{[Na1(μ-H(2)O)Na2](2)[(C(2)O(4))(2)Cr(μ-OH)(2)Cr(C(2)O(4))(2)]·H(2)O}(n), a novel hydrated form.

The unit cell of the title compound, poly[[μ-aqua-μ-hydroxido-di-μ-oxalato-chromium(III)disodium] monohydrate], {[CrNa(2)(C(2)O(4))(2)(OH)(H(2)O)]·H(2)O}(n), contains four [Na1(μ-H(2)O)Na2][(C(2)O(4))(2)Cr(μ-OH)·H(2)O] formula units, each of which consists of two crystallographically independent Na(+) sites (bridged by one aqua ligand), one half of a centrosymmetric di-μ-hydroxido-bis-[cis-bis-(oxalato)chromate(III)] dimer, [(C(2)O(4))(2)Cr(μ-OH)(2)Cr(C(2)O(4))(2)](4-), and one uncoordin-ated water mol-ecule. The structure is best described as a coordination polymer in which the three-dimensional lattice framework is realized by the inter-connection of the metallic atoms via the O atoms of the aqua, hydroxide and oxalate ligands. One Na atom is hepta-coordinated by one water, one hydroxide and five oxalate O atoms, whilst the other is penta-coordinated by one water and four oxalate O atoms. The coordination around the Cr(3+) sites is pseudo-octa-hedral, involving four aqua and two hydroxide O atoms. Adjacent Na atoms are separated by 3.593 (2) Å, whereas the intra-dimer Cr⋯Cr spacing is 2.978 (1) Å. The crystal structure is consolidated by extended relatively weak O-H⋯O hydrogen bonding with O⋯O distances ranging from 2.808 (4) to 3.276 (5) Å.