The Importance of Being (Diastereomerically) Earnest - Mechanistic Insight into Ring-Opening Polymerization Catalysts

Moshe Kol, Chemistry, Tel Aviv University, Tel Aviv, Israel

The stereoregularity of polymers has a major effect on their physical properties. Poly(lactic acid) - PLA - is prepared by the catalytic ring opening polymerization (ROP) of lactide. Lactide has two stereogenic centers. Isotactic, syndiotactic, heterotactic (as well as atactic) PLA may be formed by choice of the lactide monomer - homochiral-, racemic- or meso-LA, and choice of catalyst - most commonly a metal complex. Aluminum complexes typically exhibit the most diverse and accurate stereocontrol in lactide ROP. In this presentation, we will describe chiral tetradentate {ONNO} ligands that wrap in a fully diastereoselective manner around aluminum giving well-defined chiral-at-metal complexes. These complexes led to the revealing of parameters responsible for stereocontrol, and to PLA of all forms of stereoregularity.