Ruthenium-Immobilized Periodic Mesoporous Organosilica: Synthesis, Characterization, and Catalytic Application for Selective Oxidation of Alkanes

Article abstract of DOI:10.1002/chem.201502638

Periodic mesoporous organosilica (PMO) is a unique material that has a crystal-like wall structure with coordination sites for metal complexes. A Ru complex, [RuCl₂(CO)₃]₂, is successfully immobilized onto 2,2'-bipyridine (BPy) units of PMO to form a single-site catalyst, which has been confirmed by various physicochemical analyses. Using NaClO as an oxidant, the Ru-immobilized PMO oxidizes the tertiary C-H bonds of adamantane to the corresponding alcohols at 57 times faster than the secondary C-H bonds, thereby exhibiting remarkably high regioselectivity. Moreover, the catalyst converts cis-decalin to cis-9-decalol in a 63% yield with complete retention of the substrate stereochemistry. The Ru catalyst can be separated by simple filtration and reused without loss of the original activity and selectivity for the oxidation reactions.

Full text of DOI:10.1002/chem.201502638

DOI: 10.1002/chem.201502638
Full Paper
&
Catalysis |Very Important Paper|
Ruthenium-Immobilized Periodic Mesoporous Organosilica:
Synthesis, Characterization, and Catalytic Application for Selective
Oxidation of Alkanes
Nobuhiro Ishito,[a, b, d] Hirokazu Kobayashi,[a, b] Kiyotaka Nakajima,[a, b] Yoshifumi Maegawa,[c, d]
Shinji Inagaki,[c, d] Kenji Hara,*[a, d, e] and Atsushi Fukuoka*[a, b]
Abstract: Periodic mesoporous organosilica (PMO) is
a unique material that has a crystal-like wall structure with
coordination sites for metal complexes. A Ru complex,
[RuCl2(CO)3]2, is successfully immobilized onto 2,2’-bipyridine
(BPy) units of PMO to form a single-site catalyst, which has
been confirmed by various physicochemical analyses. Using
NaClO as an oxidant, the Ru-immobilized PMO oxidizes the
tertiary CꢀH bonds of adamantane to the corresponding al-
cohols at 57 times faster than the secondary CꢀH bonds,
thereby exhibiting remarkably high regioselectivity. More-
over, the catalyst converts cis-decalin to cis-9-decalol in
a 63% yield with complete retention of the substrate stereo-
chemistry. The Ru catalyst can be separated by simple filtra-
tion and reused without loss of the original activity and se-
lectivity for the oxidation reactions.
sults in highly efficient fluorescence.[4] A photocatalytic CO2 re-
duction system was constructed by anchoring a Re complex
onto biphenyl-incorporated PMO.[5] Recently, a PMO with incor-
porated 2,2’-bipyridyl (BPy) groups, BPy-PMO, was successfully
synthesized and exhibited a high performance as a solid che-
lating ligand for the immobilization of metal complexes to pro-
duce new types of single-site heterogeneous catalysts. An Ir-
immobilized BPy-PMO catalyzed the borylation of CꢀH bonds
in substituted benzenes to afford desired products,[6] and the
activity of the solid catalyst was higher than that of a corre-
sponding homogeneous catalyst. Immobilization of a Ru com-
plex on BPy-PMO was also reported to be promising for solar
energy conversion systems.[6] After loading Pt nanoparticles,
the Ru-supported BPy-PMO continuously reduced protons in
water into hydrogen in the presence of a sacrificial reagent
(ethylenediaminetetraacetic acid; EDTA) under visible-light irra-
diation. Direct injection of photoexcited electrons from the Ru
complex to Pt nanoparticles enabled efficient hydrogen pro-
duction, even in the absence of a typical electron mediator
such as methyl viologen.
Introduction
Periodic mesoporous organosilicas (PMOs) are unique materials
that possess uniform mesopores (2–30 nm) that consist of crys-
tal-like ordered arrays of organic moieties bridged by siloxane
bonds.[1,2] Various chemical and physical properties can be in-
troduced into the PMO materials by varying the organic
groups. Ethylene-bridged PMO provides a highly hydrophobic
environment inside the restricted mesopores that can stabilize
protein molecules.[3] A coumarin-doped biphenyl–PMO system
exhibits unique UV light absorption and subsequent fluores-
cence by a light-harvesting effect; the photoexcitation of bi-
phenyl moieties by UV light absorption induces energy transfer
to a coumarin dye immobilized within mesopores, which re-
[a] N. Ishito, Dr. H. Kobayashi, Dr. K. Nakajima, Dr. K. Hara,
Prof. Dr. A. Fukuoka
Catalysis Research Center
Hokkaido University, Sapporo, Hokkaido 001-0021 (Japan)
E-mail: fukuoka@cat.hokudai.ac.jp
We speculate that a prospective application of PMO-based
catalysts is the partial oxidation of hydrocarbons, which is a sig-
nificant challenge in catalysis.[7–10] The oxidation of hydrocar-
bons using metal complex catalysts is subject to oxidation of
the ligands by their own active oxygen species.[11] To avoid this
problem, oxidation enzymes, as typified by cytochrome P-450,
rigidly fix the active center (iron protoporphyrin-IX) in an isolat-
ed state on the pore wall of a protein.[12] It is thus expected
that the immobilization of isolated active sites directly on the
pore walls of PMOs will suppress self-oxidation, which is in
sharp contrast to conventional catalysts[13] with mobile active
centers grafted through linkers.
[b] N. Ishito, Dr. H. Kobayashi, Dr. K. Nakajima, Prof. Dr. A. Fukuoka
Graduate School of Chemical Sciences and Engineering
Hokkaido University, Sapporo, Hokkaido 060-8628 (Japan)
[c] Y. Maegawa, Dr. S. Inagaki
Toyota Central R&D Laboratories Inc., Nagakute, Aichi 480-1192 (Japan)
[d] N. Ishito, Y. Maegawa, Dr. S. Inagaki, Dr. K. Hara
Japan Science and Technology Agency (JST)/ACT-C
Nagakute, Aichi 480-1192 (Japan)
[e] Dr. K. Hara
School of Engineering, Tokyo University of Technology
Hachioji, Tokyo 192-0982 (Japan)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201502638.
Chem. Eur. J. 2015, 21, 1 – 7
1
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
Herein, we report a new and reusable Ru-immobilized BPy-
PMO catalyst that achieves selective oxidation of alkanes. The
catalyst was synthesized from [RuCl2(CO)3]2 and BPy-PMO; vari-
ous physicochemical analyses verified the formation of a uni-
form chemical structure with the Ru complex on PMO. The Ru
catalyst oxidizes adamantane and cis-decalin to the corre-
sponding tertiary alcohols with excellent regio- and stereose-
lectivity using a practical oxidant (NaClO). No solid catalyst has
achieved high selectivity or durability in the oxidation of these
alkanes. Although several homogeneous metal complexes
have already shown high selectivity, these are single-use cata-
lysts.[10,14] In contrast, the immobilization of the Ru complex on
BPy-PMO realizes both high selectivity and reusability for the
oxidation of alkanes. Tertiary alcohols of adamantane are pre-
cursors to photoresists for ArF lithography, engineering plas-
tics, and medicines.[15,16] The selective oxidation of decalin is
a model reaction for the synthesis of steroids and terpene
based antitumor medicines.[10,17] It is thus expected that the
Ru-immobilized PMO catalyst developed in this study will con-
tribute to practical industrial applications of fine chemical syn-
thesis.
Figure 1. Plausible structures of 1, 2, and 3.
Figure 2. (a) N2 adsorption isotherms and (b) NLDFT pore-diameter distribu-
tions for BPy-PMO (black) and 1 (red) at 77 K.
Ru catalysts 2, 3, and 4 are summarized in the Supporting In-
formation (Figure S2, S3, S4, Supporting Information).
Results and Discussion
EDX analysis indicated that the amount of Ru in 1 is
0.30 mmolgꢀ1 (3.0 wt.%), which corresponds to 15% of the
total BPy units on the surface. This ratio of Ru/BPy is more
than double the ratio previously reported for 3 (7.1%).[6] In
a control experiment, it was verified that no Ru complex is im-
mobilized on a mesoporous silica without BPy ligands.
Characterization of 1
PMO-based catalyst 1 was synthesized using BPy-PMO and
[RuCl2(CO)3]2 (Scheme 1) and characterized in detail. Immobili-
zation of Ru complexes on BPy-PMO was also conducted using
other Ru precursors, RuCl3·xH2O and [RuCl2(bpy)2]·2H2O, to
obtain the Ru-immobilized BPy-PMOs, denoted as 2 and 3, re-
spectively (Figure 1).
Figure 3 shows UV/Vis DRS spectra of BPy-PMO, 1, the pre-
cursor [RuCl2(CO)3]2, and [RuCl2(bpy)(CO)2] as a model of 1.
BPy-PMO gave a broad peak at 300 nm derived from p–p*
transition for BPy units within the silica framework.[19] A new
peak was observed at 410 nm after the immobilization of Ru,
which is ascribed to a metal–ligand charge-transfer (MLCT)
from Ru to BPy.[20] It was confirmed that [RuCl2(bpy)(CO)2] has
the same MLCT band at 410 nm, in which [RuCl2(CO)3]2 pro-
vides no absorption band, which indicates the complexation
between BPy units of BPy-PMO and Ru for 1.
Nitrogen adsorption experiments of BPy-PMO and 1 both
provided type-IV isotherms with no hysteresis, which indicates
uniform mesopores (Figure 2a ). Non-linear DFT (NLDFT) analy-
sis of the isotherms indicated that the pore diameter decreases
from 4.6 to 4.0 nm after Ru loading (Figure 2b ). The Bruna-
uer–Emmett–Teller (BET) specific surface area was also slightly
decreased from 690 to 530 m2 gꢀ1 by immobilization of Ru
complexes onto BPy-PMO. The amount of surface BPy units in
BPy-PMO was estimated to be 2.2 mmolgꢀ1, which was ob-
tained by dividing the BET surface area (690 m2 gꢀ1) by the
cross-sectional area of a PMO unit (310 m2 mmolꢀ1 for Si-BPy-
Si-O3; Figure 1). XRD measurements of BPy-PMO and 1 repre-
sented similar diffraction lines at 2q=1.88 (100) (Figure S1,
Supporting Information). These results clearly show that the or-
dered mesoporous structure of BPy-PMO is preserved after for-
mation of the Ru complex. Characterization data for the other
IR was employed to characterize the carbonyl groups on the
same materials as shown in Figure 4. BPy-PMO showed no
peaks derived from CꢀO stretching vibrations. The precursor to
1, [RuCl2(CO)3]2, showed two peaks at 2110 and 2160 cmꢀ1
,
which are assigned to symmetric and asymmetric CꢀO stretch-
ing vibrations.[21] Compound 1 exhibited two strong peaks at
2075 and 2012 cmꢀ1 for CO ligands of the immobilized Ru
complex. This redshift is due to an increase of the back-dona-
Scheme 1. Synthesis of Ru-immobilized BPy-PMO.
&
&
Chem. Eur. J. 2015, 21, 1 – 7
www.chemeurj.org
2
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
Figure 5. (a) Ru K-edge XANES and (b) Fourier transforms of EXAFS spectra
for 1 (red) and [RuCl2(bpy)(CO)2] (blue).
sponding to Ru–Ru was observed around 4 ꢁ in Figure 5b ,
which means that the Ru centers are isolated on BPy-PMO.
Based on these characterization data, we propose the struc-
ture of 1 in Figure 6, in which [RuCl2(CO)2] is immobilized on
BPy units of BPy-PMO. The well-defined and isolated Ru spe-
cies on the pore walls are applicable for selective catalytic re-
actions.
Figure 3. UV/Vis DRS spectra for BPy-PMO (black), [RuCl2(CO)3]2 (green),
[RuCl2(bpy)(CO)2] (blue), and 1 (red).
Oxidation of alkanes over Ru-immobilized BPy-PMO
Selective oxidation of alkanes is an important topic for the effi-
cient utilization of petroleum oil and natural gas.[7–10] Adaman-
tane was used as a model compound to evaluate the catalytic
activity and selectivity for this type of oxidation (Scheme 2).[14]
This highly symmetric alkane has four equivalent tertiary CꢀH
and twelve equivalent secondary CꢀH bonds; therefore, the
relative selectivity of the active species for tertiary and secon-
dary groups (38/28) can be easily determined from Equation (1).
Furthermore, adamantane oxygenates are precursors for the
production of photoresists, medicines, and engineering plas-
tics.[14] Some homogeneous catalysts can selectively oxidize the
tertiary or secondary CꢀH bonds of adamantane, such as
RuCl3, which has been commercially used for the synthesis of
tertiary alcohols;[14,22–27] however, these homogeneous catalysts
have drawbacks such as complicated separation and decompo-
sition of the catalysts. In addition, no solid catalyst has ach-
ieved good selectivity because of the presence of various cata-
lytic active sites.[28–32] Therefore, the oxidation of adamantane
was selected to evaluate the activity, selectivity, and reusability
of the PMO-based catalysts.
Figure 4. IR spectra of BPy-PMO (black), [RuCl2(CO)3]2 (green),
RuCl2(bpy)(CO)2 (blue), and 1 (red).
tion from Ru to CO by reducing the number of CO ligands
from three to two (see Scheme 1) and coordination of an elec-
tron-donating ligand, BPy.
Ru K-edge XAFS measurements were conducted to reveal
the electronic state and structure of the Ru center on 1. In the
X-ray absorption near-edge structure (XANES; Figure 5a ), the
edge energy of Ru immobilized on BPy-PMO (22119 eV) was in
the divalent region and the spectrum was almost identical
with that of [RuCl2(bpy)(CO)2]. This result indicates that the
electronic structures of Ru atoms in 1 and [RuCl2(bpy)(CO)2] are
similar. With respect to the extended X-ray absorption fine
structure (EXAFS; Figure S5a, Supporting Information), EXAFS
oscillation (Figure S5b, Supporting Information), and its Fourier
transforms (Figure 5b ), 1 and [RuCl2(bpy)(CO)2] yielded almost
the same spectra; therefore, the coordination structure of
ðyield of 1 ꢀ adamantanolÞ
3ꢂ=2ꢂ ¼
12
4
ꢃ
ðtotal yield of 2 ꢀ adamantanol and 2 ꢀ adamantanoneÞ
ð1Þ
Ru-immobilized BPy-PMO catalysts were tested for the oxi-
dation of adamantane (substrate/catalyst molar ratio S/C=50)
at 323 K with NaClO as a practical oxidant (Table 1). A control
experiment in the absence of a catalyst gave negligible
amounts of oxygenated products (Table 1, entry 1). Ru-immobi-
lized BPy-PMO 3 showed a very low adamantane conversion of
8.1%, as well as a 1-adamantanol yield of 4.3% (entry 5). Ru-
immobilized BPy-PMO 3 also afforded a significant amount of
1
was analyzed based on the crystallographic data for
[RuCl2(bpy)(CO)2].[18] Curve fitting for 1 indicated the presence
of RuꢀC 1.7ꢁ0.3 C atoms at 1.82 ꢁ, RuꢀN 1.9ꢁ0.4 N atoms at
2.18 ꢁ, and RuꢀCl 1.8ꢁ0.2 Cl atoms at 2.42 ꢁ. These results
suggest that a similar structure to the corresponding homoge-
neous complex, [RuCl2(bpy)(CO)2], is successfully formed on
the surface of BPy-PMO. It should be noted that no peak corre-
Chem. Eur. J. 2015, 21, 1 – 7
www.chemeurj.org
3
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
Figure 6. Proposed structure of 1.
catalyst 1. Thus, we focused on
the catalysis of 1. For the reac-
tion of 1 in entry 2, a turnover
number of Ru for oxygenation
was calculated to be 35, which
indicates that 1 acts as a catalyst
for the oxidation of adamantane.
The 38/28 ratio is 57, so that
a tertiary CꢀH bond was oxi-
dized 57 times faster than a sec-
ondary CꢀH bond. A time-course
experiment showed that the 38/
28 ratio remained almost con-
stant (Figure S6, Supporting In-
formation). This is the highest re-
gioselectivity ever reported for
Scheme 2. Oxidation of adamantane with NaClO.
Table 1. Oxidation of adamantane by Ru catalysts with NaClO.[a]
Entry Catalyst
Conv. [%] Yield [%]
1-AdOH[c] 2-AdOH[c] 2-AdO[c] 1,3-Ad(OH)2
38/28[b]
[c]
1-AdCl[c]
0.0
0.2
0.2
0.1
1.9
1.2
1.4
1
2
3
4
5
6
7
8
none
1
1-reuse
2
3
[RuCl2(bpy)(CO)2] 77
4
4-reuse
0.3
67
68
43
0.0
44
44
31
4.3
45
25
1.9
0.0
0.0
0.0
0.0
0.4
0.8
0.0
1.2
0.0
2.3
2.5
1.7
1.0
2.4
1.4
0.1
0.0
12
11
5.9
0.0
12
4.4
0.0
–
57
53
55
9
45
54
5
8.1
41
6.1
a
heterogeneous catalyst (2–
0.0
20).[28–32] The result indicates that
no radical chain reactions (38/28
<15)[33] occur and active electro-
philic oxygen species are selec-
tively formed on Ru sites.[8]
Moreover, 1 maintained the cat-
alytic activity and selectivity in
[a] Reaction conditions: catalyst (10 mg), adamantane (0.23 mmol), ethylacetate (2.4 mL), and acetate buffer
(0.39 mL, pH 4.4, 2m), reaction temperature (323 K), time of aqueous solution of NaClO (19 mm) supplied at
a rate of 27 mLhꢀ1 (12 h). [b] 38/28=(yield of 1-adamantanol)/(total yield of 2-adamantanol and 2-adamanta-
none)ꢂ3 (see Equation (1)). [c] 1-AdOH (1-adamantanol), 2-AdOH (2-adamantanol), 2-AdO (2-adamantanone),
1,3-Ad(OH)2 (1,3-adamantanediol), 1-AdCl (1-chloroadamantane).
1-chloroadamantane (1.9% yield), a typical byproduct in the a reuse experiment; the catalyst produced 1-adamantanol in
oxidation with NaClO. The new catalyst 1 provided a 67% con- 44% yield with a 38/28 ratio of 53 (entry 3). We have verified
version of adamantane, and the major products were 1-ada- that the amount of Ru loading was maintained after the oxida-
mantanol (44% yield), 1,3-adamantandiol (12%; produced by tion reaction by EDX measurements. [RuCl2(bpy)(CO)2] was
successive oxidation of 1-adamantanol), and 2-adamantanone tested as a homogeneous model of 1, which afforded 1-ada-
(2.3%) (entry 2). 2-Adamantanol was produced in less than mantanol (45% yield), 1,3-adamantandiol (12%), 2-adamanta-
0.1% yield due to rapid consecutive oxidation to 2-adamanta- nol (0.8%), and 2-adamantanone (2.4%) (entry 6). Thus, 1 was
none. It is notable that the amount of 1-chloroadamantane as active as [RuCl2(bpy)(CO)2], which suggests there is no diffu-
was as low as 0.2%. Ru-BPy-PMO catalyst 2, grafting a commer- sion limitation for 1 due to the large pores that allow quick dif-
cial catalyst RuCl3, gave a lower adamantane conversion of fusion of the bulk substrate (adamantane, 0.7 nm diameter).
43% with a 1-adamantanol yield of 31% (entry 4).[26] We pro- The 38/28 ratio for [RuCl2(bpy)(CO)2] of 45 was slightly lower
pose that the Ru center in catalyst 1 easily forms coordination than that for 1 (57), and the homogeneous catalyst also pro-
bonds with reactant molecules by releasing CO ligands, which duced a larger amount of 1-chloroadamantane (1.2%) than
results in high catalytic performance for the adamantane oxi- 1 (0.2%). Thus, 1 improved the product selectivity compared
dation. After the reaction, the Ru centers in 1 are stabilized by with the homogeneous counterpart, presumably due to the
the coordination of acetate in solution, and are repeatedly site-isolation of the Ru species for 1.
available as active sites. In contrast, because of the strong co-
The good durability of 1 could be ascribed to the rigid fixa-
ordination of ligands with the Ru center in the case of catalysts tion of the Ru species on the pore wall. To provide evidence
2 and 3, these catalysts show less activity for the reaction than for this hypothesis, an analogue of 1 was examined using
&
&
Chem. Eur. J. 2015, 21, 1 – 7
www.chemeurj.org
4
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
MCM-41 bearing BPy groups via butyl group linkers (denoted
4; Figure S7, Supporting Information). MCM-41 is also an or-
dered mesoporous material with a similar pore diameter
(3.4 nm) but consists of pure silica with an amorphous wall
structure. Therefore, a linker is necessary to immobilize Ru and
it provides mobile Ru sites.
Catalyst 4 showed a similar 38/28 ratio (54, Table 1, entry 7)
to that for 1. However, 4 had lower catalytic activity due to
quick deactivation, which was clearly observed in the catalyst
reuse experiment (almost no activity, entry 8). The catalyst was
decomposed by its own active oxygen species and significant
leaching of Ru was observed (82%). Thus, we propose that the
direct immobilization of Ru complexes on BPy groups within
the framework of BPy-PMO gives a rigid structure, thereby ach-
ieving better durability of the catalyst.
Catalyst 1 was then applied for the oxidation of cis-decalin
to evaluate the stereospecificity of the catalytic system
(Scheme 3), because stereospecific oxidation is important for
Figure 7. Reuse tests with catalyst 1 for the oxidation reaction of cis-decalin.
Reaction conditions: catalyst (10 mg), adamantane (0.23 mmol), ethylaceta-
te (2.4 mL), and acetate buffer (0.39 mL, pH 4.4, 2), reaction temperatur-
e (323 K), time of aqueous solution of NaClO (19 mm) supplied at a rate of
27 mLhꢀ1 (12 h). Denotation: cis-9-ol (cis-9-decalol), cis-1-one (cis-1-decalone),
cis-2-one (cis-2-decalone), trans-9-ol (trans-9-decalol).
Scheme 3. Oxidation of cis-decalin by 1 with NaClO.
the synthesis of fine chemicals and medicines, such as steroids
and terpenes.[10,17] The reaction was performed under the same
conditions as that for the oxidation of adamantane. Catalyst
1 gave a 70% conversion of cis-decalin and a 63% yield of cis-
9-decalol with complete retention of the substrate configura-
tion. Thus, no trans-9-decalol was detected (<0.1%) and the
only byproducts were secondary oxygenates such as cis-1-dec-
alone. This result indicates that Ru catalyst 1 directly inserts an
oxygen atom into a CꢀH bond with no free radical reaction,
which gives a mixture of cis-9-decalol and trans-9-decalol via
sp2 carbon radical intermediates.[15,34] Moreover, the activity of
the reuse catalyst was compared with that of the fresh catalyst
at 50% conversion of cis-decaline (Figure 7). Catalyst 1 was re-
usable and maintained the activity and selectivity for the ste-
reospecific oxidation of tertiary CꢀH bonds. The direct inser-
tion of oxygen is also important for good durability, because
free radicals would randomly attack the catalyst in addition to
the substrate.
achieve good durability. Furthermore, catalytically controlled
oxidation, due to the well-designed isolated metallic sites, em-
phasizes the potential of the structural advantage.
Experimental Section
Reagents
[RuCl2(CO)3]2 was purchased from Sigma–Aldrich, and dehydrated
THF was obtained from Kanto Chemical Co. Other reagents were
of the highest grade and were used without purification.
Synthesis of Ru-immobilized BPy-PMO
BPy-PMO was synthesized according to the literature method,
using 5,5’-bis(triisopropoxysilyl)-2,2’-bipyridine as a monomer and
octadecyltrimethylammonium chloride as a surfactant.[6] A Ru-im-
mobilized BPy-PMO, denoted 1, was prepared from BPy-PMO and
[RuCl2(CO)3]2 as follows. BPy-PMO (100 mg) was added to a THF so-
lution (30 mL) of [RuCl2(CO)3]2 (100 mg, 0.50 mmol) under Ar, and
the mixture was magnetically stirred under reflux conditions for
3 h. The resulting solid was filtered, washed with THF, and dried at
298 K in vacuo, to afford 1 (110 mg) as a brownish powder. A
model complex for 1, [RuCl2(bpy)(CO)2], was synthesized according
to a procedure in the literature[18] and purified by recrystallization.
Immobilization of Ru complexes on BPy-PMO was also conducted
using other Ru precursors, RuCl3·xH2O and [RuCl2(bpy)2]·2H2O, to
obtain the Ru-immobilized BPy-PMOs, denoted as 2 and 3, respec-
tively (Figure 1). Ru-immobilized BPy-PMO 3 was reported previ-
ously.[6] The synthesized materials were analyzed and characterized
using UV/Vis diffuse reflectance spectroscopy (UV/Vis DRS; Jasco,
Conclusion
Ru species were immobilized in an isolated form directly on
2,2’-bypyridine groups in the BPy-PMO framework. The coordi-
nation structure of the immobilized Ru species was similar to
that of the corresponding Ru complex, [RuCl2(bpy)(CO)2]. The
Ru-immobilized PMO was applied for the catalytic oxidation of
adamantane using NaClO as an oxidant and high selectivity
toward the oxidation of tertiary CꢀH bonds was observed in
addition to catalyst recyclability. Ru-immobilized PMO also se-
lectively oxidized tertiary CꢀH bonds of cis-decalin with perfect
retention of its configuration. From these results, we propose
that the rigid structure of Ru sites is essentially beneficial to
Chem. Eur. J. 2015, 21, 1 – 7
www.chemeurj.org
5
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
[5] H. Takeda, M. Ohashi, T. Tani, O. Ishitani, S. Inagaki, Inorg. Chem. 2010,
49, 4554–4559.
[6] 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, S. Inagaki, J. Am.
Chem. Soc. 2014, 136, 4003–4011.
[7] R. Schlçgl, In Modern Heterogeneous Oxidation Catalysis: Design, Reac-
tions and Characterization (Ed.: N. Mizuno), Wiley-VCH: Weinheim,
2009, pp. 1–42.
V-650), FTIR; Perkin–Elmer, Spectrum 100, transmission mode, tri-
glycine sulfate (TGS) detector with a 1 cmꢀ1 resolution, 16 times in-
tegration), X-ray absorption fine structure (XAFS; at the BL14B2 of
SPring-8), energy dispersive X-ray spectroscopy (EDX; Shimadzu
EDX-720), nitrogen adsorption (BEL, Belsorp-mini II), and X-ray dif-
fraction (XRD; Rigaku, Ultima IV, CuKa).
[8] A. Gunay, K. H. Theopold, Chem. Rev. 2010, 110, 1060–1081.
[9] J. Yamaguchi, K. Itami, A. D. Yamaguchi, Angew. Chem. Int. Ed. 2012, 51,
8960–9009; Angew. Chem. 2012, 124, 9092–9142.
Oxidation reactions
The substrate (230 mmol), catalyst (10 mg), ethylacetate (2.4 mL),
acetate buffer (0.39 mL, pH 4.4, 2.0m), and a magnetic stirrer were
placed into a Pyrex vial (10 mL) equipped with a screw cap. The re-
action was performed at 323 K for a designated time with an aque-
ous solution of NaClO (19 mm) supplied at a rate of 27 mLhꢀ1 using
a microfeeder (YMC, YSP-201) through a stainless steel needle
(0.15 mm diameter) that penetrated the cap. Evolved gas was re-
moved through another needle (0.1 mm diameter). After the addi-
tion of NaClO, the mixture was further stirred for 3 h to completely
consume the oxidant. Unreacted substrate and products were ex-
tracted five times with ethyl acetate and hexane and undecane
was added into the extract as an external standard. The solution
was analyzed using gas chromatography (GC; Shimadzu GC-14B,
flame ionization detector) with an HR-1 (0.25 mm diameter, 25 m
long) column and an HR-20m (0.25 mm diameter, 30 m long)
column. Products were identified by gas chromatography-mass
spectrometry (GCMS; Shimadzu GC2010/PARVUM2, electron ioniza-
[10] M. C. White, Science 2012, 335, 807–809.
[11] M. Costas, Coord. Chem. Rev. 2011, 255, 2912–2932.
[12] B. Meunier, S. P. de Visser, S. Shaik, Chem. Rev. 2004, 104, 3947–3980.
[13] A. Taguchi, F. Schꢃth, Micropor. Macropor. Mater. 2005, 77, 1–45.
[14] K. Chen, L., Jr. Que, J. Am. Chem. Soc. 2001, 123, 6327–6337.
[15] B. Mortini, C. R. Phys. 2006, 7, 924–930.
[16] A. A. Spasov, T. V. Khamidova, L. I. Bugaeva, I. S. Morozov, Pharm. Chem.
J. 2000, 34, 1–7.
[17] K. Chen, P. S. Baran, Nature 2009, 459, 824–828.
[18] M. Haukka, J. Kiviaho, M. Ahlgrꢄn, T. A. Pakkanen, Organometallics 1995,
14, 825–833.
[19] S. J. Carrington, I. Chakraborty, J. R. Alvarado, P. K. Mascharak, Inorg.
Chim. Acta 2013, 407, 121–125.
[20] A. Gabrielsson, S. Zalis, P. Matousek, M. Towrie, A. Vlcek Jr., Inorg. Chem.
2004, 43, 7380–7388.
[21] E. Eskelinen, M. Haukka, T. Venalainen, T. A. Pakkanen, M. Wasberg, S.
Chardon-Noblat, A. Deronzier, Organometallics 2000, 19, 163–169.
[22] I. Tabushi, A. Yazaki, J. Am. Chem. Soc. 1981, 103, 7371–7373.
[23] J. T. Groves, T. E. Nemo, J. Am. Chem. Soc. 1983, 105, 6243–6248.
[24] I. Yamanaka, T. Gomi, T. Nabeta, K. Otsuka, Chem. Lett. 2005, 34, 1486–
1487.
1
tion) and NMR (Jeol, ECP-400, H 400 MHz) spectroscopy.
Acknowledgements
[25] E. McNeill, J. Du Bois, J. Am. Chem. Soc. 2010, 132, 10202–10204.
[26] Y. Arai, T. Onozawa, S. Niiyama, K. Yoshida, JP Pat. 2004-51497.
[27] Y. Ishii, T. Iwahama, S. Sakaguchi, K. Nakayama, Y. Nishiyama, J. Org.
Chem. 1996, 61, 4520–4526.
[28] I. L. Viana Rosa, C. M. C. P. Manso, O. A. Serra, Y. Iamamoto, J. Mol. Catal.
A 2000, 160, 199–208.
[29] C. Nozaki, C. G. Lugmair, A. T. Bell, T. D. Tilley, J. Am. Chem. Soc. 2002,
124, 13194–13203.
[30] A. W. Holland, G. Li, A. M. Shahin, G. J. Long, A. T. Bell, T. D. Tilley, J.
Catal. 2005, 235, 150–163.
This study was supported by the Japan Science and Technolo-
gy Agency (JST) ACT-C. XAFS measurements were conducted
at the BL14B2 beamline of SPring-8 with the approval of the
Japan Synchrotron Radiation Research Institute (JASRI) (Propos-
al Nos. 2013B1833, 2014B1643, and 2014A1584).
[31] A. Dhakshinamoorthy, M. Alvaro, H. Garcia, J. Catal. 2009, 267, 1–4.
[32] S. Ikurumi, S. Okada, K. Nakatsuka, T. Kamegawa, K. Mori, H. Yamashita,
J. Phys. Chem. C 2014, 118, 575–581.
Keywords: adamantine
mesoporous organosilica · ruthenium
· alkane · oxidation · periodic
[33] G. Sꢃss-Fink, L. Gonzalez, G. B. Shul’pin, Appl. Catal. A 2001, 217, 111 –
117.
[34] H. Kobayashi, I. Yamanaka, J. Mol. Catal. A 2008, 294, 37–42.
[1] S. Inagaki, S. Guan, T. Ohsuna, O. Terasaki, Nature 2002, 416, 304–307.
[2] N. Mizoshita, T. Tani, S. Inagaki, Chem. Soc. Rev. 2011, 40, 789–800.
[3] X. Wang, D. Lu, R. Austin, A. Agarwal, L. J. Mueller, Z. Liu, J. Wu, P. Feng,
Langmuir 2007, 23, 5735–5739.
[4] S. Inagaki, O. Ohtani, Y. Goto, K. Okamoto, M. Ikai, K. Yamanaka, T. Tani,
T. Okada, Angew. Chem. Int. Ed. 2009, 48, 4042–4046; Angew. Chem.
2009, 121, 4102–4106.
Received: July 6, 2015
Published online on && &&, 0000
&
&
Chem. Eur. J. 2015, 21, 1 – 7
www.chemeurj.org
6
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
FULL PAPER
Ru species were immobilized in an iso-
lated form directly on 2,2’-bypyridine
groups in a periodic mesoporous orga-
nosilica (PMO) framework. The Ru-im-
mobilized PMO oxidizes the tertiary Cꢀ
H bonds of adamantane with signifi-
cantly high regioselectivity. Moreover,
the catalyst converts cis-decalin to cis-9-
decalol with complete retention of the
substrate stereochemistry (see scheme).
&
Catalysis
N. Ishito, H. Kobayashi, K. Nakajima,
Y. Maegawa, S. Inagaki, K. Hara,*
A. Fukuoka*
&& – &&
Ruthenium-Immobilized Periodic
Mesoporous Organosilica: Synthesis,
Characterization, and Catalytic
Application for Selective Oxidation of
Alkanes
Chem. Eur. J. 2015, 21, 1 – 7
www.chemeurj.org
7
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ