Two heterobimetallic complexes, [(TBBP)2Zn][(Na)2(THF)4] (3) and [(TBBP)2Zn][(Li)2(THF)4] (4) can initiate the ring-opening polymerization of L-lactide in a controlled fashion. Complex 3 can initiate the ring-opening polymerization of unsublimed L-lactide under moist conditions even in the presence of H2O, to yield a high conversion and with controllable molecular weight.