2,4-Diamino-6-methyl-1,3,5-triazin-1-ium tetra­fluoro­borate

Sundaramoorthy Gomathi; Packianathan Thomas Muthiah

doi:10.1107/S1600536811038797

. 2011 Sep 30;67(Pt 10):o2762. doi: 10.1107/S1600536811038797

2,4-Diamino-6-methyl-1,3,5-triazin-1-ium tetrafluoroborate

Sundaramoorthy Gomathi ^a, Packianathan Thomas Muthiah ^a,^*

PMCID: PMC3201368 PMID: 22058813

Abstract

In the crystal structure of the title salt, C₄H₈N₅ ⁺·BF₄ ⁻, centrosymmetrically related cations undergo base pairing via a pair of N—H⋯N hydrogen bonds, forming an R ₂ ²(8) ring motif. The cations and anions interact via N—H⋯F hydrogen bonds, generating supramolecular layers parallel to ( Inline graphic 20), which are in turn linked into a three-dimensional network, forming rings of R ₆ ⁶(24) graph-set motif. The crystal structure is further stabilized by π–π stacking interactions [centroid–centroid distance = 3.3361 (12) Å].

Related literature

For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶); Etter (1990 ▶). For related structures, see: Conant et al. (1964 ▶); Gokul Raj etal. (2006 ▶); Zimmermann et al. (1963 ▶); Hemamalini et al. (2005 ▶); Balasubramani et al. (2007 ▶); Li et al. (2011 ▶). For π–π stacking interactions, see: Hunter (1994 ▶).

Experimental

Crystal data

C₄H₈N₅ ⁺·BF₄ ⁻
M _r = 212.96
Triclinic,
a = 6.9982 (3) Å
b = 8.2887 (4) Å
c = 8.5353 (4) Å
α = 63.931 (2)°
β = 83.209 (3)°
γ = 85.057 (3)°
V = 441.29 (4) Å³
Z = 2
Mo Kα radiation
μ = 0.16 mm⁻¹
T = 296 K
0.06 × 0.05 × 0.04 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.990, T _max = 0.993
8850 measured reflections
2196 independent reflections
1842 reflections with I > 2σ(I)
R _int = 0.022

Refinement

R[F ² > 2σ(F ²)] = 0.066
wR(F ²) = 0.203
S = 1.09
2196 reflections
128 parameters
H-atom parameters constrained
Δρ_max = 0.52 e Å⁻³
Δρ_min = −0.54 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2009 ▶); software used to prepare material for publication: PLATON.

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811038797/rz2638sup1.cif

e-67-o2762-sup1.cif^{(19.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811038797/rz2638Isup2.hkl

e-67-o2762-Isup2.hkl^{(105.7KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811038797/rz2638Isup3.cml

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
N1—H1⋯F1	0.86	1.90	2.758 (2)	173
N2—H2A⋯F2ⁱ	0.86	2.01	2.800 (4)	152
N2—H2B⋯F4ⁱⁱ	0.86	2.02	2.877 (4)	177
N4—H4A⋯F3ⁱⁱⁱ	0.86	2.34	3.047 (3)	139
N4—H4B⋯N5^iv	0.86	2.18	3.038 (3)	178

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

Acknowledgments

The authors thank the DST-India (FIST programme) for the use of the diffractometer at the School of Chemistry, Bharathidasan University, Tiruchirappalli, Tamilnadu, India.

supplementary crystallographic information

Comment

Only a limited number of tetrafluoroborate salts like hydrazinium fluoroborate (Conant et al., 1964), L-Histidinium tetrafluoroborate (Gokul Raj et al., 2006), trimethloxosulfonium fluoroborate (Zimmermann et al., 1963) have been reported in the literature. From our laboratory, we have reported the crystal structure of trimethoprim tetrafluoroborate (Hemamalini et al., 2005) and pyrimethamine tetrafluoroborate (Balasubramani et al., 2007), and have analysed their hydrogen bonding patterns. The present investigation concerns the supramolecular patterns exhibited by acetoguanaminium fluoroborate.

The asymmetric unit of the title salt contains one 2,4-diamino-6-methyl-1,3,5-triazin-1-ium (acetoguanaminium) cation and one tetrafluoroborate anion as shown in Fig. 1. The acetoguanaminium cation is protonated at N1. Protonation of the triazine base on the N1 atom is reflected by an increase of the C1—N2—C6 bond angle (119.77 (17)°) with respect to the other C—N—C angles (mean value 115.94 (18)°). The tetrafluoroborate anion shows a slightly distorted tetrahedral geometry (Li et al., 2011). In the asymmetric unit, the acetoguanaminium cation interacts with the tetrafluoroborate anion via a nearly linear N—H···F hydrogen bond (Fig. 1, Table 1). Centrosymmetrically-related cations are paired through a pair of N—H···N hydrogen bonds to form a robust R₂²(8) ring motif (Etter, 1990; Bernstein et al., 1995) by linking an H atom of the 4-amino group with the N5 atom of the inversion related cation (Table 1). Base pairs are interlinked by R₄⁴(16) ring motifs formed by two of N—H···F hydrogen bonds (Fig. 2; Table 1). The combination of the complementary base pairs (R₂²(8)) and R₄⁴(16) motifs generates a supramolecular ribbons parallel to the [211] direction. Adjacent ribbons are interconnected by the alternating occurrence of two different ring motifs such as R₄⁴(12) and R₆⁶(28) forming a supramolecular sheet parallel to the (120) plane as shown in Fig. 2. There is a supramolecular hydrogen bonded ladder generated by the alternating arrangement of R₄⁴(16) and R₄⁴(12) ring motifs which extends along c axis. Adjacent sheets are interlinked via N—H···F hydrogen bond to form rings with graph set R₆⁶(24) as shown in Fig. 3. These rings propagate along the b axis and generates a three dimensional supramolecular network. The structure is further stabilized by nearly face to face π-π stacking interactions between acetoguanaminium rings, with interplanar distance of 3.333 Å, centroid- to-centroid distance of 3.3361 (12)Å and slip angle of 2.46° (Hunter, 1994). In addition, anion-π contacts are also observed between the acetoguanaminium ring and the F2 and F4 atoms of tetrafluoroborate anion (Cg1···F2ⁱ = 3.654 (3) Å; Cg1···F4ⁱ = 3.178 (3) Å; Cg1 is the centroid of the N1–N3/C2/C4/C6 ring; symmetry code: (i) 1-x, 2-y, 1-z).

Experimental

A hot ethanolic solutions of 2,4-diamino-6-methyl-1,3,5-triazine (acetoguanamine; 31 mg; Aldrich) and tetrafluoroboric acid (220 mg of 40% solution; Aldrich) were mixed in a 1:1 molar ratio. The resulting solution was warmed over a water bath for a few minutes and then kept at room temperature for crystallization. After a few days, colourless prismatic crystals suitable for X-ray analysis were obtained.