High Oxidation State Anion

High oxidation state anions and derived compounds... 

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

These anions are remarkable not only for the low coordination number but also for the low oxidation state of the metals in combination with oxygen which is more commonly to be found stabilizing high oxidation states. 

Stripping is easy with dilute acid or water, which deprotonates the amide and releases the metal anion. The process favors metals in high oxidation states [e.g., platinum(IV) or iridium(IV)], so that reduction of any iridium... 

Fig. 8. F Shielding parameters for the binary fluorides plotted against the atomic number of the central atom— fluoride anions, solids, and high-oxidation states of the central atom. Explanation of symbols ...

The problems associated with the storage and handling of larger amounts of fluorine at high pressures can be avoided by the use of fluorine gas generators which are based on stable solids. Two practical approaches have been demonstrated,7 8 one of which is commercially available.9 Both approaches are based on high oxidation state complex fluoro anions of transition metals such as nickel, copper, or manganese. 

The first Ag(II) compound to be isolated in the solid state was tetra-kis(pyridine)silver(2 +) peroxydisulfate.13,14 Its stability can be attributed to its insolubility, the coordination of the Ag(II) ion, and the presence of an anion with an element in a high oxidation state. It can be prepared conveniently, rapidly, and in high yield by reaction of a solution containing silver nitrate and pyridine with a solution of potassium peroxydisulfate. The corresponding, but less stable, nitrate can be prepared by the electrolytic oxidation of silver nitrate in concentrated aqueous pyridine.15... 

Some of the early transition metals are known to form mononuclear peroxo complexes. These complexes are not formed by reacting a metal complex in a low oxidation state with dioxygen, as this usually results in the formation of metal oxo species, but rather by reaction of a metal complex in a high oxidation state, eg. TiIV, Nbv or MoVI, with the peroxide anion. This frequently leads to more than one peroxide ligand per metal centre. 

It is of importance that uranium atoms remain electropositive even in rather high oxidation states. The M-OR bonds remain polar, and the molecules can act as the donors of alkoxide anions in the reactions with HC1 and organic halids, such as, for example, acylbromide [147] ... 

These are mostly associated with anions such as SbF, Sb2Fj" and fluoroanions of the d block elements in high oxidation states, e.g. PtFg, AuF6-... 

It is generally true that a given high oxidation state is thermodynamically more stable in an anionic species than in a binary compound (4). Many of the experimental observations are compatible with the electronegativity of the metal atom in the complex anion being appreciably lower than in the corresponding binary compound (73). The first successful approach to the synthesis of gold compounds of... 

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