Tetra-n-butyl­ammonium phenyl­tri­fluoro­borate

The title compound, C₁₆H₃₆N⁺·C₆H₅BF₃^-, crystallizes as discrete tetra-n-butyl­ammoniun ions and phenyl­tri­fluoro­borate ions. There are no close contacts between anions and cations.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.051
• wR factor = 0.130
• Data-to-parameter ratio = 17.5

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

Recently, potassium organotrifluoroborate salts have gained considerable interest in organic synthesis as alternatives to boronic acids in reactions such as rhodium(I)-catalyzed 1,4-additions to α,β-unsaturated carbonyl compounds (Batey et al., 1999), Lewis acid catalyzed allylation of aldehydes (Batey et al., 2000), palladium catalyzed couplings with aryldiazonium compounds (Genet et al., 1999), and the synthesis of oxazaborolidinones (Vedejs et al., 1993). Their stability towards air and moisture also makes them ideal reagents for combinatorial synthesis. One drawback to their use, however, is their decreased solubility in non-polar organic solvents.

In an attempt to synthesize phenyldifluoroborane by treating the corresponding boronic acid with hydrofluoric acid (Kinder & Katzenellenbogen, 1985), it was discovered that the organodifluoroborane species would quickly convert to an organotrifluoroborate species (confirmed by ¹¹B NMR). It was hypothesized that the species formed was the hydronium organotrifluoroborate salt; however, all attempts to isolate this compound were unsuccessful, and the compound was only observable spectroscopically in solution via ¹¹B and ¹⁹F NMR. Fortunately, treatment of the intermediate with the base tetra-n-butylammonium hydroxide affected a counterion exchange to produce the isolable title compound, (I).

The tetra-n-butylammonium derivative was found to have comparable reactivity to that of its potassium counterpart in the aforementioned reactions with the added advantage of having excellent solubility in nonpolar organic solvents. Compound (I) was also found to have greater reactivity than its potassium counterpart in palladium catalyzed Suzuki cross-coupling reactions with aryl- and alkenylhalides (Batey & Quach, 2001).

Compound (I) crystallizes as discrete tetra-n-butylammonium and phenyltrifluoroborate ions (see Fig. 1). There are no close contacts between the anions and cations in the structure. The tetra-n-butylammonium ion in (I) has three butyl groups which are in the staggered conformation and one group (containing the atoms C7, C8, C9 and C10) which is in a coiled conformation (see Table 1 for torsion angles) The structure of the related potassium phenyltrifluoroborate salt (Conole et al., 1995) has also been determined.

S2. Experimental

The title compound, (I), was synthesized by treatment of phenylboronic acid (0.52 g, 4.27 mmol), dissolved in a minimum amount of methanol (ca 1 ml), with a 5.0 M solution of hydrofluoric acid (2.65 ml, 13.25 mmol), added dropwise with vigorous stirring over a period of 1 min at room temperature. The reaction mixture was then cooled to 273 K, and a 1.54 M solution of tetra-n-butylammonium hydroxide (2.76 ml, 4.27 mmol) was added dropwise over a period of 5 min. The reaction mixture was then warmed to room temperature and stirred for another hour. Dichloromethane (10 ml) was added to dilute the biphasic reaction mixture, the layers were separated, and the aqueous layer was further extracted with dichloromethane (3 × 10 ml). The combined organic layers were dried (MgSO₄), filtered and concentrated in vacuo to afford the pale yellow crystalline solid (I). Subsequent recrystallization from ethyl acetate and hexanes yielded the desired crystals.

S3. Refinement

H atoms were included in calculated positions with C—H distances ranging from 0.95 to 0.99 Å.

Computing details

Data collection: COLLECT (Nonius, 1997-2001); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXTL (Sheldrick 1999); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. View of (I) showing the atom-labelling scheme. Ellipsoids are at the 50% probability level.

Tetra-n-butylammonium Phenyltrifluoroborate

Crystal data

C16H36N^+·C6H5BF3^−	Dx = 1.087 Mg m^−3
Mr = 387.37	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbcn	Cell parameters from 20559 reflections
a = 13.5626 (6) Å	θ = 2.6–25.4°
b = 17.1534 (7) Å	µ = 0.08 mm^−1
c = 20.3567 (7) Å	T = 150 K
V = 4735.9 (3) Å^3	Needle, colourless
Z = 8	0.40 × 0.35 × 0.34 mm
F(000) = 1696

Data collection

Nonius KappaCCD diffractometer	4341 independent reflections
Radiation source: fine-focus sealed tube	2858 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
Detector resolution: 9 pixels mm^-1	θmax = 25.4°, θmin = 2.6°
ϕ scans, and ω scans with ϕ offsets	h = −16→16
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997)	k = −20→20
Tmin = 0.970, Tmax = 0.974	l = −24→24
20559 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.130	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0564P)^2 + 1.1252P] where P = (Fo^2 + 2Fc^2)/3
4341 reflections	(Δ/σ)max = 0.002
248 parameters	Δρmax = 0.19 e Å^−3
0 restraints	Δρmin = −0.19 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
F1	0.59931 (8)	0.57296 (6)	0.92620 (5)	0.0474 (3)
F2	0.75843 (9)	0.59224 (6)	0.95963 (5)	0.0508 (3)
F3	0.65065 (8)	0.69422 (6)	0.95535 (5)	0.0415 (3)
C1	0.71260 (14)	0.64185 (10)	0.84841 (9)	0.0343 (5)
C2	0.64272 (17)	0.64701 (12)	0.79801 (10)	0.0477 (6)
H2A	0.5755	0.6374	0.8083	0.057*
C3	0.6668 (2)	0.66524 (14)	0.73437 (11)	0.0594 (7)
H3A	0.6169	0.6673	0.7017	0.071*
C4	0.7628 (2)	0.68042 (13)	0.71811 (11)	0.0582 (7)
H4A	0.7794	0.6948	0.6744	0.070*
C5	0.83502 (18)	0.67485 (13)	0.76501 (12)	0.0558 (6)
H5A	0.9019	0.6845	0.7538	0.067*
C6	0.80956 (16)	0.65481 (11)	0.82970 (10)	0.0445 (5)
H6A	0.8603	0.6500	0.8616	0.053*
B1	0.68074 (17)	0.62465 (13)	0.92269 (11)	0.0370 (5)
N1	0.65083 (11)	0.35374 (8)	0.95923 (7)	0.0317 (4)
C7	0.55031 (14)	0.39006 (11)	0.94591 (9)	0.0352 (5)
H7A	0.5171	0.3986	0.9886	0.042*
H7B	0.5609	0.4419	0.9257	0.042*
C8	0.48082 (15)	0.34400 (12)	0.90189 (11)	0.0488 (6)
H8A	0.4598	0.2958	0.9247	0.059*
H8B	0.5156	0.3288	0.8611	0.059*
C9	0.39061 (15)	0.39282 (14)	0.88469 (11)	0.0522 (6)
H9A	0.3419	0.3591	0.8623	0.063*
H9B	0.3601	0.4117	0.9259	0.063*
C10	0.41242 (19)	0.46196 (15)	0.84130 (12)	0.0707 (7)
H10A	0.3506	0.4881	0.8297	0.106*
H10B	0.4455	0.4442	0.8012	0.106*
H10C	0.4553	0.4985	0.8648	0.106*
C11	0.64050 (15)	0.27316 (10)	0.98920 (9)	0.0362 (5)
H11A	0.6035	0.2400	0.9580	0.043*
H11B	0.7072	0.2504	0.9938	0.043*
C12	0.58977 (14)	0.26878 (11)	1.05540 (9)	0.0376 (5)
H12A	0.5254	0.2959	1.0532	0.045*
H12B	0.6307	0.2952	1.0889	0.045*
C13	0.57400 (17)	0.18434 (12)	1.07489 (11)	0.0522 (6)
H13A	0.5366	0.1578	1.0396	0.063*
H13B	0.6390	0.1584	1.0785	0.063*
C14	0.51968 (19)	0.17450 (13)	1.13854 (11)	0.0595 (7)
H14A	0.5085	0.1189	1.1468	0.089*
H14B	0.4562	0.2016	1.1360	0.089*
H14C	0.5589	0.1966	1.1744	0.089*
C15	0.70366 (14)	0.40930 (10)	1.00524 (9)	0.0330 (4)
H15A	0.6640	0.4143	1.0458	0.040*
H15B	0.7058	0.4613	0.9842	0.040*
C16	0.80804 (14)	0.38684 (12)	1.02447 (9)	0.0387 (5)
H16A	0.8502	0.3848	0.9848	0.046*
H16B	0.8079	0.3345	1.0450	0.046*
C17	0.84916 (16)	0.44636 (12)	1.07262 (10)	0.0473 (5)
H17A	0.8059	0.4486	1.1117	0.057*
H17B	0.8486	0.4985	1.0517	0.057*
C18	0.95382 (17)	0.42737 (15)	1.09446 (12)	0.0637 (7)
H18A	0.9754	0.4656	1.1272	0.095*
H18B	0.9981	0.4292	1.0564	0.095*
H18C	0.9554	0.3751	1.1138	0.095*
C19	0.70862 (15)	0.34332 (10)	0.89591 (9)	0.0349 (5)
H19A	0.7698	0.3144	0.9064	0.042*
H19B	0.6691	0.3101	0.8661	0.042*
C20	0.73718 (15)	0.41645 (11)	0.85871 (9)	0.0383 (5)
H20A	0.7891	0.4449	0.8831	0.046*
H20B	0.6792	0.4511	0.8543	0.046*
C21	0.77516 (15)	0.39356 (11)	0.79091 (9)	0.0407 (5)
H21A	0.8233	0.3505	0.7956	0.049*
H21B	0.7194	0.3741	0.7642	0.049*
C22	0.82409 (17)	0.46097 (12)	0.75513 (10)	0.0477 (6)
H22A	0.8425	0.4444	0.7107	0.072*
H22B	0.8833	0.4771	0.7792	0.072*
H22C	0.7780	0.5049	0.7525	0.072*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
F1	0.0499 (7)	0.0383 (6)	0.0540 (7)	−0.0113 (6)	0.0078 (6)	−0.0029 (5)
F2	0.0560 (8)	0.0495 (7)	0.0470 (7)	0.0081 (6)	−0.0111 (6)	0.0052 (5)
F3	0.0443 (7)	0.0352 (6)	0.0450 (6)	−0.0030 (5)	0.0054 (5)	−0.0075 (5)
C1	0.0343 (12)	0.0256 (10)	0.0430 (11)	0.0018 (9)	−0.0019 (9)	−0.0051 (8)
C2	0.0443 (13)	0.0527 (13)	0.0460 (12)	0.0073 (11)	−0.0022 (11)	0.0017 (10)
C3	0.0674 (18)	0.0640 (16)	0.0468 (14)	0.0106 (13)	−0.0039 (13)	0.0071 (11)
C4	0.082 (2)	0.0487 (14)	0.0439 (13)	−0.0030 (13)	0.0106 (14)	−0.0008 (11)
C5	0.0507 (15)	0.0514 (14)	0.0654 (16)	−0.0117 (11)	0.0222 (13)	−0.0180 (12)
C6	0.0390 (13)	0.0423 (12)	0.0522 (13)	−0.0021 (10)	0.0016 (11)	−0.0150 (10)
B1	0.0363 (13)	0.0321 (12)	0.0426 (12)	−0.0013 (11)	−0.0024 (11)	−0.0022 (10)
N1	0.0345 (9)	0.0292 (8)	0.0313 (8)	0.0017 (7)	0.0005 (7)	−0.0029 (6)
C7	0.0327 (11)	0.0350 (11)	0.0378 (10)	0.0042 (9)	−0.0021 (9)	−0.0003 (9)
C8	0.0441 (13)	0.0467 (12)	0.0556 (13)	−0.0024 (11)	−0.0109 (11)	−0.0066 (10)
C9	0.0360 (13)	0.0683 (15)	0.0523 (13)	−0.0014 (11)	−0.0098 (11)	−0.0015 (12)
C10	0.0569 (16)	0.0831 (18)	0.0722 (17)	0.0013 (14)	−0.0238 (14)	0.0140 (14)
C11	0.0404 (12)	0.0291 (10)	0.0390 (11)	0.0015 (9)	0.0004 (9)	0.0000 (9)
C12	0.0380 (12)	0.0371 (11)	0.0378 (11)	0.0023 (9)	0.0005 (9)	0.0028 (9)
C13	0.0563 (15)	0.0444 (13)	0.0559 (13)	−0.0035 (11)	0.0094 (12)	0.0061 (10)
C14	0.0649 (17)	0.0516 (14)	0.0619 (15)	−0.0007 (12)	0.0111 (13)	0.0165 (11)
C15	0.0364 (11)	0.0303 (10)	0.0324 (10)	0.0007 (9)	−0.0008 (9)	−0.0016 (8)
C16	0.0379 (12)	0.0408 (11)	0.0375 (10)	0.0043 (10)	−0.0023 (9)	−0.0031 (9)
C17	0.0470 (14)	0.0493 (13)	0.0456 (12)	0.0036 (11)	−0.0089 (10)	−0.0074 (10)
C18	0.0480 (15)	0.0769 (17)	0.0661 (15)	0.0044 (13)	−0.0167 (13)	−0.0165 (13)
C19	0.0382 (11)	0.0329 (10)	0.0337 (10)	0.0030 (9)	0.0031 (9)	−0.0047 (8)
C20	0.0455 (13)	0.0355 (11)	0.0338 (10)	0.0020 (10)	0.0020 (9)	−0.0018 (8)
C21	0.0488 (14)	0.0401 (11)	0.0331 (10)	0.0067 (10)	0.0001 (9)	−0.0011 (9)
C22	0.0531 (14)	0.0530 (13)	0.0370 (11)	0.0048 (11)	0.0067 (10)	0.0030 (10)

Geometric parameters (Å, º)

F1—B1	1.418 (2)	C12—C13	1.517 (3)
F2—B1	1.409 (3)	C12—H12A	0.990
F3—B1	1.426 (2)	C12—H12B	0.990
C1—C6	1.387 (3)	C13—C14	1.500 (3)
C1—C2	1.400 (3)	C13—H13A	0.990
C1—B1	1.600 (3)	C13—H13B	0.990
C2—C3	1.372 (3)	C14—H14A	0.980
C2—H2A	0.950	C14—H14B	0.980
C3—C4	1.368 (3)	C14—H14C	0.980
C3—H3A	0.950	C15—C16	1.518 (3)
C4—C5	1.371 (3)	C15—H15A	0.990
C4—H4A	0.950	C15—H15B	0.990
C5—C6	1.404 (3)	C16—C17	1.521 (3)
C5—H5A	0.950	C16—H16A	0.990
C6—H6A	0.950	C16—H16B	0.990
N1—C15	1.516 (2)	C17—C18	1.523 (3)
N1—C11	1.517 (2)	C17—H17A	0.990
N1—C19	1.519 (2)	C17—H17B	0.990
N1—C7	1.523 (2)	C18—H18A	0.980
C7—C8	1.522 (3)	C18—H18B	0.980
C7—H7A	0.990	C18—H18C	0.980
C7—H7B	0.990	C19—C20	1.516 (3)
C8—C9	1.523 (3)	C19—H19A	0.990
C8—H8A	0.990	C19—H19B	0.990
C8—H8B	0.990	C20—C21	1.525 (3)
C9—C10	1.508 (3)	C20—H20A	0.990
C9—H9A	0.990	C20—H20B	0.990
C9—H9B	0.990	C21—C22	1.519 (3)
C10—H10A	0.980	C21—H21A	0.990
C10—H10B	0.980	C21—H21B	0.990
C10—H10C	0.980	C22—H22A	0.980
C11—C12	1.515 (2)	C22—H22B	0.980
C11—H11A	0.990	C22—H22C	0.980
C11—H11B	0.990
C6—C1—C2	115.51 (18)	C11—C12—H12B	109.6
C6—C1—B1	123.03 (18)	C13—C12—H12B	109.6
C2—C1—B1	121.43 (18)	H12A—C12—H12B	108.2
C3—C2—C1	123.0 (2)	C14—C13—C12	113.74 (18)
C3—C2—H2A	118.5	C14—C13—H13A	108.8
C1—C2—H2A	118.5	C12—C13—H13A	108.8
C4—C3—C2	119.9 (2)	C14—C13—H13B	108.8
C4—C3—H3A	120.1	C12—C13—H13B	108.8
C2—C3—H3A	120.1	H13A—C13—H13B	107.7
C3—C4—C5	119.9 (2)	C13—C14—H14A	109.5
C3—C4—H4A	120.1	C13—C14—H14B	109.5
C5—C4—H4A	120.1	H14A—C14—H14B	109.5
C4—C5—C6	119.6 (2)	C13—C14—H14C	109.5
C4—C5—H5A	120.2	H14A—C14—H14C	109.5
C6—C5—H5A	120.2	H14B—C14—H14C	109.5
C1—C6—C5	122.0 (2)	N1—C15—C16	116.13 (15)
C1—C6—H6A	119.0	N1—C15—H15A	108.3
C5—C6—H6A	119.0	C16—C15—H15A	108.3
F2—B1—F1	107.99 (16)	N1—C15—H15B	108.3
F2—B1—F3	107.19 (16)	C16—C15—H15B	108.3
F1—B1—F3	106.08 (16)	H15A—C15—H15B	107.4
F2—B1—C1	112.03 (17)	C15—C16—C17	109.73 (16)
F1—B1—C1	111.91 (16)	C15—C16—H16A	109.7
F3—B1—C1	111.33 (16)	C17—C16—H16A	109.7
C15—N1—C11	111.58 (13)	C15—C16—H16B	109.7
C15—N1—C19	110.75 (14)	C17—C16—H16B	109.7
C11—N1—C19	106.36 (13)	H16A—C16—H16B	108.2
C15—N1—C7	106.01 (13)	C16—C17—C18	112.73 (18)
C11—N1—C7	111.19 (14)	C16—C17—H17A	109.0
C19—N1—C7	111.03 (13)	C18—C17—H17A	109.0
C8—C7—N1	116.54 (15)	C16—C17—H17B	109.0
C8—C7—H7A	108.2	C18—C17—H17B	109.0
N1—C7—H7A	108.2	H17A—C17—H17B	107.8
C8—C7—H7B	108.2	C17—C18—H18A	109.5
N1—C7—H7B	108.2	C17—C18—H18B	109.5
H7A—C7—H7B	107.3	H18A—C18—H18B	109.5
C7—C8—C9	110.32 (17)	C17—C18—H18C	109.5
C7—C8—H8A	109.6	H18A—C18—H18C	109.5
C9—C8—H8A	109.6	H18B—C18—H18C	109.5
C7—C8—H8B	109.6	C20—C19—N1	117.28 (14)
C9—C8—H8B	109.6	C20—C19—H19A	108.0
H8A—C8—H8B	108.1	N1—C19—H19A	108.0
C10—C9—C8	114.17 (19)	C20—C19—H19B	108.0
C10—C9—H9A	108.7	N1—C19—H19B	108.0
C8—C9—H9A	108.7	H19A—C19—H19B	107.2
C10—C9—H9B	108.7	C19—C20—C21	109.00 (15)
C8—C9—H9B	108.7	C19—C20—H20A	109.9
H9A—C9—H9B	107.6	C21—C20—H20A	109.9
C9—C10—H10A	109.5	C19—C20—H20B	109.9
C9—C10—H10B	109.5	C21—C20—H20B	109.9
H10A—C10—H10B	109.5	H20A—C20—H20B	108.3
C9—C10—H10C	109.5	C22—C21—C20	112.67 (16)
H10A—C10—H10C	109.5	C22—C21—H21A	109.1
H10B—C10—H10C	109.5	C20—C21—H21A	109.1
C12—C11—N1	116.41 (14)	C22—C21—H21B	109.1
C12—C11—H11A	108.2	C20—C21—H21B	109.1
N1—C11—H11A	108.2	H21A—C21—H21B	107.8
C12—C11—H11B	108.2	C21—C22—H22A	109.5
N1—C11—H11B	108.2	C21—C22—H22B	109.5
H11A—C11—H11B	107.3	H22A—C22—H22B	109.5
C11—C12—C13	110.12 (16)	C21—C22—H22C	109.5
C11—C12—H12A	109.6	H22A—C22—H22C	109.5
C13—C12—H12A	109.6	H22B—C22—H22C	109.5
C7—C8—C9—C10	67.5 (2)	C15—C16—C17—C18	179.70 (18)
C11—C12—C13—C14	−177.23 (19)	C19—C20—C21—C22	−168.75 (17)