N,N′-Diisopentyl­dithio­oxamide

In the crystal structure of the centrosymmetric dithio­oxamide title compound, C₁₂H₂₄N₂S₂, one half-mol­ecule is present in the asymmetric unit and the entire molecule is generated by inversion. As is usual for secondary dithio­oxamides, the title compound shows the trans-planar conformation. Crystal packing is mainly supported by inter­molecular N—H...S and C—H...S inter­actions developing flat ribbon-like one-dimensional arrays. These are stacked vertically through π–π inter­actions of the core frames [regular mean plane distances of 3.659 (1) Å], and the three-dimensional packing is completed by nonpolar inter­actions involving the alkyl chains.

Key indicators

• Single-crystal X-ray study
• T = 571 K
• R factor = 0.034
• wR factor = 0.098
• Data-to-parameter ratio = 20.6

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S1. Comment

Secondary dithioxamides behave as binucleating ligands both in N,S–N,S (Veit et al., 1984; Ye et al., 1991; Lanza et al. 2002) and in N,N–S,S modes (Lanza et al., 2000; 2003; 2005) (Scheme 1). It has been already observed (Lanza et al., 2005) that in the trimetallic complexes [Pt{{µ-S₂C₂(NR)₂}ML_n}₂] (µ-S₂C₂(NR)₂ = bridging dianionic dithioxamidate; ML_n⁺= positively charged metal fragment) there is an electron removal from platinum to ML_n⁺ via the π^* system in the N—C—S fragments (Lanza et al. 2005). The possibility of a π donation from the bridged dithioxamide to the platinum d orbitals has been ruled out, since this latter circumstance would require a C—C double bond connecting the two N—C—S frames. In order to asses factors affecting electronic transmission between metals in polymetallic chains through binucleating dithioxamides, we think it is important to gain as much structural information as possible about free and coordinated H₂S₂C₂(NR)₂ ligands

The asymmetric unit of (I) contains one half of the symmetric molecule with the other half generated by inversion (Fig. 1). The thioamide moiety is planar [maximum deviation from the mean plane for the C1 = 0.001 (1) Å]; the trans conformation is also stabilized by the intramolecular interaction N—H···S [N1—H1 = 0.860 (1), N1···S1ⁱ = 2.945 (1) Å, N1—H1···S1ⁱ = 117.6 (1)°; symmetry code (i) -x + 1, -y + 1, -z], moreover the first C atom of the N-attached alkyl chain keeps the planarity of the core atoms [maximum deviation of C2 = 0.005 (2) Å]. On the other hand the features of the sp³ hybridized C atoms mean that the side aliphatic chains are above and below with respect to the core planar fragment. The thioamide geometrical parameters in the table are in accord with those found for similar crystal structures (Shimanouchi & Sasada, 1979; Bermejo et al., 1998; Perec et al., 1995; Jean 1994; Simonov et al. 2003).

The crystal lattice is mainly supported by intermolecular N—H^···S interactions [N1—H1 = 0.860 (1), N1···S1ⁱⁱ = 3.425 (2) Å, N1—H1···S1ⁱⁱ = 131.3 (1)°; symmetry code (ii) x, y + 1, z] together with a much weaker C—H^···S hydrogen bond [C2—H2B = 0.970 (2), C1^···S1ⁱⁱ = 3.499 (2) Å, C2—H2B···S1ⁱⁱ = 114.1 (1)°]. The interaction N—H^···S doubled by the crystallographic inversion centre leads to the "chain of rings" C(3)R₂²(10) motif (Bernstein et al., 1995). The resulting one-dimensional-array of molecules along the b crystallographic axis looks like a planar strand because of the directional self-recognition (Fig. 2). The thioamidic group also develops vertical π-π interactions [distance from the mean thioxamidic planes 3.6595 (5) Å; symmetry code for the π stacked equivalent is x + 1, y, z] generating a ladder like disposition of the planar strands running along the a crystallographic axis (Fig. 3). The non-polar nature of the alkylic chain means that very weak interactions complete the third dimension of the crystal packing. Compounds with similar structure can be regarded as forerunners of metallomesogens; actually mesophases are observed when the R groups are aryl substituents bearing long hydrocarbon chains (Aversa et al., 2000; 1997).

Related literature

For related literature, see: Aversa et al. (1997, 2000); Bermejo et al. (1998); Cremer & Pople (1975); Desseyn et al. (1978); Hurd et al. (1961); Jean (1994); Lanza et al. (2000, 2002, 2003, 2005); Perec et al. (1995); Shimanouchi & Sasada (1979); Simonov et al. (2003); Veit et al. (1984); Ye et al. (1991).

S2. Experimental

The title compound I was synthesized according to Hurd et al. (1961). crystals were obtained by recrystallization from a chloroform-petrol ether (1:1) solution.

S3. Refinement

Hydrogen atoms were localized from the difference Fourier map and idealized by the well known "riding-model technique" with distances to the parent atoms of of 0.96 to 0.98 Å. The best refinement was obtained with the psi-scan (North et al., 1968) absorption correction performed by XSCANS (Siemens, 1989).

Computing details

Data collection: XSCANS (Siemens, 1989); cell refinement: XSCANS; data reduction: XPREP (Bruker, 1997); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XPREP; software used to prepare material for publication: PARST95 (Nardelli, 1995) and WinGX-PC (Farrugia, 1999).

Figures

	Fig. 1. The molecule of (I), showing the atom numbering scheme. Displacement ellipsoids are drawn at 30% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. Part of the crystal structure of (I), showing the formation of the chain of rings C(3)R2^2(10) along [010]. Atoms marked with an asterisk (*) or an hash (#) are at the symmetry positions (-x + 1, -y + 1, -z) and (x, y + 1, z), respectively. For the sake of clarity all H atoms uninvolved in the evidenced interactions are omitted.
	Fig. 3. Ladder-like stacking of one-dimensional-arrays of (I). Strands are aligned along the [100] direction.
	Fig. 4. Bridging modes.

N,N'-Diisopentyldithiooxamide

Crystal data

C12H24N2S2	Z = 1
Mr = 260.45	F(000) = 142
Triclinic, P1	Dx = 1.112 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 4.7658 (9) Å	Cell parameters from 66 reflections
b = 6.0323 (9) Å	θ = 4.8–22.5°
c = 14.470 (2) Å	µ = 0.32 mm^−1
α = 83.082 (14)°	T = 571 K
β = 85.919 (15)°	Irregular, yellow
γ = 70.427 (15)°	0.58 × 0.44 × 0.24 mm
V = 388.90 (11) Å^3

Data collection

Bruker P4 diffractometer	Rint = 0.011
2θ/ω scans	θmax = 26.0°, θmin = 2.8°
Absorption correction: ψ scan (North et al., 1968)	h = −1→5
Tmin = 0.825, Tmax = 0.924	k = −7→7
2093 measured reflections	l = −17→17
1523 independent reflections	3 standard reflections every 197 reflections
1344 reflections with I > 2σ(I)	intensity decay: 2%

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.034	w = 1/[σ^2(Fo^2) + (0.0509P)^2 + 0.0753P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.098	(Δ/σ)max < 0.001
S = 1.12	Δρmax = 0.23 e Å^−3
1523 reflections	Δρmin = −0.17 e Å^−3
74 parameters

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
S1	0.30375 (11)	0.27375 (7)	0.08976 (3)	0.05646 (19)
N1	0.2847 (3)	0.7182 (2)	0.07141 (9)	0.0431 (3)
H1	0.3425	0.8287	0.042	0.052*
C1	0.3922 (3)	0.5069 (2)	0.04182 (10)	0.0384 (3)
C2	0.0759 (4)	0.7793 (3)	0.15000 (11)	0.0475 (4)
H2A	−0.0553	0.6852	0.1543	0.057*
H2B	−0.0457	0.9446	0.1398	0.057*
C3	0.2347 (4)	0.7371 (3)	0.24076 (12)	0.0534 (4)
H3A	0.3617	0.8346	0.2365	0.064*
H3B	0.3618	0.5731	0.2493	0.064*
C4	0.0254 (5)	0.7911 (4)	0.32571 (13)	0.0641 (5)
H4	−0.117	0.706	0.325	0.077*
C5	−0.1497 (7)	1.0529 (5)	0.32366 (19)	0.0993 (9)
H5A	−0.256	1.1057	0.2669	0.149*
H5B	−0.0152	1.1396	0.327	0.149*
H5C	−0.2888	1.0791	0.3758	0.149*
C6	0.1984 (7)	0.7021 (6)	0.41444 (15)	0.1009 (9)
H6A	0.3081	0.5365	0.4142	0.151*
H6B	0.0623	0.7259	0.4674	0.151*
H6C	0.3343	0.7875	0.4179	0.151*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0758 (3)	0.0383 (2)	0.0581 (3)	−0.0242 (2)	0.0082 (2)	−0.00594 (18)
N1	0.0514 (8)	0.0345 (6)	0.0446 (7)	−0.0147 (5)	−0.0004 (6)	−0.0075 (5)
C1	0.0432 (8)	0.0345 (7)	0.0376 (7)	−0.0117 (6)	−0.0091 (6)	−0.0036 (6)
C2	0.0481 (9)	0.0436 (8)	0.0490 (9)	−0.0110 (7)	0.0013 (7)	−0.0111 (7)
C3	0.0535 (10)	0.0558 (10)	0.0473 (9)	−0.0123 (8)	−0.0010 (7)	−0.0085 (7)
C4	0.0661 (12)	0.0776 (13)	0.0496 (10)	−0.0238 (10)	0.0056 (9)	−0.0142 (9)
C5	0.108 (2)	0.0939 (19)	0.0741 (15)	0.0040 (15)	0.0068 (14)	−0.0387 (14)
C6	0.119 (2)	0.126 (2)	0.0466 (12)	−0.0267 (19)	0.0001 (13)	−0.0040 (13)

Geometric parameters (Å, º)

S1—C1	1.6606 (15)	C3—H3B	0.97
N1—C1	1.3165 (19)	C4—C5	1.517 (3)
N1—C2	1.454 (2)	C4—C6	1.518 (3)
N1—H1	0.86	C4—H4	0.98
C1—C1^i	1.522 (3)	C5—H5A	0.96
C2—C3	1.515 (2)	C5—H5B	0.96
C2—H2A	0.97	C5—H5C	0.96
C2—H2B	0.97	C6—H6A	0.96
C3—C4	1.522 (2)	C6—H6B	0.96
C3—H3A	0.97	C6—H6C	0.96
C1—N1—C2	125.09 (14)	C5—C4—C6	110.9 (2)
C1—N1—H1	117.5	C5—C4—C3	111.70 (19)
C2—N1—H1	117.5	C6—C4—C3	110.33 (18)
N1—C1—C1^i	113.92 (16)	C5—C4—H4	107.9
N1—C1—S1	124.00 (12)	C6—C4—H4	107.9
C1^i—C1—S1	122.08 (14)	C3—C4—H4	107.9
N1—C2—C3	111.77 (13)	C4—C5—H5A	109.5
N1—C2—H2A	109.3	C4—C5—H5B	109.5
C3—C2—H2A	109.3	H5A—C5—H5B	109.5
N1—C2—H2B	109.3	C4—C5—H5C	109.5
C3—C2—H2B	109.3	H5A—C5—H5C	109.5
H2A—C2—H2B	107.9	H5B—C5—H5C	109.5
C2—C3—C4	113.83 (15)	C4—C6—H6A	109.5
C2—C3—H3A	108.8	C4—C6—H6B	109.5
C4—C3—H3A	108.8	H6A—C6—H6B	109.5
C2—C3—H3B	108.8	C4—C6—H6C	109.5
C4—C3—H3B	108.8	H6A—C6—H6C	109.5
H3A—C3—H3B	107.7	H6B—C6—H6C	109.5
C2—N1—C1—C1^i	−179.80 (15)	N1—C2—C3—C4	−178.18 (15)
C2—N1—C1—S1	0.4 (2)	C2—C3—C4—C5	−66.7 (2)
C1—N1—C2—C3	88.31 (19)	C2—C3—C4—C6	169.55 (19)

Symmetry code: (i) −x+1, −y+1, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···S1^i	0.86	2.45	2.9452 (15)	118
N1—H1···S1^ii	0.86	2.80	3.4251 (14)	131
C2—H2B···S1^ii	0.97	2.99	3.4991 (18)	114

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