Oligomerization of Ethylene Using New Tridentate Iron Catalysts Bearing α-Diimine Ligands with Pendant S and P Donors

Abstract

Stoichiometric Schiff base condensations of sterically bulky primary amines with acenaphthenequinone yield isolable monoimines. In the presence of iron(II) chloride, the remaining ketone reacts with a second primary amine bearing a pendant donor atom to give asymmetric, tridentate, α-diimine complexes that possess remarkable structural variability. A series of NNP and NNS tridentate iron(II) complexes are prepared; these coordination compounds become active catalysts for ethylene oligomerization when activated with methylalumoxanes. X-ray crystallographic studies of the precatalyst complexes confirm that the ligand binds in a tridentate fashion. Correlations between the precatalyst solid-state structures and catalyst activity and α-olefin product distribution are explored.