Synthesis And Application Of Group 4 Metal Complexes Bearing Hydroquinoline Ligands For Olefin Coordination Polymerization

Polyolefin materials have many types and are widely used.They are closely related to our lives and become an integral part of our lives.For the development of polyolefin materials,the development of polyolefin catalysts is very important.Early-transition metal catalysts have become hotspots for their research due to their high activity,monodisperse centers,high selectivity,and controllability of polymer structures.Based on the synthesis of non-metallocene early-transition metal catalysts,the effects of different ligand structures,different polymerization conditions,and different metals on the homopolymerization of ethylene and the copolymerization of ethylene with 1-octene were investigated.The structure of the catalyst was analyzed by nuclear magnetic resonance,X-ray diffraction,and elemental analysis.The polymer composition was analyzed by DSC,high-temperature GPC,and high-temperature NMR.The main work of this thesis is summarized as follows:The stoichiometric reactions of 8-（2,6-（R¹）₂-4-R²-anilide）-5,6,7-trihydroquinoline（1-3;1:R¹=ⁱPr,R²=H;2:R¹=Me,R²=H;3:R¹=Me,R²=Me）with MMe₄（M=Hf or Zr）afforded metal complexes 1-HfMe₃,2-HfMe₃,3-HfMe₃ and 1-ZrMe₃ in high yields.Treatment of ligand 1 with Ti（NMe₂）₄ resulted in the formation of1-Ti（NMe₂）₃,which reacted with SiMe₂Cl₂ to form 1-TiCl₃.1-TiMe₃ was obtained by alkylation of 1-TiCl₃ with MeMgBr.All metal complexes were characterized by NMR spectroscopy and elemental analysis.The molecular structures of complexes 1-Hf Me₃,2-HfMe₃,1-ZrMe₃ and 1-TiMe₃ were determined by single-crystal X-ray diffractions,revealing an approximate trigonal-bipyramidal geometry around the metal center in all structures.As the temperature rises,the polymerization activity gradually increases.The complexes showed extremely high activity toward ethylene polymerization(up to13860 kg（PE）·mol^-1（M）·h^-1).And under different cocatalyst conditions,the catalytic activity of the catalysts is different.In the presence of[Ph₃C][B（C₆F₅）₄]as cocatalyst,the activity was in the order of Hf>Zr>Ti;with B（C₆F₅）₃ as cocatalyst,this order followed Zr>Ti>Hf;using MAO as cocatalyst,Ti complex was highly active,while Hf and Zr complexes were inactive.Subsequently,we explored the ability of these five metal complexes to catalyze the copolymerization of ethylene and 1-octene.The complexes showed extremely high activity toward ethylene/1-octene copolymerization(up to 38640 kg（PE）·mol^-1（M）·h^-1)at 100°C.As the concentration of octene increases,the catalytic activity also increases.It is remarkable to discover that the catalytic properties are highly dependent on the matching metal and cocatalyst.In the presence of[Ph₃C][B（C₆F₅）₄]as cocatalyst,the activity was in the order of Hf>Zr>Ti;with B（C₆F₅）₃ as cocatalyst,this order followed Zr>Ti>Hf;using MAO as cocatalyst,Ti complex was highly active,while Hf and Zr complexes were inactive.