1,2-Bis[(pyridin-2-ylmeth­yl)sulfanyl]ethane and its dimorphic hydro­chloride salt

Although having been described as a liquid in the literature for 41 years, 1,2-bis­[(pyridin-2-ylmeth­yl)sulfan­yl]ethane, C₁₄H₁₆N₂S₂, (I), has now been obtained as monoclinic crystals via a new and convenient method of purification. Mol­ecules of (I) are located on crystallographic inversion centres and are held together by C-H...N and C-H...S inter­actions, resulting in the formation of a three-dimensional network structure. In addition, two polymorphs of the corres­ponding hydro­chloride salt, 2-[({2-[(pyridin-1-ium-2-ylmeth­yl)sulfan­yl]eth­yl}sulfan­yl)meth­yl]pyridin-1-ium di­chlor­ide, C₁₄H₁₈N₂S₂²⁺·2Cl^-, (II) and (III), have been isolated. Mol­ecules of (II) and (III) have similar conformations and are located on inversion centres. Both polymorphs form three-dimensional networks through N-H...Cl, C-H...Cl and C-H...S inter­actions. The structure of (III) displays voids of 35 Å³.

S1. Comment

The synthesis of 1,2-bis[(pyridin-2-ylmethyl)sulfanyl]ethane, (I), was first reported by Livingstone & Nolan (1970). It was prepared by deprotonation of ethane-1,2-dithiol using sodium ethoxide, followed by a reaction with 2-picolyl chloride. The product was obtained as an oil, which the authors failed to distil. More recent publications (Sarkar et al., 2009) also describe the compound as an oil, and when it was prepared in our laboratory we initially also obtained a golden-brown viscous oil. However, the second batch we prepared crystallized abruptly after 11 d; the crystallization occurred at ambient temperature after a small amount had been withdrawn from the bottle with a syringe. In the preceding days, the sample had been subjected to the same procedure numerous times, without nucleation. The crystallization of approximately 5 g was complete within 2 min and was accompanied by the evolution of heat. Nearly colourless crystals of (I), with a melting point of 324 K, could be separated from a small amount of brown oily residue by washing with a small amount of benzene. The crystallization of (I) therefore proved to be a perfect mode of purification. All subsequent syntheses of this compound in our laboratory have invariably yielded a crystalline product within hours.

Xylitol [systematic name: (2R,3R,4S)-pentane-1,2,3,4,5-pentaol] is another compound with a similar history. It was first obtained as a syrup in 1891, independently by Fischer & Stahel (1891) and Bertrand (1891); it was not until 1942 that crystalline xylitol was reported (Wolfrom & Kohn, 1942). Interestingly, crystalline xylitol was first obtained as a metastable hygroscopic form (monoclinic, m.p. 334 K). In 1943, a high-melting form (orthorhombic, m.p. 367 K) was reported (Carson et al.,1943), but the monoclinic form has been very difficult to obtain (Kim & Jeffrey, 1969) and its crystal structure is still not found in the Cambridge Structural Database (Version 5.32, May 2011 update; Allen, 2002).

A single crystal of (I) could be separated from the solid mass, and we report herein its crystal structure. The molecular conformation about the central CH₂—CH₂ bond in (I) is anti, and the molecule is located on an inversion centre (Fig. 1). There are two sets of intermolecular hydrogen bonds, involving the adjacent aromatic atoms H3 and H4, C3—H3···S1ⁱ and C4—H4···N1ⁱⁱ (see Table 1 for geometric details and symmetry codes). These intermolecular interactions result in the formation of a three-dimensional hydrogen-bonded network structure. Since molecules of (I) are centrosymmetric, each molecule forms eight interactions with eight adjacent molecules. The two molecules accepting hydrogen bonds from atoms H3 and H4 stack parallel to the crystallographic a axis, and so do the molecules accepting hydrogen bonds from atoms H3 and H4 at (-x, -y + 1, -z). Thus, the crystal structure is built up by stacks along the a axis (Fig. 2). There are no intermolecular interactions within the stacks.

Compound (I) was prepared in order to use it as a ligand in the formation of transition metal complexes. Two attempts to prepare complexes with vanadium(IV) and molybdenum(V) failed and led to the crystallization of the dihydrochloride salt, 2-[({2-[(pyridin-1-ium-2-ylmethyl)sulfanyl]ethyl}sulfanyl)methyl]pyridin-1-ium dichloride, which was obtained as two different polymorphs, (II) and (III), respectively. In the first case, (II) was prepared intentionally by the addition of dilute hydrochloric acid to render (I) water soluble. In the second case, hydrochloride salt (III) was obtained due to the release of hydrogen chloride as a result of hydrolysis of the molybdenum(V) chloride used as reactant. We have made no attempt to establish the reproducibility of the formation of these polymorphs, neither have we conducted any studies on the crystallization of pure 2-[({2-[(pyridin-1-ium-2-ylmethyl)sulfanyl]ethyl}sulfanyl)methyl]pyridin-1-ium dichloride. A higher density and more efficient packing in (II) than in (III) make it probable, however, that (II) would be the more favoured polymorph (Burger & Ramberger, 1979).

The molecular conformation of (II) (Fig. 3) is similar to that found in (I). Both adopt an anti conformation about the central CH₂—CH₂ bond, and both have molecules located on inversion centres. The difference between the two molecular structures is the conformation about the C5—C6 bond. In (I), the S1—C6—C5—N1 torsion angle is 94.17 (12)°, while the corresponding torsion angle in (II) is -79.25 (15)°. The shortest intermolecular distance in (II) is the N1—H1N···Cl1 hydrogen bond (Table 2). In addition, there are three sets of C—H···Cl interactions and one set of C—H···S interactions. The C—H···S interactions, involving H6A and S1(-x + 1/2, y + 1/2, -z + 3/2), are the only short interactions between adjacent cations; the cationic molecules are mainly held together by interactions with the chloride ions. The intermolecular interactions in (II) result in the formation of a three-dimensional network structure (Fig. 4).

The molecular conformation found in polymorph (III) (Fig. 5) is very similar to that found in (II), with the molecules located on crystallographic inversion centres. As in the case of (II), the shortest intermolecular contact in (III) is the N—H···Cl interaction (Table 3). In addition, there are five sets of C—H···Cl interactions involving all four aromatic H atoms and atom H7B. There is also a short C—H···S contact involving H6B and S1(x + 1, y + 1, z). As in the cases of (I) and (II), these interactions give rise to the formation of a three-dimensional network structure.

One obvious difference between the crystal packing of (II) and (III) is the twofold axis parallel to the b axis in (III), which gives an alternating orientation of molecules when viewed along the c axis (Fig. 6).

The most remarkable feature in the crystal structure of (III) is, however, the presence of voids (Fig. 7), each with a volume of 35 ų, corresponding to ca 4.3% of the unit-cell volume. The presence of voids larger than approximately 25 ų is generally considered rare (Atwood, Barbour & Jerga, 2002; Atwood, Barbour et al., 2002). These voids are only slightly smaller than the volume typically occupied by a water molecule (ca 45 ų). No significant electron density was observed within the voids. The largest peak in the difference Fourier map is located in the close vicinity of the C6—S1 bond. The voids are not likely to have arisen from loss of cocrystallized solvent molecules, since the crystals were mounted at low temperature only minutes after being removed from the mother liquor. This time is probably too short for a quantitative loss of a molecule such as water, which would be expected to form strong hydrogen bonds with the other constituents in the crystal structure, while cocrystallized diethyl ether would most likely have left a far larger void. Other recent examples of small organic molecules crystallizing with voids include guanidinium 2-phenylacetate, with voids of 86.5 ų (Smith & Wermuth, 2010), (2E,4E)-1-(6-chloro-2-methyl-4-phenyl-3-quinolyl)-5-phenylpenta-2,4-dien-1-one, with voids of 35 ų (Loh et al., 2010) and diammonium biphenyl-4,4'-disulfonate, with voids of 43 ų (Smith et al., 2008).

Related literature

For related literature, see: Allen (2002); Atwood, Barbour & Jerga (2002); Atwood, Barbour, Jerga & Schottel (2002); Bertrand (1891); Burger & Ramberger (1979); Carson et al. (1943); Fischer & Stahel (1891); Kim & Jeffrey (1969); Livingstone & Nolan (1970); Loh et al. (2010); Sarkar et al. (2009); Smith & Wermuth (2010); Smith et al. (2008); Wolfrom & Kohn (1942).

S2. Experimental

For the preparation of (I), sodium (6.4 g, 0.28 mol) was dissolved in absolute ethanol (200 ml) at 303–313 K under a nitrogen atmosphere. The solution was cooled on ice and ethane-1,2-dithiol (5.1 ml, 0.061 mol) was added. After 20 min, a solution of 2-chloromethylpyridinium chloride (19.68 g, 0.12 mol) in absolute ethanol (140 ml) was added slowly. The solution was stirred for 30 min at ambient temperature, refluxed for 4 h under a nitrogen atmosphere and finally stirred at ambient temperature overnight. Water (50 ml) was added and the ethanol was evaporated. The residue was extracted with dichloromethane (3 × 100 ml). The combined organic phases were washed with water (100 ml) and evaporated to a brown oil, which crystallized within hours. The crystalline mass was washed rapidly with a few millilitres of ice-cooled benzene to give almost colourless crystalline (I) (yield 12.1 g, 67%; m.p. 324.4–324.8 K). A second crop was recovered from the filtrate. The product can be recrystallized from hot benzene. The spectroscopic data for compound (I) are given in the archived CIF.

For the preparation of (II), vanadyl perchlorate hydrate (0.11 g, ca 0.4 mmol) and 1,2-bis[(pyridin-2-ylmethyl)sulfanyl]ethane (0.11 g, 0.4 mmol) were added to distilled water (5 ml). Hydrochloric acid (4.0 M) was added dropwise until a clear-blue solution was obtained. Colourless crystals of (II) formed after a few days upon slow evaporation of the solvent.

For the preparation of (III), molybdenum(V) chloride (0.11 g, 0.4 mmol) was dissolved in acetone (1.5 ml) and a solution of 1,2-bis[(pyridin-2-ylmethyl)sulfanyl]ethane (0.11 g, 0.4 mmol) in ??? was added. The precipitate which formed was filtered off, washed with acetone (5 ml) and dissolved in dimethyl sulfoxide (3 ml). The solution was filtered and divided into three equal parts in three vials, and diethyl ether vapour was diffused into each solution. In each vial, colourless crystals of (III) and a red microcrystalline by-product formed after a few days.

S3. Refinement

The H atoms in (I) were located in a difference Fourier map and were freely refined. In (II) and (III), the N-bound H atoms were located in difference Fourier maps and were freely refined. The C-bound H atoms in (II) and (III) were included in calculated positions and refined using a riding model, with C—H = 0.95 (aromatic) or 0.99 Å (methylene), and with U_iso(H)= 1.5U_eq(C).

Computing details

For all compounds, data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure of (I), showing the crystallographic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry code: (i) -x, -y + 1, -z.]
	Fig. 2. The hydrogen-bonded network structure of (I), viewed along the a axis. H atoms not involved in C—H···S and C—H···N interactions (dashed lines) have been omitted for clarity.
	Fig. 3. The molecular structure of (II), showing the crystallographic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry code: (ii) -x + 1, -y, -z + 2.]
	Fig. 4. The crystal packing of (II), viewed along the a axis. H atoms have been omitted for clarity.
	Fig. 5. The molecular structure of (III), showing the crystallographic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry code: (iii) -x + 1, -y, -z + 1.]
	Fig. 6. The crystal packing of (III), viewed along the c axis. H atoms have been omitted for clarity.
	Fig. 7. The location of voids (shaded; red in the electronic version of the paper) in the unit cell of (III).

(I) 1,2-bis[(pyridin-2-ylmethyl)sulfanyl]ethane

Crystal data

C14H16N2S2	F(000) = 292
Mr = 276.41	Dx = 1.335 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 9932 reflections
a = 4.6910 (2) Å	θ = 2.5–26.0°
b = 10.1688 (6) Å	µ = 0.37 mm^−1
c = 14.5806 (8) Å	T = 120 K
β = 98.679 (2)°	Needle, white
V = 687.56 (6) Å^3	0.36 × 0.20 × 0.18 mm
Z = 2

Data collection

Bruker Nonius X8 APEXII CCD area-detector diffractometer	1213 independent reflections
Radiation source: fine-focus sealed tube	1141 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
thin–slice ω and ϕ scans	θmax = 25.0°, θmin = 4.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −5→5
Tmin = 0.829, Tmax = 0.936	k = −12→12
14018 measured reflections	l = −17→17

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)] = 0.022	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.059	All H-atom parameters refined
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0287P)^2 + 0.2766P] where P = (Fo^2 + 2Fc^2)/3
1213 reflections	(Δ/σ)max < 0.001
114 parameters	Δρmax = 0.26 e Å^−3
0 restraints	Δρmin = −0.16 e Å^−3

Special details

Experimental. Spectroscopic data for compound (I): ¹H NMR (400.12 MHz, CDCl₃, δ, p.p.m.): 8.47 (d, 2H, H2), 7.60 (m, 2H, H3), 7.31 (d, 2H, H4) 7.11 (m, 2H,H3), 3.80 (s, 4H, H6A+H6B), 2.65 (s, 4H, H7A+H7B); ¹³C NMR (100.62 MHz, CDCl₃, δ, p.p.m.): 158.65 (C6), 149.34 (C1), 136.75 (C3), 123.06 (C4), 121.98 (C2), 38.01 (C6), 31.30 (C7); IR (KBr, ν, cm^-1): 3067 (m), 3042 (m), 2969(w), 2939 (m), 2927 (m), 2806 (w), 1995 (w), 1967 (w), 1936 (w), 1896 (w), 1868 (w),1650 (w), 1592 (s), 1566 (s), 1474 (s), 1434 (s), 1414 8?s), 1308 (m), 1256 (m),1256 (w), 1193 (s), 1155 (m), 1145 (m), 1123 (m), 1082 (m), 1053 (m), 993 (s), 899 (w), 870 (w), 825 (m), 791 (s), 752 (s), 724 (m), 710 (m), 676 (s), 627(m), 579 (s), 483 (m).

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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	0.1132 (3)	0.45545 (13)	0.02665 (9)	0.0205 (3)
C2	−0.1462 (3)	0.39577 (13)	0.18144 (9)	0.0206 (3)
C3	0.1062 (3)	0.41867 (12)	0.25593 (8)	0.0178 (3)
C4	0.2005 (3)	0.32004 (13)	0.31952 (9)	0.0228 (3)
C5	0.4352 (3)	0.34407 (15)	0.38670 (9)	0.0274 (3)
C6	0.5695 (3)	0.46525 (14)	0.38812 (9)	0.0257 (3)
C7	0.4633 (3)	0.55726 (13)	0.32261 (9)	0.0239 (3)
N1	0.2334 (2)	0.53680 (10)	0.25672 (7)	0.0211 (2)
S1	−0.04245 (7)	0.31637 (3)	0.07927 (2)	0.02197 (12)
H1A	0.233 (3)	0.5043 (14)	0.0748 (10)	0.022 (3)*
H1B	0.231 (3)	0.4184 (14)	−0.0156 (10)	0.025 (4)*
H2A	−0.245 (3)	0.4760 (15)	0.1625 (10)	0.023 (4)*
H2B	−0.277 (3)	0.3373 (15)	0.2029 (10)	0.025 (4)*
H4	0.102 (3)	0.2382 (17)	0.3151 (10)	0.029 (4)*
H5	0.502 (3)	0.2791 (17)	0.4316 (11)	0.036 (4)*
H6	0.727 (4)	0.4846 (15)	0.4325 (11)	0.031 (4)*
H7	0.552 (3)	0.6417 (16)	0.3214 (10)	0.027 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0172 (6)	0.0261 (7)	0.0180 (6)	0.0021 (5)	0.0017 (5)	0.0013 (5)
C2	0.0171 (6)	0.0248 (7)	0.0198 (6)	−0.0011 (6)	0.0025 (5)	0.0008 (5)
C3	0.0157 (6)	0.0217 (6)	0.0165 (6)	0.0020 (5)	0.0044 (5)	−0.0022 (5)
C4	0.0233 (7)	0.0223 (7)	0.0227 (7)	0.0000 (5)	0.0036 (5)	0.0018 (5)
C5	0.0266 (7)	0.0342 (8)	0.0205 (7)	0.0056 (6)	0.0002 (5)	0.0056 (6)
C6	0.0190 (6)	0.0377 (8)	0.0194 (6)	0.0022 (6)	−0.0007 (5)	−0.0073 (6)
C7	0.0209 (7)	0.0231 (7)	0.0277 (7)	−0.0015 (5)	0.0032 (5)	−0.0083 (5)
N1	0.0191 (5)	0.0199 (5)	0.0241 (5)	0.0013 (4)	0.0027 (4)	−0.0014 (4)
S1	0.0259 (2)	0.02070 (19)	0.01817 (18)	−0.00048 (12)	−0.00029 (13)	−0.00124 (12)

Geometric parameters (Å, º)

C1—C1^i	1.518 (2)	C3—C4	1.3919 (18)
C1—S1	1.8141 (13)	C4—C5	1.3807 (19)
C1—H1A	0.968 (15)	C4—H4	0.949 (17)
C1—H1B	0.963 (16)	C5—C6	1.383 (2)
C2—C3	1.4991 (17)	C5—H5	0.950 (17)
C2—S1	1.8239 (13)	C6—C7	1.3756 (19)
C2—H2A	0.957 (15)	C6—H6	0.927 (17)
C2—H2B	0.941 (16)	C7—N1	1.3481 (16)
C3—N1	1.3405 (16)	C7—H7	0.955 (16)
C1^i—C1—S1	112.74 (12)	C5—C4—C3	118.97 (12)
C1^i—C1—H1A	110.5 (9)	C5—C4—H4	122.1 (9)
S1—C1—H1A	108.7 (8)	C3—C4—H4	118.9 (9)
C1^i—C1—H1B	109.3 (8)	C4—C5—C6	118.77 (13)
S1—C1—H1B	105.7 (9)	C4—C5—H5	120.7 (10)
H1A—C1—H1B	109.8 (12)	C6—C5—H5	120.5 (10)
C3—C2—S1	112.44 (8)	C7—C6—C5	118.64 (12)
C3—C2—H2A	111.7 (8)	C7—C6—H6	120.5 (10)
S1—C2—H2A	108.6 (8)	C5—C6—H6	120.9 (10)
C3—C2—H2B	109.9 (9)	N1—C7—C6	123.84 (12)
S1—C2—H2B	105.1 (9)	N1—C7—H7	115.4 (9)
H2A—C2—H2B	108.9 (12)	C6—C7—H7	120.8 (9)
N1—C3—C4	122.94 (11)	C3—N1—C7	116.85 (11)
N1—C3—C2	116.56 (11)	C1—S1—C2	100.04 (6)
C4—C3—C2	120.50 (11)

Symmetry code: (i) −x, −y+1, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···N1^ii	0.950 (17)	2.695 (17)	3.6042 (17)	160.4 (12)
C5—H5···S1^iii	0.950 (17)	2.959 (16)	3.8045 (14)	149.0 (12)

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

(II) 2-[({2-[(pyridin-1-ium-2-ylmethyl)sulfanyl]ethyl}sulfanyl)methyl]pyridin-1-ium dichloride

Crystal data

C14H18N2S2^2+·2Cl^−	F(000) = 364
Mr = 349.32	Dx = 1.364 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 6521 reflections
a = 7.8247 (5) Å	θ = 2.8–26.0°
b = 7.8382 (5) Å	µ = 0.62 mm^−1
c = 14.1408 (9) Å	T = 100 K
β = 101.297 (3)°	Plate, white
V = 850.47 (9) Å^3	0.22 × 0.20 × 0.06 mm
Z = 2

Data collection

Bruker Nonius X8 APEXII CCD area-detector diffractometer	1687 independent reflections
Radiation source: fine-focus sealed tube	1499 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.038
thin–slice ω and ϕ scans	θmax = 26.1°, θmin = 3.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.620, Tmax = 0.745	k = −9→8
15273 measured reflections	l = −17→17

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)] = 0.024	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.060	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0244P)^2 + 0.428P] where P = (Fo^2 + 2Fc^2)/3
1687 reflections	(Δ/σ)max = 0.001
95 parameters	Δρmax = 0.28 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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	0.51134 (19)	−0.05294 (19)	0.95663 (10)	0.0150 (3)
H1A	0.4942	−0.1749	0.9703	0.018*
H1B	0.6319	−0.0390	0.9460	0.018*
C2	0.44800 (19)	0.21340 (19)	0.82243 (11)	0.0168 (3)
H2A	0.3623	0.2730	0.7726	0.020*
H2B	0.4677	0.2842	0.8815	0.020*
C3	0.61505 (19)	0.19412 (18)	0.78808 (10)	0.0146 (3)
C4	0.77781 (19)	0.21775 (19)	0.84614 (11)	0.0173 (3)
H4	0.7876	0.2490	0.9119	0.021*
C5	0.9260 (2)	0.1956 (2)	0.80788 (11)	0.0208 (3)
H5	1.0378	0.2126	0.8473	0.025*
C6	0.9117 (2)	0.14846 (19)	0.71199 (11)	0.0201 (3)
H6	1.0128	0.1316	0.6853	0.024*
C7	0.7483 (2)	0.1268 (2)	0.65674 (11)	0.0191 (3)
H7	0.7357	0.0956	0.5908	0.023*
N1	0.60665 (17)	0.14960 (16)	0.69522 (9)	0.0159 (3)
S1	0.36000 (5)	0.00739 (5)	0.84813 (3)	0.01617 (11)
Cl1	0.25991 (5)	0.06564 (5)	0.57149 (2)	0.01817 (11)
H1N	0.502 (3)	0.130 (2)	0.6577 (14)	0.031 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0163 (7)	0.0155 (8)	0.0122 (7)	0.0018 (6)	0.0001 (6)	0.0012 (6)
C2	0.0186 (7)	0.0159 (8)	0.0155 (7)	0.0028 (6)	0.0024 (6)	0.0022 (6)
C3	0.0191 (7)	0.0103 (7)	0.0146 (7)	0.0013 (6)	0.0038 (6)	0.0016 (6)
C4	0.0205 (8)	0.0149 (8)	0.0153 (7)	0.0003 (6)	0.0010 (6)	−0.0016 (6)
C5	0.0175 (8)	0.0172 (8)	0.0265 (9)	−0.0004 (6)	0.0014 (7)	−0.0005 (7)
C6	0.0216 (8)	0.0142 (8)	0.0272 (8)	−0.0002 (6)	0.0113 (7)	0.0011 (6)
C7	0.0289 (8)	0.0134 (8)	0.0173 (7)	−0.0008 (6)	0.0100 (6)	−0.0001 (6)
N1	0.0176 (7)	0.0158 (7)	0.0134 (6)	−0.0017 (5)	0.0011 (5)	0.0007 (5)
S1	0.01488 (19)	0.0190 (2)	0.01344 (19)	−0.00114 (15)	−0.00022 (14)	0.00031 (14)
Cl1	0.01745 (19)	0.0235 (2)	0.01338 (18)	−0.00010 (15)	0.00247 (14)	−0.00022 (14)

Geometric parameters (Å, º)

C1—C1^i	1.520 (3)	C4—C5	1.384 (2)
C1—S1	1.8077 (14)	C4—H4	0.9500
C1—H1A	0.9900	C5—C6	1.388 (2)
C1—H1B	0.9900	C5—H5	0.9500
C2—C3	1.489 (2)	C6—C7	1.372 (2)
C2—S1	1.8198 (16)	C6—H6	0.9500
C2—H2A	0.9900	C7—N1	1.3392 (19)
C2—H2B	0.9900	C7—H7	0.9500
C3—N1	1.3478 (19)	N1—H1N	0.90 (2)
C3—C4	1.386 (2)
C1^i—C1—S1	112.42 (13)	C5—C4—H4	120.2
C1^i—C1—H1A	109.1	C3—C4—H4	120.2
S1—C1—H1A	109.1	C4—C5—C6	120.13 (14)
C1^i—C1—H1B	109.1	C4—C5—H5	119.9
S1—C1—H1B	109.1	C6—C5—H5	119.9
H1A—C1—H1B	107.9	C7—C6—C5	118.48 (14)
C3—C2—S1	111.46 (10)	C7—C6—H6	120.8
C3—C2—H2A	109.3	C5—C6—H6	120.8
S1—C2—H2A	109.3	N1—C7—C6	120.36 (14)
C3—C2—H2B	109.3	N1—C7—H7	119.8
S1—C2—H2B	109.3	C6—C7—H7	119.8
H2A—C2—H2B	108.0	C7—N1—C3	122.96 (13)
N1—C3—C4	118.39 (14)	C7—N1—H1N	118.1 (12)
N1—C3—C2	117.77 (13)	C3—N1—H1N	118.9 (12)
C4—C3—C2	123.84 (13)	C1—S1—C2	101.01 (7)
C5—C4—C3	119.68 (14)

Symmetry code: (i) −x+1, −y, −z+2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···Cl1	0.90 (2)	2.10 (2)	2.9992 (14)	175.7 (17)
C1—H1A···Cl1^ii	0.99	2.82	3.6428 (16)	141
C2—H2A···S1^iii	0.99	2.85	3.8286 (15)	168
C4—H4···Cl1^iv	0.95	2.73	3.6376 (16)	161
C6—H6···Cl1^v	0.95	2.80	3.7298 (16)	168
C7—H7···Cl1^vi	0.95	2.63	3.5517 (16)	165

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

(III) 2-[({2-[(pyridin-1-ium-2-ylmethyl)sulfanyl]ethyl}sulfanyl)methyl]pyridin-1-ium dichloride

Crystal data

C14H18N2S2^2+·2Cl^−	F(000) = 728
Mr = 349.32	Dx = 1.327 Mg m^−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 9858 reflections
a = 13.6599 (9) Å	θ = 2.7–26.0°
b = 8.5928 (6) Å	µ = 0.60 mm^−1
c = 14.8979 (11) Å	T = 100 K
V = 1748.7 (2) Å^3	Needle, colourless
Z = 4	0.24 × 0.10 × 0.06 mm

Data collection

Bruker Nonius X8 APEXII CCD area-detector diffractometer	1711 independent reflections
Radiation source: fine-focus sealed tube	1558 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.035
thin–slice ω and ϕ scans	θmax = 26.0°, θmin = 3.9°
Absorption correction: multi-scan SADABS (Sheldrick, 1996)	h = −16→14
Tmin = 0.652, Tmax = 0.745	k = −8→10
32186 measured reflections	l = −15→18

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)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.082	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0493P)^2 + 0.9628P] where P = (Fo^2 + 2Fc^2)/3
1711 reflections	(Δ/σ)max = 0.001
95 parameters	Δρmax = 0.76 e Å^−3
0 restraints	Δρmin = −0.34 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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	0.45343 (11)	−0.04788 (18)	0.50345 (11)	0.0178 (3)
H1A	0.4265	−0.0375	0.5648	0.021*
H1B	0.4696	−0.1589	0.4937	0.021*
C2	0.32731 (12)	0.20118 (19)	0.46634 (11)	0.0202 (4)
H2A	0.3863	0.2680	0.4686	0.024*
H2B	0.2798	0.2502	0.4249	0.024*
C3	0.28339 (11)	0.19177 (16)	0.55761 (11)	0.0147 (3)
C4	0.33199 (12)	0.22960 (18)	0.63592 (12)	0.0185 (3)
H4	0.3973	0.2676	0.6336	0.022*
C5	0.28525 (13)	0.21196 (19)	0.71779 (12)	0.0233 (4)
H5	0.3183	0.2384	0.7718	0.028*
C6	0.18998 (13)	0.15553 (19)	0.72096 (11)	0.0235 (4)
H6	0.1576	0.1418	0.7768	0.028*
C7	0.14356 (12)	0.12002 (19)	0.64177 (12)	0.0191 (3)
H7	0.0782	0.0823	0.6425	0.023*
N1	0.19041 (10)	0.13854 (15)	0.56346 (9)	0.0149 (3)
S1	0.36099 (3)	0.01024 (5)	0.42332 (3)	0.02134 (15)
Cl1	0.07776 (3)	0.08421 (4)	0.39113 (2)	0.01488 (14)
H1N	0.1586 (16)	0.118 (3)	0.5164 (16)	0.031 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0139 (8)	0.0157 (7)	0.0239 (9)	0.0008 (7)	0.0004 (7)	−0.0027 (7)
C2	0.0192 (8)	0.0206 (8)	0.0206 (9)	0.0046 (7)	0.0016 (7)	0.0036 (7)
C3	0.0147 (8)	0.0096 (6)	0.0197 (8)	0.0024 (6)	−0.0009 (6)	0.0026 (6)
C4	0.0157 (7)	0.0153 (7)	0.0244 (9)	−0.0026 (6)	−0.0030 (7)	0.0005 (7)
C5	0.0284 (9)	0.0235 (8)	0.0181 (9)	−0.0046 (7)	−0.0073 (7)	−0.0013 (7)
C6	0.0300 (9)	0.0239 (8)	0.0165 (9)	−0.0053 (7)	0.0041 (7)	0.0000 (7)
C7	0.0164 (8)	0.0170 (7)	0.0238 (8)	−0.0031 (6)	0.0020 (7)	−0.0005 (7)
N1	0.0145 (7)	0.0141 (6)	0.0161 (7)	0.0000 (5)	−0.0038 (6)	−0.0019 (5)
S1	0.0161 (2)	0.0266 (2)	0.0212 (3)	0.00120 (17)	−0.00191 (16)	−0.00723 (16)
Cl1	0.0124 (2)	0.0176 (2)	0.0147 (2)	−0.00041 (13)	−0.00117 (14)	−0.00188 (13)

Geometric parameters (Å, º)

C1—C1^i	1.519 (3)	C4—C5	1.385 (2)
C1—S1	1.8080 (17)	C4—H4	0.9500
C1—H1A	0.9900	C5—C6	1.390 (2)
C1—H1B	0.9900	C5—H5	0.9500
C2—C3	1.488 (2)	C6—C7	1.374 (2)
C2—S1	1.8206 (17)	C6—H6	0.9500
C2—H2A	0.9900	C7—N1	1.340 (2)
C2—H2B	0.9900	C7—H7	0.9500
C3—N1	1.353 (2)	N1—H1N	0.84 (2)
C3—C4	1.381 (2)
C1^i—C1—S1	113.00 (15)	C3—C4—H4	120.1
C1^i—C1—H1A	109.0	C5—C4—H4	120.1
S1—C1—H1A	109.0	C4—C5—C6	119.99 (15)
C1^i—C1—H1B	109.0	C4—C5—H5	120.0
S1—C1—H1B	109.0	C6—C5—H5	120.0
H1A—C1—H1B	107.8	C7—C6—C5	118.72 (16)
C3—C2—S1	112.00 (11)	C7—C6—H6	120.6
C3—C2—H2A	109.2	C5—C6—H6	120.6
S1—C2—H2A	109.2	N1—C7—C6	120.06 (15)
C3—C2—H2B	109.2	N1—C7—H7	120.0
S1—C2—H2B	109.2	C6—C7—H7	120.0
H2A—C2—H2B	107.9	C7—N1—C3	123.00 (15)
N1—C3—C4	118.46 (15)	C7—N1—H1N	116.9 (15)
N1—C3—C2	117.10 (14)	C3—N1—H1N	120.1 (15)
C4—C3—C2	124.41 (15)	C1—S1—C2	101.13 (8)
C3—C4—C5	119.77 (15)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···Cl1	0.85 (2)	2.19 (2)	3.0293 (15)	175 (2)
C1—H1B···Cl1^ii	0.99	2.76	3.6022 (16)	143
C2—H2B···S1^iii	0.99	2.95	3.7522 (17)	139
C4—H4···Cl1^iv	0.95	2.80	3.7405 (17)	171
C5—H5···Cl1^v	0.95	2.74	3.6385 (17)	158
C6—H6···Cl1^vi	0.95	2.80	3.6084 (17)	143
C7—H7···Cl1^vii	0.95	2.61	3.5298 (17)	162

Symmetry codes: (ii) −x+1/2, y−1/2, z; (iii) −x+1/2, y+1/2, z; (iv) x+1/2, −y+1/2, −z+1; (v) −x+1/2, −y+1/2, z+1/2; (vi) x, −y, z+1/2; (vii) −x, −y, −z+1.