Diiodido{4-nitro-2-[2-(piperidin-1-yl)ethyliminomethyl]phenolato}zinc(II)

In the title complex, [ZnI2(C14H19N3O3)], the ZnII atom is four-coordinated by the imine N and phenolate O atoms of the Schiff base ligand, and by two iodide ions in a distorted tetrahedral coordination. In the crystal structure, molecules are linked through intermolecular N—H⋯O hydrogen bonds, forming dimers.


Experimental
Crystal data [ZnI 2 (C 14 Table 1 Selected geometric parameters (Å , ).  Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.  (Biswas et al., 2008;Wu et al., 2008;Kawamoto et al., 2008;Ali et al., 2008;Habibi et al., 2007), and their complexes have been investigated in many fields (Chen et al., 2008;Yuan et al., 2007;Tomat et al., 2007;Darensbourg & Frantz, 2007). Zinc(II) is an important element in biological systems and functions as the active site of hydrolytic enzymes, such as carboxypeptidase and carbonic anhydrase where it is in a hard-donor coordination environment of nitrogen and oxygen ligands (Lipscomb & Sträter, 1996). Recently, we have reported a few Schiff base zinc complexes (Zhu, 2008;Zhu & Yang, 2008a,b,c). In this paper, the title new zinc(II) complex, In the title complex, the Zn II atom is four-coordinated by the imine N and phenolate O atoms of the Schiff base ligand, and by two iodide ions in a tetrahedral coordination. The coordinate bond lengths (Table 1) are typical and comparable to the corresponding values observed in the Schiff base zinc complexes we reported previously and other similar Schiff base zinc complexes Wei et al., 2007;Qiu, 2006a,b).

Experimental
The Schiff base compound was prepared by the condensation of equimolar amounts of 5-nitrosalicylaldehyde with 2-piperidin-1-ylethylamine in a methanol solution. The complex was prepared by the following method. To an anhydrous methanol solution (5 ml) of ZnI 2 (31.9 mg, 0.1 mmol) was added a methanol solution (10 ml) of the Schiff base compound (27.7 mg, 0.1 mmol) with stirring. The mixture was stirred for 30 min at room temperature and filtered. Upon keeping the filtrate in air for a few days, colorless block-shaped crystals were formed.

Refinement
H2 was located from a difference Fourier map and refined isotropically, with N-H distance restrained to 0.90 (1) Å. Other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H distances in the range 0.93-0.97 Å, and with U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title complex, with ellipsoids drawn at the 30% 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 > 2sigma(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.