Synthesis And Characterization Of Lanthanide Complexes Stabilized By Ethylene Diamine-bridged Bis(Phenolate)Ligands And Their Applications In The Ring-Opening Polymerization Of Rac-lactide

Using ethylene diamine-bridged bis(phenolate)ligands with different substituent groups of phenol and bridge,a series of ethylene diamine-bridged bis(phenolate)lanthanide complexes were synthesized and characterized by X-ray structure determination.1H and 13C NMR analysis.Further research on the catalytic properties of some of these lanthanide amide complexes in the ROP of rac-LA and rac-BBL was conducted.The ligands used in this thesis are:[CH2N(Ph)CH2-(2-OH-C6H2-tBu2-3,5)]2,marked as L1H2;[CH2N(Ph)CH2-(2-OH-C6H2-Cumyl2-3,5)]2,marked as L2H2;[CH2N(Ph)CH2-(2-OH-C6H-2-Cl2-3,5)]2,marked as L3H2;[CH2N(tBu)CH2-(2-OH-C6H2-tBu2-3,5)]2,marked as L4H2;[CH2N(cyclohexyl)CH2-(2-OH-C6H2-tBu2-3,5)]2,marked as L5H2;The main contents were listed below.1.It was found that the structure of bridged bis(phenolate)ligands and reaction conditions have significant effect on the exchange reaction of ethylene diamine-bridged bis(phenol)s with rare-earth metal amide.The ligand precursor L1H2 reacted in the THF at 60 ? with Yb[N(SiMe3)2]3(?-Cl)Li(THF)3 gave a homoleptic bimetallic ytterbium complex(L1)2Yb2(?-L1)(1)as final product.When the amino elimination reaction of L1H2 with Ln[N(SiMe3)2]3(?-Cl)Li(THF)3 was conducted in toluene at 95 ?,the desired neutral rare-earth metal amido complexes L1LnN(SiMe3)2[Ln = Yb(2),Y(3),Sm(4),Nd(5)]were isolated.However,the reaction of L2H2 with Ln[N(SiMe3)2]3(?-Cl)Li(THF)3 under the same conditions,unexpected homoleptic ytterbium complex(L1)2Yb2(?-L1)(6)was obtained.Similarly,the reaction of L3H2 with Y[N(SiMe3)2]3 at the room temperature in THF also gave a homoleptic ytterbium complex(L2)2Y2(?-L2)(THF)6(7)coordinated with six THF molecules.However,L1H2 reacted with Ln[N(SiMe3)2]3(?-Cl)Li(THF)3 in toluene at 95 0C,after workup,to give the desired rare-earth metal amides L4LnN(SiMe3)2[Ln = Y(8),Yb(9)],L5LnN(SiMe3)2[Ln = Y(10),Yb(11)]in good isolated yields.Complexes 2-5 and 8-11 were characterized by IR spectroscopy,elemental analysis,and 1H and 13C NMR analysis for the yttrium complexes.2.Lanthanide cyclopentadienyl complexes could be synthesized by the proton exchange reactions of L1H2 with Cp3Ln,among these the structure of L'YCp(12)was characterized.L1LnCp reacted with the p-substituted phenols in situ,the amine-bridged bis(phenolate)ligand unexpectedly dissociated and recombined with p-substituted aiyloxy,finally the new bridged tri(phenolate)lanthanide complexes{Ln[(OC6H2-4-R)[CH2(2-O-C6H2-tBu2-3,5)]2}2(THF)2[Ln = Y,R = CH3(13);Ln = Y,R =tBu(14);Ln = Y,R = OCH3(15);Ln = Yb,R = CH3(16)]were acquired.But when the L1LaCp reacted with 4-tert-butylphenol,carbon-bridged bis(phenolate)lanthanum complex La2[CH2(OC6H2-tBu2-3,5)2]3(17)was separated.In order to study the universality of the anti-mannich reaction of amine-bridged bis(phenolate)lanthanide cyclopentadienyl complexes with the p-substituted phenols,we explored the reaction of the phenyl amine-bridged bis(phenolate)lutetium cyclopentadienyl complex with p-tert-butylphenol,bridged tri(phenolate)lutetium complex{Lu[(OC6H2-4-tBu)[CH2(2-O-C6H2-tBu2-3,5)]2}2(THF)2(18)was indeed obtained.The complexes 12-18 were characterized by IR analysis,elemental analysis,1H NMR and 13C NMR analysis for the yttrium complexes,lanthanum complex and lutetium complex.3.In the process of research on the catalysis behavior of the ROP of rac-LA,the influence of the bridging group,the polymerization solvents and central metals were explored.the experiment data indicated:(1)the change of the substituent groups of ethylene diamine affect the catalysis activity and stereoselectivity of the complexes,the activity and stereoselectivity of N for Ph amine substituent lanthanide complexes were higher than N for cyclohexyl and tBu substituent complexes;(2)the reaction media also had an effect on the catalysis activity and stereoselectivity,which the activity in toluene was higher than that in THF,but the stereoselectivity was reverse;(3)the increasing order of observed activity is in agreement with the increasing sequence of the ionic radii,and the stereoselectivity of the complexes have the same law but the increased range was not obvious;(4)catalytic amount benzyl alcohol in situ was added in the process of polymerization could improve the controllability of the complexes,but had no influence on the stereoselectivity,and the catalytic activity reduced slightly.4.The lanthanide complexes 2-5 and 10 could efficiently initiate the polymerization of rac-BBL under mild conditions,and the structure of the complexes had obvious influence on the stereoselectivity of the acquired polymers.Complexes 2-5 initiated the polymerization of rac-BBL at room temperature in toluene,showed moderate isotctic stereoselectivity,but complex 10 trended to the hetero-riched stereoselectivity.When the media was THF,both the activity and stereoselectivity of these complexes reduced.The stereoselectivity of the obtained polymers decreased with the increase of the central metal ionic radii.