Electronic structure of heteroboranes derived from the icosahedral skeleton. UV photoelectron and MNDO study

Abstract

The HeI photoelectron spectra of the 12-vertex closo-1-SB 11H 11, 11-vertex nido-7-SB 10H 12 and nido-7,8,10-C 2SB 8H 10, 10-vertex arachno-6,9-CSB 8H 12 and nine-vertex arachno-4-CB 8H 14 and arachno-4,6-C 2B 7H 13 species are reported. The highest symmetry 1-thia closo species has the simplest spectrum: The five well-resolved band systems are assigned to F(surface), D(surface + BH), F(surface), P(BH) and F(BH) orbitals in the limit of spherical symmetry. The decrease of the symmetry in the open-face systems manifests itself in a greater complexity of photoelectron spectra and in the decrease of the first ionization energy by approximately 1 eV, due to the appearance of a new well-resolved band, The HOMO has a cluster surface bonding character in the open face systems. Going from closo to arachno clusters the contribution of hydrogen s functions in HOMO increases. For the arachno species a large H 1 s contribution is found in low energy valence orbitals.