Crystal structure of tris­(3-methyl-1H-pyrazol-1-yl)methane

Margaret A Goodman; M Scott Goodman; Alexander Y Nazarenko; Ealin N Patel

doi:10.1107/S2056989015017247

. 2015 Oct 3;71(Pt 11):o816. doi: 10.1107/S2056989015017247

Crystal structure of tris(3-methyl-1H-pyrazol-1-yl)methane

Margaret A Goodman ^a, M Scott Goodman ^b, Alexander Y Nazarenko ^b,^*, Ealin N Patel ^b

PMCID: PMC4645007 PMID: 26594542

Abstract

The title molecule, C₁₃H₁₆N₆, crystallizes from hexane as a molecular crystal with no strong intermolecular interactions (the shortest C—H⋯N contact is longer than 3.38 Å). A relatively short intramolecular contact (3.09 Å) has a C—H⋯N angle of 118° which is quite small to be still considered a hydrogen bond. The three pyrazole rings form a propeller-like motif, with one methylpyrazole unit almost perpendicular to the mean plane of the three rings [82.20 (6)°]. The other two methylpyrazole units, with nitrogen donor atoms oriented in opposite directions, are oriented at 67.26 (6) and 72.53 (6)° to the mean plane.

Keywords: crystal structure; 1,1′,1′′-methanetriyltris(3-methyl-1H-pyrazole); tripyrazolylmethane

Related literature

For syntheses and reactions of trispyrazolylmethanes and their complexes with transition metals, see: Goodman et al. (2012 ▸); Jameson & Castellano (1998 ▸); Reger et al. (2000 ▸).

Experimental

Crystal data

C₁₃H₁₆N₆
M _r = 256.32
Monoclinic,
a = 12.0881 (8) Å
b = 13.4178 (10) Å
c = 9.0985 (6) Å
β = 111.630 (2)°
V = 1371.82 (16) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 173 K
0.60 × 0.48 × 0.29 mm

Data collection

Bruker Photon-100 CMOS diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2014 ▸) T _min = 0.706, T _max = 0.747
22036 measured reflections
2612 independent reflections
2171 reflections with I > 2σ(I)
R _int = 0.029

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.099
S = 1.05
2612 reflections
225 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: APEX2 (Bruker, 2013 ▸); cell refinement: SAINT (Bruker, 2013 ▸); data reduction: SAINT; program(s) used to solve structure: SHELXT (Sheldrick, 2015a ▸); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b ▸); molecular graphics: OLEX2 (Dolomanov et al., 2009 ▸); software used to prepare material for publication: OLEX2.

Supplementary Material

Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989015017247/zl2643sup1.cif

e-71-0o816-sup1.cif^{(667.1KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015017247/zl2643Isup2.hkl

e-71-0o816-Isup2.hkl^{(209.1KB, hkl)}

Click here for additional data file.^{(2.5KB, cdx)}

Supporting information file. DOI: 10.1107/S2056989015017247/zl2643Isup3.cdx

Click here for additional data file.^{(5.8KB, cml)}

Supporting information file. DOI: 10.1107/S2056989015017247/zl2643Isup4.cml

Click here for additional data file.^{(1.9MB, tif)}

. DOI: 10.1107/S2056989015017247/zl2643fig1.tif

The molecular structure of the title compound. Displacement elipsoids are drawn at the 50% probability level. Disorder of H atoms bonded to C5 are omitted for clarity.

Click here for additional data file.^{(2.4MB, tif)}

c . DOI: 10.1107/S2056989015017247/zl2643fig2.tif

Packing diagram of the title molecule. View along the c axis.

CCDC reference: 1424633

Additional supporting information: crystallographic information; 3D view; checkCIF report

Acknowledgments

Financial support from the State University of New York for acquisition and maintenance of the X-ray diffractometer is gratefully acknowledged.

supplementary crystallographic information

S1. Chemical context

This report is part of our continious effort to study substituted trispyrazolylmethanes and their complexes with various metal ions. Because all synthetic procedures yield a complex mixture of isomers, positive identification of the ligand molecule by X-ray diffractometry is essential for future research.

S2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

All hydrogen atoms were located in electron difference density Fourier maps and were refined in an isotropic approximation. One methyl group (C5) was treated as disordered (SHELXL instruction AFIX 124). Isotropic parameters of atoms H1 and of disordered methyl group hydrogen atoms were constrained as U_H = 1.2 U_C.

Reflections 1 0 0 and 1 1 0 were too close to the beamstop to be measured reliably and were excluded from refinement.

S3. Synthesis and crystallization

Following the general method of Reger et al. (2000), 3-methylpyrazole (6.0 mL, 75.0 mmol), tetrabutylammonium bromide (1.21 g, 3.75 mmol), and sodium carbonate (47.0 g, 0.45 mol) were heated together in a biphasic mixture of deionized water (75 mL) and chloroform (40 mL). The reaction mixture was allowed to gently reflux for approximately 72 hours under argon. After cooling and filtering, the organic layer was separated from the aqueous layer. The aqueous layer was extracted three times with diethyl ether (100 mL), and the combined organic portions were washed twice with 100 mL portions of H₂O. The organic mixture was dried (Na₂SO₄) and the solvents were removed under vacuum to give a dark, brown oil. ¹H NMR analysis showed this to be mainly a mixture of all four regioisomers of the tris(pyrazolyl)methanes derived from 3-methylpyrazole.

The crude mixture of tris(pyrazolyl)methane regioisomers was first isomerized according to the method of Jameson & Castellano (1998). The crude brown oil (1.0 g) was combined with a catalytic amount of p-toluenesulfonic acid (0.060 g) and a small amount (50 µL) of 3-methylpyrazole and heated at reflux in dry toluene (15 mL) for 24 hours under argon. After cooling, the mixture was washed twice with 100 mL portions of saturated NaHCO₃ (aq). The aqueous extracts were then extracted once with CH₂Cl₂ (100 mL). The organic layers were combined, dried with Na₂SO₄, and evaporated under reduced pressure to give a dark yellow oil. NMR analysis of this oil showed that it contained a 2:1 mixture of the desired tris(pyrazolyl)methane and another regioisomer.

For purification, the material was dissolved in a minimum amount of hot hexane and allowed to crystallize at room temperature for 24 hours. The resulting yellow/brown crystals were separated under a microscope. The larger, clear, and darker-colored lozenges were separated from the smaller, opaque, and lighter plates. These smaller crystals tend to form in masses, often growing on the larger crystals and the bottom of the flask. The larger crystals were scraped clean of as much of the other material as possible under the microscope. The large crystals separated in this fashion were typically at least 85% of target compound. This material was then carefully crystallized from hot hexanes after decolorization with carbon in the same solvent.

A suitable crystal was carefully cut from a larger block. A bigger crystal demonstrated the same structure in a preliminary X-ray experiment.