A Pt(0) complex with cyclic (alkyl)(amino)silylene and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane ligands: Synthesis, molecular structure, and catalytic hydrosilylation activity

Article abstract of DOI:10.1039/c7dt01113j

A platinum(0) complex bearing a cyclic (alkyl)(amino)silylene and a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVTMS) was synthesized and isolated in the form of colorless crystals. The single-crystal X-ray diffraction analysis of this complex in combination with theoretical calculations indicated that the Pt→Si π-back-donation in this complex is weaker than that in the corresponding cyclic-dialkylsilylene-ligated Pt complex. The performance of this complex in the catalytic hydrosilylation of (Me₃SiO)₂MeSi-H with various terminal alkenes that contain functional groups was comparable to that of the corresponding cyclic dialkylsilylene/DVTMS Pt(0) complex.

Full text of DOI:10.1039/c7dt01113j

Dalton
Transactions
View Article Online
View Journal
PAPER
A Pt(0) complex with cyclic (alkyl)(amino)silylene
and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane
ligands: synthesis, molecular structure, and
catalytic hydrosilylation activity†
Cite this: DOI: 10.1039/c7dt01113j
a,b
b
b
Tomohiro Iimura,
Takeaki Iwamoto
Naohiko Akasaka,
Tomoyuki Kosai
and
b
*
A platinum(0) complex bearing a cyclic (alkyl)(amino)silylene and a 1,3-divinyl-1,1,3,3-tetramethyl-
disiloxane (DVTMS) was synthesized and isolated in the form of colorless crystals. The single-crystal X-ray
diffraction analysis of this complex in combination with theoretical calculations indicated that the Pt→Si
π-back-donation in this complex is weaker than that in the corresponding cyclic-dialkylsilylene-ligated Pt
Received 28th March 2017,
Accepted 2nd May 2017
3 2
complex. The performance of this complex in the catalytic hydrosilylation of (Me SiO) MeSi–H with
DOI: 10.1039/c7dt01113j
various terminal alkenes that contain functional groups was comparable to that of the corresponding
cyclic dialkylsilylene/DVTMS Pt(0) complex.
rsc.li/dalton
Introduction
Isolable silylenes (divalent silicon species) that are stabilized
kinetically and/or electronically constitute an attractive
1
research area in organosilicon chemistry. A variety of stable
silylenes have been synthesized and used as unique reagents
for transformation reactions of organic compounds, and as
key starting materials for functional organosilicon compounds
2
such as multiply-bonded silicon compounds. Isolable silyl-
enes have also attracted much attention as useful ligands for
3
transition-metal complexes and some of these silylene-ligated
Chart 1 Dialkylsilylene 1, as well as related silylenes and DVTMS-
ligated Pt complexes.
transition-metal complexes have found applications as cata-
lysts in useful transformation reactions such as [2 + 2 + 2]
4
5
6
cycloadditions, C–H borylations, as well as Kumada,
6
7
Negishi, and Sonogashira cross-coupling reactions.
in 2 is stronger than those in N-heterocyclic carbene (NHC)/
1
0
Recently, we have synthesized a novel platinum(0) complex DVTMS ligated Pt(0) complexes (3a) or three-coordinate
9
k
(
(
(
2) that bears
a
1,3-divinyl-1,1,3,3-tetramethyldisiloxane silylene-ligated Pt complex 4, due to the presence of a low-
DVTMS) ligand and an isolable cyclic dialkylsilylene (1) lying vacant 3p orbital in 1. Interestingly, 2 showed catalytic
8
Chart 1). Although 2 demonstrated weaker π-back-donation activity in the hydrosilylation of terminal alkenes with
from Pt to Si than the corresponding bis(phosphine)-co- (Me SiO) MeSiH. Although 2 is stable at ambient temperature,
3
2
9
ordinated silylene–platinum complexes, the π-back-donation it exhibits a lower decomposition temperature (95 °C) than 3
3b: 189 °C) and 4 (244–245 °C), which may restrict the range
(
of catalytic applications for 2 (Chart 1). Considering the elec-
tronic structure and thermal stability of 1, the lower decompo-
sition temperature of 2 may be related to the lower thermal
stability of dialkylsilylene 1.
a
b
Science & Technology, Dow Corning Toray, Ichihara, Chiba 299-0108, Japan
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku,
Sendai 980-8578, Japan. E-mail: iwamoto@m.tohoku.ac.jp
Electronic supplementary information (ESI) available: Figures for NMR and
†
Very recently, we have reported the synthesis of the two-
UV-vis spectra, additional ORTEP drawings of 6 and NMR spectra of the reaction
1
i
coordinate cyclic (alkyl)(amino)silylene (CAASi) 5, which is
mixture of hydrosilylation as well as the detailed theoretical calculations. CCDC
reminiscent of the cyclic (alkyl)(amino)carbenes (CAACs) devel-
oped by Bertrand et al. CAASi 5 showed improved thermal
1
535615. For ESI and crystallographic data in CIF or other electronic format see
1
1
DOI: 10.1039/c7dt01113j
This journal is © The Royal Society of Chemistry 2017
Dalton Trans.

View Article Online
Paper
Dalton Transactions
stability compared to dialkylsilylene 1, while high reactivity crystallographically independent molecules with similar struc-
was retained. In contrast to 1, signs of degradation were not tural characteristics were observed; structural parameters of
observed for 5, even after two days at 150 °C. The high thermal one of the two molecules are discussed hereafter. The Pt
stability of 5 prompted us to examine the performance of 5 as center in 6 adopts a trigonal-planar coordination geometry
a ligand for transition-metal complexes. Herein, we report the and is ligated by one silylene and two DVTMS vinyl moieties
synthesis and properties of a Pt complex bearing DVTMS and similar to 2 (Fig. 1). The two vinyl carbon atoms (C30 and
5
(6). The thermal stability of 6 was considerably improved C34), the disiloxane unit (Si–O–Si) in the DVTMS ligand, and
compared to 2 and its catalytic performance in the catalytic the Pt atom form a chair-like six-membered ring, which is
hydrosilylation of terminal alkenes was comparable to that of 2. almost similar to that of 2. The least-squares plane of the five-
membered ring in the silylene ligand is oriented perpendicular
to the plane containing the Pt atom and the four vinyl carbon
Results and discussion
Synthesis of DVTMS/CAASi-Pt(0) complex 6
atoms of DVTMS, which includes a dihedral angle (89.7°) that
is similar to that of 2 (81.4°). The adamantylamino moiety
adopts a syn conformation with respect to the disiloxane unit
and the plane including the Si, Pt, and vinyl carbons. The Pt–C
1
2
The reaction between silylene 5 and Karstedt’s catalyst (7) in
hexane at room temperature afforded 6 in 52% yield as an air-
and moisture-sensitive white crystalline solid (Scheme 1). As
expected from the high thermal stability of 5, the decompo-
sition temperature of 6 (185 °C) is drastically increased relative
to that of 2 (95 °C). Complex 6 also exhibited considerable
stability in solution: even after several days at 70 °C in C D ,
decomposition of 6 was not observed. The molecular structure
of 6 was determined by multinuclear NMR spectroscopy,
elemental analysis, and single-crystal X-ray diffraction analysis.
(
vinyl) distances in 6 [2.139(3)–2.162(3) Å] are shorter than
those in 2 [2.170(5)–2.181(5) Å], while the CvC distances
1.421(5)–1.427(4) Å] in the DVTMS ligand of 6 are longer than
[
those in 2 [1.415(6)–1.422(4) Å]. These structural parameters
indicate that π-back-donation from the Pt center to the vinyl
moieties in the DVTMS ligand of 6 is significantly enhanced
compared to that of 2. The Si–Pt distance in 6 [Pt1–Si1: 2.2504
6
6
(
8) Å] is slightly shorter than that in 2 [2.2572(13) Å], and the
Si–N distance in 6 [Si1–N1 1.690(3) Å] is shorter than that in
1
i
free silylene 5 [1.7143(15) Å]. The shorter Pt–C(vinyl) and Si–
Pt distances in 6 compared to those in 2 might be responsible
Molecular structure of 6
Fig. 1 shows the molecular structure of 6 as determined by
X-ray diffraction (XRD) analysis. In the asymmetric unit, two
for the increased thermal stability.
1
The H NMR spectrum of 6 in C
6
D
6
exhibits two conformers
in an ∼3 : 1 ratio, while the XRD analysis exhibited only one
isomer bearing the adamantylamino moiety in a syn (6a) con-
formation with respect to the six-membered ring that contains
1
the Pt-DVTMS moiety. The presence of four singlet H NMR
signals for the geminal methyl groups on the silicon atoms in
the DVTMS group is consistent with the presence of two con-
1
formers in solution. The H NMR signals of the two confor-
Scheme 1 Synthesis of 6.
mers did not change significantly in toluene-d between −70
8
and 70 °C. Theoretical calculations at the B3PW91-D3/B level
of theory [Basis B: SDD for Pt; 6-311G(d) for Si, O, N, C, H]
suggested that the two conformers should bear the adamantyl-
amino groups in the syn (6aopt) and anti conformations (6bopt),
whereby the free energy of 6a is by 4.3 kJ mol− lower than
1
opt
1
3
that of 6bopt
,
which is consistent with the observation of
both conformers in solution.
2
9
The observed Si NMR resonances of the unsaturated
silicon nuclei (δSi) in 6 (6a: 281.3 ppm, 6b: 285.7 ppm) are
downfield shifted compared to the corresponding resonance
1
i
of free silylene 5 (274 ppm), which stands in sharp contrast
8
b
to the observed upfield shift of the δSi of 2 (478.6 ppm) rela-
8
a
tive to that of free silylene 1 (564.7 ppm). This result suggests
that the bonding between the Pt and Si atoms consists pre-
dominantly of the σ-donation from Si(silylene) to Pt, instead of
a π-back-donation. This conclusion is based on the fact that the
isotropic chemical shift of divalent silicon nuclei in silylenes
is roughly proportional to the reciprocal of the energy differ-
Fig. 1 ORTEP drawing of 6 (atomic displacement parameters set at
50% probability; hydrogen atoms are omitted for clarity). One of the two
crystallographically independent molecules is shown. The adamantyl
group on N1 is disordered over two positions (0.866(5) : 0.134(5)), and
only the structure with the major site occupancy factor is shown.
1
4
ence between the n(Si) and the vacant 3p(Si) orbitals, and
that a similar downfield shift of δSi was reported for Kato’s
Dalton Trans.
This journal is © The Royal Society of Chemistry 2017

View Article Online
Dalton Transactions
Paper
9
k
195
silylene complex 4 upon coordination. In the
Pt NMR Hydrosilylation of terminal alkenes in the presence of 6
spectrum, two signals were observed for the two different con-
formers 6a (5846 ppm) and 6b (5838 ppm). The JPtSi coupling
constants for 6a (2335 Hz) and 6b (2335 Hz) are slightly larger
than that of 2 (2250 Hz), which is consistent with the shorter
Pt–Si bond length in 6 [2.2504(8) Å] compared to that of
complex 2 [2.2572(13) Å].
The structural features of 6 were also examined theoreti-
cally by DFT calculations. The optimized structure of 6
8b
Similar to 2, 6 catalyzes the hydrosilylation of various term-
inal alkenes with (Me SiO) MeSi–H (8). In the presence of 6
30 ppm (w/w) of Pt (∼7 × 10 mol%)] at 50 °C for 5 h,
3
2
−4
[
1
-hexene (9a) was completely transformed into 10a (entry 1 in
Table 1). Even when the amount of 6 was reduced to 3 ppm,
0a was obtained in high yield within one hour (entry 2).
8
b
1
Notably, 6 also catalyzes the hydrosilylation of terminal
(
6aopt), calculated at the B3PW91-D3/B level of theory, was in
good agreement with the structural parameters of 6 deter-
mined by the single-crystal XRD analysis (for details, see
the ESI†). The HOMO and HOMO−5 represent the Si→Pt
σ-donation and the weak Pt→Si π-back-donation, respectively
a
Table 1 Hydrosilylation of terminal alkenes with 8 in the presence of 6
or related catalysts
(
Fig. 2). Our previous DFT calculations demonstrated that
both silylenes 1opt and 5opt exhibit a lone pair orbital on the
silicon atom [n(Si)] as the HOMO and an empty 3p orbital on
the silicon atom [3p(Si)] as the LUMO, which can contribute
to the Si→Pt σ-donation and the Pt→Si π-back-donation,
respectively. While the energy level of the HOMO in 5opt
(
−5.56 eV) is virtually identical to that of 1opt (−5.55 eV), the
LUMO of 5opt (−1.13 eV) lies substantially higher than that of
1opt (−1.84 eV) due to the electron donation from the neigh-
1
i
bouring amino group, which suggests a weaker Pt→Si
Cat.
(ppm)
Product
yield
π-back-donation in 6aopt compared to that in 2opt. This Entry
Cat.
Time
5 h
1 h
1 h
1 h
1 h
Alkene
1
5
notion is supported by smaller Wiberg bond indices (WBI)
for the Pt–Si bond in 6aopt (0.58) compared to that in 2opt
0.66). Nevertheless, the Si–Pt bond in 6aopt [2.255 Å] is
slightly shorter than that in 2opt [2.257 Å]. The increased
s-character of the Si orbital in the Pt–Si bond, owing to the
substitution of the more electronegative nitrogen atom at the
Si centre, may be responsible for the shorter Pt–Si bond: a
1
6
6
7
2
30
>95% (10a)
2
3
4
5
3
3
3
3
9a
9a
9a
9a
91% (10a)
85% (10a)
87% (10a)
6% (10a)
b
b
b
(
3a
6
6
30
5 h
>95% (10b)
0
.74
7
8
9
6
7
2
3a
3
3
3
3
1 h
1 h
1 h
1 h
9b
9b
9b
9b
>95% (10b)
91% (10b)
>95% (10b)
0% (10b)
natural bond orbital (NBO) analysis suggested a sp
ization for the Si orbital in the Pt–Si bond in 6aopt, while that
hybrid-
b
b
1
.14
b
in 2opt is sp
(for details, see the ESI†). The reduced Pt→Si 10
π-back-donation can thus induce an increased electron
density on the Pt center in 6aopt, which would enhance the
π-back-donation from Pt to the vinyl moiety in the DVTMS
ligand. This hypothesis is consistent with the shorter Pt–C
1
1
6
30
5 h
>95% (10c)
1
1
1
2
3
4
6
7
2
3a
3
3
3
3
1 h
1 h
1 h
1 h
9c
9c
9c
9c
65% (10c)
58% (10c)
80% (10c)
0% (10c)
b
b
b
(
vinyl) distances observed in 6 and the larger WBI values for 15
the Pt⋯CH2 [0.37 (average)] and Pt⋯CH [0.29 (average)]
bonds of 6aopt compared to the corresponding values of 2opt
16
6
3
1 h
>95% (10d)
[
0.35 and 0.26].
b
b
b
17
18
19
7
2
3a
3
3
3
1 h
1 h
1 h
9d
9d
9d
>95% (10d)
>95% (10d)
18% (10d)
20
6
30
1 h
67% (10e)
2
2
1
2
7
2
30
30
1 h
1 h
9e
9e
65% (10e)
66% (10e)
23
6
3
1 h
66% (10f)
2
2
4
5
7
2
3
3
1 h
1 h
9f
9f
49% (10f)
64% (10f)
a
Fig. 2 HOMO (left) and HOMO−5 (right) of 6opt, calculated at the
Reaction conditions: SiH/alkene = 1.2, T = 50 °C, no solvent. The con-
B3PW91-D3/B level of theory [B: SDD for Pt; 6-311G(d) for H, C, N, O, version was determined by NMR analysis using toluene as the internal
b
Si]. Hydrogen atoms are omitted for clarity.
standard. Ref. 8b.
This journal is © The Royal Society of Chemistry 2017
Dalton Trans.

View Article Online
Paper
Dalton Transactions
alkenes that contain functional groups such as 9b, 9c, 9d, 9e, and allylbis(trimethylsilyl)amine (9c) were supplied by Dow
and 9f (entries 6, 7, 11, 12, 16, 20, and 23). The catalytic per- Corning Toray. These reagents were dried with molecular
formance of 6 in this hydrosilylation is comparable to that of sieves (3A) and degassed under reduced pressure prior to use.
Karstedt’s catalyst (7) or dialkylsilylene-ligated Pt catalyst 2 1-Hexene (9a), allyl glycidyl ether (9b), vinylcyclohexene oxide
8
b
and better than that of 3a. Although the actual catalytically (9d), allyl acetate (9e), and allyl ethyl ether (9f) were obtained
active species for these reactions remains unclear at this stage, from common commercial sources, and used after drying over
the catalytic performance of 6 in the reaction of 9f (entry 23) is molecular sieves (3A) and degassing under reduced pressure.
8
b
1i
slightly superior to that of 7 (entry 24), which suggests that 6 is Complex 2 and silylene 5 were prepared according to pub-
an effective precatalyst, or that cyclic (alkyl)(amino)silylene 5 lished procedures.
works as an effective ligand for the hydrosilylation. The stron-
ger π-back-donation from Pt to Si in 6 and 2 compared to that
of other N-heterocyclic carbenes and silylenes such as 3 and 4
might reduce the π-back-donation from Pt to the vinyl moieties
Synthesis of 6
in the DVTMS ligand, which would result in facile elimination A Schlenk tube (50 mL) equipped with a magnetic stir bar was
of the vinyl moiety from Pt to open a reactive coordination site charged with Karstedt’s catalyst (20% Pt, 1.62 g, 0.34 mmol
on the Pt center.
of 7). A hexane solution (5 mL) of 5 (0.25 g, 0.68 mmol) was
added to the tube at room temperature under stirring. The
reaction mixture was stirred for one hour at room temperature,
before all volatiles were removed under reduced pressure.
Recrystallization of the resulting solid from hexane at −30 °C
Conclusions
We synthesized the novel Pt(0) complex 6, which bears a provided a colorless solid, which was washed with cold
DVTMS and a cyclic (alkyl)(amino)silylene ligand (5). The hexane. Removal of the volatiles from the solid under reduced
π-back-donation from Pt to Si in 6 is weaker than that in the pressure afforded the title compound as air-sensitive colorless
corresponding (dialkylsilylene)Pt(0) complexes with a DVTMS crystals (0.26 g, 0.35 mmol) in 52% yield.
ligand (2) on account of the higher-lying empty 3p orbital in 5
due to the electron donation of the amino group to the silylene less crystals; mp. 185 °C (decomp.); δH (500 MHz; C D ;
6a and 6b (∼3 : 1 mixture): air and moisture sensitive color-
6
6
center. Similar to analogous (dialkylsilylene)Pt(0) complexes Me Si; 298 K) −0.13 (6H, s, SiMe , 6a), −0.01 (6H, s, SiMe ,
4
2
2
with a DVTMS ligand, 6 catalyzes the hydrosilylation of various 6b), 0.17 (18H, s, SiMe , 6a), 0.22 (18H, s, SiMe , 6b), 0.62
3
3
terminal alkenes that bear functional groups. The present (6H, s, SiMe , 6a), 0.63 (6H, s, SiMe , 6b), 1.42–1.51 (6H, m,
2
2
study demonstrated that silylene 5 should be a useful ligand adamantyl (Ad), 6a and 6b), 1.78–1.94 (9H, m, Ad, 6a and 6b),
3
with both σ-donor and π-acceptor properties, as well as high 2.08 (2H, t, J = 10.0 Hz, CH C(SiMe ) , 6a and 6b), 2.17–2.27
thermal stability.
2
3 2
3
(2H, m, CH vCH–, 6a and 6b), 2.47 (2H, d, J = 15.0 Hz,
2
CHvCH
2
, 6a), 2.54 (2H, d, J = 15.0 Hz, CHvCH
2
, 6b), 2.93
3
3
(
2H, d, J = 10.0 Hz, CHvCH
2
, 6a), 2.99 (2H, d, J = 10.0 Hz,
3
Experimental
General procedures
CHvCH
2
, 6b), 3.17 (2H, t, J = 5.0 Hz, N–CH
2
–CH
Si, 298 K) −2.05 (SiMe
, 6a), 1.65 (SiMe , 6b), 1.78
2
, 6a and
1
6
b); δ
C
{ H} (126 MHz; C
6
D
6
; Me
4
2
, 6a),
−
1.26 (SiMe , 6b), 1.53 (SiMe
2
3
3
All reactions involving air-sensitive compounds were carried
out under an argon atmosphere using a high-vacuum line and
standard Schlenk techniques, or a glove box, as well as dry and
oxygen-free solvents. Multinuclear NMR spectra were recorded
(
SiMe , 6a), 1.97 (SiMe , 6b), 29.4 (N–CH CH –C, 6a), 29.5 (N–
2
2
2
2
CH
(
6
6
2
CH
2
–C, 6b), 30.3 (CH in Ad, 6a), 30.5 (CH in Ad, 6b), 33.8
in Ad, 6a), 36.8 (CH in Ad,
C in Ad, 6a and 6b), 36.7 (CH
2
2
b), 39.2 (CHvCH , 6a), 39.5 (CHvCH , 6b), 44.1 (CHvCH ,
2
2
2
1
on a Bruker Avance III 500 FT NMR spectrometer. H and
a), 44.4 (CHvCH
2
, 6b), 45.3 (CH
2
in Ad, 6b), 45.4 (CH
2
in
1
1
2
3
3
9
1
C NMR chemical shifts are referenced to residual H and
Ad, 6a), 47.8 (CH
6b], 55.2 [C(SiMe ) , 6a]; δ { H} (99 MHz, C D , Me Si, 298 K)
2
–N, 6a), 48.0 (CH
2
–N, 6b), 55.1 [C(SiMe
3
)
2
,
1
13
C signals of the solvents: C D ( H: δ 7.16 and C: δ 128.0).
1
6
6
3
2
Si
6
6
4
Si NMR chemical shifts are referenced relative to Me
4
Si
Pt NMR chemical shifts are referenced relative to
Na PtCl (δ 0.00). Sampling of air-sensitive compounds was
1
.38 (SiMe
due to coupling with
(vCH–SiMe , 6b), 281.3 [Pt–Si, s with satellites due to coup-
3
, 6a and 6b), 2.45 [vCH–SiMe
2
, s with satellites
1
95
(
δ 0.00).
195
2
29
195
Pt, J( Si– Pt) = 37 Hz, 6a], 2.78
2
6
2
carried out using a VAC NEXUS 100027 glove box. Mass spectra
were recorded on JEOL JMS-Q1050 and Bruker Daltonics
SolariX 9.4T spectrometers. UV-vis spectra were recorded on a
JASCO V-660 spectrometer.
195
1
29
195
ling with
satellites due to coupling with
δPt (106.87 MHz; C D ; Na PtCl ; 299 K) −5846 (sept with sat-
Pt, J( Si– Pt) = 2335 Hz], 285.7 [Pt–Si, s with
195
1
29
195
Pt, J( Si– Pt) = 2335 Hz],
6
6
2
6
29
2
ellites due to coupling with Si, J(Pt–H) = 5 × 10 Hz,
1
195
29
J( Pt–Si ) = 2335 Hz, 6a), −5839 (sept with satellites due
Materials
29
2
1
195
29
to coupling with Si, J(Pt–H) = 5 × 10 Hz, J( Pt–Si ) =
, hexane, and toluene were dried in a tube covered 2335 Hz, 6b); Found: C, 43.80; H, 7.58; N, 1.82%. Calcd for
with a potassium mirror, and vacuum-distilled prior to use. 55OPtSi : C, 43.52; H, 7.44; N, 1.88%; λmax (hexane, 298 K)
Karstedt’s catalyst (7), 1,1,1,3,5,5,5-heptamethyltrisiloxane (8), nm 228 (ε/dm mol cm 32 100), 329 (1077).
Benzene-d
6
C
27
H
5
−
1
3
−1
−1
Dalton Trans.
This journal is © The Royal Society of Chemistry 2017

View Article Online
Dalton Transactions
Paper
A representative catalytic hydrosilylation procedure: reaction of Me
4
Si, 298 K) 7.3 [(Me
(EI, 70 eV) m/z 293 (12.1%), 265 (11.5), 251 (9.9), 221 (90.0),
07 (100), 191 (24.5), 73 (43.9); Found: C, 46.65; H, 10.50%.
Calcd for C12 Si : C, 46.70; H, 10.45%.
3
SiO)
2
MeSi], −20.8 [(Me
3 2
SiO) MeSi], MS
9
a with 8 in the presence of 6
2
A Schlenk tube (20 mL) was charged with 1,1,1,3,5,5,5-hepta-
H
32
O
3
3
methyltrisiloxane (8; 0.50 g, 2.3 mmol) and 1-hexene
(
(
9a; 0.13 g, 1.81 mmol). As an internal standard, toluene
0.044 g, 0.48 mmol) was added to the reaction mixture. Single-crystal X-ray diffraction analysis of 6
−1
A benzene-d solution of catalyst 6 (26.0 mmol L , 3.5 μL,
9
mixture was kept at 50 °C for 5 h. The H NMR spectrum of
the reaction mixture (Fig. S10†) indicated that 3-hexyl-
6
Single crystals of 6, suitable for X-ray diffraction analysis, were
obtained by recrystallization from hexane at −35 °C. Under an
atmosphere of nitrogen, the crystals were coated with Apiezon
grease, mounted on a glass fiber, and transferred to the cold
nitrogen gas stream of the diffractometer. X-ray diffraction
data were collected on a Bruker AXS APEX II CCD diffracto-
meter using graphite monochromated Mo-Kα radiation. An
empirical absorption correction based on the multiple
measurement of equivalent reflections was applied using the
.1 × 10− mmol) was added to the reaction mixture. The
5
1
1
,1,1,3,5,5,5-heptamethyltrisiloxane (10a; 504 mg, 1.72 mmol,
5%) had formed, which was identified by comparison of its
H NMR spectral data with those reported in the literature.
9
1
16
1
The H NMR spectra of the reaction mixture for entry 1 in
Table 1 are shown in the ESI.†
1
7
program SADABS, and the structure was solved by direct
Large-scale hydrosilylation of 9e
2
methods and refined by full-matrix least-squares against F
1
8
A Schlenk tube (20 mL) was charged with 1,1,1,3,5,5,5-hepta- using all data (SHELEX-2014). For the analysis of the mole-
methyltrisiloxane (8; 0.99 g, 4.4 mmol) and allyl acetate (9e; cular structure, the Yadokari-XG software was used.
1
9
0
.37 g, 3.7 mmol). As an internal standard, toluene (0.053 g,
27 55 1 1 1 5
Crystal data. C H N O Pt Si [CCDC 1535615], M =
0
.58 mmol) was added to the reaction mixture. A benzene-d
745.26, triclinic, a = 13.0764(4), b = 15.2793(5), c = 17.7828(5)
6
−
1
−4
3
solution of 6 (3.2 mmol L , 62 μL, 2.0 × 10 mmol) was Å, V = 3369.18 Å , T = 100 K, space group P ˉ1 (no. 2), Z = 2,
added to the reaction mixture. The mixture was aged at 50 °C 63 682 reflections measured, 12 543 unique (Rint = 0.0285),
1
2
for 1 h. The H NMR spectrum of the reaction mixture indi- which were used in all calculations. The final wR(F ) was
cated the presence of 3-(1,1,1,3,5,5,5-heptamethyltrisiloxan- 0.0482 (all data).
3
-yl)propyl acetate (10e; 798 mg, 2.47 mmol, 67%) before
1
,1,1,3,5,5,5-heptamethyltrisiloxane was removed under
Theoretical calculations
reduced pressure. Product 10e was obtained in 55% after distil-
lation (114 °C, 9 hPa).
All theoretical calculations were performed using the Gaussian
0e: δH (500 MHz, C D , Me Si, 298 K) −0.08 (3H, s, SiMe), 09 and GRRM14 programs. Geometry optimizations and
–Si), 1.66–1.73 frequency analyses for 6aopt and 6bopt were carried out at the
3 2
.15 (18H, s, OSiMe ), 0.47–0.52 (2H, m, CH
2
0
21
1
6
6
4
0
(
2H, m, CH –CH –CH ), 1.69 (3H, s, CO–CH ), 4.02 (2H, t, J = B3PW91-D3/B level [Basis B: SDD for Pt; 6-311G(d) for H, C, N,
2 2 2 3
1
7
(
.0 Hz, CH –O); δ { H} (126 MHz, C D , Me Si, 298 K) −0.3 O, Si]. Imaginary frequencies were not found in any of the opti-
2
C
6
6
4
SiMe
2
3 2 3 2
), 1.9 (SiMe ), 13.8 (CH ), 20.5 (C(O)–CH ), 22.9 (CH
), mized structures. Atomic coordinates for 6aopt and 6bopt are
1
6
2
7
6.6 (CH O), 170.0 (CvO); δ { H} (99 MHz, C D , Me Si, summarized in the ESI.† The transition energies and oscillator
2 Si 6 6 4
98 K) 7.6 [(Me SiO) MeSi], −21.6 [(Me SiO) MeSi], MS (EI, strengths of the electron transition of 6aopt were calculated
3
2
3
2
0 eV) m/z 307 (9.5%), 265 (67.1), 221 (59.5), 207 (100), 191 using a time-dependent hybrid DFT method (TD DFT) at the
(
33.1), 73 (48.3); Found: C, 44.62; H, 9.47%. Calcd for B3PW91-D3/B level of theory. The NBO analysis was carried
1
5
C
12
H
30
O
4
Si
3
: C, 44.68; H, 9.37%.
out using the NBO6.0 program. UV-vis spectra of 6aopt super-
imposed with the experimental spectrum of 6 are shown in
Fig. S31.† Selected Kohn–Sham orbitals and important orbital
interactions of 6aopt are shown in Fig. S32 and S33,†
respectively.
Large-scale hydrosilylation of 9f
A Schlenk tube (20 mL) was charged with 1,1,1,3,5,5,5-hepta-
methyltrisiloxane (8; 7.1 g, 32 mmol) and allyl ethyl ether
solution of 6 (3.2 mmol L−
1
,
(
2.3 g, 26.6 mmol). A benzene-d
6
1
50 μL, 4.8 × 10− mmol) was added to the reaction mixture.
4
The mixture was aged at 50 °C for 1 h. Excess 8 was removed
Acknowledgements
under
reduced
pressure,
before
3-(3-ethoxypropyl)-
1
,1,1,3,5,5,5-heptamethyltrisiloxane (10f) was obtained in 52% This work was supported by MEXT KAKENHI grant
after distillation (86–87 °C, 6.7 hPa). JP24109004 (T. I.) (Grant-in-Aid for Scientific Research on
0f: δ (500 MHz, C , Me Si, 298 K) 0.14 (3H, s, SiMe), Innovative Areas “Stimuli-responsive Chemical Species”), JSPS
.17 (18H, s, OSiMe ), 0.65–0.69 (2H, m, CH –Si), 1.14 (3H, KAKENHI grant JPK1513634 (T. I.), and in part by the
t, J = 7.0 Hz, CH –CH ), 1.77–1.81 (2H, m, CH –CH –CH ), Cooperative Research Program “Network Joint Research Center
1
H
6
D
6
4
0
3
2
2
3
2
2
2
1
3
.32–3.35 (4H, m, CH
Me Si, 298 K) −0.1 (SiMe), 2.0 (SiMe
4.1 (CH ), 66.1 (CH ), 73.4 (CH ); δ { H} (99 MHz, C D , discussions.
2
–O–CH
2
); δ
C
{ H} (126 MHz, C
), 14.2 (CH ), 15.5 (CH
6
D
6
,
for Materials and Devices.” The authors would like to thank
4
3
2
3
), Prof. Shintaro Ishida (Tohoku University) for helpful
1
2
2
2
2
Si
6 6
This journal is © The Royal Society of Chemistry 2017
Dalton Trans.

View Article Online
Paper
Dalton Transactions
4
W. Wang, S. Inoue, S. Enthaler and M. Driess, Angew.
Chem., Int. Ed., 2012, 51, 6167–6171.
Notes and references
1
For
comprehensive
reviews
on
silylenes,
see:
5 A. Brück, D. Gallego, W. Wang, E. Irran, M. Driess and
J. F. Hartwig, Angew. Chem., Int. Ed., 2012, 51, 11478–11482.
6 C. I. Someya, M. Haberberger, W. Wang, S. Enthaler and
S. Inoue, Chem. Lett., 2013, 42, 286–288.
(
a) P. P. Gaspar and R. West, in The Chemistry of Organic
Silicon Compounds, ed. Z. Rappoport and Y. Apeloig, John
Wiley & Sons, Ltd, Chichester, UK, 1998, Volume 2, pp.
2
463–2568; (b) Y. Mizuhata, T. Sasamori and N. Tokitoh,
7 D. Gallego, A. Brück, E. Irran, F. Meier, M. Kaupp,
M. Driess and J. F. Hartwig, J. Am. Chem. Soc., 2013, 135,
15617–15626.
8 (a) M. Kira, T. Iwamoto, C. Kabuto and S. Ishida, J. Am.
Chem. Soc., 1999, 121, 9722–9723; (b) T. Iimura, N. Akasaka
and T. Iwamoto, Organometallics, 2016, 35, 4071–4076.
9 (a) S. D. Grumbine and T. D. Tilley, J. Am. Chem. Soc., 1993,
115, 7884–7885; (b) C. Watanabe, Y. Inagawa, T. Iwamoto
and M. Kira, Dalton Trans., 2010, 39, 9414–9420. For other
Chem. Rev., 2009, 109, 3479–3511; (c) M. Asay, C. Jones
and M. Driess, Chem. Rev., 2011, 111, 354–396; (d) B. Blom
and M. Driess, Struct. Bonding, 2014, 156, 85–123. For very
recent studies on isolable silylenes, see: (e) A. Schaefer,
M. Reissmann, A. Schaefer, M. Schmidtmann and
T. Müller, Chem.
f) I. Alvarado-Beltran, A. Baceiredo, N. Saffon-Merceron,
V. Branchadell and T. Kato, Angew. Chem., Int. Ed., 2016,
5, 16141–16144; (g) M. I. Arz, M. Strassmann, D. Geiss,
G. Schnakenburg and A. C. Filippou, J. Am. Chem. Soc.,
016, 138, 4589–4600; (h) T. J. Hadlington, J. A. B. Abdalla,
R. Tirfoin, S. Aldridge and C. Jones, Chem. Commun.,
016, 52, 1717–1720; (i) T. Kosai, S. Ishida and
T. Iwamoto, Angew. Chem., Int. Ed., 2016, 55, 15554–15558;
j) Z. Dong, Z. Li, X. Liu, C. Yan, N. Wei, M. Kira and
– Eur. J., 2014, 20, 9381–9386;
(
5
studies on
related
platinum(0)
complexes, see:
(c) J. D. Feldman, G. P. Mitchell, J. Nolte and T. D. Tilley,
J. Am. Chem. Soc., 1998, 120, 11184–11185; (d) J. D. Feldman,
G. P. Mitchell, J. O. Nolte and T. D. Tilley, Can. J. Chem.,
2003, 81, 1127–1136; (e) A. G. Avent, B. Gehrhus,
P. B. Hitchcock, M. F. Lappert and H. Maciejewski,
J. Organomet. Chem., 2003, 686, 321–331; (f) L. A. Leites,
S. S. Bukalov, I. A. Garbuzova, J. D. Feldman and T. D. Tilley,
Spectrochim. Acta, Part A, 2004, 60, 801–804; (g) T. Agou,
T. Sasamori and N. Tokitoh, Organometallics, 2012, 31,
1150–1154; (h) N. C. Breit, T. Szilvaśi, T. Suzuki, D. Gallego
and S. Inoue, J. Am. Chem. Soc., 2013, 135, 17958–17968;
(i) J. C. DeMott, W. Gu, B. J. Mcculloch, D. E. Herbert,
M. D. Goshert, J. R. Walensky, J. Zhou and O. V. Ozerov,
Organometallics, 2015, 34, 3930–3933; (j) A. Baceiredo,
T. Kato, R. Rodriguez, A. Prades, S. Marrot and L. Saint-
Jalmes, Patent WO 2015004396(A1), 2015; (k) T. Troadec,
A. Prades, R. Rodriguez, R. Mirgalet, A. Baceiredo, N. Saffon-
Merceron, V. Branchadell and T. Kato, Inorg. Chem., 2016,
55, 8234–8240.
2
2
(
T. Mueller, Chem.
asia.201700143.
For recent comprehensive reviews on species that contain
multiply bonded silicon, see: (a) V. Y. Lee and A. Sekiguchi,
Organometallic Compounds of Low-Coordinate Si, Ge, Sn, and
Pb: From Phantom Species to Stable Compounds, John Wiley
– Asian J., 2017, DOI: 10.1002/
2
&
Sons Ltd, Chichester, U.K., 2010; (b) R. C. Fischer and
P. P. Power, Chem. Rev., 2010, 110, 3877–3923;
c) T. Iwamoto and S. Ishida, in Structure and Bonding,
(
Springer International Publishing, Switzerland, 2014,
vol. 156, pp. 125–202.
For recent reviews on the applications of silylene-ligated
3
metal
complexes
in
catalytic
reactions,
see:
(
a) R. Waterman, P. G. Hayes and T. D. Tilley, Acc. Chem. 10 S. Dierick, E. Vercruysse, G. Berthon-Gelloz and
Res., 2007, 40, 712–719; (b) B. Blom, M. Stoezel and
M. Driess, Chem. – Eur. J., 2013, 19, 40–62; (c) B. Blom,
I. E. Markó, Chem. – Eur. J., 2015, 21, 17073–17078 and
references cited therein.
D. Gallego and M. Driess, Inorg. Chem. Front., 2014, 1, 134– 11 V. Lavallo, Y. Canac, C. Präsang, B. Donnadieu and
48; (d) S. Inoue, in Discovering the Future of Molecular G. Bertrand, Angew. Chem., Int. Ed., 2005, 44, 5705–5709.
Sciences, ed. B. Pignataro, Wiley-VCH Verlag GmbH & Co. 12 B. D. Karstedt, General Electric Company, US 3775452(A),
KGaA, 2014, pp. 243–273; (e) L. Álvarez-Rodriguez, 1973.
1
J. A. Cabeza, J. P. García-Álvarez and D. Polo, Coord. Chem. 13 At the same of level of theory, an activation free energy of
78.9 kJ mol− (298.15 (K)) from 6aopt was predicted for the
isomerization between 6aopt and 6bopt via a rotation
around the Si–Pt bond.
1
Rev., 2015, 300, 1–28. For very recent studies on the tran-
sition-metal complexes of silylenes, see: (f) B. Blom,
M. Pohl, G. Tan, D. Gallego and M. Driess, Organometallics,
2
014, 33, 5272–5282; (g) A. C. Filippou, B. Baars, 14 T. Müller, J. Organomet. Chem., 2003, 686, 251–256.
O. Chernov, Y. N. Lebedev and G. Schnakenburg, Angew. 15 Glendening; J. K. Badenhoop, A. E. Reed, J. E. Carpenter,
Chem., Int. Ed., 2014, 53, 565–570; (h) M. C. Lipke,
F. Neumeyer and T. D. Tilley, J. Am. Chem. Soc., 2014, 136,
J. A. Bohmann, C. M. Morales, C. R. Landis and
F. Weinhold, NBO 6.0. E. D, Theoretical Chemistry
Institute, University of Wisconsin, Madison, 2013.
6
092–6102; (i) B. Blom, G. Klatt, D. Gallego, G. Tan and
M. Driess, Dalton Trans., 2015, 44, 639–644; ( j) G. Tan, 16 Z. Huang and X. Jia, Nat. Chem., 2016, 8, 157–161.
S. Enthaler, S. Inoue, B. Blom and M. Driess, Angew. 17 G. M. Sheldrick, Empirical Absorption Correction Program,
Chem., Int. Ed., 2015, 54, 2214–2218; (k) S. Khan,
Göttingen, Germany, 1996.
S. Pal, N. Kathewad, I. Purushothaman, S. De and 18 G. M. Sheldrick, Program for the Refinement of Crystal
P. Parameswaran, Chem. Commun., 2016, 52, 3880–3882.
Structures, University of Göttingen, Germany, 2014.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2017

View Article Online
Dalton Transactions
Paper
1
9 K. Wakita, Release of Software (Yadokari-XG 2009) for Crystal
Structure Analyses, 2001; C. Kabuto, S. Akine, T. Nemoto
and E. Kwon, Cryst. Soc. Jpn, 2009, 51, 218–224.
J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene,
J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo,
R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin,
R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin,
K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador,
J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas,
J. B. Foresman, J. V. Ortiz, J. Cioslowski and D. J. Fox,
Gaussian 09, Revision D.01, Gaussian, Inc., Wallingford CT,
2009.
2
0 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato,
X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng,
J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda,
J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, Jr., J. A. Montgomery, J. E. Peralta, 21 S. Maeda, Y. Harabuchi, Y. Osada, T. Taketsugu,
F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers,
K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand,
K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar,
K. Morokuma and K. Ohno, GRRM14, see: http://grrm.
chem.tohoku.ac.jp/GRRM/; S. Maeda, K. Ohno and
K. Morokuma, Phys. Chem. Chem. Phys., 2013, 15, 3683–3701.
This journal is © The Royal Society of Chemistry 2017
Dalton Trans.