Salen‐Manganese Complexes and their Application in the Ring‐Opening Polymerization of Lactide and ϵ‐Caprolactone

Abstract Efficiency and sustainability are of vital concern to the polymer industry. Ring‐opening polymerizations (ROP) of lactide (LA) and ϵ‐caprolactone (ϵ‐CL) producing biodegradable polymers polylactide (PLA) and polycaprolactone (PCL) were widely researched. Owing to their abundance and non‐toxicity, manganese catalysts are a very good choice. A group of salen manganese (III) complexes were synthesized. Their catalytic activity in the ROP of LA and ϵ‐CL in propylene oxide (PO) was. Under activation of PO, manganese complexes could efficiently mediate the ROP of LA and ϵ‐CL. The molecular weight distributions could be controlled well. The influence of the bridging part and substitutions were fully discussed. Surprisingly, chlorine substituents showed a negative effect on catalytic activity. The analog computation results indicated that the metal center of 7 a did not become more electron‐deficient. By switching the ligand backbone and substituents, the configuration of polylactide (PLA) turned from slight isotactic to slight heterotactic.