Polynuclear Catalysis:  Enhancement of Enchainment Cooperativity between Different Single-Site Olefin Polymerization Catalysts by Ion Pairing with a Binuclear Cocatalyst

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-α-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( t BuN)(η5-3-ethylindenyl)ZrMe2 and Me2Si( t BuN)(η5-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.