C7 and C9 carbon-rich bridges in diruthenium systems: Synthesis, spectroscopic, and theoretical investigations of different oxidation states

Article abstract of DOI:10.1021/ja0603453

Two methodologies of C-C bond formation to achieve organometallic complexes with 7 or 9 conjugated carbon atoms are described. A C₇ annelated trans-[Cl(dppe)₂Ru=C=C=C-CH=C(CH₂)-C≡C-Ru(dppe) ₂CI][X] (X = PF₆, OTf) complex is obtained from the diyne trans-[Cl(dppe)₂Ru-(C≡C)₂-R] (R = H, SiMe ₃) in the presence of [FeCp₂][PF₆] or HOTf, and C₇ or C₉ complexes trans-[Cl(dppe)₂Ru- (C≡C)_n-C(CH₃)=C(R₁)-C(R ₂)=C=C=Ru(dppe)₂Cl][X] (n = 1, 2; R₁ = Me, Ph, R₂ = H, Me; X = BF₄, OTf) are formed in the presence of a polyyne trans-[Cl(dppe)₂Ru-(C≡C)_n-R] (n = 2, 3; R = H, SiMe₃) with a ruthenium allenylidene trans-[Cl(dppe) ₂Ru=C=C=C(CH₂R₁)R₂][X]. These reactions proceed under mild conditions and involve cumulenic intermediates [M⁺]=(C=)_nCHR (n = 3, 5), including a hexapentaenylidene. A combination of chemical, electrochemical, spectroscopic (UV-vis, IR, NIR, EPR), and theoretical (DFT) techniques is used to show the influence of the nature and conformation of the bridge on the properties of the complexes and to give a picture of the electron delocalization in the reduced and oxidized states. These studies demonstrate that the C₇ bridging ligand spanning the metal centers by almost 12 A is implicated in both redox processes and serves as a molecular wire to convey the unpaired electron with no tendency for spin localization on one of the halves of the molecules. The reactivity of the C₇ complexes toward protonation and deprotonation led to original bis(acetylides), vinylidene-allenylidene, or carbyne-vinylidene species such as trans-[Cl(dppe)₂Ru≡C-CH=C(CH₃) CH=C(CH₃)-HC=C=Ru(dppe)₂Cl][BF₄]₃.

Full text of DOI:10.1021/ja0603453

Published on Web 04/05/2006
C7 and C9 Carbon-Rich Bridges in Diruthenium Systems:
Synthesis, Spectroscopic, and Theoretical Investigations of
Different Oxidation States
Ste´phane Rigaut,*,† Ce´line Olivier,† Karine Costuas,† Sylvie Choua,‡
Omrane Fadhel,† Julien Massue,† Philippe Turek,‡ Jean-Yves Saillard,†
Pierre H. Dixneuf,† and Daniel Touchard*,†
Contribution from the UMR 6226 CNRS - UniVersite´ de Rennes 1,
Sciences Chimiques de Rennes, Campus de Beaulieu, F-35042 Rennes Cedex, France, and
the Institut Charles Sadron, UPR 22 CNRS - UniVersite´ Louis Pasteur, 6 rue Boussingault,
BP 40016, F-67083 Strasbourg Cedex, France
Received January 17, 2006; E-mail: stephane.rigaut@univ-rennes1.fr; daniel.touchard@univ-rennes1.fr
Abstract: Two methodologies of C-C bond formation to achieve organometallic complexes with 7 or 9 con-
jugated carbon atoms are described. A C7 annelated trans-[Cl(dppe)2RudCdCdCsCHdC(CH2)sCtCs
Ru(dppe)2Cl][X] (X ) PF6, OTf) complex is obtained from the diyne trans-[Cl(dppe)2Rus(CtC)2sR] (R )
H, SiMe3) in the presence of [FeCp2][PF6] or HOTf, and C7 or C9 complexes trans-[Cl(dppe)2Rus(CtC)ns
C(CH3)dC(R1)sC(R2)dCdCdRu(dppe)2Cl][X] (n ) 1, 2; R1 ) Me, Ph, R2 ) H, Me; X ) BF4, OTf) are
formed in the presence of a polyyne trans-[Cl(dppe)2Rus(CtC)nsR] (n ) 2, 3; R ) H, SiMe3) with a
ruthenium allenylidene trans-[Cl(dppe)2RudCdCdC(CH2R1)R2][X]. These reactions proceed under mild
conditions and involve cumulenic intermediates [M+]d(Cd)nCHR (n ) 3, 5), including a hexapentaenylidene.
A combination of chemical, electrochemical, spectroscopic (UV-vis, IR, NIR, EPR), and theoretical (DFT)
techniques is used to show the influence of the nature and conformation of the bridge on the properties of
the complexes and to give a picture of the electron delocalization in the reduced and oxidized states.
These studies demonstrate that the C7 bridging ligand spanning the metal centers by almost 12 Å is
implicated in both redox processes and serves as a molecular wire to convey the unpaired electron with
no tendency for spin localization on one of the halves of the molecules. The reactivity of the C7 complexes
toward protonation and deprotonation led to original bis(acetylides), vinylidene-allenylidene, or carbyne-
vinylidene species such as trans-[Cl(dppe)2RutCsCHdC(CH3)sCHdC(CH3)sHCdCdRu(dppe)2Cl][BF4]3.
pyridyl complexes.1e,21 It appears from these studies that the
Introduction
nature of the ligand mediating the metal-metal interaction may
Metal complexes which display ligand-mediated electronic
effects, including electron-transfer phenomena, have attracted
increasing interest.1,2 The understanding and control of electron-
transfer reactions constitute major challenges in science as it is
a fundamental process to numerous complex chemical systems
ranging from life processes3 to electronic devices.4,5 Electron-
transfer processes between two redox centers have been
examined with a range of linkers such as polyynes,6-18
polyenes,19 conjugated carboxylate,20 polyaromatics,1 or poly-
be more relevant than the metal separation. Research in this
area has mainly focused on the potential applications of these
compounds in the preparation of molecular wires1e,5-20 and
dyes22 and on unusual magnetic23 or nonlinear optical24 proper-
ties and quantum cell automata.25 The building of bridges with
unusual structures allowing communication between stable redox
systems constitutes a potential source of applications.
A variety of organometallic molecules in which an even
number of conjugated carbon atoms spans two metal fragments
† UMR 6226 CNRS - Universite´ de Rennes 1.
‡ UPR 22 CNRS - Universite´ Louis Pasteur.
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9
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J. AM. CHEM. SOC. 2006, 128, 5859-5876
5859

A R T I C L E S
Rigaut et al.
in various structures such as sp carbon chains M(CtC)nM with
complexes with an sp chain surrounded by sp3 aliphatic carbon
chains.11 In contrast, considering the variety of available metallic
fragments, only few complexes with an odd numbered carbon
linear or cyclic bridge have been obtained, despite their highest
interest for electron delocalization.16,26-29 Long bridges with
seven and more conjugated carbon atoms are particularly
scarce,7,29 due to a limited number of well-defined synthetic
processes.
Using the fragment [RuCl(dppe)2]+ (dppe ) 1,2-bis(diphe-
nylphosphino)ethane) offering stable redox systems, our group
has been involved in the building of new mono- and polymetallic
complexes with unusual topologies, reversible redox behavior,
that are potential molecular wires.15 This system was first shown
to be useful to afford metal cumulenylidenes trans-[Cl(dppe)2Ru-
(dC)n ) CR1R2]+, acetylides trans-[Cl(dppe)2Rus(CtC)ns
R], and carbynes trans-[Cl(dppe)2RutCsCdCR1R2], and it is
now offering easy synthesis of bimetallic complexes containing
bis-allenylidene, bis-acetylide, and bis-carbyne conjugated
bridges.30-32 Furthermore, a Ru(II) containing bis(allenylidene)
bridge has been recently found to promote very efficient
electronic communication between two carbon-rich chains.33
C2 to C28 bridges were prepared and evaluated,6-15 including
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5860 J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006

C7 and C9 Carbon-Rich Bridges
A R T I C L E S
This trans ditopic structure is of special interest to build
oligomeric structures if the metal system allows trans com-
munication between the carbon chains.33-36
to 2a-b (Scheme 1). A formal [2 + 2] addition of the CγtCδ
triple bonds takes place yielding dark purple crystals of [3][PF6].
The formation of [3][PF6] led us to imagine another possible
route by protonation of 2a-b to generate a [Ru+]dCdCdCd
CHR transient species. Indeed, a similar adduct [3][OTf] was
obtained (70% yield) via addition of 0.5 equiv of strong acid
(HOTf) to 2b. The same reaction takes place on protonation of
2a; thus spontaneous desilylation of 2a occurs in the reaction
medium, and previous deprotection is not necessary. NMR
studies are consistent with a highly delocalized structure
intermediate with those sketched in Scheme 1. Indeed, the 31P
analysis of [3][PF6] shows one singlet for the eight phosphorus
nuclei, and the 13C analysis shows only five different signals
for the symmetric unsaturated bridge. Moreover, the RusC
resonance at δ ) 247.7 ppm (quint, 2J(P,C) ) 14 Hz) is
downfield compared to that of an alkynyl (δ ) 105.5 ppm for
trans-[Cl(dppe)2RusCtCsCPh2H)])30b and upfield to that of
an allenylidene complex (δ ) 308.6 ppm for trans-[Cl-
(dppe)2RudCdCdCPh2]).30a
As a metallacumulene [Ru+]dCdCdCdCHR intermediate
is involved in the formations of both [3][OTf] and [3][PF6]
(vide infra), we attempted to react the metal diyne systems 2a-b
with other preformed proton releasing cumulenic species such
as ruthenium allenylidenes. Of interest here are the deprotona-
table ruthenium allenylidene complexes of type trans-[(dppe)2-
(Cl)RudCdCdC(CH2R1)R2]BF4 ([4a-c][BF4]) easily obtained
using the Selegue’s method,38 on reaction of corresponding
propargylic alcohol and of the 16-electron species [(dppe)2RuCl]-
[BF4] ([1][BF4]) (Scheme 2).
The low availability of odd numbered chains led us to take
profit of the [RuCl(dppe)2]+ system in the stabilization of
carbon-rich metal complexes to develop new methodologies to
build odd numbered carbon-rich bridged complexes and to
investigate their electronic properties. Herein, we report on two
novel methodologies of CsC bond formation to control the
extension of an odd numbered carbon chain via the achievement
of a class of bridged cationic carbon-rich homobimetallic
complexes with seven conjugated carbons between remote
metals with highly delocalized extended conjugated structures.
The first one consists of an unprecedented radical or proton
promoted coupling reaction occurring on the CγtCδ bond of a
1,3-diynylmetal derivative to lead to a complex [Ru]+dCdCd
CsCHdC(CH2)sCtCs[Ru] with a carbon-rich annelated
C8H3 bridge. The second method describes the coupling between
an allenylidene and a diynylmetal to provide [Ru]sCtCs
C(CH3)dC(R1)sC(R2)dCdCd[Ru]+. This strategy allowed
further access to the primary carbon-rich homonuclear bimetallic
C9 complex, which involves for the first time a hexapentae-
nylidene [M+]dCdCdCdCdCdCHR intermediate. We also
report unprecedented detailed characterizations of odd numbered
carbon bridged complexes in different oxidation states, and we
provide a picture of the electron delocalization between two
ruthenium termini using a combination of chemical, spectro-
scopic, and theoretical techniques, to improve the understanding
of the ability of unsaturated odd numbered hydrocarbons to
convey electrons in either an oxidation or a reduction process.
In the last part of this work, we describe the reactivity of C7
complexes that leads to original vinylidene-allenylidene or
carbyne-vinylidene species. Unusual synthetic aspects of this
work was presented in two communications.16
The neutral diynyl compound 2b was added to 1 equiv of
the cationic allenylidene complexes [4a-c][BF4], over a period
of 3 days, at room temperature to lead to stable dark green
crystals of [5a-c][BF4] isolated in good yields (79-85%). The
addition should be slower than initially reported16b in order to
minimize the formation of [3][BF4] as a side product (vide
infra). These complexes 5a-c were also obtained with similar
yields when the reaction was performed with the protected diyne
2a, without preliminary desilylation. The FTIR spectra for all
Results and Discussion
Synthesis of C7 and C9 Complexes. The discovery of this
new type of bridges arises from our first attempts to couple
two molecules of the mono-diynyl ruthenium trans-[Cl-
(dppe)2Rus(CtC)2sH] (2b) in order to obtain a bimetallic
RuC8Ru complex in which eight carbon atoms span the metals
as was achieved for the RuC12Ru complex with trans-[Cl-
(dppe)2Rus(CtC)3sH].31a All oxidative coupling procedures
to obtain RuC8Ru were unsuccessful, and the formation of an
unidentified product in the presence of copper(II) led us to
consider the reactivity of the chemically oxidized species trans-
[Cl(dppe)2Rus(CtC)2sR] (2a: R ) SiMe3, 2b: R ) H). The
most efficient reaction was observed with the addition of 0.5
equiv of ferrocenium hexafluorophosphate as oxidizing agent37
compounds contain an intense absorption around 1900 cm-1
,
characteristic of the cumulenic character of the chain. As
observed for [3][PF6], the NMR spectra are consistent with a
highly delocalized structure. The 31P NMR analysis shows for
[5a][BF4] one singlet at δ ) 47.1 ppm for a symmetrical
1
structure, and the H NMR spectrum is composed of a single
signal for two methyl groups at δ ) 1.35 ppm. Conversely,
NMR analysis evidences an unsymmetrical structure for the
systems [5b][BF4] and [5c][BF4]. For example, in [5c][BF4],
the 31P NMR spectrum displays two singlets at δ ) 43.8 and
49.6 ppm, and the 13C NMR spectrum, seven different signals
for the carbon chain assigned with the help of 2D HMBC and
2D HMQC experiments. The Ru-C carbon atom resonances
(33) Rigaut, S.; Costuas, K.; Touchard, D.; Saillard, J.-Y.; Golhen, S.; Dixneuf,
P. H. J. Am. Chem. Soc. 2004, 126, 4072.
(34) (a) Lebreton, C.; Touchard, D.; Le Pichon, L.; Daridor, A.; Toupet, L.;
Dixneuf, P. H. Inorg. Chem. Acta 1998, 272, 188-196. (b) Zhu, Y.; Clot,
O.; Wolf, M. O.; Yap, G. P. A. J. Am. Chem. Soc. 1998, 120, 1812-1821.
(35) (a) Xu, G.-L.; De Rosa, M. C.; Crutchley, R. J.; Ren, T. J. Am. Chem. Soc.
2004, 126, 3728-3729. (b) Jones, S. C.; Coropceanu, V.; Barlow, S.;
Kinnibrugh, T.; Timofeeva, T.; Marder, S. R. J. Am. Chem. Soc. 2004,
126, 11782-11783. (c) Schull, T. L.; Kushmerick, J. G.; Patterson, C. H.;
George, C.; Moore, M. H.; Pollack, S. K.; Shashidhar, R. J. Am. Chem.
Soc. 2003, 125, 3202-3203. (d) Stroh, C.; Mayor, M.; Von Ha¨nisch, C.;
Turek, P. Chem. Commun. 2004, 2050-2051. (e) Mayor, M.; von Ha¨nisch,
C.; Weber, H. B.; Reichert, J.; Beckmann, D. Angew. Chem., Int. Ed. 2002,
41, 1183-1186. (f) Kuang, S.-M.; Fanwick, P. E.; Walton, R. A. Inorg.
Chem. 2002, 4, 147-151.
(36) (a) Yip, J. H.; Wu, J.; Wong, K.-Y.; Ho, K. P.; Pun, C. S.-N.; Vittal, J. J.
Organometallics 2002, 21, 5292-5300. (b) Sheng, T.; Varenkamp, H. Eur.
J. Inorg, Chem. 2004, 1198-1203. (c) Berry, J. F.; Cotton, F. A.; Murillo,
C. A. Organometallics 2004, 23, 2503-2506. (d) Dewhurst, R. D.; Hill,
A. F.; Willis, A. C. Organometallics 2004, 23, 1646-1648. (e) Zuo, J. L.;
Herdtweck, E.; de Biane, F. F.; Santos, A. M.; Ku¨hn, F. E. New J. Chem.
2002, 26, 883-888. (f) Weng, W.; Bartik, T.; Brady, M.; Bartik, B.;
Ramsden, J. A.; Arif, A. M.; Glagysz, J. A. J. Am. Chem. Soc. 1995, 117,
11922-11931. (g) Zheng, Q.; Hampel, F.; Gladysz, J. A. Organometallics
2004, 23, 5896-5899.
(37) Connelly, N. G.; Geiger, W. E. Chem. ReV. 1996, 96, 877-910.
(38) Selegue, J. P. Organometallics 1982, 1, 217-218.
9
J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006 5861

A R T I C L E S
Rigaut et al.
Scheme 1. Synthetic Pathways for C7 and C9 Bridged Complexes
Scheme 2. Synthetic Pathway for Allenylidene Formations
[5a][BF4] does not allow the observation of any correlation
between the proton of the chain and the methyl group, which
is rather in favor of the presence of the “w” shaped form I, as
observed in the crystal structure (see below). For [5c][BF4], if
a very weak correlation signal between the central methyl group
and the ortho hydrogen atoms of the chain phenyl is detected,
a strong one between those aromatic protons and the other
methyl group is observed. This result also evidences the “w”
shaped form I as the preferred isomer with maybe a very small
amount of form III not detected by other techniques. Finally
for complex [5b][BF4], no correlation is observed between the
methyl group and the hydrogen atom of the chain, excluding
the form II. As the protons of the chain phenyl group are not
distinct from the dppe signals also correlated in space with the
methyl group, we are not able to determine if we are in the
presence of form I or III. It is of note that following our
preliminary report, Bruce’s group obtained recently related C7
for these three compounds are also found intermediate between
that of alkynyl and that of allenylidene complexes.
Three bridge configurations are possible for [5a-c][BF4]
owing to the three sp2 carbons of the chain (Chart 1) and to the
fact that form IV is very unlikely for steric reasons (see
theoretical calculations). However, only one set of signals is
observed for each compound. As free rotation is very improbable
(see calculations), this indicates that only one form is detectable
or that the NMR signals for the different forms are very close
to each other. A further 2D NOESY experiment performed with
(39) Bruce, M. I.; Ellis, B. G.; Skelton, B. W.; White, A. H. J. Organomet.
Chem. 2005, 690, 1772-1783.
9
5862 J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006

C7 and C9 Carbon-Rich Bridges
A R T I C L E S
Chart 1
annelated and nonannelated compounds, in low yields or as
traces, in the preparation of the acetylide [Cp*(dppe)RusCt
CsCOsCH3].39 In that case, the nonannelated complex [Cp*-
(dppe)RusCtCsC(OCH3)dC(H)sC(CH3)dCdCdRu(dppe)-
CP*][PF6], related to [5a][BF4], was present in two configurations
and two sets of signals were observed in 13C NMR spectra with
a major contribution of “w” shaped configuration.
This novel pathway to make carbon-carbon bonds between
the diynylmetal complexes 2a-b and the allenylidene [4a-c]-
[BF4] motivated the extension of the reaction to a longer
polyyne. The procedure was applied to the triyne trans-[Cl-
(dppe)2RusCtCsCtCsCtCsSiMe3](6) with the alle-
nylidene [4a][OTf], in an attempt to also generate the first
hexaheptaenylidene intermediate [M+]d(Cd)5CHR on proto-
nation of 6 by [4a][OTf] (see below). This quite slow reaction,
19 days at room temperature, with the triflate anion preferred
for solubility reasons was successful and led to the bimetallic
species [7][OTf] with nine conjugated carbon atoms between
the two metal atoms in 49% yields (Scheme 1). The H NMR
1
spectrum is composed of a singlet at δ ) 5.50 ppm for the
proton on the chain and two signals for two methyl groups.
The 31P NMR analysis shows two singlets at δ ) 48.4 and 43.9
ppm consistent with an unsymmetrical structure. Only one set
of 1H,31P, and 13C NMR signals is also observed here supporting
the existence of only one privileged conformation to the chain.
Nevertheless, we predict that the left mesomeric form repre-
sented in Scheme 1 is the most likely with an allenylidene and
a diyne moiety. To our knowledge, this complex is the first
one with nine conjugated carbon atoms spanning two identical
metal moieties.
Crystal structures of [3][PF6] and [5a][BF4] could be resolved
(Figure 1).16 It is important to note that they both show
analogous features that confirm an extended π-conjugation along
the bridges as indicated by the NMR data. The Ru1sC1, C1s
Figure 1. Molecular structure (ORTEP view) for (a) [3][PF6] and (b) [5a][BF4].
9
J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006 5863

A R T I C L E S
Rigaut et al.
Table 1. Pertinent Optimized Bond Lengths (Å) for [3]n+, [5a-c]n+ (n ) 0-2) Compared Together with the X-ray Experimental Data in
Italics;16 See Figure 1 for Labellinga
C3i
−
C4
′/
c
Ru1−C1
Ru1i
−C1i
C1
−C2
C1i
−C2i
C2
−C3
C2i−C3i
C3
−C4
C3i−
C4b
C3−C4
′
C3i−
C4
′
id
3
2.030
1.967
1.933(3)
1.946
2.045
2.040
1.988
1.923(9)
1.981
1.959
1.964
2.034
2.025
1.999
1.983
1.957
1.920
1.961
1.957
1.888
1.945
1.971
1.888
1.903
1.843
1.855
2.035
1.965
1.249
1.253
1.225(4)
1.263
1.245
1.245
1.253
1.218(12)
1.253
1.261
1.259
1.244
1.244
1.245
1.253
1.261
1.261
1.260
1.261
1.262
1.245
1.246
1.253
1.254
1.268
1.266
1.247
1.256
1.384
1.365
1.372(4)
1.362
1.411
1.406
1.391
1.390(13)
1.386
1.386
1.384
1.411
1.407
1.407
1.390
1.388
1.381
1.390
1.388
1.382
1.410
1.407
1.390
1.385
1.382
1.377
1.384
1.365
1.412
1.416
1.457(5)
1.411
1.410
1.412
1.410
1.401(11)
1.413
1.417
1.416
1.405
1.402
1.407
1.412
1.403
1.419
1.415
1.403
1.416
1.420
1.424
1.427
1.429
1.437
1.440
1.412
1.414
1.547
1.542
1.547
1.544
[3]+
1.459(5)
1.549
1.520
1.515
1.515
1.528(12)
1.508
1.511
1.507
1.516
1.525
1.517
1.512
1.522
1.508
1.509
1.522
1.506
1.517
1.516
1.515
1.510
1.512
1.509
[3]2+
5a-I
1.948
2.042
2.042
1.986
1.262
1.245
1.243
1.253
1.362
1.412
1.412
1.391
1.411
1.408
1.404
1.410
1.550
1.521
1.519
1.515
5a-II
[5a-I]+
[5a-II]+
[5a-I]2+
[5a-II]2+
5b-I
5b-II
5b-III
1.990
1.958
1.977
2.039
2.011
2.010
1.989
1.902
1.928
1.960
1.902
1.963
2.006
2.050
1.941
1.996
1.899
1.971
1.252
1.261
1.258
1.245
1.244
1.242
1.253
1.262
1.261
1.261
1.262
1.259
1.246
1.245
1.254
1.252
1.266
1.261
1.392
1.386
1.391
1.412
1.411
1.412
1.392
1.379
1.385
1.388
1.379
1.393
1.414
1.408
1.395
1.389
1.387
1.385
1.404
1.418
1.409
1.412
1.420
1.410
1.408
1.424
1.406
1.421
1.424
1.415
1.429
1.415
1.421
1.413
1.439
1.421
1.516
1.511
1.513
1.495
1.485
1.489
1.499
1.488
1.503
1.489
1.488
1.485
1.496
1.510
1.499
1.508
1.493
1.507
[5b-I]+
[5b-II]+
[5b-III]+
[5b-I]2+
[5b-II]2+
[5b-III]2+
5c-I
5c-III
[5c-I]+
[5c-III]+
[5c-I]2+
[5c-III]2+
a Numbering of the X-ray structure of [3]+ and [5a]+ was extrapolated to the whole systems. b For [3]n+, C4 ) CH. c For [3]n+, C4′ ) CH2; For
[5a-c]n+, C4′ ) CH3. d For [3]+, the distance C3i-C4′ is given; For [5a-c]n+, the distance C3i-C4′i is given with C4′i ) C(R2).
Scheme 3. Proposed Mechanisms for the Formation of the Annelated C7 Complexes
C2, C2sC3 distances (Table 1) are intermediate between
C3 and C4 are close to 120° showing the sp2 nature of these
carbon atoms, along with the C3sC4 bond length.
respective typical values found in metal allenylidenes such as
38
[(η5-C5H5)(PMe3)2RudCdCdCPh2]PF6 and metal alkynes
Reactions Mechanisms. The reaction mechanism to obtain
[3][PF6] is not straightforward and was investigated. The
protonation of 2b should first lead to a cationic butatrienylidene
intermediate [A] (Scheme 3), possibly via a vinylidene.42 This
is corroborated by our calculations on 2b of which the HOMO
is mainly and equally localized on Câ and Cδ. The latter is thus
privileged to protonation for steric reasons. A further addition
of the CγtCδ bond of another molecule 2b on the resulting
CγdCδ bond of [A] is then proposed to lead to the annelated
bimetallic complex [3][OTf]. Isolation of [A] has not been
possible yet because of its high reactivity.43,44 As a matter of
such as [Cl(dppe)2RusCtCsC6H4sp-NO2].40 With complex
[3][PF6], the bridge arrangement is linear, and the four member
ring is planar and symmetrical owing to a disorder.41 For [5a]-
[BF4], the structure is also symmetric, and the two ruthenium
fragments are connected by a slightly twisted “W” shaped C9H7
bridge in order to minimize steric repulsions, supporting the
presence of form I in solution. The different angles involving
(40) Younus, M.; Long, N. J.; Raithby, P. R.; Lewis, J.; Page, N. A.; White, A.
J. P.; Williams, D. J.; Colbert, M. C. B.; Hodge, A. J.; Khan, M. S.; Parker,
D. G. J. Organomet. Chem. 1999, 578, 198-209.
(41) No H atoms could be located in the vicinity of C4 that accounts for the
inversion centre; hence the four C-C bond lengths are identical within
the ring.
(42) Koentjoro, O. F.; Rousseau, R.; Low, P. J. Organometallics 2001, 20, 4502-
4509.
9
5864 J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006

C7 and C9 Carbon-Rich Bridges
A R T I C L E S
fact, the regioselectivity of the additions observed here is
exceptional. The general process usually involves the most
activated CRdCâ bond of a vinylidene [M]dCdCHR or of an
allenylidene [MdCdCdCR1R2] with the CRtCâ bond of a
metal acetylide [M]sCtCsR26b-i or of a polyyne.26j Indeed,
this reaction was previously shown to afford rigid four
membered cyclic bridges with a delocalized C3 skeleton between
metals and to inhibit the access to higher odd numbered carbon-
rich bridges. Here, we assign the odd selectivity to the shielding
of the CRsCâ bonds by the bulky ruthenium moieties in the
diyne complexes 2a-b and [A], the CγsCδ bonds being the
most reactive. Indeed, the HOMO and LUMO of [A] show
almost equal localization on CRdCâ and CγdCδ.58
Concerning the oxidation route with the ferrocenium ion, we
anticipate that, despite the unfavourable potential, the reaction
is initiated by an electron transfer between ferrocenium and 2b
(Epa ) 0.13 V vs ferrocene, V ) 100 mV s-1), followed by
reaction of the resulting [2b]+ with another molecule of 2b
(Scheme 3). This hypothesis is supported by the fact that the
largest computed carbon spin density on 2b+ is on Cδ.45
Additional incorporation of a hydrogen atom from the medium
leads to [3][PF6]. An alternative route involves an earlier
hydrogen incorporation to generate [A] from [2b]+, and further
reaction with another molecule of 2b leads to [3][PF6] as in
the protonation route.
and on the fact that ruthenium allenylidenes with a sCH2R1
group on Cγ are easily deprotonated into stable ruthenium
acetylides trans-[(dppe)2(Cl)RusCtCsC(dCHR1)R2].31b This
mechanism is depicted in Scheme 4 for 5b. The first proposed
step consists of the transfer of a proton from [4b][BF4] to the
nucleophilic carbon Cδ of 2b to form [A] and the acetylide 8b.
A further fast addition of the nucleophilic Cδ of 8b on the
electrophilic Cγ atom of [A] leads to the intermediate [B]. This
is in agreement with a large localization of the LUMO of [A]
on Cγ.58 The formation of [5b][BF4] would then result from an
allylic hydrogen transfer.46 Two hydrogen atoms on one group
on the Cγ of the allenylidene are required: one for the proton
exchange between 2b and [4b][BF4] and another one for the
final transfer in [B].47 When the reaction is carried out with the
allenylidene trans-[(dppe)2(Cl)RudCdCd(CH2Ph)Ph]OTf ([4d]-
[OTf]), the nucleophilic attack of the deprotonated species trans-
[(dppe)2(Cl)RusCtCsC(dCHPh)Ph] (8d) and the subsequent
formation of the analogue intermediate are not observed. Instead,
the formation of [3][OTf] is observed as the result of the reaction
of the cumulenic intermediate with another molecule of the
diyne 2b. The addition of nucleophile 8d on [A] is certainly
precluded for steric reasons, and recovering this acetylide
(mixture of Z and E configurations) confirms the protonation
reaction as the first step of the mechanism.48
The formation of the C9 bridged complex [7][OTf] is
expected to follow the same principle and is quite interesting
to this point of view (Scheme 5). First of all, the protonation of
the triyne 6 with the allenylidene [4a][OTf] should lead to an
intermediate hexapentaenylidene species trans-[(dppe)2(Cl)-
RudCdCdCdCdCdCHSiMe3)]+ [D]. Further nucleophilic
attack on the Cꢀ carbon atom of [D] by 8a, the deprotonated
form of [4a][OTf], provides [7][OTf] after a proton transfer. It
is not clear whether desilylation occurs in the medium after or
before the nucleophilic attack, but it is relevant that no attack
is observed on the Cγ carbon otherwise some C7 compound with
a pendant triple bond would have been observed. From the
orbital point of view, both attacks are equally probable, but the
atomic charges favor Cꢀ addition.58 To the best of our
knowledge, this is the first evidence for the formation of a
transient hexapentaenylidene species MdCdCdCdCdCd
CR1R2. Indeed, while LnMd(Cd)nCR2 species with n ) 1 or n
) 2 have already been widely investigated,49 very few longer
species n ) 343 and 444 are known, and the intermediate
formation of a higher heptahexaenylidene cumulene (n ) 6)
was postulated only once.50
Electronic Structure of [3]2+/+/0 and [5a-b]2+/+/0. To get
a better understanding of the structure, reactivity, and properties
of complexes [3]+ and [5a-c]+, we have undertaken DFT
calculations with the help of the ADF code (see experimental
part) on simplified models in which the phenyl groups of the
dppe ligands have been replaced by hydrogen atoms. The
monoreduced and mono-oxidized states of these models have
also been computed. These time-consuming calculations were
limited to the C7 complexes, as oxidized and reduced forms of
[7][OTf] are not stable (vide infra).
A probable mechanism for the formation of [5a-c][BF4] also
stands on the formation of the butatrienylidene intermediate [A]-
(43) (a) Bruce, M. I. Coord. Chem. ReV. 2004, 248, 1603-1625. (b) Touchard,
D.; Haquette, P.; Daridor, A.; Toupet, L.; Dixneuf, P. H. J. Am. Chem.
Soc. 1994, 116, 11157-11159
(44) (a) This cumulene was successfully isolated only with Ir and with Mn
complexes; see: Ilg, K.; Werner, H. Angew. Chem., Int. Ed. 2000, 39, 1632-
1634. Venkatesen, K.; Fernandez, F. J.; Blacque, O.; Fox, T.; Alfonso,
M.; Schmalle, H. W.; Berke, H. Chem. Commun 2002, 2006-2007. (b)
Touchard, D.; Dixneuf, P. H. Coord Chem. ReV. 1998, 178, 8-180, 409-
429.
(45) The irreversible oxidation wave for 2b confirms the high reactivity of the
generated electrophilic organometallic radical [2b]+ that should be the
driving force of the reaction.
(46) This hypothesis is supported by 31P NMR monitoring of the reaction that
shows transient signals attributed to the intermediate [B] bearing an enynyl
moiety (δ ) 53.6 ppm) and an allenylidene moiety (δ ) 43.2 ppm) and to
the deprotonated complex 8b (δ ) 51.2 ppm).
(47) The proposed mechanism resembles those in the formation of an early
bimetallic C5 Ruthenium complex, but without cyclization owing to the
bulky ligands. See: Selegue, J. P. J. Am. Chem. Soc. 1983, 105, 5921-
5923.
(48) These observations are consistent with the fact that addition of the diyne
on the allenylidene has to be as slow as possible in order to minimize the
presence of 2b in solution that could react with [A] to form [3]+ as a
byproduct.
(49) (a) Bruce, M. I. Chem. ReV. 1991, 91, 197-257. (b) Bruce, M. I. Chem.
ReV. 1998, 98, 2797-2858. (c) Cardierno, V.; Gamasa, M. P.; Gimeno, J.
Eur. J. Inorg. Chem. 2001, 571-591. (d) Werner, H. Chem. Commun. 1997,
903-910.
(50) Roth, G.; Fischer, H.; Meyer-Friedrichsen, T.; Heck, J.; Houbrechts, S.;
Persoons, A. Organometallics 1998, 17, 1511-1516.
(51) Albright, T. A.; Burdett, J. K.; Whangbo, M.-H. In Orbital Interactions in
Chemistry; John Wiley and Sons: New York, 1985.
(52) Lichtenberger, D. L.; Renshaw, S. K.; Bullock, R. M. J. Am. Chem. Soc.
1993, 115, 3276-3285.
(53) (a)Winter, R. F.; Hornung, F. M. Organometallics 1999, 18, 4005-4026.
(b) Winter, R. F.; Klinkhammer, K. W.; Zalis, S. Organometallics 2001,
20, 1317-1333. (c) Hartmann, S.; Winter, R. F.; Sarkar, B.; Lissner, F. J.
Chem. Soc., Dalton Trans. 2004, 3273-3282. (d) McGrady, J. E.; Lovell,
T.; Stranger, R.; Humphrey, M. G. Organometallics 1997, 16, 4004-4011.
(54) (a) Esteruelas, M. A.; Gomez, V. A.; Lopez, A.; Modrego, J.; On˜ate, E.
Organometallics 1997, 16, 5826-5835. (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, 2137-2147.
(55) Barrie`re, F.; Camire, N.; Geiger, W. E.; Mueller-Westerhoff, U. T.; Sanders,
R. J. Am. Chem. Soc. 2002, 124, 7262-7263.
Four different isomers (I, II, III, IV) can be considered for
the [5a-c]+ compounds as shown in Chart 1. Preliminary
calculations ruled out the possibility of the existence of isomer
IV, due to high steric hindrance. [5c-II]+ is highly unstable
because of a strong repulsion between the two neighboring
(56) Creutz, C.; Chou, M. H. Inorg. Chem. 1987, 26, 2995-3000.
(57) Rigaut, S.; Maury, O.; Touchard, D.; Dixneuf, P. H. Chem. Commun. 2001,
373-374.
(58) Auger, N.; Touchard, D.; Rigaut, S.; Halet, J.-F.; Saillard, J.-Y. Organo-
metallics 2003, 22, 1638-1644.
9
J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006 5865

A R T I C L E S
Rigaut et al.
Scheme 4. Proposed Mechanism for the Formation of the C7 Complex [5b][BF4]
Scheme 5. Proposed Mechanism for the Formation of the C9
Complex [7][OTf]
Table 2. (A) Relative Energies for Each Species in Its Three
Oxidation States, Given in eV; (B) Dipole Moments (given in
Debye) Calculated for 3, 5a, 5b, and 5c in Their Different
Geometries and Charges
n
0
1
2
(a) Relative Energies
-4.33
[3]n+
0.00
0.11
0.00
0.00
0.16
0.07
0.20
0.00
8.33
8.46
8.41
8.39
8.55
8.51
8.71
8.43
[5a-I]n+
[5a-III]n+
[5b-I]n+
[5b-II]n+
[5b-III]n+
[5c-I]n+
[5c-III]n+
-4.03
-4.28
-4.36
4.27
-4.32
-4.14
-4.34
(b) Dipole Moments
[3]n+
0.17
2.86
1.14
1.64
1.49
1.41
1.10
0.49
0.30
5.44
2.94
3.74
2.72
0.70
2.66
2.16
0.23
5.86
3.25
3.37
3.34
1.05
2.67
5.07
[5a-I]n+
[5a-III]n+
[5b-I]n+
[5b-II]n+
[5b-III]n+
[5c-I]n+
[5c-III]n+
methyl groups and, thus, was not taken into account later on.
This instability is not encountered in [5b-II]+, the phenyl group
being almost perpendicular to the conjugated chain, thus
minimizing its repulsion with the methyl group. This preliminary
conformational study allowed us to identify the systems to be
considered, i.e., [5a-I]+, [5a-II]+, [5b-I]+, [5b-II]+, [5b-III]+,
[5c-I]+, and [5c-III]+ ([5a-II]+ and [5a-III]+ are identical (R2
) CH3)). The major optimized geometrical data computed for
[3]2+/+/0 and [5a-c]2+/+/0 are reported in Table 1, together with
the X-ray experimental values of [3][PF6] and [5a][BF4] given
in italic.
The relative energies and dipole moments computed for
[3]2+/+/0 and [5a-c]2+/+/0 are reported in Table 2a and 2b. In
[5a]2+/+/0 and [5c]2+/+/0 series, conformation III is calculated
to be more stable in vacuum at 0 K. Conformation I is preferred
over III in the [5b]2+/+/0 series. Form II is much higher in
energy. The energy difference between conformers is always
lower than 0.30 eV. For example, [5a]+ is 0.11 eV more stable
in vacuum in its conformation III, but the dipole moment of
9
5866 J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006

C7 and C9 Carbon-Rich Bridges
A R T I C L E S
Figure 2. MO diagrams of [3]+ and [5a]+.
[5a-I]+ is much higher (5.44 vs 2.94 D, see Table 2), this
suggesting a strong stabilization of this form in solution.
Unfortunately, the wide range of calculated dipole moments
prevents any conclusion concerning the conformation adopted
in CH2Cl2 solution by those systems. The energy barrier needed
to go from III to I was estimated to be 1.28 eV. An
isomerization process is thus unexpected in solution, and this
distribution must result from synthesis process. The X-ray and
NMR measurements (vide supra) of [5a]+ reveal that the actual
species is [5a-I]+.This is also the case for [5c-I]+ as evidenced
by NMR data, with maybe some traces of isomer [5c-III]+.
For [5b]+ the NMR measurements exclude form II but does
not give any other information. However, in the light of what
is observed with [5a,c]+, the differences in energy and in dipolar
moment of I and III, we can reasonably consider that [5b-I]+
is the form which is present in solution. Therefore, the “w”
shaped isomer is assumed to be the actual conformation for the
three complexes [5a-c][BF4] in solution and in solid state, and
only these conformations will be discussed later on. It has to
be noted that I and III are electronically and structurally similar
with n ) 1 but also with n ) 0, 2.
These calculations indicate no significant differences between
the two molecular branches in the case of [3]2+/+/0 and [5a]2+/+/0
(as in the X-ray structures of and [3]+ and [5a]+) and small
differences in the case of [5b,c]2+/+/0. This supports the view
of equal weights for the two Lewis structures shown in Scheme
1 for [3]+ and [5a-c]+ and full delocalization of the single
electron in the case of [3]2+/0 and [5a-c]2+/0. The optimized
structures of [3]+ and [5a]+ are in good agreement with the
experimental ones, with, as usually obtained with this type of
calculations, slightly longer Ru-ligand distances. The optimized
C1-C2 distances are also slightly longer. Moreover, the
calculations on [3]+ allow us to distinguish between the C(sp2)-
C(sp2) and C(sp2)-C(sp3) distances within the central C4 ring,
which are 1.414 Å and 1.544 Å, respectively. These values were
not available from the X-ray data, due to structural disorder.
As said above, the dissymmetry induced by the presence of R2
substituents different from CH3 on [5b]+ and [5c]+ has little
effect on the π conjugated C7 chain which remains almost
symmetrical, the largest differences being, as expected, on the
bonds involving the C3 atoms (∼0.01 Å). The computed
Mulliken atomic charges follow the same trend (see Supporting
Information Table S1). Clearly, there is no significant tendency
in [5b]+ and [5c]+ for a larger weight of one of the two Lewis
structures of Scheme 1.
The MO diagrams of [3]+ and [5a]+ are sketched in Figure
2. The diagrams of [5b]+ and [5c]+ are very similar to those of
[5a]+ and therefore are not shown here. A selection of frontier
orbitals of [3]+ and [5a]+ is shown in Figure 2. It is clear that
the electronic structures of [3]+ and [5a]+ are very similar. The
presence of a strained C4 ring of [3]+ is likely to destabilize the
σ framework, but it merely perturbs the π-type system. There
are two (one in-plane and one out-of-plane) 4dπ AOs per Ru atom.
It results that in the dinuclear [3]+ and [5a]+ complexes, there
are four MOs deriving from the four 4dπ AOs. These MOs are
combinations of the so-called “t2g” sets of the octahedrally
surrounded Ru(II) atoms and therefore are occupied.51 It turns
out that these orbitals are the four highest occupied MOs of
[3]+ and [5a]+ (Figure 2). They are the in-phase and out-of-
phase combinations of the in-plane and out-of-plane 4dπ Ru AOs.
As often observed in π-conjugated RuCn complexes,58 such 4dπ
orbitals are mixed in an antibonding way with π(CdC) levels.
This is what happens in [3]+ and [5a]+, the four HOMOs of
which exhibiting comparable antibonding RusC1 and bonding
C1sC2 characters. These four MOs, which are also RusCl
antibonding,52 differ mainly by their character on C4, since only
the in-phase combinations of the RuC3 moieties can mix with
this atom by symmetry. Contrarily to their HOMOs which lie
close in energy, the LUMOs of [3]+ and [5a]+ are isolated in
the middle of a large energy gap (Figure 2). This suggests
possible thermodynamical stability for some species which
would have the same molecular structure and two more electrons
than [3]+ and [5a]+. These LUMOs have little Ru participation
(13% and 14%, respectively) and their largest coefficient on
C3 and C3i (20 and 20% for [3]+, 21 and 21% for [5a]+). They
exhibit bonding C1sC2 and antibonding C2sC3 character.
The mono-oxidation of [3]+ and [5a-c]+ corresponds to the
depopulation of the same HOMO (Figure 2). Consequently, the
RusC1 and C1sC2 bonds are shortened and elongated, respec-
tively (Table 1). As said previously, no tendency for spin local-
ization on one of the halves of the molecule can be traced for
the four complexes. A plot of the spin density of [5a]2+ is shown
9
J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006 5867

A R T I C L E S
Rigaut et al.
Figure 3. Contour plots of the calculated spin density of [3]0,2+ and [5a-I]0,2+; Contour values are (0.0045 e/bohr3.
Table 3. Atomic Spin Densities Calculated for 3, [3]2+, 5a, [5a]2+, 5b, [5b]2+, 5c, [5c]2+
Ru1
Ru1i
C1
C1i
C2
C2i
C3
C3i
C4
C4
′
C4
′
i
Cl1
Cl1i
3
0.03
0.26
0.03
0.02
0.25
0.25
0.03
0.03
0.02
0.25
0.31
0.22
0.03
0.03
0.18
0.19
0.03
0.26
0.03
0.03
0.25
0.27
0.03
0.02
0.03
0.25
0.14
0.23
0.02
0.02
0.20
0.24
0.28
0.00
0.25
0.22
0.00
-0.02
0.24
0.25
0.20
0.00
0.01
0.00
0.24
0.26
0.02
0.00
0.28
0.00
0.25
0.27
0.00
-0.01
0.25
0.22
0.25
0.00
0.00
-0.01
0.26
0.25
0.02
0.00
-0.11
0.14
-0.09
-0.08
0.16
-0.11
0.14
-0.09
-0.10
0.16
0.37
-0.02
0.37
0.37
-0.02
0.37
-0.14
0.02
-0.14
-0.14
0.20
-0.04
0.03
-0.02
-0.03
0.00
0.00
0.11
0.00
0.00
0.08
0.11
0.00
0.00
0.00
0.08
0.11
0.08
0.00
0.00
0.04
0.07
0.00
0.11
0.00
0.00
0.08
0.12
0.00
0.00
0.00
0.08
0.07
0.10
0.00
0.00
0.04
0.10
[3]2+
5a-I
5a-II
-0.03
-0.03
0.00
0.36
0.40
[5a-I]2+
[5a-II]2+
5b-I
-0.07
-0.06
0.35
0.35
0.32
-0.06
-0.04
-0.06
0.34
-0.07
-0.06
0.36
0.33
0.37
-0.06
-0.03
-0.06
0.36
0.13
0.15
0.14
0.00
0.00
-0.09
-0.09
-0.07
0.16
0.22
0.19
-0.08
-0.09
0.19
-0.09
-0.08
-0.09
0.16
0.12
0.15
-0.09
-0.09
0.19
-0.13
-0.13
-0.13
0.18
0.09
0.18
-0.13
-0.13
0.21
-0.03
-0.03
-0.02
-0.06
0.02
-0.03
-0.03
-0.04
-0.06
0.01
5b-II
5b-III
[5b-I]2+
[5b-II]2+
[5b-III]2+
5c-I
5c-III
[5c-I]2+
[5c-III]2+
0.00
0.01
-0.03
-0.03
0.01
-0.03
-0.02
0.01
0.38
-0.06
-0.06
0.37
-0.06
-0.06
0.17
0.16
0.18
0.00
0.00
in Figure 3. It fits nicely with the shape of the [5a]+ HOMO
(Figure 2). About half of the unpaired electron lies on the Ru
centers. Table 3 shows that the atomic spin densities of all the
computed bications are about the same. Similarly, the monore-
duction of [3]+ and [5a-c]+ corresponds to the occupation of
the same LUMO (Figure 2). It results in the Ru-C1 and C1-
C2 bonds being elongated and shortened, respectively (Table
1). The plot of the spin density of 5a nicely reproduces that of
the LUMO of [5a]+ (Figure 3). In particular, the Ru contribution
is very small, most of the spin density being concentrated on
the C3 and C1 atoms. Table 3 shows that all the computed
reduced species exhibit similar spin distributions with no
tendency for significant spin localization on one of the halves.
UV-Visible Spectra. In addition to classical intense short-
wavelength absorption band for the n-π* type transitions
originating from the dppe ligand at high energy below 300 nm
(not shown), all complexes show a strong and broad band with
a large extinction coefficient at lower energy (Table 4, Figure
4). The band presents a bathochromic shift from 633 nm with
[3][PF6] to 710 nm with [5a][BF4]. Introduction of a phenyl
Table 4. Cyclic Voltammetry and UV-vis Data for the Bimetallic
Complexes
electrochemistrya
b/V
UV
max/nm ( )
/mol-1 L cm-
−
visf
1
E
°
b/V
E
°
E
°
ox2/V
λ
ꢀ
red
ox1
[3]+
-1.48
-1.38
-1.24
-1.25
-1.16d
0.42
0.31
0.32
0.23
0.42e
0.91c
0.99c
0.97d
1.06c
0.96c
633 (141 000) 748 (sh)
455 (4000) 710 (127 600)
494 (4700) 746 (98 000)
502 (7600) 764 (109 000)
526 (14 600) 744(46 000)
[5a]+
[5b]+
[5c]+
[7]+
a Sample, 1 mM; Bu4NPF6 (0.1 M) in CH2Cl2; V ) 100 mV s-1
;
potentials are reported in volt vs ferrocene as an internal standard.
b Reversible redox processes ∆Ep ≈ 60 mV, Ipc/Ipa ≈ 1. c Peak potential of
an irreversible process. d Partially reversible peak ∆Ep ≈ 100 mV, Ipc/Ipa
< 1. e ∆Ep ≈ 80 mV. f In CH2Cl2, sh ) shoulder.
lower energy between 450 and 530 nm. In contrast, a higher
energy band at 748 nm (shoulder) is observed for [3][PF6].
For a monocumulenic compound such as the allenylidene
trans-[Cl(dppe)2RudCdCdCPh2]PF6, a transition with a λmax
value of 504 nm (ꢀ ) 18 000 mol-1 L cm-1) is attributed to
the allowed transition from the metal based HOMO-1 to the
LUMO which is delocalized over the allenylidene ligand (the
HOMO/LUMO symmetry is forbidden) and accounts for the
strong Metal-to-Ligand Charge Transfer (MLCT).53b The intense
bands observed here are very broad. The MO diagrams (Figure
2) suggest that they certainly include several transitions close
in energy with an MLCT character. Clearly, if the λmax values
are highly influenced by the nature of the bridge, these
group in [5b][BF4] (λmax ) 746 nm) and [5c][BF4] (λmax
)
764 nm) also contributes to the decrease in the absorption
energy. Finally, the C9 complex [7][OTf] shows a larger red
shift than the C7 analogue [5a][BF4] attributed to the longer
conjugation path but with a lower oscillator strength attributed
to a weaker coupling between the metallic centers. Compounds
[5a-c][BF4] and [7][OTf] also exhibit weak absorptions at
9
5868 J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006

C7 and C9 Carbon-Rich Bridges
A R T I C L E S
viewed as essentially involving the two RuII/RuIII couples.42,53-54
The unusually large separation of the processes (∆E° ) 650
mV, Kc ) exp(∆E°F/RT) ) 1.50 × 1011 for [5b]+) first
establishes that all the mono-oxidized species are stable in
solution with respect to disproportionation (mixed valence
species)8a,55 and supports the idea that they gain considerable
stabilization due to delocalization. However, other phenomena
such as columbic repulsion, structural distortion through the
oxidations, and ion pairing besides delocalization also contribute
to Kc, and one must therefore be careful in interpreting the
meaning of Kc trends.55 It is noteworthy that this value calculated
for [5b]+ is larger by several orders of magnitude than those
found for the well-known Creutz-Taube ion {Ru(NH3)5}2(µ-
pyrazine) (Kc ) 2.47 × 107, acetonitrile solution)56 or for related
species of comparable length such as [{Cp*(NO)(PPh3)Re}2-
(µ-C6)] (Kc ) 3.0 × 106),9a [{Cp*(NO)(PPh3)Re}2(µ-C8)] (Kc
) 3.0 × 106), and [{Cp*(dppe)Fe}2(µ-C6)] (Kc ) 5.9 × 104).8a
The present value is of the order of magnitude of that of shorter
C4 species such as [{Cp*(NO)(PPh3)Re}2(µ-C4)] (Kc ) 1.1 ×
109), [{Cp*(dppe)Fe}2(µ-C4)] (Kc ) 1.6 × 1012),8b [{Cp(PPh3)2-
Ru}2(µ-C4)] (Kc ) 1.5 × 1011),7c [{Cp*(dppe)Fe}2(µ-C4H4)]
(Kc ) 1.1 × 1012),19c and [{I(dmpe)2Mn}2(µ-C4)] (Kc ) 5.4 ×
1010).12b Regarding the reduction wave at a rather negative
potential, it is attributable at first glance to the reduction of the
unsaturated carbon chain by analogy with other cumulenic
complexes.54,57-60 Although we can ascribe the origin of the
redox processes (see below), calculated ionization potentials and
electronic affinity fluctuations between the different C7 com-
plexes are not in agreement with the experimental trends. This
is certainly the result of solvent and supporting electrolyte effects
which are not taken into account in the calculations. Indeed,
they are likely to be significant owing to the wide range of
calculated dipole moments.
We can observe that these cationic bimetallic complexes are
harder to oxidize than a neutral acetylide complex such as 2a
(E° ) 0.130 V vs FeCp2) and easier to oxidize than a cationic
allenylidene complex such as trans-[ClRu(dppe)2dCdCdCPh2]-
PF6 (E° ) 0.99 V vs FeCp2). They are also harder to reduce
than the latter (E° ) -1.03 V vs FeCp2). These observations
support a highly delocalized structure due to the nature of the
bridge. It is noteworthy that the oxidation and reduction
potentials of [7]+ are respectively closer to that of acetylides
and allenylidenes than that of [5a]+. These easier reduction and
harder first oxidation are the consequence of a longer conjugated
bridge with a subsequent weaker interaction between the remote
metals and indicate the more localized form with a positive
charge on the allenylidene side as previously suggested.
However, the charge in [7]+ is more delocalized than that of
the bimetallic trans-[Cl(dppe)2RusCtCsp-(C6H4)s(Ph)Cd
CdCdRuCl(dppe)2][CF3SO3]31c with nine carbon atoms to
connecting two ruthenium atoms that display an oxidation and
a reduction potential closer to those of the monometallic species
owing to the aromatic character of the bridge.
Figure 4. Electronic absorption spectra for [3][PF6] (‚ - ‚), [5a][BF4]
(- -), [5b][BF4] (‚‚ - ‚‚), [5c][BF4] (s), and [7][OTf] (‚ ‚ ‚) in CH2Cl2.
Figure 5. CV for [3]+ (dashed) and [5b]+ (plain); Bu4NPF6 (0.1 M) in
CH2Cl2; V ) 100 mV s-1. Inset shows the full reversibility of the first
oxidation process for [3]+.
differences are difficult to rationalize on the basis of the MO
diagrams and especially knowing the fact that the presence of
a strained C4 ring in [3][PF6] does not significantly perturb the
π-type system by comparison with [5a-c][BF4] (vide supra).
We attribute this phenomenon to the wide range of dipole
moments (Table 2b) that preclude any simple analysis in polar
solutions in which the complexes are soluble (CH2Cl2). Nev-
ertheless, these bands are similar to that of conjugated bis-
allenylidenes such as trans-[Cl(dppe)2RudCdCdC(Ph)sCt
Cs(Ph)CdCdCdRuCl(dppe)2][CF3SO3]2 (λmax ) 720 nm, ꢀ
) 60 000 mol-1 L cm-1) or that of trans-[Cl(dppe)2RusCt
Csp-(C6H4)s(Ph)CdCdCdRuCl(dppe)2][CF3SO3] (λmax
)
764 nm, ꢀ ) 63 000 mol-1 L cm-1).31c The latter with nine
conjugated carbon atoms through a phenyl group presents a very
similar spectrum to that of [7][OTf].
Electrochemical Data. These new bimetallic complexes are
composed of several redox active units. To understand the nature
of the redox behavior and the role of the linker, the cyclic
voltammograms (CV) were recorded in CH2Cl2 solutions (0.1
M Bu4NPF6). The values of the potentials for all compounds
are reported in Table 4. Typical CVs are displayed in Figure 5
for complexes [3]+ and [5b]+. All complexes exhibit a linear
dependence of the peak current on the square root of the rate
(v1/2) from 60 to 600 mv s-1 as expected for a diffusion
controlled process. They undergo a well-defined reversible one-
electron oxidation wave followed by a partially reversible
([5b]+) or irreversible ([3]+, [5a]+, [5c]+, [7]+) second oxidation
consistent with an undergoing chemical reaction of the second
oxidized species producing a new wave on the return scan
around 1.08 V. A well-defined one-electron reversible reduction
wave at a rather negative potential was also observed.
Studies of the First Oxidized and Reduced Species. To
collect more detailed information about those species, a series
of spectroscopic experiments were carried out, covering the IR,
(59) (a) Re, N.; Sgamellotti, A.; Fioriani, C. Organometallics 2000, 19, 1115.
(b) Marrone, A.; Re, N. Organometallics 2002, 21, 3562-3571.
(60) (a)Winter, R. F. Eur. J. Inorg. Chem. 1999, 2121-2126. (b) Hartmann,
S.; Winter, R. F.; Brunner, B. M.; Sarkar, B.; Kno¨dler, A.; Hartenbach, I.
Eur. J. Inorg. Chem. 2003, 876-891.
To a first approximation, the two oxidation steps are usually
9
J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006 5869

A R T I C L E S
Rigaut et al.
Table 5. EPR Data (Principal Values of the g-Tensor) for [3]2+
,
[5a]2+, [5c]2+
g1
g2
g3
<g>a
g1−g3
[3]2+
2.082
2.078
2.044
2.044
2.020
2.024
2.0007
1.918
2.0005
2.043
2.0064
2.023
0.081
0.160
0.044
[5a]2+
[5c]2+
2
2
2
a Calculated from <g> ) [(g1 + g2 + g3 )/3]1/2
.
of Ru isotopes.61a This is suggested in the following, although
the wings of the present spectrum are poorly resolved. If the
electron is well delocalized over the two metal centers, the active
set of nuclei being considered should be 31P (8 P), 99,101Ru (2
Figure 6. EPR spectrum of 5a at 295 K in THF. Upper trace: experiment.
1
31P
Lower trace: computer simulation with a ) 6.3 G (8 P), a H ) 3.1 G
1
Ru), with the various combinations of isotopes, and H (1 H).
99,101
(1 H), a Ru ) 3.9 G (2 Ru), giso ) 2.0032, 1.5 G line width. This hyperfine
With these guidelines, the observed EPR spectrum of 5a could
be properly simulated (Figure 6). As mentioned, few 99,101Ru
hfs’s have been reported in Ru based dinuclear complexes, and
the present value 3.9 G is of the same order of magnitude as
4.35 G reported for a bis-Ru(3,6-bis(2-pyridyl)tetrazine)
derivative.61a Most of the intensity of the spectrum (70%) is
given by an underlying broad feature to represent all unresolved
contributions (further H nuclei and anisotropic contributions).
A value of giso ) 2.023 has been recently reported32 for a
symmetrical bis-Ru(dppe) derivative comparable to 5a but
incorporating a bisanthracenylidene bridge instead of (CH3)s
CHdC(CH3). The present g-values for 3a and 5a,c derivatives
are much closer to the free electron g-value, thus emphasizing
a greater delocalization through the cumulene ligand. These
results support the scheme of an electron mostly localized on
the cumulene ligand with little contribution from the metal
centers in a reduction process, according to previous observa-
tions of reduced bimetallic Fe-Ru centered allenylidene
derivatives.60b The strong dependence of the electron delocal-
ization on the nature of the central bridge between the Ru-
allenylidene moieties is well emphasized.31c,32
Studies of the first oxidized species [3]2+, [5a]2+, and [5c]2+
were performed following the in situ electrolysis of the cationic
derivative solutions at room temperature, by quenching and
recording their EPR spectra at 77 K and 4 K. In fluid solution,
the bications were EPR silent probably due to the spin-orbit
contributions from the Ru nuclei being responsible for fast
relaxation. Upon decreasing temperature from 77 K to 4 K, the
intensity for all oxidized complexes increases. The three
complexes exhibit slightly rhombic EPR spectra in frozen THF
solution (see Supporting Information). Accordingly, these afford
an estimation of the principal values of the g-tensor presented
in Table 5. According to previous studies related to various Ru-
allenylidene derivatives,46a,b;61b,c the quite low g-anisotropy
estimated by (g3-g1) and the average <g> factor being not
strongly shifted from the free electron g-value do not favor a
genuine metal centered oxidation. This conclusion is further
supported by the fact that the EPR spectra are still observable
at 77 K, hence showing an attenuated metallic character. As
previously discussed,61b the g-anisotropy of dications with strong
donor substituents decreases together with the contribution from
the mixed-valent formulation Ru(II)-L-Ru(III).
pattern is superimposed to a broad 1:1 Gaussian/Lorentzian component with
a ca. 30 G line width to take account of all the unresolved structure. The
inset shows that the satellite lines in the wings (low field part) are well
reproduced upon comparing the simulated spectrum (lower trace, without
the broad component) with the experimental one (upper spectrum) with
this set of coupling constants.
NIR, visible, and UV regions of the spectrum on [3][PF6] and
[5a-c][BF4] only, as [7][OTf] show very limited stabilities of
the oxidized and reduced states. They were produced electro-
chemically (potential controlled electrolysis) by applying the
potential corresponding to respective Epa or Epc values. EPR
experiments were also performed on in situ chemically or
electrochemically generated samples.
EPR Spectroscopy: Previous works have shown the ef-
ficiency of EPR spectroscopy to probe the electron distribution
and the effective oxidation state of Ru complexes61 including
allenylidene derivatives.31c-33,60 In the case of dinuclear deriva-
tives, it is of particuliar interest to study the amount of electronic
delocalization, assessing the electronic configuration between
that of a mixed valence system Ru(II)-L-Ru(III) and that of
a radical complex Ru(II)-L•-Ru(II).31c,61a The EPR spectra of
binuclear Ru-radicals incorporating dppe show broad and usually
unresolved features due to overlapping hyperfine contributions
1
from 31P, 99,101Ru, and H nuclei.32,60b Whatever the oxidation
state in frozen solution, the principal values of the g-tensor may
be used as a qualitative estimation of the extent of the electron
over the metal and/or over the ligand upon checking the
departure from the free electron g-value.61a-c
After reduction at room temperature of [3][PF6] and [5a-
c][BF4] with cobaltocene (E° ) -1.33 V vs FeCp2),37,62 only
the isotropic g-values in fluid solution could be estimated for
the three resulting neutral species. These are very close to the
free electron g-value: giso ) 2.0019 (5c); giso ) 2.0032 (5a);
giso ) 2.0090 (3), thus emphasizing the ligand centered
reduction. Whereas the EPR spectrum of 3 shows no hyperfine
structure, hyperfine features are detected for 5c and 5a, quite
well resolved in the latter case (Figure 6). It is worth mentioning
that similar observations (complex hyperfine pattern, giso
)
2.0048) have been recently reported for mononuclear ruthenium
allenylidene derivatives with phenyl groups in the carbon-rich
fragment.31c
Inspection of the external lines in the wings of the EPR
spectra could reveal in rare cases the hyperfine splitting (hfs)
UV-vis/IR/NIR Spectroscopies: One-electron electrochemi-
cal reductions were conducted only with [5a,c][BF4], complex
[3][PF6] showing a limited stability on the electrolysis time
scale.63 Upon reduction, the discoloration of the mixtures and,
thus, the vanishing of the intense visible bands with the
development of a new broad band in the UV region character-
(61) (a) Kaim, W.; Ernst, S.; Kasack, V. J. Am. Chem. Soc. 1990, 112, 173-
178. (b) Kasack, V.; Kaim, W.; Binder, H.; Jordanov, J.; Roth, E. Inorg.
Chem. 1995, 34, 1924-1933. (c) Patra, S.; Sarkar, B.; Ghumaan, S; Fiedler,
J.; Kaim, W.; Lahiri, G. K. Dalton Trans. 2004, 754-758.
(62) The potentials of 3a and 5a are more negative compared to that of [CoCp2];
however the values are close enough to observe a slight displacement of
the equilibrium and to see the reduced species.
9
5870 J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006

C7 and C9 Carbon-Rich Bridges
A R T I C L E S
Table 6. UV-vis and NIR Data for [3]2+, [5a]2+, [5c]2+ in CH2Cl2
UV
−
visa
NIRa
1
c
λ
(
max/nm/
ν
max/cm-
∆ν
cm-
∆ν (calcd)b
Vab
1
1
1
1
λ
max/nm (
ꢀ
/mol-1 L cm-
)
ꢀ
/mol-1 L cm-
)
cm-
eV
[3]2+
592 (39 700)
428 (6200), 614 (44 500)
484 (7300), 646 (31 000)
1432/6983 (3000)
1384/7225 (6300)
1367/7315 (5400)
1680
1270
1801
4016
4085
4110
0.43
0.45
0.45
[5a]2+
[5c]2+
1/2
a In CH2Cl2. b Calculated from ∆ν1/2 ) (2310νmax
)
for symmetrical systems. c From Vab ) νmax/2.
Figure 8. NIR absorption spectrum for [5a]2+ in CH2Cl2.
observed on the low energy side, while shoulders are detected
on the high energy side. The presence of several NIR bands in
the spectra of MV complexes is common and can be clearly
related to the structure of the spacer or to the metal termini.1f,8,9,19c
Assuming that the entire low NIR band represents the lowest
energy band that should only be included in the calculation,
and that the half width is not affected, analysis of the absorption
for each complex yielded band data reported in Table 6.66 The
bandwidth of these transitions are far smaller than that predicted
by the Hush model for the lowest energy IVCT electronic
Figure 7. Electronic absorption spectra (CH2Cl2) of [3]2+ (‚ ‚ ‚), [5a]2+
(s), [5c]2+ (‚ - ‚), inset shows the spectra for 5a (s) and 5c (‚ - ‚).
istic of Ru(II) acetylides53c,60b,64 were observed (inset, Figure
7). For 5a, this new feature was detected at λmax ) 311 nm (ꢀ
) 19 000 mol-1 L cm-1) with a shoulder on the low energy
side at 390 nm. No bands were observed in the NIR region for
both complexes after reduction. IR measurements in CH2Cl2
show the loss of the cumulenic band at 1906 cm-1 for 5a and
at 1895 cm-1 for 5c, with the concomitant emergence of a
weaker vibration stretch at 2049 cm-1 for the former sym-
metrical complex and of two vibrations at 2029 and 2045 cm-1
for 5c. Added to EPR experiments, all these characteristics
expected for ligand centered radical acetylides31b,60 strongly
support a reduction process mainly attributed to the reduction
of the carbon chain with the single electron delocalized over
the bridge. Furthermore, they are consistent with the above
theoretical calculations, i.e., with the fact that the Ru-C1 (Ru-
C′1) and C1-C2 (C′1-C′2) bonds are elongated and shortened,
respectively, upon reduction and that most of the spin density
is concentrated on the carbon chain (Table 3).
transition of symmetrical class II compounds (∆ν1/2
)
(2310νmax
)
1/2).65 Together with the magnitude of the compro-
portionation constant and always keeping in mind that the bands
are broadened by unresolved subbands, the characteristics of
these bands are those of strongly coupled Robin and Day class
III systems.67 Similar measurements performed with [5c]2+ in
THF68 indicate a very weak shift from λmax ) 1367 nm (7315
cm-1) to λmax ) 1356 nm (6711 cm-1) with the polarity of the
solvents also characteristic of a class III delocalized complex.
An exact assignment of the bands is ambiguous, but they are
rather ascribed to π-π bands of delocalized complexes than to
intervalence transfer (IT) bands of localized (class II) ions. The
lower energy band could be ascribed to the superexchange
involving the bridging ligand’s orbitals (from HOMO-1 to
SOMO), whereas unresolved subbands to HOMO-n (n > 1) to
SOMO transitions. The coupling parameters Vab derived from
the Hush theory for class III complexes (Table 6), and compared
to those of class III analogues such as [{Cp*(dppe)Ru}2(µ-C4)]
Electrochemical oxidations were performed on [3][PF6] and
[5a,c][BF4].63 IR studies show the vanishing of the cumulenic
bands for all complexes, but the new vibration stretch intensities
of the bridges are apparently too low to be observed, a fact
already reported for other oxidized complexes.12c,53a-b For the
three complexes, oxidation also leads to the disappearance of
the intense band of the visible spectrum with the appearance of
a significantly weaker band around 600 nm (Figure 7, Table
6). It is of note that, with [5a]2+ and [5c]2+, the weak bands are
slightly blue shifted and a shoulder is no longer observed on
(63) Reversibility was checked by back electrolysis that shows a recovering of
the starting complexes superior to 90% on the basis of UV-vis and RMN
experiments. Chemical reduction with 1 equiv of [CoCp2] in CH2Cl2
followed by reoxidation with 1 equiv of ferricinium salt 30 min later also
led to the almost complete recovery of the starting complexes in the case
of 5a,c (>90%).
the high energy side of the more intense band for [3]2+
.
(64) Powell, C. E.; Cifuentes, M. P.; Morrall, J. P.; Stranger, R.; Humphrey,
M. G.; Samoc, M.; Luther-Davies, B.; Heath, G. A. J. Am. Chem. Soc.
2003, 125, 602-610.
Considering the ground-state electronic structure, these broad
transitions might arise from several shifted MLCT or LMCT
involving deeper occupied levels and the SOMO.
One-electron oxidations also give rise to an absorption band
in the NIR region of the spectrum around 1400 nm (Figure 8,
Table 6) which is characteristic of the formally mixed-valence
nature of these compounds.1,65 A relative sharp cutoff is
(65) Hush, N. S. Prog. Inorg. Chem. 1967, 8, 391-444.
(66) It is of note that in complex [5c]2+ the symmetry is slightly broken.
Nevertheless, the characteristics are still very similar to those of the other
complexes, suggesting also a completely delocalized compound to which
we applied the same Hush treatment.
(67) Robin, M.; Day, P. AdV. Inorg. Chem. Radiochem. 1967, 10, 247-422.
(68) Similar measurements could not be conducted in more polar solvents such
as methanol or acetonitrile for solubility or stability reasons.
9
J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006 5871

A R T I C L E S
Rigaut et al.
(0.63 eV),7b [{Cp*(dppe)Fe}2(µ-C4)] (0.47 eV),8a [{Cp*(dppe)-
Fe}2(µ-C4H4)] (0.43 eV),19c and [{Cp*(dppe)Fe}2(µ-C8)] (0.32
eV),8a are other indications of the efficiency of these C7 carbon-
rich systems for electronic delocalization over a distance of
almost 12 Å.1d This might be related to the presence of sp2
carbon atoms in the chain, as MV species with double bonds
display stronger coupling that analogous triple bonded
species.8a,19c,69 It is also worth noting that, except for [{Cp*-
(dppe)Fe}2(µ-C8)], these previous studies with even numbered
chains were limited to C4 chains if no aromatic ring is present
in the bridge8e because of the low stability of the paramagnetic
species, as we observed with the C9 species [7][OTf].
In conclusion to these oxidation processes, spectroscopic,
EPR, and theoretical results point out the delocalized nature of
the single electron in these oxidized C7 species (Table 3)
involving the two metallic centers with about half of the
unpaired electron on the Ru atoms, and with an almost equal
participation of the carbon bridge (C2, C2i, and C4). Therefore,
the dissymmetry of the bridge does not induce the localization
of the electron on one halve of the molecule toward class II
complexes.
Figure 9. Electronic absorption spectra of [5a][BF4] (s), [10a][BF4]2
(‚ - ‚), [11a][BF4]3 (‚ ‚ ‚), and 9a (inset) in CH2Cl2.
Table 7. UV-vis Data for Protonated and Deprotonated Species,
in CH2Cl2
UV
−vis
1
λ
max/nm ( )
ꢀ
/mol-1 L cm-
9a
9c
336 (9400)
340 (9200)
For several years now, it is well recognized that the structure
of the mixed valence compound is highly dependent on the
bridging ligand nature and on the metallic building blocks, the
oxidation being less metal centered with ruthenium or rhenium
complexes than with iron species.8f For example, Winter et al.70
recently reported a bimetallic complex with a divinylphenylene
bridge that dominates the anodic redox processes and that, as
do the present results, also highlights that (1) the presence of
the metal moieties endows the oxidized or reduced bridge with
stabilities that are usually not encountered in their purely organic
counterparts and (2) the bridge is a noninnocent redox ligand
which cannot be decoupled from the metal in the redox
processes.
[10a][BF4]2
[10c][BF4]2
[11a][BF4]3
[11c][BF4]3
454 (3100), 700 (45800)
494 (3500), 759 (32500)
454 (4000), 643 (65000)
494 (7500), 671 (34900)
satisfactorily identified. Considering 9a, the 31P analysis displays
two resonances at δ ) 51.0 and 49.8 ppm consistent with
1
acetylide moieties. The most distinguishing features of the H
NMR data are the two coupled ethylenic hydrogen atoms on
Cδ, and the doublets are observed at δ ) 4.70 and 4.65 ppm
with 2J(H,H) ) 3.3 Hz. In addition, characteristic IR vibration
stretches are observed, υCtC ) 2045 cm-1 and υCdC ) 1645
cm-1. Last, the intense absorption band disappears from the
visible region with the development of a less intense low-energy
shoulder superimposed on the absorptions of the aryl substituted
phosphine ligands in the near UV region of the spectrum at ca.
340 nm, typical for Ru(II) acetylides (Figure 9, Table 7).24a
Addition of 1 equiv of HBF4‚Et2O in CH2Cl2 to 9a,c led to the
clean regeneration of [5a,c][BF4].
By attempting to protonate the bimetallic compounds [5a,c]-
[BF4], we observed two stages of protonation on the two Câ
positions, in accord with Mulliken charges of [5a,c]+ (Table
S1) and the steric hindrance around CR. The first one occurs
with 1 equiv of HBF4‚Et2O owing to the acetylide character of
the complexes and led to original blue-green vinylidene-
allenylidene species [10a,c][BF4]2. For [10c][BF4]2, a broad
vinylidene proton signal is observed at δ ) 4.25 ppm, and the
31P analysis displays two singlets at δ ) 42.9 and 37.6 ppm for
the allenylidene and vinylidene moieties, respectively. The Rud
Reactivity: Protonation and Deprotonation Reactions. The
amphoteric behavior of allenylidene species bearing at least one
methyl group on the Cγ atom of cumulenic chain was previously
reported.31b Deprotonation of the methyl group leads to an
alkenyl acetylide while protonation on the Câ atom provides
an alkenyl carbyne group. As complexes [3][PF6], [5a-c][BF4],
and [7][OTf] all display an allenylidene character and present
protons on the Cδ positions, their protonation-deprotonation
occurred to be an interesting field to investigate. The sequence
was applied to the symmetrical compound [5a][BF4] and to the
unsymmetrical complex [5c][BF4].71
First of all, deprotonation were performed using 1 equiv of
DBU in CH2Cl2. The deeply colored cationic complexes [5a,c]-
[BF4] quickly led to pale yellow solutions consistent with the
loss of the cumulenic character. In accord with Mulliken charges
of [5a,c]+ (Table S1), deprotonation occurs on the Cδ position
to form the bis(acetylide) 9a,c. However, the product is highly
reactive, and attempts of purification to remove the salts led to
the partial reprotonation. Nevertheless, the crude products were
2
C resonances at δ ) 284.2 and 345.5 ppm (quint, JPC ) 14
Hz) are also consistent with that attribution, the13C analysis
showing seven different signals for the unsaturated bridges.
Two-dimensional 1H-13C NMR studies and analogies with other
ruthenium complexes suggest that the allenylidene side is the
one with the phenyl group. IR spectroscopy confirms the
allenylidene character with a characteristic vibration stretch
(1905 cm-1).
(69) For examples, see: (a) Ribou, A. C.; Launay, J.-P.; Sachtleben, M.; Li,
H.; Spangler, C. W. Inorg. Chem. 1996, 35, 3735-3741. (b) Barlow, S.;
Risko, C.; Chung, S.-J.; Tucker, N. M.; Coropceanu, V.; Jones, S. C.; Levi,
Z.; Bre´das, J.-L.; Marder, S. R. J. Am. Chem. Soc. 2005, 127, 16900-
16911.
(70) Maurer, J.; Winter, R. F.; Sarkar, B.; Fiedler, J.; Zalis, S. Chem. Commun.
2004, 1900-1901.
(71) The results of the reactions were not clear with the annelated [3][PF6] and
the C9 [7][OTf] complexes leading to mixtures of unidentified products.
The second protonation takes place on the other Câ position
to lead to deep blue carbyne-vinylidene complexes, with an
9
5872 J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006

C7 and C9 Carbon-Rich Bridges
A R T I C L E S
Scheme 6. Protonation and Deprotonation Sequences for [5a,c][BF4].
excess of HBF4‚Et2O. The delocalized symmetrical structure
of [11a][BF4]3 is supported by NMR evidence, and the actual
formula is intermediate between the mesomeric form sketched
in Scheme 6 and the other one giving the carbyne form to the
other metal. Indeed, the 31P NMR shows a singlet for the eight
phosphorus atoms at high field (δ ) 34.6 ppm), as expected
are the reactive sites, giving to these systems a high potential
to build a variety of carbon-rich bridges for molecular wire
systems. The nature and the stability of the bimetallic complexes
allow their studies in different redox states for the first time
with odd numbered species by means of EPR, IR, UV-vis,
and NIR spectroscopies and computational studies (DFT). They
established for the C7 species that the more polar “w” shaped
configuration is preferred for nonannelated compounds in the
polar solvent in which the complexes are soluble. More
importantly, they show (1) that in the reduced state the single
electron is delocalized mainly over the carbon chain with very
little metal contribution, whereas in the oxidized form the odd
electron is fully delocalized over the chain and the metal centers
(class III), over a distance of almost 12 Å, and (2) that all species
exhibit similar spin distribution in each redox state with no
tendency for spin localization on one of the halves. The
reactivity toward protonation and deprotonation of some com-
pounds was also examined and led to unique bis(acetylides),
vinylidene-allenylidene, or carbyne-vinylidene species.
If the present work evidences that this kind of carbon chain
serves as a molecular wire to delocalize the unpaired electron
over the bridging ligand in an oxidation or a reduction process,
it also confirms that a long chain with more than seven conju-
gated carbon atoms is not as suitable for a molecular wire given
the high reactivity of the reduced and oxidized forms. As mono-
metallic ruthenium complexes containing two carbon-rich chains
have been found to promote very efficient electronic com-
munication between the chains in either oxidation and reduction
processes, the potential ability of this bimetallic system for trans
chlorine atom substitution with an acetylide or a cumulenic chain
makes them very attractive building blocks for one-dimensional
nanoscaled organometallic conductive rod networks.
1
for a carbyne contribution. The H NMR spectrum displays a
signal at δ ) 5.95 ppm for the two â hydrogen atoms and one
at -0.74 ppm for the methyl groups due to the shielding of the
dppe ligands in close proximity.31b In the case of [11c][BF4]3,
the carbyne function is rather localized on the methyl group
side as evidenced by its high field 1H methyl chemical shift (δ
) -0.94 ppm), certainly for steric reasons.31b IR spectroscopy
confirms the disappearance of the characteristic allenylidene
vibration stretches, but no characteristic carbyne stretches were
observed. The â proton is very acidic, and addition of a very
weak base such as acetone or diethyl ether led to the regenera-
tion of [10a,c][BF4]2. Therefore isolation the carbyne-vinylidene
ruthenium was not possible. UV-vis studies show that the small
high energy band of [5a,c][BF4] is not markedly affected by
the protonation processes and is maybe present in the depro-
tonated forms. In contrast, the low energy band is slightly shifted
and less intense and displays a new shoulder on the high energy
side after the first protonation (Figure 9, Table 7). The second
one produces a more significant blue shift, as a consequence of
the carbyne formation. These broad bands clearly include several
transitions and are consistent with our previous observation on
other carbyne species.31b
Conclusion. This work presents two easy methods to prepare
cationic C7 and C9 carbon-rich bimetallic complexes with
original topologies and a charge delocalized over the two metal
centers, starting from simple polyyne and allenylidene precur-
sors. The proposed mechanisms for these reactions arise from
an unusual reactivity of the polyynyl ruthenium complexes that
are protonated at the terminal carbon atom to generate a
cumulenic intermediate, and especially the novel hexapentae-
nylidene species, reactive toward nucleophilic carbon-rich
systems. The originality of these ruthenium complexes is that
the terminal triple or double bond of polyynes and cumulene
Experimental Section
General Comments. The reactions were carried out under an inert
atmosphere using the Schlenk techniques. Solvents were freshly distilled
under argon using standard procedures. TBAHP was recrystallized from
methanol. Electrochemical studies were carried out under argon using
an Eco Chemie Autolab PGSTAT 30 potentiostat (CH2Cl2, 0.1 M Bu4-
9
J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006 5873

A R T I C L E S
Rigaut et al.
NPF6), the working electrode was a Pt disk, and ferrocene was the
internal reference. EPR spectra were recorded with an ESP300E
spectrometer (BRUKER) operating at X-band and equipped with a
standard rectangular cavity (TE 102). An ESR900 cryostat (Oxford
Instruments) was used for the low-temperature measurements. Computer
simulations of the EPR spectra were performed with the help of
Simfonia (BRUKER) and WINSIM (NIEH Public Software72) soft-
wares. Prior to recording their EPR spectra, the singly oxidized
complexes were generated in situ in a homemade cell. The electrolysis
under argon atmosphere was performed at controlled potential with a
three electrode configuration (platinum wire working electrode, platinum
wire auxiliary electrode, and Ag wire as pseudo reference electrode).
A dilute solution (ca. 10-3 M) of the precursor complexes was prepared
with TBAHP (0.1 M) as the supporting electrolyte. The oxidation
potentials were calibrated upon performing cyclic voltammetry before
electrolysis. Neutral radicals were generated by chemical reaction at
room temperature with cobaltocene. cis-[(dppe)2RuCl2],73 [(dppe)2RuCl]-
[BF4] ([1][BF4]), [(dppe)2RuCl][OTf],74 trans-[Cl(dppe)2RusCtCs
CtCsSiMe3](2a), trans-[Cl(dppe)2RusCtCsCtCsH](2b), trans-
[Cl(dppe)2RusCtCsCtCsCtCsSiMe3](6),31a and Ph(C2H5)C(OH)s
CtCH75 were prepared as previously reported.
300.13 MHz, 297 K): δ ) 7.47 to 7.02 (80H, Ph), 5.07 (s, 1H), 2.78
(m, 4H, PCH2CH2P), 2.65 (m, 4H, PCH2CH2P), 2.06 (s, 2H). 13C{1H}
NMR (CDCl3, 75.47 MHz, 297 K): δ ) 284.4 (quint., RusC, 2J(P,C)
) 14 Hz), 166.40 (s, C2), 147.38 (s, C3), 139.88 (s, (CH)C4), 147.43-
1
127.89 (Ph), 49.02 (s, (CH2)C4′), 30.32 (m, PCH2CH2P, | J(P,C) +
3J(P,C)| ) 23 Hz). IR (KBr): υ ) 1909 (s., dCdCdC), 838 (s., PF)
cm-1. HR-MS FAB+ (m/z): 1965.3107 ([M]+, calcd: 1965.3112).
trans-[Cl(dppe)2RudCdCdCsCHdC(CH2)sCtC-Ru(dppe)2Cl]-
OTf ([3][OTf]): In a Schlenk tube containing 2a (300 mg, 0.3 mmol)
in CH2Cl2 (10 mL), a solution of triflic acid (15 µL, 0.16 mmol) in
CH2Cl2 (10 mL) was added. The solution was stirred during 16 h at
room temperature. The solution was evaporated, and the residue was
washed with diethyl ether (3 × 25 mL). After crystallization in a
dichloromethane/pentane mixture, 225 mg of dark purple crystals of
[3][OTf] were obtained (71%). 31P{1H} NMR (CDCl3, 121.47 MHz,
297 K): δ ) 44.58 (s., PPh2). 1H NMR (CDCl3, 300.13 MHz, 297 K):
δ ) 7.50 to 7.05 (80H, Ph), 5.10(s, 1H), 2.82 (m, 8H, PCH2CH2P),
2.13 (s, 2H). 13C{1H} NMR (CDCl3, 75.47 MHz, 297 K): δ ) 284.55
(quint., Ru-C, 2J(P,C) ) 14 Hz), 166.52 (s, C2), 147.44 (s, C3), 139.95
(s, (CH)C4), 147.39-127.87 (Ph), 49.07 (s, (CH2)C4′), 30.38 (m, PCH2-
1
3
CH2P, | J(P,C) + J(P,C)| ) 23 Hz). IR (KBr): υ ) 1908 (s., ) Cd
CdC) cm-1; HR-MS FAB+ (m/z): 1965.3126 ([M]+, calcd: 1965.3112).
Computational Details: DFT calculations have been performed
with the Amsterdam Density Functional package (ADF 2004.01).76,77
Simplified molecules were used in order to reduce computational effort.
The phenyl groups of the dppe ligands were replaced by hydrogen
Alternative Route to [3][OTf] with [4d][OTf]: In a Schlenk tube,
2a (300 mg, 0.3 mmol) and [4d][OTf] (192 mg, 0.15 mmol) were
dissolved in CH2Cl2 (50 mL). The solution was further stirred during
2 days at room temperature before evaporation, and the residue was
washed with diethyl ether (3 × 25 mL). After crystallization in a
dichloromethane/pentane mixture, 206 mg of dark purple crystals of
[3][OTf] were obtained (65%). Complex trans-[Cl(dppe)2RusCtCs
C(Ph)dCHPh] (8d) was identified as a coproduct with two diastere-
oisomers Z and E. 31P{1H} NMR (CDCl3, 121.47 MHz, 297 K): δ )
49.9 and 44.6 (s, PPh2). 1H NMR (CDCl3, 300.13 MHz, 297 K): δ )
7.65-6.75 (m, 45H, Ph), 6.35 (s, 1H, CH, 60%), 5.77 (s, 1H, CH, 40%),
2.85-2.45 (m, 8 H, CH2). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K):
atoms. The geometries of 2b, [2b]+, [3]n+, [5a-I]n+, [5b-I]n+, [5c-I]n+
,
[5b-II]n+, [5a-III]n+, [5b-III]n+, and [5c-III]n+ (n ) 0-2) were fully
optimized without constraints (C1 symmetry). This was done using the
generalized gradient approximation potential BP8678 and the analytical
gradient method implemented by Verluis and Ziegler.79 The atom
electronic configurations were described by a triple-ú Slater-type orbital
(STO) basis set for H 1s, C 2s and 2p, and P 3s and 3p augmented
with a 3d single-ú polarization for C and P atoms and with a 2p single-ú
polarization for H atoms. A triple-ú STO basis set was used for Ru 4d
and 5s augmented with a single-ú 5p polarization function for Ru. A
frozen-core approximation was used to treat the core shells up to 1s
for C, 2p for P, and 4p for Ru.1 Spin-unrestricted calculations were
performed for all the open-shell systems. Representations of the
molecular structures and orbitals and spin densities were done using
MOLEKEL4.3.80
2
δ ) 131.01 (quint., RusCtCs, J(P,C) ) 14 Hz, the oher one is
masked by the phenyl groups), 136.93-127.16 (Ph), 128.38 and 128.07
(RusCtCsC), 128.26 and 126.63 (CH), 118.27 and 113.67 (Rus
1
3
CtCs), 30.50 and 28.60 (m, PCH2CH2P, | J(P,C) + J(P,C)| ) 23
Hz). IR (KBr): υ ) 2037 (CtC), 1596 (CdC) cm-1. HR-MS FAB+
(m/z): 1136.2310 ([M]+, calcd: 1136.2299).
trans-[Cl(dppe)2RudCdCdCsCHdC(CH2)sCtC-Ru(dppe)2Cl]-
PF6 ([3][PF6]): In a Schlenk tube, 2a (527 mg, 0.5 mmol) and
ferrocenium salt [FeCp2]PF6 (83 mg, 0.25 mmol) were dissolved in
THF (50 mL). The solution was stirred during 8 h at room temperature.
After filtration, the solution was evaporated, and then the residue was
washed with diethyl ether. After crystallization in a dichloromethane/
pentane mixture, 395 mg of dark purple crystals of [3][PF6] were
obtained (75%). 31P{1H} NMR (CDCl3, 121.47 MHz, 297 K): δ )
44.81 (s., PPh2), -143.95 (sept., 1J(P,F) ) 715 Hz). 1H NMR (CDCl3,
trans-[Cl(dppe)2RudCdCdC(CH3)2]BF4 ([4a][BF4]): In a Schlenk
tube, [(dppe)2RuCl]BF4 (400 mg, 0.4 mmol) and (CH3)2C(OH)sCt
CH (81 mg, 1.00 mmol) were dissolved in CH2Cl2 (40 mL). The
solution was stirred during 18 h at room temperature. After filtration,
the solution was evaporated and then the residue was washed with
diethyl ether (3 × 25 mL). Further crystallization in a dichloromethane/
pentane mixture led to 356 mg of dark crystals (82%). 31P{1H} NMR
(121 MHz, CD2Cl2, 297 K): δ ) 42.2 (s, PPh2). 1H NMR (300 MHz,
CD2Cl2, 297 K): δ ) 7.38-6.78 (m, 40H, Ph), 2.60-3.00 (m, 8 H,
CH2), 1.26 (s, 6H, CH3). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ
) 319.67 (quint., 2J(P,C) ) 14 Hz, CR), 201.21 (s, Câ), 175.80 (s, Cγ),
(72) National Institute of Environmental Health Sciences, Public EPR Software
Tools, version 0.98. http://EPR.niehs.nih.gov/.
1
(73) Chaudret, B.; Commengues, G.; Poilblanc, R. J. Chem. Soc., Dalton Trans.
1984, 1635-1639.
133.75-127.87 (Ph), 35.86 (CH3), 29.19 (m, PCH2CH2P, | J(P,C)
3J(P,C)| ) 23 Hz, CH2). IR (KBr): υ ) 1958 (dCdCdC), 1059
+
(74) Polam, J. R.; Porter, L. C. J. Coord. Chem. 1993, 29, 109-119.
(75) O’Hagan, D.; Zaidi, N. A. J. Chem. Soc., Perkin Trans. 1 1992, 947-949.
(76) ADF2004.01, Theoretical Chemistry, Vrije Universiteit: Amsterdam, The
Netherlands, SCM.
(BF) cm-1. HR-MS FAB+ (m/z): 999.1928 ([M]+, calcd: 999.1908).
Elemental analysis (%) for C57H54P4F4ClBRu: C, 62.99; H, 5.22
(Calcd: C, 63.02; H, 5.01).
(77) (a) Baerends, E. J.; Ellis, D. E.; Ros, P. Chem. Phys. 1973, 2, 41-51. (b)
te Velde, G.; Baerends, E. J. J. Comput. Phys. 1992, 99, 84-98. (c) Fonseca
Guerra, C.; Snijders, J. G.; te Velde, G.; Baerends, E. J. Theor. Chem.
Acc. 1998, 99, 391-403. (d) Bickelhaupt, F. M.; Baerends, E. J. ReV.
Comput. Chem. 2000, 15, 1-86. (e) te Velde, G.; Bickelhaupt, F.; Fonseca
Guerra, C.; van Gisbergen, S. J. A.; Baerends, E. J.; Snijders, J. G.; Ziegler,
T. J. Comput. Chem. 2001, 22, 931-967.
(78) (a) Vosko, S. D.; Wilk, L.; Nusair, M. Can. J. Chem. 1990, 58, 1200-
1211. (b) Becke, A. D. J. Chem. Phys. 1986, 84, 4524-4529. (c) Becke,
A. D. Phys. ReV. A 1988, 38, 3098-3100. (d) Perdew, J. P. Phys. ReV. B
1986, 33, 8822-8824. Ibid 34, 7406.
(79) Verluis, L.; Ziegler, T. J. Chem. Phys. 1988, 88, 322-328.
(80) Flu¨kiger, P.; Lu¨thi, H. P.; Portmann, S.; Weber, J. Molekel 4.1; Swiss Center
for Scientific Computing: Manno, 2002.
trans-[Cl(dppe)2RudCdCdC(CH3)2]OTf ([4a][OTf]): The pro-
cedure was identical with that for [4a][BF4] with [(dppe)2RuCl]OTf
(540 mg, 0.54 mmol) and (CH3)2C(OH)sCtCH (81 mg, 1.00 mmol)
and yielded 526 mg of dark crystals (85%).31P{1H} NMR (121 MHz,
1
CD2Cl2, 297 K): δ ) 42.3 (s, PPh2). H NMR (300 MHz, CD2Cl2,
297 K): δ ) 7.41-6.95 (m, 40H, Ph), 2.60-3.00 (m, 8 H, CH2), 1.26
(s, 6H, CH3). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ ) 318.81
2
2
(quint., J(P,C) ) 14 Hz, CR), 200.90 (quint., J(P,C) ) 2.5 Hz, Câ),
173.88 (s, Cγ), 132.66-126.83 (Ph), 34.82 (CH3), 28.17 (m, PCH2-
9
5874 J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006

C7 and C9 Carbon-Rich Bridges
A R T I C L E S
1
3
1
CH2P, | J(P,C) + J(P,C)| ) 23 Hz, CH2). IR (KBr): υ ) 1959 (d
CdCdC) cm-1. HR-MS FAB+ (m/z): 999.1935 ([M]+, calcd: 999.1908).
trans-[Cl(dppe)2RudCdCdC(CH3)Ph]BF4 ([4b][BF4]): The pro-
cedure was identical with that for [4a][BF4] with [(dppe)2RuCl]BF4
(408 mg, 0.4 mmol) and Ph(CH3)C(OH)-CtCH (147 mg, 1.00 mmol)
and yielded 417 mg of dark red crystals (91%). 31P{1H} NMR (121
MHz, CD2Cl2, 297 K): δ ) 40.4 (s, PPh2). 1H NMR (300 MHz, CD2-
Cl2, 297 K): δ ) 7.60-7.00 (m, 45H, Ph), 2.70-3.2 (m, 8 H, CH2),
1.55 (s, 3H, CH3). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ )
(s, PPh2). H NMR (300 MHz, CD2Cl2, 297 K): δ ) 7.41-6.83 (m,
85H, Ph), 5.79 (s, 1H, CH), 2.40-2.90 (m, 16 H, CH2), 0.92 (s, 3H,
CH3). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ ) 230.21 and
2
223.95 (quint., J(P,C) ) 14 Hz, CR and CR′), 162.61 (s, Câ′ methyl
side), 162.22 (s, Câ phenyl side), 153.61 (Cγ′ methyl side), 145.76 (s,
Cγ phenyl side), (s, Cγ and Cγ′), 137.91 (s, CH), 151.73-127.71 (Ph),
1
3
30.83 and 29.78 (m, PCH2CH2P, | J(P,C) + J(P,C)| ) 23 Hz, CH2),
25.97 (CH3). IR (KBr): υ ) 1897 (dCdCdC), 1988, 1054 (BF) cm-1
;
HR-MS FAB+ (m/z): 2043.3657 ([M]+, calcd: 2043.3581). Elemental
analysis (%) for C118H105P8Cl2Ru2BF4: C, 66.26; H, 5.31 (Calcd: C,
66.52; H, 4.97).
2
310.57 (quint., J(P,C) ) 14 Hz, CR), 210.19 (s, Câ), 162.18 (s, Cγ),
1
142.88-128.26 (Ph), 31.94 (CH3), 29.06 (m, PCH2CH2P, | J(P,C) +
3(P,C)| ) 23 Hz, CH2). IR (KBr): υ ) 1932 (dCdCdC), 1056 (BF)
cm-1. HR-MS FAB+ (m/z): 1061.2076 ([M]+, calcd: 1061.2079).
Elemental analysis (%) for C62H56P4F4ClBRu: C, 64.82; H, 5.05
(Calcd: C, 64.85; H, 4.92).
trans-[Cl(dppe)2RudCdCdC(CH3)sC(CH3)dC(Ph)sCtCs
Ru(dppe)2Cl]BF4 ([5c][BF4]): The procedure was identical with that
for [5a][BF4] with 4b (200 mg, 0.16 mmol) and acetylide 2b (172 mg,
0.2 mmol) and yielded 287 mg of dark green crystals (82%). 31P{1H}
NMR (121 MHz, CD2Cl2, 297 K): δ ) 49.6 (s, PPh2), 43.8 (s, PPh2).
1H NMR (300 MHz, CD2Cl2, 297 K): δ ) 7.68-6.40 (m, 85H, Ph),
2.40-3.00 (m, 16 H, CH2), 1.27 (s, 3H, central CH3), 1.06 (s, 3H,
other CH3). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ ) 245.26
and 220.37 (quint., 2J(P,C) ) 14 Hz, CR and CR′), 170.47 (s, Câ phenyl
side), 158.22 (s, Câ′ methyl side), 157.99 (s, Cγ phenyl side), 146.64
(Cγ′ methyl side), 152.11 (s, CδsCH3), 145.52-127.56 (Ph), 31.01 and
28.97 (m, PCH2CH2P, | J(P,C) + J(P,C)| ) 23 Hz, CH2), 30.70 (s,
CγsCH3), 22.47 (CδsCH3), IR (KBr): υ ) 1889 (dCdCdC), 1981,
1055 (BF) cm-1. HR-MS FAB+ (m/z): 2058.3908 ([M]+, calcd:
2058.3781). Elemental analysis (%) for C119H107P8Cl2Ru2BF4: C, 66.49;
H, 5.06 (Calcd: C, 66.64; H, 5.03).
trans-[Cl(dppe)2RudCdCdC(CH2CH3)Ph]BF4 ([4c][BF4]): The
procedure was identical with that for [4a][BF4] with [(dppe)2RuCl]-
BF4 (306 mg, 0.30 mmol) and Ph(C2H5)C(OH)sCtCH (112 mg, 0.75
mmol) and yielded 280 mg of dark red crystals (80%). 31P{1H} NMR
(121 MHz, CD2Cl2, 297 K): δ ) 40.1 (s, PPh2). 1H NMR (300 MHz,
CD2Cl2, 297 K): δ ) 7.55-6.82 (m, 45H, Ph), 2.70-3.20 (m, 8 H,
CH2), 2.24 (quad., J(H,H) ) 7 Hz, 2H, CH2), 1.10 (t., J(H,H) ) 7
Hz, 3H, CH3). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ ) 311.76
(quint., 2J(P,C) ) 14 Hz, CR), 210.02 (s, Câ), 169.75 (s, Cγ), 142.81-
3
3
1
3
1
128.24 (Ph), 38.51 (CH2sCH3), 29.27 (m, PCH2CH2P, | J(P,C) +
3J(P,C)| ) 23 Hz, CH2), 12.75 (CH3). IR (KBr): υ ) 1933 (dCdCd
C), 1979, υ ) 1062 (BF) cm-1. HR-MS FAB+ (m/z): 1075.2231 ([M]+,
calcd: 1075.2236). Elemental analysis (%) for C63H58P4F4ClBRu: C,
65.14; H, 5.11 (Calcd: C, 65.10; H, 5.03).
trans-[Cl(dppe)2RudCdCdC(CH3)sCHdC(CH3)sCtCsCt
CsRu(dppe)2Cl]BF4 ([7][OTf]): In a Schlenk tube, [4a][OTf] (173
mg, 0.16 mmol) was dissolved in CH2Cl2 (30 mL). In another tube,
acetylide 6 (184 mg, 0.16 mmol) was also dissolved in CH2Cl2 (100
m)L. This solution was slowly added to the first one over 3 days using
a dropping funnel. This mixture was further stirred during 19 days at
room temperature. After filtration, the solution was evaporated, and
then the residue was washed with diethyl ether (3 × 25 mL).
Crystallizations in a CH2Cl2/pentane mixture yielded 169 mg of dark
purple crystals of 7 (49%). 31P{1H} NMR (121 MHz, CD2Cl2, 297 K):
δ ) 48.4 and 43.9 (s, PPh2). 1H NMR (300 MHz, CD2Cl2, 297 K): δ
) 7.50-6.82 (m, 80H, Ph), 4.91 (s, 1H, CH), 2.40-2.40 (m, 16 H,
CH2), 2.03 (s, 3H, CH3), 1.64 (s, 3H, CH3). 13C{1H} NMR (75 MHz,
CD2Cl2, 297 K): δ ) 243.53 (RudC), 186.13 (RudCdC), 152.44
(CH), 141.83 (RudCdCdC), 135.71-127.56 (Ph), 121.41 (quad., CF3,
1J(C,F) ) 321 Hz), 119.28 (RusCtCsCtC, RusCtC and Rus
CtC not observed), 108.95 (RusCtCsCtC), 91.30 (CtCsC(CH3),
trans-[Cl(dppe)2RudCdCdC(CH2Ph)Ph]OTf ([4d][OTf]): The
procedure was identical with that for [4a][BF4] with [(dppe)2RuCl]-
OTf (540 mg, 0.54 mmol) and PhCH2(Ph)C(OH)sCtCH (290 mg,
1.2 mmol) and yielded 528 mg of dark crystals (80%). 31P{1H} NMR
(121 MHz, CD2Cl2, 297 K): δ ) 42.4 (s, PPh2). 1H NMR (300 MHz,
CD2Cl2, 297 K): δ ) 7.75-6.75 (m, 50H, Ph), 3.45 (s, 2H, CH2),
2.60-3.10 (m, 8 H, CH2). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K):
δ ) 311.4 (quint., 2J(P,C) ) 14 Hz, CR), 215.4 (s, Câ), 162.66 (s, Cγ),
1
142.90-127.10 (Ph), 48.87 (CH2), 29.12 (m, PCH2CH2P, | J(P,C) +
3J(P,C)| ) 23 Hz, CH2). IR (KBr): υ ) 1929 (dCdCdC). HR-MS
FAB+ (m/z): 1137.2390 ([M]+, calcd: 1137.2378). Elemental analysis
(%) for C68H60P4F3ClO3SRu: C, 64.25; H, 5.01 (Calcd: C, 64.07; H,
4.75).
trans-[Cl(dppe)2RudCdCdC(CH3)sCHdC(CH3)sCtCsRu-
(dppe)2Cl]BF4 ([5a][BF4]): In a Schlenk tube, [4a][BF4] (200 mg,
0.17 mmol) was dissolved in CH2Cl2 (30 mL). In another tube, 2b
(184 mg, 0.17 mmol) was dissolved in CH2Cl2 (100 mL). This solution
was slowly added to the first one over 3 days using a dropping funnel.
This mixture was further stirred during 3 days at room temperature.
After filtration, the solution was evaporated, and then the residue was
washed with diethyl ether (3 × 25 mL). Crystallizations in a CH2Cl2/
pentane mixture yielded 306 mg of dark green crystals (85%). 31P-
{1H} NMR (121 MHz, CD2Cl2, 297 K): δ ) 47.1 (s, PPh2). 1H NMR
(300 MHz, CD2Cl2, 297 K): δ ) 7.35-6.95 (m, 80H, Ph), 5.50 (s,
1H, CH), 2.40-2.90 (m, 16 H, CH2), 1.35 (s, 6H, CH3). 13C{1H} NMR
(75 MHz, CD2Cl2, 297 K): δ ) 224.20 (quint., 2J(P,C) ) 14 Hz, CR),
157.10 (s, Câ), 152.50 (s, CH), 137.4 (s, Cγ), 135.65-127.76 (Ph),
31.02 and 30.44 (m, PCH2CH2P, | J(P,C) + 3J(P,C)| ) 23 Hz), 29.08
1
(RutCsCHdC(CH3)), 21.72 (CδsCH3). IR (KBr): υ ) 1893 (dCd
CdC), 2078 (CtC), 2023, 1963 cm-1; HR-MS FAB+ (m/z): 2005.3439
([M]+, calcd: 2005.3425).
trans-[Cl(dppe)2RusCtCsC(dCH2)sCH(CH3)dC(CH3)sCt
CsRu(dppe)2Cl] (9a). In a Schlenk tube, [5a][BF4] (40 mg, 0.02
mmol) was dissolved in CH2Cl2 (10 mL). Slow addition of a DBU
solution (4.9 mL, 4 × 10-6 mol L-1) led to the discoloration of the
green solution. After further stirring for 1 h at room temperature, the
mixture was evaporated to dryness. The brown solid was washed with
pentane (10 mL). 31P{1H} NMR (121 MHz, CD2Cl2, 297 K): δ )
1
51.0 and 49.8 (s, PPh2). H NMR (300 MHz, CD2Cl2, 297 K): δ )
8.01-6.78 (m, 80H, Ph), 5.48 (s, 1H), 4.70 (d, 1H, CH, 2J(H,H) ) 3.3
Hz), 4.65 (d, 1H, CH, 2J(H,H) ) 3.3 Hz), 2.40-2.90 (m, 16 H, CH2),
1.73 (s, 3H, CH3). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ )
137.55-126.49 (Ph), 124.19 (RusCtCsCCH3), 127.83 (CH), 119.56
(quint., RusCtC, 2J(P,C) ) 15 Hz, only one CR is observed), 118.50
(RusCtCsCCH3, only one Câ is observed), 114.45 (dCH2), 115.10
30.20 (m, PCH2CH2P, | J(P,C) + 3J(P,C)| ) 23 Hz, CH2), 29.74 (CH3).
1
IR (KBr): υ ) 1903 (dCdCdC), 1995, 1054 (BF) cm-1. HR-MS
FAB+ (m/z): 1981.3527 ([M]+, calcd: 1981.3463). Elemental analysis
(%) for C113H103P8Cl2Ru2BF4: C, 65.85; H, 5.18 (Calcd: C, 65.61; H,
5.02).
trans-[Cl(dppe)2RudCdCdC(CH3)sCHdC(Ph)sCtCs
Ru(dppe)2Cl]BF4 ([5b][BF4]): The procedure was identical with that
for [5a][BF4] with [4b][BF4] (200 mg, 0.17 mmol) and acetylide 2b
(174 mg, 0.05 mmol) and yielded 352 mg of dark green crystals (79%).
31P{1H} NMR (121 MHz, CD2Cl2, 297 K): δ ) 47.0 (s, PPh2), 49.7
1
(RusCtCsCdCH2), 30.77 and 30.60 (m, PCH2CH2P, | J(P,C) +
3J(P,C)| ) 23 Hz), 26.54 (CH3). IR (KBr): υ ) 2045 (CtC), 1645
(CdC) cm-1
.
trans-[Cl(dppe)2RusCtCsC(dCH2)sC(CH3)dCPhsCtCs
9
J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006 5875

A R T I C L E S
Rigaut et al.
2
Ru(dppe)2Cl] (9c). In a Schlenk tube, [5c][BF4] (40 mg, 0.02 mmol)
was dissolved in CH2Cl2 (10 mL). Slow addition of a DBU solution
(4.8 mL, 4 × 10-6 mol L-1) led to the discoloration of the green
solution. After further stirring for 1 h at room temperature, the mixture
was evaporated to dryness. The brown solid was washed with pentane
(10 mL). 31P{1H} NMR (121 MHz, CD2Cl2, 297 K): δ ) 52.3 and
CD2Cl2, 297 K): δ ) 345.47 (quint., RudCdCH, J(P,C) ) 15 Hz),
2
284.16 (quint., RudCdCdCPh, J(P,C) ) 15 Hz), 204.47 (RudCd
CdCPh), 161.40 (RudCdCdCPh), 145.06 (RudCdCHsC), 136.85
(Cδ), 148.06-127.00 (Ph), 115.82 (RudCdCH), 29.14 and 28.99 (m,
PCH2CH2P, | J(P,C) + 3J(P,C)| ) 21 Hz), 25.22 (CγsCH3), 20.71 (Cδs
1
CH3). IR (KBr): υ ) 1905 (CdCdC) cm-1
.
1
52.1 (s, PPh2). H NMR (300 MHz, CD2Cl2, 297 K): δ ) 7.96-6.69
trans-[Cl(dppe)2RutCsCHdC(CH3)sCHdC(CH3)sHCdCd
Ru(dppe)2Cl](BF4)3 ([11a][BF4]3). In an NMR tube containing [5a]-
[BF4] (8 mg, 0.01 mmol) and CD2Cl2 (0.5 mL), HBF4‚Et2O (54% in
Et2O, 5 µL, 4 equiv) was added. The blue solution turned to purple.
2
(m, 85H, Ph), 4.73 (d, 1H, CH, J(H,H) ) 2.9 Hz), 4.31 (d, 1H, CH,
2J(H,H) ) 2.9 Hz), 2.40-2.90 (m, 16 H, CH2), 1.56 (s, 3H, CH3).
13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ ) 143.79-124.21 (Ph),
136.9 (RusCtCsCdCH2), 129.62 (RusCtCsCPh), 124.15 (Cs
CH3), 119.19 (quint., RusCtC, 2J(P,C) ) 15 Hz, only one CR is
observed), 117.65 (RusCtCsCPh), 116.18 (dCH2), 115.97 (Rus
31P{1H} NMR (121 MHz, CD2Cl2, 297 K): δ ) 34.6 (s, PPh2). H
1
NMR (300 MHz, CD2Cl2, 297 K): δ ) 7.70-5.80 (m, 85H, Ph), 6.25
(s, 1H, CδH), 5.95 (s, 2H, CâH), 3.10-2.70 (m, 16 H, CH2), -0.74 (s,
6H, CH3). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ ) (CR not
observed), 170.72 (Cγ), 134.05-128.55 (Ph), 124.21 (Câ), 120.19 (Cδ),
1
CtCsCdCH2), 31.24 and 30.79 (m, PCH2CH2P, | J(P,C) + 3J(P,C)|
) 21 Hz), 21.27 (CH3). IR (KBr): υ ) 2045, 2022 (CtC), 1647 (Cd
C) cm-1
.
1
3
28.98 (m, PCH2CH2P, | J(P,C) + J(P,C)| ) 21 Hz), 21.37 (CH3).
trans-[Cl(dppe)2RudCdCHsC(CH3)dCHsC(CH3)dCdCdRu-
(dppe)2Cl](BF4)2 ([10a][BF4]2). In a Schlenk tube, [5a][BF4] (40 mg,
0.02 mmol) was dissolved in CH2Cl2 (5 mL). Slow addition of a HBF4‚
Et2O solution (3.0 mL, 7.2 × 10-3 mol L-1) in CH2Cl2 led to a deep
blue coloration. After further stirring for 15 min at room temperature,
the mixture was evaporated to dryness. The blue solid was washed
with diethyl ether (2 × 10 mL), and 34 mg of [10a][BF4]2 were
recovered (85%). 31P{1H} NMR (121 MHz, CD2Cl2, 297 K): δ ) 41.1
trans-[Cl(dppe)2RutCsCHdC(CH3)sC(CH3)dCPhsHCdCd
Ru(dppe)2Cl](BF4)3 ([11c][BF4]3). In an NMR tube containing [5c]-
[BF4] (10 mg, 0.01 mmol) and CD2Cl2 (0.5 mL), HBF4‚Et2O (54% in
Et2O, 10 µL, 8 equiv) was added. The blue solution turned to purple.
31P{1H} NMR (121 MHz, CD2Cl2, 297 K): δ ) 39.3 and 34.6 (s, PPh2).
1H NMR (300 MHz, CD2Cl2, 297 K): δ ) 7.70-5.80 (m, 85H, Ph),
5.16 (s, 1H, RutCsCH), 4.60 (s, 1H, RudCdCH), 3.15-2.70 (m,
16 H, CH2), 1.48 (s, 3H, CH3), -0.94 (s, 3H, CH3). 13C{1H} NMR (75
MHz, CD2Cl2, 297 K): δ ) 326.10 (RutCsCH, RudCdCH not
observed), 172.67 (RutCsCHdC(CH3)), 163.68 (RudCdCHsCPh),
130.86 (Cδ), 124.56 (RutCsCH), 140.47-127.61 (Ph), 119.60 (Rud
1
and 32.9 (s, PPh2). H NMR (300 MHz, CD2Cl2, 297 K): δ ) 7.55-
6.85 (m, 80H, Ph), 6.04 (s, 1H, CδH), 5.96 (s, 1H, RudCdCH), 3.30-
3.00 (m, 16 H, CH2), 0.03 (s, 3H, CH3), -0.78 (s, 3H, CH3). 13C{1H}
NMR (75 MHz, CD2Cl2, 297 K): δ ) 336.31 (quint., RudCdCH,
2J(P,C) ) 15 Hz, RudCdCdC not observed), 191.75 (RudCdCd
C(CH3)), 159.53 (RudCdCdC(CH3)), 154.33 (RudCdCHsC), 128.84
(CδH), 134.28-127.78 (Ph), 120.20 (RudCdCH), 29.50 and 29.97
1
3
CdCH), 28.63 and 27.92 (m, PCH2CH2P, | J(P,C) + J(P,C)| ) 22
Hz), 25.49 (RutCsCHdC(CH3)), 22.98 (CδsCH3).
Acknowledgment. We thank the CNRS and the Universite´
de Rennes 1 for support, Dr. Claude Lapinte (UMR 6226) for
helpful discussions, and Dr. Pierre Gue´not from the Centre
Re´gional de Mesures Physiques de l’Ouest (Rennes) for structure
determination. DFT calculations were carried out at the PCIO
(Rennes), the IDRIS-CNRS (Orsay), and at the CINES-
MENESR (Montpellier).
1
(m, PCH2CH2P, | J(P,C) + 3J(P,C)| ) 21 Hz), 31.62 (RudCdCd
C(CH3)), 21.46 (RudCdCHsC(CH3)). IR (KBr): υ ) 1912 (CdCd
C) cm-1
.
trans-[Cl(dppe)2RudCdCHsC(CH3)dC(CH3)CPhdCdCdRu-
(dppe)2Cl](BF4)2 ([10c][BF4]2). In a Schlenk tube, [5c][BF4] (40 mg,
0.02 mmol) was dissolved in CH2Cl2 (5 mL). Slow addition of a HBF4‚
Et2O solution (3.0 mL, 7.2 × 10-3 mol L-1) in CH2Cl2 led to a deep
blue coloration. After further stirring for 15 min at room temperature,
the mixture was evaporated to dryness. The blue solid was washed
with diethylether (2 × 10 mL), and 32 mg of [10c][BF4]2 were
recovered (85%). 31P{1H} NMR (121 MHz, CD2Cl2, 297 K): δ ) 42.9
Supporting Information Available: Calculated Atomic Mul-
liken charges, and EPR spectra of 3a, 5c, [3]2+, and [5a,c]2+
This material is available free of charge via the Internet at
http://pubs.acs.org.
.
1
and 37.6 (s, PPh2). H NMR (300 MHz, CD2Cl2, 297 K): δ ) 7.55-
6.23 (m, 85H, Ph), 4.25 (s, 1H, CH), 3.15-2.70 (m, 16 H, CH2), 1.29
(s, 3H, CδsCH3), -0.37 (s, 3H, CγsCH3). 13C{1H} NMR (75 MHz,
JA0603453
9
5876 J. AM. CHEM. SOC. VOL. 128, NO. 17, 2006