Preparation of branched oligoethylene and polar functionalized oligoethylene using unsymmetrical arylamine based cationic Ni(II) and Pd(II) iminopyridyl catalysts

Abstract

In this contribution, three unsymmetrical arylamine based pyridine-imine ligands and the corresponding nickel and palladium complexes were prepared and used for ethylene oligomerization. The nickel complexes are highly active (level of 106 g·mol−1·h−1) in catalyzing ethylene oligomerization to produce highly branched (66–89/1000C) oligoethylenes (1.4–3.2 kg/mol). The corresponding palladium complexes presented moderate catalytic activities (level of 104 g·mol−1·h−1) and low molecular weight (0.4–0.6 kg/mol) oligoethylenes with high branching densities (103–126/1000C) were yielded in ethylene oligomerization. Moreover, high incorporation ratio (6.86–14.16 mol%) ester functionalized oligoethylenes with low molecular weights (ca. 0.4 kg/mol) were yielded with these palladium complexes in ethylene–methyl acrylate co-oligomerization. Methyl branching comprises the majority of all the branching for the oligoethylenes yielded by nickel complexes and branching of C3+ comprises the majority with palladium ones. Hyperbranched architecture was identified for all the produced oligoethylenes and ester functionalized oligoethylenes. Most interestingly, compared with the reported pyridine-imine catalysts with fully substituted benzothiophenes, the partially benzothiophene substituted ones exhibited significantly higher activity and yielded much higher molecular weight oligoethylenes.