1,3-Dimethoxy-1,3-dimethyl-1,3-diphenyl- and 1,3-dimethoxy-1,3-tetraphenyldisiloxanes: synthesis and structure

Article abstract of DOI:10.1007/s11172-019-2596-y

1,3-Dimethoxy- 1,3-dimethyl- 1,3-diphenyl- and 1,3-dimethoxy- 1,3-tetraphenyldisiloxanes were synthesized. Their structures were confirmed by IR and NMR spectroscopy. The structure of 1,3-dimethoxy-1,3-tetraphenyldisiloxane was determined by X-ray diffrac

Full text of DOI:10.1007/s11172-019-2596-y

Russian Chemical Bulletin, International Edition, Vol. 68, No. 8, pp. 1580—1584, August, 2019
1580
1,3-Dimethoxy-1,3-dimethyl-1,3-diphenyl- and
1,3-dimethoxy-1,3-tetraphenyldisiloxanes: synthesis and structure
A. S. Soldatenko, I. V. Sterkhova, and N. F. Lazareva
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences,
1 ul. Favorskogo, 664033 Irkutsk, Russian Federation.
E-mail: nataly_lazareva@irioch.irk.ru
1,3-Dimethoxy-1,3-dimethyl-1,3-diphenyl- and 1,3-dimethoxy-1,3-tetraphenyldisiloxanes
were synthesized. Their structures were confirmed by IR and NMR spectroscopy. The structure
of 1,3-dimethoxy-1,3-tetraphenyldisiloxane was determined by X-ray diffraction.
Key words: 1,3-dimethoxy-1,3-tetraphenyldisiloxane, 1,3-dimethoxy-1,3-dimethyl-1,3-
diphenyldisiloxane, molecular structure, X-ray diffraction.
Siloxanes are among the most important silicon com-
chloro-1,3-dimethyl-1,3-diphenyl- and 1,3-dichloro-1,3-
tetraphenyldisiloxanes with methanol affords the corre-
sponding 1,3-dimethoxy-1,3-dimethyl-1,3-diphenyl- (1)
and 1,3-dimethoxy-1,3-tetraphenyldisiloxanes (2) in high
yields (Scheme 1, pathway a). The reaction proceeds in
hexane in the presence of urea as a hydrogen chloride
acceptor.
pounds bearing the Si—O—Si group. Their structures and
properties, as well as approaches to their synthesis have
attracted great attention over several decades.1—9 Siloxanes
are widely used for the preparation of hybrid and compos-
ite materials with unique physicochemical properties.10—20
Due to high hydrophobicity, good biocompatibility, low
dielectric permittivity, low glass transition temperatures,
and high thermal stability, these materials are widely ap-
plied in instrumentation engineering, technology, medi-
cine, aerospace industry, and construction industry.
Siloxanes containing functional groups at the silicon atom
are convenient starting compounds for the preparation of
such materials. In recent years, the chemistry of (alkoxy)
organosiloxanes has been rapidly developed. The ability
of these compounds to undergo hydrolysis and poly-
condensation giving rise to new bonds offers consider-
able opportunities for their use in synthetic organic
chemistry and materials chemistry (see, for example,
publications21—27). (Alkoxy)aryldisiloxanes Ar(AlkO)
RSiOSiR(OAlk)Ar are of particular interest. The presence
of an aryl group significantly enhances the synthetic po-
tential of these compounds. The aryl group at the silicon
atom is a latent functional group,28—32 and the ease of
Si—CAr bond cleavage allows the synthesis of new organo-
silicon compounds. However, data on the synthesis and
experimental physicochemical properties of the simplest
representatives of such siloxanes are absent in the litera-
ture. The goal of this study is to develop methods for the
synthesis of 1,3-dimethoxy-1,3-dimethyl-1,3-diphenyl-
and 1,3-dimethoxy-1,3-tetraphenyldisiloxanes and to
investigate their properties.
Scheme 1
R = Me (1), Ph (2)
i. MeOH, (H2N)2C=O, n-C6H14; ii. MeOH, RhCl(PPh3)3,
C6H6; iii. H2O, HCl, C6H6.
Path
Yield (%)
1
2
a
b
c
93
78
59
90
82
67
Compounds 1 and 2 were also synthesized by methan-
olysis of the corresponding 1,3-dimethyl-1,3-diphenyl- and
1,1,3,3-tetraphenyldisiloxanes (see Scheme 1, pathway b).
(Alkoxy)phenyldisiloxanes can be synthesized by me-
thods based on exchange reactions of the Si—X bond in
functionally substituted silanes. The reaction of 1,3-di-
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1580—1584, August, 2019.
1066-5285/19/6808-1580 © 2019 Springer Science+Business Media, Inc.

1,3-Substituted disiloxanes
Russ. Chem. Bull., Int. Ed., Vol. 68, No. 8, August, 2019
1581
The reaction proceeds in benzene in the presence of the
catalyst RhCl(PPh3)3 at room temperature and is com-
pleted overnight. In this case, the yields are lower (78 and
82% for compounds 1 and 2, respectively). An increase in
the reaction time and a rise of the temperature did not
lead to a significant change in the yield of the target prod-
ucts. The reaction gave unidentified oligo- and poly-
siloxanes as by-products.
We found that siloxanes 1 and 2 are formed in signifi-
cant amounts in the synthesis of methylphenyldimeth-
oxysilane and diphenyldimethoxysilane from appropriate
chlorosilanes (see Scheme 1, pathway c). The formation
of these compounds can be attributed to the hydrolysis of
either the starting chlorosilanes or the already formed
methylphenyldimethoxysilane and diphenyldimethoxy-
silane. The hydrolysis of methylphenyl- and diphenyldi-
chlorosilanes in methanol at room temperature furnished
a mixture of di- and oligosiloxanes even when using the
reagents in an equimolar ratio. The reaction gave the
target products in yields lower than 20%. It is noteworthy
that the controlled acid hydrolysis of alkoxysilanes affords
siloxanes.33,34 The reaction of methylphenyldimethoxy-
silane and diphenyldimethoxysilane with an equimolar
amount of water at room temperature in benzene in the
presence of catalytic amounts of hydrogen chloride gave
siloxanes 1 and 2 in 59 and 67% yields, respectively.
The structures of compounds 1 and 2 were confirmed
by IR spectroscopy and multinuclear NMR spectroscopy.
a
С(8)
С(10)
С(9)
С(7)
С(6)
С(5)
O(2)
Si(1)
Si(1)
С(4)
С(13)
С(12)
С(1)
O(1)
C(11)
O(2)
С(3)
С(2)
b
c
b
a
Fig. 1. (а) Molecular structure of compound 2 with displacement ellipsoids drawn at the 20% probability level; (b) the projection
along the 0c axis (hydrogen atoms are omitted for clarity).

1582
Russ. Chem. Bull., Int. Ed., Vol. 68, No. 8, August, 2019
Soldatenko et al.
Table 1. Selected geometric parameters of compound 2
Bond
d/Å
Bond angle
φ/deg
Torsion angle
θ/deg
Si(1)—O(1)
Si(1)—O(2)
Si(1)—C(4)
Si(1)—C(5)
O(2)—C(11)
C(1)—C(2)
C(2)—C(3)
C(3)—C(4)
C(5)—C(6)
C(6)—C(7)
C(7)—C(8)
C(9)—C(10)
C(12)—C(13)
1.595(1)
1.629(3)
1.841(3)
1.855(3)
1.399(4)
1.336(6)
1.364(5)
1.387(4)
1.380(4)
1.389(5)
1.374(6)
1.375(4)
1.391(5)
O(1)—Si(1)—O(2)
O(1)—Si(1)—C(4)
O(2)—Si(1)—C(4)
O(1)—Si(1)—C(5)
O(2)—Si(1)—C(5)
C(4)—Si(1)—C(5)
Si(1)—O(1)—Si(1)
C1(1)—O(2)—Si(1)
C(1)—C(2)—C(3)
C(2)—C(3)—C(4)
C(3)—C(4)—C(13)
C(3)—C(4)—Si(1)
C(13)—C(4)—Si(1)
110.9(1)
110.2(1)
104.8(1)
107.6(1)
110.8(1)
112.6(1)
180.0(1)
126.5(3)
121.4(4)
121.4(4)
116.9(3)
121.4(2)
121.7(2)
O(1)—Si(1)—O(2)—C(11)
C(4)—Si(1)—O(2)—C(11)
C(5)—Si(1)—O(2)—C(11)
C(12)—C(1)—C(2)—C(3)
C(1)—C(2)—C(3)—C(4)
C(2)—C(3)—C(4)—C(13)
C(2)—C(3)—C(4)—Si(1)
O(1)—Si(1)—C(4)—C(3)
O(2)—Si(1)—C(4)—C(3)
C(5)—Si(1)—C(4)—C(3)
O(1)—Si(1)—C(4)—C(13)
O(2)—Si(1)—C(4)—C(13)
C(5)—Si(1)—C(4)—C(13)
68.3(3)
—172.8(3)
—51.1(4)
0.9(6)
–0.3(6)
0.0(5)
–179.2(3)
108.6(2)
–10.8(3)
–131.2(2)
–70.6(3)
170.1(2)
49.6(3)
1,3-tetraphenyldisiloxane (2), by recrystallization from pentane
(90% yield).
The recrystallization from pentane gave crystals of com-
pound 2. The structure of 2 was established by X-ray dif-
fraction. The molecular structure and a fragment of the
crystal structure are shown in Fig. 1. Selected bond lengths,
bond angles, and torsion angles are given in Table 1. The
molecule of compound 2 has a plane of symmetry passing
through the central oxygen atom O(1). There is one-half
of molecule 2 per asymmetric unit. The Si(1)—O(1) and
Si(1)—O(2) bond lengths are 1.595 Å and 1.629 Å, respec-
tively. These values differ from the ideal Si—O bond lengths
(1.603 Å) in four-coordinate silicon compounds; however,
they are similar to those in symmetrical disiloxanes.35—37
The Si—O—Si angle in compound 2 is 180, like in other
related structures.35—37
Reaction of 1,3-dimethyl-1,3-diphenyl- and 1,3-tetraphenyl-
disiloxanes with methanol. The appropriate siloxane (0.01 mol),
freshly prepared benzene (30 mL), and methanol (0.44 mL,
11 mmol) were placed in a two-neck round-bottom flask equipped
with a Teflon-coated magnetic stirrer. The solution was bubbled
with argon for 15 min. Then tris(triphenylphosphine)rhodium(I).
chloride (5 mg) was added to the reaction solution. The reaction
mixture was stirred at room temperature for 12 h. Benzene was
removed in vacuo. Compound 1 was isolated by distillation (78%);
compound 2, by recrystallization from pentane (82%).
Hydrolysis of PhMeSi(OMe)2 and Ph2Si(OMe)2. A mixture
of methanol (2 mL), distilled water (0.09 g, 5 mmol), and tri-
methylchlorosilane (0.01 g) was slowly added dropwise to a vigor-
osuly stirred solution of the appropriate silane (0.01 mol) in
methanol (10 mL). Trimethylchlorosilane was used as a source
of hydrogen chloride. The reaction mixture was stirred for 10 h
and allowed to stand for 16 h. Excess methanol was removed
in vacuo. Compound 1 (59%) was isolated by distillation; com-
pound 2 (67%), by recrystallization from pentane.
Experimental
The 1H, 13C, and 29Si NMR spectra of compounds 1 and 2
were recorded on a Bruker DPX 400 spectrometer (400.13, 100.61,
and 79.5 MHz, respectively) in CDCl3 with SiMe4 as the inter-
nal standard. The IR spectra were measured on a Varian 3100
FT-IR spectrometer.
1,3-Dimethoxy-1,3-dimethyl-1,3-diphenyldisiloxane (1). B.p.
1
155—158 C (5 Torr). H NMR, : 0.26 (s, 6 H, Me—Si); 3.36
(s, 6 H, MeO); 7.23—7.43 (m, 10 H, Ph). 13C NMR, δ: –2.92
(Me—Si); 50.06 (MeO); 127. 57, 129.74, 133.36, 134.90 (Ph).
29Si NMR, δ: –23.22. IR (film), /cm–1: 481; 584; 706, 733,
783,808, 1081; 1116; 1311; 1427; 1461; 1591; 1772; 1826; 1895;
1962; 2836; 2968; 3011; 3059. Found (%): C, 59.58; H, 6.92.
C16H22O3Si2. Calculated (%): C, 60.33; H, 6.96.
All experimental procedures were carried out under dry inert
gas atmosphere. The solvents were dried by standard procedures
prior to use.38 Commercially available phenylmethyl- and di-
phenyldichlorosilanes were purified by distillation before use.
Phenylmethyl- and diphenyldimethoxysilanes were synthesized
by standard procedures.39,40 1,3-Dichloro-1,3-dimethyl-1,3-
diphenyl- and 1,3-dichloro-1,3-tetraphenyldisiloxanes,41 as well
as 1,3-dimethyl-1,3-diphenyl- and 1,3-tetraphenyldisiloxanes42
were synthesized by procedures described in the literature.
Reaction of 1,3-dichloro-1,3-dimethyl-1,3-diphenyl- and
1,3-dichloro-1,3-tetraphenyldisiloxanes with methanol. The ap-
propriate siloxane (0.01 mol) was added dropwise to a mixture
of anhydrous methanol (0.02 mol) and carbamide (0.02 mol)
in hexane (25 mL). The reaction mixture was stirred at room
temperature for 60 min. The top layer of liquid was separat-
ed using a separatory funnel, and hexane was removed by dis-
tillation. 1,3-Dimethoxy-1,3-dimethyl-1,3-diphenyldisilox-
ane (1) was isolated by distillation (93% yield); 1,3-dimethoxy-
1,3-Dimethoxy-1,3-tetraphenyldisiloxane (2). M.p. 55 C.
1H NMR, : 3.50 (s, 6 H, MeO); 7.30—7.64 (m, 20 H, Ph).
13C NMR, : 50.66 (MeO); 127.71, 130.11, 133.31, 134.46 (Ph).
29Si NMR, : –36.83. IR (KBr), /cm–1: 421; 490; 520; 700;
719; 739; 787; 1002; 1071; 1125; 1188; 1246; 1310; 1428; 1589;
1836; 1898; 1970; 2360; 2836; 2936; 3006; 3064. Found (%):
C, 70.24; H, 5.71. C26H26O3Si2. Calculated (%): C, 70.54;
H, 5.92.
X-ray diffraction study. A single crystal of compound 2 was
obtained by recrystallization from pentane. The X-ray diffraction
data were collected on a Bruker D8 Venture diffractometer
(Mo-Kα radiation, λ = 0.71073 Å) using φ- and ω-scanning
technique. An absorption correction was applied with the

1,3-Substituted disiloxanes
Russ. Chem. Bull., Int. Ed., Vol. 68, No. 8, August, 2019
1583
Table 2. Crystallographic data for compound 2
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Parameter
2
Molecular formula
Crystal habit
Crystal size/mm
Т/K
C26H26O3Si2
Colorless prisms
0.170×0.300×0.450
293
Orthorhombic
Pccn
Crystal system
Space group
Molecular weight/g mol–1
442.64
3.10/30.08
14.7327(7)
21.2727(13)
7.8099(5)
90
θ
min/θmax
a/Å
b/Å
c/Å
α/deg
/deg
90
90
γ/deg
V/Å3
2447.7(2)
8
Z
dcalc/g cm–3
1.201
F(000)
936
Absorption coefficient/mm–1
Number of reflections
unique
Number of refined parameters
R factor (%)
Rw (based on all reflections)
Goodness of fit based on F2
Residual electron density
(max/min)/e Å–3
0.169
33942
3584
143
7.42
0.1604
1.017
0.326/–0.278
* The weighting scheme: w = 1/[σ2(Fo2) + (0.0815 P)2 + 1.2512 P],
where P = (Fo2 + 2 Fc2)/3.
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Results were obtained using analytical equipment of
the Baikal Analytical Center for Collective Use of the
Siberian Branch of the Russian Academy of Sciences.
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Received February 21, 2019;
in revised form April 9, 2019;
accepted April 29, 2019