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, R-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 R-olefin product distribution are explored.

Iron Catalysis in Organic Synthesis

“…A theoretical method for the prediction of the degree of ethylene oligomerization by bis(imino)-pyridine iron catalysts has been developed by the group of de Bruin. 795 Very active nonbis(imino)pyridine iron complexes for the oligomerization of ethylene have been reported by Small et al 796,797 High product purities of 1-hexene and 1-octene have been achieved. The highest turnover number of about 2.5 Â 10 6 mol of C 2 /mol of Fe was reported for a NNP tridentate α-diimino-(phosphine)iron complex (Figure 2).…”

Understanding the role of aluminum-based activators in single site iron catalysts for ethylene oligomerization

“…Methylaluminoxanes (MAO) [1][2][3][4] have been widely used as activators of ethylene oligomerization and polymerization iron-based catalysts, especially those belonging to the bis(imino)pyridine family, affording highly productive catalytic systems [5][6][7][8][9][10][11][12]. As high MAO/metal ratios are required, leading to high costs, considerable efforts have been undertaken to replace them in oligomerization reactions [13][14][15].…”

Synthesis, UV–Vis and CV properties of a structurally related series of bis(Arylimino)acenaphthenes (Ar‐BIANs)

“…Bis(arylimino)acenaphthenes (Ar‐BIANs) are a class of compounds that have been frequently used as sterically bulky diimine ligands. Since the first accounts by Elsevier and van Asselt in the 1990s, numerous transition metal Ar‐BIAN complexes, wherein the Ar‐BIAN acts as a neutral bidentate chelate, have been reported, many of which have been employed in catalysis and olefin polymerization . Their coordination chemistry to main group, transition metals and lanthanides has also been widely explored .…”