Synthetic, structural, and physical investigations of the large linear and branched oligogermanes Ph _3GeGePh _2GePh _2GePh _2H, Ge _5Ph _(12), and (Ph _3Ge) _4Ge

摘要

The syntheses of two linear oligogermanes, Ph _3GeGePh _2GePh _2GePh _2H and Ge _5Ph _(12), were achieved using a hydrogermolysis reaction starting with HPh _2GeGePh _2GePh _2H. The preparation of the hydride-terminated tetragermane indicates that selectivity is possible using the hydrogermolysis reaction, which had not been observed previously. The structures of both of these compounds were determined, and they were also characterized by UV/visible spectroscopy and electrochemical methods (CV and DPV). The pentagermane Ge _5Ph _(12) exhibits four irreversible oxidation waves in both its CV and DPV, as was observed for other aryl-substituted oligogermanes. The successful synthesis of the neopentane analogue (Ph _3Ge) _4Ge was also achieved by starting from GeH _4 and Ph _3GeCH _2CN. This material was structurally characterized; the structure of (Ph _3Ge) _4Ge is highly sterically congested and contains long Ge-Ge single-bond distances that average 2.497(6) ? and exhibits an nearly idealized tetrahedral geometry at the central germanium atom with an average Ge-Ge-Ge bond angle of 109.49(2)°. The UV/visible spectrum of (Ph _3Ge) _4Ge exhibits a broad absorbance maximum centered at 250 nm, and DFT calculations indicate that this compound has a stabilized HOMO at -6.223 eV and a large HOMO-LUMO gap relative to those in other branched oligogermanes.