New ionic liquids with the bis[bis(pentafluoroethyl)phosphinyl]imide anion, [(C2F5)2P(O)]2N--Synthesis and characterization

Article abstract of DOI:10.1016/j.jfluchem.2009.11.004

A new series of low melting and hydrophobic ionic liquids (ILs) containing the bis[bis(pentafluoroethyl)phosphinyl]imide anion, [(C₂F₅)₂P(O)]₂N^- (FPI), and ammonium, phosphonium, imidazolium, pyridinium or pyrrolidinium cations were prepared and characterized. Their density, viscosity, melting point, glass transition temperature, decomposition temperature and conductivity are discussed. Many of these ionic liquids are liquids at room temperature with melting points below 15 °C, viscosities below 110 mm² s^-1 and thermal stabilities above 300 °C.

Full text of DOI:10.1016/j.jfluchem.2009.11.004

Journal of Fluorine Chemistry 131 (2010) 325–332
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
New ionic liquids with the bis[bis(pentafluoroethyl)phosphinyl]imide anion,
[(C2F5)2P(O)]2Nꢀ—Synthesis and characterization
a,
Dana Bejan a, Nikolai Ignat’ev b, , Helge Willner
*
*
a Bergische Universita¨t Wuppertal, FB C – Anorganische Chemie, Gaußstr. 20, D-42097 Wuppertal, Germany
b 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
Article history:
A new series of low melting and hydrophobic ionic liquids (ILs) containing the bis[bis(pentafluor-
oethyl)phosphinyl]imide anion, [(C2F5)2P(O)]2Nꢀ (FPI), and ammonium, phosphonium, imidazolium,
pyridinium or pyrrolidinium cations were prepared and characterized. Their density, viscosity, melting
point, glass transition temperature, decomposition temperature and conductivity are discussed. Many of
these ionic liquids are liquids at room temperature with melting points below 15 8C, viscosities below
110 mm2 sꢀ1 and thermal stabilities above 300 8C.
Received 31 August 2009
Received in revised form 30 October 2009
Accepted 9 November 2009
Available online 14 November 2009
Keywords:
ß 2009 Elsevier B.V. All rights reserved.
Ionic liquid
Weakly coordinating anion
Viscosity
Conductivity
Electrochemical stability
Thermal stability
1. Introduction
properties: low viscosity, good electrical conductivity, and high
chemical, thermal and electrochemical stability [10,11]. These
Salts that are liquid at temperatures below 100 8C are called
ionic liquids (ILs). They attract considerable interest, e.g. as new
media for chemical reactions [1,2] and catalysis [3–5], in
separation processes and analytical techniques [6]. Due to their
good electrical conductivity, ionic liquids can serve as electrolytes
in various electrochemical devices [7] or in electrochemical
processes, for instance in electro deposition of metals [8]. These
applications are due to their advantageous properties such as:
negligible vapour pressure, non-flammability, high thermal
stability and liquid state over a wide temperature range. For
electrochemical applications their low viscosity and high electro-
chemical stability are of importance.
Recently, we have demonstrated that the properties of ionic
liquids, in particular their viscosity, are strongly dependent on the
anion–cation interaction [9]. Weakly coordinating anions in
combination with mono-cations, having the charge well deloca-
lized, result in room temperature ionic liquids with low viscosity.
Since the last decade thousands of ionic liquids have been
properties exhibit in particular the new generation of ionic liquids
with bis(trifluoromethylsulfonyl)imide, [TFSI] [12–15], tris(penta-
fluoroethyl)trifluorophosphate [FAP] [16] or tetracyanoborate [17]
anions. Ionic liquids with the bulky FAP anion are hydrolytically
stable and highly hydrophobic [16], probably the most hydro-
phobic ones among known ionic liquids. FAP is a complex anion
derived from the corresponding Lewis acid, tris(perfluoroalkyl)di-
fluoro-phosphorane [16,18]. Therefore FAP salts react with Lewis
acids which are stronger than tris(perfluoroalkyl)difluoro-phos-
phorane. This restricts the application of FAP ionic liquids in
processes catalysed with strong Lewis acids (for example Friedel–
Crafts alkylation or acylation), e.g. with AlCl3 or SbF5. Therefore
search for new weakly coordinating anions with improved stability
against strong Lewis acids is advised.
Recently we have developed a convenient synthesis of the
strong N-H acid bis[bis(pentafluoroethyl)phosphinyl]imide,
[(C2F5)2P(O)]2NH, and some of its metal salts [19]. The
[(C2F5)2P(O)]2NH acid, [HFPI], and the Na or K salts are suitable
starting materials for the synthesis of new hydrophobic ionic
liquids with the bis[bis(perfluoroethyl)phosphinyl]imide [FPI]
anion. The syntheses of FPI ionic liquids were carried out in a
very simple way by mixing aqueous solutions of [(C2F5)2P(O)]2NH
(or its sodium or potassium salt), with ammonium, phosphonium,
imidazolium, pyridinium or pyrrolidinium chlorides or bromides
synthesized, but only
a few of them possess the required
* Corresponding authors. Tel.: +49 0202 439 2517; fax: +49 0202 439 3053.
E-mail addresses: nikolai.ignatiev@merck.de (N. Ignat’ev),
willner@uni-wuppertal.de (H. Willner).
0022-1139/$ – see front matter ß 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2009.11.004

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D. Bejan et al. / Journal of Fluorine Chemistry 131 (2010) 325–332
(see Section 3). Ionic liquids with the FPI anion are highly
hydrophobic and can be easily separated from the aqueous phase.
After washing with water and drying, these ionic liquids are
obtained in a very high purity.
Here, we describe the preparation and characterization of some
ionic liquids with the FPI anion.
a
small signal which belongs to the hydrolysis product
–
bis(pentafluoroethyl)phosphinate.
Under basic conditions (6% aqueous KOH) at room temperature
the hydrolysis of 1-ethyl-3-methyl imidazolium FPI proceeds
much faster and within 10 days about 40% of the ionic liquid is
hydrolyzed to the phosphinate.
2. Results and discussion
2.2.2. Viscosity and density
The viscosity is an important property of ionic liquids, because
it strongly influences the diffusion of species, which are dissolved
or dispersed in the ionic liquid. This is especially important for
electrochemical applications of ionic liquids. In general, the
viscosity of ILs is essentially influenced by the cation–anion
interaction, hydrogen bonding, as well as by the coordinating
ability and symmetry of the ions [20].
It should be mentioned that the presence of water or other
impurities (for instance residual organic solvents) reduces the
viscosity of ionic liquids substantially. Therefore, we controlled
carefully the water content in all FPI ILs by Karl-Fischer titration
prior to viscosity measurement. In all studied ionic liquids the
water content was below 50 ppm which should not have a
substantial influence on the viscosity. To avoid the influence of the
halide impurities, all ionic liquids were purified as described
above, until the halide content was less that 30 ppm, controlled by
ion-chromatography.
Ionic liquids with the FPI anion possess kinematic viscosity
which is of comparable magnitude to the viscosity of ILs with the
TFSI or FAP anion. For example, the viscosity of 1-hexyl-3-
methylimidazolium IL with the TFSI anion is 44 [16], with the FAP
anion is 74 [16] and with the FPI anion is 103 mm2 sꢀ1. All three ILs
show low kinematic viscosity in comparison with 1-hexyl-3-
methylimidazolium PF6 (548 mm2 sꢀ1 [16]). Hence, the viscosity of
ionic liquids is dominated by the nature of the anion. On the other
side in the series [Cnmim][FPI] with different alkyl groups (n = 2, 4,
6) the viscosities are very similar: [emim][FPI] has the viscosity
171, [bmim][FPI] 151, and [hmim][FPI] 159 mPa s (see Fig. 1). For
these three ionic liquids the influence of the cation size on the
viscosity is minimal, because the bulky FPI anion occupies the
major volume in the ionic liquid and carries the largest part of the
molar mass (see Table 1).
2.1. Synthesis of ionic liquids with the FPI anion
ILs with the bis[bis(pentafluoroethyl)phosphinyl]imide anion
can be synthesized via metathesis reactions. The acid (HFPI) and
Cat+Aꢀ, A = Cl, Br, OH were dissolved separately in a small quantity
of water. Both aqueous solutions were then mixed together and
stirred at room temperature. The obtained ionic liquid is insoluble
in water and precipitate as a dense phase on the bottom of the
reactions flask. Vigorous stirring is essential for the reaction to
proceed quantitatively. The bottom phase was separated (in some
cases diluted with CH2Cl2) and washed several times with water. If
a solid material is formed, it can be filtered off and washed with
water until the test for chloride (or bromide) with silver nitrate is
negative. To avoid any excess of the FPI acid in the ionic liquid, the
washing water should contain small amount of K2CO3.
CatþAꢀ þ ½ðC2F5Þ2PðOÞꢁ2NH ! Catþ½ðC2F5Þ2PðOÞꢁNꢀ þ HA
(1)
Here are the chosen cations
Recently it was shown that there is a strong relationship between
the molecular volumesVm of ILs and their viscosity, conductivityand
density [21]. According to Eq. (2) the volume of the FPI anion is
estimated to be 0.467 nm3 by using Vm = 0.58 nm3 (available from
single crystalX-raydiffraction of [(CH3)4N][(C2F5)2P(O)]2N [19]) and
To remove the residual water, the FPI ILs were dried at 70 8C for
12–48 h under stirring in vacuum. The FPI ionic liquids are soluble
in alcohol, acetone, acetonitrile, chloroform, dichloromethane, but
immiscible with water, toluene and hexane.
The ionic liquids with the FPI anion were characterized by 1H,
19F, 31P NMR spectroscopy and elemental analysis. The content of
halide was controlled to be below 30 ppm.
2.2. Physico-chemical properties of ionic liquids with the FPI anion
2.2.1. Hydrolytic stability of FPI ionic liquids
The ionic liquids with FPI anion are stable against hydrolysis in
water at room temperature for more than 2 months. However,
after keeping an aqueous emulsion of 1-ethyl-3-methyl imidazo-
lium FPI for 5 days at 100 8C we observed in the 19F NMR spectrum
Fig. 1. Viscosity of a series of FPI ILs as a function of temperature.

D. Bejan et al. / Journal of Fluorine Chemistry 131 (2010) 325–332
327
Table 1
Dynamic and kinematic viscosity and density of ionic liquids with the FPI anion.
Ionic liquid
M.W.
Part of FPI anion in the
molecular weight of IL %
Dynamic viscosity
/mPa s (20 8C)
Kinematic viscosity
/mm2 sꢀ1 (20 8C)
Density r
/g cmꢀ3
h
n
[emim][FPI]
[bmim][FPI]
[hmim][FPI]
[dmim][FPI]
[omim][FPI]
[bmpl][FPI]
[p(h3)t][FPI]
695.17
723.22
751.28
807.38
919.60
726.27
1061.82
84
171
151
159
199
376
325
536
102
95
1.68
1.59
1.54
1.45
1.32
1.58
1.21
80.7
77.7
72.3
63.5
80.4
55
103
137
285
206
443
[emim] =1-ethyl-3-methylimidazolium; [bmim] = 1-butyl-3-methylimidazolium; [hmim] = 1-hexyl-3-methylimidazolium; [dmim] = 1-decyl-3-methylimidazolium;
[omim] = 1-octadecyl-3-methylimidazolium; [bmpl] = butyl-methylpyrrolidinium; [p(h3)t] = trihexyltetradecylphosphonium.
the volume for the [(CH3)4N]+ cation Vion(C+) = 0.113 nm3 [22].
Vm ¼ VionðAꢀÞ þ VionðCþÞ
This anion volume is double than that for [TFSI]ꢀ (0.232 nm3)
[23] and the large size of the FPI anion influences the viscosity of
ionic liquids (see Table 1).
Fig. 1 presents the viscosity of different FPI ILs plotted as a
function of the temperature. The difference in the viscosities of FPI
ionic liquids with various cations becomes very small at 80 8C. It
looks that above 80 8C the weak interaction between FPI anion and
organic cations is completely broken. In terms of the viscosity it
means that in Eq. (3) [9], which describes the influence of the
cation, anion and ion-pair diffusivity on the viscosity of ionic
liquids, the last component becomes very small (3a) due to the
high degree of ion-pairs self dissociation at high temperature.
2.2.3. Melting point and glass transition temperature
Table 2 presents the melting points of FPI salts in comparison to
analogous compounds with other anions. The melting point and
temperature of crystallization for the FPI ionic liquids were
measured by difference scanning calorimetry (DSC), in the
temperature range between ꢀ120 and 600 8C (see Table 3). A
typical thermogram is shown in Fig. 3 for [bmpl]FPI. This ionic
liquid shows a weak glass transition point at about ꢀ80 8C,
followed by the crystallization at ꢀ35 8C and the melting point at
about 7 8C. For [hmim]FPI, [dmim]FPI and [p(h3)t]FPI there are no
indications for any melting points on the DSC curves. For some FPI
(2)
k ꢂ T
hIL
¼
(3)
bA ꢂ DA ꢂ rA þ bC ꢂ DC ꢂ rC þ bA;C ꢂ DA;C ꢂ rA;C
where
h
—dynamic viscosity; r—radius of the anion, cation or sum
(cation + anion); DA—self-diffusion coefficient of anion; DC—self-
diffusion coefficient of cation; DA,C—self-diffusion coefficient of
ion-pair; bA = nA 4.5
p [24]; bC = nC 3.5p [24]; bA,C = nA,C 6.0p;
n = transference number
(3a)
It seems that the viscosity of FPI ionic liquids at high
temperature (>80 8C) depends on the mobility (diffusivity) of
the cations and anions only. At >80 8C the dependence of the ILs
viscosity on the anion or cation size becomes insignificant by the
reason that DAꢂrA and DCꢂrC remains practically constant at a certain
temperature. At the temperature of above 80 8C the viscosity of FPI
ionic liquids practically does not depend on the size of the cation
(see Fig. 1). It means that in Eq. (3a) all parameters at fixed
temperature (above 80 8C) are constant; if hIL is constant and the
parameters: kꢂT and bAꢂDAꢂrA (belongs to the FPI anion) are constant
as well, the parameter bCꢂDCꢂrC should be also constant. Assuming
that the transference number nC of the cations in the case of ionic
liquids with the same anion (in our case FPI anion) is constant (it
Fig. 2. Arrhenius plots of viscosity of a series of FPI ILs.
Table 2
Melting points (Tm) of FPI salts in comparison to related salts with different anions.
Cation
TEA
Anion
Tm (8C)
Ref.
Cl
110
104
95
[25]
[26]
[16]
a
TFSI
FAP
FPI
46–47
TBP
Cl
62–64
65
[27]
[28]
[16]
a
TFSI
FAP
FPI
74
means bC = nCꢂ3.5
p
is constant) we can conclude that DCꢂrC should
145
be constant as well according to Eq. (3a).
TBA
C4Py
Cl
41
[29]
[26]
[16]
a
The Arrhenius plot of the viscosity against temperature for the
FPI ionic liquids is non-linear (Fig. 2). This is similar to that
described previously for other ionic liquids [24]. In the critical
point at high temperature the viscosities of different ionic liquids
become very similar.
The density of FPI ionic liquids decreases slowly with increasing
the length of the alkyl chain (see Table 1). Again, that is probably
due to the dominant influence of the bulky and heavy FPI anion on
the density.
TFSI
FAP
FPI
90
62
150
Cl
103/162
26
[30]/[31]
TFSI
FPI
[32]
a
49
TEA = tetraethylammonium; TBP = tetrabutylphosphonium; TBA = tetrabutylam-
monium; C4Py =N-butylpyridinium; TFSI = bis(trifluoromethylsulfonyl)imide;
FAP = tris(pentafluoroethyl)trifluorophosphate; a = this work.

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D. Bejan et al. / Journal of Fluorine Chemistry 131 (2010) 325–332
Table 3
The melting point (Tm), crystallization temperature (Tcc
)
and decomposition
temperature (Td) for ionic liquids containing the FPI anion.
Compounda
Tm/8C
Tcc/8C (DSC)
Tm/8C
Td/8C (TGA)
(DSC)
(visual)
[emim][FPI]
[bmim][FPI]
[hmim][FPI]
[dmim][FPI]
[omiml][FPI]
[bmpl][FPI]
+13
+7
ꢀ52
–
17–18
300
320
320
300
300
300
300
280
b
b
b
–
–
10–15
+14
+7
–
–
16–17
ꢀ34
–
6–7
b
[p(h3)t][FPI]
[3,5-mPyr][FPI]c
ꢀ2
+19
ꢀ31
18
a
For abbreviations see Table 1.
b
c
Glass state, no melting point observed.
[3,5-mPyr] = N-butyl-3,5-dimethylpyridinium.
Fig. 5. TGA for some solid salts with the FPI anion.
the temperature at which 2% weight loss occurred at a heating rate
of 10 8C per min (at isothermal conditions the decomposition
temperatures are much lower). Above 450 8C the mass loss
becomes more than 90% and the weight of the residue remains
almost constant. The decomposition products of the FPI ILs were
not investigated.
It can be concluded that the thermal stability of ILs with the
bis[bis(pentafluoroethyl)phosphinyl]imide anion is high and
comparable with those of ionic liquids with other weekly
coordinating anions, like bis(trifluoromethylsulfonyl)imide (TFSI)
or tris(pentafluoroethyl)trifluorophosphate, (FAP) anions [16].
Fig. 3. DSC curve for [bmpl]FPI: (a) weak glass transition (ꢀ80 8C); (b)
crystallization temperature (ꢀ34 8C); (c) melting point (7 8C).
salts the glass state can be also observed visually by heating from
ꢀ80 8C to room temperature in sealed glass capillary tubes. The
difference in the visually observed melting points and those
obtained by DSC measurements may be due to differences in the
heating rates.
2.2.5. Electrochemical stability
The electrochemical stability was determined by cyclic
voltammetry. The salts with bis[bis(pentafluoroethyl)phosphiny-
l]imide anion (FPI) posses high electrochemical stability (see
Fig. 6). For example, tetrabutylammonium FPI has an electro-
chemical window of about 7 V, higher than the reported value of
5.5 V for trimethylpropyl ammonium bis(trifluoromethyl)sulfo-
nylimide (TFSI) [33], but close to the value reported for
2.2.4. Thermal stability
Figs. 4 and 5 show characteristic TGA curves for FPI salts with
organic cations. The samples were heated in an inert atmosphere
(N2) at a rate of 10 8C per min. The TGA measurements indicate that
FPI ionic liquids possess high thermal stability as the respective
FAP ionic liquids [16]. FPI ILs containing different imidazolium
cations shows rather similar thermal behaviour with a continuous
mass loss between 280 and 400 8C (Fig. 4) and a Tonset of above
320 8C. The decomposition temperature Td presented in Table 3 is
tetrabutylammonium
tris(pentafluoroethyl)trifluorophosphate
(FAP) [16]. High electrochemical stability makes the salts with
FPI anion attractive for application in electrochemical devices.
Fig. 6. Cyclic voltammogram of tetrabutylammonium FPI on a disc (Ø 3 mm) glassy
carbon electrode (surface area: 7.065 ꢃ 10ꢀ2 cm2) at room temperature (23 8C);
scan rate: 20 mV sꢀ1; auxiliary electrode is Pt and reference electrode is Ag/AgNO3
(CH3CN). The potential values are normalized to E8 of ferrocene.
Fig. 4. TGA for selected imidazolium room temperature ionic liquids with the FPI
anion.

D. Bejan et al. / Journal of Fluorine Chemistry 131 (2010) 325–332
329
3.2. Tetraethyl ammonium
bis[bis(pentafluoroethyl)phosphinyl]imide, [(C2H5)4N]+
[(C2F5)2P(O)]2Nꢀ
A 20% aqueous solution of tetraethylammonium hydroxide
(5.55 g, 7.53 mmol) was slowly added to the solution of bis[bis(-
pentafluoroethyl)phosphinyl]imide,
HN[P(O)(C2F5)2]2
(4.41 g,
7.53 mmol) in 15 mL water by stirring and cooling of the reaction
mixture with an ice water bath until the reaction mixture was
neutral.Thereactionmixturewasstirredadditionally30 minatroom
temperature. The resulting mixture was concentrated in a rotary
evaporator. The residue was dissolved and stirred in 10 mL dioxane
for 30 min. After the dioxane was distilled off, a hygroscopic
colourless solid remains in the reaction flask. The product (5 g, yield
94%) was dried at 60 8C in vacuum for ca. 12 h and subsequently
12 ppm of water was detected by Karl-Fischer titration. M.p. 46–
47 8C.
Anal. Calcd for C16H20F20N2O2P2: C 26.91; H 2.82; N 3.92.
Found: C 26.92; H 2.76; N 3.98.
Fig. 7. The conductivity curve for [emim]FAP (&) and for [emim]FPI (*) in
acetonitrile solution (c = 0.83 mol Lꢀ1).
19F NMR,
d
: ꢀ81.1 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
2JP,Fa = 80.8 Hz; JP,Fb = 86.8 Hz; JFa,Fb = 320 Hz.
2
2.2.6. Conductivity
31P NMR,
1H NMR,
3JH,H = 7.1 Hz).
d
: ꢀ8.2 quin,m (2P, JP,F = 80 Hz).
The conductivity of 0.83 mol Lꢀ1 solution of [emim]FPI in
acetonitrile is linearly increasing with increasing temperature (in
the temperature range ꢀ20 to 80 8C, see Fig. 7).
The conductivity of [emim]FAP is higher then the conductivity
of [emim]FPI, because the FAP anion is less bulky than the FPI
anion.
d
: 3.1 q (4CH2, JH,H = 7.1 Hz); 1.2 t,m (4CH3,
3
3.3. Tetra(n-butyl)ammonium bis[bis(pentafluoroethyl)
phosphinyl]imide, [(C4H9)4N]+ [(C2F5)2P(O)]2Nꢀ
To the solution of tetra(n-butyl)ammonium bromide,
[(C4H9)4N]+Brꢀ (1.23 g, 3.8 mmol) in 5 mL of water a solution of
3. Experimental
bis[bis(pentafluoroethyl)phosphinyl]imide,
HN[P(O)(C2F5)2]2
3.1. General experimental procedures
(2.23 g, 3.8 mmol) in 5 mL of water was slowly added under
stirring at room temperature. The mixture was left stirring for
30 min and the liquid bottom phase was extracted with 10 mL of
CH2Cl2. The extract was washed four times with 40 mL of water
until the test for bromide with AgNO3 was negative. The CH2Cl2
solvent was evaporated and the residue was dried 18 h in vacuum
(<10ꢀ3 mbar) at 60 8C. Yield 87%, m.p. 150–151 8C.
NMR spectra of all compounds were measured in CD3CN
solution at room temperature on a Bruker Avance DRX-400 (1H,
400.13 MHz; 19F, 376.49 MHz; 31P, 161.97 MHz) spectrometer. The
chemical shifts were referenced to external TMS (1H), CFCl3
and H3PO4
31P).
(
19F)
(
Elemental analysis was performed using a HEKATECH EA 3000
elemental analyser and the Callidus software.
Anal. Calcd for C24H36F20N2O2P2: C 34.88; H 4.39; N 3.39.
Found: C 34.95, H 4.55, N 3.34.
Impurities in all FPI salts were detected by measuring of
residual water by Karl-Fischer titration (831 KF-Coulometer,
Metrohm) and of chloride or bromide by ion-chromatography
(Metrohm Advanced IC System with Metrosep A Supp 5-150).
Viscosities and densities of ionic liquids in the temperature range
between 20 and 80 8C were measured using the Viscosimeter SVM
3000 Anton Paar.
19F NMR,
d
: ꢀ81.2 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
2JP,Fa = 76.3 Hz; JP,Fb = 82.4 Hz; JFa,Fb = 329.5 Hz.
31P NMR,
1H NMR,
d
d
: ꢀ8.4 quin,m (2P, JP,F = 79 Hz).
2
: 3.07 m (4CH2); 1.59 m (4CH2); 1.34 q,t (4CH2,
3JH,H = 7.3 Hz); 0.95 t (4CH3, JH,H = 7.4 Hz).
3
Thermo analytical measurements were performed with a
Netzsch DSC 204 and a TG STA 409 instrument. About 25–
40 mg of the samples were weighed and sealed in aluminium
crucibles or in ceramic pans for DSC or TG measurements,
respectively. A temperature range between ꢀ120 and 600 8C with
a heating rate of 10 8C minꢀ1 under an atmosphere of dry nitrogen
was employed. The data were processed with the Netzsch Proteus
4.0 software.
The electrochemical stability of the ILs were measured using an
Autolab PGSTAT 30 (Eco Chemie). Cyclic voltamogramms were
recorded for 0.1 mol Lꢀ1 solutions in CH3CN at glassy carbon (gc)
working electrode; auxiliary electrode was Pt and Ag/AgNO3
(CH3CN) was used as reference electrode. The potential values
were normalized to E8 of ferrocene.
3.4. Tetra(n-butyl)phosphonium bis[bis(pentafluoroethyl)
phosphinyl]imide, [(C4H9)4P]+ [(C2F5)2P(O)]2Nꢀ
A
solution
of
tetra(n-butyl)phosphonium
bromide,
[(C4H9)4P]+Brꢀ (1.15 g, 3.38 mmol) in 10 mL of water was slowly
added to the stirred solution of bis[bis(pentafluoroethyl)pho-
sphinyl]imide, HN[P(O)(C2F5)2]2 (1.99 g, 3.4 mmol) in 10 mL of
water at room temperature. The mixture was left stirring for
30 min and the white precipitate was filtered off and washed three
times with 30 mL of water. After drying, 2.47 g of a white solid
material was obtained. Yield 86%, m.p. 143–145 8C.
Anal. Calcd for C24H39F20NO2P3: C 34.18; H 4.30; N 1.66. Found:
C 34.42; H 4.71; N 1.65.
Conductivities data were obtained using a Conductometer 703
(Knick). The cell constant was calibrated at room temperature by
measuring the conductance of several standard solutions of KCl
19F NMR,
d
: ꢀ81.1 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
2JP,Fa = 78.8 Hz; JP,Fb = 88.7 Hz; JFa,Fb = 322.5 Hz.
2
with concentrations ranging from 0.1 to 0.01 mol Lꢀ1
.
31P NMR,
d
: 34.9 m (1P); ꢀ8.3 quin,m (2P, JP,F = 80 Hz).

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D. Bejan et al. / Journal of Fluorine Chemistry 131 (2010) 325–332
1H NMR,
3JH,H = 7.1 Hz).
d
: 2.0–2.1 m (4CH2); 1.47 m (8CH2); 0.93 t (4CH3,
3.8. 1-n-Butyl-1-methylpyrrolidinium bis[bis(pentafluoroethyl)
phosphinyl]imide [C9H20N]+ [(C2F5)2P(O)]2Nꢀ
To the stirred solution of 1-n-Butyl-1-methylpyrolidinium
chloride, (1.46 g, 8.2 mmol) [C9H20N]+Clꢀ in 4 mL of water, a
solution of bis[bis(pentafluoroethyl)phosphinyl]imide, HN[P(O)
(C2F5)2]2 (4.83 g, 8.2 mmol) in 10 mL of water was slowly added.
The reaction proceeds within few minutes. The water insoluble
material was extracted with CH2Cl2 and washed with water three
times. After drying, 5 g of liquid 1-n-butyl-1-methylpyrrolidinium
FPI was obtained (84%).
3.5. Benzyl(triphenyl)phosphonium
bis[bis(pentafluoroethyl)phosphinyl]imide,
[(C6H5)3P(CH2C6H5)]+[(C2F5)2P(O)]2Nꢀ
To the stirred solution of benzyl(triphenyl)phosphonium chlor-
ide, [(C6H5)3P(CH2C6H5)]+Clꢀ (0.83 g, 2.1 mmol) in 5 mL of water, a
solution
of
bis[bis(pentafluoroethyl)phosphinyl]imide,
HN[P(O)(C2F5)2]2 (1.25 g, 2.1 mmol) in 5 mL of water was slowly
added at room temperature. The mixture was kept stirring for 1 h at
room temperature. The water insoluble material was extracted with
CH2Cl2 and washed with water two times. After evaporation of
Anal. Calcd for C17H20F20N2O2P2: C 28.11; H 2.78; N 3.86.
Found: C 28.15; H 2.25; N 4.22.
19F NMR,
d
: ꢀ81 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
CH2Cl2 and drying, 1.48 g of
a
pure white solid
2JP,Fa = 78.2 Hz; JP,Fb = 89 Hz; JFa,Fb = 318 Hz.
[(C6H5)3P(CH2C6H5)]+[(C2F5)2P(O)]2Nꢀ was obtained. Yield 75%,
m.p. 110 8C.
31P NMR,
1H NMR,
d
: ꢀ7.9 quin,m (2P, JP,F = 80.6 Hz).
2
d
: 3.38 m (2CH2); 3.21 m (CH2); 2.92 s (CH3); 2.13 m
Anal. Calcd for C33H22F20NO2P3: C 42.28; H 2.37; N 1.49. Found:
C 42.55; H 0.56; N 1.50.
(2CH2); 1.70 m (CH2); 1.35 q,t (CH2, 3JH,H = 7.4 Hz); 0.95 t (CH3,
3JH,H = 7.3 Hz).
19F NMR,
d
: ꢀ81.1 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
2JP,Fa = 77.7 Hz; JP,Fb = 85.4 Hz; JFa,Fb = 320 Hz.
3.9. N-butylpyridinium bis[bis(pentafluoroethy)lphosphinyl]imide,
[C9H14N]+[(C2F5)2P(O)]2Nꢀ
31P NMR,
1H NMR,
d
d
: 23.7 s (1P); ꢀ8.3 quin,m (2P, JP,F = 80 Hz).
2
3
: 7.9 m (3CH, JH,H = 7.6 Hz); 7.6 m (6CH); 7.5 m
A solution of N-butylpyridinium chloride, [C9H14N]+Clꢀ (2.03 g,
11.8 mmol) in 5 mL water was added to a vigorously stirred
solution of bis[bis(pentafluoroethyl)phosphinyl]imide, HN[P(O)
(C2F5)2]2 (7 g, 11.9 mmol) in 10 mL water. The reaction mixture
was diluted with 25 mL water and stirred additionally 30 min. The
resulting solid precipitate was collected by filtration and washed
three times with water until a pH 6–7 was obtained and the test for
chloride with AgNO3 was negative. After drying in vacuum for 18 h
at 80 8C, a white solid material (8 g) was obtained. Yield 94%, m.p.
49 8C.
3
(6CH); 7.3 m (CH); 7.2 t (2CH, JH,H = 7.6 Hz); 6.9 d, m (2CH,
3JH,H = 7.1 Hz); 4.61 d (CH2P, JP,H = 14.7 Hz).
2
3.6. Trihexyl(tetradecyl)phosphonium bis[bis(pentafluoroethyl)
phosphinyl]imide, [(C6H13)3P(C14H29)]+ [(C2F5)2P(O)]2Nꢀ
To the stirred solution of 4.11 g (7.9 mmol) trihexyl(tetrade-
cyl)phosphonium chloride, [(C6H13)3P(C14H29)]+Clꢀ in 13 mL of
ethanol, 4.62 g (7.9 mmol) bis[bis(pentafluoroethyl)phosphiny-
l]imide, HN[P(O)(C2F5)2]2 in 20 mL of water was added. The
mixture was kept stirring for 1 h. After the ethanol was distilled off
in vacuum, the liquid material was washed with water three
times. After drying, 7.24 g of a liquid material was obtained. Yield
86%.
Anal. Calcd for C17H14F20N2O2P2: C 28.35; H 1.96; N 3.89.
Found: C 27.91; H 1.82; N 3.88.
19F NMR,
d
: ꢀ81.1 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
2JP,Fa = 69 Hz; JP,Fb = 79 Hz; JFa,Fb = 314 Hz.
Anal. Calcd for C40H68F20NO2P3: C 44.99; H 6.42; N 1.31. Found:
C 44.83; H 5.88; N 1.62.
31P NMR,
1H NMR,
3JH,H = 7.8 Hz);
d
: ꢀ8.2 quin,m (2P, JP,F = 79.8 Hz).
2
3
d
:
8.67
8
d
(2CH, JH,H = 6.1 Hz); 8.48
t
(CH,
(CH2,
t
(2CH, 3JH,H = 6.6 Hz); 4.5
t
19F NMR,
2JP,Fa = 74 Hz; JP,Fb = 80 Hz; JFa,Fb = 318 Hz.
31P NMR,
1H NMR,
d
: ꢀ81.04 s (4CF3); ꢀ123.6 m (4CFa); ꢀ126.7 m (4CFb);
3JH,H = 7.6 Hz); 1.92 m (CH2); 1.35 q,t (CH2, JH,H = 7.4 Hz);
0.94 t (CH3, JH,H = 7.4 Hz).
3
2 2
3
2
d
: 34.73 m (1P); ꢀ8.3 quin,m (2P, JP,F = 80 Hz).
d
: 2.01–2.08 m (4CH2); 1.4–1.54 m (8CH2); 1.28–1.33
3.10. 1-Butyl-3,5-dimethylpyridinium bis[bis(pentafluoroethy)
lphosphinyl]imide, [C11H18N]+ [(C2F5)2P(O)]2Nꢀ
m (16CH2); 0.86–0.91 m (4CH3).
3.7. Guanidinium bis[bis(pentafluoroethyl)phosphinyl]imide,
[(NH2)3C]+[(C2F5)2P(O)]2Nꢀ
To the stirred solution of 1-butyl-3,5-dimethylpyridinium
chloride, [C11H18N]+Clꢀ (2.11 g, 10.5 mmol) in 5 mL of water,
bis[bis(pentafluoroethyl)phosphinyl]imide,
HN[P(O)(C2F5)2]2
To the stirred solution of bis[bis(pentafluoroethyl)phosphiny-
l]imide, HN[P(O)(C2F5)2]2 (1.8 g, 3.1 mmol) in 5 mL water solid
(6.2 g, 10.6 mmol) in 10 mL of water was added at room
temperature. After 10 min two phases were formed. The
reaction mixture was stirred for 30 min. The upper phase,
containing unreacted starting material and HCl was removed
from the mixture. The bottom phase was collected and
approximately equal volume of CH2Cl2 was added. This solution
was transferred to a separatory funnel and washed several times
with water. The CH2Cl2 solvent was evaporated and the residue
was dried for 18 h in vacuum at 60 8C resulting in a liquid
material (6.9 g). Yield 88%.
2ꢀ
guanidinium carbonate was slowly added, [(NH2)3C]2+CO3
(0.28 g, 1.5 mmol) and the reaction mixture was cooled in an ice
bath to 0 8C. The reaction mixture was stirred at that temperature
for 30 min. The precipitate was separated by filtration and washed
with cold water three times. After drying, 1.68 g of a very
hygroscopic white solid was obtained. Yield 84%, m.p. 52 8C.
Anal. Calcd for C9H6F20N4O2P2: C 16.78; H 0.94; N 8.70. Found: C
16.83; H 0.86; N 8.54.
Anal. Calcd for C19H18F20N2O2P2: C 30.5; H 2.42; N 3.74. Found:
C 29.90; H 2.24; N 3.72.
19F NMR,
d
: ꢀ81.2 s (4CF3); ꢀ123.9 m (4CFa); ꢀ126.8 m (4CFb);
2 2
2JP,Fa = 85.8 Hz; JP,Fb = 80.6 Hz; JFa,Fb = 316 Hz.
31P NMR,
1H NMR,
d
: ꢀ6.5 quin,m (2P, JP,F = 81.7 Hz).
2
19F NMR,
2JP,Fa = 74 Hz; JP,Fb = 83 Hz; JFa,Fb = 314 Hz.
d
: ꢀ81.1 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
d
: 5.92 br.s (3NH2).

D. Bejan et al. / Journal of Fluorine Chemistry 131 (2010) 325–332
331
2
31P NMR,
1H NMR,
d
d
: ꢀ8.2 quin,m (2P, JP,F = 79.8 Hz).
19F NMR,
d
: ꢀ81.16 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
: 8.35 s (2CH); 8.11 s (CH); 4.4 t (CH2, 3JH,H = 7.6 Hz);
2.45 s (2CH3); 1.92 m (CH2); 1.34 q,t (CH2, 3JH,H = 7.4 Hz); 0.94 t
2JP,Fa = 76.3 Hz; JP,Fb = 85.4 Hz; JFa,Fb = 329.6 Hz.
31P NMR,
1H NMR,
d
d
: ꢀ8 quin,m (2P, JP,F = 79.5 Hz).
2
3
(CH3, JH,H = 7.4 Hz).
: 8.4 s (CH); 7.35 s (CH); 7.31 s (CH); 4.1 t (CH2,
3JH,H = 7.4 Hz); 3.80 s (CH3); 1.9 t,t (CH2, JH,H = 6.8 Hz); 1.3 m
3
3
(3CH2); 0.87 t (CH3, JH,H = 6.4 Hz).
3.11. 1-Ethyl-3-methylimidazolium
bis[bis(pentafluoroethy)lphosphinyl]imide [C6H11N2]+
[(C2F5)2P(O)]2Nꢀ
3.14. 1-Decyl-3-methyl imidazolium
bis[bis(pentafluoroethyl)phosphinyl]imide, [C14H27N2]+
[(C2F5)2P(O)]2Nꢀ
A
solution
[C6H11N2]+Clꢀ (2.49 g, 16.9 mmol) in 10 mL of water was added to
the solution of bis[bis(pentafluoroethyl)phosphinyl]imide,
of
1-ethyl-3-methylimidazolium
chloride,
To the stirred solution of 1-decyl-3-methylimidazolium chlor-
ide, [C14H27N2]+Clꢀ (3.08 g, 11.8 mmol) in 15 mL of water a
solution
HN[P(O)(C2F5)2]2 (7 g, 11.9 mmol) in 5 mL of water was slowly
added at room temperature. After 30 min stirring the water
insoluble material was extracted with CH2Cl2 and washed few
times with water containing a few mg of K2CO3. After evaporation
of CH2Cl2 and drying 16 h in vacuum at 60 8C, 8.98 g of a liquid
material was obtained. Yield 94%.
HN[P(O)(C2F5)2]2 (9.93 g, 16.9 mmol) in 30 mL of water at room
temperature. After 1 h stirring the water insoluble material was
extract with CH2Cl2 and washed few times with water containing of
few mg of K2CO3. After evaporation of CH2Cl2 the residue was dried
24 h in vacuum at 70 8C. A liquid material (9.8 g) was obtained. Yield
83%.
of
bis[bis(pentafluoroethyl)phosphinyl]imide,
Anal. Calcd for C14H11F20N3O2P2: C 24.19; H 1.59; N 6.04.
Found: C 24.12; H 1.6; N 6.16.
Anal. Calcd for C22H27F20N3O2P2: C 32.73; H 3.37; N 5.20.
Found: C 32.17; H 3.32; N 5.08.
19F NMR,
d
: ꢀ81.19 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
2JP,Fa = 76.3 Hz; JP,Fb = 82.4 Hz; JFa,Fb = 326 Hz.
31P NMR,
1H NMR,
d
d
: ꢀ7.9 quin,m (2P, JP,F = 80 Hz).
2
19F NMR,
d
: ꢀ81.15 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
2JP,Fa = 73.3 Hz; JP,Fb = 82.4 Hz; JFa,Fb = 326.5 Hz.
: 8.46 s (CH); 7.38 s (CH); 7.32 s (CH); 4.15 q (CH2,
3JH,H = 7.3 Hz); 3.80 s (CH3); 1.44 t (CH3, JH,H = 7.1 Hz).
3
31P NMR,
1H NMR,
d
: ꢀ8 quin,m (2P, JP,F = 79.5 Hz).
2
d
: 8.4 s (CH); 7.36 s (CH); 7.32 s (CH); 4.09 t (CH2,
3JH,H = 7.4 Hz); 3.80 s (CH3); 1.26 s (8CH2); 0.86 t (CH3,
3JH,H = 6.4 Hz).
3.12. 1-Butyl-3-methylimidazolium
bis[bis(pentafluoroethy)lphosphinyl]imide, [C8H15N2]+
[(C2F5)2P(O)]2Nꢀ
3.15. 1-Octadecyl-3-methylimidazolium
bis[bis(pentafluoroethyl)phosphinyl]imide, [C22H43N2]+
[(C2F5)2P(O)]2Nꢀ
To the stirred solution of 1-butyl-3-methylimidazolium chlor-
ide, [C8H15N2]+Clꢀ (1.13 g, 6.4 mmol) in 5 mL of water, the solution
of bis[bis(pentafluoroethyl)phosphinyl]imide, HN[P(O)(C2F5)2]2,
(3.78 g, 6.4 mmol) in 10 mL of water was slowly added at room
temperature. The mixture was left stirring for 30 min and the
bottom liquid phase was extracted with CH2Cl2 and washed with
water until the test for chloride was negative. After evaporation of
CH2Cl2, the residue was dried 48 h at 70 8C in vacuum. 3.65 g of
pure 1-butyl-3-methylimidazolium FPI was obtained. Yield 79%.
Anal. Calcd for C16H15F20N3O2P2: C 26.57; H 2.09; N 5.81.
Found: C 26.96; H 2.55; N 5.76.
A
solution of 1-octadecyl-3-methylimidazolium chloride,
[C22H43N2]+Clꢀ (3.25 g, 8.7 mmol) in 10 mL of ethanol was added
at room temperature to the stirred solution of bis[bis(pentafluor-
oethyl)phosphinyl]imide, HN[P(O)(C2F5)2]2 (5.1 g, 8.7 mmol) in
10 mL of ethanol. The mixture was left stirring for 0.5 h. The
solvent was removed in vacuum and the residue was washed with
water until the test for chloride was negative. The obtained
substance was dried 48 h at 60 8C in vacuum and 6.51 g of pure 1-
octadecyl-3-methylimidazolium FPI was obtained. Yield 81%.
Anal. Calcd for C30H43F20N3O2P2: C 39.18; H 4.71; N 4.57.
Found: C 40.19; H 5.38; N 4.57.
19F NMR,
d
: ꢀ81.2 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.8 m (4CFb);
2 2
2JP,Fa = 76.3 Hz; JP,Fb = 85.4 Hz; JFa,Fb = 329.6 Hz.
31P NMR,
1H NMR,
d
d
: ꢀ8.08 quin,m (2P, JP,F = 79.5 Hz).
2
19F NMR,
d
: ꢀ81.1 s (4CF3); ꢀ123.7 m (4CFa); ꢀ126.2 m (4CFb);
2 2
: 8.42 s (CH); 7.35 s (CH); 7.31 s (CH); 4.1 t (CH2,
3JH,H = 7.38 Hz); 3.80 s (CH3); 1.79 quin (CH2, JH,H = 7.4 Hz);
3
2JP,F = 74.2 Hz; JP,F = 86.4 Hz; JFa,Fb = 317 Hz.
3
3
31P NMR,
1H NMR,
d
d
: ꢀ8 quin,m (2P, JP,F = 79.5 Hz).
2
1.32 q,t (CH2, JH,H = 7.4 Hz); 0.92 t (CH3, JH,H = 7.4 Hz).
: 8.4 s (CH); 7.35 m (CH); 7.32 m (CH); 4.1 t (CH2,
3JH,H = 7.38 Hz); 3.80 s (CH3); 1.8 q,t (CH2, 3JH,H = 7.4 Hz); 1.26 m
3.13. 1-Hexyl-3-methyl imidazolium
bis[bis(pentafluoroethyl)phosphinyl]imide, [C10H19N2]+
[(C2F5)2P(O)]2Nꢀ
3
(15CH2); 0.87 t (CH3, JH,H = 6.8 Hz).
Acknowledgements
To the stirred solution of 1-hexyl-3-methylimidazolium chlor-
ide, [C10H19N2]+Clꢀ (2.8 g, 13.8 mmol) in 5 mL of water a solution
of bis[bis(pentafluoroethyl)phosphinyl]imide, HN[P(O)(C2F5)2]2
(8.10 g, 13.8 mmol) in 30 mL of water was slowly added at room
temperature. After 1 h stirring the water insoluble material was
extract with CH2Cl2 and washed few times with water containing a
few mg of K2CO3. After evaporation of CH2Cl2 and drying the
residue 24 h in vacuum at 70 8C, 8.4 g of a liquid material was
obtained. Yield 81%.
The authors are indebted to Dr. P. Barten (University of
Du¨sseldorf), Dr. J. Hu¨bner (University of Wuppertal) and Mrs. A.
Amann (Merck KGaA, Darmstadt) for elemental analysis, viscosity/
DSC measurements and electrochemical studies, respectively.
References
[1] P. Wasserscheid, T. Welton (Eds.), Ionic Liquids in Synthesis, Second edition,
Wiley–VCH, Weinheim, 2008.
[2] C. Chiappe, D. Pieraccini, J. Phys. Org. Chem. 18 (2005) 275–297.
[3] J.S. Wilkes, J. Mol. Catal. A: Chem. 214 (2004) 11–17.
Anal. Calcd for C18H19F20N3O2P2: C 28.78; H 2.55; N 5.59.
Found: C 29.11; H 2.65; N 6.07.

332
D. Bejan et al. / Journal of Fluorine Chemistry 131 (2010) 325–332
[4] R.A. Sheldon, R.M. Lau, M.J. Sorgedrager, F. van Rantwijk, K.R. Seddon, Green
Chem. 4 (2002) 147–151.
[20] N. Ignatyev, U. Welz-Biermann, M. Heckmeier, G. Bissky, H. Willner, WO Patent
128563 A1 (2006).
[5] D. Zhao, M. Wu, Y. Kou, E. Min, Catal. Today 2654 (2002) 1–33.
[6] M. Koel (Ed.), Ionic Liquids in Chemical Analysis, CRC Press, London, 2009.
[7] P. Hapiot, C. Lagrost, Chem. Rev. 108 (2008) 2238–2264.
[8] H. Ohno (Ed.), Electrochemical Aspects of Ionic Liquids, Wiley–Interscience,
2005 .
[9] N.V. Ignatiev, A. Kucheryna, G. Bissky, H. Willner, in: J.F. Brennecke, R.D. Rodgers,
K.R. Seddon (Eds.), Ionic Liquids IV, ACS Symposium Series 975, Washington, DC,
(2007), pp. 320–334.
[21] J.M. Slattery, C. Daguenet, P.J. Dyson, T.J.S. Schubert, I. Krossing, Angew. Chem. Int.
Ed. 46 (2007) 5384–5388.
[22] H.D.B. Jenkins, H.K. Roobottom, J. Passmore, L. Glasser, Inorg. Chem. 38 (1999)
3609–3620.
[23] J. Palomar, V.R. Ferro, J.S. Torrecilla, F. Rodriguez, Ind. Eng. Chem. Res. 46 (2007)
6041–6048.
[24] H. Tokuda, K. Hayamizu, K. Ishii, Md.A.H. Susan, M. Watanabe, J. Phys. Chem. B 108
(2004) 16593–16600.
[10] S. Zhang, N. Sun, X. He, X. Lu, X. Zhang, J. Phys. Chem. Ref. Data 35 (2006) 1475–
1517.
[25] D.A. Kochkin, V.I. Vashkov, G.V. Kiryutkin, A.R. Savel’eva, Zh. Org. Khim. 34 (1964)
4027–4029.
[11] T.L. Greaves, C.J. Drummond, Chem. Rev. 108 (2008) 206–237.
[12] J.G. Huddleston, A.E. Visser, W.M. Reichert, H.D. Willauer, G.A. Broker, R.D. Rogers,
Green Chem. 3 (2001) 156–164.
[13] H. Matsumoto, H. Kageyama, Y. Miyazaki, Chem. Lett. 30 (2001) 182–183.
[14] S.V. Dzyuba, R.A. Bartsch, Chem. Phys. Chem. 3 (2002) 161–166.
[15] C.P. Fredlake, J.M. Crosthwaite, D.G. Hert, S.N.V.K. Aki, J.F. Brennecke, J. Chem. Eng.
Data 49 (2004) 954–964.
[16] N.V. Ignat’ev, U. Welz-Biermann, A. Kucheryna, G. Bissky, H. Willner, J. Fluorine
Chem. 126 (2005) 1150–1159.
[17] N.V. Ignat’ev, U. Welz-Biermann, H. Willner, Russ. J. Chem. 48 (2005) 36–39.
[18] N. Ignat’ev, P. Sartori, J. Fluorine Chem. 103 (2000) 57–61.
[19] D. Bejan, H. Willner, N. Ignatiev, C.W. Lehmann, Inorg. Chem. 47 (2008) 9085–
9089.
[26] H.L. Ngo, K. LeCompte, L. Hargens, A.B. McEwen, Thermochim. Acta 357–358
(2000) 97–102.
[27] K. Sakizadeh, L.P. Olson, P.J. Cowdery-Corvan, T. Ishida, D.R. Whitcomb, US Patent
7163786 B1 (2007).
[28] C.A. Corley, in: Proceedings – Electrochemical Society 2006, Molten Salts XIV, vol.
24, 2004, pp. 326–339.
[29] A. Lapidus, O. Elissev, T. Bondarenko, N. Stepin, J. Mol. Catal. A: Chem. 252 (2006)
245–251.
[30] L.L. Tolstikova, B.A. Shainyan, Zh. Org. Khim. 42 (2006) 1085–1091.
[31] P.D. Vu, A.J. Boydston, C.W. Bielawski, Green Chem. 9 (2007) 1158–1159.
[32] A. Noda, K. Hayamizu, M. Watanabe, J. Phys. Chem. B 105 (2001) 4603–4610.
[33] H. Matsumoto, M. Yanagida, K. Tanimoto, M. Nomura, Y. Kitagawa, Y. Miyazaki,
Chem. Lett. 29 (2000) 922–923.