Thermal decomposition of 4-fluorobenzenediazonium perfluoroorganyl(fluoro) borates, [4-FC6H4N2]Y (Y = RFBF 3 (RF = C6F5, C6F 13, trans-C4F9CFCF, cis-C6F 13CFCF, CF3CC) and (C6F13) 2BF2)

Article abstract of DOI:10.1016/j.jfluchem.2013.08.001

Heating of the neat salts [4-FC₆H₄N ₂][R_FBF₃] (R_F = C₆F ₅, C₆F₁₃, trans-C₄F₉CFCF, cis-C₆F₁₃CFCF, CF₃CC) or in solid mixtures with NaF gives the principal product 1,4-C₆F₂H₄ besides R_FBF₂ or Na[R_FBF₃], respectively. Thermolysis of [4-FC₆H₄N₂] [(C₆F₁₃)₂BF₂] in NaF results in 1,4-C₆F₂H₄, Na[BF₄], Na[(C ₆F₁₃)₂BF₂], and a new type of product, the isomer Na[C₆F₁₃CF(BF₃)C ₅F₁₁].

Full text of DOI:10.1016/j.jfluchem.2013.08.001

Journal of Fluorine Chemistry 156 (2013) 333–338
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Thermal decomposition of 4-fluorobenzenediazonium
perfluoroorganyl(fluoro)borates, [4-FC6H4N2]Y (Y = RFBF3 (RF = C6F5,
C6F13, trans-C4F9CF55CF, cis-C6F13CF55CF, CF3CBBC) and (C6F13)2BF2)
Vadim V. Bardin a, Hermann-Josef Frohn b,
*
a N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, Acad. Lavrentjev Avenue 9, 630090 Novosibirsk, Russian Federation
b Inorganic Chemistry, University of Duisburg-Essen, Lotharstrasse 1, D-47048 Duisburg, Germany
A R T I C L E I N F O
A B S T R A C T
Article history:
Heating of the neat salts [4-FC6H4N2][RFBF3] (RF = C6F5, C6F13, trans-C4F9CF55CF, cis-C6F13CF55CF, CF3CBB C)
or in solid mixtures with NaF gives the principal product 1,4-C6F2H4 besides RFBF2 or Na[RFBF3],
respectively. Thermolysis of [4-FC6H4N2][(C6F13)2BF2] in NaF results in 1,4-C6F2H4, Na[BF4],
Na[(C6F13)2BF2], and a new type of product, the isomer Na[C6F13CF(BF3)C5F11].
ß 2013 Elsevier B.V. All rights reserved.
Received 29 May 2013
Received in revised form 27 July 2013
Accepted 1 August 2013
Available online 14 August 2013
Keywords:
Arenediazonium salts
Thermal decomposition
DSC analysis
NMR spectroscopy
1. Introduction
The availability of these salts allowed the preparation of a series of
aryldiazonium perfluoroorganyltrifluoroborates and the investi-
The Balz-Schiemann reaction is the classical method for
replacing a diazonio group by fluorine. Typically, the reaction is
performed by heating arenediazonium tetrafluoroborates,
[ArN2][BF4], in an inert solid material or in an inert solvent and
results in ArF, BF3, and N2. In some cases the thermolysis of
diazonium salts with hexacoordinated fluoroanions, [ArN2][XF6]
(X = P, As, Sb) or [ArN2]2[SiF6] etc. gives better yields of ArF.
Overviews of known procedures, their modifications, the scope and
limitation are compiled in fundamental monographs and reviews
[1]. Despite a large number of publications on this topic, there are
no data available on the thermal decomposition of arenediazonium
organyl(fluoro)borates, [ArN2][RnBF4Àn] (n = 1–4), or the related
salts [ArN2][RmXF6Àm] (X = P, As, Sb; m = 1–6). A priori two main
reaction channels can be considered in case of [ArN2][RnBF4Àn]: (a)
fluorodediazoniation of [ArN2][RnBF4Àn] to fluoroarene and (b)
replacement of the diazonio group by the organyl group R under
formation of ArR.
gation of their thermal decomposition products. We studied the
thermolysis of 4-fluorobenzenediazonium perfluoroorganyl(fluoro)
borate salts which allowed a convenient identification of the
products by 19F NMR spectroscopy.
2. Results and discussion
4-Fluorobenzenediazonium
perfluoroorganyl(fluoro)borates
were prepared by anion metathesis of [4-FC6H4N2][BF4] with
K[RFBF3] or K[(C6F13)2BF2] in dry MeCN (Scheme 1).
The visually controlled thermal decomposition was performed in
an NMR tube using 30–50 mg of the corresponding diazoniumborate
salt. To test the experimental set up, the typical Balz-Schiemann
reaction of [4-FC6H4N2][BF4] was performed. The neat salt [4-
FC6H4N2][BF4] melted under decomposition at 158–160 8C (bath)
giving 1,4-difluorobenzene in 86% yield. The new investigated
organyltrifluoroborate salts, [4-FC6H4N2][RFBF3], melted at 80–
100 8C and formed brown liquids which decomposed under
bubbling of gas at 120–140 8C (RF = C6F5, C6F13, trans-C4F9CF55CF)
or 130–160 8C (cis-C6F13CF55CF). When RF = C6F5, 1,4-C6F2H4 and
pentafluorophenyldifluoroborane (trace) were found besides penta-
fluoro-benzene and perfluorobiphenyl. The salt with RF = C6F13
gave 1,4-C6F2H4 (67%) and C6F13BF2 (85%). Thermolysis of [4-
FC6H4N2][RFBF3] with RF = trans-C4F9CF55CF and RF = cis-C6F13CF55CF
During the last two decades we have elaborated convenient
methods for the preparation of potassium perfluoroorganyltri-
fluoroborates, K[RFBF3], where RF represents a perfluoroalkyl,
perfluoroalkenyl, perfluoroalkynyl, and perfluoroaryl group [2–7].
*
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 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jfluchem.2013.08.001

334
V.V. Bardin, H.-J. Frohn / Journal of Fluorine Chemistry 156 (2013) 333–338
MeCN
[4-FC6H4N2][BF4] + K[RFBF3]
⎯⎯→
[4-FC6H4N2][RFBF3] + K[BF4] ↓
RFBF3 = C6F5BF3 (82%), C6F13BF3 (77%), trans-C4F9CF=CFBF3 (68%), cis-
C6F13CF=CFBF3 (74%), CF3C≡CBF3 (78%)
MeCN
[4-FC6H4N2][BF4] + K[(C6F13)2BF2]
⎯⎯→ [4-FC6H4N2][(C6F13)2BF2] + K[BF4] ↓
84%
Scheme 1.
gave C6F2H4 (Scheme 2) besides the corresponding boranes RFBF2 as
main products.
borane C6F13BF2 resulted, borane (C6F13)2BF was not observed
when neat [4-FC6H4N2][(C6F13)2BF2] was thermalized. However,
heating of [4-FC6H4N2][(C6F13)2BF2] with NaF resulted in 1,4-
C6F2H4, Na[(C6F13)2BF2], Na[C6F13CF(BF3)C5F11], and Na[BF4]. The
absence of bis(perfluoroalkyl)fluoroborane (with a higher fluoride
affinity than C6F13BF2) in the thermolysis without NaF can
probably be explained by a fast isomerization of (C6F13)2BF to
C6F13CF(BF2)C5F11 under the strong acidic reaction conditions
(Scheme 4).
A selected series of [4-FC6H4N2][RFBF3] salts was investigated
by differential scanning calorimetry (DSC). For comparison, neat
[4-FC6H4N2][BF4] showed an endothermal maximum at 160.6 8C
(melting) which passes into an exothermal maximum at 162.6 8C
(decomposition). In case of the neat salt [4-FC6H4N2][C6F5BF3]
melting and decomposition are more separated: melting at
Tmax = 98.0 8C (sharp endothermal peak) was followed by decom-
position at Tmax = 142.9 8C (broad exothermal peak). In case of
perfluoroalkenyl- and perfluoroalkynyltrifluoroborate salts an
endothermal process – presumably a phase transition – preceded
melting. Melting and {decomposition} occurred at Tmax = 95.2
{140.3} 8C [4-FC6H4N2][cis-C6F13CF=CFBF3], 89.4 {144.5} 8C
[4-FC6H4N2][trans-C4F9CF=CFBF3], and 65.6 {102.7 and 105.7} 8C
[4-FC6H4N2][CF3CBB CBF3]/NaF (1:3, v/v). Notably, the DSC result
of [4-FC6H4N2][trans-C4F9CF=CFBF3] mixed with NaF (1:3, v/v)
did not distinct from the sample without NaF. The DSC result of
[4-FC6H4N2][(C6F13)2BF2] with melting at Tmax = 121.9 8C
(endothermal effect) and the exothermal decomposition at
Tmax = 138.1 8C fitted well into the afore reported pattern.
The obtained data show distinctions and similarities
between the parent fluoroborate salt [4-FC6H4N2][BF4] and the
Very often the thermal decomposition of arenediazonium salts is
performed in inert solid materials (sand, CaF2, etc.). This allows a
good thermal control of the process and prevents a violent reaction.
Usually, such a performance results in a better yield of the desired
product. Although the thermolysis of [4-FC6H4N2][RFBF3] gave 1,4-
C6F2H4 in high yields (Scheme 2), the pronounced hydrolytic
sensibility of the co-product perfluoroorganyldifluoroborane leads
to several by-products in minor quantity. To overcome this problem
we performed the thermal decomposition of 4-fluorobenzenedia-
zonium perfluoroorganyl(fluoro)borates in vigorously dried NaF.
The solid matrix had no effect on the reaction route and allowed to
trap the strong Lewis-acidic boranes as practically inert sodium
perfluoroorganyl(fluoro)borates. For example, heating of [4-
FC6H4N2][C6F5BF3] in NaF gave 1,4-C6F2H4, Na[C6F5BF3], and
Na[BF4]. Thermolysis of [4-FC6H4N2][RFBF3] with RF = trans-
C4F9CF55CF and cis-C6F13CF55CF in a perfluoroalkenyl moiety of
the anion produced 1,4-C6F2H4 and the corresponding salt,
Na[RFBF3], besides Na[BF4]. Notably, the fluorodediazoniation of
[4-FC6H4N2][CF3CBB CBF3] in NaF gave 1,4-C6F2H4 only in a moderate
yield of 51% whereas Na[CF3CBB CBF3] and Na[BF4] were formed in 9
and 76%, respectively (Scheme 3). Probably, the initially formed
borane, CF3CBB CBF2, underwent parallel reactions including C–B
bond cleavage.
A specific feature was observed when [4-FC6H4N2][(C6F13)2BF2]
was thermalized. The neat borate melted at 130–140 8C with
decomposition to yield 1,4-C6F2H4, 6-difluoroborylperfluorodode-
cane, C6F13CF(BF2)C5F11, and some unidentified products. Unlike
the thermolysis of [4-FC6H4N2][C6F13BF3] (Scheme 2) where
[4-FC6H4N2][C6F5BF3] ⎯⎯→ 1,4-C6F2H4+ C6F5BF2 + N2 + C6F5H + (C6F5)2
54% trace 24% 16%
[4-FC6H4N2][C6F13BF3] ⎯⎯→ 1,4-C6F2H4 + C6F13BF2 + N2
67% 85%
[4-FC6H4N2][trans-C4F9CF=CFBF3] ⎯→ 1,4-C6F2H4 + trans-C4F9CF=CFBF2 + N2
80% 49%
[4-FC6H4N2][cis-C6F13CF=CFBF3] ⎯→ 1,4-C6F2H4 + cis-C6F13CF=CFBF2 + N2 +
90% 5%
cis-C6F13CF=CFH + C6F13C≡CF
4%
3%
Scheme 2.

V.V. Bardin, H.-J. Frohn / Journal of Fluorine Chemistry 156 (2013) 333–338
335
NaF
[4-FC6H4N2][C6F5BF3] ⎯→ 1,4-C6F2H4 + Na[C6F5BF3] + Na[BF4] + N2
79%
71%
11%
NaF
[4-FC6H4N2][trans-C4F9CF=CFBF3] ⎯→ 1,4-C6F2H4 + Na[trans-C4F9CF=CFBF3] +
95% 83%
Na[cis-C4F9CF=CFBF3] + Na[BF4] + N2
10% 5%
NaF
[4-FC6H4N2][cis-C6F13CF=CFBF3] ⎯→ 1,4-C6F2H4 + Na[cis-C6F13CF=CFBF3] +
77% 65%
Na[trans-C6F13CF=CFBF3] + C6F13C≡CF + Na[BF4] + N2
12% 3% 17%
NaF
[4-FC6H4N2][CF3C CBF3] ⎯→ 1,4-C6F2H4 + Na[CF3C≡CBF3] + Na[BF4]
=
51%
CF3C≡CH + N2
9%
9%
76%
T = 160 − 170 °C
Scheme 3.
[4-FC6H4N2][(C6F13)2BF2] ⎯⎯⎯⎯→ 1,4-C6F2H4 + C6F13CF(BF2)C5F11 + N2
140 − 145 °C
79%
27%
NaF
[4-FC6H4N2][(C6F13)2BF2] ⎯⎯⎯⎯→ 1,4-C6F2H4 + Na[(C6F13)2BF2] +
25 − 200 °C
81%
Na[C6F13CF(BF3)C5F11] + Na[BF4] + N2
33% 17%
39%
Scheme 4.
organyltrifluoroborate derivatives 4-fluorobenzenediazonium
perfluoroorganyl(fluoro)borates. While melting and decomposi-
tion practically coincided in case of [4-FC6H4N2][BF4], they are
separated by 30–40 8C for [4-FC6H4N2][RFBF3]. Generally, [4-
FC6H4N2][RFBF3] salts are less thermally stable than [4-
FC6H4N2][BF4]. A high similarity consists in the products of
thermal decomposition. In both cases the diazonio group is
replaced by fluorine. Compound 1,4-C6F2H4 is formed under
liberation of BF3 or RFBF2, respectively. No remarkable amount of
FC6H4RF (transfer of the weakly nucleophilic carbanion instead of
fluoride) was detected.
Thermolysis of neat [4-FC6H4N2][(C6F13)2BF2] offers an addition-
al interesting result. Instead of elimination of the co-product
(C6F13)2BF, itsisomer C6F13CF(BF2)C5F11 was formed. In the presence
of NaF both fluoroboranes were trapped. The corresponding sodium
salts Na[(C6F13)2BF2] and Na[C6F13CF(BF3)C5F11] were formed in
comparable amounts. Likely that the isomerization of the strong
Lewis acid (C6F13)2BF to the less acidic C6F13CF(BF2)C5F11 [8]
proceeds via an intramolecular fluoride ion abstraction (cf.
formation of C2F5CF(BF2)CF3 from (C2F5)2BF [9]).
3. Conclusion
The thermal decomposition of neat solid 4-fluorobenzenedia-
zonium perfluoroorganyl(fluoro)borates proceeds similar to the
classical Balz-Schiemann reaction under formation of 1,4-C6F2H4,
RFBF2 and N2. When the decomposition occurs in the solid mixture
with NaF, the borate Na[RFBF3] is formed instead of borane RFBF2
as co-product. The fluoride transfer in the fluorodediazotation
reaction of [4-FC6H4N2][RFBF3] proceeds at a lower temperature
(30–40 8C) compared to the parent salt with the [BF4]À anion,
despite the lower fluoride donor property of perfluoroorganyltri-
fluoroborate anions (cf. the gas phase fluoride affinity of
the corresponding perfluoroorganyldifluoroboranes [12]). The

336
V.V. Bardin, H.-J. Frohn / Journal of Fluorine Chemistry 156 (2013) 333–338
thermolysis of [4-FC6H4N2][(RF)nBF4Àn] (n = 0–2) is no solid state
reaction. It proceeds in the molten phase.
(tq(1:1:1:1), 4J(F3B,F2,6) = 11 Hz, 1J(F,B) = 43 Hz, 3F, BF3), À134.9
(m, 2F, F2,6), À161.1 (t, 3J(F4,F3,5) = 19 Hz, 1F, F4), À165.4 (m, 2F,
F3,5) (C6F5BF3). 11B NMR (CH3CN):
d
1.6 (q, 1J(B,F) = 43 Hz, BF3).
4. Experimental
[4-FC6H4N2][cis-C6F13CF55CFBF3] (yield 74%). 19F NMR (CH3CN):
À83.0 (tt, 4J(F4,H2,6) = 4 Hz, 3J(F4,H3,5) = 8 Hz, 1F, F4) (4-FC6H4N2);
d
4.1. General
À80.0 (tt, 3J(F8,F7) = 4 Hz, 4J(F8,F6) = 10 Hz, 3F, F8), À14.0
(dtq(1:1:1:1), 3J(F3,F2) = 13 Hz, 4J(F3,F5) = 13 Hz, 5J(F3,BF3) = 13 Hz,
2F, F3), À121.2 (m, CF2), À121.7 (m, 2CF2), À125.0 (qtt,
3J(F7,F8) = 4 Hz, 3J(F7,F6) = 7 Hz, 4J(F7,F5) = 9 Hz, 2F, F7), À129.8
(q(1:1:1:1), 2J(F1,B) = 22 Hz, 1F, F1), À142.1 (tdq(1:1:1:1),
5J(F3B,F3) = 13 Hz, 4J(F3B,F2) = 10 Hz, 1J(F,B) = 36 Hz, 3F, BF3),
The NMR spectra were recorded on a Bruker AVANCE 300
spectrometer (1H at 300.13 MHz, 11B at 96.29 MHz, 19F at
282.40 MHz). The chemical shifts are referenced to TMS (1H),
BF3ÁOEt2/CDCl3 (15% v/v) (11B), and CCl3F (19F) [with C6F6 as a
secondary reference (À162.9 ppm)]. The composition of the
reaction mixtures and the yield of products were determined by
19F NMR spectroscopy using C6F6 as an internal standard for
integration. DSC analyses were performed on a Netzsch 204
Phoenix instrument equipped with a CC220 controller; a TASC414/
3A microprocessor system, and a personal computer. The solid
samples (2–7 mg) were weighed in aluminum pans and closed by a
pierced aluminum lid inside a glove box. The temperature
difference between the sample and the empty reference pan with
a pierced lid was measured choosing a temperature program of
10 K/min. The raw data were processed using the Netzsch Proteus
Software Version 4.2.
À156.9 (m, 1F, F2) (cis-C6F13CF55CFBF3). 11B NMR (CH3CN):
d
À0.4 (ddq, 3J(B,F2) = 7 Hz, 2J(B,F1) = 23 Hz, 1J(B,F) = 36 Hz, BF3).
[4-FC6H4N2][trans-C4F9CF55CFBF3] (yield 68%). 19F NMR
(CH3CN):
d
À82.8 (tt, 4J(F4,H2,6) = 4 Hz, 3J(F4,H3,5) = 8 Hz, 1F, F4)
(4-FC6H4N2); À80.0 (tt, 3J(F6,F5) = 3 Hz, 4J(F6,F4) = 10 Hz, 3F, F6),
À116.2 (dtd, 3J(F3,F2) = 13 Hz, 4J(F3,F5) = 12 Hz, 4J(F3,F1) = 26 Hz, 2F,
F3), À123.7 (m, 2F, F4), À125.1 (m, 2F, F5), À152.1 (md,
3J(F1,F2) = 132 Hz, 1F, F1), À143.0 (dq(1:1:1:1), 4J(F3B,F2) = 9 Hz,
1J(F,B) = 39 Hz, 3F, BF3), À177.0 (md, 3J(F2,F1) = 132 Hz, 1F, F2)
(trans-C4F9CF55CFBF3). 11B NMR (CH3CN):
2J(B,F1) = 25 Hz, 1J(B,F) = 39 Hz, BF3).
d
À0.3 (dq,
[4-FC6H4N2][C6F13BF3] (yield 77%). 19F NMR (CH3CN):
d
À82.6
The microscale thermolysis of neat [4-FC6H4N2][RFBF3] and [4-
FC6H4N2][(C6F13)2BF2] salts or mixture with NaF (1:3, v/v) was
performed in a glass NMR tube (outer diameter 5 mm, length
178 mm under an atmosphere of dry Ar in the stirred silicone oil
bath of a Bu¨chi Melting Point B-510 device with rates of heating of
5 8C per min (25–90 8C) and 2 8C per min (90–170 8C).
(tt, 4J(F4,H2,6) = 4 Hz, 3J(F4,H3,5) = 8 Hz, 1F, F4) (4-FC6H4N2); À79.9
(tt, 3J(F6,F5) = 3 Hz, 4J(F6,F4) = 10 Hz, 3F, F6), À120.9 (m, CF2),
À121.6 (m, CF2), À122.4 (m, CF2), À124.8 (qtt, 3J(F5,F6) = 3 Hz,
3J(F5,F4) = 8 Hz, 4J(F5,F3) = 13 Hz, 2F, F5), À132.2 (m, 2F, F1), À151.1
(q(1:1:1:1), 1J(F,B) = 41 Hz, 3F, BF3) (C6F13BF3). 11B NMR (CH3CN):
À0.7 (tq, 2J(B,F1) = 20 Hz, 1J(B,F) = 41 Hz, BF3).
d
Dichloromethane (Baker) was purified by treatment in se-
quence with H2SO4, aqueous Na2CO3, and water. After distillation
[4-FC6H4N2][(C6F13)2BF2] (yield 84%). 19F NMR (CH3CN):
d –82.7
(tt, 4J(F4,H2,6) = 4 Hz, 3J(F4,H3,5) = 8 Hz, 1F, F4) (4-FC6H4N2); À80.1 (t,
4J(F6,F4) = 10 Hz, 6F, F6), À121.0 (m, 2CF2), À121.7 (m, 4CF2), À125.1
(m, 4F, F5), À130.4 (m, 4F, F1), À172.5 (q(1:1:1:1), 1J(F,B) = 62 Hz, 2F,
˚
over P4O10 it was stored over molecular sieves 3 A before use.
Acetonitrile (Baker) was purified and dried as described in Ref.
[10]. Salt [4-FC6H4N2][BF4] was prepared by the general protocol
[11] from 4-FC6H4NH2 (25.3 g, 227 mmol), 50% aq H[BF4] (115 mL),
and NaNO2 (18.2 g, 262 mmol) in 67% yield and stored under an
atmosphere of dry argon. Borates K[C6F5BF3] [2], K[C6F13BF3] [3],
BF2) ((C6F13)2BF2). 11B NMR (CH3CN):
d 0.1 (m, BF2).
[4-FC6H4N2][CF3CBB CBF3] (yield 78%). 19F NMR (CH3CN):
d
À82.9 (tt, 4J(F4,H2,6) = 4 Hz, 3J(F4,H3,5) = 8 Hz, 1F, F4) (4-FC6H4N2);
À47.8 (s, 3F, F3), À135.3 (q(1:1:1:1), 1J(F,B) = 31 Hz, 3F, BF3)
K[trans-C4F9CF55CFBF3]
[4],
K[cis-C6F13CF55CFBF3]
[4],
(CF3CBB CBF3). 11B NMR (CH3CN):
d
À2.5 (q, 1J(B,F) = 31 Hz, BF3).
K[CF3CBB CBF3] [5] were prepared as described. Salt K[(C6F13)2BF2]
[6] was prepared by a modified procedure (see 4.2). NaF was
calcinated at 400 8C for 5 h in vacuum.
The 1H NMR spectra of the above salts (in CH3CN) contained
resonances of the cation [4-FC6H4N2]+ at
d(H) 8.57 (dd,
3J(H2,H3) = 9.5 Hz, 4J(H2,F4) = 4.4 Hz, 2H, H2,6), and 7.65 (dd,
3J(H3,H2) = 9.5 Hz, 3J(H3,F4) = 8 Hz, 2H, H3,5) ppm.
4.2. Preparation of K[(C6F13)2BF2]
4.4. Thermolysis of 4-fluorobenzenediazonium fluoroborate salts
Salt K[(C6F13)2B(OMe)2] [6] (1.1 g, 1.46 mmol) was added to
cold (0–5 8C) aHF (anhydrous HF, 4 mL) with stirring. Within a few
hours the initially formed white suspension converted into a
yellow solution which was stirred overnight at 20 8C. The solution
was diluted with water (8 mL). The precipitate was filtered off and
washed with water and finally dried in a vacuum desiccator over
Sicapent1 to yield K[(C6F13)2BF2] (796 mg, 75%).
The NMR tube was tightly connected with a cooled (À20 to
À40 8C) trap filled with CH2Cl2 (0.5 mL) via an FEP tube. This trap
allowed to follow the evolution of gas, e.g., N2. The NMR tube was
charged with the borate salt and immersed (3–4 cm) in the oil bath
of the melting point device. After decomposition of the salt the
NMR tube was quickly deposited into a cooling bath (À40 8C) for 5–
10 min. The reaction products in the NMR tube were dissolved in
CH2Cl2 (0.7 mL) at 25 8C, a defined quantity of C6F6 was added and
the solution was analyzed by NMR spectroscopy. The cooled
CH2Cl2 trap contained no fluoroorganics (19F NMR).
4.3. Preparation of [4-FC6H4N2][RFBF3] and [4-FC6H4N2][(C6F13)2BF2]
salts
Syntheses were performed with 0.5 to 1.6 mmol of [4-
FC6H4N2][BF4]. The solution of K[RFBF3] (1.1 equiv.) in MeCN (3–
4 mL) was added to the stirred solution of [4-FC6H4N2][BF4] (1.0
equivalent) in MeCN (3–4 mL). The resulting suspension was
stirred for 30–40 min and centrifuged. The yellow-brownish
mother liquor was decanted. The solid residue was dried at
25 8C in vacuum and washed with dry ether (2Â 10–20 mL). After
removal of volatiles at 25 8C in vacuum, the flask was filled with
argon and stored in a glove box under an atmosphere of dry argon.
4.4.1. Thermolysis of [4-FC6H4N2][BF4]
The salt [4-FC6H4N2][BF4] (44 mg, 0.20 mmol) melted accom-
panied by decomposition at 158–160 8C to give 1,4-difluoroben-
zene (0.17 mmol, 86%). BF3 was not collected in the cooled CH2Cl2
trap under the experimental conditions.
4.4.2. Thermolysis of [4-FC6H4N2][C6F5BF3]
The salt [4-FC6H4N2][C6F5BF3] (30 mg, 83
100 8C and formed a brown liquid phase which decomposed at
120–140 8C with bubbling. The 19F NMR spectrum of the residue
mmol) melted at 95–
[4-FC6H4N2][C6F5BF3] (yield 82%). 19F NMR (CH3CN):
d
À83.1
(tt, 4J(F4,H2,6) = 4 Hz, 3J(F4,H3,5) = 8 Hz, 1F, F4) (4-FC6H4N2); À132.8

V.V. Bardin, H.-J. Frohn / Journal of Fluorine Chemistry 156 (2013) 333–338
337
showed resonances of 1,4-C6F2H4 (45
m
mol, 54%), C6F5H (20
m
mol,
25 8C. The residue was washed with CH2Cl2 (2 Â 1 mL), dried in
vacuum and extracted with CH3CN. Both extracts were analyzed by
NMR spectroscopy.
24%), (C6F5)2 (13
m
mol, 16%), and C6F5BF2 (trace). The 11B NMR
spectrum contained a weak signal of C6F5BF2 at 21.3 ppm [7e].
4.4.3. Thermolysis of [4-FC6H4N2][cis-C6F13CF55CFBF3]
4.5.1. Thermolysis of [4-FC6H4N2][C6F5BF3] in NaF
The salt [4-FC6H4N2][cis-C6F13CF55CFBF3] (47 mg, 82
melted at 90–95 8C and formed a brown liquid which decomposed
at 130–150 8C with bubbling. The 19F NMR spectrum of the products
m
mol)
Decomposition of [4-FC6H4N2][C6F5BF3] (64 mg, 178
NaF (1:3, v/v) gave 1,4-C6F2H4 (141 mol, 79%), (CH2Cl2 extract),
Na[C6F5BF3] (126 mol, 71%) and Na[BF4] (20 mol, 11%) (CH3CN
extract) (19F NMR).
mmol) in
m
m
m
in the NMR tube showed resonances of 1,4-C6F2H4 (74
cis-C6F13CF55CFBF2 (14 mol, 5%), cis-C6F13CF55CFH (3
C6F13CBB CF (2 mol, 3%), and unidentified compounds of minor
mmol, 90%),
m
mmol, 4%),
m
4.5.2. Thermolysis of [4-FC6H4N2][cis-C6F13CF55CFBF3] in NaF
Decomposition of [4-FC6H4N2][cis-C6F13CF55CFBF3] (47 mg,
quantity. The 11B NMR spectrum showed the resonance of cis-
C6F13CF55CFBF2 at 14.8 ppm [13]. Washing with an aqueous solution
of Na2CO3 and drying with K2CO3 led to the quantitative conversion
of cis-C6F13CF55CFBF2 to cis-C6F13CF55CFH. The other products were
not changed.
82
C6F13CBB CF (3
C6F13CF55CFBF3] (53
(10 mol, 12%), and Na[BF4] (14
11B, 19F NMR).
m
mol) in NaF (1:3, v/v) gave 1,4-C6F2H4 (63
mol, 3%) (CH2Cl2 extract) (19F NMR), Na[cis-
mol, 65%), Na[trans-C6F13CF55CFBF3]
mol, 17%) (CH3CN extract)
mmol, 77%) and
m
m
m
m
cis-C6F13CF55CFH. 19F NMR (CH2Cl2):
d
À81.4 (m, 3F, F8), À119.8
(
(dt, 3J(F3,F2) = 14 Hz, 4J(F3,F5) = 14 Hz, 2F, F3), À122.5 (m, CF2),
À123.2 (m, CF2), À125.5 (m, CF2), À126.5 (m, 2F, F7), À151.3 (dd,
3J(F1,F2) = 7 Hz, 2J(F1,H1) = 68 Hz, 1F, F1), À155.3 (m, 1F, F2).
4.5.3. Thermolysis of [4-FC6H4N2][trans-C4F9CF55CFBF3] in NaF
Decomposition of [4-FC6H4N2][trans-C4F9CF55CFBF3] (51 mg,
C6F13CBB CF. 19F NMR (CH2Cl2):
d
À81.4 (m, 3F, F8), À97.4 (t,
108
mmol) in NaF (1:3, v/v) gave 1,4-C6F2H4 (103 mmol, 95%)
4J(F3,F5) = 13 Hz, 2F, F3), À122 to À126.5 (3CF2), À127.8 (m, 2F, F7),
À189.4 (m, 1F, F1).
(CH2Cl2 extract) (19F NMR), Na[trans-C4F9CF55CFBF3] (90
m
mol,
mol,
83%), Na[cis-C4F9CF55CFBF3] (11
5%) (CH3CN extract) (11B, 19F NMR).
mmol, 10%), and Na[BF4] (6 m
4.4.4. Thermolysis of [4-FC6H4N2][trans-C4F9CF55CFBF3]
Melting of salt [4-FC6H4N2][trans-C4F9CF55CFBF3] (44 mg,
4.5.4. Thermolysis of [4-FC6H4N2][(C6F13)2BF2] in NaF
93
posed at 120–130 8C with bubbling. The 19F NMR spectrum of the
products showed resonances of 1,4-C6F2H4 (75 mol, 80%), trans-
C4F9CF55CFBF2 (46 mol, 49%), and minor unidentified com-
m
mol) at 80–90 8C resulted in a brown liquid which decom-
A mixture of [4-FC6H4N2][(C6F13)2BF2] (44 mg, 54 mmol) with
NaF (1:3, v/v) was heated from 25 to 200 8C (bath) within 8 min
and quickly cooled to 20 8C. The products were extracted with
m
m
CH3CN (0.7 mL). The extract contained 1,4-C6F2H4 (44
Na[(C6F13)2BF2] (21 mol, 39%), Na[C6F13CF(BF3)C5F11] (18
33%), and Na[BF4] (9
Na[C6F13CF(BF3)C5F11
À119.7 (m, 2CF2), À120.5 (m, CF2), À121.3 (m, CF2), À121.5 (m,
CF2), À125.0 (m, 4F, F2,11), À110.4 (d, 2J(F7A,F7B) = 304 Hz, 1F7A),
À111.3 (d, 2J(F7B,F7A) = 304 Hz, 1F7B), À110.4 (d, 2J(F5A,F5B) =
304 Hz, 1F5A), À111.3 (d, 2J(F5B,F5A) = 304 Hz, 1F5B), À208.7 (m,
1F6), À143.9 (q(1:1:1:1), 1J(F,B) = 37 Hz, BF3) (cf. with spectrum of
M[C2F5CF(BF3)CF3] [9]).
m
mol, 81%),
pounds. In the 11B NMR spectrum the resonance of trans-
C4F9CF55CFBF2 was detected at 13.6 ppm [13].
m
m
m
mol,
mol, 17%) (11B, 19F NMR).
]
19F NMR (CH3CN).
d
À80.1 (m, 6F, F1,12),
4.4.5. Thermolysis of [4-FC6H4N2][C6F13BF3]
The salt [4-FC6H4N2][C6F13BF3] (45 mg, 88
mmol) melted at
110–115 8C and gave a brown liquid which decomposed at 120–
130 8C with evolution of gas. The decomposition products were
dissolved in CF3CH2CF2CH3 (PFB). The 19F NMR spectrum showed
resonances of 1,4-C6F2H4 (59
85%).
mmol, 67%) and C6F13BF2 (75 mmol,
4.5.5. Thermolysis of [4-FC6H4N2][CF3CBB CBF3] in NaF
4.4.6. Thermolysis of [4-FC6H4N2][(C6F13)2BF2]
After decomposition of [4-FC6H4N2][CF3CBB CBF3] (48 mg,
When salt [4-FC6H4N2][(C6F13)2BF2] (92 mg, 113
m
mol) was
169
CH3CN (0.7 mL). The extract contained 1,4-C6F2H4 (90
Na[CF3CBB CBF3] (16 mol, 9%), CF3CBB CH (16 mol, 9%), and
Na[BF4] (129 mol, 76%) besides few minor unidentified products
11B, 19F NMR).
m
mol) in NaF (1:3/v/v) the products were extracted with
heated melting and decomposition proceeded at 140–145 8C. The
products were extracted with 1,1,1,3,3-pentafluorobutane (PFB).
The 19F NMR spectrum showed resonances of 1,4-C6F2H4
m
mol, 51%),
m
m
m
(89
m
mol, 79%), C6F13CF(BF2)C5F11 (31
m
mol, 27%), and of uniden-
(
tified compounds. The products C6F13BF2, C4F9CF55CFBF2 (cis and
trans), 4-FC6H4C6F13, and 4-FC6H4CF55CFC4F9 were not detected
19F NMR).
References
(
C6F13CF(BF2)C5F11
.
19F
NMR
(PFB):
d
À79.9
(t,
[1] (a) Methoden der Organischen Chemie (Houben-Weyl), 5/3, Thieme, Stuttgart,
1962, pp. 213–246;
4J(F1,F3) = 4J(F12,F10) = 10 Hz, 6F, F1,12), À116.8 (m, 2CF2), À124.8
(m, 4F, F2,11), À114.0 (d, 2J(F7A,F7B) = 303 Hz, 1F7A), À114.3 (d,
2J(F5A,F5B) = 303 Hz, 1F5A), À121 to À126 (2CF2, 1F5B, 1F7B), À207.8
(m, 1F6).
(b) H. Suschitzky, in: M. Stacey, J.C. Tatlow, A.G. Sharpe (Eds.), Adv. Fluorine
Chem. 4 (1965) 1–27;
(c) K.H. Saunders, R.L.M. Allen, Aromatic Diazo Compounds, 3th ed., Arnold,
London, 1985, pp. 744–748;
(d) H. Zollinger, Diazo Compounds, Weinheim, New York, 1994, pp. 228–230;
(e) M.M. Boudakian, in: M. Hudlicky, A.E. Pavlath (Eds.), Chemistry of Organic
Fluorine Compounds II. A Critital Review, ACS Monograph 187, Washington, 1995,
pp. 271–293;
4.5. Thermolysis of 4-fluorobenzenediazonium
perfluoroorganylfluoroborates in NaF
(f) B. Langlois, in: B. Baasner, H. Hagemann, J.C. Tatlow (Eds.), 4th ed., Houben-
Weyl Methods of Organic Chemistry. Organo-Fluorine Compounds, E10a, Thieme,
Stuttgart, 2000, pp. 686–740.
The corresponding perfluoroorganyborate salts and vigorously
dried NaF (1:3, v/v) were mixed in the glove box and loaded into an
NMR tube. The NMR tube was immersed (3–4 cm) into the oil bath
of the melting point device and heated to 160–170 8C within 5–
7 min and kept at 169–170 8C for 1 min. After decomposition the
NMR tube was quickly deposited into a cold (0 8C) bath for 5–
10 min and the products were extracted with CH2Cl2 (0.8–1 mL) at
[2] N.Yu. Adonin, D.E. Babushkin, V.N. Parmon, V.V. Bardin, G.A. Kostin, V.I. Mashu-
kov, H.-J. Frohn, Tetrahedron 64 (2008) 5920–5924.
[3] H.-J. Frohn, M. Giesen, D. Welting, V.V. Bardin, J. Fluorine Chem. 131 (2010) 922–
936.
[4] H.-J. Frohn, V.V. Bardin, Z. Anorg. Allg. Chem. 627 (2001) 2499–2505.
[5] V.V. Bardin, N.Yu. Adonin, H.-J. Frohn, Organometallics 24 (2005) 5311–5317.
[6] N.Yu. Adonin, H.-J. Frohn, V.V. Bardin, Organometallics 26 (2007) 2420–2425.

338
V.V. Bardin, H.-J. Frohn / Journal of Fluorine Chemistry 156 (2013) 333–338
[7] (a) H.-J. Frohn, V.V. Bardin, Z. Anorg. Allg. Chem. 629 (2003) 2465–2469;
[8] Cf. calculated F– affinities of (CF3)2BF and the isomer C2F5BF2 [9].
[9] M. Finze, E. Bernhardt, M. Za¨hres, H. Willner, Inorg. Chem. 43 (2004) 490–
505.
(b) A. Abo-Amer, N.Yu. Adonin, V.V. Bardin, P. Fritzen, H.-J. Frohn, Ch. Steinberg, J.
Fluorine Chem. 125 (2004) 1771–1778;
(c) V.V. Bardin, H.-J. Frohn, Main Group Met. Chem. 25 (2002) 589–613;
(d) H.-J. Frohn, V.V. Bardin, Z. Anorg. Allg. Chem. 628 (2002) 1853–1856;
(e) H.-J. Frohn, V.V. Bardin, Z. Anorg. Allg. Chem. 627 (2001) 15–16;
(f) H.-J. Frohn, N.Yu. Adonin, V.V. Bardin, Z. Anorg. Allg. Chem. 629 (2003) 2499–
2508;
[10] H.-J. Frohn, M.E. Hirschberg, R. Boese, D. Bla¨ser, U. Flo¨rke, Z. Anorg. Allg. Chem. 634
(2008) 2539–2550.
[11] Houben-Weyl, Methoden der Organischen Chemie, Thieme, Stuttgart, 1962p.
S220 (Bd 5/3).
[12] A. Abo-Amer, H.-J. Frohn, Ch. Steinberg, U. Westphal, J. Fluorine Chem. 127 (2006)
1311–1323.
[13] H.-J. Frohn, V.V. Bardin, J. Organomet. Chem. 631 (2001) 54–58.
(g) H.-J. Frohn, H. Franke, P. Fritzen, V.V. Bardin, J. Organomet. Chem. 598 (2000)
127–135.