Structural diversity of thiodiacetate compounds of group II metals: Synthesis and X-ray characterization of 2D coordination polymers of calcium and strontium

Two different coordination polymers containing Ca and Sr metals, connected via thiodiacetate ligand, have been isolated from aqueous solution and characterized by single-crystal X-ray diffraction. Compound [Ca(tda)(H2O)]n (1) image) is a two-dimensional polymer in which the calcium ions are disposed forming parallel zig-zag chains and are bridged by water molecules and one of the two carboxylate groups of thiodiacetate. The second carboxylate group of tda makes the connexion with the neighbouring parallel chain completing the 2D sheet. Compound [Sr(tda)]n (2) is also a two-dimensional polymer extended in the bc plane with the strontium ions, approximately coincident to the b axis, bridged by the carboxylate groups of thiodiacetate. Novel coordination modes for the thiodiacetate group have been identified in both compounds.