Mononuclear Heteroscorpionate Zwitterionic Zinc Terminal Hydride: Synthesis, Reactivity, and Catalysis for Hydrosilylation of Aldehydes

Article abstract of DOI:10.1021/acs.organomet.5b00413

Treatment of heteroscorpionate zinc benzyloxy complex LZnOBn (1, L = (^MePz)₂CP(Ph)₂NPh, ^MePz = 3,5-dimethylpyrazolyl) with phenylsilane (PhSiH₃) gave a zinc hydride complex LZnH (2) containing a rare terminal hydride fragment. X-ray diffraction analysis and the DFT calculation confirm the zwitterionic structure of complex 2. The stoichiometric reaction of 2 with CS₂ readily afforded a dithioformate complex LZnSCH(S) (3) of the C = S insertion into the Zn-H product. Moreover, complex 2 was an efficient catalyst for the hydrosilylation reaction of a series of silanes and aldehydes under mild conditions, featuring excellent functional group tolerance. The preliminary mechanistic study revealed that both zinc benzyloxy complex 1 and zinc hydride complex 2 were involved in the hydrosilylation process as the reaction intermediates. (Chemical Equation Presented).

Full text of DOI:10.1021/acs.organomet.5b00413

Article
pubs.acs.org/Organometallics
Mononuclear Heteroscorpionate Zwitterionic Zinc Terminal Hydride:
Synthesis, Reactivity, and Catalysis for Hydrosilylation of Aldehydes
Zehuai Mou,†,‡,# Hongyan Xie,†,‡,# Meiyan Wang,§ Na Liu,†,‡ Changguang Yao,†,‡ Lei Li,†,‡ Jingyao Liu,§
Shihui Li,† and Dongmei Cui*,†
†State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
Changchun 130022, China
‡University of Chinese Academy of Sciences, Changchun Branch, Changchun 130022, China
§Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun
130022, China
S
* Supporting Information
ABSTRACT: Treatment of heteroscorpionate zinc benzyloxy
complex LZnOBn (1, L = (MePz)2CP(Ph)2NPh, MePz = 3,5-
dimethylpyrazolyl) with phenylsilane (PhSiH3) gave a zinc
hydride complex LZnH (2) containing a rare terminal hydride
fragment. X-ray diffraction analysis and the DFT calculation
confirm the zwitterionic structure of complex 2. The
stoichiometric reaction of 2 with CS2 readily afforded a
dithioformate complex LZnSCH(S) (3) of the CS insertion
into the Zn−H product. Moreover, complex 2 was an efficient
catalyst for the hydrosilylation reaction of a series of silanes
and aldehydes under mild conditions, featuring excellent functional group tolerance. The preliminary mechanistic study revealed
that both zinc benzyloxy complex 1 and zinc hydride complex 2 were involved in the hydrosilylation process as the reaction
intermediates.
preparation of silicone-based materials such as coatings,
adhesives, and cured rubbers,16 has mainly relied on precious
metal catalysts for a long period,17 and few reports related to
the cheap zinc hydrido catalysts exist.3,14,15
Herein, we report the synthesis and characterization of a new
type of zwitterionic zinc terminal hydride complex based on a
rigid and bulky heteroscorpionate ligand. The hydride complex
can conduct the reaction with CS2 and catalyze hydrosilylation
of aldehydes at a low catalyst load. In addition, a possible
mechanism of the above reaction is explicated by means of
isolating a reaction intermediate.
INTRODUCTION
■
Zinc hydride (ZnH2) has been used as a reducing agent in
organic synthesis;1 however, its poor thermal stability and
insolubility in organic solvents narrow its application range.2
Therefore, considerable efforts have been directed to synthesize
more stable and soluble organozinc hydrides supported by the
anionic ancillary ligands. To date, many anionic ancillary
ligands have been synthesized, such as di(2-pyridylmethyl)-
amine,3 tris(pyrazoyl)hydroborates,4 β-diketiminates,5 2,6-dia-
lkylphenyls,6 pyridyl-substituted tris(trimethylsilyl)-
methanides,7 tris(4,4-dimethyl-2-oxazolinyl)phenylborate,8 tris-
(2-pyridylthio)methyl, 9 diamine phenolate, 1 0
bis(NHC)methyl,11 and pentamethylcyclopentadienyl
(Cp*).12 However, it is still difficult to obtain well-defined
mononuclear zinc terminal hydride complexes that may transfer
readily to dimer, cluster, or cubic structures via the formation of
hydride bridges, because the small steric hydride ligand is not
bulky enough to stabilize the hydride complex in a
mononuclear structure.13 Such structures are chemically
inactive as compared to the terminal ones. With respect to
the reactivity, the zinc hydride complexes have exhibited
promising catalysis such as in alcoholysis of silanes,8b,11,14
hydrogenation of imines,12 and hydrosilylation of carbon
dioxide,14 ketones,15 nitriles,15 and alkenes.11 Particularly, the
hydrosilylation of aldehydes involving the formation of a Si−O
bond, an important process in surface derivatization and
RESULTS AND DISCUSSION
■
Synthesis and Characterization of Zinc Terminal
Hydride Complex 2. Treatment of heteroscorpionate zinc
benzyloxy complex LZnOBn (1, L = (MePz)2CP(Ph)2NPh,
MePz = 3,5-dimethylpyrazolyl) with phenylsilane (PhSiH3) gave
a zinc terminal hydride complex LZnH (2) as a white solid in
good yield (Scheme 1, a).18 In the H NMR spectrum in
1
benzene-d6, the terminal hydride (Zn−H) resonance appears at
5.38 ppm, which is close to the corresponding zwitterionic
tris(substituted-pyrazoyl) hydroborate zinc hydrides (δ 5.36
ppm for TptBuZnH,4a 5.26 ppm for Tpp‑Tol, MeZnH4b), but shifts
Received: December 24, 2014
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.5b00413
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 1. Synthesis of Heteroscorpionate Zinc Hydride 2 and Dithioformate Complex 3
Figure 1. Crystal structure of zinc hydride 2 (left) and the isosurface for the molecular orbital HOMO−1 (right). Hydrogen atoms except Zn−H are
omitted for clarity. Selected bond lengths (Å) and angles (deg): Zn(1)−H(1) 1.57(4), Zn(1)−N(2) 2.064(3), Zn(1)−N(4) 2.100(3), Zn(1)−N(5)
2.056(3); N(5)−Zn(1)−N(2) 97.96(11), N(5)−Zn(1)−N(4) 93.30(11), N(2)−Zn(1)−N(4) 89.89(11), N(1)−C(11)−N(3) 111.7(3), N(1)−
C(11)−P(1) 113.1(2), N(3)−C(11)−P(1) 110.3(2).
a
Table 1. Hydrosilylation of Various Aldehydes Catalyzed by Complex 2
b
c
run
substrate
PhCHO
silane (equiv)
time (h)
product
1
2
PhSiH3 (1/3)
PhSiH3 (1)
10
7
PhSi(OCH2Ph)3
PhCHO
PhSi(H)x(OCH2Ph)3−x (x = 0−1)
PhSi(OCH2Ph)3
d
3
PhCHO
PhSiH3 (1/3)
Ph2SiH2 (1/2)
Ph2SiH2 (1)
EtO3SiH (1)
PhSiH3 (1/3)
PhSiH3 (1/3)
PhSiH3 (1/3)
PhSiH3 (1/3)
PhSiH3 (1/3)
PhSiH3 (1/3)
PhSiH3 (1/3)
PhSiH3 (1)
13
12
4
4
PhCHO
Ph2Si(OCH2Ph)2
5
PhCHO
Ph2SiH(OCH2Ph)
6
PhCHO
96
0.5
5
(EtO)xSi(OCH2Ph)4−x (x = 2−4)
PhSi(OCH2Py)3
7
2-PyCHO
8
o-F-PhCHO
o-Br-PhCHO
o-MeO-PhCHO
o-EtO-PhCHO
t-BuCHO
PhSi(OCH2−o-F-Ph)3
PhSi(OCH2-o-Br-Ph)3
PhSi(OCH2-o-MeO-Ph)3
PhSi(OCH2-o-EtO-Ph)3
PhSi(OCH2CMe3)3
9
7
10
11
12
13
14
15
16
10
6
5
p-vinyl-PhCHO
p-vinyl-PhCHO
2-(C4H3O)CHO
2-(C4H3S)CHO
PhCHO
6
PhSi(OCH2-p-vinyl-Ph)3
PhSi(H)x(OCH2-p-vinyl-Ph)3−x (x = 0−1)
PhSi(OCH2C4H3O)3
6
PhSiH3 (1/3)
PhSiH3 (1/3)
PhSiH3 (1/3)
6
20
10
PhSi(OCH2C4H3S)3
e
17
PhSi(OCH2Ph)3
a
Reaction conditions (unless specified otherwise): substrate (1.0 mmol), LZnH catalyst (1.0 mol %), T = 25 °C, C6D6 (ca. 0.6 mL), under N2.
b
c
Reaction times were determined via 1H NMR spectroscopy after complete consumption of substrate or silane. The identity of product was based
d
e
1
on H NMR spectra and/or GC-MS. Catalyst load 0.25 mol %. Benzyloxy complex 1 was used.
obviously downfield as compared with those in many other
neutral mononuclear zinc hydrides reported previously (3.99−
5.02 ppm).5e,10
The molecular structure of complex 2 was well resolved by a
single-crystal X-ray diffraction study (Figure 1, left), where the
heteroscorpionate ligand moiety caps the zinc ion with three
nitrogen atoms in the κ3-coordination mode, appearing as a
mononuclear structure bearing a single zinc terminal hydride
species. The terminal Zn(1)−H(1) bond length is 1.57(4) Å,
falling in the normal range for mono zinc hydride complexes
reported previously.19 The measured distance from the metal
Zn(1) to the apical carbon anion C(11) is 3.036 Å, far beyond
B
DOI: 10.1021/acs.organomet.5b00413
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 2. Proposed Catalytic Mechanism
the normal bond length range, suggesting the zwitterionic
structure. The bond angles of N−Capical−N and N−Capical−P
are 111.7(3)°, 113.1(2)°, and 110.3(2)°, respectively, close to
109.5°, meaning that the apical carbon has a nonplanar
geometry indicating the formal sp3 hybridization. Moreover, the
structure of 2 is well simulated by DFT (density functional
theory) calculations, which give the Zn(1)−H(1) bond length
of 1.557 Å, as well as comparable N−Capcal−N (111.71°) and
two N−Capical−P (112.58° and 111.80°) bond angles. The
molecular orbital HOMO−1 is predominantly localized on the
apical carbon (Figure 1, right), and the net atomic charge of the
apical carbon is −0.441 (calculated from natural bond orbital
analysis). Both the X-ray diffraction and the DFT calculation
suggest the zinc hydride complex 2 to be a zwitterion.
S17), suggesting that complex 2 can selectively catalyze the
hydrosilylation of the carbonyl group in the presence of a vinyl
group. In addition, other aromatic aldehydes (2-pyridylalde-
hyde, 2-furaldehyde, thiophene-2-aldehyde) (Table 1, runs 7,
15, 16) and aliphatic aldehyde tBuCHO (Table 1, run 12) were
also explored to react with PhSiH3 under the same conditions.
The reaction of PhSiH3 with 2-pyridylaldehyde proceeded
fastest (0.5 h), while that with thiophene-2-aldehyde the
slowest (20 h). Noteworthy is that both electron-withdrawing
groups (−Py, −F, and −Br) (Table 1, runs 7−9) and electron-
donating groups (−tBu, −OMe, and −OEt) (Table 1, runs 10−
12) could increase the reaction rates to some extent (for the
kinetic study, see Figure S1). This observation is contrary to the
previous report where the electron-withdrawing groups in the
para position accelerated the reaction while the electron-
donating groups decelerated the reaction.2g In our system, the
electron-withdrawing groups at the ortho position lower the
electron density of the aromatic ring and the carbonyl carbon
atom, which should facilitate the anionic attack of Zn−H on the
carboxyl carbon CO. On the other hand, the electron-
donating groups at the ortho position increase the electron
density, which might promote the coordination of CO
oxygen to the cationic zinc center.
Hydrosilylation Reaction of Aldehydes. To investigate
the catalytic performance of the zwitterionic zinc hydride,
hydrosilylations of aldehydes with silanes in the presence of 2
(1.0 mol %) were conducted in an NMR tube and monitored
1
by H NMR spectroscopy (benzene-d6) at room temperature
(Table 1). Benzaldehyde (PhCHO) reacted with 1/3 equiv of
PhSiH3 for 10 h to give silyl ether (PhCH2O)3SiPh as the only
product, where the zinc hydride efficiently catalyzed the
insertion of all three Si−H bonds of PhSiH3 into the CO
bond of PhCHO (Table 1, run 1). The attempt to obtain a
single insertion product under the PhCHO-to-PhSiH3 feed
ratio of 1:1 failed (Table 1, run 2), evidenced by 1H NMR and
GC-MS analyses (see the Supporting Information), which
afforded a mixture of double and triple insertion products
((PhCH2O)2SiHPh and (PhCH2O)3SiPh) without the desired
product PhCH2OSiH2Ph.20 This was probably because the silyl
ether formed during the aldehyde reduction enhanced the
reactivity of the remaining Si−H bonds.17e A low catalyst load
(0.25 mol %) of complex 2 also worked well, which is the
lowest catalyst concentration reported to date for a zinc hydride
system (Table 1, run 3). Delightedly, the hydrosilylation of
PhCHO with the secondary silane Ph2SiH2 was rather
controllable to afford the single (PhCH2OSiHPh2) or double
insertion ((PhCH2O)2SiPh2) products in the feed ratios of 1:1
and 2:1, respectively (Table 1, runs 4 and 5).3,21 When tertiary
silane (EtO)3SiH was employed, the hydrosilylation reaction
with PhCHO proceeded sluggishly (4 days) to give the
anticipated (EtO)3SiOCH2Ph as the major product accom-
panied by some byproducts (Table 1, run 6), such as (EtO)4Si,
(EtO)3SiOSi(OEt)3, and (EtO)2Si(OCH2Ph)2 according to the
GC-MS.15,22 To investigate the functional group tolerance of
this catalyst system, a series of functionalized aldehydes were
also used as substrates. The hydrosilylation of p-vinyl-
benzaldehyde with 1 equiv of PhSiH3 gave a mixture similar
to that of PhCHO mentioned above, and the residual PhSiH3
did not react with the p-vinyl group even at elevated
temperature (50 °C) for 10 h (Table 1, runs 13, 14; Figure
For the zinc-catalyzed hydrosilylation, two mechanisms have
been established: the activation of the aldehyde23 or silane
substrate15 on a Lewis acidic zinc center and insertion/
heterolytic splitting.3,14,24 In both procedures, the zinc hydride
moiety is usually proposed to be the intermediate; however, no
solid and direct evidence has been provided. To elucidate the
mechanism of the hydrosilylation by this zwitterionic system,
the reaction of zinc hydride complex 2 with PhCHO was
1
monitored by H NMR spectroscopy (Figures S31 and S32),
which revealed the formation of zinc benzyloxy complex 1,
suggesting that zinc hydride and alkoxide species might be
interconverted (complex 2 was synthesized from complex 1,
vide supra). Moreover, benzyloxy complex 1 can also catalyze
the hydrosilylation of PhCHO as efficiently as zinc hydride 2
(Table 1, run 17). On the basis of the above experimental
results, we postulated that the hydrosilylation undergoes an
insertion mechanism as shown in Scheme 2.
Reactivity with CS2. Furthermore, we also examined
whether the terminal zinc hydride could catalyze the hydro-
silylation of carbon dioxide and its derivative of carbon
disulfide. The reaction of hydride and carbon dioxide was
complicated and uncontrollable. However, the stoichiometric
reaction of 2 with CS2 in THF at room temperature readily
afforded the dithioformate complex 3 as a yellow solid (Scheme
1, b). In the process, the hydride transferred from zinc to the
carbon atom of CS2 via the insertion of the Zn−H bond into
the CS double bond. The newly generated SCH(S) group
gives a sharp singlet at 11.91 ppm (benzene-d6) in the 1H NMR
C
DOI: 10.1021/acs.organomet.5b00413
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
parameters was carried out by the SMART program package.26 The
raw frame data were processed using SAINT and SADABS to yield the
reflection data file.27 The structures were solved by using the
SHELXTL program.28 Refinement was performed on F2 anisotropi-
cally for all non-hydrogen atoms by the full-matrix least-squares
method. The hydrogen atoms were placed at calculated positions and
were included in the structure calculations without further refinement
of the parameters. The terminal hydrogen atom in complex 2 has been
refined anisotropically. Molecular structures were generated using the
ORTEP program.
spectrum. The crystal structure of 3 (Figure 2) reveals that the
dithioformate moiety adopts the σ-coordination mode in
Synthesis of Zinc Hydride Complex LZnH (2). To a solution of zinc
benzyloxy complex 1 (0.52 g, 0.8 mmol) in THF was added PhSiH3
(0.108 g, 1.0 mmol) or EtO3SiH (0.164 g, 1.0 mmol), and the mixture
was stirred for 10 h at room temperature. The volatile was removed
under reduced pressure, and hexane (5 mL) was added. The white
precipitate was isolated by filtration and dried under vacuum (yield,
0.33 g, 76%). Crystals suitable for single-crystal X-ray diffraction were
obtained from a saturated THF/hexane solution kept at −30 °C. Anal.
Calcd for C29H30N5PZn: C, 63.92; H, 5.55; N, 12.85. Found: C, 63.88;
1
H, 5.50; N, 12.83. H NMR (400 MHz, C6D6): δ 7.74−7.69 (m, 4H;
o-PPh2), 7.53 (d, 3JH−H = 8.1 Hz, 2H; o-NPh), 7.03−6.89 (m, 8H; Ph-
H), 6.66 (t, 3JH−H = 7.3 Hz, 1H; p-NPh), 5.38 (d, 3JP−H = 2.4 Hz, 1H;
Zn-H), 5.29 (s, 2H; Pz-H), 2.22 (s, 6H; Pz-CH3), 1.89 ppm (s, 6H;
1
Pz-CH3). 31P NMR (162 MHz, C6D6): δ 34.2 ppm. H NMR (400
MHz, THF-d8): δ 7.64−7.59 (m, 4H; o-PPh2), 7.42−7.38 (m, 2H; p-
3
PPh2), 7.32−7.28 (m, 4H; m-PPh2), 6.93 (d, JH−H = 8.1 Hz, 2H; o-
3
Figure 2. Crystal structure of zinc dithioformate 3. Hydrogen atoms
except the SCH(S) have been omitted for clarity. Selected bond
lengths (Å) and angles (deg): Zn(1)−S(1) 2.285(2), S(1)−C(30)
1.702(6), S(2)−C(30) 1.633(7); S(2)−C(30)−S(1) 127.2(3),
Zn(1)−S(1)−C(30) 100.81(19), N(1)−C(11)−N(3) 110.9(6),
N(1)−C(11)−P(1) 114.6(5), N(3)−C(11)−P(1) 111.9(5).
NPh), 6.78 (m, 2H; m-NPh), 6.46 (t, JH−H = 7.3 Hz, 1H; p-NPh),
3
5.59 (s, 2H; Pz-H), 4.38 (d, JP−H = 2.5 Hz, 1H; Zn-H), 2.24 (s, 6H;
Pz-CH3), 1.99 ppm (s, 6H; Pz-CH3). 31P NMR (162 MHz, THF-d8):
δ 20.5 ppm. 13C NMR (100 MHz, THF-d8): δ 151.5, 151.4 (C3 or C5),
146.0, 145.9, (C3 or C5), 148.5 133.8, 133.7, 132.2, 132.1, 129.9, 129.1,
128.9.128.8, 122.7, 122.6, 118.4, 104.4 (C4), 64.5 (d, 1JP−C = 91.4 Hz;
P-C), 13.4 (Pz-CH3), 11.8 ppm (Pz-CH3).
Synthesis of Dithioformate Complex LZnSCHS (3). A solution of
carbon disulfide (0.023 g, 0.3 mmol) in THF (2 mL) was added to a
solution of complex 2 (0.163 g, 0.3 mmol) of THF (8 mL) to give a
yellow solution. The mixture was stirred for 2.5 h at room temperature
and concentrated to about 1.0 mL; then several drops of hexane was
added. Yellow crystals were obtained at −30 °C 2 days later (yield,
0.081 g, 43%). Anal. Calcd for C30H30N5PS2Zn: C, 58.01; H, 4.87; N,
11.28. Found: C, 57.97; H, 4.82; N, 11.25. 1H NMR (400 MHz,
C6D6): δ 11.92 (s, 1H; SCHS), 7.75−7.70 (m, 4H; m-PPh2), 7.25 (d,
3JH−H = 8.4 Hz, 2H; o-NPh), 7.99−6.88 (m, 8H; Ph-H), 6.63 (t, 3JH−H
= 7.3 Hz, 1H; p-NPh), 5.24 (s, 2H; Pz-H), 2.16 (s, 6H; Pz-CH3), 1.83
ppm (s, 6H; Pz-CH3). 31P NMR (162 MHz, C6D6): δ 35.9 ppm. 13C
NMR (100 MHz, C6D6): δ 149.7, 149.6, (C3 or C5) 145.3, 145.2, (C3
or C5) 148.7, 133.1, 133.0, 131.6, 129.3, 129.0, 127.5, 122.1, 122.0,
119.3 (Ph), 104.5 (C4) 63.5 (d, 1JP−C = 96.4 Hz; P-C), 13.0 (Pz-CH3),
11.6 ppm (Pz-CH3).
agreement with the previous literature report, and the relative
bond lengths and angles also fall in the normal range.25
CONCLUSION
■
In conclusion, we have demonstrated that by using a sterically
bulky heteroscorpionate ligand, the zwitterionic zinc terminal
hydride complex has been readily synthesized by treatment of
its benzyloxy precursor with phenylsilane. The zinc hydride
reacts with CS2 under mild conditions through the Zn−H bond
insertion into the unsaturated CS bond to give a
dithioformate complex bearing the Zn-σ-S species. More
importantly, the zinc hydride can efficiently catalyze the
hydrosilylation of various aldehydes with silanes to prepare
silyl ethers with the lowest catalyst load. In addition, we prove
for the first time that both the zinc alkoxide and zinc hydride
species are the intermediates in the aldehyde hydrosilylation
process.
Catalytic Hydrosilylation Reaction of Aldehydes with Zinc
Hydride Complex 2. In a typical experiment zinc hydride complex 2
(0.0055 g, 10 μmol, 1.0 mol %) was added to a C6D6 (ca. 0.6 mL)
solution of silane and aldehyde substrate; then the mixture was
1
EXPERIMENTAL SECTION
transferred into a J. Young NMR tube and monitored by H NMR
■
spectroscopy until the resonance of CHO or SiH disappeared (it is
difficult to weigh the substrates and silanes accurately following the
feed ratio we have designed, so one of them may be residual in the in
General Procedures. All reactions were carried out under a dry
nitrogen atmosphere using standard Schlenk techniques or in a
glovebox filled with dry nitrogen. Hexane and toluene were purified
using an SPS Braun system. THF was dried by distillation over
sodium/benzophenone under a nitrogen atmosphere and was stored
over freshly cut sodium in a glovebox. Samples for NMR spectroscopic
analysis were prepared in a glovebox using NMR spectroscopy tubes
and then sealed with a paraffin film. 1H, 31P, and 13C{1H} NMR
spectra were recorded using a Bruker AV400 spectrometer.
1
situ monitoring H NMR spectra, vide infra).
Hydrosilylation of PhCHO with PhSiH3 (3:1). Zinc hydride complex
2 (0.0055 g, 10 μmol, 1.0 mol %) was added to a solution of PhSiH3
(0.036 g, 0.33 mmol) and PhCHO (0.106 g, 1.0 mmol, 3 equiv)
substrate in C6D6 (ca. 0.6 mL); then the mixture was transferred into a
1
J. Young NMR tube and monitored by H NMR spectroscopy until
the resonance of SiH disappeared. After that, volatiles were removed
under reduced pressure; then hexane (2 mL) was added. The crude
product was filtered through a short plug of silica, and removal of the
solvent gave the product PhSi(OCH2Ph)3. 1H NMR (400 MHz,
CDCl3): δ 7.77−7.75 (m, 2H; o-SiPh), 7.52−7.48 (m, 1H; p-Ph),
7.44−7.41 (m, 2H; m-SiPh), 7.36−7.28 (m, 15H; OCH2Ph-H), 4.92
X-ray Crystallographic Studies. Crystals for X-ray analysis were
obtained as described in the preparations. The crystals were
manipulated in a glovebox. Data collections were performed at
−88.5 °C on a Bruker SMART APEX diffractometer with a CCD area
detector, using graphite-monochromated Mo Kα radiation (λ =
0.710 73 Å). The determination of crystal class and unit cell
D
DOI: 10.1021/acs.organomet.5b00413
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
ppm (s, 6H; OCH2Ph). 13C NMR (100 MHz, CDCl3): δ 140.2, 135.1,
130.8, 129.9, 128.4, 128.1, 127.4, 126.8 (Ph), 65.2 ppm (OCH2Ph).
Hydrosilylation of PhCHO with PhSiH3 (1:1). Zinc hydride complex
2 (0.0055 g, 10 μmol, 1.0 mol %) was added to a solution of PhSiH3
(0.108 g, 1.0 mmol) and PhCHO (0.106 g, 1.0 mmol) substrate in
C6D6 (ca. 0.6 mL); then the mixture was transferred into a J. Young
NMR tube and monitored by 1H NMR spectroscopy until the
resonance of PhCHO disappeared. Then the mixture was analyzed
with GC-MS. PhSiH(OCH2Ph)2: tR = 13.92 min; m/z 320 (M+).
PhSi(OCH2Ph)3: tR = 17.42 min; m/z 426 (M+).
mL); then the mixture was transferred into a J. Young NMR tube and
monitored by 1H NMR spectroscopy until the resonance of SiH
disappeared. 1H NMR (400 MHz, C6D6): δ 7.78 (m, 2H; Ph-H), 7.17
(m, 3H; Ph-H), 7.07, 6.09, 6.04 (m, 3 × 3H; furan-H), 4.76 ppm (s,
6H; SiOCH2). 13C NMR (100 MHz, C6D6): δ 153.9 (C2 of furan,
142.6 (C5 of furan), 135.4, 130.9, 130.3, 128.2 (Ph), 110.6, 108.4 (C3
or C4 of furan), 57.9 ppm (SiOCH2).
PhSi(OCH2C4H3S)3. Zinc hydride complex 2 (0.0055 g, 10 μmol, 1.0
mol %) was added to a solution of PhSiH3 (0.036 g, 0.33 mmol) and
thiophene-2-aldehyde (0.112 g, 1.0 mmol, 3 equiv) substrate in C6D6
(ca. 0.6 mL); then the mixture was transferred into a J. Young NMR
Hydrosilylation of PhCHO with Ph2SiH2 (2:1). Product
1
1
tube and monitored by H NMR spectroscopy until the resonance of
(PhCH2O)2Si(Ph)2: H NMR (400 MHz, CDCl3): δ 7.64−7.52 (m,
1
SiH disappeared. H NMR (400 MHz, C6D6): δ 7.63−7.81 (m, 2H;
8H; o-SiPh), 7.45−7.27 (m, 12H; Ph-H), 4.92 ppm (s, 4H; SiO-CH2).
13C NMR (100 MHz, CDCl3): δ 140.5, 135.1, 132.5, 130.6, 128.4,
128.1, 127.3, 126.7 (Ph), 65.1 ppm (SiO-CH2). GC-MS: tR = 16.43
min; m/z 396 (M+).
Ph-H), 7.23−7.18 (m, 3H; Ph-H), 6.90, 6.79, 6.71 (m, 3 × 3H;
thiophene-H), 4.95 (s, 6H; SiOCH2). 13C NMR (100 MHz, C6D6): δ
143.8, 135.4, 131.1, 130.1, 126.8, 125.5, 60.5 ppm (SiOCH2). GC-MS:
tR = 20.91 min; m/z 444 (M+).
Hydrosilylation of PhCHO with Ph2SiH2 (1:1). Product
PhSi(OCH2Py)3. 1H NMR (400 MHz, C6D6): δ 8.41 (d, 3JH−H = 4.7
1
PhCH2OSiH(Ph)2: H NMR (400 MHz, CDCl3): δ 7.76−7.33 (m,
3
15H; Ph-H), 5.60 (s, 1H; SiH), 4.95 ppm (s, 2H; SiOCH2). 13C NMR
(100 MHz, CDCl3): δ 140.2, 134.9, 134.4, 133.8, 130.6, 128.4, 128.2,
127.5, 126.9 (Ph), 66.7 ppm (SiO-CH2). GC-MS: tR = 13.20 min; m/z
290 (M+).
Hz, 3H; Py-H), 7.88 (dd, JH−H = 1.7, 7.6 Hz, 2H, Ph-H), 7.46 (d,
3JH−H = 7.9 Hz, 3H; Py-H), 7.23−7.16 (m, 4H; Py-H × 3 and Ph-H ×
1), 7.15 (dd, 3JH−H = 1.8, 7.7 Hz, 2H; Ph-H), 6.66 (dd, 3JH−H = 5.0, 7.3
Hz, 3H; Py-H), 5.25 ppm (s, 6H; SiO-CH2).
PhSi(OCH2CMe3)3. Zinc hydride complex 2 (0.0055 g, 10 μmol, 1.0
mol %) was added to a solution of PhSiH3 (0.036 g, 0.33 mmol) and
pivaldehyde (0.0861 g, 1.0 mmol, 3 equiv) substrate in C6D6 (ca. 0.6
mL); then the mixture was transferred into a J. Young NMR tube and
monitored by 1H NMR spectroscopy until the resonance of SiH
disappeared. After complete conversion volatiles were removed under
reduced pressure, then hexane (2 mL) was added. The crude product
was filtered through a short silica plug, and removal of the solvent gave
the product PhSi(OCH2CMe3)3. 1H NMR (400 MHz, CDCl3): δ 7.70
(d, 3JH−H = 7.7 Hz, 2H; Ph-H), 7.45−7.36 (m, 3H; Ph-H), 3.50 (s, 6H;
OCH2CMe3), 0.95 ppm (s, 27H; OCH2CMe3). 13C NMR (100 MHz,
CDCl3): δ 135.1, 131.8, 130.2, 127.8 (Ph), 73.2 (OCH2CMe3), 33.0
(OCH2CMe3), 26.5 ppm (OCH2CMe3). GC-MS: tR = 7.189 min; m/z
366 (M+).
Hydrosilylation of PhCHO with EtO3SiH. Zinc hydride complex 2
(0.0055 g, 10 μmol, 1.0 mol %) was added to a solution of (EtO)3SiH
(0.164 g, 1.0 mmol) and benzaldehyde (0.106 g, 1.0 mmol) substrate
in C6D6 (ca. 0.6 mL); then the mixture was transferred into a J. Young
NMR tube and monitored by 1H NMR spectroscopy until the
resonance of SiH (δ 4.58 ppm) disappeared. Then the mixture was
analyzed with GC-MS. (EtO)3SiOCH2Ph (major product): tR = 9.757
min; m/z 270 (M+). (EtO)4Si (byproduct): tR = 4.670 min; m/z 208
(M+). (EtO)3SiOSi(OEt)3 (byproduct): tR = 6.955 min; m/z 342
(M+). (EtO)2Si(OCH2Ph)2 (byproduct): tR = 16.945 min; m/z 331
(M+).
1
PhSi(OCH2-o-F-Ph)3. H NMR (400 MHz, CDCl3): δ 7.75−7.66
(m, 2H; o-SiPh), 7.50−7.46 (m, 4H; Ph-H), 7.43−7.39 (m, 2H; m-
SiPh), 7.28−7.22 (m, 3H; Ph-H), 7.14−7.10 (m, 3H; Ph-H), 7.03−
6.98 (m, 3H; Ph-H), 4.96 ppm (s, 6H; SiO-CH2). 13C NMR (100
MHz, CDCl3): δ 161.5. 159.0, 135.1, 131.0, 129.4, 129.1, 129.0, 128.2,
127.3, 127.1, 124.1, 115.2, 115.0 (Ph), 59.3 ppm (SiO-CH2). GC-MS:
tR = 16.51 min; m/z 479 (M+).
Hydrosilylation of PhCHO with PhSiH3 Catalyzed by Zinc
Benzyloxy Complex 1. Zinc benzyloxy complex 1 (0.0065 g, 10
μmol, 1.0 mol %) was added to a solution of PhSiH3 (0.036 g, 0.33
mmol) and PhCHO (0.106 g, 1.0 mmol, 3 equiv) substrate in C6D6
(ca. 0.6 mL); then the mixture was transferred into a J. Young NMR
1
PhSi(OCH2-o-Br-Ph)3. H NMR (400 MHz, CDCl3): δ 7.82−7.79
1
3
tube and monitored by H NMR spectroscopy until the resonance of
(m, 2H; o-SiPh), 7.59 (d, JH−H = 7.5 Hz, 3H; Ph-H), 7.51 (m, 4H;
Ph-H), 7.45 (dd, 3JH−H = 7.2, 7.2 Hz, 2H; m-SiPh), 7.31 (t, 3JH−H = 7.3
Hz, 3H; Ph-H), 7.15−7.11 (m, 3H; Ph-H), 5.02 ppm (s, 6H; SiO-
CH2). 13C NMR (100 MHz, CDCl3): δ 139.0, 135.0, 132.4, 131.2,
128.8, 128.3, 128.2, 127.5, 121.7 (Ph), 65.0 ppm (SiO-CH2).
SiH disappeared. The result is similar to that of zinc hydride 2.
CCDC-1014967 (2) and 1014968 (3) contain the supplementary
crystallographic data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
1
PhSi(OCH2-o-MeO-Ph)33. H NMR (400 MHz, C6D6): δ 7.96−7.92
(m, 2H; o-SiPh), 7.75 (d, JH−H = 7.5 Hz, 3H; Ph-H), 7.17−7.06 (m,
3
3
6H; Ph-H), 6.90 (t, JH−H = 7.4 Hz, 3H; Ph-H), 6.48, (d, JH−H = 8.1
Hz, 3H; Ph-H), 5.29 (s, 6H; SiO−CH2), 3.23 ppm (s, 9H; Ph-OCH3).
ASSOCIATED CONTENT
■
1H NMR (400 MHz, CDCl3): δ 7.76 (d, JH−H = 6.7 Hz, 2H; Ph-H),
3
S
* Supporting Information
7.51 (d, 3JH−H = 7.4 Hz, 3H; Ph-H), 7.43 (t, JH−H = 7.3 Hz, 1H; Ph-
3
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.5b00413.
3
3
H), 7.36 (t, JH−H = 7.2 Hz, 2H; Ph-H), 7.22 (t, JH−H = 7.7 Hz, 3H;
3
3
Ph-H), 6.94 (t, JH−H = 7.4 Hz, 3H; Ph-H), 6.80 (d, JH−H = 8.1 Hz,
3H; Ph-H), 4.99 (s, 6H; SiO-CH2), 3.74 ppm (s, 9H; Ph-OCH3). GC-
MS: tR = 26.16 min; without molecular ion (M+) (Mw = 516.7), the
largest ion is [Si(OCH2-o-MeO-Ph)3]+ (439).
Complete crystallographic data for complexes 2 and 3,
computational details, calculated coordinates for complex
2 (PDF)
Crystallographic data for 2 and 3 (CIF)
XYZ
1
PhSi(OCH2-o-EtO-Ph)3. H NMR (400 MHz, C6D6): δ 7.95−7.93
(m, 2H; Ph-H), 7.80−7.77 (m, 3H; Ph-H), 7.17−7.07 (m, 6H; Ph-H),
3
6.94−6.90 (m, 3H; Ph-H), 6.52 (d, JH−H = 7.8 Hz, 3H; Ph-H), 5.31
3
(s, 6H; SiO-CH2), 3.52 (q, JH−H = 7.0 Hz, 6H; Ph-OCH2CH3), 1.01
3
ppm (t, JH−H = 7.0 Hz, 9H; Ph-OCH2CH3).
Hydrosilylation of p-Vinylbenzaldehyde with PhSiH3 (3:1). 1H
NMR (400 MHz, C6D6): δ 7.87 (m, 2H; Ph-H), 7.23 (m, 15H; Ph-H),
AUTHOR INFORMATION
■
3
3
6.58 (dd, JH−H = 17.6, 10.9 Hz, 3H; vinyl-H), 5.60 (d, JH−H = 17.6
Hz, 3H; vinyl-H), 5.07 (d, 3JH−H = 10.9 Hz, 3H; vinyl-H), 4.86 ppm (s,
6H; SiO-CH2).
Corresponding Author
*E-mail: dmcui@ciac.ac.cn. Fax: +86 431 85262774. Tel: +86
431 85262773.
PhSi(OCH2C4H3O)3. Zinc hydride complex 2 (0.0055 g, 10 μmol, 1.0
mol %) was added to a solution of PhSiH3 (0.036 g, 0.33 mmol) and
2-furaldehyde (0.096 g, 1.0 mmol, 3 equiv) substrate in C6D6 (ca. 0.6
Author Contributions
#Z. Mou and H. Xie contributed equally to this work.
E
DOI: 10.1021/acs.organomet.5b00413
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(15) Boone, C.; Korobkov, I.; Nikonov, G. I. ACS Catal. 2013, 3,
2336−2340.
Notes
The authors declare no competing financial interest.
(16) (a) Trewyn, B. G.; Slowing, I. I.; Giri, S.; Chen, H. T.; Lin, V. S.
Y. Acc. Chem. Res. 2007, 40, 846−853. (b) Mukherjee, D.; Thompson,
R. R.; Ellern, A.; Sadow, A. D. ACS Catal. 2011, 1, 698−702.
(17) (a) Liu, L. J.; Wang, F.; Shi, M. Organometallics 2009, 28, 4416−
4420. (b) Gordillo, A.; Forigua, J.; Lopez-Mardomingo, C.; de Jesus, E.
Organometallics 2011, 30, 352−355. (c) Ohta, H.; Fujihara, T.; Tsuji,
Y. Dalton Trans. 2008, 379−385. (d) Ohmura, T.; Oshima, K.;
Taniguchi, H.; Suginome, M. J. Am. Chem. Soc. 2010, 132, 12194−
12196. (e) Mukhopadhyay, T. K.; Flores, M.; Groy, T. L.; Trovitch, R.
J. J. Am. Chem. Soc. 2014, 136, 882−885.
ACKNOWLEDGMENTS
■
This work was partially supported by the National Natural
Science Foundation of China for project nos. 51321062,
21274143, and 21361140371.
REFERENCES
■
(1) Gao, Y.; Harada, K.; Hata, T.; Urabe, H.; Sato, F. J. Org. Chem.
1995, 60, 290−291.
(18) Mou, Z.; Liu, B.; Wang, M.; Xie, H.; Li, P.; Li, L.; Li, S.; Cui, D.
Chem. Commun. 2014, 50, 11411−11414.
(2) (a) Campbell, R.; Cannon, D.; Garcia-Alvarez, P.; Kennedy, A.
R.; Mulvey, R. E.; Robertson, S. D.; Sassmannshausen, J.; Tuttle, T. J.
Am. Chem. Soc. 2011, 133, 13706−13717. (b) Coles, M. P.; El-
Hamruni, S. M.; Smith, J. D.; Hitchcock, P. B. Angew. Chem., Int. Ed.
2008, 47, 10147−10150. (c) Lennartson, A.; Hakansson, M.; Jagner, S.
Angew. Chem., Int. Ed. 2007, 46, 6678−6680. (d) Armstrong, D. R.;
Emerson, H. S.; Hernan-Gomez, A.; Kennedy, A. R.; Hevia, E. Dalton
Trans. 2014, 43, 14229−14238. (e) Rit, A.; Spaniol, T. P.; Maron, L.;
Okuda, J. Angew. Chem., Int. Ed. 2013, 52, 4664−4667. (f) Lummis, P.
A.; Momeni, M. R.; Lui, M. W.; McDonald, R.; Ferguson, M. J.;
Miskolzie, M.; Brown, A.; Rivard, E. Angew. Chem., Int. Ed. 2014, 53,
9347−9351. (g) Rit, A.; Zanardi, A.; Spaniol, T. P.; Maron, L.; Okuda,
J. Angew. Chem., Int. Ed. 2014, 53, 13273−13277.
(19) See ref 10 and references therein.
(20) Kraft, S. J.; Sanchez, R. H.; Hock, A. S. ACS Catal. 2013, 3,
826−830.
(21) Yang, J. A.; Tilley, T. D. Angew. Chem., Int. Ed. 2010, 49,
10186−10188.
(22) (a) Peterson, E.; Khalimon, A. Y.; Simionescu, R.; Kuzmina, L.
G.; Howard, J. A. K.; Nikonov, G. I. J. Am. Chem. Soc. 2009, 131, 908−
909. (b) Khalimon, A. Y.; Simionescu, R.; Nikonov, G. I. J. Am. Chem.
Soc. 2011, 133, 7033−7053.
(23) (a) Ushio, H.; Mikami, K. Tetrahedron Lett. 2005, 46, 2903−
́
2906. (b) Gajewy, J.; Kwit, M.; Gawronski, J. Adv. Synth. Catal. 2009,
351, 1055−1063.
(3) Kahnes, M.; Gorls, H.; Gonzalez, L.; Westerhausen, M.
Organometallics 2010, 29, 3098−3108.
(4) (a) Han, R.; Gorrell, I. B.; Looney, A. G.; Parkin, G. J. Chem. Soc.,
(24) Mimoun, H.; de Saint Laumer, J. Y.; Giannini, L.; Scopelliti, R.;
Floriani, C. J. Am. Chem. Soc. 1999, 121, 6158−6166.
(25) Rombach, M.; Brombacher, H.; Vahrenkamp, H. Eur. J. Inorg.
Chem. 2002, 2002, 153−159.
Chem. Commun. 1991, 717−719. (b) Klaui, W.; Schilde, U.; Schmidt,
̈
M. Inorg. Chem. 1997, 36, 1598−1601. (c) Bergquist, C.; Koutcher, L.;
Vaught, A. L.; Parkin, G. Inorg. Chem. 2002, 41, 625−627.
(d) Brombacher, H.; Vahrenkamp, H. Inorg. Chem. 2004, 43, 6042−
6049.
(26) SMART, Version 5.054; Bruker AXS Inc.: Madison, WI, 2000.
(27) SAINT and SADABS, Version 6.22; Bruker AXS Inc.: Madison,
WI, 2000.
(28) Sheldrick, G. M. SHELXTL NT, Version 6.12; Bruker AXS Inc.:
Madison, WI, 2000.
(5) (a) Hao, H.; Cui, C.; Roesky, H. W.; Bai, G.; Schmidt, H.-G.;
Noltemeyer, M. Chem. Commun. 2001, 1118−1119. (b) Spielmann, J.;
Bolte, M.; Harder, S. Chem. Commun. 2009, 6934−6936. (c) Schulz,
S.; Eisenmann, T.; Schmidt, S.; Blaser, D.; Westphal, U.; Boese, R.
Chem. Commun. 2010, 46, 7226−7228. (d) Bendt, G.; Schulz, S.;
Spielmann, J.; Schmidt, S.; Blaser, D.; Wolper, C. Eur. J. Inorg. Chem.
̈
̈
2012, 2012, 3725−3731. (e) Spielmann, J.; Piesik, D.; Wittkamp, B.;
Jansen, G.; Harder, S. Chem. Commun. 2009, 3455−3456.
(6) (a) Zhu, Z.; Fettinger, J. C.; Olmstead, M. M.; Power, P. P.
Organometallics 2009, 28, 2091−2095. (b) Zhu, Z.; Wright, R. J.;
Olmstead, M. M.; Rivard, E.; Brynda, M.; Power, P. P. Angew. Chem.,
Int. Ed. 2006, 45, 5807−5810. (c) Zhu, Z.; Brynda, M.; Wright, R. J.;
Fischer, R. C.; Merrill, W. A.; Rivard, E.; Wolf, R.; Fettinger, J. C.;
Olmstead, M. M.; Power, P. P. J. Am. Chem. Soc. 2007, 129, 10847−
10857.
(7) Coles, M. P.; El-Hamruni, S. M.; Smith, J. D.; Hitchcock, P. B.
Angew. Chem., Int. Ed. 2008, 47, 10147−10150.
(8) (a) Mukherjee, D.; Ellern, A.; Sadow, A. D. J. Am. Chem. Soc.
2010, 132, 7582−7583. (b) Mukherjee, D.; Thompson, R. R.; Ellern,
A.; Sadow, A. D. ACS Catal. 2011, 1, 698−702. (c) Mukherjee, D.;
Ellern, A.; Sadow, A. D. J. Am. Chem. Soc. 2012, 134, 13018−13026.
(9) Sattler, W.; Parkin, G. J. Am. Chem. Soc. 2011, 133, 9708−9711.
(10) Brown, N. J.; Harris, J. E.; Yin, X.; Silverwood, I.; White, A. J. P.;
Kazarian, S. G.; Hellgardt, K.; Shaffer, M. S. P.; Williams, C. K.
Organometallics 2014, 33, 1112−1119.
(11) Rit, A.; Spaniol, T. P.; Okuda, J. Chem. - Asian J. 2014, 9, 612−
619.
(12) Jochmann, P.; Stephan, D. W. Angew. Chem., Int. Ed. 2013, 52,
9831−9835.
(13) (a) Cheng, J. H.; Hou, Z. M. Chem. Commun. 2012, 48, 814−
816. (b) Cheng, J. H.; Wang, H. Y.; Nishiura, M.; Hou, Z. M. Chem.
Sci. 2012, 3, 2230−2233. (c) Rong, W. F.; He, D. L.; Wang, M. Y.;
Mou, Z. H.; Cheng, J. H.; Yao, C. G.; Li, S. H.; Trifonov, A. A.;
Lyubov, D. M.; Cui, D. M. Chem. Commun. 2015, 51, 5063−5065.
(14) Sattler, W.; Parkin, G. J. Am. Chem. Soc. 2012, 134, 17462−
17465.
F
DOI: 10.1021/acs.organomet.5b00413
Organometallics XXXX, XXX, XXX−XXX