Soluble bimetallic μ-oxoalkoxides. VII. Characteristics and mechanism of ring-opening polymerization of lactones

The ring-opening polymerization of unsubstituted lactones by Al₂? Zn and Al₂? Co(II) μ-oxoalkoxides in homogeneous organic phase is described. Under these conditions, the chain propagation is very fast and proceeds without transfer or termination reactions. The composition and structure of the main products resulting from the first polymerization steps have been determined, and fit with a monomer insertion mechanism into the aluminum-alkoxide bonds of the catalyst.