Ruthenium acetylide oxidation: From stable radicals to allenylidene synthesis via γ-elimination of H+

Article abstract of DOI:10.1021/om0200555

Oxidation of ruthenium(II) acetylides trans-[Cl(dppe)₂Ru-C≡C-CHR₂] (R = H, CH₃, Ph) leads to cationic radicals of which the stability is found to be highly influenced by the nature of R. This oxidative process leads to a stable cationic radical (R = CH₃, H) or to its rearrangement into a neutral radical, trans-[Cl(dppe)₂Ru-C≡C-C.(R)₂] for R = Ph. This unprecedented γ-elimination of a proton provides both the allenylidene trans- [Cl(dppe)₂Ru= C=C=CR₂]PF₆ and the vinylidene trans-[Cl(dppe)₂Ru=C=CH-CHR₂]PF₆. The allenylidene can be selectively obtained from the acetylide in the presence of a base.

Full text of DOI:10.1021/om0200555

2654
Organometallics 2002, 21, 2654-2661
Ru th en iu m Acetylid e Oxid a tion : F r om Sta ble Ra d ica ls
to Allen ylid en e Syn th esis via γ-Elim in a tion of H+
Ste´phane Rigaut,* Florian Monnier, Franc¸ois Mousset, Daniel Touchard,* and
Pierre H. Dixneuf
Institut de Chimie de Rennes, UMR 6509 CNRS-Universite´ de Rennes 1: Organome´talliques
et Catalyse, Campus de Beaulieu 35042 Rennes, France
Received J anuary 25, 2002
Oxidation of ruthenium(II) acetylides trans-[Cl(dppe)2Ru-CtC-CHR2] (R ) H, CH3, Ph)
leads to cationic radicals of which the stability is found to be highly influenced by the nature
of R. This oxidative process leads to a stable cationic radical (R ) CH3, H) or to its
rearrangement into a neutral radical, trans-[Cl(dppe)2Ru-CtC-C•(R)2] for R ) Ph. This
unprecedented γ-elimination of a proton provides both the allenylidene trans-[Cl(dppe)2Rud
CdCdCR2]PF6 and the vinylidene trans-[Cl(dppe)2RudCdCH-CHR2]PF6. The allenylidene
can be selectively obtained from the acetylide in the presence of a base.
In tr od u ction
sent, for instance, valid alternatives to Grubbs’ catalysts
for olefin metathesis.4 In parallel, the development of
synthetic routes toward metal acetylides has progressed
rapidly, and there are constant studies on their proper-
ties or chemical reactivity, as they are known to promote
carbon coupling reactions as well as catalytic transfor-
mations.6,7 All these carbon-rich species also provide
valuable synthons for polymetallic species or metal-
containing polymers,8-10 supramolecular architectures,11
and molecular switches12 and are promising in molec-
ular-scaled electronics.10
Understanding and rationalizing the reactivity of
carbon-rich transition metal complexes attract current
interest.1-12 The design, preparations, and applications
of metallacumulenes [M]d(Cd)nCR1R2 are now well
documented;1-5 ruthenium allenylidenes (n ) 3) repre-
* Corresponding authors. E-mail: (D.T.) daniel.touchard@
univ-rennes1.fr; (S.R.) stephane.rigaut@univ-rennes1.fr.
(1) (a) Werner, H. Chem. Commun. 1997, 903. (b) Bruce, M. I. Chem.
Rev. 1998, 98, 2797. (c) Cardieno, V.; Gamasa, M. P.; Gimeno, J . J .
Eur. J . Inorg. Chem. 2001, 571.
Owing to the increasing demand, i.e., the development
of highly efficient selective synthetic methods and new
materials, novel compounds need to be processable and
characterizable. It is clear that great variation of ligands
and metals of different oxidation states is required.
Systematic studies of their reactivity and properties will
induce more applications. For this purpose, our current
research deals with the synthesis, the reactivity, and
the electronic properties of acetylides [M]-(CtC)n-R
and cumulenylidenes [M]d(Cd)nCR1R2 complexes.3,5,8
Stimulated by the fact that radical species have been
recently proposed as intermediates in metathesis,13 we
recently demonstrated that the reduction of cationic
ruthenium cumulenylidenes of the type [Cl(dppe)2Rud
CdCdCR2]PF6 (dppe: Ph2PCH2CH2PPh2) occurs on the
carbon chain and that the electron is located at the
termini of this chain as a general trend.5a By contrast,
concerning the oxidation of ruthenium acetylides [Ru]-
CtC-R, a large part of the electron removed originates
from the metal14 (RuII/RuIII) but little is known on the
stability of these oxidation states. Herein, we report our
results on the influence of the nature of the acetylide
ligand on the oxidation of trans-[Cl(dppe)2Ru-CtC-
CHR2] complexes. We have shown that (i) the stability
(2) Touchard, D.; Dixneuf, P. H. Coord. Chem. Rev. 1998, 178-180,
409.
(3) Bruneau, C.; Dixneuf, P. H. Acc. Chem. Res. 1999, 32, 311.
(4) (a) Furstner, A.; Picquet, M.; Bruneau, C.; Dixneuf, P. H. Chem.
Commun. 1998, 1315. (b) Picquet, M.; Bruneau, C.; Dixneuf, P. H.
Chem. Commun. 1998, 2249. (c) Fu¨rstner, A.; Hill, A. F.; Liebl, M.;
Wilton-Ely, J . D. E. T. Chem. Commun. 1999, 615. (d) Picquet, M.;
Touchard, D.; Bruneau, C.; Dixneuf, P. H. New J . Chem. 1999, 141.
(e) Osipov, S. N.; Artyushin, O. I.; Kolomiets, A. F.; Bruneau, C.;
Picquet, M.; Dixneuf, P. H. Eur. J . Org. Chem. 2001, 3891.
(5) (a) Rigaut, S.; Maury, O.; Touchard, D.; Dixneuf, P. H. Chem.
Commun. 2001, 373. (b) Touchard, D.; Haquette, P.; Daridor, A.;
Romero, A.; Dixneuf, P. H. Organometallics 1998, 17, 3844.
(6) (a) Low, P. J .; Bruce, M. I. Adv. Organomet. Chem. 2001, 48, 71.
(b) Manna, J .; J ohn, K. D.; Hopkins, M. D. Adv. Organomet. Chem.
1995, 38, 79. (c) Whittall, I. R.; McDonagh, A. M.; Humphrey, M. G.;
Samoc, M. Adv. Organomet. Chem. 1999, 43, 349.
(7) (a) Hill, H. Comprehensive Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford, 1995;
Vol. 7, pp 411-417. (b) Stang, P. J .; Diederich, F. Modern Acetylene
Chemistry; VCH: Weinheim, 1995.
(8) (a) Rigaut, S.; Le Pichon, L.; Daran, J .-C.; Touchard, D.; Dixneuf,
P. H. Chem. Commun. 2001, 1206. (b) Lebreton, C.; Touchard, D.; Le
Pichon, L.; Daridor, A.; Toupet, L.; Dixneuf, P. H. Inorg. Chim. Acta
1998, 272, 188.
(9) Wong, K. T.; Lehn, J .-M.; Peng, S.-M.; Lee, G.-H. Chem. Com-
mun. 2000, 2259.
(10) (a) Paul, F.; Lapinte, C. Coord. Chem. Rev. 1998, 178-180, 431.
(b) Martin, R. E.; Diederich, F. Angew. Chem., Int. Ed. 1999, 38, 1350.
(c) Ward, M. D. Chem. Ind. 1996, 15, 568. (d) Ziessel, R.; Hissler, M.;
El-Gayhouri, A.; Harriman, A. Coord. Chem. Rev. 1998, 178-180, 125.
(e) Whittall, I. R.; McDonagh, A. M.; Humphrey, M. G. Adv. Organomet.
Chem. 1999, 43, 349. (f) Stang, P. J .; Olenyuk, B. Acc. Chem. Res. 1997,
30, 502. (g) Kingsborough, R. P.; Swager, T. M. Prog. Inorg. Chem.
1999, 48, 123. (h) Nguyen, P.; Go´mez-Elipe, P.; Manners, I. Chem. Rev.
1999, 99, 1515. (i) Wu, I. Y.; Lin, J . T.; Wen, Y. S. Organometallics
1999, 18, 320.
(13) (a) Amir-Ebrahimi, V.; Hamilton, J . G.; Nelson, J .; Rooney, J .
J .; Thompson, J . M.; Beaumont, A. J .; Rooney, A. D.; Harding, C. J .
Chem. Commun. 1999, 1621.
(14) (a) Koentjoro, O. F.; Rousseau, R.; Low, P. J . Organometallics
2001, 20, 4502. (b) McGrady, J . E.; Lovell, T.; Stranger, R.; Humphrey,
M. G. Organometallics 1997, 16, 4004. (c) Winter, R. F. Eur. J . Inorg.
Chem. 1999, 2121. (d) Winter, R. F.; Hornung F. M. Organometallics
1999, 18, 4005.
(11) Stang, P. J . Chem. Eur. J . 1998, 4, 19.
(12) (a) Fillaut, J .-L.; Price, M.; J ohnson, A. L.; Perruchon, J . Chem.
Commun. 2001, 739. (b) Yam, V. W.-W., Tang, R. P.-L.; Wong, K. M.-
C.; Cheung, K.-K. Organometallics 2001, 20, 4476.
10.1021/om0200555 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 05/29/2002

Ruthenium Acetylide Oxidation
Organometallics, Vol. 21, No. 13, 2002 2655
F igu r e 1. Cyclic voltammetry responses (CH2Cl2, Bu4NPF6 0.1 M, ν ) 100 mV s-1) reported vs internal ferrocene for (a)
trans-[Cl(dppe)2Ru-CtC-CHPh2] (1), (b) trans-[Cl(dppe)2Ru-CtC-CH(CH3)2] (2), and (c) trans-[Cl(dppe)2Ru-CtC-
CH3] (3).
Sch em e 1
of the resulting cationic radical is highly influenced by
the nature of R; (ii) stable radical cations are formed
when R ) CH3, H; (iii) a rearrangement of these species
takes place via an unprecedented γ-elimination of a
proton when R ) Ph to afford both the vinylidene trans-
[Cl(dppe)2RudCdCH-CHR2]PF6 and the allenylidene
trans-[Cl(dppe)2RudCdCdCR2]PF6; (iv) an advantage
of this process can be taken to offer a new route to metal
allenylidene species by forcing the deprotonation, e.g.,
from the alkynyl complexes via oxidation in the presence
of pyridine.
mass spectrometry. 31P analysis exhibits one resonance
respectively at 51.54 (1) and 50.47 (2) ppm, showing that
the four phosphorus atoms are equivalent and that the
Cl atom and alkynyl ligand are in trans position. The
most characteristic features of the 1H NMR data are
the hydrogen atom on Cγ at 4.77 ppm for 1 (singlet) and
3
2.43 ppm for 2 (septuplet, J CH ) 6.5 Hz). In addition,
characteristic IR vibration stretches are obtained,
νC≡C ) 2085 (1), 2086 (2) cm-1. The third acetylide,
trans-[Cl(dppe)2Ru-CtC-CH3] (3), was obtained from
cis-[(dppe)2RuCl2] in a propyne atmosphere, with a mild
halide abstracting agent (NaPF6) followed by the depro-
tonation of the resulting vinylidene intermediate with
Et3N (Scheme 1). The acetylide structure is supported
Resu lts a n d Discu ssion
Nucleophiles are susceptible to add either on the CR
or on the Cγ atom of an allenylidene ligand.15 Complexes
with metal fragments bearing bulky phosphines lead to
the regioselective addition on Cγ.1 Ruthenium(II) trans-
[Cl(dppe)2Ru-CtC-CHPh2] (1) and trans-[Cl(dppe)2Ru-
CtC-CH(CH3)2] (2) acetylides were obtained via the
selective nucleophilic addition of H- to the correspond-
ing cationic allenylidenes trans-[Cl(dppe)2RudCdCd
CR2]PF6 (R ) Ph, CH3).5a These reductions were per-
formed using NaBH4 in THF16 (Scheme 1), and the
deeply colored cationic complexes quickly led to colorless
solutions of 1 or 2. These complexes have been charac-
1
by the H NMR spectra showing the methyl signal at
1.40 ppm and the FTIR measurement with νC≡C ) 2110
cm-1. The singlet observed at 50.46 ppm in 31P NMR
reveals the trans orientation of the propynyl group and
of the chlorine atom.
Cyclic voltammetry (CV) was used to investigate the
electrochemical behavior of the three acetylides trans-
[Cl(dppe)2Ru-CtC-CHPh2] (1), trans-[Cl(dppe)2Ru-
CtC-CH(CH3)2] (2), and trans-[Cl(dppe)2Ru-CtC-
CH3] (3) (Figure 1). Complex 1 undergoes a well-defined
one-electron reversible oxidation on the CV scale (E° )
0.02 V vs ferrocene) (Table 1). For complex 2, an easier
one-electron reversible oxidation (E° ) -0.07 V vs
ferrocene) is observed due to the electron releasing effect
of the isopropyl group. The oxidation potential of 3 is
the same as that of 2 (E° ) -0.07 V vs ferrocene),
showing an analogous acceptor character for the both
carbon ligands in 2 and 3. To a first approximation,
these reversible one-electron-step oxidations could be
viewed as essentially involving the RuII/RuIII system.14
1
terized by H, 13C, and 31P NMR and high-resolution
(15) (a) Esteruelas, M. A.; Gomez, A. V.; Lopez, A.; Modrego, J .;
On˜ate, E. Organometallics 1997, 16, 5826. (b) Cadierno, V.; Gamasa,
M. P.; Gimeno, J .; Gonza´lez-Cueva, M.; Lastra, E.; Borge, J .; Garc´ıa-
Granda, S.; Pe´rez-Carren˜o, E. Organometallics 1996, 15, 2137.
(16) Touchard, D.; Pirio, N.; Dixneuf, P. H. Organometallics 1995,
14, 4920. Nucleophilic addition in methanol leads to additional
displacement of the chlorine atom by H- to [H(dppe)2Ru-CtC-CHR2]:
Rigaut, S.; Mousset, F.; Touchard D.; Dixneuf, P. H. Unpublished
work.

2656 Organometallics, Vol. 21, No. 13, 2002
Rigaut et al.
proton as a doublet of quintets at 3.35 ppm (3J HH ) 11.1
4
Hz, J PH ) 2.7 Hz) as expected and for the hydrogen
atom on Cγ as a doublet at 4.15 ppm (3J HH ) 11.1 Hz).
In the 13C NMR, a quintet for CR is observed at 344.35
ppm (2J PC ) 13 Hz). CV studies revealed that both 4
and 5 display a reduction wave, a reversible one with
E° ) -1.03 V vs ferrocene for 4 (Epc≈ -1.06 V) and an
irreversible one with Epc) -1.93 V vs ferrocene for 5
(ν ) 400 mV s-1). These potentials match those observed
after microelectrolysis, confirming that the nature of the
products is the same in both experiments. It is note-
worthy that their oxidation potential is high and they
do not interfere with ferrocenium salt in the oxidation
reaction (Table 1).
F igu r e 2. ESR spectra resulting from the oxidation of 1,
g ) 2.0039.
The reactivities of the trans-[Cl(dppe)2Ru-CtC-CH-
(CH3)2] (2) and trans-[Cl(dppe)2Ru-CtC-CH3] (3) com-
plexes were different. Monitoring the oxidation reactions
with 31P NMR did not show a following reaction as for
1, but only the slow appearance of small amounts of
trans-[Cl(dppe)2RudCdCH-CH(CH3)2]PF6 (6) and trans-
[Cl(dppe)2RudCdCH-CH3]PF6 (7) vinylidenes, respec-
tively. To quantitatively evaluate the stability of the
oxidized forms arising from 2 and 3, oxidations were
followed after 1 h by reduction with 1 equiv of cobal-
tocene [(η5-C5H2)2Co].17b,18 With complex 2, 95% of the
starting acetylide and 5% of the trans-[Cl(dppe)2Rud
Ta ble 1. Electr och em istr y Da ta for
Com p lexes 1-5a
b
c
b
E°OX1 EpaOX2 E°RED
[Cl(dppe)2Ru-CtC-CHPh2] (1)
[Cl(dppe)2Ru-CtC-CH(CH3)2] (2)
[Cl(dppe)2Ru-CtC-CH3] (3)
[Cl(dppe)2RudCdCdCPh2]PF6 (4)
[Cl(dppe)2RudCdCH-CHPh2]PF6 (5)
0.02
-0.07
-0.07
0.99d
1.11d
1.07
1.03
0.99
-1.03
-1.93c,e
a
Measurements were performed in CH2Cl2 using Bu4NPF6 0.1
b
M, ν ) 100 mV s-1
.
Quasi reversible redox processes ∆Ep ≈ 60
mV, Ipc/Ipa ≈ 1. Potential are reported in V vs ferrocene. c Peak
d
potential of irreversible processes. ∆Ep ≈ 75 mV, Ipc/Ipa < 1.
1
CdCH-CH(CH3)2]PF6 (6) vinylidene (evaluated via H
NMR) were recovered (Scheme 2). Compound 6 was
e ν ) 400 mV s-1
.
unambiguously identified. A characteristic IR vibration
Complexes 1, 2, and 3 give a second irreversible oxida-
tion at a much higher potential (not shown) attributed
to the RuIII/RuIV system. Meanwhile, despite the chemi-
cal reversibility of the first oxidation observed for com-
1
stretch is observed at 1647 cm-1(νdCdC). The H NMR
spectrum shows the vinylidene proton as a doublet of
4
quintets at 2.02 ppm (3J HH ) 9.7 Hz, J PH ) 2.1 Hz)
and the hydrogen atom on Cγ as a doublet of septuplets
pound 1 at a scan rate down to a few mV s-1 (Ipc/Ipa
>
3
at 2.09 ppm (3J HH ) 9.7 Hz, J HH ) 6.0 Hz). The same
0.95), we noticed that when a microelectrolysis of the
solution was conducted as a pretreatment during sev-
eral seconds (∼30 s, Eapplied ) 0.5 V), the next CV scan
showed in the cathodic region two small reduction waves
at Epc1 ) -1.06 V and Epc2 ) -1.95 V (ν ) 400 mV s-1).
As the species responsible for these waves are generated
only when a pre-microelectrolysis is performed, this
suggests that the initial RuIII species undergoes a slow
chemical transformation. By contrast, complexes 2 an
3 do not show this behavior.
behavior was observed with 3: oxidation and reduction
lead back to 85% of the acetylide and to 15% of the
trans-[Cl(dppe)2RudCdCH-CH3]PF6 (7) vinylidene com-
plex. The 1H NMR spectrum of 7 presents a broad signal
for the vinylidene proton at 2.49 and a doublet at 0.91
ppm (3J HH ) 6.8 Hz) for the methyl group. The oxidized
species issued from 2 and 3 were then thermally stable,
and the formation of 6 and 7 was certainly induced by
incorporation of a proton or a hydrogen from the
medium by those cationic radicals (vide supra). For
complex 3, it is worth noting that residual water led to
partial hydrolysis of the carbon chain to trans-[Cl-
(dppe)2Ru(CO)]PF6 (8), identified by HRMS (m/z )
961.1402), via a regioselective cleavage of the CR-Câ
bond.19
Chemical oxidation of acetylides 1, 2, and 3 were
conducted with 1 equiv of ferrocenium salt [(η5-C5H5)2-
Fe]PF6 in methylene chloride. The redox potential of this
oxidant is not favorable17 for 1, but we assumed that
the driving force, i.e., the consecutive chemical reaction
observed by the electrochemical analysis, would lead to
the total displacement of the equilibrium. After 1 h the
reaction was complete and a 1:1 mixture of the well-
known ruthenium allenylidene trans-[Cl(dppe)2RudCd
CdCPh2]PF6 (4)5b along with the vinylidene trans-
[Cl(dppe)2RudCdCH-CH Ph2]PF6 (5) was recovered
(Scheme 2). The products were separated by fractional
crystallizations, and trans-[Cl(dppe)2RudCdCH-CHPh2]-
PF6 (5) was fully identified by NMR, IR, and high-
resolution mass spectroscopies. The characteristic IR
The presence of a phenyl group in the alkynyl ligand
of 1 led to a cationic radical with a specific reactivity
with respect to 2 and 3. To understand the origin of the
odd reactivity of the trans-[Cl(dppe)2Ru-CtC-CHPh2]
(1) complex and the source of the â-hydrogens of the
vinylidene complexes, we synthesized the trans-[Cl-
(18) Cobaltocene (E° ) -1.33 V vs ferrocene) is not able to reduce
vinylidene 5 and 6, which both show an irreversible reduction wave
with respectively Epc ) -1.90 V and -1.97 V (100 mV s-1, V vs
ferrocene).
(19) Hydrolysis of metal vinylidenes has already been reported to
give carbonyl species and the unsatured hydrocarbon derived from the
homologation of vinylidene substituent. See: (a) Bruce, M. I.; Swincer,
A. G.; Wallis, R. C. J . Organomet. Chem. 1979, 171, C5. (b) Bianchini,
C.; Cazares, J . A.; Peruzzini, M.; Romerosa, A.; Zanobini, F. J . Am.
Chem. Soc 1996, 118, 4585. However in the present case, 7 is not
sensitive to hydrolysis on the time scale of the reaction, and 8 then
results from the hydrolysis of the radical intermediate.
vibration stretch for RudCdC is observed at 1645 cm-1
.
31P NMR analysis exhibits one resonance at 43.78 ppm
(s). The 1H NMR shows the signal for the vinylidene
(17) (a) Quantitative prediction assuming totally reversible redox
agents leads to a ratio [1+]/[1] of 40/60, see ref b. (b) Connelly, N. G.;
Geiger, W. E. Chem. Rev. 1996, 96, 877.

Ruthenium Acetylide Oxidation
Organometallics, Vol. 21, No. 13, 2002 2657
Sch em e 2
Sch em e 3
(dppe)2Ru-CtC-CDPh2] (1D) and trans-[Cl(dppe)2Ru-
CtC-CD(CH3)2] (2D) acetylides deuterated on the Cγ
position by reduction of the allenylidene compounds
with NaBD4. When the oxidation of 1D was carried out
in the same conditions as for 1, a 1:1 mixture of the
allenylidene 4 and the vinylidene trans-[Cl(dppe)2Rud
CdCD-CDPh2]PF6 (5DD) deuterated on the Câ and Cγ
positions was obtained (Scheme 3). Indeed, the 1H NMR
spectrum of 5DD did not show any signal for the
hydrogen on both Câ and Cγ positions. This structure
was confirmed by addition of a drop of water to the
mixture, which gave fast exchange with the acidic
vinylidene hydrogen and afforded trans-[Cl(dppe)2Rud
CdCH-CDPh2]PF6 (5HD). The 1H NMR spectrum
shows a quintet at 3.25 ppm (4J PH ) 2.7 Hz) indicative
of the presence of a proton on Câ only coupled with the
four phosphorus. The oxidation performed from trans-
[Cl(dppe)2Ru-CtC-CD(CH3)2] (2D) acetylide leads to
the formation of the trans-[Cl(dppe)2RudCdCH-CD-
(CH3)2]PF6 (6HD) vinylidene deuterated only on the Cγ
H on Cγ, while a singlet is observed for the methyl
groups at 0.49 ppm. Chemical oxidation reactions of
compounds 1D and 2D were also carried out with
further fast addition of Ph3SnH, which is known as a
specific radical quencher by H• transfer.20 On the basis
of NMR data, these reactions led to the complete
disappearance of 1D and 2D, and the products formed
were the trans-[Cl(dppe)2RudCdCH-CDPh2]PF6 (5HD)
and the trans-[Cl(dppe)2RudCdCH-CD(CH3)2]PF6
(6HD) vinylidenes, respectively (Scheme 3).
These results associated with the electrochemical
experiments suggest several comments. (i) For 1 (and
1D) an intermolecular hydrogen (deuterium) transfer
occurs between two acetylide complexes (or the oxidized
forms) to lead to 4 and 5 (5DD). (ii) In the case of 2D
and 2, the small amount of vinylidene observed after
oxidation and reduction is the result of incorporation
of a hydrogen (or a proton) from the reaction medium.
(iii) The trapping reaction with Ph3SnH led to the sole
(20) (a) Tanner, D. D.; Diaz, G. E.; Potter, A. J . Org. Chem. 1985,
50, 2149. (b) Covert, K. J .; Wolczanski, P. T.; Hill, S. A.; Krusic, P. J .
Inorg. Chem. 1992, 31, 66.
1
position. The H NMR signal at 2.01 ppm suggests the
presence of one proton on Câ. No signal is present for a

2658 Organometallics, Vol. 21, No. 13, 2002
Rigaut et al.
Sch em e 4
formation of the vinylidenes complex 5HD or 6HD and
inhibited the intermolecular migration of the deuterium
on Cγ. This involves the direct oxidation of starting
acetylides as the first step of the mechanism in all cases.
Indeed, in this kind of complex, the electron is known
to be mostly located on the metal14 (form A, Scheme 3)
but a contribution resulting from a metal-carbon π
interaction where the single electron is delocalized over
the carbon chain (form B) cannot be excluded and
clarifies the formation of the vinylidenes. (iv) These two
last conclusions could be extended to 3. The weaker
steric protection of its carbon chain could explain on one
hand the larger amount of vinylidene present after
reduction and on the other hand the occurrence of
hydrolysis of the chain when traces of water are present,
as this feature is not observed for 1 and 2.
To completely rationalize the formation of 4 and 5
from 1, the reaction could be related to anodic oxidation
of organic compounds such as anilines.21 Those cationic
radicals lead to more stable neutral radicals by losing
a proton able to protonate the starting material. Con-
sidering the oxidation of 1, the most appropriate way
to form 4 and 5 is the γ-elimination of a proton, which
is able to attack another molecule of acetylide to form
trans-[Cl(dppe)2RudCdCH-CPh2H]PF6 (5) (Scheme 4),
as we assume that there is a non-negligible amount of
nonoxidized complex in the medium (vide infra). Indeed
ruthenium acetylides can be readily protonated to
vinylidene;5b,22 this was verified with complex 1 treated
with acids such as HBF4‚Et2O or diluted aqueous HPF6.
On the other hand, the neutral radical trans-[Cl-
(dppe)2Ru-CtC-C•Ph2] (4•) resulting from the γ-elim-
ination is oxidized by ferrocinium salt to one molecule
of the allenylidene trans-[Cl(dppe)2RudCdCdCPh2]PF6
(4) (E° ) -1.03 V vs ferrocene). This hypothesis is
supported by the observation of a broad ESR signal at
g ) 2.0039, when the reaction was carried out in the
ESR cavity at 100 K. This can be attributed to the
acetylide radical trans-[Cl(dppe)2Ru-CtC-C•(Ph)2]5b,23
even if the fine structure was not observed at this
temperature.24 It is noteworthy that (i) no stable dimer-
ization of 4• was detected as reported for vinylidene
oxidation,25 probably because of the fast following
electron transfer and (ii) these results associated with
the absence of reaction between 1 and Ph3SnH rule out
the hypothesis of a mechanism involving a hydrogen
atom transfer.
The fact that proton elimination does not occur with
trans-[Cl(dppe)2Ru-CtC-CH(CH3)2] (2) and trans-[Cl-
(dppe)2Ru-CtC-CH3] (3) but only with trans-[Cl-
(dppe)2Ru-CtC-CHPh2] (1) could be explained in
terms of stabilization of the neutral radical [Cl(dppe)2-
Ru-CtC-C•(R)2] where the single electron is located
on the carbon chain.5a When R ) Ph, the radical [Cl-
(dppe)2Ru-CtC-C•(Ph)2] is highly stabilized by the
(22) For examples see: (a) Bruce, M. I. Chem. Rev 1991, 91, 197.
(b) Albertin, G.; Antoniutti, S.; Bordignon, E.; Granzotto, M. J .
Oganomet. Chem. 1999, 585, 83. (c) Cardierno, V.; Gamansa, M. P.;
Gimeno, J . J . Chem. Soc., Dalton Trans. 1999, 1857. (d) Bustello, E,
J imenez-Tenorio, M.; Puerta, M. C.; Valerga, P. Eur. J . Inorg. Chem.
2001, 2391.
(23) The ESR signal of ferrocenium is too broad to be detectable
above 78 K. See: Pins, R.; Reinders, F. J . J . Am. Chem. Soc. 1969, 91,
4929.
(24) It was not possible to observe the coupling at higher temper-
ature when the solution was not frozen because of the fast reaction of
the radical with ferrocenium salt present in the medium. We could
not observe the RuIII species either.
(21) Miras, M. C.; Silber, J . J .; Sereno, L. Electrochim. Acta 1988,
7, 851.
(25) Iyer, R. S.; Selegue, J . P. J . Am. Chem. Soc. 1987, 109, 910.

Ruthenium Acetylide Oxidation
Organometallics, Vol. 21, No. 13, 2002 2659
Sch em e 5
The electrochemical studies were carried out under argon
using an Eco Chemie Autolab PGSTAT 30 potentiostat for
cyclic voltammetry with the three-electrode configuration: the
working electrode was a Pt disk, the reference electrode a
saturated calomel electrode, and the counter electrode a
platinum wire. Ferrocene was used as an internal reference,
and all the measurements were carried out in CH2Cl2 solution
with 0.1 M Bu4NPF6 as a supporting electrolyte. Mass spectra
spin delocalization over the phenyl rings. By contrast,
the electron-releasing methyl groups of 2 would make
the radical [Cl(dppe)2Ru-CtC-C•(CH3)2] very reactive.
The transition state for proton elimination is then
lowered in the case of 1 with respect to 2 and the
formations of 4• and 4 are likely to occur. As this
transition state is too high for oxidized species issued
from 2 and 3 (considering the lack of stabilizing groups
for [Cl(dppe)2Ru-CtC-C•H2]), the corresponding cat-
ionic radicals are stable.
were recorded on
a
Zab SpecETOF FAB+ spectrometer.
Elemental analyses were sent out to the Lyon-Villeurbanne
CNRS center. cis-[(dppe)2RuCl2]26 and allenylidene compounds
trans-[Cl(dppe)2RudCdCdCR2]PF6 (R ) Ph, CH3)5b were
prepared as previously reported.
Finally, it occurred to us that this mechanism could
be used to prepare a ruthenium allenylidene complex
from an acetylide bearing a hydrogen atom on the Cγ
position if the leaving proton can be trapped. We found
out that when the oxidation of 1 by ferrocenium salt
was conducted in the presence of pyridine, nearly
quantitative formation of trans-[Cl(dppe)2RudCdCd
CPh2]PF6 (4) allenylidene was obtained (Scheme 5). Two
equivalents of ferrocenium salt [(η5-C5H5)2Fe]PF6 are
necessary to complete the transformation, one for the
oxidation of the acetylide complex and one for the
oxidation of the neutral radical. During the reaction,
the pyridine can either trap the proton directly from the
cationic radical and/or deprotonate the vinylidene to
regenerate the acetylide. This method might be an
alternative pathway to obtain allenylidene species from
acetylides if propargylic alcohols are not available and
when a radical species could be stabilized on Cγ.
In conclusion, we have shown that ruthenium acetyl-
ides of the type trans-[Cl(dppe)2Ru-CtC-CHR2] could
be easily oxidized and that the stability of the metal-
centered cationic radical depends on the nature of the
substituents. If the structure is not able to stabilize a
neutral radical on the Cγ of the carbon chain (R ) H,
CH3), the cationic radical is thermally stable and only
reactions with other reagents on Câ could occur depend-
ing on the steric protection of the chain. On the contrary,
when the formation of a neutral radical can be stabilized
at the termini of the chain on Cγ (R ) Ph), proton
elimination occurs and further oxidation leads to the
cationic allenylidene species. A preparative method has
been demonstrated based on this principle, and we
anticipate that further developments should lead to the
generalization of this reaction not only to other chain
substituents or metal acetylides but also to longer
chains.
tr a n s-[Cl(d p p e)2Ru -CtC-CHP h 2] (1). In
a Schlenk
tube, 300 mg of trans-[Cl(dppe)2RudCdCdCPh2]PF6 (0.24
mmol) was introduced with 36 mg of NaBH4 (0.96 mmol), and
20 mL of THF was added using a cannula. The red solution
was discolored in 5 min. The solvent was removed under
vacuum. The residue was extracted with a 1:1 mixture of CH2-
Cl2/ether (4 × 20 mL) and filtrated. After evaporation, the pale
yellow solid was washed with pentane (10 mL), and 230 mg
(0.21 mmol) of 1 was recovered (88% yield). 31P{1H} NMR (CD2-
Cl2): δ 51.54 (s, PPh2). 1H NMR (CD2Cl2): δ 7.71-6.86 (m,
50H, Ph), 4.77 (s, 1H, CH), 2.30-2.75 (m, 8H, CH2). 13C{1H}
NMR (CD2Cl2): δ 145.65-125.95 (Ph), 111.37 (s, Ru-CtC-),
2
105.44 (quint., Ru-CtC-, J PC ) 16 Hz), 49.23 (Ru-CtC-
1
CH-), 30.95 (CH2, | J PC+3J PC| ) 24 Hz). IR: 2085 cm-1 (νC≡C).
HR-MS FAB+ (m/z): 1125.2397 ([M + H]+, calcd 1125.2378).
Anal. Found for C67H59P4ClRu‚CH2Cl2: C 67.48, H 5.17 (calcd
C 67.54, H 5.09).
tr a n s-[Cl(d p p e)2Ru -CtC-CDP h 2] (1D). The procedure
was identical with that of 1 with 500 mg of trans-[Cl-
(dppe)2RudCdCdCPh2]PF6 (0.39 mmol), 115 mg of NaBD4
(2.64 mmol), and 40 mL of THF. After evaporation, 339 mg
(0.30 mmol) of pale yellow 1D was recovered (76% yield). 31P-
1
{1H} NMR (CD2Cl2): δ 52.57 (s, PPh2). H NMR (CD2Cl2): δ
7.90-6.85 (m, 50H, Ph), 2.30-2.75 (m, 8H, CH2). 13C{1H} NMR
(CD2Cl2): δ 147.44-127.48 (Ph), 111.36 (s, Ru-CtC-), 105.15
2
1
(quint., Ru-CtC-, J PC ) 17 Hz), 32.48 (CH2, | J PC+3J PC| )
23 Hz). IR: 2067 cm-1 (νC≡C). HR-MS FAB+ (m/z): 1125.2433
([M]+, calcd 1125.2362).
tr a n s-[Cl(d p p e)2Ru -CtC-CH(CH3)2] (2). The procedure
was identical with that of 1 with 200 mg of trans-[Cl-
(dppe)2RudCdCdC(CH3)2]PF6 (0.17 mmol), 26 mg of NaBH4
(0.68 mmol), and 15 mL of THF. The green solution was
discolored in 5 min, and 140 mg (0.14 mmol) of 2 as a pale
yellow solid was recovered (80% yield). 31P{1H} NMR (CD2-
Cl2): δ 50.47 (s, PPh2). 1H NMR (CD2Cl2): δ 7.86-6.87 (m,
40H, Ph), 2.80-2.50 (m, 8H, CH2), 2.43 (sept., 1H, CH, 3J CH
)
6.5 Hz), 0.90 (d, 6H, CH3, 3J CH ) 6.5 Hz). 13C{1H} NMR (CD2-
Cl2): δ 138.3-127.18 (Ph), 116.97 (s, Ru-CtC-), 96.77
2
1
(quint., Ru-CtC-, J PC ) 16 Hz), 31.22 (CH2, | J PC+3J PC| )
22 Hz), 25.09 (Ru-CtC-CH-), 24.28 (CH3). IR: 2086 (νC≡C).
HR-MS FAB+ (m/z): 1000.2002 ([M]+, calcd 1000.1986). Anal.
Found for C57H55P4ClRu‚CH2Cl2: C 64.38, H 5.38 (calcd C
64.18, H 5.29).
Exp er im en ta l Section
Gen er a l Com m en ts. The reactions were carried out under
an inert atmosphere using Schlenk techniques. Solvents were
freshly distilled under argon using standard procedures.
Chromatography and filtration were performed using alumina
(Acros, activated neutral 50-200 µm). The EPR spectra were
recorded using a EMX-8/2,7 Bruker spectrometer equipped
with a Bruker nitrogen temperature controller ER4131VT02.
tr a n s-[Cl(d p p e)2Ru -CtC-CD(CH3)2] (2D). The proce-
dure was identical with that of 1 with 500 mg of trans-[Cl-
(26) Chaudret, B.; Commengues, G.; Poilblanc, R. J . Chem. Soc.,
Dalton Trans. 1984, 1635.

2660 Organometallics, Vol. 21, No. 13, 2002
Rigaut et al.
(dppe)2RudCdCdC(CH3)2]PF6 (0.44 mmol), 107 mg of NaBD4
(0.96 mmol), and 40 mL of THF. After evaporation, 350 mg
(0.35 mmol) of pale yellow 2D was recovered (79% yield). 31P-
{1H} NMR (CDCl3): δ 50.49 (s, PPh2). 1H NMR (CDCl3): δ
7.86-6.87 (m, 40H, Ph), 2.80-2.50 (m, 8H, CH2), 0.90 (s, 6H,
CH3). 13C{1H} NMR (CDCl3): δ 137.76-126.72 (Ph), 117.24
(s, Ru-CtC-), 96.52 (quint., Ru-CtC-, 2J PC ) 15 Hz), 31.22
6.39 (m, 50H, Ph), 3.0-2.50 (m, 8H, CH2). No signals were
observed at 4.15 and 3.35 ppm. After addition of one drop of
water and exchange of the vinylidene proton, trans-[Cl-
(dppe)2RudCdCH-CPh2D]PF6 (5HD) is obtained. Spectro-
scopic data for 5HD: 31P{1H} NMR (CD2Cl2): δ 43.78 (s, PPh2),
-143.63 (sept., PF6, 1J PF ) 710 Hz). 1H NMR (CD2Cl2): δ 7.52-
6.40 (m, 50H, Ph), 3.35 (quint., 1H, dCH, 4J PH ) 2.7 Hz), 3.0-
1
(CH2, | J PC+3J PC| ) 31 Hz), 23.98 (CH3). IR: 2084 cm-1 (νC≡C).
2.50 (m, 8H, CH2). No signal was observed at 4.15 ppm.
HR-MS FAB+ (m/z): 1001.2068 ([M]+, calcd 1001.2049).
tr a n s-[Cl(d p p e)2Ru dCdCH-CH3]P F 6 (7). In a Schlenk
tube, 830 mg of trans-[(dppe)2Cl2]PF6 (0.86 mmol) was intro-
duced with 290 mg of NaPF6 (1.72 mmol) and 30 mL of CH2-
Cl2. The mixture was then placed under a propyne atmosphere
and stirred 18 h. The brown solution was filtrated, and the
solvent was removed under vacuum. The residue was washed
with ether (3 × 15 mL) and dried. A brown solid was recovered
(670 mg, 0.60 mmol, 70%). 31P{1H} NMR (CD2Cl2): δ 42.40 (s,
PPh2), -143.67 (sept., PF6, 1J PF ) 715 Hz). 1H NMR (CD2Cl2):
δ 7.45-7.05 (m, 40H, Ph), 3.00-2.60 (m, 8H, CH2), 2.49 (m,
1H, CH), 0.91 (d, 3H, CH3, 3J HH ) 6.8 Hz). 13C{1H} NMR (CD2-
13C{1H} NMR (CD2Cl2): δ 344.47 (quint., RudCdC-, J PC
)
2
13 Hz), 143.41-127.40 (Ph), 108.07 (s, RudCdC-), 45.57 (Cd
1
CH-CHPh2), 28.23 (CH2, | J PC+3J PC| ) 22 Hz).
Oxid a tion of tr a n s-[Cl(d p p e)2Ru -CtC-CDP h 2] (1D)
a n d Ad d ition of P h 3Sn H. In a Schlenk tube, to 45 mg of 1D
(0.03 mmol) and 10 mg of ferrocinium salt [(η5-C5H5)2Fe]PF6
(0.03 mmol) was added 5 mL of CH2Cl2. Via a cannula, 21 mg
(0.06 mmol) of Ph3SnH dissolved in 5 mL of CH2Cl2 was further
added. The solution was stirred for 1 h at room temperature,
and the solvent was evaporated. 31P and 1H NMR analysis
showed that the residue contained the vinylidene trans-[Cl-
(dppe)2RudCdCH-CPh2D]PF6 (5HD).
2
Cl2): δ 352.93 (quint., RudCdC-, J PC ) 17 Hz), 134.13-
Oxid a tion a n d Red u ction of tr a n s-[Cl(d p p e)2Ru -Ct
C-CH(CH3)2] (2). In a Schlenk tube to 39 mg of 2 (0.04 mmol)
and 13.5 mg of ferrocinium salt [(η5-C5H5)2Fe]PF6 (0.04 mmol)
was added 10 mL of CH2Cl2. The solution was stirred 1 h at
room temperature, and 7.8 mg (0.04 mmol) of cobaltocene was
added to the light green solution. The medium became pale
yellow and was evaporated after 15 min. The residue was
1
128.05 (Ph), 99.82 (s, RudCdC-), 29.03 (CH2, | J PC+3J PC| )
23 Hz), 4.85 (CH3). IR: 1670 (νdCdC), 838 (νPF6) cm-1. HR-MS
FAB+ (m/z): 973.1752 ([M]+, calcd 973.1764). Cyclic voltam-
metry: (CH2Cl2, nBu4NPF6 0.1 M, 200 mV s-1, V vs ferrocene):
Epa,ox ) 1.00 V, Epc,red ) - 1.97 V.
tr a n s-[Cl(d p p e)2Ru -CtC-CH3] (3). In a Schlenk tube,
450 mg of trans-[Cl(dppe)2RudCdCHCH3]PF6 (7) (0.40 mmol)
was dissolved in 40 mL of CH2Cl2, and 155 µL of Et3N (1.2
mmol) was added using a syringe. The orange solution turned
yellow and was stirred 30 min. The mixture was washed with
water (2 × 20 mL), dried, and concentrated before filtration
on basic alumina (elution with ether). After evaporation, 253
mg (0.26 mmol) of 3 was recovered (65% yield). 31P{1H} NMR
(CD2Cl2): δ 50.46 (s, PPh2). 1H NMR (CD2Cl2): δ 7.47-6.83
(m, 40H, Ph), 2.75-2.40 (m, 8H, CH2), 1.40 (s, 3H, CH3). 13C-
{1H} NMR (CD2Cl2): δ 136.74-126.62 (Ph), 103.00 (s, Ru-
1
washed with pentane (3 × 10 mL). H NMR showed that the
residue contains a 95:5 mixture of the acetylide trans-[Cl-
(dppe)2Ru-CtC-CH(CH3)2] (2) and the vinylidene trans-[Cl-
(dppe)2RudCdCH-C(CH3)2H]PF6 (6). Spectroscopic data for
6: 31P{1H} NMR (CDCl3): δ 44.35 (s, PPh2), -143.69 (sept.,
1
1
6
PF , J PF ) 715 Hz). H NMR (CDCl3): δ 7.49-6.95 (m, 40H,
Ph), 3.05-2.55 (m, 8H, CH2), 2.09 (d sept., 1H, CH(CH3)2,
3J HH ) 9.7 Hz, J HH ) 6.0 Hz), 2.02 (d quint., 1H, dCH,
3
3J HH ) 9.7 Hz, J PH ) 2.1 Hz), 0.49 (d, 6H, CH3, J HH ) 6.0
Hz). 13C{1H} NMR (CDCl3): δ 348.57 (quint., RudCdC-,
2J PC ) 13 Hz), 133.74-127.97 (Ph), 112.69 (s, RudCdC-),
4
3
2
CtC-), 98.01 (quint., Ru-CtC-, J PC ) 16 Hz), 31.91 (CH2,
29.38 (CH2, | J PC+3J PC| ) 30 Hz), 24.70 (CH3), 24.12 (CH-
1
1
| J PC+3J PC| ) 23 Hz), 24.28 (CH3). IR: 2110 (νC≡C) cm-1. HR-
(CH3)2). IR: 1647 (νdCdC), 836 (νPF6) cm-1. HR-MS FAB+
(m/z): 1001.2067 ([M]+, calcd 1001.2065). Cyclic voltamme-
try: (CH2Cl2, nBu4NPF6 0.1 M, 200 mV s-1, V vs ferrocene):
Epa,ox ) 1.05 V, Epc,red ) -1.90 V.
MS FAB+ (m/z): 972.1666 ([M]+, calcd 972.1673). Anal. Found
for C57H55P4ClRu‚CH2Cl2: C 63.73, H 4.91 (calcd C 63.61, H
5.05).
Oxid a tion of tr a n s-[Cl(d p p e)2Ru -CtC-CHP h 2] (1). In
a Schlenk tube, to 200 mg of 1 (0.18 mmol) and 60 mg of
ferrocinium salt [(η5-C5H5)2Fe]PF6 (0.18 mmol) was added 30
mL of CH2Cl2. The solution was stirred for 1 h at room
temperature. The residue was washed with pentane (3 × 20
Oxidation of tr a n s-[Cl(dppe)2Ru -CtC-CD(CH3)2] (2D)
a n d Ad d ition of P h 3Sn H. In a Schlenk tube to 50 mg of 2D
(0.05 mmol) and 17 mg of ferrocinium salt [(η5-C5H5)2Fe]PF6
(0.05 mmol) was added 5 mL of CH2Cl2. Via a cannula, 35 mg
(0.06 mmol) of Ph3SnH dissolved in 5 mL of CH2Cl2 was added.
The solution was stirred 1 h at room temperature, and the
solvent was evaporated. 31P and 1H NMR showed that the
residue contains the vinylidene trans-[Cl(dppe)2RudCdCH-
CD(CH3)2]PF6 (6HD). 31P{1H} NMR (CD2Cl2): δ 44.16 (s,
PPh2), -145.88 (sept., PF6, 1J PF ) 710 Hz). 1H NMR (CD2Cl2):
δ 7.6-6.80 (m, 40H, Ph), 3.10-2.60 (m, 8H, CH2), 2.01 (br,
1
mL). H NMR showed that the residue was a 1:1 mixture of
trans-[Cl(dppe)2RudCdCdCPh2]PF6 (4) and the vinylidene
trans-[Cl(dppe)2RudCdCH-CPh2H]PF6 (5). After several frac-
tional crystallizations in a mixture of dichloromethane/pen-
tane, 85 mg of light pink crystals of trans-[Cl(dppe)2RudCd
CH-CPh2H]PF6 (5) (0.07 mmol) were isolated (39%). Spectro-
scopic data for 5: 31P{1H} NMR (CDCl3): δ 43.78 (s, PPh2),
-143.63 (sept., PF6, 1J PF ) 710 Hz). 1H NMR (CDCl3): δ 7.49-
3
1H, dCH), 0.49 (s, 6H, CH3, J HH ) 6.0 Hz). 13C{1H} NMR
(CD2Cl2): δ 348.89 (quint., RudCdC-, 2J PC ) 13 Hz), 134.23-
3
6.43 (m, 50H, Ph), 4.15 (d, 1H, CHPh2, J HH ) 11.1 Hz), 3.35
1
128.38 (Ph), 112.87 (s, RudCdC-), 29.68 (CH2, | J PC+3J PC| )
3
4
(d quint., 1H, dCH, J HH ) 11.1 Hz, J PH ) 2.7 Hz), 3.0-2.50
23 Hz), 24.80 (CH3). IR: 1652 (νdCdC), 839 (νPF6) cm-1
.
(m, 8H, CH2). 13C{1H} NMR (CDCl3): δ 344.35 (quint., Rud
2
CdC-, J PC ) 13 Hz), 143.02-127.08 (Ph), 107.96 (s, Rud
Oxid a tion a n d Red u ction of tr a n s-[Cl(d p p e)2Ru -Ct
C-CH3] (3). In a Schlenk tube to 20 mg of 3 (0.02 mmol) and
7.5 mg of ferrocinium salt [(η5-C5H5)2Fe]PF6 (0.02 mmol) was
added 10 mL of CH2Cl2. The solution was stirred 1 h at room
temperature, and 4.5 mg (0.02 mmol) of cobaltocene was added
to the light purple solution. The medium became pale yellow
and was evaporated after 15 min. 1H NMR showed that the
residue contains a 85:15 mixture of the acetylide [Cl(dppe)2Ru-
CtC-CH3] (3) and the vinylidene trans-[Cl(dppe)2RudCd
CH-CH3]PF6 (7).
CdC-), 45.57 (CdCH-CHPh2), 28.75 (CH2, | J PC+3J PC| ) 23
1
Hz). IR: 1645 (νdCdC), 837 (νPF6) cm-1. HR-MS FAB+ (m/z):
1125.2367 ([M]+, calcd 1125.2378). Anal. Found for C67H60P5F6-
ClRu‚CH2Cl2: C 60.01, H 4.67 (calcd C 60.25, H 4.61).
Oxid a tion of tr a n s-[Cl(d p p e)2Ru -CtC-CDP h 2] (1D).
The procedure was identical with 200 mg of 1D (0.18 mmol),
60 mg of ferrocinium salt [(η5-C5H5)2Fe]PF6 (0.18 mmol), and
1
30 mL of CH2Cl2. H NMR showed that the residue was a 1:1
mixture of trans-[Cl(dppe)2RudCdCdCPh2]PF6 (4) and the
vinylidene trans-[Cl(dppe)2RudCdCD-CPh2D]PF6 (5D). Spec-
troscopic data for 5D: 31P{1H} NMR (CDCl3): δ 43.88 (s, PPh2),
-143.60 (sept., PF6, 1J PF ) 710 Hz). 1H NMR (CDCl3): δ 7.55-
[Cl(d p p e)2Ru dCdCdCP h 2]P F 6 (4) via Oxid a tion . In a
Schlenk tube, to 69 mg of 1 (0.061 mmol) and 60 mg of
ferrocinium salt [(η5-C5H5)2Fe]PF6 (0.18 mmol) was added 10

Ruthenium Acetylide Oxidation
Organometallics, Vol. 21, No. 13, 2002 2661
mL of CH2Cl2. After 1 h at room temperature, 45 µL (0.60
mmol) of pyridine was added. The mixture was stirred
overnight, washed with water (2 × 10 mL), and dried. After
evaporation, the red residue was washed with pentane (3 ×
20 mL). Crystallization (CH2Cl2/pentane) afforded 71 mg (0.056
mmol) of trans-[Cl(dppe)2RudCdCdCPh2]PF6 (4) (92%).
Ack n ow led gm en t. We thank the CNRS and the
Universite´ de Rennes 1 for support, and P. Gue´not from
the Centre Re´gional de Mesures Physiques de l’Ouest
(Rennes) and Olivier Maury (UMR 6509) for their help.
OM0200555