MOLECULAR-STRUCTURE OF THIENYLSILOXYGERMATRANES

The molecular structures of siloxygermatranes (R(n)Me(3-n)SiOGe(OCH2CH 2)(3)N, R = 2-thienyl, n = 0-3) were determined by an X-ray diffractio n study. The value of the Si-O-Ge angle increases with the increasing number of acceptor substituents at the silicon. It equals 133.0 degree s for trimethylsiloxygermatrane (I), 134.8 degrees for [dimethyl(2-thi enyl)siloxy]germatrane (II), 139.6 degrees for [methyldi(2-thienyl)sil oxy]germatrane (III) and 180 degrees for [tri(2-thienyl)siloxy]germatr ane (IV). The Ge <-- N bond shortens from 2.156 Angstrom(n = 1) to 2.1 05 Angstrom(n = 3) in this series of germatranes. The structure in the free state of all the siloxygermatranes studied was investigated by t he quantum chemistry molecular orbital method.