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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 71| Part 12| December 2015| Pages o1008-o1009
https://doi.org/10.1107/S2056989015022136

Crystal structure of a methimazole-based ionic liquid

Jamie C. Gaitor,a Manuel Sanchez Zayas,a Darrel J. Myrthil,a Frankie White,b Jeffrey M. Hendrich,b Richard E. Sykora,b Richard A. O'Brien,b John T. Reillya and Arsalan Mirjafaria*

aDepartment of Chemistry and Physics, Florida Gulf Coast University, Fort Myers, FL 33965, USA, and bUniversity of South Alabama, Department of Chemistry, Mobile, AL 36688, USA
*Correspondence e-mail: amirjafari@fgcu.edu

Edited by P. C. Healy, Griffith University, Australia (Received 13 November 2015; accepted 19 November 2015; online 6 December 2015)

The structure of 1-methyl-2-(prop-2-en-1-ylsulfan­yl)-1H-imidazol-3-ium bromide, C7H11N2S+·Br−, has monoclinic (P21/c) symmetry. In the crystal, the components are linked by N—H⋯Br and C—H⋯Br hydrogen bonds. The crystal structure of the title compound undeniably proves that methimazole reacts through the thione tautomer, rather than the thiol tautomer in this system.

CCDC reference: 1437865

Similar articles

1. Related literature

For the biological activity of methimazole, see: Rong et al. (2013[Rong, Y., Al-Harbi, A., Kriegel, B. & Parkin, G. (2013). Inorg. Chem. 52, 7172-7182.]). For its use as a ligand, see: Crossley et al. (2006[Crossley, I. R., Hill, A. F., Humphrey, E. R. & Smith, M. K. (2006). Organometallics, 25, 2242-2247.]). For a discussion of methimazole-based ionic liquids, see: Siriwardana et al. (2008[Siriwardana, A. I., Crossley, I. R., Torriero, A. J., Burgar, I. M., Dunlop, N. F., Bond, A. M., Deacon, G. B. & MacFarlane, D. R. (2008). J. Org. Chem. 73, 4676-4679.]). For reaction chemistry of methimazole, see: Roy & Mugesh (2005[Roy, G. & Mugesh, G. (2005). J. Am. Chem. Soc. 127, 15207-15217.]).

[Scheme 1]

2. Experimental

2.1. Crystal data

  • C7H11N2S+·Br−

  • Mr = 235.15

  • Monoclinic, P 21 /c

  • a = 10.8692 (7) Å

  • b = 7.4103 (5) Å

  • c = 12.8551 (9) Å

  • β = 104.006 (7)°

  • V = 1004.62 (11) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 4.24 mm−1

  • T = 180 K

  • 0.6 × 0.32 × 0.25 mm

2.2. Data collection

  • Agilent Xcalibur, Eos diffractometer

  • Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2014[Agilent (2014). CrysAlis PRO. Agilent Technologies, Yarnton, England.]) Tmin = 0.321, Tmax = 1.000

  • 7388 measured reflections

  • 1829 independent reflections

  • 1558 reflections with I > 2σ(I)

  • Rint = 0.042

2.3. Refinement

  • R[F2 > 2σ(F2)] = 0.030

  • wR(F2) = 0.065

  • S = 1.03

  • 1829 reflections

  • 105 parameters

  • 1 restraint

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.34 e Å−3

  • Δρmin = −0.38 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A D⋯A D—H⋯A
N2—H2⋯Br1i 0.84 (3) 2.46 (3) 3.246 (2) 158 (3)
C2—H2A⋯Br1ii 0.93 2.84 3.723 (4) 159
C3—H3⋯Br1iii 0.93 2.91 3.757 (3) 152
C4—H4B⋯Br1 0.96 2.87 3.737 (3) 151
C5—H5B⋯Br1iv 0.97 2.89 3.814 (3) 161
Symmetry codes: (i) [x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]; (ii) [-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]; (iii) -x+1, -y+1, -z+1; (iv) -x+2, -y+1, -z+1.

Data collection: CrysAlis PRO (Agilent, 2014[Agilent (2014). CrysAlis PRO. Agilent Technologies, Yarnton, England.]); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: 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.]); software used to prepare material for publication: OLEX2 and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information

CCDC reference: 1437865

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: https://doi.org/10.1107/S2056989015022136/hg5463sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989015022136/hg5463Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989015022136/hg5463Isup3.cml

checkCIF report


Comment top

2-Mercapto-1-methyl­imidazole or methimazole 1 belongs to a class of five-membered heterocyclic nitro­gen compounds, which possess various biological activities (e.g. it is a widely used anti-thyroid drug under the name Tapazole), see: Rong et al. (2013). Additionally, it has found use as a multidentate ligand in the fields of inorganic and organometallic chemistry, in which the sulfur atom can serve as a soft donor towards a wide variety of transition metals, see: Crossley et al. (2006). The alkyl­ation of methimazole with alkyl halides (e.g. iodo­ethane and chloro­butane) lead to the formation of methimazole-based ionic liquids in high yields, see Siriwardana et al. (2008). To date, no methimazole-based ionic liquids have been structurally characterized by X-ray diffraction.

Methimazole exists in two tautomeric forms, equilibrating between the 2-thiol 1a and 2-thione 1b, and both N-alkyl­ation and S-alkyl­ation reactions are possible, depending upon the reaction conditions and types of substrates employed, see Roy & Mugesh (2005). They reported that only S-alkyl­ated methimazoles were formed. The product structures were established by NMR spectroscopy, which is elusive in terms of proving the exclusive formation of S-alkyl­ated products over N-alkyl­ated products. Herein, we report the crystal structure of S-allyl­ated methimazolium bromide 2, which was prepared in qu­anti­tative yield (96%) via the reaction of methimazole with allyl bromide in refluxing aceto­nitrile (Scheme S1). The crystal structure of 2 undeniably proves that methimazole reacts through the 2-thione tautomer 1b.

Synthesis and crystallization top

2-Mercapto-1-methyl­imidazole (0.57 g, 5 mmol) and allyl bromide (0.85 g, 7 mmol) were dissolved in aceto­nitrile (5.0 mL) and the mixture refluxed for 48 hours. The solvent and excess allyl bromide were removed under vacuum to afford an off-white solid. The solid was washed with toluene (3 x 10 mL) and then recrystallized in aceto­nitrile to yield pure product 2 as an off-white solid in 96% isolated yield.

Refinement top

Crystal data, data collection and structure refinement details are summarized in Table 1. The H-atom (H2) located on N2 was allowed to freely refine (isotropically). The remaining H-atoms were placed in calculated positions and allowed to ride during subsequent refinement, with Uiso(H) = 1.5Ueq(C) and C—H distances of 0.96 Å for methyl hydrogens, with Uiso(H) = 1.2Ueq(C) and C—H distances of 0.97 Å for the secondary hydrogens, and with Uiso(H) = 1.2Ueq(C) and C—H distances of 0.93 Å for all remaining hydrogen atoms.

Related literature top

For the biological activity of methimazole, see: Rong et al. (2013). For its use as a ligand, see: Crossley et al. (2006). For a discussion of methimazole-based ionic liquids, see: Siriwardana et al. (2008). For reaction chemistry of methimazole, see: Roy & Mugesh (2005).

Structure description top

2-Mercapto-1-methyl­imidazole or methimazole 1 belongs to a class of five-membered heterocyclic nitro­gen compounds, which possess various biological activities (e.g. it is a widely used anti-thyroid drug under the name Tapazole), see: Rong et al. (2013). Additionally, it has found use as a multidentate ligand in the fields of inorganic and organometallic chemistry, in which the sulfur atom can serve as a soft donor towards a wide variety of transition metals, see: Crossley et al. (2006). The alkyl­ation of methimazole with alkyl halides (e.g. iodo­ethane and chloro­butane) lead to the formation of methimazole-based ionic liquids in high yields, see Siriwardana et al. (2008). To date, no methimazole-based ionic liquids have been structurally characterized by X-ray diffraction.

Methimazole exists in two tautomeric forms, equilibrating between the 2-thiol 1a and 2-thione 1b, and both N-alkyl­ation and S-alkyl­ation reactions are possible, depending upon the reaction conditions and types of substrates employed, see Roy & Mugesh (2005). They reported that only S-alkyl­ated methimazoles were formed. The product structures were established by NMR spectroscopy, which is elusive in terms of proving the exclusive formation of S-alkyl­ated products over N-alkyl­ated products. Herein, we report the crystal structure of S-allyl­ated methimazolium bromide 2, which was prepared in qu­anti­tative yield (96%) via the reaction of methimazole with allyl bromide in refluxing aceto­nitrile (Scheme S1). The crystal structure of 2 undeniably proves that methimazole reacts through the 2-thione tautomer 1b.

For the biological activity of methimazole, see: Rong et al. (2013). For its use as a ligand, see: Crossley et al. (2006). For a discussion of methimazole-based ionic liquids, see: Siriwardana et al. (2008). For reaction chemistry of methimazole, see: Roy & Mugesh (2005).

Synthesis and crystallization top

2-Mercapto-1-methyl­imidazole (0.57 g, 5 mmol) and allyl bromide (0.85 g, 7 mmol) were dissolved in aceto­nitrile (5.0 mL) and the mixture refluxed for 48 hours. The solvent and excess allyl bromide were removed under vacuum to afford an off-white solid. The solid was washed with toluene (3 x 10 mL) and then recrystallized in aceto­nitrile to yield pure product 2 as an off-white solid in 96% isolated yield.

Refinement details top

Crystal data, data collection and structure refinement details are summarized in Table 1. The H-atom (H2) located on N2 was allowed to freely refine (isotropically). The remaining H-atoms were placed in calculated positions and allowed to ride during subsequent refinement, with Uiso(H) = 1.5Ueq(C) and C—H distances of 0.96 Å for methyl hydrogens, with Uiso(H) = 1.2Ueq(C) and C—H distances of 0.97 Å for the secondary hydrogens, and with Uiso(H) = 1.2Ueq(C) and C—H distances of 0.93 Å for all remaining hydrogen atoms.

Computing details top

Data collection: CrysAlis PRO (Agilent, 2014); cell refinement: CrysAlis PRO (Agilent, 2014); data reduction: CrysAlis PRO (Agilent, 2014); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009) and publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. A thermal ellipsoid diagram of the structure of the title compound.
[Figure 2] Fig. 2. Reaction scheme.
1-Methyl-2-(prop-2-en-1-ylsulfanyl)-1H-imidazol-3-ium bromide top
Crystal data top
C7H11N2S+·Br−F(000) = 472
Mr = 235.15Dx = 1.555 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 10.8692 (7) ÅCell parameters from 2203 reflections
b = 7.4103 (5) Åθ = 3.9–27.0°
c = 12.8551 (9) ŵ = 4.24 mm−1
β = 104.006 (7)°T = 180 K
V = 1004.62 (11) Å3Prism, colourless
Z = 40.6 × 0.32 × 0.25 mm
Data collection top
Agilent Xcalibur, Eos
diffractometer		1829 independent reflections
Radiation source: Enhance (Mo) X-ray Source1558 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.042
Detector resolution: 16.0514 pixels mm-1θmax = 25.3°, θmin = 3.2°
ω scansh = −13→13
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2014)		k = −8→8
Tmin = 0.321, Tmax = 1.000l = −15→15
7388 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.030Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.065H atoms treated by a mixture of independent and constrained refinement
S = 1.03 w = 1/[σ2(Fo2) + (0.027P)2]
where P = (Fo2 + 2Fc2)/3
1829 reflections(Δ/σ)max = 0.001
105 parametersΔρmax = 0.34 e Å−3
1 restraintΔρmin = −0.38 e Å−3
Crystal data top
C7H11N2S+·Br−V = 1004.62 (11) Å3
Mr = 235.15Z = 4
Monoclinic, P21/cMo Kα radiation
a = 10.8692 (7) ŵ = 4.24 mm−1
b = 7.4103 (5) ÅT = 180 K
c = 12.8551 (9) Å0.6 × 0.32 × 0.25 mm
β = 104.006 (7)°
Data collection top
Agilent Xcalibur, Eos
diffractometer		1829 independent reflections
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2014)		1558 reflections with I > 2σ(I)
Tmin = 0.321, Tmax = 1.000Rint = 0.042
7388 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0301 restraint
wR(F2) = 0.065H atoms treated by a mixture of independent and constrained refinement
S = 1.03Δρmax = 0.34 e Å−3
1829 reflectionsΔρmin = −0.38 e Å−3
105 parameters
Special details top

Experimental. CrysAlis Pro (Agilent, 2014) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br10.70880 (3)0.66161 (4)0.53045 (2)0.02621 (12)
N20.6562 (2)0.0414 (3)0.2392 (2)0.0273 (6)
N10.6302 (2)0.1226 (3)0.39296 (18)0.0233 (6)
C20.5297 (3)0.0739 (4)0.2258 (3)0.0316 (8)
H2A0.46690.06230.16250.038*
C30.5134 (3)0.1262 (4)0.3221 (3)0.0285 (7)
H30.43710.15870.33760.034*
C10.7171 (3)0.0704 (4)0.3410 (2)0.0234 (7)
S10.87834 (8)0.04183 (11)0.39532 (7)0.0373 (2)
C40.6547 (4)0.1637 (4)0.5076 (2)0.0370 (9)
H4A0.57560.17490.52780.055*
H4B0.70090.27500.52210.055*
H4C0.70370.06810.54810.055*
C60.9092 (3)0.3747 (4)0.3027 (3)0.0410 (9)
H60.94500.32740.24980.049*
C50.9322 (3)0.2790 (4)0.4066 (3)0.0405 (9)
H5A0.88890.34290.45320.049*
H5B1.02230.28180.44010.049*
C70.8417 (3)0.5215 (5)0.2809 (3)0.0436 (9)
H7A0.80470.57190.33230.052*
H7B0.83050.57580.21410.052*
H20.689 (3)0.007 (4)0.190 (2)0.049 (11)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.02573 (18)0.0284 (2)0.02529 (19)−0.00350 (13)0.00772 (13)−0.00185 (13)
N20.0309 (15)0.0295 (16)0.0227 (15)0.0016 (12)0.0088 (13)−0.0005 (12)
N10.0304 (15)0.0165 (13)0.0238 (14)−0.0003 (11)0.0081 (12)0.0002 (10)
C20.0256 (17)0.030 (2)0.0354 (19)−0.0008 (14)−0.0003 (15)0.0026 (15)
C30.0190 (16)0.0255 (18)0.041 (2)0.0028 (13)0.0064 (14)0.0023 (15)
C10.0253 (17)0.0180 (17)0.0264 (17)−0.0015 (13)0.0057 (14)0.0027 (13)
S10.0229 (4)0.0335 (5)0.0518 (6)0.0031 (4)0.0019 (4)0.0112 (4)
C40.059 (2)0.028 (2)0.0254 (18)−0.0016 (16)0.0128 (17)−0.0035 (14)
C60.039 (2)0.045 (2)0.044 (2)−0.0026 (17)0.0186 (18)0.0108 (18)
C50.0249 (18)0.040 (2)0.051 (2)−0.0105 (15)−0.0023 (16)0.0134 (17)
C70.049 (2)0.042 (2)0.037 (2)0.0000 (18)0.0056 (18)0.0126 (17)
Geometric parameters (Å, º) top
N2—C21.366 (4)C4—H4A0.9600
N2—C11.334 (4)C4—H4B0.9600
N2—H20.836 (17)C4—H4C0.9600
N1—C31.373 (4)C6—H60.9300
N1—C11.338 (3)C6—C51.480 (4)
N1—C41.465 (4)C6—C71.304 (4)
C2—H2A0.9300C5—H5A0.9700
C2—C31.349 (4)C5—H5B0.9700
C3—H30.9300C7—H7A0.9300
C1—S11.736 (3)C7—H7B0.9300
S1—C51.847 (3)
C2—N2—H2124 (2)N1—C4—H4B109.5
C1—N2—C2109.9 (3)N1—C4—H4C109.5
C1—N2—H2126 (2)H4A—C4—H4B109.5
C3—N1—C4125.3 (3)H4A—C4—H4C109.5
C1—N1—C3109.0 (2)H4B—C4—H4C109.5
C1—N1—C4125.7 (3)C5—C6—H6118.1
N2—C2—H2A126.7C7—C6—H6118.1
C3—C2—N2106.7 (3)C7—C6—C5123.8 (3)
C3—C2—H2A126.7S1—C5—H5A108.8
N1—C3—H3126.3S1—C5—H5B108.8
C2—C3—N1107.3 (3)C6—C5—S1113.8 (2)
C2—C3—H3126.3C6—C5—H5A108.8
N2—C1—N1107.1 (3)C6—C5—H5B108.8
N2—C1—S1126.0 (2)H5A—C5—H5B107.7
N1—C1—S1126.9 (2)C6—C7—H7A120.0
C1—S1—C5100.68 (14)C6—C7—H7B120.0
N1—C4—H4A109.5H7A—C7—H7B120.0
N2—C2—C3—N1−0.7 (3)C1—N2—C2—C30.7 (4)
N2—C1—S1—C5104.2 (3)C1—N1—C3—C20.5 (3)
N1—C1—S1—C5−77.0 (3)C1—S1—C5—C6−61.4 (3)
C2—N2—C1—N1−0.4 (3)C4—N1—C3—C2−177.7 (3)
C2—N2—C1—S1178.7 (2)C4—N1—C1—N2178.1 (3)
C3—N1—C1—N2−0.1 (3)C4—N1—C1—S1−0.9 (4)
C3—N1—C1—S1−179.1 (2)C7—C6—C5—S1121.8 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2···Br1i0.84 (3)2.46 (3)3.246 (2)158 (3)
C2—H2A···Br1ii0.932.843.723 (4)159
C3—H3···Br1iii0.932.913.757 (3)152
C4—H4B···Br10.962.873.737 (3)151
C5—H5B···Br1iv0.972.893.814 (3)161
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x+1, y−1/2, −z+1/2; (iii) −x+1, −y+1, −z+1; (iv) −x+2, −y+1, −z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2···Br1i0.84 (3)2.46 (3)3.246 (2)158 (3)
C2—H2A···Br1ii0.932.843.723 (4)159
C3—H3···Br1iii0.932.913.757 (3)152
C4—H4B···Br10.962.873.737 (3)151
C5—H5B···Br1iv0.972.893.814 (3)161
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x+1, y−1/2, −z+1/2; (iii) −x+1, −y+1, −z+1; (iv) −x+2, −y+1, −z+1.
 

Acknowledgements

The authors thank the Alice and Karl Sheffield Scholarship and the Department of Chemistry and Physics of FGCU for funding this project. They also acknowledge the National Science Foundation for their generous support (NSF–CAREER grant to RES, CHE-0846680).

References

First citationAgilent (2014). CrysAlis PRO. Agilent Technologies, Yarnton, England.  Google Scholar
 First citationCrossley, I. R., Hill, A. F., Humphrey, E. R. & Smith, M. K. (2006). Organometallics, 25, 2242–2247.  Web of Science CSD CrossRef CAS Google Scholar
 First citationDolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationRong, Y., Al-Harbi, A., Kriegel, B. & Parkin, G. (2013). Inorg. Chem. 52, 7172–7182.  Web of Science CSD CrossRef CAS PubMed Google Scholar
 First citationRoy, G. & Mugesh, G. (2005). J. Am. Chem. Soc. 127, 15207–15217.  Web of Science CrossRef PubMed CAS Google Scholar
 First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationSiriwardana, A. I., Crossley, I. R., Torriero, A. J., Burgar, I. M., Dunlop, N. F., Bond, A. M., Deacon, G. B. & MacFarlane, D. R. (2008). J. Org. Chem. 73, 4676–4679.  Web of Science CrossRef PubMed CAS Google Scholar
 First citationWestrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.  Web of Science CrossRef CAS IUCr Journals Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 71| Part 12| December 2015| Pages o1008-o1009
https://doi.org/10.1107/S2056989015022136
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