Homobimetallic ruthenium vinylidene, allenylidene, and indenylidene complexes: Synthesis, characterization, and catalytic studies

Article abstract of DOI:10.1002/adsc.200800664

Four homobimetallic ruthenium-(p-cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex [(p-cymene)Ru(μ-Cl)

Full text of DOI:10.1002/adsc.200800664

FULL PAPERS
DOI: 10.1002/adsc.200800664
Homobimetallic Ruthenium Vinylidene, Allenylidene, and
Indenylidene Complexes: Synthesis, Characterization, and
Catalytic Studies
Xavier Sauvage,a Yannick Borguet,a Guillermo Zaragoza,b Albert Demonceau,a
and Lionel Delaudea,*
a
Center for Education and Research on Macromolecules, Institut de Chimie (B6a), Universitꢀ de Liꢁge, Sart-Tilman par
4000 Liꢁge, Belgium
Fax : (+32)-4-366-3497; e-mail: l.delaude@ulg.ac.be
Unidade de Difracciꢂn de Raios X, Edificio CACTUS, Universidade de Santiago de Compostela, Campus Sur, 15782
b
Santiago de Compostela, Spain
Received: October 29, 2008; Published online: February 13, 2009
Abstract: Four homobimetallic ruthenium-(p- molecular decomposition of methylidene active spe-
cymene) complexes bearing a tricyclohexylphosphine cies into ethylene complex 7a. Vinylidene and alleny-
ligand and polyunsaturated carbon-rich fragments lidene complexes were far less efficient catalyst pre-
were obtained via a vinylidene-allenylidene-indenyli- cursors for ring-opening metathesis polymerization
dene cascade pathway from the ethylene complex (ROMP) or RCM and remained inert under an eth-
[(p-cymene)Ru
(m-Cl)3RuCl
E
G
(7a). ylene atmosphere. Their catalytic activity was, how-
All the products were isolated and fully character- ever, substantially enhanced upon addition of an
ized by IR and NMR spectroscopies. The molecular acidic co-catalyst that most likely promoted their in
structure of the indenylidene complex 11 was deter- situ transformation into indenylidene species. Due to
mined by X-ray crystallographic analysis. The cata- its straightforward synthesis and high metathetical
lytic activity of the four complexes was probed in activity, homobimetallic ruthenium-indenylidene
various types of olefin metathesis reactions and com- complex 11 is a valuable intermediate for the prepa-
pared with those of a related homobimetallic ruthe- ration
of
the
Hoveyda–Grubbs
catalyst
nium-benzylidene complex, as well as first, second, [Cl2Ru
N
ACHTUGNRTNE(NUNG PCy3)(=CH-o-O-i-PrC6H4)] via stoichiomet-
and third generation monometallic Grubbs catalysts. ric cross-metathesis with 2-isopropoxystyrene. The
In the ring-closing metathesis (RCM) of diethyl di- procedure did not require any sacrificial phosphine
ACHTUNGTRENNUNGallylmalonate, the homobimetallic ruthenium-indeny- and the transition metal not incorporated into the
lidene complex 11 outperformed all the ruthenium- final product was easily recovered and recycled at
benzylidene complexes under investigation and was the end of the process.
only slightly less efficient than its monometallic
parent. Cross-metathesis experiments with ethylene
showed that deactivation of ruthenium-benzylidene Keywords: alkenes; arene ligands; bridging ligands;
or indenylidene complexes was due to the rapid bi- catalyst design; metathesis; propargylic alcohols
Introduction
ubility,[7] recoverability,[8] or latency[9] toward specific
catalytic processes,[10] sometimes in an asymmetric
Owing to the advent of highly efficient, well-defined fashion.[11] Although a single ruthenium center is pre-
ruthenium catalysts, olefin metathesis has emerged as served in most cases, a few homo- and heterobimetal-
a powerful tool for assembling unsaturated hydrocar- lic species have also been described. In a seminal con-
bon backbones in organic synthesis and in polymer tribution from 1998, Grubbs et al. reported the graft-
chemistry.[1] Most catalytic systems investigated so far ing of a second metal onto 1a by reacting it with tran-
derive from the Grubbs first generation ruthenium- sition metal dimers containing bridging chloride li-
benzylidene complex [RuCl
(PCy3 is tricyclohexylphosphine).[2] Countless structur- (2) was reacted with complex 1a to afford complex 3a
al alterations have been made to this archetypal com- and stoichiometric amount of by-product
pound in order to tailor its activity,[3,4] stability,[5,6] sol- (Scheme 1). In 1999, Herrmann and co-workers ex-
2ACHTUNGTRENU(GNN =CHPh)ACHTNURTEGNNUNG 2ACHTNUGTRENN(UGN p-cymene)]2 dimer
(PCy3)2] (1a) gands.[12] In particular, the [RuCl
a
4
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Xavier Sauvage et al.
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Scheme 2. Synthesis of homobimetallic ruthenium-ethylene
complexes 7a, b.
In 2005, Severin and co-workers investigated the re-
action of [RuCl
PCy3 under an ethylene atmosphere. Under these
Scheme 1. Synthesis of homobimetallic ruthenium-benzyli- conditions, the ruthenium-(p-cymene) dimer 2 afford-
dene complexes 3a, b.
2ACHTUNGERTN(NUNG p-cymene)]2 with 1 equivalent of
ed a new type of molecular scaffold 7a, in which an
RuCl (PCy3) fragment was connected via
(h2-C2H4)
three m-chloro bridges to a ruthenium-arene moiety,
A
ACHTUNGTRENNUNG
tended this methodology to the synthesis of bimetallic as evidenced by X-ray diffraction analysis
ruthenium-alkylidene complex 3b bearing an N- (Scheme 2).[22] The only by-product formed was one
heteroACHTUNGTRENNUNGcyclic carbene (NHC) instead of a phosphine equivalent of p-cymene. In view of the enhancements
ancillary ligand (Scheme 1).[13–16] In both complexes brought by the replacement of phosphines with NHCs
3a and 3b, the presence of two m-chloro bridges was in monometallic ruthenium-arene catalyst precursors
postulated by analogy with the structure of the parent for olefin metathesis[23,24] and atom transfer radical re-
dimer 2, but no crystal structure was determined to actions,[25] we adopted the same strategy to synthesize
support this assumption.
two new homobimetallic complexes of type 7b bear-
A related homobimetallic complex obtained by re- ing NHCs instead of phosphine ligands.[26] Catalytic
acting the ruthenium-arene dimer 2 with a monome- tests showed that the replacement of PCy3 with car-
tallic adduct generated by treating [RuCl2ACHTNUTRGNEUNG(PPh3)3] bene ligands induced a major shift of reactivity.
with 1,1-diphenylpropargyl alcohol followed by phos- Indeed, complexes 7b were found to be highly suita-
phine exchange with PCy3 was also investigated by ble for promoting olefin metathesis, whereas complex
Hill and Fꢄrstner in 1999.[17,18] It was initially assumed 7a was essentially inactive under the same experimen-
to contain an allenylidene fragment. However, subse- tal conditions. Results from this study also indicated
quent work from the groups of Nolan[19] and Fꢄrst- that the ethylene ligand was highly labile and that
ner[20] showed that this compound actually involved a adding a small amount of terminal alkyne to the reac-
ruthenium-indenylidene moiety formed by intramolec- tion media had a beneficial influence on the metathet-
ular rearrangement (see structure 5). In yet another ical activity.[26] These observations prompted us to fur-
variation, Verpoort et al. prepared a series of homobi- ther investigate the role of the alkyne co-catalyst.
metallic ruthenium-benzylidene complexes bearing bi-
In this contribution, we explore the chemistry of
dentate Schiff base ligands 6.[21] Concomitant forma- new homobimetallic ruthenium-arene complexes
tion of ruthenium-arene complex 4 occurred in all bearing vinylidene, allenylidene, and indenylidene li-
cases.
gands prepared from complex 7a and propargyl alco-
hol derivatives. We also compare their catalytic activi-
ties toward several types of olefin metathesis reac-
tions and we show that they are valuable intermedi-
ates for the safe and efficient one-pot synthesis of the
Hoveya–Grubbs
alkoxybenzylidene
catalyst
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ACHTUNGTRENNUNG
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Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes
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Results and Discussion
pared by alkylation of 1,1-diphenylpropynol with n-
bromopropane in the presence of sodium hydride ac-
cording to standard procedures.[30–32] At room temper-
ature in dichloromethane, its reactivity toward ruthe-
nium-ethylene complex 7a closely matched the one
Synthesis and Characterization of Homobimetallic
Ruthenium Complexes
By analogy with the preparation of monometallic observed with 1,1-diphenylpropynol and resulted in
ruthenium-alkylidene complexes bearing the meta- the formation of vinylidene complex 8b in almost
ꢀ
thetically active Ru=CH CH=CPh2 or Ru=CHPh quantitative yield (Scheme 3). Spectroscopic evidence
moieties from [RuCl
N
clopropene[27] or phenyldiazomethane,[2] respectively, tensity IR band at 1669 cmꢀ1 (nC C) and a doublet at
we first investigated the reaction of homobimetallic 4.00 ppm with a coupling constant JP, H =3.8 Hz for
=
4
ruthenium-ethylene complex 7a with these two car- the vinylidene proton. The a-carbon atom resonated
2
bene precursors. Preliminary experiments along these as a doublet with a coupling constant JP, C =16.5 Hz in
lines were conducted in dichloromethane at room 13C{1H} NMR and was located much further down-
temperature. Disappointingly, there was no sign of field (339.5 ppm) than the Cb remote end (s,
evolution after a few hours and only unidentified de- 110.3 ppm). In 31P{1H} NMR, a unique singlet was ob-
composition products were detected by 31P NMR served at 54.0 ppm.
spectroscopy when the reaction media were kept for
Extended 31P NMR monitoring revealed that di-
longer periods of time. We then turned our attention chloromethane solutions of complexes 8a, b were not
to the use of propargylic alcohol derivatives, since fully stable at room temperature. Hence, 13C NMR
they are well known to afford polyunsaturated experiments that required overnight acquisitions were
carbon-rich ligands by reaction with ruthenium cen- performed at ꢀ408C. At this temperature, however,
ters.[17–20,28,29] Thus, complex 7a was reacted with a carbon atoms coupled to the phosphorus nucleus dis-
small excess of 1,1-diphenyl-2-propyn-1-ol in dichloro- played significantly broadened peaks. Signs for a slow
methane at room temperature (Scheme 3). Within albeit irreversible transformation were most visible
2 h, a clean and quantitative reaction had occurred, as for complex 8b that spontaneously expelled n-propa-
evidenced by the disappearance of the initial phos- nol to afford homobimetallic ruthenium-allenylidene
phine resonance at 44.3 ppm and the emergence of a complex 9 after 2–4 days (Scheme 4). The exact dura-
new signal located at 54.4 ppm in CH2Cl2 spiked with tion necessary to achieve a full conversion varied
CD2Cl2. After solvent evaporation and washing, ho- from one experiment to another and is most likely in-
mobimetallic ruthenium-vinylidene complex 8a was fluenced by the presence of acidic trace impurities
isolated in 90% yield. Apart from its 31P NMR signa- that could assist the departure of the propoxide
ture, characteristic spectroscopic features included a group. Yet, the reaction proceeded cleanly and com-
sharp line at 1645 cmꢀ1 (nC C) and a broad absorption plex 9 was isolated in almost quantitative yield by
=
centered at 3416 cmꢀ1 (nOH) on IR spectroscopy, a simple filtration and washing. Support in favour of an
4
doublet at 4.78 ppm with a coupling constant JP, H
=
allenylidene group came from the presence of a
1
3.5 Hz for the vinylidene proton on H NMR spec- nC
absorption at 1918 cmꢀ1 on IR spectroscopy
= =
C C
troscopy, and
a
highly deshielded doublet at and three 13C{1H} characteristic resonances for the
2
345.9 ppm with a coupling constant JP, C =18.1 Hz for Ru=C=C=CPh2 spine located at 301.5, 237.3, and
the Ru=C carbon nucleus on 13C NMR.
147.1 ppm, the former being a doublet with a coupling
2
Inspired by a report from Dixneuf et al. who constant JP, C =18.1 Hz in CD2Cl2 at 258C. Moreover,
showed that the reaction of allyl or propyl propargylic both H and 13C NMR spectra showed that the two
1
ethers with cationic ruthenium-arene complexes pro- phenyl rings were equivalent. Thus, we were eventual-
ceeded via retro-ene cleavage to afford monometallic ly able to isolate the homobimetallic ruthenium-alle-
alkenyl-carbene-ruthenium species,[30] we decided to nylidene complex initially postulated by Hill and
investigate the reaction of complex 7a with 1,1-diphe- Fꢄrstner in 1999,[17,18] although subsequent studies
nylpropynyl n-propyl ether. This substrate was pre-
Scheme 3. Synthesis of homobimetallic ruthenium-vinylidene complexes 8a, b.
Adv. Synth. Catal. 2009, 351, 441 – 455
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Xavier Sauvage et al.
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Scheme 4. Synthesis of homobimetallic ruthenium-allenylidene complex 9.
proved that these authors actually had obtained the ionic ruthenium-carbyne complex (10) (Scheme 5).
phenylindenylidene species depicted as 5 instead.[20]
This intermediate remained stable for several hours in
In the case of g-hydroxyvinylidene complex 8a, CD2Cl2 at ꢀ508C but quickly decomposed into a com-
slow conversion into allenylidene product 9 was also plex mixture of unidentified products upon warming
observed in dichloromethane at room temperature to room temperature, thereby precluding its isolation
1
(Scheme 4). Under these conditions, the dehydration and full characterization. H and 13C{1H} NMR spec-
was, however, accompanied by side-reactions leading tra recorded at ꢀ508C were difficult to interpret, due
to unidentified by-products and was therefore of little to line broadening and poor signal-to-noise ratio. It
synthetic value. Since we suspected the released water was nevertheless possible to identify a doublet at
to be responsible for this mischief, we first tried to 6.24 ppm with a coupling constant 4JP, H =2.0 Hz in
percolate a dichloromethane solution of complex 8a 1H NMR and a doublet at 311.3 ppm with a coupling
through a short column packed with acidic alumina. constant 2JP, C =23.6 Hz in 13C{1H} NMR for the
ꢁ ꢀ
Unfortunately, due to the strong affinity of product 9 Ru C CH motif.
towards the stationary phase, elution was largely inef-
Addition of 1 equivalent of trifluoroacetic acid to a
ficient and only poor yields were attained. Trapping cold CD2Cl2 solution of ruthenium-vinylidene com-
water with molecular sieves 3 ꢅ proved to be a much plexes 8a, b led to the same experimental observa-
more satisfactory strategy. In the presence of this tions that were made starting from allenylidene deriv-
drying agent, 2 days were still necessary to achieve a ative 9 and also pointed to the instant formation of
full conversion of vinylidene complex 8a into allenyli- carbyne complex 10 (Scheme 5). The only difference
dene product 9, but the isolated yield climbed to 85% was the presence of supplementary peaks due to H2O
1
and side-reactions were suppressed.
(for 8a) or n-PrOH (for 8b) in the H NMR spectra.
1
Detailed mechanistic studies by the groups of Dix- In the latter case, integration of the various H signals
neuf[33] and Schanz[29] have recently highlighted the confirmed the quantitative release of 1 equivalent of
role of acids on the rearrangement of allenylidene alcohol. The formation of n-PrOH was also evidenced
units into indenylidene groups in various monometal- by 13C NMR spectroscopy. Due to the rapidity of the
lic ruthenium complexes, either neutral or cationic. transformation, no evidence for the transient forma-
These findings prompted us to investigate the reaction tion of allenylidene complex 9 was detected, although
of homobimetallic ruthenium-allenylidene complex 9 it cannot be ruled out. Once again, the labile inter-
with a stoichiometric amount of trifluoroacetic acid. mediate 10 observed at ꢀ508C did not persist at
Upon addition of the acid to the complex dissolved in room temperature and led to several unidentified
CD2Cl2 at ꢀ508C, an instantaneous colour change products upon decomposition. When a small amount
from dark red to yellow occurred and the 31P{1H} of anhydrous calcium chloride was added to the
NMR absorption of 9 located at 54.1 ppm was re- NMR tube containing a CD2Cl2 solution of complex
placed by a new downfield signal at 68.0 ppm. These 8a or 8b at ꢀ508C prior to the introduction of tri-
observations strongly suggest the formation of a cat- fluoroacetic acid and warming to room temperature,
Scheme 5. Proposed reaction path for the formation of indenylidene complexes 5 or 11.
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Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes
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Scheme 6. Synthesis of homobimetallic ruthenium-indenylidene complex 11.
however, a cleaner reaction slowly occurred, as shown phosphine[34] or NHC ligands.[19] From these data, it
by the progressive replacement of the 31P signal at can be inferred that the genuine structure of com-
68.0 ppm by a single new line at 41.1 ppm. This reso- pound 5 actually involved a ruthenium-indenylidene
nance had previously been assigned to the ruthenium- moiety linked via three m-chloro bridges to the second
indenylidene complex 5 (Scheme 5).[17] Thus, addition metal center. The structure of homobimetallic ruthe-
of a drying agent effectively prevented side-reactions nium-benzylidene complexes 3a, b should probably
and nicely complemented the recourse to an acidic also be revised to account for the presence of three
promoter for inducing a direct vinylidene-to-indenyli- bridging chlorine atoms instead of two, but we have
dene interconversion.
not been able to obtain X-ray crystal structures to
When performing the transformation on a some- support this assumption yet.
what larger scale, we successfully employed para-tol-
The profound influence exerted by the indenyli-
uenesulfonic acid monohydrate as acidic promoter dene ligand on the chloro atom trans to it is responsi-
ꢀ
(Scheme 6). This solid reagent was found more con- ble for the significantly longer Ru2 Cl3 distance
ꢀ
venient to handle and to weigh precisely than tri- [2.6657(10) ꢅ] compared with other Ru Cl bonds in
fluoroacetic acid. We also employed molecular sieves the crystal structure of complex 11. All these meas-
3 ꢅ as dehydrating agent instead of calcium chloride urements are in line with those recorded previously
when starting from hydroxy compound 8a. Reaction by Severin et al. for various other homobimetallic
mixtures were stirred overnight in dichloromethane at ruthenium-arene complexes bearing three m-chloro
room temperature. Homobimetallic ruthenium-inden- bridges.[22,35] Based on the data acquired by the Swiss
ylidene complex 11 was isolated in 86–87% yield group, the trans effect of the indenylidene unit in
from both 8a, b after filtration and work-up. Its IR complex 11 may be ranked slightly superior to that of
and NMR spectra were identical to those reported
earlier in the literature for complex 5.[17,20] Distinctive
absorption bands for the indenylidene group were ob-
served at 1947 and 1621 cmꢀ1 on IR spectroscopy,
while the Ru=C carbon atom gave a doublet at
2
309.7 ppm with a coupling constant JP, C =15.4 Hz in
13C{1H} NMR.
Structural Analysis of Complex 11
Solid state analysis of complex 11 by X-ray crystallog-
raphy confirmed that the (p-cymene)Ru unit was
indeed connected to the Ru(Cl)ACHTNUTRGNEUNG(PCy3)(indenylidene)
fragment via three m-chloro bridges (Figure 1). A typi-
cal piano stool geometry was observed for the
ꢀ
(arene)RuCl3 moiety, with three Ru Cl bonds of
almost equal lengths (2.41–2.44 ꢅ). The other rutheni-
um atom lay in a highly distorted octahedral environ-
Figure 1. ORTEP representation of complex 11 with thermal
ellipsoids drawn at the 50% probability level. Hydrogen
atoms were omitted for the sake of clarity. Selected bond
ꢀ
ment with Ru Cl bond lengths varying between 2.44
and 2.67 ꢅ for the three face-bridging chloro ligands,
whereas the fourth terminal halogen was located
much closer to the metal center at a 2.3604(10) ꢅ dis-
tance. The Ru=C distance between the metal and the
indenylidene fragment [1.874(3) ꢅ] was similar to
ꢀ
ꢀ
lengths [ꢅ] and angles [deg]: Ru1 Cl1 2.4375(9), Ru1 Cl2
2.4352(9), Ru1 Cl3 2.4124(11), Ru2 P1 2.3473(9), Ru2 Cl1
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2.5044(10), Ru2 Cl2 2.4436(10), Ru2 Cl3 2.6658(10), Ru2
ꢀ
ꢀ
ꢀ
Cl4
2.3604(10),
Ru2 C11
1.874(3);
Cl3 Ru2 C11
ꢀ
ꢀ
ꢀ
ꢀ
those observed in monometallic complexes bearing 162.28(8),Cl2 Ru2 Cl4 167.99(2), P1 Ru2 Cl4 88.87(3).
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Xavier Sauvage et al.
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(RCM) of a,w-dienes.[15,36] For this last application,
they displayed excellent activities in the formation of
tri- or even tetrasubstituted cycloalkene products, a
performance that could not be achieved with the
monometallic complex 1a. In sharp contrast with
these trends, homobimetallic ruthenium-indenylidene
compound 5 (now 11) was repeatedly found to be a
less efficient catalyst than its monometallic parent in
the ring-closing metathesis of several dienes.[18,20,37]
To the best of our knowledge, no literature data are
available concerning the metathetical activity of ho-
mobimetallic ruthenium-vinylidene or -allenylidene
species. Thus, we decided to probe the ability of com-
plexes 8a, b and 9 as catalyst precursors for the
ROMP of cyclooctene [Eq. (1)]. In our laboratory,
Figure 2. Trans effect of various carbon-rich ligands in ho-
mobimetallic ruthenium-arene complexes (data for com-
plexes 7a and 12 from refs.[22,35b] respectively).
this reaction serves as a benchmark to appraise new
a vinylidene group and considerably higher than the catalytic systems for olefin metathesis.[24,38] Polymeri-
one exerted by the ethylene ligand in complex 7a zations were carried out in chlorobenzene at 608C
(Figure 2).
and the monomer-to-catalyst ratio was 250. For the
It should be pointed out that compound 11 is chiral sake of comparison, complexes 3a and 11 were also
due to the presence of two stereogenic centers located tested under identical conditions. These two com-
on the ruthenium atoms and that these asymmetric pounds displayed very similar behaviours (Table 1).
units are not independent, because of geometric con- Within 2 h, they both afforded a quantitative conver-
straints imposed by the m-chloro bridges. Thus, only sion of cyclooctene into high molecular weight poly-
one pair of enantiomers was obtained as a racemic octenamer. Moreover, the polymers obtained had the
mixture. This observation also applied to precursors same polydispersity index (Mw/Mn =1.7) and a pre-
8a, b and 9. Furthermore, all the homobimetallic com- dominantly trans double bond content (scisffi0.2). In
plexes investigated in this study were configurational-
ly stable on the NMR time scale. Indeed, the four ar-
omatic protons on the p-cymene ligand were non- Table 1. ROMP of cyclooctene catalyzed by various homobi-
metallic ruthenium complexes.[a]
equivalent and resonated as four separate doublets.
Likewise, the two methyl groups of the isopropyl side
chain resolved as two separate doublets.
[d]
Com- p-TsOH Monomer
Yield 10ꢀ3 Mw/
scis
[c]
[c]
plex
Conversion [%]
Mn
Mn
[%][b]
3a
11
8a
8b
9
8a
8b
9
–
–
–
–
>99
>99
45
70
63
>99
>99
>99
84
89
37
60
48
88
91
89
93
1.7
1.7
1.9
2.4
1.8
2.2
2.0
2.1
0.20
0.22
0.59
0.56
0.58
0.26
0.24
0.24
Catalytic Studies
114
199
138
88
80
75
Back in 1999, Herrmann and co-workers showed that
bimetallic ruthenium-benzylidene complexes 3a, b
were more active catalysts for the ring-opening meta-
thesis polymerization (ROMP) of 1,5-cyclooctadiene
than their monometallic counterparts. Thus, signifi-
cantly higher rate constants were recorded with cata-
lyst precursor 3b (krel =13) and to a lesser extent with
species 3a (krel =2.4) compared to the monometallic
first generation Grubbs catalyst 1a (krel =1).[13] Vari-
ous homo- and heterobimetallic ruthenium-alkylidene
complexes were also successfully employed to pro-
mote the ROMP of cyclooctene and norbornene or
norbornadiene derivatives,[16] the self-metathesis of
cis-2-pentene,[12] and the ring-closing metathesis
–
1 equiv.
1 equiv.
1 equiv.
95
[a]
Experimental conditions: Ru complex (0.03 mmol), p-
TsOH (0.03 mmol) and cyclooctene (7.5 mmol) in PhCl
(5 mL) for 2 h at 608C.
Determined by GC using the cyclooctane impurity of cy-
clooctene as an internal standard.
[b]
[c]
[d]
Determined by GPC in THF with polystyrene calibra-
tion.
Fraction of cis double bonds within the polyoctenamer,
determined by 13C NMR.
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Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes
FULL PAPERS
sharp contrast with these results, homobimetallic
ruthenium-vinylidene and allenylidene complexes (8a,
b and 9) were far less efficient for the ROMP of cy-
clooctene. Isolated polymer yields did not exceed
60% after 2 h at 608C and very high molecular weight
were reached in some instances, indicating that only
few active species had been generated. More impor-
tant, the unsaturated polyoctenamers contained a sig-
nificantly higher proportion of cis double bonds
(scisffi0.6) than those obtained from catalyst precur-
sors 3a and 11. This difference of microstructure de-
notes the intervention of two separate types of active
species, depending on the nature of the carbon-rich
ligand present on the precatalyst employed. Visual in-
spection of the reaction media sustained this dichoto-
my. The benzylidene and indenylidene complexes led
to orange solutions – believed to contain alkylidene
Figure 3. Time course of the RCM of diethyl 2,2-diallylmalo-
nate using various mono- and bimetallic ruthenium catalysts
active species – that quickly jellified, whereas the vi-
nylidene and allenylidene catalyst precursors gave a
dark red colouration when dissolved with the cyclo-
&
*
*
^
(1 mol%) in CD2Cl2 at 308C (1a: , 3a: , 8a: , 9: , 11:
!
!
^
, 13: &, 14: , 15: ).
ACHTUNGTRENNUNG
remained fluid during the 2 h allowed for the poly- and to compare them with common monometallic sys-
merization to proceed. Noteworthily, monomer con- tems currently available, we have carried out the
sumption kept increasing slowly even after they were RCM of diethyl 2,2-diallylmalonate using a standard
quenched with chloroform containing traces of buty- protocol defined by Grubbs and co-workers for evalu-
lated hydroxytoluene (BHT).
ating olefin metathesis catalysts.[39] Thus, reactions
During the course of their investigations on the were performed in CD2Cl2 at 308C using 1 mol% of
ROMP of cyclooctene mediated by cationic rutheni- catalyst and the conversion was monitored by
um-allenylidene complexes, Dixneuf et al. had shown 1H NMR spectroscopy [Eq. (2)]. Under these condi-
that polymerization rates were significantly enhanced
by the addition of strong acids, such as trifluorome-
thanesulfonic acid.[33] This co-catalyst induced the in-
tramolecular rearrangement of the allenylidene ligand
into an indenylidene group, as discussed above (cf.
Scheme 5). We have applied the same strategy to our
benchmark reaction by adding
a stoichiometric
amount of p-toluenesulfonic acid monohydrate to ho- tions, homobimetallic ruthenium-indenylidene com-
mobimetallic ruthenium-vinylidene and allenylidene plex 11 turned out to be more efficient than its ben-
complexes 8a, b and 9. Results listed in Table 1 clear- zylidene analogue 3a. Indeed, both species displayed
ly demonstrated the validity of this approach. The a very similar high initial activity, but the conversion
acid effectively altered the course of the polymeri- of diethyl diallylmalonate stopped at 85% with 3a
zation. Full monomer consumption occurred within whereas precursor 11 afforded a 98% yield of the cor-
2 h at 608C and led to high yields of polyoctenamer responding cyclopentene diester within 15 min
containing mostly trans double bonds. This micro- (Figure 3). As expected, homobimetallic vinylidene
structure closely reflected the one observed when and allenylidene precursors lagged farther behind, as
benzylidene or indenylidene complexes 3a and 11 shown for complexes 8a and 9 that afforded the RCM
served as initiators. Besides, the orange colour of the product in 8 and 23% yields, respectively, after
reaction media also revealed that alkylidene active 60 min. However, these two catalyst precursors were
species had been formed in significant amounts from also less sensitive to deactivation and conversions
the vinylidene or allenylidene precursors. Thus, p-tol- kept steadily increasing with time. Ultimately, a quan-
uenesulfonic acid is a convenient protic source to acti- titative reaction was recorded with 8a and 9 after 48 h
vate vinylidene or allenylidene complexes in situ and at 308C.
the presence of crystallization water does not inter-
fere with the catalytic system.
To quantify the activities of the various complexes
under scrutiny, we have determined the rate constants
In order to better rank the catalytic activities of ho- observed by assuming a first order behaviour in the
mobimetallic ruthenium complexes 3a, 8a, 9 and 11 RCM of diethyl 2,2-diallylmalonate (DEDAM) at
Adv. Synth. Catal. 2009, 351, 441 – 455
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Xavier Sauvage et al.
FULL PAPERS
Table 2. Pseudo-first order rate constants observed for the
RCM of diethyl 2,2-diallylmalonate catalyzed by various
mono- and bimetallic ruthenium complexes at 308C.
We next investigated the self-metathesis of styrene
in the presence of homobimetallic ruthenium com-
plexes 3a, 8a, b, 9, and 11. Experiments were carried
out by adding 0.002 molar equivalent of catalyst to a
stock solution of the olefin (1M in toluene) stirred in
an oil bath at 858C under an inert atmosphere [Eq.
(3)]. Consumption of styrene and formation of stil-
Complex
kobs [10ꢀ6 sꢀ1]
Reference
3a
11
8a
9
13
14
15
9600
8000
8
this work
this work
this work
this work
[39]
77
2200
4100[a]
9700
[39]
this work
[a]
Value calculated for the first 50% of conversion.
bene (mostly the trans isomer) were monitored by
GC. With all five catalysts under scrutiny, reactions
308C. The formalism proposed by Grubbs et al. was were sluggish and conversions levelled off without
employed to extract the rate constants from the plot going past the 10% threshold. With complexes 3a and
of lnACHTUNGTRENNUNG
([DEDAM]) vs. time.[12,39,40] Based on the kinetic 11, this plateau was reached within 30 min at 858C. In
data obtained (Table 2), the activity of homobimetal- accordance with previous data obtained for ROMP
lic ruthenium catalysts 3a, 8a, 9 and 11 followed the and RCM, allenylidene and vinylidene complexes 8a,
order: indenylideneꢂbenzylidene@allenylidene>vi- b and 9 reacted much more slowly. Up to 2 days were
nylidene.
needed before conversion stopped increasing. Adding
Comparison of our results with previous work from a stoichiometric amount of p-toluenesulfonic acid
the literature confirmed that homobimetallic rutheni- monohydrate to these systems enhanced kinetics but
um-benzylidene complex 3a was more active than the did not alter the final stilbene yield that remained un-
first generation Grubbs catalyst 1a[12] (Figure 3). It changed at ca. 10%. These poor results are most
even displayed a higher initial activity than the likely due to the rapid decomposition of the propagat-
second and third generation NHC-based ruthenium- ing species.[36] Indeed, homobimetallic ruthenium-
alkylidene species 13[4] and 14.[41] However, its decom- methylidene species are expected to be the key inter-
position occurred more rapidly and prevented com- mediates present in the reaction media after the first
pletion of the reaction. The accumulation of ethylene catalytic cycle. Detailed investigations by Grubbs and
in the septum-capped NMR tube used to monitor the co-workers showed that a sterically bulky environ-
conversion is likely to play a key role in this degrada- ment was required to stabilize homo- and heterobi-
tion (vide infra), but carrying out the RCM in a metallic ruthenium-alkylidene compounds. Attempts
closed system was mandatory to respect the standard to
protocol proposed by Grubbs et al. to evaluate meta- (=CH2)]
thesis catalysts.[39] Under these experimental condi-
[RuCl2A(PCy3)
tions, homobimetallic ruthenium-indenylidene precur- acterized ruthenium-ethylene complex instead.[12]
sor 11 was more resistant to deactivation and outper- These observations prompted us to take a closer
generate
from
2A(=CH2)] failed and afforded an unchar-
[(p-cymene)ClRu
G
ACHTUNGTRENNUNG
[RuCl2A(p-cymene)]2
CTHUNGTRENNUNG
G
N
CHTUNGTRENNUNG
formed all the ruthenium-benzylidene complexes look at the cross-metathesis of complexes 3a, 8a, b, 9,
under investigation (Figure 3 and Table 2). In accord- and 11 with ethylene. Preliminary experiments were
1
ance with earlier observations,[18,20,37] it was neverthe- performed in CD2Cl2 or C6D6 and monitored by H
less slightly less efficient than its monometallic parent and 31P NMR spectroscopies. No sign of reaction was
15, which afforded a full conversion of diethyl diallyl- detected with complexes 8a, b and 9, which remained
malonate into the corresponding RCM product within stable in the presence of C2H4 for more than two days
a few minutes at room temperature.[32]
at 25 or 608C. Conversely, when solutions of com-
plexes 3a and 11 were placed under an ethylene at-
mosphere, a clean structural change occurred within
20 min, as evidenced by the replacement of the initial
phosphorus absorptions (48.5 ppm in C6D6 at 608C
for 3a, 41.1 ppm in CD2Cl2 at 258C for 11) by a new
single resonance located at 43.6 ppm in CD2Cl2 or
44.3 ppm in C6D6. Parallel examination of the reac-
1
tion media by H NMR showed the release of styrene
or 1-methylene-1H-indene from the benzylidene or
indenylidene fragments, respectively, and the emer-
gence of two new doublets at 4.07 and 4.56 ppm as-
448
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Adv. Synth. Catal. 2009, 351, 441 – 455

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes
FULL PAPERS
Scheme 7. Reaction of homobimetallic ruthenium complexes with ethylene.
signed to a ruthenium-ethylene moiety. These spectro- chloride,[42] a gem-dichloro compound,[43] or a terminal
scopic features strongly suggested the formation of alkyne.[44] Sulfur ylides generated in situ from sulfoni-
ruthenium-ethylene complex 7a.[22] To validate this um salts were also used as carbenoid precursors along
hypothesis, we have carried out the reaction of com- these lines.[45] A second strategy takes advantage of
plexes 3a and 11 with ethylene on a preparative scale the metathetical activity of ruthenium-indenylidene
(Scheme 7). Syntheses were performed in toluene at species to convert them into alkylidene derivatives via
408C for 1 h. After solvent evaporation, the residue cross-metathesis with an appropriate alkene intro-
was extracted with n-pentane to afford 1 equivalent duced in stoichiometric proportion or in excess. Al-
of the cross-metathesis product, styrene or 1-methyl- though a further step is required to reach the desired
ene-1H-indene. In the latter case, GC-MS analysis re- product, this method has several practical assets,
vealed the presence of small amounts of isomeric owing to the ease of formation and stability of Ru-in-
side-products that were not further characterized. Full denylidene complexes. Thus, Blechert et al. prepared
NMR analysis of the remaining orange solid unambig- the second-generation Hoveyda–Grubbs catalyst from
uously demonstrated that it was pure complex 7a. [RuCl2ACTHNUGTRNEUNG(PPh3)2(3-phenyl-1-indenylidene)] via phos-
Hence, metathetically active benzylidene or indenyli- phine-NHC exchange followed by cross-metathesis
dene catalyst precursors 3a and 11 are converted into with (E)-1-(hepta-1,6-dienyl)-2-isopropoxybenzene.[46]
methylidene species 16 when the ethylene concentra- When a mixed PCy3/NHC indenylidene complex
tion is high enough. Although highly unstable, this in- served as starting material for similar reactions, cop-
termediate undergoes a remarkably clean and quanti- per(I) chloride was added in slight excess to help
tative decomposition into ruthenium-ethylene com- remove the phosphine.[47] Nolan and co-workers fur-
plex 7a. This transformation must proceed via a bimo- ther refined the concept by devising a one-pot proce-
lecular pathway, but the mechanistic details remain dure for the synthesis of Grubbs catalyst 1a starting
unknown.
from [RuCl2ACHTNGUTERNNU(G PPh3)3] and 1,1-diphenylpropargyl alco-
hol, followed by phosphine exchange with PCy3, and
cross-metathesis with excess styrene.[48] In a slightly
less efficient variation, Fꢄrstner et al. converted a tri-
cyclohexylphosphine-bearing indenylidene complex
Preparative Application
The most straightforward route to ruthenium-alkyli- into a Hoveyda-type catalyst via enyne metathesis
dene metathesis catalysts involves the reaction of suit- with 1-ethynyl-2-isopropoxybenzene in the presence
able metal precursors with diazo compounds.[2] How- of silver(I) chloride as phosphine scavenger.[49]
ever, the instability of these highly labile reagents
Since the reaction of homobimetallic ruthenium-in-
gives rise to major safety issues and severely limits denylidene complex 11 with excess styrene afforded
their availability. Alternative synthetic pathways are the highly unstable methylidene complex 16 that
thereby eagerly sought. One strategy implies the eventually decomposed into ethylene complex 7a
direct introduction of an alkylidene fragment onto an rather than the corresponding benzylidene complex
Ru(0) or Ru(II) center from a vinyl or propargyl 3a (vide supra), we chose to react complex 11 with a
Adv. Synth. Catal. 2009, 351, 441 – 455
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449

Xavier Sauvage et al.
FULL PAPERS
Scheme 8. One-pot synthesis of Hoveyda–Grubbs catalyst 17 from complex 7a.
two-fold excess of 2-isopropoxystyrene, reasoning that requires the addition of a scavenger such as CuCl or
the styrenyl ether would stabilize the alkylidene AgCl. A second advantage of the process is that
cross-metathesis product via oxygen chelation. dimer 2 was easily separated from complex 17 by se-
Indeed, a preliminary experiment carried out over- lective extraction and could be recycled into starting
night in toluene at 708C led to the quantitative for- material 7a (cf. Scheme 2).
mation of Hoveyda–Grubbs catalyst 17 and rutheni-
um-arene dimer 2 (0.5 equivalent). This was the first
time that we observed cleavage of the m-chloro Conclusions
bridges and clean formation of a monometallic prod-
uct from the series of homobimetallic compounds The labile ruthenium-ethylene complex 7a, which is
under investigation. Formation of a stable chelate readily obtained from commercially available
with oxygen is most likely responsible for opening
one of the chloro bridges, thereby weakening the ethylene,[22] is a convenient starting material to pre-
whole assembly and causing its dismantlement. pare more elaborate homobimetallic ruthenium-arene
ACHUTGTNERN[NUG RuCl2ACHTUNGTREN(NUNG p-cymene)]2 (2), tricyclohexylphosphine and
Building on this result, we set up a one-pot proce- architectures containing polyunsaturated carbon-rich
dure for the synthesis of complex 17 starting from bi- ligands. Thus, reaction of 7a with propargyl alcohol
metallic precursor 7a, without the need to isolate in- derivatives afforded quantitative yields of vinylidene
termediate indenylidene species 11 (Scheme 8). Thus, complexes 8a, b within 2 h at room temperature. Al-
ethylene complex 7a was first converted into g-hy- though they were stable enough to be fully character-
droxyvinylidene complex 8a by addition of 1,1-diphe- ized, these adducts underwent a slow albeit irreversi-
nylpropynol in dichloromethane. After 2 h at room ble transformation into ruthenium-allenylidene com-
temperature, solvent evaporation helped drive the re- plex 9 in solution. Elimination of n-propanol from the
action to completion and afforded a solid residue that g-propoxyvinylidene unit in 8b proceeded cleanly and
was brought back to air. p-Toluenesulfonic acid mon- selectively without the need for any additive. Dehy-
ohydrate and anhydrous calcium chloride were added dration of the g-hydroxyvinylidene ligand of 8a was
to the flask and its inert atmosphere was restored by better accomplished in the presence of 3 ꢅ molecular
applying three vacuum/nitrogen cycles. Dichlorome- sieves to suppress side-reactions. Although its struc-
thane was syringed in and the resulting suspension ture was erroneously reported in 1999,[17,18,20] complex
was stirred for 24 h at room temperature. Instant for- 9 had never been isolated so far. In the presence of
mation of cationic carbyne species 10 led to a yellow an acidic promoter, it rearranged into the homobime-
colouration that slowly turned dark red, as indenyli- tallic ruthenium-indenylidene compound 11, whose
dene complex 11 formed. Next, neat 2-isopropoxys- molecular structure was unambiguously determined
tyrene was added with a microsyringe and the mixture by X-ray diffraction analysis. A direct vinylidene-to-
was stirred overnight at 408C. After solvent evapora- indenylidene interconversion was also successfully
tion, selective extractions and flash chromatography carried out in the presence of a drying agent and a
were applied to separate alkoxybenzylidene catalyst strong acid, thereby affording complex 11 in three
17 from the ruthenium dimer 2 and organic by-prod- steps and 72% overall yield from [RuCl2ACTHUNGRTNE(NUG p-cymene)]2,
ucts. Gratifyingly, 31P NMR monitoring throughout one equivalent of PCy3, and 1,1-diphenylpropynol.
the process indicated that each step occurred cleanly This procedure is particularly attractive in terms of
and quantitatively, thereby affording high yields of atom economy, since it does not require the use of a
pure organometallic products. The procedure did not sacrificial phosphine, nor the formation of any ruthe-
require any sacrificial phosphine. This point is of par- nium-containing side-product such as
ticular importance, since tricyclohexylphosphine is Scheme 1).
costly and removing it from a ruthenium center often
4
(cf.
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Adv. Synth. Catal. 2009, 351, 441 – 455

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes
FULL PAPERS
13C{1H}) or external H3PO4 (31P{1H}). All assignments are
tentative, based on additivity rules[51] and comparison be-
tween related structures. Infrared spectra were recorded on
a Perkin–Elmer Spectrum One FT-IR instrument. GC analy-
ses were carried out on a Varian 3900 gas chromatograph
equipped with a CP-Sil 5 CB capillary column and an FID
detector. Gel permeation chromatography was performed in
THF at 458C on a SFD S5200 autosampler liquid chromato-
graph equipped with a SFD 2000 refractive index detector
and a battery of 4 PL gel columns fitted in series. The mo-
lecular weights (not corrected) are reported versus monodis-
perse polystyrene standards used to calibrate the instrument.
Elemental analyses were carried out in the Laboratory of
Pharmaceutical Chemistry at the University of Liꢁge.
The catalytic activity of complexes 8a, b, 9, and 11
was probed in various types of olefin metathesis reac-
tions and compared with those of homobimetallic
ruthenium-benzylidene complex 3a, as well as first
(1a), second (13), and third generation (14) monome-
tallic Grubbs catalysts. For the RCM of diethyl di-
ACHTUNGTRENNUNGallylmalonate, ruthenium-indenylidene complex 11
outperformed all the ruthenium-benzylidene com-
plexes under investigation and was only slightly less
efficient than its monometallic parent 15. Cross-meta-
thesis experiments with ethylene showed that deacti-
vation of ruthenium-alkylidene or indenylidene com-
plexes 3a and 11 was due to the rapid bimolecular de-
composition of methylidene active species 15 into eth-
ylene complex 7a. Vinylidene and allenylidene com-
plexes 8a, b and 9, on the other hand, were far less
efficient olefin metathesis initiators and remained
inert under an ethylene atmosphere. Their catalytic
activity was, however, substantially enhanced upon
addition of an acidic co-catalyst that most likely pro-
moted their in situ transformation into indenylidene
species.
Synthesis of 1,1-Diphenylpropynyl n-Propyl Ether
To a 100-mL Schlenk tube containing a solution of 1,1-di-
phenylpropynol (3 g, 14 mmol) in DMF (20 mL) at ꢀ788C,
95% sodium hydride (0.51 g, 20 mmol) was added portion-
wise in 5 min. The resulting suspension was stirred at room
temperature until the gas evolution stopped. It was cooled
again at ꢀ788C before 1-bromopropane (3 g, 24 mmol) was
added. The reaction mixture was stirred overnight at room
temperature. It was diluted with diethyl ether (40 mL),
washed with brine (3ꢆ30 mL), dried over MgSO4 and con-
centrated on a rotary evaporator to give a pale yellow oil,
which was purified by column chromatography on silica gel
with petroleum ether. Pure 1,1-diphenylpropynyl n-propyl
Due to its straightforward synthesis and high meta-
thetical activity, homobimetallic ruthenium-indenyli-
dene complex 11 was deemed an attractive intermedi-
ate to convert into alkoxyalkylidene species via stoi-
chiometric cross-metathesis with 2-isopropoxystyrene.
ether was isolated as a colourless oil, which crystallized
1
Thus, a convenient one-pot procedure was devised for upon standing; yield: 3.01 g (86%); mp 40–418C. H NMR
(400 MHz, CDCl3): d=7.59 (d, 4H, J=7.5 Hz, Ph), 7.37–
the preparation of Hoveyda–Grubbs catalyst 17 from
ethylene complex 7a via a vinylidene-allenylidene-in-
denylidene cascade pathway. Taking into account the
optimized synthesis of precursor 7a from ruthenium-
(p-cymene) dimer 2 in a preliminary step, monometal-
lic catalyst 17 was obtained in 85% overall yield. No
large excess of organic reagents was required and the
transition metal not incorporated into the final prod-
uct could easily be recovered and recycled at the end
of the process.
3
7.23 (m, 6H, Ph), 3.46 (t, 2H, JH,H =6.3 Hz, OCH2CH2CH3),
3
2.95 (s, 1H, alkyne), 1.70 (qt, 2H, JH,H =7.5 Hz and 6.3 Hz,
3
OCH2CH2CH3), 0.99 (t, 3H, JH,H =7.5 Hz, OCH2CH2CH3);
13C NMR (100 MHz, CDCl3): d=143.6 (s, Cipso), 128.3 (s,
CHmeta), 127.7 (s, CHpara), 126.7 (s, CHortho), 83.7 (s,
HCCCPh2), 79.8 (s, HCCCPh2), 77.4 (s, HCCCPh2), 66.4 (s,
OCH2CH2CH3), 23.3 (s, OCH2CH2CH3), 11.0 (s,
OCH2CH2CH3).
Synthesis of [(p-Cymene)Ru
CH C(Ph)2OH)] (8a)
(m-Cl)3RuCl
N
U
ꢀ
1,1-Diphenylpropynol (31 mg, 0.15 mmol) was added to a
solution of complex 7a (100 mg, 0.13 mmol) in CH2Cl2
(10 mL) and the mixture was stirred for 2 h at room temper-
ature. The solvent was removed under reduced pressure.
The residue was washed with diethyl ether (3ꢆ5 mL) and
dried under high vacuum to afford complex 8a as a red
powder; yield: 113 mg (90%). IR (Nujol): n= 1645 (C=C),
3416 cmꢀ1 (OH); 1H NMR (250 MHz, CD2Cl2, 298 K): d=
Experimental Section
General Information
All reactions were carried out with rigorous exclusion of air
using standard Schlenk techniques. Organic solvents were
dried by standard procedures and distilled under argon prior
to use. 1,1-Diphenylpropynol, p-toluenesulfonic acid mono-
hydrate, and 3 ꢅ molecular sieves (8–12 mesh beads) were
purchased from Aldrich and used as received. Anhydrous
calcium chloride (2–5 mm granules) was purchased from
Mallinckrodt Baker and finely powdered immediately
before use. 2-Isopropoxystyrene,[50] complex 3a,[12] and com-
3
3
7.47 (d, 2H, JH,H =7.5 Hz, Ph), 7.32 (d, 2H, JH,H =7.5 Hz,
3
Ph), 7.30–7.20 (m, 6H, Ph), 5.66 (d, 1H, JH,H =5.5 Hz, CH
3
cymene), 5.59 (d, 1H, JH,H =5.5 Hz, CH cymene), 5.45 (d,
3
3
1H, JH,H =5.5 Hz, CH cymene), 5.43 (d, 1H, JH,H =5.5 Hz,
4
CH cymene), 4.78 (d, 1H, JP, H =3.5 Hz, Ru=C=CH), 3.54 (s,
1H, OH), 2.97 [sept, 1H, JH,H =7.0 Hz, CH
3H, CH3), 2.13–1.45 (m, 24H, PCy3), 1.38 [d, 3H, JH,H =
3
(CH3)2], 2.32 (s,
1
3
plex 7a[22] were prepared according to literature. H, 13C{1H},
3
and 31P{1H} NMR spectra were recorded on a Bruker DRX
400 or a Bruker Avance 250 spectrometer at 258C unless
otherwise specified. Chemical shifts are expressed in parts
per million and are referenced to solvent residual peaks (1H,
7.0 Hz, CHACHTUNGTERU(NNG CH3)2], 1.37 [d, 3H, JH,H =7.0 Hz, CHACHTUNGTRENNUNG(CH3)2],
1.35–1.00 (m, 9H, PCy3); 13C NMR (101 MHz, CD2Cl2,
2
233 K): d=345.9 (d, JP, C =18.1 Hz, Ru=C=CH), 148.9, 148.5
(s, C phenyl), 127.4, 127.3, 126.1, 125.9, 125.5, 121.0 (s, CH
Adv. Synth. Catal. 2009, 351, 441 – 455
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Xavier Sauvage et al.
FULL PAPERS
3
phenyl), 120.99 (s, Ru=C=CH), 100.0, 96.8 (s, C cymene),
2.13–1.45 (m, 24H, PCy3), 1.40 [d, 3H, JH,H =6.8 Hz, CH-
80.0, 78.9, 77.7, 77.1 (s, CH cymene), 73.5 (s, CPh2), 35.0 (d,
(CH3)2], 1.39 [d, 3H, 3JH,H =6.8 Hz, CH
ACHTUNGTRNENUG ACHTUNTGREN(NUGN CH3)2], 1.35–1.00
1JP, C =24.3 Hz, CH PCy3), 30.6 [s, CH
A
(m, 9H, PCy3); 13C NMR (101 MHz, CD2Cl2, 298 K): d=
301.5 (d, 2JP, C =18.1 Hz, Ru=C=C=CPh2), 237.3 (s, Ru=C=
C=CPh2), 147.1 (s, Ru=C=C=CPh2), 141.5, 129.0, 128.8,
128.6 (s, Ph), 101.2, 96.6 (s, C cymene), 79.9, 79.2, 78.8, 78.5
2
ACHTUNGTRENNUNG
CD2Cl2, 298 K): d=54.4; anal. calcd. for C43H59Cl4OPRu2: C
53.42, H 6.15; found: C 53.48, H 6.20.
1
(s, CH cymene), 35.0 (d, JP, C =24.3 Hz, CH PCy3), 31.2 [s,
CH
2JP, C =10 Hz, CH2 PCy3), 27.6 (d, 2JP, C =11 Hz, CH2 PCy3),
26.4 (s, CH2 PCy3), 22.0, 21.9 [s, CH(CH3)2], 18.5 (s, CH3);
CAHTNUGTRNEN(NUG CH3)2], 29.1 (s, CH2 PCy3), 28.6 (s, CH2 PCy3), 27.8 (d,
Synthesis of [(p-Cymene)Ru
CH-C(Ph)2OCH2CH2CH3)] (8b)
ACHTUNGRTENU(GNN m-Cl)3RuClACHUTNRTGEG(NNUN PCy3)CAHTNUGTREN(NUGN =C=
AHCTUNGTRENNUNG
31P NMR (101 MHz, CD2Cl2, 298 K): d=54.1; anal. calcd.
for C43H57Cl4PRu2: C 54.43, H 6.06; found: C 54.61, H 6.26.
Complex 9 was also obtained by stirring a solution of
complex 8b (100 mg, 0.1 mmol) in CH2Cl2 (10 mL) for 2–4
days at room temperature. During this period, the initially
orange solution became dark red. It was concentrated to ca.
1 mL under reduced pressure and n-pentane (10 mL) was
added. The supernatant solution was removed with a cannu-
la and the precipitate was washed with n-pentane (3ꢆ5 mL).
It was dried under high vacuum to afford the title com-
pound a dark red powder; yield: 87 mg (92%).
1,1-Diphenylpropynyl n-propyl ether (40 mg, 0.15 mmol)
was added to a solution of complex 7a (100 mg, 0.13 mmol)
in CH2Cl2 (10 mL) and the mixture was stirred for 2 h at
room temperature. The solvent was removed under reduced
pressure. The residue was washed with n-pentane (3ꢆ5 mL)
and dried under high vacuum to afford complex 8b as an
orange powder; yield: 122 mg (93%). IR (Nujol): n=
1
1669 cmꢀ1 (C=C); H NMR (400 MHz, CD2Cl2, 298 K): d=
3
7.96 (d, 1H, JH,H =7.5 Hz, Ph), 7.67 (m, 4H, Ph), 7.34–7.13
3
(m, 5H, Ph), 5.63 (d, 1H, JH,H =5.0 Hz, CH cymene), 5.55
(d, 1H, 3JH,H =5.0 Hz, CH cymene), 5.41 (s, 2H, CH
cymene), 4.00 (d, 1H, 4JP, H =3.8 Hz, Ru=C=CH), 3.43 (qt,
Synthesis of [(p-Cymene)Ru
ACHUTGTNERN(NGU m-Cl)3RuClACHTUNGTNER(NUGN PCy3)(3-
2H, 3JH,H =7.8 Hz and 6.6 Hz, OCH2CH2CH3), 2.96 [sept,
3
phenyl-1-indenylidene)] (11)
1H, JH,H =6.8 Hz, CH
G
3
(m, 33H, PCy3), 1.62 (q, 2H, JH,H =6.6 Hz, OCH2CH2CH3),
A solution of complex 8a (100 mg, 0.1 mmol) and p-toluene-
sulfonic acid monohydrate (40 mg, 0.21 mmol) in CH2Cl2
(10 mL) was stirred overnight in the presence of 3 ꢅ molec-
3
3
1.37 [d, 3H, JH,H =6.8 Hz, CH
6.8 Hz, CH(CH3)2], 1.00
=
ACHTUNGTRENNUNG
OCH2CH2CH3); 13C NMR (100 MHz, CD2Cl2, 233 K): d=
339.5 (d, 2JP,C =16.5 Hz, Ru=C=CH), 146.6, 146.3 (s, C
phenyl), 128.7, 128.4, 127.7, 127.4, 126.2, 125.6 (s, CH
phenyl), 110.3 (s, Ru=C=CH), 99.9, 96.6 (s, C cymene), 82.0
(s, CPh2), 80.0, 78.8, 77.9, 77.6 (s, CH cymene), 64.2 (s,
OCH2CH2CH3), 33.9 (d, JP, C =24.3 Hz, CH PCy3), 30.6 [s,
2
CH
N
PCy3), 25.8 (s, CH2 PCy3), 22.9 (OCH2CH2CH3), 21.5, 21.3
[s, CHACHTUNGTRENNUNG(CH3)2], 18.3 (s, CH3 cymene), 10.6 (s,
OCH2CH2CH3); 31P NMR (101 MHz, CD2Cl2, 298 K): d=
54.0; anal. calcd. for C46H65Cl4OPRu2: C 54.76, H 6.49;
found: C 54.10, H 6.48.
ular sieves (1.6 g) at room temperature. During this period,
the dark yellow solution slowly became dark orange. It was
filtered on sintered glass and the solvent was removed
under vacuum. The remaining brown solid was washed with
cold n-pentane (5 mL) and dried under high vacuum to
afford complex 11 as an orange brown powder; yield: 86 mg
Synthesis of [(p-Cymene)Ru
C=CPh2)] (9)
ACHUTGTNERN(NGU m-Cl)3RuClACHTUNGTNER(NUGN PCy3)(=C=
1
(86%); IR (Nujol): n=1947, 1621 cmꢀ1; H NMR (250 MHz,
A solution of complex 8a (200 mg, 0.21 mmol) in CH2Cl2
(30 mL) was stirred for 2 days at room temperature in the
presence of 3 ꢅ molecular sieve (3.2 g). During this period,
the colour of the solution changed from orange to dark red
and the molecular sieves became pulverulent. The resulting
suspension was decanted and the supernatant solution was
cannulated into another flask under argon. The solvent was
removed under reduced pressure and the residue was
washed with diethyl ether (2ꢆ20 mL) followed by n-pentane
(2ꢆ20 mL). It was dried under high vacuum to afford com-
plex 9 as a dark red powder; yield: 169 mg (85%). IR
(Nujol): n=1918 cmꢀ1 (C=C=C); 1H NMR (250 MHz,
3
CD2Cl2, 298 K): d=8.84 (d, 1H, JH,H =7.0 Hz, H-8), 7.82 (d,
3
2H, JH,H =7.3 Hz, H-11), 7.55 (m, 1H, H-6), 7.41 (m, 4H,
H-12, H-7, and H-13), 7.20 (d, 1H, H-5), 6.75 (s, 1H, H-2),
3
3
5.54 (d, 1H, JH,H =5.8 Hz, CH cymene), 5.34 (d, 1H, JH,H
=
5.8 Hz, CH cymene), 5.27 (d, 1H, 3JH,H =5.8 Hz, CH
cymene), 5.12 (d, 1H, 3JH,H =5.8 Hz, CH cymene), 2.87
[sept, 1H, 3JH,H =6.8 Hz, CH
ACHTUNGRTNE(UNG CH3)2], 2.12 (s, 3H, CH3),
3
2.05–0.90 (m, 24H, PCy3), 1.35 [d, 2H, JH,H =6.8 Hz, CH-
A
ACHTUNGTRENNUNG
2
(101 MHz, CD2Cl2, 298 K): d=309.7 (d, JP, C =15.4 Hz, C1),
144.8 (s, C9), 143.7 (s, C4), 141.1 (d, JP,C =3.9 Hz, C2), 140.0
3
3
(s, C3) , 136.3 (s, C10), 130.4 (s, C8), 130.0 (s, C12), 129.4 (s,
C7), 129.2 (s, C6), 128.6 (C13), 126.1 (C11), 117.9 (s, C5),
100.4 and 96.4 (s, C cymene), 80.2, 79.8, 79.1, 78.11 (s, CH
cymene), 37.0 (d, 1JP, C =23.2 Hz, CH, PCy3), 31.1 [s, CH-
CD2Cl2, 298 K): d=7.95 (d, 4H, JH,H =7.5 Hz, Ph), 7.67 (d,
3
3
2H, JH,H =7.5 Hz, Ph), 7.34 (d, 4H, JH,H =7.5 Hz, Ph), 5.65
(d, 1H, 3JH,H =5.5 Hz, CH cymene), 5.57 (d, 1H, JH,H
=
3
5.5 Hz, CH cymene), 5.42 (d, 1H, 3JH,H =5.5 Hz, CH
cymene), 5.40 (d, 1H, 3JH,H =5.5 Hz, CH cymene), 3.02
AHCTUNGTRENNUNG
[sept, 1H, 3JH,H =6.8 Hz, CH
ACHTUNGRTNE(UNG CH3)2], 2.33 (s, 3H, CH3),
452
asc.wiley-vch.de
ꢃ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2009, 351, 441 – 455

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes
FULL PAPERS
PCy3), 26.4 (s, CH2, PCy3), 22.4, 21.6 [s, CH
(CH3)2], 18.3 (s,
of butylated hydroxytoluene (2ꢆ10 mL) and slowly poured
into MeOH (500 mL) under vigorous stirring. The precipi-
tated polyoctenamer was dried under high vacuum and char-
acterized by GPC and NMR spectroscopy.
CH3); 31P NMR (101 MHz, CD2Cl2, 298 K): d=41.1; anal.
calcd. for C43H57Cl4PRu2: C 54.43, H 6.06; found: C 55.85, H
6.50.
Complex 11 was also obtained by stirring a solution of
complex 8b (100 mg, 0.1 mmol) and p-toluenesulfonic acid
monohydrate (40 mg, 0.21 mmol) in CH2Cl2 (10 mL) over-
night at room temperature in the presence of anhydrous
CaCl2 (1.6 g). During this period, the dark yellow solution
slowly became red. After decantation, it was transferred
with a cannula into another flask under argon and the sol-
vent was removed under vacuum. The remaining red solid
was washed with cold n-pentane (5 mL) and dried under
high vacuum to afford the title compound as an orange
brown powder; yield: 82 mg (87%).
RCM of Diethyl 2,2-Diallylmalonate
Under inert atmosphere, a NMR tube with a screw-cap
septum was charged with a freshly prepared stock solution
of catalyst (10ꢀ3 M in CD2Cl2, 0.8 mL, 0.0008 mmol). The
sample was heated to 308C in the NMR probe before dieth-
yl 2,2-diallylmalonate (19.3 mL, 19.2 mg, 0.08 mmol) was
added with a microsyringe under inert atmosphere. Experi-
mental data points were collected using Bruker automation
software. The conversion of diethyl 2,2-diallylmalonate was
computed from the integrals obtained for allyl methylene
protons in the starting material (d=2.61, dt) and the prod-
uct (d=2.98, s).
X-Ray Diffraction Analysis of Complex 11
Orange-red crystals of complex 11 suitable for X-ray diffrac-
tion analysis were obtained by slow evaporation of a CD2Cl2
solution. Crystal data were collected on a Bruker APPEX II
Diffractometer using graphite-monochromated Mo-Ka radi-
ation (k=0.71073 ꢅ) from a fine-focus sealed tube source at
100 K. Computing data and reduction was made with the
APPEX II software.[52] The structure was solved using
DIRDIF,[53] and finally refined by full-matrix, least-squares
based on F2 by SHELXL.[54] An empirical absorption correc-
tion was applied using SADABS.[55] All non-hydrogen atoms
were anisotropically refined and the hydrogen atom posi-
tions were included in the model by electronic density or
were geometrically calculated and refined using a riding
model. A highly disordered distribution of solvent (CD2Cl2)
was eliminated with SQUEEZE.[56]
Self-Metathesis of Styrene
A 25-mL round-bottom flask containing a magnetic stirring
bar and capped with a three-way stopcock was charged with
a homobimetallic ruthenium complex (0.04 mmol) and pos-
sibly p-toluenesulfonic acid monohydrate (8 mg, 0.04 mmol).
The reactor was purged of air by applying three vacuum/
argon cycles before styrene (20 mL of a 1M solution in tolu-
ene, 20 mmol) was added with a dried syringe under argon.
The solution was stirred at 858C in a thermostated oil bath
under inert atmosphere. The conversion was monitored by
GC using n-dodecane as internal standard.
Reaction of Complexes 3a and 5 with Ethylene
Crystal data for [(p-cymene)RuACHTNUGTRENNUG(m-Cl)3RuClACHTUGNTERN(NUGN PCy3)(3-
A Schlenk tube containing a magnetic stirring bar was
phenyl-1-indenylidene)] (11): C43H57Cl4PRu2, M=948.8,
monoclinic, a=28.116(8), b=12.837(4), c=28.345(13) ꢅ,
b=107.431(17)8, V=9760(6) ꢅ3, T=100(2) K, space group
charged with
a
homobimetallic ruthenium complex
(0.05 mmol) and toluene (1 mL). The solution was stirred
for 1 h at 408C under an ethylene atmosphere (0.5 bar). It
quickly became orange and a solid precipitated. After cool-
ing to room temperature, n-pentane (5 mL) was added to
the suspension and the supernatant liquid was filtered off
with a cannula. The remaining solid was washed with n-pen-
tane (3ꢆ5 mL) and dried under high vacuum to afford [(p-
I2/a, Z=8, mACHTUNGTRENNUNG(Mo-Ka)=0.71073 ꢅ, 126928 reflections col-
lected, 11638 independent reflections, Rint =0.068, R1 [I>
2s(I)]=0.0356, R1 (all data)=0.0564, wR2 [I> 2s(I)]=
0.0887, wR2 (all data)=0.0972.
CCDC 706396 contains the supplementary crystallograph-
ic data (excluding structure factors) for the structure report-
ed in 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 or on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax.:
(internat.) +44–1223/336–033].
cymene)RuACHTGNUTERN(NNUG m-Cl)3RuClACHTNURGTEG(NNUN PCy3)CAHTNUGRTNE(NUNG C2H4)] (7a) as an orange
powder; yield: 36 mg (90% from 3a), 34 mg (85% from 11).
1 H, 13C, and 31P NMR spectra were identical to those report-
ed earlier in the literature.[22]
One-Pot Synthesis of [Cl2RuACHTNUTRGNEUNG(PCy3)(=CH-o-O-i-
PrC6H4)] (17) from Complex 7a
ROMP of Cyclooctene
A 25-mL round-bottom flask containing a magnetic stirring
bar and capped with a three-way stopcock was charged with
a homobimetallic ruthenium complex (0.03 mmol) and pos-
sibly p-toluenesulfonic acid monohydrate (6 mg, 0.03 mmol).
The reactor was purged of air by applying three vacuum/
argon cycles before dry chlorobenzene (5 mL) was added.
The solution was warmed to 608C in a thermostated oil bath
and cyclooctene (1 mL, 7.5 mmol) was added via a syringe.
The reaction mixture was stirred for 2 h at 608C. The con-
version was monitored by gas chromatography using the cy-
clooctane impurity of cyclooctene as an internal standard.
The resulting gel was diluted with CHCl3 containing traces
1,1-Diphenylpropynol (93 mg, 0.45 mmol) was added to a
solution of complex 7a (0.3 g, 0.39 mmol) in CH2Cl2 (30 mL)
and the mixture was stirred for 2 h at room temperature.
The solvent was removed under reduced pressure. To the
residue were added p-toluenesulfonic acid monohydrate
(0.11 g, 0.6 mmol), anhydrous CaCl2 (4.8 g) and CH2Cl2
(30 mL). The orange suspension was stirred for 24 h at room
temperature. It turned yellow after a few min and became
dark red after 24 h. Next, 2-isopropoxystyrene (10 mg,
0.6 mmol) was added with a microsyringe and the mixture
was stirred overnight at 408C. Elimination of CH2Cl2 under
reduced pressure afforded a pale orange solid. This crude
Adv. Synth. Catal. 2009, 351, 441 – 455
ꢃ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
453

Xavier Sauvage et al.
FULL PAPERS
product mixture was transferred into a Bꢄchner funnel.
Complex 17 was first extracted by adding small portions of
hot cyclohexane until the initially brown washings remained
colourless. The solid cake was then extracted with CH2Cl2
Kaczmarska, K. Mennecke, A. Kirschning, K. Grela,
Green Chem. 2006, 8, 685–688.
[8] a) L. Jafarpour, M.-P. Heck, C. Baylon, H. M. Lee, C.
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c) N. Ledoux, R. Drozdzak, B. Allaert, A. Linden, P.
Van der Voort, F. Verpoort, Dalton Trans. 2007, 5201–
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[10] For reviews, see: a) T. M. Trnak, R. H. Grubbs, Acc.
Chem. Res. 2001, 34, 18–29; b) A. H. Hoveyda, D. G.
Gillingham, J. J. Van Veldhuizen, O. Kataoka, S. B.
Garber, J. S. Kingsbury, J. P. A. Harrity, Org. Biomol.
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(25 mL) to afford an orange solution of [RuCl2ACTHUNTRGNEU(GN p-cymene)]2
(2). The cyclohexane extracts were evaporated on a rotary
evaporator. The residue was further purified by flash chro-
matography on a plug of silica gel using cyclohexane as
eluant until unsaturated organic by-products were no longer
detected by UV light on a TLC plate. Hoveyda–Grubbs
complex 17 was then removed from the column using a 3/1
v/v mixture of cyclohexane/CH2Cl2 as eluant. Evaporation
of the solvent under reduced pressure afforded pure com-
plex 17 as a brown solid; yield: 210 mg (91%). Its 1 H, 13C,
and 31P NMR spectra were identical to those reported earli-
er in the literature.[5] The [RuCl
2ACTHNUTRGNE(UNG p-cymene)]2 dimer 2 was
recovered as an orange-red solid by evaporation of the
CH2Cl2 solution under reduced pressure followed by recrys-
tallization from toluene; yield: 220 mg (93%).
Acknowledgements
[11] a) T. J. Seiders, D. W. Ward, R. H. Grubbs, Org. Lett.
2001, 3, 3225–3228; b) J. J. Van Veldhuizen, D. G. Gil-
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Funk, J. M. Berlin, R. H. Grubbs, J. Am. Chem. Soc.
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The financial support of the “Fonds de la Recherche Scientifi-
que – FNRS”, Brussels, is gratefully acknowledged for the
purchase of major instrumentation. We thank Umicore AG &
Co. KG for a generous donation of complex 15.
[12] E. L. Dias, R. H. Grubbs, Organometallics 1998, 17,
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[13] T. Weskamp, F. J. Kohl, W. Hieringer, D. Gleich, W. A.
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