Isolation of Transient Acyclic Germanium(I) Radicals Stabilized by Cyclic Alkyl(amino) Carbenes

Despite
the notable progress in the stabilization of main group
radicals by NHCs and cAACs, no germanium radicals have been isolated
so far due to synthetic challenges. Stabilization of neutral [:EIR]• (E = Si, Ge) radicals is an uphill task,
as these reactive transient species are highly susceptible to dimerization.
Herein, we report the synthesis of acyclic neutral germanium­(I) radicals
Cy-cAAC:GeN­(SiMe3)­Dip (1) and Me-cAAC:GeN­(SiPh3)­Mes (2) obtained by the reduction of [Ar­(SiR3)­NGeCl3] with KC8 in the presence of
cAAC. Compounds 1 and 2 are well characterized
by single crystal X-ray structural analysis, cyclic voltammetry, and
EPR spectroscopy. Furthermore, the structure and bonding of compounds 1 and 2 have been investigated by theoretical
methods.