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The wave functions, level energies and Mulliken population analysis of localized molecular orbitals (LMO’s) for B4Cl4, 1,5-C2B3H5 and the closo-BnHn2- (n = 6-10, 12) are calculated by using the Edmiston-Reudenberg energy localization scheme under the CNDO/2 approximation in order to reveal the nature of quasi-aromaticity of the closo-BnHn2- (n > 5). It has been found that all the B-H or B-Cl LMO’s are highly localized between the B and H (or Cl) atoms, corresponding to B-H or B-Cl o-bond, while the Bn framework bonding is formed mainly by the three-centered two-electron B-B-B bonds on the polyhedral faces. In the cases of B4Cl4 and 1,5-C2B3H5, these three-centered B-B-B bonds just fill their polyhedral faces; however, for the framework bonding of the closo-BnHn2- (n > 5), the valence electron deficiency leads to the delocalization of their three-centered B-B-B bonds, and as delocalizability of this three-centered B-B-B bond increases, some three-centered B-B-B bonds are further delocalized to become a f
The wave functions, level energies and Mulliken population analysis of localized molecular orbitals (LMO’s) for B4Cl4, 1,5-C2B3H5 and the closo-BnHn2- (n = 6-10, 12) are calculated by using the Edmiston-Reudenberg energy localization scheme under the CNDO / 2 approximation in order to reveal the nature of quasi-aromaticity of the closo-BnHn2- (n> 5). It has been found that all the BH or B-Cl LMO’s are highly localized between the B and H (or Cl) atoms, corresponding to BH or B-Cl o-bond, while the Bn framework bonding is formed mainly by the three-centered two-electron BBB bonds on the polyhedral faces. In the cases of B4Cl4 and 1,5- C2B3H5, these three-centered BBB bonds just fill their polyhedral faces; however, for the framework bonding of the closo-BnHn2- (n> 5), the valence electron deficiency leads to the delocalization of their three-centered BBB bonds, and as delocalizability of this three-centered BBB bond increases, some three-centered BBB bonds are further delocal ized to become a f