A dicationic ruthenium alkylidene complex for continuous biphasic metathesis using monolith-supported ionic liquids

Article abstract of DOI:10.1002/chem.201201199

A dicationic ruthenium-alkylidene complex [Ru(dmf)₃(IMesH ₂)(=CH-2-(2-PrO)-C₆H₄)][(BF₄) ₂] (1; IMesH₂=1,3-dimesitylimidazolin-2-ylidene) has been prepared and used in continuous metathesis reactions by exploiting supported ionic-liquid phase (SILP) technology. For these purposes, ring-opening metathesis polymerization (ROMP)-derived monoliths were prepared from norborn-2-ene, tris(norborn-5-ene-2-ylmethyloxy)methylsilane, and [RuCl ₂(PCy₃)₂(CHPh)] (Cy=cyclohexyl) in the presence of 2-propanol and toluene and surface grafted with norborn-5-en-2-ylmethyl-N,N, N-trimethylammonium tetrafluoroborate ([NBE-CH₂-NMe ₃][BF₄]). Subsequent immobilization of the ionic liquid (IL), 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BDMIM][BF ₄]), containing ionic catalyst 1 created the SILP catalyst. The use of a second liquid transport phase, which contained the substrate and was immiscible with the IL, allowed continuous metathesis reactions to be realized. High turnover numbers (TONs) of up to 3700 obtained in organic solvents for the ring-closing metathesis (RCM) of, for example, N,N-diallyltrifluoroacetamide, diethyl diallylmalonate, diethyl di(methallyl)malonate, tert-butyl-N,N- diallylcarbamate, N,N-diallylacetamide, diphenyldiallylsilane, and 1,7-octadiene, as well as in the self-metathesis of methyl oleate, could be further increased by using biphasic conditions with [BDMIM][BF ₄]/heptane. Under continuous SILP conditions, TONs up to 900 were observed. Due to the ionic character of the initiator, catalyst leaching into the transport phase was very low (<0.1 %). Finally, the IL can, together with decomposed catalyst, be removed from the monolithic support by flushing with methanol. Upon reloading with [BDMIM][BF₄]/1, the recycled support material again qualified for utilization in continuous metathesis reactions. Copyright

Full text of DOI:10.1002/chem.201201199

FULL PAPER
DOI: 10.1002/chem.201201199
A Dicationic Ruthenium Alkylidene Complex for Continuous Biphasic
Metathesis Using Monolith-Supported Ionic Liquids
Benjamin Autenrieth,[a] Wolfgang Frey,[b] and Michael R. Buchmeiser*[a, c]
Abstract: A dicationic ruthenium–alky-
lidene complex [Ru(dmf)3A(IMesH2)(=
CH-2-(2-PrO)-C6H4)][(BF4)2] (1;
1-butyl-2,3-dimethylimidazolium tetra-
fluoroborate ([BDMIM][BF4]), con-
carbamate, N,N-diallylacetamide, di-
phenyldiallylsilane, and 1,7-octadiene,
as well as in the self-metathesis of
methyl oleate, could be further in-
creased by using biphasic conditions
G
E
R
ACHTUNGTRENNUNG
G
E
taining ionic catalyst 1 created the
SILP catalyst. The use of a second
liquid transport phase, which contained
the substrate and was immiscible with
the IL, allowed continuous metathesis
reactions to be realized. High turnover
numbers (TONs) of up to 3700 ob-
tained in organic solvents for the ring-
closing metathesis (RCM) of, for exam-
ple, N,N-diallyltrifluoroacetamide, di-
ethyl diallylmalonate, diethyl di(me-
thallyl)malonate, tert-butyl-N,N-diallyl-
IMesH2 =1,3-dimesitylimidazolin-2-yli-
dene) has been prepared and used in
continuous metathesis reactions by ex-
ploiting supported ionic-liquid phase
(SILP) technology. For these purposes,
ring-opening metathesis polymerization
(ROMP)-derived monoliths were pre-
pared from norborn-2-ene, tris(nor-
born-5-ene-2-ylmethyloxy)methylsilane,
with [BDMIM]ACHTNUTRGNENU[G BF4]/heptane. Under
continuous SILP conditions, TONs up
to 900 were observed. Due to the ionic
character of the initiator, catalyst
leaching into the transport phase was
very low (<0.1%). Finally, the IL can,
together with decomposed catalyst, be
removed from the monolithic support
by flushing with methanol. Upon re-
and [RuCl2ACHTUNGTRENNUNG(PCy3)2ACHTUNGTRENNUNG(CHPh)] (Cy=cy-
clohexyl) in the presence of 2-propanol
and toluene and surface grafted with
norborn-5-en-2-ylmethyl-N,N,N-trime-
loading with [BDMIM]ACHTUNRGTNEUNG[BF4]/1, the re-
cycled support material again qualified
for utilization in continuous metathesis
reactions.
Keywords: heterogeneous catalysis ·
ionic liquids · metathesis · rutheni-
um · supported catalysts
thylammonium
([NBE-CH2-NMe3]
tetrafluoroborate
ACHTUNGTRENNUNG
immobilization of the ionic liquid (IL),
Introduction
coatings and mobile phases in liquid chromatography and
electromigration techniques,[41–45] as low-vapor-pressure sol-
vents for head-space GC analysis,[46] as coatings for GC col-
umns,[47] as well as electrolytes in fuel[48] and solar cells.[49] In
addition, applications in biocatalysis[50–52] have to be men-
tioned. The first reports on the use of molten salts as sup-
ported ionic-liquid phases (SILPs) for use in heterogeneous
catalysis were published in 1988 by Datta and Rao[53] and by
Eyman et al.[54] Following this concept, the groups of Was-
serscheid, Mehnert, Dupont, and others have since publish-
ed a series of applications of SILPs.[15,17,19–25,55–59] Using
simple adsorption and capillary forces, they immobilized
various ILs on silica- and zeolite-type supports and used
them as supported solvents for catalytic reactions, for exam-
ple, for hydroformylations, hydrogenations, methanol car-
bonylation, and also for enzyme-triggered biocatalysis. Re-
Almost 100 years after the discovery of ionic liquids
(ILs)[1–2] by Walden,[3]interest in this class of compounds has
dramatically increased and within a comparably short time
ILs have made their way from a physicochemical curiosity
into numerous chemical, technical, and industrial applica-
tions,[4] for example, as solvents for catalytic reactions[5–25]
(including asymmetric ones[26]) and polymerizations,[27–40] as
[a] Dipl.-Chem. B. Autenrieth, Prof. M. R. Buchmeiser
Lehrstuhl fꢁr Makromolekulare Stoffe und Faserchemie
Institut fꢁr Polymerchemie, Universitꢂt Stuttgart
Pfaffenwaldring 55, 70569 Stuttgart (Germany)
Fax : (+49)711-685-64050
E-mail: michael.buchmeiser@ipoc.uni-stuttgart.de
[b] Dr. W. Frey
1
cently, Le Bideau et al. confirmed by H-MAS-NMR spec-
Institut fꢁr Organische Chemie, Universitꢂt Stuttgart
Pfaffenwaldring 55, 70569 Stuttgart (Germany)
troscopy experiments that the dynamics of ILs immobilized
within the confines of siliceous materials experienced only a
minor slow down.[60] In fact, confinement preserved the ILꢀs
properties, while reducing their crystallization temperature
relative to genuine ILs. Thus, supported ILs can in fact be
compared to unsupported ones in terms of diffusion coeffi-
cients, which in turn guarantees fast reaction kinetics for the
catalytic reactions within monolith-supported ILs.
[c] Prof. M. R. Buchmeiser
Institut fꢁr Textilchemie und Chemiefaser (ITCF) Denkendorf
Kçrschtalstr. 26, 73770 Denkendorf (Germany)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201201199. It contains details on
metathesis reactions; GC chromatograms; NMR spectra of 1, 2 and
selected substrates; pore size distribution of the monolith; distribu-
tion coefficients of the substrates (IL/organic phase); and structural
data of 1.
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More recently, Wasserscheid et al. reported on metathesis
reactions in supported ILs using gaseous reactants as the
second (transport) phase.[61] Such an approach allows the
use of “standard” metathesis catalysts within the IL. Howev-
er, both the metathesis of higher (functional) olefins and
ionic Ru–alkylidene complex for metathesis reactions in ILs
had to be created. Since pseudo-halide derivatives of
Grubbs and Grubbs–Hoveyda (GH) catalysts are known to
possess high activity, resulting from high polarization of the
Ru–alkylidene moiety,[62–70] such electron-deficient cationic
catalysts may also be expected to display high activity. Such
an ionic metathesis catalyst would selectively dissolve in the
IL, but not in the second liquid transport phase, such as hep-
metathesis-based polymerizations require the use of
a
second liquid transport phase that is immiscible with the IL.
To prevent catalyst leaching into this second phase, tailored
catalysts need to be developed that selectively dissolve in
the IL. Equally important, to allow continuous reaction con-
ditions, any substrate and product must have sufficient solu-
bility in both phases to allow substantial turnover numbers
(TONs) and prevent product accumulation within the IL.
Herein, we report a new dicationic metathesis catalyst dis-
solved within a polymeric monolith-supported IL phase that
allows for the first continuous metathesis reactions using
two liquid phases. Scheme 1 illustrates the fundamental con-
cept. In addition to the primary objective to gain catalyst-
free products, our concept enables continuous product for-
mation simply by cycling liquid reactants or solutions there-
of through the support. Most importantly, the entire concept
is not limited to gaseous substrates, such as ethene, propene,
or butenes. Consequently, no high pressures need to be ap-
plied. Finally, the possibility of recycling the monolithic sup-
port has been addressed.
tane. For this reason, the ionic catalyst [Ru
ACHUTNGTRNENUG(dmf)3CAHTUNGTRNEN(UGN IMesH2)-
A
R
ACHTUNGTRENNUNG
midazolin-2-ylidene) was prepared in 95% yield by adding
three equivalents of DMF and two equivalents of AgBF4 to
the second-generation GH catalyst [RuCl
TERNN(UG 2-PrO)-C6H4)] (Scheme 2).
2ACHTUNGTNRE(UNG IMesH2)ACHTUNGTRENNUNG(=CH-2-ACHTUNG-
Scheme 2. Synthesis of the dicationic Ru complex 1.
Complex 1 crystallizes in the monoclinic space group P21/
Results and Discussion
n, a=2192.6(2) pm, b=1756.0(6) pm, c=2327.4(2) pm, b=
92.4858, Z=8 (Figure 1 and Table S3 in the Supporting In-
formation). Selected bond lengths and angles are given in
Table 1.
Synthesis and structural determination of 1: As outlined
above, the primary objective was to create a supported
metathesis catalyst, based on SILP technology, that allowed
metathesis reactions to be run under biphasic conditions
using two immiscible liquid phases. For this purpose, an
Complex 1 is a d6 low-spin complex with a distorted octa-
hedral ligand sphere with NHC and the 2-PrO ligands in
ꢀ
apical positions. The Ru1A O1A distance in 1 is significant-
ly longer than that in the
parent GH complex (232.5(3)
vs. 226.13 pm[71]). The Ru1A
ꢀ
ꢀ
O2A and Ru1A O4A distan-
ces of the two DMF ligands lo-
cated trans to each other are
virtually identical (203.7(3) vs.
205.6(3) pm). In contrast, the
ꢀ
Ru1A O3A distance of the
DMF ligand located trans to
the benzylidene ligand is sig-
ꢀ
nificantly
longer
(Ru1A
O3A=222.5(3) pm). Interest-
ꢀ
ingly, the Ru1A C1A distance
is also longer than that in the
parent GH catalyst (201.1(4)
vs. 198.1(5) pm),[71] while the
Ru–alkylidene bond is some-
what shorter in 1 than that in
the parent complex (182.5(5)
vs. 185.0(4) pm).[71] Although
some monocationic Ru–alkyli-
denes have been reported,[72–74]
Scheme 1. Continuous metathesis under biphasic conditions by using monolith-supported ILs. Y+Xꢀ =
[BDMIM]ACHTUNGTRENNUNG[BF4].
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Continuous Biphasic Metathesis
FULL PAPER
Table 1. Selected bond lengths [pm] and angles [8] for 1.
ꢀ
Ru1A C22A
185.0(4)
201.1(4)
232.5(3)
203.7(3)
222.5(3)
205.6(3)
ꢀ
Ru1A C1A
ꢀ
Ru1A O1A
ꢀ
Ru1A O2A
ꢀ
Ru1A O3A
ꢀ
Ru1A O4A
C22A-Ru1A-C1A
C22A-Ru1A-O1A
C22A-Ru1A-O2A
C22A-Ru1A-O4A
C22A-Ru1A-O3A
C1A-Ru1A-O2A
C1A-Ru1A-O4A
C1A-Ru1A-O3A
C1A-Ru1A-O1A
O2A-Ru1A-O4A
O2A-Ru1A-O3A
O2A-Ru1A-O1A
O3A-Ru1A-O1A
O4A-Ru1A-O3A
O4A-Ru1A-O1A
93.30(16)
77.50(13)
101.39(13)
94.12(13)
172.22(14)
91.70(14)
100.64(14)
94.27(12)
169.26(13)
159.59(10)
80.22(10)
84.81(10)
95.15(90)
82.69(10)
85.70(10)
Figure 1. X-ray structure of 1. Counteranions (BF4ꢀ) and hydrogen atoms
have been omitted for clarity. Ellipsoids are given at the 50% probability
level.
it is worth noting that complex 1 is one of the rare examples
of a dicationic RuII–alkylidene[75] and, to the best of our
knowledge, the first example of a metathetically highly
active one.
creased tremendously for all substrates (Table 2). Thus,
when reactions were run in toluene at 1008C, TONs up to
1300 and 1200, respectively, were obtained in the RCM re-
actions of DEDAM and 1,7-octadiene. These values are
worth highlighting because 1 is poorly soluble in toluene
and, consequently, reactions are mostly heterogeneous.
Likewise, in the case of N,N-diallylacetamide, tert-butyl-
N,N-diallylcarbamate, and diallyldiphenylsilane, an increase
in temperature resulted in increasing TONs reaching values
between 130 and 320. The reaction temperature also has a
great influence on the selectivity of the RCM of 1,7-octa-
diene. When conducted at T=408C, the formation of
purple, conjugated isomerization products was observed,
Metathesis reactions in organic solvents: Before we turned
our attention to reactions in ILs, we investigated the general
reactivity of 1 in various metathesis reactions. Ring-closing
metathesis (RCM) reactions in CH2Cl2 at T=408C with sub-
strates containing coordinating, that is, oxygen- or nitrogen-
containing groups, namely, diethyl diallylmalonate
(DEDAM), diethyl di(methallyl)malonate, tert-butyl-N,N-di-
allylcarbamate, diallyldiphenylsilane, or N,N-diallylaceta-
mide (Table 2) resulted in low TONs (ꢁ50) and conversion
(ꢁ5%). However, with the electron-poor substrate N,N-dia-
llyl trifluoroacetamide (DAFA), high TONs up to 3500 were
obtained, by far exceeding
those obtained with the parent
GH catalyst under identical
conditions (TON=730). Clear-
ly, even weakly coordinating
groups, such as esters and
amides, coordinate to the dica-
tionic center, thereby impeding
coordination of the alkene.
This is further illustrated by
comparing the RCM results of
DAFA to those of the analo-
gous, non-fluorinated deriva-
tive, that is, N,N-diallylaceta-
mide, obtained at T=408C. In
these reactions, TONs of 3500
versus 10 were observed
(Table 2). To promote the dis-
sociation of any coordinating
moieties from the cationic Ru
center, all reactions were again
run at elevated temperatures.
This way the activity of 1 in-
Table 2. Selected substrates for metathesis reactions in organic solvents promoted by catalyst 1.
Substrate
1 [mol%]
Solvent
T [8C]
t
TON
CH2Cl2
C2H4Cl2
toluene
CH2Cl2
C2H4Cl2
toluene
CH2Cl2
C2H4Cl2
toluene
CH2Cl2
C2H4Cl2
toluene
CH2Cl2
C2H4Cl2
toluene
CH2Cl2
toluene
CH2Cl2
toluene
CH2Cl2
C2H4Cl2
toluene
40
80
100
40
80
100
40
80
100
40
80
100
40
80
100
40
100
40
100
40
1 h
1 h
50
560
1300
10
DEDAM
0.05
15 min
1 h
0.5 h
0.5 h
1 h
15 min
15 min
15 min
5 min
2 min
4 h
4 h
1 h
4 h
4 h
12 h
0.5 h
12 h
4 h
tert-butyl-N,N-diallyl carbamate
1,7-octadiene
0.1
40
320
100
500
1200
3500
3500
3700
10
30
240
5
130
0
6
0.05
0.02
0.05
DAFA
N,N-diallylacetamide
diallyldiphenylsilane
0.2
1.4
diethyl di(methallyl)malonate
100
530
780
methyl oleate
0.05
80
100
4 h
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M. R. Buchmeiser et al.
and consequently, the yield in
cyclohexene was low. Howev-
er, at T=808C, no isomeriza-
tion products were observed
and cyclohexene was the only
product detected by means of
GC-MS and NMR spectrosco-
py. This suggests the absence
of any active Ru–hydride spe-
cies at elevated temperatures.
Since DAFA does not coordi-
nate to the Ru center through
the amide bond, the high TON
observed at T=408C could
not be significantly increased;
however, the reaction rate in-
creased. At T=408C a TON
Scheme 4. CM reactions between allylbenzene and cis-1,4-acetoxy-2-butene (a) and between 5-hexenyl acetate
and methyl acrylate (b). Ene–yne metathesis of N-allyl-N-propargyl trifluoroacetamide (c).
of 3500 was achieved within 15 min, whereas a TON of 3700
was achieved at T=1008C in less than 2 min. Notably, the
reactivity of diethyl di(methallyl)malonate remained low
under all conditions.
Reaction temperature also greatly influences the self-
metathesis of methyl oleate (Scheme 3). At T=408C, the re-
action proceeds slowly with low yields (ꢂ5% of primary
version was achieved within 1 h when using a catalyst load-
ing of 0.2 mol%. Finally, we applied 1 to the ene–yne meta-
thesis of N-allyl-N-propargyl trifluoroacetamide (Sche-
me 4c). When using a catalyst loading of 0.5 mol%, a TON
of 60 was obtained in CH2Cl2 at 358C. Interestingly, at ele-
vated temperatures, only red, polymeric products formed by
1-alkyne polymerization were obtained, as evidenced by the
absence of any alkyne groups in the IR spectrum (Fig-
ure S16 in the Supporting Information).
Metathesis reactions under biphasic conditions (organic sol-
vent/IL): The RCM of DAFA, DEDAM, and 1,7-octadiene,
as well as the self-metathesis of methyl oleate, were carried
out under biphasic conditions by using [BDMIM]ACHTUNGTRENNUNG[BF4] as
the IL phase and either neat reactants or heptane as the
second liquid phase (Table 3). Generally, the choice of IL
Table 3. Metathesis reactions under biphasic conditions ([BDMIM]-
AHCTUNTGREGN[NUN BF4])/heptane).
Scheme 3. Self-metathesis of methyl oleate catalyzed by 1.
Substrate
DAFA[c]
Catalyst ([mol%]) T [8C] TON[a] Ru leaching [%][b]
40
80
40
80
80
100
80
100
80
3300
3600
600
1300
1400
1650
1500
1900
810
0.09
2.4
3.1
1 (0.02)
metathesis products; TON=100). Running the reaction at
T=1008C resulted in TONs of 780. Moreover, again only
the desired primary metathesis products were obtained
(Scheme 3 and Figure S1 in the Supporting Information),
again suggesting the absence of (stable) Ru–hydrides. In
contrast, predominantly alkenes with different chain lengths,
resulting from secondary cross-metathesis (CM) reactions,
were observed with the GH catalyst (Figure S2 in the Sup-
porting Information).
DAFA
GH (0.02)
1 (0.02)
8.6
0.02
0.03
0.03
0.2
DEDAM[d]
DEDAM
GH (0.02)
0.1
1,7-octadiene[e] 1 (0.02)
100
80
100
40
80
110
40
1660
2300
2410
95
0.1
0.1
0.5
0.07
0.11
0.6
0.2
0.5
1,7-octadiene
GH (0.02)
methyl oleate[f] 1 (0.05)
800
Cross-metathesis (CM) and ene–yne metathesis reactions:
In the CM reaction between allylbenzene and cis-1,4-ace-
toxy-2-butene (Scheme 4a) no conversion was observed at
T=408C. However, at T=1008C, product formation was
quantitative within 1 h when using a catalyst loading of
0.2 mol% in toluene. The inactivity of 1 at 408C was also
noted for the CM reaction between 5-hexenyl acetate and
methyl acrylate (Scheme 4b). In turn, at 1008C, 70% con-
1000
2000
2000
2000
methyl oleate
GH (0.05)
80
110
1.4
[a] Determined by GC-MS after 12 h. [b] % of initial Ru (catalyst) load-
ing. [c] Heptane as second liquid phase; IL (0.2 g), heptane (2.0 g),
DAFA (0.8 g). [d] Heptane as second liquid phase; IL (0.2 g), heptane
(3.0 g), DEDAM (1.25 g). [e] Neat; IL (0.04 g), 1,7-octadiene (0.4 g).
[f] Neat; IL (0.05 g), methyl oleate (0.5 g).
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Continuous Biphasic Metathesis
FULL PAPER
was a crucial feature concerning ruthenium–alkylidene-pro-
moted metathesis reactions.[34,76,77] The anion in the IL
[BDMIM]ACHTUNGTRENNUNG[BF4] is non-coordinating and identical to the
counterion in complex 1. This prevents ligand scrambling,
which is often observed for Ru–alkylidenes in ionic solvents
with different counterions.[34] Furthermore, with a melting
reaction is the predominant reaction at low temperatures,
forming a less reactive E double bond, which gives rise to
low TONs. At higher temperatures, self-metathesis predomi-
nates. Despite high TONs, the use of the GH catalyst yield-
ed a multitude of products (more than 30) by subsequent
isomerization and secondary metathesis processes (see the
gas chromatogram in Figure S2 in the Supporting Informa-
tion).
point of 378C, [BDMIM]
ature of 408C. However, the most important property of
[BDMIM][BF4] is its very poor miscibility with common
ACHTUNGTNER[NUGN BF4] is liquid at a reaction temper-
ACHTUNGTRENNUNG
nonpolar organic solvents, such as toluene, diethyl ether, or
heptane. However, all substrates investigated displayed suf-
ficient solubility in the IL, as illustrated by their distribution
coefficients, Kheptane/IL (Table S2 in the Supporting Informa-
tion), which were 0.2 (DAFA), 1.2 (DEDAM), and 9 (1,7-
octadiene). Despite the comparably small amount of IL and
large amount of polar substrate, which both favor transfer
of the catalyst into the nonpolar phase, a low catalyst leach-
ing of ꢁ0.1% into the product phase was observed for most
reactions. For comparison, leaching of the GH catalyst into
the heptane phase under otherwise identical conditions was
up to 25 times higher. By running the reaction in the IL, the
TONs for the RCM of DAFA could be further increased to
3600 by increasing the temperature, although this was at the
expense of a slightly higher metal leaching (2.4%). In the
RCM of DEDAM, TONs up to 1600 were obtained, again
exceeding those observed in an organic solvent (Table 2).
Due to the low polarity of 1,7-octadiene and its immiscibili-
ty with the IL, RCM was performed without the use of an-
other liquid transport phase. An increase in reaction temper-
ature from 80 to 1008C led to an increase in the TON from
800 to 1600 without noticeably affecting catalyst leaching.
As observed in organic solvents, only the formation of cyclo-
hexene and no isomerization products were observed. Ad-
mittedly, Ru leaching was also low with the parent GH cata-
lyst, giving TONs up to 2400. However, with this catalyst,
the IL phase was purple in color, suggesting the formation
of conjugated isomerization products. In the self-metathesis
of methyl oleate (Scheme 3) catalyzed by 1, an increase in
temperature resulted in an increase in TON from 95 to
1000. Reaction monitoring by GC-MS revealed the selective
formation of the two desired CM products as well as isomer-
ization of the Z double bond in the substrate molecule (Fig-
ure S1 in the Supporting Information). This isomerization
Preparation and characterization of monolithic supports:
Polymeric monoliths represent versatile supports for hetero-
geneous catalysis. They allow high linear flow rates of up to
20 mmsꢀ1 at low counter pressure (<3 MPa) and guarantee
fast mass transfer between the transport phase and the im-
mobilized catalysts.[78] Monoliths were prepared by copoly-
merization of norborn-2-ene (NBE) with the cross-linker
(CL) tris(norborn-2-enylmethylenoxy)methylsilane ((NBE-
CH2O)3SiCH3) in the presence of the two porogenic solvents
2-propanol and toluene (Scheme 5). [RuCl
2ACHTUNGTRENNUNG(PCy3)2-
AHCTUNGTRENNUNG
since it possesses a balanced activity for both NBE and the
CL.[79,80] Next, charged groups were introduced onto the
inner surface of monoliths, which helped retain ILs that
were otherwise only physically adsorbed to the surface of
the monoliths. Taking advantage of the “living” character of
the ring-opening metathesis polymerization (ROMP)-based
protocol,[81] surface functionalization was accomplished in
situ by simply passing a solution of the ionic monomer
[NBE-CH2-NMe3]ACTHNUGTRNEUNG[BF4] (2) through the monolith immedi-
ately after its synthesis.[82–84] Finally, the living Ru–alkyli-
denes were completely removed by treatment with ethyl
vinyl ether, as proven by means of inductively-coupled
plasma optical emission spectroscopy (ICP-OES) measure-
ments, which indicated a residual Ru content of the mono-
lith of 38 ppm. Elemental analysis confirmed the effective
grafting of 2 with an average degree of oligomerization of
three. Such low degrees of oligomerization, on one hand,
guarantee binding of the IL and, on the other hand, do not
give rise to higher back pressures.
In general, a monolith consists of interconnected struc-
ture-forming microglobules. Important parameters are the
microglobule diameter (dp) and the microporosity (ep) of the
microglobules as well as the inter-microglobular porosity
Scheme 5. Preparation of a surface-functionalized monolithic support. p=3.
Chem. Eur. J. 2012, 00, 0 – 0
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M. R. Buchmeiser et al.
(ez). The total porosity (et) is defined as the sum of ep and ez.
These values, as well as the pore size distribution (Fig-
ure S17 in the Supporting Information), were determined by
inverse size exclusion chromatography (ISEC).[85] The corre-
sponding values for the surface-functionalized monolith are
summarized in Table 4.
[BDMIM]
[BDMIM][BF4]/GH catalyst (Table S1 in the Supporting In-
formation). Metal leaching into the heptane phase was
lower by a factor of 4–10 for [BDMIM][BF4]/1 compared
with [BDMIM][BF4]/GH catalyst and resulted in TONs up
ACHTUNGTRENUN[GN BF4]/1 outperformed the monolith-supported
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
to 900. Generally, leaching could be reduced by dilution of
the mobile phase with heptane, thereby decreasing the po-
larity of the transport phase. However, this was associated
with a decrease in TON. TONs could be increased by reduc-
ing the thickness of the immobilized IL layer; however, this
occurred at the expense of increased catalyst leaching. The
lower TONs obtained in comparison to the biphasic solution
experiments may be attributed to reduced contact times and
the fact that mixing of the two phases proceeded more ef-
fectively under mechanical stirring than on a monolith. Ac-
cordingly, halving the flow rate did not increase the TONs
(Table S1 in the Supporting Information). Increasing the
temperature to T=608C led to a higher product fraction in
the eluting phase within the first minutes of the reaction;
however, deactivation occurred faster than reactions per-
formed at 408C and the overall TON did not change signifi-
cantly. Plots of conversion versus time for DAFA under dif-
ferent reaction conditions are shown in Figures S18 and S19
in the Supporting Information. These results show the typi-
cal deactivation of a metathesis catalyst over time and clear-
ly demonstrate the advantages of the SILP approach pre-
sented herein over traditional immobilization strategies.
As observed for reactions in organic solvents, DEDAM
and 1,7-octadiene reacted with catalyst 1 under SILP condi-
tions only at elevated temperatures (T=808C), resulting in
TONs of 650 and 770 and Ru leaching of 0.2 and 0.05%.
While 1,7-octadiene could be passed through the monolith
neat, heptane was used as the second liquid transport phase
in the RCM of DEDAM to establish a biphasic reaction
mixture.
Table 4. Composition and structural data of the monolithic support
(Vcolumn =1.66 mL) after ROMP-based grafting of 2.
ep [vol%]
ez [vol%]
et [vol%]
Vz [mL]
Fm[a] [ꢄ]
¯
5
75
80
1.25
1160
[a] Average pore diameter.
As observed, the large void volume of 80%, with regard
to the total column volume, guarantees low back pressures
and is mainly caused by the interstitial porosity (ez =75%).
In other words, the monolith was designed to possess almost
exclusively macropores; thus favoring diffusion and allowing
high reagent throughput. In contrast to most silica-based
materials, which also have a large fraction of micro- and
mesopores, this particular feature makes polymeric mono-
liths ideal support materials for the intended continuous
metathesis reactions under biphasic conditions.
Continuous metathesis under biphasic conditions by using
monolith-supported ILs: Layers of [BDMIM]ACTHUNTRGNE[UNG BF4] on the
surface of monoliths containing 1 were prepared by simply
injecting a solution of the IL and 1 in CH2Cl2. Then, the sol-
vent was completely removed in vacuo. A homogeneous dis-
tribution of the IL over the entire support was confirmed by
cutting a monolith into pieces of equal weight, which were
1
then extracted with CDCl3 and subjected to H NMR spec-
troscopic analysis. Thus, we could also show that the IL
could be removed quantitatively by flushing the column
with methanol. Finally, NMR spectroscopic analysis helped
to confirm that, at flow rates between 0.05 and
Self-metathesis of methyl oleate under biphasic conditions
using monolith-supported ILs: Since the self-metathesis of
methyl oleate requires prolonged reaction times, even at
808C, we decided to cycle the methyl oleate phase, that is,
to pass it through the monolith several times at a flow rate
of 0.1 mLminꢀ1. After each run the conversion was checked
by GC-MS, then the reaction mixture was again flushed
through the monolithic support. This procedure was repeat-
ed three times, then catalyst leaching was checked by ICP-
OES (Table 5). A total TON of 800 was obtained within
45 min at T=808C with the highest conversion occurring
within the first cycle. Notably, again only the primary meta-
thesis products formed, suggesting the absence of any active
Ru–hydride species. This TON is in view of the low solubili-
ty of methyl oleate in the IL (Kmethyl oleate/IL =34 at T=808C;
Table S2 in the Supporting Information), which is remarka-
ble and underlines the high reactivity of 1.
2.00 mLminꢀ1, no [BDMIM]
ACTHNUTRGEN[UNG BF4] was removed from the
monolith when heptane was used as a mobile phase and up
to 20 vol% of the void volume of the monolith was filled
with the IL.
RCM of N,N-diallyl trifluoroacetamide, DEDAM, and 1,7-
octadiene under biphasic conditions using monolith-support-
ed ILs: Since catalyst 1 showed very high activity in the
RCM of DAFA in both CH2Cl2 and [BDMIM]ACTHNUTRGENUG[N BF4] at T=
408C, we chose this reaction to demonstrate the soundness
and viability of the concept of running metathesis reactions
under biphasic conditions using monolith-supported
[BDMIM]ACHTUNGTRENNUNG[BF4]/1. Due to the high polarity of DAFA, opti-
mization of the reaction conditions, that is, adjusting the
thickness of the IL layer and identifying the optimum con-
centrations was challenging. For comparison, all experiments
were additionally carried out with the GH catalyst under
identical conditions. Conversions were determined by means
of GC-MS; leaching of 1 into the heptane phase was quanti-
fied by ICP-OES. Under all conditions, monolith-supported
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Continuous Biphasic Metathesis
FULL PAPER
Table 5. Self-metathesis of methyl oleate.
Cycle
flow was 1.05 mLminꢀ1. IR spectra were measured on a Bruker IFS 28
using ATR technology in NaCl cuvettes or as KBr pellets.
Integral conversion[a] [%]
Compound 1: Under exclusion of light, AgBF4 (130 mg, 670 mmol) was
dissolved in DMF (100 mg, 1.37 mmol) and CH2Cl2 (5 mL). Then a solu-
tion of the GH catalyst (200 mg, 320 mmol) in CH2Cl2 was slowly added.
The immediate formation of AgCl was observed and stirring was contin-
ued for 1 h. After filtering off the precipitate and passing the solution
through a short pad of Celite, the solvent was removed in vacuo. A light
green solid was obtained (290 mg, 305 mmol, 95%). Green crystals suita-
ble for X-ray analysis were obtained by layering THF over a concentrat-
ed solution of 1 in CH2Cl2 at 208C. 1H NMR (400.13 MHz, CD2Cl2): d=
19.28 (s, 1H), 7.94 (s, 1H), 7.88–784 (m, 2H), 7.28 (t, J=7.3 Hz, 1H),
7.06 (d, J=8.5Hz, 1H), 6.96 (s, 4H), 5.64 (s, 2H), 4.99–4.93 (m, 1H), 4.08
(s, 3.95), 3.16–3.10 (m, 6H), 2.60 (d, J=8.0 Hz, 12H), 2.37 (s, 12H), 2.30
(s, 6H), 1.03 ppm (d, J=6.4 Hz, 5.70); 13C NMR (100.61 MHz, CD2Cl2):
d=317.7, 166.0, 154.1, 145.7, 139.4, 137.0, 136.2, 134.4, 129.7, 125.0, 124.8,
114.9, 77.3, 53.0, 39.1, 33.2, 21.7, 21.0, 18.5 ppm; 19F NMR (376.50 MHz,
CD2Cl2): d=ꢀ152.6 ppm; IR (KBr): n˜ =3438 (b), 3047 (m), 2916 (s),
2856 (m), 2729 (m), 1668 (vs), 1591 (s), 1477 (s), 1383 (s), 1282(m), 1259
(vs), 1215 (m), 1039 (vs), 930 (s), 858 (m), 750 (s), 701 (m), 680 (m), 658
(m), 579 (s), 521 (s), 422 cmꢀ1 (s); elemental analysis calcd (%) for
C40H59B2F8N5O4Ru (Mr =950.61 gmolꢀ1): C 50.49, H 6.26, N 7.27; found:
C 50.58, H 6.21, N 7.13.
1 (after 15 min)
2 (after 28 min)
3 (after 45 min)
45
56
63
total Ru leaching
0.6%
[a] Primary metathesis products; catalyst
1 (4.5 mg), [BDMIM]CAHTUNTGNRUE[GN BF4]
(90 mg), methyl oleate (1.8 g, 1300 equiv), T=808C, flow rate:
0.1 mLminꢀ1
.
Conclusion
The synthesis of new dicationic Ru–alkylidene complex 1 is
described. The catalyst can be selectively dissolved in an IL
in the presence of a second organic phase and possesses
high activity towards dienes lacking coordinating moieties.
At elevated temperatures, complex 1 shows also high activi-
ty in RCM, CM, and self-metathesis reactions. For RCM
and self-metathesis reactions under supported biphasic con-
ditions, surface-functionalized ROMP-derived monoliths
were prepared and used for the immobilization of
(exo,endo-Norborn-2-en-5-ylmethyl)dimethylamine: (exo,endo-Norborn-
2-en-5-ylmethyl)dimethylamine was prepared by Diels–Alder cycloaddi-
tion between freshly cracked cyclopentadiene (14.1 g, 214 mmol) and di-
methylallylamine (18.20 g, 214 mmol). Hydroquinone (10 mg) was added
and the reaction proceeded at 2008C for 48 h in a steel autoclave. Frac-
tional distillation (408C, 0.1 mbar) yielded (exo,endo-norborn-2-en-5-yl-
[BDMIM]ACHTUNGTRENNUNG[BF4] containing catalyst 1. High TONs and ex-
ceptionally low catalyst leaching (ꢁ0.1%) were observed.
Importantly, our concept also enables continuous product
formation, simply by cycling reactants through a monolithic
support containing a suitable catalyst dissolved in an IL.
The fact that a biphasic liquid/liquid system is used definite-
ly widens the range of potentially accessible substrates. In
contrast to any other surface-immobilized catalyst, the facile
recycling of the monolithic support by flushing with metha-
nol, for example, represents an additional advantage over
existing systems. Current efforts focus on variations in the
IL to allow increased substrate concentration in the SILP.
methyl)dimethylamine as
a colorless, oily liquid (21.34 g, 141 mmol,
66%). 1H NMR (250.13 MHz, CDCl3): d=5.90–6.13 (2ꢅm, 2H; -CH=
CH-), 2.80–2.72 (m, 2H), 2.19–2.17 (m, 6H; -N-(CH3)2), 2.05–1.97 (m,
1H), 1.87–1.77 (m, 2H), 1.17–1.43 (m, 3H), 0.54–0.47 ppm (2ꢅm, 1H);
13C NMR (62.5 MHz, CDCl3): d=136.5, 132.2, 65.9, 64.3, 49.2, 46.7, 44.5,
42.1, 36.7, 30.9 ppm; IR (film): n˜ =3067 (m), 2965 (s), 2860 (m), 2814
(m), 2768 (s), 2360 (m), 1441 (s), 1375 (m), 12223 (m), 1033 (s), 838 (s),
718 cmꢀ1 (s); GC-MS (EI, 70 eV): m/z calcd for C10H17N: 151.14; found:
151.1, tR =6.05 min.
Compound
2a:
(exo,endo-Norborn-2-en-5-ylmethyl)dimethylamine
(1.00 g, 6.6 mmol) was dissolved in CH2Cl2 (10 mL) and cooled to 08C. A
solution of methyl iodide (1.22 g, 8.6 mmol) in CH2Cl2 (3 mL) was slowly
added and the mixture was stirred for 2 h. After solvent removal, com-
pound 2a was obtained as a white solid (1.71 g, 5.9 mmol, 91%). The
product was purified by washing with diethyl ether and dried in vacuo.
1H NMR (250 MHz, DMSO): d=6.00–6.27 (2ꢅm, 2H; -CH=CH-), 3.25–
3.14 (m, 2H), 3.07–3.05 (m, 9H; -N-(CH3)3), 2.83–3.00 (m, 3H), 2.13–2.03
(m, 1H), 1.26–1.52 (m, 3H), 0.77–0.70 ppm (2ꢅm, 1H); 13C NMR
(62.5 MHz, DMSO): d=139.4, 132.3, 71.1, 53.4, 49.9, 46.9, 42.9, 34.3,
33.5 ppm; IR (KBr): n˜ =3425 (b), 3053 (s), 2995 (m), 2962 (m), 2866 (s),
2595 (m), 2341 (m), 1477 (vs), 1336 (s), 1252 (m), 1144 (m), 1078 (m),
972 (s), 912 (s), 829 (s), 715 cmꢀ1 (vs).
Experimental Section
Materials and characterization: Unless noted otherwise, all preparations
were performed in a LabMaster 130 glove box (MBraun; Garching, Ger-
many) or by standard Schlenk techniques under
a N2 atmosphere.
CH2Cl2, THF, diethyl ether, and pentane were purchased from J. T.
Baker (Devender, Netherlands) and were dried by using an MBraun
SPS-800 solvent purification system with alumina drying columns. DMF
was purchased from Sigma–Aldrich (Munich, Germany) and passed
through a pad of alumina prior to use. Starting materials were purchased
from Aldrich, TCI Europe (Zwijndrecht, Belgium), and ABCR (Karls-
ruhe, Germany) and used without further purification. Polystyrene (PS)
standards (800<Mw <2000000 gmolꢀ1) used for ISEC were purchased
from Polymer Standard Service (Mainz, Germany). The CL (NBE-
CH2O)3SiCH3 was prepared as described earlier.[80]
Compound 2: Under exclusion of light, an aqueous solution of 2a
(0.50 g, 1.76 mmol,) was added dropwise to a solution of silver tetrafluor-
oborate (0.38 g, 1.90 mmol) in water at 508C. The reaction mixture was
stirred for 1 h, then the yellow precipitate of silver iodide was filtered off
and the solvent was removed in vacuo. Compound 2 was obtained as a
colorless solid (0.40 g, 1.58 mmol, 90%). 1H NMR (400.13 MHz, D2O):
d=6.06–6.33 (2ꢅm, 2H; -CH=CH-), 3.56–3.43 (m, 1H), 3.33–3.28 (m,
1H), 3.14–3.12 (m, 9H; -N-(CH3)3), 2.97–2.85 (m, 3H), 2.13–2.20 (m,
1H), 1.59–1.29 (m, 3H), 0.85–0.80 ppm (m, 1H;); 13C NMR (100.61 MHz,
D2O): d=139.8, 138.2, 136.5, 131.6, 73.3, 72.0, 53.8, 49.4, 47.7, 46.7, 45.6,
42.8, 42.3, 34.3, 33.5 ppm; 19F NMR (376.50 MHz, D2O): d=ꢀ150.2 ppm;
IR (KBr): n˜ =3423 (b), 3060 (m), 2972 (s), 2875 (m), 1622 (m), 1487 (s),
1423 (m), 1340 (m), 1268 (m), 1051 (vs), 970 (m), 904 (s), 825 (m), 769
(m), 721 (vs), 521 cmꢀ1 (s); MS (ESI): 166.16 [C11H20N].
NMR spectra were recorded on a Bruker Avance III 400 spectrometer or
a Bruker DRX 250 spectrometer in the indicated solvent at 258C and
data are listed in parts per million downfield from tetramethylsilane
(TMS) as an internal standard. GC-MS data were obtained by using an
Agilent Technologies 5975C inert MSD with triple-axis detector, an 7693
autosampler, and a 7890A GC system equipped with a SPB-5 fused silica
column (34.13 mꢅ0.25 mmꢅ0.25 mm film thickness). The injection tem-
perature was set to 1508C. The column temperature ramped from 45 to
2508C within 8 min, and was then held for further 5 min. The column
N,N-Diallylacetamide: Over
a period of 1 h, diallylamine (15.0 g,
154 mmol) was added to ice cold acetic anhydride (26.8 g, 263 mmol)
under vigorous stirring. Then the temperature was raised to 1008C and
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M. R. Buchmeiser et al.
stirring was continued for a further 2 h. Fractional distillation yielded
N,N-diallylacetamide (708C, 0.1 mbar) as colorless liquid (18.3 g,
were mixed and dissolved in CH2Cl2 (1.2 mL). The solution was then in-
troduced into the monolith. Vacuum was applied for 3 h at 408C to
remove the solvent. Prior to use, the support was flushed with heptane
a
131 mmol, 85%). 1H NMR (400.13 MHz, CDCl3): d=5.76–5.65 (m, 2H),
5.16–5.04 (m, 4H), 3.87 (dd, J=5.8 Hz, 4H), 2.04 ppm (s, 3H); 13C NMR
(100.61 MHz, CDCl3): d=170.5, 132.8, 116.7, 48.7, 21.2 ppm; IR (film):
n˜ =3473 (b), 3078 (s), 2991 (m), 2979 (s), 2912 (m), 2354 (m), 1718 (m),
1633 (vs), 1448 (m), 1407 (vs), 1261 (s), 1241 (vs), 1192 (s), 1008 (m), 982
(s), 918 (s), 773 (m), 687 (s), 600 (s), 557 cmꢀ1 (m); GC-MS (EI, 70 eV):
m/z calcd for C8H13NO: 139.10; found: 139.1, tR =6.268 min.
for 1 h at 408C by applying a flow rate of 0.1 mLminꢀ1
.
Metathesis under biphasic conditions: Complex 1 (2.5 mg, 2.6 mmol) was
dissolved in [BDMIM][BF4] (200 mg) and the solution was heated to
AHCTUNGTRENNUNG
408C. Then a solution of the substrate (0.6–13 mmol) in heptane (2 mL)
was added and the biphasic system was stirred vigorously (600 rpm) for
12 h. Reactions were quenched by adding ethyl vinyl ether (1 mL). After
removing the nonpolar phase, the IL phase was extracted extensively
with diethyl ether. The organic phases were combined and subjected to
GC-MS analysis to determine conversion.
N-Allyl-N-propargyltrifluoroacetamide
N-Allyl-N-propargylamine: This compound was prepared according to a
procedure reported in the literature.[86] A solution of allylamine (7.660 g,
134 mmol) in 2m aqueous NaOH (50 mL) was warmed to 408C. Proparg-
yl chloride (5 g, 67 mmol) was then added dropwise over a period of 3 h.
Stirring was continued for a further 3 h, then the reaction mixture was al-
lowed to cool to ambient temperature. The mixture was extracted with
diethyl ether (3ꢅ30 mL) and the combined organic phases were washed
with brine (2ꢅ50 mL). After drying over MgSO4, the solvent was re-
moved. N-Allyl-N-propargylamine was isolated by column chromatogra-
phy (silica, pentane/diethyl ether gradient) as a colorless liquid (2.3 g,
24 mmol, 36%). 1H NMR (400.13 MHz, CDCl3): d=5.76–5.66 (m, 1H),
5.29–5.21 (m, 2H), 4.17–4.10 (m, 4H), 2.32–2.26 ppm (m, 1H); 13C NMR
(100.61 MHz, CDCl3): d=134.6, 118.5, 78.5, 73.0, 56.0, 41.5 ppm; GC-MS
(EI, 70 eV): m/z calcd for C6H9N: 95.14; found: 95.1, tR =3.258 min.
Metathesis under biphasic conditions using monolith-supported ILs:
Metathesis reactions under SILP conditions were performed in air. The
loaded monolithic support was placed inside a Merck L-5025 column
thermostat and warmed to the indicated temperature (Table S1 in the
Supporting Information). By using a syringe pump (WPT, Aladdin-1000),
the substrate (diallyl trifluoroacetamide and DEDAM dissolved in hep-
tane; 1,7-octadiene and methyl oleate as neat reactants) was flushed
through the monolith at a flow rate of 0.1 mLminꢀ1. The eluent was col-
lected and subjected to GC-MS analysis to determine conversion. Used
SILP phases were removed by subsequent flushing with methanol (5 mL)
and CH2Cl2 (5 mL). The cleaned monolithic supports were again charged
and used for catalysis.
Alongside the desired product, the dialkylated species N-allyl-N,N-dipro-
pargylamine was isolated (1.83 g, 14 mmol, 21%). H NMR (400.13 MHz,
CDCl3): d=5.86–5.76 (m, 1H), 5.22 (d, J=11.1 Hz, 2H), 3.41 (s, 4H),
3.14 (d, J=6.7 Hz, 2H), 2.21 ppm (s, 2H); 13C NMR (100.61 MHz,
CDCl3): d=134.6, 118.5, 78.5, 73.0, 56.0, 41.5 ppm; GC-MS (EI, 70 eV):
m/z calcd for C9H11N: 133.09; found: 133.1, tR =5.141 min.
Ru measurements: The Ru content was measured by ICP-OES (l=
240.272 nm, ion line, background lines at l1 =240.254 nm and l2 =
240.295 nm) using a Spectro Arcos device (Ametek GmbH; Meerbusch,
Germany). Standardization was carried out with Ru standards containing
0.1, 0.5, 1.0, 2.5, and 5 ppm of Ru. The Ru content of both the support
and in the product fraction was determined by dissolving samples
(100 mg) in aqua regia.
1
N-Allyl-N-propargyl trifluoroacetamide: A mixture of N-allyl-N-propar-
gylamine (1.00 g, 11 mmol) and triethylamine (1.34 g, 13 mmol) in
CH2Cl2 (18 mL) was cooled to 08C. Trifluoroacetic anhydride (2.66 g,
13 mmol) in CH2Cl2 (5 mL) was added dropwise over a period of 30 min.
The reaction mixture then was warmed to 308C and stirring was contin-
ued for 15 h. A saturated aqueous solution of NaHCO3 (30 mL) was
added and the mixture was then extracted with CH2Cl2 (2ꢅ30 mL). The
organic phase was washed with water (30 mL) and then dried over
MgSO4. After solvent removal, the residue was subjected to column chro-
matography (silica, diethyl ether) to yield the target compound as a col-
orless liquid (1.71 g, 8.9 mmol, 81%). 1H NMR (400.13 MHz, CDCl3):
d=5.91–5.80 (m, 1H), 5.22–5.09 (m, 2H), 3.40 (d, J=4.5 Hz, 2H), 3.31
(d, J=5.3 Hz, 2H), 2.21–2.19 ppm (m, 1H); 13C NMR (100.61 MHz,
CDCl3): d=135.9, 116.6, 81.9, 71.3, 50.8, 37.2 ppm; 19F NMR
(376.50 MHz, CDCl3): d=ꢀ75.7 ppm; IR (film): n˜ =3292 (vs), 3083 (m),
2985 (m), 2923 (m), 2343 (m), 2123 (m), 1691 (vs), 1419 (vs), 1353 (s),
1277 (s), 1205 (vs), 1141 (vs), 1003 (s), 937 (s), 756 s), 698 cmꢀ1 (s); GC-
MS (EI, 70 eV): m/z calcd for C8H8F3NO: 191.06; found: 190.1, tR =
4.964.
Determination of the distribution coefficients (Ksolvent/IL): For 1,7-octa-
diene, DEDAM, and DAFA, the distribution coefficients, Kheptane/IL
=
cðsubstrate in heptaneÞ
,
were
determined
for
the
solvent
system
cðsubstrate in ILÞ
heptane/
DAFA,
dodecane/
G
E
cðsubstrate in dodecaneÞ
cðsubstrate in ILÞ
U
were performed for each substrate/solvent/temperature system to yield
an average distribution coefficient with sufficient validity. Substrate
(50 mg) and an internal standard (15 mg) were dissolved in solvent
(200 mg) and added to [BDMIM]ACHTNUTRGNEUN[G BF4] (200 mg). Dodecane was used as
an internal standard when heptane was the organic solvent and dicyclo-
pentadiene served as the nonpolar reference for the determination in do-
decane. The biphasic system was stirred with 600 rpm at the indicated
temperature for 1 h. Then a sample was removed from the organic phase
and examined by means of GC measurements. The immiscibility of the
internal standards with the IL was checked by 1H NMR spectroscopy.
Comparing the integral areas for the substrate signal and the signal
caused by the internal standard, before and after mixing, allowed the dis-
tribution coefficient to be calculated.
Preparation of surface-functionalized monoliths: Monoliths were pre-
pared in 125ꢅ4.4 mm I.D. stainless-steel tubings, according to a well-es-
tablished procedure.[80] The polymerization mixture composed of NBE
(15 wt.-%), the CL (NBE-CH2O)3SiCH3 (15 wt%), the porogenic sol-
vents toluene (20 wt%) and 2-propanol (50 wt%), as well as the initiator
Ksubstrate/IL for neat 1,7-octadiene and methyl oleate in [BDMIM]
Substrate (200 mg) and dodecane (50 mg) as the internal standard were
added to [BDMIM][BF4] (200 mg). The biphasic system was stirred at
ACHTUNGTRENNUNG[BF4]:
AHCTUNGTRENNUNG
600 rpm at the indicated temperature for 1 h. Then a sample was re-
moved from the organic phase and analyzed by GC-MS. The ratio of the
integral areas for the substrate signal and the signal caused by the inter-
nal standard, before and after mixing, corresponded directly to the distri-
bution coefficient.
[RuCl2ACHTUNGTRENNUNG(PCy3)2ACHTUNGTRENNUNG(=CHC6H5)] (0.4 wt%). The steel column was placed verti-
cally, one end closed, in an ice bath. Polymerization proceeded at 08C for
30 min, then the temperature was raised to 208C for another 30 min.
For the grafting of monomer 2 to the surface of the monoliths, the
column was provided with adapters and flushed with CH2Cl2 for 2 h at a
flow rate of 0.1 mLminꢀ1. The monomer (10 equiv with respect to the ini-
tiator) was dissolved in CH2Cl2 (1.2 mL) and introduced into the mono-
lith. The loaded monolith was sealed and kept at 458C for 12 h. To
remove the initiator, the column was flushed with a 1:1 mixture of ethyl
vinyl ether and CH2Cl2 for 2 h at a flow rate of 0.1 mLminꢀ1. After this,
flushing was continued with pure CH2Cl2 for a further 2 h at a flow rate
X-ray measurements and structural determination of 1: Data were col-
lected on a Bruker Kappa Apex 2 duo diffractometer at 100 K. The
structure was solved by using direct methods with refinement by full-
matrix least-squares on F2, with the program system SHELXL 97 in con-
nection with
a
multiscan absorption correction.[87] All non-hydrogen
atoms were refined anisotropically.
of 0.1 mLminꢀ1
Immobilization of [BDMIM]
monoliths: Complex 1 (2.5 mg, 2.6 mmol) and [BDMIM]AHCTUNGTRENNUNG
.
CCDC-900128 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
AHCTUNGTRENNUNG
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ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Continuous Biphasic Metathesis
FULL PAPER
Inverse size exclusion chromatography (ISEC): Functionalized monoliths
were characterized by ISEC measurements in terms of inter-microglobu-
lar porosity (ez), microporosity (ep), and total porosity (et). A volume of
10 mL per sample of individual PS standard (0.25 mgmLꢀ1) dissolved in
the mobile phase (CHCl3) was injected into the column at a flow rate of
0.6 mLminꢀ1. The total accessible porosity was determined by injecting a
10 mL sample of toluene. A wavelength of 254 nm was applied to record
the chromatograms. Retention times and volumes corresponding to each
injection were determined from the peak maximum. Each retention
volume was corrected for the extra-column volume of the equipment.
For calculations it was assumed that the hydrodynamic radii of the PS
standards in CHCl3 did not differ significantly from those reported in
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Acknowledgements
We are grateful to Dipl.-Chem. Stefan Naumann (University of Stuttgart)
for his help with ICP-OES measurements. This work was supported by a
grant provided by the Deutsche Forschungsgemeinschaft (DFG, grant no.
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Received: April 9, 2012
Published online: && &&, 0000
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ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
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These are not the final page numbers!

Continuous Biphasic Metathesis
FULL PAPER
Vital support: A dicationic Ru–alkyli-
dene (see figure) was prepared and
used in continuous heterogeneous
liquid–liquid metathesis reactions by
using supported ionic-liquid-phase
technology. This approach allows reuse
of the support and synthesis of the
target compounds with low Ru con-
tamination.
Heterogeneous Catalysis
B. Autenrieth, W. Frey,
M. R. Buchmeiser* ........... &&&& — &&&&
A Dicationic Ruthenium Alkylidene
Complex for Continuous Biphasic
Metathesis Using Monolith-Supported
Ionic Liquids
Chem. Eur. J. 2012, 00, 0 – 0
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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These are not the final page numbers!