Synthesis, structure and catalytic activity of rare-earth metal complexes derived from chiral phosphoryl-sulfonylamides

Abstract A series of rare-earth metal amides derived from (S)-N-(1-(2-(diphenylphosphoryl)phenyl)ethyl)benzenesulfonamide (HL1) and (S)-N-(8-(diphenylphosphoryl)-1,2,3,4-tetrahydronaphthalen-1-ylbenzenesulfonamide(HL2) were prepared, and their catalytic activity for the polymerization of rac-lactide was explored. The amine elimination reactions of Ln[N(SiMe3)2]3 with HL1 or HL2 gave the mono-ligated rare-earth metal amides (L1)Ln[N(SiMe3)2]2 (Ln = Nd (1), Sm (2) and Yb (3)) or bis-ligated rare-earth metal amides (L2)2Ln[N(SiMe3)2] (Ln = Nd (4), Sm (5)) in good yields. All of these complexes were characterized by elemental analyses and X-ray diffraction analyses. Complexes 1–5 are efficient initiators for the ring-opening polymerization of rac-lactide, affording heterotactic-rich polylactides. The ionic radii of the central metals have a significant effect on the catalytic activity.