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Copolymerization of Epoxides and CO 2 by Cobalt(II) Oxaporphyrins with Mechanistic Explorations on Poly(Propylene Carbonate) Formation
Author(s) -
Xia Wei,
Sun XingYu
Publication year - 2018
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201700478
Subject(s) - propylene oxide , cyclohexene oxide , propylene carbonate , copolymer , cationic polymerization , polycarbonate , catalysis , polymer chemistry , cobalt , chemistry , epoxide , carbonate , cyclohexene , organic chemistry , ethylene oxide , polymer , electrode , electrochemistry
Two cobalt(II) oxaporphyrins (OTPPCoCl and OTPPCoSbF 6 ) are synthesized in this work and are characterized, including by X‐ray crystallography. Both complexes are tested as catalysts in the copolymerization of propylene oxide (PO)/cyclohexene oxide (CHO) and CO 2 . Polycarbonate is obtained in CHO/CO 2 copolymerization with OTPPCoCl as a catalyst, whereas in the case of PO, cyclic carbonate (CC) is majorly formed. An anion exchange from Cl − to SbF 6 − of the cobalt(II) oxaporphyrin leads to a drastic change in the product selectivity: sole polyether is afforded for both epoxides. The polyether formation by OTPPCoSbF 6 is postulated to proceed via a cationic mechanism. Further, an equivalent admixture of OTPPCoCl and OTPPCoSbF 6 allows the formation of poly(propylene carbonate). In this copolymerization, the latter catalyst acts as a PO activator, while OTPPCoCl functions as the initiator. In addition, density functional theory (DFT) calculations reveal a lower ring‐opening energy of PO by OTPPCoSbF 6 , compared with the usual propagating species, OTPPCo‐alkoxides and OTPPCo‐carbonates.