title: Polynuclear catalysis: enhancement of enchainment cooperativity between different single-site olefin polymerization catalysts by ion pairing with a binuclear cocatalyst.
abstract: A new multicenter ethylene polymerization process is described whereby two different single-site catalysts, one competent for producing vinyl-terminated oligomers or macromonomers and one competent for producing high-molecular weight ethylene-alpha-olefin copolymers, are held in close spatial proximity via ion-pairing with a dianionic binuclear bis-borate cocatalyst. Ethylene polymerizations mediated by stoichiometrically appropriate quantities of Me2Si(tBuN)(eta5-3-ethylindenyl)ZrMe2 and Me2Si(tBuN)(eta5-C5Me4)TiMe2 activated by the bis-borate cocatalyst [Ph3C+]2[1,4-(C6F5)3BC6F4B(C6F5)3-2] yield a more homogeneous polyethylene product when compared to control polymerizations using the mononuclear activator [Ph3C+][B(C6F5)4-]. The bulk and spectroscopic properties of the polymer produced using the binuclear activator are consistent with highly branched polyethylene.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA.
authors.forename: Graham P
authors.initials: GP
authors.lastname: Abramo
authors.forename: Liting
authors.initials: L
authors.lastname: Li
authors.forename: Tobin J
authors.initials: TJ
authors.lastname: Marks