Hybrid Polyoxotungstates as Second-Generation POM-Based Catalysts for Microwave-Assisted H₂O₂ Activation

Abstract

Organic−inorganic hybrids synthesized from lacunary polyoxotungstates (POMs) have been screened as oxidation catalysts with H 2 O 2 under MW irradiation. Yields up to 99% have been obtained in 25−50 min depending both on the POM structure and on the organic moiety. The reaction scope, optimized with the best performing catalyst [γ-SiW 10 O 36 (PhPO) 2 ] 4-, includes epoxidation of terminal and internal double bonds, alcohol oxidation, and sulfoxidation, as well as oxygen transfer to electron-deficient substrates as chalcone, ketones, and sulfoxides.

Optically Active Polyoxotungstates Bearing Chiral Organophosphonate Substituents

“…In this light, interesting results have been obtained with vacant POMs [2,49,50] and with their hybrid derivatives. [5,51] These latter display stable structures under multioxidation turnovers.…”

Selective Oxidation of Sulfides to Sulfones by H2O2 Catalyzed by Fe-Substituted Sandwich Type Polyoxometalate

“…The reaction mechanism of the oxidation of sulfides over various polyoxometalates using H 2 O 2 as an oxidant was extensively investigated by several groups [64][65][66][67][68][69][70][71][72]. A possible mechanism of this reaction involves in the formation of peroxotungstate, oxoperoxo intermediate species which was reported.…”

“…In contrast, aqueous 30 % hydrogen peroxide is an exclusively interest because it is cheap, easy to handle, easily available and environmentally benign with the formation of water as the only by-product [15]. During recent years, various catalyst systems such as organocatalysts, acid catalysts, enzymes, and metal catalysts such as Cr, Mn, Fe, Cu, Mo, Ru, Ta, W, Re, Pt, Au, and polyoxometalates have been used for oxidation of sulfides with hydrogen peroxide [16][17][18][19][20][21][22].…”

Liquid-Phase Selective Oxidation by Multimetallic Active Sites of Polyoxometalate-Based Molecular Catalysts

“…Although the lacunary POMs can activate H 2 O 2 to form peroxo species at vacant sites [47], the oxidation catalysis by lacunary POMs has scarcely been reported [73,[98][99][100] 4À and the epoxidation mechanism have been reported [104][105][106][107][108][109]. The inorganic-organic hybrid POMs have attracted much attention because the electron and steric properties of the POMs significantly affect the catalytic properties of the metal centers [110][111][112].…”