Up to seven-component adducts by unprecedented multiple alkyne and carbonyl insertions in the metal-carbon bond of chromium alkoxy alkynyl carbene complexes

Article abstract of DOI:10.1002/chem.200700776

Chromium alkoxy alkynyl Fischer carbene complexes react with symmetrical internal alkynes to form new and different organometallic species, which result from consecutive insertions of several alkyne units and carbonyl groups into the metal-carbon bond. Th

Full text of DOI:10.1002/chem.200700776

FULL PAPER
DOI: 10.1002/chem.200700776
Up to Seven-Component Adducts by Unprecedented Multiple Alkyne and
Carbonyl Insertions in the Metal–Carbon Bond of Chromium Alkoxy
Alkynyl Carbene Complexes
JosØ Barluenga,*[a] Patricia García-García,[a] Manuel A. Fernµndez-Rodríguez,[a]
Christian Rocaboy,[a, b] Enrique Aguilar,[a] Facundo Andina,[a] and Isabel Merino[c]
Abstract: Chromium alkoxy alkynyl
Fischer carbene complexes react with
symmetrical internal alkynes to form
new and different organometallic spe-
cies, which result from consecutive in-
sertions of several alkyne units and car-
bonyl groups into the metal–carbon
bond. The insertion sequence can be
controlled and, by slight modification
of the reaction conditions, it can be di-
rected to the preparation of either
seven- or five-component adducts.
Three molecules of alkyne, two carbon-
yl groups, the carbene ligand and the
chromium metal moiety partake in the
creation of seven new carbon–carbon
bonds and two five-membered carbocy-
cles in the first case while four new
À
provided; they are also able to insert a
unit of different internal alkyne
which confers more diversity to the
a
carbon–carbon bonds, a s Cr C
G
seven-component adducts. The pres-
À
bond and a cyclopentadienyl moiety
are built in the second case. Evidence
that five-component chromium com-
plexes are intermediates in the forma-
tion of seven-component adducts is
ence of the s Cr C
(sp2) bond has also
been exploited to develop the synthesis
of both cyclopentene-fused and novel
spiro-cyclopentenones as well as sym-
metrical biscyclopentenones. Finally,
the isolation of six-component adducts,
when tolane was employed as the ini-
tial alkyne, provides further support to
the proposed mechanism.
Keywords:
alkyne
insertion
carbenes · carbonyl compounds ·
cyclopentenones · multicomponent
reactions
Introduction
[a] Prof. Dr. J. Barluenga, Dr. P. García-García,
Dr. M. A. Fernµndez-Rodríguez, Dr. C. Rocaboy, Dr. E. Aguilar,
Dr. F. Andina+
Multi-component reactions (MCRs) have recently emerged
as complementary and powerful alternatives to more tradi-
tional strategies for the synthesis of complex chemical struc-
tures, with relevant applications in both combinatorial
chemistry and diversity-oriented synthesis, mainly by means
of their operational simplicity and high atom economy.[1]
Particularly, Group VI metal–heteroatom-stabilized Fischer
carbene complexes (FCCs)[2] have been conferred with a
prominent role in this arena, due both to their versatility as
well as to their ability to partake in MCRs.[3] However, the
participation of alkynyl-substituted FCCs in MCRs has been
scarcely developed.
On the other hand, alkynes have served on many occa-
sions as partners of FCCs in MCRs, as it happens, for in-
stance, in the polymerization of alkynes catalyzed by tung-
sten FCCs[4] in which many molecules of alkyne interact
with just one molecule of FCC, or in the Dçtz benzannula-
tion, in which the interaction takes place among one unit of
alkyne, the carbene ligand, and a CO ligand of the coordina-
Instituto Universitario de Química
Organometµlica “Enrique Moles”
Universidad de Oviedo, C/Juliµn Clavería, 8
33006, Oviedo, Asturias (Spain)
Fax : (+34)985-103-450
E-mail: barluenga@uniovi.es
[b] Dr. C. Rocaboy
Current address: Villapharma
Pol. Ind. Oeste. C/Paraguay
Parc. 7/5 A, Mód. A-1
30169 Murcia (Spain)
[c] Dr. I. Merino++
Unidad de RMN, Servicios Científico-TØcnicos
Universidad de Oviedo, C/Juliµn Clavería, 8
33006, Oviedo, Asturias (Spain)
[+] X-ray structure analysis
[
++] NMR spectroscopic studies
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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tion sphere of the metal complex to form a three-compo-
nent reaction product.[5] Nevertheless, very few couplings of
alkynes with alkynyl carbene complexes have been report-
ed: 1) H. Fischer has presented the insertion of just one
equivalent of an electron-donating-substituted internal
alkyne into the metal–carbon bond of a chromium or tung-
sten alkynyl FCC, without noticing further evolution of the
new inenyl carbene complex formed.[6] 2) Dçtz has shown
that, after addition of diethylzinc, an alkoxy alkynyl tung-
sten carbene complex undergoes dimerization of the car-
bene ligand to give an exo-alkenylidenecyclopentenylidene
complex.[7] 3) Wulff has pointed out an intramolecular
alkyne insertion into an amino alkynyl FCC, followed by a
metal-mediated Moore-type cyclisation, as a route for the
synthesis of 5-hydroxyindolines.[8] 4) In the fourth and, as far
as we know, last example, the nucleophilicity of propargylsi-
lanes has afforded the coupling of one equivalent of a termi-
nal alkyne to FCC 1a and the initial intermediate evolved,
by a 1,2-silicon migration and the loss of the metal moiety,
to form a conjugated dienyne.[9] However, in all those cases,
only one alkyne unit reacted with the FCC; in fact, the dis-
crete and controlled insertion of a defined number of alkyne
units into the metal–carbon bond of a carbene complex has
been rarely observed.[10] Herein, we report that alkoxy al-
kynyl chromium(0) carbene complexes are able to undergo
the controlled intermolecular insertion of up to three alkyne
units into the chromium–carbon bond leading to the forma-
tion of multi-component adducts involving up to seven com-
ponents. Moreover, by a slight modification of the reaction
conditions, the process can be directed towards the forma-
tion of five-component adducts, the reactivity of which may
be used to shed some light onto the proposed mechanism
and for the synthesis of new organic and organometallic spe-
cies.
Results and Discussion
Establishment of the reaction conditions: We initially mixed
FCC 1a and 3-hexyne 2a in toluene and, after warming the
mixture at 1108C in a sealed vessel, adduct 4a was isolated
as the major product. Further experiments indicated that:
1) the reaction did not take place at temperatures below
808C, 2) comparable results were obtained by performing it
in toluene at 80 or 1108C (Table 1, entries 1 and 2) and
Table 1. Optimization of the reaction conditions.
Entry
T [8C]
Solvent
Equivalents
2a
3a[a]
4a[a]
Abstract in Spanish: Los complejos alcoxialquinilcarbeno de
Fischer reaccionan con alquinos internos simØtricos para dar
lugar a nuevas especies organometµlicas,que se forman
como consecuencia de inserciones consecutivas de varias uni-
dades de alquino y de grupos carbonilo en el enlace metal-
carbono. La secuencia de inserción puede ser controlada y,
mediante una pequeÇa modificación de las condiciones de
reacción,dirigida hacia la preparación de aductos de siete o
de cinco componentes. Tres molØculas de alquino,dos grupos
carbonilo,el ligando carbeno y el fragmento metµlico partici-
pan en la creación de siete nuevos enlaces carbono-carbono y
dos carbociclos de cinco miembros en el primer caso,en
tanto que en el segundo caso se forman cuatro nuevos enlaces
À
1
2
3
4
5
6
7
8
110
80
80
80
80
80
80
80
toluene
toluene
THF
DME
1,4-dioxane
DCE
15
15
15
15
15
15
5
24
22
18
20
21
27
15
10
12
23
12
DCE
DCE
3
[a] Isolated yield based on 1a.
3) tungsten alkynyl FCCs were not able to insert alkynes
even at 1108C. With these initial results in hand, we turned
to optimize the reaction conditions by treating FCC 1a and
alkyne 2a with a variety of different solvents and we found
that: 4) the reaction did not take place in hexane or acetoni-
trile, 5) oxygenated ether-type solvents, such as THF, 1,2-di-
methoxyethane (DME) or 1,4-dioxane (entries 3–5), provid-
ed yields comparable to the ones reached in toluene and
6) the higher yields were obtained in 1,2-dichloroethane
(DCE) (entry 6). Along all of these tests, we could detect
variable but small amounts of adduct 3a, which was isolated
in a 12% yield from entry 6. The amount of 3a was in-
creased by reducing to five the number of equivalents of
alkyne employed, but the yield of 4a was affected (entry 7).
Performing the reaction with just three equivalents of
alkyne resulted in reduced isolated quantities of both 3a
and 4a (entry 8).
carbono-carbono,un enlace s Cr C
(sp2) y un anillo de ciclo-
G
pentadienilo. Se aportan evidencias de que los complejos de
cinco componentes de cromo son intermedios en la forma-
ción de los aductos de siete componentes; dichos complejos
son,asimismo,capaces de insertar una unidad de un alquino
interno distinto lo que aporta mayor diversidad estructural en
los aductos de siete componentes. La presencia del enlace s
À
Cr C
(sp2) ha sido utilizada para desarrollar una síntesis de
G
ciclopentenonas fusionadas a un anillo de ciclopenteno,así
como de nuevas espirociclopentenonas y de bis-ciclopenteno-
nas simØtricas. Finalmente,cuando se utiliza tolano como al-
quino inicial,ha sido posible aislar aductos de seis compo-
nentes,lo que tambiØn supone un apoyo al mecanismo pro-
puesto.
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Chromium Alkoxy Alkynyl Carbene Complexes
FULL PAPER
Structural analysis: From the NMR spectroscopic analysis,
we could establish that compound 4a contains: the metal co-
ordinated to two carbonyl ligands, three units of acetylene,
the carbene ligand moiety and two organic carbonyl groups;
therefore, it is a seven-component adduct although four of
the components come from one reactant molecule. Howev-
er, an X-ray diffraction experiment was required to com-
pletely determine the connectivity of the fragments and to
elucidate the structure of 4a (Figure 1).[11] The determined
À
Cr C bond lengths lie between 2.153 and 2.258 Š for the
carbon atoms of the cyclopentadienyl group and 2.172 and
2.288 Š for the cyclic allylic moiety and are in the same
range as the distances found for other structurally related
compounds.[10c]
On the contrary, the molecular structure for 3a was estab-
lished by HRMS, FTIR, and 1D and 2D NMR spectroscopy
data. For instance, the presence of a fac-Cr(CO)3 moiety
was clearly indicated by FTIR spectroscopy (n˜ =2005,
1924 cmÀ1) and supported by the lack of heteronuclear mul-
tiple-bond correlation (HMBC)-crosspeaks for the signals at
d (13C NMR)=245.9, 239.9 and 234.9 ppm (Figure 2). Re-
markably, the key for the elucidation of its structure was the
signal at d=219.0 ppm, which showed HMBC-correlations
with the hydrogen atoms of the C-21methyl group
(Figure 2); consequently, the option that a such signal corre-
sponded to a chromium-linked carbonyl carbon was discard-
ed. Instead, its HMBC crosspeak signal allowed its assign-
Figure 1. ORTEP diagram for 4a. Ellipsoids are shown at the 30% level.
À
À
À
Selected bond lengths (Š): Cr1 C1 2.1532(18), Cr1 C2 2.2580(18), Cr1
À
À
À
C3 2.2512(18), Cr1 C4 2.2065(18), Cr1 C5 2.1695(18), Cr1 C17
À
À
2.2694(19), Cr1 C25 2.1720(18), Cr1 C26 2.2876(19).
Figure 2. Details of the HMBC spectrum for 3a.
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J. Barluenga et al.
ment as an olefin (sp2)-carbon s-bonded to the chromium,
(entry 11). In the latter case, adduct 3h was the only identi-
fied product; seven-component adduct 4h was not detected,
even though the starting materials were treated under the
conditions of method A. We assumed then that the forma-
tion of 4h is probably impeded for steric reasons.
Next, we heated a mixture of FCC 1a and tolane 2c in a
sealed tube at 1108C expecting that a higher temperature
would promote the formation of the corresponding seven-
component adduct 4h but, on the contrary, adduct 3h was
formed together with a new product which had not retained
the chromium moiety. Spectroscopic analyses led to the
structure of the symmetrical biscyclopentenone 5b, isolated
which is consistent with the reported 13C NMR spectroscopic
À
data for other chromium derivatives bearing s-bonded Cr
C
A
ric analysis, we concluded that 3a contains two units of
alkyne, the carbene ligand, an organic carbonyl group, and
the chromium atom linked to three carbonyl ligands; it is,
therefore, a five-component product.
Scope of the reaction: Two experimental procedures, which
differed in the number of equivalents of alkyne 2 added,
were employed to test the scope of the reaction, in DCE at
808C in a sealed vessel. Method A utilized 15 equivalents of
2 and method B utilized five equivalents of 2, each one in-
volving the optimized conditions required for the formation
of either adducts 4 or 3. The process is quite general for al-
kynyl FCCs bearing aromatic rings; it tolerates both elec-
tron-deficient (Table 2, entries 1, 2) and electron-rich-substi-
À
in 30% yield, which results from the creation of a new C C
bond (Scheme 1). Interestingly, the direct sunlight exposi-
Table 2. Scope of the reaction.
Entry
R
R1 Method[a]
3
Yield
[%][b]
4
Yield
[%][b]
Scheme 1. Formation of symmetrical biscyclopentenones 5.
1
2
3
4
5
p-Cl-C6H4
p-Cl-C6H4
p-MeO-C6H4
p-MeO-C6H4
Fc[c]
Et
Et
Et
Et
Et
A
B
A
B
A
3b
3b
3c
3c
10
12
22
16
4b
4b
4c
4c
23
17
31
20
tion of 3a leads to the corresponding symmetrical four-com-
ponent biscyclopentenone, 5a, although in a modest yield.
4d 29[d]
Proposed mechanism: The formation of adduct 4a is the
result of the sequential intermolecular insertion of three
molecules of alkyne and two carbonyl ligands in a chromium
alkynyl carbene complex that reacts through all its three re-
active positions: the carbene carbon and both acetylenic car-
bons. Thus, the sequence involves the participation of four
6
Et
Et
B
3e
14
4e
21
7
8
A
4 f 31[e]
4 f 18[e]
Et
Pr
B
À
C C triple bonds and it represents an orchestrated, novel
9
1
11
Ph
Ph
Ph
A
3g
B 3g
3h
13
25
32
4g
4g
4h
34
16
–
and unique combination of seven components with the crea-
tion of seven carbon–carbon bonds in an unprecedented
process.
0
Pr
Ph
A
[a] Method A: 15 equiv of 2 in DCE at 808C in a sealed vessel; meth-
od B: 5 equiv of 2 in DCE at 808C in a sealed vessel. [b] Isolated yield
based on 1. [c] Fc=Ferrocenyl. [d] Isolated as a 1.7:1 mixture of non-sep-
arable isomers. [e] Isolated as a 1:1 mixture of isomers which could be
separated; an X-ray crystal structure for 4 f isomer B was determined.[11]
The following mechanism, depicted in Scheme 2, may ac-
count for the formation of compounds 3 and 4. An initial
thermal dissociation of a CO ligand would facilitate the in-
sertion of the first molecule of acetylene to generate enynyl
carbene intermediate I, which is stabilized by intramolecular
triple bond coordination and presents two resonance struc-
trures (Ia and Ib). Several pentacarbonyl carbene com-
plexes, analogous to such types of intermediate, have been
previously isolated and characterized,[6,13] and, although not
isolated, other structurally related species have been pro-
posed as intermediates in different processes.[8,9,13]
tuted arenes (entries 3–6) in the triple bond. It also takes
place with alkenyl-substituted alkynyl FCCs (entries 7, 8).
Low yields of each product were obtained with moderate
combined reaction yields. Occasionally, adducts 3 were not
observed (entries 5, 7, 8). Regarding the alkyne component,
the reaction does not occur for terminal acetylenes, but
other symmetrical internal alkynes were also successfully
employed, such as 4-octyne 2b (entries 9, 10) or tolane 2c
Then a 1,4-metal rearrangement should take place to
form cyclopentadienyl intermediate II; interestingly, 1,4-
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Chromium Alkoxy Alkynyl Carbene Complexes
FULL PAPER
bene carbon–metal bond forms species IV, which, in fact, is
a resonance structure of 3. Likewise, the consecutive inser-
tion of two equivalents of acetylene on III, followed by the
incorporation of another CO ligand and the evolution of the
formed intermediate VI through an intramolecular cyclisa-
tion reaction led to the formation of seven-component ad-
ducts 4. The chromium atom is formally oxidized from Cr(0)
to Cr(II) along the global sequence of events.
On the other hand, the formation of symmetrical biscyclo-
pentenones 5 may be explained by a thermally or photo-
chemically promoted h5 to h1 isomerisation of 3a,h to form
intermediate VIII (Scheme 3).
A reductive elimination
would lead to IX, which, after the addition of silica gel,
would produce 5.
Scheme 3. Proposed mechanism for the formation of symmetrical biscy-
clopentenones 5.
Reactivity of 3a: According to the mechanism depicted in
Scheme 2, five-component chromate 3 should be an inter-
mediate in the formation of 4. To prove that hypothesis, we
treated 3a with an excess of 3-hexyne 2a in DCE at 1108C
and a 45% isolated yield of 4a was obtained (Scheme 4).
Scheme 2. Proposed mechanism for the reaction of an alkynyl FCC 1
versus an internal symmetrical alkyne 2.
metal migrations have not been described in FCC chemistry
though they are known for other metals such as rhodium or
palladium.[14] Nevertheless, a [1,4]-chromium rearrangement
can alternatively be considered as the result of two consecu-
tive [1,2] and [1,3]-metal migrations, which are quite
common in this field.[15] Although displaying an endo-regio-
chemistry, this step formally represents an intramolecular
alkyne insertion in the metal–carbon bond, which typically
follows a [2+2]/retro
[2+2] cycloaddition sequence;[8,16] how-
G
ever, such endo-regiochemical insertion has not been previ-
ously reported, as far as we know, and, taking into account
that the rigidity of intermediate I would probably inhibit the
required approach of the acetylene moiety to the metal–
carbon bond, the metal migration seems as the most plausi-
ble reaction pathway.
The subsequent insertion of a carbonyl ligand[17] leads to
the formation of acyl metallate IIIa, which is probably stabi-
lized by intramolecular coordination and presents zwitter-
ionic oxy-carbene complex IIIb as a resonance structure.
The insertion of another equivalent of acetylene in the car-
Scheme 4. Reactivity of 3a.
Moreover, such a result opened the door to test the inser-
tion of different alkynes into the chromium–carbon bond of
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J. Barluenga et al.
metallates 3. In fact, 4-octyne 2b was incorporated, under
the above reported conditions, as the third alkyne unit to
form mixed compound 6 in 30% yield. The incorporation of
a terminal alkyne as the third acetylene unit was also effec-
tive and involved the removal of the metal moiety and the
On the other hand, an alternative demetalation pathway
À
was developed: a new C C bond was formed upon the
treatment with trifluoroacetic acid (TFA) to give cyclopen-
tene-fused cycopentenone 8 (Scheme 4), a metal-free adduct
which, considering the H atom provided by TFA, incorpo-
rates five components in the overall sequence from the
starting carbene complex 1a.
À
creation of two C C bonds: the treatment of 3a with phe-
nylacetylene produced spiro
A
Moreover, an experiment was carried out with 1-deutero-2-
phenylethyne as deuterated starting material, to gain some
insight about the mechanism for the formation of cyclopen-
tenones 7: the analogous spirocyclopentenone [D]7, 100%
deuterated at the a-position to the phenyl ring that comes
from the alkyne, was obtained.
Taking into account these results, a plausible mechanism
for the formation of spirocyclopentenones 7 (and [D]7) is
depicted in Scheme 5. We propose the initial dissociation of
Remarkably, 3a may undergo cyclisation through three
different positions (C1, C2 and C5, Figure 2) to form ad-
ducts 7, 5a, and 8, which may be attributed to the relative
thermodynamic stability of six-membered metalacycle inter-
mediates versus other possible and alternative seven-mem-
bered metalacycles, as well as to steric effects. Interestingly,
compounds 7 and 8 may be obtained in one-pot processes
from FCC 1a, by sequential addition of the required re-
agents, in comparable yields to the ones reached in the step-
wise procedure.
Reactivity of 3h: a support for the proposed mechanism:
The feasibility of alkyne insertion in compound 3h was also
tested; it was found that, in its reaction with 3-hexyne 2a,
chromium complex 9 was isolated as a mixture of diastereo-
mers that differ in the configuration of the new quaternary
carbon atom (Scheme 6).
Scheme 6. Reactivity of compound 3h with 3-hexyne 2a.
Their molecular structure was established by 1D and
2D NMR spectroscopic analysis, and confirmed by the X-
ray structures of both isomers (see Figure 3 for the crystal
structure of one of them):[11] they contain the same cyclo-
pentadienyl group present in 3h and an anionic h3-allylic
moiety, which is now confined into a four-membered carbo-
cycle; the chromium is linked to two carbonyl ligands and
remains as part of the molecule. Therefore, metal complexes
9 have been generated, from the initial FCC 1a, by a combi-
nation of six-components: three of them are acetylenic units
(two molecules of tolane and one of 3-hexyne), and the
other three proceed from the initial FCC 1a (the carbene
ligand, the metal moiety, formed by the chromium atom and
two carbonyl ligands, and a carbonyl ligand which acts as a
bridge between the two cycles).
The formation of compounds 9 may be explained as de-
picted in Scheme 7, based on the above proposed mecha-
nism (see Scheme 2) for the synthesis of compounds 4.
Under the reaction conditions, 3h undergoes the insertion
of a unit of 3-hexyne 2a to form intermediate XVI, (analo-
gous to intermediate V, Scheme 2) which is not able to
insert another carbonyl ligand because of steric hindrance.
Scheme 5. Proposed mechanism for the formation of compounds 7 (and
[D]7).
a CO ligand to form complex X, which bears an empty coor-
dination position. Such a coordination position would be
filled by phenylacetylene to form organometallic species XI,
which would evolve by insertion of the acetylene into the s
Cr C
(sp2) bond, thus producing chromium complex XII.
A
À
The transformation of XII into XV is particularly interest-
ing; it should involve the 1,2-migration of the chromium
fragment from a C
N
N
neous or concomitant inverse 1,2-migration of the acetylenic
hydrogen (deuterium) atom to form intermediate XIV,[18]
presumably through a species such as XIII. This rearrange-
ment must be completely diastereoselective as no evidence
of the (4Z)-isomer of 7 (and [D]7) has been observed. Final-
ly, a h5 to h1 isomerisation of XIV to XV (which presents a
six-membered metalacycle), followed by a reductive elimi-
nation would account for the formation of 7 (and [D]7).
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Chromium Alkoxy Alkynyl Carbene Complexes
FULL PAPER
kynes; in fact, they do it in a cascade process which consists
of the incorporation of up to three units of alkyne and two
carbonyl ligands. The reaction conditions can be controlled
and directed to the formation of seven-component adducts 4
or five-component adducts 3 as major reaction products, al-
though the low isolated yields reached represent a major
drawback from a synthetic point of view. Finally, the pres-
ence of a s Cr C
(sp2) bond in 3 has helped to support the
A
À
proposed mechanism by: 1) transforming 3a into 4 and
2) transforming 3h into 9, which may be considered as a six-
component adduct. Moreover, the s Cr C
(sp2) bond in 3
A
À
has also proved its usefulness: 3) to control the insertion of
the last alkyne unit and 4) in the development of the synthe-
sis of novel five-membered carbocyclic compounds.
Experimental Section
General considerations: All reactions involving air-sensitive compounds
were carried out under a N2 atmosphere (99.99%). All glassware was
oven-dried (1208C), evacuated and purged with nitrogen. All common
reagents and solvents were obtained from commercial suppliers and used
without any further purification unless otherwise indicated. Fischer car-
bene complexes 1a,[19] 1b,[20] 1c,[21] 1d,[22] 1e and[23] 1f,[24] were prepared
by following described procedures. Alkynes 2 are commercially available
and were used as received, without further purification. Solvents were
dried by standard methods. Hexane and ethyl acetate were purchased as
extra pure grade reagents and used as received. TLC was performed on
aluminum-backed plates coated with silica gel 60 with F254 indicator; the
chromatograms were visualized under ultraviolet light and/or by staining
with a Ce/Mo reagent and subsequent heating. Rf values are reported on
silica gel. Flash column chromatography was carried out on silica gel 60,
230–240 mesh. Routine NMR spectroscopic measurements were recorded
Figure 3. ORTEP diagram for 9, isomer B. Ellipsoids are shown at the
À
À
30% level. Selected bond lengths (Š): Cr1 C1 2.1439(18), Cr1 C2
À
À
À
2.1948(18), Cr1 C3 2.2424(18), Cr1 C4 2.2756(18), Cr1 C5 2.2063(18),
À
À
À
Cr1 C212.2862(18), Cr1 C30 2.1876(19), Cr1 C312.197(2).
1
on Bruker AC-300, DPX-300 or AMX-400 spectrometers. H NMR: split-
ting-pattern abbreviations are: s: singlet, brs: broad singlet, d: doublet, t:
triplet, app.t: apparent triplet, dd: double doublet, q: quartet, m: multip-
let. 13C NMR: multiplicities were determined by DEPT experiments, ab-
breviations are: q: CH3, t: CH2, d: CH, s: quaternary carbon atoms.
COSY, HSQC, HMBC, and NOESY spectroscopic experiments were car-
ried out on a Bruker AMX-400 or AV-600 spectrometer. Standard pulse
sequences were employed for the DEPT experiments. FTIR spectroscopy
was performed with a Mattson 3000 FTIR spectrometer by using sodium
chloride plates; samples were measured as films from deuterocloroform
or dichloromethane. Mass spectra were determined by Universidad de
Oviedo and Universidad de Vigo (CACTI) with a Finnigan Mat95 and a
VG AutoSpec M Mass spectrometer, respectively, for high-resolution
mass spectra (HRMS). Low-resolution mass spectra were obtained with a
Hewlett–Packard 5880A spectrometer. In both cases, either electron-
impact (70 eV) or FAB techniques were employed. Melting points were
determined on a Büchi–Tottoli apparatus and are uncorrected. Elemental
analyses were carried out with a Perkin–Elmer 240B microanalyzer.
Scheme 7. Proposed mechanism for the formation of compounds 9.
Instead, it evolves by a cyclisation step to XVII, which is fol-
lowed by coordination to the double bond and extrusion of
a CO ligand to give diastereomeric complexes 9. The forma-
tion of 9 represents a further support for the mechanism
proposed in Scheme 2 as it provides evidence for the incor-
poration of the third unit of alkyne prior to a final CO inser-
tion.
On the other hand, 3h was not able to insert tolane as the
third alkyne unit, under the tested reaction conditions (tolu-
ene, 1108C), probably due to steric effects.
General procedure for the synthesis of complexes 3 and 4: A solution of
the corresponding carbene complex 1 (1equiv, 1mmol) and the appropri-
ate acetylene 2 (15 mmol, method A; 5 mmol, method B) in dry 1,2-di-
chloroethane (15 mL) was heated at 808C in a sealed tube until complete
disappearance of the carbene complex was observed by TLC (ꢀ12 h).
Solvent was removed under reduced
pressure, and the residue was purified
by flash chromatography (hexane/
AcOEt). The corresponding com-
plexes 3 and 4 were isolated in the
yields reported in Table 2.
Conclusion
Tricarbonyl[1,2-diethyl-h5–3-(3,4-di-
ethyl-2-methoxy-5-phenylcyclopenta-
dienyl)-3-oxo-1-propen-1-yl]chrom-
We have reported that alkoxy alkynyl chromium(0) carbene
complexes are able to intermolecularly insert internal al-
Chem. Eur. J. 2007, 13, 9115 – 9126
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9121

J. Barluenga et al.
ium(II) (3a): Brown oil; yield: 12% (method A), 23% (method B); Rf:
0.42 (hexane/AcOEt 5:1); 1H NMR (300 MHz, CDCl3, 258C, TMS): d=
100.5 (s), 94.9 (s), 60.8 (q), 59.9 (q), 55.9 (q, 2 CH), 39.8 (t), 23.9 (t), 18.5
(t), 17.7 (t), 15.4 (q), 14.6 (q), 14.4 (q), 12.8 ppm (q); FTIR (film): n˜ =
2004, 1921, 1644 cmÀ1; MS (FAB): m/z (%): 563 (40) [M+1]+, 479 (57)
[MÀ3(CO)+1]+, 478 (85), 413 (100); HRMS (FAB): m/z: calcd for
C29H35CrO8: 563.1737 [M+1]+; found: 563.1734.
7.55–7.50 (m, 2H), 7.32–7.25 (m, 3H), 3.89 (s, 3H), 2.88–2.75 (m, 2H),
3
2.59–2.41 (m, 2H), 2.28–2.11 (m, 4H), 1.20 (t, J
A
(t, 3J
(H,H)=7.4 Hz, 3H); 13C NMR (CDCl3, 75 MHz, 258C): d=245.9 (s),
A
N
Tricarbonyl
[h5-3-(2-methoxy-5-phenyl-3,4-dipropylcyclopentadienyl)-3-
A
ACHTREUNG
239.9 (s), 234.9 (s), 219.0 (s), 191.3 (s), 160.5 (s), 141.4 (s), 130.7 (d, 2
CH), 130.6 (s), 128.1 (d), 127.9 (d, 2 CH), 110.7 (s), 106.4 (s), 100.8 (s),
95.1 (s), 60.0 (q), 39.7 (t), 23.8 (t), 18.3 (t), 17.7 (t), 15.1 (q), 14.6 (q), 14.3
(q), 12.6 ppm (q); FTIR (film): n˜ =2005, 1924, 1693, 1642 cmÀ1; MS
(FAB): m/z (%): 473 (5) [M+1]+, 389 (50) [MÀ3(CO)+1]+, 388 (100);
HRMS (FAB): m/z: calcd for C26H29CrO5: 473.1420 [M+1]+; found:
473.1411.
oxo-1,2-dipropyl-1-propen-1-yl]chromium(II) (3g): Brown oil; yield:
13% (method A), 25% (method B);
Rf =0.46
(hexane/AcOEt
5:1);
1H NMR (300 MHz, CDCl3, 258C,
TMS): d=7.54–7.50 (m, 2H), 7.34–
7.25 (m, 3H), 3.89 (s, 3H), 2.81–2.67
(m, 2H), 2.51–2.39 (m, 2H), 2.20–2.05
(m, 4H), 1.72–1.59 (m, 1H), 1.56–1.43
(m, 3H), 1.28–1.12 (m, 2H), 1.10–0.80
Tricarbonyl
{h5–3-[2-(4-chlorophenyl)-3,4-diethyl-5-methoxycyclopenta-
R
dienyl]-1,2-diethyl-3-oxo-1-propen-1-yl}chromium(II) (3b): Brown oil;
yield: 10% (method A), 12% (meth-
(m, 2H), 1.03 (t, 3J
3H), 0.93 (t, 3J(H,H)=6.8 Hz, 3H), 0.73 (t, 3J
0.66 ppm (t, 3J(H,H)=6.8 Hz, 3H); 13C NMR (CDCl3, 75 MHz, 258C):
A
A
N
od B); Rf =0.52 (hexane/AcOEt 5:1);
1H NMR (400 MHz, CDCl3, 258C,
AHCTREUNG
TMS): d=7.48 (d, 3J
ACHTREUNG
d=246.1 (s), 239.9 (s), 235.2 (s), 218.0 (s), 191.5 (s), 159.4 (s), 141.6 (s),
130.8 (d; 2CH+s), 128.0 (d), 127.9 (d; 2CH), 110.8 (s), 106.4 (s), 99.5
(s), 93.9 (s), 59.9 (q), 49.9 (t), 32.9 (t), 27.3 (t), 26.7 (t), 24.0 (t), 23.6 (t),
23.0 (t), 21.5 (t), 14.7 (q), 14.5 (q), 14.2 (q), 13.7 ppm (q); FTIR (film):
n˜ =2005, 1921, 1644 cmÀ1; MS (FAB): m/z (%): 529 (26) [M+1]+, 445
(57) [MÀ3(CO)+1]+, 444 (100); HRMS (FAB): m/z: calcd for
C30H37CrO5: 529.2046 [M+1]+; found: 529.2034.
2H), 7.30 (d, 3J
ACHTREUNG
3.89 (s, 3H), 2.90–2.76 (m, 2H), 2.57–
2.48 (m, 1H), 2.47–2.36 (m, 1H), 2.26–
3
2.11 (m, 4H), 1.20 (t, J
A
3H), 1.12 (t, 3J
0.86 (t, (H,H)=7.4 Hz,
3J
0.77 ppm (t, 3J
(H,H)=7.4 Hz, 3H);
ACHTREUNG
AHCTREUNG
Tricarbonyl
[h5–3-(2-methoxy-3,4,5-triphenylcyclopentadienyl)-3-oxo-1,2-
C
AHCTREUNG
13C NMR (CDCl3, 100 MHz, 258C):
d=245.5 (s), 239.9 (s), 234.6 (s), 219.7 (s), 191.2 (s), 160.7 (s), 141.5 (s),
134.0 (s), 131.9 (d, 2 CH), 129.4 (s), 128.2 (d, 2 CH), 110.7 (s), 104.8 (s),
100.8 (s), 95.3 (s), 60.0 (q), 39.9 (t), 23.9 (t), 18.3 (t), 17.7 (t), 15.1 (q),
diphenyl-1-propen-1-yl]chromium(II) (3h): Brown solid; yield: 32%
(method B); Rf =0.42 (hexane/AcOEt
5:1); m.p. decomposition was observed
upon heating above 1108C; 1H NMR
14.6 (q), 14.4 (q), 12.8 ppm (q); FTIR (film): n˜ =2006, 1926, 1644 cmÀ1
;
(300 MHz, CDCl3, 258C, TMS): d=
elemental analysis calcd (%) for C26H27ClCrO5 (506.94): C 61.60, H 5.37;
found: C 62.11, H 5.21.
Tricarbonyl{1,2-diethyl-h5–3-[3,4-diethyl-2-methoxy-5-(4-methoxyphenyl)-
cyclopentadienyl]-3-oxo-1-propen-1-yl}chromium(II) (3c): Brown oil;
yield: 22% (method A), 16% (meth-
7.52–7.20 (m, 15H), 7.18–7.07 (m,
4H), 7.05–6.92 (m, 2H), 6.85 (d, 3J-
(H,H)=6.8 Hz, 2H), 6.55 (d, 3J-
A
3H); 13C NMR (CDCl3, 75 MHz,
258C): d=246.2 (s), 237.3 (s), 236.4 (s), 213.9 (s), 190.1 (s), 157.4 (s),
151.5 (s), 138.3 (s), 138.0 (s), 131.4 (d; 2CH), 131.2 (d; 2CH), 131.0 (d;
2CH), 130.6 (s), 130.0 (d; 2CH), 128.6 (d), 128.4 (d; 2CH), 128.3 (d),
128.1 (s), 127.7 (d; 4CH), 127.4 (d; 2CH), 127.3 (d; 2CH), 126.4 (d),
126.1 (d), 124.4 (d, 2CH), 107.9 (s), 107.4 (s), 101.4 (s), 96.6 (s), 62.0 ppm
(q)—two aromatic signals, which correspond to a CH and a C, are proba-
bly overlapped with other signals as they were not detected; FTIR (film):
od B); Rf: 0.28 (hexane/AcOEt 5:1);
1H NMR (400 MHz, CDCl3, 258C,
TMS): d=7.46 (d, 3J
ACHTREUNG
2H), 6.84 (d, 3J
ACHTREUNG
3.89 (s, 3H), 3.80 (s, 3H), 2.89–2.78
(m, 2H), 2.57–2.40 (m, 2H), 2.29–2.09
(m, 4H), 1.19 (t, 3J
ACHTREUNG
n˜ =2012, 1938, 1650 cmÀ1
Dicarbonyl
{[(1S*)-h5-(3,4-diethyl-2-methoxy-5-phenylcyclopentadienyl)]-
[(1S*)-(2–4h)-1,2,3,4-tetraethyl-5-oxocyclopent-3-enyl]ketone}chromiu-
.
3H), 1.12 (t, 3J
0.87 (t,
3J
ACHTREUNG
AHCTREUNG
AHCTREUNG
AHCTREUNG
AHCTREUNG
13C NMR (CDCl3, 100 MHz, 258C):
d=246.1 (s), 240.0 (s), 235.4 (s), 219.7 (s), 191.6 (s), 160.6 (s), 159.3 (s),
141.4 (s), 132.0 (d, 2 CH), 122.5 (s), 113.4 (d, 2 CH), 111.1 (s), 106.3 (s),
100.2 (s), 95.0 (s), 60.0 (q), 55.2 (q), 39.9 (t), 24.0 (t), 18.4 (t), 17.8 (t),
15.2 (q), 14.8 (q), 14.5 (q), 12.9 ppm (q); FTIR (film): n˜ =2004, 1925,
m(II) (4a): Red solid; yield: 27%
(method A), 15% (method B); Rf =
0.32 (hexane/AcOEt 5:1); 1H NMR
(300 MHz, CDCl3, 258C, TMS): d=
7.48–7.26 (m, 3H), 7.20–7.12 (m, 2H),
3.88 (s, 3H), 2.75–2.26 (m, 7H), 2.14–
2.08 (m, 3H), 1.74–1.64 (m, 1H), 1.57–
1.47 (m, 1H), 1.31–1.20 (m, 9H), 1.12
1644 cmÀ1
;
MS (FAB): m/z (%): 503 (6) [M+1]+, 419 (45)
[MÀ3(CO)+1]+, 418 (100); HRMS (FAB): m/z: calcd for C27H31CrO6:
503.1526 [M+1]+; found: 503.1523.
(t, 3J
(H,H)=7.1Hz, 3H), 0.54 ppm (t, 3J-
(H,H)=7.1Hz, 3H);
13C NMR
(H,H)=7.1Hz, 3H), 0.83 (t, 3J-
Tricarbonyl{1,2-diethyl-h5–3-[3,4-diethyl-2-methoxy-5-(3,4,5-trimethoxy-
phenyl)cyclopentadienyl]-3-oxo-1-propen-1-yl}chromium(II) (3e): Brown
oil; yield: 14% (method B); Rf: 0.38 (hexane/AcOEt 5:1); 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=6.77 (s, 2H), 3.89 (s, 3H), 3.85 (s,
9H), 2.89–2.80 (m, 2H), 2.59–2.42 (m,
AHCTREUNG
AHCTREUNG
(CDCl3, 75 MHz, 258C): d=248.6 (s),
248.5 (s), 197.8 (s), 190.0 (s), 133.9 (s), 129.7 (s), 128.1 (d; 2CH), 127.5
(d; 3CH), 120.0 (s), 112.0 (s), 99.7 (s), 98.4 (s), 94.4 (s), 89.3 (s), 85.6 (s),
83.4 (s), 65.2 (q), 26.2 (t), 24.6 (t), 23.8 (t), 21.1 (t), 18.5 (t), 17.6 (t), 16.1
(q), 15.9 (q), 14.2 (q), 13.8 (q), 13.7 (q), 6.8 ppm (q); FTIR (film): n˜ =
1959, 1902, 1711, 1662 cmÀ1; MS (FAB): m/z (%): 555 (18) [M+1]+, 499
(51) [MÀ2(CO)+1]+, 498 (100); HRMS (FAB): m/z: [MÀ2(CO)+1]+:
calcd for C30H39CrO3: 499.2304; found: 499.2303.
2H), 2.29–2.12 (m, 4H), 1.21 (t, 3J
3
(H,H)=7.3 Hz, 3H), 1.11 (t, J
A
7.4 Hz, 3H), 0.93 (t, 3J
3H), 0.75 ppm (t, 3J
ACHTREUNG
AHCTREUNG
3H); 13C NMR (CDCl3, 100 MHz,
258C): d=245.7 (s), 240.7 (s), 234.5
(s), 219.6 (s), 191.7 (s), 160.5 (s), 152.2
(s, 2 C), 141.2 (s), 137.5 (s), 125.9 (s),
110.4 (s), 108.3 (d, 2 CH), 107.1 (s),
Dicarbonyl
methoxycyclopentadienyl]}
pent-3-enyl]ketone}chromium(II) (4b): Brown oil; yield: 23% (meth-
ACHTREUNG
AHCTREUNG
9122
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 9115 – 9126

Chromium Alkoxy Alkynyl Carbene Complexes
FULL PAPER
od A), 17% (method B); Rf =0.45
(hexane/AcOEt 5:1);
1H NMR
(400 MHz, CDCl3, 258C, TMS): d=
min), 71.5 (d; maj), 70.0 (d; maj), 69.6 (d, 5CH; maj), 69.5 (d; maj), 69.3
(d, 5CH; min), 69.0 (d; min), 68.8 (d; min), 67.3 (d; min), 66.6 (d; maj),
65.8 (q; min), 65.4 (q; maj), 26.5 (t; min), 26.0 (t; maj), 24.5 (t; min), 24.2
(t; maj), 23.8 (t; min), 23.3 (t; maj), 21.2 (t; maj), 20.8 (t; min), 20.6 (t;
maj), 19.8 (t; min), 17.9 (t; min), 17.7 (t; maj), 16.3 (q; maj), 16.1 (q;
min), 15.7 (q; maj), 15.1 (q; min), 14.5 (q), 14.3 (q; min), 14.1 (q), 13.5
(q; maj), 13.0 (q; min), 7.1 (q), 7.0 ppm (q); FTIR (film): n˜ =1956, 1900,
3
7.26 (d, J
A
3J
AHCTREUNG
2.71–2.26 (m, 7H), 2.17–2.02 (m, 3H),
1.77–1.65 (m, 1H), 1.62–1.51 (m, 1H),
1.32–1.21 (m, 9H), 1.15 (t, 3J
ACHTREUNG
1705, 1660 cmÀ1
Dicarbonyl
{{(1S*)-h5-[3,4-diethyl-2-methoxy-5-(3,4,5-
.
7.3 Hz, 3H), 0.83 (t, 3J
3H), 0.58 ppm (t, 3J
ACHTREUNG
AHCTREUNG
AHCTREUNG
trimethoxyphenyl)cyclopentadienyl]}
oxocyclopent-3-enyl]ketone}chrom-
A
3H); 13C NMR (CDCl3, 150 MHz,
258C): d=248.6 (s), 248.3 (s), 197.8
ium(II) (4e): Brown oil; yield: 21%
(method B); Rf =0.28 (hexane/AcOEt
3:1); 1H NMR (400 MHz, CDCl3,
258C, TMS): d=6.37 (s, 2H), 3.90 (s,
3H), 3.89 (s, 3H), 3.83 (s, 6H), 2.71–
2.27 (m, 7H), 2.20–2.04 (m, 3H), 1.77–
(s), 190.2 (s), 134.2 (s), 134.1 (s), 128.6
(s), 128.0 (d, 4 CH), 120.3 (s), 112.1 (s), 98.7 (s), 98.6 (s), 94.7 (s), 89.8
(s), 85.8 (s), 83.7 (s), 65.3 (q), 26.4 (t), 24.8 (t), 23.9 (t), 21.3 (t), 18.6 (t),
17.7 (t), 16.2 (q), 16.0 (q), 14.4 (q), 14.0 (q), 13.9 (q), 7.0 ppm (q); FTIR
(film): n=1958, 1902, 1712, 1660 cmÀ1; MS (FAB): m/z (%): 589 (12)
[M+1]+, 533 (51) [MÀ2(CO)+1]+, 532 (100); HRMS (FAB): m/z: calcd
for C32H38CrClO5: 589.1813 [M+1]+; found: 589.1834.
1.68 (m, 1H), 1.59–1.49 (m, 1H), 1.32–
3
1.21 (m, 9H), 1.18 (t, J
(H,H)=7.2 Hz,
3H), 0.87 (t, 3J
(H,H)=7.3 Hz, 3H),
A
Dicarbonyl
methoxyphenyl)cyclopentadienyl]}
ACHTREUNG
0.59 ppm (t, 3J
(H,H)=7.3 Hz, 3H);
C
AHCTREUNG
13C NMR (CDCl3, 100 MHz, 258C):
cyclopent-3-enyl]ketone}chromium(II)
(4c): Orange oil; yield: 31% (meth-
od A), 20% (method B); Rf =0.23
d=249.2 (s), 248.3 (s), 198.3 (s), 190.1
(s), 152.1 (s, 2 C), 138.2 (s), 133.7 (s),
125.1 (d, 2 CH), 120.2 (s), 112.3 (s),
100.2 (s), 98.0 (s), 94.4 (s), 90.0 (s), 85.4 (s), 83.9 (s), 65.2 (q), 61.1 (q),
56.2 (q, 2 CH3), 26.4 (t), 24.8 (t), 24.0 (t), 21.6 (t), 18.9 (t), 17.8 (t), 16.3
(q), 16.0 (q), 14.4 (q), 13.9 (q), 13.8 (q), 7.1 ppm (q)—an aromatic signal,
which correspond to a carbon atom, is probably overlapped with other
signals as it was not detected; FTIR (film): n˜ =1955, 1901, 1712,
(hexane/AcOEt
5:1);
1H NMR
(300 MHz, CDCl3, 258C, TMS): d=
3
7.06 (d, J
A
3J
AHCTREUNG
3.81(s, 3H), 2.80–2.25 (m, 7H), 2.22–
1.97 (m, 3H), 1.79–1.63 (m, 1H), 1.62–
1.47 (m, 1H), 1.42–1.20 (m, 9H), 1.14
1666 cmÀ1
;
MS (FAB): m/z (%): 645 (11) [M+1]+, 589 (50)
(t, 3J
ACHTREUNG
[MÀ2(CO)+1]+, 588 (100); HRMS (FAB): m/z: calcd for C35H45CrO8:
645.2520 [M+1]+; found: 645.2515; elemental analysis calcd (%) for
C35H44CrO8 (644.72): C 65.20, H 6.88; found: C 65.32, H 7.35.
3J
3J
ACHTREUNG
AHCTREUNG
(CDCl3, 100 MHz, 258C): d=248.9 (s),
248.7 (s), 198.2 (s), 190.1 (s), 159.3 (s),
Dicarbonyl
ACHTREUNG
phenylethenyl)cyclopentadienyl]}
AHCTREUNG
133.8 (s), 121.7 (s), 120.1 (s), 112.9 (d, 4CH), 112.1 (s), 100.2 (s), 97.6 (s),
94.3 (s), 89.1(s), 85.7 (s), 83.5 (s), 65.2 (q), 55.0 (q), 26.3 (t), 24.7 (t), 23.9
(t), 21.3 (t), 18.6 (t), 17.7 (t), 16.2 (q), 16.1 (q), 14.3 (q), 14.0 (q), 13.7 (q),
6.9 ppm (q); FTIR (film): n˜ =1954, 1898, 1712, 1666 cmÀ1; MS (FAB): m/
z (%): 585 (17) [M+1]+, 529 (50) [MÀ2(CO)+1]+, 528 (100); HRMS
(FAB): m/z: calcd for C33H41CrO6: 585.2308 [M+1]+; found: 585.2324.
clopent-3-enyl]ketone}chromium(II) (4 f), isomer A: Orange oil; yield:
16% (method A), 9% (method B);
Rf =0.54
(hexane/AcOEt
5:1);
1H NMR (400 MHz, CDCl3, 258C,
TMS): d=7.50–7.21(m, 5H), 6.32 (d,
3J(H,H)=16.0 Hz, 1H), 6.06 (d, 3J-
A
Dicarbonyl
methoxycyclopentadienyl)]
ACHTREUNG
A
AHCTREUNG
2.67–2.43 (m, 5H), 2.39–2.26 (m, 2H),
2.23–2.12 (m, 2H), 2.06–1.97 (m, 1H),
1.82–1.73 (m, 1H), 1.60–1.50 (m, 1H),
pent-3-enyl]ketone}chromium(II)
(4d): Brown oil; yield: 29% (meth-
od A)—as a 1.7:1 observed mixture of
non-separable isomers (ratio deter-
mined by 1H NMR spectroscopy)—
(the stereochemical descriptors indi-
cated in the name correspond to the
1.36–0.83 (m, 12H), 1.34 (t, 3J
7.6 Hz, 3H), 0.66 ppm (t, 3J
ACHTREUNG
AHCTREUNG
7.5 Hz, 3H); 13C NMR (CDCl3,
100 MHz, 258C): d=248.5 (s), 247.3
(s), 197.6 (s), 190.5 (s), 137.2 (d), 136.7 (s), 134.1 (s), 128.6 (d, 2 CH),
127.9 (d), 126.8 (d, 2 CH), 120.2 (s), 114.8 (d), 108.1 (s), 96.8 (s), 96.5 (s),
95.0 (s), 87.9 (s), 86.3 (s), 82.8 (s), 65.1(q), 25.9 (t), 24.5 (t), 23.6 (t), 20.8
(t), 19.4 (t), 17.6 (t), 16.1 (q), 15.8 (q), 15.3 (q), 14.1 (q), 13.9 (q), 7.2 ppm
(q); FTIR (film): n˜ =1955, 1901, 1708, 1667 cmÀ1; MS (EI): m/z (%): 580
(3) [M]+, 525 (44), 524 ppm (100) [MÀ2(CO)]+; HRMS (EI): m/z: calcd
for C34H40CrO5: 580.2275 [M]+; found: 580.2277.
major
diastereomer);
Rf =0.31
(hexane/AcOEt 5:1); the abbreviation
“min” refers to the signals assigned to
the minor isomer and the abbreviation
“maj” to the signals belonging to the
major one; in the cases for which
nothing is specified, either it hasnꢁt
Dicarbonyl
{{(1S*)-h5-[3,4-diethyl-2-
A
been possible to assign the signal to any of the isomers or it belongs to
both of them: H NMR (300 MHz, CDCl3, 258C, TMS): d=4.57–3.93 (m,
1
methoxy-5-(2-
phenylethenyl)cyclopentadienyl]}-
4H; maj + 4H; min), 4.17 (s, 5H; min), 4.04 (s, 5H; maj), 3.89 (s, 3H;
maj), 3.72 (s, 3H; min), 2.80–1.75 (m, 22H), 1.62–1.05 (m, 26H), 0.91–
0.82 ppm (m, 3H; maj + 3H; min), 0.66–0.58 ppm (m, 3H; maj + 3H;
min); 13C NMR (CDCl3, 75 MHz, 258C): d=250.3 (s; min), 249.3 (s;
min), 249.2 (s; maj), 248.0 (s; maj), 199.4 (s; min), 198.6 (s; maj), 193.6
(s; min), 192.5 (s; maj), 133.61 (s), 133.55 (s), 121.4 (s; min), 120.1 (s;
maj), 109.3 (min), 107.7; maj), 101.4 (s), 95.8 (s; maj), 94.4 (s; maj), 94.2
(s; min), 93.8 (s; min), 86.6 (s; maj), 86.0 (s; min), 85.8 (s; maj), 85.6 (s;
min), 84.6 (s; min), 82.4 (s; maj), 80.2 (s; min), 77.2 (s; maj), 74.8 (d;
A
cyclopent-3-enyl]ketone}chromium(II)
(4 f), isomer B: Orange oil; yield:
15% (method A), 9% (method B);
Rf:
0.48
(hexane/AcOEt
5:1);
1H NMR (400 MHz, CDCl3, 258C,
TMS): d=7.52–7.19 (m, 5H), 6.98 (d,
3J(H,H)=16.1 Hz, 1H), 6.79 (d, 3J
A
Chem. Eur. J. 2007, 13, 9115 – 9126
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9123

J. Barluenga et al.
(H,H)=16.1 Hz, 1H), 3.74 (s, 3H), 2.59–2.28 (m, 6H), 2.25–2.11 (m,
7.7 Hz, 4H), 3.80 ppm (s, 1H); 13C NMR (CDCl3, 100 MHz, 258C): d=
194.7 (s; 2C), 168.6 (s; 2C), 142.3 (s; C), 141.1 (s; 2C), 134.9 (s; 2C),
130.7 (s; 2C), 130.1 (d; 4CH), 129.8 (d; 4CH), 129.3 (d; 2CH), 128.4 (d;
2CH), 128.1 (d; 2CH), 128.0 (d; 4CH), 127.7 (d), 127.35 (d; 4CH),
127.30 (d; 2CH), 73.5 (d), 67.0 (s); FTIR (film): n˜ =1728 cmÀ1; MS (EI):
m/z (%): 514 (100) [M]+, 486 (33), 409 (26), 308 (56), 178 (95); HRMS
(EI) calcd: for C38H26O2: 514.1927 [M]+; found: 514.1930.
3H), 2.10–2.00 (m, 1H), 1.94–1.85 (m, 1H), 1.57–1.50 (m, 1H), 1.29–0.91
(m, 6H), 1.24 (t, 3J
C
ACHTREUNG
0.88 (t, 3J
A
13C NMR (CDCl3, 100 MHz, 258C): d=249.4 (s), 247.9 (s), 197.3 (s),
194.1 (s), 136.8 (s), 135.6 (s), 134.1 (d), 128.7 (d, 2 CH), 128.1 (d), 126.5
(d, 2 CH), 121.2 (s), 120.3 (d), 107.2 (s), 94.7 (s), 93.8 (s), 92.5 (s), 86.1
(s), 84.9 (s), 84.1(s), 66.0 (q), 26.4 (t), 24.8 (t), 24.3 (t), 20.9 (t), 18.9 (t),
17.8 (t), 16.2 (q), 16.1 (q), 15.5 (q), 15.0 (q), 13.2 (q), 7.1 ppm (q); FTIR
(film): n˜ =1954, 1900, 1708, 1667 cmÀ1; MS (EI): m/z (%): 580 (3) [M]+,
525 (44), 524 (100) [MÀ2(CO)]+; HRMS (EI): m/z: calcd for
C32H40CrO3: 524.2377 [MÀ2(CO)]+; found: 524.2376.
Reaction of complex 3a with internal acetylenes: A solution of complex
3a (1equiv, 0.3 mmol, 142 mg) and the corresponding acetylene
2
(1.5 mmol) in dry 1,2-dichloroethane (6 mL) was heated at 1108C in a
sealed tube until complete disappearance of complex 3a was observed by
TLC (ꢀ12 h). Solvent was removed under reduced pressure, and the res-
idue was purified by flash chromatography (hexane/AcOEt). When 3-
hexyne was used complex 4a, described above, was isolated in 45%
yield; when the acetylene was 4-octyne, complex 6 was obtained.
Dicarbonyl
ACHTREUNG
dipropylcyclopentadienyl)]
AHCTREUNG
pent-3-enyl]ketone}chromium(II) (4g): Brown oil; yield: 34% (meth-
od A), 16% (method B); Rf =0.41
Dicarbonyl
A
(hexane/AcOEt
5:1);
1H NMR
AHCTREUNG
(300 MHz, CDCl3, 258C, TMS): d=
7.51–7.25 (m, 3H), 7.20–7.05 (m, 2H),
3.88 (s, 3H), 2.71–2.25 (m, 4H), 2.24–
chromium(II) (6): Red solid; yield:
30%; Rf: 0.50 (hexane/AcOEt 5:1);
1H NMR (300 MHz, CDCl3, 258C,
TMS): d=7.32–7.27 (m, 3H), 7.18–
7.15 (m, 2H), 3.90 (s, 3H), 2.78–2.33
(m, 6H), 2.27–1.95 (m, 4H), 1.90–1.48
(m, 6H), 1.33–1.22 (m, 1H), 1.31 (t, 3J
(H,H)=7.7 Hz, 3H), 1.25 (t, 3J
(H,H)=7.7 Hz, 3H), 1.03 (t, 3J
(H,H)=7.3 Hz, 3H), 0.95 (t, 3J
(H,H)=7.3 Hz, 3H), 0.86 (t, 3J-
1.93 (m, 4H), 1.92–1.70 (m, 1H), 1.69–
1.40 (m, 8H), 1.39–0.85 (m, 19H),
0.80–0.65 ppm (m, 6H); 13C NMR
(CDCl3, 100 MHz, 258C): d=248.9 (s),
248.7 (s), 198.1 (s), 190.0 (s), 134.2 (s),
130.0 (s), 128.1 (d, 2 CH), 127.4 (d, 3
CH), 118.9 (s), 112.1 (s), 99.9 (s), 97.5
(s), 93.0 (s), 88.9 (s), 84.6 (s), 83.0 (s), 65.1(q), 35.8 (t), 34.4 (t), 33.8 (t),
30.9 (t), 27.6 (t), 26.8 (t), 25.3 (t), 24.8 (t), 22.9 (t), 22.8 (t), 22.5 (t), 15.5
(q), 15.4 (t), 15.2 (q), 15.0 (q), 14.7 (q), 14.4 (q), 13.8 ppm (q); FTIR
(film): n˜ =1956, 1900, 1713, 1662 cmÀ1; MS (EI): m/z (%): 638 (2) [M]+,
583 (41), 582 ppm (100) [MÀ2(CO)]+; HRMS (EI): calcd for
C38H50CrO5: 638.3058 [M]+; found: 638.3069.
AHCTREUNG
AHCTREUNG
248.6 (s), 197.6 (s), 190.2 (s), 134.3 (s), 129.9 (s), 128.2 (d; 2CH), 127.5
(d; 3CH), 119.1 (s), 112.0 (s), 100.0 (s), 98.7 (s), 94.5 (s), 89.3 (s), 85.1 (s),
83.4 (s), 65.1 (q), 34.3 (t), 31.0 (t), 26.2 (t), 25.2 (t), 23.8 (t), 22.6 (t), 18.6
(t), 17.7 (t), 15.7 (q), 15.1 (q), 14.8 (q), 14.0 (q), 13.7 (q), 6.9 ppm (q);
FTIR (film): n˜ =1955, 1899, 1712, 1666 cmÀ1; MS (EI): m/z (%): 582 (4)
[M]+, 527 (42), 526 (100) [MÀ2(CO)]+; HRMS (EI): m/z: calcd for
C34H42CrO5: 582.2432 [M]+; found: 582.2426.
2,3,4,5,6a-Pentaethylpentalen-1,6(3aH,6aH)dione (5a): A solution of
G
complex 3a (302 mg, 0.64 mmol) in a
9:1mixture of hexanes/ethyl acetate
(90 mL hexanes, 10 mL ethyl acetate)
was exposed to light and air until com-
plete disappearance of the carbene
complex was observed by TLC
(ꢀ24 h). The reaction mixture was fil-
tered through Celite and washed with
a 9:1mixture of hexanes/ethyl acetate.
Solvent was removed under reduced
Reaction of complex 3a with phenylacetylene: A solution of complex 3a
(1equiv, 0.44 mmol, 208 mg) and phenylacetylene (2.2 mmol, 225 mg) in
dry 1,2-dichloroethane (9 mL) was heated at 1108C in a sealed tube until
complete disappearance of complex 3a was observed by TLC (ꢀ17 h).
Solvent was removed under reduced pressure, and the residue was puri-
fied by flash chromatography (hexane/AcOEt) yielding product 7.
(4E)-2,3,7,8-Tetraethyl-6-methoxy-1-oxo-9-phenyl-4-
pressure, and the residue purified by flash chromatography (hexane/
phenylmethylydenspiro[4.4]nona-2,6,8-triene (7): Yellow oil; yield: 35%;
R
AcOEt); compound 5a was isolated in 30% yield (61mg). Yellow oil;
Rf: 0.54 (hexane/AcOEt 5:1); 1H NMR (600 MHz, CDCl3, 258C, TMS):
d=7.37–7.26 (m, 3H), 7.24–7.16 (m,
Rf =0.17 (hexane/AcOEt 5:1); 1H NMR (300 MHz, CDCl3, 258C, TMS):
3
d=7.28–7.14 (m, 3H), 6.99–6.95 (m, 2H), 3.09 (s, 1H), 2.49 (q, J
A
7.6 Hz, 4H), 2.22 (q, 3J
2H), 1.06 (t, 3J(H,H)=7.6 Hz, 6H), 0.98 ppm (t, 3J
G
A
5H), 7.09–7.04 (m, 2H), 6.57 (s, 1H),
3.67 (s, 3H), 2.48–2.42 (m, 1H), 2.41–
A
ACHTREUNG
13C NMR (CDCl3, 100 MHz, 258C): d=197.8 (s; 2C), 173.3 (s; 2 C),
142.6 (s; 2C), 140.6 (s), 128.7 (d; 2CH), 127.4 (d), 127.2 (d; 2CH), 70.5
(d), 65.0 (s), 22.9 (t; 2CH2), 17.2 (t; 2CH2), 13.7 (c; 2CH3), 12.6 ppm (c;
2CH3); FTIR (film): n˜ =1721 cmÀ1; MS (EI): m/z (%): 322 (100) [M]+,
307 (30), 293 (61), 265 (22); HRMS (EI): m/z: calcd for C22H26O2:
322.1927 [M]+; found: 322.1930.
2.34 (m, 1H), 2.32–2.23 (m, 3H), 2.22–
3
2.13 (m, 3H), 1.22 (t, J
C
ACHTREUNG
AHCTREUNG
0.42 ppm (t, 3J
(H,H)=7.5 Hz, 3H);
A
13C NMR (CDCl3, 150 MHz, 258C):
d=202.3 (s), 167.6 (s), 158.1 (s), 148.7
Synthesis of 2,3,4,5,6a-pentaphenylpentalen-1,6(3aH,6aH)dione (5b): A
A
(s), 145.8 (s), 137.6 (s), 137.2 (s), 135.6 (s), 133.7 (s), 129.9 (d, 2 CH),
128.5 (d, 2 CH), 128.1 (s), 127.9 (d, 2 CH), 127.6 (d, 2 CH), 127.3 (d),
126.7 (d), 124.6 (d), 72.5 (s), 58.9 (q), 21.0 (t), 19.9 (t), 17.7 (t), 17.0 (t),
15.1 (q), 14.7 (q), 12.9 (q), 12.7 ppm (q); FTIR (film): n˜ =1698 cmÀ1; MS
(EI): m/z (%): 438 (23) [M]+, 424 (13), 395 (100); HRMS (EI): m/z: for
C31H34O2 [M]+: calcd 438.2559; found 438.2551.
solution of carbene complex 1a (1equiv, 0.5 mmol) and tolane 2c
(2.5 mmol, 446 mg) in dry 1,2-dichloroethane (10 mL) was heated at
1108C in a sealed tube until complete disappearance of the carbene com-
plex was observed by TLC (ꢀ12 h). Solvent was removed under reduced
pressure, and the residue was purified by flash chromatography (hexane/
AcOEt) yielding compound 5b
Reaction of complex 3a with 1-deutero-2-phenylethyne: A solution of
complex 3a (1equiv, 0.44 mmol, 208 mg) and 1-deutero-2-phenylethyne
(2.2 mmol, 227 mg) in dry 1,2-dichloroethane (9 mL) was heated at
1108C in a sealed tube until complete disappearance of complex 3a was
observed by TLC (ꢀ17 h). Solvent was removed under reduced pressure,
(77 mg). Brown oil; yield: 30%; Rf:
0.20 (hexane/AcOEt 5:1); 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=
7.90 (d, 3J
ACHTREUNG
AHCTREUNG
9124
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 9115 – 9126

Chromium Alkoxy Alkynyl Carbene Complexes
FULL PAPER
and the residue purified by flash chromatography (hexane/AcOEt) yield-
ing product [D]7.
127.62 (d), 127.57 (d), 127.51 (d), 127.0 (d), 126.5 (d), 126.0 (d), 116.6 (s),
105.6 (s), 96.9 (s), 95.7 (s), 88.8 (s), 87.3 (s), 79.6 (s), 61.8 (q), 24.5 (t),
22.5 (t), 14.2 (q), 13.6 ppm (q)—some signals for the aromatic carbon
atoms are overlapped; FTIR (film): n˜ =1945, 1892, 1704 cmÀ1; MS (EI):
m/z (%): 718 (3) [M]+, 663 (57), 662 (100) [MÀ2(CO)]+, 402 (87);
HRMS (EI): m/z: calcd for C45H38CrO2: 662.2271[ MÀ2(CO)]+; found:
662.2270.
(4E)-2,3,7,8-Tetraethyl-6-methoxy-1-oxo-9-phenyl-4-(1-deutero-1-
phenylmethylyden)spiro[4.4]nona-2,6,8-triene [D]7: Brown oil; yield:
R
44%; Rf: 0.52 (hexane/AcOEt 5:1);
1H NMR (400 MHz, CDCl3, 258C,
TMS): d=7.37–7.25 (m, 3H), 7.24–
7.16 (m, 5H), 7.08–7.04 (m, 2H), 3.66
(s, 3H), 2.49–2.32 (m, 2H), 2.31–2.22
(m, 3H), 2.21–2.12 (m, 3H), 1.21 (t, 3J
(H,H)=7.6 Hz, 3H), 1.09 (t, 3J
(H,H)=7.6 Hz, 3H), 0.87 (t, 3J
(H,H)=7.6 Hz, 3H), 0.42 ppm (t, 3J
Dicarbonyl
{[(1S*)-h5-(2-methoxy-3,4,5-triphenylcyclopentadienyl)] (1S*)-
T
(2–4h)-(3,4-diethyl-1,2-diphenylcyclobut-1-enyl)ketone]chromium(II) (9),
isomer B: Brown solid; yield: 24%; Rf: 0.57 (hexane/AcOEt 5:1);
1H NMR (400 MHz, CDCl3, 258C,
TMS): d=7.31–6.69 (m, 25H), 3.74 (s,
3H), 2.93–2.78 (m, 2H), 2.69–2.54 (m,
2H), 1.27 (t, 3J
(H,H)=7.6 Hz, 3H),
C
(H,H)=7.6 Hz,
3H);
13C NMR
0.77 ppm (t, 3J
(H,H)=7.6 Hz, 3H);
T
(CDCl3, 75 MHz, 258C): d=202.1 (s), 167.4 (s), 158.0 (s), 148.5 (s), 145.7
(s), 137.4 (s), 136.9 (s), 135.5 (s), 133.6 (s), 129.8 (d; 2CH), 128.4 (d;
2CH), 127.9 (s), 127.8 (d; 2CH), 127.4 (d; 2CH), 127.2 (d), 126.5 (d),
À
13C NMR (CDCl3, 100 MHz, 258C):
d=250.0 (s), 249.7 (s), 202.6 (s), 140.6
(s), 137.6 (s), 132.7 (s), 132.2 (d), 132.0
(d), 131.7 (s), 131.4 (d,), 130.0 (s),
129.6 (s), 128.1 (d), 127.7 (d), 127.6
124.1 (this signal appears as a triplet due to C D coupling, 1J
(C,D)=
E
25.9 Hz), 72.3 (s), 58.7 (q), 20.8 (t), 19.8 (t), 17.5 (t), 16.9 (t), 14.9 (q),
14.6 (q), 12.7 (q), 12.6 ppm (q); FTIR (film): n=1694 cmÀ1; MS (EI): m/z
À1
(%): 439 (26) [M]+, 396 (58), 321(72), 419 cm
(100); HRMS (EI):
(d), 127.5 (d), 127.3 (d), 127.2 (d),
calcd for C31H33O2D: 439.2616 [M]+; found: 439.2616.
127.1 (d), 126.5 (d), 124.8 (d), 116.3 (s), 104.8 (s), 102.0 (s), 97.1 (s), 95.7
(s), 89.7 (s), 89.0 (s), 75.6 (s), 63.9 (q), 24.7 (t), 23.0 (t), 14.2 (q), 13.6 ppm
(q)—some signals for aromatic carbon atoms are overlapped; FTIR
(film): n˜ =1948, 1893, 1704 cmÀ1; MS (EI): m/z (%): 718 (2) [M]+, 663
(54), 662 (100) [MÀ2(CO)]+, 402 (68); HRMS (EI): m/z: calcd for
C45H38CrO2: 662.2271[ MÀ2(CO)]+; found: 662.2265.
Reaction of complex 3a with trifluoroacetic acid: Trifluoroacetic acid
(1mmol, 74 mL) was slowly added over solution of complex 3a
a
(1equiv, 0.4 mmol, 189 mg) in dry toluene (6 mL), and the mixture was
heated at 508C until complete disappearance of the complex 3a was ob-
served by TLC (ꢀ24 h). Solvent was removed under reduced pressure,
and the residue was purified by flash chromatography (hexane/AcOEt)
yielding product 8.
(4E)-2,3,5-Triethyl-4-ethylyden-3a,4-dihydro-6-phenylpentalen-1-
(6aH)one (8): Yellow oil; yield: 41%; Rf =0.40 (hexane/AcOEt 5:1);
1H NMR (300 MHz, CDCl3, 258C,
TMS): d=7.41–7.31 (m, 2H), 7.29–7.20
Acknowledgements
(m, 3H), 5.69 (q, 3J
ACHTREUNG
For the financial support received, we wish to thank the Ministerio de
Educación y Ciencia (Spain) (CTQ2004–08077-C02–01/BQU) and the
Consejería de Educación y Cultura del Principado de Asturias (IB05–
136). We are indebted to the Ministerio de Educación y Ciencia (Spain)
for predoctoral (P. García-García, F. Andina) and postdoctoral (C. Roca-
boy) fellowships. We also thank Dr. CØsar Pastor (UAM) and Dr.
Carmen lvarez-Rffla (UO) for their assistance in the measurement of
crystal structures.
AHCTREUNG
AHCTREUNG
AHCTREUNG
AHCTREUNG
d=206.7 (s), 173.2 (s), 144.6 (s), 141.2 (s), 139.6 (s), 139.3 (s), 136.1 (s),
128.4 (d, 2 CH), 128.0 (d, 2 CH), 127.1 (d), 116.0 (d), 58.6 (d), 46.2 (d),
22.0 (t), 18.3 (t), 16.3 (t), 16.0 (q), 13.6 (q), 13.42 (q), 13.36 ppm (q);
FTIR (film): n=1700 cmÀ1; MS (EI): m/z (%): 306 (100) [M]+, 291(60),
277 (81), 249 (42); HRMS (EI): calcd for C22H26O: 306.1978 [M]+;
found: 306.1980.
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Reaction of complex 3h with 3-hexyne: A solution of complex 3h
(1equiv, 0.3 mmol, 199 mg) and 3-hexyne 2a (1.5 mmol, 170 mL) in dry
1,2-dichloroethane (6 mL) was heated at 1108C in a sealed tube until
complete disappearance of the complex 3h was observed by TLC
(ꢀ12 h). Solvent was removed under reduced pressure, the residue was
purified by flash chromatography (hexane/AcOEt), and two diastereo-
mers of compound 9 were separately isolated.
Dicarbonyl
{[(1S*)-h5-(2-methoxy-3,4,5-triphenylcyclopentadienyl)]-
ACHTREUNG
m(II) (9), isomer A: Brown solid; yield: 28%; Rf: 0.50 (hexane/AcOEt
5:1); 1H NMR (400 MHz, CDCl3,
258C, TMS): d=7.35–7.04 (m, 21H),
7.05 (d, 3J
ACHTREUNG
(dd, 3J
N
ACHTREUNG
2H), 3.07–3.00 (m, 1H), 2.90 (s, 3H),
2.51–2.42 (m, 1H), 1.63–1.51 (m, 1H),
1.27 (t, 3J
(H,H)=7.6 Hz, 3H), 0.57–
E
0.48 (m, 1H), 0.16 ppm (t, 3J
(H,H)=
C
7.6 Hz, 3H); 13C NMR (CDCl3,
100 MHz, 258C): d=251.9 (s), 250.3
(s), 203.3 (s), 140.9 (s), 138.7 (s), 133.3 (s), 132.5 (s), 132.2 (d), 131.8 (s),
131.5 (d), 130.3 (s), 130.0 (d), 128.2 (d), 128.1 (d), 127.9 (d), 127.8 (d),
Chem. Eur. J. 2007, 13, 9115 – 9126
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9125

J. Barluenga et al.
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[14] S. Ma, Z. Gu, Angew. Chem. 2005, 117, 7680–7685; Angew. Chem.
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[15] For a recent 1,2-metal migration in FCC chemistry see: a) T. Asa-
kura, T. Kojima, T. Miura, N. Iwasawa, Angew. Chem. 2006, 118,
7028–7031; Angew. Chem. Int. Ed. 2006, 45, 6874–6877; for exam-
ples of 1,2- and 1,3-chromium migrations in FCC chemistry, respec-
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[16] For an example of the more common exo-regioselective intramolec-
ular insertion of an alkyne in an anionic oxycarbene complex see:
H. Rudler, A. Parlier, V. Certal, J. Vaissermann, Angew. Chem.
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[17] The insertions of carbonyl ligands in carbonyl metallate complexes
have been previously described for different metals: Ni: a) E. J.
Corey, L. S. Hegedus, J. Am. Chem. Soc. 1969, 91, 4926–4928; Fe:
b) J. P. Collman, Acc. Chem. Res. 1975, 8, 342–347; Co: c) H. Alper,
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Slough, A. L. Rheingold, J. Am. Chem. Soc. 1988, 110, 2575–2585;
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3-dimethylamino-3-trimethylsilylpropylidenchromium(0)
complex
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[11] Compound 4a: C32H38CrO5; Mr =554.6; crystal size=0.50”0.45”
0.27 mm3; monoclinic; P21/n; a=9.0928(4), b=18.2604(8), c=
16.9883(8) Š; a=90.000(1), b=95.635(1), g=90.000(1)8; V=
[18] As suggested by one of the reviewers, the transformation of XI into
XIV could also proceed via a vinylidene complex and subsequent al-
kenyl–vinylidene coupling. This also could explain the different
product types in the reaction of 3a with internal and terminal al-
kynes. However, we are not aware of such behaviour for chromium,
although it is well documented for other metals, such as osmium: D.
Huang, M. Olivµn, J. C. Huffman, O. Eisenstein, K. G. Caulton Or-
ganometallics 1998, 17, 4700–4706.
2807.08(4) Š3; Z=4; 1=1.312 MgmÀ3
;
m=0.447 mmÀ1
;
l=
0.71073 Š; T=100(2) K; 2qmax =56.6; reflections collected/unique
17757/6623;
R
A
R indices [I>2s(I)] R1 =0.039,
wR2 =0.095,
R
Compound 9, isomer B: C47H38CrO4; Mr =718.81; crystal size=
3
¯
0.22”0.15”0.07 mm ; triclinic; P1, a=11.4230(17), b=12.681(2), c=
13.9518(15) Š; a=78.434(12), b=79.714(11), g=72.161(14)8; V=
1869.8(5) Š3; Z=2; 1=1.277 MgmÀ3; m=0.350 mmÀ1; l=0.71073 Š;
T=293(2) K; 2qmax =51.3; reflections collected/unique 17083/6881;
[19] a) K. H. Dçtz, W. J. Kuhn, J. Organomet. Chem. 1985, 286, C23–
C26; b) K. S. Chan, W. D. Wulff, J. Am. Chem. Soc. 1986, 108, 5229–
5236.
R
(int)=0.040, final R indices [I>2s(I)] R1 =0.040, wR2 =0.116, R
[20] J. Barluenga, F. Aznar, M. A. Palomero, Chem. Eur. J. 2001, 7,
5318–5324.
[21] M. A. Palomero, Ph.D. Thesis, Universidad de Oviedo 2002, p. 217.
[22] J. Barluenga, M. A. Fernµndez-Rodríguez, P. García-García, E.
Aguilar, I. Merino, Chem. Eur. J. 2006, 12, 303–313.
[23] A. PØrez-Anes, P. García-García, E. Aguilar, A. Suµrez-Sobrino,
Eur. J. Org. Chem. 2007, 3480–3487.
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García-Granda, A. PiÇera-Nicolµs, Chem. Eur. J. 1998, 4, 2280–
2298.
indices (all data) R1 =0.046, wR2 =0.116; CCDC-616298 (4a),
-616299 (4 f isomer B) and -648137 (9 isomer B) contain the supple-
mentary crystallographic data for this paper. These data can be ob-
tained free of charge from the Cambridge Crystallographic Data
Centre via www.cccdc.cam.ac.uk/data_request/cif.
[12] a) H. G. Alt, H. E. Engelhardt, U. Thewalf, J. Riede, J. Organomet.
Chem. 1985, 288, 165–177; b) H. G. Alt, H. I. Hayen, J. Organomet.
Chem. 1986, 315, 337–352.
[13] Pentacarbonyl alkyne–carbene complexes and more rigid tetracar-
bonyl alkyne-chelated ones have also been isolated and proposed as
intermediates in a bimetal-assisted intermolecular insertion, leading
Received: May 23, 2007
Published online: August 17, 2007
9126
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Chem. Eur. J. 2007, 13, 9115 – 9126