metal-organic compounds
The structure of poly[caesium(I) [(4-ethylenediphosphonato)cobalt(II)]], {Cs[Co(C2H5O6P2)]}n, reveals a three-dimensional polymeric open framework consisting of tetrahedral CoII atoms coordinated by four different ethylenediphosphonate O atoms and intermolecular O-HO hydrogen bonds. The largest open window is made of corner-sharing CoO4 and PO3C tetrahedra, giving 16-membered rings of dimensions 9.677 (5) × 4.684 (4) Å2. There are two independent ethylenediphosphonate ligands, each lying about an inversion centre.