Well-defined sterically hindered zinc aryloxides: Excellent catalysts for ring-opening polymerization of ɛ-caprolactone and l-lactide

Three novel sterically hindered zinc aryloxides have been prepared and well characterized. Their catalytic activities toward ring-opening polymerization (ROP) of ɛ-caprolactone and l-lactide have been investigated. The reaction of 2,2′-ethylidene-bis(4,6-di-tert-butylphenol) (EDBP-H2), 2,2′-(2-methoxybenzylidene)bis(4-methyl-6-tert-butylphenol) (MEBBP-H2) and 2,2′-(2-methoxybenzylidene)bis(4,6-di(1-methyl-1-phenylethyl)phenol) (MEMPEP-H2) with ZnEt2 in THF yields dimeric zinc complexes [(μ-EDBP)Zn(THF)]2 (1), [(μ-MEBBP)Zn(THF)]2 (2) and [(μ-MEMPEP)Zn(THF)]2 (3), respectively. Experimental results show that all three compounds are good catalysts for ROP of ɛ-caprolactone and l-lactide yielding polymer in a controlled fashion with low polydispersity indexes.