Synthesis, reactivity, and characterization of amine bis(phenolate) lanthanide complexes and their application in the polymerization of ε-caprolactone

A series of amine bis(phenolato)lanthanide methyl and amido complexes were synthesized by general salt metathesis reaction in this paper. The reaction of anhydrous lanthanide trichlorides with 1 equiv of sodium amine bis(phenolate) LNa2 [L = Me2NCH2CH2N{CH 2-(2-O-C6H2-But2-3,5)} 2] in THF at room temperature gave the amine bis(phenolate) lanthanide chlorides LLnCl(THF) (Ln = Yb (1), Ln = Er (2)). Complexes 1 and 2 can be used as starting materials to prepare amine bis(phenolate) lanthanide derivatives. Complexes 1 and 2 reacted with lithium methyl and lithium amide, respectively, to give the corresponding lanthanide methyl and amido products LLnMe(THF) (Ln = Yb (3), Ln = Er (4)) and LLnNPh2(THF) (Ln = Yb (5), Ln = Er (6)). These complexes were well characterized by elemental analyses and IR spectra. The definitive molecular structures of complexes 1, 2, 3, 5, and 6 were provided by single-crystal X-ray analyses. Reactivity studies of complexes 3, 5, and 6 have shown them to be efficient initiators for the ring-opening polymerization of ε-caprolactone.