Bis(imino)diphenylamido rare-earth metal dialkyl complexes: Synthesis, structure, and catalytic activity in living ring-opening ε-caprolactone polymerization and copolymerization with γ-butyrolactone

Bis(imino)diphenylamido rare-earth metal dialkyl complexes [o-(2,6- ⁱPr₂-C₆H₃-NC-C₆H ₄)₂-N]Ln(CH₂SiMe₃)₂ (1: Ln = Sc; 2: Ln = Lu; 3: Ln = Y) have been synthesized in good yields and structurally characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction studies. They serve as highly efficient single-component catalysts both for the living ring-opening ε-caprolactone polymerization and random copolymerization with γ-butyrolactone, with the activity being dependent on the steric hindrance around the metal center, yielding high molecular weight PCLs or P(CL-co-BL)s with narrow molecular weight distributions.