Synthesis of the Elusive Branched Fluoro-oligogermane (Ph₃Ge)₃GeF: A Structural, Spectroscopic, Electrochemical, and Computational Study

Abstract

The fluorine-substituted branched oligogermane (Ph 3 Ge) 3 GeF was successfully synthesized from (Ph 3 Ge) 3 GeH and [Ph 3 C][BF 4 ] after several unfruitful attempts using other synthetic methods and was formed as a mixture with Ph 3 GeF. Pure (Ph 3 Ge) 3 GeF could be obtained from the reaction mixture by successive recrystallizations and was characterized by elemental analysis and NMR ( 1 H, 13 C, and 19 F) spectroscopy, including a variable-temperature 19 F NMR study to investigate the presence or absence of hydrogen bonding in this species. The oligogermane (Ph 3 Ge) 3 GeF is indefinitely stable in the solid state under an inert atmosphere, but gradually decomposes to Ph 3 GeF and other unidentified products in solution. The X-ray crystal structure of (Ph 3 Ge) 3 GeF was obtained and represents the only crystallographically characterized germanium−fluorine compound having unsupported Ge−Ge bonds. The Ge 4 framework of the oligogermane (Ph 3 Ge) 3 GeF is isostructural with the other previously prepared halogen-substituted analogues (Ph 3 Ge) 3 GeX (X = Cl, Br, I). The position of the fluorine atom in the structure of (Ph 3 Ge) 3 GeF is disordered by displacement of a chlorine atom 39% of the time. The UV/visible spectrum and the cyclic and differential pulse voltammograms of (Ph 3 Ge) 3 GeF were obtained, and the relative energies of the frontier orbitals were determined using DFT computations.

Substituent Control of σ-interference Effects in the Transmission of Saturated Molecules

“…Although alkyl and phenyl substituents are quite benign from a chemical point of view, they are particularly promising because they are realistic synthetical targets for silicon and germanium based molecular cores. [49][50][51][52][53][54][55][56][57] We hope these results will motivate studies of the properties of substituted cyclic and bicyclic silanes and germanes. The transmission suppression is less clear in the C222 systems than for the silanes and germanes.…”

Substituent Control of σ-Interference Effects in the Transmission of Saturated Molecules

“…Carbon-based substituents thus seem particularly promising for fine-tuning the insulating properties of Si222 and Ge222 systems. Although alkyl and phenyl substituents are quite benign from a chemical point of view, they are particularly promising because they are realistic synthetic targets for silicon- and germanium-based molecular cores. − We hope these results will motivate studies of the properties of substituted cyclic and bicyclic silanes and germanes.…”