Cerium(IV) Catalysts for the Ring-Opening Polymerization of Lactide

A rare example of a cerium(IV) alkoxide catalyst for lactide polymerization is reported. The lactide polymerization activity of the new cerium(IV) complex supported by a ferrocene Schiff base ligand, salfen, is compared to the activity of the yttrium analogue and to that of Ce(OtBu)4(THF)2. The complex Ce(salfen)(OtBu)2 is less active than Ce(OtBu)4(THF)2 and the corresponding yttrium(III) alkoxide, Y(salfen)(OtBu)(THF). The different activity was correlated with the Mulliken charges calculated by density functional theory for the two complexes.