Molecular structure of acetyldeyiethylphosphine,MeC(O)PMe2: II. CNDO/2 calculations

The sp, spd and spd' approximations of the CNDO/2 method have been applied to energy calculations for some models of the acetyldimethylphosphine molecule generated during treatment of the electron diffraction data. The results obtained for trial configurations with different angles of rotation of the acetyl group about the PC _ac bond predict two symmetric energy minima separated by a rather low barrier. This is in agreement with the electron diffraction data which are compatible with the suggestion of large amplitude torsional vibrations of the acetyl group. Energy calculations have also been performed for the final electron diffraction models. The calculations, however, fail to remove ambiguity from the question of a preferred model of the acetyldimethylphosphine molecule.