Bis(perfluoroorganyl)bromonium salts [(RF)2Br]Y (RF = aryl, alkenyl, and alkynyl)

Article abstract of DOI:10.1016/j.jfluchem.2010.06.006

Bromonium salts [(R_F)₂Br]Y with perfluorinated groups R_FC₆F₅, CF₃CFCF, C ₂F₅CFCF, and CF₃C≡C were isolated from reactions of BrF₃ with R_FBF₂ in weakly coordinating solvents (wcs) like CF₃CH₂CHF₂ (PFP) or CF₃CH₂CF₂CH₃ (PFB) in 30-90% yields. C₆F₅BF₂ formed independent of the stoichiometry only [(C₆F₅)₂Br][BF ₄]. 1:2 reactions of BrF₃ and silanes C₆F ₅SiY₃ (Y = F, Me) ended with different products - C ₆F₅BrF₂ or [(C₆F₅) ₂Br][SiF₅] - as pure individuals, depending on Y and on the reaction temperature (Y = F). With C₆F₅SiF₃ at ≥-30 °C [(C₆F₅)₂Br][SiF₅] resulted in 92% yield whereas the reaction with less Lewis acidic C ₆F₅SiMe₃ only led to C₆F ₅BrF₂ (58%). The interaction of K[C₆F ₅BF₃] with BrF₃ or [BrF₂][SbF ₆] in anhydrous HF gave [(C₆F₅) ₂Br][SbF₆]. Attempts to obtain a bis(perfluoroalkyl) bromonium salt by reactions of C₆F₁₃BF₂ with BrF₃ or of K[C₆F₁₃BF₃] with [BrF₂][SbF₆] failed. The 3:2 reactions of BrF₃ with (C₆F₅)₃B in CH₂Cl₂ gave [(C₆F₅)₂Br][(C₆F ₅)_nBF_4-n] salts (n = 0-3). The mixture of anions could be converted to pure [BF₄]^- salts by treatment with BF₃·base.

Full text of DOI:10.1016/j.jfluchem.2010.06.006

Journal of Fluorine Chemistry 131 (2010) 922–932
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Bis(perfluoroorganyl)bromonium salts [(RF)2Br]Y (RF = aryl, alkenyl, and alkynyl)
a
a
b
Hermann-Josef Frohn a, , Matthias Giesen , Dirk Welting , Vadim V. Bardin
*
a Inorganic Chemistry, University of Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg, Germany
b N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, Acad. Lavrentjev Ave. 9, 630090 Novosibirsk, Russia
A R T I C L E I N F O
A B S T R A C T
Article history:
Bromonium salts [(RF)2Br]Y with perfluorinated groups RF55C6F5, CF3CF55CF, C2F5CF55CF, and CF3CꢄC
were isolated from reactions of BrF3 with RFBF2 in weakly coordinating solvents (wcs) like CF3CH2CHF2
(PFP) or CF3CH2CF2CH3 (PFB) in 30–90% yields. C6F5BF2 formed independent of the stoichiometry only
[(C6F5)2Br][BF4]. 1:2 reactions of BrF3 and silanes C6F5SiY3 (Y = F, Me) ended with different products –
C6F5BrF2 or [(C6F5)2Br][SiF5] – as pure individuals, depending on Y and on the reaction temperature
(Y = F). With C6F5SiF3 at ꢅꢁ30 8C [(C6F5)2Br][SiF5] resulted in 92% yield whereas the reaction with less
Lewis acidic C6F5SiMe3 only led to C6F5BrF2 (58%). The interaction of K[C6F5BF3] with BrF3 or [BrF2][SbF6]
in anhydrous HF gave [(C6F5)2Br][SbF6]. Attempts to obtain a bis(perfluoroalkyl)bromonium salt by
reactions of C6F13BF2 with BrF3 or of K[C6F13BF3] with [BrF2][SbF6] failed. The 3:2 reactions of BrF3 with
(C6F5)3B in CH2Cl2 gave [(C6F5)2Br][(C6F5)nBF4ꢁn] salts (n = 0–3). The mixture of anions could be
converted to pure [BF4]ꢁ salts by treatment with BF3ꢀbase.
Received 6 May 2010
Received in revised form 8 June 2010
Accepted 9 June 2010
Available online 17 June 2010
Keywords:
Bromine trifluoride
Perfluoroorganylbromine difluorides
Bis(perfluoroorganyl)bromonium salts
Difluorobromonium salts
Perfluoroorganylboron difluoride
Tris(pentafluorophenyl)borane
Pentafluorophenyltrifluorosilane
Pentafluorophenyltrimethylsilane
Perfluoroorganyltrifluoroborate salts
NMR spectroscopy
ß 2010 Elsevier B.V. All rights reserved.
1. Introduction
An alternative route to symmetric bromonium salts consists in
the electrophilic alkylation of alkyl bromides with carbocations
The first preparation of a bis(organyl)bromonium salt was
reported in 1955 by Nesmeyanov. He obtained a bis(phenyl)bro-
monium salt by the decomposition of benzenediazonium tetra-
fluoroborate in bromobenzene [1]. Improvement allowed to
increase the yield of isolated bis(phenyl)bromonium tetrafluor-
oborate to 6–7% [2]. Further progress was achieved by reactions of
BrF3 with benzenes, C6H5R [3], bis(aryl)mercury, Ar2Hg [4], and
tetrakis(aryl)stannanes, Ar4Sn [5] (Eqs. (1)–(3)).
[6,7] (Eq. (4)).
SO2;ꢁ70 ꢂ
C
AlkBr þ AlkF þ SbF5 ꢁ! ½ðAlkÞ2ÞBrꢃ½SbF6ꢃ
(4)
Alk ¼ Me; Et; i-Pr; cyclo-C3H5
All methods compiled before are not adequate for the prepara-
tion of bis(perfluoroorganyl)bromonium salts, [(RF)2Br]Y, where RF
represent perfluorinated alkyl, alkenyl, alkynyl, and aryl groups. For
example, the reaction of C6F5H with BrF3 in weakly coordinating
solvents (CCl2FCClF2, 0 8C [8], SO2ClF, ꢁ80 8C [9,10]), or with [BrF2]Y
(Y = BF4, SbF6) (SO2ClF, ꢁ80 8C [9,10]) and with BrF3 or [BrF2][SbF6]
in a highly acidic solvent (aHF, ꢁ70 8C) led to C6F5Br and
polyfluorinated 1-X-cyclohexa-1,4-dienes (X = H, Br). In contrast
to the successful electrophilic alkylation of RBr with CH3F-SbF5 in
SO2 to methylbromonium salts, [CH3(R)Br][SbF6], the attempted
methylation of 1,4-dibromotetrafluorobenzene failed [7]. Nesmeya-
nov reported the inertness of BrF3 towards (C6F5)2Hg [4] and
(C6F5)4Sn [5] (CH2Cl2 + 2CH3CN + 3BF3ꢀOEt2) at ꢁ78 to ꢁ25 8C and
the decomposition of the solvent and the organometallic com-
pounds at higher temperature. Later the formation of C6F5BrF2 was
shown besides C6F5R (R = H, F, Br, C6F5) when BrF3 was reacted with
(C6F5)2M (M = Hg, Cd, Zn) in the absence of a Lewis acid (CH2Cl2 + 2
CH3CN, ꢁ78 to ꢁ25 8C) and no bromonium salts, [(C6F5)2Br]Y, were
found under those non-acidic conditions [11].
CH2Cl2;ꢁ70 ꢂ
C
BrF3 þ 2C6H5R þ BF3 ꢀ OEt2
ꢁ!
½ðRC6H4Þ2Brꢃ½BF4ꢃ þ ꢀ ꢀ ꢀ
(1)
R ¼ Hð50%Þ; 4-Fð41%Þ; 4-Clð13%Þ; 3-MeOCðOÞð20%Þ;
3-NO2ð6%Þ; 3-CF3ð49%Þ
CH3CN;CH2Cl2;ꢁ70 ꢂ
C
ꢁ!
BrF3 þ 2ðRC6H4Þ2Hg þ BF3 ꢀ OEt2
½ðRC6H4Þ2Brꢃ½BF4ꢃ þ ꢀ ꢀ ꢀ
R ¼ H; 4-F; 4-Cl; 3-EtOCðOÞ; 4-CH3ð16ꢁ96%Þ
(2)
CH3CN;CH2Cl2;ꢁ70 ꢂ
C
ꢁ!
BrF3 þ ðRC6H4Þ4Sn þ BF3 ꢀ OEt2
R ¼ H; 4-CH3O; 4-CH3ð52ꢁ96%Þ
½ðRC6H4Þ2Brꢃ½BF4ꢃ þ ꢀ ꢀ ꢀ
(3)
* Corresponding author. Tel.: +49 203 379 3310; fax: +49 203 379 2231.
E-mail address: h-j.frohn@uni-due.de (H.-J. Frohn).
0022-1139/$ – see front matter ß 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2010.06.006

H.-J. Frohn et al. / Journal of Fluorine Chemistry 131 (2010) 922–932
923
Up to now the bis(pentafluorophenyl)bromonium salts,
[(C6F5)2Br]Y (Y = BF4, AsF6, SbF6, PF6), are the only reported
bromonium compounds bearing perfluorinated organic groups
at bromine(III) (see review [12]). Salt [(C6F5)2Br][AsF6] was the
product of pentafluorophenylation of C6F5Br with molten
[C6F5Xe][AsF6] but only in 6% yield [13]. [(C6F5)2Br][BF4] was
obtained by the reaction of C6F5BrF2 with bis(pentafluorophe-
nyl)cadmium and BF3ꢀNCCH3 in a satisfactory yield and in excellent
yield from BrF3 and (C6F5)2BF [11] (Eqs. (5) and (6)).
Hexafluorometallates [(C6F5)2Br][EF6] were prepared from the
parent tetrafluoroborate by metathesis with K[PF6] (E = P) or by
displacement of BF3 using stronger Lewis acids like AsF5 or SbF5
[11] (E = As, Sb).
in the 11B NMR spectrum. No changes in the 11B and 19F NMR
spectra occurred at 24 8C over a period of 24 h. Decantation of the
solvent phase from the heavy density phase at ꢁ20 8C and re-
dissolution of the latter in a fresh portion of PFB resulted only in a
small shift of the NMR resonance. We assume that the above
mentioned 19F and 11B signal belong to an adduct, formally
described as ‘‘BrF3ꢀBF3’’ with a highly polarized bromine-fluorine
bond. Noteworthy, that Cyr and Brownstein [16] presented the 19
F
NMR spectrum of BrF3 and BF3 (1:1) in SO2ClF at ꢁ120 8C, which
consisted of three resonances at ꢁ60.6, ꢁ70.5, and ꢁ127.7 ppm in
the integral ratio 1:1:4. The 19F NMR spectrum of an equimolar
solution of BrF3 and AsF5 in SO2ClF at ꢁ120 8C also contained three
resonances at ꢁ61.0, ꢁ68.3 and ꢁ56.3 (As-F) ppm. With an excess
of either BrF3 or LA (LA = BF3, AsF5) there was a rapid exchange
between all fluorine atoms over the entire temperature range
(ꢁ120 to 25 8C). This picture was interpreted to arise from a
structure like F-Br(F)ꢀ ꢀ ꢀF-LA with two magnetically non-equivalent
fluorine atoms bonded to the bromine atom. In case of individual
[BrF2][SbF6] we were not able to measure its 19F NMR spectrum in
SO2ClF because of the too low solubility even at 24 8C. However,
this salt is well soluble in aHF (>163 mg (0.46 mmol) per mL at
0 8C). The 19F NMR spectrum of [BrF2][SbF6] in aHF at ꢁ40 8C
consisted of a singlet at ꢁ73.5 ppm (Dn1/2 = 106 Hz) ([BrF2]+), very
broad Sb-F resonances in the range of ca. ꢁ120 to ꢁ125 ppm and
the signal of the solvent at ꢁ190 ppm. Acidification of the solution
with SbF5 (fivefold molar excess) did not really affect the chemical
CdðC6F5Þ2 þ 2C6F5BrF2 þ 2BF3 ꢀ NCCH3CH2Clꢁ2=!< MeCN ½ðC6F5Þ2Brꢃ½BF4ꢃ
ꢁ78 to 20 ꢂC
20ꢁ30%
(5)
CH2Cl2= < MeCNꢆ
ꢁ78 to 20 ꢂC;1 h
ðC6F5Þ2BF þ BrF3
ꢁ!
½ðC6F5Þ2Brꢃ½BF4ꢃ
(6)
80ꢁ100%
*MeCN was added to increase the solubility of BrF3 at low
temperatures.
Based on our experience in the preparation of polyfluoroorga-
nylxenonium salts [14,15] and polyfluoroorgano derivatives of
polyvalent iodine and bromine [12], we studied selected promising
routes to bis(perfluoroorganyl)bromonium salts. One was based on
the direct introduction of two perfluoroorganyl groups into BrF3 or
[BrF2]+ with different types of organoboron compounds (RFBF2,
(C6F5)3B, M[RFBF3]). The second used pentafluorophenyl silanes,
C6F5SiF3 and C6F5SiMe3, of different Lewis acidity.
shift of the [BrF2]+ cation (
ture caused reversible broadening of this resonance from Dn1/2
d
(F) = ꢁ72.9). Variation of the tempera-
=
47–53 Hz (ꢁ40 8C) to ꢇ240 Hz (ꢁ20 8C) and >1000 Hz (0 8C). For
comparison, the 19F NMR spectrum of BrF3 presents a singlet at
ꢁ16.3 ppm (neat liquid, 35 8C) [17], ꢁ16.5 ppm (SO2ClF, ꢁ20 8C)
[16], ꢁ17.3 ppm (Dn1/2 = 56 Hz) (PFP, ꢁ10 8C), and ꢁ17.9 ppm
2. Results
(Dn1/2 = 27 Hz) (PFB, 24 8C).
2.1. New basic information about bromine trifluoride in organic
solvents
2.2. [(RF)2Br]Y salts by reactions of BrF3 with perfluoroorganylboranes
in weakly coordinating solvents
Bromine trifluoride is a highly reactive compound and the
choice of appropriate weakly coordinating organic solvents for
reactions with Lewis acidic perfluoroorganylboranes and -silanes
is very limited. In the past some reactions of BrF3 with organic
compounds were performed in SO2ClF, CCl3F, and CCl2FCClF2. To
increase the solubility in dichloromethane at low temperature
small quantities (2–4 equiv.) of CH3CN were added. In the absence
of MeCN, CH2Cl2 reacts with BrF3 above ca. ꢁ20 8C. Bromine
trifluoride is moderately soluble in trichlorofluoromethane, but
above 5–10 8C it reacts with CCl3F to produce mainly CCl2F2.
Saturated solutions of BrF3 in 1,1,2-trichlorotrifluoroethane
showed no decomposition at 22–25 8C within 26 h, but after 3 d
the 19F NMR signal of BrF3 disappeared and a significant amount of
CClF2CClF2 was formed. Bromine trifluoride is insoluble in
The addition of tris(pentafluorophenyl)borane (1) to a stirred
suspension of BrF3 (molar ratio 2:3) in dichloromethane at ꢁ78 8C
formed a new suspension. Gradual warming up to 35 8C and
separation of the precipitate gave bis(pentafluorophenyl)bromo-
nium pentafluorophenylfluoroborates (Eq. (7)).
CH2Cl2
2ðC6F5Þ3B þ3BrF3ꢁ78ꢁt!o 25 ꢂ ½ðC6F5Þ2Brꢃ½ðC6F5ÞnBF4ꢁnꢃðn ¼ 0ꢁ3Þ (7)
C
1
The [(C6F5)3BF]ꢁ anion (minor component) together with the
[C6F5BF3]ꢁ and [BF4]ꢁ anions (major components) indicate the
participation of the boranes (C6F5)2BF and C6F5BF2 as intermedi-
ates in the aryl transfer process. To obtain only one type of anion,
the reaction was performed in the presence of the fluoride acceptor
BF3ꢀNCCH3 and using different sequences of mixing the reagents. In
all cases, bis(pentafluorophenyl)bromonium tetrafluoroborate (2)
was obtained in a good isolated yield (Eq. (8)).
perfluorohexane,
perfluoromethylcyclohexane,
perfluoro-2-
methylpent-2-ene, and perfluorotributylamine. Fortunately, the
commercially available fluorohydrocarbons, 1,1,1,3,3-pentafluoro-
propane (PFP) (HFC-245fa) (mp. ꢁ103 8C, bp. 15 8C) and 1,1,1,3,3-
pentafluorobutane (PFB) (Solkane1 365mfc) (mp. ꢇꢁ36 8C, bp.
40 8C) displayed satisfactory properties as solvents for reactions of
bromine trifluoride e.g. with perfluoroorganyldifluoroboranes. PFP
and PFB solutions of bromine trifluoride can be stored over weeks
at 5–25 8C without remarkable decomposition.
CH2Cl2
2ðC6F5Þ3B þ3BrF3 þ BF3 ꢀ NCCH3ꢁ78 to 25 ꢂC;ꢁMeCN
ꢁ!
3½ðC6F5Þ2Brꢃ½BF4ꢃ
1
2ð60ꢁ86%Þ
(8)
For BrF3 solutions in PFB, we have found that bubbling of BF3 at
ꢁ15 8C caused the formation of a second high density phase, which
completely dissolved above 0 8C. The 11B and 19F NMR spectra
showed no resonances of the starting fluorides BrF3 and BF3.
Instead, a new 19F resonance appeared at ꢁ72 ppm in case of a
molar ratio 1:1 and its integral intensity was equal to the sum of
those of BrF3 and BF3. Parallel, a singlet at 0.16 ppm was observed
More information about the individual F/C6F5-substitution
steps in BrF3 than with (C6F5)3B and (C6F5)2BF [11] were obtained
with pentafluorophenyldifluoroborane (3). Independent of the
molar ratio of reagents salt 2 was isolated (Eq. (9)).
PFB
2C6F5BF2 þBrF3ꢁꢁ2!0 ꢂ ½ðC6F5Þ2Brꢃ½BF4ꢃ þ BF3
(9)
C
3
2ð83%Þ

924
H.-J. Frohn et al. / Journal of Fluorine Chemistry 131 (2010) 922–932
Pentafluorophenylbromine difluoride was not detected even in
but-1-ene (12) (Eq. (13)). Borate 11 and alkene 12 were not found
the equimolar reaction of borane 3 with BrF3. Salt 2 was formed in
the same yield independent of the ratio of reagents and the
stoichiometrical excess of BrF3 which remained.
in the reaction mixtures (Eq. (12)).
PFB;ꢁ20 ꢂ
C
½Bu4Nꢃ½cis-C2F5CF ¼ CFBF3ꢃ þBrF3 ꢁ! ½Bu4Nꢃ½C2F5CFBrCF2BF3ꢃ
TBA
-10
TBA-11
The successful pentafluorophenylation of bromine trifluoride
with pentafluorophenylboron difluoride inspired us to apply this
approach to the preparation of previously unknown bis(organyl)-
bromonium salts containing perfluorinated alkynyl, alkenyl, and
alkyl groups. We used our convenient synthetic procedure to
produce solutions of the required boranes RFBF2 by fluoride
abstraction from the corresponding borates K[RFBF3] with BF3 in
appropriate weakly coordinating solvents [18,19].
þ C2F5CF ¼ CF2 þ ½Bu4Nꢃ½BF4ꢃ
(13)
12
Noteworthy, that solutions of [(C6F5)2Br]Y and [(RCF55CF)
(R0CF55CF)Br]Y in MeCN showed no decomposition at 25 8C over
days whereas the salt [(CF3CꢄC)2Br][BF4] decomposed in aceto-
nitrile at ꢁ25 8C.
In contrast to perfluorinated aryl-, alkenyl-, and alkynyldi-
fluoroboranes, perfluorohexyldifluoroborane (13) (1 equiv.) did
not react with BrF3 (1 equiv.) under formation of the corresponding
bis(perfluorohexyl)bromonium salt. The only fluoroorganic pro-
ducts were 1-bromoperfluorohexane (14) and perfluorohexane
(15) (1:1) which were slowly produced at ꢁ60 8C. At ꢁ10 8C the
reaction was completed within 1 h (Eq. (14)). Remarkably, that
only 0.5 equiv. of BrF3 was consumed.
Thus trifluoropropynyldifluoroborane (4) was easily reacted
with BrF3 in PFP and the desired bis(trifluoropropynyl)bromonium
tetrafluoroborate salt (5) was isolated in moderate yield (Eq. (10)).
PFP
2 CF3C ꢄ CBF2 þBrF3ꢁꢁ4!0 ꢂ ½ðCF3C ꢄ CÞ2Brꢃ½BF4ꢃ þ BF3
(10)
C
4
5ð31%Þ
For introducing perfluoroalkenyl groups we took two perfluoro-
alkenyldifluoroboranes of different configuration, trans-penta-
fluoroprop-1-en-1-yldifluoroborane (6) and cis-heptafluorobut-
1-en-1-yldifluoroborane (7). In case of the fluoro/perfluoroalkenyl
substitution in XeF2 we had observed an influence of the
configuration on the reaction rate [20].
Borane 6 reacted with BrF3 giving a solution of salts with
bis(trans-pentafluoroprop-1-en-1-yl)bromonium ((8a), major),
(trans-pentafluoroprop-1-en-1-yl)(cis-pentafluoroprop-1-en-1-
yl)(bromonium ((8b), minor)) cations and the counteranions
cis- and trans-pentafluoroprop-1-en-1-yltrifluoroborate and per-
fluoropropyltrifluoroborate (Eq. (11)).
PFP
2 C6F13BF2 þBrF3ꢁꢁ6!0 ꢂ C6F13Br þ C6F14 þ2BF3
(14)
C
13
14
15
A priori, the conversion of 14 to 15 by BrF3 cannot be excluded.
Therefore we performed additional experiments using the closely
related 1-bromoperfluorooctane. It did not react with BrF3 in PFB at
24 8C over a period of 17 h, but in the presence of a Lewis acid
replacement of bromine by fluorine occurred (Eqs. (15) and (16)).
Bubbling of BF3 (weak Lewis acid) into a solution of C8F17Br and
BrF3 in PFB at 0 8C gave ‘‘BrF3ꢀBF3’’ (19F NMR), which converted
C8F17Br slowly into C8F18 at 24 8C (1 h, no reaction; 72 h, complete
conversion). Experiment (Eq. (15)) allows to exclude the formation
of AlkF-F from AlkF-Br and BrF3.
PFP
2trans-CF3CF¼CFBF2 þ BrF3ꢁ40 ꢁto!ꢁ30 ꢂ ½ðRCF¼CFÞðR0CF¼CFÞBrꢃY
PFB
C8F17Br þ BrF324ꢁꢂC!;17 hno reaction
(15)
(16)
C
ð8a;bÞY
(11)
R ¼ R0 ¼ trans-CF3ð8aÞ; R ¼ cis-CF3; R0 ¼ trans-CF3ð8bÞ
PFB
C8F17Br þ ‘‘BrF3 ꢀ BF3’’ ꢁ! C8F18 þ ꢀ ꢀ ꢀ
24 ꢂC;72 h
Y ¼ ½cis-and trans-CF3CF ¼ CFBF3ꢃꢁ þ ½C3F7BF3ꢃꢁ
A related reaction path occurred in the reaction of cis-
heptafluorobut-1-en-1-yldifluoroborane (7) (2 equiv.) and BrF3
where a solution of salts with bis(heptafluorobut-1-en-1-yl)bro-
monium cations (9a–c) and the counteranions heptafluorobut-1-
en-1-yltrifluoroborate and perfluorobutyltrifluoroborate was
formed (Eq. (12)).
It is noteworthy, that the treatment of C8F17Br with [BrF2][SbF6]
in aHF at 24 8C gave C8F18 in a quantitative yield within 3 h.
2.3. Reaction of the pentafluorophenyldifluoroborane-MeCN adduct
with BrF3 in PFB/MeCN
In a preceding paper [11] we reported the synthesis of salt 2
from BrF3 and (C6F5)2BF in either CH2Cl2 as a weakly coordinating
solvent or in CH2Cl2 with molar admixtures of coordinating CH3CN
in high yields. Actually we investigated the reaction (1:1) of BrF3
with the adduct C6F5BF2ꢀNCCH3 (16) in a PFB/MeCN-mixture and
obtained salt 2 too, but accompanied by significant amounts of
bromopentafluorobenzene (17) (Eq. (17)).
PFB
2cis-C2F5CF¼CFBF2 þ BrF3 ꢁ! ½ðRCF¼CFÞðR0CF¼CFÞBrꢃY
ꢁ20 ꢂ
C
ð9aꢁcÞY
R ¼ R0 ¼ cis-C2F5ð9aÞ; R ¼ cis-C2F5; R0 ¼ trans-C2F5ð9bÞ;
(12)
R ¼ R0 ¼ trans-C2F5ð9cÞ
Y ¼ ½cis- and trans-C2F5CF¼CFBF3ꢃꢁ þ ½C4F9BF3ꢃꢁ
The opposite sequence of mixing, the addition of BrF3 to a cold
solution of 7 (2 equiv.) in PFB, led to a solution of related
composition, but with incomplete conversion of 7. Further
addition of BrF3 (total 1.8 equiv.) to the solution resulted in a
suspension. After removal of the volatiles under reduced pressure,
bis(heptafluorobut-1-en-1-yl)bromonium salts with tetrafluoro-
borate and perfluorobutyltrifluoroborate counteranions were
isolated. The reaction was accompanied by cis to trans-isomeriza-
tion of the heptafluorobutenyl group in the alkenylbromonium
moiety and partially in the alkenyltrifluoroborate moiety. It seems
that the [C2F5CF55CFBF3]ꢁ anion in the bromonium salts did not
react preferentially with BrF3 and furthermore on another route
than the ‘‘naked’’ anion. Because the treatment of tetrabutylam-
monium cis-heptafluorobut-1-en-1-yltrifluoroborate (TBA-10)
with BrF3 in PFB yielded tetrabutylammonium 2-bromoperfluor-
obutyltrifluoroborate (TBA-11), tetrafluoroborate, and perfluoro-
PFB=MeCN
C6F5BF2 ꢀ NCCH3 þBrF3ꢁ20ꢁt!o 24ꢂC ½ðC6F5Þ2Brꢃ½BF4ꢃ þ C6F5Br
(17)
16
17
2
2.4. Reactions of BrF3 with 2 equiv of C6F5SiX3 (X = F, Me)
BrF3 reacted with 2 equiv. of C6F5SiF3 (18) in CH2Cl2 in the
presence of 2 equiv. of MeCN up to ꢁ60 8C only under formation of
C6F5BrF2 (19). In a slow reaction at ꢅꢁ30 8C the formation of the
bromonium salt [(C6F5)2Br][SiF5] occurred (Eqs. (18) and (19)). The
salt was isolated in 92% yield.
CH2Clꢆ2
2 C6F5SiF3 þBrF3ꢈꢁꢁ6!0 ꢂ C6F5BrF2 þC6F5SiF3 þ SiF4
(18)
(19)
C
18
19
CH2Clꢆ2
2 C6F5SiF3 þBrF3 ꢅꢁꢁ!30 ꢂ ½ðC6F5Þ2Brꢃ½SiF5ꢃ þSiF4
C
18
20ð92%Þ

H.-J. Frohn et al. / Journal of Fluorine Chemistry 131 (2010) 922–932
925
*2 equiv. of MeCN were present to increase the solubility of BrF3 at
low temperature
besides unreacted borate 22. After hydrodeboration of remaining
[C6F5BF3]ꢁ with aHF to C6F5H and [BF4]ꢁ at 25 8C, the salt
[(C6F5)2Br][SbF6] was obtained in 31% yield (Eq. (25)).
When the reaction of BrF3 was performed with C6F5SiMe3 (21)
in a similar manner up to 0 8C only C6F5BrF2 (19) (58% yield after
isolation) was formed (Eq. (20)). In a further experiment BrF3 was
reacted with a mixture of 2 equiv. of C6F5SiMe3 (21) and BF3ꢀOEt2.
After 1 h at ꢁ78 8C the starting materials BrF3 and BF3ꢀOEt2 were
consumed, but whether C6F5BrF2 (19) nor [(C6F5)2Br][BF4] (2) were
present. Besides [BF4]ꢁ (major product), C6F5Br and Me3SiF were
formed (Eq. (21)).
ꢂC
2K ½C6F5BF3ꢃ þ½BrF2ꢃ½SbF6ꢃaHF;ꢁꢁ45!to 25 ½ðC6F5Þ Brꢃ½SbF6ꢃ
(25)
2
K-22
Potassium perfluorohexyltrifluoroborate (K-26) did not react
with [BrF2][SbF6] in aHF at 25 8C (Eq. (26)).
aHF;25 ꢂ
2K ½C6F13BF3ꢃ þ½BrF2ꢃ½SbF6ꢃ ꢁ! Cno reaction
(26)
K-26
CH2Cl2
2 C6F5SiMe3 þBrF3 ꢁ! C6F5BrF2 þC6F5SiMe3 þ Me3SiF
(20)
ꢈ0 ꢂ
C
21
19
3. Discussion
The formation of organylbromonium(III) salts from BrF3 and the
organyl transfer reagent RFEXnꢁ1 in weakly coordinating solvents
CH2Cl2
BrF3 þ 2 C6F5SiMe3=2BF3 ꢀOEt2 ꢁ! ½BF4ꢃꢁ þ C6F5SiMe3
ꢈꢁ78ꢂ
C
21
like CH2Cl2 or PFP includes three steps: (a) BrF3 + RFEXnꢁ1
!
þ C6F5Br þ Me3SiF
(21)
RFBrF2 + FEXnꢁ1, (b) RFBrF2 + RFEXnꢁ1 ! (RF)2BrF + FEXnꢁ1, and (c)
(RF)2BrF + (FEXnꢁ1 or RFEXnꢁ1) ! [(RF)2Br][F2EXnꢁ1 or RFEXnꢁ1F]. In
step (c) the formation of tris(organyl)bromane is not favored.
(RF)2BrF is a good fluoride donor comparable with (RF)2IF [24].
Furthermore, the bromonium entity is stabilized by two 2c–2e C–
Br bonds and the bromonium salt by lattice energy. Therefore
bromonium salts are the final products under satisfactory acidic
conditions.
2.5. Reactions of potassium perfluoroorganyltrifluoroborates with
BrF3 in aHF
It is known, that dissolution of BrF3 in aHF leads to a fluoride ion
transfer equilibrium [21,22] accompanied by an increase of the
electrophilicity and fluorooxidizer power of Br(III) (Eq. (22)).
When the organyl transfer reagents are perfluoroorganyldi-
fluoroboranes RFBF2, these steps are substantiated in Scheme 1.
The success in the carbon-bromine(III) bond formation is
mainly determined by two factors of the organyl transfer reagent:
(a) Lewis acidity towards fluoride and (b) nucleophilicity of the C1
carbon atom in the transition state. In step A, the interaction (1) of
the acid RFBF2 with one fluorine atom of the BrF2 triad weakens one
Br–F bond and makes the bromine centre more electrophilic.
Parallel the nucleofugality of the RF group increases. As a result of
the electrophile–nucleophile interaction (2) RFBrF2 is formed. The
latter was not detected by 19F NMR spectroscopy even at low
temperature and local excess of BrF3 (addition of neat BrF3 to a
diluted solution of RFBF2) or stoichiometric excess of BrF3
(BrF3:RFBF2 = 1:1). Furthermore, reaction mixtures obtained from
BrF3 and C6F5BF2 in weakly coordinating solvents did not contain
products of the acid-assisted decomposition of C6F5BrF2 (C6F5Br,
bromoperfluorocycloalkenes C6BrF7 and C6BrF9) which occurred at
ꢁ80 to ꢁ30 8C [25]. Hence, the rate of reaction of RFBrF2 with RFBF2
(step B) exceeds both: the rate of formation of RFBrF2 (step A) and
the rate of the acid-assisted decomposition of the latter. Some hint
on the intermediate C6F5BrF2 may be the increased formation of
BrF3 þ nHFaÐHF½BrF2ꢃ½FðHFÞ ꢃ
(22)
n
The dissolution of organyltrifluoroborates in aHF results
primarily in the protonation of the fluorine atoms bonded to
boron and leads to a organylfluoroborate/-borane equilibrium and
a decrease in the acidity of hydrogen fluoride [23]. Thus, the
transformation of the organyltrifluoroborate into the correspond-
ing organyldifluoroborane was expected to favor the F/RF
substitution in BrF3 relative to the oxidative addition of fluorine
across C–C double or triple bonds in the RF-group.
However, the addition of bromine trifluoride in aHF to a cold
solution of an equimolar amount of potassium pentafluorophenyl-
trifluoroborate (K-22) in aHF gave salt 2 in only 45% yield while the
main components derived from BrF-splitting of the B–C bond and
fluorine addition across C55C double bonds: bromopentafluoroben-
zene 17, 1-bromoheptafluorocyclohexa-1,4-diene (23), and 1-
bromononafluorocyclohexene (24) (Eq. (23)).
aHF; ꢅ ꢁ40 ꢂ
C
K½C6F5BF3ꢃ þBrF3
ꢁ!
½ðC6F5Þ2Brꢃ½BF4ꢃ þ C6F5Br
17
[(cShem)_e1TD$FI]G
K-22
2
þ cyclo-1-Br-1; 4-C6F7 þ cyclo-1-BrC6F9
(23)
23
24
No perfluoroalkenylbromonium salt was obtained when
potassium cis-heptafluorobut-1-en-1-yltrifluoroborate (K-10)
was reacted with bromine trifluoride in aHF. Instead, potassium
2-bromoperfluorobutyltrifluoroborate (K-11) and 2-bromoper-
fluorobutane (25) were formed (Eq. (24)) (compare with a related
reaction in PFB, (Eq. (13))).
aHF;ꢁ30 ꢂ
K ½cis-C2F5CF ¼ CFBF3ꢃ þBrF3 ꢁ! CK½C2F5CFBrCF2BF3ꢃ
K-11
K-10
þ C2F5CFBrCF3 þK½BF4ꢃ
(24)
25
2.6. Reactions of potassium perfluoroorganyltrifluoroborate with
[BrF2][SbF6] in aHF
When [BrF2][SbF6] was added to a solution of K[C6F5BF3] (K-22)
Scheme 1.
(2 equiv.) in aHF bromonium hexafluoroantimonate resulted

926
H.-J. Frohn et al. / Journal of Fluorine Chemistry 131 (2010) 922–932
C6F5Br (17) from the 1:1 reaction of C6F5BF2ꢀNCCH3 and BrF3 in
PFB/MeCN (Eq. (17)). Previously we have found that 17 is the major
product of the BF3ꢀNCCH3 assisted decomposition of C6F5BrF2 in
CH2Cl2/MeCN [25].
salts for the preparation of organic derivatives of polyvalent
halogens or xenon is no perspective route. For the same reason, the
presence of very strong polarizing substances (solvents, acidic
admixtures, etc.) should be avoided.
Taking into account the order of the gas phase fluoride affinity in
kcal/mol of fluoroboranes BF3 (78.8) < C6F5BF2 (85.1) < CF3CꢄCBF2
(89.0) ꢈ CF3CF = CFBF2 (89.0–90.0) < C3F7BF2 (96.7) [26], step c
should result in [(RF)2Br][RFBF3] rather than in [(RF)2Br][BF4]. The
[RFBF3]ꢁ type of anion was only observed for RF = perfluoroalkenyl
(Eqs. (11) and (12)). Fluoroborates with more nucleophilic RF groups
(RF = C6F5, CF3CꢄC) give tetrafluoroborates, [(RF)2Br][BF4]. A closely
related pictures was observed for the syntheses of bis(perfluoro-
organyl)iodonium [12] and perfluoroorganylxenonium [14,15] salts
via boranes RFBF2. In the context, which anion is formed, the unique
transferofa perfluoroalkyl group should bementioned whenborane
C6F13BF2 was reacted with C6F5IF2 in PFP at ꢁ40 8C under formation
of [C6F5(C6F13)I][C6F13BF3] [27].
4. Experimental
The NMR spectra were recorded on a Bruker AVANCE 300
spectrometer (300.13 MHz, 1H; 282.40 MHz, 19F; 96.29 MHz, 11B;
75.47 MHz, 13C). The chemical shifts are referenced to TMS (1H,
13C), CCl3F (19F, with C6F6 as secondary reference (ꢁ162.9 ppm)),
and BF3ꢀOEt2/CDCl3 (15%, v/v) (11B), respectively. The composition
of the reaction mixtures was determined by 19F NMR spectroscopy
using the internal integral standards C6F6, C6F14, or PFB. The
products [(C6F5)2Br][BF4] [11], C4F9Br [29], [C4F9BF3]ꢁ [23], cis-
C2F5CF55CFBr [30], trans-C2F5CF55CFBr [30], cyclo-1-Br-1,4-C6F7,
cyclo-1-H-1,4-C6F7, and cyclo-1-BrC6F9 [31] were identified by 19
F
The attempted preparation of the bis(perfluorohexyl)bromo-
nium salt from C6F13BF2 and BrF3 (ꢇ2:1) gave C6F13Br and C6F14 in
a 1:1 ratio besides BF3. This result can be explained via the
formation of the intermediate [(C6F13)2Br][C6F13BF3] and its fast
decomposition. This assumption is in agreement with the
decomposition of [(C6F5)(C6F13)I][C6F13BF3] in PFB which resulted
in C6F5I, C6F14, and C6F13BF2 [27].
NMR spectroscopy. As a convention for the presentation of the
NMR spectral data, the fluorine atoms F2 at C2 in [RC2F255C1F1-X]
compounds (X = B, Br) are specified by cis or trans relative to the
position of X, e.g. as F2trans
.
1,1,1,3,3-Pentafluoropropane (PFP) (Honeywell), 1,1,1,3,3-pen-
tafluorobutane (PFB) (Solvay), trichlorofluoromethane (K11, Sol-
vay), 1,1,2-trichlorotrifluoroethane (K113, Solvay), and ether
˚
In case of F/C6F5 substitution in BrF3 we have investigated the
influence of the nature of the transfer reagent. Concretely, we
included C6F5SiF3 and C6F5SiMe3 in our investigations and compare
the result with that of C6F5BF2.
(Baker) were stored over molecular sieves 3 A before use. Sicapent
(Merck), boron trifluoride (Air Liquide), KF, spray-dried (Morita),
[Bu4N][BF4] (Fluka), C6F13I (Hoechst), C8F17Br (Hoechst), 40% and
71–75% aqueous HF (Fluka), K[HF2] (Riedel-de Hae¨n), were used as
supplied. B(OMe)3 (Fluka) was distilled over sodium. Antimony
pentafluoride was twice distilled under an atmosphere of dry
argon. Acetonitrile (Baker) and dichloromethane (Baker) were
purified and dried as described in ref. [32]. Anhydrous HF (aHF)
was stored over CoF3. Tris(pentafluorophenyl)borane [18], C6F5SiF3
[33], C6F5SiMe3 [34], Li[C6F13B(OMe)3] [35], K[C6F5BF3] [36], K[cis-
C2F5CF55CFBF3] [37], BF3ꢀNCCH3 [38], and solutions of cis-
C2F5CF55CFBF2, trans-CF3CF55CFBF2 [39], CF3CꢄCBF2 [40] in PFB
or PFP were prepared as described. Salt K[C6F13BF3] [41] and
solutions of C6F5BF2 [42] and C6F13BF2 [41] in PFB or PFP were
prepared by modified procedures (see below). Bromine trifluoride
was prepared by bubbling of fluorine (25%, v/v in N2) into dry
bromine at 8–20 8C and AsF5 from AsF3 with undiluted F2 at ꢈ20 8C.
All manipulations with BrF3 and perfluoroorganyldifluorobor-
anes were performed in FEP (block copolymer of tetrafluoroethy-
lene and hexafluoropropylene) or PFA (block copolymer of
tetrafluoroethylene and perfluoroalkoxytrifluoroethylene) equip-
ment under an atmosphere of dry argon.
From calculated gas phase affinities we know that the tendency
to attach a fluoride ion decreases from C6F5BF2 via C6F5SiF3 to
C6F5SiMe3 [26]. Withboth reagents of lower fluoride affinity the first
F/C6F5 substitution step in BrF3 is principally successful. The further
F/C6F5 substitution step in C6F5BrF2 was only possible in case of
C6F5SiF3 but this step proceeded slowly and afforded a temperature
of ꢅꢁ30 8C. With C6F5SiMe3 no bromonium product was formed
even at 0 8C. When the reaction of BrF3 with 2 equiv. C6F5SiMe3 was
performed in the presence of BF3ꢀOEt2 in CH2Cl2 BrF3 interacted
preferentially with the Lewis acid BF3ꢀOEt2 and attacked the solvent
and C6F5SiMe3. [BF4]ꢁ, C6F5Br, and Me3SiF were formed in
decreasing quantities. The comparison of the three C6F5-transfer
reagents in our present study allows to draw important conclusions.
In order to substitute only one fluorine atom in the hypervalent
moiety of BrF3 the equimolar reaction with C6F5BF2 is not suitable,
because the secondF/C6F5-substitutionstepproceedsfasterthanthe
first. The opposite sequence of the reaction rates is found for
C6F5SiF3. For the second F/C6F5-substitution step to the bromonium
cation a minimum acidity (fluoride affinity) is needed, which is not
provided by C6F5SiMe3. When we compare the corresponding
reactivity of hypervalent F-E-F triads in C6F5IF2 and XeF2 with that in
C6F5BrF2 we find the same tendency. Thus the unique importance of
RFBF2 compounds for the introduction of RF-groups into the Xe(II)
moiety underformation of xenonium salts becomes plausible by our
actual results.
The results of reactions between K[RFBF3] with both, BrF3 and
[BrF2][SbF6], in aHF are closely related to those obtained in
reactions with XeF2 in aHF [23,28]. Salt K[C6F5BF3] reacted with
both binary fluorides EFn giving pentafluorophenyl-containing
salts, 2 (EFn55BrF3) or [C6F5Xe][BF4] (EFn = XeF2) besides products
of fluorine addition across the C55C bond. Salt K[cis-C2F5CF55CFBF3]
underwent bromofluorination and further conversion to 25 in
reactions with BrF3, while with XeF2 fluorine addition across the
C55C bond led to K[C4F9BF3]. Salt K[C6F13BF3] was inert towards
both, [BrF2][SbF6] and XeF2, in aHF. This picture shows an increased
oxidative potential of [EFnꢁ1]+ (or a related polarized form of EFn)
which can become predominant over an increased electrophilicity
(e.g. rate of carbon-E bond formation). Hence, the use of [EFnꢁ1]Y
4.1. Preparation of K[C6F13BF3] (K-26)
(A) The reaction was performed in a three-necked, 1-L flask
equipped with a low-temperature thermometer, a gas inlet, a
Teflon-coated magnetic stir bar, and a dropping funnel which was
connected via a Sicapent-filled tube to a mineral oil gas bubbler.
The flask was charged with C6F13I (25 g, 56 mmol) and ether
(400 mL) and cooled to ꢁ70 8C under an atmosphere of dry argon.
Ethylmagnesium bromide (0.90 M in ether, 62 mL, 56 mmol) was
added drop-wise within 30 min. The solution transformed to a
white suspension which was stirred at ꢁ55 8C for 1.5 h.
Subsequently B(OMe)3 (9.0 g, 86 mmol) in ether (10 mL) was
added drop-wise using a syringe. The suspension was stirred at
ꢁ50 8C for 1 h and allowed to warm to ꢁ10 8C within 2.5 h. A
transparent solution was formed which was transferred to a round
bottom flask (1 L). After concentration on an evaporator at 25 8C a
suspension resulted, which was diluted with MeOH (50 mL) and
poured into a solution of K[HF2] (23 g, 294 mmol) in water (30 mL)
and 40% aqueous HF (30 mL) placed in a polypropylene beaker

H.-J. Frohn et al. / Journal of Fluorine Chemistry 131 (2010) 922–932
927
(400 mL). The slurry was stirred at 20 8C overnight, diluted with
water (50 mL), and neutralized by portion-wise addition of K2CO3.
The suspension was extracted with MeCN (3ꢉ 50 mL). According to
19F NMR data, the extract contained K[C6F13BF(OMe)2] (character-
istic resonances at ꢁ130.8 (CF2B) and ꢁ156.5 (q (1:1:1:1), 1J(F,
B) = 46 Hz, BF(OMe)2ꢁ) ppm), and K[C6F13BF2OMe] (characteristic
resonances at ꢁ131.7 (CF2B) and ꢁ149.1 (q (1:1:1:1), 1J(F,
B) = 50 Hz, BF2OMeꢁ) ppm) borate anions in the molar ratio 1:4.
The solution was concentrated on an evaporator to 60–70 mL
volume, poured into a polypropylene beaker (400 mL) and 71–75%
aqueous HF (30 mL) was added in one portion (moderately
exothermic reaction). The suspension was stirred for 3.5 h, cooled
by addition of crashed ice (60–70 g) and carefully neutralized with
concentrated aqueous KOH under cooling (ice bath). The suspen-
sion was extracted with MeCN (3ꢉ 50 mL) and the combined
extracts were dried with KF. The solvent was removed under
reduced pressure and the solid was finally dried in a vacuum-
desiccator over Sicapent. The salt K[C6F13BF3] was obtained in 73%
yield (17.5 g, 41 mmol).
with K[C6F5BF3] (454 mg, 1.65 mmol), PFB (3 mL) and cooled to
ꢁ15 to ꢁ20 8C under an atmosphere of dry argon. Boron trifluoride
(5–7 mmol) was bubbled into the stirred suspension for 25 min.
Excess of BF3 was removed by flushing with dry argon (0 8C, 10 min
and 20 8C, 5 min). The suspension was centrifuged at 20 8C, the
colorless mother liquor was decanted, the precipitate was washed
with PFB (1 mL) and the washing was combined with the mother
liquor. Yield of C6F5BF2 (1.62 mmol, 98%), determined from the 19
NMR spectrum using C6F14 as quantitative integral reference.
F
(B) A solution of C6F5BF2 (0.94 mmol, 95% yield) in PFP was
prepared from K[C6F5BF3] (294 mg, 1.03 mmol) in PFP (3 mL)
similarly, but the treatment after the reaction with BF3 was
performed at 0 8C (ice bath).
C6F5BF2 (3). 19F NMR (PFB, 24 8C):
d
ꢁ73.7 (s, Dn1/2 = 116 Hz, 2F,
BF2), ꢁ128.2 (m, 2F, F2,6), ꢁ144.0 (tt, 3J(F4, F3,5) = 19 Hz, 4J(F4,
F2,6) = 8 Hz, 1F, F4), ꢁ161.2 (m, 2F, F3,5). 11B NMR (PFB, 24 8C):
(s, Dn1/2 = 96 Hz).
d 22.1
4.4. Preparation of C6F13BF2 (13) in PFP
(B) The salt Li[C6F13B(OMe)3] (2.2 g, 5.1 mmol) was added in
portions to a solution of K[HF2] (1.8 g, 23 mmol) in 71–75%
aqueous HF (10 mL). The suspension was stirred for 5 h, diluted
with water (3 mL), neutralized with K2CO3 and extracted with
MeCN (3ꢉ 10 mL). The extract was dried with KF and the solvent
was removed under reduced pressure. The product was dried in a
vacuum-desiccator over Sicapent. The salt K[C6F13BF3] was
obtained in 74% yield (1.6 g, 3.8 mmol).
(A) A flame dried glass trap (10 mL) equipped with a Teflon-
coated magnetic stir bar and topped with a T-piece was charged
with K[C6F13BF3] (440 mg, 1.03 mmol), PFP (3 mL) and cooled to
ꢁ65 8C under an atmosphere of dry argon. Arsenic pentafluoride
(1.4 mmol) was condensed. The white slurry was stirred for 1 h
while the temperature rose to 0 8C. The suspension was
centrifuged at 0 8C (ice bath), the colorless mother liquor was
decanted, the precipitate was washed with PFP (2.5 mL), and the
washing was combined with the mother liquor. Yield of C6F13BF2
(0.90 mmol, 90%, determined from the 19F NMR spectrum using
PFB as a quantitative integral reference).
(B) A 11.7-mm i.d. PFA trap was charged with K[C6F13BF3]
(440 mg,1.00 mmol), PFP (2 mL) and cooled to ꢁ25 8C under an
atmosphere ofdry argon. A cold(ꢁ20 8C)solution of SbF5 (0.9 mmol)
in PFP (3 mL) was added and the white slurry was stirred for 1 h at
ꢁ20 8C. The suspension was centrifuged at 0 8C (ice bath), the
colorless mother liquor was decanted, the precipitate was washed
with PFP (1.5 mL), and the washing was combined with the mother
Solubility of K[C6F13BF3] in MeCN exceeds 533 mg per mL
(1.25 mmol per mL).
K[C6F13BF3] (K-26). 19F NMR (aHF, 0 8C):
d
ꢁ79.5 (tt, 4J(F6,
F4) = 10 Hz, 3J(F6, F5) = 2 Hz, 3F, F6), ꢁ119.8 (m, CF2), ꢁ120.5 (m, CF2),
ꢁ121.3 (m, CF2), ꢁ124.1 (m, 2F, F5), ꢁ132.1 (m, 2F, F1), ꢁ149.0 (q
(1:1:1:1), 1J(F, B) = 41 Hz, 3F, BF3ꢁ). 11B NMR (aHF, 0 8C):
d
ꢁ0.3 (m,
BF3ꢁ). 19F NMR (D2O, 24 8C):
d
ꢁ81.0 (t, 4J(F6, F4) = 9 Hz, 3F, F6),
ꢁ122.7 (m, CF2), ꢁ123.2 (m, CF2), ꢁ124.6(m, CF2), ꢁ126.3 (m, 2F, F5),
ꢁ134.1 (m, 2F, F1), ꢁ151.9 (q (1:1:1:1), 1J(F, B) = 41 Hz, 3F, BF3ꢁ). 11
B
d
NMR (D2O, 24 8C):
d
ꢁ0.7 (m, BF3ꢁ). 19F NMR (acetone-d6, 24 8C):
ꢁ80.0 (tt, 4J(F6, F4) = 10 Hz, 3J(F6, F5) = 3 Hz, 3F, F6), ꢁ120.9 (m, CF2),
ꢁ121.6 (m, CF2), ꢁ122.3 (m, CF2), ꢁ125.0 (m, 2F, F5), ꢁ132.3 (m, 2F,
F1), ꢁ151.6 (q(1:1:1:1), 1J(F, B) = 41 Hz, 3F, BF3ꢁ). 11B NMR (acetone-
liquor. Yield of C6F13BF2 (0.80 mmol, 80%, determined from the 19
NMR spectrum using PFB as a quantitative integral reference).
F
d6, 24 8C):
d
ꢁ0.6 (qt, 1J(B, F) = 41 Hz, 2J(B, F) = 20 Hz, BF3ꢁ). 13C{19F}
C6F13BF2 (13). 19F NMR (PFP, 0 8C):
d
ꢁ75.8 (s, Dn1/2 = 150 Hz, 2F,
NMR (acetone-d6, 24 8C):
d
117.5 (C6), 121.3 (q (1:1:1:1), 1J(C1,
BF2), ꢁ79.9 (t, 4J(F6, F4) = 10 Hz, 3F, F6), ꢁ119.6 (m, CF2), ꢁ121.3 (m,
CF2), ꢁ124.1 (m, CF2), ꢁ124.9 (m, 2F, F5), ꢁ132.8 (m, 2F, F1). 11B NMR
B) = 87 Hz, C1), 113.5, 112.0, 110.9 (3CF2), 109.1 (q, 2J(C5, F6) = 29 Hz,
C5). (lit. [41]: 19F NMR (CD3CN, 24 8C)): ( ꢁ80.1 (CF3), ꢁ121.3,
ꢁ121.9, ꢁ122.7, ꢁ125.1 (4CF2), ꢁ132.6 (CF2B), ꢁ151.8 (BF3); 11B
NMR (CD3CN, 24 8C): ( ꢁ0.5 (qt, 1J(B, F) = 41 Hz, 2J(B, F1) = 18 Hz).
(PFP, 24 8C):
d d
18.4 (s, Dn1/2 = 141 Hz). (lit. [41] 19F NMR (CCl3F):
ꢁ78.3 (s, 2F, BF2), ꢁ81.5 (3F, F6), ꢁ121.7, ꢁ123.2, ꢁ125.9, ꢁ126.7
(4CF2), ꢁ134.1 (m, 2F, F1); 11B NMR (CCl3F, 24 8C):
4.5. Preparation of C6F5BF2ꢀNCCH3 (16)
d 19.2 (br. s)).
4.2. Preparation of [Bu4N][cis-C2F5CF55CFBF3] (TBA-10)
A solution of K[cis-C2F5CF55CFBF3] (428 mg, 1.48 mmol) in
MeCN (0.5 mL) was poured into a stirred solution of [Bu4N][BF4]
(493 mg, 1.50 mmol) in MeCN (0.7 mL). After 15 min the suspen-
sion was centrifuged, the colorless mother liquor was decanted
and evaporated to dryness at 20 8C (0.66 hPa) to yield the white
solid [Bu4N][cis-C2F5CF55CFBF3] (579 mg, 1.17 mmol).
A solution of MeCN (14 mg, 0.34 mmol) in PFB (0.1 mL) was
added to a solution of C6F5BF2 (0.29 mmol) in PFB (0.4 mL). The
suspension was centrifuged and the white precipitate was dried in
high vacuum (yield 70 mg, 0.27 mmol). Mp. 108 8C.
C6F5BF2ꢀNCCH3 (16). 19F NMR (CH3CN, 24 8C):
d
ꢁ135.4 (m, 2F,
F2,6), ꢁ156.0 (t, 3J(F4, F3,5) = 21 Hz, 1F, F4), ꢁ163.9 (m, 2F, F3,5),
[Bu4N][cis-C2F5CF55CFBF3] (TBA-10). 19F NMR (PFB, 24 8C):
d
ꢁ138.9 (s, Dn1/2 = 54 Hz, 2F, BF2). 11B NMR (CD3CN, 24 8C):
d 1.7 (s,
ꢁ83.2 (d, 4J(F4, F2) = 8 Hz, 3F, F4), ꢁ116.9 (dq, 3J(F3, F2) = 13 Hz,
5J(F3, BF3ꢁ) = 13 Hz, 2F, F3), ꢁ130.4 (q (1:1:1:1), 2J(F1, B) = 24 Hz,
1F, F1), ꢁ157.2 (m, 1F, F2), ꢁ140.1 (q (1:1:1:1), 1J(F, B) = 36 Hz, 3F,
Dn1/2 = 46 Hz). 13C{19F} NMR (CD3CN, 24 8C): 148.7 (C2,6), 141.2
d
(C4), 137.5 (C3,5), the resonance of C1 was not detected. 1H NMR
(CD2Cl2, 24 8C):
d d
2.15 (s, 3H, CH3). 19F NMR (CD2Cl2, 24 8C):
BF3ꢁ). 11B NMR (PFB, 24 8C):
d
ꢁ0.6 (ddq, 3J(B, F2) = 7 Hz, 2J(B,
ꢁ135.3 (m, 2F, F2,6), ꢁ155.8 (t, 3J(F4, F3,5) = 20 Hz, 1F, F4), ꢁ164.4
F1) = 23 Hz, 1J(B, F) = 37 Hz, BF3ꢁ).
(m, 2F, F3,5), ꢁ136.5 (s, Dn1/2 = 33 Hz, 2F, BF2).
4.3. Preparation of C6F5BF2 in PFB or PFP
4.6. Preparation of [BrF2][SbF6]
(A) A flame dried glass trap (10 mL) equipped with a Teflon-
coated magnetic stir bar and topped with a T-piece was charged
The synthesis was performed in a 23-mm i.d. FEP trap equipped
with a Teflon-coated magnetic stir bar. The trap was connected to a

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H.-J. Frohn et al. / Journal of Fluorine Chemistry 131 (2010) 922–932
stainless steel vacuum line. The trap was charged with BrF3 (1 mL,
2.8 g, 20 mmol) and SbF5 (0.8 mL, 2.4 g, 11 mmol) was added in
portions within 5 min. The temperature was increased to 60–80 8C,
and the reddish solution was stirred for 30 min. All volatiles were
removed under reduced pressure at 80–90 8C to yield a fine lemon
powder. The product (3.3 g, 85%) was stored inside a glove-box
under an atmosphere of dry argon. The 19F NMR spectrum of
[BrF2][SbF6] in aHF at ꢁ40 8C consisted only of one BrF resonance at
ꢁ73.5 ppm (Dn1/2 = 106 Hz) ([BrF2]+) which became very broad at
0 8C. In the presence of SbF5 (five fold molar excess) the signal of
[BrF2]+ was located at ꢁ72.9 ppm and underwent a reversible
broadening from Dn1/2 = 47–53 Hz (ꢁ40 8C) to ꢇ240 Hz (ꢁ20 8C)
and >1000 Hz (0 8C). In both cases, the Sb-F resonances were
presented by very broad signals at ꢁ120 to ꢁ125 ppm.
liquor was decanted, the precipitate was washed with CH2Cl2
(4 mL) at 20 8C and pumped in vacuum for 30 min to yield
[(C6F5)2Br][BF4] (333 mg, 83%).
4.8.2. Reaction of BrF3 with C6F5BF2 (1:1)
A 23-mm i.d. FEP trap equipped with a Teflon-coated magnetic
stir bar was charged with a solution of BrF3 (146 mg, 1.06 mmol) in
PFP (4.5 mL) and cooled to ꢁ45 8C. Then a cold (ꢁ40 8C) solution of
C6F5BF2 (0.94 mmol) in PFP (3 mL) was added in portions. The
white suspension was stirred at ꢁ40 8C for 1 h and at 0 8C for
30 min. The mother liquor was decanted, the precipitate was
washed with PFP (2 mL) at 0 8C, dried in vacuum at 0 8C for 30 min
and 24 8C for 1 h to yield [(C6F5)2Br][BF4] (200 mg, 85%). The
decanted mother liquor contained cyclo-1-Br-1,4-C6F7 (yield 3%)
and cyclo-1-BrC6F9 (yield 5%) while resonances of C6F5Br and
C6F5BrF2 were not detected. To prove the presence of BrF3,
pentafluorobenzene (in excess) was added. The 19F NMR spectrum
showed the formation of C6F5Br and increasing amounts of cyclo-1-
Br-1,4-C6F7 and cyclo-1-BrC6F9.
4.7. Bromine trifluoride in fluoroorganic solvents: stability, behaviour
towards BF3, and NMR properties
A. 3.5-mm i.d. FEP inliners were charged with different organic
solvents (0.4 mL) and BrF3 (20–30 mg). The two-phase systems
were maintained for 1 h at 25 8C with periodic shaking before the
upper organic phase was decanted. No 19F NMR signal of BrF3 was
detected in case of perfluorohexane, perfluoromethylcyclohexane,
perfluoro-2-methylpent-2-ene, and perfluorotributylamine. In
case of trichlorofluoromethane and 1,1,2-trichlorotrifluoroethane
the upper phase showed the presence of BrF3. BrF3 is miscible with
PFP (5–10 8C) and PFB (25 8C) in any proportions giving yellowish
solutions. No reaction was detected in the solution of BrF3 in PFP,
PFB (25 8C, over weeks), and 1,1,2-trichlorotrifluoroethane (25 8C,
26 h). In contrast, after 3 d the signal of BrF3 in 1,1,2-C2Cl3F3
disappeared and a significant amount of CClF2CClF2 was formed.
With CCl3F bromine trifluoride reacted above 10 8C to yield
4.8.3. Reaction of BrF3 with C6F5BF2ꢀNCCH3 (1:1)
A solution of BrF3 (37 mg, 0.27 mmol) in PFB (1.2 mL) was
cooled to ꢁ20 8C and a cold (ꢁ20 8C) solution of C6F5BF2ꢀNCCH3
(0.27 mmol) in CH3CN (0.5 mL) was added in portions. The
colorless solution was stirred at ꢁ20 8C for 30 min and warmed
to 24 8C. The 19F NMR spectrum pointed out the formation of
[(C6F5)2Br][BF4] and C6F5Br (1:1).
4.8.4. Reaction of BrF3 with K[C6F5BF3] (1:1)
A cold (ꢁ40 8C) solution of BrF3 (95 mg, 0.69 mmol) in aHF
(0.7 mL) was added in portions to a cold (ꢁ40 8C) stirred solution
of K[C6F5BF3] (190 mg, 0.69 mmol) in aHF (2.5 mL). After stirring
at ꢁ30 8C for 1 h, the solution contained [(C6F5)2Br][BF4], C6F5Br,
predominantly CCl2F2 (
19F NMR).
The solubility of BrF3 was determined to 79 mg (0.57 mmol) per
mL of 1,1,2-trichlorotrifluoroethane (19F NMR, 24 8C).
and cyclo-1-Br-1,4-C6F7 (
19F NMR). The solution was extracted
with CCl4 at 0 8C. The extract contained C6F5Br (0.10 mmol), cyclo-
1-Br-1,4-C6F7 (0.16 mmol), and cyclo-4-BrC6F9 (0.06 mmol),
while the acid phase contained [(C6F5)2Br][BF4] (0.16 mmol,
45% yield) and weak signals of perfluorinated unsaturated
products.
BrF3. 19F NMR (PFB, 24 8C):
d
ꢁ17.9 (s, Dn1/2 = 27 Hz); (PFP,
ꢁ10 8C):
d
ꢁ17.3 (s, Dn1/2 = 56 Hz); (CCl2FCClF2, 24 8C):
d
ꢁ22.6 (s,
Dn1/2 = 71 Hz); (CCl3F, 0 8C):
d
ꢁ27.2 (s, Dn1/2 = 126 Hz) (lit. 19F
NMR (neat, 35 8C):
[16]).
d
ꢁ16.3 [17]; (SO2ClF, ꢁ20 8C):
d
ꢁ16.5 ppm
(B) A solution of BrF3 (147 mg, 1.07 mmol) in PFB (0.5 mL) was
cooled to ꢁ8 8C and BF3 (2 mmol) was bubbled for 15 min. A high
density red phase separated. Warming above 3–5 8C caused the
complete dissolution of the dense phase. The NMR spectra
contained only one 19F resonance at ꢁ74.8 ppm (Dn1/2 = 138 Hz)
besides signals of PFB and only one 11B resonance at 0.16 ppm
4.8.5. Reaction of [BrF2][SbF6] with K[C6F5BF3] (1:2)
A cold (ꢁ15 8C) solution of [BrF2][SbF6] (90 mg, 0.25 mmol) in
aHF (0.5 mL) was added in three portions to a cold (ꢁ55 8C) stirred
solution of K[C6F5BF3] (143 mg, 0.52 mmol) in aHF (1 mL). The
suspension was stirred at ꢁ45 8C for 1 h and at ꢁ10 8C for 20 min.
The pink solution contained [(C6F5)2Br]+, [C6F5BF3]ꢁ, [BF4]ꢁ, C6F5Br,
C6F5H (15:32:46:4:3) (19F NMR, ꢁ10 8C). The solution was stirred
at 0 8C for 1.5 h and at 25 8C for 2 h to complete the conversion of
residual K[C6F5BF3] to C6F5H and [BF4]ꢁ [43] (19F NMR). After
evaporation in vacuum at 25 8C the residue was washed with
pentane (2ꢉ 1.5 mL), dried in vacuum, and extracted with MeCN
(0.6 mL). The extract contained the salt [(C6F5)2Br][SbF6] [11]
(0.08 mmol (31%) based on K[C6F5BF3]).
(
Dn1/2 = 8 Hz). No individual signals of BrF3 and BF3 were detected
in both, the 11B and 19F NMR spectra. The solution was kept at
ꢁ22 8C for 30 min and the mother liquor was decanted from the
dense red phase. Cold (ꢁ22 8C) PFB (0.5 mL) was added and the
inliner was warmed to 24 8C. The solution showed 11B and 19F NMR
spectra which were only slightly distinguished from the spectra of
the parent solution: 19F NMR (PFB):
NMR (PFB):
d
ꢁ68.1 (s, Dn1/2 = 553 Hz). 11
B
d
2.4 (s, Dn1/2 = 8 Hz). No changes were observed when
this solution was kept at ꢇ20 8C for 24 h.
4.8.6. Reaction of BrF3 with (C6F5)3B (3:2)
BrF3 (9.9 mg, 0.072 mmol) was suspended in cold (ꢁ78 8C)
CH2Cl2 (0.25 mL). Solid (C6F5)3B (25 mg, 0.049 mmol) was added
and the mixture was vigorously agitated at ꢁ78 8C and finally
warmed up in steps (ꢁ60 8C, ꢁ50 8C) under 19F NMR control. The
relative molar ratio of products in the suspension did not change:
[(C6F5)2Br]+ (100%), [(C6F5)3BF]ꢁ (99%), C6F5Br (81%) C6F5D (17%),
(C6F5)3B (4%). After warming to 35 8C the mother liquor was
decanted and the solid residue was dried in vacuum to yield
[(C6F5)2Br]Y salts (23.1 mg, 59%) (Y = [(C6F5)3BF]ꢁ, [C6F5BF3]ꢁ,
[BF4]ꢁ) in the molar ratio [(C6F5)2Br]+:[(C6F5)3BF]ꢁ:[C6F5BF3]ꢁ:
[BF4]ꢁ = 100:2:33:65.
4.8. Preparation of [(C6F5)2Br]Y salts with pentafluorophenylboron
compounds
4.8.1. Reaction of BrF3 with C6F5BF2 (1:2)
A 23-mm i.d. FEP trap equipped with a Teflon-coated magnetic
stir bar was charged with a solution of BrF3 (0.80 mmol) in PFB
(1.2 mL) and cooled to ꢁ25 8C. Then a cold (ꢁ15 8C) solution of
C6F5BF2 (1.62 mmol) in PFB (4 mL) was added in portions. The
white suspension was stirred at ꢁ20 8C for 20 min, at 0 8C for
10 min and kept at ꢁ30 8C for 30 min without stirring. The mother

H.-J. Frohn et al. / Journal of Fluorine Chemistry 131 (2010) 922–932
929
Treatment of the mother liquor with solid BF3ꢀNCCH3 (3 mg,
0.028 mmol) resulted again in a suspension. After separation the
precipitate was dissolved in MeCN and the 19F NMR spectrum
showed the signals of [(C6F5)2Br][BF4] besides traces of BF3ꢀNCCH3
and C6F5Br. The mother liquor contained (C6F5)3BꢀNCCH3,
(C6F5)2BFꢀNCCH3, BF3ꢀNCCH3, C6F5Br, and C6F5D in the molar ratio
89:26:81:100:37.
to the trap with C6F5SiF3 within 15 min. The suspension was stirred
for further 1.5 h at ꢁ78 8C and 1 h at ꢁ60 8C. The amount of solid
corresponded to the NaF quantity. A probe of the mother liquor
contained C6F5BrF2 and C6F5SiF3 in a molar ratio of 1:1 (19F NMR).
When the temperature was increased to ꢁ30 8C overnight, a
colorless solid precipitated. The suspension was warmed to ꢁ15 8C
within 7 h before mother liquor (A) was decanted from precipitate
(A) (3.99 g, including NaF). Stirring of mother liquor (A) at ꢁ40 to
ꢁ10 8C for 12 h and at 0 8C for 24 h resulted in a suspension again.
Precipitate (B) was separated and dried in vacuum to give product
(B) (1.15 g). Both solids (A) and (B) were washed with CH2Cl2, dried
in vacuum and extracted with MeCN. The solvent was evaporated
under reduced pressure forming the colorless salt [(C6F5)2Br][SiF5]
(4.93 g, 92%).
4.8.7. Reaction of BrF3 with (C6F5)3B and BF3ꢀNCCH3 (3:2:1)
Solid BF3ꢀNCCH3 (61 mg, 0.56 mmol) was added to a cold
(ꢁ70 8C) solution of (C6F5)3B (590 mg, 1.15 mmol) in CH2Cl2
(10 mL). The suspension was warmed to 20 8C within 30 min and
after 1 h at 20 8C a solution resulted which contained (C6F5)3B
(
(
d
d
(F) = ꢁ129.5, ꢁ146.2, and ꢁ161.8) and (C6F5)3BꢀNCCH3
(F) = ꢁ134.8, ꢁ157.5, and ꢁ164.7) in the molar ratio 100:80.
[(C6F5)2Br][SiF5]. 19F NMR (CD3CN):
d
ꢁ129.0 (m, 4F, F2,6),
Boron trifluoride was not detected by 19F NMR although opening of
the trap went along with the escape of a fuming gas, presumably,
BF3. The solution was cooled to ꢁ78 8C and formed a suspension
which was quantitatively transferred to a suspension of BrF3
(237.5 mg, 1.74 mmol) in CH2Cl2 (1.2 mL, ꢁ78 8C). The cold
mixture was stirred for 1 h before it was warmed to 20 8C within
0.5 h and finally stored overnight.
ꢁ137.1 (s, Dn1/2 = 9 Hz, 5F, SiF5ꢁ), ꢁ139.0 (tt, 3J(F4, F3,5) = 20 Hz,
4J(F4, F2,6) = 7 Hz, 2F, F4), ꢁ154.7 (m, 4F, F3,5).
Salt [(C6F5)2Br][SiF5] decomposed exothermically at 207 8C
(DTA). A CDCl3 solution of the decomposition product exhibited a
1:0.8 molar ratio of C6F5Br and C6F6.
4.10. Reaction of BrF3 with C6F5SiMe3 (1:2) in the presence of MeCN
The decanted mother liquor showed 19F resonances of
[(C6F5)2Br][(C6F5)3BF] and C6F5Br (37:63). The solid was washed
with CH2Cl2 (2ꢉ 1.5 mL) and dried in vacuum to give the
bromonium salts [(C6F5)2Br][BF4] and [(C6F5)2Br][C6F5BF3]
(554 mg) (94:6) (19F NMR in MeCN).
A 23-mm i.d. FEP trap was charged with C6F5SiMe3 (2.15 g,
8.95 mmol), CH2Cl2 (5 mL) and NaF (50 mg, 1.19 mmol) and cooled
to ꢁ90 8C. A solution of BrF3 (610 mg, 4.46 mmol) in CH2Cl2
(15 mL) and MeCN (0.465 mL, 8.9 mmol) over NaF (50 mg,
1.19 mmol) was prepared in a 23-mm i.d. FEP trap as described
above (4.9). After 10 min of stirring at ꢁ78 8C (to remove traces of
HF) the BrF3 solution was added drop-wise to the trap with
C6F5SiMe3 (ꢁ90 8C). After 4 h at ꢁ90 8C, the reaction mixture was
kept at ꢁ70 8C for 12 h and then warmed to 0 8C. The mother liquor
was separated from the precipitate, evaporated to dryness in
vacuum and the solid residue was re-crystallized from CCl3F
yielding C6F5BrF2 (730 mg, 2.56 mmol) (58% related to BrF3).
Dissolution of the precipitate in an aqueous solution of Na[BF4]
confirmed the absence of [(C6F5)2Br]Y salts (19F NMR).
4.8.8. Reaction of BrF3 with (C6F5)3B (3:2) and BF3ꢀNCCH3 in CH2Cl2
Borane 1 (1.94 g, 3.79 mmol) was added to the cold (ꢁ78 8C)
suspension of BrF3 (766 mg, 5.60 mmol) in CH2Cl2 (50 mL) and
stirred at ꢁ70 8C. After 1.5 h the mother liquor did not contain
borane 1 (19F NMR). Then BF3ꢀNCCH3 (203 mg, 1.86 mmol) was
added. After stirring at ꢁ70 8C for 0.5 h, the temperature was
increased to 20 8C. The mother liquor was decanted. The solid
residue was washed with CH2Cl2 (2ꢉ 10 mL) and dried in vacuum
to yield 2.4 g (4.78 mmol, 86%) of [(C6F5)2Br][BF4].
4.8.9. Reaction of (C6F5)3B with BrF3 (2:3) and BF3ꢀNCCH3 in CH2Cl2
A solution of (C6F5)3B (945 mg, 1.85 mmol) in CH2Cl2 (20 mL)
was prepared in a FEP trap and cooled to ꢁ78 8C forming a
suspension. Bromine trifluoride BrF3 (385 mg, 2.81 mmol) was
dropped onto the cold wall of the FEP trap and solidified. After
knocking at the trap, BrF3 released from the wall and sunk into the
stirred suspension of 1. Within 2 h the temperature was increased
to ꢁ60 8C under stirring. The 19F NMR spectrum showed the
absence of (C6F5)3B and the presence of resonances at ꢁ133.0,
ꢁ142.7, and ꢁ156.5 ppm (2:1:2) (presumably (C6F5)2BrF) and
C6F5Br (10:9) besides C6F6 (traces). Then BF3ꢀNCCH3 (101 mg,
0.93 mmol) was added to the suspension and the temperature was
increased to 20 8C within 1 h. The precipitate was separated,
dissolved in MeCN (2 mL) and re-precipitated by addition of CH2Cl2
(15 mL). The mother liquor was decanted and the solid dried in
vacuum to yield [(C6F5)2Br][BF4] (1.134 g, 2.26 mmol, 82%).
4.11. Reaction of BrF3 with C6F5SiMe3 (1:2) in the presence of BF3ꢀOEt2
The reaction was performed in analogy to the above one (4.10).
A cold (ꢁ78 8C) solution of C6F5SiMe3 (4.33 g, 14.8 mmol) and
BF3ꢀOEt2 (1.8 mL, 14.6 mmol) in CH2Cl2 (8 mL) was stirred over NaF
(86 mg, 2.05 mmol) before being added drop-wise to a cold
suspension of BrF3 (1.01 g, 7.38 mmol) in CH2Cl2 (25 mL) and
MeCN (0.77 mL, 14.7 mmol) which contained NaF (90 mg,
2.14 mmol). The light-yellow suspension discolored after 1 h at
ꢁ78 8C. The mother liquor contained C6F5SiMe3, C6F5Br, Me3SiF,
and [BF4]ꢁ in the molar ratio 30:19:9:42, while no BrF3 or C6F5BrF2
was found (19F NMR). This composition was not changed after 12 h
at ꢁ78 8C. The liquid phase was separated. The solid was dried in
vacuum at ꢁ30 to 20 8C and suspended in MeCN. The 19F NMR
spectrum of the MeCN suspension showed signals of [BF4]ꢁ as
major component with its 10/11B isotopomers (ꢁ150.65/
ꢁ150.70 ppm) besides a minor unknown species (ꢁ65.1 ppm, q,
J = 17 Hz).
4.9. Reaction of BrF3 with C6F5SiF3 (1:2)
A 23-mm i.d. FEP trap was charged with C6F5SiF3 (5.283 g,
20.05 mmol), CH2Cl2 (10 mL) and NaF (102 mg, 2.43 mmol) and
cooled to ꢁ60 8C. In a second 23-mm i.d. FEP trap BrF3 (1.43 g,
10.45 mmol) was frozen at ꢁ78 8C and cold (ꢁ78 8C) CH2Cl2
(35 mL), cold (ꢁ40 8C) MeCN (1.1 mL, 21.05 mmol) and NaF
(106 mg, 2.52 mmol) were added in sequence. CAUTION! BrF3
can react violently with neat MeCN [44]. The suspension was
stirred at ꢁ78 8C for 10 min to remove traces of HF and the light-
yellow mother liquor (BrF3 in CH2Cl2/MeCN) was added drop-wise
4.12. Preparation of [(CF3CꢄC)2Br][BF4] (5)
A 11.7-mm i.d. PFA trap equipped with a Teflon-coated
magnetic stir bar was charged with a solution of BrF3 (97 mg,
0.70 mmol) in PFP (1 mL) and cooled to ꢁ45 8C. A cold (ꢁ45 8C)
solution of CF3CꢄCBF2 (0.80 mmol) in PFP (2 mL) was added in
portions within 2 min. The white suspension was stirred at ꢁ40 8C
for 1 h, centrifuged at ꢁ78 8C and the mother liquor was decanted.
The white precipitate was washed with cold (ꢁ40 8C) PFP (2 mL)

930
H.-J. Frohn et al. / Journal of Fluorine Chemistry 131 (2010) 922–932
and dried in vacuum at ꢁ30 8C for 1 h to yield [(CF3CꢄC)2Br][BF4]
(56 mg, 31%).
(ꢁ20 8C) solution of BrF3 (0.5 mmol) in PFB (0.7 mL) was added in
portions. After stirring at ꢁ20 8C for 2.5 h the 19F NMR spectrum
(ꢁ20 8C) of the colorless solution showed signals of [(cis-
C2F5CF55CF)2Br]+ (9a), [(cis-C2F5CF55CF)(trans-C2F5CF55CF)Br]+
(9b), [cis-C2F5CF55CFBF3]ꢁ, [C4F9BF3]ꢁ, C4F9Br, C2F5CFBrCF2Br, cis-
Attempts to dissolve [(CF3CꢄC)2Br][BF4] in cold (ꢁ25 8C) MeCN
led to vigorous reactions and formation of a complex mixture (19F).
[(CF3CꢄC)2Br][BF4] (5). 19F NMR (aHF, ꢁ40 8C):
d
ꢁ52.6 (s, 6F,
F3), ꢁ148.6 (q (1:1:1:1), 1J(F, B) = 12 Hz, [BF4]ꢁ). 11B NMR (aHF,
C2F5CF55CFBr,
and
trans-C2F5CF55CFBr
(molar
ratio
ꢁ40 8C):
ꢁ40 8C):
d
d
ꢁ2.1 (quintet, 1J(B, F) = 12 Hz, [BF4]ꢁ). 13C NMR (aHF,
29:8:29:8:6:3:5:12) besides a trace of [(trans-C2F5CF55CF)2Br]+
(9c). Resonances of BrF3 and [BF4]ꢁ were not detected. In order to
react still present cis-C2F5CF55CFBF2, a further portion of BrF3
(0.3 mmol) in PFB (0.1 mL) was added at ꢁ15 8C. Stirring at ꢁ15 8C
for 1 h resulted in a suspension and the 19F NMR spectrum showed
the complete consumption of cis-C2F5CF55CFBF2. Volatiles were
removed in vacuum at 20 8C, the residue was washed with CCl3F
(2ꢉ 2 mL) at 15 8C and the solid was dried in vacuum at 20 8C for
1 h to yield [(C2F5CF55CF)2Br]Y [(cis, cis):(cis, trans):(trans,
trans) = 80:18:2] [Y = [C4F9BF3]ꢁ/[BF4]ꢁ(24:76)] (167 mg).
112.4 (q, 1J(C3, F3) = 264 Hz, C3), 83.2 (q, 2J(C2,
F3) = 61 Hz, C2), 44.1 (q, 3J(C1, F3) = 8 Hz, C1).
4.13. Preparation of [(CF3CF55CF)2Br]Y salts
A 8-mm i.d. FEP trap equipped with a Teflon-coated magnetic stir
bar was charged with a solution of BrF3 (0.14 mmol) in PFP (1 mL)
and cooled to ꢁ45 8C. Then a cold (ꢁ45 8C) solution of trans-
CF3CF55CFBF2 (0.29 mmol) in PFP (1.5 mL) was added in portions.
After stirring at ꢁ40 8C for 1 h and at ꢁ30 8C for 1 h, [(trans-
CF3CF55CF)2Br]+ (8a), [trans-CF3CF55CFBF3]ꢁ and trans-CF3CF55CFBF2
were the major components of the colorless solution (19F NMR,
ꢁ30 8C). A second portion of cold (ꢁ10 8C) BrF3 (0.14 mmol) in PFP
(1 mL) was added to the cold (ꢁ40 8C) stirred reaction solution. The
solution was stirred at ꢁ35 8C for 40 min and then evaporated at
ꢁ10 8C in vacuum to dryness. A solution of the product in MeCN
contained [(trans-CF3CF55CF)2Br]+ (8a), [(cis-CF3CF55CF)(trans-
1,2-Dibromooctafluorobutane. 19F NMR (PFB, ꢁ20 8C):
d
ꢁ56.5
(d, 2J(F1A, F1B) = 178 Hz, 1F, F1A), ꢁ57.4 (d, 2J(F1B, F1A) = 178 Hz, 1F,
F1B), ꢁ77.6 (ddd, 4J(F4, F2) = 11 Hz, 3J(F4, F3A) = 5 Hz, 3J(F4,
F3B) = 6 Hz, 3F, F4), ꢁ124.8 (m, 2F, F3A, 3B), ꢁ131.1 (m, 1F, F2).
[(C2F5CF55CF)2Br][C4F9BF3]. 19F NMR (PFB, ꢁ20 8C):
d
ꢁ82.0 (t,
0
0
0
0
3J(F4, F3) = 3J(F4 , F3 ) = 6 Hz, 6F, F4,F4 ), ꢁ92.9 (md, 3J(F1, F2) = 3J(F1 ,
0
0
0
0
F2 ) = 48 Hz, 2F, F1,F1 ), ꢁ114.5 (md, 3J(F2, F1) = 3J(F2 , F1 ) = 48 Hz,
0
0
2F, F2,F2 ), ꢁ116.9 (m, 4F, F3,F3 ) (cis, cis-isomer 9a); ꢁ82.2 (m, 3F,
0
CF3CF55CF)Br]+
(8b)
(94:6),
[trans-CF3CF55CFBF3]ꢁ,
[cis-
F4), ꢁ90.2 (dd, 3J(F1, F2) = 48 Hz, 4J(F1, F1 ) = 6 Hz, 1F, F1), ꢁ115.0 (d,
CF3CF55CFBF3]ꢁ, and [C3F7BF3]ꢁ (60:32:8) (yield 0.13 mmol).
3J(F2, F1) = 48 Hz, F, F2), ꢁ117.2 (m, 2F, F3) (cis-moiety of cis, trans-
0
0
0
0
[(CF3CF55CF)2Br][CF3CF55CFBF3/C3F7BF3]. 19F NMR (CH3CN,
isomer 9b), ꢁ82.7 (m, 3F, F4 ), ꢁ107.9 (dt, 3J(F1 , F2 ) = 130 Hz, 4J(F1 ,
0
0
0
0
0
0
0
ꢁ10 8C):
d
ꢁ67.8 (dd, 3J(F3, F2) = 3J(F3 , F2 ) = 10 Hz, 4J(F3,
F3 ) = 25 Hz, 1F, F1 ), ꢁ120.3 (dd, 4J(F3 , F1 ) = 25 Hz, 3J(F3 ,
0
0
0
0
0
0
0
0
0
F1) = 4J(F3 , F1 ) = 19 Hz, 6F, F3, F3 ), ꢁ106.4 (qdd, 4J(F1, F3) = 4J(F1 ,
F2 ) = 12 Hz, 2F, F3 ), ꢁ130.8 (d, 3J(F2 , F1 ) = 130 Hz, 1F, F2 )
0
0
0
0
0
0
F3 ) = 19 Hz, 3J(F1, F2) = 3J(F1 , F2 ) = 129 Hz, 5J(F1, F2 ) = 5J(F1 ,
(trans-moiety of cis, trans-isomer 9b); ꢁ82.8 (m, 6F, F4,F4 ),
0
0
0
0
0
0
F2) = 5 Hz, 2F, F1,F1 ), ꢁ139.4 (md, 3J(F2, F1) = 3J(F2 , F1 ) = 129 Hz,
ꢁ107.0 (dt, 3J(F1, F2) = 3J(F1 , F2 ) = 130 Hz, 4J(F1, F3) = 4J(F1 ,
0
0
0
0
2F, F2,F2 ) (trans, trans-isomer (8a)); ꢁ66.5 (dd, 3J(F3, F2) = 11 Hz,
F3 ) = 25 Hz, 2F, F1,F1 ), ꢁ120.4 (m, 4F, F3,F3 ), ꢁ132.7 (d, 3J(F2,
0
0
0
4J(F3, F1) = 7 Hz, 3F, F3), ꢁ94.5 (qd, 4J(F1, F3) = 7 Hz, 3J(F1, F2) = 42 Hz,
F1) = 3J(F2 , F1 ) = 130 Hz, 2F, F2,F2 ) (trans, trans-isomer 9c); ꢁ80.1
(t, 4J(F4, F2) = 10 Hz, 3F, F4), ꢁ123.5 (m, 2F, F2), ꢁ125.5 (m, 2F, F3),
ꢁ133.6 (m, 2F, F1), ꢇ–150 (very br, 3F, BF3ꢁ) ([C4F9BF3]ꢁ)
(bromonium salt with [BF4]ꢁ counteranion is insoluble in PFB).
1F, F1), ꢁ121.3 (qd, 3J(F2, F3) = 11 Hz, 3J(F2, F1) = 42 Hz, 1F, F2) (cis-
0
0
0
moiety of cis, trans-isomer (8b)), ꢁ67.4 (dd, 3J(F3 , F2 ) = 11 Hz, 4J(F3 ,
0
0
0
0
0
F1 ) = 22 Hz, 3F, F3 ), ꢁ107.5 (qd, 4J(F1 , F3 ) = 20 Hz, 3J(F1 ,
0
0
0
0
0
F2 ) = 129 Hz, 1F, F1 ), ꢁ140.0 (d, 3J(F2 , F1 ) = 128 Hz, 1F, F2 ) (trans-
moiety of cis, trans-isomer (8b)); ꢁ80.4 (tt, 3J(F3, F2) = 3 Hz, 4J(F3,
F1) = 9 Hz, 3F, F3), ꢁ127.7 (m, 2F, F2), ꢁ134.0 (m, 2F, F1), ꢁ150.9 (q
(1:1:1:1), 1J(F, B) = 40 Hz, 3F, BF3ꢁ) ([C3F7BF3]ꢁ); ꢁ66.4 (m, 3F, F3),
[(C2F5CF = CF)2Br][BF4 + C4F9BF3]. 19F NMR (CH3CN, 24 8C):
d
0
0
0
ꢁ81.5 (m, 6F, F4,F4 ), ꢁ89.8 (md, 3J(F1, F2) = 3J(F1 , F2 ) = 44 Hz, 2F,
0
0
0
F1,F1 ), ꢁ116.8 (m, 4F, F3,F3 ), ꢁ119.1 (md, 3J(F2, F1) = 3J(F2 ,
0
0
F1 ) = 44 Hz, 2F, F2,F2 ) (cis, cis-isomer 9a); ꢁ81.7 (m, 3F, F4),
ꢁ87.2 (d, 3J(F1, F2) = 44 Hz, 1F, F1), ꢁ116.9 (m, 2F, F3), ꢁ118.8 (d,
3J(F2, F1) = 44 Hz, F, F2) (cis-moiety of cis, trans-isomer 9b), ꢁ82.6
ꢁ137.1 (m, 1F, F1), ꢁ158.8 (m, 1F, F2), ꢁ140.9 (q (1:1:1:1), 1J(F,
([cis-CF3CF = CFBF3]ꢁ); ꢁ66.8 (dd, 3J(F3,
ꢁ
B) = 38 Hz, 3F, BF3
)
0
0
0
0
0
F2) = 11 Hz, 4J(F3, F1) = 23 Hz, 3F, F3), ꢁ156.1 (d, 3J(F1, F2) = 129 Hz,
1F, F1), ꢁ179.6 (d, 3J(F2, F1) = 129 Hz, 1F, F2), ꢁ142.2 (q(1:1:1:1), 1J(F,
B) = 39 Hz, 3F, BF3ꢁ) ([trans-CF3CF55CFBF3]ꢁ).
(m, 3F, F4 ), ꢁ106.5 (dt, 3J(F1 , F2 ) = 130 Hz, 4J(F1 , F3 ) = 25 Hz, 1F,
0
0
0
0
0
0
F1 ), ꢁ120.3 (ddq, 4J(F3 , F1 ) = 25 Hz, 3J(F3 , F2 ) = 12 Hz, 3J(F3 ,
0
0
0
0
0
F4 ) = 2 Hz, 2F, F3 ), ꢁ136.1 (d, 3J(F2 , F1 ) = 128 Hz, 1F, F2 ) (trans-
0
moiety of cis, trans-isomer 9b); ꢁ82.7 (m, 6F, F4,F4 ), ꢁ105.6 (dt,
0
0
0
0
4.14. Preparation of [(C2F5CF55CF)2Br]Y salts
3J(F1, F2) = 3J(F1 , F2 ) = 128 Hz, 4J(F1, F3) = 4J(F1 , F3 ) = 26 Hz, 2F,
0 0 0 0
F1,F1 ), ꢁ120.4 (dd, 3J(F3, F2) = 3J(F3 , F2 ) = 13 Hz, 4J(F3, F1) = 4J(F3 ,
0
0
0
0
(A) A 11.7-mm i.d. PFA trap equipped with a Teflon-coated
magnetic stir bar was charged with a solution of BrF3 (0.5 mmol) in
PFB (0.7 mL) and cooled to ꢁ20 8C. A cold (ꢁ20 8C) solution of cis-
C2F5CF = CFBF2 (1.0 mmol) in PFB (1.5 mL) was added in portions.
After stirring at ꢁ20 8C for 2 h the 19F NMR spectrum (ꢁ20 8C) of
the colorless solution showed signals of [(cis-C2F5CF55CF)2Br]+ (9a),
[(cis-C2F5CF55CF)(trans-C2F5CF55CF)Br]+ (9b), [cis-C2F5CF55CFBF3]ꢁ,
[C4F9BF3]ꢁ, C4F9Br, and C2F5CFBrCF2Br (molar ratio 21:4:55:6:9:5)
besides a trace of [(trans-C2F5CF55CF)2Br]+ (9c). Resonances of BrF3,
C2F5CF55CF2, [BF4]ꢁ, and [C2F5CFBrCF2BF3]ꢁ were not detected.
Volatiles were removed in vacuum at 20 8C, the residue was
washed with CCl3F (2 mL) at 15 8C and the solid was dried in
vacuum at 20 8C for 3 h to yield [(C2F5CF55CF)2Br]Y [(cis, cis):(cis,
trans):(trans, trans) = 90:8:2] (Y = [C2F5CF55CFBF3]ꢁ (cis:trans =
63:37):[C4F9BF3]ꢁ = 70:30) (114 mg).
F1 ) = 26 Hz, 4F, F3,F3 ), ꢁ135.4 (d, 3J(F2, F1) = 3J(F2 , F1 ) = 128 Hz, 2F,
0
F2,F2 ) (trans, trans-isomer 9c); ꢁ80.6 (tt, 3J(F4, F3) = 3 Hz, 4J(F4,
F2) = 10 Hz, 3F, F4), ꢁ123.8 (m, 2F, F2), ꢁ125.4 (m, 2F, F3), ꢁ133.0
(m, 2F, F1), ꢁ150.9 (q (1:1:1:1), 1J(F, B) = 41 Hz, 3F, BF3
([C4F9BF3]ꢁ); ꢁ148.0 (s, [BF4]ꢁ).
)
ꢁ
4.15. Reaction of C6F13BF2 with BrF3
A cold (ꢁ15 8C) solution of BrF3 (0.30 mmol) in PFP (0.5 mL) was
added in one portion to a cold (ꢁ65 8C) solution of C6F13BF2
(0.50 mmol) in PFP (3 mL). After stirring at ꢁ60 8C for 1 h the
solution contained still residual C6F13BF2 besides the products
C6F13Br and C6F14 (55:22:23) (19F NMR). A second portion of BrF3
(0.20 mmol) in PFP (0.2 mL) was added at ꢁ60 8C. The solution was
stirred at ꢁ60 8C for 1 h and then at ꢁ10 8C for 1 h. The NMR
spectra displayed resonances of C6F13Br and C6F14 (1:1) besides
traces of C6F13BF2 (19F NMR) and BF3 (11B NMR). To determine the
quantity of unreacted BrF3, the solution was treated with C6F5H
(B) A 11.7-mm i.d. PFA trap equipped with a Teflon-coated
magnetic stir bar was charged with a solution of cis-C2F5CF55CFBF2
(1.0 mmol) in PFB (1.5 mL) and cooled to ꢁ20 8C. Then a cold

H.-J. Frohn et al. / Journal of Fluorine Chemistry 131 (2010) 922–932
931
(93 mg, 0.55 mmol) at ꢁ5 8C for 1.5 h. The 19F NMR spectrum
ꢁ146.8 (q (1:1:1:1), 1J(F, B) = 40 Hz, 3F, BF3ꢁ). 11B NMR (aHF,
showed partial conversion of C6F5H (0.30 mmol, unreacted) into
ꢁ20 8C):
d
ꢁ0.2 (s, Dn1/2 = 90 Hz, BF3ꢁ).
C6F5Br
(0.11 mmol),
1-H-heptafluorocyclohexa-1,4-diene
(0.08 mmol) and 1-bromoheptafluorocyclohexa-1,4-diene (trace).
Thus, ca. 0.30 mmol of BrF3 had reacted with C6F13BF2.
4.18. Reaction of [Bu4N][cis-C2F5CF55CFBF3] with BrF3 in PFB
A cold (ꢁ20 8C) solution of BrF3 (0.29 mmol) in PFB (0.1 mL) was
4.16. Reactions of C8F17Br with BrF3 and with [BrF2][SbF6]
added to
a
cold (ꢁ20 8C) stirred solution of [Bu4N][cis-
C2F5CF = CFBF3] (0.29 mmol) in PFB (0.6 mL). The colorless solution
(A) A solution of C8F17Br (179 mg, 0.35 mmol) and BrF3 (35 mg,
0.25 mmol) in PFB (0.5 mL) was stirred at 24 8C for 17 h. The 19F
NMR spectrum displayed resonances of the unchanged starting
materials C8F17Br (ꢁ62.7 (CF2Br), ꢁ80.3 (CF3), ꢁ116.2, ꢁ119.7,
ꢁ120.5, ꢁ121.5, ꢁ125.1 (6CF2) ppm) and BrF3 (ꢁ14.6 ppm) besides
PFB.
(B) The above solution was cooled to 0 8C and BF3 was bubbled
into the solution for 5 min before the solution was kept at 24 8C for
1 h. The 19F and 11B NMR spectra showed the formation of
was stirred at ꢁ20 8C for 1 h and warmed to 20 8C. The 11B and 19
F
NMR spectra showed resonances of [C2F5CFBrCF2BF3]ꢁ,
C2F5CF55CF2, and [BF4]ꢁ (53:37:10) besides signals of PFB.
[Bu4N][C2F5CFBrCF2BF3] (TBA-11). 19F NMR (PFB, 24 8C):
d
ꢁ77.1 (dt, 4J(F4, F2) = 5 Hz, 3J(F4, F3) = 10 Hz, 3F, F4), ꢁ113.6 (d,
2J(F3A, F3B) = 284 Hz, 1F, F3A), ꢁ115.1 (d, 2J(F3B, F3A) = 284 Hz, 1F,
F3B), ꢁ117.5 (d, 2J(F1A, F1B) = 324 Hz, 1F, F1A), ꢁ121.1 (d, 2J(F1B
,
F1A) = 324 Hz, 1F, F1B), ꢁ134.6 (m, 1F, F2), ꢁ147.0 (m, 3F, BF3ꢁ). 11
B
NMR (PFB, 24 8C):
BF3ꢁ).
d
ꢁ1.0 (tq, 2J(B, F1) = 20 Hz, 1J(B, F) = 40 Hz,
‘‘BrF3ꢀBF3’’ (
d
(F): ꢁ87 ppm and
d(B): 2.4 ppm) besides unchanged
C8F17Br. When the solution was kept at 24 8C for 3 d, perfluoro-
octane was formed in quantitative yield.
4.19. Reaction of K[C6F13BF3] with [BrF2][SbF6]
(C) A solution of [BrF2][SbF6] (46 mg, 0.13 mmol) in aHF (1 mL)
was cooled to ꢁ40 8C and C8F17Br (0.4 mL) was added. The mixture
was stirred at 24 8C for 3 h before the upper acidic phase was
decanted at 10 8C. The 19F NMR spectrum of the organic phase
A cold (ꢁ15 8C) solution of [BrF2][SbF6] (56 mg, 0.15 mmol) in
aHF (0.7 mL) was added in portions to a cold (ꢁ15 8C) stirred
solution of K[C6F13BF3] (151 mg, 0.35 mmol) in aHF (1.5 mL). After
stirring at 20 8C for 6 h only signals of unchanged K[C6F13BF3] were
detected in the solution.
confirmed the quantitative formation of C8F18
.
4.17. Reaction of K[cis-C2F5CF55CFBF3] with BrF3 in aHF
5. Conclusions
A solution of K[cis-C2F5CF55CFBF3] (190 mg, 0.66 mmol) in aHF
(1.6 mL) was cooled to ꢁ40 8C and a cold (ꢁ30 8C) solution of BrF3
(94 mg, 0.68 mmol) in aHF (0.6 mL) was added in portions. The
reaction mixture was stirred at ꢁ30 8C for 2 h and at ꢁ20 8C for
0.5 h forming a suspension. The 19F NMR spectrum showed the
complete consumption of [cis-C2F5CF55CFBF3]ꢁ, but signals of
[(C2F5CF55CF)2Br]+ were not detected. The reaction mixture was
extracted with CCl2FCClF2 (1 mL). The extract contained
C2F5CFBrCF3 (0.40 mmol, 60%) (19F NMR). The acidic phase was
evaporated to dryness in vacuum and the solid residue was
extracted with MeCN (1 mL). The 11B and 19F NMR spectra showed
the formation of K[C2F5CFBrCF2BF3] (0.10 mmol, 15%).
Reactions of BrF3 with RFBF2 (RF = perfluorinated aryl, alkenyl,
and alkynyl group) in weakly coordinating solvents like CH2Cl2 or
better in PFB, PFP present a convenient preparative route to
bis(perfluoroorganyl)bromonium salts. Comparing reactions of
BrF3 with C6F5BF2, C6F5SiF3, and C6F5SiMe3 showed the influence of
the acidity (fluoride affinity) on the reaction rate for the first and
second F/C6F5 substitution step: C6F5BF2 gives only bromonium
salts, C6F5SiF3 allowed the aimed synthesis as well of C6F5BrF2 as of
[(C6F5)2Br]+ salts, whereas in case of C6F5SiMe3 only C6F5BF2 is
accessible. The 1:2 reaction of BrF3 with C6F13BF2 in PFP gave
C6F13Br and C6F14 (1:1) as the only perfluoroalkyl compounds,
which may be considered as products of decomposition of the
unstable salt [(C6F13)2Br][C6F13BF3]. The instability can be attrib-
uted to electrostatic repulsion between high partial positive charge
on bromine and both ipso carbon atoms of the perfluoroalkyl
groups. The 3:2 molar reaction of BrF3 with (C6F5)3B (more acidic
than C6F5BF2) ended with [(C6F5)2Br][(C6F5)nBF4ꢁn] salts with
anion mixtures (n = 0–3) and showed that boranes (C6F5)nBF3ꢁn
(n = 1–3) operate here as intermediate transfer reagents. Finally,
salts [(C6F5)2Br]Y can be prepared from BrF3 or [BrF2][SbF6] (BrIII-
electrophile) and K[C6F5BF3] (C-nucleophile) in aHF. This route
failed for the synthesis of perfluoroalkenylbromonium and -
alkylbromonium salts [(RF)2Br]Y.
2-Bromoperfluorobutane (25). 19F NMR (CCl2FCClF2, 24 8C):
d
ꢁ75.9 (qdd, 5J(F1, F4) = 5 Hz, 4J(F1, F3A) = 8 Hz, 4J(F1, F3B) = 12 Hz, 3F,
F1), ꢁ79.0 (qd, 5J(F4, F1) = 5 Hz, 4J(F4, F2) = 11 Hz, 3F, F4), ꢁ116.6
(qdd, 4J(F3A, F1) = 8 Hz, 3J(F3A, F2) = 8 Hz, 2J(F3A, F3B) = 286 Hz, 1F,
F3A), ꢁ118.1 (qdd, 4J(F3B, F1) = 12 Hz, 3J(F3B, F2) = 10 Hz, 2J(F3B
,
F3A) = 286 Hz, 1F, F3B), ꢁ140.9 (qt, 4J(F2, F4) = 11 Hz, 3J(F2,
F3) = 9 Hz, 1F, F2) (lit. [45]: 19F NMR (neat, ꢁ20 8C):
d
ꢁ76.3 (3F),
ꢁ79.3 (3F), ꢁ117.8 (2F), ꢁ141.4 (1F)). 19F NMR (aHF, ꢁ20 8C):
d
ꢁ74.3 (qdd, 5J(F1, F4) = 4 Hz, 4J(F1, F3A) = 9 Hz, 4J(F1, F3B) = 12 Hz, 3F,
F1), ꢁ77.4 (qd, 5J(F4, F1) = 4 Hz, 4J(F4, F2) = 11 Hz, 3F, F4), ꢁ115.3
(qdd, 4J(F3A, F1) = 8 Hz, 3J(F3A, F2) = 8 Hz, 2J(F3A, F3B) = 287 Hz, 1F,
F3A), ꢁ116.2 (qdd, 4J(F3B, F1) = 12 Hz, 3J(F3B, F2) = 11 Hz, 2J(F3B
,
F3A) = 287 Hz, 1F, F3B), ꢁ139.7 (qt, 4J(F2, F4) = 11 Hz, 3J(F2,
F3) = 9 Hz, 1F, F2).
Acknowledgement
K[C2F5CFBrCF2BF3] (K-11). 19F NMR (CH3CN, 24 8C):
d
ꢁ77.3 (dt,
4J(F4, F2) = 5 Hz, 3J(F4, F3) = 9 Hz, 3F, F4), ꢁ114.3 (qddd, 3J(F3A
,
,
We gratefully acknowledge financial support by the Deutsche
Forschungsgemeinschaft and the Fonds der Chemischen Industrie.
F4) = 8 Hz, 3J(F3A
,
F1A) = 12 Hz, 3J(F3A
,
F1B) = 20 Hz, 2J(F3A
F3B) = 284 Hz, 1F, F3A), ꢁ115.6 (md, 2J(F3B, F3A) = 284 Hz, 1F, F3B),
ꢁ118.7 (d, 2J(F1A
,
F1B) = 319 Hz, 1F, F1A), ꢁ122.0 (d, 2J(F1B
,
References
F1A) = 319 Hz, 1F, F1B), ꢁ136.1 (m, 1F, F2), ꢁ149.4 (q (1:1:1:1),
1J(F, B) = 40 Hz, 3F, BF3ꢁ). 11B NMR (CH3CN, 24 8C):
d
ꢁ0.7 (tq, 2J(B,
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