Ammonium 2-amino­pyrazine-3-carboxyl­ate

Martin Lutz; Arjen J Jakobi

doi:10.1107/S1600536811010865

. 2011 Mar 26;67(Pt 4):o984. doi: 10.1107/S1600536811010865

Ammonium 2-aminopyrazine-3-carboxylate

Martin Lutz ^a,^*, Arjen J Jakobi ^a

PMCID: PMC3099982 PMID: 21754242

Abstract

The title compound NH₄ ⁺·C₅H₄N₃O₂ ⁻ crystallizes with two formula units in the asymmetric unit. In each anion, the carboxylate is deprotonated and the planar amino group [angle sums of 359 (3) and 355 (3)° at N] remains protonated. In the crystal, the cations and anions are bridged by N—H⋯O and N—H⋯N hydrogen bonds, forming a three-dimensional network.

Related literature

For the crystal structure of the free acid, see: Dobson & Gerkin (1996 ▶); Ptasiewicz-Bak & Leciejewicz (1997 ▶). For the metal complex with nickel, see: Ptasiewicz-Bak & Leciejewicz (1999 ▶). For the coordination chemistry of 2-pyrazinecarboxylic acid, see: Ptasiewicz-Bak et al. (1995 ▶); Ellsworth & zur Loye (2008 ▶). In the present study a half-normal probability plot (Abrahams & Keve, 1971 ▶), a quaternion fit (Mackay, 1984 ▶) and rigid-body analysis (Schomaker & Trueblood, 1998 ▶) have been used.

Experimental

Crystal data

NH₄ ⁺·C₅H₄N₃O₂ ⁻
M _r = 156.15
Orthorhombic,
a = 12.5066 (6) Å
b = 3.8833 (2) Å
c = 27.9659 (14) Å
V = 1358.22 (12) Å³
Z = 8
Mo Kα radiation
μ = 0.12 mm⁻¹
T = 150 K
0.40 × 0.19 × 0.09 mm

Data collection

Bruker Kappa APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2008a ▶) T _min = 0.70, T _max = 0.75
16898 measured reflections
1580 independent reflections
1540 reflections with I > 2σ(I)
R _int = 0.018

Refinement

R[F ² > 2σ(F ²)] = 0.026
wR(F ²) = 0.072
S = 1.05
1580 reflections
247 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.33 e Å⁻³
Δρ_min = −0.16 e Å⁻³

Data collection: APEX2 (Bruker, 2010 ▶); cell refinement: SAINT (Bruker, 2010 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008b ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008b ▶); molecular graphics: PLATON (Spek, 2009 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: manual editing of SHELXL cif file.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811010865/zl2357sup1.cif

e-67-0o984-sup1.cif^{(18.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811010865/zl2357Isup2.hkl

e-67-0o984-Isup2.hkl^{(77.9KB, 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
N31—H31A⋯N22ⁱ	0.92 (3)	2.20 (3)	3.103 (2)	169 (2)
N31—H31B⋯O21	0.90 (3)	2.07 (3)	2.726 (2)	129 (2)
N32—H32A⋯N21ⁱⁱ	0.88 (3)	2.23 (3)	3.100 (2)	168 (2)
N32—H32B⋯O22	0.86 (3)	2.06 (3)	2.686 (2)	129 (2)
N3—H3B⋯O21	0.93 (3)	1.97 (3)	2.849 (2)	157 (2)
N3—H3C⋯O11ⁱⁱⁱ	0.96 (3)	2.58 (3)	3.287 (2)	131 (2)
N3—H3C⋯N11ⁱⁱⁱ	0.96 (3)	2.00 (3)	2.909 (2)	159 (2)
N3—H3D⋯O11^iv	0.89 (3)	2.13 (3)	2.944 (2)	152 (2)
N4—H4A⋯O12	0.86 (3)	2.13 (3)	2.897 (2)	148 (3)
N4—H4A⋯N12	0.86 (3)	2.23 (3)	2.912 (2)	135 (3)
N4—H4B⋯O11	0.95 (4)	1.86 (4)	2.793 (2)	166 (3)
N4—H4C⋯O11^v	0.84 (3)	2.01 (4)	2.839 (2)	170 (3)
N4—H4D⋯O22^vi	0.87 (3)	1.87 (3)	2.742 (2)	176 (3)

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

supplementary crystallographic information

Comment

2-Pyrazinecarboxylic acid is a complexation reagent in transition metal chemistry (Ptasiewicz-Bak et al., 1995) with a large variety of coordination modes (Ellsworth & zur Loye, 2008). The corresponding 3-aminopyrazine-2-carboxylic has been used in a similar way for the complexation of nickel (Ptasiewicz-Bak & Leciejewicz, 1999). The crystal structure of the free acid has been determined by Dobson & Gerkin (1996) and Ptasiewicz-Bak & Leciejewicz (1997).

The asymmetric unit of the crystal structure of the title compound (I) consists of two formula units (Z' = 2). The anions are essentially planar with a maximal deviation from the least-squares plane of 0.059 (2) and 0.093 (1) Å for the two molecules, respectively (Fig. 1). The molecular planes form angles of 5.54 (3) and 0.58 (3)° with the c axis. Also the amino moieties are planar with angle sums of 359 (3) and 355 (3)° at N31 and N32.

The two independent molecules are very similar, as can be seen in a quaternion fit (Fig. 2). This allows the generation of a half-normal probability plot (Fig. 3). The largest differences between the two molecules are in the C–O distances (Δ = 3.5σ). A possible explanation is the different hydrogen bonding situation of the four O atoms. If the anions in (I) are compared with the neutral molecule of the free acid (Dobson & Gerkin, 1996) the geometries are again very similar. As expected, the only difference is in the carboxylate, which is deprotonated in (I) and protonated in the free acid. The distances C51–O11 and C52–O12 in (I) are 1.266 (2) and 1.256 (2)Å compared to the C–OH distance of 1.328 (2)Å in the free acid. This is accompanied by a change of the corresponding C–C–O angles, which are 116.01 (14) and 116.79 (14)° in (I) compared to 118.20 (10)° in the free acid.

The two independent molecules in (I) can be modelled by rigid body model using the program THMA11 (Schomaker & Trueblood, 1998). The fit of this TLS model is good, as indicated by R-values (R={[Σ(wΔU)²]/[Σ(wU_obs)²]}^1/2) of 0.080 and 0.085 for the two molecules. The two molecules can thus be appropriately described as rigid bodies. The T tensor has eigenvalues of 0.01925, 0.01329, and 0.01076 Å² for the first independent molecule in (I), and 0.02060, 0.01368, and 0.01227 Å² for the second molecule. The L tensor has eigenvalues of 13.62, 6.42, and 4.28 deg.² for the first molecule, and 12.96, 7.20, and 4.22 deg.² for the second molecule.

The amino moieties of the anions act as donors of two hydrogen bonds, respecively. One is intramolecular to the carboxylate [graph set S₁¹(6)], and one is intermolecular to a pyrazine N atom [graph set D₁¹(2)]. Overall, this results in one-dimensional hydrogen-bonded chains along the b axis. These chains are interconnected by the ammonium cations to form a three-dimensional network. Hydrogen atoms H3C and H4A of the ammonium cations are involved in bifurcated hydrogen bonds (Table 1, Fig. 4).

Experimental

212 mg of 2-aminopyrazine-3-carboxylic acid were suspended in 20 ml water. A concentrated solution of ammonium hydroxide was added dropwise until the suspension became clear. Slow evaporation at room temperature gave crystals of (I) suitable for the diffraction experiment.