Ethylene Polymerization And1-Hexene Oligomerization Using Titanium And Zirconium Catalysts With Tridentate [ONO] Ligands

In all aspects of industrial production and our daily life, polyolefins are widely used as synthetic materials. And in the development of polyolefin materials, catalysts have played a very important role. In recent years, in order to avoid the patent barrier of the metallocene catalyst, more and more researchers have been concentrating on the the design and synthesis of non-metallocene catalysts. And they have been producing a variety of high performance polyolefin products, including linear low-density polyethylene, isotactic polypropylene, syndi-otactic polypropylene, isotactic polystyrene, copolymers of ethylene with olefins, comprising propylene, polar monomer, conjugated dienes etc. However, the catalysts obtained always had a short polymerization life, in other words, the catalysts lost their activity easily. Therefore, there are many important application values of developing long-lived catalytic systems, which will be apparently great challenges.In this paper,5ligands and11metal complexes were synthesized. Through the condens-ation reactions by substituent aldehydes and amines,5tridentate ligands [4-tBu-6-R-2-CH=N(4-tBu-6-R’-2-OHC6H2)C6H2OH](LH2)[R=R’=tBu (L1H2); R=CMe2Ph, R’=tBu (L2H2); R=adamantyl, R’=tBu (L3H2); R=R’=CMe2Ph (L4H2); R=SiMe2tBu, R’=CMe2Ph (L5H2)] were synthesized. Reactions of TiCl4with one equivalent lithium salts of the above ligands LlLi2-L5Li2in toluene afford five-coordinate titanium complexes with general formula LTiCl2[L=L1(1); L2(2); L3(3); L4(4); L5(5)]. The addition of THF to titanium complex5readily gives THF-solvated six-coordinate complex6, which also was obtained by reaction of TiCl4with one equivalent ligand L5H2in THF. Reactions of ZrCl4with one or two equivalent lithium salts of the ligands LlLi2-L5Li2afford3zirconium mono(ligand) complexes LZrCl2(THF)[L=L2(7); L4(8); L5(9)], and2bis(ligand) complexes L2Zr [L=L1(10); L4(11)]. The molecular structures of complexes2,8, and11were established by single-crystal X-ray diffraction studies.Upon activation with MAO(methylaluminoxane), complexes1-9are active for ethylene polymerization. The catalytic activities and half-lives observed for the zirconium complexes are particularly notable, exceeding106g polyethylene (mol Zr)-1h-1and6h, respectively. Complex9is more active and long-lived, with a turnover frequency (TOF) of2.6×105(mol C2H4)(mol Zr)-1h-1, a half-life exceeding16h, and a total turnover number (TON) exceeding106(mol C2H4)(mol Zr)-1at20℃and0.5MPa pressure. At the same time, the catalysts also have excellent thermal stability, even at80℃, complex9/MAO catalyst system has a long lifetime (t1/2>2h), as well as high activity that is comparable with that at20℃.When activated with MAO, complexes1-9also show moderate catalytic activity and more than99%2,1-regioselectivity for1-hexene oligomerization.