Synthesis And Characterization Of Neutral Phenoxyamido Lanthanide Complexes And Their Catalytic Behavior

A series of rare-earth metal complexs supported by three kinds of phenoxyamido ligands were synthesized, and their activity for the polymerization of lactide were studied. The phenoxyamido ligands used in here are ortho-MeO substituted phenoxyamido ligandο-OCH3-C₆H₄NHCH₂(3,5-di-tBu-C₆H₂-2-OH) ,abbreviated as [NO]¹H₂ ; ortho-N modified phenoxyamido ligand C5H₄N2HCH₂(3,5-di-tBu-C₆H₂-2-OH) , abbreviated as [NO]²H₂ and 2,6-di-methylphenyl substituted phenoxyamido ligand 2,6-di- CH3-C₆H₄NHCH₂(3,5-di-tBu -C₆H₂-2-OH),abbreviated as [NO]³H₂.1. Amine elimination reactions of La[N(TMS)2]³(THF)2 or Ln[N(TMS)2]³(μ-Cl)Li(THF)3 with [NO]¹H₂ in a 1:1 molar ratio in toluene gave the neutral orth-MeO substituted phenoxyamido lanthanide amido complexes {[NO]¹LnN(TMS)2}2 (Ln = La(1), Nd(2), Sm(3)) and anionic phenoxyamido lanthanide complexes [NO]¹LnLi (THF) 2 (Ln = Yb(4), Y(5)). Complexes 1?5 were characterized by IR, elemental analysis, and NMR spectroscopy in the cases of complexes 1 and 5. Structural determination revealed that complexes 1?3 have dimeric structure.2. Reactions of nBuLi with [NO]¹H₂ in a 2:1 molar ratio in THF and then dropped slowly into LnCl3 pre-activitied by tetrahydrofuran, gave phenoxyamido lanthanide cholorides {[NO]¹LnCl(THF)}2 (Ln = Yb(6), Y(7)). Complexes 6 and 7 were characterized by IR, elemental analysis. Definitive structure of complex 7 was elucidated by single crystal X-ray diffraction and NMR spectroscopy.3. Reactions of {[NO]¹LnCl(THF)}2 with NaN(TMS)2, NaOAr (Ar = 2,6-di-tBu-4-Me-C₆H₂) and [(TMS)2NC(NPri)2]^Na in a 1:2, 1:4 and 1:2 molar ratio in THF, respectively, afforded the corresponding dimeric lanthanide amides {[NO]¹LnN(TMS)2}2 (Ln = Yb(8), Y(9)), the anionic aryloxo complexs {[NO]¹(μ-OAr)Ln(μ-OAr)Na(THF)2}2 (Ln = Yb(10), Y(11)) and the dimeric guanidinate complexs {[NO]¹Ln[(iPrN)2CN(TMS)2]^}2 (Ln = Yb(12), Y(13)) in moderate isolated yields. All of these complexes were characterized by IR, elemental analysis and single crystal X-ray diffraction.4. Reactions of YR3 (R = CH₂C₆H₄NMe2-o) with [NO]¹H₂ in a 1:1 molar ratio in THF afforded the neutral dimeric lanthanide alkyl complex {[NO]¹Ln (CH₂C₆H₄NMe2-o)}2 (Ln = Y (14)) in moderate yields. Complex 14 was characterized by IR, elemental analysis, NMR spectroscopy and single crystal X-ray diffraction.5. Reactions of La[N(TMS)2]³(THF)2 or Ln[N(TMS)2]³(μ-Cl)Li(THF)3 with [NO]²H₂ in a 1:1 molar ratio in toluene gave the neutral phenoxyamido lanthanide amido complexes {[NO]²Ln[N(TMS)2]^THF}2 (Ln = La(15), Nd(16)). Complexes 15?16 were characterized by IR, elemental analysis, and NMR spectroscopy in the cases of complexes 15. Structural determination revealed that complexes 15?16 have solvated dimeric structures.6. Reactions of La[N(TMS)2]³(THF)2 or Ln[N(TMS)2]³(μ-Cl)Li(THF)3 with [NO]³H₂ in a 1:1 molar ratio in toluene gave the neutral phenoxyamido lanthanide complexes {[NO]³Ln[NOH]³}2 (Ln =La(17), Nd(18), Yb(19)). Complexes 17?19 were characterized by IR, elemental analysis, and NMR spectroscopy in the cases of complexes 17 and structure determination.7. Complexes 1?3, 8?9, 12?16, and 18 can initiate the polymerization of L-lactide and rac-lactide with high activity.8. Preliminary studies revealed that the ionic complexes 4?5 can initiate effectively the polymerization of L-lactide under mild polymerization conditions in a controlled manner.