Cationic Ru-Se Complexes for Cooperative Si-H Bond Activation

Article abstract of DOI:10.1021/acs.organomet.0c00719

The preparation and structural characterization of mononuclear tethered ruthenium(II) complexes of type [(DmpSe)Ru(PR3)]+BArF4- (DmpSe = 2,6-dimesitylphenyl selenolate, ArF = 3,5-bis(trifluoromethyl)phenyl) are described. Unlike relevant known selenolate

Full text of DOI:10.1021/acs.organomet.0c00719

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Cationic Ru−Se Complexes for Cooperative Si−H Bond Activation
Marvin Oberling, Elisabeth Irran, Yasuhiro Ohki,* Hendrik F. T. Klare,* and Martin Oestreich*
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ABSTRACT: The preparation and structural characterization of
mononuclear tethered ruthenium(II) complexes of type
[(DmpSe)Ru(PR3)]+BArF − (DmpSe = 2,6-dimesitylphenyl sele-
4
nolate, ArF = 3,5-bis(trifluoromethyl)phenyl) are described. Unlike
relevant known selenolate complexes, the reported family of
complexes is cationic with a single monodentate selenolate ligand.
The ability of these complexes to engage in cooperative Si−H bond
activation at the Ru−Se bond is investigated, and a hydrosilane
adduct has been fully characterized by multinuclear NMR
spectroscopy and X-ray diffraction. The usefulness of these
complexes as catalysts for various ionic dehydrogenative silylation and hydrosilylation reactions is assessed. At all stages, the new
complexes are compared with their thiolate homologues [(DmpS)Ru(PR3)]+BArF − (DmpS = 2,6-dimesitylphenyl thiolate). The
4
differences between the selenolate and thiolate complexes are marginal, but measurable. The larger selenium atom provides more
space around the Ru−Se bond than sulfur does for the Ru−S bond, and hence, the selenolate complexes can accommodate sterically
more demanding hydrosilanes.
INTRODUCTION
■
The ability of [NiFe] hydrogenases1 to split dihydrogen has
inspired biomimetic approaches to metal thiolates2 as novel
catalysts for cooperative bond activation.3 [NiFeSe] hydro-
genases, a subclass of these enzymes with a selenocysteine
residue coordinated to the nickel center instead of a cysteine,
have emerged as a special point of interest, showing higher
tolerance toward O2 and enhanced H2 production activity.4,5
This sparked investigations employing various model com-
plexes.6 Despite these promising features, only a few metal
selenolate complexes with catalytic application have been
reported (Figure 1).7−9 For example, Seino, Mizobe, and co-
workers prepared rhodium(III) bis(selenolate) complex 1,
which was found to have a higher catalytic activity in the
chemoselective hydrogenation of N-benzylideneaniline than
the corresponding thiolate complex.8 Also, Zhang, Luo, and
co-workers recently presented nickel(II) diselenolate complex
2 and its thiolate analogue.9a A comparison of these two
variants regarding their ability to produce H2 revealed that the
selenolate complex has a 13-times higher turnover frequency.
Our laboratories have had a long-standing interest in
cooperative El−H bond activation at the Ru−S bond of
cationic ruthenium(II) thiolate complexes 4 (w/ El = Si, B, Al,
and Sn).2a,c,d These were introduced by Ohki and Tatsumi10
and further developed in collaboration with Oestreich.2d The
interaction of the El−H bond and the Ru−S bond generally
increases the electrophilicity of the El atom and leads to
heterolytic cleavage in the case of hydrosilanes.11 The resulting
sulfur-stabilized silicon electrophiles [S−Si]+ together with the
ruthenium hydride were broadly applicable in catalysis,2a,d e.g.,
Figure 1. Selected molecular metal−selenolate complexes applied to
small-molecule activation (top) and terphenyl-based complexes
(bottom).
sila-Friedel−Crafts reactions,12 pyridine hydrosilylation,13 and
dehydrogenative silylation of enolizable carbonyl com-
Received: November 10, 2020
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pounds.14 Despite these advances, we asked ourselves whether
the electrophility of the silicon center could be enhanced by
replacing the sulfur atom by a less Lewis-basic selenium atom.
Moreover, the larger size of selenium could provide more space
around the Ru−Ch bond, thereby accommodating hydro-
silanes with sterically demanding substitution patterns. We
describe here the synthesis of cationic ruthenium(II) complexes
5 containing a single Ru−Se bond. The structurally similar
neutral copper(I) complex 3 was recently prepared by
Walensky and co-workers, but their work was confined to its
structural analysis.15,16 Just as our earlier work on ruthenium-
(II) thiolate complexes 4,2d,10 the present study includes the
structural characterization of a ruthenium(II) selenolate
complex 5 and its hydrosilane adduct, followed by an
assessment of its performance in various catalytic trans-
formations.
Scheme 1. Preparation of the Cationic Ruthenium(II)
Selenolate Complexes
RESULTS AND DISCUSSION
■
Synthesis and Characterization of the Cationic Ru−
Se Complexes. Initially, we tried to access the selenolate
complexes 5 via the established protocol for the preparation of
thiolate analogues 4 by replacing the SDmp with the SeDmp
ligand (Scheme 1, Route a).10 Treatment of commercially
available [(p-cymene)RuCl2]2 (6) with LiSeDmp17 in THF
slowly resulted in a deep-blue solution, indicative of the
formation of coordinatively unsaturated complex 7 (6 → 7).
However, the subsequent reaction with Et3P did not provide
the desired complex 8a, but led to decomposition of 7. We
therefore turned to a modified procedure in which the order of
addition of the two ligands was reversed, thus avoiding a highly
sensitive 16-electron intermediate (Scheme 1, Route b). As
previously reported,18 the addition of a phosphine to chloride-
bridged dimer 6 gave monomeric complexes 9 (6 → 9), which
were converted to ruthenium(II) selenolates 10 by substitution
of one chloride atom with LiSeDmp (9 → 10). A change from
CH2Cl2 to THF as solvent allowed performing this sequence as
a one-pot process without isolating complexes 9. Heating a
solution of 10 in toluene at 95 °C led to displacement of the p-
cymene ligand by one of the mesityl groups of the SeDmp
ligand (10 → 8) to obtain complexes 8 as dark red powders in
isolated yields of 69−78% over three steps starting from 6.
Chloride abstraction from 10 was finally achieved with 1 equiv
vs 2.212 Å),19 as expected due to the larger size of the
selenium atom compared to the sulfur atom. This is also
reflected by the elongated Se−C1 bond of the SeDmp ligand
in 5a (1.936 Å vs 1.791 Å of SDmp in 4a). Consistent with the
increase of these bond lengths, the Ru−Se−C1 bond angle
decreases from 101.4° for 4a to 98.5° for 5a. Overall, these
structural parameters suggest a more exposed Ru−Se bond in
5a compared to the Ru−S bond in 4a, which could facilitate
interaction with larger external reactants and substrates.
of NaBArF , affording cationic ruthenium(II) selenolate
4
complexes 5 as air-sensitive green solids in high yields ranging
from 83% to 96% (8 → 5). The use of fluoro- or
chlorobenzene as solvent was crucial in these reactions, since
routinely used CH2Cl2 resulted in chloride abstraction from
CH2Cl2 by in-situ-generated complexes 5 (for the crystallo-
graphic characterization of a Ru−Cl/SeCH2Cl adduct, see the
Supporting Information).
The new cationic selenolate complexes 5 were fully
characterized by multinuclear NMR spectroscopy (see Table
2 and the Supporting Information for details). The H NMR
Cooperative Si−H Bond Activation at the Ru−Se
Bond. To verify this hypothesis, we probed the reactivity of
selenolate complexes 5a (R3P = Et3P) and 5d (R3P = (4-
FC6H4)3P) toward hydrosilanes in the same way as we did for
the corresponding thiolate complexes 4.11 Treatment of 5a
with 2 equiv of Me2PhSiH (11a) at room temperature resulted
in an immediate color change from green to yellow, indicating
successful Si−H bond activation. NMR spectroscopic measure-
ments were consistent with the formation of hydrosilane
adduct 12aa (Table 2). The ruthenium hydride was confirmed
by a doublet at δ(1H) = −9.06 ppm (2JH,P = 46.7 Hz) in the 1H
NMR spectrum. Since chirality is (re)introduced by the
additional hydride ligand, six instead of four signals are
1
spectra revealed Cs symmetry of complexes 5 in solution, as
indicated by a total of four signals for the methyl groups of the
SeDmp ligand. The structural assignment was further verified
by successful crystallographic characterization of complex 5a.
Single crystals suitable for X-ray diffraction analysis were
obtained from a solution of 5a in a mixture of Et2O and
(Me3Si)2O at room temperature. The solid-state structure of
selenolate 5a (Figure 2) resembles that of the thiolate
congener 4a (Table 1).10 However, the Ru−Se bond length
in 5a is significantly longer than the Ru−S bond in 4a (2.315 Å
B
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Table 1. Selected Bond Lengths (Å) and Angles (deg) of Thiolate 4a and Selenolate 5a (R3P = Et3P) and the Hydrosilane
Adducts with Me2PhSiH
a
b
4a (Ch = S)
5a (Ch = Se)
4a·Me2PhSiH
5a·Me2PhSiH = 12aa
Ru−Ch
Ch−C1
Ru−P
Ru−H
2.2117(9)
1.791(3)
2.3833(10)
2.3153(5)
1.936(4)
2.3674(14)
2.3882(10)
1.815(3)
2.3049(10)
1.58(4)
2.4807(5)
1.975(4)
2.2960(12)
1.58(4)
Ch−Si
Si···H
2.2445(11)
3.17(4)
2.3855(14)
3.38(5)
P−Ru−Ch
Ru−Ch−C1
Ru−Ch−Si
Si−Ch−C1
ΣR−Si−R
89.29(3)
101.38(12)
93.06(3)
98.45(9)
94.67(4)
102.38(12)
107.59(5)
114.36(10)
331.4
92.74(3)
98.40(12)
106.93(4)
111.60(15)
332.7
a
b
Data from ref 10. Data from ref 11.
Table 2. Selected NMR Spectroscopic Data of the Cooperative Si−H Bond Heterolysis of Me2PhSiH by Selenolates 5a and 5d
(Data of Thiolates 4a and 4d for Comparison)
b
compound
δ(1H)
δ(29Si)
δ(31P)
δ(77Se)
a
4a (Ch = S)
23.0 ppm
30.0 ppm
23.4 ppm
31.9 ppm
40.4 ppm
48.7 ppm
38.7 ppm
50.3 ppm
a
4d (Ch = S)
5a (Ch = Se)
5d (Ch = Se)
4a·Me2PhSiH
4d·Me2PhSiH
5a·Me2PhSiH = 12aa
5d·Me2PhSiH = 12da
1408.5 ppm
1522.5 ppm
a
−8.26 ppm (2JH,P = 48.8 Hz)
−7.67 ppm (2JH,P = 48.5 Hz)
−9.06 ppm (2JH,P = 46.7 Hz)
28.4 ppm
29.8 ppm
22.0 ppm
25.2 ppm
a
151.1 ppm (2JSe,P = 15.3 Hz)
151.2 ppm (2JSe,P = 31.2 Hz)
−8.27 ppm (2JH,P = 47.5 Hz)
a
b
Data in CD2Cl2 from ref 11. Determined by H/29Si HMQC NMR spectroscopy.
1
are typically observed for η1 and η2 hydrosilane complexes,
further supported heterolytic Si−H bond cleavage and the
generation of a silyl cation. Its stabilization by the selenium
atom was evident in the 77Se NMR spectrum, which showed a
resonance at δ(77Se) = 151.1 ppm (2JSe,P = 15.3 Hz). The
significant high-field shift compared to the precursor 5a
(δ(77Se) = 1408.5 ppm) is a clear indication for an increase of
the coordination number at the selenium atom due to the
interaction with the positively charged silicon atom. The high-
field-shifted 29Si NMR chemical shift of hydrosilane adduct
12aa compared to the corresponding thiolate congener
(Δδ(29Si) = 6.4 ppm) indicates a stronger interaction of the
silyl cation with the selenium atom. This result is in line with
studies by Muller and co-workers, who had shown for a series
̈
of intramolecular silylchalconium ions that the covalent
character and stabilization of the silyl cation increases from
the [S−Si]+ to the [Se−Si]+ linkage.20
The reversibility of the Si−H bond activation by selenolate
complex 5a became apparent by a 1H/1H NOESY NMR
experiment, showing chemical exchange between the ruthe-
nium hydride of 12aa at δ(1H) = −9.06 ppm and the hydride
of free Me2PhSiH at δ(1H) = 4.55 ppm (Figure 3). In a control
experiment, an equimolar mixture of Me2PhSiH (11a) and
deuterium-labeled Et3SiD (11b-d1) was exposed to catalytic
Figure 2. Molecular structure of complex 5a. Thermal ellipsoids are
shown at the 50% probability level. The counteranion and all
hydrogen atoms are omitted for clarity. See Table 1 for selected bond
lengths and angles.
observed for the methyl groups of the SeDmp ligand. Likewise,
the meta-protons of the mesityl rings gave four instead of two
signals. The 29Si NMR chemical shift at δ(29Si) = 22.0 ppm is
considerably downfield-shifted relative to free Me2PhSiH at
δ(29Si) = −17.3 ppm. The absence of any 1JH,Si satellites, which
C
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Me2PhSiH (2.3855(14) Å vs 2.2445(11) Å).21 The average
C−Si−C bond angle is 110.9° and thus closer to a tetrahedral
(109.5°) than a trigonal planar (120°) coordination geometry.
The slightly more pronounced pyramidalization at the silicon
atom than in 4a·Me2PhSiH (average C−Si−C bond angle of
110.5°) indicates an increased covalent character of the [Se−
Si]+ linkage compared to [S−Si]+, which is consistent with the
observed shift of the 29Si NMR resonance toward higher field
(vide supra).20
Changing the electronic and steric nature of the phosphine
ligand in ruthenium(II) selenolates 5 had no significant
influence on the Si−H bond activation event. The NMR
spectroscopic analysis of complex 5d with an electron-deficient
para-fluorinated triarylphosphine showed the overall same
trends as those of complex 5a (cf. Table 2). The heterolysis of
Me2PhSiH also proceeded smoothly with 5b decorated with
the sterically more demanding iPr3P ligand (see the Supporting
Information for the crystallographic characterization of the
hydrosilane adduct 5b·Me2PhSiH).
1
Figure 3. Selected segment of the H/1H NOESY NMR spectrum
(500/500 MHz, C6D5Cl, 300 K, Tm = 600 ms) of hydrosilane adduct
12aa.
Application in Catalysis. We applied Ru−Se complex 5a
as a catalyst in various reactions involving Si−H bond
activation in order to contrast its qualities against its congener
Ru−S complex 4a (both with Et3P as ligand). For this, we
chose a number of established transformations (Scheme 3):
electrophilic aromatic substitution of N-methylated indole (13
→ 14, top),12 dearomative hydrosilylation of pyridine (15 →
16, middle),13 and dehydrogenative silylation versus hydro-
silylation of acetophenone (17 → 18/19, bottom).14
Beginning with the electrophilic C−H silylation,12 the results
with 5a and 4a were essentially identical when using
Me2PhSiH (11a), Et3SiH (11b), and MePh2SiH (11c).
However, the reaction outcome was drastically different with
sterically more hindered Ph3SiH (11d). No reaction was seen
with 4a as catalyst, whereas 61% yield of the silylated indole
14d was obtained with 5a. Apparently, the pocket with the
Ru−Se bond in complex 5a can accommodate larger
hydrosilanes than that of Ru−S complex 4a. Moving to an
even bulkier hydrosilane brought out the space limitation; tert-
butyl-substituted tBuMe2SiH (11e) did not participate in the
Si−H bond activation. Interestingly, in-situ-generated Ru−Se
complex 5d with electron-deficient (4-FC6H4)3P as the
ancillary ligand afforded product 14e in 20% yield. As expected
for an SEAr, the silylation occurred exclusively in the C3
position of the indole (as verified by NMR spectroscopy and
X-ray diffraction analysis of 14d; see the Supporting
Information). A control experiment with N-methylindole
bearing another methyl group at C3 showed showed full
conversion after 48 h (not shown). With the C3 position
blocked, three different indoles formed with silylation at C5 or
C2 or both (see the Supporting Information for details). This
result hints that the Ru−Se complex 5a is more reactive than
the Ru−S complex 4a which was reported not to catalyze this
reaction.12
1
Scheme 2. H/2H Scrambling Experiment
amounts of complex 5a at room temperature, resulting in
complete scrambling of the deuterium label (Scheme 2).
The molecular structure of hydrosilane adduct 12aa was
eventually determined by X-ray diffraction analysis (Figure 4).
Figure 4. Molecular structure of hydrosilane adduct 12aa. Thermal
ellipsoids are shown at the 50% probability level. The counteranion
and all hydrogen atoms, except for the ruthenium hydride, are omitted
for clarity. See Table 1 for selected bond lengths and angles.
We then turned toward the regioselective hydrosilylation of
pyridine (15)13 using hydrosilanes 11a−d. A similar picture
unfolded for this pyridine reduction compared to the above
silylation of indoles. The Ru−Se complex 5a promoted the
formation of the N-silylated 1,4-dihydrosilanes 16a−d, no
matter how bulky the hydrosilane is. The majority of these
reactions had not been possible with the Ru−S complex 4a.13a
Another reduction catalyzed by these cationic Ru−Ch
complexes is the hydrosilylation of carbonyl compounds.14
There is a twist to this reaction because these reductions
Single crystals were obtained from a solution of selenolate
complex 5a in neat Me2PhSiH (11a) layered with n-hexane at
−30 °C. The solid-state structure shows the same features as
the corresponding thiolate analogue 4a·Me2PhSiH (see Table
1). The most notable changes are again the longer bond
lengths of the selenium atom. The distance of 3.38 Å between
the silicon atom and the ruthenium hydride proves complete
cleavage of the Si−H bond. The Se−Si bond in adduct 12aa is
elongated by around 6% compared to the S−Si bond in 4a·
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As cooperative activation of H−H at the Ru−Ch bond is
also involved in the above dehydrogenation−hydrogenation
reaction sequence, we also tested the hydrogenation of
acetophenone (17 → 20, Scheme 4).22 At 5 bar H2 pressure,
Scheme 3. Assessment of the Ruthenium(II) Selenolate
Complexes in Representative Catalytic Reactions Involving
Si−H Bond Activation
Scheme 4. Hydrogenation of Acetophenone Catalyzed by a
Ruthenium(II) Selenolate Complex
a
1
Monitored by H NMR spectroscopy.
there was no difference between catalyst 4a and 5a, but we
found slightly higher reactivity of Ru−Se complex 5a at a lower
H2 pressure of 1 bar. As before, the effect is not sufficiently
strong to justify a detailed comparison, but measurable.
CONCLUSION
■
The goal of the present study was to compare Ohki−Tatsumi
ruthenium(II) thiolate complexes [(DmpS)Ru(PR3)]+BArF −
4
with their higher homologues, the corresponding selenolate
complexes [(DmpSe)Ru(PR3)]+BArF −, in terms of their
4
ability to cooperatively activate Si−H bonds and their
performance as catalysts in various ionic dehydrogenative
silylation and hydrosilylation reactions. The reactivity differ-
ences are in fact minor but still existent. With the selenium
atom being larger than the sulfur atom, the expected finding is
that the selenolate complexes can accommodate larger
hydrosilanes than the thiolate complexes, e.g., Ph3SiH.
However, the catalytically generated selenium-stabilized silicon
electrophile [Se−Si]+ is not more reactive, i.e., electrophilic,
than [S−Si]+ due to more covalent character and stabilization
of that linkage.20 That stronger interaction is also seen from
the 29Si NMR chemical shifts of the hydrosilane adducts: high-
field-shifted resonance signal for [Se−Si]+ relative to [S−Si]+
(Δδ(29Si) = 4.6−6.4 ppm). There is therefore no gain in
reactivity, but the new complexes expand the hydrosilane scope
and are rare examples of cooperative catalysis at a metal−
selenium bond.
a
Isolated yields after purification by flash chromatography on silica gel
b
and subsequent Kugelrohr distillation under vacuum. Isolated yields
after removal of the catalyst by filtration through a short plug of
deactivated silica gel. The chemoselectivity was determined by H
NMR spectroscopy.
c
1
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.0c00719.
■
mainly proceed through dehydrogenative silylation of the
enolizable carbonyl compound, followed by hydrogenation of
the resulting silyl enol ether with the dihydrogen released in
the previous step to eventually furnish the silyl ether.14b Several
parameters such as reaction time and closed/open vessels
govern the product distribution with more silyl ether being
formed at prolonged reaction times and in a closed vessel (with
no escape of dihydrogen). The Lewis basicity of the chalcogen
atom in the Ru−Ch complex could also become a controlling
factor. The formation of the silyl enol ether traces back to α
deprotonation of an intermediate silylcarboxonium ion, and
this is less likely with selenium than with sulfur as the Lewis-
basic site. Accordingly, the reaction of acetophenone (17) and
Me2PhSiH (11a) yielded a 63:37 mixture of silyl enol ether
18a and silyl ether 19a within minutes. Conversely, the same
reaction catalyzed by Ru−S complex 4a led to an 85:15
mixture, corroborating more facile α deprotonation and hence
dehydrogenation.14a The same outcome was obtained with
MePh2SiH (11c).
sı
Experimental details, characterization data including
NMR spectra, and crystallographic data (PDF)
Accession Codes
CCDC 2026739−2026741, 2032583−2032587, and 2039007
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge via www.ccdc.ca-
m.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 Authors
■
Yasuhiro Ohki − Department of Chemistry, Graduate School
of Science, Nagoya University, Nagoya 464-8602, Japan;
E
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orcid.org/0000-0001-5573-2821; Email: ohki@
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Article
(7) For a review of selenium-based ligands in catalysis, see: Kumar,
A.; Rao, G. K.; Saleem, F.; Singh, A. K. Organoselenium ligands in
catalysis. Dalton Trans. 2012, 41, 11949−11977.
chem.nagoya-u.ac.jp
Hendrik F. T. Klare − Institut für Chemie, Technische
Universität Berlin, 10623 Berlin, Germany; orcid.org/
0000-0003-3748-6609; Email: hendrik.klare@tu-berlin.de
Martin Oestreich − Institut für Chemie, Technische
Universität Berlin, 10623 Berlin, Germany; orcid.org/
0000-0002-1487-9218; Email: martin.oestreich@tu-
berlin.de
(8) Seino, H.; Misumi, Y.; Hojo, Y.; Mizobe, Y. Heterolytic H2
activation by rhodium thiolato complexes bearing the hydrotris-
(pyrazolyl)borato ligand and application to catalytic hydrogenation
under mild conditions. Dalton Trans. 2010, 39, 3072−3082.
(9) (a) Pan, Z.-H.; Tao, Y.-W.; He, Q.-F.; Wu, Q.-Y.; Cheng, L.-P.;
Wei, Z.-H.; Wu, J.-H.; Lin, J.-Q.; Sun, D.; Zhang, Q.-C.; Tian, D.;
Luo, G.-G. The Difference Se Makes: A Bio-Inspired Dppf-Supported
Nickel Selenolate Complex Boosts Dihydrogen Evolution with High
Oxygen Tolerance. Chem. - Eur. J. 2018, 24, 8275−8280. See also:
(b) Downes, C. A.; Marinescu, S. C. Bioinspired Metal Selenolate
Polymers with Tunable Mechanistic Pathways for Efficient H2
Evolution. ACS Catal. 2017, 7, 848−854. (c) Xie, A.; Tao, Y.-W.;
Peng, C.; Luo, G.-G. A nickel pyridine-selenolate complex for the
photocatalytic evolution of hydrogen from aqueous solutions. Inorg.
Chem. Commun. 2019, 110, 107598.
Authors
Marvin Oberling − Institut für Chemie, Technische
Universität Berlin, 10623 Berlin, Germany; orcid.org/
0000-0002-4917-5608
Elisabeth Irran − Institut für Chemie, Technische Universität
Berlin, 10623 Berlin, Germany; orcid.org/0000-0001-
6098-1996
(10) Ohki, Y.; Takikawa, Y.; Sadohara, H.; Kesenheimer, C.;
Engendahl, B.; Kapatina, E.; Tatsumi, K. Reactions at the Ru-S Bonds
of Coordinatively Unsaturated Ruthenium Complexes with Tethered
2,6-Dimesitylphenyl Thiolate. Chem. - Asian J. 2008, 3, 1625−1635.
(11) Stahl, T.; Hrobarik, P.; Konigs, C. D. F.; Ohki, Y.; Tatsumi, K.;
Kemper, S.; Kaupp, M.; Klare, H. F. T.; Oestreich, M. Mechanism of
the cooperative Si-H bond activation at Ru-S bonds. Chem. Sci. 2015,
6, 4324−4334.
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.0c00719
́
̈
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(12) Klare, H. F. T.; Oestreich, M.; Ito, J.-I.; Nishiyama, H.; Ohki,
Y.; Tatsumi, K. Cooperative Catalytic Activation of Si-H Bonds by a
Polar Ru-S Bond: Regioselective Low-Temperature C-H Silylation of
Indoles under Neutral Conditions by a Friedel-Crafts Mechanism. J.
Am. Chem. Soc. 2011, 133, 3312−3315.
This work was supported by Grants-in-Aid for Scientific
Research (19H02733 and 20K21207 for Y.O.) from the
Japanese Ministry of Education, Culture, Sports, Science and
Technology (MEXT), the Tatematsu Foundation, and the
Yazaki Memorial Foundation. M.O. is indebted to the Einstein
Foundation Berlin for an endowed professorship. We also
thank Dr. Sebastian Kemper (TU Berlin) for expert advice
with the NMR measurements.
̈
(13) (a) Konigs, C. D. F.; Klare, H. F. T.; Oestreich, M. Catalytic
1,4-Selective Hydrosilylation of Pyridines and Benzannulated
Congeners. Angew. Chem., Int. Ed. 2013, 52, 10076−10079.
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