Tetraaquabis(1,10-phenanthroline-κ2 N,N′)strontium 5,5′-diazenediylditetrazolide

The title complex, [Sr(C12H8N2)2(H2O)4](C2N10), contains an [Sr(phen)2(H2O)4]2+ cation (phen is 1,10-phenanthroline) and a 5,5′-diazenediylditetrazolide anion (site symmetry 2). The Sr2+ cation (site symmetry 2) is coordinated by four N atoms from two chelating phen and four water molecules. In the crystal structure, the water molecules and the N atoms in the tetrazolide rings form an extensive range of O—H⋯N hydrogen bonds which link the complex into a two-dimensional structure. An adjacent layer further yields a three-dimensional supramolecular network by offset face-to-face π–π stacking interactions of the phen ligands [with centroid–centroid distances of 3.915 (2) and 4.012 (2) Å]. The two bridging N atoms of the anion are equally disordered about the twofold rotation axis.

The title complex, [Sr(C 12 H 8 N 2 ) 2 (H 2 O) 4 ](C 2 N 10 ), contains an [Sr(phen) 2 (H 2 O) 4 ] 2+ cation (phen is 1,10-phenanthroline) and a 5,5 0 -diazenediylditetrazolide anion (site symmetry 2). The Sr 2+ cation (site symmetry 2) is coordinated by four N atoms from two chelating phen and four water molecules. In the crystal structure, the water molecules and the N atoms in the tetrazolide rings form an extensive range of O-HÁ Á ÁN hydrogen bonds which link the complex into a two-dimensional structure. An adjacent layer further yields a threedimensional supramolecular network by offset face-to-facestacking interactions of the phen ligands [with centroidcentroid distances of 3.915 (2) and 4.012 (2) Å ]. The two bridging N atoms of the anion are equally disordered about the twofold rotation axis.

Related literature
Tetrazole compounds have been investigated as potential energy materials; see: Singh et al. (2006); Klapö tke et al. (2009). In particular, complexes of tetrazole containing cations such as strontium, barium or copper are components for pyrotechnical mixtures (Hartdegen et al., 2009;Klapö tke et al., 2008). Additionally, the 5,5 0 -azotetrazole with ten nitrogen atoms is predicted to be involved in the hydrogen-bonding motif to construct a supramolecule (Wang et al., 2009).

Comment
The high nitrogen content of tetrazole has led to investigation for their use as potential energy materials (Singh et al., 2006;Klapötke et al., 2009). Especially, complex of tetrazole containing cations like strontium, barium, or copper are sought components for pyrotechnical mixtures, by combination of the ligand and the colorantmetal cation (Hartdegen et al., 2009;Klapötke et al., 2008). Additionally, the 5,5'-azotetrazole with ten nitrogen atoms are predicted to be involved in the hydrogen bonds motif to construct supramolecule (Wang et al., 2009). Herein, we report the crystal structure of the title compound, [Sr(phen) 2 (H 2 O) 4 ][AT] (I), where phen = 1,10-phenanthroline and AT = 5,5'-diazenediylditetrazolide. The crystal structure of (I) consists of a discrete [Sr(phen) 2 (H 2 O) 4 ] 2+ cation and one 5,5'-diazenediylditetrazolide anion. As illustrated in Figure 1, the Sr 2+ ion is coordinated by eight atoms with four N atoms from two phen molecules and four O atoms from water molecules, giving to a quadrangular prism structure. The N7 atom in the 5,5'-diazenediylditetrazolide anion is positional disordered and the occupancy of N7 must be set to 0.5 to get rational structure model and thermal displacement parameters. Strong hydrogen bonds between the 5,5'-diazenediylditetrazolide anion and water molecules link neighboring [Sr(phen) 2 (H 2 O) 4 ] 2+ cations, which giving to a two dimensional supramolecular layer, as shown in the Figure   2. Furthermore, the adjacent layers were form to a three dimensional supramolecular network, by the off-set face to face π-π stacking interactions of the phen molecules, with the centroid distance 3.915 and 4.012 Å.
Experimental 30 ml H 2 O containing 2.0 mmol (0.6003 g) disodium 5,5'-azotetrazole pentahydrate was mixed with 30 ml e thanol containing 4.0 mmol (0.7929 g) 1,10-phenanthroline. 15 ml H 2 O containing 2.0 mmol (0.5332 g) SrCl 2 .6H 2 O was added to the above mixture. Yellow single crystals were obtained from the mixture solution which was allowed to evaporate at the room temperature for two weeks.

Refinement
The H atoms of C atoms were positioned geometrically and refined with a riding model, with C-H = 0.93 Å and Å and U iso (H) = 1.2U eq (C).The water H atoms were located in difference Fourier maps,with distance restraints of O-H = 0.85±0.02 Å, and then refined with isotropic thermal parameters 1.5 times those of O atoms.  Tetraaquabis(1,10-phenanthroline-κ 2 N,N')strontium 5,5'-diazenediylditetrazolide Crystal data [Sr(C 12