Trimethylphosphine

Trimethylphosphine is the chemical compound with the formula P(CH₃)₃, commonly abbreviated PMe₃. This colorless liquid has a strongly unpleasant odour, which characteristic of alkylphosphines. It is a pyramidal molecule with C_3v symmetry, similar to ammonia (NH₃) and phosphine (PH₃). As a ligand, its cone angle is 118°.^[1]

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PMe₃ is prepared using Grignard reagents:^[2]

3 CH₃MgBr + P(OC₆H₅)₃ → P(CH₃)₃ + 3 MgBrOC₆H₅

The synthesis is conducted in a dibutyl ether, from which the more volatile PMe₃ can be distilled.

Coordination chemistry

Trimethylphosphine is a highly basic ligand that forms complexes with most metals. The synthesis of an illustrative example is shown:

PMe₃ + Fe(CO)₅ → Fe(CO)₄PMe₃ + CO

Its complex with silver iodide, AgI(PMe₃) is a weighable, air stable compound that releases PMe₃ upon heating.

Safety

PMe₃ is potentially pyrophoric, as well as toxic.

References

1. ^ G. L. Miessler and D. A. Tarr “Inorganic Chemistry” 3rd Ed, Pearson/Prentice Hall publisher, ISBN 0-13-035471-6.
2. ^ Leutkens, Jr., M. L.; Sattelberger, A. P.; Murray, H. H.; Basil, J. D.; Fackler, Jr., J. P. (1990). "Trimethylphosphine". Inorganic Syntheses 28: 305-310. doi:10.1002/9780470132593.ch76.