Diaquabis(thiocyanato-κN)bis[6-(4H-1,2,4-triazol-4-yl-κN 1)pyridin-2-amine]cadmium

In the title compound, [Cd(NCS)2(C7H7N5)2(H2O)2], the CdII cation lies on an inversion center and is coordinated by the N atoms of two thiocyanate anions, by N atoms of two 6-(4H-1,2,4-triazol-4-yl)pyridin-2-amine ligands and by the O atoms of two water molecules in a distorted N4O2 octahedral geometry. The dihedral angle between the triazole and pyridine rings is 23.15 (12)°. In the crystal, molecules are linked by N—H⋯N and O—H⋯S hydrogen bonds. Offset π–π stacking between parallel pyridine rings of adjacent molecules is also observed, the centroid–centroid distance being 3.6319 (14) Å.

In the title compound, [Cd(NCS) 2 (C 7 H 7 N 5 ) 2 (H 2 O) 2 ], the Cd II cation lies on an inversion center and is coordinated by the N atoms of two thiocyanate anions, by N atoms of two 6-(4H-1,2,4-triazol-4-yl)pyridin-2-amine ligands and by the O atoms of two water molecules in a distorted N 4 O 2 octahedral geometry. The dihedral angle between the triazole and pyridine rings is 23.15 (12) . In the crystal, molecules are linked by N-HÁ Á ÁN and O-HÁ Á ÁS hydrogen bonds. Offset stacking between parallel pyridine rings of adjacent molecules is also observed, the centroid-centroid distance being 3.6319 (14) Å .

Comment
Recently, considerable efforts have been devoted to crystal engineering of supramolecular architecture sustained by coordination covalent bonding, hydrogen bonding or some molecular interaction and their combination owing to their fascinating structural diversity and potential application in design of porous materials with novel inclusion or reactivity properties and in supramolecular devices such as sensor and indicator (Moulton et al., 2001;Pan et al., 2001;Ma et al., 2001;Prior et al., 2001). Our interest is toexploit the coordination chemistry of 1,2,4-triazole and its derivatives together with their potential application in material science (Liu et al., 2007;Ding et al., 2006).
In the report, the mono-nuclear Cadmium(II) complex was obtained via the reaction of 2-amino-6-(4-triazoyl)pyridine, L is mono-dentate terminal ligand coordinated via its pyridine nitrogen atoms. The weak N···N interactions between L triazole rings (N-H···N, 3.080 (2) and 3.422 (3) \%A) between L triazole rings can be observed, The offset π···π stacking interactions between two neighboring pyridine rings are also important for the assembly of the supra-molecular structure,the ring centroid-centroid distance being 3.632 (3) Å. As shown in Figure 2, A two-dimensional supra-molecular network can be observed stablized via N···N interactions and π···π stacking interactions.
Further the non-classic O-H···S hydrogen bonds (O-H···S, 3.346 (8) and 3.357 (5) \%A) also can be observed, which further assembly these two-dimensional supramolecular network to form a three-dimensional supra-molecular structure.
The three-dimensional packing architecture in the unit cell of the complex is shown in Figure 3.

Experimental
The organic ligand L was prepared according to the previously reported literature methods (Gioia et al., 1988). A mixture of CdBr 2 (27.2 mg, 0.1 mmol), NH 4 NCS (7.6 mg, 0.1 mmol), L (14.6 mg, 0.1 mmol) and water (10 ml) was stirred for 5 h and filtered. Suitable single crystals for X-ray diffraction study were obtained after a few days, yield 23% (based on

Refinement
The H atoms of the aromatic rings were placed at calculated positions, with C-H = 0.93 \%A and O-H = 0.85 \%A. All H atoms were assigned fixed isotropic displacement parameters, with Uιso(H) = 1.2 Ueq (C) or 1.5 Ueq (O).

Figure 1
The molecular structure of (I) with atom labels and 30% probability dis-placement ellipsoids for non-H atoms..

Figure 2
The two-dimensional supra-molecular network stabilized via N···N hydrogen bonds and offset π···π stacking interactions, Blue lines represent N-H···N hydrogen bonds.  The three-dimensional supramolecular packing architecture of (I). Red lines represent O-H···S hydrogen bonds and Blue lines represent N-H···N hydrogen bonds.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. Rfactors 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.