Mesoionic and <i>N</i>‐Heterocyclic Carbenes Coordinated N⁺ Center: Experimental and Computational Analysis

Abstract

Abstract N ‐Heterocyclic carbenes, carbocyclic carbenes, remote N ‐heterocyclic carbenes and N ‐heterocyclic silylenes are known to form L→N + coordination bonds. However, mesoionic carbenes (MICs) are not reported to form coordination bonds with cationic nitrogen. Herein, synthesis and quantum chemical studies were performed on 1,2,3‐triazol‐5‐ylidene stabilized N + center. Six compounds with MIC→N + ←NHC were synthesized. Density functional theory calculations and energy decomposition analysis were carried out to explore the bonding situation between MIC and N + center. The C→N + bond lengths were in the range of 1.295–1.342 Å and bond dissociation energies were &lt;400 kcal/mol. Natural bond orbital analysis supported the presence of excess electron density (&gt;3 electrons) at the N + center. The computational and X‐ray diffraction analysis results confirmed the presence of divalent N I character of center nitrogen and MIC→N + ←NHC coordination interactions.