K. Wang, X. Liu, B. Liu et al.
Journal of Organometallic Chemistry 948 (2021) 121931
3.65 (m, 67H), 3.38 (s, 3H), 3.03 (s, 12H); 13CNMR (126 MHz,
CDCl3) δC = 162.0, 71.9, 71.4, 70.6, 59.0, 44.5, 40.0. Elemental Anal-
ysis C42H80O20N3Rh1: Calcd. C 48.04, H 7.67, N 4.00 %. Found C
48.21, H 7.85, N 4.13 %.
2.2.3. Preparation of [Ph(EO)8TMG][Rh(CO)4] and its characterization
A 100 mL schlenk flask was charged with K[Rh(CO)4] (2.54 g,
10 mmol), [Ph(EO)8TMG][CH3SO3] (6.39 g, 10 mmol) and 25 mL
of degassed THF under Ar atmosphere. The mixture was stirred at
25°C for 2 h and the reaction solution was filtered after the com-
pletion of the reaction. Then, the filtrate was evaporated under
reduced pressure to obtain dark red-brown viscous ionic liquids
with the yield of 83.2%. 1HNMR (500 MHz, CDCl3) δH = 7.25 (d,
J = 8.8 Hz, 3H), 6.82 (d, J = 8.8 Hz, 2H), 4.11 (t, J = 4.7Hz, 2H), 3.84
(t, J = 5.1 Hz, 2H), 3.76-3.64 (m, 34H), 2.97 (s, 12H); 13CNMR (126
MHz, CDCl3) δC = 162.2, 156.3, 142.4, 127.0, 113.7, 71.3, 70.5, 69.8,
44.4, 39.8. Elemental Analysis C31H53O12N3Rh1: Calcd. C 48.81, H
7.65, N 5.50 %. Found C 48.97, H 7.87, N 5.63 %.
Fig. 1. Solubility of Rh(CO)4-PolyGILs in solvents of different polarity.
2.2.4. Preparation of [Ph(EO)16 TMG][Rh(CO)4] and its characterization
A 100 mL schlenk flask was charged with K[Rh(CO)4] (2.54 g,
10 mmol), [Ph(EO)16 TMG][CH3SO3] (9.91 g, 10 mmol) and 25 mL
of degassed THF under Ar atmosphere. The mixture was stirred at
25°C for 2 h and the reaction solution was filtered after the com-
pletion of the reaction. Then, the filtrate was evaporation under
reduced pressure to obtain dark red-brown viscous ionic liquids
with the yield of 81.5%. 1HNMR (500 MHz, CDCl3) δH = 7.26 (d,
J = 8.8 Hz, 3H), 6.82 (d, J = 8.8 Hz, 2H), 4.11 (t, J = 4.8Hz, 2H), 3.85
(t, J = 5.0 Hz, 2H), 3.68-3.64 (m, 66H), 2.97 (s, 12H); 13CNMR (126
MHz, CDCl3) δC = 163.3, 156.4, 142.4, 127.0, 113.8,71.4, 70.6, 69.8,
44.5, 39.8. Elemental Analysis C47H85O20N3Rh1: Calcd. C 50.62, H
7.68, N 3.76 %. Found C 50.83, H 7.82, N 3.85 %.
[α]tD
[α]tDstandard
ee =
× 100%
3. Results and discussion
3.1. Solubility of Rh(CO)4-PolyGILs
Whether the Rh(CO)4-PolyGILs would form homogeneous or
biphasic system was dependent on the solubility of Rh(CO)4-
PolyGILs in various solvents. Fig.
1 showed the solubility of
Rh(CO)4-PolyGILs in various solvents of different polarity. Complete
solubility of the PolyGILs was observed in polar solvents (H2O,
MeOH, EtOH and i-PrOH) and some weakly polar solvents (CHCl3
and CH2Cl2), but in the non-polar solvents (n-C7H16 ) they were
immiscible indicating the presence of ionic bond in the PolyGILs.
Identical solubility behavior was observed for the Rh(CO)4-PolyGIL.
This indicated the possibility of using polar solvent as the reaction
medium, and non-polar solvent as the extraction medium. These
results laid significant foundation for constructing the HCBS sys-
tem.
2.3. Asymmetric hydroformylation of styrene catalyzed by
[Me(EO)16 TMG][Rh[(R)-BINAP](CO)2]
Under Ar atmosphere, [Me(EO)16 TMG][Rh(CO)4], (R)-BINAP,
styrene and solvent were charged into the autoclave. The auto-
clave was sealed and replaced with Ar and CO for 3 times in the
same sequence. Then, the autoclave was pressurized with syngas
(CO:H2 = 1:1) and was maintained at the specified temperature for
4 h. Then, the reactor was cooled to room temperature. After re-
leasing the gas, certain amount of the product was taken out for
GC analysis and spectrophotometric determination (conversion of
styrene, yield, ee). Next, n-heptane was added to the autoclave to
extract the alkene and the aldehyde, and the upper heptane layer
was decanted, after which fresh styrene was added to the catalyst
present in the lower layer for the next cycle.
3.2. Thermal stability of Rh(CO)4-PolyGILs
Taking [Me(EO)16 TMG][Rh(CO)4] as an example, the thermal
stability of Rh(CO)4-PolyGILs were studied and the result was
shown in Fig. 2. The temperature range used for the analysis was
from room temperature to 600°C. The first weight loss of about
8% occurred in the temperature range of 35-150°C, due to evap-
oration of the water confined in the Rh(CO)4-PolyGILs and ther-
mal dissociation of carbonyl compounds. Under the low CO partial
pressure and high temperature conditions, the carbonyl rhodium
may be decomposed to release CO. The major weight loss of about
80% occurred between 150-360°C and could be attributed to the
thermal decomposition of the polyether long chains of Rh(CO)4-
PolyGILs. This result indicated an initial decomposition tempera-
ture of 150°C for [Me(EO)16 TMG][Rh(CO)4]. Since the reaction tem-
perature of AHF is generally below 100°C, Rh(CO)4-PolyGILs met
the requirements of AHF.
2.4. The determination of conversion, yield and ee
Conversion = (converted
styrene)/(unconverted
styrene +
converted styrene) × 100%, the conversion rate of styrene was
determined on GC with a SE-30 MS capillary column.
2-phenylpropionaldehyde
selectivity = 2-phenylpropional-
dehyde/(benzenepropanal + 2-phenylpropionaldehyde).
Yield = Conversion × 2-phenylpropionaldehyde selectivity.
l/b is the ratio of benzenepropanal to 2-phenylpropionaldehyde.
The ee of (S)-2-phenylpropionaldehyde was determined by au-
tomatic polarizer. The standard conditions of the product were as
follows: solvent chloroform, temperature 25°C, and standard value
was +192.
3.3. Infrared study of Rh(CO)4-PolyGILs
FT-IR spectrum of (A) [Me(EO)8TMG][CH3SO3], (B) K[Rh(CO)4]
in THF solution and (C) [Me(EO)8TMG][Rh(CO)4] were depicted
in Fig. 3. The absorption band at around 2877 cm−1 could be
The formula of ee:
α
[α]tD=
L · C
3