Synthesis and properties of stable 1,2-bis(metallocenyl)disilenes: Novel d-π conjugated systems with a Si=Si double bond

Article abstract of DOI:10.1246/bcsj.82.793

Stable 1,2-bis(metallocenyl)disilenes were synthesized for the first time and were characterized by spectroscopic and X-ray crystallographic analyses. On the basis of cyclic voltammograms, (E)-1,2-bis(ferrocenyl)-1,2-bis(2,4,6- triisopropylphenyl)disilene

Full text of DOI:10.1246/bcsj.82.793

© 2009 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 82, No. 7, 793–805 (2009)
793
BCSJ Award Article
Synthesis and Properties of Stable 1,2-Bis(metallocenyl)disilenes:
Novel d-³ Conjugated Systems with a Si=Si Double Bond
Akihiro Yuasa,1 Takahiro Sasamori,1 Yoshinobu Hosoi,2 Yukio Furukawa,2 and Norihiro Tokitoh*1
1Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011
2Department of Chemistry, School of Science and Engineering, Waseda University,
3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555
Received December 12, 2008; E-mail: tokitoh@boc.kuicr.kyoto-u.ac.jp
Stable 1,2-bis(metallocenyl)disilenes were synthesized for the first time and were characterized by spectroscopic
and X-ray crystallographic analyses. On the basis of cyclic voltammograms, (E)-1,2-bis(ferrocenyl)-1,2-bis(2,4,6-
triisopropylphenyl)disilene (1a) was found to be a stable five-electron redox system with four steps, while (E)-1,2-
bis(ruthenocenyl)-1,2-bis(2,4,6-triisopropylphenyl)disilene (1b) showed four-step redox couples with four electrons. The
UV-vis spectra and theoretical calculations for these disilenes suggested that they should be novel d-³ conjugated
systems containing a disilene unit. In addition, chalcogenation reactions of 1a resulted in the formation of new
heterocyclic compounds bearing ferrocenyl units. For example, the first stable 1,2,3,4-dithiadisiletane derivative was
obtained by the sulfurization reaction of 1a.
Organic compounds containing ³-electron systems such as
ethylene, benzene, and ketones are of great importance.
Especially, extended ³-electron-conjugated systems of organic
compounds exhibit lower HOMO-LUMO gaps than those
of olefins, showing unique electronic character and possibly
applicable to semiconductors, organic electroluminescence,
and so on.1 On the other hand, ferrocene is known to show
unique electrochemical properties as a stable redox system.2
d-³ Electron-conjugated systems, e.g., multinuclear transition-
metal complexes bridged by organic ³-conjugated systems
such as phenylene and C=C units, have attracted consid-
erable attention from the viewpoint of their electrochemical
properties.3 Particularly, stable multistep redox systems
should be good model systems for the elucidation of the prop-
erties of mixed-valence states.4 Therefore, there has been much
interest in the chemistry of ferrocene oligomers bearing a
³-electron spacer, e.g., Fc(Ph)C=C(Ph)Fc,5 FcN=NFc,6 and
TbtP=PFc (Fc = ferrocenyl),7 as models of mixed-valence
states (Figure 1).
The first stable disilene as a novel ³-bond system between
two silicon atoms was synthesized and isolated by West and his
co-workers in 1981.8 Since disilenes are highly reactive due to
the weak ³ bond between silicon atoms, kinetic stabilization
should be necessary to isolate and handle disilene derivatives.9
Since the first isolation of the stable disilene, Mes2Si=SiMes2,
numerous examples have been reported for the syntheses and
properties of kinetically stabilized silenes,10 disilenes,9 and
disilynes11 bearing bulky substituents. Recently, a number of
reports on interesting properties of low-coordinated silicon
compounds have attracted much attention, e.g., photochemical
properties, redox behaviors, and magnetic properties. It has
been elucidated that disilenes generally have higher HOMO
and lower LUMO levels than those of olefins due to the smaller
overlap between the 3p orbitals of Si atoms.10 Such unique
properties of disilenes have prompted many chemists to explore
the chemistry of novel extended ³-conjugated systems con-
taining a Si=Si unit from the standpoint of material science.
Recently, Bejan and Scheschkewitz12a and Tamao et al.12b
independently reported the synthesis of novel ³-conjugated
systems containing Si=Si units. These disilenes have extended
³-conjugated systems with bridged and terminal phenylene or
phenyl groups, showing unique photochemical properties
(Figure 2).
SiMe3
Fe
Ph
Fe
Me3Si
Me3Si
Tbt
Ph
Fe
SiMe3
SiMe3
C C
N N
P P
We have preliminarily reported the synthesis of the first
stable 1,2-bis(ferrocenyl)disilene, Tip(Fc)Si=Si(Fc)Tip (1a,
Tip = 2,4,6-triisopropylphenyl), as a novel stable redox system
consisting of a disilene and ferrocenyl units.13 1,2-Bis(ferro-
SiMe3
Fe
Fe
Tbt
Figure 1. d-³ Conjugated systems.
Published on the web July 10, 2009; doi:10.1246/bcsj.82.793

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Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009) BCSJ AWARD ARTICLE
Et
Et
Et
Et
Ar
Ar' Si
Ar
Ar
Ar'
Ar
Ar
Et
Et
Et
Et
Eind
Si
Si
Si Si
Si Ar'
Ph
Ar
Ar = Eind, Ar' = Ph
Ar = Ar' = Tip
Figure 3. ORTEP drawing of 2a (50% probability).
Benezene molecules and hydrogen atoms were omitted
for clarity.
Tip
Figure 2. Extended ³-conjugated systems with disilene
units.
Tip
M
Li
SiCl2
LiNaph
Tip
M
TipSiCl3
Si Si
M
M
THF
–78 °C
THF
–78 °C
Tip
2a: M = Fe
2b: M = Ru
1a: M = Fe
1b: M = Ru
Scheme 1. Syntheses of 1a and 1b.
Figure 4. ORTEP drawing of 2b (50% probability). Hydro-
gen atoms were omitted for clarity.
cenyl)disilene 1a exhibits unique redox properties reflecting the
stable redox system of ferrocene moieties. On the other hand,
ruthenocene, a group 8 metallocene, exhibits higher oxidative
potential [half-wave potential (E1/2) around +0.5 V vs. FcH/
FcH+] than that of ferrocene.14 Thus, ruthenocene should
afford electronic effects different from those shown by
ferrocene toward the Si=Si ³-electron system, were it to be
introduced to the Si=Si unit as in the case of 1a. In this paper,
we describe the synthesis and properties of ferrocenyl- and
ruthenocenyl-substituted disilenes to reveal the effects and role
of metallocene units in the novel d-³ conjugated systems.
The 29Si NMR spectra of 1a and 1b in benzene-d6 showed
characteristic signals at 72.6 (for 1a) and 70.6 ppm (for 1b),
which were in the typical range for the sp2 silicon atom of the
previously reported disilenes (tetraaryldisilenes, 53-66 ppm;
1
tetraalkyldisilenes, 90-103 ppm).9d The H NMR spectra of 1a
and 1b in benzene-d6 exhibited a couple of pseudo triplet peaks
at 3.80 and 3.98 ppm (for 1a) and 4.15 and 4.34 ppm (for 1b),
which could be assigned to the protons of the cyclopentadienyl
rings. Although the 1H NMR spectrum of 1a suggested that the
ferrocenyl and Tip groups should freely rotate around the Si-C
bonds without any steric restriction at rt, two doublet signals
were observed for the methyl groups [CH3(A) and CH3(B) in
Figure 5] of ortho-isopropyl groups. That is, these two methyl
groups (A) and (B) exhibited two independent doublet signals
at 1.514 and 1.529 ppm (at 20 °C), suggesting the trans-bent
structure of 1a in solution as judged by the diastereotopically
independent methyl groups. Interestingly, the two methyl
groups were observed separately at relatively higher field
at elevated temperature (1.496 and 1.514 ppm at 50 °C) as
compared with the case at 20 °C, while other signals showed
almost no change in the VT-1H NMR spectra (20-50 °C).
Accordingly, the trans-bent angle of 1a should slightly change
at 50 °C while maintaining the disilene structure.
Results and Discussion
In Scheme 1 are shown the synthetic routes for the 1,2-
bis(ferrocenyl)disilene 1a and 1,2-bis(ruthenocenyl)disilene
1b. Dichlorosilanes 2a and 2b bearing a Tip group as steric
protection were prepared by reaction of the corresponding
16
metallocenyllithium15 with TipSiCl3 in THF at ¹78 °C in
49% (2a) and 51% (2b) yields, respectively. These dichloro-
silanes 2a and 2b are stable enough to be handled in open air.
The structures of 2a and 2b were characterized by spectro-
scopic and X-ray crystallographic analyses (Scheme 1 and
Figures 3 and 4). The reduction of 2a and 2b with lithium
naphthalenide (2.2 equiv) in THF at ¹78 °C afforded 1,2-
bis(metallocenyl)disilenes 1a (49%) and 1b (53%) as orange-
red and yellow crystals, respectively. After heating the toluene-
d8 solution of 1a in a sealed tube at 90 °C for 10 days, no
change was observed in the 1H NMR spectra, showing the high
thermal stability of 1a in solution. In addition, 1a was found to
be inert toward photoirradiation (medium pressure Hg lamp,
through Pyrexµ glass) in C6D6 solution for 24 h.
Single crystals of 1a and 1b suitable for X-ray crystallo-
graphic analysis were obtained by recrystallization from THF,
and their molecular structures were clearly revealed (Figures 6
and 7 and Table 1). Both disilenes 1a and 1b exhibit trans-
bent conformations as in the case of the previously reported
disilenes, and have a crystallographic center of symmetry at the

A. Yuasa et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009)
795
Figure 5. VT-1H NMR spectra of 1a in benzene-d6 (in the methyl-group region).
Figure 6. ORTEP drawing of 1a (30% probability). A THF
molecule and hydrogen atoms were omitted for clarity.
Figure 7. ORTEP drawing of 1b (50% probability). Hydro-
gen atoms were omitted for clarity.
Table 1. Selected Bond Lengths and Angles of 1a and 1b
Bond lengths/¡
Bond angles/deg
Trans-bent angles/deg
1,2-Bis(ferrocenyl)disilene 1a
Si(1)-Si(1)*
Si(1)-C(1)
Si(1)-C(11)
2.1733(15)
1.848(3)
1.880(3)
C(1)-Si(1)-C(11)
C(1)-Si(1)-Si(1)*
C(11)-Si(1)-Si(1)*
119.31(12)
117.94(10)
115.08(10)
27.9
1,2-Bis(ruthenocenyl)disilene 1b
Si(1)-Si(1)*
Si(1)-C(1)
Si(1)-C(11)
2.1851(12)
1.845(2)
1.887(2)
C(1)-Si(1)-C(11)
C(1)-Si(1)-Si(1)*
C(11)-Si(1)-Si(1)*
115.98(10)
116.26(8)
116.95(7)
32.3
center of the Si=Si bond. The trans-bent angles17 of 1a and 1b
are 27.9 and 32.3°, respectively, in contrast to the case of
Tip2Si=SiTip2, which was reported to have an almost planar
structure. The Si=Si bond lengths of 1a and 1b are 2.1733(15)
and 2.1851(12) ¡, respectively, suggesting the considerable
Si=Si double-bond characters of 1a and 1b in the solid state
as compared with those for the previously reported disilenes
(2.14-2.26 ¡).9 The Si-C (ipso-metallocenyl) bond lengths of
1a [1.848(3) ¡] and 1b [1.845(2) ¡] are slightly shorter than
those of the Si-C (ipso-Tip) bonds [1.880(3) ¡ for 1a, and
1.887(2) ¡ for 1b], suggesting the conjugative interaction
between the ³-electrons of the disilene units with those of the
Cp rings in both 1a and 1b.
state.9 The Raman spectra of 1a and 1b were measured in the
solid state with 532 nm excitation in a degassed and sealed
tube. In Figure 8 are shown the enlarged partial Raman spectra
of 1a and 1b, where the most intense signals were observed at
595 and 600 cm¹1, respectively. Theoretical calculations for 1a
and 1b showed that the ¯sisi vibrational frequencies should be
estimated as 606 and 602 cm ,
¹1 18,19 respectively, which were in
good agreement with the experimentally observed values. Since
the intense Raman shifts corresponding to the Si=Si stretching
for the previously reported disilenes bearing carbon-substitu-
ents are known to be observed in the range from 500 to
¹1 9,20
550 cm
,
the ¯sisi values for 1a and 1b are slightly higher
than those of the previously reported disilenes. Considering
these results, it was found that 1a and 1b exhibit enough Si=Si
double-bond character in the solid state.
Raman spectroscopy may be one of the most useful methods
to evaluate the double-bond character of a disilene in the solid

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Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009) BCSJ AWARD ARTICLE
1b : LUMO
Ru
1a : LUMO
1a
Si
Si
Fe
Fe
Si
Si
Ru
1b : HOMO
1a : HOMO
800
600
400
Si
Fe
Si
Ru
Si
Fe
1b
Ru
Si
Figure 10. Molecular orbitals of 1a and 1b.
800
600
wavenumber / cm-1
400
There have been a number of reports on the electrochemical
properties of tetraaryl- or tetrasilyldisilenes.9,21 The electro-
chemical properties of disilenes are known to depend on their
substituents. For example, tetramesityldisilene showed irrever-
sible waves in oxidation and reduction regions,21 and Tip2-
Si=SiTip2 exhibited irreversible two-electron oxidation and
one-electron reduction waves,21b while silyl-substituted disi-
lenes show irreversible one-electron oxidation and one-electron
reversible and irreversible reduction couples by cyclic voltam-
metry.21b The redox behavior of 1a and 1b was revealed by
cyclic and differential pulse voltammetries, and their voltam-
mograms are shown in Figures 11 and 12, respectively. The
observed redox potentials of 1a and 1b are summarized in
Tables 2 and 3, respectively. In an o-dichlorobenzene solution,
two reversible one-electron redox couples corresponding to the
stepwise oxidation of the two intramolecular redox centers
Figure 8. Raman spectra of 1a (top) and 1b (bottom).
1.0
: 1a
: 1b
0.5
300
250
400
500
600
Wavelength / nm
were observed at E1/2 = +0.05 and +0.24 V (1a) and E1/2
=
Figure 9. UV-vis spectra of 1a and 1b in hexane at rt
(3.0 © 10¹4 mol dm¹3, 1.0 cm cell).
+0.36 and +0.56 V (1b) versus FcH/FcH+. Such electro-
chemical properties of 1a and 1b should be most likely
interpreted in terms of two conjugated oxidative centers, i.e.,
two metallocene units, though the HOMOs of 1a and 1b seem
to dominantly consist of the ³-orbitals of the Si=Si moieties.
Furthermore, both two-step oxidative potentials (E1/2 values) of
1b are higher than those of 1a, probably reflecting the intrinsic
nature of metallocenes, i.e., the higher oxidative potential of
ruthenocene than that of ferrocene. Thus, the electrochemical
properties of metallocenes should be reflected in the unique
redox properties of 1,2-bis(metallocenyl)disilenes 1a and
1b. The difference between the two oxidation potentials are
¦E1/2 = 0.19 (for 1a) and 0.20 (for 1b), respectively, which
are comparable to that of the corresponding carbon analogue,
(E)-Ph(Fc)C=C(Fc)Ph (3) (¦E1/2 = 0.18 V),5a indicating the
significant coupling between the two metallocenyl groups of 1a
and 1b through the Si=Si ³ bond. It should be noted that the
two ruthenocenyl moieties of disilene 1b were found to
electrochemically communicate with each other through the
Si=Si ³-electrons, in contrast to the case of carbon analogue of
1b, (E)-Me(Rc)C=C(Rc)Me (4) (Rc = ruthenocenyl), which is
reported to exhibit only one-step oxidation couples with two-
electrons, indicating no electronic communication between the
two ruthenocenyl moieties bridged by the C=C unit.22 Thus,
the C=C ³-electron system cannot play a role for the d-³
electron conjugation between the two ruthenocenyl moieties
The UV-vis spectra of 1a and 1b in hexane showed two
characteristic absorption maxima at 332 (¾ = 5900) and
427 nm (¾ = 24000) for 1a, and 340 (¾ = 5000) and 430 nm
(¾ = 22000) for 1b, respectively, as shown in Figure 9.
Tetraaryldisilenes generally show absorption maxima around
400-460 nm assignable to the ³-³* electron transitions of the
Si=Si chromophore.9 TD-DFT calculation for 1a and 1b
suggested that the observed absorptions at larger wavelength
(427 nm for 1a and 430 nm for 1b) should be assignable to the
mix of electron transitions from Si=Si ³ (HOMO) to Si=Si ³*
(LUMO) and those from a d-orbital of metallocenyl moiety to
the Si=Si ³*-orbital.18,19 In addition, the absorption observed
at shorter wavelength (332 nm for 1a and 340 nm for 1b)
should be due to the d-³* electron transitions from metal-
locenyl moiety to the Si=Si ³*-orbital. Thus, the two largely
observed absorptions should contain several types of d-³*
electron transitions to some extent on the basis of the
theoretical calculations. The HOMOs and LUMOs of 1a and
1b (Figure 10) predominantly consist of the Si=Si ³- and ³*-
orbitals, respectively, while ³- and d-orbitals of ferrocene and
ruthenocene units should contribute to the frontier orbitals to
some extent. It should be noted that the absorptions for d(M)-
³*(Si=Si) (M = Fe and Ru) electron transitions of 1a and 1b
were clearly observed in the visible light region.

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Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009)
797
Figure 11. Cyclic voltammograms of 1a (top) and 1b (bottom). On the left are reductive regions and on the right are oxidative
regions.
Figure 12. Differential pulse voltammograms of 1a (top) and 1b (bottom). On the left are reductive regions and on the right are
oxidative regions.
probably due to the large difference in size of the orbitals
between ruthenocene and ethylene moieties. The large ³-
orbital of a disilene unit (Si=Si) can be effectively conjugated
with d-orbitals of the ruthenocenyl groups. Therefore, such
effective conjugation between the two ruthenocenyl groups
through Si=Si ³-electrons seems to be observed in the case of
1b. On the other hand, cyclic voltammograms of 1a and 1b
measured in THF solution showed two-step reversible redox
couples in the reduction regions at E1/2 = ¹2.64 (two
electrons) and ¹3.09 V (one electron) for 1a and E1/2
=
¹2.38 (one electron) and ¹2.83 V (one electron) for 1b (vs.
FcH/FcH+), in contrast to the case of 3 and 4, which were
reported to show no evident reduction wave. Such unique
properties of the reductions of 1a and 1b should be affected by
the nature of disilene, since the LUMOs of 1a and 1b mainly
consist of the ³*-orbital of their Si=Si unit. While Mes2Si=

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Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009) BCSJ AWARD ARTICLE
Table 2. Redox Potentials (V vs. FcH/FcH+) of 1a
Oxidationa)
solutions of 1a and 1b to air afforded the corresponding four-
membered ring compounds, 1,3,2,4-dioxadisiletane 5a (81%)
and 5b (93%), while Mes2Si=SiMes2 and Tip2Si=SiTip2 were
reported to undergo oxidation with ambient oxygen leading to
the formation of the corresponding 1,2,3,4-dioxadisiletanes
followed by isomerization giving the 1,3,2,4-dioxadisiletane
derivatives as final products.23 Chemical shifts in the 29Si NMR
spectra were observed at 2.50 ppm for 5a and 12.4 ppm for 5b,
which were within the range of those for the previously reported
carbon-substituted 1,3,2,4-dioxadisiletanes (¹6.4-13.2 ppm).23
Next, 1a was treated with S8 (5 equiv as S) in benzene at rt for
10 min to afford two heterocyclic compounds, thiadisilirane 6
(81%) and 1,2,3,4-dithiadisiletane 7 (13%). In the case of
sulfurization reactions of other stable disilenes, RR¤Si=SiRR¤
(R = R¤ = Mes, R = t-Bu, R¤ = Mes, Tip), with S8 or epi-
sulfide, the corresponding thiadisiliranes were obtained as a sole
product.23a,24 Thus, it should be notable that the sulfurization
reaction of 1a gave 7, which is the first stable 1,2,3,4-
dithiadisiletane derivative. In the 29Si NMR spectra, character-
istic signals were observed at ¹50.8 ppm for 6 and 25.5 ppm for
7, respectively. The observed 29Si NMR chemical shift for 6 was
within the range of those for the previously reported carbon-
substituted thiadisiliranes (¹59.0- ¹28.9 ppm).24 The observed
Epa
Epc
E1/2
+0.10
+0.00
+0.05
+0.28
+0.19
+0.24
Reductionb)
Epc
Epa
E1/2
¹2.71
¹2.58
¹2.64
¹3.14
¹3.04
¹3.09
¹3
a) 0.1 mol dm
(n-Bu)4NB(C6F5)4 in o-DCB, E1/2 (FcH/
FcH+) = +0.34 V vs. Ag/Ag+. b) 0.1 mol dm (n-Bu)4NPF6
in THF, E1/2 (FcH/FcH+) = +0.57 V vs. Ag/Ag+.
¹3
Table 3. Redox Potentials (V vs. FcH/FcH+) of 1b
Oxidationa)
Epa
Epc
E1/2
+0.42
+0.31
+0.36
+0.62
+0.50
+0.56
Reductionb)
¤
value for 7 (25.5 ppm) was reasonably supported by the
si
Epc
Epa
E1/2
¹2.44
¹2.32
¹2.38
¹2.87
¹2.76
¹2.83
GIAO-calculations as described below, while that of the
imaginary species, 1,3,2,4-dithiadisiletane isomer 8, was com-
puted as ¹1.6 ppm at the same calculation level, which is far
from the observed value. It the case of tetraaryl-substituted
1,2,3,4-dioxadisiletanes, i.e., oxygen analogues of 7, the
isomerization reaction occurred to give the corresponding
1,3,2,4-dioxadisiletanes at >¹30 °C.23a,23e However, 7 was
stable even at rt for several days. Although one can simply guess
that 7 was formed by the further sulfurization of thiadisilirane 6
with S8, the reaction of isolated 6 with an excess of S8 in
benzene-d6 at 80 °C resulted in no change even in the presence
of NEt3 as an activator of S8.27 On the contrary, 6 may be formed
by the desulfurization of 7 with loss of one S atom. However, 7
was found to be inert toward an excess of PPh3 in benzene-d6
even at 80 °C. That is, it can be concluded that 6 and 7 should be
generated by the sulfurization of 1a directly and the reaction
should be kinetically controlled. On the other hand, the reaction
of 1a with elemental selenium (grey Se, 10 equiv) in benzene
solution afforded selenadisilirane 9 (95%) exclusively. While
the selenization reactions of stable disilenes are known to give
the corresponding three-, four-, and six-membered ring hetero-
cyclic compounds containing silicon and selenium atoms
depending on the bulkiness and electronic nature of the
substituents on the silicon atoms,25,26,28 Mes2Si=SiMes2 is
known to undergo ready selenization leading to the formation of
the corresponding selenadisilirane derivative.25 Thus, the
reactivity of 1a should be very similar to those of Mes2Si=
SiMes2. Chemical shifts observed in 29Si and 77Se NMR spectra
of 9 were observed at ¹56.4 and ¹310 ppm, respectively, with
29Si and 77Se satellites of 1JSiSe = 77 Hz. Those for Mes-
substituted selenadisilirane were reported to be ¤si = ¹64.8
and ¤se = ¹287, respectively, with 29Si and 77Se satellites of
1JSiSe = 78 Hz.25 As the results of NMR study, it is suggested
that 9 and Mes2Si(®-Se)SiMes2 exhibit structural similarities.
In contrast to the case of the sulfurization of 1a, four-membered
¹3
a) 0.1 mol dm
(n-Bu)4NB(C6F5)4 in o-DCB, E1/2 (FcH/
FcH+) = +0.37 V vs. Ag/Ag+. b) 0.1 mol dm (n-Bu)4NPF6
¹3
in THF, E1/2 (FcH/FcH+) = +0.35 V vs. Ag/Ag+.
SiMes2 was reported to undergo electrochemical reduction
irreversibly,21a the properties of metallocene units should be
reflected in the reversibility of the reduction waves of 1a and
1b, that is, the anionic species of 1a and 1b should be stabilized
by their two metallocene units by effective d-³ conjugation.
Interestingly, the first step of the reduction of 1a should be two-
electron transfer, while that of 1b should concern only one
electron. In addition, both 1a and 1b undergo further reduction
by one electron after the first step, respectively, i.e., they can be
reduced by three (1a) and two (1b) electrons to afford the
corresponding trianion and dianion species. In the case of 1b,
further sweep in the strongly reductive region was unsuccessful
under these conditions. Although the difference of the reductive
potentials between 1a and 1b should be due to the interaction
of the metallocene moieties, such phenomena cannot be
reasonably explained at present. Thus, it was demonstrated
that the metallocenyl groups of 1a and 1b should stabilize the
corresponding anion and cation species, probably due to the
d-³ electronic conjugative interaction, which should lead
to electron delocalization on the extended frontier orbitals
of the Si=Si and metallocenyl moieties, in contrast to the case
21
of tetraaryldisilenes such as Mes2Si=SiMes2 and Tip2Si=
SiTip2,21b which show only irreversible reduction in the cyclic
voltammogram.
We examined the reactions of 1a with elemental chalcogens
(O2, S8, and Se), since a disilene should be a good precursor for
heterocyclic compounds.23-26 At first, the reactions of 1a and 1b
with atmospheric oxygen were examined. Exposure of benzene

A. Yuasa et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009)
799
M
M
Fe
Fe
ambient oxygen
Tip
Tip
M
O
O
Tip
Fe
Tip
Fe
S8
Si Si
Si
Si
+ 7/8 S8
Si Si
Si
Si
C6H6
r.t.
Tip
Tip
Tip
Tip
S
M
1a: M = Fe
1b: M = Ru
5a: M = Fe, 81%
5b: M = Ru, 93%
1a
6
0 kcal/mol (0 kcal/mol)
−55.8 (−51.3)
S
S
S
Si Si
Fe
Tip
Fc Tip
+
Tip Fc
Fc
S8
Si Si
Tip
C6H6
r.t.
M = Fe
Fc
Tip
Si
Si
+ 6/8 S8
6, 81%
7, 13%
Tip
S
S
Fe
7
Se
Si Si
Tip
Fc
Fc
Se
−51.2 (−42.9)
Tip
C6H6
r.t.
M = Fe
9, 95%
Fe
S
S
Tip
Si
Tip
Si
+ 6/8 S8
Scheme 2. Reactivities of 1a and 1b.
Fe
ring compounds such as 1,2,3,4-diselenadisiletane were not
observed. In some previous reports, deselenization is known
to give original low-coordinated species.29 Attempted desele-
nization of 9 in a benzene solution by heating or light
irradiation with a medium pressure mercury lamp in the
presence of PPh3 resulted in no change and no formation of 1a
8
−101.7 (−93.8)
Figure 13. Theoretical calculations for the sulfurization of
1a with elemental sulfur. SCF energies in kcal mol (free
energy, 0 atm, 25 °C) are shown in parenthetical refer-
¹1
ence.30
1
as judged by H NMR spectra (Scheme 2).
We performed theoretical calculations on the relative
reaction heat of sulfurization of 1a leading to the formation
of 6, 7, and the 1,3,2,4-dithiadisiletane isomer 8, where the
reaction heats were estimated as ¹55.8 (for 6), ¹51.2 (for 7),
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
S8
+ 7/8 S8
Si Si
Si
Si
S
¹1
and ¹101.7 kcal mol (1 kcal mol¹1 = 4.184 kJ mol¹1) (for 8)
1a
10
(Figure 13).19,30 1,3,2,4-Dithiadisiletane 8 should be the ther-
modynamic product in the reaction of 1a with S8, while the
obtained products, 6 and 7, should be the kinetic products.
These results are not likely to be specific to ferrocenyl- and
Tip-substituted disilene 1a but general for tetraaryldisilenes,
since theoretical calculations for the reactions of Ph2Si=SiPh2
with S8 leading to the formation of the corresponding
thiadisilirane 10, 1,2,3,4,- and 1,3,2,4-dithiadisiletanes 11
and 12 showed results similar to those for 1a as shown
in Figure 14.19,30 The experimental observation that thermal
transformation of 7 into 1,3,2,4-dithiadisiletane fails even at
140 °C is most likely interpreted in terms of the severe steric
congestion around the two sulfur atoms of 7 due to the
ferrocenyl and Tip groups.
0 kcal/mol (0 kcal/mol) −59.2 (−58.2)
Ph
Ph
Ph
Ph
Si
Si
+ 6/8 S8
S
S
11
−65.2 (−59.8)
Ph
S
Ph
Ph
Si
Si
+ 6/8 S8
Ph
S
12
−112.6 (−107.1)
Single crystals of 5a, 5b, 6, 7, and 9 suitable for X-ray
diffraction study were obtained by recrystallization from
hexane (for 5a, 5b, 6, and 7) and toluene (for 9)
(Figures 15-19). The Si-O bond lengths of 5a and 5b were
ca. 1.67 ¡, which were within the bond lengths between silicon
and oxygen of previously reported 1,3,2,4-dioxadisiletanes
(1.66-1.72 ¡).23 Sums of the internal angles of the central
four-membered ring systems of 5a and 5b were ca. 360° in
both cases, showing the planar structures of the Si-O-
Figure 14. Theoretical calculations for the sulfurization
of Ph2Si=SiPh2 with elemental sulfur. SCF energies
in kcal mol (free energy, 0 atm, 25 °C) are shown in
parenthetical reference.30
¹1
On the other hand, the sum of the internal angles of the Si-S-
S-Si square of 1,2,3,4-dithiadisiletane 7 was found to be ca.
338°, showing its folded-square structure as in the case of Si-O-
O-Si and Sn-S-S-Sn squares of previously reported 1,2,3,4-
dioxadisiletane23e and 1,2,3,4-dithiadistannetane31 derivatives.
23b
Si-O squares, as in the cases of Mes2Si(®-O)2SiMes2 and
Tip2Si(®-O)2SiTip2.23d

800
Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009) BCSJ AWARD ARTICLE
Figure 15. ORTEP drawing of 5a (50% probability).
Hydrogen atoms were omitted for clarity.
Figure 18. ORTEP drawing of 7 [50% probability, side
view (top) and top view (bottom)]. Hydrogen atoms were
omitted for clarity.
Figure 16. ORTEP drawing of 5b (30% probability).
Hydrogen atoms were omitted for clarity.
Figure 19. ORTEP drawing of 9 (50% probability). A
toluene molecule and hydrogen atoms were omitted for
clarity.
shorter than the typical Si-Si single bond lengths (2.33-
2.37 ¡)32 and that of 7 [2.3685(12) ¡]. In previous reports,
tetramesitylchalcogenadisiliranes were found to have slightly
shorter Si-Si bonds, which can be most likely interpreted in
terms of the ³-complex character of chalcogenadisilirane
derivatives.24,25 Thus, 6 and 9 were thought to exhibit consid-
erable ³-complex character of chalcogenadisiliranes (Table 4).
Theoretical calculations for 5a, 5b, 6, 7, and 9 were
performed.19,30 In all cases, the optimized structural parameters
are in good agreement with those experimentally observed. On
the other hand, the ¤si chemical shifts were computed as 1.4
for 5a, ¹2.45 for 5b, ¹56.9 for 6, 28.2 and 26.5 for 7, and
¹53.4 for 9 by GIAO calculations,19,30 the values of which
are reasonably in good agreement with the corresponding
observed chemical shifts, supporting their molecular structures
in solution. In addition, ¤si value of 1,3,2,4-dithiadisiletane 8
was computed as ¹1.6 ppm, showing a large difference from
those observed and calculated for 1,2,3,4-dithiadisiletane 7. In
Figure 17. ORTEP drawing of 6 (30% probability). Hexane
molecule and hydrogen atoms were omitted for clarity.
The structures of the obtained chalcogenadisiliranes, 6 and 9,
were similar to each other with a Si-Si-Ch (Ch = S and Se)
isosceles triangle. The Si-Si bond lengths of 6 and 9 are
2.2782(13) and 2.2876(12) ¡, respectively, which are slightly

A. Yuasa et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009)
801
Table 4. Selected Bond Lengths and Angles of Chalcoge-
nation Products
π -complex
three-membered ring
Ch
Ch
Bond lengths/¡
Bond angles/deg
Ferrocenyldioxadisiletane 5a
Si
Si
Si
Si
Ch = S, Se
Scheme 3. Resonance structures of chalcogenadisilirane.
Si(1)-Si(1)* 2.4111(9)
Si(1)-O(1) 1.6855(12)
Si(1)-O(1)* 1.6798(12)
O(1)-Si(1)-O(1)*
Si(1)-O(1)-Si(1)*
O(1)-Si(1)-Si(1)*
88.48(6)
91.52(6)
44.14(4)
O(1)*-Si(1)-Si(1)* 44.33(4)
of the calculated HOMOs of 6 and 9 were computed to
dominantly consist of ³-orbitals of the Si=Si moiety and ³-
orbitals of the chalcogen atom (S for 7 and Se for 9), indicating
the ³-complex character (Scheme 3).24,25,33
The reactivity of 1a should be predominantly characterized
by the Si=Si unit rather than the ferrocenyl unit. The redox
behavior of chalcogenacyclic compounds with ferrocenyl and
ruthenocenyl groups will be clarified in the future.
Ruthenocenyldioxadisiletane 5b
Si(1)-Si(1)* 2.409(2)
Si(1)-O(1) 1.689(3)
Si(1)-O(1)* 1.675(3)
O(1)-Si(1)-O(1)*
Si(1)-O(1)-Si(1)*
O(1)-Si(1)-Si(1)*
88.55(13)
91.45(13)
44.04(10)
O(1)*-Si(1)-Si(1)* 44.51(9)
Thiadisilirane 6
Conclusion
Si(1)-Si(2) 2.2782(13)
Si(1)-S(1)
Si(2)-S(1)
Si(1)-Si(2)-S(1)
Si(1)-S(1)-S(2)
S(1)-Si(1)-Si(2)
63.30(4)
58.38(4)
58.32(4)
We have successfully synthesized the first stable 1,2-
bis(metallocenyl)disilenes as novel d-³ conjugated systems
with a Si=Si double bond. They are the first disilenes with
functionality afforded by metallocenyl units. They showed
multi-step reversible redox couples in contrast to 1,2-bis-
(metallocenyl)ethenes and tetraaryldisilenes. The d-orbital of
the metal at the metallocenyl center and the ³-orbital of the
disilene units appear to be conjugated via the cyclopentadienyl
rings on the basis of spectroscopic analyses. The d-³ electron
transitions were observed by UV-vis spectra. In addition, we
have succeeded in the synthesis of new ferrocenyl-substituted
heterosilacyclic compounds by the chalcogenation reaction of
1a. Significantly, the first 1,2,3,4-dithiadisiletane was obtained
as a stable compound.
2.1717(13)
2.1702(14)
Dithiadisiletane 7
Si(1)-Si(2) 2.3685(12)
Si(1)-Si(2)-S(2)
Si(2)-Si(1)-S(1)
Si(1)-S(1)-S(2)
Si(2)-S(2)-S(1)
82.19(4)
80.56(4)
88.25(4)
86.88(5)
Si(1)-S(1)
Si(2)-S(2)
S(1)-S(2)
2.1875(12)
2.1782(12)
2.1095(12)
Selenadisilirane 8
Si(1)-Si(2) 2.2876(12)
Si(1)-Se(1) 2.3134(9)
Si(2)-Se(1) 2.3035(8)
Si(1)-Si(2)-Se(1)
Si(1)-Se(1)-Si(2)
Se(1)-Si(1)-Si(2)
60.51(3)
59.40(3)
60.08(3)
Experimental
General Comments. All experiments were performed under
an argon atmosphere unless otherwise noted. All solvents were
purified by standard methods and then dried by using an Ultimate
Solvent System (Glass Contour Co.).34 Solvents used in spec-
troscopy (benzene-d6) were dried by using a potassium mirror and
o-dichlorobenzene was distilled from CaH2. Preparative gel
permeation liquid chromatography (GPLC) was performed on an
LC-908 or LC-918 apparatus equipped with JAI-gel 1H and 2H
columns (Japan Analytical Industry Co., Ltd.) with toluene as an
eluent. 1H NMR (400 or 300 MHz) and 13C NMR (100 or 75 MHz)
spectra were measured in C6D6 with a JEOL AL-400 or -300
spectrometer using signals for C6HD5 (¤ 7.15), C6D5CH3 (¤
2.10), and C6D6 (¤ 128.0) as internal standards for 1H and
13C NMR spectra, respectively. 29Si NMR (59 MHz) spectra were
measured in C6D6 with a JEOL AL-300 spectrometer using the
signal for SiMe4 (¤ 0) in C6D6 as an external standard. 77Se NMR
(76 or 57 MHz) spectra were measured in C6D6 with a JEOL AL-
400 or -300 spectrometer using Ph2Se2 in C6D6 (¤ 460) as an
external standard. High-resolution mass spectral data were ob-
tained on a JEOL JMS-700 spectrometer (FAB) or a Bruker
microTOF (APPI-TOF). Electronic spectra were recorded on a
JASCO V-570 UV-vis spectrometer. Raman spectra were mea-
sured on a Raman spectrometer consisting of a Spex 1877
Triplemate and an EG&G PARC 1421 intensified photodiode
array detector. An NEC GLG 108 He-Ne laser was used for
Raman excitation. The electrochemical experiments were carried
S
S
Fe
Fe
Fe
Fe
Si Si
Si Si
Figure 20. HOMO (left) and LUMO (right) orbitals of 6.
Se
Si
Se
Si
Fe
Fe
Fe
Fe
Si
Si
Figure 21. HOMO (left) and LUMO (right) orbitals of 9.
the case of 9, the calculated ¤se value of ¹321 is similar to
that observed for 9 in C6D6 solution. Thus, the molecular
structures of the newly obtained chalcogenacycles were
reasonably supported by the results of theoretical calculations.
Here, the calculated HOMO of chalcogenadisiliranes 6 and 9
should be notable, since it should be indicative of their
³-complex character (Figures 20 and 21). As expected, both

802
Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009) BCSJ AWARD ARTICLE
out with an ALS 602A electrochemical analyzer using a glassy
carbon disk working electrode, a Pt wire counter electrode, and
Ag/0.01 M AgNO3 reference electrode. The measurements were
carried out in o-dichlorobenzene or THF solution containing 0.1 M
(n-Bu)4NB(C6F5)4 or (n-Bu)4NPF6 as a supporting electrolyte with
scan rates of 10 mV s¹1 in a glovebox filled with argon at ambient
temperature. All melting points were determined on a Yanaco
micro melting point apparatus and are uncorrected. Elemental
analyses were performed by the Microanalytical Laboratory of the
Institute for Chemical Research, Kyoto University. All calcula-
tions were conducted using the Gaussian 03 series of electronic
(59 MHz, rt, C6D6): ¤ 7.59. HRMS (FAB) m/z: Calcd for
C25H3235Cl2102RuSi 532.0694 [M]+. Found 532.0692 [M]+. Anal.
Calcd for C25H32Cl2RuSi: C, 56.38; H, 6.06; Cl, 13.31%. Found:
C, 56.53; H, 6.14; Cl, 13.01%.
Synthesis of (E)-1,2-Bis(ferrocenyl)-1,2-bis(2,4,6-triisopro-
pylphenyl)disilene (1a).
To a THF solution (15 mL) of 2a
(200 mg, 0.410 mmol) was added a THF solution of lithium
naphthalenide (0.300 mol dm¹3, 3.00 mL, 0.900 mmol) at ¹78 °C.
After stirring for 30 min at the same temperature, the reaction
mixture was warmed to room temperature. After the removal of
solvent, the mixture was extracted with hexane several times and
then filtered with Celiteµ. The solvent of the filtrate was removed
under reduced pressure to afford Tip(Fc)Si=Si(Fc)Tip (1a, 84.3
16
structure programs.35 FcI15 and TipSiCl3 were prepared accord-
ing to reported procedures. It was confirmed by frequency
calculations that the optimized structures have minimum energies.
Computation time was provided by the Supercomputer Laboratory,
Institute for Chemical Research, Kyoto University.
mg, 0.101 mmol, 49%). 1a; red crystals; mp 160.4-163.3 °C;
3
1H NMR (300 MHz, rt, C6D6): ¤ 1.28 (d, 12H, p-iPr-Me, JHH
=
6.6 Hz), 1.51 (d, 12H, o-iPr-Me, 3JHH = 6.6 Hz), 1.53 (d, 12H,
o-iPr-Me, 3JHH = 6.6 Hz), 2.89 (sept, 2H, p-iPr-CH, 3JHH = 6.6
Hz), 3.80 (pseudo-t, 4H), 3.96 (s, 10H, Cp), 3.98 (pseudo-t, 4H),
4.29 (sept, 4H, o-iPr-CH, 3JHH = 6.6 Hz), 7.34 (s, 4H, Ar-H);
13C NMR (75 MHz, rt, C6D6): ¤ 24.19 (q), 24.33 (q), 26.39
(q), 34.87 (d), 38.73 (d), 68.77 (s), 69.12 (d), 71.27 (d), 73.42
(d), 121.40 (d), 130.71 (s), 151.85 (s), 156.61 (s); 29Si NMR
(59 MHz, rt, C6D6): ¤ 72.6. UV-vis (hexane) -max/nm (¾) = 332
(5.9 © 103), 427 (2.4 © 104). HRMS (APPI-TOF) m/z Calcd for
C50H6556Fe2Si2 833.3321 [M + H]+. Found 833.3371 [M + H]+.
Anal. Calcd for C50H64Fe2Si2: C, 72.10; H, 7.74%. Found: C,
72.35; H, 7.98%.
Synthesis of Dichloro(ferrocenyl)(2,4,6-triisopropylphenyl)-
silane (2a).
To a THF solution (30 mL) of FcI (914 mg,
¹3
2.93 mmol) was added a pentane solution of t-BuLi (1.58 mol dm
,
3.91 mL, 6.15 mmol) at ¹78 °C. After stirring the solution for
30 min at the same temperature, the reaction mixture was warmed
to room temperature. To the reaction mixture containing the
resulting FcLi was added a THF solution (60 mL) of TipSiCl3
(1.00 g, 2.93 mmol) at ¹78 °C. After stirring for 30 min at the
same temperature, the reaction mixture was warmed to room
temperature. After removal of the solvent, the reaction mixture
was filtered through Celiteµ with hexane, and the solvent of the
filtrate was removed under reduced pressure. The residue was
subjected to GPLC (toluene) to give TipFcSiCl2 (2a, 704 mg,
Synthesis of (E)-1,2-Bis(ruthenocenyl)-1,2-bis(2,4,6-triiso-
propylphenyl)disilene (1b). To a THF solution (5 mL) of 2b
(100 mg, 0.188 mmol) was added a THF solution of lithium
naphthalenide (0.300 mol dm¹3, 1.38 mL, 0.414 mmol) at ¹78 °C.
After stirring for 30 min at the same temperature, the reaction
mixture was warmed to room temperature. After the removal of
solvent, the mixture was extracted with hexane several times and
then filtered with Celiteµ. The solvent of the filtrate was removed
under reduced pressure to afford Tip(Rc)Si=Si(Rc)Tip (1b,
92.0 mg, 0.100 mmol, 53%). 1b; light yellow crystals; mp 180.2-
183.0 °C; 1H NMR (300 MHz, rt, C6D6): ¤ 1.25 (d, 12H, p-iPr-Me,
1.44 mmol, 49%). 2a; orange crystals; mp 162.6-164.0 °C;
3
1H NMR (300 MHz, rt, C6D6): ¤ 1.14 (d, 6H, p-iPr-Me, JHH
=
3
6.6 Hz), 1.22 (d, 12H, o-iPr-Me, JHH = 6.6 Hz), 2.69 (sept, 1H,
p-iPr-CH, 3JHH = 6.6 Hz), 3.91 (sept, 2H, o-iPr-CH, 3JHH = 6.6
Hz), 4.20 (pseudo-t, 2H), 4.23 (s, 5H, Cp), 4.41 (pseudo-t, 2H),
7.12 (s, 2H, Ar-H); 13C NMR (75 MHz, rt, C6D6): ¤ 23.82 (q),
25.09 (q), 33.06 (d), 34.76 (d), 70.48 (d), 72.25 (d), 74.61 (d),
74.74 (s), 122.51 (d), 128.09 (s), 152.62 (s), 156.39 (s); 29Si NMR
(59 MHz, rt, C6D6): ¤ 9.53. HRMS (FAB) m/z: Calcd for
C25H3235Cl256FeSi 486.1001 [M]+. Found 486.1017 [M]+. Anal.
Calcd for C25H32Cl2FeSi: C, 61.61; H, 6.62; Cl, 14.55%. Found:
C, 61.51; H, 6.68; Cl, 14.28%.
3
3JHH = 6.9 Hz), 1.50 (d, 12H, o-iPr-Me, JHH = 6.6 Hz), 1.52 (d,
3
3
12H, o-iPr-Me, JHH = 6.6 Hz), 2.85 (sept, 2H, o-iPr-CH, JHH
=
=
3
6.9 Hz), 4.15 (pseudo-t, 4H), 4.21 (sept, 4H, o-iPr-CH, JHH
Synthesis of Dichloro(ruthenocenyl)(2,4,6-triisopropylphen-
6.6 Hz), 4.34 (pseudo-t, 4H), 4.40 (s, 10H, Cp), 7.30 (s, 4H,
Ar-H); 13C NMR (75 MHz, rt, C6D6): ¤ 24.16 (q), 24.30 (q),
26.49 (q), 34.84 (d), 38.75 (d), 71.27 (s), 71.42 (d), 72.78 (d),
75.48 (d), 121.27 (d), 130.66 (s), 151.74 (s), 156.49 (s); 29Si NMR
(59 MHz, rt, C6D6): ¤ 70.6. UV-vis (hexane) -max/nm (¾) = 340
(5.0 © 103), 430 (2.2 © 104). HRMS (APPI-TOF) m/z Calcd for
C50H65102Ru2Si2 925.2730 [M + H]+. Found 925.2709 [M + H]+.
Anal. Calcd for C50H64Ru2Si2: C, 65.04; H, 6.99%. Found: C,
64.83; H, 7.15%.
yl)silane (2b).
To a THF solution (30 mL) of ruthenocene
(342 mg, 1.48 mmol) was added a pentane solution of t-BuLi
(1.58 mol dm¹3, 1.13 mL, 1.77 mmol) at ¹78 °C. After stirring the
solution for 30 min at the same temperature, the reaction mix-
ture was warmed to room temperature. To the reaction mixture
containing the resulting RcLi was added a THF solution (60 mL)
of TipSiCl3 (500 mg, 1.48 mmol) at ¹78 °C. After stirring for
30 min at the same temperature, the reaction mixture was warmed
to room temperature. After removal of the solvent, the reaction
mixture was filtered through Celiteµ with hexane, and the solvent
of the filtrate was removed under reduced pressure. The residue
was subjected to GPLC (toluene) to give TipRcSiCl2 (2b, 401 mg,
Irradiation of a Benzene Solution of 1a.
A benzene-d6
solution (4 mL) of 1a (5.0 mg, 6.0 ¯mol) in a sealed tube was
irradiated with a medium pressure mercury lamp for 1 h through a
Pyrexµ NMR tube. No change was observed as judged by 1H NMR
spectra.
0.752 mmol, 51%). 2b; colorless crystals; mp 150.0-151.6 °C;
3
1H NMR (300 MHz, rt, C6D6): ¤ 1.16 (d, 6H, p-iPr-Me, JHH
=
Reaction of (E)-1,2-Bis(ferrocenyl)-1,2-bis(2,4,6-triisopro-
3
6.6 Hz), 1.26 (d, 12H, o-iPr-Me, JHH = 6.6 Hz), 2.71 (sept, 1H,
p-iPr-CH, 3JHH = 6.6 Hz), 4.03 (sept, 2H, o-iPr-CH, 3JHH = 6.6
Hz), 4.58 (pseudo-t, 2H), 4.62 (s, 5H, Cp), 4.80 (pseudo-t, 2H),
7.12 (s, 2H, Ar-H); 13C NMR (75 MHz, rt, C6D6): ¤ 23.83 (q),
25.41 (q), 33.32 (d), 34.65 (d), 72.98 (d), 73.82 (d), 76.04 (d),
78.80 (s), 122.52 (d), 127.90 (s), 152.62 (s), 156.46 (s); 29Si NMR
pylphenyl)disilene (1a) with Oxygen.
A benzene solution
(5 mL) of 1a (20.0 mg, 24.0 ¯mol) was exposed to open air at room
temperature. The solution then turned colorless. After removal of
solvent, the reaction mixture was separated by GPLC to afford
corresponding 1,3,2,4-dioxadisiletane, Tip(Fc)Si(®-O)2Si(Fc)Tip
(5a, 16.9 mg, 19.5 ¯mol, 81%). 5a; yellow crystals; sublimation

A. Yuasa et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009)
803
3
point 265.2-266.4 °C; 1H NMR (300 MHz, rt, C6D6): ¤ 1.23 (d,
2.98 (sept, 2H, p-iPr-CH, JHH = 6.6 Hz), 3.98 (m, 2H, Cp), 3.99
(m, 2H, Cp), 4.00 (m, 2H, Cp), 4.03 (m, 2H, Cp), 4.11 (s, 10H,
Cp), 4.81 (sept, 2H, o-iPr-CH, 3JHH = 6.6 Hz), 7.10 (d, 2H, Ar-H,
4JHH = 1.2 Hz), 7.41 (d, 2H, Ar-H, 4JHH = 1.2 Hz); 13C NMR
(75 MHz, rt, C6D6): ¤ 24.03 (q), 24.11 (q), 24.51 (q), 26.22 (q),
26.40 (q), 27.76 (q), 32.99 (d), 34.56 (d), 35.81 (d), 68.88 (d),
70.51 (d), 71.94 (d), 73.82 (s), 74.82 (d), 76.66 (d), 121.47 (d),
122.97 (d), 125.04 (s), 151.09 (s), 151.21 (s), 156.48 (s); 29Si NMR
(59 MHz, rt, C6D6): ¤ 25.5. HRMS (FAB) m/z Calcd for
C50H6456Fe2Si232S2 896.2687 [M]+. Found 896.2690 [M]+. Anal.
Calcd for C50H64Fe2Si2S2: C, 66.95; H, 7.19%. Found: C, 66.63;
H, 6.89%.
3
12H, p-iPr-Me, 3JHH = 6.6 Hz), 1.38 (d, 12H, o-iPr-Me, JHH
=
3
6.6 Hz), 1.64 (d, 12H, o-iPr-Me, JHH = 6.6 Hz), 2.82 (sept, 2H,
p-iPr-CH, 3JHH = 6.6 Hz), 4.02 (ABq, 4H, Cp, 3JHH = 9.6 Hz),
4.03 (sept, 4H, o-iPr-CH, 3JHH = 6.6 Hz), 4.10 (s, 10H, Cp),
4.11 (ABq, 4H, Cp, JHH = 9.6 Hz), 7.41 (s, 4H, Ar-H); 13C NMR
3
(75 MHz, rt, C6D6): ¤ 24.07 (q), 25.30 (q), 25.83 (q), 34.60 (d),
34.80 (d), 68.81 (s), 68.97 (d), 71.81 (d), 74.55 (d), 121.39 (d),
128.53 (s), 151.98 (s), 156.39 (s); 29Si NMR (59 MHz, rt, C6D6): ¤
2.50. HRMS (FAB) m/z Calcd for C50H64O256Fe2Si2 864.3147
[M]+. Found 864.3140 [M]+. Anal. Calcd for C50H64O2Fe2Si2: C,
69.43; H, 7.46%. Found: C, 69.29; H, 7.41%.
Reaction of (E)-1,2-Bis(ruthenocenyl)-1,2-bis(2,4,6-triiso-
propylphenyl)disilene (1b) with Oxygen. A benzene solution
(5 mL) of 1b (20.0 mg, 21.6 ¯mol) was exposed to open air at room
temperature. The solution then turned colorless in next to no time.
After removal of solvent, the reaction mixture was separated by
GPLC to afford corresponding 1,3,2,4-dioxadisiletane, Tip(Rc)-
Si(®-O)2Si(Rc)Tip (5b, 19.2 mg, 20.1 ¯mol, 93%). 5b; colorless
crystals; sublimation point 266.1-270.4 °C; 1H NMR (300 MHz, rt,
Reaction of (E)-1,2-Bis(ferrocenyl)-1,2-bis(2,4,6-triisopro-
pylphenyl)disilene (1a) with Elemental Se.
To a benzene
solution (10 mL) of 1a (20.0 mg, 24.0 ¯mol) was added elemental
selenium (grey Se, 18.9 mg, 0.240 mmol, 10 equiv) at room
temperature and the solution turned orange. The solution was
then filtered with Celiteµ to remove excess Se. After the removal
of solvent, the reaction mixture was separated by GPLC to the
afford corresponding selenadisilirane, Tip(Fc)Si(®-Se)Si(Fc)Tip
(9, 20.7 mg, 22.7 ¯mol, 95%). 9; orange crystals; mp 171.6-
3
C6D6): ¤ 1.20 (d, 12H, p-iPr-Me, JHH = 6.6 Hz), 1.39 (d, 12H,
o-iPr-Me, 3JHH = 6.6 Hz), 1.62 (d, 12H, o-iPr-Me, 3JHH = 6.6 Hz),
172.4 °C; H NMR (300 MHz, rt, C6D6): ¤ 1.15 (d, 6H, o-iPr-Me,
1
3
2.80 (sept, 2H, p-iPr-CH, JHH = 6.6 Hz), 3.90 (sept, 4H, o-iPr-
3JHH = 6.6 Hz), 1.19 (d, 6H, o-iPr-Me, 3JHH = 6.6 Hz), 1.24 (d,
CH, 3JHH = 6.6 Hz), 4.35 (pseudo-t, 4H), 4.37 (pseudo-t, 4H), 4.50
(s, 10H, Cp), 7.25 (s, 4H, Ar-H); 13C NMR (75 MHz, rt, C6D6):
¤ 24.77 (q), 25.72 (q), 25.57 (q), 35.14 (d), 34.91 (d), 67.31
(s), 67.97 (d), 69.87 (d), 72.24 (d), 121.10 (d), 128.84 (s), 151.73
(s), 156.24 (s); 29Si NMR (59 MHz, rt, C6D6): ¤ 12.4. HRMS
(FAB) m/z Calcd for C50H65O2102Ru2Si2 956.2532 [M + H]+.
Found 956.2564 [M + H]+.
6H, o-iPr-Me, 3JHH = 6.6 Hz), 1.25 (d, 6H, o-iPr-Me, JHH
=
3
6.6 Hz), 1.61 (d, 6H, p-iPr-Me, 3JHH = 6.6 Hz), 1.84 (d, 6H, p-iPr-
Me, 3JHH = 6.6 Hz), 2.83 (sept, 2H, o-iPr-CH, 3JHH = 6.6 Hz),
3.69 (sept, 2H, o-iPr-CH, JHH = 6.6 Hz), 3.75 (m, 2H, Cp), 3.86
3
(m, 2H, Cp), 3.93 (m, 2H, Cp), 3.98 (m, 2H, Cp), 4.20 (s, 10H,
Cp), 4.81 (sept, 2H, p-iPr-CH, 3JHH = 6.6 Hz), 7.16 (d, 2H, Ar-H,
4JHH = 1.2 Hz), 7.34 (d, 2H, Ar-H, 4JHH = 1.2 Hz); 13C NMR
(75 MHz, rt, C6D6): ¤ 24.04 (q), 24.07 (q), 24.27 (q), 25.57 (q),
26.09 (q), 26.50 (q), 34.66 (d), 36.38 (d), 37.41 (d), 68.49 (d),
69.05 (s), 70.60 (d), 71.48 (d), 73.26 (d), 76.99 (d), 121.06 (d),
122.68 (d), 127.32 (s), 151.60 (s), 155.51 (s), 157.26 (s); 29Si NMR
(59 MHz, rt, C6D6): ¤ ¹56.4 (s, 1JSiSe = 77 Hz); 77Se NMR
Reaction of (E)-1,2-Bis(ferrocenyl)-1,2-bis(2,4,6-triisopro-
pylphenyl)disilene (1a) with S8.
To a benzene solution
(15 mL) of 1a (50.0 mg, 60.0 ¯mol) was added S8 (9.6 mg,
37.5 ¯mol, 5 equiv as S) at room temperature and the solution
turned orange. The solution was then filtered with Celiteµ to
remove excess S8. After removal of the solvent of the filtration,
the reaction mixture was separated by GPLC to afford the
corresponding thiadisilirane, Tip(Fc)Si(®-S)Si(Fc)Tip (6, 42.0 mg,
48.6 ¯mol 81%) and 1,2,3,4-dithiadisiletane, Tip(Fc)Si(®-S2)Si-
(Fc)Tip (7, 7.25 mg, 8.09 ¯mol 13%). 6; orange crystals; mp
181.2-183.0 °C; 1H NMR (300 MHz, rt, C6D6): ¤ 1.18 (d, 6H,
1
(76 MHz, rt, C6D6): ¤ ¹309.8 (s, JSiSe = 77 Hz). HRMS (FAB)
m/z Calcd for C50H6456Fe280SeSi2 912.2421 [M]+. Found
912.2408 [M]+. Anal. Calcd for C50H64Fe2SeSi2 + C7H8: C,
68.19; H, 7.23%. Found: C, 68.40; H, 7.36%.
Heating 7 in Toluene Solution. A toluene-d8 solution (4 mL)
of 7 (5.0 mg, 5.6 ¯mol) in a sealed tube was heated at 140 °C for
3
3
1
p-iPr-Me, JHH = 6.6 Hz), 1.20 (d, 6H, p-iPr-Me, JHH = 6.6 Hz),
1.23 (d, 6H, o-iPr-Me, 3JHH = 6.6 Hz), 1.25 (d, 6H, o-iPr-Me,
3JHH = 6.6 Hz), 1.62 (d, 6H, o-iPr-Me, 3JHH = 6.6 Hz), 1.84 (d,
20 h. No change was observed as judged by H NMR spectra.
Attempted Sulfurization of 6 in Benzene Solution. To a
benzene-d6 solution (4 mL) of 6 (5.0 mg, 5.6 ¯mol) was added S8
(2.2 mg, 7.0 ¯mol, 10 equiv as S) and NEt3 (1.8 mg, 7.0 ¯mol, 10
equiv as S) in a sealed tube. The sealed tube was then heated at
80 °C for 1 h. No change was observed as judged by 1H NMR
spectra.
3
3
6H, o-iPr-Me, JHH = 6.6 Hz), 2.83 (sept, 2H, o-iPr-CH, JHH
6.6 Hz), 3.71 (sept, 2H, p-iPr-CH, JHH = 6.6 Hz), 3.72 (m, 2H,
=
3
Cp), 3.84 (m, 2H, Cp), 3.91 (m, 2H, Cp), 3.94 (m, 2H, Cp), 4.24
3
(s, 10H, Cp), 4.68 (sept, 2H, o-iPr-CH, JHH = 6.6 Hz), 7.13 (d,
2H, Ar-H, 4JHH = 1.8 Hz), 7.34 (d, 2H, Ar-H, 4JHH = 1.8 Hz);
13C NMR (75 MHz, rt, C6D6): ¤ 24.06 (q), 24.07 (q), 24.50 (q),
25.30 (q), 25.85 (q), 26.25 (q), 34.70 (d), 36.17 (d), 37.12 (d),
68.85 (d), 69.29 (s), 70.66 (d), 71.70 (d), 73.13 (d), 76.83 (d),
122.09 (d), 122.42 (d), 128.12 (s), 151.64 (s), 155.61 (s), 156.95
(s); 29Si NMR (59 MHz, rt, C6D6): ¤ ¹50.8. HRMS (FAB) m/z
Calcd for C50H6456Fe2Si232S 864.2966 [M]+. Found 864.2926
[M]+. Anal. Calcd for C50H64Fe2Si2S: C, 69.43; H, 7.46; S, 3.71%.
Found: C, 69.22; H, 7.73; S, 3.53%. 7; orange crystals; mp 193.4-
Attempted Desulfurization of 7 in Benzene Solution. To a
benzene-d6 solution (4 mL) of 7 (5.0 mg, 5.8 ¯mol) was added
excess PPh3 (14.6 mg, 55.7 ¯mol, 10 equiv) in a sealed tube. The
sealed tube was then heated at 80 °C for 1 h. No change was
1
observed as judged by H NMR spectra.
Attempted Deselenization of 9 in a Benzene Solution. To a
benzene-d6 solution (4 mL) of 9 (5.0 mg, 5.5 ¯mol) was added
excess PPh3 (14.4 mg, 54.8 ¯mol, 10 equiv) in a sealed tube. The
sealed tube was then heated at 60 °C for 3 days or light irradiated
with a medium pressure mercury lamp for 1 h through Pyrexµ
1
195.7 °C; H NMR (300 MHz, rt, C6D6): ¤ 0.91 (d, 6H, p-iPr-Me,
3JHH = 6.6 Hz), 1.18 (d, 6H, p-iPr-Me, 3JHH = 6.6 Hz), 1.28 (d,
glass. No change was observed as judged by H NMR spectra.
1
3
6H, o-iPr-Me, 3JHH = 6.6 Hz), 1.29 (d, 6H, o-iPr-Me, JHH
=
X-ray Crystallographic Analyses of 1a, 1b, 2a, 2b, 5a, 5b,
6, 7, and 9. The intensity data were collected on a Rigaku/MSC
Mercury CCD diffractometer with graphite monochromated
6.6 Hz), 1.53 (d, 6H, o-iPr-Me, 3JHH = 6.6 Hz), 1.94 (d, 6H, o-iPr-
Me, 3JHH = 6.6 Hz), 2.87 (sept, 2H, o-iPr-CH, 3JHH = 6.6 Hz),

804
Bull. Chem. Soc. Jpn. Vol. 82, No. 7 (2009) BCSJ AWARD ARTICLE
Mo K¡ radiation (- = 0.71070 ¡) for 1a, 2a, and 5b and on a
RIGAKU Saturn70 CCD(system) with VariMax Mo Optic using
Mo K¡ radiation (- = 0.71070 ¡) for 1b, 2b, 5a, 6, 7, and 9.
Single crystals suitable for X-ray analysis were obtained by
slow recrystallization from THF (for 1a and 1b), benzene (for 2a
and 2b), hexane (for 5a, 5b, 6, and 7), and toluene (for 9) at room
temperature (Figures 3, 4, 6, 7, and 15-19 and Table 5). Each
crystal was mounted on a glass fiber. The structures were solved
by direct method (SIR-9736) and refined by full-matrix least-
squares procedures on F2 for all reflections (SHELXL-9737). All
hydrogen atoms were placed using AFIX instructions, while all
other atoms were refined anisotropically. Crystallographic data
(excluding structure factors) for the structure reported in this paper
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication nos. CCDC 701201 for 1a,13
CCDC 712630 for 1b, CCDC 701202 for 2a,13 CCDC 712631 for
2b, CCDC 699677 for 5a,38 CCDC 712632 for 5b, CCDC 712633
for 6, CCDC 712634 for 7, and CCDC 699678 for 9.38 Copies of
the data can be obtained free of charge on application to CCDC,
12, Union Road, Cambridge, CB2 1EZ, U.K. (fax: +44 1223
336033; E-mail: deposit@ccdc.cam.ac.uk).
This work was partially supported by Grants-in-Aid for
Creative Scientific Research (No. 17GS0207), Science Re-
search on Priority Areas (Nos. 19027024 and 20036024
“Synergy of Elements”), and the Global COE Program
(“Integrated Materials Science”), Kyoto University from
Ministry of Education, Culture, Sports, Science and Technol-
ogy, Japan.
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