4,5-Propyl­enedi­thio-1,3-di­thiole-2-thione and 4,5-propyl­enedi­thio-1,3-di­thiol-2-one

4,5-Propyl­ene­di­thio-1,3-di­thiole-2-thione, C₆H₆S₅, (I), crystallizes in the centrosymmetric space group P2₁/c. The molecular packing is characterized by pairs of S...S intermolecular contacts between neighbouring mol­ecules, which may account for the rather high thermal stablity of the crystal. 4,5-Propyl­ene­di­thio-1,3-di­thiol-2-one, C₆H₆OS₄, (II), in which an O atom replaces the terminal S atom of (I), crystallizes in the non-centrosymmetric polar space group Cc. The packing pattern of (II) indicates that the macropolarization direction is along [101]. Although the packing patterns are qualitatively significantly different, the molecular structures of (I) and (II) are similar, each exhibiting a chair conformation.

S1. Comment

TTF (tetrathiafulvalene) and BEDT-TTF (bis(ethylenedithio)-tetrathiafulvalene) derivatives and their charge-transfer salts have received a lot of attention because of their high electronic conductivity or superconductivity (Williams et al., 1992). Replacement of the two ethylene units of BEDT-TTF with two propylene units gives another donor, namely BPDT-TTF [bis(propylenedithio)-tetrathiafulvalene] (Porter et al., 1987). In the course of synthesizing new BPDT-TTF-based molecular electronic conductors, we have determined the crystal structures of (I) and (II), which are the precursors of BPDT-TTF.

The molecular geometries of (I) and (II) are illustrated in Figs. 1 and 2, and bond lengths and angles are listed in Tables 1 and 2. In (I), the S5—C1 distance [1.652 (3) Å] is slightly longer than the typical C═S double bond. The C2=C3 distance [1.341 (4) Å] corresponds to a double bond. The bonds involving the methylene C atoms, S3—C4 and S4—C6, have lengths of 1.816 (3) and 1.814 (4) Å, respectively, characteristic of S—C single bonds. The remaining six S—C bonds are in the range 1.723 (3)–1.756 (3) Å, which lies between the typical values for single S—C and double S=C bonds. As a result of replacing the terminal S atom of (I) by an O atom, the terminal C=O bond length [1.228 (8) Å] in (II) is drastically shorter than the corresponding C=S bond length in (I). This shortening is accompanied by an apparent increase in the neighboring C1—S1 and C1—S2 bond lengths, which average to 1.745 (6) Å [cf. 1.724 (3) Å for (I)]. This behaviour indicates that conjugation is more prominent in (I) than in (II). The other bond lengths in (II) are similar to their counterparts in (I).

Both (I) and (II) have planar five-membered rings (S1/C1/S2/C2/C3), with the maximum deviations from their least-squares planes being 0.011 (3) Å for atom C1 in (I) and 0.021 (7) Å for atom C1 in (II). In fact, as shown in Fig. 1 and 2, eight atoms (S5, C1, S1, S2, C2, C3, S3 and S4) in (I) are virtually coplanar. Three planes – plane 1 (S5/C1/S1/S2/C2/C3/S3/S4), plane 2 (S3/C4/C6/S4) and plane 3 (C4–C6) – form an overall chair conformation. The dihedral angle between planes 1 and 2 is 65.9 (1)°. Compound (II) also has a chair conformation, with the dihedral angle between plane 1 (O1/C1/S1/S2/C2/C3/S3/S4) and plane 2 (S3/C4/C6/S4) being 61.2 (2)°.

Compound (I) crystallizes in the centrosymmetric space group P2₁/c. As shown in Fig.3, there are several intermolecular S···S contacts shorter than 3.70 Å (the sum of the van der Waals radii). The S1···S1B(1 − x, 2 − y, 1 − z), S5···S1B(1 − x, 2 − y, 1 − z) and S2···S2C(1 − x, 1 − y, 1 − z) distances are 3.388 (2), 3.607 (2) and 3.637 (2) Å, respectively. Although there is also a short intermolecular S···S contact in (II) [S3···S4(x, −y, −1/2 + z) = 3.685 (2) Å], the S···S interactions in (II) are clearly less important than those in (I). The remarkable S···S intermolecular interactions of (I) endow the crystal with extra thermal stability, and the measured melting point of (I) (432.6 K) is considerably higher than that of (II) (393.5 K). Another important factor contributing to the thermal stability of (I) is the antiparallel packing mode of the molecular dipole moments, which results in strong intermolecular dipole–dipole interactions. The interesting packing feature of (II) is that all molecular dipole moments are basically in the same direction (see Fig. 4); this parallel packing arrangement results in a non-centrosymmetric polar space group, Cc, with the macropolarization direction along [1 0 1]. Most polar molecules crystallize in centrosymmetric structures with an antiparallel packing motif, as is the case with (I). Moreover, the probability of polar molecules crystallizing with a non-centrosymmetric polar structure, such as in the case of (II), is quite small.

S2. Experimental

Compound (I) was prepared according to the method of Kumasaki et al. (1998). (Bu₄N)₂[Zn(dmit)₂] (dmit is the 2-thioxo-1,3-dithiole-4,5-dithiolate dianion, C₃S₅²⁻) (57 g) was dissolved in acetonitrile (200 ml) and 1,3-dibromopropane (26 g) was added. The solution was stirred for 2 d at room temperature. The resulting orange precipitate was filtered off, chloroform was added to the residue and the solution was filtered. Activated charcoal was added to the filtrate and the solution was refluxed for 1.5 h. The solution was filtered and methanol was added. Compound (I) was obtained from this solution at room temperature. Compound (II) was obtained by the following procedure. Compound (I) (2.4 g) and Hg(CH₃COO)₂ (8 g) were added to chloroform–acetic acid (3:1; 120 ml). The solution was stirred at room temperature for 2 h. A white precipitate was obtained and filtered off. The filtered solution was washed with water and with a saturated aqueous NaHCO₃ solution. The solution was filtered and methanol was added. Milky white crystals were obtained.

S3. Refinement

The positions of the H atoms were checked in a difference Fourier map, and then all H atoms were positioned geometrically and allowed to ride on their attached atoms [C—H = 0.93–0.97 Å and U_iso(H) = 1.2U_eq(C)].

Computing details

For both compounds, data collection: XSCANS (Bruker, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL (Bruker, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL.

Figures

	Fig. 1. Molecular structure of (I). Displacement ellipsoids are drawn at the 50% level.
	Fig. 2. Molecular structure of (II). Displacement ellipsoids are drawn at the 50% level.
	Fig. 3. Packing in the structure of (I). The intermolecular S1···S1B(1 − x, 2 − y, 1 − z), S5···S1B(1 − x, 2 − y, 1 − z), S1···S5B(1 − x, 2 − y, 1 − z) and S2···S2C(1 − x, 1 − y, 1 − z) distances are 3.388 (2), 3.607 (2), 3.607 (2) and 3.637 (2) Å, respectively.
	Fig. 4. Packing of (II), showing the macropolarization direction along [1 0 1].

(I)

Crystal data

C6H6S5	Dx = 1.711 Mg m^−3
Mr = 238.41	Melting point: 432.6 K
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 4.6572 (13) Å	Cell parameters from 15 reflections
b = 10.9765 (14) Å	θ = 5.7–12.5°
c = 18.1026 (17) Å	µ = 1.18 mm^−1
β = 90.147 (11)°	T = 293 K
V = 925.4 (3) Å^3	Prism, pale yellow
Z = 4	0.22 × 0.16 × 0.12 mm
F(000) = 488

Data collection

Bruker P4 diffractometer	1331 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.026
Graphite monochromator	θmax = 27.5°, θmin = 2.2°
ω scans	h = −6→1
Absorption correction: ψ scan XSCANS (Bruker, 1996)	k = −14→1
Tmin = 0.791, Tmax = 0.868	l = −23→23
3160 measured reflections	3 standard reflections every 97 reflections
2110 independent reflections	intensity decay: 1%

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)] = 0.036	H-atom parameters constrained
wR(F^2) = 0.093	w = 1/[σ^2(Fo^2) + (0.033P)^2 + 0.1689P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max < 0.001
2110 reflections	Δρmax = 0.34 e Å^−3
101 parameters	Δρmin = −0.30 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0145 (13)

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
S5	0.8413 (2)	0.84196 (10)	0.41231 (5)	0.0560 (3)
S1	0.5764 (2)	0.88534 (8)	0.55954 (4)	0.0437 (2)
S2	0.4518 (2)	0.66204 (8)	0.48310 (4)	0.0427 (2)
S3	0.2061 (2)	0.82882 (8)	0.69005 (4)	0.0447 (2)
S4	0.0646 (2)	0.56337 (8)	0.60079 (5)	0.0462 (3)
C1	0.6330 (7)	0.7989 (3)	0.48127 (16)	0.0392 (8)
C2	0.3417 (7)	0.7858 (3)	0.60344 (15)	0.0350 (7)
C3	0.2820 (7)	0.6815 (3)	0.56797 (15)	0.0348 (7)
C4	0.3671 (8)	0.7153 (3)	0.75024 (17)	0.0452 (8)
H4A	0.5666	0.7057	0.7362	0.054*
H4B	0.3647	0.7467	0.8003	0.054*
C5	0.2285 (8)	0.5902 (3)	0.75068 (17)	0.0472 (9)
H5A	0.0246	0.6005	0.7595	0.057*
H5B	0.3063	0.5448	0.7921	0.057*
C6	0.2648 (8)	0.5134 (3)	0.68137 (17)	0.0466 (9)
H6A	0.2078	0.4305	0.6927	0.056*
H6B	0.4671	0.5118	0.6688	0.056*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S5	0.0586 (6)	0.0692 (6)	0.0403 (5)	−0.0012 (6)	0.0166 (4)	0.0100 (5)
S1	0.0573 (6)	0.0393 (4)	0.0345 (4)	−0.0049 (4)	0.0069 (4)	0.0026 (3)
S2	0.0536 (6)	0.0428 (5)	0.0318 (4)	0.0016 (4)	0.0085 (4)	−0.0032 (3)
S3	0.0600 (6)	0.0402 (5)	0.0340 (4)	0.0080 (5)	0.0114 (4)	−0.0023 (4)
S4	0.0457 (5)	0.0495 (5)	0.0434 (4)	−0.0103 (4)	0.0050 (4)	−0.0016 (4)
C1	0.0409 (18)	0.0451 (19)	0.0316 (15)	0.0050 (16)	0.0018 (14)	0.0029 (14)
C2	0.0397 (18)	0.0366 (16)	0.0288 (14)	0.0051 (15)	0.0055 (14)	0.0026 (13)
C3	0.0359 (17)	0.0375 (17)	0.0309 (15)	0.0032 (15)	0.0015 (13)	0.0001 (13)
C4	0.051 (2)	0.054 (2)	0.0314 (16)	0.0035 (18)	0.0004 (16)	0.0040 (15)
C5	0.054 (2)	0.050 (2)	0.0369 (16)	0.0054 (19)	0.0070 (16)	0.0114 (15)
C6	0.055 (2)	0.0384 (18)	0.0462 (18)	0.0033 (18)	0.0113 (17)	0.0085 (15)

Geometric parameters (Å, º)

S5—C1	1.652 (3)	C2—C3	1.341 (4)
S1—C1	1.726 (3)	C4—C5	1.518 (5)
S1—C2	1.739 (3)	C4—H4A	0.9700
S2—C1	1.723 (3)	C4—H4B	0.9700
S2—C3	1.743 (3)	C5—C6	1.521 (4)
S3—C2	1.756 (3)	C5—H5A	0.9700
S3—C4	1.816 (3)	C5—H5B	0.9700
S4—C3	1.750 (3)	C6—H6A	0.9700
S4—C6	1.814 (4)	C6—H6B	0.9700
C1—S1—C2	97.31 (15)	C5—C4—H4B	108.1
C1—S2—C3	97.67 (15)	S3—C4—H4B	108.1
C2—S3—C4	101.67 (15)	H4A—C4—H4B	107.3
C3—S4—C6	101.55 (16)	C4—C5—C6	116.7 (3)
S5—C1—S2	123.55 (19)	C4—C5—H5A	108.1
S5—C1—S1	123.6 (2)	C6—C5—H5A	108.1
S2—C1—S1	112.80 (18)	C4—C5—H5B	108.1
C3—C2—S1	116.6 (2)	C6—C5—H5B	108.1
C3—C2—S3	125.6 (2)	H5A—C5—H5B	107.3
S1—C2—S3	117.83 (18)	C5—C6—S4	116.0 (2)
C2—C3—S2	115.6 (2)	C5—C6—H6A	108.3
C2—C3—S4	126.1 (2)	S4—C6—H6A	108.3
S2—C3—S4	118.21 (18)	C5—C6—H6B	108.3
C5—C4—S3	116.7 (2)	S4—C6—H6B	108.3
C5—C4—H4A	108.1	H6A—C6—H6B	107.4
S3—C4—H4A	108.1

(II)

Crystal data

C6H6OS4	Dx = 1.621 Mg m^−3
Mr = 222.35	Melting point: 393.5 K
Monoclinic, Cc	Mo Kα radiation, λ = 0.71073 Å
a = 16.358 (4) Å	Cell parameters from 40 reflections
b = 4.5009 (11) Å	θ = 8.9–14.2°
c = 13.066 (3) Å	µ = 0.98 mm^−1
β = 108.736 (15)°	T = 293 K
V = 911.0 (4) Å^3	Plate, pale yellow
Z = 4	0.34 × 0.22 × 0.02 mm
F(000) = 456

Data collection

Bruker P4 diffractometer	925 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.035
Graphite monochromator	θmax = 27.5°, θmin = 2.6°
θ/2θ scans	h = −1→20
Absorption correction: ψ scan XSCANS (Bruker, 1996)	k = −5→1
Tmin = 0.665, Tmax = 0.982	l = −16→16
1439 measured reflections	3 standard reflections every 97 reflections
1150 independent reflections	intensity decay: 1%

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)] = 0.044	H-atom parameters constrained
wR(F^2) = 0.107	w = 1/[σ^2(Fo^2) + (0.0612P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
1150 reflections	Δρmax = 0.26 e Å^−3
100 parameters	Δρmin = −0.39 e Å^−3
2 restraints	Absolute structure: The Flack parameter was refined (Flack, 1983), but did not give a clear result. This structure does not involve an absolute configuration question, and the absolute structure determination does not influence the interpretation of the chemical structure.
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.3 (2)

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
O1	0.2758 (3)	0.6940 (15)	0.3317 (4)	0.0885 (17)
S1	0.42429 (9)	0.5282 (5)	0.31386 (10)	0.0633 (5)
S2	0.37451 (9)	0.4254 (5)	0.50660 (11)	0.0619 (5)
S3	0.59282 (9)	0.2158 (4)	0.39996 (10)	0.0528 (4)
S4	0.53331 (11)	0.0880 (4)	0.62378 (12)	0.0589 (4)
C1	0.3453 (4)	0.5705 (17)	0.3749 (4)	0.0611 (17)
C2	0.4977 (4)	0.3332 (14)	0.4199 (4)	0.0457 (12)
C3	0.4752 (4)	0.2816 (13)	0.5084 (4)	0.0461 (13)
C4	0.6738 (4)	0.4126 (15)	0.5074 (5)	0.0550 (14)
H4A	0.7256	0.4304	0.4871	0.066*
H4B	0.6528	0.6121	0.5119	0.066*
C5	0.6981 (4)	0.2747 (14)	0.6182 (4)	0.0541 (14)
H5A	0.7517	0.3637	0.6627	0.065*
H5B	0.7090	0.0649	0.6116	0.065*
C6	0.6323 (4)	0.3049 (16)	0.6766 (4)	0.0581 (15)
H6B	0.6165	0.5128	0.6758	0.070*
H6A	0.6598	0.2489	0.7515	0.070*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.050 (3)	0.140 (5)	0.063 (3)	0.033 (3)	0.001 (2)	−0.003 (3)
S1	0.0449 (8)	0.1028 (13)	0.0375 (6)	0.0088 (9)	0.0067 (5)	0.0087 (7)
S2	0.0418 (8)	0.0947 (13)	0.0525 (7)	0.0073 (9)	0.0197 (6)	0.0011 (8)
S3	0.0437 (7)	0.0749 (10)	0.0419 (6)	0.0051 (8)	0.0166 (5)	−0.0090 (7)
S4	0.0591 (9)	0.0665 (10)	0.0538 (7)	0.0105 (9)	0.0217 (7)	0.0180 (7)
C1	0.045 (3)	0.086 (5)	0.047 (3)	0.006 (3)	0.008 (3)	−0.007 (3)
C2	0.035 (3)	0.059 (3)	0.041 (2)	−0.002 (3)	0.009 (2)	−0.007 (2)
C3	0.041 (3)	0.052 (3)	0.044 (2)	−0.003 (3)	0.013 (2)	−0.003 (2)
C4	0.036 (3)	0.067 (4)	0.060 (3)	−0.001 (3)	0.013 (3)	−0.012 (3)
C5	0.044 (3)	0.054 (3)	0.053 (3)	0.007 (3)	0.001 (2)	−0.011 (3)
C6	0.058 (3)	0.068 (4)	0.042 (2)	0.010 (3)	0.007 (2)	−0.009 (3)

Geometric parameters (Å, º)

O1—C1	1.228 (8)	C2—C3	1.342 (7)
S1—C1	1.733 (6)	C4—C5	1.507 (8)
S1—C2	1.750 (6)	C4—H4A	0.9700
S2—C1	1.757 (6)	C4—H4B	0.9700
S2—C3	1.763 (6)	C5—C6	1.512 (9)
S3—C2	1.740 (5)	C5—H5A	0.9700
S3—C4	1.821 (6)	C5—H5B	0.9700
S4—C3	1.736 (6)	C6—H6B	0.9700
S4—C6	1.826 (7)	C6—H6A	0.9700
C1—S1—C2	96.6 (3)	C5—C4—H4B	108.2
C1—S2—C3	96.2 (3)	S3—C4—H4B	108.2
C2—S3—C4	101.6 (3)	H4A—C4—H4B	107.4
C3—S4—C6	103.4 (3)	C4—C5—C6	115.9 (5)
O1—C1—S1	123.7 (5)	C4—C5—H5A	108.3
O1—C1—S2	122.6 (5)	C6—C5—H5A	108.3
S1—C1—S2	113.7 (3)	C4—C5—H5B	108.3
C3—C2—S3	125.6 (4)	C6—C5—H5B	108.3
C3—C2—S1	117.4 (4)	H5A—C5—H5B	107.4
S3—C2—S1	116.9 (3)	C5—C6—S4	116.7 (4)
C2—C3—S4	127.6 (4)	C5—C6—H6B	108.1
C2—C3—S2	116.0 (4)	S4—C6—H6B	108.1
S4—C3—S2	116.4 (3)	C5—C6—H6A	108.1
C5—C4—S3	116.3 (5)	S4—C6—H6A	108.1
C5—C4—H4A	108.2	H6B—C6—H6A	107.3
S3—C4—H4A	108.2