A Facile and Scalable α-Diimine Platform for Nickel-Catalyzed Ethylene Polymerization

The structural design and facile synthesis of ligands are crucial for the development of innovative catalysts. Advances have enabled the iterative design of benchmark α-diimine nickel catalysts for the synthesis of polyolefins, which represent the largest class of polymers. In this work, a versatile post-synthetic modification (PSM) strategy is introduced for the synthesis of a new family of α-diimine nickel catalysts, deviating from the conventional methods. Based on the commercial butanedione ligand backbone that is found in α-diimine nickel catalysts, target groups were introduced into the backbone via a one-pot substitution reaction. This simple and efficient approach enabled the large-scale production of the target systems without purification. Using this protocol, 20 new ligands (50 g-level) and 20 new nickel catalysts were easily and rapidly synthesized. The catalysts demonstrated significant enhancements in their catalytic activities (4.4 × 10⁸ g mol^-1 h^-1), thermostabilities (from 90 to 150 °C), and polymer molecular weights (8.3-fold those of polyethylenes produced by the unmodified catalyst) during ethylene polymerization. These improvements are comparable to those achieved through complicated and tedious aniline modifications in pioneering reports, thereby facilitating the kg-scale synthesis of polyethylenes, varying from semi-crystalline plastics to thermoplastic elastomers and ultimately to wax-like and oil-like products.