Synthesis and reactivity of copper carbyne anion complexes

Carbyne anions (R-C-) are one of the least explored and most poorly understood subvalent carbon species and, so far, have only been observed in the gas phase. In this study, we report the synthesis and isolation of copper phosphinocarbyne anion complexes. The combination of a pi-donor substituent and an electropositive transition metal enables the isolation of copper carbyne anion complexes at room temperature. The electronic structure of the isolated copper phosphinocarbyne anion complexes was probed using density functional theory calculations. These calculations reveal the dominance of ionic interactions between the copper and carbon atoms and the singlet ground state of the phosphinocarbyne anion, featuring a planar phosphorus atom and a short phosphorus-carbon bond. These complexes exhibit the reactivity of a carbyne anion, as demonstrated through the synthetic transformations to form silyl- and germanyl-substituted carbenes, diazaphospholidinyl-substituted alkenes and ethenimines. Carbyne anions are under explored and poorly understood, owing to their isolation being unknown. Now, the synthesis and isolation of copper phosphinocarbyne anion complexes are reported. Displaying the reactivity of a carbyne anion, these complexes provide access to singlet carbenes, alkenes and ethenimines.