catena-Poly[[bis[1-(2-hydroxyethyl)-1H-tetrazole-κN 4]copper(II)]-di-μ-chlorido]: a powder study

The crystal structure of the title polymeric complex, [CuCl2(C3H6N4O)2]n, was obtained by the Rietveld refinement from laboratory X-ray powder diffraction data collected at room temperature. The unique CuII ion lies on an inversion center and is in a slightly distorted octahedral coordination environment. In the hydroxyethyl group, all H atoms, the O atom and its attached C atom are disordered over two positions; the site occupancy factors are ca 0.6 and 0.4. The OH group is involved in an intramolecular O—H⋯N hydrogen bond.

The crystal structure of the title polymeric complex, [CuCl 2 (C 3 H 6 N 4 O) 2 ] n , was obtained by the Rietveld refinement from laboratory X-ray powder diffraction data collected at room temperature. The unique Cu II ion lies on an inversion center and is in a slightly distorted octahedral coordination environment. In the hydroxyethyl group, all H atoms, the O atom and its attached C atom are disordered over two positions; the site occupancy factors are ca 0.6 and 0.4. The OH group is involved in an intramolecular O-HÁ Á ÁN hydrogen bond.

catena-Poly[[bis[1-(2-hydroxyethyl)-1H-tetrazole-N 4 ]copper(II)]-di--chlorido
The Cu atom lies on inversion center and shows a slightly distorted octahedral coordination environment. Equatorial sites are occupied by two trans positioned N atoms and two Cl atoms; Cl atoms lying in axial positions are essentially more distant from the Cu atom (Table 1). Each Cl atom is a bridge between the neighbouring Cu atoms, forming two different in length Cu-Cl bonds, with Cu-Cl-Cu angle of 143.4 (2)°. These bonds are responsible for the formation of polymeric layers parallel to the yz plane (Fig. 2). Within a layer, the shortest Cu···Cu distance is 4.9835 (4) Å, whereas between two neighbouring layers, the closest Cu centers are separated by cell dimension a. Only van der Waals interactions are between the layers.
The 2-hydroxyethyl substituent at the tetrazole ring atom N1 was found to be disordered over two positions, with almost equal occupancies of 0.562 (12) for C71-O1 and 0.438 (12) for C72-O2 (Fig. 1). For both positions, OH groups are involved in intramolecular hydrogen bonds O-H···N. There are also hydrogen bonds C-H···Cl (Table 2).

Refinement
The monoclinic unit-cell dimensions of (I) were determined with the indexing program TREOR90 (Werner et al., 1985).
The obtained values indicated isotypism of (I) with layered coordination polymers CuCl 2 L 2 (L = 1-alkyltetrazole) that crystallize in the monoclinic space group P2 1 /c. This space group and the atomic coordinates of CuCl 2 L 2 with L = 1-ethyltetrazole (Virovets et al., 1995) were used as starting parameters for the Rietveld refinement with the FULLPROF program supplementary materials sup-2 (Rodríguez-Carvajal, 2001). Background intensity was found by Fourier filtering technique as implemented in the FULL-PROF program, under visual inspection of the resulting background curve. Correction for profile asymmetry was made for reflections up to 2θ=30°. A Marsh-Dollase correction of intensities for [100] preferred orientation of plate-like grains in the sample (Marsh, 1932;Dollase, 1986) was applied.
The Rietveld refinement, performed primarily by using individual isotropic displacement parameters for non-H atoms, revealed rather high values of B iso for atoms of C-O fragment. From this fact an assumption was made that C-O fragment was disordered over two positions. It was confirmed in subsequent refinement by introducing disorder positions for the above C and O atoms. In final refinement, all non-H atoms were refined with overall B iso parameter.
All H atoms were placed in geometrically calculated positions, using the program SHELXL97 (Sheldrick, 2008), with displacement parameter B iso (H)=1.2B iso (C) for H atom at C5 tetrazole ring atom and B iso (H)=1.5B iso (C,O) for the methylene and hydroxyl groups.
Soft restraints on some interatomic distances and bond angles of ligand molecule, based on a geometric analysis of a large number of 1-substituted tetrazoles (Cambridge Structural Database, version 5.29 of November 2007;Allen, 2002), were used in the Rietved refinement. Observed, calculated and difference difraction patterns are shown in Fig. 3. Fig. 1. The asymmetric unit of (I) with the atomic numbering scheme. 2-hydroxyethyl substituent is shown as disordered over two positions.