1-Methylpiperazine-1,4-diium tetrachloridozincate hemihydrate

The crystal structure of the title compound, (C5H14N2)[ZnCl4]·0.5H2O, is built up from discrete 1-methylpiperazinediium cations with chair conformation, tetrahedral tetrachloridozincate anions and uncoordinated solvent water molecules linked together by three types of intermolecular hydrogen bonds, viz. N—H⋯Cl, N—H⋯O and O—H⋯Cl.

Grateful thanks are expressed to Dr J. Jaud (Service Rayons X, CEMES/CNRS Toulouse) for the X-ray data collection.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: ZQ2122).

Comment
Preparation of organic-inorganic hybrid materials attracts great attention in chemistry and materials sciences because of their abilities to combine the properties of organic and inorganic compounds within one single molecular scale, such as second-order nonlinear optical (NLO) response, luminescence, magnetism and even multifonctional properties (Mitzi, 2001;Pecaut et al., 1993;Lacroix et al., 1994). In connection with ongoing studies (Walha et al., 2010;Walha et al., 2011), we report here the crystal structure of a new organic-inorganic hybrid with cations and tetrachloridozincate anions.
The asymmetric unit of the title compound (  et al., 1984). The ZnCl 4 tetrahedra are linked to water molecules into zig-zag chains by O-H···Cl hydrogen bonds along the c axis, as illustrated in Fig. 3. The organic species adopts a typical chair conformation with average C-C and C-N of 1.501 (4) and 1.491 (3) Å, respectively (Fowkes & Harrison, 2004). The water molecules are located above and below the layers and they connect them via hydrogen bonds. Indeed, they participate in two types of hydrogen bonds O-H···Cl and N-H···O as donor or acceptor, respectively (Table 2), playing a subordinative role in the stabilization of the crystal structure.

Experimental
ZnCl 2 (1 mmol) and methylpiperazine dihydrochloride (1 mmol) were dissolved in water. The solution was mixed with hydrochloric acid (1 mmol) and allowed to stand. Colourless plate-shaped crystals of the title compound were formed by slow evaporation of the solvent and separated from the solution after three days.

Refinement
H atoms bonded to C and N atoms were positioned geometrically and allowed to ride on their parent atom, with C-H = 0.96 Å, N-H = 0.89 Å and U iso = 1.2U eq (C, N).
supplementary materials sup-2 Figures   Fig. 1. The asymmetric unit of the title compound, with the non-H atoms represented by 50% probability displacement ellipsoids. H atoms are shown as spheres of arbitrary radius.   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.