Hexaaquacobalt(II) and hexaaquanickel(II) bis(μ-pyridine-2,6-dicarboxylato)bis[(pyridine-2,6-dicarboxylato)bismuthate(III)] dihydrate

The title complexes, hexaaquacobalt(II) bis(mu-pyridine-2,6-dicarboxylato)bis[(pyridine-2,6-dicarboxylato)bismuthate(III)] dihydrate, [Co(H2O)(6)][Bi-2(C7H4NO4)(4)]center dot 2H(2)O, (I), and hexaaquanickel(II) bis(mu-pyridine-2,6-dicarboxylato)bis[(pyridine-2,6-dicarboxylato)bismuthate(III)] dihydrate, [Ni(H2O)(6)][Bi-2(C7H4NO4)(4)]center dot 2H(2)O, (II), are isomorphous and crystallize in the triclinic space group P <file type="gif" name="AYC_sq3274_mu1.gif"/> . The transition metal ions are located on the inversion centre and adopt slightly distorted MO6 (M = Co or Ni) octahedral geometries. Two [Bi(pydc)(2)]- units (pydc is pyridine-2,6-dicarboxylate) are linked via bridging carboxylate groups into centrosymmetric [Bi-2(pydc)(4)]2- dianions. The crystal packing reveals that the [M(H2O)(6)]2+ cations, [Bi-2(pydc)(4)]2- anions and solvent water molecules form multiple hydrogen bonds to generate a supramolecular three-dimensional network. The formation of secondary Bi...O bonds between adjacent [Bi-2(pydc)(4)]2- dimers provides an additional supramolecular synthon that directs and facilitates the crystal packing of both (I) and (II).