Novel 2D or 3D alkaline-earth metal sulfonate–phosphonates based on [O3S–C2H4–PO3H]2− ligand

Three novel alkaline-earth metal sulfonate–phosphonates based on [O3S–C2H4–PO3H]2− ligand, namely, [Ca(O3SC2H4PO3H)(H2O)2] (1), [Sr(O3SC2H4PO3H)] (2) and [Ba2(O3SC2H4PO3H)2] (3), have been synthesized by hydrothermal reactions. They represent the first structurally characterized alkaline-earth metal complexes of phosphonic acid attached with a sulfonate group. The structure of compound 1 features a 2D layer based on 1D chains of [Ca2(PO3)2] bridged by –CH2–CH2–SO3– groups. Compounds 2 and 3 show pillar-layer architecture based on two different inorganic layers linked by –CH2–CH2– groups. The inorganic layer in compound 2 features a 1D chain of edge-sharing SrO8 polyhedra whereas that in compound 3 features an edge-sharing Ba2O14 di-polyhedral unit which is further corner-shared with four neighboring ones. The [O3S–C2H4–PO3H]2− ligand shows diverse coordination modes in the three alkaline-earth metal sulfonate–phosphonates.