Diaquabis(2-hydroxy-5-methoxybenzoato-κO 1)zinc

The title compound, [Zn(C8H7O4)2(H2O)2], has been synthesized by hydrothermal methods. The ZnII atom, whose symmetry element is a twofold axis, is four coordinated by two O atoms from 5-methoxysalicylate anions and two aqua O atoms in a distorted tetrahedral geometry. In the crystal, molecules are linked into a layer by O—H⋯O hydrogen bonds, which stabilize the packing.

The title compound, [Zn(C 8 H 7 O 4 ) 2 (H 2 O) 2 ], has been synthesized by hydrothermal methods. The Zn II atom, whose symmetry element is a twofold axis, is four coordinated by two O atoms from 5-methoxysalicylate anions and two aqua O atoms in a distorted tetrahedral geometry. In the crystal, molecules are linked into a layer by O-HÁ Á ÁO hydrogen bonds, which stabilize the packing.
Diaquabis(2-hydroxy-5-methoxybenzoato-O 1 )zinc T. Li, L.-R. Tang, L. Yang and B. Huang Comment Generally, the self-assembly of inorganic metal species and organic ligands can be achieved by the use of noncovalent contacts. Among the noncovalent contacts, hydrogen bonds have the great influence in determining the geometry of the obtained metal complexes (Li et al. 2006;Jiang et al. 2011). In the other hand, the reactions of transition metal ions with 5-MeOsal ligands and its analogues are relatively rare (Valigura et al., 2006;Púčeková-Repická et al.,2007). In this paper A single-crystal X-ray diffraction study of (I) reveals a discrete coordination complex that crystallizes in the space group C2/c. Coordination of the Zn atoms in (I) is a slightly distorted tetrahedral geometry with each Zn atom bonding to four oxygen atoms, in which two from the monodentate 5-MeOSal ligands and two from the waters (Fig.1). Further inspection into the structure reveals that there are O-H-O intramolecular and intermolecular hydrogen bonds. (Table 1). As described in Figure 2, the intramolecular hydrogen bonds from hydroxyl hydrogen atom of the 5-MeOsal anions to the coordinated carboxylate oxygen atoms O3-H-O1 with the distance of 2.577 (1) Å, then create sixmemberedrings(O 2 C 3 H), and stabilize the structure. The mean deviation from the planes C(2)-C(3)-C(4)-C(5)-C(6)-  (2) and 2.790 (2) Å, respectively. As a result every coordinated water molecule is connected by two oxygen atoms through hydrogen bonds and the isolated units are to be form a 2-D layer. A prospective view of the structure packing from a direction is presented in Fig. 3.

Experimental
The title compound was hydrothermally synthesized under autogenous pressure. A mixture of ZnCl 2 (68 mg, 0.5 mmol), 5-MeOsal (84 mg, 0.5 mmol), and H 2 O (6 ml) was sealed in a stainless reactor with Teflon liner, which was heated to 358 K for two days. After slow cooling to room temperature, prism pale yellow crystals were obtained as a major phase by filtration, which were washed with distilled water, and finally dried in air(65% yield).Anal. calc. for C 16

Refinement
All the hydrogen atoms were discernible in the difference electron density maps. However, the H atoms were situated into idealized positions and constrained by the riding model approximation: O-H hydroxyl = 0.869, C aryl -H aryl = 0.95, supplementary materials sup-2 C methyl -H methyl = 0.98 and U iso H aryl = 1.2U eq (C), U iso H methyl = 1.5U eq (C). The highest electron-density peak is situated 1.2 Å from Zn1 and the deepest hole 0.78 Å from Zn1.  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