Self-activation of a cluster-bound alkyne toward carbon-carbon bond forming reactions

Article abstract of DOI:10.1021/om950835w

The methanol-catalyzed elimination of Cl^- from the activated anionic species [PPN][Ru₃-(μ-Cl)(M-PhCCPh)(CO)₉] (1) in the presence of bis(diphenylphosphino)methane (dppm) constitutes a rational high-yield route (>90%) to either the unique unsaturated 46-e (alkyne)-triruthenium cluster, Ru₃(μ-PhCCPh)(CO)₇(dppm) (2), or its 48-e CO adduct, Ru₃(μ-PhCCPh)-(CO)₈(dppm) (3). Whereas the CO-induced conversion of 2 into 3 is complete within few seconds at 25 °C under 1 atm of CO, the reverse transformation takes 1 h at 80 °C. The X-ray structure analysis of 2 is reported, revealing a perpendicular conformation of the alkyne relative to the metal triangle. The high reactivity of 2 is substantiated by a high chemical reactivity toward 2-e donors. Its reaction with 1 equiv of dppm (25 °C, 3 h) leads to the bis-dppm-substituted complex, Ru₃(μ-PhCCPh)(CO)₆(dppm)₂ (4) (53% yield). Reaction of 2 with hydrogen gas (1 atm, 25 °C, 10 min) yields the dihydrido species, Ru₃(μ-H)₂(μ-PhCCPh)-(CO)₇(dppm) (5) (89% yield) existing as a mixture of two isomers differing in the orientation of the alkyne relative to the edge-bridging dppm ligand. Complex 2 reacts with a terminal alkyne like phenylacetylene under mild conditions to afford a mixture of the fly-over type compound Ru₃{μ-HCC(Ph)C(O)(Ph)CCPh}(dPPm)(CO)₆ (6) (57% yield) and the diruthenacyclopentadiene derivative Ru₂{μ-HCC(Ph)(Ph)CCPh}(μ-dppm)(CO)₄ (7) (20% yield). The structure of 6 reveals the occurrence of a disymmetric edge-bridging dialkenyl ketone ligand HC=C(Ph)C(O)(Ph)C=CPh, resulting from regioselective coupling between the two alkynes and a carbonyl group. The formal unsaturation of 6 is masked by a weak interaction between the terminal C-Ph bond of the organic chain and one of the metal centers. Facile loss of this interaction is induced by mild thermolysis of 6. As a consequence, free rotation of the organic moiety around the metal-metal edge brings the opposite end of the organic chain (i.e., the C-H bond) close to the opposite face, thereby favoring CH activation to convert the alkenyl end into a vinylidene. This leads to quantitative formation of the vinylidene alkenyl ketone derivative, Ru₃(μ-H){μ-CC(Ph)C(O)(Ph)CCPh}(dppm)(CO)₆ (8) (94% yield). The X-ray structure of 8 is reported. Unsuccessful attempts to release the organic moiety from the cluster core are described. The reaction of a THF solution of 6 with CO in a reactor [P(CO) = 10 atm, T = 80 °C] leads to the new binuclear fly-over species Ru₂{μ-HCC(Ph)C-(O)(Ph)CCPh}(CO)₆ (9a), thereby indicating that elimination of the edge-bridging dppm and cluster fragmentation are more favorable than elimination of a free ketone from the intact cluster. The X-ray structure of Ru₂{μ-HCC(C₃H₇)C(O)(Ph)CCPh}(CO)₆ (9b) (resulting from the coupling between diphenylacetylene and 1-pentyne) is reported.

Full text of DOI:10.1021/om950835w

Organometallics 1996, 15, 1195-1207
1195
Self-Activa tion of a Clu ster -Bou n d Alk yn e tow a r d
Ca r bon -Ca r bon Bon d F or m in g Rea ction s
Soa Rivomanana, Carole Mongin, and Guy Lavigne*
Laboratoire de Chimie de Coordination du CNRS, UPR No. 8241, 205 route de Narbonne,
31077 Toulouse Cedex, France
Received October 23, 1995X
The methanol-catalyzed elimination of Cl- from the “activated” anionic species [PPN][Ru3-
(µ-Cl)(µ-PhCCPh)(CO)9] (1) in the presence of bis(diphenylphosphino)methane (dppm)
constitutes a rational high-yield route (>90%) to either the unique unsaturated 46-e (alkyne)-
triruthenium cluster, Ru3(µ-PhCCPh)(CO)7(dppm) (2), or its 48-e CO adduct, Ru3(µ-PhCCPh)-
(CO)8(dppm) (3). Whereas the CO-induced conversion of 2 into 3 is complete within few
seconds at 25 °C under 1 atm of CO, the reverse transformation takes 1 h at 80 °C. The
X-ray structure analysis of 2 is reported, revealing a perpendicular conformation of the alkyne
relative to the metal triangle. The high reactivity of 2 is substantiated by a high chemical
reactivity toward 2-e donors. Its reaction with 1 equiv of dppm (25 °C, 3 h) leads to the
bis-dppm-substituted complex, Ru3(µ-PhCCPh)(CO)6(dppm)2 (4) (53% yield). Reaction of 2
with hydrogen gas (1 atm, 25 °C, 10 min) yields the dihydrido species, Ru3(µ-H)2(µ-PhCCPh)-
(CO)7(dppm) (5) (89% yield) existing as a mixture of two isomers differing in the orientation
of the alkyne relative to the edge-bridging dppm ligand. Complex 2 reacts with a terminal
alkyne like phenylacetylene under mild conditions to afford a mixture of the “fly-over” type
compound Ru3{µ-HCC(Ph)C(O)(Ph)CCPh}(dppm)(CO)6 (6) (57% yield) and the diruthena-
cyclopentadiene derivative Ru2{µ-HCC(Ph)(Ph)CCPh}(µ-dppm)(CO)4 (7) (20% yield). The
structure of 6 reveals the occurrence of a disymmetric edge-bridging dialkenyl ketone ligand
HCdC(Ph)C(O)(Ph)CdCPh, resulting from regioselective coupling between the two alkynes
and a carbonyl group. The formal unsaturation of 6 is masked by a weak interaction between
the terminal C-Ph bond of the organic chain and one of the metal centers. Facile loss of
this interaction is induced by mild thermolysis of 6. As a consequence, free rotation of the
organic moiety around the metal-metal edge brings the opposite end of the organic chain
(i.e., the C-H bond) close to the opposite face, thereby favoring CH activation to convert
the alkenyl end into a vinylidene. This leads to quantitative formation of the vinylidene
alkenyl ketone derivative, Ru3(µ-H){µ-CC(Ph)C(O)(Ph)CCPh}(dppm)(CO)6 (8) (94% yield).
The X-ray structure of 8 is reported. Unsuccessful attempts to release the organic moiety
from the cluster core are described. The reaction of a THF solution of 6 with CO in a reactor
[P(CO) ) 10 atm, T ) 80 °C] leads to the new binuclear “fly-over” species Ru2{µ-HCC(Ph)C-
(O)(Ph)CCPh}(CO)6 (9a ), thereby indicating that elimination of the edge-bridging dppm and
cluster fragmentation are more favorable than elimination of a free ketone from the intact
cluster. The X-ray structure of Ru2{µ-HCC(C3H7)C(O)(Ph)CCPh}(CO)6 (9b) (resulting from
the coupling between diphenylacetylene and 1-pentyne) is reported.
In tr od u ction
face-bound alkynes, which, in principle, are themselves
prone to direct the creation and stabilization of a vacant
coordination site onto the trimetal core via a simple
dynamic process known as the “windshield wiper”
motion.5-11 For ruthenium, the first, and still unique,
Fundamental studies in the field of cluster activation1
have revealed that a number of cluster-mediated carbon-
carbon bond forming reactions involving alkynes or
olefins can be made to occur under very mild conditions
and with enhanced selectivity, when the accessibility
of coordination sites is facilitated by the presence of
labile2,3 or hemilabile4 ancillary ligands. A priori, the
assistance of such ligands is unnecessary in the case of
(2) For selected examples of C-C bond forming reactions in bimetal-
lic complexes involving labile ligands, see: (a) Bruce, G. C.; Knox, S.
A. R.; Phillips, A. J . J . Chem. Soc., Chem. Commun. 1990, 716. (b)
Knox, S. A. R. J . Cluster Sci. 1992, 3, 385.
(3) For selected examples of C-C bond forming reactions in “acti-
vated” cluster complexes involving halides as labile bridging ligands,
see: (a) Kampe, C. E.; Boag, N. M.; Kaesz, H. D. J . Am. Chem. Soc.
1983, 105, 2896. (b) Morrison, E. D.; Bassner, S. L.; Geoffroy, G. L.
Organometallics 1986, 5, 408. (c) Morrison, E. D.; Geoffroy, G. L. J .
Am. Chem. Soc. 1985, 107, 3541.
(4) (a) Lugan, N.; Laurent, F.; Lavigne, G.; Newcomb, T. P.;
Liimatta, E. W.; Bonnet, J .-J . J . Am. Chem. Soc. 1990, 112, 8607. (b)
Nombel, P.; Lugan, N.; Mulla, F.; Lavigne, G. Organometallics 1994,
13, 4673.
X Abstract published in Advance ACS Abstracts, J anuary 15, 1996.
(1) For 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) 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.
0276-7333/96/2315-1195$12.00/0 © 1996 American Chemical Society

1196 Organometallics, Vol. 15, No. 4, 1996
Rivomanana et al.
observation of such a clean and reversible interconver-
sion between parallel and perpendicular conformations
of the alkyne was reported in 1991 in a preliminary
communication of a part of the present work (eq 1),
where it was also shown that the unsaturation of the
46-e derivative is not a pure formalism, but is effectively
substantiated by high chemical reactivity.12
other incoming alkyne molecules under mild conditions.
Considering that the incorporation of a new alkyne (4-e
donor) into the 46-e cluster would bring two electrons
more than required to achieve a closed shell, we were
anticipating that the supersaturation of the incipient
50-e adduct would have a chance to be released via
spontaneous carbon-carbon bond formation, provided
that the experimental conditions were mild enough to
avoid the loss of CO as an alternate elimination process.
Thus, we were prompted to verify the preceding
working hypothesis that might allow us to address a
general question of fundamental relevance: How far can
we predict and control the directed formation of carbon-
carbon bonds from a cluster-bound alkyne ligand? The
present study is a logical extension of our earlier work
on halide-promoted CO labilization.16
Given that oligomerization reactions involving cluster-
bound alkynes13-15 currently require thermal activation
and are sometimes deceptively unselective, it was also
of interest to determine whether the unsaturation of the
46-e prototype could be exploited for the purpose of
activating the µ-alkyne ligand toward coupling with
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 by using standard
Schlenk techniques. Tetrahydrofuran was distilled under
argon from sodium benzophenone ketyl just before use.
Dichloromethane was distilled under nitrogen from P2O5 and
stored under nitrogen. The following reagent grade chemicals
were used without further purification: RuCl3, nH2O (J ohnson
Matthey), bis(triphenylphosphoranylidene)ammonium chloride
([PPN]Cl) (Aldrich), phenylacetylene (Fluka), and diphenyl-
acetylene (Lancaster).
(5) (a) Blount, J . F.; Dahl, L. F.; Hoogzand, C.; Hu¨bel, W. J . Am.
Chem. Soc. 1966, 88, 292. (b) Carty, A. J .; Taylor, N. J .; Sappa, E.
Organometallics 1988, 7, 405.
(6) (a) Schilling, B. E. R.; Hoffmann, R. J . Am. Chem. Soc. 1979,
101, 3456. (b) Granozzi, G.; Tondello, E.; Casarin, M.; Aime, S.; Osella,
D. Organometallics 1983, 2, 430. (c) Halet, J .-F.; Saillard, J .-Y.;
Lissilour, R.; McGlinchey, M. J .; J aouen, G. Inorg. Chem. 1985, 24,
218. (d) Mlekuz, M.; Bougeard, P.; Sayer, B. G.; Peng, S.; McGlinchey,
M. J .; Marinetti, A.; Saillard, J .-Y.; Naceur, J . B.; Mentzen, B.; J aouen,
G. Organometallics 1985, 4, 1123. (e) Osella, D.; Gobetto, R.; Mon-
tangero, P.; Zanello, P.; Cinquantini, A. Organometallics 1986, 5, 1247.
(f) Aime, S.; Bertoncello, R.; Busetti, V.; Gobetto, R.; Granozzi, G.;
Osella, D. Inorg. Chem. 1986, 25, 4004. (g) Sappa, E. J . Organomet.
Chem. 1987, 323, 83. (h) Deeming, A. J .; Kabir, S. E.; Nuel, D.; Powell,
N. I. Organometallics 1989, 8, 717. (i) Nomikou, Z.; Halet, J . F.;
Hoffmann, R.; Tanner, J . T.; Adams, R. Organometallics 1990, 9, 588.
(j) Riehl, J .-F.; Koga, N.; Morokuma, K. Organometallics 1994, 13,
4765.
Ru3(CO)12 was prepared according to a published proce-
dure.17 Its halide adduct [PPN][Ru3(µ-Cl)(CO)10] was prepared
in situ and then used to prepare the starting compound [PPN]-
[Ru3(µ-Cl)(µ-PhCCPh)(CO)9] (1).16b
IR spectra were recorded on a Perkin-Elmer 225 grating
spectrophotometer; they were calibrated against water vapor
absorptions. NMR spectra were recorded on a Bruker WM250.
Mass spectra were recorded on a Ribermag R10-10.
P r ep a r a tion of th e In ter con ver tible Sp ecies Ru 3(µ-
P h CCP h )(CO)7(d p p m ) (2) a n d R u 3(µ-P h CCP h )(CO)8-
(d p p m ) (3). Crystals of the salt [PPN][Ru3(µ-Cl)(µ-PhCCPh)-
(CO)9] (1) (900 mg, 0.688 mmol) and bis(diphenylphos-
phino)methane (264 mg, 0.688 mmol) were dissolved in the
minimum amount of dichloromethane (3-4 mL) in a Schlenk
tube at room temperature. The addition of methanol (6 mL)
caused a rapid color change from yellow to intense violet, while
a violet crystalline precipitate progressively appeared. After
10 min, the solution was evaporated to dryness, and the
residue was chromatographed on a silica gel column. A unique
violet band eluted with a 1/3 dichloromethane/hexane mixture.
The complex, subsequently characterized as Ru3(µ-PhCCPh)-
(CO)8(dppm) (3), was recrystallized from dichloromethane/
hexane mixtures in the form of a very thin pale violet powder
(600 mg, 0.551 mmol, 80% yield). Since the preceding reaction
appeared to be spectroscopically clean and quantitative, at-
tempts were made to avoid chromatographic workup. Filtra-
tion of a methanol suspension of the reaction product effec-
tively allowed the removal of the soluble [PPN]Cl released in
solution. However, such a procedure did not allow quantitative
recovery of complex 3 due to its slight solubility in methanol.
(7) Busetto, L.; Green, M.; Howard, J . A. K.; Hessner, B.; J effrey,
J . C.; Mills, R. M.; Stone, F. G. A.; Woodward, P. J . Chem. Soc., Chem.
Commun. 1981, 1101.
(8) Busetti, V.; Granozzi, G.; Aime, S.; Gobetto, R.; Osella, D.
Organometallics 1984, 3, 1510.
(9) (a) Clucas, J . A.; Dolby, P. A.; Harding, M. M.; Smith, A. K. J .
Chem. Soc., Chem. Commun. 1987, 1829. (b) Brown, M. P.; Dolby, P.
A.; Harding, M. M.; Mathews, A. J .; Smith, A. K.; Osella, D.; Arbrun,
M.; Gobetto, R.; Raithby, P. R.; Zanello, P. J . Chem. Soc., Dalton Trans.
1993, 827.
(10) Osella, D.; Pospisil, L.; Fiedler, J . Organometallics 1993, 12,
3140.
(11) For reviews on alkyne-substituted clusters, see: (a) Sappa, E.;
Tiripicchio, A.; Braunstein, P. Chem. Rev. 1983, 33, 203. (b) Raithby,
P. R.; Rosales, M. J . Adv. Inorg. Chem. Radiochem. 1985, 29, 169. (c)
Adams, R. D.; Daran, J . C.; J eannin, Y. J . Cluster Sci. 1992, 3, 1. (d)
Sappa, E. J . Cluster Sci. 1994, 5, 211.
(12) Rivomanana, S.; Lavigne, G.; Lugan, N.; Bonnet, J .-J . Inorg.
Chem. 1991, 30, 4110.
(13) (a) Knox, S. A. R. J . Organomet. Chem. 1990, 400, 255. (b)
Adams, R. D.; Babin, J . E.; Tasi, M.; Wang, J .-G. Organometallics 1988,
7, 755. (c) Riaz, U.; Curtis, M. D.; Rheingold, A. L.; Haggerty, B. S.
Organometallics 1990, 9, 2647. (d) Bruce, M. I. J . Organomet. Chem.
1990, 400, 321. (e) Corrigan, J . F.; Doherty, S.; Taylor, N. J .; Carty, A.
J . Organometallics 1992, 11, 3160. (f) Nishio, M.; Matsuzaka, H.;
Mizobe, Y.; Tanase, T.; Hidai, M. Organometallics 1994, 13, 4214. (g)
J eannin, S.; J eannin, Y.; Robert, F.; Rosenberger, C. Inorg. Chem. 1994,
33, 243. (h) J eannin, S.; J eannin, Y.; Rosenberger, C. C.R. Acad. Sci.
Paris 1992, 314, 1165. (i) J eannin, S.; J eannin, Y.; Rosenberger, C.
Inorg. Chim. Acta 1993, 212, 323. (j) J oh, T.; Doyama, K.; Fujiwara,
K.; Maeshima, K.; Takahashi, S. Organometallics 1991, 10, 508.
(14) (a) Bruce, M. I.; Humphrey, P. A.; Miyamae, H.; Skelton, B.
W.; White, A. H. J . Organomet. Chem. 1992, 429, 187. (b) Bruce, M.
I.; Humphrey, P. A.; Horn, E.; Tiekink, E. R. T.; Skelton, B. W.; White,
A. H. J . Organomet. Chem. 1992, 429, 207.
Spectroscopic and analytical data for 3: IR (CH2Cl2) ν (cm-1
)
2052m, 2000vs, 1970m, 1945sh, 1830w,br (CdO); 31P NMR
(200 MHz, CDCl3) δ 35.0 [s (broad signal), 2P]. Anal. Calcd
(found) for C47H32O8P2Ru3: C, 51.79 (51.79); H, 2.96 (2.97).
(16) (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) Lavigne, G.; Lugan, N.; Rivomanana, S.; Mulla, F.;
Soulie´, J .-M.; Kalck, P. J . Cluster Sci. 1993, 4, 49.
(15) For reviews, see: (a) Hu¨bel, W. In Organic Syntheses via Metal
Carbonyls; Wender, I., Pino, P., Eds.; J . Wiley, Interscience: New York,
1968; Vol. I, p 273. (b) Schore, N. Chem. Rev. 1988, 88, 1081. (c)
Dickson, R. S. Polyhedron 1991, 10, 1995. (d) Su¨ss-Fink, G.; Meister,
G. Adv. Organomet. Chem. 1993, 35, 41.
(17) Mantovani, A.; Cenini, S. Inorg. Synth. 1972, 16, 47.

Self-Activation of a Cluster-Bound Alkyne
Organometallics, Vol. 15, No. 4, 1996 1197
Complex 3 (600 mg, 0.551 mmol) was dissolved in benzene
(30 mL) and heated under reflux at 70-80 °C for 1 h under a
stream of inert gas. A progressive color change from dark
violet to dark green was observed. The reaction was monitored
by following the disappearance of the characteristic bridging
ν(CO) band of complex 3. After evaporation of the solvent
under reduced pressure, the residue was passed through a
chromatographic column. Elution with 1/4 dichloromethane/
hexane afforded a unique green band corresponding to a new
complex, which was subsequently characterized as Ru3(µ-
PhCCPh)(CO)7(dppm) (2) and crystallized from the same
solvent mixture (465 mg, 0.438 mmol, 79% yield). Spectro-
scopically quantitative conversion of 2 into 3 was achieved
within seconds by bubbling CO into a dichloromethane solution
of complex 2 at 25 °C.
CCP h }(d p p m )(CO)6 (6) a n d Ru 2{µ-HCC(P h )(P h )CCP h }-
(µ-d p p m )(CO)4 (7). In a typical experiment, crystals of Ru3(µ-
PhCCPh)(CO)7(dppm) (2) (465 mg, 0.438 mmol) were dissolved
in dichloromethane (30 mL). An excess of phenylacetylene
(0.09 mL, 0.876 mmol) was added via a microsyringe, and the
solution was stirred at room temperature. A progressive color
change from green to red was observed. The reaction was
monitored by infrared spectroscopy, following the appearance
of two very characteristic bands at 1768 and 1685 cm-1
,
respectively. These bands were maximized within about 15
min (it is noteworthy that the same addition reaction could
be alternately carried out in benzene or acetone, but appeared
to be much slower when a donor solvent like THF was used).
Chromatographic workup on silica gel allowed the separation
of two phases, namely, a violet-brown band, eluted with
dichloromethane/hexane (1/3), and a red band, eluted slowly
with pure dichloromethane. Attempts to crystallize the first
violet phase from dichloromethane/hexane mixtures led to
colorless crystals contaminated by small amounts of an un-
tractable dark residue. The colorless crystals were subse-
quently identified by NMR and mass spectrometry as Ru2{µ-
HCC(Ph)(Ph)CCPh}(µ-dppm)(CO)4 (7). The yield, on the order
of 10-20%, could not be determined more accurately due to
the difficulty in separating the crystals from the above-
mentioned dark residue. The major red phase was crystallized
from dichloromethane/hexane mixtures, giving a new com-
pound that was subsequently identified as Ru3{µ-HCC(Ph)C-
(O)(Ph)CCPh}(dppm)(CO)6 (6) (290 mg, 57% yield). Suitable
crystals for X-ray diffraction analysis were obtained by re-
crystallization from acetone/methanol (1/5) mixtures.
Spectroscopic and analytical data for 2: IR (CH2Cl2) ν (cm-1
)
2055s, 1987vs, 1925m (CdO); 31P NMR (200 MHz, CDCl3) δ
40.6 (s, 2P). The extreme sensitivity of 2 was found to affect
the precision of the elemental analysis; best result was Anal.
Calcd (found) for C46H32O7P2Ru3: C, 52.03 (51.66); H, 3.04
(3.11).
P r ep a r a tion of Ru 3(µ-P h CCP h )(CO)6(d p p m )2 (4). Com-
plex 2 (161 mg, 0.152 mmol) and dppm (58 mg, 0.152 mmol)
were dissolved in THF (20 mL) in a Schlenk tube. The solution
was stirred for 3 h at 25 °C, giving exclusively 114 mg of the
red-violet compound 4 crystallized from dichloromethane/
hexane, as well-defined platelets (yield, 53%). The moderate
yield obtained for this complex may be due to its visible partial
alteration on the chromatographic silica gel column.
Spectroscopic data for 4: IR (CH2Cl2) ν (cm-1) 2077vw,
2005s, 1972m, 1941m, 1920mw (CdO); 31P NMR (250 MHz,
CDCl3) δ 27.8 (m, P1, J (P1-P2) ) 18 Hz, J (P1-P3) ) 57 Hz),
22.9 (m, P2, J (P1-P2) ) 18 Hz, J (P2-P4) ) 82 Hz), 21.7 (m,
P3, J (P3-P4) ) 37 Hz, J (P1-P3) ) 57 Hz), 7.5 (m, P4, J (P3-P4)
) 37 Hz, J (P2-P4) ) 82 Hz).
Spectroscopic and analytical data for 6: IR (THF) ν (cm-1
)
2002vs, 1957m, 1924ms, 1768m,br, 1685m (CdO); 31P NMR
(250 MHz, CDCl3) δ 64.6 (d, P1, J (P1-P2) ) 59 Hz), 38.7 (d,
1
P2); H NMR (250 MHz, CDCl3) δ 7.9 (d, 1H, J (P2-H) ) 17
Hz), 3.6 (m, 2H (methylene)). Anal. Calcd (found) for
P r ep a r a tion of Ru 3(µ-H)2(µ-P h CCP h )(CO)7(d p p m ) (5).
Hydrogen gas (1 atm) was bubbled through a dichloromethane
solution (20 mL) of 2 (191 mg, 0.180 mmol) at 25 °C. This
resulted in a progressive color change from dark green to gold-
yellow, whereas monitoring by infrared spectroscopy indicated
the formation of a new complex. After 10 min, the solvent
was evaporated under vacuum, and the resulting complex,
subsequently identified as 5a , was purified by chromatography
and crystallized (171 mg, 89%).
C
54H38O7P2Ru3: C, 55.72 (55.80); H, 3.29 (3.26).
Spectroscopic and analytical data for 7: IR (CH2Cl2) ν (cm-1
)
2065w, 2000m, 1973vs, 1942m, 1910m (CdO); 31P NMR (250
MHz, CDCl3) δ 29.0 (d, P1, J (P1-P2) ) 52 Hz), 45.6 (d, P2); 1H
NMR (250 MHz, CDCl3) δ 7.7 (d, 1H (metallacycle HCdC(Ph)-
(Ph)CdCPh), J (P-H) ) 17 Hz), 3.5 (m (AB pattern), 2H
(methylene)); MS (DCI/NH3) parent ion multiplet MH+, 981.
The spectrum also clearly showed the successive loss of four
carbonyls.
Con ver sion of Ru 3{µ-HCC(P h )C(O)(P h )CCP h }(d p p m )-
(CO)6 (6) in to Ru 3(µ-H){µ-CC(P h )C(O)(P h )CCP h }(d p p m )-
(CO)6 (8). Crystals of complex 6 (320 mg) were dissolved in
30 mL of THF in a Schlenk flask and stirred for a few minutes
at 40-50 °C under a nitrogen atmosphere. A progressive
lightening of the color from blood-red to orange was observed,
accompanied by slight changes in the IR. The reaction was
stopped after ca. 20 min, corresponding to the total disappear-
ance of the characteristic bridging ν(CO) absorption at 1768
cm-1. The new complex, subsequently formulated as Ru3(µ-
H){µ-CC(Ph)C(O)(Ph)CCPh}(dppm)(CO)6 (8), was purified on
a silica gel column (dichloromethane eluent) and crystallized
from acetone/ethanol (1/5) mixtures as orange platelets (301
mg, 94% yield).
Spectroscopic and analytical data for 5: IR (CH2Cl2) ν (cm-1
)
2085w, 2055vs, 2025s, 1995vs, 1940m (CdO). Anal. Calcd
(found) for C46H34O7P2Ru3: C, 51.93 (51.84); H, 3.22 (3.62). Two
isomers were detected by NMR at -80 °C; they differ in the
orientation of the alkyne with respect to the edge-bridging
dppm ligand. P and H nuclei are labeled as indicated:
Spectroscopic data for 8: IR (THF) ν (cm-1) 2046s, 2028m,
2004vs, 1980ms, 1947ms, 1907mw, 1675w (CdO); 31P NMR
(250 MHz, CDCl3) δ 17.0 (d, P1, J (P1-P2) ) 72 Hz), 30.3 (d,
Isomer 5a : 31P NMR (200 MHz, CDCl3) δ 17.51 (d, Pa, J (Pa-
Pb) ) 51 Hz), 8.38 (d, Pb, J (Pa-Pb) ) 51 Hz); 1H NMR (200
MHz, CDCl3) δ 7.5-6.4 (m, 30H, C6H5), 3.04 (m, 2H, CH2,
J (Hc-Hd) ) 13 Hz, J (Hc-Pb) ) J (Hd-Pb) ) 11 Hz, J (Hc-Pa)
) J (Hd-Pa) ) 12 Hz), -14.01 (dd, Ha (µ-hydride), J (Pa-Ha) )
14 Hz, J (Pb-Ha) ) 12 Hz), -18.89 (d, Hb (µ-hydride), J (Pa-
Hb) ) 37 Hz). Isomer 5b (tentative assignment): 31P NMR
(200 MHz, CDCl3) δ 39.94 (s, 2Pc); 1H NMR (200 MHz, CDCl3)
δ 7.5-6.4 (m, 30H, C6H5), 2.27 (dd, Hc, CH2, J (Hc-Hd) ) 13
Hz, J (Hc-Pc) ) 21 Hz), 3.51 (dd, Hd, CH2, J (Hc-Hd) ) 13 Hz,
J (Hd-Pc) ) 22 Hz), -15.25 (t, Ha (µ-hydride), J (Pc-Ha) ) 5
Hz), -18.76 (t, Hb (µ-hydride), J (Pc-Hb) ) 15 Hz).
1
P2); H NMR (250 MHz, CDCl3) δ -13.4 (dd, hydride, J (H-
P1) ) 44 Hz, J (H-P2) ) 6 Hz).
P r elim in a r y Attem p ts To Relea se th e Or ga n ic Moiety
fr om t h e Clu st er Cor e. Isola t ion of t h e Bin u clea r
Com plex Ru 2{µ-HCC(P h )C(O)(P h )CCP h }(CO)6 (9a). Treat-
ment of THF or dichloromethane solutions of complex 6 with
nucleophiles [CO (1 atm), PPh2H, [PPN]Cl] at 0-25 °C led to
rapid and quantitative formation of 1/1 adducts. Although
these adducts remain incompletely characterized, their respec-
tive IR spectra are displayed here. IR data of the yellow CO
adduct (obtained after 2-3 min at 25 °C): ν (cyclohexane)
Reaction of Ru 3(µ-P h CCP h )(CO)7(dppm ) (2) with P h en -
yla cet ylen e: P r ep a r a t ion of R u 3{µ-H CC(P h )C(O)(P h )-

1198 Organometallics, Vol. 15, No. 4, 1996
Ta ble 1. Cr ysta l a n d In ten sity Da ta for th e Com p lexes 2, 6, 8, a n d 9b
Rivomanana et al.
compound
2
6
8
9b
solvent molecules in lattice
none
two MeOH
C56H46O9P2Ru3
1228.13
14.822(2)
20.460(2)
17.281(2)
105.47(1)
5050(1)
4
one CH3COCH3
C57H44O8P2Ru3
1222.12
13.550(3)
21.785(3)
18.406(3)
107.65(2)
5177(2)
4
none
formula
Fw (amu)
a (Å)
b (Å)
c (Å)
C
46H32O7P2Ru3
C26H18O7Ru2
644.56
18.886(2)
8.3889(7)
15.631(6)
102.43(1)
2418(1)
4
1061.91
10.958(2)
19.224(3)
20.340(2)
100.694(9)
4211.1(9)
4
1.67
P21/n
20
â (deg)
V (Å3)
Z
Fcalcd (g cm-3
space group
T (°C)
)
1.64
P21/n
20
1.56
P21/n
20
1.77
P21/c
20
radiation, wavelength (Å)
Mo KR, λ(Mo KR1) ) 0.7093 (monochromator)
linear abs coeff (cm-1
crystal shape
)
11.66
eight faces
8.97
9.60
12.68
six faces
six faces
ill defined
boundary faces
{011}, {100}, {111},{010}
0.011, 0.014, 0.015, 0.016
0.733, 0.854
4.0 × 4.0
2.5
{010}, {001}, {101}
0.0125, 0.015, 0.0063
0.725, 0.894
4.0 × 4.0
3.4
{001}, {111}, {111}
0.004, 0.021, 0.021
0.660, 0.914
4.0 × 4.0
distances from faces to orgn (cm)
min and max transm factors
receiving aperture (mm)
take-off angle (deg)
4.0 × 4.0
3.0
2.5
scan mode
ω-2θ
ω-2θ
ω-2θ
ω-2θ
scan widtha (deg)
0.85
0.9
0.8
0.8
scan speed (deg min-1
θ limit (deg)
no. data collected
)
4.1
4.1
4.1
variable (tmax, 50 s)
1.0-25.0
1.5-28
1.0-27
1.0-23.0
10977
11712
7759
4236
2
2
2
2
unique data used in final ref
final no. of variables
6328 (Fo > 4σ(Fo2))
5794 (Fo > 4σ(Fo2))
4659 (Fo > 4σ(Fo2))
3169 (Fo > 4σ(Fo2))
529
472
346
388
p value in weighting schemeb
0.025 (refined)
0.033
0.041
0.03
0.040
0.051
1.59
0.03
0.045
0.061
1.31
0.02
0.020
0.029
1.19
R (on Fo, Fo > 4σ(Fo2))c
2
Rw (on Fo, Fo > 4σ(Fo2))d
2
error in observn of unit weight (Å2)
a
b
d
2
∆θ below KR1 and above KR2. Weighting scheme: w ) 1/(σ(Fo)2 + p2Fo2). c R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/(∑w|Fo| )]1/2
.
(cm-1) 2066vs, 2055sh, 2020vs,br, 1976s, 1956m, 1908m,
1890m, 1670m. IR data of the PPh2H adduct (obtained after
5 min at 25 °C): ν (THF) (cm-1) 2024vs, 2000s, 1960s, 1650m.
IR data of the green anionic chloro adduct (obtained upon
CCPh}(CO)6 (9b) (prepared via a parallel reaction sequence
starting with the addition of 1-pentyne to 2), gave beautiful
lozenge-shaped single crystals.
X-r a y Str u ctu r e Deter m in a tion s. Table 1 summarizes
crystal and intensity data for compounds 2, 6, 8, and 9b.
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(MoKR1) < 28°. Data reduction was carried
out by using the MOLEN crystallographic computing pack-
age.18 The quality of the crystals obtained for compounds 2,
6, and 9b allowed the precise identification and measurement
of boundary faces. The intensities were then accurately
corrected for absorption by using a numerical method based
on Gaussian integration.19
The structures were solved by using the SHELXS package20a
and refined by using the SHELX-76 package.20b In all three
cases, direct methods allowed the location of at least Ru and
P atoms, whereas all remaining non-hydrogen atoms were
located by the usual combination of full-matrix least-squares
refinement and difference electron density syntheses.
Sp ecific Deta ils for th e Str u ctu r e of Com p lex 2. In a
first approximation, phenyl rings were refined as rigid groups,
with the corresponding hydrogen atoms entered in idealized
riding positions (C-H ) 0.97 Å). In a second step, all carbon
atoms of the phenyl rings were refined independently with
anisotropic thermal parameters, whereas the corresponding
hydrogen atoms were held fixed. The two hydrogen atoms of
the methylene group were refined independently. In the final
refinement, all non-hydrogen atoms were allowed to vibrate
treatment with [PPN]Cl after 20 min at 30 °C): ν (THF) (cm-1
)
2023m, 2007vs, 1977m, 1944s, 1910w, 1670m.
Whereas the disappearance of the bridging ν(CdO) absorp-
tion was observed in all cases, the position of the ketonic ν-
(CdO) absorption in the IR was shifted only slightly, thereby
indicating that the dialkenyl ketone ligand remained un-
changed and did not cyclize.
Thus, following these experiments, the reaction of 6 with
CO was carried out under more forcing conditions in a 100
mL stainless steel autoclave. In a series of typical experi-
ments, 250 mg of complex 6 was introduced in the autoclave,
which was subsequently closed and degassed under vacuum.
THF (20 mL) was then introduced, and the autoclave was
pressurized with 10 atm of CO (at 25 °C) and immersed in a
thermostated oil bath (80 °C).
A
31P NMR spectrum of the
solution taken after 30 min revealed the presence of two
doublets at δ 32.7 and -27.5 (J (P-P) ) 58 Hz), respectively,
thereby revealing the presence of a coordinated dppm ligand
with a dangling phosphorus atom. The corresponding inter-
mediate product was not isolated. The same reaction, carried
out over a longer period (1 h), led to a yellow solution that
was chromatographed on silica gel. Traces of Ru3(CO)12 were
identified in the initial wide, fast-moving band eluted with
pure hexane. The second band, eluted with 1/1 dichlo-
romethane/hexane, contained traces of Ru3(CO)10(dppm). Fi-
nally, elution with pure dichloromethane afforded a major
yellow band corresponding to a new complex that was subse-
quently characterized as the binuclear “fly-over” species, Ru2-
{µ-HCC(Ph)C(O)(Ph)CCPh}(CO)6 (9a ).
(18) MOLen, Package for Crystal Structure Analysis; Enraf-Non-
ius: Delft, The Netherlands, 1990.
(19) Coppens, P.; Leiserowitz, L.; Rabinovitch, D. Acta Crystallogr.
1965, 18, 1035.
(20) (a) Sheldrick, G. M. SHELXS Program for Crystal Structure
Solution; University of Go¨ttingen: Go¨ttingen, Federal Republic of
Germany, 1986. (b) Sheldrick, G. M. SHELX-76 Program for Crystal
Structure Determination; University of Cambridge: Cambridge, En-
gland, 1976.
Spectroscopic and analytical data for 9a : IR (CH2Cl2) ν
(cm-1) 2088s, 2065vs, 2022s,br, 1680m; MS (DCI/NH3) MH+,
681.
Whereas crystals of 9a were not suitable for X-ray diffrac-
tion, the isostructural species, Ru2{µ-HCC(C3H7)C(O)(Ph)-

Self-Activation of a Cluster-Bound Alkyne
Organometallics, Vol. 15, No. 4, 1996 1199
Ta ble 2. Selected In ter a tom ic Dista n ces (Å) for th e Com p lex Ru 3(µ3,η2-(C6H5)CC(C6H5))(µ,η2-d p p m )(CO)7 (2),
w ith Esd ’s in P a r en th esesa
Ru-Ru
Ru(1)-Ru(2)
2.6520(6)
2.317(1)
Ru(2)-Ru(3)
Ru(3)-P(2)
2.6683(6)
2.298(1)
Ru(1)-Ru(3)
2.8120(7)
Ru-P
Ru(1)-P(1)
Ru-C (Carbonyl Groups)
Ru(1)-C(1)
Ru(1)-C(2)
Ru(2)-C(4)
1.903(5)
1.882(5)
1.888(6)
Ru(3)-C(6)
Ru(3)-C(7)
Ru(2)-C(5)
1.897(5)
1.895(5)
1.891(6)
Ru(2)-C(3)
1.893(5)
Ru-C (Bridging Alkyne)
Ru(1)-C(9)
Ru(1)-C(10)
2.108(4)
2.202(4)
Ru(3)-C(9)
Ru(3)-C(10)
2.083(4)
2.265(4)
Ru(2)-C(10)
2.202(4)
C-O (Carbonyl Groups)
C(1)-O(1)
C(2)-O(2)
1.132(6)
1.141(7)
C(6)-O(6)
C(7)-O(7)
1.147(6)
1.134(7)
C(3)-O(3)
1.126(6)
C(4)-O(4)
1.113(9)
C(5)-O(5)
1.129(8)
C-C (Multiple Bond of the Alkyne)
C(9)-C(10) 1.409(6)
a
Note: The noncrystallographic mirror plane symmetry of the molecule can be evaluated by comparison of the “equivalent” distances
that are listed on the same line throughout the table.
Ta ble 3. Selected Bon d An gles (d eg) for th e
Com p lex Ru 3(µ3,η2-(C6H5)CC(C6H5))-
thermal vibration of the above-mentioned solvent molecules,
it was not possible to locate their respective hydrogen atoms.
Selected interatomic distances and bond angles of interest
for 6 are given in Tables 4 and 5, respectively.
(µ-η2-d p p m )(CO)7 (2), w ith Esd ’s in P a r en th eses
Ru-Ru-Ru
Ru(2)-Ru(1)-Ru(3) 58.37(2) Ru(2)-Ru(3)-Ru(1) 57.81(2)
Ru(1)-Ru(2)-Ru(3) 63.81(2)
Sp ecific Deta ils for th e Str u ctu r e of Com p lex 8. All
phenyl rings were treated as rigid groups, including H atoms
in idealized positions. The hydride ligand was located on the
final Fourier difference map. Attempts to refine its positional
parameters led to reasonable values. At the end of refinement,
the presence of four residual peaks was found, consistent with
the presence of a disordered acetone molecule in the lattice.
The thermal vibration of such a molecule was too high to allow
a distinction between oxygen and carbon atoms. This also
suggested the possible occurrence of a statistical disorder in
which three orientations of the molecule would result from
120° rotations around the central carbon, leading to the
superimposition of oxygen and carbon sites. Nevertheless, to
a reasonable approximation, all four atoms of this solvent
molecule were refined by using the f table of carbon.
Selected interatomic distances and bond angles of interest
for 8 are given in Tables 6 and 7, respectively.
Sp ecific Deta ils for th e Str u ctu r e of Com p lex 9b.
Beautiful lozenge-shaped crystals of the complex Ru2{µ-HCC-
(C3H7)C(O)(Ph)CCPh}(CO)6 (9b) were used for intensity data
collection. All non-hydrogen atoms were refined with aniso-
tropic thermal parameters. All hydrogen atoms were located
from the final Fourier difference map, and their atomic
coordinates were refined.
P-Ru-Ru
96.08(3) P(2)-Ru(3)-Ru(1)
150.81(3) P(2)-Ru(3)-Ru(2)
P(1)-Ru(1)-Ru(3)
P(1)-Ru(1)-Ru(2)
89.48(3)
136.48(3)
C(alkyne)-Ru-Ru
C(9)-Ru(1)-Ru(3)
C(9)-Ru(1)-Ru(2)
47.5(1)
85.3(1)
C(9)-Ru(3)-Ru(1)
C(9)-Ru(3)-Ru(2)
48.2(1)
85.3(1)
C(10)-Ru(1)-Ru(3) 52.0(1)
C(10)-Ru(1)-Ru(2) 53.0(1)
C(10)-Ru(2)-Ru(1) 53.0(1)
C(10)-Ru(3)-Ru(1) 50.01)
C(10)-Ru(3)-Ru(2) 52.2(1)
C(10)-Ru(2)-Ru(3) 54.4(1)
C(alkyne)-Ru-C(alkyne)
38.1(2) C(9)-Ru(3)-C(10)
C(9)-Ru(1)-C(10)
37.5(2)
C(alkyne)-C(alkyne)-Ru
C(10)-C(9)-Ru(1)
C(9)-C(10)-Ru(1)
C(9)-C(10)-Ru(2)
C(11)-C(9)-Ru(1)
74.6(2)
67.3(2)
C(10)-C(9)-Ru(3)
78.3(2)
64.2(2)
C(9)-C(10)-Ru(3)
126.9(3)
135.1(3)
C(11)-C(9)-Ru(3)
C(21)-C(10)-Ru(3) 143.3(3)
135.8(3)
C(21)-C(10)-Ru(1) 138.5(3)
C(21)-C(10)-Ru(2) 114.7(3)
Ru-Ru-C(carbonyl)
Ru(3)-Ru(1)-C(1) 104.7(2)
Ru(2)-Ru(1)-C(1) 78.5(2)
Ru(2)-Ru(1)-C(2) 111.9(2)
Ru(1)-Ru(2)-C(4) 92.1(2)
Ru(1)-Ru(2)-C(3) 114.9(2)
Ru(1)-Ru(3)-C(6) 115.3(2)
Ru(2)-Ru(3)-C(6)
Ru(2)-Ru(3)-C(7) 127.0(2)
Ru(3)-Ru(2)-C(5) 97.1(2)
Ru(3)-Ru(2)-C(3) 111.0(2)
76.5(2)
Selected interatomic distances and bond angles of interest
for 9b are given in Tables 8 and 9, respectively.
Tables of atomic coordinates, anisotropic thermal param-
eters, and complete listings of interatomic distances and bond
angles are available as supporting information.
anisotropically. Selected interatomic distances and bond
angles of interest for 2 are given in Tables 2 and 3, respec-
tively.
Sp ecific Deta ils for th e Str u ctu r e of Com p lex 6. All
non-hydrogen atoms were refined with anisotropic thermal
parameters except the phenyl rings of the dppm ligand, which
were treated as rigid groups, to reduce the important number
of variable parameters. After refinement of the entire cluster
unit, the R and Rw values were of 0.057 and 0.102, respectively.
At that stage, a Fourier difference map revealed the occurrence
of four additional residues, which was consistent with the
presence of two molecules of methanol trapped in the lattice.
Further full-matrix least-squares refinements of the structure,
including these additional atoms, led to a significant lowering
of the final R indices (see Table 1). However, due to the high
Resu lts a n d Discu ssion
F r om th e “Activa ted ” An ion ic Sp ecies [P P N]-
[Ru 3(µ-Cl)(µ-P h CCP h )(CO)9] (1) to th e Un sa tu r -
a ted 46-e Com p lex Ru 3(µ-RCCR)(CO)7(d p p m ) (2).
A simple methodology for the preparation of alkyne-
substituted triruthenium carbonyl complexes is to start
from the “activated” anionic species [PPN][Ru3(µ-Cl)-
(CO)10], which can be readily generated in situ upon the
treatment of triruthenium dodecacarbonyl with [PPN]-
Cl (PPN ) bis(triphenylphosphine)iminium cation).16

1200 Organometallics, Vol. 15, No. 4, 1996
Rivomanana et al.
Ta ble 4. Selected In ter a tom ic Dista n ces (Å) for
th e Com p lex Ru 3{µ-HCC(C6H5)C(O)(C6H5)CC-
(C6H5))(µ,η2-d p p m )(CO)6 (6), w ith Esd ’s in
P a r en th eses
Ta ble 5. Selected Bon d An gles (d eg) for th e
Com p lex Ru 3{µ-HCC(C6H5)C(O)(C6H5)-
CC(C6H5))(µ,η2-d p p m )(CO)6 (6), w ith Esd ’s in
P a r en th eses
Ru-Ru
Ru-Ru-Ru
Ru(1)-Ru(3)
Ru(2)-Ru(3)
3.0017(9)
2.7905(8)
Ru(1)-Ru(2)
Ru(3)-P(2)
2.8969(8)
2.354(2)
Ru(2)-Ru(1)-Ru(3) 56.43(2) Ru(2)-Ru(3)-Ru(1) 59.89(2)
Ru(1)-Ru(2)-Ru(3) 63.68(2)
Ru-P
P-Ru-Ru
107.93(5) P(1)-Ru(1)-Ru(3)
96.35(4) P(2)-Ru(3)-Ru(1)
Ru(1)-P(1)
2.252(2)
P(1)-Ru(1)-Ru(2)
P(2)-Ru(3)-Ru(2)
91.73(5)
88.61(5)
Ru-C (Carbonyl Groups)
Ru(1)-C(1)
Ru(2)-C(2)
Ru(2)-C(4)
Ru(3)-C(6)
1.843(7)
2.175(7)
1.867(8)
1.919(7)
Ru(1)-C(2)
Ru(2)-C(3)
Ru(3)-C(5)
1.973(6)
1.928(6)
1.905(8)
C(dialkenyl ketone)-Ru-Ru
C(9)-Ru(3)-Ru(1)
C(9)-Ru(3)-Ru(2)
55.6(2)
47.0(1)
C(9)-Ru(2)-Ru(1)
C(9)-Ru(2)-Ru(3)
59.3(2)
55.4(2)
C(10)-Ru(3)-Ru(1) 88.9(2)
C(20)-Ru(3)-Ru(1) 110.4(2)
C(20)-Ru(3)-Ru(2) 51.3(2)
C(30)-Ru(2)-Ru(1) 130.1(1)
C(11)-Ru(1)-Ru(2) 73.3(2)
C(10)-Ru(3)-Ru(2) 71.5(2)
C(20)-Ru(2)-Ru(1) 110.2(2)
C(20)-Ru(2)-Ru(3) 47.3(2)
C(30)-Ru(2)-Ru(3) 70.6(2)
C(11)-Ru(1)-Ru(3) 78.9(2)
Ru-C (Side-On Linkage of C-Ph Bond)
Ru(1)-C(11) 2.343(7) Ru(1)-C(9)
2.564(7)
2.076(6)
Ru-C (σ Bonds, Dialkenyl Ketone Ligand)
2.090(5) Ru(3)-C(20)
Ru(2)-C(9)
C-C-Ru
80.6(4)
Ru-C (π Bonds, Dialkenyl Ketone Ligand)
C(9)-C(11)-Ru(1)
C(11)-C(9)-Ru(2)
C(10)-C(9)-Ru(2)
C(7)-C(10)-Ru(3)
C(30)-C(20)-Ru(2)
C(20)-C(30)-Ru(2)
C(11)-C(9)-Ru(3)
C(10)-C(9)-Ru(3)
C(9)-C(10)-Ru(3)
C(7)-C(30)-Ru(2)
125.0(5)
70.4(4)
74.1(4)
104.6(4)
Ru(3)-C(9)
Ru(2)-C(20)
2.351(6)
2.205(7)
Ru(3)-C(10)
Ru(2)-C(30)
2.302(7)
2.331(7)
122.9(4)
116.4(4)
103.4(4)
77.0(4)
C-O (Carbonyl Groups)
C(30)-C(20)-Ru(3) 117.1(4)
C(1)-O(1)
C(3)-O(3)
C(5)-O(5)
1.147(9)
1.129(8)
1.125(9)
C(2)-O(2)
C(4)-O(4)
C(6)-O(6)
1.160(8)
1.15(1)
1.150(8)
67.2(4)
C(10)-C(9)-Ru(3)
70.4(4)
Ru-Ru-C(carbonyl)
Ru(3)-Ru(1)-C(1) 157.7(2)
Ru(2)-Ru(1)-C(2) 48.6(2)
Ru(2)-Ru(1)-C(1) 145.0(2)
C-O (Dialkenyl Ketone Ligand)
Ru(1)-Ru(2)-C(2)
42.9(2)
C(7)-O(7)
1.213(9)
Ru(1)-Ru(2)-C(3) 116.3(2)
Ru(3)-Ru(2)-C(3) 113.0(2)
Ru(2)-Ru(3)-C(5) 136.9(2)
Ru(1)-Ru(2)-C(4) 118.1(2)
Ru(3)-Ru(2)-C(4) 154.5(2)
Ru(1)-Ru(3)-C(5) 162.8(2)
Ru(2)-Ru(3)-C(6) 127.9(2)
C-C (Dialkenyl Ketone Ligand)
C(9)-C(10)
C(7)-C(30)
C(9)-C(11)
C(30)-C(31)
1.418(9)
1.505(8)
1.492(8)
1.496(9)
C(10)-C(7)
C(30)-C(20)
C(10)-C(21)
1.49(1)
1.40(1)
1.504(8)
Ru(1)-Ru(3)-C(6)
69.3(2)
lar rearrangement might be prevented by the use of a
ligand prone to stabilize the trinuclear architecture.
Effectively, when a concentrated dichloromethane
solution of [PPN][Ru3(µ-Cl)(µ-RCCR)(CO)9] (1) is treated
with 1 equiv of bis(diphenylphosphino)methane at 25
°C in a Schlenk tube, a color change from gold-yellow
to violet is obtained over a period of few minutes. The
reaction is visibly accelerated by the addition of metha-
nol and produces a unique violet compound crystallizing
from the solution over a period of 10 min (Scheme 2).
This neutral complex was formulated as Ru3(µ-RCCR)-
(CO)8(dppm) (3) (yield, 80-85%), a dppm-substituted
analog of the above-mentioned species Ru3(µ-RCCR)-
(CO)10.16 We noted that when the addition of dppm was
carried out under slightly reduced pressure, the yield
of 3 was reduced, whereas an additional green species
2 was formed simultaneously. When complex 3 was
heated in benzene at 70-80 °C for 1 h under a stream
of inert gas, it was cleanly converted into the above-
mentioned green species, which was subsequently for-
mulated as Ru3(µ-RCCR)(CO)7(dppm) (2). The reverse
transformation, leading to complete recovery of the
violet species 3, was achieved within few seconds under
1 atm of carbon monoxide (Scheme 2).
Thus, we realized that we were observing, for the first
time, a clean and reversible interconversion between an
unsaturated (alkyne)triruthenium cluster and its CO
adduct. Stabilization of the perpendicular coordination
mode of the alkyne in the preceding complex may be
interpreted in terms of the increased back-donating
ability of the metal induced by the dppm ligand, as
recently suggested by Osella and co-workers.10
Notably, following our preliminary communication on
the synthesis of compounds 2 and 3,12 Bruce and co-
workers reported a thermal reaction between Ru3(CO)10-
(dppm) and acetylenedicarboxylate, leading rather un-
selectively to the formation of the 48-e complex Ru3{µ-
C-H (Dialkenyl Ketone Ligand)
C(20)-H(20)
0.90(7)
P-C Bonds within the Bis(diphenylphosphino)methane Ligand
P(1)-C(8)
P(1)-C(41)
P(2)-C(61)
1.826(7)
1.832(5)
1.839(5)
P(2)-C(8)
P(1)-C(51)
P(2)-C(71)
1.826(7)
1.820(5)
1.832(4)
C-C (within the Phenyl Substituents of the dppm Ligand)
rigid groups: C-C ) 1.395
C-H (within the Phenyl Substituents of the dppm Ligand)
riding position: C-H ) 0.97
Kinetic studies by Basolo and Shen have recently shown
that opening of the µ-Cl bridge in this anion provides a
vacant site that is readily available for the coordination
of an alkyne under ambient conditions.21 Subsequent
loss of CO leads to only one species, formulated as [PPN]-
[Ru3(µ-Cl)(µ-RCCR)(CO)9] (1).16
The weakly coordinated Cl- ligand is easily labilized
by simple interaction with a protic solvent. Then, the
cluster can be engaged in a variety of addition reactions
of the type exemplified in Scheme 1, thereby exhibiting
the apparent reactivity of the elusive unsaturated
species “Ru3(µ-RCCR)(CO)9”.16b Attempts to intercept
such an intermediate by halide abstraction from 1 in
the absence of incoming ligand remained unsuccessful.
Alternatively, attempts to induce the thermal loss of CO
from Ru3(µ-RCCR)(CO)10 led to the formation of the
known butterfly complex, Ru4(µ-RCCR)(CO)11,16b,22
thereby indicating that, under the effect of temperature,
the transient unsaturation of the cluster is spontane-
ously released by an intermolecular metal-atom ag-
gregation. We thus reasoned that such an intermolecu-
(21) Shen, J .-K.; Basolo, F. Gazz. Chim. Ital. 1994, 124, 439.
(22) (a) J ohnson, B. F. G.; Lewis, J .; Schorpp, K. T. J . Organomet.
Chem. 1975, 91, C13. (b) J ohnson, B. F. G.; Lewis, J .; Reichert, B. E.;
Schorpp, K. T.; Sheldrick, G. M. J . Chem. Soc., Dalton Trans. 1977,
1417.

Self-Activation of a Cluster-Bound Alkyne
Organometallics, Vol. 15, No. 4, 1996 1201
Ta ble 6. Selected In ter a tom ic Dista n ces (Å) for th e Com p lex
Ru 3{µ-CC(C6H5)C(O)(C6H5)CC(C6H5))(µ,η2-d p p m )(CO)6 (8), w ith Esd ’s in P a r en th eses
Ru-Ru
Ru(1)-Ru(3)
Ru(2)-Ru(3)
2.921(1)
2.698(1)
Ru(1)-Ru(2)
2.8731(9)
Ru-hydride
Ru-P
Ru(1)-Hyd
Ru(1)-P(1)
1.98(6)
Ru(2)-Hyd
Ru(3)-P(2)
1.89(7)
2.319(2)
2.384(2)
Ru-C (Carbonyl Groups)
Ru(1)-C(1)
Ru(2)-C(3)
Ru(3)-C(5)
1.96(1)
1.85(1)
1.92(1)
Ru(1)-C(2)
1.88(1)
1.89(1)
1.89(1)
Ru(2)-C(4)
Ru(3)-C(6)
Ru-C (σ Bonds, Alkenyl Vinylidene Ketyl Ligand)
Ru(1)-C(20)
Ru(2)-C(9)
1.984(7)
2.094(9)
Ru(3)-C(20)
2.093(9)
Ru-C (π Bonds, Alkenyl Vinylidene Ketyl Ligand)
Ru(3)-C(9)
Ru(2)-C(20)
2.204(7)
2.160(7)
Ru(3)-C(10)
Ru(2)-C(30)
2.289(7)
2.351(8)
C-O (Carbonyl Groups)
C(1)-O(1)
C(3)-O(3)
C(5)-O(5)
1.13(1)
1.16(1)
1.15(1)
C(2)-O(2)
C(4)-O(4)
C(6)-O(6)
1.13(1)
1.12(1)
1.15(1)
C-O (Ketyl Group)
C(7)-O(7)
1.23(1)
C-C (Alkenyl Vinylidene Ketyl Ligand)
C(9)-C(10)
C(7)-C(30)
C(9)-C(11)
C(30)-C(31)
1.43(1)
1.49(1)
1.49(1)
1.51(1)
C(10)-C(7)
C(30)-C(20)
C(10)-C(21)
1.50(1)
1.36(1)
1.53(1)
P-C Bonds within the Bis(diphenylphosphino)methane Ligand
P(1)-C(8)
P(1)-C(41)
P(2)-C(61)
1.82(1)
P(2)-C(8)
P(1)-C(51)
P(2)-C(71)
1.843(9)
1.805(6)
1.814(7)
1.813(6)
1.818(6)
C-C (within Phenyl Substituents, All Treated as Rigid Groups)
C-C )
1.395
0.97
C-H
)
Ta ble 7. Selected Bon d An gles (d eg) for th e
Com p lex Ru 3(µ-H){µ-CC(C6H5)C(O)(C6H5)-
CC(C6H5))(µ,η2-d p p m )(CO)6 (8), w ith Esd ’s in
P a r en th eses
Ta ble 8. Selected In ter a tom ic Dista n ces for
Ru 2{µ-HCC(C3H7)C(O)(P h )CCP h }(CO)6 (9b), w ith
Esd ’s in P a r en th eses
Ru-Ru
Ru(1)-Ru(2)
2.7164(6)
Ru-Ru-Ru
Ru(2)-Ru(1)-Ru(3) 55.49(2) Ru(2)-Ru(3)-Ru(1) 61.34(2)
Ru(1)-Ru(2)-Ru(3) 63.16(2)
Ru-C (Carbonyl Groups)
Ru(1)-C(1)
Ru(1)-C(2)
Ru(1)-C(3)
1.965(3)
1.919(4)
1.900(3)
Ru(2)-C(5)
Ru(2)-C(6)
Ru(2)-C(4)
1.957(3)
1.930(3)
1.921(3)
P-Ru-Ru
P(1)-Ru(1)-Ru(2)
P(2)-Ru(3)-Ru(2)
144.81(6) P(1)-Ru(1)-Ru(3)
142.87(7) P(2)-Ru(3)-Ru(1)
93.64(6)
89.12(6)
C-O
C(1)-O(1)
C(2)-O(2)
C(3)-O(3)
1.135(4)
1.129(5)
1.136(4)
C(5)-O(5)
C(6)-O(6)
C(4)-O(4)
1.120(4)
1.120(4)
1.131(4)
C(vinylidene alkenyl ketyl)-Ru-Ru
C(9)-Ru(3)-Ru(1) 110.2(2) C(9)-Ru(2)-Ru(1) 115.7(2)
C(9)-Ru(3)-Ru(2) 49.3(2) C(9)-Ru(2)-Ru(3) 53.0(2)
C(10)-Ru(3)-Ru(1) 119.2(2)
C(20)-Ru(3)-Ru(1) 42.7(2)
C(20)-Ru(3)-Ru(2) 51.7(2)
C(30)-Ru(2)-Ru(1) 74.3(2)
C(10)-Ru(3)-Ru(2) 72.8(2)
C(20)-Ru(2)-Ru(1) 43.6(2)
C(20)-Ru(2)-Ru(3) 49.5(2)
C(30)-Ru(2)-Ru(3) 72.8(2)
Ru-C (Divinyl Ketyl Group)
Ru(1)-C(7)
Ru(1)-C(8)
Ru(1)-C(11)
2.264(2)
2.320(2)
2.072(3)
Ru(2)-C(11)
Ru(2)-C(10)
Ru(2)-C(7)
2.204(3)
2.310(3)
2.096(2)
C-C-Ru
118.6(5)
114.1(6)
68.2(4)
98.7(5)
C-O (Ketyl Group)
C(11)-C(9)-Ru(2)
C(10)-C(9)-Ru(2)
C(9)-C(10)-Ru(3)
C(7)-C(30)-Ru(2)
C(11)-C(9)-Ru(3)
C(10)-C(9)-Ru(3)
C(7)-C(10)-Ru(3)
C(20)-C(30)-Ru(2)
129.6(5)
74.7(4)
108.7(5)
64.8(4)
C(9)-O(9)
1.210(4)
C-C (Divinyl Ketyl Group)
C(7)-C(8)
C(8)-C(9)
1.422(4)
1.508(4)
C(10)-C(11)
C(9)-C(10)
1.389(4)
1.499(4)
C(30)-C(20)-Ru(1) 143.1(7)
C(30)-C(20)-Ru(2) 80.2(4)
C(30)-C(20)-Ru(3) 119.5(6)
C(20)-C(30)-Ru(2) 64.8(4)
C-C and C-H (Substituents)
C(7)-C(71)
C(8)-C(81)
C(12)-C(13)
1.487(4)
1.503(3)
1.506(6)
C(11)-H(11)
C(10)-C(12)
C(13)-C(14)
0.95(3)
1.520(4)
1.534(5)
C2(CO2Me)2}(CO)8(dppm), obtained in 30% yield, among
other compounds.14
Str u ctu r e of th e 46-e Com p lex Ru 3(µ-P h CCP h )-
(CO)7(d p p m ) (2). The structure of complex 2 was
determined by X-ray diffraction. The compound is
isostructural with the corresponding osmium analog
Os3(µ-PhCCPh)(CO)7(dppm), which was isolated and
crystallized some years ago by Smith and co-workers.9
The molecular structure of 2 is shown in Figure 1. It
consists of a triangular array of ruthenium atoms, one
edge of which is supported by a bridging dppm ligand
occupying two pseudoequatorial coordination sites. The
diphenylacetylene ligand is bound to one face of the
cluster in a µ3,η2-coordination mode, with the carbon-
carbon bond positioned perpendicular to the Ru(1)-

1202 Organometallics, Vol. 15, No. 4, 1996
Rivomanana et al.
Ta ble 9. Selected In ter a tom ic Bon d An gles for
Ru 2{µ-HCC(C3H7)C(O)(P h )CCP h }(CO)6 (9b), w ith
Esd ’s in P a r en th eses
Ru-Ru-C
Ru(2)-Ru(1)-C(1)
Ru(2)-Ru(1)-C(2)
Ru(2)-Ru(1)-C(3)
Ru(2)-Ru(1)-C(7)
Ru(2)-Ru(1)-C(8)
Ru(2)-Ru(1)-C(11)
120.96(9) Ru(1)-Ru(2)-C(5)
146.87(9) Ru(1)-Ru(2)-C(6)
87.40(9) Ru(1)-Ru(2)-C(4)
48.74(6) Ru(1)-Ru(2)-C(11)
72.63(6) Ru(1)-Ru(2)-C(10)
52.75(8) Ru(1)-Ru(2)-C(7)
111.16(9)
148.75(8)
100.00(8)
48.45(7)
72.33(7)
54.29(7)
C-Ru-C
C(1)-Ru(1)-C(2)
C(1)-Ru(1)-C(3)
C(1)-Ru(1)-C(7)
C(1)-Ru(1)-C(8)
C(2)-Ru(1)-C(3)
C(2)-Ru(1)-C(11)
C(2)-Ru(1)-C(8)
C(3)-Ru(1)-C(11)
91.2(1)
91.9(1)
92.3(1)
102.2(1)
100.2(1)
95.6(1)
94.2(1)
84.5(1)
C(5)-Ru(2)-C(6)
C(5)-Ru(2)-C(4)
C(5)-Ru(2)-C(11)
C(5)-Ru(2)-C(10)
C(6)-Ru(2)-C(4)
C(6)-Ru(2)-C(7)
C(6)-Ru(2)-C(10)
C(4)-Ru(2)-C(7)
94.9(1)
89.2(1)
83.2(1)
96.5(1)
97.0(1)
99.1(1)
88.4(1)
92.5(1)
F igu r e 1. Perspective view of the unsaturated complex
2.
Sch em e 1
normal reactivity trend observed for carbonyl clusters
of these two metals. Let us recall that the unsaturated
osmium prototype, Os3(µ-PhCCPh)(CO)9, whose struc-
ture is still unknown, was also found to be very
reactive.23
Attem p ts To Clea ve th e CtC Tr ip le Bon d of th e
Un satu r ated Com plex Ru 3(µ-P h CCP h )(CO)7(dppm )
(2). Keeping in mind earlier observations that the
cluster-mediated cleavage of CtC bonds may be facili-
tated in complexes bearing an alkyne coordinated in the
perpendicular mode,24 we first attempted to determine
whether a thermolysis of the unsaturated prototype 2
would induce such a reaction that might have produced
a dialkylidyne complex. However, complex 2 was found
to be rather stable over the temperature range of our
experiments (up to 110 °C) and reluctant to undergo
intramolecular scission of the alkyne, which was in
sharp contrast with a well-established example where
CtC bond cleavage was seen to take place on a triiron
cluster unit at a temperature as low as -50 °C.24d To
date, we have no explanation for such a dramatic
difference in reactivity, which may be ascribed to (i) the
nature of the metal or (ii) the nature of the alkyne
substituents. In fact, alkyne scission does not appear
to be a general reaction since known examples of alkyne
CtC bond cleavage by iron cluster complexes are
limited to a few cases where the alkyne bears specific
substituents (H, OMe, OEt), not including phenyl
groups.24c,d
Sch em e 2
Rea ctivity of Ru 3(µ-P h CCP h )(CO)7(d p p m ) (2)
tow a r d 2-e Don or s. Previous observations that the
prototype Fe3(RCCR)(CO)9 undergoes substitution reac-
tions rather than additions were interpreted in terms
of Wade’s PSEPT formalism, considering this cluster as
a closo 48-e species.6g It is also noteworthy that the
known decacarbonyl species Fe3(RCCR)(CO)10 was ob-
tained from a lightly stabilized intermediate and not
by simple CO addition to the nonacarbonyl derivative.25
By contrast, complex 2 is highly reactive, as evidenced
by the formation of the CO adduct 3 within seconds
Ru(3) edge already supported by the bridging dppm
ligand. The structural analogies between 2 and the
osmium derivative, Os3(µ-PhCCPh)(CO)7(dppm), are
such that the differences between the respective Ru-
C(alkyne) and Os-C(alkyne) bonds are, in all cases,
very close to the esd’s. However, as shown in the
following, the ruthenium compound appears to react
with 2-e donors more rapidly than its osmium analog,
Os3(µ-PhCCPh)(CO)7(dppm). This is in line with the
(23) (a) Tachikawa, M.; Shapley, J . R.; Pierpont, C. G. J . Am. Chem.
Soc. 1975, 97, 7172. (b) Clauss, A. D.; Shapley, J . R.; Wilson, S. R. J .
Am. Chem. Soc. 1981, 103, 7387.
(24) (a) Allison, N. T.; Fritch, J . R.; Vollhardt, K. P. C.; Walborsky,
E. C. J . Am. Chem. Soc. 1983, 105, 1384. (b) Clauss, A. D.; Shapley, J .
R.; Wilker, C. N.; Hoffmann, R. Organometallics 1984, 3, 619. (c) Nuel,
D.; Dahan, F.; Mathieu, R. Organometallics 1985, 4, 1436. (d) Hriljac,
J . A.; Shriver, D. F. J . Am. Chem. Soc. 1987, 109, 6010.
(25) Lentz, D.; Reuter, M. Chem. Ber. 1991, 124, 773.

Self-Activation of a Cluster-Bound Alkyne
Organometallics, Vol. 15, No. 4, 1996 1203
Sch em e 3
Sch em e 4
F igu r e 2. Perspective view of complex 6. The four phenyl
rings of the bis(diphenylphosphino)methane ligand have
been omitted for clarity.
Sch em e 5
under ambient conditions (vide supra). Relevant addi-
tion reactions were observed in the presence of other
2-e donors. They were all found to take place readily
with concomitant reversion of the alkyne conformation
back to the parallel mode. For example, addition of 1
equiv of dppm at 25 °C led to the bis-dppm derivative
Ru3(µ3,η2-(C6H5)CC(C6H5))(µ,η2-dppm)2(CO)6 (4) (yield,
53%) (Scheme 3).
The transient intermediate adduct “Ru3(µ3,η2-(C6H5)-
CC(C6H5))(µ,η2-dppm)2(CO)7” (supposed to exhibit a
pending phosphorus ligand) was not intercepted, due
to the rapidity of the closure of the dppm bridge
accompanied by the loss of CO.26 The structural draw-
ing shown for 4 in Scheme 3 is based on the X-ray
structure analysis,12 which will be published in full
separately.27
Rea ctivity of Ru 3(µ-P h CCP h )(CO)7(d p p m ) (2)
tow a r d Hyd r ogen . The facile reaction of 2 with
hydrogen (1 atm, 10 min, 25 °C) provided the dihydrido
complex, Ru3(µ-H)2(µ3,η2-(C6H5)CC(C6H5))(µ,η2-dppm)-
(CO)7 (5), in 89% yield (Scheme 4). An NMR study of
the solution at -80 °C revealed the existence of two
isomers in solution (approximate ratio 5a /5b ) 10/1).
The X-ray structure of the major isomer 5a was also
determined12 and will be published in full separately.27
The minor isomer 5b shown in Scheme 4 represents the
alternate possibility, where rotation of the alkyne brings
the C-C bond into a position where it lies parallel to
the Ru-Ru bond supported by the bridging dppm.
Reaction of Ru 3(µ-P h CCP h )(CO)7(dppm ) (2) with
P h en yla cetylen e. The addition of 1 equiv of phenyl-
acetylene to a solution of the 46-e cluster prototype Ru3-
(µ-PhCCPh)(µ-dppm)(CO)7 (2) above 0 °C resulted in the
characteristic color change from green to red. The
reaction proceeded to completion within less than 10
min at room temperature in non-coordinating solvents
(benzene or CH2Cl2). IR monitoring indicated the
appearance of two characteristic low-frequency ν(CO)
bands at 1760 and 1670 cm-1, corresponding to a major
red compound. Chromatographic workup revealed the
systematic presence of two phases, namely, a minor fast-
moving violet-brown band, eluted with 1/4 dichlo-
romethane/hexane mixtures, and a major red band,
eluted slowly with pure dichloromethane, and exhibiting
in particular the two characteristic infrared bands
mentioned ealier.
(a ) Ch a r a cter iza tion of th e Red HCtCP h Ad -
d u ct of Com p lex 2. Crystallization of the chromato-
graphed red product afforded red crystals, isolated in
57% yield. They were formulated as Ru3{µ-HCC(Ph)C-
(O)(Ph)CCPh}(dppm)(CO)6 (6) on the basis of spectro-
scopic, analytical, and X-ray data. The structure of the
compound is represented in Figure 2 and in a simplified
structural drawing shown in Scheme 5.
Clearly, the formation of two carbon-carbon bonds
has taken place (without any detectable intermediate)
to produce the dialkenyl ketone fragment HCdC(Ph)C-
(O)(Ph)CdCPh, resulting from the linkage of the two
alkynes through one carbonyl group. The two alkenyl
ends symmetrically bridge the Ru(2)sRu(3) edge of the
metal triangle in a σ-/π-fashion, giving a “fly-over” type
arrangement. Although alkyne and CO coupling reac-
tions are now very well-documented for polymetallic
complexes,15,28 trinuclear fly-over derivatives are rare,28a
and such an arrangement is more common in binuclear
complexes.13i,29 The alkenyl end derived from diphenyl-
(26) (a) Intramolecular bridge formation involving dppm is known
to be a facile process (ref 26b). (b) Poe¨, A.; Sekhar, V. C. J . Am. Chem.
Soc. 1984, 106, 5034.
(27) Rivomanana, S.; Lavigne, G. Manuscript in preparation.

1204 Organometallics, Vol. 15, No. 4, 1996
Rivomanana et al.
acetylene is σ-bound to Ru(2) and π-bound to Ru(3),
whereas the alkenyl end derived from phenylacetylene
is π-bound to Ru(2) and σ-bound to Ru(3). Selective
NMR decoupling experiments indicated that the phen-
ylacetylene-CO linkage is completely regioselective,
with the phenyl substituent of the alkyne being adjacent
to the ketonic CO group. Given that formation of the
dialkenyl ketone fragment (6-e donor) involves one of
the carbonyl groups of the antecedent unsaturated
species 2, the resulting cluster 6 should be coordina-
tively unsaturated. Indeed, it appears that the defi-
ciency of one CO on the metal center Ru(1) is compen-
sated by an unusual “side-on” coordination of the
CsC(Ph) bond of the organic chain. Interactions of a
related type have been previously observed for the
PsC(Ph) bond of a cluster-bound diphenylphosphido
group.30a,b It is noteworthy that the type of coordination
encountered in 6 does not involve any of the double
bonds of the phenyl ring, contrary to what was previ-
ously found for the metallacyclic compound Fe2(CO)6-
{HCCHC(Me)Ph}.30c Another characteristic feature of
the structure is that the two phosphorus donor atoms
of the bis(diphenylphosphino)methane ligand have moved
from their initial equatorial sites in 2 to pseudoaxial
coordination sites in the present adduct.
(b) Ch a r a cter iza tion of th e Min or P r od u cts
Obta in ed fr om th e Rea ction of HCtCP h w ith
Com p lex 2. As noted earlier and in the Experimental
Section, the reaction of 2 with phenylacetylene produced
both the above-mentioned “fly-over” species 6 and also
(systematically) an additional violet-brown compound,
appearing in the initial fast-moving chromatographic
fraction. Curiously, attempts to crystallize that com-
pound yielded colorless needles as the only tractable
material, which was subsequently formulated as the
binuclear ruthenacyclopentadiene derivative Ru2{µ-
HCC(Ph)(Ph)CCPh}(µ-dppm)(CO)4 (7) on the basis of its
mass spectrum.
rivative, although such a compound, apparently more
stable in the case of osmium,31 may well be the elusive
violet species appearing in the fast-moving chromato-
graphic fraction described earlier.
The observation of facile cluster fragmentation lead-
ing to 7 may be surprising at first sight, if we consider
that binuclear ruthenole derivatives of the type Ru2{µ-
RCC(R)(R)CCR}(CO)6 generally are obtained only upon
prolonged thermal reactions between Ru3(CO)12 and
alkynes.32 However, there are precedents for the facile
extrusion of metal carbonyl fragments from trinuclear
precursors, particularly in the chemistry of the edge-
double-bridged triruthenium species studied some years
ago by Kaesz and co-workers.33 Indeed, these authors
noted that the presence of two 3-e donors in bridging
positions over the (open) edge of a triangular cluster is
prone to trigger the elimination of one metal fragment,
provided that the system can readily compensate for the
loss by forming a metal-metal bond between the two
remaining metal centers. A similar situation is encoun-
tered here, where the C4 oligomer acts as a 6-e donor.
By contrast, it is noteworthy that a trinuclear ruthena-
cyclopentadiene derivative, Ru3{µ-RCC(R)(R)CCR}-
(dppm)(CO)6, resulting from direct coupling between two
alkynes was obtained by Bruce and co-workers among
the products of the thermal reaction between Ru3(CO)10-
(dppm) and acetylenedicarboxylate.14a In that case, one
oxygen of the carboxylate group was found to be
coordinated to one of the metal centers, thereby prob-
ably favoring the retention of the trinuclear structure.
Notably, attempts to modify the distribution of the
reaction products 6 and 7 by varying the temperature
over the range 0-40 °C were unsuccessful. Indeed, even
at the minimum temperature required to observe a
reaction, namely, 0 °C, the yield of complex 6 remained
very close to 50%. Furthermore, it was verified that 6
is not the antecedent of 7.
R ea ct ivit y of R u 3{µ-H CC(P h )C(O)(P h )CCP h }-
(dppm )(CO)6 (6) towar d Str on g Nu cleoph iles. Rapid
formation of adducts was observed at room temperature
when complex 6 was stirred in the presence of nucleo-
philes, including CO (1 atm, 25 °C, 5 min), PPh2H (30
°C, 10 min), or Cl- (25 °C, 15 min). At the present stage
of our investigation, these adducts were characterized
only by infrared spectroscopy. In the absence of X-ray
data, we cannot firmly establish whether these addition
reactions take place via loss of the metal-phenyl
interaction or, alternatively, by opening of a metal-
metal bond. The latter possibility should also be
considered since the semibridging carbonyl group found
The production of 7 indicates that direct coupling
between the two alkynes takes place in competition with
alkyne-CO-alkyne coupling and is accompanied by
cluster fragmentation, even under ambient conditions.
Unfortunately, to date, we have been unable to intercept
any transient trinuclear ruthenacyclopentadiene de-
(29) (a) Giordano, R.; Sappa, E.; Cauzzi, D.; Predieri, G.; Tiripicchio,
A.; Tiripicchio Camellini, M. J . Organomet. Chem. 1991, 412, C14. (b)
Gervasio, G.; Giordano, R.; Sappa, E.; Costa, M.; Predieri, G.; Tirip-
icchio, A. J . Cluster Sci. 1993, 4, 33. (c) Blake, A. J .; Dyson, P. J .;
Ingham, S. L.; J ohnson, B. F. G.; Martin, C. M. Organometallics 1995,
14, 862.
(30) (a) MacLaughlin, S. A.; Carty, A. J .; Taylor, N. J . Can. J . Chem.
1982, 60, 87. (b) MacLaughlin, S. A.; Taylor, N. J .; Carty, A. J .
Organometallics 1984, 3, 392. (c) Gervasio, G.; Sappa, E. Organome-
tallics 1993, 12, 1458.
(31) (a) Related trinuclear metallacyclopentadiene complexes are
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N. M.; Dolgushin, F. M.; Yanovsky, A. I.; Struchkov, Y. T.; Petrovskii,
P. V. Organometallics 1995, 14, 2167.
(32) (a) Sears, C. T.; Stone, F. G. A. J . Organomet. Chem. 1968, 11,
644. (b) Cetini, G.; Gambino, O.; Sappa, E.; Valle, M. J . Organomet.
Chem. 1969, 17, 437. (c) Gambino, O.; Cetini, G.; Sappa, E.; Valle, M.
J . Organomet. Chem. 1969, 20, 195.
(33) Kampe, C. E.; Boag, N. M.; Kaesz, H. D. J . Mol. Catal. 1983,
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(28) (a) J ackson, W. G.; J ohnson, B. F. G.; Kelland, J . W.; Lewis, J .;
Schorpp, K. T. J . Organomet. Chem. 1975, 88, C17. (b) Knox, S. A. R.
Pure Appl. Chem. 1984, 56, 81. (c) Hogarth, G. H.; Kayser, F.; Knox,
S. A. R.; Morton, D. A. V.; Orpen, A. G.; Turner, M. L. J . Chem. Soc.,
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J ohnson, K. A.; Gladfelter, W. L. Organometallics 1992, 11, 2534. (f)
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R. D.; Chen, L.; Wu, W. Organometallics 1993, 12, 4112. (i) Adams, R.
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W. L. Organometallics 1995, 14, 461.

Self-Activation of a Cluster-Bound Alkyne
Organometallics, Vol. 15, No. 4, 1996 1205
F igu r e 4. Perspective view of complex 9b.
F igu r e 3. Perspective view of complex 8. The four phenyl
rings of the bis(diphenylphosphino)methane ligand have
been omitted for clarity. A sphere of arbitrary radius is
used to represent the bridging hydride ligand, which was
located and refined. Since 8 results from an intramolecular
transformation of 6, an identical labeling scheme has been
used for the two structures.
group in the antecedent 6. Such an unstable interaction
would then trigger H transfer to the metal, converting
the dialkenyl ketone fragment into the vinylidene
alkenyl ketone fragment actually found in the final
derivative 8.
in 6 appears to have moved into a terminal position in
the adducts. Furthermore, the yellow color of the CO
adduct may well be consistent with the occurrence of
an open trinuclear framework.
Attem p ts To Relea se a F r ee Keton e Molecu le
fr om th e Clu ster -Bou n d Dia lk en yl Keton e F r a g-
m en t F ou n d in Com p lex 6. We were interested in
determining whether the construction of a free ketone
could be achieved from any of the preceding complexes.
A logical approach appeared to be the treatment of
complex 6 with CO, which might be expected to favor
closure of the dialkenyl ketone fragment via carbon-
carbon bond formation to give either a cyclopentadi-
enone or a quinone. As noted earlier, the addition of
CO under mild conditions (1 atm, 25 °C, 5 min) led to a
fairly stable yellow adduct, still exhibiting the charac-
teristic ν(CO) absorption of the ketonic fragment in its
IR spectrum. Thus, further attempts to release the
organic moiety were made in a reactor under forcing
conditions, using various temperatures and pressures
of carbon monoxide. To date, all such attempts failed.
As one might expect, the number of metal-containing
species was seen to increase with the increasing severity
of reaction conditions. Only the most abundant com-
pounds obtained from such experiments were isolated
and characterized. Nevertheless, as shown in the
following, their identification allowed us to understand
why no organic substrate was released from the cluster
under the conditions of these experiments.
The most significant point to be stressed is the fact
that elimination of the edge-bridging dppm ligand from
the cluster apparently is the most favorable reaction
taking place under CO. Typically, the 31P NMR spec-
trum of a solution of complex 6 stirred under 10 atm of
CO for 1 h at 80 °C showed two doublets at 32.0 and
-27.5 ppm, respectively (J (P-P) ) 60 Hz). Although
such an intermediate was not isolated, the negative
chemical shift observed for the second doublet signal is
consistent with the existence of an intermediate bearing
a pending phosphorus atom. There is precedent for such
a binding mode of dppm in a previously reported fly-
over species.29a Under more forcing conditions, traces
of Ru3(CO)12 were then detected, whereas the major
species isolated from the reactor was characterized as
the binuclear “fly-over” complex, Ru2{µ-HCC(Ph)C(O)-
(Ph)CCPh}(CO)6 (9) (Scheme 7).
In tr a m olecu la r vs In ter m olecu la r Rea ctivity of
Ru 3{µ-HCC(P h )C(O)(P h )CCP h }(dppm )(CO)6 (6). We
were interested in determining whether the presence
of a masked unsaturation in complex 6 would favor the
incorporation of one more alkyne into the organic chain,
just as observed by Knox and co-workers in the case of
a bimetallic iron complex.28c Since there was no uptake
of phenylacetylene under ambient conditions, attempts
were made to initiate the addition upon gentle heating.
During the course of such experiments, we were led to
observe that the addition of alkynes (much less nucleo-
philic than the above-mentioned 2-e donors) is in fact
hindered by a preferred intramolecular transformation
of complex 6 that takes place at the expense of the
available coordination site. Typically, when solutions
of complex 6 were warmed above 35 °C (regardless of
the presence or absence of an alkyne in the solution), a
progressive lightening of the characteristic red color of
the complex was observed, whereas changes in the IR
spectrum indicated the quantitative formation of a new
species over a period of 20 min. The new complex was
isolated in 90% yield as orange crystals and subse-
quently formulated as Ru3(µ-H){µ-CC(Ph)C(O)(Ph)-
CCPh}(dppm)(CO)6 (8) on the basis of NMR and X-ray
diffraction studies.
Ch ar acter ization of Ru 3(µ-H){µ-CC(P h )C(O)(P h )-
CCP h }(d p p m )(CO)6 (8). The structure of the hydrido
complex 8 is represented in Figure 3. The formation of
this new complex can be rationalized by the simple
reaction sequence shown in Scheme 6. We propose that
the observed ligand transformation is initiated by the
loss of the labile phenyl-metal interaction. Subsequent
migration of the dialkenyl ketone ligand to the opposite
face of the cluster would take place via simple free
rotation around the metal-metal edge Ru(2)-Ru(3) to
give a transient isomeric form of 6, namely, 6*, in which
the C-H bond of the phenylacetylene moiety would
come into agostic contact with the metal center Ru(1),
in roughly the same geometrical situation as the phenyl
The structure of the binuclear species 9 was estab-

1206 Organometallics, Vol. 15, No. 4, 1996
Rivomanana et al.
Sch em e 6
Sch em e 7
lished by an X-ray diffraction study of the complex 9b
(Figure 4). The latter was obtained through a parallel
reaction sequence starting from the intermediate fly-
over species 6b, which was obtained upon the addition
of 1-pentyne to complex 2 [it is noteworthy that the
isostructural symmetric complex Ru2{µ-PhCC(Ph)C(O)-
(Ph)CCPh}(CO)6 has been obtained recently by J ohnson
and co-workers in the reaction of a (benzene)triruthe-
nium cluster with an excess of diphenylacetylene].29c
Clearly, under our reaction conditions, the formation
of the bimetallic “fly-over” species 9 via stepwise loss of
dppm and loss of a mononuclear “Ru(CO)4” fragment
(that further reaggregates to produce Ru3(CO)12) ap-
pears to be thermodynamically more favorable than
direct reductive elimination of a cyclic unsaturated
ketone from the trinuclear species. Small amounts of
the substituted derivative Ru3(CO)10(dppm) were also
detected under prolonged reaction with CO. Such a
compound arises from further reaction between mol-
ecules of Ru3(CO)12 and dppm that are both released in
solution.
exploited as a self-activation process, permitting us to
trigger cycloaddition reactions. While adopting a per-
pendicular conformation relative to the metal triangle,
the diphenylacetylene ligand stabilizes a vacant coor-
dination site that can be subsequently intercepted by
an incoming 1-alkyne under very mild conditions. The
spontaneous C-C coupling that is then observed reflects
the tendency of the cluster to release its incipient
supersaturation. Both indirect coupling of the two
alkynes through a carbonyl group to give a trinuclear
“fly-over” type compound and direct coupling to give a
ruthenacyclopentadienyl derivative are seen to take
place via two parallel competing pathways.
Unfortunately, in the present case, the preceding
concept does not appear to be directly applicable to
organic synthesis since the oligomeric fragment gener-
ated here is too tightly bound to the cluster to be
properly liberated without degradation of the polyme-
tallic framework. Although one may think of alternate
stoichiometric means to recover the organic moiety (such
as, for example, protonation by HCl),28h,34 the fact that
the ongoing cyclocarbonylation falls into a dead end (in
Con clu d in g Rem a r k s
We have seen a specific case where the mobility of
an alkyne onto a triruthenium cluster core may be
(34) Sailor, M. J .; Sabat, M.; Shriver, D. F. Organometallics 1988,
7, 728.

Self-Activation of a Cluster-Bound Alkyne
Organometallics, Vol. 15, No. 4, 1996 1207
fact, a thermodynamic sink) with the formation of stable
bimetallic “fly-over” species raises recurrent questions
regarding the participation of an intact cluster in Ru3-
(CO)12-based catalytic cyclocarbonylations, such as, for
example, the Lonza synthesis of hydroquinone from
acetylene, CO, and H2O.35 Accordingly, one may rea-
sonably suggest that even though the initial carbon-
carbon bond forming step in such a reaction may be a
“cluster-assisted” process36 of the type modeled here, the
final elimination step releasing the cyclic product is very
likely to take place from lower nuclearity fragments that
may further recombine before another cycle is started.
Such a proposal is fully consistent with the early
pioneering observations that a prolonged thermal reac-
tion between Ru3(CO)12 and diphenylacetylene gives a
mononuclear complex of tetraphenylcyclopenta-
dienone.32a,b,37 Let us also keep in mind that first-row
polymetallic metal carbonyls derived from iron or cobalt
are known to be valuable precursors for a number of
useful cycloaddition reactions.15 Their ability to release
pure organic molecules more readily than the corre-
sponding second-row metal carbonyl derivatives appears
to be in line with the lower energies of their metal-
metal and metal-ligand bonds.
In conclusion, if we keep in mind the challenge to
develop cluster-mediated coupling reactions involving
alkynes, a strategy based only on the design of unsatur-
ated cluster prototypes is certainly not the best one. This
is the reason why we are already developing an alter-
nate approach based on the use of nucleophilic hemi-
labile ancillary ligands that are prone to assisting both
the stepwise incorporation of several molecules of
substrate and the liberation of the resulting oligomers
via a repeated intramolecular bridge opening/closing
sequence.4,38
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 helpful discussions under the
support of NATO Grant 931414.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data including tables of atomic coordinates, anisotropic ther-
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