“Dinucleating Ligand Platforms Supporting Indium and Zinc Catalysts for Cyclic Ester Polymerization”
The syntheses of the first alkoxide bridged indium complex supported by a chiral dinucleating ligand platform (1), along with its zinc analogue (2), are reported. Both complexes are synthesized in a one pot reaction starting from a chiral dinucleating bis(diamino)phenolate ligand platform, NaOEt, and respective metal salts. The dinucleating indium analogue (7) based on an achiral ligand backbone is also reported. Indium complexes bearing either the chiral or achiral ligand catalyze the ring opening polymerization of racemic lactide to afford highly heterotactic PLA (Pr > 0.85). The indium complex bearing an achiral ligand affords essentially atactic PLA from meso-LA. The role of the dinucleating ligand structure in catalyst synthesis and polymerization activity is discussed.