title: Regarding initial ring opening of propylene oxide in its copolymerization with CO2 catalyzed by a cobalt(III) porphyrin complex.
abstract: Cobalt(III) tetraphenylporphyrin chloride (TPPCoCl) was experimentally proved to be an active catalyst for poly(propylene carbonate) production. It was chosen as a model catalyst in the present work to investigate the initiation step of propylene oxide (PO)/CO2 copolymerization, which is supposed to be the ring opening of the epoxide. Ring-opening intermediates (1-7) were detected by using (1) H NMR spectroscopy. A first-order reaction in TPPCoCl was determined. A combination of monometallic and bimetallic ring-opening pathways is proposed according to kinetics experiments. Addition of onium salts (e.g., bis(triphenylphosphine)iminium chloride, PPNCl) efficiently promoted the PO ring-opening rate. The existence of axial ligand exchange in the cobalt porphyrin complex in the presence of onium salts was suggested by analyzing collected (1) H NMR spectra.
authors.affiliation: WACKER-Lehrstuhl für Makromolekulare Chemie, Technische Universität München, Lichtenbergstraße 4, 85747, Garching (Germany).
authors.forename: Wei
authors.initials: W
authors.lastname: Xia
authors.forename: Sergei I
authors.initials: SI
authors.lastname: Vagin
authors.forename: Bernhard
authors.initials: B
authors.lastname: Rieger
keywords: NMR spectroscopy; carbon dioxide; onium salts; porphyrinoids; ring-opening polymerization