594-09-2

Clear colorless liquid

ChEBI: Trimethylphosphine is a tertiary phosphine.

All operations should be carried out in an efficient fume cupboard because it is flammable, toxic and has a foul odor. Distil trimethylphosphine at atmospheric pressure in a stream of dry N2 (apparatus should be held together with springs to avoid loss of gas from increased pressure in the system) and the distillate run into a solution of AgI in aqueous KI whereby the silver complex [Me3PAgI]4 separates steadily. Filter off the complex, wash it with saturated aqueous KI solution, then H2O and dry it in a vacuum desiccator over P2O5. The dry complex is heated in a flask (in a stream of dry N2) in an oil bath at 140o, when pure Me3P distils off (bath temperature can be raised up to 260o). The vapour pressure of Me3P at 20o is 466mm and the b is 37.8o [Thomas & Eriks Inorg Synth IX 59 1967]. Alternatively, freshly distilled Me3P (6g) is shaken with a solution of AgI (13.2g, 1.1mol) in saturated aqueous KI solution (50mL) for 2hours. A white solid, not wetted with H2O, separates rapidly. It is collected, washed with the KI solution, H2O, and dried [Mann et al. J Chem Soc 1829 1937]. The silver complex is stable if kept dry in the dark, in which state it can be kept indefinitely. Me3P can be generated from the complex when required. Store it under N2 in a sealed container. It has been distilled in a vacuum line at -78o in vacuo and condensed at -96o [IR and NMR: Crosbie & Sheldrick J Inorg Nucl Chem 31 3684 1969]. The pK2 2 by NMR was 8.80 [Silver & Lutz J Am Chem Soc 83 786 1961, pK2 5 8.65: Henderson & Strueuli J Am Chem Soc 82 5791 1960].