Halogen Substituted Bis(arylimino)Pyridine Transition Metal Complexes as Catalysts for the Oligomerization and Polymerization of Ethylene

A series of 15 complexes containing 3d transition metals ranging from titanium to nickel and halogen functionalized bis(arylimino)pyridine ligands was synthesized and characterized. After activation with methylalumoxane (MAO), these catalysts oligomerized ethylene to give a-olefins with 4-40 carbon atoms. The influence of the metal center, the halogen substituents, and the reaction parameters on the product compositions are discussed. Some of the described catalyst precursors showed the potential to isomerize a-olefins and to generate olefins with uneven numbers of carbon atoms. Quantum mechanical calculations (DFT, B88LYP) helped explaining the isomerization behaviour of 5-halide-2-methyl substituted transition metal compounds. Relationships between the structure of the catalyst precursors or the parameters of the reactions and the activity or the product compositions were confirmed by experiments.