Crystal structure of bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2 N 2,N 3]bis(thiocyanato-κS)copper(II)

The structure of the title compound is similar to that of the related complexes [Co(C12H8N4S)2(N3)2] and [Ni(C12H8N4S)2(N3)2] in which the azide ion is substituted by the thiocyanate group. The CuN4S2 octahedron is more distorted than the CoN6 and NiN6 octahedra.

The mononuclear title complex, [Cu(SCN) 2 (C 12 H 8 N 4 S) 2 ], was obtained by the reaction of 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole and potassium thiocyanate with copper(II) chloride dihydrate. The copper cation lies on an inversion centre and displays an elongated octahedral coordination geometry. The equatorial positions are occupied by the N atoms of two 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole ligands, whereas the axial positions are occupied by the S atoms of two thiocyanate anions. The thiadiazole and the pyridyl rings linked to the metal are approximately coplanar, with a maximum deviation from the mean plane of 0.190 (2) Å . The cohesion of the crystal structure is ensured by weak C-HÁ Á ÁN hydrogen bonds andinteractions between parallel pyridyl rings of neighbouring molecules [centroid-to-centroid distance = 3.663 (2) Å ], leading to a three-dimensional network.
We have recently reported the synthesis and characterization of monomeric complexes of Ni II and Co II with bptd in the presence of the pseudohalide azide (Laachir et al., 2015a,b). In this context, we report here the synthesis and crystal structure of a new Cu II complex with bptd and thiocyanate as co-ligands.

Structural commentary
The title complex has crystallographically imposed inversion symmetry, the copper atom lying on the Wyckoff special position 2b of the space group P2 1 /c. The elongated octahedral coordination polyhedron around the metal cation is provided by four nitrogen atoms of pyridine and thiadiazole rings occupying the equatorial plane and by the sulfur atoms of two thiocyanate anions at the apical positions (Fig. 1). The Cu-N distances are 2.0267 (16) and 2.0463 (15) Å , the Cu-S bond length is 2.8125 (7) Å . A bond-valence-sum calculation (Brown & Altermatt, 1985) for Cu gives the expected BVS value of 2.11 valence units. The conformation of the ligand is approximately planar, with a maximum deviation from the least-squares plane of 0.190 (2) Å for atom C12. The dihedral angles formed by the thiadiazole ring with the N1/C2-C6 and N4/C8-C12 pyridine rings are 1.94 (8) and 6.96 (5) , respectively.

Database survey
The structure of the title compound is similar to that of the related complexes [Co(C 12 H 8 N 4 S) 2 (N 3 ) 2 ] (Laachir et al., 2015b) and [Ni(C 12 H 8 N 4 S) 2 (N 3 ) 2 ] (Laachir et al., 2015a), in which the azide ion is substituted by the thiocyanate group. The CuN 4 S 2 octahedron is more distorted than the NiN 6 and CoN 6 octahedra.

Bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ 2 N 2 ,N 3 ]bis(thiocyanato-κS)copper(II)
Crystal data 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.