Electronic structure of boron hydrides. Ab initio study of B10H14, B10H 2–14, and B10H 2–12

Abstract

All electron ab initio SCF-MO calculations of B₁₀H₁₄, B₁₀H^2–₁₄ and B₁₀H^2–₁₂ are described. B₁₀H₁₄ in the 4620 topology is predicted to be 59 kcal mol^–1 more stable than in the two-bridge (2802) topology, while the two-bridge(2632) topology of B₁₀H^2–₁₄ is predicted to be 134 kcal mol^–1 more stable than the four-bridge (4450) topology. The calculated wavefunction for B₁₀H₁₄ is used to make a tentative assignment of the He(I) and He(II) p.e. spectra. An analysis of the multi-centre bonding in these electron deficient species is made using electron density difference maps, and by transforming the delocalised molecular orbitals to localised orbitals, using the methods due to Boys, and Magnasco and Perico. The preference of localisation criteria for valence structures with fractional three-centre framework bonds over those containing open three-centre bonds is demonstrated using the latter transform. Energy localised orbitals are generated from semi-empirical INDO wavefunctions, and it is found that all three localisation criteria favour the fractional three-centre bond description in each molecule.