Binuclear half-metallocene chromium(III) complexes mediated ethylene polymerization with alkylaluminium as cocatalyst

Area of Science:

• Organometallic Chemistry
• Polymer Science
• Catalysis

Background:

• Half-metallocene chromium complexes are investigated for olefin polymerization.
• The influence of ligand structure on catalyst activity and polymer properties is crucial.

Purpose of the Study:

• To synthesize and characterize novel binuclear and mononuclear half-metallocene chromium complexes.
• To evaluate their catalytic performance in ethylene polymerization.

Main Methods:

• Synthesis and characterization of chromium complexes using spectroscopy (MS, UV-vis, NMR) and elemental analysis.
• X-ray crystallography for structural determination of key complexes.
• Ethylene polymerization experiments activated by aluminum alkyls.

Main Results:

• Binuclear complexes demonstrated higher catalytic activity than mononuclear analogues.
• High molecular weight linear polyethylene was produced with unimodal molecular weight distributions.
• A complex with a bulky 2,6-diisopropylphenyl group achieved a record activity of 2.87 × 10^6 g PE (mol Cr)^-1 h^-1.

Conclusions:

• Binuclear half-metallocene chromium complexes are highly effective catalysts for ethylene polymerization.
• Ligand design, particularly steric bulk, significantly impacts catalytic performance.
• These catalysts yield high-quality linear polyethylene suitable for various applications.