Hybrid density functional theory study of low reactivity of imidazol-2-ylidine toward insertion and addition reactions

Abstract

A hybrid functional theory study was performed with the target being to evaluate reasons for the exceptional stability of imidazol-2-ylidine. Computed structural properties for this carbene were compared with its chlorinated analog, as well as with unsaturated analogues for both of these carbenes. The aromaticity was evaluated through the enthalpy of hydrogenation of the carbenes and their reactivity through activation barriers for the hydrogen insertion and ethylene addition reactions. Activation barriers for saturated carbenes were compared with the activation barriers for unsaturated carbenes to assess their aromatic character and the influence of electron-withdrawing substituents on their reactivity.