Synthesis of 6-, 7- and 8-membered cyclosiloxanes having multifunctional groups

Article abstract of DOI:10.1016/j.jorganchem.2011.04.025

Cyclosiloxanes having intramolecular donor atoms, a Si-Si bond, and vinyl groups were synthesized as useful precursors for ring-opening polymerization. 1,1,3,3-Tetrakis(dimethylaminomethylphenyl)-5,5-dimethylcyclotrisiloxane was also synthesized and chara

Full text of DOI:10.1016/j.jorganchem.2011.04.025

Journal of Organometallic Chemistry 696 (2011) 2754e2757
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Note
Synthesis of 6-, 7- and 8-membered cyclosiloxanes having multifunctional groups
,
b
Hyeon Mo Cho a, Ji-Eun Lee a, Myong Euy Lee a , Kang Mun Lee
*
a Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University, Wonju, Gangwondo 220-710, South Korea
b Department of Chemistry, KAIST, Daejeon 305-701, South Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Cyclosiloxanes having intramolecular donor atoms, a SieSi bond, and vinyl groups were synthesized as
useful precursors for ring-opening polymerization. 1,1,3,3-Tetrakis(dimethylaminomethylphenyl)-5,5-
dimethylcyclotrisiloxane was also synthesized and characterized by single crystal X-ray structural
analysis, which shows strong coordination from N to Si in the solid state.
Received 16 March 2011
Received in revised form
19 April 2011
Accepted 26 April 2011
Ó 2011 Elsevier B.V. All rights reserved.
Keywords:
Organosilicon compound
Cyclic siloxane
Intramolecular donor atom
Vinylsiloxane
SieSi bond
1. Introduction
structure as temperature decreases since the coordination of N to Si
is intensified. Furthermore the incorporation of transition metals
The cyclic siloxanes (R2SiO)n, have great importance as ring-
opening polymerization precursors to high molecular weight
siloxane polymers [1], and are widely used in industry. Recently we
synthesized diastereomeric 1,3-dihydroxy-1,3-divinyldisiloxanes [2]
(1) having intramolecular donor atoms, which are useful precursor
for cyclosiloxanes, linear siloxanes and metallosiloxanes [3].
into polysiloxanes is possible through N-metal coordination bonds.
Second, SieSi bonds in cyclic polysilanes exhibit unusual chemical
and physical properties [5], such as having electronic transitions in
the UVeVis region, forming radicals by their reductive bond
cleavages, and electrochemical/thermal oxidation resulting in the
formation of SieOeSi bonds [6]. Third, the attachment of vinyl
groups to cyclosiloxanes allows their vulcanization by photolysis
and SieC bond formations by hydrosilylation [7]. To incorporate
these three functionalities into a cyclosiloxane, a cyclosiloxane
having donor atoms, a SieSi bond, and vinyl groups was designed.
We report here syntheses and characterizations of 6-, 7- and
8-membered ring 2-(N,N-dimethylaminomethyl)phenylsiloxane
derivatives as well as crystal structure of 1,1,3,3-tetrakis(dimethy-
laminomethylphenyl)-5,5-dimethylcyclotrisiloxane.
HO
N
Si
O
Si
N
OH
1
Our interest in this area focuses on the synthesis of cyclic
siloxanes having intramolecular donor atoms, SieSi bonds and
vinyl moieties as functional groups. First, disiloxane-1,3-diols with
intramolecular donor atoms can give polysiloxanes with variable
physical properties depending on the temperature, because the
degree of coordination of the intramolecular donor atom with
silicon atom is temperature-dependent [4]. For example, poly-
siloxanes bearing intramolecular donor atoms may have a rigid
2. Experimental
2.1. Materials and instruments
In all reactions in which air-sensitive chemicals were used, the
reagents and solvents were dried prior to use. Diethyl ether was
distilled from Na/Ph2CO. Other starting materials were purchased
as reagent grade and used without further purification. Glassware
was flame-dried under nitrogen or argon flushing prior to use. All
manipulations were performed using standard Schlenk techniques
under a nitrogen or argon atmosphere. 1H, 13C and 29Si NMR spectra
* Corresponding author. Tel.: þ82 33 760 2237; fax: þ82 33 760 2182.
E-mail address: melgg@yonsei.ac.kr (M.E. Lee).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.04.025

H.M. Cho et al. / Journal of Organometallic Chemistry 696 (2011) 2754e2757
2755
were recorded on a Bruker Avance IIþ BBO 400 MHz S1 spec-
trometer. The chemical shift were referenced to internal CDCl3 (1H
and 13C NMR) or external tetramethylsilane (29Si NMR). Analyses of
product mixtures were accomplished using an HP 5890 II Plus
instrument with FID (HP-5, 30m column) with dried n-decane as an
internal standard and with TCD (OV-1, 1/8 in. 6 ft column). Mass
spectra were recorded on a low-resolution (Agilent Technologies
GC/MS: 6890N, 5973N mass selective detector) EI mass spectrom-
eter and a high-resolution (JEOL JMS-600W-Agilent 6890 Series)
instrument. The preparations of disiloxane-1,3-diols 1 and 5 were
reported in a previous paper [2,8].
132.2, 134.7, 136.2, 137.8, 146.2 (CH2]CH, C6H4). 29Si NMR (80 MHz,
CDCl3):
ꢁ44.3 (SiAr), ꢁ8.5 (SiMe2).
d
2.3. Synthesis of 3
To a solution of 1.0 g (2.3 mmol) of 1 and 0.80 mL (5.7 mmol) of
triethylamine in 25 mL of diethyl ether was slowly added 0.43 g
(2.3 mmol) of 1,2-dichloro-1,1,2,2-tetramethyldisilane at ꢁ78 ꢀC.
The reaction mixture was allowed to warm to room temperature
and stirred for 10 h. After filtration of the precipitated Et3NHCl,
volatiles were distilled under vacuum. The crude reaction product
was purified by preparative GC to afford 3 as oil. The NMRs were
tentatively assigned to cis/trans isomers (81%, 1.0 g). HRMS:
C26H42N2O3Si4 542.2272 (Mþ, calcd) 542.2265 (Mþ, found). Trans-
2.2. Synthesis of 2
3: 1H NMR (400 MHz, CDCl3):
d 0.33 (s, 12H), 2.16 (s, 12H), 3.48 (AB
To a solution of 1.0 g (2.3 mmol) of 1 and 0.80 mL (5.7 mmol) of
triethylamine in 25 mL of diethyl ether was slowly added 0.30 g
(2.3 mmol) of dichlorodimethylsilane at 0 ꢀC. The reaction mixture
was allowed to warm slowly to room temperature and stirred for
12 h. After filtration of the precipitated Et3NHCl, volatiles were
distilled under vacuum. The crude reaction product was purified by
preparative GC to afford 2 as oil. The NMRs were tentatively
assigned to cis/trans isomers (86%, 0.96 g). HRMS: C24H36N2O3Si3
484.2034 (Mþ, calcd), 484.2031 (Mþ, found). Trans-2: 1H NMR
system, J ¼ 13.2 Hz, 2H), 3.73 (AB system, J ¼ 13.2 Hz, 2H),
5.72e6.32 (m, 6H), 7.11e7.93 (m, 8H). 13C NMR (100 MHz, CDCl3):
d
1.9, 2.0 (Si(CH3)2), 45.2 (N(CH3)2), 64.2 (NCH2), 126.2, 128.1, 129.9,
132.7, 134.8, 136.2, 137.5, 146.0 (CH2]CH, C6H4). 29Si NMR (80 MHz,
CDCl3):
CDCl3):
d
ꢁ45.46 (SiAr), 3.16 (SiMe2). Cis-3: 1H NMR (400 MHz,
d
0.25 (s, 6H), 0.27 (s, 6H), 2.09 (s, 12H), 3.40 (AB system,
J ¼ 13.2 Hz, 2H), 3.58 (AB system, J ¼ 13.2 Hz, 2H), 5.72e6.32 (m,
6H), 7.11e7.93 (m, 8H). 13C NMR (100 MHz, CDCl3):
d
1.9, 2.2
(Si(CH3)2), 45.2 (N(CH3)2), 64.0 (NCH2), 126.1, 127.9, 129.9, 132.7,
(400 MHz, CDCl3):
5.63e6.28 (m, 6H), 7.08e7.84 (m, 8H). 13C NMR (100 MHz, CDCl3):
1.1 (Si(CH3)2), 45.0 (N(CH3)2), 64.0 (NCH2), 126.3, 127.4, 129.5,
d 0.15 (s, 6H), 2.15 (s, 12H), 3.45e3.60 (m, 4H),
134.6, 136.1, 137.7, 146.0 (CH2]CH, C6H4). 29Si NMR (80 MHz,
CDCl3):
d
ꢁ45.38 (SiAr), 3.23 (SiMe2).
d
131.5, 134.7, 136.5, 137.6, 146.4 (CH2]CH, C6H4). 29Si NMR (80 MHz,
CDCl3):
CDCl3):
d
ꢁ45.6 (SiAr), ꢁ8.8 (SiMe2). Cis-2: 1H NMR (400 MHz,
0.10 (s, 3H), 0.27 (s, 3H), 2.10 (s, 12H), 3.45e3.60 (m, 4H),
2.4. Synthesis of 4
d
5.63e6.28 (m, 6H), 7.08e7.84 (m, 8H). 13C NMR (100 MHz, CDCl3):
To a solution of 1 and triethylamine in diethyl ether was added
1,3-dichloro-1,1,2,2,3,3-hexamethyltrisilane at ꢁ78 ꢀC in a manner
d
1.0, 1.3 (Si(CH3)2), 44.9 (N(CH3)2), 63.9 (NCH2), 126.3, 127.4, 129.8,
N
Me2SiCl2
Et2O/Et3N, 0 oC - rt
O
Si
O
Si
O
N
Si
Me2
2
, 86%
N
ClMe2SiSiMe2Cl
Et2O/Et3N, -78 oC - rt
O
1
Si
Si
O
O
N
Me2Si SiMe2
3
, 81%
Si
O
ClMe2Si(SiMe2)SiMe2Cl
Et2O/Et3N, -78 oC - rt
O
Si
O
N
N
Me2Si
Si SiMe2
Me2
4, 72%
Scheme 1. Synthesis of 6-, 7- and 8-membered cyclosiloxanes.

2756
H.M. Cho et al. / Journal of Organometallic Chemistry 696 (2011) 2754e2757
Table 1
similar to that described above. The purification procedure was
analogous to that for 3. The cis/trans mixture 4 was obtained as oil
in 72% yield (0.98 g). HRMS: C28H48N2O3Si5 600.2511 (Mþ, calcd)
Crystallographic data and structure refinement for 6
Empirical formula
C38H54N4O3Si3
600.2507 (found). 1H NMR (400 MHz, CDCl3):
d
(ꢁ)0.35e0.37 (m,
Formula weight
Wavelength (Å)
Crystal system
Space group
a (Å)
699.12
0.71073
Monoclinic
C2/c
15.2425(17)
12.0426(12)
18H), 2.07 (s, 6H), 2.14 (s, 6H), 3.36e3.52 (m, 4H), 5.65e6.25 (m,
6H), 7.11e7.82 (m, 8H). 13C NMR (100 MHz, CDCl3):
d
ꢁ6.94, ꢁ6.88, ꢁ6.6 (Si(CH3)2), 45.4, 45.5 (N(CH3)2), 63.6, 63.8
(NCH2), 126.0e137.4 (CH2]CH, C6H4).
b (Å)
c (Å)
22.051(2)
90
95.785(6)
90
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
2.5. Synthesis of 6
0.10 g (0.78 mmol) of dichlorodimethyldisilane at 0 ꢀC was
slowly added to a solution of 0.50 g (0.78 mmol) of 5 and 0.35 mL
(2.5 mmol) of triethylamine in 15 mL of diethyl ether in a manner
similar to that described above. Product 6 was obtained as colorless
crystals in 83% yield (0.45 g) by recrystallization from cosolvent
V (Å3)
4027.0(7)
Z
4
rcalc(g cmꢁ3
)
1.153
0.157
1504
296(2) K
m
(mmꢁ1
)
F(000)
T (K)
Crystal size
hkl range
Measd reflns
(n-hexane:diethyl ether ¼ 1:1). 1H NMR (400 MHz, CDCl3):
d 0.14 (s,
0.20*0.20*0.15
6H),1.86 (s, 24H), 3.26 (AB system, J ¼ 13.8 Hz, 4H), 3.46 (AB system,
ꢁ20 ꢂ h ꢂ 18,ꢁ15 ꢂ k ꢂ 15,ꢁ28 ꢂ l ꢂ 29
J ¼ 13.8 Hz, 4H), 7.04e7.67 (m, 16H, C6H4). 13C NMR (100 MHz,
43647
Unique reflns (Rint
)
4848 (0.0396)
CDCl3):
d 1.3 (Si(CH3)2), 45.3 (N(CH3)2), 63.9 (NCH2), 126.0, 127.4,
Final R indices (I > 2
R indices (all data)
GOF on F2
s
(I))a,b
R1 ¼ 0.0421, wR2 ¼ 0.1179
R1 ¼ 0.0603, wR2 ¼ 0.1322
1.001
0.440 and ꢁ0.219
129.5, 135.9, 136.6, 145.0 (C6H4). 29Si NMR (80 MHz, CDCl3):
d
ꢁ15.8
(SiMe2), ꢁ43.3 (SiAr). Anal. Calcd for C38H54N4O3Si3: C, 65.28; H,
rfin (max/min) (e Åꢁ3
)
7.79; N, 8.01. Found: C, 65.24; H, 7.82; N, 7.98.
P
P
jjFoj ꢁ jFcjj/ jFoj.
P
a
R1
¼
P
b
wR2 ¼ {[ w(Fo2 ꢁ Fc2)2]/[ w(Fo2)2]}1/2
.
2.6. X-ray structure determination
A specimen of suitable size and quality was coated with Paratone
oil and mounted onto a glass capillary. Reflection data for 6 were
collected on a Bruker APEX II CCD-based diffractometer with
The reactions of 1 with ClMe2SiSiMe2Cl and ClMe2Si(SiMe2)
SiMe2Cl were carried out in a manner similar to that described
above. The corresponding 7- and 8-membered ring siloxanes, 3 and
4 were obtained as oils in less than 60% yield. To increase yields of 3
and 4, lower initial reaction temperatures (ꢁ78 ꢀC) were applied
than that (0 ꢀC) in the preparation of 6-membered cyclosilane.
Under this condition, compounds 3 and 4 were formed in rather
high yields considering the ring strain of 7- and 8-membered cyclic
compounds. It is noteworthy that compound 4 having three
SieOeSi bonds and three consecutive Si atoms is a promising
precursor for block copolymer consisting of siloxanes and trisilanes.
Polysilane-siloxanes hybrid materials could not only improve the
desired properties of polysilanes such as their solubility and ther-
moformability, but could also lead to new features of these
polymers. For example, the spectral properties of hybrid polysilane-
siloxanes were discovered, which were applied as radiation sensi-
tive materials (photoresists) in a lithographic process [13].
Compounds 3 and 4 were purified by preparative GC. Unfortu-
nately the cis/trans isomers could not be fully separated, and several
trials to recrystallize them failed. Thus we were not able to identify
whether the N atom was coordinated to Si atom or not. This
prompted us to design a model cyclic siloxane containing two
dimethylaminomethylphenyl groups bonded to the same silicon
atom, which naturally allows only one cyclic product to be formed
graphite-monochromated MoK
hemisphere of reflection data were collected as
a
radiation (
l
¼ 0.71073Å). The
u
scan frames with
0.3O/frame and an exposure time of 10s/frame. Cell parameters were
determined and refined by SMART program [9]. Data reduction was
performed using SAINT software [10]. The data were corrected for
Lorentz and polarization effects. An empirical absorption correction
was applied using the SADABS program [11]. The structures of the
compounds were solved by direct methods and refined by full matrix
least-squares methods using the SHELXTL program package with
anisotropic thermal parameters for all non-hydrogen atoms [12]. X-
ray crystal structures of 6 were drawn by Mercury program ver. 2.3.
3. Results and discussion
First, dimethyldichlorosilane was used as a ring closer in order
to synthesize cyclosiloxane using diastereomeric disiloxane-1,3-
diols 1. The reaction of 1 with Me2SiCl2 in the presence of trie-
thylamine as HCl acceptor, gave the corresponding 6-membered
ring isomeric siloxanes 2, which were monitored by GC/MS
(Scheme 1). The product 2 was obtained as oil in 86% yield which
was separated by preparative GC. In 1H NMR data, three resonances
from SiCH3 group in 2 indicate the formation of a cis/trans mixture.
N
N
N
N
Me2SiCl2
Et2O/Et3N, 0 C - rt
O
Si
N
N
O
N
N
Si
O
Si
o
Si
Si
OH
O
OH
Me2
N
N
5
6
, 83%
Scheme 2. Synthesis of 6.

H.M. Cho et al. / Journal of Organometallic Chemistry 696 (2011) 2754e2757
2757
without cis/trans isomers. 1,1,3,3-Tetrakis(dimethylaminomethyl-
phenyl)cyclosiloxane 6 as a model compound was synthesized
Å) bonds, possibly due to the coordination of the N2 atom. The
structure shows a distorted trigonal bipyramid geometry, of which
three atoms, C1, C10 and O2, construct a deformed trigonal plane
(angles: N2-Si1-C1, 76.75(6)ꢀ; N2-Si1-C10, 71.58(6)ꢀ; N2-Si1-O2,
74.41(5)ꢀ) and two atoms, N2 and O1, occupy axial positions. The
distortion along the axial direction is demonstrated by the
N2ꢁSi1ꢁO1 angle of 175.54(6)ꢀ. The sum of internal angles in the 6-
membered ring is almost 720ꢀ (718.4ꢀ) showing only a small devi-
ation from planarity.
from the reaction of disiloxane-1,3-diol
5 with dimethyldi-
chlorosilane. Compound 6 was isolated as colorless crystals in 83%
yield by recrystallization from cosolvent (n-hexane:diethyl
ether ¼ 1:1) (Scheme 2).
The structure of 6 bearing pentacoordinate silicon atoms was
characterized by X-ray crystallography (Table 1). The nitrogen (N2)
atoms are situated 2.892 Å from the silicon atom which is similar to
the normal coordination distance of 2.8 Å [4], while the nitrogens
(N1) do not coordinate to Si in the condensed phase (Fig. 1). Inter-
estingly, our result for the coordination mode of amino groups toSi is
somewhat different from other examples: silicon atoms in cyclo-
tetrasiloxane [(Me)(C6H4CH2NMe2-2)-SiO]4 were tetra-coordinated
[14] and silicon atoms in cyclodisiloxane [(C6H4CH2NMe2-2)2SiO]2
were hexa-coordinated [15]. The Si1-O1 bonds (1.6502(7) Å) which
are located opposite to the amino groups (N2), are slightlyelongated
in comparisonwith the Si1-O2 (1.6373(11) Å) and Si2-O2 (1.6346(11)
Thermal and base-catalyzed ring-opening polymerizations are
now being applied to the synthesized cyclosiloxanes.
Acknowledgements
This research was supported by a grant from the Fundamental
R&D Program for Core Technology of Materials funded by the
Ministry of Knowledge Economy, Republic of Korea.
Appendix A. Supplementary Material
CCDC 816353 contains the supplementary crystallographic data
for 6. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_
request/cif.
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Fig. 1. ORTEP drawing of 6 shown with 30% thermal ellipsoid. Selected bond lengths
(Å) and angles (ꢀ): Si1-C10, 1.8779(18); Si2-C19, 1.836(2); O(2)-Si(1)eO(1), 105.58(6);
Si1#eO(1)-Si1, 134.24(10); O2#-Si2-O2, 107.57(8); Si2-O2-Si1, 132.95(7); C9-N1-C7,
111.21(18); C9-N1-C8, 110.48(19); C7-N1-C8, 110.55(18); C16-N2-C18, 110.90(18);
C16-N2-C17, 112.39(16); C18-N2-C17, 110.80(17). (a) Top view. Hydrogen atoms are
omitted for clarity. (b) Side view. Two dimethylaminomethylphenyl groups (except C1)
and hydrogen atoms are omitted for clarity.
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