Concerning the Deactivation of Cobalt(III)-Based Porphyrin and Salen Catalysts in Epoxide/CO 2 Copolymerization

Handle URI:
http://hdl.handle.net/10754/597827
Title:
Concerning the Deactivation of Cobalt(III)-Based Porphyrin and Salen Catalysts in Epoxide/CO 2 Copolymerization
Authors:
Xia, Wei; Salmeia, Khalifah A.; Vagin, Sergei I.; Rieger, Bernhard
Abstract:
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP=tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides. CO2 saves: The deactivation of cobalt(III)-porphyrin and salen catalysts in propylene oxide/carbon dioxide copolymerization is systematically investigated, revealing a proposed mechanism for the catalyst reduction (see scheme).
Citation:
Xia W, Salmeia KA, Vagin SI, Rieger B (2015) Concerning the Deactivation of Cobalt(III)-Based Porphyrin and Salen Catalysts in Epoxide/CO 2 Copolymerization . Chem Eur J 21: 4384–4390. Available: http://dx.doi.org/10.1002/chem.201406258.
Publisher:
Wiley-Blackwell
Journal:
Chemistry - A European Journal
KAUST Grant Number:
UK-C0020/KSA-C0069
Issue Date:
5-Feb-2015
DOI:
10.1002/chem.201406258
PubMed ID:
25656829
Type:
Article
ISSN:
0947-6539
Sponsors:
W.X. and K.A.S. thank the King Abdullah University of Science and Technology (KAUST) for the financial support of this work (UK-C0020/KSA-C0069).
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorXia, Weien
dc.contributor.authorSalmeia, Khalifah A.en
dc.contributor.authorVagin, Sergei I.en
dc.contributor.authorRieger, Bernharden
dc.date.accessioned2016-02-25T12:57:23Zen
dc.date.available2016-02-25T12:57:23Zen
dc.date.issued2015-02-05en
dc.identifier.citationXia W, Salmeia KA, Vagin SI, Rieger B (2015) Concerning the Deactivation of Cobalt(III)-Based Porphyrin and Salen Catalysts in Epoxide/CO 2 Copolymerization . Chem Eur J 21: 4384–4390. Available: http://dx.doi.org/10.1002/chem.201406258.en
dc.identifier.issn0947-6539en
dc.identifier.pmid25656829en
dc.identifier.doi10.1002/chem.201406258en
dc.identifier.urihttp://hdl.handle.net/10754/597827en
dc.description.abstract© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP=tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides. CO2 saves: The deactivation of cobalt(III)-porphyrin and salen catalysts in propylene oxide/carbon dioxide copolymerization is systematically investigated, revealing a proposed mechanism for the catalyst reduction (see scheme).en
dc.description.sponsorshipW.X. and K.A.S. thank the King Abdullah University of Science and Technology (KAUST) for the financial support of this work (UK-C0020/KSA-C0069).en
dc.publisherWiley-Blackwellen
dc.subjectCarbon dioxideen
dc.subjectCatalyst deactivationen
dc.subjectCobalten
dc.subjectEpoxidesen
dc.subjectRing-opening polymerizationen
dc.titleConcerning the Deactivation of Cobalt(III)-Based Porphyrin and Salen Catalysts in Epoxide/CO 2 Copolymerizationen
dc.typeArticleen
dc.identifier.journalChemistry - A European Journalen
dc.contributor.institutionTechnische Universitat Munchen, Munich, Germanyen
dc.contributor.institutionForschungsinstitution fur Materialwissenschaften Und Technologie Eth-Bereichs, Dubendorf, Switzerlanden
kaust.grant.numberUK-C0020/KSA-C0069en
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