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Y.-S. Choi et al. / Applied Catalysis A: General 404 (2011) 87–92
[BMIm][TeO2(OCH3)] was produced as a viscose liquid. Any Te-
containing product was not observed on the basis of FAB-Mass
spectrometric analysis, indicating that TeO2 is not involved in the
reaction. In fact, [BMIm][HCO3] was obtained from the reaction of
[BMIm]Cl with K2CO3 in methanol even in the absence of TeO2.
Herein, we report on the synthesis of imidazolium-based ILs
with a bicarbonate anion and their catalytic activities for the car-
bonylation of amines to produce formamides as well as on the
activities of various ILs bearing an anion other than bicarbonate.
The mechanistic investigation of the carbonylation of amines is also
discussed on the basis of experimental and computational results.
DMSO, 25 ◦C): ı = 0.96 (t, 3H, CH3); 3.89 (s, 3H, NCH3); 4.25 (t, 2H,
NCH2); 7.43, 7.48 (d, 2H, CHN).
2.2.3. Synthesis of 1,3-dimethylimidazolium hydrogen carbonate
([DMIm][HCO3])
[DMIm][HCO3]
was
prepared
by
reacting
1,3-
dimethylimidazolium chloride ([DMIm]Cl) with K2CO3 in a similar
manner to that employed for the synthesis of [BMIm][HCO3]
(Yield: 85%).
Anal. Calcd for C6H10N2O3: C, 45.57; H, 6.37; N, 17.71; O, 30.35.
Found: C, 45.88; H, 6.09; N, 17.92; O, 30.29. 1H NMR (400 MHz,
CDCl3, 25 ◦C): ı = 3.92 (s, 6H, NCH3); 7.69 (d, 2H, CHN); 9.06 (s, H,
NCHN).
2. Experimental
2.1. General
2.2.4. Synthesis of 1-butyl-2,3-dimethylimidazolium hydrogen
carbonate [BDMIm][HCO3]
All of the chemicals used for the carbonylation reac-
tions and for the preparation of ILs were purchased from
Aldrich Chemical Co. and used as received. Solvents used
were all reagent grades and were distilled from appropri-
[BDMIm][HCO3] was prepared by reacting [BDMIm]Cl with
K2CO3 in a similar manner to that employed for the synthesis of
[BMIm][HCO3] (Yield: 87%).
Anal. Calcd for C10H18N2O3: C, 56.06; H, 8.47; N, 13.07; O, 22.40.
Found: C, 56.22; H, 8.52; N, 13.01; O, 22.46. 1H NMR (400 MHz,
CDCl3, 25 ◦C): ı = 0.96 (t, 3H, CH3); 1.38, 1.80 (m, 4H, CH2); 2.60 (s,
3H, CH3); 4.02 (s, 3H, NCH3); 4.22 (t, 2H, NCH2); 7.54, 7.80 (d, 2H,
NCH).
ate drying agents under
a nitrogen atmosphere prior to
use [25]. Carbon monoxide (99% pure) was obtained from
Air Liquide Korea Co. ILs, 1-butyl-3-methylimidazolium
chloride ([BMIm]Cl), 1-butyl-3-methylimidazolium acetate
([BMIm][AcO]),
([BDMIm][AcO]), 1-butyl-3-methylimidazolium dimethylphos-
phate ([BMIm][Me2PO4]), 1-butyl-3-methylimidazolium
([BMIm][MePHO3]), 1-butyl-3-
methylsulfate ([BMIm][MeSO4]), and
1-butyl-2,3-dimethylimidazolium
acetate
methylphosphite
Single crystals suitable for X-ray structural analysis were
methylimidazolium
obtained by dissolving [BDMIm][HCO3] in
a mixed solvent
1-butyl-3-methylimidazolium methylsulfonate ([BMIm][MeSO3]),
were prepared according to the literature procedures [3,26–29].
Gas chromatographic analysis of liquid samples for the car-
bonylation experiments were made on an Agilent 6890 gas
chromatograph equipped with a FID and a DB-5 capillary column.
Characterization of products was made using a 400 MHz Bruker
NMR spectrometer and an Agilent 6890-5973 MSD GC–mass
spectrometer equipped with a HP-MS capillary column.
(acetone/CH2Cl2 = 6/4) and stored at 0 ◦C in a refrigerator for
several days. Single crystal with appropriate dimensions was
mounted on a glass fiber in random orientation. X-ray data for
[BDMIm][HCO3] were collected on a Bruker SMART APEXII diffrac-
tometer equipped with graphite monochromated MoK␣ radiation
˚
(ꢀ = 0.71073 A). Preliminary orientation matrix and cell parameters
were determined from three sets of ω scans at different starting
angles. Data frames were obtained at scan intervals of 0.5◦ with an
exposure time of 10 s per frame. The reflection data were corrected
for Lorentz and polarization factors. Absorption corrections were
carried out using SADABS. The structures were solved by direct
methods and refined by full-matrix least-squares analysis using
anisotropic thermal parameters for non-hydrogen atoms with
the SHELXTL program. All hydrogen atoms were calculated at
idealized positions and refined with the riding models. Crystal data
of [BDMIm][HCO3]: Mw = 213.26, monoclinic, space group P21/c,
2.2. Synthesis of ILs bearing a hydrogen carbonate anion
Four imidazolium-based ILs with a hydrogen carbonate anion
were synthesized by reacting dialkylimidazolium chloride or tri-
alkylimidazolium chloride with K2CO3 in CH3OH.
2.2.1. Synthesis of 1-butyl-3-methylimidazolium hydrogen
carbonate ([BMIm][HCO3])
◦
˚
,
ꢁ = 0.093 mm−1
,
In a 100 mL one-neck flask, [BMIm]Cl (17.4 g, 0.1 mol) was
reacted with K2CO3 (13.8 g, 0.1 mol) in CH3OH (20 mL) for 6 h at
room temperature. After the completion of the reaction, the solid
precipitates were removed by filtration and the remaining solution
was dried in vacuum to produce [BMIm][HCO3] as a viscous pale
yellow liquid (Yield: 86%).
T = 100 K, 16,660 reflections collected, 2000 unique (Rint = 0.0388),
R1 = 0.0604, wR2 = 0.1408 [I > 2ꢂ(I)] and for all reflections,
and relevant structure refinement parameters are listed in
Table S1 in Supplementary data.
Anal. Calcd for C9H16N2O3: C, 53.98; H, 8.05; N, 13.99; O, 23.97.
Found: C, 54.12; H, 8.41; N, 13.81; O, 24.10. 1H NMR (400 MHz,
CDCl3, 25 ◦C): ı = 0.97 (t, 3H, CH3); 1.37, 1.87 (m, 4H, CH2); 4.03 (s,
3H, NCH3); 4.27 (t, 2H, NCH2); 7.42, 7.49 (d, 2H, CHN).
2.4. Catalytic carbonylation reaction
Carbonylation reactions were conducted in a 100 mL stainless
steel reactor equipped with a magnetic stirrer and an electrical
heater. The reactor was first charged with requisite amounts of an
amine, solvent, an appropriate IL, and toluene (2 mL) as an inter-
nal standard. The reactor was pressurized with carbon monoxide
at 2 MPa and then heated to a specified temperature. The pressure
inside the reactor was maintained at 4 MPa throughout the reac-
tion using a gas reservoir equipped with a high pressure regulator
and a pressure transducer. After the reaction was completed, the
reactor was cooled to room temperature and the reaction mixture
was analyzed by means of GC and GC–MS.
2.2.2. Synthesis of 1-ethyl-3-methylimidazolium hydrogen
carbonate ([EMIm][HCO3])
[EMIm][HCO3] was prepared by reacting 1-ethyl-3-
methylimidazolium chloride ([EMIm]Cl) with K2CO3 in a similar
manner to that employed for the synthesis of [BMIm][HCO3]
(Yield: 84%).
Anal. Calcd for C7H12N2O3: C, 48.83; H, 7.02; N, 16.27; O, 27.88.
Found: C, 49.24; H, 7.27; N, 16.11; O, 27.59. 1H NMR (400 MHz,