organic papers o1892 Trilleras et al. C 23 H 19 ClN 2 O 2 S 2 doi:10.1107/S1600536805015886 Acta Cryst. (2005). E61, o1892–o1894 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 3-(5-Chloro-3-methyl-1-phenylpyrazol-4-yl)-1,5-di- 2-thienylpentane-1,5-dione: centrosymmetric dimers formed by C—Hp(thiophene) hydrogen bonds Jorge Trilleras, a Jairo Quiroga, a Justo Cobo, b John N. Low c and Christopher Glidewell d * a Grupo de Investigacio ´ n de Compuestos Heterocı ´clicos, Departamento de Quı ´mica, Universidad de Valle, AA 25360 Cali, Colombia, b Departamento de Quı ´mica Inorga ´- nica y Orga ´nica, Universidad de Jae ´n, 23071 Jae ´n, Spain, c Department of Chemistry, Univer- sity of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and d School of Chemistry, University of St Andrews, Fife KY16 9ST, Scot- land Correspondence e-mail: cg@st-andrews.ac.uk Key indicators Single-crystal X-ray study T = 120 K Mean (C–C) = 0.003 A ˚ Disorder in main residue R factor = 0.046 wR factor = 0.117 Data-to-parameter ratio = 17.5 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. # 2005 International Union of Crystallography Printed in Great Britain – all rights reserved Molecules of the title compound, C 23 H 19 ClN 2 O 2 S 2 , are linked into cyclic centrosymmetric dimers by paired C—H(thio- phene) hydrogen bonds. Comment The title compound, (I), was obtained adventitiously during the attempted synthesis of the intermediate 3-(5-chloro-3- methyl-1-phenyl-4,5-dihydro-1H-pyrazol-4-yl)-1-thiophen-2- yl-propenone, (II), by base-catalysed condensation of 5- chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde with 2-aceylthiophene. Evidently, the expected product, (II), has undergone a Michael-type reaction with a further mole of 2- acetylthiophene to form the observed product, (I). Within the molecule of (I), the thiophene ring containing S9 exhibits orientational disorder about the C9—C91 bond, with occupancies of 0.623 (3) and 0.377 (3): all bond distances and angles show normal values. The supramolecular aggregation is determined by C— H(thiophene) hydrogen bonds (Table 1). Atom C8 in the molecule at (x, y, z) acts as a hydrogen-bond donor to the disordered thiophene ring of the molecule at (1 x,1 y, 1 z), so generating a centrosymmetric dimer (Fig. 2) whose formation is independent of the orientation of the thiophene acceptor (Table 1). The only other possible intermolecular interaction is a fairly short contact between atom Cl5 in the molecule at (x, y, z) and aryl atom C14 in the molecule at ( 1 2 + x, y, 3 2 z), with a ClC distance of 3.137 (2) A ˚ and a C— ClC angle of 153.5 (2) ; this distance is not particularly short in terms of the polar flattening model for van der Waals contacts (Nyburg & Faerman, 1985) and is probably not structurally significant. Received 17 May 2005 Accepted 18 May 2005 Online 28 May 2005