The catalytic properties of the complexes (RCp)2ZrCl2 (R=H, Me, Pri, Bun, Bui, Me3Si,cyclo-C6H11), and Me2SiCp*NBuiZrCl2 (Cp*=C5(CH3)4) combined with the AlBui3−CPh3B(C6F5)4 cocatalyst in ethylene polymerization were studied. The specific activity of the substituted bis-cyclopentadienyl complexes decreases in the sequence: Me>Pri>Bun>Bui>Me3Si>cyclo-C6H11, which corresponds to the activity sequence for these complexes activated by polymethylaluminoxane (MAO) but is 4–20 times lower in absolute value. Comparison of the polyethylene samples obtained in the presence of the same complexes with MAO and AlBui3−CPh3B(C6F5)4 cocatalysts showed that polyethylene with much higher molecular mass, melting point, and crystallinity is formed in the presence of the ternary catalytic systems, and this indicates a different nature of the active sites of the catalytic systems. The effective activation energy of polymerization (≈3.6 kcal mol−1), first order with respect to monomer and ≈0.4 order with respect to organoaluminum component, was found for the (PriCo)2ZrCl2−AlBui3−CPh3B(C6F5)4 catalytic system. It was proposed on the basis of the kinetic data that AliBu3 enters into the composition of the active site to form a bridged heteronuclear cationic complex.
metallocene catalysts zirconocenes ethylene polymerization kinetics of polymerization active site perfluorophenyl borates polymethylaluminoxane effect of substituents