Crystal structure of (3-carb­oxy­prop­yl)tri­phenyl­phospho­nium hexa­fluorido­phosphate

Patrick C Hillesheim; Kent A Scipione; Sean L Stokes

doi:10.1107/S160053681402323X

. 2014 Oct 24;70(Pt 11):o1197–o1198. doi: 10.1107/S160053681402323X

Crystal structure of (3-carboxypropyl)triphenylphosphonium hexafluoridophosphate

Patrick C Hillesheim ^a,^*, Kent A Scipione ^a, Sean L Stokes ^a

PMCID: PMC4257321 PMID: 25484826

Abstract

In the title molecular salt, C₂₂H₂₂O₂P⁺·PF₆ ⁻, the side chain of the cation adopts an anti–gauche conformation [P—C—C—C and C—C—C—C torsion angles = −179.11 (10) and −77.18 (16)°, respectively]. In the crystal, the cations are linked into carboxylic acid inversion dimers by pairs of O—H⋯O hydrogen bonds. Weak C—H⋯F and C—H⋯(F,F) hydrogen bonds connect the components into a three-dimensional network, but there are no aromatic π–π stacking interactions.

Keywords: crystal structure, phosphonium salt, hydrogen bonding

Related literature

For structures of related compounds, see: Li & Mak (1996 ▶); Wu et al. (2007 ▶). For compounds containing related metallated structures, see: Li & Mak (1997 ▶); Sabounchei et al. (2011 ▶). For the use of phosphonium compounds as Wittig reagents, see: Hoffman (2001 ▶), as biocodal agents, see: Kanazawa et al. (1993 ▶) and as phase transfer agents, see: Starks (1971 ▶).

Experimental

Crystal data

C₂₂H₂₂O₂P⁺·PF₆ ⁻
M _r = 494.33
Triclinic,
a = 9.3307 (1) Å
b = 10.6773 (2) Å
c = 12.8129 (2) Å
α = 72.460 (1)°
β = 82.307 (1)°
γ = 65.495 (1)°
V = 1107.46 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.26 mm⁻¹
T = 100 K
0.29 × 0.16 × 0.07 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2014 ▶) T _min = 0.865, T _max = 0.947
37843 measured reflections
5269 independent reflections
4426 reflections with I > 2σ(I)
R _int = 0.035

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.087
S = 1.06
5269 reflections
290 parameters
H-atom parameters constrained
Δρ_max = 0.42 e Å⁻³
Δρ_min = −0.36 e Å⁻³

Data collection: APEX2 (Bruker, 2014 ▶); cell refinement: SAINT (Bruker, 2013 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXT (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008 ▶); molecular graphics: OLEX2 (Dolomanov et al., 2009 ▶); software used to prepare material for publication: OLEX2.

Supplementary Material

Crystal structure: contains datablock(s) I. DOI: 10.1107/S160053681402323X/hb7304sup1.cif

e-70-o1197-sup1.cif^{(761.3KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681402323X/hb7304Isup2.hkl

e-70-o1197-Isup2.hkl^{(288.8KB, hkl)}

Click here for additional data file.^{(3.1KB, mol)}

Supporting information file. DOI: 10.1107/S160053681402323X/hb7304Isup3.mol

Click here for additional data file.^{(2.6MB, tif)}

. DOI: 10.1107/S160053681402323X/hb7304fig1.tif

Crystal structure and labeling scheme of compound (1). 50% probablility ellipsoids. Phosphorous is in green, oxygen in red, fluorine in purple, and carbon in grey.

CCDC reference: 1030392

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (, ).

DHA	DH	HA	D A	DHA
O1H1O2ⁱ	0.84	1.80	2.6285(15)	171
C1H1AF2	0.99	2.48	3.455(2)	168
C1H1AF3	0.99	2.50	3.1656(19)	124
C22H22F4ⁱⁱ	0.95	2.51	3.3924(18)	155

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

Acknowledgments

The authors wish to acknowledge the Mississippi State University Department of Chemistry for funding.

supplementary crystallographic information

S1. Synthesis and crystallization

A 1.0g (2.3mmol) sample of 3-carboxypropyltriphenylphosphonium chloride and 0.4g (2.4mmol) of sodium hexafluorophosphate were dissolved in 40mL of water. A white precipitate immediately formed and the slurry was stirred for 1 hour. The mixture was filtered, the solid was washed with water (3 x 25mL), and dried under high vacuum to yield a white solid. Yield: 0.65g (80.8%). Single crystals suitable for X-ray diffraction were grown from slow evaporation of dichloromethane. ¹H NMR (CHLOROFORM-d ,300MHz): δ = 7.90–8.02 (m, 9H), 7.77–7.89 (m, 6H), 3.54–3.72 (m, 2H), 2.66 (t, J = 6.6 Hz, 2H), 2.04–2.07 p.p.m. (m, 2H). ¹³C NMR (CHLOROFORM-d ,75MHz): δ = 174.0, 136.4, 134.9, 131.6, 120.3, 119.1, 34.2, 34.0, 22.0, 19.2 p.p.m. HRMS (ESI–TOF) m/z: [M⁺] Calcd for C₂₂H₂₂O₂P⁺ 349.381; found 349.1355. [M^-] Calcd for PF₆ 144.965; found 144.9632.

S2. Refinement

Carbon-bound H-atoms were placed in calculated positions (C—H = 0.95 to 0.99 Å, O—H = 0.84 Å) and were included in the refinement in the riding model approximation with U_iso(H) = 1.2U_eq(C) or 1.5U_eq(O).

S3. Comment

Organic phosphonium cations have been used as phase transfer catalysts (Starks, 1971), biocidal agents (Kanazawa et al. 1993), and as reagents for Wittig reactions (Hoffman, 2001). There are few examples in the crystallographic literature, however, of triphenylphosphonium cations bearing a carboxylic acid functional group.

In the title compound, 3-carboxypropyltriphenylphosphonium hexafluorophosphate (Fig. 1), crystallizes in a triclinic unit cell with a single cation-anion pair in the asymmetric unit. The dominant intermolecular interactions is hydrogen bonding from the carboxylic acid moiety on the cation (Table 1). The alkyl chain attached to the phosphorous deviates from the expected staggered conformation, showing a rotation at the C1—C2 carbons. This twist in the carbons is likely the cause of the unusual torsion angles observed in the three phenyl rings (Table 2). The phenyl ring that is located under the C2 hydrogens is nearly perpendicular when compared to the other two rings. It is suspected that this perpendicular arrangement of the phenyl ring is assumed to minimize potential steric interactions with the bent portion of the alkyl chain. Interestingly, there are no observed π–π interactions from any of the phenyl rings and there are no weak C—H···F interactions.