The molecular structures of the gaseous dimeric molecules Me ₂ Ga(µ-H) ₂ GaMe ₂ and Me ₂ Ga(µ-Cl) ₂ GaMe ₂ as determined by electron diffraction

The structures of gaseous dimethylgallane and dimethylgallium chloride have been determined by electron diffraction. The results indicate that the predominant vapour species at low pressures and temperatures of 290–350 K are dimeric molecules with diborane-like structures, Me2Ga(µ-X)2GaMe2(where X = H or Cl), with heavy-atom skeletons conforming to D2h symmetry. Salient structural parameters in the ra structures are: (i) for [Me2GaH]2, r(Ga ⋯ Ga) 261.0(0.5), r(Ga–C) 195.4(0.4), and r(Ga–Hb) 170.8(1.4) pm; Ga–Hb–Ga 99.6(1.4) and C–Ga–C 123.2(1.5)°; (ii) for [Me2GaCl]2, r(Ga ⋯ Ga) 330.3(1.9), r(Ga–C) 194.6(0.3), and r(Ga–Clb) 237.8(0.4) pm; Ga–Clb–Ga 88.0(0.9) and C–Ga–C 132.1 (2.7)°(‘b’ denotes a bridging atom). Dimethylgallane thus represents the first gallium hydride containing a Ga(µ-H)2Ga bridging unit to be characterised structurally; it is notable for the shortness of the Ga[graphic omitted]Ga distance. The two molecules invite structural comparisons with related systems like [Me2EH]2(E = B or Al), [Me2AlCl]2, and Ga2Cl6.