Tungsten hexachloride

Template:Chembox Template:Use American English Tungsten hexachloride is an inorganic chemical compound of tungsten and chlorine with the chemical formula Template:Chem2. This dark violet-blue compound exists as volatile crystals under standard conditions. It is an important starting reagent in the preparation of tungsten compounds. Other examples of charge-neutral hexachlorides are rhenium(VI) chloride and molybdenum(VI) chloride. The highly volatile tungsten hexafluoride is also known.

As a d⁰ atom, tungsten hexachloride is diamagnetic.

Preparation and structure

Tungsten hexachloride can be prepared by chlorinating tungsten metal in a sealed tube at 600 °C:

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Tungsten hexachloride exists in both blue and red polymorphs, referred to respectively as α and β. The wine-red β can be obtained by rapid cooling, whereas the blue α form is more stable at room temperature. Although these polymorphs are distinctly colored, their molecular structures are very similar. Both polymorphs feature Template:Chem2 molecules that have octahedral geometry, in which all six W–Cl bonds are equivalent, and their length is equal to 224–226 pm. The densities are very similar: 3.68 g/cm³ for α and 3.62 g/cm³ for β. The low-temperature form is slightly more dense, as expected.

Reactions

Tungsten hexachloride is readily hydrolyzed, even by moist air, giving the orange oxychlorides [[Tungsten(VI) oxytetrachloride|Template:Chem2]] and [[Tungsten dichloride dioxide|Template:Chem2]], and subsequently, tungsten trioxide. Template:Chem2 is soluble in carbon disulfide, carbon tetrachloride, and phosphorus oxychloride.

Methylation with trimethylaluminium affords hexamethyl tungsten:

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Treatment with butyl lithium affords a reagent that is useful for deoxygenation of epoxides.

The chloride ligands in Template:Chem2 can be replaced by many anionic ligands including: bromide, thiocyanate, alkoxide, alkyl and aryl.

Reduction of Template:Chem2 can be effected with a mixture of tetrachloroethylene and tetraphenylarsonium chloride:

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The W(V) hexachloride is a derivative of tungsten(V) chloride.

It reacts with arsenic or hydrogen arsenide to form tungsten arsenide.

Safety considerations

Template:Chem2 is an aggressively corrosive oxidant, and hydrolyzes to release hydrogen chloride.