Iron Complexes Bearing 2-Imino-1,10-phenanthrolinyl Ligands as Highly Active Catalysts for Ethylene Oligomerization

Abstract

A series of iron complexes ligated by 2-imino-1,10-phenanthrolinyl ligands, LFeCl 2 (L ) 2-(ArNd CR)-1,10-phen), were synthesized and sufficiently characterized by elemental and spectroscopic analysis along with X-ray diffraction analysis. Activated with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), these iron(II) complexes show high catalytic activities up to 8.95 × 10 7 g mol -1 (Fe) h -1 for ethylene oligomerization. The distribution of oligomers produced follows Schluz-Flory rules with high selectivity for R-olefins. Both the steric and electronic effects of coordinative ligands affect the catalytic activity and the properties of the catalytic products. The parameters of the reaction conditions were also investigated to explore the catalytic potentials of these complexes.

Bi- and tri-dentate imino-based iron and cobalt pre-catalysts for ethylene oligo-/polymerization

“…93 In addition, 35 it was found that the substituent on the arylimino moiety affected the product formed, for example, for the phenyl bearing an Et substituent, ie 172b, the best activity was observed, whilst stronger electron withdrawing groups decreased the ethylene reactivity (when the phenyl substituent 40 R 1 was a halogen, the activity order decreased as follows: Br > Cl > F). 91 Variation of the R substituent on the imino-C of ligands of the type, 2-(ArN=CR)-1,10-phenanthroline, also resulted in changes to the catalytic performance. The aldimine (R = H, 172a), ethyl-ketimine (R = Et, 172c) and phenyl-45 ketimine (R = Ph, 172d) complexes showed relatively lower catalytic activities than did the corresponding methyl-ketimine (R = Me, 172b) complex.…”

“…However, upon treatment with MAO or MMAO, 172c, which bears an ethyl substituent 50 on the imine-C, revealed a better thermal stability (10 °C higher compared to 172b) and possessed a higher content of α-olefins (C6-C16). 91,94,95 When a phenyl substituent was introduced at the 9-position of the 1,10-phenanthroline by reaction of PhLi with 2-acetyl-1,10-phenanthroline, the 55 resultant 2-imino-9-phenyl-1,10-phenanthrolines complexes 174a, 174b, 174d exhibited much lower activities (2.33 × 10 6 g mol -1 h -1 ) in comparison to their analogues 172a-d, and the products included butene (major product, > 90 %) and hexene; there was no polymer formation. 96 Replacement of the imine 60 group with benzimidazoles resulted in iron complexes of type 176, bearing 2-(benzimidazol-2-yl)-1,10-phenanthrolines.…”

“…98 It should be emphasised that most of the previous research on bis(imino)pyridyl iron pre-catalysts has recorded ethylene 80 polymerization and oligomerization, with much of the focus being on the polymerization products. However, iron catalytic systems bearing 2-iminophenanthrolines can readily deliver oligomerization products 91 and have recently been successfully scaled up for use in a 500 tonne pilot plant. 85 To highlight the catalytic performances of the different complex pre-catalysts, a summary of promising model complexes is collected in Table 11.…”

Iron-Based and Cobalt-Based Olefin Polymerisation Catalysts

“…While the 2,6-bis(imino)pyridine ligand frame has continued to lead the way, the past 10 years has also seen the development of alternative ligand sets that can act as compatible supports for iron and cobalt ethylene oligomerisation/polymerisation catalysts ( Table 4 ) [46,50,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,208,209] ; active catalysts based on bimetallic iron and cobalt precatalysts have also started to emerge ( Table 5 ) [54,210,211,212,213,214,215] . In the main, these systems show lower activities than the prototype bis(imino)pyridine-based catalysts, although several of these systems have significantly started to approach their catalytic performances (e.g.…”

Nickel Complexes Bearing 2‐(Benzimidazol‐2‐yl)‐1,10‐phenanthrolines: Synthesis, Characterization and Their Catalytic Behavior Toward Ethylene Oligomerization

“…In addition to the P ∧ O chelating nickel complexes used in the SHOP process, [2,6] there are numerous nickel catalysts being investigated with bidentate ligands, such as N ∧ O, [7,8] P ∧ N, [9,10] and N ∧ N, [3,[11][12][13] and tridentate ligands, such as N ∧ N ∧ O, [14] N ∧ P ∧ N, [15] P ∧ N ∧ P, [16] P ∧ N ∧ N, [13d,16] and N ∧ N ∧ N, [17,18] as well as organometallic compounds. [15a] Considering N ∧ N ∧ N tridentate nickel complexes as catalysts for ethylene oligomerization, several models with high activities have been developed in our group by using 2-imino-1,10-phenanthrolines (A), [18b] 2-(2-benzimidazole)-6-iminopyridine (B) ligands, [19] and 6-imino-2-quinoxalinylpyridines.…”