Tungsten anions

Cyclopentadienyl-manganese, -molybdenum and -tungsten anions react with organic halides to give species with five independent ligands - (Scheme 16) ... 

Similarly, exposure of the tungsten anion TpW(CO)3 to TPP+ in dichloromethane immediately results in the same qualitative color change, but the deeper red-orange solution together with intense visible bands at 512,... 

Cyclopentadienyl tricarbonyl tungsten anion arylated by benzene-diazonium tetrafluoroborate gave t7-C5H5W(C6H5)(CO)3 in a yield as low as 3%- The main product was identified as 7t-C5H5W(CO)2N=NC6H5,... 

Production of metal carbonyl anions andcyclopentadienyl derivatives have received attentionand alkyl- and aryl-pentacarbonyl tungsten anions [RW(CO)j] have been prepared. The mechanisms of reduction of M(CO) (M = Mo or W) have been studied and found to be similar. ... 

Phase Transfer Catalysis (PTC) with tungsten anionic peroxo species for epoxidation of la... 

Each Mo atom in the anion is 7-co-ordinate, being bonded to three bridging and one terminal I atom, and three terminal CO ligands. The analogous tungsten anion was also prepared. The synthesis and reactivities of salts of fao-and mer-[Ru(C0)3l3]" have been examined. On heating the /ac-isomer in an argon atmosphere, the dimeric dianion [Ru2(C0)i,l6]2- of 2 symmetry is formed.is ... 

Contant on tungsten polyanions and phosphate-tungsten anions. 

Anionic Complexes. Compounds of tungsten with acid anions other than haUdes and oxyhaUdes are relatively few in number, and are known only in the form of complex salts. A number of salts containing hexavalent tungsten are known. Potassium octafluorotungstate [57300-87-5] K WFg, can be prepared by the action of KI on W(CO)g in an IF medium. The addition of tungstates to aqueous hydrofluoric acid gives salts that are mostly of the type M(I)2(W2F. Similarly, double salts of tungsten oxydichloride are known. 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenyiarsonium chloride in an organic solvent. Titanium(IV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenyiarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates deterrnined spectrophotometricaHy. Cobalt, palladium, tungsten, niobium, and molybdenum have been deterrnined in a similar manner. In addition to their use for the deterrnination of metals, anions such as perchlorate and perrhenate have been deterrnined as arsonium salts. Tetraphenyiarsonium permanganate is the only known insoluble salt of this anion. 

Molybdenum and tungsten hexacarbonyls are able to form anionic complexes (AsPli4)2[(OC)4M( -pz)2M(CO)4] upon reaction with sodium pyrazolate and PluAsCl (72CB3203). The cationic complexes [(rj -Cp)2Mo(/Lt-pz)2Mo(rj -Cp)2] " (n = 2, 3) are known as well (74HCA1988). The other representatives of the complexes containing an exobidentate ligand (26) are derived from 4//-pyrazoles [70ZAAC(379)169]. 

When methylene chloride was used as a solvent, it was found that 28 are obtained in minor amounts, while the dominating product is the -coordinated chloro-carbyne species [(> -Tp )Mo(CO)2(=CCl)], whose yield increases abruptly with substitution in the pyrazol-l-yl fragments (3-methyl-, 3,4,5-trimethyl-, and 3,5-dimethyl-4-chloro derivatives) [90AX(C)59,95JCS(D) 1709]. The tungsten analog can be prepared similarly. The chlorocarbyne molybdenum complex follows also from the reaction of the parent anion with triphenylsulfonium cation but conducted in dichloromethane. The bromo- and iodocarbyne derivatives are made similarly. 

Epoxidation systems based on molybdenum and tungsten catalysts have been extensively studied for more than 40 years. The typical catalysts - MoVI-oxo or WVI-oxo species - do, however, behave rather differently, depending on whether anionic or neutral complexes are employed. Whereas the anionic catalysts, especially the use of tungstates under phase-transfer conditions, are able to activate aqueous hydrogen peroxide efficiently for the formation of epoxides, neutral molybdenum or tungsten complexes do react with hydrogen peroxide, but better selectivities are often achieved with organic hydroperoxides (e.g., TBHP) as terminal oxidants [44, 45],... 

A particularly interesting system for the epoxidation of propylene to propylene oxide, working under pseudo-heterogeneous conditions, was reported by Zuwei and coworkers [61]. The catalyst, which was based on the Venturello anion combined with long-chained alkylpyridinium cations, showed unique solubility properties. I11 the presence of hydrogen peroxide the catalyst was fully soluble in the solvent, a 4 3 mixture of toluene and tributyl phosphate, but when no more oxidant was left, the tungsten catalyst precipitated and could simply be removed from the... 

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