Acridine PNP-Pincer Ligands Enabling Transition Metal-Catalyzed Photoreactions

Transition metal-catalyzed reactions are developed together with ligands. While transition metal-catalyzed photoreactions have been extensively reported in recent years, the development of ligands for photoreactions is limited to only a few cases. Therefore, establishing ligands that shed light on transition metal-catalyzed photoreactions is an important research goal. We successfully synthesized four acridine-containing PNP-pincer ligands and formed transition metal complexes with Ni, Pd, Pt, Cu, and Co. We found that the platinum complex induced photoreactions of olefins under visible light irradiation: transfer hydrogenation, which required only a stoichiometric amount of hydrogen source, and hydroxy/alkoxy alkylation of olefins. These reactions did not proceed with existing well-known ligands, demonstrating that the development of photoreaction-oriented ligands reveals unknown reactivities of transition metals.