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

Two new cobalt(II) phosphonate salts, {3[Co(H2O)6]2(C12H18O9P3)}·11H2O (1) and {[Co(H2O)6](C12H19O9P3)}·6H2O (2), were obtained in crystalline form. Compound 1 crystallises in the centrosymmetric space group of the triclinic system, whereas compound 2 crystallises in the P21/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.

Synthesis and structure of two new metal phosphonate salts, as well as their IR spectra and magnetic properties are presented. Both compounds form a three-dimensional supramolecular network held together by a number of hydrogen bonds and show paramagnetic behaviour with very weak antiferromagnetic interactions through H-bonds.Figure optionsDownload as PowerPoint slide