Absorption, electrochemical, theoretical, and 73Ge NMR spectral characterization of the germanium neo-pentane analogue (Me3Ge)4Ge

The germanium-based neo-pentane analogue (Me3Ge)4Ge has been characterized by UV/visible spectroscopy, cyclic voltammetry, and 73Ge NMR spectroscopy as well as by density functional theory (DFT) calculations. The absorption maximum for (Me3Ge)4Ge is blue-shifted relative to those for other related branched oligogermanes (Ph3Ge)3GeH and (Ph3Ge)3GePh, and this species is also the most difficult to oxidize among these three compounds. DFT calculations indicate the HOMO of (Me3Ge)4Ge is stabilized relative to those for both tetragermanes by ca. 0.5 eV and therefore the theoretical and experimental results are in agreement. The 73Ge NMR spectrum of (Me3Ge)4Ge exhibits two resonances and the feature corresponding to the central formally zero-valent germanium atom is shifted far upfield and was observed at δ −339 ppm.