3-Chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)picolinic acid–triphenylphosphine oxide (1/1)

In the title 1:1 adduct, C11H10ClN3O2·C18H15OP, the dihedral angle between the pyridine and pyrazole rings is 10.3 (2)°. The two components of the adduct are linked by an O—H⋯O hydrogen bond.


Comment
Pyrazoles have been investigated extensively, owing to their chelating ability with metal ions and their potentially beneficial biological activities (e.g. Mann et al., 1992). As part of our studies on these compounds, we report here the synthesis and crystal structure of the title compound, (I), (Fig. 1).
Experimental 3-Chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)picolinic acid (1 mmol, 251.04 mg) was dissolved in distilled water (15 ml) and triphenylphosphine oxide (0.5 mmol, 139.04 mg) in distilled water (5 ml) was added with stirring at 323 K. The resulting solution was allowed to react for 5 h and was then filtered. Colourless blocks of (I) were obtained by slow evaporation of a water solution over a period of one month (yield 75%).

Refinement
The C-bound H atoms were positoned geometrically (C-H = 0.93-0.96Å) and refined as riding with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C). The O-bound H atom was located in a difference map and refined as riding in its as-found relative position with U iso (H) =1.5U eq (O). Fig. 1. The molecular structure of (I) showing 30% probability displacement ellipsoids for the non-hydrogen atoms. The hydrogen bond is indicated by a double-dashed line.

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 calculat-supplementary materials sup-3 ing 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.