Controlled synthesis of cyclosiloxanes by NHC-catalyzed hydrolytic oxidation of dihydrosilanes

Article abstract of DOI:10.1039/c6dt04882j

Hydrolytic oxidation of various hydrosilanes in acetonitrile and in the absence of organic solvents catalyzed by an N-heterocyclic carbene organocatalysis is described. The NHC organocatalyst exhibited a very high activity with only 0.1 mol% loading of the catalyst in acetonitrile for aryl-substituted dihydrosilanes to produce hydrogen gas and cyclosiloxanes almost quantitatively in several minutes. The calculated TOF (15 000 h^-1) of this organocatalyst is comparable to those of precious metal-based heterogeneous catalysts and much superior to those of the existing homogeneous metal catalysts. The catalytic reaction selectively yielded cyclosiloxanes in high yield without the contamination of silanols. Furthermore, the catalytic reaction can also be furnished under solvent-free conditions at elevated temperatures with 2.5 mol% loading of the NHC in 5-12 hours.

Full text of DOI:10.1039/c6dt04882j

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Controlled synthesis of cyclosiloxanes by NHC-
catalyzed hydrolytic oxidation of dihydrosilanes†
Cite this: DOI: 10.1039/c6dt04882j
Guoping Qinga and Chunming Cui*a,b
Hydrolytic oxidation of various hydrosilanes in acetonitrile and in the absence of organic solvents cata-
lyzed by an N-heterocyclic carbene organocatalysis is described. The NHC organocatalyst exhibited a
very high activity with only 0.1 mol% loading of the catalyst in acetonitrile for aryl-substituted dihydro-
silanes to produce hydrogen gas and cyclosiloxanes almost quantitatively in several minutes. The calculated
TOF (15 000 h−1) of this organocatalyst is comparable to those of precious metal-based heterogeneous
catalysts and much superior to those of the existing homogeneous metal catalysts. The catalytic reaction
selectively yielded cyclosiloxanes in high yield without the contamination of silanols. Furthermore, the
catalytic reaction can also be furnished under solvent-free conditions at elevated temperatures with
2.5 mol% loading of the NHC in 5–12 hours.
Received 27th December 2016,
Accepted 17th January 2017
DOI: 10.1039/c6dt04882j
www.rsc.org/dalton
tally benign process because it produces hydrogen gas as the
only by-product. It has been shown that the hydrolytic oxi-
Introduction
Cyclosiloxanes are basic building blocks for the synthesis of dation of hydrosilanes containing high contents of hydride
various silicon materials that have been applied in both indus- groups such as HC(SiH3)3 has been potentially useful as an
try and academia.1 The industrial process for the synthesis of alternative energy source.3 Compared to other hazard hydride
cyclosiloxanes has been largely based on the hydrolysis of sources such as lithium aluminum hydrides, which generate
chlorosilanes and alkoxylsilanes. However, the hydrolysis hydrogen gas in an uncontrolled manner upon hydrolysis,
required a large amount of bases and high temperatures for hydrosilanes are generally stable to water and their hydrolytic
the completion with the formation of a number of side pro- oxidation require suitable catalysts.
ducts including oligomeric and polymeric silicones and
In recent years, there have been extensive investigations on
cannot be well controlled (Scheme 1). In recent years, catalytic the catalytic oxidation of hydrosilanes with water catalysed by
oxidation of hydrosilanes has become an appealing and selec- metal-based catalysts.2 A number of transition metal-based
tive approach for the production of silanols and siloxanes.2 homogeneous and heterogeneous catalysts, especially those
Among the known oxidation processes by using various based on precious metals such as gold, rhodium, iridium and
oxidants, hydrolytic oxidation of hydrosilanes with water ruthenium, have been developed.2,4–7 However, most of these
undoubtedly represents the most economic and environmen- studies have been concentrated on the hydrolytic oxidation of
tertiary hydrosilanes (R3SiH) for the controlled synthesis of
silanols and the hydrolytic oxidation of primary and secondary
silanes (RSiH3 and R2SiH2) has been much less studied prob-
ably due to the complexity of the reactions associated with
complex products including silanols, cyclosiloxanes and poly-
meric materials, which cannot be easily controlled. Thus, the
catalysts for the selective formation of a single product are
highly desirable.
Scheme 1 Traditional hydrolysis of chlorosilanes vs. catalytic hydrolytic
N-Heterocyclic carbenes have emerged as environmentally
oxidation of hydrosilanes.
benign, efficient and cheap metal-free organocatalysts. The
use of NHCs as catalysts for silane transformations such as the
aState Key Laboratory of Elemento-Organic Chemistry, Nankai University,
silylation of CO2 and other unsaturated substrates has been
reported.8 We have recently shown that NHCs could efficiently
Tianjin 300071, China
bCollaborative Innovation Center of Chemical Science and Engineering (Tianjin),
catalyze the dehydrogenative coupling of hydrosilanes with
Tianjin 300072, China. E-mail: cmcui@nankai.edu.cn
various alcohols.9a The organocatalytic oxidation of tertiary
†Electronic supplementary information (ESI) available: NMR and GC-MS spectra
silanes with H2O2 to silanols has also been reported.9b Herein,
for the resulting cyclosiloxanes. See DOI: 10.1039/c6dt04882j
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we report on the hydrolytic oxidation of secondary hydro-
silanes with water for the selective formation of hydrogen gas
and cyclosiloxanes by using an N-heterocyclic carbene as the
catalyst. NHC catalysis can be carried out either in organic sol-
vents or under solvent free-conditions with high efficiency and
selectivity. Remarkably, the clean and selective formation of
cyclosiloxanes can be furnished in acetonitrile in several
minutes with only 0.1 mol% loadings of the NHC.
Scheme 2 Results for the NHC-catalyzed hydrolytic oxidation of
tertiary silanes.
acetonitrile with different loadings of IiPr at room temperature
(Scheme 3). The results are given in Table 2. The reaction was
monitored by the collection of hydrogen gas by water displace-
ment in a graduated cylinder. All of the reactions catalysed by
0.1–2.5% mol% (entries 1–5) of IiPr are almost complete in
several minutes. It is noted that the reaction catalysed by
0.1 mol% of IiPr gradually released hydrogen gas in 4 min and
the product cyclosiloxane (Ph2SiO)4 can be isolated in high
yield. It appeared that the hydrogen release rate is noticeably
slowed down by the increase of the amount of water. For
example, the hydrolysis of Ph2SiH2 with three equivalents of
water was complete in 12 min under the same conditions.
There is no reaction observed in the absence of the NHC (entry
6) (Scheme 4).
Results and discussion
In order to examine the feasibility of the NHC-catalyzed hydro-
lytic oxidation of hydrosilanes, the oxidation of the selected
tertiary silanes Et3SiH, PhMe2SiH, Ph3SiH and (EtO)3SiH has
been investigated in THF and acetonitrile at room temperature
using 2.5 mol% loading of 1,3-diisopropyl-4,5-dimethyl-
imidazol-2-ylidene (IiPr). The reactions in THF proved to be
relatively slow to yield a mixture containing the corresponding
silanol and siloxane. For example, the hydrolysis of Ph3SiH in
THF using an excess of water at 0 °C for 3 h yielded Ph3SiOH
and Ph3SiOSiPh3 in the molar ratio of 7 : 3 based on the NMR
Under the optimized conditions with 0.1 mol% of IiPr as
the catalyst in acetonitrile, the hydrolytic oxidation of various
dihydrosilanes has been studied. The results are summarized
in Table 3. The hydrolytic oxidations of Et2SiH2 and (tBu)2SiH2
are much slower than that of phenyl-substituted hydrosilanes
at room temperature. The two reactions should be performed
at 40 °C for 8 h (entries 7 and 8). In contrast, the hydrolytic
reactions of the diaryl-substituted hydrosilanes were complete
in several minutes at room temperature to yield the single
analysis, and
a complete conversion of Ph3SiOH into
Ph3SiOSiPh3 was observed in 5 h (Table S1 in the ESI†), in-
dicating the NHCs may also promote the Si–O coupling of the
silanol with the hydrosilane. In contrast, the reactions in
acetonitrile were much faster and a complete conversion was
observed in 2 h at 0 °C. Thus, the reactions of these silanes
with water catalyzed by a 2.5% mol loading of IiPr were con-
ducted in CH3CN at room temperature, and the results are
summarized in Table 1. All of the reactions exclusively resulted
in the formation of the corresponding siloxanes in 1–3 hours.
The hydrolytic oxidation of an alkoxylsilane (Table 1, entry 4)
led to the formation of the corresponding alkoxylsiloxane in
high yield (88%) while the alkoxyl groups remained intact. The
selective formation of siloxanes by the catalytic hydrolytic
oxidation of tertiary hydrosilanes has not been reported
previously (Scheme 2).2a
Scheme 3 NHC-catalyzed hydrolytic oxidation of Ph2SiH2.
The selective hydrolytic oxidation of dihydrosilanes is of
great interest in that it may present an atom-economical and
practical route for the production of cyclosiloxanes. To opti-
mize the conditions for the hydrolytic oxidation of secondary
hydrosilanes, the hydrolysis of Ph2SiH2 was carried out in
Table 2 Results for the hydrolytic oxidation of dihydrosilanes in CH3CN
T
Time
(min)
Yield
(%)
Entry
Hydrosilane
(°C)
Product
1
2
3
4
5
6
7
8
Ph2SiH2
PhMeSiH2
Ph(CH2CHCH2)SiH2
Ph(PhCH2CH)SiH2
Ph(2-OMePh)SIH2
Ph(4-C2H3Ph)SiH2
tBu2SiH2
20
20
20
20
20
20
40
40
5
6
16
12
7
7
480
480
D4
91
92
85
88
92
90
83
83
D3–4
D3–4
D3–4
D4
D4
D2
Table 1 Optimization of the reaction conditions for the hydrolytic oxi-
dation of Ph2SiH2
Entry
Loading of IiPr (%)
Time (min)
Ph2-D4 yield (%)
Et2SiH2
D3–5
1
2
3
4
5
6
2.5
1.5
1.0
0.5
0.1
0
2
2.5
2.5
2.5
4
91
90
90
92
92
0
120
Conditions: Ph2SiH2 (5 mmol), 1 mL of 5.0 M H2O in CH3CN, isolated
yield.
Scheme 4 Hydrolytic oxidation of dihydrosilanes in CH3CN.
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Table 3 Results for the hydrolytic oxidation of dihydrosilanes under
solvent-free conditions
with the molar ratios of water to a dihydrosilane ranging from
5 to 20. The results for the hydrolytic oxidation of different sec-
ondary hydrosilanes are summarized in Table 3. All of the
hydrosilanes listed in Table 3 were converted to the corres-
ponding cyclosiloxanes (83–98%) in high yields at elevated
temperatures for 5–12 h. The substituents on the silicon atom
have no noticeable effects on the reaction rate. This observ-
ation is in contrast to that for the hydrolytic reactions of the
hydrosilanes in acetonitrile, in which the hydrolytic oxidation
of phenyl-substituted hydrosilanes is much faster at ambient
temperature than that of the alkyl-substituted Et2SiH2. This
indicated that acetonitrile played significant roles in the
activation of phenyl-substituted hydrosilanes.
Entry Hydrosilane
T (°C) Time (h) Product Yield (%)
1
2
3
4
5
6
7
8
Ph2SiH2
PhMeSiH2
Ph(CH2CHCH2)SiH2 60
Ph(PhCH2CH)SiH2
Ph(o-OMePh)SIH2
Ph(p-C2H3Ph)SiH2
t-Bu2SiH2
90
60
10
10
8
D4
90
98
95
88
95
90
83
83
D3–4
D3–4
D3–4
D4
D4
D2
60
60
90
60
60
5
12
10
5
Et2SiH2
6
D3–5
Conditions: IiPr (0.041 mmol), hydrosilane (1.6 mmol), H2O
(16 mmol), isolated yield.
The mechanism for the hydrolytic oxidation of hydrosilanes
catalyzed by the NHC is yet to be investigated. It might be
similar to the dehydrogenative coupling of hydrosilanes with
alcohols.9 However, the activation of a hydrosilane by an NHC
to from the corresponding hypervalent silicon hydride might
also be possible.8 The significant solvent effects observed in
acetonitrile indicated that the catalytic reaction might involve
polarized intermediates.10 Furthermore, the Lewis acidity of
silicon centers also shows effects on the reaction rate signifi-
cantly in acetonitrile. Based on the solvent and substituent
effects observed in acetonitrile, the proposed mechanism for
the hydrolytic oxidation is given in Scheme 6. The activation of
a dihydrosilane by a Lewis basic NHC yielded the NHC-silane
adduct A featuring the significant zwitterionic character.8 This
activation process could significantly increase the hydride
character of the hydrogen atom on the silicon center.
The intermediate A reacted with a water molecule to yield
intermediate B, a hypervalent silanol, with the elimination of
hydrogen. Intermediate B then underwent either intra or inter-
molecular reaction to from the cyclosiloxane with the elimin-
ation of hydrogen gas. Under solvent-free conditions, the same
mechanism may be operative, the high loading (2.5%) of the
NHC required in this case compared to that in acetonitrile
may be due to the stabilization effects of the polar solvent on
the zwitterionic intermediates A and B.
cyclic tetramer D4 in high yields (entries 1, 5 and 6), indicating
that the Lewis acidity of the silicon center has significant
effects on the reaction rate. The steric factors of the substitu-
ents on the silicon atom have pronounced effects on the ratios
of different sizes of cyclosiloxanes (D3–D5). The hydrolytic reac-
tion of (tBu)2SiH2 yielded the dimer [(tBu)2SiO]2 (entry 7) as
the only product while a mixture containing D3–D5 (entry 8)
was obtained in the hydrolytic reaction of Et2SiH2, and mix-
tures of D3 and D4 (entries 2–4) were obtained in the hydrolysis
of the phenyl–alkenyl-substituted Ph(CH2vCH)SiH2, phenyl–
allyl-substituted Ph(CH2CHvCH2)SiH2 and PhMeSiH2. The
mixtures containing the different cyclosiloxanes have been
characterized by GC-MS spectroscopy, which indicated that the
tetramer D4 is the major product in all of these cases (for
the Dn ratios of the product, see the Experimental section in
the ESI†). These results demonstrated that the hydrolytic reac-
tion is viable for the typical alkyl, phenyl, alkenyl and allyl-
substituted hydrosilanes. No partial hydrolytic products and poly-
meric materials were observed in these reactions (Scheme 5).
The hydrolytic oxidation of the dihydrosilanes was also
studied under solvent-free conditions. The hydrolysis of
Ph2SiH2 with 0.1, 1.0 and 2.5 mol% of loadings of IiPr at
different temperatures was investigated for the optimization of
the reaction conditions. Almost no conversions were obsevered
at room temperature, heating the mixture of the 10/1 molar
ratio of water/silane with 2.5 mol% of IiPr at 90 °C for 11 h,
however, resulted in the formation of the cyclosiloxane D4 in
ca. 90% yield; less loading of IiPr (1.0 mol%) led to a low yield
(34%). It is noted that the increase of the amount of water
accelerated the reaction to some extent but not significantly,
indicating that the hydrolysis reaction under solvent-free con-
ditions can be conducted without the strict control of the
amount of water. The reaction can be furnished in ca. 10 h
Scheme 5 Hydrolytic oxidation of dihydrosilanes under solvent-free
Scheme 6 Proposed mechanism for the NHC-catalyzed hydrolytic oxi-
conditions.
dation of dihydrosilanes.
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vigorous evolution of H2 was noted. The reaction was moni-
tored by TLC. After the reaction was complete, the product was
Summary and conclusions
In summary, we have developed the first efficient and selective purified by flash column chromatography on neutral Al2O3
organocatalyst for the hydrolytic oxidation of various dihydro- using n-hexane/ethyl acetate (10 : 1) as an eluent or was
silanes with water for the clean formation of cyclosiloxanes. washed with n-hexane.
The catalytic process in acetonitrile for phenyl-substituted
hydrosilanes is very fast and produces cyclosiloxanes in several
minutes. The reaction can also be furnished under solvent-free
conditions to yield cyclosiloxanes at elevated temperatures
Reactions in CH3CN and spectroscopic data for the Si–O coup-
ling products
Et3SiOSiEt3 .13 3 h at room temperature, colorless oil, 90%
with a relative low catalyst loading. In all of these reactions, yield. 1H NMR (400 MHz, CDCl3): δ 0.94 (t, J = 8.0 Hz, 18H,
partial hydrolytic products and polymeric siloxanes were not CH2CH3), 0.52 (q, J = 8.0 Hz, 12H, CH2CH3); 13C{1H} NMR
observed. This catalytic system represents one of the highly (101 MHz, CDCl3): δ 6.95 (CH2CH3), 6.58 (CH2CH3); 29Si NMR
efficient and selective catalysts for the hydrolytic oxidation of (79 MHz, CDCl3): δ 78.8 (s).
hydrosilanes. This catalytic process is safe and practical
Ph3SiOSiPh3 .14 1 h at room temperature, white solid, 98%
1
without using any hazardous materials, and thus potentially yield. H NMR (400 MHz, CDCl3): δ 7.51–7.49 (m, 12H, C6H5),
useful for the routine synthesis of cyclosiloxanes. The studies 7.42–7.38 (m, 6H, C6H5), 7.31–7.27 (m, 12H, C6H5); 13C{1H}
of this catalytic system for the hydrolytic oxidation of trihydro- NMR (101 MHz, CDCl3): δ 135.5, 135.2, 129.8, 127.7 (C6H5);
silanes are currently in progress in our laboratory.
29Si NMR (79 MHz, CDCl3): δ −18.6 (s).
(EtO)3SiOSi(OEt)3 .13 2 h at room temperature, colourless oil,
88% yield. 1H NMR (400 MHz, CDCl3): δ 3.64 (q, J = 7.1 Hz,
12H, CH2CH3), 1.20 (t, J = 7.1 Hz, 18H, CH2CH3); 13C{1H} NMR
(101 MHz, CDCl3): δ 57.3 (CH2CH3), 18.0 (CH2CH3); 29Si NMR
(79 MHz, CDCl3): δ 8.87 (s).
Experimental
Materials and methods
PhMe2SiOSiPhMe2 .14 1 h at room temperature, colorless oil,
95% yield. 1H NMR (400 MHz, CDCl3): δ 7.62–7.60 (m, 4H,
o-C6H5), 7.43–7.38 (m, 6H, m, p-C6H5), 0.40 (s, 12H, Me2);
13C{1H} NMR (101 MHz, CDCl3): δ 140.0, 133.2, 129.4, 127.9,
1.01 (Me2); 29Si NMR (79 MHz, CDCl3): δ 1.17 (s).
CH3CN was dried over P2O5 and distilled prior to use.
Commercial hydrosilanes were purchased from Alfa Aesar and
purified by distillation. The N-heterocyclic carbene 1,3-diiso-
propyl-4,5-dimethylimidazol-2-ylidene (IiPr) was prepared
according to the literature.11 The other hydrosilanes used in
this work were prepared according to the literature12 or by
modified procedures. Elemental analysis was carried out on an
Elemental Vario EL analyzer. The 1H, 13C and 29Si spectra
were recorded on a Bruker Mercury Plus 400 NMR spectro-
meter. Chemical shifts are referenced against external Me4Si
(1H, 13C).
Hydrolysis of diphenylsilane (D4).15 5 min at room tempera-
1
ture, white solid, 91% yield. H NMR (400 MHz, C6D6): δ 7.71
(d, J = 8 Hz, 16H, C6H5), 7.11 (t, J = 8.0 Hz, 8H, p-C6H5), 7.03
(t, J = 8 Hz, 16H, m-C6H5); 13C{1H} NMR (101 MHz, CDCl3):
δ 134.5, 134.5, 130.1, 127.7; 29Si NMR (79 MHz, C6D6):
δ −42.82 (s).
Hydrolysis of di(tert)butylsilane (tBuD2). 12 h at 40 °C, white
solid, 83% yield. 1H NMR (400 MHz, C6D6): δ 1.05 (s, 36H,
General procedure for hydrolytic oxidation in CH3CN
C(CH3)3); 13C{1H} NMR (101 MHz, C6D6):
δ 27.3 (tBu),
19.8 (tBu); 29Si NMR (79 MHz, CDCl3): δ −7.19 (s); MS (EI): m/z
176.1 [tBuD2/2 + H2O]+.
In a glove box, to a Schlenk tube were added IiPr (0.1%,
0.9 mg, 0.005 mmol) and a hydrosilane (5 mmol). The tube
was removed from the glove box and was placed in an oil bath
at a specified temperature for a specific time. To this mixture
was added 1 mL of CH3CN containing water (5.0 M of H2O in
CH3CN) by syringe. In most cases, vigorous evolution of H2
was noted. The reaction was monitored by thin layer chromato-
graphy (TLC). After the reaction was complete, the solvent was
removed under vacuum and the product was purified by flash
column chromatography on neutral Al2O3 using n-hexane/ethyl
acetate (10 : 1) as an eluent or was washed with n-hexane.
Hydrolysis of o-methoxy-phenylphenylsilane (OMeD4). 6 min
at room temperature, white solid, 92% yield. 1H NMR
(400 MHz, C6D6): δ 7.92–7.89 (m, 2H), 7.83–7.81 (m, 2H),
7.57–7.54 (m, 4H), 7.50–7.46 (m, 2H), 7.42–7.32 (m, 5H),
7.29–7.27 (m, 2H), 7.25–7.04 (m, 11H), 6.77–6.52 (m, 6H),
6.28–6.22 (m, 2H), 3.37 (s, 3H), 3.30 (s, 3H), 2.98 (s, 3H), 2.84
(s, 3 H). 13C{1H} NMR (101 MHz, CDCl3): δ 139.0, 136.9, 134.6,
134.5, 134.3, 133.9, 130.1, 127.7, 125.4, 114.6, 53.9 (OMe);
29Si NMR (79 MHz, C6D6): δ −42.82 (s); MS (ESI): m/z 930.2736
[
OMeD4 + H2O]+.
General procedure for hydrolytic oxidation under solvent-free
conditions
Hydrolysis of p-vinyl-phenylphenylsilane (p-vinylD4). 7 min at
1
room temperature, white solid, 90% yield. H NMR (400 MHz,
A Schlenk tube was charged with IiPr (2.5%, 0.0074 g, C6D6): δ 7.80–7.77 (m, 8H), 7.69–7.65 (m, 8H), 7.13–7.07 (m,
0.041 mmol) and a hydrosilane (1.6 mmol). The Schlenk tube 20H), 6.49 (dd, J = 12 Hz, 4H, CHCH2), 5.57 (d, J = 12 Hz, 4H,
was placed in an oil bath at a specified temperature and H2O CHCH2), 5.05 (d, J = 12 Hz, 4H, CHCH2); 13C{1H} NMR
(16 mmol) was added to the solution by syringe. The mixture (101 MHz, CDCl3): δ 139.0, 136.9, 134.6, 134.5, 134.3, 133.9,
was heated to 60 or 90 °C for a specific time. In most cases, 130.1, 127.7, 125.4 (CHCH2), 114.6 (CHCH2); 29Si NMR
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(79 MHz, CDCl3): δ −42.9 (s); MS (ESI): m/z 914.2942 [p-vinyD4 +
H2O]+.
2012, 2, 1539; (b) B. P. S. Chauhan, A. Sarkar and
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Hydrolysis of diethylsilane.16 12 h at 40 °C, colorless oil,
83% yield. A mixture containing EtD3, EtD4 and EtD5 was
obtained, and the ratio of EtD3/EtD4/EtD5 = 22/67/11 was esti-
1
mated by GC-MS. H NMR (400 MHz, C6D6): δ 1.10–1.06 (t, J =
8 Hz, CH2CH3), 0.66–0.64 (q, J = 8 Hz, CH2CH3). GC-MS: m/z
481.2 [D5 − C2H5]+, 379.0 [D4 − C2H5]+, 277.0 [D3 − C2H5]+.
Hydrolysis of vinylphenylsilane.17 12 min at room tempera-
ture, colorless oil, 88% yield. A mixture containing vinyD3 and
vinyD4 was obtained, and the ratio of vinyD3 and vinyD4 = 5/95
was estimated by GC-MS. 1H NMR (400 MHz, C6D6):
δ 7.93–7.62, 7.25–7.02 (C6H5), 6.39–5.75 (C2H3). MS (EI): m/z
714.0 [vinyD5 − C2H3]+, 565.1 [vinyD4 − C2H3]+.
Hydrolysis of allylphenylsilane. 16 min at room temperature.
Colorless oil. 85% yield. A mixture containing allyD3 and allyD4
was obtained, and the ratio of allyD3 and allyD4 = 12/88 was esti-
mated by GC-MS. 1H NMR (400 MHz, C6D6): δ 7.90–7.47,
7.29–6.98 (m, C6H5), 6.09–5.55 (CH2CHvCH2), 5.15–4.64
(CH2CHvCH2), 2.09–1.69 (CH2CHvCH2). MS (EI): m/z 649.2
[
[
allylD4]+, 607.2 [allyD4 − C3H5]+, 571.2 [allyD4 − C6H5]+, 549.1
allyD4 − C6H5 − C3H5 + H2O]+, 487.1 [allylD3]+, 447.1 [allyD3
7 For the iron-catalyzed hydrolytic oxidation of hydrosilanes,
see: A. K. Liang-Teo and W. Y. Fan, Chem. Commun., 2014,
50, 7191.
8 (a) M. J. Fuchter, Chem. – Eur. J., 2010, 16, 12286;
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Ed., 2009, 48, 3322; (c) F. Huang, G. Lu, L. Zhao, H. Li and
Z.-X. Wang, J. Am. Chem. Soc., 2010, 132, 12388.
−
C3H5]+, 409.0 [allyD3 − C6H5]+.
Hydrolysis of methylphenylsilane.18 6 min at room tempera-
CH3
ture, colorless oil, 92% yield. A mixture containing
D3 and
CH3
CH3
CH3
D4 was obtained, and the ratio of
D3 and
D4 = 3/97
was estimated by GC-MS. 1H NMR (400 MHz, C6D6):
δ 7.84–7.49, 7.27–7.04 (m, C6H5), 0.56–0.26 (Me). MS (EI): m/z
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529.2 [CH D4 − CH3]+, 451.1 [CH D4 − C6H5 − CH3]+, 393.2
3
3
CH3
[
D3 − CH3]+, 315.1 [CH3D3 − C6H5 − CH3]+.
Reactions under solvent-free conditions and spectroscopic
data for the Si–O coupling products
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Data are given in the ESI.†
Acknowledgements
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We are grateful to the National Natural Science Foundation of
China (Grant No. 21632006 and 21472098) for financial
support.
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Dalton Trans.