Synthesis,characterization And Catalytic Properties Of [NNO~-O~-] Tetradentate Ligands And Their Trivalent Rare Earth Metal Complexes

In this dissertation,a series of rare earth metal aryloxy complexes have been synthesized and characterized by different ligands.At the same time,we explored the effect of the structure of rare earth metal complexes on the ring-opening polymerization of racemic lactide(rac-LA)through the polymerization experiment of lactide.1.In this paper,p-tert-butylphenol as a basic raw material,by changing the phenol ortho substituents(R1,R2):(R1=CPh3;R2=C(Me)2Ph(L1H2),CMePh2(L2H2),CPh3(L3H2),C(Toyl)3(L4H2)).A series of[N N O-O-]tetradentate ligands with asymmetric structure were designed and synthesized.Their structures were characterized by 1H NMR,13C NMR and so on.After reaction with[Ln{N(SiMe3)2}3](THF)(Ln = Y,Sm,Nd)at room temperature,1.0 equivalent of isopropanol or benzyl alcohol were added to obtain lanthanide rare earth metals complexes:L1YCl(OiPr)(C1);L2YCl(OiPr)(C2);L3YCl(OiPr)(C3);L4YCl(OiPr)(C4);L1YCl(OCH2Ph)(C5);L2YCl(OCH2Ph)(C6);L3YCl(OCH2Ph)(C7);L4YCl(OCH2Ph)(C8);L12Sm2Cl2(THF)2(C9);L22Sm2Cl2(THF)2(C10);L32Sm2Cl2(THF)2(C11);L42Sm2Cl2(THF)2(C12);L12Nd2Cl2(C13);L22Nd2Cl2(C14);L32Nd2Cl2(C15);L42Nd2Cl2(C16).And the complexes were characterized by elemental analysis,1H NMR and 13C NMR.The X-ray single crystal structures of the complexes C3,C9 and C15 were obtained.The two nitrogen atoms in the metal yttrium complex coordinate to the metal center,and another chlorine atom is connected to the metal center.The oxygen atoms of isopropanol and benzyl alcohol are coordinated to the metal center;The catalysts of metal samarium and neodymium are the same,the two nitrogen atoms in the body coordinate to the center of the metal,but the difference is that a chlorine atom joins the two metal centers in the form of a chlorine bridge to form a dinuclear structure.2.The catalytic activity of the compound C1-C16 for the ring-opening polymerization of rac-LA was investigated.The effects of different metal centers,different ligand substituent sizes and polymerization temperatures on the polymerization activity,especially stereoselectivity,were investigated.The results show that:(1)The activities of C1-C8 complexes of yttrium compounds are similar.The polymerization activity of samarium complexes and neodymium compound C9-C16 is higher than that of yttrium complexes.(2)The size of the ortho substituents did not affect the polymerization activity greatly,but with increasing steric hindrance of the substituents,the stereoselectivity Pm of the polymer increased significantly(R2 = CMe2Ph<CMePh2<CPh3<C(Toyl)3).(3)By lowering the polymerization temperature and prolonging the reaction time,the complexes of yttrium and samarium give isotactic polylactides with high yields and selectivity.The ring-opening polymerization of lactide gives a very good stereoselectivity under the proper catalyst ratio,temperature and good catalysis system of higher isotactic polylactide(Pm = 0.74).Horever,Neodymium complexes are only able to get hetero-polylactide.