A Series of Novel Dendritic Salicylaldimine Iron Catalysts: Synthesis, Characterization, and Application in Ethylene Oligomerization

Abstract

A series of novel dendritic salicylaldimine ligands and their corresponding iron complexes have been synthesized using 1.0 generation (1.0 G) dendritic macromolecules, salicylaldehyde and FeCl₂ · 4H₂O as raw materials. The structures of the ligands and iron complexes were characterized by FT-IR, ¹H NMR, UV, ESI-MS, and elemental analysis. The dendritic salicylaldimine iron complexes presented moderate catalytic activity in ethylene oligomerization and selectivity for higher carbon number olefins products (≥C₈) when they were activated with methylaluminoxane (MAO). The catalytic activity and product selectivity were related to the co-catalyst, solvent, bridged group length and reaction parameters such as reaction temperature, Al/Fe molar ratio and ethylene pressure. The complex C3 showed the highest catalytic activity (up to 13.75 × 10⁴ g (mol Fe h)^–1) and the selectivity of higher carbon number olefins (35.31%) at the optimized conditions. Moreover, the catalytic properties of dendritic salicylaldimine iron complex C3 was better than non-dendritic iron complex.