Heteroleptic palladium(II) complexes containing N-heterocyclic carbenes and 4-phenyl-1H-1,2,3-triazole: Synthesis, characterization, and catalytic application

Reaction of the dimeric N-heterocyclic carbene (NHC) palladium compounds [Pd(μ-Cl)(Cl)(NHC)]₂ with 4-phenyl-1H-1,2,3-triazole gave four mono- and dinuclear complexes 1–4. Mononuclear complexes 1 and 2 [(NHC)PdCl₂(4-phenyl-1H-1,2,3-triazole)] were obtained when the reactions were performed in CH₂Cl₂, whereas dinuclear complexes 3 and 4 [Pd₂(μ-Cl)(μ-4-phenyl-1H-1,2,3-triazole)Cl₂(NHC)₂] were obtained when the reactions were performed in THF in reflux with Et₃N as the base. Further explorations of the catalytic properties of 1–4 for Pd-catalyzed transformations have been performed and these complexes exhibited moderate to high catalytic activities for Suzuki–Miyaura coupling and arylation of benzoxazoles with aryl bromides.