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Title: Peroxo-cerium(IV)-containing polyoxometalates: [CeIV6(O2)9(GeW10O37)3]24–, a recyclable homogeneous oxidation catalyst
Authors: Qasim, Hafiz M.
Ayass, Wassim W.
Donfack, Patrice
Mougharbel, Ali S.
Bhattacharya, Saurav
Nisar, Talha
Bassil, Bassem 
Affiliations: Department of Chemistry 
Issue Date: 2019
Part of: Journal of inorganic chemistry
Volume: 58
Issue: 17
Start page: 11300
End page: 11307
The class of peroxo-cerium-containing polyoxometalates has been discovered via the synthesis of the 9-peroxo-6-cerium(IV)-containing 30-tungsto-3-germanate, [CeIV6(O2)9(GeW10O37)3]24– (1). Polyanion 1 consists of a cyclic [Ce6(O2)9]6+ assembly that is stabilized by three dilacunary [GeW10O37]10– Keggin fragments. The title polyanion 1 is solution-stable, on the basis of 183W nuclear magnetic resonance, and was shown to act as a recyclable homogeneous catalyst for the selective, microwave-activated sulfoxidation of the model substrate methionine to the sulfoxide in the absence and to the sulfone in the presence of hydrogen peroxide. Solution and solid-state Raman as well as solid-state infrared studies of 1 demonstrated the complete loss (and regain) of the nine peroxo groups in situ during the catalytic cycle, suggesting that the peroxo-free {Ce6(GeW10)3} skeleton remains most likely intact during the catalytic cycle. Solid-state X-ray photoelectron spectroscopy measurements showed that peroxo loss is accompanied by reduction of the cerium ions from +4 to +3, which is fully reversible. Density functional theory calculations are in complete agreement with all of these observations and furthermore suggest that the reduction of the six cerium(IV) ions is accompanied by the formation of molecular dioxygen.
DOI: 10.1021/acs.inorgchem.9b01164
Ezproxy URL: Link to full text
Type: Journal Article
Appears in Collections:Department of Chemistry

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