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Tungsten hexachloride

Tungsten hexachloride

General
Systematic name	Tungsten(VI) chloride
Other names	Tungsten hexachloride
Molecular formula	WCl₆
Molar mass	396.61 g/mol
Appearance	dark blue crystals moisture sensitive
CAS number	[13283-01-7]
Properties
Density and phase	3.52 g/cm³
Solubility in water	hydrolyzes
Other solvents	chlorocarbons
Melting point	275 °C
Boiling point	346.7 °C
Structure
Coordination geometry	octahedral
Crystal structure	α:rhombohedral, β: hexagonal
Dipole moment	0 D
Hazards
MSDS	External MSDS
Main hazards	oxidizer hydrolysis releases HCl
NFPA 704
R/S statement	R: 34 S: 26-36/37/39-45
RTECS number	YO7710000
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid
Spectral data	UV, IR, NMR, MS
Related compounds
Related compounds	Molybdenum(V) chloride chromyl chloride tungsten hexafluoride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Tungsten hexachloride is the chemical compound 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.^[1] WCl₆ is a rare example of a charge neutral hexachloride, another example being ReCl₆. MoCl₆ cannot be prepared. Better known than WCl₆ is the still more volatile WF₆.

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As a d⁰ ion, W(VI) forms diamagnetic derivatives. The hexachloride is octahedral with equivalent W-Cl distances of 2.24 - 2.26 Å.^[2] In the WCl₆, the chloride ligands are donors in both sigma- and pi sense. Methylation with trimethylaluminium affords hexamethyl tungsten. Treatment with butyl lithium affords a reagent that is useful for deoxygenation of epoxides.^[3]

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.

References

^ J. W. Herndon "Tungsten(VI) Chloride” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.
^ J. C. Taylor and P. W. Wilson "The structure of [beta]-tungsten hexachloride by powder neutron and X-ray diffraction" Acta Crystallographic (1974). B30, 1216-1220.doi:10.1107/S0567740874004572.
^ M. A. Umbreit, K. B. Sharpless (1990). "Deoxygenation of Epoxides with Lower Valent Tungsten Halides: trans-Cyclododecene". Org. Synth.; Coll. Vol. 7: 121.