Monolith- And Silica-Supported Carboxylate-Based Grubbs -Herrmann-Type Metathesis Catalysts

Article abstract of DOI:10.1002/adsc.200303037

The synthesis of silica- and monolith-supported Grubbs-Herrmann-type catalysts is described. Two polymerizable, carboxylate-containing ligands, exo, exo-7-oxanorborn-2-ene-5,6-dicarboxylic anhydride and 7-oxanorborn-2-ene-5- carboxylic acid were surface-immobilized onto silica- and ring-opening metathesis (ROMP-) derived monolithic supports using "grafting-from" techniques. The "1^st generation Grubbs catalyst", RuCl ₂(=CHPh)(PCy₃)₂, was used for these purposes. In addition, a poly(norborn-2-ene-b-exo, exo-norborn-2-ene-5,6-dicarboxylic anhydride) -coated silica 60 was prepared. The polymer supported anhydride and carboxylate groups were converted into the corresponding mono- and disilver salts, respectively, and reacted with the Grubbs-Herrmann catalyst RuCl ₂(=CHPh)(IMesH₂)(PCy₃) [IMesH₂ = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene]. Heterogenization was accomplished by exchange of one chlorine ligand with the polymeric, immobilized silver carboxylates to yield monolith-supported catalysts 4, 5, and 6 as well as silica-supported systems 7, 8 and 9. The actual composition of these heterogenized catalysts was proven by the synthesis of a homogeneous analogue, RuCl[7-oxanorbornan-2-(COOAg)-3-COO](=CHPh)(IMesH₂) (PCy₃) (3). All homogeneous and heterogeneous catalysts were used in ring-closing metathesis (RCM) of diethyl diallylmalonate, 1,7-octadiene, diallyldiphenylsilane, methyl trans-3-pentenoate, diallyl ether, N,N-diallyltrifluoracetamide and t-butyl N,N-diallylcarbamate allowing turnover numbers (TON's) close to 1000. In a flow-through set-up, an auxiliary effect of pendant silver carboxylates was observed with catalyst 5, where the silver moiety functions as a (reversible) phosphine scavenger that both accelerates initiation and stabilizes the catalyst by preventing phosphine elution. Detailed catalytic studies were carried out with the monolith-supported systems 4 and 6 in order to investigate the effects of temperature and chain-transfer agents (CTA's) such as cis-1,4-diacetoxybut-2-ene. In all RCM experiments Ru-leaching was low, resulting in a Ru-content of the RCM products ≤3.5 μg/g (3.5 ppm).

Full text of DOI:10.1002/adsc.200303037

FULL PAPERS
Monolith- and Silica-Supported Carboxylate-Based Grubbs
Herrmann-Type Metathesis Catalysts
Jens O. Krause,b Said Lubbad,a Oskar Nuyken,b,* Michael R. Buchmeisera,*
a
Institut f¸r Analytische Chemie und Radiochemie, Universit‰t Innsbruck, Innrain 52 a, 6020 Innsbruck, Austria
Fax: ( ‡ 43)-512-507-2677, e-mail: michael.r.buchmeiser@uibk.ac.at
b
Lehrstuhl f¸r Makromolekulare Stoffe, Technische Universit‰t M¸nchen, Lichtenbergstr. 4, 85747 Garching, Germany
Fax: ( ‡ 49)-89-289-13571, e-mail: oskar.nuyken@ch.tum.de
Received: February 12, 2003; Accepted: April 4, 2003
Abstract: The synthesis of silica- and monolith- synthesis of a homogeneous analogue, RuCl[7-oxanor-
ˆ
supported Grubbs Herrmann-type catalysts is de- bornan-2-(COOAg)-3-COO]( CHPh)(IMesH2)(PCy3)
scribed. Two polymerizable, carboxylate-containing (3). All homogeneous and heterogeneous catalysts
ligands, exo, exo-7-oxanorborn-2-ene-5,6-dicarboxylic were used in ring-closing metathesis (RCM) of
anhydride and 7-oxanorborn-2-ene-5-carboxylic acid diethyl diallylmalonate, 1,7-octadiene, diallyldiphen-
were surface-immobilized onto silica- and ring-open- ylsilane, methyl trans-3-pentenoate, diallyl ether,
ing metathesis (ROMP-) derived monolithic supports N,N-diallyltrifluoracetamide and t-butyl N,N-diallyl-
using ™grafting-from∫ techniques. The ™1st generation carbamate allowing turnover numbers (TON×s) close
ˆ
Grubbs catalyst∫, RuCl2( CHPh)(PCy3)2, was used to 1000. In a flow-through set-up, an auxiliary effect
for these purposes. In addition, a poly(norborn-2-ene- of pendant silver carboxylates was observed with
b-exo, exo-norborn-2-ene-5,6-dicarboxylic anhydride) catalyst 5, where the silver moiety functions as a
-coated silica 60 was prepared. The polymer support- (reversible) phosphine scavenger that both acceler-
ed anhydride and carboxylate groups were converted ates initiation and stabilizes the catalyst by preventing
into the corresponding mono- and disilver salts, phosphine elution. Detailed catalytic studies were
respectively, and reacted with the Grubbs Herrmann carried out with the monolith-supported systems 4
ˆ
catalyst RuCl2( CHPh)(IMesH2)(PCy3) [IMesH2 ˆ
and 6 in order to investigate the effects of temper-
ature and chain-transfer agents (CTA×s) such as cis-
1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-
ylidene]. Heterogenization was accomplished by ex- 1,4-diacetoxybut-2-ene. In all RCM experiments Ru-
change of one chlorine ligand with the polymeric, leaching was low, resulting in a Ru-content of the
immobilized silver carboxylates to yield monolith- RCM products ꢀ 3.5 mg/g (3.5 ppm).
supported catalysts 4, 5, and 6 as well as silica-
supported systems 7, 8 and 9. The actual composition Keywords: carboxylate ligands; heterogeneous catal-
of these heterogenized catalysts was proven by the ysis; metathesis; polymers; ruthenium
Introduction
consequence the catalysts of choice for non-asymmetric
RCM. For heterogeneous RCM, we already reported on
Hardly any other field in synthetic organic chemistry has the synthesis of monolith- and silica-supported Grubbs
experienced such a rapid development as transition Herrmann catalysts.[16,17] The catalytic systems described
[1 3]
Among there were obtained by heterogenization of a 1st
À
metal-catalyzed C C coupling reactions.
these, ring-closing metathesis (RCM), cross and tandem generation Grubbs catalyst via the NHC ligand, easily
metathesis have gained a strong position. In RCM, N- accomplished by an NHC/phosphine exchange. These
heterocyclic carbene(NHC)-based ruthenium benzyli- supported catalysts were characterized by excellent
denes,[4 6] better known as ™2nd generation Grubbs∫ or stability, low Ru-bleeding and high turnover numbers
™Grubbs Herrmann∫ catalysts, are now in the center of (TON×s) upto280. In our search for other heterogenized
interest.[7,8] Molybdenum-based Schrock carbenes metathesis catalysts we were encouraged by the reports
[Mo( N-2,6-R2-C6H3)( CHCMe2Ph)(OCR×)2] are still of Buchowicz et al. and Nieczypor et al. on monomeric
the compounds of preference in case the reaction needs and supported carboxylate-derived 1st generation
to be carried out in an asymmetric fashion.[9 15] Never- Grubbs catalysts.[18,19] We therefore investigated the
theless, their ruthenium analogues are characterized by general applicability of a halogen exchange between a
an enhanced stability towards oxygen and protic com- Grubbs Herrmann catalyst and a supported functional
pounds including water, which makes them in due group, in particular with silver carboxylates.
ˆ
ˆ
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DOI: 10.1002/adsc.200303037
Adv. Synth. Catal. 2003, 345, 996 1004

Monolith- and Silica-Supported Carboxylate-Based Grubbs Herrmann Catalysts
FULL PAPERS
Scheme 1. Synthesis of compound 2.
Scheme 2. Synthesis of compound 3.
Results and Discussion
Synthesis of Ligands and Homogeneous Catalysts
Scheme 3. Synthesis of monolith-supported Grubbs Herr-
mann catalysts [DMN-H6-based 4, (NBE-CH2O)3SiMe-based
5] using a dicarboxylate.
exo, exo-7-Oxanorbornan-2,3-dicarboxylic anhydride
(1) was prepared via catalytic hydrogenation of 7-
oxanorborn-2-ene-5,6-dicarboxylic anhydride and was
then converted into the disilver salt by treatment with
Ag(NH3)2NO3. The product (2) was conveniently col- catalyst. This is in contrast to our findings with the
lected by filtration (Scheme 1). dihydroimidazolylidene-based Grubbs Herrmann cat-
Halogen exchange of the starting compounds with the alyst, which appears to be much more tolerant to ligand
Grubbs Herrmann catalyst was carried out at elevated variation and where the NHC ligand provides enough
temperature to form the new catalyst 3. Interestingly, steric protection to effectively prevent the formation of
only one chlorine ligand was exchanged (Scheme 2).
Catalyst 3 was characterized both by H NMR and
bridged, dinuclear systems.
1
MALDI-TOF-MS. A single resonance for the alkyli-
dene proton at d ˆ 17.41 ppm was indicative for the Synthesis of Monolith-Supported Catalysts
formation of 3. Although the molecule ion peak was not
observed, the m/z of 955.476 was indicative for the Metathesis-derived, monolithic supports have already
presence ofa Rucomplex containingone chlorine ligand. been identified as excellent and easy to make carriers for
The presence of a second free Ag carboxylate was proven catalytic systems as well as for separation devices.[16,20 22]
by reaction of 3 with trimethylchlorosilane. Precipitation In particular the low back pressure, the accessibility
of AgCl occurred and the chemical shift for the alkyli- of the solely surface-bound catalytic sites as well as
dene proton shifted to d ˆ16.82 ppm. Unfortunately, the the non-porous character of the support allow the
resulting compound, presumably RuCl[7-oxanorbornan- running of such devices in a (continuous) flow-through
ˆ
2-(COOSiMe3)-3-COO]( CHPh)(IMesH2)(PCy3) could set-up with high TON×s and low catalyst (i.e., rutheni-
not be isolated. All efforts to obtain a catalyst by um) bleeding. Monolith-supported systems were pre-
substitution of both chlorines, e.g., by using the bis-Tl or pared according to a protocol similar to the ones
bis-Cs salts, by adding excess of PCy3 or by using a described earlier.[16,23] Briefly, monoliths were synthe-
phosphine scavenger failed, only decomposition of the sized in a one-step procedure within the confines of
catalyst was observed. We tentatively attribute this to PEEK (poly ether ether ketone) columns from norborn-
the phosphine-scavenging property of the second Ag 2-ene, and 1,4,5,8,8a-hexahydro-1,4,5,8-exo, endo-dime-
carboxylate group (vide infra), which results in the thanonaphthalene (DMN-H6) or tris(norborn-2-ene-5-
formation of AgCl ¥ PCy3 in course of the (slow) reaction ylmethylenoxy)methylsilane [(NBE-CH2O)3-SiMe], tol-
with the second chlorine ligand. This is in strong contrast uene and 2-propanol. The ™living∫ ruthenium termini
to the reaction of silver trifluoroacetate or pentafluor- located at the surface were used for the graft polymer-
opropionate with the 1st generation catalyst, where ization of exo, exo-7-oxanorborn-2-ene-5,6-dicarboxylic
bridged m-carboxylato-diruthenium complexes are anhydride. The grafted anhydride moieties were finally
formed.[18] As a result of their investigations, Buchowitz converted into the bis-silver salt and reacted with
ˆ
et al. proposed that the carboxylates had to possess a RuCl2( CHPh)(IMesH2)(PCy3)toyieldtheimmobilized
pKa between À 7 and 4 in order to allow the synthesis of catalysts 4 and 5 (Scheme 3). Acatalyst loading of 10 and
stable carboxylate-containing 1st generation Grubbs 7 mg/g, respectively, was achieved.
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Jens O. Krause et al.
FULL PAPERS
ˆ
RuCl2( CHPh)(PCy3)2 and exo, exo-7-oxanorborn-2-
ene-5,6-dicarboxylic anhydride or, respectively, 7-oxa-
norborn-2-ene-5-carboxylic acid. By this grafting-from
approach, satisfactory amounts of both monomers were
grafted onto the support. Thus, anhydride loadings of
0.22 mmol/g (LiChrospher 300 5) and 1.2 mmol/g
(Nucleosil 300 7) were achieved. Conversion into the
corresponding di- and mono-silver salts and reaction
ˆ
with RuCl2( CHPh)(IMesH2)(PCy3) gave the desired
supported catalysts 7 and 8 (Scheme 5).
Scheme 4. Synthesis of monolith-supported Grubbs Herr-
mann catalyst 6 based on a monocarboxylate.
The catalyst-loading was in the range 42 mg (Nucle-
osil 300 7) to 63 mg catalyst/g (Lichrospher). Comple-
mentary, a poly(norborn-2-ene-b-7-oxanorborn-2-ene-
5,6-anhydride)-coated silica was prepared from silica-60
and poly(norbornene-b-7-oxanorborn-2-ene-5,6-dicar-
boxylate) and used for catalyst immobilization. The
corresponding supported catalyst 9, containing 7.0 mg
Ru/g silica, corresponding to 77 mg catalyst/g, was used
as an additional benchmark in the ranking of the
catalytic activity.
Catalytic Activity
Non-Supported Catalysts
In order to benchmark all the new systems in terms of
reactivity, diethyl diallylmalonate (DEDAM), 1,7-octa-
diene, diallyldiphenylsilane, 1,1-diallylethanol, diallyl
ether, N,N-diallyltrifluoroacetamide, and t-butyl N,N-
diallylcarbamamate were used in RCM. In addition,
methyl trans-3-pentenoate was used in cross-metathesis.
In a first step, the homogeneous catalyst 3 was inves-
tigated. The turnover numbers (TON×s) that were
achieved (TON ˆ 520, Table 1, entries 7 13) were
Scheme 5. Synthesis of a silica-supported Grubbs Herrmann
catalyst based on a dicarboxylate (Nucleosil 300 7-based 7,
LiChrospher 300 5-based 8).
In order to investigate whether the second (™free∫) found to be reduced by a factor of 2 compared to the
silver carboxylate had any influence on either the ones obtained with the Grubbs Herrmann catalyst
stability or catalytic activity of this system, the same (Table 1, entries 1 6) indicating that substitution of
synthetic protocol was applied for the synthesis of a one chlorine ligand does in fact change the catalytic
poly(7-oxanorborn-2-ene-5-carboxylic acid) grafted activity of the system. The importance of appropriate
monolith, which was in due consequence used for reaction conditions is illustrated by the low values for
catalyst immobilization to yield 6 (Scheme 4).
TON accomplished in complementary experiments
As expected, a similar ruthenium loading of 0.8 mg carried out in a different (coordinating) solvent such
Ru/g support, corresponding to 9 mg catalyst/g was as THF and at different conditions such as higher
obtained; nevertheless, a significant difference was concentrations (Table 1, entries 14 20).
observed in catalytic reactivity (vide infra).
Monolith-Supported Catalysts
Synthesis of Silica-Supported Catalysts
The catalytic activity of the carboxylate-based systems
Silica-derived supports were fabricated according to a was first studied with a DMN-H6-derived monolith-
synthetic procedure elaborated in our group.[24] Briefly, supported system (4). As can be deduced from Figure 1,
the corresponding support was surface-derivatized with the optimum conditions for this catalyst entailed a
norborn-2-ene-5-yl-trichlorosilane (exo/endo-mixture) reaction temperature of 458C and the use of a chlori-
or norborn-2-ene-5-yl-triethoxysilane (exo/endo-mix- nated solvent.
ture) to obtain surface-immobilized silyl-norborn-2-
In fact, we could not find any significant difference
ene groups. These were consecutively reacted with between dichloromethane and dichloroethane. The
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Table 1. Summary of catalytic activity of homogeneous systems.
#
Compound
Catalyst
T [8C]
Solvent (mol % compound)
TON
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
DEDAM
1,7-octadiene
Grubbs Herrmann
Grubbs Herrmann
Grubbs Herrmann
Grubbs Herrmann
Grubbs Herrmann
Grubbs Herrmann
3
3
3
3
3
3
3
3
3
3
3
3
3
3
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
CH2Cl2 (0.05)
CH2Cl2 (0.1)
CH2Cl2 (0.1)
CH2Cl2 (0.01)
CH2Cl2 (0.1)
CH2Cl2 (0.1)
CH2Cl2 (0.05)
CH2Cl2 (0.1)
CH2Cl2 (0.1)
CH2Cl2 (0.1)
CH2Cl2 (0.01)
CH2Cl2 (0.1)
CH2Cl2 (0.1)
THF (9.3)
THF (3.8)
THF (9.1)
THF (4.3)
THF (5.6)
THF (3.4)
THF (6.0)
1300
1000
400
600
770
150
520
520
140
25
280
50
190
40
20
30
diallyldiphenylsilane
methyl trans-3-pentenoate
t-butyl N,N-diallylcarbamate
N,N-diallyltrifluoroacetamide
DEDAM
1,7-octadiene
diallyldiphenylsilane
1,1-diallylethanol
methyl trans-3-pentenoate
diallyl ether
N,N-diallyltrifluoroacetamide
DEDAM
1,7-octadiene
diallyldiphenylsilane
1,1-diallylethanol
10
10
90
2
methyl trans-3-pentenoate
diallyl ether
N,N-diallyltrifluoroacetamide
porosity,[23] smaller amounts of the anhydride or,
respectively, the catalyst (i.e., 7 mg/g) could be immo-
bilized. Nevertheless, with the corresponding monolith-
supported catalyst 5 we could achieve the highest TON×s
ever reported for a supported system, partially reaching
the TON×s that were observed with the Grubbs
Herrmann catalyst in solution (e.g., for 1,7-octadiene,
Table 2, entries 22 28). The finding that TON×s were
even higher than those obtained with 3 is attributed to
the immobilization itself, which eliminates bimolecular
reactions between two catalyst moieties.[25] CTA×s
(chain-transfer agents) are often used to enhance the
stability of a system.[16,17] More detailed investigations
carried out with DEDAM revealed that neither higher
nor lower temperatures (Table 2, entries 30 and 31) nor
the use of a CTA(Table 2, entry 29) had a positive
influence on the persistence, i.e., stability of this system
as reflected by the corresponding TON×s.
Figure 1. Catalytic activities of 4 and 5 vs. DEDAM. Flow
*
rate ˆ 0.1 mL/min, c(DEDAM) ˆ 10 wt % in ClCH2CH2Cl.
In order to shed some light on the (potentially
synergistic) role of the second silver-carboxylate ligand
present in the system we prepared a monolith-supported
catalyst starting with a mono-silver carboxylate (6). As
~
!
(5, Tˆ 458C),
(5, Tˆ 358C),
[5, Tˆ 458C, c(CTA) ˆ 1
&
wt %], (4, Tˆ 458C).
TON found for DEDAM was 180 (Table 2, entry 21). can be seen (Table 2, entry 32, Figure 2), the TON for
From previous investigations concerning the micro- DEDAM (110) was comparably low under conditions
structure of DMN-H6-derived monoliths we found that identical to the ones previously used. In addition, we
a significant percentage of this rigid cross-linker did not could monitor increased amounts of free PCy3 in the
take part in the cross-linking reaction, resulting in the effluent.
presence of a substantial number of norborn-2-ene-
This is in strong contrast to what was observed with
subunits.[23] Since these are highly reactive, we could not catalyst 5, were no PCy3 was observed at all. In view of
rule out an interference with the RCM reactions of this and the differences in catalytic activity of 5 and 6 we
interest. We therefore changed the polymeric matrix by conclude that the second, pendant silver carboxylate
using the more flexible (NBE-CH2O)3-SiMe as a cross- functions as an internal reversible phosphine scavenger
linker instead of DMN-H6. Due to a reduced meso- during the RCM process, which reduces the loss of
Adv. Synth. Catal. 2003, 345, 996 1004
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Table 2. Summary of catalytic activity of heterogeneous systems.
#
Compound
Catalyst
T [8C]
Solvent (Conc. [wt. %])
TON
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
DEDAM
DEDAM
1,7-octadiene
diallyldiphenylsilane
methyl trans-3-pentenoate
methyl trans-3-pentenoate
N,N-diallyltrifluoroacetamide
t-butyl N,N-diallylcarbamate
DEDAM
DEDAM
DEDAM
DEDAM
DEDAM
DEDAM
DEDAM
DEDAM
1,7-octadiene
4
5
5
5
5
5
5
5
5
5
5
6
7
7
7
8
8
8
8
8
9
9
9
45[a]
45[a]
45[a]
45[a]
45[a]
45[a]
45[a]
45[a]
45[a, c]
35[a]
55[a]
45[a]
50[b]
65[b]
50[b, c]
45[b]
45[b]
45[b]
45[b]
45[b]
45[a]
50a, d]
50[b, c]
ClCH2CH2Cl (10)
ClCH2CH2Cl (10)
CH2Cl2 (10)
180
940
900
90
340
30
CH2Cl2 (10)
ClCH2CH2Cl (47.5)
ClCH2CH2Cl (10)
ClCH2CH2Cl (10)
ClCH2CH2Cl (10)
ClCH2CH2Cl (10)
ClCH2CH2Cl (10)
ClCH2CH2Cl (10)
ClCH2CH2Cl (10)
ClCH2CH2Cl (1.5)
ClCH2CH2Cl (1.5)
ClCH2CH2Cl (1.5)
CH2Cl2 (2)
CH2Cl2 (2)
CH2Cl2 (2)
CH2Cl2 (2)
CH2Cl2 (2)
CH2Cl2 (10)
CH2Cl2 (10)
CH2Cl2 (5)
70
140
280
442
220
110
10
10
1
90
50
40
70
60
20
3
0.1
diallyldiphenylsilane
N,N-diallyltrifluoroacetamide
t-butyl N,N-diallylcarbamate
DEDAM
DEDAM
DEDAM
[a]
[b]
[c]
[d]
Flow-through.
Stirred batch.
1% cis-1,4-diacetoxy-2-butene.
0.1% cis-1,4-diacetoxy-2-butene.
phosphine and thus stabilizes the ruthenium core in the
absence of a diene.
Silica-Supported Catalysts
Synthetic routes based on combinatorial chemistry
usually entail the use of combi-chem machines. If used
in catalytic processes, stirred reactions are usually the
preferred set-up. For this purpose, the silica-based
systems 7, 8 and 9 were prepared. After verifying the
optimum conditions (Table 2, entries 33 35), a surface-
grafted system based on Nucleosil 300 5 was used in
stirred batch RCM reactions. TON×s in the range of 60
90 were achieved (Table 2, entries 36 40). This defi-
nitely allows its use in combinatorial chemistry. Fur-
thermore, the surface-grafting of silica provided sup-
ports that were really comparable to their monolithic
analogues because of the identical set-up. In view of the
quite different catalytic data achieved with these two
supports, one obtains a nice illustration of the superi-
Figure 2. Catalytic activity of 6 for DEDAM. Tˆ 458C, flow
rate ˆ 0.1 mL/min, c(DEDAM) ˆ 10 wt % in ClCH2CH2Cl.
ority of monolith-based systems used in a flow-through located within the polymer film deposited on the silica
set-up over classic supports.
Amore straightforward synthetic route to silica-based
surface. Not unexpected, if used in a flow-through or
stirred batch set-up (Table 2, entries 41 43), compara-
supports is the synthesis of coated analogues. These are bly low TON×s were achieved with the coated support 9,
easy and straightforward to prepare, yet suffer from a which justifies the synthesis of defined surfaces via
reduced accessibility of the catalytic sites, since these are grafting techniques in heterogeneous catalysis. In order
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Monolith- and Silica-Supported Carboxylate-Based Grubbs Herrmann Catalysts
FULL PAPERS
diallytrifluoroacetamide, diallyldiphenylsilane, methyl trans-
3-pentenoate, t-butyl N,N-diallycarbamate, cis-1,4-diacetoxy-
to determine the Ru content of the final RCM products,
ICP analyses were carried out. These revealed a Ru-
content as low as ˆ 3.5 mg Ru/g, which gives another nice
illustration of the applicability of these systems.
ˆ
2-butene, ethyl vinyl ether (EVE), RuCl2( CHPh)(PCy3)2, and
ˆ
RuCl2( CHPh)(IMesH2)(PCy3) [IMesH2 ˆ 1,3-bis(2,4,6-tri-
methylphenyl)-4,5-dihydroimidazol-2-ylidene] were pur-
chased from Fluka (Buchs, Switzerland). Aruthenium stand-
ard containing 1000 ppm of ruthenium was purchased from
Alfa Aesar/Johnson Matthey (Karlsruhe, Germany). Bicy-
clo[2.2.1]hept-2-ene-5-yl(trichloro)silane and bicyclo[2.2.1]-
hept-2-ene-5-yl(triethoxy)silane were purchased from ABCR
(Darmstadt, Germany). exo, exo-7-Oxanorborn-2-ene-5,6-di-
carboxylic anhydride,[27] methyl 7-oxanorborn-2-ene-5-car-
boxylate,[28] 7-oxanorborn-2-ene-5-carboxylic acid,[29] tri-
(norborn-2-ene-5-yl-methyloxy)methylsilane (NBE-CH2O)3-
SiMe,[23] and 1,4,4a,5,8,8a hexahydro-1,4,5,8-exo, endo-dime-
thanonaphthalene (DMN-H6),[30] were prepared according to
literature procedures and checked for purity by means of
NMR. Nucleosil 300 7 (300 ä, 7 mm, pore volume 1.0 mL/g),
LiChrospher wp300 (300 ä, 5 mm, 80 m2/g) and silica 60 (230
400 mesh, 40 63 mm, 480 540 m2/g, pore volume ˆ 0.74
0.84 mL/g) were purchased from Merck, Germany. C-18
derivatization of silica-60[31] as well as the synthesis of poly-
(norborn-2-ene-b-7-oxanorborn-2-ene-5,6-anhydride)-coated
silica[32] were carried out according to the literature.
Conclusion
For the first time, Grubbs Herrmann-type catalysts
have been immobilized on monolithic and silica-based
supports via exchange of one chlorine ligand. The
disilver salts of vic-diarboxylates turned out to be
superior to silver carboxylates since the second, pendant
silver carboxylate functions as a reversible phosphine
scavenger. Both the monolith- and silica-based catalytic
systems turned out to be stable, allowing high TON×s in
RCM for a large number of compounds. Ruthenium
leaching was low, resulting in virtually Ru-free products.
The catalytic systems described here can be used as
monolith-based flow-through reactors as well as sur-
face-grafted silica-based supports in slurry-type reac-
tions. Together with their stability and high activity, this
is believed to make them attractive for both combina-
torial chemistry and large-scale industrial applications.
exo, exo-4,10-Dioxatricyclo[5.2.1.02,6]decane-3,5-dione
(7-Oxanorbornan-2,3-dicarboxylic Anhydride)
Experimental Section
exo, exo-7-Oxanorborn-2-ene-5,6-dicarboxylic anhydride (1,
25 g, 150 mmol) was dissolved in 100 mL of dry DMFand Pd/C
(10%, 1.3 g) was added. Hydrogenation was carried out at 1 bar
for 6 h. After addition of 50 mL Et2O the mixture was filtered
over celite, reduced to 5 mL and filtered again. After
evaporating to dryness the residue was recrystallized from
CHCl3. The crystals were dried giving the anhydride as a white
General Remarks
NMR data were obtained at 300.13 MHz for proton and at
75.74 MHz for carbon in the indicated solvent at 258C on a
Bruker Spectrospin 300 and are listed in parts per million
downfield from tetramethylsilane for proton and carbon. IR
spectra were recorded on a Bruker Vector 22 using ATR
technology. GC-MS investigations were carried out on a
Shimadzu GCMS-QP5050, using a SPB-5 fused silica column
(30 m  0.25 mm  25 mm film thickness). Elemental analyses
were carried out at the Institute of Physical Chemistry,
University of Vienna and at the Mikroanalytical Laboratory,
Anorganisch-Chemisches Institut, TU M¸nchen, Germany. A
Jobin Yvon JY 38 plus was used for ICP-OES measurements,
an MLS 1200 mega for microwave experiments. PEEK
columns (100 Â 4 mm i.d., 125 Â 4 mm i.d. and 150 Â 4 mm
i.d.) were purchased from Berger (Linz, Austria). Further
instrumentation is described elsewhere[26]. MALDI-TOF ex-
periments were carried out on a Bruker Biflex III using an N2
laser (l ˆ 337 nm). Dithranol (1,8-dihydroxyanthron) was
used as the matrix.
Syntheses of the ligands and polymerizations were per-
formed under an argon atmosphere by standard Schlenk
techniques or in an N2-mediated dry-box (MBraun, Germany)
unless stated otherwise. Reagent grade diethyl ether, pentane,
THF and toluene were distilled from sodium benzophenone
ketyl under argon. Reagent grade triethylamine, dichloro-
methane, 1,2-dichloroethane were distilled from calcium
hydride under argon. Other solvents and reagents were used
as purchased. Deionized water was used throughout. Diethyl
diallylmalonate (DEDAM), 1,7-octadiene, diallyl ether, N,N-
1
solid; yield: 21.85 g (130 mmol, 86%); H NMR (DMSO-d6,
258C): d ˆ 4.86 (s, 2H, CH2CH), 3.40 (s, 2H, COCH), 1.65 (s,
4H, CH2); 13C NMR (DMSO-d6, 258C): d ˆ 171.4 (CO), 80.2
Ä
(CHO), 50.6 (CHCO), 28.1 (CH2); FT-IR (ATR-mode): n ˆ
3478.11 (w), 3379.01 (w), 2883.83 (w), 2627.02 (w), 1841.36 (w),
1769.84 (s), 1681.46 (s) cmÀ1; GC-MS (EI, 70 eV): calcd. for
‡
C8H8O4: m/z ˆ 168.04 (M. ); found: 168.0.
Diargento-exo, exo-[2.2.1]bicycloheptane-2,3-
dicarboxylate (2)
Asolution of NH in water (1:5) was added dropwise to a
3
stirred solution of AgNO3 (1.009 g, 5.94 mmol) in 10 mL water
until the precipitate of silver hydroxide had disappeared.
exo, exo-4,10-Dioxatricyclo[5.2.1.02,6]decane-3,5-dione (0.5 g,
2.97 mmol, 0.5 equiv.), dissolved in 2 mL of THF, was added
to the clear solution resulting in the formation of a white
precipitate. After stirring for 30 minutes, the precipitate was
separated from the solution and washed consecutively with
water, THF and Et2O. Finally, the white solid was dried under
vacuum; yield: 0.57 g (1.43 mmol, 48%); FT-IR (ATR-mode):
Ä
n ˆ 3381.07 (s), 3190.38 (w), 3000.85 (w), 2946.94 (w), 2873.07
(w), 1629.33 (vs), 1540.95 (vs), 1445.40 (s), 1395.29 (vs) cmÀ1;
anal. calcd. for C8H8Ag2O5 (Mr ˆ 399.88 g/mol): C 24.03, H
2.02, Ag 53.95; found: C 24.33, H 2.12, Ag 53.60.
Adv. Synth. Catal. 2003, 345, 996 1004
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1001

Jens O. Krause et al.
FULL PAPERS
ˆ
to a ratio of (NBE-CH2O)3-SiMe:2-propanol:toluene:initiator
of 20:20:45.7:13.9:0.4 (all wt-%). Monolith synthesis was
carried out as described above. Surface-grafting and initiator-
immobilization was accomplished according to the procedure
described above using a solution of exo, exo-7-oxanorborn-2-
ene-5,6-dicarboxylic anhydride (0.32 g, 1.93 mmol) in DMF
(20 wt %), AgNO3 (340 mg, 2.0 mmol) in 2 mL of a 1:5 mixture
of NH3/water and RuCl2( CHPh)(IMesH2)(PCy3) (50 mg,
0.059 mmol) in 2 mL of THF. Ru-loading 0.6 mg/g, corre-
sponding to 7 mg catalyst/g.
RuCl(COO[C6H8O]COOAg)( CHPh)(IMesH2)
(PCy3) (3)
Compound 2 (23.6 mg, 0.059 mmol) was added to a stirred
ˆ
solution
of
RuCl2( CHPh)(IMesH2)(PCy3)
(50 mg,
0.059 mmol) in 10 mL of dry THF. The solution was stirred
for 20 min at 658C. The color of the solution changed from red
to green, the precipitate was filtered off and the filtrate
evaporated to dryness. It was re-dissolved in a small amount of
benzene and the solid was separated and washed with benzene,
ˆ
giving the product as
a
green powder; yield: 10 mg
Ä
(0.009 mmol, 15%); FT-IR (ATR): n ˆ 2960 (w), 2921 (s),
2847 (w), 1781 (w), 1651 (s), 1585 (w), 1478 (w), 1444 (w), 1411
(s), 1259 (vs), 1173 (w), 1090 (vs), 1016 (vs), 851 (s), 798 (vs)
Synthesis of Monolith-Supported Catalysts Based on
Mono-Carboxylates (6)
1
cmÀ1; H NMR (CDCl3, 258C): d ˆ 17.41 (s, 1H, PhCH), 7.87
(d, 2H, CHCCH), 7.06 À 7.22 (m, 7H, aromatics), 4.57 (d, 2H,
CHO), 3.91 (b, 4H, NCH2), 3.80 (m, 2H, CHCO), 2.30 (s, 12H,
NCCCH3), 2.14 (s, 6H, CHCCH3), 1.94 (s, 3H, PCH), 1.80 (s,
12H, PCHCH2), 1.60 (s, 12H, CHCH2CH2), 1.21 (m, 6H,
CHCH2CH2CH2); MALDI-TOF calcd. for C54H73AgClN2O5-
Column dimensions: Vˆ 1.26 mL (100 mm  4 mm). The
following amounts were used: NBE (0.5 g mmol), (NBE-
CH2O)3SiMe (0.5 mL, 0.54 mg, 1.28 mmol), 2-propanol
ˆ
(1.455 mL), toluene (0.391 mL), RuCl2( CHPh)(PCy3)2
(10 mg, 0.012 mmol). This corresponds to
a ratio of
‡
m/z ˆ 1104.304; found: 955.476 (MH COOAg); anal. calcd.
20:20:45.7:13.9:0.4 (all wt %). Monolith synthesis was carried
out as described above. Surface-grafting and initiator-immobi-
lization was accomplished according to the procedure describ-
ed above using a solution of 7-oxanorborn-2-ene-5-carboxylic
acid (0.32 g, 2.28 mmol) in DMF (20 wt %), AgNO3 (300 mg,
1.76 mmol) in 2 mL of a 1:5 mixture of NH3/water and
for C54H73AgClN2O5PRu (Mr ˆ 1105.549 g/mol): C 58.67, H
6.66, N 2.53; found: C 58.53, H 6.28, N 3.78.
Synthesis of Monolith-Supported Catalysts Based on
Dicarboxylates
ˆ
RuCl2( CHPh)(IMesH2)(PCy3) (50 mg, 0.059 mmol) in 2 mL
of THF. Ru-loading 0.8 mg/g, corresponding to 9 mg catalyst/g.
A. Using DMN-H6 as Cross-linker (4): Column dimensions:
Vˆ 1.57 mL (125  4 mm i. d.). The following amounts
were used: norborn-2-ene (NBE, 1.00 g, 10.6 mmol), DMN-
H6 (0.96 mL, 1 ˆ 1.038 g/mL, 6.3 mmol), 2-propanol 2.94 mL,
Synthesis of Silica-Supported Catalysts 7 and 8 Based
on Dicarboxylates
ˆ
toluene 0.63 mL, RuCl2( CHPh)(PCy3)2 (20 mg, 0.024 mmol),
PPh3 (0.07 mL of a solution containing 30 mg PPh3/10 mL of
toluene). This corresponds to a ratio of NBE:DMN-H6:2-
propanol:toluene:initiator:PPh3 of 20:20:46.2:13.4:0.4 (all
Preparation of Norborn-2-ene Derivatized Nucleosil 300 7
(NBE-Nucleosil 300 7): Nucleosil 300 7 was suspended in
200 mL of toluene and refluxed in a Dean-Stark apparatus for
24 h until all water was removed. The silica was filtered off,
dried under vacuum and re-suspended in 150 mL of dry
CH2Cl2. Dry triethylamine (3.36 mL 2.44 g, 24.63 mmol) and
wt %). Asolution of 2-propanol, NBE and DMN-H was
6
stirred for 30 minutes and added to a stirred solution of toluene,
the initiator and the PPh3 solution, chilled to À 308C. Stirring
was continued for 2 min after which the column (chilled to
08C) was filled with the reaction mixture. After polymerization
for 30 minutes at 08C and another 30 minutes at room
temperature the column was washed with dry THF. Asolution
of exo, exo-7-oxanorborn-2-ene-5,6-dicarboxylic anhydride
(0.2 g, 1.2 mmol) in dry DMF (20 wt %) was added and graft-
polymerization was carried out at 458C over 12 h. The column
was washed with a 40 vol. % solution of EVE in THF, followed
by pure THF. Asolution of AgNO 3 (340 mg, 2.0 mmol) in 2 mL
of a 1:5 mixture of NH3 and water was prepared and passed
through the column maintaining a temperature of 458C. The
support was consecutively washed with water until a base- and
silver-free effluent was assured, then with dry THF.
(norborn-2-ene-5-yl)trichlorosilane
(0.79 mL,
1.02 g,
4.5 mmol) were added to the stirred suspension. After reflux-
ing for 6 h, trimethylchlorosilane (0.68 mL, 0.58 g, 5.38 mmol)
and dimethyldichlorosilane (0.34 mL, 0.36 g, 2.78 mmol) were
added and the suspension was refluxed for another 2 h. 25 mL
of dry MeOH were added and the mixture was stirred for
15 min, then the suspension was filtered off, washed with dry
MeOH, dry CH2Cl2, dry Et2O and dried under vacuum.
Elemental anal. found: C 2.98, H 0.47, N 0.00.
Determination of Norborn-2-ene Loading: Br2 (65 mL,
1.26 mmol) was added to 500 mL of MeOH and the solution
was saturated with NaBr. Titration of the solution with a
solution of 2.5 mmol/L Na2S2O3 revealed a concentration of
2.97 x 10À6 mol Br2/mL. Three samples (180 mg each) of the
derivatized Nucleosil were suspended in MeOH and 10 mL of
the Br2 solution and 1 mL of a saturated NaI solution in water
were added. Afew drops of a freshly prepared aqueous starch
solution were added and stirring was continued for 20 min.
Then the suspension was titrated with a 2.5 mmol/L Na2S2O3
solution revealing a loading of 7.7 Â 10À5 mol norborn-2-ene/g
Nucleosil.
ˆ
RuCl2( CHPh)(IMesH2)(PCy3) (50 mg, 0.059 mmol) dis-
solved in 2 mL of dry THF was added and reaction was
allowed to proceed at 658C over 20 min. Finally, the monolith
was washed with dry THF until the washings were colorless.
Ru-loading 0.9 mg/g, corresponding to 10 mg catalyst/g.
B. Using (NBE-CH2-O)3-SiMe as a Cross-linker (5): Col-
umn dimensions: Vˆ 1.57 mL (125  4 mm i. d.). The follow-
ing amounts were used: NBE (0.5 g), (NBE-CH2O)3SiMe
(0.5 mL), 2-propanol (1.46 mL), toluene (0.39 mL),
Grafting of NBE-Nucleosil 300 7: NBE-Nucleosil 300
(3.37 g) was suspended in 50 mL dry DMF, RuCl2( CHPh)-
7
ˆ
ˆ
RuCl2( CHPh)(PCy3)2 (10 mg, 0.012 mmol). This corresponds
1002
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Monolith- and Silica-Supported Carboxylate-Based Grubbs Herrmann Catalysts
FULL PAPERS
(PCy3)2 (221 mg, 0.268 mmol) was added to the stirred solution
and stirring was continued for 30 minutes. exo, exo-7-Oxanor-
born-2-ene-5,6-dicarboxylic anhydride (1.29 g, 7.75 mmol) was
added and polymerization was allowed to proceed for 18 h at
458C. In course of the reaction, the color of the suspension
changed from yellow to green. Finally, ethyl vinyl ether (74 mg,
1.03 mmol) was added and stirring was continued for another
15 min at 458C. The product was filtered off, washed three
times with DMF, THF, Et2O and dried under vacuum. FT-IR
Conversion of Grafted NBE-LiChrospher 300 5 into the
SilverSalt: The same protocolas described for Nucleosil 300
was applied using 2.00 g of the grafted Nucleosil-300-7 and
7
AgNO3 (200 mg, 1.18 mmol) in 1:5 NH3/H2O. FT-IR (ATR):
À1
Ä
n ˆ 2541.41 (w), 2285.82 (w) and 1057.33 (vs) cm ; elemental
anal. found: C 0.94, H 0.13, N 0.00.
ˆ
Fixation of RuCl2( CHPh)(IMesH2)(PCy3) on Grafted
LiChrospher 300 5 (Silver-Form) (8): The same protocol as
described for Nucleosil 300 7 was applied using 1.4 g of the
silver salt in 20 mL of THF, 115 mg (0.135 mmol) of
Ä
(ATR): n ˆ 2324 (w), 1985 (w), 1125 (s), 1050 (vs), 964 (s), 721
(s) cmÀ1; anal. found: C 13.66, H 1.36.
ˆ
RuCl2( CHPh)(IMesH2)(PCy3) in 2 mL of THF. FT-IR
À1
Ä
(ATR): n ˆ 2360.80 (w), 2340.39 (w), 1057.33 (vs) cm ;
Titration of Grafted NBE-Nucleosil 300 7: The grafted
NBE-Nucleosil 300 7 (0.100 g) was suspended in 15 mL of
water and 20 mL of a 0.05 mol/L solution of NaOH were
added. The mixture was stirred for 5 h, filtered and titrated
with 0.05 mol/L HCl versus phenolphthalein. This procedure
revealed 1.2 mmol anhydride/g silica, corresponding to an
average degree of polymerization (DP) of 20.
Conversion of Grafted NBE-Nucleosil 300 7 into the
Disilver Salt: The grafted NBE-Nucleosil 300 7 (3.40 g) was
suspended in 20 mL of THFand a solution of AgNO3 (2.06 mg,
12.14 mmol) in 10 mL of a 1:5 mixture of NH3/H2O was added.
After stirring for 30 minutes, the product was filtered off and
washed three times with H2O, THFand Et2O. The product was
dried over night under vacuum resulting in a white product;
elemental anal. found: C 1.88, H 0.44, N 0.16. This corresponds
to 63 mg catalyst/g.
Determination of Anhydride Capacity of Coated Silica
60
Poly(norborn-2-ene-b-7-oxanorborn-2-ene-5,6-anhydride)-
coated silica (200 mg) was stirred in 10 mL of 0.05 M NaOH for
24 h. The resin was filtered off and washed with water. The
combined washings were titrated with 0.05 M HCl vs.
phenolphthalein. Capacity: 0.96 mmol acid/g silica.
Ä
yield: 3.6 g; FT-IR (ATR): n ˆ 2541 (w), 2286 (w), 1057 (vs)
cmÀ1.
Disilver Salt of Poly(norborn-2-ene-b-7-oxanorborn-2-
ene-5,6-anhydride)-Coated Silica 60
ˆ
Fixation of RuCl2( CHPh)(IMesH2)(PCy3) on Grafted
Nucleosil 300 7 (Disilver-Form) (7): The disilver salt of the
grafted Nucleosil 300 7 (1.50 g) was suspended in dry toluene,
RuCl2( CHPh)(IMesH2)(PCy3) (100 mg, 0.12 mmol) was add-
ed and the mixture was stirred at 658C for 20 min. The product
was filtered off and washed with dry Et2O until the washings
were colorless to give a brownish solid; yield: 1.33 g; FT-IR
Poly(norborn-2-ene-b-7-oxanorborn-2-ene-5,6-anhydride)-
coated silica (0. 500 g) was dissolved in 5 mL of THF and 2
equiv. of NaOH (191 mg, 14.8 mmol) dissolved in 22 mL of
water were added. After 2 h of stirring, the polymer was
filtered off and washed three times with water. The polymer
was re-dissolved in 5 mL of THFand 2 mL of water. AgNO3 (2
equiv., 815 mg, 4.8 mmol) was added and stirring was con-
tinued for another 4 h. The polymer was filtered off, washed
twice with water, THF, Et2O and dried under vacuum to give a
ˆ
Ä
(ATR):n ˆ 2981 (b), 2285 (w), 2118 (w), 1731 (s), 1665 (s), 1562
(s), 1392 (s), 1056 (vs) cmÀ1. Ru-loading: 3.9 mg/g correspond-
ing to 42 mg catalyst/g.
Preparation of Norborn-2-ene-Derivatized LiChrospher
300 5 (NBE-LiChrospher 300 5): The same protocol as
described for Nucleosil 300 7 was applied using LiChro-
sphere, 200 mL of toluene for drying, NBESi(OEt)3 (2.56 g,
Ä
white solid; yield: 4.9 g (98%); FT-IR (ATR): n ˆ 2363.5 (w),
1747.3 (w), 1056.0 (vs) cmÀ1.
10.0 mmol),
11.08 mmol),
trimethylchlorosilane
dimethyldichlorosilane
(1.4 mL,
(1.4 mL,
1.19 g,
1.48 g,
ˆ
Fixation of RuCl2( CHPh)(IMesH2)(PCy3) on
Poly(norbornene-b-7-oxanorborn-2-ene-5,6-
11.45 mmol), triethylamine (7 mL, 5.08 g, 51.31 mmol) and
dry MeOH (25 mL); elemental anal. found: C 1.30, H 0.67, N
0.00.
dicarboxylate)-Coated Silica 60 (Disilver Form) (9)
Determination of Norborn-2-ene Loading: The same pro-
tocol as described for Nucleosil 300 7 was applied using Br2
(65 mL), 500 mL of MeOH saturated with NaBr, 0.0025 mol/L
Na2S2O3. The NBE loading was 3.0 Â 10À4 mol NBE/g Nucle-
osil.
Thedisilver salt ofpoly(norborn-2-ene-b-7-oxanorborn-2-ene-
5,6-anhydride)-coated silica 60 (1 equiv., 123 mg) was sus-
pended in 5 mL of THF and added to a stirred solution of
RuCl2( CHPh)(IMesH2)(PCy3) (50 mg, 0.059 mmol) in 5 mL
of THF. After stirring for 30 minutes at 558C, the support was
ˆ
Grafting of NBE-LiChrospher 300 5: The same protocol as
described for Nucleosil 300 7 was applied using NBE-
Nucleosil-300-5 (3.00 g), 50 mL of dry DMF, 1 equiv. of
RuCl2( CHPh)(PCy3)2 (0.9 mmol, 0.74 g), 30 equiv. of 7-
oxanorborn-2-ene-5-carboxylic acid (27 mmol, 4.48 g), and
filtered off, washed with diethyl ether and evaporated to
Ä
dryness under vacuum. FT-IR (ATR): n ˆ 3337 (b), 2282 (w),
2115 (w), 1733 (s), 1372 (w), 1049 (vs), 798 (s) cmÀ1
.
ˆ
Ä
74 mg of EVE. FT-IR (ATR): n ˆ 2324.15 (w), 1984.74 (w),
RCM-Experiments (Slurry Reactions)
1125.19 (s) and 1049.57 (vs) cmÀ1; elemental anal. found: C
1.32, H 0.60, N 0.00.
The following procedure is representative for all experiments.
DEDAM (20 mg, 0.08 mmol) was dissolved in the correspond-
ing solvent (e.g., 1,2-dichloroethane, 2 mL) and the supported
catalyst (40 mg) was added. The reaction mixture was heated to
Titration of Grafted NBE-LiChrospher 300 5: The same
protocol as described for NBE-Nucleosil-300-7 was applied. A
loading of 0.22 mmol anhydride/g Nucleosil was found.
Adv. Synth. Catal. 2003, 345, 996 1004
asc.wiley-vch.de
¹ 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1003

Jens O. Krause et al.
FULL PAPERS
458C for 2 hours. After removal of the catalyst by filtration, the
yield was determined by GC-MS and 1H NMR in CDCl3,
respectively.
[7] M. R. Buchmeiser, Chem. Rev. 2000, 100, 1565 1604.
[8] U. Frenzel, O. Nuyken, J. Polym. Sci., Part A: Polym.
Chem. 2002, 40, 2895 2916.
[9] A. H. Hoveyda, R. R. Schrock, Chem. Eur. J. 2001, 7,
945 950.
[10] D. R. Cefalo, A. F. Kiely, M. Wuchrer, J. Y. Jamieson,
R. R. Schrock, A. H. Hoveyda, J. Am. Chem. Soc. 2001,
123, 3139 3140.
[11] S. L. Aeilts, D. R. Cefalo, P. J. Bonitatebus, J. H. Houser,
A. H. Hoveyda, R. R. Schrock, Angew. Chem. 2001, 113,
1500 1504; Angew. Chem. Int. Ed. 2001, 40, 1452 1456.
[12] G. S. Weatherhead, J. H. Houser, J. G. Ford, J. Y. Jamie-
son, R. R. Schrock, A. H. Hoveyda, Tetrahedron Lett.
2000, 41, 9553 9559.
RCM-Experiments (Flow-Through Reactions)
The following procedure is representative for all experiments.
DEDAM (20 mg, 0.08 mmol) was dissolved in the correspond-
ing solvent (e.g., 1,2-dichloroethane, 2 mL) and this solution
was pumped through a cartridge filled with the supported
catalyst (either monolith- or silica-based) heated to 458C at a
flow rate of 0.1 mL/min unless stated otherwise. The effluent
was collected in 0.5 mL portions and the yield was determined
by GC-MS and 1H NMR in CDCl3, respectively.
[13] D. S. La, E. S. Sattely, J. G. Ford, R. R. Schrock, A. H.
Hoveyda, J. Am. Chem. Soc. 2001, 123, 7767 7778.
[14] R. R. Schrock, J. Y. Jamieson, S. J. Dolman, S. A. Miller,
P. J. Bonitatebus Jr., A. H. Hoveyda, Organometallics
2002, 21, 409 417.
[15] A. F. Kiely, J. A. Jernelius, R. R. Schrock, A. H. Hovey-
da, J. Am. Chem. Soc. 2002, 124, 2868 2869.
[16] M. Mayr, B. Mayr, M. R. Buchmeiser, Angew. Chem.
2001, 113, 3957 3960; Angew. Chem. Int. Ed. 2001, 40,
3839 3842.
Leaching of the Support
All volatiles were removed from the combined effluents and
aqua regia (3.0 mL) was added. The mixture was placed inside
high-pressure Teflon tubes and leaching was carried out under
Microwave conditions (50, 600, and 450 W pulses, respectively,
t ˆ 32 minutes). After cooling to room temperature, the
mixture was filtered and water was added up to a volume of
10.00 mL.
[17] M. Mayr, M. R. Buchmeiser, K. Wurst, Adv. Synth. Catal.
2002, 355, 712 719.
[18] W. Buchowicz, F. Ingold, J. C. Mol, M. Lutz, A. L. Spek,
Chem. Eur. J. 2001, 7, 2842 2847.
Ru Measurements
[19] P. Nieczypor, W. Buchowicz, W. J. N. Meester, F. P. J. T.
Rutjes, J. C. Mol, Tetrahedron Lett. 2001, 42, 7103 7105.
[20] F. Sinner, M. R. Buchmeiser, Angew. Chem. 2000, 112,
1491 1494; Angew. Chem. Int. Ed. 2000, 39, 1433 1436.
[21] B. Mayr, R. Tessadri, E. Post, M. R. Buchmeiser, Anal.
Chem. 2001, 73, 4071 4078.
Ru was measured by ICP-OES (l ˆ 240.272 nm, ion line). The
background was measured at l ˆ 240.287 and 240.257 nm,
respectively. Standardization was carried out with Ru stand-
ards containing 0, 5 and 10 ppm of Ru.
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Acknowledgements
Financial support provided by the Austrian Science Fund (FWF
Vienna, project Y-158) and the Freistaat Bayern is gratefully
acknowledged.
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asc.wiley-vch.de
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