(3-Acetyl-4-methyl-1H-pyrazol-1-ide-5-carboxylato)bis(1,10-phenanthroline)nickel(II) 3.5-hydrate

The title compound, [Ni(C7H6N2O3)(C12H8N2)2]·3.5H2O, crystallizes as a neutral mononuclear complex with 3.5 solvent water molecules. One of the water molecules lies on an inversion centre, so that its H atoms are disordered over two sites. The coordination environment of NiII has a slightly distorted octahedral geometry, which is formed by one O and five N atoms belonging to the N,O-chelating pyrazol-1-ide-5-carboxylate and two N,N′-chelating phenanthroline molecules. In the crystal, O—H⋯O, N—H⋯O and O—H⋯N hydrogen bonds involving the solvent water molecules and pyrazole-5-carboxylate ligands form layers parallel to the ab plane. These layers are linked further via weak π–π interactions between two adjacent phenanthroline molecules, with centroid-to-centroid distances in the range 3.886 (2)–4.018 (1) Å, together with C—H⋯π contacts, forming a three-dimensional network.

The title compound, [Ni(C 7 H 6 N 2 O 3 )(C 12 H 8 N 2 ) 2 ]Á3.5H 2 O, crystallizes as a neutral mononuclear complex with 3.5 solvent water molecules. One of the water molecules lies on an inversion centre, so that its H atoms are disordered over two sites. The coordination environment of Ni II has a slightly distorted octahedral geometry, which is formed by one O and five N atoms belonging to the N,O-chelating pyrazol-1-ide-5carboxylate and two N,N 0 -chelating phenanthroline molecules. In the crystal, O-HÁ Á ÁO, N-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds involving the solvent water molecules and pyrazole-5carboxylate ligands form layers parallel to the ab plane. These layers are linked further via weakinteractions between two adjacent phenanthroline molecules, with centroid-tocentroid distances in the range 3.886 (2)-4.018 (1) Å , together with C-HÁ Á Á contacts, forming a three-dimensional network.
Cg is the centroid of the N1/N2/C2/C3/C4 pyrazole ring. The bridging nature of pyrazolate provides the possibility to bring metal ions into close proximity, which results in arrays with interesting magnetic and catalytic properties (Klingele et al., 2009;Malinkin et al., 2012b;Ng et al., 2011).
Therefore, research focused on pyrazolate complexes with higher nuclearity is of special interest in the field of supramolecular and bioinorganic chemistry Meyer & Pritzkow, 2000;Bauer-Siebenlist et al., 2005). Mononuclear pyrazolate-based complexes bearing non-coordinated donor groups can potentially be used as building blocks for the synthesis of discrete clusters as well as extended frameworks that offer a wide range of possible applications. On the other hand, phenanthroline is often used in the synthesis of discrete polynuclear complexes in order to prevent formation of coordination polymers by blocking a certain number of vacant sites in the coordination sphere of a metal ion (Fritsky et al., 2004(Fritsky et al., , 2006. Herein we report the synthesis and crystal structure of the title compound, (I), as a continuation of our earlier work devoted to complexes based on non-symmetrical pyrazole ligands Malinkin et al., 2012a,b), in particular, 3-acetyl-4-methyl-1H-pyrazole-5 carboxylic acid (Malinkin et al., 2009(Malinkin et al., , 2012c. As shown in Figure 1, the Ni II ion is coordinated by one pyrazolate ligand via N,O-chelating groups and two N,Nchelating phenanthroline molecules forming a slightly distorted octahedral coordination environment. The Ni-N pz , Ni-N phen and Ni-O distances are consistent with the reported data for related complexes (Fang & Wang, 2010;Zheng et al., 2009;Zhong et al., 2009;Bouchene et al., 2013).
In the crystal packing the complex molecules are associated via intermolecular hydrogen bonds ( which are parallel to the xy plane (Fig. 2). In addition layers are stabilized by a weak π-π interactions between phenanthroline moieties with intercentroid distances of 4.018 (1) Å. Further complex species are united into threedimensional motif through a π-π interactions found between two adjacent phenanthroline molecules belonging to the different layers (intercentroid distances 3.886 (2) and 3.950 (2) Å) and a C-H(phenanthroline)···π(pyrazole) contacts (the shortest H-centroid separation is around 2.77 Å).

Refinement
The OH and NH hydrogen atoms were located from the difference Fourier map, and their positional and isotropic thermal parameters were included into the further stages of refinement. The C-H hydrogen atoms were positioned geometrically and were constrained to ride on their parent atoms, with C-H = 0.95-0.97 Å, and U iso = 1.2-1.5 U eq (parent atom).
Large value of ratio U eq (max)/U eq (min) for O6 and O7 is caused by a slight disorder of the atoms. For this reason a command ′ISOR′ was applied as a weak restraint.

Figure 2
A portion of the packing, viewed down the y axis. Intermolecular hydrogen bonds link the molecules into a twodimensional network. Hydrogen bonds and π-interactions are shown as red and black dashed lines, respectively.

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. 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 Occ. (