Polyoxometalates oxidation

Johnson, R.P., Hill, C.L. (1999). Polyoxometalate oxidation of chemical warfare agent simulants in fluorinated media. J. Appl. Toxicol. 19 S71-5. 

Grigoriev, V. Hill, C. L. Weinstock, I. A. Polyoxometalate Oxidation of Phenolic Lignin Models. In Oxidative Delignification Chemistry. Fundamental and Catalysis Argyropoulos, D. S., Ed., 2001 American Chemical Society Washington DC. pp 297-312. 

C. L. Hill, R. B. Brown Jr., Sustained epoxidation of olefins by oxygen donors catalyzed by transition metal-substituted polyoxometalates, oxidatively resistant inorganic analogs of metalloporphyrins, J. Am. Chem. Soc. 108 (1986) 536. 

P. T. Witte, S. Roy Chowdhury, J. E. ten Elshof, D. Sloboda-Rozner, R. Neumann, P. L. Alsters, Highly efficient recycling of a sandwich" type polyoxometalate oxidation catalyst using solvent resistant nanofiltration, Chem. Commun. (2005) 1206. 

VA Grigoriev, CL Hill, IA Weinstock. Polyoxometalate oxidation of phenolic lignin models. In DS Argyropoulos, ed. Oxidative Delignification Chemistry Fundamentals and Catalysis. ACS Symposium Series, 785, pp. 297-312, 2001. 

Related to 18-tungsto-2-phosphates (a- and P-Isomers), J. Chem. Res. Synop. 1977, 222 /. Chem. Res. Miniprint 1977, 2601. (b) Lyon, D. K. Miller, W. K. Novet, T. Domaille, P. J. Evitt, E. Johnson, D. C. Finke, R. G. Highly Oxidation Resistant Inorganic-Porphyrin Analog Polyoxometalate Oxidation Catalysts. 1. The Synthesis and Characterization of Aqueous-Soluble Potassium-Salts of o -2-P2Wi70fii(M. 0H2)" and Organic- Solvent Soluble Tetra-Normal-Butylammonium Salts of Qi -2-p2Wi70fti(M. Br) " (M =... 

Mansuy D, Bartoli JF, Battioni P, Lyon DK, Finke RG (1991) Highly oxidation resistant inorganic-porphyrin analog polyoxometalate oxidation catalysts. J Am Chem Soc 113 7222-7226 Langpape M, Millet JCM (2000) Effect of iron counter-ions on the redox properties of the Keggin-type molybdophosphoric heteropolyacid Part I. An experimental study on isobutane oxidation catalysts. J Mol Catal A Gen 200 89-101... 

Various types metal-carbonyls, metal-Cp, biomimetic M-S clusters (analogs to biological electron-transfer mediators), polyoxometallates, oxides, sulfides, halides, nanoparticles. 

Figure I. Oxygen uptake by supported clusters and vanadium oxide. Samples were pre-reduced and re-oxidized at the temperatures indicated on the abscissa. Silica-supported polyoxometalates PVl ( ), PV3 (A), PVI4 ( ). Bulk V2O5 (+, after [10])...

The development of catalysts for the oxidation of organic compounds by air under ambient conditions is of both academic and practical importance (1). Formaldehyde is an important intermediate in synthetic chemistry as well as one of the major pollutants in the human environment (2). While high temperature (> 120 °C) catalytic oxidations are well known (3), low temperature aerobic oxidations under mild conditions have yet to be reported. Polyoxometalates (POMs) are attractive oxidation catalysts because these extensively modifiable metal oxide-like structures have high thermal and hydrolytic stability, tunable acid and redox properties, solubility in various media, etc. (4). Moreover, they can be deposited on fabrics and porous materials to render these materials catalytically decontaminating (5). Here we report the aerobic oxidation of formaldehyde in water under mild conditions (20-40 °C, 1 atm of air or 02) in the presence of Ce-substituted POMs (Ce-POMs). 

The applications of polyoxometalates in catalytic dehalogenation of halocar-bons have been succinctly reviewed by Hill and coworkers [188]. This reaction involves the photocatalytic transformation of organic halides coupled with the oxidation of sacrificial organic reductants (secondary alcohols or tertiary amides) (Eq. (9)) [189, 190] ... 

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. 

Polyoxometalates (POMs) have been the object of growing interest as photocatalysts for the oxidation or reduction of organic or inorganic compounds [225-230], Many of these POM systems share the same general photochemical characteristics as semiconductor photocatalysts. For example,... 

The versatility and accessibility of polyoxometalates (POMs) have led to the various applications in the fields of structural chemistry, analytical chemistry, surface science, medicine, electrochemistry, photochemistry, and catalysis. Especially, POMs have received much attention in the area of oxidation and acid catalysis [25-31]. Several categories of POMs are formed by proper selection of the starting components and by the adjustment of pH and temperature. Typical examples are shown in Figure 13.1 (i) isopolyoxometalates of the general formula, MxO> 1, produced by condensation... 

Various types of polyoxometalates are effective catalysts for the H202- and Oz-based oxidations. Give some examples. 

Polyoxometalate-catalyzed oxidations are carried out in homogeneous or heterogeneous systems. Write advantages and disadvantages of homogeneous and heterogeneous systems, respectively. 

Liquid-phase oxidations catalyzed by polyoxometalates are covered by Mizuno, Kamata, and Yamaguchi (Chapter 13). Finally, the developing field of enantioselective heterogeneous catalysis is presented by Coman, Poncelet, and Parvulescu (Chapter 14). 

A convenient application uses an inorganic salt (e.g., a polyoxometallate)" or a semiconductor oxide as the sensitizer. Such materials are often chemically more stable with respect to organic molecules, and again can be conveniently used for the generation of a radical from unconventional precursors. 

---