Crystalline monometal-substituted free carbenes

Summary

The rich chemistry of transition-metal (TM) carbyne complexes has fueled their application in a wide range of fields, from synthetic chemistry to materials science. The isomeric forms of these complexes are monometal-substituted carbenes and have so far been detected only in the gas phase. In this article, we describe the synthesis of crystalline monometal-substituted free carbenes. To isolate these molecules, we selected a bulky π-donor substituent and a closed-shell electron-rich TM center as the substituents around the carbene center. This combination allows these metallocarbenes to exhibit a nucleophilic carbenic character with a high-lying highest occupied molecular orbital (HOMO) arising from the metal substituent. Additionally, we report a formal rearrangement of the metallocarbene to a zwitterionic species containing a carbyne anion, which makes these free compounds not only synthetic astonishments but also attractive for the development of novel subvalent carbon-transfer reactions.