Comparison of pi-Bond Strengths in M-E (M = B, Al, Ga; E = O, N, S) Compounds. Ab Initio Calculation of Rotational Barriers.
Results of ab initio calculations of the electronic structure of compounds of the type R(2)MER'(x) and R(2)MEMR'(2) with R = H, Me, M = Al, Ga, and E = O, N, S are reported at the Hartree-Fock level with split-valence, polarization basis sets for all atoms except hydrogen where a split-valence basis set is used. Full optimizations for the equilibrium geometry and partial optimization at constrained rotational transition states have been performed to evaluate the barriers to rotation as a measure of the pi interactions in these compounds. We conclude that, although important for determining the final conformational equilibrium geometries, pi interactions are weak in these compounds as the rotational barriers are smaller than that for ethylene by 1 or 2 orders of magnitude.
Fink
William H.
WH
Department of Chemistry, University of California, Davis, California 95616.
Power
Philip P.
PP
Allen
Thomas L.
TL