The `super acid' BF₃H₂O stabilized by 1,4-dioxane: new preparative aspects and the crystal structure of BF₃H₂O·C₄H₈O₂

Highly Brønsted-acidic boron trifluoride monohydrate, a widely used `super acid-catalyst', is a colourless fuming liquid that releases BF₃ at room temperature. Com­pared to the liquid com­ponents, i.e. boron trifluoride monohydrate and 1,4-dioxane, their 1:1 adduct, BF₃H₂O·C₄H₈O₂, is a solid with pronounced thermal stability (m.p. 401–403 K). The crystal structure of the long-time-stable easy-to-handle and weighable com­pound is reported along with new preparative aspects and the results of ¹H, ¹¹B, ¹³C and ¹⁹F spectroscopic investigations, particularly documenting its high Brønsted acidity in aceto­nitrile solution. The remarkable stability of solid BF₃H₂O·C₄H₈O₂ is attributed to the chain structure established by O—H⋯O hydrogen bonds of exceptional strength {O2⋯H1—O1 [O⋯O = 2.534 (3) Å] and O1—H1⋯O3ⁱ [2.539 (3) Å] in the concatenating unit >O2⋯H1—O1—H2⋯O3ⁱ<}, taking into account the mol­ecular (non-ionic) character of the structural moieties. Indirectly, this structural feature documents the outstanding acidification of the H₂O mol­ecule bound to BF₃ and reflects the super acid nature of BF₃H₂O. In detail, the C₂²(7) zigzag chain system of hydrogen bonding in the title structure is characterized by the double hydrogen-bond donor and double (κO,κO′) hydrogen-bond acceptor functionality of the aqua ligand and dioxane molecule, respectively, the almost equal strength of both hydrogen bonds, the approximatety linear arrangement of the dioxane O atoms and the two neighbouring water O atoms. Furthermore, the approximately planar arrangement of B, F and O atoms in sheets perpendicular to the c axis of the ortho­rhom­bic unit cell is a characteristic structural feature.

1. Chemical context

Solutions of boron trifluoride in water have been under investigation for more than 200 years (Gay-Lussac & Thenard, 1809; Davy, 1812; Berzelius, 1824). Meerwein (1933) was able to isolate the BF₃ dihydrate and, after addition of one further equivalent of BF₃ at low temperature, the BF₃ monohydrate also. Both hydrates were examined in detail (Klinkenberg & Ketelaar, 1935; McGrath et al., 1944; Greenwood & Martin, 1951; Wamser, 1951; Pawlenko, 1959) and while the dihydrate was shown to be distillable without decom­position under reduced pressure, boron trifluoride monohydrate releases BF₃ above its melting point of 279.2 K. At room temperature, it is a colourless fuming liquid with a density of 1.8 g ml⁻¹. To examine the acidity of the monohydrate, reactions with ethers, alcohols and carb­oxy­lic acids etc. were performed by Meerwein & Pannwitz (1934). They obtained BF₃H₂O·C₄H₈O₂, which they called the dioxane salt of boron trifluoride monohydrate, by adding BF₃H₂O to a solution of 1,4-dioxane in petroleum naphta. BF₃H₂O·C₄H₈O₂ (1) precipitates as needle-shaped crystals which melt at 401–403 K with decom­position (Meerwein & Pannwitz, 1934). Unexpectedly, the experiment described in §6 resulted in the same product. The primordial idea of this experiment was to prepare an anhydrous solution of HBF₄ from HBF₄/H₂O (1:1 w:w) by distilling off water as the 1,4-dioxane/water azeotrope with coincident replacement of water by an excess of 1,4-dioxane. The dioxane adduct 1 starts to precipitate after a short period of time if a small amount of water remains in the resulting liquid. The formation of 1 in a `HBF<sub>4</sub> solution' impressively illustrates how efficently BF<sub>3</sub> is stabilized by water and dioxane. The reactions and equilibria of HBF<sub>4</sub>-, BF<sub>3</sub>-, H<sub>2</sub>O- and HF-containing systems have been examined in detail (Pawlenko, 1968; Gascard & Mascherpa, 1973; Christe et al., 1975; Mootz & Steffen, 1981a; Yeo & Ford, 2006; Dubey et al., 2007) and it remains amazing that BF<sub>3</sub>H<sub>2</sub>O, unlike the other boron trihalide/water mixtures, releases the strong Lewis-acid (BF<sub>3</sub>) unhydrolysed. Investigations by Greenwood & Martin (1951) showed that BF<sub>3</sub>H<sub>2</sub>O is highly ionized in the liquid state and that the Hammett acidity of H[BF<sub>3</sub>OH] is H<sub>0</sub> = −11.4. By NMR spectroscopic determination of the thermodynamic acidity function from <sup>13</sup>C chemical-shift changes of the signals of unsaturated ketones at infinite dilution in the acid under investigation, Farcasui & Ghenciu (1992) found boron trifluoride monohydrate to be super acidic, with H<sub>0</sub> < −14. The applications of this super acid are numerous, e.g. as a highly effective catalyst for several Friedel–Craft reactions (Yoneda et al., 1969; Oyama et al., 1978; Liu et al., 2003; Prakash et al., 2016, and references therein). The long-time-stable and easy-to-handle solid 1 provides the `super acid BF₃H₂O' in a safe and efficient way.

Although Meerwein & Pannwitz (1934) isolated com­pound 1 (m.p. 401–403 K) and a solid, in which BF₃H₂O is stabilized by 1,8-cineole (m.p. 344–346 K) more than 80 years ago, the crystal structures of these com­pounds are still unknown and the reasons for the unexpected high thermal stability, especially of the dioxane adduct, are still unknown. Generally, there are very rare examples of crystal structures with BF₃H₂O moieties bound to O-donor mol­ecules. The crystal structure of boron trifluoride monohydrate itself has been reported by Mootz & Steffen (1981b), after redetermination of the crystal structure of the dihydrate in the same year (Mootz & Steffen, 1981c; Bang & Carpenter, 1964). Stabilization of the mono- and dihydrate with 18-crown-6 (Bott et al., 1991; Feinberg et al., 1993; Simonov et al., 1995) or of BF₃H₂O with di­cyclo­hexane-18-crown-6 (Fonar et al., 1997) led to three further crystal structures containing the BF₃H₂O moiety and, as the most recent example, stabilization with tri­phenyl­phosphane oxide (Chekhlov, 2005) gave a crystalline 1:2 adduct of BF₃H₂O and (C₆H₅)₃PO.

2. Structural commentary

Compound 1 was found to crystallize in the ortho­rhom­bic space group Pbca with eight formula units in the unit cell and all com­ponents in general positions. Fig. 1 shows the asymmetric unit of the crystal structure, which contains aqua­tri­fluorido­boron and 1,4-dioxane mol­ecular moieties. The dioxane moiety is free of any kind of conformational disorder often recognized in the case of saturated six-membered ring species. Bond lengths, angles and torsion angles defining the chair conformation are in excellent agreement with the expectations for a `fully ordered' dioxane mol­ecule, e.g. found in the structure of uncom­plexed 1,4-dioxane at 153 K (Buschmann et al., 1986). Compared to the mean equivalent isotropic displacement parameter (U<sub>eq</sub>) of the C and O atoms in the 1,4-dioxane moiety [= 0.0427 (6) Å<sup>2</sup>], the mean U<sub>eq</sub> value of B1, O1 and F1 to F3 in the aqua­tri­fluorido­boron moiety [0.0867 (8) Å<sup>2</sup>] is dramatically higher and correction for libration is needed prior to com­parison with the geometries of BF<sub>3</sub>H<sub>2</sub>O moieties in related com­pounds. In Table 1, the uncorrected and corrected (Schomaker & Trueblood, 1968; RG = 0.0241) B—O and B—F bond lengths of 1 are given in com­parison to the bond lengths of BF<sub>3</sub>H<sub>2</sub>O (Mootz & Steffen, 1981c) and BF<sub>3</sub>H<sub>2</sub>O·H<sub>2</sub>O (Mootz & Steffen, 1981b). After correction, the values of 1 agree well with those of the hydrates and those in almost undistorted BF<sub>4</sub><sup>−</sup> as found in Li[BF<sub>4</sub>] at 200 K [1.387 (3)–1.391 (3) Å; Matsumoto et al., 2006] or in H<sub>5</sub>O<sub>2</sub>[BF<sub>4</sub>] [1.381 (2)–1.399 (2) Å; Mootz & Steffen, 1981a]. The bond-valence sum of B1 is as expected taking into account the `uncorrected' nature of the r₀ values used (Brown & Altermatt, 1985). Inter­estingly, for all com­pounds mentioned in Table 1, the B—F bond perpendicular to the plane of the aqua ligand (1: B1—F3; BF₃H₂O: B1—F2; BF₃H₂O·H₂O: B1—F3) is slightly but significantly longer than the other two B—F bonds, probably attributable to a small destabilizing inter­action with the oxygen lone pair. The F—B—O angles in all three com­pounds [1: 105.6 (3)–109.8 (3)°; BF₃H₂O: 105.9 (4)–108.1 (4)°; BF₃H₂O·H₂O: 106.3 (1)–109.8 (1)°] are smaller than the F—B—F angles [1: 109.9 (3)–112.1 (3)°; BF₃H₂O: 111.2 (4)–113.0 (4)°; BF₃H₂O·H₂O: 109.8 (1)–114.0 (1)°]. This fits to the observation (Table 1) that the B—O bond in the BF₃H₂O moiety is relatively weaker than the B—F bonds and the planar geometry of BF₃ is preserved in the aqua com­plex to some extent. Furthermore, for all three com­pounds, the O—B—F angle including the F atom that is approximately in plane with the aqua ligand [1: O1—B1—F1 = 105.6 (3)°; BF₃H₂O: O—B—F3 = 105.9 (4)°; BF₃H₂O·H₂O: O1—B—F2 = 106.3 (1)°] is significantly smaller than the other O—B—F angles. This observation may be attributed to an attractive F⋯H inter­action within the moiety.

Table 1
Selected bond lengths (Å)

Values for BF₃H₂O·C₄H₈O₂, BF₃H₂O (Mootz & Steffen, 1981b) and BF₃H₂O·H₂O (Mootz & Steffen, 1981c) in the left, middle and right columns, respectively; in square brackets are the corresponding bond valences and the valence sums calculated using the Brown formalism {r₀[B—O(F)] = 1.371 (1.281), B = 0.37; Brown & Altermatt, 1985}; in braces are the values corrected for libration (Schomaker & Trueblood, 1968).

B1—O1	1.473 (4) [0.76] {1.528 (4) [0.65]}	1.532 (6) [0.64]	1.512 (2) [0.68]
B1—F1	1.361 (4) [0.81] {1.409 (4) [0.71]}	1.383 (5) [0.76]	1.377 (2) [0.77]
B1—F2	1.332 (4) [0.87] {1.396 (4) [0.73]}	1.399 (5) [0.73]	1.382 (2) [0.76]
B1—F3	1.333 (4) [0.87] {1.410 (4) [0.71]}	1.382 (5) [0.76]	1.390 (2) [0.74]
Σs(B–O,F)	[3.31] {[2.80]}	[2.89]	[2.96]

Figure 1 Diagram of the asymmetric unit of the crystal structure of com­pound 1, displaying the atom-labelling scheme. Anisotropic displacement ellipsoids are drawn at the 40% probability level and the radii of H atoms are chosen arbitrarily. The direction of hydrogen bonding is given by dashed lines.

Although both BF₃H₂O and 1,4-dioxane are liquids at room temperature, adduct 1 is a solid with a remarkably high melting point (401–403 K), mainly resulting from the concatenation of the mol­ecular com­ponents via O—H⋯O hydrogen bonding, as shown in Fig. 2. The high stability might be correlated to the exceptional strength of both O2⋯H1—O1 [O⋯O = 2.534 (3) Å] and O1—H1⋯O3ⁱ [2.539 (3) Å] in the concatenating >O2⋯H1—O1—H2⋯O3ⁱ< unit. Indirectly, this structural feature documents the outstanding acidification of the H₂O mol­ecule bound to BF₃ and reflects the super acid nature of BF₃H₂O. Further details of the hydrogen bonding are given in Table 2. To the best of our knowledge, there is no example of a water ligand bonded to a nonmetal or a metal with the ligand engaged in a hydrogen bond of similar strength (O⋯O < 2.60 Å) to an O atom of a dioxane mol­ecule. In the adduct 18-crown-6·BF₃H₂O (m.p. 345 K), mentioned in §1, the aqua ligand is hydrogen bonded to two O-donor atoms and the O⋯O distances are 2.76 and 2.80 Å (Feinberg et al., 1993). In the structure of BF₃H₂O·H₂O, the nonligating water mol­ecule plays a similar role as bridging species as the dioxane mol­ecule in 1. The O⋯O distances in the characteristic ⋯H—O—H⋯O(H₂)⋯H—O—H⋯ unit are 2.631 and 2.643 Å (Mootz & Steffen, 1981c), i.e. as com­pared to the very strong Brønsted acids fluoro­sulfuric acid [O⋯O = 2.643 (1) Å] or tri­fluoro­methane­sulfonic acid [O⋯O = 2.640 (4) Å] (Bartmann & Mootz, 1990), for example, the hydrogen bonding is of the same strength in the dihydrate and much stronger in the adduct 1.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O2	0.82 (5)	1.72 (5)	2.534 (3)	175 (5)
O1—H2⋯O3^i	0.82 (5)	1.72 (5)	2.539 (3)	170 (5)
Symmetry code: (i) .

Figure 2 The zigzag chain of hydrogen-bonded moieties in the crystal of 1 [view direction [001]; 30% probability ellipsoids; symmetry codes: (A) −x + , y − , z; (B) x, y + 1, z]. Features indicative for the mode of concatenation of the characteristic building blocks by hydrogen bonding are: (i) double hydrogen-bond donor and double (κO,κO′) hydrogen-bond acceptor functionality of the aqua ligand and dioxane moiety, respectively; (ii) almost equal strength of both hydrogen bonds; (iii) an approximatety linear arrangement of the dioxane O atoms and the two neighbouring water O atoms (e.g. O1, O3A, O2A and O1A); (iv) an approximately planar arrangement of B1, F1, O1, O2 and O3.

3. Supra­molecular features

As mentioned before, in the solid of 1 the aqua ligand of the BF₃H₂O moiety acts as a hydrogen-bond donor in two directions, establishing a C₂²(7) graph set (Etter, 1990) (Fig. 2). The propagation vector of the zigzag chain is parallel to the b axis of the unit cell. Note the almost equal strength of both hydrogen bonds. Fig. 3 shows the arrangement of the chains in the solid due to van der Waals inter­actions.

Figure 3 Packing diagram of 1 (view direction [010]) documenting the arrangement of the zigzag chains to flat sheets perpendicular to the c axis. Inspection of the inter­molecular distances gives no evidence for inter­actions stronger than van der Waals forces between the chains.

4. Database survey

A search of the Cambridge Structural Database (CSD; Version 5.40, November 2018 update; Groom et al., 2016) for the BF₃H₂O moiety yielded six structures: the crown ether adducts 18-crown-6 mono­aqua­tri­fluorido­boron toluene semisolvate (CSD refcode SIXFOU; Bott et al. 1991), 18-crown-6 bis­(mono­aqua­tri­fluorido­boron) dihydrate (LEKYIJ; Feinberg et al. 1993, Simonov et al., 1995) and di­cyclo­hexano-18-crown-6 bis­(mono­aqua­tri­fluorido­boron) (NIYGAD; Fonar et al., 1997); the phosphane oxide adduct mono­aqua­tri­fluorido­boron bis­(tri­phenyl­phosphane oxide) (XATWAR; Chekhlov, 2005); two transition-metal coordination com­pounds [CIGVUJ10 (Van Rijn et al., 1987) and UKAJIA (Orain et al., 2010)], containing cocrystallized mono­aqua­tri­fluorido­boron moieties. As mentioned above, in addition to these reports on com­pounds having organic com­ponents, there is the report of Mootz & Steffen (1981b) on the inorganic parent com­pound BF₃H₂O and there are two reports on the dihydrate BF₃H₂O·H₂O (Mootz & Steffen, 1981c; Bang & Carpenter, 1964).

5. NMR spectroscopy

NMR studies of BF₃H₂O·C₄H₈O₂ have not been published so far. Ford & Richards (1956) have shown by low-temperature NMR investigations that, in the solid state, BF₃H₂O and BF₃H₂O·H₂O are not ionized. Diehl (1958) reported the ¹⁹F NMR spectra of BF₃H₂O in aqueous solution. He observed separate broad resonances which he attributed to HBF₃OH, HBF₄, HBF₂(OH)₂ and HBF(OH)₃ in concentrated solutions at 243 K with coalescence of the peaks at higher temperatures. Gillespie & Hartman (1967) have shown by low-temperature (193 K) ¹H and ¹⁹F NMR spetroscopy that BF₃H₂O is formed in dilute solutions in acetone containing both water and BF₃. They found two major peaks in the ¹⁹F NMR spectrum and assigned the low-field peak (−146.05 ppm) to the 1:1 com­plex of BF₃ with acetone and the high-field peak (−146.59 ppm) to BF₃H₂O in acetone. The corresponding ¹H NMR signals were detected by Gillespie & Hartmann at 12.42 ppm as multipletts. In our experiments, in the presence of CD₃CN and 1,4-dioxane and at a significantly higher temperature (297 K), the protons were detected as a broad singlet at 9.41 ppm. Gottlieb et al. (1997) indicated that the influence of temperature on the NMR shift overcom­pensates the influence of the solvent if the basicity of the solvents is similar. Apart from this effect, the high acidity of the oxygen-bonded ¹H nuclei in the title com­pound is depicted by a shift of more than 7 ppm to higher frequencies (H₂O in CD₃CN: s, 2.13 ppm; Fulmer et al. 2010). The chemical shifts of the NMR signals belonging to 1,4-dioxane are close to those of the uncom­plexed com­pound (C₄H₈O₂ in CD₃CN: ¹H: s, 3.60 ppm; ¹³C: 68.5 ppm; Fulmer et al., 2010). Due to the com­parable donor numbers (Gutmann, 1976) of aceto­nitrile (NMR solvent) and 1,4-dioxane, it can be concluded that the acidity of BF₃H₂O is not critically reduced by 1,4-dioxane with respect to its application as a super acid-catalyst.

The NMR sample was investigated in a 5 mm precision glass NMR tube (Wilmad 507) at 297 K in the deuterium-locked mode on a Bruker Avance III 400 MHz spectrometer operating at 400.17, 376.54, 128.23 or 100.62 MHz for ¹H, ¹⁹F, ¹¹B and ¹³C nuclei, respectively. The ¹H NMR and ¹³C chemical shifts were referenced with respect to tetra­methyl­silane yielding the chemical shift for CD₃CN (contains CD₂HCN) as 1.96 ppm and CD₃CN as 118.7 ppm. The ¹⁹F chemical shifts were referenced with respect to CFCl₃ (0 ppm) as external standard. The ¹¹B chemical shifts were referenced with respect to BF₃·(C₂H₅)₂O (0 ppm) as external standard. 68 mg of ground crystals were dissolved in 0.5 ml CD₃CN to prepare the NMR sample: ¹H NMR: 3.71 (s, 8H, C₄H₈O₂), 9.41 (s, 2H, H₂O). ¹⁹F NMR: −148.10 (s, ¹¹BF₃), −148.04 (s, ¹⁰BF₃). ¹¹B NMR: −0.1 (s, ¹¹BF₃). ¹³C NMR: 68.0 [t, ¹J_(C,H) = 189 Hz, C₄H₈O₂].

6. Synthesis and crystallization

All preparations and sample manipulations were carried out in tetra­fluoro­ethyl­ene hexa­fluoro­propyl­ene block copolymer (FEP) vessels. Tetra­fluoro­boric acid solution (50 wt% in water; Fluka Chemicals) was probed for its content of [BF₃OH]⁻ by ¹⁹F NMR spectroscopy. Depending on the qu­antity of these anions, hydro­fluoric acid (48 wt% in water, Sigma–Aldrich) was added. In a typical experiment, to 131.4 g (1.24 mol) of HBF₄/H₂O, 4.53 g (0.11 mol) HF/H₂O was added at 273 K. The mixture was stirred for 15 min, before 430 g of 1,4-dioxane was added at the same temperature. Subsequently, the reaction mixture was heated and the 1,4-dioxane–water azeotrope was distilled off under normal pressure until the boiling point (361 K) began to change. 368 g of azeotrope was removed by the distillation and the residue was a pale-brown solution. This solution was stored in a sealed FEP flask under an atmosphere of dry argon (Argon 5.0). After 1 h, the formation of colourless crystals of 1 started and was allowed to continue for 9 d. The crystals were isolated under an argon atmosphere and washed with hexa­ne/1,4-dioxane (10:1 v/v) three times using Schlenk techniques. 40.7 g (0.23 mol) were collected after drying the almost hexa­gonal colourless crystals in an argon stream (40 min). Compound 1 is stable at room temperature and shows a poor solubility in 1,4-dioxane, but a good solubility in aceto­nitrile.

An elemental analysis was performed with a HEKATECH EA 3000 elemental analyser using Callidus 2E3 software. 1.7 mg of freshly ground crystals were used and a modifier was added to suppress the influence of the high fluorine content. Analysis calculated (%) for C₄H₁₀BF₃O₃: 27.62 C, 5.80 H; found: 27.84 C, 5.87 H.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. The positions of all H atoms were identified via subsequent ΔF syntheses. In the refinement, a riding model was applied, using idealized C—H bond lengths, as well as H—C—H and C—C—H angles. The U_iso values were set at 1.2U_eq(C) for methyl­ene H atoms. For the H atoms of the aqua ligand, positional parameters and U_iso values were refined.

Table 3
Experimental details

Crystal data
Chemical formula	H2BF3O·C4H8O2
Mr	173.93
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	223
a, b, c (Å)	7.6835 (5), 12.929 (1), 15.2326 (13)
V (Å^3)	1513.2 (2)
Z	8
Radiation type	Mo Kα
μ (mm^−1)	0.16
Crystal size (mm)	0.69 × 0.48 × 0.42
Data collection
Diffractometer	Stoe IPDS
Absorption correction	Multi-scan (Blessing, 1989)
Tmin, Tmax	0.673, 0.920
No. of measured, independent and observed [I > 2σ(I)] reflections	19913, 1481, 932
Rint	0.085
(sin θ/λ)max (Å^−1)	0.617
Refinement
R[F^2 > 2σ(F^2)], wR(F^2), S	0.067, 0.138, 1.38
No. of reflections	1481
No. of parameters	108
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å^−3)	0.60, −0.42
Computer programs: X-AREA (Stoe & Cie, 2009), SHELXS (Sheldrick, 2008), SHELXL2014 (Sheldrick, 2015), SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010).

Supporting information

Computing details

Data collection: X-AREA (Stoe & Cie, 2009); cell refinement: X-AREA (Stoe & Cie, 2009); data reduction: X-AREA (Stoe & Cie, 2009); program(s) used to solve structure: SHELXS (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

Aquatrifluoridoboron–1,4-dioxane (1/1)

Crystal data

H2BF3O·C4H8O2	Dx = 1.527 Mg m^−3
Mr = 173.93	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 7579 reflections
a = 7.6835 (5) Å	θ = 2.7–25.9°
b = 12.929 (1) Å	µ = 0.16 mm^−1
c = 15.2326 (13) Å	T = 223 K
V = 1513.2 (2) Å^3	Prisms, colourless
Z = 8	0.69 × 0.48 × 0.42 mm
F(000) = 720

Data collection

Stoe IPDS diffractometer	932 reflections with I > 2σ(I)
Radiation source: sealed tube	Rint = 0.085
φ–scan	θmax = 26.0°, θmin = 2.7°
Absorption correction: multi-scan (Blessing, 1989)	h = −9→9
Tmin = 0.673, Tmax = 0.920	k = −15→15
19913 measured reflections	l = −18→18
1481 independent 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)] = 0.067	Hydrogen site location: difference Fourier map
wR(F^2) = 0.138	H atoms treated by a mixture of independent and constrained refinement
S = 1.38	w = 1/[σ^2(Fo^2) + 1.3744P] where P = (Fo^2 + 2Fc^2)/3
1481 reflections	(Δ/σ)max < 0.001
108 parameters	Δρmax = 0.60 e Å^−3
0 restraints	Δρmin = −0.42 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

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

	x	y	z	Uiso*/Ueq
F1	0.2228 (2)	0.10315 (15)	0.11881 (16)	0.0760 (7)
F2	0.2173 (4)	−0.0515 (2)	0.05362 (17)	0.1020 (9)
F3	0.2125 (4)	−0.0419 (2)	0.19661 (18)	0.1177 (11)
O1	0.4628 (3)	0.0027 (2)	0.1262 (3)	0.0968 (14)
H1	0.516 (6)	0.057 (4)	0.133 (3)	0.108 (17)*
H2	0.515 (6)	−0.053 (4)	0.128 (3)	0.109 (17)*
O2	0.6367 (2)	0.16850 (14)	0.13995 (14)	0.0435 (5)
O3	0.8588 (2)	0.33805 (14)	0.11459 (14)	0.0425 (5)
C1	0.8229 (3)	0.1569 (2)	0.1462 (2)	0.0409 (7)
H11	0.8705	0.1372	0.0889	0.049*
H12	0.8511	0.1021	0.1883	0.049*
C2	0.9021 (4)	0.2567 (2)	0.1756 (2)	0.0435 (8)
H21	0.8585	0.2745	0.2341	0.052*
H22	1.0288	0.2493	0.1792	0.052*
C3	0.6730 (3)	0.3498 (2)	0.1084 (2)	0.0410 (7)
H31	0.6449	0.4046	0.0663	0.049*
H32	0.6256	0.3696	0.1657	0.049*
C4	0.5934 (4)	0.2498 (2)	0.0791 (2)	0.0448 (8)
H41	0.4666	0.2573	0.0756	0.054*
H42	0.6366	0.2319	0.0205	0.054*
B1	0.2712 (4)	0.0021 (3)	0.1232 (3)	0.0412 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
F1	0.0439 (11)	0.0559 (12)	0.128 (2)	0.0169 (9)	0.0004 (13)	0.0007 (12)
F2	0.0930 (18)	0.113 (2)	0.1005 (19)	−0.0035 (16)	−0.0243 (16)	−0.0500 (16)
F3	0.118 (2)	0.141 (2)	0.0942 (19)	−0.035 (2)	0.0120 (17)	0.0528 (18)
O1	0.0264 (12)	0.0294 (13)	0.234 (4)	0.0014 (11)	−0.008 (2)	−0.0130 (18)
O2	0.0295 (10)	0.0357 (10)	0.0652 (14)	−0.0044 (8)	−0.0025 (9)	0.0052 (10)
O3	0.0292 (10)	0.0355 (10)	0.0629 (14)	−0.0033 (8)	0.0010 (10)	0.0012 (10)
C1	0.0308 (16)	0.0374 (15)	0.0544 (18)	0.0027 (12)	−0.0045 (13)	0.0001 (14)
C2	0.0314 (14)	0.0430 (17)	0.056 (2)	0.0027 (13)	−0.0078 (14)	−0.0035 (14)
C3	0.0318 (15)	0.0367 (15)	0.0544 (19)	0.0014 (12)	−0.0022 (13)	0.0054 (14)
C4	0.0348 (15)	0.0442 (17)	0.055 (2)	−0.0003 (13)	−0.0100 (15)	0.0025 (14)
B1	0.0299 (16)	0.0422 (18)	0.052 (2)	−0.0037 (15)	−0.0039 (18)	0.0006 (15)

Geometric parameters (Å, º)

F1—B1	1.361 (4)	C1—C2	1.495 (4)
F2—B1	1.332 (4)	C1—H11	0.9800
F3—B1	1.333 (4)	C1—H12	0.9800
O1—B1	1.473 (4)	C2—H21	0.9800
O1—H1	0.82 (5)	C2—H22	0.9800
O1—H2	0.82 (5)	C3—C4	1.499 (4)
O2—C4	1.440 (3)	C3—H31	0.9800
O2—C1	1.442 (3)	C3—H32	0.9800
O3—C3	1.439 (3)	C4—H41	0.9800
O3—C2	1.442 (3)	C4—H42	0.9800
B1—O1—H1	121 (3)	O3—C3—H31	109.8
B1—O1—H2	119 (3)	C4—C3—H31	109.8
H1—O1—H2	120 (4)	O3—C3—H32	109.8
C4—O2—C1	110.4 (2)	C4—C3—H32	109.8
C3—O3—C2	110.4 (2)	H31—C3—H32	108.2
O2—C1—C2	109.5 (2)	O2—C4—C3	110.1 (2)
O2—C1—H11	109.8	O2—C4—H41	109.6
C2—C1—H11	109.8	C3—C4—H41	109.6
O2—C1—H12	109.8	O2—C4—H42	109.6
C2—C1—H12	109.8	C3—C4—H42	109.6
H11—C1—H12	108.2	H41—C4—H42	108.2
O3—C2—C1	110.1 (2)	F3—B1—F2	109.9 (3)
O3—C2—H21	109.6	F3—B1—F1	111.0 (3)
C1—C2—H21	109.6	F2—B1—F1	112.1 (3)
O3—C2—H22	109.6	F3—B1—O1	108.3 (3)
C1—C2—H22	109.6	F2—B1—O1	109.8 (3)
H21—C2—H22	108.2	F1—B1—O1	105.6 (3)
O3—C3—C4	109.5 (2)
C4—O2—C1—C2	58.7 (3)	C2—O3—C3—C4	−58.7 (3)
C3—O3—C2—C1	59.2 (3)	C1—O2—C4—C3	−58.9 (3)
O2—C1—C2—O3	−58.6 (3)	O3—C3—C4—O2	58.5 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2	0.82 (5)	1.72 (5)	2.534 (3)	175 (5)
O1—H2···O3^i	0.82 (5)	1.72 (5)	2.539 (3)	170 (5)

Symmetry code: (i) −x+3/2, y−1/2, z.