Preparation, characterization of mixed-valence antimony-tin phosphomolybdic polyoxometalates and application in the cyclohexanone oxidation in the presence of hydrogen peroxide

Résumé fourni par la source

In this work, a series of polyoxometalates (POMs), as soluble salts of formula Sn 1.5 PMo 12 O 40 , SbPMo 12 O 40 and H 3 - x Sn x 1 Sb x 2 PMo 12 O 40 ( x = 2 x 1 + 3 x 2 and x 1 , x 2 = 0–0.75) were synthesized using the cationic exchange method under stoichiometric conditions. They were characterized and tested in the oxidation of cyclohexanone using hydrogen peroxide in the absence of organic solvent, co-catalyst phase transfer compounds or surfactants. UV–Visible and X-ray photoelectron spectroscopic analyses showed a partially reduced state of POM with coexistence of the couples Mo(VI)/Mo(V), Sb(V)/Sb(III) and Sn(IV)/Sn(II), without affecting their structure, results confirmed by FT-IR and Raman spectroscopies. The reversible cyclic voltammetry analysis evidenced the valence change of the Mo species, Mo(VI)/Mo(V). The POMs are found to be active in the cyclohexanone oxidation reaction and among them the most efficient is H 0 . 75 Sb 0 . 75 PMo 12 O 40 with 49% of adipic acid yield.

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