3-Tungstophosphates

Protonic initiation is also the end result of a large number of other initiating systems. Strong acids are generated in situ by a variety of different chemistries (6). These include initiation by carbenium ions, eg, trityl or diazonium salts (151) by an electric current in the presence of a quartenary ammonium salt (152) by halonium, triaryl sulfonium, and triaryl selenonium salts with uv irradiation (153—155) by mercuric perchlorate, nitrosyl hexafluorophosphate, or nitryl hexafluorophosphate (156) and by interaction of free radicals with certain metal salts (157). Reports of "new" initiating systems are often the result of such secondary reactions. Other reports suggest standard polymerization processes with perhaps novel anions. These latter include (Tf)4Al (158) heteropoly acids, eg, tungstophosphate anion (159,160) transition-metal-based systems, eg, Pt (161) or rare earths (162) and numerous systems based on tri flic acid (158,163—166). Coordination polymerization of THF may be in a different class (167). 

Tungstocobaltate and 12-Tungstophosphate Ions in Acidic Aqueous Solution. 630... 

Electrochemistry of a New Family of Wells-Dawson Anions Semivacant Tungstophosphates and Arsenates [H4XWi8062] (X = P or As)... 

At present count, some 68 elements (other than Mo and W) have been observed as heteroatoms in polyanions (see Table 5). Since each element may form more than one heteropoly anion (e.g. at least 18 tungstophosphates) and there are polyanions with combinations of several heteroatoms, the total number of known heteropolyanions is extremely large. It is therefore out of the question to attempt a complete accounting of every type of heteropolyanion on the following pages. We shall restrict discussion to the main structural types. More complete reviews are available.1-3... 

Heteropolyacids are prepared in solution by acidifying and heating in the appropriate pH range (], 49-54). For example, 12-tungstophosphate is formed according to Eq. (1). Free acids are synthesized primarily by the following two methods (1) by extraction with ether from acidified aqueous solutions and (2) by ion exchange from salts of heteropolyacids. Dawson-type heteropolyanions,... 

Several compounds of tungsten, which is a transition metal closely related to molybdenum, are able to catalyze the selective oxidation of secondary alcohols with hydrogen peroxide as secondary oxidant. These include tris(cetylpyridinium) 12-tungstophosphate,33 peroxotungstopho-sphate (PCWP)34 and Na2W04 in the presence of a phase transfer catalyst.35 Tungstophosphoric acid is able to catalyze the selective oxidation of secondary alcohols in the presence of ferric nitrate as secondary oxidant.36... 

Desideri, P.G., Lepri, L., Merlini, L., and Checchini, L., High-performance liquid chromatography of amino acids and peptides on silica coated with ammonium tungstophosphate, J. Chromatogr., 370, 75, 1986. 

Name Ammonium tungstophosphate on silica Structure Tungstophosphoric acid with ammonium nitrate... 

Akira T., Takayuki A.and Masakazu I., Non-silica-based mesostructured material. 2 Synthesis of hexagonal superstructure consisting of ll-tungstophosphate anions and dodecyltrimethylammonium cations, Microporous and Mesoporous Materials 21 (1998) pp. 387-393. 

Ostuni, A. and Pope, M.T. (2000) A large heteropolytungstotetracerate(III) based on a new divacant lacunary derivative of the Wells-Dawson tungstophosphate anion. Comptes Rendus de VAcademie des Sciences, Paris, Serie IIc Chemie, 3, 199-204. 

SYNS SODIUM TUNGSTOPHOSPHATE TUNGSTOPHOSPHORIC ACID, SODIUM SALT... 

Tungstophosphates (PoOg W03=l 22).—The free acid corresponding to this series of salts has not been isolated. The salts are ver stable and are obtained bA careful hydrolysis of the 12-tungsto-... 

The potassium salt, similar manner by adding potassium carbonate to a suspension of the potassium 12-tungstophosphate until a clear solution is obtained. 

These salts are all soluble in water, and the solutions react neutral to litmus.. cid salts of this series have not been obtained. The addition of strong mineral acids to 11-tungstophosphates causes decomposition into the 12-timgstophosphate and the 21 2-tungstophosphate (see below) the following formula has therefore been suggested as an expression of their constitution ... 

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