Tungsten hexacarbonyl


Tungsten hexacarbonyl is the chemical compound with the formula W6. This complex gave rise to the first example of a dihydrogen complex.
This colorless compound, like its chromium and molybdenum analogs, is noteworthy as a volatile, air-stable derivative of tungsten in its zero oxidation state.

Preparation, properties, and structure

W6 is prepared by the reduction of WCl6 under a pressure of carbon monoxide. 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.
W6 adopts an octahedral geometry consisting of six rod-like CO ligands radiating from the central W atom with dipole moment 0 D.

Reactivity

All reactions of W6 commence with displacement of some CO ligands in W6. W6 behaves similarly to the Mo6 but tends to form compounds that are kinetically more robust. 2W2 is produced from W6..
Treatment of tungsten hexacarbonyl with sodium cyclopentadienide followed by oxidation of the resulting NaW3 gives cyclopentadienyltungsten tricarbonyl dimer.
One derivative is the dihydrogen complex W32.
Three of these CO ligands can be displaced by acetonitrile.
W6 has been used to desulfurize organosulfur compounds and as a precursor to catalysts for alkene metathesis.

Safety and handling

Like all metal carbonyls, W6 is a dangerous source of volatile metal as well as CO.