4-Chloroanilinium (4-chlorophenyl)guanidinium dichloride hemihydrate

In the title hydrated molecular salt, C6H7ClN+·C7H9ClN3 +·2Cl−·0.5H2O, the water O atom lies on a crystallographic twofold axis. In the crystal, intermolecular N—H⋯Cl and O—H⋯Cl hydrogen bonds form layers perpendicular to the ac plane in which both the water molecule and the chloride anion are involved in connecting the layers into a three-dimensional structure.

In the title hydrated molecular salt, C 6 H 7 ClN + ÁC 7 H 9 ClN 3 + Á-2Cl À Á0.5H 2 O, the water O atom lies on a crystallographic twofold axis. In the crystal, intermolecular N-HÁ Á ÁCl and O-HÁ Á ÁCl hydrogen bonds form layers perpendicular to the ac plane in which both the water molecule and the chloride anion are involved in connecting the layers into a threedimensional structure.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HG2652).

Comment
The guanidine-containing compounds have been employed as anti-microbials and fungicides on a considerable scale (Yonehara & Otake, 1966). The drugs containing guanidine framework are not only easy to transport (Berlinck, 1995), but also make the functions of absorption and osmosis more selective due to the good solubility of their various acid salts in aqueous solution (Gobbi & Frenking, 1993). We report here the cocrystal structure of title compound.
Title compound crystallizes with one 4-chloropenylguanidinium cation , one 4-chloroanilinium cation, two chloride anion and half water molecular in the asymmetric unit ( Fig. 1). All bond lengths and angles are normal (Ploug-Sørenson & Andersen, 1985;Kolev et al., 1997;Glidewell et al., 2005;Smith et al., 2005). The forces between cations and anions consist of hydrogen bonding and ion-pairing. Intermolecular N-H···Cl and O-H···Cl hydrogen bonds form layers perpendicular to the ac plane in which both the water molecule and the chloride anion are involved in structure extension (Table 1).

Experimental
The 4-chlorophenylguanidine (0.01 mol) was added to a solution of 4-chlorobenzenamine (0.01 mol) in ethanol (20 ml) and stirred half hour at room temperature. The mixture was adjusted to pH 2-3 with concentrated hydrochloric acid, and the desired products then precipitated, which was collected by filtration. Single crystals suitable for X-ray measurements were obtained by recrystallization from methanol and water (v/v 1:1) at room temperature for one week.

Refinement
Hydrogen atoms bonded to O and 4-chloroanilinium N were located by difference methods and their positional and isotropic displacement parameters were refined but these were constrained in the final refinement cycles. H atoms bonded to C and 4-chlorophenylguanidinium N atoms were treated as riding atoms, with C-H distances of 0.93 Å and N-H distances of 0.86 Å and U iso (H) values of 1.2U eq (C,N). Fig. 1. View of the title compound (I), with displacement ellipsoids drawn at the 40% probability level.