On the topology of highly branched polyethylenes prepared by amine−imine nickel and palladium complexes: the effect of ortho‐aryl substituents

Abstract

ABSTRACTSeries of nickel and palladium complexes bearing amine−imine ligands in various ortho‐aryl and backbone positions were prepared and investigated in ethene polymerization. Ethene polymerization initiated by symmetrically ortho‐substituted nickel and palladium amine−imine catalysts is controlled. Mono‐substitution in the ortho‐aryl positions of nickel complexes is not as efficient in protecting centers from chain transfer as di‐substitution. Both the central metal and the size of the ortho‐aryl substituent have a significant effect on the polyethylene (PE) topology. Based on detailed characterization by high temperature SEC‐IR‐η, SEC with multi‐angle laser light scattering and 13C NMR data, PEs prepared by nickel amine−imine complexes have a linear rather than dendritic topology. In contrast, palladium amine−imine complexes with small ortho‐aryl substituents at low ethene pressure were shown for the first time to form dendritic PEs with topology comparable to PEs formed by α‐diimine palladium catalyst. © 2018 Society of Chemical Industry