Highly Active, Productive, and Syndiospecific Yttrium Initiators for the Polymerization of Racemic β‐Butyrolactone

Alternate tacticities: The ring-opening polymerization of rac-β-butyrolactone (rac-BBL) using a six-coordinate yttrium complex bearing a dianionic amine-bis(phenolate) ligand as initiator proceeds readily at room temperature to give the corresponding poly(3-hydroxybutyrate) (PHB) with up to 94 % syndiotacticity and narrow molecular-weight distributions (see scheme).