Synthesis and characterization of chiral germanium compounds for asymmetric hydrogermylation of organic compounds

Abstract

Oligogermanes have long been studied and analyzed due to their innate ability to undergo o-delocalization along the Ge-Ge backbone. Due to this property, oligogermanes can exhibit unique optical and electrical properties, along with a tunable band gap that is dependent on their size, structure, and substituents. The focus of this dissertation will be around the synthesis of a new class of trigermanes and tetragermanes.

The trigermanes ButMe2GeGePh2GeMe2But and PhMe2GeGePh2GeMe2Ph and the tetragermanes Et3Ge(GePh2)2GeEt3 and Bun3Ge(GePh2)2GeBun3 were synthesized via the hydrogermolysis reaction. These species were characterized by UV/visible spectroscopy, cyclic voltammetry, and differential pulse voltammetry. The properties of the two trigermanes were also compared with those of Bun3GeGePh2GeBun3, and the UV/visible absorption maxima of these three trigermanes fall in the narrow range of 246 - 249 nm while their oxidation potentials differ by 233 mV. Both ButMe2GeGePh2GeMe2But and Bun3GeGePh2GeBun3 exhibit two irreversible oxidation waves in their CVs and DPVs. Similarly, the absorption maxima for the two tetragermanes are similar and their oxidation potentials differ by only 58 mV. The CV and DPV of Et3Ge(GePh2)2GeEt3 exhibits three irreversible oxidation waves while that of Bun3Ge(GePh2)2GeBun3 contains only one. This dissertation will focus on gaining an understanding of the electronic properties, stability, and decomposition of these oligogermane catenates when oxidized using cyclic and differential pulse voltammetry studies.

This dissertation will also focus on synthesizing and characterizing germanium aryloxide compounds for hydrogermylation applications. Through the use of chiral auxiliaries and polyfunctional phenols, a germanium (II) and germanium (IV) species can be readily synthesized. The addition of a halide and an organic substituent can be added via an oxidative addition to the germanium (II) center, followed by a reduction to form a germanium hydride species. For the germanium (IV) center, a C2-symmetric chiral germanium halide species can be formed readily, followed by a reduction to form a chiral germanium hydride for hydrogenation of other compounds. Further functionality studies on the chiral germanium (IV) species have been performed as this compound readily undergoes the formation of a chiral germylium species when introduced to AlCl3. Such germylium species are rare, and with the use of a chiral auxiliary ligand, this compound to the best of our knowledge has yet to be reported.