Cluster-Mediated Conversion of Diphenylacetylene into α-Phenylcinnamaldehyde. Construction of a Catalytic Hydroformylation Cycle Based on Isolated Intermediates

Article abstract of DOI:10.1021/om9806747

The present paper deals with a rational attempt to achieve the hydroformylation of diphenylacetylene onto a hydrido triruthenium cluster complex incorporating the 2-(methylamino)pyridyl group (abbreviation: MeNpy) as a hemilabile ancillary ligand [note: in all species discussed below, the bridgehead μ₂-N atom is linked to the centers labeled as Ru(1) and Ru(2), whereas the pyridyl nitrogen is bound to Ru(3)]. The complex Ru₃(μ-H)(μ-MeNpy)-(CO)₉ (1) is shown to react cleanly with diphenylacetylene to give the alkenyl complex Ru₃-(μ-MeNpy)(μ-PhC=CHPh)(CO)₈ (2), the structure of which is reported. The reaction of 2 with 1 equiv of PPh₃ proceeds to completion within less than 3 min at 25 °C, giving two propenoyl complexes, namely, Ru₃(μ-MeNpy)(μ-O=C-PhC=CHPh)(PPh₃)(CO)₇ (3) (48% yield) and Ru₃(μ-MeNpy)(μ-O=C-PhC=CHPh)(PPh₃) ₂(CO)₆ (4) (19% yield), both fully characterized by spectroscopic methods and X-ray analysis. Complex 3 is an adduct of 2 with PPh₃. The incorporation of the phosphine has caused a migratory CO insertion of the alkenyl group. The phosphine occupies an equatorial coordination site on Ru(1), in cis position relative to the nitrogen atom of the amido bridge. The newly formed propenoyl group occupies an equatorial bridging position across the Ru(1)-Ru(3) edge, with the acyl oxygen bound to Ru(1), in cis position relative to both the bridgehead nitrogen atom and the phosphine. The molecular structure of the second propenoyl compound, Ru₃(μ-MeNpy)(μ-O=C-PhC=CHPh)-(PPh₃) ₂(CO)₆ (4), is formally derived from the previous one, 3, by a simple substitution of an equatorial CO of Ru(2) by PPh₃. The use of a 2-fold amount of phosphine for the above reaction modifies only slightly the relative abundance of 3 (30%) and 4 (44%). This indicates that 3 is not the kinetic product of the reaction between 2 and a phosphine. Further reaction of 4b with CO induces loss of one PPh₃ and incorporation of two CO ligands. This produces the open 50e cluster Ru₃(μ-MeNpy)(μ-O=C-PhC=CHPh)(PPh₃)(CO)₈ (5), in which the bridging propenoyl group now spans the open edge Ru(1)-Ru(2) (the remaining phosphine occupies an equatorial site cis to the acyl oxygen). Treatment of 2b with CO (1 atm, 25 °C, 20 min) also promotes migratory CO insertion, giving the 50e propenoyl complex Ru₃(μ-MeNpy)(μ-O=C-PhC=CHPh)(CO)₉ (6b), whose structure has been determined. The propenoyl group spans the open edge Ru(1)-Ru(2). Although stable in CO-saturated solutions under CO atmosphere, the complex reverts rapidly to 2 within 30 s under inert atmosphere. Treatment of 6 with CO/H₂ gas mixtures under ambient conditions produces α-phenylcinnamaldehyde with concomitant recovery of 1, showing that the hydroformylation of diphenylacetylene can be achieved in a stepwise manner through the cyclic reaction sequence 1 → 2 → 6 → 1. Under nonoptimized catalytic conditions, the amount of α-phenylcinnamaldehyde obtained corresponds to about eight cycles. The metal-containing species recovered in the reactor through the catalytic runs is isolated and formulated as the bimetallic carboxamido complex [Ru{-C(O)-MeNpy}(CO)₃]₂ (7). Thus, it appears that deactivation of the system has taken place via CO insertion into the metal-amide bond.

Full text of DOI:10.1021/om9806747

Organometallics 1999, 18, 187-196
187
Clu ster -Med ia ted Con ver sion of Dip h en yla cetylen e in to
r-P h en ylcin n a m a ld eh yd e. Con str u ction of a Ca ta lytic
Hyd r ofor m yla tion Cycle Ba sed on Isola ted In ter m ed ia tes
Paul Nombel, Noe¨l Lugan, Bruno Donnadieu, and Guy Lavigne*
Laboratoire de Chimie de Coordination du CNRS, UPR No. 8241, 205 Route de Narbonne,
31077 Toulouse Cedex, France
Received August 6, 1998
The present paper deals with a rational attempt to achieve the hydroformylation of di-
phenylacetylene onto a hydrido triruthenium cluster complex incorporating the 2-(methyl-
amino)pyridyl group (abbreviation: MeNpy) as a hemilabile ancillary ligand [note: in all
species discussed below, the bridgehead µ2-N atom is linked to the centers labeled as Ru(1)
and Ru(2), whereas the pyridyl nitrogen is bound to Ru(3)]. The complex Ru3(µ-H)(µ-MeNpy)-
(CO)9 (1) is shown to react cleanly with diphenylacetylene to give the alkenyl complex Ru3-
(µ-MeNpy)(µ-PhCdCHPh)(CO)8 (2), the structure of which is reported. The reaction of 2
with 1 equiv of PPh3 proceeds to completion within less than 3 min at 25 °C, giving two
propenoyl complexes, namely, Ru3(µ-MeNpy)(µ-OdC-PhCdCHPh)(PPh3)(CO)7 (3) (48% yield)
and Ru3(µ-MeNpy)(µ-OdC-PhCdCHPh)(PPh3)2(CO)6 (4) (19% yield), both fully characterized
by spectroscopic methods and X-ray analysis. Complex 3 is an adduct of 2 with PPh3. The
incorporation of the phosphine has caused a migratory CO insertion of the alkenyl group.
The phosphine occupies an equatorial coordination site on Ru(1), in cis position relative to
the nitrogen atom of the amido bridge. The newly formed propenoyl group occupies an
equatorial bridging position across the Ru(1)-Ru(3) edge, with the acyl oxygen bound to
Ru(1), in cis position relative to both the bridgehead nitrogen atom and the phosphine. The
molecular structure of the second propenoyl compound, Ru3(µ-MeNpy)(µ-OdC-PhCdCHPh)-
(PPh3)2(CO)6 (4), is formally derived from the previous one, 3, by a simple substitution of an
equatorial CO of Ru(2) by PPh3. The use of a 2-fold amount of phosphine for the above reaction
modifies only slightly the relative abundance of 3 (30%) and 4 (44%). This indicates that 3
is not the kinetic product of the reaction between 2 and a phosphine. Further reaction of 4b
with CO induces loss of one PPh3 and incorporation of two CO ligands. This produces the
open 50e cluster Ru3(µ-MeNpy)(µ-OdC-PhCdCHPh)(PPh3)(CO)8 (5), in which the bridging
propenoyl group now spans the open edge Ru(1)-Ru(2) (the remaining phosphine occupies
an equatorial site cis to the acyl oxygen). Treatment of 2b with CO (1 atm, 25 °C, 20 min)
also promotes migratory CO insertion, giving the 50e propenoyl complex Ru3(µ-MeNpy)(µ-
OdC-PhCdCHPh)(CO)9 (6b), whose structure has been determined. The propenoyl group
spans the open edge Ru(1)-Ru(2). Although stable in CO-saturated solutions under CO
atmosphere, the complex reverts rapidly to 2 within 30 s under inert atmosphere. Treatment
of 6 with CO/H2 gas mixtures under ambient conditions produces R-phenylcinnamaldehyde
with concomitant recovery of 1, showing that the hydroformylation of diphenylacetylene
can be achieved in a stepwise manner through the cyclic reaction sequence 1 f 2 f 6 f 1.
Under nonoptimized catalytic conditions, the amount of R-phenylcinnamaldehyde obtained
corresponds to about eight cycles. The metal-containing species recovered in the reactor
through the catalytic runs is isolated and formulated as the bimetallic carboxamido complex
[Ru{-C(O)-MeNpy}(CO)3]2 (7). Thus, it appears that deactivation of the system has taken
place via CO insertion into the metal-amide bond.
In tr od u ction
erty in view of bringing this reagent into reaction with
organic compounds. Although CO can cause cluster
degradation, there is still the possibility to observe truly
cluster-mediated carbonylations, provided we work un-
der the mildest possible conditions with cluster proto-
types exhibiting enhanced kinetic lability.3 The present
paper deals with a rational attempt to achieve the
hydroformylation of diphenylacetylene onto a hydrido
triruthenium cluster complex modified by a hemilabile
ancillary ligand.
The ability of certain transition-metal clusters to
reversibly coordinate CO1,2 constitutes a desirable prop-
(1) (a) Huttner, G.; Schneider, J .; Mu¨ller, H. D.; Mohr, G.; von Seyerl,
J .; Wohlfahrt, L. Angew. Chem., Int. Ed. Engl. 1979, 18, 76. (b)
Huttner, G.; Knoll, K. Angew. Chem., Int. Ed. Engl. 1987, 26, 743.
(2) For leading references in the case of ruthenium, see: (a) Lugan,
N.; Bonnet, J .-J .; Ibers, J . A. Organometallics 1988, 7, 1538. (b) Lugan,
N.; Lavigne, G.; Bonnet, J .-J .; Re´au, R.; Neibecker, D.; Tkatchenko, I.
J . Am. Chem. Soc. 1988, 110, 5369.
10.1021/om9806747 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 12/24/1998

188 Organometallics, Vol. 18, No. 2, 1999
Nombel et al.
The catalytic hydroformylation of olefins in the pres-
ence of K[Ru3(µ-H)(CO)11] reported some years ago by
Su¨ss-Fink and co-workers4 remains an interesting
example where the results of a reliable mechanistic
study including labeling experiments were at least
consistent with the hypothesis of a cluster-catalyzed
reaction.5 However, as it is often the case for numerous
active systems in homogeneous catalysis, no direct
evidence for the proposed intermediates could be ob-
tained from the actual working catalyst’s solution.
Valuable mechanistic information on the initial el-
ementary steps involved in a typical “cluster-mediated”
olefin hydroformylation is found in Kaesz’s pioneering
work on the reactivity of the complex Ru3(µ-H)(µ-Cl)-
(CO)10.6 Indeed, as shown in eq 1, the latter incorporates
both ethylene and CO within minutes at 25 °C to
produce the 50e propionyl derivative Ru3{µ-OdC(CH2-
CH3)}(µ-Cl)(CO)10 as a result of ethylene insertion into
a Ru-H bond, followed by migratory CO insertion.
which the bridging amido group of the ancillary ami-
dopyridyl ligand was also exhibiting a hemilabile be-
havior.9,10 The hydrido species 1 was originally found
to react cleanly with alkynes to afford the alkenyl
species Ru3(µ3-PhNpy)(µ-R′CdCHR′′)(CO)8 (2) (see an
example in eq 2).9
Both 1 and 2,9a as well as relevant complexes bearing
modified amidopyridyl ligands,11 were shown to act as
catalyst precursors in the hydrogenation of diphenyl-
acetylene. More recently, several alkyne oligomerization
and co-oligomerization reactions were found to take
place in the presence of 1a .12 Whereas this seemed to
indicate a remarkable ability of this complex to accom-
modate several molecules of the reactants in its coordi-
nation shell, the systematic detection of the alkenyl
complex Ru3(µ3-PhNpy)(µ-R′CdCHR′′)(CO)8 (2a ) under
catalytic conditions revealed only how the first of these
alkyne molecules was interacting with the cluster. To
identify the more accessible coordination site for further
reaction with a second hypothetical incoming substrate
molecule, we treated the alkenyl complex Ru3(µ3-MeNpy)-
(µ-PhCdCHPh)(CO)8 (2b) with triphenylphosphine, re-
garded as a model two-electron donor ligand. To our
surprise, this not only confirmed the existence of a
privileged reaction site in this complex but also revealed
a remarkable aptitude of its alkenyl group to undergo
migratory CO insertion. With a view to possible impli-
cations in the hydroformylation of alkynes,13 the parallel
reaction of 2b with CO was also examined. This led to
the isolation of a novel trinuclear propenoyl derivative,
later shown to participate in a cyclic cluster-mediated
transformation of diphenylacetylene into R-phenylcin-
namaldehyde.
A transient opening of the chloride bridge favoring
the coordination of ethylene was originally proposed to
account for the mild conditions of this reaction.3a Ad-
ducts bearing terminal halide ligands were effectively
isolated later upon reaction of anionic triruthenium
carbonyl halide complexes with various ligands.3c,7,8
On the basis of the model of the reactive prototype
Ru3(µ-H)(µ-Cl)(CO)10 previously developed by Kaesz, we
were led to devise the more robust derivatives Ru3(µ-
H)(µ3-RNpy)(CO)9 (1a ,b) (a , R ) Ph; b, R ) Me),9 in
(3) For specific reviews dealing with cluster activation, see: (a)
Lavigne, G.; Kaesz, H. D. In Metal Clusters in Catalysis; Gates, B.,
Guczi, L., Kno¨zinger, H., Eds.; Elsevier: Amsterdam, 1986; Chapter
4, p 43. (b) Lavigne, G. In The Chemistry of Metal Clusters; Shriver,
D., Adams, R. D., Kaesz, H. D., Eds.; VCH: New York, 1990; Chapter
5, p 201, and references therein; (c) Lavigne, G.; de Bonneval, B. In
Catalysis by Di- and Polynuclear Metal Cluster Complexes; Adams, R.
D., Cotton, F. A., Eds: J ohn Wiley & Sons: New York, 1998, Chapter
2, p 39.
Resu lts
P h osph in e-In du ced Migr ator y CO In ser tion on to
th e Alk en yl Com p lex 2. Whereas nucleophilic attack
of triphenylphosphine onto the amidopyridyl complex
Ru3(µ-H)(µ-RNpy)(CO)9 (1) leads to regioselective CO
substitution at one of the two equivalent metal centers
bearing the bridging nitrogen of the amido group, the
corresponding sites in Ru3(µ-MeNpy)(µ-PhCdCHPh)-
(CO)8 (2b) are differentiated by the ligand environ-
ment: whereas the alkenyl group is π bound to the
(4) (a) Su¨ss-Fink, G.; Herrmann, G. J . Chem. Soc., Chem. Commun.
1985, 735. (b) Langenbahn, K.; Bernauer, K.; Su¨ss-Fink, G. J .
Organomet. Chem. 1989, 379, 165.
(5) For general recent reviews dealing with cluster-catalyzed reac-
tions, see: (a) Gladfelter, W. L.; Roesselet, K. J . In The Chemistry of
Metal Clusters; Shriver, D., Adams, R. D., Kaesz, H. D., Eds.; VCH:
New York, 1990; Chapter 7, p 329, and references therein. (b) Su¨ss-
Fink, G.; Meister, G. Adv. Organomet. Chem. 1993, 35, 41. (c) Su¨ss-
Fink, G.; J ahncke, M.Catalysis by Di- and Polynuclear Metal Cluster
Complexes; Adams, R. D., Cotton, F. A., Eds.; J ohn Wiley & Sons: New
York, 1998; Chapter 6, p 167.
(6) (a) Kampe, C. E.; Boag, N. M.; Kaesz, H. D. J . Am. Chem. Soc.
1983, 105, 2896. (b) Kampe, C. E.; Kaesz, H. D. Inorg. Chem. 1984,
23, 4646.
(9) (a) Lugan, N.; Laurent, F.; Lavigne, G.; Newcomb, T. P.;
Liimatta, E. W.; Bonnet, J .-J . J . Am. Chem. Soc. 1990, 112, 8607. (b)
Lugan, N.; Laurent, F.; Lavigne, G.; Bonnet, J .-J . Organometallics
1992, 11, 1351.
(10) Shen, J .-K.; Basolo, F.; Nombel, P.; Lugan, N.; Lavigne, G.
Inorg. Chem. 1996, 35, 755.
(11) Cabeza, J . A.; Fernandez-Colinas, J . M.; Llamazares, A.; Riera,
V. Synlett. 1995, 579.
(12) Nombel, P.; Lugan, N.; Mulla, F.; Lavigne, G. Organometallics
1994, 13, 4673.
(7) (a) Chin-Choy, T.; Harrison, W. T.; Stucky, G. D.; Keder, N.; Ford,
P. C. Inorg. Chem. 1989, 28, 2028. (b) Han, S.-H.; Geoffroy, G. L.;
Rheingold, A. L. Inorg. Chem. 1987, 26, 3426. (c) Han, H. S.; Song,
J .-S.; Macklin, P. D.; Nguyen, T.; Geoffroy, G. L.; Rheingold, A. L.
Organometallics 1989, 8, 2127. (d) Ramage, D. L.; Geoffroy, G. L.;
Rheingold, A. L.; Haggerty, B. S. Organometallics 1992, 11, 1242.
(8) (a) Rivomanana, S.; Lavigne, G.; Lugan, N.; Bonnet, J .-J .; Yanez,
R.; Mathieu, R. J . Am. Chem. Soc. 1989, 111, 8959. (b) Rivomanana,
S.; Lavigne, G.; Lugan, N.; Bonnet, J .-J . Organometallics 1991, 10,
2285. (c) Shen, J .-K.; Basolo, F. Gazz. Chim. Ital. 1994, 124, 439.
(13) J ohnson, J . R.; Cuny, G. D.; Buchwald, S. L. Angew. Chem.,
Int. Ed. Engl. 1995, 16, 1760.

Construction of a Catalytic Hydroformylation Cycle
Organometallics, Vol. 18, No. 2, 1999 189
F igu r e 2. Perspective view of the propenoyl complex 3b.
The phenyl groups of the triphenylphosphine ligand are
omitted for clarity. Selected interatomic distances (Å) and
bond angles (deg): Ru(1)-Ru(2) ) 2.7169(6); Ru(1)-Ru(3)
) 2.7792(6); Ru(2)-Ru(3) ) 2.7354(6); Ru(1)-N(1) ) 2.210-
(4); Ru(2)-N(1) ) 2.186(5); Ru(3)-N(2) ) 2.150(5); Ru(1)-
O(8) ) 2.180(4); Ru(3)-C(8) ) 2.046(6); C(8)-O(8) )
1.254(6); C(8)-C(17) ) 1.494(8); C(17)-C(18) ) 1.339(9);
Ru(1)-P(1) ) 2.420(1); Ru(3)-C(8)-O(8) ) 110.4(4); Ru-
(3)-C(8)-C(17) ) 133.4(4); O(8)-C(8)-C(17) ) 115.4(5).
F igu r e 1. Perspective view of the alkenyl complex 2b.
Selected interatomic distances (Å) and bond angles (deg):
Ru(1)-Ru(2) ) 2.7229(6); Ru(1)-Ru(3) ) 2.8107(6); Ru-
(2)-Ru(3) ) 2.7701(6); Ru(1)-N(1) ) 2.237(4); Ru(2)-N(1)
) 2.175(4); Ru(3)-N(2) ) 2.159(4); Ru(1)-C(9) ) 2.289-
(5); Ru(1)-C(10) ) 2.309(5); Ru(3)-C(9) ) 2.112; C(9)-
C(10) 1.392(7); Ru(3)-C(9)-C(10) ) 121.4(4).
Sch em e 1
propenoyl group occupies an equatorial bridging position
accross the Ru(1)-Ru(3) edge, which is also supported
by the N-CdN bridge of the ancillary ligand. The acyl
type carbon is σ bound to Ru(3), whereas the acyl oxygen
is bound to the ruthenium center Ru(1), in cis position
relative to both the bridgehead nitrogen atom and the
phosphine. Such a geometrical situation might be
consistent with the occurrence of a remote CO insertion
(vide infra), provided the derivative detected here is the
kinetic isomer.
The structure of the second propenoyl compound, Ru3-
(µ-MeNpy)(µ-OdC-PhCdCHPh)(PPh3)2(CO)6 (4b), is
shown in Figure 3. This complex is formally derived
from the previous one, 3b, by a simple phosphine-
induced CO displacement taking place at the metal
center Ru(2). The new phosphine occupies an equatorial
coordination site in cis position relative to the bridge-
head nitrogen atom, whereas the global arrangement
of all other ligands remains unchanged.
center referred to as Ru(1), Ru(2) is surrounded only
by carbonyl groups (see the perspective view displayed
in Figure 1).14
At first sight, the formation of the latter bisphosphine
derivative 4b in reasonable yield (19%) from a stoichio-
metric reaction based upon a 1:1 ratio might be indica-
tive of a low kinetic barrier for CO dissociation from
the adduct 3b, enabling it to compete favorably with
its precursor 2b for the capture of the phosphine. Quite
surprisingly, however, the use of a 2-fold amount of
phosphine under otherwise identical conditions (see
Experimental Section) affected only moderately the
relative abundance of 3b and 4b [a modification of the
phosphine/triruthenium ratio from 1 to 2 caused the
yields to vary from 48% to 30% for 3b and from 19% to
44% for 4b], thus ruling out the preceding working
hypothesis. In an additional experiment, it was ef-
fectively found that the reaction of 3b with PPh3 does
not work under ambient conditions, although the sub-
stituted derivative 4b is obtained within 30 min at 50-
60 °C.
The addition of 1 equiv of triphenylphosphine to 2b
was found to proceed rapidly to completion within less
than 3 min at 25 °C (Scheme 1), giving two new
complexes that were both fully characterized by spec-
troscopic methods as well as by X-ray diffraction analy-
ses.
The first complex, Ru3(µ-MeNpy)(µ-OdC-PhCdCH-
Ph)(PPh3)(CO)7 (3b), recovered in 48% yield, is an
adduct resulting from the incorporation of PPh3 without
loss of CO. Its molecular structure is shown in Figure
2. The phosphine occupies an equatorial coordination
site onto Ru(1), in cis position relative to the bridgehead
nitrogen atom. Nucleophilic attack by the phosphine has
triggered a migratory CO insertion. The newly formed
(14) The determination of the structure of 2b was found necessary
to ascertain the nature of the isomer we had in hand, which proved to
be the same as for 2a .9b

190 Organometallics, Vol. 18, No. 2, 1999
Nombel et al.
F igu r e 3. Perspective view of the propenoyl complex 4b.
The phenyl groups of the two triphenylphosphine ligands
are omitted for clarity. Selected interatomic distances (Å)
and bond angles (deg): Ru(1)-Ru(2) ) 2.638(4); Ru(1)-
Ru(3) ) 2.758(4); Ru(2)-Ru(3) ) 2.721(4); Ru(1)-N(1) )
2.18(2); Ru(2)-N(1) ) 2.17(2); Ru(3)-N(2) ) 2.11(3); Ru-
(1)-O(8) ) 2.23(2); Ru(3)-C(8) ) 1.97(3); C(8)-O(8) )
1.35(4); C(8)-C(17) ) 1.41(4); C(17)-C(18) ) 1.21(4); Ru-
(1)-P(1) ) 2.40(1); Ru(2)-P(2) ) 2.36(1); Ru(3)-C(8)-O(8)
) 111(2); Ru(3)-C(8)-C(17) ) 138(3); O(8)-C(8)-C(17) )
110(3).
F igu r e 4. Perspective view of the propenoyl complex 5b.
The phenyl groups of the triphenylphosphine ligand are
omitted for clarity. Selected interatomic distances (Å) and
bond angles (deg): Ru(1)-Ru(3) ) 2.7742(9); Ru(2)-Ru(3)
) 2.7623(8); Ru(1)-N(1) ) 2.269(6); Ru(2)-N(1) ) 2.202-
(6); Ru(3)-N(2) ) 2.172(6); Ru(2)-P(1) ) 2.457(2); Ru(1)-
C(9) ) 2.073(7)); Ru(2)-O(9)) 2.093(5); C(9)-O(9) )
1.243(8); C(9)-C(10) 1.515(9); C(10)-C(11) ) 1.35(1); Ru-
(1)-Ru(3)-Ru(2) ) 76.11(2); Ru(1)-C(9)-O(9) ) 118.2(5);
O(9)-C(9)-C(10) ) 112.0(6); C(9)-C(10)-C(11) ) 120.6-
(7).
Such a behavior indicates that 3b is not the kinetic
product of the reaction between 2b and a phosphine.
There must be a transient metastable phosphine adduct
A that may statistically decay via one of two competing
pathways, namely, either (i) an intramolecular rear-
rangement leading to the adduct 3b or (ii) the capture
of a second phosphine ligand followed by intramolecular
rearrangement and loss of CO to produce 4b.
A kinetic study was undertaken15 in order to gain
further insight into the mechanism. The results indicate
that the rate for disappearance of the reactant is first-
order in complex and first-order in PPh3 concentration.
The second-order kinetics, as well as the activation
parameters (low ∆Hq, negative ∆Sq), indicate that the
initial reaction step is an associative nucleophilic ad-
dition of the ligand to the metal cluster complex.
Obser va tion of a CO-In d u ced Migr a tion of th e
P r op en oyl Liga n d a t th e P er ip h er y of th e Clu ster .
Direct attempts to intercept the above-mentioned ad-
duct A at low temperature remained unsuccessful. So,
while observing that the formation of 4b involved loss
of one carbonyl ligand, we reasoned that treatment of
the latter with CO gas might constitute a retrosynthetic
route to the intermediate A. Complex 4b was effectively
found to react with CO under ambient temperature
conditions to produce the new derivative Ru3(µ-MeNpy)-
(µ-OdC-PhCdCHPh)(PPh3)(CO)8 (5b) (Scheme 2, Fig-
ure 4). However, the latter is not the intermediate A
we are looking for since it results from the incorporation
of two carbonyls.
Sch em e 2
substrate like CO via metal-metal bond opening (the
open edge in 5b is the one supporting the amido bridge
(Ru(1)‚‚‚Ru(2) ) 3.413(1) Å)).
The interconvertibility of the compounds 4b and 5b
reveals an interesting aptitude of the bridging propenoyl
group to migrate reversibly between the edge supported
by the N-CdN bridge and the one supported by the
µ-N atom.
F a cile a n d Rever sible Migr a tor y CO In ser tion
u n d er Ca r bon Mon oxid e. Following the observation
that the addition of triphenylphosphine to 2b causes
migratory CO insertion, it was of interest to determine
whether the addition of CO would have the same effect.
Thus, a stream of CO gas was bubbled through a
solution of 2b at 20 °C. Infrared monitoring indicated
When a stream of nitrogen gas was bubbled through
a solution of the newly formed compound 5b under
ambient conditions, a mixture of 2, 3, and 4 was
obtained.
From the above experiments, we learn that the
phosphine ligands are labile in these complexes and that
the cluster 4b is prone to accommodate an incoming
(15) Shen, J .-K.; Basolo, F.; Lugan, N.; Lavigne, G. Unpublished
observations.

Construction of a Catalytic Hydroformylation Cycle
Organometallics, Vol. 18, No. 2, 1999 191
Sch em e 4
F igu r e 5. Perspective view of the propenoyl complex 6b.
Selected interatomic distances (Å) and bond angles (deg):
Ru(1)-Ru(3) ) 2.7948(7); Ru(2)-Ru(3) ) 2.7559(7); Ru-
(1)-N(1) ) 2.233(5); Ru(2)-N(1) ) 2.194(5); Ru(3)-N(2)
) 2.159(6); Ru(1)-C(10) ) 2.075(6)); Ru(2)-O(10) ) 2.103-
(4); C(10)-O(10) ) 1.251(8); C(10)-C(17) 1.510(8); C(17)-
C(18) ) 1.332(9); Ru(1)-C(10)-O(10) ) 121.3(4); O(10-
C(10)-C(17) ) 113.3(5); C(10)-C(17)-C(18) ) 118.0(5).
Ch a r t 1
Sch em e 3
indicated that hydrogenolysis of the propenoyl ligand
takes place under ambient temperature conditions
under 3 atm of hydrogen to yield R-phenylcinnamalde-
hyde with concomitant recovery of the starting complex
1b. Thus, the hydroformylation of diphenylacetylene is
achieved in a stepwise manner through the cyclic
reaction sequence 1b f 2b f 6b f 1b (Scheme 4).
Ca t a lyt ic R u n s a n d An a lysis of t h e Met a l-
Con ta in in g Sp ecies Recover ed in th e Rea ctor . In
preliminary catalytic runs, it was found that the pro-
duction of R-phenylcinnamaldehyde is effective, even
though the turnover numbers did not exceed 8-10
under nonoptimized standard experimental conditions.
The principal metal-containing species present in the
reactor through these catalytic runs was isolated,
crystallized, and subject to an X-ray diffraction analysis
that allowed its formulation as the bimetallic carbox-
amido complex [Ru{-C(O)-MeNpy}(CO)3]2 (7). Its struc-
ture is shown both in Chart 1 and in Figure 6.
The complex consists of the fusion of two identical
mononuclear Ru fragments linked together through a
metal-metal bond allowing the metal centers to achieve
an octahedral environment. Each Ru center possesses
a carbamoyl ligand derived from the original amido-
pyridyl moiety by CO insertion into the metal-amide
bond. This newly formed ligand is also bound to the
same Ru center by its pyridyl group, thus forming a five-
membered metallacycle which is roughly located in the
plane perpendicular to the unique Ru-Ru bond. The
octahedral environment of each center is completed by
three carbonyl groups adopting a fac arrangement.
the quantitative formation of the new adduct Ru3(µ-
MeNpy)(µ-OdC-PhCdCHPh)(CO)9 (6b) without ob-
servable intermediate (see Scheme 3).
Although stable in CO-saturated solutions under CO
atmosphere, the complex was found to revert rapidly
to the alkenyl complex 2b under inert atmosphere.
Nevertheless, we succeeded in growing suitable crystals
of 6b from CO-saturated solutions at low temperature.
The structure of the compound is shown in Figure 5.
Clearly, two carbonyl groups have been incorporated,
causing (i) an opening of the trinuclear structure, (ii) a
migratory CO insertion of the alkenyl group, and (iii) a
migration of the resulting propenoyl ligand from the site
where it was originally formed (namely, Ru(3)), toward
the open edge Ru(1)‚‚‚Ru(2) of the cluster.
Tr ea tm en t of th e P r op en oyl Com p lex 6b w ith
CO/H2 Mixtu r es; F or m a tion of r-P h en ylcin n a m -
a ld eh yd e. Following the isolation of the propenoyl
adduct Ru3(µ-MeNpy)(µ-OdC-PhCdCHPh)(CO)9 (6b),
it was of interest to investigate its reaction with
hydrogen. Experiments carried out directly in an NMR
tube on CO-presaturated solutions of this complex

192 Organometallics, Vol. 18, No. 2, 1999
Nombel et al.
Sch em e 5
F igu r e 6. Perspective view of the complex 7b. Selected
interatomic distances (Å): Ru(1)-Ru(2) ) 2.9395(3); Ru-
(1)-N(1) ) 2.119(3); Ru(1)-C(4) ) 2.074(3); C(4)-O(4) )
1.223(4); Ru(2)-N(3) ) 2.124(3); Ru(1)-C(8) ) 2.068(3);
C(8)-O(8) ) 1.223(4)
the remarkable ability of this complex to accommodate
extra ligands. One may reasonably expect that the metal
center connected to the rest of the molecule through the
largest number of weak bonds, namely, Ru(1), will be
the more accessible one.
An interesting point is that the phosphine apparently
triggers a remote CO insertion. A speculative mecha-
nism suggesting how this could work is given in Scheme
5, where the proposed intermediates (or transition
states) are based on known structural types (vide infra).
While we believe such a mechanistic proposal is useful
to rationalize the observed behavior, it should be
considered with care, since there is no absolute evidence
that the species we have identified are effectively the
reacting kinetic isomers.
Here, it is assumed that nucleophilic attack of the
phosphine onto Ru(1) (to which the alkenyl group is π
bound) is assisted by opening of the metal-metal bond
Ru(1)‚‚‚Ru(3) and involves a concomitant shift of the two
equatorial edge-bridging carbonyls in terminal position
to give a 50e adduct. The subsequent migratory CO
insertion into the Ru-C(alkenyl) bond may be regarded
as the means by which the cluster relieves its super-
saturation to recover a stable 48e configuration.18 We
suggest that such a migration process does not require
opening of the alkenyl-to-metal π bond. The reduction
in the number of electrons available to the cluster
causes the reformation of the metal-metal bond Ru-
(1)-Ru(3) accompanied by a simultaneous shift of two
equatorial carbonyls back to edge-bridging positions.
This gives a metastable 48e intermediate A being lightly
stabilized by coordination of the π bond of its propenoyl
Attempts to initiate the catalysis by using 7 as a
catalyst precursor were unsuccessful.
Thus, insertion of CO into the Ru-N bond of the
trinuclear species may have affected the linkage of the
supporting ancillary ligand, thereby facilitating a deg-
radation of the cluster followed by recombination of
some of its mononuclear fragments.
Discu ssion
P h osp h in e-In d u ced Migr a tor y CO In ser tion . The
observation of an associative nucleophilic addition of the
phosphine to the alkenyl complex 2b suggests that the
formation of the first metal-phosphine bond is assisted
by a concomitant opening of a particularly weak metal-
ligand or metal-metal bond. In fact, there are several
of such bonds that are supposed to be weak: these
include (i) the metal-nitrogen bonds that constitute the
amido bridge,9,10 (ii) the π bond connecting the alkenyl
group to the metal, and (iii) the metal-metal bonds.
Hypotheses considering the rupture of any of these
bonds are equally reasonable, although reality may be
more complex: indeed, the possibility of a global expan-
sion of the structure via lengthening of several of these
bonds without localized rupture17 may also account for
(16) (a) An independent examination by Cabeza et al.16b of the
parallel reaction between closely related alkenyl complexes (prepared
from 2-amino-6-methylpyridine) and CO led to an erroneous formula-
tion of the reaction product as a terminal σ-alkenyl derivative. The
compound was subsequently re-formulated16c as a propenoyl complex
similar to the one originally identified in our preliminary communica-
tion.12 (b) Cabeza, J . A.; Fernandez-Colinas, J . M.; Llamazares, A.;
Riera, V.; Garcia-Granda, S.; Van der Maelen, J . F. Organometallics
1994, 13, 4352. (c) Cabeza, J . A.; Fernandez-Colinas, J . M.; Llamazares,
A.; Riera, V.; Garcia-Granda, S.; Van der Maelen, J . F. Organometallics
1995, 14, 3120.
(18) (a) There are several reported examples where a cluster relieves
its supersaturation by reductive formation of CN18b or CC18c bonds,
see: (b) Ramage, D. L.; Geoffroy, G. L.; Rheingold, A. L.; Haggerty, B.
S. Organometallics 1992, 11, 1242. (c) Rivomanana, S.; Mongin, C.;
Lavigne, G. Organometallics 1996, 15, 1195.
(17) Lugan, N.; Fabre, P. L.; de Montauzon, P. L.; Lavigne, G.;
Bonnet, J .-J .; Saillard, J .-Y.; Halet, J . F. Inorg. Chem. 1994, 33, 434.

Construction of a Catalytic Hydroformylation Cycle
Organometallics, Vol. 18, No. 2, 1999 193
Ch a r t 2
Qu estion s Rega r d in g th e Rever sible Migr a tion
of P r op en oyl Gr ou p s a t th e P er ip h er y of th e
Clu ster . It is noteworthy that the reaction of 4b with
CO (Scheme 3) not only results in the opening of a
metal-metal bond but also induces a migration of the
propenoyl group at the periphery of the cluster. Also,
in the reaction of 2b with CO, the observed isomer for
the propenoyl derivative 6b is not the one that would
result from a simple migratory CO insertion. At the
present stage of our investigation, we do not understand
why such migrations do occur and why they are so
cleanly reversible.
group to the metal center Ru(1). The kinetic lability of
this bond will favor the formation of an unsaturated
intermediate Ai bearing a terminal propenoyl ligand.
The latter may enter in equilibrium with an isomeric
form Aii in which the unsaturation that originally
appeared onto Ru(1) has been transferred onto Ru(2)
by a simple migration of a bridging carbonyl into a
terminal position. Each of these isomers is susceptible
to decay by a different pathway: on one hand, free
rotation around the Ru-C(acyl) bond in Ai allows
intramolecular capture of the vacant coordination site
by the acyl oxygen atom to produce 3b. On the other
hand, the vacant site available in Aii may be intercepted
by a second incoming phosphine prior to the intramo-
lecular rearrangement of the propenoyl group. Further
rearrangement of this group then takes place in the
final reaction step and involves geminal CO labilization
by the propenoyl oxygen atom to produce 4b.
Satisfactory models for the migration of acyl groups
at two metal centers have been proposed by Kaesz and
co-workers24 on the basis of the existence of a bimetallic
acyl species in which both C and O atoms were seen to
occupy edge-bridging positions.25 Alternatively, migra-
tion of the acyl from its original equatorial position to
an axial position may be also considered. This would
favor the interaction of the acyl CdO bond with three
metal centers, as previously observed with other trime-
tallic cluster species.26 A “windshield wiper” motion of
the propenoyl group onto the face opposed to the
amidopyridyl group would account for the formation of
the observed isomer in which the propenoyl ligand is
effectively adopting a pseudoaxial position. In addition
to the above hypotheses, however, we cannot exclude
the alternate possibility of a rotation of the anilino-
pyridyl group itself onto the metal triangle, although
evidence for such a process would be difficult to obtain.
For m ation of r-P h en ylcin n am aldeh yde. The step-
wise stoichiometric production of R-phenylcinnamalde-
hyde from 1b via the intermediacy of 2b and 6b is of
some practical interest on a laboratory scale since (i)
the reaction can be carried out under very mild condi-
tions, (ii) R-phenylcinnamaldehyde is easily separated
by simple crystallization from the solution in which it
has been prepared, and (iii) the starting cluster can be
recovered in solution. Unfortunately, the limited vi-
ability of the cluster under catalytic conditions (8-10
cycles) constitutes a drawback to more extensive ap-
plications of this system. It may be that a precise
optimization of the CO and H2 pressures as well as the
use of more reactive alkynes would give better results.
However, we are now convinced that the domain of
experimental conditions under which the reaction can
cycle catalytically without alteration of the metal frame-
work will remain too narrow for intensive exploitation.
Arguments that are consistent with the proposed
reaction scheme are the following.
(a) Models for the nucleophilic addition of various
ligands to a species of type 2 are found in the chemistry
2b
of the isostructural complex Ru3(µ-PhPpy)(µ-PR2)(CO)8
(see Chart 2, in which a phosphido group is seen to
occupy the same edge-bridging equatorial position as
the alkenyl group in 2).
Indeed, it was previously found2b that CO addition
to Ru3(µ-PhPpy)(µ-PR2)(CO)8 results in an opening of
the metal-metal bond bearing the equatorial diphen-
ylphosphido ligand and a concerted shift of edge-
bridging carbonyls to terminal positions, to produce the
50e adduct Ru3(µ-PhPpy)(µ-PR2)(CO)9.
(b) The recent report of a triruthenium complex
bearing a σ-η1 propenoyl ligand19 strengthens our
proposal of a similar structural arrangement in the
transient species Ai and Aii.
(c) Propenoyl ligands stabilized by π donation from
their carbon-carbon double bond to the metal are
known in the chemistry of mononuclear complexes.20
Bridged forms of these have been independently pos-
tuladed by Ojima21 and Seyferth22 as intermediates in
multicentered migratory CO insertion processes. Fi-
nally, while the present paper was reviewed, the first
cluster compound bearing a π-bound R,â-unsaturated
acyl group was effectively reported by Hogarth.23
Con clu sion
The triruthenium cluster complex Ru3(µ3-RNpy)(µ-
PhCdCHPh)(CO)8 exhibits an interesting behavior
enabling its use as a prototype in model studies of
cluster-mediated carbon-carbon bond forming reactions
involving an alkenyl group. Indeed, this cluster under-
goes associative nucleophilic addition of electron donor
substrates such as PPh3 or CO under very mild condi-
tions. The supersaturation of the resulting adduct is
(19) Kabir, S. E.; Rosenberg, E.; Milone, L.; Gobetto, R.; Osella, D.;
Ravera, M.; McPhillips, T.; Day, M. W.; Carlot, D.; Hajela, S.; Wolf,
E.; Hardcastle, K. Organometallics 1997, 16, 2674.
(20) Mitsudo, T.; Fujita, K.; Nagano, S.; Suzuki, T.; Watanabe, Y.;
Masuda, H. Organometallics 1995, 14, 4228.
(21) Ojima, I.; Ingallina, P.; Donovan, R. J .; Clos, N. Organometallics
1991, 10, 38
(22) Seyferth, D.; Archer, C. M.; Ruschke, D. P. Organometallics
1991, 10, 3363
(23) Doherty, S.; Hogarth, G. Inorg. Chem. Commun. 1998, 1, 257.
(24) J ensen, C. M.; Chen, Y.-J .; Knobler, C. B.; Kaesz, H. D. New J .
Chem. 1988, 12, 649.
(25) Sunkel, K.; Schloter, K.; Beck, W.; Ackerman, K.; Schubert, U.
J . Organomet. Chem. 1983, 241, 333.
(26) Blake, A. J .; Dyson, P. J .; J ohnson, B. F. G.; Martin, C. M. J .
Organomet. Chem. 1995, 492, C17

194 Organometallics, Vol. 18, No. 2, 1999
Nombel et al.
P r ep a r a tion of Ru 3{µ3-(CH3)N(C5H4N)}{µ-(C6H5)CdCH-
(C6H5)}(CO)8 (2b). Crystals of the complex 1b (200 mg, 0.30
mmol) and diphenylacetylene (54 mg, ca. 0.30 mmol) were
dissolved in heptane (20 mL). The solution was heated at 60
°C for 45 min. This initially caused a gradual color change
from orange to red, followed by a lightening of the solution
accompanying the progressive formation of a garnet-red
precipitate. The resulting suspension was then allowed to cool
to room temperature, and the precipitate was subsequently
recovered by filtration under nitrogen, washed several times
with heptane, and dried under vacuum (yield 85-95%). It is
noteworthy that this complex (unlike alkenyl species of the
same type obtained with other alkynes) is only very slightly
soluble in most usual solvents, which prevents the recording
of its NMR spectrum.
then spontaneously relieved by a facile migration of the
alkenyl group to a coordinated carbonyl ligand. Hydro-
genolysis of the newly formed propenoyl group under
CO/H2 gas mixtures leads to the liberation of the
corresponding R,â-unsaturated aldehyde, which can be
easily separated. Unfortunately, the viability of such a
system under catalytic conditions is limited by competi-
tive CO insertion into the Ru-N bond of the bridging
methylamidopyridyl group, converting the latter into a
carboxamido group. Such a change in the ancillary
ligand’s anchorage to the cluster inevitably leads to a
deadend with the liberation of mononuclear fragments
that further reaggregate into a stable but inactive
bimetallic species.
Ru 3{µ3-(CH3)N(C5H4N)}{µ-(C6H5)CdCH(C6H5)}(CO)8 (2b).
Anal. Calcd (found) for C28H18N2O8Ru3: C, 41.33 (41.11); H,
2.23 (2.40); N, 3.44 (3.37).
A tantalizing observation in this work is that the
cluster exhibits its most attractive and valuable proper-
ties under mild experimental conditions that are yet still
very close to those susceptible to cause its degradation.
R ea ct ion of t h e Alk en yl Com p lex R u 3{µ3-(CH 3)N-
(C5H4N)}{µ-(C6H5)CdCH(C6H5)}(CO)8 (2b) w ith 1 equ iv of
Tr ip h en ylp h osp h in e: P r ep a r a tion of th e Ad d ition P r od -
u ct Ru 3{µ3-(CH3)N(C5H4N)}{µ-OdC-(C6H5)CdCH(C6H5)}-
{P (C6H5)3}(CO)7 (3b). In a typical experiment, a suspension
of complex 2b (250 mg, 0.31 mmol) was stirred in 20 mL of
dichloromethane. The addition of triphenylphosphine (80 mg,
0.31 mmol) caused the rapid dissolution of the suspension
within less than 3 min, giving a limpid solution exhibiting an
intense dark red color. This solution was reduced in volume
under vacuum and chromatographed on alumina. Elution with
pure pentane allowed the separation of trace amounts of a
yellow oil (insufficient amount for proper characterization).
Further elution with 2:3 pentane/dichloromethane allowed the
separation of two distinct fractions. The first one, of pink color,
contained small amounts of unreacted starting complex 2b,
whereas the second one, of red color, gave a red oil after solvent
evaporation. Further recrystallization of this oil from dichlo-
romethane/pentane at -30 °C gave red crystals of a new
complex subsequently characterized as 3b (160 mg, 0.15 mmol,
48% yield). A third fraction, of black color, was eluted with
1:2 pentane/dichloromethane. After solvent evaporation, it was
recovered as a red oil, subsequently characterized as 4b (85
mg, 0.06 mmol, 19%). Larger amounts of the latter species
were subsequently obtained by using a more appropriate
metal/ligand ratio, as described in the following paragraph.
R u 3{µ3-(CH 3)N(C5H 4N)}{µ-OdC-(C6H 5)CdCH (C6H 5)}-
{P (C6H5)3}(CO)7 (3b): red color; IR (CH2Cl2) ν [cm-1] ) 2030-
(vs), 1994(vs), 1969(m), 1935(m), 1860(vw), 1817(m), 1610(vw)
(CdO); 1H NMR (CDCl3) δ ) 8.15-6.20 (m, aromatic protons),
8.10 (s, vinylic CH), 2.58 (s, NCH3); 31P NMR {1H} (CDCl3) δ
) 21.13 (PPh3); 13C{1H} NMR δ ) 263.74 (CO, acyl), 239.53
229.10 (µ-CO), 203.96-196.82 (CO), 170.46, 152.97, 115.22,
112.23 (pyridyl carbons), 56.40 (NCH3). Anal. Calcd (found)
for C47H35N2O8Cl2P1Ru3 (3b‚CH2Cl2): C, 48.63 (48.52); H, 3.04
(2.73); N, 2.41 (2.33).
R ea ct ion of R u 3{µ3-(CH 3)N(C5H 4N)}{µ-(C6H 5)CdCH -
(C6H5)}(CO)8 (2b) w ith 2 equ iv of Tr ip h en ylp h osp h in e:
P r ep a r a tion of Ru 3{µ3-(CH3)N(C5H4N)}{µ-OdC-(C6H5)Cd
CH(C6H5)}{P (C6H5)3}2(CO)6 (4b). The preceding reaction was
reproduced under the same experimental conditions, but using
a 2-fold amount of triphenylphosphine in a typical experiment,
where the exact quantities of reagents were the following: 2b
(220 mg, 0.27 mmol), PPh3 (139 mg, 0.53 mmol), dichlo-
romethane (20 mL). The reaction was complete within 7-10
min. The solvent was then reduced in volume and chromato-
graphed in the same way as in the previous experiment (vide
supra). Chromatographic workup revealed the absence of any
trace of starting material, whereas the relative abundance of
3b and 4b was modified: the complex 3b (90 mg, 0.08 mmol,
30% yield) was still present in unexpectedly large amounts,
whereas 4b (160 mg, 0.12 mmol, 44% yield) was the major
species obtained under these experimental conditions. Suitable
Exp er im en ta l Section
Gen er a l Com m en ts. All synthetic manipulations were
carried out under a nitrogen atmosphere, using standard
Schlenk techniques. Tetrahydrofuran was distilled under
argon from sodium benzophenone ketyl just before use. Dichlo-
romethane, pentane, and hexane were distilled under nitrogen
from CaH2 and stored under nitrogen. The following reagent
grade chemicals were used without further purification: RuCl3‚
nH2O (J ohnson Matthey), phenylacetylene (Fluka), dipheny-
lacetylene (Lancaster), 2-(methylamino)pyridine (Aldrich).
Ru3(CO)12 was prepared according to a published proce-
dure.27 The syntheses of methylamidopyridyl complexes Ru3-
(µ-H)(µ3-MeNpy)(CO)9 (1b) and Ru3(µ3-MeNpy)(µ-PhCdCHPh)-
(CO)8 (2b) described below are slight modifications of relevant
procedures published for the corresponding anilinopyridyl
complexes.9b Chromatographic separations of the complexes
were carried out either on Silicagel 60 (SDS, 70-230 mesh)
or on aluminum oxide 90 active neutral (Merck, 70-230 mesh
astm), as specified in the detailed procedures (vide infra).
The reactions were monitored by IR spectroscopy, following
the evolution of ν(CO) absorptions. These spectra were re-
corded on a Perkin-Elmer 225 grating spectrophotometer and
calibrated against water vapor absorptions. NMR spectra were
recorded on Bruker AC 200 and Bruker WM 250. Mass spectra
were recorded on a Ribermag R10-10.
P r ep a r a tion of Ru 3(µ-H){µ3-(CH3)N(C5H4N)}(CO)9 (1b).
The complex Ru3(C0)12 (1.0 g, 1.6 mmol) and 2-(methylamino)-
pyridine (1.0 g, 1.6 mmol) were dissolved in benzene (90 mL)
in a Schlenk flask equipped with a reflux condenser and
connected to a vacuum line. The solution was heated under
reflux until complete disappearance of the characteristic
absorption bands of Ru3(CO)12 (ca. 3 h). It was then allowed
to cool to room temperature. After complete evaporation of the
solvent under vacuum, the solid residue was recovered with
the minimum amount of dichloromethane and chromato-
graphed on a silicagel column. Traces of residual Ru3(CO)12
were eluted first with pure hexane, whereas further elution
with a 1:3 dichloromethane/hexane mixture resulted in a
unique orange fraction containing the pure reaction product,
which was recrystallized from the same reaction mixture at
-30 °C (yield 85-90%).
Ru 3(µ-H){µ3-(CH3)N(C5H4N)}(CO)9 (1b): orange crystals;
IR (heptane) ν [cm-1] ) 2076(m), 2046(s), 2026(s), 1999(s),
1988(vs), 1972(w), 1965(mw) (ν CO); 1H NMR (200 MHz,
CDCl3) δ 8.16-6.47 (aromatic protons), 3.08 (s, CH3), -10.68
(s, hydride).
(27) Mantovani, A.; Cenini, S. Inorg. Synth. 1972, 16, 47.

Construction of a Catalytic Hydroformylation Cycle
Organometallics, Vol. 18, No. 2, 1999 195
Ta ble 1. Cr ysta l Da ta , Da ta Collection , a n d Refin em en t P a r a m eter s for Com p ou n d s 2b-7b
2b
3b
4b
5b
6b
7b
Crystal Data
chemical formula
C
28H18N2O8Ru3 C47H35Cl2N2O8- C63H48N2O7P2Ru3 C48H33Cl2N2O9- C30H18O10N2Ru3 C20H14O8N4Ru2
PRu3
PRu3
solvent molecules
molecular weight
crystal system
space group
a (Å)
0.5 CH2Cl2
1369.43
monoclinic
P21/n
14.579
16.763
27.174
90.00
100.87
90.00
6522
4
1.39
813.67
monoclinic
P21/c
12.037(2)
16.613(1)
14.466(2)
90.00
104.34(1)
90.00
2803(1)
4
1158.88
monoclinic
P21/n
12.798(5)
22.290(4)
16.328(2)
90.00
93.54(2)
90.00
4649(3)
4
1186.89
monoclinic
P21/c
10.130(1)
21.545(3)
22.088(2)
90.00
93.98(1)
90.00
4809(1)
4
869.69
monoclinic
P21/n
10.600(1)
10.002(1)
29.721(6)
90.00
99.13(1)
90.00
3111(1)
4
640.49
triclinic
P1h
8.983(4)
10.653(3)
12.043(3)
104.23(2)
101.14(3)
93.90(3)
1087.9(7)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
Fcalcd (g cm-3
)
1.93
16.2
1.66
11.5
1.64
11.1
1.85
14.7
1.96
14.2
µ (mm-1
)
10.2
Data Collection
radiation
data collection method ω/2θ
graphite monochromated, Mo KR (λ ) 0.710 73 Å)
ω/2θ
ω/2θ
ω/2θ
ω/2θ
ω/2θ
no. of obsd reflns
observation criterion
θ max (deg)
2896
Fo > 3σFo
23
0 e h e 13
0 e k e 18
-15 e l e 15
4497
1837
Fo > 3σFo
23
3969
Fo > 3σFo
23
4706
Fo > 3σFo
23
3821
2
2
2
2
2
2
2
2
2
2
2
2
Fo > 3σFo
Fo > 3σFo
23
23
range of h, k, l
0 e h e 15
0 e k e 26
-19 e l e 19
-14 e h e 13
0 e k e 16
0 e l e 26
-12 e h e 12
0 e k e 25
0 e l e 26
0 e h e 12
0 e k e 11
-35 e l e 35
0 e h e10
-12 e k e 12
-14 e l e 314
scan range θ (deg)
0.8 + 0.35 tan θ 0.9 + 0.35 tan θ 0.9 + 0.35 tan θ
0.8 + 0.35 tan θ 0.8 + 0.35 tan θ 0.9 + 0.35 tan θ
Refinement
R
0.0293
0.0262
0.0939
0.0350
0.0721
0.0342
Rw
0.0342
0.0296
0.1062
0.0402
0.0772
0.0313
weighting scheme
coeff Ar
Chebyshev
1.02, 0.525,
0.628
Chebyshev
2.58, -0.813,
1.84
Chebyshev
1.25, 0.693,
0.834
Chebyshev
0.744, 0.183,
0.471
Chebyshev
3.80, 2.59,
2.62
Chebyshev
1.520, 0.208,
0.165
no. of reflns used
no. of params refined
GOFa
2896
370
0.8836
4497
568
0.9622
1837
201
1.11
3969
586
1.0837
4706
406
0.9968
3821
307
1.2422
residual electron
-0.887/0.750
-0.647/0.608
-0.811/1.552
-0.474/0.970
-1.575/0.867
-1.63/0.99
density (e.Å-3
)
a
Goodness of fit ) [∑w(|Fo| - |Fo|)2/(Nobs - Nparams)]1/2
.
crystals for an X-ray structure analysis of the latter compound
were grown from a benzene/hexane mixture.
under the influence of the gas stream, 10 mL of hexane was
added, causing the precipitation of orange crystals of the new
compound 5b (40 mg, 0.036 mmol, 47% yield).
R u 3{µ3-(CH 3)N(C5H 4N)}{µ-OdC-(C6H 5)CdCH (C6H 5)}-
{P (C6H5)3}2(CO)6 (4b): black color; IR (CH2Cl2) ν [cm-1] )
2008(vs), 1955(m), 1940(vs), 1853(w), 1755(m), 1608(vw) (Cd
O);1H NMR (CDCl3) δ ) 8.46-5.88 (m, aromatic protons), 8.04
(s, vinylic CH), 1.61 (s, NCH3); 31P NMR {1H} (CDCl3) δ )
44.07 (d, PPh3, 3J (PP) ) 25.8 Hz); 13C{1H} NMR δ ) 257.89 (CO,
acyl), 240.55, 237.39 (µ-CO), 204.74-198.00 (CO), 170.86,
154.06, 113.81, 112.18 (pyridyl carbons), 22.48 (NCH3). Anal.
Calcd (found) for C63H48N2O7P2Ru3 (3b‚CH2Cl2): C, 57.77
(57.75); H, 3.69 (3.70); N, 2.14 (2.12).
Rea ction of th e Ad d u ct 3b w ith Tr ip h en ylp h osp h in e
Un d er Th er m a l Activa tion : Syn th esis of th e Disu bsti-
tu ted Der iva tive 4b. Crystals of the complex 3b (130 mg,
0.12 mmol) and 1 equiv of triphenylphosphine (32 mg, 0.12
mmol) were dissolved in 15 mL of toluene. No reaction was
observed when this solution was stirred at room temperature
for 1 h. However, the formation of 4b started when the
temperature was raised to 50 °C; the reaction was then
spectroscopically quantitative within 30 min.
Rea ction of Ru 3{µ3-(CH3)N(C5H4N)}{µ-OdC-(C6H5)Cd
CH(C6H5)}{P (C6H5)3}2(CO)6 (4b) w ith Ca r bon Mon ox-
id e: Syn th esis of Ru 3{µ3-(CH3)N(C5H4N)}{µ-OdC-(C6H5)-
CdCH(C6H5)}{P (C6H5)3}(CO)8 (5b). Crystals of the complex
4b were dissolved in dichloromethane (15 mL) in a Schlenk
tube. A continuous stream of gaseous carbon monoxide was
bubbled through this solution for 6 h at room temperature. A
progressive lightening of the solution was observed, whereas
IR monitoring indicated the formation of a new compound.
After partial evaporation of the solution to a third of its volume
R u 3{µ3-(CH 3)N(C5H 4N)}{µ-OdC-(C6H 5)CdCH (C6H 5)}-
{P (C6H5)3}(CO)8 (5b): orange color: IR (CH2Cl2) ν [cm-1] )
2051(s), 2019(vs), 1990(s), 1965(m), 1950(m) (CdO);1H NMR
(CDCl3) δ ) 8.14-6.20 (m, aromatic protons and vinylic CH),
1.57 (s, NCH3); 31P NMR {1H} (CDCl3)d ) 15.50 (s, PPh3).
Tr a n sfor m a t ion of R u 3{µ3-(CH 3)N(C5H 4N)}{µ-OdC-
(C6H5)CdCH(C6H5)}{P (C6H5)3}(CO)8 (5b) u n d er a Str ea m
of In er t Ga s. Crystals of the complex 5b (50 mg, 0.05 mmol)
were dissolved in dichloromethane (5 mL). A continuous
stream of nitrogen gas was then bubbled through the solution
at room temperature. IR monitoring indicated the progressive
transformation of the initial complex over a period of 15 min.
Evaporation of the resulting solution under reduced pressure
produced a red oil, which was dried under vacuum. NMR
analysis of the redissolved product showed it to consist of a
mixture of 3b, 4b, and 2b.
R ea ct ion of R u 3{µ3-(CH 3)N(C5H 4N)}{µ-(C6H 5)CdCH -
(C6H5)}(CO)8 (2b) w ith Ca r bon Mon oxid e: P r ep a r a tion
of Ru 3{µ3-(CH3)N(C5H4N)}{µ-(C6H5)CdCH(C6H5)}(CO)9 (6b).
A suspension of 2b (100 mg, 0.12 mmol) in 10 mL of dichlo-
romethane was stirred at room temperature in a Schlenk tube
under nitrogen. A continuous stream of gaseous carbon
monoxide was bubbled into the liquid through a gas inlet. Total
dissolution of the initial suspension was obtained within 20
min. At that stage, the CO gas inlet was raised above the
solution, and magnetic agitation was stopped. The addition of
10 mL of hexane caused the slow crystallization of the new
complex 6b recovered as yellow crystals (85 mg, 0.10 mmol,

196 Organometallics, Vol. 18, No. 2, 1999
Nombel et al.
83% yield) directly suitable for an X-ray structure analysis.
Although the complex is fairly stable as a solid, its solutions
must be kept under carbon monoxide (1 atm). Otherwise, it
reverts to the starting alkenyl complex within less than 1 min.
R u 3{µ3-(CH 3)N(C5H 4N)}{µ-OdC-(C6H 5)CdCH (C6H 5)}-
(CO)9 (6b): yellow color; IR (CH2Cl2) ν [ cm-1] ) 2070(vw),
2047(s), 2017(s), 1992(m), 1978(m), 1955(sh) (CdO);1H NMR
(CDCl3) δ ) 8.02-6.30 (m, aromatic protons and vinylic CH),
3.09 (s, NCH3); 13C NMR {1H} (CDCl3) δ ) 302.17 (CO, acyl),
204.54-199.46 (CO (terminal ligands)), 180.67, 153.42, 138.82,
117.69, 106.02 (C, pyridine), 155.76 (PhC(CO)), 136.77, 135.17
(C, ipso), 133.76 (C(H)Ph), 60.30 (NCH3).
Tr ea tm en t of 6b w ith H2/CO: F or m a tion of r-P h en yl-
cin n a m a ld eh yd e. The reaction was first carried out in an
NMR tube and then reproduced on a preparative scale.
(a ) NMR Exp er im en t. A suspension of 2b (70 mg, 0.08
mmol) in deuterated chloroform was subject to treatment with
CO gas in the same way as described above. The resulting
limpid CO-saturated solution was then introduced in an NMR
tube. 1H NMR indicated the presence of 6b as the only species
in solution. The tube was then charged with hydrogen (1 atm).
A new NMR spectrum taken after 24 h indicated the presence
of a mixture of 1b, 6b, and R-phenylcinnamaldehyde.
(b) Stoich iom etr ic Syn th esis of r-p h en ylcin n a m a ld e-
h yd e. A suspension of complex 2b (150 mg, 0.18 mmol) in
dichloromethane (5 mL) was introduced in a glass reactor. The
complex 6b was then generated in situ by treatment with CO
gas in the same way as described above. A limpid CO-
saturated solution of 6b was thus obtained. The reactor was
then closed, pressurized with 5 atm of hydrogen, and stirred
at 40 °C overnight. After evaporation of the solvent, the residue
was characterized as a mixture of complex 1b and R-phenyl-
cinnamaldehyde.
containing R-phenylcinnamaldehyde subsequently recovered
as white crystals (178 mg, 0.82 mmol), corresponding to a
turnover of 8. Further elution with 2:1 hexane/dichloromethane
allowed the recovery of a yellow fraction from which crystals
of the new dimeric complex 7 (27 mg, 0.043 mmol) were
isolated and subject to an X-ray structure analysis.
[Ru {C(O)N(CH3)(C5H4N)}]2: yellow; IR (CH2Cl2) ν [ cm-1
) 2077(s), 2072(sh), 2043(vs), 2008(s), 1983(s) (CdO).
]
X-r a y Str u ctu r e Deter m in a tion s. Table 1 summarizes
crystal and intensity data for compounds 2b, 3b, 4b, 5b, 6b,
and 7b. Intensity data were collected on an Enraf-Nonius
CAD4 diffractometer. The cell constants were obtained by
least-squares refinement of the setting angles of 25 reflections
in the range 24° < 2θ(Mo KR1) < 28°. Data reductions were
carried out using the CRYSTALS package.28 The structures
were solved by direct methods, using SIR92,29 and refined with
CRYSTALS. Perspective views of the molecules were drawn
with the program CAMERON.30 Selected bond distances and
angles for the compounds 2b-7b are included in the captions
of the corresponding Figures 1-6.
Note: Due to the limited number of reflections available
for 4b, inherent to the poor quality of the crystal, only a few
atoms were refined with anisotropic thermal parameters,
whereas phenyl rings were treated as rigid groups.
Ack n ow led gm en t. Financial support of this work
by the CNRS is gratefully acknowledged. We also thank
Herbert D. Kaesz for discussion of this work under
support of NATO Grant 931414, and Fred Basolo for
the personal communication of his kinetic study.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data for compounds 2b-7b including tables of atomic coordi-
nates, hydrogen coordinates, anisotropic thermal parameters,
and interatomic distances and bond angles (44 pages). Order-
ing information is given on any current masthead page.
P h HCdCP h CHO: IR (CH2Cl2) ν [cm-1] ) 1685(s) (CdO);
1H NMR (CDCl3) δ ) 9.78 (s, CHO), 7.45-7.18 (m, aromatic
protons and vinylic protons); 13C {1H} NMR (CDCl3) δ ) 193.8
(CHO), 150.1 (Ca), 141.6 (ipso R-Ph), 133.8 (ipso â-Ph)
Ca ta lytic Hyd r ofor m yla tion of Dip h en yla cetylen e.
The catalyst precursor 1b (70 mg, 0.11 mmol), diphenylacet-
ylene (940 mg, 5.30 mmol), and 15 mL of dichloromethane were
introduced in an autoclave, which was subsequently pressur-
ized with 5 atm of CO and 15 atm of hydrogen. The solution
was continuously stirred with a magnetic agitator, and the
temperature was raised to 70 °C. After 24 h, the reaction was
stopped and the residue was chromatographed on an alumi-
num column. Elution with hexane gave a first fraction
containing diphenylacetylene, followed by a second fraction
OM9806747
(28) Watkin, D. J .; Carruthers, J . R.; Betteridge, P. W. CRYSTALS
User Guide; Chemical Crystallography Laboratory, University of
Oxford: Oxford, U.K., 1985.
(29) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guargliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. SIR92, a program for automatic
solution of crystal Structures by direct methods. J . Appl. Crystallogr.
1994, 27, 435.
(30) Watkin, D. J .; Prout, C. K.; Pearce, L. J . CAMERON; Chemical
Crystallography Laboratory: University of Oxford, Oxford, U.K., 1996.