A robust Ni(II) α-diimine catalyst for high temperature ethylene polymerization

Area of Science:

• Organometallic Chemistry
• Polymer Science
• Catalysis

Background:

• Nickel(II) α-diimine complexes are effective catalysts for olefin polymerization.
• Steric hindrance around the metal center can influence catalyst activity and polymer properties.
• Developing catalysts with high thermal stability is crucial for industrial applications like gas-phase polymerization.

Purpose of the Study:

• To synthesize novel, sterically demanding Ni(II) α-diimine precatalysts.
• To evaluate the catalytic activity and performance of these precatalysts in polyethylene production.
• To assess the thermal stability of the resulting catalyst system for industrial polymerization conditions.

Main Methods:

• Synthesis of Ni(II) α-diimine precatalysts using 2,6-bis(diphenylmethyl)-4-methyl aniline.
• Activation of the precatalyst with methylaluminoxane (MAO).
• Polymerization of ethylene at temperatures up to 100 °C and characterization of the produced polyethylene.

Main Results:

• The synthesized Ni(II) catalyst (NiBr2(ArN═C(Me)-C(Me)═NAr)) exhibited high activity upon activation with MAO.
• Well-defined polyethylene with narrow molecular weight distributions (Mw/Mn = 1.09-1.46) was produced.
• The catalyst demonstrated remarkable thermal stability at polymerization temperatures of 80-100 °C.

Conclusions:

• Sterically demanding Ni(II) α-diimine precatalysts are highly effective for producing well-defined polyethylene.
• The catalyst system exhibits excellent thermal stability, making it suitable for industrial gas-phase polymerization.
• This research contributes to the development of advanced catalysts for efficient polymer production.