Piperazinediium tetrachloridocadmate monohydrate

In the title compound, (C4H12N2)[CdCl4]·H2O, the [CdCl4]2− anions adopt a slightly distorted tetrahedral configuration. In the crystal, O—H⋯Cl hydrogen bonds link the anions and water molecules into corrugated inorganic chains along the b axis which are interconnected via piperazinediiumN—H⋯O and N—H⋯Cl interactions into a three-dimensional framework structure.

In the title compound, (C 4 H 12 N 2 )[CdCl 4 ]ÁH 2 O, the [CdCl 4 ] 2À anions adopt a slightly distorted tetrahedral configuration. In the crystal, O-HÁ Á ÁCl hydrogen bonds link the anions and water molecules into corrugated inorganic chains along the b axis which are interconnected via piperazinediiumN-HÁ Á ÁO and N-HÁ Á ÁCl interactions into a three-dimensional framework structure.

Related literature
For common applications of organic-inorganic hybrid materials, see: Kobel & Hanack (1986); Pierpont & Jung (1994). For a related structure and discussion of geometrical features, see: Sutherland & Harrison (2009). For the coordination around the Cd II cation, see: El Glaoui et al. (2009).
Data collection: Kappa-CCD Server Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97 and WinGX (Farrugia, 1999). Organic-inorganic hybrid materials continue to attract much attention due to their potential applications in various field (Kobel & Hanack, 1986;Pierpont & Jung, 1994). In this work, we report the crystal structure of one such compound, C 4 H 12 N 2 that two such layers cross the unit cell at z = 1/4 and z = 3/4 and the bodies of the organic groups are located between these layers and connect them by weak C-H···Cl hydrogen bonds [C···Cl, 3.535 (3) Å], giving a three-dimensional framework structure. In the organic entity, the piperazium ring adopts a typical chair conformation and all the geometrical features agree with those found in piperazindiium tetrachlorozincate(II) (Sutherland & Harrison, 2009). It is worth noting that in the anion of (I), the Cd-Cl bond lengths and Cl-Cd-Cl bond angles are not equal, but vary with the environment around the Cl atom. The Cd-Cl bond lengths vary between 2.4418 (6) and 2.4892 (7) Å and the Cl-Cd-Cl angles range from 103.07 (2) to 115.19 (2) °. These values are in good agreement with those reported previously, clearly indicating that the [CdCl 4 ] 2anion has a slightly distorted tetrahedral stereochemistry (El Glaoui et al. (2009).

Experimental
An aqueous solution of piperazine (4 mmol, 0.344 g), cadmium chloride (4 mmol, 0.732 g) and HCl (10 ml, 0.8 M) in a Petri dish was slowly evaporated at room temperature. Single crystals of the title compound, suitable for X-ray diffraction analysis, were obtained after several days (yield 68%).

Refinement
All N-H hydrogen atoms were found in the difference Fourier map and refined isotropically. The water hydrogen atoms were also found in the difference Fourier but their positions were kept fixed during the refinement and their U iso values were given a value equal to 1.2 times U eq of the parent oxygen. All C-H atoms were allowed to ride with C-H = 0.97 Å and U iso (H) = 1.2U eq (C).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 Rfactors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq