Nickel(ii) complexes chelated by 2,6-pyridinedicarboxamide: syntheses, characterization, and ethylene oligomerization

Abstract

ABSTRACT：N,N′-Bis(2,6-R-phenyl)-2,6-pyridinedicarboxamide (L: R = Cl, L1; R = F, L2; R = H, L3; R = Me, L4; R = Et, L5; R = i Pr, L6) were designed as neutral ligands, and the corresponding nickel complexes LNiBr 2 (Ni1-Ni6) were synthesized as precatalysts for ethylene oligomerization. All new ligands were fully characterized by NMR, FT-IR spectra, and elemental analysis, while the nickel complexes were examined by FT-IR spectra and elemental analysis. The coordination mode of ligand with nickel in complexes Ni5 and Ni6 was tridentate by O^N^O as established by single crystal X-ray diffractions. All the nickel complexes Ni1-Ni6 were tested for ethylene oligomerization with different alkylaluminums as cocatalysts, and diethylaluminum chloride (Et 2 AlCl) was proved to be the most effective. Upon activation with Et 2 AlCl, all nickel complexes showed high catalytic activity (up to 7.55 × 10 5 g·mol -1 (Ni)·h -1 ·atm -1 ) with good selectivity for α-C 4 .

Nickel Catalyzed Olefin Oligomerization and Dimerization

“…Consequently, small chains R1 and long alkyl chains R2 lead to higher activity of the catalytic system (Table 5, example for 36a). 120 The reactivity of nickel(II) complexes bearing 2,6-pyridinecarboxamide ligands 37 was discussed by Ye et al 121 (Figure 20). Activated by AlEt 2 Cl, these complexes produce high selectivity for butenes and good selectivity towards 1-butene in the butene fraction.…”

Electrochemical Synthesis of Zirconium Pre-Catalysts for Homogeneous Ethylene Oligomerization

“…The formation of longer chain oligomers may indicate the existence of a certain similarity between the length of the alkyl chain in Zr-R catalytic intermediate and the length of the carboxylate moiety in the initial pre-catalyst. The increase in activity upon transition from [Zr(Ac) x ] to [Zr(Oct) x ] and [Zr(Laur) x ] may be due to the increase of their solubility in toluene [47]. The electrochemically synthesized zirconium carboxylates are superior in activity to ZrCl 4 and provide the formation of a smaller amount of polymer (entries 1 and 3-5, Table 3).…”

Alkene oligomerization via metallacycles: Recent advances and mechanistic insights

“…Several nickel (II) precursors were reported to selectively dimerize ethylene into butenes after activation. [92][93][94][95] Le Floch, Adamo and co-workers carried out a DFT study on their catalytic system using P,N bidentate ligands [95] to compare Cossee-Arlman and metallacyclic mechanism. [96] Because the exact nature of the catalytically active complex was not known because of activation by excess MAO under ethylene, these authors evaluated the reactivity at the Ni center at different oxidation states.…”