Tungsten hexacarbonyl (also called tungsten carbonyl) is an organometallic compound with the formula W(CO)6. This complex gave rise to the first example of a dihydrogen complex.[1]
Like its chromium and molybdenum analogs, this colorless compound is noteworthy as a volatile, air-stable derivative of tungsten in its zero oxidation state.
Like many metal carbonyls, W(CO)6 is generally prepared by "reductive carbonylation", which involves the reduction of a metal halide with under an atmosphere of carbon monoxide. As described in a 2023 survey of methods "most cost-effective routes for the synthesis of group 6 hexacarbonyls are based on the reduction of the metal chlorides (CrCl3, MoCl5 or WCl6) with magnesium, zinc or aluminium powders... under CO pressures".[2] The compound is relatively air-stable. It is sparingly soluble in nonpolar organic solvents. Tungsten carbonyl is widely used in electron beam-induced deposition technique - it is easily vaporized and decomposed by the electron beam providing a convenient source of tungsten atoms.[3]
W(CO)6 adopts an octahedral geometry consisting of six rod-like CO ligands radiating from the central W atom with dipole moment 0 debye.
All reactions of W(CO)6 commence with displacement of some CO ligands in W(CO)6. W(CO)6 behaves similarly to the Mo(CO)6 but tends to form compounds that are kinetically more robust. thumb|left|144px|Cyclopentadienyltungsten tricarbonyl dimer ((C5H5.)2W2(CO)6) is produced from W(CO)6.
Treatment of tungsten hexacarbonyl with sodium cyclopentadienide followed by oxidation of the resulting NaW(CO)3(C5H5) gives cyclopentadienyltungsten tricarbonyl dimer.[4]
One derivative is the dihydrogen complex W(CO)3[P(C<sub>6</sub>H<sub>11</sub>)<sub>3</sub>]2(H2).
Three of these CO ligands can be displaced by acetonitrile.[5] W(CO)6 has been used to desulfurize organosulfur compounds and as a precursor to catalysts for alkene metathesis.
Like all metal carbonyls, W(CO)6 is a dangerous source of volatile metal as well as CO.