Poly[diaqua[3,5-bis(trifluoromethyl)pyrazolido]potassium]

The asymmetric unit of the title compound, [K(C5HF6N2)(H2O)2]n, is composed of two 3,5-bis(trifluoromethyl)pyrazolide anions, two potassium cations and four water molecules. The water molecules and 3,5-bis(trifluoromethyl)pyrazolide anions act as bridges between the potassium cations. Each potassium cation is surrounded by four O atoms [K—O = 2.705 (3)–2.767 (3) Å] and four F atoms [K—F = 2.870 (7)–3.215 (13) Å]. The water molecules and the 3,5-bis(trifluoromethyl)pyrazolide anions are connected by O—H⋯N hydrogen bonds, forming layers in the ab plane. All –CF3 groups show rotational disorder between two orientations each.


Experimental
Crystal data [K(C 5

Comment
Recently we have reported the structures of pyrazolides which possess substituents in a 3-or 4-position (Bieller et al., 2006).
In this paper we report the synthesis and the crystal structure of the 3,5-substituted potassium pyrazolide [K(H 2 O) 2 ][3,5-(CF 3 ) 2 C 3 HN 2 ] (I). The starting matrial for the synthesis of (I), 3,5-bis(trifluoromethyl)pyrazole, was prepared from hexafluoroacetylacetone CF 3 COCH 2 COCF 3 and hydrazine hydrate N 2 H 4 . H 2 O. By a following reaction of one equivalent of KH and one equivalent of 3,5-bis(trifluoromethyl)pyrazole in ethanol the potassium pyrazolide (I) was accessible in nearly quantitive yield.
Potassium 3,5-bis(trifluoromethyl)pyrazolide (I): To a slurry of KH (138 mg, 3.44 mmol) in 15 ml of tetrahydrofuran was added a solution of 3,5-bis(trifluoromethyl)pyrazole (820 mg, 4.02 mmol) in 15 ml tetrahydrofuran at 273 K. The resulting solution was allowed to warm up to room temperature. After removing the solvent in vacuo the obtained residue was recrystallized from wet tetrahydrofuran (yield 92%).

Refinement
H atoms were found in a difference map but those bonded to C were refined with fixed individual displacement parameters   Fig. 1. Perspective view of the asymmetric unit of the title compound with the atom numbering scheme; displacement ellipsoids are at the 50% probability level; H atoms are drawn as small spheres of arbitrary radii. Only major components of the disordered CF 3 groups are shown.