Synthesis of multinuclear Rh(I) complexes bearing triazolylidenes and their application in C-C and c-Si bond forming reactions

Article abstract of DOI:10.1021/acs.organomet.0c00517

Multidentate carbene ligands are valuable frameworks for the preparation of carbene complexes displaying higher nuclearity. In the present work, we report the synthesis of a series of mono- to tetra-[Rh(COD)I] complexes (3a- d) supported by mesoionic triazol-5-ylidenes. The general synthetic procedure involves the one step reaction of the appropriate triazolium (2a-d) salt in the presence of KHMDS and stoiquiometric amounts of the rhodium(I) precursor. Treatment of complexes 3a-d with an excess of carbon monoxide allows for the quantitative preparation of complexes 4a-d featuring a [Rh(CO)₂I] fragment used for the detemination of the donor properties of the new triazolylidene ligands. All complexes have been fully characterized by means of ¹H and ¹³C NMR spectroscopy, melting point, elemental analysis, and in the case of complex 3a, by X-ray crystallography. Comparison of the catalytic activity of the new rhodium complexes in C-C and C-Si bond forming processes demonstrate the enhanced performance of the tetranuclear species suggesting the possibility of strong cooperative effects in these multinuclear complexes.

Full text of DOI:10.1021/acs.organomet.0c00517

pubs.acs.org/Organometallics
Article
Synthesis of Multinuclear Rh(I) Complexes Bearing Triazolylidenes
and Their Application in C−C and C−Si Bond Forming Reactions
́
́
́
́
́
David Rendon-Nava, Jose M. Vasquez-Perez, Cesar I. Sandoval-Chavez, Alejandro Alvarez-Hernandez,
and Daniel Mendoza-Espinosa*
Cite This: https://dx.doi.org/10.1021/acs.organomet.0c00517
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: Multidentate carbene ligands are valuable frameworks for the
preparation of carbene complexes displaying higher nuclearity. In the present work,
we report the synthesis of a series of mono- to tetra-[Rh(COD)I] complexes (3a−
d) supported by mesoionic triazol-5-ylidenes. The general synthetic procedure
involves the one step reaction of the appropriate triazolium (2a−d) salt in the
presence of KHMDS and stoiquiometric amounts of the rhodium(I) precursor.
Treatment of complexes 3a−d with an excess of carbon monoxide allows for the
quantitative preparation of complexes 4a−d featuring a [Rh(CO)2I] fragment used
for the detemination of the donor properties of the new triazolylidene ligands. All
complexes have been fully characterized by means of 1H and 13C NMR
spectroscopy, melting point, elemental analysis, and in the case of complex 3a, by
X-ray crystallography. Comparison of the catalytic activity of the new rhodium
complexes in C−C and C−Si bond forming processes demonstrate the enhanced
performance of the tetranuclear species suggesting the possibility of strong
cooperative effects in these multinuclear complexes.
complexes possessing 1,2,3-triazol-5-ylidene ligands are of
mononuclear type. In fact, only a few dinuclear and trinuclear
complexes possessing a MIC donor at each metal center have
been reported in the literature,9 and the presence of tetra-
triazolylidene ligands has only recently been described.8d,10
The increasing interest in developing cleaner chemical
processes has risen particular attention in multifunctional
complexes owing to its superiority in terms of enhanced
reactivity and selectivity over their monometallic counter-
parts.11 A number of these multinuclear complexes have
demonstrated to be highly efficient as catalysts for a variety of
chemical reactions including C−C and C−N bond forming
processes, hydroaminations, and olefin polymerizations, among
others.12 The improvement in the catalytic activity and
selectivity achieved by these catalysts is attributed mainly to
cooperative interactions between proximal metal centers where
features such as intermetallic distances, three-dimensional
structures, and the enhanced probability of interaction with the
substrates play a key role.13
INTRODUCTION
■
Ever since the isolation of the first stable crystalline 1,2,3-
triazol-5-ylidene,1 and later the bis(1,2,3-triazol-5-ylidene)2
reported by Bertrand, the studies of the chemistry related to
mesoionic carbenes (MICs) has growth exponentially.
Mesoionic 1,2,3-triazolylidene ligands have received consid-
erable attention owing to their intrinsic mesoionic character
and to the fact that they have been postulated as better sigma
donors compared to their classical N-heterocyclic carbene
(NHC) counterparts.3 It is well-known that the copper(I)-
catalyzed 1,3-dipolar cycloaddition reaction of an azide to an
alkyne, known as the “click” reaction, typically leads to the
formation of 1,2,3-triazoles.4 This procedure is highly flexible
and allows numerous functionalities to be introduced in the
ligand backbone.5 Further N-alkylation results in the formation
of the substituted 1,2,3-triazolium salts, which can act as
precursors for the preparation of MICs.6
Owing to this synthetic versatility, a vast family of metal
complexes bearing 1,2,3-triazol-5-ylidenes has been reported in
the literature with the main target of testing the performance of
these complexes in various homogeneous catalytic processes.7
Recently, we have reported on such types of complexes as
catalysts for various organic transformations including Suzuki−
Miyaura cross coupling reactions, alpha arylations of ketones,
alkyne cyclizations, C−N bond forming processes, and
hydroaminations.8 Surprisingly, despite the easy access to
various triazolium frameworks, to date most of the reported
Received: July 31, 2020
https://dx.doi.org/10.1021/acs.organomet.0c00517
© XXXX American Chemical Society
Organometallics XXXX, XXX, XXX−XXX
A

Organometallics
pubs.acs.org/Organometallics
Article
In line with our interest in multimetallic complexes for
catalytic applications, we report herein the preparation and full
characterization of a series of mono- to tetra-triazolylidene-
[Rh(COD)I] complexes (3a-3d) which are obtained by the
one-step treatment of triazolium precursors (2a-d) with
KHMDS in the presence of the [Rh(COD)Cl]dimer. Reaction
of 3a-d with an excess of carbon monoxide permitted the
preparation of complexes 4a-d displaying a [Rh(CO)2I]
fragment that allowed the quantification of the sigma-donor
properties of the new ligands. Complexes 3a-d were tested in
the cross-coupling of 2-cyclohexenone with boronic acid and in
the hydrosilylation of terminal alkynes. In both catalytic
processes, the tetranuclear complex 3d displayed the best
performance and selectivity of the series, suggesting cooper-
ative effects in the multinuclear complexes. Details of the full
characterization of the new complexes and their catalytic
comparison will be discussed.
groups displayed single peaks in the range of 4.55 and 4.72
1
ppm. In solution, the H and 13C NMR patterns of triazolium
salts 2b and 2c display C2 and C3 fold axis owing to the high
symmetry in the molecules. All the NMR characterization data
for prepared triazolium 2d is consistent with the reported
literature.8d
In order to get access to the desired rhodium triazolylidene
complexes, we initially tested the reaction of triazolium salt 2a
with equimolar amounts of hexamethyldisilazane (KHMDS)
and a half equivalent of the [Rh(COD)Cl] dimer in THF at
−78 °C. After work up and purification by column
chromatography, complex 3a was isolated in 63% yield as an
air-stable yellow solid (Scheme 2).
Scheme 2. Synthesis of Complex 3a
RESULTS AND DISCUSSION
Mono- to tris-triazolium salts 2a−c were prepared according to
the procedure described in Scheme 1. The triazole precursors
■
Scheme 1. Synthesis of Triazoliums 2a−d
NMR spectroscopy studies confirmed the formation of
complex 3a by the disappearance of the acidic CH+ proton in
the 1H NMR spectra, and the observation of a low field signal
at 172.8 ppm (doublet, J = 45.7 Hz) in 13C NMR which
corresponds to the carbenic carbon bound to rhodium. With
respect to the ligands, the hydrogens of the methylene bridge
in the MIC are observed now as a pair of doublets (geminal
coupling due to nonequivalent methylene protons), while fully
asymmetric patterns for the olefinic cyclooctadiene protons are
observed. The full set of NMR patterns are consistent with
neutral square planar NHC−Rh(COD)X type complexes
where the cyclooctadiene ligand occupies two coordination
sites and the carbene and iodine centers complete the metal
coordination sphere.14 To gain further insight into the
structural features of complexes 2a and 3a, single crystals
were grown from a mixture of acetonitrile and hexanes at room
temperature (Figure 1).
(1a−d) are readily obtained in moderate to good yields (65−
98%) by the reaction of mesityl azide with the proper alkyne
through the click process. Further N-alkylation with methyl
iodide affords the corresponding triazolium salts, 2a−c, in
good yields (70−98%) after column chromatography purifica-
tion. The synthesis of triazolium salt 2d was carried out in a
similar procedure starting from tetrakis(2-propynyloxymethyl)-
methane and mesityl azide following the literature procedure
(Scheme 1).8d
Formation of triazolium salts 2a−c was easily confirmed in
1H NMR spectroscopy by the presence of the characteristic
chemical shift values of the triazolyl hydrogens (singlets)
located between 9.03 and 9.38 ppm, and the N-bound methyl
Figure 1. Molecular structures of triazolium 2a (top) and rhodium
complex 3a (bottom). Ellipsoids are shown at 40% of probability.
Coordinated solvents are omitted for clarity.
B
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Complex 3a crystallizes in the monoclinic system with the
P21/c space group (Table 1), and the monomeric structure
Scheme 3. Synthesis of Complexes 3b−d
Table 1. Crystallographic Data and Summary of Data
Collection and Structure Refinement
2a
3a
formula
fw
cryst syst
space group
T, K
a, Å
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
C38H46I2N6O4
904.61
monoclinic
P21/c
293(2)
15.4985(4)
14.8445(3)
18.7010(4)
90
112.096(3)
90
3986.50(18)
4
C27H33IN3ORh
645.37
monoclinic
P21/c
293(2)
14.4357(4)
12.2861(3)
16.4385(4)
90
109.202(3)
90
2753.30(14)
4
1.557
1.764
Z
dcalc (g·cm−3
μ, mm−1
)
1.507
12.753
41616
refl collected
min/Tmax
193149
0.898
T
0.922
Nmeasd
[Rint]
8421
7645
0.0441
0.0380
0.0654
0.0861
0.1059
1.098
in the 13C NMR spectra are displayed for 2 and 3, respectively.
In the case of complex 3d, along with the asymmetry observed
for the N-methyl hydrogens and the two core OCH2− protons,
four overlapping (171.7, 171.7, 171.5, and 171.5 ppm, J = 46.0
Hz) set of doublets for the carbenic carbon bound to rhodium
are observed. The asymmetric NMR patterns observed in
complexes 3b−d are similar to previously reported multi-
nuclear analogues8a and is related to the bulkiness associated
with the cyclooctadiene ligands and the mesityl moieties which
deter the N-methyl and methylene free rotation in these
complexes. Surprisingly, we observed that in complex 3d by
simply changing the NMR solvent from CDCl3 to CD3CN at
25 °C the N-methyl group protons were resolved as a single
peak (4.20 ppm), while the peaks for the COD hydrogens
broaden considerably. The symmetrical patterns are also
observed in the 13C NMR spectra, as only one doublet for
the carbenic carbon bound to rhodium is observed (171.73
ppm, J = 46.8 Hz). This solution behavior could be explained
by the rapid exchange of the COD ligands with CD3CN, which
allows for the Rh-carbene free rotation in complexes 3b−d.
In order to assess the donor properties of the new
triazolylidene ligands, corresponding rhodium(I) carbonyl
complexes 4a−d were prepared from the reaction of precursors
3a−d with excess of carbon monoxide in dichloromethane
(Scheme 4). Each of rhodium complexes 4a−d present only
two Rh−CO bands in agreement with the symmetric patterns
observed in NMR spectroscopy. The average CO vibration
frequency for complexes 4a (νav = 2018 cm−1), 4b (νav = 2029
cm−1), 4c (νav = 2031 cm−1), and 4d (νav = 2028 cm−1) and
the calculated TEP values15a for 4a (2034 cm−1), 4b (2043
cm−1), 4c (2045 cm−1), and 4d (2034 cm−1) indicate that the
new triazolylidenes are stronger donors compared to conven-
tional NHCs (νav = 2039−2041 cm−1)16 and cyclic(alkyl)-
(amino) carbenes (νav = 2036 cm−1)17 but slightly lower than
0.1004
0.0595
0.0678
0.1632
0.1735
1.057
R[I > 2σ(I)]
R (all data)
Rw[I > 2σ(I)]
Rw (all data)
GOF
displays a carbene−rhodium bond distance of 2.048(3) Å and
a Rh−I bond distance of 2.646(10) Å, which are in the range
of recently reported MIC−Rh analogues.15
The rhodium center is bound to the triazolylidene ligand,
the cyclooctadiene fragment (η2), and the iodine atom in a
slightly distorted square planar geometry, and no short contact
with the phenoxy moiety is observed. The carbene bond angle
in complex 3a [101.8(3)°] is slightly more acute than the
corresponding angle of triazolium salt 2a [105.5(3)°]. This
feature is consistent with the increased σ-character of the σ
lone pair orbital on the carbene atom in 3a as compared with
the C−H+ bond orbital in cationic precursor 2a (Figure 1).
With the successful metalation of monotriazolium salt 2a, we
followed a similar strategy for the preparation of the bis-, tris-,
and tetra-rhodium triazolylidene complexes. Thus, as depicted
in Scheme 3, the one-pot reaction of triazolium salts 2b−d
with excess of KHMDS and the required amounts of the
[Rh(COD)Cl] dimer (according to the MIC centers available)
produces complexes 3b−d in adequate yields (65−72%).
Purification of the complexes was achieved by chromatography
column using a mixture of hexanes/ethyl acetate as eluent and
interestingly, despite of the high degree of metalation in
complexes 3b−d, all of them display excellent solubility in
benzene, toluene, and a variety of chlorinated solvents.
Characterization of complexes was achieved by NMR
spectroscopy, melting point, and elemental analysis. In the
1
case of multinuclear complexes 3b and 3c, asymmetric H
other imidazol- and triazole-based mesoionic carbenes (νav
=
NMR patterns for N-methyl, methylene, and cyclooctadiene
protons are observed. Interestingly, two (172.3 and 172.2 ppm,
J = 45.7 Hz) and three (173.5, 173.4, and 173.3 ppm, J = 45.5
Hz) set of doublets for the carbenic carbon bond to rhodium
2016−2025 cm−1).18
Additional to the electron-donor properties of the new
ligands, the NMR data after the carbonylation process
indicates that complexes 4a−d recover symmetry in solution.
C
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
moieties also fall in the normal parameters for monodentate
MIC−rhodium complexes reported in the literature15 and
close to the values reported in the crystal structure of complex
1 (Figure 2).
Scheme 4. Synthesis of Complexes 4a−d
Some interesting trends are discovered by the calculated
structures of 3c, 3d, 4c, and 4d. In the case of the carbonyl
complexes (3c and 3d), rhodium atoms were coordinated in a
square-planar geometry with the two carbonyls always
occupying adjacent positions in the vertices of the square.
Moreover, these complexes showed an overall extended
conformation where iodine atoms are separated from nearby
atoms by distances larger than the sum of their van der Waals
radii. In contrast, complexes 4c and 4d resulted in compact
geometries with the cyclooctadiene and mesitylene groups
arranged as close as possible around the iodine atoms. The
higher proximity between the COD ligands with the vicinal
mesityl fragments in complexes 3c and 3d result in fully
asymmetric structures that are consistent with the asymmetric
For instance, all the N-methyl groups and the methylene
fragments are resolved as single sharp peaks in the H NMR
1
spectra. In 13C NMR, the removal of the cyclooctadiene
fragment is confirmed by the appearance of two new doublets
between 187.2 and 182.1 ppm, which are consistent with the
cis-arrangement of the carbonyl groups around the metal
center. Owing to the equivalence in solution, complexes 4a−d
display only one doublet for the MIC−Rh bonds (165.8−
164.2 ppm) which shift upfield when compared to the
precursors 3a−d (173.5−171.5 ppm) due to the more
electron-poor nature of the carbonylated rhodium center.
Despite our numerous efforts to crystallize the multimetallic
rhodium complexes, we were unsuccessful in obtaining X-ray
quality samples. Thus, in order to get more insight into the
structural features of the new rhodium complexes, we carried
out density functional theory (DFT) calculations, at the
B3LYP/6-31G(d,p)/LANL2DZ level of theory with Grimme’s
D3 correction and using the LANL2DZ pseudopotentials only
for transition metal atoms. As illustrated in Figure 2, the
rhodium centers in the tri- and tetranuclear complexes are
close to the expected square planar geometries which is
common for Rh(CO)2X and Rh(COD)X fragments coordi-
nated to a triazolylidene ligand. The calculated bond distances
for the Rh−MIC (2.036−2.80 Å) and Rh−I (2.767−2.838 Å)
1
patterns observed in H and 13C NMR spectroscopy.
Rhodium catalysts have shown great impact across a broad
range of organic transformations.19 Their versatility is related
to their high reactivity for both polar and nonpolar chemical
bonds such as dihydrogen, Si−H, B−H, and C−H bonds.
Additionally, in situ generated organometallic rhodium species
are highly prone to transmetalations, migratory insertions, and
reductive eliminations which increase their catalytic activity.
Owing to the high cost of rhodium(I) precursors, its use in
small amounts in catalytic processes is imperative, and a great
deal of research is focused on improving this important task. In
this context, the use of multinuclear complexes as catalysts to
enhance the rate and selectivity of catalyzed reactions is of
significant interest. A multimetallic catalyst is often substan-
tially more efficient than a monometallic catalyst of similar
structure owing to cooperative interactions among the several
metal centers and the reaction substrate.20 Motivated by the
hitherto documented enhanced performance of carbene-based
multinuclear precatalysts,12 and to evaluate the possible
cooperative effects of the multinuclear species, we decided to
test the efficiency of complexes (3a−d) in the 1,4-conjugated
addition of phenyl boronic acid to 2-cyclohexenone which has
been successfully achieved with NHC-Rh based precatalysts.21
Initial reaction conditions employed mononuclear complex 3a
in 3 mol % loading at 110 °C for 24 h of reaction in toluene. As
observed in Table 2, the conversion under these conditions is
quantitative (entry 1) and challenging the catalyst performance
by decreasing the loading to 0.1 mol % presents no change in
the conversions (entries 2−5). Changing the reaction temper-
ature to 80 °C affects the catalytic performance with a decrease
in the conversion to 82% (entry 6). The best conditions
regarding the temperature are observed with catalyst loadings
of 0.5 mol % and using benzene as solvent (entries 8−11).
With the optimized reaction conditions, we then compared
the efficiency of complexes 3a−d in the cross-coupling process
using the conditions described in the entry 10 of Table 2.
1
Monitoring of the conversions was carried out via H NMR
spectroscopy analyzing the product formation every 15 min for
a period of 2 h. We observed that conversions after the first 15
min increases gradually as the number of metal centers
increases (Table S1). Remarkably, the performance of the
tetranuclear complex (3d) is by far the most effective with
conversions of 93% after 15 min and presenting full
conversions after 45 min. After 2 h, complex 3a reaches 84%
Figure 2. Calculated geometries of complexes 3c (top right), 3d (top
left), 4c (bottom right), and 4d (bottom left) optimized at the
B3LYP/6-31G(d,p)/LANL2DZ level of theory. Mesityl groups and
hydrogen atoms omitted for clarity.
D
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
99%) using boronic acids bearing electron-donor and -with-
drawing groups. The more challenging trifluoromethylated
boronic acid (entry 6) needs heating at 110 °C to reach a
maximum conversion of 83%.
Table 2. Optimization of the 1,4-Addition of Boronic Acid
to 2-Cyclohexenone Using Complex 3a
a
Vinyl silanes are highly important reactants in organic
synthesis that can be successfully produced by means of the
metal-catalyzed hydrosilylation of alkynes.22 Despite the
relevance of this process, the quest for active and selective
catalyst still represents an important challenge as the
hydrosilylation of alkynes usually produces up to three isomers
namely, b-(Z), b-(E). and a isomers.23 With the positive results
observed in the cross-coupling reaction, we decided to further
test the activities of complexes 3a−d in the hydrosilylation of
alkynes to produce vinylsilanes. As initial screening test for the
hydrosilylation process, we carried out the reaction of
phenylacetylene with triethylsilane at 80 °C, in benzene-d6
and catalyst loadings of 0.5 mol % (based in the metal).
entry
3a (mol %)
temp (°C)
time
solvent
yield (%)
1
2
3
4
5
6
7
8
3
1
110
110
110
110
110
80
80
80
80
80
24 h
24 h
24 h
5 h
2 h
2 h
1 h
8 h
4 h
2 h
1 h
toluene
toluene
toluene
toluene
toluene
toluene
toluene
benzene
benzene
benzene
benzene
99
99
99
99
99
82
74
99
99
98
90
0.1
0.1
0.1
0.1
0.1
0.5
0.5
0.5
0.5
1
9
10
11
Monitoring of the conversions was performed by H NMR
spectroscopy analyzing the products formation at different
times over 1 h.
80
a
Reaction conditions: Phenylboronic acid (0.11 mmol), 2-cyclo-
The performance of tetranuclear complex 3d is once again
the best of the series, reaching conversions of 97% after only
20 min of reaction (Table S2). The overall yields after 1 h of
reaction reach completion for complexes 3b−d, while
mononuclear complex 3a achieves a maximum of 73% yield.
Regarding the selectivity, all four complexes are highly E-
selective with the tetranuclear complex displaying the highest
selectivity value (93%). Monitoring of the reaction using
hexenone (0.10 mmol), solvent (0.6 mL).
yield, while the conversions for the dinuclear (3b) and
trinuclear (3c) complexes are 91 and 93%, respectively.
With complex 3d as the best of the series, we then examined
the scope of the conjugated addition of a variety of boronic
acids to cyclohexenone. As depicted in Table 3, complex 3d
produces the respective addition products in high yields (91−
1
complex 3d by H NMR spectroscopy in C6D6 (Supporting
Information) demonstrated that the E/α ratio remained
constant during the reaction course, suggesting that the Z-
vinylsilane is not an intermediate in the formation of the E-
isomer or that there is not an appreciable accumulation of this
isomer.
Table 3. Scope of the 1,4-Addition of a Variety of Boronic
Acids to 2-Cyclohexenone Catalyzed by 3d
a
Once tetranuclear complex 3d was established as the best
catalyst of the series, we then explored the scope of the
hydrosylation of a variety of alkynes with triethylsilane. As
observed in Table 4, the catalytic system is compatible with a
variety of substituted phenylacetylenes featuring electron-
donor and -withdrawing groups (entries 1−10), reaching
conversions over 98% and displaying a good selectivity for the
E-isomer in all examples. The presence of potential oxygen
coordination atoms did not interfere in the hydrosilylation
although the selectivity is highly affected (entry 11). Finally,
the challenging hydrosilane addition to propargyl alcohol and
ethynyltrimethylsilane present good conversions with a high
preference to the E-isomer.
Owing to the high temperature used in the hydrosilylation
process and in order to rule out the formation of colloidal
rhodium particles as the active catalyst, the reaction of
phenylacetylene and triethylsilane using complex 3d was
disturbed by the addition of elemental mercury at different
reaction times (t = 0, 15, 30, and 60 min). We observed that
regardless of the mercury addition time the conversions are not
affected significantly. For instance, addition of mercury at t = 0
and 30 min decreases the conversions by only 7 and 3%,
respectively (Scheme S1). The small change in conversions
strongly suggest that at 80 °C the catalytic conversions of
tetranuclear complex 3d are essentially performed by
molecular species.
a
Reaction conditions: Phenylboronic acid (0.11 mmol), 2-cyclo-
Among the various catalysts employed for alkyne hydro-
silylation, those based in NHC-rhodium architectures have
attracted great attention owing to their high performance
hexenone (0.10 mmol), complex 3d (0.5 mol %, based in the metal),
b
C6D6 (0.6 mL), 2 h. Isolated yields as the average of two runs.
c
Reaction carried out at 110 °C.
E
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
complex,26 it performs better than the other catalysts presented
in Table 5.
Table 4. Scope of the Hydrosilylation of Various Alkynes
with Triethylsilane Catalyzed by Complex 3d
a
To gain deeper insight into the catalytic performance of new
complexes 3a−d, we sought on investigating the reaction order
with respect to the catalyst. Thus, we have performed a
comparative study on the hydrosilylation of phenylacetylene
with triethylsilane using different concentrations (1.0 mol %,
0.5 mol % and 0.25 mol %) of catalysts 3a−d and with a
starting concentration of phenylacetylene of 1.63 mmol.
n
Following the normalized time scale method t[cat]T reported
by Bures and co-workers,27 we found that mononuclear
complex 3a fit for a first-order reaction, while the order in
dinuclear complex 3b is not very clear under the conditions
used (Figures S62 and S63). In contrast, a second-order
reaction with respect to the catalyst is easily observed in
complexes 3c and 3d (Figures S64 and S65). Although
catalytic cooperativity in multinuclear complexes is very
difficult to prove and more formal mechanistic studies are
necessary, the results of catalyst order in 3a−d suggest that the
presence of various metals in the same ligand exert a positive
effect in the catalytic performance, suggesting an increased
local concentration of active catalytic sites under homogeneous
conditions.
CONCLUSIONS
■
In summary, we have reported the synthesis of a series of
mono- to tetra-[Rh(COD)I] complexes (3a−d) supported by
mesoionic triazol-5-ylidenes. The treatment of complexes 3a−
d with an excess of carbon monoxide allows for the
quantitative preparation of complexes 4a−d featuring a
[Rh(CO)2I] fragment which were used for the determination
of the donor properties of the new triazolylidene ligands. All
1
complexes have been fully characterized by means of H and
13C NMR spectroscopy, melting point, elemental analysis, and
in the case of complex 3a, by X-ray crystallography.
Comparison of the catalytic activity of the new rhodium
complexes in C−C and C−Si bond forming processes
demonstrate the enhanced performance of the tetranuclear
species suggesting the possibility of cooperative effects in these
multinuclear species. Interestingly, the hydrosilylation process
is highly selective toward the E-isomer in a variety of alkyne
substrates. Mercury poisoning tests indicate that at 80 °C the
hydrosilylation process catalyzed by complex 3d is essentially
performed by molecular species. Further exploration of the
catalytic potential of complexes of type 3a−d is currently being
explored in our laboratory.
a
Reaction conditions: Alkyne (0.10 mmol), triethylsilane (0.12
mmol), catalyst (0.5 mol %, based in the metal), C6D6 (0.6 mL).
Yield and E/Z/α ratios were determined by H NMR spectroscopy
using mesitylene as internal standard.
1
EXPERIMENTAL SECTION
■
Synthesis of Triazolium Salts 2a−c. Triazolium Salt 2a.
Methyl iodide (2.04 mL, 32.8 mmol) was added to 15 mL of an
acetonitrile solution of triazole 1a (640 mg, 2.18 mmol), and the
resulting clear solution was refluxed for 18 h. After reaching room
temperature, the solvent was reduced to 2/3 of the original volume,
and diethyl ether was added until a precipitate was formed. The solid
was collected by filtration and washed thoroughly with cold diethyl
ether. Pure product is obtained as yellow solid in 79% yield (749 mg,
under mild reaction conditions. Table 5 show a comparison of
the catalytic performance of complex 3d with recently reported
NHC-rhodium-based catalysts. In general, complex 3d
compares well with the few reported multinuclear NHC-
rhodium catalysts in terms of catalyst loading, conversions,
time, and reaction temperatures.24 Interestingly, complex 3d
displays a better selectivity toward the (b)-E vinylsilane isomer
compared to these dinuclear complexes; however, its selectivity
is still behind the pyridyl functionalized NHC-Rh complex
reported by Suarez and co-workers.25 Even though complex 3d
is not as active as the known Crabtree (Triso)Ir(C2H4)2
1
1.72 mmol) after removing the solvent under reduced pressure. H
NMR (CDCl3, 400 MHz) δ = 9.03 (s, 1H, CHtz), 7.22 (dd, J = 8.6,
7.8 Hz, 2H, CHar), 7.04 (d, J = 7.9 Hz, 2H, CHar), 6.98−6.93 (m, 3H,
CHar + CHmes), 5.80 (s, 2H, CH2), 4.55 (s, 3H, NCH3), 2.29 (s, 3H,
CH3), 2.02 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3) δ: 156.7
(Car), 142.7 (Ctz), 141.1 (Cmes), 134.4 (Cmes), 132.7 (Cmes), 131.0
(CHtz), 129.9 (CHar), 129.9 (CHmes), 122.7 (CHar), 115.3 (CHar),
F
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Table 5. Comparison of Complex 4 with Recently Reported NHC-Rh-Based Hydrosylation Catalyst
a
b
c
d
e
Ref 24a. Ref 24b. This work. Ref 25. Ref 26.
59.6 (CH2), 40.9 (NCH3), 21.2 (CH3), 18.1 (CH3). Found: C, 52.51;
H, 5.33; N, 9.28. Calcd for C19H22IN3O: C, 52.42; H, 5.09; N, 9.65.
Triazolium Salt 2b. Methyl iodide (1.3 mL, 20.7 mmol) was added
to 7 mL of an acetonitrile solution of bistriazole 1b (350 mg, 0.68
mmol), and the resulting clear solution was refluxed for 18 h. After
reaching room temperature, the solvent was reduced to 2/3 of the
original volume and diethyl ether was added until a precipitate was
formed. The solid was collected by filtration and washed thoroughly
with cold diethyl ether. Pure product is obtained as white solid in 68%
yield (367 mg, 0.462 mmol) after column chromatography
purification using a mixture of dichloromethane/petroleum ether
(1:1) as eluent. 1H NMR (CDCl3, 400 MHz) δ = 9.15 (s, 2H, CHtz),
7.22 (t, J = 2.3 Hz, 1H, CHar), 7.11 (t, J = 8.2 Hz, 1H, CHar), 6.96 (s,
4H, CHmes), 6.73 (dd, J = 8.2, 2.3 Hz, 2H, CHar), 5.93 (s, 4H, CH2),
4.64 (s, 6H, NCH3), 2.30 (s, 6H, CH3), 2.03 (s, 12H, CH3). 13C
NMR (100 MHz, CDCl3) δ = 158.0 (Car), 142.5 (Ctz), 141.1 (Cmes),
134.3 (Cmes), 132.3 (Cmes), 131.0 (CHar), 130.6 (CHtz), 129.8
(CHmes), 110.2 (CHar), 102.8 (CHar), 60.3 (CH2), 41.5 (NCH3),
21.2 (CH3), 18.0 (CH3). Found: C, 48.21; H, 5.01; N, 10.77. Calcd
for C32H38I2N6O2: C, 48.50; H, 4.83; N, 10.60.
NMR (100 MHz, CDCl3) δ = 158.8 (Car), 142.2 (Cmes + Ctz), 134.5
(Cmes), 132.1 (CHtz), 131.3 (Cmes), 129.9 (CHmes), 98.1 (CHar), 62.0
(CH2), 42.4 (NCH3), 21.2 (CH3), 18.4 (CH3). Found: C, 47.33; H,
4.52; N, 11.12. Calcd for C45H54I3N9O3: C, 47.01; H, 4.73; N, 10.96.
Synthesis of Complexes 3a−c. Complex 3a. Rhodium(I)
cyclooctadiene chloride dimer (28.0 mg, 0.057 mmol), potassium
hexamethyl disilazide (30.0 mg, 0.149 mmol), and triazolium salt 2a
(50.0 mg, 0.115 mmol) were combined in a Schlenk flask and
dissolved in THF (9 mL) at −78 °C. The resulting mixture was
stirred for 16 h while reaching room temperature. The final clear
suspension was dried under vacuum, and the residue was extracted
with dichloromethane (10 mL). After cannula filtration and removal
of the solvent, the crude product is purified by column
chromatography using a mixture of hexanes/ethyl acetate (8:2) as
eluent providing the title product as yellow solid in 63% yield (63 mg,
0.073 mmol). Single crystals were obtained by the slow evaporation of
a concentrated THF/acetronitrile (1:1) solution. Mp = 198−202 °C.
1H NMR (CDCl3, 400 MHz) δ = 7.41−7.34 (m, 2H, CHar), 7.21−
7.16 (m, 2H, CHar), 7.10−7.02 (m, 2H, CHmes + CHar), 6.93 (s, 1H,
CHmes), 6.30 (d, J = 12.8 Hz, 1H, CH2), 5.21 (d, J = 12.8 Hz, 1H,
CH2), 5.15−5.08 (m, 1H, CHCOD), 5.02−4.95 (m, 1H, CHCOD), 4.17
(s, 3H, NCH3), 3.69−3.63 (m, 1H, CHCOD), 3.15−3.07 (m, 1H,
CHCOD), 2.46 (s, 3H, CH3), 2.38 (s, 3H, CH3), 2.16−1.95 (m, 3H,
CH2−COD), 1.82−1.74 (m, 4H, CH3 + CHCOD), 1.72−1.58 (m, 2H,
CH2−COD), 1.54−1.46 (m, 1H, CH2−COD), 1.44−1.34 (m, 1H,
CH2−COD). 13C NMR (CDCl3, 100 MHz) δ = 172.8 (d, J = 45.7
Hz, CRh), 157.9 (Car), 141.3 (Ctz), 140.0 (Cmes), 136.2 (Cmes),
135.8 (Cmes), 134.5 (Cmes), 129.7 (CHmes), 129.7 (CHar), 128.2
(CHmes), 122.0 (CHar), 115.3 (CHar), 94.4 (d, J = 7.2 Hz, CHCOD),
93.8 (d, J = 6.9 Hz, CHCOD), 72.8 (d, J = 13.9 Hz, CHCOD), 71.0 (d, J
= 13.8 Hz, CHCOD), 63.3 (CH2), 37.2 (NCH3), 33.5 (CH2−COD),
Triazolium Salt 2c. Methyl iodide (1.6 mL, 24.8 mmol) was added
to 10 mL of an acetonitrile solution of tristriazole 1c (400 mg, 0.55
mmol), and the resulting clear solution was refluxed for 18 h. After
reaching room temperature, the solvent was reduced to 2/3 of the
original volume, and diethyl ether was added until a precipitate was
formed. The solid was collected by filtration and washed thoroughly
with cold diethyl ether. Pure product is obtained as yellow solid in
98% yield (620 mg, 0.54 mmol) after removing the solvent under
1
reduced pressure. H NMR (CDCl3, 400 MHz) δ = 9.38 (s, 3H,
CHtz), 7.09 (s, 3H, CHar), 6.93 (s, 6H, CHmes), 5.97 (s, 6H, CH2),
4.72 (s, 9H, NCH3), 2.29 (s, 9H, CH3), 2.06 (s, 18H, CH3). 13C
G
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
31.1 (CH2−COD), 30.1 (CH2−COD), 28.7 (CH2−COD), 21.2 (CH3),
21.2 (CH3), 17.6 (CH3). FT-IR in KBr (cm−1): 3432, 2926, 2873,
2830, 2348, 1601, 1495, 1453, 1236, 1177, 1152, 1074, 1032, 856,
753. Found: C, 50.13; H, 5.25; N, 6.77. Calcd for C27H32IN3ORh: C,
50.33; H, 5.01; N, 6.52.
CH2−COD). 13C NMR (CDCl3, 100 MHz) δ = 171.7 (d, J = 44.1 Hz,
CRh), 171.7 (d, J = 45.4 Hz, CRh), 171.5 (d, J = 45.9 Hz, C
Rh), 171.5 (d, J = 46.0 Hz, CRh), 141.9 (Ctz), 141.9 (Ctz), 139.9
(Cmes), 136.2 (Cmes), 136.0 (Cmes), 134.6 (Cmes), 134.5 (Cmes), 129.8
(CHmes), 128.8 (Cmes), 128.4 (CHmes), 94.2 (CHCOD), 93.5
(CHCOD), 93.4 (CHCOD), 72.6 (CHCOD), 72.5 (CHCOD), 70.8
Complex 3b. Following the procedure for the synthesis of complex
3a and using rhodium(I) cyclooctadiene chloride dimer (31.0 mg,
0.063 mmol), potassium hexamethyl disilazide (32.0 mg, 0.164
mmol), and bistriazolium salt 2b (50.0 mg, 0.063 mmol), the title
product is purified by column chromatography using a mixture of
hexanes/ethyl acetate (8:2) as eluent. Yellow solid, 72% yield (55 mg,
(CH2−C ), 70.6 (CH2−Cpent), 66.1 (CH2), 66.0 (CH2), 46.9
pent
(Cpent), 38.2 (NCH3), 38.1 (NCH3), 34.3 (CH2−COD), 30.7
(CH2−COD), 30.5 (CH2−COD), 28.7 (CH2−COD), 28.6 (CH2−COD),
28.1 (CH2−COD), 21.3 (CH3), 21.2 (CH3), 18.0 (CH3), 18.0 (CH3).
Found: C, 45.32; H, 5.37; N, 7.02. Calcd for C89H120I4N12O4Rh4: C,
45.70; H, 5.08; N, 7.19. FT-IR in KBr (cm−1): 3446, 2916, 2872,
2823, 1614, 1447, 1326, 1262, 1153, 1072, 1030, 956, 853, 799. [ESI-
MS, positive mode]: M+ = 2340.6 m/z; [M+ − I]+ 2213.6 m/z.
General Synthesis of Carbonylated Complexes 4a−c.
Carbon monoxide was bubbled for 15 min to a solution of the
appropriate [Rh(COD)Cl]-triazolylidene (0.05 mmol) in 10 mL of
CH2Cl2. The light-orange solution turned slightly yellow. The solvent
was removed under vacuum, and the residue was washed thrice with 5
mL of petroleum ether to produce the pure carbonylated complex.
Complex 4a. Yellow solid, 89% yield (0.0445 mmol). Mp = 238−
240 °C. 1H NMR (CDCl3, 400 MHz) δ = 7.36−7.31 (m, 2H, CHar),
7.14−7.10 (m, 2H, CHar), 7.05−7.01 (m, 1H, CHar), 6.99 (s, 2H,
CHmes), 5.54 (s, 2H, CH2), 4.27 (s, 3H, NCH3), 2.37 (s, 3H, CH3),
2.03 (s, 6H, CH3). 13C NMR (CDCl3, 100 MHz) δ = 187.1 (d, J =
52.7 Hz, Rh−CO), 182.2 (d, J = 77.3 Hz, Rh−CO), 165.8 (d, J = 38.8
Hz, CRh), 157.0 (Car), 143.2 (Ctz), 143.2 (Ctz), 140.8 (Cmes),
135.7 (Cmes), 134.7 (Cmes), 129.8 (CHar), 129.4 (CHmes), 122.2
(CHar), 115.3 (CHar), 62.0 (CH2), 37.8 (NCH3), 21.3 (CH3), 18.6
(CH3). FT-IR in KBr (cm−1): 3444,2919, 2850, 2052 (CO), 1983
(CO), 1598, 1586, 1487, 1462, 1231, 1169, 1078, 1034, 1016,
1014, 861, 845. Found: C, 42.77; H, 3.89; N, 7.51. Calcd for
C21H21IN3O3Rh: C, 42.52; H, 3.57; N, 7.08.
1
0.045 mmol). Mp = 163−166 °C. H NMR (CDCl3, 400 MHz) δ =
7.39 (t, J = 8.16, 1H, CHar), 7.08 (s, 2H, CHmes), 6.94 (s, 2H, CHmes),
6.93−6.88 (m, 3H, CHar), 6.34−6.28 (m, 2H, CH2), 5.25−5.17 (m,
2H, CH2), 5.13−5.05 (m, 2H, CHCOD), 5.02−4.95 (m, 2H, CHCOD),
4.22−4.17 (m, 6H, NCH3), 4.76−4.68 (m, 2H, CHCOD), 3.18−3.10
(m, 2H, CHCOD), 2.46 (s, 6H, 2CH3), 2.39 (s, 6H, 2CH3), 2.19−2.09
(m, 2H, CH2−COD), 2.07−1.95 (m, 4H, CH2−COD), 1.88−1.74 (m,
8H, CH3 + CH2−COD), 1.69−1.55 (m, 4H, CH2−COD), 1.54−1.45 (m,
2H, CH2−COD), 1.43−1.33 (m, 2H, CH2−COD). 13C NMR (CDCl3,
100 MHz) δ = 172.3 (d, J = 45.7 Hz, CRh), 172.2 (d, J = 45.7 Hz,
CRh), 158.3 (Car), 139.9 (Ctrz), 130.0 (Cmes), 135.2 (Cmes), 134.8
(Cmes), 133.5 (Cmes), 129.5 (CHar), 128.7 (CHmes), 127.2 (CHmes),
107.1 (CHar), 101.9 (CHar), 101.8 (CHar), 93.3 (CHCOD),93.3
(CHCOD), 93.2 (CHCOD), 93.2 (CHCOD), 93.0 (CHCOD), 93.0
(CHCOD), 92.9 (CHCOD), 92.9 (CHCOD), 71.9 (CHCOD), 71.8
(CHCOD), 69.9 (CHCOD), 69.8 (CHCOD), 62.1 (s, CH2), 36.1
(NCH3), 32.6 (CH2−COD), 29.9 (CH2−COD), 29.2 (CH2−COD), 27.6
(CH2−COD), 20.1 (CH3), 16.7 (CH3). FT-IR in KBr (cm−1): 3446,
2923, 2364, 2059, 1606, 1446, 1382, 1330, 1283, 1236, 1156, 1132,
1035, 908, 850, 760. Found: C, 47.41; H, 4.66; N, 6.69. Calcd for
C48H59I2N6O2Rh2: C, 47.58; H, 4.91; N, 6.94.
Complex 3c. Following the procedure for the synthesis of complex
3a and using rhodium(I) cyclooctadiene chloride dimer (32.0 mg,
0.065 mmol), potassium hexamethyl disilazide (34.0 mg, 0.169
mmol), and tristriazolium salt 2c (50.0 mg, 0.043 mmol), the title
product is purified by column chromatography using a mixture of
dichloromethane/ethanol (95:5) as eluent. Yellow solid, 65% yield
Complex 4b. Yellow solid, 99% yield (0.0498 mmol). Mp = 236−
1
238 °C. H NMR (CDCl3, 400 MHz) δ = 7.27 (t, J = 8.3 Hz, 1H,
CHar), 6.99 (s, 4H, CHmes), 6.88 (t, J = 2.3 Hz, 1H, CHar), 6.80 (dd, J
= 8.3, 2.4 Hz, 2H, CHar), 5.51 (s, 4H, CH2), 4.29 (s, 6H, NCH3),
2.37 (s, 6H, CH3), 2.03 (s, 12H, CH3). 13C NMR (CDCl3, 100 MHz)
δ = 187.1 (d, J = 52.7 Hz, Rh−CO), 182.2 (d, J = 77.4 Hz, Rh−CO),
165.8 (d, J = 38.9 Hz, CRh), 158.5 (Car), 143.0 (Ctz), 143.0 (Ctz),
140.9 (Cmes), 135.7 (Cmes), 134.8 (Cmes), 130.6 (CHar), 129.5
(CHmes), 108.5 (CHar), 103.2 (CHar), 62.1 (CH2), 37.8 (NCH3),
21.4 (CH3), 18.7 (CH3). FT-IR in KBr (cm−1): 3450, 2924, 2850,
2066 (CO), 1992 (CO), 1599, 1489, 1450,1328, 1248, 1180,
1147, 1031, 850. Found: C, 39.31; H, 3.52; N, 7.30. Calcd for
C36H36I2N6O6Rh2: C, 39.01; H, 3.27; N, 7.58.
1
(50 mg, 0.028 mmol). Mp = 250−252 °C. H NMR (CDCl3, 400
MHz) δ = 7.02 (s, 3H, CHmes), 6.89 (s, 3H, CHmes), 6.62−6.55 (m,
3H, CHar) 6.32−6.22 (m, 3H, CH2), 5.15−5.08 (m, 3H, CH2), 5.03−
4.96 (m, 3H, CHCOD), 4.95−4.89 (m, 3H, CHCOD), 4.16 (s, 9H,
NCH3), 3.75−3.68 (m, 3H, CH2−COD), 3.13−3.05 (m, 3H,
CH2−COD), 2.40 (s, 9H, CH3), 2.33 (s, 9H, CH3), 2.15−2.05 (m,
3H, CH2−COD), 1.98−1.88 (m, 6H0, CH2−COD), 1.83−1.68 (m, 12H,
CH3 + CH2−COD), 1.60−1.50 (m, 6H, CH2−COD), 1.47−1.38 (m, 3H,
CH2−COD), 1.37−1.28 (m, 3H, CH2−COD). 13C NMR (CDCl3, 100
MHz) δ = 173.5 (d, J = 45.5 Hz, CRh), 173.4 (d, J = 45.6 Hz, C
Rh), 173.3 (d, J = 45.5 Hz, CRh), 160.4 (Car), 140.8 (Ctz), 140.1
(Cmes), 136.2 (Cmes), 135.9 (Cmes), 134.7 (Cmes), 129.8 (CHmes),
128.4 (CHmes), 95.4 (CHar), 95.3 (CHar), 94.3 (CHCOD), 94.2
(CHCOD), 73.3 (CHCOD), 73.2 (CHCOD), 63.0 (CH2), 37.3 (NCH3),
33.9 (CH2−COD), 30.9 (CH2−COD), 30.4 (CH2−COD), 28.6
(CH2−COD), 21.3 (CH3), 18.1 (CH3), 18.0 (CH3). Found: C,
46.51; H, 5.12; N, 7.24. Calcd for C70H90I3N9O3Rh3: C, 46.84; H,
5.05; N, 7.02. FT-IR in KBr (cm−1): 3433, 2916, 2372, 2172, 1605,
1439, 1377, 1329, 1245, 1159, 1042, 854. [ESI-MS, positive mode]:
M+ = 1794.9 m/z; [M+ − I]+ 1669.9 m/z.
Complex 4c. Yellow solid, 80% yield (0.040 mmol). Mp = 233−
1
234 °C. H NMR (CDCl3, 400 MHz) δ = 6.99 (s, 6H, CHmes), 6.57
(s, 3H, CHar), 5.49 (s, 6H, CH2), 4.30 (s, 9H, NCH3), 2.37 (s, 9H,
CH3), 2.04 (s, 18H, CH3). 13C NMR (CDCl3, 100 MHz) δ = 187.2
(d, J = 52.6 Hz, Rh−CO), 182.1 (d, J = 77.2 Hz, Rh−CO), 165.6 (d, J
= 38.9 Hz, CRh), 159.4 (Car), 142.8 (Ctz), 142.8 (Ctz), 140.9
(Cmes), 135.7 (Cmes), 134.7 (Cmes), 129.4 (CHmes), 96.2 (CHar), 62.1
(CH2), 37.9 (NCH3), 21.3 (CH3), 18.7 (CH3). Found: C, 38.56; H,
3.42; N, 7.88. Calcd for C52H54I3N9O9Rh3: C, 38.12; H, 3.32; N, 7.69.
FT-IR in KBr (cm−1): 3450, 2924, 2855, 2176, 2067 (CO), 1995
(CO), 1951, 1605, 1453, 1378, 1330, 1252, 1155, 1036, 851.
[MALDI-TOF MS, positive mode], M+ = 1623.4529 m/z; [M+
5CO]+ = 1479.977 m/z.
−
Complex 3d. Following the procedure for the synthesis of complex
3a and using rhodium(I) cyclooctadiene chloride dimer (33.0 mg,
0.066 mmol), potassium hexamethyl disilazide (34.0 mg, 0.173
mmol), and tetratriazolium salt 2d (50.0 mg, 0.033 mmol), the title
product is purified by precipitation with petroleum ether. Yellow
solid, 69% yield (54 mg, 0.023 mmol). Mp = 260−261 °C. 1H NMR
(CDCl3, 400 MHz) δ = 6.99 (s, 4H, CHmes), 6.86 (s, 4H, CHmes),
5.08−5.37 (m, 8H, CH2), 4.92 (s, 8H, CHCOD), 4.25−4.10 (m, 12H,
NCH3), 3.95−3.80 (m, 8H, CH2), 3.54 (s, 4H, CHCOD), 3.02 (s, 4H,
CHCOD), 2.37 (s, 12H, CH3), 2.31 (s, 12H, CH3), 2.27−2.15 (m, 4H,
CH2−COD), 2.05−1.90 (m, 8H, CH2−COD), 1.77−1−67 (m, 16H, CH3
+ CH2−COD), 1.66−1.57 (m, 4H, CH2−COD), 1.42−1.25 (m, 8H,
Complex 4d. Yellow solid, 99% yield (0.0498 mmol). Mp = 218−
1
220 °C. H NMR (CDCl3, 400 MHz) δ = 6.98 (s, 8H, CHmes), 5.58
(s, 8H, CH2), 4.31 (s, 12H, NCH3), 3.76 (s, 8H, CH2), 2.36 (s, 12H,
CH3), 2.07 (s, 24H, CH3). 13C NMR (CDCl3, 100 MHz) δ = 187.1
(d, J = 52.5 Hz, Rh−CO), 182.3 (d, J = 77.4 Hz, Rh−CO), 164.2 (d, J
= 38.7 Hz, CRh), 143.6 (d, J = 2.0 Hz, Ctz), 140.8 (Cmes), 135.7
(Cmes), 134.7 (Cmes), 129.5 (CHmes), 70.3 (CH2), 64.6 (CH2), 38.3
(NCH3), 21.3 (CH3), 18.8 (CH3). Found: C, 36.05; H, 3.64; N, 8.02.
Calcd for C65H72I4N12O12Rh4: C, 36.61; H, 3.41; N, 7.88. FT-IR in
KBr (cm−1): 3453, 2922, 2855, 2064 (CO), 1992 (CO), 1607,
H
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
1449, 1327, 1259, 1166, 1075, 1030, 853, 802. [MALDI-TOF MS,
positive mode] M+ = 2132.6029 m/z [M+ + H − I+] 2003.964 m/z.
Catalytic 1,4-Addition of Boronic Acids to 2-Cyclohexe-
none. A scintillation vial was charged with the proper phenyl boronic
acid (0.11 mmol), KOH (42 mg, 0.75 mmol), 2-cyclohexenone (10
mg, 0.10 mmol), and catalyst 3d (0.5 mol %, based in the metal).
Benzene (5 mL) was added, and the mixture heated at 80 °C. Product
formation was monitored by TLC. The solvent was removed under
vacuum, and the products were purified by column chromatography
using proper hexanes/ethyl acetate mixtures as eluent.
ACKNOWLEDGMENTS
■
D.M.-E. is grateful to CONACYT for financial support (project
A1-S-8892). C.I.S−C is grateful to Grant Catedra-CONACYT-
2016-222.
́
REFERENCES
■
(1) Guisado-Barrios, G.; Bouffard, J.; Donnadieu, B.; Bertrand, G.
Crystalline 1H-1,2,3-triazol-5-ylidenes: New Stable Mesoionic Car-
benes. Angew. Chem., Int. Ed. 2010, 49, 4759−4762.
(2) Guisado-Barrios, G.; Bouffard, J.; Donnadieu, B.; Bertrand, G.
Bis(1,2,3-triazol-5-ylidenes) (i-bitz) as Stable 1,4-Bidentate Ligands
Based on Mesoionic Carbenes (MICs). Organometallics 2011, 30,
6017−6021.
General Procedure for the Catalytic Hydrosilylation
Reactions. An NMR tube was charged with the tiethylsylane (1.2
equiv), the proper alkyne (1.0 equiv), and the catalyst (0.5 mol %,
based in the metal). Deuterated benzene was added (0.7 mL), and the
mixture heated at 80 °C. Product formation and selectivity were
1
(3) (a) Albrecht, M. C4-bound imidazolylidenes: from curiosities to
high-impact carbene ligands. Chem. Commun. 2008, 3601−3610.
(b) Schuster, O.; Yang, L.; Raubenheimer, H. G.; Albrecht, M.
Beyond Conventional N-Heterocyclic Carbenes: Abnormal, Remote,
and Other Classes of NHC Ligands with Reduced Heteroatom
Stabilization. Chem. Rev. 2009, 109, 3445−3478. (c) Schweinfurth,
D.; Hettmanczyk, L.; Suntrup, L.; Sarkar, B. Metal Complexes of
Click Derived Triazoles and Mesoionic Carbenes: Electron Transfer,
Photochemistry, Magnetic Bistability, and Catalysis. Z. Anorg. Allg.
Chem. 2017, 643, 554−584. (d) Guisado-Barrios, G.; Soleilhavoup,
M.; Bertrand, G. 1H-1,2,3-Triazol-5-ylidenes: Readily Available
Mesoionic Carbenes. Acc. Chem. Res. 2018, 51, 3236−3244.
(e) Vivancos, A.; Segarra, C.; Albrecht, M. Mesoionic and Related
Less Heteroatom-Stabilized N-Heterocyclic Carbene Complexes:
Synthesis, Catalysis, and Other Applications. Chem. Rev. 2018, 118,
9493−9586. (f) Crabtree, R. H. Abnormal, Mesoionic and Remote N-
Heterocyclic Carbenes. Coord. Chem. Rev. 2013, 257, 755−766.
(4) (a) Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Click Chemistry:
Diverse Chemical Function from a Few Good Reactions. Angew.
Chem., Int. Ed. 2001, 40, 2004−2021. (b) Rostovtsev, V. V.; Green, L.
G.; Fokin, V. V.; Sharpless, K. B. A Stepwise Huisgen Cycloaddition
Process: Copper(I)-catalyzed Regioselective “Ligation” of Azides and
Terminal Alkynes. Angew. Chem., Int. Ed. 2002, 41, 2596−2599.
(c) Tornøe, C. W.; Christensen, C.; Meldal, M. Peptidotriazoles on
Solid Phase: [1,2,3]-Triazoles by Regiospecific Copper(I)-Catalyzed
1,3-Dipolar Cycloadditions of Terminal Alkynes to Azides. J. Org.
Chem. 2002, 67, 3057−3064.
(5) For selected reviews, see (a) Liang, L.; Astruc, D. The copper(I)-
catalyzed alkyne-azide cycloaddition (CuAAC) “click” reaction and its
applications. An overview. Coord. Chem. Rev. 2011, 255, 2933−2945.
(b) Diez-Gonzalez, S. Well-defined copper(I) complexes for Click
azide-alkyne cycloaddition reactions: one Click beyond. Catal. Sci.
Technol. 2011, 1, 166−178. (c) Hein, J. E.; Fokin, V. V. Copper-
catalyzed azide-alkynecycloaddition (CuAAC) and beyond: new
reactivity of copper(I) acetylides. Chem. Soc. Rev. 2010, 39, 1302−
1315. (d) Meldal, M.; Tornøe, C. W. Cu-Catalyzed Azide-Alkyne
Cycloaddition. Chem. Rev. 2008, 108, 2952−3015. (e) Bock, V. D.;
Hiemstra, H.; van Maarseveen, J. H. CuI-Catalyzed Alkyne-Azide
“Click” Cycloadditions from a Mechanistic and Synthetic Perspective.
Eur. J. Org. Chem. 2006, 2006, 51−68.
determined by H NMR spectroscopy using mesitylene as internal
standard.
ASSOCIATED CONTENT
■
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.0c00517.
Experimental procedures. Sample H and 13C NMR for
new compounds and catalytic products (PDF)
1
Cartesian coordinates (XYZ)
Accession Codes
CCDC 1977420 and 1977421 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
■
Corresponding Author
Daniel Mendoza-Espinosa − Área Académica de Química,
Universidad Autónoma del Estado de Hidalgo, Mineral de la
Reforma, Hidalgo 42090, México; orcid.org/0000-0001-
9170-588X; Email: daniel_mendoza@uaeh.edu.mx
Authors
́
David Rendon-Nava − Área Académica de Química,
Universidad Autónoma del Estado de Hidalgo, Mineral de la
Reforma, Hidalgo 42090, México
Jose M. Vasquez-Perez − Conacyt Research Fellow, Área
Académica de Química, Universidad Autónoma del Estado de
Hidalgo, Mineral de la Reforma, Hidalgo 42090, México;
orcid.org/0000-0002-2389-2646
Cesar I. Sandoval-Chavez − Conacyt Research Fellow, Área
Académica de Química, Universidad Autónoma del Estado de
Hidalgo, Mineral de la Reforma, Hidalgo 42090, México
́
́
(6) See, for example, (a) Mathew, P.; Neels, A.; Albrecht, M. 1,2,3-
Triazolylidenes as Versatile Abnormal Carbene Ligands for Late
Transition Metals. J. Am. Chem. Soc. 2008, 130, 13534−13535.
(b) Karthikeyan, T.; Sankararaman, S. Palladium complexes with
abnormal N-heterocyclic carbene ligands derived from 1,2,3-
triazolium ions and their application in Suzuki coupling. Tetrahedron
Lett. 2009, 50, 5834−5837. (c) Poulain, A.; Canseco-Gonzalez, D.;
Hynes-Roche, R.; Muller-Bunz, H.; Schuster, O.; Stoeckli-Evans, H.;
Neels, A.; Albrecht, M. Synthesis and Tunability of Abnormal 1,2,3-
Triazolylidene Palladium and Rhodium Complexes. Organometallics
2011, 30, 1021−1029.
́
́
Alejandro Alvarez-Hernandez − Área Académica de
Química, Universidad Autónoma del Estado de Hidalgo,
Mineral de la Reforma, Hidalgo 42090, México;
orcid.org/0000-0002-4937-6944
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.0c00517
(7) For recent reports on the coordination chemistry of MICs, see
(a) Saravanakumar, R.; Ramkumar, V.; Sankararaman, S. Synthesis
and Structure of 1,4-Diphenyl-3-methyl-1,2,3-triazol-5-ylidene Palla-
dium Complexes and Application in Catalytic Hydroarylation of
Notes
The authors declare no competing financial interest.
I
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Alkynes. Organometallics 2011, 30, 1689−1694. (b) Schulze, B.;
Complexes of Rh2, Ir2, and RhIr: A Stepwise Metalation Strategy
for the Synthesis of di-MIC-Bridged Mixed-Metal Systems. Organo-
metallics 2012, 31, 5384−5395. (e) Keske, E. C.; Zenkina, O. V.;
Wang, R.; Crudden, C. M. Synthesis and Structure of Silver and
Rhodium 1,2,3-Triazol-5-ylidene Mesoionic Carbene Complexes.
Organometallics 2012, 31, 456−461. (f) Mejuto, C.; Guisado-
Barrios, G.; Gusev, D.; Peris, E. First homoleptic MIC and
heteroleptic NHC-MIC coordination cages from 1,3,5-triphenylben-
zene-bridged tris-MIC and tris-NHC ligands. Chem. Commun. 2015,
51, 13914−13917. (g) Sinha, N.; Tan, T. T. Y.; Peris, E.; Hahn, E.
High-Fidelity, Narcissistic Self-Sorting in the Synthesis of Organo-
metallic Assemblies from Poly-NHC Ligands. Angew. Chem., Int. Ed.
2017, 56, 7393−7397. (h) Al-Shnani, F.; Guisado-Barrios, G.; Sainz,
D.; Peris, E. Tris-triazolium Salts as Anion Receptors and as
Precursors for the Preparation of Cylinder-like Coordination Cages.
Organometallics 2019, 38, 697−701.
̈
̈
Escudero, D.; Friebe, C.; Siebert, R.; Gorls, H.; Kohn, U.; Altuntas, E.;
Baumgaertel, A.; Hager, M. D.; Winter, A.; et al. A Heteroleptic
Bis(tridentate) Ruthenium(II) Complex of a Click-Derived Abnormal
Carbene Pincer Ligand with Potential for Photosensitzer Application.
Chem. - Eur. J. 2011, 17, 5494−5498. (c) Bezuidenhout, D. I.;
Kleinhans, G.; Guisado- Barrios, G.; Liles, D. C.; Ung, G.; Bertrand,
G. Isolation of a potassium bis(1,2,3-triazol-5-ylidene)carbazolide: a
stabilizing pincer ligand for reactive late transition metal complexes.
Chem. Commun. 2014, 50, 2431−2433. (d) Hohloch, S.; Kaiser, S.;
Duecker, F. L.; Bolje, A.; Maity, R.; Kosmrlj, J.; Sarkar, B. Catalytic
oxygenation of sp3 “C-H” bonds with Ir(III) complexes of chelating
triazoles and mesoionic carbenes. Dalton Trans. 2015, 44, 686−693.
(e) Mendoza-Espinosa, D.; Alvarez-Hernandez, A.; Angeles- Beltran,
D.; Negron-Silva, G. E.; Suarez-Castillo, O. R.; Vasquez- Perez, J. M.
Bridged N-Heterocyclic/Mesoionic (NHC/MIC) Heterodicarbenes
as Ligands for Transition Metal Complexes. Inorg. Chem. 2017, 56,
2092−2099. (f) Ruiz-Mendoza, F. J.; Mendoza-Espinosa, D.;
Gonzalez-Montiel, S. Synthesis and Catalytic Activity of Coumarin-
and Chrysin-Tethered Triazolylidene Gold(I) Complexes. Eur. J.
Inorg. Chem. 2018, 2018, 4622−4629. (g) Schweinfurth, D.;
Hettmanczyk, L.; Suntrup, L.; Sarkar, B. Metal Complexes of Click-
Derived Triazoles and Mesoionic Carbenes: Electron Transfer,
Photochemistry, Magnetic Bistability, and Catalysis. Z. Anorg. Allg.
Chem. 2017, 643, 554−584. (h) Priante-Flores, A.; Salazar-Pereda, V.;
Rheingold, A. L.; Mendoza-Espinosa, D. Synthesis and character-
ization of a gold(I) bis(triazolylidene) complex featuring a large
[(TpMe2)2K] anion. New J. Chem. 2018, 42, 15533−15537. (i) Mejuto,
C.; Royo, B.; Guisado-Barrios, G.; Peris, E. Rhodium, Iridium and
Nickel Complexes with a 1,3,5-triphenylbenzene tris-MIC ligand.
Study of the Electronic Properties and Catalytic Activities. Beilstein J.
Org. Chem. 2015, 11, 2584−2590.
(10) Frutos, M.; de la Torre, M. C.; Sierra, M. A. Steroid Derived
Mesoionic Gold and Silver Mono- and Polymetallic Carbenes. Inorg.
Chem. 2015, 54, 11174−11185.
(11) (a) Shibasaki, M.; Yamamoto, Y. Multimetallic Catalysts in
Organic Synthesis; Wiley-VHC: Weinheim, Germany, 2005. (b) Haak,
R. M.; Wezenberg, S. J.; Kleij, A. W. Cooperative multimetallic
catalysis using metallosalens. Chem. Commun. 2010, 46, 2713−2723.
(c) Sammis, G. M.; Danjo, H.; Jacobsen, E. N. Cooperative Dual
Catalysis: Application to the Highly Enantioselective Conjugate
Cyanation of Unsaturated Imides. J. Am. Chem. Soc. 2004, 126, 9928−
9929. (d) Yamagiwa, N.; Qin, H.; Matsunaga, S.; Shibasaki, M. Lewis
Acid-Lewis Acid Heterobimetallic Cooperative Catalysis: Mechanistic
Studies and Application in Enantioselective Aza-Michael Reaction. J.
Am. Chem. Soc. 2005, 127, 13419−13427.
(12) (a) Rajabi, F.; Thiel, W. R. An Efficient Palladium N-
Heterocyclic Carbene Catalyst Allowing the Suzuki-Miyaura Cross-
Coupling of Aryl Chlorides and Arylboronic Acids at Room
Temperature in Aqueous Solution. Adv. Synth. Catal. 2014, 356,
1873−1877. (b) Magano, J.; Dunetz, J. R. Large-Scale Applications of
Transition Metal-Catalyzed Couplings for the Synthesis of Pharma-
ceuticals. Chem. Rev. 2011, 111, 2177−2250. (c) Maity, A.; Sulicz, A.
N.; Deligonul, N.; Zeller, M.; Hunter, A. D.; Gray, T. G. Suzuki-
Miyaura coupling of arylboronic acids to gold(III). Chem. Sci. 2015, 6,
981−986. (d) Broussard, M. E.; Juma, B.; Train, S. G.; Peng, W. J.;
Laneman, S. A.; Stanley, G. G. A bimetallic hydroformylation catalyst:
high regioselectivity and reactivity through homobimetallic coopera-
tivity. Science 1993, 260, 1784−1788. (e) Gonell, S.; Poyatos, M.;
Peris, E. Triphenylene-Based Tris(N-Heterocyclic Carbene) Ligand:
Unexpected Catalytic Benefits. Angew. Chem., Int. Ed. 2013, 52,
7009−7013. (f) Poyatos, M.; Mata, J. A.; Peris, E. Complexes with
Poly(N-heterocyclic carbene) Ligands: Structural Features and
Catalytic Applications. Chem. Rev. 2009, 109, 3677−3707.
(13) See, for example, (a) Bratko, I.; Gomez, M. Polymetallic
complexes linked to a single-frame ligand: cooperative effects in
catalysis. Dalton Trans. 2013, 42, 10664−10681. (b) Park, J.; Hong, S.
Cooperative bimetallic catalysis in asymmetric transformations. Chem.
Soc. Rev. 2012, 41, 6931−6943. (c) Allen, A. E.; MacMillan, D. W. C.
Synergistic catalysis: A powerful synthetic strategy for new reaction
development. Chem. Sci. 2012, 3, 633−658. (d) van der Vlugt, I. J.
Cooperative Catalysis with First-Row Late Transition Metals. Eur. J.
Inorg. Chem. 2012, 2012, 363−375. (e) van den Beuken, E. K.;
Feringa, L. B. Bimetallic Catalysis by the Late Transition Metal
Complexes. Tetrahedron 1998, 54, 12985−13011. (f) Mata, J. A.;
Hahn, F. E.; Peris, E. Heterometallic Complexes, Tandem Catalysis
and Catalytic Cooperativity. Chem. Sci. 2014, 5, 1723−1732.
(14) (a) Jimenez, M. V.; Perez-Torrente, J. J.; Bartolome, M. I.;
Gierz, V.; Lahoz, F. J.; Oro, L. A. Rhodium(I) Complexes with
Hemilabile N-Heterocyclic Carbenes: Efficient Alkyne Hydrosilyla-
tion Catalysts. Organometallics 2008, 27, 224−234. (b) Praetorius, J.
M.; Crudden, C. M. N-Heterocyclic carbene complexes of rhodium:
structure, stability and reactivity. Dalton Trans. 2008, 31, 4079−4094.
(c) Jansen, E.; Lutz, M.; de Bruin, B.; Elsevier, C. J. Charge-
́
́
(8) (a) Mendoza-Espinosa, D.; Gonzalez-Olvera, R.; Negron-Silva,
́
́
́
́
G. E.; Angeles-Beltran, D.; Suarez-Castillo, O. R.; Alvarez-Hernandez,
A.; Santillan, R. Phenoxy-Linked Mesoionic Triazol-5-ylidenes as
Platforms for Multinuclear Transition Metal Complexes. Organo-
́
metallics 2015, 34, 4529−4542. (b) Mendoza-Espinosa, D.; Gonzalez-
́
́
́
Olvera, R.; Osornio, C.; Negron-Silva, G. E.; Alvarez-Hernandez, A.;
́
Bautista-Hernandez, C. I.; Suarez-Castillo, O. R. Structural diversity of
phenoxy functionalized triazol-5-ylidene palladium(II) complexes and
their application in C-N bond formation. J. Organomet. Chem. 2016,
803, 142−149. (c) Mendoza-Espinosa, D.; Rendon-Nava, D.; Alvarez-
́
Hernandez, A.; Angeles-Beltran, D.; Negron-Silva, G. E.; Suarez-
I
III
Castillo, O. R. Visible-Light-Promoted Au to Au
Oxidation in
Triazol-5-ylidene Complexes. Chem. - Asian J. 2017, 12, 203−207.
(d) Flores-Jarillo, M.; Mendoza-Espinosa, D.; Salazar-Pereda, V.;
Gonzalez-Montiel, S. Synthesis and Catalytic Benefits of Tetranuclear
Gold(I) Complexes with a C4-Symmetric Tetratriazol-5-ylidene.
Organometallics 2017, 36, 4305−4312. (e) Flores-Jarillo, M.;
́
Salazar-Pereda, V.; Ruiz-Mendoza, F. J.; Alvarez-Hernandez, A.;
Suarez-Castillo, O. R.; Mendoza-Espinosa, D. Expedient Synthesis of
Highly Functionalized Abnormal Carbenegold(I) Complexes. Inorg.
́
Chem. 2018, 57, 28−31. (f) Rendon-Nava, D.; Alvarez-Hernandez, A.;
Rheingold, A. L.; Suarez-Castillo, O. R.; Mendoza-Espinosa, D.
Hydroxyl-functionalized triazolylidene-based PEPPSI complexes:
metallacycle formation effect on the Suzuki coupling reaction. Dalton
Trans 2019, 48, 3214−3222.
(9) (a) Maity, R.; Mekic, A.; van Der Meer, M.; Verma, A.; Sarkar, B.
Triply cyclometalated trinuclear iridium(III) and trinuclear
palladium(II) complexes with a tri-mesoionic carbene ligand. Chem.
Commun. 2015, 51, 15106−15109. (b) Maity, R.; van der Meer, M.;
Hohloch, S.; Sarkar, B. Di- and Trinuclear Iridium(III) Complexes
with Poly-Mesoionic Carbenes Synthesized through Selective Base-
Dependent Metalation. Organometallics 2015, 34, 3090−3096.
(c) Vivancos, A.; Albrecht, M. Influence of the Linker Length and
Coordination Mode of (Di)Triazolylidene Ligands on the Structure
and Catalytic Transfer Hydrogenation Activity of Iridium(III)
Centers. Organometallics 2017, 36, 1580−1590. (d) Zamora, M. T.;
Ferguson, M. J.; Cowie, M. Di-Mesoionic Carbene-Bridged
J
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Delocalized κ2C,N-NHC-Amine Complexes of Rhodium, Iridium, and
Ruthenium. Organometallics 2014, 33, 2853−2861.
Compounds. Chem. Rev. 1997, 97, 2063−2192. (c) Denmark, S. E.;
Sweis, R. F. Design and Implementation of New, Silicon-Based,
Cross-Coupling Reactions: Importance of Silicon-Oxygen Bonds. Acc.
Chem. Res. 2002, 35, 835−846. (d) Komiyama, T.; Minami, Y.;
Hiyama, T. Recent Advances in Transition-Metal-Catalyzed Synthetic
Transformations of Organosilicon Reagents. ACS Catal. 2017, 7,
631−651.
(23) (a) Marciniec, B.; Maciejewski, H.; Pietraszuk, C.; Pawluc, P.
Hydrosilylation of Alkynes and their derivatives. In Hydrosilylation. A
Comprehensive Review of Recent Advances; Marciniec, B., Ed.; Springer:
Berlin, 2009. (b) Lim, D. S. W.; Anderson, E. A. Synthesis of
Vinylsilanes. Synthesis 2012, 44, 983−1010. (c) Trost, B. M.; Ball, Z.
T. Addition of Metalloid Hydrides to Alkynes: Hydrometallation with
Boron, Silicon, and Tin. Synthesis 2005, 2005, 853−887.
(15) See, for example, (a) Tolley, L. C.; Strydom, I.; Louw, W. J.;
Fernandes, M. A.; Bezuidenhout, D. I.; Guisado-Barrios, G. Diverse
Coordination Modes of Bidentate COC and Tridentate CNC Ligands
Comprising 1,2,3-Triazol-5-ylidenes. ACS Omega 2019, 4, 6360−
6374. (b) Sluijter, S. N.; Elsevier, C. J. Synthesis and Reactivity of
Heteroditopic Dicarbene Rhodium(I) and Iridium(I) Complexes
Bearing Chelating 1,2,3-Triazolylidene-Imidazolylidene Ligands.
Organometallics 2014, 33, 6389−6397. (c) Makhloufi, A.; Frank,
W.; Ganter, C. Diamino- and Mixed Amino-Amido-N-Heterocyclic
Carbenes Based on Triazine Backbones. Organometallics 2012, 31,
2001−2008. (d) Lazaro, G.; Iglesias, M.; Fernandez-Alvarez, F. J.;
Sanz Miguel, P. J.; Perez-Torrente, J. J.; Oro, L. A. Synthesis of
Poly(silyl ether)s by Rhodium(I)-NHC Catalyzed Hydrosilylation:
Homogeneous versus Heterogeneous Catalysis. ChemCatChem 2013,
5, 1133−1141. (e) Steinbeck, M.; Frey, G. D.; Schoeller, W. W.;
Herrmann, W. A. Synthesis and characterization of chiral mono N-
heterocyclic carbene-substituted rhodium complexes and their
catalytic properties in hydrosilylation reactions. J. Organomet. Chem.
2011, 696, 3945−3954.
(24) (a) Diachenko, V.; Page, M. J.; Gatus, M. R. D.; Bhadbhade,
M.; Messerle, B. A. Bimetallic N-Heterocyclic Carbene Rh(I)
Complexes: Probing the Cooperative Effect for the Catalyzed
Hydroelementation of Alkynes. Organometallics 2015, 34, 4543−
4552. (b) Huckaba, A. J.; Hollis, T. K.; Howell, T. O.; Valle, H. U.;
Wu, Y. Synthesis and Characterization of a 1,3-Phenylene-Bridged N-
Alkyl Bis(benzimidazole) CCC-NHC Pincer Ligand Precursor:
Homobimetallic Silver and Rhodium Complexes and the Catalytic
Hydrosilylation of Phenylacetylene. Organometallics 2013, 32, 63−69.
(25) Morales-Ceron, J. P.; Lara, P.; Lopez-Serrano, J.; Santos, L. L.;
Salazar, V.; Alvarez, E.; Suarez, A. Rhodium(I) Complexes with
Ligands Based on N-Heterocyclic Carbene and Hemilabile Pyridine
Donors as Highly E Stereoselective Alkyne Hydrosilylation Catalysts.
Organometallics 2017, 36, 2460−2469.
(16) Furstner, A.; Alcarazo, M.; Krause, H.; Lehmann, C. W.
Effective Modulation of the Donor Properties of N-Heterocyclic
Carbene Ligands by “Through-Space” Communication within a
Planar Chiral Scaffold. J. Am. Chem. Soc. 2007, 129, 12676−12677.
(17) Lavallo, V.; Canac, Y.; Dehope, A.; Donnadieu, B.; Bertrand, G.
A rigid cyclic (alkyl)(amino)carbene ligand leads to isolation of low-
coordinate transition-metal complexes. Angew. Chem., Int. Ed. 2005,
44, 7236−7239.
(18) (a) Melaimi, M.; Soleilhavoup, M.; Bertrand, G. Stable cyclic
carbenes and related species beyond diaminocarbenes. Angew. Chem.,
Int. Ed. 2010, 49, 8810−8849. (b) Donnelly, K. F.; Petronilho, A.;
Albrecht, M. Application of 1,2,3-triazolylidenes as versatile NHC-
type ligands: synthesis, properties, and application in catalysis and
beyond. Chem. Commun. 2013, 49, 1145−1159.
(26) Tanke, R. S.; Crabtree, R. H. Unusual activity and selectivity in
alkyne hydrosilylation with an iridium catalyst stabilized by an
oxygen-donor ligand. J. Am. Chem. Soc. 1990, 112, 7984−7989.
́
(27) Bures, J. A Simple Graphical Method to Determine the Order
in Catalyst. Angew. Chem., Int. Ed. 2016, 55, 2028−2031.
(19) (a) Beller, M.; Bolm, C. Transition Metals for Organic Synthesis:
Building Blocks and Fine Chemicals; Wiley-VCH, 2004. (b) Evans, P.
A. Modern Rhodium-Catalyzed Organic Reactions; Wiley-VCH, 2005.
(20) (a) Gavrilova, A. L.; Bosnich, B. Principles of Mononucleating
and Binucleating Ligand Design. Chem. Rev. 2004, 104, 349−384.
(b) Shibasaki, M.; Matsunaga, S. Design and application of linked-
BINOL chiral ligands in bifunctional asymmetric catalysis. Chem. Soc.
Rev. 2006, 35, 269−279. (c) Delferro, M.; Marks, T. J. Multinuclear
Olefin Polymerization Catalysts. Chem. Rev. 2011, 111, 2450−2485.
(d) Park, J.; Hong, S. Cooperative bimetallic catalysis in asymmetric
transformations. Chem. Soc. Rev. 2012, 41, 6931−6943.
(21) (a) Ramasamy, B.; Prakasham, A. P.; Gangwar, M. K.; Ghosh,
P. 1,4-Conjugate Addition of Aryl boronic Acids on Cyclohexenone as
Catalyzed by Rhodium(I) Complexes of C2-Symmetric Bioxazoline
Fused N-heterocyclic Carbenes. Chem. Select 2019, 4, 8526−8533.
(b) Mejuto, C.; Escobar, L.; Guisado-Barrios, G.; Gusev, D.; Ballester,
P.; Peris, E. Self-Assembly of Di-N-Heterocyclic Carbene-Gold-
Adorned Corannulenes on C60. Chem. - Eur. J. 2017, 23, 10644−
10651. (c) Bratko, I.; Guisado-Barrios, G.; Favier, I.; Mallet-Ladeira,
S.; Teuma, E.; Peris, E.; Gomez, M. Triazolium Salts as Appropriate
Catalytic Scaffolds for 1,4-Additions to a, b-Unsaturated Carbonyls.
Eur. J. Org. Chem. 2014, 2014, 2160−2167. (d) Mejuto, C.; Guisado-
Barrios, G.; Peris, E. Novel Rhodium and Iridium Complexes
Coordinated to C3-symmetric Tris-NHC ligands Based on a 1,3,5-
Triphenylbenzene Core. Electronic and Catalytic Properties. Organo-
metallics 2014, 33, 3205−3211. (e) Penafiel, I.; Pastor, I. M.; Yus, M.;
̃
Esteruelas, M. A.; Olivan, M. Preparation, Hydrogen Bonds, and
Catalytic Activity in Metal Promoted Addition of Arylboronic Acids
to Enones of a Rhodium Complex Containing an NHC Ligand with
an Alcohol Funtion. Organometallics 2012, 31, 6154−6161.
(22) (a) Langkopf, E.; Schinzer, D. Uses of Silicon-Containing
Compounds in the Synthesis of Natural Products. Chem. Rev. 1995,
95, 1375−1408. (b) Fleming, I.; Barbero, A.; Walter, D. Stereo-
chemical Control in Organic Synthesis Using Silicon-Containing
K
https://dx.doi.org/10.1021/acs.organomet.0c00517
Organometallics XXXX, XXX, XXX−XXX