Oxidation polyoxometalate catalyst

Marchal-Roch, C. Bayer, R. Moisan, J.F. Teze, A. Herve, G. Oxidative dehydrogenation of isobu-tyric acid Characterization and modeling of vanadium containing polyoxometalate catalysts. Top. Catal. 1996, 5,407-419. 

D. Sloboda-Rozner, P. Witte, P. L. Alsters, R. Neumann, Aqueous biphasic oxidation A water-soluble polyoxometalate catalyst for selective oxidation of various functional groups with hydrogen peroxide, Adv. Synth. Catal. 346 (2004) 339. 

An example of a system for photocatalytic water oxidation with a molecular catalyst based on abundant metals is shown in Fig. Id. The Cobalt polyoxometalate catalyst is oxidized with Ru —trisbipyridine that is generated by quenching of the photo-excited Ru —trisbipyridine sensitizer with peroxodisulfate as sacrificial electron acceptor. The system operates at pH 8 and exhibits a high (30 %) photon-to-02 yield while the stability of the catalyst allowed for turnover numbers >220 that were limited by depletion of electron acceptor only [7]. This performance of the abundant-metal-based catalyst is superior to that of an analogue ruthenium polyoxometalate water oxidation catalyst. 

As a consequence of showing that alkylated polyethyleneimines can facilitate aqueous biphasic catalysis, we extended the concept by the preparation of a cross-linked polyethyleneimine assembly that encapsulated a polyoxometalate catalyst, which resulted in the Upophiloselective oxidation of secondary alcohols (Scheme 9.17) [152]. Thus, even though reactions were carried out in water, competitive oxidation of a more hydrophobic alcohol in the presence of a hydrophilic alcohol significantly favored the former. The lipophiloselectivity was proportional to the relative partition coefficient of the substrates. 

Methacryhc acid is a major chemical conunodity produced annually via a multistep route that does, unfortunately, produce many environmentally undesirable by-products.Methacrylic acid, however, can also be direcily formed by oxidation of isobutane over polyoxometalate Keggin catalysts (e.g. H3PM012O40 and its vanadium-substituted analogs H3+xPMoi2-xVx04o) and such a green process has been investigated by several researchers. This possibility has resulted in many oxidation studies with polyoxometalate catalysts over the past two decades. 

Polyoxometalates Catalysts for Sustainable Oxidations and Energy Applications... 

Haimov, A. and Neumann, R. (2006). An Example of Lipophiloselectivity The Preferred Oxidation, in Water, of Hydrophobic 2-Alkanols Catalyzed by a Cross-Liiiked Polyethyleneimine-Polyoxometalate Catalyst Assembly, J. Am. Chem. Soc., 128, pp. 15697-15700. 

Huynh, Q., Schuurman,Y.,Delichere, R.,etal. (2009). Study of Te and V as Counter-Cations in Keggin Type Phosphomolyhdic Polyoxometalate Catalysts for Isohutane Oxidation, J. Catal, 261, pp. 166-176. 

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