catena-Poly[[trans-di­chloro­copper(II)]-μ-1,4,7,10,13,16-hexa­thia­cyclo­octa­decane-S¹:S¹⁰]

In the title complex, [CuCl₂(C₁₂H₂₄S₆)]_n, the CuCl₂ unit and the ligand lie on and about inversion centres, respectively. The coordination geometry at Cu^II is a tetragonally elongated octahedron with the equatorial positions occupied by two chlorides, Cu—Cl 2.2786 (12) Å, and two S donors, Cu—S 2.3710 (13) Å. The apical positions of the octahedron are defined by two S donors at distances of 2.8261 (14) Å from the metal. The macrocyclic ligand adopts a very puckered and distorted conformation. Eight of the 18 torsion angles are less than 90° and all S-donors are oriented exo to the ring.

S1. Comment

Over the last decade, the coordination chemistry of cyclic thioether ligands has assumed great interest as a consequence of the observation that they can bind a wide range of soft second and third row transition metal ions, forming stable metal complexes in many of which the metal centre is forced to adopt unusual coordination geometries or oxidation states (Blake & Schröder, 1990). As free ligands, thioether macrocycles tend to adopt conformations in which the lone pairs on the S donors are in exodentate positions – pointing out of the ring cavity – and the number of gauche placements of the C—S bonds is maximized (Wolf et al., 1987). For an in-cavity coordination, a reorganisational energy needs to be expended: this accounts for the diminished thermodynamic macrocyclic effect observed for some thioether crowns compared to their open-chain analogues. Generally, long periods of refluxing are necessary to facilitate these conformational changes. However, a few examples are known in which the thioether donors bind exo to the ring, allowing bridging between two metal centres. Crystal structure determinations on [CuCl₂([12]aneS₃)], [(NbCl₅)₂([14]aneS₄)], [ReBr(CO)₃([15]aneS₅)] and [(HgCl₂)₂([14]aneS₄)], where [12]aneS₃ = 1,5,9-trithiacyclododecane, [14]aneS₄ = 1,4,8,11-tetrathiacyclotetradecane and [15]aneS₅ = 1,4,7,10,13-pentathiacyclopentadecane (Blake & Schröder, 1990), clearly exemplify this aspect of the coordination chemistry of thioether crowns and support the general observation that the kinetic product involves exo coordination of the thioether donors to the metal centre. We report herein the X-ray crystal structure of the polymeric complex [CuCl₂([18]aneS₆)]_∞, (I), obtained by reacting [18]aneS₆ and CuCl₂ in MeCN/CH₂Cl₂ at room temperature. \sch

In the title compound, CuCl₂ units alternate with [18]aneS₆ ligand molecules to form infinite polymeric chains which run along the [001] direction (see Figure 1). The CuCl₂ units lie on, while the ligand molecules are disposed about, inversion centres: both therefore have crystallographically imposed C_i symmetry. The coordination geometry around the Cu^II metal centre can be viewed as a tetragonally distorted octahedron with the equatorial positions occupied by two trans symmetry-equivalent chlorides, Cu—Cl 2.2786 (12) Å, and two trans symmetry-equivalent S donors, Cu—S 2.3710 (13) Å, from two symmetry-related macrocyclic ligands. Another two symmetry-equivalent S donors from the same molecules of [18]aneS₆ occupy the apical positions of the octahedron with long-range Cu—S distances of 2.8261 (14) Å. The macrocyclic ligand adopts a very puckered and distorted conformation. Eight torsion anglesa are less than 90° and all S-donors are exo-oriented with respect to the ring cavity.

It is noteworthy that the complex [Cu([18]aneS₆)](picrate)₂, obtained by reacting the thioether ligand with copper(II) picrate at 323 K, is monomeric and the metal centre is disposed within the ring cavity of the ligand and coordinated to all six S donors in a tetragonally distorted octahedral geometry (Hartman & Cooper, 1986). In the case of the title compound, the very mild experimental conditions used in the synthesis appear to have prevented the macrocyclic ligand from encapsulating the metal centre by displacement of the two chloride atoms, resulting in the preferential formation of the kinetic product (out-of-cavity coordination) instead of the thermodynamic one (in-cavity coordination).

S2. Experimental

A mixture of [18]aneS₆ (50 mg, 0.139 mmol) and CuCl₂ (18.95 mg, 0.139 mmol) in MeCN/CH₂Cl₂ (30 ml, 1:1 v/v) was stirred at room temperature for 3 h. A dark green solid was formed and collected by filtration. Diffusion of Et₂O vapour into a solution of the green solid in dmf gave deep green crystals suitable for X-ray diffraction studies (66 mg, 95.7% yield, m.p. 415–417 K). Found (calculated for C₁₂H₂₄CuCl₂S₆): C 28.75 (29.12); H 4.45% (4.89%). FAB mass spectrum (3-NOBA matrix), found: m/z 460; calculated for [CuCl([18]aneS₆)]⁺ 460. IR spectrum (KBr pellet): ν/cm¹ 2968m, 2923m, 1427 s, 1408 s, 1267m, 1203m, 924w, 849w, 830w, 694w.

S3. Refinement

The presence of the low temperature device (Cosier & Glazer, 1986) imposed an upper limit on θ of 60° during data collection. Furthermore, the omega circle obscured a number of reflections in the range 47 < θ < 60°.

Computing details

Data collection: STADI-4 (Stoe & Cie, 1997); cell refinement: STADI-4; data reduction: X-RED (Stoe & Cie, 1997); program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL/PC (Sheldrick, 1994); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2000).

Figures

Fig. 1. A view of (I) showing the atom-numbering scheme and 50% probability displacement ellipsoids. Hydrogen atoms are omitted for clarity, as are the long Cu—S axial contacts. The one-dimensional polymer, part of which is shown here, runs parallel to the c axis. Symmetry codes: (i) 1 - x, 1 - y, 1 - z; (ii) 1 - x, 1 - y, 2 - z.

(I)

Crystal data

[CuCl2(C12H24S6)]	F(000) = 510
Mr = 495.18	Dx = 1.672 Mg m^−3
Monoclinic, P21/c	Cu Kα radiation, λ = 1.5418 Å
a = 8.9499 (9) Å	Cell parameters from 46 reflections
b = 14.500 (2) Å	θ = 20–22°
c = 7.7348 (11) Å	µ = 9.94 mm^−1
β = 101.63 (1)°	T = 220 K
V = 983.2 (2) Å^3	Plate, brown
Z = 2	0.23 × 0.12 × 0.04 mm

Data collection

Stoe Stadi-4 four-circle diffractometer	1047 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.032
Graphite monochromator	θmax = 60.1°, θmin = 5.1°
ω/θ with on–line profile–fitting (Clegg, 1981) scans	h = −8→10
Absorption correction: ψ scan (North et al., 1968)	k = −16→14
Tmin = 0.336, Tmax = 0.672	l = −8→8
1518 measured reflections	3 standard reflections every 60 min
1255 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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.107	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.054P)^2 + 1.712P] where P = (Fo^2 + 2Fc^2)/3
1251 reflections	(Δ/σ)max = 0.002
97 parameters	Δρmax = 0.44 e Å^−3
0 restraints	Δρmin = −0.44 e Å^−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 on F² for ALL reflections except for 4 with very negative F² or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating _R_factor_obs 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	0.5000	0.5000	0.5000	0.0333 (3)
Cl	0.6030 (2)	0.56793 (8)	0.7627 (2)	0.0384 (3)
S2	0.53208 (15)	0.34677 (8)	0.6082 (2)	0.0335 (3)
S3	0.95022 (15)	0.33319 (9)	1.0175 (2)	0.0385 (4)
C2	0.2791 (6)	0.3958 (4)	0.7500 (7)	0.0399 (13)
H2A	0.3565 (6)	0.4205 (4)	0.8469 (7)	0.048*
H2B	0.1946 (6)	0.3714 (4)	0.7994 (7)	0.048*
C3	0.3473 (6)	0.3200 (4)	0.6553 (8)	0.0419 (13)
H3A	0.2767 (6)	0.3065 (4)	0.5439 (8)	0.050*
H3B	0.3563 (6)	0.2641 (4)	0.7277 (8)	0.050*
C4	0.6494 (6)	0.3411 (4)	0.8270 (6)	0.0350 (12)
H4A	0.6182 (6)	0.3890 (4)	0.9017 (6)	0.042*
H4B	0.6369 (6)	0.2809 (4)	0.8800 (6)	0.042*
C5	0.8149 (6)	0.3551 (4)	0.8151 (7)	0.0375 (12)
H5A	0.8279 (6)	0.4187 (4)	0.7783 (7)	0.045*
H5B	0.8384 (6)	0.3143 (4)	0.7231 (7)	0.045*
C6	0.9224 (6)	0.4319 (4)	1.1522 (7)	0.0376 (12)
H6A	1.0203 (6)	0.4478 (4)	1.2285 (7)	0.045*
H6B	0.8900 (6)	0.4847 (4)	1.0746 (7)	0.045*
C1	0.1938 (6)	0.5837 (4)	0.7339 (7)	0.0404 (13)
H1A	0.2934 (6)	0.5956 (4)	0.8102 (7)	0.049*
H1B	0.1649 (6)	0.6386 (4)	0.6609 (7)	0.049*
S1	0.2105 (2)	0.48637 (9)	0.5913 (2)	0.0378 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu	0.0450 (6)	0.0270 (5)	0.0272 (6)	−0.0012 (5)	0.0053 (5)	−0.0011 (4)
Cl	0.0486 (7)	0.0349 (7)	0.0309 (6)	−0.0020 (6)	0.0058 (6)	−0.0044 (5)
S2	0.0404 (7)	0.0286 (6)	0.0330 (7)	0.0024 (6)	0.0111 (6)	−0.0005 (5)
S3	0.0378 (7)	0.0391 (7)	0.0407 (7)	0.0077 (6)	0.0128 (6)	0.0005 (6)
C2	0.039 (3)	0.043 (3)	0.042 (3)	0.001 (3)	0.017 (2)	0.007 (3)
C3	0.042 (3)	0.031 (3)	0.052 (3)	−0.004 (3)	0.008 (3)	0.004 (3)
C4	0.037 (3)	0.038 (3)	0.031 (3)	0.007 (2)	0.010 (2)	0.008 (2)
C5	0.044 (3)	0.039 (3)	0.032 (3)	0.001 (3)	0.013 (2)	0.003 (2)
C6	0.041 (3)	0.037 (3)	0.037 (3)	−0.004 (2)	0.015 (2)	−0.005 (2)
C1	0.047 (3)	0.040 (3)	0.037 (3)	0.003 (3)	0.015 (3)	−0.003 (3)
S1	0.0408 (7)	0.0404 (8)	0.0327 (7)	0.0064 (6)	0.0084 (6)	−0.0023 (6)

Geometric parameters (Å, º)

Cu—Cl	2.2786 (12)	C2—C3	1.516 (7)
Cu—S2	2.3710 (13)	C2—S1	1.817 (5)
Cu—S1	2.8261 (14)	C4—C5	1.516 (7)
S2—C4	1.805 (5)	C6—C1^i	1.509 (7)
S2—C3	1.806 (6)	C1—C6^i	1.509 (7)
S3—C5	1.804 (5)	C1—S1	1.816 (5)
S3—C6	1.816 (5)
Cl^ii—Cu—Cl	180	C5—S3—C6	102.3 (3)
S2^ii—Cu—S2	180	C3—C2—S1	108.1 (4)
Cl—Cu—S2	95.28 (4)	C2—C3—S2	114.6 (4)
Cl^ii—Cu—S2	84.72 (4)	C5—C4—S2	109.1 (3)
Cl—Cu—S1	91.93 (4)	C4—C5—S3	114.6 (3)
S2—Cu—S1	84.16 (4)	C1^i—C6—S3	114.0 (4)
C4—S2—C3	100.6 (2)	C6^i—C1—S1	112.9 (4)
C4—S2—Cu	112.3 (2)	C1—S1—C2	102.1 (3)
C3—S2—Cu	102.8 (2)
S1—C2—C3—S2	75.1 (4)	C5—S3—C6—C1^i	91.6 (4)
C2—C3—S2—C4	71.6 (4)	S3^i—C6^i—C1—S1	−176.5 (3)
C3—S2—C4—C5	175.9 (4)	C6^i—C1—S1—C2	−63.3 (5)
S2—C4—C5—S3	−170.6 (3)	C1—S1—C2—C3	−161.8 (4)
C4—C5—S3—C6	−72.5 (4)

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