Tris(5-methyl-3-phenyl-1H-pyrazol-1-yl)methane

The first crystal structure of a second-generation tris(pyrazolyl)methane, namely the title compound, C31H28N6, is reported. The molecule exhibits a helical conformation with an average twist of 35.1°. In addition, there are C—H⋯π interactions of 3.202 (2) Å between the pyrazole C—H group and neighbouring phenyl groups.

The first crystal structure of a second-generation tris(pyrazolyl)methane, namely the title compound, C 31 H 28 N 6 , is reported. The molecule exhibits a helical conformation with an average twist of 35.1 . In addition, there are C-HÁ Á Á interactions of 3.202 (2) Å between the pyrazole C-H group and neighbouring phenyl groups.

Comment
Tris-(pyrazolyl)methanes (tpzm R,R' ), neutral analogues of the more widely studied tris-(pyrazolyl)borates (tp R,R' ), are an increasing important class of ligands with a wide variety of coordination and organometallic complexes now reported (Pettinari & Pettinari, 2005). In most of these studies only the simplest members of the series tpzm and tpzm Me,Me which generally form inert sandwich complexes with first row transition metals are utilized (Astley et al., 1993;Reger et al., 2002).
In contrast, second generation tris-(pyrazolyl)methane ligands (tpzm Ph , tpzm i-Pr and tpzm t-Bu ) remain poorly represented owing to their time consuming synthesis and low yields. However, Reger (Reger et al., 2000) recently reported an improved procedure for these ligands, while Fujisawa and co-workers (Fujisawa et al., 2004) have shown that even tzpm i-Pr,i-Pr may be prepared. Structural studies of tris-(pyrazolyl)methanes are even rarer and to date only tpzm Me,Me has been reported (Declercq & Van Meerssche, 1984;Ochando et al., 1997). Herein, we report the synthesis and the first structural characterization of a second generation tris-(pyrazolyl)methane ligand namely, tpzm Ph,Me (I).
Colourless block shaped crystals of I were grown from CH 2 Cl 2 /n-hexane, the compound crystallizing in a monoclinic  (Declercq & Van Meerssche, 1984)] and triphenylmethane [30°, 34° and 53°, and 21°, 38° and 47° for each one of the two molecules in the asymmetric unit (Riche & Pascard-Billy, 1974)]. A further method for describing this helical twist is through H1A-C1-N-N torsion angles (Ochando et al., 1997). The torsion angles for I are 133.7 (3)°, Assuming an α-conformation when the torsion angle is negative and β-when positive, it follows that the conformation in the case of I is β-α-β-, identical to the most stable conformer of tpzm Me,Me (Declercq & Van Meerssche, 1984).
supplementary materials sup-2 A further point of interest is the packing within the structure of I which reveals C-H···π interactions between the pyrazole C3-H3 and the centroid of the ring C14/C15/C16/C17/C18/C19 (Cg), the phenyl group attached to the α-pyrazole (Fig.   2). All these interactions occur within a single layer of molecules with adjacent layers, which are related by inversion, exhibiting interactions in the opposite direction. Thus, the interactions H3 (x+1/2, y-1/2, z)···Cg (x, y, z) and H3 (x-1/2,

Experimental
Distilled water (20 ml) was added to a 250 ml flask containing a mixture of Hpz Ph,Me (6.33 g, 40 mmol) and NBu 4 Br (0.68 g, 2 mmol). With vigorous stirring Na 2 CO 3 (8.5 g, 80 mmol) was added to the reaction mixture. After cooling CHCl 3 (75 ml) was added and the mixture refluxed for four days yielding a dark yellow-orange emulsion. The mixture was allowed to cool to room temperature and filtered through a Buchner funnel. The organic layer was separated from the aqueous layer, washed with water (3 × 30 ml) and dried over sodium sulfate. The solution was filtered to remove the drying agent and the solvent removed on a rotary evapourator to give a yellow solid. The solid was redissolved in toluene (70 ml) and a catalytic amount of p-toluenesulfonic acid (0.1 g, 0.53 mmol) was added. The solution was refluxed for a day giving a yellow solution. The solution was then cooled to room temperature, neutralized with a 5% aqueous Na 2 CO 3 solution and washed with distilled water (3 × 15 ml). The solution was then dried over sodium sulfate, filtered and the solvent removed on a rotary evapourator resulting in a light brown solid. The solid was dissolved in CH 2 Cl 2 (20 ml) and chromatographed on a silica gel column that was packed with a CH 2 Cl 2 :toluene (1:1) solution. The fractions containing the desired product were combined and the solvent removed by rotary evapouration to give an off-white solid (1.83 g, 29%  Fig. 3) was previously reported as a by-product in the synthesis of more complex tris-(pyrazolyl)methanes (Goodman & Bateman, 2001). However, it was not isolated and the above represents the first designed synthesis of I.

Refinement
H atoms were placed geometrically and refined with a riding model (including torsional freedom for methyl groups) and with Uĩso~ constrained to be 1.2 (1.5 for CH~3~ groups) times U~eq~ of the carrier atom.
The two restraints are generated automatically to prevent the whole structure from wandering in the a-and c-directions.  Fig. 1. The molecular structure of the title compound showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are presented as a spheres of arbitrary radius.  Tris(5-methyl-3-phenyl-1H-pyrazol-1-yl)methane

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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.