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 D_2d 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.