(2,6-Bis{5-amino-3-tert-butyl-4-[(3-methyl-1,2,4-thiadiazol-5-yl)diazenyl]-1H-pyrazol-1-yl}-4-oxo-1,4-dihydro-1,3,5-triazin-1-ido)methanol(phenol)sodium phenol tetrasolvate

The title compound, [Na(C23H28N17OS2)(CH3OH)(C6H5OH)]·4C6H5OH, is a five-coordinate NaI complex. The Na+ cation is bound to three N atoms of the triazinide ligand, two from each pyrazole ring and one from the central deprotonated triazine ring system. O atoms from a methanol and a phenol molecule complete the five-coordinate NaN3O2 coordination environment. The asymmetric unit also includes three complete and two half phenol molecules, four of which are hydrogen bonded to the N atoms of the thiadiazole ring. Two of the phenol solvent molecules are disordered over two discrete inversion centres. The triazinide ligand is essentially planar (mean deviation from the least-squares plane = 0.0524 Å), with the methyl groups of the tert-butyl substituents on the pyrazole rings located above and below the plane. The planarity of this system is further assisted by the formation of four intramolecular N—H⋯N hydrogen bonds between the N—H bonds of both amino groups on the pyrazole rings and the N atoms of the triazine ring and also from each of the adjacent diazene (–N=N–) bonds. The highly polar molecules are stacked along the a axis through the central Na atom sandwiched by two kinds of alternating intermolecular hydrogen bonds: O(carbonyl)⋯H—O(methanol)/Na/O—H(phenol)⋯O(carbonyl). These interactions form two polymer chains per molecule.

The title compound, [Na(C 23 H 28 N 17 OS 2 )(CH 3 OH)(C 6 H 5 -OH)]Á4C 6 H 5 OH, is a five-coordinate Na I complex. The Na + cation is bound to three N atoms of the triazinide ligand, two from each pyrazole ring and one from the central deprotonated triazine ring system. O atoms from a methanol and a phenol molecule complete the five-coordinate NaN 3 O 2 coordination environment. The asymmetric unit also includes three complete and two half phenol molecules, four of which are hydrogen bonded to the N atoms of the thiadiazole ring. Two of the phenol solvent molecules are disordered over two discrete inversion centres. The triazinide ligand is essentially planar (mean deviation from the least-squares plane = 0.0524 Å ), with the methyl groups of the tert-butyl substituents on the pyrazole rings located above and below the plane. The planarity of this system is further assisted by the formation of four intramolecular N-HÁ Á ÁN hydrogen bonds between the N-H bonds of both amino groups on the pyrazole rings and the N atoms of the triazine ring and also from each of the adjacent diazene (-N N-) bonds. The highly polar molecules are stacked along the a axis through the central Na atom sandwiched by two kinds of alternating intermolecular hydrogen bonds: O(carbonyl)Á Á ÁH-O(methanol)/Na/O-H(phenol)Á Á ÁO(carbonyl). These interactions form two polymer chains per molecule.

Related literature
For details of azo pigments, see: Herbst & Hunger (2004). For the synthesis of the title compound, see: Nagata & Tateishi (2009)

Comment
Azo pigments are widely used in imaging and painting industries because of their versatile colors, high tinctorial strength as well as their low price (Herbst & Hunger, 2004). Some novel azo pigments have recently been reported by Nagata et al. (2009) which include 2,6-bis[5-amino-3-tert-butyl-4-(3-methyl-1,2,4-thiadiazol-5-yldiazenyl)-1H-pyrazol-1-yl]-1,3,5triazin-4(1H)-one (i.e. Na-free compound of the title compound with one additional H atom at the N atom of the triazine one). In the course of our structural studies on this compound, however, we have isolated two kinds of single crystals from the reaction product: bis-azo and mono-azo compounds. To our surprise, the former is found to include a Na I -atom as the central metal (i.e. the title compound); whereas the latter is a Na I -free mono-azo compound. In the synthesis of azo pigments, it is quite common to use sodium nitrite for the preparation of diazonium salts. However, the inclusion of Na in the final product has not been reported to date. This paper deals with the structure of the Na I -containing bis-azo compound, while the Na I -free mono-azo compound will be reported elsewhere (Shibata & Mizuguchi, 2010).
The title compound, C 30 H 38 N 17 NaO 3 S 2 . 4(C 6 H 6 O), is a five-coordinate Na-bisazo complex, comprising as ligands two N atoms of each pyrazol ring and one N atom of the central triazine one as well as two O atoms of the solvent molecules: one methanol and one phenol. Fig. 1 shows the ORTEP plot of I. The asymmetric unit also includes three full phenol molecules (C30-C35/O3, C36-C41/O4, and C42-C47/O5) and two half molecules (C48-C50/O6 and C51-C53/O7). In four of these molecules, the O-H group of the molecule is hydrogen-bonded to the N atom of the 1,2,4-thiadiazol ring (N1, N2, N14, and N15) through O-H···N hydrogen bonds. On the other hand, the fifth phenol molecule (C48-C50/O6) remains free. There are four N-H···N intramolecular hydrogen bonds formed between the N-H of the amino group of the pyrazol ring and the N atom of the azo bond: N16-H16M···N3, N16-H16N···N9, N17-H17M···N13, and N17-H17N···N8. It is remarkable to note that the central Na atom bridges two monoazo moieties in a cis fashion to make the molecule entirely flat (mean deviation from the least-squares plane with a methyl group from the t-butyl substituent on the pyrazol ring above and below that plane: 0.0524 Å). Additionally, the four intramolecular N-H···N hydrogen bonds also contribute to the planarity of the system. The occurrence of the cis form is quite unusual, because the trans form of the Na-free structure as formed by free rotation around C7-N6 or C9-N10 is more stable according to molecular orbital calculations. However, the Na-coordination appears here to be the driving force to form the cis structure.

Experimental
The title compound was synthesized as described by Nagata et al. (2009). The structure reported here is of the Na I complex product which made up approximately 80% of the product mixture according by emission spectrochemical analysis. A single crystal suitable for X-ray analysis was grown from a mixed solvent of methanol and phenol (1:1 in molar ratio) prepared at 80 °C. Needle shaped crystals were obtained in a closed system saturated with methanol vapor after standing for one week.
The benzene rings of these disordered phenol molecules were refined anisotropically as rigid groups. The two half phenol-molecules were disordered about a center of symmetry (C48-C50/O6 and C51-C53/O7) with an occupancy of 0.5.