catena-Poly[[[tetraaquacadmium(II)]-μ-4,4′-bipyridine] fumarate tetrahydrate]

In the crystal structure of the title compound, [Cd(C10H8N2)(H2O)4](C4H2O4)·4H2O, the CdII atom, on an inversion centre, is six-coordinated by four O atoms from four water molecules and two N atoms from 4,4′-bpy molecules in a distorted octahedral coordination geometry. Weak C—H⋯O interactions between uncoordinated carboxylate O atoms of fumaric acid and water molecules contribute to the crystal packing stability.

In the crystal structure of the title compound, [Cd(C 10 H 8 N 2 )-(H 2 O) 4 ](C 4 H 2 O 4 )Á4H 2 O, the Cd II atom, on an inversion centre, is six-coordinated by four O atoms from four water molecules and two N atoms from 4,4 0 -bpy molecules in a distorted octahedral coordination geometry. Weak C-HÁ Á ÁO interactions between uncoordinated carboxylate O atoms of fumaric acid and water molecules contribute to the crystal packing stability.
The author thanks Tong Hua Teachers' College for financial support.
There are weak C-H···O hydrogen bonds between uncoordinated carboxylate O atoms of fumaric acid and lattice water molecules, which extend one-dimensional chain into three-dimensional supramolecular packing structure (Fig. 2, Table 2).

S3. Refinement
Water H atoms were located in a difference Fourier map and refined as riding in their as-found relative positions; U iso (H) View of the local coordination of Cd(II) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Symmetry code: (i) -x,-y,-z + 2.

Figure 2
A packing diagram for the two-dimensional supramolecular hydrogen-bonding framework via C-H···O interactions. The view shows a layer parallel to the ac plane; the view direction is parallel to the b axis. Hydrogen bonds are indicated by dashed lines.

Data collection
Rigaku R-AXIS RAPID diffractometer Radiation source: fine-focus sealed tube Graphite monochromator Detector resolution: 10 pixels mm -1 ω scan Absorption correction: multi-scan (Higashi, 1995 Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.