New iron-based bis(imino)pyridine and acetyliminopyridine complexes as single-site catalysts for the oligomerization of ethylene

Abstract

New iron-based bis(imino)pyridine complexes 6, 7 and the acetyliminopyridine complex 8a are active catalysts together with the co-catalyst MAO for the oligomerization of ethylene. The ligands 1–4 with electron donating methoxy- and electron withdrawing trifluoromethyl-substituents react with FeCl2(thf)2 to the Fe(II) complexes 6–8a. Especially p-methoxy substituents in 6b increase the selectivity in the production of α-olefins. The distribution of oligomers obtained in the catalyzed ethylene oligomerization with 5–8a follows Schulz–Flory rules for oligomers >C4. The probability of chain propagation α is increased by lowering the reaction temperature, while higher pressure of the ethylene gas in the reaction has nearly no effect on the α-values.