On the Significance of Lone Pair/Lone Pair and Lone Pair/Bond PairRepulsions in the Cation Affinity and Lewis Acid/Lewis BaseInteractions

摘要

Interaction of H2O, H2S, H2Se, NH3, PH3, and AsH3 with cations H+, CH3+,Cu+, Al+, Li+, Na+, and K+ was studied from the energetic and structural viewpoint usingB3LYP/6-311++G(d,p) method. The charge transfer from the Lewis bases to the cationsreduces lone pair/lone pair (LP/LP) repulsion in H2O, H2S, and H2Se and LP/bond pair(LP/BP) repulsion in NH3, PH3, and AsH3. In parallel, changes in the H?M?H angles (M= O, S, Se, N, P, and As) are observed. The change in the H?M?H angle during theinteractions was proportional to the amount of charge transferred from the bases to thecations and electron density (ρ) at the molecule/cation bond critical point. Also, theopposite trend for proton affinities of these two families, that is, NH3 > PH3 > AsH3 andH2O < H2S < H2Se, was interpreted on the basis of LP/BP repulsion in their neutral andprotonated forms. Interaction of the Lewis bases with neutral Lewis acids including BeH2,BeF2, and BH3 was studied energetically and structurally. The calculated energies forinteractions of H2O and NH3 with BeH2, BeF2, and BH3 are larger than the correspondingvalues for H2S, H2Se, PH3, and AsH3. This difference was interpreted on the basis of thelower stability of H2O and NH3 because of large LP/LP and LP/BP repulsion in H2O and LP/BP repulsion in NH3.