Supercritical Fluid−Ionic Liquid Biphasic Catalysis
A R T I C L E S
both a flame ionization detector (GCFID for quantitative analyses) and
a mass selective detector (GCMS for qualitative analyses). The gas
chromatograph was interfaced with a Hewlett-Packard Chemstation for
the determination of peak areas by electronic integration. The GCMS
and GCFID methods employed a Supelco Meridian MDN-35 low
polarity, cross-linked phase comprised of a (35% phenyl)-methylpoly-
siloxane fused silica capillary column (30 m × 0.25 mm × 0.25 µm).
Rhodium analyses of recovered fractions were measured by induc-
tively coupled mass spectrometry (ICPMS) on an Agilent 7500a
instrument. The instrument was modified for direct analyses of the
organic fractions by using O2 as a makeup gas to prevent carbon
deposition on the sample and skimmer cones. Platinum cones were
used together with a self-aspirating nebulizer held at -5 °C. Samples
were diluted by 10% in a mixture of xylene and toluene (50:50) and
ion counts were referenced against calibration curves obtained from
standard solutions of [Rh(acac)(CO)2] (acacH is 2,4-dimethylpentanedi-
one) in xylene/toluene (50:50). Standard solutions were run intermit-
tently between samples to ensure that there were no drifts in instrument
response and that the rate of aspiration was constant.
ichiometric quantities. After stirring at room temperature for 24 h, the
aqueous phase was decanted and the ionic liquid washed with water
until the washings were free from chloride. The ionic liquid was then
dissolved in acetone and stirred in the presence of activated charcoal
for 24 h. The solution was filtered through diatomaceous earth and the
solvent removed in vacuo. The ionic liquid was again washed with
water and dried in vacuo to yield (2) as a colorless liquid. The imidazole
hexafluorophosphates were analyzed by 1H NMR and compared to
literature data.
(2a) 1-Butyl-2,3-dimethylimidazolium Hexafluorophosphate [BD-
MIM]PF6. 1-butyl-2,3-dimethylimidazolium hexafluorophosphate was
similarly prepared using 1,2-dimethylimidazolium chloride. Elemental
analysis calcd. for C9H17N2PF6: C 36.25 H 5.75 N 9.39; found: C
36.38 H 5.68 N 9.36. 1H NMR (300 MHz, CD2Cl2, 298 K): δ ) 0.98
(3H, t, CH3), 1.39 (2H, sext, CH2CH3), 1.81 (2H, pent, NCH2CH2),
2.60 (3H, s, NC(CH3)N), 3.80 (3H, s, NCH3), 4.05 (2H, t, NCH2), 7.18,
7.21 (2H, 2 × d, NC(H)C(H)N) ppm. 13C NMR (75.4 MHz, CD2Cl2,
298K): δ ) 144.3 (s, NCN), 122.9, 121.3 (2 × s, NCCN), 49.0 (s,
NCH2), 35.6 (s, NCH3), 32.0, 19.6 (2 × s, CH2), 13.7 (s, NC(CH3)N),
9.7 (s, CH3) ppm.
A. Syntheses. (1) 1-Alkyl-3-methylimidazolium Chloride. N-
Methyl imidazole and a 1.3-fold excess of the corresponding chloro-
alkane were refluxed at 70 °C for 3 days. After cooling, the upper
layer was discarded and the IL was washed with ethyl acetate and then
dried in vacuo at 50 °C for 5 h. The product was then dissolved in
water and stirred at room temperature in the presence of activated
charcoal for 24 h. The solution was filtered through diatomaceous earth,
and again dried in vacuo to yield (1) as a colorless liquid in all cases
except the propyl, butyl, and decyl analogues which crystallized at room
temperature as white solids. The imidazole chlorides were analyzed
(3) 1-Alkyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)-
amide. The bis(trifluoromethanesulfonyl)amide salts were similarly
prepared using N-lithio bis(trifluoromethanesulfonyl)amide for the salt
exchange reaction. Full analysis is provided for the imidazole sulfonyl
amides which have not yet been fully characterized.
(3a) 1-Octyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)-
amide [OctMIM]NTf2. Elemental analysis calcd. for C14H23O4N3S2-
F6: C 35.37 H 4.87 N 8.84; found: C 35.00 H 5.52 N 9.16. 1H NMR
(300 MHz, CD2Cl2, 298 K): δ ) 0.88 (3H, t, CH3), 1.27-1.33 (10H,
m, CH2), 1.86 (2H, pent, NCH2CH2), 3.92 (3H, s, NCH3), 4.15 (2H, t,
NCH2), 7.30, 7.31 (2H, 2 × s, NC(H)C(H)N) 8.61 (1H, s, NC(H)N)
ppm. 13C NMR (75.4 MHz, CD2Cl2, 298 K): δ ) 136.3 (s, NCN),
124.3, 122.9 (2 × d, NCCN), 120.4 (q, CF3, JCF ) 321 Hz), 50.8 (s,
NCH2), 36.8 (s, NCH3), 32.2, 30.6, 29.5, 29.3, 26.6, 23.1 (6 × s, CH2),
14.3 (s, CH3) ppm.
1
by H NMR and compared to literature data. NMR data is provided
for those compounds which have not yet been fully characterized. We
were unable to obtain accurate microanalysis for the imidazole chlorides
because of their hygroscopic nature.
(1a) 1-Propyl-3-methylimidazolium Chloride [PrMIM]Cl. 1H
NMR (300 MHz, CD2Cl2, 298 K): δ ) 0.67 (3H, t, CH3), 1.68 (2H,
sext, CH2CH3), 3.85 (3H, s, NCH3), 4.09 (2H, t, NCH2), 7.71, 7.73
(2H, 2 × t, NC(H)C(H)N), 10.29 (1H, s, NC(H)N) ppm. 13C NMR
(75.4 MHz, CD2Cl2, 298 K): δ ) 137.2 (s, NCN), 123.4, 122.1 (2 ×
s, NCCN), 50.6 (s, NCH2), 35.9 (d, NCH3), 23.3 (s, CH2), 10.2 (s,
CH3) ppm.
(3b) 1-Decyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)-
amide [DecMIM]NTf2. Elemental analysis calcd for C16H27O4N3S2F6:
C 38.17 H 5.40 N 8.35; found: C 37.87 H 5.84 N 8.88. 1H NMR (300
MHz, CD2Cl2, 298 K): δ ) 1.00 (3H, t, CH3), 1.40-1.46 (14H, m,
CH2), 1.99 (2H, pent, NCH2CH2), 4.05 (3H, s, NCH3), 4.28 (2H, t,
NCH2), 7.42, 7.43 (2H, 2 × d, NC(H)C(H)N), 8.75 (1H, s, NC(H)N)
ppm. 13C NMR (75.4 MHz, CD2Cl2, 298 K): δ ) 136.4 (s, NCN),
124.2, 122.8 (2 × s, NCCN), 120.4 (q, CF3, JCF ) 321 Hz), 50.9 (s,
NCH2), 36.9 (s, NCH3), 32.4, 30.6, 30.0, 29.9, 29.8, 29.4, 26.6, 23.1
(8 × s, CH2), 14.4 (s, CH3) ppm.
(1b) 1-Octyl-3-methylimidazolium Chloride [OctMIM]Cl. 1H
NMR (300 MHz, CD2Cl2, 298 K): δ ) 0.81 (3H, t, CH3), 1.21-1.27
(10H, m, CH2), 1.85 (2H, pent, NCH2CH2), 4.03 (3H, s, NCH3), 4.26
(2H, t, NCH2), 7.48, 7.63 (2H, 2 × t, NC(H)C(H)N), 10.64 (1H, s,
NC(H)N) ppm. 13C NMR (75.4 MHz, CD2Cl2, 298 K): δ ) 138.4 (s,
NCN), 123.9, 122.3 (2 × s, NCCN), 50.2 (s, NCH2), 36.7 (s, NCH3),
32.0, 30.6, 29.4, 29.3, 26.6, 22.9 (6 × s, CH2), 14.2 (s, CH3) ppm.
(1c) 1-Decyl-3-methylimidazolium Chloride [DecMIM]Cl. 1H
NMR (300 MHz, CD2Cl2, 298 K): δ ) 0.87 (3H, t, CH3), 1.26-1.32
(14H, m, CH2), 1.88 (2H, pent, NCH2CH2), 4.06 (3H, s, NCH3), 4.28
(2H, t, NCH2), 7.28, 7.36 (2H, 2 × t, NC(H)C(H)N), 10.39 (1H, s,
NC(H)N) ppm. 13C NMR (75.4 MHz, CD2Cl2, 298 K): δ ) 138.7 (s,
NCN), 123.7, 122.1 (2 × s, NCCN), 50.6 (s, NCH2), 37.0 (s, NCH3),
32.4, 30.8, 30.0, 29.9, 29.8, 29.6, 26.8, 23.2 (8 × s, CH2), 14.4 (s,
CH3) ppm.
(1d) 1-Butyl-2,3-dimethylimidazolium Chloride [BDMIM]Cl. 1H
NMR (300 MHz, CD2Cl2, 298 K): δ ) 0.95 (3H, t, CH3), 1.37 (2H,
sext, CH2CH3), 1.78 (2H, pent, NCH2CH2), 2.74 (3H, s, NC(CH3)N),
3.99 (3H, s, NCH3), 4.19 (2H, t, NCH2), 7.58, 7.87 (2H, 2 × d, NC-
(H)C(H)N) ppm. 13C NMR (75.4 MHz, CD2Cl2, 298 K): δ ) 144.3
(s, NCN), 123.7, 121.7 (2 × s, NCCN), 49.1 (s, NCH2), 36.2 (s, NCH3),
32.3, 20.1 (2 × s, CH2), 13.8 (s, NC(CH3)N), 10.8 (s, CH3) ppm.
(2) 1-Alkyl-3-methylimidazolium Hexafluorophosphate. Prepara-
tions of the imidazolium PF6 salts were carried out as follows: A
solution of sodium hexafluorophosphate in water was added to an
aqueous solution of the corresponding imidazolium chloride in sto-
(4) 1-Propyl-3-methylimidazolium Diphenyl(3-sulfonatophenyl)-
phosphine ([PrMIM][TPPMS]). [PrMIM]Cl (1a) (14.31 g, 89.1 mmol)
was added dropwise to a rapidly stirred solution of sodium diphenyl-
(3-sulfonatophenyl)phosphine dihydrate33 (25.74 g, 64.3 mmol) in THF,
resulting in immediate formation of a fine white precipitate. The solution
was stirred at room temperature for a further 24 h, filtered through
diatomaceous earth, and the solvent removed in vacuo. The resulting
residue was taken up into dichloromethane, again filtered, and the
solvent removed in vacuo. The crude product, which contains an excess
of the imidazolium chloride, was left at -10 °C to afford (4) as colorless
rhomboidal crystals (15.28 g, 32.8 mmol, 50.9%) mpt 88-90 °C.
Elemental analysis calcd for C25H27O3N2PS: C 64.36 H 5.83 N 6.00;
found: C 64.42 H 5.64 N 6.14. IR (CsI): ν˜ ) 3156 (w), 3097 (m),
3047 (m), 2969 (w), 2883 (w), 1580 (m), 1479 (m), 1461 (w), 1434
(m), 1394 (w), 1309 (w), 1202 (s, br), 1139 (m), 1091 (m), 1070 (w),
1031 (s), 995 (w), 890 (w), 796 (m), 784 (m), 749 (s), 698 (s), 673
1
(m), 617 (s), 595 (w), 555 (w) cm-1. H NMR (300 MHz, CD2Cl2,
298 K): δ ) 0.99 (3H, t, CH3), 1.92 (2H, sext, CH2CH3), 3.97 (3H, s,
(33) Joo´, F.; Kova´cs, J.; Katho´, A.; Be´nyei, A. C.; Decuir, T.; Dahrensbourg,
D. J. 1998, 32, 2.
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J. AM. CHEM. SOC. VOL. 125, NO. 50, 2003 15579