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

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ISSN: 2414-3146

1-Ethyl-4-iso­propyl-1,2,4-triazolium bromide

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aDepartment of Chemistry, Millersville University, Millersville, PA 17551, USA, and bDepartment of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
*Correspondence e-mail: edward.rajaseelan@millersville.edu

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 30 August 2023; accepted 7 September 2023; online 14 September 2023)

An ionic compound consisting of a triazolium cation and bromide anion, C7H14N3+·Br, has been synthesized and structurally characterized using single-crystal X-ray diffraction and NMR. The compound crystallizes in the monoclinic space group P21/m with the non-hydrogen atoms of one cation lying on general positions and the others lying on a mirror plane. One bromide ion also lies on the mirror. The extended structure exhibits only weak inter­molecular inter­actions between heterocyclic C—H groups and Br ions.

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

Structure description

Asymmetric 1,2,4-triazolium cations are of inter­est due to their utility as cations in ionic liquids (ILs) and as precursors to N-heterocyclic carbenes (NHCs) (Dwivedi et al., 2014[Dwivedi, S., Gupta, S. & Das, S. (2014). Curr. Organocatalysis, 1, 13-39.]; Nelson, 2015[Nelson, D. J. (2015). Eur. J. Inorg. Chem. pp. 2012-2027.]; Strassner et al., 2013[Strassner, T., Unger, Y., Meyer, D., Molt, O., Münster, I. & Wagenblast, G. (2013). Inorg. Chem. Commun. 30, 39-41.]; Riederer et al., 2011[Riederer, S. K., Bechlars, B., Herrmann, W. A. & Kühn, F. E. (2011). Dalton Trans. 40, 41-43.]; Chianese et al., 2004[Chianese, A. R., Kovacevic, A., Zeglis, B. M., Faller, J. W. & Crabtree, R. H. (2004). Organometallics, 23, 2461-2468.]). The crystal structures of several triazolium salts have been reported (Peña Hueso et al., 2022[Peña Hueso, A., Esparza Ruiz, A. & Flores Parra, A. (2022). IUCrData, 7, x220172.]; Kumasaki et al., 2021[Kumasaki, M., Gontani, S., Mori, K., Matsumoto, S. & Inoue, K. (2021). Acta Cryst. C77, 197-201.]; Ponjan et al., 2020[Ponjan, N., Aroonchat, P. & Chainok, K. (2020). Acta Cryst. E76, 137-140.]; Guino-o et al., 2015[Guino-o, M. A., Talbot, M. O., Slitts, M. M., Pham, T. N., Audi, M. C. & Janzen, D. E. (2015). Acta Cryst. E71, 628-635.]). We have synthesized many imidazolium and triazolium salts as precursors in the synthesis of NHC complexes of rhodium and iridium (Castaldi et al., 2021[Castaldi, K. T., Astashkin, A. V., Albert, D. R. & Rajaseelan, E. (2021). IUCrData, 6, x211142.]; Gnanamgari et al., 2007[Gnanamgari, D., Moores, A., Rajaseelan, E. & Crabtree, R. H. (2007). Organometallics, 26, 1226-1230.]; Idrees et al., 2017[Idrees, K. B., Astashkin, A. V. & Rajaseelan, E. (2017). IUCrData, 2, x171081.]; Nichol et al., 2011[Nichol, G. S., Rajaseelan, J., Walton, D. P. & Rajaseelan, E. (2011). Acta Cryst. E67, m1860-m1861.]; Newman et al., 2021[Newman, E. B., Astashkin, A. V., Albert, D. R. & Rajaseelan, E. (2021). IUCrData, 6, x210836.]; Rushlow et al., 2022[Rushlow, J., Astashkin, A. V., Albert, D. R. & Rajaseelan, E. (2022). IUCrData, 7, x220685.]).

The mol­ecular structure of the title compound is shown in Fig. 1[link]. There are one and a half mol­ecules in the asymmetric unit with the non-hydrogen atoms of the N1 cation (except C4) and Br1 lying on the (x, 3/4, z) mirror plane. All the atoms of the N4 cation and Br2 occupy general positions. The bond lengths in the triazolium rings indicate aromaticity with C—N bonds exhibiting distances in the range of 1.305 (2)–1.366 (2) Å and N—N bond distances near 1.365 Å; the N—C—N bond angles in the triazolium ring range from 106.93 (18) to 111.35 (18)°. The C1—N2—C5—C6 torsion angle of the ethyl side chain in the N1 cation is constrained to be 0° by symmetry and the corresponding C8—N5—C12—C13 torsion angle in the N4 cation is 24.4 (2)°.

[Figure 1]
Figure 1
The mol­ecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level. The N1 mol­ecule (except C4) and Br1 lie on the (x, 3/4, z) mirror plane. Atom C4i is generated by the symmetry operation x, [{3\over 2}] − y, z.

The crystal packing of the title compound is displayed in Fig. 2[link]. There are weak non-classical hydrogen-bonding inter­actions between the heterocyclic C—H groupings and bromide ions. These weak inter­actions are shown as dotted red lines in Fig. 2[link] and summarized in Table 1[link].

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C1—H1⋯Br1i 0.95 2.67 3.610 (2) 170
C2—H2⋯Br2i 0.95 2.70 3.6344 (18) 166
C7—H7⋯Br2i 0.95 2.69 3.6316 (15) 170
C8—H8⋯Br2i 0.95 2.68 3.5635 (15) 156
Symmetry code: (i) [x, y, z-1].
[Figure 2]
Figure 2
Crystal packing of the title compound shown along the a axis. Non-classical C—H⋯Br hydrogen-bonding inter­actions are shown as dotted red lines.

Synthesis and crystallization

1-Ethyl triazole was purchased from AmBeed. All other compounds used in the syntheses of the title compound were obtained from Sigma-Aldrich. All materials in the synthesis were used as received. The synthesis was performed under nitro­gen using reagent grade solvents, which were used as received without further purification. NMR spectra were recorded at room temperature in CDCl3 on a 400 MHz Varian spectrometer and referenced to the residual solvent peak (δ in p.p.m.).

1-Ethyl-1,2,4-triazole (2.01 g, 20.61 mmol) and isopropyl bromide (10.14 g, 82.4 mmol) were added to toluene (20 ml) and the mixture was refluxed for 48 h. Once cooled, the liquid was deca­nted, the white solid product that formed was washed with ether, filtered, and dried. The title compound crystallized as clear needles by slow diffusion of pentane into a CH2Cl2 solution. Yield: 1.04 g (23%). 1H NMR: CDCl3, δ (p.p.m.) 11.99 (s, 1 H, N—C5H—N), 8.85 (s, 1 H, N—C3H—N), 5.13 (m, 1 H, CH(CH3)2), 4.63 (q, 2 H, N—CH2), 1.74 (d, 6 H, CH(CH3)2), 1.65 (t, 3 H, CH2CH3). 13C NMR: δ (p.p.m.) 142.27 (N—CH—N), 141.84 (N—CH—N), 53.15 [CH(CH3)2], 48.36 (N—CH2), 23.14 [CH(CH3)2], 14.22 (N—CH2CH3).

Refinement

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

Table 2
Experimental details

Crystal data
Chemical formula C7H14N3+·Br
Mr 220.12
Crystal system, space group Monoclinic, P21/m
Temperature (K) 100
a, b, c (Å) 8.1283 (2), 21.3822 (7), 8.6376 (2)
β (°) 101.713 (3)
V3) 1469.96 (7)
Z 6
Radiation type Mo Kα
μ (mm−1) 4.14
Crystal size (mm) 0.38 × 0.25 × 0.04
 
Data collection
Diffractometer Rigaku XtaLAB Synergy-S
Absorption correction Multi-scan (CrysAlis PRO; Rigaku OD; 2022[Rigaku OD (2022). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.])
Tmin, Tmax 0.483, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections 23168, 3747, 3142
Rint 0.036
(sin θ/λ)max−1) 0.667
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.022, 0.052, 1.04
No. of reflections 3747
No. of parameters 168
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.38, −0.29
Computer programs: CrysAlis PRO (Rigaku OD, 2022[Rigaku OD (2022). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2018/3 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]), and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Structural data


Computing details top

Data collection: CrysAlis PRO 1.171.42.79a (Rigaku OD, 2022); cell refinement: CrysAlis PRO 1.171.42.79a (Rigaku OD, 2022); data reduction: CrysAlis PRO 1.171.42.79a (Rigaku OD, 2022); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015b); molecular graphics: Olex2 1.3 (Dolomanov et al., 2009); software used to prepare material for publication: publCIF (Westrip, 2010).

1-Ethyl-4-isopropyl-1,2,4-triazolium bromide top
Crystal data top
C7H14N3+·BrF(000) = 672
Mr = 220.12Dx = 1.492 Mg m3
Monoclinic, P21/mMo Kα radiation, λ = 0.71073 Å
a = 8.1283 (2) ÅCell parameters from 9609 reflections
b = 21.3822 (7) Åθ = 3.1–28.2°
c = 8.6376 (2) ŵ = 4.14 mm1
β = 101.713 (3)°T = 100 K
V = 1469.96 (7) Å3Plate, colourless
Z = 60.38 × 0.25 × 0.04 mm
Data collection top
Rigaku XtaLAB Synergy-S
diffractometer
3747 independent reflections
Radiation source: micro-focus sealed X-ray tube, PhotonJet (Mo) X-ray Source3142 reflections with I > 2σ(I)
Mirror monochromatorRint = 0.036
Detector resolution: 10.0000 pixels mm-1θmax = 28.3°, θmin = 2.6°
ω scansh = 1010
Absorption correction: multi-scan
(CrysAlis PRO; Rigaku OD; 2022)
k = 2728
Tmin = 0.483, Tmax = 1.000l = 1111
23168 measured reflections
Refinement top
Refinement on F2Primary atom site location: dual
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.022H-atom parameters constrained
wR(F2) = 0.052 w = 1/[σ2(Fo2) + (0.0235P)2 + 0.254P]
where P = (Fo2 + 2Fc2)/3
S = 1.04(Δ/σ)max = 0.001
3747 reflectionsΔρmax = 0.38 e Å3
168 parametersΔρmin = 0.29 e Å3
0 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Br10.65535 (3)0.7500000.86475 (2)0.01997 (6)
Br20.36575 (2)0.58378 (2)1.16793 (2)0.01912 (5)
N10.5536 (2)0.7500000.34816 (19)0.0180 (4)
N20.3012 (2)0.7500000.22004 (19)0.0181 (4)
N30.2904 (2)0.7500000.3756 (2)0.0225 (4)
C10.4576 (3)0.7500000.2031 (2)0.0175 (4)
H10.4955110.7500000.1060690.021*
C20.4471 (3)0.7500000.4505 (2)0.0209 (4)
H20.4820970.7500000.5623680.025*
C30.7407 (3)0.7500000.3888 (3)0.0277 (5)
H30.7775840.7500000.5065290.033*
C40.8056 (2)0.80896 (8)0.3239 (2)0.0324 (4)
H4A0.7724890.8090400.2083370.049*
H4B0.9284410.8102480.3550410.049*
H4C0.7579250.8456900.3665380.049*
C50.1468 (3)0.7500000.0987 (3)0.0315 (6)
H5A0.0796110.7874110.1129210.038*0.5
H5B0.0796110.7125890.1129210.038*0.5
C60.1791 (3)0.7500000.0638 (3)0.0353 (6)
H6A0.2259460.7905280.0855980.053*0.5
H6B0.0736050.7427190.1395170.053*0.5
H6C0.2593080.7167540.0737900.053*0.5
N40.45707 (16)0.58697 (5)0.70657 (14)0.0163 (3)
N50.71989 (15)0.59178 (5)0.80363 (14)0.0170 (3)
N60.70540 (17)0.59818 (6)0.64405 (15)0.0234 (3)
C70.5439 (2)0.59462 (7)0.58810 (18)0.0223 (3)
H70.4933580.5970460.4789940.027*
C80.57173 (19)0.58536 (6)0.84100 (17)0.0167 (3)
H80.5504090.5804760.9444600.020*
C90.27440 (18)0.57739 (7)0.69275 (18)0.0198 (3)
H90.2490960.5768780.8013140.024*
C100.1780 (2)0.63095 (8)0.6001 (2)0.0296 (4)
H10A0.2184680.6707940.6496690.044*
H10B0.0579660.6263960.5996360.044*
H10C0.1955250.6301780.4911080.044*
C110.2264 (2)0.51438 (8)0.61529 (19)0.0287 (4)
H11A0.2400930.5156440.5051860.043*
H11B0.1090540.5050460.6182080.043*
H11C0.2991900.4818090.6725080.043*
C120.88457 (19)0.59542 (8)0.9095 (2)0.0242 (3)
H12A0.9171690.6398480.9275130.029*
H12B0.9692760.5747990.8590480.029*
C130.8832 (2)0.56445 (8)1.06588 (18)0.0246 (3)
H13A0.8473260.5208231.0480130.037*
H13B0.8049070.5865851.1192660.037*
H13C0.9963250.5657791.1320880.037*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.02633 (12)0.01928 (12)0.01483 (11)0.0000.00543 (8)0.000
Br20.01946 (8)0.02267 (9)0.01542 (8)0.00045 (5)0.00400 (6)0.00014 (5)
N10.0180 (9)0.0217 (9)0.0145 (8)0.0000.0036 (7)0.000
N20.0193 (9)0.0205 (9)0.0149 (8)0.0000.0043 (7)0.000
N30.0242 (10)0.0261 (10)0.0194 (9)0.0000.0094 (7)0.000
C10.0181 (10)0.0194 (11)0.0142 (10)0.0000.0015 (8)0.000
C20.0265 (11)0.0219 (11)0.0154 (10)0.0000.0066 (9)0.000
C30.0196 (11)0.0469 (15)0.0148 (10)0.0000.0009 (9)0.000
C40.0238 (8)0.0396 (10)0.0359 (9)0.0128 (7)0.0108 (7)0.0165 (8)
C50.0159 (11)0.0541 (16)0.0222 (12)0.0000.0021 (9)0.000
C60.0224 (12)0.0617 (18)0.0196 (11)0.0000.0007 (9)0.000
N40.0165 (6)0.0197 (7)0.0132 (6)0.0001 (5)0.0040 (5)0.0014 (4)
N50.0169 (6)0.0181 (7)0.0171 (6)0.0005 (5)0.0059 (5)0.0009 (4)
N60.0244 (7)0.0275 (7)0.0204 (7)0.0008 (5)0.0093 (5)0.0004 (5)
C70.0236 (8)0.0278 (9)0.0167 (7)0.0001 (6)0.0068 (6)0.0005 (6)
C80.0170 (7)0.0164 (7)0.0170 (7)0.0000 (5)0.0041 (6)0.0013 (5)
C90.0138 (7)0.0284 (9)0.0169 (7)0.0003 (6)0.0023 (6)0.0025 (6)
C100.0242 (8)0.0386 (10)0.0273 (8)0.0118 (7)0.0077 (7)0.0102 (7)
C110.0231 (8)0.0329 (9)0.0280 (8)0.0061 (7)0.0003 (7)0.0008 (7)
C120.0134 (7)0.0286 (9)0.0302 (9)0.0012 (6)0.0035 (6)0.0032 (7)
C130.0187 (8)0.0305 (9)0.0232 (8)0.0006 (6)0.0013 (6)0.0004 (6)
Geometric parameters (Å, º) top
N1—C11.335 (2)N4—C71.366 (2)
N1—C21.357 (3)N4—C81.3337 (19)
N1—C31.490 (3)N4—C91.4795 (19)
N2—N31.364 (2)N5—N61.3662 (18)
N2—C11.308 (3)N5—C81.316 (2)
N2—C51.463 (3)N5—C121.4618 (19)
N3—C21.307 (3)N6—C71.305 (2)
C3—C41.517 (2)C9—C101.520 (2)
C3—C4i1.517 (2)C9—C111.520 (2)
C5—C61.480 (3)C12—C131.507 (2)
C1—N1—C2106.43 (18)C7—N4—C9128.25 (12)
C1—N1—C3126.56 (18)C8—N4—C7106.21 (13)
C2—N1—C3127.01 (17)C8—N4—C9125.39 (13)
N3—N2—C5119.20 (18)N6—N5—C12120.41 (13)
C1—N2—N3111.63 (16)C8—N5—N6111.24 (12)
C1—N2—C5129.18 (18)C8—N5—C12128.29 (13)
C2—N3—N2103.67 (18)C7—N6—N5104.00 (13)
N2—C1—N1106.93 (18)N6—C7—N4111.31 (13)
N3—C2—N1111.35 (18)N5—C8—N4107.24 (13)
N1—C3—C4i109.14 (11)N4—C9—C10109.85 (12)
N1—C3—C4109.14 (11)N4—C9—C11108.78 (12)
C4—C3—C4i112.4 (2)C11—C9—C10112.16 (13)
N2—C5—C6112.79 (19)N5—C12—C13111.39 (13)
N2—N3—C2—N10.000 (1)N5—N6—C7—N40.69 (16)
N3—N2—C1—N10.000 (1)N6—N5—C8—N40.42 (15)
N3—N2—C5—C6180.000 (1)N6—N5—C12—C13158.90 (13)
C1—N1—C2—N30.000 (1)C7—N4—C8—N50.01 (15)
C1—N1—C3—C4i61.59 (13)C7—N4—C9—C1056.70 (19)
C1—N1—C3—C461.59 (13)C7—N4—C9—C1166.41 (18)
C1—N2—N3—C20.000 (1)C8—N4—C7—N60.46 (16)
C1—N2—C5—C60.000 (1)C8—N4—C9—C10128.34 (14)
C2—N1—C1—N20.000 (1)C8—N4—C9—C11108.55 (15)
C2—N1—C3—C4i118.41 (13)C8—N5—N6—C70.69 (16)
C2—N1—C3—C4118.41 (13)C8—N5—C12—C1324.4 (2)
C3—N1—C1—N2180.000 (1)C9—N4—C7—N6176.18 (13)
C3—N1—C2—N3180.000 (1)C9—N4—C8—N5175.89 (12)
C5—N2—N3—C2180.000 (1)C12—N5—N6—C7177.94 (13)
C5—N2—C1—N1180.000 (1)C12—N5—C8—N4177.41 (13)
Symmetry code: (i) x, y+3/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1···Br1ii0.952.673.610 (2)170
C2—H2···Br2ii0.952.703.6344 (18)166
C7—H7···Br2ii0.952.693.6316 (15)170
C8—H8···Br2ii0.952.683.5635 (15)156
Symmetry code: (ii) x, y, z1.
 

Acknowledgements

AM was supported in this work by the Millersville University Murley Summer Undergraduate Research Fellowship.

References

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