Crystal structure of bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2 N 2,N 3]cobalt(II)

The structure of the title compound is isotypic with that of the analogous nickel(II) complex, in which the CoN6 core shows an axially weakly compressed octahedral geometry as opposed to the almost regular geometry exhibited by the NiN6 octahedron.

In the mononuclear title complex, [Co(N 3 ) 2 (C 12 H 8 N 4 S) 2 ], the cobalt(II) atom is located on an inversion centre and displays an axially weakly compressed 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 N atoms of the azide anions. The thiadiazole and pyridine rings linked to the metal are almost coplanar, with a maximum deviation from the mean plane of 0.0273 (16) Å . The cohesion of the crystal is ensured by weak C-HÁ Á ÁN hydrogen bonds and byinteractions between pyridine rings [intercentroid distance = 3.6356 (11) Å ], forming a layered arrangement parallel to (001). The structure of the title compound is isotypic with that of the analogous nickel(II) complex [Laachir et al. (2013). Acta Cryst. E69, m351-m352].

Chemical context
In recent years, the use of the ligand 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole has been studied for the synthesis of numerous complexes with transition-metal salts. An interesting feature of the metal-ligand chemistry of these compounds is that the resulting complexes can be mononuclear (Bentiss et al., 2011a;2012;Kaase et al., 2014) or binuclear (Bentiss et al., 2004;Laachir et al., 2013). Another preparation method involves the use of the organic ligand and pseudohalide ions, especially the azide ion which is known to exhibit different coordination modes (Nath & Baruah, 2012;Ray et al., 2011).

Structural commentary
The structure of the title compound ( Fig. 1) is isotypic with its nickel(II) analogue (Laachir et al., 2015) and similar to that of ISSN 2056-9890 the homologous compound, [Co(C 12 H 8 N 4 S) 2 (H 2 O) 2 ]Á2BF 4 , in which the water molecules are substituted by azide ions which at the same time neutralize the positive charge of Co 2+ (Bentiss et al., 2011b). The main difference between the two structures lies in the values of the dihedral angle between the two pyridine rings: this is 18.72 (6) in the hydrated molecule, whereas it is 3.03 (2) in the title molecule, (I). The dihedral angles formed by the thiadiazole ring and the pyridine rings N1/C1-C4 and N2/C8-C11 in (I) are 2.87 (9) and 1.1 (2) , respectively. The cobalt cation, which is located on an inversion centre, shows an axially weakly compressed octahedral coordination geometry with the equatorial plane provided by four nitrogen atoms belonging to the pyridine and thiadiazole rings of two organic ligands [Co1-N3 = 2.1301 (14) and Co1-N4 = 2.1535 (14) Å ] and the axial positions occupied by two nitrogen atoms from azide anions [Co1-N5 = 2.1132 (17) Å ].

Figure 2
Partial crystal packing of the title compound, showing intermolecularinteractions between pyridine rings (dashed green lines) and intermolecular C-HÁ Á ÁN hydrogen bonds (dashed blue lines).

Bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ 2 N 2 ,N 3 ]cobalt(II)
Crystal data 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.