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Deng, Jingyuan Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo
Ratanasak, Manussada Institute for Catalysis, Hokkaido University
Sako, Yuma Graduate School of Natural Science and Technology, Okayama University
Tokuda, Hideki Graduate School of Natural Science and Technology, Okayama University
Maeda, Chihiro Graduate School of Natural Science and Technology, Okayama University Kaken ID researchmap
Hasegawa, Jun-ya Institute for Catalysis, Hokkaido University
Nozaki, Kyoko Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo
Ema, Tadashi Graduate School of Natural Science and Technology, Okayama University ORCID Kaken ID publons researchmap
Abstract
Bifunctional AlIII porphyrins with quaternary ammonium halides, 2-Cl and 2-Br, worked as excellent catalysts for the copolymerization of cyclohexene oxide (CHO) and CO2 at 120 °C. Turnover frequency (TOF) and turnover number (TON) reached 10 000 h−1 and 55 000, respectively, and poly(cyclohexene carbonate) (PCHC) with molecular weight of up to 281 000 was obtained with a catalyst loading of 0.001 mol%. In contrast, bifunctional MgII and ZnII counterparts, 3-Cl and 4-Cl, as well as a binary catalyst system, 1-Cl with bis(triphenylphosphine)iminium chloride (PPNCl), showed poor catalytic performances. Kinetic studies revealed that the reaction rate was first-order in [CHO] and [2-Br] and zero-order in [CO2], and the activation parameters were determined: ΔH‡ = 12.4 kcal mol−1, ΔS‡ = −26.1 cal mol−1 K−1, and ΔG‡ = 21.6 kcal mol−1 at 80 °C. Comparative DFT calculations on two model catalysts, AlIII complex 2′ and MgII complex 3′, allowed us to extract key factors in the catalytic behavior of the bifunctional AlIII catalyst. The high polymerization activity and carbonate-linkage selectivity originate from the cooperative actions of the metal center and the quaternary ammonium cation, both of which facilitate the epoxide-ring opening by the carbonate anion to form the carbonate linkage in the key transition state such as TS3b (ΔH‡ = 13.3 kcal mol−1, ΔS‡ = −3.1 cal mol−1 K−1, and ΔG‡ = 14.4 kcal mol−1 at 80 °C).
Published Date
2020-05-18
Publication Title
Chemical Science
Volume
volume11
Issue
issue22
Publisher
Royal Society of Chemistry
Start Page
5669
End Page
5675
ISSN
2041-6520
NCID
AA12555653
Content Type
Journal Article
language
英語
Copyright Holders
© The Royal Society of Chemistry
File Version
publisher
DOI
Web of Science KeyUT
Related Url
isVersionOf https://doi.org/10.1039/D0SC01609H
License
https://creativecommons.org/licenses/by-nc/3.0/
Funder Name
Ministry of Education, Culture, Sports, Science and Technology
助成番号
JP15H05796
JP15H05805
JP16H01030