2-Benzoxazolyl-6-[1-(arylimino)ethyl]pyridyliron(II) chlorides as ethylene oligomerization catalysts

A series of iron(II) dichloride complexes (Fe1–Fe7) ligated by 2-(2-benzoxazolyl)-6-[1-(arylimino)ethyl]pyridines was synthesized and characterized [aryl = 2,6-R¹₂C₆H₃; R¹ = Me (1), Et (2), iPr (3), Cl (4), Br (5); 2,6-Me₂C₆H₂-4-R², R² = Me (6), Br (7)]. The molecular structures of Fe1, Fe3, and Fe5 were determined by the single-crystal X-ray diffraction. Complexes Fe1 and Fe3 both display distorted trigonal-bipyramidal geometries, whereas complex Fe5 is a distorted square pyramid. Upon activation with modified methylaluminoxane, all iron complexes showed moderate to good activities [up to ca. 10⁶ g(product)?×?(mol Fe)^–1 h^–1?bar^–1] for the oligomerization and polymerization of ethylene, with high selectivity for vinyl-terminated oligomers or polyethylene waxes.