Tetrakis[μ3-4-nitro-N-(5-phenyl-1,3,4-oxadiazol-2-yl)benzamidato]tetrakis[methanolsodium(I)]

In the title compound, [Na4(C15H9N4O4)4(CH3OH)4], the N3O3 environment around the Na+ ion is distorted octahedral. In the unit cell, four Na+ ions are bridged by four Schiff base anions, leading to a tetranuclear complex with -4 symmetry. O—H⋯N hydrogen bonds between the methanol molecule and the Schiff base anion stabilize the structural set-up.

In the title compound, [Na 4 (C 15 H 9 N 4 O 4 ) 4 (CH 3 OH) 4 ], the N 3 O 3 environment around the Na + ion is distorted octahedral. In the unit cell, four Na + ions are bridged by four Schiff base anions, leading to a tetranuclear complex with 4 symmetry. O-HÁ Á ÁN hydrogen bonds between the methanol molecule and the Schiff base anion stabilize the structural set-up.
In the title compound, each Na I atom is six-coordinated by one O atom from a methyl alcohol, two O atoms and three N atoms from the ligands, forming a distorted octahedral geometry. In the asymmetric unit, the four Na I ions are bridged by four Schiff base anions, leading to a tetranuclear complex ( Fig. 1 and Fig. 2), the coordination geometry of sodium ions can be described as distorted quadrilateral.

Experimental
Reagents and solvents were of commercially available quality. The preparation of 2-Amino-5-phenyl-1,3,4-oxadiazole is based on a published method (Gibson, 1962). Bromine (0.66 ml) in glacial acetic acid (1.34 ml) was added to a stirred slurry of benzaldehyde semicarbazone (2.0 g) and powdered, anhydrous sodium acetate (4.0 g) in acetic acid (12 ml). The solids were dissolved giving a red solution, which suddenly grew warm and rapidly faded with white precipitate formed (sodium bromide). After 15 minutes, the mixture was poured into water (100 ml), and the precipitated solid (1.8 g) collected, washed and dried. Crystallization from ethanol gave stout needles.

Refinement
H atoms were positioned geometrically and refined using a riding model with C-H =0.93-0.96 Å and with U iso (H) = 1.2 (1.5 for methyl groups) times U eq (C).  The molecular structure of the title complex with displacement ellipsoids drawn at the 50% probability level.

Figure 2
The molecular structure of the title complex with displacement ellipsoids drawn at the 50% probability level. Hydrogen atoms are omitted for clarity.

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