Synthesis and reactivities of dihydrosilanes tethered with two thioether moieties

Article abstract of DOI:10.1002/hc.20706

Dihydrosilanes tethered with two thioether moieties, [2-(RSCH ₂)C₆H₄]₂SiH₂(1a: R = t-Bu; 1b: R = i-Pr; 1c: R = Ph), were synthesized. Dihydrosilane 1b did not react with methanol, benzaldehyde, and ca

Full text of DOI:10.1002/hc.20706

Heteroatom Chemistry
Volume 22, Number 3/4, 2011
Synthesis and Reactivities of Dihydrosilanes
Tethered with Two Thioether Moieties
Nobuhiro Takeda, Tetsu Nakamura, Ayako Imamura,
and Masafumi Unno
Department of Chemistry and Chemical Biology, and International Education and Research
Center for Silicon Science, Graduate School of Engineering, Gunma University, Kiryu,
Gunma 376-8515, Japan
Received 1 September 2010; revised 27 December 2010
due to their unique structures and reactivities as
ABSTRACT: Dihydrosilanes tethered with two
well as their application to organic synthesis [1,2].
thioether moieties, [2-(RSCH2)C6 H ]2SiH2(1a: R = t-
4
As for five- and six-coordinate neutral silicon com-
Bu; 1b: R = i-Pr; 1c: R = Ph), were synthesized.
pounds intramolecularly coordinated by donors,
Dihydrosilane 1b did not react with methanol, ben-
there have been some compounds intramolecu-
zaldehyde, and carboxylic acids; this result may sug-
larly coordinated by nitrogen atoms; however, five-
gest very weak activation of the Si H bonds in 1b.
and six-coordinate silicon compounds intramolec-
The corresponding dibromosilanes 4 and diiodosi-
ularly coordinated by thioether moieties are very
lanes 5 were synthesized by dihalogenation of 1 us-
few. For example, Jutzi and co-workers have re-
ing N-bromosuccinimide and I2, respectively, whereas
ported the synthesis of some neutral five-coordinate
the dichlorosilanes 3 were synthesized by reaction of 2-
hydrosilanes bearing thioether moiety such as (2-
(RSCH2)C6 H Li with SiCl4. Reaction of 1b with [PtCl2
4
MeSCH2)C6H4SiHXY (X = Y = H; X = Ph, Y =
(cod)] in the presence of Et3N gave the correspond-
OTf; X = H, Y = Cl) [3]; however, the reactivities of
ing bissilylplatinum complex, [Pt{SiH[2-(RSCH2)-
such compounds are rarely known. In this paper, we
C6 H ]2}2], the structure of which was determined by
4
present the synthesis and reactivities of dihydrosi-
lanes 1a–c tethered with two thioether moieties, [(2-
NMR and IR spectrometry and X-ray crystallogra-
ꢀ
C
phy.
2011 Wiley Periodicals, Inc. Heteroatom Chem
RSCH2)C6H4]2SiH2 (1a: R = t-Bu, 1b: R = i-Pr, 1c:
22:438–445, 2011; View this article online at wileyonlineli-
brary.com. DOI 10.1002/hc.20706
R = Ph).
RESULTS AND DISCUSSION
INTRODUCTION
Synthesis and Properties of Dihydrosilanes 1a–c
Much attention has been focused on the chem-
istry of five- and six-coordinate silicon compounds
Synthesis of 1-bromo-2-(tert-butylthiomethyl) ben-
zene 2a and its derivatives were performed by mod-
ifying the reported synthetic method for 2a [4]. Re-
action of 1-bromo-2-bromomethylbenzene [5] with
thiolates prepared from thiols and NaH gave the cor-
responding sulfides 2a–c in good yields (Scheme 1).
Dihydrosilanes 1a–c were synthesized by lithia-
tion of 2a–c with butyllithium in ether at 0◦C fol-
lowed by treatment with SiHCl3, and subsequent
Dedicated to Professor Kin-ya Akiba on the occasion of his 75th
birthday.
Correspondence to: N. Takeda; e-mail: ntakeda@chem-
bio.gunma-u.ac.jp.
Contract grant sponsor: Grant-in-Aid for Scientific Research
(C) from Japan Society for the Promotion of Science.
c
ꢀ
2011 Wiley Periodicals, Inc.
438

Synthesis and Reactivities of Dihydrosilanes Tethered with Two Thioether Moieties 439
Br
Br
together with the formation of H2 [11]. In addition,
it has been reported that thermolysis of the resulting
2a: R = t-Bu, 94%
2b: R = i-Pr, 92%
2c: R = Ph, 95%
RSH, NaH
THF
R
Br
S
silyl carboxylates affords the corresponding aldehy-
des and cyclotrisiloxanes [12]. This activated dihy-
drosilane also undergoes the addition of the Si H
bond to carbonyl moieties of arylaldehydes to af-
ford benzyloxysilanes, hydration of which gives the
corresponding benzylalcohol and disiloxane [11]. In
this paper, we examined reaction of dihydrosilane
1b with methanol, benzaldehyde, acetic acid, and
3-nitrobenzoic acid.
Thermolysis of 1b in methanol at reflux for 13 h,
reaction of 1b with PhCHO in C6D6 at 150◦C for 16
h in a sealed tube, reaction of 1b with CH3CO2H in
C6D6 at 150◦C for 1 h in a sealed tube, and reaction of
1b with 3-NO2C6H4COOH at 150◦C for 1 h, in every
case, resulted in quantitative recovery of the start-
ing material 1b. These results are in sharp contrast
to the reactions of the five-coordinate dihydrosilane
activated by the intramolecular coordination of an
amine moiety, (8-Me2NCH2-1-C10H6)PhSiH2, giving
the corresponding products [11,12]. The low reactiv-
ity of the Si H bonds in 1b may suggest very weak or
no coordination of thioether moieties to the silicon
atom in 1b. These results do not contradict the slight
up-field shift of the 29Si NMR signal of 1b compared
with that of Ph2SiH2.
SCHEME 1 Synthesis of sulfides 2a–c.
°
Br
Li
1) SiHCl3, 0 C ~ r.t.
2) LiAlH4, r.t.
n-BuLi
R
R
R
S
S
°
ether, 0 C
2a–c
S
1a: R = t-Bu, 68%
1b: R = i-Pr, 59%
1c: R = Ph, 55%
H
H
Si
S
R
SCHEME 2 Synthesis of dihydrosilanes 1a–c.
hydrogenation with LiAlH4 (Scheme 2). In this
synthesis of 1a from 2a, a trisubstituted compound,
[2-(t-BuSCH2)C6H4]3SiH [6], was also obtained in
6% yield as a by-product. On the other hand, a sim-
ilar reaction of 1a in THF at −78◦C resulted in the
formation of an unidentifiable mixture along with
t-BuSCH2Ph (41%), which was probably formed by
hydration of 2-(t-BuSCH2)C6H4Li.
It has been known that six- and five-coordinate
silicon compounds show up-field shifts of the 29Si
NMR resonances compared with the corresponding
four-coordinate compounds [3]. For example, {2-
(Me2NCH2)C6H4}NpSiH2 (Np = naphthyl) and (8-
Me2N-1-C10H6)PhSiH2, the X-ray structures of which
indicate five-coordinate trigonal bipyramidal struc-
tures [7,8], show signals at −47.3 and −44.1 ppm,
respectively, in the 29Si NMR spectra, whereas the
29Si NMR spectrum of PhNpSiH2 indicates a res-
onance at −35.6 ppm [8,9]. The 29Si NMR spectra
of dihydrosilanes 1a–c showed slight up-field shifts
(δSi = −41.3 ppm for 1a, −40.9 ppm for 1b, and
−40.1 ppm for 1c) compared with that of Ph2SiH2
(δSi = −34.5 ppm) [10]. These values suggest weak
or no interaction between silicon and sulfur atoms.
Dihalogenation of Dihydrosilanes 1a–c
Attempted dichlorination of 1b with N-
chlorosuccinimide (NCS) or trichloroisocyanuric
acid (TCC) resulted in the formation of a complex
mixture. Therefore, the synthesis of dichlorosilanes
3a, b was examined by reaction of 2-(RSCH2)C6H4Li
with SiCl4. Lithiation of 2a and 2b in ether at 0◦C,
followed by addition of 0.5 molar amounts of SiCl4
at −40◦C resulted in the formation of dichlorosilanes
3a, b (Scheme 3). Although the isolation of 3a was
unsuccessful, dichlorosilane 3b, which was unstable
under the air, was purified by Kugelrohr distillation,
to be isolated in 58% (for 3b) yields.
R
S
Br
Reactivities of Dihydrosilane 1b as Reductant
Cl
Cl
n-BuLi
SiCl4 (0.5 eq)
R
Si
S
It has been reported that Si H bonds are activated
by coordination of nucleophiles such as amines and
fluorides [1]. For example, a five-coordinate dihy-
drosilane activated by intramolecular coordination
of an amine moiety, (8-Me2NCH2-1-C10H6)PhSiH2,
reacts with ROH and RCOOH to give the correspond-
ing alkoxysilanes and silyl carboxylates, respectively,
°
–
ether, 0 C
40°C ~ r.t.
2a,b
S
R
3a: R = t-Bu, ~20%
3b: R = i-Pr, 58%
SCHEME 3 Synthesis of dichlorosilanes 3a, b.
Heteroatom Chemistry DOI 10.1002/hc

440 Takeda et al.
i-Pr
i-Pr
R
S
R
R
R
R
S
S
S
i-Pr
i-Pr
S
S
Pt
S
H
H
Br
Si
Br
H
H
I
I
[PtCl2(cod)], Et3N
CH2Cl2, r.t., 3 d
I2
NBS
i-Pr
Si
Si
Si
Si
Si
benzene
r.t., 12 h
benzene
r.t., 30 min
H H
i-Pr
S
S
S
S
S
R
1b
6b: 5%
4a: R = t-Bu, 92%
4b: R = i-Pr, 96%
4c: R = Ph, 95%
5a: R = t-Bu, 95%
5b: R = i-Pr, 96%
1a–c
SCHEME 5 Reaction of dihydrosilane 1b with [PtCl2(cod)].
SCHEME 4 Synthesis of dibromosilanes 4a–c and diiodosi-
lanes 5a, b.
ference may suggest the five- or six-coordinate struc-
ture of 4a–c. In addition, theoretical calculation for
(2-MeSCH2C6H4)2SiBr2 showed a four-coordinate
structure as an optimized structure, where the cal-
culated 29Si NMR chemical shift (30.5 ppm) is sim-
ilar to that of the optimized structure of Ph2SiBr2
(36.8 ppm), and very different from the observed val-
ues of 4a–c (δSi = −21.9 to −21.3 ppm). These calcu-
lations may also support the five- or six-coordinate
structure of 4a–c.
The 29Si NMR spectra of dichlorosilanes 3a,
b showed signals at −3.6 and −3.2 ppm, respec-
tively, which are shifted to higher field by −10.1
and −9.7 ppm, respectively, compared with the 29Si
NMR chemical shift of Ph2SiCl2 (δSi = 6.5 ppm)
[10]. Since the 29Si NMR chemical shift of
a five-coordinate dichlorosilane, [2-(Me2NCH2)C6
H4]2SiCl2, (δSi = −30.1 ppm) [13] has reportedly
shown the large up-field shift (ꢀδSi = −36.6 ppm)
compared with that of Ph2SiCl2, it may be suggested
that the interaction between the silicon atom and
thioether moieties in dichlorosilanes 3a, b is absent
or very weak.
Dibromosilanes 4a–c and diiodosilanes 5a,
b were successfully synthesized from dihydrosi-
lanes 1a–c. Dihydrosilanes 1 were treated with N-
bromosuccinimide (NBS) and iodine to give the cor-
responding dibromosilanes 4 and diiodosilanes 5,
respectively, in good yields (Scheme 4). Dibromosi-
lane 4b and diiodosilane 5b are highly sensitive to
moisture to afford the corresponding silanediols, [2-
(i-PrSCH2)C6H4]2Si(OH)2.
Reaction of Dihydrosilane 1b with [PtCl2(cod)]
Hydrosilanes have been used for the synthesis of
transition metal complexes bearing silyl ligands,
and some examples for synthesis of silylplatinum(II)
complexes by using hydrosilanes have been reported
[15,16]. Tilley and a co-worker had reported a reac-
tion of bis(8-quinolyl)methylsilane with [PtCl2(cod)]
in the presence of Et3N, giving [PtCl{SiMe(8-
quinolyl)2}] [17], whereas we have recently re-
ported that the reaction of [2-(t-BuSCH2)C6H4]3SiH
with [PtCl2(cod)] in the presence of Et3N affords
[PtCl{Si[2-(t-BuSCH2)C6H4]3}] [6]. We examined
the reaction of dihydrosilane 1b with [PtCl2(cod)]
in the presence of Et3N.
When dihydrosilane 1b was allowed to re-
act with 2.9 molar amounts of [PtCl2(cod)] in
the presence of Et3N in CH2Cl2 at room temper-
ature, bissilylplatinum complex 6b was isolated
in 5% yield (Scheme 5). The similar reaction of
1b with 2.7 molar amounts and an equimolar
amount of [PtCl2(cod)] resulted in the formation
of complex mixtures in both cases. This result
is in sharp contrast to the reaction of triarylsi-
lanes, [2-(RSCH2)C6H4]3SiH (R = t-Bu, i-Pr), with
[PtCl2(cod)], giving the corresponding square planar
platinum(II) complexes [PtCl{Si[2-(RSCH2)C6H4]3}]
with silyl ligand: Pt = 1:1 in good yields [6,18]. The
isolation of bissilylplatinum 6b in low yield may
be explained by the less hindered structure of dihy-
drosilane 1b compared with the triarylsilane, that is,
the 1:1 product of 1b and [PtCl2(cod)], [PtCl{SiH[2-
(i-PrSCH2)C6H4]2}], can further react with 1b or
The 29Si NMR spectra of dibromosilanes 4a–c
and diiodosilanes 5a and 5b showed signals at
around −21 ppm (−21.4 ppm for 4a, −21.3 ppm for
4b, and −21.9 ppm for 4c) and −40 ppm (−39.9 ppm
for 5a and −39.5 ppm for 5b), respectively. Since
examples for the measurement of 29Si NMR spec-
tra on diaryldibromosilanes and diaryldiiodosilanes
are very few, it may be difficult to estimate the
coordination number by their 29Si NMR chemical
shifts. However, the 29Si NMR values of 4a–c are
shifted to higher field by ꢀδSi = −24 ppm as com-
pared with that of a very bulky diaryldibromosi-
lane, Tbt(Dip)SiBr2 [Tbt = 2,4,6-[(Me3Si)2CH]3C6H2;
Dip = 2,6-(i-Pr)2C6H3] (δSi = 3.0 ppm) [14],
and the down-field shifts on dibromosilanes 4a–c
(ꢀSi = 19.9 ppm for 4a, 19.6 ppm for 4b, and
18.2 ppm for 4c) compared with the corresponding
dihydrosilanes 1a–c are much smaller than that on
Tbt(Dip)SiBr2 (ꢀSi = 67.0 ppm); therefore, this dif-
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Reactivities of Dihydrosilanes Tethered with Two Thioether Moieties 441
of 1 using NBS and I2, respectively, whereas the
dichlorosilanes 3 were synthesized by reaction of
2-(RSCH2)C6H4Li with SiCl4. Reaction of 1b with
[PtCl2(cod)] in the presence of Et3N gave the corre-
sponding bissilylplatinum complex 6b, the structure
of which was determined by NMR and IR spectrom-
etry and X-ray crystallography.
EXPERIMENTAL
General Procedures
All reactions were carried out under an argon at-
mosphere unless otherwise noted. Tetrahydrofuran
(THF) and ether were purified by distillation from
sodium diphenylketyl before use. All solvents used in
the reactions were purified by the reported methods.
Wet column chromatography (WCC) was performed
with Merck Silica Gel 60 (70–230 mesh ASTM). The
1H NMR (500 or 300 MHz) spectra were measured in
CDCl3 or C6D6 with a JEOL JNM-λ500 or JEOL JNM-
AL300 spectrometer using SiMe4 (0 ppm) as internal
standards. The 13C NMR (126 MHz) and 29Si NMR
(99 MHz) spectra were measured in CDCl3 or C6D6
with a JEOL JNM-λ500 spectrometer using CDCl3
(77.0 ppm) or C6D6 (128.0 ppm) as those for 13C
NMR spectroscopy and SiMe4 (0 ppm) as internal
standards for 29Si NMR spectroscopy. Infrared spec-
tra were recorded on a Shimadzu FTIR-8400S spec-
trometer. All melting points were determined on a
Yanaco micro melting point apparatus MP-J3 and
are uncorrected.
FIGURE 1 ORTEP drawing of 6b with thermal ellipsoids
(50% probability). Hydrogen atoms were omitted for clar-
◦
˚
ity. Selected bond lengths (A) and angles ( ): Pt1 Si1,
2.3127(13); Pt1 S1, 2.4016(13); Si1 Pt1 S1, 94.52(5);
Si1 Pt1 Si1∗, 82.33(7); S1–Pt1 S1∗, 88.69(7).
[PtCl2(cod)] due to its less steric hindrance around
the platinum and silicon atoms.
The structure of 6b was determined by NMR and
IR spectrometry and X-ray crystallography (Fig. 1).
1
The H NMR signal at 4.89 ppm and the IR absorp-
tion at 2052 cm−1 indicated the presence of Si H
bonds, and the X-ray structure showed that the ratio
of silyl ligand to metal is 2:1, and 6b has a square
planar structure around the platinum atom (sum of
the bond angles around the Pt1 atom = 360◦). The
two silicon and two sulfur atoms on the platinum
center are arranged in cis-form, and the isopropyl
groups on the coordinated sulfur atoms and the 2-
(isopropylthiomethyl)phenyl groups on the silicon
atoms are situated in trans-configuration.
Synthesis of 1-Bromo-2-(tert-butylthiomethyl)
benzene (2a) and Its Isopropyl and Phenyl
Derivatives, 2b and 2c
A
THF suspension (300 mL) of 2-methyl-2-
propanethiol (14 mL, 0.13 mmol) and sodium
hydride (3.0 g, 0.13 mmol) was stirred at room
temperature for 1 h. To the reaction mixture, a
THF solution of 1-bromo-2-(bromomethyl)benzene
[5] (30.0 g, 0.120 mol) was added and then the mix-
ture was refluxed for 16 h. After addition of a satu-
rated aqueous solution of NH4Cl, the mixture was ex-
tracted with ether. The organic layer was dried with
anhydrous Na2SO4, and the solvents were removed
under reduced pressure. The residue was separated
by WCC (SiO2, hexane:ether = 4:1) to afford 2a [4]
(29.1g, 0.112 mol, 94%) as colorless oil.
CONCLUSION
Dihydrosilanes tethered with two thioether moieties,
[2-(RSCH2)C6H4]2SiH2 (1a: R = t-Bu; 1b: R = i-Pr;
1c: R = Ph), were synthesized by reaction of 2-
(RSCH2)C6H4Li with SiHCl3 followed by hydrogena-
tion using LiAlH4. The 29Si NMR spectra of 1 showed
slight up-field shifts compared with that of Ph2SiH2,
and this result suggests very weak or no coordina-
tion of thioether moieties to the silicon atom. Di-
hydrosilane 1b did not react with MeOH, PhCHO,
CH3CO2H, and 3-NO2C6H4COOH. These low reac-
tivities of 1b suggest very weak or no activation of
the Si H bonds in 1b, probably due to very weak
or no coordination of thioether moieties to the sili-
con atom. The corresponding dibromosilanes 4 and
diiodosilanes 5 were synthesized by dihalogenation
1-Bromo-2-(isopropylthiomethyl)benzene (2b)
and 1-bromo-2-(phenylthiomethyl)benzene (2c)
were prepared in a manner similar to those for
2a described above, in the yields of 92% and 95%,
1
respectively. 2b: colorless oil; H NMR (300 MHz,
Heteroatom Chemistry DOI 10.1002/hc

442 Takeda et al.
3
CDCl3): δ 1.20 (d, 3 JHH = 6.6 Hz, 6H), 2.81 (sep, 3 JHH
=
7.0 Hz, 2H), 7.30 (dd, JHH = 7.0, 7.0 Hz, 2H), 7.51
6.6 Hz, 1H), 3.77 (s, 2H), 7.00 (dd, 3 JHH = 7.2, 7.2 Hz,
(d, JHH = 7.0 Hz, 2H); 13C NMR (125 MHz, CDCl3):
3
3
3
1H), 7.16 (dd, JHH = 7.2, 7.2 Hz, 1H), 7.31 (d, JHH
= 7.2 Hz, 1H), 7.45 (d, 3 JHH = 7.2 Hz, 1H); 13C NMR
(125 MHz, CDCl3): δ 23.19 (q), 34.80 (d), 35.16 (t),
124.22 (s), 127.28 (d), 128.28 (d), 130.49 (d), 132.83
(d), 138.05 (s). 2c: colorless oil; 1H NMR (300 MHz,
δ 39.66 (t), 126.30 (d), 126.86 (d), 128.72 (d), 129.50
(d), 129.79 (d), 130.38 (d), 131.34 (s), 136.10 (s),
137.57 (d), 143.29 (s); 29Si NMR (99 MHz, CDCl3) δ
−40.12.
3
CDCl3): δ 4.11 (s, 2H), 6.99 (dd, JHH = 7.5, 7.5 Hz,
Synthesis of Bis[2-(tert-butylthiomethyl)phenyl]
dichlorosilane (3a) and Its Isopropyl Derivative
3b
1H), 7.20 (m, 6H), 7.22 (dd, 3 JHH = 7.5, 7.5 Hz, 1H),
3
7.45 (d, JHH = 7.5 Hz, 1H); 13C NMR (125 MHz,
CDCl3): δ 35.76 (t), 125.21 (d), 125.78 (d), 127.98 (d),
128.75 (d), 129.13 (d), 129.35 (d), 130.23 (d), 132.45
(s), 134.29 (s), 135.61 (d), 140.75 (s).
To an ether solution (100 mL) of 2b (10.1 g,
40.8 mmol), a hexane solution of butyllithium
(1.57 M, 26.0 mL, 40.8 mmol) was added at 0◦C.
After stirring the mixture at this temperature for 2
h, tetrachlorosilane (2.4 mL, 20.6 mmol) was added
at −40◦C and the mixture was warmed to room
temperature. After stirring for 16 h, the reaction
mixture was filtered and the solvents of the filtrate
were removed under reduced pressure. Purification
by Kugelrohr distillation (165◦C, 0.3 mmHg) gave
bis[2-(isopropylthiomethyl)phenyl]dichlorosilane3b
Synthesis of Bis[2-(tert-butylthiomethyl)
phenyl]silane (1a) and Its Isopropyl and Phenyl
Derivatives, 1b and 1c
To an ether solution (50 mL) of 2a (4.50 g,
18.3 mmol), a hexane solution of butyllithium
(1.59 M, 11.5 mL, 18.3 mmol) was added at 0◦C.
After stirring the mixture at this temperature for 2
h, trichlorosilane (1.2 mL, 9.2 mmol) was added at
−40◦C, and the mixture was warmed to room tem-
perature. LiAlH4 (0.40 g, 11.7 mmol) was added to
the mixture, and the mixture was stirred for 1 h. After
addition of a saturated aqueous solution of NH4Cl,
the mixture was extracted with ether and the organic
layer was dried with anhydrous Na2SO4. The solvents
were removed under reduced pressure, and purifi-
cation by Kugelrohr distillation (170◦C, 0.3 mmHg)
gave hydrosilane 1a (1.60 g, 68%). 1a: yellow oil;
1H NMR (300 MHz, CDCl3): δ 1.23 (s, 18H), 3.75 (s,
1
(5.00 g, 58%). 3b: yellow oil; H NMR (500 MHz,
C6D6): δ 0.93 (d, 3 JHH = 7.0 Hz, 12H), 2.42 (sep, 3 JHH
3
= 7.0 Hz, 2H), 3.83 (s, 4H), 6.99 (dd, JHH = 7.5,
3
7.5 Hz, 2H), 7.12 (dd, JHH = 7.5, 7.5 Hz, 2H), 7.49
3
3
(d, JHH = 7.5 Hz, 2H), 8.07 (d, JHH = 7.5 Hz, 2H);
29Si NMR (99 MHz, C6D6): δ −3.2.
Dichlorosilane (3a) was prepared in a manner
similar to those for 3b described above, in the yields
of ∼20%, although the isolation of 3a was unsuccess-
ful. 3a: yellow oil; 1H NMR (300 MHz, C6D6): δ 1.15
3
(s, 18H), 3.81 (s, 4H), 6.86 (dd, JHH = 7.5, 7.5 Hz,
1
3
4H), 5.09 (s, JHSi = 204 Hz, 2H), 7.12 (dd, JHH
=
2H), 7.04 (dd, 3 JHH = 7.5, 7.5 Hz, 2H), 7.42 (d, 3 JHH
=
3
3
7.5, 7.5 Hz, 2H), 7.29 (dd, JHH = 7.5, 7.5 Hz, 2H),
7.5 Hz, 2H), 8.01 (d, JHH = 7.5 Hz, 2H); 29Si NMR
3
3
7.36 (d, JHH = 7.5 Hz, 2H), 7.41 (d, JHH = 7.5 Hz,
2H); 13C NMR (125 MHz, CDCl3): δ 30.66 (q), 34.1 (t),
42.94 (s), 126.40 (d), 129.55 (d), 130.33 (d), 131.24
(s), 137.43 (d), 144.26 (s); 29Si NMR (99 MHz, CDCl3)
δ −41.29.
(99 MHz, C6D6): δ − 3.6.
Synthesis of Dibromobis[2-(tert-butylthiometh-
yl)phenyl]silane (4a) and Its Isopropyl and
Phenyl Derivatives, 4b and 4c
Bis[2-(isopropylthiomethyl)phenyl]silane (1b)
and bis[2-(phenylthiomethyl)phenyl]silane (1c)
were prepared in a manner similar to those for
1a described above, in the yields of 59 and 55%,
respectively. 1b: yellow oil; 1H NMR (500 MHz,
CDCl3): δ 1.17 (d, 3 JHH = 6.5 Hz, 12H), 2.71 (sep, 3 JHH
A mixture of 1a (257 mg, 0.66 mmol) and N-
bromosuccinimide (254 mg, 1.43 mmol) in benzene
(3 mL) was stirred at room temperature for 30 min.
After removal of the resulting succinimide by filtra-
tion under argon atmosphere, the solvent of the fil-
trate was evaporated under reduced pressure to give
4a (340 mg, 0.62 mmol, 94%). 4a: yellow oil; 1H NMR
(300 MHz, C6D6): δ 1.11 (s, 18H), 4.00 (s, 4H), 7.10
1
= 6.5 Hz, 2H), 3.78 (s, 4H), 5.13 (s, JSiH = 204 Hz,
2H), 7.23 (dd, 3 JHH = 7.5, 7.5 Hz, 2H), 7.35 (dd, 3 JHH
3
= 7.5, 7.5 Hz, 2H), 7.38 (d, JHH = 7.5 Hz, 2H), 7.52
(d, JHH = 7.5 Hz, 2H); 13C NMR (125 MHz, CDCl3):
(dd, JHH = 7.5, 7.5 Hz, 2H), 7.20 (dd, JHH = 7.5,
3
3
3
3
δ 23.10 (q), 34.73 (d), 36.02 (t), 126.40 (d), 129.20
7.5 Hz, 2H), 7.72 (d, JHH = 7.5 Hz, 2H), 8.26 (d,
(d), 130.10 (d), 131.60 (s), 137.61 (d), 144.71 (s);
3 JHH = 7.5 Hz, 2H); 13C NMR (125 MHz, C6D6): δ
30.02 (q), 32.00 (t), 42.65 (s), 127.13 (d), 131.08 (d),
131.83 (d), 132.34 (s), 136.06 (d), 144.09 (s); 29Si
NMR (99 MHz, C6D6): δ −21.12.
1
29Si NMR (99 MHz, CDCl3): δ −40.86. 1c: H NMR
1
(500 MHz, CDCl3): δ 4.14 (s, 4H), 5.11 (s, JSiH
=
3
204 Hz, 2H), 7.22 (m, 12H), 7.30 (dd, JHH = 7.0,
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Reactivities of Dihydrosilanes Tethered with Two Thioether Moieties 443
Dibromobis[2-(isopropylthiomethyl)phenyl]si-
Reaction of 1b with [PtCl2(cod)]
lane (4b) and dibromobis[2-(phenylthiomethyl)-
phenyl]silane (4c) were prepared in a manner
similar to those for 4a described above, in the yields
of 96% and 95%, respectively. 4b: yellow oil; 1H
A dichloromethane solution (6 mL) of 1b (161 mg,
0.45 mmol), [PtCl2(cod)] (57 mg, 0.15 mmol), and
triethylamine (0.18 mL, 1.30 mmol) was stirred at
room temperature for 3 d. After addition of a satu-
rated aqueous solution of NH4Cl and NaCl, the mix-
ture was extracted with dichloromethane. The or-
ganic layer was dried with Na2SO4, and the solvent
of the mixture was removed under reduced pres-
sure. The resulting yellow solid (205 mg) was re-
crystallized from hexane/dichloromethane to give 6b
(7 mg, 0.0077 mmol, 5%) as pale yellow crystals. 6b:
3
NMR (500 MHz, C6D6): δ 0.91 (d, JHH = 7.0 Hz,
3
12H), 2.40 (sep, JHH = 7.0 Hz, 2H), 3.85 (s, 4H),
3
3
7.01 (dd, JHH = 7.5, 7.5 Hz, 2H), 7.10 (dd, JHH
=
3
7.5, 7.5 Hz, 2H), 7.50 (d, JHH = 7.5 Hz, 2H), 8.19
(d, JHH = 7.5 Hz, 2H); 13C NMR (125 MHz, C6D6):
3
δ 23.15 (q), 35.66 (d), 36.00 (t), 128.54 (d), 128.71
(d), 131.80 (d), 132.27 (s), 136.37 (d), 144.41 (s); 29Si
1
NMR (99 MHz, C6D6): δ −21.30. 4c: yellow oil; H
1
pale yellow crystals; mp 127◦C (decomp.); H NMR
NMR (500 MHz, C6D6): δ 4.30 (s, 4H), 6.98 (m, 6H),
3
(500 MHz, CDCl3): δ 1.16 (d, JHH = 6.2 Hz, 12H),
3
7.08 (m, 4H), 7.25 (m, 4H), 7.45 (d, JHH = 7.5 Hz,
3
1.19 (d, JHH = 6.2 Hz, 12H), 2.82 (m, 4H), 3.76 (d,
2H), 8.20 (d, 3 JHH = 7.5 Hz, 2H); 13C NMR (125 MHz,
C6D6): δ 39.10 (t), 126.34 (d), 127.58 (d), 128.54
(d), 129.55 (d), 130.62 (d), 131.43 (s), 132.47
(d), 136.37 (d), 136.71 (s), 142.86 (s); 29Si NMR
(99 MHz, C6D6): δ −21.28.
2
2 JHH = 13.3 Hz, 4H), 4.10 (d, JHH = 13.3 Hz, 4H),
4.89 (s, 2H), 7.05–7.28 (m, 12 H), 7.85 (d, 4H); 29Si
NMR (99.3 MHz, CDCl3): δ −7.82 (1 JSiPt = 1465 Hz);
IR (KBr) 2052 (Si H stretch) cm−1.
Bis[2-(isopropylthiomethyl)phenyl]silanediol:
1H NMR (500 MHz, CDCl3): δ 1.04 (d, 3 JHH = 7.0 Hz,
12H), 2.62 (sep, 3 JHH = 7.0 Hz, 2H), 3.95(s, 4H), 5.37
3
(s, 2H), 7.09 (dd, JHH = 7.5, 7.5 Hz, 2H), 7.15 (dd,
X-Ray Structural Analysis of 6b
3 JHH = 7.5, 7.5 Hz, 2H), 7.23 (d, JHH = 7.5 Hz, 2H),
3
8.04 (d, JHH = 7.5 Hz, 2H); 13C NMR (125 MHz,
3
Single crystals of 6b suitable for X-ray struc-
tural analysis were obtained by slow recrystalliza-
tion from hexane/CH2Cl2. The crystal was mounted
on a glass fiber. The intensity data were col-
lected on Rigaku R-AXIS IV++ diffractometer with
graphite monochromated Mo Kα radiation (λ =
CDCl3): δ 23.62 (q), 36.08 (d), 36.78 (t), 127.21
(d), 130.74 (d), 130.94 (d), 136.55 (s), 137.22 (d),
144.40 (s); 29Si NMR (99 MHz, CDCl3): δ −26.63.
˚
0.71070 A). The structure was solved by direct meth-
Synthesis of Bis[2-(tert-butylthiomethyl)phenyl]
diiodosilane (5a) and Its Isopropyl Derivative 5b
ods (SHELXS-97 [19]) and refined by full-matrix
least-squares procedures on F2 for all reflections
(SHELXL-97 [19]). All the non-hydrogen atoms
were refined anisotropically, and all hydrogens were
placed using AFIX instructions. The structural data
are shown in Table 1. CCDC No. 790749 for 6b con-
tains the supplementary crystallographic data for
this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html (or
from the Cambridge Crystallographic Data Centre,
12, Union Road, Cambridge CB2 1EZ, UK; fax: +44
1223 336033; or deposit@ccdc.cam.ac.uk).
A mixture of 1a (152 mg, 0.391 mmol) and io-
dine (99 mg, 0.390 mmol) in benzene (3 mL) was
stirred at room temperature for 12 h. Removal of
the solvent under reduced pressure gave 5a (237 mg,
0.370 mmol, 95%). 5a: yellow oil; 1H NMR (300 MHz,
C6D6): δ 1.11 (s, 18H), 3.50 (s, 4H), 7.60 (m, 6H), 7.25
3
(d, JHH = 7.5 Hz, 2H); 13C NMR (125 MHz, C6D6):
δ 28.91 (q), 30.36 (t), 34.75 (s), 127.03 (d), 127.02
(d), 128.26 (d), 128.54 (s), 128.75 (d), 129.37 (s); 29Si
NMR (99 MHz, C6D6): δ − 39.91.
Bis[2-(isopropylthiomethyl)phenyl]diiodosilane
(5b) was prepared in a manner similar to those for
5a described above, in the yields of 96%. 5b: yellow
3
oil; 1H NMR (500 MHz, C6D6): δ 0.91 (d, JHH
=
Theoretical Calculations
3
7.0 Hz, 12H), 2.38 (sep, JHH = 7.0 Hz, 2H), 3.85(s,
4H), 6.97 (dd, 3 JHH = 7.5, 7.5 Hz, 2H), 7.08 (dd, 3 JHH
The geometries of (2-MeSCH2C6H4)2SiBr2 and
Ph2SiBr2 were optimized by using the Gaussian
03 program [20] with density functional theory at
the B3LYP/6-31G(d) level. The 29Si NMR chemical
shifts were calculated by GIAO-B3LYP with the 6-
311+G(2d,p) basis sets.
3
= 7.5, 7.5 Hz, 2H), 7.46 (d, JHH = 7.5 Hz, 2H), 8.39
(d, JHH = 7.5 Hz, 2H); 13C NMR (125 MHz, C6D6):
3
δ 23.31 (q), 35.77 (d), 35.97 (t), 127.24 (d), 128.19
(d), 131.29 (d), 131.89 (s), 137.54 (d), 143.67 (s); 29Si
NMR (99 MHz, C6D6): δ −39.50.
Heteroatom Chemistry DOI 10.1002/hc

444 Takeda et al.
TABLE 1 Crystal Data and Refinement Details for 6b
REFERENCES
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1445.
6b
Empirical formula
Formula weight
Temperature
Crystal system
Space group
C40H54PtS4Si2
914.34
123(2) K
Monoclinic
C2/c (#15)
˚
a (A)
13.721(2)
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˚
b (A)
14.4201(17)
20.395(3)
90
98.576(2)
90
3990.1(10)
4
˚
c (A)
α (◦)
β (◦)
γ (◦)
3
˚
V (A )
Z
Dcalc (Mg m−3
)
1.522
3.814
0.30 × 0.20 × 0.10
2.39–25.50◦
13,137
Absorption coefficient (mm−1
Crystal size (mm3)
θ range
)
Number of reflections
measured
Number of independent
reflections
3705
Rint
0.0226
99.5%
3705 / 0 / 213
Completeness
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I )]a
R indices (all data)a
Largest difference peak and
hole (e A
1.356
R1 = 0.0425 wR2 = 0.0815
R1 = 0.0434 wR2 = 0.0819
0.842 and –1.208
−3
˚
)
[12] Corriu, R. J. P.; Lanneau, G. F.; Perrot, M.
Tetrahedron Lett 1987, 28, 3941–3944.
aR1 = ꢀꢁFo| – |Fc||/ꢀ|Fo|, wR2 = [(ꢀw(Fo2 – Fc2)2/ꢀw(Fo2)2]1/2
.
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SUPPORTING INFORMATION
1H NMR spectra of 1a–c, 3b, 4a–c, and 5a, b,
13C NMR spectra of 1b, c, 3b, and 5a, b, and
atomic coordinates for the calculated molecules,
(2-MeSCH2C6H4)2SiBr2 and Ph2SiBr2 are available
from the corresponding author (ntakeda@chem-
bio.gunma-u.ac.jp) on request.
[17] Sangtrirutnugul, P.; Tilley, T. D. Organometallics
2008, 27, 2223–2230.
[18] Takeda, N.; Watanabe, D.; Unno, M. Unpublished
results, 2010.
[19] Sheldrick, G. M.; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
[20] Calculations were carried out using the Gaussian 03
program: Frisch, M. J.; Trucks, G. W.; Schlegel, H.
B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.;
Montgomery, Jr., J. A.; Vreven, T.; Kudin, K. N.;
Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi,
J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani,
G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada,
M.; Ehara, M.; Toyota, K.; Fukuda, R. Hasegawa, J.
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai,
H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.;
Cross, J. B.; Adamo, C.; Jaramillo, J.; Gomperts, R.;
Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi,
R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.;
ACKNOWLEDGMENTS
We are grateful to Prof. Soichiro Kyushin, Gradu-
ate School of Engineering, Gunma University for
his kind permission to use his single-crystal X-
ray diffractometer. In addition, we thank Associate
Prof. Shinichi Kondo, Faculty of Science, Yamagata
University and Assistant Prof. Masaki Yamamura,
Department of Chemistry, Tsukuba University, Dr.
Ryoji Tanaka, Sagami Chemical Research Institute
for valuable discussions.
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Reactivities of Dihydrosilanes Tethered with Two Thioether Moieties 445
Morokuma, K.; Voth, G. A.; Salvador, P.;
A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox,
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Heteroatom Chemistry DOI 10.1002/hc