Organometallic Tungsten Compounds

A large number of tungsten organometallic compounds plays an important role, or can be regarded as prominent candidates, as catalyst in organic syntheses. Tungsten as well as molybdenum and rhenium catalysts are closely associated with metathesis polymerization. 

Aspects of the apparatus for the synthesis using metal atoms are described. The reactions of the atoms of rhenium, tungsten, and osmium with hydrocarbons including alkanes are described. It is shown that metal atom reactions with alkanes can give isolable organometallic compounds including l-alkylidene compounds. 

The results in Table V show that active disproportionation catalysts are obtained when molybdenum and tungsten hydrocarbyls are supported on silica or alumina. These catalytic systems have not been optimized, and it is highly probable that more active catalysts based on these systems can be obtained. No obvious pattern emerges from the results both silica and alumina supports confer activity on the organometallic compounds which are themselves inactive in homogeneous solution under similar conditions. 

By far the greatest number of tungsten compounds are those in which the element is hexavalent. These include all common halides except the iodide, i.e.. WF. WCl, as well as a number of oxvhalrdes, WOF4, WOCI4, WO Cl , WOBr4, and WO Br2, the Irioxide. trisullide, dibonde, and diphosphide already mentioned, various complexes and organometallic compounds, and the anions. 

Further surveys of the reactivity of HB(C6F5)2 with simple organometallic compounds have led to the discovery of more novel boron-based ligand systems. For example, reactions with Schrock s tungsten methylidyne family L4W(X)=CH63 (L = phosphine, X = Cl, OTf) result in electrophilic attack on the methylidyne ligand hydride abstraction... 

Cluster Compounds Inorganometallic Compounds Containing Transition Metal Main Group Elements Heterogeneous Catalysis by Metals Oxidation Catalysis by Transition Metal Complexes Polyoxometalates Tungsten Organometallic Chemistry. Tungsten Proteins. 

Also. J. B. Pedley, ed., Computer Analysis of Thermochemical Data (CATCH Tables)." Univ. of Sussex, Brighton, 1972. (i) Halogen compounds (1972), (ii) nitrogen compounds (1972), (iii) phosphorus compounds (1972), (iv) silicon compounds (1972), (v) chromium, molybdenum, and tungsten compounds (1974). Booklets (iv), (v) give data on organometallic compounds. The book by Cox and Pilcher (A149) is to be updated under the same system. 

Introduction.—Reviews on the molecular structure of co-ordination compounds and organometallic compounds containing molybdenum and tungsten as determined by X-Tdiy diffraction have appeared. Structural aspects of Mo , Mo, and Mo complexes have been examined and molybdenum complexes themselves have also been specifically reviewed. A discussion of molybdenum and tungsten dialkyl-amides and disilylamides has been included in a recent review and the co-ordination chemistry of aryldiazonium cations (ArNj) of molybdenum and tungsten has been discussed. ... 

The catalyst may be homogeneous or heterogeneous. The former usually consists of a transition metal compound such as tungsten hexachloride with a Lewis acid or organometallic compound such as ethylaluminium chloride, tetramethyl or tetrabutyltin, or triethylboron. Heterogeneous catalysts are usually oxides or carbonyls of molybdenum or tungsten on alumina or silica. 

Sen, A. Thomas, R. R. Catalysis by solvated transition-metal cations. 3. Novel catalytic transformations of alkenes by cationic compounds of molybdenum and tungsten. Organometallics 1982, 1, 1251-1254. 

R. Stegmann, A. Neuhaus, and G. Frenking,/. Am. Chem. Soc., 115,11930 (1993). Theoretical Studies of Organometallic Compounds. V. Alkyne and Vinylidene Complexes of Molybdenum and Tungsten in High Oxidation States. 

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