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RESEARCH PRODUCT

Stability of Borane−Adduct Complexes:  A G-2 Molecular Orbital Study

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Complexation energies of H3BXHn and [H3BXHn-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 (C3v symmetry group), H3BOH2 (Cs symmetry group), and H3BFH (Cs 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 = XHn and [XHn-1]-, n = 3, 2, 1) and complexation energies of the H3BL compounds calculated at the G-2 level of th...