1. No category

16:00-
ケイ素-ケイ素三重結合化合物ジシリンとアゾベンゼンとの
反応による Si2N2 四員環ビラジカロイドの合成
Access to a Stable Si2N2 4-Membered Ring with
Non-Kekulé Singlet Biradical Character from a Disilyne
竹内 勝彦 先生
Dr. Katsuhiko Takeuchi
講演者プロフィール
竹内 勝彦（たけうち かつひこ）
京都大学 化学研究所 助教
2007年3月 筑波大学 第一学群 自然学類 化学専攻 卒業
2009年3月 筑波大学大学院 数理物質科学研究科 化学専攻 博士前期課程 修了
2012年3月 筑波大学大学院 数理物質科学研究科 化学専攻 博士後期課程 修了
2012年4月∼2012年4月 トロント大学 博士研究員 (JSPS海外特別研究員)
2013年8月∼現在 京都大学 化学研究所 遷移金属錯体化学研究領域 小澤研究室 助教
Reaxys Prize Club Symposium in Japan 2014.3.28
Reaxys Prize Club Symposium in Japan 2014.3.28
ケイ素―ケイ素三重結合化合物ジシリンとアゾベンゼン
との反応によるSi2N2四員環ビラジカロイドの合成
Access to a Stable Si2N2 4-Membered Ring with
Non-Kekulé Singlet Biradical Character from a Disilyne
N
Si
Si
N
竹内 勝彦
京都大学 化学研究所 遷移金属錯体化学研究領域 小澤研究室
Reaxys Prize Club Symposium in Japan, March 28, 2014
Profile
01
2007年 3月
筑波大学 第一学群 自然学類 化学専攻 卒業（関口研究室）
2009年 3月
筑波大学大学院 数理物質科学研究科 化学専攻 博士前期課程 修了（関口研究室）
2012年 3月
筑波大学大学院 数理物質科学研究科 化学専攻 博士後期課程 修了（関口研究室）
2012年 4月 ∼ 2013年 7月
カナダ トロント大学 JSPS海外特別研究員（Stephan研究室）
2013年 8月 ∼
京都大学 化学研究所 助教（小澤研究室）
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Reaxys Prize Club Symposium in Japan 2014.3.28
Research
02
１．ケイ素–ケイ素三重結合化合物の反応性
disilyne
２．シリルホスフィンのフラストレイティドルイスペアとしての反応性
+
Bulky
Bulky
Lewis Base Lewis Acid
Frustrated Lewis Pair
３．ホスファアルケンを有する多座配位子の研究
tBu
N
Mes*
P
N
P
P
Mes*
P
Mes*
tBu
Research
03
ケイ素―ケイ素三重結合化合物ジシリンとアゾベンゼン
との反応によるSi2N2四員環ビラジカロイドの合成
Ar = 3,5-Me2C6H3
Si2N2 4-membered ring biradicaloid
N
Si
N
2
Si
Reaxys Prize Club Symposium in Japan 2014.3.28
Introduction: Disilyne
Si
04
Si
the first isolable Si=Si double bonded compound
disilene
West (1981)
Me 3Si
Me 3Si
SiMe3
Si
Me 3Si
Robert C. West
University of Wisconsin–Madison
Br
Br
Si
Si
Br
Br
Si
SiMe3
SiMe3
SiMe3
Me 3Si
4 KC8
THF
Me 3Si
Me 3Si
Si
SiMe3
Si
Si
Me 3Si
Si
Me 3Si
SiMe3
SiMe3
SiMe3
the first isolable disilyne 1
Sekiguchi (2004)
Introduction: Disilyne
05
Isolable Disilynes
tBu
Me 3Si
Me 3Si
Me 3Si
Si
SiMe3
Si
Si
Me 3Si
Si
SiMe3
Me 3Si
Me 3Si
SiMe3
SiMe3
Me 3Si
Sekiguchi (2004)
Me 3Si
Si
SiMe3
Si
Me 3Si
Me 3Si
Me 3Si SiMe
3
SiMe3
SiMe3
SiMe3
Sekiguchi (2010)
unsymmetrically substituted disilyne
Me 3Si SiMe
3
SiMe3
Si
Me 3Si
SiMe3
Si
Si
Me 3Si
Me 3Si
Me 3Si
Si
SiMe3
C
SiMe3
Me 3Si
tBu
Si
Si
tBu
SiMe3
C
SiMe3
SiMe3
Iwamoto, Ishida (2013)
the first alkyl substituted disilyne
Tokitoh (2008)
the first aryl substituted disilyne
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Reaxys Prize Club Symposium in Japan 2014.3.28
Introduction: Disilyne
Si1
06
Si2´
Si1´
Si2
137.44(4)º
2.3698(6) Å
2.0622(9) Å
cf. Typical Bond Lengths
Si–Si 2.34 ~ 2.37 Å
Si=Si 2.14 ~ 2.29 Å
Introduction: Disilyne
07
R
160
R
R
C
C
Si
Si
R
140
rmax (pm)
p-orbital
120
R
100
R
s-orbital
80
R
60
C
Si
Ge
Sn
R
Pb
R
Orbital radius of group 14 elements
4
R
Reaxys Prize Club Symposium in Japan 2014.3.28
Introduction: Disilyne
08
E (eV)
HF/6-31G(d)
5.92
LUMO+1
1.88
1.03
0
–6.69
LUMO
–7.10
–10.89
HOMO
H
C
C
H
HOMO–1
Introduction: Disilyne
09
1)
2,3)
or
R2NH
stereo specific
1)
PhC
CH
R2BH
2,4)
disilyne 1
tBuNC
Me3SiCN
Me 3Si
N
N
C
Si
Dsi 2iPrSi
SiMe3
5)
C
Si
Dsi 2iPrSi
Si
SiiPrDsi
SiiPrDsi 2
NC
6)
Si
CN
2
1) R. Kinjo, M. Ichinohe, A. Sekiguchi, N. Takagi, M. Sumimoto, and S. Nagase, J. Am. Chem. Soc., 129, 7766 (2007).
2) K. Takeuchi, M. Ikoshi, M. Ichinohe, and A. Sekiguchi, J. Am. Chem. Soc., 132, 930 (2010).
3) K. Takeuchi, M. Ikoshi, M. Ichinohe, and A. Sekiguchi, J. Organomet. Chem., 696, 1156 (2011).
4) K. Takeuchi, M. Ichinohe, and A. Sekiguchi, Organometallics, 30, 2044 (2011).
5) K. Takeuchi, M. Ichinohe, and A. Sekiguchi, J. Am. Chem. Soc., 130, 16848 (2008).
Dsi
6) K. Takeuchi, M. Ichinohe, and A. Sekiguchi, J. Am. Chem. Soc., 134, 2954 (2012).
5
= CH(SiMe3)2
Reaxys Prize Club Symposium in Japan 2014.3.28
Introduction: Biradicaloid
10
Biradicals
pair of doublet monoradicals
singlet biradical
triplet biradical
biradicaloid
Cyclicbiradicaloids
Niecke (1995)
Bertrand (2002)
Power (2004)
Mes* = 1,3,5-tBu3C6H2
Lappert (2004)
Ar* = C6H3-2,6-(C6H3-2,6-iPr2)2
Reaction with Azobenzenes
11
Ar = 3,5-Me2C6H3
THF
r.t. / in dark
1 day
disilyne 1
THF
r.t. / in dark
<5 min
Si2N2 4-membered ring biradicaloid 2
purple crystals
(y. = 58%)
1)
cf. Power s Work
hexane
E = Ge, Sn
Ar* = C6H3-2,6-(C6H3-2,6-iPr2)2
1) C. Cui, M. M. Olmsted, J. C. Fettinger, G. H. Spikes, and P. P. Power, J. Am. Chem. Soc., 127, 17530 (2005).
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Reaxys Prize Club Symposium in Japan 2014.3.28
Possible Reaction Mechanism
12
Ar
N–N
cleavage
π* LUMO
SiiPrDsi 2
N
Si
Si
Dsi 2iPrSi
N
Ar
Ar
N
Ar
SiiPrDsi 2
N
Si
Si
Si=Si
cleavage
Dsi 2iPrSi
cf. Reaction with 2-Butene
1)
‡
1 day
disilyne 1
or
30 min
hexane
1) R. Kinjo, M. Ichinohe, A. Sekiguchi, N. Takagi, M. Sumimoto, and S. Nagase, J. Am. Chem. Soc., 129, 7766 (2007).
Possible Reaction Mechanism
12
Ar
π* LUMO
N–N
cleavage
SiiPrDsi 2
N
Si
Si
Dsi 2iPrSi
N
Ar
Ar
N
Ar
SiiPrDsi 2
N
Si
Si
Dsi 2iPrSi
Si=Si
cleavage
B3LYP/6-31G(d)
2'
cyclobutene-2'
butadiene-2'
bis(silylene)-2'
0.0 kcal/mol
+43.6 kcal/mol
+29.9 kcal/mol
not found
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Reaxys Prize Club Symposium in Japan 2014.3.28
Molecular Structure of Biradicaloid 2
a purple crystal
from THF
C1
13
1.758(3)
2.4658(15)
2.618(2)
N1
Si2
Si1'
Si1
1.756(3)
Si2'
N1'
C1'
Monoclinic C2/c Z=4
R1 = 0.0394 [I>2σ(I)]
wR2 = 0.1193 [All Data]
GOF = 1.032
Σ(Si1) = 318º
Σ(N1) = 360º
in Å
sum of the internal angles of the ring = 360º
Figure 1. ORTEP drawing and selected structural parameters of 2.
cf. Related Compounds
1)
2)
3)
Σ(Ge) = 322º
Σ(Sn) = 256º
Si–Si = 2.697 Å
1) C. Cui, M. M. Olmsted, and P. P. Power, J. Am. Chem. Soc., 126, 6510 (2004).
2) H. Cox, P. B. Hitchcock, M. F. Lappert, and L. J.-M. Pierssens, Angew. Chem., Int. Ed., 43, 4500 (2004).
3) N. Wiberg, H. Schuster, A. Simon, and K. Peters, Angew. Chem., Int. Ed., 25, 79 (1986).
AIM Analysis of Biradicaloid 2
14
N
2'
Si
2
(Ar = 3,5-Me2C6H3)
Si
N
calc
(exp)
Si–N
1.785 Å
(1.757 Å)
Si···Si
2.651 Å
(2.618 Å)
Σ(Siring)
304º
(318º)
Σ(Nring)
360º
(360º)
Bond Critical Point
Figure 1. Optimized structure and bond paths of the model compound 2'.
B3LYP/6-31G(d)
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Reaxys Prize Club Symposium in Japan 2014.3.28
NMR Studies of Biradicaloid 2
15
skeletal Si
δ 19.4
(Me3Si)2CH
(Me3Si)2CH
δ 1.0, –0.3
2
(Ar = 3,5-Me2C6H3)
iPrSi
Dsi2
(Me3Si)2CH
Me
Ar
2
4
[ppm]
6
8
δ 10.4
iPr
0
50
Figure 1. 1H NMR spectrum of 2 in THF-d8.
25
0
[ppm]
–25
–50
Figure 2. 29Si NMR spectrum of 2 in THF-d8.
cf. Theoretical Studies
GIAO/B3LYP6-311G(3d)//B3LYP6-31G(d)
2' (singlet)
2' (triplet)
planar-2' (TS)
0.0 kcal/mol
δ(skeletal Si) 14.7
+12.8 kcal/mol
+36.8 kcal/mol
δ(skeletal Si) 52.3
UV-Vis Spectrum of Biradicaloid 2
16
[eV]
–0.38
60000
0.02
529 nm [ε = 32000]
40000
LUMO+1
(σ* orbital of Si2N2 ring)
–2.39
[f ]
LUMO
[ε]
–4.60
0.01
20000
b
356 nm
[ε = 4300]
HOMO
a
–5.33
c
0
200
0.00
400
[nm]
600
800
HOMO–1
–8.98
TDDFT Calculation
transition a: 515 nm (f = 0.0115) HOMO–1 → LUMO
HOMO–12
transition b: 514 nm (f = 0.0123) HOMO → LUMO
6π aromaticity?
transition c: 367 nm (f = 0.0016) HOMO → LUMO+1
B3LYP/6-31G(d)
2'
Figure 1. UV-Vis spectrum of 2 in hexane superimposed by the calculated band position of 2' (left) and MOs of 2' (right) .
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Reaxys Prize Club Symposium in Japan 2014.3.28
Aromaticity of Biradicaloid 2
17
in Å
1.7479(14)
1.758(3)
2.618(2)
2.5889(8)
1.756(3)
1.7536(13)
Σ(Si1) = 318º
Σ(N1) = 360º
Σ(Si1)except Cl1 = 325º Σ(N1) = 360º
sum of the internal angles of the ring = 360º
sum of the internal angles of the ring = 360º
Figure 1. Selected structural parameters of biradicaloid 2 (left) and Cl2-adduct 4 (right).
cf. NICS Values of Model Compounds
2'
NICS(1) = –4.2
4'
NICS(1) = –2.1
B3LYP/6-31G(d)
Reactivity of Biradicaloid 2
18
MeOH
(excess)
+
THF
r.t. / 1 h
cis-3
(y. = 65%)
trans-3
closed-shell reactivity
2
Ar = 3,5-Me2C6H3
O1
N1
Si1
N2
Si2
Figure 1. ORTEP drawing of cis-3.
cf.
intra- or inter-molecular H+ transfer
LUMO of 2
10
cis- or trans-3
Reaxys Prize Club Symposium in Japan 2014.3.28
Reactivity of Biradicaloid 2
19
MeOH
(excess)
+
THF
r.t. / 1 h
cis-3
(y. = 65%)
trans-3
closed-shell reactivity
CCl4
(excess) 2
Ar = 3,5-Me2C6H3
N1
Si1
THF
r.t. / 20 min
Cl1'
Si1'
Cl1
N1'
4
(y. = 55%)
radical-type reactivity
Figure 1. ORTEP drawing of 4.
cf. Reactivity of Silyl Radical
No Reaction
MeOH
CCl4
Summary
20
Ar = 3,5-Me2C6H3
disilyne 1
2
• Si2N2 4-membered ring 2 was synthesized by the reaction of disilyne 1 with azobenzen
• NMR data of 2 suggest that 2 has a singlet ground state.
• Theoretical calculations show no bonding interaction between the skeletal Si atoms of 2.
• Although 2 has 6π-electrons in the 4-membered ring, the NICS value indicates small aromaticity.
• Reactions of 2 with MeOH and CCl4 show that 2 has both closed-shell and radical-type reactivity.
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Reaxys Prize Club Symposium in Japan 2014.3.28
Acknowledgment
21
University of Tsukuba
Prof. Dr. Akira Sekiguchi
A/Prof. Dr. Masaaki Ichinohe
Dr. Vladimir Ya. Lee
Dr. Masaaki Nakamoto
and
all members of Sekiguchi,
Stephan, and Ozawa groups!
University of Toronto
Prof. Dr. Doug W. Stephan
Kyoto University
Prof. Dr. Fumiyuki Ozawa
Dr. Masayuki Wakioka
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