a-Adduct [triethyl(1-phenylethyl)silane]. 1H NMR (CDCl3,
400 MHz) d (ppm): 0.69 (q, J = 8 Hz, 6H, Si–CH2), 0.97
(t, J = 8 Hz, 9H, CH3), 1.21 (d, J = 9 Hz, 3H, CH3), 3.58
(q, J = 8 Hz, 6H, O–CH2), 7.15–7.23 (m, 5H, Ph).
1H and 13C NMR spectra were measured using a Bruker
AV400 MHz spectrometer operating at 400.13 and 100.62 MHz,
respectively. Chemical shifts for 1H and 13C NMR spectra
were recorded (in ppm) relative to the residual proton of
1
CDCl3. H NMR d 7.24; 13C NMR d 77.0.
Unsaturated adduct [triethyl(styryl)silane]. 1H NMR
(CDCl3, 400 MHz) d (ppm): 0.93 (t, J = 9 Hz, 9H, CH3),
1.33 (q, J = 8 Hz, 6H, Si–CH2), 6.47 (d, J = 12 Hz, 1H,
SiCH), 6.98 (d, J = 12 Hz, 1H, CHPh), 7.16–7.34 (m, 5H, Ph).
3.2 Hydrosilylation of alkylene with triethoxysilane
A typical hydrosilylation reaction procedure was as follows:
IL, catalyst, styrene and triethoxysilane were charged into a
100 cm3 stainless steel autoclave reactor (high pressure chemical
reactor; HPR-series, Supercritical Fluid Technologies, Inc.).
A high pressure pump was used to introduce CO2 into the
reactor, which was maintained at the desired temperature. The
reaction in CO2 took place with stirring (about 500 rpm) for 2 h.
After the reaction, the reactor was cooled to room temperature
and the pressure released slowly. The product phase was
separated from the catalyst by scCO2, and the conversion of
alkene and selectivity determined by GC analysis. The catalyst
was recharged with fresh alkene and silane, and the crude
product purified by distillation. All data in the tables are the
average values of three experiments (Scheme 1).
3.3 Synthesis of the rhodium N-heterocyclic carbine complex
Synthesis of 1-methyl-3-butylimidazolium-2-carboxylate. A
mixture of 10.23 g (0.036 mol) of 1-methyl-3-butylimidazolium
hexafluorophosphate, 4.03 g (0.036 mol) of KtOBu and 30 mL
of dry dimethylformamide was placed into a stainless steel
autoclave fitted with a stirrer (Scheme 2). The autoclave was
closed and pressurised by the introduction of CO2 to 80 bars
(1 bar = 0.1 MPa). The mixture was heated to 100 1C and kept
at that temperature for 12 h. The reaction was stopped, the
reactor cooled and the CO2 released. The reaction mixture was
filtered and transferred into a 100 mL tube at room tempera-
ture. After evaporation of the solvent under reduced pressure
and recrystallization from CH3CN, 4.59 g (70% yield) of a
light yellow solid was obtained and characterized as 1-methyl-
3-butylimidazolium-2-carboxylate. 1H NMR (CDCl3, 400 MHz)
d (ppm): 0.96 (t, J = 8 Hz, 3H, CH3), 1.39 (m, 2H, CH2), 1.90
(m, 2H, CH2), 4.16 (s, 3H, N–CH3), 4.34 (t, J = 8 Hz, 2H,
N–CH2), 7.59 (br s, 1H, Im), 7.74 (br s, 1H, Im)
Analysis of the products of the hydrosilylation reaction of
styrene with triethoxysilane21
b-Adduct [triethoxy(phenylethyl)silane]. 1H NMR (CDCl3,
400 MHz) d (ppm): 1.00 (t, J = 8 Hz, 2H, Si–CH2), 1.24
(t, J = 8 Hz, 9H, CH3), 2.74 (t, J = 8 Hz, 2H, CH2), 3.84
(q, J = 8 Hz, 6H, O–CH2), 7.16–7.27 (m, 5H, Ph).
a-Adduct [triethoxy(1-phenylethyl)silane]. 1H NMR
(CDCl3, 400 MHz) d (ppm): 1.18 (t, J = 8 Hz, 9H, CH3),
1.33 (d, J = 8 Hz, 3H, CH3), 3.65 (q, J = 8 Hz, 1H, Si–CH),
3.76 (q, J = 8 Hz, 6H, O–CH2), 7.12–7.19 (m, 5H, Ph).
Chloro(1,5-cyclooctadiene)(1-butyl-3-methylimidazole-2-ylidene)-
rhodium (I). This compound was prepared by stirring a mixture
of 500 mg (1.01 mmol) of bis(1,5-cyclooctadiene) dichloro-
dirhodium and 404 mg (2.2 mmol) of 1-methyl-3-butylimid-
azolium-2-carboxylate in 10 mL of acetonitrile in a Schlenk
flask for 40 min at room temperature. The reaction mixture
was evaporated under reduced pressure and washed with
diethyl ether (3 Â 10 mL). The yellow solid was dissolved in
dichloromethane (2 mL) and purified by repeated recrystalli-
zation from diethyl ether to give 683 mg (88% yield) of a
yellow powder. 1H NMR (CDCl3, 400 MHz) d (ppm): 6.81
(d, J = 4 Hz, 2H), 5.01 (m, 2H, COD CH), 4.49 (m, 2H, N–CH2),
4.07 (s, 3H, N–CH3), 3.34 (br s, 1H, COD CH), 3.25 (br s, 1H,
1
Ethylbenzene. H NMR (CDCl3, 400 MHz) d (ppm): 1.15
(t, J = 8 Hz, 3H, CH3), 2.64 (q, J = 8 Hz, 2H, CH2),
7.11–7.25 (m, 5H, Ph).
Hydrosilylation reaction of 1-hexene with triethoxysilane
b-Adduct [hexyltriethoxysilane]. 1H NMR (CDCl3, 400 MHz)
d (ppm): 0.64 (t, J = 6 Hz, 2H, Si–CH2), 0.89 (t, J = 8 Hz, 3H,
CH3), 1.22–1.42 (m, 17H, CH2 CH3), 3.81 (q, J = 8 Hz, 6H,
O–CH2).
Hydrosilylation reaction of styrene with triethylsilane
b-Adduct [triethyl(phenylethyl)silane]. 1H NMR (CDCl3,
400 MHz) d (ppm): 0.66 (q, J = 8 Hz, 6H, Si–CH2), 0.92
(t, J = 8 Hz, 9H, CH3), 0.98 (t, J = 8 Hz, 2H, Si–CH2), 2.71
(t, J = 8 Hz, 2H, CH2), 7.11–7.27 (m, 5H, Ph).
Scheme 1 The hydrosilylation of alkenes with triethoxysilane or
triethylsilane catalyzed by rhodium complexes.
Scheme 2 Synthesis of the N-heterocyclic carbene–rhodium complex.
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 1330–1334 | 1333
Li, Jiayun
