organic papers o2388 Jaganyi et al. C 18 H 20 N 2 S 3 doi:10.1107/S1600536807016017 Acta Cryst. (2007). E63, o2388–o2390 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 A tripodal tris(thiophene) derivative of hexahydropyrimidine and its ladder-like extended structure Deogratius Jaganyi, Allen Mambanda and Orde Q. Munro* School of Chemistry, University of KwaZulu- Natal, Peitermaritzburg, Private Bag X01, Scottsville 3209, South Africa Correspondence e-mail: munroo@ukzn.ac.za Key indicators Single-crystal X-ray study T = 110 K Mean (C–C) = 0.002 A ˚ R factor = 0.029 wR factor = 0.082 Data-to-parameter ratio = 27.2 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. Received 20 March 2007 Accepted 31 March 2007 # 2007 International Union of Crystallography All rights reserved In the title compound, 2-(2-thienyl)-1,3-bis(2-thienylmethyl)- perhydropyrimidine, C 18 H 20 N 2 S 3 , a new hexahydropyrimidine derivative with no formal crystallographic symmetry (but approximate C s molecular symmetry), the thiophene rings are approximately orthogonal to the mean plane of the saturated pyrimidine ‘core’ of the molecule, with the three S atoms positioned on one side of the six-atom mean plane. The S atom of the directly attached thiophene ring is involved in an unconventional (alkyl)C—HS hydrogen bond (HS= 2.87 A ˚ ) with a thiophene CH group of the closest neigh- bouring molecule, leading to a ladder-like one-dimensional chain as the extended structure. The crystal specimen used for data collection was an inversion twin [twin fraction x = 0.41 (4)]. Comment Sato et al. (1992) have described a method for the synthesis of N,N 0 -bis(2-pyridylmethyl)-N,N 0 -bis(2-thienylmethyl)-1,2- ethanediamine. Our goal was to synthesize the tetra(thio- phene) analogue with a propyldiamine core for binding two Pt II ions. Contrary to expectation, addition of two equivalents of thiophene-2-carbaldehyde to N,N 0 -bis(2-thienylmethyl)- 1,2-propanediamine, (II), followed by NaBH 4 reduction afforded the title compound, (I), the Mannich cyclization product (Buchen et al., 1997). Compound (I) is a hexahydropyrimidine derivative, and the six-membered ring core adopts a chair conformation (Fig. 1). This was confirmed quantitatively by Cremer–Pople ring puckering (CPRP) analysis (Cremer & Pople, 1975), which gave a value closer to 0 (chair) than 50.8 (half-chair). [The CPRP amplitudes were Q = 0.594 (2) A ˚ , = 4.1 (1) and ’ = 89 (2) .] Each atom of the six-membered ring thus deviates systematically from the six-atom mean plane: atom N1 by 0.243 (1), C6 by 0.263 (1), N2 by 0.263 (1), C16 by 0.241 (2), C17 by 0.221 (2) and C18 by 0.221 (2) A ˚ . The weighted average absolute torsion angle for the six-membered ring is 59 (6) and reflects a near-ideal (+)-synclinal confor- mation. The thiophene rings are oriented with the three S atoms lying within the same plane. The dihedral angles of each