Synthesis and structural characterization of 1-butyl-2,3-dimethylimid- azolium bromide and iodide

Article abstract of DOI:10.1515/znb-2007-0618

1-Butyl-2,3-dimethylimidazolium bromide {(bdmim)Br} (1) and iodide {(bdmim)I} (2) were prepared conveniently by the reaction of 1,2-dimethylimidazole and the corresponding 1-halobutane. The compounds were characterized by ¹H and ¹³C{¹H} NMR spectroscopy as well as by X-ray single crystal crystallography. 1 crystallizes in the monoclinic crystal system, space group P2₁/n, with Z = 4, and unit cell dimensions a = 8.588(2), b = 11.789(1), c = 10.737(2) ?, β= 91.62(3)°. Compound 2 crystallizes in the monoclinic crystal system, space group P2₁/c, with Z = 8, and unit cell dimensions a = 10.821(2), b = 14.221(3), c = 15.079(2) ?, β= 90.01(3)°. The lattices of the salts are built up of 1-butyl-2,3-dimethylimidazolium cations and halide anions. The cations of 1 form a double layer with the imidazolium rings stacked together due to n interactions. The Br^- anions lie approximately in the plane of the imidazolium ring, and the closest interionic Br?H contacts span a range of 2.733(1) - 2.903(1) ?. Compound 2 shows no π stacking interactions. The closest interionic I?H contacts are 2.914(1)-3.196(1)?.

Full text of DOI:10.1515/znb-2007-0618

868
Note
Synthesis and Structural Character-
ization of 1-Butyl-2,3-dimethylimid-
azolium Bromide and Iodide
Johanna Kutuniva, Raija Oilunkaniemi, Risto S.
Laitinen, Janne Asikkala, Johanna K a¨ rkk a¨ inen,
and Marja K. Lajunen
Department of Chemistry, P.O. Box 3000, FI-90014
University of Oulu, Finland
Fig. 1. The crystal structure of (bdmim)Br (1) indicating
the numbering of atoms (displacement ellipsoids at the 50 %
probability level).
Reprint requests to Prof. Risto Laitinen.
Fax: +358-8-553-1608. E-mail: risto.laitinen@oulu.fi
Z. Naturforsch. 2007, 62b, 868 – 870;
received January 22, 2007
tal structures have been reported for (bdmim)Cl [3],
II
III
(
(
bdmim)[HSO ] [3], (bdmim) [Fe Cl ][Fe Cl ] [3],
4 4 4 4 2
1
-Butyl-2,3-dimethylimidazolium bromide {(bdmim)Br}
bdmim)[BF ] [4], (bdmim)[PF ] [4], [bdmim][SbF ]
4
6
6
(
1) and iodide {(bdmim)I} (2) were prepared conveniently
by the reaction of 1,2-dimethylimidazole and the correspond- [4], and (bdmim) [CH6B11Cl6] [5].
1
ing 1-halobutane. The compounds were characterized by H
13
1
and C{ H} NMR spectroscopy as well as by X-ray sin- Experimental Section
gle crystal crystallography. 1 crystallizes in the monoclinic
The NMR spectra were recorded on a Bruker DPX200
crystal system, space group P2 /n, with Z = 4, and unit cell
1
1
˚
spectrometer operating at 200.13 and 50.32 MHz for H and
dimensions a = 8.588(2), b = 11.789(1), c = 10.737(2) A, β =
◦
13
1
9
1.62(3) . Compound 2 crystallizes in the monoclinic crystal
C{ H}, respectively. Tetramethylsilane (TMS) was used as
system, space group P2 /c, with Z = 8, and unit cell dimen-
1
an internal standard. All spectra were recorded in CDCl that
3
served as an internal H lock. Chemical shifts (ppm) of H
and C are reported relative to TMS.
˚
sions a = 10.821(2), b = 14.221(3), c = 15.079(2) A, β =
2
1
◦
9
0.01(3) . The lattices of the salts are built up of 1-butyl-2,3-
13
dimethylimidazolium cations and halide anions. The cations
of 1 form a double layer with the imidazolium rings stacked
−
together due to π interactions. The Br anions lie approx- Synthesis
imately in the plane of the imidazolium ring, and the clos-
(
bdmim)Br (1): 19.8 mL (21 mmol) of 1,2-dimethylimid-
est interionic Br···H contacts span a range of 2.733(1) –
˚
.903(1) A. Compound 2 shows no π stacking interac-
azole and 36 mL (33 mmol) of 1-bromobutane were mixed
2
◦
tions. The closest interionic I···H contacts are 2.914(1) – at 88 C over a period of 72 h under dinitrogen. The prod-
˚
3
.196(1) A.
uct was washed twice with ethyl acetate (15 mL) and then
◦
crystallized at 5 C from an ethyl acetate/acetonitrile mix-
Key words: 1-Butyl-2,3-dimethylimidazolium Bromide,
ture (1 : 1). The crystals obtained were recrystallized from
1-Butyl-2,3-dimethylimidazolium Iodide,
CH CN, washed with small amounts of cold EtOAc, and
3
X-Ray Crystal Structure
dried. Yield: 42 g (86 %). – Anal. calcd. for C H N Br:
9
17
2
C 46.36, H 7.35, N 12.02; found: C 46.37, H 7.17, N 11.98. –
1
H NMR: δ = 0.95 (t, J = 7.0 Hz, 3H, 7-CH ), 1.39 (m, J =
3
7
.1 Hz, 2H, 6-CH ), 1.82 (m, J = 7.6 Hz, 2H, 5-CH ), 2.84
2
2
Introduction
(
s, 3H, 8-CH ), 4.05 (s, 3H, 9-CH ), 4.24 (t, J = 7.5 Hz,
3 3
2
2
1
1
H, 4-CH ), 7.56 (d, J = 2.1 Hz, 1H, 3-CH), 7.78 (d, J =
2
Ionic liquids, especially those based on imidazolium
cations, have seen an intense research activity and
have attracted interest because of their use in syn-
thetic applications [1, 2]. However, the solid state
structural information of the ionic liquids based on
13
.1 Hz, 1H, 2-CH). – C NMR: δ = 10.75 (C8), 13.37 (C7),
9.55 (C6), 31.83 (C5), 36.00 (C9), 48.63 (C4), 121.30 (C2),
23.00 (C3), 143.74 (C1); for numbering of atoms, see Fig. 1.
(
bdmim)I (2): Compound 2 was synthesized with the
same procedure as 1 using 19.4 mL (21 mmol) of 1,2-
dimethylimidazole and 33 mL (29 mmol) of 1-iodobutane.
The reaction time was 20 h. Yield: 49 g (85 %). – Anal. calcd.
1
,2,3-trialkylimidazolium cations is still rather scat-
tered. In this paper, we report the crystal structures of
two 1-butyl-2,3-dimethylimidazolium (bdmim) salts, for C H N I: C 38.59, H 6.12, N 10.00; found: C 38.55,
namely of (bdmim)Br (1) and (bdmim)I (2). Crys- H 6.16, N 9.91. – H NMR: δ = 0.98 (t, J = 7.3 Hz,
9
17 2
1
0932–0776 / 07 / 0600–0868 $ 06.00 © 2007 Verlag der Zeitschrift f u¨ r Naturforschung, T u¨ bingen · http://znaturforsch.com
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Note
869
Table 1. Crystal data and details of the crystal structure de-
terminations of 1 and 2.
1
2
Empirical formula
Relative molecular mass
Crystal system
C9H17N2Br
233.16
monoclinic
P21/n
C9H17N2I
280.15
monoclinic
P21/c
Space group
˚
a [A]
8.588(2)
11.789(2)
10.737(2)
91.62(3)
1086.7(4)
4
10.821(2)
14.221(3)
15.079(3)
90.01(3)
2320.5(8)
8
˚
b [A]
˚
c [A]
β [deg]
˚
3
V [A ]
Z
F(000) [e]
480
1.425
3.737
1104
1.604
2.718
Dc [g cm−3]
µ (MoKα ) [mm−1]
Crystal size [mm]
T [K]
0.20×0.15×0.15 0.15×0.12×0.10
Fig. 2. The crystal structure of (bdmim)I (2) indicating the
numbering of atoms (displacement ellipsoids at the 50 %
probability level).
120(2)
2.80 – 26.00
7632
120(2)
3.29 – 25.00
4057
4057
3321
θ Range [deg]
Reflections collected
Unique reflections
Observed reflectionsa
Parameters / restraints
Rint
2115
1877
113/0
0.0827
0.0399
0.0994
0.0465
0.1046
1.1061
0.484, −0.410
3
H, 7-CH ), 1.42 (m, J = 7.6 Hz, 2H, 6-CH ), 1.82 (m,
3
2
J = 7.7 Hz, 2H, 5-CH ), 2.84 (s, 3H, 8-CH ), 4.01 (s, 3H,
2
3
218/0
9
-CH ), 4.20 (t, J = 7.5 Hz, 2H, 4-CH ), 7.46 (d, J = 2.1 Hz,
3
2
0.0830
0.0506
0.1482
0.0617
0.1542
1.401
13
1H, 3-CH), 7.62 (d, J = 2.1 Hz, 1H, 2-CH). – C NMR:
a,b
R1
δ = 11.44 (C8), 13.39 (C7), 19.62 (C6), 31.77 (C5), 36.52
a,b
wR2
R1 (all data)
b
(
C9), 48.89 (C4), 121.24 (C2), 122.86 (C3), 143.85 (C1); for
b
numbering of atoms, see Fig. 2.
wR2 (all data)
GOOF
Max. and min. heights in
final diff. synthesis [e A
0.816, −0.905
X-Ray crystallography
˚
−3
]
Diffraction data for 1 and 2 were collected on a Nonius
a
b
2
I ≥ 2σ(I); R1 = [ΣꢀFo| − |Fcꢀ]/[Σ|Fo|], wR2 = {[Σw(Fo
−
1
/2
Kappa CCD diffractometer using graphite monochromated
2
2
2 2
Fc ) / [Σw(Fo ) ]}
.
˚
MoKα radiation (λ = 0.71073 A). Crystal data and details of
the structure determinations are given in Table 1. The struc- pared to the values of the analogous chloride salt [3] which
tures were solved by Direct Methods using SIR-92 [6] and is in fact isomorphic with 1. The asymmetric unit of 1 con-
refined using SHELXL-97 [7]. After full-matrix least-squares sists of one cation and anion whereas the asymmetric unit of
refinement of the non-hydrogen atoms with anisotropic ther- 2 contains two independent cations and anions. The differ-
mal parameters, the hydrogen atoms were placed in calcu- ences in the packing of 1 and 2 are shown in Figs. 3(a) and
˚
3(b), respectively.
lated positions (C–H = 0.95, 0.99, and 0.98 A in the case
of arene hydrogen atoms, methylene hydrogen atoms, and
In the crystals of 1 the cations form a double layer with
methyl hydrogen atoms, respectively). In the final refine- the imidazolium rings stacked together due to π interac-
ment the calculated hydrogen atoms were riding with the car- tions. The closest distance between the centroids of two im-
bon atoms to which they are bonded. The isotropic thermal idazolium rings (the second ring is generated by the sym-
parameters of the hydrogen atoms were fixed at 1.2 (arene metry operation 1 − x, 1 − y, 1 − z) is 3.445(1) A˚ , which
and methylene hydrogens) or 1.5 (methyl hydrogens) times is similar to that described recently for the chloride ana-
−
that of the corresponding carbon atom. The scattering fac- logue [3]. The Br anions lie approximately in the plane of
tors for the neutral atoms were those incorporated in the pro- the imidazolium ring. The closest interionic Br···H contacts
grams.
in this plane span a range of 2.733(1) – 2.903(1) A˚ [Br···C
˚
3
.653(3) – 3.827(3) A].
Results and Discussion
The packing of the compounds in crystals of 2 dif-
(
Bdmim)X [X = Br (1), I (2)] can conveniently be synthe- fers from that observed in 1 and in its chloride ana-
sized by the reaction of 1,2-dimethylimidazole and the corre- logue by showing no π stacking interactions between the
sponding 1-halobutane. The crystal structures of 1 and 2 to- imidazolium rings [see Fig. 3(b)]. The closest interionic
˚
gether with the numbering scheme of the atoms are shown in I···H contacts involving I(1) are 3.136(1) – 3.196(1) A
˚
Figs. 1 and 2, respectively. The bond lengths and angles are [I(1)···C 3.874(7) – 3.927(8) A], and those involving I(2) are
˚
˚
within the normal ranges (see Table 2) and they can be com- 2.914(1) – 3.118(1) A [I(2)···C 3.884(1) – 4.073(1) A].
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870
Note
˚
Table 2. Selected bond lengths (A) and angles (deg) of 1 and 2.
1
2
1
2
n = 1
n = 2
n = 1
n = 2
N(1)–C(1) 1.332(4) N(n1)–C(n1) 1.33(1)
N(1)–C(3) 1.388(4) N(n1)–C(n3) 1.38(1)
1.37(1) N(1)–C(1)–N(2) 108.2(3) N(n1)–C(n1)–N(n2) 108.7(7) 107.1(7)
1.37(1) N(1)–C(1)–C(8) 127.2(3) N(n1)–C(n1)–C(n8) 127.2(7) 126.7(8)
N(1)–C(4) 1.475(4) N(n1)–C(n4) 1.457(9) 1.50(1) N(1)–C(4)–C(5) 111.4(3) N(n1)–C(n4)–C(n5) 112.6(7) 110.9(6)
N(2)–C(1) 1.336(4) N(n2)–C(n1) 1.34(1)
N(2)–C(2) 1.387(4) N(n2)–C(n2) 1.37(1)
N(2)–C(9) 1.465(4) N(n2)–C(n9) 1.43(1)
C(1)–C(8) 1.484(4) C(n1)–C(n8) 1.49(1)
C(2)–C(3) 1.335(4) C(n2)–C(n3) 1.36(1)
C(4)–C(5) 1.521(4) C(n4)–C(n5) 1.53(1)
C(5)–C(6) 1.523(4) C(n5)–C(n6) 1.51(1)
C(6)–C(7) 1.504(5) C(n6)–C(n7) 1.49(1)
1.32(1) N(2)–C(1)–C(8) 124.5(3) N(n2)–C(n1)–C(n8) 124.6(8) 126.0(8)
1.36(1) C(1)–N(1)–C(3) 108.4(3) C(n1)–N(n1)–C(n3) 108.9(7) 106.9(7)
1.51(1) C(1)–N(1)–C(4) 126.2(3) C(n1)–N(n1)–C(n4) 127.7(7) 128.0(6)
1.49(1) C(1)–N(2)–C(2) 108.7(3) C(n1)–N(n2)–C(n2) 108.6(7) 109.8(7)
1.31(1) C(1)–N(2)–C(9) 125.2(2) C(n1)–N(n2)–C(n9) 124.9(7) 125.4(8)
1.50(1) C(2)–N(2)–C(9) 126.0(3) C(n2)–N(n2)–C(n9) 126.5(7) 124.2(7)
1.55(1) C(2)–C(3)–N(1) 107.6(3) C(n2)–C(n3)–N(n1) 106.5(7) 108.7(7)
1.55(1) C(3)–N(1)–C(4) 125.3(3) C(n3)–N(n1)–C(n4) 123.3(6) 125.1(6)
C(3)–C(2)–N(2) 107.1(3) C(n3)–C(n2)–N(n2) 107.7(7) 107.5(7)
C(4)–C(5)–C(6) 113.4(3) C(n4)–C(n5)–C(n6) 113.6(7) 108.7(6)
C(5)–C(6)–C(7) 112.2(3) C(n5)–C(n6)–C(n7) 114.9(7) 111.6(6)
(a)
b
a
c
Fig. 3. (a) The cation-anion interactions in 1. The cations and anions form layers showing π stacking interactions. The anions
lie approximately in the plane of the imidazolium rings. (b) The cation-anion interactions in 2. No π stacking interactions are
discernible.
Supplementary material
Acknowledgement
CCDC 634383 and 634384 contain the supplementary
crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data request/cif.
Financial support from the Academy of Finland and the
Tauno T o¨ nning Foundation is gratefully acknowledged.
[
1] J. G. Huddleston, A. E. Visser, W. M. Reichert, H. D.
[5] A. S. Larsen, J. D. Holbrey, F. S. Tham, C. A. Reed,
J. Am. Chem. Soc. 2000, 122, 7264 – 7272.
[6] A. Altomare, G. Cascarano, C. Giacovazzo, A. Gualar-
di, J. Appl. Cryst. 1993, 26, 343 – 350.
[7] G. M. Sheldrick, SHELXL-97, Program for the Refine-
ment of Crystal Structures, University of G o¨ ttingen,
G o¨ ttingen (Germany) 1997.
Willauer, G. A. Broker, R. D. Rogers, Green Chem.
2001, 3, 156 – 164.
[
[
2] T. Welton, Coord. Chem. Rev. 2004, 248, 2459 – 2477.
3] P. K o¨ lle, R. Dronskowski, Inorg. Chem. 2004, 43,
2
803 – 2809.
4] P. K o¨ lle, R. Dronskowski, Eur. J. Inorg. Chem. 2004,
313 – 2320.
[
2
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