Lanthanide isopropoxides supported by carbon-bridged bisphenolate ligands of 2,2'-ethylene-bis(4,6-di-tert-butylphenoxo) {[(EDBP)Ln(mu-OPri)(THF)(2)](2), where Ln is Nd (1), Sm (2), or Yb (3) and THF is tetrahydrofuran} were synthesized by protic exchange reactions in high yields with Cp(3)Ln compounds as raw materials, and complex 1 was structurally characterized. Complexes 1-3 were shown to be efficient initiators for the ring-opening polymerization of epsilon-caprolactone (epsilon-CL) and 2,2dimethyltrimethylene carbonate (DTC). Complexes 1-3 could initiate the controlled polymerization of epsilon-CL, and the polymerization rate was first-order with respect to the monomer. The influence of the reaction conditions on the monomer conversion, molecular weight, and molecular weight distribution of the resultant polymers was investigated. End-group analyses of the oligomers of epsilon-CL and DTC showed that the polymerization underwent a coordination-insertion mechanism. (c) 2006 Wiley Periodicals, Inc.