Batchwise and continuous organophilic nanofiltration of Grubbs-type olefin metathesis catalysts

Article abstract of DOI:10.1002/chem.200802153

A mass-tagged N-mesityl imidazolinium salt with four additional -CH ₂NCy₂ substituents was synthesized, leading to a molecular mass of nearly 1100 g mol^-1 in the corresponding carbene ligand. This mass-tagged ligand was used to generate the respective Grubbs II and Grubbs-Hoveyda type complexes. The catalytic activity of the latter complex was tested in several olefin metathesis reactions and found to be slightly superior to that of the related N-mesityl based complex. In batchwise solvent resistant nanofiltration experiments the ruthenium complex dissolved in toluene and following a metathesis reactions was efficiently retained (>99.8%) by a single nanofiltration; the permeate contained less than 4 ppm of Ru. Equally efficient catalyst retention was observed in a membrane reactor utilized for the continuous synthesis of a RCM product.

Full text of DOI:10.1002/chem.200802153

DOI: 10.1002/chem.200802153
Batchwise and Continuous Organophilic Nanofiltration of Grubbs-Type
Olefin Metathesis Catalysts
Dirk Schoeps,[a] Kristian Buhr,[b] Marga Dijkstra,[b] Katrin Ebert,[b] and
Herbert Plenio*[a]
Abstract:
A
mass-tagged N-mesityl
eral olefin metathesis reactions and
found to be slightly superior to that of
the related N-mesityl based complex.
In batchwise solvent resistant nanofil-
tration experiments the ruthenium
complex dissolved in toluene and fol-
lowing a metathesis reactions was effi-
ciently retained (>99.8%) by a single
nanofiltration; the permeate contained
less than 4 ppm of Ru. Equally efficient
catalyst retention was observed in a
membrane reactor utilized for the con-
tinuous synthesis of a RCM product.
imidazolinium salt with four additional
-CH2NCy2 substituents was synthe-
sized, leading to a molecular mass of
nearly 1100 gmolÀ1 in the correspond-
ing carbene ligand. This mass-tagged
ligand was used to generate the respec-
tive Grubbs II and Grubbs–Hoveyda
type complexes. The catalytic activity
of the latter complex was tested in sev-
Keywords: carbenes
· homogene-
ous catalysis · nanofiltration · olefin
metathesis · ruthenium
Introduction
quently numerous concepts, aimed towards catalyst recov-
ery[8] and the use of supported (olefin metathesis) catalysts
have been developed.[9]
Typical homogeneous catalysts rely on expensive transition
metals decorated with carefully designed and valuable li-
gands to enable the fine tuning of the catalytic activity of
the metal center.[1] Following catalytic transformations, the
valuable catalyst complexes are normally lost during the
product work-up.[2–4] Apart from the obvious economic dis-
advantages associated with this, low thresholds for the con-
tamination of organic products with toxic metals may re-
quire complex purification techniques to meet the specified
limits.[5] The economic impact is aggravated due to the soar-
ing price of platinum group metals,[6] while at the same time
new limits for metal impurities are being imposed in the Eu-
ropean union.[7] Obviously, these are fundamental problems
for the application of homogeneous catalysis and conse-
Olefin metathesis is a very important synthetic transfor-
mation;[10,11] unfortunately it often (but not always)[12,13] re-
quires high catalyst loadings—typically around 1 mol%—re-
sulting in considerable ruthenium contamination of the reac-
tion products requiring elaborate Ru removal proce-
dures.[14–18] Work from Barrett et al. in the total synthesis of
the antibiotic viridiofungin derivatives illustrates typical pu-
rifications problems: repeated chromatography was required
to remove ruthenium from the product, which was isolated
in 57% yield only, despite near quantitative conversion by
the olefin metathesis catalyst.[19] These problems may have
motivated Clavier, Grela, Kirschning, Mauduit and Nolan[20]
and Blechert[21] to summarize sustainable concepts in olefin
metathesis.
Solvent resistant nanofiltration (SRNF) with organic and
ceramic membranes and the related approach by Rothen-
berg et al.[22] of immobilizing catalyst in a multilayered
porous membrane cylinder have been applied in homogene-
ous catalyst separation,[23–27] but so far not in olefin metathe-
sis.
Consequently, we want to report here on the synthesis of
Grubbs-type olefin-metathesis catalysts in which high cata-
lytic activity is combined with an increased molecular mass
of the Ru complex. This enables the efficient separation of
the catalyst complexes from olefin-metathesis products in
[a] Dipl.-Ing. D. Schoeps, Prof. Dr. H. Plenio
Anorganische Chemie im Zintl-Institut, Petersenstr. 18
Technische Universitꢀt Darmstadt, 64287 Darmstadt (Germany)
Fax : (+49)
E-mail: plenio@tu-darmstadt.de
[b] Dipl.-Ing. K. Buhr, Dr. M. Dijkstra, Dr. K. Ebert
GKSS-Forschungszentrum Geesthacht GmbH
Institut fꢁr Polymerforschung, Max-Planck-Str. 1
21502 Geesthacht (Germany)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200802153.
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Chem. Eur. J. 2009, 15, 2960 – 2965

FULL PAPER
batchwise filtration experiments and in a continuous mem-
brane reactor. In order to achieve just this several condi-
tions have to be met:
a) The large group(s) determining the retention properties
of olefin-metathesis catalyst must be linked to a ligand
which is permanently bound to ruthenium throughout
the catalytic cycle. This is especially important in a con-
tinuous membrane reactor, since otherwise the active
species may be lost as it permeates through the mem-
brane.
b) The nanofiltration tag should not decrease the activity of
the olefin-metathesis catalyst.
c) The choice of the nanofiltration membrane must ensure
efficient retention of the catalyst complex as well as ex-
cellent product permeation and solvent flow across the
chosen membrane.
Scheme 1. a) HNCy2, 1008C, cyclohexane; b) H2SO4, HNO3, neat, 08C;
c) SnCl2, HCl, HOAc; d) glyoxal, HCOOH; EtOH, MTBE; e) LiAlH4,
THF; f) HCACHTNUTRGNE(UGN OEt)3, NH4Cl, 1008C.
It follows from a) that nanofiltration tags need to be cova-
lently attached to the N-heterocyclic carbene, since active
catalyst is generated by dissociation of the 2-isopropoxyben-
zylidene unit from Grubbs–Hoveyda-type pre-catalysts.
Nonetheless, in experiments aimed at catalyst recovery, tag-
ging of the benzylidene in Grubbs II or Grubbs–Hoveyda
complexes[28–33] appears to be more frequently applied than
NHC tagging.[34–36] It follows from b) that the large groups
attached to the N-heterocyclic carbene ligand should be
electron-releasing since this will lead to increased catalyst
activity.[37] For the nanofiltration experiments we aimed for
a catalyst with a molecular mass of around 1500 Dalton,
while using a membrane with a 500 Dalton cut-off.
um salt 7 ·HCl according to the standard protocol via 5 and
6.[39] The overall yield of the imidazolinium salt over six
steps from 1 to 7 is 32% yield. The synthesis can be conven-
iently carried out on a large scale to easily yield several
dekagrams of the NHC precursor 7·HCl as a microcrystal-
line powder. The yield for the ring-closing reaction of 6 to
give 7 of only 55% is by far the poorest in the synthetic se-
quence. It is likely, that the recently improved synthesis of
imidazolinium salts as reported by Grubbs and Cavell, Der-
visi, Fallis is more efficient.[40,41] Application of the former
standard protocol resulted in the formation of the Grubbs II
Results and Discussion
complex
8 and the Grubbs–Hoveyda-type species 9
Synthesis of mass-tagged Grubbs–Hoveyda-type complex:
The synthesis of the enlarged imidazolinium salts as precur-
sors to N-heterocyclic carbenes starts from the known pen-
tamethylbenzene derivative 1. Reaction with Cy2NH leads
to the diamine 2; we chose this amine since it represents a
good compromise between a high molecular mass of the re-
sulting imidazolinium salt while retaining a reasonable mass
content of active centers in the resulting catalyst complex.
Furthermore the relatively rigid cyclohexyl group normally
renders easily handled solid products. However, when
needed it will be easy to introduce other long chain amines
such as commercially available didodecylamine or dioctade-
cylamine to increase the NHC mass to 2500 Dalton.
The nitration of 2 requires carefully controlled conditions.
Nonetheless, the nitro-substituted arene 3 is formed in 90%
yield, even though the nitration of pentamethylbenzene is
problematic under the same reaction conditions.[38] We attri-
bute the facile formation of 3 (Scheme 1) to the presence of
the two ammonium groups during the reaction which render
the aromatic system less electron-rich than with five methyl
groups. Reduction of 3 with SnCl2/HCl gives the aniline 4 in
near quantitative yields, which is reacted to the imidazolini-
Scheme 2. The tagged NHC ligand is electron-rich as it car-
ries five electron-donating alkyl groups on each N-aryl
group.
Catalytic activity of Grubbs–Hoveyda complex 9: We first
studied the activity of the Grubbs–Hoveyda type complex 9
against that of the normally employed mesityl (SIMes) sub-
stituted Grubbs–Hoveyda complex. Both catalysts gave
close to quantitative yields for the RCM of diethyl diallyl-
malonate at 0.1 mol% catalyst loading and 408C, with com-
plex 9 being slightly more active (Figure 1). At lower tem-
peratures (208C) the performance difference is increasing.
Due to the increased electron donation[39] of NHC 7 the cat-
alytic activity of the mass tagged complex 9 turns out to be
higher than that of the normal mesityl-substituted Grubbs–
Hoveyda catalyst (Figure 1). Additional screening results
are reported in Table 2. Various ring-closing metathesis
(RCM) of diolefins (Table 1, entries 1, 2, 4, 9) and the cross-
metathesis reaction give good results, comparable to litera-
ture results for the related mesityl-substituted complex.[42–44]
As expected there is only modest activity in the RCM of
sterically demanding substrates (entries 3, 5).[45]
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H. Plenio et al.
and continuous experiments) are composite membranes
consisting of a porous poly(acrylonitrile) membrane support
with a 5 mm layer of chemically and radiationally cross-
linked poly(dimethylsiloxane) (PDMS). Following the con-
version of the reactants, the reaction mixture underwent
nanofiltration; the permeate solvent was evaporated and the
remaining product analyzed for Ru with ICP-OES. For all
batch filtration experiments catalyst retention exceeds 99–
99.8%. The amount of Ru in the permeate remains always
below the ICP-OES detection limit, which for our experi-
ments is at about 4 ppm of Ru (Table 1). This corresponds
to a Ru retention in excess of 99.8% by a single filtration
(entries 2, 3). We expect the Ru retention in the first entry
in table 1 to be in the same range. However, due to the ini-
tially much smaller amount of Ru in the reaction mixture,
only a >99% threshold can be given.
Olefin metathesis in continuous membrane reactor: In the
continuous mode three samples were taken, for each of
them the feed during 45 min was collected. In the first batch
(60–105 min) 4 ppm, in the second (240–285 min) 7 ppm and
in the third (450–495 min) 7 ppm of Ru were detected. The
total amount of Ru retained by the membrane during the
full duration of the experiment was found to be 97.6%.
The conversion in the membrane reactor reached a maxi-
mum of approximately 37% after about 120 minutes. After
that time the conversion decreased to a final value of about
6% after 500 minutes. The reason for this shape of the con-
version curve is not clear yet, but it is likely that the increas-
ing ethene concentration in the reaction volume leads to a
slow down of the catalytic conversion. Nonetheless, the total
turnover number during the first 500 min is 866 mol product
per mol of catalyst, which is respectable. It is noteworthy,
that the products both from the batch and the continuous
experiments contain significantly less than the 10 ppm Ru
threshold set by EMEA for oral exposure.[7]
Scheme 2. g) Grubbs I complex, 7, KOtBu; h) 2-vinyl-isopropoxybenzene,
CuI.
Figure 1. Time/conversion curve for the RCM reaction of diethyl diallyl-
malonate at 0.1 mol% catalyst loading in toluene (complex 9 vs. mesityl
(SIMes) Grubbs–Hoveyda reference).
Summary and Conclusions
Table 1. Nanofiltration of olefin metathesis catalyst 7 from three meta-
thesis reactions in toluene solvent.
The tagging of an N-heterocyclic carbene with four
-CH2NCy2 -groups results in a nearly fourfold increase in
the molecular mass of the ligand and at the same time to en-
hanced electron-donating properties with respect to the nor-
mally used N-mesityl substituents. These modifications lead
to a marked increase in the catalytic activity and enable the
effective retention (>99.8%) of the catalyst complex in the
batch nanofiltration experiment, resulting in less than 4 ppm
Ru contamination of the products. This is lower than the
threshold set by EMEA. The effective retention was demon-
strated in catalytic experiments with batchwise filtration as
well as in continuous filtration experiments in a membrane
reactor. The mass-tagged NHC ligand (or related ligands de-
rived thereof) should also allow the separation of other val-
uable NHC ligated transition metal catalyst complexes, such
as in Pd-mediated cross-coupling reactions and Pt-mediated
hydrosilylation, which is the subject of current studies.
Reaction
max. Ru
421 ppm
Ru found
RCM of diethyl diallylmalonate
0.1 mol% catalyst
CM of allylbenzene
0.2 mol% catalyst
RCM of N,N-diallyltosylamide
0.5 mol% catalyst
< 4 ppm
>99% retention
< 4 ppm
>99.8% retention
< 4 ppm
>99.8% retention
1710 ppm
2013 ppm
Catalyst retention in batchwise nanofiltration: The retention
of the catalyst was tested in three different batch type nano-
filtration experiments in toluene solution (Figure 2): the
RCM of diethyl diallylmalonate employing 0.1 mol% cata-
lyst, the cross-metathesis of allylbenzene (0.2 mol% cata-
lyst) and the RCM of N,N-diallyltosylamide (0.5 mol% cata-
lyst). In all batch experiments very good conversion of the
reactants to the desired products was observed. The mem-
branes used for the nanofiltration experiments (both batch
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FULL PAPER
Table 2. Olefin metathesis reactions using complex 9.
Entry
1
Metathesis reaction
T [8C]
Cat. loading [mol%]
t
Conversion [%]
50
40
21
1
0.1
0.1
15 min
60 min
240 min
99
99
>90
2
3
40
0.1
60 min
99
50
70
0.1
0.5
24 h
24 h
8
51
4
5
50
50
0.1
0.1
15 min
62
26
240 min
6
40
0.2
240 min
99
7
8
40
40
0.1
0.1
240 min
240 min
>90
76
9
50
1
15 min
99
84
10
50
1
120 min
scale (d) and are referenced to tetramethylsilane (1H, 13C NMR=0 ppm)
or PMe3 (=À63 ppm). Abbreviations for NMR data: s=singlet; d=dou-
blet; t=triplet; q=quartet; sep=septet; m=multiplet; brs=broad
signal.
2,4-Bis(N,N-dicyclohexylaminomethyl)-1,3,5-trimethylbenzene (2):
A
mixture of 2,4-bis-(bromomethyl)-1,3,5-trimethylbenzene[46] (1; 9.3 g,
30.4 mmol, 1 equiv) and dicyclohexylamine (28 g, 152 mmol, 31 mL,
5 equiv) was dissolved in cyclohexane (200 mL) and stirred at 1008C for
a period of 3 d. After cooling the reaction mixture to room temperature
and evaporation of the solvent in vacuo, the crude product was treated
with NaOH solution (2n) and extracted with dichloromethane. The or-
ganic phase was dried with MgSO4 and the residues were removed under
reduced pressure. To purify the remaining colorless product, MeOH
(100 mL) were added and the suspension was stirred vigorously. Filtra-
tion, washing with MeOH and drying in vacuo afforded product
2
(11.05 g, 21.8 mmol, 72%) as a colorless powder. 1H NMR (300 MHz,
CDCl3): d = 6.74 (s, 1H, CHaryl), 3.75 (s, 4H, CH2-aryl), 2.45 (s, 3H, p-
CH3), 2.37 (m, 4H, CHcyclohexyl), 2.33 (s, 6H, o-CH3), 1.71–0.97 ppm (m,
40H, CH2-cyclohexyl); 13C NMR (75 MHz, CDCl3): d = 139.3, 136.3, 134.5,
129.8, 56.4, 44.1, 32.2, 26.3, 25.1, 20.4, 15.6 ppm.
Figure 2. Time/conversion curve for the continuous-mode RCM reaction
of diethyl diallylmalonate.
Experimental Section
3,5-Bis(N,N-dicyclohexylaminomethyl)-2,4,6-trimethyl-nitrobenzene (3):
Concentrated sulfuric acid (21 mL) and fuming HNO3 (15 mL) were
mixed at 08C. The benzylamine 2 (11.0 g, 21.7 mmol) was added in small
portions while keeping the temperature at 08C. The mixture was kept at
08C for an additional hour and then neutralized with NaOH-solution
(2n). The pH was raised to 9–10 and the mixture extracted twice with di-
chloromethane (200 mL). After drying with MgSO4 and evaporation of
the remaining solvent, nitrobenzene 3 (11.43 g, 20.7 mmol, 95%) was ob-
tained as a light yellow powder. 1H NMR (300 MHz, CDCl3): d = 3.80
All reactions involving ruthenium complexes were performed under an
atmosphere of argon. The solvents were purchased ACS reagent grade
and dried by passing through a column with dry alox with argon pressure.
1H, 13C and 31P NMR spectra were recorded on Bruker DRX 500 at
500 MHz (1H), 126 MHz (13C) and 202 MHz (31P), respectively, on
Bruker DRX 300 at 300 MHz (1H), 75 MHz (13C) and 121 MHz (31P).
The chemical shifts are given in parts per million (ppm) on the delta
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H. Plenio et al.
(s, 4H, CH2-aryl), 2.50 (s, 3H, p-CH3), 2.34 (m, 4H, CHcyclohexyl), 2.27 (s,
6H, o-CH3), 1.75–0.97 ppm (m, 40H, CH2-cyclohexyl); 13C NMR (75 MHz,
CDCl3): d = 152.3, 141.2, 136.0, 126.9, 56.7, 44.4, 32.2, 26.2, 24.9, 16.0,
14.3 ppm.
150.5, 139.3, 138.3, 136.7, 134.7, 134.5, 126.5, 55.5, 51.8, 50.6, 43.9, 31.5–
31.1, 30.3, 30.1, 29.8, 26.8, 25.7, 25.4, 25.3, 25.2, 15.1, 14.6 ppm.
ACHUTNGRENNU(G 1,3-BisAHCUTNGTREN(NUGN 3,5-bis(dicyclohexylaminomethyl)-2,4,6-trimethylphenyl)-4,5-di-
hydro-1H-imidazoline)dichloro-(2-iso-propoxy-benzylidene)rutheniu-
m(II) (9): Grubbs II complex 8 (130 mg, 0.08 mmol, 1 equiv) was dis-
solved in dry toluene (20 mL) and stirred at 508C. After addition of iso-
propoxystyrene 10 (26 mg, 27 mL, 0.16 mmol, 2 equiv) and CuCl (24 mg,
0.24 mmol, 3 equiv), the mixture stirred at 508C for 1 h. Evaporation of
the solvent in vacuo and column chromatography on silica gel with cyclo-
hexane/ethyl acetate 10:1 afforded Grubbs–Hoveyda complex 9 (87 mg,
3,5-Bis(N,N-dicyclohexylaminomethyl)-2,4,6-trimethyl-aniline (4): Nitro-
benzene
3 (11.4 g, 20.66 mmol, 1 equiv) and SnCl2·2H2O (18.6 g,
82.6 mmol, 4 equiv) were suspended in conc. HCl (200 mL) and acetic
acid (100 mL). The reaction mixture was stirred at 1108C for 24 h. After
cooling to room temperature and neutralizing with NaOH (120 g with
500 mL ice), the pH was raised to 9–10 and the mixture extracted with
MTBE (2ꢃ400 mL). The aqueous phase was washed with MTBE
(200 mL) and the combined organic phases with water (1 L) and dried
with MgSO4. After evaporation of the solvent and drying in vacuo, ani-
line 4 (10.0 g, 19.16 mmol, 93%) was obtained as a colorless powder.
1H NMR (300 MHz, CDCl3): d = 3.79 (s, 4H, CH2-aryl), 3.51 (brs, 2H,
NH2), 2.40 (m, 4H, CH), 2.38 (s, 3H, p-CH3), 2.23 (s, 6H, o-CH3), 1.71–
1.01 ppm (m, 40H, CH2-cyclohexyl); 13C NMR (75 MHz, CDCl3): d 140.1,
134.1, 129.5, 121.7, 56.2, 44.4, 32.4, 26.7, 26.3, 15.4, 13.7 ppm.
0.06 mmol, 78%) as a green solid. 1H NMR (500 MHz, CDCl3): d
=
16.42 (s, 1H, CHbenzylidene), 7.35 (dt, J=7.4, 2.3 Hz, 1H, CHstyrene), 6.83 (t,
J=7.8 Hz, 1H, CHstyrene), 6.80 (d, J=8.5 Hz, 1H, CHstyrene), 6.65 (d, J=
8.4 Hz, 1H, CHstyrene), 4.76 (sep, J=6.0 Hz, 1H, CHpropoxy), 4.12 (s, 4H,
CH2-imidazoline), 3.79 (s, 8H, CH2-aryl), 2.55 (s, 6H, p-CH3), 2.45 (s, 12H, o-
CH3), 2.35 (dt, J=10.2 Hz, 8H, CHcyclohexyl), 1.69–0.92 (m, 80H,
CH2-cyclohexyl), 1.27 ppm (d, J=6.0 Hz, 6H, CH3-propoxy); 13C NMR
(125 MHz, CDCl3): 296.0, 210.1, 151.1, 144.6, 139.6, 136.8, 134.7, 131.0,
127.6, 125.5, 73.7, 55.7, 43.8, 31.4, 31.2, 25.7, 25.4, 20.0, 15.1 ppm; IR
(KBr): n˜ =2928, 2851, 1451, 1262, 1097, 1023, 800 cmÀ1; ESI-MS (ion po-
larity positive): found mass allocation fits calculated mass allocation;
N,N-BisACHTUNGTRENNUNG(3,5-bis(dicyclohexylaminomethyl)-2,4,6-trimethylphenyl)ethane-
1,2-diimine (5): Aniline 4 (9.8 g, 18.8 mmol, 2 equiv) was dissolved in a
mixture of EtOH (100 mL) and MTBE (100 mL) and treated with glyox-
al solution (1.08 mL, 40% w/w in water). After addition of formic acid (3
drops), the mixture was stirred overnight at room temperature. The re-
sulting solid was filtered and washed with cold EtOH. Diimine 5 (9.31 g,
8.74 mmol, 93%) was obtained as a yellow powder. 1H NMR (500 MHz,
CDCl3): d = 8.04 (s, 2H, CHimine), 3.85 (s, 8H, CH2-aryl), 2.49 (s, 6H, p-
CH3), 2.38 (m, 8H, CHcyclohexyl), 2.20 (s, 12H, o-CH3), 1.71–1.02 ppm (m,
80H, CH2-cyclohexyl); 13C NMR (125 MHz, CDCl3): d = 162.9, 147.2, 135.0,
133.9, 124.3, 55.3, 43.3, 31.4, 25.9, 25.3, 14.7, 14.1 ppm; EI-MS: m/z: 1065
found mass of NHC fragment: 1080.4 [M +], calculated mass of NHC
C
fragment: 1079.95 [M +].
C
General procedure
for
metathesis
reaction,
nanofiltration
Nanofiltration membrane: For the retention of catalysts composite mem-
branes from GKSS consisting of a technical non-woven, a porous layer of
poly(acrylonitrile) and on top of it an about 5 mm thick layer of poly(di-
methyl siloxane) (PDMS) which was thermally and radiationally cross-
linked. The membranes are referred to as PAN/PDMS membranes. Mem-
branes were treated for several hours in toluene to enable full swelling.
Prior to the nanofiltration process, the membrane was put in a Millipore
cell (300 mL, pmax =6 bar). When the metathesis reaction is finished, the
reaction mixture was poured into the Millipore cell. After closing the cell
and applying pressure (5 bar Argon), the permeate was collected in a
flask. The desired product was obtained after removing the volatiles in
vacuo.
+
+
+
+
+
+
[M ], 982 [M ÀCy ], 884 [M ÀNCy2 ], 869 [M ÀCH2NCy2+], 801
C
C
C
C
+
C
+
+
+
[M ÀNCy2 , ÀCy ], 704 [M À2NCy2+].
C
1,3-BisACHTUNGTRENNUNG(3,5-bis(dicyclohexylaminomethyl)-2,4,6-trimethylphenyl)-4,5-dihy-
dro-1H-imidazol-3-ium (7): Diamine 6 (6.66 g, 6.23 mmol, 1 equiv) and
NH4Cl (666 mg, 12.45 mmol, 2 equiv) were suspended in HC(OEt)3
AHCTUNGTRENNUNG
(9.5 mL). The mixture was stirred at 1008C for 18 h and after cooling to
room temperature treated with MeOH (100 mL). The precipitate was fil-
tered and washed with MeOH (50 mL). After drying under reduced pres-
sure, imidazolinium salt 7 (3.83 g, 3.43 mmol, 55%) was obtained as a
Membrane characterization: Membrane stamps with
a diameter of
colorless powder. 1H NMR (500 MHz, CDCl3):
d = 7.76 (s, 1H,
7.5 cm were installed in test cells with an effective membrane area of
34 cm2. Oxygen and nitrogen flows were measured at a pressure differ-
ence of 4 bar with a soap bubble meter. For each membrane stamp ten
measurements were performed to calculate an average flux. Using these
values the oxygen/nitrogen selectivity was calculated. Only stamps with
an oxygen/nitrogen selectivity of 2.1 were used for retention experiments.
CHimidazoline), 4.80 (s, 4H, CH2-imidazoline), 3.79 (s, 8H, CH2-aryl), 2.47 (s, 6H,
p-CH3), 2.46 (s, 12H, o-CH3), 2.32 (m, 8H, CHcyclohexyl), 1.73–0.97 ppm
(m, 80H, CH2-cyclohexyl); 13C NMR (125 MHz, CDCl3, [D6]DMSO): d =
165.9, 141.3, 135.7, 133.0, 129.8, 55.8, 52.4, 43.7, 31.4, 26.9, 26.2, 15.2,
14.1 ppm; ESI-MS (ion polarity positive): m/z: calcd for [M +]: 1079.9,
C
1081.0, 1082.0, 1083.0, 1084.0; found: 1080.1, 1081.0, 1082.1, 1083.1,
1084.0.
Batch experiments: The reaction yield was determined via gas chroma-
tography on a CP-Sil 8 CB column (15 m, di =0.25 mm, Varian) with a
Perkin Elmer Clarus 500 GC AutoSystem or via NMR spectroscopy on a
Bruker DRX 300 spectrometer at 300 MHz (1H NMR).
Benzylidene-(1,3-bisACHTUNGTRENNUNG(3,5-bis(dicyclohexylaminomethyl)-2,4,6-trimethyl-
phenyl)-4,5-dihydro-1H-imidazoline)dichlorotricyclohexylphosphineru-
thenium(II) (8): Dichlorobenzylidenebis(tricyclohexylphosphine)ruthe-
nium(II) (“Grubbs I”, 368 mg, 0.45 mmol, 1 equiv) was mixed with the
imidazolinium salt 7 (600 mg, 0.54 mmol, 1.2 equiv) and dried under
vacuum. After dissolving the mixture in toluene (20 mL) and degassing
(three times), KOtBu (91 mg, 0.81 mmol, 1.5 equiv) was added to deprot-
onate the imidazolinium salt. The reaction mixture was stirred at 508C
for 2 h. In between additional imidazolinium salt 7 (200 mg, 0.18 mmol,
0.4 equiv) and KOtBu (28 mg, 0.24 mmol, 0.6 equiv) were added after 1 h
reaction time. After evaporation of the solvent in vacuo, the remaining
brown foam was chromatographed on silica gel with cyclohexane/ethyl
acetate 10:1. The resulting pink solid is washed with degassed acetone
until the liquid remained colorless (4ꢃ20 mL). The crude Grubbs II com-
plex 8 (370 mg, 0.23 mmol, 51%) was obtained as a rose-colored fine
powder. Complex 8 was used as such, as substantial losses are experi-
enced during chromatographic purification. 1H NMR (500 MHz, CDCl3):
Continuous mode experiments: Quantitative analysis of reactants and
products were performed with a Varian 3400 gas chromatograph which
was equipped with a CP-Sil 8 CB column and a flame ionisation detector
(FID). The injector temperature was set at 2708C. The analysis was per-
formed by running a temperature programme with 1508C for 3 min and
subsequent heating to 2758C with a heating rate of 258C per minute.
Single organophilic nanofiltration: RCM of diethyl diallylmalonate,
0.1 mol% catalyst: Diethyl diallylmalonate (1.27 g, 5.29 mmol) was dis-
solved in toluene (200 mL) in a 250 mL Schlenk flask under argon. The
octacyclohexyl Grubbs–Hoveyda complex
9
(7.4 mg, 5.29 mmol,
0.1 mol%) was added and the reaction vessel was stirred at 408C for 3 h.
After cooling the reaction mixture to room temperature, the solution was
poured into the Millipore cell and the filtration process was started.
Nanofiltration: Membrane: GKSS PDMS 05/069 #KB55, flow:
1.67 mLminÀ1 (toluene), Dp 5 bar (argon), pre feed: 10 mL (5%), perme-
ate: 50 mL (25%), retentate: 140 mL (70%), yield (1,1-bis(ethylcarboxy-
late)-cyclopent-3-ene) >99% (GC), ruthenium in starting material:
421 ppm, Ruthenium in product <4 ppm (below detection level), Ruthe-
nium retention at the membrane >99%.
3
d 19.02 (s, 1H, CHbenzylidene), 8.98 (brs, 1H, CHo-styrene), 7.82 (t, J=7.6 Hz,
1H, CHp-styrene), 7.02 (brs, 2H, CHm-styrene), 6.70 (brs, 1H, CHo-styrene), 3.91–
3.58 (m, 12H, CH2-imidazoline, CH2-aryl), 2.78–1.92 (m, 26H, p-CH3-aryl,
o-CH3-aryl, CHcyclohexyl), 1.74–0.63 ppm (m, 113H, CH2-cyclohexyl, CH2-phosphine);
13C NMR (125 MHz, CDCl3): d = 293.1, 218.3 (d, C,PJ=95 Hz, NHC-C),
2964
www.chemeurj.org
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 2960 – 2965

Nanofiltration
FULL PAPER
Single organophilic nanofiltration: CM of allylbenzene, 0.2 mol% cata-
lyst: Allylbenzene (1.4 g, 11.9 mmol) was dissolved in toluene (200 mL)
in a 250 mL schlenk flask under argon. The octacyclohexyl Grubbs–Hov-
eyda complex 9 (33 mg, 24 mmol, 0.2 mol%) was added and the reaction
vessel was stirred at 408C for 3 h. After cooling the reaction mixture to
room temperature, the solution was poured into the Millipore cell and
the filtration process was started.
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Nanofiltration: Membrane: GKSS PDMS 05/069 #KB99, flow:
1.54 mLminÀ1 (toluene), Dp: 5 bar (argon), pre feed: 10 mL (5%), per-
meate: 50 mL (25%), retentate: 140 mL (70%), yield (1,4-diphenylbut-2-
ene) >99% (GC); E/Z ratio 5:1, ruthenium in starting material:
1710 ppm (mgkgÀ1), Ruthenium in product <4 ppm (below detection
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Single organophilic nanofiltration: RCM of N,N-diallyltosylamide,
0.5 mol% catalyst: N,N-Diallyltosylamide (1.2 g, 4.77 mmol) was dis-
solved in toluene (200 mL) in a 250 mL schlenk flask under argon. The
octacyclohexyl Grubbs–Hoveyda complex 9 (33 mg, 24 mmol, 0.5 mol%)
was added and the reaction vessel was stirred at 408C for 3 h. After cool-
ing the reaction mixture to room temperature, the solution was poured
into the Millipore cell and the filtration process was started.
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Nanofiltration: Membrane: GKSS PDMS 05/069 #KB101, flow:
1.44 mLminÀ1 (toluene), Dp: 5 bar (argon), pre feed: 10 mL (5%), per-
meate: 50 mL (25%), retentate: 140 mL (70%), yield (N-tosyl-2,5-dihy-
dro-1H-pyrrol) >99%, ruthenium in starting material: 2013 ppm
(mgkgÀ1), ruthenium in product <4 ppm (below detection level), rutheni-
um retention at the membrane >99.8%.
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General procedure for metathesis screen: Dry 25 mL Schlenk tube, argon
atmosphere, toluene (5 mL), 0.2 mmol substrate (diethyl diallylmalonate,
N,N-diallyltosylamide, allylbromide, allylbenzene, diethyl 2,2-bis(2-meth-
ylallyl)malonate, N,N-bis(2-methylallyl)tosylamide); 0.4 mmol substrate
(allyl alcohol, 2-methylallyl (3-methylbut-3-enyl) ether, diallyl ether, hex-
enyl acetate, methylacrylate, N,N-diallylethylcarbamate), catalyst was
added via toluene stock solution. Conversion determined via GC analysis
after terminating reaction with ethyl vinyl ether.
Acknowledgement
This work was supported by the BMBF project (01R/05111): “Organo-
phile Nanofiltration fꢁr die nachhaltige Produktion in der Industrie”. We
wish to thank the Evonik-Oxeno GmbH for a generous gift of MTBE.
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Received: October 17, 2008
Published online: February 5, 2009
Chem. Eur. J. 2009, 15, 2960 – 2965
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2965