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
摘要:
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 [(Bu4N)-N-n](3) {PO4[WO(O-2)(2)](4)} is isolated, binuclear anion [W2O3(O-2)(4)(H2O2)](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 [(Bu4N)-N-n](3){PO4[WO(O-2)(2)](4)} was tested in oxidation of cyclic alkenes and alcohols with hydrogen peroxide. Complex [(Bu4N)-N-n](3){PO4[WO(O-2)(2)](4)} was proved to provide higher yields of mono- and dicarbonic acids in comparison to in situ synthesized catalyst. (C) 2010 Elsevier B.V. All rights reserved.
Selective epoxidation of cyclohexene to cyclohexene oxide catalyzed by Keggin-type heteropoly compounds using anhydrous urea–hydrogen peroxide as oxidizing reagent and acetonitrile as the solvent
作者:Yong Ding、Qiang Gao、Guixian Li、Hanpeng Zhang、Jianmin Wang、Liang Yan、Jishuan Suo
DOI:10.1016/j.molcata.2004.04.019
日期:2004.8
The epoxidation of cyclohexene catalyzed by Keggin-type heteropolycompounds (HPAs) were investigated using anhydrous urea–hydrogen peroxide adduct (UHP) as an oxidant and acetonitrile as a solvent. Among a series of Keggin-type heteropolycompounds, tris(cetylpyridinium)12-tungstophosphate (CWP) showed the highest activity. By optimizing the reaction conditions, 80% conversion of cyclohexene and 97%
TUNGSTEN PEROXOPOLYOXO COMPLEXES ARE PROSPECTIVE
CATALYSTS FOR THE OXIDATION OF ORGANIC COMPOUNDS. I. STRUCTURE OF COMPLEX [(BUn)4N]3{PO4[WO(O2)2]4}
ACCORDING TO SMALL-ANGLE X-RAY SCATTERING
作者:Yu. V. Larichev、N. V. Selivanova、P. V. Berdnikova、F. V. Tuzikov、Z. P. Pai
DOI:10.1134/s002247662010008x
日期:2020.10
The structure of the H3PW12O40 oxometalate precursor and that of the [(Bun)4N]3PO4[WO(O2)2]4} peroxo complex which was synthesized from it are studied by small-angle X-ray scattering (SAXS) in solutions. It is shown that the structure of H3PW12O40 is partially destroyed as a result of the interaction with hydrogen peroxide to form the PO4[WO(O2)2]4}3– anion. The synthesized peroxo complex [(Bun)4N]3PO4[WO(O2)2]4}