Structure and properties of tungsten peroxopolyoxo complexes – Promising catalysts for organics oxidation. I. Structure of peroxocomplexes studied during the stepwise synthesis of tetra(diperoxotungsten)phosphate-tetra-n-butyl ammonium

Catalysis via metal complexes has been studied using EXAFS and Raman spectroscopy. Main polyoxo- and peroxopolyoxocomplexes of tungsten, resulting from the interaction of phosphorus tungsten heteropolyacid with hydrogen peroxide in water solutions, were investigated with regard to their form and structure. Interaction was shown to reduce the nuclearity of forming complexes with respect to their precursor – H3PW12O40. The symmetry of oxygen environment of tungsten was found to change, distances W–W remaining the same. After complex [Bun4N]3{PO4[WO(O2)2]4} is isolated, binuclear anion [W2O3(O2)4(H2O)2]2− stays in the solution. Raman scattering, EXAFS and IR spectroscopy show that isolated peroxocomplex in its crystal state has four nuclei, and most probably retains this structure being dissolved in acetonitrile.Synthesized catalytic complex [Bun4N]3{PO4[WO(O2)2]4} was tested in oxidation of cyclic alkenes and alcohols with hydrogen peroxide. Complex [Bun4N]3{PO4[WO(O2)2]4} was proved to provide higher yields of mono- and dicarbonic acids in comparison to in situ synthesized catalyst.

EXAFS combined with Raman spectroscopy used to study the complex [Bun4N]3{PO4[WO(O2)2]4} in its solid state shows that it most likely has four-nuclear structure, which is retained, when complex is dissolved in acetonitrile.Figure optionsDownload high-quality image (63 K)Download as PowerPoint slideResearch highlightsCatalysis via metal complexes has been studied using EXAFS and Raman spectroscopy. Main polyoxo- and peroxopolyoxocomplexes of tungsten, resulting from the interaction of phosphorus tungsten heteropolyacid with hydrogen peroxide in water solutions, were investigated with regard to their form and structure. Interaction was shown to reduce the nuclearity of forming complexes with respect to their precursor – H3PW12O40. The symmetry of oxygen environment of tungsten was found to change, distances W–W remaining the same. After complex [Bun4N]3{PO4[WO(O2)2]4} is isolated, binuclear anion [W2O3(O2)4(H2O)2]2− stays in the solution. Raman scattering, EXAFS and IR spectroscopy show that isolated peroxocomplex in its crystal state has four nuclei, and most probably retains this structure being dissolved in acetonitrile. Synthesized catalytic complex [Bun4N]3{PO4[WO(O2)2]4} was tested in oxidation of cyclic alkenes and alcohols with hydrogen peroxide. Complex [Bun4N]3{PO4[WO(O2)2]4} was proved to provide higher yields of mono- and dicarbonic acids in comparison to in situ synthesized catalyst.