Methyl 4-nitro­phenyl sulfoxide: [pi]-stacked chains of hydrogen-bonded R(10) dimers

Molecules of the title compound, C₇H₇NO₃S, are linked into centrosymmetric R(10) dimers by paired C-H...O hydrogen bonds, and these dimers are linked into [110] chains by a single aromatic [pi]-[pi] stacking interaction.

S1. Comment

Molecules of the title compound, (I), are chiral, but the centrosymmetric space group accommodates equal numbers of the (R) and (S) enantiomers; the selected reference molecule (Fig. 1) is of the (R) configuration. Within the molecule, the ring C—C distances span the very narrow range 1.384 (2)–1.392 (2) Å. The two independent C—S distances (Table 1) are very similar but with the distance to the aryl C marginally the longer of the two. The reference mean values for C_aryl—S(O)- and Csp³—S(O)- distances (Allen et al., 1987) are 1.790 and 1.809 Å, respectively, while the reference mean value for S═O distances in sulfoxides is 1.497 Å, so that the S—O distance in (I) is entirely characteristic. \sch

The internal C—C—C angles at C1 and C4 in (I), ipso to the electron-withdrawing substituents NO₂ and S(O)CH₃, respectively, are both greater than 120°, as expected (Domenicano & Murray-Rust, 1979). At the pyramidal S atom, the bond angles involving the sulfoxide atom O41 are both significantly larger than the C—S—C angle. The conformation of the S(O)—CH₃ fragment, with the sulfonyl O atom almost coplanar with the aryl ring, may be controlled by an intramolecular dipolar attraction involving the positively charged atom H3 and the negatively charged atom O41. The nitro group is essentially coplanar with the aryl group, and a similar conformation was found in the isomeric compound methyl 2-nitrophenyl sulfoxide, (II) (Ianelli et al., 1992).

The molecules of (I) are weakly linked into centrosymmetric dimers by a nearly linear C—H···O hydrogen bond, and these weak dimers are further linked into chains by a single aromatic π–π stacking interaction. Ring atom C6 in the molecule at (x, y, z), which is adjacent to the nitro group and hence has the most polarized C—H bond in the molecule, acts as hydrogen-bond donor to nitro atom O2 in the molecule at (1 − x, 1 − y, 1 − z), so forming an R₂²(10) dimer (Bernstein et al., 1995) centred at (1/2, 1/2, 1/2) (Table 2, Fig. 2). The aryl rings of the molecules at (x, y, z) and (2 − x, 2 − y, 1 − z), which are components of the R₂²(10) dimers centred, respectively, at (1/2, 1/2, 1/2) and (3/2, 3/2, 1/2), are parallel, with an interplanar spacing of 3.367 (2) Å. The centroid separation is 3.666 (2) Å, corresponding to a nearly ideal centroid offset of 1.450 (2) Å. Propagation by inversion of this stacking interaction then generates a chain of π-stacked dimers running parallel to the [110] direction (Fig. 3).

The supramolecular structure of (II) was not discussed at all in the original report (Ianelli et al., 1992). However, use of the atom coordinates for (II) retrieved from the Cambridge Structural Database (CSD; Allen, 2002), CSD refcode KONKON, shows that, in contrast with the supramolecular structure of (I), that of (II) consists of isolated C(7) zigzag chains built from a single C—H···O hydrogen bond and generated by a glide plane in space group P2₁/c (Fig. 4). π–π stacking interactions are absent from the structure of (II).

S2. Experimental

A sample of compound (I) was prepared by oxidation of a commercial sample of methyl 4-nitrophenyl sulfide (Aldrich), using hydrogen peroxide and TiCl₃, following the published procedure of Watanabe et al. (1981). Crystals of (I) suitable for single-crystal X-ray diffraction were grown by slow evaporation of a solution in ethanol (m.p. 430–432 K).

S3. Refinement

Crystals of (I) are triclinic. Space group P-1 was selected and confirmed by the successful structure analysis. All H atoms were located from difference maps and subsequently treated as riding atoms, with C—H distances 0.95 (aromatic) and 0.98 Å (methyl).

Computing details

Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: OSCAIL (McArdle, 2003) and SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: OSCAIL and SHELXL97 (Sheldrick, 1997; molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) and PRPKAPPA (Ferguson, 1999).

Figures

	Fig. 1. The (R) enantiomer of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. Part of the crystal structure of (I), showing formation of a centrosymmetric R2^2(10) dimer. For the sake of clarity, the H atoms not involved in the motif shown have been omitted. The atoms marked with an asterisk (*) are at the symmetry position (1 − x, 1 − y, 1 − z).
	Fig. 3. Stereoview of part of the crystal structure of (I), showing formation of a [110] chain of π-stacked R2^2(10) dimers. For the sake of clarity, the H atoms not involved in the motif shown have been omitted.
	Fig. 4. Part of the crystal structure of (II) (Ianelli et al., 1992), showing formation of a zigzag C(7) chain along [001]. Atomic coordinates and atom labels are as given in the original report. For the sake of clarity, the H atoms not involved in the motif shown have been omitted. The atoms marked with an asterisk (*) or a hash (#) are at the symmetry positions (x, 1/2 − y, 1/2 + z) and (x, y, 1 + z), respectively.

Methyl 4-nitrophenyl sulfoxide

Crystal data

C7H7NO3S	Z = 2
Mr = 185.20	F(000) = 192
Triclinic, P1	Dx = 1.603 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.1522 (2) Å	Cell parameters from 1739 reflections
b = 7.8550 (3) Å	θ = 3.3–27.5°
c = 7.9939 (3) Å	µ = 0.38 mm^−1
α = 83.684 (3)°	T = 120 K
β = 89.320 (2)°	Block, colourless
γ = 88.430 (3)°	0.35 × 0.35 × 0.30 mm
V = 383.81 (2) Å^3

Data collection

Nonius KappaCCD area-detector diffractometer	1739 independent reflections
Radiation source: rotating anode	1588 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.038
ϕ scans, and ω scans with κ offsets	θmax = 27.5°, θmin = 3.3°
Absorption correction: multi-scan (SORTAV; Blessing, 1995, 1997)	h = −7→8
Tmin = 0.878, Tmax = 0.894	k = −10→9
6313 measured reflections	l = −10→10

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) = 0.079	H-atom parameters constrained
S = 1.11	w = 1/[σ^2(Fo^2) + (0.033P)^2 + 0.1817P] where P = (Fo^2 + 2Fc^2)/3
1739 reflections	(Δ/σ)max = 0.001
110 parameters	Δρmax = 0.32 e Å^−3
0 restraints	Δρmin = −0.41 e Å^−3

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

	x	y	z	Uiso*/Ueq
C1	0.9138 (2)	0.70819 (17)	0.43727 (17)	0.0137 (3)
C2	1.1127 (2)	0.78276 (17)	0.40236 (17)	0.0155 (3)
C3	1.2219 (2)	0.84396 (17)	0.53340 (18)	0.0152 (3)
C4	1.1294 (2)	0.82927 (17)	0.69301 (17)	0.0139 (3)
C5	0.9277 (2)	0.75597 (18)	0.72548 (17)	0.0166 (3)
C6	0.8181 (2)	0.69342 (18)	0.59590 (17)	0.0156 (3)
N1	0.79667 (19)	0.64214 (15)	0.29973 (15)	0.0155 (2)
O1	0.87916 (18)	0.65772 (15)	0.15837 (13)	0.0230 (3)
O2	0.62245 (17)	0.57405 (14)	0.33273 (13)	0.0226 (2)
S4	1.26776 (5)	0.91596 (4)	0.86053 (4)	0.01619 (12)
O41	1.45691 (18)	1.01004 (14)	0.78095 (13)	0.0226 (2)
C41	1.3715 (2)	0.71571 (19)	0.96114 (18)	0.0184 (3)
H2	1.1728	0.7918	0.2918	0.019*
H3	1.3591	0.8955	0.5138	0.018*
H5	0.8659	0.7490	0.8354	0.020*
H6	0.6809	0.6417	0.6151	0.019*
H41A	1.4571	0.6566	0.8798	0.028*
H41B	1.2501	0.6444	1.0033	0.028*
H41C	1.4641	0.7366	1.0553	0.028*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0144 (7)	0.0121 (6)	0.0143 (6)	0.0003 (5)	−0.0036 (5)	−0.0005 (5)
C2	0.0159 (7)	0.0163 (7)	0.0138 (6)	−0.0004 (5)	0.0021 (5)	0.0001 (5)
C3	0.0121 (6)	0.0148 (7)	0.0186 (7)	−0.0020 (5)	0.0004 (5)	−0.0004 (5)
C4	0.0143 (7)	0.0122 (6)	0.0152 (6)	0.0000 (5)	−0.0031 (5)	−0.0020 (5)
C5	0.0152 (7)	0.0206 (7)	0.0139 (6)	−0.0021 (5)	0.0010 (5)	−0.0006 (5)
C6	0.0120 (6)	0.0186 (7)	0.0159 (7)	−0.0034 (5)	−0.0008 (5)	−0.0001 (5)
N1	0.0168 (6)	0.0141 (6)	0.0154 (6)	−0.0006 (4)	−0.0026 (4)	−0.0011 (4)
O1	0.0236 (6)	0.0334 (6)	0.0124 (5)	−0.0031 (5)	0.0002 (4)	−0.0045 (4)
O2	0.0215 (6)	0.0260 (6)	0.0208 (5)	−0.0113 (4)	−0.0032 (4)	−0.0020 (4)
S4	0.0161 (2)	0.01682 (19)	0.01650 (19)	−0.00319 (13)	−0.00132 (13)	−0.00508 (13)
O41	0.0238 (6)	0.0236 (6)	0.0211 (5)	−0.0123 (4)	−0.0001 (4)	−0.0031 (4)
C41	0.0187 (7)	0.0209 (7)	0.0159 (7)	−0.0015 (5)	−0.0040 (5)	−0.0030 (5)

Geometric parameters (Å, º)

C1—C2	1.3835 (19)	C5—H5	0.95
C1—C6	1.3863 (19)	C6—H6	0.95
C1—N1	1.4704 (17)	N1—O2	1.2240 (16)
C2—C3	1.387 (2)	N1—O1	1.2283 (16)
C2—H2	0.95	S4—O41	1.4937 (11)
C3—C4	1.385 (2)	S4—C41	1.7909 (15)
C3—H3	0.95	C41—H41A	0.98
C4—C5	1.392 (2)	C41—H41B	0.98
C4—S4	1.8003 (14)	C41—H41C	0.98
C5—C6	1.3841 (19)
C2—C1—C6	123.20 (13)	C5—C6—C1	118.23 (13)
C2—C1—N1	118.68 (12)	C5—C6—H6	120.9
C6—C1—N1	118.11 (12)	C1—C6—H6	120.9
C1—C2—C3	118.10 (13)	O2—N1—O1	123.63 (12)
C1—C2—H2	120.9	O2—N1—C1	118.07 (11)
C3—C2—H2	120.9	O1—N1—C1	118.30 (12)
C4—C3—C2	119.49 (13)	C4—S4—C41	96.61 (6)
C4—C3—H3	120.3	C4—S4—O41	106.29 (6)
C2—C3—H3	120.3	O41—S4—C41	107.10 (7)
C3—C4—C5	121.67 (13)	S4—C41—H41A	109.5
C3—C4—S4	119.14 (11)	S4—C41—H41B	109.5
C5—C4—S4	119.13 (10)	H41A—C41—H41B	109.5
C6—C5—C4	119.30 (13)	S4—C41—H41C	109.5
C6—C5—H5	120.4	H41A—C41—H41C	109.5
C4—C5—H5	120.4	H41B—C41—H41C	109.5
C6—C1—C2—C3	0.7 (2)	N1—C1—C6—C5	−179.80 (12)
N1—C1—C2—C3	−179.75 (11)	C3—C4—S4—O41	6.56 (13)
C1—C2—C3—C4	−0.2 (2)	C5—C4—S4—O41	−170.63 (11)
C2—C3—C4—C5	−0.7 (2)	C3—C4—S4—C41	−103.45 (12)
C2—C3—C4—S4	−177.79 (10)	C5—C4—S4—C41	79.36 (12)
C3—C4—C5—C6	1.1 (2)	C2—C1—N1—O1	−0.87 (19)
S4—C4—C5—C6	178.24 (10)	C2—C1—N1—O2	178.88 (12)
C4—C5—C6—C1	−0.7 (2)	C6—C1—N1—O2	−1.51 (19)
C2—C1—C6—C5	−0.2 (2)	C6—C1—N1—O1	178.74 (12)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···O41	0.95	2.49	2.907 (2)	106
C6—H6···O2^i	0.95	2.56	3.478 (2)	164

Symmetry code: (i) −x+1, −y+1, −z+1.