Hydroxo-rhodium-N-heterocyclic carbene complexes as efficient catalyst precursors for alkyne hydrothiolation

Article abstract of DOI:10.1021/cs400739y

The new Rh-hydroxo dinuclear complexes stabilized by an N-heterocyclic carbene (NHC) ligand of type [Rh(μ-OH)(NHC)(η²-olefin)] ₂ (coe, IPr (3), IMes (4); ethylene, IPr (5)) are efficient catalyst precursors for alkyne hydrothiolation

Full text of DOI:10.1021/cs400739y

Research Article
pubs.acs.org/acscatalysis
Hydroxo−Rhodium−N-Heterocyclic Carbene Complexes as Efficient
Catalyst Precursors for Alkyne Hydrothiolation
Laura Palacios,† Maria Jose Artigas,† Victor Polo,‡ Fernando J. Lahoz,† Ricardo Castarlenas,*,†,§
Jesus J. Perez-Torrente,† and Luis A. Oro*,†,∥
́
́
†Departamento de Química Inorgan
́
ica − Instituto de Síntesis Química y Catal
́
isis Homogen
́
ea-ISQCH, Universidad de Zaragoza −
CSIC. C/Pedro Cerbuna 12, Zaragoza, Spain
‡Departamento de Química Física − Instituto de Biocomputacion
́
y Física de Sistemas complejos (BIFI), Universidad de Zaragoza,
Spain
§ARAID Foundation
∥Center for Refining & Petrochemicals, King Fahd University of Petroleum & Minerals, Dhahran, 31261, Saudi Arabia
S
* Supporting Information
ABSTRACT: The new Rh−hydroxo dinuclear complexes stabilized by an N-heterocyclic
carbene (NHC) ligand of type [Rh(μ-OH)(NHC)(η2-olefin)]2 (coe, IPr (3), IMes (4);
ethylene, IPr (5)) are efficient catalyst precursors for alkyne hydrothiolation under mild
conditions, presenting high selectivity toward α-vinyl sulfides for a varied set of substrates,
which is enhanced by pyridine addition. The structure of complex 3 has been determined
by X-ray diffraction analysis. Several intermediates relevant for the catalytic process have
been identified, including RhI-thiolato species Rh(SCH2Ph)(IPr)(η2-coe)(py) (6) and
Rh(SCH2Ph)(IPr)(η2-HCCCH2Ph)(py) (7), and the RhIII-hydride-dithiolato derivative
RhH(SCH2Ph)2(IPr)(py) (8) as the catalytically active species. Computational DFT
studies reveal an operational mechanism consisting of sequential thiol deprotonation by
the hydroxo ligand, subsequent S−H oxidative addition, alkyne insertion, and reductive
elimination. The insertion step is rate-limiting with a 1,2 thiometalation of the alkyne as
the more favorable pathway in accordance with the observed Markovnikov-type selectivity.
KEYWORDS: homogeneous catalysis, N-heterocyclic carbene, rhodium, hydroxides, hydrothiolation, DFT calculations
center.2f However, it has been shown that a bulky and powerful
INTRODUCTION
■
electron-donor ligand such as an N-heterocyclic carbene
The development of new and efficient transition-metal
(NHC)13 can stabilize these types of derivatives.4c,5h,8c,9d,14
catalyzed transformations still continues to push forward
Following our interest in the development of selective organic
organic synthesis and material science. That great level of
success has been achieved mainly due to a detailed study of the
factors that govern the reactivity of catalytic intermediate
species whose understanding is essential in order to rationally
transformations mediated by Rh−NHC catalysts,15 and
particularly on alkyne hydrothiolation16 as a direct and an
atom economical method for the preparation of vinyl sulfides,17
design active and selective catalysts.1 In this context, metal-
alkoxides, and particularly hydroxides, represent a versatile type
of derivatives that exhibit highly valuable catalytic applications
as well as interesting utility as precursors for further elaborated
organometallic complexes.2 Metal-hydroxides can be directly
involved in catalysis as key intermediates for several oxygen
nucleophile additions,3 or, alternatively, they can play the role
of initiator, behaving as an internal base that triggers varied
transformations such as hydrogenations,4 arylations,5 alkynyla-
tions,6 and cyclizations,7 among others.8 Moreover, metal-
hydroxo species are relevant synthetic organometallic pre-
cursors,9 as well as intermediates in water-splitting processes10
or advanced materials with interesting properties.11
we envisage the application of Rh−NHC−hydroxo derivatives
as promising catalysts for this transformation. In this context, it
is interesting to point out that the selectivity toward branched
or lineal derivatives can be modulated as a function of the
nature of the active organometallic catalyst.18,19 If the more
common catalytic alkyne hydrothiolation mechanism is
operative, which encompasses thiol oxidative addition, alkyne
insertion, and reductive elimination, the formation of vinyl
sulfides can be achieved through four catalytic pathways, which
arise from consecutive oxidative addition of the thiol to the
metallic center and subsequent 1,2 or 2,1 insertion of the
alkyne into Rh−H or Rh−SR bonds (Scheme 1). It becomes
evident that the understanding of the factors that govern the
The relative scarcity of late transition metal−hydroxo
complexes12 can be in part ascribed to the weakness of the
M−OH bond due to a mismatch between the hard base nature
of the hydroxo ligand and the soft acid character of the metal
Received: August 27, 2013
Revised: October 28, 2013
Published: October 30, 2013
© 2013 American Chemical Society
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Scheme 1. Insertion Pathways for the Control of the
Regioselectivity in Alkyne Hydrothiolation
elemental steps of each divergent route is fundamental for the
control of the selectivity outcome. In this direction, we have
recently found that the addition of pyridine to Rh−NHC
precursors directs the coordination of the alkyne trans to the
hydride ligand, and consequently cis to the Rh−SR bond, thus
blocking the hydrometalation pathways and allowing for the
selective formation of α-vinyl sulfide via 1,2 insertion within the
thiometalation route.15f Now, we report herein on the synthesis
and catalytic application in alkyne hydrothiolation of new Rh−
NHC−hydroxo complexes with particular emphasis on their
influence on the reaction mechanism induced by the presence
of the hydroxo bridging ligands in the catalyst precursors in
comparison with the related chlorido bridged counterparts.
Figure 1. Molecular diagram of 3. Selected bond lengths (Å) and
angles (deg): Rh−C(1) 1.935(6), Rh−O 2.077(4), Rh−O′ 2.113(4),
Rh−C(28) 2.095(6), Rh−C(29) 2.099(6), C(28)−C(29) 1.419(8);
O−Rh−O′ 75.4(2), C(1)−Rh−O 97.9(2), C(1)−Rh−O′ 172.9(2).
Complex 3 displays slightly distorted square-planar rhodium
centers with the NHC ligands disposed anti to each other and
the wingtips of the IPr and the η2-coe moiety located out of
plane. The bridging Rh2O2 core is asymmetric, presenting
different Rh−O bond distances of 2.077(4) and 2.113(4) Å, as
in other Rh−NHC dinuclear complexes.15f,21 The rhodium−
carbene separation [Rh−C(1) 1.935(6) Å] compares well with
previously reported rhodium−NHC single bond distances.13b
Catalytic Alkyne Hydrothiolation. The catalytic perform-
ance of complexes 3−5 in alkyne hydrothiolation was
examined. The addition of thiophenol to phenylacetylene was
chosen as a benchmark reaction. A 1:1 alkyne/thiol catalytic
sample was monitored in an NMR tube in 0.5 mL of C6D6
using 2 mol % loading of the catalyst (Table 1 and Figure 2).
RESULTS AND DISCUSSION
■
Preparation of Rh−NHC−Hydroxo Complexes. Prece-
dents for RhI−hydroxo derivatives stabilized by an NHC ligand
of type Rh(cod)(NHC)(OH) (cod = 1,5-cyclooctadiene) have
been very recently disclosed by the Nolan group.5h,8e Our
interest was to prepare RhI−hydroxo complexes bearing labile
mono-olefin ligands, such as ethylene or cyclooctene (coe), that
presumably could be more active in alkyne hydrothiolation with
regard to the cod counterparts, as previously shown in our
group for the halogenated derivatives.15f Thus, treatment of the
Table 1. Phenylacetylene Hydrothiolation with Thiophenol
a
(1:1)
20
chlorido bridged [Rh(μ-Cl)(NHC)(η2-coe)]2 (NHC = 1,3-
bis(2,6-diisopropylphenyl)imidazol-2-carbene (IPr), 1; 1,3-bis-
(2,4,6-trimethylphenyl)imidazol-2-carbene (IMes), 2) with
NaOH in THF led to the hydroxo bridged dinuclear complexes
[Rh(μ-OH)(NHC)(η2-coe)]2 (IPr (3), IMes (4)), which were
isolated as very air-sensitive yellow solids in 63% and 51%
yields, respectively (Scheme 2). Mono-olefin was exchanged by
Scheme 2. Preparation of Rhodium Hydroxo-Bridge
Dinuclear Compounds 3, 4, and 5
a
Reaction conditions: 0.5 mL of C6D6, 2 mol % of catalyst, 25 °C,
b
c
[alkyne] = [thiol] = 1.0 M. 10 equiv per mole of metal. Formation of
α + β-E-vinyl sulfides relative to phenylacetylene. α-Terpinene.
d
The thiol was consumed after 17 h at 25 °C when using
compound 3 as a catalyst precursor (Table 1, entry 1). The
main product was the α-vinyl sulfide, but the selectivity reached
only 79%. The formation of around 6% disulfide was detected
by GC-MS analysis. The Rh-IMes catalyst 4 displayed lower
catalytic activity and selectivity but also showed a decrease in
the formation of disulfide (Table 1, entry 3). In contrast,
catalyst 5, bearing η2-ethylene ligands, was more active and
selective, showing a turnover frequency calculated at 50%
conversion (TOF1/2) of 41 h−1. Although relatively low
selectivity was attained, a clear tendency toward the α-isomer
simply bubbling ethylene through a toluene solution of 3 to
generate [Rh(μ-OH)(IPr)(η2-ethylene)]2 (5) in 69% isolated
yield. The more noticeable resonances in the H NMR spectra
of 3−5 are those corresponding to the hydroxo-bridges
between −3.3 and −4.2 ppm. The 13C{1H} NMR spectra
confirmed the presence of the corresponding carbene and η2-
olefin ligands. The dinuclear formulation of the complexes was
further confirmed by an X-ray diffraction study of 3 (Figure 1).
1
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hexyne and benzylacetylene afforded 86% and 93% Markovni-
kov-type addition products without isomerization to internal
olefins (Table 2, entries 2 and 3). The presence of a
heteroatom in the alkyne substituent does not hamper catalytic
activity. For instance, propargyl methyl ether reacted with
thiophenol with a conversion of 91% after 21 h and 91%
selectivity to α-vinyl sulfide (Table 2, entry 4). In contrast,
hydrothiolation of 2-ethynylpyridine showed an opposite
selectivity toward the β-Z isomer (89%), which was not
detected for other substrates throughout this study (Table 2,
entry 5). Coordination of the pyridine moiety of the alkyne to
the rhodium active species probably accounts for that
unexpected result. Preferred hydrothiolation of a triple over a
double C−C bond was observed for 1-ethynyl-1-cyclohexene,
although with poor selectivity (Table 2, entry 6). Aliphatic
thiols also reacted efficiently (Table 2, entries 7−9);
particularly, hydrothiolation of a doubly protected cysteine
derivative showed the highest selectivity of 95%. Interestingly,
functionalization of cysteine is an important goal for the
synthesis of biologically active derivatives.
Figure 2. Monitoring of phenylacetylene hydrothiolation with
thiophenol catalyzed by 3−5, in the presence or absence of pyridine.
was observed for the hydroxo catalysts, in marked contrast to
the chlorido bridged counterparts 1 and 2 with which only
around 30% α-vinyl sulfide was obtained.15f We have previously
shown that the addition of pyridine to Rh-NHC based catalytic
systems results in a remarkable increase of selectivity toward
gem products probably as a result of the stabilization of
intermediate species.15f,j,22 Pleasingly, selectivity toward α-vinyl
sulfide was increased by the addition of 10 equiv of pyridine, up
to 96% for 5, although with a slight reduction in the catalytic
activity (Table 1, entries 2, 4, 6, Figure 2). Moreover, the
addition of pyridine reduced the formation of disulfide to trace
amounts (<0.5%). Addition to α-terpinene (α-TH) as a radical
scavenger to a catalytic sample of 3 and 10 equiv of pyridine did
not significantly affect either the activity or the selectivity, thus
excluding a mechanism via radical species operating with our
catalytic system (Table 1, entry 7). Indeed, the absence of any
β-Z-vinyl sulfide isomer throughout this study gives further
evidence that the metal catalyst is not competing with a
significant radical side reaction.
Mechanistic Studies. In order to disclose the mechanism
operating in the hydroxo Rh−NHC-based catalytic systems, a
series of stoichiometric low temperature reactions with complex
3 have been performed (Scheme 3). Rather surprisingly, the
Scheme 3. Detected Intermediates Relevant to the
Mechanism of Alkyne Hydrothiolation
The performance of hydroxo-catalyst precursor 3 with 10
equiv of pyridine was studied for a wide range of alkynes and
thiols (Table 2). In general, selectivity to α-vinyl sulfide was
very high, except for 1-ethynyl-1-cyclohexene and 2-ethynylpyr-
idine, although catalytic activity was lower than that found for
phenylacetylene and thiophenol. Aliphatic alkynes such as 1-
a
Table 2. Alkyne Hydrothiolation with 3 + 10 equiv py
hydroxo complexes 3−5 were stable toward bridge-cleavage by
coordinating ligands, such as PPh3 or pyridine, in contrast to
the reactivity observed for their chlorido counterparts 1 and
2.15f However, they are reactive toward acidic thiols such as
thiophenol, benzylthiol, or n-butylthiol to generate unidentified
mixtures of complexes, probably due to the formation of
intricate thiolato bridged metallic structures.23 In contrast, the
addition of benzylthiol to 3 in the presence of pyridine at room
temperature led to the formation of a new thiolato complex
24
1
Rh(SCH2Ph)(IPr)(η2-coe)(py) (6). The H and 13C{1H}
NMR spectra agree with the proposed structure. Particularly,
the singlet at δ 2.68 ppm, which correlates with a CH2−carbon
1
signal at 35.0 ppm in the H−13C HSQC spectrum, can be
ascribed to the benzylthiolato ligand, whereas the IPr and η2-
olefin show two doublets at 186.8 (JC−Rh = 55.5 Hz) and 59.4
ppm (JC−Rh = 12.9 Hz), respectively, in the 13C{1H} NMR
spectrum. Moreover, the chlorido counterpart RhCl(IPr)(η2-
coe)(py), which was characterized by X-ray diffraction analysis,
showed similar NMR data.15f Several attempts for isolation of
the new complex were unsuccessful.
a
Reaction conditions: 0.5 mL of C6D6, 2 mol % of catalyst 3 plus 10
equiv of pyridine per mole of metal, 25 °C, [alkyne] = [thiol] = 1.0 M.
b
β-Z isomer.
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The next step was the study of the behavior of the metal−
thiolato intermediate with alkynes. Treatment of a freshly
prepared sample of 6 with 2 equiv of benzylacetylene at −40 °C
gave rise to the formation of Rh(SCH2Ph)(IPr)(η2-HC
CCH2Ph)(py) (7) as a result of alkyne-coe ligand exchange
Scheme 4. Mechanistic Proposal for the Formation of α-
Vinyl Sulfides
1
(Scheme 3). The H NMR spectrum of 7 displays, in addition
to the typical signals for coordinated pyridine and IPr, a broad
signal at δ 3.70 ppm (≡CH) and two doublets at 2.50 and 1.87
ppm (CH2, JH−H = 18.5 Hz) corresponding to the η2-alkyne.25
The CH2 protons of the benzylthiolato ligand are also
diastereotopic and appear as doublets at 3.47 and 3.10 ppm
(JH−H = 17.2). Moreover, the 13C{1H}-APT NMR experiment
at −40 °C shows three doublets at 185.4 (JC−Rh = 56.5 Hz),
99.2 (JC−Rh = 12.4 Hz), and 70.7 ppm (JC−Rh = 12.5 Hz)
corresponding to the IPr and the η2-alkyne ligands, respectively.
The insertion of the alkyne into the RhI-thiolato bond could
result in the formation of a new C−S bond.26 However, for this
process to be operative, a cis alkyne-thiolato disposition is
required which is not the case in 7. In fact, heating 7 to 40 °C
for 4 h did not lead to the insertion of the alkyne into the Rh−S
bond but rather resulted in the decomposition of the sample.
The affinity of IPr and pyridine to adopt a mutually trans
disposition in RhI square-planar complexes may account for the
lack of the desired reactivity (see theoretical part for further
details).15f,27
In view that alkyne-thiolato coupling within a RhI
intermediate is hampered by the mutually trans configuration
of both ligands in 7, new catalytic pathways were explored.
Thus, the addition of 1 equiv of benzylthiol to a freshly
prepared toluene-d8 solution of 6 at −40 °C led to the
formation of the RhIII−hydride−dithiolato complex RhH-
be stabilized by the coordination of alkene, alkyne, or thiol,
being the last complex (F) which continues the catalytic cycle
through S−H oxidative addition.
DFT Calculations on the Alkyne Hydrothiolation
Mechanism. In order to support the mechanistic picture
proposed in Scheme 4, a detailed computational study using
DFT calculations (B3LYP method) has been carried out.
Theoretical calculations dealing with alkyne hydrothiolation or
insertion of an alkyne into metal−thiolato bonds are
scarce.15f,28 Because of the role of steric hindrance in the
reaction regioselectivity, the full IPr ligand has been considered
explicitly in the calculations. This mechanistic study starts at
putative complex Rh(OH)(IPr)(py)(η2-ethylene) (A) and
includes the thiol deprotonation by the hydroxo ligand (Figure
3) and the proposed alkyne hydrothiolation catalytic cycle (see
Scheme 4) via two thiometalation pathways leading to both α
and β-E-vinyl sulfides (Figure 4). All energies are relative to the
complex A and the corresponding reactants. The hydro-
metalation pathways have been also considered and reported in
the Supporting Information.
1
(SCH2Ph)2(IPr)(py) (8). The H NMR spectrum displays a
shielded metal-hydride signal at −17.54 ppm, whereas a trans
disposition of the two benzylthiolato ligands can be inferred by
the presence of two doublets at 2.69 and 2.28 ppm (JH−H = 12.2
Hz), integrating each by two protons, ascribed to the
1
diastereotopic SCH2 protons, which correlate in the H−13C
HSQC experiment with only one resonance at 35.4 ppm,
thereby confirming the chemical equivalence of both
benzylthiolato ligands. Coordination of a second molecule of
pyridine to 8 was observed at −80 °C, indicating a dynamic
equilibrium process between 8 and 8-py, as was previously
observed for similar organometallic complexes (Scheme 3).15f,j
Unfortunately, no intermediate species resulting from alkyne
insertion into a rhodium-thiolato bond could be observed after
the addition of phenylacetylene or benzylacetylene to 8;
instead, the formation of organic α-vinyl sulfides was observed,
indicating that 8 is involved in the hydrothiolation process.
Reactivity studies on 3 strongly suggest that the Markonikov-
selective alkyne hydrothiolation proceeds via RhIII−hydride−
dithiolato intermediates. A plausible mechanism is depicted in
Scheme 4. The first step is the activation of the thiol by the
hydroxo ligand to generate a RhI−thiolato intermediate
stabilized by a pyridine ligand (E), similar to 6. Then, thiol-
coe ligand exchange generates a tetracoordinated RhI species
(F) that undergoes oxidative addition of the thiol S−H bond to
form RhIII−hydride−dithiolato species (H) related to 8. The
higher trans-influence of the hydride ligand accounts for the
disposition of the vacant site in H opposite to this ligand and
thus directs coordination of the alkyne at this position in I.
Then, 1,2 insertion of the alkyne into the Rh−S bond and
subsequent hydride−alkenyl reductive elimination leads to the
α-vinyl sulfide and a putative tricoordinated species that could
Figure 3. DFT calculated ΔE (in kcal mol−1) energy profile for the
thiol deprotonation by rhodium−hydroxo precursor.
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Figure 4. DFT calculated ΔE (in kcal mol−1) along the energy surface of formation of vinyl sulfides through thiometalation. Structures J to M
correspond to α-vinyl sulfide (R1 = H, R2 = Ph, red line), and structures J′ to M′ lead to linear vinyl sulfides (R1 = Ph, R2 = H, blue line).
The initiation step of the catalytic process involves the
activation of the thiol by the hydroxo ligand of complex A to
generate a RhI−thiolato intermediate (E) similar to 6, which is
stabilized by 9.6 kcal mol−1. The external protonation of the
hydroxo ligand by the acidic thiol presents a very favorable
energetic profile via intermediates B and D and the transition
state C-TS (Figure 3).29 Compound E may exchange the
alkene ligand by another thiol molecule to yield F, which is the
starting point of the catalytic cycle. The first step of this cycle is
the S−H activation by the metal through the G-TS transition
structure, leading to the hydride-dithiolato intermediate H,
similar to 8. The activation energy of this step is 16.6 kcal mol−1
(with respect to E), and it is exothermic. The vacant site in H is
located trans to the hydride ligand, and both pyridine and
alkyne ligands can be coordinated there. The former leads to a
nonreactive species H-py with a relative energy of −16.3 kcal
mol−1, and the latter yields compound I, which is slightly more
stable (−17.3 kcal mol−1), and it can follow the catalytic cycle.
Because of the possible orientations of the coordinated
alkyne, the profile bifurcates into the two pathways leading to α
or β-E-vinyl sulfides. Hence, alkyne insertion into the Rh−S
bond takes place through transition states J-TS and J′-TS with
activation energies of 27.8 and 35.0 kcal mol−1, respectively.
Figure 5. Optimized structures for the intermediates and transition
states for migratory insertion including selected distances (Å) and
Thus, according to transition state theory, the formation of the
α-vinyl sulfide is kinetically more favorable due to the lower
energetic barrier. Both transition states display a roughly
metalacyclobutene structure including the metal, sulfur, and the
two carbon atoms of the former alkyne (Figure 5). Inspection
of the geometry of the structures reveals that J-TS is a more
advanced transition structure than J′-TS, the Rh−C bond
distance of 2.274 Å in J-TS being much shorter than that in J′-
TS (2.655 Å). Another notable fact that arises from the
comparison of both key transition states is that the phenyl
group of the former alkyne suffers from higher steric hindrance
from IPr substituents on J′-TS that may account for its relative
destabilization. Also of note is the spatial structure of the Rh−
hydride pentacoordinated species K and K′ that can be
described as a distorted trigonal bipyramid with C−Rh−S
angles of 143.8° and 137.2°, respectively.
angles (deg).
mol−1 for the α or β-E-vinyl sulfides, respectively. The
hydrometalation pathways have also been computed but
showed higher energetic barriers for the rate-limiting insertion
step (see Supporting Information).
A possible alternative reaction pathway for alkyne hydro-
thiolation could be a nonoxidative process in which the
insertion step takes place within a RhI−π-alkyne−thiolato
species. The computed coe-alkyne ligand exchange and
subsequent insertion step are presented in Figure 6. Compound
N′ represents a square-planar derivative similar to 7 in which
isomerization to a cis alkyne−thiolate species N is necessary for
the subsequent alkyne insertion into the Rh−SR bond to
generate the rhodium−alkenyl intermediate P. In this case, the
energetic barrier for the transition state O-TS is 32.8 kcal mol−1
(with regard to the lowest intermediate N′), higher than the
energetic barrier calculated for J-TS (27.8 kcal mol−1),
The cycle is closed by C−H reductive elimination through Y-
shaped transition states, L-TS and L′-TS. The energetic barriers
are considerably smaller than in the previous step, and the
overall reaction is highly exothermic, −18.8 and −22.6 kcal
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CONCLUDING REMARKS
■
The catalytic system [Rh(μ-OH)(NHC)(η2-olefin)]2/py per-
forms alkyne hydrothiolation selectively toward α-vinyl sulfides
for a varied range of alkynes and thiols under mild conditions.
Several intermediates relevant for the catalytic process have
been identified by means of NMR low temperature experi-
ments, including RhI−thiolato species, Rh(SCH2Ph)(IPr)(η2-
coe)(py) and Rh(SCH2Ph)(IPr)(η2-HCCCH2Ph)(py), and
the RhIII−hydride−dithiolato derivative RhH(SCH2Ph)2(IPr)-
(py). Computational DFT studies reveal an operational
mechanism consisting of sequential thiol deprotonation by a
hydroxo ligand, subsequent thiol SH oxidative addition, alkyne
insertion, and reductive elimination with the 1,2 thiometalation
insertion as the rate-limiting step. Further work on the
application of this catalytic system to other hydrofuntionaliza-
tion reactions is currently being developed in our laboratories.
Figure 6. DFT calculated ΔE (in kcal mol−1) energy profile for the
insertion step within a RhI−π-alkyne−thiolato square-planar inter-
mediate.
EXPERIMENTAL SECTION
■
All reactions were carried out with rigorous exclusion of air
using Schlenk-tube techniques. THF was dried over sodium
and distilled under argon prior to use; the other solvents were
obtained oxygen- and water-free from a solvent purification
system (Innovative Technologies). The organometallic pre-
cursors [Rh(μ-Cl)(NHC)(η2-coe)]2 (IPr, 1; IMes, 2)20 were
prepared as previously described in the literature. NMR spectra
were recorded either on a Varian Gemini 2000 300 MHz, a
Bruker ARX 300 MHz, a Bruker Avance 400 MHz, or a Bruker
Avance 500 MHz instrument. Chemical shifts (expressed in
parts per million) are referenced to residual solvent peaks (1H,
13C{1H}). Coupling constants, J, are given in Hz. Spectral
assignments were achieved by a combination of 1H−1H COSY,
indicating that the pathway presented in Figure 4 is more
favorable.
Interestingly, the activity and selectivity of the catalytic
systems [Rh(μ-OH)(NHC)(η2-olefin)]2/py and [Rh(μ-Cl)-
(NHC)(η2-olefin)]2/py15f can be straightforwardly compared
because the respective active species, RhH(SR)2(IPr)(py) and
RhHCl(SR)(IPr)(py), are closely related RhIII−hydride species.
Experimentally, it is found that the hydroxo-based [Rh(μ-
OH)(NHC)(η2-olefin)]2/py catalytic system is less active but
slightly more selective than the chlorido-based system. The
calculated reaction mechanism is quite similar for both catalysts
with the migratory insertion being the rate-limiting step and
that decisive for shifting the catalytic outcome toward the
formation of the thermodynamically less favorable product. The
DFT studies show that the activation energies for the rate-
limiting step are 27.8 and 24.0 kcal mol−1 for the [Rh]−OH
and [Rh]−Cl catalysts, respectively. The different selectivity
between [Rh]−OH and [Rh]−Cl catalysts can be explained
considering the energy differences between the activation
energies of the rate-limiting steps of the paths leading to α or β-
E-vinyl sulfides, which are 7.2 and 4.3 kcal mol−1, respectively.
These values are in agreement with the better selectivity
observed for the [Rh]−OH catalyst compared to [Rh]−Cl
(Figure 7).
1
13C{1H}-APT, and H−13C HSQC/HMBC experiments. GC-
MS analyses were recorded on an Agilent 5973 mass selective
detector interfaced to an Agilent 6890 series gas chromatograph
system, using an HP-5MS 5% phenyl methyl siloxane column
(30 m × 250 mm with a 0.25 mm film thickness). The nature
of organic products was compared with previously reported
data: phenyl (1-phenylvinyl) sulfide,30 phenyl (hex-1-en-2-yl)
sulfide,31 phenyl (3-phenylprop-1-en-2-yl) sulfide,17a phenyl (3-
methoxyprop-1-en-2-yl) sulfide,19c 2-(2-(phenylthio)vinyl)-
pyridine,18l phenyl 1-(cyclohex-1-en-1-yl)vinyl sulfide,32 benzyl
(1-phenylvinyl) sulfide,18c phenyl S-(1-phenylvinyl)-N-Boc-L-
cysteine-methylester,15f and butyl (1-phenylvinyl) sulfide.33
Preparation of [Rh(μ-OH)(IPr)(η2-coe)]2 (3). A yellow
solution of 1 (160 mg, 0.126 mmol) in THF (20 mL) was
treated with NaOH (130 mg, 3.25 mmol) and stirred at room
temperature for 4 h. After filtration through Celite, the THF
was removed in vacuo and n-hexane added to induce the
precipitation of a yellow solid, which was washed with n-hexane
(3 × 3 mL) and dried in vacuo. Yield: 89 mg (63%). Anal.
Calcd for C70H102N4O2Rh2: C, 67.95; H, 8.31; N, 4.53. Found:
C, 67.63; H, 8.28; N, 4.42. 1H NMR (300 MHz, C6D6, 25 °C):
δ 7.4−7.1 (m, 12H, HPh‑IPr), 6.31(s, 4H, CHN), 3.44 (sept,
JH−H = 6.8, 8H, CHMeIPr), 2.06 (m, 4H, CHcoe), 1.71 and
1.05 (both d, JH−H = 6.8, 48H, CHMeIPr), 1.6−1.3 (br, 24H,
CH2‑coe), −3.83 (s, 2H, OH). 13C{1H}-APT NMR (75.1 MHz,
C6D6, 25 °C): δ 188.6 (d, JC−Rh = 62.2, Rh−CIPr), 145.7 (s,
C
q‑IPr), 137.9 (s, CqN), 128.8 and 124.1 (s, CHPh‑IPr), 123.5 (s,
Figure 7. Comparative information on [Rh(μ-OH)(NHC)(η2-
olefin)]2/py versus [Rh(μ-Cl)(NHC)(η2-olefin)]2/py catalytic sys-
tems from DFT studies (energies in kcal mol−1).
CHN), 55.9 (d, JC−Rh = 15.8, CHcoe), 30.0, 28.3, and 26.8
(all s, CH2‑coe), 28.3 (s, CHMeIPr), 25.6 and 24.0 (both s,
CHMeIPr).
2915
dx.doi.org/10.1021/cs400739y | ACS Catal. 2013, 3, 2910−2919

ACS Catalysis
Research Article
Preparation of [Rh(μ-OH)(IMes)(η2-coe)]2 (4). The
complex was prepared as described for 3 starting from 2
(303 mg, 0.274 mmol) and NaOH (130 mg, 3.25 mmol). A
yellow solid was obtained. Yield: 146 mg (51%). Satisfactory
microanalysis figures could not be obtained due to high air-
139.7 and 138.9 (both s, CqN), 138.0 (s, CqS), 136.0 (s, Cq‑Ph),
133.7 (s, C4‑py), 130−122 (CHPh), 123.2 and 122.7 (both s, 
CHN), 122.6 (s, C3‑py), 99.2 (d, JC−Rh = 12.4, HCC), 70.7
(d, JC−Rh = 12.5, HCC), 32.8 (s, CH2S), 31.5 (s, CCH2),
29.27, 28.9, 28.6, and 28.5 (all s, CHMeIPr), 27.0, 26.1, 25.2,
25.1, 24.0, 23.37, 23.0, and 22.8 (all s, CHMeIPr).
1
sensitivity. H NMR (300 MHz, C6D6, 25 °C): δ 6.85 (s, 2H,
CHPh‑IMes), 6.01 (s, 4H, CHN), 2.47 (s, 12H, CH3‑o‑IMes),
2.47 (s, 6H, CH3‑m‑IMes), 1.6−1.0 (br, 28H, CHcoe, CH2‑coe),
−3.31 (s, 2H, OH). 13C{1H}-APT NMR (75.1 MHz, C6D6, 25
°C): δ 187.8 (d, JC−Rh = 59.1, Rh−CIMes), 138.2 (s, Cqo‑IMes),
137.0 (s, CqN), 138.2 (s, Cqm‑IMes), 128.9 (s, CHPh‑IMes), 121.9
(s, CHN), 55.6 (d, JC−Rh = 16.4, CHcoe), 30.7, 28.1, and
27.3 (all s, CH2‑coe), 20.9 (s, CH3‑o‑IMes), 19.1 (s, CH3‑m‑IMes).
Preparation of [Rh(μ-OH)(IPr)(η2-CH2CH2)]2 (5). Eth-
ylene was bubbled through a yellow solution of 3 (159 mg,
0.121 mmol) in toluene (10 mL) at room temperature for 15
min to give a yellow solution. Then, the solution was
concentrated to ca. 1 mL and n-hexane added to induce the
precipitation of a yellow solid, which was washed with n-hexane
(3 × 3 mL) and dried in vacuo. Yield: 96 mg (69%). Anal.
Calcd for C58H82N4O2Rh2: C, 64.92; H, 7.70; N, 5.22. Found:
C, 64.78; H, 7.90; N, 5.00. 1H NMR (300 MHz, C6D6, 25 °C):
δ 7.2−7.1 (m, 12H, HPh‑IPr), 6.23 (s, 4H, CHN), 3.11 (sept,
JH−H = 6.8, 8H, CHMeIPr), 1.74 (br, 8H, CH2CH2), 1.59 and
1.01 (both d, JH−H = 6.8, 48H, CHMeIPr), −4.24 (s, 2H, OH).
13C{1H}-APT NMR (75.1 MHz, C6D6, 25 °C): δ 186.8 (d,
JC−Rh =59.5, Rh−CIPr), 146.4 (s, Cq‑IPr), 137.4 (s, CqN), 128.9
(s, CHp‑Ph‑IPr), 123.8 (s, CHm‑Ph‑IPr), 122.7 (s, CHN), 40.0
(d, JC−Rh = 16.5, CH2CH2), 28.6 (s, CHMeIPr), 25.6 and 23.7
(both s, CHMeIPr).
In Situ Formation of RhH(SCH2Ph)2(IPr)(py) (8) and
RhH(SCH2Ph)2(IPr)(py)2 (8-py). A freshly prepared solution
of 6 (0.5 mL of toluene-d8, NMR tube) from 3 (32 mg, 0.026
mmol), benzylthiol (6.1 μL, 0.052 mmol), and pyridine (8.7
μL, 0.11 mmol) was treated with benzylthiol (6.1 μL, 0.052
mmol) at −40 °C and measured immediately. Complexes 8 and
1
8-py are in dynamic equilibrium. H NMR (300 MHz, tol-d8,
−40 °C): δ 8.95 (d, JH−H = 5.0 2H, H2‑py), 7.4−6.4 (16H, HPh),
6.31 (br, 2H, CHN), 6.33 (t, JH−H = 7.4, 1H, H4‑py), 6.12
(dd, JH−H = 7.4, 5.0, 2H, H3‑py), 3.58 and 3.43 (both sept, JH−H
= 6.5, 4H, CHMeIPr), 2.69 and 2.38 (both d, JH−H = 12.2, 4H,
CH2S), 1.89, 1.21, 1.08, and 0.84 (all d, JH−H = 6.5, 24H,
1
CHMeIPr), −17.54 (d, JH−Rh = 20.2, Rh−H). H NMR (300
MHz, tol-d8, −80 °C): δ 9.47 (br, 2H, H2‑pyb), 9.08 (br, 2H,
H2‑pya), −17.32 (d, JH−Rh = 19.4, Rh−H).13C{1H}-APT NMR
(75.1 MHz, tol-d8, −40 °C): δ 176.6 (d, JC−Rh = 52.7, Rh−
CIPr), 153.8 (s, C2‑py), 147.5 and 145.8 (both s, Cq‑IPr), 146.4 (s,
CqS), 137.3 (s, CqN), 135.1 (s, C4‑py), 129.5, 129.1, 128.5,
123.7, and 123.1 (all s, CHPh), 125.5 (s, CHN), 123.7 (s,
C
3‑py), 35.4 (s, CH2S), 29.1 and 28.3 (both s, CHMeIPr), 27.5,
27.2, 23.6, and 22.8 (all s, CHMePr).
Standard Conditions for the Catalytic Alkyne Hydro-
thiolation. In a NMR tube, 0.01 equiv of catalyst was dissolved
in 0.5 mL of C6D6, and then 0.50 mmol of thiol and 0.50 mmol
of alkyne were added. The alkyne conversion to vinyl sulfide
was quantified by integration of the 1H NMR spectra. Reaction
product formation was also monitored at periodic time intervals
by using GC-MS analysis. One equivalent of α-terpinene
relative to thiol was used in the radical scavenger experiment.
Crystal Structure Determination. X-ray diffraction data
were collected at 100(2) K with graphite-monochromated Mo
Kα radiation (λ = 0.71073 Å) using narrow ω rotation (0.3°)
on a Bruker APEX DUO CCD diffractometer. Intensities were
integrated and corrected for absorption effects with SMART,34
SAINT-PLUS,35 and SADABS36 programs, included in APEX2
package. The structures were solved with the Patterson method
and refined using full matrix least-squares on F2, with SHELXS-
97 and SHELXL-97 programs, respectively.37
In-situ formation of Rh(SCH2Ph)(IPr)(py)(η2-coe) (6). A
solution 3 (32 mg, 0.026 mmol) in toluene-d8 (0.5 mL, NMR
tube) at room temperature was treated with benzylthiol (6.1
1
μL, 0.052 mmol) and pyridine (8.7 μL, 0.11 mmol). H NMR
(400 MHz, tol-d8, −10 °C): δ 8.51 (d, JH−H = 5.5, 2H, H2‑py),
7.4−6.8 (11H, HPh), 6.62 (s, 2H, CHN), 6.48 (t, JH−H = 7.6,
1H, H4‑py), 6.14 (dd, JH−H = 7.6, 5.5, 2H, H3‑py), 4.62 and 2.65
(both sept, JH−H = 6.7, 4H, CHMeIPr), 3.36 (br, 2H, CHcoe),
2.68 (s, 2H, CH2S), 1.6−1.0 (br, 12H, CH2‑coe), 1.77, 1.53,
1.11, and 1.03 (all d, JH−H = 6.7, 24H, CHMeIPr). 13C{1H}-APT
NMR (100.6 MHz, tol-d8, 25 °C): δ 186.8 (d, JC−Rh = 55.5,
Rh−CIPr), 154.4 (s, C2‑py), 148.2 and 145.6 (both s, Cq‑IPr),
147.0 (CqS), 137.1 (s, CqN), 134.8 (s, C4‑py), 129.3, 129.1,
128.8, 124.3, 123.3, and 124.3 (all s, CHPh), 123.1 (s, CHN),
122.4 (s, C3‑py), 59.4 (d, JC−Rh = 12.9, CHcoe), 35.0 (s,
CH2S), 30.3, 30.1, and 29.1 (all s, CH2‑coe), 28.8 and 28.6 (both
s, CHMeIPr), 26.8, 26.6, 24.5, and 22.5 (all s, CHMePr).
Crystal Data for Compound 3. C70H102N4O2Rh2; M =
1237.38; yellow block 0.114 × 0.086 × 0.050 mm3; triclinic; P1;
̅
a = 11.021(5), b = 11.519(5), c = 14.052(6), α = 68.604(7), β
= 73.514(6), γ =74.287(6)°; Z = 1; V = 1564.5(11) Å3; Dc
=1.313 g/cm3; μ = 0.575 mm−1; minimum and maximum
In Situ Formation of Rh(SCH2Ph)(IPr)(η2-HCCCH2Ph)-
(py) (7). A freshly prepared solution of 6 in toluene-d8 (0.5 mL,
NMR tube) from 3 (32 mg, 0.026 mmol), benzylthiol (6.1 μL,
0.052 mmol), and pyridine (8.7 μL, 0.11 mmol) was treated
absorption correction factors 0.8058 and 0.9649; 2θmax
50.70°; 11 059 reflections collected, 5529 unique (Rint
=
=
1
0.1060); number of data/restraints/parameters 5529/0/349;
final GOF 0.951; R1 = 0.0628 (3305 reflections, I > 2σ(I));
wR(F2) = 0.1317 for all data; largest difference peak 0.906 e/Å3.
Two carbon atoms of the coe ligand were found to be
disordered. They were included in the model in two different
positions with complementary occupancy factors (0.60/
0.40(1)).
Computational Details. The geometry of all structures has
been optimized with the G09 program package38 at the DFT
level using the B3LYP method39 combined with the 6-
31G(d,p) basis set for H, C, N, Cl, and S atoms40 and the
SDD pseudopotential41 for Rh. The nature of the stationary
with benzylacetylene (6.0 μL, 0.048 mmol) at −40 °C. H
1
NMR was immediately recorded at low temperature. H NMR
(400 MHz, toluene-d8, −40 °C): δ 8.44 (overlapped with free
py, H2‑py), 7.2−6.9 (16H, HPh), 6.52 and 6.30 (both d, JH−H
=
2.2, 2H, CHN), 6.38 (t, JH−H = 7.1, 1H, H4‑py), 5.97 (dd,
JH−H = 7.1, 5.1, 2H, H3‑py), 4.36, 4.04, 3.28, and 2.26 (all sept,
JH−H = 6.7, CHMeIPr), 3.70 (br, 1H, HCC), 3.47 and 3.10
(both d, JH−H = 17.2, 2H, CH2S), 2.50 and 1.87 (both d, JH−H
=
18.5, 2H, CCH2), 1.99, 1.65, 1.59, 1.15, 1.13, 1.06, 1.01, and
0.94 (all d, JH−H = 6.7, CHMeIPr). 13C{1H}-APT NMR (100.5
MHz, toluene-d8, −40 °C): δ 185.4 (d, JC−Rh = 56.5, Rh−CIPr),
152.4 (s, C2‑py), 147.6, 147.0, 145.5, and 145.1 (all s, Cq‑IPr),
2916
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ACS Catalysis
Research Article
Y.; Ogasawara, M. J. Am. Chem. Soc. 2002, 124, 5052. (e) Itooka, R.;
Miyaura, N. J. Org. Chem. 2003, 68, 6000. (f) Miura, T.; Shimada, M.;
Murakami, M. J. Am. Chem. Soc. 2005, 127, 1094. (g) Korenaga, T.;
Maenishi, R.; Hayashi, K.; Sakai, T. Adv. Synth. Catal. 2010, 352, 3247.
(h) Truscott, B. J.; Fortman, G. C.; Slawin, A. M. Z.; Nolan, S. P. Org.
Biomol. Chem. 2011, 9, 738.
points has been confirmed by frequency analysis, and intrinsic
reaction paths have been traced connecting the transition
structures with the respective minima.
ASSOCIATED CONTENT
* Supporting Information
■
S
(6) Nishimura, T.; Tokuji, S.; Sawano, T.; Hayashi, T. Org. Lett.
2009, 11, 3222.
X-ray crystallographic information files containing full details of
the structural analysis of complex 3 (CIF format). Energetic
profile of the alkyne hydrothiolation catalytic cycle via an
alternative hydrometalation pathway (Figure S1), selected
NMR spectra, and Cartesian coordinates for theoretical
calculations. This material is available free of charge via the
Internet at http://pubs.acs.org.
(7) (a) Shintani, R.; Okamoto, K.; Hayashi, T. J. Am. Chem. Soc.
2005, 127, 2872. (b) Miura, T.; Murakami, M. Org. Lett. 2005, 7, 3339.
(c) Sun, Z.-M.; Chen, S.-P.; Zhao, P. Chem.Eur. J. 2010, 16, 2619.
(8) (a) Boogaerts, I. I. F.; Nolan, S. P. J. Am. Chem. Soc. 2010, 132,
8858. (b) Motokura, K.; Nakayama, K.; Miyaji, A.; Baba, T.
ChemCatChem 2011, 3, 1419. (c) Nun, P.; Fortman, G. C.; Slawin,
A. M. Z.; Nolan, S. P. Organometallics 2011, 30, 6347. (d) Gom
́
ez-
Suarez, A.; Oonishi, Y.; Meiries, S.; Nolan, S. P. Organometallics 2013,
́
AUTHOR INFORMATION
■
32, 1106. (e) Truscott, B. J.; Slawin, A. M. Z.; Nolan, S. P. Dalton
Trans. 2013, 42, 270.
Corresponding Authors
*E-mail: rcastar@unizar.es.
*E-mail: oro@unizar.es.
(9) (a) Uson, R.; Oro, L. A.; Cabeza, J. A.; Bryndza, H. E.; Stepro, M.
P. Inorg. Synth. 1985, 23, 126. (b) Woerpel, K. A.; Bergman, R. G. J.
Am. Chem. Soc. 1993, 115, 7888. (c) Werner, H.; Wiedemann, R.;
Notes
Laubender, M.; Windmuller, B.; Wolf, J. Chem.Eur. J. 2001, 7, 1959.
̈
The authors declare no competing financial interest.
(d) Gaillard, S.; Slawin, A. M. Z.; Nolan, S. P. Chem. Commun. 2010,
46, 2742.
ACKNOWLEDGMENTS
Financial support from the Spanish Ministerio de Economia y
Competitividad (MEC/FEDER) of Spain Project (CTQ2010-
(10) (a) Milstein, D.; Calabrese, J. C.; Williams, I. D. J. Am. Chem.
Soc. 1986, 108, 6387. (b) Burn, M. J.; Fickes, M. G.; Hartwig, J. F.;
Hollander, F. J.; Bergman, R. G. J. Am. Chem. Soc. 1993, 115, 5875.
(c) Sala, X.; Romero, I.; Rodríguez, M.; Escriche, L.; Llobet, A. Angew.
Chem., Int. Ed. 2009, 48, 2482.
(11) (a) Katsoulis, D. E. Chem. Rev. 1998, 98, 359. (b) Braga, D.;
Grepioni, F. J. Chem. Soc., Dalton Trans. 1999, 1. (c) Ammam, M. J.
Mater. Chem. A 2013, 1, 6291.
■
́
́ ́
15221, CTQ2012-35665), the Diputacion General de Aragon
and the European Social Fund (E07), the ARAID Foundation,
and CONSOLIDER INGENIO-2010, under the Project
MULTICAT (CSD2009-00050), are gratefully acknowledged.
V.P. also thankfully acknowledges the resources from the
supercomputer “Memento,” technical expertise and assistance
provided by the Institute for Biocomputation and Physics of
Complex Systems (BIFI)Universidad de Zaragoza.
(12) Representative examples: (a) Oro, L. A.; Carmona, D.; Lamata,
M. P.; Apreda, M. C.; Foces-Foces, C.; Cano, F. H.; Maitlis, P. M. J.
Chem. Soc., Dalton Trans. 1984, 1823. (b) Fish, R. H.; Kim, H.-S.;
Babin, J. E.; Adams, R. D. Organometallics 1988, 7, 2250. (c) Grushin,
V. V.; Kuznetsov, V. F.; Bensimon, C.; Alper, H. Organometallics 1995,
14, 3927. (d) Gevert, O.; Wolf, J.; Werner, H. Organometallics 1996,
15, 2806. (e) Hikichi, S.; Yoshizawa, M.; Sasakura, Y.; Komatsuzaki,
H.; Moro-oka, Y.; Akita, M. Chem.Eur. J. 2001, 7, 5011. (f) Tejel, C.;
REFERENCES
■
(1) (a) Elsevier, C. J.; Reedijk, J.; Walton, P. H.; Ward, M. D. Dalton
Trans. 2003, 1869. (b) Crabtree, R. H. New J. Chem. 2011, 35, 18.
(c) Noffke, A. L.; Habtemariam, A.; Pizarro, A. M.; Sadler, P. J. Chem.
Commun. 2012, 48, 5219.
́
Ciriano, M. A.; Bordonaba, M.; Lopez, J. A.; Lahoz, F. J.; Oro, L. A.
Inorg. Chem. 2002, 41, 2348. (g) Singh, A.; Sharp, P. R. Inorg. Chim.
Acta 2008, 361, 3159. (h) Okazaki, M.; Hayashi, A.; Fu, C.-F.; Liu, S.-
T.; Ozawa, F. Organometallics 2009, 28, 902. (i) Meier, S. K.; Young,
K. J. H.; Ess, D. H.; Ten, W. J., III; Oxgaard, J.; Goddard, W. A., III;
(2) (a) Fernan
Organometallics 1986, 5, 1519. (b) Fernan
́
dez, M. J.; Esteruelas, M. A.; Jimen
́
ez, M. S.; Oro, L. A.
́
dez, M. J.; Esteruelas, M. A.;
Oro, L. A.; Apreda, M.-C.; Foces-Foces, C.; Cano, F. H. Organo-
metallics 1987, 6, 1751. (c) Bryndza, H. E.; Tam, W. Chem. Rev. 1988,
88, 1163. (d) Gilje, J. W.; Roesky, H. W. Chem. Rev. 1994, 94, 895.
(e) Bergman, R. G. Polyhedron 1995, 14, 3227. (f) Fulton, J. R.;
Holland, A. W.; Fox, D. J.; Bergman, R. G. Acc. Chem. Res. 2002, 35,
44. (g) Roesky, H. W.; Singh, S.; Yusuff, K. K. M.; Maguire, J. A.;
́
Periana, R. A. Organometallics 2009, 28, 5293. (j) Jove, F. A.; Pariya,
C.; Scoblete, M.; Yap, G. P. A.; Theopold, K. H. Chem.Eur. J. 2011,
17, 1310.
(13) (a) Hermann, W. Angew. Chem., Int. Ed. 2002, 41, 1290.
(b) Praetorius, J. M.; Crudden, C. M. Dalton Trans. 2008, 4079.
(c) Díez-Gonzalez, S.; Marion, N.; Nolan, S. P. Chem. Rev. 2009, 109,
́
Hosmane, N. S. Chem. Rev. 2006, 106, 3813. (h) Webb, J. R.; Bolano,
̃
3612. (d) Arduengo, A. J., III; Iconaru, L. I. Dalton Trans. 2009, 6903.
(e) Mata, J. A.; Poyatos, M. Curr. Org. Chem. 2011, 15, 3309.
(f) Velazquez, E. D.; Verpoort, F. Chem. Soc. Rev. 2012, 41, 7032.
(14) (a) Jazzar, R. F. R.; Bhatia, P. H.; Mahon, M. F.; Whittlesey, M.
K. Organometallics 2003, 22, 670. (b) Dible, B. R.; Sigman, M. S. J. Am.
Chem. Soc. 2003, 125, 872. (c) Braband, H.; Przyrembel, D.; Abram, U.
Z. Anorg. All. Chem. 2006, 632, 779. (d) Anantharaman, G.; Elango, K.
Organometallics 2007, 26, 1089. (e) Kownacki, I.; Kubicki, M.; Szuber,
K.; Marciniec, B. J. Organomet. Chem. 2008, 693, 321. (f) Zhou, Y.; Xi,
Z.; Chen, W.; Wang, D. Organometallics 2008, 27, 5911. (g) Saker, O.;
Mahon, M. F.; Whittlesey, M. K. Organometallics 2009, 28, 1976.
(h) Samantaray, M. K.; Shaikh, M. M.; Ghosh, P. Organometallics
2009, 28, 2267. (i) Fortman, G. C.; Slawin, A. M. Z.; Nolan, S. P.
Organometallics 2010, 46, 3966. (j) Cross, W. B.; Daly, C. G.;
Ackerman, R. L.; George, I. R.; Singh, K. Dalton Trans. 2011, 40, 495.
(k) Egbert, J. D.; Chartoire, A.; Slawin, A. M. Z.; Nolan, S. P.
Organometallics 2011, 47, 4494. (l) Mena, I.; Jaseer, E. A.; Casado, M.
T.; Gunnoe, T. B. ChemSusChem. 2011, 4, 37.
(3) (a) Jensen, C. M.; Trogler, W. C. J. Am. Chem. Soc. 1986, 108,
723. (b) Munro-Leighton, C.; Delp, S. A.; Blue, E. D.; Gunnoe, T. B.
Organometallics 2007, 26, 1483. (c) Kawamoto, T.; Hirabayashi, S.;
Guo, X.-X.; Nishimura, T.; Hayashi, T. Chem. Commun. 2009, 3528.
́
(d) Gaillard, S.; Bosson, J.; Ramon, R. S.; Nun, P.; Slawin, A. L. Z.;
Nolan, S. P. Chem.Eur. J. 2010, 13729. (e) Buil, M. L.; Cadierno, V.;
Esteruelas, M. A.; Gimeno, J.; Herrero, J.; Izquierdo, S.; Onate, E.
̃
Organometallics 2012, 31, 6861.
(4) (a) Morales-Morales, D.; Lee, D. W.; Wang, Z.; Jensen, Z. M.
Organometallics 2001, 20, 1144. (b) Hamilton, R. J.; Bergens, S. H. J.
Am. Chem. Soc. 2006, 128, 13700. (c) Castarlenas, R.; Esteruelas, M.
A.; Onate, E. Organometallics 2008, 27, 3240.
̃
(5) (a) Lautens, M.; Roy, A.; Fukuoka, K.; Fagnou, K.; Martín-
Matute, B. J. Am. Chem. Soc. 2001, 123, 5358. (b) Hayashi, T.; Inoue,
K.; Taniguchi, M.; Ogasawara, N. J. Am. Chem. Soc. 2001, 123, 9918.
(c) Mori, A.; Danda, Y.; Fujii, T.; Hirabayashi, K.; Osakada, K. J. Am.
Chem. Soc. 2001, 123, 10774. (d) Hayashi, T.; Takahashi, M.; Takaya,
A.; García-Orduna, P.; Lahoz, F. J.; Oro, L. A. Chem.Eur. J. 2013, 19,
̃
2917
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5665. (m) Truscott, B. J.; Nelson, D. J.; Lujan
́
, C.; Slawin, A. M. Z.;
M. I.;
(20) Yu, X. Y.; Patrick, B. O.; James, B. R. Organometallics 2006, 25,
4870.
Nolan, S. P. Chem.Eur. J. 2013, 24, 7904.
(15) (a) Jimen
́
ez, M. V.; Per
́
ez-Torrente, J. J.; Bartolome,
́
(21) (a) Zenkina, O. V.; Keske, E. C.; Wang, R.; Crudden, C. M.
Angew. Chem., Int. Ed. 2011, 50, 8100. (b) Zenkina, O. V.; Keske, E.
C.; Wang, R.; Crudden, C. M. Organometallics 2011, 30, 6423.
(c) Zenkina, O. V.; Keske, E. C.; Kochhar, G. S.; Wang, R.; Crudden,
C. M. Dalton. Trans. 2013, 42, 2282.
Gierz, V.; Lahoz, F. J.; Oro, L. A. Organometallics 2008, 27, 224. (b) Di
Giuseppe, A.; Castarlenas, R.; Perez-Torrente, J. J.; Lahoz, F. J.; Polo,
V.; Oro, L. A. Angew. Chem., Int. Ed. 2011, 50, 3938. (c) Palacios, L.;
́
Miao, X.; Di Giuseppe, A.; Pascal, S.; Cunchillos, C.; Castarlenas, R.;
Per
Organometallics 2011, 30, 5208. (d) Jimen
Tornos, J.; Perez-Torrente, J. J.; Modrego, F. J.; Winterle, S.;
Cunchillos, C.; Lahoz, F. J.; Oro, L. A. Organometallics 2011, 30,
́
ez-Torrente, J. J.; Lahoz, F. J.; Dixneuf, P. H.; Oro, L. A.
(22) (a) Berrisford, D. J.; Bolm, C.; Sharpless, K. B. Angew. Chem.,
́
ez, M. V.; Fernandez-
́
Int. Ed. Engl. 1995, 34, 1059. (b) Romao, C. C.; Kuhn, F. E.;
̃
̈
́
Herrmann, W. A. Chem. Rev. 1997, 97, 3197. (c) Vogl, E. M.; Groger,
̈
H.; Shibasaki, M. Angew. Chem., Int. Ed. 1999, 38, 1570. (d) Nishimura,
T.; Onoue, T.; Ohe, K.; Uemura, S. J. Org. Chem. 1999, 64, 6750.
(e) Ferreira, E. M.; Stoltz, B. M. J. Am. Chem. Soc. 2003, 125, 9578.
(f) Nasielski, J.; Hadei, N.; Achonduh, G.; Kantchev, E. A. B.; O’Brien,
C. J.; Lough, A.; Organ, M. G. Chem.Eur. J. 2010, 16, 10844.
(g) Pardey, A. J.; Longo, C. Coord. Chem. Rev. 2010, 254, 254.
(h) Neufeldt, S. R.; Sanford, M. S. Acc. Chem. Res. 2012, 45, 936.
(23) (a) Evans, D. R.; Huang, M.; Senagish, W. M.; Chege, E. W.;
Lam, Y.-F.; Fettinger, J. C.; Williams, T. N. Inorg. Chem. 2002, 41,
2633. (b) Seino, H.; Yoshikawa, T.; Hidai, M.; Mizobe, Y. Dalton
Trans. 2004, 3593. (c) Oster, S. S.; Grochowski, M. R.; Lachicotte, R.
J.; Brennessel, W. W.; Jones, W. D. Organometallics 2010, 29, 4923.
5493. (e) Mena, I.; Casado, M. A.; García-Orduna, P.; Polo, V.; Lahoz,
̃
F. J.; Fazal, A.; Oro, L. A. Angew. Chem., Int. Ed. 2011, 50, 11735.
́
(f) Di Giuseppe, A.; Castarlenas, R.; Perez-Torrente, J. J.; Crucianelli,
M.; Polo, V.; Sancho, R.; Lahoz, F. J.; Oro, L. A. J. Am. Chem. Soc.
2012, 134, 8171. (g) Azpíroz, R.; Di Giuseppe, A.; Castarlenas, R.;
Per
(h) Laz
J.; Perez-Torrente, J. J.; Oro, L. A. ChemCatChem. 2013, 5, 1133.
(i) Palacios, L.; Di Giuseppe, A.; Opalinska, A.; Castarlenas, R.; Perez-
Torrente, J. J.; Lahoz, F. J.; Oro, L. A. Organometallics 2013, 32, 2768.
(j) Rubio-Perez, L.; Azpíroz, R.; Di Giuseppe, A.; Polo, V.; Castarlenas,
R.; Per
́
ez-Torrente, J. J.; Oro, L. A. Chem.Eur. J. 2013, 19, 3812.
́
aro, G.; Iglesias, M.; Fernandez-Alvarez, F. J.; Sanz-Miguel, P.
́
́
́
́
́
ez-Torrente, J. J.; Oro, L. A. Chem.Eur. J. 2013, 19, 15304.
(d) Nguyen, D. H.; Modrego, F. J.; Cetina-Casas, J. M.; Gom
Bautista, D.; Jimenez, M. V.; Castarlenas, R.; Lahoz, F. J.; Oro, L. A.;
Perez-Torrente, J. J. Organometallics 2012, 31, 6395.
(24) (a) Osakada, K.; Hataya, K.; Yamamoto, T. Inorg. Chem. 1993,
32, 2360. (b) García, M. P.; Jimenez, M. V.; Luengo, T.; Oro, L. A. J.
ez-
́
(16) (a) Bichler, P.; Love, J. In Topics of Organometallic Chemistry;
Vigalok, A., Ed.; Springer: Heidelberg, Germany, 2010; Vol. 31, pp
36−64. (b) Beletskaya, I. P.; Ananikov, V. P. Chem. Rev. 2011, 111,
́
́
́
1596. (c) Castarlenas, R.; Di Giuseppe, A.; Perez-Torrente, J. J.; Oro,
́
L. A. Angew. Chem., Int. Ed. 2013, 52, 211. (d) Ogawa, A. In Topics of
Organometallic Chemistry; Ananikov, V. P., Tanaka, M., Eds.; Springer:
Heidelberg, Germany, 2013; Vol. 43, pp 325−360.
(17) (a) Trost, B. M.; Lavoie, A. C. J. Am. Chem. Soc. 1983, 105,
5075. (b) Johannesson, P.; Lindeberg, G.; Johansson, A.; Nikiforovich,
Organomet. Chem. 1996, 510, 189. (c) Hirano, N.; Tatesawa, S.-Y.;
Yabukami, M.; Ishihara, Y.; Hara, Y.; Komine, N.; Komiya, S.
Organometallics 2011, 30, 5110. (d) Cimadevila, F.; García, M. E.;
García-Vivo, D.; Ruiz, M. A.; Graiff, C.; Tiripicchio, A. Inorg. Chem.
2012, 51, 10427.
̀ ́
G. V.; Gogoll, A.; Synnergren, B.; LeGreves, M.; Nyberg, F.; Karlen,
(25) (a) Werner, H.; Schafer, M.; Wolf, J.; Peters, K.; von Schnering,
H. G. Angew. Chem., Int. Ed. Engl. 1995, 34, 191. (b) Alvarez, A.;
Macías, R.; Bould, J.; Cunchillos, C.; Lahoz, F. J.; Oro, L. A. Chem.
Eur. J. 2009, 15, 5428. (c) Okamoto, K.; Omoto, Y.; Ohe, K. Dalton
Trans. 2012, 41, 10926.
̈
́
A.; Hallberg, A. J. Med. Chem. 2002, 45, 1767. (c) Schaumann, E. Top.
Curr. Chem. 2007, 274, 1. (d) Fernandez de la Pradilla, R.; Tortosa,
M.; Viso, A. Top. Curr. Chem. 2007, 275, 103. (e) Ahmed, E.; Kim, F.
S.; Xin, H.; Jenekhe, S. A. Macromolecules 2009, 42, 8615. (f) Cui, Y.;
Floreancing, P. E. Org. Lett. 2012, 14, 1720.
́
(26) (a) Schollhammer, P.; Cabon, N.; Capon, J.-F.; Petillon, F. Y.;
(18) (a) Burling, S.; Field, L. D.; Messerle, B. A.; Vuong, K. Q.;
Turner, P. Dalton Trans. 2003, 4181. (b) Han, L.-B.; Zhang, C.;
Yazawa, H.; Shimada, S. J. Am. Chem. Soc. 2004, 126, 5080. (c) Cao,
C.; Fraser, L. R.; Love, J. A. J. Am. Chem. Soc. 2005, 127, 17614.
(d) Misumi, Y.; Seino, H.; Mizobe, Y. J. Organomet. Chem. 2006, 691,
3157. (e) Shoai, S.; Bichler, P.; Kang, B.; Buckley, H.; Love, J. A.
Organometallics 2007, 26, 5778. (f) Delp, S. A.; Munro-Leighton, C.;
Goj, L. A.; Ramírez, M. A.; Gunnoe, T. B.; Petersen, J. L.; Boyle, P. D.
Inorg. Chem. 2007, 46, 2365. (g) Yang, J.; Sabarre, A.; Fraser, L. R.;
Patrick, B. O.; Love, J. A. J. Org. Chem. 2009, 74, 182. (h) Field, L. D.;
Messerle, B. A.; Vuong, K. Q.; Turner, P. Dalton Trans. 2009, 3599.
(i) Yang, Y.; Rioux, R. M. Chem. Commun. 2011, 47, 6557. (j) Liu, J.;
Lam, J. W. Y.; Jin, C. K. W.; Ng, J. C. Y.; Shi, J.; Su, H.; Yeung, K. F.;
Hong, Y.; Faisal, M.; Yu, Y.; Wong, K. S.; Tang, B. Z. Macromolecules
2011, 44, 68. (k) Zhao, H.; Peng, J.; Cai, M. Catal. Lett. 2012, 142,
138. (l) Gerber, R.; Frech, C. M. Chem.Eur. J. 2012, 18, 8901.
Talarmin, J.; Muir, K. W. Organometallics 2001, 20, 1230. (b) Ikada,
T.; Mizobe, Y.; Hidai, M. Organometallics 2001, 20, 4441. (c) Kuniyasu,
H.; Yamashita, F.; Terao, J.; Kambe, N. Angew. Chem., Int. Ed. 2007,
46, 5929.
(27) (a) Sandford, M. S.; Love, J. A.; Grubbs, R. H. Organometallics
2001, 20, 5314. (b) Urbina-Blanco, C. A.; Leitgeb, A.; Slugovc, C.;
Bantreil, X.; Clavier, H.; Slawin, A. M. Z.; Nolan, S. P. Chem.Eur. J.
2011, 17, 5045.
(28) (a) Cui, Q.; Musaev, D. G.; Morokuma, K. Organometallics
1998, 17, 1383. (b) Zheng, W.; Ariafard, A.; Lin, Z. Organometallics
2008, 27, 246. (c) Wang, M.; Cheng, L.; Wu, Z. Dalton Trans. 2008,
3879. (d) Ananikov, V. P.; Gayduck, K. A.; Orlov, N. V.; Beletskaya, I.
P.; Khrustalev, V. N.; Antipin, M. Y. Chem.Eur. J. 2010, 16, 2063.
(29) (a) Oxgaard, J.; Tenn, W. J., III; Nielsen, R. J.; Periana, R. A.;
Goddard, W. A., III. Organometallics 2007, 26, 1565. (b) Silantyev, G.
A.; Filippov, O. A.; Tolstoy, P. M.; Belkova, N. V.; Epstein, L. M.;
Weisz, K.; Shubina, E. S. Inorg. Chem. 2013, 52, 1787.
(30) Silveira, C. C.; Santos, P. C. S.; Mendes, S. R.; Braga, A. L. J.
Organomet. Chem. 2008, 693, 3787.
́
(m) Cabrero-Antonino, J. R.; Leyva-Perez, A.; Corma, A. Adv. Synth.
Catal. 2012, 354, 678.
(19) (a) Kuniyasu, H.; Ogawa, A.; Sato, K.-I.; Ryu, I.; Kambe, N.;
Sonoda, N. J. Am. Chem. Soc. 1992, 114, 5902. (b) Ogawa, A.; Ikeda,
T.; Kimura, K.; Hirao, J. J. Am. Chem. Soc. 1999, 121, 5108.
(c) Ananikov, V. P.; Malyshev, D. A.; Beletskaya, I. P.; Aleksandrov, G.
G.; Eremenko, I. L. Adv. Synth. Catal. 2005, 347, 1993. (d) Ananikov,
V. P.; Orlov, L. V.; Beletskaya, I. P. Organometallics 2006, 25, 1970.
(e) Ananikov, V. P.; Orlov, N. V.; Beletskaya, I. P.; Khrustalev, V. N.;
Antipin, M. Y.; Timofeeva, T. V. J. Am. Chem. Soc. 2007, 129, 7252.
(f) Weiss, C. J.; Marks, T. J. J. Am. Chem. Soc. 2010, 132, 10533.
(g) Weiss, C. J.; Wobser, S. D.; Marks, T. J. Organometallics 2010, 29,
6308. (h) Ananikov, V. P.; Orolov, N. V.; Zalesskiy, S. S.; Beletskaya, I.
P.; Khrustalev, V. N.; Morokuma, K.; Musaev, D. G. J. Am. Chem. Soc.
2012, 134, 6637.
(31) Fiandanese, V.; Marchese, G.; Naso, F.; Ronzini, L. Synthesis
1987, 1034.
(32) Backvall, J.-E.; Ericsson, A. J. Org. Chem. 1994, 59, 5850.
̈
(33) Ikehira, H.; Tanimoto, S.; Oida, T. Bull. Chem. Soc. Jpn. 1983,
56, 2537.
(34) SMART, 5.611; Bruker AXS, Inc.: Madison, WI, 2000.
(35) SAINT+, 6.01; Bruker AXS, Inc.: Madison, WI, 2000.
(36) Sheldrick, G. M. SADABS; University of Gottingen: Gottingen,
̈
̈
Germany, 1999.
(37) (a) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(b) Sheldrick, G. M. Methods Enzymol. 1997, 276, 628. (c) Sheldrick,
G. M. Acta Crystallogr. 2008, A64, 112.
2918
dx.doi.org/10.1021/cs400739y | ACS Catal. 2013, 3, 2910−2919

ACS Catalysis
Research Article
(38) 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, J. M.; 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 A.1; Gaussian, Inc.: Wallingford, CT, 2004.
(39) (a) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
(b) Becke, A. D. J. Chem. Phys. 1993, 98, 1372. (c) Becke, A. D. J.
Chem. Phys. 1993, 98, 5648.
(40) (a) Hehre, W. J.; Ditchfield, R.; Pople, J. A. J. Chem. Phys. 1972,
56, 2257. (b) Hariharan, P. C.; Pople, J. A. Theor. Chim. Acta 1973, 28,
213−222.
(41) (a) Andrae, D.; Haussermann, U.; Dolg, M.; Stoll, H.; Preuss, H.
Theor. Chem. Acta 1990, 77, 123. (b) Dolg, M.; Stoll, H.; Preuss, H.;
Pitzer, R. M. J. Phys. Chem. 1993, 97, 5852.
2919
dx.doi.org/10.1021/cs400739y | ACS Catal. 2013, 3, 2910−2919