Syntheses of Sterically Bulky Schiff-Base Magnesium Complexes and Their Application in the Hydrosilylation of Ketones

Article abstract of DOI:10.1002/ejic.201600899

The sterically bulky Schiff-base ligand 1 (L¹H) was treated with CH₃MgI in toluene to give the unexpected homoleptic magnesium complex 2 (L¹MgL¹) in good yield. However, the reaction of sterically more bulky lig

Full text of DOI:10.1002/ejic.201600899

DOI: 10.1002/ejic.201600899
Full Paper
Mg Hydrosilylation Catalysts
Syntheses of Sterically Bulky Schiff-Base Magnesium Complexes
and Their Application in the Hydrosilylation of Ketones
[
a]
[a]
[a]
[a]
[b]
[a]
Mengtao Ma,* Xingchao Shen, Weifan Wang, Jia Li, Weiwei Yao, and Lijun Zhu*
1
Abstract: The sterically bulky Schiff-base ligand 1 (L H) was structures of all new magnesium complexes were determined
treated with CH MgI in toluene to give the unexpected homo- by single-crystal X-ray diffraction. All new magnesium com-
3
1
1
leptic magnesium complex 2 (L MgL ) in good yield. However, plexes have been investigated as catalysts for the hydrosilyl-
the reaction of sterically more bulky ligand 3 (L H) with CH MgI ation of ketones with (EtO) SiH. The study showed that catalytic
2
3
3
in diethyl ether yielded the desired heteroleptic magnesium activity of the Mg–Na dimetallic complex 5 is superior to those
2
iodide 4 [L MgI(OEt )], which was further reduced with sodium of monometallic magnesium complexes 2 and 4 and is applica-
2
to produce the Mg–Na heterodimetallic complex 5. The crystal ble to a series of subatrates.
1
. Introduction
examples of Mg-catalyzed hydrosilylations have been reported
so far. One is the 1,4-hydrosilylation of α,ꢀ-unsaturated esters
Hydrosilylation refers to the addition of organic and inorganic
silicon hydrides to multiple bonds, such as carbon–carbon,
carbon–heteroatom, and heteroatom–heteroatom bonds.
Leo Sommer et al. reported the first example of a hydrosilyl-
ation reaction between trichlorosilane and 1-octene in the pres-
ence of acetyl peroxide 70 years ago. Catalytic reduction of
ketones to secondary alcohols is one of the most fundamental
transformations in organic chemistry. Catalytic hydrosilylation is
one of the most important and convenient methods for the
catalyzed by magnesium hydridoborate recently reported by
[21]
Sadow and co-workers.
The other one is the hydrosilylation
[
1–6]
of 2-adamantanone and benzophenone with phenylsilane
PhSiH ) as hydride source catalyzed by a series of sterically
(
3
demanding magnesium phosphinoamide complexes at 70 °C
[
7]
[22]
reported by Stasch et al.
There is no previous report of
hydrosilylation catalyzed by Mg/metal dimetallic complexes to
date.
On the other hand, Schiff-base ligands are popular in coordi-
nation chemistry and catalytic chemistry due to their ease of
[
8–13]
reduction of C=O bonds.
The hydrosilylation of ketones
gives in a single step silyl ethers, which can be easily trans-
formed into alcohols by an additional hydrolysis step. The most
common mechanisms for the metal-catalyzed hydrosilylation
include conventional oxidative addition/reductive elimination,
hydride abstraction involving Lewis acid activation, single-elec-
preparation, high yield, and good complexing ability by reac-
[23–28]
tion with metal ions.
Various Schiff-base ligands have
been widely used in transition-metal and p-block-metal chemis-
try. For instance, the catalytic asymmetric syn-selective nitro-
Mannich reaction is promoted by Cu/Sm heterodimetallic
[
14]
tron processes, or σ-bond metathesis. Most catalysts used in
hydrosilylation are transition-metal and main-group metal com-
plexes. For example, Gade et al. recently reported that a chiral
iron alkoxide complex bearing a boxmi pincer as stereodirect-
ing ligand has been employed as catalyst for enantioselective
[29]
Schiff-base complexes.
However, the reports about s-block-
[30–35]
metal Schiff-base compounds are relatively few.
For exam-
ple, Rood et al. have prepared three (salicylaldiminato)magne-
sium complexes and studied the coordination environment
around the magnesium center dependend on the local steric
[
15]
hydrosilylation reactions with high activity and selectivity.
[35]
environment of the ligand.
Subsequently, Chakraborty et al.
However, examples using other earth-abundant metals, such as
alkaline earth metals, are less common. There are only a few
reports about alkene hydrosilylation catalyzed by heavy
group 2 metal complexes, and carbonyl hydrosilylation is much
reported that similar imino(phenoxido)magnesium complexes
were found to be active towards the controlled ring opening
polymerization (ROP) of lactides and the copolymerization of
[37]
carbon dioxide with cyclohexene oxide and styrene oxide.
[
16–20]
less common.
To the best of our knowledge, only two
Encouraged by the excellent reactivity in calcium- and mag-
nesium-catalyzed hydrosilylations of various kinds of ket-
[
21,22,38]
ones,
we became interested in the replacement of pre-
[
[
a] College of Science, Nanjing Forestry University,
Nanjing 210037, People's Republic of China
E-mail: mengtao@njfu.edu.cn
lxyzlj@njfu.edu.cn
www.njfu.edu.cn
b] College of Pharmacy, Nanjing University of Chinese Medicine,
Nanjing 210023, People's Republic of China
cious metal catalysts with cheaper and environmentally more
benign systems such as magnesium, which is inexpensive,
earth-abundant, and biocompatible. Here we report the synthe-
ses and characterization of a series of sterically bulky Schiff-
base magnesium complexes and their applications in the ket-
one hydrosilylation.
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2
. Results and Discussion
is shown in Figure 2. Selected bond lengths and angles for 2
are presented in Table 2. The structure of 2 contains a four-
coordinate magnesium centre in an ideal planar parallelogram
geometry, which is coordinated by two salicylaldiminato li-
gands. This is quite different from the similar Schiff-base mag-
nesium complexes in which the metal centre has a distorted
2
.1 Syntheses of Mg Complexes
A
mixture of 2,4,6-tri-tert-butylaniline, 3,5-di-tert-butyl-2-
hydroxybenzaldehyde and a catalytic amount of p-toluene-
sulfonic acid in ethanol was heated to reflux for 2 d. The
sterically bulky Schiff-base ligand 1 (L H) was obtained as pale-
yellow crystals in high yield (Scheme 1). The formation and mo-
lecular structure of 1 was confirmed by H, C{ H} NMR spec-
troscopy and single-crystal X-ray diffraction. The newly gener-
ated CH=N resonance of ligand 1 appeared at δ = 7.92 ppm in
the H NMR spectrum and at δ = 169.8 ppm in the C{ H} NMR
spectrum. The crystal structure of 1 is shown in Figure 1. Se-
lected bond lengths and angles for 1 are presented in Table 1.
[
36,37]
1
tetrahedral or square-pyramidal geometry.
The bond angle
of N(1)–Mg(1)–N(1)′ is 180.0°, which is the same as that of O(1)–
Mg(1)–O(1)′.
1
13
1
1
13
1
Figure 1. Molecular structure of compound 1. Hydrogen atoms omitted for
clarity.
Table 1. Selected bond lengths [Å] and angles [°] for 1.
N(1)–C(7)
O(1)–C(9)
C(8)–C(9)
1.2805(19)
1.3523(18)
1.406(2)
N(1)–C(6)
C(7)–C(8)
O(1)–H(1)
1.4352(19)
1.453(2)
0.8400
Figure 2. Molecular structure of complex 2. Hydrogen atoms omitted for clar-
ity.
C(7)–N(1)–C(6)
C(9)–C(8)–C(7)
116.02(12)
121.68(13)
N(1)–C(7)–C(8)
O(1)–C(9)–C(8)
123.60(14)
119.98(13)
Table 2. Selected bond lengths [Å] and angles [°] for 2.
Reaction of the ligand 1 with 1 equiv. of CH MgI in toluene
3
Mg(1)–O(1)
N(1)–C(19)
C(19)–C(20)
O(1)–Mg(1)–O(1)′
O(1)–Mg(1)–N(1)
C(21)–O(1)–Mg(1)
1.9596(10)
1.295(2)
1.431(2)
180.0
85.54(5)
137.19(10)
Mg(1)–N(1)
O(1)–C(21)
C(20)–C(21)
O(1)′–Mg(1)–N(1)
N(1)–Mg(1)–N(1)′
C(19)–N(1)–Mg(1)
2.1814(13)
1.3188(19)
1.416(2)
94.46(5)
180.0
afforded the unexpected homoleptic complex 2 as colorless
crystals in moderate yield, which is different from the desired
magnesium iodide complex (Scheme 1). The reaction between
1
and 2 equiv. of CH MgI also produced the same product 2 in
3
123.27(11)
higher yield. The CH=N resonance in complex 2 appeared at
1
δ = 8.05 and 8.30 ppm in the H NMR spectrum and at δ =
1
77.2 and 177.6 ppm in the 13C NMR spectrum, which is down-
We think that the formation of the homoleptic product 2 is
field from those of the free ligand 1. The crystal structure of 2 due to the lesser bulk of ligand 1, which could have an impor-
Scheme 1. Syntheses of 1 and 2.
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Scheme 2. Syntheses of 4 and 5.
tant effect on the final product; hence, it was changed to the
more bulky ligand 3 (L H). Treatment of the ligand 3 with
Table 3. Selected bond lengths [Å] and angles [°] for 4.
2
Mg(1)–I(1)
2.6530(12)
1.880(3)
1.290(4)
1.440(4)
1.312(4)
114.95(9)
89.96(11)
113.16(12)
117.9(2)
122.3(3)
124.4(2)
Mg(1)–N(1)
Mg(1)–O(2)
N(1)–C(8)
C(1)–C(6)
2.062(3)
1
equiv. of CH MgI in diethyl ether afforded the desired magne-
3
Mg(1)–O(1)
N(1)–C(7)
2.001(3)
1.452(4)
1.425(5)
sium iodide 4 as yellow crystals in very high yield (96 %)
Scheme 2). This suggested that the steric hindrance of the sub-
C(6)–C(7)
C(1)–O(1)
(
stituted amine group has a great impact on the structure of the
O(1)–Mg(1)–I(1)
O(1)–Mg(1)–N(1)
O(2)–Mg(1)–N(1)
C(7)–N(1)–Mg(1)
C(1)–C(6)–C(7)
C(1)–O(1)–Mg(1)
O(1)–Mg(1)–O(2)
O(2)–Mg(1)–I(1)
N(1)–Mg(1)–I(1)
N(1)–C(7)–C(6)
O(1)–C(1)–C(6)
105.48(12)
115.17(9)
115.14(9)
127.0(3)
final products. The CH=N resonance in 4 appeared at δ =
1
7
.60 ppm in the H NMR spectrum and at δ = 178.9 ppm in the
1
3
C NMR spectrum. The crystal structure of 4 is shown in Fig-
121.6(3)
ure 3. Selected bond lengths and angles for 4 are presented in
Table 3. The bond length Mg–O(1) between the magnesium
atom and the salicylaldiminato oxygen atom is 1.880(3) Å,
which is much shorter than that of homoleptic complex 2
[
1.9596(10) Å].
were obtained from THF and hexane solution (Scheme 2). The
crystal structure of 5 is shown in Figure 4. Selected bond
lengths and angles for 5 are presented in Table 4.
Figure 4. Molecular structure of the anionic component of complex 5. Substit-
uents in the ligand and hydrogen atoms omitted for clarity.
Figure 3. Molecular structure of complex 4. Hydrogen atoms omitted for clar-
ity.
The geometry of the magnesium atom in 5 is a slightly dis-
We attempted to reduce the iodide complex 4 to prepare torted tetrahedron; it is coordinated by two nitrogen and two
[
39–41]
the corresponding subvalent magnesium(I) complex.
oxygen atoms of the Schiff-base ligands. The sodium center is
However, when it was stirred in the presence of a sodium mirror also four-coordinate, bonded to two oxygen atoms from the
in toluene at room temperature for 2 d, the unexpected di- Schiff-base ligands and two oxygen atoms from the coordi-
metallic complex 5 was generated. Pale-yellow crystals of 5 nated THF molecules, in a distorted tetrahedral geometry. The
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Table 4. Selected bond lengths [Å] and angles [°] for 5.
Complex 5 was also active toward sterically more hindered aryl-
substituted ketones (Table 6, Entries 1–2), although in these
cases, significantly longer reaction times were required to
achieve a high yield at room temperature. The bulky ketone
Mg(1)–O(1)
Mg(1)–N(1)
Na(1)–O(1)
Na(1)–O(3)
N(1)–C(7)
O(1)–C(1)
O(1)–Mg(1)–N(1)
O(2)–Mg(1)–O(1)
O(2)–Mg(1)–N(2)
O(1)–Na(1)–O(2)
O(1)–Na(1)–C(51)
O(2)–Na(1)–C(51)
1.985(4)
2.014(5)
2.291(4)
2.285(4)
1.475(6)
1.341(6)
93.38(17)
96.28(13)
93.56(17)
79.94(11)
97.97(14)
26.80(13)
Mg(1)–O(2)
Mg(1)–N(2)
Na(1)–O(2)
Na(1)– O(4)
N(2)–C(57)
O(2)–C(51)
O(1)–Mg(1)–N(2)
O(2)–Mg(1)–N(1)
N(1)–Mg(1)–N(2)
O(1)–Na(1)–C(1)
O(2)–Na(1)–C(1)
C(1)–Na(1)–C(51)
1.981(3)
2.026(5)
2.307(4)
2.276(5)
1.481(6)
1.331(6)
113.34(18)
113.68(18)
139.73(15)
25.19(13)
95.46(13)
118.65(13)
2
,4,6-trimethylacetophenone resisted the hydrosilylation and
gave a low yield at high temperature after 10 h (Table 6, En-
try 3). Electron-donating substituent such as the methoxy
group in the aryl ring resulted in faster hydrosilylation (Table 6,
Entry 4), while the amino group needed a longer time to reach
high conversion (Table 6, Entry 5). 1-Cyclohexylethanone was
also hydrosilylated in a high yield at room temperature in a
short time (Table 6, Entry 6). The catalytic hydrosilylation activ-
ity of the sterically bulky Schiff-base magnesium complex 5 is
similar to those of similar alkali-metal complexes. For example,
bond length of Mg(1)–O(1) is 1.985(4) Å, which is much longer
than that of 4 [1.880(3) Å]. The bond angle of O(1)–Mg(1)–N(1)
the (silyl)alkali metal [K(L)SiPh ] (L = 18-crown-6 ether) can cata-
3
[
93.38(17)°] is much larger than that of 4 [89.96(11)°]. The ge-
[5]
lyze the hydrosilylation of activated C=C double bonds, and
ometry of the cationic sodium atom in 5 is slightly distorted
square-planar, coordinated by four oxygen atoms of the coordi-
nated THF molecules.
tertiary amides were reduced to enamines under hydrosilylation
conditions with trimethoxy- or triethoxysilane as hydride source
in the presence of catalytic amounts of potassium tert-butoxide
[
43]
(tBuOK); however, slightly higher reaction temperatures (60–
6
5 °C) were needed.
2
.2 Application of Mg Complexes: Catalytic Hydrosilylation
of Ketones
Table 6. Hydrosilylation of ketones under the catalysis of complex 5.
A similar ketone hydrosilylation reaction catalyzed by DippNac-
nacZnH has been reported to yield a mixture of (EtO) -
3
42]
[
SiOCH Ph, (EtO) Si(OCH Ph) , (EtO)Si(OCH Ph) and (EtO) Si.
2
2
2
2
2
3
4
Thus, we used excessive silane to reduce the influence of the
by-product (EtO) Si. In a control experiment, for complexes 2
4
and 4, a higher temperature of 70 °C and a longer time of
22 h were required to ensure full conversions (Table 5, En-
tries 1–2), while the Mg/Na complex 5 afforded a high yield at
room temperature after 2 h (Table 5, Entry 3), which is the most
active catalyst amongst the three new magnesium complexes.
This could be due to an Mg–Na dimetallic collaboration effect.
Compared to (EtO) MeSiH and Et SiH, (EtO) SiH as silane source
2
3
3
is more reactive (Table 5, Entries 4–5). When we further lowered
the catalyst loadings of 5 from 10 % to 3 %, a much longer time
of 48 h was required to ensure full conversion (Table 5, Entry 6).
Table 5. Hydrosilylation of acetophenone by different magnesium catalysts.
Entry
Cat.
R
3
SiH
Time [h] Temp. [°C] Yield [%][a]
1
2
3
4
5
6
2
4
5
5
(EtO)
(EtO)
(EtO)
3
3
3
SiH
SiH
SiH
22
22
2
24
24
48
70
70
25
25
25
25
90
70
93
75
20
91
(EtO)
Et
(EtO)
2
MeSiH
SiH
SiH
1
[
a] Determined by H NMR spectroscopy. [b] 40 °C, 10 h; 80 °C 3 h.
5
3
5 (3 mol-%)
3
1
[
a] Determined by H NMR spectroscopy.
3
. Conclusions
In a simple test reaction, we found that acetophenone was
hydrosilylated by (EtO) SiH in the presence of 10 mol-% of com- A series of sterically bulky Schiff-base magnesium complexes
3
plex 5 at room temperature after 2 h to afford a mixture of were prepared. The crystal structures of all new magnesium
compounds Si(OCHMePh) (OEt) (x = 1–4) (Table 5, Entry 3). complexes have been characterized by single- crystal X-ray dif-
x
4–x
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fraction. It was found that the steric hindrance had an impact temperature and stirred overnight. The mixture was concentrated
to ca. 10 mL. Complex 2 was obtained as colorless crystals at –30 °C
after several days (1.40 g, 64 %). M.p. 240–242 °C. H NMR (600 MHz,
on the structure of the magnesium complexes. We have exam-
ined the catalytic hydrosilylation of ketones by magnesium
complexes and found that the catalytic activity of the Mg/Na
dimetallic complex 5 is superior to those of monometallic mag-
nesium complexes 2 and 4.
1
C D ): δ = 1.03 [s, 9 H, C(CH ) , isomer 1], 1.22 [s, 9 H, C(CH ) ], 1.25
6
6
3 3
3 3
[
s, 9 H, C(CH ) , isomer 1], 1.28 [s, 9 H, C(CH ) ], 1.31 [s, 9 H, C(CH ) ,
3 3 3 3 3 3
isomer 1], 1.38 [s, 9 H, C(CH ) ], 1.46 [s, 18 H, C(CH ) ], 1.60 [s, 9 H,
3
3
3 3
C(CH ) , isomer 1], 1.63 [s, 9 H, C(CH ) , isomer 1], 6.86 (d, J =
3
3
3 3
H-H
2
.4 Hz, 1 H, Ar-H), 7.03 (d, JH-H = 2.4 Hz, 1 H, Ar-H, isomer 1), 7.42
d, JH-H = 2.4 Hz, 1 H, Ar-H, isomer 1), 7.54 (s, 2 H, Ar-H), 7.58 (d,
JH-H = 1.8 Hz, 1 H, Ar-H, isomer 1), 7.61 (d, JH-H = 2.4 Hz, 1 H, Ar-H),
.71 (d, JH-H = 3.0 Hz, 1 H, Ar-H, isomer 1), 8.05 (s, 1 H, CH=N), 8.30
(
Experimental Section
7
General Methods: All air-sensitive compounds were carried out us-
ing standard Schlenk-line or glovebox techniques under high-purity
argon. Diethyl ether, toluene, THF and hexane were dried and dis-
13
1
(
s, 1 H, CH=N, isomer 1) ppm. C{ H} NMR (151 MHz, C D ): δ =
6 6
2
3
1
1
9.9, 30.6, 31.57, 31.64, 31.7, 33.1, 33.6, 33.97, 33.99, 34.8, 35.0, 35.4,
5.7, 35.9, 36.6, 36.7, 38.1, 118.9, 120.1, 123.8, 125.5, 128.4, 129.9,
30.0, 130.7, 131.6, 135.7, 135.9, 141.5, 141.8, 142.2, 142.6, 142.8,
46.7, 147.4, 149.4, 151.7, 167.9, 169.3, 177.2 (CH=N), 177.6 (CH=N)
1
13
1
tilled from molten sodium. H and C{ H} NMR spectra were re-
corded at 25 °C with a Bruker Avance III 600 MHz spectrometer and
were referenced to the resonances of the solvent used. Elemental
analysis was performed by the Elemental Analysis Laboratory of the
Advanced Analysis and Testing Center at Nanjing Forestry Univer-
sity. Melting points were determined with an INESA-WRR apparatus
and are uncorrected. Ligand 3 was prepared according to a litera-
ture procedure.[ Ketones and silanes were degassed and dried
using 4 Å molecular sieves. Other chemicals were purchased and
used without further purification.
ppm. C H MgN O (977.83): calcd. C 81.07, H 10.31, N 2.86; found
66
100
2 2
C 81.36, H 10.52, N 2.61.
Synthesis of Complex 4: MeMgI (1.22 mL, 3.0
M in Et O, 3.66 mmol)
2
was slowly added at –70 °C to a solution of ligand 3 (2.50 g,
.66 mmol) in Et O (30 mL). The suspension was warmed to room
44]
3
2
temperature and stirred overnight. The mixture was concentrated
to ca. 10 mL, hexane was added. Complex 4 was obtained as yellow
1
crystals at room temperature (3.20 g, 96 %). M.p. 229–231 °C.
H
Synthesis of Compound 1: A mixture of 3,5-di-tert-butyl-2-
hydroxybenzaldehyde (2.35 g, 10.04 mmol), 2,4,6-tri-tert-butyl-
aniline (2.63 g, 10.04 mmol), and a catalytic amount of p-toluene-
sulfonic acid (0.35 g, 1.82 mmol) in ethanol (100 mL) was refluxed
for 2 d. The solution was then cooled to ca. 4 °C, ligand 1 was
NMR (600 MHz, C D ): δ = 0.95 [d, J
H-H
= 7.2 Hz, 6 H, CH(CH3)2],
6
6
0
2
5
.97 [m, 6 H, CH (Et O)], 1.28 [s, 9 H, C(CH ) ], 1.67 [s, 9 H, C(CH ) ],
3 2 3 3 3 3
.46 [sept, JH-H = 7.2 Hz, 1 H, CH(CH ) ], 3.50 [m, 4 H, OCH (Et O)],
3 2
2
2
.53 (s, 1 H, CHPh ), 6.29 (s, 1 H, CHPh ), 6.78–7.43 (m, 24 H, Ar-H),
2
2
13
1
1
7.60 (s, 1 H, CH=N) ppm. C{ H} NMR (151 MHz, C D ): δ = 14.1,
obtained as pale-yellow crystals (4.32 g, 90 %). M.p. 178–180 °C. H
6 6
2
1
1
3.7, 29.6, 31.0, 31.3, 31.6, 33.5, 33.6, 35.3, 52.5, 67.0, 126.3, 126.4,
27.0, 127.5, 127.7, 129.8, 130.0, 130.4, 131.0, 138.4, 140.0, 143.3,
NMR (600 MHz, C D ): δ = 1.26 [s, 9 H, C(CH ) ], 1.38 [s, 9 H, C(CH ) ],
6
6
3 3
3 3
1
.39 [s, 18 H, C(CH ) ], 1.65 [s, 9 H, C(CH ) ], 7.03 (d, J = 2.4 Hz,
3
3
3 3
H-H
43.4, 145.9, 146.2, 178.9 (CH=N) ppm. C H IMgNO (908.30):
1
(
H, Ar-H), 7.56 (s, 2 H, Ar-H), 7.63 (d, J
= 2.4 Hz, 1 H, Ar-H), 7.92
54 62
2
H-H
s, 1 H, CH=N), 14.14 (s, 1 H, OH) ppm. 1 C{ H} NMR (151 MHz, C D ):
3
1
calcd. C 71.41, H 6.88, N 1.54; found C 71.73, H 7.07, N 1.21.
6
6
δ = 29.8, 31.6, 31.8, 32.4, 34.3, 35.0, 35.5, 36.1, 118.1, 122.2, 126.8,
28.4, 128.6, 137.8, 140.9, 141.0, 146.0, 148.5, 159.1, 169.8 (CH=N)
ppm.
Synthesis of Complex 5: A solution of complex 4 (2.63 g,
1
2.90 mmol) in toluene (40 mL) was stirred vigorously in the pres-
ence of a sodium mirror (0.50 g, 22 mmol) at room temperature for
2 d. The resultant solution was filtered, all volatiles were removed
in vacuo, and the residue was extracted with THF (30 mL). The
brown-yellow filtrate was concentrated under reduced pressure to
Synthesis of Complex 2: MeMgI (1.50 mL, 3.0
M in Et O, 4.50 mmol)
2
was added dropwise to a solution of ligand 1 (1.08 g, 2.25 mmol)
in toluene (30 mL) at –80 °C. The suspension was warmed to room
Table 7. Crystallographic data for compound 1 and complexes 2, 4 and 5.
1
2
4
5
Empirical formula
Formula mass
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
C
33
H
51NO
C
80
H
116MgN
2
O
2
C
54
H
62IMgNO
2
C
132 2 2 10
H170MgN Na O
477.74
monoclinic
P2
9.2732(4)
27.1163(11)
12.0663(5)
90
1162.05
monoclinic
P2
11.8072(4)
16.6029(6)
18.4271(6)
90
908.25
monoclinic
P2 /n
1
16.2949(8)
25.8245(14)
27.0757(14)
90
2014.98
monoclinic
Cc
30.7838(11)
14.2484(5)
27.4639(11)
90
1
/c
1
/c
ꢀ
γ [°]
V [A ]
Z
[°]
98.4796(14)
90
3001.0(2)
4
100.9702(12)
90
3546.3(2)
2
99.6359(15)
90
11232.9(10)
8
105.0786(12)
90
11631.5(7)
4
3
T [K]
D
130(2)
1.057
130(2)
1.088
130(2)
1.074
130(2)
1.151
calcd. [g cm–3
]
λ [Å]
0.71073
0.062
1056
0.71076
0.071
1276
0.71073
0.615
3792
0.71073
0.082
4360
μ [mm–1
F(000)
]
R
1
(obsd. data)
0.0507
0.1257
1.030
0.0471
0.1008
1.027
0.0611
0.1395
1.030
0.0600
0.1204
1.010
2
wR (obsd. data)
GOF on F2
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ca. 15 mL, and complex 5 was obtained as pale-yellow crystals at
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1
H NMR (600 MHz, C D ): δ = 0.96 [s, 18 H, C(CH ) ], 1.02 [d, J =
6
6
3 3
H-H
[
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3
1
1
3.6, 33.8, 33.9, 34.0, 34.1, 34.5, 35.2, 35.7, 51.9, 52.4, 52.6, 63.8, 67.8,
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[
[
[
C124H148MgN Na O (1864.83): calcd. C 79.87, H 8.00, N 1.50; found
2
2 8
C 80.23, H 8.37, N 1.24.
Typical Procedure for the Catalytic Hydrosilylation of Ketones:
In a glovebox, complex 5 (15.0 mg, 10 mol-%) was added to a
solution of triethoxysilane (27.1 μL, 0.148 mmol) and acetophenone
[
[
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6
6
1
monitored by H NMR spectroscopy; 93 % conversion was achieved
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X-ray Crystal Structure Determination: Crystallographic data for
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F by full-matrix least-squares methods using the SHELXTL crystallo-
2
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[
[
2
1
494875 (for 4) and 1494876 (for 5) contain the supplementary
2
crystallographic data for compound 1) contain the supplementary
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Financial supports from the National Natural Science Founda-
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of Jiangsu Province, China (no. BK20141468, BK20130952), the
Qing Lan Project of Jiangsu Province are gratefully acknowl-
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Keywords: Hydrosilylation · Ketones · Magnesium · Schiff
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Received: July 21, 2016
Published Online: ■
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Mg Hydrosilylation Catalysts
A series of sterically bulky Schiff-base
magnesium complexes have been pre-
pared, which could be used as cata-
lysts for the hydrosilylation of ketones
M. Ma,* X. Shen, W. Wang, J. Li,
W. Yao, L. Zhu* ................................... 1–7
Syntheses of Sterically Bulky Schiff-
Base Magnesium Complexes and
Their Application in the Hydrosilyl-
ation of Ketones
with (EtO) SiH.
3
DOI: 10.1002/ejic.201600899
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim