Catalytic hydrosilylation of olefins and ketones by base metal complexes bearing a 2,2′:6′,2″-terpyridine ancillary ligand

Article abstract of DOI:10.1016/j.ica.2021.120403

The activities of [M(tpy)Br₂] (M = Mn, Co, Ni, or Cu) for the hydrosilylation of olefins and ketones were investigated in the presence of NaBHEt₃ as an activator. [Co(tpy)Br₂] and [Ni(tpy)Br₂] showed catalytic a

Full text of DOI:10.1016/j.ica.2021.120403

Inorganica Chimica Acta 523 (2021) 120403
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Research paper
Catalytic hydrosilylation of olefins and ketones by base metal complexes
bearing a 2,2′:6′,2′′-terpyridine ancillary ligand
Katsuaki Kobayashi, Hiroshi Nakazawa*
Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
A R T I C L E I N F O
A B S T R A C T
Keywords:
The activities of [M(tpy)Br2] (M = Mn, Co, Ni, or Cu) for the hydrosilylation of olefins and ketones were
investigated in the presence of NaBHEt3 as an activator. [Co(tpy)Br2] and [Ni(tpy)Br2] showed catalytic activities
for the hydrosilylation of 1-octene with diphenylsilane. In particular, [Co(tpy)Br2] showed good catalytic ac-
tivity. The linear anti-Markovnikov hydrosilylation product was predominant; however, a small quantity of the
branched Markovnikov product was also produced. Generation of the branched product was suppressed by the
addition of THF and pyridine as solvents. The reactivities of other olefins and silanes were also examined. In the
hydrosilylation of ketones, unlike the hydrosilylation of 1-octene, all four complexes used in this study exhibited
catalytic activity. Interestingly, in the reaction between diphenylsilane and acetophenone, the dominant product
was the 1:2 double hydrosilylation product, not the 1:1 single hydrosilylation product, even in a reaction mixture
of equal parts diphenylsilane and acetophenone.
Hydrosilylation
Catalytic reaction
Terpyridine ligand
Olefines and ketones
1. Introduction
catalytic activity for hydrosilylation of base metal complexes with tpy as
a ligand. Some base metal complexes bearing a tpy ligand have been
Hydrosilylation of unsaturated organic compounds catalyzed by
transition metal complexes is among the best methods to obtain orga-
nosilane compounds due to their simplicity and atom economy. In this
field, the creation and development of base metal catalysts as alterna-
tives to conventional Pt catalysts is a popular topic. A number of base
metal catalysts exhibit catalytic activity for hydrosilylation, and many of
them have a pincer-type ligand, such as NNN [1–4] and PNN types [1,5].
These ligands usually contain bulky substituents that promote stereo-
and/or regioselective hydrosilylation products. Our group reported Fe
and Co complexes bearing an iminobipyridine ligand. The Fe complexes
show good catalytic activity for both olefins and ketones [3,4], while the
Co complexes have good chemoselectivity for olefin hydrosilylation,
which can easily be switched to ketone selectivity by the addition of
pyridine to the reaction system [4b]. These sophisticated stereo- and
chemo-selectivities are due to the well-organized ligands. If base metal
complexes with ubiquitous pincer ligands, not specially customized li-
gands, show good catalytic activities, these complexes could have useful
applications.
prepared, but their catalytic activities for hydrosilylation have not been
reported. The catalytic activity has been reported only for [Co(tpy)Cl2]
[1b] and [Co(tpy)(OAc)(THF)2](OAc) [2h]. However, since these com-
plexes have different chemical formulas and their catalytic activities
were measured under different reaction conditions, their catalytic ac-
tivities cannot be directly compared.
In this study, we synthesized base metal complexes with the same
chemical formula containing one tpy ligand, and then examined and
compared their catalytic activities under the same hydrosilylation con-
ditions. The first-row transition metals from groups 7 to 11, viz. Mn, Fe,
Co, Ni, and Cu, were selected, and the syntheses of their [M(tpy)Br2]
complexes were attempted. The complexes for Mn, Co, Ni, and Cu were
successfully prepared. In contrast, [Fe(tpy)Br2] could not be obtained.
This is consistent with the following findings [6]; [Fe(tpy)X2] (X = Cl,
Br) with unsubstituted tpy cannot be isolated because it becomes [Fe
(tpy)2][FeX4] due to disproportionation, whereas [Fe(tpy)X2] with
substituted tpy at the 6 and/or 6′′ position can be isolated because the
disproportionation is disturbed by steric repulsion between the
substituted tpy’s.
2,2′:6′,2′′-Terpyridine (tpy) is one of the simplest pincer ligands and
is thermally and chemically stable, inexpensive, and commercially
available. Therefore, it is important to evaluate and compare the
* Corresponding author.
E-mail addresses: kobayash@sci.osaka-cu.ac.jp (K. Kobayashi), nakazawa@sci.osaka-cu.ac.jp (H. Nakazawa).
https://doi.org/10.1016/j.ica.2021.120403
Received 30 November 2020; Received in revised form 7 April 2021; Accepted 8 April 2021
Available online 13 April 2021
0020-1693/© 2021 Elsevier B.V. All rights reserved.

K. Kobayashi and H. Nakazawa
Inorganica Chimica Acta 523 (2021) 120403
2. Experimental section
2.3. General procedure of hydrosilylation
2.1. General information
[M(tpy)Br2] (5.4 μmol) was dispersed in a mixture of 1-octene (0.85
mL, 5.4 mmol) and diphenylsilane (1.0 mL, 5.4 mmol) with/without 1.0
mL of a solvent in the Schlenk tube under N2. Sodium triethylborohy-
All the reactions were carried out under N2 using Schlenk techniques.
1H NMR spectra were recorded using a JEOL JNM-AL 400 spectrometer.
The residual peaks of the solvent or TMS were used as internal stan-
dards. GC analyses were carried out using a Shimadzu GC-2014 equip-
dride (NaBHEt3) (108 μL, 1.0 M in toluene) was then added to the sus-
pension to initiate the reaction. The solution was stirred at a controlled
temperature. After 24 h, the reaction was halted by the removal of the
catalyst and excess NaBHEt3 using a flash column (silica). The yields and
turnover numbers (TONs) of the products were determined by GC. The
yield and TON of hydrosilylation products from styrene and PhMe2SiH
(8l and 8v) [11] were determined by NMR using an internal standard
(dimethyl sulfone).
ped with an Rtx-5MS (RESTEC, 30 m, 0.25 mm ID, 0.25 μm) capillary
column. Product yields were determined based on the calibration curve
of each authentic sample. FAB-MS measurements were recorded using a
JEOL JMS-700(2).
2.2. Materials
2.4. Hydrosilylation of 1-octene with diphenylsilane by changing the
concentration of [Co(tpy)Br2]
[Cu(tpy)Br2] was synthesized according to a reported procedure [7].
[M(tpy)Br2] (M = Mn, Co, and Ni) were prepared by reported proced-
ures with a slight modification, as shown below. All other reagents were
purchased from commercial sources and used as received.
In Schlenk tubes, 2.4, 12, and 24 mg of [Co(tpy)Br2] (5.4, 27, and 54
mmol for 0.1, 0.5, and 1.0 mol%, respectively) were dispersed in a
mixture of 1-octene (0.85 mL, 5.4 mmol) and diphenylsilane (1.0 mL,
5.4 mmol) under N2. Sodium triethylborohydride (NaBHEt3) (1.0 M in
toluene, 20 times the amount of [Co(tpy)Br2]) was then added to the
suspension to initiate the reaction. After stirring for 24 h, the reaction
was halted by the removal of the catalyst and excess NaBHEt3 using a
flash column (silica). The yields and TONs of the products were deter-
mined by GC.
2.2.1. Preparation of [Mn(tpy)Br2]
[Mn(tpy)Br2] was synthesized by a procedure similar to that of [Mn
(tpy)Cl2] reported previously [8]. MnBr2 (107 mg, 0.50 mmol) was
dissolved in EtOH (2.0 mL), and a solution of 2,2′:6′,2′′-terpyridine (117
mg, 0.50 mmol) in EtOH (2.0 mL) was added. During stirring, a pale
yellow precipitate formed. After 15 min of stirring, the resulting pre-
cipitate was collected by filtration, washed with EtOH (10 mL) and ether
(10 mL), and dried in vacuo. Yield: 207 mg (92%). Anal. Calcd for
3. Results and discussion
C
15H11Br2N3Mn: C, 40.26; H, 2.67; N, 9.19. Found: C, 40.21; H, 2.47; N,
9.38. HRMS (FAB): [M-Br]+ Calcd. for C15H11BrN3Mn: 366.9517.
Found: 366.9498.
3.1. Catalytic activity of [M(tpy)Br2]
In general, [M(tpy)Br2] is considered not to be a real catalytic species
but a pre-catalyst instead. To produce the active species, [M(tpy)Br2] is
often reduced in advance or in situ [1–5]. In this study, an excess of
NaBHEt3 was used to reduce [M(tpy)Br2]. The hydrosilylation of 1-
octene with diphenylsilane (Ph2SiH2) was employed as a model reac-
tion (Eq. 1) to evaluate the catalytic activity of each complex.
In a 1:1 M mixture of 1-octene and Ph2SiH2, [M(tpy)Br2] (0.1 mol%
of the olefin or hydrosilane) was dispersed under N2. Then, 2.0 mol% of
NaBHEt3 in toluene solution was added to initiate the reaction. After
stirring the solution for 24 h at 25 ◦C, the reaction mixture was analyzed
by GC.
2.2.2. Preparation of [Co(tpy)Br2]
This compound was prepared by the published procedures for [Co
(tpy)Cl2] [9] with a slight modification. CoBr2 (87.5 mg, 0.40 mmol)
and tpy (93.3 mg, 0.40 mmol) were dissolved in THF (15 mL). During
stirring, a brown precipitate was formed. MeOH (3.0 mL) was added,
resulting in a color change from brown to emerald green. After stirring
for 24 h, the precipitate was collected by filtration. The emerald green
powder obtained was washed with small portions of MeOH and ether,
and then dried in vacuo. Yield: 170 mg (94%). Anal. Calcd for
C
15H11Br2N3Co⋅0.5H2O (M + 0.5H2O): C, 39.08; H, 2.62; N, 9.11.
Found: C, 39.34; H, 2.53; N, 9.14. HRMS(FAB): [M-Br]+ Calcd. for
C
15H11BrN3Co: 370.9468. Found: 370.9479.
(1).
2.2.3. Preparation of [Ni(tpy)Br2]
The results are shown in Table 1. Hydrosilylation of 1-octene with
Ph2SiH2 (Eq. (1)) produces two possible product types: the linear (anti-
Markovnikov) (1l) and branched (Markovnikov) (1b) products. [Co(tpy)
This complex was prepared by the procedure similar to that in the
previous report [10] with a little modification. To a solution of
NiBr2⋅3H2O (117 mg, 0.43 mmol) in THF (25 mL), 2,2′:6′,2′′-terpyridine
(100 mg, 0.43 mmol) in THF was added drop-wise over 10 min. The
mixture was stirred for 24 h, resulting in the formation of a pale green
precipitate. The precipitate was collected by filtration and washed with
THF (10 mL) and ether (10 mL). Vacuum drying yielded 194 mg of [Ni
Table 1
Hydrosilylation of 1-octene with Ph2SiH2 in the presence of [M(tpy)Br2] and
NaBHEt3.
Entry
Pre-catalyst
Yield of 1la,b
(tpy)Br2] as
a
pale green powder (84%). Anal. Calcd for
1
2
3
4
[Mn(tpy)Br2]
[Co(tpy)Br2]
[Ni(tpy)Br2]
[Cu(tpy)Br2]
No reaction
84%
C
15H11Br2N3Ni⋅1.5H2O: C, 37.63; H, 2.95; N, 8.87. Found: C, 37.76; H,
3.37; N, 9.33. HRMS(FAB): [M-Br]+ Calcd. for C15H11BrN3Ni: 369.9190.
Found: 369.9494.
40%
No reaction
a
Determined by GC. bBased on 1-octene, namely also Ph2SiH2.
2

K. Kobayashi and H. Nakazawa
Inorganica Chimica Acta 523 (2021) 120403
Br2] and [Ni(tpy)Br2], activated by NaBHEt3, served as catalysts to
generate the corresponding hydrosilylation compounds, which mainly
comprised the linear product (1l); 84% and 40% for [Co(tpy)Br2] and
[Ni(tpy)Br2], respectively. On the other hand, when [Mn(tpy)Br2] and
[Cu(tpy)Br2] were used as pre-catalysts, no products were detected.
Therefore, [Co(tpy)Br2] demonstrated the best catalytic activity for
hydrosilylation among the four base metal complexes; a small amount of
the branched product (1b) (4.0%) was also formed.
Table 3
Concentration dependence of [Co(tpy)Br2] on hydrosilylation of 1-octene with
Ph2SiH2.
Entry
Amount of [Co
Yielda,b
Total
yield
TON
Selectivity for
(tpy)Br2]b
1lc
1l
1b
1
2
3
0.1 mol%
0.5 mol%
1.0 mol%
84%
85%
84%
4.0%
12%
15%
88%
97%
99%
880
194
99
0.95
0.88
0.85
The catalytic activity of [M(tpy)Br2] in the absence of NaBHEt3 and
that of NaBHEt3 itself were also investigated. Both [Co(tpy)Br2] and [Ni
(tpy)Br2] showing catalytic activity with the help of NaBHEt3 did not
show any catalytic activity in the absence of NaBHEt3. Addition of 2.0
mol% of NaBHEt3 to the mixture of 1-octene and Ph2SiH2 in the absence
of any [M(tpy)Br2] produced a small amount of 1l (7.0% based on the
substrate). These results indicate that the complex derived from [M(tpy)
Br2] and NaBHEt3 is an actually active species
a
Determined by GC. bBased on 1-octene, namely also Ph2SiH2. cSelectivity for
1l = (yield of 1l)/(total yield).
Table 4
Solvent effect on hydrosilylation of 1-octene with Ph2SiH2 catalyzed by [Co(tpy)
Br2].
Entry
Solvent
Yielda,b
Total yield
Selectivity for 1lc
1l
1b
3.2. Optimization of [Co(tpy)Br2] catalysis
1
2
3
4
toluene
hexane
THF
85
82
98
90
4.0
89
0.96
0.91
8.0
90
Since [Co(tpy)Br2] exhibited good catalytic activity, the temperature
dependence of the hydrosilylation with Ph2SiH2 using [Co(tpy)Br2] was
examined (Table 2). As the temperature was increased from 25 ◦C, the
yield of the hydrosilylation product (1l) gradually decreased. At 100 ◦C,
only 54% yield was recorded. This may be due to decomposition of the
active species derived from [Co(tpy)Br2] at higher temperatures. The
regioselectivity for 1l was ranged from 0.94 to 0.98 at each temperature.
Since the reaction at 25 ◦C showed the best result, subsequent reactions
were performed at this temperature
2.0
100
0.98
pyridine
N.D.
90
>0.99
Determined by GC. bBased on 1-octene, namely also Ph2SiH2. cSelectivity for
a
1l = (yield of 1l)/(total yield).
and hexane (Table 4, Entries 1 and 2) were similar to those in the
absence of solvent (Table 3, Entry 1). The results for THF were the best
in terms of yield and regioselectivity (Entry 3). We previously reported
that a Co complex with an iminobipyridine derivative ligand showed
catalytic activity for the hydrosilylation of olefins, and the addition of
pyridine to the reaction system suppressed hydrosilylation [4]. In
contrast, the results of Entry 4 in Table 4 show that pyridine behaved as
a favorable solvent (90% yield of 1l and quite high selectivity (>0.99) of
1l).
Next, the hydrosilylation of 1-octene with Ph2SiH2 in the presence of
various amount of [Co(tpy)Br2] was examined at 25 ◦C (Table 3). When
the amount of the pre-catalyst [Co(tpy)Br2] was changed from 0.1 mol%
to 1.0 mol% based on 1-actene, namely also Ph2SiH2 (concentration of
the complex; ca. 2.9–29 mM), the yield of 1l was approximately constant
(84%), but the yield of 1b increased from 4.0% to 15%. In addition, the
total yield increased from 88% to 99%. Therefore, an increase in the
amount of catalyst from 0.1 mol% to 1.0 mol% caused an increase in the
yield of the branched product but not that of the linear product, which
led to an increase in total yield. However, this also led to a decrease in
selectivity and a significant decrease (almost one-tenth) in the catalytic
TON. In terms of regioselectivity and TON, it can be said that a reaction
using 0.1 mol% [Co(tpy)Br2] (Entry 1) is preferable.
With THF and pyridine as a solvent, the total yield and the selectivity
were improved, respectively. Since both solvents have coordination
ability, it is possible that they act as additional ligands during hydro-
silylation. For simple reasons that tpy is used as a metal ligand in this
study and is a pyridine analog, the effect of adding tpy was examined.
Excess tpy (10 eq toward [Co(tpy)Br2], 1.0 mol% based on 1-octene,
namely also Ph2SiH2) was added to the reaction system shown in Eq.
1. As a result, the yields of 1l and 1b were 85% and 3.3%, repsevtively,
and the selectivity was 0.96. These results were very similar to those
obtained without tpy (Table 2, Entry 1). In other words, the effect
observed with pyridine was not observed with the addition of tpy. The
details of the effect of pyridine are currently unknown.
3.3. Solvent effect on [Co(tpy)Br2] catalysis
Hydrosilylation reagents, such as hydrosilanes and olefins, are usu-
ally liquid, implying that no solvent is required for the reaction. How-
ever, when solid reactants are used, a solvent is needed. Thus, solvent
effects on hydrosilylation catalyzed by [Co(tpy)Br2] were investigated.
Toluene, THF, hexane, and pyridine were employed as solvents. An
equal volume of solvent to that of Ph2SiH2 was added, and the same
reaction conditions used for Entry 1 in Table 3 were applied. The results
of the product examination are shown in Table 4. The results for toluene
3.4. Hydrosilylation of olefins with a functional group
Hydrosilylation of functionalized olefins with Ph2SiH2 catalyzed by
[Co(tpy)Br2] was conducted under the same reaction conditions as
described for Eq. 1, as shown in Eq. 2. The results are summarized in
Table 5. When styrene and vinylcyclohexane were employed as olefin
substrates, the corresponding linear hydrosilylation products were
generated in excellent yields (Entries 1 and 2). In both cases, the cor-
responding branched products were not formed; when 1-octene was
used, a small amount of the branched product was formed (Table 2).
Dimethylallylamine was also converted to the corresponding product
(4), but the yield was moderate (53%). When 1,2-epoxy-5-hexene was
used (Entry 4), a complicated process took place. The hydrosilylated
product was formed, but the yield was very low (7%); the other products
could not be identified. Allyl chloride, vinyl acetate, and methyl acrylate
(Entries 5–7) were not converted into the corresponding hydrosilylation
products, and the olefins remained unchanged according to NMR mea-
surements. These functional groups probably inactivate the catalytically
active species.
Table 2
Temperature dependence on hydrosilylation of 1-octene with Ph2SiH2 catalyzed
by [Co(tpy)Br2].
Entry
Temperature
Yielda,b
Total yield
Selectivity for 1lc
1l
1b
1
2
3
4
5
25 ◦
40 ◦
60 ◦
80 ◦
C
C
C
C
84%
84%
79%
74%
54%
4.0%
5.4%
3.0%
2.7%
1.1%
88%
89%
82%
77%
55%
0.95
0.94
0.96
0.96
0.98
100 ◦
C
a
Determined by GC. bBased on 1-octene, namely also Ph2SiH2. cSelectivity for
1l = (yield of 1l)/(total yield).
3

K. Kobayashi and H. Nakazawa
Inorganica Chimica Acta 523 (2021) 120403
Table 5
Hydrosilylation of olefins with a functional group.
Entry
Product
Yielda,b
91%
1
2
93%
3
4
53%
7%
5
6
0
0
7
0
a
Determined by GC. bBased on olefin, namely also Ph2SiH2.
(2).
Table 6
Hydrosilylation of acetophenone with Ph2SiH2 catalyzed by [M(tpy)Br2].
Yield (TON)a,b
Total yield
(TON)
Selectivity for
3.5. Hydrosilylation using various silanes
Entry
Catalyst
9dc
9s
9d
Since hydrosilylation reactions with a secondary silane have been
described above, this section describes the results when primary and
tertiary silanes are used. Here, styrene was used as an olefin to simplify
the reaction system. When 1-octene was used, linear and branched
hydrosilylation products were formed, whereas when styrene was used,
only a linear product was formed (Table 5). When phenylsilane (PhSiH3)
was used, only the linear product (6) was produced in good yield (Eq. 3).
Triethoxysilane (HSi(OEt)3) and dimethylphenylsilane (PhMe2SiH)
were selected as tertiary silanes. Triethoxysilane afforded the linear
hydrosilylation product (7) with a moderate yield (Eq. 4). For dime-
thylphenylsilane (Eq. 5), the linear hydrosilylation product (8l) was
produced in 66% yield. In addition, the vinyl (dehydrogenative silyla-
tion) product (8v) was produced in 11% yield. The vinyl product was
found only in the reaction using PhMe2SiH. The reaction mechanism is
unclear; however, these results indicate that the [Co(tpy)Br2] catalyst
1
2
3
4
[Mn(tpy)
Br2]
30%
29%
59% (880)
56% (870)
47% (830)
51% (820)
0.49
0.55
0.77
0.60
(300)
25%
(580)
31%
[Co(tpy)
Br2]
(250)
11%
(620)
36%
[Ni(tpy)
Br2]
(110)
20%
(720)
31%
[Cu(tpy)
Br2]
(200)
(620)
a
Determined by GC. bBased on acetophenone, namely also Ph2SiH2. cSe-
lectivity for 9d = (yield of 9d)/(total yield).
system may be applied to tertiary silanes, even though tertiary silanes
are generally known to have poor participation in hydrosilylation re-
actions.
(3).
4

K. Kobayashi and H. Nakazawa
Inorganica Chimica Acta 523 (2021) 120403
(4).
(5).
(tpy)Br2] (Entry 3). Since 9d is generated from the reaction of 9s with
another molecule of acetophenone, the higher yield of 9d than 9s in-
dicates that acetophenone reacts faster with 9s than with Ph2SiH2 in this
system. The mechanism through which 9d production is favored over 9s
production is under investigation.
3.6. Hydrosilylation of acetophenone
It is well known that first-row transition metals often catalyze the
hydrosilylation of ketones [4,12], which can facilitate the reduction of
(6).
ketones under mild conditions [13]. Therefore, ketone hydrosilylation
catalyzed by [M(tpy)Br2] (Mn, Co, Ni, and Cu) was investigated and
compared with olefin hydrosilylation. Acetophenone was selected as a
model ketone substrate and treated with Ph2SiH2 in the presence of
catalytic quantities of [M(tpy)Br2] and NaBHEt3. The results are sum-
marized in Table 6. Unlike in the case of 1-octene, all four complexes
catalyzed hydrosilylation. The association constant of acetophenone to
the active species of [M(tpy)Br2] is likely to be much higher than that of
1-octene owing to the strong oxophilicity of the first-row transition
metals; this would explain the difference in reactivity between aceto-
phenone and olefins.
4. Conclusions
Co and Ni complexes bearing 2,2′:6′,2′′-terpyridine, [Co(tpy)Br2],
and [Ni(tpy)Br2], demonstrated catalytic activity for olefin (1-octene)
hydrosilylation in the presence of NaBHEt3 as a reducing activator,
whereas [Mn(tpy)Br2] and [Cu(tpy)Br2] did not show such activity. [Co
(tpy)Br2] exhibited better catalytic activity than [Ni(tpy)Br2]. The main
product was a linear hydrosilylation product, but a small amount of a
branched hydrosilylation product was also produced. The generation of
this by-product was suppressed by the addition of pyridine or THF. The
catalytic system using [Co(tpy)Br2] was applicable to hydrosilylations
involving primary and tertiary silanes. On the other hand, for ketone
(acetophenone) hydrosilylation, all complexes used in this study showed
catalytic activity. The 1:2 (Ph2SiH2:acetophenone) double hydro-
silylation product (9d) was the main product, even in the reaction of a
1:1 mixture of acetophenone and Ph2SiH2. Although the double hydro-
silylation product (9d) is expected from the stepwise hydrosilylation of
Ph2SiH2 through a single hydrosilylation product (9s), the yield of 9d
was higher than that of 9s. The detailed reaction mechanism is still
unclear, but it should be noted that the hydrosilylation of 1-octene with
Ph2SiH2 catalyzed by [M(tpy)Br2] did not produce the double hydro-
silylation product Ph2Si(C8H17)2. This difference seems to be due to the
In the reaction of 1:1 mixture of acetophenone and Ph2SiH2 cata-
lyzed by [M(tpy)Br2] (Eq. 6), the 2:1 (acetophenone:Ph2SiH2) double
hydrosilylation product (9d) was surprisingly the major product
(Table 6), although, in the case of [Mn(tpy)Br2], the yields of 9d and 9s
were approximately equal (Entry 1). A 1:1 single hydrosilylation prod-
uct (9s) is usually predominant in the reaction of a 1:1 mixture of ke-
tones and hydrosilanes [4,12]. To form 9d, two hydrosilylation
reactions are required; therefore, the TON should be two per molecule of
9d. Thus, the total TON using [Mn(tpy)Br2] was the highest, but the
selectivity for 9d was the lowest among the complexes shown in Table 6.
The highest selectivity for 9d was recorded for the reaction using [Ni
5

K. Kobayashi and H. Nakazawa
Inorganica Chimica Acta 523 (2021) 120403
Jpn. 92 (2019) 105. (d) D. Taguchi, K. Kobayashi, T. Moriuchi, H. Nakazawa, Bull.
Chem. Soc. Jpn. 93 (2020) 1086.
high oxophilicity of the first-row transition metals; the details are under
consideration.
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CRediT authorship contribution statement
[5] (a) D. Peng, Y. Zhang, X. Du, L. Zhang, X. Leng, M.D. Walter, Z. Huang, J. Am.
Chem. Soc. 135 (2013) 19154. (b) R. Gilbert-Wilson, W.-Y. Chu, T.B. Rauchfuss,
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Rauchfuss, Organometallics 35 (2016) 2900.
Katsuaki Kobayashi: Conceptualization, Data curation, Formal
analysis, Investigation, Methodology, Resources, Software, Validation,
Writing - original draft. Hiroshi Nakazawa: Conceptualization, Formal
analysis, Funding acquisition, Investigation, Methodology, Project
administration, Supervision, Validation, Writing - review & editing.
[6] (a) Y. Nakayama, Y. Baba, H. Yasuda, K. Kawakita, N. Ueyama, Macromolecules 36
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(2012) 3825.
Declaration of Competing Interest
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[7] M.I. Arriortua, J.L. Mesa, T. Rojo, T. Debaerdemaeker, D. Beltran-Porter,
H. Stratemeier, D. Reinen, Inorg. Chem. 27 (1988) 2976.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
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[8] C. Mantel, C. Baffert, I. Romero, A. Deronzier, J. Pecaut, M.-N. Collomb, C. Duboc,
Inorg. Chem. 43 (2004) 6455.
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52 (2013) 11290. (b) J. Peng, J.H. Docherty, A.P. Dominey, S.P. Thomas, Chem.
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Acknowledgements
[10] M. Khrizanforov, V. Khrizanforova, V. Mamedov, N. Zhukova, S. Strekalova,
V. Grinenko, T. Gryaznova, O. Sinyashin, Y. Budnikova, J. Organomet. Chem. 820
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This work was supported by the “Development of Innovative Cata-
lytic Processes for Organosilicon Functional Materials” project (PL: K.
Sato) from the New Energy and Industrial Technology Development
Organization (NEDO).
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