Synthesis and characterisation of quinoline functionalised imidazolium salts

Abstract

A series of quinoline based imidazolium salts were prepared and characterised as nucleophilic heterocyclic carbene (NHC) ligand precursors. The symmetrically saturated imidazolium salt prepared by ring closure of achiral tetradentate diquinolyl-diamine with triethyl orthoformate is a tridentate ligand and can function as pincer ligand while the two asymmetric imidazolium salts are bidentate and have different steric bulk which may have interesting implication in catalysis. The solubility of the symmetrical dihydroimidazolium salt was enhanced by replacing the counter ion tetraflouroborate with tetrakis (3,5-bis(triflouromethyl)phenyl)borate (Barf ) and its structure
confirmed by X- ray crystallography.

Keywords: Nucleophilic heterocyclic carbene (NHC), Imidazolium salt, ligand, ring closure.