Solid state anion-π interactions involving polyhalides

Article abstract of DOI:10.1039/c3dt52960f

The stabilization of polyhalides in the solid state with the support of electron-deficient pentafluorophenyl groups is described. Furthermore, a synthetic approach towards the sensitive tetraiodide dianion is described and ESI mass spectrometric evidence for its presence in solution is reported. The Royal Society of Chemistry.

Full text of DOI:10.1039/c3dt52960f

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Solid state anion–π interactions involving
polyhalides†
Cite this: Dalton Trans., 2014, 43,
1873
Michael Giese,‡a Markus Albrecht,*a Christian Bohnen,a Tatjana Repenko,a
Arto Valkonen§b and Kari Rissanen*b
Received 21st October 2013,
Accepted 1st November 2013
The stabilization of polyhalides in the solid state with the support of electron-deficient pentafluorophenyl
groups is described. Furthermore, a synthetic approach towards the sensitive tetraiodide dianion is
described and ESI mass spectrometric evidence for its presence in solution is reported.
DOI: 10.1039/c3dt52960f
www.rsc.org/dalton
the anion–π interactions on the electron density of the arene
have shown that the attractive interaction in highly fluorinated
Introduction
Anions are of high relevance in various biological as well as in arenes turns into a repulsive interaction with tri- or difluori-
synthetic systems and take essential roles in those systems.1 nated phenyl units.11 Moreover, we studied the influence of
One prominent example is enzymes. The majority of enzymes the anion.12 The crystallographic results reveal no dependence
and enzymatic cofactors possess a negative charge.2 Further- of the interaction on the anion geometry. However, the anion
more, a malfunction of anion channels can lead to an increased size and its polarizability play a significant role.
heart attack risk or blood pressure as well as to diseases like
cystic fibrosis.3 Moreover, anions like nitrate, phosphate and extremely labile tetraiodide dianion13 in crystals of pentafluoro-
pertechnetate can cause serious harm for living creatures.4
benzyl ammonium and phosphonium salts. The linear poly-
Just recently we reported on the stabilization of the rare and
On this account the sensing and selective recognition of iodides are stabilized by cooperative CH–anion and anion–π
anions is a substantial goal. Commonly, anion receptors are interactions. Primarily, the terminal iodine atoms of the tetra-
based on electrostatic interactions or hydrogen bonds.5 iodide show close distances to the perfluorinated arenes.
However, within the last 20 years the non-covalent interaction However, the linear tetraiodides were obtained by serendipity
between anions and electron-deficient arenes has received con- during the crystallization under an oxidizing atmosphere.
siderable attention.6 Computational7 as well as crystallographic
Due to their reactivity in oxidation processes or addition
investigations6 have led to the suggestion of the attractive reactions with organic substrate14 polyhalides are interesting.
nature of this intermolecular force. In contrast to these, the role Besides, they are potential materials for organic conductors.15
of the interaction in solution remains an open question.8
Starting from this, the present study focuses on a directed syn-
Since 2008 we have been investigating anion–π interactions thesis of pentafluorophenyl ammonium salts for the stabiliz-
using pentafluorophenyl ammonium and phosphonium salts.9 ation of oligohalide anions, e.g. the rare tetraiodide dianion.
First crystallographic results revealed a high versatility in the Few derivatives containing tetraiodide dianions are known in
position of an anion above a C6F5-unit. However, this position the literature.16
can be controlled by directing substituents in the periphery of
the electron-deficient moiety.10 Studies on the dependence of
Results and discussion
aInstitut für Organische Chemie, RWTH Aachen, Landoltweg 1, 52074 Aachen,
On the way to an effective pentafluorophenyl receptor for the
stabilization of reactive oligohalide anions previously obtained
Germany. E-mail: markus.albrecht@oc.rwth-aachen.de; Fax: +49 241 809 2385;
Tel: +49 241 809 4678
solid phase structures were analysed. Thereby, three target
systems seem to be promising candidates to be able to bind
this kind of anion: the 8-pentafluorobenzyloxy quinoline (1)
system, which can capture linear anions like tribromide, the
well-investigated 1-pentafluoro benzylammonium-4-aza-1-
azonia bicyclo[2.2.2]octane iodide (PfbDABCO iodide, 3) and
the bis(pentafluorobenzyl)-tetramethylammonium ethylene
diiodide (5). Earlier studies of the various systems show
bDepartment of Chemistry, Nanoscience Center, University of Jyväskylä, Survontie 9,
40014 Jyväskylä, Finland. E-mail: kari.t.rissanen@jyu.fi; Fax: +358 14 260 2672;
Tel: +358 50 562 3721
†CCDC 967127–967130. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3dt52960f
‡Present address: Department of Chemistry, University of British Columbia,
2036 Main Mall, Vancouver, B.C., Canada V6T 1Z1.
§Present address: Tampere University of Technology, Department of Chemistry
and Bioengineering, P.O. Box 541, FI-33101 Tampere, Finland.
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their appropriateness in anion–π interactions. Especially the qui-
noline13 and the bispentafluorobenzyl tetramethyl ammonium
ethylene17 based cations should be able to bind linear anions.
Synthesis of polyiodide salts
Polyhalide anions are charge-transfer adducts of the dihalogen
and a halide anion. Polyhalides can be formed in situ by oxi-
dative dimerization of two halide anions to the dihalide fol-
lowed by further aggregation. Well-known are the trihalides
like tribromide or triiodide, but also polyanions of higher-
order can be observed.18 The directed synthesis of polyiodides
can be performed by stoichiometric addition of the dihalide to
a solution of the halide.
We tested three routes in order to obtain tetraiodide salts.
In the first approach we prepared solutions of 1 and iodine in
various solvents. By diffusing HI into the solution of 1 the qui-
noline is protonated. The quinolinium proton should direct
the iodide anion above the electron-deficient arene and due to
the stabilizing effect of the anion–π interaction an oligoiodide
should be formed (Scheme 1, Route 1). In addition to this,
Fig. 1 Samples of a physical mixture of iodine with iodide salt 3 (left)
and compound 4b (right) at 90 °C showing that the iodine is bound in
4b but not in the mixture.
The obtained materials were heated in a flask to 80–90 °C.
The same was done with a simple mixture of the iodide salt
and iodine. In the latter case, iodine sublimed out of the
sample, but from the solids of 4a and 4b iodine could not be
extruded. This indicates that here the iodine reacted with
iodide to form an oligoanion (Fig. 1).
Finally, following the work of Metrangolo and Resnati
et al.17 salt 5 was synthesized and mixed with iodine in metha-
nolic solution (Scheme 1, Route 3). Compounds 2c, 3, 4, 5 and
6 are fully characterized by standard analytical methods (1H,
19F NMR, MS, IR, CHN). In order to investigate the polyiodides
in detail without single crystals UV-Vis spectral as well as col-
lision induced dissociation (CID) ESI mass spectrometric
experiments were performed for 4a and 4b in solution.
corresponding interhalides were crystallized by using
a
mixture of 1·HBr and BrI in dichloro methane.
For the second route the PfbDABCO iodide (3) was dis-
solved in methanol and was mixed with a solution of iodine in
methanol. By varying the iodine to 3 ratio the triiodide or the
tetraiodide should be available (Scheme 1, Route 2).
Solid state structures
The crystal structures of starting compounds for Route 1 (1)
and Route 2 (3) in Scheme 1 have previously been character-
ized by us.10,13 Two different crystal structures were obtained
for 1 with HI and I2 (2a and 2b). Crystal structures of 2a–2c
and 6 are shown and discussed in the present paper. Unfortu-
nately, the crystallization efforts for 4a and 4b have not been
successful so far.
Weak intermolecular forces like anion–π or π–π interactions
play a crucial role for the arrangement of molecules in the
crystal. The following discussion of the solid phase structures
will focus only on the relevant interactions between the poly-
halide anions and the electron-deficient arenes. The overall
crystal structure will not be described in detail.
8-Pentafluorobenzyloxy quinoline hydropolyhalides 2a–c. 2a
ˉ
crystallized in the triclinic space group P1 from chloroform.
The structure shows the protonation of every second quinoline
molecule and both unprotonated and cationic forms with half
2−
an I8 anion in asymmetric unit (AU). Therefore, two mole-
cules of 1 are bridged by a proton (NH+⋯N = 1.900 Å), which
enables a π–π-stacking of the pentafluorophenyl and the qui-
noline systems (π⋯π = 3.435 and 3.469 Å). Due to the dimeriza-
tion of the quinolines, the proton is blocked and is not able to
bind to the anion and thus to direct it on top of the C6F5-unit.
The I82− anion can be described to have an usual out-stretched
Z-shaped conformation and I2–I−⋯I2⋯I−–I2 form (I1–I2
=
2.863, I2–I3 = 3.000, I3⋯I4 = 3.378, I4–I5 = 2.760 Å; I2–I3⋯I4 =
Scheme 1 Routes to polyhalide salts.
1874 | Dalton Trans., 2014, 43, 1873–1880
114°), like recently reported for three structures.19,20 The two
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ends of the anion are related by centre of inversion. The linear
−
−
I3 end of the anion is parallel to another I3 end of the adja-
cent anion and shows a closest I2⋯I2 distance of 4.844 Å to
each other. Only one short C–Haryl⋯I type contact with a dis-
tance (3.165 Å) shorter than the sum of standard van der
Waals (vdW) radii was found between anions and cations. The
iodine atom I3 is in close contact with the three carbon atoms
of the pentafluorophenyl moiety (C⋯I = 3.798–4.216 Å; η2-type)
(Fig. 2).
In contrast, in 2b each quinoline unit is protonated. The
structure contains 5 cations and complex and partly dis-
ordered polyhalide network with 21 iodine atoms in AU. Four
Fig. 3 Side and top view of one ion pair (transversal case) in the crystal
structure of 2b (a and b) as well as a representative view of the crystal
packing (c) (black: carbon, white: hydrogen, green: fluorine, red: oxygen,
blue: nitrogen, violet: iodine).
−
quinolinium cations seem to donate NH⋯I contacts to I3
moieties of the polyhalide network. Two of them show inter-
actions to I3 of triiodide nearly axial to N–H bond (NH⋯I3
=
shortest distance of 4.590 Å (I⋯Br2) to each other and are sur-
rounded by six π-stacked units of 1·1H+ (π⋯π = 3.495 Å). The
nearly linear (BrIBr)− anions (∠BrIBr = 176.69°) are slightly
unsymmetric (Br1–I = 2.715, I–Br2 = 2.745 Å) and show CH–
anion interactions with benzylic as well as with phenylic
protons (CHaryl⋯I = 3.144, CHbenzyl⋯Br2 = 2.911 Å). One of the
terminal bromine atoms interacts with two pentafluorophenyl
units in two different η2 fashions (C⋯Br2 = 3.887, 3.817, 3.926,
4.076 Å) (Fig. 4).
Crystals of compound 6 could be obtained by slow evapor-
ation of methanol. The solid state structure with the centre of
inversion in the middle and only half molecule in AU shows
that each bispentafluorobenzyl ammonium ethylene cation is
surrounded by four triiodide anions. Two anions are located
above the electron-deficient moieties at both ends of the
cation (C⋯I1 = 3.749–4.074 Å). The anions interact via various
CH–anion interactions with the alkyl and benzyl groups
of the neighbouring cations (CHmethyl⋯I3 = 3.090, 3.107 Å;
CHbenzyl⋯I2 = 3.083, 3.089 Å) (Fig. 5).
2.702, 2.716 Å), while the other two interact with the end atom
of transversal and symmetry related anions (NH⋯I = 2.785,
2.809 Å, see Fig. 3). The pentafluorophenyl unit of the same
quinolinium cation donating NH⋯I contact accepts η3 or η2
type anion–π contacts from two iodine atoms of the connected
−
I3 anion in all of these four cases (C⋯I = 3.673–4.392 Å). The
C6F5-unit of the fifth cation in AU shows also an equivalent
η3 anion–π contact with the polyhalide chain (C⋯I
=
3.674–4.096 Å) without fixing NH⋯I interaction. The other
faces of the C6F5-units interact with the next continuous poly-
halide chains by various anion–π contacts (3.573–4.045 Å).
The organic part in 2c is structurally related to 2a and only
half of the pyridinium units are protonated (NH+⋯N =
1.812 Å). Two parallel interhalide anions are located in a
A comparison of the obtained crystal structures of 2a–c and
6 shows that the polyhalides are embedded in various CH–
anion and anion–π contacts in the crystalline lattice. Since
polyhalides are charge transfer complexes of the dihalides and
Fig. 4 Side and top view of the ion pair in the crystal structure of 2c (a
and b) as well as a view of the crystalline packing (c). Two molecules of 1
are hydrogen bonded by NH+⋯N hydrogen bridges to form 1·1H+
(black: carbon, white: hydrogen, green: fluorine, red: oxygen, blue:
nitrogen, violet: iodine, dark-red: bromide).
Fig. 2 Two representative views of the crystalline packing (a and b) as
−
observed in the solid phase for 2a showing the zigzag I3−⋯I2⋯I3 chains
embedded in the channels of electron-deficient arenes (black: carbon,
white: hydrogen, green: fluorine, red: oxygen, blue: nitrogen, violet: iodine).
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CID ESI MS-experiment
In order to figure out which iodine species is present in the
solution of 4b an ESI mass spectrometric analysis was per-
formed. To our surprise the high-resolution mass spectrum
shows three different iodine species at m/z = 126.90 (I−),
253.89 (I42− or I2−•) and 380.71 (I3−) (Fig. 7).
The same experiment was performed with a solution of
only iodine to exclude that diiodine might be the source for a
diiodine radical anion at m/z = 253.89. No corresponding
signal was observed for this sample.
Fig. 5 Side (a) and top view (b) of the bispentafluorobenzyl tetramethyl
ammonium ethylene cation of 6 including the adjacent anions (black:
carbon, white: hydrogen, green: fluorine, blue: nitrogen, violet: iodine).
Since the signal at m/z = 253.89 can be due to the tetra-
iodide dianion as well as the diiodine radical anion, collision
induced dissociation (CID) experiments were performed.
Therefore, a methanolic solution of 4b was sprayed, the peak
at m/z = 253.89 was isolated and CID voltage was applied and
raised from 10 V up to 30 V in 5 V steps. It is found that the
additional halide anions, their negative charge in rod-like
anions is located at the end of the rod. Therefore, the anions
exhibit anion–π interactions mainly with the ends of the linear
anions. Both the quinolinium as well as the bispentafluoro-
benzyl tetramethyl ammonium ethylene system are appropri-
ate to form anion–π contacts in the crystal.
2−
species at m/z = 253.89 (I4 or I2−•) becomes weaker while the
signal at m/z = 126.90 (I−) rises with higher voltage (Fig. 8).
The formation of the iodide anion from the species at m/z =
253.89 can be explained by the decomposition of the diiodine
radical anion into iodide and an iodine radical (invisible by
MS). In the case of a possible formation of iodide and iodine
(invisible) from the tetraiodide dianion, the triiodide anion
should be observed as an intermediate. However, the obser-
vation of only the diiodide radical anion already suggests the
presence of the tetraiodide dianion, which according to our
experiments should be the only source for I2−•. Thus, the
UV-vis spectroscopic investigations of 4a and 4b
To get some more insight into the properties and behaviour of
the polyanions in solution, UV-Vis spectra of 4a and 4b were
recorded in methanol. Therefore, equimolar solutions (0.01
M−1) of 3, 4a, and 4b were prepared corresponding to the
anion. In addition a related solution of iodine was used for
comparison. For both the triiodide 4a as well as the tetraiodide
salt 4b two strong absorption bands were observed (4a/4b:
293 nm, 361 nm). The spectrum of 4b shows the highest inten-
sity of the absorption, followed by 4a and iodine. The strong
absorption in 4a and 4b is due to the formation of the charge-
transfer complex of iodine and iodide. The reference sample of
3 reveals a weak absorption at 293 nm and 361 nm as well. For
iodine a weak signal is found at 270 nm. As an alternative, it
might be possible that the UV-Vis spectrum of 4b is caused by
triiodide. In this case the stronger absorption can be explained
by concentration effects caused by deviating stoichiometry in
the synthesis (Fig. 6).
2−
dianion I4 cannot be observed directly but the MS experi-
ments provide evidence for its existence.
Conclusions
In conclusion, we were able to show that polyhalides interact
with electron-deficient arenes in the solid state. Our approach
to fix the linear anions above the pentafluorophenyl unit was
successful. In the crystals of 2a and 2c the position above the
C6F5 unit was blocked due to the dimerization. In contrast to
Fig. 6 UV-Vis spectra of 0.01 M solutions of 4a, 4b, 3 and I2 in
methanol.
Fig. 7 High-resolution mass spectrometric analysis of 4b in methanol
(ESI: 100.00–2000.00 V).
1876 | Dalton Trans., 2014, 43, 1873–1880
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The IR spectra were measured using a PerkinElmer FTIR
spectrometer Spektrum 100 in KBr (4000–650 cm−1). A CHN-O-
Rapid Vario EL from Heraeus was used for elemental analysis
and melting points were obtained on a Büchi B-540 without
correction. X-ray analyses are described in the end of the
Experimental section. Compounds 2a and 2b were directly
obtained by crystallization and only characterized by X-ray
analyses.
8-Pentafluorobenzyloxy quinoline hydroiododibromide 2c
To a solution of 200 mg 8-pentafluorobenzyloxy quinoline (1.0
eq., 0.62 mmol) in 10 mL of THF 150 µL of an aqueous solu-
tion of HBr (48%, 1.4 eq., 0.89 mmol) were added. The
mixture was stirred for 1 h and the solvent was removed under
reduced pressure. The remaining solid was dried in vacuo.
Yield: 245 mg (M = 404.98 g mol−1, 0.62 mmol, quant.),
m.p.: 192 °C. 1H-NMR (300 MHz, CDCl3): δ (ppm) = 16.68
(br. s, 1H, NH), 9.46 (br. s, 1H, Haryl), 8.95 (br. d, J = 7.8 Hz,
1H, Haryl), 8.12 (br. s, 1H, Haryl), 7.89 (t, J = 7.8 Hz, 1H,
H
H
aryl), 7.81 (d, J = 7.8 Hz, 1H, Haryl), 7.59 (d, J = 7.8 Hz, 1H,
aryl), 5.52 (s, 2H, Hbenzyl). 19F-NMR (300 MHz, CDCl3):
δ (ppm) = −141.12 (m, 2F, Fortho), −151.26 (m, 1F, Fpara),
−161.03 (m, 2F, Fmeta). MS (EI, 70 eV): m/z (%) = 325.1 (100,
[M]+, C16H9F5NO+). IR (KBr): ν (cm−1) = 3393 (w), 3061 (w),
2995 (w), 2899 (w), 2613 (w), 2037 (w), 1936 (w), 1855 (w),
1747 (w), 1703 (w), 1662 (m), 1629 (w), 1596 (m), 1544 (s),
1507 (vs), 1387 (s), 1296 (vs), 1201 (m), 1131 (s), 1113 (s),
1055 (s), 972 (s), 937 (s), 876 (s), 821 (s), 770 (s), 751 (s), 751 (s),
666 (m). Elemental analysis (%): calc. C16H8F5NOHBr·2H2O: C
43.46, H 2.96, N 3.17; found: C 43.26, H 3.04, N 3.13.
Fig. 8 CID experiment of a solution of 4b in methanol to observe the
decomposition of tetraiodide (ESI: [90.00–500.00 V]).
these, in 2b as well as in 6 the polyhalide anions are fixed
close to the electron-deficient arene. The presented receptors
are model systems for an optimized π-acceptor for selective
stabilization of sensitive anions like the tetraiodide dianion.
Therefore, an appropriate electron-deficient cavity has to be
generated in the crystal lattice, which is able to stabilize the
tetraiodide dianion.
Herein, we described a preparative method to obtain tetra-
iodide dianions. First spectroscopic and spectrometric investi-
gations indicate that most probably the desired dianion is
formed by this technique.
The obtained UV-Vis spectra show the formation of a poly-
halide in the solution of 4a and 4b in methanol. In addition to
this an ESI MS experiment shows signals for both the triiodide
as well as most probably the tetraiodide (or its symmetric
decomposition product) in the high-resolution mass-spectro-
metric analysis of 4b. Further experimental as well as compu-
tational studies have to be performed in order to clarify the
mechanism of the decomposition and to find systems in
which I42− is stabilized.
Synthesis of 1-pentafluorobenzylammonium-4-aza-1-azonia
bicycle[2.2.2]octane triiodide 4a
To a solution of 204 mg pentafluorobenzyl-1,4-diazoniabicyclo-
[2.2.2]-octane iodide (1.0 eq., 0.48 mmol) in 5 mL of methanol
a solution of 120 mg iodine (1.0 eq., 0.48 mmol) in 3 mL of
methanol was added dropwise. The precipitating black solid
was filtered off and dried in a vacuum.
Yield: 120 mg (M = 673.82 g mol−1, 0.18 mmol, 58%), m.p.:
1
207 °C. H-NMR (300 MHz, DMSO-d6): δ (ppm) = 4.57 (s, 4H,
H
benzyl), 3.38 (t, J = 7.3 MHz, 6H, CH2), 3.01 (t, J = 7.3 MHz,
6H, CH2). 19F-NMR (300 MHz, DMSO-d6): δ (ppm) = −134.78
(m, 2F, Fortho), −150.79 (m, 1F, Fpara), −161.49 (m, 2F, Fmeta).
+
MS (ESI): m/z (%) = 293.3 (100, [M]+, C13H14F5N2 ), 381.9 (15,
I3−). IR (KBr): ν (cm−1) = 2955 (m), 2889 (w), 2647 (w), 2512 (w),
2296 (w), 2112 (m), 1996 (w), 1910 (w), 1657 (m), 1597 (m),
1525 (s), 1501 (vs), 1458 (s), 1428 (m), 1403 (m), 1371 (s),
1320 (m), 1241 (w), 1185 (w), 1133 (s), 1054 (vs), 981 (s),
947 (s), 890 (m), 840 (s), 797 (m), 745 (w), 692 (m), 669 (m).
Experimental section
Commercially available reagents were used as received and sol- Elemental analysis (%): calc. C13H14F5N2I3: C 23.17, H 2.09, N
vents were distilled before use. Products 2c, 4a and b as well as 4.16; found: C 23.51, H 2.27, N 4.22.
5 and 6 were fully characterized by standard analytical
Synthesis of 1-pentafluorobenzylammonium-4-aza-1-azonia
bicycle[2.2.2]octane tetraiodide 4b
methods using a Varian Mercury 300 NMR spectrometer for 1H
(300 MHz) and the 19F (282 MHz). Samples were measured in
deuteric solvents. Mass spectrometric data were recorded on A solution of 201 mg of pentafluoro-benzyl-1,4-diazoniabicyclo-
Finnigan SSQ 7000 and Thermo Deca XP as EI (70 eV) or ESI. [2.2.2]-octane iodide (1.0 eq., 0.48 mmol) in 5 mL of methanol
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was mixed with a solution of 61 mg of iodine (0.5 eq., 1657 (m), 1507 (vs), 1432 (m), 1353 (w), 1309 (w), 1265 (w),
0.22 mmol) in 3 mL of methanol. The mixture was stirred for 1234 (w), 1133 (s), 1032 (s), 965 (s), 899 (m), 868 (m), 807 (m),
1 h and the precipitating black solid was removed by filtration. 720 (m), 683 (m). Elemental analysis (%): calc. C20H20F10I6N2:
After removing the solvent under reduced pressure the remain- C 19.38, H 1.63, N 2.26; found: C 20.01, H 1.88, N 2.68.
ing solid was dried in a vacuum.
Single crystal X-ray analyses
Yield: 109 mg (M = 1093.83 g mol−1, 0.1 mmol, 42%), m.p.:
1
210 °C. H-NMR (300 MHz, DMSO-d6): δ (ppm) = 4.66 (s, 2H, Single crystal X-ray data were collected at 123(2) K using a
H
benzyl), 3.38 (t, J = 7.5 Hz, 6H, CH2), 3.02 (t, J = 7.5 MHz, 6H, Bruker-Nonius KappaCCD diffractometer with an APEX-II
CH2). 19F-NMR (300 MHz, DMSO-d6): δ (ppm) = −134.78 (m, detector and graphite monochromatized Mo-Kα (λ = 0.71073 Å)
2F, Fortho), −150.62 (m, 1F, Fpara), −161.49 (m, 2F, Fmeta). MS radiation. COLLECT21 software was used for the data collection
(ESI): m/z (%) = 800.27 (25, [M+ + I42−]−, C13H14F5N2I4−). IR (θ and ω scans) and DENZO-SMN22 for the processing. The
(KBr): ν (cm−1) = 3010 (w), 2974 (m), 2889 (w), 2774 (w), structures were solved by direct methods with SIR200423 and
2645 (w), 2511 (w), 2444 (w), 2273 (w), 2224 (w), 2193 (w), refined by full-matrix least-squares methods with WinGX-soft-
2107 (m), 1992 (w), 1936 (w), 1849 (w), 1753 (w), 1656 (m), ware,24 which utilizes the SHELXL-97 module.25 Lorentzian
1593 (w), 125 (s), 1502 (vs), 1458 (s), 1371 (s), 1320 (m), 1242 polarization and multi-scan absorption correction (SADABS26)
(w), 1185 (w), 1133 (s), 1055 (vs), 980 (s), 947 (s), 890 (s), were applied on all data. The badly disordered solvent mole-
840 (s), 796 (m), 745 (w), 691 (m), 669 (m). Elemental analysis cule was removed from the data of 2c by the SQUEEZE27
(%): calc. C26H28F10N4I4: C 28.54, H 2.58, N 5.12; found: C method. All C–H hydrogen positions were calculated and
28.74, H 2.52, N 5.12.
refined as a riding atom model with 1.2 or 1.5 times the
thermal parameter of the C atoms. H-atoms bonded to N were
found from the electron density maps and restrained (by DFIX,
s = 0.02) to a distance of 0.88 Å from N atom with thermal
Synthesis of bispentafluorobenzyl tetramethyl ammonium
ethylene diiodide 5
A solution of 700 mg mixture of tetramethylpentafluorobenzyl- parameters of 1.2 times the N atom parameter. The disordered
ethyleneammonium iodide (1.0 eq., 1.66 mmol) in 10 mL of interatomic distances in 2b were restrained more rationally
methanol was mixed with a solution of 500 mg of pentafluoro- (SADI, s = 0.02).
benzyl iodide (1.0 eq., 1.66 mmol) in 5 mL of methanol. The
mixture was stirred for 20 h and the precipitating white solid
Crystal data
was separated by filtration, washed with ethyl acetate and 2a: Brown plates from MeOH, C32H17F10I4N2O2, F.W.
=
dried in a vacuum.
1159.08, crystal size 0.22 × 0.08 × 0.04 mm, triclinic, space
Yield: 1.05 g (M = 731.96 g mol−1, 1.43 mmol, 88%), m.p.: group P1 (no. 2), a = 11.8967(3), b = 12.0724(3), c = 13.1001(4)
ˉ
1
240 °C. H-NMR (300 MHz, DMSO-d6): δ (ppm) = 4.82 (s, 4H, Å, α = 104.328(2), β = 101.508(2), γ = 103.452(2)°, V = 1705.67(8)
H
benzyl), 4.24 (s, 4H, CH2), 3.13 (s, 12H, CH3). 19F-NMR Å3, Z = 2, Dcalc = 2.257 Mg m−3, μ = 3.743 mm−1, F(000) = 1082,
(300 MHz, DMSO-d6): δ (ppm) = −135.50 (m, 4F, Fortho), 10 298 collected reflections (θmax = 25.25°) of which 6158 inde-
−149.85 (m, 2F, Fpara), −160.97 (m, 4F, Fmeta). MS (ESI): m/z (%) pendent [Rint = 0.0281] and 5005 with I > 2σ(I), Tmax = 0.8647,
= 605.47 (100, [MI]−, C20H20F10IN2−). IR (KBr): ν (cm−1) = 3006 Tmin = 0.4931, full-matrix least-squares on F2 with 1 restraint
(w), 2972 (w), 2656 (w), 2322 (w), 2199 (w), 2164 (w), 1983 (w), and 454 parameters, GOF = 1.090, R1 = 0.0370 [I > 2σ(I)], wR2
1657 (m), 1505 (vs), 1399 (m), 1359 (m), 1308 (m), 1234 (w), (all data) = 0.0786, largest peak/hole = 0.671/−0.743 e− Å−3
.
1131 (s), 1031 (s), 964 (vs), 900 (m), 870 (m), 808 (m), 764 (w),
2b: Red rods from MeOH, C80H45F25I21N5O5, F.W. =
719 (m), 680 (m). Elemental analysis (%): calc. C20H20F10I2N2: 4296.11, crystal size 0.28 × 0.05 × 0.05 mm, monoclinic, space
C 32.81, H 2.75, N 3.83; found: C 32.95, H 3.40, N 3.68.
group P21/c (no. 14), a = 19.1205(2), b = 24.7516(3), c =
24.1817(3) Å, β = 109.8840(10)°, V = 10 762.0(2) Å3, Z = 4, Dcalc
2.651 Mg m−3, μ = 6.126 mm−1, F(000) = 7752, 37 100 collected
reflections (θmax = 25.25°) of which 19 379 independent [Rint
=
Synthesis of bispentafluorobenzyl tetramethyl ammonium
ethylene bistriiodide 6
=
To a solution of 100 mg of 5 (1.0 eq., 0.11 mmol) in 2 mL of 0.0452] and 13 059 with I > 2σ(I), Tmax = 0.7493, Tmin = 0.2788,
methanol a solution of 60 mg of iodine (2.0 eq., 0.22 mmol) in full-matrix least-squares on F2 with 9 restraints and 1306 para-
1 mL of methanol was added. After stirring for 24 h the meters, GOF = 1.058, R1 = 0.0471 [I > 2σ(I)], wR2 (all data) =
solvent was removed under reduced pressure and the remain- 0.0908, largest peak/hole = 1.206 (0.69 Å from I11)/−1.930 e−
ing violet solid was dried in a vacuum.
Å−3 (0.94 Å from I6).
Yield: 118 mg (M = 1239.80 g mol−1, 0.119 mmol, quant.),
2c: Brown plates from MeOH–EtOAc, C32H17Br2F10IN2O2,
m.p.: 175 °C. 1H-NMR (400 MHz, MeOD): δ (ppm) = 4.86 (s, F.W. = 938.20, crystal size 0.42 × 0.40 × 0.05 mm, triclinic,
4H, C6F5CH2), 4.32 (s, 4H, CH2), 3.25 (s, 12H, CH3). 19F-NMR space group P1 (no. 2), a = 11.8915(3), b = 11.9676(4), c =
ˉ
(400 MHz, MeOD): δ (ppm) = −137.35 (m, 4F, Fortho), −149.65 12.8426(4) Å, α = 93.975(2), β = 104.276(3), γ = 104.760(3)°, V =
(m, 2F, Fpara), −161.744 (m, 4F, Fmeta). MS (ESI): m/z (%) = 1695.66(9) Å3, Z = 2, Dcalc = 1.838 Mg m−3, μ = 3.388 mm−1
,
858.33 (100, MI3−, C20H20F10I3N2−). IR (KBr): ν (cm−1) = F(000) = 904, 21 901 collected reflections (θmax = 25.25°) of
3007 (w), 2973 (w), 2658 (w), 2458 (w), 2204 (w), 2155 (w), which 6122 independent [Rint = 0.0452] and 4910 with I > 2σ(I),
2096 (w), 2053 (w), 2023 (w), 1985 (w), 1952 (w), 1952 (w), Tmax = 0.8489, Tmin = 0.3303, full-matrix least-squares on F2
1878 | Dalton Trans., 2014, 43, 1873–1880
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with 1 restraint and 445 parameters, GOF = 1.092, R1 = 0.0397
[I > 2σ(I)], wR2 (all data) = 0.1057, largest peak/hole = 1.987
A. Frontera, P. Ballester, A. Costa and P. M. Deya, J. Phys.
Chem. A, 2005, 109, 9341; D. Quinonero, C. Garau,
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(0.79 Å from Br2)/−0.993 e− Å−3
.
6: Orange plates from MeOH, C20H20F10I6N2, F.W.
=
1239.78, crystal size 0.32 × 0.13 × 0.02 mm, monoclinic, space
group P21/c (no. 14), a = 13.7486(6), b = 8.7173(4), c =
13.7027(6) Å, β = 102.305(2)°, V = 1604.55(12) Å3, Z = 2 (Z′ =
0.5), Dcalc = 2.566 Mg m−3, μ = 5.880 mm−1, F(000) = 1124, 5128
collected reflections (θmax = 25.25°) of which 2917 independent
8 (a) P. Ballester, Acc. Chem. Res., 2013, 46, 874–884; (b) S. Li,
S.-X. Fa, Q.-Q. Wang, D.-X. Wang and M.-X. Wang, J. Org.
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13053–13057; (e) S. Guha and S. Saha, J. Am. Chem. Soc.,
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4750–4752, (Angew. Chem., Int. Ed., 2004, 43, 4650–4652);
( j) O. B. Berryman, F. Hof, M. J. Hynes and D. W. Johnson,
Chem. Commun., 2006, 506–508; (k) M. Staffilani,
K. S. B. Hancock, J. W. Steed, K. T. Holman, J. L. Atwood,
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[Rint = 0.0280] and 2434 with I > 2σ(I), Tmax = 0.8915, Tmin
=
0.2548, full-matrix least-squares on F2 with 0 restraint and
172 parameters, GOF = 1.075, R1 = 0.0371 [I > 2σ(I)], wR2 (all
data) = 0.0755, largest peak/hole = 1.076 (0.86 Å from I3)/
−0.912 e− Å−3
.
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