Hydrosilane synthesis via catalytic hydrogenolysis of halosilanes using a metal-ligand bifunctional iridium catalyst

Article abstract of DOI:10.1016/j.jorganchem.2018.05.024

Hydrogenolysis of various halosilanes was catalysed by iridium amido complexes to produce hydrosilanes. Selective monohydrogenolysis of di- and trichlorosilanes similarly proceeded, resulting in the formation of chlorohydrosilanes (R₂SiHCl or RSiHCl₂) as synthetically important building blocks for various organosilicon compounds. A mechanistic study supported the in-situ formation of an iridium hydride species as a key intermediate, which could transfer the hydride to the silicon atom through a metal–ligand bifunctional mechanism. One-pot hydrotrimethylsilylation of olefins was achieved via successive hydrogenolysis and hydrosilylation reactions starting from Me₃SiCl.

Full text of DOI:10.1016/j.jorganchem.2018.05.024

Accepted Manuscript
Hydrosilane synthesis via catalytic hydrogenolysis of halosilanes using a metal-ligand
bifunctional iridium catalyst
Teruo Beppu, Kei Sakamoto, Yumiko Nakajima, Kazuhiro Matsumoto, Kazuhiko Sato,
Shigeru Shimada
PII:
S0022-328X(18)30435-2
10.1016/j.jorganchem.2018.05.024
JOM 20458
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 7 March 2018
Revised Date: 15 May 2018
Accepted Date: 30 May 2018
Please cite this article as: T. Beppu, K. Sakamoto, Y. Nakajima, K. Matsumoto, K. Sato, S. Shimada,
Hydrosilane synthesis via catalytic hydrogenolysis of halosilanes using a metal-ligand bifunctional
iridium catalyst, Journal of Organometallic Chemistry (2018), doi: 10.1016/j.jorganchem.2018.05.024.
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ACCEPTED MANUSCRIPT
Hydrosilane Synthesis via Catalytic Hydrogenolysis of Halosilanes Using a Metal-Ligand
Bifunctional Iridium Catalyst
Teruo Beppu, Kei Sakamoto, Yumiko Nakajima,* Kazuhiro Matsumoto, Kazuhiko Sato, and
Shigeru Shimada*
Interdisciplinary Research Center for Catalytic Chemistry (IRC3), National Institute of Advanced Industrial Science
and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
e-mail: yumiko-nakajima@aist.go.jp (Y. Nakajima) s-shimada@aist.go.jp (S. Shimada)
Abstract Hydrogenolysis of various halosilanes was catalysed by iridium amido complexes to
produce hydrosilanes. Selective monohydrogenolysis of di- and trichlorosilanes similarly proceeded,
resulting in the formation of chlorohydrosilanes (R SiHCl or RSiHCl ) as synthetically important
2
2
building blocks for various organosilicon compounds. A mechanistic study supported the in-situ
formation of an iridium hydride species as a key intermediate, which could transfer the hydride to
the silicon atom through a metal–ligand bifunctional mechanism. One-pot hydrotrimethylsilylation
of olefins was achieved via successive hydrogenolysis and hydrosilylation reactions starting from
Me SiCl.
3
Keywords: Hydrogenolysis, Halosilane, Hydrosilane, Iridium amido complex
1

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1. Introduction
Hydrosilanes are widely recognized as one of the most useful basic silicon compounds for
the synthesis of various organosilicon compounds. For example, the addition of hydrosilanes
to alkenes and alkynes (hydrosilylation reactions) enables us to prepare various functional
organosilicon compounds including industrially important silane-coupling agents [1,2]. The
reaction is also important for the curing of silicone materials [3]. Moreover, hydrosilanes are
highly useful in organic synthesis, particularly as versatile and mild reducing agents for
various organic compounds [4]. As a result, hydrosilanes are nowadays utilized in a wide
range of reactions to produce not only commodity chemicals but also high-performance
materials.
Hydrosilanes are usually synthesized by the reduction of chlorosilanes and alkoxysilanes
using strong reducing agents such as LiAlH and iBu AlH [5,6], although some hydrosilanes
2
4
such as Me Cl SiH (n = 0–2) are obtained as minor products of the Müller–Rochow
n
3–n
“
Direct Process” for the industrial production of organosilicon compounds [7]. In the
conventional reductions, equimolar metal wastes are concomitantly formed and low
functional group tolerance limits the substrate scope. In this regard, development of an
2

ACCEPTED MANUSCRIPT
efficient synthetic method of hydrosilanes under mild conditions is of great importance.
Motivated by these facts, our group has focused on hydrogenolysis reactions with H as a
2
potentially environmentally benign and inexpensive synthetic route to hydrosilanes [8]. To
this end, we focused on iridium complexes 1–4 (Chart 1) in this study [9,10]. They are
known to catalyse hydrogenation of imines and ketones via a six-membered transition state,
in which the metal-hydride and the amino-proton are simultaneously transferred to the
substrates. [11] We expected that Si–X bond cleavage of halosilanes using
1–4 would
proceed efficiently by following this cooperative “metal-ligand bifunctional mechanism”.
In this communication, we report efficient hydrogenolysis of halosilanes using iridium
catalysts. By combining this method with halogen exchange, various hydrosilanes were
efficiently synthesized starting from chlorosilanes.
Chart 1. Iridium amido complex 1-4
2. Results and discussions
3

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2
.1 Condition screening of catalytic hydrogenolysis reaction of Me SiX
3
The catalytic performance of 1–4 was initially surveyed using Me SiI as a substrate.
3
Although complex
1 did not exhibit catalytic activity (Table 1, entry 1) for hydrogenolysis
of Me SiI, it was successfully catalysed by the combination of
1 and LiOTf under basic
3
conditions. In the presence of
1 (10 mol %), LiOTf (10 mol %) and iPr EtN (1.1 equiv),
2
Me SiI reacted with H (4 atm) at 60 °C to form Me SiH in 87% yield (Table 1, entry 2).
3
2
3
Complex 2, which was alternatively prepared by the reaction of 1 with AgOTf, exhibited a
good catalytic activity without any co-catalysts, leading to the formation of Me SiH in the
3
highest yield of 91% (Table 1, entry 3). Complexes
3 and 4 were less reactive than 2, giving
Me SiH in 61 and 19% yields, respectively (Table 1, entries 4 and 5). Using the best catalyst
3
2
, hydrogenolysis of other Me SiX (X = OTf, Br, Cl) was investigated. The reaction of
3
Me SiOTf also efficiently proceeded to give Me SiH in 95% yield (Table 1, entry 6).
3
3
Although a diminished yield of 11% was observed in the reaction of Me SiBr, the yield was
3
significantly improved to 80% using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) instead of
i
Pr EtN as the base (Table 1, entries 7 and 8). It is reported that DBU increased the
2
4

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reactivity of chlorosilanes toward nucleophiles by forming an ionic complex, [12] and such
an effect of DBU probably improved the hydrosilane yield.
Next, hydrogenolysis of Me SiCl was performed. Since chlorosilanes are cheap and readily
3
available, they are arguably one of the most attractive raw materials in the silicon industry.
Thus, it is a great challenge to synthesize hydrosilanes from chlorosilanes. However, even
with DBU, hydrogenolysis of Me SiCl resulted in a trace production of Me SiH (Table 1,
3
3
entry 9).
2.2 Hydrogenolysis reaction of mono- and dichlorosilane
We found that the reactions of Me SiCl can be remarkably improved by pre-treatment with NaI,
3
which is known to undergo halogen exchange with chlorosilanes to give the corresponding
iodosilanes [13]. Thus, Me SiCl was initially mixed with 1 equiv of NaI, and successively treated
3
with 2 (10 mol%), iPr EtN (1.1 equiv), and H (4 atm) to give Me SiH in 84% yield (Table 2, entry
2
2
3
1). Hydrogenolysis of various chlorosilanes with bulkier substituents was examined by following
the same procedure. (nOct)Me SiCl underwent the reaction to give (nOct)Me SiH in 78% yield
2
2
(
Table 2, entry 2). A good yield of 61% was observed in the reaction of Et SiCl (Table 2, entry 3).
3
Hydrogenolysis of Me PhSiCl and MePh SiCl similarly proceeded, yielding the corresponding
2
2
5

ACCEPTED MANUSCRIPT
a
Table 1. Hydrogenolysis of Me SiX (X = I, Br, Cl, OTf) catalysed by 1-4
3
cat (10 mol%)
iPr EtN (1.1 equiv.)
2
Me
3
Si
X
+
H
4 atm)
2
3
Me Si H
C D , 60 ºC, 48 h
(
6 6
b
Entry
Cat
R SiX
Yield/ %
–
3
1
2
3
4
5
6
7
1
Me SiI
3
1 + LiOTf
Me SiI
3
87
2
3
4
2
2
2
2
Me SiI
3
91
Me SiI
61
3
Me SiI
19
3
Me SiOTf
95
3
Me SiBr
11
3
c
8
Me SiBr
80
3
c
9
Me SiCl
Trace
3
a
Reaction conditions: Me SiX (60 µmol), iPr EtN (66 µmol), cat (6.0 µmol), and H (4 atm) in
3
2
2
o
b
c
C D (0.5 mL) at 60 C for 48 h. NMR yield. DBU was used instead of iPr EtN.
6
6
2
hydrosilanes in 65% and 49%, respectively (Table 2, entries 4 and 5). Hydrogenolysis of a
dichlorosilane, Me SiCl , was also performed after the treatment with 2 equiv of NaI, resulting in
2
2
the formation of Me SiH albeit with a slightly decreased yield of 58%, which could be attributed to
2
2
the high volatility of Me SiH (Table 2, entry 6).
2
2
2.3 Hydrochlorosilane synthesis via selective monohydrogenolysis reaction of di- and
trichlorosilanes
6

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a
Table 2. Hydrogenolysis of chlorosilanes
2
(10 mol%)
H2 (4 atm)
NaI
n equiv)
iPr EtN
2
(
(1.1 × n equiv)
R
4–nSiCl
n
R4–nSiH
n
C H /THF
C
6
H
6
/THF
6
6
n = 1, 2
60 ºC, 48h
RT, 2h
b
Entry
Substrate
Product: Yield/ %
d
1
2
3
4
5
Me SiCl
Me SiH: 84
3
3
d
(nOct)Me SiCl
(nOct)Me SiH: 78 (71)
2
2
d
Et SiCl
Et SiH: 61 (54)
3
3
d
Me PhSiCl
Me PhSiH: 65 (58)
2
2
d
MePh SiCl
MePh SiH: 49 (42)
2
2
c
d
6
Me SiCl2
Me SiH : 58
2
2
2
a
Reaction conditions: chlorosilane (0.5 mmol), NaI (0.5 mmol) in C H /THF at RT for 2 h, and then
6
6
o
b
iPr EtN (0.55 mmol), 2 (0.05 mmol), and H (4 atm) at 60 C for 48 h. NMR yield (isolated yield).
2
2
c
d
NaI (1.0 mmol ) and iPr EtN (1.1 mmol) were used. Unreacted chrolosilanes remained in the
2
yields of 11 % (entry 1), 13 % (entry 2), 27 % (entry 3), 14 % (entry 4), 25 % (entry 5) and 8 %
(entry 6).
Next, we set our target at the selective monohydrogenolysis of di- and trichlorosilanes to produce
organochlorohydrosilanes, R SiHCl (n = 2, 3). Although they are highly useful organosilicon
4–n
n–1
compounds due to the orthogonal reactivity of Si–H and Si–Cl functions [14], selective synthesis of
these compounds via monoreduction of di- and trichlorosilanes using the conventional reducing
agents is very difficult. Thus far, chlorination of RSiH or R SiH has been reported as one
3
2
2
alternative route to organohydrochlorosilanes [15]. However, there is only one report that archived
monochlorination to selectively form R SiHCl and RSiH Cl in moderate to good yields [16].
2
2
7

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Considering the fact that hydrosilanes are normally prepared by the reduction of chlorosilanes as
mentioned above, direct synthesis of chlorohydrosilanes from cheap and versatile di- and
trichlorosilanes is more straightforward [7,15]. Thus, we initially treated Me SiCl with 1 equiv of
2
2
NaI at –35 °C and then conducted the hydrogenolysis. As a result, Me SiCl was selectively
2
2
converted to Me SiHCl in 61% yield (Table 3, entry 1). Monohydrogenolysis of (nHex)MeSiCl2
2
and Ph SiCl was also achieved with good selectivity, forming (nHex)MeSiHCl (57%) and
2
2
Ph SiHCl (71%), respectively (Table 3, entries 2 and 3). Monohydrogenolysis of a trichlorosilane,
2
PhSiCl , was also performed using 1 equiv of NaI, leading to the selective formation of PhSiHCl in
3
2
64% yield (Table 3, entry 4). It is noteworthy that almost no multihydrogenolysis was observed,
though only a trace amount of (nHex)MeSiH was detected in the reaction of (nHex)MeSiCl . To
2
2
the best of our knowledge, this is the first example of selective synthesis of
organochlorohydrosilanes from chlorosilanes by a reductive approach.
2
.4 One-pot hydrotrimethylsilylation of olefin with in-situ generated Me SiH
3
One notable feature of this method is that Me SiCl can be efficiently converted to Me SiH, which is
3
3
a highly flammable gas and rarely applied in synthetic processes, especially on a laboratory scale
[
17]. Because our method can generate Me SiH directly from Me SiCl, we applied our method for
3 3
8

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a
Table 3. Monohydrogenolysis of di-, and trichlorosilanes
2
(10 mol%)
NaI
1.0 equiv)
H2 (4 atm)
(
iPr EtN (1.1 equiv)
2
R
4–nSiCl
n
R4–nSiHCln–1
C H /THF
35 ºC to RT, 2h
C
6
H
6
/THF
6
6
n = 2, 3
–
60 ºC, 48h
b
Entry
Substrate
Product: Yield/ %
e
1
2
3
Me SiCl2
Me SiHCl: 61
2
2
d,e
(nHex)MeSiCl2
(nHex)MeSiHCl: 57 (51)
d,e
Ph SiCl2
Ph SiHCl: 71 (65)
2
2
c
e
4
PhSiCl3
PhSiHCl : 64
2
a
o
Reaction conditions: chlorosilane (0.5 mmol), NaI (0.5 mmol) in C H /THF at –35 C for 2 h,
6
6
o
b
and then iPr EtN (0.55 mmol), 2 (0.05 mmol), and H (4 atm) at 60 C for 48 h. NMR yield
2
2
c
d
e
(
isolated yield). NaI was added at –78 °C. Isolated as ethoxysilane. Unreacted chrolosilanes
remained in 22 % (entry 1), 26 % (entry 2), 12 % (entry 3), and 21 % (entry 4).
one-pot olefin hydrosilylation reactions to evaluate the utility of the system. As shown in Scheme 1,
after hydrogenolysis of Me SiCl, 1-octene (1 equiv) and a catalytic amount of Pt-based
3
hydrosilylation catalyst (5 mol%) were successively added to the reaction mixture, resulting in the
formation of Me (nOct)Si in 86% yield after 24 h at room temperature. Ethyl-3-butenoate was
3
similarly converted to Me Si[CH (CH ) COOEt] in 71% yield. Styrene and its derivatives also
3
2
2 2
underwent the hydrosilylation to afford the desired products in good yields.
2.5 Reaction mechanism
1
To shed light on the mechanism, the reaction of 2 with H was monitored by H NMR
2
9

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Scheme 1. One-pot hydrosilylation of olefins with in-situ generated Me SiH.
3
Pt-cat (5 mol%)
R
1
2
. halogen exchange
. hydrogenolysis
(1 equiv)
Me
Me
NMR yield (isolated yield)
Me Si
3
SiCl
Me SiH
3
C
6
6
H /THF
C H /THF
6
6
3
Si
R
O
3
Me Si
3
4
OEt
8
6 (78)%a
1 (58)%a
7
Me Si
Me Si
3
3
OMe
7
2 (64)%b
79 (69)%b
(α : β = 8: 92)
(
α : β = 7: 93)
a
b
H PtCl
was used as Pt-cat.
Pt (dvtms) /IMes were used as Pt-cat. dvtms:
2 3
2
6
divinyltetramethyldisiloxane, IMes: 1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene.
spectroscopy. On treatment of 2 with H (4 atm), complex 2 was partially converted to an iridium
2
1
hydride species 5 (42%), which exhibited IrH (–11.78 ppm) and NH (12.44 ppm) signals in the H
NMR spectrum. Complex 5 easily liberated H under vacuum, reproducing 2. Thus, isolation of 5
2
was not successful at this moment. Formation of Me SiH (33% yield based on 5) was confirmed
3
when Me SiI was added to a C D –CD Cl solution of the in-situ prepared 5. Based on these
3
6
6
2
2
experiments, we postulated one possible reaction pathway for the hydrogenolysis of halosilanes,
in which 2 plays a pivotal role to assist hydrogen-atom-transfer to halosilanes (Scheme 2). It is
known that metal-ligand bifunctional catalysts promote hydrogenation of carbonyl compounds and
imines via a six-membered transition state, in which the metal-hydride and the amino-proton
simultaneously migrate to the substrates [11]. It is likely that such the cooperative action of 2 would
1
0

ACCEPTED MANUSCRIPT
be important for the observed efficient hydrogenolysis of halosilanes. Further mechanistic study is
now underway.
Scheme 2. Plausible reaction pathway of hydrogenolysis reaction of halosilane
+
Ir
N
3
R Si H
+
N
HX·base
Ar
O
2
H
2
+
R Si
X
3
+
H
H
Ir
base
N
N
Ar
O
5
3. Conclusion
In conclusion various hydrosilanes were efficiently prepared via hydrogenolysis of halosilanes
catalysed by a metal-ligand bifunctional iridium catalyst 2. The method is applicable to the reaction
of a wide variety of chlorosilanes, which are commercially available at low cost, when the system
was combined with the pretreatment with NaI. Selective monohydrogenolysis of di- and
trichlorosilanes was achieved to form monohydrochlorosilanes, which are good precursors for the
synthesis of various organosilicon compounds. We also demonstrated the utility of our method for
11

ACCEPTED MANUSCRIPT
hydrotrimethylsilylation of olefins using in-situ prepared Me SiH from Me SiCl. We believe that
3
3
the present method could provide one alternative synthetic route to produce various useful silicon
compounds including chlorohydrosilanes.
4. Experimental
4.1. General considerations
Unless otherwise noted, all manipulations were performed under a nitrogen atmosphere using
Schlenk techniques or a glove box. n-Hexane, tetrahydrofuran, and dichloromethane were purified
by a solvent purification system (MBraun SPS-800 or Glass Contour Ultimate Solvent System).
C D was dried over sodium benzophenone ketyl and distilled. CD Cl was dried over CaH and
6
6
2
2
2
distilled. Complex 1 was purchased from Kanto Chemical Co., Inc. Complex 3, and 4 were
synthesized by reported procedures [10]. H gas (purity > 99.99999 vol%) was purified by gas clean
2
column (CC-X, NIKKA SEIKO CO., LTD) and gas dry column (DC-A4, NIKKA SEIKO CO.,
LTD). H PtCl was purchased from Wako Pure Chemical Industrial, Ltd. All other reagents were
2
6
purchased from commercial suppliers and used without further purification unless otherwise noted.
1
13
1
19
29
1
1
13
19
29
H, C{ H}, F and Si{ H} NMR spectra ( H, 600 MHz; C, 150 MHz; F, 564 MHz; Si, 119
1
2

ACCEPTED MANUSCRIPT
MHz) were recorded using a Bruker AVANCE 600 spectrometer. Chemical shifts are reported in �
2
9
(
ppm) and are referenced to the 1,4-bis-(trimethylsilyl)benzene for Si (C D , –4.20 ppm), to the
6 6
1
9
1
fluorobenzene for F (C D , –112.75 ppm) and to the residual solvent signals for H (7.16 ppm for
6
6
1
3
C D and 7.26 ppm for CDCl ) and C (128.06 ppm for C D and 77.16 ppm for CDCl ).
6
6
3
6
6
3
Elemental analyses were performed on a Thermo Scientific FLASH2000 CHNS analyzer. Column
chromatography was performed with silica gel (Kanto Chemical CO., INC. Silica gel 60 N,
100-210 µm) or a Yamazen EPCLC AI-580S using Universal Column Premium (silica gel, 30 µm).
4.2. Synthesis of 2
To a CH Cl (15 mL)-MeCN (2 mL) solution of 1 (250 mg, 370 µmol) was added AgOTf (95 mg,
2
2
370 µmol) at room temperature. After stirring for 30 min, the mixture was filtered through a Celite
pad and the filtrate was evaporated under vacuum. The resulting solid was extracted with a 20 mL
of CH Cl –hexane (9:1, v/v) mixture and the solution was again filtered through a Celite pad to
2
2
completely remove AgCl. The solution was evaporated and further dried under vacuum at 60 ºC for
1
3
h to give 2 as an orange powder (226 mg, 88%). Spectroscopic data for 2: H NMR [C D –CD Cl
6
6
2
2
(
3:2, v/v), 25 ºC]: δ 1.12 (s, 15H, C Me ), 2.69 (s, 6H, NMe ), 6.59 (dd, 2H, J = 8.2 Hz, 1.6 Hz,
5 5 2
1
3

ACCEPTED MANUSCRIPT
Ar-H), 7.00 (dd, 1H, J = 6.2 Hz, J = 1.2 Hz, pyridyl), 7.44–7.46 (m, 3H, Ar-H, pyridyl), 7.91 (dd,
1
3
1
H, J = 6.2 Hz, 1.2 Hz, pyridyl), 8.28 (dd, 1H, J = 6.2 Hz, 1.2 Hz, pyridiyl). C NMR [C D –
6 6
CD Cl ]: δ 8.40 (C Me ), 41.0 (NMe ), 86.7 (C Me ), 112.6 (Ar), 120.4 (Ar), 122.5 (Ar), 126.0 (q,
2
2
5
5
2
5
5
JCF = 318 Hz, CF ), 128.2 (Ar), 138.6 (Ar), 138.9 (Ar), 148.4 (Ar), 150.0 (Ar), 156.1 (Ar), 169.0
3
1
9
(
C=O). F NMR [C D –CD Cl (3:2, v/v), 25 °C]: δ –79.13. Anal. Calcd for C H F IrN O S: C,
6 6 2 2 25 29 3 3 4
41.09; H, 4.08; N, 5.86; S, 4.47. Found: C, 41.31; H, 3.83; N, 5.41; S, 4.09.
4
.3. Catalytic hydrogenolysis of Me SiX (X = I, OTf, Br)
3
A typical procedure (Table 1, entry 3) is as follows. A J-Young NMR tube was charged with a
C D (0.50 mL) suspension of 2 (4.3 mg, 6.0 µmol), 1,4-bis(trimethylsilyl)benzene (6.7 mg, 30
6
6
µmol) as an internal standard, iPr EtN (11 µL, 66 µmol), and Me SiI (8.3 µL, 60 µmol). After the
2
3
mixture was degassed by freeze-pump-thaw cycles (×2), H (1 atm) was introduced to the NMR
2
tube at –196 °C [18]. By following the same procedure, H was introduced to the NMR tube again.
2
The reaction mixture was warmed to 60 °C and kept at this temperature for 48h. Formation of
1
Me SiH (55 µmol, 91%) was confirmed by H NMR spectroscopy.
3
1
4

ACCEPTED MANUSCRIPT
4
.4. Successive halogen exchange and hydrogenolysis of Me SiCl
3
A typical procedure (Table2, entry 1) is as follows. A Schlenk tube equipped with a Teflon valve
was charged with a 5.0 mL of C D –THF (3:2, v/v) suspension of cyclohexane (47 µL, 500 µmol)
6
6
as an internal standard, NaI (75 mg, 500 µmol), and Me SiCl (63 µL, 500 µmol). After the mixture
3
was stirred at room temperature for 2 h, 2 (30 mg, 50 µmol) and iPr EtN (87 µL 550 µmol) were
2
added. After the solution was degassed by freeze-pump-thaw cycles (×2), H (1 atm) was
2
introduced to the Schlenk tube at –196 °C. By following the same procedure, H was introduced to
2
the NMR tube again. The reaction mixture was kept at 60 °C for 48 h and cooled to –35 ºC, and the
NMR sample was prepared at the temperature. Formation of Me SiH (420 � mol, 84%) was
3
1
confirmed by H NMR spectroscopy.
4.5. Successive halogen exchange and hydrogenolysis of chlorosilanes
A typical procedure (Table 2, entry 3) is as follows. Hydrogenolysis of Et SiCl (84 µL, 500
3
µmol) was performed following the same procedure for hydrogenolysis of Me SiCl. After 48h at
3
1
6
0 °C, formation of Et SiH (310 µmol, 61%) was confirmed by H NMR spectroscopy. The
3
1
5

ACCEPTED MANUSCRIPT
reaction mixture was diluted with hexane (15 mL) and separated by column chromatography
(
silica-gel, n-hexane) to give Et SiH (31 mg, 270 µmol, 54%) as a colorless oil.
3
4
.6. Selective monohydrogenolysis of R SiCl
4-n n
A typical procedure (Table 3, entry 3) is as follows. A Schlenk tube equipped with a Teflon valve
was charged with a 2.5 mL of C H –THF (4:1, v/v) solution of Ph SiCl (104 µL, 500 µmol) and
6
6
2
2
cyclohexane (47 µL, 500 µmol). The solution was cooled to –35 ºC in the glove box freezer to
which was slowly added 2.5 mL of a C H –THF (2:3, v/v) suspension of NaI (75 mg, 500 µmol).
6
6
The mixture was stirred at room temperature for 2 h. To the suspension, was added 2 (30 mg, 50
µmol) and iPr EtN (87 µL, 550 µmol). After the solution was degassed by two freeze-pump-thaw
2
cycles (×2), H (1 atm) was introduced to the Schlenk tube at –196 °C. By following the same
2
procedure, H was introduced to the NMR tube again. The reaction mixture was warmed to 60 °C
2
1
and stirred for 48 h to give Ph SiHCl (360 µmol, 71% by H NMR). Unreacted Ph SiCl (60 µmol,
2
2
2
1
1
2%) was also detected by H NMR. The mixture was treated with EtOH (0.50 mL, 860 µmol) and
iPr EtN (0.85 mL, 860 µmol) at room temperature and stirred for 30 min. The solution was diluted
2
1
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with hexane (40 mL) and purified by column chromatography (silica-gel, hexane) to give
Ph SiH(OEt) (81 mg, 325 µmol, 65%).
2
4
.7. Synthesis of (n-Oct)Me Si via successive hydrogenolysis and hydrosilylation using H PtCl as a
3
2
6
catalyst
Successive halogen exchange and hydrogenolysis of Me SiCl (63 µL, 500 µmol) was similarly
3
performed following the above mentioned procedure for the entry 1 in Table 2. To the resulting
solution containing Me SiH, was added a THF solution of H PtCl (0.1 M, 250 µL, 25 µmol) and
3
2
6
1-octene (72 µL, 500 µmol) at –196 ºC. The mixture was stirred at room temperature for 24 h to
1
give (n-Oct)Me Si [420 µmol, 86% yield by H NMR analysis using cyclohexane (47 µL, 500
3
µmol) as an internal standard]. The reaction mixture was diluted with hexane (15 mL), filtered
through a silica-gel pad, and evaporated. The resulting colorless oil was purified by flash silica-gel
column chromatography (eluent: hexane) to give (n-Oct)Me Si (78 mg, 390 µmol, 78%) as a
3
colorless oil.
4
.8. Synthesis of Me SiCH CH Ph via successive hydrogenolysis and hydrosilylation using
3 2 2
1
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Pt (dvtms) /IMes as a catalyst
2
3
Successive halogen exchange and hydrogenolysis of Me SiCl (63 µL, 500 µmol) was similarly
3
performed following the above mentioned procedure for the entry 1 in Table 2. To the resulting
solution containing Me SiH, was added a xylene solution of Pt (dvtms) (0.1 M, 150 µL, 12.5
3
2
3
µmol), IMes (7.6 mg, 25 µmol), and styrene (57 µL, 500 µmol) at –196 ºC. The mixture was stirred
at room temperature for 24 h to give CH CH(SiMe )Ph (α-isomer) and Me SiCH CH Ph
3 2 2
3
3
1
(β-isomer) [α : β = 7 : 93, 360 µmol, 72% by H NMR analysis using cyclohexane (47 µL, 500
µmol) as an internal standard]. The reaction mixture was diluted with hexane (30 mL), filtered
through a silica-gel pad, and evaporated. The resulting colorless oil was purified by flash silica-gel
column chromatography (eluent: hexane) to give Me SiCH CH Ph (β-isomer) (57 mg, 320 µmol,
3
2
2
64%) as a colorless oil.
4.9. Compound Characterization
Me SiH [19], (n-Oct)Me SiH [20], Et SiH [21], Me PhSiH [21], MePh SiH [21], Me SiHCl [22],
3
2
3
2
2
2
(
n-Hex)MeSiHCl [23], (n-Hex)MeSiH(OEt) [23], Ph SiHCl [24], Ph SiH(OEt) [25], PhSiHCl [26],
2 2 2
1
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(
n-Oct)SiMe [16a], Me Si[(CH ) COOEt] [27], CH CH(SiMe )Ph [28], Me SiCH CH Ph [16a],
3
3
2 3
3
3
3
2
2
CH CH(SiMe )-4-(OMe)C H [29], and Me Si[CH CH -4-(OMe)C H ] [30], were identified by
3
3
6
4
3
2
2
6
4
1
13
1
29
comparing their H, C{ H}, and/or Si NMR data with those previously reported.
4
.10. Successive reaction of 2 with H and Me SiI
2 3
A J-Young NMR tube was charged with a 0.5 mL of C D –CD Cl (3:2 v/v) suspension of 2 (10.
6
6
2
2
mg, 15 µmol), and 1,4-bis(trimethylsilyl)benzene (6.7 mg, 30 µmol) as an internal standard. The
solution was degassed by two freeze-pump-thaw cycles, and H (1 atm) was introduced to the NMR
2
tube at –196 °C. This procedure was repeated twice. The reaction mixture was gradually warmed to
1
room temperature and the reaction was monitored by H NMR spectroscopy at the same
temperature. After 30 min, 5 was formed (42%, 6.3 µmol, Figure S2) the reaction mixture was
cooled to –35 ºC in the glove box freezer and added Me SiI (2.6 µL, 15 µmol) and iPr EtN (2.1 µL,
3
2
1
5 µmol) under N atmosphere. After 2 h at 60 ºC, formation of Me SiH (2.1 µmol, 33% based on
2
3
1
1
5
) was confirmed by H NMR spectroscopy (Figure S3). Spectroscopic data for 5: H NMR [C D –
6 6
CD Cl (3:2, v/v), 25 ºC]: δ –11.78 (s, 1H, Ir-H), 1.29 (s, 15H, C Me ), 2.67 (s, 6H, NMe ), 6.46
2
2
5
5
2
(dd, J = 8.4, 1.2 Hz, 2H, Ar-H), 6.99 (dd, 1H, J = 5.8, 1.2 Hz, pyridyl), 7.31 (dd, J = 6.0, 1.5 Hz, 1H,
1
9

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pyridyl), 7.69 (dd, 2H, J = 8.1, 1.3Hz, Ar-H), 7.84 (dd, 1H, J = 6.0, 1.4 Hz, pyridyl)), 8.74 (dd, 1H,
1
3
1
J = 5.8, 1.4 Hz, pyridyl)), 12.44 [br, 1H, NH(C=O)]. C{ H} NMR [C D –CD Cl (3:2, v/v), 25
6
6
2
2
ºC]: δ 9.40 (C Me ), 40.7 (NMe ), 88.5 (C Me ), 115.0 (Ar), 117.6 (Ar), 124.2 (Ar), 120.6 (q, J =
5
5
2
5
5
CF
3
19 Hz, CF ), 126.8 (Ar), 138.2 (Ar), 140.4 (Ar), 144.2 (Ar), 147.5 (Ar), 149.5 (Ar), 169.7
3
1
9
[
NH(C=O)]. F NMR [C D –CD Cl (3:2, v/v), 25 ºC]: δ –78.41.
6 6 2 2
Appendix A. Supplementary material
NMR spectra of the reaction of 2 with H and Me SiI. This material is available free of charge
2
3
via the Internet.
Acknowledgements
This research was supported by the project “Development of Innovative Catalytic Processes for
Organosilicon Functional Materials” (Project Leader: K. Sato) of the Ministry of Economy, Trade
and Industry, Japan (METI), and the New Energy and Industrial Technology Development
Organization (NEDO). The authors thank Prof. J. Ichikawa (University of Tsukuba, Japan) for the
helpful discussion.
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0

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Notes and references
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3
generated via hydride-abstraction from 3-trimethylsilylcyclohexa-1,4-diene, and the Me SiH source
3
2
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was synthesized from Me SiCl and lithiated cyclohexadiene. See the following references (a) A.
3
Simonneau, M. Oestreich, Angew. Chem. Int. Ed. 52 (2013) 11905–11907 [Angew. Chem. 125
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[
18] The H pressure (4 atm) during the reaction was checked by the alternative experiment using
2
an autoclave: Hydrogenolysis of Me SiI (17 µL, 120 µmol) was similarly performed in the presence
3
of 2 (8.6 mg, 12 µmol), iPr EtN (22 µL, 132 µmol), C D (1.0 mL), and
2
6
6
1,4-bis(trimethylsilyl)benzene (13 mg, 60 µmol) in an autoclave (20 mL) equipped with a pressure
gauge. It was confirmed that the H pressure of the autoclave become 4 atm during the reaction at
2
6
0 °C. The use of reaction vessel with a larger headspace resulted in the decreased yield of Me SiH,
3
thus yielding Me SiH (102 µmol, 85% by NMR analysis) after 48 h.
3
[
[
[
[
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•
We reported the catalytic hydrosilanes synthesis from R SiX (X = I, Br, Cl, OTf) via
3
Ir-catalyzed hydrogenolysis reaction.
•
This reaction was a first example of selective hydrochlorosilanes synthesis from
chlorosilanes by reductive reaction.
•
We have also developed efficient one-pot hydrotrimethylsilylation reactions of various
olefins with in-situ generated Me SiH from Me SiCl.
3
3