Soft C—H...O hydrogen bonds in methyl 2,4-di­nitro­benzene­sulfenate: sheets built from R₂²(10) and R₆⁶(42) rings

Molecules of the title compound, C₇H₆N₂O₅S, are linked into sheets containing R₂²(10) and R₆⁶(42) rings by C—H...O hydrogen bonds [C...O 3.405 (3) and 3.511 (2) Å; C—H...O 159 and 169°], in which both acceptors are in the same nitro group. Comparisons are made with the hydrogen bonding in other nitro­benzene­sulfenate esters.

S1. Comment

We have recently discussed the interplay of intra- and intermolecular forces in 2-nitrobenzenethiolates of type 2-O₂NC₆H₄SX in examples where the α-atom of the group X is variously C (Low, Storey et al., 2000; Glidewell et al., 2000c), N (Low, Storey et al., 2000; Glidewell et al., 2000b), S (Low, Glidewell & Wardell et al., 2000; Glidewell et al., 2000a) or Pd (Aupers et al., 2000). In particular we have been concerned with the correlation between the conformational behaviour of the 2-nitro group and that of the thiolate fragment, and with the influence upon this of intermolecular forces, especially soft hydrogen bonds of the C—H···O type. We have now extended this study to an example where the α-atom of X is O; we report here the structure of methyl 2,4-dinitrobenzenesulfenate, 2,4-(O₂N)₂C₆H₃SOCH₃, (I), and we compare the C—H···O hydrogen bonding in (I) with that in structures of related nitrobenzenesulfenate esters, retrieved via the Cambridge Structural Database (CSD: Allen & Kennard, 1993). \sch

The ester O and the 2-nitro group are both very slightly twisted out of the plane of the aryl ring (Table 1), consistent with the correlation discussed in previous papers: on the other hand, the 4-nitro group is essentially coplanar with the ring. The C—S—O—C torsional angle is close to 90°, determined primarily by the expected near-orthogonality of the adjacent lone-pair orbitals on S and O. The dimensions of the ring indicate a modest degree of o-quinonoid bond-fixation, consistent with a small contribution from the canonical form (1a): there is, however, no evidence for the very marked development of p-quinonoid bond fixation as observed in 2-O₂N-4-CH₃C₆H₃SCH═CHPh (Low, Storey et al., 2000). Consistent with a contribution from (Ia), the C—S bond length is somewhat less than is typical for C(aryl)-S– bonds: mean value 1.773 Å, lower quartile value 1.765 Å (Allen et al., 1987).

The molecules of (I) are linked by two soft C—H···O hydrogen bonds (Table 2) into two-dimensional sheets; although neither hydrogen bond has particularly short H···O or C···O distances, the values in (1) are well within the ranges accepted for such bonds (Desiraju, 1991, 1996), and the C—H···O angles are both close to the optimally observed 160°. Unexpectedly, the shorter H···O and C···O distances are associated with the less acidic C—H bond. Aromatic C3 in the molecule at (x, y, z) acts as donor to nitro O41 in the molecule at (1 - x, 1 - y, 1 - z), while C3 at (1 - x, 1 - y, 1 - z) acts as donor to O41 at (x, y, z), so generating a centrosymmetric R²₂(10) motif within a dimer centred at (1/2, 1/2, 1/2) (Fig. 2). The second C—H···O hydrogen bond then links these dimeric units into continuous sheets parallel to (103), which take the form of (4,4) nets (Batten & Robson, 1998) in which the dimer units act as the nodes of the net. Methyl C7 in the molecule at (x, y, z) acts as hydrogen-bond donor, via H72, to nitro O42 at (-1/2 - x, 1/2 + y, 3/2 - z); the symmetry-related C7 in the dimer centred at (1/2, 1/2, 1/2) is at (1 - x, 1 - y, 1 - z) and this acts as donor to O42 at (3/2 + x, 0. - y, -1/2 + z). Each R²₂(10) dimer thus acts as a double donor and as a double acceptor of hydrogen bonds of this type and, in this manner, the dimer centred at (1/2, 1/2, 1/2) is directly linked to the dimers centred at (2, 0, 0), (2, 1, 0), (-1, 0, 1) and (-1, 1, 1). Propagation of these hydrogen bonds by the space group generates the (103) sheet built from alternating R²₂(10) and R⁶₆(42) rings (Fig. 2); despite the presence of large rings, adjacent sheets are not interwoven.

It is noteworthy that while both O atoms of the 4-nitro group act as hydrogen-bond acceptors, neither of the O atoms in the 2-nitro group does so. Hence it is of interest to compare the hydrogen-bonding behaviour of (I) with that of the related compounds (II) - (VIII). In compound (II) (CSD code NUPPUJ; Green et al., 1997), both O atoms of the 4-nitro group act as acceptors, with an adjacent pair of aromatic C atoms acting as the donors: in this manner a C(5) C(6)[R²₂(7)] chain of rings (Bernstein et al., 1995) is formed (Fig. 3) which contains the unusual synthon (IIa), not listed in Desiraju's compilation of supramolecular synthons (Desiraju, 1995). By contrast, in the closely related ester (III) (NUPPIX; Green et al., 1997) neither of the nitro groups is involved in the hydrogen bonding; instead the ester O acts as the acceptor from an aromatic C, and a simple C(5) spiral chain is formed (Fig. 4). However, there are no intermolecular C—H···O hydrogen bonds in either of (IV) (MENBZS01; Kucsman et al., 1989) or (V) (EACBOZ; Craine et al., 1993), both of which are evidently very closely related to compound (I); nor are there any such bonds in either the trans (TELKUQ; White et al., 1996) or cis (TELKUQ01; Chan et al., 1996; inadvertently described in the original report, and thence in the CSD, as trans) isomers of (VI), but in the isostructural pair (VII) (TOTRID; Chan et al., 1996) and (VIII) (TOTREZ; Chan et al., 1996) a C atom in the cyclohexyl unit acts as donor to one of the O atoms of the 4-nitro group, forming a C(11) spiral chain (Fig. 5). Thus, within the rather closely-related series of esters (I)-(V), the soft C—H···O hydrogen bonds generate a two-dimensional supramolecular structure in (I), and two quite different one-dimensional arrays in (II) and (III) respectively, while there is no specific supramolecular aggregation in (IV) and (V); similarly the closely-related esters (VI)-(VIII) differ in their behaviour. In none of the original reports on compounds (II), (III) and (VI)-(VIII) was there any comment on this aggregation.

Related literature

For related literature, see: Allen & Kennard (1993); Allen et al. (1987); Aupers et al. (2000); Batten & Robson (1998); Bernstein et al. (1995); Chan et al. (1996); Craine et al. (1993); Desiraju (1991, 1995, 1996); Glidewell et al. (2000a, 2000b, 2000c); Green et al. (1997); Kucsman et al. (1989); Low, Glidewell & Wardell (2000); Low, Storey, McCarron, Wardell, Ferguson & Glidewell (2000); White et al. (1996).

S2. Experimental

A sample of compound (I) was prepared by reaction of 2,4-dinitrobenzenesulfenyl chloride with methanol: crystal suitable for single-crystal X-ray diffraction werre grown from methanol solution.

S3. Refinement

Compound (I) crystallized in the monoclinic system; space group P2₁/n was uniquely assigned from the systematic absences. H atoms were treated as riding atoms with C—H 0.93 Å (aromatic) or 0.96 Å (methyl).

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2000); software used to prepare material for publication: SHELXL97 and PRPKAPPA (Ferguson, 1999).

Figures

	Fig. 1. The molecule 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 (103) sheet built from R^22(10) and R^66(42) rings. Atoms marked with a star (*), hash (#) or dollar sign () are at the symmetry positions (1 - x, 1 - y, 1 - z), (-1/2 - x, 1/2 + y, 3/2 - z) and (3/2 + x, 1/2 - y, -1/2 + z), respectively.
	Fig. 3. Part of the crystal structure of (II) showing formation of a C(5) C(6)[R^22(7)] chain of rings. Atoms marked with a star (*) or hash (#) are at the symmetry positions (-x, 1/2 + y, -1/2 - z) and (x, 1 + y, z), respectively.
	Fig. 4. Part of the crystal structure of (III) showing formation of a C(5) spiral chain. Atoms marked with a star (*) or hash (#) are at the symmetry positions (-1/2 + x, 3/2 - y, 1 - z) and (-1 + x, y, z), respectively.
	Fig. 5. Part of the crystal structure of (7) showing formation of a C(11) spiral chain. Atoms marked with a star (*) or hash (#) are at the symmetry positions (2 - x, 1/2 + y, -1/2 - z) and (x, 1 + y, z), respectively.

Methyl 2,4-dinitrobenzenesulfenate

Crystal data

C7H6N2O5S	F(000) = 472
Mr = 230.20	Dx = 1.625 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 4.0413 (2) Å	Cell parameters from 2643 reflections
b = 16.6702 (10) Å	θ = 2.9–29.7°
c = 14.0749 (8) Å	µ = 0.35 mm^−1
β = 97.183 (1)°	T = 295 K
V = 940.77 (9) Å^3	Block, yellow
Z = 4	0.30 × 0.20 × 0.20 mm

Data collection

Bruker SMART area CCD detector diffractometer	3370 independent reflections
Radiation source: fine-focus sealed tube	1920 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.036
ϕ–ω scans	θmax = 32.6°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Bruker, 1997)	h = −6→5
Tmin = 0.903, Tmax = 0.934	k = −12→25
9619 measured reflections	l = −21→19

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)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.141	H-atom parameters constrained
S = 0.90	w = 1/[σ^2(Fo^2) + (0.0836P)^2] where P = (Fo^2 + 2Fc^2)/3
3370 reflections	(Δ/σ)max = 0.001
137 parameters	Δρmax = 0.40 e Å^−3
0 restraints	Δρmin = −0.29 e Å^−3

Special details

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	−0.1474 (3)	0.76321 (10)	0.51697 (10)	0.0401 (3)
S1	−0.29309 (10)	0.85383 (3)	0.46521 (3)	0.05327 (16)
O1	−0.4346 (3)	0.89634 (8)	0.55651 (10)	0.0618 (4)
C7	−0.1966 (6)	0.94450 (13)	0.61738 (16)	0.0692 (6)
C2	0.0124 (4)	0.70494 (10)	0.46748 (10)	0.0422 (3)
N2	0.0589 (4)	0.71954 (10)	0.36886 (9)	0.0545 (4)
O21	−0.0662 (4)	0.78125 (10)	0.33211 (8)	0.0665 (4)
O22	0.2229 (5)	0.67316 (11)	0.32747 (10)	0.0921 (6)
C3	0.1306 (4)	0.63358 (10)	0.50802 (11)	0.0445 (4)
C4	0.0846 (4)	0.61974 (10)	0.60154 (11)	0.0438 (3)
N4	0.2140 (4)	0.54539 (10)	0.64745 (11)	0.0600 (4)
O41	0.3590 (5)	0.49897 (10)	0.60188 (14)	0.0920 (5)
O42	0.1735 (5)	0.53473 (11)	0.73044 (12)	0.0984 (6)
C5	−0.0760 (4)	0.67448 (11)	0.65373 (10)	0.0463 (4)
C6	−0.1897 (4)	0.74511 (11)	0.61237 (10)	0.0451 (4)
H71	−0.0015	0.9131	0.6377	0.104*
H72	−0.2952	0.9619	0.6724	0.104*
H73	−0.1352	0.9904	0.5823	0.104*
H3	0.2373	0.5962	0.4733	0.053*
H5	−0.1066	0.6633	0.7168	0.056*
H6	−0.2968	0.7818	0.6479	0.054*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0337 (7)	0.0512 (9)	0.0349 (6)	−0.0043 (6)	0.0021 (5)	−0.0028 (6)
S1	0.0496 (2)	0.0592 (3)	0.0499 (2)	0.00549 (19)	0.00178 (17)	0.00340 (19)
O1	0.0497 (6)	0.0645 (8)	0.0723 (8)	0.0088 (6)	0.0121 (6)	−0.0067 (7)
C7	0.0762 (13)	0.0595 (12)	0.0748 (13)	−0.0020 (10)	0.0211 (11)	−0.0164 (10)
C2	0.0409 (7)	0.0568 (9)	0.0296 (6)	−0.0064 (7)	0.0064 (5)	−0.0038 (6)
N2	0.0602 (9)	0.0712 (10)	0.0333 (6)	−0.0015 (7)	0.0111 (6)	−0.0011 (6)
O21	0.0737 (9)	0.0853 (10)	0.0399 (6)	0.0071 (7)	0.0049 (6)	0.0121 (6)
O22	0.1339 (15)	0.1009 (13)	0.0502 (7)	0.0296 (11)	0.0456 (9)	−0.0002 (8)
C3	0.0447 (8)	0.0489 (9)	0.0409 (7)	−0.0031 (7)	0.0094 (6)	−0.0062 (6)
C4	0.0425 (7)	0.0484 (9)	0.0403 (7)	−0.0072 (6)	0.0046 (6)	0.0016 (6)
N4	0.0616 (9)	0.0586 (10)	0.0601 (9)	−0.0031 (8)	0.0081 (7)	0.0094 (8)
O41	0.1170 (13)	0.0693 (10)	0.0941 (11)	0.0315 (10)	0.0303 (10)	0.0129 (9)
O42	0.1372 (16)	0.0921 (13)	0.0704 (10)	0.0226 (11)	0.0310 (11)	0.0377 (9)
C5	0.0470 (8)	0.0607 (10)	0.0316 (6)	−0.0096 (7)	0.0064 (6)	−0.0020 (6)
C6	0.0441 (8)	0.0552 (10)	0.0371 (7)	−0.0032 (7)	0.0097 (6)	−0.0076 (6)

Geometric parameters (Å, º)

C1—C2	1.399 (2)	N4—O42	1.213 (2)
C2—C3	1.379 (2)	C1—S1	1.7471 (17)
C3—C4	1.372 (2)	S1—O1	1.6322 (13)
C4—C5	1.383 (2)	O1—C7	1.448 (2)
C5—C6	1.367 (2)	C3—H3	0.930
C1—C6	1.407 (2)	C5—H5	0.930
C2—N2	1.4445 (19)	C6—H6	0.930
C4—N4	1.464 (2)	C7—H71	0.960
N2—O21	1.231 (2)	C7—H72	0.960
N2—O22	1.214 (2)	C7—H73	0.960
N4—O41	1.203 (2)
C2—C1—C6	116.41 (15)	O41—N4—C4	118.69 (16)
C2—C1—S1	123.04 (11)	O42—N4—C4	117.74 (17)
C6—C1—S1	120.55 (13)	C4—C5—C6	119.80 (14)
C1—S1—O1	100.38 (7)	C1—C6—C5	121.09 (15)
S1—O1—C7	115.74 (11)	C2—C3—H3	121.3
C1—C2—N2	119.01 (15)	C4—C3—H3	121.3
C3—C2—N2	117.59 (14)	C4—C5—H5	120.1
C1—C2—C3	123.40 (14)	C6—C5—H5	120.1
O21—N2—O22	123.43 (15)	C5—C6—H6	119.4
O22—N2—C2	119.89 (16)	C1—C6—H6	119.4
O21—N2—C2	116.64 (15)	O1—C7—H71	109.5
C2—C3—C4	117.44 (15)	O1—C7—H72	109.5
C3—C4—C5	121.84 (15)	O1—C7—H73	109.5
C3—C4—N4	118.84 (15)	H71—C7—H72	109.5
C5—C4—N4	119.31 (14)	H72—C7—H73	109.5
O41—N4—O42	123.56 (19)	H73—C7—H71	109.5
C2—C1—S1—O1	−177.65 (13)	C1—S1—O1—C7	89.37 (14)
C1—C2—N2—O21	−4.6 (2)	C3—C4—N4—O41	0.5 (3)
C1—C2—N2—O22	173.38 (17)	C3—C4—N4—O42	179.28 (17)
C3—C2—N2—O21	175.67 (16)	C5—C4—N4—O41	−178.55 (18)
C3—C2—N2—O22	−6.4 (3)	C5—C4—N4—O42	0.2 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···O41^i	0.93	2.59	3.511 (2)	169
C7—H72···O42^ii	0.96	2.49	3.405 (3)	159

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x−1/2, y+1/2, −z+3/2.