Tungsten halides

Various appHcations such as lubricant additives, dyes, pigments, and catalysts are under investigation. Tungsten can be deposited from tungsten hexacarbonyl, but carbide formation and gas-phase nucleation present serious problems (1,2). As a result, tungsten halides are the preferred starting material. 

Tungsten halides, 3, 974, 984, 988 synthesis, 3,974 Tungsten hexaalkoxides physical properties, 2,347 Tungsten oxide ruthenium oxide support... 

The Diels-Alder adduct of 1,5-cyclooctadiene with hexachlorocyclo-pentadiene was homopolymerized or copolymerized (113) with cyclic olefins using tungsten halide salts with either organoaluminum or organo-tin cocatalyst to give thermally stable flame- and oil-resistant polymers. 

For the tungsten halides the trend in A/7°sub (MtXJ on changing from chloride to fluoride is the opposite to that shown by the aluminium halides. Thus, this is not a term with respect to which overall generalisation is possible and great care must be taken whenever numerical values for this term are not available. 

Figure 4.32. The key structural unit [Mo6Cl8]4+ is shown (Cl atom black), which is found in molybdenum (and similarly in tungsten) halides. The edges of the Cl8 cube (around the Mo6 octahedron) have not been indicated emphasis has been given to the interatomic connections.

Lowering the temperature at which cluster-forming solid-state reactions can be carried out is of some interest, particularly as a means of gaining a measure of kinetic control over the process. Several decades ago, it was discovered that the yields for forming tungsten halide cluster phases could be improved by... 

DEOXYGENATION WITH LOWER VALENT TUNGSTEN HALIDES... 

Sharpless KB, Umbreit MA, Nieh MT, Flood TC (1972) Lower Valent Tungsten Halides. A New Class of Reagents for Deoxygenation of Organic Molecules. J Am Chem Soc 94 6538... 

Simple olefins undergo cycloaddition, one way or another, in the metathesis process with remarkable ease e.g., with a tungsten halide catalyst at room temperature, 2-pentene is converted to an equilibrium mixture of 2-butene, 2-pentene and 3-hexene in a few seconds >. One should reasonably expect a similar transformation of simple acetylenes, e.g., 26 - -27. The transformation 26 27 might appear, at first inspection, to be symmetry-allowed. 

Deoxygemtion. Sharpless et al. have prepared a series of lower valent tungsten halides from tungsten hexachloride as shown ... 

CMP. In addition, the melting points of tungsten halides are low (200-300°Q compared to tungsten (3410°C) or tungsten oxides... 

There are many varieties of metal halide lamps, the most familiar being the tungsten-halide lamps found in many homes, or the sodium and mercury vapor lamps found on streets and in auditoriums, convention centers and large space commercial buildings. Many have seen the change in color given off as these lamps warm up to their operating temperature. 

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