The layered structure of poly­[[di-μ-chloro-bis­[chloro(2-ethyl­tetrazole-κN⁴)copper(II)]]-di-μ-2-ethyl­tetrazole-κ²N¹:N⁴]

In the polymeric title complex, [CuCl₂(C₃H₆N₄)₂]_n, there are two ligands in the asymmetric unit. The Cu atom adopts an elongated octahedral geometry, with two 2-ethyl­tetrazole ligands [Cu—N = 2.0037 (16) and 2.0136 (16) Å] and two Cl atoms [Cu—Cl = 2.2595 (6) and 2.2796 (6) Å] in equatorial positions. A Cl atom and a symmetry-related 2-ethyl­tetrazole mol­ecule [Cu—Cl = 2.8845 (8) Å and Cu—N = 2.851 (2) Å] lie in the axial positions of the octahedron. One of the two 2-­ethyltetrazole ligands of the asymmetric unit exhibits bidentate binding to two Cu atoms through two N atoms of the tetrazole ring, whereas the other ligand is coordinated in a monodentate fashion via one tetrazole N atom. The Cu-atom octahedra form dimer entities by sharing edges with equatorial and axial Cl atoms. The dimers are linked together through the 2-ethyl­tetrazole ligands to form one-dimensional polymeric zigzag chains extending along the b axis. The chains are connected into infinite layers parallel to the (10) plane via the 2-ethyl­tetrazole ligands.

S1. Comment

This work is a part of a project dealing with the synthesis, structures and properties of complexes of copper(II) chloride with 2-monosubstituted tetrazoles. To date, only two such complexes have been structurally characterized, namely CuCl₂L, where L is 2-tertbutyltetrazole (Lyakhov, Gaponik, Degtyarik & Ivashkevich, 2003), and Cu₃Cl₆L₄, where L is 2-allyltetrazole (Lyakhov, Gaponik, Degtyarik, Matulis, et al., 2003). Only one complex, [NiL₆](BF₄)₂, where L is 2-methyltetrazole (van den Heuvel et al., 1983), exists in the Cambridge Structural Database (Version 5.24 of November 2002; Allen, 2002) with respect to 2-substituted tetrazole complexes. A new complex of copper(II) chloride, CuCl₂L₂, where L is 2-ethyltetrazole, (I) (Fig. 1), has been synthesized and investigated in the present work. There are two 2-ethyltetrazole ligands in the asymmetric unit of (I), and these are denoted by A and B.

The geometric parameters of the tetrazole rings of the two 2-ethyltetrazole molecules in (I) are very similar (Table 1). Bond lengths and angles are comparable to those obtained earlier for copper(II) chloride complexes with 2-tertbutyltetrazole (Lyakhov, Gaponik, Degtyarik & Ivashkevich, 2003) and 2-allyltetrazole (Lyakhov, Gaponik, Degtyarik, Matulis et al., 2003), and also for nickel(II) tetrafluoroborate with 2-methyltetrazole (van den Heuvel et al., 1983).

The tetrazole rings in the 2-ethyltetrazole molecules are planar to within 0.002 (3) and 0.003 (3) Å for ligands A and B, respectively.

The Cu atom exhibits axially elongated octahedral coordination, with two 2-ethyltetrazole ligands [Cu1—N4A=2.0037 (16) and Cu1—N4B=2.0136 (16) Å] and two Cl atoms [Cu1—Cl1=2.2796 (6) and Cu1—Cl2=2.2595 (6) Å] in the equatorial positions. Atom Cl1 and a symmetry-related 2-ethyltetrazole molecule lie in the axial positions of the octahedron [Cu1—Cl1ⁱⁱ=2.8845 (8) and Cu1—N1Aⁱ=2.851 (2) Å; symmetry codes: (i) 1/2 + x, 1/2 − y, 1/2 + z; (ii) 1 − x, −y, −z]. Ligand A thus exhibits bidentate binding with the two Cu atoms through atoms N4 and N1 of the tetrazole ring, whereas ligand B is coordinated in a monodentate fashion via atom N4.

In the crystal structure of (I), the Cu-atom octahedra are associated with dimer entities, by sharing edges with symmetry-related Cl1 atoms (Fig. 2). The separation between the Cu atoms in the dimer is 3.6557 (10) Å. The dimer entities are linked by ligand A to form one-dimensional polymeric zigzag chains extended along the b axis. Via ligand A, the chains are connected to infinite layers parallel to the (1 0 1) plane. Only van der Waals interactions exist between the sheets. Ligand B and atom Cl2 do not participate in the formation of the polymeric structure of (I).

Recently, we discussed an example? of bidentate bridge coordination of the 2-allyltetrazole ligand via atoms N3 and N4 of the tetrazole ring in the complex Cu₃Cl₆L₄ (Lyakhov, Gaponik, Degtyarik, Matulis, et al., 2003). The structural data obtained for (I) revealed bidentate bridge coordination of the 2-ethyltetrazole ligand A through atoms N4 and N1. By comparison with structures in the Cambridge Structural Database (Version 5.24, November 2002 release; Allen, 2002) that contain 1-monosubstituted tetrazoles having only N4-coordination, it can be concluded that 2-monosubstituted tetrazoles exhibit more multiform coordination. Further results on complexes of 2-monosubstituted tetrazoles will show how often bidentate coordination takes place for these ligands.

The bidentate bridge coordination of 2-substituted tetrazoles is probably responsible for the difference in the crystal structures of Cu^II chloride complexes with 1-ethyltetrazole (Virovets et al., 1995) and 2-ethyltetrazole. These compounds are of the same composition; both have octahedrally coordinated Cu atoms and layered polymeric structures. However, whereas all the Cl atoms (and only these atoms) participate in polymeric structure formation in the complex with 1-ethyltetrazole, only one Cl atom, Cl1, plays a bridging role in the polymeric structure of (I), but bidentate bridge coordination of ligand A makes it possible to form a two-dimensional polymeric network.

S2. Experimental

The title complex was prepared by dissolving CuCl₂·2H₂O (0.0025 mol) in 2-ethyltetrazole (0.025 mol). The fine-grained complex that precipitated immediately was separated by decanting (yield 46%). Two months later, more of the title complex (0.35 g, 42%), in the form of light-green prismatic crystals, was obtained from the decanted solution. Analysis calculated for CuCl₂(C₃H₆N₄)₂: Cu 19.2, Cl 21.2%; found: Cu 19.3, Cl 21.1 (the results are identical for both obtained fractions).

S3. Refinement

H atoms were placed in calculated positions, with C—H distances of 0.93–0.97 Å, and were included in the refinement in a riding-model approximation, with U_iso(H) equal to 1.5U_eq(carrier atom) for the methyl group and 1.2U_eq(carrier atom) for other H atoms.

Computing details

Data collection: R3m software (Nicolet, 1980); cell refinement: R3m software (Nicolet, 1980); data reduction: OMNIBUS (Galdecka, 2002); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997), PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. ORTEP-3 (Farrugia, 1997) plot of the asymmetric unit of (I). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitrary radii.
	Fig. 2. Fragment of the crystal structure of (I), showing a polymeric sheet parallel to the (1 0 1) plane.

poly[[[di-µ-chloro-bis[chloro(2-ethyltetrazole-kN⁴)copper(II)]]- di-µ-ethyltetrazole-k²N¹:N⁴]

Crystal data

[CuCl2(C6H12N8)]	F(000) = 668
Mr = 330.68	Dx = 1.713 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 10.234 (2) Å	θ = 22.0–24.1°
b = 13.690 (4) Å	µ = 2.11 mm^−1
c = 10.478 (2) Å	T = 293 K
β = 119.174 (15)°	Prism, blue
V = 1281.9 (5) Å^3	0.60 × 0.60 × 0.52 mm
Z = 4

Data collection

Nicolet R3m four-circle diffractometer	3444 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.019
Graphite monochromator	θmax = 30.1°, θmin = 2.3°
ω/2θ scans	h = 0→14
Absorption correction: ψ scan (North et al., 1968)	k = 0→19
Tmin = 0.298, Tmax = 0.333	l = −14→12
4079 measured reflections	3 standard reflections every 100 reflections
3763 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.098	H-atom parameters constrained
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0535P)^2 + 0.5059P] where P = (Fo^2 + 2Fc^2)/3
3763 reflections	(Δ/σ)max < 0.001
156 parameters	Δρmax = 0.57 e Å^−3
0 restraints	Δρmin = −0.59 e Å^−3

Special details

Experimental. Because of instability in air, the single-crystal was mounted in a glass capillary.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq
Cu1	0.57901 (2)	0.123100 (17)	0.04226 (2)	0.03685 (9)
Cl1	0.52049 (5)	0.02443 (3)	0.18239 (5)	0.03839 (11)
Cl2	0.64953 (6)	0.23024 (4)	−0.07677 (6)	0.05315 (14)
N1A	0.1548 (2)	0.22734 (17)	−0.24365 (19)	0.0545 (5)
N2A	0.15985 (18)	0.23031 (13)	−0.11470 (18)	0.0413 (3)
N3A	0.28670 (18)	0.20117 (14)	−0.00508 (18)	0.0431 (4)
N4A	0.37140 (17)	0.17808 (12)	−0.06414 (17)	0.0382 (3)
C5A	0.2906 (2)	0.19436 (17)	−0.2072 (2)	0.0473 (5)
H5A	0.3251	0.1839	−0.2735	0.057*
C6A	0.0295 (3)	0.2595 (2)	−0.0991 (3)	0.0581 (6)
H61A	−0.0540	0.2167	−0.1581	0.070*
H62A	0.0005	0.3255	−0.1355	0.070*
C7A	0.0612 (3)	0.2552 (3)	0.0542 (3)	0.0686 (7)
H71A	0.0992	0.1917	0.0938	0.103*
H72A	−0.0293	0.2671	0.0580	0.103*
H73A	0.1341	0.3039	0.1106	0.103*
N1B	0.9880 (2)	−0.00382 (16)	0.1502 (2)	0.0513 (4)
N2B	1.00320 (17)	0.02045 (13)	0.27913 (18)	0.0412 (3)
N3B	0.88395 (18)	0.06117 (15)	0.27274 (18)	0.0448 (4)
N4B	0.78574 (16)	0.06495 (13)	0.13237 (17)	0.0391 (3)
C5B	0.8505 (2)	0.02601 (19)	0.0605 (2)	0.0502 (5)
H5B	0.8044	0.0205	−0.0407	0.060*
C6B	1.1409 (2)	0.0025 (2)	0.4187 (3)	0.0603 (6)
H61B	1.1429	−0.0651	0.4474	0.072*
H62B	1.1409	0.0436	0.4941	0.072*
C7B	1.2771 (3)	0.0234 (2)	0.4061 (3)	0.0664 (7)
H71B	1.2830	−0.0221	0.3394	0.100*
H72B	1.3644	0.0171	0.5005	0.100*
H73B	1.2716	0.0887	0.3705	0.100*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.02610 (12)	0.04774 (15)	0.03535 (13)	0.00211 (8)	0.01393 (9)	0.00712 (8)
Cl1	0.0366 (2)	0.0452 (2)	0.0351 (2)	0.00032 (16)	0.01886 (16)	0.00204 (16)
Cl2	0.0471 (3)	0.0618 (3)	0.0529 (3)	−0.0049 (2)	0.0263 (2)	0.0136 (2)
N1A	0.0445 (9)	0.0771 (13)	0.0356 (8)	0.0232 (9)	0.0147 (7)	0.0080 (8)
N2A	0.0330 (7)	0.0501 (9)	0.0381 (7)	0.0098 (6)	0.0152 (6)	0.0066 (7)
N3A	0.0326 (7)	0.0573 (10)	0.0378 (8)	0.0089 (7)	0.0160 (6)	0.0074 (7)
N4A	0.0324 (7)	0.0448 (8)	0.0362 (7)	0.0054 (6)	0.0157 (6)	0.0044 (6)
C5A	0.0422 (10)	0.0610 (12)	0.0367 (9)	0.0151 (9)	0.0176 (8)	0.0049 (8)
C6A	0.0410 (11)	0.0791 (16)	0.0586 (13)	0.0209 (11)	0.0276 (10)	0.0155 (12)
C7A	0.0551 (13)	0.097 (2)	0.0678 (16)	0.0141 (14)	0.0412 (13)	0.0123 (14)
N1B	0.0370 (8)	0.0712 (12)	0.0446 (9)	0.0085 (8)	0.0190 (7)	−0.0025 (8)
N2B	0.0296 (7)	0.0550 (9)	0.0378 (8)	0.0024 (6)	0.0156 (6)	0.0071 (7)
N3B	0.0315 (7)	0.0656 (11)	0.0364 (8)	0.0039 (7)	0.0159 (6)	0.0030 (7)
N4B	0.0289 (7)	0.0524 (9)	0.0351 (7)	0.0009 (6)	0.0149 (6)	0.0032 (6)
C5B	0.0342 (9)	0.0763 (15)	0.0376 (9)	0.0048 (9)	0.0155 (8)	−0.0043 (9)
C6B	0.0377 (10)	0.0933 (18)	0.0407 (10)	0.0118 (11)	0.0120 (8)	0.0189 (11)
C7B	0.0340 (10)	0.094 (2)	0.0599 (14)	0.0102 (11)	0.0141 (10)	0.0063 (13)

Geometric parameters (Å, º)

Cu1—N4A	2.0037 (16)	C7A—H71A	0.9600
Cu1—N4B	2.0136 (16)	C7A—H72A	0.9600
Cu1—Cl2	2.2595 (6)	C7A—H73A	0.9600
Cu1—Cl1	2.2796 (6)	N1B—C5B	1.319 (3)
Cu1—N1A^i	2.851 (2)	N1B—N2B	1.325 (3)
Cu1—Cl1^ii	2.8845 (8)	N2B—N3B	1.313 (2)
N1A—N2A	1.328 (2)	N2B—C6B	1.475 (3)
N1A—C5A	1.328 (3)	N3B—N4B	1.317 (2)
N2A—N3A	1.308 (2)	N4B—C5B	1.333 (3)
N2A—C6A	1.476 (3)	C5B—H5B	0.9300
N3A—N4A	1.326 (2)	C6B—C7B	1.490 (4)
N4A—C5A	1.331 (2)	C6B—H61B	0.9700
C5A—H5A	0.9300	C6B—H62B	0.9700
C6A—C7A	1.477 (4)	C7B—H71B	0.9600
C6A—H61A	0.9700	C7B—H72B	0.9600
C6A—H62A	0.9700	C7B—H73B	0.9600
N4A—Cu1—N4B	175.10 (6)	H61A—C6A—H62A	107.9
N4A—Cu1—Cl2	89.22 (5)	C6A—C7A—H71A	109.5
N4B—Cu1—Cl2	88.29 (5)	C6A—C7A—H72A	109.5
N4A—Cu1—Cl1	92.33 (5)	H71A—C7A—H72A	109.5
N4B—Cu1—Cl1	90.55 (5)	C6A—C7A—H73A	109.5
Cl2—Cu1—Cl1	174.32 (2)	H71A—C7A—H73A	109.5
N4A—Cu1—N1A^i	88.63 (7)	H72A—C7A—H73A	109.5
N4B—Cu1—N1A^i	95.40 (7)	C5B—N1B—N2B	101.72 (17)
Cl2—Cu1—N1A^i	86.01 (5)	N3B—N2B—N1B	114.20 (16)
Cl1—Cu1—N1A^i	88.56 (5)	N3B—N2B—C6B	122.44 (18)
N4A—Cu1—Cl1^ii	87.26 (5)	N1B—N2B—C6B	123.36 (18)
N4B—Cu1—Cl1^ii	88.74 (5)	N2B—N3B—N4B	104.94 (16)
Cl2—Cu1—Cl1^ii	94.86 (3)	N3B—N4B—C5B	107.21 (16)
Cl1—Cu1—Cl1^ii	90.67 (2)	N3B—N4B—Cu1	126.48 (13)
N1A^i—Cu1—Cl1^ii	175.79 (4)	C5B—N4B—Cu1	126.27 (14)
N2A—N1A—C5A	101.65 (16)	N1B—C5B—N4B	111.91 (19)
N3A—N2A—N1A	114.45 (16)	N1B—C5B—H5B	124.0
N3A—N2A—C6A	123.30 (17)	N4B—C5B—H5B	124.0
N1A—N2A—C6A	122.18 (17)	N2B—C6B—C7B	111.3 (2)
N2A—N3A—N4A	104.94 (15)	N2B—C6B—H61B	109.4
N3A—N4A—C5A	107.31 (15)	C7B—C6B—H61B	109.4
N3A—N4A—Cu1	125.96 (12)	N2B—C6B—H62B	109.4
C5A—N4A—Cu1	126.68 (13)	C7B—C6B—H62B	109.4
N1A—C5A—N4A	111.65 (18)	H61B—C6B—H62B	108.0
N1A—C5A—H5A	124.2	C6B—C7B—H71B	109.5
N4A—C5A—H5A	124.2	C6B—C7B—H72B	109.5
N2A—C6A—C7A	112.28 (19)	H71B—C7B—H72B	109.5
N2A—C6A—H61A	109.1	C6B—C7B—H73B	109.5
C7A—C6A—H61A	109.1	H71B—C7B—H73B	109.5
N2A—C6A—H62A	109.1	H72B—C7B—H73B	109.5
C7A—C6A—H62A	109.1
C5A—N1A—N2A—N3A	−0.5 (3)	C5B—N1B—N2B—N3B	1.0 (3)
C5A—N1A—N2A—C6A	−177.6 (2)	C5B—N1B—N2B—C6B	−179.7 (2)
N1A—N2A—N3A—N4A	0.4 (2)	N1B—N2B—N3B—N4B	−0.7 (2)
C6A—N2A—N3A—N4A	177.4 (2)	C6B—N2B—N3B—N4B	180.0 (2)
N2A—N3A—N4A—C5A	−0.2 (2)	N2B—N3B—N4B—C5B	0.1 (2)
N2A—N3A—N4A—Cu1	−177.60 (13)	N2B—N3B—N4B—Cu1	−177.83 (13)
Cl2—Cu1—N4A—N3A	−134.61 (17)	Cl2—Cu1—N4B—N3B	118.58 (17)
Cl1—Cu1—N4A—N3A	39.92 (17)	Cl1—Cu1—N4B—N3B	−55.86 (17)
N1A^i—Cu1—N4A—N3A	−48.58 (17)	N1A^i—Cu1—N4B—N3B	32.75 (18)
Cl1^ii—Cu1—N4A—N3A	130.48 (17)	Cl1^ii—Cu1—N4B—N3B	−146.51 (17)
Cl2—Cu1—N4A—C5A	48.43 (19)	Cl2—Cu1—N4B—C5B	−59.00 (19)
Cl1—Cu1—N4A—C5A	−137.04 (18)	Cl1—Cu1—N4B—C5B	126.56 (19)
N1A^i—Cu1—N4A—C5A	134.46 (19)	N1A^i—Cu1—N4B—C5B	−144.83 (19)
Cl1^ii—Cu1—N4A—C5A	−46.48 (18)	Cl1^ii—Cu1—N4B—C5B	35.90 (19)
N2A—N1A—C5A—N4A	0.4 (3)	N2B—N1B—C5B—N4B	−0.9 (3)
N3A—N4A—C5A—N1A	−0.2 (3)	N3B—N4B—C5B—N1B	0.5 (3)
Cu1—N4A—C5A—N1A	177.27 (16)	Cu1—N4B—C5B—N1B	178.47 (16)
N3A—N2A—C6A—C7A	2.0 (4)	N3B—N2B—C6B—C7B	−140.3 (2)
N1A—N2A—C6A—C7A	178.8 (2)	N1B—N2B—C6B—C7B	40.5 (3)

Symmetry codes: (i) x+1/2, −y+1/2, z+1/2; (ii) −x+1, −y, −z.