Electronic Structure and Reactivity of Cobalt-Nitrenoid Species in Catalytic C‒H Amidation

Abstract

The amino compounds are versatile and important in various fields. Thus, development of efficient C-N bond-forming methods has been extensively explored. Herein the mechanism of the Co(III)-catalyzed C-N coupling reaction, which is the key step for catalytic C-H amidation, was investigated. DFT calculations elucidated the electronic structure and reactivity of Co-nitrenoid complex, which is the key intermediate, implying that the triplet species can be involved in the cobalt-catalyzed reaction. Comparative study on the reductive coupling step of the Group 9 [M = Co, Rh and Ir] metal complexes revealed that energy barrier becomes smaller down the group, and stability of the desired product is increased. The transition states change their characters to more reactant-like down the group, leading to lower reaction barrier. These findings are expected to be useful for development of the novel cobalt-catalysts.