Crystal structure of tri­phenyl(vinyl)­phospho­nium tetra­phenyl­borate

Joseph L Bradfield; Richard A Braun; Frankie White; Jeffrey M Hendrich; Richard E Sykora; Arsalan Mirjafari

doi:10.1107/S1600536814021357

. 2014 Sep 30;70(Pt 10):o1143. doi: 10.1107/S1600536814021357

Crystal structure of triphenyl(vinyl)phosphonium tetraphenylborate

Joseph L Bradfield ^a, Richard A Braun ^a, Frankie White ^b, Jeffrey M Hendrich ^b, Richard E Sykora ^b, Arsalan Mirjafari ^a,^*

PMCID: PMC4257183 PMID: 25484719

Abstract

The title ionic salt, C₂₁H₂₀P⁺·C₂₄H₂₀B⁻, crystallized with two independent vinyltriphenylphosphonium cations and two independent tetraphenylborate anions per asymmetric unit. These four independent moieties contain nearly perfect tetrahedral symmetry about their respective central C atoms. In the crystal, there are no π-stacking or other intermolecular interactions present.

Keywords: crystal structure, ionic salt, vinyltriphenylphosphonium, tetraphenylborate

Related literature

For background to the study of phosphine compounds, see: Bellina et al. (2012 ▶). For information on ionic liquids, see: Chowdhury et al. (2007 ▶). graphic file with name e-70-o1143-scheme1.jpg

Experimental

Crystal data

C₂₁H₂₀P⁺·C₂₄H₂₀B⁻
M _r = 622.55
Monoclinic,
a = 9.2752 (4) Å
b = 35.7838 (15) Å
c = 10.9515 (5) Å
β = 100.721 (4)°
V = 3571.4 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.11 mm⁻¹
T = 180 K
0.43 × 0.18 × 0.17 mm

Data collection

Agilent Xcalibur, Eos diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2014 ▶) T _min = 0.958, T _max = 1.000
24267 measured reflections
12797 independent reflections
9444 reflections with I > 2σ(I)
R _int = 0.038

Refinement

R[F ² > 2σ(F ²)] = 0.058
wR(F ²) = 0.105
S = 1.01
12797 reflections
849 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.35 e Å⁻³
Δρ_min = −0.23 e Å⁻³
Absolute structure: Flack (1983 ▶)
Absolute structure parameter: 0.02 (7)

Data collection: CrysAlis PRO (Agilent, 2014 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: OLEX2 (Dolomanov et al., 2009 ▶); software used to prepare material for publication: OLEX2 and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, New_Global_Publ_Block. DOI: 10.1107/S1600536814021357/hg5407sup1.cif

e-70-o1143-sup1.cif^{(40.1KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536814021357/hg5407Isup2.hkl

e-70-o1143-Isup2.hkl^{(625.6KB, hkl)}

Click here for additional data file.^{(3MB, tif)}

I . DOI: 10.1107/S1600536814021357/hg5407fig1.tif

A ball-and-stick representaion of the structure of I. Only one of the two cation/anion pairs are shown. Hydrogen atoms on the aromatic rings have been removed for clarity.

Click here for additional data file.^{(39.1KB, tif)}

I . DOI: 10.1107/S1600536814021357/hg5407fig2.tif

Reaction scheme for the synthesis of I.

CCDC reference: 1026273

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

Acknowledgments

The authors are grateful to the Department of Chemistry and Physics of FGCU for the financial support of this work. They also acknowledge the National Science Foundation for their generous support (NSF-CAREER grant to RES, CHE-0846680).

supplementary crystallographic information

S1. Chemical Context

In recent years, phosphorus-carbon bond-forming reactions have been the object of interest in the modern organophosphorus chemistry due to the importance of these products in a variety of fields ranging from material science to the synthesis of biologically active molecules. Phosphonium salts have been known since the 1980s; however, they were rarely employed until the 1990s, when phosphines were used as precursors on the large scale, see: Bellina et al. (2012).

Phosphonium-based ionic liquids emerged as a very promising alternative to imidazolium analogs due to their superior thermal stability and inertness in the basic environment. The presence of an acidic hydrogen at the C2 position of imidazolium rings in many ionic liquids, leads to the thermal instability that limits the applications of these interesting organic fluids, see: Chowdhury et al. (2007).

In this study, we found that the vinyltriphenylphosphonium bromide could be synthesized via the nucleophilic attack of triphenylphosphine to allyl bromide to form the corresponding betaine 1, followed by the intra-hydrogen shift reaction (Figure 2). In the next step, metathesis reaction of vinyltriphenyphosphonium bromide 2 with sodium tetraphenylborate led to the formation vinyltriphenyphosphonium tetraphenylborane 3 (T_m= 72–74° C) as the final product in high yield (78%).

S2. Experimental

Triphenylphosphine (0.5 mmol) and allyl bromide (0.7 mmol) were dissolved in toluene (2.0 ml) and the mixture refluxed for 48 h. The solvent was removed in a vacuum and the crude product was dissolved in 4.0 ml of H₂O. Then, a solution of sodium tetraphenylborate (0.6 mmol) in 2.0 ml of H₂O was added to the original solution of crude product and was stirred for 24 h. The final product was separated via filtration and washed with H₂O (3 x 5 ml) to yield white crystals of the title complex.