Hemilabile α-Diimine Nickel Catalyzed Olefin Polymerization

For coordination-insertion olefin polymerization, the development of novel transition-metal catalysts has drawn extensive attention in this field. In this contribution, we designed a series of hemilabile α-diimine nickel catalysts bearing oxygen atom as neighboring group. The steric hindrance and oxygen atom number of these nickel complexes (Ni1—Ni4) could be adjusted, which influenced ethylene (co)polymerization processes. The introduction of oxygen atoms could enhance the thermal stability during ethylene polymerization for Ni2 compared to the counterpart without oxygen atoms. And for the copolymerization process of ethylene with polar monomers, higher catalytic activity (1.4 × 10⁶ g·mol⁻¹·h⁻¹) and polar monomer incorporation ratio (1.2 mol%) were achieved. However, Ni4 with four oxygen atoms in this work was not active in ethylene polymerization due to the interaction between the oxygen atom and nickel catalytic center. The hemilabile effect in this work presented an example to enhance the stability of the α-diimine nickel catalysts in olefin polymerization.