(Fluoroorgano)fluoroboranes and -borates. 7 [1]. The reaction of RFBF2 and K [RFBF3] (RF = perfluorophenyl-, perfluoroalk-1-enyl- and perfluoroalkyl) with xenon difluoride in anhydrous HF

Article abstract of DOI:10.1002/1521-3749(200208)628:8<1853::AID-ZAAC1853>3.0.CO;2-M

The dissolution of (perfluoroorgano)difluoroboranes R_FBF₂ in anhydrous HF (aHF) resulted in equilibrium mixtures of the starting borane and different kinds of acid-base products: [H₂F] [R_FBF₂(F · HF)]

Full text of DOI:10.1002/1521-3749(200208)628:8<1853::AID-ZAAC1853>3.0.CO;2-M

(Fluoroorgano)fluoroboranes and -borates. 7 [1]
The Reaction of RFBF2 and K [RFBF3] (RF ؍ perfluorophenyl-, perfluoroalk-
1-enyl- and perfluoroalkyl) with Xenon Difluoride in Anhydrous HF
H.-J. Frohna,* and V. V. Bardinb
a Duisburg, Fachgebiet Anorganische Chemie, Gerhard-Mercator-Universität
b Novosibirsk/Russia, N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS
Received January 21st, 2002.
Dedicated to Professor Dieter Naumann on the Occasion of his 60th Birthday
Abstract. The dissolution of (perfluoroorgano)difluoroboranes
RFBF2 in anhydrous HF (aHF) resulted in equilibrium mixtures of
the starting borane and different kinds of acid-base products: [H2F]
[RFBF2(F · HF)] (RF ϭ C6F5, cis-C2F5CFϭCF, trans-C4F9CFϭ
CF) or [H2F] [RFBF3] (RF ϭ C6F13). In aHF the aryl compounds
C6F5BF2 and K [C6F5BF3] showed two parallel reactivities with
XeF2: xenodeborylation (formation of the [C6F5Xe]ϩ cation) and
fluorine addition to the aryl group. In aHF perfluoroalk-1-enyldi-
fluoroboranes RFBF2 as well as potassium perfluoroalk-1-enyltri-
fluoroborates K [RFBF3] (RF ϭ cis-C2F5CFϭCF, trans-C4F9CFϭ
CF) underwent only fluorine addition across the carbon-carbon
double bond under the action of XeF2. Potassium perfluorohexyl-
trifluoroborate K [C6F13BF3] did not react with XeF2 in aHF.
Keywords: Fluoroboranes; Fluoroborates; Fluorine addition;
Xenodeborylation; NMR spectroscopy
(Fluororgano)fluorborane und -fluoroborate. 7 [1]
Die Reaktion von RFBF2 und K [RFBF3] (RF ؍ Perfluorphenyl-, Perfluoralk-1-enyl-
und Perfluoralkyl) mit Xenondifluorid in wasserfreiem Fluorwasserstoff
Inhaltsübersicht. Beim Lösen von (Perfluororgano)difluorboranen
RFBF2 in wasserfreier HF (aHF) stellten sich Gleichgewichtsgemi-
sche zwischen den Ausgangsboranen und unterschiedlichen Arten
aktivitäten auf: die Xenodeborylierung (Bildung des [C6F5Xe]ϩ
Kations) und die Fluoraddition an die Arylgruppe. Sowohl bei den
Perfluoroalk-1-enyldifluorboranen RFBF2 als auch bei den Kali-
von Säure-Base Produkten ein: [H2F] [RFBF2(F · HF)] (RF
ϭ
umperfluoralk-1-enyltrifluoroboraten K [RFBF3] (RF ϭ cis-
C6F5, cis-C2F5CFϭCF, trans-C4F9CFϭCF) oder [H2F] [RFBF3]
(RF ϭ C6F13). Die Arylverbindungen C6F5BF2 und K [C6F5BF3]
wiesen in ihren Umsetzungen mit XeF2 in aHF zwei parallele Re-
C2F5CFϭCF, trans-C4F9CFϭCF) erfolgte mit XeF2 in aHF nur
Fluoraddition an die C-C Doppelbindung. Kaliumperfluorhexyl-
trifluoroborat K [C6F13BF3] reagierte nicht mit XeF2 in aHF.
Introduction
resistance towards the hydrodeboration in aHF was ob-
served for perfluoro-trans-hex-1-enyldifluoroborane [2].
The inertness of these perfluorinated trifluoroborates in
aHF prompted us to extend our previous research into the
xenodeborylation of tris(pentafluorophenyl)borane and the
borate Cs[(C6F5)3BF] with xenon difluoride in aHF [3, 4],
and to investigate some prototypes of perfluorinated or-
ganotrifluoroborates and -difluoroboranes in the reaction
with XeF2 in aHF.
Recent studies of the reaction of potassium organotrifluo-
roborates K [RBF3] with protic acids of different strength
showed that the salts with R ϭ alkyl, alk-1-enyl, phenyl and
the fluorine-containing alk-1-enyl group RЈCFϭCF (RЈ ϭ
F, Cl, C3F7O, trans-C4H9) underwent hydrodeboration
when treated with CH3CO2H, CF3CO2H or aqueous HF at
20 Ϫ 50 °C. When R was a perfluorinated alkyl, alk-1-enyl
or phenyl group, the salts K [RBF3] did not react even with
the strong acid, aHF, at room temperature [1]. A similar
Results and Discussion
Solvolysis of (perfluoroorgano)difluoroboranes in aHF
* Prof. Dr. H.-J. Frohn
Fachgebiet Anorganische Chemie der Universität
Lotharstr. 1
D-47048 Duisburg
Fax: (ϩ49)2 03-379 22 31
e-mail: frohn@uni-duisburg.de
In contrast to boron trifluoride, perfluorohexyldifluorobor-
ane 1, perfluoro-trans-hex-1-enyldifluoroborane 2, per-
fluoro-cis-but-1-enyldifluoroborane
3 and pentafluoro-
phenyldifluoroborane 4 were well soluble in aHF at room
temperature, but below Ϫ20 to Ϫ30 °C their solubility was
Z. Anorg. Allg. Chem. 2002, 628, 1853Ϫ1856  WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 0044Ϫ2313/02/628/1853Ϫ1856 $ 20.00ϩ.50/0
1853

H. -J. Frohn, V. V. Bardin
significantly decreased and white suspensions were formed.
Reactions of RFBF2 with XeF2 in aHF (“acidified”
HF)
Previously we have shown that the reaction of pentafluoro-
phenyldifluoroborane with xenon difluoride in CH2Cl2 gave
pentafluorophenylxenon(II) tetrafluoroborate in high yield
[8]. However, in aHF the formation of a mixture of perflu-
orinated phenyl- and cyclohexa-1,4-dienylxenonium cat-
ions, cyclohexa-1,4-dienyltrifluoroborate and tetrafluoro-
borate anions was found after the quantitative conversion
of the reactants (19F NMR). The observed excess of anions
over cations can be explained by the presence of [H2F]ϩ
(eq. (1b). Fast fluoride exchange did not allow to detect the
19F NMR signal of [H2F]ϩ.
As strong Lewis acids, the boranes RFBF2 1 Ϫ 4 inter-
acted with the fluoride donor aHF to a different extent. For
instance, the 19F NMR spectrum of the alkyldifluoroborane
1
in aHF (Ϫ20 °C) contained a BFx resonance at
Ϫ150.60 ppm with a relative intensity equal to that of the
trifluoromethyl group (δ ϭ Ϫ80.71) of the perfluorinated
hexyl chain. Ϫ150.60 ppm is a characteristic position of
BF3 groups [5]. However, the 19F NMR spectra of the less
acidic alkenyl and aryl difluoroboranes 2 Ϫ 4 showed no
resonances of the boron-bonded fluorine atoms whereas the
19F NMR spectra of CF2ϭCFBF2 and ClCFϭCFBF2 in
aHF (Ϫ40 °C) did not differ from the spectra in CH2Cl2
[2]. This means that the less acidic alkenylboranes RFBF2
(RF ϭ CF2ϭCF, CClFϭCF) did not abstract the fluoride
ion from aHF, while the more acidic boranes (RF ϭ cis-
C2F5, trans-C4F9, C6F5) partially abstracted fluoride. In the
case of the most acidic alkylborane 1 the equilibrium was
practically completely shifted to the trifluoroborate anion
(eqs. (1a) and (1b)).
The same products were recently obtained by the reaction
of tris(pentafluorophenyl)borane with XeF2 in aHF, but a
direct quantitative comparison is difficult because of the
heterogeneous nature of that reaction [3]. But in both cases
the pentafluorophenyl-containing boranes C6F5BX2 (X ϭ
F, C6F5) underwent both xenodeborylation and fluorine ad-
dition to the pentafluorophenyl ring.
In contrast, no organoxenon compounds were formed in
the reaction of xenon difluoride with the alkenylboranes 2
and 3. Essentially fluorine addition across the carbon-car-
bon double bond took place at Ϫ30 to Ϫ20 °C.
In order to understand the reactivity of RFBF2 towards
XeF2 it is important to emphasize two main aspects of the
system RFBF2/aHF: (a) the significant increase in acidity
of the media after dissolution of the boranes RFBF2 in aHF
(“acidified” HF) and (b) the presence of the trifluoroborate
anions [RFBF3]Ϫ or the donor-acceptor complexes
[RFBF2(F · HF)]Ϫ in these solutions. Both aspects play a
significant role in the reactions with xenon difluoride. In-
deed, the high Brønsted acidity of the media increases the
contribution of the polarized form of XeF2 (borderline for-
mulation: [FXe]ϩ) which is
a very strong oxidant
{EA([FXe]ϩ) ϭ 10.6 Ϫ 10.9 eV [6, 7]}.
Reactions of K [RFBF3] with XeF2 in aHF (“basic”
HF)
The dissolution of organotrifluoroborates in aHF results
primarily in the protonation of the fluorine atoms bonded
to boron. This leads to a fluoroborate/fluoroborane equilib-
rium and a decrease in the acidity of HF. The transform-
ation of the organotrifluoroborate into the corresponding
organodifluoroborane is accompanied by the reduction of
the coordination number at boron [1] and was expected to
favour the xenodeborylation reaction relative to the oxidat-
ive addition of fluorine. Indeed, the reaction of potassium
pentafluorophenyltrifluoroborate 5 with xenon difluoride
in aHF gave predominantly pentafluorophenylxenon(II)
Furthermore, the products of the solvolysis of RFBF2 -
[RFBF3]Ϫ or [RFBF2(F · HF)]Ϫ are more electron-rich spec-
ies than the parent organodifluoroboranes and can be more
readily oxidized. Consequently, the oxidation (addition of
fluorine to CϭC double bonds) should be expected as a
competitive reaction route to xenodeborylation when the
unsaturated perfluoroorganodifluoroboranes are allowed to
react with xenon difluoride in aHF.
1854
Z. Anorg. Allg. Chem. 2002, 628, 1853Ϫ1856

(Fluoroorgano)fluoroboranes and -borates. 7
tetrafluoroborate. The oxidative fluorination of the
[C6F5BF3]Ϫ anion occurred to a minor extent.
It should be noted that the treatment of Cs[(C6F5)3BF]
with XeF2 (3 equiv.) in aHF (20 °C, 15 minutes) yielded a
similar ratio of xenodeborylation to oxidative fluorine ad-
dition [3].
However, a decrease of the acidity of the media did not
influence the reaction route of potassium perfluoroalk-1-
enyltrifluoroborates with xenon difluoride. Salts 6, 7 and 8
were quickly converted at Ϫ30 °C into the potassium per-
fluoroalkyltrifluoroborates 9, 10 and 11, respectively. The
additional presence of KF (1 equiv.) reduced the reaction
rate of the borate 7 with XeF2 but had no effect on the
course of the reaction.
The second reason is the higher reducing potential of
fluoroalkenyl or aryl groups in organotrifluoroborate
anions, compared to that of the corresponding organodi-
fluoroboranes. Both aspects are important for the reaction
of perfluoroalk-1-enyldifluoroboranes with XeF2 in aHF
and explain the fast oxidative addition of fluorine.
Experimental
NMR spectra were recorded on Bruker spectrometers, WP 80 SY
(19F at 75.39 MHz), AVANCE 300 (11B at 96.29 MHz, 19F at
282.40 MHz). The chemical shifts are referenced to BF3 · OEt2/
CDCl3 15 % v/v (11B) and CFCl3 (19F) (C6F6 as a secondary refer-
ence, δ ϭ Ϫ162.9). Superscripts with the number of the related
carbon atom are used for the designation of the fluorine atoms of
fluoroorganic chains. The composition of the reaction mixtures and
the yields of products were determined by 19F NMR spectroscopy.
The IR spectra were recorded on a Bruker Vector 22 FT-spec-
trometer on KBr pellets. The elemental analysis was performed in
the N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry
(Novosibirsk, Russia).
Hydrogen fluoride was dried by electrolysis (stainless steel cell, Ni-
electrodes). All manipulations with anhydrous HF were performed
in FEP (block copolymer of tetrafluoroethylene and hexafluoro-
propylene) equipment.
The potassium (perfluoroorgano)trifluoroborates 5 [9], 6 Ϫ 8 [10],
11 [11] and (perfluoroorgano)difluoroboranes 1, 2, 3, 4 [2, 9, 11]
were prepared using literature procedures.
Potassium perfluorohexyltrifluoroborate 11 did not react
with XeF2 in aHF at room temperature within 1.5 hours.
Within the framework of the proposed mechanism of the
xenodeborylation [4] the inertness of potassium perfluoro-
alkyltrifluoroborates towards xenon difluoride in aHF is ex-
plained by the negligible equilibrium concentration of per-
fluoroalkyldifluoroborane which is necessary for the realiz-
ation of the F-Xe · F · F2BR transition state [4]. This is in
agreement with the earlier explanation of the inertness of
[Me4N] [(C6F5)4B] towards XeF2 in aHF solution [3].
The oxidative addition of fluorine with XeF2 in aHF to
the CϭC bond of perfluoroalk-1-enyldifluoroboranes as
well as potassium perfluoroalk-1-enyltrifluoroborates oc-
curred for two essential reasons. First, the highly acidic me-
dia cause a dramatic increase of the oxidation potential of
xenon difluoride. The role of the [FXe]ϩ cation or a related
polarized form of XeF2 in the oxidative fluorination of
(C6F5)3B in aHF was discussed in [3]. This aspect was
underlined by the model reaction of XeF2 with hexafluoro-
benzene. C6F6 did not react with XeF2 in aHF in the pres-
ence of K [HF2] (“basic” HF) while in neat anhydrous hy-
drogen fluoride the fluorine addition proceeded within a
few minutes.
Solvolysis of (perfluoroorgano)difluoroboranes in aHF.
The solution of C6F5BF2 (0.32 mmol) in CH2Cl2 (1.5 ml) was
stirred with aHF (1 ml) at Ϫ20 °C. The upper acidic phase was
decanted into a pre-cooled FEP trap. The solutions of cis-
C2F5CFϭCFBF2
(0.42 mmol),
trans-C4F9CFϭCFBF2
(0.22 mmol) and C6F13BF2 (0.12 mmol) in aHF (0.5 Ϫ 1 ml) were
prepared in a similar manner. After recording the 19F NMR spectra
these solutions were used for the following reactions with xenon di-
fluoride.
C6F5BF2. 19F NMR (aHF, Ϫ20 °C): δ ϭ Ϫ131.88 (2F, o-F), Ϫ149.54 (t,
3J(p-F,m-F) 18 Hz, 1F, p-F), Ϫ162.05 (2F,m-F); the resonance of the boron-
bonded fluorine atoms was not observed.
cis-C2F5CFϭCFBF2. 19F NMR (aHF, Ϫ20 °C): δ ϭ Ϫ83.18 (3F, F4),
Ϫ118.43 (2F, F3), Ϫ126.15 (1F, F2), Ϫ145.64 (1F, F1); the resonance of the
boron-bonded fluorine atoms was not observed.
trans-C4F9CFϭCFBF2. 19F NMR (aHF, Ϫ20 °C): δ ϭ Ϫ79.53 (3F, F6),
Ϫ115.83 (2F, F3), Ϫ122.83 and Ϫ124.50 (2 CF2), Ϫ159.83 (d, 1F, F1),
Ϫ169.17 (d, 3J(F2,F1) 132 Hz, 1F, F2); the resonance of boron-bonded fluor-
ine atoms was not observed (see also [2]).
C6F13BF2. 19F NMR (aHF, Ϫ20 °C): δ ϭ Ϫ80.71 (3F, F6), Ϫ121.64 (2 CF2),
Ϫ122.62 (CF2), Ϫ125.57 (2F, F5), Ϫ133.54 (2F, F1), Ϫ150.60 (3F, unresolved
signal, BF3).
Z. Anorg. Allg. Chem. 2002, 628, 1853Ϫ1856
1855

H. -J. Frohn, V. V. Bardin
(19F NMR) and after work up K [C4F9BF3] (149 mg, 93 % yield)
was isolated.
C4BF12K (325,93): calculated C 14.74, F 69.95; found C 14.7, F
69.4 %.
Reactions of (perfluoroorgano)difluoroboranes with
xenon difluoride in aHF
Solid xenon difluoride (total amount 0.61 mmol) was added in
small portions at Ϫ30 °C to the stirred solution of cis-C2F5CFϭ
CFBF2 in aHF (see above). Evolution of xenon took place immedi-
ately. After addition of K [HF2] in excess the solution was diluted
with water, neutralized with K2CO3, and extracted with MeCN.
The 19F NMR spectrum showed the presence of K [C4F9BF3] (70
Ϫ 75 % yield), unreacted K [cis-C2F5CFϭCFBF3] (5 Ϫ 7 %) and
an unknown product (15 Ϫ 20 %).
Similar treatment of the solution of trans-C4F9CFϭCFBF2 in aHF
with solid XeF2 (1 equiv.) at Ϫ20 °C led to the quantitative forma-
tion of [H2F] [C6F13BF3] (19F NMR).
The reaction of C6F5BF2 (0.17 mmol) in aHF (1 ml) with solid
XeF2 (0.17 mmol) at Ϫ30 °C caused the immediate evolution of
xenon and after 5 Ϫ 10 minutes the 19F NMR spectrum displayed
the resonances of [C6F5Xe]ϩ, [1,4-C6F7Xe]ϩ, [1,4-C6F7BF3]Ϫ and
[BF4]Ϫ (molar ratio 6 : 2 : 10 : 13), besides the resonance of aHF
(Ϫ190 ppm). No signals of C6F5BF2 and XeF2 were still observed.
19F NMR (CD3CN): δ ϭ Ϫ80.37 (tt, 4J(F4,F2) 9.9 Hz, 3J(F4,F3) 3.8 Hz, 3F,
F4), Ϫ123.60 (m, 2F, F2), Ϫ125.38 (m, 2F, F3), Ϫ132.90 (m, 2F, F1), Ϫ151.96
(q, 1J(F,B) 40 Hz, 3F, BF3). 11B NMR (CD3CN): δ ϭ Ϫ0.68 (qt, 1J(B,F)
41 Hz, 2J(B,F1) 19 Hz).
IR ν (cm-1): 1361 w, 1315 m, 1272 m, 1221 vs, 1194 s, 1151 s, 1133 vs, 1067 s,
¯
1038 vs, 988 m, 975 m, 854 w, 823 w, 797 m, 736 s, 694 m, 656 w, 619 w,
599 w, 569 w, 534 w.
Xenon difluoride (290 mg, 1.71 mmol) was added to the stirred sus-
pension of K [C6F13BF3] (700 mg, 1.64 mmol) in aHF (10 ml) at
Ϫ30 °C. The reaction mixture was stirred for 2 h at Ϫ30 °C and
for 1.5 h at 20 °C. The resulting solution contained unreacted K
[C6F13BF3] (19F NMR) (the resonance of XeF2 interfered with the
broad signal of aHF at Ϫ192 ppm).
Reaction of hexafluorobenzene with XeF2 in aHF of
different acidity
Xenon difluoride (48 mg, 0.28 mmol) was added in portions to the
stirred mixture of C6F6 (53 mg, 0.28 mmol) in aHF (0.2 ml) at
Ϫ15 °C. After each addition the reaction mixture was kept for sev-
eral minutes at 20 °C until the evolution of xenon was completed.
Octafluoro-1,4-cyclohexadiene was obtained in quantitative yield
(19F NMR).
Xenon difluoride (53 mg, 0.31 mmol) was added in one portion to
the stirred mixture of C6F6 (53 mg, 0.28 mmol) and K [HF2]
(71 mg, 0.91 mmol) in aHF (0.2 ml) at Ϫ15 °C. The mixture was
kept at 20 °C for 30 minutes but there was no sign of a reaction.
After 13 h only traces of octafluoro-1,4-cyclohexadiene were de-
tected, besides unreacted C6F6 (19F NMR).
Reaction of potassium (perfluoroorgano)trifluoro-
borates with xenon difluoride in aHF
K [C6F5BF3] (168 mg, 0.61 mmol) was dissolved in aHF (1.5 ml)
at Ϫ30 °C and the cold (0 °C) solution of XeF2 (119 mg,
0.70 mmol) in aHF (0.5 ml) was added. Gas evolution occurred
and a yellow solution was formed. The reaction mixture was stirred
at Ϫ30 °C for 10 min. and then 15 min. at 20 °C. The 19F NMR
spectrum (0 °C) showed the absence of XeF2 and K [C6F5BF3] and
the formation of [C6F5Xe]ϩ, [BF4]Ϫ, [1,4-C6F7BF3]Ϫ (molar ratio
15 : 15 : 6) and C6F6 (traces), besides the resonance of aHF
(Ϫ190 ppm).
K [CF2ϭCFBF3] (140 mg, 0.74 mmol) was suspended in aHF
(2 ml) at Ϫ60 °C and solid XeF2 (132 mg, 0.78 mmol) was added
with stirring. Slow warming to Ϫ30 °C was accompanied by the
evolution of gas which was completed within 20 min. Evaporation
of aHF in vacuum at 20 °C gave K [C2F5BF3] (140 mg, 84 % yield).
C2BF8K (225,92): calculated C 10.63, F 67.28; found C 10.5, F
66.6 %.
We gratefully acknowledge financial support by the Deutsche For-
schungsgemeinschaft, the Russian Foundation for Basic Research,
and the Fonds der Chemischen Industrie.
References
[1] V. V. Bardin, S. G. Idemskaya, H.-J. Frohn, Z. Anorg. Allg.
Chem. 2002, 628, 883.
19F NMR (CH3CN): δ ϭ Ϫ83.08 (q, 4J(F2,BF3) 4.8 Hz, 3F, F2), Ϫ135.92 (q,
2J(F1,B) 19.6 Hz, 2F, F1), Ϫ152.91 (q, 1J(F,B) 41 Hz, 3F, BF3). 11B NMR
(CH3CN): δ ϭ Ϫ0.74 (qt, 1J(B,F) 41 Hz, 2J(B,F1) 20 Hz).
[2] H.-J. Frohn, V. V. Bardin, J. Organomet. Chem. 2001, 631, 54.
[3] H.-J. Frohn, Th. Schroer, J. Fluorine Chem. 2001, 112, 259.
[4] H.-J. Frohn, V. V. Bardin, Organometallics 2001, 20, 4750.
[5] D. J. Brauer, H. Bürger, Y. Chebude, G. Pawelke, Inorg. Chem.
1999, 38, 3972.
[6] F. Sladky, P. Bulliner, N. Bartlett, J. Chem. Soc. (A) 1969,
2179.
[7] G. J. Schrobilgen, Lewis Acid Properties of Fluorinated Nobel
Gas Cations. In Synthetic Fluorine Chemistry. Olah, G. A.;
Chambers, R. D.; Prakash, G. K. S., Eds.; Wiley: New York,
1992, pp 1 Ϫ 30.
[8] H.-J. Frohn, H. Franke, V. V. Bardin, Z. Naturforsch. 1999,
54b, 1495.
[9] H.-J. Frohn, H. Franke, P. Fritzen, V. V. Bardin, J. Organomet.
Chem. 2000, 598, 127.
[10] H.-J. Frohn, V. V. Bardin, Z. Anorg. Allg. Chem. 2001, 627,
2499.
[11] H.-J. Frohn, V. V. Bardin, Z. Anorg. Allg. Chem. 2001, 627, 15.
Similarly, the reaction of K [trans-C4F9CFϭCFBF3] (143 mg,
0.36 mmol) with XeF2 (72 mg, 0.42 mmol) in aHF (2 ml) at Ϫ30 °C
resulted in K [C6F13BF3] which was isolated in 95 % yield (145 mg).
The reaction of K [cis-C2F5CFϭCFBF3] (120 mg, 0.41 mmol) with
XeF2 (83 mg, 0.49 mmol) in aHF (2 ml) at Ϫ30 °C yielded K
[C4F9BF3] (116 mg, 87 %).
K [cis-C2F5CFϭCFBF3] (143 mg, 0.49 mmol) and KF (42 mg,
0.53 mmol) were dissolved in aHF (1.5 ml) at Ϫ30 °C and the cold
(0 °C) solution of XeF2 (93 mg, 0.55 mmol) in aHF (0.5 ml) was
added with stirring. After 15 min. the 19F NMR spectrum (Ϫ30 °C)
revealed the resonances of the anions [cis-C2F5CFϭCFBF3]Ϫ [δ ϭ
Ϫ82.81 (3F, F4), Ϫ119.14 (2F, F3), Ϫ139.57 (4F, F1 and BF3),
Ϫ148.00 (1F, F2)], [C4F9BF3]Ϫ [δ ϭ Ϫ79.43 (3F, F4), Ϫ122.34 (2F,
F2), Ϫ124.36 (2F, F3), Ϫ132.45 (2F, F1), Ϫ148.47 (3F, BF3)], and
XeF2 (Ϫ195.90 ppm) (molar ratio 1 : 1 : 1.2). The solution was
stirred at 20 °C for 1.5 h until the fluorine addition was completed
1856
Z. Anorg. Allg. Chem. 2002, 628, 1853Ϫ1856