Grafting of cyclopentadienyl ruthenium complexes on aminosilane linker modified mesoporous SBA-15 silicates

Article abstract of DOI:10.1039/b611550k

Cyclopentadienyl ruthenium phosphane and carbene complexes are grafted on the surface of mesoporous SBA-15 molecular sieves through an aminosilane linker. The nature of the support after the grafting is examined by powder XRD, TEM and N₂ adsorption/desorption analysis. Elemental analysis, FT-IR, DRIFTS, TG-MS and MAS-NMR studies confirm the successful grafting of the complexes on the surface. The grafted materials are applied for catalytic aldehyde olefination and cyclopropanation. The Royal Society of Chemistry.

Full text of DOI:10.1039/b611550k

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Grafting of cyclopentadienyl ruthenium complexes on aminosilane linker
modified mesoporous SBA-15 silicates†
Ayyamperumal Sakthivel,a Filipe M. Pedro,a Anthony S. T. Chiangb and Fritz E. Ku¨hn*a,c
Received 10th August 2006, Accepted 24th October 2006
First published as an Advance Article on the web 15th November 2006
DOI: 10.1039/b611550k
Cyclopentadienyl ruthenium phosphane and carbene complexes are grafted on the surface of
mesoporous SBA-15 molecular sieves through an aminosilane linker. The nature of the support after
the grafting is examined by powder XRD, TEM and N2 adsorption/desorption analysis. Elemental
analysis, FT-IR, DRIFTS, TG-MS and MAS-NMR studies confirm the successful grafting of the
complexes on the surface. The grafted materials are applied for catalytic aldehyde olefination and
cyclopropanation.
and amine derivatives, which were also exclusively heterogenized
Introduction
on hydrothermally less stable mesoporous MCM-41 materials.15
Organic synthesis has made remarkable progress due to transition
These particularly effective immobilized catalysts were mainly
metal catalysts in recent decades.1 In particular, the implementa-
tion of organometallic complexes as catalysts for organic syntheses
is a continuously developing field. Ruthenium compounds of
the general formula Cp*RuX(PR3)2, Cp*RuX(PR3)(C3N2R5), etc.,
have found widespread applications in catalysis.2–5 Recently, vari-
ous research groups have started to apply this compound family
for aldehyde olefination2–6 and more recently for cyclopropa-
nation reactions.7,8 Aldehyde olefination is an important trans-
formation for the production of carbon–carbon double bonds.8
Ruthenium complexes, such as CpRuCl(PPh3)2, Cp*RuX(PR3)2,
Cp*RuX(PR3)(C3N2R5), (1–3) besides displaying a high activity,
are among the most selective catalysts for this reaction reported
to date.6 On the other hand cyclopropanation of olefinic bonds
utilizing diazo compounds as a carbene source is one of the best de-
veloped and most useful transformations available to the synthetic
organic chemist.9,10 The ruthenium-catalysed cyclopropanation
reaction experienced a fast development in recent years. The main
reasons for this lay in the lower price of the ruthenium based
catalysts, when compared to rhodium derivatives, and their richer
reaction chemistry.10
Catalyst heterogenization, i.e. the immobilization of the catalyst
on a supporting material allowing an easy product isolation and
catalyst recycling, attracts also considerable industrial attention.11
Among the various supporting materials studied, the mesoporous
silicate known as SBA-1512 with a regular pore size, a large
surface area, a large number of surface silanol groups, and a
high chemical and thermal stability, is a potential and promising
candidate as both catalyst and catalyst support.13,14 To the
best of our knowledge the only extensive studies published on
ruthenium catalysts heterogenization deal with Ru(II) porphyrin
applied in alkene epoxidation15b,8g and in a few cases also in
intermolecular cyclopropanation.15f
In the present work, cyclopentadienyl ruthenium phosphane
complexes 1–3 are grafted on the surface of aminosilane linker
modified mesoporous SBA-15 silicate material (designated as
SBA-15SNH2) (Scheme 1). Complexes 1–3 grafted in samples
of SBA-15SNH2 are designated as SBA-15SNH2CpRu, SBA-
15SNH2Cp*Ru and SBA-15SNH2Cp*RuNHC, respectively. The
grafted materials were systematically characterized and applied
as catalysts for benzaldehyde olefination, as well as for styrene
cyclopropanation using ethyl diazoacetate (EDA).
Experimental
Synthetic procedure
SBA-15 silicas were synthesized in a similar way as originally
reported by Zhao et al.12,13d using Pluronic 123 triblock copolymers
(poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide);
(Aldrich)) EOnPO70EOn as templates. In a typical synthesis, 4.0 g
of the EO20PO70EO20 copolymer was dissolved in 150 g of 1.6 M
HCl. To this solution 8.50 g of TEOS (tetraethyl orthosilicate),
was added and the resulting mixture was stirred until TEOS was
dissolved. The final molar gel composition of the synthesis mixture
was 6.89 × 10−4 P123 triblock copolymers: 0.24 HCl : 0.041 TEOS :
7.88 H2O. The mixture was placed in an oven for 24 h at 308 K
and then additional 24 h at 373 K under static conditions. Silica
products were filtered, dried, and calcined at 823 K under air.
Solvents were dried by standard procedures (THF, toluene
with Na/benzophenone ketyl; CH2Cl2 with CaH2), distilled under
˚
argon and kept over 4 A molecular sieves. Grafting experiments
aDepartment fu¨r Chemie der Technischen Universita¨t Mu¨nchen, Lichten-
bergstraße 4, D-85747, Garching bei Mu¨nchen, Germany
(Scheme 1) were carried out using standard Schlenk techniques
under argon atmosphere with the following procedure: prior to
the grafting the SBA-15 molecular sieve was heated at 523 K
under vacuum (10−3 mbar) for 6 h to remove physisorbed water.
The activated mesoporous molecular sieve (SBA-15; 1 g) was
treated with aminopropyl trimethoxy silane (2 mmol) using dry
toluene (30 mL) as solvent under argon atmosphere at 383 K
bNational Central University, Chung-Li, Taiwan, 320, Republic of China
cDepartment of Chemistry, Instituto Tecnolo´gico e Nuclear (ITN), Estrada
Nacional No 10, 2686-953, Sacave´m, Portugal. E-mail: fekuhn@itn.pt;
Fax: +351-219946185
† Electronic supplementary information (ESI) available: Spectroscopic
details (Fig. S1–S3). See DOI: 10.1039/b611550k
320 | Dalton Trans., 2007, 320–326
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Scheme 1
for 24 h. Then excess silane was removed by filtration followed
by repeated washing with dichloromethane. The resulting solid
was dried under vacuum at room temperature. The aminosilane
modified sample is designated as SBA-15SNH2.
at room temperature in the spectral range of 400–4000 cm−1
with a Nicolet Impact 410 spectrophotometer equipped with a
DRIFT chamber. The fine powders were loaded into a sample cell
equipped with a CaF2 window. The spectra thus obtained were
converted into Kubelka-Munk units. Thermogravimetric analyses
were performed using a Netzsch TG209 system at a heating rate of
10 K min−1 under argon. Elemental analyses were measured at the
Mikroanalytisches Labor of the TU Mu¨nchen (M. Barth). Powder
XRD data were collected with a Philips X’pert diffractometer
using Cu Ka radiation filtered by Ni. Nitrogen adsorption–
desorption measurements were carried out at 77 K, using a
gravimetric adsorption apparatus equipped with a CI electronic
MK2-M5 microbalance and an Edwards Barocel pressure sensor.
Before analysis, the calcined SBA-15 samples were degassed
at 723 K overnight to a residual pressure of ca. 10–24 mbar.
A degassing temperature of 413 K was used for the modified
materials (to minimize destruction of the grafted complex).
The specific surface areas (SBET) were determined by the BET
method. The total pore volume was estimated from the N2 uptake
at p/p0 = 0.95, using the liquid nitrogen density of 0.8081 g cm−3.
Grafting experiments are carried out using standard Schlenk
techniques under argon atmosphere with the following procedure:
the cyclopentadienyl ruthenium complexes 1–3 are synthesized as
described earlier.6,7 SBA-15SNH2 is again pre-activated at 473 K
under vacuum (10−3 mbar) for 4 h to remove any physisorbed
water. Then, the sample (1 g) is treated with 0.6 mmol of complexes
1–3 in 30 mL of dry THF under an argon atmosphere. The
mixtures are stirred at 313 K for 3 d. The resulting solutions are
filtered off and the white solids are repeatedly washed with THF
until all physisorbed complexes are removed from the surfaces.
The washed samples are dried under vacuum at RT.
Characterization techniques
FT-IR spectra were recorded on a Perkin Elmer FT-IR spectrom-
eter using KBr pellets as matrix. DRIFT spectra were recorded
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The pore size distribution curves (PSD, the differential volume
adsorbed with respect to the differential pore size per unit mass
as a function of pore width) were computed from the desorption
branch of the experimental isotherms, using a method based on the
area of the pore walls. Transmission electron microscopy (TEM)
was recorded on a JEOL JEM2010 operated at 120 kV. 29Si CP
MAS NMR spectra were recorded at 59.627 MHz, with a (7.05 T)
Bruker Avance 300 spectrometer, with 5.5 ls 1H 90◦ pulses, 8 ms
1
contact time, a spinning rate of 5 kHz and 4 s recycle delays. H
MAS NMR spectra were recorded at 300 MHz using a Bruker
Avance 300 spectrometer with 3.0 ls 1H 90◦ pulses and a spinning
rate of 8 kHz.
Typical procedure for styrene cyclopropanation
Fig. 1 Low angle powder XRD pattern of (a) SBA-15, (b) SBA-15SNH2-
CpRu, (c) SBA-15SNH2Cp*Ru and (d) SBA-15SNH2Cp*RuNHC.
EDA (0.114 g, 1.0 mmol) in 2.0 mL of dichloromethane is slowly
added (addition time 1 h) to a 4.0 mL dichloromethane solution
of styrene (0.520 g, 5.0 mmol) and catalyst (0.02 mmol; based
on Ru content). The reaction is followed by GC-MS. After the
reaction is finished the Z : E products distribution was identified
by GC-MS. The products were isolated by flash chromatography,
using ethyl acetate : hexane (1 :10 ) as eluent. Isolated yields were
calculated based on the amount of EDA used.
15SNH2Cp*RuNHC, respectively) and also a decrease in the inter-
planar distance (see Table 1). These changes originate from the
immobilization of the bulky organometallic Ru complexes inside
the channels of SBA-15.13,14
Fig. 2 depicts the FT-IR spectra of parent calcined mesoporous
SBA-15, aminosilane grafted SBA-15 and of the grafted samples.
The bands at 1216, 1076, and 802 cm−1 are attributed to stretching
vibrations of the mesoporous framework (Si–O–Si). The presence
of weak bands around 1564 cm−1 is due to amino group of the
linker, which is largely masked by the hydroxyl vibrations. New,
comparatively weak bands around 3000, 2957, and 2927 cm−1
can be assigned to the cyclopentadienyl (Cp, Cp*) moiety, and
triphenylphosphane group vibrations of the grafted compounds.
Furthermore, the presence of another band in the range of
2853 cm−1 is due to C–H stretching vibrations, originating from
Typical procedure for benzaldehyde olefination
Benzaldehyde (0.318 g, 3 mmol), PPh3 (0.865 g, 3.3 mmol),
catalyst (0.01 mmol, based on Ru content, i.e. 337, 49 and
36 mg of SBA-15SNH2CpRu, SBA-15SNH2Cp*Ru and SBA-
15SNH2Cp*RuNHC, respectively), and fluorene (0.2 g, used as
internal standard) were dissolved in 15 mL of toluene. The mixture
was heated to 353 K and EDA (0.410 g, 3.6 mmol) was—all at
once—added to the solution. The reaction was monitored by GC-
MS. Yields were determined by GC using a previously recorded
calibration curve (R2>0.999).
Results and discussion
The low angle powder XRD pattern of the grafted Ru complex
samples is depicted in Fig. 1. The XRD pattern of SBA-15
(Fig. 1a), where the main reflection corresponds to a hexagonal
unit cell12,13d is observed at a 2h range of 0.84◦, and two other
weak reflections are found in the 2h range of 1–2◦, with an
indexing referring to the (110) and (200) planes. The grafted
ruthenium complex samples exhibit a main reflection correspond-
ing to the (100) plane. However, compared to parent SBA-15
(Fig. 1a),13d the grafted samples show a decrease in the relative
intensities and line broadenings of the XRD reflections and there
is a clear shift to higher 2h values (2h range 0.94, 0.97 and
0.98◦ for SBA-15SNH2CpRu, SBA-15SNH2Cp*Ru and SBA-
Fig. 2 FT-IR spectra of (a) SBA-15, (b) SBA-15SNH2, (c) SBA-15SNH2-
CpRu, (d) SBA-15SNH2Cp*Ru and (e) SBA-15SNH2Cp*RuNHC.
Table 1 Textural properties of SBA-15 and the grafted Ru samples
Ru/wt%
Sample
Fresh
Recycled
Interplane distance/nm BET surface area/m2 g−1
Pore volume/cm3 g−1
Pore diameter/nm
SBA-15
__
__
10.5
9.39
9.04
8.99
750
380
340
260
1.1
0.5
0.4
0.3
7.4
6.5
6.0
5.5
SBA-15SNH2CpRu
SBA-15SNH2Cp*Ru
SBA-15SNH2Cp*RuNHC
0.3
1.9
2.8
0.3
1.7
2.0
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Fig. 3 DRFT-IR spectra of (a) SBA-15, (b) SBA-15SNH2, (c) SBA-15SNH2CpRu, (d) SBA-15SNH2Cp*Ru and (e) SBA-15SNH2Cp*RuNHC.
the CH2 groups present in the silane ligand. Additional bands
appear at 697 and 721 cm−1, due to C–C bending vibration from
the phenyl ring.16
The DRIFT spectra of SBA-15, aminosilane grafted SBA-
15 and of the grafted samples are shown in Fig. 3. After the
aminosilane grafting new bands appear at 2863, 2939, 2970, 1438,
1456, 1540 and 1560 cm−1, characteristic of C–H vibrations,
further evidencing the CH2 group vibration of the aminosilane
ligand. The appearance of broad bands at 3062 and 1603 cm−1
are typical of NH vibrations. The broadening of peak areas near
3245 cm−1 and also the appearance of a weak band at 699 and
721 cm−1 are observed from phenyl groups of the phosphane
ligand. Elemental analyses (EA) indicate (Table 1) that the RuCp
complex 1 shows relatively low loading in comparison to the
RuCp* complex, which may probably be due to the enhancement
of the leaving ability of the chloride ions by the Cp* moiety, thus
favouring very high loadings in the case of compounds 2 and 3.
The low temperature N2 adsorption/desorption isotherms
are of type (IV) according to IUPAC17 and characteristic for
mesoporous solids. However, compared to the parent mesoporous
sample (Fig. 4a),13d the samples bearing grafted Ru complexes
(Fig. 4b–4d) exhibit a drastic decrease in N2 uptake due to
the presence of aminosilane linkers and the relatively bulky
organometallic compounds on the surface of the mesoporous
channels. Furthermore, the parent SBA-15 sample exhibits a
narrow pore size distribution with average pore diameters of
7.4 nm. The grafted materials exhibit an overall decrease of pore
size and a broadening of the pore size (6.5–5.5 nm) distribution.
Additionally they display a decrease in surface area and pore
volume (see Table 1). The decrease of the pore volume and the pore
size evidences that the aminosilane linker and the organometallic
complexes in the grafted mesoporous samples are mainly located
on the internal surfaces of the mesoporous materials. However,
the micropore volume is not affected much after grafting, which
might be due to the difficulty of bulky organometallic complexes
to access small micropores.
The TEM images (see Fig. 5) of the parent and grafted
samples (SBA-15SNH2CpRu, SBA-15SNH2Cp*Ru and SBA-
15SNH2Cp*RuNHC) provide strong evidence that the meso-
porous structures have an uniform pore size distribution and
Fig. 4 N2 adsorption–desorption analysis of (a) SBA-15, (b) SBA-15S-
NH2CpRu, (c) SBA-15SNH2Cp*Ru and (d) SBA-15SNH2Cp*RuNHC.
Fig. 5 TEM images of (a) SBA-15, (b) SBA-15SNH2CpRu, (c) SBA-15SNH2Cp*Ru and (d) SBA-15SNH2Cp*RuNHC.
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a well ordered pore structure. The long range ordering12,13 is
kept throughout the grafting process and the channels remain
accessible. The well resolved ED pattern spots of the grafted
samples, typical of (110) and (100) planes, further support the
presence of long range ordering in the samples, even after blocking
of some pores by linker molecules and Ru complexes.
and the Cp*Ru(PPh3)(C3N2H2(Cy)2) moieties. The expected mass
loss for SBA-15SNH2Cp*Ru and SBA-15SNH2Cp*RuNHC
is 14 and 19%, respectively, based on the TG-MS spectra
of the organometallic complexes, the TG-MS of the SBA
support with aminosilane linker and the complex loadings.
The observed mass values m/z+ = 77, 31 and 15 correspond
to the phenyl, phosphorous and methyl groups of complexes 2
and 3. The observed mass values m/z+ = 83, 69, 14 in case of
SBA-15SNH2Cp*RuNHC originates from the carbene ligand,
the peak m/z+ = 83 being characteristic of the cyclohexyl group.
In addition, the presence of mass values m/z+ = 14 and 31 in the
grafted sample are characteristic of methylene (CH2) and residual
methoxy groups of the silane linker. All the above-described
observations support the successful grafting of complex 1–3 in
the mesoporous channels of the SBA-15 molecular sieves.
The homogeneous catalysts (1–3) and the grafted materials
containing complexes 1–3 are applied in styrene cyclopropanation
with EDA at room temperature for 24 h (Scheme 2) and the
results are displayed in Table 2. The catalytic activities increase
in the order 1 < 2 < 3. The grafted materials show comparable
activity to their homogeneous counterparts (see Table 2),7b with
prevailing E-selectivity, as expected. However, in the case of SBA-
15SNH2CpRu the catalyst reaches only relatively low yields as
well as an equivalent amount of E- and Z-isomers, possibly due
to the relatively low ruthenium content and therefore a significant
diffusion limitation slowing down the reaction.
The parent SBA-15 and the grafted samples were examined by
solid-state 29Si CP MAS NMR spectroscopy. The parent SBA-15
material exhibits two broad elaborate resonances in the 29Si CP
MAS NMR spectrum at d = −110.3 and −100.5 ppm, assigned to
the Q4 and Q3 species of the silica framework, respectively, [Qn =
Si(OSi)n(OH)4−n].11–14 A weak shoulder is also observed at d =
−96.2 ppm for the Q2 species. The grafting of (MeO)3Si(CH2)3NH2
also results in the reduction of the Q2 and Q3 resonances, and a
concurrent increase of the Q4 resonance. The changes of the Q4
resonances are more pronounced due to the comparatively high
loading. This is consistent with an esterification of the isolated
silanol groups (single and geminal) by nucleophilic substitution
at the silicon atom of the organic ligand.13 The 29Si CP MAS
NMR spectra also exhibit two additional signals at d = −59.2 and
−64.3 ppm assigned to T2 and T3 organosilica species, respectively,
[Tm = RSi(OSi)m(OR)3 − m]. However, as expected, the silylated
samples show (nearly) identical 29Si CP MAS NMR spectra before
and after the grafting with the organo-ruthenium samples, thus
indicating that during the grafting process no significant changes
in the silicon environment take place. The observed changes in
the 29Si CP MAS NMR spectra arise only during the silylating
1
procedure using aminosilane. The H MAS NMR spectra (see
ESI†) of all the samples show broad signals between d = 8.1–4.5
(centre at 5.2, 7.3 ppm) and 1.9 ppm characteristic for the Cp,
phenyl and methyl groups of the complexes 1–3. The additional
peak at 3.30 ppm for the grafted samples is due to the residual
OMe groups attached to silane.
TG-MS spectra of SBA-15SNH2Cp*Ru and SBA-
15SNH2Cp*RuNHC show (Fig. 6) 12 and 18% of weight
loss up to 1000 ◦C, due to decomposition of the Cp*Ru(PPh3)2
Scheme 2
Fig. 6 TG-MS spectra of (a) SBA-15SNH2Cp*Ru and (b) SBA-15SNH2Cp*RuNHC.
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Table 2 Cyclopropanation of styrene over the grafted ruthenium complexesa
Product distribution
Samples
Ru content/atom nm−2
Isolated yieldb (%)
cis-(Z)
trans-(E)
Compound 1
__
__
__
0.047
0.33
__
__
0.637
__
47
56
77
21
50
42
46
73
63
66
47.8
31.3
24.9
46.7
30.1
29.1
23.7
20.1
22.3
19.9
52.2
68.7
75.1
53.3
69.9
70.9
76.3
79.9
77.1
80.1
Compound 2
Compound 3
SBA-15SNH2CpRu
SBA-15SNH2Cp*Ru
1st recycle
2nd recycle
SBA-15SNH2Cp*RuNHC
1st recycle
2nd recycle
__
a Catalyst : styrene = 1 : 250. b Based on EDA conversion; temperature = 298 K; time = 24 h. The error range in the product isolation by column is 2%.
Table 3 Benzaldehyde olefination over the heterogenized ruthenium
The yields are considerably higher, after the same pe-
riod of time, in the case of SBA-15SNH2Cp*Ru and SBA-
15SNH2Cp*RuNHC. The presence of more ruthenium atoms per
nm2 of the catalyst promotes the higher activities. Importantly,
all the catalysts are re-usable for several catalytic runs. There is
a slight decrease of activity on the second run, but the fact that
the catalysts remain equally active for a third run shows that the
grafted compounds are stable on the surface. The small decrease
in catalytic activity during the first catalytic run (5–8%) may be
due to slight leaching of the ruthenium complexes on the surface
of the SBA-15 materials, which is supported by elemental analysis
of the residual ruthenium content in the filtrate. However, the
lack of Ru in the filtrate solution of subsequent runs, as well as
the absence of catalytic conversion in the filtrate, indicate that
the catalysts are then stable and the leaching is insignificant
after the first run. There are no C–H insertion side products,
which are observed in homogeneous catalysis.7b This is a clear
advantage over the homogeneous catalyst system. The similarity
between the homogeneous and heterogeneous results, regarding
both selectivity and overall yield is noteworthy, showing that
the silica mesopores are not imposing significant structural or
electronic perturbations on the immobilized metal centre.
Complexes 1–3 and the corresponding grafted materials are
applied for the benzaldehyde olefination (Table 3) (using the
same catalyst : benzaldehyde ratio based on the Ru content on
the samples), with ethyldiazoacetate (EDA) in the presence of
triphenylphosphane (PPh3) (Scheme 3). Again the homogeneous
catalysts show the same general trend as observed for cyclopropa-
nation, i.e. the olefin yields are higher in the case of the Cp*
compounds when compared to the Cp derivatives due to the
better leaving ability of phosphane from the more electron rich
ruthenium complexes.6b
complexes
Ratio of olefin
Catalysts
Yieldb (%)
cis
trans
Compound 1
25
73
35
43
10
30
33
8
10
9
5
14
4
92
90
91
95
86
96
96
Compound 2
Compound 3
SBA-15SNH2CpRu
SBA-15SNH2CpRu–PPO
SBA-15SNH2Cp*Ru
SBA-15SNH2Cp*RuNHC
4
a Catalyst : benzaldehyde = 1 : 325; temperature = 353 K; time = 24 h.
b The error range in the GC results is 2%.
SBA-15SNH2CpRu the initial activity is lower, however, slightly
higher olefin yields of ca. 43% are reached after 24 h with an E : Z
ratio of 95 : 5. Although the ruthenium content is quite low, the
overall yield is better than in the case of the other two catalysts.
As can be seen from Fig. 7, the initial catalytic activity is high in
the case of SBA-15SNH2Cp*Ru and SBA-15SNH2Cp*RuNHC,
probably due to the high ruthenium loading per unit volume.
However, the reaction velocity slows down during the course of
the reaction. The observed slowing down of the catalytic process
during the course of time seems to be due to adsorption of the
bulky triphenyl phosphine or triphenyl phosphine oxide (PPh3 or
PPh3O) molecules on the surface of the supporting material. This is
evident from the phosphorus elemental analysis of fresh and used
catalysts, where the phosphorus content is increased from 0.4–0.6
to 0.8–3.4 wt%. The adsorption of phosphine on the surface of
SBA-15 is further confirmed by treatment of SBA-15 with PPh3
or PPh3O under identical reaction conditions, which results in
adsorptions of 6–8 wt% of PPh3 or PPh3O (TGA and EA). Thus,
the PPh3 or PPh3O molecules block the SBA-15 channels and
reduce the reaction rate, resulting in an overall low yield. However,
in case of SBA-15SNH2CpRu although the initial activity is lower
The heterogeneous catalysts show comparable yields with con-
siderable azine formation. Both SBA-15SNH2Cp*Ru and SBA-
15SNH2Cp*RuNHC show similar olefin yields, in the range 30–
33%, with an E : Z ratio of 96 : 4 in the olefinic products. In case of
Scheme 3
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References
1 L. S. Hegedus, Transition Metals in the Synthesis of Complex Organic
Molecules, University Science Books, New York, 2nd edn, 1999.
2 (a) W. Baratta, A. del Zotto and P. Rigo, Chem. Commun., 1997, 2163;
(b) W. Baratta, A. del Zotto and P. Rigo, Organometallics, 1999, 18,
5091; (c) A. del Zotto, W. Baratta, F. Miani, G. Verardo and P. Rigo,
Eur. J. Org. Chem., 2000, 3731; (d) W. Baratta, W. A. Herrmann,
P. Rigo and J. Schwarz, J. Organomet. Chem., 2000, 593–594, 489;
(e) W. Baratta, A. del Zotto, E. Herdtweck, S. Vuano and P. Rigo,
J. Organomet. Chem., 2001, 617, 511.
3 (a) O. Fujimura and T. Honma, Tetrahedron Lett., 1998, 39, 625; (b) P.
Schwab, R. H. Grubbs and J. Ziller, J. Am. Chem. Soc., 1996, 118, 100.
4 (a) S. T. Nguyen, L. K. Johnson and R. H. Grubbs, J. Am. Chem. Soc.,
1992, 114, 3975; (b) P. Schwab, M. B. France, J. W. Ziller and R. H.
Grubbs, Angew. Chem., Int. Ed. Engl., 1996, 35, 1169; (c) M. Mayr,
M. R. Buchmeiser and K. Wurst, Adv. Synth. Catal., 2002, 344, 712.
5 (a) W. A. Herrmann, W. C. Schattenmann, O. Nuyken and S. C.
Glander, Angew. Chem., Int. Ed. Engl., 1996, 35, 1087; (b) T. Weskamp,
W. C. Schattenmann, M. Spiegler and W. A. Herrmann, Angew. Chem.,
Int. Ed., 1998, 37, 2490; (c) T. Weskamp, F. J. Kohl, W. Hieringer, D.
Gleich and W. A. Herrmann, Angew. Chem., Int. Ed., 1999, 38, 2416.
6 (a) H. Lebel, V. Paquet and C. Proulx, Angew. Chem., Int. Ed., 2001,
40, 2887; (b) F. E. Ku¨hn, A. M. Santos, A. A. Jogalekar, F. M Pedro, P.
Rigo and W. Baratta, J. Catal., 2004, 227, 253.
Fig. 7 Kinetic profiles for benzaldehyde olefination reaction over
(a) SBA-15SNH2CpRu, (b) SBA-15SNH2CpRu-PPO, (c) SBA-15SNH2-
Cp*Ru and (d) SBA-15SNH2Cp*RuNHC.
7 (a) W. Baratta, W. A. Herrmann, R. M. Kratzer and P. Rigo,
Organometallics, 2000, 19, 3664; (b) O. Tutusaus, S. Delfosse, A.
Demonceau, A. F. Noels, R. Nu´n˜ez, C. Vin˜as and F. Teixidor,
Tetrahedron Lett., 2002, 43, 983; (c) W. Baratta, E. Herdtweck, W. A.
Herrmann, P. Rigo and J. Schwarz, Organometallics, 2002, 21, 2101.
8 F. E. Ku¨hn and A. M. Santos, Mini-Rev. Org. Chem., 2004, 1, 55.
9 (a) P. M. Treichel, D. A. Komar and P. J. Vincenti, Synth. React.
Inorg. Met.-Org. Chem., 1984, 14, 383; (b) H. Lebel, J.-F. Marcoux,
C. Molinaro and A. B. Charette, Chem. Rev., 2003, 103, 977.
10 (a) M. P. Doyle and D. C. Forbes, Chem. Rev., 1998, 98, 911; (b) S. B.
Park, H. Nishiyama, Y. Itoh and K. Itoh, J. Chem. Soc., Chem.
Commun., 1994, 1315; (c) G. Maas, Chem. Soc. Rev., 2004, 33, 183.
11 (a) A. Corma and H. Garcia, Chem. Rev., 2002, 102, 3837; (b) D. E. De
Vos, M. Dams, B. F. Sels and P. A. Jacobs, Chem. Rev., 2002, 102, 3615;
(c) N. E. Leadbeater and M. Marco, Chem. Rev., 2002, 102, 3217.
12 D. Y. Zhao, J. L. Feng, Q. S. Huo, N. Melosh, G. H. Fredrickson, B. F.
Chmelka and G. D. Stucky, Science, 1998, 279, 548.
the kinetic curve shows a steady increase in yield during the course
of the reaction. Due to the higher amounts of supporting material
necessary (337 mg in case of 1 compared to 49 and 36 mg in
the case of 2 and 3) to reach the same catalyst amount, higher
amounts of phosphine or phosphine oxide can be adsorbed before
the pores get blocked and the catalytic reaction comes to a halt.
This result is supported by the catalytic reaction carried out
on PPh3O pre-treated SBA-15SNH2CpRu catalyst (designated as
SBA-15SNH2CpRuPPO). Such pre-treated samples give only very
low yield (10%) and the kinetic curve also shows no significant
improvement in yield with time (see Fig. 7b).
13 (a) A. Sakthivel and P. Selvam, Catal. Lett., 2002, 84, 37; (b) A.
Sakthivel, J. Zhao, M. Hanzlik, A. S. T. Chiang, W. A. Herrmann
and F. E. Ku¨hn, Adv. Synth. Catal., 2005, 347, 473; (c) A. Sakthivel,
S. J. Huang, W. H. Chen, L. Z. Huang, K. H. Chen, H. P. Lin, C. Y.
Mou and S. B. Liu, Adv. Funct. Mater., 2005, 15, 253; (d) A. Sakthivel,
J. Zhao and F. E. Ku¨hn, Microporous Mesoporous Mater., 2005, 86,
341.
14 (a) D. E. De Vos, M. Dams, B. F. Sels and P. A. Jacobs, Chem. Rev.,
2002, 102, 1085; (b) C. Bianchini and P. Barbaro, Top. Catal., 2002, 19,
17; (c) C. Li, Catal. Rev. Sci. Eng., 2004, 46, 419; (d) J. M. Thomas, R.
Raja and Lewis, Angew. Chem., Int. Ed., 2005, 44, 6456; (e) F. E. Ku¨hn,
A. M. Santos and W. A. Herrmann, Dalton Trans., 2005, 2483.
15 (a) C. B. Hansen, G. J. Hoogers and W. Drenth, J. Mol. Catal., 1993,
79, 153; (b) Chun-Jing, S.-G. Li, W.-Q. Pang and C.-M. Che, Chem.
Commun., 1997, 65; (c) C.-J. Liu, W.-Y. Yu, S.-G. Li and C.-M. Che,
J. Org. Chem., 1998, 63, 7364; (d) X.-Q. Yu, J.-S. Huang, W.-Y. Yu and
C.-M. Che, J. Am. Chem. Soc., 2000, 122, 5337; (e) O. Nestler and K.
Severin, Org. Lett., 2001, 3, 3907; (f) J.-L. Zhang and C.-M. Che, Org.
Lett., 2002, 4, 1911; (g) J. L. Zhang, Y. L. Liu and C. M. Che, Chem.
Commun., 2002, 2906; (h) K. Fujishima, A. Fukuoda, A. Yamagishi,
S. Inagaki, Y. Fukushima and M. Ichikawa, J. Mol. Catal. A: Chem.,
2001, 166, 211; (i) D. Bru¨hwiler and H. Frei, J. Phys. Chem. B, 2003,
107, 8547; (j) A. Sakthivel, F. E. Pedro, A. S. T. Chiang and F. E. Ku¨hn,
Synthesis, 2006, 10, 1682.
Conclusions
Ruthenium phosphane and carbene complexes are successfully
grafted on the aminosilane modified surface of SBA-15 materials.
The grafted samples are stable and the structures of the supporting
materials remain intact. The heterogenized catalysts are active in
the aldehyde (benzaldehyde) olefination and cyclopropanation of
styrene with EDA. The catalytic activities remain in the same order
of magnitude even after three catalytic runs for the cyclopropa-
nation reactions, therefore catalyst leaching can be considered as
being minimal. In the case of benzaldehyde olefination, however,
the catalytic reaction is hampered by adsorption of PPh3 or PPh3O
on the carrier material.
Acknowledgements
A.S. is grateful to the Bayerische Forschungsstiftung for financial
support. F.M.P. thanks the Fundac¸a˜o para a Cieˆncia e a Tecnolo-
gia for a Ph.D. scholarship. The authors also thank Dr Marianne
Hanzlik, and Dr G. Raudaschl-Sieber for experimental support.
The Fonds der Chemischen Industrie and the Leonhard-Lorenz-
Stiftung are acknowledged for financial support.
16 G. M. Edwards, I. R. Lewis and P. H. Turner, Inorg. Chim. Acta, 1994,
216, 191.
17 S. W. Sing, D. H. Everett, R. A. W. Haul, L. Moscow, R. A. Pierotti, T.
Rouquerol and T. Siemienewska, Pure Appl. Chem., 1985, 57, 603.
326 | Dalton Trans., 2007, 320–326
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