Theoretical conformational analysis of unsaturated phospines and phosphinechalcogenides

A theoretical conformational analysis was performed for vinylphosphine CH₂=CHPH₂ and three vinylphosphinechalcogenides CH₂=CHPXH₂ (X = O, S, Se). According to the quantum-chemical calculations on the level of the second order perturbation theory MP2/6-311G** the prevailing conformations, their molar ratios, and relative energies were established for each compound. The analysis of the angular distribution of the probability density for the population of the rotational conformations calculated proceeding from the potential curves of the internal rotation made it possible to establish that each compound from this series existed as a mixture of two conformers, planar s-cis and twice degenerate orthogonal. The conformers transform into each other through the corresponding transition states whose nature was established as a result of the harmonic vibration analysis carried out in every case.