Poly[triaqua-(μ-butane-1,2,3,4-tetra-carboxyl-ato)dicadmium(II)].

The asymmetric unit of the title Cd(II) coordination polymer, [Cd(2)(C(8)H(6)O(8))(H(2)O)(3)](n), contains two crystallographically independent Cd(II) cations, one-half each of two independent anionic butane-1,2,3,4-tetra-carboxyl-ate units (L) and three water mol-ecules. Both anionic units lie on inversion centers. One of the Cd(II) ions is six-coordinated by four carboxyl-ate O atoms from four L anions and two water O atoms in a distorted octa-hedral coordination environment. The other Cd(II) ion is eight-coordinated by seven carboxyl-ate O atoms from four L anions and one water O atom. The anionic units bridge neighboring Cd(II) centers, forming a three-dimensional framework. O-H⋯O hydrogen-bonding inter-actions between the water mol-ecules and carboxyl-ate O atoms further stabilize the structure.