Tungsten hexachloride

Tungsten hexachloride
IUPAC name Tungsten hexachloride Tungsten(VI) chloride
Identifiers
CAS number	13283-01-7 Y
PubChem	83301
RTECS number	YO7710000
Properties
Molecular formula	Cl6W
Molar mass	396.61 g/mol
Appearance	dark blue crystals, moisture sensitive
Density	3.52 g/cm3
Melting point	275 °C
Boiling point	346.7 °C
Solubility in water	hydrolyzes
Solubility in chlorocarbons	soluble
Structure
Crystal structure	α:rhombohedral, β: hexagonal
Coordination geometry	octahedral
Dipole moment	0 D
Hazards
EU Index	Not listed
Main hazards	oxidizer; hydrolysis releases HCl
Related compounds
Other anions	Tungsten hexafluoride Tungsten hexabromide
Other cations	Molybdenum(V) chloride Chromyl chloride
Y hexachloride (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.^[1] Cl₆W is a rare example of a charge-neutral hexachloride, another example being ReCl₆. Better known than Cl₆W is the still more volatile F₆W.

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 Cl₆W, the chloride ligands are donors in both sigma- and pi sense.^{[citation needed]} 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 Cl₆W 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

1. ^ 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.
2. ^ 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.
3. ^ M. A. Umbreit, K. B. Sharpless (1990), "Deoxygenation of Epoxides with Lower Valent Tungsten Halides: trans-Cyclododecene", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV7P0121 ; Coll. Vol. 7: 121