An ab initio valence bond (VB) calculation of the π delocalization energy in borazine, B₃N₃H₆

Valence bond (VB) calculations using a double‐zeta D95 basis set have been performed for borazine, B 3 N 3 H 6 and for benzene, C 6 H 6 in order to determine the relative weights of individual standard Lewis structures. In the delocalized resonance scheme of borazine, the structure ( I ) with no double bonds and three lone pairs of electrons at the three nitrogen atoms is the major contributor with a structural weight of 0.17, followed by six equivalent Lewis structures with one double bond and two lone pairs at two nitrogen atoms ( II ) with weights of 0.08 each. In the case of benzene, the two Kekulé structures ( III ) contribute with structural weights of 0.15 each, followed by 12 equivalent ionic structures ( IV ) with weights of 0.03 each, followed by the three equivalent Dewar‐type structures ( V ) with structural weights of 0.02 each. The values of 54.1 and 45.8 kcal mol −1 for the delocalization energies of borazine and benzene were estimated. Therefore, B 3 N 3 H 6 is calculated to have substantial aromatic character, similar to benzene, when we assume that the resonance energy can provide a criterion for aromaticity.