Approximate localised orbitals for some boron compounds

Abstract

Approximate localised molecular orbitals have been calculated for B₂H₆, B₄H₁₀, B₅H₉, B₁₀H₁₄, and for an octahedron and an icosahedron of boron atoms. The localised molecular orbitals were calculated from ‘Extended Hückel’ type delocalised molecular orbitals by maximising the electron population of the molecular orbitals in regions chosen by symmetry and chemical criteria. The localised molecular orbitals can be divided into two groups. Those of one group bond boron atoms to hydrogen atoms or other external groups, correspond closely to two-centre terminal bonds and three-centre B ⋯ H ⋯ B bridge bonds, and are strongly transferable. Those of the other group bond together the atoms of the boron frameworks and are not as strongly localised. However, if additional approximations are made, some can be described as three-, four- or five-centre molecular orbitals which show varying degrees of transferability.