Synthesis, Characterization And Catalytic Activity Of Bridged Phenolate (Alkoxylate) 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 rac-β-butyrolactone were studied. Using bridged phenolate alkoxylate ligand, some lanthanide ionic complexes and alkoxides were prepared, and the langthanide ionic complexes'activity for the polymerization of rac-lactide were also stydied. The bridged bis(phenolate) ligand used in this thesis is amine-bridged bis(phenolate) ligand Me₂NCH₂CH₂N[CH₂-(2-HO-C₆H₂-Bu₂^t-3,5)]₂, abbreviated as H₂L¹. The bridged phenolate alkoxylate ligand (2-HO-C₆H₂-Bu₂^t-3,5)CH₂(NC₄H₇-2-Ph₂CHO-) was abbreviated as H₂L².1. Protic exchange reactions of (C₅H₅)₃Ln(THF) with amine bridged bis(phenol) H₂L¹ in a 1:1 molar ratio, and then with 1/2 equiv of p-benzenediol in situ in THF gave the neutral lanthanide aryloxides p-C₆H₄[OLnL¹(THF)]₂ [Ln=Y (1), Yb (2), Sm (3)] in high isolated yields. These complexes were well characterized by IR spectra, elemental analyses and single crystal X-ray diffraction.2. Reactions of L¹YbNPh₂ with 1,4-benzenedimethanol in a 2:1 molar ratio in THF afforded the neutral ytterbium alkoxides of p-C₆H₄[CH₂OYL(THF)]₂ (4). The complexe was well characterized by IR spectra, elemental analyses and single crystal X-ray diffraction.3. Reaction of anhydrous LnCl₃ with L¹Na2 in THF in 1:1 molar ratio afforded ionic complexes (L¹)2SmNa(THF) (6) instead of L¹SmCl(THF). But reactions of (^tBuCp)₂SmCl with amine bridged bis(phenol) H₂L¹ in a 1:1 molar ratio in THF gave the neutral complexe L¹SmCl(DME) (7)。The complexe was well characterized by IR spectra, elemental analyses and single crystal X-ray diffraction.4. Reaction of anhydrous LnCl₃ with L²Li₂ in THF in 1:2 molar ratio afforded ionic complexes [Ln(L²)₂][{(THF)₃Li}₂(μ-Cl)]·THF [Ln=Y (8), Yb (9), Sm (10), Nd(11)]. All of these compleces were characterized by IR spectra, elemental analyses and single crystal X-ray diffraction. 5. Reaction of (C₅H₅)₃Ln(THF) with bridged phenolate alkoxylate ligand H₂L² in a 1:1 molar ratio, and then with 1 equiv of benzyl alcohol in situ in THF gave the lanthanide alkoxides [(L²)₃Ln₃(μ₃-OH)(μ-OCH₂Ph)₃]^-[Na(THF)₆]⁺ [Ln=Y (13), Yb (14)], which were stabilized by sodium hydroxide. All of these compleces were characterized by IR spectra, elemental analyses and single crystal X-ray diffraction.6. It was found that complexes 1-4 showed high activity for the ring-opening polymerization of rac-β-butyrolactone, giving the polymers with relatively narrow molecular weight distributions and heterotactic PHB was abtainded with the highest Pr of 0.88.7. Complexes 8-11 can initiate the ring-opening polymerization of D, 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. Heterotactic PLA was abtainded and the value of Pr ranged from 0.65 to 0.74.