Highly active self-assembled group-IV-metal multinuclear catalysts for ethylene polymerization

• Highly active multinuclear Group-IV-metal catalysts were developed.
• Multinuclear catalysts were prepared by three linking strategies.
• Multinuclear catalysts displayed higher activity and better thermal stability.
• Polyethylene with higher MW was produced using multinuclear catalysts.
• Multinuclear catalyst with shorter spacer displayed better propylene incorporation.

Group-IV metals play an important role in the production of practical catalysts for polyethylene industry. To develop new highly active catalysts, we designed a new self-assembly strategy that leads to a new family of group-IV-metal multinuclear catalysts with bis-phenoxy-imine ligands. These multinuclear catalysts are formed via three bridging strategies, by linking the imine-N, the 4-position of phenolate, or the mixed linking strategy. The coordination environment of the catalysts was investigated with far-IR and Raman. The multiple imine-H shift found in 1H NMR revealed that the multinuclear catalysts are typical multi-site catalysts comprising of different coordination geometries. All the multinuclear catalysts were more active and stable, and produced polyethylene of higher MW than the corresponding mono-nuclear catalysts. The bridging spacer has an evident effect on catalytic activity, stability, polymer MW and incorporation rate of propylene into the polyethylene backbone.

A new family of multinuclear catalysts was developed by self-assemble of group-IV metals with bis-phenoxy-imine ligands via three linking strategies. All the new multinuclear catalysts displayed higher activity and better stability compared to corresponding mono-nuclear catalysts.Figure optionsDownload as PowerPoint slide