The first bipodal thio­carbamic acid ester, O,O'-diethyl N,N'-(p-phenylene­di­carbonyl)­bis(­thio­carbamate)

The title compound, C₁₄H₁₆N₂O₄S₂, is the first reported X-ray crystallographic structure determination of a bipodal O-alkyl N-benzoyl­thio­carbamate. This compound crystallizes in a cis-S,O orientation (Z,Z' configuration), with the two S/O moieties anti relative to one another, as indicated by the twofold rotation axis located at the center of the benzene ring.

S1. Comment

N,N-dialkyl- and N-alkyl-N\'-aroylthioureas have been studied extensively, as has the complexation of these ligands with several transition metals (Koch, 2001). Moreover, the bipodal ligands 3,3,3',3'-tetraalkyl-1,1'-isophthaloylbis(thioureas) and 3,3,3',3'-tetraalkyl-1,1'-terephthaloylbis(thioureas) have been shown to readily form 2:2 and 3:3 metallomacrocyclic complexes in high yield, with the general structure cis[M(L—S,O)]_n [n = 2 and 3, and M = Pt^II (Koch et al., 1999); n = 2, and M = Pd^II and Ni^II (Koch et al., 2001); n =2 and M = Ni^II (Bourne et al., 2004)]. The latter Ni^II metallomacrocyclic complexes also show some interesting host–guest chemistry. In this context, the bipodal N-benzoyl-thiocarbamic-O-alkyl esters are of interest as potential structural analogues to the well studied bipodal N',N',N''',N'''-tetraalkyl-N,N''-aroylbis(thioureas). In recent years, N-benzoyl-thiocarbamic-O-alkyl esters have also been proposed as intermediates for regio- and chemoselective deoxygenation of primary and secondary alcohols (Oba et al., 1994). The similarities between the bipodal N,N-dialkyl- and N-alkyl-N\'-aroylthioureas and the bipodal N-benzoyl- thiocarbamic-O-alkyl esters stimulated an investigation into the synthesis and characterization of this class of ligands, in order to better understand their potential coordination to transition metals. A survey of the literature yields few detailed structural studies of these N-benzoyl-thiocarbamic-O-alkyl esters. To date, only one crystal structure similar to that of the title compound, (I), has been reported in the literature, viz. that of O-isopropyl-N-(2-furoyl) thiocarbamate (Morales et al., 2000).

The observed cis-S,O orientation (Z,Z' configuration) of (I) (Fig. 1) differs from the reported trans-S,O orientation of the analogous monopodal and bipodal N,N-dialkyl- and N-alkyl-N\'-aroyl(acyl)thioureas, as well as from the configuration observed for N-(2-furoyl)thiocarbamic)-O-isopropyl ester (Koch, 2001; Koch et al., 1995; Köning et al., 1985; Morales et al., 2000). Compound (I) has a twofold rotation axis located at the center of the benzoyl ring and crystallizes in an s-cisoid s-cisoid conformation with respect to the C6—N7—C3 system. The two S/O groups are thus anti relative to one another, as indicated by the twofold rotation axis. The cis-S,O configuration of the title compound results in a 1–4 H7···O2 interaction, as indicated by the H7···O2 distance of 2.21 Å [N7···O2 = 2.181 (3) Å]. Atom H7 participates in a clear intermolecular hydrogen bond (N7—H7···O1) as shown in Fig. 2 and Table 2. Atom O1 of one molecule in turn forms a hydrogen bond with atom H7 of the adjacent molecule, resulting in each molecule being linked to four other molecules within the crystal structure. Atoms S1, C6, N7, C3 and O1 adopt an essentially planar arrangement, the S1—C6—N7—C3 and C6—N7—C3—O1 torsion angles being −1.6 (4) and −5.8 (4)°, respectively. As a result, the entire molecule is effectively planar, in contrast to what is usually observed in the related 3,3,3\',3\'-tetraalkyl-1,1\'-terephthaloylbis(thioureas) (Koch et al., 2001) and 3,3,3\',3\'-tetraethyl-1,1\'-terephthaloylbis(thiourea) (Ugar et al., 2003).

In (I), the C6—N7 bond distance (Table 1) is shorter than that observed for the corresponding bipodal 3,3,3\',3\'-tetraethyl-1,1\'-terephthaloylbis(thiourea) [1.4173 (16) Å; Ugar et al., 2003] and 3,3,3\',3\'-tetraethyl-1,1\'-isophthaloylbis(thiourea) [1.428 (4) Å; Koch et al. 2001], suggesting a greater degree of double-bond character in the C—N bond in question for (I). Moreover, the C3—N7 bond length in the title compound is comparable in length to the corresponding bonds in the aforementioned N',N',N''',N'''-tetraalkyl-N,N''-aroylbis(thioureas) bipodal thioureas. The partial double-bond character of the C—N bonds observed here is consistent with that suggested by Schröeder et al. (1995) on the basis of spectroscopic studies.

The asymmetry of the C7—C1—C3 and C4—C1—C3 angles (Table 1) may be caused by a repulsion between the N7—H7···H4—C4 system [N7···C4 = 2.923 (3) Å] and an attraction between the C7—H7A···O1 system [C7···O1 = 2.749 (3) Å and H7A···O1 = 2.43 Å]. A similar asymmetry of bond angles around the carbonyl group relative to the furoyl group within the monopodal N-(2-furoyl)thiocarbamic)-O-isopropyl ester has been reported (Morales et al., 2000).

S2. Experimental

All reactions were carried out under a dry argon atmosphere using standard Schlenk and vacuum-line techniques. The title compound was synthesized using a modification of the procedure initially reported for the preparation of thioureas by Douglas et al. (1934). The reagents, terephthaloyl dichloride and KSCN, were used as supplied without further purification. Acetone (calcium carbonate) and ethanol (Mg, I₂) were rendered anhydrous and distilled prior to use. Terephthaloyl dichloride (2.5 mmol) in acetone (25 ml) was added to KSCN (5 mmol) in acetone (25 ml) under an inert atmosphere. The mixture heated under reflux for 1 h and then cooled to room temperature, after which ethanol (5 mmol) in acetone (25 ml) was added dropwise with stirring and the mixture was further warmed to 333 K for 2 h. Water (50 ml) was added, followed by the extraction of the product into chloroform. Removal of the solvent in vacuo resulted in a pale-yellow amorphous residue containing a mixture of products (thin-layer chromatography). The title compound was crystallized from a 1:1 mixture of chloroform and ethanol, yielding crystals suitable for single-crystal diffraction analysis [yield 84.8% (based on terephthaloyl dichloride used), m.p. 410.3–411.2 K]. ¹H NMR (CDCl₃): δ 9.29 (br, s, 2H), 7.93 (s, 4H, Ph), 4.65 (qu, 4H, CH₂), 1.44 (tr, 6H, CH₃). ¹³C{¹H} NMR (CDCl₃): δ 188.9 (CO), 161.9 (CS), 136.9 (ipso-Ph), 128.3 (ortho-Ph), 69.6 (CH₂), 13.7 (CH₃). FT–IR (KBr disks): 3260 (s), 1697 (s), 1542 (s), 1281 (s), 1186 (m) cm⁻¹. Analysis calculated for C₁₄H₁₆N₂O₄S₂ (340.42 g mol⁻¹): C 50.58, H 4.50, N 8.23, S 18.84%; found C 50.40, H 4.74, N 8.60, S 17.64%.

S3. Refinement

H atoms were placed in calculated positions, with C—H distances of 0.99 Å (for CH₂ H atoms), 0.98 Å (for CH₃ H atoms) and 0.95 Å (for phenyl H atoms), and refined using a riding model, with U_iso(H) values of 1.2U_eq(parent atom) (for CH₂ and phenyl) and 1.5U_eq(parent atom) (for CH₃).

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: X-SEED (Barbour, 1999); software used to prepare material for publication: X-SEED.

Figures

	Fig. 1. The molecular structure of the title compound, showing the numbering scheme used. There is a twofold axis passing through the center of the phenyl ring. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. A view of the structure of the title compound, showing the N7—H7···O1 intermolecular hydrogen bond (dashed lines). All H atoms, apart from atom H7, have been omitted for clarity. Displacement ellipsoids are drawn at the 50% probability level.

O,O'-diethyl N,N'-(p-phenylenedicarbonyl)dithiocarbamate

Crystal data

C14H16N2O4S2	Dx = 1.435 Mg m^−3
Mr = 340.41	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P43212	Cell parameters from 1547 reflections
a = 10.5794 (4) Å	θ = 2.4–26.0°
c = 14.0773 (12) Å	µ = 0.36 mm^−1
V = 1575.58 (16) Å^3	T = 100 K
Z = 4	Needle, colourless
F(000) = 712	0.43 × 0.06 × 0.06 mm

Data collection

Bruker SMART APEX CCD diffractometer	1547 independent reflections
Radiation source: fine-focus sealed tube	1448 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.050
ω scans	θmax = 26.0°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 2002)	h = −13→13
Tmin = 0.975, Tmax = 0.979	k = −13→13
16377 measured reflections	l = −17→17

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)] = 0.041	H-atom parameters constrained
wR(F^2) = 0.104	w = 1/[σ^2(Fo^2) + (0.0605P)^2 + 0.9712P] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max = 0.002
1547 reflections	Δρmax = 0.35 e Å^−3
96 parameters	Δρmin = −0.22 e Å^−3
0 restraints	Absolute structure: Flack (1983), 599 Friedel pairs?
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.08 (15)

Special details

Experimental. All reactions were carried out under a dry argon atmosphere using standard Schlenk and vacuum-line techniques. NMR spectra were recorded on a Varian INOVA 600 spectrometer (¹H, 600 MHz; ¹³C{1H}, 151 MHz) at 298 K. Chemical shifts are reported in units of p.p.m. relative to the residual ¹H and ¹³C signals from the deuterated solvents. The infrared spectra were measured with a NEXUS model FR—IR instrument, which was custom made for the department by Thermo Nicolet instruments, USA. Samples were prepared as KBr disks and measured over the MID-IR range 4000–400 cm⁻¹ at a standard resolution of 4 cm⁻¹. The operating and data manipulation was performed with the basic OMNIC software package for spectroscopy. Elemental analyses were performed using a Carlo Erba EA 1108 elemental analyzer in the microanalytical laboratory of the University of Cape Town.

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
S1	0.50424 (7)	0.29813 (7)	0.10655 (4)	0.0287 (2)
O1	0.65558 (18)	0.13729 (18)	−0.02677 (12)	0.0226 (4)
N7	0.6513 (2)	0.0888 (2)	0.13129 (15)	0.0181 (5)
H7	0.6790	0.0338	0.1733	0.022*
O2	0.55202 (19)	0.15719 (19)	0.25700 (13)	0.0256 (5)
C1	0.7918 (2)	−0.0268 (2)	0.02294 (16)	0.0158 (5)
C2	0.4699 (3)	0.2414 (3)	0.31099 (19)	0.0280 (6)
H2A	0.3809	0.2310	0.2907	0.034*
H2B	0.4950	0.3306	0.3010	0.034*
C3	0.6940 (2)	0.0740 (2)	0.03903 (17)	0.0174 (5)
C4	0.8564 (2)	−0.0898 (2)	0.09491 (17)	0.0166 (5)
H4	0.8391	−0.0709	0.1596	0.020*
C6	0.5697 (3)	0.1809 (3)	0.16446 (19)	0.0230 (6)
C7	0.8203 (2)	−0.0545 (2)	−0.07197 (16)	0.0164 (5)
H7A	0.7770	−0.0111	−0.1213	0.020*
C5	0.4847 (3)	0.2056 (3)	0.4137 (2)	0.0344 (7)
H5A	0.4647	0.1158	0.4218	0.052*
H5B	0.4270	0.2565	0.4526	0.052*
H5C	0.5720	0.2212	0.4338	0.052*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0382 (4)	0.0256 (4)	0.0222 (3)	0.0108 (3)	0.0016 (3)	0.0002 (3)
O1	0.0249 (10)	0.0242 (10)	0.0188 (9)	0.0096 (8)	0.0013 (7)	0.0026 (8)
N7	0.0198 (10)	0.0200 (11)	0.0147 (10)	0.0059 (9)	0.0034 (8)	0.0019 (8)
O2	0.0305 (10)	0.0292 (10)	0.0172 (9)	0.0083 (8)	0.0024 (8)	−0.0003 (8)
C1	0.0166 (12)	0.0168 (12)	0.0138 (11)	−0.0017 (10)	0.0011 (9)	−0.0006 (9)
C2	0.0286 (15)	0.0313 (15)	0.0242 (13)	0.0105 (12)	0.0020 (11)	−0.0067 (12)
C3	0.0185 (13)	0.0178 (13)	0.0158 (11)	−0.0040 (11)	0.0010 (10)	−0.0017 (10)
C4	0.0173 (12)	0.0190 (12)	0.0134 (11)	−0.0017 (10)	0.0026 (9)	0.0001 (9)
C6	0.0226 (14)	0.0254 (15)	0.0211 (13)	−0.0010 (11)	0.0011 (10)	−0.0020 (11)
C7	0.0196 (13)	0.0172 (12)	0.0124 (11)	−0.0001 (10)	−0.0033 (9)	0.0019 (9)
C5	0.0395 (17)	0.0407 (17)	0.0229 (14)	0.0083 (15)	0.0047 (13)	−0.0015 (13)

Geometric parameters (Å, º)

S1—C6	1.638 (3)	C2—C5	1.503 (4)
O1—C3	1.213 (3)	C2—H2A	0.9900
N7—C6	1.383 (3)	C2—H2B	0.9900
N7—C3	1.384 (3)	C4—C7^i	1.377 (4)
N7—H7	0.8800	C4—H4	0.9500
O2—C6	1.340 (3)	C7—H7A	0.9500
O2—C2	1.458 (3)	C5—H5A	0.9800
C1—C4	1.392 (3)	C5—H5B	0.9800
C1—C7	1.401 (3)	C5—H5C	0.9800
C1—C3	1.503 (4)
N7···C4	2.923 (3)	C7···O1	2.749 (3)
C6—N7—C3	126.9 (2)	C7^i—C4—C1	119.7 (2)
C6—N7—H7	116.6	C7^i—C4—H4	120.1
C3—N7—H7	116.6	C1—C4—H4	120.1
C6—O2—C2	118.4 (2)	O2—C6—N7	106.5 (2)
C4—C1—C7	119.2 (2)	O2—C6—S1	124.5 (2)
C4—C1—C3	124.6 (2)	N7—C6—S1	129.0 (2)
C7—C1—C3	116.1 (2)	C4^i—C7—C1	121.0 (2)
O2—C2—C5	106.6 (2)	C4^i—C7—H7A	119.5
O2—C2—H2A	110.4	C1—C7—H7A	119.5
C5—C2—H2A	110.4	C2—C5—H5A	109.5
O2—C2—H2B	110.4	C2—C5—H5B	109.5
C5—C2—H2B	110.4	H5A—C5—H5B	109.5
H2A—C2—H2B	108.6	C2—C5—H5C	109.5
O1—C3—N7	123.0 (2)	H5A—C5—H5C	109.5
O1—C3—C1	120.5 (2)	H5B—C5—H5C	109.5
N7—C3—C1	116.5 (2)
C6—O2—C2—C5	−170.9 (2)	C2—O2—C6—N7	179.4 (2)
C6—N7—C3—C1	174.6 (2)	C2—O2—C6—S1	−0.5 (4)
C4—C1—C3—O1	169.1 (2)	C3—N7—C6—O2	178.4 (2)
C7—C1—C3—O1	−9.0 (4)	C4—C1—C7—C4^i	0.6 (3)
C4—C1—C3—N7	−11.3 (4)	C3—C1—C7—C4^i	178.8 (2)
C7—C1—C3—N7	170.6 (2)	S1—C6—N7—C3	−1.6 (4)
C7—C1—C4—C7^i	−1.1 (3)	C6—N7—C3—O1	−5.8 (4)
C3—C1—C4—C7^i	−179.2 (2)

Symmetry code: (i) y+1, x−1, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N7—H7···O1^ii	0.88	2.17	2.895 (3)	140

Symmetry code: (ii) y+1/2, −x+1/2, z+1/4.