Gas-phase electron diffraction studies of the icosahedral carbaboranes, ortho-, meta- and para-C2B10H12

Abstract

The molecular structures of the three closo-carbaboranes, ortho-, meta- and para-C₂B₁₀H₁₂, were experimentally determined using gas-phase electron diffraction (GED). All unique bond distances for ortho and meta carbaboranes were determined experimentally for the first time. For ortho-carbaborane (R_G = 0.046), a model with C_2v symmetry refined to give bond distances of 1.624(8) Å for C–C, 1.093(8) Å for C–H and 1.192(3)–1.196(3) Å for B–H. For meta-carbaborane (R_G = 0.040) a model with C_2v symmetry refined to give a C⋯C distance of 2.575(9) Å. For para-carbaborane (R_G = 0.062) a model with D_5d symmetry refined to give a C–B bond distance of 1.698(3) Å, B(2)–B(3) of 1.785(1), B(2)–B(7) of 1.774(4) and C⋯C of 3.029(5) Å. These GED structures are compared with geometries from other experimental diffraction methods (neutron, X-ray) and ab initio calculations.