Molecular structure of tetramethoxygermane, Ge(OCH3)(4), determined by gas-phase electron diffraction and ab initio molecular orbital calculations

The structure of tetramethoxygermane, Ge(OCH3)(4), has been determined by g as-phase electron diffraction (GED) and ab initio molecular orbital calcula tions. Two distinct conformational geometries are feasible for this molecul e, one having S-4 symmetry and the other D-2d symmetry. The S-4 conformer w as calculated to be about 3 kcal mol(-1) lower in energy than the D-2d conf ormer. Refinements, based upon a dynamic model with S-4 symmetry, gave a sa tisfactory fit to the experimental data. Results for the principal distance s (r(g)) and angles angle(alpha) from the combined GED/ab initio, with esti mated 2 sigma uncertainties are: r(Ge-O) = 1.743(3), r(C-O) = 1.413(5), r(C -H)(ave) = 1.075(13)Angstrom; angle O2GeO7 = 110.1(19), angle GeOC = 122.7( 8), angle OCHave = 109.9(24), Phi(C3O2GeO7) = 72 degrees (ab initio), Phi(H 6C3O2Ge) = 176 degrees (ab initio). (C) 2000 Elsevier Science B.V. All righ ts reserved.