Synthesis, crystal structure, and photoreaction of a disiloxane bearing two 2-(phenylazo)phenyl groups

Article abstract of DOI:10.1016/S0022-328X(03)00447-9

An E,E-1,1,3,3-tetrafluoro-1,3-bis[2-(phenylazo)phenyl]-1,3-disiloxane (E,E-2) was synthesized by hydrolysis of E-trifluoro[2-(phenylazo)phenyl] silane (E-1). Its structure was characterized by ¹H-, ¹³C-, ¹⁹F-, and ²⁹

Full text of DOI:10.1016/S0022-328X(03)00447-9

Journal of Organometallic Chemistry 686 (2003) 192ꢃ197
/
www.elsevier.com/locate/jorganchem
Synthesis, crystal structure, and photoreaction of a disiloxane bearing
two 2-(phenylazo)phenyl groups
Naokazu Kano, Masaki Yamamura, Fuminori Komatsu, Takayuki Kawashima *
Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
Received 3 April 2003; received in revised form 13 May 2003; accepted 13 May 2003
Abstract
An E,E-1,1,3,3-tetrafluoro-1,3-bis[2-(phenylazo)phenyl]-1,3-disiloxane (E,E-2) was synthesized by hydrolysis of E-trifluoro[2-
(phenylazo)phenyl]silane (E-1). Its structure was characterized by 1H-, 13C-, 19F-, and 29Si-NMR spectroscopy and X-ray
crystallographic analysis showing two pentacoordinate silicon atoms with Siꢀ/N interactions. Photoirradiation of E,E-2 caused both
isomerization of the azo group and formation of the corresponding Z-1 in a short time, while upon standing in the dark the E-1 was
formed very slowly.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Silicon; Disiloxane; Isomerization; Irradiation; Azobenzene; X-ray crystallographic analysis
1. Introduction
zo)phenyl groups, which work as both chromophores
and coordination sites and a comparison of its reactiv-
ities with these photoswitched isomers.
Pentacoordinate organosilicon compounds have been
extensively studied because of the considerable interests
in the structures, the properties and reactivities, some of
which are distinct from those of the tetracoordinate ones
[1]. If the pentacoordinate state of a neutral tetravalent
organosilicon compound could be reversibly changed to
the tetracoordinate state by external stimuli such as
light, heat, electricity, and magnetism, without addition
of external reagents, its structure, reactivities, and
various properties would be dramatically changed in
company with the coordination number. On the other
hand, we recently reported the photoswitching of the
coordination state of silicon between penta- and hexa-
coordinate states in an anionic organosilicon compound
bearing a 2-(phenylazo)phenyl group [2]. The intramo-
lecular coordination of an azo unit would also be
applicable to photoswitching of the coordination num-
ber of the silicon between a usual tetracoordinate state
and a high coordinate state, such as pentacoordinate
state. We report here the synthesis and X-ray structural
analysis of a neutral disiloxane bearing two 2-(phenyla-
2. Results and discussion
2.1. Synthesis and spectral properties of a disiloxane
Teterafluorodisiloxane E,E-2 bearing two 2-(phen-
ylazo)phenyl groups was synthesized by hydrolysis of
trifluorosilane E-1 and the subsequent condensation in
wet CDCl3 at room temperature in 23% yield (Scheme 1)
[2,3]. The yield was calculated assuming that 1 mol of E-
1 gave 0.5 mol of E,E-2. The E,E-isomer was obtained
as the sole geometrical isomer of product 2. In the 29Si-
NMR spectra of E,E-2 in CDCl3, it showed the signal at
dSi
ꢀ
/
88.0 as a triplet (1JSiF
ꢁ233 Hz) by coupling with
/
two fluorine nuclei at 25 8C, while the signal due to
1,1,3,3-tetrafluoro-1,3-diphenyl-1,3-disiloxane (3) was
1
observed at lower field (dSi
ꢀ
/
74.0 (t, JSiF
ꢁ
/
260 Hz))
135.80
234 Hz) at 25 8C was split at
96 8C showing an AA?XX? system at dF 132.70,
137.20 with the coupling constants JAA?ꢁ10.0 Hz,
JAX 370.0 Hz, JAX?ꢁ 50.0 Hz, and JXX?ꢁ10.0
Hz. These coupling constants were determined by
[4]. In its VT-19F-NMR spectra, a singlet at dF ꢀ
with satellite peaks (1JSiF
/
ꢁ
/
ꢀ
/
ꢀ
/
ꢀ
/
/
ꢁ
/
ꢀ
/
/
ꢀ
/
/
* Corresponding author. Tel./fax: ꢂ81-3-5800-6899.
/
E-mail address: takayuki@chem.s.u-tokyo.ac.jp (T. Kawashima).
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00447-9

N. Kano et al. / Journal of Organometallic Chemistry 686 (2003) 192ꢃ
/197
193
Table 1
˚
Selected bond lengths (A) and angles (8) for compound E,E-2
Bond lengths
Si1ꢀ
Si1ꢀ
Si1ꢀ
Si1ꢀ
Si1ꢀ
N1ꢀ
/
N2
F1
F2
O1
C1
N2
2.459(3)
1.603(3)
1.582(2)
1.596(3)
1.845(3)
1.259(4)
Si2ꢀ
Si2ꢀ
Si2ꢀ
Si2ꢀ
Si2ꢀ
N3ꢀ
/
N4
F3
F4
O1
C2
N4
2.440(3)
1.602(2)
1.579(2)
1.603(3)
1.843(4)
1.261(4)
/
/
/
/
/
/
/
/
/
/
Bond angles
N2ꢀ
N2ꢀ
N2ꢀ
N2ꢀ
F1ꢀSi1ꢀ
F1ꢀSi1ꢀ
F1ꢀSi1ꢀ
C1ꢀSi1ꢀ
C1ꢀSi1ꢀ
F2ꢀSi1ꢀ
Si1ꢀO1ꢀ
/
Si1ꢀ
Si1ꢀ
Si1ꢀ
Si1ꢀ
/
F1
F2
O1
C1
174.83(11)
81.83(13)
82.36(12)
73.6(1)
N4ꢀ
N4ꢀ
N4ꢀ
N4ꢀ
F3ꢀSi2ꢀ
F3ꢀSi2ꢀ
F3ꢀSi2ꢀ
C2ꢀSi2ꢀ
C2ꢀSi2ꢀ
F4ꢀSi2ꢀ
/
Si2ꢀ
Si2ꢀ
Si2ꢀ
Si2ꢀ
/
F3
F4
O1
C2
175.15(13)
82.13(11)
82.71(11)
73.88(13)
98.74(13)
101.31(13)
101.6(2)
/
/
/
/
/
/
/
/
/
/
/
/
/
/
F2
O1
C1
99.4(1)
/
/
F4
O1
C2
/
/
101.7(1)
101.4(2)
116.1(2)
121.4(1)
112.07(13)
167.3(2)
/
/
Scheme 1.
/
/
/
/
/
/
F2
O1
O1
/
/
F4
O1
O1
118.2(2)
120.2(2)
111.6(1)
comparison to the result of the simulation [5]. Such
coupling patterns and chemical shifts indicate that non-
equivalency of fluorine atoms of each silicon atom of
disiloxane E,E-2 at low temperature is due to a trigonal
bipyramidal (TBP) geometry constructed by the coordi-
nation of nitrogen of each azo group in E-form. Fast
pseudorotation of the ligands compared to the time
scale of NMR spectroscopy would result in a singlet in
the 19F-NMR spectrum at room temperature.
/
/
/
/
/
/
/
/
/
/
Si2
that of tetrafluorosilicate bearing the same ligand
˚
(2.260(3) A) and those of disiloxanes bearing 2-dimethy-
˚
lamino-1-naphthyl groups (2.614(2)ꢃ2.921(2) A), are
much shorter than the sum of the corresponding van
/
˚
der Waals radii (3.65 A) [2,7]. Taking into consideration
that a hypervalent bond is generally long, the intramo-
lecular interaction between N2 and Si1 in E,E-2 seems
to be strong enough to construct a pentacoordinate
structure of the silicon. The structure of E,E-2 is most
likely explained to be an intermediate between tetrahe-
dral structure and TBP structure with a nitrogen and a
fluorine atoms at apical positions and a carbon, an
oxygen, and a fluorine atoms at equatorial positions,
respectively. The pentacoordinate characters, %TBPa
and %TBPe, for two silicon atoms on the average (45.2
and 67.6%, respectively) support this interpretation [8].
2.2. X-ray crystallographic analysis of a disiloxane
Pentacoordinate state of silicon of E,E-2 in the
crystalline state was established by X-ray crystallo-
graphic analysis (Fig. 1). Selected bond lengths and
angles are shown in Table 1. The N2 and N4 atoms of
the azo moieties are directed to the Si1 and Si2 atoms,
respectively, in spite of the steric repulsion derived from
a bulky silyl group [6]. The intramolecular N
˚
distances (2.459(3) and 2.440(3) A), which are between
/
Á Á Á
/
Si
The Si1ꢀ
/
O1ꢀSi2 bond angle (167.3(2)8) shows a typical
/
value for a disiloxane. The azobenzene units are found
to stack in almost parallel in the crystal cell as judged by
the intramolecular distances between two sets of ben-
˚
zene rings (3.4 and 3.6 A). Such a pꢃp stacking is also
/
found between intermolecular benzene rings of E,E-2
˚
(3.7 A).
2.3. Transformation of a disiloxane into a trifluorosilane
Disiloxanes are usually stable in the solution state
under neutral conditions. For example, 3 did not
decompose at all on standing in CDCl3 solution in the
dark at room temperature for 7 days. On the other hand,
the stability of E,E-2 in the solution state makes
contrast to that of 3 although E,E-2 is stable in the
air in the crystalline state.
Upon standing in the dark at room temperature for 2
days, the CDCl3 solution of E,E-2 gave E-1 (56%)
Fig. 1. ORTEP drawing of E,E-2 with thermal ellipsoid plot (30%
probability for all non-hydrogen atoms).

194
N. Kano et al. / Journal of Organometallic Chemistry 686 (2003) 192ꢃ197
/
Scheme 4.
tetracoordinate 2-(phenylazo)phenylsilanes suggesting
the perturbation of the electronic structure of the azo
Scheme 2.
moiety [6]. Irradiation (lꢁ360 nm) of E,E-2 in CDCl3
/
(8 mM) at room temperature with a high-pressure Hg
lamp equipped with a monochromator for 2 h gave Z-1
(64%) and Z,Z-2 (19%) (Scheme 5) [3]. In VT-19F-NMR
together with a mixture of at least two oligosiloxanes 42
and 43 in 55% conversion (Scheme 2) [3]. Oligosiloxanes
4n were characterized by FABMS spectra (m/zꢁ
/
998
754
spectra, the signal of Z,Z-2 was observed at dF ꢀ
/
134.74
[F(PhNꢁ
/
NC6H4SiFO)3SiF2C6H4Nꢁ
/
NPh]ꢂ,
NPh]ꢂ).
as a sharp singlet and did not split even at ꢀ60 8C in
/
[F(PhNꢁ
/
NC6H4SiFO)2SiF2C6H4Nꢁ
/
contrast to that of E,E-2. These results suggest that
fluorine nuclei are equivalent or exchange rapidly
compared with the time scale of 19F-NMR spectro-
Furthermore, almost quantitative formation of only
trifluorosilane E-1 by treatment of these products with
scopy. In 29Si-NMR spectrum at ꢀ
Z,Z-2 was observed at dSi ꢀ
/
60 8C, the signal of
excess BF3×/OEt2 also supports this characterization.
74.8 as a triplet (1JSiF
ꢁ
/
251
The formation mechanism of E-1 from E,E-2 is
explained as follows. Since the nucleophilicity and
electrophilicity of the fluorine and silicon atoms, respec-
tively, in pentacoordinate E,E-2 are increased by the
/
Hz), which shifted significantly downfield compared to
that of E,E-2. The chemical shift is similar to that of 3.
These results indicate that Z,Z-2 bears a tetracoordi-
nate silicon atom in the absence of the coordination of
the nitrogen atom. This is because the configuration of
the lone pair of the nitrogen atom in Z-form of each
azobenzene is too far away from the silicon to coordi-
nate. These results clearly indicate the coordination
number change of the silicon atoms from five to four by
irradiation. Compounds Z-1 and Z,Z-2 thus obtained
are thermally labile, and they completely disappeared to
give E-1 (92%) together with unidentified polymer-like
formation of the Siꢀ/N hypervalent bond, a fluorine
atom which is formed probably by hydrolysis of E,E-2
with a trace amount of water in the reaction solution can
attack readily at the silicon of E,E-2 inter- or intramo-
lecularly giving E-1 and the corresponding silyloxide
anion E-5 (Scheme 3). Subsequent attack of the result-
ing E-5 at the silicon atom of E,E-2 affords the
corresponding trisiloxane 42 with elimination of a
fluoride ion, whereas attack of E-5 at the silicon atom
of 42 gives the corresponding tetrasiloxane 43. The
fluoride ion thus generated is used again for the above
attack at E,E-2 and constitutes a catalytic cycle. In fact,
treatment of E,E-2 with 0.1 molar equivalent of
tetrabutylammonium fluoride in THF at room tempera-
ture also yielded E-1 (72%) (Scheme 4) [3]. This result
indicates that a catalytic amount of fluoride ion can
induce transformation of the disiloxane 2 into the
corresponding trifluorosilane 1 and about one equiva-
lent of fluoride ion of 1 thus obtained must originate
1
products showing a broad signal in H- and 19F-NMR
spectra within 5 h upon standing at room temperature in
the dark [3]. Interestingly, neither E,E-2 nor E,Z-2 was
observed in the reaction mixture (Scheme 6).
The formation mechanism of Z-1 from E,E-2 by
irradiation is unclear at present. However, considerable
acceleration of the transformation reaction by irradia-
tion compared to that in the dark and no observation of
E,Z-isomer of 2 suggests the possibility that E,Z-2 is a
reactive intermediate and that it undergoes a similar
fluoride ion catalyzed reaction to give E-1 and silyloxide
ion Z-5, the latter of which affords unidentified poly-
mer-like products in a different manner from that of
silyloxide anion E-5, for example, generation of the
from the Siꢀ
/
F bond of the tetrafluorodisiloxane.
2.4. Irradiation of a disiloxane
In UVꢃ
imum assignable to pꢃ
nm (oꢁ3.0ꢄ
104) in CDCl3. The color of E,E-2 is
/
vis spectrum of E,E-2, an absorption max-
/
p* transition was observed at 341
/
/
yellow in sharp contrast to red of previously reported
Scheme 3.
Scheme 5.

N. Kano et al. / Journal of Organometallic Chemistry 686 (2003) 192ꢃ
/197
195
using Fleon† as an external standard. Preparative gel
permeation liquid chromatography (GPLC) was per-
formed by LC-908 with JAIGEL 1H and 2H columns
(Japan Analytical Industry) with toluene as solvent.
Elemental analysis was performed by the Microanalyt-
ical Laboratory of Department of Chemistry, Faculty of
Science, The University of Tokyo.
Scheme 6.
4.2. Synthesis of E,E-1,1,3,3,-tetrafluoro-1,3-bis[2-
(phenylazo)phenyl]-1,3-disiloxane (E,E-2)
corresponding silanone, fluoro[2-(phenylazo)phenyl]sil-
anone, by elimination of fluoride ion of Z-5 followed by
polymerization. On contrary, irradiation of 3 resulted in
no reaction under similar conditions. For the photo-
reaction, the photoisomerized E,Z-isomer of 2 is
strongly suggested to act as a key intermediate for
formation of Z-1, considering formation of Z,Z-2 and
Z-1 without observation of E,Z-2 and decomposition of
Z,Z-2 giving neither E,Z-2 nor E,E-2 but E-1. The
intermediary E,Z-2 would have a suitable conformation
to afford E-1, Z-1 and Z-5.
A CDCl3 solution of E-trifluoro[2-(phenylazo)phe-
nyl]silane (E-1) (2.07 g, 7.77 mmol) containing excess
amount of water was allowed to stand at room
temperature for 8 h to give E,E-1,1,3,3-,-tetrafluoro-
1,3-bis[2-(phenylazo)phenyl]-1,3-disiloxane
(E,E-2)
(0.466 g, 23%). After the solvent was removed in vacuo,
the residue was washed with hexane to give a crude
solid. Recrystallization from ether gave yellow crystals
of E,E-2. E,E-2: yellow crystals, m.p. 79.1ꢃ
/
80.0 8C. 1H-
NMR (500 MHz, CDCl3) d 7.32ꢃ7.43 (m, 8H), 7.61 (dt,
/
4
3
3Jꢁ
4Jꢁ
4H), 7.87 (d, 3Jꢁ
/
7.6 Hz, Jꢁ
/
1.5 Hz, 2H), 7.66 (dd, Jꢁ
/
7.2 Hz,
1.2 Hz,
3. Conclusion
3
4
/
1.1 Hz, 2H), 7.82 (dd, Jꢁ
/
7.9 Hz, Jꢁ
/
/
7.6 Hz, 2H). 13C{1H}-NMR (126
We achieved synthesis and crystallographic analysis
of a neutral disiloxane bearing two pentacoordinate
silicon atoms. Irradiation of disiloxane E,E-2 caused
not only isomerization of the azo group, but also
formation of trifluorosilane Z-1 in a short time, whereas
upon standing in the dark the CDCl3 solution of
disiloxane E,E-2 gave E-1 very slowly. It is interesting
that irradiation caused considerable acceleration of the
formation of the trifluorosilane although further inves-
tigation is needed for the elucidation of reason for this
acceleration. Considering the inertness of 3 for such a
transformation reaction, both in the dark and under
irradiation, the coordination of azo group to silicon
seems to play an important role in the present reaction.
2
MHz, CDCl3) d 115.75 (t, JCF
128.98 (s), 129.18 (s), 129.49 (s), 132.06 (s), 133.09 (s),
137.55 (s), 148.07 (s), 155.97 (s). 19F-NMR (254 MHz,
ꢁ24.3 Hz), 123.20 (s),
/
1
CDCl3) d ꢀ
MHz, CDCl3) d ꢀ
(CHCl3) lmax 341 nm (oꢁ
/
135.85 (s, JSiF
ꢁ
234.9 Hz). 29Si-NMR (99
/
1
/
88.0 (t, JSiF
ꢁ
/
233.2 Hz). UVꢃvis
104). Anal. Calc. for
/
ꢁ
/
/
3.0ꢄ
/
C24H18F4N4OSi2: C, 56.46; H, 3.55; N, 10.97. Found: C,
56.58; H, 3.83; N, 10.68%.
4.3. X-ray crystallographic analysis of disiloxane E,E-2
[9]
4.3.1. Crystallographic data
E,E-2: C24H18F4N4OSi2, monoclinic, P21/n, aꢁ
/
˚
9.8623(5), bꢁ
91.0350(9)8, Vꢁ
Tꢁ110 K, mꢁ
2.1 cmꢀ1, R1ꢁ
0.142, GOFꢁ0.84.
/
21.102(2), cꢁ
/
11.1851(5) A, bꢁ
/
4. Experimental
3
˚
/
2327.4(2) A , Zꢁ
/
4, FWꢁ510.60,
0.050, wR2(all data)ꢁ
/
/
/
/
/
4.1. General comments
/
Trifluorosilane E-1 and disiloxane 3 were prepared
according to the literatures [2,4]. Solvents were purified
by reported methods before use. All reactions were
carried out under argon atmosphere unless otherwise
noted. The yields of the products derived from E,E-2
were calculated assuming that 1 mol of E,E-2 gave 1
mol of the products in each case [3]. Melting points were
4.3.2. Data collection and reduction
A yellow chip crystal of E,E-2 having approximate
dimensions of 0.70ꢄ0.15ꢄ0.05 mm was mounted on a
/
/
glass fiber. All data for E,E-2 were recorded on a
Rigaku Mercury CCD diffractometer with graphite
˚
monochromated Moꢃ
/
Ka radiation (lꢁ0.71070 A). Of
/
1
uncorrected. The H-NMR (500 MHz), 13C-NMR (126
the 23 438 reflections which were collected, 4720 were
unique; equivalent reflections were merged. Data were
collected and processed using CrystalClear (Rigaku).
The data were corrected for Lorentz and polarization
effects.
MHz), 29Si-NMR (99 MHz) spectra were measured with
a JEOL A500 spectrometer using tetramethylsilane as
an external standard. The 19F-NMR (254 MHz) spectra
were taken with a JEOL EXcalibur270 spectrometer

196
N. Kano et al. / Journal of Organometallic Chemistry 686 (2003) 192ꢃ197
/
4.3.3. Structure solution and refinement
4.7. Irradiation of disiloxane E,E-2
The structure was solved by direct methods (SIR-92)
and expanded using Fourier techniques. The non-
hydrogen atoms were refined anisotropically. Hydrogen
atoms were refined isotropically. The final cycle of full-
matrix least-squares refinement on F2 was based on 4720
observed reflections and 334 variable parameters and
converged with unweighted and weighted agreement
factors of R1 (0.050) and wR2 (0.142), respectively. All
calculations were performed using the CrystalStructure
(Rigaku and MSC).
A CDCl3 solution (0.5 ml) of E,E-2 (8 mM) was
irradiated with a high-pressure Hg lamp equipped with a
monochromator to give Z-trifluoro[2-(phenylazo)phe-
nyl]silane (Z-1) (64%) and Z,Z-2 (19%). The reaction
solution was allowed to stand in the dark at room
temperature for 5 h to give E-1 (92%) together with
polymer-like products which showed broad signals in
1H- and 19F-NMR spectra and high molecular weight
1
peak in GPLC. Z-1: H-NMR (270 MHz, CD2Cl2) d
6.23 (d, 3Jꢁ
/
7.3 Hz, 1H), 6.82 (dd, 3Jꢁ
/
8.0 Hz, 4Jꢁ
/
1.5
7.5 Hz, 4Jꢁ
Hz, 2H), 7.25ꢃ
/
7.33 (m, 5H), 7.92 (dd, 3Jꢁ
/
/
4.4. Attempted decomposition of disiloxane 3 in the dark
[4]
1.5 Hz, 1H); 19F-NMR (254 MHz, CDCl3) d ꢀ
/
138.00
262.3 Hz); 29Si-NMR (53 MHz, CDCl3) d
1
(s, JSiF
ꢁ
/
1
70.6 (q, JSiF
ꢀ
/
ꢁ
/
261.1 Hz). Z,Z-2. 1H-NMR (270
3
A CDCl3 solution (0.5 ml) of 1,1,3,3-tetrafluoro-1,3-
diphenyl-1,3-disiloxane (3) (ca. 20 mg, 0.07 mmol) was
allowed to stand in the dark at room temperature for 2
days resulting in no reaction. 3: 13C{1H}-NMR (126
MHz, CD2Cl2) d 6.13 (d, Jꢁ
/
8.4 Hz, 1H), 6.79 (d,
7.85 (d, 1H);
134.74 (s); 19F-
134.76 (s); 29Si-
3Jꢁ
19F-NMR (254 MHz, CDCl3, r.t.) d ꢀ
NMR (254 MHz, CDCl3, ꢀ96 8C) d ꢀ
NMR (54 MHz, CDCl3) d ꢀ
/
8.5 Hz, 2H), 7.21ꢃ
/
7.26 (m, 5H), 7.82ꢃ
/
/
/
/
3
MHz, CDCl3) d 123.06 (t, JCF
1
ꢁ
/
27.2 Hz), 128.58 (s),
/
74.8 (t, JSiF
ꢁ251.2 Hz).
/
132.84 (s), 134.33 (s). 19F-NMR (254 MHz, CDCl3) d
1
137.39 (s, JSiF
ꢀ
/
ꢁ
262.6 Hz). 29Si-NMR (99 MHz,
/
1
74.0 (t, JSiF
CDCl3) d ꢀ
/
ꢁ260.1 Hz).
/
Acknowledgements
This study was supported by the Grant-in-Aid for The
21st Century COE Program for Frontiers in Funda-
mental Chemistry (T.K.) and for Scientific Research
(T.K. and N.K.) from the Ministry of Education,
Culture, Sports, Science and Technology of Japan. We
thank Shin-etsu Chemical Co., Ltd, and Tosoh Fine-
chem Corporation for the generous gift of chlorosilanes
and alkyllithiums, respectively.
4.5. Decomposition of disiloxane E,E-2 in the dark and
successive fluorination with BF3×OEt2
/
A CDCl3 solution (0.5 ml) of disiloxane E,E-2 (14
mM) was allowed to stand in the dark at room
temperature for 2 days. The 55% of the starting material
was converted, and triflurosilane E-1 (56%) and a
mixture of oligosiloxanes 4n were formed. The solvent
was removed to give a crude oil which was dissolved in
ether (5 ml). BF3×OEt2 (300 ml, 0.24 mmol) was added to
/
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ether at room temperature and it was stirred for 2 h. The
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1
solvents were removed to give a crude oil, and its H-
and 19F-NMR spectra showed quantitative formation of
triflurosilane E-1. Oligosiloxanes 4n: MS (FAB) m/z 998
(b) R.R. Holmes, Chem. Rev. 90 (1990) 17;
(c) C. Chuit, R.J.P. Corriu, C. Reye, J.C. Young, Chem. Rev. 93
(1993) 1371;
(Mꢂ for a tetrasiloxane 43 (nꢁ
[Mꢂꢀ
[M?ꢂꢀ
[Mƒꢂꢀ
/
3)), 979 [Mꢂꢀ
2)), 735
PhN2], 510 (Mƒꢂ for 2) 491
/
F], 893
/
PhN2], 754 (M?ꢂ for a trisiloxane 42 (nꢁ
F], 649 [M?ꢂꢀ
F].
/
(d) C.Y. Wong, J.D. Woolins, Coord. Chem. Rev. 130 (1994) 175;
(e) R.R. Holmes, Chem. Rev. 96 (1996) 927;
/
/
/
(f) C. Chuit, R.J.P. Corriu, C. Reye, J.C. Young, in: K.-y. Akiba
(Ed.), Chemistry of Hypervalent Compounds, Wiley-VCH, New
York, 1999, p. 81;
(g) M. Kira, L.-C. Zhang, in: K.-y. Akiba (Ed.), Chemistry of
Hypervalent Compounds, Wiley-VCH, New York, 1999, p. 147;
(h) D. Kost, I. Kalikhman, in: S. Patai, Y. Apeloig (Eds.), The
Chemistry of Organic Silicon Compounds, vol. 2, Wiley, New
York, 1998, p. 1339.
4.6. Reaction of disiloxane E,E-2 with
tetrabutylammonium fluoride
To a THF solution (1 ml) of E,E-2 (10.2 mg, 20 mmol)
was added tetrabutylammonium fluoride in THF (0.1
M, 20 ml, 2 mmol) at room temperature for 1.5 h. The
[2] N. Kano, F. Komatsu, T. Kawashima, J. Am. Chem. Soc. 123
(2001) 10778.
[3] The yields of the products were determined by 19F-NMR spectra.
[4] K. Kuroda, N. Ishikawa, Kogyo Kagaku Zasshi 74 (1971) 2132.
[5] The simulation was carried out by using gNMR ver. 4.1.0,
Cherwell Scientific Ltd.
1
solvents were removed to give a crude oil, and its H-
and 19F-NMR spectra showed formation of triflurosil-
ane E-1 (72%).

N. Kano et al. / Journal of Organometallic Chemistry 686 (2003) 192ꢃ
/197
197
[6] N. Kano, F. Komatsu, T. Kawashima, Chem. Lett. (2001) 338.
[7] (a) M. Spieniello, J.M. White, Organometallics 19 (2000) 1350;
(b) K. Tamao, M. Asahara, T. Saeki, S. Feng, A. Kawachi, A.
Toshimitsu, Chem. Lett. (2000) 660.
tion characters of Si1 atom, Lap is F1 atom, and Leq are C1, F2 and
O1 atoms, respectively. For the pentacoordination characters of
Si2 atom, Lap is F3 atom, and Leq are C2, F4 and O1 atoms,
respectively. See, (a) K. Tamao, T. Hayashi, Y. Ito, M. Shiro,
Organometallics 11 (1992) 2099. (b) N. Kano, A. Kikuchi, T.
Kawashima, Chem. Commun., (2001) 2096.
[8] The pentacoordination characters, %TBPa and %TBPe, have been
defined
by
1/3(anꢁ1un )}/(109.58ꢀ
109.58}/(1208ꢀ109.58)ꢄ100, where un and 8n are the angles
Lap Leq and Leq SiꢀLeq, respectively. For the pentacoordina-
Siꢀ
the
following
schemes:
%TBPaꢁ
/
{109.58
3
3
ꢀ/
/
908)ꢄ100,
/
%TBPeꢁ
/
{1/3(anꢁ18n )ꢀ
/
[9] Crystallographic data for the structural analysis has been deposited
with the Cambridge Crystallographic Data Centre, CCDC No.
207212 for compound E,E-2.
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/
ꢀ
/
/
ꢀ
/
/