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Tris(trimethylsilyl)phosphine

Tris(trimethylsilyl)phosphine is the organophosphorus compound with the formula P(SiMe<sub>3</sub>)<sub>3</sub> (Me = methyl). It is a colorless liquid that ignites in air and hydrolyses readily.

Synthesis

Tris(trimethylsilyl)phosphine is prepared by treating trimethylsilyl chloride, white phosphorus, and sodium-potassium alloy:

1/4 P<sub>4</sub> + 3 Me<sub>3</sub>SiCl + 3 K → P(SiMe<sub>3</sub>)<sub>3</sub> + 3 KCl

Several other methods exist.

Reactions

The compound hydrolyzes to give phosphine:

P(SiMe<sub>3</sub>)<sub>3</sub> + 3 H<sub>2</sub>O → PH<sub>3</sub> + 3 HOSiMe<sub>3</sub>

Treatment of certain acyl chlorides with tris(trimethylsilyl)phosphine gives phosphaalkynes, one example being tert-butylphosphaacetylene.

Reaction with potassium tert-butoxide cleaves one P-Si bond, giving the phosphide salt:

P(SiMe<sub>3</sub>)<sub>3</sub> + KO-t-Bu → KP(SiMe<sub>3</sub>)<sub>2</sub> + Me<sub>3</sub>SiO-t-Bu

It is a reagent in the preparation of metal phosphido clusters by reaction with metal halides or carboxylates. In such reactions the silyl halide or silyl carboxylate is liberated as illustrated in this idealized reaction:

P(SiMe<sub>3</sub>)<sub>3</sub> + 3 CuCl → Cu<sub>3</sub>P + 3 ClSiMe<sub>3</sub>

Safety

Tris(trimethylsilyl)phosphine spontaneously ignites in air, thus it is handled using air-free techniques.

References