Concerning the silicon-germanium bond. The structures of isomeric Ph3E-E'Me3, E = Ge, E' = Si and E = Si, E' = Ge.

Article abstract of DOI:10.1016/0022-328X(90)87051-E

The synthesis and structure of the unknown trimethylgermyltriphenylsilane (I, Ph3SiGeMe3) is reported.The molecular geometry is compared to that of the isomeric Me3SiGePh3 (II) and the related Ph3SiSiMe3 (III) and (η⁵-C5H5)Fe(CO)2SiMe2GePh3 (IV).The Si-Ge bond of I is significantly longer than that for II.We suggest that this is due to expansion of Ge bonding orbitals by the relatively electron-donating methyl groups in conjunction with the contraction of the corresponding orbitals of Si due to the electron-withdrawing phenyl groups.The overall result is a better orbital overlap between the Si and Ge atoms for II.