Catalysis of NHC–Pd Complexes in the Suzuki–Miyaura Cross-Coupling Reaction ^†

Abstract

Introduction: N-heterocyclic carbenes (NHCs) are considered important preferred auxiliary ligands for transition metals due to their strong σ-donor and weak π-acceptor properties and ease of structural modification in catalyst design. The functionalization of NHC by adding different substituent groups is an effective strategy for designing complexes with desired electronic and steric properties. NHC–Pd complexes are of particular importance due to their resistance to air, moisture and heat and their strong stability under catalytic and biological conditions. It is known that NHC–Pd complexes show excellent performance in the Suzuki–Miyaura cross-coupling reaction. The traditional Suzuki–Miyaura reaction involves the cross-coupling reaction of alkyl and arylboronic acids with aryl halides. This reaction has some advantages over other C-C coupling reactions. The use of water as a suitable and reliable solvent in the reaction, the fact that the reaction products are generally poorly soluble in water and can be easily separated from the reaction mixture, the use of non-toxic chemicals, the moderation of reaction conditions, and good functional group compatibility make it useful and worth studying. There are many examples of studies on the application of NHC–Pd complexes in the Suzuki–Miyaura reaction in aqueous media, and the highly effective catalytic activities and versatility of these reactions have been proven. Methods: In this study, a series of benzimidazole-based Pd–NHC complexes were synthesized. The synthesized complexes were characterized by spectroscopic methods. All complexes were tested as catalysts in the Suzuki–Miyaura cross-coupling reaction. Results: According to the obtained results, the synthesized benzimidazole-based Pd–NHC complexes were found to have high catalytic activity in the Suzuki–Miyaura cross-coupling reaction. Conclusions: The synthesized NHC-Pd complexes can be used as potential catalysts due to their high catalytic activity. It is thought that these catalysts can be used in different biochemical studies in the future.