Exploring the potential of metal-catalysis with N, N-type ligands in [3+2] cycloaddition reactions of azides and alkynes using theoretical tools

In this study, we meticulously analyzed the catalysis of azide-alkyne [3+2] cycloaddition reactions facilitated by metal-complexes with N, N-type ligands using MN12-L functional with Def2-TZVP/Def2-SVP basis sets. Specifically, the study contrasted mononuclear and binuclear mechanisms for silver (Ag) and copper (Cu) catalyzed reactions, employing ligands L1(2,2′-bipyridin), L2(1,10-phnanthroline) and L3(some derivative of 1,3-oxazole), under both gas phase and solvated conditions using toluene. Our results highlight that the binuclear mechanism is energetically favored over the mononuclear pathway, with activation energies for the former being notably lower. For instance, in the presence of toluene, the binuclear pathway for Cu-complexes with the L1 ligand demonstrated an activation energy of merely 2.3 kcal/mol, in stark contrast to the 11.8 kcal/mol required for the mononuclear process. This significant reduction in energy barrier elucidates the efficiency of binuclear complexes in facilitating [3+2] cycloaddition, potentially guiding the design of novel catalysts for synthetic chemistry applications. Furthermore, the study reveals that the transition state energies and the overall reaction energetics are critically dependent on the choice of metal and ligand, underscoring the complex interplay between metal coordination chemistry and catalytic performance in azide-alkyne cycloadditions. Analysis of computational results indicate that Cu-complexes with studied different ligands show higher activity compared to Ag-complexes in terms of energy barriers.

Graphical abstract