Zinc/magnesium–sodium/lithium heterobimetallic triphenolates: Synthesis, characterization, and application as catalysts in the ring-opening polymerization of l-lactide and CO2/epoxide coupling

•Four metal atoms in these heterobimetallic complexes are nearly collinear.•Complexes 1 and 2 are efficient catalysts for ring-opening polymerization of l-lactide even in an air atmosphere.•Cycloaddition of CO2 with cyclohexene oxide catalyzed by 1 and 2 was performed with high conversion.

A series of heterobimetallic complexes supported by a bulky trisphenol ligand were synthesized and characterized. Treatment of 2,6-bis(3,5-bis-t-butyl-2-hydroxybenzyl)-4-t-butyl phenol with 1 equivalent sodium/nBuLi and 1 equiv. Zn(Et)2 in THF solution afforded complex 1 or 2; metal complexes 3 and 4 were obtained in quantitative yields by alternating Zn(Et)2 to Mg(nBu)2. The X-ray structures of 2 and 3 indicated that four metal atoms in the complexes are nearly collinear. Catalysis employing complexes 1–3 for l-lactide (l-LA) was systematically studied, and experimental results showed that 1 and 2 can catalyze the ring-opening polymerization of l-LA in a controlled fashion; what is more, both of these two complexes could catalyze l-LA with high conversion even in an air atmosphere. Complexes 1 and 2 also can effectively catalyze the coupling reaction of carbon dioxide with cyclohexene oxide using n-Bu4NBr/n-Bu4NCl as co-catalysts.

Graphical abstractA series of heterobimetallic complexes catalyzed the ring-opening polymerization of l-LA in a controlled fashion. What is more, both of these two complexes could catalyze l-LA with high conversion even in the air. The application catalyzed by 1 and 2 in the presence of n-Bu4NX (X = Cl, Br) were also investigated under mild conditions.Figure optionsDownload full-size imageDownload high-quality image (150 K)Download as PowerPoint slide