1,3,5,7-Tetraselena-2,4,6,8(2,5)-tetrathiophenaoctaphane

The novel title tetraselenacalix[4]arene, C₁₆H₈S₄Se₄ or [(C₄H₂S)Se]₄, has a centrosymmetric cyclic molecular structure with approximate C_2h molecular symmetry. The four thienyl rings are joined together by Se bridges and exhibit a syn-syn-anti-anti arrangement around the mol­ecule. The lattice consists of skewed stacks of mol­ecules, with chalcogen-chalcogen close contacts binding the stacks together, forming a two-dimensional network of mol­ecules.

S1. Comment

While the preparation, structural characterization and electrochemical properties of cyclic thiacalix[4]-, thiacalix[5]-, and thiacalix[6]arenes, and of some related species, have been reported (Nakyama et al., 1997; Katano et al., 1998; König et al. 1997a,b; Nakabayashi et al., 1999), no structural information on the analogous cyclic selenacalixarenes has been published to date. Tiecco et al. (2000) have recently demonstrated the formation of related open-chain oligomeric seleno-2,5-thienylenes by treatment of a large excess of thiophene or 2-methylthiophene with an electrophilic selenenylating agent derived from dithienyl diselenide. With only a small excess of thiophene, insoluble polymeric material was obtained.

Upon reinvestigation of this reaction by treating thiophene with a mixture of dithienyl diselenide and PhI(OAc)₂ (molar ratio 50:1:2) in acetonitrile, we also obtained, in addition to the insoluble polymer Is this added text OK?, a yellow, sparingly soluble precipitate that partially dissolves in tetrahydrofuran. Yellow crystals of the title compound, (I), {(C₄H₂S)Se}₄, were grown by slow evaporation of the solvent. \sch

The lattice of (I) is composed of discrete cyclic molecules, in which the four thienyl rings are joined together by four approximately coplanar Se bridges (Fig. 1). Selected bond distances and angles are given in Table 1. The asymmetric unit contains one half of the molecule, the other half being completed by symmetry. The C—Se bonds are in the range 1.900 (4)–1.910 (5) Å and show typical single-bond values. Also, the C—C and C—S bonds within the thienyl rings show expected values. The C—Se—C bond angles span a range of 97.9 (2)–98.8 (2)° and are in agreement with the value found in Me₂Se (96.18°; Beecher, 1966). The respective C—S bond lengths and C—S—C angles in cyclic [(C₄H₂S)S]_n (n = 4–6) of 1.736–1.768 Å and 100.82–105.15° (Nakayama et al., 1997; Katano et al., 1998) are consistent with the geometric parameters found in (I).

The molecule of (I) exhibits an approximately C_{2 h} molecular symmetry, with the two thienyl rings bound to Se1 exhibiting a syn arrangement, while those bound to Se2 exhibit an anti arrangement. This syn,syn,anti,anti arrangement is also observed in [(C₄H₂S)S]₄ (Katano et al., 1998).

While the molecular structures of [(C₄H₂S)S]₄ (Katano et al., 1998) and (I) are similar, their packing in the lattice is different. While molecules of both (I) and [(C₄H₂S)S]₄ form skewed stacks, the geometry of close chalcogen-chalcogen contacts is different. In the case of (I), the S2···S2 and Se1···S1 contacts [3.649 (2) and 3.472 (2) Å, respectively] form a two-dimensional network (Fig. 2), whereas in [(C₄H₂S)S]₄, the corresponding S···S contacts of 3.396 (9)–3.657 (5) Å assemble the molecules into a three-dimensional lattice (Katano et al., 1998).

S2. Experimental

Thiophene (4 ml, 50.63 mmol) was added to a mixture of dithienyl diselenide (0.3252 g, 1.00 mmol) and PhI(OAc)₂ (0.6451 g, 2.00 mmol) in acetonitrile (6 ml). The reaction mixture was stirred overnight, during which time a yellow sparingly soluble precipitate was obtained. Analysis found: C 31.74, H 1.51, S 19.49%; calculated for C₁₆H₈S₄Se₄: C 29.82, H 1.25, S 19.91%. The precipitate was partially dissolved in tetrahydrofuran. Yellow crystals of (I) were obtained upon slow evaporation of the solvent.

S3. Refinement

H atoms were treated as riding, with C—H = 0.93 Å and U_iso(H) = 1.2U_eq(C). Are these the correct constraints?

Computing details

Data collection: KappaCCD Server Software (Bruker-Nonius, 2002); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg & Berndt, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. A view of the molecular structure of (I) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Primed atoms are generated by the symmetry operation (1 - x, 1 - y, 2 - z).
	Fig. 2. The packing of the molecules of (I), indicating the close chalcogen-chalcogen contacts.

1,3,5,7-Tetraselena-2,4,6,8(2,5)-tetrathiophenaoctaphane

Crystal data

C16H8S4Se4	Z = 1
Mr = 644.34	F(000) = 304
Triclinic, P1	Dx = 2.192 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.3186 (13) Å	Cell parameters from 1636 reflections
b = 8.0176 (16) Å	θ = 3.1–26.0°
c = 9.7493 (19) Å	µ = 7.94 mm^−1
α = 97.96 (3)°	T = 293 K
β = 92.49 (3)°	Block, yellow
γ = 92.68 (3)°	0.20 × 0.15 × 0.15 mm
V = 487.99 (17) Å^3

Data collection

Nonius KappaCCD area-detector diffractometer	1908 independent reflections
Radiation source: fine-focus sealed tube	1636 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.046
ϕ scans, and ω scans with κ offsets	θmax = 26.0°, θmin = 3.1°
Absorption correction: ψ (XPREP in SHELXTL; Bruker 2001)	h = −7→7
Tmin = 0.238, Tmax = 0.304	k = −9→9
6496 measured reflections	l = −12→11

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)] = 0.033	H-atom parameters constrained
wR(F^2) = 0.091	w = 1/[σ^2(Fo^2) + (0.0291P)^2 + 0.7694P] where P = (Fo^2 + 2Fc^2)/3
S = 1.16	(Δ/σ)max = 0.001
1908 reflections	Δρmax = 0.66 e Å^−3
110 parameters	Δρmin = −0.48 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0063 (17)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Se1	0.76538 (9)	0.67066 (6)	0.64754 (5)	0.0509 (2)
Se2	0.22756 (8)	0.03773 (6)	0.73549 (5)	0.04943 (19)
S1	0.4135 (2)	0.40825 (15)	0.71767 (14)	0.0509 (3)
S2	0.33863 (19)	0.16367 (16)	1.05346 (12)	0.0483 (3)
C1	0.6556 (7)	0.4459 (5)	0.6514 (4)	0.0410 (10)
C2	0.7465 (7)	0.3015 (6)	0.6052 (5)	0.0445 (10)
H2	0.8752	0.2971	0.5623	0.053*
C3	0.6237 (8)	0.1569 (6)	0.6295 (5)	0.0447 (10)
H3	0.6650	0.0473	0.6055	0.054*
C4	0.4405 (7)	0.1940 (5)	0.6909 (4)	0.0402 (9)
C5	0.1658 (7)	0.1535 (5)	0.9115 (4)	0.0409 (10)
C6	−0.0188 (8)	0.2263 (6)	0.9460 (5)	0.0523 (12)
H6	−0.1317	0.2325	0.8829	0.063*
C7	−0.0197 (8)	0.2913 (6)	1.0885 (5)	0.0525 (12)
H7	−0.1338	0.3444	1.1291	0.063*
C8	0.1620 (7)	0.2681 (5)	1.1592 (4)	0.0410 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Se1	0.0779 (4)	0.0403 (3)	0.0334 (3)	−0.0081 (2)	0.0073 (2)	0.00381 (19)
Se2	0.0609 (3)	0.0463 (3)	0.0368 (3)	−0.0130 (2)	0.0055 (2)	−0.0049 (2)
S1	0.0559 (7)	0.0392 (6)	0.0563 (7)	0.0024 (5)	0.0172 (6)	−0.0028 (5)
S2	0.0487 (7)	0.0544 (7)	0.0387 (6)	0.0060 (5)	0.0010 (5)	−0.0047 (5)
C1	0.050 (2)	0.041 (2)	0.031 (2)	−0.0024 (19)	0.0056 (18)	0.0001 (17)
C2	0.048 (2)	0.048 (2)	0.037 (2)	0.002 (2)	0.0086 (19)	0.0032 (19)
C3	0.054 (3)	0.035 (2)	0.043 (2)	0.0043 (19)	0.000 (2)	−0.0023 (18)
C4	0.050 (2)	0.038 (2)	0.032 (2)	−0.0022 (18)	0.0001 (18)	0.0022 (17)
C5	0.050 (2)	0.039 (2)	0.032 (2)	−0.0053 (19)	0.0022 (18)	0.0006 (17)
C6	0.055 (3)	0.057 (3)	0.044 (3)	0.004 (2)	−0.003 (2)	0.005 (2)
C7	0.054 (3)	0.054 (3)	0.050 (3)	0.008 (2)	0.010 (2)	0.002 (2)
C8	0.051 (3)	0.035 (2)	0.035 (2)	−0.0004 (18)	0.0059 (18)	−0.0006 (17)

Geometric parameters (Å, º)

Se1—C1	1.906 (4)	C2—H2	0.9300
Se1—C8^i	1.910 (4)	C3—C4	1.352 (7)
Se2—C5	1.900 (4)	C3—H3	0.9300
Se2—C4	1.901 (4)	C5—C6	1.363 (7)
S1—C1	1.717 (5)	C6—C7	1.415 (7)
S1—C4	1.719 (4)	C6—H6	0.9300
S2—C5	1.716 (4)	C7—C8	1.347 (7)
S2—C8	1.720 (4)	C7—H7	0.9300
C1—C2	1.347 (6)	C8—Se1^i	1.910 (4)
C2—C3	1.417 (7)
C1—Se1—C8^i	98.75 (18)	C3—C4—Se2	126.8 (3)
C5—Se2—C4	97.86 (18)	S1—C4—Se2	122.4 (3)
C1—S1—C4	91.7 (2)	C6—C5—S2	111.2 (3)
C5—S2—C8	91.6 (2)	C6—C5—Se2	126.7 (3)
C2—C1—S1	111.7 (3)	S2—C5—Se2	121.9 (3)
C2—C1—Se1	127.5 (4)	C5—C6—C7	112.6 (4)
S1—C1—Se1	120.8 (2)	C5—C6—H6	123.7
C1—C2—C3	112.3 (4)	C7—C6—H6	123.7
C1—C2—H2	123.9	C8—C7—C6	112.9 (4)
C3—C2—H2	123.9	C8—C7—H7	123.5
C4—C3—C2	113.4 (4)	C6—C7—H7	123.5
C4—C3—H3	123.3	C7—C8—S2	111.6 (3)
C2—C3—H3	123.3	C7—C8—Se1^i	128.6 (3)
C3—C4—S1	110.8 (3)	S2—C8—Se1^i	119.8 (3)
C4—S1—C1—C2	2.9 (4)	C5—Se2—C4—S1	−44.1 (3)
C4—S1—C1—Se1	−177.6 (3)	C8—S2—C5—C6	−0.5 (4)
C8^i—Se1—C1—C2	−107.5 (4)	C8—S2—C5—Se2	−176.0 (3)
C8^i—Se1—C1—S1	73.1 (3)	C4—Se2—C5—C6	113.1 (5)
S1—C1—C2—C3	−2.8 (5)	C4—Se2—C5—S2	−72.1 (3)
Se1—C1—C2—C3	177.7 (3)	S2—C5—C6—C7	0.2 (6)
C1—C2—C3—C4	1.2 (6)	Se2—C5—C6—C7	175.5 (4)
C2—C3—C4—S1	1.0 (5)	C5—C6—C7—C8	0.3 (7)
C2—C3—C4—Se2	177.8 (3)	C6—C7—C8—S2	−0.7 (6)
C1—S1—C4—C3	−2.2 (4)	C6—C7—C8—Se1^i	−178.8 (4)
C1—S1—C4—Se2	−179.1 (3)	C5—S2—C8—C7	0.7 (4)
C5—Se2—C4—C3	139.4 (4)	C5—S2—C8—Se1^i	179.0 (3)

Symmetry code: (i) −x+1, −y+1, −z+2.