Osmium Replica of Mesoporous Silicate MCM-48: Efficient and Reusable Catalyst for Oxidative Cleavage and Dihydroxylation Reactions

Full text of DOI:10.1021/ja034137b

Published on Web 05/17/2003
Osmium Replica of Mesoporous Silicate MCM-48: Efficient and Reusable
Catalyst for Oxidative Cleavage and Dihydroxylation Reactions
Kwangyeol Lee, Yong-Ho Kim, Soo Bong Han, Hongkyu Kang, Soyoung Park, Won Seok Seo,
Joon T. Park,* Bongsoo Kim,* and Sukbok Chang*
Department of Chemistry and School of Molecular Science (BK 21), Korea AdVanced Institute of Science and
Technology (KAIST), Daejeon, 305-701, Korea
Received January 12, 2003; E-mail: jtpark@mail.kaist.ac.kr; bongsoo@kaist.ac.kr; sbchang@mail.kaist.ac.kr
Nanostructured materials have received considerable attention
because of their novel size- and shape-dependent electronic,
magnetic, optical, and catalytic properties that differ drastically from
those of bulk materials,1 and current research efforts are focused
on the preparation of nanomaterials with new morphologies.2 Metals
with designed three-dimensional (3-D) nanostructures, in particular,
are expected to find useful applications in catalysis.3 Recently,
replication of mesoporous silicate templates by thermal vapor
infiltration or solution-phase infiltration techniques has led to the
formation of 3-D networks of nanosized Pd4 and Pt.5 The tedious
Figure 1. XRD pattern of N-Os.
experimental procedures and rather low incorporated metal contents
(6-30 wt % of SiO2 weight), however, make their applications
impractical.
The Os-catalyzed organic transformations such as dihydroxyla-
tion and oxidative cleavage of olefins are highly versatile synthetic
methods for the preparation of key intermediates in organic
synthesis.6 High volatility and toxicity of Os components in the
homogeneous catalysis, however, severely limit their large-scale
application. Although several approaches have been reported to
immobilize OsO4,7 it is still highly desirable to develop an easily
handled and recyclable Os catalyst system with high catalytic
activity comparable to that of OsO4 and preferably with lower
toxicity. Herein, we report a highly efficient replication of MCM-
48 to give a 3-D networked osmium nanomaterial and its superior
heterogeneous catalytic activity in oxidative cleavage and dihy-
droxylation.
A Pyrex glass ampule containing MCM-48 (0.2 g) and Os3(CO)12
(0.75 g) was evacuated and then flame-sealed. To induce decom-
Figure 2. TEM micrographs of N-Os at various magnifications.
position of Os3(CO)12 into Os metal, the ampule was heated in a
furnace at 265 °C for 3 days,8 further heated at 350 °C for 6 h, and
(Figure 2a,b) show a substructure of 3-D networked Os nanopar-
finally maintained at 400 °C for 24 h. The ampule was broken
ticles with a diameter of ∼3 nm. The high-resolution TEM image
(CAUTION!),9 and the obtained black powder was treated with H2
in Figure 2c shows the lattice fringe images (d spacing ) 2.37 Å)
at 400 °C for 6 h to remove carbon impurities. After subsequent
thermal annealing at 550 °C under Ar, the furnace was cooled to
room temperature. To remove the SiO2-based template, the resulting
black powder was treated with aqueous 48% HF (CAUTION!).10
Repeated washing with methanol, centrifugation, and drying under
vacuum gave a voluminous black powder (0.45 g, 225 wt % of
SiO2 weight).11
The X-ray powder diffraction (XRD) pattern (Rigaku D/MAX-
RC (12 kW), Cu KR, 40 kV, 45 mA, 25 °C) of the black powder
shows broad peaks at 43°, 69°, 78°, and 84°, which correspond to
(101), (110), (103), and (112) reflections of nanostructured hcp-
Os (JCPDS card no: 06-0662), respectively (Figure 1). It also shows
a low angle peak at 2θ ) 2.2°, suggesting that the black powder
retains some degree of long-range order transferred from the MCM-
48 host. Such a long-range ordered structure is further supported
by transmission electron microscopy (TEM, Philips F20Tecnai
operated at 200 kV) studies. The TEM images of the black powder
from the (100) plane of highly crystalline Os. A very high BET
surface area (126 m2/g) has been obtained for the 3-D networked
Os nanomaterial (N-Os) from N2 adsorption isotherms.
Triggered by recent reports on the direct cleavage of olefins into
carboxylic acids using OsO4 catalyst,12 oxidative cleavage of
unsaturated compounds by N-Os was scrutinized. Various substrates
were smoothly converted to the corresponding carboxylic acids in
high yields within a few hours at room temperature in the presence
of stoichiometric oxidant (Oxone) and N-Os catalyst (0.05 equiv)
(Table 1). While Oxone was most efficient among the various
oxidants tested, no reaction was observed in the absence of N-Os
catalyst. As demonstrated in entries 1-5, the efficiency of the
catalyst is little affected by substituents with different electronic
properties. Cleavage of trans-stilbene produced 2 equiv of benzoic
acid in good yield (entry 8), and 1,1-disubstituted olefin afforded
the corresponding ketone (entry 9). It is particularly noteworthy
that alkynes were also cleaved to carboxylic acids, which has never
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J. AM. CHEM. SOC. 2003, 125, 6844-6845
10.1021/ja034137b CCC: $25.00 © 2003 American Chemical Society

C O M M U N I C A T I O N S
Table 1. Oxidative Cleavage of Alkenes (Alkynes) with Oxone in
run, the N-Os was recovered quantitatively by centrifugation, and
inductively coupled plasma (ICP) analysis of the filtrate showed
that leaching of Os from the matrix was negligible during the
recycles.17 Further studies on detailed mechanistic pathways,
especially regarding substructures of osmium during the oxygen
transfer steps, are in progress.
the Presence of N-Os Catalysta
In summary, we have shown an efficient preparative protocol
of 3-D networked osmium nanomaterial by utilizing the capillary
action of mesopores of MCM-48 toward molten organometallic
precursors as well as its high catalytic activity18 and excellent
reusability in certain oxidation reactions. We believe that other 3-D
networked nanostructured metals could also be prepared by a similar
method and further related studies would undoubtedly produce
various nanocatalysts with novel catalytic activities.
Acknowledgment. S.C. thanks the CMDS, and J.T.P. thanks
the NRL Program of MOST and the KOSEF (1999-1-122-001-5).
B.K. thanks MOST (National R&D Project for Nano Sci. & Tech.).
We thank staffs of KBSI and KAIST for TEM analysis.
Supporting Information Available: Preparation and characteriza-
tion details for the Os nanomaterial and experimental details of catalytic
reactions (PDF). This material is available free of charge via the Internet
at http://pubs.acs.org.
a Reactions were carried out with a substrate (1 equiv), Oxone (4 equiv),
and N-Os (0.05 equiv). b Isolated yield by column chromatography. c Based
on 2 equiv of benzoic acid. d Acetophenone. e Benzoic acid.
Table 2. Dihydroxylation of Alkenes in the Presence of N-Os
Catalysta
References
entry
olefin
time (h)
yield (%)b
(1) (a) Steigerwald, M. L.; Brus, L. E. Acc. Chem. Res. 1990, 23, 183. (b)
Schmid, G. Chem. ReV. 1992, 92, 1709. (c) Alivisatos, A. P. Science 1996,
271, 933. (d) Sun, S.; Murray, C. B.; Weller, D.; Folks, L.; Moser, A.
Science 2000, 287, 1989.
(2) (a) Hu, J.; Odom, T. W.; Lieber, C. M. Acc. Chem. Res. 1999, 32, 435.
(b) Patzke, G. R.; Krumeich, F.; Nesper, R. Angew. Chem., Int. Ed. 2002,
41, 2446.
(3) (a) Schmid, G.; Chi, L. F. AdV. Mater. 1998, 10, 515. (b) Johnson, B. F.
G. Coord. Chem. ReV. 1999, 190, 1269. (c) Roucoux, A.; Schulz, J.; Patin,
H. Chem. ReV. 2002, 102, 3757.
(4) Kang, H.; Jun, Y.-W.; Park, J.-I.; Lee, K.-B.; Cheon, J. Chem. Mater.
2000, 12, 3530.
1
2
3
4
5
6
7
8
9
1-hexene
styrene
trans-stilbene
cyclohexene
indene
1-methylcyclohexene
R-methylstyrene (1st run)
R-methylstyrene (2nd run)
R-methylstyrene (3rd run)
R-methylstyrene (4th run)
R-methylstyrene (5th run)
2
3
4
2
4
4
4
4
4
4
4
81
99
88
89
78
89
91
90
87
92
82
10
11
(5) Shin, H. J.; Ryoo, R.; Liu, Z.; Terasaki, O. J. Am. Chem. Soc. 2001, 123,
1246.
(6) (a) Schro¨der, M. Chem. ReV. 1980, 80, 187. (b) Kolb, H. C.; Van
Nieuwenhze, M. S.; Sharpless, K. B. Chem. ReV. 1994, 94, 2483.
(7) For selected recent examples of the recyclable Os-catalyst system in
dihydroxylation, see: (a) Bolm, C.; Gerlach, A. Eur. J. Org. Chem. 1998,
21. (b) Kobayashi, S.; Endo, M.; Nagayama, S. J. Am. Chem. Soc. 1999,
121, 11229. (c) Severeyns, A.; De Vos, D. E.; Fiermans, L.; Verpoort,
F.; Grobet, P. J.; Jacobs, P. A. Angew. Chem., Int. Ed. 2001, 40, 586. (d)
Choudary, B. M.; Chowdari, N. S.; Kantam, M. L.; Raghavan, K. V. J.
Am. Chem. Soc. 2001, 123, 9220. (e) Yao, Q. Org. Lett. 2002, 4, 2197.
(8) At 265 °C, Os3(CO)12 decomposes to form a brown liquid containing Os5C-
(CO)15, Os6(CO)18, and Os7(CO)21, which easily enters mesopores of
MCM-48 via a capillary action.
(9) The ampule was cooled in liquid N2 before breakage, because the pressure
buildup from liberated CO was very high.
(10) Use an efficient fume hood with a special care to avoid skin contact.
(11) The X-ray photoelectron spectroscopy (XPS) of the black powder shows
peaks due to Os and O, indicating surface oxidation of the Os nanomaterial,
but no discernible osmium oxide phase is observed either in the TEM or
in XRD analysis. See Supporting Information.
(12) (a) Henry, J. R.; Weinreb, S. M. J. Org. Chem. 1993, 58, 4745. (b) Travis,
B. R.; Narayan, R. S.; Borhan, B. J. Am. Chem. Soc. 2002, 124, 3824.
(13) While aldehydes reacted readily to give carboxylic acids in good yields
under the reaction conditions, no conversion was detected with 1,2-diols.
(14) For the oxidation of aldehydes with Oxone, see: Webb, K. S.; Ruszkay,
S. J. Tetrahedron 1998, 54, 401.
(15) Pappo, R.; Allen, D. S.; Lemieux, R. U.; Johnson, W. S. J. Org. Chem.
1956, 21, 478.
(16) See Supporting Information for detailed experimental procedure.
(17) ICP analysis of the filtrate showed that Os contents were less than <5
ppm in each run.
a All reactions were performed with olefin (1 equiv), 4-methylmorpholine
N-oxide (1.2 equiv), and N-Os (0.05 equiv) in acetone/water/tBuOH at 25
°C. b Purified yield by column chromatography.
been reported to the best of our knowledge, although it took a little
longer to get satisfactory yields (entries 10-12). As suggested by
Borhan,12b the oxidative catalytic cleavage of alkenes seems to
proceed via aldehyde rather than 1,2-diol intermediacy.13 However,
use of less oxidant did not guarantee the preferential formation of
aldehydes. For example, reaction of benzyl alcohol with 1.0 equiv
of Oxone in the presence of N-Os catalyst (0.05 equiv) gave
benzaldehyde only in 30-40% yield with comparable formation
of benzoic acid under a variety of conditions.14 In contrast, use of
NaIO4 as an oxidant (2 equiv) in aqueous dioxane gave benzalde-
hyde in 90% yield.15
Dihydroxylation of alkenes into vicinal diols is another prominent
example where OsO4 has displayed an excellent catalytic activity.
Under Upjohn conditions, diverse types of alkenes were oxidized
to the corresponding 1,2-diols in good yields in the presence of
N-Os catalyst without overoxidation of the diol products (Table
2). It was found that N-Os could be quantitatively recovered by a
simple workup procedure after reaction.16 A TEM image showed
that the integrity of the recovered osmium particle was not changed
during the reaction. The recovered N-Os could be recycled several
times without much loss of catalytic activity (entries 7-11). In each
(18) No catalytic conversion was observed for the oxidative cleavage and
dihydroxylation reactions with commercially available Os powder under
otherwise identical conditions.
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