A series of new alkyl mono-and bimetallic aluminum complexes supported by novel amidinate ligands has been prepared in very high yields. These complexes were fully characterized by spectroscopic methods. Alkyl aluminum complexes 1-6 were investigated as catalysts for the ring-opening polymerization and copolymerization of e-caprolactone and L-lactide. Under the optimal reaction conditions, complex 5 acts as an efficient single-component initiator for the ring-opening polymerization and copolymerization of cyclic esters to yield biodegradable polyester materials with narrow polydispersities. (C) 2017 Wiley Periodicals, Inc.