Synthesis, characterization, and ethylene polymerization behavior of Cr(III) catalysts based on bis(pyrazolylmethyl)pyridine and its derivatives

• 2,6-Bis(pyrazol-1-ylmethyl) pyridine derivatives and their Cr(III) complexes were prepared.
• These new Cr complexes exhibited moderate activities in ethylene polymerization.
• Their catalytic performances were affected by the substituents on the pyrazole units.

New chromium(III) [Cr(III)] catalysts based on 2,6-bis(pyrazol-1-ylmethyl) pyridine derivatives have been synthesized, characterized, and evaluated for ethylene polymerization. All ligands with substituents on the pyrazole rings were analyzed by single-crystal X-ray diffraction to clearly identify isomer structures. Additionally, X-ray analyses of the new Cr(III) complex bearing 2,6‑bis[(4,5-dimethyl-1H-pyrazol-1-yl) methyl]pyridine showed tridentate coordination on the mer-octahedral chromium sphere. Upon activation with dry methyaluminoxane, the precatalysts produce polyethylene (PE) as a major product, and their catalytic performances were affected by the substituents on the pyrazole units; the introduction of functional groups on the pyrazole raised PE compositions and the molecular weight of the PE.

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