Study of Karstedt's Catalyst for Hydrosilylation of a Wide Variety of Functionalized Alkenes with Triethoxysilane and Trimethoxysilane

Article abstract of DOI:10.1002/cjoc.201700024

The hydrosilylation is one of the most important methods for the synthesis of organosilicon compounds. Karstedt's catalyst [Pt_n(H₂C=CHSiMe₂OSiMe₂CH=CH₂)_m] is a kind of platinum catalyst which is widely used in the hydrosilylation. In this paper, we studied the catalytic activity of Karstedt's catalyst for the hydrogenation of olefins and especially aminated alkenes with trimethoxysilane and triethoxysilane, and demonstrated the excellent performance in terms of the yield and selectivity.

Full text of DOI:10.1002/cjoc.201700024

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DOI: 10.1002/cjoc.201700024
Study of Karstedt’s Catalyst for Hydrosilylation of a Wide Vari-
ety of Functionalized Alkenes with Triethoxysilane and
Trimethoxysilane
Zhenhuan Pan,‡ Minglun Liu,‡ Chaoyue Zheng, Deqing Gao,* and Wei Huang*
Key Laboratory of Flexible Electronics & Institute of Advanced Materials, Jiangsu National Synergistic
Innovation Center for Advanced Materials, Nanjing Tech University, Nanjing, Jiangsu 211816, China
The hydrosilylation is one of the most important methods for the synthesis of organosilicon compounds.
Karstedt’s catalyst [Ptn(H2C＝CHSiMe2OSiMe2CH＝CH2)m] is a kind of platinum catalyst which is widely used in
the hydrosilylation. In this paper, we studied the catalytic activity of Karstedt’s catalyst for the hydrogenation of
olefins and especially aminated alkenes with trimethoxysilane and triethoxysilane, and demonstrated the excellent
performance in terms of the yield and selectivity.
Keywords Karstedt’s catalyst, hydrosilylation, aminated alkenes, selectivity
Introduction
widely used at present. The discovery of the Karstedt’s
catalyst is a significant advance in the field of hydrosi-
lylation catalyst research.
The hydrosilylation is the reaction of organosilicon
compounds containing Si－H bond with unsaturated
compounds. Silicon hydrogen addition reaction is one of
the most widely studied and widely used reactions in
organosilicon chemistry, and many silicon monomers
containing functional groups have been synthesized via
this reaction. Since Sommer et al. reported the hydrosi-
lylation reaction in 1947,[1] its reaction mechanism,[2]
catalytic system[3] and application[4] become hot topics
of research work.
A lot of catalysts have been developed for the hy-
drosilylation.[5] Since Speier found that chloroplatinic
acid (H2PtCl6) was a selective and efficient homogene-
ous alkene hydrosilylation catalyst in 1957,[6] transition
metal catalysts on the basis of metals such as platinum,[7]
rhodium,[8] copper[9] and cobalt[10] with high catalytic
activity and selectivity have attracted much attention in
theoretical and practical applications. At present, plati-
num catalyst is the most comprehensive and widely
used catalyst in the study of hydrosilylation catalyst,
due to the high catalytic activity and selectivity, and the
high stability towards heat, oxygen and moisture.[11]
In 1973, Karstedt reported that the platinum(0) and
divinyltetramethyldisiloxane complex ([Ptn(H2C ＝
CHSiMe2OSiMe2CH＝CH2)m], as shown in Figure 1),
termed as Karstedt’s catalyst, was an effective catalyst
for hydrosilylation.[12] Karstedt’s catalyst is a kind of
homogeneous catalyst with high catalytic efficiency,
wide application range and small amount, etc., so it is
The hydrosilylation reactivity is usually affected us-
ing aminated alkenes, because the amino groups are
involved in the reaction and produce undesired byprod-
ucts,[13] and cause a kind of hydrolyzation of ethoxy-/
methoxy-silane groups in the presence of trace water.
Up to now, there are few reports on the hydrosilylation
of aminated alkenes substrates.[13,14] In this paper, we
described the hydrosilylation reaction of different ami-
nated alkenes with trimethoxysilane and triethoxysilane
in the presence of the Karstedt’s catalyst, and further
extended the hydrosilylation reaction with a series of
other functionalized alkenes substrates.
Figure 1 Structure of Karstedt’s catalyst.
Experimental
The reaction was carried out by modifying the re-
ported method.[15] Into the mixture of a certain amount
of alkene and equimolar amount of trimethoxysilane or
triethoxysilane in a Schlenk tube was added plati-
num(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane
(Karstedt’s catalyst) (i.e., 20 µmol per mol of silane).
*
E-mail: iamdqgao@njtech.edu.cn, iamwhuang@njtech.edu.cn
Received January 10, 2017; accepted February 22, 2017; published online XXXX, 2017.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201700024 or from the author.
‡ The first two authors contributed equally to this work.
Chin. J. Chem. 2017, XX, 1—X
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Pan et al.
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Then the mixture was stirred under argon at 80 ℃ for
20 h (Scheme 1). After being cooled to room tempera-
ture, the crude was purified by vacuum distillation or by
chromatography on a silica gel column to afford the
desired product.
of Si-CH2 at δ 0.45－0.65 (m, 2H) was chosen as the
characteristic peak of γ-isomer, the H chemical shift of
1
Si－CH－CH3 at δ 0.90－1.05 (m, 3H) was chosen as
the characteristic peak of β-isomer.[19]
As can be seen from Table 1, the yields of the hy-
drosilylation of the aminated alkenes with trimethox-
ysilane and triethoxysilane using Karstedt’s catalyst
were higher than 90%. The γ-isomer is often the desired
product in the hydrosilylation of allyl derivatives.[20] For
the primary allylamine (Entry 1), the reaction yields
with trimethoxysilane and triethoxysilane were more
than 94%, and the ratio of γ-isomer/β-isomer was 84/16.
For the secondary allylamine (Entry 2), the yield of each
hydrosilylation reaction was more than 93%, and the
selectivity with the trimethoxysilane reagent was better
than that with the triethoxysilane reagent. The ratios of
γ-isomer/β-isomer of the two groups were 83/17 and
78/22, respectively. For the tertiary allylamine (Entry 3),
the yield of the hydrosilylation reaction of N,N'-
dimethylallylamine with trimethoxysilane or triethox-
ysilane was about 95%, and the ratios of γ-isomer/
β-isomer of N,N'-dimethylallylamine with trimethox-
ysilane and triethoxysilane were 86/14 and 95/5, respec-
tively. The hydrosilylation reaction of N-ethyl-2-
methylallylamine (Entry 4) showed the highest yield of
97.1% and 98.2%, the ratios of γ-isomer/β-isomer of
N-ethyl-2-methylallylamine with trimethoxysilane and
triethoxysilane were 81/19 and 77/23, respectively.
Scheme 1 Hydrosilylation reactions of different functionalized
alkenes with trimethoxysilane and triethoxysilane
H
O
O
Karstedt's catalyst
Si
R1
+
O
O
R1
O
+
Si
O
R1
Si
O
O
O
H
O
O
Si
Karstedt's catalyst
R1
+
O
1
......
R = -NH2, -NHR, -OH, -COR, -COOR, -R, -COOH
R1
O
O
Si
O
Si
O
R1
+
O
O
Results and Discussion
Table 1 Karstedt’s catalyst for the hydrosilylation of different
aminated alkenes with the trimethoxysilane and triethoxysilane
reagents, respectively
The products of the hydrosilylation reaction of ole-
fins with trimethoxysilane or triethoxysilane include
γ-isomer (anti-Markovnikov isomer) and β-isomer
(Markovnikov isomer), and they could be determined
Entry Alkene Yielda/% Ratioa (γ/β) Yieldb/% Ratiob (γ/β)
1
from 1H NMR spectra. Based on the H NMR data, it
1
94.3 84/16
94.2
84/16
was found that the main product was γ-isomer and there
was little β-isomer, this is due to steric effect of the re-
actants.[16]
N
2
93.2 83/17
91.9
78/22
H
The yield and the selectivity were calculated on the
basis of 1H NMR spectrum using the Eq. 1:[17]
3
4
95.6 86/14
97.1 81/19
94.8
98.2
95/5
Mx Nstd mstd Ax
P＝P ×
×100%
(1)
x
std
Mstd Nx mx A
77/23
std
where Pstd is the purity (g•g1) of the internal standard;
Ax and Astd are the integral value of the signals belong-
ing to the analyte and the internal standard, respectively;
Mx and Mstd are the relative molar mass (molecular
weight, g•mol1) of the analyte and internal standard
(Mstd＝226.44 g•mol−1), respectively; Nx and Nstd corre-
spond to the number of spins of the analyte and the in-
ternal standard (Nstd＝2), respectively; mx and mstd are
the weighted mass of the analyte and the internal stand-
ard, respectively. The purity Px which stands for the
yield was calculated for each isomer and the ratio of γ-
to β-isomers was correspondingly determined. In the
work, 2,4,6-trichloronitrobenzene was used as the in-
1
The yield and the selectivity were calculated on the basis of H
NMR spectra. a Hydrosilylation of olefins with trimethoxysilane.
b Hydrosilylation of olefins with triethoxysilane.
The catalytic effect of many catalysts on the hydros-
ilylation of aminated alkenes is not satisfactory, which
may be attributed to poisoning of the catalyst by the
amino function, which reduces the activity and selectiv-
ity of the catalysts. As indicated in Table 1, the hydrosi-
lylation of these three aminated alkenes with Karstedt’s
catalyst showed higher selectivity and the ratio of
γ-isomer/β-isomer was not less than 3/1. It can be seen
that Karstedt’s catalyst has good yield and selectivity in
catalytic hydrosilylation addition of aminated alkenes
with trimethoxysilane and triethoxysilane.
1
1
ternal standard from H NMR spectrum with the H
chemical shift at δ 7.46 (t, 2H),[18] the 1H chemical shift
2
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Chin. J. Chem. 2017, XX, 1—X

Study of Karstedt’s Catalyst of Hydrosilylation
Conclusions
Moreover, in order to obtain more information of the
catalytic activity and selectivity of the Karstedt’s cata-
lyst, the hydrosilylation of various functionalized al-
kenes with trimethoxysilane and triethoxysilane using
Karstedt’s catalyst was tested under similar conditions.
The results are summarized in Table 2.
In summary, we comprehensively studied the cata-
lytic activity of Karstedt’s catalyst for the hydrogenation
of a variety of functionalized olefins and especially
aminated alkenes with trimethoxysilane and triethox-
ysilane, demonstrating that the Karstedt’s catalyst has
the excellent performance for the hydrosilylation in
terms of the yield and selectivity. Further studies are
underway to expand the scope of the applications of the
hydrosilylation reaction.
Table 2 Karstedt’s catalyst for the hydrosilylation of different
functionalized alkenes with the trimethoxysilane and triethox-
ysilane reagents, respectively
Ratioa
Ratiob
Entry Alkene
Yielda/%
Yieldb/%
Acknowledgement
(γ/β)
(γ/β)
1
2
92.0
91.5
85/15
100/0
94.9
92.8
84/16
100/0
This work was supported by the National Natural
Science Foundation of China under grant No.
21371096.
3
4
5
95.2
97.6
91.6
95/5
97.6
93.8
94.7
92/8
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