Lanthanum complexes containing a bis(phenolate) ligand with a ferrocene-1,1′-diyldithio backbone: synthesis, characterization, and ring-opening polymerization of rac-lactide

Abstract

Lanthanum complexes [(L)LaX] (X = N(SiMe₃)₂1, OⁱPr 2, BH₄3) supported by a ferrocene-based (OSSO)-type ligand LH₂ were synthesized and characterized by elemental analysis, NMR spectroscopy and cyclic voltammetry. The structure of 1 was confirmed by single crystal X-ray diffraction. These complexes were highly active initiators for the ring-opening polymerization of rac-lactide (rac-LA). The activity depended on the initiating group in the order of 1 ≈ 2 > 3. The activities of 2 and 3 during polymerization were controlled in situ with external redox reagents by reversibly switching the oxidation state of the iron center.