Heterogeneous hydrosilylation reaction catalysed by platinum complexes immobilized on bipyridine-periodic mesoporous organosilicas

Article abstract of DOI:10.1039/c9dt00078j

The utility of a bipyridine periodic mesoporous organosilica, BPy-PMO, as a support material of a hydrosilylation catalyst was investigated in the hydrosilylation of phenylacetylene with trimethoxysilane. [PtMe₂(BPy-PMO)] (1) exhibited a modera

Full text of DOI:10.1039/c9dt00078j

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: Y. Naganawa, Y.
Maegawa, H. Guo, S. S. Gholap, S. Tanaka, K. Sato, S. Inagaki and Y. Nakajima, Dalton Trans., 2019, DOI:
10.1039/C9DT00078J.
This is an Accepted Manuscript, which has been through the
Volume 45 Number
1 7 January 2016 Pages 1–398
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
Accepted Manuscripts are published online shortly after
An international journal of inorganic chemistry
www.rsc.org/dalton
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1477-9226
PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
framework
a Zr-metal–organic
rsc.li/dalton

Please do not adjust margins
Page 1 of 7
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT00078J
Journal Name
ARTICLE
Heterogeneous hydrosilylation reaction catalysed by platinum
complexes immobilized on bipyridine-periodic mesoporous
organosilicas
Received 00th January 20xx,
Accepted 00th January 20xx
Yuki Naganawa,a Yoshifumi Maegawa, b Haiqing Guo,a Sandeep Suryabhan Gholap,a Shinji Tanaka,a
Kazuhiko Sato,a Shinji Inagaki,*b and Yumiko Nakajima*a
DOI: 10.1039/x0xx00000x
www.rsc.org/
The utility of a bipyridine periodic mesoporous organosilica, BPy-PMO, as a support material of a hydrosilylation catalyst
was investigated in the hydrosilylation of phenylacetylene with (MeO)3SiH. [PtMe2(BPy-PMO)] (1) exhibited a moderate
catalytic activity, whereas the reaction was successfully catalysed by [PtMe2(BPy-PMO-TMS)] (2) bearing end-capped TMS
groups on the surface. Spectroscopic analyses of 2 revealed that the porous structure of BPy-PMO-TMS remained almost
unchanged through the reaction. The hot filtration test supported the nonleaching property of 2, thereby exhibiting good
reusability without the loss of the product yields.
surface-area solids without a linker.7 In this context, we focus
on a periodic mesoporous organosilica containing a 2,2-
bipyridine (bpy) unit within the framework (bipyridine-periodic
Introduction
Hydrosilylation is one of the most important methods for the
synthesis of various organosilicon compounds.1 Platinum
catalysts, such as Speier’s catalyst (H2PtCl6)2 and Karstedt’s
catalyst,3 are widely utilized in the silicon industry because they
exhibit high catalytic activity, selectivity, and high stability
toward oxygen and moisture. As a result, significant amounts of
Pt are consumed in the silicon industry (5.6 tons in 2007, ca. 3%
of the annual global platinum production),4 and the high cost
and uncertainty of the long-term supply of precious platinum
are becoming a larger issue. In addition, separating the catalyst
from the reaction mixture is often problematic in some
industrial processes.1c As a result, the development of a
hydrosilylation process using immobilized Pt catalysts, which
has the advantage of easy catalyst recovery, is attracting great
interest.5
To prepare immobilized hydrosilylation catalysts, a wide variety
of support materials have been used to date, including both
organic polymers and inorganic substrates.6 The substrates
normally possess functional linkages and connect with active
metal centers, which sometimes interact with neighboring
metals due to the flexible nature of the linkers, leading to a
decrease in their catalytic performances. An alternative way to
develop novel heterogeneous catalysts from effective
homogeneous catalysts is to support them directly on high-
mesoporous organosilica: BPy-PMO)8-16 as a solid chelating
ligand (Figure 1). In the structure of BPy-PMO, the 2,2-
bipyridine ligands are regularly and densely arranged in the
siloxane network and exposed on the pore surface with a large
specific surface area (>600 m2 g–1). Thus, BPy-PMO enables us
to directly immobilize various homogeneous catalysts on the
molecularly well-defined pore surface and thus suppress
undesired interaction and aggregation of the metal centers.
Another notable feature of BPy-PMO is the large pore size (3.8
nm in diameter), which allows the smooth diffusion of reactant
molecules in the mesochannel. By utilizing these characteristic
properties, we have thus far synthesized various BPy-PMO-
based metal complexes including Ir,8-10 Ru,8,11,12 Re,8,13 Pd,8 Au,14
Mo,15 and Rh16 on the PMO pore surface and demonstrated
their utility as heterogeneous catalysts for organic
syntheses.8,9,13,14
X
O
O
Si
O
N
Si
O
X
O
X
O
N
Si
N
Si
O
O
O
N
O
Si
O
X
O
Si
Si
O
O
nm
O
N
Si
3.8
O
Si
X
O
O
N
Si
O
O
X
O
X
BPy-PMO ( = H)
X
BPy-PMO-TMS ( = SiMe3)
BPy-PMOs
a. Interdisciplinary Research Center for Catalytic Chemistry
National Institute of Advanced Industrial Science and Technology
Tsukuba, Ibaraki 305-8565, Japan. E-mail: yumiko-nakajima@aist.go.jp
b. Toyota Central R&D Laboratories, Inc.
Figure 1. Bipyridine-periodic mesoporous organosilica (BPy-PMO, X
= H) and end-capped BPy-PMO (BPy-PMO-TMS, X = SiMe3).
Nagakute, Aichi 480-1192, Japan. E-mail: inagaki@mosk.tytlabs.co.jp
† Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any supplementary
information available should be included here]. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 2 of 7
ARTICLE
Journal Name
Herein, we synthesized BPy-PMO-based Pt complexes17 as
hydrosilylation catalysts. A carrier support of hydrosilylation
catalysts should be thermally and chemically stable during the
reaction and must provide good accessibility and dispersion of
the active sites to apply the catalyst system for the curing of
silicone products. Considering this, we were motivated to
examine the utility of BPy-PMO as the support of the
hydrosilylation catalyst. In this study, we tested two types of
BPy-PMO bearing different siloxane frameworks with silanol
groups (X = H; BPy-PMO) or TMS-protected silanol groups (X =
SiMe3; BPy-PMO-TMS) as shown in Figure 1.
Me
View Article Online
Me
Pt
DOI: 10.1039/C9DT00078J
N
N
N
N
[PtMe2(µ-SMe2)]2
(1 equiv of bpy unit on surface)
TMS
TMS
O
O
O
Si
Si
Si
Si
OR
O
OR
O
OR
O
OR
O
O
O
O
R = Me or i-Pr
PtMe2(BPy-C4-FSM-16) (
3a
BPy-C4-FSM-16
BPy-C4-Silica gel
)
3b
PtMe2(BPy-C4-Silica gel) (
)
Results and Discussion
Formation of Pt complexes on solid supports
Scheme 2. Synthesis of [PtMe2(BPy-C4-FSM-16)] (3a) and
[PtMe2(BPy-C4-Silica gel)] (3b).
First, the formation of bipyridine-based Pt complex17 was
attempted by simply mixing BPy-PMO and Karstedt’s catalyst as
a precursor complex in solution. However, the reaction was not
successful, leading to the formation of the compounds with a
small Pt loading amount of ~30 mol g–1. This result indicates
that BPy-PMO is not a suitable support for the Karstedt’s
catalysts. Formation of Pt(II) complex was then performed by
following the synthetic procedure of [PtMe2(bpy)],18 in which
[PtMe2(-SMe2)]2 was used as a precursor. Rigorous stirring of
the powder of BPy-PMOs (X = H and SiMe3; Figure 1) in a
benzene solution containing [PtMe2(-SMe2)]2 (0.15 equiv of
bpy unit on surface) at 6 °C resulted in the formation of
[PtMe2(BPy-PMO)] (1) (Scheme 1; see the Supporting
Information). The white color of BPy-PMO changed to light pink
(1) or purple (2), implying the formation of Pt-bipyridine
complex on the pore surface of BPy-PMO. Graft-type Pt-
bipyridine complexes 3a and 3b were also prepared for
comparison using TMS-protected mesoporous silica (FSM-16)
and silica gel as a support, respectively (Scheme 2; Figures S1
and S2).
Characterization of Pt-complex-immobilized solid supports
The amounts of bipyridine ligand in solid supports and Pt in
catalysts 1, 2, 3a, and 3b were measured by CHN elemental
analysis and energy-dispersive X-ray spectrometry (EDX)
analysis, respectively. The results are summarized in Table 1.
The amounts of bipyridine ligand in BPy-PMO and BPy-PMO-
TMS were 3.18 and 2.92 mmol g–1. Pt loading amounts in 1 and
2 were 0.26 and 0.36 mmol g–1. When all Pt ions coordinated
with bipyridine ligands in 1:1 ratio, this EDX result indicates that
there are large amounts of free bipyridine units (88% for 1 and
82% for 2) on the pore surface (see, Experimental Section). In
contrast, although the loading amounts of Pt in 3a and 3b were
similar to those of bipyridine ligands in the supports (0.38 mmol
g–1 for 3a and 0.36 mmol g–1 for 3b), almost no free bipyridine
ligands exist in 3a and 3b.
To investigate the structural change of solid supports during the
immobilization of Pt complex, powder X-ray diffraction (XRD)
patterns and nitrogen adsorption/desorption isotherms were
measured (Figure S3-S6). The XRD patterns of 1, 2, and 3a
showed an intense peak at 2 values of 1.86°, 1.82°, and 1.88°,
respectively, indicating that well-ordered mesostructures of
parent solid supports remained (Figures S3–S5). For PMO
complexes 1 and 2, four additional peaks were observed at
scattering angles of 7.60°, 15.2°, 22.9°, and 30.8° due to the
molecular-scale periodicity of the bipyridine groups in the pore
walls (Figures S3 and S4). Table 1 summarizes the values of the
Brunauer–Emmett–Teller surface area (SBET) and t-plot pore
volume (Vt-plot), and the density functional theory pore diameter
(dDFT) obtained from nitrogen adsorption/desorption isotherms
of four solid catalysts and parent solid supports (Figures S7 and
S8). For 1, SBET, Vt-plot, and dDFT values were decreased compared
with those of parent BPy-PMO, indicating the occurrence of
partial structural change by immobilization of the Pt complex.
In contrast, SBET, Vt-plot, dDFT values of 2 and BPy-PMO-TMS were
nearly constant, meaning the preservation of uniform
mesoporous structure even after the immobilization of the Pt
complex. This result is ascribed to improvement in the
structural stability of the pore framework by TMS protection. A
similar positive effect by the TMS group was also previously
reported for BPy-PMO.15 For 3a and 3b, SBET, Vt-plot, and dDFT
values were slightly reduced compared with those of parent
X
O O
O
OX
Si
Si
O
N
N
N
N
O
X
BPy-PMO ( = H)
X
X
Si O
OX
Si
O
O Si
XO
Si
O
O
X
BPy-PMO-TMS ( = SiMe3)
O
[PtMe2(µ-SMe2)]2
(0.15 equiv of bpy unit on surface)
X
O O
O
OX
Si
Si
O
Si O
O
N
N
O
X
O Si
X
O O
1
PtMe2(BPy-PMO) ( )
Pt
X
Me Me
X
2
O
PtMe2(BPy-PMO-TMS) ( )
Si
Si
O
N
N
O
Scheme 1. Synthesis of [PtMe2(BPy-PMO)] (1) and [PtMe2(BPy-
PMO-TMS)] (2).
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 7
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
supports, suggesting the almost complete preservation of The catalytic activity of 1 and 2 toward hydrosilylation was
View Article Online
DOI: 10.1039/C9DT00078J
original porous structures by TMS protection.
examined using phenylacetylene as a model substrate (Table 2).
Pt-catalyzed hydrosilylation of terminal alkynes has been
Table 1. Physicochemical properties of PMO complexes 1 and 2, extensively examined as one of the common preparation
and graft-type complexes 3a and 3b.
methods of a series of vinylsilanes, which are valuable synthetic
intermediates in organic chemistry, although the mixture of -
trans and  adducts was often obtained in the reactions.20 In
the presence of a catalytic amount of 1 (5 mol% Pt), the reaction
of phenylacetylene with (MeO)3SiH proceeded at 60 °C, and the
hydrosilylated product was obtained after 15 h as the mixture
of -trans and  adducts (β-trans/ = 70/30), albeit in a low
yield (10%) (Table 2, Entry 1). Complex 2 also catalysed the
hydrosilylation reaction to give the hydrosilylated products in
higher yield, 82%, with the similar ratio of -trans/ = 72/28
(Table 2, entry 2). The yield was improved to 98% after a longer
reaction time of 24 h (Table 2, entry 3).
A catalytic activity of a homogeneous catalyst, [PtMe2(bpy)],
was also tested for reference. This reaction afforded the
hydrosilylated product in 97% yield with the β-trans/ ratio of
73/27 (Table 2, entry 4). Thus, no deleterious effect on the
catalytic activity was observed after the immobilization on BPy-
PMO.
sample
bpy unit
Pt
SBET
Vt-pot
dDFT
[nm]c)
c)
c)
[mmol
amount
[m2 g–1
]
[cc g–1
]
a)
bpy g–1
]
[mmol Pt
b]
g–1
]
BPy-PMO
3.18
―
―
0.26
―
764
478
654
0.58
0.31
0.45
4.4
3.9
4.0
1
BPy-PMO-
2.92
TMS
2
―
0.36
632
575
0.42
0.44
3.9
3.8
BPy-C4-
FSM-16
3a
0.38
―
―
0.38
528
402
0.36
0.46
3.8
5.7
BPy-C4-
Silica gel
3b
0.42
―
―
0.36
373
0.37
5.5
a The amounts of bpy unit in support were determined by CHN
b
c
Table 2. Hydrosilylation of phenylacetylene.a)
elemental analysis.
Determined by EDX analysis.
Ph
Determined from nitrogen adsorption/desorption isotherms
at liquid nitrogen temperature and calculated using the BET
method (SBET), t-plot method (Vt-plot), or density functional
theory (dDFT).
Ph
(MeO)3Si
Ph
H
Cat (5 mol% Pt)
+
+
benzene
60 °C, Time
Si(OMe)3
-trans
(MeO)3SiH

entry
cat (Time)
% conv.b)
% conv.b)
% yieldb)
[-trans/]
10 [70/30]
78 [72/28]
98 [72/28]
97 [72/28]
alkyne
80
hydrosilane
Complexation of Pt and bipyridine was confirmed by UV-vis
diffuse reflectance spectroscopy (Figure S9). The UV-vis
absorption spectrum of the model complex [PtMe2(bpy)] in
toluene showed partly structured absorption in the range of
400–600 nm due to the metal-to-ligand charge transfer (MLCT)
band of the Pt-bipyridine complex.19 However, complex 1
showed a weak absorption in the same range. Because the
absorption intensity is weak, a small amount of the desired Pt-
bipyridine complex seems to form on the pore surface. It is also
likely that an undesired Pt complex was formed by the reaction
of the Pt precursor with the surface silanol groups. In contrast,
2 showed a broad absorption band centered at 540 nm in the
range of 450–650 nm, which can be attributed to the Pt-
bipyridine complex on the pore surface. The red-shift of the
absorption band compared with that of [PtMe2(bpy)] might be
due to the changes in electronic state of the Pt-bipyridine
complex by direct attachment of silicon atoms at both sides of
the bipyridine ligand and end-capping of surface silanol groups
with TMS groups. The red-shift of the MLCT band due to the
silicon substitution was also reported in other metal-
immobilized BPy-PMO.8 Graft-type complexes 3a and 3b
showed a broad absorption band centered at ~470 nm, which is
similar to that of PtMe2(bpy) in toluene solution, indicating that
Pt complexes in 3a and 3b were located in a hydrophobic
environment.
1
2
3
4
1 (15 h)
2 (15 h)
2 (24 h)
65
82
85
>99
>99
>99
>99
[PtMe2(bpy)]
(24 h)
5
6
3a (24 h)
3b (24 h)
97
93
>99
97
97 [72/28]
93 [71/29]
a
Reaction conditions: catalyst (0.01 mmol Pt), alkyne (0.2
b
mmol), hydrosilane (0.2 mmol) in benzene (1 mL) at 60 °C.
Determined by H NMR analysis with mesitylene (0.2 mmol)
1
as an internal standard.
It is noteworthy that both phenylacetylene and (MeO)3SiH were
considerably consumed, with 80% and 65% conversion,
respectively, in the reaction catalysed by 1, although the
reaction gave only 10% yield of the products. We tentatively
ascribe this lower product yield to the reactive silanol groups on
the PMO-siloxane surface, which could react with
hydrosilylated product, (trimethoxysilyl)styrene, to give the
end-capped BPy-PMO.21 To elucidate this point, the solid-state
29Si MAS NMR analysis was conducted. The 29Si MAS NMR
spectrum of 1 displayed two signals at 66.9 ppm and 78.3 ppm
assignable to the T2 unit and T3 unit of siloxane matrix,
respectively (Figure 2(a)). The clear disappearance of the T2 unit
of 1 after the catalytic reaction suggests the occurrence of a
silane-coupling reaction between BPy-PMO and product, which
leads to the conversion of the T2 unit to the corresponding T3
Catalytic activity of Pt catalysts immobilized on BPy-PMO
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 4 of 7
ARTICLE
Journal Name
unit (Figure 2(b)). Because the signal intensity of the Qn unit was catalysed by 3a or 3b was partly promoted by leaching Pt
View Article Online
not sufficiently high to be identified under this measurement species, such as Pt nanoparticles.7b,22 Considering that 2
DOI: 10.1039/C9DT00078J
conditions, it is likely that the dehydrogenative coupling of possesses many spare bipyridine units (82%) that are densely
silanol with (MeO)3SiH hardly proceeded. The spectrum of 2 arranged on the pore surface as determined above, we
shows an additional signal due to the TMS protecting group at postulated that the free bipyridine would be helpful for
12.9 ppm instead of the T2 unit, indicating that the T2 unit in 1 suppression of leaching of Pt species from the pore surface.
was mostly consumed by TMS protection (Figure 2(c)). As
Si(OMe)3
expected, there was no significant difference in 29Si NMR
spectrum after the hydrosilylation by 2. Thus, the utility of TMS-
end-capping to enhance chemical stability of the mesoporous
structure was supported (Figure 2(d)).
Pt cat
(5 mol% for
(0.1 mol% for
2
3
)
-trans
)
+
Filtered at 60 °C
(0.1 m filter)
benzene (5 mL)
60 °C, 1 h
(MeO)3Si
60 °C, Time
+
(MeO)3SiH

Figure 3. Time course in the hot filtration test of hydrosilyllation
of phenylacetylene and trimethoxysilane with cat 2 and 3.
Reaction conditions: catalyst (0.01 mmol Pt for 2, 0.001 mmol
Pt for 3), alkyne (0.2 mmol for 2, 1.0 mmol for 3), hydrosilane
(0.2 mmol for 2, 1.0 mmol for 3) in benzene (1 mL for 2, 5 mL
for 3) at 60 °C. Determined by 1H NMR analysis with mesitylene
(0.2 mmol for 2, 1.0 mmol for 3) as an internal standard.
Figure 2. 29Si MAS NMR analyses of (a) 1, (b) 1 after
hydrosilylation, (c) 2, and (d) 2 after hydrosilylation.
Recycle experiments of Pt catalyst immobilized on BPy-PMO
Encouraged by the leaching experiments, we next examined the
reusability of 1 and 2 (Figure 4). The reaction of phenylacetylene
with (MeO)3SiH was performed for 15 h and the catalyst was
recovered by simple filtration. It was found that the recovered
2 maintained good catalytic activity with slight loss of product
yields for at least five times, indicating the good recyclability of
2. Through the whole cycles, the ratio of two regioisomers (-
trans/) remained almost unchanged. Complex 1 were less
active than 2 for each reaction cycle. This is probably because
Pt atoms are partially immobilized on the silanol surface in 1.
Interestingly, the catalytic activity of 1 was slightly improved
after the second cycle. Since the hydrosilylated product reacts
with silanol groups on the BPy-PMO surface, as noted above, it
is likely that passivation of the surface proceeded during the
reaction, and thus the catalytic activity could be somewhat
improved after the reaction cycles.
Complexes 3a and 3b exhibited similar catalytic activity to 2.
Thus, under similar reaction conditions, the hydrosilylated
products were obtained quantitatively with the -trans/ ratio
of 72/28 and 71/29, respectively (Table 2, entries 5 and 6). In
contrast, hot filtration experiments showed significant
differences in the leaching behavior of 2, 3a, and 3b. The
reactions catalysed by 2, 3a, and 3b were conducted at 60 °C at
the catalyst loading of 5 mol% Pt for 2 and 0.1 mol% Pt for 3a
1
and 3b and monitored by H NMR spectroscopy. After stirring
for 1 h, filtration of the reaction mixture was performed at 60
°C and the filtrate was further stirred at this temperature. The
results are summarized in Figure 3. In the reaction catalysed by
2, the yield of the hydrosilylated products was 22% after 1 h and
this value remained unchanged for 20 h. Therefore, the
possibility of leaching of 2 was excluded. The reactions
catalysed by 3a and 3b were conducted similarly. To our
surprise, the yields gradually increased after the filtration and
then reached 88% (3a) and 44% (3b) after stirring the filtrate for
19 h. These results strongly suggested that the reaction
To confirm the preservation of the mesoporous structure after
the hydrosilylation, we measured XRD patterns and nitrogen
adsorption/desorption isotherms of recovered PMO complex 2
after the fifth reaction. The XRD pattern for recovered 2 showed
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 7
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
strong reflection at low angle of 1.80° and four diffraction peaks temperature (–196 °C). Brunauer–Emmett–Teller V(BiewETA)rtiscluerOfnalcinee
DOI: 10.1039/C9DT00078J
at 7.60°, 15.2°, 22.9°, and 30.8°, suggesting the preservation of areas were calculated from the linear sections of BET plots (P/P0
periodic mesoporous and crystal-like pore wall structures due = 0.1–0.2). Pore-size distributions were calculated using the DFT
to the robust covalent siloxane networks (Figure S10). The SBET
,
method (DFT kernel: N2 at –196 °C on silica, cylindrical pores,
Vt-plot, and dDFT values of recovered 2 were 625 m2 g–1, 0.39 cc g– nonlinear density functional theory (NLDFT) equilibrium
1, 3.8 nm, respectively, clearly indicating preservation of the model). Pore volumes were estimated using the t-plot method.
periodic mesoporous structure (Figure S11). The TEM images of Energy-dispersive X-ray spectrometry (EDX) was performed
recovered 2 suggested no formation of Pt particles, indicating using a Hitachi S-3600N instrument. TEM observations were
that the Pt-bipyridine complex remained without aggregation performed using a Jeol JEM-EX2000 operating at 5 kV and 200
even after the fifth reaction. (Figure S12)23
kV, respectively. UV-vis diffuse reflectance and absorption
spectra were obtained using a Jasco V-670.
Synthesis of PtMe2(BPy-PMO) (1) and PtMe2(BPy-PMO-TMS) (2)
A 50 mL Schlenk tube was equipped with a stir bar, BPy-PMO
(629 mg, 2.12 mmol BPy/g on the surface) or BPy-PMO-TMS
(684 mg, 1.95 mmol BPy/g on the surface), and dry benzene (8
mL). The mixture was stirred at 60 °C. Then, a solution of
[PtMe2(-SMe2)]2 (57 mg, 0.1 mmol) in dry benzene (20 mL) was
added dropwise at 60 °C. After stirring for ca. 5 min at the same
temperature, the mixture was cooled to 6 °C and kept stirred
for an additional 24 h. The resulting suspension was filtered and
then washed with dry benzene. The material was dried under
reduced pressure to give PtMe2(BPy-PMO) (1) and PtMe2(BPy-
BPy-TMS) (2), respectively. The loading amounts of Pt in PMO
complexes 1 and 2 were determined from the Pt/Si ratios
measured by energy-dispersive X-ray spectroscopy (EDX). The
EDX analysis showed that the Pt/Si ratios were 0.041 and 0.037
for PMO complexes 1 and 2, respectively. Because of the Si/BPy
molar ratios are 2/1 for BPy-PMO and 10/3 for BPy-PMO-TMS,8
the Pt/BPy molar ratios in 1 and 2 were calculated to be 0.082
and 0.12, and thus corresponding to 0.26 and 0.36 mmol Pt g-1,
respectively. In the case of 2, Pt complexes should be exclusively
formed on the BPy ligands exposed on the surface layer of BPy-
PMO pore wall which is composed of three layers of Si-BPy-Si
unit. Therefore, the Pt/BPysurface are determined to be 18% for
PMO complexes 2 and there are 82% of free bipyridine units on
the pore surface.
Figure 4. Yields in recycle experiments on hydrosilylation of
phenylacetylene and trimethoxysilane with 5 mol% of 1 and 2.
The values in parentheses represent regioselectivity (-
trans/). Reaction conditions: catalyst (0.01 mmol Pt), alkyne
(0.2 mmol), hydrosilane (0.2 mmol) in benzene (1 mL) at 60 °C
1
for 15 h. Determined by H NMR analysis with mesitylene (0.2
mmol) as an internal standard.
Experimental
Materials
All chemicals were purchased from commercial suppliers
(Sigma-Aldrich, Tokyo Chemical Industry Co., Ltd., and Wako
Pure Chemical Industries, Ltd.) and used without further
purification. BPy-PMO and BPy-PMO end-capped with TMS
Synthesis of PtMe2(BPy-C4-FSM-16) (3a) and PtMe2(BPy-C4-Silica
gel) (3b)
groups (BPy-PMO-TMS) were prepared according to
a
previously reported procedure.8 BPy-C4-FSM-16 and BPy-C4-
Silica gel were prepared according to a previously reported
procedure with slight modification.
A 50 mL Schlenk tube was equipped with a stir bar, BPy-C4-FSM-
16 (500 mg, 0.38 mmol BPy/g) or BPy-C4-Silica gel (500 mg, 0.42
mmol BPy/g), and dry benzene (5 mL). The mixture was stirred
at 60 °C. Then, a solution of [PtMe2(-SMe2)]2 (73 mg, 0.127
mmol) in dry benzene (6 mL) was added at 60 °C. The reaction
mixture was stirred at 6 °C for 20 h. The resulting suspension
was filtered and then washed with dry benzene. The material
was dried under reduced pressure to give PtMe2(BPy-C4-FSM-
16) (3a) and PtMe2(BPy-C4-Silica gel) (3b), respectively.
Characterization of immobilized Pt complexes
29Si dipolar decoupling (DD) MAS NMR measurement was
performed at 79.49 MHz at a sample spinning frequency of 4
kHz using a Bruker Avance III 400 spectrometer with a 7 mm
zirconia rotor. For the 29Si MAS NMR measurements, the
repetition delay was 60 s, and the pulse width was 1.5 s.
Chemical shifts were referenced to hexamethylcyclotrisiloxane
at –9.68 ppm as external standard for 29Si NMR. X-ray diffraction
Typical procedure for hydrosilylation of phenylacetylene and
(MeO)3SiH
(XRD) profiles were recorded by
diffractometer using Cu-K radiation (50 kV, 300 mA). Nitrogen
adsorption/desorption isotherms were obtained using
a Rigaku RINT-TTR
A 20 mL Schlenk tube equipped with a stir bar was charged with
phenylacetylene (22 L, 0.2 mmol), mesitylene (28 L, 0.2
mmol), and PtMe2(BPy-PMO-TMS) (2) (28 mg, 0.01 mmol Pt) in
a
Quantachrome Nova3000e sorptometer at liquid nitrogen
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 6 of 7
ARTICLE
Journal Name
Marciniec, Coord. Chem. Rev. 2005, 249, 2374-2390; (e) D.
dry benzene (1 mL). Then, (MeO)3SiH (25 L, 0.2 mmol) was
added dropwise to the suspension. The reaction mixture was
stirred for 15 h at 60 °C. The heterogeneous catalyst was
removed by passing through a membrane filter (0.1 m). The
View Article Online
Xiaoyong, H. Zheng, ACS Catal. 2017, 7D, O12I:2170.-1102349/3C.9DT00078J
(a) J. L. Speier, J. A. Webster and G. H. Barnes, J. Am. Chem.
Soc. 1957, 79, 974-979; (b) J. L. Speier, Adv. Organomet.
Chem. 1979, 17, 407−447.
2
1
yield of the product was determined by H NMR analysis with
3
4
5
B. D. Karstedt, General Electric Company, US3775452A, 1973.
A. J. Holwell, Platinum Met. Rev. 2008, 52, 243-266.
(a) M. Pagliaro, R. Ciriminna, V. Pandarus and F. Béland, Eur.
J. Org. Chem. 2013, 6227-6235; (b) Y. Bai, J. Peng, J. Li, G. Lai,
and X. Li, Prog. Chem. 2011, 23, 2466-2477; (c) H. Bai, Ind. Eng.
Chem. Res. 2014, 53, 1588-1597.
(a) L. Wang and Y. Jiang, J. Organomet. Chem. 1983, 251, 39-
44; (b) C.-Y. Hu, X.-M. Han and Y.-Y. Jiang, J. Mol. Catal. 1986,
35, 329-333; (c) W. R. Cullen and N. F. Han, J. Organomet.
Chem. 1987, 333, 269-280; (d) R. Drake, R. Dunn, D. C.
Sherrington and S. J. Thomson, Chem. Commun. 2000, 1931-
1932; (e) Z. M. Michalska, Ł. Rogalskia, K. Rózga-Wijas, J.
Chojnowski, W. Fortuniak and M. Ścibiorek, J. Mol. Catal. A:
Chem. 2004, 208, 187-194; (f) J. Li, C. Yang, L. Zhang and T.
Ma, J. Organomet. Chem. 2011, 696, 1845-1849.
(a) Q. J. Miao, Z. Fang and G. P. Cai, Catal. Commun. 2003, 4,
637-639; (b) T. Galeandro-Diamant, R. Sayah, M. Zanota, S.
Marrot, L. Veyre, C. Thieuleux and V. Meille, Chem. Commun.
2017, 53, 2962-2965.
mesitylene as an internal standard. 1H NMR spectra of the
products, -trans- and -(trimethoxysilyl)styrene, were
reported in the literature.24
6
Conclusions
In this study, we prepared the Pt complex directly immobilized
on BPy-PMO, and BPy-PMO-TMS as well as Pt complexes with
other silica-based bipyridine ligands possessing functional
linkages. The reaction of both BPy-PMO and BPy-PMO-TMS with
[PtMe2(-SMe2)]2 provided the corresponding Pt complexes 1
and 2, respectively. Complex 1 exhibited moderate catalytic
activity in the hydrosilylation of phenylacetylene with
(MeO)3SiH, probably due to the partial formation of undesired
Pt complex coordinated with free silanol moieties. It is also to
be mentioned that the reaction of silanol moieties with the
hydrosilylatd product also lead to the decrease in the apparent
production yield. In contrast, complex 2 with BPy-PMO-TMS,
which was end-capped with TMS groups on the surface silanol
groups, effectively catalysed the hydrosilylation reaction. Hot
filtration experiments excluded the occurrence of leaching of 2
during the reactions. In contrast, leaching of the grafted
complexes 3a and 3b was observed. We postulated that the
utility of free bipyridine units in 2, which are densely arranged
on the pore surface, could suppress the leaching behavior.
Complex 2 showed good reusability without the loss of the
product yield for at least five reuse cycles in hydrosilylation.
Overall, the superior utility of BPy-PMO-TMS as a solid-support
ligand for Pt-catalysed hydrosilylation was demonstrated.
7
8
9
M. Waki, Y. Maegawa, K. Hara, Y. Goto, S. Shirai, Y. Yamada,
N. Mizoshita, T. Tani, W.-J. Chun, S. Muratsugu, M. Tada, A.
Fukuoka and S. Inagaki, J. Am. Chem. Soc. 2014, 136, 4003-
4011.
Y. Maegawa and S. Inagaki, Dalton Trans. 2015, 44, 13007-
13016.
10 X. Liu, Y. Maegawa, Y. Goto, K. Hara and S. Inagaki, Angew.
Chem. Int. Ed. 2016, 55, 7943-7947.
11 N. Ishito, H. Kobayashi, K. Nakajima, Y. Maegawa, S. Inagaki,
K. Hara and A. Fukuoka, Chem. Eur. J. 2015, 21, 15564-15569.
12 Y. Kuramochi, M. Sekine, K. Kitamura, Y. Maegawa, Y. Goto, S.
Shirai, S. Inagaki and H. Ishida, Chem. Eur. J. 2017, 43, 10301-
10309.
13 M. Waki, K.-i. Yamanaka, S. Shirai, Y. Maegawa, Y. Goto, Y.
Yamada and S. Inagaki, Chem. Eur. J. 2018, 24, 3846-3853.
14 N. Ishito, K. Nakajima, Y. Maegawa, S. Inagaki and A. Fukuoka,
Catal. Today 2017, 298, 258-262.
15 S. Ishikawa, Y. Maegawa, M. Waki and S. Inagaki, ACS Catal.
2018, 8, 4160-4169.
16 K. Matsui, Y. Maegawa, M. Waki, S. Inagaki and Y. Yamamoto,
Catal. Sci. Technol. 2018, 8, 534-539.
17 M. Yoshida, K. Saito, H. Matsukawa, S. Yanagida, M. Ebina, Y.
Maegawa, S. Inagaki, A. Kobayashi and M. Kato, J. Photochem.
Photobiol. A 2018, 358, 334-344.
Conflicts of interest
There are no conflicts to declare.
18 (a) J. D. Scott and R. J. Puddephatt, Organometallics 1983, 2,
1643-1648; (b) P. K. Monaghan and R. J. Puddephatt,
Organometallics 1984, 3, 444-449; (c) D. Minniti, G. Alibrandi,
M. L. Tode and R. Romeo, Inorg. Chem. 1987, 26, 3956-3958;
(d) M. Rehdi, Z. Fakhroeian and R. J. Puddephatt, J.
Organomet. Chem. 1991, 406, 261-267.
Acknowledgements
This work was supported by the “Development of Innovative
Catalytic Processes for Organosilicon Functional Materials”
project (Project Leader: K. Sato) from the New Energy and
Industrial Technology Development Organization (NEDO). The
authors thank Dr. Yasutomo Goto and Dr. Masamichi Ikai
(Toyota Central R&D Laboratories, Inc.) for TEM observations
and SEM-EDX analysis.
19 A. Klein, J. van Slageren and S. Záliš, Eur. J. Inorg. Chem., 2003,
1917-1928.
20 A review, see: (a) B. M. Trost and Z. T. Ball, Synthesis. 2005,
853-887. Pioneering examples of Pt-catalyzed hydrosilylation
of alkynes, see: (b) L. N. Lewis, K. G. SyG. L. Bryant, Jr. and P.
E. Donahue, Organometallics 1991, 10, 3750-3759; (c) M. G.
Voronkov, V. B. Pukhnarevich, I. I. Tsykhanskaya, N. I.
Ushakova, Y. L. Gaft and I. A. Zakharova, Inorg. Chim. Acta.
1983, 68, 103-105; (d) M. Green, J. L. Spencer, F. G. A. Stone
and C. A. Tsipis, J. Chem. Soc., Dalton Trans. 1977, 1525-1529;
(e) C. A. Tsipis, J. Organomet. Chem. 1980, 187, 427-446.
21 H. Noda, K. Motokura, A. Miyaji and T. Baba, Angew. Chem.
Int. Ed. 2012, 51, 8017-8020.
Notes and references
1
(a) L. N. Lewis, J. Stein, Y. Gao, R. E. Colborn and G. Hutchins,
Platinum Met. Chem. 1997, 41, 66-75; (b) Y. Nakajima and S.
Shimada, RSC ADV. 2015, 5, 20603-20616; (c) D. Troegel and
J. Stohrer, Coord. Chem. Rev. 2011, 255, 1440-1459; (d) B. G.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 7
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
22 (a) L. N. Lewis, J. Stein, Y. Gao, R. E. Colborn and G. Hutchins,
Platinum Met. Rev. 1997, 41, 66-75; (b) R. Ciriminna, V.
Pandarus, G. Gingras, F. Béland and M. Pagliaro, ACS
Sustainable Chem. Eng. 2013, 1, 249-253.
View Article Online
DOI: 10.1039/C9DT00078J
23 Examples of single atom catalysts (SACs) based on Pt, see: (a)
X. Cui, K. Junge, X. Dai, C. Kreyenschulte, M. M. Pohl, S.
Wohlrab, F. Shi, A. Brückner and M. Beller, ACS Cent. Sci. 2017,
3, 580-585; (b) J. L. Liu, F. R. Lucci, M. Yang; S. Lee, M. D.
Marcinkowski, A. J. Therrien, C. T. Williams, E. C. Sykes and M.
Flytzani-Stephanopoulos, J. Am. Chem. Soc. 2016, 138, 6396-
6399; (c) F. Dvořák, M. F. Camellone, A. Tovt, N.-D. Tran, F. R.
Negreiros, M. Vorokhta, T. Skála, I. Matolínová, J. Mysliveček,
V. Matolín and S. Fabris, Nat. Commun. 2016, 7, 10801-10807;
(d) B. Qiao, A. Wang, X. Yang, L. F. Allard, Z. Jiang, Y. Cui, J. Liu,
J. Li and T. Zhang, Nat. Chem. 2011, 3, 634-641; (e) H. Wei, X.
Liu, A. Wang, L. Zhang, B. Qiao, X. Yang, Y. Huang, S. Miao, J.
Liu and T. Zhang, Nat. Commun. 2014, 5, 5634-5640; (f) S.
Yang, J. Kim, Y. J. Tak, A. Soon and H. Lee, Angew. Chem. Int.
Ed. 2016, 55, 2058-2062; (g) B. Zhang, H. Asakura, J. Zhang, J.
Zhang, S. De and N. Yan, Angew. Chem. Int. Ed. 2016, 55, 8319-
8323; (h) M. Moses-DeBusk, M. Yoon, L. F. Allard, D. R.
Mullins, Z. Wu, X. Yang, G. Veith, G. M. Stocks and C. K. Narula,
J. Am. Chem. Soc. 2013, 135, 12634-12645; (i) J. Wang, X.
Zhao, N. Lei, L. Li, L. Zhang, S. Xu, S. Miao, X. Pan, A. Wang and
T. Zhang, ChemSusChem 2016, 9, 784-790.
24 C.-H. Jun and R. H. Crabtree, J. Organomet. Chem. 1993, 447,
177-187.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins