Tungsten hexachloride

Tungsten hexachloride
Names
IUPAC names
Tungsten hexachloride
Tungsten(VI) chloride
Identifiers
3D model (JSmol)
ECHA InfoCard 100.032.980
EC Number 236-293-9
RTECS number YO7710000
Properties
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)
hydrolyzes
Solubility in chlorocarbons soluble
−71.0·10−6 cm3/mol
Structure
α:rhombohedral, β: hexagonal
octahedral
0 D
Hazards
Main hazards oxidizer; hydrolysis releases HCl
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.[1] Other examples of charge-neutral hexachlorides are ReCl6 and MoCl6. The highly volatile WF6 is also known.

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]

Preparation

Tungsten hexachloride can be prepared by chlorinating tungsten metal in a sealed tube at 600 °C: [3]

W + 3 Cl2 → WCl6

Properties and Reactions

Tungsten (VI) chloride is a blue-black 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, even by moist air, giving the orange oxychlorides WOCl4 and WO2Cl2, and subsequently, tungsten trioxide. WCl6 is soluble in carbon disulfide, carbon tetrachloride, and phosphorus oxychloride.[3]

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.[4]

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

Reduction of WCl6 gives, sequentially, tungsten(V) chloride and tungsten(IV) chloride.

Safety considerations

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

References

  1. ↑ J. W. Herndon (2004). "Tungsten(VI) Chloride". Encyclopedia of Reagents for Organic Synthesis. Wiley. doi:10.1002/047084289. .
  2. ↑ J. C. Taylor, P. W. Wilson (1974). "The Structure of β-Tungsten Hexachloride by Powder Neutron and X-ray Diffraction". Acta Crystallographica. B30: 1216–1220. doi:10.1107/S0567740874004572. .
  3. 1 2 M. H. Lietzke; M. L. Holt (1950). "Tungsten(VI) Chloride (Tungsten Hexachloride)". Inorganic Syntheses. 3: 163. doi:10.1002/9780470132340.ch4.
  4. ↑ M. A. Umbreit, K. B. Sharpless (1990). "Deoxygenation of Epoxides with Lower Valent Tungsten Halides: trans-Cyclododecene". Organic Syntheses. ; Collective Volume, 7, p. 121
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