Compounds of Group 14 Elements with an Element–Element (E = Si, Ge, Sn) Bond: Effect of the Nature of the Element Atom

Two series of germanium compounds,
(p-Tol)3Ge-MMe3 (M = Si (1), Ge (2), Sn (3)) and (Me3Si)3Ge-MPh3 (M = Ge (4),
Sn (5)), were prepared
using lithium or potassium intermediates. The changing of the reaction
conditions results in trigermane Ph3Ge-Ge­(SiMe3)2-GePh3 (6). The molecular structures
of 1, 2, and 6 were investigated
by X-ray analysis. By UV/visible spectroscopy it is established that
introduction of a tin atom results in a significant bathochromic absorption
shift. Furthermore, according to cyclic voltammetry, oxidation potentials
decrease in the order 1 > 2 > 3. The electronic structures of 1–4 and related (Me3Si)3Ge-SiPh3 were
investigated by DFT calculations. Fluorescence properties of 1–3 were studied in the solid state and
in solution; for compound 3 phosphorescence (lifetime
is 4.58 ms) is observed in the solid state.