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((OBu)-Bu-t)(4)(THF)(2). The complex Ce(salfen)((OBu)-Bu-t)(2) is less active than Ce ((OBu)-Bu-t)(4)(THF)(2) and the corresponding yttrium(III) alkoxide, Y(salfen)((OBu)-Bu-t)(THF). The different activity was correlated with the Mulliken charges calculated by density functional theory for the two complexes.