(N-Heterocyclic Carbene)-Palladate Complexes in Anionic Mizoroki-Heck Coupling Cycles: A Combined Experimental and Computational Study

Article abstract of DOI:10.1021/om5012038

The reaction of complex (SIPr)PdCl₂(TEA) (SIPr = 1,3-bis(2,6-diisopropylphenyl)-2-imidazolidinylidene, TEA = triethylamine) with tertbutylammoniun chloride (TBAC) at room temperature affords the new ionic complex [TBA][(SIPr)PdCl₃] in quantitative yield. The activity of this complex as a precatalyst for Heck coupling reactions has been explored. Experimental results and DFT calculations support a plausible anionic Amatore-Jutand-type mechanism for the Heck reaction involving anionic (NHC)-palladium(0) catalytic species. (Chemical Equation Presented).

Full text of DOI:10.1021/om5012038

Article
pubs.acs.org/Organometallics
(
N-Heterocyclic Carbene)-Palladate Complexes in Anionic Mizoroki−
Heck Coupling Cycles: A Combined Experimental and Computational
Study
†
‡
‡
†
Daniel Guest, Vitor H. Menezes da Silva, Ana P. de Lima Batista, S. Mark Roe,
Ataualpa A. C. Braga,* and Oscar Navarro*
,
‡
,†
†
Department of Chemistry, University of Sussex, Brighton, BN1 9QJ, United Kingdom
‡
Departamento de Química Fundamental, Instituto de Química, Universidade de Sao
̃ ̃ ̃
Paulo, Sao Paulo, Sao Paulo, 05508-000, Brazil
*
S Supporting Information
ABSTRACT: The reaction of complex (SIPr)PdCl (TEA) (SIPr
2
=
1,3-bis(2,6-diisopropylphenyl)-2-imidazolidinylidene, TEA =
triethylamine) with tertbutylammoniun chloride (TBAC) at
room temperature affords the new ionic complex [TBA][(SIPr)-
PdCl ] in quantitative yield. The activity of this complex as a
3
precatalyst for Heck coupling reactions has been explored.
Experimental results and DFT calculations support a plausible
anionic Amatore−Jutand-type mechanism for the Heck reaction
involving anionic (NHC)-palladium(0) catalytic species.
INTRODUCTION
elimination of the coupling product. Unfortunately, the
mechanism of the reaction is far more complicated than this
and is greatly affected by the different components of the
reaction: coupling partners, solvent, base, additives, temper-
ature, and even the nature of the catalyst/precatalyst. This
complexity has resulted in extensive and detailed studies, both
experimental and theoretical, which have emphasized even
■
The Mizoroki−Heck reaction, involving the coupling of organic
halides or pseudohalides with alkenes, is one of the most
studied and utilized palladium-catalyzed reactions. The
textbook” catalytic cycle is depicted in Scheme 1 (A),
involving the oxidative addition of the halide, syn addition
and β-hydride elimination of the alkene, followed by reductive
1
“
2
,3
more the particular character of this ubiquitous reaction.
A very important contribution to the body of knowledge on
this reaction was made by Amatore and Jutand in the 1990s,
proposing a Heck mechanism that diverged from the classical
one in that in-situ-formed anionic species played a key role in
Scheme 1. “Textbook” (A) and Amatore−Jutand (B) Heck
Catalytic Cycles
4
nonligandless, homogeneous systems: using electrochemical
techniques they postulated that in Pd(OAc) + phosphine
2
−
mixtures the anionic 16-electron species (PPh ) Pd(OAc)
3
2
undergoes oxidative addition with aryl halides, generating
short-lived anionic pentacoordinated arylpalladium(II) com-
plexes. This key modification resulted in the commonly known
Amatore−Jutand Heck cycle (Scheme 1 (B)), which can be in
fact extended to all palladium cross-coupling reactions.
Moreover, the authors remark on the effect of ionic additives
in the reaction such as TBAC (TBAC = tetrabutylammonium
chloride) on the formation of active anionic species such as
−
5
L Pd(0)Cl , stabilized by the corresponding cation. All this
2
work was compiled in two excellent reviews published in 1999
6
and 2000.
Special Issue: Mike Lappert Memorial Issue
Received: November 28, 2014
©
XXXX American Chemical Society
A
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Our group recently reported on the use of (NHC)-
PdCl (TEA) complexes (NHC = N-heterocyclic carbene,
2
7
TEA = triethylamine) as precatalysts for Heck couplings of
unactivated aryl bromides and activated aryl chlorides with
8
9
alkenes, following standard Jeffery reaction conditions. In that
protocol we made use of tetrabutylammonium bromide
(
TBAB) in equimolar quantities as additive, after realizing
that reactions carried out in its absence did not afford the
desired products. More recently, we have decided to further
investigate the effect of the quaternary salt on the catalytic
process. An initial screening of the same substrates subjected to
the same reaction conditions but substituting TBAB with
TBAC showed that the reaction outcome was not altered by
this modification. We then turned our attention to the effect of
the additive on the precatalyst, (SIPr)PdCl (TEA) (1) (SIPr =
2
1,3-bis(2,6-diisopropylphenyl)-2-imidazolidinylidene). The re-
action of 1 with TBAC in anhydrous acetone, in air and at
room temperature, led to the formation of the novel ionic
complex [TBA][(SIPr)PdCl ] (2) in 88% yield in 5 h,
3
quantitatively if the reaction time was extended to 12 h
Scheme 2. Synthesis of [(SIPr)PdCl ][TBA]
3
Figure 1. Crystal structure of [TBA][(SIPr)PdCl ] (2), cocrystallized
3
with one molecule of H O. Hydrogen atoms are omitted for clarity
2
except those in the backbone of the NHC. Selected bonds (Å) and
angles (deg): C1−Pd1: 1.959(2); Pd1−Cl2: 2.3770(7); Pd1−Cl1:
2
.3020(6); Pd1−Cl3: 2.3080(6); C1−Pd1−Cl1: 89.89(6); C1−Pd1−
Cl3: 88.61(6).
1
(
Scheme 2). This complex was fully characterized by H and
C NMR and elemental analysis. Slow evaporation of a
1
3
solution of 2 in technical grade acetone and hexane led to the
formation of crystals suitable for X-ray diffraction, in which a
molecule of water cocrystallized with a molecule of 2 (Figure
1). In the complex, the Pd center adopts an expected square
planar geometry. Regarding the bond distances in the anion,
the Pd1−Cl2 distance is longer than the other two Pd1−Cl
bonds, due to the trans influence imparted by the NHC. The
Pd−C1 distance is, as expected, in the range of a single bond
and slightly shorter than that for 1 (1.959(2) vs 1.970(3) Å,
1
0
respectively). The structure features a tetrabutylammonium
cation, with a separation distance of 4.62 Å between the closest
chlorine and the quaternized nitrogen.
A literature search revealed that while non-NHC-bearing
complexes of the type [NR ][LPdX ] (L = amine, arsine,
4
3
phosphine; X = halide) were already described in the early
1
970s, only one previous example of an [(NHC)PdX3]−
1
1
anion has been reported, featuring a benzylimidazolium as
cation (Figure 2, 3). A handful of other [(NHC)PdX3]−
complexes have been reported in which the negative charge is
neutralized by a pendant imidazolium or triazolium N-
1
2
−
Figure 2. Previous examples of [(NHC)PdX ] -containing complexes
in the literature (X = halide).
3
13
substituent in the NHC (Figure 2, 4−6). To the best of
our knowledge, the use of these complexes in catalysis has not
been explored.
catalytic cycle. In a first comparison to the use of 1 + TBAC
(Table 1, entry 2), we found that 2 performed as well for the
coupling of 4-Br-anisole and styrene under the same reaction
conditions (Table 1, entry 3) in the absence of the quaternary
salt. The addition of 1 equiv (0.5 mmol) of TBAC to a reaction
catalyzed by 2 did not increase the yields nor reduce the
reaction time (Table 1, entry 4), reinforcing further that the
role of the ammonium salt in our early protocol was solely to
participate in the formation of 2. Switching the base to
HCO3− led to a considerable decrease in the reaction time
(Table 1, entry 5), which ultimately allowed us to decrease the
We then carried out test reactions to explore the possibility
that 2 could be generated in situ in our previous protocol for
the Heck reaction, playing the role of catalyst precursor in an
Amatore−Jutand Heck-type mechanism. The reduction of
(
NHC)-Pd(II) complexes to the corresponding (NHC)-Pd(0)
species by carbonate bases at high temperatures is well
documented and in our case would potentially lead to the
formation of an [(NHC)Pd(0)Cl] species that could start the
1
4
15
−
B
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Table 1. Comparison of the Activity of 1 and 2 in the
Coupling of 4-Br-Anisole and Styrene
The coupling between PhBr (8) and styrene (9) in the
presence of HCO3− (10) as the base was considered. The
explored mechanism is based on experimental evidence of
anionic palladium complexes as the reactive species in the
a
6
b,21
catalytic cycle.
Anionic Pd complexes are more likely to be
found in a reaction medium using polar solvents and under
22,23
high temperature,
i.e., conditions similar to the one
entry
complex
base
yield (%)
time (min)
employed in the current experimental work. In addition,
theoretical findings have proposed plausible catalytic cycles
b
1
1
1
2
2
2
2
K CO
92
93
91
91
94
97
60
75
75
75
30
75
2
3
3
3
3
c
2
K CO
2
involving anionic palladium intermediates in analogous cross-
d
3
K CO
2
24,25
coupling reactions.
The overall computed profile of this
c
4
K CO
2
model reaction is displayed in Figure 3. The prefixes I and TS
stand for intermediates and transition states, respectively, in the
text. As shown in the energy profile of Figure 3, there are four
main steps in the considered Heck catalytic cycle: oxidative
addition, migratory insertion, β-hydride elimination, and
reductive elimination. Although the first and last steps are
more sensitive to the nature of the solvent, the general
energetic trends are maintained throughout the reaction path.
The energetic difference between products and reactants is
d
5
KHCO3
KHCO3
e
6
a
Reaction conditions: 2-Br-anisole, 0.5 mmol; styrene, 0.55 mmol;
b
TBAB, 0.5 mmol; base, 1 mmol; DMF, 1 mL; complex, 1 mol %. See
c
d
e
ref 8. TBAC instead of TBAB. No TBAB. No TBAB, complex
loading 0.5 mol %.
catalyst loading by half without any detriment to the yield of
the desired product (Table 1, entry 6). With these new
optimized reaction conditions, a variety of aryl bromides and
chlorides were coupled with styrene (Scheme 3). In all cases,
the yields obtained are equal to or higher than those obtained
using 1 + TBAB in comparable reactions times (in
parentheses).
−1
−
50.3 kcal mol , characterizing a quite exoergic process. The
overall reaction profile goes downhill and occurs very smoothly.
In the first step, bromobenzene adds to the [(NHC)PdCl]−
species. Scheme 4 presents the proposed mechanism for the
oxidative addition step, and Figure 4 shows optimized
geometries of selected structures (I1 and TS1) for this process.
The initial approach between the catalyst 7 and the reactant 8
yields the intermediate I1. It corresponds to the coordination of
Scheme 3. Heck Couplings of Aryl Chlorides and Bromides
with Styrene
2
the benzene ring to the Pd complex through an η -coordination
−1
mode. This intermediate is −10.4 kcal mol with respect to the
separated reactants. The oxidative addition process continues
through TS1 to yield the intermediate I2. The formation of I2
−1
is quite exoergic (−43.5 kcal mol ) and goes through TS1,
which is higher by 4.7 kcal mol− in relation to I1. Clearly, the
oxidative addition is the rate-determining step of the overall
reaction mechanism. The energy profile for this reaction shows
the anionic oxidative addition step as a suitable and irreversible
process. The inclusion of the effect of the solvent raises this
value to 9.1 kcal mol− above the separated reactants. In the
overall profile, it is noted that the solvent has the greatest
influence over the oxidative addition step. This behavior was
expected, because herein there is a bulky charged transition
state that is largely affected by the action of the polar solvent.
Once the oxidative addition has been accomplished, in order to−
continue the Heck reaction, the olefin 9 should replace the Br
ligand in the coordination sphere of the Pd center in the
intermediate I2. Despite our efforts, we were unable to locate a
1
1
−
transition state for the direct Br substitution by 9. Given the
fact that a vacant coordination site is necessary to allow the
olefin coordination to the metal center and that Pd−Cl and
26
Pd−NHC bonds are stronger than the Pd−Br bond, the Pd−
Br bond dissociation was assumed. Several constrained
optimizations along a LLM (linear least motion) path were
performed in order to estimate the value of an existing
dissociation barrier of the Pd−Br bond. It was possible to infer
that the bromine dissociation should either involve a very small
barrier or not proceed through a saddle point on the explored
potential energy surface (PES). The LLM was obtained by
To gain further insight into the mechanism under this
specific set of conditions and the potential role of an
−
[
(NHC)PdCl] species (7), computational studies were carried
using MacMolPlt. After Br− leaves the metal center, the
system becomes neutral.
27
out on a model system in which, for simplicity, the 2,6-
diisopropyl groups were replaced by methyl groups. The use of
model systems is a common tool in computational chemistry to
The insertion of 9 into the vacant site can create two possible
intermediates, I3a and I3b (Figure 5). The structure of I3b
shows that the olefin is coordinated following a perpendicular
16−20
provide insights into their respective real systems,
yielding very good results.
often
C
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Article
Figure 3. M06L/6-31+G(d) integrated relative energy profile for a plausible pathway on the studied model Mizoroki−Heck system reaction. M06L-
−1
SMD/6-31+G(d)//M06L/6-31+G(d) energies are in italics. All energies are given in kcal mol with respect to the infinitely separated reactants.
Only the stationary points with the lowest energy in the explored PES (potential energy surface) are shown.
Scheme 4. Proposed Mechanism for the Oxidative Addition
Figure 5. Starting intermediates, I3a and I3b, in the migratory
insertion step. Relative energies are given in kcal mol− and bond
distances in angstroms.
1
orientation to the metal plane, whereas an olefin in-plane
arrangement is observed in the case of the I3a intermediate.
I3b is 4 kcal mol− lower in energy than I3a. Styrene rotation
around the metal−olefin bond axis leads from I3b to I3a. The
transition state going from I3a to I3b, TS_I3ab, is −25.8 kcal
1
−1
mol with respect to the separated reactants and 6.8 kcal
−1
mol above I3b (see the Supporting Information for more
details about the TS_I3ab geometry, as well the optimized
geometries for all structures discussed in the text).
The migratory insertion of 9 into the Pd−C bond is usually
the step responsible for the regioselectivity of the Heck
28−30
reaction.
This step has two associated transition states,
TS2a and TS2b (Figure 6). The transition state TS2a involves
the β-carbon styrene addition to the terminal carbon of the
olefin double bond, while TS2b is responsible for the C−C
bond formation between the α-carbon from the olefin and the
Figure 4. Optimized structures of intermediate I1 and the transition
state TS1 for the anionic oxidative addition step. Relative energies are
given in kcal mol− and bond distances in angstroms.
1
aryl group (Figure 7). TS2a is connected to I3a, and it is found
1
2
0.7 kcal mol− below the separated reactants and 4.6 kcal
D
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Article
two competitive paths going through the transitions states,
TS3a and TS3b. Figure 7 shows their respective M06L/6-
3
1+G(d)-optimized structures. To achieve such four-mem-
bered-ring transition states, it is necessary to reorient the β-
hydrogen in the PhCH group of I4a and I4b toward the metal
2
center. After the isomerization of the intermediates I4a and I4b
to the agostic intermediates I5a and I5b, the reaction takes
place via the transition states TS3a and TS3b, respectively.
Figure 8 displays the competitive pathways related to the β-
Figure 6. Migratory insertion step and the transition states, TS2a and
TS2b, associated with the pathways. Relative energies are given in kcal
−1
mol with respect to the separated reactants.
Figure 8. β-Hydride syn-elimination step and the pathways related to
the transition states, TS3a and TS3b. Relative energies are given in
−1
kcal mol with respect to the separated reactants.
hydride syn-elimination. The energetics of the mechanism
shows that this step is more likely to proceed via the transition
−1
state TS3a, which is 32.2 kcal mol below the separated
reactants and about 3 kcal mol− lower in energy than TS3b.
Therefore, the trans Heck adduct (11) is expected as the major
product. The intermediates I6a and I6b are respectively −35.8
1
−1
and −30.1 kcal mol with respect to the reactants. However,
such intermediates present higher relative energies than their
related I5a and I5b, reflecting an endoergic process. When I6
intermediates are achieved, the product is already formed but
remains coordinated to the metal center. The separation of 11
−1
from Pd has an energy cost of 12.7 kcal mol . After the Heck
adduct 11 releases the metal center, the Pd-hydride complex I7
is formed. This intermediate is 23.1 kcal mol− below the
reactants.
1
The final part of the catalytic cycle is the reductive
elimination step, which is depicted in Scheme 5. At this
2+
0
point, the metal center undergoes a reduction, Pd → Pd , and
Figure 7. Analyzed TSs for the migratory insertion (TS2a and TS2b)
and β-hydride syn-elimination (TS3a and TS3b) steps. Relative
energies are given in kcal mol and bond distances in angstroms.
−
the starting active species [(NHC)PdCl] is regenerated. The
HCO3− base is proposed as responsible for abstracting the
proton from the palladium center. The reductive elimination
occurs almost barrierlessly. The relative energy of the transition
−1
mol− lower in energy than TS2b. The intermediate I4a is 6.9
kcal mol− lower in energy than I4b, and it is expected to be the
major product for the insertion process. This model reaction
predicts a high regioselectivity of the (NHC)Pd-catalyzed C−C
bond formation.
1
state associated with this step, TS4, is −48.0 kcal mol , with
−1
1
respect to the separated reactants. This transition state develops
a charge (the negatively charged active catalyst is being
regenerated) and the impact of the solvent effect becomes more
pronounced than during the neutral steps. It is worth
mentioning, once again, that it does not change the overall
trend over the energetic profile of the reaction. When solvent
effects are included, the relative electronic energy is −35.8 kcal
The following neutral process is the β-hydride syn-
elimination. Previous reports have shown that the stereo-
31,32
selectivity is controlled in this step.
Once more, there are
E
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Scheme 5. Reductive Elimination and Catalyst Regeneration
Scheme 6. Plausible Mechanism Pathway for the
−
[(NHC)PdCl] -Catalyzed Mizoroki−Heck Reaction
mol− with respect to the separated reactants. Figure 9 displays
1
optimized geometries for I8 and TS4. I8 and TS4 have very
1
.33−1.25 (m 8H), 1.20 (d, J = 6.5 Hz 12H), 0.95 (t, J = 7.3 Hz 12H).
1
3
1
C{ H} NMR (100 MHz, C D ): δ 190.4, 147.6, 136.5, 128.5, 124.1,
6
6
5
8.3, 53.3, 28.6, 26.6, 24.7, 24.0, 19.7, 13.9. Anal. Calcd for
Figure 9. Optimized I8 and TS4 geometries for selected structures
C H Cl N Pd: C, 61.06; H, 8.82; N, 4.97. Found: C, 60.94; H,
43
74
3
3
associated with the reductive elimination step. Relative energies are
8
.77; N, 4.94.
−1
given in kcal mol and distances in angstroms.
General Procedure for Heck Reactions. In open air, a 4 mL
screw-capped vial equipped with a magnetic stirring bar was charged
with potassium carbonate (1 mmol), aryl halide (0.5 mmol), 2 (0.5
mol %), anhydrous DMF (1 mL), and the alkene (0.55 mmol). The
vial was sealed with a screw-cap fitted with a septum, and the reaction
mixture allowed to stir at 140 °C and monitored by gas
chromatography. When the reaction was complete or there was no
further increase in conversion, it was cooled to room temperature,
similar structures, with the main difference being the Pd−H
bond distance, 1.59 and 1.64 Å, respectively. The protonated
base, H CO , is still bonded to the Pd in I9, which is 50.3 kcal
2
3
−1
mol below the reactants. Finally, catalyst 7 is regenerated
after the departure of H CO (12).
2
3
In summary, a plausible Amatore−Jutand-type mechanism
for a model Mizoroki−Heck reaction was explored by DFT
calculations, based on our experimental results and the
poured into water (10 mL), and extracted with Et O or EtOAc (3 ×
2
1
0 mL). The combined organic layers were washed with water (3 × 10
mL) and brine (10 mL), dried over MgSO , and filtered. The resulting
4
synthesis of a new [TBA][(NHC)PdCl ] complex. The
3
solution was concentrated onto Celite under reduced pressure for
purification by column chromatography. All reported yields are an
average of two runs.
potential energy profile presented revealed that a mechanistic
proposal involving anionic (NHC)-palladium(0) species is
feasible, through a combination of neutral and anionic steps and
with high regio- and stereoselectivity (Scheme 6). Ongoing
work aims to investigate other feasible pathways, including a
more realistic model of the NHC ligand, as well as the
application of this type of precatalyst to other Pd-catalyzed
cross-coupling reactions.
Computational Studies. All electronic structure calculations were
carried out within the Kohn−Sham density functional theory (DFT)
3
3−35
formalism
with the Gaussian09 suite of quantum chemical
37
3
6
programs. The M06L functional was used in the current study,
because it has been proved to be an efficient and reliable method for
38
transition metal thermochemistry. The SDD basis set was adopted to
39
40
Pd and Br atoms and the 6-31+G(d) basis set for the remaining
4
1
atoms. Full geometry optimizations without any symmetry
restriction followed by frequency calculations on all stationary points
were performed to verify their nature as a minimum or a transition
state (TS) on the potential energy surface. The vibrational analysis was
performed within the harmonic approximation with thermochemical
data calculated at 298 K and 1 atm. Intrinsic reaction coordinate
EXPERIMENTAL SECTION
■
Synthesis of [TBA][(SIPr)PdCl ] (2). A reaction vial was loaded
3
with a magnetic stirring bar, (SIPr)PdCl (TEA) (502 mg, 0.75 mmol),
2
tetrabutylammonium chloride (231 g, 0.83 mmol), and 2 mL of dry
acetone. The solution was allowed to stir at room temperature
overnight. Removal of the solvent in vacuo afforded a yellow oil, which
was dissolved in ethyl acetate and triturated with hexane to yield the
4
2
(IRC) calculations were used to further authenticate doubtful TSs.
Solvent effects were taken into account with the continuum solvation
1
43
title compound as a pale yellow solid (613 mg, 97%). H NMR (500
model SMD with DMF as the solvent. The SMD calculations were
MHz, C D ); δ 7.28−7.20 (m, 6H), 3.88−3.79 (m, 4H), 3.55 (s 4H),
performed as single-point energy calculations (SMD-M06L) on the
M06L/6-31+G(d), SDD(Pd,Br) optimized gas-phase geometries. The
6
6
3
.16−3.09 (m, 8H), 1.77 (d, J = 6.5 Hz, 12H), 1.46−1.37 (m 8H),
F
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results obtained with this approach are denoted SMD-M06L/6-
2011. (c) Díez-Gonzal
́
ez, S., Ed. N-Heterocyclic Carbenes. From
3
1+G(d)//M06L/6-31+G(d). The relative energies of all minima and
Laboratory Curiosities to Efficient Synthetic Tools; RSC Publishing:
London, U.K., 2010. (d) Glorius, F., Ed. N-Heterocyclic Carbenes in
Transition Metal Catalysis; Springer Science: Heidelberg, Germany,
2007.
TSs are presented in terms of potential energies including zero-point
energy (ZPE) corrections. The results are not discussed in terms of
free energies in solution, since the use of continuum solvation models
combined with gas-phase rigid rotor-harmonic oscillator statistical
mechanics can introduce significant errors to the discussion. All
energies are presented in kcal mol with respect to the infinitely
(8) Gallop, C. W. D.; Zinser, C.; Guest, D.; Navarro, O. Synlett 2014,
4
4
25, 2225−2228.
−1
(9) Jeffery, T. J. Chem. Soc., Chem. Commun. 1984, 1287−1289.
separated reactants, unless otherwise specified.
(10) Chen, M.-T.; Vicic, D. A.; Turner, M. L.; Navarro, O.
Organometallics 2011, 30, 5052−5056.
ASSOCIATED CONTENT
Supporting Information
Characterization of products and details on computational
studies. This material is available free of charge via the Internet
at http://pubs.acs.org.
(11) (a) Goggin, P. L.; Goodfellow, R. R.; Reed, F. J. S. J. Chem. Soc.,
Dalton Trans. 1972, 1298−1303. (b) Duddell, D. A.; Goggin, P. L.;
Goodfellow, R. J.; Norton, M. G.; Smith, J. G. J. Chem. Soc. A 1970,
■
*
S
5
(
2
(
45−564.
12) Huynh, H. V.; Han, Y.; Ho, J. H. H.; Tan, G. K. Organometallics
006, 25, 3267−3274.
13) (a) Hermann, W. A.; Schwarz, J.; Gardiner, M. G. Organo-
AUTHOR INFORMATION
Corresponding Authors
E-mail: ataualpa@iq.usp.br.
E-mail: o.navarro@sussex.ac.uk.
■
metallics 1999, 18, 4082−4089. (b) Heckenroth, M.; Kluser, E.; Neels,
A.; Albrecht, M. Dalton Trans. 2008, 6242−6249. (c) Zamora, M. T.;
Ferguson, M. J.; McDonald, R.; Cowie, M. Dalton Trans. 2009, 7269−
7287. (d) Zamora, M. T.; Ferguson, M. J.; McDonald, R.; Cowie, M.
Organometallics 2012, 31, 5463−5477.
*
*
Notes
(14) Some recent examples in the literature: (a) Tessin, U. I.;
The authors declare no competing financial interest. The
findings in this paper are addressed in patent application
GB1321706.2.
Bantreil, X.; Songis, O.; Cazin, C. S. J. Eur. J. Inorg. Chem. 2013, 2007−
2
2
010. (b) Gao, T.-T.; Jin, A.-P.; Shao, L.-X. Beilstein J. Org. Chem.
012, 8, 1916−1919. (c) Lin, Y.-C.; Hsueh, H.-H.; Kanne, S.; Chang,
L.-K.; Liu, F.-C.; Lin, I. J. B. Organometallics 2013, 32, 3859−3869.
(d) Keske, E. C.; Zenkina, O. V.; Wang, R.; Crudden, C. M.
Organometallics 2012, 31, 6215−6221.
ACKNOWLEDGMENTS
O.N. gratefully acknowledges the Enterprise Development
Fund of the University of Sussex for support. V.H.M.S. and
■
(
15) Pytkowicz, J.; Roland, S.; Mangeney, P.; Meyer, G.; Jutand, A. J.
Organomet. Chem. 2003, 678, 166−179.
16) Amarante, G. W.; Benassi, M.; Milagre, H.; Braga, A. A.;
A.P.L.B. are thankful to Fundaca
̃
̀
̧ o de Amparo a Pesquisa do
(
Estado de Sao Paulo (grants 13/04813-6 and 13/22235-0).
̃
Maseras, F.; Eberlin, M. N.; Coelho, F. Chem.Eur. J. 2009, 15,
1
2460−12469.
DEDICATION
Dedicated to the memory of Prof. Mike Lappert.
■
(17) Perez-Rodríguez, M.; Braga, A. A. C.; Garcia-Melchor, M.;
Perez-Temprano, M. H.; Casares, J. A.; Ujaque, G.; deLera, A. R.;
Alvarez, R.; Maseras, F.; Espinet, P. J. Am. Chem. Soc. 2009, 131,
́
́
́
REFERENCES
3650−3657.
■
(18) García-Cuadrado, D.; Braga, A. A. C.; Maseras, F.; Echavarren,
(
1) (a) Heck, R. F.; Nolley, J. P. J. Org. Chem. 1972, 37, 2320−2322.
b) Mizoroki, T.; Mori, K.; Ozaki, A. Bull. Chem. Soc. Jpn. 1971, 44,
A. M. J. Am. Chem. Soc. 2006, 128, 1066−1067.
19) Braga, A. A. C.; Ujaque, G.; Maseras, F. Organometallics 2006,
5, 3647−3658.
20) García-Melchor, M.; Braga, A. A. C.; Lledos
(
(
2
581.
(
2) (a) Oestreich, M., Ed. The Mizoroki-Heck Reaction; John Wiley &
(
́
, A.; Ujaque, G.;
Sons: Chichester, U.K., 2009. (b) de Meijere, A., Diederich, F., Eds.;
Metal-Catalyzed Cross-Coupling Reactions, 2nd ed.; Wiley-VCH:
Weinheim, Germany, 2004. (c) Phan, N. T. S.; Van Der Sluys, M.;
Jones, C. W. Adv. Synth. Catal. 2006, 348, 609−679. (d) Santos, C. I.
M.; Barata, J. F. B.; Faustino, M. A.; Lodeiro, C.; Neves, M. G. P. M. S.
RSC Adv. 2013, 3, 19219−19238. (e) Whitcombe, N. J.; Hii, K. K.;
Gibson, S. E. Tetrahedron 2001, 7449−7476. (f) Kumar, A.; Rao, G.
K.; Kumar, S.; Singh, A. K. Organometallics 2013, 33, 2921−2943.
Maseras, F. Acc. Chem. Res. 2013, 46, 2626−2634.
(
(
21) Carrow, B. P.; Hartwig, J. F. J. Am. Chem. Soc. 2010, 132, 79−81.
22) Phan, N.; VanDerSluys, M.; Jones, C. Adv. Synth. Catal. 2006,
3
(
48, 609−679.
23) Proutiere, F.; Schoenebeck, F. Angew. Chem., Int. Ed. 2011, 50,
8192−8195.
(24) Goossen, L. J.; Koley, D.; Hermann, H. L.; Thiel, W. J. Am.
Chem. Soc. 2005, 127, 11102−11114.
(
(
2
g) Knowles, J. P.; Whiting, A. Org. Biomol. Chem. 2007, 5, 31−44.
3) Some representative examples: (a) de Vries, J. G. Dalton Trans.
006, 421−429. (b) Shaw, B. L.; Perera, S. D. Chem. Commun. 1998,
863−1864. (c) Ruan, J.; Iggo, J. A.; Berry, N. G.; Xiao, J. J. Am. Chem.
(25) Goossen, L. J.; Koley, D.; Hermann, H. L.; Thiel, W.
Organometallics 2006, 25, 54−67.
1
(26) (a) Kozuch, S.; Shaik, S.; Jutand, A.; Amatore, C. Chem.Eur. J.
Soc. 2010, 132, 16689−16699. (d) Montoya, V.; Pons, J.; Branchadell,
̈
2004, 10, 3072−3080. (b) Albert, K.; Gisdakis, P.; Rosch, N.
V.; Garcia-Anton, J.; Solans, X.; Font-Bardía, M.; Ros, J. Organo-
́
Organometallics 1998, 17, 1608−1616.
(27) Bode, B.; Gordon, M. S. J. Mol. Graphics Mod. 1998, 16, 133−
138.
(28) Bac
108−113.
metallics 2008, 27, 1084−1091. (e) Fiddy, S. G.; Evans, J.; Nelsius, T.;
Newton, M. A.; Tsoureas, N.; Tulloch, A. A. D.; Danopoulos, A. A.
Chem.Eur. J. 2007, 13, 3652−3659.
́
4) Amatore, C.; Carre, E.; Jutand, A.; M’Barki, M. A.; Meyer, G.
̈
ktorp, C.; Norrby, P.-O. J. Mol. Catal. A: Chem. 2010, 328,
(
Organometallics 1995, 14, 5605−5614.
5) This mechanism has also been suggested for soluble Pd(0)
colloids or nanoparticles; see ref 3a.
6) (a) Amatore, C.; Jutand, A. J. Organomet. Chem. 1999, 576, 254−
78. (b) Amatore, C.; Jutand, A. Acc. Chem. Res. 2000, 33, 314−321.
7) (a) Nolan, S. P., Ed. N-Heterocyclic Carbenes: Effective Tools for
Organometallic Synthesis; Wiley-VCH: Weinheim, Germany, 2014.
b) Cazin, C. S. J., Ed. N-Heterocyclic Carbenes in Transition Metal
Catalysis and Organocatalysis; Springer Science: Heidelberg, Germany,
(29) Dang, Y.; Qu, S.; Wang, Z.; Wang, X. J. Am. Chem. Soc. 2014,
136, 986−998.
(
(30) Xu, L.; Hilton, M. J.; Zhang, X.; Norrby, P.-O.; Wu, Y.-D.;
Sigman, M. S.; Wiest, O. J. Am. Chem. Soc. 2014, 136, 1960−1961.
(31) Henriksen, S. T.; Tanner, D.; Cacchi, S.; Norrby, P.-O.
Organometallics 2009, 28, 6201−6205.
(
2
(
̈
(32) Skold, C.; Kleimark, J.; Trejos, A.; Odell, L. R.; Nilsson Lill, S.
(
O.; Norrby, P.-O.; Larhed, M. Chem.Eur. J. 2012, 18, 4714−4722.
(33) Hohenberg, P.; Kohn, W. Phys. Rev. 1964, 136, B864−B871.
G
DOI: 10.1021/om5012038
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(
(
34) Kohn, W.; Sham, L. J. Phys. Rev. 1965, 140, A1133−A1138.
35) Parr, R. G.; Weitao, Y. Density-Functional Theory of Atoms and
Molecules; Oxford University Press: New York, USA, 1994.
(
36) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci,
B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H.
P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,
K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega,
N.; Millam, M. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.;
Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.;
Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.;
̈
Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.;
Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09,
Revision D.01; Gaussian Inc.: Wallingford, CT, 2009.
(37) Zhao, Y.; Truhlar, D. G. Theor. Chem. Acc. 2008, 120, 215−241.
(38) Zhao, Y.; Truhlar, D. G. Acc. Chem. Res. 2008, 41, 157−167.
(39) Andrae, D.; Huermann, U.; Dolg, M.; Stoll, H.; Preu, H. Theor.
Chim. Acta 1990, 77, 123−141.
40) Bergner, A.; Dolg, M.; Kchle, W.; Stoll, H.; Preu, H. Mol. Phys.
993, 80, 1431−1441.
41) Francl, M. M.; Pietro, W. J.; Hehre, W. J.; Binkley, J. S.; Gordon,
M. S.; DeFrees, D. J.; Pople, J. A. J. Chem. Phys. 1982, 77, 3654−3665.
42) Hratchian, H. P.; Schlegel, H. B. J. Chem. Theory Comput. 2005,
, 61−69.
43) Marenich, A. V.; Cramer, C. J.; Truhlar, D. G. J. Phys. Chem. B
009, 113, 6378−6396.
44) Harvey, J. N. Faraday Discuss. 2010, 145, 487−505.
(
1
(
(
1
(
2
(
H
DOI: 10.1021/om5012038
Organometallics XXXX, XXX, XXX−XXX