Tungsten hexachloride

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Tungsten hexachloride
Tungsten hexachloride 3D view
Identifiers
CAS number 13283-01-7 YesY
PubChem 83301
EC number 236-293-9
RTECS number YO7710000
Jmol-3D images Image 1
Properties
Molecular 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
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
Except where noted otherwise, 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] 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.[2] In acceptor, the chloride ligands are donors in both sigma- and pi sense.[citation needed]

Preparation[edit]

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

W + 3 Cl2 → WCl6

Properties and Reactions[edit]

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.[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).

Safety considerations[edit]

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

References[edit]

  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. ^ a b Ludwig F. Audrieth (2007). Inorganic Syntheses. McGraw-Hill Book Company. p. 165. ISBN 9780470131626. 
  4. ^ M. A. Umbreit, K. B. Sharpless (1990), "Deoxygenation of Epoxides with Lower Valent Tungsten Halides: trans-Cyclododecene", Org. Synth. ; Coll. Vol. 7: 121