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Abnormal N-Heterocyclic Carbene Gold(I) Complexes: Synthesis, Structure, and Catalysis in Hydration of Alkynes

Cited 59 time in Web of Science Cited 57 time in Scopus
Authors
Xu, Xiangya; Kim, Seung Hyo; Zhang, Xi; Das, Atanu Kumar; Hirao, Hajime; Hong, Soon Hyeok
Issue Date
2013-01
Publisher
American Chemical Society
Citation
Organometallics, Vol.32 No.1, pp. 164-171
Keywords
복합학
Abstract
Two abnormal N-heterocyclic carbene (aNHC) gold(l) complexes, [(aNHC)AuCl], were prepared from C2-protected imidazolium salts. The air-stable complexes chloro(1-isopropyl-3-methyl-2,4-diphenylimidazol-5-ylidene)gold(I) (5) and chloro(1,4-diisopropyl-3-methyl-2-phenylimidazol-5-ylidene)gold(I) (6) were synthesized via transmetalation using (SMe2)AuCl and the corresponding silver salt such as [(aNHC)AgI] or [(aNHC)(2)Ag][I] and were fully characterized by NMR and mass spectroscopy and by X-ray crystallography. To investigate the structure, bonding, and catalytic activity of the aNHC-based Au complexes in comparison with their traditional NHC analogues, the sterically similar NHC-based Au complexes chloro(1,3-diisopropylimidazol-2-ylidene)gold(I) (7) and chloro(3-isopropyl-1-phenylimidazol-2-ylidene)gold(1) (8) were prepared from 1,3-diisopropylimidazolium iodide (3) and 3-isopropyl-1-phenylimidazolium iodide (4), respectively. X-ray crystallography and density functional theory (DFT) calculations showed that the aNHC complexes have longer Au-C-carbene bond distances than the NHC complexes. Furthermore, DFT calculations predicted that, despite their longer Au-C-carbene distances, aNHC complexes have stronger binding energies. It is suggested on the basis of additional theoretical analyses that these counterintuitive trends can be rationalized by considering individual factors that comprise the molecular interaction. The efficient back-donation of electrons and the smaller overlap repulsion in NHC complexes render the Au-C-carbene distance shorter, whereas the stronger Au-C-carbene bonding in the aNHC-Au complexes is attributed to the greater electrostatic attraction and the higher electron-donating ability of the carbene lone pair orbital. Catalytic activities of the NHC-based Au complexes were also compared in the alkyne hydration. Traditional NHC-based Au complexes exhibited higher efficiency in the reaction.
ISSN
0276-7333
Language
English
URI
https://hdl.handle.net/10371/91675
DOI
https://doi.org/10.1021/om3009603
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College of Natural Sciences (자연과학대학)Dept. of Chemistry (화학부)Journal Papers (저널논문_화학부)
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