Zinc substituted carbenes: synthesis, structure, and ambiphilic reactivity

Metal-substituted carbenes are fundamentally important as they represent the limiting configurations of metal carbynes. However, structurally characterized examples are still rare, and their reactivity remains underexplored. Herein, we report the first synthesis, characterization, and reactivity studies of zinc-substituted carbenes. UV irradiation of zinc diazoalkyl complexes LZnC(N₂)<i>P</i> [L = [(ArNCMe)₂CH]^-, <i>P</i> = (DippNCH₂)₂P, Ar = Dipp or Mes, Dipp = 2,6- ^<i>i</i> Pr₂C₆H₃, Mes = 2,4,6-Me₃C₆H₂] generates Zn(ii)-substituted carbenes LZnC<i>P</i> with concomitant N₂ release. The Zn-C-<i>P</i> moiety features nearly linear carbene centers, deviating from conventional carbene geometry. Computational studies indicate a singlet ground state stabilized through synergistic effects of C-P π-interaction and carbene lone-pair delocalization towards the Zn center. Treatment of LZnC<i>P</i> with CO₂ selectively affords zincated ketene <i>via</i> nucleophilic attack and tandem C[double bond, length as m-dash]O double bond cleavage. It reacts with 4-dimethylaminopyridine to form a carbene-Lewis base adduct exhibiting electrophilic reactivity. Furthermore, zinc-substituted carbenes enable direct transition metals coordination to give the heterobimetallic Zn/M (M = Ag⁺, Au⁺, Ni) μ-carbyne complexes.