Synthesis and characterization of lanthanide amides bearing phenoxy(quinolinyl)amide ligand and their application in the ring-opening polymerization of 1,4-dioxan-2-one

The amine elimination reaction of quinolinyl aminophenol (LH2) with Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 in THF afforded lanthanide-lithium aminophenoxy complexes L2LnLi(THF)2 (Ln = Yb (1), Sm (2)), while the similar reaction with Ln[N(SiMe3)2]3 in toluene gave normal monoamido lanthanide complexes LLnN(SiMe3)2(DME) (Ln = Sm (3), Nd (4), La (5)). All complexes have been fully characterized. X-ray structural determination revealed that complexes 1 and 2 have a monomeric C2-symmetric heterobimetallic structure, in which the lanthanide atom is connected to the lithium atom by two oxygen bridges from two phenoxy(quinolinyl)amide ligands. Complexes 4 and 5 have a solvated monomeric structure, and the lanthanide metal centers adopt a distorted octahedral geometry. It was found that complexes 3–5 initiated the ring-opening polymerization of 1,4-dioxan-2-one (PDO) with high activity.