Theoretical study of the electronic structure of the diboron and tetraboron tetrahalides

Abstract

The electronic structures of B2F4, B2Cl4, B4F4 and B4Cl4 are discussed using the results of all electron ab initio SCF–MO calculations in bases of Gaussian type functions. The diboron tetrahalides are predicted to have a staggered D2d configuration, with a barrier to rotation of 1.48 kcal/mol for B2Cl4 and 0.39 kcal/mol for B2F4. The calculated wavefunctions from both minimal and extended basis set calculations are used to interpret the low energy photoelectron spectrum of B4Cl4. The bonding in these molecules is analysed by electron density difference maps and by transforming the valence SCF–MOs to localized orbitals using the method due to Boys. Reasons for the observed stability of B4Cl4 and presumed instability of B4F4 are discussed.