Butane-1,4-diyl bis­­(benzene­carbodi­thio­ate)

The title compound, C₁₈H₁₈S₄, which lies on an inversion center, adopts a trans–gauche⁺–trans–gauche⁻–trans (tg⁺tg⁻t) conformation of the S—CH₂—CH₂—CH₂—CH₂—S bond sequence. In the crystal, a π–π inter­action with a centroid–centroid distance of 3.8797 (16) Å is observed.

Related literature

For crystal structures and conformations of C₆H₅C(=S)S(CH₂)₂SC(=S)C₆H₅ and C₆H₅C(=O)S(CH₂)₄SC(=O)C₆H₅, see: Abe et al. (2011, 2013). For related compounds, see: Sawanobori et al. (2001); Sasanuma et al. (2002). For the synthesis of piperidinium di­thio­benzoate, see: Kato et al. (1973).

Experimental

Crystal data

• C₁₈H₁₈S₄

• M_r = 362.56

• Monoclinic, P 2₁ /n

• a = 11.0205 (6) Å

• b = 7.2535 (5) Å

• c = 11.3090 (7) Å

• β = 110.805 (2)°

• V = 845.06 (9) ų

• Z = 2

• Cu Kα radiation

• μ = 5.09 mm⁻¹

• T = 173 K

• 0.40 × 0.20 × 0.01 mm

Data collection

• Bruker APEXII CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2001) T_min = 0.235, T_max = 0.951

• 4872 measured reflections

• 1480 independent reflections

• 1468 reflections with I > 2σ(I)

• R_int = 0.028

Refinement

• R[F² > 2σ(F²)] = 0.037

• wR(F²) = 0.100

• S = 1.13

• 1480 reflections

• 100 parameters

• H-atom parameters constrained

• Δρ_max = 0.35 e Å⁻³

• Δρ_min = −0.31 e Å⁻³

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL.

Supporting information

S1. Comment

The aromatic polyesters, [–O(CH₂)_nO(C=O)C₆H₄(C=O)-]_x (n = 2– 4), have been mass-produced and used as fibers, films, bottles, and engineering plastics. In a series of our studies, we have investigated conformational characteristics and configurational properties of their analogs, [–X(CH₂)_nX(C=Y)C₆H₄(C=Y)-]_x, that is, polythioesters (X = S, Y = O, abbreviated herein as PnTS₂) and polydithioesters (X = Y = S, PnTS₄). As model compounds of PnTS₂ and PnTS₄, we have adopted oligomethylenedithiobenzoate (nDBS₂) and oligomethylenetetrathiobenzoate (nDBS₄), respectively. This paper describes synthesis and X-ray diffraction analysis of one of them, 4DBS₄.

Figure 1 shows the molecular structure of 4DBS₄. The S—CH₂—CH₂—CH₂—CH₂—S bonds lie in the trans– gauche⁺–trans–gauche^-–trans (tg⁺tg^-t) conformation. On the other hand, 4DBS₂, a model of P4TS₂, crystallizes to form the g⁺tttg^- conformation (Abe & Sasanuma, 2013). In general, the S—CH₂ single bond prefers the gauche state (Sawanobori et al., 2001; Sasanuma et al., 2002). For instance, the crystalline 2DBS₄ molecule adopts the g⁺tg^- conformation in the S—CH₂–CH₂—S linkage (Abe et al., 2011). By contraries, the two S—CH₂ bonds of 4DBS₄ were found here to be in the trans conformation. Our molecular orbital calculations at the MP2/6–311+G(2 d,p)//B3LYP/6–311+G(2 d,p) level for gaseous 4DBS₄ yielded free energies (relative to the all-trans state) of the two conformers: 0.49 kcal mol^-1 (tg⁺tg^-t) and -0.86 kcal mol^-1 (g⁺tttg^-). Therefore, 4DBS₄ is not allowed to crystallize in the most stable conformation.

In differential scanning calorimetric measurements, a 4DBS₄ sample, which was recrystallized from methanol, exhibited only one endothermic peak at 68 °C on heating, whereas its melt-crystallized sample showed two endothermic peaks at 48 and 68 °C. The former and latter samples yielded powder X-ray diffraction patterns different from each other.

Interestingly, nDBS₄'s (n = 2, 3, 4, and 5) show odd-even effects in melting; 2DBS₄ and 4DBS₄, respectively, melt at 109 and 68 °C, whereas 3DBS₄ and 5DBS₄ are liquid at room temperature but exhibit grass transitions at -51 °C (n = 3) and -54 °C (n = 5).

Related literature

For crystal structures and conformations of C₆H₅C(=S)S(CH₂)₂SC(=S)C₆H₅ and C₆H₅C(=O)S(CH₂)₄SC(=O)C₆H₅, see: Abe et al. (2011, 2013); For related compounds, see: Sawanobori et al. (2001); Sasanuma et al. (2002). For the synthesis of piperidinium dithiobenzoate, see: Kato et al. (1973).

S2. Experimental

Piperidinium dithiobenzoate (1.26 g, 5.3 mmol) was prepared according to the literature (Kato et al., 1973). Dibromobutane (0.54 g, 2.5 mmol) was added dropwise into piperidinium dithiobenzoate dissolved in dimethylformamide (DMF, 15 ml) and then stirred for 8 h under nitrogen atmosphere. The reaction mixture was diluted with a mixture of ethyl acetate and n-hexane (1:4 in volume) and washed thrice with water, and the organic layer was dried overnight over anhydrous magnesium sulfate. The solution was condensed, dissolved in a toluene/n-hexane mixture (1:2 in volume), and fractionated by silica-gel chromatograph (R_f = 0.3–0.5). The collected fractions were condensed and recrystallized from a methanol/n-hexane mixture (1:1 in volume) to yield 4DBS₄ (0.37 g, 41%).

The product was dissolved in chloroform in an open vessel. The vessel was placed in a larger one containing n-hexane, a poor solvent for 4DBS₄, to facilitate precipitation of crystals by vapor diffusion of n-hexane into the chloroform solution.

S3. Refinement

All C—H hydrogen atoms were geometrically positioned with C—H = 0.95 and 0.99 Å for the aromatic and methylene groups, respectively, and refined as riding by U_iso(H) = 1.2 U_eq(C).

Computing details

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. Molecular structure of S,S'-butane-1,4-diyl bis(benzenecarbodithioate) (4DBS4). Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. Packing diagrams of 4DBS4, viewed down the a (a), b (b), and c (c) axes.

Butane-1,4-diyl bis(benzenecarbodithioate)

Crystal data

C18H18S4	F(000) = 380
Mr = 362.56	Dx = 1.425 Mg m^−3
Monoclinic, P21/n	Melting point: 341 K
Hall symbol: -P 2yn	Cu Kα radiation, λ = 1.54178 Å
a = 11.0205 (6) Å	Cell parameters from 5003 reflections
b = 7.2535 (5) Å	θ = 4.8–67.8°
c = 11.3090 (7) Å	µ = 5.09 mm^−1
β = 110.805 (2)°	T = 173 K
V = 845.06 (9) Å^3	Plate, pink
Z = 2	0.40 × 0.20 × 0.01 mm

Data collection

Bruker APEXII CCD area-detector diffractometer	1480 independent reflections
Radiation source: Bruker TXS fine-focus rotating anode	1468 reflections with I > 2σ(I)
Bruker Helios multilayer confocal mirror monochromator	Rint = 0.028
Detector resolution: 8.333 pixels mm^-1	θmax = 68.1°, θmin = 4.8°
ϕ and ω scans	h = −13→13
Absorption correction: multi-scan (SADABS; Bruker, 2001)	k = −8→7
Tmin = 0.235, Tmax = 0.951	l = −13→13
4872 measured reflections

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)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.100	H-atom parameters constrained
S = 1.13	w = 1/[σ^2(Fo^2) + (0.0393P)^2 + 1.0478P] where P = (Fo^2 + 2Fc^2)/3
1480 reflections	(Δ/σ)max < 0.001
100 parameters	Δρmax = 0.35 e Å^−3
0 restraints	Δρmin = −0.31 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 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
C1	−0.0082 (2)	0.2157 (3)	0.3798 (2)	0.0226 (5)
C2	0.0225 (2)	0.2350 (4)	0.5097 (2)	0.0271 (5)
H2	0.1068	0.2029	0.5658	0.033*
C3	−0.0686 (2)	0.3004 (4)	0.5579 (2)	0.0309 (5)
H3	−0.0463	0.3138	0.6467	0.037*
C4	−0.1921 (2)	0.3461 (4)	0.4770 (3)	0.0314 (6)
H4	−0.2547	0.3904	0.5100	0.038*
C5	−0.2237 (2)	0.3270 (4)	0.3480 (3)	0.0347 (6)
H5	−0.3085	0.3581	0.2923	0.042*
C6	−0.1329 (2)	0.2628 (4)	0.2992 (2)	0.0300 (5)
H6	−0.1556	0.2508	0.2103	0.036*
C7	0.0885 (2)	0.1450 (3)	0.3270 (2)	0.0222 (5)
C8	0.3424 (2)	0.0498 (4)	0.3534 (2)	0.0288 (5)
H8A	0.3123	−0.0796	0.3375	0.035*
H8B	0.3313	0.1080	0.2710	0.035*
C9	0.4854 (2)	0.0543 (4)	0.4385 (2)	0.0270 (5)
H9A	0.5121	0.1841	0.4594	0.032*
H9B	0.5381	0.0031	0.3913	0.032*
S1	0.04887 (5)	0.05242 (9)	0.18505 (5)	0.0286 (2)
S2	0.24732 (5)	0.17228 (9)	0.42927 (5)	0.0278 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0177 (10)	0.0217 (12)	0.0276 (11)	−0.0011 (9)	0.0072 (9)	0.0005 (9)
C2	0.0197 (11)	0.0330 (13)	0.0271 (11)	0.0003 (10)	0.0064 (9)	0.0023 (10)
C3	0.0304 (12)	0.0364 (14)	0.0286 (12)	−0.0004 (11)	0.0136 (10)	−0.0013 (11)
C4	0.0255 (12)	0.0310 (14)	0.0429 (14)	0.0014 (10)	0.0186 (11)	−0.0034 (11)
C5	0.0189 (11)	0.0430 (16)	0.0389 (14)	0.0067 (11)	0.0063 (10)	−0.0015 (12)
C6	0.0210 (11)	0.0391 (15)	0.0269 (11)	0.0026 (10)	0.0047 (9)	−0.0026 (10)
C7	0.0169 (10)	0.0228 (12)	0.0255 (11)	0.0010 (8)	0.0058 (8)	0.0044 (9)
C8	0.0178 (11)	0.0406 (15)	0.0283 (11)	0.0071 (10)	0.0087 (9)	−0.0003 (10)
C9	0.0172 (11)	0.0335 (14)	0.0312 (12)	0.0040 (9)	0.0097 (9)	0.0022 (10)
S1	0.0211 (3)	0.0387 (4)	0.0246 (3)	−0.0006 (2)	0.0062 (2)	−0.0052 (2)
S2	0.0143 (3)	0.0394 (4)	0.0271 (3)	0.0035 (2)	0.0040 (2)	−0.0065 (2)

Geometric parameters (Å, º)

C1—C2	1.392 (3)	C6—H6	0.9500
C1—C6	1.395 (3)	C7—S1	1.649 (2)
C1—C7	1.487 (3)	C7—S2	1.732 (2)
C2—C3	1.386 (4)	C8—C9	1.527 (3)
C2—H2	0.9500	C8—S2	1.807 (2)
C3—C4	1.383 (4)	C8—H8A	0.9900
C3—H3	0.9500	C8—H8B	0.9900
C4—C5	1.381 (4)	C9—C9^i	1.530 (5)
C4—H4	0.9500	C9—H9A	0.9900
C5—C6	1.384 (3)	C9—H9B	0.9900
C5—H5	0.9500
C2—C1—C6	118.6 (2)	C1—C6—H6	119.8
C2—C1—C7	121.2 (2)	C1—C7—S1	123.48 (16)
C6—C1—C7	120.2 (2)	C1—C7—S2	113.01 (16)
C3—C2—C1	120.7 (2)	S1—C7—S2	123.51 (13)
C3—C2—H2	119.6	C9—C8—S2	109.43 (16)
C1—C2—H2	119.6	C9—C8—H8A	109.8
C4—C3—C2	120.1 (2)	S2—C8—H8A	109.8
C4—C3—H3	120.0	C9—C8—H8B	109.8
C2—C3—H3	120.0	S2—C8—H8B	109.8
C5—C4—C3	119.6 (2)	H8A—C8—H8B	108.2
C5—C4—H4	120.2	C8—C9—C9^i	113.5 (2)
C3—C4—H4	120.2	C8—C9—H9A	108.9
C4—C5—C6	120.5 (2)	C9^i—C9—H9A	108.9
C4—C5—H5	119.7	C8—C9—H9B	108.9
C6—C5—H5	119.7	C9^i—C9—H9B	108.9
C5—C6—C1	120.4 (2)	H9A—C9—H9B	107.7
C5—C6—H6	119.8	C7—S2—C8	104.20 (11)
C6—C1—C2—C3	−0.3 (4)	C2—C1—C7—S1	158.30 (19)
C7—C1—C2—C3	−179.8 (2)	C6—C1—C7—S1	−21.2 (3)
C1—C2—C3—C4	0.5 (4)	C2—C1—C7—S2	−22.3 (3)
C2—C3—C4—C5	−0.3 (4)	C6—C1—C7—S2	158.2 (2)
C3—C4—C5—C6	−0.1 (4)	S2—C8—C9—C9^i	66.7 (3)
C4—C5—C6—C1	0.3 (4)	C1—C7—S2—C8	172.54 (17)
C2—C1—C6—C5	−0.1 (4)	S1—C7—S2—C8	−8.11 (19)
C7—C1—C6—C5	179.4 (2)	C9—C8—S2—C7	−176.88 (17)

Symmetry code: (i) −x+1, −y, −z+1.