Late transition-metal-based catalysts have been extensively used in olefin oligomerizations for decades. In this study, a series of N-terphenyl pyridine-imine Ni(II) and Pd(II) complexes bearing rigid-flexible double-layer steric substituents were...

Hyperbranched ethylene oligomers and polar functionalized co-oligomers synthesized via ethylene chain walking (co) oligomerization is a very attractive strategy. In this study, a series of dibenzhydryl iminopyridyl ligands with benzocycloalkyl and naphthyl moieties and the corresponding Ni(II) and Pd(II) complexes were synthesized and characterized. The Ni(II) complexes were highly effective in ethylene oligomerization and ethylene oligomers with hyperbranched microstructures were generated from this system. The corresponding Pd(II) complexes showed moderate oligomerization activities in ethylene oligomerization and hyperbranched ethylene oligomers were also yielded from the system. More significantly, the Pd(II) complexes can also effectively promote the co-oligomerization of ethylene with methyl acrylate (MA) to obtain hyperbranched polar functionalized ethylene-MA co-oligomers. The reaction temperature, catalyst ligand structure and metal type all have significant effects on ethylene (co) oligomerization with respect to catalytic activity, molecular weight and topology of the oligomers.

Comprehensive SummaryUsually, the aniline‐based late‐transition‐metal catalysts often require bulky steric substituents on both sides of the ortho‐aryl position to achieve efficient suppression of chain transfer in ethylene polymerization. In this contribution, we demonstrated that α‐diimine catalysts based on naphthylamine with only one bulky ortho‐aryl substituent also demonstrated excellent capabilities to suppress the chain transfer. Firstly, a class of α‐diimine nickel and palladium complexes with only one o‐aryl‐dibenzhydryl or o‐aryl‐dibenzosuberyl substituent were synthesized and characterized. Secondly, the as‐prepared naphthylamine‐based nickel catalysts demonstrated outstanding activities (up to 13.02 × 106 g·mol–1·h–1) and yielded lightly branched (16—40/1000C) polyethylenes with very high molecular weights (445.8—854.3 kg/mol) in ethylene polymerization. In comparison, the corresponding palladium catalysts showed moderate activities (level of 104—105 g·mol–1·h–1), generating moderately branched (47—78/1000C) polyethylenes with moderate molecular weights (21.6—82.0 kg/mol). Moreover, the palladium catalysts could also copolymerize ethylene and methyl acrylate (MA), albeit in low activities (level of 103 g·mol–1·h–1), providing E‐MA copolymers with low to moderate molecular weights (1.4—16.3 kg/mol) and a moderate level of incorporation ratio (2.4—7.4 mol%) and branching density (53—84/1000C). As compared with aniline‐based nickel and palladium catalysts, the naphthylamine‐based catalysts displayed a superior ability to suppress the chain transfer reactions and could give access to (co)polymers with orders of magnitude higher molecular weight in ethylene (co)polymerization.

Usually, the aniline-based late-transition-metal catalysts often require bulky steric substituents on both sides of the ortho-aryl position to achieve efficient suppression of chain transfer in ethylene polymerization. In this contribution, we demonstrated that α-diimine catalysts based on naphthylamine with only one bulky ortho-aryl substituent also demonstrated excellent capabilities to suppress the chain transfer. Firstly, a class of α-diimine nickel and palladium complexes with only one o-aryl-dibenzhydryl or o-aryl-dibenzosuberyl substituent were synthesized and characterized. Secondly, the as-prepared naphthylamine-based nickel catalysts demonstrated outstanding activities and yielded lightly branched (16-40/1000C) polyethylenes with very high molecular weights (445.8-854.3 kg/mol) in ethylene polymerization. In comparison, the corresponding palladium catalysts showed moderate activities, generating moderately branched polyethylenes with moderate molecular weights (21.6-82.0 kg/mol). Moreover, the palladium catalysts could also copolymerize ethylene and methyl acrylate (MA), albeit in low activity (level of 103 g·mol-1·h-1)，providing E-MA copolymers with low to moderate molecular weight (1.4-16.3 kg/mol) and a moderate level of incorporation ratio (2.4-7.4 mol%) and branching density. As compared with aniline-based nickel and palladium catalysts, the naphthylamine-based catalysts displayed a superior ability to suppress the chain transfer reactions and could give access to (co)polymers with orders of magnitude higher molecular weight in ethylene (co)polymerization.