title: Enantio- and Stereoselective Cyclopolymerization of Hexa-1,5-diene Catalyzed by Zirconium Complexes Possessing Optically Active Bis(phenolato) Ligands.
abstract: Enantio- and stereoselective cyclopolymerization of hexa-1,5-diene was achieved by enantiomerically pure dichloro zirconium(IV) pre-catalysts 2 possessing chiral [OSSO]-type bis(phenolate) ligands (-)-1 and (+)-1 in combination with dried methylaluminoxane (dMAO) as an activator. The corresponding activities were recorded with quite high values up to 1,960 g mmol(2)-1h-1, which are extremely larger than those of the related complexes. The microstructure analysis for the PMCPs furnished by pre-catalysts (Λ,S,S)-2 and (Δ,R,R)-2 showed good isotacticity factors (α = 75-78%) and relatively high proportions of trans-cyclopentane rings (σ = 14-21%). These enantiomeric PMCPs exhibited large specific optical rotations ([α]D= +28 to +32° from (Λ,S,S)-2, -26 to -34° from (Δ,R,R)-2).
authors.affiliation: Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Nakata
authors.affiliation: Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Toda
authors.affiliation: Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ishii
keywords: cyclopolymerization; hexa-1,5-diene; isoselective; optically active polymers; zirconium