Synthesis And Catalytic Performance Of Rare-earth Complexes Supported By A Phenylene Linked Bis(Amidinate) Ligand

"Bridged" is an important strategy for designing and synthesizing ligands with specific structures.Combining two ligands through a bridge has become an effective way for the design and synthesis of special geometric metal complexes.In this paper,two kinds of bridged amid ligands were synthesized and the ligands were react with[(Me3 Si)2N]3RE(?-Cl)Li(THF)3(RE = Er,Y,La,Nd,Yb)or RE[N(SiMe3)2]3(RE = La,Nd)to give the corresponding complex.Examine the differences between the coordination patterns of a series of complexes.The performance of complexes in the ring-opening polymerization of ?-CL was investigated.Ortho-phenyl-bridged bis(amidinate)ligands was firstly heated with O-phenylenediamine and two equivalents of pivaloyl chloride were heated refluxing for a certain period of time,washed with water,and spin-dried to give a white solid.The white solid was recrystallized from dichloromethane.After obtaining 1,2-C6H4(NHCOtBu)2 in a yield of 95%.By using Schlenk technology,adding phosphorus pentachloride and 1,2-C6H4(NHCOtBu)2 in the treated with anhydrous toluene which as solvent.The solvent is removed by reduced pressure after reaction at room temperature 2 d.The 1,2-C6H4(N=CtBuCl)2 was obtained after using the filtration,and the yield was 72%.Two equivalents of aniline and two equivalents of triethylamine were reacted with it.The 1,2-C6H4[NHC(tBu)=NC6H5]2 was obtained by column chromatography.1,3-C6H4[NHC(tBu)=NC6H5]2 which has not been reported in the literature can be synthesized in the same manner.[(Me3Si)2N]3RE(?-Cl)Li(THF)3(RE = Er,Y)is reacted with 1,2-C6H4{NHC(tBu)=NC6H5}2 is expressed as an equivalent ratio of 1:1.Reaction was carried out at 80? in toluene for 12 h.Use of n-hexane recrystallized and placed at0? to give complex C6H4-1,2-[NC(tBu)N(C6H5)]2REN(SiMe3)2THF[RE = Er(1),Y(2)].The central metal ion of the complexes 1,2 and the ligand are coordinated by?2N,N'.The central metal ions Er3+ and Y3+ of the complexes 1 and 2 are respectively coordinated with the two amidinate groups of the ligand to form a 6-coordinate bis(amidinate)complex.When the metal center is La3+,Nd3+ reacts 12h under the same dosage of toluene at 80?,use of n-hexane recrystallized and placed at 0? to give complex {?-?4:?2:?1:?1-C6H4-1,2-[NC(tBu)N(C6H5)]2}2REN(SiMe3)2(?-Cl)LiTHF}2[RE = La(3),Nd(4)].The metal center of complexes 3,4 is coordinated with the ligand in the form of ?-?2:?1:?1,Li+ and amiate ligands are coordinated by ?4 to form Geteronuclear metal complexes.In order to investigate the influence of rare earth centers and Li+coordination,the reaction of RE[N(SiMe3)2]3(RE = La,Nd)synthesized by the literature with 1,2-C6H4[NHC(tBu)=NC6H5]2.The complexes{C6H4-1,2-[NC(tBu)N(C6H5)]2RE}2-?-{?-?2:?1:?2:?1-C6H4-1,2-[NC(tBu)N(C6H5)]2}[RE = La(5),Nd(6)]was obtained.The metal centers of the complexes 5,6 are in the form of ?2:?1:?2:?1 in coordination with the amidinate group.The structure of complex 5,6 is a bi-nuclear tri-ligands metal complex.We also investigated the performance of ring-opening polymerization of ?-CL catalyzed by the corresponding complexes obtained by 1,2-C6H4[NHC(tBu)=NC6H5]2.The results show that factors such as solvent,solvent ratio,temperature and type of catalyst have a great influence on the polymerization effect of ?-CL.The conclusion is complexes 3,4 have a better result which the polymerization effect of?-CL in toluene at room temperature with a solvent ratio of 1:10 and the relative molecular weight distribution is moderate.The catalytic activity is high,the reaction speed is fast,and the relative molecular weight of the polymer is relatively large.By comparing the catalytic effect of[Mc3Si)2N]3RE(?-Cl)Li(THF)3(RE = Er,Y,La,Nd)with the complex 1-4,it is concluded that the structure of the ligand in the complex,the coordinated Li+ ion and the central metal ion have a significant effect on the catalytic effect of e-CL polymerization.1,3-C6H4[NHC(tBu)=NC6H5]2 and[(Me3Si)2N]3RE(?-Cl)Li(THF)3(RE = Er,Yb)were reacted with the feed ratio of 1:1.5,and the complexes 7,8 were obtained.The coordination modes of the ligands with the metal centers in the complexes 7 and 8 are ?2N,N'.The central metal ion coordinates with the amidinate groups on the three ligands,forming a deformed octahedral complex with a coordination number of six.Crystal structures were confirmed by X-ray and were analyzed by IR and ES.Complexes 2,3,5 were analyzed by NMR.