Y-shaped tris-N-heterocyclic-carbene ligand for the preparation of multifunctional catalysts of iridium, rhodium, and palladium

Article abstract of DOI:10.1021/om300569w

A series of homo- and hetero-dimetallic complexes of Ir, Rh, and Pd have been obtained using our previously reported Y-shaped tris-NHC ligand. The new complexes can be obtained through the isolation of the corresponding monometallic intermediates (in which the ligand always coordinates in a chelating form) or by a one-pot stepwise synthetic protocol that avoids the isolation of the intermediate. The catalytic properties of the Ir-Pd complexes have been explored in two tandem processes: dehalogenation/transfer hydrogenation of haloacetophenones and Suzuki-coupling/transfer hydrogenation of p-bromoacetophenone. These two complexes have been also tested in two model reactions typically catalyzed by iridium (cyclization of 2-aminophenyl ethyl alcohol to yield indole) and palladium (acylation of bromobenzene with n-hexanal).

Full text of DOI:10.1021/om300569w

Article
pubs.acs.org/Organometallics
Y-Shaped Tris-N-Heterocyclic-Carbene Ligand for the Preparation of
Multifunctional Catalysts of Iridium, Rhodium, and Palladium
Sergio Gonell, Macarena Poyatos,* Jose A. Mata, and Eduardo Peris*
́
́ ́ ́
Departamento de Química Inorganica y Organica, Universitat Jaume I, Avenida Vicente Sos Baynat s/n. 12071 Castellon, Spain
S
* Supporting Information
ABSTRACT: A series of homo- and hetero-dimetallic
complexes of Ir, Rh, and Pd have been obtained using our
previously reported Y-shaped tris-NHC ligand. The new
complexes can be obtained through the isolation of the
corresponding monometallic intermediates (in which the
ligand always coordinates in a chelating form) or by a one-
pot stepwise synthetic protocol that avoids the isolation of the
intermediate. The catalytic properties of the Ir−Pd complexes
have been explored in two tandem processes: dehalogenation/
transfer hydrogenation of haloacetophenones and Suzuki-
coupling/transfer hydrogenation of p-bromoacetophenone.
These two complexes have been also tested in two model reactions typically catalyzed by iridium (cyclization of 2-aminophenyl
ethyl alcohol to yield indole) and palladium (acylation of bromobenzene with n-hexanal).
Chart 1. 1,2,4-Trimethyltriazol-di-ylidene (ditz) Ligand and
the Y-Shaped Tris-NHC Ligand (A) Employed in This Work
INTRODUCTION
■
Bimetallic catalysis by late transition metal complexes has
recently emerged as an effective tool to promote organic
transformations.1 Bimetallic catalysts can display synergistic
effects between the proximate metal centers, leading to
improved reactivities and selectivities compared to their
monometallic counterparts. In this regard, the search for
multifunctional catalysts has promoted an increasing demand of
ligands capable of combining several metal centers in a
cooperative manner.2 For the synthesis of well-defined
dimetallic catalysts the choice of the ligand is of major
importance, because the coordination environment determines
the metal fragments that can be bound. Moreover, ligand effects
such as flexibility, stereoelectronic properties, and metal−metal
separation should determine the suitability of the bimetallic
system for a specific catalytic process.1e
During the last five years, we have been working on the
development of hetero-dimetallic catalysts for the tandem or
sequential transformation of a substrate via two (or more)
mechanistically distinct processes.2,3 For the preparation of the
bimetallic catalysts, we decided to use rigid NHC-based ligands,
which may help to maintain a fixed metal−metal distance. Apart
from the examples described below and reported by us, there is
a small number of examples described in the literature of rigid
NHC-based ligands that allow the coordination of two metals,4
and only a very few have been used for the preparation of
heterometallic complexes.4f,g In this regard, the use of 1,2,4-
trimethyltriazol-di-ylidene (ditz, Chart 1),5 as a bridging ligand
for the preparation of homo- and hetero-dimetallic complexes,
was extraordinarily useful in the development of a wide range of
tandem catalytic reactions.6 Although ditz constituted an
excellent starting point for the development of catalysts with
excellent applications in tandem catalysis, we thought that it
may not be stable enough to endure the harsh conditions
required for some catalytic reactions, and this also does not
allow for the modification of its stereoelectronic properties.
Within this context, we recently described a Y-shaped tris-NHC
ligand potentially capable of coordinating two metals, affording
two different coordination environments (A, Chart 1), while
maintaining a short metal−metal separation.7 We first
coordinated A to palladium, envisaging that it would also
offer the possibility to obtain hetero-dimetallic complexes, an
issue that initially remained elusive to us.
We now describe the preparation of a series of homo- and
hetero-dimetallic complexes of Pd, Ir, and Rh, together with the
facile preparation of their monometallic intermediates. An
exploratory study of the catalytic activity of the Ir−Pd
complexes is also described and compared with our previously
related results using the ditz-based complexes.6b
Received: June 21, 2012
Published: July 17, 2012
© 2012 American Chemical Society
5606
dx.doi.org/10.1021/om300569w | Organometallics 2012, 31, 5606−5614

Organometallics
Article
Scheme 1. Synthesis of Complexes 2 to 8
ppm (1JRh−C = 47.2 Hz), also attributed to the carbene carbon.
It is important to mention that the coordination of the salt 1 to
the rhodium source did not provide any clean reaction products
in the absence of KI. However, when 1 was reacted with
[IrCl(COD)]2 under the same conditions depicted in Scheme
1, but with addition of KI, still the Ir(I) complex 4 was
obtained. At this point we do not have a suitable explanation of
the different outcome of the reactions when Ir or Rh sources
were used. The fact that the coordination of 1 first proceeds via
the chelating part of the ligand facilitates the design of
sophisticated hetero-dimetallic complexes, by simply modifying
the order of addition of the adequate metal sources. For
example, the formation of an Ir−Pd hetero-dimetallic complex
RESULTS AND DISCUSSION
■
The reactions of the triazolium salt 17 with equimolecular
amounts of [Pd(OAc)2] or [MCl(COD)]2 (M = Rh or Ir)
under the reaction conditions depicted in Scheme 1 afford the
preparation of the monometallic complexes of Pd,7 Ir, or Rh (2,
4, and 6, respectively, Scheme 1), in which the ligand
coordinates to the metal in a chelating form. The iridium
complex 4 was obtained in very good yield (83%), while the
rhodium complex 6 could be obtained only in moderate-low
yield (33%). Interestingly, complex 4 contains an Ir(I) center,
as shown by the characteristic 13C NMR resonance at 181.2
ppm due to the carbene carbon, while complex 6 contains a
Rh(III) center, as suggested by the 13C NMR doublet at 163
5607
dx.doi.org/10.1021/om300569w | Organometallics 2012, 31, 5606−5614

Organometallics
Article
Chart 2. Representation of the Minor and Major Isomers of Complex 3 and the Observed Isomer for 7 and 8
can proceed from the reaction of either intermediate 2 or 4, by
adding [IrCl(COD)]2 or [Pd(OAc)2], to afford 3 or 5,
respectively, under the reaction conditions shown in Scheme 1.
Complex 3 has a chelate-palladium/monodentate-iridium
NHC-based structure, while 5 has an inverted coordination
of the ligand, with a chelate-iridium/monodentate-palladium
structure. More interesting is the fact that both 3 and 5 can be
obtained in a one-pot process without the isolation of the
corresponding monometallic intermediates, by sequentially
adding the desired metal sources and taking into account that
the first metal added to the reaction vessel will be the one to
coordinate in the chelate form. As will be discussed later, 3 and
5 (having the same two metals and the same bridging ligand)
show distinct reactivity patterns, as a consequence of the two
different coordination environments of the two metals.
Apart from complexes 4 and 5, which slowly decompose in
the solid state at room temperature, all the other complexes are
air stable. Complex 4 can be transformed into more stable
monoiridium complexes by bubbling carbon monoxide to yield
the biscarbonyl complex 9 or by oxidation with I2 in acetonitrile
to afford the Ir(III) complex 10 (Scheme 2).
Scheme 2. Synthesis of Complexes 9 and 10
The Ir−Pd hetero-dimetallic complexes 3 and 5 were
characterized by NMR and mass spectroscopy. The more
representative NMR signals are those observed in the 13C
NMR spectra, at 178.8 and 166.0 ppm (3, Ir−Ccarbene and Pd−
C
carbene, respectively) and 180.7 and 163.6 ppm (5, Ir−Ccarbene
and Pd−Ccarbene, respectively).
Starting from the rhodium complex 6, the hetero-dimetallic
Rh(III)/Ir(I) complex 7 and the mixed-valence Rh(I)/Rh(III)
complex 8 can be obtained. Again, for the preparation of 7 and
8, the isolation of the monometallic intermediate 6 can be
circumvented if the complexes are obtained by a one-pot
synthetic protocol implying the sequential addition of the two
metal sources under the reaction conditions indicated in
Scheme 1, thus greatly simplifying the experimental synthetic
procedure. The 13C NMR spectrum of 8 shows the two distinct
resonances attributed to the carbene-carbon bound to Rh(I)
(185.7 ppm, 1JRh−C = 50.5 Hz) and Rh(III) (162.7 ppm, 1JRh−C
= 47.4 Hz), and in 7, the signals due to the carbene-carbons
The molecular structures of 3 and 8 were confirmed by
means of X-ray diffraction studies. The molecular structure of 3
consists of a hetero-dimetallic complex of palladium and
iridium in which the tris-NHC ligand is bridging the two metal
centers in bis-chelating (Pd) and monodentate (Ir) forms
(Figure 1). The bis-chelating palladium fragment completes its
coordination sphere with two iodide ligands. The iridium
fragment completes its pseudo-square-planar coordination
sphere with a 1,5-cyclooctadiene (COD) and an iodide ligand.
The molecular structure depicted in Figure 1 corresponds to
that of the rotamer that we have assigned as the minor one for
complex 3 (Chart 2), in which the three iodide ligands are
pointing toward the same side of the molecule. The two
coordination planes of the two metal fragments are in a quasi-
perpendicular disposition (88.17°). The Pd−Ccarbene distances
in the chelate fragment are 1.975(9) and 1.967(8) Å, and the
Ir−Ccarbene distance is 2.032(9) Å. The chelating imidazolyli-
denes are at an angle of 61.5° with respect to the metal
coordination plane. The coordination plane of the chelate
palladium fragment is quasi-perpendicular with respect to the
plane of the monocarbene azole ring that is coordinated to the
iridium center (88.2°), a “chair angle” that is very similar to our
previously reported dipalladium complex with the same tris-
NHC ligand.7 The through-space Ir−Pd distance is 6.76 Å.
bound to Ir(I) and Rh(III) appear at 182.3 and 163.1 (1JRh−C
=
47.5 Hz) ppm, respectively.
It is interesting to point out that compound 3 is obtained as a
mixture of two isomers (55:45 molar ratio) as a consequence of
the restricted rotation around the Ir(I)−Ccarbene bond, due to
the steric hindrance afforded by the presence of the bulky
iodide ligand at the iridium center, and the two iodide ligands
at the palladium coordination sphere. In principle, we have
attributed the structure of the major rotamer to that in which
the iodide ligands of the two metal centers are avoiding each
other, yielding a more sterically relieved configuration (see
Chart 2). A similar situation can be envisaged for complexes 7
and 8, but in this case the octahedral coordination of the
Rh(III) center is approaching one of the iodide ligands of the
coordination sphere to the M(I) (M = Rh, Ir) fragment, thus
avoiding the formation of the more sterically constrained
rotamer in which the M(I)−I would be oriented close to the
Rh(III)−I bond, as shown in Chart 2.
5608
dx.doi.org/10.1021/om300569w | Organometallics 2012, 31, 5606−5614

Organometallics
Article
Figure 1. Molecular diagram of 3 (ellipsoids at 50% probability). All
hydrogen atoms and solvent (CH3CN) have been omitted for clarity.
Selected bond distances (Å) and angles (deg): Ir(1)−C(2) 2.032(9),
Ir(1)−I(3) 2.6664(7), Ir(1)−C(25) 2.157(10), Ir(1)−C(26)
2.191(9), Ir(1)−C(29) 2.112(9), Ir(1)−C(30) 2.108(9), Pd(4)−
C(18) 1.975(9), Pd(4)−C(19) 1.967(8), Pd(4)−I(5) 2.6606(9),
Pd(4)−I(6) 2.6347(9), C(2)−Ir(1)−I(3) 89.2(2), I(6)−Pd(4)−I(5)
95.97(3), C(19)−Pd(4)−C(18) 87.1(3).
Figure 2. Molecular diagram of 8 (ellipsoids at 50% probability). All
hydrogen atoms have been omitted for clarity. Selected bond distances
(Å) and angles (deg): Rh(1)−C(6) 1.992(4), Rh(1)−I(4) 2.6435(6),
Rh(1)−I(3) 2.6876(6), Rh(1)−O(16) 2.163(3), Rh(2)−C(15)
2.008(6), Rh(2)−I(5) 2.6513(6), Rh(2)−C(19) 2.102((5), Rh(2)−
C(22) 2.209(5), I(4)−Rh(1)−I(3) 178.86(2), C(6)−Rh(1)−C(6′)
95.0, I(5)−Rh(2)−C(15) 86.86(17).
The molecular structure of 8 consists of a dimetallic Rh(I)−
Rh(III) complex bound by the tris-NHC ligand (Figure 2). The
bis-chelating part of the ligand binds to the Rh(III) center,
while the monodentate part is bound to Rh(I). The pseudo-
square-planar coordination sphere of the Rh(I) fragment is
completed by an iodide and a COD ligand, while the pseudo-
octahedral Rh(III) center completes its sphere with an acetate
and two iodides in a relative trans disposition. The relative
disposition of the ligands about the two metal fragments
corresponds to the less hindered situation, with the iodide
ligands of the two metals avoiding the steric interaction. The
Rh(III)−Ccarbene distance is 1.992(4) Å, and the Rh(I)−Ccarbene
distance is 2.008(6) Å. Due to the higher steric constraint about
the Rh(III) octahedral fragment, the chelating imidazolylidenes
are at an angle of 32.7° with respect to the meridional plane of
metal fragment, a lower angle than the related one in 3 (61.5°).
Interestingly, the chair angle (defined as the angle between the
coordination plane of the chelate fragment and the plane of the
monocarbene azole ring) is 108.2° (compare to 88.2° in 3),
thus implying that the ligand is flexible enough to afford a
situation of minimum steric repulsion between the two metal
coordination spheres. As a consequence, the distance between
the two metals is slightly longer (7.003 Å) than the one shown
in 3 (6.76 Å).
Because we wanted to test the catalytic capabilities of our
complexes, we decided to use the Ir−Pd complexes 3 and 5
since the two metals contained in these two complexes display
distinct catalytic properties. As we previously described,6b for
the study of the catalytic properties of these complexes we
considered that haloacetophenones should be excellent starting
substrates because they combine a halide−aryl bond that can be
activated by the palladium fragment and a CO bond that can
be transformed by the iridium center. We first studied a simple
reaction consisting of the dehalogenation/transfer hydro-
genation of 4-bromoacetophenone, because this reaction may
allow us to compare the new results with those previously
obtained by us with catalysts 11−15 (Chart 3).6b This simple
model reaction was also recently used by other authors in the
catalytic test of their hetero-dimetallic complex of Ir−Ni.8
The results for the dehalogenation/transfer hydrogenation of
4-bromoacetophenone in iPrOH in the presence of Cs2CO3 at
100 °C are shown in Table 1. For comparative purposes, our
previously reported results for catalysts 11−15 are also shown
(entries 8−11).6b As can be seen from the data shown, catalyst
5 gives better catalytic outcomes than 3. The catalytic outcome
of 5 compares well with our best previously reported Ir−Pd
catalysts 12 and 13 (compare entry 5 with entries 9 and 10).
Both 3 and 5 show better catalytic activities than the mixture of
the two homo-dimetallic complexes 14 and 15 (entry 11).
Interestingly, complex 5 affords full conversion to the final 1-
phenylethanol when using a low catalyst loading of 1 mol %,
although the time needed for the completion of the reaction
was longer (48 h, entry 7).
In all cases, the reaction is very clean, and we did not observe
the formation of any other products apart from A, B, and C.
This gave us the opportunity to study the reaction time course
(Figure 3), which has a similar profile to that previously
reported,6b confirming that the debromination is faster than the
reduction of the carbonyl group and that the transfer
hydrogenation is accelerated at the point of maximum
formation of acetophenone (A), 3 h, suggesting that the
transfer hydrogenation is faster for acetophenone than for p-
bromoacetophenone, in agreement with previously published
results.9
On the basis of these results, we decided to extend our study
to another tandem reaction combining the Suzuki coupling and
transfer hydrogenation of 4-bromoacetophenone, since we
already demonstrated the compatibility of these two catalytic
processes.6b This model reaction has a straightforward
application, because biphenyl-substituted ketones are known
to behave as nonsteroidal inhibitors of 5α-reductase, the
enzyme that catalyzes the conversion of testosterone to
dihydrotestosterone.10 Table 2 shows the most representative
data for the Suzuki coupling of 4-bromoacetophenone with
phenylboronic acid in a mixture of iPrOH and THF and
includes the results provided by our previously reported catalyst
13 for comparison. As can be seen, 5 affords a good yield on
5609
dx.doi.org/10.1021/om300569w | Organometallics 2012, 31, 5606−5614

Organometallics
Article
Chart 3. Complexes Studied in the Different Catalytic Tests
product E after 24 h (72%, entry 5), although this result is
worse than the one provided by 13 in terms of both product
yield and completion time (entry 7). Again, the catalytic activity
of 5 is much better than that shown by the mixture of the two
homodimetallic complexes 14 and 15, a result that confirms our
previous finding that the use of one heterometallic catalyst
usually renders better catalytic outcomes than the use of two
homometallic catalysts.6b,d,e
Table 1. Tandem Dehalogenation/Transfer Hydrogenation
of 4-Bromoacetophenone
a
In order to widen the applicability of the hetero-dimetallic
complexes 3 and 5, we decided to complement our study with
two separate model reactions typically catalyzed by Ir and Pd.
We tried to test the complexes in catalytic reactions with more
mechanistically distinct cycles than those implied in the
reactions shown before (transfer hydrogenation, dehalogena-
tion of aryl halides, and Suzuki−Miyaura coupling). For the Ir-
catalyzed process, we studied the cyclization of 2-aminophenyl
ethyl alcohol.6a,11 Because indole-based compounds are found
in many natural products with pharmaceutical applications, new
environmentally benign and efficient methods for indole
synthesis and its functionalization continue to attract
attention.12 As can be seen from the data shown in Table 3,
both iridium-containing complexes (3 and 5) afforded excellent
yields in the formation of indole from 2-aminophenyl ethyl
alcohol (entries 3 and 4), while the bis-palladium complex (16,
Chart 3) showed a similar outcome to that achieved in the
absence of catalyst, therefore implying that the catalytic activity
attributed to the palladium complex 16 is negligible.
cat. loading (mol
b
b
b
entry catalyst
%)
t (h) A (%) B (%) C (%)
1
3
2
2
1
1
2
1
1
2
2
2
20
48
20
48
20
20
48
20
20
20
20
70
51
89
82
1
9
8
5
5
0
3
0
0
0
0
0
21
41
6
2
3
3
3
4
3
13
99
42
5
5
6
5
55
0
7
5
99
d
8
11
22
0
75
d
d
d
9
12
95
99
25
10
11
13
0
c
14 + 15
1 + 1
72
a
Reaction conditions: 4-haloacetophenone (0.36 mmol), Cs2CO3
(0.43 mmol), anisole as internal reference (0.36 mmol), and 2 mL
of 2-propanol. The solution was heated to 100 °C in aerobic
conditions. Yields determined by GC. 1 mol % of 14 + 1 mol % of
b
c
d
15. Data taken from ref 6b.
Complexes 3 and 5 also showed good activity in the acylation
of bromobenzene with n-hexanal (Chart 4). The acylation of
aryl halides with aldehydes, described by Xiao and co-
workers,13 allows the direct preparation of alkyl aryl ketones,
avoiding the traditionally used Friedel−Crafts method, which
involves hazardous reagents and does not work when electron-
deficient arenes are used.14 Despite the obvious interest in the
reaction, the number of articles describing effective catalysts for
this reaction is still very low.15 Both 3 and 5 provided full
conversion to the final product using a 2 mol % catalyst loading
in DMF at 115 °C in 16 h. For comparative purposes we also
checked the catalytic activity of the Ir−Rh complex 7 and
confirmed that it showed negligible activity, therefore
suggesting that the catalytic activity of 3 and 5 in this reaction
is located at the palladium fragment of the bimetallic structures.
Figure 3. Time course of the transformation of 4-bromoacetophenone
using 2 mol % of 5.
5610
dx.doi.org/10.1021/om300569w | Organometallics 2012, 31, 5606−5614

Organometallics
Article
a
Table 2. Tandem Suzuki−Miyaura/Transfer Hydrogenationof 4-Bromoacetophenone
b
b
b
b
b
entry
catalyst
t (h)
A (%)
B (%)
C (%)
D (%)
E (%)
1
2
3
4
5
6
7
5
0.5
4
13
10
5
2
0
85
52
38
16
13
58
2
0
5
0
5
31
47
69
72
28
88
5
7
0
10
12
13
−
−
−
5
20
24
4
3
0
5
2
0
d
d
13
−
−
−
−
−
−
13
7
c
d
8
14 + 15
4
55
5
a
Reaction conditions: 4-bromoacetophenone (0.36 mmol), phenylboronic acid (0.55 mmol), Cs2CO3 (1.08 mmol), anisole as internal reference
b
c
(0.36 mmol), catalyst (2 mol %), 2 mL of iPrOH, and 2 mL of THF. The solution was heated at 100 °C. Yields determined by GC. 1 mol % of 14
+ 1 mol % of 15. Data taken from ref 6b.
d
a
related homodimetallic complexes, a fact that strengthens the
idea that some catalytic cooperativity may be at play.6b We
found that the activities shown are similar to those previously
reported by us for our most active ditz-based heterometallic
complex (13, Chart 3), but now we have the additional benefit
provided by the simpler and higher yielding procedure to
obtain 3 and 5. Both complexes have also been tested in two
model reactions typically catalyzed by iridium (cyclization of 2-
aminophenyl ethyl alcohol to yield indole) and palladium
(acylation of bromobenzene with n-hexanal), where they
showed excellent catalytic activity, therefore illustrating the
wide multifunctionality of these sophisticated (although easy-
to-make) catalysts.
Table 3. Cyclization of 2-Aminophenyl Ethyl Alcohol
b
entry
catalyst
cat. loading (%)
time (h)
indole (%)
1
2
3
4
−
16
3
−
2
2
2
2
2
52
56
2
>99
>99
5
2
a
Reaction conditions: 2-aminophenyl ethyl alcohol (0.25 mmol),
KOH (0.5 mmol), anisole as internal reference (0.25 mmol), and 1
b
mL of toluene. The reaction mixture was stirred at 110 °C. Yields
determined by GC.
EXPERIMENTAL SECTION
■
Chart 4. Acylation of Bromobenzene with n-Hexanal
General Procedures. Compounds 1 and 2 were prepared
according to literature procedures.7 All operations were carried out
by using standard Schlenk techniques under a nitrogen atmosphere.
All other reagents were used as received from commercial suppliers.
NMR spectra were recorded on a Varian Innova 300 and 500 MHz,
using CDCl3, acetone-d6, MeCN-d3, or DMSO-d6 as solvents.
Electrospray mass spectra (ESI-MS) were recorded on a Micromass
Quatro LC instrument; nitrogen was employed as drying and
nebulizing gas. Exact mass analysis was realized using a Q-TOF
premier mass spectrometer with electrospray source (Waters,
Manchester, UK) operating at a resolution of ca. 16 000 (fwhm).
Elemental analyses were carried out on a EuroEA3000 Eurovector
analyzer. Infrared spectra (FTIR) were obtained on a Bruker
EQUINOX 55 spectrometer with a spectra window of 4000−600
cm−1.
CONCLUSIONS
■
In this work we have described the preparation of a series of
mono- and bimetallic complexes of Ir, Rh, and Pd, using our
previously reported Y-shaped tris-NHC ligand.7 The ligand can
bind to two different metals by a stepwise procedure in which
the first step invariably implies coordination via the chelating
side of the ligand, therefore facilitating the rational design of
hetero-dimetallic complexes. All dimetallic complexes can be
obtained via the isolation of their corresponding bis-chelate
monometallic intermediates, although the stepwise one-pot
synthesis also affords good yield to the final complexes, thus
affording an important simplification of the experimental
workups.
Synthesis of Compound 3. A mixture of [Pd(OAc)2] (50 mg,
0.223 mmol), 1 (115.7 mg, 0.223 mmol), and KI (74.7 mg, 0.446
mmol) in acetonitrile was refluxed for 2 h under an inert atmosphere.
[IrCl(COD)]2 (74 mg, 0.11 mmol), NaOAc (24.6 mg, 0.3 mmol), and
KI (74 mg, 0.446 mmol) were then added, and the resulting mixture
was refluxed overnight. The solvent was removed under vacuum, and
the crude solid was purified by column chromatography. Elution with a
mixture 9:1 dichloromethane/acetone afforded the separation of a
yellow band that contained compound 3. Precipitation with a mixture
of acetone/diethyl ether gave the desired product as a yellow solid.
The two Ir−Pd hetero-dimetallic complexes 3 and 5 were
tested in two different tandem processes, combining reactions
that are typically catalyzed by Ir and Pd: dehalogenation/
transfer hydrogenation of haloacetophenones and Suzuki-
coupling/transfer hydrogenation of p-bromoacetophenone.
Both complexes achieved excellent conversions to the final
products and also showed better outcomes than the sum of
1
Yield: 70 mg, 30%. H NMR (300 MHz, DMSO-d6) for the minor
isomer (45%): δ 8.20 (s, 2H, CHimid), 7.72 (s, 2H, CHimid), 4.68 (m,
2H, CH-COD), 3.85 (s, 12H, NCH3), 2.98 (m, 2H, CH-COD), 2.16
(m, 4H, CH2-COD), 1.47 (m, 4H, CH2-COD); for the major isomer
(55%): δ 8.11 (s, 2H, CHimid), 7.74 (s, 2H, CHimid), 4.68 (m, 2H, CH-
COD), 3.89 (s, 12H, NCH3), 3.35 (m, 2H, CH-COD), 2.16 (m, 4H,
5611
dx.doi.org/10.1021/om300569w | Organometallics 2012, 31, 5606−5614

Organometallics
Article
CH2-COD), 1.78 (m, 4H, CH2-COD). 13C NMR (75 MHz, DMSO-
d6) for the minor isomer: δ 178.8 (Ir-Ccarbene), 166.0 (Pd-Ccarbene),
126.0 (CHimid), 124.1 (Cq), 122.0 (CHimid), 83.0 (CH-COD), 55.6
(CH-COD), 39.5 (NCH3), 34.9 (NCH3), 32.3 (CH2−COD), 29.8
(CH2-COD); for the major isomer: δ 178.1 (Ir-Ccarbene), 167.5 (Pd-
Ccarbene), 126.0 (CHimid), 122.7 (CHimid), 122.1 (Cq), 82.4 (CH-COD),
55.4 (CH-COD), 39.7 (NCH3), 35.2 (NCH3), 32.4 (CH2-COD), 29.9
(CH2-COD). Anal. Calcd for PdIrI3N6C21H28(2H2O) (1079.85): C,
23.36; H, 3.00; N, 7.78. Found: C, 23.00; H, 3.27; N, 7.61.
Electrospray MS (20 V, m/z): 958.2 [M − I + MeCN]+, 917.2 [M −
I]+.
temperature, [IrCl(COD)]2 (68.14 mg, 0.101 mmol), NaOAc (25 mg,
0.3 mmol), and KI (68.1 mg, 0.406 mmol) were added, and the
resulting mixture was refluxed for an additional 3 h. The solution was
then filtered, and the solvent was removed under vacuum. The crude
solid was purified by column chromatography. Elution with a 95:5
mixture of dichloromethane/acetone afforded the separation of an
orange band that contained compound 7. Precipitation with a mixture
of dichloromethane/hexane gave the desired product as a brown solid.
1
3
Yield: 72 mg, 32%. H NMR (300 MHz, CDCl3): δ 7.36 (d, JH−H
=
3
2.2 Hz, 2H, CHimid), 7.19 (d, JH−H = 2.2 Hz, 2H, CHimid), 4.86 (m,
2H, CH-COD), 4.19 (s, 6H, NCH3), 3.82 (s, 6H, NCH3), 3.10 (m,
2H, CH-COD), 2.14 (m, 4H, CH2-COD), 1.99 (s, 3H, COOCH3),
1.82 (m, 4H, CH2-COD). 13C NMR (75 MHz, CDCl3): δ 190.7
Synthesis of Compound 4. A mixture of compound 1 (78 mg,
0.149 mmol), [IrCl(COD)]2 (50 mg, 0.0745 mmol), and NaOAc
(49.2 mg, 0.6 mmol) in acetonitrile (15 mL) was refluxed for 1 h
under an inert atmosphere. The mixture was then filtered at 0 °C.
Removal of the volatiles afforded 4 as a red, air-sensitive solid. Yield:
90 mg, 83%. 1H NMR (300 MHz, DMSO-d6): δ 9.44 (s, 1H, NCHN),
1
(COOCH3), 182.3 (Ir-Ccarbene), 163.1 (d, JRh−C = 47.5 Hz, Rh-
Ccarbene), 126.3 (CHimid), 124.8 (Cq), 122.1 (CHimid), 84.9 (CH-COD),
57.5 (CH-COD), 42.9 (NCH3), 36.7 (NCH3), 32.7 (CH2-COD), 31.1
(COOCH3), 30.5 (CH2−COD). Anal. Calcd for RhIr-
I3O2N6C23H31(CH2Cl2)2 (1269.22): C, 23.66; H, 2.78; N, 6.62.
Found: C, 23.57; H, 2.53; N, 6.55. Electrospray MS (20 V, m/z): 1014
[M − I + MeCN]+, 973.1 [M − I]+.
3
3
8.00 (d, JH−H = 2.2 Hz, 2H, CHimid), 7.73 (d, JH−H = 2.2 Hz, 2H,
CHimid), 4.34 (m, 2H, CH-COD), 4.07 (m, 2H, CH-COD), 4.00 (s,
6H, NCH3), 3.82 (s, 6H, NCH3), 2.31 (m, 4H, CH2-COD), 1.75 (m,
4H, CH2-COD). 13C NMR (75 MHz, DMSO-d6): δ 181.2 (Ir-
Ccarbene), 134.2 (Cq), 125.8 (NCHN), 123.9 (CHimid), 121.7 (CHimid),
80.3 (CH-COD), 75.8 (CH-COD), 37.4 (NCH3), 34.1 (NCH3), 30.6
(CH2-COD), 30.5 (CH2-COD). Satisfactory elemental analysis could
not be obtained due to the low stability of the compound. Electrospray
MS (15 V, m/z): 645.4 [M + BF4]+, 279.1 [M]2+. Electrospray HR-MS
(15 V, m/z): 645.2126 [M + BF4]+, 279.1038 [M]2+.
Synthesis of Compound 8. A mixture of compound 1 (105.4 mg,
0.203 mmol), [RhCl(COD)]2 (50 mg, 0.101 mmol), NaOAc (66.54
mg, 0.812 mmol), and KI (136.16 mg, 0.812 mmol) in acetonitrile (20
mL) was refluxed overnight under an inert atmosphere. Once at room
temperature, [RhCl(COD)]2 (50 mg, 0.101 mmol), NaOAc (33.3 mg,
0.406 mmol), and KI (68.1 mg, 0.406 mmol) were added, and the
resulting mixture was refluxed for an additional 3 h. The solution was
then filtered, and the solvent was removed under vacuum. The crude
solid was purified by column chromatography. Elution with a 95:5
mixture of dichloromethane/acetone afforded the separation of a band
that contained the desired product. After removal of the volatiles, 8
was isolated as a yellow solid. Yield: 68 mg, 33%. 1H NMR (300 MHz,
CDCl3): δ 7.35 (s, 2H, CHimid), 7.18 (d, 2H, CHimid), 5.27 (m, 2H,
CH-COD), 4.19 (s, 6H, NCH3), 3.94 (s, 6H, NCH3), 3.59 (m, 2H,
CH-COD), 2.31 (m, 4H, CH2-COD), 1.99 (s, 3H, COOCH3), 1.84
(m, 4H, CH2-COD). 13C NMR (75 MHz, CDCl3): δ 190.7
Synthesis of Compound 5. A mixture of compound 1 (78 mg,
0.149 mmol), [IrCl(COD)]2 (50 mg, 0.0745 mmol), and NaOAc
(49.2 mg, 0.6 mmol) in acetonitrile (15 mL) was refluxed for 1 h
under an inert atmosphere. [Pd(OAc)2] (33.7 mg, 0.149 mmol) and
KI (100.6 mg, 0.6 mmol) were then added, and the reaction was
refluxed for an additional 1 h. The mixture was filtered through a pad
of Celite, and the solvent was removed under vacuum. The crude solid
was purified by column chromatography. Elution with a 7:3 mixture of
dichloromethane/acetone afforded the separation of an orange band
that contained compound 5. Precipitation with a mixture of acetone/
diethyl ether gave the desired product as a brown, air-sensitive solid.
1
(COOCH3), 185.7 (d, JRh−C = 50.5 Hz, Rh-Ccarbene), 162.7 (d,
1JRh−C = 47.4 Hz, Rh-Ccarbene), 126.3 (CHimid), 124.9 (Cq), 122.1
(CHimid), 98.0 (d, 1JRh−C = 6.7 Hz, Rh-CHCOD), 74.3 (d, 1JRh−C = 13.9
Hz, Rh-CHCOD), 42.9 (NCH3), 37.3 (NCH3), 32.2 (CH2−COD), 29.7
(CH2-COD), 25.1 (COOCH3). Anal. Calcd for Rh2I3O2N6C23H31
(1010.06): C, 27.35; H, 3.09; N, 8.32. Found: C, 27.51; H, 3.21; N,
8.59. Electrospray MS (20 V, m/z): 923.9 [M − I + MeCN]+, 882.9
[M − I]+.
1
Yield: 70 mg, 45%. H NMR (300 MHz, DMSO-d6): δ 8.07 (s, 2H,
CHimid), 7.67 (s, 2H, CHimid), 4.27 (m, 2H, CH-COD), 3.93 (m, 2H,
CH-COD), 3.88 (s, 6H, NCH3), 3.80 (s, 6H, NCH3), 2.30 (m, 2H,
CH2-COD), 2.09 (s, 3H, CH3CN), 2.04 (m, 4H, CH2-COD), 1.66 (m,
2H, CH2-COD). 13C NMR (75 MHz, DMSO-d6): δ 180.7 (Ir-
Ccarbene), 163.6 (Pd-Ccarbene), 125.4 (CHimid), 124.3 (Cq), 122.0
(CHimid), 79.3 (CH-COD), 75.1 (CH-COD), 37.2 (NCH3), 36.2
(NCH3), 30.7 (CH2-COD), 30.4 (CH2-COD), CH3CN not observed.
Satisfactory elemental analysis could not be obtained due to the low
stability of the compound. Electrospray MS (20 V, m/z): 958.1 [M]+,
917.1 [M − MeCN]+. Electrospray HR-MS (20 V, m/z): 957.9382
[M]+.
Synthesis of Compound 9. CO gas (1 atm, 10 mL/min) was
passed through a solution of complex 4 (90 mg, 0.123 mmol) in
methanol (15 mL) for 15 min at 0 °C. After this time, the solution was
concentrated under reduced pressure. After addition of ether, a yellow
1
solid precipitated. Yield: 77 mg, 92%. H NMR (300 MHz, MeCN-
d3): δ 8.7 (s, 1H, NCHN), 7.6 (d, 3JH−H = 2.1 Hz, 2H, CHimid), 7.5 (d,
3JH−H = 2.2 Hz, 2H, CHimid), 3.9 (s, 6H, NCH3), 3.9 (s, 6H, NCH3).
13C NMR (75 MHz, DMSO-d6): δ 172.0 (Ir-Ccarbene), 171.4 (Ir-CO),
135.5 (NCHN), 126.5 (CHimid), 122.9 (CHimid), 122.3 (Cq), 34.6
(NCH3), 21.0 (NCH3). Satisfactory elemental analysis could not be
obtained due to the low stability of the compound. IR (KBr): 2079
(νCO), 2017 (νCO) cm−1. Electrospray MS (20 V, m/z): 593.0 [M
+ BF4]+, 252.9 [M]2+. Electrospray HR-MS (20 V, m/z): 593.1091 [M
+ BF4]+, 253.0516 [M]2+.
Synthesis of Compound 6. A mixture of compound 1 (105.4 mg,
0.203 mmol), [RhCl(COD)]2 (50 mg, 0.1015 mmol), NaOAc (66.54
mg, 0.812 mmol), and KI (136.16 mg, 0.812 mmol) in acetonitrile (20
mL) was refluxed overnight under an inert atmosphere. Afterward, the
solvent was removed under vacuum. The crude solid was purified by
column chromatography. Elution with a mixture of acetone/KPF6
afforded the desired compound as an orange solid. Yield: 55 mg, 33%.
1H NMR (300 MHz, acetone-d6): δ 9.32 (s, 1H, NCHN), 8.17 (d,
3JH−H = 2.2 Hz, 2H, CHimid), 7.84 (d, 3JH−H = 2.2 Hz, 2H, CHimid), 4.21
Synthesis of Compound 10. A mixture of compound 1 (78 mg,
0.149 mmol), [IrCl(COD)]2 (50 mg, 0.0745 mmol), and NaOAc
(49.2 mg, 0.6 mmol) in acetonitrile (15 mL) was refluxed for 1 h
under an inert atmosphere. Once at room temperature, I2 (50.8 mg,
0.2 mmol) was added and the mixture was stirred for 3 h. The solution
was then filtered, and volatiles were removed under vacuum. The
crude solid was purified by column chromatography. Elution with a 1:1
mixture of dichloromethane/acetonitrile afforded the separation of a
yellow band that contained compound 10. Precipitation with a mixture
of acetonitrile/diethyl ether gave the desired product as a yellow solid.
(s, 6H, NCH3), 4.04 (s, 6H, NCH3), 1.87 (s, 3H, COOCH3). 13C
1
NMR (75 MHz, MeCN-d3): δ 191.3 (COOCH3), 163.0 (d, JRh−C
=
47.2 Hz, Rh-Ccarbene), 136.3 (NCHN), 129.3 (CHimid), 126.4 (Cq),
124.2 (CHimid), 43.4 (NCH3), 36.9 (NCH3), 30.2 (COOCH3). Anal.
Calcd for RhI2O2N6C15H20PF6(H2O)3 (872.1): C, 20.66; H, 3.01; N,
9.64. Found: C, 20.77; H, 3.51; N, 9.23. Electrospray MS (20 V, m/z):
672.8 [M]+.
Synthesis of Compound 7. A mixture of compound 1 (105.4 mg,
0.203 mmol), [RhCl(COD)]2 (50 mg, 0.101 mmol), NaOAc (66.54
mg, 0.812 mmol), and KI (136.16 mg, 0.812 mmol) in acetonitrile (20
mL) was refluxed overnight under an inert atmosphere. Once at room
1
Yield: 49 mg, 38%. H NMR (300 MHz, MeCN-d3): δ 8.69 (s, 1H,
3
3
NCHN), 7.64 (d, JH−H = 2.3 Hz, 2H, CHimid), 7.45 (d, JH−H = 2.3
5612
dx.doi.org/10.1021/om300569w | Organometallics 2012, 31, 5606−5614

Organometallics
Article
Hz, 2H, CHimid), 4.18 (s, 6H, NCH3), 3.75 (s, 6H, NCH3), 2.70 (s,
6H, CH3CN). 13C NMR (75 MHz, DMSO-d6): δ 135.1 (Ir-Ccarbene),
128.6 (Cq), 127.8 (NCHN), 124.4 (CHimid), 122.7 (CHimid), 118.0
(CH3CN), 43.5 (NCH3), 34.9 (NCH3), 1.1 (CH3CN). Anal. Calcd for
IrI2N8C17H23B2F8(Et2O)2 (1107.31): C, 27.12; H, 3.91; N, 10.12.
Found: C, 26.91; H, 4.23; N, 9.91. Electrospray MS (20 V, m/z):
393.1 [M]2+, 352.0 [M − 2MeCN]2+.
data in the form of cif files of complexes 3 and 8. This material
is available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: poyatosd@uji.es, eperis@uji.es.
Catalytic Reactions: General Procedures. Tandem Dehaloge-
nation/Transfer Hydrogenation of 4-Bromoacetophenone. In a
typical run, a capped vessel containing a stirring bar was charged with
4-bromoacetophenone (0.36 mmol), Cs2CO3 (0.43 mmol), anisole as
internal reference (0.36 mmol), catalyst (2% or 1% mmol), and 2 mL
of 2-propanol. The reaction mixture was heated at 100 °C for the
appropriate time. Reaction monitoring, yields, and conversions were
determined by GC.
Suzuki−Miyaura Coupling/Transfer Hydrogenation. In a typical
run, a capped vessel containing a stirring bar was charged with 4-
bromoacetophenone (0.36 mmol), phenylboronic acid (0.55 mmol),
Cs2CO3 (1.08 mmol), anisole as internal reference (0.36 mmol),
catalyst (2% mmol), 2 mL of 2-propanol, and 2 mL of THF. The
reaction mixture was heated at 100 °C for the appropriate time.
Reaction monitoring, yields, and conversions were determined by GC.
Cyclization of 2-Aminophenyl Ethyl Alcohol. In a typical run, a
capped vessel containing a stirring bar was charged with 2-
aminophenyl ethyl alcohol (0.25 mmol), KOH (0.5 mmol), anisole
as internal reference (0.25 mmol), catalyst (2% or 1% mmol), and 1
mL of toluene. The reaction mixture was heated at 110 °C for the
appropriate time. Reaction monitoring, yields, and conversions were
determined by GC.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We gratefully acknowlegde financial support from MEC of
Spain (CTQ2011-24055/BQU) and Bancaixa (P1.1B2010-02,
́
P1.1B2011-22). We would also like to thank the Ramon y Cajal
Program (M.P.). We would also like to thank the Ministerio de
Economia y Competitividad for a fellowship (S.G.). The
authors are grateful to the “Serveis Centrals d’Instrumentacio
Cientifica” (SCIC) of the Universitat Jaume I for providing us
with spectroscopic and X-ray facilities.
́
́
́
REFERENCES
■
(1) (a) Shibasaki, Y.; Yamamoto, Y. Multimetallic Catalysts in Organic
Synthesis; Wiley-VCH: Weinheim, 2004. (b) Perez-Temprano, M. H.;
Casares, J. A.; Espinet, P. Chem.Eur. J. 2012, 18, 1864. (c) Adams, R.
D.; Cotton, F. A. Catalysis by Di- and Polynuclear Metal Cluster
Complexes; Wiley-VCH: New York, 1998. (d) Shibasaki, M.; Sasai, H.;
Arai, T. Angew. Chem., Int. Ed. Engl. 1997, 36, 1237. (e) van den
Beuken, E. K.; Feringa, B. L. Tetrahedron 1998, 54, 12985. (f) Burke,
A. J.; Marinho, V. R.; Furtado, O. M. R. Curr. Org. Synth. 2010, 7, 94.
(g) Patil, N. T.; Shinde, V. S.; Gajula, B. Org. Biol. Chem. 2012, 10,
211.
Acylation of Bromobenzene with n-Hexanal. The catalyst (2%
mol of 3 or 5), TBAB (0.024 mmol), and 4 Å molecular sieves (0.5 g)
were placed together in a thick-walled Schlenk tube fitted with a
Teflon cap. The tube was evacuated and filled with nitrogen three
times. Bromobenzene (0.24 mmol), n-hexanal (0.29 mmol),
pyrrolidine (0.48 mmol), and dry N,N-dimethylformamide (DMF)
(1 mL) were added. The reaction mixture was heated at 115 °C for 16
h. After cooling to room temperature, 8 mL of EtOAc was added, and
the mixture was washed with H2O (3 × 2.5 mL) to remove the DMF,
dried over Na2SO4, and concentrated under vacuum. Conversions
(2) Lee, J. M.; Na, Y.; Han, H.; Chang, S. Chem. Soc. Rev. 2004, 33,
302.
(3) (a) Fogg, D. E.; dos Santos, E. N. Coord. Chem. Rev. 2004, 248,
2365. (b) Ajamian, A.; Gleason, J. L. Angew. Chem., Int. Ed. 2004, 43,
3754. (c) Wasilke, J. C.; Obrey, S. J.; Baker, R. T.; Bazan, G. C. Chem.
Rev. 2005, 105, 1001.
1
were determined by H NMR spectroscopy.
X-ray Diffraction Studies. Diffraction data were collected on a
Agilent SuperNova diffractometer equipped with an Atlas CCD
detector using Mo Kα radiation (λ = 0.71073 Å). Single crystals were
mounted on a MicroMount polymer tip (MiteGen) in a random
orientation. Absorption corrections based on the multiscan method
were applied.16 The structures were solved by direct methods in
SHELXS-97 and refined by the full-matrix method based on F2 with
the program SHELXL-97 using the OLEX software package.17
Crystal Data and Structure Refinement for Complex 3. Crystals
suitable for X-ray study of 3 were obtained by slow diffusion of diethyl
ether into a concentrated solution of the complex in acetonitrile.
Crystal system, monoclinic; space group, P21; a (Å), 13.2740(5); b
(Å), 16.7105(4); c (Å), 14.4848(5); α (deg), 90.00; β (deg),
108.107(4); γ (deg), 90.00; Z, 4; independent reflections, 14702
[R(int) = 0.0476]; GOF, 1.026; final R indices [I > 2σ(I)], R1 =
0.0430, wR2 = 0.0525; min./max. resid dens (e Å−3), −0.90 and 1.21.
Crystal Data and Structure Refinement for Complex 8. Crystals
suitable for X-ray study of 8 were obtained by slow diffusion of diethyl
ether into a concentrated solution of the complex in chloroform.
Crystal system, monoclinic; space group, P21/m; a (Å), 10.4283(3); b
(Å), 12.2666(3); c (Å), 11.9217(3); α (deg), 90.00; β (deg),
96.174(2); γ (deg), 90.00; Z, 2; independent reflections, 4649
[R(int) = 0.0492]; GOF, 1.065; final R indices [I > 2σ(I)], R1 =
0.0356, wR2 = 0.0823; min./max. resid dens (e Å−3), −1.10 and 1.29.
(4) (a) Boydston, A. J.; Bielawski, C. W. Dalton Trans. 2006, 4073.
(b) Boydston, A. J.; Rice, J. D.; Sanderson, M. D.; Dykhno, O. L.;
Bielawski, C. W. Organometallics 2006, 25, 6087. (c) Sanderson, M. D.;
Kamplain, J. W.; Bielawski, C. W. J. Am. Chem. Soc. 2006, 128, 16514.
(d) Tennyson, A. G.; Ono, R. J.; Hudnall, T. W.; Khramov, D. M.; Er,
J. A. V.; Kamplain, J. W.; Lynch, V. M.; Sessler, J. L.; Bielawski, C. W.
Chem.Eur. J. 2010, 16, 304. (e) Mercs, L.; Neels, A.; Albrecht, M.
Dalton Trans. 2008, 5570. (f) Vujkovic, N.; Cesar, V.; Lugan, N.;
Lavigne, G. Chem.Eur. J. 2011, 17, 13151. (g) Ruiz, J.; Garcia, L.;
Perandones, B. F.; Vivanco, M. Angew. Chem., Int. Ed. 2011, 50, 3010.
(h) Rit, A.; Pape, T.; Hahn, F. E. J. Am. Chem. Soc. 2010, 132, 4572.
(i) Prades, A.; Poyatos, M.; Mata, J. A.; Peris, E. Angew. Chem., Int. Ed.
2011, 50, 7666.
(5) (a) Mas-Marza, E.; Mata, J. A.; Peris, E. Angew. Chem., Int. Ed.
2007, 46, 3729. (b) Curphey, T. J.; Prasad, K. S. J. Org. Chem. 1972,
37, 2259. (c) Buron, C.; Stelzig, L.; Guerret, O.; Gornitzka, H.;
Romanenko, V.; Bertrand, G. J. Organomet. Chem. 2002, 664, 70.
(d) Guerret, O.; Sole, S.; Gornitzka, H.; Teichert, M.; Trinquier, G.;
Bertrand, G. J. Am. Chem. Soc. 1997, 119, 6668. (e) Guerret, O.; Sole,
S.; Gornitzka, H.; Trinquier, G.; Bertrand, G. J. Organomet. Chem.
2000, 600, 112.
(6) (a) Zanardi, A.; Corberan, R.; Mata, J. A.; Peris, E.
Organometallics 2008, 27, 3570. (b) Zanardi, A.; Mata, J. A.; Peris,
E. J. Am. Chem. Soc. 2009, 131, 14531. (c) Zanardi, A.; Mata, J. A.;
Peris, E. Organometallics 2009, 28, 4335. (d) Zanardi, A.; Mata, J. A.;
Peris, E. Chem.Eur. J. 2010, 16, 13109. (e) Zanardi, A.; Mata, J. A.;
Peris, E. Chem.Eur. J. 2010, 16, 10502. (f) Sabater, S.; Mata, J. A.;
Peris, E. Chem.−Eur. J. 2012, 18, DOI: 10.1002/chem.201103657.
(7) Gonell, S.; Poyatos, M.; Mata, J. A.; Peris, E. Organometallics
2011, 30, 5985.
ASSOCIATED CONTENT
■
S
* Supporting Information
Details of the catalytic experiments and the high-resolution
mass spectra of compounds 4, 5, and 9 and X-ray diffraction
5613
dx.doi.org/10.1021/om300569w | Organometallics 2012, 31, 5606−5614

Organometallics
Article
(8) Zhong, R.; Wang, Y. N.; Guo, X. Q.; Chen, Z. X.; Hou, X. F.
Chem.Eur. J 2011, 17, 11041.
(9) Cuervo, D.; Gamasa, M. P.; Gimeno, J. Chem.Eur. J. 2004, 10,
425.
(10) (a) McCarthy, A. R.; Hartmann, R. W.; Abell, A. D. Bioorg. Med.
Chem. Lett. 2007, 17, 3603. (b) Picard, F.; Schulz, T.; Hartmann, R. W.
Bioorg. Med. Chem. 2002, 10, 437.
(11) Fujita, K.; Yamamoto, K.; Yamaguchi, R. Org. Lett. 2002, 4,
2691.
(12) (a) Kuethe, J. T. Chimia 2006, 60, 543. (b) Humphrey, G. R.;
Kuethe, J. T. Chem. Rev. 2006, 106, 2875.
(13) Ruan, J. W.; Saidi, O.; Iggo, J. A.; Xiao, J. L. J. Am. Chem. Soc.
2008, 130, 10510.
(14) Olah, G. A. Friedel-Crafts Chemistry; Wiley-Interscience: New
York, 1973.
(15) (a) Colbon, P.; Ruan, J. W.; Purdie, M.; Xiao, J. L. Org. Lett.
2010, 12, 3670. (b) Alvarez-Bercedo, P.; Flores-Gaspar, A.; Correa, A.;
Martin, R. J. Am. Chem. Soc. 2010, 132, 466.
(16) Clark, R. C.; Reid, J. S. Acta Crystallogr. A 1995, 51, 887.
(17) (a) Sheldrick, G. M. Acta Crystallogr. A 2008, 64, 112.
(b) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.;
Puschmann, H. J. Appl. Crystallogr. 2009, 42, 339.
5614
dx.doi.org/10.1021/om300569w | Organometallics 2012, 31, 5606−5614