Polyoxometalates transition-metal complexes

Hydrodesulfurization Hydrodenitrogenation Molybdenum MPT-containing Enzymes Molybdenum Organometal-lic Chemistry Oxidation Catalysis by Transition Metal Complexes Polyoxometalates. 

The vast majority of homogeneous catalysts are transition metal complexes and many systems have been reported, for example, Ru(III) [129], W(VI) [130], polyoxometallates [131], Re(V) [132], Fe(III) [133], and Pt(II) [134] with hydrogen peroxide, Mn(II) [135-137] with peracetic acid, and Ti-tartrate with alkyl hydroperoxides [75]. The subject of epoxidation by H2O2 has been reviewed [138-140]. 

Shivaiah and Dah [69] reported the characterization of Al " and Cr " polyoxometalate-supported transition metal complexes (Figure 9). 

The situation is not significantly different when the polymer films are modified by catalytic centers, such as clusters of transition metals [329,330,332,334,338, 344,345], polyoxometallates [327,335,371], porphyrins, phthalocyanines and their analogs [307,335], other transition metal complexes [341,342], biomolecules [372], arenas and rotaxane [328,336], etc. see [7,15, 312-314,331, 340,343,373] for reviews. 

Detailed discussions on supramolecular structures of giant polyoxometalate clusters have been reported by Muller and co-workers." " The number of ionic lattices formed from anionic POM clusters and organic cations-coordination complex cations resulting in supramolecular structures is substantial and literally more than hundreds of new compounds in this class appear annuallyIn this overview, the supramolecular features of POM-based systems will be discussed mainly under three headings (a) supramolecular features of polyoxometalate supported transition metal complexes, (b) polyoxometalate-crown ether complexes with supramolecular cations, and (c) supramolecular water clusters associated with polyoxometalates. 

II. SUPRAMOLECULAR FEATURES OF POLYOXOMETALATE-SUPPORTED TRANSITION-METAL COMPLEXES... 

In this volume we have collected 10 review chapters from distinguished scientists who have contributed extensively to the study and development of supramolecular assemblies that contain metals and metal-like elements with unusual structures and morphologies and possess potentially useful (and applicable) physical and biological properties. The first chapter by K. Ariga et al. is a general discussion of supramolecular structures that contain inorganic building blocks for hybrid lipid thin films, layer-by-layer assemblies, structure transcription, and functional mesoporous hybrids. This is followed by two chapters, the first by M. L. Kistler et al., who describe the self-assembly of hydrophilic polyoxometalate (POM) macro-anions and examine the structure and behavior of POM macro-ions in solution. This is followed by a chapter by S. K. Das, who provides an overview of the supramolecular features of POM-supported transition metal complexes, POM-crown ether complexes with supramolecular cations, and supramolecular water clusters associated with POMs. 

Tributsch H (1982) Photoelectrochemical Energy Conversion Involving Transition Metal d-States and Intercalation of Layer Compounds. 49 127-175 Truter MR (1973) Structures of Organic Complexes with Alkali Metal Ions. 16 71-111 Tytko KH, Mehmke J, Kurad D (1999) Bond Length-Bond Valence Relationships, With Particular Reference to Polyoxometalate Chemistry. 93 1-64 Tytko KH (1999) A Bond Model for Polyoxometalate Ions Composed of M06 Octahedra (MOk Polyhedra with k > 4). 93 65-124... 

Goals and five limitations in conjunction with the development of selective catalytic homogeneous oxidation systems are evaluated. Systems are presented that address several of the problems or goals. One involves oxidation of alkenes by hypochlorite catalyzed by oxidatively resistant d-electron-transition-metal-substituted (TMSP) complexes. A second involves oxidation of alkenes by H2O2 catalyzed by specific TMSP complexes, and a third addresses functionalization of redox active polyoxometalate complexes with organic groups. 

The first popular photocatalysts in homogeneous media were transition metal carbonyls (eg M(CO)6, where M=Cr, Mo, W Fe(CO)5, Fe3(CO)i2, Ru3(CO)i2, Mn2(CO)10) and their derivatives [28], Recently, other systems have been intensively studied, eg iron(III) complexes, especially in the photo-Fenton reactions [63-78, 139-142],polyoxometallates,porphyrins, metalloporphyrins,and other porphyrinoid sensitizers. 

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