organic papers o5268 Boufas et al.  C 10 H 12 N 2 2+ 2Cl  doi:10.1107/S1600536806043868 Acta Cryst. (2006). E62, o5268–o5270 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 Naphthalene-1,5-diammonium dichloride Sihem Boufas, a * Hocine Merazig, a Lamia Bendjeddou, a Adel Beghidja b and Georges De ´ne ´s c a Laboratoire de Chimie Mole ´culaire, du Contro ˆ le de l’Environnement et des Mesures Physico-Chimiques, Faculte ´ des Sciences, De ´partement de Chimie, Universite ´ Mentouri de Constantine, 25000 Constantine, Algeria, b Laboratoire DECMET, ILB, Universite ´, Louis Pasteur Strasbourg I, 4 rue Blaise Pascal, 67000 Strasbourg, France, and c Department of Chem- istry and Biochemistry, 7141 Sherbrooke Street West, Montreal, Qc, Canada H4B 1R6 Correspondence e-mail: boufas_sihem@yahoo.fr Key indicators Single-crystal X-ray study T = 173 K Mean (C–C) = 0.002 A ˚ R factor = 0.036 wR factor = 0.083 Data-to-parameter ratio = 22.7 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. Received 10 October 2006 Accepted 20 October 2006 # 2006 International Union of Crystallography All rights reserved In the title compound, C 10 H I2 N 2+ 2CI  , the naphthalene-1,5- diammonium ion lies on an inversion center; the asymmetric unit contains half of the cation and one Cl  anion. The structure can be described as consisting of alternating layers of C 10 H I2 N 2+ and CI  ions perpendicular to the a axis. The structure contains N—HCl hydrogen bonds, which build up a two-dimensional network. Comment Aromatic diamines are valuable building units for the design of interesting ligands, allowing the preparation of a wide array of Schiff bases, which are used in coordination chemistry (Togni & Venanzi, 1994). Recently, it was found (Fukuyama et al., 2005) that the three isomers of diaminonaphthalene (1,5- DAN, 2,3-DAN and 1,8-DAN) reduce disulfide bonds of insulin. When insulin was reacted with each of these isomers, the highest amount of reduced insulin was obtained using 1,5- DAN. Furthermore, 1,5-DAN (Berne ´s et al. , 2004) has been used as a donor in the molecular charge-transfer complex chloranil-1,5-diaminonaphthalene (Tamura & Ogawa, 1977). These interesting results drew our attention to its possible use for the preparation of other new compounds. We report here the structure of the title compound, (I) The molecule possesses a crystallographic inversion center at the mid-point of the bond shared by the two rings (Fig. 1). A similar situation was observed in the related compounds N,N 0 - bis(2-pyridyl)-1,5-diaminonaphthalene (Bensemann et al., 2002), 1,5-diaminonaphthalene and naphthalene-1,5-di- ammonium diiodide dihydrate. As reported previously for naphthalene-1,5-diammonium diiodide dihydrate (Lemmerer