Steric and electronic effects on Si-Ge bond lengths: An experimental and theoretical structural study of Me2Ge(SiCl3)(2) and Me3GeSiCl3

摘要

The molecular structures of dimethylbis(trichlorosilyl)germane [Me2Ge(SiCl3)(2)] and trimethyl(trichlorosilyl) germane (Me3GeSiCl3) have been determined in the gas phase. Me3GeSiCl3 was found ab initio to possess C-3v symmetry, with a low-lying torsional motion of the SiCl3 group relative to the GeMe3 group. The gas electron diffraction data were modelled with C-3 symmetry, although little deviation from C-3v symmetry was observed. Me2Ge(SiCl3)(2) (C-2v symmetry) was also found to have a very low-lying vibrational frequency relating to the rotation of the SiCl3 groups. This led to the gas electron diffraction data being modelled in C-2 symmetry, with the observed combined deviation of the SiCl3 groups being 14 degrees from the eclipsed structure calculated ab initio. The Ge-C bond lengths were unaffected by the addition of an extra SiCl3 group to the central germanium atom, but the Ge-Si bond lengths were observed to increase by over 1 pm. (c) 2006 Elsevier B.V. All rights reserved.