New dipyridylamine ruthenium complexes for transfer hydrogenation of aryl ketones in water

Article abstract of DOI:10.1021/om100127f

A new family of cationic organometallic chloro compounds of the type [(arene)Ru(N,N)(Cl)]⁺ containing N,N-chelating dipyridylamine ligands has been synthesized and isolated as the chloride salts, which are water soluble and stable to hydrolysis. The resulting mononuclear ruthenium complexes catalyze the transfer hydrogenation of aryl ketones in aqueous solution to give the corresponding alcohols with good conversion and interesting recyclability.

Full text of DOI:10.1021/om100127f

1
992 Organometallics 2010, 29, 1992–1995
DOI: 10.1021/om100127f
New Dipyridylamine Ruthenium Complexes for Transfer Hydrogenation
of Aryl Ketones in Water
†
¨
Charles Romain, Sylvain Gaillard, Mohammed K. Elmkaddem, Loıc Toupet,
†
†
†
,
†
,‡
,§
C ꢀe dric Fischmeister,* Christophe M. Thomas,* and Jean-Luc Renaud*
†
‡
University of Rennes 1, UMR CNRS 6226, 35042 Rennes Cedex, France, Chimie ParisTech, UMR CNRS
§
223, 75005 Paris, France, and Laboratoire de Chimie Mol eꢀ culaire et Thioorganique, UMR CNRS 6507,
INC3M, FR 3038, ENSICAEN, University of Caen, 14050 Caen, France
7
Received February 16, 2010
Summary: A new family of cationic organometallic chloro
compounds of the type [(arene)Ru(N,N)(Cl)] containing N,
this technique follows from its operational simplicity and
reduction of the risks associated with the use of high pre-
ssures of an easily flammable gas of high diffusibility.
Furthermore, the donor and the acceptor are environmen-
tally friendly and are also easy to handle.
þ
N-chelating dipyridylamine ligands has been synthesized and
isolated as the chloride salts, which are water soluble and stable
to hydrolysis. The resulting mononuclear ruthenium complexes
catalyze the transfer hydrogenation of aryl ketones in aqueous
solution to give the corresponding alcohols with good conver-
sion and interesting recyclability.
There have been several attempts to develop active catalytic
systems for the transfer hydrogenation of ketones in aqueous
5-12
10
In this regard, Ogo and S u€ ss-Fink
8a,11,12
media.
have
recently reported transfer hydrogenation reactions of ketones
with sodium formate or formic acid, catalyzed in aqueous
2
þ
þ
Introduction
solution by [(arene)Ru(bipy)(OH2)] and related iridium(III)
2
0
complex or [(arene)Ru(phen)(OH2)] (bipy=2,2 -bipyridine,
phen = chelating 1,10-phenanthroline ligands). We have re-
cently investigated the synthesis and characterization of new
Environmental concerns in chemistry increase the demand
for more selective chemical processes with a minimum of
waste. For that reason, water-soluble organometallic com-
plexes attract continuously growing interest for applications
in catalysis, because of environmentally friendly processing,
simple product separation, and pH-dependent selectivity in
0
13
bidentate 2,2 -dipyridylamine ligands, which have shown
interesting coordination abilities for the synthesis of well-
14
defined Mg(II) and Zn(II) complexes. We envisaged that
some of these ligands (i.e., the less sterically encumbered) would
1
,2
aqueous media. Therefore, metal-catalyzed synthesis in
two-phase or even purely aqueous media has gained increas-
ing attention during the last decades with remarkable in-
dustrial success in CdC and CdO bond hydrogenation,
(
5) (a) Wu, X. F.; Li, X. G.; Hems, W.; King, F.; Xiao, J. Org. Biomol.
Chem. 2004, 2, 1818. (b) Li, X. G.; Wu, X. F.; Chen, W. P.; Hancock, F. E.;
King, F; Xiao, J. Org. Lett. 2004, 6, 3321. (c) Wu, X. F.; Li, X. G.; King, F.;
Xiao, J. Angew. Chem., Int. Ed. 2005, 44, 3407. (d) Wu, X. F.; Vinci, D.;
Ikariya, T.; Xiao, J. Chem. Commun. 2005, 4447. (e) Xiao, J.; Wu, X. F.;
Zanotti- Gerosa, A.; Hancock, F. Chim. Oggi-Chem. Today 2005, 23, 50.
f) Wu, X. F.; Li, X. H.; McConville, M.; Saidi, O.; Xiao, J. J. Mol. Catal. A:
Chem. 2006, 247, 153. (g) Wu, X. F.; Liu, J. K.; Li, X. H.; Zanotti-Gerosa, A.;
Hancock, F.; Vinci, D.; Ruan, J. W.; Xiao, J. Angew. Chem., Int. Ed. 2006,
1-3
alkene hydroformylation, and carbonylation reactions.
The reduction of carbonyl compounds to alcohols is an
industrially relevant reaction for the preparation of fine
(
3
b
chemicals, perfumes, agrochemicals, and pharmaceuticals.
Metal-catalyzed pathways to these kinds of alcohols include
4
2
5, 6718. (h) Li, X. H.; Blacker, J.; Houson, I.; Wu, X. F.; Xiao, J. Synlett
006, 1155.
H hydrogenation, hydrosilylation, or transfer hydrogena-
2
tion and use catalysts based on palladium, rhodium, iridium,
(
6) (a) Cortez, N. A.; Rodrı
Parra-Hake, M.; Cole, T.; Somanathan, R. Tetrahedron Lett. 2006, 47,
515. (b) Cortez, N. A.; Aguirre, G.; Parra-Hake, M.; Somanathan, R.
Tetrahedron Lett. 2007, 48, 4335.
7) (a) Li, L.; Wu, J.; Wang, F.; Liao, J.; Zhang, H.; Lian, C.; Zhu, J.;
´
guez-Apodaca, R.; Aguirre, G.;
3
b
and ruthenium. In particular, transfer hydrogenation has
emerged as a powerful, practical, and versatile tool for the
reduction of carbonyl compounds in which a substrate-
selective catalyst transfers hydrogen between the substrate
8
(
Deng, J. Green Chem. 2007, 9, 23. (b) Wu, J.; Wang, F.; Ma, Y.; Cui, X; Cun,
L.; Zhu, J.; Deng, J.; Yu, B. Chem. Commun. 2006, 1766.
(
8) (a) Canivet, J.; S u€ ss-Fink, G. Green Chem. 2007, 9, 391. (b) Zeror,
S.; Collin, J.; Fiaud, J.-C.; Aribi Zouioueche, L. Adv. Synth. Catal. 2008,
4
and a hydrogen donor or acceptor. The method is attractive
as an alternative to hydrogenation: the increasing success of
3
50, 197.
(9) Zeror, S.; Collin, J.; Fiaud, J.-C.; Zouioueche, L. A. J. Mol. Catal.
*Corresponding authors. (C.F.) E-mail: cedric.fischmeister@
univ-rennes1.fr. Fax: þ33(0)223236939. Tel: þ33(0)223235998. (C.M.T.)
E-mail: christophe-thomas@chimie-paristech.fr. Fax: þ33(0)143260061.
Tel: þ33(0)144276721. (J.-L.R.) E-mail: jean-luc.renaud@ensicaen.fr.
Fax: þ33(0)231452877. Tel: þ33(0)144276721.
2006, 256, 85.
(10) (a) Ogo, S.; Makihara, N.; Watanabe, Y. Organometallics 1999,
18, 5470. (b) Ogo, S.; Abura, T.; Watanabe, Y. Organometallics 2002, 21,
2964. (c) Ogo, S.; Uehara, K.; Abura, T.; Watanabe, Y.; Fukuzumi, S.
Organometallics 2004, 23, 3047.
(
1) Cornils, B.; Hermann, W. A. Aqueous-Phase Organometallic
Catalysis, 2nd ed.; Wiley-VCH, 2002.
(11) Canivet, J.; Labat, G.; Stoeckli-Evans, H.; S u€ ss-Fink, G. Eur. J.
Inorg. Chem. 2005, 4493.
(12) Canivet, J.; S u€ ss-Fink, G.; Stepnicka, P. Eur. J. Inorg. Chem.
(2) Lindstrom, U. M. Chem. Rev. 2002, 102, 2751.
(3) (a) Sinou, D. Adv. Synth. Catal. 2002, 344, 221. (b) Meyer, N.;
Lough, A. J.; Morris, R. H. Chem.;Eur. J. 2009, 15, 5605.
4) For recent reviews, see: (a) Ikariya, T.; Murata, K.; Noyori, R.
Org. Biomol. Chem. 2006, 4, 393. (b) Samec, J. S. M.; B €a ckvall, J. E.;
Andersson, P. G.; Brandt, P. Chem. Soc. Rev. 2006, 35, 237. (c) Gladiali, S.;
Alberico, E. Chem. Soc. Rev. 2006, 35, 226. (d) Clapham, S. E.; Hadzovic,
A.; Morris, R. H. Coord. Chem. Rev. 2004, 248, 2201.
2007, 4736.
(
(13) Elmkaddem, M. K.; Fischmeister, C.; Thomas, C. M.; Renaud,
J.-L. Chem. Commun. 2010, 46, 925.
(14) Zheng, Z.; Elmkaddem, M. K.; Fischmeister, C.; Roisnel, T.;
Thomas, C. M.; Carpentier, J.-F.; Renaud, J.-L. New J. Chem. 2008, 32,
2150.
pubs.acs.org/Organometallics
Published on Web 03/29/2010
r 2010 American Chemical Society

Note
Organometallics, Vol. 29, No. 8, 2010 1993
Scheme 1. Catalytic Reduction of Ketones
Table 1. Catalytic Activities of the Ru Compounds in the
a
Reduction of Acetophenone
b
entry
compound
conversion (%)
Figure 1. Synthesis of ruthenium compounds 2-5.
1
2
3
4
2
3
4
5
89
51
100
65
a
[
S]/[cat.] = 20, 65 °C, H
2
O, 24 h, HCO
2 2
H/HCO Na (5 equiv/
b
1
equiv). Determined by H NMR.
5
complex are very similar to those reported for related,
15
three-legged piano-stool ruthenium complexes. In particular,
˚
Ru-C distances fall within the range 2.169(3)-2.237(3) A. As
expected, the two amino groups of the N,N-ligand are in
12
equatorial positions, which is the more stable conformation.
Moreover, the central (secondary amine) N atom is nearly
planar.
Having isolated these complexes, we then carried out our
catalytic investigations in hydride transfer (Scheme 1). On
1
0,11
the basis of previous studies,
describing arene ruthenium
complexes containing bipyridine or phenantholine ligands
for the transfer hydrogenation of ketones with formic acid
and/or sodium formate as hydrogen donor source in water,
we have evaluated the catalytic potential of our complexes in
this reaction using acetophenone as a model substrate.
Considering the pH-dependence of the catalytic activity of
such complexes, we first studied the influence of the hydro-
gen donor ratio in the presence of catalyst 5.
6
Figure 2. Molecular structure of the cationic complex in [(η -
-
p-cymene)Ru(1)Cl]PF . The PF anion is omitted for clarity.
6
6
Best results were obtained at pH = 3.8 (i.e., pK of formic
a
have the potential to stabilize ruthenium(II) derivatives in
water. Herein we report the initial results of our studies on a
series of water-soluble arene ruthenium complexes containing
an N,N-chelating 2,2 -dipyridylamine ligand. We also describe
the catalytic activity and the recycling of these complexes in the
transfer hydrogenation of aromatic ketones.
acid) for an equimolar ratio of HCO H/HCO Na (5 equiv of
2
2
5
each compared to the substrate). Under these conditions,
the secondary alcohol was obtained in 65% yield within 24 h
0
(entry 4, Table 1). A decrease of the amount of HCO H/
HCO Na to 2.5 equiv of formic acid and 2.5 of formate led to
2
2
a decrease of the catalytic activity, and the alcohol was
obtained in 14% yield. The use of 10 equiv of formic acid
or sodium formate led to lower reactivity (11% and 3%,
respectively). Consequently, a buffer solution with 5 equiv of
formic acid and sodium formate has been prepared to
evaluate the catalytic activities of the complexes previously
synthesized.
Results and Discussion
0
Our attention was drawn to the 2,2 -dipyridylamine ligand
(Figure 1), which was supposed to be more hydrophilic
1
than the archetypical bypy or phen ligands. The dimeric
arene ruthenium complexes [(arene)RuCl ] (arene = benzene,
2
2
As showed in Table 1, all the chloro complexes 2-5 were
found to catalyze transfer hydrogenation of acetophenone in
aqueous solution; however the reactivity depends on the
nature of the ancillary arene ligand. In the presence of 5%
of catalyst 4, the reduction of acetophenone in phenylethanol
is complete within 24 h, whereas with the other catalysts the
yields are lower (entries 1-4, Table 1). As previously des-
cribed by S u€ ss-Fink, the catalytic activity is dependent on the
arene. However, in contrast to his results, it is worth
noticing that the conversion with hexamethylbenzene did
not provide the best result. In our case, p-cymene as arene
seems to be the best compromise between steric effects and
electron density on the ruthenium. Even with only 1% of
catalyst 4, the catalytic activity is maintained and the secondary
mesitylene, p-cymene, hexamethylbenzene) react at 50 °C in
methanol with the N,N-donor ligand 1 to give the expected
cationic chloro complexes [(arene)Ru(1)Cl]Cl (2-5) as the
only product in good yields ranging from 72% to 87%.
All the complexes, which were isolated as chloride salts,
are water soluble and air stable. They have been characteri-
1
13
zed by H, C NMR and HRMS. The NMR spectra reveal
symmetrical structures that prove no coordination from the
bridging nitrogen atom and only the coordination of the two
pyridyl moieties. Suitable crystals for X-ray analysis were
obtained for the analogous hexafluorophosphate salt of
compound 4. The molecular structure of the cationic
8
a
6
þ
complex [(η -p-cymene)Ru(1)Cl] is depicted in Figure 2.
The structure of the cation consists of a pseudotetrahedral
arrangement of a ruthenium atom coordinated to the
p-cymene ligand, the two nitrogen atoms of the N,N-ligand,
and a chlorine atom. The bond lengths for this cationic
(
15) Therrien, B.; Ward, T. R.; Pilkington, M.; Hoffmann, C.;
Gilardoni, F.; Weber, J. Organometallics 1998, 17, 330.

1
994 Organometallics, Vol. 29, No. 8, 2010
Romain et al.
a
Table 2. Reduction of Several Ketones Catalyzed by 4 via
a
Hydride Transfer
Table 3. Recycling of Catalyst 4
HCO H/HCO Na
b
entry
run
2
2
conversion (%)
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
1
2
3
4
5
6
5/5 (starting conditions)
0.5/0.5
0.5/0.5
0.5/0.5
0.5/0.5
5/5
5/5 (starting conditions)
0/0
0/0
0/0
0/0
5/5
97
90
43
43
36
86
97
45
15
7
1
1
1
0
1
2
5
5
a
b
O, 24 h. Determined by GC.
[
S]/[cat.] = 20, 65 °C, H
2
a
[
equiv). Determined by H NMR.
2 2 2
S]/[cat.] = 20, 65 °C, H O, 24 h, HCO H/HCO Na (5 equiv/
b
1
5
alcohol is produced in quantitative yield within 24 h (TON =
00). In order to determine the potential applicability of
1
this catalytic system, we then extended the reaction to a wider
range of aromatic ketones. Whatever the substituent on the
aromatic ring (electron-donating or -withdrawing on ortho
and/or para position), the conversion and the isolated yields
were good (entries 1-6, Table 2). However, it is worth
mentioning that with 4-bromobenzophenone some trace of
reduction of the C-Br bond was also observed in the reaction
conditions.
2
Figure 3. Recycling of catalyst 4. [S]/[cat.] = 20, 65 °C, H O,
Having demonstrated the potential of these new com-
plexes in the reduction of acetophenone, we envisioned to
24 h. Conversion determined by GC.
2þ
HCO H/5 equiv HCO Na) restored the conversion obtained
2 2
prepare the aqua complexes [(arene)Ru(1)(H O)] (isolated
2
in the second run. This result demonstrated that the catalytic
system remains active after several runs, but its activity
depends on the amount of hydrogen donor source in solution
and needs to be adjusted before a new reaction. The lower
hydrogen concentration after each run might be explained by
the consumption of more than 1 equiv of hydrogen donor
during the reaction. Indeed, in aqueous phase, it is known
that such a catalytic system can transform formic acid or
as tetrafluoroborate or chloride salts) in order to increase the
activity of our ruthenium catalysts and to compare their
catalytic activity to the corresponding chloro complexes
þ
[
(arene)Ru(1)(Cl)] in the transfer hydrogenation of aceto-
phenone in water. Both complexes were soluble in water in
our previous conditions and found to have catalytic activities
for this reaction. However, no noticeable difference was
observed between the chloro complexes and the corres-
ponding aqua complexes, which seems to indicate that the
same active catalytic species is involved in this reaction (i.e.,
presumably a hydride complex).
An important goal of this work was to study the recycl-
ability of our ruthenium catalysts. Indeed, due to the high
solubility and stability of the precatalytic species in water,
separation and recycling should be easy to perform. Thus, at
the end of the reduction, diethyl ether could be added to
extract the organic compounds and the ruthenium complex
immobilized in the water phase reused directly. For this
purpose, two different sequences for recycling have been
carried out: a first set of experiments (entries 1-6, Table 3)
for which donor hydrogen sources were added at the end of
each run, and a second one (entries 7-12, Table 3) without
addition of donor hydrogen source. In both cases, recycling
is possible. However, the catalytic activity decreased run
after run, even if the drop is less important by adding
1
0,11
formate into CO and H .
2
The dramatically decreasing
2
catalytic activity observed in the second series (entries 7-12,
Table 3) shows again the crucial importance of the amount of
hydrogen donor. During the third run (entry 9) the solution
turned from yellow to green, indicating an evolution of
the catalytic species such as a decoordination of at least
one of the ligands and then formation of a nonreactive
intermediate. The last entry of the table provided evidence
of the decomposition of the catalyst, as the addition of
hydrogen donor does not lead to any conversion (entry 12,
Table 3).
In conclusion, we have synthesized several (arene)Ru-
dipyridylamine) complexes that are interesting catalysts
(
for the transfer hydrogenation of aromatic ketones in water.
Moreover, we also demonstrated that such complexes could
be reused several times. We will then proceed to the extension
of this methodology to chiral auxiliaries, in order to develop
a library of ruthenium-based complexes for enantioselective
catalysis.
0.5 equiv of formic acid and formate at the end of the
reaction (Figure 3).
However, in the two series of experiments, the reason for
this decrease is different. In the first series, the decrease could
be explained by a diminution of the quantity of the hydrogen
donor source. Indeed, after the fifth run, the addition of a
donor hydrogen source (an equimolar ratio of 5 equiv
Experimental Section
General Procedures. All experiments were carried out in an
inert atmosphere using standard Schlenk techniques and freshly
distilled solvents. The starting materials [(arene)RuCl ] and the
2 2

Note
Organometallics, Vol. 29, No. 8, 2010 1995
1
6,17
ligand 1 were prepared according to the published methods.
141.7 (d), 154.6 (s), 155.4 (d). HRMS (ESI): m/z 470.0935
[C22
þ
All other reagents were commercially available and were used
without further purification. NMR spectra were recorded on an
ARX Bruker 400 MHz spectrometer using solvent residual peak
as locking agent. Electro-spray mass spectra were obtained on a
Micromass ZABSpecTOF spectrometer.
H27ClN
3
Ru] .
Transfer Hydrogenation Catalysis with Acetophenone. Trans-
fer hydrogenation reactions of acetophenone (0.50 mmol) using
2-5 (0.025 mmol) were carried out under inert atmosphere in
water (4 mL) using a buffer of HCOOH (2.5 mmol) and
HCOONa (2.5 mmol) as hydrogen donor source. The products
Preparation of the Arene Ruthenium Compounds [(arene)Ru-
1)Cl]Cl (arene = C
(
6
H
6
, mesitylene, p-cymene, C
6
Me
6
). Ligand
(2 equiv, 0.10 mmol) was added to a suspension of [(arene)-
2
were extracted by Et O and identified by gas chromatography.
1
Transfer Hydrogenation Catalysis. Transfer hydrogenation
reactions of the appropriate ketones (0.50 mmol) using 4 (0.025
mmol) were carried out under inert atmosphere in water (4 mL)
using a buffer of HCOOH (2.5 mmol) and HCOONa (2.5 mmol)
RuCl2]2 (0.05 mmol) in methanol (5 mL). The mixture was
stirred overnight at 50 °C. After evaporation to dryness, the
residue was washed with ether (3 ꢀ 2 mL) to give the expected
product in 72-87% yields.
as hydrogen donor source. The products were extracted by
Et O, and conversions were calculated by H NMR from the
1
1
[
CD
(C H )Ru(1)Cl]Cl (2). Yield: 72%. H NMR (400 MHz, δ,
6
6
2
3
OD): 5.85 (s, 6H), 7.18-7.22 (m, 2H), 7.25 (dq, J = 0.6 Hz,
crude product. After purification by column chromatography
using silica gel and ethyl acetate/cyclohexane (80/20) as eluant,
the isolated products were identified by H NMR.
8
2
.4 Hz, 2H), 7.91-7.95 (m, 2H), 8.72 (ddd, J = 5.9, 1.7, 0.5 Hz,
13
1
H), NH not observed. C NMR (100 MHz, δ, CD
3
OD): 88.1
1
(
(
d), 115.0 (d), 120.7 (d), 141.9 (d), 154.9 (s), 155.8 (d). HRMS
ESI): m/z 386.0001 [C16
1-p-Tolylethanol. H NMR (400 MHz, δ, CDCl ): 1.49 (d,
3
þ
H15ClN
3
Ru] .
(mesitylene)Ru(1)Cl]Cl (3). Yield: 80%. H NMR (400 MHz,
J = 6.5 Hz, 3H), 2.35 (s, 3H), 4.88 (dq, J = 6.5, 2.7 Hz, 1H), 7.17
(d, J = 2.7 Hz, 2H), 7.27 (d, J = 2.7 Hz, 2H).
1
[
1
δ, CD OD): 1.82 (s, 9H), 5.26 (s, 3H), 7.22-7.28 (m, 4H), 7.94
ddd, J = 8.4, 7.3, 1.7 Hz, 2H), 8.60 (ddd, J = 5.9, 1.7, 0.6 Hz,
1-(4-Methoxyphenyl)ethanol. H NMR (400 MHz, δ, CDCl ):
3
3
(
2
1.35 (d, J = 6.5 Hz, 3H), 3.69 (s, 3H), 4.71 (q, J = 6.4 Hz, 1H),
6.77 (d, J = 8.4 Hz, 2H), 7.17 (d, J = 8.4 Hz, 2H).
1
3
H), NH not observed. C NMR (100 MHz, δ, CD
q), 78.3 (d), 109.2 (s), 114.9 (d), 121.3 (d), 141.6 (d), 154.9 (s),
3
OD): 18.5
1
(
1
1-Naphthylethanol. H NMR (400 MHz, δ, CDCl
3
): 1.57 (d,
þ
55.4 (d). HRMS (ESI): m/z 428.0455 [C H ClN Ru] .
1
[
J = 6.5 Hz, 3H), 5.02 (q, J = 6.5 Hz, 1H), 7.53-7.46 (m, 3H),
9
1
21
3
( p-cymene)Ru(1)Cl]Cl (4). Yield: 87%. H NMR (400 MHz,
δ, CD OD): 1.23 (d, J = 6.9 Hz, 6H), 2.10 (s, 3H), 2.62 (hept,
J = 6.9 Hz, 1H), 5.57 (d, J = 6.3 Hz, 2H), 5.67 (d, J = 6.3 Hz,
7.77-7.86 (m, 4H).
1
3
1-(2-methoxyphenyl)ethanol. H NMR (400 MHz, δ, CDCl
3
):
1.40 (d, J = 6.6 Hz, 3H), 3.74 (s, 3H), 5.00 (q, J = 6.5, 1H), 6.77
(dd, J = 8.2, 0.8 Hz, 1H), 6.86 (dt, J = 7.5, 1.1 Hz, 1H),
7.17-7.12 (m, 1H), 7.25 (dd, J = 7.5, 1.1 Hz, 1H).
2
1
H), 7.19-7.23 (m, 4H), 7.91-7.95 (m, 2H), 8.63 (ddd, J = 5.9,
13
.7, 0.8 Hz, 2H), NH not observed. C NMR (100 MHz, δ,
): 18.4 (d), 22.4 (q), 32.2 (q), 85.3 (d), 86.9 (d), 101.4 (s),
08.1 (s), 115.1 (d), 120.7 (d), 141.8 (d), 154.5 (s), 155.8 (d).
CDCl
3
1
Acknowledgment. We are grateful to the Agence Na-
tionale pour la Recherche (ANR) for grant “Jeunes
Chercheurs-Jeunes Chercheuses” (ANR-06-JCJC-0013),
the ENSCP, the CNRS, and the French Ministry of
Higher Education and Research for financial support.
þ
HRMS (ESI): m/z 442.0621 [C H ClN Ru þ K] .
2
0
23
3
1
[
(C
CD OD): 1.92 (s, 18H), 7.23-7.29 (m, 4H), 7.91-7.96 (m, 2H),
.33 (ddd, J = 5.9, 1.7, 0.6 Hz, 2H), NH not observed. C NMR
100 MHz, δ, CD OD): 15.7 (q), 95.9 (s), 115.1 (d), 121.6 (d),
6 6
Me )Ru(1a)Cl]Cl (5). Yield: 81%. H NMR (400 MHz, δ,
3
1
3
8
(
3
Supporting Information Available: Crystallographic data for
(16) Bennet, M. A. Coord. Chem. Rev. 1997, 166, 225.
(17) Gaillard, S.; Elmkaddem, M. K.; Fischmeister, C.; Thomas,
6
[
(η -p-cymene)Ru(1)Cl]PF as a CIF file. This material is avail-
6
C. M.; Renaud, J.-L. Tetrahedron Lett. 2008, 49, 3471.
able free of charge via the Internet at http://pubs.acs.org.