Heteropolytungstates

Structures of heteropolytungstate and isopolytungstate compounds have been determined by x-ray diffraction. The anion stmctures are represented by polyhedra that share corners and edges with one another. Each W is at the center of an octahedron, and an O atom is located in each vertex of the octahedron. The central atom is similarly located at the center of an XO tetrahedron or XO octahedron. Each such polyhedron containing the central atom is generally surrounded by octahedra, which share corners, edges, or both with it and with one another. Thus, the correct total number of... 

Commercially, heteropolytungstates, particulady the heteropolytungstates, are produced in large quantities as precipitants for basic dyes, with which they form colored lakes or toners (see also Dyes and dye intermediates). They are also used in catalysis, passivation of steel, etc. 

Antonio et al100 have performed an in situ EXAFS spectro-electrochemical study of heteropolytungstate anions. 

The kinetics of the catalytic oxidation of cyclopentene to glutaraldehyde by aqueous hydrogen peroxide and tungstic acid have been studied and a compatible mechanism was proposed, which proceeds via cyclopentene oxide and /3-hydroxycyclopentenyl hydroperoxide. " Monosubstituted heteropolytungstate-catalysed oxidation of alkenes by t-butyl hydroperoxide, iodosobenzene, and dioxygen have been studied a radical mechanism was proved for the reaction of alkenes with t-BuOOH and O2, but alkene epoxidation by iodosobenzene proceeds via oxidant coordination to the catalyst and has a heterolytic mechanism. ... 

All these considerations apply also to heteropolymolybdates, with the general remark that they are more easily reduced than heteropolytungstates and that the... 

Electrochemical Probing of Siderophoric Behavior in Sandwich-type Multi-iron Wells-Dawson Heteropolytungstates... 

The formation of sandwich-type POMs from solutions of metal cations and triva-cant heteropolytungstate species may alternatively be viewed as means to sequester cations from solution [116]. The question then arises if reversible dissociation of the metal cations from the multidentate ligands is possible as well. The sequestration and subsequent release of metal cations under appropriate conditions is of considerable interest in waste decontamination technology as well as in medicine [124]. Following these ideas, the demetallation process of ten multi-iron Wells-Dawson polyoxometalates is studied by cyclic... 

Hexacyanoferrates were immobilized on Au covered with SAM of 3,3 -thiodipropionic acid [86]. It has been found from voltammetric studies that the surface coverage of hexacyanoferrate is close to one monolayer and such an electrode exhibits very good surface redox behavior. Cheng et al. [87] have described the formation of an extremely thin multilayer film of polybasic lanthanide heteropolytungstate-molybdate complex and cationic polymer of quaternary poly(4-vinylpyridine), partially complexed with osmium bis(2,2 -bipyridine) on a gold electrode precoated with a cysteamine SAM. Consequently, adsorption of inorganic species might also be related to the properties of SAMs. This problem will be discussed in detail in a separate section later. 

TRANSITION METAL COMPLEXES OF THE LACUNARY HETEROPOLYTUNGSTATE, [PaWnOn]"-... 

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