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Acta Cryst. (2010). E66, o844    [ doi:10.1107/S1600536810008408 ]

2-Amino-4-methylpyridinium trifluoroacetate: a monoclinic polymorph

M. Pourayoubi, M. Toghraee, A. L. Rheingold and J. A. Golen

Abstract top

The title salt, C6H9N2+·C2F3O2-, is a monoclinic polymorph of a previously reported structure [Hemamalini & Fun (2010). Acta Cryst. E66, o781-o782]. In the crystal structure, the cations and anions are linked by two different types of N-H...O hydrogen bonds, forming cation-anion pairs. These pairs are hydrogen bonded to neighbouring pairs via another N-H...O hydrogen bonds involving an H atom of the NH2 group and one of the O atoms of the COO- group into a chain extended along the b axis.

Comment top

In the previous works, the structure determinations of 2-aminopyridinium trifluoroacetate and the triclinic polymorph of 2-amino-4-methylpyridinium trifluoroacetate (Hemamalini & Fun, 2010a,b) have been investigated; we report here on the crystal structure of title compound, 4-methyl-2-aminopyridinium trifluoroacetate (Fig. 1). The cation and anion are linked by two different types of N—H···O hydrogen bonds, forming the cation-anion pair. The pairs are hydrogen bonded to neighbouring pairs via another N—H···O hydrogen bonds between the hydrogen of NH2 moiety and one of the oxygen atom of COO- group into chain extended along the b axis (Fig. 2).

Related literature top

For a related structure and the triclinic polymorph of the title salt, see: Hemamalini & Fun (2010a,b).

Experimental top

The title compound was obtained accidently from the reaction between 2,2,2-trifluoroacetamide, phosphorus pentachloride and formic acid and then the treatment of 2-amino-4-methylpyridine and triethylamine. The crystal was obtained from chloroform and n-heptane at room temperature.

Refinement top

The H atoms of the NH2 group were located from the difference Fourier synthesis and refined isotropically, no restraints were used. Finally, the geometrical and thermal parameters obtained for these H-atoms, as well as parameters of the hydrogen bonds for these H-atoms included, were rather realistic. The H(C) atom positions were calculated and refined in isotropic approximation in riding model with the Uiso(H) parameters equal to 1.2 Ueq(Ci) for the aromatic C atoms, for methyl groups equal to 1.5 Ueq(Cii), where U(Ci) and U(Cii) are respectively the equivalent thermal parameters of the carbon atoms to which corresponding H atoms are bonded.

Computing details top

Data collection: SMART (Bruker, 2005); cell refinement: SAINT (Bruker 2005); data reduction: SAINT (Bruker 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title salt, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50 % probability level.
[Figure 2] Fig. 2. A view of crystal packing along the b axis, hydrogen bonds are shown by dashed lines.
2-Amino-4-methylpyridinium trifluoroacetate top
Crystal data top
C6H9N2+·C2F3O2−F(000) = 456
Mr = 222.17Dx = 1.549 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 5265 reflections
a = 8.5315 (7) Åθ = 2.7–28.0°
b = 11.4901 (9) ŵ = 0.15 mm−1
c = 9.7206 (8) ÅT = 100 K
β = 90.820 (1)°Block, colorless
V = 952.79 (13) Å30.30 × 0.20 × 0.10 mm
Z = 4
Data collection top
Bruker SMART APEX
diffractometer		1784 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.036
graphiteθmax = 28.2°, θmin = 2.4°
φ and ω scansh = −5→11
10752 measured reflectionsk = −14→14
2197 independent reflectionsl = −12→12
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.035H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.098 w = 1/[σ2(Fo2) + (0.0474P)2 + 0.2454P]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max = 0.001
2197 reflectionsΔρmax = 0.29 e Å−3
150 parametersΔρmin = −0.23 e Å−3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0084 (16)
Crystal data top
C6H9N2+·C2F3O2−V = 952.79 (13) Å3
Mr = 222.17Z = 4
Monoclinic, P21/cMo Kα radiation
a = 8.5315 (7) ŵ = 0.15 mm−1
b = 11.4901 (9) ÅT = 100 K
c = 9.7206 (8) Å0.30 × 0.20 × 0.10 mm
β = 90.820 (1)°
Data collection top
Bruker SMART APEX
diffractometer		1784 reflections with I > 2σ(I)
10752 measured reflectionsRint = 0.036
2197 independent reflectionsθmax = 28.2°
Refinement top
R[F2 > 2σ(F2)] = 0.035H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.098Δρmax = 0.29 e Å−3
S = 1.06Δρmin = −0.23 e Å−3
2197 reflectionsAbsolute structure: ?
150 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
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.

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 > σ(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
F10.16929 (11)0.27679 (7)1.06142 (10)0.0350 (2)
F20.08357 (10)0.40806 (8)0.92121 (10)0.0358 (2)
F30.25375 (10)0.45302 (7)1.07851 (9)0.0316 (2)
O10.36035 (11)0.23798 (8)0.85540 (11)0.0259 (2)
O20.41240 (11)0.42938 (8)0.83832 (10)0.0257 (2)
N10.61429 (13)0.37742 (9)0.62595 (12)0.0212 (2)
H1B0.544 (2)0.3930 (17)0.699 (2)0.048 (5)*
N20.56684 (13)0.18015 (10)0.63958 (12)0.0223 (3)
H2C0.504 (2)0.1964 (16)0.711 (2)0.040 (5)*
H2B0.588 (2)0.1040 (16)0.6158 (18)0.034 (5)*
C10.68436 (16)0.47274 (12)0.56989 (15)0.0251 (3)
H1A0.66180.54800.60490.030*
C20.78596 (16)0.46100 (12)0.46475 (15)0.0250 (3)
H2A0.83410.52770.42610.030*
C30.81986 (15)0.34848 (12)0.41287 (14)0.0214 (3)
C40.74763 (14)0.25417 (11)0.47012 (13)0.0206 (3)
H4A0.76890.17840.43590.025*
C50.64122 (14)0.26797 (11)0.58005 (14)0.0196 (3)
C60.93335 (16)0.33574 (13)0.29694 (15)0.0260 (3)
H6A0.92870.25600.26120.039*
H6B1.03980.35230.33070.039*
H6C0.90550.39050.22330.039*
C70.34308 (14)0.34184 (11)0.88424 (14)0.0200 (3)
C80.21258 (15)0.36940 (11)0.98849 (15)0.0236 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
F10.0412 (5)0.0257 (5)0.0385 (5)−0.0036 (4)0.0209 (4)0.0027 (4)
F20.0220 (4)0.0367 (5)0.0488 (6)0.0070 (3)0.0017 (4)−0.0026 (4)
F30.0328 (5)0.0271 (5)0.0350 (5)−0.0012 (3)0.0096 (4)−0.0114 (4)
O10.0294 (5)0.0168 (5)0.0319 (6)−0.0008 (4)0.0099 (4)−0.0027 (4)
O20.0292 (5)0.0179 (5)0.0303 (6)−0.0033 (4)0.0105 (4)0.0005 (4)
N10.0223 (5)0.0177 (5)0.0237 (6)0.0006 (4)0.0044 (4)−0.0015 (5)
N20.0250 (6)0.0168 (6)0.0253 (6)−0.0007 (4)0.0073 (5)−0.0007 (5)
C10.0272 (7)0.0168 (6)0.0314 (8)−0.0007 (5)0.0026 (6)−0.0014 (5)
C20.0250 (7)0.0200 (7)0.0302 (8)−0.0033 (5)0.0032 (5)0.0040 (5)
C30.0181 (6)0.0239 (7)0.0223 (7)−0.0005 (5)0.0013 (5)0.0008 (5)
C40.0206 (6)0.0187 (6)0.0224 (7)0.0006 (5)0.0019 (5)−0.0010 (5)
C50.0185 (6)0.0181 (6)0.0221 (6)0.0003 (4)−0.0005 (5)−0.0005 (5)
C60.0236 (7)0.0298 (7)0.0247 (7)−0.0021 (5)0.0052 (5)0.0023 (6)
C70.0200 (6)0.0185 (6)0.0217 (7)−0.0005 (5)0.0022 (5)−0.0010 (5)
C80.0227 (6)0.0182 (6)0.0299 (7)−0.0008 (5)0.0060 (5)−0.0015 (5)
Geometric parameters (Å, °) top
F1—C81.3337 (15)C1—H1A0.9500
F2—C81.3475 (16)C2—C31.4190 (19)
F3—C81.3429 (16)C2—H2A0.9500
O1—C71.2352 (15)C3—C41.3688 (18)
O2—C71.2523 (15)C3—C61.5033 (18)
N1—C51.3552 (16)C4—C51.4209 (17)
N1—C11.3650 (17)C4—H4A0.9500
N1—H1B0.952 (19)C6—H6A0.9800
N2—C51.3290 (16)C6—H6B0.9800
N2—H2C0.901 (18)C6—H6C0.9800
N2—H2B0.923 (18)C7—C81.5490 (18)
C1—C21.356 (2)
C5—N1—C1122.40 (12)N2—C5—N1118.49 (12)
C5—N1—H1B122.1 (12)N2—C5—C4123.85 (12)
C1—N1—H1B115.5 (12)N1—C5—C4117.67 (12)
C5—N2—H2C118.0 (12)C3—C6—H6A109.5
C5—N2—H2B121.1 (11)C3—C6—H6B109.5
H2C—N2—H2B120.5 (16)H6A—C6—H6B109.5
C2—C1—N1120.62 (12)C3—C6—H6C109.5
C2—C1—H1A119.7H6A—C6—H6C109.5
N1—C1—H1A119.7H6B—C6—H6C109.5
C1—C2—C3119.61 (12)O1—C7—O2129.54 (12)
C1—C2—H2A120.2O1—C7—C8115.80 (11)
C3—C2—H2A120.2O2—C7—C8114.62 (11)
C4—C3—C2118.79 (12)F1—C8—F3107.24 (12)
C4—C3—C6121.75 (12)F1—C8—F2106.89 (11)
C2—C3—C6119.46 (12)F3—C8—F2106.54 (10)
C3—C4—C5120.90 (12)F1—C8—C7113.06 (11)
C3—C4—H4A119.5F3—C8—C7112.88 (11)
C5—C4—H4A119.5F2—C8—C7109.85 (11)
C5—N1—C1—C2−0.3 (2)C3—C4—C5—N2179.68 (13)
N1—C1—C2—C3−0.1 (2)C3—C4—C5—N1−0.10 (19)
C1—C2—C3—C40.5 (2)O1—C7—C8—F118.42 (18)
C1—C2—C3—C6−179.60 (13)O2—C7—C8—F1−163.72 (12)
C2—C3—C4—C5−0.37 (19)O1—C7—C8—F3140.38 (12)
C6—C3—C4—C5179.73 (12)O2—C7—C8—F3−41.76 (17)
C1—N1—C5—N2−179.33 (12)O1—C7—C8—F2−100.87 (14)
C1—N1—C5—C40.46 (19)O2—C7—C8—F276.99 (14)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1B···O20.952 (19)1.82 (2)2.7724 (14)177.4 (18)
N2—H2C···O10.901 (18)1.938 (19)2.8376 (15)176.3 (17)
N2—H2B···O2i0.923 (18)2.055 (18)2.8946 (15)150.5 (15)
Symmetry codes: (i) −x+1, y−1/2, −z+3/2.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1B···O20.952 (19)1.82 (2)2.7724 (14)177.4 (18)
N2—H2C···O10.901 (18)1.938 (19)2.8376 (15)176.3 (17)
N2—H2B···O2i0.923 (18)2.055 (18)2.8946 (15)150.5 (15)
Symmetry codes: (i) −x+1, y−1/2, −z+3/2.
Acknowledgements top

Support of this investigation by Ferdowsi University of Mashhad is gratefully acknowledged.

references
References top

Bruker (2005). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.

Hemamalini, M. & Fun, H.-K. (2010a). Acta Cryst. E66, o691–o692.

Hemamalini, M. & Fun, H.-K. (2010b). Acta Cryst. E66, o781–o782.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.