4,5-Bis(2-cyano­ethyl­thio)-1,3-di­thiol-2-one

The crystal structure of the title compound, C₉H₈N₂OS₄, is characterized by the planar, conjugated moiety of 4,5-dimercapto-1,3-di­thiole-2-one (dmio), which is substituted by two cyano­ethyl groups, lying on opposite sides of the five-membered ring. This molecular conformation is similar to that of the computationally optimized free mol­ecule with minimum energy. The presence of O and N atoms in the mol­ecule produces many weak interactions in the crystal, quite different from the classical dmit (4,5-dimercapto-1,3-di­thiole-2-thione) alkyl compounds.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.037
• wR factor = 0.141
• Data-to-parameter ratio = 19.8

checkCIF results

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ADDSYM reports no extra symmetry


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          *  none
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S1. Comment

TTF (tetrathiafulvalene), BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene] derivatives and their charge-transfer salts have received great interest for their high electronic conductivity or superconductivity (Williams et al., 1992). The conductivity of the molecular based conductors is directly influenced by the close pack of the molecules in the crystal via various intermolecular interactions such as S···S quasi-bond. The title compound, (I), is a precursor of TTF derivatives and several structures of similar compounds have been investigated. The crystal structures of 2,5,7,9-tetrathiabicyclo[4,3,0]non-1(6)-en-8-one (Scheme; –R—R'- = –CH₂CH₂–) and 4,5-bis(methylthio)-2H-1,3-dithiole-2-one (Scheme; R,R' = –CH₃) have been reported in 1987 (Tucker et al., 1987) and in 1990 (Simonsen et al., 1990), respectively. In the former crystal, the molecule is planar, except for the two methylenes which lie at opposite sides of the plane of the five-membered ring and in the latter crystal, the molecule is also planar, except for one of the two methyl groups. These two compounds are characterized by unsubstituted alkyl groups which connect to the sulfur in the 4- and 5-position; however, structures of the analogues with substituted alkyls possessing electron-attracting groups are rare. In order to understand the structure–conductivity correlations for this kind of compound, an X-ray structural analysis of the title compound (Scheme; R, R' = –CH₂CH₂CN) has been carried out.

The molecular stucture, along with the atom-numbering scheme, is illustrated in Fig. 1. As expected, the atoms of the five-membered dithiole ring and its double-bonded O atom (atom O1) are nearly coplanar, with a maximum deviation from the least-square plane of only 0.003 (2) Å (C2). However, the S3 and S4 atoms have considerable deviations from the plane [-0.196 (1) Å for S3 and 0.047 (1) Å for S4, respectively]. As shown in Fig. 1 and Table 1, C4—S3 and C7—S4 are typical single bonds, while the other C—S bond lengths in the five-membered ring and in the linkage to its two neighboring S atoms are considerably shorter than that of single C—S bond, showing some conjugate character. Combined with the planarity in above discussion, we can see that the conjugacy of 4,5-dimercapto-1,3-dithiole-2-one (dmio) moiety in the title compound is remarkable.

In the crystal, the molecule adopts a conformation with the two cyanoethyl arms located on opposites side of the five-membered ring (see Fig. 1). To check the favorable molecular conformation for a free title molecule, an optimization procedure [by the criterion of energy minimum by using PCMODEL Version 6.0 (Serena Software, 1996)] has been carried out and two optimized conformations were obtained (see Figs. 2 and 3). One is the same-side conformation with its two cyanoethyl arms located on the same side of the five-membered ring corresponding to the MMX energy of -8.784 kcal mol^-1, and the other is the opposite-side conformation with its two cyanoethyls on opposite sides of the ring corresponding to the MMX energy of -18.367 kcal mol^-1. This opposite-side conformation of the free molecule is very similar to the experimentally determined molecular conformation in the crystal. The energy difference between the two free conformations is obvious and so the molecules in the crystal adopt an energy-advantageous conformation.

As shown in Fig. 4 and Table 2, the introduction of O and N atoms produces weak intermolecular interaction in the crystal, such as C7—H7A···O1 and C8—H8A···N1, which set some head-to-tail and tail-to-tail interactions between neighboring molecules. Besides, there is another weak interaction observed, C5—H5A···S3, and this kind of interaction may be responsible for the large deviation from the least-squares plane of the S3 atom. The title compound was easily crystallized as large pale-yellow crystals compared with its precursor compound 4,5-bis(2-cyanoethylthio)-1,3-dithiole-2-thione. This means that the introduction of more weak intermolecular interactions by substituting an S atom (of thiocarbonyl group) for an O atom has a positive effect in improving the stability and packing quality of the crystal.

S2. Experimental

The title compound was prepared according to the literature (Svenstrup et al., 1994). A mixture of 4,5-bis(2-cyanoethylthio)-1,3-dithiole-2-thione (0.03 mol) in chloroform/acetic acid (3:1, 250 ml) and mercury acetate (0.08 mol) was stirred under nitrogen at 313–323 K for 24 h. The resulting precipitate was filtered using Celite and washed thoroughly with chloroform. The combined organic phase was heated to reflux with activated charcoal, cooled to room temperature, washed with sodium hydrogen carbonate solution, water, dried (anhydrous magnesium sulfate) and concentrated in vacuo. The residue was transferred into a 100 ml beaker and several days later large pale crystals were obtained after evaporation of chloroform at room temperature.

S3. Refinement

After checking their presence in the difference map, all H atoms were fixed geometrically and allowed to ride on their attached atoms, which C—H = 0.93–0.97 Å and U_iso(H) = 1.2U_eq(C).

Computing details

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: PLATON (Spek, 2001).

Figures

	Fig. 1. The molecular structure of the title compound showing 15% probability displacement ellipsoids and the atom-numbering scheme. H atoms are drawn as small spheres of arbitrary radii.
	Fig. 2. The molecular structure (view using ORTEP) of the title compound with the two cyanoethyls lying on the same side of the five-membered ring plane. (Depending on the drawing in PCMODEL, the MMX energy may differ in different drawings but the trend is consistent.)
	Fig. 3. The molecular structure (view using ORTEP) of the title compound with the two cyanoethyls lying on the opposite side of the five-membered ring plane.
	Fig. 4. Packing diagram for the title compound showing the weak intermolecular interactions.

4,5-Bis(2'-cyanoethylthio)-1,3-dithiole-2-one

Crystal data

C9H8N2OS4	F(000) = 592
Mr = 288.41	Dx = 1.525 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 9.0334 (12) Å	Cell parameters from 32 reflections
b = 10.0491 (9) Å	θ = 4.9–12.5°
c = 13.860 (2) Å	µ = 0.74 mm^−1
β = 93.539 (12)°	T = 293 K
V = 1255.8 (3) Å^3	Prism, pale yellow
Z = 4	0.58 × 0.4 × 0.3 mm

Data collection

Bruker P4 diffractometer	2399 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.018
Graphite monochromator	θmax = 27.5°, θmin = 2.5°
θ/2θ scans	h = −1→11
Absorption correction: π scan (XSCANS; Bruker, 1996)	k = −1→13
Tmin = 0.236, Tmax = 0.263	l = −18→18
3815 measured reflections	3 standard reflections every 97 reflections
2889 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)] = 0.037	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.141	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max < 0.001
2889 reflections	Δρmax = 0.34 e Å^−3
146 parameters	Δρmin = −0.29 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: 0.013 (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
O1	0.2823 (3)	0.2458 (2)	−0.20010 (14)	0.0985 (8)
S1	0.18015 (7)	0.28950 (5)	−0.02973 (4)	0.0524 (2)
S2	0.34609 (9)	0.48672 (7)	−0.13457 (4)	0.0633 (2)
S3	0.12265 (7)	0.47606 (5)	0.13295 (4)	0.04752 (19)
S4	0.33734 (7)	0.69353 (6)	0.01885 (4)	0.0557 (2)
C1	0.2719 (3)	0.3244 (2)	−0.13591 (16)	0.0621 (6)
C2	0.2104 (2)	0.44367 (19)	0.02595 (14)	0.0397 (4)
C3	0.2867 (3)	0.5335 (2)	−0.02178 (15)	0.0456 (5)
C4	0.1615 (3)	0.3259 (2)	0.20139 (15)	0.0523 (5)
H4A	0.1038	0.3268	0.2581	0.063*
H4B	0.1293	0.2500	0.1622	0.063*
C5	0.3239 (3)	0.3079 (2)	0.23349 (18)	0.0622 (7)
H5A	0.3370	0.2219	0.2646	0.075*
H5B	0.3822	0.3084	0.1770	0.075*
C6	0.3791 (3)	0.4115 (3)	0.30018 (18)	0.0583 (6)
N1	0.4210 (3)	0.4901 (3)	0.3531 (2)	0.0790 (7)
C7	0.2099 (2)	0.7940 (2)	−0.05741 (17)	0.0486 (5)
H7A	0.2009	0.7566	−0.1220	0.058*
H7B	0.1126	0.7931	−0.0315	0.058*
C8	0.2654 (2)	0.9362 (2)	−0.06206 (18)	0.0520 (5)
H8A	0.1906	0.9899	−0.0969	0.062*
H8B	0.2787	0.9711	0.0031	0.062*
C9	0.4044 (3)	0.9486 (2)	−0.10888 (17)	0.0542 (5)
N2	0.5146 (3)	0.9590 (3)	−0.1431 (2)	0.0823 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.166 (2)	0.0740 (14)	0.0575 (11)	0.0074 (16)	0.0269 (13)	−0.0207 (10)
S1	0.0724 (4)	0.0365 (3)	0.0488 (3)	−0.0038 (2)	0.0081 (3)	−0.0051 (2)
S2	0.0845 (5)	0.0606 (4)	0.0470 (3)	0.0006 (3)	0.0210 (3)	0.0087 (3)
S3	0.0590 (3)	0.0417 (3)	0.0426 (3)	0.0063 (2)	0.0086 (2)	−0.00028 (19)
S4	0.0694 (4)	0.0411 (3)	0.0549 (3)	−0.0126 (2)	−0.0111 (3)	0.0091 (2)
C1	0.0927 (18)	0.0533 (13)	0.0412 (11)	0.0096 (13)	0.0125 (11)	−0.0020 (10)
C2	0.0484 (10)	0.0342 (9)	0.0363 (9)	0.0016 (8)	0.0001 (8)	0.0011 (7)
C3	0.0545 (12)	0.0399 (10)	0.0421 (10)	−0.0015 (9)	0.0010 (9)	0.0034 (8)
C4	0.0761 (15)	0.0386 (11)	0.0437 (10)	−0.0093 (10)	0.0154 (10)	0.0019 (8)
C5	0.0893 (18)	0.0461 (12)	0.0523 (12)	0.0203 (12)	0.0144 (12)	0.0101 (10)
C6	0.0543 (13)	0.0663 (15)	0.0549 (12)	0.0088 (12)	0.0080 (10)	0.0095 (12)
N1	0.0636 (14)	0.0956 (19)	0.0762 (16)	−0.0086 (14)	−0.0070 (12)	−0.0021 (15)
C7	0.0430 (10)	0.0445 (11)	0.0579 (12)	−0.0047 (8)	0.0000 (9)	0.0048 (9)
C8	0.0486 (12)	0.0401 (11)	0.0678 (13)	0.0022 (9)	0.0080 (10)	0.0007 (10)
C9	0.0599 (13)	0.0433 (11)	0.0601 (13)	−0.0045 (10)	0.0105 (11)	0.0081 (10)
N2	0.0807 (17)	0.0785 (17)	0.0917 (18)	−0.0140 (13)	0.0374 (15)	0.0053 (14)

Geometric parameters (Å, º)

O1—C1	1.198 (3)	C4—H4B	0.9700
S1—C2	1.745 (2)	C5—C6	1.460 (4)
S1—C1	1.768 (2)	C5—H5A	0.9700
S2—C3	1.748 (2)	C5—H5B	0.9700
S2—C1	1.763 (3)	C6—N1	1.127 (4)
S3—C2	1.755 (2)	C7—C8	1.516 (3)
S3—C4	1.805 (2)	C7—H7A	0.9700
S4—C3	1.756 (2)	C7—H7B	0.9700
S4—C7	1.820 (2)	C8—C9	1.454 (3)
C2—C3	1.335 (3)	C8—H8A	0.9700
C4—C5	1.517 (4)	C8—H8B	0.9700
C4—H4A	0.9700	C9—N2	1.134 (3)
C2—S1—C1	97.07 (11)	C6—C5—H5A	109.0
C3—S2—C1	96.91 (10)	C4—C5—H5A	109.0
C2—S3—C4	101.87 (10)	C6—C5—H5B	109.0
C3—S4—C7	100.32 (10)	C4—C5—H5B	109.0
O1—C1—S2	124.8 (2)	H5A—C5—H5B	107.8
O1—C1—S1	123.3 (2)	N1—C6—C5	178.7 (3)
S2—C1—S1	111.86 (12)	C8—C7—S4	110.40 (15)
C3—C2—S1	116.91 (17)	C8—C7—H7A	109.6
C3—C2—S3	124.55 (17)	S4—C7—H7A	109.6
S1—C2—S3	118.15 (11)	C8—C7—H7B	109.6
C2—C3—S2	117.24 (17)	S4—C7—H7B	109.6
C2—C3—S4	126.35 (19)	H7A—C7—H7B	108.1
S2—C3—S4	116.39 (13)	C9—C8—C7	113.36 (19)
C5—C4—S3	114.00 (16)	C9—C8—H8A	108.9
C5—C4—H4A	108.8	C7—C8—H8A	108.9
S3—C4—H4A	108.8	C9—C8—H8B	108.9
C5—C4—H4B	108.8	C7—C8—H8B	108.9
S3—C4—H4B	108.8	H8A—C8—H8B	107.7
H4A—C4—H4B	107.6	N2—C9—C8	178.2 (3)
C6—C5—C4	112.80 (19)
C3—S2—C1—O1	−179.7 (3)	S1—C2—C3—S4	−177.97 (12)
C3—S2—C1—S1	−0.21 (17)	S3—C2—C3—S4	9.3 (3)
C2—S1—C1—O1	179.9 (3)	C1—S2—C3—C2	−0.1 (2)
C2—S1—C1—S2	0.38 (17)	C1—S2—C3—S4	178.44 (14)
C1—S1—C2—C3	−0.5 (2)	C7—S4—C3—C2	−106.9 (2)
C1—S1—C2—S3	172.73 (13)	C7—S4—C3—S2	74.76 (15)
C4—S3—C2—C3	−140.2 (2)	C2—S3—C4—C5	67.85 (18)
C4—S3—C2—S1	47.15 (15)	S3—C4—C5—C6	63.7 (2)
S1—C2—C3—S2	0.4 (3)	C3—S4—C7—C8	−160.14 (17)
S3—C2—C3—S2	−172.32 (11)	S4—C7—C8—C9	65.0 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5A···S3^i	0.97	2.86	3.830 (2)	177
C7—H7A···O1^ii	0.97	2.48	3.401 (3)	158
C8—H8A···N1^iii	0.97	2.50	3.340 (3)	145

Symmetry codes: (i) −x+1/2, y−1/2, −z+1/2; (ii) −x+1/2, y+1/2, −z−1/2; (iii) x−1/2, −y+3/2, z−1/2.