Reaction of Organyltrifluorosilanes with Dimethylsulfoxide and Dimethylformamide and Its Spectroscopic Investigation

Article abstract of DOI:10.1023/A:1014271706096

Reaction of Organyltrifluorosilanes RSiF3 (R = C6H5, 3-02NC6H4, and C6H5CH2) with DMSO and DMF (B) results in formation of the complexes 2B*SiF4 and R2SiF2. Besides, biphenyl, benzene, methyl(fluoromethyl)sulfoxide, and S,S'-dimethyldisulfide-S,S'-dioxide

Full text of DOI:10.1023/A:1014271706096

Russian Journal of General Chemistry, Vol. 71, No. 12, 2001, pp. 1865 1868. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 12, 2001,
pp. 1970 1973.
Original Russian Text Copyright
2001 by Voronkov, Boyarkina, Gavrilova, Basenko.
Reaction of Organyltrifluorosilanes with Dimethylsulfoxide
and Domethylformamide and Its Spectroscopic Investigation
M. G. Voronkov, E. V. Boyarkina, G. A. Gavrilova, and S. V. Basenko
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, Russia
Received May 5, 2001
Abstract Reaction of organyltrifluorosilanes RSiF3 (R = C6H5, 3-O2NC6H4, and C6H5CH2) with DMSO
and DMF (B) results in formation of the complexes 2B SiF4 and R2SiF2. Besides, biphenyl, benzene, me-
thyl(fluoromethyl)sulfoxide, and S,S -dimethyldisulfide-S,S -dioxide CH3S(O)S(O)CH3 were either isolated or
identified by chromatomass-spectrometry. Speculative mechanism of the reaction proceeding is discussed. IR
spectra of the reaction mixtures and those of 2B SiF4 adduct were studied in details; they indicate octahedron
structure of the complex with cis arrangement of B ligands.
We found that reaction of PhSiF3 with DMSO (1:1
mole ratio) at 20 C for 48 72 h unexpectedly results
in formation of stable crystalline adduct 2Me2SO
SiF4 (I) [1]. Other reaction products were diphenyl-
dichlorosilane, biphenyl, benzene, methyl(fluoro-
the formation of biphenyl. In the absence of DMSO
or DMF such a rearrangement does not occur.
The adduct 2Me2SO.SiF4 is also formed in the
reaction of dimethylsulfoxide with other organyl-
fluorosilanes RSiF3 (R = PhCH2 and 3-NO2C6H4). In
the last case, nitrobenzene was isolated, similarly.
Similarly to DMSO, DMF reacts with phenyltrifluoro-
silane under the same conditions forming the complex
2Me2NCHO SiF4 and diphenyldifluorosilane.
methyl)sulfoxide
and
S,S -dimethyldisulfide-
S,S -dioxide CH3S(O)S(O)CH3. Their formation was
proven by chromatomassspectrometry; obviously it
can be illustrated by the steps 1 7.
Me2SO
2PhSiF3
2[(Me2SO) PhSiF3]
2PH + Si2F6,
It is noteworthy that tertiary amines (Et3N and
pyridine) and acetonitrile does not enter to the reac-
tion (7). Reaction (7) of PhSiF3 with DMSO in CS2
proceeds poorly with no formation of complex I.
(1)
Si2F6
2Me2SO + SiF4
SiF4 + F2Si:,
2(Me2SO) SiF4,
Ph2SiF2,
(2)
(3)
(4)
We studied IR adsorption spectra in the range of
1
4000 400 cm of the products in the reactions of
RSiF3 (R = C6H5, 3-NO2C6H4 and C6H5CH2) in 1:1
ratio with dimethylsulfoxide and dimethylformamide.
The IR spectra of stable crystalline complexes isolated
from the mixtures of the organyltrifluorosilanes with
dimethylsulfoxide are identical and correspond to the
spectrum of the complex 2Me2SO SiF4 (I). Similar
complex, 2Me2NCHO Sif4 (II) is formed in the reac-
tion of phenyltrifluorosilane with dimethylformamide.
2Ph
(5)
PhPh.
Benzene is obviously formed due to splitting off a
hydrogen atom from DMSO by phenyl radical.
Ph + CH3S(O)CH3
PhH + CH2S(O)CH3. (6)
The fate of the last formed radical from DMSO is
not established yet.
In the spectrum of complex I (Fig. 1a) the stron-
gest broad and structurized band with maximum at
1
735 cm occurs in the region of (Si F) stretching
It cannot also be excluded that SiF4 is formed in
the disproportion reaction induced by the initially
formed Me2SO PhSiF3 adduct.
vibrations at hexacoorsinated silicon atom [2, 3].
Bending vibrations (Si F) induce
a band at
1
480 cm . Other bands in the IR spectra of all the
samples of adduct I correspond to vibrations in the
DMSO molecule coordinated with silicon atom [4]:
stretching as(C H) and s(C H) at 2990 and
Me2SO
2PhSiF3
Ph2SiF2 + SiF4.
(7)
1
However, reaction (7) does not allow to explain
2920 cm , and planar bending vibrations of methyl
1070-3632/01/7112-1865$25.00 2001 MAIK Nauka/Interperiodica

1866
VORONKOV et al.
(a)
(b)
(c)
s(CH)
as(CH)
(S O)
(Si F)
(Si F)hexa
(Si O)
(S=O)
(Si F)
s(Si F)
as(Si F)
(Si F)
(Si F)hexa
(Si F)hexa
(d)
(Si F)
(C=O)
1500
(Si F)hexa
500 cm
1
4000
3500
3000
2500
2000
1000
1
IR spectra of the complexes of tetrafluorosilane in the region of 4000 400 cm . (a) 2Me SO SiF , a pellet with KBr;
2
4
(b) Me SO + PhSiF in CS ; (c) 2Me S OSiF in CH CN; (d) 2Me NCHO SiF4, a pellet with KBr. The disconti-
2
3
2
2
4
3
2
nuities in the spectra (b) and (c) correspond to the areas of solvents absorption.
groups as1(Me) at 1430, 1416 and s(Me) at 1317,
cular, as compared with free free sulfoxide group
(1040 cm ) reliably confirm coordination of DMSO
1
1330 cm . Stretching vibration of sulfoxide group
coordinated with silicon appears as two bands at 960
molecules with tetrafluorosilane through oxygen atom.
This fact does not contradict to the discussion about
donor type of the DMSO reaction center (O or S) at
its coordination with a Lewis acid [5, 6]. The com-
plexes of SiF4 with dimethylsulfoxide (1:2) similarly
to the complexes with other oxygencontaining ligands
are well studied with various physico-chemical
methods, in part by vibration spectroscopy [7, 8].
1
and 1030 cm . The multiple structure with the
1
maximum at 960 cm is probably induced by mixing
of stretching vibration (S=O)coord with energetically
close out-of-plane bending vibration (Me) (in the
spectrum of DMSO there is a related band at
1
920 cm ). Position of the maxima of the above
bands and a lowfrequency shift of (S=O) in parti-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 12 2001

REACTION OF ORGANYLTRIFLUOROSILANES WITH DIMETHYLSULFOXIDE
1867
1
Hexacoordinated tetrafluorosilane complexes 2B SiF4
have octahedron structure [8]. The ligands B in such
complexes can be cis or trans arranged, and such
complexes have Cs or C4v symmetry, respectively. In
the case of trans-octahedral structure of complex I
only asymmetric stretching vibrations of two sulf-
oxide groups, as(S=O), are active and should induce
one band only. As we noted above, in the spectra of
the complexes occur two absorption bands correspond-
ing to the stretching vibrations of the sulfoxide groups
coordinated with the silicon atom, with the maxima
frequency band at 790 cm corresponding to the
stretching vibration of axial Si F bond and the bands
of symmetric and asymmetric vibrations of the Si F
bonds in the equatorial plane of the trigonal bipyramid
1
(880 and 955 cm , respectively). Hence, in aceto-
nitrile medium there is an equilibrium between the
complexes with penta- and hexacoordinated silicon
atom, that is, Me2SO SiF4 and 2Me2SO SiF4.
The solvents CCl4 and THF do not affect IR spec-
trum of the complex I.
1
at 960 and 1030 cm . This points to cis-octahedral
In the reaction of C6H5SiF3 with DMF (1:1 mole
ratio) at 20 C for 48 72 h crystalline adduct
2Me2NCHO SiF4 (II) is formed. The complex II was
prepared earlier by reaction of gaseous SiF4 with
DMF. Its structure was proven by X-ray structural
analysis [9]. The IR absorption spectrum of the com-
plex II in the region of 4000 400 cm studied by us
(Fig. 1d) does not contradict to the earlier published
spectrum in 1900 700 cm region. The spectrum of
the adduct II has the strongest band at 730 cm ,
corresponding to (Si F) at hexacoordinated silicon
atom. The doublet structure of (C=O) absorption
band attests cis-octahedric configuration of the com-
plex II. The band at 475 cm corresponds to
(Si F)hexa stretching vibrations.
structure of complex I with no symmetry elements.
1
The band at higher frequency 1030 cm is obviously
belongs to sulfoxide group in the equatorial plane (in
cis position) of the octahedron, and therefore it is less
shifted to the low-frequency region relatively to the
1
1
(S=O) 1040 cm of free sulfoxide group, in the
1
comparison with the band at 960 cm corresponding
1
to the sulfoxide group with its oxygen atom interact-
ing with both silicon atom and the electronegative
fluorine atom in the axial fragment of the octahedron.
In this fragment the bond orders Si Fax and S=O are
considerably reduced due to electron density redistri-
bution at the three-center four-electron bonding, as
compared with the equatorial plane of the octahedron.
1
1
According to the IR data, liquid mixtures of
DMSO with RSiF3 contain compounds R2SiF2, to-
The problem of effect of organic solvents with
different macro characteristics on the thermodynamic
gether with the adduct I. Their presence is indicated composition of equilibrium mixtures of hypervalent
by the bands (C H) >3000, (C=C) 1595, 1580,
(Si C) 1139 cm , as well as (Si F) bands charac-
silicon derivatives was studied by us in details for
intracomplex compounds with pentacoordinated
silicon, the aroyloxymethyltrifluorosilanes and their
analogs [10]. For the intermolecular fluorosilane
complexes with bases this problem was not discussed
in literature comprehensively and gives rise to further
separate investigations.
1
teristic of tetracoordinated silicon, as(Si F) 950,
1
s(Si F) 854, and (Si F) 467 cm . The data of
mass-spectrometry confirm this conclusion. IR spectra
of liquid mixtures of DMSO and RSiF3 contain also
bands of free DMSO molecules, (C H) 2920, 3000,
as(C H) 1404, 1415, s(C H) 1308, 1327, and
1
(S=O)free 1056 cm .
EXPERIMENTAL
The IR spectroscopy method allowed us also to
establish unusual influence of nature of a solvent on
the reaction of C6H5SiF3 with DMSO. The IR spec-
trum of the ternary system C6H5SiF3 DMSO CS2
(Fig. 1b) contains no (Si F) or (Si F) bands of
complex I which would be corresponding to hexa-
coordinated silicon atom. The spectrum contains
bands corresponding to vibration of free DMSO,
C6H5SiF3 and (C6H5)2SiF2 molecules. Spectrum of
solution of complex I in acetonitrile (Fig. 1c) together
with the bands of Si F bond of hexacoordinated
IR spectra were recorded in the range 4000
400 cm for liquid samples of DMSO, PhSiF3 (in
1
micro layer), crystalline adducts 2Me2S OSiF4 (in
KBr pellets) and solutions of 2Me2SO SiF4 in CS2
and CH3CN (in KBr cells with layer thickness 0.1 mm,
concentration 0.1 M) on a Specord IR-75 instrument.
19F NMR spectra were registered on a Jeol FX-90Q
instrument (90 MHz) for the 15 20% solutions in
CDCl3 (CCl3F).
Reaction of phenyltrifluorosilane with dimethyl-
sulfoxide. To dimethylsulfoxide (7.8 g) was added
dropwise phenyltrichlorosilane (16.2 g). On keeping
the solution at room temperature after 2 3 days
dropped colorless crystals of cubic form. The crystals
were filtered off and dried in a vacuum (10 mm). We
1
silicon [ (Si F)hexa 730, (Si F)hexa480 cm ] contains
the bands (Si F) of pebntacoordinated silicon.
Therewith, occurs typical for trigonal-bipyramidal
environment of silicon atom splitting of the bands of
Si F bonds into three components: the strongest low-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 12 2001

1868
VORONKOV et al.
obtained 8.3 g (32%) of complex I, with sublimation
temperature 110 C. IR spectrum, cm : 734 [ (Si F)],
Liquid pase contained the following compounds.
(1) Diphenylfluorosilane. IR spectrum, cm : 467
1
1
478 [ (Si F)hexa], 940, 951 [ (S=O)coord], 1025,
1045 [ (Me)], 1317, 1330 [ (C H)], 1416, 1430
[
24.47. C4H12F4O2S2Si. Calculated, %: C 18.45; H
4.65; F 29.19; S 24.63.
[ (Si F)], 854 [ (Si F)], 950 [ as(Si F)], 1139
s
[ (Si C)], 1581, 1595 [ (C=C)], >3000 [ (C H)].
Mass spectrum, m/z (I, %): 220 (100) (M+ ), 154 (50),
143 (15) (M C6H5)+, 77 (35) (C6H+5). (2) Biphenyl.
Mass spectrum, m/z (I, %): 154 (100) (M+ ), 77 (25)
(C6H+5). (3) Benzene.
as(C H)]. Found, %: C 18.73s; H 4.87; F 29.23; S
The following compounds were registered in the
liquid phase. (1) Diphenyldifluorosilane. IR spectrum,
REFERENCES
1
cm : 467 [ (Si F)], 854 [ (Si F)], 950 [ as(Si F)],
s
1139 [ (Si C)], 1581, 1595 [ (C=C)], >3000
[ (C H)]. 19F NMR spectrum (CCl3F), F, ppm: 142
(JSiF 290.11, JCF 110.23 Hz). Mass spectrum, m/z (I,
%): 220 (100) (M+ ), 154 (55), 143 (16) (M C6H5)+,
77 (34) (C6H+5). (2) Biphenyl (from trace amount to
2 4%). Mass spectrum, m/z (I, %): 154 (100) (M+.),
77 (27) (C6H+5). (3) (Benzene, 0.95 g (12%), bp 77 C
(730 mm). (4) Methylfluoromethylsulfoxide. Mass
spectrum, m/z (I, %): 96 (52) (M+ ), 61 (100), 47 (57).
(5) S,S -Dimethyldisulfide-S,S -dioxide CH3S(O)S(O)
CH3. Mass spectrum, m/z (I, %): 111 (53) (M+ CH3),
81 (100), 79 (93), 47 (37).
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was also isolated, bp 61 62 C (4 mm). Mass spec-
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added dropwise 16.2 g of phenyltrifluorosilane. On
keeping the solution at room temperature, after
2 3 days dropped colorless crystals. The crystals were
filtered off and dried in a vacuum (10 mm). We
obtained 7.3 g (28%) of complex II with sublimation
temperature 135 C (published sublimation point
135 C [9]). Found, %: C 28.73; H 5.77; F 30.29; N
11.27. C6H14F4N2O2Si. Calculated, %: C 28.80; H
5.64; F 30.36; N 11.19.
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 12 2001