title: Bis(1,3-di-tert-butylimidazolin-2-iminato) titanium complexes as effective catalysts for the monodisperse polymerization of propylene.
abstract: The use of bis(1,3-di-tert-butylimidazolin-2-iminato) titanium dichloride (1) and dimethyl (2) complexes in the polymerization of propylene is presented. The complexes were activated using different amounts of methylalumoxane (MAO), giving in each case a very active catalytic mixture and producing polymers with a narrow molecular weight distribution (polydispersity = 1.10). The use of the cocatalyst triphenylcarbenium (trityl) tetra(pentafluorophenyl)borate totally inhibits the reaction, producing the corresponding bis(1,3-di-tert-butylimidazolin-2-iminato) titanium(III) methyl complex, the trityl radical ((•)CPh(3)), the anionic MeB(C(6)F(5))(4)(-), B(C(6)F(5))(3), and the bis(1,3-di-tert-butylimidazolin-2-iminato) titanium(IV) dimethyl·B(C(6)F(5))(3) complex. The use of a combination of physical methods such as NMR, ESR-C(60), and MALDI-TOF analyses enabled us to propose a plausible mechanism for the polymerization of propylene, presenting that the polymerization is mainly carried out in a living fashion. In addition, we present a slow equilibrium toward a small amount of a dormant species responsible for 2,1-misinsertions and chain transfer processes.
authors.affiliation: Schulich Faculty of Chemistry, Institute of Catalysis Science and Technology, Technion-Israel Institute of Technology, Technion City, 32000 Haifa, Israel.
authors.forename: Manab
authors.initials: M
authors.lastname: Sharma
authors.forename: Haneen Simaan
authors.initials: HS
authors.lastname: Yameen
authors.forename: Boris
authors.initials: B
authors.lastname: Tumanskii
authors.forename: Sabina-Alexandra
authors.initials: SA
authors.lastname: Filimon
authors.forename: Matthias
authors.initials: M
authors.lastname: Tamm
authors.forename: Moris S
authors.initials: MS
authors.lastname: Eisen
mesh_terms: D000475:Alkenes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D058105:Polymerization
chemical_list: D000475:Alkenes; D009942:Organometallic Compounds; C578650:bis(1,3-di-tert-butylimidazolin-2-iminato) titanium; C013658:propylene