Carboxylate breaks the arene C–H bond via a hydrogen-atom-transfer mechanism in electrochemical cobalt catalysis. Issue 22 (27th May 2020)

• Record Type: Journal Article
• Authors: Chen, Xin-Ran; Zhang, Shuo-Qing; Meyer, Tjark H.; Yang, Chun-Hui; Zhang, Qin-Hao; Liu, Ji-Ren; Xu, Hua-Jian; Cao, Fa-He; Ackermann, Lutz; Hong, Xin
• Is Part Of: Chemical science. Volume 11:Issue 22(2020)
• Page Start: 5790
• Page End: 5796
• Publication Date: 2020-05-27
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d0sc01898h
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : A formal Co(iv ) intermediate in electrochemical cobalt-catalyzed C–H oxygenation allows pivalate to break the arene C–H bond via a hydrogen-atom-transfer mechanism. Abstract : Combined computational and experimental studies elucidated the distinctive mechanistic features of electrochemical cobalt-catalyzed C–H oxygenation. A sequential electrochemical–chemical (EC) process was identified for the formation of an amidylcobalt(iii ) intermediate. The synthesis, characterization, cyclic voltammetry studies, and stoichiometric reactions of the related amidylcobalt(iii ) intermediate suggested that a second on-cycle electro-oxidation occurs on the amidylcobalt(iii ) species, which leads to a formal Co(iv ) intermediate. This amidylcobalt(iv ) intermediate is essentially a cobalt(iii ) complex with one additional single electron distributed on the coordinating heteroatoms. The radical nature of the coordinating pivalate allows the formal Co(iv ) intermediate to undergo a novel carboxylate-assisted HAT mechanism to cleave the arene C–H bond, and a CMD mechanism could be excluded for a Co(iii /i ) catalytic scenario. The mechanistic understanding of electrochemical cobalt-catalyzed C–H bond activation highlights the multi-tasking electro-oxidation and the underexplored reaction channels in electrochemical transition metal catalysis.