Iron(II) and Cobalt(II) 2-(Benzimidazolyl)-6-(1-(arylimino)ethyl)pyridyl Complexes as Catalysts for Ethylene Oligomerization and Polymerization

Abstract

A series of iron(II) (7a-11a) and cobalt(II) (7b-11b) 2-(1-methyl-2-benzimidazolyl)-6-(1-(arylimino)ethyl)pyridyl complexes were synthesized, as well as bidentate iron(II) and cobalt(II) complexes ligated by 2-(2-benzimidazolyl)-6-methylpyridine, 2-(carboethoxyl)-6-(2-benzimidazolyl)pyridine, and 2-(1methyl-2-benzimidazolyl)-6-acetylpyridine. All organic compounds were fully characterized by NMR and IR spectroscopy and elemental analysis, while the metal complexes were carefully examined by IR spectroscopy and elemental analysis. Their molecular structures were determined by single-crystal X-ray diffraction analysis. The bidentate metal complexes display a distorted-tetrahedral coordination geometry; however, 2a is an exception, with a distorted-trigonal-bipyramidal geometry due to coordination of one DMF molecule. The X-ray crystallographic studies on all of the tridentate metal complexes revealed the coordination geometry as a distorted trigonal bipyramid. Upon activation with MAO or MMAO, the iron(II) 2-(2-benzimidazolyl)-6-(1-(arylimino)ethyl)pyridyl complexes showed high activities with good R-olefin selectivity, while the cobalt(II) analogues displayed moderate to good catalytic activities. However, other bidentate metal complexes showed considerable moderate catalytic activity. The oligomers and polyethylene waxes obtained were R-olefins, and the distribution of oligomers resembled Schulz-Flory rules with some exceptions. Various reaction parameters were investigated, and the results revealed that both the steric and electronic effects of ligands affect the catalytic activities of their metal complexes as well as the distribution of products.

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.…”

Synthesis, characterization and ethylene oligomerization behavior of 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridylnickel dihalides

“…Beyond our efforts for iron procatalysts in ethylene reactivity [25,26], some nickel procatalysts were also investigated and possessed good activities [27][28][29][30][31]. More recently, the metal complexes ligated by 2-(benzimidazol-2-yl)-6-(1-aryliminoethyl)pyridines have been explored [32][33][34][35][36][37][38], and the metal complexes ligated by 2-(1-alkylbenzimidazol-2-yl)-6-(1-aryl-iminoethyl)pyridines (model A, Scheme 1) [32][33][34][35] possessed lower activity than their analogs bearing 2-(1H-benzimidazol-2-yl)-6-(1-aryliminoethyl)pyridines (model B, Scheme 1) [36][37][38]. Extensive work was conducted on substituting the phenyl group of the benzimidazoles, and nickel complexes bearing 6-(methyl-substituted-1H-benzoimidazol-2-yl)-2-iminopyridines were studied in ethylene oligomerization (model C, Scheme 1) [39].…”

Nickel(II) Dibromide Complexes Bearing Bis(benzimidazolyl)amine and Bis(benzimidazolyl)pyridine Ligands for Ethylene Oligomerizations

“…Oligomers were produced with high selectivity towards a-olefins, and polyethylenes were produced with extremely broad polydispersity. Variants of the bis(imino)pyridine ligand where only one imino arm has been replaced with benzimidazole have been reported bound to iron, cobalt, and nickel, all of which successfully initiated ethylene oligomerization [34][35][36]. The Gibson group reported a mechanism study of ethylene oligomerization by chromium complex bearing 2,6-bis(1H-benzo[d]imidazol-2-yl)pyridine [37].…”