A base-coordinated multiply functionalized Ge(II) compound and its reversible dimerization to the corresponding digermene

Stable compounds with Ge=Ge bond are usually prepared under relatively harsh reaction conditions that are incompatible with many functional groups. In particular, unsaturated functionalities are not tolerated due 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), which is obtained by reaction of an isonitrile with a heavier NHC-coordinated vinylidene. Removal of the NHC by a Lewis-acid results in dimerization to give the corresponding digermene with Ge=Ge double bond. The reversibility of this process is demonstrated by addition of two equivalents of NHC to the isolated digermene.