Electron Diffraction Study of the Structure of Trimethylphosphine

The structural parameters of gaseous trimethylphosphine, including standard errors, were found to be as follows: center of gravity bond distances were rCP=1.8465±0.003 A, and rCH=1.091±0.006 A; angles were <C–P–C=98.6±0.3°, and <P–C–H=110.7±0.5°; root-mean-square amplitudes of vibration were lCP=0.054±0.003 A, lCH=0.073±0.006 A, lP— —H=0.110±0.006 A, and lC— —C=0.084±0.005 A. The methyl groups were observed to be in staggered configurations analogous to those in ethane, with rotational barriers probably 1.5 kcal/mole or higher. A brief structural comparison with halogen derivatives and hydrides is presented.