Synthesis Of The Transition Metal Complexes Based On Cyclopenta[b]pyridine And Their Catalytic Behavior Towards Ethylene Oligomerization And Polymerization

In this dissertation,2-chloro-6,6-dimethylcyclopenta[b]pyridin-7-one was used as the starting matieral to afford 6,6-dimethylcyclopenta[b]pyridin-7-one,6,6-dimethyl-2-phenylcyclopenta[b]pyridin-7-one and 2-acetyl-6,6-dimethylcyclopenta [b]pyridin-7-one.Then the obtained ketones reacted with substituted anilines to yield their corresponding pyridine-imine ligands,which converted into the desired N^N bidentate nickel complexes and N^N^N tridentate chromiums complexes by treatment with NiCl₂ and CrCl₃?THF?₃.On activation with cocatalysts,the relationships between polymerization conditions and the properties of resultant polyethylenes,such as molecular weight,molecular weight distribution,branching content,oligomeric product distribution and ?-olefin selectivity,were studied.Various efforts have been made to finely control the microstructure of polymers and oligomers through tuning the steric hindrance and electric effect around the active center,including the substituents on imino-aryl motif and/or the ligand framework.Based on the summarization of literature in this research field,the dissertation is focusing on the catalytic ethylene polymerization with N^N bidentate nickel catalysts and N^N^N tridentate chromium catalysts and summarizing in the following three parts.1.Starting from 2-chloro-6,6-dimethylcyclopenta[b]pyridin-7-one,6,6-dimethyl-2-phenylcyclopenta[b]pyridin-7-one was synthesized via Suzuki coupling with phenylboronic acid,then two ketones reacted with substituted anilines to yield their corresponding pyridine-imine ligands.Finally,treatment of ligands with NiCl₂ affords the desired N^N bidentate nickel complexes,whose structures are fully characterized.Upon activation with either MAO or EASC,all resulted nickel precatalysts exhibit high activities toward ethylene oligomerization;and oligomeric products range from C₄ to C₁₂ with chloro-substituted nickel precatalysts,while C₄ to C₆ with phenyl-substituted nickel precatalysts.Moreover,in comparison with EASC,the higher ?-olefin selectivity is observed using MAO as cocatalyst.2.With a catalytic hydrogen dechlorination of 2-chloro-6,6-dimethylcyclopenta [b]pyridin-7-one,6,6-dimethylcyclo penta[b]pyridin-7-one was prepared,then react with substituted anilines to generate the pyridine-imine ligands.Finally,treatment of resulted ligands with NiCl₂ affords their corresponding N^N bidentate nickel complexes,whose structures are fully characterized.Upon activation with either MAO or MMAO,all nickel precatalysts showed high activities toward ethylene polymerization;and the obtained polyethylenes possessing low molecular weight,narrow molecular weight distribution and high branch degree.Moreover,the high temperature NMR indicated the existence of double bonds either at the terminal position or within the polyethylene chain,and probable mechnism also was proposed.3.2-Acetyl-6,6-dimethylcyclopenta[b]pyridin-7-one is prepared via Stille coupling of 2-chloro-6,6-dimethylcyclopenta[b]pyridin-7-one,then react with substituted anilines to afford the pyridine-diimine ligands.Finally,treatment of ligands with CrCl₃?THF?₃ generates their corresponding N^N^N tridentate chromium complexes,and the complexes were fully characterized.Upon activation with MMAO or EASC,all chromium precatalysts exhibit moderate activities towards ethylene polymerization for the highly linear polyethylene,and this catalyst model can achieve the transformation of the single-site to multi-site active species in ethylene polymerization.