Structural, spectral, and electrochemical investigations of para-tolyl-substituted oligogermanes

The synthesis of four new oligogermanes containing para-tolyl-substituents has been achieved via the hydrogermolysis reaction, including the digermane Tol3GeGePh3, the trigermanes Tol3GeGePh2GeTol3 and Tol3GeGeTol2GeTol3, and the tetragermane Tol3GeGePh2GePh2GeTol3 (Tol = p-CH3C6H4). These four oligogermanes have been structurally characterized and their structures have been compared with those of their per-phenyl-substituted analogs. The digermane Tol3GeGePh3 exhibits an unusually short Ge–Ge bond distance of 2.408(1) Å. The four para-tolyl-substituted oligogermanes have also been characterized by UV/visible spectroscopy and cyclic voltammetry. The expected red shift in the absorbance maximum with increasing catenation was observed for this series of compounds. Their cyclic voltammograms each contain n − 1 irreversible oxidation waves (n = the number of Ge atoms), which is atypical since oligogermanes generally exhibit only one irreversible oxidation wave regardless of the degree of catenation.