Multinuclear Zinc–Magnesium Hydroxide Carboxylates: A Predesigned Model System for Copolymerization of CO(2) with Epoxides

[Image: see text] Among numerous catalysts in the ring-opening copolymerization of epoxides with carbon dioxide (CO(2)), zinc dicarboxylate complexes are the most common type, and in the family of metal-based homogeneous catalysts, zinc and magnesium complexes have attracted widespread attention. We report on the synthesis and structural characterization of a zinc–magnesium benzoate framework templated by the central hydroxide anion with μ(3)-κ(2):κ(2):κ(2) coordination mode, [ZnMg(2)(μ(3)-OH)(O(2)CPh)(5)](n) (n = 1 or 2). The resulting heterometallic system forms stable Lewis acid–base adducts with tetrahydrofuran (THF) and cyclohexene oxide (CHO), which crystallize as the hexanuclear zinc–magnesium hydroxide carboxylate cluster [ZnMg(2)(μ(3)-OH)(O(2)CPh)(5)(L)(2)](2) (L = THF or CHO). Their X-ray crystal structure analysis revealed that the Zn center prefers 4-fold coordination and the Mg centers demonstrated the ability to accommodate higher coordination numbers, and as a result, the heterocyclic molecules are exclusively bonded to 6-fold Mg atoms. The heteronuclear carboxylate aggregates appeared active in the copolymerization reaction at elevated temperatures to produce an alternating poly(cyclohexene carbonate).