Ethylene Polymerization and Copolymerization with Polar Monomers by Cationic Phosphine Phosphonic Amide Palladium Complexes

The synthesis, characterization, and olefin (co)-polymerization studies of a series of palladium complexes bearing phosphine phosphonic amide ligands were investigated. In this ligand framework, substituents on three positions could be modulated independently, which distinguishes this class of ligand and provides a great deal of flexibilities and opportunities to tune the catalytic properties. The palladium complex with an o-MeO-Ph substituent on phosphine is one of the most active palladium catalysts in ethylene polymerization, with 1 order of magnitude higher activity than the corresponding classic phosphine-sulfonate palladium complex. Meanwhile, the polyethylene generated by this new palladium complex showed ca. 6 times higher molecular weight in comparison to that by the classic phosphine-sulfonate palladium complex. In ethylene/methyl acrylate copolymerization, the new palladium complex showed lower activity, generating copolymer with similar methyl acrylate incorporation and much higher molecular weight. The new palladium complex was also able to copolymerize ethylene with other polar monomers, including butyl vinyl ether and allyl acetate, making it one of the very few catalyst systems that can copolymerize ethylene with multiple industrially relevant polar monomers.