Synthesis of (Salicylaldinato) nickel Complexes and Their Catalysis for Ethylene Polymerization

A series of substituted salicylaldiminato ligands L₁—L₅ and corresponding nickel(II) complexes C₁—C₅ were prepared and characterized by ¹H-NMR, IR, Mass and EA. Using C₃ as a single-component catalyst, ethylene polymerization was investigated under different polymerization conditions. C₃ exhibited the highest activity in CH₂Cl₂ among the applied solvents, and even medium activity in mixed solvent of CH₂Cl₂ and H₂O. Under optimal conditions, the polymerization activities of C₁—C₅ were compared. Complexes with bulky substituents on the ortho-position of salicylaldiminato displayed high activity, while those with electron-withdrawing groups in ortho-position or para-position, provided low catalytic activities.