Neodymium-based catalysts coordinated with phosphate ligands (NdCl33L), where L=triethyl phosphate (TEP) or tris(2-ethylhexyl) phosphate (TEHP), were synthesized. The ring-opening polymerizations (ROP) of -caprolactone (-CL) with these catalysts in the presence of benzyl alcohol initiator were performed, yielding polymers with well-defined molecular weights and relatively narrow polydispersity index (PDI=1.22-1.65). In situ NMR analysis of the reaction between NdCl33TEP and benzyl alcohol indicated that ROP proceeds through a coordination-insertion mechanism. The end groups of the resultant polymers were determined using MALDI-ToF mass spectrometry and NMR spectroscopy. The quasi-living nature of this catalytic system was demonstrated by kinetic studies and the successful synthesis of the block copolymer poly(-caprolactone)-block-poly(l-lactide) by sequential monomer addition. Kinetic studies revealed that the catalyst with the bulkier TEHP ligand increased the rate of ROP of -CL as compared to the TEP ligand. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1289-1296