Polynuclear olefin polymerization catalysis: Proximity and cocatalyst effects lead to significantly increased polyethylene molecular weight and comonomer enchainment levels

Weight watching: In ethylene polymerization, approximately 70 fold increases in molecular weight are achieved with C1-Zr₂ compared to ethylene-bridged C2-Zr₂ (see scheme). With MAO as the cocatalyst, approximately 600 fold increases in polyethylene (PE) molecular weight are achieved with C2-Zr₂Cl₄ and C1-Zr₂Cl ₄ compared to a mononuclear analogue. These results support the argument that Zr-Zr proximity significantly influences chain-transfer rates, and such effects are highly cocatalyst-sensitive.