S. P. Nolan, C. Slugovc et al.
(CH), 127.2 (CH), 126.7 (2 CH), 124.5 (4 CH), 124.6 (CH), 123.9 (2 CH),
volume) originate from a species faster than 6. It is notewor-
thy that each fraction exhibits an ideally narrow weight dis-
tribution with a PDI value smaller than 1.1.
At the moment we can only speculate about the nature
and the origin of this second active species. We believe that
a fast decomposition of initiator leads to a yet unknown but
highly active initiator species. To elucidate this phenomen-
on, the chemistry behind the bimodal molecular-weight dis-
tributions is further being investigated.
117.5 (CH), 55.5
N
ACHTUNGTREN(NUGN 3CH), 28.8 (CH), 28.0 (CH3),
27.5 (CH3), 26.8 (CH3), 26.6AHCTNUGTRENNNUG
21.9 ppm (CH3); elemental analysis calcd (%) for C47H53N3Cl2Ru
(831.27): C 67.86, H 6.42, N 5.05; found: C 67.85, H 6.23, N 5.18.
A
R
ACHTUNGTREN(NUNG 3-BrPy)(3-phenylinden-1-ylidene)] (7): In a glovebox, com-
5
(1.00 g, 0.97 mmol) was dissolved in 3-bromopyridine (1 mL,
12.4 mmol, 12.8 equiv) the mixture was stirred for 30 min and then fol-
lowed by addition of pentane (20 mL). The mixture was then place inside
the freezer at À408C overnight, after which an orange precipitate was
formed. The solid was filtered and washed with pentane (2ꢃ10 mL), thus
affording the ruthenium complex 6 as a orange microcrystalline solid
(0.65 g, 73%). 1H NMR (300 MHz, CD2Cl2): d=8.07 (d, J=2.0 Hz, 1H;
HAr), 7.97 (d, J=7.3 Hz, 1H; HInd), 7.47–7.69 (m, 6H; HAr), 7.28–7.47 (m,
5H; HAr), 7.14–7.27 (m, 1H; HAr), 7.05 (d, J=7.0 Hz, 1H; HAr), 6.91 (t,
J=7.5 Hz, 1H; HAr), 6.72–6.85 (m, 3H; HAr), 6.46–6.59 (m, 1H; HAr),
5.75 (s, 1H; HAr), 4.66 (brs, 1H; CH), 4.52 (brs, 1H; CH2), 4.20 (brs,
2H; CH2), 3.94 (brs, 1H; CH2), 3.81 (brs, 1H; CH), 3.34 (brs, 1H; CH),
2.58 (brs, 1H; CH), 1.66 (brs, 3H; CH3), 1.54 (brs, 3H; CH3), 1.08–1.45
(m, 12H), 0.73–0.99 (m, 3H; CH3), 0.50 ppm (brs, 3H; CH3); 13C NMR
(75.5 MHz, CD2Cl2): d=302.0 (C), 214.8 (C), 153.6 (CH), 152.3 (CH),
151.3(C), 150.3(C), 147.8(C), 147.2(C), 142.2 (C), 141.6 (C), 140.9 (C),
139.9 (2 CH), 137.0 (2 C), 135.5 (C), 130.6 (CH), 129.9 (2 CH), 129.4
(CH), 129.0 (2 CH), 128.3 (CH), 127.3 (CH), 126.8 (2 CH), 124.9 (CH),
124.6 (4 CH), 119.4 (C), 117.6 (CH), 55.5 (CH2), 54.3 (CH2), 30.1 (2 CH),
28.8 (CH), 28.0 (CH3), 27.6 (CH3 + CH), 26.7 (2 CH3), 24.3 (CH3), 23.0
(2 CH3), 21.9 ppm (CH3); elemental analysis calcd (%) for
C47H52BrCl2N3Ru (910. 82): C 61.98, H 5.75, N 4.61; found: C 61.61, H
5.60, N 4.34.
Conclusion
The synthesis of two new complexes, [RuCl
2ACHUTGTNREN(NUG SIPr)(Py)ACHTUNGTNER(NUGN Ind)]
(6) and [RuCl2A(SIPr)(3-BrPy)(Ind)] (7), has been described.
C
R
ACHTUNGTRENNUNG
These were shown to be highly active olefin metathesis cata-
lysts even at room temperature and low catalyst loading.
These characteristics make them excellent choices for the
synthesis of low hindered olefins by ring closing enyne and
cross metathesis. As for ROMP, initiators bearing a SIPr-
NHC ligand show distinctly different behavior in ROMP
than their SIMes analogues. Most striking, complex 5, which
contains the SIPr ligand, significantly outperforms 3 and
shows equal initiation rates as pyridine adducts 4, 6, and 7.
However, the propagating species turned out to be slower
with the SIPr complexes, presumably because of steric hin-
drance. Bimodal, yet well-defined weight distributions were
observed for all SIPr initiators. Further investigations in that
matter are currently being carried out.
General procedure for RCM reactions at high catalyst loading:
A
Schlenk flask was charged under nitrogen with the substrate (0.5 mmol)
and dry dichloromethane (5 mL, c=0.1m), then catalyst (5ꢃ10À6 mol)
was added. The reaction mixture was magnetically stirred at room tem-
perature and the progress of the reaction was monitored by TLC. After
completion of the reaction, the volatiles were removed under vacuum
and the crude 1H NMR of the reactions was analyzed. The crude residue
was purified by flash column chromatography (pentane/ether 9:1) to
yield the pure product.
Experimental Section
General procedure for RCM reactions at low catalyst loading: Inside the
glovebox stock solutions of substrate 2.5 mmol/1 mL and catalyst
0.025 mmol/4 mL in CH2Cl2 were prepared. An aliquot of 100 mL of sub-
strate was then measured into a 4 mL vial, then a volume of CH2Cl2 re-
quired to reach concentration of 0.5m was added, followed with a corre-
sponding aliquot of the catalyst to reach the desired catalyst loading. The
reaction was stirred for 1 h and 1H NMR of the reaction mixture was re-
corded to determine conversion. The crude residue was purified by flash
column chromatography (pentane/ether 9:1) to yield the pure product.
General considerations: All reagents were used as received. Dichloro-
ACHTUNGTRENNUNGmethane was dispensed from a solvent-purification system from Innova-
tive Technology. Catalyst syntheses were performed in a MBraun glove-
box containing dry argon and less than 1 ppm oxygen. 1H, 31P, and
13C NMR spectra were recorded on a Bruker Avance 300 or Bruker
Avance II 400 Ultrashield NMR spectrometers. Complexes 3 and 4 are
commercially available from Umicore AG or Strem Chemicals Inc. Com-
plexes 1,[21] 5,[8b] and substrates and products 8–16,[10a] 17,[22] 18,[15] 19,[23]
20,[4c] and 21[4c] have previously been described in the literature.
Typical procedure for a ROMP reaction: Catalyst (2–3 mg) was weighed
into a Schlenk flask and dissolved in a measured amount of dry and
freshly degassed CH2Cl2. The monomer (300 equiv) was weighed into a
vial and dissolved in the missing amount of solvent to reach a concentra-
tion of 0.2 mol/L with respect to monomer. The solution is then quickly
transferred to the stirred catalyst solution using a pipette. The reaction is
monitored by TLC (cyclohexane/EtOAc 3:1) with KMnO4 as staining
agent. After completion the reaction is quenched with excess ethylvinyl-
ACHTUNGTRENNUNG[RuCl2ACHTUNGTRENNUNG(SIPr)(Py)(3-phenylinden-1-ylidene)] (6): In a glovebox, complex
5, (2 g, 1.96 mmol) was dissolved in a minimum volume of pyridine
(ca. 2 mL). The mixture was stirred 30 min at room temperature before
adding pentane (50 mL). The mixture was again stirred 30 min at room
temperature before cooling at À408C overnight. The resulting precipitate
was filtered on a collection frit, washed with pentane (3 X 10 mL), and
dried under vacuum to yield a dark-red solid. (1.30 g, 81% yield).
1H NMR (CD2Cl2,400 MHz): d=7.99 (d, J=7.0 Hz, 1H; Hind), 7.78–7.83
(m, 2H; HAr), 7.46–7.66 (m, 6H; HAr), 7.30–7.45 (m, 5H; HAr), 7.20 (td,
J=7.4, 1.1 Hz, 1H; HAr), 7.06 (d, J=7.0 Hz, 1H; HAr), 6.98–7.03 (m, 2H;
HAr), 6.84–6.94 (m, 1H; HAr), 6.81 (brs, 2H; HAr), 6.49–6.57 (m, 1H;
AHCTUNGERTGeNNUN ther and stirred for another 15 min. The solvent amount is reduced to
approximately 2 mL before the mixture is added to cold methanol. The
polymer is collected by filtration and dried on the vacuum line.
Reaction profiling for ROMP using NMR spectroscopy: Standard experi-
ments contained initiator/monomer (1:50) and solvent in a concentration
of 0.1m with respect the monomer. Monomer Mon2 (ca. 20 mg) was
weighed into a NMR tube that was then evacuated and purged with
argon. The monomer was dissolved in freshly degassed CDCl3 (400 mL).
To minimize errors (balance, complete transfer of solution), double the
appropriate amount of catalyst needed to reach a 1:50 ratio was weighed
into a vial, placed under argon, and dissolved in twice the amount of sol-
vent required to reach an overall monomer concentration of 0.1m. Half
of the solution was quickly transferred into the NMR tube using a micro-
HAr), 5.79 (s, 1H; HAr), 4.68–4.81 (m, 1H; CHSIPr), 4.55 (brs, 1H;
SIPr
CH2SIPr), 4.19 (brs, 2H; CH2SIPr), 3.95 (brs, 2H; CH2
+ CHSIPr), 3.85
(brs, 1H; CHSIPr), 3.67–3.74 (m, 1H; CHSIPr), 3.21–3.44 (m, 1H; CHSIPr),
2.57 (brs, 1H; CHSIPr), 1.68 (d, J=5.1 Hz, 3H; CH3SIPr), 1.54 (d, J=
5.3 Hz, 3H; CH3SIPr), 1.14–1.41 (m, 12H; CH3SIPr), 0.82–1.02 (m, 3H;
CH3SIPr), 0.46–0.59 ppm (m, 3H; CH3SIPr); 13C NMR (75.5 MHz, CD2Cl2):
d=301.5(C) 216.1 (C), 153.3 (2 CH), 151.2 (C), 150.2 (C), 150.1 (C),
147.7 (C), 147.2 (C), 142.0 (C), 141.8 (C) 140.9(C), 139.7 (CH), 137.3
(CH), 137.3 (C), 135.8 (C), 130.4 (CH), 129.8 (CH), 129.7 (2 CH), 128.8
5052
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 5045 – 5053