Luo Xu, Yang Dali, He Xiaoqian, Wang Shengchun, Zhang Dongchao, Xu Jiaxin, Pao Chih-Wen, Chen Jeng-Lung, Lee Jyh-Fu, Cong Hengjiang, Lan Yu, Alhumade Hesham, Cossy Janine, Bai Ruopeng, Chen Yi-Hung, Yi Hong, Lei Aiwen
College of Chemistry and Molecular Sciences, the Institute for Advanced Studies (IAS), Wuhan University, Wuhan, 430072, P.R. China.
School of Chemistry and Chemical Engineering, Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing, 400030, P.R. China.
Nat Commun. 2023 Aug 2;14(1):4638. doi: 10.1038/s41467-023-40269-y.
Ligands and additives are often utilized to stabilize low-valent catalytic metal species experimentally, while their role in suppressing metal deposition has been less studied. Herein, an on-cycle mechanism is reported for CoClbpy catalyzed Negishi-type cross-coupling. A full catalytic cycle of this kind of reaction was elucidated by multiple spectroscopic studies. The solvent and ligand were found to be essential for the generation of catalytic active Co(I) species, among which acetonitrile and bipyridine ligand are resistant to the disproportionation events of Co(I). Investigations, based on Quick-X-Ray Absorption Fine Structure (Q-XAFS) spectroscopy, Electron Paramagnetic Resonance (EPR), IR allied with DFT calculations, allow comprehensive mechanistic insights that establish the structural information of the catalytic active cobalt species along with the whole catalytic Co(I)/Co(III) cycle. Moreover, the acetonitrile and bipyridine system can be further extended to the acylation, allylation, and benzylation of aryl zinc reagents, which present a broad substrate scope with a catalytic amount of Co salt. Overall, this work provides a basic mechanistic perspective for designing cobalt-catalyzed cross-coupling reactions.
配体和添加剂在实验中常被用于稳定低价催化金属物种，然而它们在抑制金属沉积方面的作用却鲜有研究。在此，报道了一种CoClbpy催化的Negishi型交叉偶联反应的循环机理。通过多种光谱研究阐明了这类反应的完整催化循环。发现溶剂和配体对于催化活性Co(I)物种的生成至关重要，其中乙腈和联吡啶配体可抵抗Co(I)的歧化反应。基于快速X射线吸收精细结构（Q-XAFS）光谱、电子顺磁共振（EPR）以及结合密度泛函理论（DFT）计算的红外光谱进行的研究，能够提供全面的机理见解，从而确定催化活性钴物种的结构信息以及整个催化Co(I)/Co(III)循环。此外，乙腈和联吡啶体系可进一步扩展至芳基锌试剂的酰化、烯丙基化和苄基化反应，在使用催化量的钴盐时展现出广泛的底物范围。总体而言，这项工作为设计钴催化的交叉偶联反应提供了基本的机理视角。
