Bis[5-(pyridin-2-yl)pyrazine-2-carbonitrile-κ2 N 4,N 5]silver(I) perchlorate

In the mononuclear title complex, [Ag(C10H6N4)2]ClO4, the AgI ion is surrounded by two 5-(pyridin-2-yl)pyrazine-2-carbonitrile ligands, forming a considerably distorted square-planar N4-coordination geometry, with two short and two long Ag—N distances. Each perchlorate anion links two mononuclear coordination units through C—H⋯O(perchlorate) hydrogen bonding, forming an infinite tape structure along [110]. Intermolecular π–π stacking interactions between adjacent pyridine and pyrazine rings [centroid–centroid distances of 3.777 (3) and 3.879 (2) Å] further assemble the tape motifs into a three-dimensional supramolecular structure.


Experimental
The ligand 5-(2-pyridyl)-2-cyanopyrazine was obtained commercially. To a clear solution of 3 ml methanol containing the ligand (18.2 mg, 0.1 mmol), AgClO 4 (22 mg, 0.1mmol) was added with stirring at room temperature. 1 ml acetonitrile was subsequently added dropwise to make the solution clear. After filtration the clear solution was kept in air for one week at room temperature to yield colorless rod-like crystals (19.0 mg, 66% yeild).

Refinement
All the H atoms were discernible in the difference electron density maps. Nevertheless, the hydrogen atoms were placed into idealized positions and allowed to ride on the carrier atoms, with C-H = 0.93 Å for aryl hydrogens.U iso (H) = 1.2U eq (C) aryl .  interactions, while the purple balls represent the Ag I ions. Symmetry codes: i -x + 2, -y + 2, -z + 1; ii -x + 1, -y + 1, -z + 1.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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