Reactions of alkynes with [RuCl(cyclopentadienyl)] complexes: The important first steps

Article abstract of DOI:10.1002/chem.201000855

Cyclopentadienyl-ruthenium half-sandwich complexes with η²-bound alkyne ligands have been suggested as catalytic intermediates in the early stages of Ru-catalyzed reactions with alkynes. We show that electronically unsaturated complexes of the formula [RuCl(Cp)(η²-RC=CR')] can be stabilized and crystallized by using the sterically demanding cyclopentadienyl ligand Cp (Cp = η⁵-l-methoxy-2,4tert-butyl-3-neopentyl-cyclopentadienyl). Furthermore we demonstrate that [RuCl₂(Cp)]₂ is an active and regioselective catalyst for the [2+2+2] cyclotrimerization of alkynes. The first elementary steps of the reaction of mono(η²- alkyne) complexes containing {RuCl(Cp*)} (Cp* = η⁵- C₅Me₅) and (RuCl(Cp)} fragments with alkynes were investigated by DFT calculations at the M06/6-31G* level in combination with a continuum solvent model. Theoretical results are able to rationalize and complement the experimental findings. The presence of the sterically demanding Cp ligand increases the activation energy required for the formation of the corresponding di(η²alkyne) complexes, enhancing the initial regioselectivity, but avoiding the evolution of the system towards the expected cyclotrimerization product when bulky substituents are present. Theoretical results also show that the electronic structure and stability of a metallacyclic intermediate is strongly dependent on the nature of the substituents present in the alkyne.

Full text of DOI:10.1002/chem.201000855

DOI: 10.1002/chem.201000855
Reactions of Alkynes with [RuCl(cyclopentadienyl)] Complexes: The
Important First Steps
Barnali Dutta, Basile F. E. Curchod, Pablo Campomanes, Euro Solari, Rosario Scopelliti,
Ursula Rothlisberger, and Kay Severin*[a]
Abstract: Cyclopentadienyl–ruthenium
half-sandwich complexes with h2-bound
alkyne ligands have been suggested as
catalytic intermediates in the early
stages of Ru-catalyzed reactions with
alkynes. We show that electronically
unsaturated complexes of the formula
trimerization of alkynes. The first ele-
mentary steps of the reaction of
mono(h2-alkyne) complexes containing
{RuCl
{RuClACTHGUNTRNE(NUG Cp^)} fragments with alkynes
were investigated by DFT calculations
at the M06/6-31G* level in combina-
tion with a continuum solvent model.
Theoretical results are able to rational-
ize and complement the experimental
findings. The presence of the sterically
demanding Cp^ ligand increases the
activation energy required for the for-
mation of the corresponding di(h2-
alkyne) complexes, enhancing the ini-
tial regioselectivity, but avoiding the
evolution of the system towards the ex-
(Cp*)} (Cp*=h5-C5Me5) and
ACHTUNGTRENNUNG
[RuClACHTUNGTRENNUNG
bilized and crystallized by using the
sterically demanding cyclopentadienyl
ligand Cp^ (Cp^=h5-1-methoxy-2,4-
tert-butyl-3-neopentyl-cyclopentadien-
yl). Furthermore we demonstrate that
pected
cyclotrimerization
product
when bulky substituents are present.
Theoretical results also show that the
electronic structure and stability of a
metallacyclic intermediate is strongly
dependent on the nature of the sub-
stituents present in the alkyne.
Keywords: alkynes · cyclotrimeriza-
tion · density functional calcula-
tions · organometallic chemistry ·
ruthenium
[RuCl2ACHTUNGTRENNUNG(Cp^)]2 is an active and regiose-
lective catalyst for the [2+2+2] cyclo-
Introduction
rated aldehydes by reaction with allyl alcohol,[6] and the for-
mation of silylated 1,3-dienes by reaction with trimethylsilyl-
diazomethane[7] (Scheme 1).
Half-sandwich complexes containing the {RuClCAHTUNGTRENNNUG
ment (Cp*=h5-C5Me5), such as [RuCl
ACTHNUGERTN(NUNG cod)ACHTUGNTRENNNUG
1,5-cyclooctadiene), [RuCl
G
N
ACHTUNGTRENNUNG
are potent and versatile catalysts for organic transformations
involving alkynes.[1] The catalytic reactions include the for-
mation of arenes by [2+2+2] cyclotrimerizations,[2] the for-
mation of triazoles by [2+3] cycloadditions,[3] the formation
of cyclobutenes by [2+2] cycloadditions with bicyclic al-
kenes,[4] the formation of dienylesters by the coupling of al-
kynes with carboxylic acids,[5] the formation of g,d-unsatu-
[a] B. Dutta, B. F. E. Curchod, Dr. P. Campomanes, Dr. E. Solari,
Dr. R. Scopelliti, Prof. U. Rothlisberger, Prof. K. Severin
Institut des Sciences et Ingꢀnierie Chimiques
ꢁcole Polytechnique Fꢀdꢀrale de Lausanne (EPFL)
1015 Lausanne (Switzerland)
Fax : (+41)21-693-9305
E-mail: kay.severin@epfl.ch
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201000855.
Scheme 1.
ACHUTNGTREN[NUG RuClACHTUNTGREN(NGUN Cp*)(L2)] complexes (L=PR3, olefin) are versatile cat-
alysts for organic transformations of alkynes.
8400
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 8400 – 8409

FULL PAPER
For most of these reactions, it is assumed that the trans-
formation is mediated by the {RuCl(Cp*)} fragment and
gioselectivity of the reaction, 3) the C–C coupling process
between the alkyne substrates proceeds in a stepwise fash-
ion, and 4) the formation of di(h2-alkyne) complexes II re-
quires a large activation energy when bulky substituents are
present in both substrate and ligands thus explaining the
key role played by such substituents in the reactivity of
mono(h2-alkyne) complexes.
AHCTUNGTRENNUNG
that additional ligands of the catalyst precursors, such as
PPh3 or cod, are cleaved off prior to catalysis. The generally
accepted mechanism[2,8] for the [RuCl(cyclopentadienyl)]-
catalyzed trimerization of terminal alkynes involves h2-
alkyne complexes of types I and II (Scheme 2). The latter
Results and Discussion
Recently, we have reported the synthesis of the dinuclear
2ACTHNUTRGNEUNG
RuIII complex [RuCl (Cp^)]2 (1) (Cp^=h5-1-methoxy-2,4-
tert-butyl-3-neopentyl-cyclopentadienyl ).[10] It can be ob-
tained in a simple one-pot reaction by heating [RuCl3-
AHCTUNGTERG(NUNN solv.)n] with tert-butyl acetylene in methanol (Scheme 3).
Scheme 2. Proposed mechanism for the cyclotrimerization of terminal al-
kynes in the presence of [RuCl(Cp)] catalysts.
rearrange to give ruthenacyclopentatriene complexes of
type III, which react with additional alkyne to give the aro-
matic [2+2+2] cyclization products with regeneration of the
catalytically active [RuCl(cyclopentadienyl)]m species. Inter-
mediates of type III have been isolated and structurally
characterized,[2j,k,5b,9] but spectroscopic or structural data on
Scheme 3. Synthesis of the dinuclear complexes 1 and 2.
Complex 1 is a structural analogue of the frequently used
2
complexes of type [RuCl
(Cpx)
N
starting material [RuCl
is to some extent similar to that of [RuCl
ple, it can easily be converted into mononuclear RuII com-
(Cp*)]2. The reactivity of complex 1
ꢀ
2
(Cpx)
G
CHTUNGTRENNUNG
ꢀ
not been reported. The conversion of di(h2-alkyne) com-
plexes II into ruthenacyclopentatriene complexes III
(Scheme 2, step c) and the subsequent coupling reaction
with alkynes (Scheme 2, step d) have both been investigated
in detail by computational studies.[2j,8] All studies agree that
the formation of the products proceeds via ruthenabicyclo-
plexes of the general formula [RuClACTHNUTRGNEN(UG Cp^)(L2)] (L=phos-
phines, olefins).[10,11] However, the Cp^ ligand is sterically
more demanding than the classical Cp* ligand. As a result,
it is possible to stabilize electronically unsaturated 16eꢁ
complexes, which are not accessible with the complex con-
A
taining the {Ru
for example, was shown to be a chloro-bridged dimer
(Scheme 3),[12] whereas the corresponding [RuCl
(Cp*)] com-
plex is a tetramer with additional m-Cl bridges.[13]
(Cp*)} fragment.[10–12] The RuII complex 2,
ACHTUNGTRENNUNG
step is the oxidative cyclization of two alkynes to give ruthe-
nacycles III (Scheme 2, step c). However, most of the calcu-
lations were performed with the nonsubstituted {RuCl(Cp)}
fragment (Cp=h5-C5H5) and simple acetylene as the sub-
strate, and no computations were carried out on the early
steps of the reaction mechanism, that is, the conversion of
the mono(h2-alkyne) complexes I into the corresponding
di(h2-alkyne) complexes II.
Below we describe results of a combined experimental
and theoretical study that shows that: 1) it is possible to iso-
late complexes of type I, 2) steric interactions between the p
ligand and the substrate have a pronounced effect on the re-
AHCTUNGTRENNUNG
The ability of the sterically demanding Cp^ ligand to sta-
bilize reactive intermediates prompted us to investigate the
reactions of complexes containing the {RuACTHUNRTGNEUNG(Cp^)} fragment
with alkynes under different conditions. First, we focused on
the organometallic chemistry of the dimer 2. When an
excess of tert-butyl acetylene was added to a pentane solu-
tion of complex 2, an instantaneous change of the color of
the solution from red to violet was observed. Cooling of the
solution to ꢁ208C led to the formation of crystals of the
Chem. Eur. J. 2010, 16, 8400 – 8409
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8401

K. Severin et al.
2
ꢀ
monoalkyne adduct [RuCl
(Cp^)(h -HC CCMe3)] (3) in
excess of tert-butyl acetylene. Decomposition of complex 3
also occurred when the crystals were subjected to high
vacuum.
61% isolated yield (Scheme 4). The structure of 3 was evi-
denced by X-ray crystallography (Figure 1) and elemental
The reaction of complex 2 with phenyl acetylene in pen-
tane gave similar results: the color of the solution turned
violet upon addition of the alkyne, and crystals of the mono-
adduct [RuClCAHTUNGTRENNNUG
temperature. Complex 4 turned out to be even more labile
than complex 3: the solid material decomposed slowly upon
storage at room temperature in the glove box. This instabili-
ty precluded carrying out an elemental analysis but the
structure of 4 could be established by X-ray crystallography
(Figure 1). It is interesting to note that the reaction of phe-
nylacetylene with [RuCl
ACHUTNGTRENNUG(cod)ACHTUNGTERN(NUGN Cp*)] produces cleanly a
ruthenacyclopentatriene complex of type III[5b,9a] and not an
alkyne complex as observed for [RuClACTHNUTRGEN(UNG Cp^)]2 (2). The dif-
ference in reactivity points to the fact that di(h2-alkyne)
complexes of type B are easier to access with Cp* p ligands,
a finding that is confirmed by the theoretical studies de-
scribed below.
Scheme 4. Synthesis of the alkyne adducts 3–7.
Next, we investigated the reaction of 2 with 1,1-diphenyl-
2-propyn-1-ol. This alkyne is known for its tendency to form
allenylidene complexes by elimination of water.[14] However,
the propargyl alcohol behaved in a similar manner to tert-
butyl acetylene and phenyl acetylene and gave violet crys-
tals of the monoadduct 5 in 50% isolated yield. With the in-
ternal alkynes 3-hexyne and dimethyl acetylene dicarboxy-
late, it was likewise possible to obtain h2-alkyne adducts in
the form of violet crystals (6 and 7). For reactions with the
ester, however, it was important to use only one equivalent
of alkyne with respect to Ru, because an excess of alkyne
lead to subsequent reactions, which are described in more
detail below.
Since the solution-based characterization of the com-
plexes 3–7 was hampered by the decomplexation of the
alkyne, we have carried out crystallographic analyses for all
five complexes. Graphic representations of the structures
are depicted in Figure 1, and key structural parameters are
summarized in Table 1. All complexes show a ꢃpiano-stoolꢄ
geometry with the chloride and the h2-bound alkyne ligand
being positioned opposite to the Cp^ ligand. For complexes
ꢀ
3–5 with terminal alkynes RC CH, the alkyne is coordinat-
ed in such a fashion that the R group points away from the
p ligand. The asymmetry of the alkyne is reflected in the
ꢁ
ꢁ
Ru C bond lengths, with the Ru C1 bonds being consistent-
ꢁ
ly shorter than the Ru C2 bonds. For the complexes 6 and 7
Figure 1. Molecular structures of the complexes 3–7 in the crystal. The
hydrogen atoms are not shown for clarity. The thermal ellipsoids are set
at 50% probability.
with internal alkynes, the differences between the two bond
Table 1. Key bond lengths [ꢅ] and angles [8] of complexes 3–7
3
4
5
6
7
analysis. Complex 3 turned out to be very labile. Attempts
ꢁ
Ru Cl
2.416(3)
2.036(13)
2.123(10)
1.262(16)
35.2(5)
2.387(3)
1.979(12)
2.082(11)
1.271(13)
36.4(4)
2.4210(9)
2.026(4)
2.095(3)
1.249(5)
35.25(14)
149.3(3)
148(3)
2.4103(6)
2.072(2)
2.101(2)
1.256(3)
35.03(8)
151.8(2)
147.7(2)
2.3897(8)
2.033(3)
2.058(3)
1.262(4)
35.93(12)
147.9(3)
141.7(3)
to characterize
3 by NMR spectroscopy in solution
ꢁ
Ru C1
([D8]toluene) resulted in the cleavage of the alkyne ligand
and the reformation of the starting material 2. An excess of
the alkyne seems to shift the equilibrium in favor of the for-
mation of 3. It should be noted that alkyne trimerization
was not observed, despite the fact that we have used a large
ꢁ
Ru C2
ꢁ
C1 C2
C1-Ru-C2
C1-C2-R
C2-C1-R’
147.2(11)
134(9)
147.6(11)
139(5)
8402
www.chemeurj.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 8400 – 8409

Reactions of Alkynes with [RuCl(cyclopentadienyl)] Complexes
lengths are less pronounced. With values between 2.39 and
FULL PAPER
ꢁ
lengths: with 1.406(7) and 1.427(7) ꢅ, the C1 C2 and the
ꢁ
ꢁ
ꢁ
2.42 ꢅ, the Ru Cl lengths of the five complexes are similar
C3 C4 bonds are longer than the C2 C3 bond with
to what has been observed for the 16eꢁ complex [RuCl-
1.370(8) ꢅ. Furthermore, the Ru C1 and the Ru C4 bond
lengths (1.997(5) and 1.976(6) ꢅ) are in the range of a
double bond. 19F NMR spectroscopy of a CD2Cl2 solution of
crystalline 8 showed one signal indicating the formation of
only one isomer. Broad and strongly temperature-dependent
signals were observed in the 1H NMR spectrum of 8
(CD2Cl2), possibly due to hindered rotation of the Cp^
ligand arising from the presence of the 3,5-bis(trifluorome-
thyl)arene groups. More detailed NMR spectroscopic stud-
ies were not performed as similar complexes are known
with the Cp* ligand.[2j,k,5b,9]
ꢁ
ꢁ
ACHTUNGTRENNUNG(Cp^)ACHTUNGTRENNUNG
(PCy3)].[10a] The coordinated alkyne ligands are mark-
edly bent with C1-C2-R and C2-C1-R angles between 134
ꢀ
and 1528. The amount of bending and the enlarged C C
triple bond (1.26ꢂ0.01 ꢅ) is in line with what has been ob-
served for other Ru–(h2-alkyne) complexes.[15] For complex
5, one can observe an internal hydrogen bond between the
hydroxyl group and the chloride ligand (OH···Cl: 2.27,
ˆ
ꢁ
O···Cl: 3.056(2) ꢅ; O H···Cl: 1558).
As a representative example, complex 3 has also been
characterized by 13C CP-MAS NMR spectroscopy in the
solid state. While NMR spectroscopic studies of organome-
tallic complexes in the solid state are not very frequent, it
proved to be informative in our case. Signals for the coordi-
nated alkyne carbons C1 and C2 were observed at d=130
and 158 ppm, respectively. The other carbon atoms were as-
signed by comparison with the 13C{1H} NMR spectrum of
complex 2 in solution.
During our attempts to prepare alkyne complexes from
the dimer [RuClACHTNUTRGNEUNG(Cp^)]2 (2) and dimethyl acetylene dicar-
boxylate, we observed that arenes were formed when an
excess of alkyne with respect to the Ru complex was em-
ployed. This finding was not unexpected in view of the fact
that [RuClACTHNUGRTNEUNG(Cp*)] complexes are known to be potent cata-
lysts for the cyclotrimerization of electron-deficient alky-
nes.[2j] To examine the catalytic behavior of the Cp^ com-
plexes in more detail, we have investigated the trimerization
of the terminal alkyne ethyl propiolate with catalytic
amounts of complexes 1 and 2 (0.5 mol% Ru) in CD2Cl2.
After only 10 min at room temperature, the nearly quantita-
tive conversion of the alkyne was observed by 1H NMR
spectroscopy for both catalysts. Since the RuIII complex 1 is
easier to make and handle than the very sensitive RuII com-
plex 2, we decided to pursue all further studies with complex
1. For comparison, we also employed the standard catalyst
When complex 2 was allowed to react with an excess of
3,5-bis(trifluoromethyl)phenylacetylene in pentane, a violet
coloration indicated the formation of an h2-alkyne complex.
However, on storing the solution at ꢁ208C for two days, we
were able to isolate the ruthenacyclopentatriene complex 8
in the form of red crystals (Scheme 5).
precursor [RuClACTHNUTRGENNGU(cod)ACHTUNGTERN(NUGN Cp*)]. The results for six different al-
kynes are summarized in Table 2. Between 0.25 and
1.0 mol% of complex 1 (0.5–2.0 mol% Ru) were sufficient
to obtain good to excellent yields of the [2+2+2] cyclotri-
merization products. The catalytic activity of 1 was compara-
ble to that of the known catalyst [RuClACTHNUTRGNENG(U cod)ACHTUNTGNER(NUGN Cp*)]. Howev-
er, striking differences were observed for the regioselectivity
in the case of terminal alkynes. Reactions with the catalyst
Scheme 5. Synthesis of the ruthenacyclopentatriene complex 8.
Evidence for the formation of a ruthenacyclopentatriene
complex was obtained by crystallographic analysis
(Figure 2). The coordination around the Ru center can be
described as distorted tetrahedral, assuming that the Cp^
ligand occupies one coordination site. The description as a
ruthenacyclopentatriene complex is justified by the bond
[RuClACTHUNGTRENNU(G cod)ACHTUNGTREN(NGNU Cp*)] showed only a minor preference for the
formation of the 1,2,4-isomer over the 1,3,5-isomer (~6:4).
The Cp^ complex 1, on the other hand, promoted the
formation of the 1,2,4-isomer with excellent selectivity
(ꢃ9:1).[16] The improved selectivity can be attributed to the
increased steric demand of the Cp^ ligand relative to the
Cp* ligand (see below). It should be noted that a related
correlation between regioselectivity and steric demand of
the p ligand was observed for the cycloaddition of unsym-
metrical 1,6-diynes with terminal alkynes catalyzed by com-
plexes containing {RuCl
The results presented above demonstrate that reactions of
(Cp*)} and {RuCl(Cp)} fragments.[2j]
ACHTUNGTRENNUNG
alkynes with [RuClACTHNUTRGNEUNG
(Cpx)] complexes are very sensitive to
the nature of both the alkyne and Cpx ligands. While
ꢀ
MeO2CC CCO2Me gives a cyclotrimerization product, the
reaction does not proceed beyond the monoalkyne adduct
for tert-butyl acetylene. To investigate the mechanistic origin
of these effects, we performed DFT/M06/6-31G* calcula-
Figure 2. Molecular structures of the complex 8 in the crystal. The hydro-
gen atoms are not shown for clarity. The thermal ellipsoids are set at
50% probability.
2
ꢀ
tions of the reactions of the complexes [RuCl
(Cp^)
G
Chem. Eur. J. 2010, 16, 8400 – 8409
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8403

K. Severin et al.
(Cp*)].[a]
Table 2. Cyclotrimerization of alkynes with the catalysts [RuCl2ACHTUNGTREN(NNUG Cp^)]2 and [RuClACHNUTRTGEG(NNUN cod)ACHTNUGTRNENGUN
Entry
Substrate
Catalyst [mol% Ru]
{Ru(Cp^)} {Ru(Cp*)}
t
T
Yield [%][b]
{Ru
Product ratio 1,2,4/1,3,5
{Ru(Cp^)} {Ru(Cp*)}
G
G
{Ru
E
(Cp*)}
N
ACHTUNGTRENNUNG
ꢀ
1
2
3
4
5
6
HC CCO2Me
0.5
0.5
2.0
0.5
1.0
1.0
0.5
0.5
2.0
0.5
1.0
1.0
10 min
30 min
8 h
20 min
90 min
3 h
RT
RT
608C
RT
RT
RT
98
97
70
99
70
75
98
96
92
76
81
85
92:08
90:10
93:07
94:06
60:40
68:32
60:40
57:43
ꢀ
HC CCO2Et
ꢀ
HC COEt
ꢀ
HC CCOMe
ꢀ
MeO2CC CCO2Me
ꢀ
EtO2CC CCO2Et
[a] The reactions were performed in CD2Cl2 at RT or in 1,2-dichloroethane at 608C. [b] The yields are based on the formation of the product as deter-
1
mined by H NMR spectroscopy.
2
ꢀ
C
G
R
saturated [RuACTHNGUTERNNUG
(alkyne)(Cp)(L2)] complexes.[15a] The orienta-
7) with a second molecule of the corresponding alkyne. The
same reaction has been studied for the Cp* complex [RuCl-
(CH3)3)] (9) to understand the effects in-
duced by the sterically demanding Cp^ ligand.
As a first test of the performance of our computational
scheme, the M06/6-31G* -optimized geometries of the
tion adopted by the alkyne moiety is optimal for avoiding
“four-electron” destabilizing interactions between the
doubly occupied p orbital of the alkyne and the filled dz2 or-
bital localized on the Ru atom (see Figure 3) while main-
taining maximal overlap with the other metal orbitals.
Earlier theoretical studies have focused on the reactivity
of the metallacyclic intermediate III (Scheme 2),[2j,8] but the
initial steps of the reaction were not examined in detail. Our
experimental results show that these steps are crucial for the
rate and the regioselectivity of the cyclotrimerization reac-
tion. For this reason, we focused our investigation on the
first steps of the reaction. By starting from the mono(h2-
alkyne) complexes 3, 7, and 9, we studied the addition reac-
tion of another alkyne molecule and the subsequent forma-
tion of a metallacycle. The obtained free-energy profiles in
solution for the three cases considered in this study are dis-
played in Figure 4.
A
2
mono
and [RuCl
alkyne complexes [RuCl
(h -HC C
ꢀ
(Cp^)(h -MeO2CC CCO2Me)] (7) were validated
with the available X-ray structures. The theoretical results
are in excellent agreement for both bond lengths and angles
(Table 3).[17] Furthermore, the M06/6-31G* calculations ac-
Table 3. Computationally and experimentally determined bond lengths
[ꢅ] and angles [8] for the complexes 3 and 7.
3 (exptl.)
7 (calcd)
Ru Cl
Ru C1
Ru C2
C1 C2
C1-Ru-C2
C1-C2-R
2.416(3)
2.036(13)
2.123(10)
1.262(16)
35.2(5)
2.44
2.06
2.06
1.28
36.2
153.6
According to our calculations, the reaction between
2
ꢀ
ꢀ
[RuCl
(Cp*)
E
(CH3)3)] and HC C
N
three-step mechanism. The initial coordination of the alkyne
to the Ru complex leads to the formation of a pseudo-octa-
hedral, formally 18eꢁ organometallic compound, B, which is
6.5 kcalmolꢁ1 less stable than the initial adduct complex A.
The activation free-energy barrier that has to be overcome
for the coordination of the second alkyne ligand is of
7.2 kcalmolꢁ1. Subsequently, B evolves through the TS TSBC
(14.5 kcalmolꢁ1) into the metallabicyclic intermediate C
(ꢁ8.7 kcalmolꢁ1), which in turn yields the final metallacycle,
D, after surmounting a free-energy barrier of 6.7 kcalmolꢁ1
corresponding to the TS TSCD. In summary, our calculations
predict that the global process leading to the formation of
the metallacycle is exothermic by ꢁ12.9 kcalmolꢁ1 and is
characterized by a rate-determining step that corresponds to
TSBC with a Gibbs free-energy barrier in solution of
14.5 kcalmolꢁ1 relative to A. Note that our computations
147.2(11)
curately reproduce the experi-
mentally found orientation of
the alkyne ligand. In these elec-
tronically unsaturated com-
plexes, the plane defined by the
Ru atom and the carbon atoms
of the alkyne group (C1, C2) is
oriented perpendicular to the
plane defined by cyclopenta-
dienyl ligand (see Figures 1 and
3), which is in contrast to what
is observed for electronically
Figure 3. M06/6-31G*-opti-
mized geometry of compound
3. HOMO-1 is superimposed.
Isovalue is set to 0.07 a.u.
8404
www.chemeurj.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 8400 – 8409

Reactions of Alkynes with [RuCl(cyclopentadienyl)] Complexes
FULL PAPER
Figure 4. Gibbs-free-energy profile in dichloromethane solution for the addition of a second alkyne ligand to the complexes 3, 7, and 9. Relative free en-
ergies are given in kcalmolꢁ1. a: 9+tert-butyl acetylene; c: 7+dimethyl acetylene dicarboxylate; g: 3+tert-butyl acetylene.
predict a stepwise pathway for the formation of D from the
intermediate B, which is in contrast with previous theoreti-
cal studies on systems with the Cp ligand and unsubstituted
alkynes, in which the formation of the metallacycle from the
intermediate B has been described as a concerted process.[8]
It appears, therefore, that the occurrence of an additional in-
termediate C is favored upon introduction of sterically de-
manding ligands.
To study the effect caused by the presence of the more
bulky Cp^ ligand, we investigated the corresponding free-
2
ꢀ
energy reaction profile between [RuCl
G
(h -HC C-
ꢀ
(CH3)3)] and HC C
(CH3)3. The stationary structures located
for this process (see Figure 5) are qualitatively analogous to
2
ꢀ
those just described in the case of [RuCl
A
(h -HC C-
(CH3)3)]. However, with the Cp^ ligand, the formation of
the metallacycle is both kinetically and thermodynamically
unfavorable. The rate-determining free-energy barrier found
for the process is 10.7 kcalmolꢁ1 higher than the correspond-
ing one in the case of the reaction between [RuCl
N
(h2-
ACHTUNGTRENNUNG
ꢀ
ꢀ
HC CACHTUNGTRENNUNG(CH3)3)] and HC CCATHUNGTRENNNUG
Figure 5. M06/6-31G*-optimized geometry of intermediates in the addi-
tion of tert-butyl acetylene to compound 3. Short contacts are given for
structure B.
sponds to a decrease in the rate constant by a factor of 107.
Therefore, in agreement with the experimental observations,
the barrier is too high to permit the evolution of the [RuCl-
2
ꢀ
(Cp^)
G
(CH3)3)] complex to the metallacycle with
the sterically demanding tert-butyl acetylene. This difference
in the barriers can be mainly attributed to the presence of
unfavorable steric interactions (see Figure 5) that take place
between the substituents of the Cp^ ligand and the tert-
ꢀ
ed in a previous study,[8c] we observed that the orientation of
the alkynes when coordinating to the Ru is strongly deter-
mined by steric effects. Addition of a second tert-butyl acet-
ylene with its tert-butyl group in an anti-position with re-
spect to the one already present in the system is indeed pro-
hibited by the presence of the Cp^ ligand (see Figure 6).
According to the experimental evidence presented above,
the use of different alkynes leads to distinct variations of
the reactivity. To investigate the possible origin of this
butyl groups of HC CACHTUNRGTNEUNG(CH3)3. Interestingly, our computa-
tions show that a rotation of the Cp^ ligand similar to the
orientation found in the crystal structure of compound 8
(Figure 2) must take place to facilitate the formation of the
metallacycle (see Figure 5). Furthermore, as already report-
Chem. Eur. J. 2010, 16, 8400 – 8409
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8405

K. Severin et al.
Table 4. M06/6-31G*-selected bond lengths [ꢅ] for the metallacycles D
formed from complexes 3, 7, and 9. See Figure 2 for notation.
3
7
9
ꢁ
Ru C1
1.94
1.92
1.44
1.36
1.44
2.01
2.00
1.38
1.43
1.37
1.93
1.93
1.44
1.36
1.44
ꢁ
Ru C2
ꢁ
C1 C2
ꢁ
C2 C3
ꢁ
C3 C4
Figure 6. Side view of the M06/6-31G*-optimized geometry of intermedi-
ate 3B. Steric interactions with the Cp^ p ligand would strongly disfavor
an anti configuration of the two alkyne ligands.
of these complexes in the Ru-catalyzed cyclotrimerization of
alkynes.
Conclusion
effect, we also computed the corresponding free-energy pro-
[Ru(h2-alkyne)nCl(Cp)] (n=1, 2) complexes have been sug-
gested as intermediates in catalytic reactions involving
[RuCl(Cp)] complexes and alkynes.[2,8] The isolation and
structural characterization of the adducts 3–7 represents, to
the best of our knowledge, the first experimental evidence
for complexes of this kind. The bonds between the h2-bound
ꢀ
file of the addition of MeO2CC CCO2Me to [RuCl-
2
ꢀ
N
bles the ones previously described for the other two cases
(see Figure 4) with a rate-determining energy barrier that is
only ~4 kcalmolꢁ1 higher than in the case of complex 9. No
significant electronic differences were found for the station-
ary structures with respect to those in the other two systems
we studied, once more pointing to steric interactions as the
major source for the difference in barrier height. It is inter-
esting to note that in spite of the relatively large size of the
alkyne ligands and the {RuClACTHNUTRGNEUGN(Cp^)} fragment are weak, as
demonstrated by the rapid dissociation of the ligand upon
dissolving the complexes in organic solvents. It is interesting
to note that we have not observed vinylidene complexes, al-
2
1
ꢀ
ꢀ
MeO2CC CCO2Me ligands, they can adopt a quasi-planar
though the facile h -HC CR!h -C=CHR rearrangement is
well documented for half-sandwich Ru complexes.[15] Com-
plex 1 was found to be an active catalyst for the [2+2+2] cy-
clotrimerization of alkynes. The activity of 1 was similar to
conformation that efficiently minimizes the steric interac-
tions with the other ligands, which renders the formation of
the metallacycle structure energetically feasible. The final
metallacycle is much more stable in this case with the global
reaction being exothermic by 27.9 kcalmolꢁ1.
that of the frequently used catalyst [RuCl
its regioselectivity was significantly better.
ACHUTGTNREN(NUG cod)AHCTUNGTRENN(GUN Cp*)], but
Analysis of the frontier orbitals (see Figure 7) suggests
that this increase in stability might be due to electronic ef-
fects. In fact, the metallacycle 7D can be described as a
ruthenacyclopentadiene, whereas those formed by com-
plexes 3 and 9 are better described as ruthenacyclopenta-
trienes. The more pronounced diene character of 7D is also
evident from the carbon–carbon bond lengths of the ring
(see Table 4). These electronic differences can induce varia-
tions in the reactivity of the corresponding ruthenacycles
and thus have important consequences concerning the usage
The experimental results were complemented and ration-
alized by means of theoretical studies. The calculations show
that alkyne addition to the [Ru(h2-alkyne)Cl(Cp)] complex
is strongly dependent on steric effects between the alkyne
and the p ligand. They also predict that the subsequent C–C
coupling process to form the ruthenacycle takes place fol-
lowing a two-step reaction mechanism via a metallabicyclic
intermediate. The higher stability of the ruthenacycle
formed with electron-withdrawing alkyne substituents is due
to differences appearing in the electronic structure of the
system during the last step of the reaction.
Experimental Section
General: All experiments were performed inside a glove box under an
atmosphere of dinitrogen containing less than 1 ppm of dioxygen and
water. Thoroughly dried and deoxygenated solvents were used. The com-
pounds RuCl3·nH2O (Precious Metals Online), tert-butyl acetylene (TCI),
phenyl acetylene, 1,1-diphenyl-2-propyn-1-ol, dimethyl acetylene dicar-
boxylate, diethyl acetylene dicarboxylate, ethoxyacetylene, 3,5-bis(tri-
fluoromethyl)phenylacetylene (Sigma–Aldrich), methyl propiolate (May-
bridge), ethyl propiolate (Fluka), 3-butyne-2-one, and 3-hexyne (VWR
International) were obtained from commercial suppliers. All liquid acety-
lenes were distilled under vacuum. 1H and 13C spectra were recorded on
a Bruker Avance DPX 400 and 19F NMR spectra on a Bruker AV 200
spectrometer equipped with QNP probe by using deuterated solvents. 13C
Figure 7. LUMO and HOMO-1 of the metallacycles 3D and 7D. Isoval-
ues are set to 0.07 a.u.
8406
www.chemeurj.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 8400 – 8409

Reactions of Alkynes with [RuCl(cyclopentadienyl)] Complexes
FULL PAPER
CP-MAS spectra were recorded on a Bruker Avance 800 MHz spectrom-
eter at room temperature with a 2.5 mm rotor at 31.25 kHz MAS. All
deuterated solvents were degassed by three freeze-pump-thaw cycles and
then purified by vacuum transfer at room temperature. Fluorotrichloro-
Crystallographic investigations: The relevant details of the crystals, data
collection, and structure refinement can be found in Table 5. Diffraction
data for 3, 6, and 8 were collected by using MoKa radiation on a 4-circle
kappa goniometer equipped with a Bruker APEX II CCD at 100(2) K
and all data were reduced by EvalCCD.[19] Data collection for 4, 5, and 7
was performed at 140(2) K by using MoKa radiation on an Oxford Dif-
fraction Sapphire/KM4 CCD with a kappa geometry goniometer. Data
were reduced by using Crysalis PRO.[20] Absorption correction was ap-
plied to all data sets by using a semi-empirical method.[21] Solution and
refinement for both crystal structures were performed by SHELX.[22] The
structures were refined by using full-matrix least-squares on F2 with all
non-hydrogen atoms anisotropically defined. Hydrogen atoms were
placed in calculated positions by means of a “riding” model. In some
cases (3, 7, and 8), restraints have been used to treat disordered moieties
or solvent. In the case of 4, the SQUEEZE algorithm of PLATON[23] has
been used to treat very disordered solvent. Compound 8 shows an addi-
tional problem due to twinning, the law was identified [TWIN 1 0 0.5 0
ꢁ1 0 0 0 ꢁ1] and a BASF parameter was obtained in the last stages of re-
finement [0.0069(7)]. CCDC-771760–771765 contain the supplementary
crystallographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
methane was used as an internal standard for 19F NMR spectroscopy. The
[10a]
complexes [RuCl
G
(Cp^)]2,[12] and [RuCl (Cp*)][18]
[RuClACHTUNGERTNUNGN ACHTUNGTREG(NNUN cod)CAHTNUGTRENNGUN
were prepared according to published procedures.
[RuCl
(Cp^)(h2-HCꢀCCMe3)] (3): An excess of tert-butyl acetylene
(50 mL) was added to solution of complex [RuCl(Cp^)]2 (50 mg,
A
ACHTUNGTRENNUNG
a
ACHTUNGTRENNUNG
60 mmol) in pentane (2 mL) at RT. The color of the solution instantane-
ously turned violet. Crystals, appropriate for diffraction studies, appeared
on keeping the solution in the freezer at ꢁ208C for several days. The
crystals were collected and kept in the glove box for few hours to elimi-
nate the remaining traces of pentane. Yield: 37 mg (61%); 13C CP-MAS
ꢁ
NMR (258C): d=158 (HCCtBu), 130 (HCCtBu), 110, 104, 94, 85 (C
ꢁ
ꢁ
Cp^ ring), 61 (OCH3), 59 (CH CP^ ring), 38 (CH2), 38–31 ppm (C
tBu); elemental analysis calcd (%) for C25H43ClORu: C 60.52, H 8.74;
found: C 60.13, H 8.76.
2
ꢀ
[RuCl
E
was added to a solution of complex [RuCl
pentane (2 mL) at RT. The color of the solution instantaneously turned
violet. A small amount of crystals, appropriate for diffraction studies, ap-
peared on keeping the solution in the freezer at ꢁ208C for 1 day. Com-
plex 4 decomposed upon isolation or prolonged storage and elemental
analysis was thus not performed.
Computational details: Full geometry optimizations were performed with
DFT by using the M06 functional,[24] with the relativistic effective core
pseudo-potential LANL2DZ[25] for ruthenium and the 6-31G* basis set
for the remaining atoms. Remarkably, the use of more flexible basis sets
including diffuse functions showed no significant changes in the main
geometrical features of the optimized compounds. An ultrafine grid for
the numerical evaluation of the exchange and correlation integrals and
tight convergence criteria were used in all the calculations, which were
carried out with the Gaussian 09 series of programs.[26] The nature of the
stationary points located was further checked, and zero-point vibrational
energies (ZPVE) were evaluated by analytical computations of harmonic
vibrational frequencies at the same theory level. Intrinsic reaction coordi-
nate calculations were carried out to check the connection between the
transition states (TS) and the minimum-energy structures by using the
Gonzalez and Schlegel method[27] implemented in Gaussian 09. QST
computations[28] were also employed to confirm such connections in some
problematic cases. DGgas values were calculated within the ideal gas, rigid
rotor, and harmonic oscillator approximations.[29] A pressure of 1 atm.
and a temperature of 298.15 K were assumed in the calculations.
2
ꢀ
[RuCl
E
propyn-1-ol (50 mg) was added to a solution of complex [RuCl
(50 mg, 60 mmol) in THF (0.5 mL) at RT. The color of the solution in-
stantaneously turned violet. Pentane (2 mL) was added and the solution
was placed in a freezer. Crystals, appropriate for diffraction studies, ap-
peared on keeping the solution in the freezer at ꢁ208C for several days.
The crystals were collected and kept in the glove box for a few hours to
eliminate the remaining traces of the solvent. Yield: 38 mg (50%); ele-
mental analysis calcd (%) for C34H45ClO2Ru: C 65.63, H 7.29; found: C
65.71, H 7.15.
2
ꢀ
[RuCl
E
added to a solution of complex [RuCl
tane (2 mL) at RT. The color of the solution instantaneously turned
violet. Crystals, appropriate for diffraction studies, appeared on keeping
the solution in the freezer at ꢁ208C for several days. The crystals were
collected and kept in the glove box for few hours to eliminate the re-
maining traces of pentane. Yield: 38 mg (64%); elemental analysis calcd
(%) for C25H43ClORu: C 60.52, H 8.74; found: C 60.51, H 8.54.
To take into account condensed-phase effects, we used a self-consistent
reaction-field (SCRF) model in which the solvent is implicitly represent-
ed by a dielectric continuum characterized by its relative static dielectric
permittivity e. The solute, which is placed in a cavity created in the con-
tinuum after spending some cavitation energy, polarizes the continuum,
which in turn creates an electric field inside the cavity. This interaction
can be taken into account when using quantum chemical methods by
minimizing the electronic energy of the solute plus the Gibbs energy
change corresponding to the solvation process.[30] Addition of the solva-
2
ꢀ
G
G
acetylene dicarboxylate (14.8 mL, 120 mmol) was added to a solution of
complex [RuClACHTUNGTRENNUNG(Cp^)]2 (50 mg, 60 mmol) in pentane (2 mL) at RT. The
color of the solution instantaneously turned violet. Crystals, appropriate
for diffraction studies, appeared on keeping the solution in the freezer at
ꢁ208C for 1 day. The crystals were collected and washed with a few
drops of pentane. Yield: 47 mg (70%); elemental analysis calcd (%) for
C25H39ClO5Ru: C 54.00, H 7.07; found: C 54.04, H 7.09.
tion energy to DGgas gives the Gibbs free energy in solution, DGsoln
.
Within the different approaches that can be followed to calculate the
electrostatic potential created by the polarized continuum in the cavity,
we have employed the integral equation formalism of the polarizable
continuum model (IEFPCM).[31] The solvation Gibbs energies along the
reaction coordinates were evaluated from single-point calculations on the
gas-phase-optimized geometries at the same level of theory. A relative
permittivity of 8.93 was employed to simulate dichloromethane as the
solvent used in the experimental work.
ꢁ
[RuCl
E
E
(CF3)2}C=CH CH=C
G
G
3,5-bis(trifluoromethyl)phenylacetylene (90 mL) was added to a solution
of complex [RuClACHTUNGTRENNUNG(Cp^)]2 (50 mg, 60 mmol) in pentane (2 mL) at RT. The
color of the solution instantaneously turned violet and it was immediately
cooled to ꢁ208C. Red crystals, appropriate for diffraction studies, ap-
peared on keeping the solution in the freezer at ꢁ208C for 2 days. The
crystals were collected and washed with pentane. Yield: 50 mg (47%);
19F NMR (CD2Cl2, 258C): d=ꢁ63.03 ppm; elemental analysis calcd (%)
for C39H41ClF12ORu: C 52.62, H 4.64; found: C 52.73, H 4.68.
General procedure for cyclotrimerization reactions: A stock solution
(12.5 mm) of the catalyst 1 was prepared in degassed CD2Cl2 or dichloro-
ethane. The desired amount of the stock solution was added to a solution
of the substrate containing a suitable internal standard (dioxane or p-
xylene) (final volume=1000 mL, substrate=0.5 mmol). The solutions
were stirred at room temperature or at 608C. After a given time, a
sample (20 mL) was removed from the reaction mixture, diluted with
Acknowledgements
This work was supported by the Swiss National Science Foundation and
by the EPFL. The authors thank Dr. Simone Cavadini for assistance with
the solid-state (CP-MAS) NMR spectroscopic measurements.
1
CD2Cl2 (350 mL), and instantaneously analyzed by H NMR spectroscopy.
Chem. Eur. J. 2010, 16, 8400 – 8409
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8407

K. Severin et al.
Table 5. Crystallographic data for the complexes 3–8.
Complex
3
4
5
6
7
8
empirical formula
C25H43ClORu
496.11
0.16ꢈ0.13ꢈ0.10
monoclinic
P21/n
12.7932(19)
14.4178(17)
14.4804(19)
90
109.589(11)
90
C27H39ClORu
516.10
0.38ꢈ0.25ꢈ0.12
monoclinic
I2/a
25.363(3)
11.7763(9)
37.710(3)
90
92.085(14)
90
C37.5H49ClO2Ru
668.29
0.30ꢈ0.25ꢈ0.19
triclinic
C28H48ClORu
537.18
0.25ꢈ0.16ꢈ0.13
monoclinic
P21/n
10.6248(10)
17.728(2)
15.6814(16)
90
108.889(8)
90
C29H47ClO6Ru
628.19
0.33ꢈ0.30ꢈ0.25
monoclinic
P21/c
15.4925(5)
12.9986(3)
16.1385(5)
90
112.418(4)
90
C39H41ClF12ORu
890.24
0.26ꢈ0.20ꢈ0.09
monoclinic
P21/c
15.2196(13)
18.4821(18)
14.1551(18)
90
101.153(9)
90
Mw [gmolꢁ1
]
crystal size [mm3]
crystal system
space group
a [ꢅ]
P-1
9.6006(3)
12.5728(4)
15.1786(5)
81.173(3)
73.336(3)
72.131(3)
1666.23(9)
2
b [ꢅ]
c [ꢅ]
a [8]
b [8]
g [8]
V [ꢅ3]
2516.3(6)
4
1.310
11256.2(17)
16
1.218
2794.6(5)
4
1.277
3004.37(15)
4
1.389
3906.5(7)
4
1.514
Z
1 [gcmꢁ3
T [K]
]
1.332
140(2)
100(2)
140(2)
100(2)
140(2)
100(2)
absorption coeff.
0.742
0.666
0.582
0.673
0.649
0.557
[mmꢁ1
]
V range [8]
index ranges
3.29 to 25.02
ꢁ15ꢄ15
2.43 to 25.03
ꢁ30ꢄ30
0ꢄ14
2.81 to 26.02
ꢁ10ꢄ11
3.58 to 27.50
ꢁ13ꢄ13
2.73 to 26.37
ꢁ19ꢄ17
3.31 to 27.5
ꢁ19ꢄ19
ꢁ23ꢄ24
ꢁ18ꢄ18
87602
ꢁ17ꢄ16
ꢁ15ꢄ14
ꢁ23ꢄ22
ꢁ16ꢄ16
ꢁ17ꢄ17
0ꢄ44
ꢁ17ꢄ18
ꢁ20ꢄ20
ꢁ19ꢄ20
reflns collected
31846
9864
14755
62115
23872
independent reflns
4425
9864
6499
6405
6088
8943
(Rint=0.1294)
semi-empirical
(Rint=0.0000)
semi-empirical
(Rint=0.0407)
semi-empirical
(Rint=0.0439)
semi-empirical
(Rint=0.0399)
semi-empirical
(Rint=0.1945)
semi-empirical
absorption correc-
tion
max. and min. trans- 0.928, 0.788
mission
1.00000, 0.87565
9864/4/547
0.895, 0.850
6499/1/383
0.874, 0.738
6405/0/280
0.850, 0.754
6088/5/334
0.951, 0.835
8943/30/498
data/restraints/
param.
4425/13/267
GoF on F2
1.135
0.775
1.028
1.207
1.029
1.165
final R indices
[I>2s(I)]
R indices (all data)
R1=0.1008,
wR2=0.2279
R1=0.1355,
wR2=0.2458
1.598, ꢁ1.044
R1=0.0795,
wR2=0.1442
R1=0.2173,
wR2=0.1734
0.581, ꢁ0.618
R1=0.0438,
wR2=0.0955
R1=0.0618,
wR2=0.1001
1.637, ꢁ0.527
R1=0.0305,
wR2=0.0571
R1=0.0386,
wR2=0.0599
0.520, ꢁ0.454
R1=0.0367,
wR2=0.0888
R1=0.0526,
wR2=0.0948
0.986, ꢁ0.413
R1=0.0850,
wR2=0.1139
R1=0.1434,
wR2=0.1300
0.921, ꢁ0.637
larg. diff. peak/hole
[eꢅꢁ3
]
[3] a) B. C. Boren, S. Narayan, L. K. Rasmussen, L. Zhang, H. Zhao, Z.
Lin, G. Jia, V. V. Fokin, J. Am. Chem. Soc. 2008, 130, 8923–8930;
b) U. Pradere, V. Roy, T. R. McBrayer, R. F. Schinazi, L. A. Agrofo-
glio, Tetrahedron 2008, 64, 9044–9051; c) L. K. Rasmussen, B. C.
Boren, V. V. Fokin, Org. Lett. 2007, 9, 5337–5339; d) A. Tam, U.
Arnold, M. B. Soellner, R. T. Raines, J. Am. Chem. Soc. 2007, 129,
12670–12671; e) S. Oppilliart, G. Mousseau, L. Zhang, G. Jia, P.
Thuꢀry, B. Rousseau, J.-C. Cintrat, Tetrahedron 2007, 63, 8094–
8098; f) M. M. Majireck, S. M. Weinreb, J. Org. Chem. 2006, 71,
8680–8683; g) L. Zhang, X. Chen, P. Xue, H. H. Y. Sun, I. D. Wil-
liams, B. K. Sharpless, V. V. Fokin, G. Jia, J. Am. Chem. Soc. 2005,
127, 15998–15999.
[1] For reviews see: a) B. M. Trost, M. U. Frederiksen, M. T. Rudd,
Angew. Chem. 2005, 117, 6788–6825; Angew. Chem. Int. Ed. 2005,
44, 6630–6666; b) S. Dꢀrien, P. H. Dixneuf, J. Organomet. Chem.
2004, 689, 1382–1392; c) S. Dꢀrien, F. Monnier, P. H. Dixneuf, Top.
Organomet. Chem. 2004, 11, 1–44; d) R. Schmid, K. Kirchner, Eur.
J. Inorg. Chem. 2004, 2609–2626; e) C. Bruneau, Top. Organomet.
Chem. 2004, 11, 125–153; f) B. M. Trost, F. D. Toste, A. B. Pinker-
ton, Chem. Rev. 2001, 101, 2067–2096; g) P. H. Dixneuf, C. Bruneau,
S. Dꢀrien, Pure Appl. Chem. 1998, 70, 1065–1070.
[2] a) K. C. Nicolaou, Y. Tang, J. Wang, Angew. Chem. 2009, 121, 3501–
3505; Angew. Chem. Int. Ed. 2009, 48, 3449–3453; b) L. Severa, J.
ˇ
ˇ
ˇ
ˇ
´
Vꢆvra, A. Kohoutovꢆ, M. Cꢇzkovꢆ, T. Sꢆlovꢆ, J. Hyvl, D. Saman, R.
[4] a) N. Cockburn, E. Karimi, W. Tam, J. Org. Chem. 2009, 74, 5762–
5765; b) A. Allen, K. Villeneuve, N. Cockburn, E. Fatila, N. Riddell,
W. Tam, Eur. J. Org. Chem. 2008, 4178–4192; c) R. W. Jordan, P. Le
Marquand, W. Tam, Eur. J. Org. Chem. 2008, 80–86; d) R. R.
Burton, W. Tam, J. Org. Chem. 2007, 72, 7333–7336; e) R. R.
Burton, W. Tam, Org. Lett. 2007, 9, 3287–3290; f) A. Tenaglia, S.
Gaillard, Org. Lett. 2007, 9, 3607–3610; g) P. Liu, W. Tam, J. D.
Goddard, Tetrahedron 2007, 63, 7659–7666; h) K. Villeneuve, W.
Tam, Organometallics 2006, 25, 843–848; i) R. W. Jordan, K. Ville-
neuve, W. Tam, J. Org. Chem. 2006, 71, 5830–5833; j) P. Liu, R. W.
Jordan, S. P. Kibbee, J. D. Goddard, W. Tam, J. Org. Chem. 2006, 71,
3793–3803; k) R. R. Burton, W. Tam, Tetrahedron Lett. 2006, 47,
7185–7189; l) K. Villeneuve, W. Tam, Angew. Chem. 2004, 116,
620–623; Angew. Chem. Int. Ed. 2004, 43, 610–613; m) K. Ville-
neuve, N. Riddell, R. W. Jordan, G. C. Tsui, W. Tam, Org. Lett. 2004,
6, 4543–4546; n) R. W. Jordan, P. R. Khoury, J. D. Goddard, W.
´
Pohl, L. Adriaenssens, F. Teply, Tetrahedron Lett. 2009, 50, 4526–
4528; c) Y. Yamamoto, K. Hattori, H. Nishiyama, J. Am. Chem. Soc.
2006, 128, 8336–8340; d) Y. Yamamoto, K. Hattori, J.-i. Ishii, H.
Nishiyama, Tetrahedron 2006, 62, 4294–4305; e) Y. Yamamoto, J.
Ishii, H. Nishiyama, K. Itoh, J. Am. Chem. Soc. 2005, 127, 9625–
9631; f) Y. Ura, Y. Sato, H. Tsujita, T. Kondo, M. Imachi, T. Mitsu-
do, J. Mol. Catal. A 2005, 239, 166–171; g) Y. Yamamoto, K. Kin-
para, T. Saigoku, H. Nishiyama, K. Itoh, Org. Biomol. Chem. 2004,
2, 1287–1294; h) Y. Yamamoto, J. Ishii, H. Nishiyama, K. Itoh, J.
Am. Chem. Soc. 2004, 126, 3712–3713; i) Y. Ura, Y. Sato, M. Shiot-
suki, T. Kondo, T. Mitsudo, J. Mol. Catal. A 2004, 209, 35–39; j) Y.
Yamamoto, T. Arakawa, R. Ogawa, K. Itoh, J. Am. Chem. Soc.
2003, 125, 12143–12160; k) Y. Yamamoto, K. Hata, T. Arakawa, K.
Itoh, Chem. Commun. 2003, 1290–1291; l) Y. Yamamoto, R. Ogawa,
K. Itoh, Chem. Commun. 2000, 549–550.
8408
www.chemeurj.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 8400 – 8409

Reactions of Alkynes with [RuCl(cyclopentadienyl)] Complexes
FULL PAPER
Tam, J. Org. Chem. 2004, 69, 8467–8474; o) R. W. Jordan, W. Tam,
Tetrahedron Lett. 2002, 43, 6051–6054; p) R. W. Jordan, W. Tam,
Org. Lett. 2001, 3, 2367–2370; q) R. W. Jordan, W. Tam, Org. Lett.
2000, 2, 3031–3034; r) T. Mitsudo, H. Naruse, T. Kondo, Y. Ozaki,
Y. Watanabe, Angew. Chem. 1994, 106, 595–597; Angew. Chem. Int.
Ed. Engl. 1994, 33, 580–581.
Jacobi, Eur. J. Inorg. Chem. 2000, 33–50; d) J. R. Lomprey, J. P. Se-
legue, J. Am. Chem. Soc. 1992, 114, 5518–5523.
[16] The regioselective formation of 1,2,4-trisubstituted benzene deriva-
tives can be achieved with Co-based catalysts, see: G. Hilt, C.
Hengst, W. Hess, Eur. J. Org. Chem. 2008, 2293–2297.
[17] In contrast, significantly distorted geometries were obtained when
using the B3LYP functional. This fact is in agreement with previous
theoretical investigations on similar organometallic Ru compounds
that have already indicated the superior performance of M06 to cap-
ture correlation effects at the origin of the dispersion interactions
between bulky ligands present in the molecular skeleton, see: a) Y.
Zhao, D. G. Truhlar, J. Chem. Theory Comput. 2009, 5, 324–333;
b) C. J. Cramer, D. G. Truhlar, Phys. Chem. Chem. Phys. 1989, 9,
10757–10816, and references therein.
[18] U. Koelle, J. Kossakowski, J. Chem. Soc. Chem. Commun. 1988,
549–551.
[19] A. J. M. Duisenberg, L. M. J. Kroon-Batenburg, A. M. M. Schreurs,
J. Appl. Crystallogr. 2003, 36, 220–229.
[20] CrysAlis PRO, Oxford Diffraction Ltd., Oxfordshire, 2009.
[21] R. H. Blessing, Acta Crystallogr. Sect. A 1995, 51, 33–38.
[22] SHELX: G. M. Sheldrick, Acta Crystallogr. Sect. A 2008, 64, 112–
122.
[5] a) J. Le Paih, S. Dꢀrien, B. Demerseman, C. Bruneau, P. H. Dixneuf,
L. Toupet, G. Dazinger, K. Kirchner, Chem. Eur. J. 2005, 11, 1312–
1324; b) J. Le Paih, F. Monnier, S. Dꢀrien, P. H. Dixneuf, E. Clot, O.
Eisenstein, J. Am. Chem. Soc. 2003, 125, 11964–11975; c) J. Le Paih,
S. Dꢀrien, P. H. Dixneuf, Chem. Commun. 1999, 1437–1438.
[6] a) S. Dꢀrien, D. Jan, P. H. Dixneuf, Tetrahedron 1996, 52, 5511–
5524; b) S. Dꢀrien, P. H. Dixneuf, J. Chem. Soc. Chem. Commun.
1994, 2551–2552; c) B. M. Trost, J. A. Flygare, J. Org. Chem. 1994,
59, 1078–1082; d) B. M. Trost, J. A. Flygare, Tetrahedron Lett. 1994,
35, 4059–4062; e) B. M. Trost, J. A. Martinez, R. J. Kulawiec, A. F.
Indolese, J. Am. Chem. Soc. 1993, 115, 10402–10403; f) B. M. Trost,
R. J. Kulawiec, A. Hammes, Tetrahedron Lett. 1993, 34, 587–590;
g) B. M. Trost, J. A. Flygare, J. Am. Chem. Soc. 1992, 114, 5476–
5477; h) B. M. Trost, R. J. Kulawiec, J. Am. Chem. Soc. 1992, 114,
5579–5584; i) B. M. Trost, G. Dyker, R. J. Kulawiec, J. Am. Chem.
Soc. 1990, 112, 7809–7811.
[7] a) F. Monnier, D. Castillo, S. Dꢀrien, L. Toupet, P. H. Dixneuf,
Angew. Chem. 2003, 115, 5632–5635; Angew. Chem. Int. Ed. 2003,
42, 5474–5477; b) J. Le Paih, S. Dꢀrien, I. ꢉzdemir, P. H. Dixneuf, J.
Am. Chem. Soc. 2000, 122, 7400–7401.
[8] a) J. A. Varela, C. Saꢆ, J. Organomet. Chem. 2009, 694, 143–149;
b) K. Kirchner, M. J. Calhorda, R. Schmid, L. F. Veiros, J. Am.
Chem. Soc. 2003, 125, 11721–11729; c) K. Kirchner, Monatsh.
Chem. 2008, 139, 337–348.
[9] a) L. Zhang, H. H.-Y. Sung, I. D. Williams, Z. Lin, G. Jia, Organo-
metallics 2008, 27, 5122–5129; b) Y. Yamada, J. Mizutani, M. Kuri-
hara, H. Nishihara, J. Organomet. Chem. 2001, 637–639, 80–83;
c) C. Ernst, O. Walter, E. Dinjus, J. Organomet. Chem. 2001, 627,
249–254; d) C. Ernst, O. Walter, E. Dinjus, S. Arzberger, H. Gçrls,
J. Prakt. Chem. 1999, 341, 801–804; e) C. Gemel, A. LaPensꢀe, K.
Mauthner, K. Mereiter, R. Schmid, K. Kirchner, Monatsh. Chem.
1997, 128, 1189–1199; f) M. O. Albers, D. J. A. de Waal, D. C. Liles,
D. J. Robinson, E. Singleton, M. B. Wiege, J. Chem. Soc. Chem.
Commun. 1986, 1680–1682.
[10] a) B. Dutta, E. Solari, S. Gauthier, R. Scopelliti, K. Severin, Organo-
metallics 2007, 26, 4791–4799; b) S. Gauthier, E. Solari, B. Dutta, R.
Scopelliti, K. Severin, Chem. Commun. 2007, 1837–1839.
[11] B. Dutta, C. Scolaro, R. Scopelliti, P. J. Dyson, K. Severin, Organo-
metallics 2008, 27, 4791–4799.
[23] PLATON, A Multipurpose Crystallographic Tool, A. L. Spek,
Utrecht University, Utrecht, 2010.
[24] Y. Zhao, D. G. Truhlar, Theor. Chem. Acc. 2008, 120, 215–241.
[25] P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 299–310.
[26] Gaussian 09, Revision A.02, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V.
Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X.
Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Son-
nenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven,
J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J.
Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar,
J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox,
J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E.
Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W.
Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A.
Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, ꢉ.
Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian,
Inc., Wallingford CT, 2009.
[27] a) C. Gonzalez, H. B. Schlegel, J. Chem. Phys. 1989, 90, 2154–2161;
b) C. Gonzalez, H. B. Schlegel, J. Phys. Chem. 1990, 94, 5523–5527.
[28] C. Peng, P. Y. Ayala, H. B. Schlegel, M. J. Frisch, J. Comput. Chem.
1996, 17, 49–56.
[29] D. A. McQuarrie, Statistical Mechanics, Harper, New York, 1986.
[30] P. Claverie in Quantum Theory of Chemical Reactions (Ed.: R.
Daudel, A. Pullman, L. Salem, A. Veillard), Reidel, Dordrecht,
1982.
[12] B. Dutta, R. Scopelliti, K. Severin, Organometallics 2008, 27, 423–
429.
[13] P. J. Fagan, W. S. Mahoney, J. C. Calabrese, I. D. Williams, Organo-
metallics 1990, 9, 1843–1852.
[14] M. I. Bruce, Chem. Rev. 1991, 91, 197–257.
[15] a) E. Bustelo, J. J. Carbo, A. Lledos, K. Mereiter, M. C. Puerta, P.
Valerga, J. Am. Chem. Soc. 2003, 125, 3311–3321; b) C. M. Older,
J. M. Stryker, Organometallics 2000, 19, 2661–2663; c) K. Urtel, A.
Frick, G. Huttner, L. Zsolnai, P. Kircher, P. Rutsch, E. Kaifer, A.
[31] J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 2005, 105, 2999–
3093.
Received: April 6, 2010
Published online: June 25, 2010
Chem. Eur. J. 2010, 16, 8400 – 8409
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8409