Molecular structure of 1,10-dicarba-closo-decaborane(10), 1,10-C2B8H10, by gas-phase electron diffraction

The molecular structure of the title compound has been determined by gas-phase electron diffraction, assuming that the C₂B₈ unit has the form of a bicapped square antiprism (D_4d symmetry). The amplitudes of vibration and the shrinkage corrections were calculated from the force field transferred mainly from 1,6-C₂B₄H₆. The molecular parameters (r_g, φ_α) and uncertainties (3σ) are: B-C = 1.602(2), B2-B3 (basal) = 1.850(5), B2-B6 (equatorial) = 1.829(4), B-H = 1.164(14), C-H = 1.14(2) and ∠C-B-H = 117.5(1.8)°. Comparisons are made with structural data for other carboranes studied in the gas phase.