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The asymmetric unit of the optically resolved title salt, C8H12N+·C4H5O4S-, contains a 1-phenyl­ethanaminium monocation and a thio­malate (3-carb­oxy-2-sulfanyl­propano­ate) monoanion. The absolute configurations of the cation and the anion are determined to be S and R, respectively. In the crystal, cation-anion N-H...O hydrogen bonds, together with anion-anion O-H...O and S-H...O hydrogen bonds, construct a two-dimensional supra­molecular sheet parallel to the ab plane. The two-dimensional sheet is linked with the upper and lower sheets through C-H...[pi] inter­actions to stack along the c axis.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270112032933/uk3047sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270112032933/uk3047Isup2.hkl
Contains datablock I

CCDC reference: 908129

Comment top

Thiomalic acid (2-mercaptosuccinic acid, H3msa) is one of the simplest chiral thiol-containing dicarboxylic acids and has been widely employed as a raw material for sulfur-containing organic materials. Because commercially available H3msa is a racemic mixture of the S and R enantiomers, the preparation of enantiopure H3msa has been intensively investigated, prompted by the finding of efficient antirheumatic activity in a gold(I) adduct of the thiomalate ion, viz. {Na2[Au(msa)].1.75H2O}n, by Nomiya et al. (1995). For example, LeBlanc et al. (1997) reported the asymmetric synthesis of pure (R)-thiomalic acid from L-aspartic acid in three steps, while Shiraiwa et al. (1998) reported the optical resolution of the racemic H3msa with the use of (S)-pea (pea = 1-phenylethanamine), which led to the preferential crystallization of the title compound, (S)-Hpea (R)-H2msa, (I). The latter method is undoubtedly superior to the former, but the resulting salt, (I), has not been crystallographically characterized.

As part of our studies on the rational construction of coordination systems based on chiral thiol-containing multidentate ligands (Konno, 2004; Igashira-Kamiyama & Konno, 2011), we started to investigate the coordination system derived from H3msa. In the course of this investigation, we obtained an optically active single crystal of (I) from the reaction of racemic H3msa and (S)-pea, and its structure was determined by X-ray crystallography.

The asymmetric unit of (I) contains an (S)-Hpea+ cation and an (R)-H2msa- anion, the absolute configurations of which are consistent with the previous prediction made by the optical rotation measurement (Shiraiwa et al., 1998). In (I), the amine group of pea is protonated to form a Hpea+ cation, while one of the two carboxy groups of thiomalic acid (C3, O1 and O2) is protonated and the other (C4, O3 and O4) is deprotonated to form a H2msa- anion (Fig. 1). Reflecting the protonation of the O1 atom, the C3—O1 bond length [1.297 (3) Å] is obviously longer than that of C3—O2 [1.213 (3) Å]. On the other hand, the difference between the C4—O3 [1.276 (2) Å] and C4—O4 [1.237 (3) Å] bond lengths is smaller, which is consistent with the deprotonation form of the COO- group. The other bond lengths and angles of the cation and the anion are in the range normally observed for related compounds.

In the crystal, the protonated carboxy group of each (R)-H2msa- anion acts as a hydrogen-bond donor, forming an intermolecular O—H···O hydrogen bond with a deprotonated carboxylate group of a neighbouring anion [O1···O3ii = 2.501 (2) Å; symmetry code: (ii) -x, y-1/2, -z+1]. In addition, its protonated carboxy group also acts as a hydrogen-bond acceptor, forming an intermolecular S—H···O hydrogen bond with a thiol group of another neighbouring anion [S1···O2i = 3.2741 (19) Å; symmetry code: (i) -x+1, y+1/2, -z+1]. Based on these two kinds of hydrogen bonds, (R)-H2msa- anions construct a two-dimensional grid network having rectangular cavities surrounded by four anions parallel to the ab plane (Fig. 2). It is noted that each rectangular cavity accommodates an ammonium group of an (S)-Hpea+ cation through three N—H···O hydrogen bonds [N1···O4 = 2.751 (3) Å, N1···O3iii = 2.797 (2) Å and N1···O2iv = 2.845 (3) Å; symmetry codes: (iii) -x, y+1/2, -z+1; (iv) x, y+1, z]. Besides these hydrogen-bonding interactions, two kinds of C—H···π interactions exist in the crystal; one is a contact between a methine group of an (R)-H2msa- anion and a phenyl group of an (S)-Hpea+ cation (H1E···Cgii = 2.62 Å; Cg is the centroid of the C6–C12 ring), and the other is between a methine group of an (S)-Hpea+ cation and a phenyl group of a neighbouring cation [H6···Cgv = 2.85 Å; symmetry code: (v) -x, y+1/2, -z] (Fig. 3). The latter interaction connects the two-dimensional grids along the c axis, giving a dense three-dimensional structure in (I).

From these structural features, it is likely that the cationic (S)-Hpea+ selects the R isomer of the anionic H2msa- such that each (S)-Hpea+ ammonium group forms multiple hydrogen bonds with three H2msa- carboxy groups and that each (S)-Hpea+ phenyl group forms a C—H···π interaction with a H2msa- methine group, leading to the excellent optical resolution of the racemic H3msa with the use of (S)-pea.

Related literature top

For related literature, see: Igashira-Kamiyama & Konno (2011); Konno (2004); LeBlanc, Smith, Wang, Howard-Lock & Lock (1997); Nomiya et al. (1995); Shiraiwa et al. (1998).

Experimental top

Compound (I) was prepared according to the method of Shiraiwa et al. (1998). (RS)-H3msa (5.0 g, 33 mmol) and (S)-pea (4.0 g, 33 mmol) were dissolved in propan-1-ol (27 ml). After allowing the mixture to stand in a freezer for 1 week, the crude product of (I) (4.6 g) was collected by filtration. This product was dissolved in propan-1-ol at 353 K to give a colourless solution. The solution was cooled slowly to room temperature and colourless plate-shaped crystals of (I) appeared after several hours.

Refinement top

H atoms bound to C atoms were placed at calculated positions [C—H = 0.98 (CH3), 0.99 (CH2) and 1.00 Å (CH)] and refined as riding, with Uiso(H) = 1.2Ueq(C) for CH2 and CH groups, and 1.5Ueq(C) for methyl groups (rotating group model). H atoms bound to O and S atoms were located in a difference Fourier map and were refined with constrained displacement parameters [Uiso(H) = 1.2Ueq(O,S)]. H atoms bound to N atoms were located in a difference Fourier map and refined with distance restraints and constrained displacement parameters [N—H = 0.89 (2) Å and Uiso(H) = 1.5Ueq(N)].

Computing details top

Data collection: RAPID-AUTO (Rigaku, 2000); cell refinement: RAPID-AUTO (Rigaku, 2000); data reduction: RAPID-AUTO (Rigaku, 2000); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Yadokari-XG 2009 (Kabuto et al., 2009); software used to prepare material for publication: Yadokari-XG 2009 (Kabuto et al., 2009).

Figures top
[Figure 1] Fig. 1. A view of the asymmetric unit of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. The two-dimensional grid network of (R)-H2msa- anions which incorporates ammonium groups of (S)-Hpea+ cations in (I), viewed parallel to the crystallographic c axis. (S)-Hpea+ cations, except for their NH3+ groups, have been omitted for clarity. The grey dashed lines (red in the electronic version of the paper) show the hydrogen bonds between anions and the black broken lines show the hydrogen bonds between anions and cations. [Symmetry codes: (i) -x+1, y+1/2, -z+1; (ii) -x, y-1/2, -z+1; (iii) -x, y+1/2, -z+1; (iv) x, y+1, z.]
[Figure 3] Fig. 3. A view of the C—H···π interaction network in (I). Dashed lines indicate the C—H···π interactions.
(S)-1-phenylethanaminium (R)-3-carboxy-2-sulfanylpropanoate top
Crystal data top
C8H12N+·C4H5O4SF(000) = 288
Mr = 271.33Dx = 1.301 Mg m3
Monoclinic, P21Mo Kα radiation, λ = 0.71075 Å
Hall symbol: P 2ybCell parameters from 4466 reflections
a = 9.0547 (7) Åθ = 3.1–27.5°
b = 8.2304 (5) ŵ = 0.24 mm1
c = 9.3016 (7) ÅT = 200 K
β = 92.760 (2)°Platelet, colourless
V = 692.39 (9) Å30.30 × 0.15 × 0.05 mm
Z = 2
Data collection top
Rigaku R-AXIS RAPID
diffractometer
3100 independent reflections
Radiation source: rotating-anode X-ray tube2723 reflections with I > 2σ(I)
Detector resolution: 10.000 pixels mm-1Rint = 0.034
ω scansθmax = 27.5°, θmin = 3.1°
Absorption correction: multi-scan
(ABSCOR; Rigaku, 1995)
h = 1111
Tmin = 0.788, Tmax = 0.988k = 1010
6800 measured reflectionsl = 1212
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)] = 0.041H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.107 w = 1/[σ2(Fo2) + (0.0561P)2 + 0.051P]
where P = (Fo2 + 2Fc2)/3
S = 1.12(Δ/σ)max < 0.001
3100 reflectionsΔρmax = 0.40 e Å3
179 parametersΔρmin = 0.26 e Å3
4 restraintsAbsolute structure: Flack (1983), 1408 Friedel pairs
0 constraintsAbsolute structure parameter: 0.07 (8)
Primary atom site location: structure-invariant direct methods
Crystal data top
C8H12N+·C4H5O4SV = 692.39 (9) Å3
Mr = 271.33Z = 2
Monoclinic, P21Mo Kα radiation
a = 9.0547 (7) ŵ = 0.24 mm1
b = 8.2304 (5) ÅT = 200 K
c = 9.3016 (7) Å0.30 × 0.15 × 0.05 mm
β = 92.760 (2)°
Data collection top
Rigaku R-AXIS RAPID
diffractometer
3100 independent reflections
Absorption correction: multi-scan
(ABSCOR; Rigaku, 1995)
2723 reflections with I > 2σ(I)
Tmin = 0.788, Tmax = 0.988Rint = 0.034
6800 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.041H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.107Δρmax = 0.40 e Å3
S = 1.12Δρmin = 0.26 e Å3
3100 reflectionsAbsolute structure: Flack (1983), 1408 Friedel pairs
179 parametersAbsolute structure parameter: 0.07 (8)
4 restraints
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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
S10.42305 (6)0.38313 (8)0.79560 (6)0.04537 (17)
H10.498 (3)0.440 (3)0.700 (3)0.054*
O10.10777 (16)0.1497 (2)0.46721 (18)0.0386 (4)
H1A0.041 (3)0.076 (4)0.418 (3)0.046*
O20.28726 (19)0.0139 (3)0.3674 (3)0.0688 (7)
O30.06554 (15)0.46249 (17)0.66908 (16)0.0358 (3)
O40.23275 (17)0.5239 (2)0.50889 (17)0.0421 (4)
N10.1426 (2)0.7201 (2)0.2819 (2)0.0361 (4)
H1B0.154 (3)0.658 (3)0.367 (2)0.054*
H1C0.056 (2)0.777 (3)0.284 (3)0.054*
H1D0.220 (2)0.786 (3)0.287 (3)0.054*
C10.2845 (2)0.3014 (3)0.6675 (2)0.0320 (4)
H1E0.22020.22550.72060.038*
C20.3547 (2)0.2056 (3)0.5492 (3)0.0374 (5)
H20.41080.28150.48980.045*
H2A0.42610.12730.59400.045*
C30.2457 (2)0.1138 (3)0.4524 (2)0.0363 (5)
C40.1875 (2)0.4410 (2)0.6086 (2)0.0310 (4)
C50.2609 (3)0.5042 (4)0.1466 (4)0.0635 (8)
H50.25570.42990.22860.095*
H5A0.35370.56540.15480.095*
H5B0.25680.44160.05690.095*
C60.1313 (3)0.6215 (3)0.1460 (2)0.0422 (5)
H60.13940.69710.06260.051*
C70.0189 (2)0.5413 (2)0.1337 (2)0.0339 (4)
C80.1179 (3)0.5811 (3)0.0209 (3)0.0444 (5)
H80.08920.65550.05070.053*
C90.2589 (3)0.5132 (4)0.0114 (3)0.0526 (6)
H90.32630.54260.06570.063*
C100.3007 (2)0.4033 (3)0.1138 (3)0.0470 (6)
H100.39700.35740.10770.056*
C110.2021 (2)0.3603 (3)0.2254 (3)0.0420 (5)
H110.23080.28440.29570.050*
C120.0616 (2)0.4273 (2)0.2353 (2)0.0354 (5)
H120.00600.39560.31140.043*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0360 (3)0.0627 (4)0.0367 (3)0.0065 (3)0.0065 (2)0.0025 (3)
O10.0312 (7)0.0395 (8)0.0447 (9)0.0006 (6)0.0028 (6)0.0084 (7)
O20.0384 (9)0.0769 (14)0.0922 (16)0.0091 (10)0.0151 (9)0.0504 (13)
O30.0322 (7)0.0350 (7)0.0402 (8)0.0034 (6)0.0029 (6)0.0012 (7)
O40.0401 (8)0.0445 (8)0.0420 (9)0.0004 (7)0.0040 (7)0.0079 (7)
N10.0380 (10)0.0339 (9)0.0367 (10)0.0040 (8)0.0042 (8)0.0038 (8)
C10.0273 (9)0.0361 (10)0.0322 (10)0.0032 (8)0.0010 (8)0.0001 (9)
C20.0267 (9)0.0402 (11)0.0451 (12)0.0009 (8)0.0003 (9)0.0031 (10)
C30.0324 (10)0.0357 (11)0.0410 (12)0.0029 (8)0.0055 (9)0.0045 (9)
C40.0304 (9)0.0319 (9)0.0302 (10)0.0035 (8)0.0039 (8)0.0038 (8)
C50.0436 (13)0.0740 (19)0.0746 (19)0.0067 (14)0.0206 (13)0.0354 (17)
C60.0494 (13)0.0451 (13)0.0331 (11)0.0123 (11)0.0117 (9)0.0058 (10)
C70.0421 (11)0.0303 (10)0.0294 (10)0.0003 (9)0.0036 (8)0.0044 (8)
C80.0616 (14)0.0388 (12)0.0322 (11)0.0003 (11)0.0033 (10)0.0002 (9)
C90.0566 (15)0.0544 (14)0.0449 (13)0.0085 (12)0.0177 (11)0.0060 (13)
C100.0379 (11)0.0470 (14)0.0559 (13)0.0016 (11)0.0021 (9)0.0098 (13)
C110.0437 (11)0.0369 (11)0.0457 (12)0.0023 (10)0.0072 (9)0.0007 (11)
C120.0382 (10)0.0341 (11)0.0339 (10)0.0032 (8)0.0008 (8)0.0014 (8)
Geometric parameters (Å, º) top
S1—C11.817 (2)C5—C61.519 (4)
S1—H11.24 (3)C5—H50.9800
O1—C31.297 (3)C5—H5A0.9800
O1—H1A0.96 (3)C5—H5B0.9800
O2—C31.213 (3)C6—C71.511 (3)
O3—C41.276 (2)C6—H61.0000
O4—C41.237 (3)C7—C81.386 (3)
N1—C61.501 (3)C7—C121.399 (3)
N1—H1B0.943 (17)C8—C91.392 (4)
N1—H1C0.917 (17)C8—H80.9500
N1—H1D0.886 (17)C9—C101.380 (4)
C1—C21.518 (3)C9—H90.9500
C1—C41.531 (3)C10—C111.382 (3)
C1—H1E1.0000C10—H100.9500
C2—C31.507 (3)C11—C121.385 (3)
C2—H20.9900C11—H110.9500
C2—H2A0.9900C12—H120.9500
C1—S1—H193.1 (13)H5—C5—H5A109.5
C3—O1—H1A113.0 (16)C6—C5—H5B109.5
C6—N1—H1B114.3 (18)H5—C5—H5B109.5
C6—N1—H1C105.7 (18)H5A—C5—H5B109.5
H1B—N1—H1C109 (2)N1—C6—C7108.94 (18)
C6—N1—H1D113.3 (19)N1—C6—C5108.6 (2)
H1B—N1—H1D103 (2)C7—C6—C5114.5 (2)
H1C—N1—H1D111 (3)N1—C6—H6108.2
C2—C1—C4112.52 (18)C7—C6—H6108.2
C2—C1—S1111.56 (14)C5—C6—H6108.2
C4—C1—S1108.82 (14)C8—C7—C12118.7 (2)
C2—C1—H1E107.9C8—C7—C6120.0 (2)
C4—C1—H1E107.9C12—C7—C6121.3 (2)
S1—C1—H1E107.9C7—C8—C9120.7 (2)
C3—C2—C1114.12 (17)C7—C8—H8119.6
C3—C2—H2108.7C9—C8—H8119.6
C1—C2—H2108.7C10—C9—C8120.0 (2)
C3—C2—H2A108.7C10—C9—H9120.0
C1—C2—H2A108.7C8—C9—H9120.0
H2—C2—H2A107.6C9—C10—C11119.9 (2)
O2—C3—O1123.7 (2)C9—C10—H10120.1
O2—C3—C2121.0 (2)C11—C10—H10120.1
O1—C3—C2115.36 (19)C10—C11—C12120.4 (2)
O4—C4—O3125.38 (19)C10—C11—H11119.8
O4—C4—C1118.54 (18)C12—C11—H11119.8
O3—C4—C1116.08 (18)C11—C12—C7120.3 (2)
C6—C5—H5109.5C11—C12—H12119.8
C6—C5—H5A109.5C7—C12—H12119.8
C4—C1—C2—C366.1 (2)N1—C6—C7—C1263.2 (3)
S1—C1—C2—C3171.31 (16)C5—C6—C7—C1258.6 (3)
C1—C2—C3—O2169.0 (2)C12—C7—C8—C92.1 (3)
C1—C2—C3—O111.0 (3)C6—C7—C8—C9177.3 (2)
C2—C1—C4—O441.8 (2)C7—C8—C9—C100.9 (4)
S1—C1—C4—O482.4 (2)C8—C9—C10—C110.3 (4)
C2—C1—C4—O3138.90 (18)C9—C10—C11—C120.2 (4)
S1—C1—C4—O396.94 (18)C10—C11—C12—C71.1 (3)
N1—C6—C7—C8116.3 (2)C8—C7—C12—C112.2 (3)
C5—C6—C7—C8121.9 (3)C6—C7—C12—C11177.2 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
S1—H1···O2i1.24 (3)2.16 (3)3.2741 (19)148.0 (19)
O1—H1A···O3ii0.96 (3)1.54 (3)2.501 (2)177 (3)
N1—H1B···O40.94 (2)1.84 (2)2.751 (3)162 (3)
N1—H1C···O3iii0.92 (2)1.94 (2)2.797 (2)154 (3)
N1—H1D···O2iv0.89 (2)2.10 (2)2.845 (3)141 (3)
C1—H1E···Cgii1.002.623.56156
C6—H6···Cgv1.002.853.83166
Symmetry codes: (i) x+1, y+1/2, z+1; (ii) x, y1/2, z+1; (iii) x, y+1/2, z+1; (iv) x, y+1, z; (v) x, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC8H12N+·C4H5O4S
Mr271.33
Crystal system, space groupMonoclinic, P21
Temperature (K)200
a, b, c (Å)9.0547 (7), 8.2304 (5), 9.3016 (7)
β (°) 92.760 (2)
V3)692.39 (9)
Z2
Radiation typeMo Kα
µ (mm1)0.24
Crystal size (mm)0.30 × 0.15 × 0.05
Data collection
DiffractometerRigaku R-AXIS RAPID
diffractometer
Absorption correctionMulti-scan
(ABSCOR; Rigaku, 1995)
Tmin, Tmax0.788, 0.988
No. of measured, independent and
observed [I > 2σ(I)] reflections
6800, 3100, 2723
Rint0.034
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.041, 0.107, 1.12
No. of reflections3100
No. of parameters179
No. of restraints4
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.40, 0.26
Absolute structureFlack (1983), 1408 Friedel pairs
Absolute structure parameter0.07 (8)

Computer programs: RAPID-AUTO (Rigaku, 2000), SIR92 (Altomare et al., 1994), SHELXL97 (Sheldrick, 2008), Yadokari-XG 2009 (Kabuto et al., 2009).

Selected bond lengths (Å) top
S1—C11.817 (2)O3—C41.276 (2)
O1—C31.297 (3)O4—C41.237 (3)
O2—C31.213 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
S1—H1···O2i1.24 (3)2.16 (3)3.2741 (19)148.0 (19)
O1—H1A···O3ii0.96 (3)1.54 (3)2.501 (2)177 (3)
N1—H1B···O40.943 (17)1.838 (19)2.751 (3)162 (3)
N1—H1C···O3iii0.917 (17)1.94 (2)2.797 (2)154 (3)
N1—H1D···O2iv0.886 (17)2.10 (2)2.845 (3)141 (3)
C1—H1E···Cgii1.002.623.56156
C6—H6···Cgv1.002.853.83166
Symmetry codes: (i) x+1, y+1/2, z+1; (ii) x, y1/2, z+1; (iii) x, y+1/2, z+1; (iv) x, y+1, z; (v) x, y+1/2, z.
 

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