Synthesis And Characterization Of Heteroleptic Lanthanide(La/Gd) Amides Complexes Bearing Carbon-Bridged Bis(Phenolate) Ligands And Their Catalytic Behavior

In this thesis, a series of heteroleptic lanthanide(La/Gd) amides complexes bearing carbon-bridged bis(phenolate) ligands were designed and synthesized. The complexes obtained were characterized by elemental analysis, 1H NMR, 13 C NMR and X-ray single crystal diffraction. The catalytic properties of the complexes on the ring-opening polymerization of ε-caprolactone have been studied. The research work includes the following two parts:Part one: Synthesis and characterization of carbon-bridged bis(phenolate)lanthanide(La/Gd) bis(trimethylsilyl)amide complexes and their application as catalyst in the polymerization of ε-caprolactone.The carbon-bridged bis(phenolate) ligands R2CH(C6H2-3- tBu-5-R1-2-OH)2(H2L1: R1 = tBu, R2 = Ph; H2L2: R1 = Me, R2 = Ph; H2L3: R1 = tBu, R2 = Ph(p-Me); H2L4: R1 = Me, R2 = Ph(p-Me); H2L5: R1 = tBu, R2 = Ph(o-CH3); H2L6: R1 = Me, R2 = Ph(o-CH3)) were synthesized through electrophilic substitution reaction. A series of carbon-bridged bis(phenolate)lanthanide bis(trimethylsilyl)amide complexes 2a- 2l {L1La[N(Si Me3)2](2a) 、 L1Gd[N(Si Me3)2](2b) 、 L2La[N(Si Me3)2](2c) 、L2Gd[N(Si Me3)2](2d)、L3La[N(Si Me3)2] 2(2e)、L3Gd[N(Si Me3)2](2f)、L4La[N(Si Me3)2](2g)、L4Gd[N(Si Me3)2](2h)、L5La[N(Si Me3)2](2i)、L5Gd[N(Si Me3)2](2j)、L6La[N(Si Me3)2](2k)、L6Gd[N(Si Me3)2](2l)]} were synthesized by amine elimination reaction of bis(phenolate) ligands with Ln[N(Si Me3)2]3(Ln = La, Gd). The catalytic properties of complexes 2a- 2l on the ring-opening polymerization of ε-caprolactone have been studied, and the mechanism for the formation of PCL was also studied and discussed.Part two: Synthesis and characterization of carbon-bridged bis(phenolate)lanthanide(La/Gd) pyrazolato/1,2,4-triazolato complexes and their application as catalyst in the polymerization of ε-caprolactone.These complexes could be synthesized through the following two methods:Method A: LnLn[N(Si Me3)2](n = 5, Ln = La, 2i; Ln = Gd, 2j;n = 6, Ln = La, 2k; Ln = Gd, 2l) further reacted with 1 equiv of Me2 Pz H, Me2 Tz H and Ph2 Tz H respectively in THF to yield the bis(phenolato)lanthanide(La/Gd) pyrazolato/1, 2, 4-triazolato complexes 3a- 3l [LnLn Me2Pz(THF)3(n = 5, Ln = La, 3a; Ln = Gd, 3b;n = 6, Ln = La, 3c; Ln = Gd, 3d), LnLn Me2Tz(THF)3(n = 5, Ln = La, 3e; Ln = Gd, 3f;n = 6, Ln = La, 3g; Ln = Gd, 3h), LnLn Ph2Tz(THF)3(n = 5, Ln = La, 3i; Ln = Gd, 3j;n = 6, Ln = La, 3k; Ln = Gd, 3l)] in high yields. Complexes 3a – 3d and 3k have been characterized by X-ray crystal structural analysis. The catalytic properties of complexes 3a- 3l on the ring-opening polymerization of ε-caprolactone have been studied, and the mechanism for the formation of PCL was also studied and discussed.Method B: Reaction of Ln[N(Si Me3)2]3(Ln = La, Gd) with H2Ln(n = 5, 6) in a 1:1 molar ratio produced the bis(phenolato)lanthanide(La/Gd) complexes LnLn N(Si Me3)(n = 5, 6; Ln = La, Gd) in nearly quantitative yields. Therefore, complexes 3a- 3l can also be synthesized by the direct reaction of Ln[N(Si Me3)2]3 with H2Ln(n = 5, 6) in a 1:1 molar ratio and then with 1 equiv of Me2 Pz H, Me2 Tz H and Ph2 Tz H in situ respectively.