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Switchable Polymerization Triggered by Fast and Quantitative Insertion of Carbon Monoxide into Cobalt–Oxygen Bonds
Author(s) -
Wang Yong,
Zhao Yajun,
Zhu Shuaishuai,
Zhou Xingping,
Xu Jing,
Xie Xiaolin,
Poli Rinaldo
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201914216
Subject(s) - polymerization , copolymer , cobalt , intramolecular force , polymer chemistry , carbon monoxide , chemistry , photochemistry , polymer , catalysis , stereochemistry , organic chemistry
A strategy that uses carbon monoxide (CO) as a molecular trigger to switch the polymerization mechanism of a cobalt Salen complex [salen=( R , R )‐ N,N′ ‐bis(3,5‐di‐ tert ‐butylsalicylidene)‐1,2‐cyclohexanediamine] from ring‐opening copolymerization (ROCOP) of epoxides/anhydrides to organometallic mediated controlled radical polymerization (OMRP) of acrylates is described. The key phenomenon is a rapid and quantitative insertion of CO into the Co−O bond, allowing for in situ transformation of the ROCOP active species (Salen)Co III ‐OR into the OMRP photoinitiator (Salen)Co III ‐CO 2 R. The proposed mechanism, which involves CO coordination to (Salen)Co III ‐OR and subsequent intramolecular rearrangement via migratory insertion has been rationalized by DFT calculations. Regulated by both CO and visible light, on‐demand sequence control can be achieved for the one‐pot synthesis of polyester‐ b ‐polyacrylate diblock copolymers ( Đ <1.15).