An Oxalate-Functionalized Tetra-ZrIV-Substituted Sandwich-Type Silicotungstate: Hydrothermal Synthesis, Structural Characterization, and Catalytic Oxidation of Thioethers

A previously unknown inorganic-organic hybrid polyoxidometalate constructed from oxalate-functionalized tetra-Zr-IV-substituted dimeric silicotungstate, (NH4)(3)Na5K6[Zr-4(mu(3)-O)(2)(mu-OH)(2)(ox)(2)(SiW10O37)(2)]center dot 23H(2)O (1, ox = oxalate) has been synthesized under mild hydrothermal conditions and characterized by FTIR spectroscopy, elemental analysis, thermogravimetric analysis, single-crystal and powder X-ray diffraction. Compound 1 contains a centrosymmetric polyoxidoanion structure with two [SiW10O37](10-) units sandwiching a [Zr-4(mu(3)-O)(2)(mu-OH)(2)(ox)(2)](6+) cluster. The catalytic performances of 1 involving oxygenation reactions of thioethers by H2O2 were evaluated, showing that 1 is an excellent catalyst for the catalytic oxidation of thioethers to sulfoxides/sulfones.