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Title: Syntheses, structures, and catalytic activities of hemilabile thioether-functionalized NHC complexes
Authors: Huynh, H.V. 
Yeo, C.H.
Chew, Y.X.
Issue Date: 22-Mar-2010
Citation: Huynh, H.V., Yeo, C.H., Chew, Y.X. (2010-03-22). Syntheses, structures, and catalytic activities of hemilabile thioether-functionalized NHC complexes. Organometallics 29 (6) : 1479-1486. ScholarBank@NUS Repository.
Abstract: Four imidazolium (5a/b) and benzimidazolium (6a/b) salts with hemilabile alkyl-aryl thioether functions have been prepared via a straightforward and modular pathway in order to compare their reactivities toward palladation. Reaction of 5a/b with Pd(OAc)2 gave complex product mixtures, whereas 6a/b afforded the desired bis(benzimidazolin-2-ylidene) complexes 8a/b in good yields. The difference in reactivities of benzimidazole versus imidazole derivatives was attributed to the presence of additional acidic protons at C4/5 positions of the imidazolium ring, leading to competing and unselective deprotonation reactions. The milder Ag-NHC transfer reaction, on the other hand, provided either mono- or bis(imidazolin-2-ylidene) complexes (9 or 7a/b) in good yields depending on the ligand:metal ratio. The interesting hemilability in monocarbene complex 9 was investigated by spectroscopy and thioether displacement reaction with PPh3, yielding the mixed. NHC-PPh 3 complex 1.0 in high yields. An initial, comparative catalytic study also reveals that the mixed-donor complex 1.0 exhibits the highest activity among the complexes tested. © 2010 American Chemical Society.
Source Title: Organometallics
ISSN: 02767333
DOI: 10.1021/om9010966
Appears in Collections:Staff Publications

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