Crystal structure of bis(2-amino-5-chloropyridinium) tetrachloridocobaltate(II)

In the structure of bis(2-amino-5-chloropyridinium) tetrachloridocobaltate(II), the essentially planar cations are connected through N—H⋯Cl hydrogen bonds to the tetrahedral anion.


Chemical context
Organic-inorganic hybrid compounds frequently exhibit selforganized structures and can combine organic and inorganic characteristics (Parent et al., 2007;Zheng et al., 2010;Chang et al., 2011). In particular, anionic cobalt halides associated with organic counter-cations have some interesting physical properties, such as luminescence, in which we are interested. In this communication, we report the synthesis and crystal structure of the new organic-inorganic hybrid compound bis(2-amino-5-chloropyridinium) tetrachloridocobaltate(II), (C 5 H 6 ClN 2 ) 2 - [CoCl 4 ].
The organic cations are nearly planar exhibiting small maximum deviations of 0.010 (3) and 0.014 (3) Å for atoms N2 and C6, respectively. The two least-squares planes of the two cations are nearly perpendicular to each other [84.12 (7) ]. The bond angles C4-N2-C5 [123.6 (3) ] and C9-N3-C10 [123.3 (3) ] in the rings of cat1 and cat2, respectively, confirm the presence of pyridinium cations. Previous studies (Jin et al., 2001) showed that a pyridinium cation possesses an expanded C-N(H)-C angle in comparison with the parent pyridine (117 ). This geometrical characteristic is in agreement with an imine-enamine resonance (Jin et al., 2005) and contributes to the structural stability.
In the [CoCl 4 ] 2À anion, the Co-Cl bond lengths range from 2.2645 (12) to 2.2934 (12) Å and the Cl-Co-Cl angles range from 104.84 (5) to 118.58 (5) , revealing considerable distortions from the ideal tetrahedral geometry. These values are in agreement with those observed in similar compounds (Dhieb et al., 2014;Mghandef & Boughzala, 2014;Oh et al., 2011). The different Co-Cl bond lengths in the [CoCl 4 ] 2À anion are related to the number of hydrogen bonds accepted by the Cl atoms. The Co-Cl1 and Co-Cl4 bonds are longer than the Co-Cl2 and Co-Cl3 bonds because atoms Cl1 and Cl4 are each acceptors of two hydrogen bonds from cat2 and cat1, respectively.

Figure 3
The environment around the cations (cat1 or cat2).

Figure 4
Projection of the crystal structure along

Synthesis and crystallization
A mixture of cobalt(II) chloride and 2-amino-5-chloropyridine (molar ratio 1:1) was dissolved in an aqueous solution of hydrochloric acid with 5 ml of ethanol. The mixture was stirred and then kept at room temperature. Blue crystals of the title compound were obtained after two weeks.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were placed geometrically and included as riding contributions, with N-H = 0.86 Å and C-H = 0.93 Å and with U iso (H) = 1.2U eq (N,C).  program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Geometric parameters (Å, º)