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(376.50 MHz, CD2Cl2): d=À78.9 ppm; IR (KBr): n˜ =3452 (b), 3107
(m), 3046 (m), 2960 (m), 2913 (m), 2850 (m), 1946 (m), 1722 (m),
1637 (s), 1571 (m), 1479 (m), 1398 (m), 1301 (m), 1257 (s), 1138 (m),
1091 (m), 1026 (s), 926 (m), 852 (m), 795 (m), 769 (m), 681 (m), 638
(vs), 571 (s), 515 (s), 467 (m), 420 cmÀ1 (m); elemental analysis (%)
calcd. for C47H53F6N4O11RuS2 (Mr =1129.13 gmolÀ1): C 50.00, H 4.73,
N 4.98; found: C 49.98, H 4.75, N 5.16.
Ru measurements
The Ru content was measured by inductively coupled plasma opti-
cal emission spectroscopy (ICP-OES, l=240.272 nm, ion line, back
ground lines at l1 =240.254 nm and l2 =240.295 nm) using a Spec-
tro Arcos device (Ametek GmbH; Meerbusch, Germany). Standardi-
zation 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 the
product fraction was determined by dissolving 100 mg samples in
aqua regia.
Synthesis
of
[RuCl[(4-CO2)(1-CH3)Py+)](IMesH2)(=CH-2-(2-PrO)-
C6H4)][OTfÀ] (2): A solution of [RuCl(CF3SO3)(IMesH2)(=CH-2-(2-PrO)-
C6H4)] (200 mg, 0.27 mmol) in CH2Cl2 (5 mL) was quickly added to
a suspension of [(1-CH3)(4-CO2K)Py+][BF4À] (71 mg, 0.27 mmol) in
CH2Cl2 (15 mL). A color change from green to red was observed
and stirring was continued for 1 h at RT. The precipitate was re-
moved by filtering the reaction mixture through a pad of celite.
After solvent removal, 2 was obtained as a red powder, which was
redissolved in CH2Cl2 (3 mL) and precipitated in diethyl ether
(15 mL). Yield: 210 mg, 0.24 mmol, 89%. 1H NMR (400.13 MHz,
CD2Cl2): d=17.18 (s, 1H), 8.79 (d, J=6.5 Hz, 2H), 8.02 (d, J=6.7 Hz,
2H), 7.47–7.42 (m, 1H), 7.24 (s, 2H), 7.07 (s, 2H), 7.06–7.02 (m, 1H),
6.99–6.93 (m, 1H), 6.73 (d, J=8.3 Hz, 1H), 4.78–4.69 (m, 1H), 4.47
(s, 3H), 4.16–4.08 (m, 4H), 2.55 (s, 6H), 2.49 (s, 6H), 2.12 (s, 6H),
1.30 (d, J=6.1 Hz, 3H), 0.91 ppm (d, J=6.1 Hz, 3H); 13C NMR
(100.61 MHz, CD2Cl2): d=304.4, 208.7, 162.6, 151.9, 147.1, 144.6,
142.8, 138.7, 138.0, 136.5, 134.6, 130.3, 129.1, 128.9, 128.6, 126.5,
126.3, 121.8, 121.5, 112.3, 111.5, 73.9, 50.7, 47.9, 29.3, 20.1, 20.0,
18.1, 17.6 ppm; 19F NMR (376.50 MHz, CD2Cl2): d=À79.0 ppm; IR
(KBr): n˜ =3417 (vb), 2955 (m), 29113 (m), 2846 (m), 2353 (vs), 1643
(vs), 1574 (m), 1471 (s), 1381 (m), 1319 (m), 1265 (vs), 1149 (s), 1097
(m), 1026 (s), 926 (m), 845 (m), 791 (m), 665 (m), 633 (s), 571 cmÀ1
(m); elemental analysis (%) calcd. for C39H45F3N3O6RuS (Mr =
877.37 gmolÀ1): C 53.39, H 5.17, N 4.79; found: C 53.59, H 5.17, N
4.77.
Results and Discussion
Catalyst Preparation
As outlined above, the primary objective was to create an ioni-
cally tagged, Ru–alkylidene complex for metathesis reactions
under biphasic conditions, which would retain the ionic charge
throughout the entire metathesis reaction and be more active
at lower temperatures towards substrates bearing coordinating
functionalities than [Ru(DMF)3(IMesH2)(=CH-2-(2-PrO)-C6H4)2+
][(BF4 )2].[24,27] Such an ionically tagged metathesis catalyst
À
would selectively dissolve in an ionic liquid but not in the
second non-polar liquid transport phase, e.g., heptane, which
should allow for low metal contamination of the products. For
this purpose, the bis-ionically tagged catalyst [Ru[(4-CO2)(1-
CH3)Py+)]2(IMesH2)(=CH-2-(2-PrO)-C6H4)][OTfÀ]2 (1) was pre-
pared in 82% isolated yield and was obtained as a red solid by
adding two equivalents of [(1-CH3)(4-CO2K)Py+][BF4 ] to the
À
modified Grubbs–Hoveyda type catalyst [Ru(CF3SO3)2(IMesH2)(=
CH-2-(2-PrO)-C6H4)] (Scheme 1). Typically, silver salts were used
to replace the chlorides in the Grubbs-Hoveyda type complex
[RuCl2(IMesH2)(=CH-2-(2-PrO)-C6H4)] by the desired ligands. As
the very poor solubility of the pyridinium salt used in the syn-
thesis described herein did not allow for the preparation of
highly pure silver salts, we decided to use the corresponding
potassium salts to substitute the more weakly bound triflate li-
gands in the complex [Ru(CF3SO3)2(IMesH2)(=CH-2-(2-PrO)-
C6H4)] instead (Scheme 1).
Metathesis under biphasic conditions
1 (2.5 mg, 2.2 mmol) was dissolved in 1-butyl-2,3-dimethylimidazoli-
um tetrafluoroborate, [BDMIM+][BF4À], (200 mg) and the solution
was heated to 408C. Then a solution of the substrate (0.1–
4.4 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 ionic-liquid phase was extracted extensively with diethyl
ether (3ꢁ1 mL; stirring for 20 min at 600 rpm). The organic phases
were combined and subjected to GC–MS analysis to determine
conversion.
In an analogous manner, the ionic monocarboxylato mono-
chloro Ru–alkylidene [RuCl[(4-CO2)(1-CH3)Py+)](IMesH2)(=CH-
2-(2-PrO)-C6H4)][OTfÀ] (2) was prepared in 89% isolated yield
by adding one equivalent of [(1-CH3)(4-CO2K)Py+][BF4 ] to
À
[RuCl(CF3SO3)(IMesH2)(=CH-2-(2-PrO)-C6H4)] (Scheme 1). This
catalyst 2 can be expected to be more active than the bis-
ionic Ru–alkylidene 1. Thus, compared to the pyridinium car-
boxylate ligand, the chloride is more electron withdrawing and
should therefore lead to a more polarized Ru=C bond than in
1. The absence of a signal for BF4À in the 19F NMR spectrum im-
Metathesis under biphasic conditions using monolith--
supported ionic liquids
Metathesis reactions under supported ionic liquid phase (SILP) con-
ditions were performed under air, comparable to a method pub-
lished earlier.[24] The loaded monolithic support was placed inside
a Merck l-5025 column thermostat and warmed to 458C. Using
a syringe pump (WPT, Aladdin-1000), the substrate (1,7-octadiene
and methyl oleate as neat reactants) was flushed through the
monolith at a flow rate of 0.1 mLminÀ1. The eluent was collected
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 thus cleaned monolithic support was
again recharged with catalyst dissolved in [BDMIM+][BF4À] and
used for further catalysis.
À
plies its substitution by the triflate (OTfÀ, CF3SO3 ) ligand,
which now acts as the counter ion. Thus, solely the signal for
OTfÀ was observed, whereas BF4 was detected in the precipi-
À
tate of KBF4 that formed during the reaction in CH2Cl2. After re-
moval of the potassium tetrafluoroborate, the product was
precipitated in diethyl ether. The fact that complex 2 was ob-
tained as a pure compound is remarkable because monocar-
boxylato-monochloro-Ru–alkylidenes are known to undergo
fast ligand scrambling, and thereby disproportionate into the
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