Tungsten hexachloride

Tungsten hexachloride

Tungsten hexachloride 3D view
Names
IUPAC names Tungsten hexachloride Tungsten(VI) chloride
Identifiers
CAS Number	13283-01-7 N
EC Number	236-293-9
Jmol 3D model	Interactive image
PubChem	83301
RTECS number	YO7710000
InChI InChI=1S/6ClH.W/h6*1H;/q;;;;;;+6/p-6
SMILES Cl[W](Cl)(Cl)(Cl)(Cl)Cl
Properties
Chemical formula	WCl6
Molar mass	396.61 g/mol
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
Structure
Crystal structure	α:rhombohedral, β: hexagonal
Coordination geometry	octahedral
Dipole moment	0 D
Vapor pressure	{{{value}}}
Related compounds
Other anions	Tungsten hexafluoride Tungsten hexabromide
Other cations	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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Infobox references

Tungsten hexachloride is the chemical compound of tungsten and chlorine with the formula WCl₆. This dark violet blue species exists as a volatile solid under standard conditions. It is an important starting reagent in the preparation of tungsten compounds. WCl₆ is a rare example of a charge-neutral hexachloride, another example being ReCl₆. Better known than WCl₆ is the still more volatile WF₆.

As a d⁰ ion, W(VI) forms diamagnetic derivatives. The hexachloride is octahedral with equivalent W–Cl distances of 2.24–2.26 Å. In acceptor, the chloride ligands are donors in both sigma and pi sense.

Preparation

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

W + 3 Cl₂ → WCl₆

Properties and Reactions

Tungsten (VI) chloride is a blue-black crystalline solid at room temperature. At lower temperatures, it becomes wine-red in color. A red form of the compound can be made by rapidly condensing its vapor, which reverts to the blue-black form on gentle heating. It is readily hydrolyzed in moist air, giving the orange oxychlorides WOCl₄ & WO₂Cl₂, and subsequently, tungsten trioxide. WCl₆ is soluble in carbon disulfide, carbon tetrachloride and phosphorus oxychloride.

Methylation with trimethylaluminium affords hexamethyl tungsten:

WCl₆ +3 Al₂(CH₃)₆ → W(CH₃)₆ + 3 Al₂(CH₃)₄Cl₂

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

The chloride ligands in WCl₆ can be replaced by many anionic ligands including: Br⁻, NCS⁻, and RO⁻ (R = alkyl, aryl).

Safety considerations

WCl₆ is an aggressively corrosive oxidant, and hydrolyzes to release hydrogen chloride.