A Multiply Functionalized Base-Coordinated GeII Compound and Its Reversible Dimerization to the Digermene

Stable compounds with a GeGe bond are usually prepared under relatively harsh reaction conditions that are incompatible with many functional groups. In particular, unsaturated functionalities are not tolerated owing to their facile reaction with low-coordinate germanium compounds. We now report the synthesis of an imino-functionalized germanium(II) species, stabilized by coordination of an N-heterocyclic carbene (NHC), by reaction of an isonitrile with a heavier NHC-coordinated vinylidene. Removal of the NHC by a Lewis acid results in dimerization to the corresponding digermene with a GeGe bond. The reversibility of this process is demonstrated by addition of two equivalents of NHC to the isolated digermene.