Tri-tert-butyl­phospho­nium hy­droxy­tris­(penta­fluoro­phen­yl)borate

Marcus Klahn; Anke Spannenberg; Uwe Rosenthal

doi:10.1107/S1600536812018144

. 2012 Apr 28;68(Pt 5):o1549. doi: 10.1107/S1600536812018144

Tri-tert-butylphosphonium hydroxytris(pentafluorophenyl)borate

Marcus Klahn ^a,^*, Anke Spannenberg ^a, Uwe Rosenthal ^a

PMCID: PMC3344648 PMID: 22590410

Abstract

The ionic title compound, C₁₂H₂₈P⁺·C₁₈HBF₁₅O⁻, was obtained by the stoichiometric reaction of ^tBu₃P, B(C₆F₅)₃ and water in toluene. A weak P—H⋯O hydrogen bond is observed in the crystal structure.

Related literature

For general aspects of related compounds, see: Welch et al. (2007 ▶); Stephan & Erker (2010 ▶). For related structures, see: Roesler et al. (2003 ▶); Di Saverio et al. (2005 ▶); Welch & Stephan (2007 ▶).

Experimental

Crystal data

C₁₂H₂₈P⁺·C₁₈HBF₁₅O⁻
M _r = 732.31
Triclinic,
a = 9.798 (2) Å
b = 12.042 (2) Å
c = 15.389 (3) Å
α = 112.31 (3)°
β = 94.51 (3)°
γ = 108.93 (3)°
V = 1546.2 (8) Å³
Z = 2
Mo Kα radiation
μ = 0.21 mm⁻¹
T = 200 K
0.30 × 0.23 × 0.15 mm

Data collection

Stoe IPDS II diffractometer
24084 measured reflections
6557 independent reflections
4256 reflections with I > 2σ(I)
R _int = 0.031

Refinement

R[F ² > 2σ(F ²)] = 0.030
wR(F ²) = 0.069
S = 0.84
6557 reflections
450 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.24 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2005 ▶); cell refinement: X-AREA; data reduction: X-RED32; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP in SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812018144/hg5215sup1.cif

e-68-o1549-sup1.cif^{(24.4KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812018144/hg5215Isup2.hkl

e-68-o1549-Isup2.hkl^{(320.9KB, hkl)}

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
P1—H2⋯O1ⁱ	1.288 (14)	2.276 (14)	3.4080 (13)	144.6 (9)

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Symmetry code: (i) Inline graphic .

Acknowledgments

This work was supported by the Leibniz-Institut für Katalyse e·V. an der Universität Rostock.

supplementary crystallographic information

Comment

The concept of "frustrated Lewis pairs" has been explored in depth and coined by Welch et al. (2007). The key issue is the sterical hindrance between the Lewis acids and bases preventing a classical adduct formation which gives rise to a unique reactivity due to the interaction of the basic and acidic centres. During the last years, this feature has been shown in reactions with a wide variety of reagents, these can be either small molecules like H₂, CO₂, and N₂O, or larger ones like terminal olefins, alkynes, dienes, B–H bonds, disulfides and the C–O bonds of cyclic ethers (Stephan & Erker 2010). The reaction of tri-tert-butylphosphine, tris(pentafluorophenyl)borane and water proceeds in a similar way to the conversion of tris(pentafluorophenyl)borane with water in the presence of triethylamine (Di Saverio et al., 2005). Roesler et al. (2003) obtained an intramolecular salt of the type 1-[N(H)Ph₂]-2-[B(OH)(C₆F₅)₂]C₆H₄ with a phenyl bridge between nitrogen and boron. The title compound consists of the phosphonium cation [tBu₃PH]⁺ and the boranate anion [HOB(C₆F₅)₃]^- (Figure 1), which are probably generated via subsequent protonation of the phosphine by the formed borane water adduct. The phosphonium cation is comparable to that in the compound [tBu₃PH][HB(C₆F₅)₃], which is the product of dihydrogen activation (Welch & Stephan 2007). Besides the unexceptional metric parameters both ions exhibit a geometry of a distorted tetrahedron at the phosphorous and the boron centre, respectively. Noteworthy, a weak P—H···O hydrogen bond was obtained with following geometric parameters: P1—H2 1.288 (14), H2···O1 2.276 (14), P1···O1 3.4080 (13) Å, P1—H2···O1 144.6 (9)°.

Experimental

Solid tris(pentafluorophenyl)borane (0.256 g, 0.5 mmol) and tri-tert-butylphosphine (0.101 g, 0.5 mmol) were dissolved in 20 ml of toluene resulting in a pale yellow solution. After stirring this mixture for 30 minutes 9 µL of water (0.5 mmol) was added. The reaction mixture was allowed to stir for 12 h at 40 °C during which the solution turned colorless. The reaction was concentrated until the first precipitate was formed, which was resolved by gentle heating. Leaving the solution at -78 °C gave colorless prisms in an isolated yield of 0.127 g (35%) The colorless compound was fully characterized by standard analytical methods, NMR (295 K, CDCl₃): ¹H: d = 5.96 (d, 1H, ¹J_HP = 451 Hz, PH), 2.05 (br s, 1H, HOB), 1.58 (d, 27H, ³J_HP = 15.3 Hz, {(CH₃)₃C}₃). ¹¹B: d = -3.74 (s). ³¹P{¹H}: d = 54.8 (s). ³¹P: d = 54.8 (dm, ¹J_PH = 452 Hz, ³J_HP = 15.4 Hz). ¹⁹F: d = -135.0 (d, 6 F, ³J_FF = 21.6 Hz, o-F), -161.8 (t, 3 F, ³J_FF = 20.1 Hz, p-F), -165.5 (m, 6 F, m-F).