New symmetrical N^N^N palladium(II) pincer complexes: synthesis, characterization and catalytic evaluation in the Suzuki-Miyaura cross-coupling reaction

Abstract

Owing to their activity, versatility and ease of synthesis, N^N^N complexes with a central pyridine unit are of significance in organic synthesis. However, these complexes are relatively uncommon in comparison to their benzene analogues. In addition, neutral complexes of this pincer type ligand that consists of a pyridine core are rare. In view of this, a series of cationic palladium(II) N^N^N pincer complexes derived from neutral ligands that are based on a rigid pyridine backbone were synthesized, characterized and then evaluated as precatalysts in the Suzuki-Miyaura cross coupling reaction. At a catalyst loading of 0.1 mol%, the complexes were found to be effective pre-catalysts in the cross-coupling reactions under aqueous conditions. The scope, structure-activity relationships and limitations of these complexes are discussed.