2-[5-(Benzo[d]thia­zol-2-yl)thio­phen-2-yl]benzo[d]thia­zole

Potgieter, K.; Mayer, P.; Hosten, E.; Gerber, T.I.A.

doi:10.1107/S1600536810004009

organic compounds

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ISSN: 2056-9890

Volume 66| Part 3| March 2010| Page o531

doi:10.1107/S1600536810004009

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2-[5-(Benzo[d]thiazol-2-yl)thiophen-2-yl]benzo[d]thiazole

Kim Potgieter,^a Peter Mayer,^b Eric Hosten ^a and Thomas I. A. Gerber ^a ^*

^aDepartment of Chemistry, Nelson Mandela Metropolitan University, 6031 Port Elizabeth, South Africa, and ^bDepartment of Chemistry, Ludiwig-Maximilians University, D-81377 München, Germany
^*Correspondence e-mail: thomas.gerber@nmmu.ac.za

(Received 22 January 2010; accepted 1 February 2010; online 6 February 2010)

The structure of the title compound, C₁₈H₁₀N₂S₃, consists of a central thiophene ring and two terminal thiazole rings. The two S atoms of the thiazole rings are trans to the thiophene S atom sulfur. The thiazole rings are approximately coplanar with the thiophene ring, with dihedral angles of 6.23 (11) and 4.81 (11)° between them. In the crystal, zigzag chains are formed along [010] by weak C—H⋯N interactions.

Related literature

For the synthesis of thiophene derivatives, see: Kaleta et al. (2006 ); Minetto et al. (2005 ); Bayh et al. (2005 ). For their conformation, see: Alberti et al. (1986 ); Hagen (1986 ); Salman (1982 ) and for their applications, see: Seed et al. (2003 ); Cheylan et al. (2006 ); Karimian (2009 ); Kiryanov et al. (2001 ); Shi et al. (1996 ).

Experimental

Crystal data

C₁₈H₁₀N₂S₃
M_r = 350.48
Monoclinic, P 2₁ /c
a = 15.7297 (14) Å
b = 8.2396 (5) Å
c = 12.8160 (12) Å
β = 112.872 (11)°
V = 1530.4 (2) Å³
Z = 4
Mo Kα radiation
μ = 0.48 mm⁻¹
T = 200 K
0.34 × 0.15 × 0.01 mm

Data collection

Oxford XCalibur diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Abington, England.]$ ) T_min = 0.839, T_max = 1.000
5789 measured reflections
3086 independent reflections
1452 reflections with I > 2σ(I)
R_int = 0.053

Refinement

R[F² > 2σ(F²)] = 0.043
wR(F²) = 0.051
S = 0.72
3086 reflections
208 parameters
H-atom parameters constrained
Δρ_max = 0.29 e Å⁻³
Δρ_min = −0.30 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C16—H16⋯N1ⁱ	0.95	2.63	3.444 (4)	144
Symmetry code: (i) $[-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Data collection: CrysAlis PRO (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Abington, England.]$ ); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ) and Mercury (Macrae et al., 2006 ); software used to prepare material for publication: publCIF (Westrip, 2010 ) and PARST (Nardelli, 1995 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810004009/ez2199sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810004009/ez2199Isup2.hkl

checkCIF report

Comment top

Derivatives of thiophene have shown promise in photovoltaic (Cheylan et al., 2006), liquid crystal (Kiryanov et al. 2001) and therapeutic applications (Seed et al., 2003). On the other hand, thiazole derivatives have been evaluated for biological activity (Karimian, 2009), especially against certain breast carcinoma cell lines (Shi et al. 1996).

In the present work the structure of 2-(5-benzo[d]thiazol-2-yl)thiophen-2-yl)benzo[d]thiazole has been determined to explore its suitability as a tridentate ligand for various metal ions.

The structure consists of a central thiophenyl ring and two terminal thiazolyl rings, with the two sulfur atoms of the latter rings in trans positions to the thiophenyl sulfur atom (see Fig. 1). The thiazolyl rings with S1 and S3 are approximately coplanar with the thiophenyl ring, with dihedral angles of 6.23 (11)° and 4.81 (11)° respectively. The dihedral angle between the two thiazolyl rings is 10.39 (8)°.

The bonding parameters illustrate that C8—C9 and C10—C11 bonds in the thiophenyl ring are localized double bonds (1.354 (5) and 1.358 (4) Å respectively), as are the N1—C7 and N2—C12 bonds (1.286 (4) and 1.308 (4) Å respectively).

Taking into account merely interactions with hydrogen-acceptor distances at least 0.1 Å shorter than the sum of van der Waals radii, the molecules are linked by weak interactions of the type C16—H16···N1, which lead to the formation of zig-zag-chains along [010] (see Fig. 2). The shortest distance in the parallel stacking of the molecules is 3.6371 (17) Å, observed for the planes through the thiophenyl ring and the phenyl ring (C13 to C18) of a neighboring molecule.

Related literature top

For the synthesis of thiophene derivatives, see: Kaleta et al. (2006); Minetto et al. (2005); Bayh et al. (2005). For their conformation, see: Alberti et al. (1986); Hagen (1986); Salman (1982) and for their applications, see: Seed et al. (2003); Cheylan et al. (2006); Karimian (2009); Kiryanov et al. (2001); Shi et al. (1996).

Experimental top

All chemicals used (reagent grade) were commercially available. A mass of 0.281 g (0.0020 mol) of 2,5-thiophenedicarboxaldehyde was dissolved in methanol (20 cm³), and 0.502 g (0.0040 mol) of 2-aminothiophenol was added with stirring. The mixture was heated under reflux for an hour, then cooled to room temperature and filtered. After standing at 0°C for 24 h, a yellow precipitate was collected. Recrystallization from ethanol gave yellow needles (0.378 g, 54 %), with the formulation C₁₈H₁₀N₂S₃ and suitable for X-ray analysis. M.p. 203–206 °C.

Computing details top

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: publCIF (Westrip, 2010) and PARST (Nardelli, 1995).

Figures top

	Fig. 1. The molecular structure of the title compound (anisotropic displacement ellipsoids drawn at the 50% probablility level).
	Fig. 2. The zig-zag-chains established by weak interactions of the type C–H···N.

2-[5-(Benzo[d]thiazol-2-yl)thiophen-2-yl]benzo[d]thiazole top

Crystal data top

C₁₈H₁₀N₂S₃	F(000) = 720
M_r = 350.48	D_x = 1.521 (1) Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 15.7297 (14) Å	Cell parameters from 1275 reflections
b = 8.2396 (5) Å	θ = 4.2–26.2°
c = 12.8160 (12) Å	µ = 0.48 mm⁻¹
β = 112.872 (11)°	T = 200 K
V = 1530.4 (2) Å³	Needles, yellow
Z = 4	0.34 × 0.15 × 0.01 mm

Data collection top

Oxford XCalibur diffractometer	3086 independent reflections
Radiation source: fine-focus sealed tube	1452 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.053
Detector resolution: 15.9809 pixels mm^-1	θ_max = 26.3°, θ_min = 4.2°
ω scans	h = −19→19
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009)	k = −9→10
T_min = 0.839, T_max = 1.000	l = −9→15
5789 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.051	H-atom parameters constrained
S = 0.72	w = 1/[σ²(F_o²) + (0.006P)²] where P = (F_o² + 2F_c²)/3
3086 reflections	(Δ/σ)_max < 0.001
208 parameters	Δρ_max = 0.29 e Å⁻³
0 restraints	Δρ_min = −0.30 e Å⁻³

Crystal data top

C₁₈H₁₀N₂S₃	V = 1530.4 (2) Å³
M_r = 350.48	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 15.7297 (14) Å	µ = 0.48 mm⁻¹
b = 8.2396 (5) Å	T = 200 K
c = 12.8160 (12) Å	0.34 × 0.15 × 0.01 mm
β = 112.872 (11)°

Data collection top

Oxford XCalibur diffractometer	3086 independent reflections
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009)	1452 reflections with I > 2σ(I)
T_min = 0.839, T_max = 1.000	R_int = 0.053
5789 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.043	0 restraints
wR(F²) = 0.051	H-atom parameters constrained
S = 0.72	Δρ_max = 0.29 e Å⁻³
3086 reflections	Δρ_min = −0.30 e Å⁻³
208 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
S1	0.19188 (5)	−0.01268 (9)	0.55789 (7)	0.0372 (2)
S2	0.40390 (5)	0.14749 (8)	0.43819 (7)	0.0294 (2)
S3	0.65397 (5)	0.41064 (8)	0.64495 (7)	0.0351 (2)
N1	0.22730 (15)	−0.0478 (2)	0.3780 (2)	0.0306 (7)
N2	0.57525 (15)	0.3239 (2)	0.4337 (2)	0.0258 (6)
C1	0.11335 (19)	−0.1200 (3)	0.4461 (3)	0.0294 (8)
C2	0.1446 (2)	−0.1266 (3)	0.3573 (3)	0.0299 (8)
C3	0.0918 (2)	−0.2090 (3)	0.2584 (3)	0.0393 (9)
H3	0.1119	−0.2156	0.1975	0.047*
C4	0.0108 (2)	−0.2802 (3)	0.2499 (3)	0.0421 (9)
H4	−0.0250	−0.3369	0.1825	0.051*
C5	−0.0200 (2)	−0.2717 (3)	0.3369 (3)	0.0436 (9)
H5	−0.0766	−0.3220	0.3284	0.052*
C6	0.0300 (2)	−0.1917 (3)	0.4350 (3)	0.0383 (9)
H6	0.0084	−0.1851	0.4946	0.046*
C7	0.25959 (18)	0.0157 (3)	0.4775 (3)	0.0252 (7)
C8	0.34453 (18)	0.1056 (3)	0.5237 (3)	0.0233 (7)
C9	0.38812 (19)	0.1676 (3)	0.6290 (3)	0.0321 (8)
H9	0.3656	0.1568	0.6875	0.039*
C10	0.46999 (19)	0.2493 (3)	0.6426 (2)	0.0292 (8)
H10	0.5091	0.2988	0.7115	0.035*
C11	0.48737 (18)	0.2503 (3)	0.5468 (2)	0.0242 (7)
C12	0.56531 (19)	0.3212 (3)	0.5304 (3)	0.0252 (8)
C13	0.70982 (19)	0.4587 (3)	0.5569 (3)	0.0278 (8)
C14	0.6576 (2)	0.4025 (3)	0.4477 (3)	0.0280 (8)
C15	0.6891 (2)	0.4295 (3)	0.3612 (3)	0.0372 (8)
H15	0.6546	0.3929	0.2862	0.045*
C16	0.7711 (2)	0.5105 (3)	0.3873 (3)	0.0401 (9)
H16	0.7925	0.5313	0.3287	0.048*
C17	0.8235 (2)	0.5627 (3)	0.4957 (3)	0.0392 (9)
H17	0.8806	0.6163	0.5109	0.047*
C18	0.79350 (19)	0.5377 (3)	0.5819 (3)	0.0370 (9)
H18	0.8291	0.5735	0.6567	0.044*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S1	0.0338 (5)	0.0475 (5)	0.0327 (6)	−0.0084 (4)	0.0156 (4)	−0.0013 (4)
S2	0.0278 (4)	0.0338 (4)	0.0285 (5)	−0.0019 (4)	0.0131 (4)	−0.0010 (4)
S3	0.0355 (5)	0.0414 (5)	0.0292 (6)	−0.0081 (4)	0.0136 (4)	−0.0030 (4)
N1	0.0267 (16)	0.0288 (16)	0.039 (2)	−0.0070 (12)	0.0154 (14)	−0.0019 (12)
N2	0.0235 (14)	0.0293 (14)	0.0270 (18)	−0.0032 (12)	0.0124 (13)	0.0000 (12)
C1	0.0301 (18)	0.0262 (18)	0.031 (2)	0.0001 (15)	0.0110 (16)	0.0036 (14)
C2	0.0319 (19)	0.0250 (18)	0.031 (2)	0.0034 (15)	0.0107 (17)	0.0043 (15)
C3	0.046 (2)	0.045 (2)	0.032 (2)	−0.0112 (17)	0.0211 (19)	−0.0050 (17)
C4	0.037 (2)	0.047 (2)	0.037 (3)	−0.0182 (17)	0.0080 (19)	−0.0047 (17)
C5	0.035 (2)	0.048 (2)	0.048 (3)	−0.0127 (17)	0.016 (2)	0.0046 (19)
C6	0.033 (2)	0.046 (2)	0.039 (3)	−0.0050 (17)	0.0173 (19)	0.0065 (18)
C7	0.0272 (19)	0.0201 (16)	0.031 (2)	0.0017 (15)	0.0142 (17)	0.0023 (16)
C8	0.0214 (17)	0.0226 (16)	0.028 (2)	−0.0018 (14)	0.0125 (16)	0.0004 (15)
C9	0.0338 (19)	0.0379 (18)	0.030 (2)	−0.0021 (15)	0.0182 (18)	0.0067 (16)
C10	0.0250 (18)	0.0350 (18)	0.025 (2)	−0.0007 (15)	0.0066 (16)	−0.0008 (15)
C11	0.0260 (18)	0.0194 (16)	0.025 (2)	0.0006 (14)	0.0079 (17)	0.0001 (14)
C12	0.0295 (19)	0.0170 (16)	0.029 (2)	0.0018 (14)	0.0107 (17)	0.0010 (14)
C13	0.0241 (18)	0.0270 (18)	0.036 (2)	0.0003 (14)	0.0154 (17)	0.0032 (15)
C14	0.0318 (19)	0.0253 (17)	0.029 (2)	0.0035 (15)	0.0148 (17)	0.0016 (15)
C15	0.045 (2)	0.0423 (19)	0.029 (2)	−0.0049 (17)	0.0191 (18)	−0.0056 (16)
C16	0.041 (2)	0.0410 (19)	0.051 (3)	−0.0025 (17)	0.033 (2)	0.0007 (19)
C17	0.031 (2)	0.0324 (18)	0.056 (3)	−0.0053 (16)	0.020 (2)	−0.0017 (18)
C18	0.0306 (19)	0.039 (2)	0.033 (2)	−0.0048 (15)	0.0033 (17)	−0.0002 (16)

Geometric parameters (Å, º) top

S1—C1	1.728 (3)	C6—H6	0.9500
S1—C7	1.761 (3)	C7—C8	1.438 (3)
S2—C11	1.720 (3)	C8—C9	1.353 (3)
S2—C8	1.729 (3)	C9—C10	1.403 (3)
S3—C13	1.725 (3)	C9—H9	0.9500
S3—C12	1.747 (3)	C10—C11	1.357 (3)
N1—C7	1.286 (3)	C10—H10	0.9500
N1—C2	1.384 (3)	C11—C12	1.445 (3)
N2—C12	1.308 (3)	C13—C18	1.389 (3)
N2—C14	1.397 (3)	C13—C14	1.398 (4)
C1—C6	1.394 (3)	C14—C15	1.396 (4)
C1—C2	1.404 (4)	C15—C16	1.374 (3)
C2—C3	1.392 (3)	C15—H15	0.9500
C3—C4	1.368 (4)	C16—C17	1.380 (4)
C3—H3	0.9500	C16—H16	0.9500
C4—C5	1.379 (4)	C17—C18	1.375 (4)
C4—H4	0.9500	C17—H17	0.9500
C5—C6	1.366 (4)	C18—H18	0.9500
C5—H5	0.9500

C1—S1—C7	89.01 (14)	C8—C9—H9	123.5
C11—S2—C8	90.91 (14)	C10—C9—H9	123.5
C13—S3—C12	89.42 (14)	C11—C10—C9	112.8 (3)
C7—N1—C2	111.1 (3)	C11—C10—H10	123.6
C12—N2—C14	109.4 (2)	C9—C10—H10	123.6
C6—C1—C2	120.8 (3)	C10—C11—C12	127.9 (3)
C6—C1—S1	129.9 (3)	C10—C11—S2	111.7 (2)
C2—C1—S1	109.2 (2)	C12—C11—S2	120.3 (2)
N1—C2—C3	125.9 (3)	N2—C12—C11	124.4 (3)
N1—C2—C1	115.2 (3)	N2—C12—S3	116.0 (2)
C3—C2—C1	118.9 (3)	C11—C12—S3	119.5 (2)
C4—C3—C2	119.3 (3)	C18—C13—C14	121.4 (3)
C4—C3—H3	120.4	C18—C13—S3	129.3 (3)
C2—C3—H3	120.4	C14—C13—S3	109.2 (2)
C3—C4—C5	121.5 (3)	C15—C14—N2	124.7 (3)
C3—C4—H4	119.3	C15—C14—C13	119.4 (3)
C5—C4—H4	119.3	N2—C14—C13	115.9 (3)
C6—C5—C4	120.8 (3)	C16—C15—C14	118.3 (3)
C6—C5—H5	119.6	C16—C15—H15	120.9
C4—C5—H5	119.6	C14—C15—H15	120.9
C5—C6—C1	118.6 (3)	C15—C16—C17	122.2 (3)
C5—C6—H6	120.7	C15—C16—H16	118.9
C1—C6—H6	120.7	C17—C16—H16	118.9
N1—C7—C8	124.3 (3)	C18—C17—C16	120.3 (3)
N1—C7—S1	115.5 (2)	C18—C17—H17	119.8
C8—C7—S1	120.2 (2)	C16—C17—H17	119.8
C9—C8—C7	129.4 (3)	C17—C18—C13	118.3 (3)
C9—C8—S2	111.5 (2)	C17—C18—H18	120.8
C7—C8—S2	119.1 (2)	C13—C18—H18	120.8
C8—C9—C10	113.0 (3)

C7—S1—C1—C6	−178.8 (3)	C9—C10—C11—C12	−179.3 (2)
C7—S1—C1—C2	0.3 (2)	C9—C10—C11—S2	−0.9 (3)
C7—N1—C2—C3	−179.5 (3)	C8—S2—C11—C10	0.7 (2)
C7—N1—C2—C1	0.5 (3)	C8—S2—C11—C12	179.2 (2)
C6—C1—C2—N1	178.7 (2)	C14—N2—C12—C11	179.5 (2)
S1—C1—C2—N1	−0.5 (3)	C14—N2—C12—S3	−0.6 (3)
C6—C1—C2—C3	−1.3 (4)	C10—C11—C12—N2	−176.7 (3)
S1—C1—C2—C3	179.5 (2)	S2—C11—C12—N2	5.1 (4)
N1—C2—C3—C4	−179.5 (3)	C10—C11—C12—S3	3.4 (4)
C1—C2—C3—C4	0.5 (4)	S2—C11—C12—S3	−174.81 (13)
C2—C3—C4—C5	0.3 (5)	C13—S3—C12—N2	0.6 (2)
C3—C4—C5—C6	−0.3 (5)	C13—S3—C12—C11	−179.5 (2)
C4—C5—C6—C1	−0.6 (5)	C12—S3—C13—C18	−179.6 (3)
C2—C1—C6—C5	1.4 (4)	C12—S3—C13—C14	−0.4 (2)
S1—C1—C6—C5	−179.6 (2)	C12—N2—C14—C15	−178.8 (3)
C2—N1—C7—C8	−180.0 (2)	C12—N2—C14—C13	0.2 (3)
C2—N1—C7—S1	−0.3 (3)	C18—C13—C14—C15	−1.5 (4)
C1—S1—C7—N1	0.0 (2)	S3—C13—C14—C15	179.3 (2)
C1—S1—C7—C8	179.7 (2)	C18—C13—C14—N2	179.4 (2)
N1—C7—C8—C9	−174.9 (3)	S3—C13—C14—N2	0.2 (3)
S1—C7—C8—C9	5.4 (4)	N2—C14—C15—C16	179.2 (2)
N1—C7—C8—S2	5.6 (4)	C13—C14—C15—C16	0.3 (4)
S1—C7—C8—S2	−174.02 (14)	C14—C15—C16—C17	1.2 (4)
C11—S2—C8—C9	−0.3 (2)	C15—C16—C17—C18	−1.4 (5)
C11—S2—C8—C7	179.2 (2)	C16—C17—C18—C13	0.1 (4)
C7—C8—C9—C10	−179.6 (2)	C14—C13—C18—C17	1.3 (4)
S2—C8—C9—C10	−0.1 (3)	S3—C13—C18—C17	−179.7 (2)
C8—C9—C10—C11	0.7 (4)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C16—H16···N1ⁱ	0.95	2.63	3.444 (4)	144

Symmetry code: (i) −x+1, y+1/2, −z+1/2.

Experimental details

Crystal data
Chemical formula	C₁₈H₁₀N₂S₃
M_r	350.48
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	200
a, b, c (Å)	15.7297 (14), 8.2396 (5), 12.8160 (12)
β (°)	112.872 (11)
V (Å³)	1530.4 (2)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.48
Crystal size (mm)	0.34 × 0.15 × 0.01

Data collection
Diffractometer	Oxford XCalibur diffractometer
Absorption correction	Multi-scan (CrysAlis PRO; Oxford Diffraction, 2009)
T_min, T_max	0.839, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	5789, 3086, 1452
R_int	0.053
(sin θ/λ)_max (Å⁻¹)	0.624

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.043, 0.051, 0.72
No. of reflections	3086
No. of parameters	208
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.29, −0.30

Computer programs: CrysAlis PRO (Oxford Diffraction, 2009), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2006), publCIF (Westrip, 2010) and PARST (Nardelli, 1995).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C16—H16···N1ⁱ	0.95	2.63	3.444 (4)	144.4

Symmetry code: (i) −x+1, y+1/2, −z+1/2.

Acknowledgements

The authors thank Professor P. Klüfers for generous allocation of diffractometer time.

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