2-Amino-5-chloro­pyridinium trifluoro­acetate

Madhukar Hemamalini; Hoong-Kun Fun

doi:10.1107/S1600536810008196

. 2010 Mar 10;66(Pt 4):o783–o784. doi: 10.1107/S1600536810008196

2-Amino-5-chloropyridinium trifluoroacetate

Madhukar Hemamalini ^a, Hoong-Kun Fun ^a,^*,^‡

PMCID: PMC2983973 PMID: 21580623

Abstract

The asymmetric unit of the title salt, C₅H₆ClN₂ ⁺·C₂F₃O₂ ⁻, contains two independent 2-amino-5-chloropyridinium cations and two independent trifluoroacetate anions. The F atoms of both anions are disordered over two sets of positions, with occupancy ratios of 0.672 (12):0.328 (12) and 0.587 (15):0.413 (15). In the crystal, the cations and anions are linked via N—H⋯O and C—H⋯O hydrogen bonds, forming a two-dimensional network parallel to (001).

Related literature

For background to the chemistry of substituted pyridines, see: Pozharski et al. (1997 ▶); Katritzky et al. (1996 ▶). For related structures, see: Pourayoubi et al. (2007 ▶); Hemamalini & Fun (2010a ▶,b ▶,c ▶). For details of hydrogen bonding, see: Jeffrey & Saenger (1991 ▶); Jeffrey (1997 ▶); Scheiner (1997 ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₅H₆ClN₂ ⁺·C₂F₃O₂ ⁻
M _r = 242.59
Monoclinic,
a = 5.0377 (1) Å
b = 11.2923 (2) Å
c = 17.5386 (3) Å
β = 90.001 (1)°
V = 997.72 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.41 mm⁻¹
T = 296 K
0.43 × 0.26 × 0.14 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.842, T _max = 0.945
17652 measured reflections
4388 independent reflections
3191 reflections with I > 2σ(I)
R _int = 0.027

Refinement

R[F ² > 2σ(F ²)] = 0.036
wR(F ²) = 0.094
S = 1.03
4388 reflections
375 parameters
110 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.12 e Å⁻³
Δρ_min = −0.15 e Å⁻³
Absolute structure: Flack (1983 ▶), 2096 Friedel pairs
Flack parameter: 0.01 (7)

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810008196/ci5043sup1.cif

e-66-0o783-sup1.cif^{(21.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810008196/ci5043Isup2.hkl

e-66-0o783-Isup2.hkl^{(210.6KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1A—H1NA⋯O1Aⁱ	0.94 (3)	1.79 (3)	2.727 (3)	173 (3)
N2A—H2NA⋯O2Aⁱ	0.90 (3)	1.95 (3)	2.840 (4)	175 (3)
N2A—H3NA⋯O1Bⁱⁱ	0.87 (3)	2.00 (2)	2.863 (3)	171 (4)
N1B—H1NB⋯O1Bⁱⁱⁱ	0.87 (3)	1.87 (3)	2.734 (3)	175 (3)
N2B—H2NB⋯O2Bⁱⁱⁱ	0.90 (2)	1.94 (2)	2.838 (4)	170 (2)
N2B—H3NB⋯O1A	0.87 (3)	1.99 (2)	2.861 (3)	175 (4)
C5A—H5AA⋯O2Bⁱ	0.97 (3)	2.29 (3)	3.210 (4)	158 (3)
C5B—H5BA⋯O2A^iv	0.96 (3)	2.31 (3)	3.208 (3)	157 (3)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) .

Acknowledgments

MH and HKF thank the Malaysian Government and Universiti Sains Malaysia (USM) for the Research University Golden Goose grant No. 1001/PFIZIK/811012. MH thanks USM for a post-doctoral research fellowship.

supplementary crystallographic information

Comment

Pyridine and its derivatives play an important role in heterocyclic chemistry (Pozharski et al., 1997; Katritzky et al., 1996). They are often involved in hydrogen-bond interactions (Jeffrey & Saenger, 1991; Jeffrey, 1997; Scheiner, 1997). We have recently reported the crystal structures of 2-amino-5-chloropyridinium 4-hydroxybenzoate (Hemamalini & Fun, 2010a), 2-amino-5-chloropyridine benzoic acid (Hemamalini & Fun, 2010b) and 2-amino-5-chloropyridinium hydrogen succinate. (Hemamalini & Fun, 2010c). In continuation of our studies of pyridinium derivatives, the crystal structure determination of the title compound has been undertaken.

The asymmetric unit of the title compound consists of two crystallographically independent 2-amino-5-chloropyridinium cations (A and B) and two trifluoroacetate anions (A and B) (Fig. 1). Each 2-amino-5-chloropyridinium cation is planar, with a maximum deviation of 0.017 (3) Å for atom C3A in cation A and 0.026 (1) Å for atom C1B in cation B. In the cations, protonation at atoms N1A and N1B lead to a slight increase in the C1A–N1A–C5A [122.7 (3)°] and C1B—N1B—C5B [123.2 (3)°] angles compared to those observed in an unprotonated structure (Pourayoubi et al., 2007). Bond lengths and angles are normal (Allen et al., 1987).

In the crystal packing (Fig. 2), the A/B type 2-amino-5-chloropyridinium cations interact with the carboxylate groups of the A/B type trifluoroacetate anions through a pair of N—H···O hydrogen bonds, forming an R₂²(8) (Bernstein et al., 1995) ring motif. The packing is further stabilized by weak C5A—H5AA···O2B and C5B—H5BA···O2A (Table 1) hydrogen bonds.

Experimental

To a hot methanol solution (20 ml) of 2-amino-5-chloropyridine (27 mg, Aldrich) was added a few drops of trifluoroacetic acid. The solution was warmed over a water bath for a few minutes. The resulting solution was allowed to cool slowly to room temperature. Crystals of the title compound appeared after a few days.