title: Isospecific polymerization of 1-hexene by C1-symmetric half-metallocene dimethyl complexes of group 4 metals with bidentate N-substituted iminomethylpyrrolyl ligands.
abstract: Non-bridged half-metallocene dimethyl complexes of group 4 metals 2a-4a with an N-4-methoxyphenyl(iminomethyl)pyrrolyl ligand 1a were synthesized and characterized by NMR spectroscopy and X-ray analysis. Upon activation with [Ph3C][B(C6F5)4], these complexes became active catalysts for the polymerization of 1-hexene. A series of hafnium complexes with various N-substituents on the imine group of ligands 1b-1g were also prepared and applied as catalysts for 1-hexene polymerization. The activation parameters for the exchange process between the two methyl groups bound to the metal for Cp*MMe2(R-pyr) complexes were estimated by NMR shape analysis at various temperatures. The findings indicated that the transition state of the ligand flipping process might be associated with the isoselectivity of the polymerization reaction.
authors.affiliation: Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yasumoto
authors.forename: Keishi
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Hayato
authors.initials: H
authors.lastname: Tsurugi
authors.forename: Kazushi
authors.initials: K
authors.lastname: Mashima
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D058105:Polymerization; D011758:Pyrroles / Q000737:chemistry*; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D000475:Alkenes; D008024:Ligands; D009942:Organometallic Compounds; D011758:Pyrroles; D028561:Transition Elements; C117224:1-hexene