A rigid-flexible double-layer steric strategy for ethylene (co)oligomerization with pyridine-imine Ni(ii) and Pd(ii) complexes

Abstract

Late transition-metal-based catalysts have been extensively used for decades in olefin oligomerizations. In this study, a series of N-terphenyl pyridine-imine Ni(II) and Pd(II) complexes bearing rigid-flexible double-layer steric substituents were designed and synthesized. The Ni(II) complexes were highly effective and afforded hyperbranched ethylene oligomers in ethylene oligomerization. Moreover, low-molecular-weight ethylene oligomers and ethylene-methyl acrylate (MA) co-oligomers with hyperbranched microstructures were produced using the corresponding Pd(II) complexes. Most notably, there was a significant difference in the branching type distribution for the ethylene oligomers obtained using the Ni(II) and Pd(II) complexes. The rigid-flexible double-layer steric strategy enhances the molecular weight of the resulting ethylene oligomers and promotes the co-oligomerization of ethylene and MA.