Bis{tris[3-(2-pyridyl)-1H-pyrazole]cadmium(II)} dodecamolybdo(V,VI)phosphate hexahydrate

The hydrothermally prepared title compound, [Cd(C8H7N3)3]2[PMo12O40]·6H2O, is isotypic with its MnII analogue [Hao et al. (2010 ▶). Acta Cryst. E66, m231–m232]. The CdII cation is in a distorted octahedral environment, coordinated by six N atoms from three chelating 3-(2-pyridyl)-1H-pyrazole ligands. In the reduced heteropolyanion, two O atoms of the central PO4 group ( symmetry) are equally disordered about an inversion centre. N—H⋯O and O—H⋯O hydrogen bonds contribute to the crystal packing. Compared with the MnII analogue, the Cd—N bond lengths are longer at 2.316 (7)–2.334 (6) Å, versus 2.224 (6)–2.283 (5) Å for Mn—N, whereas all other bond lengths and angles and the hydrogen-bonding motifs are very similar in the two structures.

. Acta Cryst. E66, m231-m232]. The Cd II cation is in a distorted octahedral environment, coordinated by six N atoms from three chelating 3-(2pyridyl)-1H-pyrazole ligands. In the reduced heteropolyanion, two O atoms of the central PO 4 group (1 symmetry) are equally disordered about an inversion centre. N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds contribute to the crystal packing. Compared with the Mn II analogue, the Cd-N bond lengths are longer at 2.316 (7)-2.334 (6) Å , versus 2.224 (6)-2.283 (5) Å for Mn-N, whereas all other bond lengths and angles and the hydrogen-bonding motifs are very similar in the two structures.

Comment
The design and synthesis of polyoxometalates has attracted continuous research interest not only because of their appealing structural and topological novelties, but also due to their interesting optical, electronic, magnetic, and catalytic properties, as well as their potential medical applications (Pope & Müller, 1991). In our research group, organic amines, such as 3-(2-pyridyl)pyrazole and pyrazine, are used to effectively modify polyoxomolybdates under hydrothermal condictions . Here, we describe the synthesis and structural characterization of the title compound.
As shown in Fig. 1 Artero & Proust (2000); Kurmoo et al. (1998);Niu et al. (1999). The employed organic ligand appears to adjust the pH value, and additionally supplies reducing electrons, which is a commonly observed feature of hydrothermal syntheses when organic amines are used to prepare various hybrid materials, zeolites or metal phosphates (Yang et al., 2003).
In the Keggin-type heteropolyanion, each Mo atom is surrounded by six O atoms and the P atom is located at the center  Table 2).

Refinement
All hydrogen atoms bound to aromatic carbon atoms were refined in calculated positions using a riding model with a C-H distance of 0.93 Å and U iso = 1.2U eq (C). Hydrogen atoms attached to aromatic N atoms were refined with a N-H distance of 0.86 Å and U iso = 1.2U eq (N). The hydrogen atoms of the three uncoordinated water molecules could not be located unambiguously from difference Fourier maps, probably due to disorder of the water molecules. Thus the structure was refined without the H atoms of the water molecules (which includes the water O atoms O1W, O2W, O3W). In the PO 4 unit, the two oxygen atoms (O19 and O21) are equally disordered about the inversion centre. In the final difference Fourier map the highest peak is 2.70 Å from atom O2w and the deepest hole is 0.46 Å from atom Mo1. The highest peak is located in the voids of the crystal structure and may be associated with an additional water molecule. However, refinement of this position did not result in a reasonable model. Hence this position was also excluded from the final refinement. Fig. 1. The building blocks of the title compound with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level; H atoms are given as spheres of arbitrary radius.

Figures
Crystal data [Cd(C 8

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.