期刊
INORGANIC CHEMISTRY
卷 61, 期 43, 页码 17330-17341出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.inorgchem.2c02953
关键词
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资金
- NSFC
- Anhui Provincial Natural Science Foundation
- Innovation and Entrepreneurship Project of Overseas Returnees in Anhui Province
- [22003001]
- [2108085Y04]
- [2020LCX006]
This study reveals the facilitating role of coordinating substrates and the potential impact of heteroatom-containing substrates in rare-earth-catalyzed C-H activation processes through careful theoretical studies on a model reaction. Switchable mechanisms were found to be effective in other types of C-H bonds by adjusting catalyst steric surroundings.
Although considerable progress has been achieved in C-H functionalization by cationic rare-earth alkyl complexes, the potential facilitating roles of heteroatom-containing substrates during the catalytic cycle remain highly underestimated. Herein, theoretical studies on the model reaction of C(sp2)-H addition of pyridines to allenes by scandium catalyst were carefully carried out to reveal the detailed mechanism. A coordinating pyridine substrate as a ligand can effectively stabilize some key structures. An obvious facilitating role delivered by the coordinating pyridine was found for allene insertion, while the pyridine-free mechanism prefers to occur for C(sp2)-H activation processes. Importantly, the elusive role of heteroatom-containing substrates was systematically revealed for the C-H activation event by designing a metal/ligand combination of catalysts and substrates. We found that the pyridyl C(sp2)-H activation would be switched to the pyridine-coordinated mechanism in the cases of the designed Y and La catalysts. To date, this is the first time to realize the potential substrate-facilitating role in cationic rare-earth-catalyzed C-H activation processes. Moreover, theoretical predictions show that similar switchable mechanisms also work for other types of C-H bonds and other heteroatom-involved substrates by fine-adjusting the steric surroundings of catalysts. The two C-H activation mechanisms are mainly the result of the delicate balance between electronic and steric factors. In general, the catalytic system with less steric hindrance prefers to undergo the substrate-coordinated mechanism. In contrast, the substrate-free mechanism is favorable due to steric repulsion. These results are helpful for us to better understand the variant mechanisms in rare-earth-catalyzed C-H functionalization at the atomistic level and may help guide the rational design of new catalytic reactions. In addition, the origins of the regio-and stereoselectivity were discussed through geometric parameters and distortion/interaction analysis.
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