Three novel sterically hindered zinc aryloxides have been prepared and well characterized. Their catalytic activities toward ring-opening polymerization (ROP) of E-caprolactone and L-lactide have been investigated. The reaction of 2,2'-ethylidene-bis(4,6-di-tert-butylphenol) (EDBP-H-2), 2,2'-(2-methoxybenzylidene)bis(4-methyl-6-tert-butylphenol) (MEBBP-H-2) and 2,2'-(2-methoxybenzylidene)bis(4,6-di(1-methyl-1-phenylethyl)phenol) (MEMPEP-H-2) with ZnEt2 in THF yields dimeric zinc complexes [(mu-EDBP)Zn(THF)](2) (1), [(mu-MEBBP)Zn(THF)](2) (2) and [(mu-MEMPEP)Zn(THF)](2) (3), respectively. Experimental results show that all three compounds are good catalysts for ROP of epsilon-caprolactone and L-lactide yielding polymer in a controlled fashion with low polydispersity indexes. (c) 2006 Elsevier Ltd. All rights reserved.