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Acta Crystallogr Sect E Struct Rep Online. 2010 May 1; 66(Pt 5): o1118.
Published online 2010 April 21. doi:  10.1107/S1600536810013565
PMCID: PMC2979250

(R)-1-Phenyl­ethyl­ammonium trifluoro­acetate

Abstract

In the crystal structure of the title salt, C8H12N+·C2F3O2 , all of the ammonium H atoms serve as donors for hydrogen bonds to carboxyl­ate O atoms, forming an R 4 3(10) ring motif based on two cations and two anions. Since both cations and anions act as inter-ion bridging groups, R(10) rings aggregate in a one-dimensional supra­molecular network by sharing the strongest N—H(...)O bond. Edge-sharing motifs lie on the twofold screw axis parallel to [010], and anti­parallel packing of these 21-column structural units results in the crystal structure. This arrangement is one of the most commonly occurring in conglomerates of chiral 1-phenyl­ethyl­amine with achiral monocarboxylic acids, confirming that these ionic salts are particularly robust supra­molecular heterosynthons useful in crystal engineering.

Related literature

For graph-set analysis, see: Etter (1990 [triangle]); Bernstein et al. (1995 [triangle]). For characteristic structural patterns found in crystal salts of 1-phenyl­ethyl­amine and monocarboxylic acids, see: Kinbara, Hashimoto et al. (1996 [triangle]); Kinbara, Kai et al. (1996 [triangle]); Lemmerer et al. (2008 [triangle]). For related chiral salt structures, see: Johansen et al. (1998 [triangle]); Boussac et al. (2002 [triangle]); Lemmerer et al. (2008 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-66-o1118-scheme1.jpg

Experimental

Crystal data

  • C8H12N+·C2F3O2
  • M r = 235.21
  • Orthorhombic, An external file that holds a picture, illustration, etc.
Object name is e-66-o1118-efi1.jpg
  • a = 6.7821 (5) Å
  • b = 6.9887 (8) Å
  • c = 24.378 (2) Å
  • V = 1155.49 (19) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.13 mm−1
  • T = 298 K
  • 0.60 × 0.44 × 0.40 mm

Data collection

  • Siemens P4 diffractometer
  • 3079 measured reflections
  • 1808 independent reflections
  • 1288 reflections with I > 2σ(I)
  • R int = 0.020
  • 3 standard reflections every 97 reflections intensity decay: 1%

Refinement

  • R[F 2 > 2σ(F 2)] = 0.041
  • wR(F 2) = 0.112
  • S = 1.03
  • 1808 reflections
  • 156 parameters
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.16 e Å−3
  • Δρmin = −0.13 e Å−3

Data collection: XSCANS (Siemens, 1996 [triangle]); cell refinement: XSCANS; data reduction: XSCANS (Siemens, 1996 [triangle]); program(s) used to solve structure: SHELXTL-Plus (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXTL-Plus; molecular graphics: Mercury (Macrae et al., 2008 [triangle]); software used to prepare material for publication: SHELXTL-Plus.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810013565/pb2025sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810013565/pb2025Isup2.hkl

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

Acknowledgments

This work was supported by CONACyT (grant 83049).

supplementary crystallographic information

Comment

In their works about optical resolution of conglomerates, Kinbara et al. noted that characteristic hydrogen-bond networks were formed in the salt crystals of 1-phenylethylamine and 1-(4-isopropylphenyl)ethylamine with cinnamic acid (Kinbara, Kai et al., 1996). They suggested that "the pattern of hydrogen bonds plays a significant role in the formation of conglomerates" (Kinbara, Hashimoto et al., 1996). In the specific case of salts of chiral 1-phenylethylamine with achiral monocarboxylic acids, a number of structural determinations indeed showed that two predominant supramolecular arrangements are favored by the charge assisted N—H···O hydrogen bonds, which result in crystals belonging to P21 or P212121 space groups (Lemmerer et al., 2008): cations and anions associate through quite strong hydrogen bonds to form C21(4)C22(6)[R43(10)] motifs (Etter, 1990; Bernstein et al., 1995). This basic unit has hydrogen bonds with translational units, forming an infinite columnar structure, which generates a screw axis in the crystal structure (invariably a 21 axis). This supramolecular structure, referred as '21–column' in the Kinbara's reports, may be arranged in a parallel packing in the crystal, which then belongs to P21 space group, or in an antiparallel fashion, generating P212121 crystals.

The chiral title salt (Fig. 1) clearly falls in the latter category. Both the cation and anion are placed in general positions in an orthorhombic unit cell. All ammonium H atoms form hydrogen bonds with carboxylate O atoms, giving a ring motif R43(10), as shown in Fig. 2. The strongest hydrogen bond, N1—H1C···O2ii is common to two rings motifs. The repetition of the motif in the [010] direction generates homochiral (R)–21–columns. This 1D supramolecular network includes larger ring motifs, which appear if shared contacts are omitted. The sequence of sub-rings nest is R43(10) →R65(16) →R87(22) →R109(28) → ··· →R2n2n-1(6n-2) [with n > 1]. The shortest contact between neighboring 21–columns is N1—H1B···F2i, which should be regarded as a van der Waals contact rather than as an actual hydrogen bond. As a consequence, an antiparallel arrangement of 21–columns is favored (Fig. 2, inset), which is, in turn, reflected in the P212121 space group. Such crystal structures were obtained for numerous 1-phenylethylamine salts including different anions, e.g. bromofluoroacetate (Boussac et al., 2002), m-iodobenzoate (Lemmerer et al., 2008) or more complex, bulky carboxylate derivatives (Johansen et al., 1998).

The above description is thus in line with expectations from previous reported structures, and confirms that salts based on chiral 1-phenylethylamine and achiral monocarboxylic acids are robust heterosynthons, useful for crystal engineering and crystal structure prediction. The feature should however not been transferred to other salts (or worse, to cocrystals) of 1-phenylethylamine, which stabilize different supramolecular motifs, if any.

Experimental

The title salt crystallized when attempting to synthesize a diimine organic ligand. A mixture of (S)-6-acetyloxy-5-methyl-2,3-hexanedione (1 g, 5.37 mmol) and Na2SO4 (4 g) in chloroform (10 ml) was stirred for 5 min. A catalytic amount of trifluoroacetic acid and 2 equiv. of (R)-(+)-α-phenylethylamine (10.6 mmol) were added and the mixture was refluxed (ca. 353 K) under inert atmosphere, until starting materials were not detected by TLC (ca. 2 h). After evaporation under reduced pressure, the crude was recrystallized from CH2Cl2 at 298 K, affording, among other products, the title salt.

Refinement

As no heavy atoms are present in the crystal and data were measured at room-temperature using Mo Kα radiation, no absorption correction was applied to the raw data. Because of insufficient anomalous scattering effects, the Flack parameter could not be reliably determined, and measured Friedel pairs (796) were merged. Absolute configuration was assigned by reference to the chiral amine used as starting material, assuming that no inversion occurred during crystallization. Ammonium H atoms were refined with free coordinates, in order to get accurate dimensions for hydrogen bonds. Other H atoms were placed in idealized positions and refined as riding to their carrier atoms, with bond lengths fixed to 0.93 (aromatic CH), 0.96 (methyl CH3) or 0.98 Å (methine CH). Isotropic displacement parameters for H atoms were calculated as Uiso(H) = 1.2Ueq(C) for aromatic CH groups and Uiso(H) = 1.5Ueq(C, N) for other groups. The methyl group was considered as a rigid group free to rotate about its C—C bond.

Figures

Fig. 1.
The structure of the title compound, with displacement ellipsoids at the 50% probability level for non-H atoms.
Fig. 2.
The hydrogen-bonding network in the title compound (hydrogen bonds are dashed). The inset represent the packing structure viewed down the axis of the 21–column (b axis). H atoms have been omitted for clarity. In both figures, cations are green ...

Crystal data

C8H12N+·C2F3O2F(000) = 488
Mr = 235.21Dx = 1.352 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 70 reflections
a = 6.7821 (5) Åθ = 4.5–12.5°
b = 6.9887 (8) ŵ = 0.13 mm1
c = 24.378 (2) ÅT = 298 K
V = 1155.49 (19) Å3Prism, colorless
Z = 40.60 × 0.44 × 0.40 mm

Data collection

Siemens P4 diffractometerRint = 0.020
Radiation source: fine-focus sealed tubeθmax = 29.0°, θmin = 1.7°
graphiteh = −9→4
2θ/ω scansk = −9→1
3079 measured reflectionsl = −33→1
1808 independent reflections3 standard reflections every 97 reflections
1288 reflections with I > 2σ(I) intensity decay: 1%

Refinement

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) = 0.112w = 1/[σ2(Fo2) + (0.0464P)2 + 0.1579P] where P = (Fo2 + 2Fc2)/3
S = 1.03(Δ/σ)max < 0.001
1808 reflectionsΔρmax = 0.16 e Å3
156 parametersΔρmin = −0.13 e Å3
0 restraintsExtinction correction: SHELXTL-Plus (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 constraintsExtinction coefficient: 0.045 (4)
Primary atom site location: structure-invariant direct methods

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/Ueq
N10.9254 (3)0.1712 (3)0.19995 (7)0.0480 (4)
H1C1.002 (5)0.206 (4)0.2286 (11)0.072*
H1B0.853 (5)0.062 (5)0.2039 (11)0.072*
H1A0.840 (5)0.268 (5)0.1966 (11)0.072*
C11.0532 (3)0.1429 (4)0.15044 (8)0.0513 (5)
H11.13770.03160.15710.062*
C21.1846 (5)0.3153 (5)0.14290 (11)0.0818 (9)
H2C1.26170.30000.11020.123*
H2B1.27090.32730.17390.123*
H2A1.10490.42830.13980.123*
C30.9260 (3)0.1001 (4)0.10055 (8)0.0502 (5)
C40.9482 (5)−0.0721 (4)0.07311 (11)0.0706 (7)
H41.0390−0.16160.08570.085*
C50.8359 (6)−0.1118 (5)0.02695 (12)0.0893 (10)
H50.8526−0.22720.00860.107*
C60.7020 (5)0.0165 (5)0.00854 (11)0.0819 (10)
H60.6265−0.0114−0.02230.098*
C70.6776 (4)0.1863 (5)0.03497 (10)0.0743 (8)
H70.58590.27440.02210.089*
C80.7891 (4)0.2282 (4)0.08117 (9)0.0633 (7)
H80.77100.34420.09920.076*
C90.6937 (4)0.6770 (3)0.19540 (9)0.0482 (5)
O10.6911 (4)0.5019 (3)0.19191 (10)0.0921 (7)
O20.8190 (3)0.7849 (3)0.21505 (7)0.0620 (5)
C100.5086 (4)0.7725 (4)0.17224 (11)0.0613 (6)
F10.4723 (3)0.7214 (4)0.12145 (7)0.1175 (8)
F20.5178 (3)0.9610 (2)0.17221 (11)0.1065 (8)
F30.3482 (2)0.7254 (3)0.20053 (8)0.0914 (6)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
N10.0484 (10)0.0459 (9)0.0498 (9)−0.0030 (9)−0.0118 (9)0.0002 (9)
C10.0420 (10)0.0574 (13)0.0545 (11)0.0045 (11)−0.0077 (10)−0.0010 (10)
C20.0655 (16)0.105 (2)0.0744 (16)−0.029 (2)−0.0104 (14)0.0154 (17)
C30.0429 (11)0.0622 (13)0.0455 (10)0.0012 (12)−0.0017 (9)0.0003 (10)
C40.0760 (17)0.0669 (16)0.0689 (14)0.0113 (16)−0.0136 (15)−0.0104 (13)
C50.116 (3)0.082 (2)0.0699 (15)−0.003 (2)−0.0199 (18)−0.0186 (16)
C60.085 (2)0.106 (3)0.0544 (13)−0.022 (2)−0.0162 (15)−0.0043 (16)
C70.0650 (16)0.099 (2)0.0585 (13)0.0027 (18)−0.0157 (13)0.0114 (15)
C80.0618 (14)0.0706 (16)0.0576 (12)0.0107 (14)−0.0108 (12)−0.0038 (12)
C90.0487 (12)0.0465 (12)0.0495 (10)0.0049 (10)−0.0017 (10)−0.0005 (9)
O10.0946 (16)0.0488 (11)0.1330 (18)0.0160 (11)−0.0199 (16)−0.0080 (11)
O20.0575 (10)0.0609 (10)0.0677 (9)−0.0061 (9)−0.0241 (8)0.0114 (8)
C100.0477 (13)0.0611 (14)0.0753 (14)−0.0048 (13)−0.0089 (12)0.0110 (13)
F10.1021 (14)0.173 (2)0.0768 (10)−0.0089 (18)−0.0389 (10)0.0115 (13)
F20.0614 (10)0.0583 (10)0.200 (2)0.0064 (9)−0.0258 (13)0.0349 (11)
F30.0526 (8)0.0911 (13)0.1303 (14)−0.0024 (10)0.0155 (9)0.0106 (12)

Geometric parameters (Å, °)

N1—C11.499 (3)C5—C61.352 (5)
N1—H1C0.90 (3)C5—H50.9300
N1—H1B0.92 (3)C6—C71.361 (4)
N1—H1A0.90 (3)C6—H60.9300
C1—C21.510 (4)C7—C81.388 (3)
C1—C31.521 (3)C7—H70.9300
C1—H10.9800C8—H80.9300
C2—H2C0.9600C9—O11.227 (3)
C2—H2B0.9600C9—O21.233 (3)
C2—H2A0.9600C9—C101.530 (3)
C3—C81.374 (3)C10—F11.312 (3)
C3—C41.385 (3)C10—F21.319 (3)
C4—C51.387 (4)C10—F31.329 (3)
C4—H40.9300
C1—N1—H1C109.1 (18)C5—C4—H4119.8
C1—N1—H1B106.6 (18)C6—C5—C4120.4 (3)
H1C—N1—H1B117 (2)C6—C5—H5119.8
C1—N1—H1A113.5 (18)C4—C5—H5119.8
H1C—N1—H1A104 (2)C5—C6—C7120.2 (3)
H1B—N1—H1A107 (2)C5—C6—H6119.9
N1—C1—C2109.5 (2)C7—C6—H6119.9
N1—C1—C3109.99 (17)C6—C7—C8120.1 (3)
C2—C1—C3113.23 (19)C6—C7—H7119.9
N1—C1—H1108.0C8—C7—H7119.9
C2—C1—H1108.0C3—C8—C7120.7 (3)
C3—C1—H1108.0C3—C8—H8119.7
C1—C2—H2C109.5C7—C8—H8119.7
C1—C2—H2B109.5O1—C9—O2130.3 (3)
H2C—C2—H2B109.5O1—C9—C10113.4 (2)
C1—C2—H2A109.5O2—C9—C10116.2 (2)
H2C—C2—H2A109.5F1—C10—F2106.3 (2)
H2B—C2—H2A109.5F1—C10—F3105.6 (2)
C8—C3—C4118.3 (2)F2—C10—F3106.6 (3)
C8—C3—C1122.0 (2)F1—C10—C9112.6 (2)
C4—C3—C1119.7 (2)F2—C10—C9113.4 (2)
C3—C4—C5120.4 (3)F3—C10—C9111.85 (19)
C3—C4—H4119.8
N1—C1—C3—C861.4 (3)C4—C3—C8—C7−0.6 (4)
C2—C1—C3—C8−61.5 (3)C1—C3—C8—C7178.9 (2)
N1—C1—C3—C4−119.1 (2)C6—C7—C8—C30.4 (4)
C2—C1—C3—C4118.0 (3)O1—C9—C10—F1−54.5 (3)
C8—C3—C4—C50.7 (4)O2—C9—C10—F1126.5 (2)
C1—C3—C4—C5−178.8 (3)O1—C9—C10—F2−175.2 (3)
C3—C4—C5—C6−0.7 (5)O2—C9—C10—F25.8 (3)
C4—C5—C6—C70.5 (5)O1—C9—C10—F364.2 (3)
C5—C6—C7—C8−0.4 (5)O2—C9—C10—F3−114.8 (3)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
N1—H1A···O10.90 (3)1.92 (3)2.812 (3)171 (3)
N1—H1B···O2i0.92 (3)1.97 (3)2.818 (3)154 (3)
N1—H1C···O2ii0.90 (3)1.92 (3)2.816 (2)175 (3)
N1—H1B···F2i0.92 (3)2.50 (3)3.202 (3)134 (2)

Symmetry codes: (i) x, y−1, z; (ii) −x+2, y−1/2, −z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PB2025).

References

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