tungsten hexachloride
{{chembox
|Watchedfields = changed
|verifiedrevid = 448559102
|Name = Tungsten hexachloride
|ImageFile = Tungsten(VI) Chloride.jpg
|ImageCaption = α-Tungsten hexachloride
|ImageFile1 = Β-tungsten hexachloride.png
|ImageCaption1 = β-Tungsten hexachloride
|ImageFileL2 = Hexachlorotungsten.svg
|ImageSizeL2 = 115px
|ImageNameL2 = Tungsten hexachloride
|ImageFileR2 = Tungsten-hexachloride-from-xtal-3D-balls.png
|ImageSizeR2 = 100px
|ImageNameR2 = 3D view
|IUPACName = Tungsten hexachloride
Tungsten(VI) chloride
|Section1 = {{Chembox Identifiers
|CASNo_Ref = {{cascite|correct|CAS}}
|CASNo = 13283-01-7
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = L32HZV95ZE
|PubChem = 83301
|RTECS = YO7710000
|EINECS = 236-293-9
|InChI = 1S/6ClH.W/h6*1H;/q;;;;;;+6/p-6
|SMILES = Cl[W](Cl)(Cl)(Cl)(Cl)Cl
}}
|Section2 = {{Chembox Properties
|Formula = {{chem2|WCl6}}
|W=1|Cl=6
|Appearance = dark blue crystals, moisture sensitive
|Density = 3.52 g/cm3
|Solubility = Hydrolyzes
|Solvent = chlorocarbons
|SolubleOther = soluble
|MeltingPtC = 275
|BoilingPtC = 346.7
|MagSus = −71.0·10−6 cm3/mol}}
|Section3 = {{Chembox Structure
|Coordination = Octahedral
|CrystalStruct = α:rhombohedral, β: hexagonal
|Dipole = 0 D
}}
|Section4 = {{Chembox Hazards
|MainHazards = oxidizer; hydrolysis releases HCl
}}
|Section5 = {{Chembox Related
|OtherAnions = {{ubl|Tungsten hexafluoride|Tungsten hexabromide}}
|OtherCations = {{ubl|Molybdenum(VI) chloride|Uranium hexachloride}}
|OtherCompounds = {{ubl|Tungsten(VI) oxytetrachloride|Tungsten dichloride dioxide|Tungsten(V) chloride|Tungsten(IV) chloride|Tungsten(III) chloride|Tungsten(II) chloride|Molybdenum(V) chloride|Chromyl chloride}}
}}
}}
{{Use American English|date=May 2024}}
Tungsten hexachloride is an inorganic chemical compound of tungsten and chlorine with the chemical formula {{chem2|WCl6|auto=1}}. This dark violet-blue compound exists as volatile crystals under standard conditions. It is an important starting reagent in the preparation of tungsten compounds.{{cite encyclopedia|author1=J. W. Herndon|author2=M. E. Jung|title=Encyclopedia of Reagents for Organic Synthesis|chapter=Tungsten(VI) Chloride |year=2007|publisher=Wiley|doi=10.1002/9780470842898.rt430.pub2|isbn=978-0-471-93623-7}}.
Other examples of charge-neutral hexachlorides are rhenium(VI) chloride and molybdenum(VI) chloride. The highly volatile tungsten hexafluoride is also known.
As a d0 atom, tungsten hexachloride is diamagnetic.
Preparation and structure
Tungsten hexachloride can be prepared by chlorinating tungsten metal in a sealed tube at 600 °C:{{cite book| title= Inorganic Syntheses| author1 = M. H. Lietzke| author2 = M. L. Holt| chapter= Tungsten(VI) Chloride (Tungsten Hexachloride)| volume = 3| year = 1950| doi = 10.1002/9780470132340.ch44 | page = 163| isbn= 978-0-470-13162-6}}
:{{chem2|W + 3 Cl2 → WCl6}}
Tungsten hexachloride exists in both blue and red polymorphs, referred to respectively as α and β. The wine-red β can be obtained by rapid cooling, whereas the blue α form is more stable at room temperature. Although these polymorphs are distinctly colored, their molecular structures are very similar. Both polymorphs feature {{chem2|WCl6|auto=1}} molecules that have octahedral geometry, in which all six W–Cl bonds are equivalent, and their length is equal to 224–226 pm. The densities are very similar: 3.68 g/cm3 for α and 3.62 g/cm3 for β. The low-temperature form is slightly more dense, as expected.{{cite journal |author1=J. C. Taylor |author2=P. W. Wilson |title=The Structure of β-Tungsten Hexachloride by Powder Neutron and X-ray Diffraction |journal=Acta Crystallographica |year=1974 |volume=B30 |issue=5 |pages=1216–1220 |doi=10.1107/S0567740874004572 |doi-access=free|bibcode=1974AcCrB..30.1216T }}.
Reactions
Tungsten hexachloride is readily hydrolyzed, even by moist air, giving the orange oxychlorides Tungsten(VI) oxytetrachloride and Tungsten dichloride dioxide, and subsequently, tungsten trioxide. {{chem2|WCl6}} is soluble in carbon disulfide, carbon tetrachloride, and phosphorus oxychloride.
Methylation with trimethylaluminium affords hexamethyl tungsten:
:{{chem2|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.{{OrgSynth | author = M. A. Umbreit, K. B. Sharpless | title = Deoxygenation of Epoxides with Lower Valent Tungsten Halides: trans-Cyclododecene | collvol = 7 | collvolpages = 121| year = 1990 | prep = CV7P0121}}
The chloride ligands in {{chem2|WCl6}} can be replaced by many anionic ligands including: bromide, thiocyanate, alkoxide, alkyl and aryl.
Reduction of {{chem2|WCl6}} can be effected with a mixture of tetrachloroethylene and tetraphenylarsonium chloride:{{cite journal |doi=10.1002/zaac.19834970221 |title=Über die Reaktion von 2,2-Dimethylpropylidinphosphan mit Wolframhexachlorid; die Kristallstrukturen von [(Cl3PO)WCL4(H9C4CCC4H9)] und [(H5C6)4As][WCL6] |year=1983 |last1=Uhl |first1=G. |last2=Hey |first2=E. |last3=Becker |first3=G. |last4=Weller |first4=F. |last5=Dehnicke |first5=K. |journal=Zeitschrift für Anorganische und Allgemeine Chemie |volume=497 |issue=2 |pages=213–223 |url=http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-57717 |url-access=subscription }}
:{{chem2|2 WCl6 + Cl2C\dCCl2 + 2 (C6H5)4AsCl -> 2 (C6H5)4As[WCl6] + Cl3C\sCCl3}}
The W(V) hexachloride is a derivative of tungsten(V) chloride.
It reacts with arsenic or hydrogen arsenide to form tungsten arsenide.{{cite book | last1=Lassner | first1=Erik | last2=Schubert | first2=Wolf-Dieter | title=Tungsten | publisher=Springer Science & Business Media | date=2012-12-06 | isbn=978-1-4615-4907-9|page=145}}{{cite book | last=Meyer | first=R. J. | title=Wolfram | publisher=Springer-Verlag | date=2013-09-03 | isbn=978-3-662-13401-6 | language=de|page=207}}
Safety considerations
{{chem2|WCl6}} is an aggressively corrosive oxidant, and hydrolyzes to release hydrogen chloride.
References
{{reflist}}
{{Tungsten compounds}}
{{Chlorides}}