trans-Bis(acetonitrile-κN)tetraaquacobalt(II) tetrachloridocobaltate(II)

In the title complex, [Co(CH3CN)2(H2O)4][CoCl4], the CoII ions are octahedrally coordinated in the cation, with trans-disposed acetonitrile ligands, and tetrahedrally coordinated in the anion. An extensive network of O—H(water)⋯Cl hydrogen bonds between cations and anions connects the ions into a three-dimensional network. The Co—Cl distances correlate with the number of hydrogen bonds accepted by the Cl atoms.

In the title complex, [Co(CH 3 CN) 2 (H 2 O) 4 ][CoCl 4 ], the Co II ions are octahedrally coordinated in the cation, with transdisposed acetonitrile ligands, and tetrahedrally coordinated in the anion. An extensive network of O-H(water)Á Á ÁCl hydrogen bonds between cations and anions connects the ions into a three-dimensional network. The Co-Cl distances correlate with the number of hydrogen bonds accepted by the Cl atoms.

trans-Bis(acetonitrile-N)tetraaquacobalt(II) tetrachloridocobaltate(II) V. Patroniak and M. Kubicki
Both cations and anions are connected by the three dimensional network of O-H(water)···Cl hydrogen bonds. Interestingly, there is a correlation between the number of hydrogen bonds accepted by the Cl atom and the lengths of the Co-Cl bond: shorter the bond, less hydrogen bonds it accepts. The hydrogen bond network is built predominantly from the different rings, with 4 donors (4 different hydrogen atoms) and 2, 3, or 4 different chlorine atoms. The most important motifs found -not taking into account simple non-cyclic dimers of the form O-H···Cl -can be described with graph set symbols as R 4 2 (10), R 4 3 (10) and R 4 4 (14).

Experimental
The complex was prepared as described previously (Stefankiewicz et al., 2008). The main product of this reaction was complex [Co(C 22 H 18 N 4 )(H 2 O)Cl](BF 4 ).

Refinement
Hydrogen atoms were located geometrically, in case of the water molecules on the basis of potential hydrogen bonds, and refined as the 'riding model' with U iso 's set at 1.3 times U eq 's of appropriate oxygen atoms. The relatively large values of residual electron density is probably an effect of unresolved twinning; the efforts on describing this twinning did not improve the model.
The Flack parameter (0.28 (4)) could suggest the possibility of a wrong absolute structure; however, the refinement of the inverted structure led to the higher values of the R-parameters (R(F) of 6.66% for observed and 7.13% for all reflections, wR2 is 16.35%) as well as for Flack parameter, which is 0.65 (4) in this case.
supplementary materials sup-2 Figures   Fig. 1. Anisotropic ellipsoid representation of compound I with atom labelling scheme (Siemens, 1989). The ellipsoids are drawn at the 50% probability level, hydrogen atoms are depicted as spheres of arbitrary radii. Hydrogen bonds are drawn as dashed lines. Fig. 2. The crystal packing as seen approximately along a direction (Macrae et al., 2008). Hydrogen bonds are depicted as dashed lines.

trans-Bis(acetonitrile-κN)tetraaquacobalt(II) tetrachloridocobaltate(II)
Crystal data [Co(C 2  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.