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Acta Crystallogr C. 2009 September 15; 65(Pt 9): o444–o446.
Published online 2009 August 8. doi:  10.1107/S0108270109029667
PMCID: PMC2737424

(E)-3-(4-Methyl­phen­yl)-2-(2-thien­yl)­acrylonitrile has Z′ = 0.75 in the space group C2/m: fourfold disordered mol­ecules lie in channels enclosed by fully ordered mol­ecules

Abstract

The title compound, C14H11NS, crystallizes with Z′ = 0.75 in the space group C2/m. Two independent mol­ecules are present, one of which lies with all the non-H atoms on a mirror plane, while the other is fourfold disordered across a site of 2/m symmetry. The ordered mol­ecules are stacked such that they enclose continuous channels running along twofold rotation axes, and the disordered mol­ecules are positioned within these channels.

Comment

We report here the structure of the title compound, (I) (Fig. 1 [triangle]). Although related pairs of compounds containing, respectively, Me and Cl substituents, such as (I) and (II), are not infrequently isomorphous, the crystal structure of (I) shows some significant differences from the pair of analogues (II) (Cobo et al., 2005 [triangle]) and (III) (Cobo, Quiroga et al., 2006 [triangle]), which are isomorphous and isostructural with one another.

An external file that holds a picture, illustration, etc.
Object name is c-65-0o444-scheme1.jpg

Figure 1
The independent mol­ecular components of (I), with the atom-labelling schemes, showing (a) mol­ecule 1, (b) a single orientation of mol­ecule 2, and (c) the four orientations of mol­ecule 2 across a site of 2/m symmetry ...

While the isomorphous pair of compounds (II) and (III) both crystallize with Z′ = 1 in the common space group P21/n, compound (I) crystallizes in the rather uncommon space group C2/m with Z′ = 0.75. There are two independent mol­ecules of (I) in the unit cell. For mol­ecule 1 containing atom S1 (Fig. 1 [triangle] a), all of the non-H atoms lie on a mirror plane, selected for the reference mol­ecule 1 as that at y = An external file that holds a picture, illustration, etc.
Object name is c-65-0o444-efi1.jpg, so providing four mol­ecules per unit cell. Mol­ecule 2 containing atom S31 (Fig. 1 [triangle] b) lies across a site of 2/m symmetry, selected for the reference mol­ecule 2 as that at (0, 0, An external file that holds a picture, illustration, etc.
Object name is c-65-0o444-efi1.jpg), so that each such mol­ecule is disordered over four sets of atomic sites (Fig. 1 [triangle] c), and thus provides a further two mol­ecules per unit cell. Hence, there are, overall, six mol­ecules of (I) per unit cell, giving Z′ = 0.75. The June 2009 release of the Cambridge Structural Database (Allen, 2002 [triangle]) records a total of 2477 structures in this space group, fewer than 0.8% of the total, of which only 17 have Z′ = 0.75; of these 17 entries, coordinates have been deposited for only 14, so that a Z′ value of 0.75 in the space group C2/m is indeed rare for both organic and organometallic compounds.

For mol­ecule 1 of (I), the non-H atoms are constrained to be coplanar, and the rather short intra­molecular C—H(...)N contact distance (Table 2 [triangle]) may be a direct consequence of this. In mol­ecule 2, the non-H atoms are planar within experimental uncertainty, although not constrained by symmetry, as shown by the key torsion angles (Table 1 [triangle]). There is no evidence for any orientational disorder of the 2-thienyl unit in mol­ecule 1. By contrast, both (II) and (III) show orientational disorder of the thienyl unit, with unequal populations for the two orientations in an approximate 4:1 ratio (Cobo et al., 2005 [triangle]; Cobo, Quiroga et al., 2006 [triangle]). In addition, the non-H skeletons of (II) and (III) are not planar, with the aryl ring markedly displaced from the plane of the rest of the mol­ecule in both cases; the respective C27—C17—C11—C12 torsion angles in (II) and (III) are 37.9 (3) and 38.7 (4)°. On the other hand, the mol­ecules of (IV) (Cobo, Quiroga et al., 2006 [triangle]) are almost planar apart from the C atom of the central meth­oxy group. As in compounds (II)–(IV), the nitrile units in (I) show long C—C distances and short C—N distances (Table 1 [triangle]), but otherwise the bond distances in (I) show no unexpected features.

Table 1
Selected geometric parameters (Å, °)
Table 2
Hydrogen-bond geometry (Å, °)

The mol­ecules in each of (II) and (III) are linked into simple C(5) (Bernstein et al., 1995 [triangle]) chains by a single C—H(...)N hydrogen bond, while the structure of (IV) shows no direction-specific inter­molecular inter­actions of any kind, but in (I) the mol­ecular aggregation is quite complex. Type 1 mol­ecules related by a twofold rotation axis form pairs of short C—H(...)N contacts in an An external file that holds a picture, illustration, etc.
Object name is c-65-0o444-efi3.jpg(12) motif (Table 2 [triangle]), although these contacts are probably too long to be regarded as genuine hydrogen bonds. There are no other direction-specific inter­actions between the type 1 mol­ecules, but nonetheless, these mol­ecules are arranged such that they enclose channels running parallel to [010] (Fig. 2 [triangle]). The channels lie along the twofold rotation axes at z = An external file that holds a picture, illustration, etc.
Object name is c-65-0o444-efi1.jpg, and they are approx­i­mately recta­ngular with approximate dimensions 13.3 × 3.7 Å, giving a cross-sectional area of ca 49.2 Å2. The disordered type 2 mol­ecules lie within the channels generated by the ordered type 1 mol­ecules, such that the long axes of the type 2 mol­ecules lie approximately along the long diameter of the channels (Fig. 3 [triangle]).

Figure 2
A space-filling projection on to (010) of part of the crystal structure of (I), showing only the ordered type 1 mol­ecules and the channels running parallel to [010]. H atoms have been retained to emphasize the size and shape of the channels.
Figure 3
A projection on to (010) of part of the crystal structure of (I), showing the relative locations and orientations of the mol­ecules of types 1 and 2. As in Fig. 2 [triangle], H atoms have been retained to emphasize the spacing of the mol­ecules. ...

Isomeric with (I) is the 3-thienyl analogue (V) (Cobo, Cobo et al., 2006 [triangle]), which crystallizes with Z′ = 1 in P21/c with fully ordered mol­ecules. In both (V) and the unsubstituted analogue (VI) (Cobo, Quiroga et al., 2006 [triangle]), pairs of mol­ecules again form short contacts involving paired C—H(...)N inter­actions, leading to an An external file that holds a picture, illustration, etc.
Object name is c-65-0o444-efi3.jpg(12) motif similar to that in (I), except that in (V) and (VI) the participating mol­ecules are related by inversion, whereas in (I) they are related by rotation. Compounds (I) and (V) show very similar dimensions for this contact, but only in compound (VI) are the dimensions of the C—H(...)N inter­action such that it can be regarded as a genuine hydrogen bond.

Hence, within the closely similar series of compounds (I)–(VI), the crystallization characteristics and the supra­molecular aggregation show some surprising and unexpected variations.

Experimental

A solution of 2-thio­phene­acetonitrile (1 mmol) and potassium tert-butoxide (1 mmol) in anhydrous ethanol (3 ml) was stirred at room temperature for 15 min; a solution of 4-methyl­benzaldehyde (1 mmol) in anhydrous ethanol (3 ml) was added, and the mixture was then heated under reflux for 3 h. The resulting solid product was collected by filtration, washed with ethanol, dried and finally crystallized from dimethyl­formamide to give yellow crystals suitable for single-crystal X-ray diffraction (yield 55%, m.p. 379–381 K). MS EI (30 eV) m/z (%): 225 (100, M +), 210 (10), 177 (31), 176 (11), 165 (10), 152 (9), 150 (17), 105 (26) 93 (22), 89 (11), 76 (25), 65 (29), 28 (26).

Crystal data

  • C14H11NS
  • M r = 225.31
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is c-65-0o444-efi6.jpg
  • a = 21.4869 (7) Å
  • b = 7.0302 (3) Å
  • c = 14.1810 (5) Å
  • β = 126.173 (2)°
  • V = 1729.22 (12) Å3
  • Z = 6
  • Mo Kα radiation
  • μ = 0.25 mm−1
  • T = 120 K
  • 0.22 × 0.18 × 0.16 mm

Data collection

  • Bruker–Nonius KappaCCD diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003 [triangle]) T min = 0.943, T max = 0.961
  • 9286 measured reflections
  • 2133 independent reflections
  • 1956 reflections with I > 2σ(I)
  • R int = 0.028

Refinement

  • R[F 2 > 2σ(F 2)] = 0.058
  • wR(F 2) = 0.132
  • S = 1.25
  • 2133 reflections
  • 238 parameters
  • 39 restraints
  • H-atom parameters constrained
  • Δρmax = 0.31 e Å−3
  • Δρmin = −0.28 e Å−3

It was apparent at any early stage in the structure solution that, while one of the two independent mol­ecules (mol­ecule 1 containing S1) is fully ordered with all of its non-H atoms lying on a mirror plane in C2/m, the second mol­ecule (mol­ecule 2, containing S31) is lying across a site of 2/m symmetry and is thus disordered over four sets of sites (see Fig. 1 [triangle] c). A structural model for mol­ecule 2 was initially developed on geometric grounds and then refined using a substantial number of individually specified geometric restraints, with the bonded distances usually subject to s.u. values of 0.01 Å and the 1,3 nonbonded distances to s.u. values of 0.02 Å. Once this refinement model had stabilized, the individually specified restraints were all removed, and the bonded and 1,3 nonbonded distances in mol­ecule 2 were all restrained to have the same values as the corresponding distances in mol­ecule 1, subject in all cases to an s.u. of 0.005 Å. On this basis, satisfactory convergence was achieved, but attempts to remove these similarity restraints led to unsatisfactory behaviour of the atomic displacement parameters. The H atoms in mol­ecule 1 were all clearly located in difference maps, but it was necessary to introduce those in mol­ecule 2 in calculated positions; thereafter all H atoms were treated as riding atoms in geometrically idealized positions, with C—H distances of 0.98 (meth­yl) or 0.95 Å (all other H atoms) and U iso(H) = kU eq(C), where k = 1.5 for the methyl groups, which were permitted to rotate but not to tilt, and k = 1.2 for all other H atoms. Because methyl atom C18 lies on a mirror plane, the three H atoms bonded to it are disordered over two sets of sites, with each of these H-atom sites having 0.5 occupancy. The torsion angles C13—C14—C18—H18x (where x represents A, B or C) for the six sites have values of ±19, ±139 and ±101° for x = A, B and C, respectively.

Data collection: COLLECT (Hooft, 1999 [triangle]); cell refinement: DENZOSMN (Otwinowski & Minor, 1997 [triangle]); data reduction: DENZOSMN and SCALEPACK (Otwinowski & Minor, 1997 [triangle]); program(s) used to solve structure: SIR2004 (Burla et al., 2005 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: PLATON (Spek, 2009 [triangle]); software used to prepare material for publication: SHELXL97 and PLATON.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S0108270109029667/gg3209sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S0108270109029667/gg3209Isup2.hkl

Acknowledgments

X-ray data were collected at the EPSRC National Crystallography Service, University of Southampton, England. JC thanks the Consejería de Innovación, Ciencia y Empresa (Junta de Andalucía, Spain) and the Universidad de Jaén for financial support. JQ and DC thank COLCIENCIAS and UNIVALLE (Universidad del Valle, Colombia) for financial support.

Footnotes

Supplementary data for this paper are available from the IUCr electronic archives (Reference: GG3209). Services for accessing these data are described at the back of the journal.

References

  • Allen, F. H. (2002). Acta Cryst. B58, 380–388. [PubMed]
  • Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl.34, 1555–1573.
  • Burla, M. C., Caliandro, R., Camalli, M., Carrozzini, B., Cascarano, G. L., De Caro, L., Giacovazzo, C., Polidori, G. & Spagna, R. (2005). J. Appl. Cryst.38, 381–388.
  • Cobo, D., Cobo, J., Low, J. N. & Glidewell, C. (2006). Acta Cryst. E62, o5179–o5180.
  • Cobo, D., Quiroga, J., Cobo, J., Low, J. N. & Glidewell, C. (2005). Acta Cryst. E61, o3639–o3641.
  • Cobo, D., Quiroga, J., de la Torre, J. M., Cobo, J., Low, J. N. & Glidewell, C. (2006). Acta Cryst. C62, o550–o553. [PubMed]
  • Hooft, R. W. W. (1999). COLLECT Nonius BV, Delft, The Netherlands.
  • Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.
  • Sheldrick, G. M. (2003). SADABS. Version 2.10. University of Göttingen, Germany.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Spek, A. L. (2009). Acta Cryst. D65, 148–155. [PMC free article] [PubMed]

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