Cyclic Amido Carbenes ( <i>am</i> NHCs): A Comparative Electronic Structure Analysis to Distinguish Nucleophilic vs Ambiphilic <i>am</i> NHCs

<i>N</i>-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 (<i>am</i>NHCs) has been carried out in this work by using density functional theory (DFT) methods to explore ambiphilicity. The stability parameters (Δ<i>G</i>_S-T, carbene stabilization energy, dimerization energy), the basicity parameter (proton affinity), the nucleophilicity parameters (<i>N</i>, Δ<i>G</i>_AuCl, and TEP), and the electrophilicity parameters (hydride ion affinity, fluoride ion affinity, ω values, and Δ<i>G</i>_B) were estimated to perform comparative analysis. The tendency to exhibit greater nucleophilicity vs electrophilicity can be established using the Δ<i>G</i>_B value estimation. Fine-tuning of the structural features of <i>am</i>NHCs helps in realizing the parameters responsible in identifying ambiphilic <i>am</i>NHCs in relation to those of purely nucleophilic <i>am</i>NHCs.