Bis(imino)pyridine Iron Complexes Bearing Imino-Carbon Thioether Substituents as Highly Active Catalysts for Ethylene Oligomerization

A series of bis-(imino)-pyridine iron complexes bearing thioether substituents on the imino-carbon atom has been synthesized and evaluated for ethylene oligomerization. All of the iron complexes exhibited high catalytic activity for ethylene oligomerization. By tuning the electronic and steric effects of the substituents, most catalysts produce a very low waxy content while maintaining a very high activity. The catalytic performance can be further optimized by changing the reaction conditions (including catalyst loading, reaction temperature, cocatalyst amount, and ethylene pressure). Among them, the phenyl thioether-substituted iron complex can reach a very high activity of 1.56 × 10⁸ g mol^-1(Fe) h^-1 with a considerable <i>K</i> value of 0.68 and 94.1% α-olefin selectivity, while it only gave 0.1 wt % waxy solids.