[N(CF3)2], effect of fluorine substituents on aryl groups of iodonium cations and of coordinating bases on the fluoride transfer from the anion to the cation

Article abstract of DOI:10.1016/j.jfluchem.2012.03.004

Three prototypical fluoroaryliodonium salts with the [N(CF ₃)₂]^- anion were obtained by metathesis in the corresponding tetrafluoroborate salts [Ar(Ar′)I][BF₄] (Ar/Ar′ = C₆H₅/4-FC₆

Full text of DOI:10.1016/j.jfluchem.2012.03.004

Journal of Fluorine Chemistry 138 (2012) 24–27
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
[Ar(Ar0)I][N(CF3)2], effect of fluorine substituents on aryl groups of iodonium
cations and of coordinating bases on the fluoride transfer from the anion
to the cation
a
c
Markus E. Hirschberg a, , Andre Wenda , Hermann-Josef Frohn
*
b,**
, Nikolai V. Ignat’ev
´
a Inorganic Chemistry, Bergische Universita¨t Wuppertal, Gaußstr. 20, D-42097 Wuppertal, Germany
b Inorganic Chemistry, Universita¨t Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg, Germany
c PM-ABE, Merck KGaA, Frankfurter Str. 250, D-64293 Darmstadt, Germany
A R T I C L E I N F O
A B S T R A C T
Three prototypical fluoroaryliodonium salts with the [N(CF3)2]ꢀ anion were obtained by metathesis in
the corresponding tetrafluoroborate salts [Ar(Ar0)I][BF4] (Ar/Ar0 = C6H5/4-FC6H4, 3-FC6H4/4-FC6H4, C6F5/
C6F5) with in situ generated Rb[N(CF3)2]. The kinetic lability of the [N(CF3)2]ꢀ anion (potential fluoride
donor like [OCF3]ꢀ) in combination with the gradual change in fluoride affinity of the three [Ar(Ar0)I]+
fluoroaryliodonium cations allowed to distinguish the fluoride acceptor property of the three [Ar(Ar0)I]+
fluoroaryliodonium cations. Coordinating solvents or ligands suppressed the fluoride transfer from the
[N(CF3)2]ꢀ anion to the fluoroaryliodonium cation.
Article history:
Received 5 January 2012
Received in revised form 1 March 2012
Accepted 5 March 2012
Available online 16 March 2012
Dedicated to Professor Norbert Kuhn on the
Occasion of his 65th Birthday.
ß 2012 Elsevier B.V. All rights reserved.
Keywords:
Fluoroaryliodonium salts
Anion metathesis
Bis(trifluoromethyl)imide anion
Fluoride affinity
Fluoride transfer
1. Introduction
2. Results and discussion
Iodonium salts were first synthesized by Viktor Meyer in 1894,
namely phenyl(p-iodophenyl)iodonium salts with the anions Clꢀ,
Brꢀ, Iꢀ, and NO3ꢀ [1]. Generally, iodonium salts represent the most
common type of iodine(III) compounds and have found numerous
applications, e.g. as cationic photoinitiators or reagents in organic
chemistry [2–4]. The starting materials for the present investiga-
tion, symmetric and asymmetric fluoroaryliodonium tetrafluor-
oborates, were accessible in good yields by a common procedure,
the reaction of ArIF2 with Ar0BF2 in weakly coordinating solvents
like CH2Cl2 or other halocarbons [5,6].
2.1. Syntheses of the fluoroaryliodonium bis(trifluoromethyl)imides
The [N(CF3)2]ꢀ anion was in situ generated by the reaction of
CF3SO2N(CF3)2 with RbF [9] and was used for the anion metathesis
in fluoroaryliodonium tetrafluoroborates [Ar(Ar0)I][BF4]. Fluoroar-
yliodonium bis(trifluoromethyl)imides [Ar(Ar0)I][N(CF3)2] were
prepared in the coordinating solvent CH3CN (1). The co-product
Rb[BF4] precipitated quantitatively and was characterized by
Raman spectroscopy.
CF3
CF3
CH3CN
0 °C
Ar
I
Ar
I
With the present paper we continue our investigations of as
well fluoroaryliodonium salts as [N(CF3)2]ꢀ anion chemistry [7,8].
BF4
+ Rb[N(CF3)2]
+ Rb[BF4]
N
Ar'
Ar'
(Ar/Ar’ = C6H5/4-FC6H4, 3-FC6H4/4-FC6H4, C6F5/C6F5)
ð1Þ
2.2. How N-base coordination to the fluoroaryliodonium cation
influences the fluoride transfer from the [N(CF3)2]ꢀ anion to the
fluoroaryliodonium cation?
* Corresponding author. Tel.: +49 202 439 3460; fax: +49 32121 109129.
** Corresponding author. Tel.: +49 203 379 3310; fax: +49 203 379 2231.
E-mail addresses: Markus.Hirschberg@uni-wuppertal.de (M.E. Hirschberg),
h-j.frohn@uni-due.de (H.-J. Frohn).
While at 20 8C solutions of [C6H5(4-FC6H4)I][N(CF3)2] and [3-
FC6H4(4-FC6H4)I][N(CF3)2] in CH3CN showed no products of
0022-1139/$ – see front matter ß 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2012.03.004

M.E. Hirschberg et al. / Journal of Fluorine Chemistry 138 (2012) 24–27
25
fluoride transfer, namely ArAr0IF and CF3–N55C(F)–N(CF3)2, under
2.4. Multinuclear magnetic resonance spectra of the
fluoroaryliodonium bis(trifluoromethyl)imides
comparable conditions the solution of [(C6F5)2I][N(CF3)2] con-
tained a significant admixture of (C6F5)2IF after degassing in
vacuum besides the iodonium bis(trifluoromethyl)imide. In the
series Ar/Ar0 = C6H5/4-FC6H4, 3-FC6H4/4-FC6H4, C6F5/C6F5, the
electrophilicity – or to be more precise, the fluoride affinity – of
the fluoroaryliodonium cation increased parallel to the instability
of [Ar(Ar0)I][N(CF3)2] in CH3CN solution.
In general, a coordinating solvent like CH3CN is essential for the
stability of [Ar(Ar0)I][N(CF3)2] since coordination reduces the
electrophilicity at the iodine(III) atom. The removal of CH3CN
led to the transfer of fluoride from the [N(CF3)2]ꢀ anion to the
iodonium cation and Ar(Ar0)IF [10] and CF3–N55C(F)–N(CF3)2 [11]
were obtained (2).
The 19F NMR spectra of [C6H5(4-FC6H4)I][N(CF3)2] and [3-
FC6H4(4-FC6H4)I][N(CF3)2] in CH3CN solution displayed the signal
of the [N(CF3)2]ꢀ anion at ꢀ39 ppm as a singlet. This shift value is
akin to that of Rb[N(CF3)2]in situ
aryldiazonium bis(trifluoromethyl)imides (
(
d
(
19F) = ꢀ36 ppm) or to that of
d
(
19F) = ꢀ37 ppm) in
CH3CN at 24 8C [7] and proved the separation of the cations and the
[N(CF3)2]ꢀ anion by solvent molecules. Surprisingly and in contrast
to the above examples, the chemical shift of the [N(CF3)2]ꢀ anion in
[(C6F5)2I][N(CF3)2] occurred at ꢀ49.6 ppm. This shift is in between
the shift of N(CF3)2 groups in ionic and covalent vicinity. In 4-
FC6H4N(CF3)2 the resonance of the N(CF3)2 group in the solvent
CCl3F was observed at ꢀ56.4 ppm [13]. In 4-F2IC6H4N(CF3)2 in the
þ
þ½NðCF3 2ꢁꢀ
0
½NðCF3Þ ꢁꢀþ½Aꢀrð!Ar ÞIꢁ CF3ꢀN¼CF2 ꢀ!Þ CF3N¼CðFÞꢀNðCF3Þ
presence of the strong s-electron withdrawing substituent IF2 the
2
2
ꢀArAr0IF
resonance in CH2Cl2 solution was found at ꢀ55.9 ppm [8]. The shift
value at ꢀ49.6 ppm in [(C6F5)2I][N(CF3)2]/CH3CN solution is a
strong hint for a cation–anion interaction, even in the well
coordinating solvent CH3CN.
þ Fꢀ
(2)
In case of the CH3CN solution of [3-FC6H4(4-FC6H4)I][N(CF3)2]
we demonstrated the influence of N-base coordination to the
iodine center. After addition of one equivalent of 1,10-phenanthro-
line the removal of CH3CN in vacuum was possible without
The 13C NMR spectroscopic information for the [N(CF3)2]ꢀ anion
of [Ar(Ar0)I][N(CF3)2] (Ar/Ar0 = C6H5/4-FC6H4, 3-FC6H4/4-FC6H4) in
CH3CN solution depended on temperature. The resonance of
[N(CF3)2]ꢀ was detected at 24 8C in 0.8 molar solutions only in
the 13C{19F*} mode (S/N ꢃ 400), but not in the 13C or 13C{1H} mode,
whereas atꢀ30 8C a singlet (13C{19F*}) ora quartetof quartets (13C or
decomposition
(fluoride
transfer)
of
the
[3-FC6H4(4-
FC6H4)I][N(CF3)2] entity. 1,10-phenanthroline is a stronger coor-
dinating base in comparison to CH3CN. The 19F and 1H resonances
of the base-coordinated cation were slightly shifted to lower
frequencies. N-base coordination to the cation reduced the
electrophilicity of the iodonium cation and prevented the fluoride
transfer from the anion to the cation.
1
3
13C{1H}, JC,F = 247 Hz and JC,F = 10 Hz) was observed at 125 ppm,
(*N(CF3)2 selectively decoupled). Both coupling constants are akin to
those in diazonium bis(trifluoromethyl)imide salts [7].
CF255NCF3 is the fluoride acceptor form which corresponds to
the [N(CF3)2]ꢀ anion. The gas-phase fluoride affinity (B3LYP
method, 6-31+G* basis set) of CF255NCF3 was calculated to be
60.2 kcal/mol and is larger than that of C(O)F2 (49.9 kcal/mol), the
corresponding fluoride acceptor form to the [OCF3]ꢀ anion, and of
the moderate Lewis acid (CH3)3SiCl (53.7 kcal/mol), but smaller
than that of SiF4 (71.8 kcal/mol). The gas-phase fluoride affinity of
fluoroaryliodonium cations is larger by order of magnitude than
the afore given values.
It is worth mentioning that our earlier attempts to synthesize
[Ar(Ar0)I][OCF3] salts were not successful. Fluoride transfer
proceeded from the labile [OCF3]ꢀ anion to the electrophilic
[Ar(Ar0)I]+ cations. That property was in agreement with the lower
gas-phase fluoride affinity of C(O)F2 relative to CF255NCF3. The
pronounced fluoride acceptor property of fluoroaryliodonium
cations in [Ar(Ar0)I][N(CF3)2] reduces their application potential
to generate Ar–N(CF3)2 or Ar0–N(CF3)2 molecules on a thermal
route.
3. Conclusions
[Ar(Ar0)I][N(CF3)2] salts (Ar/Ar0 = C6H5/4-FC6H4, 3-FC6H4/4-
FC6H4, C6F5/C6F5) were prepared by anion metathesis and could
be stabilized in solution by the solvent CH3CN (Ar/Ar0 = C6H5/4-
FC6H4, 3-FC6H4/4-FC6H4) or in the solid state by coordination of
1,10-phenanthroline (Ar/Ar0 = 3-FC6H4/4-FC6H4). N-base stabiliza-
tion avoided fluoride transfer from the labile anion to the
electrophilic cation. The extend of the fluoride transfer depended
on the degree of fluorine substituents on the aryl groups in the
[Ar(Ar0)I]+ cation. Fluoride transfer – the intrinsic reactivity of
[Ar(Ar0)I][N(CF3)2] salts – reduces an alternative potential reactivi-
ty of the [Ar(Ar0)I]+ cation, namely to phenylate the [N(CF3)2]ꢀ
anion on a non-catalyzed route and to form arylbis(trifluoro-
methyl)anilines. Despite of the perfluorinated moiety of the
[N(CF3)2]ꢀ anion and its low charge, it does not belong to the
class of weakly coordinating anions. It possesses a pronounced
kinetic lability and is an effective source of fluoride.
2.3. C6H5(4-FC6H4)IF – an effective fluoride donor – able to convert
CF3SO2N(CF3)2 into the [N(CF3)2]ꢀ anion
4. Experimental part
Moisture sensitive compounds were handled under an atmo-
sphere of dry argon. Reactions were carried out in standard glass
equipment or in traps made from FEP tubes (o.d. = 4.1 mm,
i.d. = 3.5 mm or o.d. = 9.0 mm, i.d = 8.0 mm). CH3CN (KMF) was
purified by reflux and distillation in sequence over KMnO4 and
P4O10, respectively.
The fluoride donor property of C6H5(4-FC6H4)IF offered
an interesting new route to the corresponding [C6H5
(4-FC6H4)I][N(CF3)2] salt, alternatively to the afore discussed
metathesis.
C6H5(4-FC6H4)IF acted in the coordinating solvent CH3CN as a
source of fluoride. Fluoride attacked the electrophilic sulfur center
of the reagent CF3SO2N(CF3)2 [12]. As shown in (3), the
bis(trifluoromethyl)imide anion was eliminated and the co-
product trifluoromethylsulfonylfluoride was formed.
NMR spectra were recorded on
a Bruker AVANCE 300
spectrometer (13C at 75.47 MHz, 19F at 282.40 MHz, and 1H at
300.13 MHz). The chemical shifts were referenced to TMS (13C, 1H),
CCl3F (19F, with C6F6 as secondary reference,
d
= ꢀ162.9 ppm). The
ratio of 19F and 1H nuclei in the products was determined by NMR
spectroscopy after the addition of the internal standards 1,3,5-
trifluorobenzene or benzotrifluoride, respectively. Raman spectra
were recorded on the Bruker FT-Raman spectrometer RFS 100/S
using the 1064 nm line of a Nd/YAG laser. The back-scattered
C6H5ð4-FC6H4ÞIF
CH3CN
þ CF3SO2NðCF3Þ2 ꢀ! ½C6H5ð4-FC6H4ÞIꢁ½NðCF3Þ2ꢁþCF3SO2F
0
ꢂC
(3)

26
M.E. Hirschberg et al. / Journal of Fluorine Chemistry 138 (2012) 24–27
(1808) radiation was sampled and analyzed (Stoke range: 50–
C6H5(4-FC6H4)IF: 19F NMR (CH3CN, ꢀ30 8C)
IF), ꢀ107.8 (m, 1F, 4-FC6H4).
d, ppm: 11.0 (br, 1F,
4000 cmꢀ1). The samples were placed in glass capillaries.
4.1. Syntheses of fluoroaryliodonium bis(trifluoromethyl)imides
4.2.2. Removal of the solvent from a [3-FC6H4(4-FC6H4)I][N(CF3)2]/
CH3CN solution
4.1.1. Synthesis of [C6H5(4-FC6H4)I][N(CF3)2]
A [3-FC6H4(4-FC6H4)I][N(CF3)2]/CH3CN solution which con-
tained 2% [3-FC6H4(4-FC6H4)I][BF4] was evacuated (0.05 hPa) at
20 8C for 10 min and formed a white foamy solid which consisted
of 56% [3-FC6H4(4-FC6H4)I][N(CF3)2], 42% 3-FC6H4(4-FC6H4)IF,
besides 2% [3-FC6H4(4-FC6H4)I][BF4] (19F NMR in CH3CN at 24 8C).
CF3SO2N(CF3)2 (0.288 g, 1.010 mmol) was added to a cold
suspension (0 8C) of RbF (0.089 g, 0.852 mmol) in CH3CN (0.5 mL).
After 30 min the suspension turned into a solution which was
subsequently added to
a cold solution (0 8C) of [C6H5(4-
FC6H4)I][BF4] (0.302 g, 0.783 mmol) in CH3CN (0.5 mL). The
reaction mixture was stirred for 15 min. The supernatant was
separated and degassed in vacuum (0.05 hPa, ꢀ35 8C, 15 min).
Based on 19F NMR, 98% [C6H5(4-FC6H4)I][N(CF3)2] were present
besides 2% CF3SO2N(CF3)2. The solid (99% yield) consisted of
3-FC6H4(4-FC6H4)IF: 19F NMR (CH3CN, 24 8C)
d, ppm: 8.9 (br, 1F,
IF) –107.3 (m, 1F, 4-FC6H4), ꢀ107.8 (m, 1F, 3-FC6H4).
4.2.3. Removal of the solvent from the CH3CN solution of a
[(C6F5)2I][N(CF3)2] metathesis
Rb[BF4] and was characterized by Raman spectroscopy
770 (100), 526 (18), 356 (21) [14].
n
=cmꢀ1
:
The CH3CN solution of the metathesis reaction contained 82%
[(C6F5)2I][N(CF3)2] and 18% (C6F5)2IF besides the co-product CF3–
N55C(F)–N(CF3)2
(
19F NMR
d
, ppm: ꢀ53.8 (d, 4J(F,F) = 15 Hz, 3F,
4.1.2. [C6H5(4-FC6H4)I][N(CF3)2]
CF3–N), ꢀ20.8 (m, 1F, CF), ꢀ54.5 (d, 4J(F,F) = 15 Hz, 6F, N(CF3)2).
After degassing and removal of CH3CN from the solution in vacuum
(0.05 hPa) at 20 8C over 10 min a white foamy residue resulted
which showed in CH3CN solution the presence of (C6F5)2IF
exclusively.
19F NMR (CH3CN, 24 8C)
d
, ppm: ꢀ39.0 (s, 6F, N(CF3)2), ꢀ106.6
(m, 1F, 4-FC6H4). 1H NMR (CH3CN, 24 8C) , ppm: 8.00 (m, 4H, H2,6
4-FC6H4 and C6H5), 7.57 (m, 1H, H4, C6H5), 7.42 (m, 2H, H3,5, C6H5),
d
,
7.15 (m, 2H, H3,5, 4-FC6H4). 13C{19F*} NMR (CH3CN, 24 8C)
d, ppm:
1
1
165.1 (dm, JC,F = 249 Hz, C4, 4-FC6H4), 138.4 (dm, JC,H = 171 Hz,
(C6F5)2IF: 19F NMR (CH3CN, 24 8C)
C6F5) –147.9 (t, 3J(F4,F3,5) = 20 Hz, 2F, p-C6F5) –157.9 (m, 4F, m-
d
, ppm: ꢀ124.3 (m, 4F, o-
C2,6, 4-FC6H4), 135.6 (dm, JC,H = 169 Hz, C2,6, C6H5), 132.5 (dm,
1
1JC,H = 164 Hz, C4, C6H5), 132.3 (dm, JC,H = 166 Hz, C3,5, C6H5),
C6F5), the IF-signal was too broad to determine a reliable
maximum.
1
125.3 (s, N(CF3)2), 119.6 (dd, JC,F = 15 Hz, JC,H = 4 Hz, C3,5, 4-
FC6H4), 118.5 (m, C1, C6H5), 112.0 (m, C1, 4-FC6H4), (*N(CF3)2
selectively decoupled).
2
2
4.3. Suppression of the fluoride transfer from the anion to the cation in
[3-FC6H4(4-FC6H4)I][N(CF3)2] by N-base coordination
[3-FC6H4(4-FC6H4)I][N(CF3)2] and [(C6F5)2I][N(CF3)2] were pre-
pared in an analogous manner.
An equimolar amount of 1,10-phenanthroline (0.144 mmol)
was added to a [3-FC6H4(4-FC6H4)I][N(CF3)2]/CH3CN solution.
CH3CN was distilled off in vacuum (0.05 hPa) at 0 8C over 1 h and at
20 8C over 10 min. The primary oily product turned to a foamy
solid. After dissolution in CH3CN the 19F NMR confirmed that 3-
4.1.3. [3-FC6H4(4-FC6H4)I][N(CF3)2]
19F NMR (CH3CN, 24 8C)
d
, ppm: ꢀ39.5 (s, 6F, N(CF3)2), ꢀ106.3
(m, 1F, 4-FC6H4), ꢀ107.3 (m, 1F, 3-FC6H4). 1H NMR (CH3CN, 24 8C)
d
, ppm: 8.01 (m, 2H, H2,6, 4-FC6H4), 7.77 (m, 2H, H2,6, 3-FC6H4), 7.44
(m, 1H, H5, 3-FC6H4), 7.31 (m, 1H, H4, 3-FC6H4), 7.17 (m, 2H, H3,5, 4-
FC6H4(4-FC6H4)IF was absent and that the ratio of [3-FC6H4(4-
+
FC6H4). 13C{19F*} NMR (CH3CN, 24 8C)
d
,
ppm: 165.3 (d,
FC6H4)I phen] to [N(CF3)2]ꢀ was 1:1.
.
1JC,F = 252 Hz, C4, 4-FC6H4), 163.2 (d, JC,F = 253 Hz, C3, 3-FC6H4),
[3-FC6H4(4-FC6H4)I phen][N(CF3)2]: 19F NMR (CH3CN, 24 8C)
d,
1
.
138.6 (dm, 1JC,H = 172 Hz, C2,6, 4-FC6H4), 133.9 (dm, 1JC,H = 168 Hz,
ppm: ꢀ38.6 (s, 6F, N(CF3)2), ꢀ107.0 (m, 1F, 4-FC6H4), ꢀ107.8 (m, 1F,
3-FC6H4). 1H NMR (CH3CN, 24 8C)
ppm: 8.95 (dd,
3J(H2,9,H3,8) = 4 Hz, 4J(H2,9,H4,7) = 2 Hz, 2H, H2,9), 8.20 (dd,
3J(H4,7,H3,8) = 8 Hz, 4J(H4,7,H2,9) = 2 Hz, 2H, H4,7), 7.99 (m, 2H, H2,6
1
C5, 3-FC6H4), 131.6 (dm, JC,H = 171 Hz, C6, 3-FC6H4), 125.2 (s,
d,
N(CF3)2), 122.7 (dm, JC,H = 172 Hz, C2, 3-FC6H4), 119.9 (dm,
1
1JC,H = 168 Hz, C4, 3-FC6H4), 119.8 (dm, JC,H = 173 Hz, C3,5, 4-
,
1
FC6H4), 117.9 (m, C1, 3-FC6H4), 112.4 (t, 2JC,H = 10 Hz, C1, 4-FC6H4),
(*N(CF3)2 selectively decoupled).
4-FC6H4), 7.72 (m, 2H, H2,6, 3-FC6H4), 7.69 (s, 2H, H5,6), 7.55 (dd,
3J(H3,8,H4,7) = 8 Hz, 3J(H3,8,H2,9) = 4 Hz, 2H, H3,8), 7.33 (m, H5, 1H, 3-
FC6H4), 7.20 (m, H4, 1H, 3-FC6H4), 7.06 (m, 2H, H3,5, 4-FC6H4).
4.1.4. Mixture of [(C6F5)2I][N(CF3)2] with 18 mol-% (C6F5)2IF
[(C6F5)2I][N(CF3)2]: 19F NMR (CH3CN, 24 8C)
d
, ppm: ꢀ49.6 (s,
4.4. C6H5(4-FC6H4)IF, an effective fluoride donor able to convert
CF3SO2N(CF3)2 into the [N(CF3)2]ꢀ anion
3
6F, N(CF3)2), ꢀ124.2 (m, 4F, o-C6F5), ꢀ148.0 (t, JF,F = 20 Hz, 2F, p-
C6F5), ꢀ158.1 (m, 4F, m-C6F5); (C6F5)2IF: 19F NMR (CH3CN, 24 8C)
d,
ppm: ꢀ18.5 (br, 1F, IF), ꢀ124.2 (m, 4F, o-C6F5), ꢀ148.0 (t,
The above mentioned mixture in CH3CN which contained 32%
C6H5(4-FC6H4)IF, 63% [C6H5(4-FC6H4)I][N(CF3)2], besides 5%
3JF,F = 20 Hz, 2F, p-C6F5), ꢀ158.1 (m, 4F, m-C6F5).
[C6H5(4-FC6H4)I][BF4]
CF3SO2N(CF3)2 (referred to C6H5(4-FC6H4)IF) and stirred for 1 h
at 0 8C. Iodonium imide was formed besides CF3SO2F (19F NMR
was
treated
with
1.3 equiv.
of
4.2. Fluoride transfer from the anion to the cation in
fluoroaryliodonium bis(trifluoromethyl)imides in the absence of an N-
base
d
,
ppm: 39.2 (q, 3J(F,F) = 18 Hz, 1F), ꢀ71.2 (d, 3J(F,F) = 18 Hz, 3F). The
mixture was degassed in vacuum (0.05 hPa) at ꢀ40 8C for 2 min
and at ꢀ35 8C for 10 min and finally analyzed by 19F NMR. 95%
[C6H5(4-FC6H4)I][N(CF3)2] were present besides 5% [C6H5(4-
FC6H4)I][BF4].
4.2.1. Removal of the solvent from a [C6H5(4-FC6H4)I][N(CF3)2]/
CH3CN solution
The solvent was distilled off from a [C6H5(4-FC6H4)I][N(CF3)2]/
CH3CN solution which contained 5% [C6H5(4-FC6H4)I][BF4] (non-
reacted starting material from the metathesis) in vacuum
(0.05 hPa) at ꢀ40 to ꢀ20 8C over 7 h. A white fibered solid
resulted. After dissolution in CH3CN at ꢀ30 8C the composition was
determined by 19F NMR: 63% [C6H5(4-FC6H4)I][N(CF3)2], 32%
C6H5(4-FC6H4)IF, besides 5% [C6H5(4-FC6H4)I][BF4].
Acknowledgements
We gratefully acknowledge financial support and granting
(MEH) by Merck KGaA and thank Dr. M. Schulte (Merck KGaA) for
the good cooperation.

M.E. Hirschberg et al. / Journal of Fluorine Chemistry 138 (2012) 24–27
27
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