Snapshot of a chelation-assisted C-H/alkyne coupling: A ruthenium complex caught in the act of C-C bond formation

Article abstract of DOI:10.1021/om7005003

The complex Ru(CO)₂(PPh₃ )₂ (1) reacts with o-(diphenylphosphanyl)benzaldehyde within 2 min at 20 °C to give the hydrido acyl complex Ru(H){P(C₆H₅ )₂ (C ₂ H₄ )C(O))(CO)₂ (PPh₂ ) (2) via selective activation of the C-H bond of the aldehyde function. Further addition of diphenylacetylene (110 °C, 3 h) affords the novel complex Ru{P(C ₆ H₅ )₂ (C₆ H₄ )C(O)(C₆ H₅ )C==CH(C₆H₅ )}(CO){P(C₆ H₅ )₃ } (3), incorporating the newly assembled o-(diphenylphosphanyl)phenyl (E)-stilbenyl ketone ligand. The α,β-unsaturated ketone moiety of the latter is bound to the metal in an η⁴ coordination mode involving both a side-on coordination of the carbonyl group and a more classical η² linkage of the olefinic bond. Both complexes were fully characterized by spectroscopic methods and by X-ray diffraction. The whole reaction sequence provides a valuable experimental model for the chelation-assisted hydroacylation of an alkyne with a tethered aldehyde.

Full text of DOI:10.1021/om7005003

Organometallics 2007, 26, 4673-4676
4673
Snapshot of a Chelation-Assisted C-H/Alkyne Coupling: A
Ruthenium Complex Caught in the Act of C-C Bond Formation
Laure Benhamou, Vincent Ce´sar, Noe¨l Lugan, and Guy Lavigne*
Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne, 31077 Toulouse Cedex, France
ReceiVed May 21, 2007
The complex Ru(CO)2(PPh3)3 (1) reacts with o-(diphenylphosphanyl)benzaldehyde within 2 min at 20
°C to give the hydrido acyl complex Ru(H){P(C6H5)2(C6H4)C(O)}(CO)2(PPh3) (2) via selective activation
of the C-H bond of the aldehyde function. Further addition of diphenylacetylene (110 °C, 3 h) affords
the novel complex Ru{P(C6H5)2(C6H4)C(O)(C6H5)CdCH(C6H5)}(CO){P(C6H5)3} (3), incorporating the
newly assembled o-(diphenylphosphanyl)phenyl (E)-stilbenyl ketone ligand. The R,â-unsaturated ketone
moiety of the latter is bound to the metal in an η4 coordination mode involving both a side-on coordination
of the carbonyl group and a more classical η2 linkage of the olefinic bond. Both complexes were fully
characterized by spectroscopic methods and by X-ray diffraction. The whole reaction sequence provides
a valuable experimental model for the chelation-assisted hydroacylation of an alkyne with a tethered
aldehyde.
Introduction
The development of transition metal catalysts for the func-
tionalization of a broad range of substrates via C-H bond
activation has been recognized as one of the major challenges
in modern chemistry.1,2
A benchmark example illustrating the use of directing groups
in transition-metal-catalyzed C-H/olefin coupling can be found
in the early pioneering work of Suggs3 on the rhodium-catalyzed
hydroacylation of ethylene. In that case, a chelation auxiliary,
2-amino-3-methylpyridine, was introduced to convert reversibly
the aldehyde into an aldimine, thus being directly suitable for
a chelating interaction of type (a) with the metal (see graphic
below).3 An elegant modern illustration of this concept can be
found in the Ru-catalyzed coupling of aldimines with arylbo-
ronates for the production of aromatic ketones.4 A related
chelation-assistance strategy (interaction of type (b)) was
extensively developed by Murai and Kakiuchi2,5 beyond their
original discovery of the Ru-catalyzed ortho-functionalization
of acetophenone.5
coordinating groups are not chelation-assisted,8 the concept is
now currently generalized to a growing number of important
new types of coupling reactions.1,2,4,9 Quite surprisingly,
however, whereas theoretical investigations have offered reliable
models for Murai-type CC bond forming steps under C-H
activation,10 there are only rare examples of effective isolation
of intermediate complexes involved in any of the above types
of substrate transformations.11
Keeping in mind our previous findings in collaboration with
Kalck on the ruthenium-catalyzed hydroesterification of ethylene
with methyl formate12 and the more recent report by Chang and
co-workers13 that a pyridine-functionalized formate undergoes
a chelation-assisted C-H functionalization with an elusive
ruthenium catalyst generated in situ from Ru3(CO)12, we became
In the latter case, the concept was extended to olefinic C-H
bond activation,6 applied to a variety of directing groups1,2 as
well as to other metals.7 Although it has been demonstrated
that a few selective additions to Ir of C-H bonds ortho to
(7) (a) Lenges, C. P.; Brookhart, M. J. Am. Chem. Soc. 1999, 121, 6616.
(b) Wiedemann, S. H.; Lewis, J. C.; Ellman, J. A.; Bergman, R. G. J. Am.
Chem. Soc. 2006, 128, 2452. (c) Thu, H.-Y.; Yu, W.-Y.; Che, C. M. J. Am.
Chem. Soc. 2006, 128, 9048.
(8) Zhang, X.; Kanzelberger, M.; Emge, T. J.; Goldman, A. S. J. Am.
Chem. Soc. 2004, 126, 13192.
(9) (a) Colby, D. A.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc.
2006, 128, 5604. (b) Ackerman, L.; Althammer, A.; Born, R. Angew. Chem.,
Int. Ed. 2006, 45, 2619. (c) Kakiuchi, F.; Matsuura, Y.; Kan, S.; Chatani,
N. J. Am. Chem. Soc. 2005, 127, 5936. (d) Kakiuchi, F.; Kan, S.; Igi, K.;
Chatani, N.; Murai, S. J. Am. Chem. Soc. 2003, 125, 1698. (e) Kakiuchi,
F.; Usui, M.; Ueno, S.; Chatani, N.; Murai, S. J. Am. Chem. Soc. 2004,
126, 2706. (f) Jun, C.-H.; Lee, H. J. Am. Chem. Soc. 1999, 121, 880. (g)
Martinez, R.; Chevalier, R.; Darses, S.; Genet, J. P. Angew. Chem., Int.
Ed. 2006, 45, 8232, and references therein.
(10) (a) Matsubara, T.; Koga, N.; Musaev, D. G.; Morokuma, K. J. Am.
Chem. Soc. 1998, 120, 12692. (b) Matsubara, T.; Koga, N.; Musaev, D.
G.; Morokuma, K. Organometallics 2000, 19, 2318.
(11) (a) Drouin, S. D.; Amoroso, D.; Yap, G. P. A.; Fogg, D. E.
Organometallics 2002, 21, 1042. (b) Jazzar, R. F. R.; Varrone, M.; Burrows,
A. D.; Macgregor, S. A.; Mahon, M. F.; Whittlesey, M. K. Inorg. Chim.
Acta 2006, 359, 815. (c) Jazzar, R. F. R.; Mahon, M. F.; Whittlesey, M. K.
Organometallics 2001, 20, 3745.
* Corresponding author. E-mail: Guy.Lavigne@lcc-toulouse.fr.
(1) (a) Dyker, G. Handbook of C-H Transformations; Wiley-VCH:
Weinheim, 2005. (b) Kakiuchi, F.; Chatani, N. AdV. Synth. Catal. 2003,
345, 1077, and references therein. (c) Ritleng, V.; Sirlin, C.; Pfeffer, M.
Chem. ReV. 2002, 102, 1731. (d) Dyker, G. Angew. Chem., Int. Ed. 1999,
38, 1698. (e) Guari, Y.; Sabo-Etienne, S.; Chaudret, B. Eur. J. Inorg. Chem.
1999, 1047.
(2) (a) Kakiuchi, F.; Murai, S. Acc. Chem. Res. 2002, 35, 826. (b) Murai,
S.; Kakiuchi, F.; Sekine, S.; Tanaka, Y.; Kamatani, A.; Sonoda, M.; Chatani,
N. Pure Appl. Chem. 1994, 66, 1527. (c) Kakiuchi, F.; Murai, S. In Topics
in Organometallic Chemistry; Murai, S., Ed.; Springer: Berlin 1999; Vol.
3, p 47. (d) Jia, C.; Kitamura, T.; Fujiwara, Y. Acc. Chem. Res. 2001, 34,
633. (e) Horino, Y. Angew. Chem., Int. Ed. 2007, 46, 2144.
(3) Suggs, J. W. J. Am. Chem. Soc. 1979, 101, 489.
(4) Park, Y. J.; Jo, E.-A.; Jun, C. H. Chem. Commun. 2005, 1185.
(5) Murai, S.; Kakiuchi, F.; Sekine, S.; Tanaka, Y.; Katamani, A.; Sonoda,
M.; Chatani, N. Nature 1993, 366, 529.
(6) (a) Trost, B. M.; Imi, K.; Davies, I. W. J. Am. Chem. Soc. 1995,
117, 5371. (b) Kakiuchi, F.; Tanaka, Y.; Sato, T.; Chatani, N.; Murai, S.
Chem. Lett. 1995, 79.
10.1021/om7005003 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 08/04/2007

4674 Organometallics, Vol. 26, No. 18, 2007
Benhamou et al.
Scheme 1. Stepwise Reaction of 1 with
interested in examining the possibility to use a well-defined
Ru(0) complex for modeling the challenging hydroacylation3,14-16
of an olefin or an alkyne with an aldehyde possessing a directing
group in appropriate position along its aromatic or aliphatic
chain, as elegantly achieved with rhodium by Willis et al.15 To
our knowledge, Kondo and Mitsudo14d reported one of the rare
examples of efficient Ru-catalyzed intermolecular hydroacyla-
tion of an olefin.
2-Diphenylphosphanylbenzaldehyde and Diphenylacetylene
Roper’s complex Ru(CO)2(PPh3)3 (1),17 already known as one
of the best precatalysts for the Murai reaction,2 might be a priori
regarded as a suitable candidate for that purpose, because of its
high substitutional lability and well-established ability to activate
C-H and C-C bonds.18 We report here a clean stoichiometric
sequence in which the latter complex is seen to achieve the
intermolecular hydroacylation of an internal alkyne with a
tethered aldehyde.
Results and Discussion
In the experimental model reaction presented here, 2-diphe-
nylphosphanylbenzaldehyde19 was selected as a simple substrate
possessing a phosphorus donor atom as strongly directing group
susceptible of favoring a chelation-assisted hydroacylation. As
shown in Scheme 1 (first equation), its reaction with 1 was found
to proceed to completion at room temperature by the time of
mixing the reactants, producing only one compound in good
yield (68%), with no detectable intermediate. Monitoring by
infrared spectroscopy indicated that the carbonyl stretching
vibrations of Roper’s complex (1909 and 1857 cm-1) were
shifted to 2024 and 1979 cm-1 during the course of the reaction,
which is indicative of the formation of a Ru(II) complex. In 1H
NMR spectra, the appearance of a doublet of doublets at -5.81
ppm confirmed the presence of a hydrido ligand Ru-H in
connection with two distinct phosphine ligands. All analyses
were consistent with the occurrence of a hydrido acyl Ru(II)
species resulting from the oxidative addition of the C-H bond
of the aldehyde function to the metal,20,21 formulated as
Ru(H){P(C6H5)2(C6H4)C(O)}(CO)2(PPh3) (2).
To firmly confirm the structure, single crystals of 2 were
grown by slow diffusion of pentane into a solution of 2 in
CH2Cl2 and were submitted to an X-ray diffraction analysis.
Crystal data are presented in Table 1, whereas a perspective
view of the molecule is shown in Figure 1. The complex is
octahedral. Activation of the C-H bond has produced the
chelating phosphino acyl group “(C6H5)2P(C6H4)C(O)”, whereas
the hydrido ligand is effectively seen to occupy a cis position
relative to the acyl group. The two carbonyls are mutually cis,
whereas the two phosphorus ligands are in trans position. NMR
data confirm that this is the only isomer existing in solution.
Let us note that an early observation by Rauchfuss20 that the
reaction of o-(diphenylphosphino)benzaldehyde with RuCl3‚
3H2O involves no C-H bond activation had led the author to
conclude that the reaction is “mechanistically different” from
that observed with other platinum metals.20 In reality, what we
see here is that the aptitude of the metal center to cleave such
a bond depends on its oxidation state, which can also be inferred
from related recent observations in the literature.21
Complex 2 was subsequently found to react cleanly with
diphenylacetylene (Scheme 1, second equation). Here, the uptake
of the alkyne was observed only under thermal activation, as
required for the creation of a vacant coordination site. Gratify-
ingly, the position of the unique rising single ν(CO) absorption
band at 1930 cm-1 for the final compound was consistent with
the expected regeneration of a Ru(0) species. NMR data on this
new compound indicated in particular that the hydride signal
had disappeared and was replaced by a triplet at δ ) 2.74 ppm
(JPH ) 7 Hz), which is characteristic for the proton signal of
an olefin coordinated to a ruthenium(0) center. The compound,
identified as Ru{P(C6H5)2(C6H4)C(O)(C6H5)CdCH(C6H5)}-
(CO){P(C6H5)3} (3), was isolated in 78% yield, whereas its
(12) (a) Fabre, S.; Kalck, P.; Lavigne, G. Angew. Chem., Int. Ed. Engl.
1997, 36, 1092. (b) Lugan, N.; Lavigne, G.; Soulie´, J. M.; Fabre, S.; Kalck,
P.; Saillard, J.-Y.; Halet, J. F. Organometallics 1995, 14, 1713. (c) Lavigne,
G.; Lugan, N.; Kalck, P.; Soulie´, J. M.; Lerouge, O.; Saillard, J.-Y.; Halet,
J. F. J. Am. Chem. Soc. 1992, 114, 10669.
(13) Ko, S.; Na, Y.; Chang, S. J. Am. Chem. Soc. 2002, 124, 750.
(14) For selected leading references on hydroacylation, see: (a) Marder,
T. B.; Roe, C. D.; Milstein, D. Organometallics 1988, 7, 1451. (b) Lenges,
C. P.; Brookhart, M. J. Am. Chem. Soc. 1997, 119, 3165. (c) Lenges, C. P.;
White, P. S.; Brookhart, M. J. Am. Chem. Soc. 1998, 120, 6965. (d) Kondo,
T.; Hiraishi, N.; Morisaki, Y.; Wada, K.; Watanabe, Y.; Mitsudo, T.
Organometallics 1998, 17, 2131.
(15) For recent leading references on chelation-controlled hydroacylation
with rhodium, see: (a) Tanaka, M.; Imai, M.; Yamamoto, Y.; Tanaka, K.;
Shimowatari, M.; Nagumo, S.; Kawahara, N.; Suemune, H. Org. Lett. 2003,
5, 1365. (b) Willis, M. C.; McNally, S. J.; Beswick, P. J. Angew. Chem.,
Int. Ed. 2004, 43, 340. (c) Willis, M. C.; Randell-Sly, H. E.; Woodward,
R. L.; McNally, S. J.; Currie, G. S. J. Org. Chem. 2006, 71, 5291. (d)
Moxham, G. L.; Randell-Sly, H. E.; Brayshaw, S. K.; Woodward, R. L.;
Weller, A. S.; Willis, M. C. Angew. Chem., Int. Ed. 2006, 45, 7618.
(16) For recent leading references on the hydroacylation of olefins or
alkynes in the presence of a chelation auxiliary, see: (a) Miura, M.; Nomura,
M. J. Synth. Org. Chem. Jpn. 2000, 58, 578. (b) Jun, C. H.; Moon, C. W.;
Lee, D.-Y. Chem.-Eur. J 2002, 8, 2423. (c) Jun, C.-H.; Lee, H.; Hong,
J.-B.; Kwon, B.-I. Angew. Chem., Int. Ed. 2002, 41, 2146. (d) Lee, D.-Y.;
Hong, B.-S.; Cho, E.-G.; Lee, H.; Jun, C.-H. J. Am. Chem. Soc. 2003, 125,
6372. (e) Kakiuchi, F.; Sato, T.; Tsujimoto, T.; Yamauchi, M.; Chatani,
N.; Murai, S. Chem. Lett. 1998, 1053.
(17) Complex 1 is now readily available in high yield through a very
simple procedure; see: Sentets, S.; Rodriguez Martinez, M.; Vendier, L.;
Donnadieu, B.; Huc, V.; Lugan, N.; Lavigne, G. J. Am. Chem. Soc. 2005,
127, 14554.
(18) (a) Ogasawara, M.; Macgregor, S. A.; Streib, W. E.; Folting, K.;
Eisenstein, O.; Caulton, K. G. J. Am. Chem. Soc. 1996, 118, 10189. (b)
Alcock, N. W.; Hill, A. F.; Melling, R. P.; Thompsett, A. R. Organometallics
1993, 12, 641. (c) Dewhurst, R. D.; Hill, A. F.; M. K. Smith, Angew. Chem.,
Int. Ed. 2004, 43, 476. (d) Hill, A. F.; Rae, A. D.; Schultz, M.; Willis, A.
C. Organometallics 2004, 23, 81. (e) Hill, A. F.; Schultz, M.; Willis, A. C.
Organometallics 2004, 23, 5729. (f) Dewhurst, R. D.; Hill, A. F.; Smith,
M. K. Organometallics 2005, 24, 6295. (g) Bartlett, M. J.; Hill, A. F.; Smith,
M. L. Organometallics 2005, 24, 5795. (h) Dewhurst, R. D.; Hill, A. F.;
Rae, A. D.; Willis, A. C. Organometallics 2005, 24, 3043.
(20) Rauchfuss, T. B. J. Am. Chem. Soc. 1979, 101, 1045.
(21) Garralda, M. A.; Hernandez, R.; Ibarlucea, L.; Pinilla, E.; Torres,
M. R.; Zarandona, M. Organometallics 2007, 26, 1031.
(19) For a straightforward preparation of this ligand, see: Laue, S.;
Greiner, L.; Wo¨ltinger, J.; Liese, A. AdV. Synth. Catal. 2001, 343.

Chelation-Assisted C-H/Alkyne Coupling
Organometallics, Vol. 26, No. 18, 2007 4675
Table 1. Crystal and Intensity Data for Complexes 2 and 3
Crystal Data
formula
fw
C
39H30O3P2Ru, CH2Cl2
C52H40O2P2Ru‚0.5(C6H6)
898.90
794.57
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V [Å3]
monoclinic
P21/a (No. 14)
20.0815(12)
9.2617(5)
20.7209(13)
90.00
111.883(6)
90.00
3576.2(4)
4
monoclinic
C2/c (No. 15)
33.6265(15)
12.5816(7)
20.6793(10)
90.00
90.588(4)
90.00
8748.4(8)
8
Z
D(calc) (g/cm3)
1.476
1.365
0.474
3704
µ(Mo KR) (mm-1) 0.715
F(000)
1616
cryst size (mm)
0.30 × 0.50 × 0.50
0.15 × 0.20 × 0.40
Figure 2. Molecular structure of complex 3 (thermal ellipsoids
shown at the 30% probability level). Selected interatomic distances
(Å): Ru(1)-P(1) 2.3398(8); Ru(1)-P(2) 2.3480(7); Ru(1)-C(1)
1.824(3); Ru(1)-C(3) 2.116(3); Ru(1)-O(3) 2.158(2); C(3)-O(3)
1.329(3); Ru(1)-C(4) 2.202(3); Ru(1)-C(5) 2.233(3); C(4)-C(5)
1.452(4); C(3)-C(4) 1.425(4); C(3)-C(12) 1.501(4).
Data Collection
temperature (K)
radiation,
Mo KR (Å)
θ min., max. (deg) 2.8, 32.0
data set
total, unique no.
of data, R(int)
no. of obsd data
(I > 2.0σ(I))
180
0.71073
180
0.71073
3.1, 32.1
-29: 28; -11: 13; -30: 30 -49: 49; -12: 18; -30: 30
37 012, 11 674, 0.021
46 051, 14 337, 0.065
tion of the alkyne is obtained by loss of one CO rather than
loss of PPh3, in agreement with Morokuma’s theoretical model
of the Murai reaction, where the active species is proposed to
be a monocarbonyl derivative.10 The subsequent transient
elementary steps, namely, (i) insertion of the alkyne into the
Ru-H bond and (ii) reductive CC bond formation between the
adjacent acyl and cis-stilbenyl groups, are seen to take place
selectively without any undesirable side reaction. Very char-
acteristically, the resulting newly assembled R,â-unsaturated
ketone moiety of the final (E)-1-(2-diphenylphosphino)phenyl)-
2,3-diphenylpropen-1-one23 ligand is bound to the metal in an
η4 coordination mode involving both a classical η2 coordination
of the olefinic bond and a rather uncommon “side-on” coordina-
tion of the CO bond. Although such a coordination mode has
been already identified as a result of the complexation of
preformed R,â-unsaturated ketones,24 there is no precedent for
its direct visualization as the effective CC bond forming step
in the construction of such molecules. Interestingly, whereas
the reductive elimination pathway observed here would normally
create an unsaturation susceptible of allowing the complex to
start another catalytic cycle, such a peculiar coordination mode
reflects the tendency of the Ru(0) center to achieve a closed-
shell configuration while apparently awaiting a new incoming
substrate.
8618
7668
Refinement
11 674, 451
0.0290, 0.0752, 1.09
N
ref, Npar
14 337, 542
0.0525, 0.1137, 0.92
0.00, 0.00
R, wR2, Sa
max. and av shift/ 0.00, 0.00
error
min. and max. resd -0.54, 0.83
dens (e/Å3)
-0.98, 1.33
a w ) 1/[σ2(Fo ) + (0.0408P)2 + 0.1607P] where P ) (Fo + 2Fc )/3.
2
2
2
At the present stage of our investigation, our attempts to
transpose the reaction to the case of olefins such as styrene or
triethoxyvinylsilane remained unsuccessful, probably due to the
fact that olefins insert less easily than alkynes into a Ru-H
bond. Indeed, in such cases, we do observe the formation of
Ru(CO)3(PPh3)2 as a prevailing side reaction. This is understood
as a decarbonylation of the acyl moiety of the cyclometalated
ligand Ph2P(C6H4)C(O) from 2 to give an elusive ortho-
metalated intermediate,25 which ortho-demetalates by reductive
coupling with the hydride to give a coordinated triphenylphos-
phine ligand.
Figure 1. Molecular structure of the hydrido acyl complex 2
(thermal ellipsoids shown at the 30% probability level). Selected
interatomic distances (Å) and angles (deg): Ru(1)-P(1) 2.3092(4);
Ru(1)-P(2) 2.3773(4); Ru(1)-C(1) 1.924(2); Ru(1)-C(2) 1.936(2);
Ru(1)-C(3) 2.110(1); C(3)-O(3) 1.225(2); Ru(1)-C(3)-O(3)
125.8(1); P(1)-Ru(1)-C(3) 82.32(3).
molecular structure was unambiguously established by X-ray
diffraction. Crystal data are presented in Table 1, whereas a
perspective view of the molecule is shown in Figure 2.
Clearly, the whole sequence observed here provides a realistic
experimental model for the hydroacylation of diphenylacetylene
with an aldehyde tethered onto a Ru(0) center. Whereas the
presence of a directing group appears to be essential to trigger
the activation of the C-H bond of the aldehyde under very
mild conditions,22 the vacant site required for further coordina-
(23) Although the hydroacylation on diphenylacetylene occurs as a formal
syn addition, the CIP descriptor of the stilbenyl moiety is E according to
the priority rules.
(24) For selected examples of such a coordination mode with preformed
R,â-unsaturated ketones, see: (a) Graham, C. R.; Scholes, G.; Brookhart,
M. J. Am. Chem. Soc. 1977, 99, 1180. (b) Zhang, W.-Y.; Jakiela, D. J.;
Maul, A.; Knors, C.; Lauher, J. W.; Helquist, P.; Enders, D. J. Am. Chem.
Soc. 1988, 110, 4652. (c) Hiraki, K.; Nonaka, A.; Matsunaga, T.; Kawano,
H. J. Organomet. Chem. 1999, 574, 121.
(22) By contrast, with 2-bromobenzaldehyde, namely, in the absence of
a better directing group than the oxygen of the acyl, we do observe “normal”
activation at the ortho position, with competing cleavage of C-Br and C-H
bonds (Benhamou, L.; Cesar, V.; Lugan, N.; Lavigne, G., in preparation).
(25) Bennet, M. A.; Clark, A. M.; Contel, M.; Rickard, C. E. F.; Roper,
W. R.; Wright, L. J. J. Organomet. Chem. 2000, 601, 299.

4676 Organometallics, Vol. 26, No. 18, 2007
Benhamou et al.
) 11.0 Hz), 133.8 (d, JCP ) 11.3 Hz), 131.4 (d, JCP ) 11.3 Hz),
130.9 (d, JCP ) 2.8 Hz), 130.7 (br s), 130.5 (d, JCP ) 6.0 Hz),
In the case of diphenylacetylene, we also attempted to perform
the hydroacylation reaction in a catalytic way with either
2-ethoxybenzaldehyde (as a more synthetically useful aldehyde)
or benzaldehyde (with the assistance of a chelation auxiliary
such as 2-amino-3-methylpyridine), albeit with no success.
Based on such observations, our future strategy in the quest for
catalytically active species will require specific modifications
of the metal’s coordination sphere, in particular by incorporation
of certain types of N-heterocyclic carbenes known to act as much
better stabilizing ligands than triphenylphosphine.
129.8 (d, JCP) 2.3 Hz), 129.6 (d, JCP ) 2.8 Hz), 128.5 (d, JCP
)
10.2 Hz), 127.2 (d, JCP ) 9.8 Hz), 120.6 (d, JCP ) 16.8 Hz,
o-C(C6H4CO)) ppm. 31P{1H} NMR (81.015 MHz, CD2Cl2, 293
2
2
K): δ 75.6 (d, JPP ) 213 Hz, PPh2,), 49.2 (d, JPP ) 213 Hz,
PPh3) ppm. MS (FAB, MNBA): m/z (%) 682 (12) [M - CO],
654 (29) [M - 2CO], 626 (47) [RuC36H30P2], 363 (100) [Ru(PPh3)].
Anal. Calcd (%) for C39H30O3P2Ru (709.67): C 66.00, H 4.26.
Found: C 65.10, H 4.00.
Ru{η5-P(C6H5)2(C6H4CO-C(C6H5)CH(C6H5))}(CO){P(C6-
H5)3} (3). Complex 2 (90 mg, 0.13 mmol) and diphenylacetylene
(27 mg, 0.15 mmol) were dissolved in 10 mL of toluene in a
Schlenk flask connected with a reflux condenser. The solution was
heated at 110 °C for 3 h, cooled to room temperature, and
concentrated under vacuum. The resulting complex was precipitated
with pentane and was then filtered, washed with pentane, and
weighed (78% yield). Slow diffusion of pentane into a concentrated
solution of 3 in benzene gave suitable crystals for the X-ray structure
analysis.22
Experimental Section
General Considerations. All manipulations were performed
under an inert atmosphere of dry nitrogen by using standard vacuum
line and Schlenk tube techniques. THF and diethyl ether were
distilled from sodium/benzophenone and toluene was distilled from
sodium. Pentane and dichloromethane were dried over CaH2 and
subsequently distilled. Deuterated dichloromethane (CD2Cl2) was
dried over CaH2, vacuum distilled, degassed by three cycles of
freeze-pump-thaw, and stored under nitrogen atmosphere in
Teflon valve ampules. NMR spectra were recorded on Bruker
AC200, AV300, or AV500 spectrometers. Infrared spectra were
obtained as solutions on a Perkin-Elmer 1725 FT-IR spectrometer.
Microanalyses were performed by the Laboratoire de Chimie de
Coordination Microanalytical Service. 2-Diphenylphosphanylben-
zaldehyde was prepared according to a literature procedure.19
Diphenylacetylene was purchased from Aldrich. Ru(CO)2(PPh3)3
(1)17 was prepared using our new synthetic procedure from
Ru(CO)3Cl2(thf).26 RuCl3‚3H2O was generously supplied by Johnson
Matthey.
1
IR (ν(CO), THF): 1931(vs) cm-1. H NMR (500 MHz, CD2-
Cl2, 293 K): δ 2.74 (t, 1H, JHP ) 7.0 Hz, CdCH), 6.53 (d, 2H,
JHH ) 5.0 Hz, CHarom), 6.85-6.98 (m, 5H, CHarom), 7.13-7.31
(m, 28H, CHarom), 7.44-7.48 (m, 4H, CHarom) ppm. 13C{1H} NMR
(125.8 MHz, CD2Cl2, 293 K): δ 206.0 (t, Ru-CO, JCP ) 12.6 Hz),
148.5 (dd, JCP ) 40.3, 6.3 Hz, COenone), 145.8 (d, JCP ) 21.4 Hz),
143.3 (d, JCP ) 3.8 Hz), 138.3 (m), 136.4 (s), 135.8 (d, JCP ) 40.3
Hz), 134.6 (d, JCP ) 28.9 Hz), 134.2 (s), 133.3 (d, JCP ) 11.3 Hz),
132.1 (d, JCP ) 11.3 Hz), 131.8 (d, JCP ) 10.1 Hz), 129.9 (d, JCP
) 1.3 Hz), 129.5 (d, JCP ) 1.3 Hz), 129.2 (d, JCP ) 1.3 Hz), 128.7
(d, JCP ) 1.3 Hz), 128.4 (d, JCP ) 10.1 Hz), 127.9 (s), 127.8 (d,
JCP ) 10.1 Hz), 127.7 (s), 127.4 (s), 126.5 (s), 123.4 (s); 106.9 (t,
JCP ) 3.8 Hz, dC(Ph)(COR)), 55.3 (d, JCP ) 28.9 Hz, dCH) ppm.
31P{1H} NMR (202.5 MHz, CD2Cl2, 293 K): δ 46.9 (s, PPh3),
30.9 (s, PPh2-C6H4CO) ppm. MS (FAB, MNBA): m/z (%) 860
(30) [M], 831 (3) [M - CO], 570 (42) [M - CO - PPh3], 542
(91) [RuC32H25P], 362 (100) [Ru(PPh3)]. Anal. Calcd (%) for
C52H40O2P2Ru (859.89): C 72.63, H 4.69. Found: C 72.44, H 4.67.
Crystal Structure Analyses. Crystal and intensity data for 2
and 3 were collected on an Oxford Diffraction XCALIBUR
diffractometer equipped with a low-temperature device. Crystal and
intensity data are listed in Table 1. Perspective views of these two
complexes are shown in Figures 1 and 2, respectively, along with
a selection of the main interatomic distances and bond angles. A
full listing of crystallographic data is available in the CIF files
provided as Supporting Information.
Ru(H){η2-P(C6H5)2(C6H4CO)}(CO)2{P(C6H5)3} (2). A Schlenk
tube equipped with a stir bar was charged with Ru(CO)2(PPh3)3
(1) (280 mg, 0.30 mmol) and then with 20 mL of freshly distilled
tetrahydrofuran. After complete dissolution, solid P(C6H5)2(C6H4-
CHO) (100 mg, 0.35 mmol) was added all at once, which resulted
in rapid disappearance of the initial yellow color. After 2-3 min,
IR monitoring indicated the spectroscopically quantitative formation
of a Ru(II) species. The solution was concentrated to one-fourth
of its volume, and the new complex was precipitated upon addition
of pentane. It was filtered with a filter paper tipped cannula, washed
with pentane, dried, and weighed (145 mg, 68% yield). Slow
recrystallization from dichloromethane/pentane afforded pale yellow
crystals of 2 directly suitable for the X-ray structure analysis.
IR (ν(CO), THF): 2024(s), 1979(vs), ν (CdO) ) 1607(w) cm-1).
2
1H NMR (200 MHz, CD2Cl2, 293 K): δ -5.81 (dd, JHP ) 17.5,
20.7 Hz, Ru-H,), 7.33-7.53 (m, 19H, CHarom), 7.67-7.75 (m, 7H,
CHarom), 7.99-8.10 (m, 3H, CHarom) ppm. 13C{1H} NMR (75.5
MHz, CD2Cl2, 293 K): δ 258.4 (dd, 2JCP) 6.5,8.2 Hz, CdO), 200.6
(t, 2JCP ) 8.6 Hz, CO), 198.5 (t, 2JCP ) 8.1 Hz, CO), 157.8 (d, JCP
) 41.0 Hz, Ph2P-C (C6H4CO)), 139.3 (d, JCP ) 45.3 Hz), 137.2
(d, JCP ) 45.1 Hz), 136.2 (dd, JCP ) 43.0, 1.3 Hz), 133.9 (d, JCP
Acknowledgment. The authors thank the CNRS for financial
support and Johnson Matthey for generous gifts of RuCl3‚nH2O.
Supporting Information Available: CIF files giving crystal-
lographic data and including a full list of interatomic bond lengths
and angles for compounds 2 and 3. This material is available free
of charge via the Internet at http://pubs.acs.org.
(26) Faure, M.; Maurette, L.; Donnadieu, B.; Lavigne, G. Angew. Chem.,
Int. Ed. 1999, 38, 518.
OM7005003