Tungsten compounds fluorides

Tungsten(VI) fluoride, with a molecular weight of 297.92, is one of the heaviest gases known and as such would be expected to have some interesting uses. Its reactive character may detract from possible applications, but where this property would not interfere the compound could be used. It was prepared and characterized by Ruff and his coworkers, who used the hexachloride as a starting material. The method of direct synthesis used in the following procedure has proved to be very satisfactory and simple. ... 

The reactivity of fluorine compounds varies from extremely stable, eg, compounds such as sulfur hexafluoride [2551-62 ] nitrogen trifluoride [7783-54-2] and the perfluorocarbons (see Fluorine compounds, organic) to extremely reactive, eg, the halogen fluorides. Another unique property of nonionic metal fluorides is great volatiUty. Volatile compounds such as tungsten hexafluoride [7783-82-6] molybdenum hexafluoride [7783-77-9] ... 

The validity of this approach can be demonstrated by the example of several complex fluoride compounds that exhibit ferroelectric properties, such as compounds that belong to the SrAlF5 family [402, 403]. The crystal structure of the compounds is made up of chains of fluoroaluminate octahedrons that are separated by another type of chains - ramified chains. Other examples are the compounds Sr3Fe2Fi2 and PbsWjOgFio. In this case, the chains of iron- or tungsten-containing octahedrons are separated from one another by isolated complexes with an octahedral configuration [423,424]. 

Chromium Compounds and the Lower Oxide Fluorides of Molybdenum and Tungsten... 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

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