Combinatorial Approach to the Catalytic Hydrosilylation of Styrene Derivatives: Catalyst Systems Composed of Organoiron(0) or (II) Precursors and Isocyanides

Article abstract of DOI:10.1021/acs.organomet.5b00201

(COT)₂Fe and the open ferrocenes (MPDE)₂Fe (MPDE = η⁵-3-methylpentadienyl) and (DMPDE)₂Fe (DMPDE = η⁵-2,4-dimethylpentadienyl) were found to function as catalyst precursors for the hydrosilylation of alkenes in the presence of auxiliary ligands. Screening trials determined that the optimal catalyst system was composed of (COT)₂Fe and adamantyl isocyanide, allowing the selective hydrosilylation of styrene derivatives with trisubstituted hydrosiloxanes and a polydimethylsiloxane bearing Me₂SiH moieties as the end groups. Under the appropriate conditions, the dehydrogenative silylation side reaction was completely suppressed, and the reaction TON exceeded 5000. (Chemical Equation Presented).

Full text of DOI:10.1021/acs.organomet.5b00201

Article
pubs.acs.org/Organometallics
Combinatorial Approach to the Catalytic Hydrosilylation of Styrene
Derivatives: Catalyst Systems Composed of Organoiron(0) or (II)
Precursors and Isocyanides
Yusuke Sunada, Daisuke Noda, Hiroe Soejima, Hironori Tsutsumi, and Hideo Nagashima*
Institute for Materials Chemistry and Engineering and Graduate School of Engineering Sciences, Kyushu University, and CREST,
Japan Science and Technology Agency (JST), Kasuga, Fukuoka 816-8580, Japan
S
* Supporting Information
ABSTRACT: (COT)2Fe and the open ferrocenes (MPDE)2Fe
(MPDE = η5-3-methylpentadienyl) and (DMPDE)2Fe (DMPDE =
η5-2,4-dimethylpentadienyl) were found to function as catalyst
precursors for the hydrosilylation of alkenes in the presence of
auxiliary ligands. Screening trials determined that the optimal
catalyst system was composed of (COT)2Fe and adamantyl
isocyanide, allowing the selective hydrosilylation of styrene
derivatives with trisubstituted hydrosiloxanes and a polydimethylsi-
loxane bearing Me2SiH moieties as the end groups. Under the
appropriate conditions, the dehydrogenative silylation side reaction
was completely suppressed, and the reaction TON exceeded 5000.
when treated with strong organometallic activators.8,9 Fe
carbonyls, such as Fe(CO)5 and Fe3(CO)12, are conventional
Fe-based catalysts and may possibly function in the hydro-
silylation of alkenes is one of the most useful reactions for
INTRODUCTION
■
The transition metal-promoted homogeneous catalytic hydro-
producing organosilicon compounds.1 In general, salts and
complexes of second and third row transition metals, including
Pt, Pd, Rh Ir, and Ru, have been applied as effective catalysts for
this reaction,1 and Pt catalysts are especially useful for
synthesizing a variety of organosilicon compounds and silicones
on both laboratory and industrial scales.1c However, there are
increasing demands for the development of more environ-
mentally benign as well as more cost-effective synthetic
processes, in which precious metal catalysts are replaced by
less toxic and more abundant metals.2 In this context, Fe-based
hydrosilylation catalysts and catalyst systems have recently
received considerable attention.3
Several iron complexes have been reported to be active for
the hydrosilylation of alkenes.3−7 The well-defined Fe(0)-
dinitrogen complexes bearing bis(imino)pyridine ligands
reported by Chirik and co-workers are an example of successful
hydrosilylation catalysts exhibiting high catalytic activity and
good selectivity to generate anti-Markovnikov adducts from 1-
alkenes.4 In earlier work with hydrosilanes intended for
hydrosilylation, the available compounds were limited to
Ph2SiH2 and PhSiH3;4a however, the appropriate choice of
substituents on the bis(imino)pyridine ligands led to the
successful hydrosilylation of alkenes with trisubstituted hydro-
silanes and hydrosiloxanes.4b A drawback of these bis(imino)-
pyridine Fe(0) complexes is their significant instability in
contact with air and moisture. To mitigate this, Fe(II)
complexes bearing bis(imino)pyridine, terpyridine, or related
tridentate ligands have been reported that generate various
active species including Fe hydrides or alkyliron compounds
silylation reaction of RCHCH2 and H-SiR′3 to give the
desired product RCH2CH2SiR′3.3,6a−c Fe carbonyls are
generally stable and easy to handle but have the unfortunate
tendency to promote the simultaneous dehydrogenative
silylation reaction, giving a 1:1 mixture of RCHCHSiR′3
and RCH2CH3. In response to this shortcoming, our group has
previously developed an Fe(II) carbonyl compound having a
disilaferracyclic structure, [1,2-(SiMe2)2C6H4]Fe(CO)2[1,2-
{η2-(H-SiMe2)2}C6H4]. This compound represents a unique
Fe catalyst that is moderately stable in response to air and
moisture, and selectively affords the hydrosilylation product
without contamination with byproducts derived from dehydro-
genative silylation.7a
In these previous studies, the Fe complexes were isolated and
subsequently applied to the catalytic reactions. In our
continuous efforts to develop new Fe catalysts for the
hydrosilylation of alkenes, we were interested in developing a
convenient means of synthesizing catalytically active species
from isolable Fe precursors and auxiliary ligands. If the
appropriate Fe precursors can be determined, screening of
the ligand should be readily performed, making it possible to
apply a combinatorial-type approach to the search for new
catalyst systems. The catalysts reported in the literature suggest
that Fe(0) complexes capable of reacting with the desired
ligands to form catalytically active species represent one
possible series of candidates for the catalyst precursor. An
Received: March 14, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
organoiron(II) precursor containing an Fe−H or Fe−C moiety
that generates an active species when in contact with the ligand
is another possibility. In this article, we report an Fe(0)
complex, (COT)2Fe (COT = 1,3,5,7-cyclotetraene),10 and
Fe(II) complexes consisting of two open ferrocenes,
(MPDE)2Fe (MPDE = η5-3-methylpentadienyl) and
(DMPDE)2Fe (DMPDE = η5-2,4-dimethylpentadienyl),11 as
effective catalyst precursors that allow ligand screening. As
noted above, the catalytic hydrosilylation of alkenes is
sometimes accompanied by products representing Markovni-
kov addition and dehydrogenative silylation. We selected
styrene derivatives as the alkene substrates for use in catalyst
screening because it is well-known that the hydrosilylation of
styrene tends to give a mixture of regioisomers (a and b)12 in
addition to products resulting from dehydrogenative silylation
(c and d)6 (Scheme 1). It is also known that dehydrogenative
Table 1. Hydrosilylation of Styrene with PMDS Catalyzed by
(COT)2Fe in the Presence of the Ligands
a
yield (%)
ligand
loading
conv.
a
entry
ligand
(mol %)
(%)
1a
1c
1d
1
none
0
0
0
0
2
Me2PDI
3
3
6
6
3
3
6
6
6
6
3
6
3
9
6
6
6
75
0
75
0
0
0
3
2,2′:6′,6″-terpyridine
0
0
b
4
IPr
0
0
0
0
Scheme 1. General Scheme for Hydrosilylation of Styrene to
Form a−d
5
NEt3
0
0
0
0
c
6
TMEDA
0
0
0
0
d
7
PMDETA
0
0
0
0
8
PPh3
PtBu3
0
0
0
0
9
0
0
0
0
10
11
12
13
14
15
16
17
18
P(OCH2)3CEt
Me2S
0
0
0
0
0
0
0
0
MeSCH2CH2CH2SMe
CNAd
0
0
0
0
>99
72
90
>99
>99
>99
74
56
66
73
75
0
12
9
14
7
CNAd
CNAd
CNtBu
12
19
11
49
12
17
14
51
silylation is a serious side reaction in the Fe-catalyzed
hydrosilylation of styrene and that this reaction occurs to the
exclusion of other reactions in extreme cases.6a In the screening
aimed at the selective formation of a, we found that isocyanides
worked as effective ligands for the catalyst systems when
combined with the Fe precursors, thus producing a catalytic
system that has never before been applied to the Fe-catalyzed
hydrosilylation of alkenes.
CNCy
CNMes
a
b
1
Determined by H NMR. IPr = 1,3-Bis(2,6-diisopropylphenyl)-1,3-
c
dihydro-2H-imidazol-2-ylidene. TMEDA = N,N,N′,N′-tertramethyle-
d
thylenediamine. PMDETA = N,N,N′,N″,N″-pentamethyldiethylene-
triamine.
RESULTS AND DISCUSSION
other than Me2PDI. As shown in entries 3−12 of Table 1,
mono-, di-, and tridentate nitrogen, phosphorus, and sulfur
ligands were examined, along with an NHC ligand, and none
were found to generate a hydrosilylation catalyst under the
present conditions. However, we did determine that
isocyanides (RNC) were effective for the reaction in
combination with (COT)2Fe. Isocyanides are isoelectronic
with CO but have advantages over CO in that their electronic
and structural environments can be finely tuned by changing
the substituent (R) on the nitrogen atom. Entries 13−18
showed the results using adamantyl, t-butyl, cyclohexyl, and
mesityl isocyanides. In all cases, styrene was completely
consumed within 3 h. As shown in entry 13, the combination
of (COT)2Fe (3 mol %) and CNAd (6 mol %) generated the
hydrosilylated product 1a in 74% yield. The optimal ratio of
(COT)2Fe to CNAd in terms of obtaining the highest
conversion of styrene was 1:2 (entries 14 and 15). It should
be noted, however, that, although the regio-isomer 1b was not
formed, the simultaneous formation of 1c (12%) and 1d (14%)
was not suppressed under these reaction conditions (entry 13).
Two other alkylisocyanides, tert-butyl isocyanide and cyclohexyl
isocyanide, were effective (entries 16 and 17), but gave the
same byproducts as in entry 13. When mesityl isocyanide was
used as a means of assessing the utility of an arylisocyanide
ligand, only a 1:1 mixture of 1c and 1d was formed (entry 18).
■
Search for Ligands Using (COT)2Fe as the Fe Catalyst
Precursor. As a catalyst precursor, (COT)2Fe, in which
cyclooctatetraene ligands bound to the Fe center in an η4- or
η6-fashion, was chosen since the COT ligands are known to
participate in substitution reactions.13,14As noted, Fe(0)
dinitrogen complexes supported by Me2PDI (Me2PDI = 2,6-
(2,6-Me2-C6H3NCMe)2C5H3N) or Et2PDI (Et2PDI = 2,6-
(2,6-Et2-C6H3NCMe)2C5H3N) exhibited excellent catalytic
activity during the hydrosilylation of alkenes.4b We therefore
examined the potential generation of catalytically active species
from a mixture of (COT)2Fe and Me2PDI during the reaction
of styrene with HMe2SiOSiMe3 (PMDS). In a typical
experiment, a 1:1 mixture of (COT)2Fe and Me2PDI was
treated with styrene (1 mmol) and PMDS (1.3 mmol) at 80 °C
for 3 h. The reaction of styrene with PMDS in the presence of
(COT)2Fe and Me2PDI was successful, affording the
corresponding hydrosilylated compound 1a as the single
product in 75% yield (Table 1, entry 2). Other possible
byproducts, such as 1b, 1c, and 1d, were not evident in the 1H
NMR spectrum of the crude product. It was also determined
that, in the absence of Me2PDI, no reaction took place (entry
1).
Additional results indicated that catalytically active species
could be formed from a mixture of (COT)2Fe and ligands
B
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Table 2. Hydrosilylation of Styrene Derivatives with PMDS Catalyzed by (COT)2Fe with CNAd
a
b
c
The conversion and product selectivity were determined by 1H NMR of the crude products. The products 1a−8a were isolated by distillation. 1H
NMR revealed that the crude product contained 5a and two byproducts, 1,1,1,3,3-pentamethyl-3-[(1E)-2-(p-methoxy)-phenylethenyl]-disiloxane
d
(5c) and 1-ethyl-4-methoxybenzene (5d) in a ratio of 98:1:1. The product 5a was isolated as a single product by distillation (6 Pa, 70−75 °C). 1H
NMR revealed that crude product contained 8a and two byproducts, 1,1,1,3,3-pentamethyl-3-[(1E)-2-(o-methyl)-phenylethenyl]-disiloxane (8c) and
1-ethyl-2-methylbenzene (8d), in a ratio of 92:4:4. The product 8a was isolated as a single product by distillation (3 Pa, 120−125 °C).
We carried out further studies by using CNAd as a
representative of the three alkyl isocyanides described above.
Performing the reaction at temperatures below 80 °C
represented a breakthrough in terms of increasing the
selectivity for 1a, such that the selective synthesis of 1a was
achieved either at 50 °C or at room temperature. Under these
conditions, 1a was isolated in 94 or 95% yield after 23 h of
reaction time via distillation (Table 2, entries 1 and 2), with no
evidence for the formation of either vinylsilane or ethylbenzene.
The high catalytic efficiency of this system was demonstrated
by the reaction of styrene with PMDS at lower catalyst
loadings; a reaction using only 0.02 mol % (COT)2Fe and 0.04
mol % CNAd was found to provide 1a in high yields (TON =
5000) (entry 3). It should be noted that no reaction took place
when CNtBu or CNCy was used as the ligand under the same
conditions. In this context, CNAd is the best ligand among the
isocyanides we examined. In addition, the reaction of a series of
substituted styrenes by the Fe(COT)2/CNAd catalyst system
showed that the present catalyst system is able to function in
4a, and 6a were obtained in high yields (entries 4−6, 8).
Although the selectivity was slightly decreased (97%), the
hydrosilylation of p-methoxystyrene proceeded at a lower
temperature (40 °C) to afford 5a in 96% yield (entry 7). The
hydrosilylation reactions of 2-vinylnaphthalene and sterically
hindered o-methylstyrene required slightly higher catalyst
loadings (3 mol %) but still gave the corresponding products
7a and 8a, respectively, in high yields (entries 9 and 10). In the
case of o-methylstyrene, some amounts of the byproducts 8c
and 8d were also formed.
The screening of several hydrosilanes under the conditions
indicated that the hydrosilylation of styrene with trialkylsilanes
such as PMDS, Me2PhSiH, and EtMe2SiH resulted in the
formation of the corresponding hydrosilylated products with
good selectivity (details are given in the Supporting
Information). Concomitant dehydrogenative silylation remains
a significant side reaction in the reaction with sterically
hindered hydrosilanes such as Et3SiH and 1,1,1,3,5,5,5-
heptamethyltrisiloxane (MD’M) to give a mixture of the
homologues of 1a and 1b, as well as ethylbenzene (1d) as
shown in Table S-1 in Supporting Information.
t
the presence of several functional groups, including Bu, F, Cl,
and CO2Et. Styrenes bearing these substituents at the para
position underwent the reaction smoothly under the same
reaction conditions as those used for the hydrosilylation of
styrene, and the corresponding hydrosilylated products 2a, 3a,
Table 3 summarizes the reactions of styrene derivatives with
dimethylphenylsilane, all of which afford the corresponding
products in high yields with high selectivity under the same
C
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
organoiron complexes during the present study.15 Although
ferrocenes represent potential candidates for Fe(II) catalyst
precursors, they were found to be too stable to react with
isocyanides. We thus considered that the open ferrocenes
(Chart 1) previously reported by Ernst and co-workers11 could
be more reactive than ferrocenes and possibly generate
catalytically active species in contact with CNAd.
Table 3. Hydrosilylation of Styrene with
Dimethylphenylsilane Catalyzed by (COT)2Fe with CNAd
Chart 1. Structures of Two Open Ferrocenes, (MPDE)2Fe
and (DMPDE)2Fe
In fact, (MPDE)2Fe (MPDE = η5-3-methylpentadienyl)11
a
showed catalytic activity comparable to that of (COT)2Fe for
the reaction of styrene with PMDS and PhMe2SiH to give 1a as
the sole product in good yields (entries 1 and 3, Table 4).
Another open ferrocene, (DMPDE)2Fe (DMPDE = η5-2,4-
dimethylpentadienyl),11 also exhibited catalytic activity,
although somewhat lower than that of (MPDE)2Fe.
(COT)2Fe is moderately thermally stable but sensitive to air
and so must be handled in a glovebox. In contrast, the open
ferrocenes are sufficiently stable in air such that they can be
weighed out under ambient atmosphere in a short time without
decomposing. Selected substituted styrenes were applied to the
hydrosilylation reaction with either PMDS or PhMe2SiH, and
both p-chlorostyrene and p-methoxystyrene were found to
convert to the corresponding hydrosilylated products in high
yields and selectivities (entries 4−7).
Mechanistic Considerations. (COT)2Fe and open
ferrocenes are useful as catalyst precursors and generate active
species in contact with CNR because of facile changes in the
hapticity of the conjugated π-ligands. The carbon−carbon
double bonds in these hydrocarbon ligands assist in stabilizing
the catalyst precursors to keep them in a coordinatively
saturated state. Under the reaction conditions employed in the
present study, these ligands dissociated from the Fe center and
generated open coordination sites for isocyanides, hydrosilanes,
and styrene.
a
The conversion and product selectivity were determined by 1H NMR
b
of the crude products. The products 1a′−8a′ were isolated by
c
distillation. 1H NMR revealed that crude product contained 3a′ and
two byproducts, 1-chloro-4-(dimethylphenylsilyl)-benzene (3c′), and
1-chloro-4-ethylbenzene (3d) in a ratio of 98:1:1. The product 3a′ was
isolated as a single product by distillation (14 Pa, 80−85 °C).
reaction conditions previously applied when using PMDS
(Table 2).
As briefly noted in the introduction, the hydrosilylation of
polysiloxanes bearing Si−H groups with alkenes is an important
reaction with regard to industrial applications.1 It is thus worth
noting that the reaction of styrene with polydimethylsiloxane
having Si−H end groups also proceeded at 50 °C to give the
corresponding polydimethylsiloxane bearing β-phenethyl
groups at the polymer ends, in quantitative yield (Scheme 2).
When employing (COT)2Fe as the catalyst precursor, it is
apparent that both of the COT ligands are eliminated during
the catalytic reactions. In fact, when the crude product obtained
by the hydrosilylation of styrene with PMDS mediated by a
Scheme 2. Hydrosilylation of Styrene with Polymeric
Hydrosiloxane
1
combination of (COT)2Fe and CNAd was assessed by H
NMR, the spectrum indicated the formation of 2 equiv (based
on Fe) of 1,3,5,7-cyclooctatetraene. It should be mentioned
that hydrosilylation of 1,3,5,7-cyclooctatetraene did not take
place in the course of this reaction. To gain further insight into
the reaction mechanism, stoichiometric reactions of (COT)2Fe
with 1 or 3 equiv of CNAd in toluene were performed at room
temperature for 1 h, from which two types of Fe(0)-isocyanide
complexes, (η4-COT)2Fe(CNAd) (10) and (η4-COT)Fe-
(CNAd)3 (11), were isolated in 62 and 63% yields, respectively.
The reaction of (COT)2Fe with 2 equiv of CNAd gave a 1:1
mixture of 10 and 11. 1H NMR spectrum of 10 and 11 at room
temperature exhibited only one singlet attributed to the COT
ligands at 4.52 and 5.46 ppm, respectively. No spectral changes
were observed from room temperature to −90 °C. This
indicates the COT ligand to be fluxional. The IR spectra of 10
Open Ferrocenes as Fe(II) Catalyst Precursors in the
Presence of CNAd. As discussed, it is known that the Fe(II)-
alkyl complex [bis(imino)pyridine]Fe(CH2SiMe3)2 is able to
act as an alternative catalyst in place of the Fe(0) catalyst
[bis(imino)pyridine]Fe(N2)2 for the hydrosilylation of alke-
nes.4d This prompted us to examine several homoleptic
D
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Table 4. Hydrosilylation of Styrene Derivatives with PMDS or Dimethylphenylsilane Catalyzed by (MPDE)2Fe or(DMPDE)2Fe
with CNAd
a
b
c
The conversion and product selectivity were determined by 1H NMR of the crude products. The products were isolated by distillation. 1H NMR
revealed that crude product contained 5a and two byproducts, 1,1,1,3,3-pentamethyl-3-[(1E)-2-(p-methoxy)-phenylethenyl]-disiloxane (5c) and 1-
ethyl-4-methoxybenzene (5d), in a ratio of 98:1:1. Product 5a was isolated as a single product by distillation (6 Pa, 70−75 °C).
and 11 exhibited characteristic CN stretching bands at 2119
cm−1 for 10 and 2104, 2041, and 1937 cm−1 for 11. The
spectral features of 11 are consistent with those reported for an
analogous complex bearing the CNtBu ligand, (η4-COT)Fe-
(CNtBu)3.17
The molecular structures of 10 and 11 were determined by
X-ray diffraction and are depicted in Figure 1. The associated
1.166(7) Å. The CC bond distances bound to the iron
center in an η4-fashion are in the range of 1.381(9)−1.415(9)
Å, which are considerably longer compared with those of
noncoordinated CC (1.312(9)−1.363(9) Å). The Fe center
of 11 adopted a three-legged piano stool coordination
geometry with one η4-coordinated COT ligand as the seat
and three CNAd ligand as the legs. The bond distances
between Fe and the η4-coordinated C atoms as well as the C
N distance in 11 were comparable to those reported for (η4-
C6H8)Fe(CO)2(CNEt) and (η4-C7H8)Fe(CO)2(CNMe) (Fe−
C = 2.041(3) to 2.202(3) Å, CN = 1.168(3) to 1.192(3)
Å).18 The C−C bond distances of η4-coordinated CC
moieties (C(1)−C(2) = 1.431(4) and C(3)−C(4) =1.432(4)
Å) are significantly lengthened relative to those of the
noncoordinated CC moieties (C(5)−C(6) = 1.355(4) and
C(7)−C(8) = 1.352(4) Å). Although the variable temperature
1H NMR studies of 10 indicated rapid exchange of the
coordination sites of the iron species on the COT ligand in the
solution state, X-ray diffraction analysis revealed that the four
carbon atoms (C(1)−C(4) and C(9)−C(12)) of the COT
ligand in 10 coordinated to the iron center in an η4-fashion in
the solid state. The other four carbon atoms, C(5)−C(8) and
C(13)−C(16), did not coordinate to the iron center. Similarly,
COT ligand in 11 coordinated to the iron center in an η4-
manner with four carbon atoms (C(1)−C(4)) in the solid
state.
Figure 1. Molecular structures of complexes 10 and 11. With 50%
probability ellipsoids. Hydrogen atoms were omitted for clarity.
bond distances and angles are summarized in the Supporting
Information. Complex 10 evidently consisted of two η4-
coordinated COT ligands and one CNAd ligand, and its
overall molecular geometry can be regarded as a bent-sandwich
structure together with a CNAd ligand. The bond distances
between Fe and the η4-coordinated carbon atoms ranged from
2.031(6) to 2.195(6) Å, while the CN bond distance was
Table 5. Hydrosilylation of Styrene with PMDS Catalyzed by (COT)2Fe, 10, and 11
a
a
b
entry
Fe catalyst
(COT)2Fe
(η4-COT)2Fe(CNAd) (10)
(η4-COT)2Fe(CNAd) (10)
(η4-COT)Fe(CNAd)3 (11)
CNAd loading (mol %)
CNAd/Fe ratio
conv. (%)
selectivity (%)
isolated yield (%)
1
2
3
4
2
0
1
0
2
1
2
3
>99
67
>99
>99
>99
>99
98
63
97
80
>99
82
a
b
1
The conversion and product selectivity were determined by H NMR of the crude products. Product 1a was isolated by distillation.
E
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
As stated, a (COT)2Fe to CNAd ratio of 1:2 was found to be
optimal for the effective hydrosilylation of styrene with PMDS
(Table 5, entry 1) under conditions consisting of 1 mol % of
the Fe complex at 50 °C for 23 h. Reactions employing 10 (Fe/
CNAd = 1:1) or 11 (Fe/CNAd = 1:3) as the catalyst under the
same conditions demonstrated that both 10 and 11 exhibited
somewhat lower catalytic performance, generating yields of 1a
below 85% under the same reaction conditions (entries 2 and
4). Importantly, this catalytic activity was comparable to that
reported in entry 1, the case for which 1 equiv of CNAd was
added to 10 (entry 3). These results indicate that two
molecules of CNAd were bound to the catalytically active Fe
species. In other words, “(η4-COT)Fe(CNAd)2L (L = alkene,
η2-(H-SiR3), or a vacant coordination site)” may be a primary
intermediate in this reaction, followed by the generation of
coordinatively unsaturated iron species “Fe(CNAd)2” via the
dissociation of the η4-COT moiety to create the coordination
sites for both alkene and the “H−Si” bond of hydrosilane.
Oxidative addition of the Si−H bond to an iron center gives the
“H−Fe−Si” species followed by insertion of CC, then
reductive elimination took place to afford the hydrosilylated
product. This is consistent with our previous observation that
the “Fe(CO)2” species was responsible for the efficient catalytic
hydrosilylation of amides and alkenes.7a,19
Scheme 3. Proposed Reaction Mechanism for the
Generation of Catalytically Active Species from the Reaction
of (η5-Pentadienyl)2Fe with CNAd and Hydrosilane
1
monitoring the H NMR spectrum of the reaction of styrene
with PMDS in the presence of (COT)2Fe (10 mol %) and
CNAd (20 mol %), thus intermediary iron species were not
characterized by spectroscopy. This mechanism is similar to
that which generates active species in the reactions of
[bis(imino)pyridine]Fe-dialkyl catalysts, compounds that ex-
hibit catalytic activity for the hydrosilylation of alkenes similar
to those of Fe(0) bis(imino)pyridine compounds. It has been
reported that the reaction of these compounds likely generates
active species by homolysis of Fe−C bonds, although a detailed
mechanism has not been determined.4d Further investigations
including the theoretical calculations are required to elucidate
the reaction mechanism and the possible active iron species
generated during hydrosilylation.
Hydrosilylation of Aliphatic Alkenes. Although iron
catalysts other than Chirik’s bis(imino)pyridine complexes
usually results in dehydrogenative silylation of styrene as a
major reaction pathway,6a−c the (COT)2Fe/CNAd catalyst
system demonstrated high activity and selectivity for the
hydrosilylation of styrene derivatives with trisubstituted hydro-
silanes. The next challenge should be applications of this
catalyst system to hydrosilylation of aliphatic alkenes. Use of
the Fe(COT)2 (3 mol %)/CNAd (6 mol %) catalyst system for
the reaction of 1-octene with PMDS gave rise to the complete
consumption of 1-octene within 3 h at 80 °C. However, the
products were a mixture of desired 1,1,3,3,3-petamethyl-1-
octyldisiloxane and three byproducts, a vinylsilane, an allylic
silane, and n-octane in a ratio of 13:9:38:40. Similarly,
dehydrogenative hydrosilylation predominantly proceeded in
the reaction of methyl 10-undecenoate with PMDS (see
Supporting Information).21 The selectivity was not improved
by lowering the reaction temperature to 40 °C. 1,1-
Disubstituted alkenes like ( )-limonene and cyclic alkenes
such as cyclopentene and cyclohexene did not undergo the
reaction. In contrast, aliphatic alkenes such as 1-octene and
cyclopentene were successfully hydrosilylated by the iron
carbonyl complex [1,2-(SiMe2)2C6H4]Fe(CO)2[1,2-{η2-(H-
SiMe2)2}C6H4] in good yields with high selectivity as reported
in our previous paper.7a Since isocyanides are isoelectronic to
CO, we consider that further search for new isocyanide ligands,
which have electronic properties similar to those of CO, could
solve the problem.
Studies aimed at generating active species from (η5-
DMDPE)2Fe provided the following results. First, the reaction
of styrene with PMDS was performed in the presence of
(DMDPE)2Fe (10 mol %) and CNAd (20 mol %). The crude
product was passed through a pad of alumina, from which the
formation of 2,4-dimethyl-1,3-pentadiene was confirmed based
1
on assessments by H NMR and gas chromatography−mass
spectrometry (GC-MS). This indicates that the DMDPE
ligands were converted to 2,4-dimethyl-1,3-pentadiene. It
should be mentioned that hydrosilylation of 2,4-dimethyl-1,3-
pentadiene did not take place in the course of this reaction,
suggesting that hydrosilylation of styrene preferentially
proceeded over that of 2,4-dimethyl-1,3-pentadiene. Unfortu-
nately, attempts to identify the iron species by monitoring the
reaction of styrene with PMDS in the presence of (COT)2Fe
1
(10 mol %) and CNAd (20 mol %) by H NMR spectroscopy
were hampered due to the formation of paramagnetic species.
Second, the coordination mode of one of the DMDPE ligands
transitioned from η5 to η3 when CNAd was added to a solution
of (η5-DMDPE)2Fe. 1H NMR data suggested that the resulting
Fe species was (η5-DMDPE)(η3-DMDPE)Fe(CNAd) since
four signals due to the H2CCMe- group of the η5-DMDPE
moiety were detected with a 1:1:1:1 integral ratio at 0.12, 0.17,
2.66, and 4.38 ppm, demonstrating their nonequivalency. Three
protons derived from the η3-coordinated moiety appeared at
1.73, 1.87, and 2.90 ppm, respectively, while two signals were
observed at 4.32 and 4.34 ppm, attributed to the terminal
MeCCH2 group. These data indicated a change in the
hapticity of the two η5-DMPE ligands, generating open
coordination sites for the two CNAd ligands, the hydrosilane
and the styrene. Coordination of the hydrosilane was followed
by reaction of the Si−H bond with the Fe−C bond to produce
2,4-dimethyl-1,3-pentadiene. We have previously reported the
reaction of 1,2-bis(dimethylsilyl)benzene with [Fe(mesityl)2]2,
in which the Si−H bond reacts with the Fe−C(mesityl) moiety
to form Fe−Si and C−H bonds.20 In an analogous manner,
compounds with the general formula “(R3Si)2Fe(CNR)2” are
expected to be formed during the present catalytic reaction
(Scheme 3). Only very broad peaks were observed by
F
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
standard. The conversion of styrene and the yields of the products
were analyzed by H NMR spectroscopy.
CONCLUSIONS
■
1
The above results clearly demonstrate that both (COT)2Fe and
various open ferrocenes function as useful Fe(0) and Fe(II)
precursors for combinatorial-type surveys of appropriate ligands
for the Fe-catalyzed hydrosilylation of styrene derivatives.
Experimental trials using a series of auxiliary ligands confirmed
that the bis(imino)pyridine ligand Me2PDI21 was suitable for
use with Fe(0) and Fe(II) species during catalytic hydro-
silylation and that isocyanides are also effective ligands. To the
best of our knowledge, isocyanides have rarely been used as
ligands for Fe-catalyzed reactions,2 and the present report is the
first example of Fe-isocyanide species catalyzing the hydro-
silylation of alkenes. Alkylisocyanides such as CNAd are also
effective ligands in combination with (COT)2Fe or
(MPDE)2Fe for the hydrosilylation of styrene derivatives with
PMDS or PhMe2SiH with high selectivity between ambient
temperature and 50 °C to give the desired hydrosilylated
products without dehydrogenative silylation byproducts and
produced only the anti-Markovnikov adducts. Under the
optimized conditions, the TON value typically exceeded 100
and, in the most successful example, reached 5000. These
findings solve the general problem of the hydrosilylation of
styrene derivatives, which is often accompanied by the
formation of byproducts and, in some cases, the polymerization
of styrene. The Fe(0) and Fe(II) precursors presented in this
article should allow further screening of ligands to solve the
problems remaining unsolved, e.g., selective hydrosilylation of
aliphatic or cyclic alkenes, and active studies including a survey
of appropriate isocyanide ligands having appropriate electronic
and/or steric properties for highly efficient selective hydro-
silylations are under way.
Hydrosilylation of Styrene with PMDS Catalyzed by
(COT)2Fe with CNAd (Table 2, Entries 1 and 2). (COT)2Fe (2.6
mg, 0.01 mmol) and 1-isocyanoadamantane (3.2 mg, 0.02 mmol) were
placed in a 4 mL glass vial, then the mixture of styrene (115 μL 1.0
mmol) and PMDS (254 μL 1.3 mmol) was added. The resulting
mixture was stirred at 50 °C (entry 1) or at room temperature (entry
2) for 23 h. After the reaction, the mixture was cooled to room
temperature, then anisole (108 mg, 1.0 mmol) was added into the
mixture as an internal standard. The conversion of styrene was
determined by 1H NMR spectroscopy, and the product 1a was isolated
by distillation (8 Pa, 65−70 °C). Isolated yield (entry 1), 237 mg (0.94
1
mmol, 94%); (entry 2), 245 mg (0.95 mmol, 95%). H NMR (400
MHz, CDCl3) δ: 0.07 (s, 6H, -SiMe2-), 0.08 (s, 9H, -SiMe3), 0.86−
0.92 (m, 2H, −CH2Si), 2.61−2.68 (m, 2H, −CH2−), 7.13−7.22 (m,
3H, Ar−H), 7.24−7.29 (m, 2H, Ar−H). 13C NMR (100 MHz,
CDCl3) δ: 0.3, 2.0, 20.4, 29.4, 125.5, 127.8, 128.3, 145.2. 29Si NMR
(119 MHz, CDCl3) δ: 7.09, 7.52. HRMS (EI) calcd for [C13H24OSi2]:
252.1366. Found: 252.1369.
Hydrosilylation of Styrene with PMDS Catalyzed by
(COT)2Fe with CNAd (Table 2, Entry 3). (COT)2Fe (5.4 mg,
0.02 mmol) and 1-isocyanoadamantane (6.8 mg, 0.04 mmol) were
placed in a 20 mL Schlenk tube, then the mixture of styrene (10.42 g,
100 mmol) and PMDS (14.84 g, 100 mmol) was added. The resulting
mixture was stirred at 50 °C for 23 h. Product 1a was isolated by
distillation (8 Pa, 65−70 °C). Isolated yield: 22.41 g (88.7 mmol,
89%).
Hydrosilylation of 4-t-Butylstyrene with PMDS Catalyzed by
(COT)2Fe with CNAd (Table 2, Entry 4). (COT)2Fe (2.6 mg, 0.01
mmol) and 1-isocyanoadamantane (3.2 mg, 0.02 mmol) were placed
in a 4 mL glass vial, then the mixture of 4-t-butylstyrene (180 μL 1.0
mmol) and PMDS (254 μL 1.3 mmol) was added. The resulting
mixture was stirred at 50 °C for 23 h. After the reaction, the mixture
was cooled to room temperature, then anisole (108 mg, 1.0 mmol)
was added into the mixture as an internal standard. The conversion of
1
4-t-butylstyrene was determined by H NMR spectroscopy, and the
EXPERIMENTAL SECTION
product 2a was isolated by distillation (6 Pa, 70−75 °C). Isolated
yield: 293 mg (0.93 mmol, 93%).1H NMR (400 MHz, CDCl3) δ: 0.08
(s, 9H, -SiMe3), 0.08 (s, 6H, -SiMe2-), 0.85−0.92 (m, 2H, −CH2Si),
1.31 (s, 9H, -CMe3), 2.58−2.65 (m, 2H, −CH2−), 7.14 (d, J = 7.7 Hz,
2H, Ar−H), 7.30 (d, J = 7.7 Hz, 2H, Ar−H). 13C NMR (100 MHz,
CDCl3) δ: 0.3, 2.0, 20.2, 28.8, 31.4, 34.3, 125.1, 127.4, 142.1, 148.3.
29Si NMR (119 MHz, CDCl3) δ: 7.13, 7.44. HRMS (EI) calcd for
■
General. Manipulation of air and moisture sensitive compounds
was carried out under a dry nitrogen atmosphere using Schlenk tube
techniques associated with a high-vacuum line or in the glovebox
which was filled with dry nitrogen. All solvents were distilled over
appropriate drying reagents prior to use. 1H, 13C, and 29Si NMR
spectra were recorded on a JEOL Lambda 400 or a Lambda 600
spectrometer at ambient temperature. 1H, 13C, 19F, and 29Si NMR
chemical shifts (δ values) were given in ppm relative to the solvent
signal (1H and 13C) or standard resonances (19F, external trifluoro-
acetic acid; 29Si, external tetramethylsilane). Elemental analyses were
performed by a PerkinElmer 2400II/CHN analyzer. IR spectra were
recorded on a JASCO FT/IR-550 spectrometer. (COT)2Fe,10 bis(η5-
3-methylpentadienyl)Fe,11 bis(η5-2,4-dimethylpentadienyl)Fe,11 and
ethyl 4-vinylbenzoate,22 mesitylisocyanide,23 and 2,6-(2,6-Me2-
C6H3NCMe)2C5H3N24 were synthesized by the method reported
in the literature. Isocyanides (CNAd, CNtBu, and CNCy) were
purchased from Tokyo Chemical Industries Co., Ltd., and were used
without further purification. Hydrosilanes, PhMe2SiH, Et3SiH,
(EtO)3SiH, Ph2SiH2, and PhSiH3, were purchased from Tokyo
Chemical Industries Co., Ltd., and EtMe2SiH was purchased from
Sigma-Aldrich and was used after distillation. PMDS, MD’M, and the
polymeric hydrosiloxane were obtained from Shin-Etsu Chemical Co.
Ltd.
[C17H32OSi2]: 308.1992. Found: 308.1989.
Hydrosilylation of 4-Chlorostyrene with PMDS Catalyzed by
(COT)2Fe with CNAd (Table 2, Entry 5). (COT)2Fe (2.6 mg, 0.01
mmol) and 1-isocyanoadamantane (3.2 mg, 0.02 mmol) were placed
in a 4 mL glass vial, then the mixture of 4-chlorostyrene (127 μL 1.0
mmol) and PMDS (254 μL 1.3 mmol) was added. The resulting
mixture was stirred at 50 °C for 23 h. After the reaction, the mixture
was cooled to room temperature, then anisole (108 mg, 1.0 mmol)
was added into the mixture as an internal standard. The conversion of
1
4-chlorostyrene was determined by H NMR spectroscopy, and the
product 3a was isolated by distillation (8 Pa, 80−85 °C). Isolated
yield: 277 mg (0.97 mmol, 97%).1H NMR (400 MHz, CDCl3) δ: 0.07
(s, 6H, -SiMe2-), 0.08 (s, 9H, -SiMe3), 0.82−0.88 (m, 2H, −CH2Si),
2.58−2.64 (m, 2H, −CH2−), 7.12 (d, J = 8.2 Hz, 2H, Ar−H), 7.23 (d,
J = 8.2 Hz, 2H, Ar−H). 13C NMR (100 MHz, CDCl3) δ: 0.3, 2.0, 20.3,
28.8, 128.3, 129.2, 131.1, 143.6. 29Si NMR (119 MHz, CDCl3) δ: 6.90,
7.71. HRMS (EI) calcd for [C13H23ClOSi2]: 286.0976. Found:
286.0963.
Hydrosilylation of 4-Fluorostyrene with PMDS Catalyzed by
(COT)2Fe with CNAd (Table 2, Entry 6). (COT)2Fe (2.6 mg, 0.01
mmol) and 1-isocyanoadamantane (3.2 mg, 0.02 mmol) were placed
in a 4 mL glass vial, then the mixture of 4-fluorostyrene (154 μL 1.0
mmol) and PMDS (254 μL 1.3 mmol) was added. The resulting
mixture was stirred at 50 °C for 23 h. After the reaction, the mixture
was cooled to room temperature, then anisole (108 mg, 1.0 mmol)
was added into the mixture as an internal standard. The conversion of
General Procedure for the Hydrosilylation of Styrene with
1,1−3,3,3-Pentamethyldisiloxane (PMDS) Catalyzed by
(COT)2Fe and Various Ligands (Table 1). (COT)2Fe (7.9 mg,
0.03 mmol) and the ligand (0.03 or 0.06 or 0.09 mmol) were placed in
a 4 mL glass vial, then the mixture of styrene (115 μL, 1.0 mmol) and
1,1,3,3,3-pentamethyldisiloxane (PMDS) (254 μL, 1.3 mmol) was
added. The resulting mixture was stirred at 80 °C for 3 h. After the
reaction, the mixture was cooled to room temperature, then anisole
(108 mg, 1.0 mmol) was added into the mixture as an internal
G
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1
4-fluorostyrene was determined by H NMR spectroscopy, and the
product 4a was isolated by distillation (8 Pa, 65−70 °C). Isolated
yield: 257 mg (0.95 mmol, 95%). 1H NMR (400 MHz, CDCl3) δ: 0.07
(s, 6H, -SiMe2-), 0.08 (s, 9H, -SiMe3), 0.83−0.89 (m, 2H, −CH2Si),
2.58−2.65 (m, 2H, −CH2−), 6.92−6.98 (m, 2H, Ar−H), 7.12−7.17
(m, 2H, Ar−H). 13C NMR (100 MHz, CDCl3) δ: 0.3, 2.0, 20.5, 28.7,
114.9 (d, JC−F = 21.3 Hz), 129.1 (d, JC−F = 8.2), 140.7 (d, JC−F = 3.3
Hz), 161.0 (d, JC−F = 242.8 Hz). 19F-NMR (565 MHz, CDCl3) δ:
−119.27. 29Si NMR (119 MHz, CDCl3) δ: 6.94, 7.63. HRMS (EI)
calcd for [C13H23FOSi2]: 270.1272. Found: 270.1255.
was cooled to room temperature, then anisole (108 mg, 1.0 mmol)
was added into the mixture as an internal standard. The conversion of
styrene was determined by 1H NMR spectroscopy, and the product 8a
was isolated by distillation (3 Pa, 120−125 °C). Isolated yield: 224 mg
1
(0.84 mmol, 84%). H NMR (395 MHz, CDCl3) δ: 0.09 (s, 9H,
-SiMe3), 0.10 (s, 6H, -SiMe2-), 0.80−0.85 (m, 2H, −CH2Si), 2.30 (s,
3H, -Me), 2.58−2.62 (m, 2H, −CH2−), 7.06−7.17 (m, 4H, Ar−H).
13C NMR (99 MHz, CDCl3) δ: 0.4, 2.2, 19.3 (two peaks due to the o-
Me-C6H4MeCH2 and o-Me-C6H4MeCH2 are overlapped), 26.9, 125.8,
126.2, 128.1, 130.3, 135.6, 143.5. 29Si NMR (119 MHz, CDCl3) δ:
7.09, 7.59. HRMS (EI) calcd for [C14H26OSi2]: 266.1522. Found:
266.1521.
Hydrosilylation of 4-Methoxystyrene Derivatives with
PMDS Catalyzed by (COT)2Fe with CNAd (Table 2, Entry 7).
(COT)2Fe (2.6 mg, 0.01 mmol) and 1-isocyanoadamantane (3.2 mg,
0.02 mmol) were placed in a 4 mL glass vial, then the mixture of 4-
methoxystyrene (134 μL 1.0 mmol) and PMDS (254 μL 1.3 mmol)
was added. The resulting mixture was stirred at 40 °C for 23 h. After
the reaction, the mixture was cooled to room temperature, then anisole
(108 mg, 1.0 mmol) was added into the mixture as an internal
standard. The conversion of 4-methoxystyrene was determined by H
NMR spectroscopy, and the product 5a was isolated by distillation (6
Pa, 70−75 °C). Isolated yield: 271 mg (0.96 mmol, 96%). H NMR
(400 MHz, CDCl3) δ: 0.07 (s, 6H, -SiMe2-), 0.08 (s, 9H, -SiMe3),
0.83−0.89 (m, 2H, −CH2Si), 2.56−2.62 (m, 2H, −CH2−), 3.79 (s,
3H, O−CH3), 6.82 (d, J = 8.7 Hz, 2H, Ar−H), 7.12 (d, J = 8.7 Hz, 2H,
Ar−H). 13C NMR (100 MHz, CDCl3) δ: 0.3, 2.0, 20.6, 28.5, 55.3,
113.7, 128.6, 137.3, 157.6. 29Si NMR (119 MHz, CDCl3) δ: 7.09, 7.48.
HRMS (EI) calcd for [C14H26O2Si2]: 282.1471. Found: 282.1460.
Hydrosilylation of Ethyl 4-Vinylbenzoate with PMDS
Catalyzed by (COT)2Fe with CNAd (Table 2, Entry 8).
(COT)2Fe (2.6 mg, 0.01 mmol) and 1-isocyanoadamantane (3.2
mg, 0.02 mmol) were placed in a 4 mL glass vial, then the mixture of
ethyl 4-vinylbenzoate (176 mg 1.0 mmol) and PMDS (254 μL 1.3
mmol) was added. The resulting mixture was stirred at 50 °C for 23 h.
After the reaction, the mixture was cooled to room temperature, then
anisole (108 mg, 1.0 mmol) was added into the mixture as an internal
Hydrosilylation of Styrene Derivatives with PhMe2SiH
Catalyzed by (COT)2Fe with CNAd (Table 3, Entry 1).
(COT)2Fe (26 mg, 0.1 mmol) and 1-isocyanoadamantane (32 mg,
0.2 mmol) were placed in a 20 mL Schlenk tube, then the mixture of
styrene (1.04 g 10.0 mmol) and PhMe2SiH (1.77 g 13.0 mmol) was
added. The resulting mixture was stirred at 50 °C for 23 h. After the
reaction, the mixture was cooled to room temperature, then anisole
(108 mg, 1.0 mmol) was added into the mixture as an internal
standard. The conversion of styrene was determined by 1H NMR
spectroscopy, and the product 1a′ was isolated by distillation (14 Pa,
1
1
1
75−80 °C). Isolated yield: 2.03 g (8.5 mmol, 85%). H NMR (395
MHz, CDCl3) δ: 0.30 (s, 6H, -SiMe2), 1.11−1.18 (m, 2H, −CH2Si),
2.62−2.68 (m, 2H, −CH2−), 7.14−7.20 (m, 3H, Ar−H), 7.24−7.30
(m, 2H, Ar−H), 7.36−7.40 (m, 3H, Ar−H), 7.53−7.57 (m, 2H, Ar−
H). 13C NMR (99 MHz, CDCl3) δ: −3.0, 17.7, 30.0, 125.5, 127.8,
127.8, 128.3, 128.9, 133.6, 139.0, 145.0. 29Si NMR (119 MHz, CDCl3)
δ: −2.89. HRMS (EI) calcd for [C16H20Si]: 240.1334. Found:
240.1336.
Hydrosilylation of 4-t-Butylstyrene with PhMe2SiH Cata-
lyzed by (COT)2Fe with CNAd (Table 3, Entry 2). (COT)2Fe (2.6
mg, 0.01 mmol) and 1-isocyanoadamantane (3.2 mg, 0.02 mmol) were
placed in a 4 mL glass vial, then the mixture of 4-t-butylstyrene (180
μL 1.0 mmol) and PhMe2SiH (202 μL 1.3 mmol) was added. The
resulting mixture was stirred at 50 °C for 23 h. After the reaction, the
mixture was cooled to room temperature, then anisole (108 mg, 1.0
mmol) was added into the mixture as an internal standard. The
1
standard. The conversion of 4-vinylbenzoate was determined by H
NMR spectroscopy, and the product 6a was isolated by distillation (6
Pa, 135−140 °C). Isolated yield: 324 mg (0.99 mmol, 99%). 1H NMR
(400 MHz, CDCl3) δ: 0.08 (s, 6H, -SiMe2-), 0.09 (s, 9H, -SiMe3),
0.86−0.92 (m, 2H, −CH2Si), 1.39 (t, J = 7.2 Hz, 3H, −CH3), 2.66−
2.72 (m, 2H, −CH2−), 4.36 (q, J = 7.2 Hz, 2H, O−CH2−), 7.26 (d, J
= 8.2 Hz, 2H, Ar−H), 7.95 (d, J = 8.2 Hz, 2H, Ar−H). 13C NMR (100
MHz, CDCl3) δ: 0.3, 2.0, 14.3, 20.1, 29.6, 60.7, 127.8, 127.9, 129.6,
150.7, 166.7. 29Si NMR (119 MHz, CDCl3) δ: 6.90, 7.79. HRMS (EI)
calcd for [C16H28O3Si2]: 324.1577. Found: 324.1566.
Hydrosilylation of 4-Vinylnaphthalene with PMDS Cata-
lyzed by (COT)2Fe with CNAd (Table 2, Entry 9). (COT)2Fe (7.9
mg, 0.03 mmol) and 1-isocyanoadamantane (9.7 mg, 0.06 mmol) were
placed in a 4 mL glass vial, then the mixture of 4-vinylnaphthalene
(154 mg 1.0 mmol) and PMDS (254 μL 1.3 mmol) was added. The
resulting mixture was stirred at 50 °C for 23 h. After the reaction, the
mixture was cooled to room temperature, then anisole (108 mg, 1.0
mmol) was added into the mixture as an internal standard. The
conversion of 4-vinylnaphthalene was determined by 1H NMR
spectroscopy, and the product 7a was isolated by distillation (6 Pa,
1
conversion of 4-t-butylstyrene was determined by H NMR spectros-
copy, and the product 2a′ was isolated by distillation (8 Pa, 125−130
1
°C). Isolated yield: 281 mg (0.95 mmol, 95%). H NMR (395 MHz,
CDCl3) δ: 0.29 (s, 6H, -SiMe2), 1.10−1.16 (m, 2H, −CH2Si), 1.31 (s,
9H, -CMe3), 2.58−2.65 (m, 2H, −CH2−), 7.12 (d, J = 8.7 Hz, 2H,
Ar−H), 7.28 (d, J = 8.2 Hz, 2H, Ar−H), 7.29−7.39 (m, 3H, Ar−H),
7.51−7.55 (m, 2H, Ar−H). 13C NMR (99 MHz, CDCl3) δ: −3.1, 17.5,
29.3, 31.4, 34.3, 125.1, 127.4, 127.8, 128.9, 133.6, 139.1, 141.9, 148.3.
29Si NMR (119 MHz, CDCl3) δ: −2.89. HRMS (EI) calcd for
[C20H28Si]: 296.1960. Found: 296.1961.
Hydrosilylation of 4-Chlorostyrene Derivatives with
PhMe2SiH Catalyzed by (COT)2Fe with CNAd (Table 3, Entry
3). (COT)2Fe (26 mg, 0.1 mmol) and 1-isocyanoadamantane (32 mg,
0.2 mmol) were placed in a 20 mL Schlenk tube, then the mixture of
4-chlorostyrene (1.39 g 10.0 mmol) and PhMe2SiH (1.77 g 13.0
mmol) was added. The resulting mixture was stirred at 50 °C for 23 h.
After the reaction, the mixture was cooled to room temperature, then
anisole (108 mg, 1.0 mmol) was added into the mixture as an internal
1
120−125 °C). Isolated yield: 297 mg (0.98 mmol, 98%). H NMR
1
(400 MHz, CDCl3) δ: 0.08 (s, 6H, -SiMe2-), 0.08 (s, 9H, -SiMe3),
0.85−0.92 (m, 2H, −CH2Si), 1.39 (t, J = 7.2 Hz, 3H, −CH3), 2.66−
2.72 (m, 2H, −CH2−), 4.36 (q, J = 7.2 Hz, 2H, O−CH2−), 7.26 (d, J
= 8.2 Hz, 2H, Ar−H), 7.95 (d, J = 8.2 Hz, 2H, Ar−H). 13C NMR (100
MHz, CDCl3) δ: 0.3, 2.0, 20.3, 29.6, 124.9, 125.4, 125.8, 127.1, 127.4,
127.6, 127.8, 131.9, 133.7, 142.7. 29Si NMR (119 MHz, CDCl3) δ:
7.13, 7.63. HRMS (EI) calcd for [C17H26OSi2]: 302.1522. Found:
302.1517.
standard. The conversion of 4-chlorostyrene was determined by H
NMR spectroscopy, and the product 3a′ was isolated by distillation
(14 Pa, 80−85 °C). Isolated yield: 2.505 g (9.1 mmol, 91%). 1H NMR
(395 MHz, CDCl3) δ: 0.32 (s, 6H, -SiMe2), 1.08−1.15 (m, 2H,
−CH2Si), 2.59−2.65 (m, 2H, −CH2−), 7.09−7.13 (m, 2H, Ar−H),
7.21−7.25 (m, 2H, Ar−H), 7.37−7.41 (m, 3H, Ar−H), 7.52−7.57 (m,
2H, Ar−H). 13C NMR (99 MHz, CDCl3) δ: −3.1, 17.7, 29.4, 127.8,
128.3, 129.0, 129.1, 131.2, 133.5, 138.8, 143.4. 29Si NMR (119 MHz,
CDCl3) δ: −2.89. HRMS (EI) calcd for [C16H19ClSi]: 274.0945.
Found: 274.0938.
Hydrosilylation of 4-Fluorostyrene with PhMe2SiH Cata-
lyzed by (COT)2Fe with CNAd (Table 3, Entry 4). (COT)2Fe (2.6
mg, 0.01 mmol) and 1-isocyanoadamantane (3.2 mg, 0.02 mmol) were
placed in a 4 mL glass vial, then the mixture of 4-fluorostyrene (154
Hydrosilylation of 2-Methylstyrene with PMDS Catalyzed by
(COT)2Fe with CNAd (Table 2, Entry 10). (COT)2Fe (7.9 mg, 0.03
mmol) and 1-isocyanoadamantane (9.7 mg, 0.06 mmol) were placed
in a 4 mL glass vial, then the mixture of 2-methylstyrene (129 μL 1.0
mmol) and PMDS (254 μL 1.3 mmol) was added. The resulting
mixture was stirred at 50 °C for 23 h. After the reaction, the mixture
H
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
μL 1.0 mmol) and PhMe2SiH (202 μL 1.3 mmol) was added. The
resulting mixture was stirred at 50 °C for 23 h. After the reaction, the
mixture was cooled to room temperature, then anisole (108 mg, 1.0
mmol) was added into the mixture as an internal standard. The
Hydrosilylation of Styrene with Polymeric Hydrosiloxane
Catalyzed by (COT)2Fe with 1-Isocyanoadamantane. (COT)2Fe
(7.2 mg, 0.03 mmol) and 1-isocyanoadamantane (9.7 mg, 0.06 mmol)
were placed in a 4 mL glass vial, then the mixture of styrene (299 μL,
2.6 mmol) and polymeric hydrosilanes, Me2Si(H)O(SiMe2O)nSi(H)-
1
conversion of 4-fluorostyrene was determined by H NMR spectros-
1
Me2 (n = ca. 27, determined by H NMR) (2.14 g, ca. 2.0 mmol for
copy, and the product 4a′ was isolated by distillation (8 Pa, 95−100
1
Si−H) was added. The resulting mixture was stirred at 50 °C for 23 h.
After the reaction, the mixture was cooled to room temperature, then
anisole (108 mg, 1.0 mmol) was added into the mixture as an internal
standard. The conversion of styrene (>99%) and the yield of the
product (>99%) were determined by 1H NMR spectroscopy. The
crude product was stirred for 3 h under air to decompose the iron
residue, then the resulting mixture was passed through a pad of Al2O3.
The filtrate was dried under vacuum, then the product 9a was obtained
in 99% yield (2.32 g). 1H NMR (395 MHz, CDCl3) δ: 0.09 (s, 156H,
-SiMe2-), 0.11 (s, 18H, -SiMe2-), 0.87−0.98 (m, 4H, −CH2Si), 2.61−
2.73 (m, 4H, −CH2−), 7.13−7.31 (m, 10H, C6H5). 13C NMR (99
MHz, CDCl3) δ: 0.29, 0.81, 1.18, 1.24, 1.34, 1.56, 20.4, 29.5, 125.6,
127.9, 128.4, 145.3. 29Si NMR (119 MHz, CDCl3) δ: 7.09, −20.70,
−21.28, −21.86.
General Procedure for Hydrosilylation of Styrene Deriva-
tives with PMDS or PhMe2SiH Catalyzed by (MPDE)2Fe with 1-
Isocyanoadamantane (Table 4, Entries 1 and 3−7). (MPDE)2Fe
(1.9 mg, 0.01 mmol) and 1-isocyanoadamantane (3.2 mg, 0.02 mmol)
were placed in a 4 mL glass vial, then the mixture of styrene derivatives
(1 mmol) and hydrosilanes (PMDS or PhMe2SiH) (1.3 mmol) was
added. The resulting mixture was stirred at 50 °C for 23 h. After the
reaction, the mixture was cooled to room temperature, then anisole
(108 mg, 1.0 mmol) was added into the mixture. The conversion of
styrene derivatives and the yield of the product were determined by 1H
NMR spectroscopy. The product was isolated by distillation under
reduced pressure.
°C). Isolated yield: 252 mg (0.98 mmol, 98%) H NMR (395 MHz,
CDCl3) δ: 0.29 (s, 6H, -SiMe2), 1.07−1.13 (m, 2H, −CH2Si), 2.57−
2.64 (m, 2H, −CH2−), 6.93 (t, J = 8.7 Hz, 2H, Ar−H), 7.08−7.13 (m,
2H, Ar−H), 7.35−7.38 (m, 3H, Ar−H), 7.50−7.54 (m, 2H, Ar−H).
13C NMR (99 MHz, CDCl3) δ: −3.1, 17.9, 29.2, 114.9 (d, JC−F = 20.5
Hz), 127.8, 129.0, 129.0 (d, JC−F = 8.2 Hz), 133.6, 138.9, 140.5 (d, JC−F
= 3.3 Hz), 161.1 (d, JC−F = 242.0 Hz). 19F-NMR (565 MHz, CDCl3)
δ: −119.11. 29Si NMR (119 MHz, CDCl3) δ: −2.93. HRMS (EI) calcd
for [C16H19FSi]: 258.1240. Found: 258.1241.
Hydrosilylation of 4-Methoxystyrene with PhMe2SiH Cata-
lyzed by (COT)2Fe with CNAd (Table 3, Entry 5). (COT)2Fe (26
mg, 0.1 mmol) and 1-isocyanoadamantane (32 mg, 0.2 mmol) were
placed in a 20 mL Schlenk tube, then the mixture of 4-methoxystyrene
(1.34 g 10.0 mmol) and PhMe2SiH (1.77 g 13.0 mmol) was added.
The resulting mixture was stirred at 50 °C for 23 h. After the reaction,
the mixture was cooled to room temperature, then anisole (108 mg,
1.0 mmol) was added into the mixture as an internal standard. The
conversion of 4-methoxystyrene was determined by 1H NMR
spectroscopy, and the product 5a′ was isolated by distillation (14
Pa, 85−90 °C). Isolated yield: 2.20 g (8.2 mmol, 82%). 1H NMR (395
MHz, CDCl3) δ: 0.30 (s, 6H, -SiMe2), 1.09−1.15 (m, 2H, −CH2Si),
2.58−2.64 (m, 2H, −CH2−), 3.80 (s, 3H, O−CH3), 6.81−6.84 (m,
2H, Ar−H), 7.09−7.12 (m, 2H, Ar−H), 7.36−7.40 (m, 3H, Ar−H),
7.53−7.57 (m, 2H, Ar−H). 13C NMR (99 MHz, CDCl3) δ: −3.1, 17.9,
29.0, 55.3, 113.7, 127.8, 128.6, 128.9, 133.6, 137.1, 139.1, 157.6. 29Si
NMR (119 MHz, CDCl3) δ: −3.01. HRMS (EI) calcd for
[C17H22OSi]: 270.1440. Found: 270.1441.
Hydrosilylation of Styrene with PMDS Catalyzed by
(DMPDE)2Fe with 1-Isocyanoadamantane (Table 4, Entry 2).
(DMPDE)2Fe (2.5 mg, 0.01 mmol) and 1-isocyanoadamantane (3.2
mg, 0.02 mmol) were placed in a 4 mL glass vial, then the mixture of
styrene (115 μL 1.0 mmol) and PMDS (254 μL, 1.3 mmol) was
added. The resulting mixture was stirred at 50 °C for 23 h. After the
reaction, the mixture was cooled to room temperature, then anisole
(108 mg, 1.0 mmol) was added into the mixture. The conversion of
Hydrosilylation of 4-Vinylbenzoate with PhMe2SiH Cata-
lyzed by (COT)2Fe with CNAd (Table 3, Entry 6). (COT)2Fe (2.6
mg, 0.01 mmol) and 1-isocyanoadamantane (3.2 mg, 0.02 mmol) were
placed in a 4 mL glass vial, then the mixture of ethyl 4-vinylbenzoate
(176 mg 1.0 mmol) and PhMe2SiH (202 μL 1.3 mmol) was added.
The resulting mixture was stirred at 50 °C for 23 h. After the reaction,
the mixture was cooled to room temperature, then anisole (108 mg,
1.0 mmol) was added into the mixture as an internal standard. The
1
styrene and the yield of the product were determined by H NMR
spectroscopy.
1
conversion of 4-vinylbenzoate was determined by H NMR spectros-
S y n t h e s i s o f B i s ( c y c l o o c t a t e t r a e n e ) ( 1 -
isocyanoadamantane)iron (10). COT)2Fe (50 mg, 0.19 mmol)
and toluene (2 mL) were placed in a 20 mL Schlenk tube, then 1-
isocyanoadamantane (33 mg, 0.21 mmol) was added to this solution at
room temperature. The solution was stirred at room temperature for 1
h, then the resulting mixture was passed through a short pad of Celite.
The mother liquid was collected, and pentane (10 mL) was added.
Complex 10 was obtained as black crystals by recrystallization at −35
°C (50 mg, 0.12 mmol, 62%). 1H NMR (600 MHz, C6D6) δ: 1.37 (br,
6H), 1.79 (s, 3H), 1.97 (s, 6H), 4.52 (br, 16H). 13C NMR (151 MHz,
C6D6) δ: 29.3, 35.8, 44.4, 55.7, 101.0 (br), 166.6. FT-IR (KBr, pellet):
νC−N = 2119 cm−1 Anal. calcd for C27H31NFe; C 76.23, H 7.35, N
3.29; found, C 76.18, H 7.85, N 3.10.
copy, and the product 6a′ was isolated by distillation (4 Pa, 130−135
1
°C). Isolated yield: 312 mg (0.99 mmol, 99%). H NMR (395 MHz,
CDCl3) δ: 0.30 (s, 6H, -SiMe2), 1.09−1.16 (m, 2H, −CH2Si), 1.38 (t,
J = 7.2 Hz, 3H, −CH3), 2.64−2.71 (m, 2H, −CH2−), 4.36 (q, J = 7.2
Hz, 2H, O−CH2−), 7.22 (d, J = 8.2 Hz, 2H, Ar−H), 7.35−7.39 (m,
3H, Ar−H), 7.50−7.55 (m, 2H, Ar−H), 7.93 (d, J = 8.2 Hz, 2H, Ar−
H). 13C NMR (99 MHz, CDCl3) δ: −3.2, 14.3, 17.5, 30.1, 60.7, 127.7,
127.8, 127.9, 129.0, 129.6, 133.5, 138.6, 150.3, 166.6. 29Si NMR (119
MHz, CDCl3) δ: −2.78. HRMS (EI) calcd for [C19H24O2Si]:
312.1546. Found: 312.1548.
Hydrosilylation of 2-Methylstyrene with PMDS Catalyzed by
(COT)2Fe with CNAd (Table 3, Entry 7). (COT)2Fe (2.6 mg, 0.01
mmol) and 1-isocyanoadamantane (3.2 mg, 0.02 mmol) were placed
in a 4 mL glass vial, then the mixture of 2-methylstyrene (129 μL 1.0
mmol) and PhMe2SiH (202 μL 1.3 mmol) was added. The resulting
mixture was stirred at 50 °C for 23 h. After the reaction, the mixture
was cooled to room temperature, then anisole (108 mg, 1.0 mmol)
was added into the mixture as an internal standard. The conversion of
S y n t h e s i s o f ( C y c l o o c t a t e t r a e n e ) t r i s ( 1 -
isocyanoadamantane)iron (11). In a 20 mL Schlenk tube were
placed (COT)2Fe (100 mg, 0.38 mmol), 1-isocyanoadamantane (185
mg, 1.15 mmol), and toluene (4 mL). The solution was stirred at
room temperature for 1 h, then the resulting mixture was passed
through a short pad of Celite. The mother liquid was collected, and
pentane (40 mL) was added. Complex 11 was obtained as red crystals
1
2-methylstyrene was determined by H NMR spectroscopy, and the
1
product 8a′ was purified by distillation (8 Pa, 115−120 °C). Isolated
yield: 244 mg (0.96 mmol, 96%). 1H NMR (395 MHz, CDCl3) δ: 0.33
(s, 6H, -SiMe2), 1.04−1.10 (m, 2H, −CH2Si), 2.25 (s, 3H, −CH3),
2.57−2.63 (m, 2H, −CH2−), 7.09−7.15 (m, 4H, Ar−H), 7.36−7.40
(m, 3H, Ar−H), 7.54−7.58 (m, 2H, Ar−H). 13C NMR (99 MHz,
CDCl3) δ: −3.2, 16.6, 19.0, 27.3, 125.6, 126.0, 127.8, 127.9, 128.9,
130.1, 133.6, 135.3, 139.0, 143.2. 29Si NMR (119 MHz, CDCl3) δ:
−2.78. HRMS (EI) calcd for [C17H22Si]: 254.1491. Found: 254.1482.
by recrystallization at −35 °C (168 mg, 0.24 mmol, 63%). H NMR
(600 MHz, C6D6) δ: 1.32 (br, 18H), 1.72 (s, 9H), 1.86 (s, 18H), 5.46
(br, 8H). 13C NMR (151 MHz, C6D6) δ: 29.5, 35.8, 45.1, 56.4, 97.1
(br), 183.8. FT-IR (KBr, pellet): νC−N = 2104, 2041, 1937 cm−1 Anal.
calcd for C41H53N3Fe; C 76.50, H 8.30 N 6.53; found, C 76.48, H
8.74, N 6.48.
Hydrosilylation of Styrene with PMDS Catalyzed by
(COT)2Fe(CNAd) (10) (Table 5, Entry 2). (COT)2Fe(CNAd) (10)
I
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(4.3 mg, 0.01 mmol) were placed in a 4 mL glass vial, then the mixture
of styrene (115 μL 1.0 mmol) and PMDS (254 μL 1.3 mmol) was
added. The resulting mixture was stirred at 50 °C for 23 h. After the
reaction, the mixture was cooled to room temperature, then anisole
(108 mg, 1.0 mmol) was added. The conversion of styrene (67%) and
the yield of the product (67%) were determined by 1H NMR
spectroscopy. The product was isolated by distillation under reduced
pressure (8 Pa, 65−70 °C). Isolated yield: 159 mg (0.63 mmol, 63%).
Hydrosilylation of Styrene with PMDS Catalyzed by
(COT)2Fe(CNAd) (10) in the Presence of CNAd (Table 5, Entry
3). (COT)2Fe(CNAd) (10) (4.3 mg, 0.01 mmol) and CNAd (1.6 mg,
0.01 mmol) were placed in a 4 mL glass vial, then the mixture of
styrene (115 μL 1.0 mmol) and PMDS (254 μL 1.3 mmol) was added.
The resulting mixture was stirred at 50 °C for 23 h. After the reaction,
the mixture was cooled to room temperature, then anisole (108 mg,
1.0 mmol) was added. The conversion of styrene (>99%) and the yield
ACKNOWLEDGMENTS
■
This work was supported by the Core Research Evolutional
Science and Technology (CREST) Program of Japan Science
and Technology Agency (JST) Japan, and Grant in Aid for
Young Scientist (A) (No. 24685011), and Grant-in-Aid for
Scientific Research on Innovative Areas “Stimuli-responsive
Chemical Species” (No. 25109534) from Ministry of
Education, Culture, Sports, Science and Technology, Japan.
We thank Shin-Etsu Chemical Co. Ltd. for the gift of PMDS,
MD’M, and the polymeric hydrosiloxane.
REFERENCES
■
(1) (a) Marciniec, B.; Gulinsky, J.; Urbaniak, W.; Kornetka, Z. W. In
Comprehensive Handbook on Hydrosilylation; Marciniec, B., Ed.;
Pergamon: Oxford, U.K., 1992. (b) Hydrosilylation: A Comprehensive
Review on Recent Advances; Marciniec, B.; Springer: New York, 2009.
(c) Speier, J. L. Adv. Organomet. Chem. 1979, 17, 407−447.
(2) For general catalysis of iron (a) Plietker, B. In Iron Catalysis in
Organic Chemistry; Plietker, B., Ed.; Wiley-VCH: Weinheim, Germany,
2008. (b) Bolm, C.; Legros, J.; Paith, J. L.; Zani, L. Chem. Rev. 2004,
104, 6217−6254.
1
of the product (>99%) were determined by H NMR spectroscopy.
The product was isolated by distillation under reduced pressure (8 Pa,
65−70 °C). Isolated yield: 245 mg (0.97 mmol, 97%).
Hydrosilylation of Styrene with PMDS Catalyzed by (COT)-
Fe(CNAd)3 (11) (Table 5, Entry 4). (COT)Fe(CNAd)3 (11) (6.4
mg, 0.01 mmol) was placed in a 4 mL glass vial, then the mixture of
styrene (115 μL 1.0 mmol) and PMDS (254 μL 1.3 mmol) was added.
The resulting mixture was stirred at 50 °C for 23 h. After the reaction,
the mixture was cooled to room temperature, then anisole (108 mg,
1.0 mmol) was added into the mixture. The conversion of styrene
(3) For earlier reports (a) Schroeder, M. A.; Wrighton, M. S. J.
Organomet. Chem. 1977, 128, 345−358. (b) Mitchener, J. C.;
Wrighton, M. S. J. Am. Chem. Soc. 1981, 103, 975−977.
(c) Nesmeyanov, A. N.; Freidlina, R. K.; Chukovskaya, E. C.;
Petrova, R. G.; Belyavsky, A. B. Tetrahedron 1962, 17, 61−68.
(4) (a) Bart, S. C.; Lobkovsky, E.; Chirik, P. J. J. Am. Chem. Soc. 2004,
126, 13794−13807. (b) Tondreau, A. M.; Atienza, C. C.; Weller, K. J.;
Nye, S. A.; Lewis, K. M.; Delis, J. G.; Chirik, P. J. Science 2012, 335,
567−570. (c) Hojilla Atienza, C. C.; Tondreau, A. M.; Weller, K. J.;
Lewis, K. M.; Cruse, R. W.; Nye, S. A.; Boyer, J. L.; Delis, J. G. P.;
Chirik, P. J. ACS Catal. 2012, 2, 2169−2172. (d) Tondreau, A. M.;
Atienza, C. C. H.; Darmon, J. M.; Milsmann, C.; Hoyt, H. M.; Weller,
K. J.; Nye, S. A.; Lewis, K. M.; Boyer, J.; Delis, J. G. P.; Lobkovsky, E.;
Chirik, P. J. Organometallics 2012, 31, 4886−4893.
1
(82%) and the yield of the product (82%) were determined by H
NMR spectroscopy. The product was isolated by distillation under
reduced pressure (8 Pa, 65−70 °C). Isolated yield: 202 mg (0.80
mmol, 80%).
X-ray Data Collection and Reduction. X-ray crystallography was
performed on a Rigaku Saturn CCD area detector with graphite
monochromated Mo−Kα radiation (λ = 0.71075 Å). The data were
collected at 123(2) K using ω scan in the θ range of 2.77 ≤ θ ≤ 30.81°
(10) and 2.45 ≤ θ ≤ 30.74° (11). The data obtained were processed
using Crystal-Clear (Rigaku) on a Pentium computer and were
corrected for Lorentz and polarization effects. The structures were
solved by direct methods25 and expanded using Fourier techniques.26
Hydrogen atoms were refined using the riding model. The final cycle
of full-matrix least-squares refinement on F2 was based on 4586
observed reflections and 262 variable parameters for 10, and 7618
observed reflections and 406 variable parameters for 11. Neutral atom
scattering factors were taken from Cromer and Waber.27 All
calculations were performed using SHELXL-97.28 Details of the final
refinement as well as the bond lengths and angle are summarized in
Tables S2 and S3 (Supporting Information), and the numbering
scheme employed is also shown in Figures S1 and S2 in the
Supporting Information, which were drawn with ORTEP at a 50%
probability ellipsoid.
(5) For the hydrosilylation of 1,3-dienes Wu, J. Y.; Stanzl, B. N.;
Ritter, T. J. Am. Chem. Soc. 2010, 132, 13214−13216.
(6) (a) Kakiuchi, F.; Tanaka, Y.; Chatani, N.; Murai, S. J. Organomet.
Chem. 1993, 456, 45−47. (b) Marciniec, B.; Kownacka, A.; Kownacki,
I.; Taylor, R. Appl. Catal. A 2014, 486, 230−238. (c) Marciniec, B.;
Majchrzak, M. Inorg. Chem. Commun. 2000, 3, 371−375. (d) Naumov,
R. N.; Itazaki, M.; Kamitani, M.; Nakazawa, H. J. Am. Chem. Soc. 2012,
134, 804−807.
(7) (a) Sunada, Y.; Tsutsumi, H.; Shigeta, K.; Yoshida, R.;
Hashimoto, T.; Nagashima, H. Dalton. Trans. 2013, 42, 16687−
16692. (b) Sunada, Y.; Soejima, H.; Nagashima, H. Organometallics
2014, 33, 5936−5939.
(8) (a) Kamata, K.; Suzuki, A.; Nakai, Y.; Nakazawa, H.
Organometallics 2012, 31, 3825−3828. (b) Greenhalgh, M. D.;
Frank, D. J.; Thomas, S. J. Adv. Synth. Catal. 2014, 356, 584−590.
(c) Greenhalgh, M. D.; Jones, A. S.; Thomas, S. J. ChemCatChem
2015, 7, 190−222.
(9) (a) Peng, D.; Zhang, Y.; Du, X.; Zhang, L.; Leng, X.; Walter, M.
D.; Huang, Z. J. Am. Chem. Soc. 2013, 135, 19154−19166. (b) Chen,
J.; Cheng, B.; Cao, M.; Lu, Z. Angew. Chem., Int. Ed. 2015, 54, 4661−
4664.
(10) (a) Gerlach, D. H.; Schunn, R. A. Inorg. Synth. 1974, 15, 1−4.
(b) Garbonaro, A.; Greco, A.; Dallasta, G. J. Organomet. Chem. 1969,
20, 177−186.
(11) Wilson, D. R.; Ernst, R. D.; Cymbaluk, T. H. Organometallics
1983, 2, 1220−1228.
(12) (a) Junquera, L. B.; Puerta, M. C.; Valerga, P. Organometallics
ASSOCIATED CONTENT
■
S
* Supporting Information
Details of additional experiments, the molecular structures of
10 and 11, and details of crystallographic studies, and the copy
of the actual NMR chart for all products. The Supporting
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.organomet.5b00201.
AUTHOR INFORMATION
■
Corresponding Author
2012, 31, 2175−2183. (b) Poyatos, M.; Mas-Marza,
́
E.; Mata, J. A.;
*Tel: +81-92-583-7819. Fax: +81-92-583-7819. E-mail:
nagasima@cm.kyushu-u.ac.jp.
Sanau, M.; Peris, E. Eur. J. Inorg. Chem. 2003, 1215−1221.
́
(c) Onopchenko, A.; Sabourin, E. T.; Beach, D. L. J. Org. Chem.
1983, 48, 5101−5105. (d) Takeuchi, R.; Yasue, H. Organometallics
Notes
The authors declare no competing financial interest.
1996, 15, 2098−2102. (e) Poyatos, M.; Maisse-Franco̧ is, A.; Bellemin-
J
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Laponnaz, S.; Gade, L. H. Organometallics 2006, 25, 2634−2641.
(f) Taige, M. A.; Ahrens, S.; Strassner, T. J. Organomet. Chem. 2011,
696, 2918−2927. (g) Bernhammer, J. C.; Huynh, H. V. Organo-
metallics 2014, 33, 172. (h) Caseri, W.; Pregosin, P. S. Organometallics
1988, 7, 1373−1380. (i) Lewis, L. N. J. Am. Chem. Soc. 1990, 112,
5998−6004. (i) Sprengers, J. W.; de Greef, M.; Duin, M. A.; Elsevier,
C. J. Eur. J. Inorg. Chem. 2003, 3811−3819. (j) Sprengers, J. W.; Mars,
M. J.; Duin, M. A.; Cavell, K. J.; Elsevier, C. J. J. Organomet. Chem.
2003, 679, 149−152.
(26) DIRDIF99: Beurskens, P. T.; Admiraal, G.; Beurskens, G.;
Bosman, W. P.; de Gelder, R.; Israel, R.; Smits, J. M. M. The DIRDIF-
99 Program System. Technical Report of the Crystallography Laboratory;
University of Nijmegen: Nijmegen, The Netherlands, 1999.
(27) Cromer, D. T.; Waber, J. T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol. 4.
(28) SHELX97: Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64,
112−122.
(13) Carbonaro, A.; Greco, A.; Dall’Asta, G. Tetrahedron. Lett. 1967,
8, 2037−2040.
(14) (b) Felkin, H.; Lednor, P. W.; Normant, J.-M.; Smith, R. A. J. J.
Organomet. Chem. 1978, 157, C64−C66. (c) Lavallo, V.; Grubbs, R. H.
Science 2009, 326, 559−562. (d) Lavallo, V.; El-Batta, A.; Bertrand, G.;
Grubbs, R. H. Angew. Chem., Int. Ed. 2011, 50, 268−271.
(15) A homoleptic [Fe(mesityl)2]2 complex also behaved as a catalyst
for the hydrosilylation of styrene in the presence of CNAd. In this
case, CNAd was possibly inserted between the Fe-C bond of the
complex, and the resulting imidoyliron species may have been
responsible for the catalysis.16
(16) (a) Klose, A.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.;
Re, N. J. Am. Chem. Soc. 1994, 116, 9123−9135. (b) Klose, A.; Solari,
E.; Ferguson, R.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Organo-
metallics 1993, 12, 2414−2416.
(17) Bassett, J. M.; Barker, G. K.; Green, M.; Howard, J. A. K.; Stone,
F. G. A.; Wolsey, W. C. J. Chem. Soc. Dalton. Trans. 1981, 219−227.
(18) (a) Cunningham, D.; Higgins, T.; McArdle, P.; Corrigan, W.;
Manning, A. R. J. Organomet. Chem. 1994, 479, 103−108. (b) Behrens,
H.; Thiele, G.; Purzer, A.; Wurstl, P.; Moll, M. J. Organomet. Chem.
̈
̈
1978, 160, 255−262.
(19) (a) Sunada, Y.; Kawakami, H.; Imaoka, T.; Motoyama, Y.;
Nagashima, H. Angew. Chem., Int. Ed. 2009, 48, 9511−9514. (b) Zhou,
S.; Junge, K. D.; Addis, D.; Das, S.; Beller, M. Angew. Chem., Int. Ed.
2009, 48, 9507−9510. (a) Tsutsumi, H.; Sunada, Y.; Nagashima, H.
Chem. Commun. 2011, 47, 6581−6583.
(20) (a) Sunada, Y.; Imaoka, T.; Nagashima, H. Organometallics
2013, 32, 2112−2120. (b) Sunada, Y.; Imaoka, T.; Nagashima, H.
Organometallics 2010, 29, 6157−6160.
(21) Use of a bis(imino)pyridine ligand instead of CNAd provided a
partial solution to this drawback, giving the hydrosilylated product 1-
silyl-octane selectively in 55% isolated yield (60% conversion of 1-
octene) during the reaction mediated by (COT)2Fe (3 mol%) and
Me2PDI (3 mol%) under the same reaction conditions. The low
conversion of alkenes in these reactions may be attributed to the
insufficient generation of the active (Me2PDI)Fe species as a result of
the relatively strong coordination of the COT ligand to the iron
center. However, a prolonged reaction time (23 h) at 80 °C gave the
desired product in 88% isolated yield with full conversion of the 1-
octene. Another deficit associated with the disclosed catalysis system
arises from the fact that only dehydrogenative silylation took place in
the reaction of styrene with sterically hindered hydrosilanes such as
MD’M. This could be mitigated by using Me2PDI as the ligand, and
selective hydrosilylation of styrene with MD’M was achieved following
a reaction at 80 °C over 23 h in the presence of (COT)2Fe (3 mol%)
and Me2PDI (3 mol%) to afford the desired product in 92% isolated
yield. The combination of (MPDE)2Fe (3 mol%) with Me2PDI (3 mol
%) also gave satisfactory results; hydrosilylation of 1-octene with
PMDS or styrene with MD’M at 80 °C for 23 h afforded the expected
hydrosilylated product selectively in quantitative yield.
(22) Cho, S.-H.; Ma, B.; Nguyen, S.B. T.; Hupp, J. T.; Albrecht-
Schmitt, T. E. Chem. Commun. 2006, 2563−2565.
(23) Tanabiki, M.; Tsuchiya, K.; Kumanomido, Y.; Matsubara, K.;
Motoyama, Y.; Nagashima, H. Organometallics 2004, 23, 3976−3981.
(24) Schmidt, R.; Welch, M. B.; Knudsen, R. D.; Gottfried, S.; Alt, H.
G. J. Mol. Catal. A: Chem. 2004, 222, 9−15.
(25) SIR2008: Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini,
B.; Cascarano, G. L.; De Caro, L.; Giacovazzo, C.; Polidori, G.; Siliqi,
D.; Spagna, R. J. Appl. Crystallogr. 2007, 40, 609−613.
K
DOI: 10.1021/acs.organomet.5b00201
Organometallics XXXX, XXX, XXX−XXX