Monitoring of the Phosphine Role in the Mechanism of Palladium-Catalyzed Benzosilole Formation from Aryloxyethynyl Silanes

Article abstract of DOI:10.1021/acs.organomet.8b00102

Understanding the formation of benzosiloles by the intramolecular palladium-catalyzed annulation of alkynyl(aryl)silanes is crucial for achieving synthetic diversity toward the enhancement of the chemistry of siloles. By a combination of density functional theory calculations and experiments, we describe not only the whole mechanism of reaction but also the drawbacks that block this type of reaction. We also unravel the role of the phosphine ligand, without which the reactions could not go forward. Moreover, in silico predictive catalysis is presented here since the substitution of the phosphine ligand by an N-heterocyclic carbene (NHC) promises milder experimental conditions. A screening of substrates with different electronic properties was carried out to further understand the two fundamental steps of the reaction: stereoisomerization and concerted metalation-deprotonation.

Full text of DOI:10.1021/acs.organomet.8b00102

Article
Cite This: Organometallics XXXX, XXX, XXX−XXX
Monitoring of the Phosphine Role in the Mechanism of Palladium-
Catalyzed Benzosilole Formation from Aryloxyethynyl Silanes
Martí Gimferrer,† Yasunori Minami,*,‡ Yuta Noguchi,§ Tamejiro Hiyama,‡ and Albert Poater*,†
†Institut de Química Computacional i Catal
Catalonia, Spain
̀
isi and Departament de Química, Universitat de Girona, Campus Montilivi, 17003 Girona,
‡Research and Development Initiative, Chuo University, 1-13-27, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
§Department of Applied Chemistry, Chuo University, 1-13-27, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
S
* Supporting Information
ABSTRACT: Understanding the formation of benzosiloles by
the intramolecular palladium-catalyzed annulation of alkynyl-
(aryl)silanes is crucial for achieving synthetic diversity toward
the enhancement of the chemistry of siloles. By a combination
of density functional theory calculations and experiments, we
describe not only the whole mechanism of reaction but also
the drawbacks that block this type of reaction. We also unravel
the role of the phosphine ligand, without which the reactions
could not go forward. Moreover, in silico predictive catalysis is
presented here since the substitution of the phosphine ligand
by an N-heterocyclic carbene (NHC) promises milder
experimental conditions. A screening of substrates with
different electronic properties was carried out to further understand the two fundamental steps of the reaction:
stereoisomerization and concerted metalation−deprotonation.
Scheme 1. Palladium-Catalyzed Anti-Hydroarylation Using
Alkynyl(aryl)Silanes for Benzosilole Formation13
INTRODUCTION
■
Substituting carbon by silicon atoms on an organic compound
drastically modifies its chemical and physicochemical proper-
ties, opening, for the resulting silicon-based compounds, the
gate to potential applications including high-electron-affinity
materials, building blocks for organic synthesis, and solid-state
luminescence. For this reason, in recent years interest in
organic π-conjugated molecules with silicon atoms incorpo-
rated1,2 has increased. Consequently, numerous catalytic
reactions for their preparation3,4 have been reported, including
the formation of dibenzo-5,6 and benzosiloles.7 In comparison
with the dibenzosilole formation, there are only a few synthetic
strategies developed that give access to benzosiloles, on the
basis of metal-catalyzed annulation protocols: (a) cyclization of
o-alkynylphenylsilanes via anulation with additives such as
electrophiles,8 (b) annulation of aryl vinyl silanes via Mizoroki−
Heck reactions9 or Grubbs olefin metathesis catalysts,10 (c)
intramolecular C−H ortho silylation,11 (d) annulation of
alkynes with arylsilanes via Si−H bond cleavage,12 and (e)
trans-hydroarylation by alkynyl aryl silanes.13
Among the benzosilole formation reactions, the majority
require the transformation of the Si−C bond, which often acts
as a key step.14,15 Computationally, Si−C bond cleavage was
studied using rhodium-based transition-metal complexes.16
Alternatively, in 2016, Minami et al. achieved the synthesis of
benzosiloles by palladium-/acid-catalyzed intramolecular anti-
hydroarylation of alkynyl(aryl)silanes (see Scheme 1).13 Due to
the simplicity of synthesizing the silane reagents, an under-
standing of the reaction mechanism is crucial to achieve
synthetic diversity toward the enhancement of the chemistry of
siloles. For this purpose, in the current work we present a
computational study by density functional theory (DFT)
calculations of the full reaction mechanism for benzosilole
formation from aryloxyethynyl silane reagents, investigating
also the role of the phosphine ligand and disclosing the
drawbacks which block this type of reaction.
RESULTS AND DISCUSSION
■
The full reaction mechanism of the formation of the benzosilole
P from the aryloxyethynyl silane R is depicted in Figure 1. For
the sake of simplicity, the experimentally used triethylphos-
phine (PEt3) was replaced by trimethylphosphine (PMe3).
Once both dba ligands of the Pd(dba)2 catalyst were
substituted by a PMe3 ligand and a pivalic acid, with a minimal
Received: February 20, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.8b00102
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Figure 1. Full reaction pathway for Pd-catalyzed benzosilole formation from aryloxyethynyl silane, including selected values for ligands alternative to
PMe3 (M06/cc-pVTZ∼sdd//BP86-d3/SVP∼sdd; Gibbs free energies referenced to complex 1 in kcal/mol).
loss of energy of 0.2 kcal/mol, whereas the species in between,
Pd(dba)(PMe3), is only 0.8 kcal/mol higher in energy, the first
step consists of the π coordination of the aryloxyethynyl silane
R to the pivalic Pd(0) complex 1 to form I.17 Then, a syn-
hydropalladation18 occurs, providing the vinyl palladium
pivalate II. The formation energy of II is strongly dependent
on the presence of the phosphine ligand. For instance, II is
almost 12 kcal/mol lower and 23 kcal/mol higher in energy
than 1+R when the phosphine is coordinated to Pd or when
the phosphine is absent, respectively. Once the E complex II is
achieved, the formation of the Z complex III takes place via
stereoisomerization,19,20 overcoming an energy barrier of 24.1
kcal/mol. This transition state II-III is based on the rotation of
the C−C bond (dihedral angle of 84°; see Figure 2a).
barrierless formation of an agostic interaction between the
metallic center and an ortho carbon of the phenyl group (IIIag)
and hydrogen transfer from the phenyl to the pivalate ligand
(IIIag-IV). The latter transition state IV-1 finishes the
annulation process (see Figure 2b). Once the metallacycle IV
is obtained, a reductive elimination occurs, restoring the
catalytically active species 1 and forming the benzosilole
product P. The energy required to overcome the barrier
defined by the transition state IV-1 is rather low (less than 11
kcal/mol); however, that calculated from the intermediate III
turns out to be 27.4 kcal/mol bearing PMe3 as a phosphine.
Consequently, this is the rate-determining step (rds) of the
whole reaction pathway.
In previous studies, it was assumed that the isomerization
occurs (1) due to the steric repulsion of the Dipp and the two
isopropyl groups on silicon and (2) by the donation of the lone
pair electrons from the oxygen atom to the C−C double bond.
We demonstrate here that the electronic properties and the
sterics of the phosphine ligand (see Scheme 2) affect the energy
The next step consists of a concerted metalation−
deprotonation (CMD), which can be separated into the
Scheme 2. Catalyst Screening for Benzosilole Formation
barrier corresponding to this step, spanning from 15.9 kcal/mol
for the SIMes ligand to 24.1 kcal/mol for the PMe3 ligand.
Then, the choice of the phosphine ligand is crucial to reduce
the energy required to overcome the transition state II-III that
leads to intermediate III, and this becomes rather facile with
more sterically hindered ligands, such as PtBu3 and SIMes.21
Figure 2. DFT-optimized geometries for the transition states (a) II-III
and (b) IV-1 with the main distances given in Å.
B
DOI: 10.1021/acs.organomet.8b00102
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
For the rds, defined by the transition state IV-1, the step
requires roughly at least 25 kcal/mol independently of the
phosphine ligand used, and this barrier hardly decreases using
SIMes. Thus, even though the rds is not that affected by the
nature of the phosphine, more sterically demanding phosphines
facilitate this step, with energy barriers of 27.4 and 25.4 kcal/
mol, for PMe3 and PtBu3, respectively. Overall, the catalytic
cycle is strongly exergonic (34.2 kcal/mol).
Scheme 3. Substrate Screening for Benzosilole Formation
An alternative pathway for the formation of intermediate II,
again starting from the catalytic species 1, was also tested (see
Figure 3). First, an intramolecular oxidative addition occurs,
formation that leads to the cyclized organic product P. First, we
substituted the para position of the phenyl group of the reagent
R by electron-donating (ED) and -withdrawing (EW)
substituents, having methoxy and diphenylamine of ED
character and trifluoromethyl and nitro as EW moieties.
Second, we substituted the isopropyl groups on Si by bulkier
ones; finally, the ODipp substituent was substituted by carbon-
coordinated species. Thus, we would see to what extent the
sterics and the electronic character of the substituents affect the
reactivity. The results obtained for the different substrates,
referenced to the corresponding former species, are compiled in
Table 1.
For the substrates with the phenyl group differently para
substituted, we observed that the stereoisomerization and syn-
hydropalladation steps of the reaction are unaffected by the
electronic character of the substituents, presenting in all cases
energy barriers of around 22.0−25.0 and 11.0−12.0 kcal/mol,
respectively. The NPh2 case will be discussed below. For the
rate-determining step, the electron-donating groups OMe and
NPh2 impose higher energy barriers in comparison to the
electron-withdrawing groups CF3 and NO2. However, the
difference in the energy barriers is at least 2 kcal/mol, making it
very difficult to determine if the difference is caused by the
electronic character of the substituents or by the different
repulsive/attractive interactions from each moiety with the rest
of the molecular system. Here, we also considered another
pathway for the H extraction, via electrophilic aromatic
substitution (SEAr). Since it is known that electron-rich arenes
stabilize a positive charge in the arene rings, the reaction
through this pathway should be more facile. However, we
found that for neither NO2 nor OMe para-substituted arenes
was the SEAr pathway favored. The H extraction required 17.6
and 20.0 kcal/mol more, respectively, in comparison with the
proposed pathway from Figure 1.
On the other hand, clear differences are observed for the
second group of reagents from the substrate screening. Due to
the different electronic character of the Ph substituent on the
alkyne, in comparison with ODipp, a more difficult scenario
was expected in order to achieve the formation of intermediate
II. However, we observed that the energy barrier defined by the
transition state I-II is more than 10 kcal/mol lower than that
for the rate-determining step of the reaction. From the two
fundamental steps of the reaction, we observe that both are
highly sensitive to the electronic character of the R2 group (see
Scheme 3). The steps of stereoisomerization and C−C bond
Figure 3. Alternative pathway for the formation of intermediate II
(M06/cc-pVTZ∼sdd//BP86-d3/SVP∼sdd; Gibbs free energies in
kcal/mol referenced to complex 1).
transferring the hydrogen from the pivalic acid ligand to the
metallic center, oxidizing the Pd(0) metal center to +2. This
step forms the pivalate-coordinated square-planar complex 2 for
an energy cost of 17.0 kcal/mol. It is important to mention that
the thermodynamic equilibrium here is slightly displaced to the
former species 1, by 3.6 kcal/mol. Next, the aryloxyethynyl
silane R approaches intermediate 2, forming the relatively
unstable intermediate I′, which is even 3.2 kcal/mol less stable
than 2. Then, the phosphine ligand dissociates (I′-NP), with a
thermodynamic cost of 18.5 kcal/mol, which reduces the steric
hindrance around the metal sphere, allowing the metallic center
of the square planar moiety to achieve the desired π
coordination with the alkyne reagent. Finally, species I′-NP
undergoes a syn-hydropalladation that leads to intermediate II′,
followed by the recoordination of the phosphine ligand leading
to intermediate II, which species is shared for both reaction
pathways. Overall, kinetically this alternative pathway requires
26.8 kcal/mol to form intermediate II, whereas in the general
pathway in Figure 1 only 11.5 kcal/mol is required.
We expanded the mechanistic study to other aryloxyethynyl
silane substrates (see Scheme 3), focusing on the energy
barriers of the three fundamental steps of the mechanistic cycle:
i.e., syn-hydropalladation, stereoisomerization, and C−C bond
C
DOI: 10.1021/acs.organomet.8b00102
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
a
Table 1. Energy Data (in kcal/mol) for the Reaction Pathways for the Substrate Screening of Benzosilole Formation
a
b
c
d
e
f
g
h
i
j
k
l
1+R
I
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
−8.2
3.3
−14.6
−1.4
−17.2
7.0
−16.7
−4.1
−25.9
6.2
−15.6
−2.7
−18.4
5.8
−15.4
−3.5
−18.8
4.9
−13.7
−1.5
−27.7
5.2
−7.1
7.3
−10.7
−0.7
−21.6
8.8
−8.7
1.0
−12.3
−4.9
−23.6
5.2
−12.0
−7.0
−22.8
6.4
−12.0
−2.8
−18.9
6.0
I-II
II
−11.5
12.6
−9.8
28.0
−23.9
14.5
II-III
III
−23.0
4.4
−29.9
−2.3
−35.0
−29.9
−2.7
−35.8
−30.8
−4.5
−36.5
−29.4
−5.0
−35.4
−31.6
−2.7
−38.7
−13.3
16.0
−23.5
6.0
−24.1
5.5
−30.3
−2.2
−35.0
−26.7
−1.8
−35.1
−28.3
−1.1
−33.6
IV-1
1+P
−34.2
−17.2
−31.6
−32.5
a
PMe3 used as the phosphine in all series of data.
formation giving P require overcoming energy barriers of 37.8
and 29.3 kcal/mol, respectively, for R2 = Ph. More than 5 kcal/
mol differentiates the stereoisomerization processes with and
without the ODipp group. To clearly separate the steric and
electronic effects of the substituents, we studied the R2 =
ODipp molecular system. In this case, the only difference in the
energy barriers comes from the steric effect of the Si
substituents. In the stereoisomerization step, the energy barrier
increased from 24.1 to 32.9 kcal/mol due only to sterics. This
significant quantitative difference confirms that the energy
barrier for R1 = NPh2, 32.1 kcal/mol, is guided more by sterics
than by the electronic character of the substituent. Thus, the
energy barriers are sensitive not only to the electronic character
of the alkyne substituent but also to the steric repulsion
provided by the Si atom substituents. Moreover, we observed a
change in the rds of the reaction, becoming the stereo-
isomerization step instead of the barrier defined by the
transition state IV-P.
situation. The formation of P′, starting from intermediate I″,
requires 36.0 kcal/mol; meanwhile, the formation of P requires
32.9 kcal/mol. Thus, achieving P is kinetically more favorable.
Moreover, even though I″ is more stable than I, by 0.2 kcal/
mol, the energy difference between both species is small
enough to not affect the thermodynamic equilibrium, which
favors the formation of P. These results are in good agreement
with experiments.13
Since computationally SIMes turned out to be competitive
with respect to the most favorable phosphines, experiments
were undertaken using substrate m (see Table 2). Unexpect-
Table 2. Examination of Benzosilole Formation Using PEt3
a
and SIMes Ligands
Experimentally, the reaction with R2 = O-3,5-Xyl led to a
rather poor yield of the product P. Computationally the kinetic
cost was found to be relatively high, 38.4 kcal/mol, but it is still
affordable. Then, to reach good agreement between experi-
ments and computation, we studied the formation of its
undesired product (HOXyl) and the reaction for R2 = ODipp
(HODipp), depicted in Figure 4. For R2 = OXyl, the formation
of P′ goes through an energy barrier of 34.5 kcal/mol starting
from I, due to intermediate I″ being less stable than I. In
comparison with the formation of P, where the rds requires
38.4 kcal/mol, the formation of HOXyl is kinetically more
favorable. In the R2 = ODipp case we face the opposite
b
run
ligand
PEt3
conversion of m (%)
yield of P-m (%)
1
2
3
>99
22
58
4
SIMes
c
SIMes·HCl
11
5
a
Conditions: alkyne m, Pd(dba)2 (10 mol %), ligand (10 mol %),
tBuCO2H (10 mol %), in toluene (1.0 M), at 120 °C. Determined by
b
c
NMR. KOtBu (10 mol %) as an additive.
edly, the yield decreased to only 4% of the product P-m (run
2). When SIMes·HCl was used with KOtBu as a base, the yield
was improved by only 1% but the conversion of the substrate
became lower (22% vs 11%). To understand this poor
performance of the NHC ligand, the undesired reaction
studied in Figure 4 was tested for this ligand and was also
disfavored, with an energy requirement of 35.0 kcal/mol from I
to overcome the transition state I″-P′, thus being very similar
to the phosphine-based systems included in Figure 4.
Studies on the sterics and electronics were carried out for the
phosphine ligands. First, they confirmed that the computational
work on PMe3 instead of PEt3 is valid. Further, this study was
expanded to compare the phosphines used here by the NHC
ligand SIMes. For the sterics, we used the SambVca package
developed by Cavallo et al.,22,23 which allows the direct
comparison of phosphines and NHC ligands24 and, by
extension, any ligand.25 Taking into account the first
Figure 4. Reaction pathway for the undesired parallel reaction (M06/
cc-pVTZ∼sdd//BP86-d3/SVP∼sdd; Gibbs free energies in kcal/mol
referenced to complex 1).
D
DOI: 10.1021/acs.organomet.8b00102
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
single-point calculations on the optimized geometries with the M06
functional and the cc-pVTZ basis set, and solvent effects were
estimated with the polarizable continuous solvation model PCM using
toluene as solvent.35 The reported free energies in this work include
energies obtained at the M06/cc-pVTZ∼sdd level of theory corrected
with zero-point energies, thermal corrections, and entropy effects
evaluated at 298 K, achieved at the BP86-D3/SVP∼sdd level.
coordination sphere around the metal is where catalysis occurs,
and the buried volume is the amount of the first coordination
sphere of the metal occupied by a given ligand, we calculated
the total %VBur and also a more detailed analysis by evaluating
the %VBur in the single quadrants around the Pd center and
plotted them as steric contour steric maps (Figure S1), see the
Supporting Information for further details. Splitting the total %
VBur into quadrant contributions quantifies any asymmetry in
the way the ligand wraps around the metal. Here, this analysis
shows how the shape of the reactive pocket is modified on
moving from PtBu3 (36.3%) to PPh3 (29.4%), PEt3 (27.1%),
and PMe3 (24.1%). Even though the NHC ligand SIMes
(37.9%) displays a %VBur value close to and even higher than
that of the PtBu3 ligand, one quadrant is 2.6% less crowded but
is still much more crowded than the active PEt3-based catalysis.
This leads us to conclude, that apart from the effect of the
NHC and phosphine on the rds, it is very important to form
the active catalytic species 1 from Pd(dba)2 in combination
with PivOH, and for this step, the probability is much higher
for relatively small phosphines such as PEt3.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00102.
■
S
Computational details (PDF)
Cartesian coordinates and energies of all species (XYZ)
AUTHOR INFORMATION
Corresponding Authors
*E-mail for Y.M.: yminami@kc.chuo-u.ac.jp.
*E-mail for A.P.: albert.poater@udg.edu.
■
ORCID
CONCLUSIONS
■
Yasunori Minami: 0000-0002-2435-1951
Tamejiro Hiyama: 0000-0003-4749-1161
Albert Poater: 0000-0002-8997-2599
We have determined the whole reaction mechanism for
palladium-catalyzed benzosilole formation using different
phenylsilylalkynes as starting materials. We clarified the role
of the phosphine, since it became the driving force. Further, this
formation is not only a question of sterics; the choice of the
electronic nature of this ligand is also crucial to reduce the
energy cost of the stereoisomerization step. Even though the
rate-determining step is not that affected by the choice of this
ligand, its presence becomes mandatory to facilitate the
annulation, and a more sterically hindered phosphine slightly
facilitates this step. From the substrate scope, we observed not
only that the stereoisomerization step becomes the rate-
determining step of the reaction but also that the electronic
characters of the substituents of the alkyne reagent are much
more important than the effects of steric repulsion from nearby
groups.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
A.P. thanks the Spanish MINECO for the project CTQ2014-
59832-JIN and the EU for a FEDER fund (UNGI08-4 × 10−
003). Y.M. and T.H. thank the JST for ACT-C (JPMJCR12Z1).
Y.M. also acknowledges a Grant-in-Aid for Challenging
Research (Exploratory) (17K19127) from the JSPS.
REFERENCES
■
(1) Yamaguchi, S.; Tamao, K. J. Chem. Soc., Dalton Trans. 1998,
3693−3702.
(2) Yamaguchi, S.; Tamao, K. Chem. Lett. 2005, 34, 2−7.
(3) Kobayashi, J.; Kawashima, T. Science of Synthesis Knowledge
Updates, 2014/1.
EXPERIMENTAL DETAILS
■
General Procedure. Substrate m (0.10 mmol) was added to a
solution of Pd(dba)2 (0.010 mmol), PEt3 (0.010 mmol), and
tBuCO2H (0.010 mmol) in toluene (0.1 mL) prepared in a 3 mL
vial under an argon atmosphere in a drybox. The vial was closed with a
screw cap, taken outside the drybox, and heated at 90 °C for 24 h. The
reaction mixture was filtered through Celite, and the filtrate was
evaporated and dried in vacuo. The crude product was analyzed by 1H
NMR to determine the yield of the product P-m by comparing the
(4) Oestreich, M., Ed.; Metal-Catalyzed Cross-Coupling Reactions and
More; Thieme: Stuttgart, 2014; pp 351−369.
(5) (a) Matsuda, T.; Kadowaki, S.; Goya, T.; Murakami, M. Org. Lett.
2007, 9, 133−136. (b) Yabusaki, Y.; Ohshima, N.; Kondo, H.;
Kusamoto, T.; Yamanoi, Y.; Nishihara, H. Chem. - Eur. J. 2010, 16,
5581−5585. (c) Ureshino, T.; Yoshida, T.; Kuninobu, Y.; Takai, K. J.
Am. Chem. Soc. 2010, 132, 14324−14326. (d) Liang, Y.; Zhang, S.; Xi,
Z. J. Am. Chem. Soc. 2011, 133, 9204−9207.
1
reported H NMR data of P-m.
(6) (a) Kuninobu, Y.; Yamauchi, K.; Tamura, N.; Seiki, T.; Takai, K.
Angew. Chem., Int. Ed. 2013, 52, 1520−1522. (b) Shintani, R.; Takagi,
C.; Ito, T.; Naito, M.; Nozaki, K. Angew. Chem., Int. Ed. 2015, 54,
1616−1620. (c) Zhang, Q.-W.; An, K.; Liu, L.-C.; Yue, Y.; He, W.
Angew. Chem., Int. Ed. 2015, 54, 6918−6921. (d) Murai, M.;
Matsumoto, K.; Takeuchi, Y.; Takai, K. Org. Lett. 2015, 17, 3102−
3105. (e) Murai, M.; Okada, R.; Nishiyama, A.; Takai, K. Org. Lett.
2016, 18, 4380−4383. (f) Zhang, Q.-W.; An, K.; Liu, L.-C.; Guo, S.;
Jiang, C.; Guo, H.; He, W. Angew. Chem., Int. Ed. 2016, 55, 6319−
6323.
COMPUTATIONAL DETAILS
■
All of the DFT static calculations were performed with the Gausian09
set of programs,26 using the BP86 functional of Becke and
Perdew,27−29 together with the Grimme D3 correction term to the
electronic energy.30 The electronic configuration of the molecular
systems was described with the double-ζ basis set with the polarization
of Ahlrichs for main-group atoms (SVP keyword in Gaussian),31
whereas for palladium the small-core quasi-relativistic Stuttgart/
Dresden effective core potential, with an associated valence basis set
(standard SDD keywords in Gaussian09), was employed.32−34 The
geometry optimizations were performed without symmetry con-
straints, and analytical frequency calculations enabled the character-
ization of the located stationary points. These frequencies were used to
calculate unscaled zero-point energies (ZPEs) as well as thermal
corrections and entropy effects at 298 K. Energies were obtained by
(7) (a) Wu, B.; Yoshikai, N. Org. Biomol. Chem. 2016, 14, 5402−
5416. (b) Mochida, K.; Shimizu, M.; Hiyama, T. J. Am. Chem. Soc.
2009, 131, 8350−8351. (c) Zhang, Q.-W.; An, K.; He, W. Angew.
Chem., Int. Ed. 2014, 53, 5667−5671. (d) Omann, L.; Oestreich, M.
Organometallics 2017, 36, 767−776.
(8) (a) Arii, H.; Nakabayashi, K.; Mochida, K.; Kawashima, T.
Molecules 2016, 21, 999. (b) Matsuda, T.; Kadowaki, S.; Murakami, M.
E
DOI: 10.1021/acs.organomet.8b00102
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Chem. Commun. 2007, 43, 2627−2629. (c) Matsuda, T.; Kadowaki, S.;
Yamaguchi, Y.; Murakami, M. Chem. Commun. 2008, 44, 2744−2746.
(d) Ilies, L.; Tsuji, H.; Sato, Y.; Nakamura, E. J. Am. Chem. Soc. 2008,
130, 4240−4241. (e) Matsuda, T.; Yamaguchi, T.; Shigeno, M.; Sato,
S.; Murakami, M. Chem. Commun. 2011, 47, 8697−8699. (f) Matsuda,
T.; Ichioka, Y. Org. Biomol. Chem. 2012, 10, 3175−3177. (g) Ilies, L.;
Tsuji, H.; Nakamura, E. Org. Lett. 2009, 11, 3966−3968. (h) Ilies, L.;
Sato, Y.; Mitsui, C.; Tsuji, H.; Nakamura, E. Chem. - Asian J. 2008, 41,
1376−1381.
(9) Ouyang, K.; Liang, Y.; Xi, Z. Org. Lett. 2012, 14, 4572−4575.
(10) Matsuda, T.; Yamaguchi, Y.; Murakami, M. Synlett 2008, 2008,
561−564.
(11) Teo, W. J.; Wang, C.; Tan, Y. W.; Ge, S. Angew. Chem., Int. Ed.
2017, 56, 4328−4332.
N.; Millam, N. 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 E.01; Gaussian, Inc., Wallingford, CT, 2009.
(27) Becke, A. Phys. Rev. A: At., Mol., Opt. Phys. 1988, 38, 3098−
3100.
(28) Perdew, J. P. Phys. Rev. B: Condens. Matter Mater. Phys. 1986, 33,
8822−8824.
(29) Perdew, J. P. Phys. Rev. B: Condens. Matter Mater. Phys. 1986, 34,
7406−7406.
(30) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. J. Chem. Phys.
2010, 132, 154104.
(12) (a) Liang, Y.; Geng, W.; Wei, J.; Xi, Z. Angew. Chem., Int. Ed.
2012, 51, 1934−1937. (b) Tobisu, M.; Onoe, M.; Kita, Y.; Chatani, N.
J. Am. Chem. Soc. 2009, 131, 7506−7507. (c) Shirakawa, E.; Masui, S.;
Narui, R.; Watabe, R.; Ikeda, D.; Hayashi, T. Chem. Commun. 2011,
47, 9714−9716.
(31) Schafer, S.; Horn, H.; Ahlrichs, R. J. Chem. Phys. 1992, 97,
̈
2571−2577.
(32) Haussermann, U.; Dolg, M.; Stoll, H.; Preuss, H.;
Schwerdtfeger, P.; Pitzer, R. M. Mol. Phys. 1993, 78, 1211−1224.
(33) Kuchle, W.; Dolg, M.; Stoll, H.; Preuss, H. J. Chem. Phys. 1994,
̈
(13) Minami, Y.; Noguchi, Y.; Hiyama, T. J. Am. Chem. Soc. 2017,
139, 14013−14016.
100, 7535−7542.
(34) Leininger, T.; Nicklass, A.; Stoll, H.; Dolg, M.; Schwerdtfeger, P.
J. Chem. Phys. 1996, 105, 1052−1059.
(14) Itami, K.; Terakawa, K.; Yoshida, J.; Kajimoto, O. Bull. Chem.
Soc. Jpn. 2004, 77, 2071−2080.
(35) (a) Barone, V.; Cossi, M. J. Phys. Chem. A 1998, 102, 1995−
2001. (b) Tomasi, J.; Persico, M. Chem. Rev. 1994, 94, 2027−2094.
(15) Itami, K.; Terakawa, K.; Yoshida, cJ.-i.; Kajimoto, O. J. Am.
Chem. Soc. 2003, 125, 6058−6059.
(16) Yu, Z.; Lan, Y. J. Org. Chem. 2013, 78, 11501−11507.
(17) (a) Runzi, T.; Tristschler, U.; Roesle, P.; Gottker-Schnetmann,
̈
I.; Moller, H. M.; Caporaso, L.; Poater, A.; Cavallo, L.; Mecking, S.
Organometallics 2012, 31, 8388−8406. (b) Meconi, G. M.; Vummaleti,
S. V. C.; Luque-Urrutia, J. A.; Belanzoni, P.; Nolan, S. P.; Jacobsen, H.;
̀
Cavallo, L.; Sola, M.; Poater, A. Organometallics 2017, 36, 2088−2095.
(18) Shen, R.; Chen, T.; Zhao, Y.; Qiu, R.; Zhou, Y.; Yin, S.; Wang,
X.; Goto, M.; Han, L.-B. J. Am. Chem. Soc. 2011, 133, 17037−17044.
(19) (a) Brady, K. A.; Nile, T. A. J. Organomet. Chem. 1981, 206,
299−304. (b) Ojima, I.; Clos, N.; Donovan, R. J.; Ingallina, P.
Organometallics 1990, 9, 3127−3133.
(20) Murakami, M.; Yoshida, T.; Kawanami, S.; Ito, Y. J. Am. Chem.
Soc. 1995, 117, 6408−6409.
(21) (a) Czerwinski, P.; Molga, E.; Cavallo, L.; Poater, A.; Michalak,
M. Chem. - Eur. J. 2016, 22, 8089−8094. (b) Leitgeb, A.; Abbas, M.;
Fischer, R. C.; Poater, A.; Cavallo, L.; Slugovc, C. Catal. Sci. Technol.
2012, 2, 1640−1643.
(22) Poater, A.; Cosenza, B.; Correa, A.; Giudice, S.; Ragone, F.;
Scarano, V.; Cavallo, L. Eur. J. Inorg. Chem. 2009, 2009, 1759−1766.
(23) Falivene, L.; Credendino, R.; Poater, A.; Petta, A.; Serra, L.;
Oliva, R.; Scarano, V.; Cavallo, L. Organometallics 2016, 35, 2286−
2293.
(24) (a) Jacobsen, H.; Correa, C.; Poater, A.; Costabile, C.; Cavallo,
L. Coord. Chem. Rev. 2009, 253, 687−703. (b) Poater, A.; Falivene, L.;
Urbina-Blanco, C. A.; Manzini, S.; Nolan, S. P.; Cavallo, L. Dalton
Trans. 2013, 42, 7433−7439. (c) Ahmed, S. M.; Poater, A.; Childers,
M. I.; Widger, P. C. B.; LaPointe, A. M.; Lobkovsky, E. B.; Coates, G.
W.; Cavallo, L. J. Am. Chem. Soc. 2013, 135, 18901−18911.
(25) (a) Richmond, C. J.; Matheu, R.; Poater, A.; Falivene, L.; Benet-
Buchholz, J.; Sala, X.; Cavallo, L.; Llobet, A. Chem. - Eur. J. 2014, 20,
17282−17286. (b) Rouen, M.; Queval, P.; Borre,
́
E.; Falivene, L.;
O.; Olivier-
Poater, A.; Berthod, M.; Hugues, F.; Cavallo, L.; Basle,
́
Bourbigou, H.; Mauduit, M. ACS Catal. 2016, 6, 7970−7976.
(c) Luque-Urrutia, J. A.; Poater, A. Inorg. Chem. 2017, 56, 14383−
14387.
(26) 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,
F
DOI: 10.1021/acs.organomet.8b00102
Organometallics XXXX, XXX, XXX−XXX