Diborane as a molecular complex was studied by using a double zeta ab initio MO method and energy decomposition analyses. For diborane, a qualitatively major contribution of HOMO-LUMO transfers was reported by Yamabe et al. on the basis of configuration analyses by using a single zeta basis set. However, no quantitative work on the origin on the complex formation has been reported. In this note, we show that the charge transfer energy is the dominant contributor to the complex formation (2BH3→B2H6). The charge transfer energy and the exchange repulsion are analyzed at the molecular orbital (MO) levels.
