Comment

This work continues our X-ray studies of transition metal complexes with bulky 1-alkyltetrazole ligands. In an earlier paper (Ivashkevich et al., 2002) we reported the structure of a complex of CuCl₂ with 1-tert-butyltetrazole. The present paper is concerned with the crystal structure of the new title complex, (I) (Fig. 1). The structure of 2,4,6-trimethylphenyltetrazole was determined previously (Lyakhov et al., 2000).

There are two substituted tetrazole ligands in the asymmetric unit of (I), and these are denoted as A and B in Fig. 1. The tetrazole rings of molecules A and B have very similar geometries, close to those previously observed for 1-substituted tetrazoles (Cambridge Structural Database; Version 5.23 of September 2002; Allen, 2002). The rings are essentially planar, with mean deviations of tetrazole ring atoms from their least-squares planes of 0.0023 (17) and 0.0023 (19) Å for ligands A and B, respectively. The dihedral angle between the planes of the tetrazole rings of the A and B ligands is 63.27 (12)°.

The tetrazole and benzene rings in each of the ligands are not coplanar, the dihedral angles formed by the least-squares planes of the benzene and tetrazole rings being equal to 74.74 (8) and 76.51 (10)° for ligands A and B, respectively. The N1-C6 bond lengths in both ligands are identical [1.438 (3) Å]; this value is typical for a normal N-C(benzene) single bond.

The ligand geometries are close to that of the uncoordinated 2,4,6-trimethylphenyltetrazole molecule (Lyakhov et al., 2000).

In the title compound, (I), the coordination polyhedron of the Cu atom is an elongated octahedron (Table 1). Its equatorial positions are occupied by two Cl atoms [Cu-Cl1 2.2767 (8) Å and Cu-Cl2 2.2669 (8) Å] and two N⁴ atoms of 2,4,6-trimethylphenyltetrazole ligands [Cu-N4A 2.016 (2) Å and Cu-N4B 2.038 (2) Å]. The Cu-Cl distances for the axial Cl1ⁱ and Cl2ⁱⁱ atoms are 2.9769 (11) and 2.8995 (11) Å, respectively [symmetry codes: (i) 1 -x, 1-y, 2-z; (ii) -x, 1-y, 2-z].

The coordination polyhedra of the adjacent Cu atoms in crystal share edges, forming a one-dimensional polymeric structure composed of [CuCl₂(C₁₀H₁₂N₄)₂] units. These infinite chains are extended along the a axis (Fig. 2) and linked together only by van der Waals interactions. There are no classical hydrogen bonds in the structure of (I), but the intermolecular contacts C5A-H5ACl2ⁱ and C5B-H5BCl1ⁱⁱ are noteworthy (Table 2) (Steiner, 1996). Remarkably, these contacts are within the chain, and therefore may not account for holding the chains together in the crystal.

Thus, the structure of (I) is similar to that of the CuCl₂L₂ complex, where L is 1-tert-butyltetrazole (Ivashkevich et al., 2002). However, they are both different from the structures of the complexes of this composition, but with non-bulky 1-alkyltetrazole ligands L = 1-ethyl- (Virovets et al., 1995), 1-allyl- (Virovets et al., 1996) and 1-azidoethyltetrazole (Ivashkevich et al., 2001), which were found to have layered polymeric structures. The difference is probably due to steric effects.

Figure 1 A view of the asymmetric unit of (I), showing the atom-numbering scheme. Displacement ellipsoids are plotted at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.

Figure 2 Fragment of the structure of (I), showing a chloro-bridged chain extended along the a axis. The dashed lines show C-HCl contacts presented in Table 2.

Experimental

2,4,6-Trimethylphenyltetrazole (m.p. 400-401 K, uncorrected) was prepared by the method described by Grigoriev et al. (1997). Single crystals of (I) were grown by slow crystallization from a solution in methanol-butanol-2-propanol-triethyl orthoformate-hexane (v/v 8:2:1:0.1:0.3) of a mixture containing CuCl₂·2H₂O and 2,4,6-trimethylphenyltetrazole in a 1:2.1 molar ratio over a period of 8-10 d at 293 K.

Crystal data

[CuCl2(C10H12N4)2] Mr = 510.91 Triclinic,  a = 7.283 (2) Å b = 12.032 (3) Å c = 13.912 (3) Å = 85.97 (2)° = 84.19 (2)° = 75.82 (2)° V = 1174.6 (5) Å3 Z = 2 Dx = 1.445 Mg m-3 Mo K radiation Cell parameters from 25 reflections = 15.5-17.9° = 1.18 mm-1 T = 293 (2) K Prism, green 0.60 × 0.10 × 0.10 mm

Data collection

Nicolet R3m four-circlediffractometer /2 scans Absorption correction: scan (North et al., 1968) Tmin = 0.537,  Tmax = 0.891 6068 measured reflections 5445 independent reflections 4277 reflections with I > 2(I) Rint = 0.014 max = 27.6° h = -2 9 k = -15 15 l = -18 18 3 standard reflections every 100 reflections intensity decay: none

Refinement

Refinement on F2 R[F2> 2(F2)] = 0.038 wR(F2) = 0.121 S = 1.05 5445 reflections 280 parameters H-atom parameters constrained w = 1/[2(Fo2) + (0.0674P)2 + 0.5007P] where P = (Fo2 + 2Fc2)/3 (/)max = 0.001 max = 0.49 e Å-3 min = -0.53 e Å-3

Table 1 Selected geometric parameters (Å, °) Cu-N4A 2.016 (2) Cu-N4B 2.038 (2) Cu-Cl1 2.2767 (8) Cu-Cl2 2.2669 (8) Cu-Cl1i 2.9769 (11) Cu-Cl2ii 2.8995 (11) N4A-Cu-N4B 89.29 (9) N4A-Cu-Cl1 90.55 (6) N4A-Cu-Cl2 170.21 (6) N4B-Cu-Cl1 167.31 (7) N4B-Cu-Cl2 89.16 (6) Cl2-Cu-Cl1 93.07 (3) N4A-Cu-Cl2ii 85.43 (6) N4B-Cu-Cl2ii 95.15 (7) Cl2-Cu-Cl2ii 85.08 (3) Cl1-Cu-Cl2ii 97.49 (3) N4A-Cu-Cl1i 88.56 (6) N4B-Cu-Cl1i 87.14 (7) Cl2-Cu-Cl1i 101.02 (3) Cl1-Cu-Cl1i 80.16 (3) Cl2ii-Cu-Cl1i 173.539 (19) Symmetry codes: (i) 1-x,1-y,2-z; (ii) -x,1-y,2-z.

Table 2 Hydrogen-bonding geometry (Å, °) D-HA D-H HA DA D-HA C5A-H5ACl2i 0.93 2.58 3.458 (3) 159 C5B-H5BCl1ii 0.93 2.63 3.458 (3) 148 Symmetry codes: (i) 1-x,1-y,2-z; (ii) -x,1-y,2-z.

H atoms were included in their idealized positions, with C-H = 0.96 Å, and refined using a riding model with U_iso(H) = 1.5U_eq(C) for methyl H atoms and with U_iso(H) = 1.2U_eq(C) for other H atoms.

Data collection: R3m Software (Nicolet, 1980); cell refinement: R3m Software; data reduction: R3m Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.