catena-Poly­[[bis­[μ-1,2-bis(1-methyl­tetrazol-5-yl)­ethane-κ²N⁴:N^4′]bis[chloro­copper(II)]]-di-μ-chloro]

In the title compound, [Cu₂Cl₄(C₆H₁₀N₈)₂]_n, the ligand has C₂ symmetry, and the Cu and Cl atoms lie on a mirror plane. The coordination polyhedron of the Cu atom is a distorted square pyramid, with the basal positions occupied by two N atoms from two different ligands [Cu—N = 2.0407 (18) Å] and by the two Cl atoms [Cu—Cl = 2.2705 (8) and 2.2499 (9) Å], and the apical position occupied by a Cl atom [Cu—Cl = 2.8154 (9) Å] that belongs to the basal plane of a neighbouring Cu atom. The [CuCl₂(C₆H₁₀N₈)]₂ units form infinite chains extending along the a axis via the Cl atoms. Intermolecular C—H...Cl contacts [C...Cl = 3.484 (2) Å] are also present in the chains. The chains are linked together by intermolecular C—H...N interactions [C...N = 3.314 (3) Å].

S1. Comment

Complexes of mononuclear N-alkyl- and N-alkenyltetrazoles with copper(II) chloride have been found to be low-temperature ferromagnets (Lavrenova et al., 1993, 1996). For this reason, the crystal structures of such complexes have been studied intensively in the past few years (Ivashkevich et al., 2001, 2002; Stassen et al., 2002). However, the data on analogous complexes of N-substituted bistetrazoles are limited, as the crystal structures of only two chelate complexes of binuclear N-substituted tetrazoles with copper (II) chloride have been described so far, viz. Cu(btop)Cl₂ and Cu(mtop)Cl₂, where btop is 1,5-bis(2-tert-butyl-5-tetrazolyl)-3-oxopentane and mtop is 1,5-bis(1-methyl-5-tetrazolyl)-3-oxopentane (Voitekhovich et al., 2002; Lyakhov et al., 2001). In the present paper, we report the crystal structure of the coordination compound of copper(II) chloride with 1,2-bis(1-methyltetrazol-5-yl)ethane, (I).

In the title compound, the ligand has crystallographically imposed? C₂ symmetry (Fig. 1) and exhibits bidentate properties. The geometry of the tetrazole ring is close to that previously observed for 1,5-substituted tetrazoles (Cambridge Structural Database, Version 5.24 of November 2002; Allen, 2002). The ring is essentially planar, with a mean deviation of the tetrazole ring atoms from their least-squares plane of 0.0038 (12) Å.

The Cu atom and all the Cl atoms lie on the mirror plane. The coordination polyhedron of the Cu atom is a distorted square pyramid (Table 1), in which the basal positions are occupied by atoms N4 and N4ⁱ [symmetry code: (i) x, y, −z; Cu—N=2.0407 (18) Å] and by the two Cl atoms [Cu—Cl1=2.2705 (8) and Cu—Cl2=2.2499 (9) Å]. The apical position is occupied by atom Cl1ⁱⁱ [symmetry code: (ii) −x, −y, z; Cu—Cl=2.8154 (9) Å], which belongs to the basal plane of the neighbouring Cu atom.

The [CuCl₂(C₆H₁₀N₈)]₂ units shown in the scheme may be found in the structure of (I). The coordination polyhedra of Cu atoms of neighbouring units share edges with the Cl atoms, forming polymeric chains extended along the a axis. C7—H7B···Cl1ⁱⁱⁱ interactions [symmetry code (iii): 1 − x, −y, z], with a C···Cl distance of 3.484 (2) Å, are also present in these chains. The chains are linked together by intermolecular C6—H6B···N3^iv interactions [symmetry code (iv): 1/2 + x, 1/2 − y, 1/2 − z; Fig. 2], with a C···N distance of 3.314 (3) Å (Steiner, 1996).

S2. Experimental

1,2-Bis(1-methyl-1H-tetrazol-5-yl)ethane was obtained according to the method described by Koren et al. (1995) for the selective synthesis of mononuclear 1,5-disubstituted tetrazoles from 5-monosubstituted tetrazoles. Tert-butanol (2.2 ml, 23 mmol) was added dropwise with stirring to a solution of 1,2-bis(5-tetrazolyl)ethane [obtained from succinonitrile, sodium azide and ammonium chloride according to the method described by Finnegan et al. (1958)] (1.83 g, 11 mmol) in sulfuric acid (96%, 15 ml). The mixture was further stirred at room temperature for 2 h, and the reaction mixture was then poured into ice (50–70 g). The precipitate was filtered off, washed with cold water and dried in vacuo. Crystallization from diethyl ether–hexane (1:1) gave 1,2-bis(2-tert-butyl-1H-tetrazol-5-yl)ethane (2.3 g, 78%; m.p. 351–352 K). Spectroscopic analysis ¹H NMR [(CD₃)₂-SO]: δ 1.69 (s, 18H, 6 × CH₃), 3.33 (s, 4H, 2 × CH₂—C₍₅₎-tetrazole). A solution of 1,2-bis(2-tert-butyl-1H-tetrazol-5-yl)ethane (2.3 g, 8.2 mmol) and dimethyl sulfate (2.3 ml, 24.6 mmol) in acetonitrile or trichloromethane (5 ml) was stirred at room temperature for 4 d. Hydrochloric acid (36%, 40 ml) was added, and the mixture was stirred for 1 h. The upper aqueous layer of the mixture was separated and heated on a water bath for 5 h. After neutralization of the reaction mixture by sodium hydroxide, the solvent was removed in vacuo. The residue was extracted with boiling ethanol, and the extract was cooled to 273–278 K. The obtained precipitate was recrystallized from water, yielding colorless crystals of 1,2-bis(1-methyl-1H-tetrazol-5-yl)ethane (0.98 g, 62%; total yield 46%; m.p. 426–427 K). Spectroscopic analysis ¹H NMR [100 MHz, CD₃—CN]: δ 3.44 (s, 4H, 2 × CH₂), 4.05 (s, 6H, 2 × CH₃); ¹³C NMR [25 MHz, (CD₃)₂-SO]: δ 23.6 (2 × CH₂), 37.1 (2 × CH₃), 157.7 (2 × C₍₅₎-tetrazole). The title complex was prepared by the reaction of copper(II) chloride dihydrate (0.17 g, 1 mmol) and 1,2-bis(1-methyl-1H-tetrazol-5-yl)ethane (0.19 g, 1.0 mmol) in ethanol (20 ml) at room temperature. Single crystals were grown by slow evaporation (2–3 d) from the reaction mixture [0.19 g; yield 58%; decomposed at 484 K].

S3. Refinement

H atoms were included in idealized positions, with C—H=0.96 Å, and refined using a riding model with U_iso(H) values equal to 1.5U_eq(C) for methyl H atoms and 1.2U_eq(C) for methylene 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: SHELXS97 (Sheldrick, 1997); 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. A view of (I), showing the atom-numbering scheme. [Symmetry code: (i) −x, −y, z.] Displacement ellipsoids are plotted at the 50% probability level, and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The crystal packing of (I), viewed along the a axis. Dashed lines show the C—H···Cl and C—H···N contacts presented in Table 2.

(I)

Crystal data

[Cu2Cl4(C6H10N8)2]	F(000) = 660
Mr = 657.32	Dx = 1.926 Mg m^−3
Orthorhombic, Pnnm	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2 2n	Cell parameters from 25 reflections
a = 6.732 (1) Å	θ = 14.3–26.1°
b = 11.500 (2) Å	µ = 2.39 mm^−1
c = 14.640 (3) Å	T = 293 K
V = 1133.4 (3) Å^3	Prism, blue
Z = 2	0.58 × 0.32 × 0.24 mm

Data collection

Nicolet R3m four-circle diffractometer	1637 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.013
Graphite monochromator	θmax = 30.1°, θmin = 2.3°
ω/2θ scans	h = 0→9
Absorption correction: ϕ-scan (North et al., 1968)	k = 0→16
Tmin = 0.318, Tmax = 0.562	l = −1→20
1917 measured reflections	3 standard reflections every 100 reflections
1733 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.031	H-atom parameters constrained
wR(F^2) = 0.103	w = 1/[σ^2(Fo^2) + (0.0501P)^2 + 0.7797P] where P = (Fo^2 + 2Fc^2)/3
S = 1.26	(Δ/σ)max < 0.001
1733 reflections	Δρmax = 0.55 e Å^−3
83 parameters	Δρmin = −0.56 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.064 (3)

Special details

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
Cu	0.17007 (5)	0.12557 (3)	0.0000	0.02443 (16)
Cl1	0.23641 (11)	−0.06800 (6)	0.0000	0.02763 (18)
Cl2	0.21727 (15)	0.31926 (7)	0.0000	0.0397 (2)
N1	0.1765 (2)	0.11767 (14)	0.28509 (13)	0.0237 (3)
N2	−0.0099 (3)	0.15263 (16)	0.26511 (12)	0.0282 (3)
N3	−0.0212 (3)	0.15912 (17)	0.17736 (12)	0.0301 (4)
N4	0.1551 (3)	0.12729 (13)	0.13921 (12)	0.0241 (4)
C5	0.2774 (3)	0.10270 (16)	0.20719 (13)	0.0212 (3)
C6	0.2361 (4)	0.1012 (2)	0.38024 (15)	0.0371 (5)
H6A	0.1268	0.1201	0.4197	0.056*
H6B	0.3466	0.1510	0.3939	0.056*
H6C	0.2739	0.0216	0.3896	0.056*
C7	0.4892 (3)	0.06675 (17)	0.20180 (14)	0.0269 (4)
H7A	0.5609	0.0988	0.2535	0.032*
H7B	0.5477	0.0980	0.1465	0.032*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu	0.0324 (2)	0.0246 (2)	0.0162 (2)	0.00322 (12)	0.000	0.000
Cl1	0.0331 (3)	0.0285 (3)	0.0213 (3)	0.0046 (2)	0.000	0.000
Cl2	0.0581 (5)	0.0277 (4)	0.0333 (4)	−0.0068 (3)	0.000	0.000
N1	0.0246 (7)	0.0276 (8)	0.0189 (8)	0.0017 (6)	0.0011 (5)	0.0007 (5)
N2	0.0245 (7)	0.0350 (8)	0.0251 (8)	0.0044 (6)	0.0018 (6)	−0.0041 (7)
N3	0.0259 (7)	0.0384 (9)	0.0261 (8)	0.0088 (7)	−0.0011 (6)	−0.0040 (7)
N4	0.0266 (8)	0.0259 (8)	0.0199 (8)	0.0054 (5)	0.0001 (6)	−0.0021 (5)
C5	0.0226 (7)	0.0211 (7)	0.0199 (8)	0.0019 (6)	0.0017 (6)	0.0006 (6)
C6	0.0420 (12)	0.0503 (12)	0.0189 (9)	0.0004 (10)	−0.0019 (8)	0.0048 (9)
C7	0.0212 (7)	0.0276 (8)	0.0319 (9)	0.0029 (6)	0.0030 (7)	0.0020 (7)

Geometric parameters (Å, º)

Cu—N4^i	2.0407 (18)	N3—N4	1.362 (2)
Cu—N4	2.0407 (18)	N4—C5	1.322 (2)
Cu—Cl2	2.2499 (9)	C5—C7	1.486 (3)
Cu—Cl1	2.2705 (8)	C6—H6A	0.9600
Cu—Cl1^ii	2.8154 (9)	C6—H6B	0.9600
N1—C5	1.338 (2)	C6—H6C	0.9600
N1—N2	1.350 (2)	C7—C7^iii	1.542 (4)
N1—C6	1.462 (3)	C7—H7A	0.9700
N2—N3	1.289 (2)	C7—H7B	0.9700
N4^i—Cu—N4	174.24 (10)	N3—N4—Cu	117.07 (13)
N4^i—Cu—Cl2	89.85 (4)	N4—C5—N1	107.34 (17)
N4—Cu—Cl2	89.85 (4)	N4—C5—C7	128.07 (17)
N4^i—Cu—Cl1	91.10 (4)	N1—C5—C7	124.58 (18)
N4—Cu—Cl1	91.10 (4)	N1—C6—H6A	109.5
Cl2—Cu—Cl1	160.54 (4)	N1—C6—H6B	109.5
N4^i—Cu—Cl1^ii	87.39 (5)	H6A—C6—H6B	109.5
N4—Cu—Cl1^ii	87.39 (5)	N1—C6—H6C	109.5
Cl2—Cu—Cl1^ii	111.72 (3)	H6A—C6—H6C	109.5
Cl1—Cu—Cl1^ii	87.74 (3)	H6B—C6—H6C	109.5
C5—N1—N2	108.98 (17)	C5—C7—C7^iii	111.6 (2)
C5—N1—C6	131.00 (18)	C5—C7—H7A	109.3
N2—N1—C6	120.01 (18)	C7^iii—C7—H7A	109.3
N3—N2—N1	106.75 (16)	C5—C7—H7B	109.3
N2—N3—N4	109.97 (17)	C7^iii—C7—H7B	109.3
C5—N4—N3	106.94 (16)	H7A—C7—H7B	108.0
C5—N4—Cu	135.98 (14)
C5—N1—N2—N3	−0.3 (2)	N3—N4—C5—N1	0.9 (2)
C6—N1—N2—N3	−179.57 (19)	Cu—N4—C5—N1	−177.97 (14)
N1—N2—N3—N4	0.8 (2)	N3—N4—C5—C7	−178.21 (18)
N2—N3—N4—C5	−1.1 (2)	Cu—N4—C5—C7	3.0 (3)
N2—N3—N4—Cu	178.03 (14)	N2—N1—C5—N4	−0.4 (2)
Cl2—Cu—N4—C5	−100.42 (18)	C6—N1—C5—N4	178.8 (2)
Cl1—Cu—N4—C5	60.14 (18)	N2—N1—C5—C7	178.71 (17)
Cl1^ii—Cu—N4—C5	147.83 (18)	C6—N1—C5—C7	−2.1 (3)
Cl2—Cu—N4—N3	80.84 (14)	N4—C5—C7—C7^iii	−93.53 (19)
Cl1—Cu—N4—N3	−118.60 (14)	N1—C5—C7—C7^iii	87.56 (18)
Cl1^ii—Cu—N4—N3	−30.91 (14)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7B···Cl1^iii	0.97	2.61	3.484 (2)	150
C6—H6B···N3^iv	0.96	2.58	3.314 (3)	134

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