ISSN 0012ꢀ5008, Doklady Chemistry, 2009, Vol. 428, Part 1, pp. 210–212. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © S.V. Basenko, M.G. Voronkov, L.E. Zelenkov, A.I. Albanov, 2009, published in Doklady Akademii Nauk, 2009, Vol. 428, No. 2, pp. 191–193.
CHEMISTRY
Unusual Transformations of the PhSiFCl Group
S. V. Basenko, Academician M. G. Voronkov, L. E. Zelenkov, and A. I. Albanov
Received March 27, 2009
DOI: 10.1134/S001250080909002X
The reactions of phenyltrihalosilanes PhSiX3
(where X = F, Cl) with Si–O–Si, Si–O–C, and
C⎯O–C groups proceed in different directions. Thus,
the cleavage of the Si–O bond in hexamethyldisiloxꢀ
ane (HMDS) with phenyltrichlorosilane occurs only
The yield and product composition of reaction (3)
do not change when an excess of HMDS is used
(the molar ratio 1 : 1.5 at 25
resulting phenylfluorosiloxane (III) does not cleave
Si–O–Si group under these conditions.
°С). This indicates that
≡
≡
at temperatures above 200–250°С under enhanced
pressure or under milder conditions in the presence of
catalysts [1–3].
The reaction of phenylfluorodichlorosilane (II
)
with HMDS under the same conditions over 12–14 h
leads to 1,1,1ꢀtrimethylꢀ3ꢀphenylꢀ3ꢀchloroꢀ3ꢀfluoroꢀ
disiloxane (IV), containing asymmetric silicon atom,
in 55–60% yield.
Previously, we found that phenyltrifluorosilane
cleaves the ≡Si–O–Si≡ group in HMDS even at ambiꢀ
ent temperature over 6–8 h [4]:
PhSiFCl2 + Me3SiOSiMe3
PhSiF3 + Me3SiOSiMe3
PhSiFClOSiMe3 + Me3SiCl.
(4)
PhSiF2OSiMe3 + Me3SiF.
(1)
IV
As distinct from this reaction, we revealed that pheꢀ
nyltrifluorosilane does not cleave the Si–O–C group
in trimethylacyloxysilanes at reflux.
The cleavage of the Si–O–Si group with phenylꢀ
chlorofluorodisiloxane (IV) at ambient temperature
proceeds slowly (24–48 h) to yield 1,1,1,5,5,5ꢀhexꢀ
It is noteworthy that such reactions take place at
ambient temperature if PhSiX3 are replaced by mixed
amethylꢀ3ꢀphenylꢀ3ꢀfluorotrisiloxane (V):
phenylfluorochlorosilanes PhSiF3 – nCln at
n = 1 (I)
PhSiFCl2 + 2Me3SiOSiMe3
and 2 (II). These compounds were obtained by the disꢀ
proportionation of PhSiF3 and PhSiCl3 in the presꢀ
ence of aluminum chlorides [5], bromides, and fluoꢀ
PhSiF(OSiMe3)2 + 2Me3SiCl.
(5)
V
rides at 105–120°C
Its low yield (7–15%) seems to result from steric
hindrances. The same reason explains the low yield
(10ꢀ15%) of 1,1,1ꢀtriethylꢀ3ꢀphenylꢀ3,3ꢀdifluoroꢀ
PhSiF3 + PhSiCl3
(2)
PhSiF2Cl + PhSiFCl2.
disiloxane (VI) in the reaction of PhSiF2Cl
hexaethyldisiloxane at ambient temperature during
48 72 h.
(I) with
I
II
⎯
Phenyldifluorochlorosilane (
I
) almost quantitaꢀ
tively cleaves the Si–O bond in HMDS over 1 h at
ambient temperature to give 1,1,1ꢀtrimethylꢀ3ꢀpheꢀ
nylꢀ3,3ꢀdifluorodisiloxane (III) and trimethylchloꢀ
rosilane:
PhSiF2Cl + (Et3Si)2O
PhSiF2OSiEt3 + Et3SiCl.
(6)
VI
The large difference in the reactivity of
PhSiF2Cl ( and PhSiF3 is convincingly confirmed by
PhSiF2Cl + Me3SiOSiMe3
I)
(3) the competitive reaction of their mixture with HMDS
in a 1 : 1 : 1 molar ratio at ambient temperature. The
reaction leads only to phenylfluorosiloxane (III) and
trimethylchlorosilane in accordance with equation
(3). At the same time, no trimethylfluorosilane was
detected in the reaction mixture, while all PhSiF3
remained unchanged.
PhSiF2OSiMe3 + Me3SiCl.
III
Favorskii Institute of Chemistry, Siberian Branch,
Russian Academy of Sciences, ul. Favorskogo 1, Irkutsk,
664033 Russia
210