Electron deficient zinc complexes: Enhanced lactide polymerization activity achieved through rational ligand design

Modification of a neutral bis(phosphinimine) pincer ligand, whereby alkyl groups were placed at the P and N positions of the phosphinimine moieties, has been performed. A cationic zinc-lactate complex of this ligand displays enhanced activity relative to the previous generation catalyst for the polymerization of rac-lactide.

Graphical abstractA new bis(phosphinimine) pincer ligand with alkyl groups at the P and N sites, has been prepared. A cationic zinc-lactate complex of this ligand displays high activity for the polymerization of rac-lactide.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► An alkyl substituted dibenzofuran-based bis(phosphinimine) pincer ligand was prepared. ► Cationic methylzinc (1) and zinc-lactate (2) complexes were synthesized in high yield. ► Complex 2 was structurally characterized. ► Complex 2 is an extremely active lactide polymerization catalyst. ► Complex 2 polymerizes lactide via a coordination-insertion mechanism.