Ethylene (Co)oligomerization in alkane solvents facilitated by rigid-flexible double-layer steric strategy

Abstract

A series of double-layer steric iminopyridyl ligands containing bulky dibenzhydryl substituents with remote 4-cycloalkyl or -phenyl substituents and the corresponding metalized complexes (Ni(II) and Pd(II)) were designed, synthesized and characterized. The rigid-flexible double-layer steric iminopyridyl Ni(II) and Pd(II) complexes exhibited high efficiency for the ethylene (co)oligomerization in alkane solvents, which are more compatible with industrial production and environmental protection requirements than aromatic solvents as the reaction media in transition metal-catalyzed ethylene polymerization. Compared to rigid-rigid double-layer steric Ni(II) and Pd(II) catalyst with remote phenyl substituents, both of the novel rigid-flexible double-layer steric Ni(II) and Pd(II) catalysts with remote cyclohexyl substituents performed higher activities and produced higher molecular weight ethylene oligomers. In addition, the ethylene oligomers and co-oligomers obtained from this system contain hyperbranched microstructures.