A second monoclinic polymorph of 2-(3,5-dimethyl-1H-pyrazol-1-yl)-2-hydroxyimino-N′-[1-(pyridin-2-yl)ethylidene]acetohydrazide

The title compound, C14H16N6O2, is a second monoclinic polymorph of 2-[1-(3,5-dimethyl)pyrazolyl]-2-hydroxyimino-N′-[1-(2-pyridyl)ethylidene] acetohydrazide, with two crystallographically independent molecules per asymmetric unit. The non-planar molecules are chemically equal having similar geometric parameters. The previously reported polymorph [Plutenko et al. (2012 ▶). Acta Cryst. E68, o3281] was described in space group Cc (Z = 4). The oxime group and the O atom of the amide group are anti with respect to the C—C bond. In the crystal, molecules are connected by N—H⋯N hydrogen bonds into zigzag chains extending along the b axis.

The title compound, C 14 H 16 N 6 O 2 , is a second monoclinic polymorph of 2-[1-(3,5-dimethyl)pyrazolyl]-2-hydroxyimino-N 0 -[1-(2-pyridyl)ethylidene] acetohydrazide, with two crystallographically independent molecules per asymmetric unit. The non-planar molecules are chemically equal having similar geometric parameters. The previously reported polymorph [Plutenko et al. (2012). Acta Cryst. E68, o3281] was described in space group Cc (Z = 4). The oxime group and the O atom of the amide group are anti with respect to the C-C bond. In the crystal, molecules are connected by N-HÁ Á ÁN hydrogen bonds into zigzag chains extending along the b axis.
Data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2008); software used to prepare material for publication: SHELXL97. Oximes are one of the most efficient bridging ligands class. Polydentate ligands containing both oxime and other donor functions are of special interest due to their potential for the bridging coordination modes and mediation of strong magnetic superexchange between metal ions (Penkova et al., 2009;Kanderal et al., 2005;Moroz et al., 2010). Oxime ligands having the pyridyl groups in the molecule have been used in the preparation of complexes with a variety of transition metals, binding to metals in different modes most commonly as chelates or serving as bridge to metals, and the resulting species have been employed in molecular magnetism and supramolecular chemistry (Moroz et al., 2010(Moroz et al., , 2012. Herein we report a second polymorph of 2-[1-(3,5-dimethyl)pyrazolyl]-2-hydroxyimino-N′-[1-(2-pyridyl)ethylidene] acetohydrazide (II) (Fig. 1). In comparison, the first polymorph I described previously (Plutenko et al., 2012), crystallized in monoclinic space group Cc, Z = 4, while the title compound II crystallized in space group P21/n with Z = 8 ( Fig. 1).
In the crystal packing both molecules A and B are each connected by N-H···N hydrogen bonds, where the oxime nitrogen acts as donor and the pyrazole nitrogen atom acts as acceptor (Table 1)
5g, 2.54 mmol) in methanol (30 ml) was treated with 2acetylpyridine (0.307g, 2.54 mmol) and the mixture was heated under reflux for 3 hours. After that the solvent was evaporated in vacuum and the product was crystallized from methanol. Yield 0.65g (85 %).

Refinement
OH, NH and CH 3 hydrogen atoms were located from difference Fourier maps, other hydrogen atoms were positioned geometrically and all but H(N) and H(O) were refined at idealized positions riding on the parent atoms, with C-H = 0.95-0.98 Å, and U iso = 1.2-1.5 U eq (parent atom). H(N) and H(O) atoms were refined freely with Uiso(H) = 1.2U eq (N) or 1.5U eq (O). All CH 3 hydrogen atoms were allowed to rotate but not to tip. The highest peak is located 0.74 Å from atom C9 and the deepest hole is located 1.03 Å from atom N4.

Computing details
Data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).    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.