H₂O (Te₂W₈Cu₂) and Na₆[Te^VIW₆O₂₄Cu(NH₂CH₂CO₂)₂]·6H₂O (TeW₆Cu). The two compounds were synthesized by a simple one-pot method and characterized by single-crystal X-ray diffraction (XRD), powder XRD, FT-IR spectroscopy, elemental analysis, and thermogravimetric analysis in the solid state. Furthermore, their catalytic properties for the selective oxidation of thioethers were also studied systematically. The catalytic experiment results indicate that the tungstotellurate(VI) Te₂W₈Cu₂ is an effective heterogeneous catalyst for the selective oxidation of thioethers to sulfoxides or sulfones by an H₂O₂ oxidant at room temperature. Under the ambient conditions, Te₂W₈Cu₂ can convert 99% of methyl(phenyl)sulfane to sulfoxides or sulfones with 96% or 99% selectivity, respectively, and the utilization rate of H₂O₂ is up to 80%. Furthermore, Te₂W₈Cu₂ as a heterogeneous catalyst is stable in the reaction and could be reused at least five cycles with conserved activity.