O-functionalised NHC ligands for efficient nickel-catalysed c-o hydrosilylation

Article abstract of DOI:10.2533/CHIMIA.2020.483

A series of C,O-bidentate chelating mesoionic carbene nickel(ii) complexes [Ni(NHC^PhO)₂] (NHC = imidazolylidene or triazolylidene) were applied for hydrosilylation of carbonyl groups. The catalytic system is selective towards aldehyde reduction and tolerant to electron-donating and -withdrawing group substituents. Stoichiometric experiments in the presence of different silanes lends support to a metal-ligand cooperative activation of the Si-H bond. Catalytic performance of the nickel complexes is dependent on the triazolylidene substituents. Butyl-substituted triazolylidene ligands impart turnover numbers up to 7,400 and turnover frequencies of almost 30,000 h^-1, identifying this complex as one of the best-performing nickel catalysts for hydrosilylation and demonstrating the outstanding potential of O-functionalised NHC ligands in combination with first-row transition metals.

Full text of DOI:10.2533/CHIMIA.2020.483

NoN-Noble Metals iN Catalysis
CHIMIA 2020, 74, No. 6 483
doi:10.2533/chimia.2020.483
Chimia 74 (2020) 483–488 © S. Bertini, M. Albrecht
O-Functionalised NHC Ligands for Efficient
Nickel-catalysed C–O Hydrosilylation
Simone Bertini and Martin Albrecht*
Abstract: A series of C,O-bidentate chelating mesoionic carbene nickel(ii) complexes [Ni(NHC^PhO)2] (NHC =
imidazolylidene or triazolylidene) were applied for hydrosilylation of carbonyl groups. The catalytic system is
selective towards aldehyde reduction and tolerant to electron-donating and -withdrawing group substituents.
Stoichiometric experiments in the presence of different silanes lends support to a metal–ligand cooperative ac-
tivation of the Si–H bond. Catalytic performance of the nickel complexes is dependent on the triazolylidene sub-
stituents. Butyl-substituted triazolylidene ligands impart turnover numbers up to 7,400 and turnover frequencies
of almost 30,000 h-1, identifying this complex as one of the best-performing nickel catalysts for hydrosilylation
and demonstrating the outstanding potential of O-functionalised NHC ligands in combination with first-row
transition metals.
Keywords: NHC ligands · Nickel catalysis
Simone Bertini received his BSc and MSc isation, a popular approach constitutes the implementation of
in Chemistry from the University of Rome N-donor groups.[3] Less common is the introduction of O-donor
TorVergata.In2016hemovedtoSwitzerland sites,[4] despite the attractiveness of this type of donors for se-
for his doctoral studies in the group of Prof. lected applications. For example, oxygen sites are fundamen-
Albrecht, where he earned his PhD as a tal for hydrogen bonding.[5] In addition, this functionalisation
early stage researcher (ESR) for the Marie is key for stabilising typically oxophilic first-row transition
Sklodowska-Curie Initial Training Network metals for catalytic applications, one of the major challenges
Non-Noble Metal Catalysis (NoNoMeCat). for developing sustainable catalysts based on Earth-abundant
His research focus is the synthesis, charac- metals.[6] In the absence of chelating stabilization, the M–CNHC
terization and catalytic applications of first- bond is generally unstable and limits the catalytic application.
row transition metal complexes bearing strong donor ligands such This instability was demonstrated to be a key issue for the ap-
as (mesoionic) N-heterocyclic carbenes.
plication of triazolylidene-based mesoionic NHC nickel com-
plexes in Suzuki-cross coupling, which takes place with high
Martin Albrecht studied Chemistry in initial turnover frequencies but rapidly stalls due to Ni–C bond
Bern and graduated with Gerard van Koten cleavage and ensuing catalyst degradation.[7] We have therefore
at Utrecht University (NL) in 2000. After become interested in enhancing the stability of these complex-
postdoctoral work with Bob Crabtree at es by ligand functionalisation and have developed a new class
Yale and with Ciba SC (Basel), he started of O-donor substituted NHC ligands based on the imdazole,[8]
independent research as an Alfred Werner as well as the triazole scaffold. Nickelation under mild condi-
Assistant Professor in Fribourg, then joined tions afforded the bis-carbene nickel(ii) complexes 1a–c, 2 (Fig.
the faculty at University College Dublin and 1).[9] Here, these complexes were investigated as precursors for
returned in 2015 to his alma mater. His re- the catalytic hydrosilylation of carbonyl groups, providing one
search revolves around the ligand-induced of the fastest and most robust nickel-based catalytic systems
control and expansion of the reactivity of metal centres, particu- known to date.[10,11]
larly for catalytic applications. He is fascinated by new ligand
classes such as mesoionic N-heterocyclic carbenes, and recently
also by their N-donor analogues.
N
N
N
N
N
N
N
N
1. Introduction
N
N
O
O
O
O
O
The use of chelating ligands has become an established
methodology for the development of homogeneous catalysts
with long lifetime.[1] This concept has also been implemented to
N-heterocycliccarbene(NHC)complexes,whichisfacilitatedby
thesyntheticversatilityandeasyaccessibilityofNHCscaffolds.[2]
Introduction of chelating sites has been successfully employed
to tailor properties of the metal centre such as coordination
geometry, electron density, and stability of the metal–carbon
N
N
R
R
Mes
Ni
Ni
Ni
Mes
O
N
N
N
N
R: Ph 1a
R: Bu 1b
1c
2
bond. Among the countless possibilities for NHC functional- Fig. 1. Oxygen-functionalized NHC nickel(ii) complexes.
*Correspondence: Prof. M. Albrecht, E-mail: martin.albrecht@dcb.unibe.ch
Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland

484 CHIMIA 2020, 74, No. 6
NoN-Noble Metals iN Catalysis
ous relevance and both the trans configured complex 1c as well
as the cis isomers (1a,b) show catalytic performance that is in
line with wingtip substituent effects only. The relatively low ac-
tivity of complex 2 indicates that the nickel complexes contain-
ing mesoionic ligands outperform the imidazolylidene analogue.
Performing the reaction in the presence of simple nickel chloride
as precatalyst did not lead to any detectable conversion (entry 5),
suggesting an essential role of the carbene ligand for enabling
catalytic activity.
2. Results and Discussion
Hydrosilylation with complexes 1a–c and 2 was initially
probed at a 2 mol% catalyst loading using 4-methylbenzaldehyde
as model substrate and phenylsilane as hydrosilylation agent. The
reaction proceeded to completion with complex 1b in 1,2-dichlo-
roethane, affording 4-methylbenzyloxysilane in 99% within 30 h
(entry 1, Table 1). Since hydrosilylation with PhSiH3 afforded
mixtures of products, this mixture was subsequently treated with
methanolic NaOH (1 M) for 16 h to generate the corresponding
alcohol. Analysis of this alcohol provided the actual product yield
for each reaction. Increasing the temperature to 40 °C resulted in
considerably enhanced activity, affording the product quantita-
tively in 30 min (entry 2). Replacing phenylsilane by diphenyl-
silane or triethylsilane under otherwise identical conditions gave
only very slow or negligible substrate conversion (entries 3 and 4).
Changing the solvent from dichloroethane to THF considerably
lowered the catalytic performance (entry 5), whereas conducting
the reaction in dichloromethane affected the reaction only slightly
(entry 6). A blank experiment under the same conditions but in
absence of the nickel catalyst revealed no detectable activity even
over extended reaction time (entry 7), thus confirming the catalyt-
ic role of the nickel species.
Table 2. Hydrosilylation of 4-methylbenzaldhehyde with complexes
1a-c, 2.a
OH
O
1) 1a-c,2, PhSiH3
H
H
2) NaOH
entry [Ni]
time
conv
[%]b
yield
[%]c
k [h–1]
[min]
120
30
1
2
3
4
5
1a
98
99
98
97
<1
94
96
94
95
2.4
6.6
3.6
1.2
1b
1c
Table 1. Hydrosilylation of 4-methylbenzaldhehyde with complex 1b.a
60
O
OH
1) 1b, PhSiH3
2
180
360
H
H
NiCl2
2) NaOH
aReactions were carried out with benzaldehyde (0.5 mmol), PhSiH3
(0.6 mmol) and Ni complex (2 mol%) in 1,2-dichloroethane (0.4 mL)
with C6Me6 (0.05 mmol) as internal standard at 40 °C; bconversion
determined by 1H NMR spectroscopy; cyield determined by 1H NMR
spectroscopy after treatment with NaOH (1 M) in MeOH.
entry solvent
silane
T
[°C]
time
conv yield
[min] [%]b [%]c
1
2
3
4
5
6
7d
C2H4Cl2 PhSiH3 25
C2H4Cl2 PhSiH3 40
C2H4Cl2 Ph2SiH2 40
1,800 99
97
96
30
60
60
60
30
60
99
14
<1
73
84
<1
C2H4Cl2 Et3SiH
40
THF
PhSiH3 40
PhSiH3 40
68
76
CH2Cl2
C2H4Cl2 PhSiH3 40
aReactions were carried out with 4-Me-benzaldehyde (0.5 mmol), PhSiH3
(0.6 mmol) and complex 1b (2 mol %) in the corresponding solvent
(0.4 mL) with C6Me6 (0.05 mmol) as internal standard; bconversion deter-
mined by 1H NMR spectroscopy; cyield determined by 1H NMR spec-
troscopy after treatment with NaOH (1 M) in MeOH; dreaction performed
in the absence of 1b (blank run).
Fig. 2. Hydrosilylation of 4-methylbenzaldehyde with complexes 1a-c
and 2. Inset: linear correlation of the time (min) with [ln([A]t/[A]0)] for each
catalyst, [ln([A]t/[A]0)] = –k time, R2=0.99 (green line), 0.98 (orange line),
0.93 (blue line) and 0.92 (red line).
Based on these results, the activity of catalysts 1a–c and 2
were compared with the model substrate 4-methylbenzaldehyde
under the best conditions (phenylsilane, dichloroethane, 40 °C).
All complexes reached full conversion in less than 3 h (Table 2,
Fig. 2) and show similar time-conversion profiles with high re-
action rates with 80–90% conversions. Different C4 substituents
on the triazolylidene complexes affected the activity of the metal
complexes and the activity is consistent with the electron density
on the metal centre as imparted by the ligand, with triazolylidene
ligands in 1a–c more donating than imidazolylidene in complex
2 (entries 1–4). Within the triazolylidene series, alkyl groups im-
part higher electron density than mesityl groups, consistent with
a higher activity of complex 1b vs. 1c and complex 1a with a
phenyl substituent displaying lowest activity of the triazolylidene
complexes. We note that the complex configuration has no obvi-
2.1 Substrate Scope
The scope of this catalytic hydrosilylation system was inves-
tigated by using the most active nickel complex, 1b, and a variety
of functionalised benzaldehydes. These studies revealed a high
tolerance of the nickel catalyst towards various functional groups
including halides, ethers, and amines (Fig. 3, Table 3). Electron-
rich benzaldehydes with substituents such as −NMe2, −OMe, and
−Me, as well as electron-poor ones with substituents such as −F,
−Br, and−CF3, are converted completely within 7−180 min (en-
tries 1−7).

NoN-Noble Metals iN Catalysis
CHIMIA 2020, 74, No. 6 485
Fig. 3. Conversion profile for the hydrosilylation of different 4-substituted
benzaldehydes with complex 1b.
Fig. 4. Linear correlation of the Hammett parameter (σP) with turnover
frequency at 50% conversion (TOF50), TOF50 = –488σp + 197, R2 = 0.98.
Table 3. Substrate scope for hydrosilylation with complex 1b.a
turnover numbers and frequencies of hydrosilylation using 4-anis-
aldehyde as the substrate. When using 2 mol% of the catalyst pre-
cursor 1b, the reaction is completed at 40 °C within 12 min (Table
4, entry 1). This reactivity is three times faster when compared
to runs using unsubstituted benzaldehyde as substrate (Table 3,
entry 4). Quantitative formation of the product alcohol was al-
so observed upon reducing the loading of complex 1b to 1 and
0.5 mol%, although reaction times were slightly longer to reach
completion under these conditions (14 and 18 min, respective-
ly, entries 2 and 3). The reaction time is considerably shortened
when the reaction temperature was increased to 60 °C, affording
full conversion within 6 min with 2 mol% loading of complex 1b
(entry 4). Successively decreasing of the precatalyst to 0.02 mol%
does not compromise the yield of the reaction (entries 5−10). Full
conversion at this low loading implies turnover numbers as high
as 5,000, and maximum turnover frequencies of 27,000 h−1 (entry
10). When the loading of complex 1b was lowered even further to
0.01 mol%, conversions were incomplete even when the reaction
was run for extended periods of time, yet these conditions allowed
to determine the maximum turnover number TON = 7,400 (60
min, 63%; entry 11). In the absence of nickel complex 1b no con-
version was detected also at these slightly elevated temperatures
(entry 12).
The TOFmax values accomplished with complex 1b are higher
than other known nickel-based hydrosilylation catalyst with[10] or
without a NHC ligand,[11,12] and similar to those of the best-per-
forming iron complexes,[13] yet about two-times lower when com-
pared to the best-performing manganese-based catalyst.[14] The
high catalytic performance of 1b in terms of turnover numbers and
frequencies suggests a marked influence imparted by chelation
of the triazolylidene ligand when bound to nickel. Its key role is
confirmed when comparing complex 3 as the best nickel catalyst
reported so far with the Ni-O(NHC) system 1b (Fig. 5). Under the
same catalytic conditions, the O-chelated nickel complex 1b out-
performs the N-chelated system 3 and reaches higher TON (7,400
vs 5,500) and higher TOF50 values (27,000 vs 23,000 h–1).[10]
OH
O
1) 1b, PhSiH3
H
H
2) NaOH
R
R
entry R–PhCHO time
conv yield
TOF50
[h–1]
σp
[min] [%]b [%]c
1
2
3
4
5
6
7
8
4-NMe2
4-OMe
4-Me
4-H
6
99
98
99
97
98
96
98
13
95
95
96
95
93
92
92
n.d.
-0.83 730
-0.27 340
-0.17 210
12
30
36
0.00
0.06
0.23
0.54
0.78
150
95
32
6
4-F
48
4-Br
120
180
180
4-CF3
4-NO2
n.d.
aReactions were carried out with benzaldehyde (0.5 mmol), PhSiH3
(0.6 mmol) and complex 1b (2 mol%) in 1,2-dichloroethane (0.4 mL)
with C6Me6 (0.05 mmol) as internal standard at 40 °C; bconversion
determined by 1H NMR spectroscopy. cYield determined by 1H NMR
spectroscopy after treatment with NaOH (1 M) in MeOH; n.d. = not
determined.
Comparison of the reaction rates as TOF50 values with the
Hammett parameter σp shows an inverse correlation, with a lower
Hammett parameter inducing faster turnover (Fig. 4). The correla-
tion is satisfactory (R2 = 0.98) and the considerable slope suggests
a strong influence of the substituent’s electronic properties on the
reaction rate, which provides a rationale also for the very low
conversion of nitrobenzaldehyde (Table 3, entry 8). The inverse
correlation between the Hammett parameter (σp) and the turnover
frequency indicates that positive charge is built up in the transi-
tion state. This observation is reminiscent of related carbene Cp
nickel complexes and consistent with a turnover-limiting step that
involves a hypervalent Si centre.[10] Notably, acetophenone is not
a suitable substrate for hydrosilylation with nickel complex 1b
and essentially no conversion was observed even after 3 h. The
low activity of these complexes toward ketone hydrosilylation in-
dicates a clear selectivity for aldehydes vs ketones, which may be
attractive in multifunctional substrates.
2.2 Stoichiometric Experiments
In order to better understand the observed activities of cata-
lyst 1b and more generally the potential role of oxygen chelation
during hydrosilylation, a set of stoichiometric experiments was
performed. Adding a slight excess (1.2 equiv) of phenylsilane to
complex 1b in a CD2Cl2 solution containing SiMe as an internal
standard resulted in an immediate change in colour4of the solution
1
and different sets of new signals appeared in the H NMR spec-
trum, suggesting the formation of new species. The resonances
of complex 1b disappeared and no triazolium salt formation was
detected, while two singlets appeared in the hydride region at δ
= –7.19 and –8.21 ppm in a 1:1 relative ratio and accounting foHr
The catalytic potential of complex 1b was further investigated
by variation of the catalyst loading in order to identify maximum

486 CHIMIA 2020, 74, No. 6
NoN-Noble Metals iN Catalysis
Table 4. Hydrosilylation of 4-anisaldehyde with complexes 1b.a
OH
O
1) 1b, PhSiH3
H
H
2) NaOH
O
O
entry
mol% 1b
T [°C]
40
time [min]
conv [%]b
yield [%]c
TON
48
TOF50 [h–1]
340
1
2
12
14
18
6
99
98
99
99
99
98
99
99
99
93
74
<1
96
94
95
96
95
96
93
96
94
89
63
2
1
40
96
460
3
0.5
2
40
192
48
636
4
60
568
5
1
60
6
96
960
6
0.5
0.25
0.1
0.05
0.02
0.01
0
60
8
192
384
892
1,850
4,500
7,400
2,600
2,200
3,800
14,500
27,000
6,500
7
60
16
20
20
20
60
120
8
60
9
60
10
11
12d
60
60
60
aReactions were carried out with 4-anisaldehyde (0.5 mmol), PhSiH3 (0.6 mmol) and complex 1b in 1,2-dichloroethane (0.4 mL) with C6Me6
(0.05 mmol) as internal standard; bconversion determined by 1H NMR spectroscopy; cyield determined by 1H NMR spectroscopy after treatment with
NaOH (1 M) in MeOH; dIn absence of any nickel complex.
OTf
N
N
N
O
O
Ni
R
R
Bu
Ni
N
N
N
N
N
N
N
1b
3
TOF50 = 23,000 h-1
TOF50 = 27,000 h-1
Fig. 6. 29Si NMR spectrum of a solution of complex 1b after the addition
of PhSiH3 (1.2 equiv) and TMS used as internal standard.
Fig. 5. Best performing Ni NHC supported catalysts known for the
hydrosilylation of aldehydes.[10]
troscopic changes of complex 1b according to 1H and 29Si NMR
spectroscopy. Since Et SiH is also catalytically inactive, these
data suggesting that the3silane addition and formation of the sily-
lether is inhibited, suggesting that this step is essential for catalyst
activation. These observations therefore lend support to a met-
almost 80% when compared to the internal standard. These ob-
servations suggest the formation of two metal hydride species.
The 13C NMR signals were less clear, yet, two new resonances
at 152 and 154 ppm were observed and attributed to phenolate
C–O groups. These resonances are shifted upfield compared to the
C–O resonance in 1b (δC–O = 160 ppm) and compatible with the
values of free phenol C-O groups that are not metal-coordinated,
as for example in the triazolium ligand precursor (δC-OH = 150
ppm). The 29Si NMR spectrum supports the formation of two new
species as two new signals appeared in the –25 to –30 ppm region
(Fig. 6). Their chemical shift is substantially downfield from the
signal of PhSiH (δ = –60) and indicative of a more electrophilic
silicon nucleus.3AllSithese data are consistent with cleavage of the
Ni–O bond and concomitant formation of the two isomers of a
nickel-hydride complex containing a phenylsilylether, cis-5 and
trans-5 as a result of the addition of a Si–H bond across the Ni–O
bond (Scheme 1).[15]
OSiPhH2
OSiPhH2
N
N
N
N
N
N
N
N
N
N
N
N
O
O
H
H
N
PhSiH3
r.t.
Bu
Bu
Bu
Bu
Bu
Ni
Ni
Ni
Bu
O
O
N
N
N
N
N
cis-5
trans-5
Interestingly, an identical experiment using stoichiometric
Scheme 1. Proposed Ni–O bond cleavage and formation of cis-5 and
amounts of Et3SiH instead of PhSiH3 did not induce any spec- trans-5 from reaction of complex 1b with phenylsilane.

NoN-Noble Metals iN Catalysis
CHIMIA 2020, 74, No. 6 487
al–ligand cooperative mechanism for the activation of the Si–H bers in the thousands, indicating a reliable control of the catalytic
bond and a beneficial role of the anionic oxygen functionality in nickel centre through ligand modification. The catalytic system is
hydrosilylation catalysis.
selective towards aldehyde reduction and tolerant to electron-rich
Several different mechanisms have been put forward for the and -poor benzaldehydes. These results provide useful guidelines
hydrosilylation of C=C and C=O bonds over the years.[16–19] Based for installing O-containing functional groups to promote ligand
on our observations, a tentative mechanism is proposed (Scheme cooperativity in catalytic systems based on first-row transition
2), involving catalyst activation via Ni–O bond cleavage to form metals. Moreover, this work demonstrates that appropriate ligand
the hydride species 5. This step may be under rigorous steric con- design provides a powerful methodology for approaching the cat-
trol due to the bulkiness of the carbene ligand as well as the shield- alytic activity of noble metal catalysts by using Earth-abundant
ing of the silicon nucleus, thus providing a rationale for the loss metal complexes.
in activity when changing the hydrosilylation agent from PhSiH3
Acknowledgements
to Ph SiH2 or Et SiH. Different pathways are conceivable from
this h2ydride spec3ies 5. We propose that the aldehyde substrate is
coordinating to the nickel hydride 5 to form the pentacoordinate
Ni adduct A. Subsequent activation of the carbonyl unit produces
We gratefully acknowledge generous financial support from the
European Research Council (CoG 615653) and the European Union
Marie Sklodowska-Curie Initial Training NoNoMeCat (675020-MSCA-
ITN-2015-ETN).
+
transition state B comprised of a carbon with a strong δ charac-
ter, which is in line with the inverse correlation of the Hammett
parameter and the reaction rate, as well as the dependence of cat-
alytic activity on the electron density at the nickel centre. The
higher the electron density at the metal centre is, the more reactive
the hydride. Completing the migratory insertion step affords the
alkoxide nickel intermediate C, which is presumed to react with
phenylsilane via heterolytic Ni–O bond cleavage to conclude the
cycle and release the product with concomitant regeneration of the
nickel hydride 5. An alternative mechanism consistent with our
data involves the formation of a silylene in analogy to the catalytic
systems developed by Tilley and coworkers.[20]
Received: March 30, 2020
[1] a) G. C. Vougioukalakis, R. H. Grubbs, Chem. Rev. 2010, 110, 1746; b) D. A.
Colby, A. S. Tsai, R. G. Bergman, J. A. Ellman, Acc. Chem. Res. 2012, 45,
814; c) J. F. Hartwig, Acc. Chem. Res. 2008, 41, 1534.
[2] a) W. A Herrmann, Angew. Chem. Int. Ed. 2002, 41, 1290; b) F. E. Hahn, M.
C. Jahnke, Angew. Chem. Int. Ed. 2008, 47, 3112.
[3] a) E. Peris, Chem. Rev. 2018, 118, 9988; b) S. T. Liddle, I. S. Edworthy, P. L.
Arnold, Chem. Soc. Rev. 2007, 36, 1732; c) C. Valente, S. Calimsiz, K. H. Hoi, D.
Mallik, M. Sayah, M. G. Organ, Angew. Chem. Int. Ed. 2012, 51, 3314 – 3332.
[4] S. Hameury, P. de Frèmont, P. Braunstein Chem. Soc. Rev. 2017, 46, 632.
[5] O. Kühl, Chem. Soc. Rev. 2007, 36, 592.
[6] R. M. Bullock, ‘Catalysis without precious metals’, 2011, Wiley-VCH,
Weinheim, Germany.
[7] Y. Wei, A. Petronilho, H. Mueller-Bunz, M. Albrecht, Organometallics
2014, 33, 5834.
[8] Y. N. Kotovshchikov, G. V. Latyshev, M. A. Navasardyan, D. A. Erzunov, I.
P. Beletskaya, N. V. Lukashev, Org. Lett. 2018, 20, 4467.
[9] S. Bertini, F. Gloaguen, M. Rahaman, S. Huemann, P. Broekmann, P.
Schollhammer, M. Albrecht, submitted.
3. Conclusions
Nickel(ii) complexes with C,O-bidentate chelating mesoionic
carbene ligands display remarkable activity in the hydrosilyla-
tion of C=O bonds. Complexes supported by mesoionic ligands
outperformed non-mesoionic analogues and can be rationally tai-
lored to reach very high turnover frequencies and turnover num-
Scheme 2. Proposed mechanistic
cycle for hydrosilylation of C=O
with complex 1.
N
N
R R
‡
N
N
N
trz
PhSiH3
trz
trz
N
trz
Ni
Ni
O
Ni
O
O
O
O
H
O
1
H
Si
H
Ph
trz
trz OSiH2Ph
Ni
5
O
OSiH2Ph
O
H
Ar
Ar
PhSiH3
trz
trz OSiH2Ph
Ni
trz
trz OSiH2Ph
Ni
O
H
O
O
C
O
Ar
Ar
A
‡
trz
trz OSiH2Ph
Ni
O
H
O
Ar
B

488 CHIMIA 2020, 74, No. 6
NoN-Noble Metals iN Catalysis
[10] Y. Wei, S.-X. Liu, H. Mueller-Bunz, M. Albrecht, ACS Catal. 2016, 6, 8192.
[11] L. Postigo, B. Royo, Adv. Synth. Catal. 2012, 354, 2613.
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[12] a) B. Chatterjee, C. Gunanathan, Chem. Commun. 2014, 50, 888; b) S. N.
MacMillan, W. Hill Harman, J. C. Peters, Chem. Sci. 2014, 5, 590.
[13] A. J. Ruddy, C. M. Kelly, S. M. Crawford, C. A. Wheaton, O. L. Sydora, B.
L. Small, M. Stradiotto, L. Turculet, Organometallics 2013, 32, 5581.
[14] a) T. K. Mukhopadhyay, M. Flores, T. L. Groy, R. J. Trovitch, J. Am. Chem.
Soc. 2014, 136, 882; b) C. Ghosh, T. K. Mukhopadhyay, M. Flores, T. L.
Groy, R. J. Trovitch, Inorg. Chem. 2015, 54, 10398.
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chimia.ch/component/sppagebuilder/?view=page&id=12).
The definitive version of this article is the electronic one that can be
[15] T. Stahl, P. Hrobarik, C. D. F. Konigs, Y. Ohki, K. Tatsumi, S. Kemper, M. found at doi:10.2533/chimia.2020.483.
Kaupp, H. F. T. Klare, M. Oestreich, Chem. Sci. 2015, 6, 4324.
[16] L. Wang, H. Sun, X. Li, Organometallics 2015, 34, 5175.
[17] B. H. Lipshutz, B. A. Frieman, Angew. Chem., Int. Ed. 2005, 44, 6345.
[18] K. Revunova, G. I. Nikonov, Chem. Eur. J. 2014, 20, 839.
[19] L. Monsigny, P. Thuéry, J.-C. Berthet, T. Cantat, ACS Catalysis 2019, 9,
9025.
[20] a) P. B. Glaser, T. D. Tilley, J. Am. Chem. Soc. 2003 125, 13640; b) R.
Waterman, P. G. Hayes, T. D. Tilley, Acc. Chem. Res. 2007, 40, 712.