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Elucidation of the structure of a highly active catalytic system for CO2/epoxide copolymerization: A salen-cobaltate complex of an unusual binding mode

Title
Elucidation of the structure of a highly active catalytic system for CO2/epoxide copolymerization: A salen-cobaltate complex of an unusual binding mode
Authors
Na S.J.Sujith S.Cyriac A.Kim B.E.Yoo J.Kang Y.K.Han S.J.Lee C.Lee B.Y.
Ewha Authors
이종목
SCOPUS Author ID
이종목scopus
Issue Date
2009
Journal Title
Inorganic Chemistry
ISSN
0020-1669JCR Link
Citation
vol. 48, no. 21, pp. 10455 - 10465
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Salen-type ligands comprised of ethylenediamine or 1,2-cyclohexenediamine, along with an salicylaldehyde bearing a methyl substituent on its 3-position and a -[CR(CH2CH2CH2N+Bu 3)2] (R = H or Me) on its 5-position, unexpectedly afford cobalt(III) complexes with uncoordinated imines. In these complexes, two salen-phenoxys and two 2,4-dinitrophenolates (DNPs), which counter the quaternary ammonium cations, coordinate persistently with cobalt, while two other DNPs are fluxional between a coordinated and an uncoordinated state in THF at room temperature. The complexes of this binding mode show excellent activities in carbon dioxide/propylene oxide copolymerization (TOF, 8300-13000 h-1) but with some fluctuation in induction times (1 -10 h), depending on how dry the system is. The induction time is shortened (<1.0 h) and activity is increased ̃1.5 times upon the replacement of the two fluxional DNPs with 2,4-dinitrophenol-2,4-dinitrophenolate homoconjugation ([DNP • • • H • • • DNP]-). Imposing steric congestion either by replacing the methyl substituent on the salicylaldehyde with tert-butyl or by employing H2NCMe2CMe 2NH2 instead of ethylenediamine or 1,2-cyclohexenediamine results in conventional imine-coordinating complexes, which show lower activities than uncoordinated imine complexes. © 2009 American Chemical Society.
DOI
10.1021/ic901584u
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자연과학대학 > 화학·나노과학전공 > Journal papers
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