Studies On Synthesis,characterization,and Catalytic Properties Of Metal Complexes Supported By Asymmetric Amine-bis(phenolate) Tetradentate Ligands

As a kind of polymer material,the polyolefin,which is productive and versatile,has been used in packaging,building,electrical components and many other aspects all over the world,on account of its excellent performance such as inexpensiveness good mechanical property and thermal property,etc.In addition,the demand in the world for the polyolefin materials will keep increasing.The development of polyolefin materials is closely related to the development of catalyst because the catalyst determines the morphology,structure and properties of the polymers.As the polyolefin industry developing,people's demand for more polyolefin products with special properties increases too,so it is still extremely important to research and develop new catalyst with excellent performance.In this paper,a series of amine-bis(phenolate)ligands with asymmetric structures were designed and synthesized using p-tert-butylphenol as the basic raw material,which were characterized by 1H NMR,13 C NMR.The red or dark red titanium complexes could be get in high yield by the method of one-pot reaction.recrystallization.The complexes were characterized by 1H NMR,13 C NMR and elemental analysis.In addition,the structures of C3,C4 and C5 confirmed by X-ray single crystal diffraction analysis indicated that the metal center had a six-coordinated coordination structure.In the ligands,one of the N atoms is attached to two methyl groups while the other N' atom is connected with two different substituents.When the reaction between the ligands and the metal finished,the nitrogen atoms and O-formed a coordination bond and a ? bond with the metal center,respectively.The complexes exhibited asymmetric structures in space.We studied the catalytic activity of complexes C1-C6 in the last chapter.Under the same polymerization conditions,the complexes C1-C6 exhibited high catalytic activity for the polymerization of ethylene and the highest activity was 3640 kg PE(mol Ti)-1h-1.When the Al/Ti is 800,which is the most suitable,the highest molecular weight of the polymer was got with C3.The Mw reached 36.6 × 104 g mol-1,and the molecular weight distribution of the polymer is within 1-4.The catalyst still had a high activity when the polymer temperature is heated to 80 oC which refleted the good thermal stability.We found the long life of the catalysts by prolonging the polymerization time.We studied the catalytic properties for copolymerization reaction of the catalyst.Under the same conditions,the activity decreased with the increasing of the substituents of R1 and R2.The initial concentration of hexene also affected the properties of the polymerization and the polymerization product.When the hexene content is 0.75 mol L-1,the activity of the catalyst reached the highest value.The copolymerization activity decreased with the increasing of hexene concentration as well as the molecular weight changed.The molecular weight Mw of the copolymer is in the range of 3×104 g mol-1 to 1.7×105 g mol-1,and the molecular weight distribution is narrowly distributed in 2-3.