Significant Proximity and Cocatalyst Effects in Binuclear Catalysis for Olefin Polymerization

We describe here the implementation of methylene-bridged binuclear “constrained geometry catalyst” (μ-CH2-3,3‘){(η5-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 (C1-Zr2) to produce high-Mw branched polyethylene. In ethylene homopolymerization, ∼70× increases in molecular weight are achieved with(C1-Zr2) vs (μ-CH2CH2-3,3‘){(η5-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 (C2-Zr2) under identical polymerization conditions using(Ph3C+)2[1,4-(C6F5)3BC6F4B(C6F5)3]2- (B2) as the cocatalyst for both. With MAO as the cocatalyst, ∼600× increases in polyethylene molecular weight are achieved with (μ-CH2CH2-3,3‘){(η5-indenyl)[1-Me2Si(tBuN)](ZrCl2)}2 (C2-Zr2Cl4) and (μ-CH2-3,3‘){(η5-indenyl)[1-Me2Si(tBuN)](ZrCl2)}2 (C1-Zr2Cl4) vs mononuclear [1-Me2Si(3-ethylindenyl)(tBuN)]ZrCl2 (Zr1Cl2). In the ethylene + 1-hexene copolymerization, C1-Zr2 enchains 3× more 1-hexene than does C2-Zr2 under identical polymerization conditions (B2 as cocatalyst). With MAO as the cocatalyst, C2-Zr2Cl4 enchains 3.5× more, and C1-Zr2Cl4 4.2× more, 1-hexene than doe...