Synthesis of ferrocenyl imidazolium salts and their novel PEPPSI-type N-heterocyclic carbene (NHC) palladium complexes

[Display omitted] •The ferrocenyl-functionalized N-heterocyclic carbene (NHCs) precursors were synthesized.•The novel ferrocenyl-bearing PEPPSI-type palladium complexes were synthesized.•Imidazole-2-thione derivative was synthesized via the deprotonation method.•The excess base play a role in cleavage the C–N bond in the imidazole salt. 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 S8 gave imidazole-2-thione (5). All ligand precursors and all palladium complexes were characterized by elemental analysis, 1H and 13C NMR, and X-ray diffraction methods for two examples.