title: Computational Investigation of the Role Played by Rhodium(V) in the Rhodium(III)-Catalyzed ortho-Bromination of Arenes.
abstract: In this study, M11-L was used to evaluate the feasibility of the formation of rhodium(V) species using the rhodium(III)-catalyzed ortho-bromination of arenes as a model reaction. In most cases for these types of reactions, DFT calculations reveal that the bromination step involves a Br transfer from N-bromosuccinimide to the reacting arylrhodium to form a bromonium intermediate, followed by a Br shift to generate a new C-Br bond, which is more favorable than the previously proposed RhIII/RhVcatalytic cycle. The rhodium catalyst remains in its +3 oxidation state throughout. The substituent effects of the reacting arene were studied, and computational results showed that the introduction of electron-donating groups on the reacting arene was favorable for this pathway. In contrast, the inclusion of a strong electron-withdrawing group on the aromatic ring would hinder the formation of a bromonium intermediate. Therefore, the RhIII/RhVcatalytic cycle is favorable in cases that involve a RhVintermediate, which is generated by oxidative addition with NBS. In this pathway, the C-Br bond is formed by reductive elimination from the RhVintermediate. Additionally, a distortion-interaction analysis model along the reaction pathway was used to explain the directing-group effects. The results showed that the interaction energy controlled the reactivity because of the difference in electronic nature of various directing groups.
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400030, P.R. China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400030, P.R. China.
authors.forename: Xiaotian
authors.initials: X
authors.lastname: Qi
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400030, P.R. China.
authors.forename: Song
authors.initials: S
authors.lastname: Liu
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400030, P.R. China.
authors.forename: Ruopeng
authors.initials: R
authors.lastname: Bai
authors.affiliation: State Key Laboratory for Oxo Synthesis and Selective Oxidation, Suzhou Research Institute of LICP, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences, Lanzhou, P.R. China.
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400030, P.R. China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Lan
keywords: arenes; bromine; density functional calculations; reaction mechanisms; rhodium