Aquabis(2-amino-1,3-thiazole-4-acetato-κ2 O,N 3)nickel(II)

In the crystal structure of the title compound, [Ni(C5H5N2O2S)2(H2O)], the NiII cation is located on a twofold rotation axis and chelated by two 2-amino-1,3-thiazole-4-acetate (ata) anions in the basal coordination plane; a water molecule located on the same twofold rotation axis completes the distorted square-pyramidal coordination geometry. Intermolecular O—H⋯O and N—H⋯O hydrogen bonding, as well as π–π stacking between parallel thiazole rings [centroid–centroid distance 3.531 (8) Å], helps to stabilize the crystal structure.


Related literature
For general background to the potential use of discrete and polymeric metal-organic complexes as functional materials in catalysis, molecular recognition, separation and non-linear optics, see: Batten & Robson (1998) ;Fujita et al. (1994); Han et al. (2008); Wu et al. (2001).

Comment
The rational design and synthesis of novel discrete and polymeric metal-organic complexes have attracted intense interest owing to the realisation of their potential for use as functional materials in catalysis, molecular recognition, separation, and nonlinear optics (Batten & Robson, 1998;Fujita et al., 1994). As for the construction of these inorganic/organic hybrid materials, carboxylate ligands have proven to be an efficacious choice (Wu et al., 2001). The employment of multifunctional ligands bearing both anionic and neutral donor atoms, such as nicotinate, isonicotinate, and various pyridinedicarboxylates, has resulted in the preparation of many functional coordination polymers, some with intriguing optical or gas sorption properties (Han et al., 2008). Herein we report the hydrothermal synthesis, structural characterization of the title complex.
The molecular structure of the title complex is shown in Fig. 1. The Ni II ion is located on a twofold rotation axis and has a slightly distorted square-pyramidal geometry formed by two oxygen atoms, two nitrogen atoms from ata ligands and one coordinated water molecules (Table 1). The amido N atoms forms N-H···O hydrogen bonds with carboxylate O atoms, linking the molecules into one dimentional chains, which are then linked into a two-dimensional sheet by aromatic π-π stacking between S1-thiazole and S1 i -thiazole [symmetry code: (i) -x, 1 -y, 1 -z] rings [centroid-centroid distance 3.531 (8) Å]. Furthermore, the two-dimensional layers are extended to a three-dimensional supramolecular structure by O-H···O hydrogen bonds (Table 2).

Experimental
A mixture of Ni(CH 3 COOH) 2 .4H 2 O (0.025 g, 0.1 mmol), 2-amino-4-thiazoleacetic acid (0.0316 g, 0.2 mmol) and distilled water (10 ml) was sealed in a 25 ml Teflon-lined stainless autoclave. The pH value of the mixture was adjusted to 6 by a aqueous solution of NaOH (0.1 mol/L), and then heated at 393 K for 3 d. Green crystals were obtained on cooling to room temperature.  Fig. 1. The molecular structure of the title compound with thermal ellipsoids plotted at 50% probability [symmetry code: (i) -x, y, -z + 1/2].
Aquabis(2-amino-1,3-thiazole-4-acetato-κ 2 O,N 3 )nickel(II) Crystal data [Ni(C 5  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 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq