Crystal Structure and Ethylene Oligomerization Catalytic Activity of {2‐Carbethoxy‐6‐[1‐[(2,6‐diethyl‐phenyl)imino]ethyl]pyridine}CoCl₂

Abstract

The unsymmetric precursor ethyl 6-acetylpyridine-2-carboxylate (4) was synthesized from 2,6-dimethylpyridine (1). On the basis of this precursor, a new mono(imino)pyridine ligand (5) and the corresponding Co(II) complex {2-carbethoxy-6-[1-[(2,6-diethylphenyl)imino]ethyl]pyridine}CoCl 2 (6) were prepared. The crystal structure of complex indicates that the 2-carbethoxy-6-iminopyridine is coordinated to the cobalt as a tridentate ligand using [N, N, O] atoms, and the coordination geometry of the central cobalt is a distorted trigonal bipyramid, with the pyridyl nitrogen atom and the two chlorine atoms forming the equatorial plane. Being applied to the ethylene oligomerization, this cobalt complex shows catalytic activity of 1.820×10 4 g/mol-Co•h at 101325 Pa of ethylene at 15.5 ℃ for 1 h, when 1000 equiv. of methylaluminoxane (MAO) is employed as the cocatalyst.

Nickel(II) complexes with mono(imino)pyrrole ligands: preparation, structure and ethylene polymerization behavior

“…Although a number of mono(imino)pyrrole ligands were developed, nearly all of the reported ligands bore H side arms [10][11][12][13][14][15][16]. We have expanded this work to mono(imino) pyrrole ligands with a -CH 3 side arm in order to have greater electronic and steric effects.…”

“…Bis(imino)pyridyl-metal catalysts have been an attractive research field because of their flexible structural modifications and complexation between ligand and metal, as well as outstanding catalytic performance. Studies have mainly concentrated on adjusting the structure of the ligand, usually using the following ways [5][6][7][8]: (1) introducing heteroatoms to the pyridine ring to get an N-based sixmembered heterocyclic imino ligand, such as pyrimidine, pyrazine, and triazine ligands; (2) replacing the six-membered heterocycle with a five-membered heterocycle such as a pyrrole, thiophene, or furan ring; (3) modifying the imino substituent to get ligands with different side arms, such as carbazole or Pybox ligands [9]; or (4) changing the symmetric bis (imino) structure to an asymmetric structure [10][11][12][13]. For example, zirconium and titanium complexes bearing mono(imino)pyrrole ligands, reported by Fujita [14,15] and Bochmann et al [7], were demonstrated to be good catalysts for ethylene polymerization.…”