Synthesis of 1,2,3-Triazolo[1,5-а]Pyridin-8-Ium-3-Olates

Mesoionic and N-Heterocyclic Carbenes Coordinated N+ Center: Experimental and Computational Analysis

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 <400 kcal/mol. Natural bond orbital analysis supported the presence of excess electron density (>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.

Crystal structure of 4-aminopyridinium 4-acetyl-(pyridin-4-yl)-1H-1,2,3-triazol-5-olate monohydrate, C14H16N6O3

C14H16N6O3, triclinic, space group P1̅ (no. 2), a = 7.7890(5) Å, b = 8.6069(6) Å, c = 12.4753(8) Å, α = 77.064(4)°, β = 72.754(3)°, γ = 67.148(3)°, V = 730.40(9) Å3, Z = 2, R gt(F) = 0.0594, wR ref(F 2) = 0.1542, T = 297(2) K.