organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2414-3146

(3,5-Di­methyl-1H-pyrazol-1-yl)tri­methyl­silane

aInstitut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany
*Correspondence e-mail: uwe.boehme@chemie.tu-freiberg.de

Edited by J. Simpson, University of Otago, New Zealand (Received 23 October 2020; accepted 30 October 2020; online 6 November 2020)

The title compound, C8H16N2Si, crystallizes in the the ortho­rhom­bic space group P212121 with one mol­ecule in the asymmetric unit. The Si—N bond is 1.782 (2) Å, which is substanti­ally longer than is found in comparable (3,5-di­methyl­pyrazol­yl)silanes. The tri­methyl­silyl group adopts a staggered conformation with respect to the planar 3,5-di­methyl­pyrazolyl unit. C—H⋯N hydrogen bonds between neighboring mol­ecules form a strand of mol­ecules along the b-axis direction.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

Silanes substituted with 3,5-di­methyl­pyrazolyl units have been investigated over the last twenty years as an alternative to the long-known pyrazolylborates (Pullen et al., 2000[Pullen, E. E., Rabinovich, D., Incarvito, C. D., Concolino, T. E. & Rheingold, A. L. (2000). Inorg. Chem. 39, 1561-1567.]; Kuzu et al., 2008[Kuzu, I., Krummenacher, I., Meyer, J., Armbruster, F. & Breher, F. (2008). Dalton Trans. pp. 5836-5865.]; Armbruster et al. 2009[Armbruster, F., Fernández, I. & Breher, F. (2009). Dalton Trans. pp. 5612-5626.]). Such (3,5-di­methyl­pyrazol­yl)silanes form potent multidentate ligands with a `podand topology' (Gade 2002a[Gade, L. H. (2002a). Acc. Chem. Res. 35, 575-582.],b[Gade, L. H. (2002b). J. Organomet. Chem. 661, 85-94.],c[Gade, L. H. (2002c). Eur. J. Inorg. Chem. pp. 1257-1268.]).

The title compound (3,5-dimethyl-1H-pyrazol-1-yl)tri­methyl­silane is a key compound in the preparation of different (3,5-di­methyl­pyrazol­yl)silanes by transsilylation (Armbruster et al., 2009[Armbruster, F., Fernández, I. & Breher, F. (2009). Dalton Trans. pp. 5612-5626.]; Bitto et al., 2012[Bitto, F., Wagler, J. & Kroke, E. (2012). Eur. J. Inorg. Chem. pp. 2402-2408.], 2013[Bitto, F., Kraushaar, K., Böhme, U., Brendler, E., Wagler, J. & Kroke, E. (2013). Eur. J. Inorg. Chem. pp. 2954-2962.], 2016a[Bitto, F., Brendler, E., Böhme, U., Wagler, J. & Kroke, E. (2016a). Eur. J. Inorg. Chem. pp. 4207-4215.]). The solid-state structure of this compound has never been determined, since it is a liquid at room temperature. In situ cryo-crystallization of low-melting compounds has been practiced for many years (Atoji et al., 1955[Atoji, M., Lipscomb, W. N. & Wheatley, P. I. (1955). J. Chem. Phys. 23, 1176-1176.]; Smith & Lipscomb, 1965[Smith, H. W. & Lipscomb, W. N. (1965). J. Chem. Phys. 43, 1060-1064.]; Brodalla et al., 1985[Brodalla, D., Mootz, D., Boese, R. & Osswald, W. (1985). J. Appl. Cryst. 18, 316-319.]). Different in situ cryo-crystallization techniques have been described in a review (Boese & Nussbaumer, 1994[Boese, R. & Nussbaumer, M. (1994). In situ Crystallization Techniques. In Correlations, Transformations, and Interactions in Organic Crystal Chemistry, IUCr Crystallographic Symposia Vol. 7, edited by D. W. Jones and A. Katrusiak, pp. 20-37. Oxford University Press.]). State of the art of in situ crystallization is summarized recently in a special issue of Zeitschrift für Kristallographie (Boese, 2014[Boese, R. (2014). Z. Kristallogr. 229, 595-601.]). We have performed several single-crystal structure determinations of pyrophoric liquids by in situ crystallization on the diffractometer (Schmidt et al., 2013[Schmidt, D., Böhme, U., Seidel, J. & Kroke, E. (2013). Inorg. Chem. Commun. 35, 92-95.]; Gerwig et al. 2020[Gerwig, M., Böhme, U., Friebel, M., Gründler, F., Franze, G., Rosenkranz, M., Schmidt, H. & Kroke, E. (2020). ChemistryOpen 9, 762-773.]). With the experience gained in these processes, we were able to crystallize the title compound on the diffractometer and we report its crystal structure here.

The title compound crystallizes in the ortho­rhom­bic space group P212121 with one mol­ecule in the asymmetric unit (Fig. 1[link]). The Si1—N1 bond is 1.782 (2) Å long. This is substanti­ally longer than comparable bonds in tris­(3,5-di­methyl­pyrazol­yl)methyl­silane [1.745 (5) Å; Vepachedu et al., 1995[Vepachedu, S., Stibrany, R. T., Knapp, S., Potenza, J. A. & Schugar, H. J. (1995). Acta Cryst. C51, 423-426.]] and tetra­kis­(3,5-di­methyl­pyrazol­yl)silane [from 1.712 (3) to 1.725 (3) Å; Armbruster et al. 2009[Armbruster, F., Fernández, I. & Breher, F. (2009). Dalton Trans. pp. 5612-5626.]). The pyrazol ring is planar with an r.m.s. deviation of 0.003 Å from the ring plane. The tri­methyl­silyl group adopts a staggered conformation with respect to the plane of the 3,5-di­methyl­pyrazolyl unit. This can be seen in the torsion angles C8—Si1—N1—N2 with −35.1 (2)° and C6—Si1—N1—C2 with 36.3 (2)°. The methyl group C7 is orientated perpendicular to the 3,5-di­methyl­pyrazolyl unit. There is a hydrogen bond between the hydrogen atom at C6 and the nitro­gen atom N2 from a neighboring mol­ecule (see Table 1[link]). These hydrogen bonds form a strand of mol­ecules generated by a twofold screw axis (21) along the crystallographic b axis (see Fig. 2[link]).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C6—H6B⋯N2i 0.97 2.75 3.670 (3) 159
Symmetry code: (i) [-x+2, y-{\script{1\over 2}}, -z+{\script{1\over 2}}].
[Figure 1]
Figure 1
The mol­ecular structure of the title compound, drawn with 50% probability displacement ellipsoids.
[Figure 2]
Figure 2
Hydrogen bonds between N2 and H6B of neighboring mol­ecules along a twofold screw axis (21) parallel to the crystallographic b axis.

Synthesis and crystallization

The title compound was prepared from 3,5-di­methyl­pyrazol (19.23 g, 0.2 mol) and chloro­tri­methyl­silane (22.81 g, 0.21 mol). The reaction was performed in 300 ml THF as solvent and in the presence of tri­ethyl­amine (21.25 g, 0.21 mol). Tri­ethyl­amine hydro­chloride is formed during the reaction as a voluminous white precipitate. This precipitate is filtered off. After that the solvent is distilled off in vacuo. The title compound is isolated by vacuum distillation at 107°C and 1.3 kPa. It is a colourless liquid (26.97 g, 0.16 mol, 80% yield) (Bitto 2016b[Bitto, F. (2016b). Ph. D. thesis (3,5-Dimethylpyrazolylsilane - experimentelle und quantenchemische Untersuchungen), in Freiberger Forschungshefte, ISBN 978-3-86012-534-2.]).

The compound was filled as liquid with 10% n-pentane in a glass capillary with 0.5 mm diameter. A single crystal was grown on the diffractometer at 255 K. The data collection was perfomed at a slightly lower temperature in order to have a stable crystal on the diffractometer.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link].

Table 2
Experimental details

Crystal data
Chemical formula C8H16N2Si
Mr 168.32
Crystal system, space group Orthorhombic, P212121
Temperature (K) 250
a, b, c (Å) 6.1056 (3), 10.8114 (7), 15.5867 (9)
V3) 1028.88 (10)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.18
Crystal size (mm) 0.50 × 0.40 × 0.40
 
Data collection
Diffractometer STOE IPDS 2
Absorption correction Integration (X-RED; Stoe, 2009[Stoe (2009). X-RED and X-AREA. Stoe & Cie, Darmstadt, Germany.])
Tmin, Tmax 0.708, 0.932
No. of measured, independent and observed [I > 2σ(I)] reflections 8249, 2346, 2258
Rint 0.048
(sin θ/λ)max−1) 0.650
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.030, 0.080, 1.09
No. of reflections 2346
No. of parameters 106
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.12, −0.15
Absolute structure Flack x determined using 896 quotients [(I+)−(I)]/[(I+)+(I)] (Parsons et al., 2013[Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249-259.])
Absolute structure parameter 0.07 (9)
Computer programs: X-AREA and X-RED (Stoe, 2009[Stoe (2009). X-RED and X-AREA. Stoe & Cie, Darmstadt, Germany.]), SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2014/7 (Sheldrick 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]) and ORTEP-3 for Windows (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]).

Structural data


Computing details top

Data collection: X-AREA (Stoe, 2009); cell refinement: X-AREA (Stoe, 2009); data reduction: X-RED (Stoe, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL2014/7 (Sheldrick 2015).

(3,5-Dimethyl-1H-pyrazol-1-yl)trimethylsilane top
Crystal data top
C8H16N2SiDx = 1.087 Mg m3
Mr = 168.32Melting point: 260 K
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
a = 6.1056 (3) ÅCell parameters from 32385 reflections
b = 10.8114 (7) Åθ = 2.3–29.7°
c = 15.5867 (9) ŵ = 0.18 mm1
V = 1028.88 (10) Å3T = 250 K
Z = 4Capillary, colourless
F(000) = 3680.50 × 0.40 × 0.40 mm
Data collection top
STOE IPDS 2
diffractometer
2346 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus2258 reflections with I > 2σ(I)
Plane graphite monochromatorRint = 0.048
Detector resolution: 6.67 pixels mm-1θmax = 27.5°, θmin = 2.3°
rotation method scansh = 76
Absorption correction: integration
(X-RED; Stoe, 2009)
k = 1414
Tmin = 0.708, Tmax = 0.932l = 1920
8249 measured reflections
Refinement top
Refinement on F2H-atom parameters constrained
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0384P)2 + 0.1226P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.030(Δ/σ)max < 0.001
wR(F2) = 0.080Δρmax = 0.12 e Å3
S = 1.09Δρmin = 0.15 e Å3
2346 reflectionsExtinction correction: SHELXL-2014/7 (Sheldrick 2015, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
106 parametersExtinction coefficient: 0.038 (8)
0 restraintsAbsolute structure: Flack x determined using 896 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.07 (9)
Hydrogen site location: inferred from neighbouring sites
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Si11.09038 (8)0.83129 (5)0.28856 (3)0.03560 (16)
N10.9829 (3)0.91025 (15)0.37963 (9)0.0371 (3)
N20.8044 (3)0.98582 (17)0.36345 (11)0.0449 (4)
C11.2467 (4)0.8620 (3)0.49915 (16)0.0604 (6)
H1A1.27040.89050.55740.091*
H1B1.37650.87820.46510.091*
H1C1.21710.77380.49960.091*
C21.0558 (3)0.92883 (18)0.46120 (11)0.0390 (4)
C30.9227 (4)1.01575 (19)0.49782 (12)0.0443 (4)
H30.93171.04690.55400.053*
C40.7709 (4)1.04880 (18)0.43507 (13)0.0422 (4)
C50.5894 (5)1.1411 (2)0.44085 (18)0.0670 (7)
H5A0.65041.22300.44930.100*
H5B0.49511.12040.48880.100*
H5C0.50491.13970.38820.100*
C61.2361 (4)0.6905 (2)0.32373 (15)0.0544 (6)
H6A1.37210.71360.35160.082*
H6B1.26770.63900.27430.082*
H6C1.14500.64490.36370.082*
C71.2781 (5)0.9387 (2)0.23290 (16)0.0593 (6)
H7A1.19871.01270.21630.089*
H7B1.33680.89890.18210.089*
H7C1.39720.96100.27110.089*
C80.8569 (4)0.7920 (3)0.21896 (16)0.0589 (6)
H8A0.75180.74330.25110.088*
H8B0.90840.74470.17010.088*
H8C0.78750.86750.19900.088*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Si10.0353 (2)0.0376 (3)0.0339 (2)0.0038 (2)0.0023 (2)0.00083 (19)
N10.0377 (8)0.0398 (8)0.0338 (7)0.0062 (7)0.0010 (6)0.0016 (6)
N20.0477 (10)0.0474 (9)0.0395 (8)0.0141 (8)0.0014 (7)0.0014 (7)
C10.0550 (13)0.0720 (16)0.0541 (13)0.0143 (12)0.0176 (10)0.0073 (11)
C20.0396 (10)0.0414 (9)0.0361 (8)0.0028 (8)0.0016 (8)0.0000 (7)
C30.0515 (11)0.0435 (10)0.0380 (8)0.0020 (10)0.0016 (9)0.0049 (8)
C40.0452 (11)0.0375 (10)0.0438 (10)0.0042 (8)0.0072 (8)0.0007 (7)
C50.0701 (16)0.0590 (14)0.0718 (16)0.0264 (14)0.0064 (14)0.0074 (11)
C60.0651 (14)0.0476 (12)0.0506 (12)0.0175 (11)0.0024 (11)0.0007 (9)
C70.0599 (14)0.0557 (13)0.0623 (14)0.0014 (12)0.0219 (12)0.0060 (10)
C80.0500 (12)0.0713 (15)0.0554 (13)0.0044 (11)0.0075 (10)0.0176 (12)
Geometric parameters (Å, º) top
Si1—N11.7816 (15)C4—C51.494 (3)
Si1—C81.841 (2)C5—H5A0.9700
Si1—C61.847 (2)C5—H5B0.9700
Si1—C71.848 (2)C5—H5C0.9700
N1—C21.362 (2)C6—H6A0.9700
N1—N21.385 (2)C6—H6B0.9700
N2—C41.324 (3)C6—H6C0.9700
C1—C21.494 (3)C7—H7A0.9700
C1—H1A0.9700C7—H7B0.9700
C1—H1B0.9700C7—H7C0.9700
C1—H1C0.9700C8—H8A0.9700
C2—C31.367 (3)C8—H8B0.9700
C3—C41.394 (3)C8—H8C0.9700
C3—H30.9400
N1—Si1—C8107.15 (10)C4—C5—H5A109.5
N1—Si1—C6109.63 (9)C4—C5—H5B109.5
C8—Si1—C6110.98 (13)H5A—C5—H5B109.5
N1—Si1—C7107.53 (10)C4—C5—H5C109.5
C8—Si1—C7110.39 (13)H5A—C5—H5C109.5
C6—Si1—C7111.02 (13)H5B—C5—H5C109.5
C2—N1—N2109.87 (15)Si1—C6—H6A109.5
C2—N1—Si1133.98 (14)Si1—C6—H6B109.5
N2—N1—Si1115.29 (11)H6A—C6—H6B109.5
C4—N2—N1105.74 (16)Si1—C6—H6C109.5
C2—C1—H1A109.5H6A—C6—H6C109.5
C2—C1—H1B109.5H6B—C6—H6C109.5
H1A—C1—H1B109.5Si1—C7—H7A109.5
C2—C1—H1C109.5Si1—C7—H7B109.5
H1A—C1—H1C109.5H7A—C7—H7B109.5
H1B—C1—H1C109.5Si1—C7—H7C109.5
N1—C2—C3107.29 (18)H7A—C7—H7C109.5
N1—C2—C1123.58 (18)H7B—C7—H7C109.5
C3—C2—C1129.12 (19)Si1—C8—H8A109.5
C2—C3—C4106.16 (17)Si1—C8—H8B109.5
C2—C3—H3126.9H8A—C8—H8B109.5
C4—C3—H3126.9Si1—C8—H8C109.5
N2—C4—C3110.94 (18)H8A—C8—H8C109.5
N2—C4—C5120.6 (2)H8B—C8—H8C109.5
C3—C4—C5128.5 (2)
C8—Si1—N1—C2156.8 (2)Si1—N1—C2—C3169.00 (16)
C6—Si1—N1—C236.3 (2)N2—N1—C2—C1179.88 (19)
C7—Si1—N1—C284.5 (2)Si1—N1—C2—C111.4 (3)
C8—Si1—N1—N235.13 (18)N1—C2—C3—C40.7 (2)
C6—Si1—N1—N2155.65 (15)C1—C2—C3—C4179.8 (2)
C7—Si1—N1—N283.55 (17)N1—N2—C4—C30.3 (2)
C2—N1—N2—C40.1 (2)N1—N2—C4—C5179.69 (19)
Si1—N1—N2—C4171.00 (14)C2—C3—C4—N20.6 (3)
N2—N1—C2—C30.5 (2)C2—C3—C4—C5179.4 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C6—H6B···N2i0.972.753.670 (3)159
Symmetry code: (i) x+2, y1/2, z+1/2.
 

Funding information

Funding for this research was provided by: Open Access Funding by the Publication Fund of the TU Bergakademie Freiberg.

References

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