Effects of ancillary ligands on molecular structure and catalytic properties of tridentate α-sulfonate-β-diimine nickel complexes toward ethylene (co)polymerization

• Synthesis and characterization of a series of tridentate α-sulfonate-β-diimine nickel complexes. • Ancillary ligands impact the geometry and stabilization of nickel complexes. • Ancillary ligands impact catalytic activity and thermal stabilization of catalysts. • Pivotal roles that ancillary ligands play in ethylene (co)polymerization. In the design of olefin polymerization catalysts, ancillary ligands attract less attention than ligands and the effects of ancillary ligands on olefin polymerization has been rarely studied because they are commonly regarded as auxiliary complexing agents for transition metal complexes. We herein report the synthesis and characterization of a series of tridentate α -sulfonate- β -diimine nickel complexes with coordinating solvents (CH 3 CN, PhCN, THF, and H 2 O) to study the effects of ancillary ligands on the molecular structure of complexes and catalytic properties toward ethylene (co)polymerization. Ancillary ligands impact the geometry and stabilization of α -sulfonate- β -diimine nickel complexes, which are closely related to their coordination ability to the metal center. Ethylene (co)polymerization results show that ancillary ligands have an important influence on polymerization activity and thermal stabilization of the catalyst through their dissociation from the metal and the coordination completion between ancillary ligands and ethylene monomer.