The Electronic Structures of Hydrides, Halides and Alkyl Compounds of Boron and Aluminum. II. Dimers

Abstract

Abstract The electronic structures of dimers containing boron and aluminum atoms, i. e., B2H6, B2H2-(CH3)4, Al2Cl6, Al2Cl2(CH3)4 and Al2(CH3)6, are investigated by an extended Huckel method. The calculations show that the central linkages are weak and that their bonding natures are very different from those of the bonds between the metals and terminal atoms. Judging from the orbital energies and populations, these dimers still hold a strong acidity, like that in the monomers, an acidity which depends mainly on the existence of the almost unfilled pπ orbitals of the metal atoms, where the electrons occupying the lower vacant orbitals in these dimers are almost localized. The results are compared with other calculations and experimental results. It is, further, shown by examining the electronic structures of two hypothetical compounds that these dimers can be easily formed by using the vacant valence orbitals of the metal atoms, and that the metal-metal bonds in some dimers are considerably strong.