title: Mechanistic Studies of Cyclohexene Oxide/CO2Copolymerization by a Chromium(III) Pyridylamine-Bis(Phenolate) Complex.
abstract: Chromium(III) chlorido amine-bis(phenolate) complexes paired with nucleophilic co-catalysts are a promising family of catalysts for the copolymerization of CO2and epoxides to selectively produce polycarbonates with a very high degree of carbonate linkages. Single-component catalyst systems can be prepared, where the neutral nucleophile, 4-dimethylaminopyridine (DMAP), is coordinated to the metal site to provide a stable octahedral CrIIIcomplex. These complexes possess the potential for both anionic (from the chlorido ligand) or neutral (DMAP) nucleophilic epoxide ring-opening during the proposed rate-determining initiation step. Concentration effect studies support a first-order dependence of the polymerization rate on the concentration of single-component catalyst. End-group analysis of polycarbonates by MALDI-TOF MS indicate the presence of predominantly DMAP-initiated chains as well as the occurrence of chain-transfer events resulting in ether linkages, likely from the presence of cyclohexene diol formed by the reaction of cyclohexene oxide and adventitious water.
authors.affiliation: Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X7, Canada.
authors.forename: Katalin
authors.initials: K
authors.lastname: Devaine-Pressing
authors.affiliation: Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X7, Canada.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Kozak
mesh_terms: D015761:4-Aminopyridine / Q000031:analogs & derivatives* / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry*; D002384:Catalysis; D002857:Chromium / Q000737:chemistry*; D053138:Cyclohexenes / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D058105:Polymerization
chemical_list: D053138:Cyclohexenes; D009942:Organometallic Compounds; D002857:Chromium; D002245:Carbon Dioxide; C007193:cyclohexene oxide; D015761:4-Aminopyridine; C003885:4-dimethylaminopyridine
keywords: CO2 fixation; chromium pyridylamino-bis(phenolate); epoxide; kinetics; polycarbonates