Synthesis And Application Of Nickel Complexes Containing Large Hindered Substituents

This paper describes synthesis of ten asymmetric N,N'-bis(imino)fluorine-nickel(?)halide complexes(Nil-Ni10),[1-[2,6-{(4-MeOC6H4)2CH}2-4-MeC6H2N]-2-(ArN)C2C10H6]NiX2(X=Br:Ar=2,6-Me2C6H3 Nil,2,6-Et2-C6H3 Ni2,2,6-i-Pr2C6H3 Ni3,2,4,6-Me3C6H2 Ni4,2,6-Et2-4-MeC6H2 Ni5)and(X=Cl:Ar=2,6-Me2C6H3 Ni6,2,6-Et2C6H3 Ni7,2,6-i-Pr2C6H3 Ni8,2,4,6-Me3C6H2 Ni9,2,6-Et2-4-MeC6H2 Ni10),and its catalytic performance for ethylene polymerization.In addition,the unilateral ligand(1),the bilateral ligand(L1-L5)and the complex(Nil-Ni10)prepared by the experiment were also characterized by nuclear magnetic,infrared and elemental analysis.At the same time,Nil,Ni3,Ni5 and Ni6 were subjected to single crystal growth,and the resulting molecular structure revealed a change in the space protection provided by the non-equivalent N-aryl group,resulting in a twisted tetrahedral geometry per nickel center.The polymerization activity of ethylene and the change in properties of polyethylene were observed by changing the type of cocatalyst,the amount of cocatalyst,the polymerization temperature,the polymerization time,etc.by a high pressure polymerization method.The newly synthesized polyethylene is characterized by measurement of molecular weight,melting temperature,and the like.This paper includes the following four chapters:Chapter 1:Introduction.Chapter 2:Synthesis of ?-diimine-type nickel complexes containing large hindered substituents 1-(2,6-bis(4,4'-dimethoxybenzhydryl)-4-methylaniline-2-amine imine is combined with a nickel halide,and the synthesized unilateral ligands,bilateral ligands,and complexes are characterized by nuclear magnetic and infrared spectroscopy.The complexes Nil,Ni3,Ni5 and Ni6 were subjected to single crystal culture to obtain crystal structures of the complexes,all of which were twisted tetrahedral geometry.Chapter 3:The nickel complex catalyzes the high-pressure polymerization of ethylene.By changing the polymerization conditions such as the molar ratio of Al:Ni,polymerization time,polymerization temperature,etc.,it can be observed that when the temperature is 30?,the polymerization activity is highest.The optimum conditions were obtained when Nil/Et2AlCl was used as the catalyst(molecular weight:9.32×106 g·PE·mol-1·(Ni)·h-1),ie,the molar ratio of Al:Ni was 700,the temperature was 30°C,and the running time was 30 minutes.The optimum conditions were obtained when Nil/MAO was used as the catalyst(molecular weight:9.29×106 g·PE·mol-1·(Ni)·h-1),that is,the Al:Ni molar ratio was 2750,the temperature was 30?,and the running time was 30 minutes.At the same time,the resulting polymer is a high molecular weight,narrow molecular weight distribution polyethylene.By branching degree measurement,it is known that the polymer obtained by using Et2AlCl as a cocatalyst exhibits a higher branching content than the polymer obtained by using MAO as a cocatalyst(Et2AlCl:about 115 branches per 1000 carbons;MAO:about 29 branches per 1000 carbons).Stress-strain testing and dynamic mechanical analysis(DMA)studies have shown that polyethylene exhibits good tensile strength and elastic recovery.Chapter 4:Summary.