Zinc substituted carbenes: synthesis, structure, and ambiphilic reactivity

Abstract

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)P [L = [(ArNCMe)₂CH]⁻, P = (DippNCH₂)₂P, Ar = Dipp or Mes, Dipp = 2,6-ⁱPr₂C₆H₃, Mes = 2,4,6-Me₃C₆H₂] generates Zn(II)-substituted carbenes LZnCP with concomitant N₂ release. The Zn–C–P 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 LZnCP with CO₂ selectively affords zincated ketene via nucleophilic attack and tandem CO 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.