Attractive Ni^…O Interactions Enable Non-Alternating Ethylene-Carbon Monoxide Copolymerization

Area of Science:

• Polymer Chemistry
• Catalysis
• Materials Science

Background:

• Incorporating functional groups into polyethylene chains can improve waste management and recyclability.
• Non-alternating copolymerization of ethylene and carbon monoxide yields keto-polyethylene, but existing catalysts have low carbon monoxide tolerance.

Purpose of the Study:

• To develop novel catalysts that overcome the limitations of existing systems for ethylene and carbon monoxide copolymerization.
• To enhance the sustainability of polyolefins through improved catalyst design and processability.

Main Methods:

• Design and synthesis of novel neutral nickel catalyst motifs featuring P-bound 2,6-diphenoxyphenyl moieties.
• Utilizing phosphine-imidate and phosphine-phenolate ligand frameworks.
• Employing theoretical calculations to elucidate reaction mechanisms and catalyst behavior.

Main Results:

• Developed highly active and robust nickel catalysts that enable the production of keto-polyethylenes previously unattainable.
• Demonstrated that Ni···O interactions lower ethylene isomerization barriers, promoting non-alternating insertion.
• Showcased how steric constraints suppress undesired carbon monoxide insertion and catalyst deactivation.

Conclusions:

• The novel Ni···O interaction strategy significantly advances catalyst performance for ethylene and carbon monoxide copolymerization.
• This approach allows for unprecedented control over in-chain functional group concentration and catalyst productivity.
• The findings offer a pathway towards practical, environmentally benign polyolefin production.