Synthesis and Ethylene Oligomerization of Hyperbranched Salicylaldimine Nickel Complexes

Abstract

A series of new hyperbranched salicylaldimine nickel complexes were synthesized by the Schiff's base and the complexation reactions with 1.0 generation hyperbranched macromolecules, salicyladehyde and nickel chloride hexahydrate as materials by employing two-step synthesis and one-pot synthesis, respectively. The hyperbranched salicylaldimine ligands and the complexes were characterized by FT-IR, 1 H NMR, UV, and ESI-MS. All nickel complexes, activated with Methylaluminoxane, exhibited high activities for ethylene oligomerization (TOF = 1.92-4.93 g/mol Ni h) and showed good selectivities for the longer chain oligomers produced (36.35-60.33%). When activated with ethylaluminum dichloride, it was found that a tandem process occurred in which ethylene oligomerization was followed by Friedel-Crafts alkylation of the reaction solvent, toluene. On increasing the pressure of ethylene and Al/Ni ratio, the catalytic activities of precatalyst increased and the processes became more selective for the shorter oligomers. Not only the polymerized parameters but also the length of alkyl chain of the ligands influenced the catalytic activities and selectivities for the longer chain oligomers. The catalytic activities and selectivities for the longer chain oligomers declined with the increase in length of alkyl chain of ligand.

Nickel Catalyzed Olefin Oligomerization and Dimerization

“…Increasing the carbon chain length in both positions (n and R) leads to less soluble pre-catalysts, and thus decreases the rate of oligomerization (49a-c). [134][135][136] Replacing the linear alkyl R 49c with a cyclic alkyl 49d induces higher activity of the catalytic system without changing the selectivity (Table 6, example for 49d). 137 Bidentate phenoxide-iminophosphorane nickel(II) complexes 50 and 51 (Figure 27 The complexes 50 and 51 were evaluated and compared for the catalytic oligomerization of ethylene in the presence of AlEt 2 Cl.…”

“…Wang et al − developed hyperbranched salicylaldimine nickel complex 49 (Figure ) with the intention of combining the best properties of homogeneous and heterogeneous catalyst. The choice of the cocatalyst has a great impact on the selectivity of the catalytic system.…”

Structural and ethylene oligomerization studies of chelating (imino)phenol Fe(ii), Co(ii) and Ni(ii) complexes: an experimental and theoretical approach

“…This data is also consistent with the absence of the halides in the metal coordination sphere. 38 For example, the quinoline ligand L3H showed the OH vibration signal at 3062 cm −1 (Fig. S9, ESI†), while this signal is absent in the corresponding complexes Fe3 , Co3 and Ni3 (Fig.…”

Synthesis of New Dendritic Titanium Catalysts and Catalytic Ethylene Polymerization

“…Toluene was used as a solvent, and methylaluminoxane (MAO) was used as a cocatalyst in the ethylene polymerization. 34 To probe the effect of reaction parameters on the ethylene polymerization behaviors, we investigated the complexes by changing the reaction temperature, the concentration of MAO, and ethylene pressure. The detailed results are summarized in Table 1.…”