Molecular Orbital Study on the Structure and Barrier to Internal Rotation of Phosphine-Borane
キーワード:
energy decomposition
1981 年 29 巻 2 号 p. 287-292
詳細
1981 年 29 巻 2 号 p. 287-292
The heat of complex formation of H3PBH3 was calculated to be -15.3 kcal/mol by double zeta ab initio LCAO MO SCF calculations ; this is very similar to the experimental values for (CH3)3PB(CH3)3 and (CH3)3PBF3. The origin of complex formation of H3PBH3 was elucidated by energy decomposition methods. The order of contributions is ES-(41%)>CT (37%)> PL (22%). The d atomic orbitals on phosphorus play a role in increasing the polarization energy upon complex formation. The barrier to internal rotation of H3PBH3 was calculated to be 2.4 kcal/mol, which is in very good agreement with the experimental value of 2.47kcal/mol. The exchange repulsion and the charge transfer energy related to the staggered form contribute to the barrier to internal rotation. The change of the charge transfer energy corresponds to the difference of the barrier heights between H3PBH3 and H3SiCH3. The energies of complex formation of F3PBH3 and (CH3)3PBH3 were calculated, to investigate the origin of the barrier to internal rotation.
