A tetrahedrally coordinated cobalt(II) phosphonate with a three-dimensional framework containing two-dimensional channels

The structure of poly[caesium(I) [(micro(4)-ethylenediphosphonato)cobalt(II)]], {Cs[Co(C(2)H(5)O(6)P(2))]}(n), reveals a three-dimensional polymeric open framework consisting of tetrahedral Co(II) atoms coordinated by four different ethylenediphosphonate O atoms and intermolecular O-H...O hydrogen bonds. The largest open window is made of corner-sharing CoO(4) and PO(3)C tetrahedra, giving 16-membered rings of dimensions 9.677 (5) x 4.684 (4) A(2). There are two independent ethylenediphosphonate ligands, each lying about an inversion centre.