Bis{4-[(3,5-dimethyl-1H-pyrazol-4-yl)selanyl]-3,5-dimethyl-1H-pyrazol-2-ium} chloride monohydrate

In the title compound, 2C10H15N4Se+·Cl−·OH−, a singly protonated molecule of the organic selenide participates in hydrogen bonding with neighboring molecules, forming zigzag chains along [001]. The molecule adapts a cis bridging mode with a C—Se—C angle of 102.13 (15)°. π–π stacking interactions are observed between the closest pyrazole rings of neighboring chains [centroid–centroid distance = 3.888 (1) Å] and hydrogen bonding occurs through bridging chloride anions and hydroxide groups. Additionally, O—H⋯Cl hydrogen bonds are formed.

In the title compound, 2C 10 H 15 N 4 Se + ÁCl À ÁOH À , a singly protonated molecule of the organic selenide participates in hydrogen bonding with neighboring molecules, forming zigzag chains along [001]. The molecule adapts a cis bridging mode with a C-Se-C angle of 102.13 (15) .stacking interactions are observed between the closest pyrazole rings of neighboring chains [centroid-centroid distance = 3.888 (1) Å ] and hydrogen bonding occurs through bridging chloride anions and hydroxide groups. Additionally, O-HÁ Á ÁCl hydrogen bonds are formed.
In the cation of the title compound, a singly protonated molecule of the organic selenide (C 10 H 15 N 4 Se) + participates in Additionally, a hydrogen bond Ow-H···Cl 3.166 (4)Å is found.
In the title compounds, the pyrazole rings exhibits C-C, C-N, N-N bond lengths which are normal for the substituted pyrazole molecules and close to those reported for related compounds.

Experimental
A solution of a batch of bis(3,5-dimethyl-1H-pyrazol-4-yl)selenide (Seredyuk et al., 2007)) in aqueous HCl conc was disposed in a fridge at 277 K for one week. The obtained well formed colourless crystals were filtered off and air dried.

Refinement
The chlorine ion and the oxygen and hydrogen atoms of the hydroxide anion were found to occupy special positions (2fold axis) with occupancy factors of 0.5. The H atoms from NH and OH were located from the difference Fourier map.
The H atoms lined to N2 and N4 nitrogen atoms were refined freely, while hydrogen atoms of OH group and that linked to N1 nitrogen atom were constrained to ride on their parent atom, with U iso = 1.5U eq (parent atom). The methyl H atoms were positioned geometrically and refined as riding atoms, with C-H = 0.96Å and U iso = 1.5U eq (C).

Figure 1
The title molecule with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
Zigzag chains of the organic selenide formed due to hydrogen bonding (dashed lines). Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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.