A Dialkylsilylene-Pt(0) Complex with a DVTMS Ligand for the Catalytic Hydrosilylation of Functional Olefins

Article abstract of DOI:10.1021/acs.organomet.6b00741

A platinum(0) complex, bearing a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVTMS) and an isolable dialkylsilylene ligand, was successfully synthesized by the reaction between the dialkylsilylene and Karstedt’s catalyst. The downfield-shifted ²⁹Si NMR resonance, the smaller ¹J_Si,Pt value, and the longer Si-Pt distance in this complex relative to the corresponding parameters in related bis(phosphine)-coordinated silylene-platinum complexes suggest weaker π-back-donation from the Pt center to the silylene, which is, however, still significant when compared to related DVTMS-ligated Pt complexes bearing N-heterocyclic carbenes, N-heterocyclic two-coordinate silylenes, or base-stabilized three-coordinate silylenes. The title complex displays excellent catalytic activity in the hydrosilylation of terminal olefins that contain functional groups such as epoxide and amine moieties.

Full text of DOI:10.1021/acs.organomet.6b00741

Article
pubs.acs.org/Organometallics
A Dialkylsilylene-Pt(0) Complex with a DVTMS Ligand for the
Catalytic Hydrosilylation of Functional Olefins
Tomohiro Iimura,† Naohiko Akasaka, and Takeaki Iwamoto*
,‡
‡
,‡
†
Science & Technology, Dow Corning Toray Co., Ltd, 2-2, Chigusa-Kaigan, Ichihara 299-0108, Japan
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
‡
*
S Supporting Information
ABSTRACT: A platinum(0) complex, bearing a 1,3-divinyl-
,1,3,3-tetramethyldisiloxane (DVTMS) and an isolable
1
dialkylsilylene ligand, was successfully synthesized by the
reaction between the dialkylsilylene and Karstedt’s catalyst.
2
9
1
The downfield-shifted Si NMR resonance, the smaller J
Si,Pt
value, and the longer Si−Pt distance in this complex relative to
the corresponding parameters in related bis(phosphine)-
coordinated silylene-platinum complexes suggest weaker π-
back-donation from the Pt center to the silylene, which is,
however, still significant when compared to related DVTMS-ligated Pt complexes bearing N-heterocyclic carbenes, N-
heterocyclic two-coordinate silylenes, or base-stabilized three-coordinate silylenes. The title complex displays excellent catalytic
activity in the hydrosilylation of terminal olefins that contain functional groups such as epoxide and amine moieties.
INTRODUCTION
DVTMS-stabilized Pt complex with a strongly donating three-
■
coordinate silylene ligand (3) that was able to catalyze the
A wide range of stable silylenes has been used to prepare a
variety of silylene-ligated transition-metal complexes, which
have received much attention due to their characteristic
molecular structures and their utility in catalytic trans-
2j,k
hydrosilylation of 1-octene more effectively than 1 or 2.
We have previously reported the synthesis and isolation of
H
H
cyclic dialkylsilylenes R Si (4, R = 1,1,4,4-tetrakis(trimethyl-
2
2
8
1
silyl)butane-1,4-diyl), which are kinetically stabilized by bulky
formations. Among the reported silylene-ligated transition-
H
2
R
substituents and can be used as ligands for transition-metal
9
fragments. As the LUMO of silylene 4 is the vacant 3p orbital
on Si, which is energetically lower than those of other stable N-
heterocyclic silylenes, it can stabilize low-coordinate transition-
metal centers kinetically (steric bulk) and thermodynamically
Chart 1. Examples of DVTMS-Ligated Pt Complexes
(
σ-donation and π-back-donation). During the course of our
studies on silylenes as ligands for transition-metal fragments, we
successfully synthesized a novel dialkylsilylene-Pt complex
containing a DVTMS ligand (5), which was structurally
characterized by multinuclear NMR spectroscopy, single-crystal
X-ray diffraction (XRD) analysis, mass spectrometry, and
elemental analysis. We found that 5 efficiently catalyzes not
only the hydrosilylation of 1-hexene, similarly to 1 and 2, but
also the hydrosilylation of terminal alkenes that contain
functional groups such as amine and epoxy moieties, which
remained intact during the reaction.
metal complexes, the main focus has been placed on
2
,3
platinum, as Pt(0) catalysts are often used in hydrosilylation
4
reactions. However, catalytically active silylene-Pt(0) com-
plexes still remain rare, as the reactivity of their Pt centers is
often reduced by the coordination of strong donor ligands such
as phosphines. Silylene-Pt(0) complexes that are stabilized by
RESULTS AND DISCUSSION
■
Complex 5 was obtained in 69% yield from the reaction of
dialkylsilylene 4 and Karstedt’s catalyst (1) in hexane at room
temperature (Scheme 1). Recrystallization from hexane
afforded analytically pure 5 as air- and moisture-sensitive
yellow crystals that exhibited a decomposition temperature of
1
,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVTMS), which co-
ordinates weakly to the active Pt center and thus maintains the
reactivity of the metal, should represent a promising catalyst
class for hydrosilylation reactions. Among the family of
5
6
DVTMS-coordinated Pt complexes, Karstedt’s catalyst (1)
and the NHC/DVTMS-stabilized Pt complexes (2) by Marko
et al. have been reported as efficient catalysts for such reactions
́
7
Received: September 21, 2016
(Chart 1). Very recently, Baceiredo and Kato et al. reported a
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.6b00741
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 1. Synthesis of Dialkylsilylene/DVTMS-Stabilized Pt
Complex 5
it is stronger than in DVTMS-Pt complexes 2 and 3, owing to
the presence of the low-lying vacant 3p orbital in 4, which is
supported by the corresponding 29Si NMR resonances and
DFT calculations (vide infra).
1
The H NMR spectrum of 5 in solution revealed a facile
rotation around the Si(silylene)−Pt bond, which is reflected in
the appearance of two singlets for the 36 protons of the four
trimethylsilyl groups and the four methylene protons on the
silacyclopentane ring. Conversely, two singlets, due to the
geminal methyl groups on the silicon atoms of DVTMS, were
observed, suggesting that the conformation around the
DVTMS ligand remains unchanged on the NMR time scale.
The 29Si NMR resonance corresponding to the unsaturated
9
5 °C. Complex 5 also exhibited considerable stability in
solution: even after several days at 70 °C in C D ,
decomposition of 5 was not observed, indicating that 4 does
not dissociate from 5 at this temperature.
The XRD analysis of 5 revealed a trigonal planar Pt center
that is coordinated to one silylene ligand and two vinyl moieties
from one DVTMS ligand (Figure 1). The silacyclopentane ring
6
6
8
silicon nuclei in 5 (δ = 478.6 ppm) is upfield-shifted compared
Si
to the corresponding resonance of free silylene 4 (δ = 567.4
Si
8
ppm), but considerably downfield-shifted relative to those of
bis(phosphine)-stabilized two-coordinate silylene-Pt(0) com-
2
b
2c
plexes such as 6a (δ = 358 ppm), 6b (δ = 367 ppm), or 7
Si
Si
2
f
29
195
(
(
δ = 394.6 ppm). The Si− Pt coupling constant for 5
Si
1
1
J
Si,Pt
= 2250 Hz) is also smaller than that for 6b ( J = 2973
Si,Pt
2
c
29
Hz). The downfield-shifted Si NMR resonance and small
JSi,Pt value observed for 5 suggest weaker π-back-donation from
1
Pt to Si in 5 than in 6 and 7, which is consistent with the
correspondingly longer Si−Pt distance in 5 compared to those
in 6 and 7. Interestingly, the upfield shift of δ upon
Si
coordination to Pt observed for 5 [Δδ = δ (Pt complex) −
Si
Si
δ (free silylene) = −88.8 ppm] stands in contrast to the
Si
downfield shift observed for a DVTMS-stabilized Pt complex of
a base-stabilized three-coordinate silylene 3 [Δδ = +63.0 ppm;
Si
3
: δ = −24.4 ppm; 8: −87.4 ppm (Chart 3)]. As the δ of
Si
Si
Figure 1. ORTEP drawing of 5 (atomic displacement parameters set
at 50% probability; hydrogen atoms omitted for clarity).
Chart 3. Related Silylenes and Silylene-Ligated Complex
of silylene 4 adopts an almost orthogonal orientation relative to
the plane defined by the Pt center and the four vinyl carbons of
DVTMS, which includes a dihedral angle of 81.4°. The six-
membered ring formed by the Pt atom and the DVTMS ligand
7
2k
adopts a chairlike structure, similar to those of 2 and 3. The
Si−Pt bond length in 5 [2.2572(10) Å] is longer than the
corresponding Si−Pt distance in related base-free bisphosphine
2b
silylene-Pt(0) complexes 6a [2.210(2) Å] and 7 [2.2117(11)
silylenes is roughly proportional to the reciprocal of the
excitation energy from the n(Si) to 3p(Si) orbitals, the upfield
2
f
11
Å] (Chart 2) but shorter than that in DVTMS-stabilized Pt
shift of δ in 5 suggests that the π-back-donation from Pt to Si
Si
Chart 2. Related Base-Free Silylene-Ligated
Bis(phosphine)platinum(0) Complexes
elevates the energy level of the 3p(Si) orbital, which thus still
contributes to the bonding between Si and Pt atoms. This
result is also consistent with the shorter Si−Pt distance in 5
compared to that in 3, wherein a σ-donation from the three-
coordinate silylene center to Pt contributes predominantly to
the Si−Pt bond. Thus, the intrinsic characteristics of the
silylene remain preserved in 5 upon complexation to the Pt
center.
2k
The weaker π-back-donation in 5 compared to those in 6 and
7 was also supported by theoretical studies at the B3PW91-D3/
B1 level of theory (Basis B1: SDD for Pt, 6-311G(d) for P, Si,
2
k
complex 3 [2.3015(15) Å]. The Pt−C(vinyl) distances in 5
[
[
[
2.170(5)−2.181(5) Å] are significantly longer than those in 2a
10 7b
2.107(4)−2.141(3) Å], 2b [2.130(6)−2.150(8) Å], 2c
O, C, H) (Figure 2). The optimized structure of 5 (5 ) was in
opt
7b
2k
2.115(5)−2.139(5) Å], and 3 [2.122(5)−2.150(5) Å]. In
good agreement with the experimentally observed structure of
5. The HOMO shows a σ-donation from the silylene to the Pt
d-orbital, while the HOMO-4 clearly represents the π-back-
donation from the Pt center. However, the contribution of the
Si 3p orbital to the HOMO-4 is small. Evidence for the weaker
π-back-donation in 5 compared to that in 6 and 7 is provided
by the significantly lower Wiberg bond index (WBI) of the Si−
Pt bond in 5 (0.93) relative to those in 6a (1.04) and 7
opt
contrast, the CC distances in the DVTMS ligand in 5
[
[
1
1.415(6)−1.424(6) Å] are slightly shorter than those in 2a
10
7b
1.422(5)−1.436(5) Å], 2b [1.433(6) Å], 2c [1.420(9)−
7
b
2k
.436(8) Å], and 3 [1.426(7)−1.434(7) Å]. These
structural features of 5 suggest that π-back-donation from Pt
to Si is weaker in 5 than in 6 and 7, probably due to the
absence of phosphine ligands as effective donors. Nevertheless,
opt
opt
B
DOI: 10.1021/acs.organomet.6b00741
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Table 1. Hydrosilylation of Terminal Alkenes with 11 in the
a
Presence of Catalytic Amounts of 5 or Related Catalysts
Figure 2. Selected orbitals of 5opt calculated at the B3PW91-D3/B1
level of theory [Basis B1: SDD for Pt, 6-311G(d) for Si, O, C, H]. (a)
HOMO [d(Pt) + n(Si)], (b) HOMO-4 [d(Pt) + 3p(Si)];
−
3
isoelectronic surface = 0.04 e /Å .
(1.18). This weaker π-back-donation should be attributed to
the absence of phosphine ligands.
To further understand the characteristic electronic properties
of 5, a comparison between the theoretically derived bonding
situation in 5opt with those of the corresponding Pt-DVTMS
complex containing West’s unsaturated cyclic diaminosilylene
[
[
CHN(t-Bu)] Si: 10Si (9 , Chart 3), N-heterocyclic carbene
2 opt
CHNMe] C: 10C (2a , Chart 1), and base-stabilized three-
2
opt
coordinate dialkylsilylene 8 (3 ) should be most helpful. Our
opt
9b
previous theoretical study on model silylenes, a recent
systematic theoretical study on various silylene ligands by
1
2
́
Szilvasi et al., and the following theoretical calculations
suggest that the dialkylsilylene acts as a strong σ-donor relative
to N-heterocyclic carbenes and N-heterocyclic two-coordinate
silylenes, as a weak σ-donor relative to base-stabilized three-
coordinate dialkylsilylenes (8, Chart 3), and as a strong π-
acceptor relative to N-heterocyclic carbenes, N-heterocyclic
two-coordinate silylenes, and base-stabilized three-coordinate
dialkylsilylene. The lone pair orbital of the low coordinate Si
center in dialkylsilylene 4opt (−5.55 eV at the B3PW91-D3/6-
3
11G(d) level of theory; see Figure S33), which should
contribute to the electron donation toward the Pt center, is
slightly higher in energy than those of cyclic diaminosilylene
1
0Siopt (−6.16 eV) and cyclic diaminocarbene 10C (−5.69
opt
a
eV), but lower in energy than that of base-stabilized three-
coordinate silylene 8opt (−4.78 eV). Conversely, the vacant
orbital of the low-coordinate Si center in 4opt (−1.84 eV),
which can participate in π-back-donation, is much lower than
Reaction conditions: SiH/alkene = 1.2, T = 50 °C. The conversion
was determined by NMR analysis using toluene as the internal
b
c
standard. R = Me. Yield after isolation.
those of 10Siopt (−0.45 eV), 10C (+1.30 eV), and 8opt (+1.28
opt
eV). Accordingly, the WBI of the Pt−Si bond in 5 (0.93) is
opt
higher than those of 9 (0.89), 2a (0.65), and 3 (0.77),
xylene, product yield = 81%) was recently reported by
Baceiredo and Kato. Notably, 5 also catalyzes the hydro-
opt
opt
opt
13
2j,k
when calculated at the same level of theory. The natural
population analysis (NPA) charge on the Pt atom of 5opt
silylation of terminal alkenes that contain functional groups,
e.g., 12b, 12c, and 12d (entries 7, 8, 11, 12, and 15). In these
cases, 5 performs substantially better than 2a (entries 10, 14,
[
−0.290] at the B3PW91-D3/B1 level of theory is similar to
those of silylene complexes 3 [−0.141] and 9 [−0.290],
opt
opt
but much more negative compared to that of carbene complex
aopt [0.278], which should be attributed to the more
́
and 17). Marko et al. reported that the hydrosilylation of 12b
2
and 12d with 11 in the presence of NHC/DVTMS-ligated Pt
catalysts 2d (R = 2,6-diisopropylphenyl) or 2c (R = cyclohexyl)
at higher catalyst loadings (13b: 0.1 mol %, T = 60 °C, t = 1 h,
electropositive nature of the Si atom.
The catalytic activity of 5 was assessed for the hydrosilylation
of (Me SiO) SiMe−H (11) and 1-hexene (12a) in the
3
2
14
no solvent, product yield = 78%, and 13d: 30 ppm, T = 72
−4
presence of 30 ppm (w/w) of Pt (∼7 × 10 mol %) at 50
C for 5 h. In this reaction, 12a was completely transformed
7a
°
C, in xylene, product yield = >95%). Although it remains
°
difficult at this stage to ascertain whether 5 represents the
into 13a (entry 1 in Table 1). This reaction provided only the α
regioisomer. When the catalyst loading was reduced to 3 or 0.3
ppm, 5 still exhibited high performance levels (entries 2 and 5)
similar to that of Karstedt’s catalyst 1 (entries 3 and 6) and
catalytically active species, or merely a source of platinum
15
colloids, the catalytic performance of 5 in the reaction of 12b
and 12c (e.g., entries 8 vs 9 and 12 vs 13) is superior to that of
Karstedt’s catalyst 1, which suggests that 5 is an effective
precatalyst or at least that dialkylsilylene 4 works as an effective
ligand for the hydrosilylation.
7
superior to that of 2a (entry 4) under the same conditions.
The catalytic hydrosilylation of 1-octene with 11 using similarly
−
5
low loadings of 3 (3 × 10 mol %, t = 24 h, T = 72 °C in
C
DOI: 10.1021/acs.organomet.6b00741
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
7
2
53.25148. Found: 753.25154; UV−vis (hexane, 298 K) λmax/nm (ε)
31 (26200), 323 (740), 389 (163).
A Representative Hydrosilylation Procedure: Hydrosilyla-
CONCLUSION
■
In conclusion, we successfully synthesized dialkylsilylene-Pt(0)
complex 5 bearing a DVTMS ligand. The spectroscopic data
suggest that π-back-donation from Pt to Si in 5 is weaker than
those in analogous (silylene)bis(phosphine)platinum(0) com-
plexes, but still significant when compared to those in DVTMS-
ligated Pt complexes bearing N-heterocyclic carbenes, N-
heterocyclic silylenes, and base-stabilized three-coordinate
dialkylsilylene. Even though 5 bears a silylene ligand without
significant electronic perturbation from the substituents to the
silicon center, it is an efficient catalyst for the hydrosilylation of
terminal alkenes that contain functional groups.
tion of 1-Hexene (12a) in the Presence of 5. 1,1,1,3,5,5,5-
Heptamethyltrisiloxane (11) (600 μL, 2.21 mmol) and 1-hexene
(12a) (170 μL, 1.64 mmol) were loaded in a Schlenk tube (20 mL).
As an internal standard, toluene (50 μL, 0.47 mmol) was added to the
reaction mixture. A benzene-d solution of catalyst 5 (23.6 mmol/L,
6
−5
3
.6 μL, 2.45 × 10 mmol) was added to the reaction mixture. The
1
mixture was kept at 50 °C for 5 h. The H NMR spectrum of the
reaction mixture (Figure S7) indicated that 3-hexyl-1,1,1,3,5,5,5-
16
heptamethyltrisiloxane (13a) (480 mg, 1.58 mmol, 95%) had
formed. Product 13b was identified by comparison of its H NMR
1
1
4
1
spectral data with those reported in the literature. The H NMR
spectra of the reactions mixture for entries 1−17 in Table 1 are shown
in the Supporting Information.
Large-Scale Hydrosilylation of Allylbis(trimethylsilyl)amine
12c in the Presence of 5 (Entry 11 in Table 1). A Schlenk flask
was loaded with 1,1,1,3,5,5,5-heptamethyltrisiloxane (11) (15.0 g, 67.4
EXPERIMENTAL SECTION
■
General Procedures. All reactions involving air-sensitive com-
pounds were carried out under an argon atmosphere using a high-
vacuum line and standard Schlenk techniques, or a glovebox, as well as
dry and oxygen-free solvents. NMR spectra were recorded on a Bruker
Avance III 500 FT NMR spectrometer. The H and C NMR
chemical shifts were referenced to residual H and C signals of the
−3
mmol) and a benzene-d solution (66.0 mmol/L, 58.8 μL, 1.10 × 10
6
mmol) of 5, before allylbis(trimethylsilyl)amine (12c) (10.4 g, 51.7
mmol) was added gradually. The mixture was kept at 50 °C for 5 h,
before excess 1,1,1,3,5,5,5-heptamethyltrisiloxane was removed under
reduced pressure. 1,1,1,3,5,5,5-Heptamethyl-3-[3-(bis(trimethylsilyl)-
amino)propyl)]trisiloxane (13c) (20.5 g, 48.4 mmol) was obtained in
93.3% yield after distillation (70−72 °C, 1 Pa).
1
13
1
13
1
13
29
solvents: benzene-d ( H: δ 7.16 and C: δ 128.0). The Si NMR
6
195
chemical shifts were referenced relative to Me Si (δ 0.00). The Pt
NMR chemical shifts were referenced relative to Na PtCl (δ 0.00).
4
2
6
1
Sampling of air-sensitive compounds was carried out using a VAC
NEXUS 100027 type glovebox. Mass spectra were recorded on JEOL
JMS-600W and Bruker Daltonics SolariX 9.4T spectrometers. X-ray
diffraction analyses were carried out using a Bruker AXS APEXII CCD
diffractometer. UV−vis spectra were recorded on a JASCO V-660
spectrometer.
13c: A moisture-sensitive colorless liquid; bp. 70−72 °C (1 Pa); H
NMR (500 MHz, C D , 299 K) 0.159 (s, 3H, SiCH ), 0.191 (s, 18H,
6
6
3
Si(CH ) ), 0.211 (s, 18H, Si(CH ) ), 0.461−0.495 (m, 2H,
3
3
3 3
SiCH CH ), 1.565−1.632 (m, 2H, −CH CH CH −), 2.819−2.852
2
2
2
2
2
13
1
(m, 2H, CH −N−); C{ H} NMR (125.8 MHz, C D , 299 K) 0.06
2
6
6
(SiCH ), 2.17 (Si(CH ) ), 2.47 (Si(CH ) ), 15.60 (SiCH CH CH N),
3
3
3
3
3
2
2
2
29
1
Materials. Benzene-d , hexane, and toluene were dried in a tube
29.58 (SiCH CH CH N), 49.61(SiCH CH CH N); Si{ H} NMR
6
2 2 2 2 2 2
covered with a potassium mirror, and then vacuum-distilled prior to
use. Karstedt’s catalyst (1), 1,1,1,3,5,5,5-heptamethyltrisiloxane (11),
and allylbis(trimethylsilyl)amine (12c) were supplied by Dow Corning
Toray. These reagents were dried by molecular sieves (3A) and
degassed under reduced pressure prior to use. Allyl glycidyl ether
(99.4 MHz, C D , 299 K) −21.46 (SiMe), 5.41 (SiMe ), 7.34
6
6
3
(NSiMe ); MS (EI, 70 eV) m/z (%) 423 (0.08), 355 (33.9), 281
3
(13.7), 207 (100), 208 (21.1), 96 (12.5), 73 (19.0); Anal. Calcd for
C H NO Si ; C, 45.33; H, 10.70; N, 3.30%. Found: C, 45.38; H,
16
45
2
5
10.77; N, 3.42%.
(12b), 1-hexene (12a), and vinylcyclohexene oxide (12d) were
Hydrosilylation of Vinylcyclohexene Oxide in the Presence
of 5 (Entry 15 in Table 1). A Schlenk flask was loaded with
1,1,1,3,5,5,5-heptamethyltrisiloxane (11) (0.49 g, 2.20 mmol), a
mixture of cis and trans isomers of vinylcyclohexene oxide (12d;
obtained from common commercial sources and used after drying over
molecular sieves (3A) and degassing under reduced pressure.
8
Dialkylsilylene 4 was prepared according to a published procedure.
NHC carbene catalyst 2 (R = Me, 2a) was prepared according to a
previously published procedure.
0.224 g, 1.80 mmol), and a benzene-d solution of 5 (66.0 mmol/L,
4.5 μL, 2.97 × 10 mmol). The mixture was kept at 50 °C for 1 h,
6
7b
−5
Synthesis of 5. A Schlenk tube (50 mL) equipped with a magnetic
stir bar was loaded with 1 (4% Pt atom, 13.1 g, 2.69 mmol). A hexane
solution (10 mL) of dialkylsilylene 4 (1.0 g, 2.69 mmol) was added to
the mixture at room temperature under stirring. The reaction mixture
was stirred for an hour at room temperature, before the volatiles,
including the solvent and excess 1,3-divinyl-1,1,3,3-tetramethyldisilox-
ane, were partially removed under reduced pressure. The resulting
solid and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane were separated by
filtration, before the solid was washed with cold hexane and dried
under reduced pressure to afford crystalline 5 in 69.0% yield (1.41 g,
before excess 11 was removed under reduced pressure. The resulting
cis and trans isomers of (2-(7-oxa-bicyclo[4.1.0]heptan-3-yl)ethyl)bis-
(trimethylsiloxy)methylsilane (13d) (0.58 g, 1.67 mmol) were isolated
in 92.7% yield by Kugelrohr distillation (74−78 °C, 1 Pa).
1
13d: A colorless liquid; bp. 74−78 °C (1 Pa); H NMR (500 MHz,
C D , 299 K) 0.110 (s, 3H, SiMe), 0.117 (s, 3H, SiMe), 0.162 (s, 18H,
6
6
SiMe ), 0.169 (s, 18H, SiMe ), 0.449−0.512 (m, 4H, SiCH CH ),
3
3
2
2
0.605−0.690 (m, 1H, proton of the cyclohexylepoxy group (CY)),
0.877−0.969 (m, 1H, CY), 0.982−1.036 (ddd, 1H, J = 14.5, 10.5, 2.0
Hz, CY), 1.172−1.262 (m, 6H, overlapping CY and CH CH -Si),
2
2
1
.87 mmol). 5: air- and moisture-sensitive pale yellow crystals; mp. 95
1.334−1.409 (m, 3H, CY), 1.430−1.514 (m, 1H, CY), 1.606−1.665
(m, 1H, CY), 1.702−1.801 (m, 2H, CY), 1.943−1.990 (m, 1H, CY),
1
°
C (decomp.); H NMR (500 MHz, C D , 299 K) −0.018 (s, 6H,
6
6
1
3
1
SiMe(vinyl)), 0.224 (s, 36H, SiMe ), 0.579 (s, 6H, SiMe(vinyl)), 2.119
2.049−2.093 (m, 1H, CY), 2.816−2.889 (m, 4H, O-CH); C{ H}
NMR (125.8 MHz, C D , 299 K) −0.16 (SiMe), −0.13 (SiMe), 2.00
3
(
2
s, 4H, CH CH ), 2.308 (dd, J = 12 Hz, 15 Hz, 2H, CH CH−),
2
2
2
6
6
195
3
2
.505 (d with satellites due to Pt, J = 15 Hz, J = 58 Hz, 2H,
(SiMe), 14.8 (CH Si), 14.9 (CH Si), 24.0 (CH ), 24.5 (CH ), 25.8
H,H
H,Pt
2 2 2 2
195
3
2
CH CH−), 2.939 (d with satellites due to Pt, J = 12 Hz, J
(CH ), 27.2 (CH ), 30.0 (CH ), 30.5 (CH ), 30.8 (CH ), 32.0 (CH ),
2 2 2 2 2 2
2
H,H
H,Pt
1
3
1
29
1
=
56 Hz, 2H, CH CH−); C{ H} NMR (125.8 MHz, C D , 299
32.4 (CH), 35.7 (CH), 51.2 (CH), 52.0 (CH), 52.6 (CH); Si{ H}
NMR (99.4 MHz, C D , 299 K) −20.7 (SiMe), 7.26 (SiMe ), 7.29
2
6
6
K) −1.19 (CH−SiC), 1.79 (CH−SiC), 3.56 (SiCH ), 34.77 (s
3
6
6
3
195
1
with satellites due to Pt, J
= 53 Hz, CH CH ), 45.17 (s with
(SiMe ); MS (EI, 70 eV) m/z (%) 346 (0.002), 307 (0.11), 303
C,Pt
2
2
3
satellites due to 195Pt, JC,Pt = 74 Hz, CH CH−), 49.93
1
2
(3.34), 277 (18.4), 249 (7.13), 221 (100), 191 (16.5), 133 (17.1), 73
(65.6); Anal. Calcd for C H O Si ; C, 51.97; H, 9.86. Found: C,
195
1
(C(SiMe ) ), 50.83 (s with satellites due to Pt, J
= 74 Hz,
3
2
C,Pt
15 34
3
3
2
9
1
CH CH); Si{ H} NMR (99.4 MHz, C D , 299 K) −0.20
52.12; H, 9.89.
2
6
6
(
C(SiMe ) ), 3.61 (CH−SiMe O), 478.6 (s with satellite due to
X-ray Diffraction Analyses of 5 and 2a. Single crystals suitable
for an X-ray diffraction analysis were obtained by recrystallization from
hexane (5) or toluene (2a) at −35 °C under an inert atmosphere. For
data collection, single crystals coated in Apiezon grease were mounted
3
2
2
1
95
1
195
Pt, Pt−Si, J
= 2250 Hz), Pt NMR (106.87 MHz, C D , 299
Si, Pt
6
6
K) −5702; Anal. Calcd for C H OPtSi ; C, 38.21; H, 7.75%. Found:
C, 38.60; H, 7.79%; HRMS (APCI) m/z Calcd for C H OPtSi :
24
58
7
24
58
7
D
DOI: 10.1021/acs.organomet.6b00741
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
on a glass fiber and transferred into the cold nitrogen gas stream of the
diffractometer. X-ray diffraction data were collected on a Bruker AXS
APEX II CCD diffractometer using graphite-monochromated Mo−Kα
radiation. An empirical absorption correction based on the multiple
measurement of equivalent reflections was applied using the program
(2) For reports on silylene-platinum complexes, see: (a) Grumbine,
S. D.; Tilley, T. D.; Arnold, F. P.; Rheingold, A. L. J. Am. Chem. Soc.
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J. D.; Mitchell, G. P.; Nolte, J.-O.; Tilley, T. D. Can. J. Chem. 2003, 81,
17
SADABS, and the structure was solved by direct methods and
1
127−1136. (d) Avent, A. G.; Gehrhus, B.; Hitchcock, P. B.; Lappert,
M. F.; Maciejewski, H. J. Organomet. Chem. 2003, 686, 321−331.
e) Leites, L. A.; Bukalov, S. S.; Garbuzova, I. A.; Feldman, J. D.;
Tilley, T. D. Spectrochim. Acta, Part A 2004, 60, 801−804.
f) Watanabe, C.; Inagawa, Y.; Iwamoto, T.; Kira, M. Dalton Trans.
010, 39, 9414−9420. (g) Agou, T.; Sasamori, T.; Tokitoh, N.
Organometallics 2012, 31, 1150−1154. (h) Breit, N. C.; Szilvasi, T.;
Suzuki, T.; Gallego, D.; Inoue, S. J. Am. Chem. Soc. 2013, 135, 17958−
7968. (i) DeMott, J. C.; Gu, W.; McCulloch, B. J.; Herbert, D. E.;
2
refined by full-matrix least-squares against F using all data (SHELEX-
18
2
014). 1T9he molecular structure was analyzed using the Yadokari-XG
software.
Theoretical Calculations. All theoretical calculations were
(
(
2
2
0
21
performed using the Gaussian 09 or GRRM14 programs.
Geometry optimizations and frequency analyses for 2aopt, 3opt, 4opt
,
́
5opt, 6aopt, 7opt, 8opt, 9opt, 10Siopt, and 10Copt were carried out at the
B3PW91-D3/B1 level of theory (basis B1: SDD for Pt and 6-311G(d)
for Si, P, O, C, and H). Imaginary frequencies were not encountered in
any of the optimized structures. The XYZ file in the Supporting
Information contains the calculated Cartesian coordinates of all
molecules reported in this study. The transition energies and oscillator
strengths of the electron transition of 5opt were calculated using a time-
dependent hybrid DFT method (TD-DFT) at the B3PW91-D3/B1
level of theory (Table S1). A superimposition of the calculated UV−vis
1
Goshert, M. D.; Walensky, J. R.; Zhou, J.; Ozerov, O. V.
Organometallics 2015, 34, 3930−3933. (j) Baceiredo, A.; Kato, T.;
Rodriguez, R.; Prades, A.; Marrot, S.; Saint-Jalmes, L. Patent
WO2015004396(A1), 2015. (k) Troadec, T.; Prades, A.; Rodriguez,
R.; Mirgalet, R.; Baceiredo, A.; Saffon-Merceron, N.; Branchadell, V.;
Kato, T. Inorg. Chem. 2016, 55, 8234−8240.
(
3) For reports on silylene/transition-metal complexes in hydro-
silylations, see: (a) Calimano, E.; Tilley, T. D. J. Am. Chem. Soc. 2009,
31, 11161−11173. (b) Gigler, P.; Bechlars, B.; Herrmann, W. A.;
Kuhn, F. E. J. Am. Chem. Soc. 2011, 133, 1589−1596. (c) Stoelzel, M.;
Prasang, C.; Inoue, S.; Enthaler, S.; Driess, M. Angew. Chem., Int. Ed.
spectrum of 5 with the experimentally obtained spectrum of 5 is
opt
22
shown in Figure S30. The NBO analyses of 2aopt, 3opt, 5opt, 6aopt
,
1
7opt, and 9opt were carried out at the same level. Selected Kohn−Sham
orbitals of 5opt are shown in Figure S31. A comparison of the frontier
̈
Kohn−Sham orbitals and their energy levels for 5 and 7opt is shown
̈
opt
in Figure S32. A comparison of the frontier Kohn−Sham orbitals and
2012, 51, 399−403. (d) Blom, B.; Enthaler, S.; Inoue, S.; Irran, E.;
Driess, M. J. Am. Chem. Soc. 2013, 135, 6703−6713. (e) Xie, H.; Lin,
Z. Organometallics 2014, 33, 892−897. (f) Gallego, D.; Inoue, S.;
Blom, B.; Driess, M. Organometallics 2014, 33, 6885−6897.
their energy levels for 4 , 8 , 10Si , and 10C is shown in Figure
opt opt
opt
opt
S33.
ASSOCIATED CONTENT
Supporting Information
(4) For reviews on hydrosilylations, see: (a) Tamao, K.; Ishida, N.;
Tanaka, T.; Kumada, M. Organometallics 1983, 2, 1694−1696.
■
*
S
(b) Fleming, I.; Henning, R.; Plaut, H. J. Chem. Soc., Chem. Commun.
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00741.
1
9
2
984, 29−31. (c) Hatanaka, Y.; Hiyama, T. J. Org. Chem. 1988, 53,
18−920. (d) Fleming, I.; Barbero, A.; Walter, D. Chem. Rev. 1997, 97,
063−2192. (e) Denmark, S. E.; Regens, C. S. Acc. Chem. Res. 2008,
Experimental and theoretical details (PDF)
Crystallographic data for 5 and 2a (CIF)
Cartesian coordinates for calculated structures (XYZ)
41, 1486−1499. (f) Marciniec, B. Hydrosilylation; Springer: Nether-
lands, 2009. (g) Nakajima, Y.; Shimada, S. RSC Adv. 2015, 5, 20603−
2
0616.
(5) For other examples of Pt catalysts with DVTMS ligands, see:
Chandra, G.; Lo, P. Y.; Hitchcock, P. B.; Lappert, M. F.
Organometallics 1987, 6, 191−192.
AUTHOR INFORMATION
Corresponding Author
E-mail: iwamoto@m.tohoku.ac.jp.
ORCID
Takeaki Iwamoto: 0000-0002-8556-5785
Notes
The authors declare no competing financial interest.
■
(6) Karstedt, B. D. (General Electric Company). Patent
US3775452(A), 1973.
*
(
7) (a) Marko,
P.; Tinant, B.; Declercq, J.-P. Science 2002, 298, 204−206. (b) Marko,
I. E.; Michaud, G.; Berthon, G.; Buisine, O.; Sterin, S.; Tinant, B.;
́ ́
I. E.; Sterin, S.; Buisine, O.; Mignami, G.; Branland,
́
́
Declercq, J.-P. Adv. Synth. Catal. 2004, 346, 1429−1434. (c) Buisine,
O.; Berthon-Gelloz, G.; Brier
P.; Tinant, B.; Declercq, J.-P.; Marko,
́
e, J.-F.; Ster
́
in, S.; Mignani, G.; Branlard,
́
I. E. Chem. Commun. 2005,
ACKNOWLEDGMENTS
3856−3858. (d) Berthon-Gelloz, G.; Buisine, O.; Brier
Michaud, G.; Sterin, S.; Mignani, G.; Tinant, B.; Declercq, J.-P.;
Chapon, D.; Marko, I. E. J. Organomet. Chem. 2005, 690, 6156−6168.
8) Silylene 4 may easily undergo a thermal 1,2-silyl migration to
́
e, J.-F.;
■
́
This work was supported by MEXT KAKENHI grant
JP24109004 (T.I.) (Grant-in-Aid for Scientific Research on
Innovative Areas “Stimuli-responsive Chemical Species”) and
the JSPS KAKENHI grant JPK1513634 (T.I.). The authors
would like to thank Prof. Shintaro Ishida (Tohoku University)
for helpful discussions.
́
(
afford the corresponding silene; see: Kira, M.; Iwamoto, T.; Kabuto,
C.; Ishida, S. J. Am. Chem. Soc. 1999, 121, 9722−9723.
(9) (a) Watanabe, C.; Iwamoto, T.; Kabuto, C.; Kira, M. Chem. Lett.
2
007, 36, 284−285. (b) Watanabe, C.; Iwamoto, T.; Kabuto, C.; Kira,
M. Angew. Chem., Int. Ed. 2008, 47, 5386−5389. (c) Inagawa, Y.;
Ishida, S.; Iwamoto, T. Chem. Lett. 2014, 43, 1665−1667. See also: ref
2f.
(10) As standard deviations of bond lengths for 2a reported in ref 7d
are relatively large, we carried out XRD analysis of a single crystal of 2a
bearing a space group and unit-cell dimensions different from those
reported previously.
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DOI: 10.1021/acs.organomet.6b00741
Organometallics XXXX, XXX, XXX−XXX