Nickel(II) Complexes Chelated by 2-Arylimino-6-benzoxazolylpyridine: Syntheses, Characterization, and Ethylene Oligomerization

Abstract

2-(2-Benzoxazolyl)-6-(1-(arylimino)-ethyl)pyridines (L) were designed as ligands, and their nickel complexes LNiX2 (X = Cl, 1a−7a; X = Br, 1b−7b) were formed. All ligands were fully characterized by NMR, FT-IR spectra, and elemental analyses, while the nickel complexes were examined by FT-IR spectra and elemental analyses. The molecular structures of nickel complexes were established by single-crystal X-ray diffraction. Complex 6a possesses coordination number 6 by coordination of one ligand, two moles of methanol, and one chloride anion, whereas complexes 1b and 5b possess coordination number 5 with distinct distortions, for 1b toward trigonal-bipyramidal geometry and for 5b toward square-pyramidal geometry. The nickel complex 1a was evaluated in the catalytic oligomerization of ethylene with different alkylaluminums as cocatalysts, and diethylaluminum chloride (Et2AlCl) proved to be the most effective. Upon activation with Et2AlCl, all nickel complexes showed outstanding thermal stability and good catalytic activity toward ethylene dimerization with high selectivity for α-C4.

2‐Benzoxazolyl‐6‐[1‐(arylimino)ethyl]pyridyliron(II) Chlorides as Ethylene Oligomerization Catalysts

“…[28] On treating these ligands with ferrous dichloride in ethanol at room temperature for 10 h the product complexes precipitated as blue powders in high yield (Scheme 1). The complexes are air stable in the solid state.…”

“…For practical applications, iron catalyst show two advantageous features: high selectivity in forming vinyl-terminated products and good activity for linear α-olefins from C 4 to C 28 . Highly active catalytic systems are of great interest for the preparation of α-olefins, [24] and this is the basis of a joint venture between PetroChina and DuPont in the ironcatalyzed oligomerization of ethylene.…”

“…[27] Replacing one of the imino groups in 2,6-diiminopyridine [1,2] resulted in 2-(benzimidazolyl)-6-iminopyridines B, which formed iron(II) complexes with high ethylene oligomerization activities. [16] 2-(2-Benzoxazolyl)-6-[1-(arylimino)ethyl]pyridines, which have previously been shown to give nickel complexes with high ethylene oligomerization activities, [28] could also be of interest in iron catalysts. We describe here the synthesis and characterization of new iron(II) complexes with ligands bearing one heterocyclic substituent, as well as their behavior in ethylene oligomerization and polymerization.…”

Covalent organic frameworks as supports for a molecular Ni based ethylene oligomerization catalyst for the synthesis of long chain olefins

“…It is indeed well known that the rate of the -H elimination displays the lowest activation energy and may become the rate limiting step at higher temperatures (see Figure 6.1), leading to higher selectivities to C 6+ olefins and to lower overall reaction rates. [83] However, even for those cases where similar reaction temperatures were used (table 4 entries 9, 11 and 13) the selectivity shown by the PAF based catalysts to longer hydrocarbons is striking. In the same line, experiments performed with the Ni@IL-PON at room temperature (table 4, entry 5) display at least a three-fold increase in selectivity to C 6+ compared to other systems.…”

Preparation, Characterization, and Catalytic Property of a Cu(II) Complex with 2-Carboxybenzaldehyde-p-Toluenesulfonyl Hydrazone Ligand

“…For example, they have been widely exploited for luminescence [1][2][3][4], antitumor [5][6][7][8], antibacterial [9][10][11][12], gas storage [13], as well as magnetic [14][15][16][17]. Meanwhile, metal complex materials have also been attracted interests due to their excellent catalytic activities for many organic reactions [18][19][20][21][22].…”