Tetranuclear complexes of group 12 and 13 supported on a polynucleating ligand and activity studies in the ROP of rac-lactide

Abstract

A polynucleating ligand (L-H4) containing four N,O bidentate sites was cleanly metallated by four equivalents of AlMe3, GaMe3 and ZnEt2 resulting in tetranuclear complexes L(MMe2)4 (M = Al (1), Ga (2)) and L(ZnEt(CH3CN)0.5)4 (3). The Al complex shows the best catalytic activity for the ring-opening polymerization (ROP) of rac-lactide (rac-LA) in the present family of tetranuclear compounds. Polymerization studies indicate the lack of cooperativity between metal centers in the ROP of rac-LA, despite having a ligand platform which binds to four metal centers.