Cyclic Amido Carbenes (amNHCs): A Comparative Electronic Structure Analysis to Distinguish Nucleophilic vs Ambiphilic...

N-Heterocyclic carbenes (NHCs) containing an amide group in the ring are a rare class of cyclic carbenes, but increasingly more examples are being reported. Most of them were designed to participate as electrophiles; however, they exhibit electrophilic as well as nucleophilic characteristics. A comprehensive analysis of the electronic characteristics of the cyclic amido carbenes (amNHCs) has been carried out in this work by using density functional theory (DFT) methods to explore ambiphilicity. The stability parameters (ΔG_S-T, carbene stabilization energy, dimerization energy), the basicity parameter (proton affinity), the nucleophilicity parameters (N, ΔG_AuCl, and TEP), and the electrophilicity parameters (hydride ion affinity, fluoride ion affinity, ω values, and ΔG_B) were estimated to perform comparative analysis. The tendency to exhibit greater nucleophilicity vs electrophilicity can be established using the ΔG_B value estimation. Fine-tuning of the structural features of amNHCs helps in realizing the parameters responsible in identifying ambiphilic amNHCs in relation to those of purely nucleophilic amNHCs.