Efficient alkene hydrosilation with bis(8-quinolyl)phosphine (NPN) nickel catalysts. The dominant role of silyl-over hydrido-nickel catalytic intermediates

Article abstract of DOI:10.1039/d0sc00997k

A cationic nickel complex of the bis(8-quinolyl)(3,5-di-tert-butylphenoxy)phosphine (NPN) ligand, [(NPN)NiCl]⁺, is a precursor to efficient catalysts for the hydrosilation of alkenes with a variety of hydrosilanes under mild conditions and low catalyst loadings. DFT studies reveal the presence of two coupled catalytic cycles based on [(NPN)NiH]⁺and [(NPN)NiSiR₃]⁺active species, with the latter being more efficient for producing the product. The preferred silyl-based catalysis is not due to a more facile insertion of alkene into the Ni-Si (vs.Ni-H) bond, but by consistent and efficient conversions of the hydride to the silyl complex.

Full text of DOI:10.1039/d0sc00997k

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ARTICLE
Efficient Alkene Hydrosilation with Bis(8-quinolyl)phosphine
(NPN) Nickel Catalysts. The Dominant Role of Silyl- over Hydrido-
Nickel Catalytic Intermediates
Received 00th January 20xx,
Accepted 00th January 20xx
Jian Yang,a,§ Verònica Postils,b,c,d,§ Michael I. Lipschutz,a Meg Fasulo,a Christophe Raynaud,b Eric
Clot,b Odile Eisenstein*,b,e and T. Don Tilley*,a
DOI: 10.1039/x0xx00000x
A cationic nickel complex of the bis(8-quinolyl)(3,5-di-tert-butylphenoxy)phosphine (NPN) ligand, [(NPN)NiCl]+, is a precursor
to efficient catalysts for the hydrosilation of alkenes with a variety of hydrosilanes under mild conditions and low catalyst
loadings. DFT studies reveal the presence of two coupled catalytic cycles based on [(NPN)NiH]+ and [(NPN)NiSiR3]+ active
species, with the latter being more efficient for producing the product. The preferred silyl-based catalysis is not due to a
more facile insertion of alkene into the Ni–Si (vs. Ni–H) bond, but by consistent and efficient conversions of the hydride to
the silyl complex.
11
hydrosilation of a variety of alkenes with PhSiH3 and some
tertiary silanes.12
Introduction
Catalytic systems based on nickel would seem promising
The hydrosilation of alkenes is a widely practiced catalytic
transformation, and is of great importance for the production
of organosilanes and materials based on poly(siloxane)s.1–6 For
industrial applications, the most common and active
hydrosilation catalysts are based on platinum, and to a lesser
degree other precious metals. Due to the high cost associated
with such metals, there is increasing interest in utilization of less
expensive first-row transition metal catalysts for this
transformation.7,8 There has been notable progress toward this
goal,9–12 including the pioneering work of Brookhart and
coworkers on a cationic Cp*Co system for the catalytic
hydrosilation of 1-hexene with Et3SiH.9 More recently, Weix,
Holland and coworkers have described an effective cobalt
catalyst system for anti-Markovnikov hydrosilation of alkenes.10
Also, Chirik et al. have described neutral bis(imino)pyridine iron
bis(dinitrogen) complexes as catalyst precursors for the
given the congeneric relationship of this metal to
platinum.7,8,13,14 For example, nickel(II) and nickel(0) complexes
such
as
Ni(PPh3)2Cl2
and
exhibit
[{Ni(_CH2=CHSiMe2)2O}2{_(_CH2=CHSiMe2)2O}]
activity toward hydrosilation, but are associated with harsh
reaction conditions or limited substrate scope, and usually
involve extensive dehydrosilation and/or silane redistribution
as processes that compete with hydrosilation.13–15 Indenyl
nickel complexes have been reported by Zargarian and
coworkers, for the regioselective hydrosilation of styrene with
PhSiH3.16,17 In 2012, this laboratory reported the rapid and
selective (> 95%) anti-Markovnikov hydrosilation of 1-octene
with Ph2SiH2, with the two-coordinate Ni(II) amido
Ni[N(SiMe3)DIPP]2 as catalyst.18 In recent years, a number of
new nickel catalyst precursors have been reported, including
examples featuring chelating, pincer, or redox-active ligands as
well as a Ni-MOF species.19–29 The catalytic systems reported by
Chirik24 and Hu28 demonstrate the use of commercially relevant
alkoxysilanes in hydrosilations.
In general, the development of generally effective and
useful alkene hydrosilations using first-row metals such as
manganese, iron, cobalt and nickel is still at an early stage of
development. Notably, a challenging impediment concerns the
lack of mechanistic information for hydrosilations with such
metals, which thwarts attempts to rationally design and
discover more efficient catalysts by optimizing electronic and
structural properties that promote preferred mechanistic
pathways. A prominent mechanistic issue relates to the
tendency of first-row metals to undergo one-electron
processes, unlike more effective heavier metal catalysts that
promote bond-making and -breaking via two-electron oxidative
addition and reductive elimination as in the well-known Chalk-
a. Department of Chemistry, University of California, Berkeley, California 94720, USA.
b. ICGM, Université de Montpellier, CNRS, ENSCM, Montpellier, France.
c. Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química,
Universitat de Girona, Campus Montilivi, 17071, Girona, Spain.
d. Kimika Fakultatea, Euskal Herriko Unibertsitatea, PK 1072, 20080, Donostia, Spain.
e. Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry,
University of Oslo, P.O. Box 1033, Blindern, N-0315, Oslo, Norway.
The manuscript was written through contribution of all authors. All authors have given
approval to the final version of the manuscript. §These authors contributed equally.
Electronic Supplementary Information (ESI) available. It contains the experimental
details (synthesis and characterization), the computational details, the microkinetic
study and the calculated energies of all species discussed, the Gibbs energy profiles
for the Ni-H and Ni-Silyl catalytic cycles (including competing pathways) and additional
chemical reactions. The coordinates of all calculated species are provided as an .xyz
file directly readable by Mercury. The crystallographic data of 3b is registered as CCDC
1981795 See DOI: 10.1039/x0xx00000x
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Harrod mechanism.1–6 Thus, some attention has focused on
attempts to develop new mechanisms for hydrosilation that
may not require two-electron processes, such as those based on
silylene complex intermediates,30 redox active ligands,24,29 and
the electrophilic activation of silanes.31
View Article Online
DOI: 10.1039/D0SC00997K
In an approach to discovery of new first-row metal catalysts
for alkene hydrosilation, this laboratory is investigating
tridentate ligands containing a central, strong donor atom. Such
ligands are expected to promote stability for the catalytic
centre, and high reactivity toward substrate activations.32–35
Previous studies centered on bis(8_quinolyl)silyl (NSiN)
complexes of platinum, which were found to be unusually active
toward Si_H bond oxidative addition.36,37 In the work described
here, the central anionic silyl group of the NSiN ligand is
replaced by a neutral phosphorous donor. The resulting NPN
ligand combines a soft, strong donor and two harder, hemilabile
quinolyl groups in a chelating scaffold expected to promote
catalytic bond activations.38–45 Cationic nickel complexes of the
NPN ligand bis(8_quinolyl)(3,5_di_tert_butylphenoxy)phosphine
(1) are shown to be highly effective, general catalysts for
hydrosilations of alkenes. Importantly, these catalysts appear to
operate by an unusual mechanism that has important
implications for the use of first-row metals in hydrosilation and
related catalytic reactions. In particular, a DFT investigation
shows that the key mechanistic steps in this catalysis involve
non-oxidative, concerted cycloadditions of Si–H with Ni–C
bonds that proceed through four-centered transition states. A
notable aspect to this mechanism is that the preferred
hydrosilation pathway is associated with alkene insertion into a
Ni–Si (rather than a Ni–H) bond, even though this step is
inherently less favorable. It is the subsequent, rate-determining
regioselective addition of the Si–H to the Ni–C bond that
controls this preference.
Scheme 1 Synthesis of NPN ligand and Ni complexes.
excess of Li(OEt2)3B(C6F5)4 or AgSbF6.‡ While multiple attempts
to obtain X-ray quality crystals of 3a inevitably produced oily
material, the crystal structure of 3b revealed a dimeric structure
in the solid state (Fig. 1). A rather unusual structural feature of
3b is coordination of the "weakly coordinating" SbF6 anion,
characterized by a short Ni-F distance of 2.262(4) Å. The Sb-F
distance associated with this interaction is 1.904(4) Å, about
0.03 Å longer than the average terminal Sb-F bond.46,47
Fig. 1 ORTEP drawing of the X-ray crystal structure of 3b. Hydrogen atoms and
C6H5F are omitted for clarity. Key bond distances (Å): Ni(1)_N(1) = 2.092(6),
Ni(1)_N(2) = 2.070(7), Ni(1)_P(1) = 2.347(2), Ni(1)_F(1) = 2.262(4), Sb(1)_F(1) =
1.904(4), Sb(1)_F(2) = 1.873(5), Sb(1)_F(3) = 1.877(5), Sb(1)_F(4) = 1.874(5),
Sb(1)_F(5) = 1.867(5), Sb(1)_F(6) = 1.869(5)
Results and discussion
Catalyst synthesis
The
new
ligand
1
was
obtained
via
bis(8-
Catalytic hydrosilation
quinolyl)(dimethylamino)phosphine in moderate yield by
lithiation of 8-bromoquinoline followed by addition of 0.5
equivs of (Me2N)PCl2. Treatment of this synthetic intermediate
with 3,5-di-tert-butylphenol in refluxing toluene provided
ArtBuO-NPN (1) in 77% yield. Reaction of 1 with Ni(DME)Cl2 (DME
= dimethoxyethane) in dichloromethane afforded an insoluble
product characterized as the dichloride (ArtBuO-NPN)NiCl2 (2,
Scheme 1). Abstraction of chloride from 2 with 1.1 equiv of
Li(OEt2)3B(C6F5)4 in bromobenzene-d5 generated the
corresponding, presumably solvated cationic nickel
monochloride complex in situ. In a preliminary screen, addition
of tert-butylethylene (90 equiv.) and Ph2SiH2 (114 equiv.) to this
solution cleanly yielded the hydrosilation product
Complexes 3a,b were investigated as precatalysts for the
hydrosilation of alkenes. While 3b exhibits modest activities for
hydrosilations of cyclopentene with Ph2SiH2 (ca. 26% conversion
after 18 h. at 23 °C with 0.56 mol% Ni loading), its [B(C6F5)4]
anion analogue 3a is much more effective and results in
complete conversion within 1 h. (Table 1, entries 1 and 2). The
-
lower activity of the SbF6 complex is presumably due to the
stronger association of this anion with the Ni center, making a
coordination site for substrates less available. Secondary
hydrosilanes are the most efficient substrates for hydrosilations
catalyzed by 3a. Reactions were generally carried out in
bromobenzene-d5, but fluorobenzene, chlorobenzene and 1,2-
dichlorobenzene are also suitable solvents. Results of typical
catalytic runs are listed in Table 1. Yields were determined by
1H-NMR spectroscopy via integration against an added internal
standard and the identities of the products were further
confirmed by GC-MS analysis. With Ph2SiH2 as the substrate,
t
Ph2SiHCH2CH2 Bu within 1 h. at 23 °C.
This finding motivated a more detailed study of (ArtBuO-
NPN)Ni cationic complexes as hydrosilation catalysts, and
attempts to isolate the cationic nickel complexes (Scheme 1, X
= B(C6F5)4, 3a; X = SbF6, 3b) via treatment of 2 with a slight
2 | J. Name., 2012, 00, 1-3
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Table 1 Nickel-Catalyzed Hydrosilation of Alkenes.a,b
complete hydrosilation of tert-butylethylene, cyclopentene, 4-
methyl-1-pentene, and 1-hexene proceeded to completion at
View Article Online
DOI: 10.1039/D0SC00997K
23 °C within 1 h. with 0.56 mol% Ni loading (entries 2-5). The
hydrosilation product distribution appears to depend on the
steric properties of the alkene substrates. In general, the mono-
hydrosilation product is dominant but especially with less
hindered alkenes, small quantities of the double-hydrosilation
product are produced (entries 2, 4 and 5). Thus, the relative
reactivities of alkene substrates for double-hydrosilation follow
the trend: 1-hexene > 4-methyl-1-pentene > cyclopentene >
tert-butylethylene. Note that with the sterically encumbered
alkene tert-butylethylene, the mono-hydrosilation product
entr
y
Ni (mol %)
0.56
Olefin
Silane
t (h) Yieldc %
1
cyclopentene
Ph2SiH2
18
26
2d
3
0.56
0.56
cyclopentene
tBuCH=CH2
Ph2SiH2
Ph2SiH2
1
1
98
97
t
Ph2SiHCH2CH2 Bu is exclusively formed (entry 3).
Further reduction of the catalyst loading proved possible, as
demonstrated by use of 0.1 mol% Ni loading to achieve the
hydrosilation of 1-hexene in 17 h. at 23 °C (ca. 970 turnovers;
entry 6). Hydrosilation reactions may also be carried out in neat
1-hexene and complete reaction occurred within 3 h. at 23 °C at
a catalyst loading of 0.23 mol% (entry 7). Other secondary
hydrosilanes, such as PhMeSiH2 and Et2SiH2, were also effective
for this reaction (entries 8 and 9).
Attempts to hydrosilylate cyclopentene with tertiary silanes
in bromobenzene, with 3a as catalyst, often led to
decomposition of the catalyst and low conversions, presumably
due to reaction of active nickel species with aryl bromide. More
effective catalysis with tertiary silanes is observed with less
reactive solvents, such as 1,2-dichlorobenzene or
chlorobenzene (entries 10-14). In the presence of 0.56 mol%
catalyst, the hydrosilation of 4-methyl-1-pentene with
Ph2MeSiH proceeds to completion in less than 1.5 h. (entry 10).
4_methyl_1_
pentene
4e
5f
0.56
Ph2SiH2
1
96
0.56
0.10
0.23
1_hexene
1_hexene
1_hexene
Ph2SiH2
Ph2SiH2
Ph2SiH2
1
17
3
98
97
98
f
6
g
7
0.5
28
92
98
8
9
0.56
0.56
0.56
cyclopentene PhMeSiH2
tBuCH=CH2
Et2SiH2
26
99
98
4_methyl_1_
pentene
h
Ph2MeSiH
1.5
10
11
1.0
0.56
0.56
3.0
cyclopentene Ph2MeSiH
2
2
98
98
98
Cyclopentene
and
tert-butylethylene
were
readily
12
13
14
tBuCH=CH2
cyclopentene
cyclopentene
cyclopentene
cyclopentene
Ph2MeSiH
hydrosilylated with Ph2MeSiH (entries 11 and 12). At a Ni
loading of 0.56 mol%, the complete hydrosilation of
cyclopentene with the commercially relevant silane
(Me3SiO)2MeSiH occurred within 1.5 h. at 23 °C (entry 13).
Hydrosilation of cyclopentene with Ph2SiClH is relatively slow,
requiring 65 h. for approximately 95% conversion at 3.0 mol%
of Ni loading (entry 14).
The catalytic activity of 3a was compared to that of some
simple Ni(II) complexes and their [B(C6F5)4]- salts to evaluate the
enhancement to hydrosilation afforded by the ArtBuO-NPN
ligand. The hydrosilation of 4-methyl-1-pentene with Ph2MeSiH
(conditions identical to table 1, entry 10) was attempted using
Ni(DME)Cl2, (Ph3P)2NiCl2, and their respective [B(C6F5)4]- salts
R2MeSiH
(R= Me3SiO)
1.5
42
65
90
95
Ph2ClSiH
PhSiH3
20
41
22
30
i
0.56
0.56
15
i
MesSiH3
1.1
75
16
a Hydrosilation catalysis was carried out using 3a, except entry 1 which involves 3b.
b General conditions: entries 1, 6 and 9, silanes (1.27 equiv), 23 °C, C6D5Br; entries
8 and 10-16, silanes (1.27 equiv), 23 °C, o-C6H4Cl2. c Yields were determined by NMR
spectroscopy by integrating the product signals against an internal standard, and
the identities of the products were confirmed by GC-MS. Where more than one
hydrosilation product is generated, yields represent the combination of both
products. d In addition to Ph2SiH(cyclopentyl), Ph2Si(cyclopentyl)2 (< 5%) was also
Hydrosilation product distribution: Ph2SiH(CH2)3CH(CH3)2 and
Ph2Si[(CH2)3CH(CH3)2]2 (5.3:1 ratio).
Ph2SiH(CH2)5CH3 and Ph2Si[(CH2)5CH3]2 (3:1 ratio). The reaction was carried out
without solvent; hydrosilation product distribution: Ph2SiH(CH2)5CH3 and
Ph2Si[(CH2)5CH3]2 (7.3:1 ratio). h Small amounts (ca. 8%) of unidentified products in
addition to the hydrosilation product were observed. i In addition to the expected
hydrosilation product, small amounts of cyclopentane and other unidentified
silicon-containing products were observed.
(generated in situ) as precatalysts. Only the (Ph3P)2NiCl2
+
Li[B(C6F5)4] catalyst precursor resulted in any observable
hydrosilation product, and only in 4% yield. These results, along
with comparisons to those cited above,13–20,22–29 indicate that
the ArtBuO-NPN complex 3a is exceptionally active as a nickel-
based hydrosilation catalyst.
Hydrosilations catalyzed by 3a are generally less efficient for
primary (vs. secondary) silanes. Entry 15 shows that
hydrosilation of cyclopentene with PhSiH3 occurred at a 0.56
mol% Ni loading but with only 30% conversion after 41 h. at 23
°C. Interestingly, under identical reaction conditions
hydrosilation with the bulkier silane MesSiH3 (Mes = 2,4,6-
C6H2Me3) is much more rapid (entry 16). The origin of this
e
formed.
f
Hydrosilation product distribution:
g
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unusual selectivity is still unclear but may relate to the crowded coordinated. Only the preferred pathway is presented and brief
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DOI: 10.1039/D0SC00997K
nature of the transition states for silane activation (vide infra).
mention of other pathways is made when appropriate.
Catalyst generation likely occurs by reaction of the cationic
The mechanism of hydrosilation catalyzed by paramagnetic
3a has been challenging to probe experimentally, given the catalyst precursor, {[(NPN)NiCl]2}2+, with the silane substrate.
(presumably) multi-step transformation of [(NPN)NiCl]+ to the This is indicated by experimental observations that implicate
active catalyst (vide infra), and a lack of success in isolating reaction of this paramagnetic dinuclear nickel chloride with a
complexes from catalytic or stoichiometric reactions. Also, it hydrosilane to produce a putative diamagnetic nickel complex
has not been possible to identify metal-containing species from (vide supra). The nickel product would appear to be the hydride
the complex NMR spectra of reaction mixtures; however, [(NPN)NiH]+, and though nickel hydrides are now well
reaction of 3a with Ph2SiH2 results in rapid formation of established,53,54 cationic nickel hydrides of this type are more
Ph2SiHCl, and sharp NMR resonances suggest that several unusual but have precedence.55–59 In evaluating the energetics
diamagnetic nickel species are present. Also, monitoring of this reaction, it was assumed that the starting chloride
catalytic reactions by 1H-NMR spectroscopy revealed the complex dissociates to a monomer that possesses a more
formation of Ph2SiHCl during catalysis. These results suggest accessible and thus more reactive Ni-Cl bond. Exchange of the
that a nickel hydride is formed as an intermediate; however, silane Si-H and catalyst precursor Ni-Cl bonds gives the
such a species could not be identified by NMR spectroscopy. observed chlorosilane PhSiH2Cl and presumably the hydride
Also, a catalytic reaction with diphenylsilane-d2 and tert- [(NPN)NiH]+. This exchange reaction is accompanied by a spin
butylethylene with a Ni loading of 1.0 mol% yielded an cross-over, since the precatalyst is paramagnetic while the
t
approximately 1:1.6 ratio of Ph2SiDCHDCH2 Bu and active catalyst species appears to be diamagnetic. In addition,
Ph2SiDCH2CHDtBu (Scheme 2). This implies a rapid and the computational studies are based on the reasonable
reversible insertion/deinsertion step involving a nickel hydride, assumption that the catalytic cycle occurs on a singlet electronic
such as [(NPN)NiH]+, in an "off-cycle" process or prior to surface, especially since interaction between the nickel and the
elimination of the hydrosilation product. Future mechanistic substrates should stabilize closed-shell electronic states.
studies will involve exploratory synthetic efforts to obtain Validation of a functional via comparison with experimental
isolable, single-site catalytic species, primarily hydride and silyl data is currently not possible given the lack of key
derivatives of the [(NPN)Ni]+ fragment. To gain more crystallographic data. Test calculations with several functionals
mechanistic information, a DFT study was carried out.
indicated that the singlet electronic state is relatively more
preferred for [(NPN)NiH]+ in comparison to [(NPN)NiCl]+, as
expected from the stronger ligand field in the former. In view of
these considerations, the hybrid functional PBE0, considered as
reliable for determination of reaction pathways, was
selected.60,61
Scheme 2 Tert-butylethylene hydrosilation with diphenylsilane-d2 catalyzed by 3a.
The Cl/H exchange reaction involving monomeric
[(NPN)NiCl]+ and PhSiH3 is similar to the related generation of
an (indenyl)nickel hydride, by reaction of the corresponding
chloride with PhSiH3.62 On the singlet electronic surface, the
reaction is endoergic (∆G = 11 kcal mol-1) and requires a Gibbs
activation energy of 19.8 kcal mol-1 relative to the separated
reagents (ESI Fig S4). These energetics do not account for any
stabilization of the hydride (e.g., by dimerization or facile
reactions with species present in solution, such as the silane or
olefin substrates present under catalytic conditions, as
developed below). The nickel hydride was therefore considered
to be the initial reactive species and the origin of energies was
therefore [(NPN)NiH]+, corrected by inclusion of the
appropriate substrates for mass balance.
The reaction of [(NPN)NiH]+ with the silane PhSiH3 is
calculated as an essentially thermoneutral reaction (∆G = -0.6
kcal mol-1) that yields [(NPN)NiSiH2Ph]+ and H2 (central reaction
equilibrium of Scheme 3) via a transition state with ∆G‡ of 6.9
kcal mol-1 relative the energy reference. However, this
thermoneutrality corresponds to a situation where H2 remains
in solution. This reaction should be driven more strongly toward
formation of the silyl complex by the poor solubility of H2.63
Reactions of the cationic nickel hydride initially with
cyclopentene and then with PhSiH3 provide a viable catalytic
cycle for hydrosilation (Fig 2 and cycle A of Scheme 3). As shown
Computational studies
To gain a better understanding of the mechanism of this
catalytic hydrosilation, DFT studies were carried out with a
dispersion corrected hybrid functional and an implicit model for
the solvent (1,2-dichlorobenzene). Full computational details
are given in the ESI. The Ni complexes with the pincer ligand,
labelled as (NPN), and the substrates (cyclopentene and PhSiH3)
were represented in full. These substrates were selected
because they are associated with smaller conformational
diversity, though they are not the most reactive, and therefore
allow manageable computation times. Although PhSiH3 is not
one of the better substrates in this catalysis, we presume that
this results from side reactions of the smaller silane, leading to
condensed and inactive nickel-silicon species formed via
multiple Si-H activations in the silane. The latter trend is well
known for reactions of silanes with nickel complexes.48–52
Exploration of potential energy surfaces revealed that
numerous, slightly different, pathways give the same products.
For these pathways, the intermediates and transition states
differ by subtle changes in the structures of the NPN ligand,
which can be folded or flat and which can be 3– or 2–
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Scheme 3 Proposed Mechanisms for Nickel-Catalyzed Hydrosilation of Alkenes.
in Fig 2, this reaction sequence begins with coordination of alkane, consistent with this reactivity, are observed in catalytic
cyclopentene to the nickel centre, assisted by decoordination of reaction mixtures (vide supra). Note that, as mentioned above,
a quinolyl group to give a square planar alkene hydride complex the hydride also has another pathway to the silyl complex by
with a dangling group (2-NPN) and the alkene double bond direct reaction with the silane and elimination of H2 (Scheme 3).
perpendicular to the Ni coordination plane. Pathways of higher Note that the silyl complex has a viable pathway back to the
energy for alkene binding were obtained for the fully hydride, via insertion of alkene to give a -silyl alkyl complex
coordinated 3-NPN ligand (see ESI, page S-28). Insertion of the that will react with silane to generate a 1,2-bis(silyl)alkane in
cyclopentene -bond into the Ni-H bond is achieved with a low addition to the nickel-hydride (vide infra).
Gibbs energy barrier (∆G‡ = 4.6 kcal mol-1, relative to the -
complex, i.e. -2.3 kcal mol-1 relative to the energy reference)
and yields a cyclopentyl complex stabilized by a -agostic C–H
bond trans to a quinolyl. During this step the NPN ligand
remains 2-coordinated. The formation of this cyclopentyl
intermediate is favoured by thermodynamics (∆G = -13.9 kcal
mol-1). Coordination of the silane to the cyclopentyl
intermediate (for which the loss of entropy dominates the
enthalpy of coordination) can occur with two orientations of the
Si-H bond relative to the Ni-cyclopentyl bond. If the silyl group
is closer to the cyclopentyl ligand, a silyl group migrates and a
silylcyclopentane is obtained along with the nickel hydride. If
the hydrogen atom of the Si-H bond is closer to the cyclopentyl
ligand, a hydrogen atom migrates and a cyclopentane and a
Fig 2 Gibbs energy profile (kcal mol-1) for cycle A of the hydrosilation catalyzed by
nickel silyl complex are formed. These two reactions are
concerted and the Gibbs energy profiles of Fig 2 show that the
migration of H is preferred over that of the silyl group (TSA2 is
lower than TSA1 by 2.4 kcal mol-1 ) and the corresponding
products (cyclopentane and nickel silyl) are energetically
preferred by ∆G = 8.7 kcal mol-1 over the silylcyclopentane and
nickel hydride. These kinetic and thermodynamic factors have
significant consequences for the reaction mechanism for
hydrosilation. Importantly, the hydride should rapidly exit
catalytic cycle A by way of alkane formation and production of
the corresponding silyl complex. Indeed, small amounts of
[(NPN)NiH]+.
Especially given the accumulation of the nickel silyl complex
[(NPN)NiSiH2Ph]+ in the reaction sequences described above, its
role as a potential hydrosilation catalyst was investigated. In
fact, catalysis with this species (Figure 3 and cycle B of Scheme
3) was found to involve a pathway that is lower in energy than
that of cycle A (see Fig S5 and S6 in ESI for detailed numerical
values). This is due to the fact that the catalytic cycle initiated
by the silyl complex starts at -23.9 kcal mol-1 relative to the
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energy reference, due to the exoergicity of the hydrogenation the reaction is evidenced by the fact that variVoieuwsAritsicolemOenlrinice
DOI: 10.1039/D0SC00997K
of cyclopentene as described in Figure 2. Qualitatively, the forms, relatively close in energy, were found for several minima
elementary steps of cycle B are similar to those of cycle A. and transition states leading to the same product. Thus, In the
Coordination of cyclopentene to the nickel silyl is marginally case of the hydride, the lowest transition state for cyclopentene
exoergic and occurs without decoordination of a quinolyl group. coordination is accompanied by a 3- to- 2- change in
The transition state for insertion of the alkene into the Ni–Si coordination mode; however, transition states with fully
bond is only 6.2 kcal mol-1 above that of the alkene complex. coordinated 3-NPN were located at slightly higher energies. In
This insertion step yields an alkyl ligand with the silyl group in contrast, the preferred transition state for cyclopentene
the  position, and results in a relatively short Ni···Si contact coordination to the silyl has a 3-NPN ligand and higher-energy
(2.66 Å) indicative of a -agostic C()–Si() bond, as has been transition states have the NPN ligand with a coordination
observed for numerous alkyl complexes.64–69 This silyl- intermediate between 2 and 3.
substituted alkyl intermediate reacts with PhSiH3, to yield either
The 1,2 addition of the silane to the Ni-cyclopentyl cation,
the silyl or the hydride complex. As expected, the energetically to form cyclopentane and the Ni-silyl complex or the silyl-
more favourable transition state corresponds to a transfer of H cyclopentane and hydride complex (Figure 2), occurs in a
(TSB2) and leads directly to the hydrosilation product concerted manner without formation of any intermediate. The
Ph(C5H11)SiH2 with regeneration of the silyl catalyst (cycle B of calculations indicate that the transition state for hydrogen
Scheme 3). The transition state (TSB1) for the silyl transfer is 2 transfer is systematically preferred over silyl transfer although
kcal mol-1 higher in energy. Thus, the release of the 1,2- the difference in energy between the two transition states is
bis(silyl)alkane and the hydride [(NPN)NiH]+ is both kinetically only 2 kcal mol-1. Similar features have been obtained for the
and thermodynamically (11.9 kcal mol-1) disfavoured. hydrosilation of olefins by lanthanide complexes.70–73 However,
Consistent with earlier results, the net effect of the competing the 4-centre transition state for a metathesis reaction with a d0
reactions is that the silyl species should accumulate in favour of metal is calculated to be planar, whereas TSA2 is butterfly-
the hydride. In addition, the major organic product (determined shaped with the transferring H atom closest to Ni (1.460 Å) and
by cycle B) is the hydrosilation product, in good agreement with about midway between Si (1.700 Å) and the cyclopentyl carbon
the experimental evidence.
(1.673 Å). Similar features are observed for TSB2 (Ni···H: 1.455
Å, Si···H: 1.769 Å, C···H: 1.645 Å). To understand these unusual
features, an NBO analysis is presented for TSB2 (Scheme 3 and
Fig 4), which is associated with formation of the major product.
The second-order perturbation and NLMO analyses reveal a 3-
centre 2-electron interaction involving Ni (9%), Si (37 %) and H
(54%), which describes a donation of the Si-H bond into a 4s Ni
orbital. In addition, this Ni-H-Si orbital (mostly located on H–Si)
acts as a strong donor to the Ni-C(cyclopentyl) * orbital. This
electron delocalization induces a concerted cleavage of the Si–
H and Ni–C bonds, and formation of the Ni–Si and C–H bonds.
The NBO analysis does not attribute a bond to the Ni···H
interaction, but indicates a very weak donation from a Ni lone
pair to H. Consequently, there is no oxidative addition of the Si–
H bond in this step. This is also supported by the NBO charges
(+0.85 e for Si, 0.00 e for H, 0.49 e for Ni and -0.46 e for C), which
suggest a rather high density on Ni that is not compatible with
oxidation.
Fig
3 Gibbs energy profile for cycle B of the hydrosilation catalyzed by
[(NPN)NiSiH2Ph]+.
Discussion of the mechanism
Globally, all reactions have rather low energies of activation
suggesting that in this catalytic system, both the hydride and
silyl complexes of Ni are very reactive. One reason for the high
reactivity could relate to the high flexibility and hemilability of
the NPN ligand. For instance, the solid state structure of the
dinuclear precatalyst shows a highly folded NPN ligand with an
angle between the two N-Ni-P planes of around 90°, and similar
features are obtained for computed structures of 3–NPN
pincer complexes. However, the NPN pincer can be significantly
flattened as it is in (NPN)NiH+ and (NPN)NiSiH2Ph+, which have
fold angles of 162° and 170°, respectively. Additional proof of
the importance of the flexibility of the NPN ligand in facilitating
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bond, with A proceeding via TSA2 and B utilizingVTieSwBA1rt.iclTehOinslinies
DOI: 10.1039/D0SC00997K
consistent with the well-known trend for hydrogen migration
being energetically preferred over silyl migration. Also, for the
hydride intermediate, it is more efficient to undergo silylation
via TSA2, which converts the hydride to the silyl complex,
further favouring cycle B. A microkinetic study using the
calculated activation energies confirms the strongly dominant
formation of the alkylsilane over that of the alkane or the
bis(silyl)alkane (see full description of the microkinetic model in
the ESI).82
Interestingly, the unusual preference for hydrosilation
catalysis promoted by a silyl complex, in the presence of the
corresponding hydride, does not arise from preferential
insertion of the olefin into the Ni–Si bond. Alkene insertion into
a M–Si bond has been experimentally observed for various
metals, but on the basis of experiments83 and calculations84
(notably for platinum), it is thought that this step generally
requires a higher energy relative to analogous insertions into
M–H bond. This difference has been used to conclude that the
Chalk-Harrod mechanism for hydrosilation with platinum occurs
via alkene insertion into Pt–H.1–6 In fact, for the system
described here, the calculations are consistent with the known
preference for insertion into the Ni–H bond. The preference for
the catalytic cycle based on the nickel silyl catalyst arises from
the fact that the hydride complex quickly exits its cycle due to
the kinetic and thermodynamic preference for formation of the
silyl complex, by way of alkane elimination (Figure 2 and
Scheme 3).
Fig 4 Transition state TSB2 for reaction of PhSiH3 with [(NPN)Ni(C5H9)SiiH2Ph]+. The
atoms involved in the reaction (Si, H, Ni and C) are represented by sphere (green for Ni,
yellow for Si, white for H and black for C). Other atoms are represented by stick and
wire.
Using a Bader atoms-in-molecule analysis, Vastine and Hall
proposed that a general bonding continuum exists among the
variously named "oxidative addition", "–bond metathesis" and
"metal-assisted metathesis" reactions.74,75 Ess, Goddard and
Periana used an energy decomposition analysis (ALMO-EDA) to
classify such C–H activation reactions as electrophilic,
ambiphilic or nucleophilic on the basis of the net direction of
charge transfer energy stabilization.76 The NBO method used in
this work is related to the ALMO-EDA because it identifies the
donor and acceptor and ranks the associated stabilization
energy. Within this scheme, it is very clear that the Si–H bond
acts as a strong donor and that the stabilization energy
associated with donation of the Ni–C bond is an order of
magnitude smaller. There is thus significant electronic
reorganization within the Ni orbitals, which is necessary for
cleaving the Ni–C bond and forming the Ni–Si bonds. We
suggest that the reaction should be viewed as electrophilic -
bond metathesis within the classification of Goddard et al.76
This is also compatible with the large exoergicity of the
transformation, which is in part driven by transformation of a
weak Si–H into a strong C–H bond (an energy gain of ~20 kcal
mol-1). Donation of the Si–H bond to nickel is actually already
present in the (Si-H) complexes of PhSiH3 with
[(NPN)Ni(C5H9)SiH2Ph]+, which was located as an energetically
high-lying minimum before the transition state TSB2 (see IX and
XI, Fig S6 in ESI). This highlights the role of -complexes in 1,2-
addition to metal-carbon bonds.77,78 Additionally, it is
interesting to note that the non-planarity of this TSB2 transition
state suggests that a variety of 4-centre transition state
structures with similar electronic characteristics are possible.
Finally, the lack of an oxidizing Ni···H interaction at the
transition state is not solely due to the expected difficulty in
oxidizing a Ni(II) cationic centre, as a similar absence of redox
character has been suggested for -bond exchanges involving
Ni(0) centres,79,80 but this does not extend to heavier metals of
Group 10.81
Conclusions
This study identifies a readily accessible and potentially
tunable nickel-based catalytic system for the hydrosilation of
alkenes. The catalysis is exceptionally efficient, exhibits high
activity towards a broad spectrum of hydrosilanes, and involves
an abundant transition metal. These results therefore raise
interesting questions regarding the influence of structural
modifications of the catalyst on hydrosilation activities and
selectivities.
A DFT computational study indicates that catalysis with the
2+
precatalyst [(ArOtBu–NPN)NiCl]2 (3) involves two possible
catalytic cycles, using Ni–hydride or Ni–silyl catalysts, but the
preferred pathway involves an alkene insertion into a Ni–Si
bond and low energy barriers for the fundamental steps. The
low-energy profiles are likely associated with the high flexibility
of the NPN ligand, manifested in its ability to readily cycle
between 3- and 2-coordination, and "fold" to vary bond
angles. In the two possible catalytic cycles, the rate-determining
step is the 1,2-addition of silane to the Ni-alkyl bond and not the
insertion of the olefin into the Ni–H or Ni–Si bonds. This
product-forming step involves a favoured transition state with
H adding to the alkyl ligand and formation of a Ni–Si bond (H in
the  position of the 4-membered transition state). Other bond
activation processes are possible, including those of a catalytic
cycle for hydrosilation by the nickel hydride, but the consistent
positioning of hydrogen  to the metal centre in concerted 4-
membered transition states results in rapid exit of the hydride
The two catalytic cycles of Scheme 3 are quite similar and
are based on reactions of analogous hydride (cycle A) or silyl
(cycle B) complexes. In A, the silyl group migrates to an alkyl
ligand, while in B, hydride migrates to a silyl-substituted alkyl
ligand. Thus, both cycles lead to the hydrosilation product. Each
of these cycles is associated with a transition state variant
differing only by the way the Si–H bond adds across the Ni–C
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from its catalytic cycle, with formation of the silyl complex.
Thus, the preferred catalysis based on the silyl complex is not
due to a more facile insertion of alkene into the Ni–Si (vs. Ni–H)
bond, but by consistent, efficient conversions of the hydride to
the silyl complex. Also, analysis of the electronic structure of the
1,2-addition of the Si–H bond to the Ni–alkyl complex shows
that no redox process has occurred at the metal and that the
electronic density of the Si–H bond serves to cleave the Ni–C
sigma bond. Thus, the reaction is best seen as an electrophilic
-bond metathesis following the classification proposed by
Goddard et al.76 The key transition state has a folded,
"butterfly" structure, and as such is very different from the
planar structures associated with -bond metathesis
reactions,85 demonstrating that planarity of the 4-centered
transition state is not a requirement for this type of reaction.
2
D. Troegel and J. Stohrer, Coord. Chem. Rev., 2011, 255,
View Article Online
1440–1459.
DOI: 10.1039/D0SC00997K
3
4
5
A. K. Roy, Adv. Organomet. Chem., 2007, 55, 1–59.
B. Marciniec, Coord. Chem. Rev., 2005, 249, 2374–2390.
I. Ojima, Z. Li and J. Zhu, in The Chemistry of Organic Silicon
Compounds, eds. Z. Rappoport and Y. Apeloig, John Wiley
& Sons, Ltd, Chichester, UK, First Edit., 198AD, pp. 1687–
1792.
L. N. Lewis, J. Stein, Y. Gao, R. E. Colborn and G. Hutchins,
Platin. Met. Rev., 1997, 41, 66–79.
X. Du and Z. Huang, ACS Catal., 2017, 7, 1227–1243.
J. V Obligacion and P. J. Chirik, Nat. Rev. Chem., 2018, 2,
15–34.
6
7
8
9
M. Brookhart and B. E. Grant, J. Am. Chem. Soc., 1993, 115,
2151–2156.
10
C. Chen, M. B. Hecht, A. Kavara, W. W. Brennessel, B. Q.
Mercado, D. J. Weix and P. L. Holland, J. Am. Chem. Soc.,
2015, 137, 13244–13247.
Conflicts of interest
The authors have no conflicts to declare.
11
12
S. C. Bart, E. Lobkovsky and P. J. Chirik, J. Am. Chem. Soc.,
2004, 126, 13794–13807.
A. M. Tondreau, C. C. H. Atienza, K. J. Weller, S. A. Nye, K.
M. Lewis, J. G. P. Delis and P. J. Chirik, Science, 2012, 335,
567–570.
Acknowledgements
Dow Corning is gratefully acknowledged for financial support of
the experimental aspects of this research. The authors further
wish to acknowledge the National Science Foundation for
partial support, under grant no. CHE-1566538. O.E. was partially
supported by the Research Council of Norway through its
Centres of Excellence Scheme Project 262695. V.P.R. thanks
MINECO for the Grant BES-2012-052801 and the fellowship
EEBB-I-14-07908, which paid for her stay at the University of
Montpellier.
Richard Taylor, Binh Nguyen and Misha Tzou (Dow Corning)
are thanked for valuable discussions. O.E. is grateful to the
Miller foundation which has fostered this international
collaboration.
13
14
15
16
Y. Kiso, M. Kumada, K. Tamao and M. Umeno, J.
Organomet. Chem., 1973, 50, 297–310.
Y. Kiso, M. Kumada, K. Maeda, K. Sumitani and K. Tamao, J.
Organomet. Chem., 1973, 50, 311–318.
H. Maciejewski, B. Marciniec and I. Kownacki, J.
Organomet. Chem., 2000, 597, 175–181.
F.-G. Fontaine, R.-V. Nguyen and D. Zargarian, Can. J.
Chem., 2003, 81, 1299–1306.
Y. Chen and D. Zargarian, Can. J. Chem., 2009, 87, 280–287.
M. I. Lipschutz and T. D. Tilley, Chem. Commun., 2012, 48,
7146–7148.
17
18
19
20
L. Benı́tez Junquera, M. C. Puerta and P. Valerga,
Organometallics, 2012, 31, 2175–2183.
A. Kuznetsov and V. Gevorgyan, Org. Lett., 2012, 14, 914–
917.
Z. Zhang, L. Bai and X. Hu, Chem. Sci., 2019, 10, 3791–3795.
V. Srinivas, Y. Nakajima, W. Ando, K. Sato and S. Shimada,
Catal. Sci. Technol., 2015, 5, 2081–2084.
J. Mathew, Y. Nakajima, Y.-K. Choe, Y. Urabe, W. Ando, K.
Sato and S. Shimada, Chem. Commun., 2016, 52, 6723–
6726.
I. Pappas, S. Treacy and P. J. Chirik, ACS Catal., 2016, 6,
4105–4109.
T. J. Steiman and C. Uyeda, J. Am. Chem. Soc., 2015, 137,
6104–6110.
I. Buslov, J. Becouse, S. Mazza, M. Montandon-Clerc and X.
Hu, Angew. Chem. Int. Ed., 2015, 54, 14523–14526.
I. Buslov, S. C. Keller and X. Hu, Org. Lett., 2016, 18, 1928–
1931.
I. Buslov, F. Song and X. Hu, Angew. Chem. Int. Ed., 2016,
55, 12295–12299.
C. L. Rock and R. J. Trovitch, Dalton Trans., 2019, 48, 461–
467.
R. Waterman, P. G. Hayes and T. D. Tilley, Acc. Chem. Res.,
Additional authors information
Corresponding Authors *E-mail:
21
22
odile.eisenstein@umontpellier.fr, tdtilley@berkeley.edu
23
ORCID ID:
Verònica Postils: 0000-0002-7467-9277
Christophe Raynaud: 0000-0003-0979-2051
Eric Clot: 0000-0001-8332-5545
Odile Eisenstein: 0000-0001-5056-0311
T. Don Tilley: 0000-0002-6671-9099
24
25
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29
30
Notes and references
‡ 3a can also be generated in situ via treatment of 3b with 2.1 equiv
of Li(OEt2)3B(C6F5)4. See supporting information for details.
1
B. Marciniec, Hydrosilylation: A Comprehensive Review on
Recent Advances, Springer Netherlands, Dordrecht, First
Edit., 2009, vol. 1.
8 | J. Name., 2012, 00, 1-3
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Page 9 of 11
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ARTICLE
2007, 40, 712–719.
58
59
T. Steinke, B. K. Shaw, H. Jong, B. O. Patrick and M. D.
View Article Online
Fryzuk, Organometallics, 2009, 28, 2830–2836.
I. Morales-Becerril, M. Flores-Álamo, A. Tlahuext-Aca, A.
Arévalo and J. J. García, Organometallics, 2014, 33, 6796–
6802.
DOI: 10.1039/D0SC00997K
31
32
33
34
M. C. Lipke, A. L. Liberman-Martin and T. D. Tilley, Angew.
Chem. Int. Ed., 2017, 56, 2260–2294.
M. E. van der Boom and D. Milstein, Chem. Rev., 2003, 103,
1759–1792.
M. Albrecht and G. van Koten, Angew. Chem. Int. Ed., 2001, 60
40, 3750–3781.
A. Mahler, B. G. Janesko, S. Moncho and E. N. Brothers, J.
Chem. Phys., 2018, 148, 244106-1-9.
S. Dohm, A. Hansen, M. Steinmetz, S. Grimme and M. P.
Checinski, J. Chem. Theory Comput., 2018, 14, 2596–2608.
Y. Chen, C. Sui-Seng, S. Boucher and D. Zargarian,
Organometallics, 2005, 24, 149–155.
E. Brunner, J. Chem. Eng. Data, 1985, 30, 269–273.
L. Perrin, L. Maron, O. Eisenstein and M. F. Lappert, New J.
Chem., 2003, 27, 121–127.
M. P. Conley, G. Lapadula, K. Sanders, D. Gajan, A. Lesage,
I. del Rosal, L. Maron, W. W. Lukens, C. Copéret and R. A.
Andersen, J. Am. Chem. Soc., 2016, 138, 3831–3843.
P. D. Bolton, E. Clot, N. Adams, S. R. Dubberley, A. R.
Cowley and P. Mountford, Organometallics, 2006, 25,
2806–2825.
H. Fan, B. C. Fullmer, M. Pink and K. G. Caulton, Angew.
Chem. Int. Ed., 2008, 47, 9112–9114.
E. J. Stoebenau and R. F. Jordan, J. Organomet. Chem.,
2006, 691, 4956–4962.
J. Arnold, T. D. Tilley, A. L. Rheingold and S. J. Geib,
Organometallics, 1987, 6, 473–479.
L. Perrin, L. Maron, O. Eisenstein and T. D. Tilley,
Organometallics, 2009, 28, 3767–3775.
N. Barros, O. Eisenstein and L. Maron, Dalton Trans., 2010,
39, 10749–10756.
N. Barros, O. Eisenstein and L. Maron, Dalton Trans., 2010,
39, 10757–10767.
J. Y. Corey, Chem. Rev., 2016, 116, 11291–11435.
B. A. Vastine and M. B. Hall, J. Am. Chem. Soc., 2007, 129,
12068–12069.
B. A. Vastine and M. B. Hall, Coord. Chem. Rev., 2009, 253,
1202–1218.
D. H. Ess, W. A. Goddard and R. A. Periana,
Organometallics, 2010, 29, 6459–6472.
R. N. Perutz and S. Sabo-Etienne, Angew. Chem. Int. Ed.,
2007, 46, 2578–2592.
D. Morales-Morales and C. M. Jensen, The chemistry of
pincer compounds, Elsevier, Amsterdam, The Netherlands,
First edit., 2007.
61
62
35
36
M. D. Fryzuk, Can. J. Chem., 1992, 70, 2839–2845.
M. Stradiotto, K. L. Fujdala and T. D. Tilley, Chem.
Commun., 2001, 1200–1201.
63
64
37
38
P. Sangtrirutnugul and T. D. Tilley, Organometallics, 2007,
26, 5557–5568.
P. A. Aguirre, C. A. Lagos, S. A. Moya, C. Zúñiga, C. Vera-
Oyarce, E. Sola, G. Peris and J. C. Bayón, Dalton Trans.,
2007, 5419–5426.
65
66
39
W.-H. Sun, Z. Li, H. Hu, B. Wu, H. Yang, N. Zhu, X. Leng and
H. Wang, New J. Chem., 2002, 26, 1474–1478.
T. Suzuki, Bull. Chem. Soc. Jpn., 2004, 77, 1869–1876.
P. Wehman, H. M. A. van Donge, A. Hagos, P. C. J. Kamer
and P. W. N. M. van Leeuwen, J. Organomet. Chem., 1997,
535, 183–193.
T. Suzuki, K. Kashiwabara and J. Fujita, Bull. Chem. Soc.
Jpn., 1995, 68, 1619–1626.
H. A. Hudali, J. V. Kingston and H. A. Tayim, Inorg. Chem.,
1979, 18, 1391–1394.
40
41
67
68
69
70
71
72
42
43
44
J. Flapper, H. Kooijman, M. Lutz, A. L. Spek, P. W. N. M. van
Leeuwen, C. J. Elsevier and P. C. J. Kamer, Organometallics,
2009, 28, 1180–1192.
45
A. Kermagoret, F. Tomicki and P. Braunstein, Dalton Trans.,
2008, 2945–2955.
W. H. Hersh, J. Am. Chem. Soc., 1985, 107, 4599–4601.
R. Bröchler, I. H. T. Sham, M. Bodenbinder, V. Schmitz, S. J.
Rettig, J. Trotter, H. Willner and F. Aubke, Inorg. Chem.,
2000, 39, 2172–2177.
R. Beck and S. A. Johnson, Organometallics, 2012, 31,
3599–3609.
R. Beck and S. A. Johnson, Organometallics, 2013, 32,
2944–2951.
S. Shimada, M. L. N. Rao, T. Hayashi and M. Tanaka,
Angew. Chem. Int. Ed., 2001, 40, 213–216.
D. Schmidt, T. Zell, T. Schaub and U. Radius, Dalton Trans.,
2014, 43, 10816.
R. C. Handford, P. W. Smith and T. D. Tilley,
Organometallics, 2018, 37, 4077–4085.
N. A. Eberhardt and H. Guan, Chem. Rev., 2016, 116, 8373–
8426.
73
74
46
47
75
76
77
78
79
80
48
49
50
51
52
53
54
55
56
57
D. Balcells, E. Clot and O. Eisenstein, Chem. Rev., 2010, 110,
749–823.
J. Guihaumé, S. Halbert, O. Eisenstein and R. N. Perutz,
Organometallics, 2012, 31, 1300–1314.
J. S. Bair, Y. Schramm, A. G. Sergeev, E. Clot, O. Eisenstein
and J. F. Hartwig, J. Am. Chem. Soc., 2014, 136, 13098–
13101.
S. Tang, O. Eisenstein, Y. Nakao and S. Sakaki,
Organometallics, 2017, 36, 2761–2771.
S. Hoops, S. Sahle, R. Gauges, C. Lee, J. Pahle, N. Simus, M.
Singhal, L. Xu, P. Mendes and U. Kummer, Bioinformatics,
2006, 22, 3067–3074.
81
82
J. Wenz, A. Kochan, H. Wadepohl and L. H. Gade, Inorg.
Chem., 2017, 56, 3631–3643.
L. Sacconi, A. Orlandini and S. Midollini, Inorg. Chem., 1974,
13, 2850–2859.
M. J. Sgro and D. W. Stephan, Organometallics, 2012, 31,
1584–1587.
R. Cariou, T. W. Graham and D. W. Stephan, Dalton Trans.,
2013, 42, 4237–4239.
83
84
A. K. Roy and R. B. Taylor, J. Am. Chem. Soc., 2002, 124,
9510–9524.
S. Sakaki, N. Mizoe, M. Sugimoto and Y. Musashi, Coord.
Chem. Rev., 1999, 190–192, 933–960.
This journal is © The Royal Society of Chemistry 20xx
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Chemical Science
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ARTICLE
Journal Name
85
R. Waterman, Organometallics, 2013, 32, 7249–7263.
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DOI: 10.1039/D0SC00997K
10 | J. Name., 2012, 00, 1-3
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Page 11 of 11
Chemical Science
View Article Online
DOI: 10.1039/D0SC00997K