The synthesis, structure and magnetic properties of two cobalt phosphonate salts

Two new cobalt(II) phosphonate salts, (3[Co(H2O)(6)](2)(C12H18O9P3))center dot 11H(2)O (1) and {[Co(H2O)(6)](C12H19O9-P-3)}center dot 6H(2)O (2), were obtained in crystalline form. Compound 1 crystallises in the centrosymmetric space group of the triclinic system, whereas compound 2 crystallises in the P2(1)/n space group of the monoclinic system. The asymmetric unit of 1 consists of one and a half hexaaqua cobalt(II) ions, one phosphonic acid residue and five and a half lattice water molecules. One Co2+ ion lies in a special position and the other one in a general position. In 1, both independent Co2+ cations are surrounded by water molecules forming distorted octahedral coordination geometry. The asymmetric unit of 2 consists of one hexaaqua cobalt(II) ion, phosphonic acid residue and six lattice water molecules. In crystal 2, similarly as in crystal 1, the environment of the Co2+ consists of water molecules that form distorted octahedral coordination geometry. The hexaaqua cobalt(II) cations interact with phosphonate counter ions and together with the solvated water molecules they form a three-dimensional hydrogen bonding supramolecular network. Magnetic susceptibility measurements exhibit paramagnetic behaviour with very weak antiferromagnetic interactions for both compounds. (C) 2014 Elsevier Ltd. All rights reserved.