Hydrosilylation of diene derivatives catalyzed by Fe-iminobipyridine complexes aiming at syntheses of organosilane compounds containing a terminal olefin portion

Article abstract of DOI:10.1246/bcsj.20180197

The catalytic ability of Fe-iminobipyridine complexes ((BPI)FeBr₂, BPI = iminobipyridine) for hydrosilylation of both a non-conjugated diene and a conjugated diene was investigated aiming at the production of organosilane compounds bearing a te

Full text of DOI:10.1246/bcsj.20180197

Document type: Article
BCSJ Award Article
Hydrosilylation of Diene Derivatives Catalyzed by Fe-Iminobipyridine
Complexes Aiming at Syntheses of Organosilane Compounds Containing
a Terminal Olefin Portion
Katsuaki Kobayashi,* Sayaka Teratani, Yosuke Izumori,
Kazumasa Hayasaka, and Hiroshi Nakazawa*
Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
E-mail: kobayash@sci.osaka-cu.ac.jp
Received: July 18, 2018; Accepted: October 18, 2018; Web Released: December 28, 2018
Katsuaki Kobayashi
Katsuaki Kobayashi received his B. Sc and M. Sc in 1997 and 1999, respectively, from Science University of
Tokyo, and obtained his Ph. D from Graduate University for Advanced Studies in 2003. From 2003 to 2006,
he was a postdoctoral fellow at Institute for Molecular Science (IMS). From 2006 to 2009, he was an
assistant professor at Chuo University, and then moved to Konan University as a lecturer in 2009. From 2010
to 2012, he worked at IMS as a research assistant professor. From 2012 to 2017, he was a research
assistant professor at Integrated Cell-Material Sciences (iCeMS) of Kyoto University. Since 2017, he has
been a specially-appointed lecturer at Osaka City University.
Hiroshi Nakazawa
Hiroshi Nakazawa received his B.Sc. degree in 1975 from Science University of Tokyo, M.Sc. and Ph.D.
degrees in 1978 and 1981, respectively, from Hiroshima University. From 1981 to 1982 he worked at Tokyo
Institute of Technology and from 1982 to 1984 at University of Utah as a postdoctoral research fellow. He
became a research associate at Hiroshima University in 1984, and was promoted as an associate professor
in 1990. From 1994 to 1996 he was appointed as associate professor at Institute for Molecular Science. He
was promoted to full professor at Osaka City University in 2002. He has been an appointed professor at the
same university since 2018.
Abstract
a conjugated diene, (BPI)FeBr2 with any substituents selec-
tively generated 1,4-hydrosilylated compound in hydrosilyla-
tion of 2,3-dimethyl-1,3-butadiene with Ph2SiH2. In this case,
higher steric hindrance of (BPI)FeBr2 simply decreased the
yield of the product.
The catalytic ability of Fe-iminobipyridine complexes
((BPI)FeBr2, BPI = iminobipyridine) for hydrosilylation of
both a non-conjugated diene and a conjugated diene was inves-
tigated aiming at the production of organosilane compounds
bearing a terminal olefin portion. Steric effects of (BPI)FeBr2
were controlled by the substituents at the terminal pyridine ring
(R1), the imino carbon (R2), and the imino nitrogen (Ar) of the
BPI ligand. As regards a non-conjugated diene, hydrosilylation
of 1,7-octadiene with diphenylsilane (Ph2SiH2) produced a
mixture of mono- and di-hydrosilylated compounds. To obtain
the mono-hydrosilylated compound preferably in the 1:1 reac-
tion of non-conjugated diene and silane, the substituent effect
of the BPI ligand was investigated. As a result, larger steric hin-
drance of (BPI)FeBr2 based on substituents slowed the hydro-
silylation, instead the selectivity of the mono-hydrosilylated
compound was substantially improved. The 6¤-Me group on a
terminal pyridine was most effective. Finally, production of
the mono-hydrosilylated compound from 1,7-octadiene and
Ph2SiH2 reached 77% yield and 0.94 selectivity. In the case of
Keywords: Hydrosilylation catalyst
j
Fe complex
j
Hydrosilylation of diene
1. Introduction
Organosilane compounds and materials have attracted a great
deal of interest because of their versatile and excellent proper-
ties. For example, a silane coupling agent often modifies surface
properties of solid materials, and assists the linkage between the
solid surfaces and functional organics leading to new compo-
sites in not only industrial application but also dentistry.1-3
Creation of a simple and convenient synthesis of organosilane
compounds bearing functional groups may contribute to the
development of a wide range of research fields and applications.
Bull. Chem. Soc. Jpn. 2019, 92, 105–114 | doi:10.1246/bcsj.20180197
© 2019 The Chemical Society of Japan | 105

Hydrosilylation of olefin is a widely-used and atom-
economical methodology to obtain organosilane compounds
on the basis of the generation of a Si-C bond. Pt cata-
lysts4-6 such as Speier’s4 and Karstedt’s5 are generally used for
hydrosilylation, despite the rarity of Pt. In order not to depend
on the use of precious metals, alternative catalysts composed of
earth-abundant metals, such as Fe,7-14 Co,10,11,15-22 and Ni,23,24
have been significantly developed. Especially, Fe catalysts
have drawn considerable attention because of an absolute
advantage in earth abundance.
SiH(4-n)Rn
Catalyst
n = 1-3
SiH(3-n)Rn
RnH(3-n)Si
a
c
One recent interest in this research field is the creation of a
practical catalytic system to obtain organosilane compounds in
hydrosilylation reaction of olefins with a functional group.
Several hydrosilylation reactions in which a functional group in
the olefin remains intact have been reported: chemoselective
hydrosilylation of olefin bearing halogeno,10,14,17,20,21,24 hy-
droxy,19,21 carbonyl,9,19,20 epoxy,8,11,19,20,22,24,25 amino,14,16,20,24
and thioether26 groups. In contrast, the application of hydro-
silylation for the preparation of organosilanes bearing a C=C
double bond portion is limited. If only one C=C double bond
in a diene derivative is hydrosilylated, the desired organosilane
would be produced.
RnH(3-n)Si
SiH(3-n)Rn
b
n = 1-2
H(2-n)Rn
Si
SiH(2-n)Rn
x
d
e
Scheme 1. Possible products obtained from hydrosilylation
of 1,5-hexadiene.
Hydrosilylation of internal olefins catalyzed by a transition
metal complex is generally rare. Although several examples
have been reported, iron complexes showing such activity have
been little reported. Moreover, silane compounds having an
olefin portion in a terminal position are more useful as a silane
coupling agent than those in an internal position. Therefore, we
sought a reaction system in which an Fe complex catalyzes
mono hydrosilylation of terminal dienes to yield organosilanes
bearing an olefin portion in the terminal position. Terminal
diene derivatives can be classified into non-conjugated dienes
and conjugated ones. A non-conjugated diene which has two
alkenyl groups at both ends (α, ω-non-conjugated diene) pos-
sibly affords several products by hydrosilylation. For example,
there are several reports for hydrosilylation of 1,5-hexadiene
which produces the mono-hydrosilylated compound (a), the
di-hydrosilylated (b), cyclized products (c and d), and poly-
mer (e) (Scheme 1).27 Cyclized compounds (c and d) were
often obtained from 1,5-hexadiene.27-29 Dienes longer than
1,5-hexadiene would not be suitable for the cyclization except
4,4-substiduted-1,6-heptadiene and 4,4,5,5-substiduted-1,7-
octadiene.30 Mono-hydrosilylated compound undergoes poly-
merization through intermolecular hydrosilylation except using
tertiary silane derivatives as substrates.28 Similarly, oligo-
hydrosiloxane derivatives which have multiple Si-H bonds
often form inorganic/organic hybrid polymers (polyorgano-
siloxane).31 Mono- and di-hydrosilylated compounds are
obtained from any reaction conditions and any chain length.
However, the selective mono hydrosilylation of α, ω-non-
conjugated diene has been rarely reported.
R1 = H, 5'-Me, 6'-Me
R2
R2 = H, Me
N
N
Fe
N
Ar = Mes, Dipp
R1
Ar
Br
Br
Figure 1. Molecular structure of (BPI)FeBr2.
Table 1. Abbreviations of (BPI)FeBr2 in this study
R1
R2
Ar
Reference
1HM
1MM
1HD
1MD
H
H
H
H
H
Me
H
Mes
Mes
Dipp
Dipp
13
14
13
14
Me
2HM
2MM
2HD
2MD
5¤-Me
5¤-Me
5¤-Me
5¤-Me
H
Me
H
Mes
Mes
Dipp
Dipp
This work
This work
This work
This work
Me
3HM
3MM
3HD
3MD
6¤-Me
6¤-Me
6¤-Me
6¤-Me
H
Me
H
Mes
Mes
Dipp
Dipp
13
This work
13
This work
Me
Our group developed Fe complexes aiming at hydrosilyla-
tion.12-14,36 Recently, we found that Fe-iminobipyridine com-
plexes ((BPI)FeBr2, BPI = iminobipyridine, Figure 1 and
Table 1) were good pre-catalysts for olefin hydrosilylation.13,14
These complexes were activated by NaBHEt3, leading to
extremely high catalytic ability for hydrosilylation. It was also
reported that steric effects around a catalytic Fe center can be
controlled by the introduction of substituents at the terminal
pyridine ring (R1), the imino carbon (R2), and the imino nitro-
gen (Ar).14 Best turnover number (TON), 42,000, was recorded
in 1MM catalyzed reaction between 1-octene and diphenylsilane
(Ph2SiH2).14 To our knowledge, this TON is the highest among
Fe catalysts reported so far.
As regards conjugated dienes, butadiene derivatives can
be converted to organosilane compounds having a terminal
olefin portion through 1,2-additon of silane. However, 1,4-
hydrosilylation commonly takes place on butadiene deriva-
tives.15,23,25,32,33 Although there have been three reports
about selective 1,2-hydrosilylation of dienes to date,34,35 only
a Pt catalyst succeeded in 1,2-hydrosilylation of butadiene
derivatives.34
106 | Bull. Chem. Soc. Jpn. 2019, 92, 105–114 | doi:10.1246/bcsj.20180197
© 2019 The Chemical Society of Japan

In this paper, we attempted to apply the series of (BPI)FeBr2
to hydrosilylation of both linear non-conjugated and conju-
gated dienes with the hope that one unsaturated bond of diene
is used for hydrosilylation and the other unsaturated part
remains unreacted in the catalytic system. Substituent effect of
R1, R2, and Ar in BPI (Figure 1) on hydrosilylation selectivity
was investigated.
(7a-f). Finally, 1:1 reaction between FeBr2 and the BPI ligand
in THF under N2 resulted in the formation of the precipitate
of pure (BPI)FeBr2. BPI ligands and their precursors were
characterized by NMR, DART mass, and elemental analysis.
The iron complexes were characterized by FAB mass and
elemental analysis. NMR measurements of all iron complexes
were difficult due to their poor solubility in common solvents.
These iron complexes can be easily handled under ambient
conditions prior to the formation of the active species induced
by NaBHEt3 reduction.
2. Results and Discussion
Preparation of Iminobipyridine Derivatives Bearing 5¤-
Me and 6¤-Me Group and Their Fe Complexes.
Fe-
Hydrosilylation of a Non-Conjugated Diene.
Among
iminobipyridine complexes, (BPI)FeBr2, used in this paper are
shown in Figure 1, which consist of a combination of three
substituents at the terminal pyridine ring (R1), the imino carbon
(R2), and the imino nitrogen (Ar). The abbreviations of them
are summarized in Table 1. Complexes 1, 2, and 3 repre-
sent (BPI)FeBr2 with H, 5¤-Me, and 6¤-Me groups on the ter-
minal pyridine, respectively. First and second suffixes of each
number represent R2 and Ar, where H and M at R2, M and D
at Ar indicate a hydrogen atom, Me, Mes, and Dipp groups,
(BPI)FeBr2, 1HM has the simplest ligand with the smallest steric
hindrance. Therefore, we firstly employed 1HM as a catalyst
for non-conjugated diene hydrosilylation.
1,7-octadiene was employed as a substrate, since longer
diene is suitable because it may not form cyclization products.
Similarly, with respect to silane source, we selected diphenyl-
silane (Ph2SiH2), since SiH4, phenylsilane (PhSiH3) and
hydrosiloxane derivatives are used as polymer production.28,31
Thus, the catalytic ability and product selectivity of (BPI)FeBr2
was evaluated by the reaction between 1,7-octadiene and
Ph2SiH2 (Scheme 3).
respectively
(Mes = 2,4,6-trimethylphenyl,
Dipp = 2,6-
diisopropylphenyl).
Synthetic routes of new ligands in this paper are similar
to those of aldimine type iminobipyridine ligands (R2 = H)
reported to date (Scheme 2).13 Stille coupling between 4a and
5a or 5b, 4b and 5b afforded bipyridine derivatives bearing a
carbonyl group, 6a, 6b, and 6c, respectively. Imino bond for-
mation was performed by the condensation reaction between
formyl- or acetylbipyridine derivatives (6a, 6b, or 6c) and
ArNH2 (Ar = Mes, Dipp) to give corresponding BPI ligands
Hydrosilylation of a diene was conducted according to the
previous report of (BPI)FeBr2 catalysts.14 To a mixture of 1,7-
octadiene and Ph2SiH2 without any other solvent 0.1 mol %
1HM was added and then 2.0 mol % NaBHEt3 was added to
initiate hydrosilylation. The mono-hydrosilylated compound
(A) and the di-hydrosilylated one (B) were obtained as prod-
ucts, and cyclic silanes and polymer were not detected at all.
Table 2 shows the yield and selectivity of products of hydro-
silylation in various molar ratios of 1,7-octadiene and Ph2SiH2.
TON indicates turnover number of hydrosilylation based on
the Fe complex; the production of the mono-hydrosilylated
compound (A) counts once, and that of the di-hydrosilylated
R1 = 5-Me (4a)
R1
6-Me (4b)
N
SnnBu3
R2
R2
0.1 mol% (BPI)FeBr2
2.0 mol% NaBHEt3
ArNH2
Br
N
N
Ph2SiH2
+
MeOH
60 C
Pd(PPh3)4,
Toluene,
reflux
O
N
O
2
48 h, r.t.
Ph2HSi
R1
R2 = H (5a)
Me (5b)
(R1,R2)=5'-Me,H (6a) 53%
+
SiPh2H
2
2
SiPh2H
5'-Me,Me (6b) 62%
A
B
6'-Me,Me (6c) 83%
Scheme 3. Hydrosilylation of 1,7-octadiene with Ph2SiH2
catalyzed by (BPI)FeBr2.
R2
R2 FeBr2
N
Fe
Table 2. Hydrosilylation catalyzed by 1HM in the various
ratio of 1,7-octadiene and Ph2SiH2
N
N
a
N
N
THF
N
Ar
R1
Ar
R1
Br Br
Yieldb,c (TON)b,d
[Octadiene]:
Entry
Selectivitye
[Ph2SiH2]
A
B
(R1,R2,Ar) =
(R1,R2,Ar) =
1
2
2
3
1:1
2:1
3:1
5:1
74% (740) 21% (420)
78% (780) 17% (340)
0.78
0.82
0.97
0.99
5'-Me, H, Mes (7a) 89% 5'-Me, H, Mes (2HM) 94%
5'-Me, Me, Mes (7b) 74% 5'-Me, Me, Mes (2MM) 98%
5'-Me, H, Dipp (7c) 90% 5'-Me, H, Dipp (2HD) 90%
5'-Me, Me, Dipp (7d) 71% 5'-Me, Me, Dipp (2MD) 71%
6'-Me, Me, Mes (7e) 64% 6'-Me, Me, Mes (3MM) 95%
6'-Me, Me, Dipp (7f) 71% 6'-Me, Me, Dipp (3MD) 89%
88% (880)
86% (860)
3% (60)
1% (20)
aReaction conditions: Neat, r.t., 48 h, under N2, 0.1 mol % 1HM
,
b
c
2.0 mol % NaBHEt3. Determined by HPLC. The yields are
based on the initial concentration of Ph2SiH2. dTONs are based
e
on the initial concentration of the Fe complex. Selectivity =
Scheme 2. Synthetic route of (BPI)FeBr2.
[A]/[Total yield].
Bull. Chem. Soc. Jpn. 2019, 92, 105–114 | doi:10.1246/bcsj.20180197
© 2019 The Chemical Society of Japan | 107

Table 3. Hydrosilylation between 1,7-octadiene and
Ph2SiH2 catalyzed by R2 substituted (BPI)FeBr2 (R2 = H
or Me)a
Table 4. Hydrosilylation of 1,7-octadiene with Ph2SiH2
catalyzed by R1 substituted (BPI)FeBr2 (R1 = 5¤-Me or
6¤-Me)a
Yieldb,c (TON)b,d
Total
Yieldb,c (TON)b,d
Total
Entry Cat.
Selectivitye
Entry Cat.
Selectivitye
yield
yields
A
B
A
B
1
2
3
4
1HM 74% (740) 21% (420) 95%
1MM 73% (730) 16% (320) 89%
1HD 72% (720) 20% (400) 92%
1MD 69% (690) 17% (340) 86%
0.78
0.82
0.78
0.80
1
2
3
4
2HM 77% (770) 17% (340)
2MM 71% (710) 12% (240)
2HD 67% (670) 19% (380)
2MD 65% (650) 18% (360)
94%
83%
86%
83%
0.82
0.86
0.78
0.78
aReaction conditions: Neat, r.t., 48 h, under N2, [1,7-octadiene]:
[Ph2SiH2] = 1:1, 0.1 mol % (BPI)FeBr2, 2.0 mol % NaBHEt3.
5
6
7
8
3HM 65% (650)
3MM 64% (640)
3HD 69% (690) 12% (240)
3MD 66% (660) 5% (100)
9% (180)
8% (160)
71%
72%
81%
71%
0.97
0.89
0.85
0.93
c
bDetermined by HPLC. The yields are based on the initial
concentration of Ph2SiH2. dTONs are based on the initial
concentration of the Fe complex. eSelectivity = [A]/[Total
yield].
aReaction conditions: Neat, r.t., 48 h, under N2, [1,7-octadiene]:
[Ph2SiH2] = 1:1, 0.1 mol % (BPI)FeBr2, 2.0 mol % NaBHEt3.
bDetermined by HPLC. The yields are based on the initial
c
concentration of Ph2SiH2. dTONs are based on the initial
concentration of the Fe complex. eSelectivity = [A]/[Total
yield].
compound (B) counts twice. And the selectivity of A is defined
as yield(A)/total yield.
With increase of the content of diene, the selectivity of A
increased. It was reported that a Pt catalyst selectively gen-
erated the mono-hydrosilylated compound in the reaction of
1,5-hexadiene with 2-fold SiHCl3 with 90% yield and 0.90
selectivity.37 1HM exhibited similar performance in the catalytic
reaction between 1,7-octadiene and Ph2SiH2. However, in this
case, more than three molar equivalents of diene were required
to effectively suppress the generation of the di-hydrosilylated
compound (B). From the viewpoint of atom economical strat-
egy, excess diene was wasteful. Thus, we tried to improve the
catalytic system.
Substituents Effect of (BPI)FeBr2 on Catalytic Hydro-
silylation of a Non-Conjugated Diene. At first, the sub-
stituent effect of R2 on the yield and selectivity of hydro-
silylation of 1,7-octadiene was examined in the 1:1 mixture of
diene and silane (Table 3). 1HM showed the highest total yield
(95%, Entry 1 in Table 3). Introduction of a Me group at R2
slightly reduced the total yields of the product (Entries 2, 4 in
Table 3) both in the Ar = Mes and Dipp system, while the
selectivity of the mono-hydrosilylated compound increased
with decrease of total yield. Di-hydrosilylated compound is
generated from the mono-silylated one which has more steric
hindrance than the original substrate, 1,7-octadiene. This steric
effect was enhanced by the introduction of a Me group at R2.
As a substituent at R2 may not have a direct effect on the
catalytic center of (BPI)FeBr2, introduction of R2 results in
small decrease in yield and increase of selectivity.
To increase the steric effect in the vicinity of the Fe center, a
Me group was introduced at the 5¤- or 6¤-positon of the terminal
pyridine of (BPI)FeBr2 (R1 = 5¤-Me or 6¤-Me). Catalytic abil-
ities of 5¤- and 6¤-substituted Fe complexes are summarized in
Table 4.
In the case of 5¤-subsituted complexes with/without a Me
group at R2 (2HM-2MD in Table 1), total yields and selectivity
(Table 4 Entries 1-4) were quite similar to those of non-
substituted complexes (R1 = H, Table 3).
On the other hand, the introduction of 6¤-Me group at R1
significantly decreased total yield of hydrosilylated com-
pounds, which resulted from the steric barrier to the approach
of the substrates (Entries 5-8), since the 6¤-Me group directly
covers the coordination site of Fe for the substrate binding. On
the contrary, the selectivity of the mono-hydrosilylated com-
pound (A) increased with decrease of total yield. 3HM and 3MD
showed good selectivity of the mono-hydrosilylated product
(0.97 and 0.93) and even lower yield (71%). These facts indi-
cate that the low yield with high selectivity originates from
slower production of the di-hydrosilylated compound (B) than
that of the mono-hydrosilylated one (A), i.e., the difference of
the production rate between A and B is subject to the selec-
tivity. Moreover, it is worth noting that the production of B
never starts without enough concentration of A in the reaction
mixture.
Reaction Time and Temperature Dependence on Cata-
lytic Hydrosilylation of a Non-Conjugated Diene.
The
aforementioned findings suggested longer reaction time by
using 3HM and 3MD as catalysts to make total yields higher and
selectivity lower. Time dependence on the product yield and
selectivity of hydrosilylation of 1,7-octadiene catalyzed by 3HM
and 3MD was examined, and the results are shown in Table 5.
Those of 1HM are also shown for comparison.
In the all cases, the elongation of reaction time increased
total yields and decreased selectivity (Table 5), since the time
elongation also increased the yield of the di-hydrosilylated
compound (B). Catalytic hydrosilylation by 3HM and 3MD was
quite slow compared to that by 1HM. The reaction catalyzed by
3HM kept high selectivity during the reaction. However, the
total yield by 3HM leveled off around 80%. The best result was
obtained from the reaction using 3MD. Total yield by 3MD
increased up to 89% at 168 h with good selectivity (0.87). In
this case, the yield of A hit a peak at 72 h and slightly decreased
after 72 h with gradual increase of B.
In order to improve the yield and selectivity, the hydro-
silylation catalyzed by 1HM, 3HM, and 3MD at higher temper-
ature was conducted. Table 6 showed the results of hydro-
silylation of 1,7-octadiene with Ph2SiH2 at 120 °C. Total yield
by 1HM substantially got worse compared to that at r.t., while
the selectivity was improved. Although hydrosilylation by 3HM
maintained 0.95 selectivity even at 120 °C, total yield at 48 h
108 | Bull. Chem. Soc. Jpn. 2019, 92, 105–114 | doi:10.1246/bcsj.20180197
© 2019 The Chemical Society of Japan

0.1 mol% 3MD
2.0 mol% NaBHEt3
Table 5. Time dependence of hydrosilylation of 1,7-octa-
diene with Ph2SiH2 catalyzed by 1HM, 3HM, and 3MD at
room temperaturea
Si-H
+
n
48 h, 120 C
Yieldb,c
(TON)b,d
Si
Si
Si
Time
(h)
Total
yield
+
Entry Cat.
Selectivitye
n
n
A
B
Mono
Di
1
2
1HM
1
38% (380) 10% (200) 48%
0.79
0.78
Si-H = PhSiH3, Ph2SiH2, Ph2MeSiH
1HM 48 74% (740) 21% (420) 95%
n = 4~6
3
4
5
6
3HM 15% (300) 0.9% (18) 16%
1
0.95
0.95
0.93
0.91
3HM 48 69% (540) 4% (80) 71%
3HM 72 74% (740) 5% (100) 79%
3HM 168 75% (750) 7% (140) 82%
Scheme 4. Hydrosilylation of various non-conjugated dienes
and silanes at catalyzed by 3MD at 120 °C.
Table 7. Hydrosilylation of various non-conjugated dienes
and silanes catalyzed by 3MD at 120 °Ca
7
8
9
3MD
1
11% (110) 0.6% (60) 12%
0.95
0.93
0.92
0.87
3MD 48 66% (390) 5% (100) 71%
3MD 72 78% (780) 7% (140) 85%
Chain
Entry Length
(n)
Yieldb,c (TON)b,d
Mono Di
10 3MD 168 77% (720) 12% (240) 89%
Total
yield
Si-H
Selectivitye
aReaction conditions: Neat, r.t., under N2, [1,7-octadiene]:
[Ph2SiH2] = 1:1, 0.1 mol % (BPI)FeBr2, 2.0 mol % NaBHEt3.
1
2
3
4
4
4
5
6
PhSiH3 57% (570) 38% (760) 95%
0.60
®
bDetermined by HPLC. The yields are based on the initial
c
Ph2MeSiH
N.D.
N.D.
®
concentration of Ph2SiH2. dTONs are based on the initial
Ph2SiH2 35% (350) 3% (6)
Ph2SiH2 28% (280) 2% (4)
38%
30%
0.92
0.93
e
concentration of the Fe complexes. Selectivity = [A]/[Total
yield].
aReaction conditions: Neat, 120 °C, under N2, [diene]:
[Si-H] = 1:1, 0.1 mol % 3MD, 2.0 mol % NaBHEt3. bDeter-
Table 6. Hydrosilylation of 1,7-octadiene with Ph2SiH2
catalyzed by 1HM, 3HM, and 3MD at 120 °Ca
c
mined by HPLC. The yields are based on the initial concen-
tration of Ph2SiH2. dTONs are based on the initial concen-
tration of the Fe complexes. eSelectivity = [Mono]/[Total
yield].
Yieldb,c (TON)b,d
Total
Entry Cat. Time
Selectivitye
yield
1HM 48 69% (690) 11% (220) 80%
3HM 48 54% (540) 3% (8) 57%
3MD 48 77% (770) 5% (100) 82%
A
B
1
2
3
0.86
0.95
0.94
Hydrosilylation by Using Primary and Tertiary Silanes
and Terminal Dienes with Longer Chain Length.
As
aReaction conditions: Neat, 120 °C, under N2, [1,7-octadiene]:
[Ph2SiH2] = 1:1, 0.1 mol % (BPI)FeBr2, 2.0 mol % NaBHEt3.
mentioned above, the steric hindrance of an iminobipyridine
ligand greatly affected the selectivity for mono-hydrosilylated
compound by the hydrosilylation of a diene. Next, we exam-
ined hydrosilylation by using primary and tertiary silanes and
terminal dienes with longer chain length. 3MD was selected as a
catalyst, since it showed best performance for the selective
production of the mono-hydrosilylated compound at 120 °C
(Entry 3 in Table 6). PhSiH3 and Ph2MeSiH were employed as
primary and tertiary silane substrates. Hydrosilylation of 1,7-
octadiene (n = 4 in Scheme 4) with them are summarized in
Table 7 (Entry 1 and 2).
Total yield of the hydrosilylated compounds from the reac-
tion between 1,7-octadiene (n = 4) with PhSiH3 was quite high
(95%), but it consisted of 57% of mono-hydrosilylated com-
pound (Mono) and 38% of di-hydrosilylated compound (Di)
Therefore, the selectivity of Mono was quite low (0.60). In the
reaction of 1,7-octadiene with Ph2MeSiH, no products were
detected. It was already reported that hydrosilylation of an
olefin with a tertiary silane by (BPI)FeBr2 hardly proceed-
ed.13,14 Less catalytic activity of (BPI)FeBr2 for a tertiary silane
in this study was well consistent with previous reports.
Hydrosilylation of dienes longer than 1,7-octadiene were
also carried out to elucidate the influence of the chain length
of the diene. Hydrosilylation of 1,8-nonadiene (n = 5 in
Scheme 4) and Ph2SiH2 afforded 35% of mono-hydrosilylated
compound (Mono) and 2% of di-hydrosilylated one (Di)
(Entry 3 in Table 7). 1,9-decadiene (n = 6 in Scheme 4) was
bDetermined by HPLC. The yields are based on the initial
c
concentration of Ph2SiH2. dTONs are based on the initial
e
concentration of the Fe complexes. Selectivity = [A]/[Total
yield].
was lowered from 71% to 57% by the elevation of the reaction
temperature. In contrast, the total yield (82%) and selectivity
(0.94) by 3MD were improved at higher temperature. This
difference apparently originates from the thermal stability of
the active species of Fe complexes; unstable active species of
1HM and 3HM decomposed at higher temperature, and stable
that of 3MD led to the better yield and selectivity. Among
(BPI)FeBr2 in this study, 3MD has the bulkiest ligand. There-
fore, the active site of the catalytically active species derived
from 3MD has tolerance against decomposition at higher tem-
perature, leading to thermal stability of the active species and
concomitantly longer reaction time. Bulkiness of the ligand
would contribute to not only the selectivity for mono-
hydrosilylated compound but also the thermal stability of the
catalyst.
Thus, the best yield and selectivity for mono-hydrosilylated
compound (A) were accomplished in the reaction conditions
exhibited by Entry 3 in Table 6, 77% yield of A with 0.94
selectivity.
Bull. Chem. Soc. Jpn. 2019, 92, 105–114 | doi:10.1246/bcsj.20180197
© 2019 The Chemical Society of Japan | 109

0.1 mol% (BPI)FeBr2
2.0 mol% NaBHEt3
Insertion to Fe-H
Fe
Insertion to Fe-Si
Ph2SiH2
+
72 h, r.t.
Fe
H
Fe
Si
Si
SiPh2H
+
SiPh2H
H
H
Si
C
D
π-ally lintermediate
π-ally lintermediate
Scheme 5. Hydrosilylation of 2,3-dimethyl-1,3-butadiene
with Ph2SiH2 catalyzed by (BPI)FeBr2.
Fe
Table 8. Catalytic hydrosilylation of 2,3-dimethyl-1,3-buta-
diene with Ph2SiH2 using (BPI)FeBr2 as catalystsa
Fe
Si
Si
H
Entry
Cat.
Yieldb,c of D (TON)b,d
Si
1
2
3
4
1HM
1MM
1HD
1MD
88% (880)
67% (670)
92% (920)
64% (640)
Product
Figure 2. Suggested mechanism of 1,4-hydrosilylated com-
pound production by hydrosilylation of a butadiene
derivative.
5
6
7
8
2HM
2MM
2HD
2MD
84% (840)
33% (330)
80% (800)
23% (230)
hydrosilylation proceeds through the intermediate of the π-allyl
complex (Figure 2).33,34 There are two possible pathways to
form π-allyl complexes via diene insertion to Fe-Si or Fe-H
(Figure 2). It remains unclear whether the reaction proceeds via
diene insertion to Fe-Si or Fe-H. However both intermediates
have similar steric hindrance around Fe. Thus, to form the π-
allyl intermediates, large space is required in the vicinity of the
Fe center. Therefore the steric hindrance of the BPI ligand is
more effective on conjugated diene activation than that on non-
conjugated diene.
9
3HM
3MM
3HD
3MD
30% (300)
21% (210)
39% (390)
26% (260)
10
11
12
aReaction conditions: Neat, r.t., 72 h, under N2, [2,3-dimethyl-
1,3-butadiene]: [Ph2SiH2] = 1:1, 0.1 mol % (BPI)FeBr2, 2.0
mol % NaBHEt3. bDetermined by HPLC. cThe yields are based
d
on the initial concentration of Ph2SiH2. TONs are based on
the initial concentration of the Fe complexes.
3. Conclusion
also selected as a substrate, which produced Mono compound
and Di compound with 28% and 2% yield, respectively, in the
same reaction conditions (Entry 4 in Table 7). Total yields of
both reactions (n = 5 and 6) were quite low (38% and 30% for
n = 5 and n = 6, respectively), though the selectivity of both
reactions (0.92 and 0.93 for n = 5 and n = 6) was similar to the
reaction between 1,7-octadiene and Ph2SiH2 (0.94, Entry 3 in
Table 6).
These results indicate that steric hindrance of substrates also
drastically affects the yield and selectivity, similar to that of an
iminobipyridine ligand; bulky substrate increases the selectiv-
ity for mono-hydrosilylated compound and decreases the yield.
Hydrosilylation of a Conjugated Diene. For the hydro-
silylation of a conjugated diene, the reactions of 2,3-dimethyl-
1,3-butadiene with Ph2SiH2 were employed (Scheme 5).
Although possible products were 1,2-hydrosilylated compound
(C) and 1,4-hydrosilylated one (D), (BPI)FeBr2 generated only
the 1,4-addition product in all cases (Table 8).
Among (BPI)FeBr2 complexes, 1HD was most active for
hydrosilylation of 2,3-dimethyl-1,3-butadiene (92%). Introduc-
tion of a Me group at R2 largely decreased the product yield
(even number Entries in Table 8), especially, by using the Fe
complex with R1 = 5¤-Me, the yields were reduced to one-third
or less of those by non-substituted complexes at R1 (Entries 6
and 8 in Table 7). Similarly, the steric effect of 6¤-Me group at
R1 on catalytic hydrosilylation was tremendously large; the
product yields obtained from 3HM-3MD catalysis dramatically
decreased (Entries 9-12 in Table 7). It is suggested that 1,4-
In order to obtain an organosilane compound bearing a
terminal olefin portion, we tried hydrosilylation of a non-
conjugated diene and a conjugated diene using Fe-iminobipyr-
idine complexes ((BPI)FeBr2) as catalysts. Upon the hydro-
silylation of a non-conjugated diene, 1HM produced both the
mono-hydrosilylated compound and the di-hydrosilylated one
by the reaction between 1,7-octadiene and Ph2SiH2. For the
selective production of the desired compound (the mono-
hydrosilylated compound) by 1HM catalysis, more than three
molar equivalents of 1,7-octadiene were required. To decrease
excess diene in this reaction, the effect of substituents of
(BPI)FeBr2 on hydorosilylation of 1,7-octadiene was inves-
tigated. Steric hindrance of the BPI ligand based on three
substituents (R1, R2, and Ar) slowed the reaction, instead it
improved the selectivity of a desired compound. Particularly,
6¤-Me group on the terminal pyridine of BPI was most effec-
tive, since it covers the Fe center directly. Yield and selectivity
for the mono-hydrosilylated compound in the reaction between
1,7-octadiene and Ph2SiH2 reached 77% and 0.94, respectively.
Selectivity of the mono-hydrosilylated compound is kineti-
cally controlled, therefore steric effect of the BPI ligand is
advantageous to improve the selectivity. Similarly, steric hin-
drance of substrates also affected the selectivity of the mono-
hydrosilylated compound. However, large steric hindrance of
both an iminobipyridine ligand and substrates decrease the
yield of hydrosilylation product. Thus, in order to obtain vari-
ous mono-hydrosilylated compounds from dienes selectively,
the steric effect of an iminobipyridine ligand should be
110 | Bull. Chem. Soc. Jpn. 2019, 92, 105–114 | doi:10.1246/bcsj.20180197
© 2019 The Chemical Society of Japan

adjusted for substrates. On the other hand, upon the application
of (BPI)FeBr2 to hydrosilylation of a conjugated diene (2,3-
dimethyl-1,3-butadiene), 1,4-hydrosilylatied compound was
selectively formed. In this case, the steric effect based on three
substituents simply decreased the yield of a product. Although
1,2-hydrosilylated compound would be a desired product in
this study, production of it was not observed at all. Selective
1,2-hydrosilylation is quite rare, and there have been only three
reports so far.34,35 Only one report of them succeeded in the for-
mation of an organosilane compound bearing a terminal olefin
portion by 1,2-hydrosilylation of 1,3-butadiene.34 To obtain a
target compound in this study through the hydrosilylation of
conjugated diene derivatives, further improvement and strategy
of catalytic system should be required.
4a (37.1 g, 97.1 mmol), 5b (19.3 g, 96.5 mmol), and Pd(PPh3)4
(5.61 g, 4.86 mmol) in toluene (205 mL). 6b was obtained as a
brown solid (12.7 g, 59.8 mmol, 62%). 1H NMR (400 MHz,
CDCl3): ¤ (ppm) 2.41 (s, 3H, PyCH3), 2.83 (s, 3H, O=CCH3),
7.65 (dd, 1H, J = 8.1, 2.1 Hz, Py), 7.93 (td, 1H, J = 7.8,
0.67 Hz, Py), 8.02 (m, 1H, Py), 8.41 (d, 1H, J = 8.1 Hz, Py),
8.51 (m, 1H, Py), 8.57 (m, 1H, Py). 13C{1H} NMR (100 MHz,
CDCl3): ¤ (ppm) 18.55 (PyCH3), 25.89 (O=CCH3), 120.78,
121.21, 124.09, 134.08, 137.67, 137.83, 149.71, 152.88,
152.94, 155.55 (Py), 200.42 (O=CCH3). Anal. Calcd for
C13H12N2O: C, 73.56; H, 5.70; N, 13.20. Found: C, 73.56;
H, 6.20; N, 12.78. HRMS (DART): [M + H]+ Calcd. for
C13H13N2O: 213.10279; Found: 213.10149.
1-[6¤-Methyl-2,2¤-bipyridine-6-yl]ethanone (6c).
This
compound was prepared by the same procedure with 6a from
4b (45.0 g, 118 mmol), 5b (21.4 g, 107 mmol), and Pd(PPh3)4
(6.38 g, 5.52 mmol) in toluene (214 mL). 6c was obtained as a
4. Experimental
Instruments. 1H and 13C{1H} NMR were recorded on a
JEOL JMN-AL400. The residual peaks of the solvent were
used as an internal standard of the chemical shifts. HPLC
analyses were performed with a Shimadzu Prominence UFLC
(LC-20 series) equipped with an ODS column (Cosmosil
5C18-MS-II (250 © 4.6 mm)), column oven, and UV detector.
Acetonitrile (100%) was used as carrier phase of which flow
rate was 1.0 mL/min. Column temperature was kept at 40 °C
during analyses. Products were detected by the absorption at
199 nm. Quantification of the products was performed using
calibration curves prepared by the plot of peak area vs con-
centration of authentic samples.
1
white powder (18.9 g, 88.8 mmol, 83%). H NMR (400 MHz,
CDCl3): ¤ (ppm) 2.65 (s, 3H, PyCH3), 2.84 (s, 3H, O=CCH3),
7.21 (m, 1H, Py), 7.74 (m, 1H, Py), 7.94 (m, 1H, Py), 8.04 (d,
1H, J = 7.7 Hz, Py), 8.32 (d, 1H, J = 7.8 Hz, Py), 8.65 (d, 1H,
J = 7.8 Hz, Py). 13C{1H} NMR (100 MHz, CDCl3): ¤ (ppm)
24.66 (PyCH3), 25.80 (O=CCH3), 118.12, 121.26, 123.73,
124.35, 137.17, 137.70, 152.89, 154.71, 155.69, 158.03 (Py),
200.38 (O=CCH3). Anal. Calcd for C13H12N2O: C, 73.56; H,
5.70; N, 13.20. Found: C, 73.46; H, 6.20; N, 12.93. HRMS
(DART): [M + H]+ Calcd. for C13H13N2O: 213.10279; Found:
213.10125.
Materials.
Fe-iminobipyridine complexes, 2HM, 2MM
,
N-([5¤-Methyl-2,2¤-bipyridin-6-yl]methylene)-2,4,6-tri-
methylbenzenamine (7a). 2,4,6-trimethylaniline (2.42 mL,
15.1 mmol) and 6a (3.0 g, 15.1 mmol) were dissolved in MeOH
(30.0 mL) and stirred at 60 °C for 3 days. Cooling the reaction
mixture to room temperature resulted in the precipitation of a
yellow solid. The yellow solid of 7a was filtered and washed
with two 10 mL portions of MeOH, then dried in vacuo (4.23 g,
2
HD, 2MD, 3HM, and 3HD were prepared according to pre-
vious reports.13,14 5-Methyl-2-tributylstannyl-pyridine (4a), 6-
methyl-2-tributylstannyl-pyridine (4b), and 6-bromopyridine-
2-carboaldehyde (5a) were also prepared according to the
literature.12,13 Super dehydrated grade hexane, THF, and tolu-
ene were purchased from Kanto Chemical Co. Inc. and used as
solvents. All other chemicals were purchased from commercial
sources and used as received.
1
13.4 mmol, 89%). H NMR (400 MHz, CDCl3): ¤ (ppm) 2.16
(s, 6H, o-CH3, PhCH3), 2.30 (s, 3H, p-CH3, PhCH3), 2.41 (s,
3H, PyCH3), 6.91 (s, 2H, m-H, Ph), 7.64 (dd, 1H, J = 8.0,
1.8 Hz, Py), 7.94 (t, 1H, J = 7.8 Hz, Py), 8.29 (dd, 1H, J = 7.8,
0.85 Hz, Py), 8.37 (d, 1H, J = 8.1 Hz, Py), 8.42 (s, 1H,
N=CH), 8.47 (dd, 1H, J = 7.8, 0.85 Hz, Py), 8.53 (d, 1H,
J = 1.8 Hz, Py). 13C{1H} NMR (100.4 MHz, CDCl3): ¤ (ppm)
18.43, 18.57, 20.93 (ArCH3), 120.72, 120.90, 122.43, 126.96,
128.91, 133.47, 133.85, 137.63, 137.66, 148.15, 149.85,
153.32, 154.17, 156.27, 164.17 (N=CH, Ar, and Py). Anal.
Calcd for C21H21N3: C, 79.97; H, 6.71; N, 13.32. Found: C,
79.83; H, 6.86; N, 13.31. HRMS (DART): [M + H]+ Calcd.
for C21H22N3: 316.1814; Found: 316.1816.
[5¤-Methyl-2,2¤-bipyridine]-6-carboxaldehyde (6a).
4a
(37.1 g, 97.1 mmol), 5a (18.0 g, 96.8 mmol), and Pd(PPh3)4
(5.59 g, 4.84 mmol) were dissolved in toluene (180 mL) under
N2, and the solution was heated at reflux for 12 h. After cooling
to room temperature, 6 M HClaq (230 mL) and CHCl3 were
added. The water phase was neutralized with 10 M NaOHaq
(150 mL) and ice-cooling, resulting in a white precipitate of
crude 6a. The crude product was extracted with three 300 mL
portions of CHCl3, and purified by silica gel column chro-
matography eluted with AcOEt. 10.2 g of 6a was obtained as a
1
white powder (51.5 mmol, 53%). H NMR (400 MHz, CDCl3):
¤ (ppm) 2.42 (s, 3H, PyCH3), 7.68 (d, 1H, J = 8.0, Py), 7.96
(m, 2H, Py), 8.44 (d, 1H, J = 8.1, Py), 8.53 (s, 1H, 6¤-H, Py),
8.62 (dd, 1H, J = 6.8, 1.7 Hz, Py), 10.16 (s, 1H, O=CH).
13C{1H} NMR (100 MHz, CDCl3): ¤ (ppm) 18.57 (PyCH3),
120.93, 121.22, 124.99, 134.31, 137.71, 137.96, 149.92,
152.38, 152.59, 156.95 (Py), 193.92 (O=CH). Anal. Calcd
for C12H10N2O: C, 71.71; H, 5.09; N, 14.13. Found: C, 72.51;
H, 5.19; N, 14.02. HRMS (DART): [M + H]+ Calcd. for
C12H11N2O: 199.0871; Found: 199.0873.
N-(1-[5¤-Methyl-2,2¤-bipyridin-6-yl]ethylidene)-2,4,6-tri-
methylbenzenamine (7b). 2,4,6-trimethylaniline (2.42 mL,
15.1 mmol) and 6b (3.0 g, 14.1 mmol) were dissolved in MeOH
(30.0 mL), and finally 10 drops of HCOOH was added. The
mixture was stirred at 60 °C for 3 days. Cooling the reaction
mixture to room temperature resulted in the precipitation of a
yellow solid. The yellow solid of 7b was filtered and washed
with two 10 mL portions of MeOH, then dried in vacuo (3.43 g,
1
10.4 mmol, 74%). H NMR (400 MHz, CDCl3): ¤ (ppm) 2.02
1-[5¤-Methyl-2,2¤-bipyridine-6-yl]ethanone (6b).
compound was prepared by the same procedure with 6a from
This
(s, 6H, o-CH3, PhCH3), 2.28 (s, 3H, N=CCH3 or p-CH3,
PhCH3), 2.30 (s, 3H, N=CCH3 or p-CH3, PhCH3), 2.41 (s, 3H,
Bull. Chem. Soc. Jpn. 2019, 92, 105–114 | doi:10.1246/bcsj.20180197
© 2019 The Chemical Society of Japan | 111

PyCH3), 6.90 (s, 2H, m-H, Ph), 7.64 (bd, 1H, J = 8.0 Hz, Py),
7.91 (t, 1H, J = 7.8 Hz, Py), 8.36 (bd, 1H, J = 7.8 Hz, Py), 8.43
(d, 1H, J = 8.0 Hz, Py), 8.48 (bd, 1H, J = 7.8 Hz, Py), 8.52
(s, 1H, 6¤-H, Py). 13C{1H} NMR (100.4 MHz, CDCl3): ¤ (ppm)
16.65 (N=CCH3), 18.05, 18.57, 20.90 (ArCH3), 120.76,
120.96, 121.75, 125.46, 128.68, 132.28, 133.66, 137.44,
137.57, 146.47, 149.75, 153.70, 155.12, 155.83, 167.76
(N=CCH3 and Ar). Anal. Calcd for C22H23N3: C, 80.21; H,
7.03; N, 12.76. Found: C, 80.20; H, 7.10; N, 12.73. HRMS
(DART): [M + H]+ Calcd. for C22H24N3: 330.1970; Found:
330.1965.
(200 °C, 120 pa). 7e was obtained as a yellow solid (2.97 g,
9.02 mmol, 64%). H NMR (400 MHz, CDCl3): ¤ (ppm) 2.03
1
(s, 6H, o-CH3, PhCH3), 2.30 (s, 3H, N=CCH3 or p-CH3,
PhCH3), 2.31 (s, 3H, N=CCH3 or p-CH3, PhCH3), 2.68 (s, 3H,
PyCH3), 6.91 (s, 2H, m-H, Ph), 7.20 (d, 1H, J = 7.6 Hz, Py),
7.74 (t, 1H, J = 7.8 Hz, Py), 7.92 (t, 1H, J = 7.8 Hz, Py), 8.36
(d, 1H, J = 7.9 Hz, Py), 8.39 (d, 1H, J = 7.8 Hz, Py), 8.59
(d, 1H, J = 7.8 Hz, Py). 13C{1H} NMR (100.4 MHz, CDCl3):
¤ (ppm) 16.38 (N=CCH3), 18.08, 20.92, 24.73 (ArCH3),
118.33, 121.22, 122.25, 123.62, 125.49, 128.70, 132.33,
137.40, 137.45, 146.40, 155.02, 155.45, 155.82, 158.01,
167.84 (N=CCH3 and Ar). Anal. Calcd for C22H23N3: C,
80.21; H, 7.04; N, 12.76. Found: C, 80.31; H, 7.05; N, 12.82.
HRMS (DART): [M + H]+ Calcd. for C22H24N3: 330.19702;
Found: 330.19666.
N-([5¤-Methyl-2,2¤-bipyridin-6-yl]methylene)-2,6-diiso-
propylbenzenamine (7c). 2,6-diisopropylaniline (3.17 mL,
15.1 mmol) and 6a (3.0 g, 15.1 mmol) were dissolved in MeOH
(30.0 mL) and stirred at 60 °C for 3 days. Cooling the reaction
mixture to room temperature resulted in the precipitation of a
yellow solid. The yellow solid of 7c was filtered and washed
with two 10 mL portions of MeOH, then dried in vacuo (4.86 g,
N-(1-[6¤-Methyl-2,2¤-bipyridin-6-yl]ethylidene)-2,6-diiso-
propylbenzenamine (7f). 2,6-diisopropylaniline (3.04 mL,
14.5 mmol) and 6b (3.08 g, 14.5 mmol) were dissolved in
MeOH (25.0 mL), and finally 20 drops of HCOOH were added.
The mixture was stirred at 60 °C for 7 days. Cooling the reac-
tion mixture to room temperature resulted in the precipitation
of a white solid. The white solid of 7d was filtered and washed
with two 10 mL portions of MeOH, then dried in vacuo (3.83 g,
1
13.6 mmol, 90%). H NMR (400 MHz, CDCl3): ¤ (ppm) 1.20
(d, 12H, J = 6.9 Hz, PhCH(CH3)2), 2.41 (s, 3H, PyCH3), 3.01
(sept, 2H, J = 6.9 Hz, PhCH(CH3)2), 7.11-7.21 (m, 3H, Ph),
7.64 (dd, 1H, J = 8.0, 2.0 Hz, Py), 7.96 (t, 1H, J = 7.8 Hz, Py),
8.29 (dd, 1H, J = 7.8, 0.92 Hz, Py), 8.39 (m, 2H, N=CH
and Py), 8.49 (dd, 1H, J = 7.8, 0.92 Hz, Py), 8.54 (m, 1H,
6¤-H, Py). 13C{1H} NMR (100.4 MHz, CDCl3): ¤ (ppm) 18.58,
23.61, 28.14 (PyCH3 and o-iPr, Ph iPr), 120.88, 120.98,
122.54, 123.20, 124.56, 133.90, 137.39, 137.70, 137.73,
148.72, 149.77, 153.25, 154.04, 156.29, 163.65 (N=CH and
Ar). Anal. Calcd for C24H27N3: C, 80.63; H, 7.61; N, 11.75.
Found: C, 80.38; H, 7.75; N, 11.78. HRMS (DART): [M + H]+
Calcd. for C24H28N3: 358.2283; Found: 358.2284.
1
10.3 mmol, 71%). H NMR (400 MHz, CDCl3): ¤ (ppm) 1.17
(d, 12H, J = 6.9 Hz, PhCH(CH3)2), 2.33 (s, 3H, N=CCH3),
2.66 (s, 3H, PyCH3), 2.79 (sept, 2H, J = 6.9 Hz, PhCH(CH3)2),
7.11 (dd, 1H, J = 8.5, 6.6 Hz, p-H, Ph), 7.19 (m, 3H, Py and
m-H, Ph), 7.73 (t, 1H, J = 7.8 Hz, Py), 7.93 (t, 1H, J = 7.8 Hz,
Py), 8.35 (d, 1H, J = 7.8 Hz, Py), 8.38 (d, 1H, J = 7.8 Hz, Py),
8.56 (d, 1H, J = 7.8 Hz, Py). 13C{1H} NMR (100.4 MHz,
CDCl3): ¤ (ppm) 17.41, 23.09, 23.38, 24.85, 28.40 (N=CCH3,
i
N-(1-[5¤-Methyl-2,2¤-bipyridin-6-yl]ethylidene)-2,6-diiso-
propylbenzenamine (7d). 2,6-diisopropylaniline (3.04 mL,
14.5 mmol) and 6b (3.08 g, 14.5 mmol) were dissolved in
MeOH (25.0 mL), and finally 20 drops of HCOOH were added.
The mixture was stirred at 60 °C for 7 days. Cooling the reac-
tion mixture to room temperature resulted in the precipitation
of a white solid. The white solid of 7d was filtered and washed
with two 10 mL portions of MeOH, then dried in vacuo (3.83 g,
PyCH3 and o-iPr, Ph Pr), 118.19, 121.12, 122.10, 123.12,
123.53, 123.64, 136.00, 137.18, 137.46, 146.71, 155.31,
155.57, 155.71, 158.08, 167.33 (N=CCH3 and Ar). Anal.
Calcd for C25H29N3: C, 80.82; H, 7.87; N, 11.31. Found: C,
80.77; H, 7.99; N, 11.30. HRMS (DART): [M + H]+ Calcd. for
C25H30N3: 372.24397; Found: 372.24431.
N-([5¤-Methyl-2,2¤-bipyridin-6-yl]methylene)-2,4,6-tri-
methylbenzenamine Iron (II) Bromide (2HM). 731 mg of
7a (2.32 mmol) were dissolved in THF (25 mL) under N2. After
the addition of FeBr2 (500 mg, 2.32 mmol) to the solution, a
precipitate appeared. The mixture was stirred for 12 h. The
resulting precipitate was collected by filtration, and washed with
THF (5 mL © 3) and hexane (5 mL © 3), then dried in vacuo.
2HM was obtained as dark brown powder (1.16 g, 2.18 mmol,
94%). Anal. Calcd for C21H21Br2FeN3: C, 47.49; H, 3.99;
N, 7.91. Found: C, 47.74; H, 4.40; N, 7.19. HRMS(FAB):
[M ¹ Br]+ Calcd. for C22H23BrFeN3: 450.0268; Found:
450.0277.
1
10.3 mmol, 71%). H NMR (400 MHz, CDCl3): ¤ (ppm) 1.19
(d, 12H, J = 6.9 Hz, PhCH(CH3)2), 2.35 (s, 3H, N=CCH3),
2.42 (s, 3H, PyCH3), 2.81 (sept, 2H, J = 6.9 Hz, PhCH(CH3)2),
7.13 (dd, 1H, J = 8.4, 6.7 Hz, p-H, Ph), 7.20 (d, 2H, J =
7.2 Hz, m-H, Ph), 7.66 (bd, 1H, J = 8.0 Hz, Py), 7.94 (t, 1H,
J = 7.8 Hz, Py), 8.40 (d, 1H, J = 7.8 Hz, Py), 8.47 (d, 1H, J =
8.1 Hz, Py), 8.51-8.57 (m, 2H, Py). 13C{1H} NMR (100.4
MHz, CDCl3): ¤ (ppm) 17.43, 18.59, 23.11, 23.41, 28.44
i
(N=CCH3, PyCH3 and o-iPr, Ph Pr), 120.85, 121.07, 121.85,
123.15, 123.69, 133.75, 135.98, 137.53, 137.74, 146.72,
149.63, 153.59, 155.03, 155.73, 167.26 (N=CCH3 and Ar).
Anal. Calcd for C25H29N3: C, 80.82; H, 7.87; N, 11.31. Found:
C, 80.85; H, 7.89; N, 11.28. HRMS (DART): [M + H]+ Calcd.
for C25H30N3: 372.24397; Found: 372.24340.
N-(1-[5¤-Methyl-2,2¤-bipyridin-6-yl]ethylidene)-2,4,6-tri-
methylbenzenamine Iron (II) Bromide (2MM). 2MM was
obtained from the reaction between 7b (764 mg, 2.32 mmol)
and FeBr2 (500 mg, 2.32 mmol) according to the procedure
N-(1-[6¤-Methyl-2,2¤-bipyridin-6-yl]ethylidene)-2,4,6-tri-
methylbenzenamine (7e). 2,4,6-trimethylaniline (2.03 mL,
14.1 mmol) and 6c (3.0 g, 14.1 mmol) were dissolved in MeOH
(25.0 mL), and finally 20 drops of HCOOH were added. The
mixture was stirred at 60 °C for 7 days. The solvent was evapo-
rated, and the residue was purified by Kugelrohr distillation
of 2HM.
Brownish gray powder, Yield: 1.23g (2.27 mmol, 98%). Anal.
Calcd for C22H23Br2FeN3¢C4H8O (M + THF): C, 49.60; H,
4.68; N, 7.23. Found: C, 49.94; H, 4.92; N, 6.94. HRMS(FAB):
[M ¹ Br]+ Calcd. for C22H23BrFeN3: 464.0425; Found:
464.0442.
112 | Bull. Chem. Soc. Jpn. 2019, 92, 105–114 | doi:10.1246/bcsj.20180197
© 2019 The Chemical Society of Japan

N-([5¤-Methyl-2,2¤-bipyridin-6-yl]methylene)-2,6-diiso-
propylbenzenamine Iron (II) Bromide (2HD). 2HD was ob-
tained from the reaction between 7c (500 mg, 1.40 mmol) and
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Greenish gray powder, Yield: 721 mg (1.26 mmol, 90%).
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49.52; H, 4.85; N, 7.22. Found: C, 49.73; H, 4.72; N, 7.44.
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N-(1-[5¤-Methyl-2,2¤-bipyridin-6-yl]ethylidene)-2,6-diiso-
propylbenzenamine Iron (II) Bromide (2MD). 2MD was ob-
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2
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6.94. Found: C, 49.78; H, 4.90; N, 6.93. HRMS(FAB):
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506.0881.
N-(1-[6¤-Methyl-2,2¤-bipyridin-6-yl]ethylidene)-2,4,6-tri-
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3
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7
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8
A. M. Tondreau, C. C. H. Atienza, J. M. Darmon, C.
Typical Procedure for the Catalytic Hydrosilylation of
Olefins with Silanes. (BPI)FeBr2 (0.0057 mmol) was placed
in a Schlenk tube in air at room temperature. Next, the air in
the Schlenk tube was replaced with nitrogen. 1,7-octadiene
(0.86 mL, 5.6 mmol) and diphenylsilane (1.1 mL, 5.6 mmol)
were placed in the Schlenk tube. Amount of 1,7-octadiene
was increased as appropriate. Sodium triethylborohydride
(NaBHEt3) (1.0 M in toluene, 115 ¯L, 0.115 mmol) was then
added to the suspension to start the reaction. The solution was
stirred at room temperature or 120 °C. The reaction was
stopped by exposure to air at appropriate time. The reaction
mixture was subjected to HPLC analysis to determine the yield
and TON.
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This work was supported by the “Development of Innovative
Catalytic Processes for Organosilicon Functional Materials”
project (PL: K. Sato) from the New Energy and Industrial
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© 2019 The Chemical Society of Japan