Bis(melaminium) succinate succinic acid monosolvate dihydrate

Barbara Froschauer; Matthias Weil

doi:10.1107/S1600536812033387

. 2012 Jul 25;68(Pt 8):o2555. doi: 10.1107/S1600536812033387

Bis(melaminium) succinate succinic acid monosolvate dihydrate

Barbara Froschauer ^a, Matthias Weil ^b,^*

PMCID: PMC3414998 PMID: 22904985

Abstract

The asymmetric unit of the solvated title salt, 2C₃H₇N₆ ⁺·C₄H₄O₄ ²⁻·C₄H₆O₄·2H₂O, contains one essentially planar melaminium (2,4,6-triamino-1,3,5-triazin-1-ium) cation (r.m.s. deviation of the non-H atoms = 0.0097 Å), one-half of a succinate anion, one-half of a succinic acid solvent molecule and one water molecule of crystallization; full molecules are generated by inversion symmetry. Supramolecular layers parallel to (12-1) are formed through extensive intermolecular hydrogen bonding of the types O—H⋯O, N—H⋯N and N—H⋯O between the components.

Related literature

For the use of melaminium salts in polymer science, see: Weinstabl et al. (2001 ▶). For a list of structurally determined melaminium salts of purely organic carboxylic acids, see: Froschauer & Weil (2012 ▶).

Experimental

Crystal data

2C₃H₇N₆ ⁺·C₄H₄O₄ ²⁻·C₄H₆O₄·2H₂O
M _r = 524.48
Triclinic,
a = 7.1193 (7) Å
b = 8.1650 (8) Å
c = 9.5595 (9) Å
α = 88.013 (2)°
β = 84.647 (2)°
γ = 88.093 (2)°
V = 552.68 (9) Å³
Z = 1
Mo Kα radiation
μ = 0.13 mm⁻¹
T = 293 K
0.23 × 0.18 × 0.12 mm

Data collection

Siemens SMART CCD diffractometer
5533 measured reflections
2719 independent reflections
1545 reflections with I > 2σ(I)
R _int = 0.028

Refinement

R[F ² > 2σ(F ²)] = 0.047
wR(F ²) = 0.142
S = 0.97
2719 reflections
173 parameters
3 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.30 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Data collection: SMART (Siemens, 1996 ▶); cell refinement: SAINT (Siemens, 1996 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Mercury (Macrae et al., 2006 ▶) and ATOMS (Dowty, 2006 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812033387/cv5324sup1.cif

e-68-o2555-sup1.cif^{(21KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812033387/cv5324Isup2.hkl

e-68-o2555-Isup2.hkl^{(133.5KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812033387/cv5324Isup3.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
N4—H3⋯N2ⁱ	0.86	2.10	2.959 (2)	176
N1—H1⋯O1	0.86	2.01	2.844 (2)	164
N5—H4⋯O3ⁱⁱ	0.86	2.13	2.976 (2)	170
N6—H6⋯N3ⁱⁱⁱ	0.86	2.16	3.015 (2)	173
N1—H1⋯O2	0.86	2.50	3.199 (2)	138
N4—H2⋯O3^iv	0.86	2.14	2.799 (2)	134
N4—H2⋯O1	0.86	2.56	3.268 (2)	141
N6—H7⋯O2	0.86	1.94	2.782 (2)	166
N5—H5⋯O1W ^v	0.86	2.11	2.912 (2)	154
O1W—H1W⋯O4	0.88 (2)	2.35 (2)	3.195 (2)	162 (3)
O1W—H2W⋯O2^vi	0.86 (2)	1.89 (2)	2.726 (2)	167 (3)
O4—H12⋯O1^iv	1.02 (2)	1.55 (2)	2.5673 (19)	177 (3)

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

Acknowledgments

The X-ray centre of the Vienna University of Technology is acknowledged for financial support and for providing access to the single-crystal diffractometer.

supplementary crystallographic information

Comment

The potential substitution of melamine through organic melaminium salts for production of melamine urea formaldehyde (MUF) resins (Weinstabl et al., 2001) render the structural investigation of these compounds interesting. A list of already determined structures of purely organic melaminium salts has been compiled recently by Froschauer & Weil (2012).

The pK_a values of 4.21 and 5.72 for the first and second deprotonation step of succinic acid (the pK_a of the first deprotonation step of melamine is 5.10) led to a doubly deprotonated anion in the title compound, bis-melaminium succinate succinic acid solvate dihydrate, 2(C₃H₇N₆)^+.C₄H₄O₄^-.C₄H₆O₄^.2(H₂O). However, besides lattice water, there is also one succinic acid solvent molecule present in the unit cell. The succinic acid molecule and the succinate anion are located with their central C—C bond on inversion centres. As observed for all single protonated melaminium cations, the protonation of melamine takes place at one of the triazine N ring atoms (Fig. 1).

The melaminium cation is essentially planar with a r.m.s. deviation of 0.0097 Å. Likewise, the anion (r.m.s. deviation 0.039 Å) and the succinic acid molecule (r.m.s. deviation 0.060 Å) can be considered as planar. The angles between the least-squares planes of 6.59 (9) ° and 5.76 (12) ° between the anion and the cation and the succinic acid molecule, respectively, lead to the formation of supramolecular layers where cations are arranged in rows alternating with rows of anions, succinic acid solvent and lattice water molecules (Fig. 2). Extensive intermolecular hydrogen bonding of the types O—H···O, N—H···N and N—H···O between the molecular components is present. Details are reported in Table 1. The motif for the hydrogen-bonded assembly of two melaminium cations in such a layer is the same as in the hydrogenmalonate salt and other melaminium salts (Froschauer & Weil, 2012). In the crystal, the supramolecular layers are arranged parallel to (121) (Fig. 3) with an interplanar distance of approximately 3.15 Å.

Experimental

79.3 mmol melamine was dissolved under refluxing conditions in 200 ml distilled water. The stoichiometric quantity (1:1) of succinic acid was added within five minutes. The mixture was then refluxed for 30 minutes and then cooled to room temperature. The precipitate formed on cooling was separeted by filtration and washed with cold methanol. The crystalline product was then dried in vacuo at 303–313 K. Single crystal growth was accomplished by dissolution of 1 g of the crystalline product under refluxing conditions in an aqueous methanol solution (2:1 v/v) to get a saturated solution. Then the solution was slowly cooled down to room temperature. Suitable crystals were obtained by slow evaporation of the solvents during five days. The crystals were washed with methanol and dried in vacuo at room temperature giving analytical pure samples. CHN analysis (found/calc.): C (32.13/32.10), H (5.50/5.38), N (31.93/32.05). NMR: (solution, DMSO) chemical shift [p.p.m.]: ¹H 10.37 (s, 2H), 6.22 (s, 6H), 2.39 (s, 4H); ¹³C 174.32, 166.43, 29.29.