Several nickel and zirconium complexes(i.e. Ni: [N, N]NiBr2, in which [N, N] indicates bidentate nitrogen containing ligands (1: [N, N]=N-(2,6-diisopropylphenyl)pyridine-2- carboxaldimine (C18H22N2); 2: N-(2,6-diisopropylphenyl)-6-methylpyridine-2-carboxaldimine (C19H24N2); 3: N-(2,4,6- trimethylphenyl)pyridine-2-carboxaldimine(C15H16N2); 4: N-(2,4,6-trimethylphenyl)-6-methylpyridine-2-carboxaldimine (C16H18-N2),(Zr :[N-O]2ZrCl2, were synthesized. Some of the nickel and zirconium complexes exhibit high activity for ethylene oligomerization in the presence of an organoaluminum activator. The main factor affecting the activity and the structure of oligomers is the satiric effect of constituents on [N, N] and {N-O} ligands. Methylaluminoxane (MAO) -activated catalysts showed higher activities and produced oligomers with higher molecular weight than Et2AlCl activated ones. The oligomerization in toluene rather than hexane results in much higher activity, and the oligomers produced in toluene have relatively high molecular weight. With activation of MAO or Et2AlCl, the [N, N]NiBr2 and [ N-O]Zr system tended to produce highly branched oligomers with low alpha-olefins content, but the alpha-olefins content could be increased by changing the reaction conditions.
Catalytic ethylene oligomerization represents a topic of considerable current academic and industrial interest, in particular for the production of linear R-olefins in the C4-C10 range, whose demand is growing fast. Identifying and fine-tuning the parameters that influence the activity and selectivity of metal catalysts constitute major challenges at the interface between ligand design, coordination/ organometallic chemistry, and homogeneous catalysis. In this work, we show how comparative studies aiming at modulatingthe coordinating properties of functional ligands for a metal, such as nickel and zirconium, which is used in industrial processes, lead to beneficial effects in catalytic ethylene oligomerization.
Most of the recent studies point out to continued sharp increase for the demand for the production of alpa Olefins due to its use in meany industries, as shown in Fig.1, whereas fig 2 shows Its worldwide consumptions distribution
