The molecular structure of hexaborane(12) in the gas phase as determined by electron diffraction

Abstract

The structure of gaseous arachno-B₆H₁₂, the only simple binary borane for which crystallographic data are not available, has been determined by electron diffraction. The analysis showed unequivocally that the molecule has C₂ symmetry, with two BH₂ terminal groups, four other terminal hydrogen atoms, and four bridging hydrogen atoms, two of which are asymmetric. Models with C_i or C_s symmetries gave unsatisfactory R factors, and were rejected. The boron framework is a chiral six-atom fragment of a closed triangular dodecahedron from which two adjacent five-connected vertices have been removed. The results establish a clear structural relationship between the three arachno boranes B₄H₁₀, B₅H₁₁, and B₆H₁₂.