New heterosilocanes, 1,1-difluoroand 1-Phenyl-1-fluoro-2,8-dioxa-5- chalcogenosilocanes

Article abstract of DOI:10.1134/S1070363210070108

The earlier unknown Si-fluorinated 2,8-dioxa-5-chalcogenosilocanes RFSi(OCH₂CH₂)₂Y (R = Ph, F; Y = O, S) were synthesized. According to calculations, there is a weak transannular coordinate interaction Y→Si (Y = O, S), whi

Full text of DOI:10.1134/S1070363210070108

ISSN 1070-3632, Russian Journal of General Chemistry, 2010, Vol. 80, No. 7, pp. 1276–1282. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © M.G. Voronkov, O.M. Trofimova, E.A. Grebneva, A.I. Albanov, T.N. Aksamentova, N.N. Chipanina, A.S. Soldatenko, 2010,
published in Zhurnal Obshchei Khimii, 2010, Vol. 80, No. 7, pp. 1110–1116.
New Heterosilocanes, 1,1-Difluoro-
and 1-Phenyl-1-fluoro-2,8-dioxa-5-chalcogenosilocanes
M. G. Voronkov, O. M. Trofimova, E. A. Grebneva, A. I. Albanov,
T. N. Aksamentova, N. N. Chipanina, and A. S. Soldatenko
Favorskii Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: omtrof@irioch.irk.ru
Received July 23, 2009
Abstract—The earlier unknown Si-fluorinated 2,8-dioxa-5-chalcogenosilocanes RFSi(OCH2CH2)2Y (R = Ph,
F; Y = O, S) were synthesized. According to calculations, there is a weak transannular coordinate interaction
Y→Si (Y = O, S), which is much weaker than that in the isostructural quasisilatranes (Y = N). At low
temperatures, 1,1-difluoro-2,5,8-trioxasilocane forms a dimer, in which two molecules of the monomer are
linked by four fluorine bridges Si–F→Si located in pairs in the two orthogonal planes SiF2Si.
DOI: 10.1134/S1070363210070108
Heterosilocanes are derivatives of silocanes
RR'Si(CH2)7, in whose eight-membered ring some
endocyclic carbon atoms are replaced by heteroatoms
O, S, N, etc. The first representative of this class of
compounds, Me2Si(OCH2CH2)2О, was prepared by the
reaction of diethylene glycol with dimethyldichloro-
silane, dimethyldiethoxysilane, or dimethyldibutoxy-
silane [1–3]. Later on, a procedure for preparation of
1,1-diorganyl-2,5,8-trioxasilocanes by the reaction of
diorganyldialkoxysilanes with О,О-bis(trimethylsilyl)
diethylene glycol was suggested [4]. Their sulfur
analog (Y = S) was synthesized by transetherification
of dimethyldibutoxysilane with thiodiglycol in the
presence of sodium metal as a catalyst [2, 3]. Another
representative of heterosilocanes is 1,1-dimethyl-2,8-
dioxasilocane Me2Si(OCH2CH2)2CH2 [2, 3, 5]. Hetero-
silocanes with Y = NR (R = H, Et) were prepared by
the reaction of diethanolamine with dimethyldibutoxy-
silane [2, 3]. Of special interest are nitrogen-containing
heterosilocanes (1,3-dioxa-6-aza-2-silacyclooctanes)
YXSi(OCH2CH2)2NR [6–12]. We called them quasi-
silatranes [13–16] since many of them contain an intra-
molecular coordination bond N→Si. They can be con-
sidered as the corresponding silatranes XSi(OCH2CH2)3N
with one OCH2CH2 rib removed from the skeleton of
the molecule and replaced by substituents Y and R.
molecule of the compound of this series with R = H
contains unusually short transannular coordination
bond N→Si (1.98 Å) [16, 17]. This allowed us to
assume that its structural analogs F2Si(OCH2CH2)2Y
with Y = O or S can also contain an intramolecular
coordination bond Y→Si. In order to check this assump-
tion we made an attempt to synthesize 1,1-difluoro-
2,8-dioxa-5-chalcogenosilocanes F2Si(OCH2CH2)2Y
(Y = O, S) and to study their structure and properties.
The results are described in the present paper.
For the synthesis we have used the reaction opened
by us of protodesililation of the C–Si bond in phenyl-
trifluorosilane with diethanolamine and its N-methyl-
substituted analog [14].
It turned out, however, that the reaction of phenyl-
trifluorosilane with diethylene glycol or thiodiglycol
results in the rupture of the two Si–F bonds rather than
the C–Si bond leading to the earlier unknown bicyclic
compounds, 1-phenyl-1-fluoro-2,8-dioxa-5-chalcogeno-
silocanes I (Y = O), II (Y =S) [scheme (1)].
PhSiF3 + (HOCH2CH2)2Y
CHCl3
PhFSi(OCH2CH2)2Y,
(1)
−2HF
I, II
Y = O (I), S (II).
Nevertheless, we succeeded in synthesis of the
expected 1,1-difluoro-2,8-dioxa-5-chalcogenosilocanes
1,1-Difluoroquasisilatranes
(R = H, Me) attracted our special attention. The
F2Si(OCH2CH2)2NR
1276

NEW HETEROSILOCANES, 1,1-DIFLUORO-...
1277
1
Table 1. Н, 13С, 19F, 29Si NMR parameters of heterosilocanes RFSi(OCH2CH2)2Y (I–IV) and the model compounds VI and
VII
δH, ppm
δC, ppm
Comp.
no.
Compound
δSi, ppm
δF, ppm
JSi–F, Hz
СН2О–3,7
СН2Y–4,6
СН2О–3,7
СН2Y–4,6
PhFSi(OCH2CH2)2Oа
PhFSi(OCH2CH2)2Sb
F2Si(OCH2CH2)2Oа
F2Si(OCH2CH2)2Sb
3.43
3.50
3.66
3.53
–
3.53
2.54
3.94
2.59
–
61.11
61.42
62.62
61.10
–
72.82
34.55
69.22
34.26
–
–58.7
–58.6
–98.46
–
–130.20
–130.65
–154.68
–
247.2
248.0
171.7
–
I
II
III
IV
VI
VII
а
PhFSi(OCH2CH3)2
–61.4
–95.71
–142.36
–154.7
262.0
193.4
а
F2Si(OCH2CH3)2
–
–
–
–
а In CDCl3. b In DMSO-d6.
III (Y = O) and IV (Y = S) by passing tetrafluoro-
silane into the solution of О,О-bis(2-trimethylsilyl)-
diethyleneglycol or bis(2-trimethylsiloxyethyl)sulfide
in hexane. The reaction proceeds as transsilylation
followed by elimination of trimethylfluorosilane and
formation of the earlier unknown heterosilocanes III
and IV [scheme (2)].
I. At the same time, this assumption is not supported
by the 29Si chemical shift in I, since the signal is
slightly shifted downfield relative to that in the
spectrum of compound VI (Table 1).
Comparison of the three spectral parameters δF, δSi,
JSi–F
for
the
model
difluorodiethoxysilane
F2Si(OCH2CH3)2 (VII) and heterosilocane III shows
that the 29Si chemical shift in the latter is shifted
upfield and the value of JSi–F decreases (Table 1).
However, the 19F chemical shift does not show any
notable downfield shift.
F4Si + (Me3SiOCH2CH2)2Y
F2Si(OCH2CH2)2Y + 2Me3SiF,
III, IV
(2)
Y = O (III), S (IV).
29
In the NMR spectra of dimer V the Si signals are
shifted upfield (–104.35 ppm), and the 19F signals
downfield (–153.07 ppm) relative to III;
simultaneously the absolute value of the (29Si–19F)
coupling constant decreases (166.9 Hz). This result
suggests stronger O→Si interaction in dimer V than in
molecule III. When the temperature of the solution of
the reaction mixture of heterosilocane III and the
As distinct from that, SiF4 does not react with
diethyleneglycol under similar conditions.
It should be noted that in reaction (2), according to
the NMR data, along with heterosilocane III (Y = O),
its dimer in which two molecules of III are linked by
the fluorine bridges [FSi(OCН2CH2)2O]2F (V) is
formed in the molar ratio of 2.5:1.
29
dimer V decreases to –70°С the Si chemical shift of
heterosilocane III is shifted upfield by 2 ppm, whereas
that of dimer V remains practically unchanged. These
data approve the suggested structure of the dimer,
where the silicon atoms of the two molecules are
linked by four fluorine bridges Si–F→F–Si, located in
pairs in the two orthogonal planes Si2–F2:
The composition and structure of the synthesized 1-
fluoro-1-phenyl- (I, II) and 1,1-difluoro-2,8-dioxa-5-
chalcogenosilocanes (III, IV) was proved by elemental
analysis, 1Н, 13С, 19F, 29Si NMR spectroscopy (Table 1)
and IR spectroscopy.
The 1H and 13C chemical shifts in the NMR spectra
of heterosilocanes I–IV (Table 1) do not suggest the
presence of of an intramolecular coordination inter-
action Y→Si in their molecules.
F
F
O
O
Si
Si
F
O
O
O
O
Still, a downfield shift of the 19F resonance in the
spectrum of compound I by 12 ppm and the value of
the (29Si–19F) coupling constant which is by 16 Hz less
than that in the model compound PhFSi(OEt)2 (VI)
[18], allows to assume the presence of a weak intra-
molecular coordination interaction O→Si in molecule
Unfortunately, poor solubility of heterosilocane IV,
the sulfur analog of III, did not allow to register its 19F
and 29Si NMR spectra.
The effect of substituents at the Si atom and of the
nature of atom Y in heterosilocanes RFSi(OCH2CH2)2Y
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 7 2010

1278
VORONKOV et al.
(I–IV) on their stereoelectronic structure has been also
studied by the methods of IR spectroscopy and
quantum chemistry at the DFT (B3LYP/6-311G**)
level of theory.
membered heterocycle has the crown conformation,
which, apparently, is stabilized by the O→Si inter-
action. Bond angles at the silicon atom in molecule
VIII only slightly differ from the tetrahedral con-
formation.
In the IR spectra of heterosilocanes I–IV strong
bands of the stretching vibrations of the C–O and Si–O
bonds are observed at 1000–1100 and 700–750 cm–1,
respectively [4, 19]. The skeletal vibration frequencies
of the eight-membered ring in these compounds appear
at 480–560 cm–1 as narrow or widened bands.
Deviation of the normal configuration of the silicon
atom from tetrahedral to trigonal bipyramidal is
usually characterized by a geometrical parameter (ηeq)
[24]. This parameter is calculated by the formula
3
ηeq = [1 – (120 – 1/3Σθn)/(120 – 109.5)]×100%,
From the X-ray diffraction data, the shortest donor-
acceptor bond N→Si among the Si-fluorinated
quasisilatranes RFSi(OCH2CH2)2NR' (R = F, Me, Ph;
R' = H, Me) [16, 17, 20, 21] is that in 1,1-difluoro-
quasisilatrane (1.98 Å [17]). The coordination poly-
hedron of the silicon atom in this molecule is trigonal
bipyramid, whose geometrical parameters are very
close to the ideal ones [16, 17]. Both five-membered
coordination heterocycles of this quasisilatrane have a
half-open envelope conformation with the carbon atom
in the β-position to the nitrogen atom deviating from
the four-atom plane CaNSiO.
n=1
where Σθn is the sum of the three angles between the
equatorial bonds in a trigonal bipyramidal surrounding
of the silicon atom. The value of ηeq = 0% (θn = 109.5º)
corresponds to the ideal terahedral configuration and
ηeq = 100 % (θn = 120.0º), to the trigonal bipyramid
configuration (Table 2).
The O→Si transannular interaction in molecules I–
III and VIII is substantially weaker than in the iso-
structural quasisilatrane Ph2Si(OCH2CH2)2N [25, 26],
that corresponds to a higher donor ability of the
nitrogen atom relative to oxygen.
The only heterosilocane studied by the X-ray
diffraction method was 1,1-diphenyl-2,5,8-trioxa-
silocane Ph2Si(OCH2CH2)2O (VIII) [22]. The distance
between the oxygen and silicon atoms in the molecule
is 2.98 Å. The sum of the van der Waals radii of the O
and Si atoms is equal to 3.60 Å [23], which is
indicative of a weak O→Si transannular coordination
interaction in this molecule; with this, the eight-
According to calculations, in the isolated molecule
VIII the O→Si distance (3.289 Å) is ~0.3 Å larger
than in the crystal (2.98 Å), and the OSiC(Phax) angle
is 154° (in the crystal 164°).
Conformations of the SiO1C1C2O3 and SiO2C3C4O3
fragments correspond to envelopes with the oppositely
bent angles (atoms С1 and С3). The atoms of silicon
and oxygen О3 are arranged on the same side of the
plane О1С2С4О2 (syn form). In the isolated molecules
I, III, VIII as well as the model structures Ia, IX
(Table 2) the interatomic distance O3···Si lies within
2.865 (III) – 3.289 Å (VIII).
Table 2. Calculated (B3LYP/6-311G**) bond lengths
Y→Si (lY→Si, Å) and criterion of pyramidality of the silicon
atom (ηeq, %) in the molecules of heterosilocanes
RR'Si(OCH2CH2)2Y
Comp. no.
RR'
Y
lY→Si
ηeq
30
The values of lO ···Si in molecules I, III are by 0.4
3
PhFax
PhaxF
PhFax
PhaxF
F2
O
3.136
3.022
3.619
3.571
2.865
3.438
3.289
3.592
3.125
3.787
3.394
I
and 0.6 Å less than the sum of the van der Waals radii
of the O and Si atoms, angles O3SiF1 are 158.0 and
173.4º respectively, parameter ηeq is ~30%. Ap-
parently, there is a weak interaction between the O3
and Si atoms in the isolated molecules I and III. An
indirect indication to this is the fact that only the syn
form of their eight-membered heterocycle is stable.
The anti form in which the oxygen atom O3 and the
silicon atom are most remote from each other being
located on the opposite sides from the О1С2С4О2 plane
transformed into the syn form during the geometry
optimization.
O
S
8
27
1
Ia
II
S
IIa
III
IV
VIII
VIIIа
IX
X
O
S
32
F2
25
6 (33)а
Ph2
O
O
O
S
Ph2
~0
10
~0
13
Me2
Ph2
F2
CH2
XI
а The value of ηeq for crystal is given in parentheses.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 7 2010

NEW HETEROSILOCANES, 1,1-DIFLUORO-...
1279
Si
O2
C3
O3
C1
Si
C3
O3
O2
O1
O1
C2 C4
C4
C1
C2
Fig. 1. Molecular structure (syn-conformer) of 1,1-diphenyl-2,5,8-trioxasilocane (VIII).
C1
C2
O1
O3
Si
C3
F2
F1
O3
C1
O2
C4
F1
C4
C2
Si
O1
O2
C3
Fig. 2. Molecular structure of 1,1-difluoro-2,5,8-trioxasilocane (III).
The anti form VIIIа with a larger distance between
the O3 and Si atoms exists in molecule VIII, although
the energy difference from that of the syn form is only
0.6 kcal mol–1. On the opposite sides from the
SiC1O3C3 plane in form VIIIa are O1 and C4 atoms,
rather than Si and O3. The O3···Si distance in VIIIa is
3.592 Å (Tables 2, 3).
The O3···Si interatomic distance in the isolated
molecules Ia, VIII, and IX is longer than in molecule
III by 0.2, 0.4, and 0.3 Å, and the degree of
pentacoordination ηeq is lower by 24, 26 and 22%
respectively. The O···Si interatomic distance in the Si-
substituted 2,5,8-trioxasilocanes (I, III, VIII, IX)
decreases in the order: Ph2 (VIII) > PhFax (I) > Me2
(IX) > PhaxF (Ia) > F2 (III).
The calculated geometrical parameters of molecules
VIII, IX, and XI (Table 2) are close, which implies the
absence of the coordination interaction between the Si
and O atoms. Nevertheless, the presence of trans-
annular interaction between the endocyclic atoms Si
and O in these molecules is suggested by the values of
ηeq (Table 2).
The calculated Si···S interatomic distances in the Si-
substituted 2,8-dioxa-5-thiasilocanes RR'Si(OCH2CH2)2S
(II, IIa, IV, X) (Table 2) fall within 3.44–3.62 Å.
O3
C2
Si
Si
O1
C2
C4
O1
C1
C3
Fig. 4. anti-Form of compounds I and III.
C1
C3
C4
O2
O2
O3
Fig. 3. syn-Form of compounds I and III.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 7 2010

1280
VORONKOV et al.
O1
C1
O3
C1
O1
C2
C2
C4
C3
O2
O3
C4
Si
Si
O2
C3
Fig. 5. Molecular structure (anti-conformer) of 1,1-diphenyl-2,5,8-trioxasilocane (VIIIa).
For RR' = PhFax the degree of coordination (ηeq) is
and S atoms in 2,8-dioxa-5-thiasilocanes (II, IV) or it
may have electrostatic character.
maximum, 27%. In general, for all studied thio-
derivatives the value of ηeq decreases in the order FaxPh
(II) > F2 (IV) > Ph2 (X) > FPhax (IIa) (Table 2). In all
cases the Si…S interatomic distance is larger than the
Si···Н2 distance in molecule XI (Y = CH2). Apparently,
this proves the absence of interaction between the Si
EXPERIMENTAL
IR spectra of the synthesized compounds were
1
recorded on a Specord IR-75 spectrometer in KBr. H,
13C, 19F and 29Si NMR spectra were obtained on a
Table 3. Calculated geometry (B3LYP/6-311G**) of heterosilocanes RR'Si(OCH2CH2)2Y
Bond angles, deg
Bond length, Å
Si–O1
Comp. no.
RR'
Y
O1SiO2
112.91
O1SiR'
110.62
O2SiR'
114.37
RSiY
Si–R
Si–R'
Si–O2
1.6471
1.6488
1.6481
1.6470
1.6467
1.6471
1.6477
1.6438
1.6311
1.6324
1.6650
1.6666
1.6694
1.6668
1.6720
1.6726
1.6650
1.6666
1.6242
1.6228
PhFax
PhaxF
PhFax
PhaxF
F2
O
O
S
157.99
1.6174
1.8540
1.6180
1.8526
1.5990
1.8731
1.8724
1.8668
1.8731
1.5968
1.8533
I
112.01
111.19
111.78
115.46
109.69
110.59
110.33
109.69
112.88
109.07
110.30
107.91
111.62
113.62
106.94
112.37
113.62
111.02
110.03
115.43
109.25
111.57
106.33
112.81
109.02
106.33
108.65
174.63
156.69
169.17
173.37
150.92
153.50
164.02
150.92
164.80
1.6199
1.8510
1.6178
1.6015
1.8697
1.8735
1.8705
1.8697
1.6041
Ia
II
S
IIa
III
IV
VIII
IX
X
O
S
F2
Ph2
O
O
S
Me2
Ph2
F2
CH2
XI
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 7 2010

NEW HETEROSILOCANES, 1,1-DIFLUORO-...
1281
F2
F2
O1
S
F1
O1
O2
C1
C3
C3
C2
Si
S
C2
C1
C4
C4
O2
Fig. 6. Molecular structure of 1,1-difluoro-2,8-oxa-5-thiosilocane (IV).
Bruker DРХ-400 instrument (400.13, 100.61, 376.50
and 79.5 MHz, respectively) in CDCl3 and DMSO-d6,
internal standard TMS.
C4H8O2F2SiS. Calculated, %: С 25.78, Н 4.29, F
20.41, Si 15.08. S 17.22.
ACKNOWLEDGMENTS
Quantum-chemical calculations were performed
using the GAUSSIAN 98 program suite [27].
This work was performed with financial support
from the Council on Grants of the President of Russian
Federation (grant no. NSh-255.2008.3).
1-Fluoro-1-phenyl-2,5,8-trioxasilocane (I). To
5.0 g of diethylene glycol in 10 ml of dry chloroform
7.64 g of phenyltrifluorosilane was added dropwise at
room temperature. The reaction mixture was stirred at
35–45°С for 18 h. The precipitate formed was washed
with chloroform and filtered off. Yield 12.6 g (73%),
mp 174–180°С (decomp.). Found, %: С 52.38, Н 5.4,
F 8.76, Si 12.35. C10H13O3FSi. Calculated, %: С 52.60,
Н 5.70, F 8.33, Si 12.32.
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 7 2010

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