Aryldiazonium bis(trifluoromethyl)imides

Article abstract of DOI:10.1016/j.jfluchem.2011.10.016

Aryldiazonium bis(trifluoromethyl)imides, [ArN₂][N(CF ₃)₂], are the first examples of diazonium salts with this type of anion. Their syntheses and properties will be presented and compared to aryldiazonium bis(trifluoromethylsulfonyl)imides. [ArN₂][N(CF ₃)₂] are less stable diazonium salts in comparison to [ArN₂][N(SO₂CF₃)₂] due to the higher nucleophilicity of the [N(CF₃)₂]^- anion.

Full text of DOI:10.1016/j.jfluchem.2011.10.016

Journal of Fluorine Chemistry 135 (2012) 183–186
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Aryldiazonium bis(trifluoromethyl)imides
a
c
a
M.E. Hirschberg a, , N.V. Ignat’ev
, A. Wenda , H.-J. Frohn , H. Willner
*
b,**
a Inorganic Chemistry, Bergische Universita¨t Wuppertal, Gaußstr. 20, D-42097 Wuppertal, Germany
b PM-ABE, Merck KGaA, Frankfurter Str. 250, D-64293 Darmstadt, Germany
c Inorganic Chemistry, Universita¨t Duisburg-Essen, D-47048 Duisburg, Lotharstr. 1, Germany
A R T I C L E I N F O
A B S T R A C T
Article history:
Aryldiazonium bis(trifluoromethyl)imides, [ArN2][N(CF3)2], are the first examples of diazonium salts
with this type of anion. Their syntheses and properties will be presented and compared to aryldiazonium
bis(trifluoromethylsulfonyl)imides. [ArN2][N(CF3)2] are less stable diazonium salts in comparison to
[ArN2][N(SO2CF3)2] due to the higher nucleophilicity of the [N(CF3)2]À anion.
ß 2011 Elsevier B.V. All rights reserved.
Received 25 August 2011
Received in revised form 17 October 2011
Accepted 19 October 2011
Available online 17 December 2011
Keywords:
Aryldiazonium bis(trifluoromethyl)imide
Aryldiazonium
bis(trifluoromethylsulfonyl)imide
Aryldiazonium salt
Metathesis
1. Introduction
2. Results and discussion
First aryldiazonium salts were synthesised by Peter Griess [1] in
1858 through the reaction of 2-amino-4,6-dinitrophenol with
nitrous acid. Now, this class of compounds is well investigated and
has broad applications in the syntheses of various chemicals, for
example via Balz–Schiemann reaction, Sandmeyer reaction,
Meerwein arylation, Gomberg–Bachmann reaction, Japp–Klinge-
mann reaction, azo coupling, reduction to hydrazine, solvolysis, or
palladium catalysed cross coupling reaction [2]. With exception of
the Japp–Klingemann reaction, the reduction to hydrazine and the
azo coupling, most reactions of aryl diazonium salts are based on
dediazoniation processes. The stability of aryldiazonium salts
depends on the substituents in the aromatic ring and the nature of
the counter anion. Aryldiazonium salts with nucleophilic and
easily oxidisable anions tend to be less stable.
Here, we report the synthesis of the previously unknown
aryldiazonium bis(trifluoromethyl)imides, [ArN2][N(CF3)2], which
are convenient reagents for introduction of the N(CF3)2 group in
aromatic compounds. The properties of these new aryldiazonium
salts are compared to the related aryldiazonium bis(trifluoro-
methylsulfonyl)imides, [ArN2][N(SO2CF3)2] [3,4].
2.1. Syntheses of aryldiazonium bis(trifluoromethyl)imides,
[ArN2][N(CF3)2]
The common source for the [N(CF3)2]À anion is the addition of
CsF to perfluoroazopropene, CF3–N55CF2 [5]. However, this
reaction is not convenient for practical application because it
yields also to the dimer of CF3–N55CF2 (Scheme 1) and in addition
CF3–N55CF2 is highly toxic and not commercial available.
Much more suitable is the precursor N,N-bis(trifluoromethyl)-
trifluoromethylsulfonyl amide, CF3SO2N(CF3)2, synthesised by
electrochemical fluorination (Simons process) of CF3SO2N(CH3)2
(Scheme 2) [6].
The [N(CF3)2]À anion is generated in situ by the reaction of
CF3SO2N(CF3)2 with RbF (Scheme 3) [7] and used for the preparation
of aryldiazonium bis(trifluoromethyl)imides without isolation.
The reaction of Rb[N(CF3)2] with aryldiazonium tetrafluorobo-
rates results in a fast metathesis to the hitherto unknown
aryldiazonium bis(trifluoromethyl)imides in good yields (79 to
98%) (Scheme 4).
A similar procedure was used to prepare 2-(methoxycarbo-
nyl)thiophene-3-diazonium bis(trifluoromethyl)imide (Scheme 5).
Parallel to the synthesis of aryldiazonium bis(trifluoromethyl)
imides a series of aryldiazonium bis(trifluoromethylsulfonyl)
imides, [ArN2][N(SO2CF3)2], have been prepared for comparison
purposes. [ArN2][N(SO2CF3)2] salts are well known [3,4] and
synthesised by metathesis of aryldiazonium chlorides with
* Corresponding author. Tel.: +49 202 439 3460; fax: +49 32121 109129.
** Corresponding author. Tel.: +49 151 1454 3102; fax: +49 (0)6151 728587.
E-mail addresses: Markus.Hirschberg@uni-wuppertal.de,
Markus.Hirschberg@gmx.de (M.E. Hirschberg), Nikolai.Ignatiev@merckgroup.com
(N.V. Ignat’ev).
0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2011.10.016

184
M.E. Hirschberg et al. / Journal of Fluorine Chemistry 135 (2012) 183–186
Cs[N(CF3)2] + CF3-N=CF2
CF3-N=CF-N(CF3)2 + CsF
reflects the increase in the coordination ability (nucleophilicity) of
these anions.
In the 19F NMR spectra, the resonance of the bis(trifluoro-
methyl)imide anion in [4-FC6H4N2][N(CF3)2] or in [4-
Scheme 1.
BrC6H4N2][N(CF3)2]
deshielded in comparison to the signal of the covalently bonded
(
d
F = À37 ppm; solvent: CH3CN) appears
CH3
CF3SO2N
CH3
CF3
CF3SO2N
CF3
e-, Ni
aHF
N,N-bis(trifluoromethyl)amino group in 4-FC6H4N(CF3)2 or in 4-
BrC6H4N(CF3)2 (
bis(trifluoromethylsulfonyl)imide salt, [4-FC6H4N2] [N(SO2CF3)2]
F = À80 ppm; CH3CN) and the covalently bonded compound 4-
FC6H4N(SO2CF3)2
d
F = À56 ppm; solvent: CCl3F) [8]. In the case of the
Scheme 2.
(
d
(
d
F = À80 ppm; CCl3F) [4] the chemical shift of
N,N-bis(trifluoromethylsulfonyl)imide, (CF3SO2)2NH or its sodi-
um salt.
the N,N-bis(trifluoromethylsulfonyl)amino moiety is almost the
same.
We have modified this method by using the more stable
aryldiazonium tetrafluoroborates as starting compounds and
commercially available Li[N(SO2CF3)2] as a source of the bis(tri-
fluoromethylsulfonyl)imide anion. Besides known [4-FC6H4N2]
[N(SO2CF3)2], the new substances [X-C6H4N2][N(SO2CF3)2] (X = 2-
Br, 3-Br, 4-Br, 4-I) have been prepared and characterised (Table 1).
In the 13C NMR spectra the signal of the N(CF3)2 group is
1
displayed at about 125 ppm as quartet of quartets: JC,F ꢀ 243 Hz
and 3JC,F ꢀ 11 Hz. However, the N(SO2CF3)2 group shows in the 13
C
NMR spectra only one quartet (1JC,F ꢀ 321 Hz) at 121 ppm. The
3
coupling constant JC,F is too small to be observed.
The coordination ability of both types of anions also influences
the NBB N stretching vibrations (Table 1). In the Raman spectra of
2.2. Properties of aryldiazonium bis(trifluoromethyl)imides in
comparison to aryldiazonium bis(trifluoromethylsulfonyl)imides
[4-BrC6H4N2][N(CF3)2] and [4-FC6H4N2][N(CF3)2] the n(NBB N)
values are slightly shifted to higher wavenumbers (2283 cmÀ1
and 2288 cmÀ1) in comparison to the corresponding bis(trifluoro-
methylsulfonyl)imides (2279 cmÀ1 and 2281 cmÀ1).
The diazonium salts [2-CF3C6H4N2][N(CF3)2] and [4-
IC6H4N2][N(CF3)2] are solids which are intrinsically unstable at
room temperature. They decompose at room temperature within
hours into several compounds. Other aryldiazonium bis(trifluoro-
methyl)imides were isolated at 0 8C as oily substances which
undergo decomposition at room temperature, in some cases
explosively. All diazonium salts with the [N(CF3)2]À anion are
moisture sensitive and react vigorously with water. In contrast to
the aryldiazonium bis(trifluoromethyl)imides, solid aryldiazo-
nium bis(trifluoromethylsulfonyl)imides are much more stable
(can be stored over months at room temperature) and are not
moisture sensitive.
Aryldiazonium bis(trifluoromethylsulfonyl)imides melt above
50 8C (DSC measurements, TOnset) and the melt decomposes into a
mixture of phenyl-N and phenyl-O compounds. At higher
temperature (135 8C) the reaction follows Scheme 6 as described
in literature [3,4].
3. Experimental part
All moisture sensitive compounds were handled under an
atmosphere of dry argon. Reactions were carried out in glass
vessels 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 (supplier:
KMF) was purified by reflux and distillation in sequence over
KMnO4 and P4O10
.
NMR spectra were recorded on a Bruker NMR spectrometer
AVANCE 300 (13C at 75.47 MHz, 19F at 282.40 MHz, and 1H at
300.13 MHz) and a Bruker spectrometer AVANCE 400 (13C at
100.61 MHz, 19F at 376.50 MHz, and 1H at 400.13 MHz) with
external Deuterium lock (CD3CN) if non-deuterated solvents were
used for the NMR-measurements. The chemical shifts were
referenced to TMS (13C, 1H), CCl3F (19F) (C6F6 as a secondary
The products can be considered as aryl esters of triflic acid in
which one oxygen atom is replaced by a 55NSO2CF3 group.
The diazonium salts with [N(CF3)2]À and [N(SO2CF3)2]À anions
have lower melting points than their analogues with the [BF4]À
anion. The thermal stability of aryldiazonium salts are decreasing
in the following order [BF4]À > [N(SO2CF3)2]À > [N(CF3)2]À which
reference,
d
= À162.9 ppm). The ratio of 19F and 1H nuclei in
products was determined by NMR spectroscopy after addition of
1,3,5-trifluorobenzene or benzotrifluoride. Raman spectra were
recorded on a Bruker FT-Raman spectrometer FRA 106/S using the
1064 nm line of a Nd/YAG laser. The backscattered (1808) radiation
was sampled and analysed (Stoke range: 50–4000 cmÀ1). The
samples were placed in glass capillaries or FEP tubes.
CH3CN, 0 °C
CF3SO2N(CF3)2
RbF
Rb[N(CF3)2]
+
- CF3SO2F
Scheme 3.
CF3
CH3CN
0 °C
+ Rb[BF4]
N2 [BF4]
N2
N
+ Rb[N(CF3)2]
X
X
CF3
isolated yield for X = p-F: 98%, p-Br: 86%,
p-I: 79%, H: 91%, o-CF3: 80%
Scheme 4.
N2
N2
C(O)OCH3
CF3
CH3CN
20 °C
+ Rb[BF4]
N
[BF4]
+ Rb[N(CF3)2]
C(O)OCH3
CF3
S
S
isolated yield: 80%
Scheme 5.

M.E. Hirschberg et al. / Journal of Fluorine Chemistry 135 (2012) 183–186
185
3
CF3
(CH3CN, À30 8C)
d
, ppm: 8.42 (d, JH,H = 8.6 Hz, 2H, H2,6), 8.04 (d,
135 °C, 15 min
-N2
3JH,H = 8.6 Hz, 2H, H3,5). 13C NMR (CH3CN, À30 8C)
d, ppm: 138.4 (tt,
[ArN2][N(SO2CF3)2]
ArO
S
N
SO2CF3
2JC,H = 10 Hz, JC,H = 2 Hz), 135.0 (dd, JC,H = 177 Hz, JC,H = 5 Hz),
3
1
O
1
1
133.4 (dd, JC,H = 181 Hz, JC,H = 4 Hz), 125.0 (qq, JC,F = 243 Hz,
3JC,F = 12 Hz, N(CF3)2), 113.5 (tt, JC,H = 12 Hz, JC,H = 3 Hz).
2
3
Scheme 6.
[4-IC6H4N2][N(CF3)2]: Yield 79% (0.473 g, 1.234 mmol). 19F NMR
(CH3CN, À30 8C)
d
, ppm: À36.8 (s, 6F, N(CF3)2). 1H NMR (CH3CN,
3
3.1. Chemicals
À30 8C)
d
,
ppm: 8.26 (d, JH,H = 9.0 Hz, 2H, H2,6), 8.17 (d,
3JH,H = 9.0 Hz, 2H, H3,5). 13C{1H} NMR (CH3CN, À30 8C)
d, ppm:
Diazonium tetrafluoroborates were prepared according to the
methods described in the literature [9]: [4-FC6H4N2][BF4] (yield
141.1 (s), 132.4 (s), 124.9 (qq, 1JC,F = 244 Hz, 3JC,F = 11 Hz, N(CF3)2),
114.7 (s), 113.8 (s).
92%, m.p. 157 8C,
77%, m.p. 139 8C,
n
(NBB N) 2297 cmÀ1), [4-BrC6H4N2][BF4] (yield
[2-CF3C6H4N2][N(CF3)2]: Yield 81% (0.50 g, 1.54 mmol). 19F NMR
n
(NBB N) 2288 cmÀ1), [4-IC6H4N2][BF4] (yield 91%,
(CH3CN, À30 8C)
d
, ppm: À37.4 (s, 6F, N(CF3)2), À60.1 (s, 3F, CF3). 1H
m.p. 130 8C,
m.p. 143 8C,
m.p. 155 8C,
m.p. 140 8C,
n
n
n
n
(NBB N) 2285 cmÀ1), [3-BrC6H4N2][BF4] (yield 80%,
(NBB N) 2309 cmÀ1), [2-BrC6H4N2][BF4] (yield 69%,
NMR (CH3CN, À30 8C)
d, ppm: 8.96 (m, 1H), 8.42 (m, 1H), 8.30 (m,
1H), 8.20 (m, 1H). 13C NMR (CH3CN, À30 8C)
d, ppm: 142.3 (dd,
(NBB N) 2294 cmÀ1), [2-CF3C6H4N2][BF4] (yield 65%,
1JC,H = 173 Hz, JC,H = 7 Hz), 135.5 (ddd, JC,H = 181 Hz, JC,H = 8 Hz,
1
1
(NBB N) 2299 cmÀ1), [C6H5N2][BF4] (yield 76%, m.p.
JC,H = 2 Hz), 135.2 (dd, JC,H = 176 Hz, JC,H = 8 Hz), 131.7 (m), 129.6
(qm, JC,F = 36 Hz), 124.8 (qq, JC,F = 243 Hz, JC,F = 11 Hz, N(CF3)2),
1
3
105 8C,
n
(NBB N) 2297 cmÀ1).
1
2-(Methoxycarbonyl)thiophene-3-diazonium
tetrafluorobo-
120.5 (qd, JC,F = 274 Hz, JC,H = 5 Hz, CF3), 111.9 (t, JC,H = 12 Hz).
rate was prepared by the method presented in [10] which has
been optimised to improve the yield and to characterise the
isolated product (see description below).
N,N-dimethylmethanesulfonamide was obtained by reaction of
dimethyl amine and trifluoromethanesulfonic acid anhydride in
diethyl ether.
[C6H5N2][N(CF3)2]: Yield 91% (0.61 g, 2.37 mmol). 19F NMR
(CH3CN, À30 8C)
À30 8C)
d
, ppm: À38.3 (s, 6F, N(CF3)2). 1H NMR (CH3CN,
d
, ppm: 8.49 (m, 2H), 8.19 (m, 1H), 7.87 (m, 2H). 13C{1H}
NMR (CH3CN, À30 8C)
d, ppm: 142.0 (s), 132.5 (s), 131.8 (s), 124.8
(qq, JC,F = 244 Hz, JC,F = 11 Hz, N(CF3)2), 114.8 (s).
1
3
3.3. Syntheses of 2-(methoxycarbonyl)thiophene-3-diazonium
tetrafluoroborate and bis(trifluoromethyl)imide [C6H5N2O2S][BF4]
3.2. Syntheses of aryldiazonium bis(trifluoromethyl)imides
3.2.1. Synthesis of [4-FC6H4N2][N(CF3)2]
To the stirred suspension of methyl-3-aminothiophene-2-
carboxylate (4.2 g, 26.8 mmol) in HBF4 (50%, 8 mL, 128 mmol)
an aqueous solution of NaNO2 (2.0 g, 29.0 mmol) was added at 0 8C.
The reaction mixture was left stirring for 5 min at 0 8C and for
20 min at 20 8C. The precipitant was filtered off and washed first
with the mixture of acetone/diethyl ether (10 mL/15 mL) and than
with 20 mL of diethyl ether. The residue was dried in vacuum
(1.6 hPa, 20 8C, 2 h). 2-(Methoxycarbonyl)thiophene-3-diazonium
tetrafluoroborate was obtained as white solid material in 88% yield
(6.01 g, 23.48 mmol).
CF3SO2N(CF3)2 (0.98 g, 3.41 mmol) was added to
a cold
suspension (0 8C) of RbF (0.354 g, 3.385 mmol) in CH3CN (4 mL).
After 35 min the RbF was consumed and the suspension turned to a
solution which subsequently was added to a cold solution (0 8C) of
[4-FC6H4N2][BF4] (0.646 g, 3.077 mmol) in CH3CN (2.5 mL). The
reaction mixture was stirred for 15 min and the pale orange
supernatant was separated from the precipitate. The solvent was
removed in vacuum and the residue was dried in vacuum
(0.05 hPa, À42 8C, 2 h; À42 8C to À20 8C, 2 h; À15 8C, 2 h). Orange
oil was obtained in 98% yield (0.833 g, 3.028 mmol).
M.p. 143.9 8C (DSC: endothermic; TOnset; lit.: 142–143 8C [10]).
19F NMR (CH3CN, À30 8C)
d
, ppm: À36.9 (s, 6F, N(CF3)2), À84.2
19F NMR (CD3CN, 27 8C)
d
, ppm: À151.5 (s, 4F, BF4). 1H NMR
(tt, 3JF,H = 8 Hz, 4JF,H = 4 Hz, 1F, 4-FC6H4). 1H NMR (CH3CN, À30 8C)
(CD3CN, 27 8C)
(CD3CN, 27 8C)
d
, ppm: 8.14 (s, 2H, H3,4), 4.04 (s, 3H, CH3). 11B NMR
d
, ppm: 8.70 (m, 2H, H2,6), 7.66 (m, 2H, H3,5). 13C NMR (CH3CN,
d
, ppm: À1.21 (s, BF4). 13C{1H} NMR (CD3CN, 27 8C)
À30 8C)
C4), 136.6 (ddd, JC,H = 181 Hz, JC,F = 13 Hz, JC,H = 5 Hz, C2,6),
125.0 (qq, 119.7
1JC,F = 243 Hz, 3JC,F = 11 Hz, N(CF3)2),
d
, ppm: 169.5 (dtt, 1JC,F = 270 Hz, 2JC,H = 10 Hz, 3JC,H = 5 Hz,
d, ppm: 158.0 (s), 149.9 (s), 136.0 (s), 129.9 (s), 108.5 (s), 55.0 (s).
1
3
2
Raman spectrum: n .
(NBB N): 2285 cmÀ1
[C6H5N2O2S][N(CF3)2]: CF3SO2N(CF3)2 (0.50 g, 1.75 mmol) was
added to a cold suspension (À10 8C) of RbF (0.15 g, 1.44 mmol) in
CH3CN (1.1 mL). After 20 min the RbF was consumed and the
suspension turned to a solution which subsequently was added to
a suspension (20 8C) of 2-(methoxycarbonyl)thiophene-3-diazoni-
um tetrafluoroborate (0.35 g, 1.37 mmol) in CH3CN (2 mL). The
reaction mixture was stirred for 15 min and the pale yellow
(ddd, 1JC,H = 176 Hz, 2JC,F = 25 Hz, 2JC,H = 4 Hz, C3,5), 110.0
2
4
(td, JC,H = 12 Hz, JC,F = 3 Hz, C1).
The other aryldiazonium bis(trifluoromethyl)imides, [X-
C6H4N2][N(CF3)2], were prepared using similar procedures.
[4-BrC6H4N2][N(CF3)2]: Yield 86% (0.365 g, 1.086 mmol). 19F
NMR (CH3CN, À30 8C)
d
, ppm: À36.8 (s, 6F, N(CF3)2). 1H NMR
Table 1
Synthesis and some properties of aryldiazonium bis(trifluoromethyl)imides and aryldiazonium bis(trifluoromethylsulfonyl)imides.
Compound
Method of synthesis (solvent)
Yield (%)
M.p. (8C)
n )
(NBB N) (cmÀ1
[4-FC6H4N2][N(CF3)2]
A
98
59
88
82
66
79
56
58
64
81
91
–
81
–
2288
2281
–
[4-FC6H4N2][N(SO2CF3)2]
B (acetone)
B (CH3CN)
[4-BrC6H4N2][N(CF3)2]
[4-BrC6H4N2][N(SO2CF3)2]
[4-IC6H4N2][N(CF3)2]
A
–
2283
2279
–
B (acetone)
69
–
A
[4-IC6H4N2][N(SO2CF3)2]
[3-BrC6H4N2][N(SO2CF3)2]
[2-BrC6H4N2][N(SO2CF3)2]
[2-CF3C6H4N2][N(CF3)2]
[C6H5N2][N(CF3)2]
B (acetone)
88
89
57
–
2281
2294
2276
–
B (acetone/CH3CN)
B (H2O)
A
A
–
–
(A) metathesis with Rb[N(CF3)2] in CH3CN, (B) metathesis with Li[N(SO2CF3)2].

186
M.E. Hirschberg et al. / Journal of Fluorine Chemistry 135 (2012) 183–186
supernatant was separated from the precipitate. The solvent was
removed in vacuum and the residue was dried in vacuum (2 hPa,
20 8C, 3 h). 0.35 g (1.09 mmol) of pale-orange solid 2-(methoxy-
carbonyl)thiophene-3-diazonium bis(trifluoromethyl)imide was
obtained in 80% yield.
NMR (CD3CN, 20 8C) d, ppm: 142.1 (s), 132.9 (s), 120.6 (q,
1JC,F = 321 Hz, N(SO2CF3)2), 114.4 (s), 114.2 (s).
[3-BrC6H4N2][N(SO2CF3)2]: Yield 58% (3.01 g, 6.48 mmol). 19F
NMR (CD3CN, 20 8C)
(CD3CN, 20 8C)
d
, ppm: À80.4 (s, 6F, N(SO2CF3)2). 1H NMR
d
, ppm: 8.61 (m, 1H), 8.49 (m, 1H), 8.39 (m, 1H),
7.84 (m, 1H). 13C{1H} NMR (CD3CN, 20 8C)
d, ppm: 146.0 (s),
19F NMR (CD3CN + 1,3,5-F3C6H3, 27 8C)
d
, ppm: À41.3 (s, 6F,
N(CF3)2). 1H NMR (CD3CN + 1,3,5-F3C6H3, 27 8C)
d
, ppm: 8.14 (s,
134.6 (s), 133.8 (s), 132.3 (s), 124.3 (s), 120.6 (q,
1JC,F = 321 Hz, N(SO2CF3)2), 116.7 (s).
2H), 4.05 (s, 3H, CH3).
[2-BrC6H4N2][N(SO2CF3)2]: Yield 64% (7.94 g, 17.11 mmol). 19F
3.4. Syntheses of aryldiazonium bis(trifluoromethylsulfonyl)imides
NMR (CD3CN, 20 8C)
(CD3CN, 20 8C)
d
, ppm: À80.5 (s, 6F, N(SO2CF3)2). 1H NMR
d
, ppm: 8.57 (m, 1H), 8.15 (m, 2H), 7.92 (m, 1H).
13C{1H} NMR (CD3CN, 20 8C)
d, ppm: 143.9 (s), 136.8 (s), 135.9 (s),
3.4.1. Synthesis of [4-FC6H4N2][N(SO2CF3)2]
CH3CN (10 mL) was added to the mixture of solid [4-
FC6H4N2][BF4] (2.33 g, 11.0 mmol) and Li[N(SO2CF3)2] (4.2 g,
14.6 mmol). After 30 min of stirring the solution was concentrated
in vacuum (0.05 hPa, 20 8C, 2 h). The residue was washed three
times with H2O (3 Â 30 mL) and with Et2O (3 Â 10 mL). The white
solid product was dried in vacuum (0.05 hPa, 20 8C, 2 h). Yield of
[4-FC6H4N2][N(SO2CF3)2] was 88% (3.96 g, 9.82 mmol).
131.6 (s), 125.9 (s), 120.7 (q, 1JC,F = 321 Hz, N(SO2CF3)2), 117.7 (s).
Acknowledgement
We thank Dr. Jane Hu¨bner (Bergische Universita¨t Wuppertal,
Germany) for analytical measurements.
19F NMR (CD3CN, 20 8C)
d
, ppm: À80.5 (s, 6F, N(SO2CF3)2), À84.8
References
3
4
(tt, JF,H3,5 = 8 Hz, JF,H2,6 = 4 Hz, 1F, 4-FC6H4). 1H NMR (CD3CN,
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Trans. 2 (2002) 1135–1150.
20 8C)
(CD3CN, 20 8C)
d
, ppm: 8.60 (m, 2H, H2,6), 7.67 (m, 2H, H3,5). 13C{1H} NMR
1
d
, ppm: 170.7 (d, JC,F = 271 Hz, C4), 137.4 (d,
3JC,F = 12 Hz, C2,6), 120.8 (d, JC,F = 25 Hz, C3,5), 120.6 (q,
2
1JC,F = 320 Hz, N(SO2CF3)2), 110.6 (d, JC,F = 3 Hz, C1).
4
The other aryldiazonium bis(trifluoromethylsulfonyl)imides, [X-
C6H4N2][N(SO2CF3)2], were prepared in a similar manner.
[4-BrC6H4N2][N(SO2CF3)2]: Yield 66% (3.42 g, 7.34 mmol). 19F
NMR (CD3CN, 20 8C)
(CD3CN, 20 8C)
d
, ppm: À80.4 (s, 6F, N(SO2CF3)2). 1H NMR
d
, ppm: 8.35 (m, 2H, H2,6), 8.10 (m, 2H, H3,5). 13C{1H}
NMR (CD3CN, 20 8C) d, ppm: 139.7 (s), 136.1 (s), 134.1 (s), 120.6 (q,
1JC,F = 321 Hz, N(SO2CF3)2), 113.9 (s).
[4-IC6H4N2][N(SO2CF3)2]: Yield 56% (2.69 g, 5.26 mmol). 19F
NMR (CD3CN, 20 8C)
(CD3CN, 20 8C)
d
, ppm: À80.4 (s, 6F, N(SO2CF3)2). 1H NMR
[10] C. Corral, A. Lasso, J. Lissavetzky, A.S. Alvarez-Insua, A.M. Valdeolmillos, Hetero-
cycles 23 (1985) 1431–1435.
d
, ppm: 8.34 (m, 2H, H2,6), 8.13 (m, 2H, H3,5). 13C{1H}