Oxidative Dehydrogenation of Coordinated Amines Assisted by Metal Ions

Abstract Oxidative dehydrogenation (OD) of amines involves the elimination of two protons and two electrons ─(2H + + 2e) that results in the transformation of ─CH─NH─ to ─C═N─ moiety. A variety of amines coordinated to the transition metal ion, including iron, cobalt, nickel, copper, ruthenium, rhodium, and iridium, also rare earth metals undergo OD reaction. The reaction occurs mainly under a basic medium in the presence of air/O 2 , which is a green oxidant. The metal ions play a significant role in the OD reaction. They can participate in redox reactions as an internal oxidant and can also influence the deprotonation of the ─NH function to form an amido intermediate, crucial for the OD reaction of amines. Not only that, the photosensitized metal ion or metal‐stabilized ligand‐centered radical activates O 2 to promote OD reaction. This review presents the OD reaction of amines that occurred in air/O 2 to explore the role of metal ions and fates of O 2 . The study reveals that along with the oxidation state of the metal ion, other factors like the redox potential of M n + /M ( n −1)+ , the geometry of the complex, the coordination mode of the ligand, substituents on the ligand, co‐ligands, and steric crowding also influence OD. The different spectroscopies, including single‐crystal X‐ray diffraction, which is employed to study the OD reactions, are also interpreted.