Preparation of High Purity Trimethylborane1

The preparation of high-purity trimethylborane is described. Impurities were removed by fractionation of the ammonia adduct, NH(3):B(CH3)(3). Mass spectrometric analyses were used during the fractionation to determine these impurities. After purification of the B (CH(3))(3) in the form of its ammonia adduct, high-purity hydrogen chloride was used to regenerate the B(CH(3))(3). This reaction and the subsequent distillation were carried out in a stainless steel system. Storage as a gas in stainless steel cylinders, rather than as a solid addition complex in glass vessels, eliminated the possibility of recontamination on regeneration. The purity of B(CH(3))(3) was determined cryoscopically to be 99.9 mole percent.