Tungsten hexacarbonyl (also called tungsten carbonyl) is an organometallic compound with the formula W(CO)<sub>6</sub>. This complex gave rise to the first example of a dihydrogen complex.
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)<sub>6</sub> 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 (CrCl<sub>3</sub>, MoCl<sub>5</sub> or WCl<sub>6</sub>) with magnesium, zinc or aluminium powders... under CO pressures". Another means of preparation involves heating iron pentacarbonyl and WCl<sub>6</sub>, resulting in the formation of ferrous chloride. 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.
W(CO)<sub>6</sub> 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)<sub>6</sub> commence with displacement of some CO ligands in W(CO)<sub>6</sub>. W(CO)<sub>6</sub> behaves similarly to the Mo(CO)<sub>6</sub> but tends to form compounds that are kinetically more robust.
Treatment of tungsten hexacarbonyl with sodium cyclopentadienide followed by oxidation of the resulting NaW(CO)<sub>3</sub>(C<sub>5</sub>H<sub>5</sub>) gives cyclopentadienyltungsten tricarbonyl dimer.
One derivative is the dihydrogen complex W(CO)<sub>3</sub>[<nowiki/>P(C<sub>6</sub>H<sub>11</sub>)<sub>3</sub><nowiki/>]<sub>2</sub>(H<sub>2</sub>).
Three of these CO ligands can be displaced by acetonitrile. W(CO)<sub>6</sub> has been used to desulfurize organosulfur compounds and as a precursor to catalysts for alkene metathesis.
Like all metal carbonyls, W(CO)<sub>6</sub> is a dangerous source of volatile metal as well as CO.