Complexation energies of H3BXH n and [H3BXH n - 1]- complexes (X = N, O, F, P, S, and Cl) (n = 3, 2, 1) have been computed at the G-2 level of theory. The formation of H3BXH3 (X = N, P) is found to be more favored than the formations of H3BXH2 (X = O, S) and H3BXH (X = F, Cl). The qualitative features of the molecular orbital interaction (the correlation diagrams) of H3BNH3 (C 3 v symmetry group), H3BOH2 (C s symmetry group), and H3BFH (C s symmetry group) complexes are presented. These diagrams show that the σ character of the B−X bond decreases and the π character increases when the electronegativity of X increases and indicate that the B−X bond cannot be treated only in terms of the simplest model of the HOMO−LUMO interaction (i.e., a two-level and two-electron model system). Two linear correlations were established and discussed. The first one was between proton affinities of the Lewis bases L (L = XH n and [XH n - 1]-, n = 3, 2, 1) and complexation energies of the H3BL compounds calculated at the G-2 level of theory. The second correlation was between the 11B NMR coupling constant 1 J B - H and the complexation energies of H3BL (L = OH-, PH2 - , SH-, Cl-, NH3, and PH3).

The structural parameters, nature of the bonding, and stability of H 3 YBX 3 (X ) H, F, and Cl; Y ) N, P) complexes have been studied at the G2(MP2) level of theory. G2(MP2) results show that the ammonia complexes are more stable than the corresponding phosphine complexes. This stability varies in the same order as the acidity of BX 3 Lewis acids. The NBO partitioning scheme shows that there is a stronger charge transfer from PH 3 to BX 3 than from NH 3 . It proves also that the shortening of the P-H bond length upon complexation is due to an increasing "s" character in this bond.

Analysis of the global and local electrophilicity/nucleophilicity indices allows correct explanation of the behaviors of the copper(i) catalyzed 32CA reaction.

[H3AlXH3]- (X = C, Si, and Ge) and H3AlYH3 (Y = N, P, and As) have been investigated as donor−acceptor complex types at the G2(MP2) level of theory. Both staggered and eclipsed conformations have been examined. For all complexes, the first one is found to be favored. The G2(MP2) results show that the anionic complexes are more stable than the neutral ones. They show also that this stability decreases when going from carbon to germanium for [H3AlXH3]- complexes and from nitrogen to arsenic for H3AlYH3 complexes. The interaction diagrams prove that the evolution of complexation energy depends on the coordination mode. In fact, this is a simple “HOMO−LUMO” interaction for [H3AlXH3]- anionic complexes, while for the H3AlYH3 neutral ones it is a result of two interaction types:  interaction between “a1” symmetry fragments orbital (stabilizing) and interactions between “e” symmetry fragments orbital (destabilizing). A linear relationship has been established and discussed between the G2(MP2) complexation energy and the ligand G2(MP2) proton affinity, whereas no correlation has been found with the charge transfer.