Synthesis, characterization and catalytic behavior toward ethylene of cobalt(II) and iron(II) complexes bearing 2-(1-aryliminoethylidene)quinolines

A series of 2-(1-aryliminoethylidene)quinolines (L) were synthesized and used as bidentate N^N ligands in coordinating with metal (cobalt and iron) chlorides to form complexes of the type LMCl₂, cobalt(II) (Co1–Co5) and iron(II) (Fe1–Fe5). All organic compounds and metal complexes were fully characterized, and the molecular structures of the representative complexes Co3·DMF and Fe4·DMF were confirmed as distorted bipyramidal geometry at the metal by single-crystal X-ray diffraction. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO) under 10 atm ethylene, all complexes showed high activities in ethylene dimerization with activities of up to 1.82 × 10⁶ g mol^-1 (Co) h^-1 and 5.89 × 10⁵ g mol^-1 (Fe) h^-1, respectively.