Synthesis, Characterization And Catalytic Activity Of Bridged Bis(Phenolate) And Bis(Guanidinate) Lanthanide Complexes

A series of lanthanide metal aryloxides and alkoxides supported by bridged bis(phenolate) ligand were synthesized, and their catalytic activity for the polymerization of lactide were studied. Using bridged bis(guanidinate) ligand, some lanthanide cyclopentadienyl and amido complexes were prepared. The bridged bis(phenolate) ligand used in this thesis is amine-bridged bis(phenolate) ligand Me2NCH2CH2N[CH2-(2-O-C6H2-But2-3,5)]2, abbreviated as [ONNO].1. Protic exchange reactions of (C5H5)3Ln(THF) with amine bridged bis(phenol) [ONNO]H2 in a 1:1 molar ratio, and then with 1 equiv of 2,6-diisopropylphenol, p-cresol or 4-methoxyphenol, respectively, in situ in THF gave the neutral lanthanide aryloxides [ONNO]Ln(OC6H3-2,6-Pri2)(THF) [Ln = Nd (1), Sm (2), Yb (3), Y (4)], [ONNO]Ln(OC6H4-4-CH3)(THF)n [Ln = La (5), Nd (6), Sm (7), n = 2; Ln = Yb (8), Y (9), n = 1] and [ONNO]Ln(OC6H4-4-OCH3)(THF)n [Ln = Nd (10), Sm (11), n = 2; Ln = Yb (12),n = 1] in high isolated yields. These complexes were well characterized by elemental analyses, IR spectra, single crystal X-ray diffraction and NMR spectroscopy in the case of complexes 4, 5 and 9. Structural determination revealed that complexes 1?11 have a solvated monomeric structure.2. Reactions of (C5H5)3Ln(THF) with amine bridged bis(phenol) [ONNO]H2 in a 1:1 molar ratio, and then with 1 equiv of 2, 2, 2-trifluoroethanol in situ in THF gave the neutral lanthanide alkoxides [ONNO]Ln(OCH2CF3)(THF) [Ln = Er (13), Yb (14), Y (15)]. Complexes 12?15 were characterized by IR, elemental analysis and single crystal X-ray diffraction and NMR spectroscopy in the case of complex 15.3. Reactions of (C5H5)2LnCl with [(CH2)2NC(NiPr)2Li]2 in a 2:1 molar ratio in THF afforded the neutral bimetallic lanthanide bi(cyclopentadienyl) (C5H5)2Ln[(CH2)2NC(NiPr)2]2Ln(C5H5)2 [Ln = Er (16), Yb (17), Y (18)] in moderate yields. Reaction of (CH3C5H4)2SmCl with [(CH2)2NC(NiPr)2Li]2 in a 2:1 molar ratio in THF afforded the neutral bimetallic samarium bi(methylcyclopentadienyl) (CH3C5H4)2Sm[(CH2)2NC(NiPr)2]2Sm(CH3C5H4)2(19). All the complexes were characterized by IR and elemental analysis. Definitive structures of these complexes were elucidated by single crystal X-ray diffraction.4. [N(TMS)2]2LnCl reacted with [(CH2)2NC(NiPr)2Li]2 in a 2:1 molar ratio in THF to give bridged bis(guanidinate) rare-earth metal complexes [(TMS)2N]2Ln[(CH2)2NC(NiPr)2]2Ln[N(TMS)2]2 [Ln = Sm(20), Yb(21)], which were characterized by IR, elemental analysis and single crystal X-ray diffraction.5. Complexes 1?12 can initiate the ring-opening polymerization of L-lactide with high activity. The ionic radii of the central metals have a significant effect on the catalytic activity and the molecular weight distributions are relatively broad. Preliminary results revealed that complex 11 is efficient initiator for the polymerization of D, L-lactide, and heterotactic PLA was abtainded with the highest Pr of 0.99.6. Complexes 13?15 can initiate the polymerization of L-lactide with high activity. In comparison with the lanthanide aryloxides, they showed high activity towards L-lactide polymerization to give the polymers with relatively narrow molecular weight distributions.