Chemistry:Tungsten hexachloride

Tungsten hexachloride

α-Tungsten hexachloride
β-Tungsten hexachloride
Names
IUPAC names Tungsten hexachloride Tungsten(VI) chloride
Identifiers
CAS Number	13283-01-7 Y
3D model (JSmol)	Interactive image
EC Number	236-293-9
PubChem CID	83301
RTECS number	YO7710000
UNII	L32HZV95ZE Y
InChI InChI=1S/6ClH.W/h6*1H;/q;;;;;;+6/p-6
SMILES Cl[W](Cl)(Cl)(Cl)(Cl)Cl
Properties
Chemical formula	WCl 6
Molar mass	396.54 g·mol−1
Appearance	dark blue crystals, moisture sensitive
Density	3.52 g/cm3
Melting point	275 °C (527 °F; 548 K)
Boiling point	346.7 °C (656.1 °F; 619.8 K)
Solubility in water	Hydrolyzes
Solubility in chlorocarbons	soluble
Magnetic susceptibility (χ)	−71.0·10−6 cm3/mol
Structure
Crystal structure	α:rhombohedral, β: hexagonal
Coordination geometry	Octahedral
Dipole moment	0 D
Hazards
Main hazards	oxidizer; hydrolysis releases HCl
Related compounds
Other anions	Tungsten hexafluoride Tungsten hexabromide
Related compounds	Tungsten(IV) chloride Tungsten(V) chloride Molybdenum(V) chloride Chromyl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Tungsten hexachloride is an inorganic chemical compound of tungsten and chlorine with the chemical formula WCl
6. 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:

W + 3 Cl
2 → WCl
6

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 WCl
6 molecules that have octahedral, 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 WOCl
4 and WO
2Cl
2, and subsequently, tungsten trioxide. WCl
6 is soluble in carbon disulfide, carbon tetrachloride, and phosphorus oxychloride.

Methylation with trimethylaluminium affords hexamethyl tungsten:

WCl
6 + 3 Al
2(CH
3)
6 → W(CH
3)
6 + 3 Al
2(CH
3)
4Cl
2

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

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

Reduction of WCl
6 can be effected with a mixture of tetrachloroethylene and tetraphenylarsonium chloride:

2 WCl
6 + Cl
2C=CCl
2 + 2 (C
6H
5)
4AsCl → 2 (C
6H
5)
4As[WCl
6] + Cl
3C–CCl
3

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

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

Safety considerations

WCl
6 is an aggressively corrosive oxidant, and hydrolyzes to release hydrogen chloride.