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

• Published in: Organometallics 2018-06, Vol.37 (12), p.1852-1859
• Main Authors: Hayatifar, Ardalan, Shumaker, F. Alexander, Komanduri, Sangeetha P, Hallenbeck, Sydney A, Rheingold, Arnold L, Weinert, Charles S
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.8b00095

The fluorine-substituted branched oligogermane (Ph3Ge)3GeF was successfully synthesized from (Ph3Ge)3GeH and [Ph3C]­[BF4] after several unfruitful attempts using other synthetic methods and was formed as a mixture with Ph3GeF. Pure (Ph3Ge)3GeF could be obtained from the reaction mixture by successive recrystallizations and was characterized by elemental analysis and NMR (1H, 13C, and 19F) spectroscopy, including a variable-temperature 19F NMR study to investigate the presence or absence of hydrogen bonding in this species. The oligogermane (Ph3Ge)3GeF is indefinitely stable in the solid state under an inert atmosphere, but gradually decomposes to Ph3GeF and other unidentified products in solution. The X-ray crystal structure of (Ph3Ge)3GeF was obtained and represents the only crystallographically characterized germanium–fluorine compound having unsupported Ge–Ge bonds. The Ge4 framework of the oligogermane (Ph3Ge)3GeF is isostructural with the other previously prepared halogen-substituted analogues (Ph3Ge)3GeX (X = Cl, Br, I). The position of the fluorine atom in the structure of (Ph3Ge)3GeF is disordered by displacement of a chlorine atom 39% of the time. The UV/visible spectrum and the cyclic and differential pulse voltammograms of (Ph3Ge)3GeF were obtained, and the relative energies of the frontier orbitals were determined using DFT computations.