Cobalt Complexes Featuring N,O‐Bidentate Ligands with N‐Oxide Moieties: Synthesis, Characterization and Catalytic Activity in Acceptorless Dehydrogenative Coupling of Benzylic Alcohols with Aryl Amines

Comprehensive Summary The transition metal‐catalyzed acceptorless dehydrogenative coupling of alcohols and amines is one of the attractive and important strategies for the construction of C=N bonds from the perspective of environmental friendliness and economy. Herein, we report the synthesis of four novel phosphine‐free cobalt(II) complexes ( Co‐1 — Co‐4 ) with N,O‐bidentate ligands incorporating N‐oxide units and their catalytic activity in acceptorless dehydrogenative coupling of benzylic alcohols and aryl amines. X‐ray diffraction analyses revealed that the central cobalt atoms in three of the cobalt complexes ( Co‐1 , Co‐2 , Co‐4 ) were six‐coordinated and adopted an octahedral geometry configuration. Catalytic evaluation of cobalt complexes demonstrated that Co‐4 exhibited higher activity than the other three cobalt complexes. This system could provide a series of corresponding imine products with good functional groups compatibility and high yields. Especially, the use of phosphine‐free and inexpensive cobalt complexes, along with readily accessible N,O‐bidentate ligands featuring N‐oxide moieties, offers significant advantages for this reaction.