Syntheses, Structures, and Electronic Properties of the Branched Oligogermanes (Ph₃Ge)₃GeH and (Ph₃Ge)₃GeX (X = Cl, Br, I)

The branched oligogermanium hydride (Ph₃Ge)₃GeH was synthesized via a hydrogermolysis reaction from GeH₄ and Ph₃GeNMe₂ and was converted to the halide series of compounds (Ph₃Ge)₃GeX (X = Cl, Br, I) upon reaction with [Ph₃C][PF₆] in CH₂X₂ solvent (X = Cl, Br, I). These species were fully characterized by NMR (¹H and ¹³C) and UV/visible spectroscopy, cyclic voltammetry, and elemental analysis. In addition, (Ph₃Ge)₃GeH was analyzed by ⁷³Ge NMR spectroscopy and exhibits two resonances at δ −56 and −311 ppm. A Ge−H coupling constant of 191 Hz was observed in the proton-coupled ⁷³Ge NMR spectrum of (Ph₃Ge)₃GeH. The X-ray crystal structures of (Ph₃Ge)₃GeH and (Ph₃Ge)₃GeX (X = Cl, Br, I) were obtained and represent the first examples of branched oligogermane hydrides or halides to be characterized in this fashion. The Ge−Ge bond distances in (Ph₃Ge)₃GeH are short (average value 2.4310(5) Å), while those in the halide compounds (Ph₃Ge)₃GeX are similar to one another and range from 2.4626(7) to 2.4699(5) Å. The UV/visible and cyclic voltammetry data for these species have been correlated with DFT computations, and excellent agreement was found between the experimental and theoretical data.