Bidentate Iron(II) Dichloride Complexes Bearing Substituted 8-(Benzimidazol-2-yl)quinolines: Synthesis, Characterization, and Ethylene Polymerization Behavior

The series of N-benzimidazolyl-substituted 2-alkyl-8-(benzimidazol-2-yl)quinolines (L1–L10) and 2-phenyl-8-(benzimidazol-2-yl)quinolines (L11–L14) and their respective bidentate iron(II) dichloride complexes (C1–C14) were synthesized and fully characterized. The molecular structures of a representative ligand (L5) and iron complexes (C2, C7) were determined by X-ray crystal structure analyses, and the distorted tetrahedral coordination geometry was observed around the iron center in both complexes C2 and C7. After activation of the iron complexes with methylaluminoxane, the iron catalysts showed activities up to 106 g·mol–1·h–1 in ethylene polymerization at elevated temperature (100 °C), yielding linear polyethylenes. The reaction parameters of the polymerization reactions were optimized, and the effect of the substituents of the different ligands on the catalytic activity and on the obtained polyethylene was discussed.