The formation of oxygen-containing perfluorocyclohexadien-1-yliodine tetrafluorides

Article abstract of DOI:10.1016/j.jfluchem.2005.08.014

The electrophilic oxygenation of pentafluorophenyl iodo compounds C ₆F₅IF_n with iodine in different valencies (n = 0, 2, 4) using XeF₂-H₂O in HF allowed access to new organoiodine(V) compounds, namely isomeric oxopentafluorocyclohexadien-1- yliodine tetrafluorides, C₆(O)F₅IF₄.

Full text of DOI:10.1016/j.jfluchem.2005.08.014

Journal of Fluorine Chemistry 127 (2006) 18–21
www.elsevier.com/locate/fluor
The formation of oxygen-containing perfluorocyclohexadien
-1-yliodine tetrafluorides§
b
Hermann-Josef Frohn a, , Vadim V. Bardin
*
a Department of Chemistry, Inorganic Chemistry, University 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
Received 13 June 2005; received in revised form 24 August 2005; accepted 26 August 2005
Available online 17 November 2005
Abstract
The electrophilic oxygenation of pentafluorophenyl iodo compounds C6F5IFn with iodine in different valencies (n = 0, 2, 4) using XeF2–H2O in
HF allowed access to new organoiodine(V) compounds, namely isomeric oxopentafluorocyclohexadien-1-yliodine tetrafluorides, C6(O)F5IF4.
# 2005 Elsevier B.V. All rights reserved.
Keywords: Xenon difluoride; Electrophilic oxygenation; Organoiodine(V) tetrafluorides
1. Introduction
products were formed by two parallel reaction paths: the
oxidative addition of fluorine to the iodine atom and the
addition of fluorine to the perfluoroaryl group (Scheme 2).
Based on these experiences, we studied the electrophilic
oxygenation of C6F5IFn (n = 0, 2, 4) with xenon difluoride
and H2O in hydrogen fluoride as a promising route to
oxygen—containing perfluorocyclohexadien-1-yliodine tetra-
fluorides.
In 1996, we found that solutions of pentafluorobenzene
derivatives (C6F5X) in HF formed oxopentafluorocyclohexa-
dienes (C6(O)F5X) when treated with an equivalent amount of
XeF2 in the presence of 1–2 equivalents of water [1,2] (Scheme
1). The nature of potential reactive key intermediates such as
XeII–oxygen compounds or HOF was discussed in [2].
Formally, this reaction can be described as an electrophilic
oxygenation because in addition to the fluorine substituents one
oxygen atom is bonded to the C6-skeleton. But in reality the
reaction proceeded via hydroxyhexafluorocyclohexadienes as
unstable intermediates. When the initial reaction steps are taken
into account this process should be termed an electrophilic
hydroxyfluorination.
2. Results and discussion
The treatment of pentafluorophenyliodine tetrafluoride (1) in
HF with XeF2 (1.3 equivalent) and H2O (1 equivalent) did not
result in oxygenation of 1 at À25 8C, but warming to 12 8C
caused the immediate evolution of xenon and the formation of
3-oxopentafluorocyclohexa-1,4-dien-1-yliodine tetrafluoride
(2), 6-oxopentafluorocyclohexa-1,4-dien-1-yliodine tetrafluoride
(3), 4,5-epoxypentafluorocyclohex-1-en-1-yliodine tetrafluor-
ide (4), 3-oxo-4,5-epoxypentafluorocyclohex-1-en-1-yliodine
tetrafluoride (5), 5-oxopentafluorocyclohexa-1,3-dien-1-ylio-
dine tetrafluoride (6), and 6-oxopentafluorocyclohexa-1,3-
dien-1-yliodine tetrafluoride (7) (trace) in the ratio
2:3:4:5:6 = 76:6:6:6:6 in 77% overall yield (Scheme 3).
Oxygen-containing perfluorocycloalkenyliodine tetrafluor-
ides 2–7 can be directly obtained from commercially available
iodopentafluorobenzene (8) by in situ generation of 1. Thus,
mixing of 8 with XeF2 (2.6 equivalents) in HF at À20 8C and
the subsequent addition of water (1.2 equivalents) and further
When solutions of C6F5X in anhydrous hydrogen fluoride
(aHF) reacted with XeF2 in the absence of water, the addition of
two fluorine atoms preferentially occurred to yield polyfluori-
nated cyclohexadienes C6F7X [3]. Using this method of fluorine
addition, we recently prepared the previously unknown
cycloalkenyliodine tetrafluorides from polyfluoroaryliodine
tetrafluorides, as well as -aryliodine difluorides and -aryl
iodides C6F5IFn (n = 0, 2, 4) [4]. When n = 0 or 2, the desired
§
Part 3 in the series ‘‘Electrophilic oxygenation with XeF2–H2O in hydrogen
fluoride’’ [1].
* Corresponding author. Tel.: +49 203 379 3310; fax: +49 203 379 2231.
E-mail address: frohn@uni-duisburg.de (H.-J. Frohn).
0022-1139/$ – see front matter # 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2005.08.014

H.-J. Frohn, V.V. Bardin / Journal of Fluorine Chemistry 127 (2006) 18–21
19
Scheme 1.
Scheme 4.
Scheme 2.
XeF2 (1 equivalent) resulted in, after warming to 12–16 8C, the
same products (Scheme 4).
electron-withdrawing substituents X = Cl, Br, CF3, Me3N+ [1],
Xe+ [2].
To also extend the investigation to trivalent iodine
compounds, we performed the electrophilic oxygenation of
pentafluorophenyliodine difluoride (9) in two modified ways.
When a solution of 9 in HF was treated with H2O (1.3
equivalents) and XeF2 (2.2 equivalents) at À30 8C, no gas
evolution and reaction were observed, but upon warming from
5 to 20 8C, gas evolution occurred and compounds 2–7 were
obtained in addition to C6F5IF4 (1) (Scheme 5).
It is noteworthy that the conversion of 9 by XeF2–H2O in HF
into products 1–7 was not inhibited by the addition of KF.
Diminishing the acidity of HF by water as well as fluoride ions
plays a less important role here than in the electrophilic
fluorination with XeF2 in aHF. For example, C6F6 did not react
with XeF2 in ‘‘basic’’ aHF, which contained KF, but was rapidly
converted into 1,4-C6F8 in the absence of KF [10].
Reactions of C6F5I or C6F5IF2 with either XeF2 in aHF or
XeF2–H2O in HF yield organoiodine(V) tetrafluorides
(mainly, cycloalkenyl derivatives). Although the relative
contribution of routes A and B (Scheme 6) has not been
determined, the exclusive formation of C6F5I(OR)2
from C6F5I and the strong oxidants CF3C(O)OOH or 100%
HNO3/(CF3C(O))2O (R = C(O)CF3) [5,6] or (CF3)3COCl
(R = OC(CF3)3) [7] allows one to assume the preference of
route A over B at least for iodopentafluorobenzene.
4. Experimental details
The NMR spectra were recorded on a Bruker AVANCE 300
spectrometer (19F at 282.40 MHz) at 24 8C. The chemical shifts
are referenced to CCl3F (19F) [with C6F6 as secondary reference
(À162.9 ppm)]. The molar composition of the reaction
mixtures and the yields of products were determined by 19F
NMR spectroscopy using the quantitative internal standard
1,1,2-trichlorotrifluoroethane (Merck).
3. Conclusions
The ratio of 3-oxo- to 6-oxopentafluorocycloalkenes
(2 + 5 + 6):(3 + 7) = 88:12 establishes that carbon atoms C-3
or C-5 of 1 are the predominant sites of reaction. This finding is
very similar to the electrophilic oxygenation (hydroxyfluorina-
tion) of other pentafluorobenzene derivatives (C6F5X) bearing
C6F5IF2 was prepared by low-temperature fluorination of
C6F5I in CCl3F [8]. C6F5IF4 was obtained by the reaction of IF5
with Bi(C6F5)3 in MeCN [9]. Iodopentafluorobenzene (Bristol
Organics) was used as supplied.
Scheme 3.

20
H.-J. Frohn, V.V. Bardin / Journal of Fluorine Chemistry 127 (2006) 18–21
Scheme 5.
4,5-Epoxypentafluorocyclohex-1-en-1-yliodine tetrafluoride
4
(4). 19F NMR (CH2Cl2): d À5.7 (d J(IF4, F6A) = 11 Hz, d
4
4J(F4I, F6B) = 24 Hz, d J(IF4, F2) = 28 Hz, 4F, IF4), À87.8
(m, d 2J(F6A, F6B) = 295 Hz, 1F, F6A), À94.5 (m, 1F, F2),
À110.2 (d 2J(F3A, F3B) = 302 Hz, d 3J(F3A, F4) = 18 Hz, d
3J(F3A, F2) = 29 Hz, 1F, F3A), À114.2 (d 2J(F6B, F6A) = 295 Hz,
1F, F6B), À123.5 (d, 2J(F3B, F3A) = 302 Hz, 1F, F3B), À175.4 (d
3J(F5, F4) = 19 Hz,
d
3J(F5, F6A) = 19 Hz,
d
3J(F5,
F6B) = 19 Hz, 1F, F5), À178.3 (m, 1F, F4).
3-Oxo-4,5-epoxypentafluorocyclohex-1-en-1-yliodine tetra-
fluoride (5). 19F NMR (CH2Cl2): d À6.2 (d 4J(IF4,
4
4
F6A) = 11 Hz, d J(IF4, F6B) = 24 Hz, d J(IF4, F2) = 27 Hz,
Scheme 6.
4F, IF4), À88.7 (d 2J(F6A
,
F6B) = 297 Hz,
IF4) = 11 Hz,
d
3J(F6A
4J(F6A
,
,
F5) = 18 Hz, quintet 4J(F6A
,
d
F2) = 10 Hz, 1F, F6A), À90.5 (m, 1F, F2), À114.7 (m, 1F,
3
3
All manipulations were performed in FEP (block copolymer
of tetrafluoroethylene and hexafluoropropylene) equipment
under an atmosphere of dry argon.
F6B), À173.9 (d J(F5, F4) = 18 Hz, d J(F5, F6A) = 18 Hz, d
3J(F5, F6B) = 18 Hz, 1F, F5), À174.8 (d J(F4, F2) = 10 Hz, d
4
3J(F4, F5) = 18 Hz, d J(F4, F6A) = 3 Hz, d J(F4, F6B) = 2 Hz,
4
4
1F, F4).
4.1. Reaction of C6F5IF4 (1) with XeF2 and H2O in HF
5-Oxopentafluorocyclohexa-1,3-dien-1-yliodine tetrafluor-
4
ide (6). 19F NMR (CH2Cl2): d À8.7 (d J(IF4, F2) = 26 Hz, t
Pentafluorophenyliodine tetrafluoride (84 mg, 0.22 mmol)
was suspended in aHF (2.5 mL) at À25 8C, and a cold (À25 8C)
solution of water (4 mg, 0.22 mmol) in HF (0.5 mL) was
added. The suspension was stirred for 5 min before XeF2
(49 mg, 0.29 mmol) was added in one portion. The reaction
mixture was allowed to warm to À17 8C over a 1 h period.
When the reactor was placed in a 12 8C cold bath, gas evolution
was observed. Stirring was continued for 1 h and the
temperature was raised to 16 8C. The suspension was cooled
to 0 8C and C6F6 (ca. 0.05 mL) was added to consume excess
XeF2. The reactor was maintained at 18–20 8C for 15 min.
After cooling to À5 8C, the products were extracted with
dichloromethane (1 mL). The 19F NMR spectrum showed the
formation of 2 (0.13 mmol), 3 (0.01 mmol), 4 (0.01 mmol), 5
(0.01 mmol), and 6 (0.01 mmol) besides traces of 7, C6F5IF4,
and IF5 (the amount of each was <0.01 mmol) (molar ratio
2:3:4:5:6 = 76:6:6:6:6).
4J(IF4, F6) = 15 Hz, 4F, IF4), À86.8 (m, 1F, F2), À97.7 (m, 2F,
3
4
F6,6),–128.9 (d J(F3, F2) = 5 Hz, t J(F3, F6) = 4 Hz, 1F, F3),
À144.0 (d J(F4, F2) = 14 Hz, t J(F4, F6) = 8 Hz, 1F, F4).
4
4
6-Oxopentafluorocyclohexa-1,3-dien-1-yliodine tetrafluor-
ide (7). 19F NMR (CH2Cl2): d À11.1 (d J(IF4, F2) = 22 Hz,
4
4F, IF4), À90.4 (m, 1F, F2), À106.0 (d J(F5, F2) = 2 Hz, d
5
4J(F5, F3) = 12 Hz, d J(F5, F4) = 23 Hz, 2F, F5,5), À133.9 (d
3
4J(F4, F2) = 23 Hz, t J(F4, F5) = 23 Hz, 1F, F4), À149.1 (d
3
3J(F3, F2) = 10 Hz, t J(F3, F5) = 12 Hz, 1F, F3).
4
4.2. Reaction of C6F5I (8) with XeF2 and H2O in HF
Iodopentafluorobenzene (73 mg, 0.24 mmol) was dissolved
in aHF (1.5 mL) at À30 8C and XeF2 (107 mg, 0.63 mmol) was
added in one portion. The colourless solution was stirred at
À20 8C for 1 h before a cold (À25 8C) solution of water
(5.5 mg, 0.30 mmol) in HF (0.5 mL) was added. After stirring
at À24 to À20 8C for 15 min, a further portion of XeF2 (48 mg,
0.28 mmol) was added and the solution was allowed to warm to
À12 8C over a period of 1 h. A white suspension was formed.
The reactor was placed in a 4 8C cold bath and warmed to 12 8C
over a period of 1 h. The excess of XeF2 was removed by
reaction with C6F6 (ca. 0.05 mL). After cooling the suspension
to À60 8C, the supernatant HF was decanted and residual HF
was removed under vacuum at ꢀ 20 8C to yield a white solid
product (81 mg). The 19F NMR spectrum of the reaction
mixture in dichloromethane (1.5 mL) showed the formation of
1 (trace), 2 (0.15 mmol), 3 (0.01 mmol), 4 (0.01 mmol), 5
(0.01 mmol), 6 (0.01 mmol), and 7 (trace), besides IF5
(0.01 mmol).
3-Oxopentafluorocyclohexa-1,4-dien-1-yliodine tetrafluor-
4
ide (2). 19F NMR (CH2Cl2): d À6.8 (t J(IF4, F6) = 18 Hz, d
4J(IF4, F2) = 27 Hz, 4F, IF4), À93.8 (m, 1F, F2), À99.7 (m, 2F,
F6,6), À133.3 (d 5J(F5, F2) = 5 Hz, d 3J(F5, F4) = 5 Hz, t 3J(F5,
3
4
F6) = 23 Hz, 1F, F5), À152.5 (d J(F4, F5) = 5 Hz, d J(F4,
F2) = 6 Hz, t J(F4, F6) = 10 Hz, 1F, F4).
6-Oxopentafluorocyclohexa-1,4-dien-1-yliodine tetrafluor-
4
ide (3). 19F NMR (CH2Cl2): d À9.7 (d J(IF4, F2) = 24 Hz,
4
4F, IF4), À107.8 (m, 1F, F2), À112.5 (d J(F3, F2) = 24 Hz, d
3
3J(F3, F4) = 22 Hz, d J(F3, F5) = 10 Hz, 2F, F3,3), À144.8 (d
4
5J(F5, F2) = 3 Hz, d 3J(F5, F4) = 6 Hz, t 4J(F5, F3) = 10 Hz, 1F,
F5), À146.4 (d J(F4, F5) = 6 Hz, d J(F4, F2) = 3 Hz, t J(F4,
3
4
3
F3) = 22 Hz, 1F, F4).

H.-J. Frohn, V.V. Bardin / Journal of Fluorine Chemistry 127 (2006) 18–21
21
4.3. Reaction of C6F5IF2 (9) with XeF2 and H2O in HF
NMR spectrum of the extract showed the presence of 1
(0.02 mmol), 2 (0.11 mmol), 3 (0.01 mmol), 4 (trace), 5 (trace),
6 (0.01 mmol), and 7 (trace) (molar ratio 1:2:3:4:5:6:7 =
13:69:6:1:2:8:1; overall yield 80%), in addition to IF5
(0.02 mmol).
Pentafluorophenyliodine difluoride (140 mg, 0.42 mmol)
was cooled to À30 8C before a cold (À30 8C) solution of water
(10 mg, 0.55 mmol) in HF (1.7 mL) was added. The solution
was stirred for 5 min before XeF2 (159 mg, 0.94 mmol) was
added in one portion. The solution was stirred for an additional
5 min before the trap was placed in a 5 8C cold bath. Gas
evolution occurred and a white suspension was formed. Finally,
the reaction mixture was stirred at 15–20 8C for 1 h before
being extracted with CH2Cl2 (1.5 mL) at À10 to À20 8C. The
19F NMR spectrum of the extract showed the formation
of 1 (0.04 mmol), 2 (0.22 mmol), 3 (0.02 mmol), 4 (trace), 5
(trace), 6 (0.03 mmol), and 7 (0.01 mmol), in addition to IF5
(0.04 mmol).
Acknowledgements
We gratefully acknowledge financial support from the
Deutsche Forschungsgemeinschaft and the Fonds der Che-
mischen Industrie.
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