Crystal structures of the potassium and rubidium salts of (3,5-di­chloro­phen­oxy)acetic acid: two isotypic coordination polymers

The two-dimensional coordination polymeric structures of the hydrated potassium and rubidium salts of (3,5-di­chloro­phen­oxy)acetic acid (3,5-D), namely, poly[μ-aqua-bis­[μ(3)-2-(3,5-di­chloro­phen­oxy)acetato]­dipotassium], [K(2)(C(8)H(5)Cl(2)O(3))(2)(H(2)O)](n), and poly[μ-aqua-bis­[μ(3)-2-(3,5-di­chloro­phen­oxy)acetato]­dirubidium], [Rb(2)(C(8)H(5)Cl(2)O(3))(2)(H(2)O)](n), respectively, have been determined and are described. The two compounds are isotypic and the polymeric structure is based on centrosymmetric dinuclear bridged complex units. The irregular six-coordination about the alkali cations comprises a bridging water mol­ecule lying on a twofold rotation axis, the phen­oxy O-atom donor and a triple bridging carboxyl­ate O atom of the oxo­acetate side chain of the 3,5-D ligand, and the second carb­oxy­ate O-atom donor also bridging. The K—O and Rb—O bond-length ranges are 2.7238 (15)–2.9459 (14) and 2.832 (2)–3.050 (2) Å, respectively, and the K⋯K and Rb⋯Rb separations in the dinuclear units are 4.0214 (7) and 4.1289 (6) Å, respectively. Within the layers which lie parallel to (100), the coordinating water mol­ecule forms an O—H⋯O hydrogen bond to the single bridging carboxyl­ate O atom.