Molecular Structure and Internal Rotation Potential of Dimethylphenylphosphine, According to Gas-Phase Electron Diffraction Data and Quantum-Chemical Calculations

Abstract

Geometric parameters of dimethylphenylphosphine molecule were determined by gas-phase electron diffraction using a dynamic model in which the rotation of the PMe2 group is treated as large-amplitude motion. Refinement of the structural parameters and parameters of the potential function was performed taking into account the geometry relaxation on the basis of HF/6-311++G** calculations. The internal rotation potential has a single minimum at ϕ 0° (ϕ is the angle between the bisector of the MePMe angle and the phenyl ring plane) and may be described by the function of the form V(ϕ) = 0.5V2(1 - cos2ϕ), where V2 = 0.38±0.36 kcal mol-1. The data obtained are compared with those for related molecules. Steric effects affect the geometry of the phenylphosphine molecule more significantly than does p-π interaction.