Synthesis, characterization, and catalytic activities of rare-earth metal complexes with iminopyrrolyl ligands

A series of rare-earth metal complexes with substituted iminopyrrolyl ligands were prepared and characterized. Reactions of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 with 3 equiv. of 2-(2,6-Et2C6H3N═CH)C4H3NH (1a) in toluene generated tris-iminopyrrolyl rare-earth metal complexes with formula [2-(2,6-Et2C6H3N═CH)C4H3N]3Ln(THF)n [n = 0, Ln = Y (2a), Eu (2b); n = 1, Ln = Nd (2c), Sm (2d)] in moderate yields. Treatments of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 with 3 equiv. of 2-(2,4,6-Me3C6H2N═CH)C4H3NH (1b) in toluene afforded tris-iminopyrrolyl rare-earth metal complexes with formula [2-(2,4,6-Me3C6H2N═CH)C4H3N]3Ln(THF) [Ln = Y (3a), Sm (3b), Eu (3c)]. The catalytic properties of all rare-earth metal complexes on the ring-opening polymerization of ε-caprolactone have been studied. The results represent rare example of the pyrrolyl ligands as initiators for ε-caprolactone polymerization.