Controlled synthesis of dinuclear acetylide-bridged ruthenium complexes

Article abstract of DOI:10.1021/om901019y

A series of dinuclear and trinuclear, acetylide-bridged ruthenium(II) complexes was synthesized by the condensation of terminal acetylenes with methyl ruthenium complexes. Dinuclear ruthenium(II) complexes trans,trans-(RC=C) Ru(dmpe)₂(μ-C=CC₆H₄C=C)Ru(C=CR')(dmpe) ₂ (R = R' = Ph; R = R/ = 'Bu; R = Ph, R' = 'Bu; R = 'Bu, R' = 3,5-'Bu₂-C₆H₃) were synthesized by the reaction of trans-(CH₃)Ru(dmpe)₂(C=CR) with the unsymmetrical bis(acetylido)ruthenium(II) complex trans-(R'C=C)Ru(dmpe)₂(C=CC ₆H₄C=CH) at ambient temperature and pressure. These complexes were fully characterized by NMR spectroscopy, and trans,trans-('BuC=C) Ru(dmpe)₂(μ-C=CC₆H₄C=C)Ru(dmpe) ₂(C=C'Bu) was characterized crystallographically. The symmetrical trinuclear ruthenium(II) complexes trans,trans,trans-(RC=C)Ru(dmpe) ₂(μ-C=CC₆H₄C=C)Ru(depe)2(μ-C=CC ₆H₄C=C)-Ru(dmpe)₂(C=CR) (R = Ph, 'Bu, SiMe ₃) were also prepared and characterized, and the redox behavior of a subset of the complexes was studied using cyclic voltammetry.

Full text of DOI:10.1021/om901019y

Organometallics 2010, 29, 957–965 957
DOI: 10.1021/om901019y
Controlled Synthesis of Dinuclear Acetylide-Bridged Ruthenium
Complexes
Leslie D. Field,*,† Alison M. Magill,† Timothy K. Shearer,† Stephen B. Colbran,†
Sang T. Lee,† Scott J. Dalgarno,‡ and Mohan M. Bhadbhade§
†School of Chemistry, University of New South Wales, Sydney, Australia, 2052, ‡School of Engineering and
Physical Sciences-Chemistry, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, U.K., and
§UNSW Analytical Centre, University of New South Wales, Sydney, Australia, 2052
Received November 24, 2009
A series of dinuclear and trinuclear, acetylide-bridged ruthenium(II) complexes was synthesized by
the condensation of terminal acetylenes with methyl ruthenium complexes. Dinuclear ruthenium(II)
complexes trans,trans-(RCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(CtCR0)(dmpe)2 (R = R0 = Ph;
R = R0 = tBu; R = Ph, R0 = tBu; R = tBu, R0 = 3,5-tBu2-C6H3) were synthesized by the reaction of
trans-(CH3)Ru(dmpe)2(CtCR) with the unsymmetrical bis(acetylido)ruthenium(II) complex
trans-(R0CtC)Ru(dmpe)2(CtCC6H4CtCH) at ambient temperature and pressure. These
complexes were fully characterized by NMR spectroscopy, and trans,trans-(tBuCtC)Ru(dmpe)2-
(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu) was characterized crystallographically. The symmetrical
trinuclear ruthenium(II) complexes trans,trans,trans-(RCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru-
t
(depe)2(μ-CtCC6H4CtC)-Ru(dmpe)2(CtCR) (R = Ph, Bu, SiMe3) were also prepared and
characterized, and the redox behavior of a subset of the complexes was studied using cyclic
voltammetry.
Introduction
luminescent,7,8 or liquid crystalline materials.9 All of these
properties depend on their extended linear structures, high
stability, and their π-electron configuration.2
Until recently, most transition-metal σ-alkynyl complexes
have been synthesized either by the reaction of an alkali-
metal alkynide or an alkaline-earth-metal alkynide RCtCM
(M = Li, Na, Mg, etc.) with a transition-metal halide
“Rigid-rod” transition-metal σ-alkynyl complexes have
been an active area of research in recent years1,2 as a
consequence of their potential applications as nonlinear
optical,3,4 electronic communication (“molecular wire”),4-6
*To whom correspondence should be addressed. Tel: þ61 2 9385
2700. Fax: þ61 2 9385 8008. E-mail: L.Field@unsw.edu.au.
(1) Manners, I. Angew. Chem., Int. Ed. 1996, 35, 1603–1621.
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2586–2617.
0
LnMXn (X = Cl, Br, I) or by the reaction of a terminal
alkyne with a transition-metal complex.2,6 When these routes
are applied to the synthesis of oligomeric or polymeric metal-
alkynyl complexes, they usually result in an uncontrolled
reaction with the formation of high molecular weight mate-
rials. Thus, the development of methods allowing controlled
(step-by-step) condensation of metal centers with acetylides
is highly desirable. The controlled formation of dimeric,
trimeric, and oligomeric complexes also permits the proper-
ties of the materials (e.g., solubility and crystal packing) to be
more easily explored and tuned.
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Adv. Organomet. Chem. 2008, 55, 61–136. (b) Whittall, I. R.; McDonagh,
A. M.; Humphrey, M. G.; Samoc, M. Adv. Organomet. Chem. 1999, 43,
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a reaction pioneered by Dixneuf and co-workers.7,10-14 We have
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Dixneuf, P. H. Organometallics 1997, 16, 184–189.
r
2010 American Chemical Society
Published on Web 01/15/2010
pubs.acs.org/Organometallics

958 Organometallics, Vol. 29, No. 4, 2010
Field et al.
Scheme 1
The chemical shift is typical of bis(acetylido)ruthenium(II) com-
plexes with the 1,2-bis(dimethylphosphino)ethane ligand.16,17
The 1H NMR spectrum confirms the 1,4-diethynylbenzene
ligand has coordinated, as the aromatic protons of the acetylide
appear as two apparent doublets in a second-order AA0XX0 spin
system and the intensity of the resonance corresponding to the
terminal alkynyl hydrogen is reduced to a single proton. Com-
plex 2a is poorly soluble in most common organic solvents, with
the exception of DCM, toluene, and THF, in which it displays
only moderate solubility.
The analogous reaction of trans-(CH3)Ru(dmpe)2-
(CtCtBu) (1b) with excess 1,4-diethynylbenzene afforded
the somewhat more soluble trans-(tBuCtC)Ru(dmpe)2-
(CtCC6H4CtCH) (2b), which was recrystallized from pen-
tane. The 31P{1H} NMR spectrum again confirms a trans
arrangement of the acetylide ligands around the ruthenium
center, while the 1H NMR spectrum is indicative of unsym-
metrical trans substitution, with the phosphorus-bound
methyl groups exhibiting two distinct resonances owing to
the unsymmetrical substitution. The structure of the com-
plex was established by X-ray crystallography (Figure 1,
Table 1).
been interested in the controlled stepwise synthesis of alkyne-
bridged oligomers via the reaction of a terminal alkyne with a
metal center and have previously described the development of a
route to mono- and bis-acetylido complexes of ruthenium(II).15
We now report the synthesis of a synthetically more elaborate
ruthenium bis(acetylide) complex and the first dinuclear and
trinuclear complexes prepared by this approach (Scheme 1).
The structure of 2b confirms the expected trans octahedral
geometry, with the metal center coordinated in the equatorial
plane by two bidentate dmpe ligands, while the axial positions
are occupied by acetylide ligands. The Ru-C bond distances
˚
˚
(Ru(1)-C(10), 2.087(5) A; Ru(1)-C(11), 2.106(5) A) are
Results and Discussion
slightly longer than previously reported for similar com-
pounds (e.g., trans-Ru(CtCPh)2(dmpe)2, 2.042(5) A;17 trans-
˚
t
15
˚
Mononuclear Complexes. We have previously reported the
synthesis of unsymmetrically substituted bis(acetylido)-
ruthenium(II) complexes bearing two different acetylide
moieties via the reaction of a methylacetylidoruthenium(II)
complex with an excess of a second terminal alkyne.15 The
methylacetylidoruthenium(II) complexes trans-(CH3)Ru(dmpe)2-
(CtCPh) (1a), trans-(CH3)Ru(dmpe)2(CtCtBu) (1b), trans-
(CH3)Ru(dmpe)2(CtCC6H3-3,5-(tBu)2) (1c), and trans-(CH3)-
Ru(dmpe)2(CtCSiMe3) (1d) were all synthesized by the reaction
of the appropriate terminal alkyne with trans-(CH3)2Ru(dmpe)2
under controlled conditions.15 The complexes 1a and 1b have
been structurally characterized previously,15 and complex 1c was
characterized crystallographically during the course of this work;
its structure is unexceptional (see Supporting Information).
Using the reaction between a methylacetylidoruthenium-
(II) complex and 1,4-diethynylbenzene, bis(acetylide) com-
plexes trans-(RCtC)Ru(dmpe)2(CtCC6H4CtCH) (R =
Ru(CtCPh)(CtC Bu)(dmpe)2, 2.056(4) and 2.074(4) A ).
This is coupled with a significant shortening of the CtC
˚
bonds inthe molecule (C(9)-C(10), 1.134(6) A; C(11)-C(12),
1.172(6) A) when compared with similar compounds (e.g.,
˚
trans-Ru(CtCPh)2(dmpe)2, 1.226(7) A;17 trans-Ru(CtCPh)-
˚
t
(CtC Bu)(dmpe)2, 1.208(6) and 1.219(6) A ).
15
˚
Dinuclear Complexes. Both trans-(PhCtC)Ru(dmpe)2-
(CtCC6H4CtCH) (2a) and trans-(tBuCtC)Ru(dmpe)2-
(CtCC6H4CtCH) (2b) are important starting materials
for the synthesis of dinuclear acetylide-bridged ruthenium(II)
complexes (Scheme 3).
Excess trans-(CH3)Ru(dmpe)2(CtCPh) (1a) was added to
a solution of 2a in toluene, followed by the addition of
methanol, to yield the symmetrical dinuclear acetylide-
bridged ruthenium(II) complex trans,trans-(PhCtC)Ru-
(dmpe)2(μ-CtCC6H4CtC)Ru(dmpe)2(CtCPh) (3a). Com-
plex 3a was purified by successive washes with a range of
organic solvents due to its relatively low solubility. All phos-
phorus groups are chemically equivalent, and the 31P{1H}
NMR spectrum shows only a singlet at δ 40.3, slightly down-
field from the starting unsymmetrical ruthenium(II) acetylide
t
Ph 2a, R = Bu 2b) were prepared, and these contain a
synthetically useful, free terminal alkyne moiety (Scheme 2).
Treatment of trans-(CH3)Ru(dmpe)2(CtCPh) (1a) (dmpe=
1,2-bis(dimethylphosphino)ethane) with excess 1,4-diethynylben-
zene in toluene, in the presence of a small quantity of methanol,
furnished trans-(PhCtC)Ru(dmpe)2(CtCC6H4CtCH) (2a) in
good yield. In the absence of methanol, the reaction does not
proceed. While the role of methanol in this reaction is still not
clear, it is possible that this more acidic solvent promotes proto-
demethylation of the complex to yield methane and an inter-
mediate ruthenium methoxide complex, where the methoxide
ligand acts as a more effective leaving group that can be displaced
by the terminal alkyne.
1
(2a). The H NMR spectrum shows the resonances for the
phosphorus-bound methyl groups are near coincident; it was
not possible to record a 13C NMR spectrum due to the low
solubility of the complex.
The symmetrical dinuclear complex trans,trans-
(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu)
(3b) was synthesized in an analogous manner. The 31P{1H}
NMR spectrum of 3b shows a single resonance slightly downfield
from the starting unsymmetrical ruthenium(II) acetylide (2b).
The 31P{1H} NMR spectrum of 2a shows a single reso-
nanceat δ 40.3 ppm, indicativeof a trans-substituted product.
(16) Day, P.; Robin, M. B. Adv. Inorg. Chem. Radiochem. 1967, 10,
247–422.
(17) Field, L. D.; George, A. V.; Hockless, D. C. R.; Purches, G. R.;
(15) Field, L. D.; Magill, A. M.; Shearer, T. K.; Dalgarno, S. J.;
Turner, P. Organometallics 2007, 26, 4776–4780.
White, A. H. J. Chem. Soc., Dalton Trans. 1996, 2011–2016.

Article
Organometallics, Vol. 29, No. 4, 2010 959
Scheme 2
Scheme 3
Figure 1. Molecular projection of trans-(tBuCtC)Ru(dmpe)2-
(CtCC6H4CtCH) (2b). Thermal ellipsoids are shown at the
50% probability level; selected hydrogen atoms have been
removed for clarity.
Table 1. Selected Bond Lengths and Angles for
trans-(tBuCtC)Ru(dmpe)2(CtCC6H4CtCH) (2b)
˚
bond length (A)
bond angle (deg)
Ru(1)-C(10)
Ru(1)-C(11)
C(9)-C(10)
C(11)-C(12)
C(1)-C(2)
2.087(5)
2.106(5)
1.134(6)
1.172(6)
1.1741
C(10)-Ru(1)-C(11)
Ru(1)-C(11)-C(12)
Ru(1)-C(10)-C(9)
C(11)-C(12)-C(13)
C(6)-C(9)-C(10)
178.44(17)
174.9(4)
178.5(4)
177.1(5)
175.2(5)
A
crystal of trans,trans-(tBuCtC)Ru(dmpe)2(μ-Ct
CC6H4CtC)Ru(dmpe)2(CtCtBu) (3b), suitable for X-ray
crystallography, was grown by slow evaporation of a solu-
tion of the complex in DCM/pentane (Figure 2, Table 2). The
complex occupies a special position in the unit cell, posses-
sing an inversion center about the center of the aromatic ring.
To the best of our knowledge, this represents the first 1,4-
diethynylbenzene-bridged diruthenium system to be crystallo-
graphically characterized.
The aromatic protons are clearly visible as a singlet in the 1H
NMR spectrum, in contrast to the aromatic resonances in the
starting material 2b, which appear as a two multiplets (an
t
AA0XX0 spin system). The Bu-substituted complex 3b is
significantly more soluble than 3a. The 13C{1H} NMR spec-
trum clearly demonstrates the C2 symmetry of the complex,
with the aryl ring displaying only two resonances: the first at δ
129.3 ppm for the protonated carbons and the second at δ
125.7 ppm for the ipso carbons. In addition, there are four
resonances corresponding to alkynyl carbons at δ 131.1,
114.1, 108.3, and 101.8 ppm.
There are some interesting comparisons between the
bonds lengths and angles of trans,trans-(tBuCtC)Ru-
(dmpe)2(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu) (3b), trans-
(tBuCtC)Ru(dmpe)2(CtCC6H4CtCH) (2b), and the pre-
viously reported trans-(tBuCtC)Ru(dmpe)2(CtCPh)15
(Table 2). The ruthenium-acetylide bond lengths of
trans,trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru-
The unsymmetrically substituted dinuclear complexes trans,
trans-(PhCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(dmpe)2-
(CtCtBu) (3c) and trans,trans-(tBuCtC)Ru(dmpe)2(μ-Ct
CC6H4CtC)Ru(dmpe)2(CtCC6H3-3,5-(tBu)2) (3d) were also
prepared using this approach.
t
˚
(dmpe)2(CtC Bu) (3b) (2.079(6), 2.056(5) A) are slightly
shorter than those of trans-(tBuCtC)Ru(dmpe)2(CtCC6-
˚
H4CtCH) (2b) (2.106(5), 2.087(5) A) and identical with
trans-(tBuCtC)Ru(dmpe)2(CtCPh) (2.074(4), 2.056(4)
˚
A), while the CtC distances of 3b (1.223(8), 1.201(9) A)
˚
In 3c and 3d, each of the ruthenium centers has a different
auxiliary acetylide group, so the set of four phosphorus
nuclei surrounding each of the ruthenium atoms is different.
Consequently, the 31P{1H} NMR spectra of complexes 3c
and 3d appear as two distinct singlet resonances of equal
intensity, corresponding to the phosphine ligands around
each of the metal centers. trans,trans-(PhCtC)Ru(dmpe)2-
(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu) (3c) exhibits dis-
tinct singlet resonances at δ 40.79 and 40.80 ppm in the
31P{1H} NMR spectrum. One phosphorus environment may
be described as having aryl acetylide moieties on both faces
of the metal complex, while the other environment has a
metal complex with one aryl and one alkyl acetylide moiety
in the two axial coordination sites.
˚
are slightly longer than those of 2b (1.172(6), 1.134(6) A).
There is a slight distortion from linearity in 2b, in parti-
cular the C(10)-C(9)-C(6) and C(12)-C(11)-Ru(1) bond
angles (175.2(5)° and 174.9(4)°, respectively), which are
significantly smaller than the expected 180°. This slight
distortion from linearity is evident in 3b also, in particular
the C(7)-C(8)-C(9) and C(8)-C(7)-Ru(1) bond angles
(172.9(7)° and 176.1(6)°, respectively). This bending of the
alkynyl core has been noted previously18,19 in dinuclear
acetylide-bridged complexes. The metal centers of 3b are
˚
separated by ca. 12.2 A.
The dinuclear ruthenium(II) complexes were also charac-
terized by high-resolution mass spectrometry (HRMS) using

960 Organometallics, Vol. 29, No. 4, 2010
Field et al.
Figure 2. Molecular projection of trans,trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu) (3b). Thermal ellipsoids
are shown at the 50% probability level, and selected hydrogen atoms have been removed for clarity.
˚
Table 2. Selected Bond Lengths (A) and Angles (deg) for trans,
trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(dmpe)2-
(CtCtBu) (3b) and trans-(tBuCtC)Ru(dmpe)2(CtCPh).15
trans-(tBuCtC)-
Ru(dmpe)2(CtCPh)
3b
Ru(1)-C(6)
2.079(6)
2.056(5)
1.223(8)
1.201(9)
179.0(9)
178.5(6)
178.0(3)
176.1(6)
172.9(7)
2.074(4)
2.056(4)
1.208(6)
1.219(6)
178.8(5)
177.1(4)
178.54(16)
176.8(4)
175.3(4)
Ru(1)-C(7)
C(5)-C(6)
C(7)-C(8)
C(4)-C(5)-C(6)
Ru(1)-C(6)-C(5)
C(6)-Ru(1)-C(7)
Ru(1)-C(7)-C(8)
C(7)-C(8)-C(9)
positive-ion electrospray ionization. The spectra clearly
show the formation of the dinuclear complexes by their
characteristic isotopic distribution pattern and their unique
m/z values. The calculated isotope distribution pattern for
trans,trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru-
(dmpe)2(CtCtBu) (3b) (C46H86P8Ru2) correlates well with
the experimental spectra (Figure 3).
The redox properties of the acetylide-bridged conjugated
complexes are closely related to their ability to act as
molecular wires.7 Consequently, cyclic voltammetry traces
(CVs) were obtained for trans,trans-(tBuCtC)Ru(dmpe)2-
(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu) (3b) and were com-
pared with its mononuclear precursor trans-(tBuCtC)Ru-
(dmpe)2(CtCC6H4CtCH) (2b) (Figure 4, Table 3). The
mononuclear complex 2b undergoes a single electron oxida-
tion step involving the RuIII/RuII couple at -0.26 V (relative
Figure 3. High-resolution mass spectrum of trans,trans-
(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu)
(3b) (C46H86P8Ru2) showing both experimental (top) and simu-
lated (bottom) spectra.
to Fcþ/Fc) as well as an irreversible process to a second oxidized
species, and this is consistent with the oxidation potentials of
similar complexes Ru(CtCPh)2(dmpe)2 and Ru(CtCC6H4Ct
CPh)2(dmpe)2.19 The dinuclear complex 3b displays two succes-
sive reversible redox processes at -0.51 and -0.22 V (in addition
to an irreversible process at higher potential) originating from
II,II
II,III
II,III
and then Ru2
successive oxidation of Ru2 to Ru2
to
Ru2III,III, respectively. The separation (280 mV) between the two
redox couples is an indicator of electronic coupling between the
metal centers, with the ΔE1/2 values being correlated to the
comproportionation constant (Kc) (defined by the expression
Kc=exp[ΔE1/2/25.69] at 298 K) and the thermodynamic stability
of the Ru2II,III mixed-valence complex.20 While it is well known
that other phenomena can contribute to redox potentials and
consequently Kc values,10,21 closely related complexes10,11,14,17,20
have demonstrated these values to be directly related to the
electronic coupling between metal centers and ligands. These
values are consistent with those of other diruthenium systems
with the 1,4-diethynylbenzene-conjugated organic bridge (Table 2).
The comproportionation constant, KC, of 5.4 ꢀ 104 for
the dinuclear complex trans,trans-(tBuCtC)Ru(dmpe)2-
(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu) (3b) suggests that
the electrogenerable RuIIRuIII monocation 3bþ belongs to
the Robin-Day “Class II” (slightly delocalized) mixed-
valent species,16 indicative of some degree of electronic
communication between the two metal centers.
(18) (a) Berenguer, J. R.; Bernechea, M.; Fornies, J.; Lalinde, E.;
Torroba, J. Organometallics 2005, 24, 431–438. (b) Chao, H. Y.; Lu, W.; Li,
Y. Q.; Chan, M. C. W.; Che, C. M.; Cheung, K. K.; Zhu, N. Y. J. Am. Chem.
Soc. 2002, 124, 14696–14706. (c) Cifuentes, M. P.; Humphrey, M. G.;
Morrall, J. P.; Samoc, M.; Paul, F.; Lapinte, C.; Roisnel, T. Organometallics
2005, 24, 4280–4288. (d) Field, L. D.; George, A. V.; Malouf, E. Y.; Slip,
I. H. M.; Hambley, T. W. Organometallics 1991, 10, 3842–3848. (e) Garcia,
A.; Lalinde, E.; Moreno, M. T. Eur. J. Inorg. Chem. 2007, 3553–3560. (f)
Khairul, W. M.; Porres, L.; Albesa-Jove, D.; Senn, M. S.; Jones, M.; Lydon,
D. P.; Howard, J. A. K.; Beeby, A.; Marder, T. B.; Low, P. J. J. Cluster Sci.
2006, 17, 65–85. (g) Lam, S. C. F.; Yam, V. W. W.; Wong, K. M. C.; Cheng,
E. C. C.; Zhu, N. Y. Organometallics 2005, 24, 4298–4305. (h) Powell, C. E.;
Cifuentes, M. P.; Humphrey, M. G.; Willis, A. C.; Morrall, J. P.; Samoc, M.
Polyhedron 2007, 26, 284–289. (i) Tao, C. H.; Zhu, N. Y.; Yam, V. W. W.
Chem. Eur. J. 2005, 11, 1647–1657. (j) Whittall, I. R.; Cifuentes, M. P.;
Humphrey, M. G.; Luther-Davies, B.; Samoc, M.; Houbrechts, S.; Persoons,
A.; Heath, G. A.; Hockless, D. C. R. J. Organomet. Chem. 1997, 549, 127–
137. (k) Whittall, I. R.; Humphrey, M. G.; Hockless, D. C. R. Aust. J. Chem.
1997, 50, 991–998. (l) Whittall, I. R.; Humphrey, M. G.; Hockless, D. C. R.
Aust. J. Chem. 1998, 51, 219–227. (m) Wong, K. M. C.; Lam, S. C. F.; Ko,
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Article
Organometallics, Vol. 29, No. 4, 2010 961
Figure 4. Cyclic voltammogram traces obtained for (a) trans-(tBuCtC)Ru(dmpe)2(CtCC6H4CtCH) (2b) and (b) trans,
trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu) (3b) in CH2Cl2 (0.1 M Bu4NPF6, v = 100 mV s-1).
Table 3. Electrochemical Data for trans-(tBuCtC)Ru(dmpe)2(CtCC6H4CtCH) (2b), trans,trans-(tBuCtC)Ru(dmpe)2(μ-
CtCC6H4CꢁC)Ru(dmpe)2(CtCtBu) (3b), and Similar Complexesa,b
complex
E1/2I (V)
E1/2II (V)
ΔE1/2 (mV)
Kcom
trans-(tBuCtC)Ru(dmpe)2(CtCC6H4CtCH) (2b)c
trans-Ru(CtCPh)2(dmpe)2
trans-Ru(CtCC6H4CtCPh)2(dmpe)2
-0.26
-0.21
-0.14
-0.51
-0.520
0.030
-0.328
-0.30
-0.24
-0.20
19
19
trans,trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu) (3b)
-0.22
-0.195
0.250
0.013
0.00
280
325
220
341
300
300
310
5.4 ꢀ 104
3.1 ꢀ 105
5.2 ꢀ 103
6.0 ꢀ 105
1.2 ꢀ 105
1.5 ꢀ 105
1.5 ꢀ 105
12
Ru2(μ-CtCC6H4CtC)(bph)2(PPh3)4
12
Ru2(μ-CtCC6H4CtC)(phtpy)2(PPh3)4[ClO4]2
13
Ru2(μ-CtCC6H4CtC)Cl2(dppe)4
11
Ru2(μ-CtCC6H4CtC)Cl2(dppm)4
7
Ru2(μ-CtCC6H4CtC)(CtCPh)(CtCC6H4NC)(dppe)4
0.06
0.11
7
Ru2(μ-CtCC6H4CtC)(CtCC6H4NC)2(dppe)4
a All E1/2 values are referenced to FeCp2. E1/2I and E1/2II are the first and second electrode potentials of the dinuclear species. ΔE1/2 = E1/2II - E1/2
.
I
b Conditions: in CH2Cl2, 0.1 M NBu4PF6, 100 mV/s scan rate, glass working electrode, Pt aux. electrode, Ag ref electrode. c This work.
Scheme 4
Trinuclear Complexes. The symmetrical trinuclear
ruthenium(II) complexes trans,trans,trans-(RCtC)Ru(dmpe)2-
(μ-CtCC6H4CtC)Ru(depe)2(μ-CtCC6H4CtC)-Ru(dmpe)2-
(CtCR) (R = Ph (4a), tBu (4b), SiMe3 (4c)) were prepared by
the reaction of 2 equiv of the appropriate acetylidomethyl-
ruthenium(II) complex trans-Ru(CH3)(CtCR)(dmpe)2 (R =
Ph (1a), tBu (1b), SiMe3 (1d)) with trans-Ru(CtCC6-
H4CtCH)2(depe)2 in toluene and methanol (Scheme 4). The
complexes obtained were poorly soluble in most organic
solvents.
trans-Ru(CtCC6H4CtCH)2(depe)2 was used as the
central unit in the complex in preference to trans-Ru-
(CtCC6H4CtCH)2(dmpe)2 to improve the solubility of
the trinuclear product. Complex solubility was expected to
be an issue, as the dinuclear complexes 3a-d synthesized
so far were relatively insoluble in many organic solvents.

962 Organometallics, Vol. 29, No. 4, 2010
Field et al.
Figure 5. High-resolution mass spectrum of trans,trans,trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(depe)2( μ-CtCC6H4CtC)-
Ru(dmpe)2(CtCtBu) (4b) (left) and trans,trans,trans-(SiMe3CtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(depe)2( μ-CtCC6H4CtC)Ru-
(dmpe)2(CtCSiMe3) (4c) (right) showing both experimental (top) and calculated (bottom) spectra.
In addition, trans-Ru(CtCC6H4CtCH)2(depe)2 is readily
available from the reaction of 1,4-diethynylbenzene with
trans-RuCl2(depe)2.17
The 31P{1H} NMR spectra of the trinuclear ruthenium(II)
complexes each displayed two singlet resonances, due to the
presence of two distinct sets of phosphine ligands (each
complex contains both dmpe and depe ligands). For example,
trans,trans,trans-(PhCtC)Ru(dmpe)2( μ-CtCC6H4CtC)-
Ru(depe)2( μ-CtCC6H4CtC)Ru(dmpe)2(CtCPh) (4a) exhi-
bited singlet resonances at δ 51.48 and 39.73 ppm. The low-field
and high-field resonances are typical of bis(acetylido)ruthenium-
(II) complexes with depe and dmpe ligands, respectively, and
the high-field resonance integrates to twice the low-field
resonance.
1
1
The H and H{31P} NMR spectra of 4a-c were signifi-
cantly more complicated than those of the dinuclear species,
mainly due to the presence of two different types of phos-
phine ligands with overlapping resonances. In most cases,
resonances were assigned using a range of 2D NMR experi-
ments, including NOESY, 1H-13C HMBC and 1H-13C
HMQC.
Figure 6. Cyclic voltammogram trace obtained for trans,trans,
trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(depe)2(μ-Ct
CC6H4CtC)Ru(dmpe)2(CtCtBu) (4b) in CH2Cl2 (0.1 M
Bu4NPF6, v = 100 mV s-1).
( μ-CtCC6H4CtC)Ru(dmpe)2(CtCtBu) (4b) (Figure 6).
The trinuclear complex, 4b, displays two successive oxida-
tion processes (in addition to a higher potential irrever-
sible process), and on the basis of peak intensities, the
second oxidation can be considered to be a result of two
overlapping one-electron processes. Closer inspection
reveals that this second process is significantly broader
(ΔEp = 120 mV) than the second oxidation couple for the
dinuclear complex 3b (ΔEp = 64 mV) and for the other
couples measured in this work (ΔEp ≈ 65 mV). This
indicates the first oxidation at -0.48 V for 4b is followed
by two one-electron couples separated by ca. 55 mV
at -0.18 and -0.13 V. The first couple is attributed to
the oxidation of the central ruthenium center (Ru3II,II,II to
Ru3II,III,II). The following consecutive, merged couples
are attributed to successive oxidations of the outer
The low solubility of the complexes hampered the acquisition
of 13C{1H} NMR spectra, and only trans,trans,trans-
(tBuCtC)Ru(dmpe)2( μ-CtCC6H4CtC)Ru(depe)2( μ-Ct
CC6H4CtC)Ru(dmpe)2(CtCtBu) (4b) was fully charac-
terized by 13C{1H} NMR spectroscopy. The 13C{1H,31P}
NMR spectrum of 4b shows six alkynyl resonances at δ
137.3, 131.2, 114.5, 111.7, 108.6, and 102.1 ppm, consistent
with the proposed C2 symmetry. The remaining spectral
data are also consistent with the proposed product (see
Experimental Section).
The trinuclear ruthenium(II) complexes were also char-
acterized by high-resolution mass spectrometry (HRMS).
The HRMS spectra clearly show the formation of the tri-
nuclear complexes by their characteristic isotopic distri-
bution pattern and their unique m/z values. The calculated
isotope distribution patterns for trans,trans,trans-(tBuCtC)-
Ru(dmpe)2( μ-CtCC6H4CtC)Ru(depe)2( μ-CtCC6H4CtC)-
Ru(dmpe)2(CtCtBu) (4b) and trans,trans,trans-(SiMe3CtC)-
Ru(dmpe)2( μ-CtCC6H4CtC)Ru(depe)2( μ-CtCC6H4Ct
C)Ru(dmpe)2(CtCSiMe3) (4c) correlate extremely well with the
experimental spectra (Figure 5).
two ruthenium centers (i.e., Ru3II,III,II to Ru3III,III,II, then
III,III,II
at 55 mV higher potential Ru3
to Ru3III,III,III),
which indicates communication between these centers is
˚
significant even though they are estimated to be ∼24 A
apart. Overall, these observations support an electronic
communication along the trinuclear complexes in differ-
ent oxidized states. These results are again consistent
with those of the other reported trinuclear ruthenium(II)
systems.7,13
Cyclic voltammograms (CVs) were obtained for trans,trans,
trans-(tBuCtC)Ru(dmpe)2( μ-CtCC6H4CtC)Ru(depe)2-

Article
In summary, we have developed a route to di- and
Organometallics, Vol. 29, No. 4, 2010 963
-1.29 (p, 3JPH = 5.7 Hz, 3H, RuCH3) ppm. 13C{1H,31P} (75.49
MHz, benzene-d6): δ 150.4 (CC(CH3)3), 132.7 (ArC), 131.7
(RuCtC), 125.3 (ArCH), 117.3 (ArCH), 110.8 (RuCtC),
35.3 (C(CH3)3), 32.3 (C(CH3)3), 31.0 (PCH2), 17.9 (PCH3), 13.7
trinuclear acetylide-bridged ruthenium(II) complexes via
the unsymmetrically substituted bis(acetylido)ruthenium-
(II) complexes. The controlled nature of these reactions
allows the stepwise synthesis and isolation of these com-
plexes in a high yield and purity with minimal workup. We
are also currently continuing the investigation into the
electrochemical and nonlinear optical properties of these
series of complexes.
(PCH3), -23.2 (RuCH3) ppm. IR:νmax (KBr): 2046 ν(CtC) cm-1
.
trans-Ru(CtCC6H4CtCH)(CtCPh)(dmpe)2 (2a). trans-Ru-
(CH3)(CtCPh)(dmpe)2 (1a) (0.33 g, 0.64 mmol) was dissolved
in toluene (6 mL), and excess 1,4-diethylbenzene (0.50 g,
4.0 mmol) was added. Methanol (3 mL) was added, and the
reaction was left stirring at room temperature for 45 min. The
solvent was removed under reduced pressure. The unsymme-
trical bisacetylide trans-Ru(CtCC6H4CtCH)(CtCPh)-
(dmpe)2 (0.361 g, 90%) was isolated as an orange powder
after being washed with pentane (3 ꢀ 5 mL). Anal. Calcd for
C30H42P4Ru: C, 57.41; H, 6.75. Found: C, 56.99; H, 6.67. MS
(MALDI, 4HCCA matrix): m/z 628 (8, M), 555 (73), 531 (100),
503 (40, M - CtCC6H4CtCH), 402 (55, M - CtCC6H4CtCH,
- CtCC6H5). HRMS: 629.135749 (calcd for M þ 1 629.135324).
Experimental Section
All syntheses and manipulations involving air-sensitive com-
pounds were carried out using standard vacuum line and
Schlenk techniques under an atmosphere of dry nitrogen or
argon. Methanol, toluene, and benzene were dried and degassed
by refluxing over standard drying agents under an atmosphere
of dry nitrogen and were freshly distilled prior to use. All other
solvents were dried according to standard methods. Nuclear
magnetic resonance spectra were recorded on a Bruker
DMX500 (operating at 500.13, 125.92, and 202.45 MHz for
1H, 13C, and 31P, respectively), Bruker AVANCE DRX400
(operating at 400.13, 125.76, and 161.98 MHz for 1H, 13C, and
31P, respectively), or Bruker DPX300 (operating at 300.13 and
121.49 MHz for 1H and 31P, respectively) spectrometers at 300 K
unlessotherwisestated. 1H and 13C NMRspectra were referenced
to residual solvent resonances, while 31P NMR spectra were
referenced to external H3PO4. Infrared spectra were recorded
on a Shimadzu 8400 series FTIR. Where indicated, mass spectra
were recorded by electrospray ionization (ESI) mass spectra on a
Finnigan LCQ mass spectrometer or by matrix-assisted laser
desorption/ionization-time-of-flight (MALDI-tof) on a Micro-
massTOF SPEC 2E spectrometer witha 2-amino-5-nitropyridine
(ANP) matrix. Cyclic voltammetry measurements were carried
out under nitrogen using a conventional three-electrode cell using
a computer-controlled Pine Instrument Co. AFCBP1 bipotentio-
stat (as described in detail elsewhere22). The reported data were
recorded with a 0.5 mm glassy carbon working electrode at a scan
rate of 100 mV s-1. Potentials are referenced to the ferroce-
nium-ferrocene (FeIII-FeII) couple measured under identical
experimental conditions (concentrations, solvent, support elec-
trolyte, electrodes, temperature, and scan rate).
1
31P{1H} NMR (121.51 MHz, C6D6): δ 40.33 (s) ppm. H{31P}
NMR (300.17 MHz, CD2Cl2): δ 7.09 (AA0 of AA0XX0, 2H,
ArH(2)), 6.95 (m, 4H, ArH(20,30)), 6.89 (XX0 of AA0XX0, 2H,
ArH(3)), 6.80(m, 1H, ArH(40), 3.34(s, 1H, CtCH), 1.71(s, 8H, P-
CH2), 1.58 (s, 24H, P-CH3) ppm. 13C{1H,31P} NMR (125.76
MHz, CD2Cl2): δ 137.3 (RuCtCC6H4), 132.7 (Ar(10)), 132.2
(Ar(1)), 131.7 (ArH(2)), 131.0 (Ar(30)), 130.2 (ArH(3)), 129.5
(RuCtCC6H5), 128.2 (ArH(20), 123.1 (ArH(40)), 115.0 (Ar(4)),
110.1 and 110.5 (RuCtCC6H5, RuCtCC6H4), 84.7 (CtCH),
76.4 (CtCH), 30.3 (P-CH2), 15.6 (P-CH3), 15.6 (P-CH3) ppm.
ν
CtC (KBr disk): 2049 cm-1
trans-Ru(CtCC6H4CtCH)(CtCtBu)(dmpe)2 (2b). trans-
.
Ru(CH3)(CtCtBu)(dmpe)2 (1b) (0.50 g, 1.0 mmol) was dis-
solved in toluene (7 mL), and excess 1,4-diethylbenzene (0.75 g,
5.9 mmol) was added. Methanol (3 mL) was added, and the
reaction was left stirring at room temperature for 45 min. The
solvent was removed under reduced pressure. The unsymme-
trical bisacetylide trans-Ru(CtCC6H4CtCH)(CtCtBu)-
(dmpe)2 (0.53 g, 87%) was recrystallized as an orange-red
crystalline material from pentane. MS (ESI): m/z 609 (22,
M þ 1), 568 (25), 524 (30), 511 (100), 442 (55), 401 (20). HRMS:
609.170371 (calcd for M þ 1 609.168478). 31P{1H} NMR
1
(121.51 MHz, C6D6): δ 40.31 (s) ppm. H{31P} NMR (300.17
MHz, CD2Cl2): δ 7.14 (AA0 of AA0XX0, 2H, CH), 6.89 (XX0 of
AA0XX0, 2H, CH), 3.06 (s, 1H, CtCH), 1.64 (s, 8H, P-CH2),
1.52 (s, 12H, P-CH3), 1.49 (s, 12H, P-CH3), 1.03 (s, 9H,
C-(CH3)3) ppm. 13C{1H,31P} NMR (125.76 MHz, CD2Cl2): δ
138.9 (RuCtCC6H4), 132.4 (Ar(1)), 131.5 (ArH(3)), 129.8
(ArH(2)), 114.8 (RuCtCC(CH3)3), 114.3 (Ar(4)), 109.1
(RuCtCC6H4), 102.1 (RuCtCC(CH3)3), 84.8 (CtCH), 76.3
(CtCH), 33.0 (C(CH3)3), 30.2 (P-CH2), 29.3 (C(CH3)3), 15.7
Complexes trans-Ru(CH3)(CtCPh)(dmpe)2 (1a), trans-Ru-
(CH3)(CtCtBu2)(dmpe)2 (1b), trans-Ru(CH3)(CtCSiMe3)-
(dmpe)2 (1d), and trans-RuMe2(dmpe)2 were prepared as
described previously.15 trans-Ru(CtCC6H4CtCH)2(depe)2
was prepared according to the literature procedure.17 Terminal
alkynes were purchased from Aldrich and used as received.
trans-Ru(CH3)(CtCC6H3-3,5-tBu2)(dmpe)2 (1c). 3,5-Di-tert-
butylphenylacetylene (0.50 g, 2.3 mmol) was added to a solu-
tion of trans-Ru(CH3)2(dmpe)2 (0.40 g, 0.93 mmol) in toluene
(30 mL). The solution was stirred under nitrogen at 40 °C for
120 h. The solvent was removed under reduced pressure, and
the residue was recrystallized from pentane to give trans-Ru-
(CH3)(CtCC6H3-3,5-tBu2)(dmpe)2 (34) was as a white crystal-
line solid (0.54 g, 92%). Anal. Calcd for C29H56P4Ru: C, 55.31,
H, 8.96. Found: C, 55.58, H, 8.66. MS (ESIþ) (%): m/z 828
[M þ CtCC6H3-3,5-tBu2]þ (15), 655 [M þ MeCN - CH3]þ
(13), 630 [M þ H]þ (15), 457 [M þ MeCN - CtCC6H3-
3,5-tBu2]þ (25), 441 [M þ MeCN - (CtCC6H3-3,5-tBu2)-
(CH3)]þ (100), 401 [M - (CtCC6H3-3,5-tBu2)(CH3)]þ (30).
(P-CH3), 15.2 (P-CH3) ppm. νCtC (KBr disk): 2049, 2030 cm-1
.
Crystals suitable for X-ray diffraction were isolated by cooling a
pentane solution of the complex. Crystal data and refinement
details for 2b are given in Table 4.
trans,trans-(PhCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(CtCPh)-
(dmpe)2 (3a). trans-Ru(CtCC6H4CtCH)(CtCPh)(dmpe)2 (2a)
(0.22 g, 0.35 mmol) was mixed with toluene (5 mL), and trans-
Ru(CH3)(CtCPh)(dmpe)2 (1a) (0.32 g, 0.62 mmol) was added.
Methanol (3 mL) was added, and the reaction was left stirring
at room temperature for 1 h. The solvent was removed under
reduced pressure, and the light brown powder was washed with
benzene (2 ꢀ 2 mL) and DCM (2 ꢀ 2 mL) to yield the
symmetrically substituted dinuclear acetylide-bridged ruthenium-
(II) complex trans,trans-(PhCtC)Ru(dmpe)2(μ-CtCC6H4CtC)-
Ru(CtCPh)(dmpe)2 (0.27 g, 68%). MS (ESI): m/z 1130 (85,
M þ 1), 631 (10), 531 (90), 447 (75), 401 (100). HRMS:
1130.202275 (calcd for M þ 1 1130.211227). 31P{1H} NMR
(121.51 MHz, CD2Cl2): δ 40.60 (s) ppm. 1H{31P} NMR (300.13
MHz, CD2Cl2): δ 7.05-6.95 (m, 8H, ArH), 6.85 (m, 2H, ArH),
6.70 (s, 4H, ArH), 1.75 - 1.62 (m, 16H, P-CH2), 1.53 (s, 48H,
31P{1H} NMR (121.51 MHz, benzene-d6): δ 43.64 (s) ppm.
3
1H{31P} NMR (300.13 MHz, benzene-d6): δ 7.35 (d, JHH
=
3
1.8 Hz, 2H, ArH), 7.21 (t, JHH = 1.8 Hz, 1H, ArH), 1.51
(s, 12H, PCH3), 1.51-1.39 (m, 4H, PCH2), 1.34 (s, 18H,
C(CH3)3), 1.29-1.20 (m, 4H, PCH2), 1.08 (s, 12H, PCH3),
(22) He, Z. C.; Colbran, S. B.; Craig, D. C. Chem. Eur. J. 2003, 9, 116–
129.
P-CH3). νCtC (KBr disk): 2054 cm-1
.

964 Organometallics, Vol. 29, No. 4, 2010
Field et al.
Table 4. Crystallographic and Structure Refinement Data for 2b and 3b
2b
3b
chemical formula
Mr
C28H46P4Ru
607.60
C23H43P4Ru
544.52
cell syst, space group
temp (K)
monoclinic, P21/n
173(2)
9.6302(18)
12.118(2)
26.325(5)
triclinic, P1
150(2)
˚
a (A)
9.0216(8)
9.1604(7)
17.2534(15)
96.199(4)
92.234(3)
104.126(4)
1371.5(2)
2
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
91.897(7)
3
˚
V (A )
Z
3070.3(9)
4
1.314
0.734
red block
Dx (Mg m-3
)
1.319
0.812
μ(Mo KR) (mm-1
cryst form, color
cryst size (mm)
Tmin
)
light yellow thin plate
0.21 ꢀ 0.12 ꢀ 0.02
0.8479
0.40 ꢀ 0.30 ꢀ 0.25
0.5559
0.8379
Tmax
N, Nind
Nobs (I > 2σ(I))
Rint
0.9879
22 007, 5782
3855
0.0638
35 383, 4791
2958
0.1404
θ
max (deg)
25.90
25.00
R[F2 > 2σ(F2)], wR(F2), S
no. of reflns
no. of params
0.0465, 0.0897, 1.040
5782
314
0.0427, 0.1048, 0.884
4791
253
H-atom treatment
mixture of independent
and constrained refinement
w = 1/[σ2(Fo2) þ
(0.0331P)2 þ 4.9015P]
riding model
weighting scheme
w = 1/[σ2(Fo2) þ
(0.1000P)2 þ 0.1591P]
where P = (Fo þ 2Fc2)/3
where P = (Fo þ 2Fc2)/3
2
2
ΔFmax, ΔFmin
0.520, -0.594
0.484, -0.531
1
trans,trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(Ct
CtBu)(dmpe)2 (3b). trans-Ru(CtCC6H4CtCH)(CtCtBu)-
(dmpe)2 (2b) (0.19 g, 0.25 mmol) was mixed with toluene (5 mL),
and trans-Ru(CH3)(CtCtBu)(dmpe)2 (1b) (0.30 g, 0.6mmol) was
added. Methanol (4 mL) was added, and the reaction was left
stirringatroomtemperaturefor 45 min. The solvent was removed
under reduced pressure, and the residual brown-orange powder
was washed with benzene (2 ꢀ 2 mL) and DCM (2 ꢀ 2 mL)
to yield the symmetrically substituted dinuclear acetylide-brid-
ged ruthenium(II) complex trans,trans-(tBuCtC)Ru(dmpe)2-
(μ-CtCC6H4CtC)Ru(CtCtBu)(dmpe)2 (0.11 g, 41%). The
product was recrystallized by slow evaporation of a DCM/
pentane solution (1:2). Anal. Calcd for C46H86P8Ru2: C, 50.73;
H, 7.96. Found: C, 50.90; H, 7.93. MS (ESI): m/z 1090 (24, M þ 1),
1048 (10), 524 (32), 511 (15), 442 (25), 402 (100), 351 (28). HRMS:
1090.273542 (calcd for M þ 1 1090.267632). 31P{1H} NMR (121.51
DCM-d2): δ 40.80 (s, 4P), 40.79 (s, 4P) ppm. H{31P} NMR
(300.13 MHz, DCM-d2): δ 7.01 (t, 3JHH = 7.3 Hz, 2H, ArH), 6.96
(d, 3JHH = 8 Hz, 2H, ArH), 6.84 (t, 3JHH = 7.3 Hz, 1H, ArH),
6.66 (s, 4H, ArH), 1.71-1.58 (m, 16H, PCH2), 1.52-1.48
(m, 48H, PCH3), 0.96 (s, 9H, C(CH3)3) ppm. 13C{1H,31P}
NMR (100.61 MHz, DCM-d2): δ 132.0 (RuCtC), 131.8
(RuCtC), 131.7 (RuCtC), 131.5 (ArC), 129.9 (ArCH), 129.3
(2 ꢀ ArCH), 129.2(ArCH), 127.7(ArCH), 122.2(2ꢀ ArC), 114.2
(RuCtCC(CH3)3), 109.2 (RuCtC), 108.6 (RuCtC), 108.3
(RuCtC), 101.7 (RuCtCC(CH3)3), 33.0 (C(CH3)3), 30.2
(PCH2), 29.5 (C(CH3)3), 15.6 (PCH3), 15.3 (PCH3) ppm. IR
ν
max (KBr): 2055 ν(CtC) cm-1
trans,trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(Ct
.
CC6H3-3,5-tBu2)(dmpe)2 (3d).trans-Ru(CH3)(CtCC6H3-3,5-tBu2)-
(dmpe)2 (1c) (0.080 g, 0.13 mmol) was added to a solution of trans-
Ru(CtCC6H4CtCH)(CtCtBu)(dmpe)2 (2b) (0.050 g, 0.082
mmol) in toluene (3 mL). Methanol (3 mL) was added, and the
reaction mixture was stirred at room temperature for 45 min. The
solvent was removed under reduced pressure, and the light brown
residue was washed with pentane (4 ꢀ 2 mL) to afford the
unsymmetrically substituted dinuclear acetylide-bridged ruthenium-
(II) complex trans,trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)-
Ru(CtCC6H3-3,5-tBu2)(dmpe)2 (3d) as a dark brown powder
(0.090 g, 90%). Anal. Calcd for C56H98P8Ru2: C, 55.07; H, 8.09.
Found: C, 55.19; H, 7.99. HRMS (ESIþ, MeOH): m/z 1254.3575
(calcd for M þ MeOH 1254.3913). 31P{1H} NMR (121.51 MHz,
DCM-d2): δ 40.91 (s, 4P), 40.82 (s, 4P) ppm. 1H{31P} NMR (300.13
MHz, DCM-d2): δ 6.96 (s, 1H, ArH), 6.83 (s, 2H, ArH), 6.67 (s, 4H,
ArH), 1.71-1.59 (m, 16H, PCH2), 1.54-1.48 (m, 48H, PCH3), 1.23
(s, 18H, C(CH3)3), 1.00 (s, 9H, C(CH3)3) ppm. 13C{1H, 31P} NMR
(150.92 MHz, DCM-d2): δ 149.9 (ArCC(CH3)), 129.3 (4 ꢀ ArCH),
129.0 (2 ꢀ RuCtCC6H4), 128.5 (RuCtCC6H3), 126.2 (ArC),
125.9 (ArC), 125.4 (ArC), 124.0 (2 ꢀ ArCH), 116.9 (ArCH),
114.2 (RuCtCC(CH3)3), 109.5 (RuCtC), 109.2 (RuCtC),
108.4 (RuCtC), 101.8 (RuCtCC(CH3)3), 34.4 (ArCC(CH3)3),
33.0 (CtCC(CH3)3), 31.2 (ArCC(CH3)3), 30.2 (PCH2), 29.3
(CtCC(CH3)3), 15.6 (PCH3), 15.3 (PCH3) ppm. IR νmax (KBr):
1
MHz, CD2Cl2): δ 40.70 (s) ppm. H{31P} NMR (300.13 MHz,
CD2Cl2): δ 6.64 (s, 4H, ArH), 1.62-1.56 (m, 16H, P-CH2), 1.48 (s,
24H, P-CH3), 1.46 (s, 24H, P-CH3), 1.00 (s, 9H, C-(CH3)3) ppm.
13C{1H} NMR (150.90 MHz, CD2Cl2): δ 131.1 (m, RuCtCC6H4),
129.3 (ArH), 125.7 (Ar), 114.1 (RuCtCC(CH3)3), 108.3 (RuCt
CC6H4),101.8(m, RuCtCC(CH3)3), 33.0 (C(CH3)3), 30.2 (P-CH2),
29.2 (C(CH3)3), 15.7 (P-CH3), 15.3 (P-CH3) ppm. νCtC (KBr disk):
2049 cm-1. Crystals suitable for X-ray diffraction were isolated by
slow evaporation of a DCM/pentane solution of the complex. Crystal
data and refinement details for 3b are given in Table 4.
trans,trans-(PhCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(Ct
CtBu)(dmpe)2 (3c). trans-Ru(CH3)(CtCtBu)(dmpe)2 (1b) (0.15 g,
0.30 mmol) was added to a solution of trans-Ru(CtCC6-
H4CtCH)(CtCPh)(dmpe)2 (2a) (0.070 g, 0.11 mmol) in toluene
(3 mL). Methanol (3 mL) was added, and the reaction mixture
was stirred at room temperature for 45 min. The solvent was
removedunder reduced pressure, andthe lightbrown powder was
washed with pentane (4 ꢀ 2 mL) to afford the unsymmetrically
substituted dinuclear acetylide-bridged ruthenium(II) complex
trans,trans-(PhCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(CtCtBu)-
(dmpe)2 (3c) (0.10 g, 82%). HRMS (ESIþ, MeOH): 1142.2301
(calcd for M þ MeOH 1142.2661). 31P{1H} NMR (121.51 MHz,
2048 ν(CtC) cm-1
.

Article
trans,trans,trans-(PhCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru-
Organometallics, Vol. 29, No. 4, 2010 965
PCHHCH3), 1.85 (m, 8H, PCHHCH3), 1.68 (m, 16H, PCH2),
1.60 (m, 8H, PCH2), 1.52-42 (m, 48H, PCH3), 1.15 (s, 24H,
PCH2CH3), 0.99 (s, 18H, C(CH3)3) ppm. 13C{1H,31P} NMR
(150.92 MHz, DCM-d2): δ 137.3 (Ru(depe)2CtCC6H4), 131.2
(Ru(dmpe)2CtCC6H4), 129.6 (ArCH), 126.2 (ArC), 126.0
(ArC), 114.5 (RuCtCC(CH3)3), 111.7 (Ru(depe)2CtCC6H4),
108.6 (Ru(dmpe)2CtCC6H4), 102.1 (RuCtCC(CH3)3), 33.3
(C(CH3)3), 30.6 (PCH2 of dmpe), 29.6 (C(CH3)3), 21.9 (PCH2
of depe), 20.8 (PCH2CH3), 16.0 (PCH3), 15.6 (PCH3), 9.2
(depe)2(μ-CtCC6H4CtC)Ru(CtCPh)(dmpe)2 (4a). trans-Ru-
(CH3)(CtCPh)(dmpe)2 (1a) (0.30 g, 0.58 mmol) was added to a
solution of trans-Ru(CtCC6H4CtCH)2(depe)2 (0.10 g,
0.13 mmol) in toluene (4 mL). Methanol (3 mL) was added,
and the reaction mixture was left stirring at room temperature
for 1 h. The solvent was removed under reduced pressure, and
the dark brown powder was washed with benzene (2 ꢀ 2 mL)
and DCM (2 ꢀ 2 mL) to afford the symmetrically substituted
trinuclear acetylide-bridged ruthenium(II) complex trans,
trans,trans-(PhCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(depe)2-
(μ-CtCC6H4CtC)Ru(CtCPh)(dmpe)2 (4a) as a dark brown-
orange powder (0.21 g, 90%). MS (ESIþ) (%): m/z 1266 [M -
1 - Ru(dmpe)2(CtCPh)]þ (30), 1097 (20), 667 (95), 639 (100).
31P{1H} NMR (121.51 MHz, DCM-d2): δ 51.48 (s, 4P, PEt2),
39.73 (s, 8P, PMe2) ppm. 1H{31P} NMR (600.13 MHz, DCM-
d2): δ 7.16 (AA0 of AA0XX0, 4H, ArH), 7.00 (m, 4H, ArH), 6.91
(m, 4H, ArH), 6.89 (XX0 of AA0XX0, 4H, ArH), 6.84 (m, 2H,
ArH), 2.24 (m, 8H, PCHHCH3), 1.89 (m, 8H, PCHHCH3), 1.71
(m, 24H, PCH2), 1.54 (s, 24H, PCH3), 1.46 (s, 24H, PCH3), 1.17
(m, 24H, PCH2CH3) ppm. 13C{1H,31P} NMR (150.92 MHz,
DCM-d2): 131.4 (ArCH), 129.5 (ArCH), 129.1 (ArCH), 127.4
(ArCH), 121.9 (ArCH), 29.1 (PCH2 of dmpe), 21.2 (PCH2 of
depe), 20.2 (PCH2CH3), 14.4 (PCH3), 12.7 (PCH3), 8.6
(PCH2CH3) ppm. Remaining resonances not observed. IR
(PCH2CH3) ppm. IR νmax (KBr): 2080, 2047 ν(CtC) cm-1
.
trans,trans,trans-(SiMe3CtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru-
(depe)2(μ-CtCC6H4CtC)Ru(CtCSiMe3)(dmpe)2 (4c). trans-Ru-
(CH3)(CtCSiMe3)(dmpe)2 (1d) (0.20 g, 0.39 mmol) was added to a
solution of trans-Ru(CtCC6H4CtCH)2(depe)2 (0.10 g, 0.13
mmol) in toluene (5 mL). Methanol (4 mL) was added, and the
reaction mixture was left stirring at room temperature for 1 h. The
solvent was removed under reduced pressure. The brown-orange
powder was washed with benzene (2 ꢀ 2 mL) and DCM (2 ꢀ 2 mL)
to afford the symmetrically substituted trinuclear acetylide-bridged
ruthenium(II) complex trans,trans,trans-(SiMe3CtC)Ru(dmpe)2-
(μ-CtCC6H4CtC)Ru(depe)2(μ-CtCC6H4CtC)Ru(CtCSiMe3)-
(dmpe)2 (4c) as a light brown powder (0.20 g, 88%). HRMS (ESIþ,
MeOH): 1759.4362 (calcd for Mþ 1759.4416). 31P{1H} NMR
(121.51 MHz, DCM-d2): δ 51.51 (s, 4P, PEt2), 39.91 (s, 8P, PMe2)
ppm. 1H{31P} NMR (600.13 MHz, DCM-d2): δ 6.66 (m, 8H, ArH),
2.23 (m, 8H, PCHHCH3), 1.86 (m, 8H, PCHHCH3), 1.68 (m, 16H,
PCH2), 1.62 (m, 8H, PCH2), 1.50 (s, 24H, PCH3), 1.47 (s, 24H,
PCH3), 1.15 (s, 24H, PCH2CH3), 0.07 (s, 18H, Si(CH3)3) ppm.
13C{1H,31P} NMR (150.92 MHz, DCM-d2): δ 129.4 (ArCH), 129.3
(ArCH), 125.6 (ArC), 125.5 (ArC), 111.5 (Ru(depe)2CtCC6H4),
109.3 (Ru(dmpe)2CtCC6H4), 30.2 (PCH2 of dmpe), 21.6 (PCH2 of
depe), 20.5(PCH2CH3), 15.6 (PCH3), 15.3(PCH3), 8.9(PCH2CH3),
1.7 (Si(CH3)3) ppm. Remaining resonances not observed. IR νmax
ν
max (KBr): 2061, 2055, 2049 ν(CtC) cm-1
trans,trans,trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru-
.
(depe)2(μ-CtCC6H4CtC)Ru(CtCtBu)(dmpe)2 (4b). trans-Ru-
(CH3)(CtCtBu)(dmpe)2 (1b) (0.24 g, 0.48 mmol) was added to a
solution of trans-Ru(CtCC6H4CtCH)2(depe)2 (0.15 g, 0.20
mmol) in toluene (5 mL). Methanol (4 mL) was added, and the
reaction mixture was left stirring at room temperature for 1 h.
The solvent was removed under reduced pressure. The dark
brown-orange powder was washed with benzene (2 ꢀ 2 mL) and
DCM (2 ꢀ 2 mL) to afford the symmetrically substituted
trinuclear acetylide-bridged ruthenium(II) complex trans,trans,
trans-(tBuCtC)Ru(dmpe)2(μ-CtCC6H4CtC)Ru(depe)2(μ-Ct
CC6H4CtC)Ru(CtCtBu)(dmpe)2 (4b) as a light brown-orange
powder (0.29 g, 84%). HRMS (ESIþ, MeOH): 1727.4771 (calcd
for Mþ 1727.4797). 31P{1H} NMR (121.51 MHz, DCM-d2): δ
(KBr): 2048, 1989 ν(CtC) cm-1
.
Acknowledgment. The authors thank the Australian
Research Council for funding.
Supporting Information Available: Crystallographic files (.cif)
of 1c, 2b, and 3b. This material is available free of charge via the
Internet at http://pubs.acs.org.
1
51.76 (s, 4P, PEt2), 39.59 (s, 8P, PMe2) ppm. H{31P} NMR
(600.13 MHz, DCM-d2): δ 6.64 (m, 8H, ArH), 2.23 (m, 8H,