73Ge NMR Spectral Investigations of Singly Bonded Oligogermanes

The synthesis of the two digermanes (Bu3GeGePh3)-Ge-s and PhMe2GeGePh3, as well as the branched tetragermane PhGe(GeBu3n)(3), was achieved using the hydrogermnolysis reaction. These species were fully characterized by NMR (H-1, C-13) spectroscopy and elemental analysis, and the crystal structure of PhMe2GeGePh3 was determined. These three species, along with I I other oligogermanes, were also characterized by Ge-73 NMR spectroscopy. Chemical shifts of the Ge-73 NMR resonances for these oligogermanes have been correlated with the substitution pattern at germanium and also with the number of germanium-germanium bonds at the individual Ge centers. Germanium centers having only one attached germanium atom result in resonances appearing in the range delta -30 to -65 ppm, while those having two or three bonded germanium atoms exhibit resonances in the respective ranges delta -100 to -120 and delta -195 to -210 ppm. Chemical shifts of resonances for germanium centers bearing phenyl substituents appear upfield from those having alkyl substituents.