Influence of Silica-Supported Alkylaluminum on Heterogeneous Zwitterionic Anilinonaphthoquinone Nickel and Palladium-Catalyzed Ethylene Polymerization and Copolymerization with Polar Monomers

Abstract

The development of the heterogeneous late transition metal-catalyzed olefin (co)polymerization is a challenge in current research. Here, we report the preparation of heterogeneous anilinonaphthoquinone nickel and palladium catalysts by the binding of SiO2-supported alkylaluminums to a quinone oxygen of the ligand (Mt-AlR3/SiO2). The heterogeneous nickel catalyst exhibited a very high activity (up to 10.4 × 106 g mol–1 h–1) for ethylene polymerizations to produce semicrystalline high-molecular-weight (Mn up to 54.3 × 104 g mol–1) polyethylenes with a low degree of branching (<11.1/1000 C), high Tm values (121–131 °C), and well-regulated particle morphologies. The polymerization behavior depended on the electron density of the metal center modulated by the Lewis acidity of the remotely bound alkylaluminum as can be analyzed and verified through model optimizations and density functional theory (DFT) calculations. Most importantly, these nickel catalysts were able to produce semicrystalline ethylene/5-hexene-1-yl copolymers with a high activity and high molecular weight. The heterogeneous palladium catalyst can promote the copolymerization of ethylene with commercial methyl acrylate or polar norbornene derivatives with a moderate activity, affording a polar functionalized polyethylene and a cyclic olefin copolymer.