On the solid state inclusion of tetrabutylammonium cation in the imidazolium/trifluoromethanesulfonate H-bonds network observed in ionic co-crystals

Article abstract of DOI:10.1016/j.molstruc.2008.06.025

Three co-crystals of tetrabutylammonium and 1-alkyl-3-methylimidazolium bistrifluoromethanesulfonate, where alkyl are: ethyl (co-crystal I), butyl (co-crystal II) or (±)-2-methylbutyl (co-crystal III) have been crystallized by slow evaporation of a chloroform solution. The X-rays diffraction studies on single co-crystals revealed that the three crystalline materials obtained are respectively triclinic (P over(1, ?)) for I, monoclinic (P2₁/c) for II and triclinic (P over(1, ?)) for III . In each structure, the tetrabutylammonium cations are included in the H-bonds network that link all the imidazolium cations and trifluoromethanesulfonate anions. The H-bonds occur between the acidic protons of the imidazolium ring and the oxygen atoms of the counter ion. No supramolecular interaction (except obviously electrostatic) is observed between the tetrabutylammonium cations and the trifluoromethanesulfonate anions.

Full text of DOI:10.1016/j.molstruc.2008.06.025

Journal of Molecular Structure 892 (2008) 433–437
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Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
On the solid state inclusion of tetrabutylammonium cation
in the imidazolium/trifluoromethanesulfonate H-bonds
network observed in ionic co-crystals
*
Loïc Leclercq, Isabelle Suisse, Guy Nowogrocki, Francine Agbossou-Niedercorn
Université des Sciences et Technologie de Lille 1, CNRS Unité de Catalyse et de Chimie du Solide UMR 8181, ENSCL(CHIMIE), BT C7, BP 90108, 59652 Villeneuve d’Ascq, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Three co-crystals of tetrabutylammonium and 1-alkyl-3-methylimidazolium bistrifluoromethanesulfo-
nate, where alkyl are: ethyl (co-crystal I), butyl (co-crystal II) or ( )-2-methylbutyl (co-crystal III) have
been crystallized by slow evaporation of a chloroform solution. The X-rays diffraction studies on single
Received 23 April 2008
Received in revised form 16 June 2008
Accepted 17 June 2008
ꢀ
co-crystals revealed that the three crystalline materials obtained are respectively triclinic ðP1Þ for I,
Available online 2 July 2008
ꢀ
monoclinic (P21/c) for II and triclinic ðP1Þ for III . In each structure, the tetrabutylammonium cations
are included in the H-bonds network that link all the imidazolium cations and trifluoromethanesulfonate
anions. The H-bonds occur between the acidic protons of the imidazolium ring and the oxygen atoms of
the counter ion. No supramolecular interaction (except obviously electrostatic) is observed between the
tetrabutylammonium cations and the trifluoromethanesulfonate anions.
Keywords:
Imidazolium
Tetrabutylammonium
Co-crystal
Inclusion compound
Hydrogen bonding
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
cation surrounded by at least three anions and each anion is sur-
rounded by at least three imidazolium cations [21]. The strongest
The chemistry of ionic liquid (ILs) constitutes an attractive field
of investigation. ILs are defined as ‘‘molten salts” with melting
points below 100 °C. The significant interest devoted to them is re-
lated to their chemical characteristics and potentially useful sol-
vent properties [1,2]. 1,3-dialkylimidazolium salts constitute a
very popular IL family. They are generally used as green solvents
in organic synthesis, organometallic, and enzymatic catalysis
[3–11]. Many applications have been reported in the fields of
separation processes, nanochemistry, electrochemistry, and new
materials [12–14]. Recent studies have demonstrated that pure
1,3-disubstituted imidazolium salts are better described as hydro-
gen-bonded supramolecular networks in the solid phase. The
H-bonds are proposed to be maintained to a great extent in the li-
quid or gas phases as well [15]. Imidazolium salts possess pre-or-
ganized structures mainly through three H-bond donors, which are
three acid protons located on the imidazolium ring, and oriented in
hydrogen bond always involves the most acidic H2 (pKa = 23.0 for
the 1,3-dimethylimidazolium cation) [22,23] followed by H4 and
H5 of the imidazolium ring. These hydrogen bonds are weak to
moderate (HꢀꢀꢀX bond lengths >2.2 Å; C–HꢀꢀꢀX bond angles between
100° and 180°) [24]. The number of anions that surround the cation
(and vice-versa) varies according to the anion size and the nature
of the imidazolium residues.
Recently, we have reported on the use of imidazolium trifluoro-
methanesulfonate substituted by heterocyclic residues as medium
for allylic alkylation. Curiously, after catalysis, a solid has formed in
the reaction medium and after crystallization, we have obtained
single crystals suitable for X-ray structure determination. The
X-rays diffraction revealed that the crystals are, in fact, co-crystals
of imidazolium/tetrabutylammonium bistrifluoromethanesulfo-
nate formed in situ after anion metathesis between imidazolium
trifluoromethanesulfonate and tetrabutylammonium acetate [25].
Most recently, we have reported that the ionic liquid medium
can interact with all the reactive species ‘‘solubilised” in the imi-
dazolium-based solution [6]. In fact, despite their homogeneous
appearance, imidazolium ionic liquids can retain some defined lo-
cal structure and the solid state analysis offers a unique opportu-
nity to obtain direct and quantitative structural evidences usable
to describe the liquid state [26]. Because of our interest in applying
imidazolium salt in catalysis and in understanding the interactions
existing in such media, we performed a crystallographic study of
a divergent fashion. In 3-D, p-stacking can also occur (Fig. 1) [15].
In fact, an overview of the X-ray studies reported in the past
decade on the structure of 1,3-dialkylimidazolium salts [16–20]
reveals a general trend: in the solid state they form an extended
network of cations and anions connected together by hydrogen
bonds. The unimeric unit is always constituted by one imidazolium
* Corresponding author. Fax: +33 3 20 43 65 85.
E-mail address: francine.agbossou@ensc-lille.fr (F. Agbossou-Niedercorn).
0022-2860/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2008.06.025

434
L. Leclercq et al. / Journal of Molecular Structure 892 (2008) 433–437
dard methods: dichloromethane from CaH2, toluene from Na/Hg
amalgam.
a
b
5 a 4
H
H
N
N
2.2. Synthesis of ( )-1-[2-methylbutyl]-3-methylimidazolium
trifluoromethanesulfonate
4
5
2
X-
+
N
N
2
A dry flask (1 L), equipped with a magnetic stir bar and a sep-
tum-inlet for nitrogen, was charged with a solution of ( )-2-meth-
ylbutanol (6.28 g, 71.2 mmol) in dichloromethane (300 mL), and
poly(vinylpyridine) (18.0 g, 63.8 mmol). At 0 °C, trifluoromethane-
sulfonic anhydride (8.6 g, 30.6 mmol) was added in a drop wise
fashion. The reaction mixture was stirred for 5 min between 0 °C
and room temperature and then filtered under gravity. The
poly(vinylpyridinium trifluoromethanesulfonate) precipitate was
washed with 5 mL of dichloromethane. The combined organic lay-
ers were first washed with saturated NaHCO3 until they became
transparent and then dried (MgSO4) and finally concentrated under
vacuum to give the ( )-2-methylbutyltrifluoromethanesulfonate
(yellowish oil). The methylene group adjacent to the trifluoro-
methanesulfonate group gives a characteristic dd at 4.38 ppm
(2H) in the 1H NMR spectrum. This oil compound was used as is
in the next step. Thus, after dissolution in anhydrous toluene under
a nitrogen atmosphere, the solution was cooled to 0 °C. 1-methyl-
imidazole (6.18 g, 75.2 mmol) was added and the resulting solu-
tion was stirred for an hour. The ionic liquid layer appeared
beneath the toluene phase. After extraction, the ionic liquid was
washed with toluene to remove unreacted 1-methylimidazole.
The pale-yellow ionic liquid was dried overnight at 120 °C under
vacuum. The product was stored under dry nitrogen (21.28 g, 99%).
1H NMR (300 MHz, CDCl3, 20 °C, TMS): d = 0.6-0.8 ppm (m, 6H;
CH3), 0.9 ppm (qd, 3J(H,H) = 7.3 Hz, 3J(H,H) = 9.1 Hz, 1H; CH2),
1.2 ppm (qd, 3J(H,H) = 7.3 Hz, 3J(H,H) = 9.1 Hz, 1H; CH2), 1.7 ppm
(m, 1H; CH), 3.8 ppm (s, 3H; NCH3), 3.9–4.1 ppm (m, 2H; NCH2),
7.2 ppm (s, 1H; CH@CH), 7.3 ppm (s, 1H; CH@CH), 8.8 ppm (s,
1H; NCHN); 13C NMR (75 MHz, CDCl3, 20 °C): d = 10.6 ppm (CH3),
15.9 ppm (CH3), 26.0 ppm (CH2), 35.3 ppm (NCH3), 36.0 ppm
(CH), 55.2 ppm (NCH2), 122.7 ppm (CH@CH), 123.6 ppm (CH@CH),
X-
H
Fig. 1. (a) The three T-stacking and H-bond donors of an imidazolium ring and their
directionality and (b) -stacking.
p
this new family of co-crystals. We explored three co-crystals ob-
tained from 1-alkyl-3-methylimidazolium trifluoromethanesulfo-
nate salts (where alkyl is ethyl, butyl or ( )-2-methylbutyl) and
tetrabutylammonium trifluoromethanesulfonate. To simplify the
notation, on the basis of the residues located on the imidazolium
ring, the co-crystals are named I, II and III for ethyl, butyl and
( )-2-methylbutyl residues, respectively (Scheme 1).
2. Experimental
2.1. Materials
All reactions were carried in oven-dried glassware under nitro-
gen, using standard Schlenk and vacuum line techniques. The 1H
and 13C NMR spectra were recorded on an Advance 300 Brucker,
spectrometer at 300.13 and 75.49 MHz, respectively. Chemical
shifts are given in ppm (d) and measured relative to residual sol-
vent. Elemental analysis were performed by the ‘‘Service Central
d’Analyse du CNRS”. IR analyses were performed on a Nicolet
510 FTIR. CDCl3 was obtained from Euriso-top. Trifluoromethane-
sulfonic anhydride was freshly prepared prior to use by distillation
of a 1:1 w/w mixture of trifluoromethanesulfonic acid and phos-
phorus pentoxide. 1-methylimidazole was freshly distilled under
KOH. All other chemicals were purchased from Acros or Aldrich
and used without further purification. Solvents were distilled un-
der positive pressure of dry nitrogen before use and dried by stan-
136.4 ppm (NCHN); IR:
m
= 3115 and 3155 cmꢁ1 (C–HꢀꢀꢀF); Anal.
Calc. for C10H17F3N2O3S: C, 39.73%; H, 5.67%. Found: C, 39.83%; H,
5.70%.
2.3. Crystallization and X-rays diffraction
O-
All the co-crystallizations were performed in an open flask by
dissolving the 1-alkyl-3methylimidazolium trifluoromethanesulfo-
nate (1 equiv.) and tetrabutylammonium trifluoromethanesulfo-
nate (1 equiv.) in hot chloroform (10 mL). After a week at room
temperature, single co-crystals are obtained which were suitable
for X-rays diffraction characterization. X-ray data were collected
on a Bruker SMART CCD area-detector diffractometer with Mo-
O-
O
F
F
S
O
F
F
S
I
N+
N+
O
F
N
N
O
;
F
O-
S
Ka radiation (k = 0.71073 Å) at T = 100 K. The structure was solved
O
O-
S
F
F
by direct method with ShelxS-97. All non-H atoms were refined by
full-matrix least-squares with anisotropic displacement parame-
ters while hydrogen atoms were placed in idealized position.
II
O
N+
F
F
N+
O
F
;
O
O
F
3. Results and discussion
O-
S
All products for co-crystallization are commercially available
except the ( )-1-(2-methylbutyl)-3-methyimidazolium trifluoro-
methanesulfonate. The synthesis of this imidazolium salts is very
simple [25]. Our strategy is based on the reaction of an intermedi-
ate (trifluoromethanesulfonic)acid ester with a substituted imi-
dazolium. Indeed, alcohols can be easily converted into
alkyltrifluoromethansulfonates in the presence of (trifluorometh-
anesulfonic)anhydride and a non nucleophilic base providing the
expected intermediate which is further reacted with a substituted
O-
S
O
F
F
O
F
F
III
N+
N+
O
F
N
;
F
Scheme 1. The three co-crystals studied in this work.

L. Leclercq et al. / Journal of Molecular Structure 892 (2008) 433–437
435
imidazole. In order to avoid the base alkylation and to facilitate the
purification of the new imidazolium trifluoromethanesulfonate
salt, we used poly(4-vinylpyridine) (PVP) as the base. The highly
pure ionic liquids ( )-1-(2-methylbutyl)-3-methylimidazolium tri-
fluoromethanesulfonate were isolated in excellent yields (99%).
Crystallizations of the imidazolium/tetrabutylammonium
bistrifluoromethanesulfonate salts were obtained efficiently from
hot chloroform solutions. Thus, chloroform solutions of the imi-
dazolium trifluoromethanesulfonate (1 equiv.) and the tetrabutyl-
ammonium trifluoromethanesulfonate salt (1 equiv.) were heated
until homogenisation and then left at room temperature. After a
week, crystals suitable for X-ray analysis were obtained. The co-
ꢀ
crystals I and III crystallize in triclinic cells, space group ðP1Þ (Table
1 and Figs. 2 and 4). It is important to notice that for the co-crystal
III, a disorder on the lateral ( )-2-methylbutyl residue is observed
with a occupancy rate of 50% due to the rotation of C(7)–C(8) bond.
For II, the cell is monoclinic, space group P21/c (Table 1 and Fig. 3).
In all three cases, it must be noted that, even at 100 K, the displace-
ment parameters are high for fluorine and oxygen atoms of the tri-
fluoromethanesulfonate ions and that the residual electronic
densities at the end of the refinement are all located in the vicinity
of O and F positions: this can point to some rotational disorder in
the trifluoromethanesulfonate ion.
Fig. 2. ORTEP view of I with the numbering scheme adopted. Ellipsoids drawn at
50% probability level. Hydrogen atoms are omitted for the sake of clarity.
Table 1
Crystal data of co-crystals I, II and IIIa
Compound
I
II
III
Cation formula
C16H36
N
C16H36
N
C16H36N
C6H11N2
2(CF3SO3)
651.77
C8H15N2
2(CF3SO3)
679.82
Monoclinic
P21/c
9.63390 (10)
9.77980 (10)
37.3359 (4)
90
95.8160 (6)
90
C9H17N2
2(CF3SO3)
693.84
Anion formula
Molecular weight
Crystal system
Space group
a (Å)
Triclinic
Triclinic
ꢀ
ꢀ
ðP1Þ
ðP1Þ
9.6051 (1)
9.7295 (2)
18.1787 (3)
89.3188 (7)
79.6087 (7)
88.2304 (7)
1670.16 (5)
2
9.5672 (1)
9.7987 (1)
19.3233 (3)
89.4303 (6)
87.6106 (7)
87.8136 (7)
1808.53 (4)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
3499.59 (6)
4
Z
Color
Colorless
Colorless
Colorless
Crystal dim. (mm)
0.52 ꢂ 0.42 ꢂ 0.33 0.49 ꢂ 0.35 ꢂ 0.18 0.35 ꢂ 0.28 ꢂ 0.13
l
(mmꢁ1
)
0.231
0.224
0.218
Fig. 3. ORTEP view of II with the numbering scheme adopted. Ellipsoids drawn at
50% probability level. Hydrogen atoms are omitted for the sake of clarity.
Temperature (K)
Dcalc. (Mg mꢁ3)
F(000)
100 (2)
1.296
692
100 (2)
1.290
1448
100 (2)
1.275
740
Theta range for
collection (°)
Limiting indices
2.16–26.00
2.12–28.00
1.05–26.00
ꢁ11 6 h 6 11
ꢁ11 6 k 6 11
ꢁ22 6 l 6 22
24,454/6483
ꢁ12 6 h 6 12
ꢁ12 6 k 6 12
ꢁ49 6 l 6 49
61,361/8445
ꢁ11 6 h 6 11
ꢁ12 6 k 6 12
ꢁ23 6 l 6 23
41,985/7099
Reflections
collected/unique
Rint
0.0192
98.8
0.0346
100.0
0.0234
100.0
Completeness to
theta max. (%)
Data/restraints/
parameters
Goodness-of-fit on
F2
6483/0/376
1.061
8445/0/394
1.037
7099/0/419
1.299
Final R indices
[I > 2
R1
wR2
r(I)]
0.0369
0.0928
0.0389
0.0933
0.0651
0.1440
R indices (all data)
R1
0.0413
0.0501
0.0674
wR2
0.0953
0.0978
0.1447
Largest diff. peak
0.555; ꢁ0.378
0.521; ꢁ0.388
0.412; ꢁ0.346
and hole (e Åꢁ3
)
a
Diffractometer, Bruker SMART CCD; radiation, Mo-K
a
fine-focus sealed tube
Fig. 4. ORTEP view of III with the numbering scheme adopted. Ellipsoids drawn at
40% probability level. C10 and C12 have both an occupancy rate of ½. Hydrogen
atoms are omitted for the sake of clarity.
graphite monochromated (0.71073 Å); absorption correction, empirical (SADABS);
refinement method, full-matrix least-squares on F2.

436
L. Leclercq et al. / Journal of Molecular Structure 892 (2008) 433–437
Fig. 5. Comparison between the two cations in the co-crystal I, II and III.
In each case, the crystal is composed of one imidazolium cation,
3-D network of cations and anions connected together by hydro-
gen bonds [21]. In the present system, the hydrogen bond network
between the imidazolium cations and the trifluoromethanesulfo-
nate anions is weak according to published data [16,27,28]. Each
imidazolium is surrounded closely by four anions and the connec-
tion of these are due to weak hydrogen bonds (2.3 Å < HꢀꢀꢀO < 2.6 Å;
C–HꢀꢀꢀO between 120° and 170°) (Tables 2–4). The three structures
can be described as a supramolecular H-bond network where the
imidazolium cations are connected via trifluoromethanesulfonate
anions. All tetrabutylammonium are trapped between the imi-
dazolium/tetrabutylammonium network to form the crystalline
network (Fig. 6).
No particular stacking interactions can be observed in these
structures (distances between two imidazolium rings are at least
9.6 Å). This can be due to the fact that the trifluoromethanesulfo-
nate anion is far bulkier than halide anions. In fact, an anion is
placed between two imidazolium rings. The structure can be de-
scribed as a supramolecular H-bonds network, within which tetra-
butylammonium cations are included but without special
supramolecular interaction except electrostatic interactions. The
structure can be seen as a solid inclusion compound where the
one tetrabutylammonium cation and two trifluoromethanesulfo-
nate anions. It is worth mentioning that for all three cases, no
water or residual solvent molecules were present in the lattice
implying that the cohesion of the crystal is ensured only by the
ionic components.
For each case, the C(2)–N(1) or C(2)–N(3) distance and the
N(1)C(2)N(3) angle of the imidazolium ring are in the ranges of
ca. 1.33–1.34 Å and ca. 108.6°–108.9°. The C(4)–N(3) or C(5)–
N(1) distance and the C(4)N(3)C(2) or C(5)N(1)C(2) angles of the
imidazolium ring are around 1.38–1.34 Å and ca. 108.4°–108.7°.
The C(4)–C(5) in imidazolium ring distance is around 1.35 Å in
each case. The C(2)N(1)C(7)C(8) dihedral angles vary between ca.
105.7° and ꢁ70.1° for I; ꢁ103.1° and 69.43° for II; and 107.0°
and ꢁ66.3° for III. For the tetrabutylammonium, the geometry
adopted is the same in the three co-crystals. The three co-crystals
are very similar in term of molecular geometry. A superposition of
the different cations is given in Fig. 5.
In term of supramolecular association, the imidazolium part of
the crystal reveals a typical organization compared to those previ-
ously observed for other imidazolium salts, i.e. an extended
Table 2
Distances and angles of C–HꢀꢀꢀO hydrogen bonds in Ia
0
0
0
CꢀꢀꢀH (AÅ)
HꢀꢀꢀO (AÅ)
CꢀꢀꢀO (AÅ)
C–HꢀꢀꢀO (°)
Symmetry operators for O
C2–H2ꢀꢀꢀO1
C4–H4ꢀꢀꢀO4
C5–H5ꢀꢀꢀO3
0.93
0.93
0.93
2.339(1)
2.555(1)
2.412(1)
3.033(2)
3.447(2)
3.308(2)
131.2(1)
160.8(1)
161.7(1)
1ꢁx, 1ꢁy, 1ꢁz
2ꢁx, 1ꢁy, 1ꢁz
1ꢁx, 2ꢁy, 1ꢁz
a
Only HꢀꢀꢀO that have significant interactions are reported.
Table 3
Distances and angles of C–HꢀꢀꢀO hydrogen bonds in IIa
0
0
0
CꢀꢀꢀH (AÅ)
HꢀꢀꢀO (AÅ)
CꢀꢀꢀO (AÅ)
C–HꢀꢀꢀO (°)
Symmetry operators for O
C2–H2ꢀꢀꢀO1
C4–H4ꢀꢀꢀO5
C5–H5ꢀꢀꢀO2
0.93
0.93
0.93
2.361(1)
2.576(1)
2.546(1)
2.972(2)
3.467(2)
3.429(2)
122.9(1)
160.6(1)
158.9(1)
x, 1ꢁy, z
1+x, y, z
x, y, z
a
Only HꢀꢀꢀO that have significant interactions are reported.
Table 4
Distances and angles of C–HꢀꢀꢀO hydrogen bonds in IIIa
0
0
0
CꢀꢀꢀH (AÅ)
HꢀꢀꢀO (AÅ)
CꢀꢀꢀO (AÅ)
C–HꢀꢀꢀO (°)
Symmetry operators for O
C2–H2ꢀꢀꢀO2
C4–H4ꢀꢀꢀO4
C5–H5ꢀꢀꢀO3
0.93
0.93
0.93
2.276(2)
2.643(3)
2.501(3)
2.966(4)
3.526(4)
3.418(4)
130.5(2)
158.7(2)
169.1(2)
x, y, z
x, y, z
x, yꢁ1, z
a
Only HꢀꢀꢀO that have significant interactions are reported.

L. Leclercq et al. / Journal of Molecular Structure 892 (2008) 433–437
437
Fig. 6. (a) View of the local assembly around a tetrabutylammonium cation and (b) space-filled view of the co-crystal I.
[2] P. Wasserscheid, T. Welton, in: Ionic Liquids in Synthesis, VCH-Wiley,
Weinheim, 2002.
[3] H. Zhao, S.V. Malhotra, Aldrichim. Acta 35 (2002) 75.
[4] K.R. Seddon, J. Chem. Technol. Biotechnol. 68 (1997) 351.
[5] C. Baudequin, J. Baudoux, J. Levillain, D. Cahard, A.C. Gaumont, J.C. Plaquevent,
Tetrahedron: Asymmetry 14 (2003) 3081–3093.
tetrabutylammonium ions are included in a H-bond network that
connect the imidazolium cations and the trifluoromethanesulfo-
nate anions. The inclusion compound of benzene into an ionic li-
quid is forming chlatrates [29] which have been characterized by
X-ray crystal analysis and the influence of water in the in ionic liq-
uids network on hydroformylation [30] have been reported.
[6] L. Leclercq, I. Suisse, F. Agbossou-Niedercorn, Chem. Commun. (2008)
311–313.
[7] C.P. Mehnert, Chem. Eur. J. 11 (2005) 50–56.
[8] H.-U. Blaser, M. Studer, Green Chem. 5 (2003) 112–117.
[9] C.E. Song, Chem. Commun. (2004) 1033–1043.
4. Conclusions
[10] S. Park, R.J. Kazlauskas, Curr. Opin. Biotechnol. 14 (2003) 432–437.
[11] U. Kragl, M. Eckstein, N. Kaftzik, Curr. Opin. Biotechnol. 13 (2002)
565–571.
[12] C.F. Poole, J. Chromatogr. A 1037 (2004) 49–82.
[13] A.M. Stalcup, B. Cabovska, J. Liq. Chromatogr. Related Technol. 27 (2004)
1443–1459.
[14] M. Antonietti, D.B. Kuang, B. Smarsly, Z. Yong, Angew. Chem. Int. Ed. 43 (2004)
4988–4992.
[15] J. Dupont, J. Braz. Chem. Soc. 15 (2004) 341–350.
[16] C.M. Gordon, J.D. Holbrey, A.R. Kennedy, K.R. Seddon, J. Mater. Chem. 8 (1998)
2627–2636.
[17] J. Dupont, P.A.Z. Suarez, R.F. de Souza, R.A. Burrow, J.P. Kintzinger, Chem. Eur. J.
6 (2000) 2377–2381.
[18] S. Saha, S. Hayashi, A. Kobayashi, H.-O. Hamaguchi, Chem. Lett. 32 (2003)
740–741.
[19] D.G. Golovanov, K.A. Lyssenko, M.Y. Antipin, Y.S. Vygoskii, E.I. Lozinskaya, A.S.
Shaplov, Cryst. Eng. Commun. 6 (2005) 53–56.
[20] A. Getsis, A.-V. Mudring, Acta Crystallogr. E61 (2005) 2945–2946.
[21] J. Dupont, P.A.Z. Suarez, Phys. Chem. Phys. Chem. 8 (2006) 2441–2452.
[22] R.W. Alder, P.R. Allen, S.J.J. Williams, Chem. Soc., Chem. Commun. (1995)
1267–1268.
In summary, the detailed structures of new co-crystals of 1-al-
kyl-3-methylimidazolium tetrabutylammonium bistrifluorome-
thanesulfonate salts have been obtained. Given the precise X-ray
crystal data, we are now able to understand the structural organi-
zation obtained previously with a co-crystal structure (see CCDC
621900). In fact, the co-crystal structures are very similar for the
three imidazolium investigated in this study. The structure of the
imidazolium cation is not essential in dictating the co-crystal
self-assembly in the solid state. Due to the current interest in the
development of new ionic liquids in organometallic catalysis, the
knowledge of the solid organization with tetrabutylammonium
salts can of great utility for the rationalization of experimental re-
sults obtained during catalysis.
Appendix A. Supplementary data
[23] T.L. Amyes, S.T. Diver, J.P. Richard, F.M. Rivas, K. Toth, J. Am. Chem. Soc. 126
(2004) 4366–4374.
[24] G.A. Jeffrey, An Introduction to Hydrogen Bonding, Oxford University Press,
Oxford, 1997.
[25] L. Leclercq, I. Suisse, G. Nowogrocki, F. Agbossou-Niedercorn, Green Chem. 9
(2007) 1097–1103.
[26] D.T. Bowron, C. Hardacre, J.D. Holbrey, S.E.J. McMath, M. Nieuwenhuyzen, A.K.
Soper, in: R.D. Rogers, K.R. Seddon (Eds.), Ionic Liquids as Green Solvents:
Progress and Prospects, ACS Symposium Series 856, American Chemical
Society, Washington, DC, 2003, pp. 151–161.
[27] P.B. Hitchcock, K.R. Seddon, T. Welton, J. Chem. Soc., Dalton Trans. (1993)
2639–2643.
[28] G.R. Desiraju (Ed.), Crystal Design: Structure and Function. Perspectives in
Supramolecular Chemistry, vol. 7, Wiley, Chichester, England, 2004, p. 6.
[29] J.D. Holbrey, W.M. Reichert, M. Nieuwenhuyzen, O. Sheppard, C. Hardacre, R.D.
Rogers, Chem. Commun. (2003) 476–477.
Crystallographic data for the structural analysis of I, II and III
have been deposited with the Cambridge Crystallographic Data
Center, CCDC Reference Nos.: CCDC 685809, 695810 and 685811,
respectively. Data can be obtained free of charge at www.ccdc.ca-
m.ac.uk/conts/retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK;
fax: +44 1223 336 033; E-mail: deposit@ccdc.cam.ac.uk).
References
[1] R.D. Rogers, K.R. Seddon, in: Ionic Liquids as Green Solvents: Progress and
Prospects, ACS Symposium Series 856, American Chemical Society,
Washington, DC, 2003.
[30] J. Dupont, S.M. Silva, R.F. de Souza, Catal. Lett. 77 (2001) 131–133.