Copolymerization of carbon dioxide with cyclohexene oxide catalyzed by bimetallic dysprosium complexes containing hydrazine-functionalized Schiff-base derivatives

A series of dinuclear DyIII acetate complexes containing three different hydrazine-functionalized Schiff-base ligands (hmb, hmi, and hb) have been synthesized by one-pot reaction with Dy(OAc)3·4H2O as the metal precursor. [Dy2(hmb)2(OAc)4]·MeCN (1·MeCN) and [Dy2(hmi)2(OAc)2(MeOH)2]·H2O (2·H2O) with keto and enol forms of the corresponding ligands, respectively, were shown the similar core structures but different ratio of DyIII to OAc–. Moreover, the different coordination environments of complex [Dy2(hb)2(μ-OAc)2(OAc)2(H2O)2]·DMF·H2O (3·DMF·H2O) also offered an opportunity to understand the relationship between structural model and catalytic properties. Bimetallic dysprosium complexes 1–3 were demonstrated to be active catalysts for copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) without cocatalysts. To the best of our knowledge, well-defined catalyst 2 appears to be the first example of an air-stable bimetallic dysprosium complex that is effective for CO2/CHO copolymerization and the formation of the perfectly alternating poly(cyclohexenecarbonate) with a high molecular weight. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 321–328