Synthesis of Ferrocenyl Imidazolium Salts and Their Novel PEPPSI-Type N-Heterocyclic Carbene (NHC) Palladium Complexes

Abstract

The novel PEPPSI-type palladium complexes of ferrocenyl-functionalized N-heterocyclic carbenes (NHCs) with different substituents were synthesized. The synthesis of these ferrocenyl-NHCs ligands involves the reaction of the alcohol 1-(ferrocenyl)ethanol successively with 1-substituted imidazole in glacial acetic acid. Following that, the novel PEPPSI-type NHC palladium complexes were prepared by heating their imidazolium salts with PdCl2, K2CO3 in neat pyridine. In addition, deprotonation of N-ferrocenylethyl-N '-(2,4,6-trimethylphenyl)imidazolium chloride (2a) and then its reaction with S-8 gave imidazole-2-thione (5). All ligand precursors and all palladium complexes were characterized by elemental analysis, H-1 and C-13 NMR, and X-ray diffraction methods for two examples.