Diaquatetrakis(1H-imidazole-κN 3)magnesium dichloride

In the title compound, [Mg(C3H3N2)4(H2O)2]Cl2, the MgII cation lies on a crystallographic inversion centre and is coordinated by two water molecules and four N-atom donors from monodentate imidazole ligands, giving a slightly distorted octahedral stereochemistry. In the crystal, water O—H⋯Cl and imidazole N—H⋯Cl hydrogen bonds give rise to a three-dimensional structure.

In the title compound, [Mg(C 3 H 3 N 2 ) 4 (H 2 O) 2 ]Cl 2 , the Mg II cation lies on a crystallographic inversion centre and is coordinated by two water molecules and four N-atom donors from monodentate imidazole ligands, giving a slightly distorted octahedral stereochemistry. In the crystal, water O-HÁ Á ÁCl and imidazole N-HÁ Á ÁCl hydrogen bonds give rise to a three-dimensional structure.

Related literature
For a similar structure, see: Reiss et al. (2011).

Comment
In the title compound, [Mg(C 3 H 3 N 2 ) 4 (H 2 O) 2 ] . 2Cl, the Mg II cation lies on a crystallographic inversion centre and is coordinated by two water molecules and four N-atom donors from monodentate imidazole ligands, (Fig. 1), giving a slightly distorted octahedral geometry (Table 1). In the crystal, O-H···Cl and N-H···Cl hydrogen bonds between both the aqua ligands and the imidazole ligands and the chloride counter-anions (Table 2) generate a three-dimensional structure (Fig. 2). These water-chloride hydrogen-bonding interactions are in the typical range as observed in the redetermined structure of diaquatetrakis(dimethylformamide-κO)magnesium dichloride (Reiss et al., 2011).

Experimental
A solution of MgCl 2 (0.2 mmol) in water (6 ml) was added dropwise to a solution of imidazole (0.8 mmol) in ethanol.
After stirring for 30 min, the mixture was filtered. Crystals suitable for X-ray analysis were obtained by evaporating the filtrate at room temperature (yield 56%).

Refinement
Carbon-bound H atoms were placed at calculated positions and treated as riding on the parent atom, with, C-H = 0.93 Å and with U iso (H) = 1.2U eq (C). The O-bound and N-bound H atoms were located in a difference Fourier map and refined freely.

Computing details
Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 and SAINT (Bruker, 2004); data reduction: SAINT and XPREP (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009  The molecular structure of the title compound showing atom numbering, with displacement ellipsoids drawn at the 40% probability level. For symmetry code (i): -x + 1/2, -y + 3/2, -z + 1.   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.17 e Å −3 Δρ min = −0.25 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0093 (6) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 R-factors(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.