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.

含Ge=Ge键的稳定化合物通常需在相对严苛的反应条件下制备，此类条件与诸多官能团不相兼容。尤为关键的是，不饱和官能团无法耐受该类反应环境，因其易与低配位锗化合物发生反应。本研究报道了一种经氮杂环卡宾（N-heterocyclic carbene, NHC）配位稳定的亚氨基官能化锗(II)物种：该物种可通过异氰化物与经氮杂环卡宾配位的重亚乙烯基反应制得。通过路易斯酸（Lewis-acid）移除配位的NHC后，该物种会发生二聚反应，生成对应含Ge=Ge双键的二锗烯。向分离得到的二锗烯中加入两当量的NHC，即可证明该过程具有可逆性。