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The Real Role of N-Heterocyclic Carbene in Reductive Functionalization of CO2: An Alternative Understanding from Density Functional Theory Study
Alternative Title氮杂环卡宾(NHC)在CO2还原官能团化中真实角色的理论研究
Zhou QH(周庆海); Li YX(李玉学)
2015
Source PublicationJ. Am. Chem. Soc.
Volume137Issue:32Pages:10182-10189
AbstractThe mechanisms of reductive functionalization of CO2 to formamide catalyzed by N-heterocyclic carbene (NHC) were comprehensively studied with DFT calculations. New activation mode with much lower energy barrier than those proposed before was discovered. In this reaction, NHC acts as neither a CO2, nor a silane activator, but as a precursor of the real catalyst, i.e., the in situ formed ionic liquid [NHCH](+)[Carbamate](-). In this loose contact ion pair, the negatively charged O atom of the carbamate anion becomes the new active site and is free to do nucleophilic attack. When amine is absent, CO2 will be converted into methanol. In this case, the NHC-CO2 adduct is the real catalytic species; the active site shifted from the carbene C atom to the negatively charged O atom. These new activation modes follow a pattern of "S(N)2@Si-Acceptor", in which the Si-H bond is activated via concerted backside S(N)2 nucleophilic attack by the negatively charged O atom, and the leaving hydride is directly accepted by a free CO2 molecule. The advantages of these new activation modes originate from the following points: (1) The ionic liquid [NHCH](+)[Carbamate](-) and NHC-CO2 adduct are thermodynamically more stable than NHC. (2) The active site of the NHC catalyst is extended outside a lot. Consequently, the large steric effect between the NHC arms and the substrates in transition state can be avoided to some extent. (3) The O atom has good silicon affinity. In addition, a free CO2 molecule, whose carbon atom is more electrophilic than those of the CO2 moieties in NHC-CO2 adduct and carbamate, acts as an efficient hydride acceptor.
Subtype论文
Subject Area金属有机化学
DOI10.1021/jacs.5b03651
URL查看原文
Indexed BySCI
Language英语
WOS IDWOS:000359962000037
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Document Type期刊论文
Identifierhttp://ir.sioc.ac.cn/handle/331003/39634
Collection金属有机化学国家重点实验室
Corresponding AuthorLi YX(李玉学)
Affiliation中科院上海有机化学研究所, 金属有机化学国家重点实验室
Recommended Citation
GB/T 7714
Zhou QH,Li YX. The Real Role of N-Heterocyclic Carbene in Reductive Functionalization of CO2: An Alternative Understanding from Density Functional Theory Study[J]. J. Am. Chem. Soc.,2015,137(32):10182-10189.
APA 周庆海,&李玉学.(2015).The Real Role of N-Heterocyclic Carbene in Reductive Functionalization of CO2: An Alternative Understanding from Density Functional Theory Study.J. Am. Chem. Soc.,137(32),10182-10189.
MLA 周庆海,et al."The Real Role of N-Heterocyclic Carbene in Reductive Functionalization of CO2: An Alternative Understanding from Density Functional Theory Study".J. Am. Chem. Soc. 137.32(2015):10182-10189.
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