A new strategy towards tridentate N-heterocyclic carbene ligands derived from benzimidazolium and mixed-azolium salt

The tridentate N-heterocyclic carbenes (NHC) ligands derived from tris azolium salts by a new synthetic approach are described. The tris azolium salts have been obtained by reacting the initially synthesized precursor 3-(2-bromoethyl)-1-methylbenzimidazolium bromide (I) with benzimidazole/imidazole resulting in the tris azolium salts namely, 1 and 2. The ligand potential of the salts 1 and 2 was investigated by the formation of NHC-Ag(I) complexes 3 and 4, using Ag2O. The most downfield resonances in 13C NMR around 180-190 ppm indicates the successful coordination of carbene with Ag(I).