Dichloridotris(2-methyl-1H-imidazole-κN 3)cadmium

In the title compound, [CdCl2(C4H6N2)3], the CdII atom displays a pentacoordinate CdN3Cl2 coordination geometry, being coordinated by an N atom of three 2-methylimidazole ligands and two Cl atoms. In the crystal, the mononuclear complexes are linked by N—H⋯Cl hydrogen bonds into a two-dimensional network in the ab plane.


Experimental
Crystal data [CdCl 2 (C 4 Table 1 Hydrogen-bond geometry (Å , ). As part of our ongoing studies of potential ferroelectric phase change materials we have determined the structures of several chromium complexes and examined the changes in their dielectric constants with temperature, which is the usual method for detecting such behaviour, as shown by (Fu et al., 2009;Ye et al., 2006;Zhang et al., 2008;Zhang et al., 2010). The dielectric constant of the title cadmium(II) compound indicates the onset of a ferroelectric phase change over the range 80-298 K.
As shown in Fig. 1, the Cd II ion adopts a pentacoordinate geometry and is coordinated by an N atom from three independent 2-methyl-imidazole ligands and by two Cl atoms. The bond length of the middle Cd1-N3 bond is 2.357 (3) Å, which is longer than the other two Cd-N bond lengths [Cd1-N1= 2.276 (3) Å and Cd1-N5= 2.289 (3) Å].
In the crystal, the mononuclear complexes are linked by N-H···Cl hydrogen bonds to form a two-dimensional network in the ab plane ( Fig. 2 and Table 1).

Experimental
An aqueous solution of 2-methyl-imidazole (1.64 g, 20 mmol) and hydrochloric acid (10 ml) was treated with CdCl 2 (1.35 g, 10 mmol). After the mixture had been stirred for a few minutes, it was left to stans for a few days. Slow evaporation of the solution yielded colourless X-ray quality crystals.

Refinement
The NH and C-bound H-atoms were included in calculated positions and treated as riding atoms: N-H = 0.86 Å, C-H = 0.93 and 0.96 Å for CH, and CH 3 H-atoms, respectively, with U iso (H) = k × U eq (N,C), where k = 1.5 for CH 3 H-atoms and = 1.2 for other H-atoms.  A view of the moolecular structure of the title compound, with the atom numbering. The displacement ellipsoids are drawn at the 30% probability level.

Figure 2
A view along the c axis of the two-dimensional hydrogen bonded network of the title compound. The N-H···Cl bonds are shown as dashed lines; see Table 1 for details.  (9) 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.