Aquaglutarato(2,4,6-tri-2-pyridyl-1,3,5-triazine)nickel(II) trihydrate

In the title compound, [Ni(C5H6O4)(C18H12N6)(H2O)2]·3H2O, the NiII atom shows a distorted octahedral coordination by three N atoms of the tridentate chelating ligand and three O atoms of two aqua ligands and an O atom of one carboxylate group of the glutarate anion. Molecules are self-assembled via intermolecular O—H⋯O and O—H⋯N hydrogen-bonding interactions and π–π stacking interactions [centroid–centroid distance = 3.836 (3) Å] into a supramolecular network.


Comment
As an interesting polydentate nitrogen donor ligand, 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) has attracted increasing attention in the synthesis of novel transition metal complexes (Glaser, et al., 2004;Zibaseresht & Hartshorn, 2005;Zheng, et al., 2006;Zhou, et al., 2007). It was applied in the extraction and separation of metal ions, and in the preparation of DNA cleaving agents. It has also been widely empolyed to determine the concentration of mono-and polysaccharides in seawater (Gupta, et al., 1993;Witter & Luther, et al., 2002). Our interest in tptz transition metal complexes prompts us to report a new tptz containing structure, [Ni(C 18   (1)° with the N3 ring displaying the highest degree of twisting. The [Ni(C 18 H 12 N 6 )(C 5 H 6 O 4 )(H 2 O) 2 ] complex molecules are assembled into a 3D network by hydrogen bonds between the coordinated water and lattice water molecules and the carboxylate group and pyridyl nitrogen atoms with the distances from 2.651 (4) Å to 2.938 (5) Å (Table 1). The crystal structure is also stabilized by intermolecular π-π stacking interactions between tptz ligands [centroid-centroid distance = 3.836 (3) Å].

Experimental
Dropwise addition of 2.0 ml NaOH (1.0 M) to a stirred solution of NiCl 2 .6H 2 O (0.238 g, 1.00 mmol) in 5.0 ml H 2 O produced a green precipitate, which was then centrifuged and washed with double-distilled water until no Clanions were detectable.
supplementary materials sup-2 Refinement All H atoms bound to C were position geometrically and refined as riding, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C). H atoms attached to O atoms were found in a difference Fourier map and refined freely with U iso (H) = 1.5U eq (O). Fig. 1. The asymmetric unit of the title compound, with the atom-labelling scheme. Displacement ellisoids are drawn at the 45% probability level.

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 > 2σ(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.