Hexamethyl tungsten
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| Other names
Tungsten hexamethyl
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3D model (Jmol)
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| Properties | |||
| C6H18W | |||
| Molar mass | 274.05 g·mol−1 | ||
| Appearance | Red crystalline solid / Vivid red gas | ||
| Structure | |||
| Trigonal prismatic | |||
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Hexamethyltungsten is the chemical compound W(CH3)6. Classified as an organometallic compound, hexamethyltungsten is an air-sensitive, red, crystalline solid at room temperature; however, it is extremely volatile and sublimes at −30 °C. Owing to its six methyl groups it is extremely soluble in petroleum, aromatic hydrocarbons, ethers, carbon disulfide, and carbon tetrachloride.
Hexamethyltungsten was first reported in 1973 by Wilkinson and Shortland, who described its preparation by the reaction of methyllithium with tungsten hexachloride in diethyl ether. The synthesis was motivated in part by previous work which indicated that tetrahedral methyl transition metal compounds are thermally unstable, in the hopes that an octahedral methyl compound would prove to be more robust. In 1976, Wilkinson and Galyer disclosed an improved synthesis using trimethylaluminium in conjunction with trimethylamine, instead of methyllithium. The stoichiometry of the improved synthesis is as follows:
Alternatively, the alkylation can employ dimethylzinc:
W(CH3)6 adopts a distorted trigonal prismatic geometry with D3hsymmetry. The trigonal prismatic geometry is unusual in that the vast majority of six-coordinate organometallic compounds adopt octahedral molecular geometry. In the initial report, the IR spectroscopy results were interpreted in terms of an octahedral structure. In 1978, a study using photoelectron spectroscopy appeared to confirm the initial assignment of an Oh structure.
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