Substitution polyoxometallates

The ample field of transition metal substituted polyoxometallates (POM), which are often other precursors for peroxo derivatives in catalytic processes, will be discussed in brief. 

Oxygenation of alkanes with hydrogen peroxide in homogeneous reactions can be obtained also with Keggin-type iron-substituted polyoxometalates. Evidence against radical reactions has been offered. 

E° values of several other Dawson-type V-substituted polyoxometalates can be found in Ref. 35 and the citations therein. Selected equilibria ... 

The interest in the redox, catalytic, and electrocatalytic properties of unsubstituted and substituted polyoxometalates arouses much attention [2-15] because they are a versatile family of molecular metal-oxide clusters with applications in catalysis as well as in medicine and material science. Such versatility must be traced to at least two main characteristics. First, the size and mass of these unique molecular oxides place their solution chemistry in an intermediate position between small molecule solution chemistry and infinite lattice solid-state chemistry. Second, their redox behaviors may be very flexible and finely tuned on purpose, by changing smoothly their composition, with a... 

Ben-Daniel, R Weiner, L. and Neumann, R. (2002) Activation of nitrous oxide and selective epoxidation of alkenes catalyzed by the manganese-substituted polyoxometalate, [Mnnl2ZnW... 

Table 6 Ruthenium-substituted polyoxometalates as catalysts for the oxidation of alcohols...

Gaspar, A., Evtuguin, D. V, and Neto, C. P., Oxygen bleaching of kraft pulp catalysed by Mn(III)-substituted polyoxometalates. Appl Catalysis A-General 2003, 239 (1-2), 157-168. 

A relatively recent field of study, which, will be expanded upon later, is that of transition metal substituted polyoxometallates.43 The fact that they are, in most cases, completely inorganic means that they are inherently robust to oxidative degradation, hence, offering good prospects for industrial application. 

Very few methods have been reported for direct aerobic oxidation of alkanes using a perfluorinated ruthenium catalyst [Ru30(0C0CF2CF2CF3)6(Et20)3] [120c] and a ruthenium-substituted polyoxometalate [WZnRu2(0H)(H20)(ZnW9034)2] (Eqs. 3.102 and 3.103) [159, 160[. 

Homogeneous Catalysis by d-electron-metal-substituted Polyoxometalates... 

Zhang, X. Hill, C. L. Alkene Epoxidation by p-Cyano-lV-lV-dimethylaniline IV-oxide Catalyzed by d-Electron-transition-metal-substituted Polyoxometalates. In Catalysis of Organic Reactions. Malz, R. E. J., Ed. Marcel Dekker New York, 1996 pp 445-450. 

N. Mizumo, C. Nozaki, 1. Kiyoto, M. Misono, Highly efficient utilization of hydrogen peroxide for selective oxygenation of alkanes catalyzed by Diiron-substituted polyoxometalate precursor, J. Am. Chem. Soc. 120 (1998) 9267. 

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. 

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