Title
Enantioselective binding of structural epoxide isomers by a chiral vanadyl salen complex: a pulsed EPR, cw-ENDOR and DFT investigation Enantioselective binding of structural epoxide isomers by a chiral vanadyl salen complex: a pulsed EPR, cw-ENDOR and DFT investigation
Author
Faculty/Department
Faculty of Sciences. Physics
Publication type
article
Publication
Cambridge ,
Subject
Physics
Source (journal)
Physical chemistry, chemical physics / Chemical Society [London] - Cambridge, 1999, currens
Volume/pages
11(2009) :31 , p. 6757-6769
ISSN
1463-9076
1463-9084
ISI
000268481200022
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
The mode of chiral interaction between a series of asymmetric epoxides (propylene oxide, butylene oxide, epifluorohydrin and epichlorohydrin) and a chiral vanadyl salen complex, N, N-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamino-vanadium (IV) oxide, [VO( 1)], was investigated by a range of electron magnetic resonance techniques (EPR, ENDOR, HYSCORE) and DFT. Enantiomer discrimination of the weakly bound epoxides by the vanadyl complex was evident by cw-ENDOR. The origin of this discrimination was attributed to a number of factors including H-bonds, steric properties and electrostatic contributions, which collectively control the outcome of the chiral interaction. DFT revealed the role of a key H-bond, formed between the epoxide oxygen atom (Oepoxide) and the methine proton (Hexo) attached to the asymmetric carbon atom of the chiral vanadyl salen complex, thereby providing a direct pathway for stereochemical communication between complex and substrate. These findings reveal the potential importance of weak outer sphere interactions in stereoselectivities of enantioselective homogeneous catalysis.
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