The cationic rearrangement of (3-hydroxy-1-propenyl)tris(trimethylsilyl)-silanes into (1-trimethylsilyl-2-propenyl)bis(trimethylsilyl)silanols - Experimental and theoretical studies

Article abstract of DOI:10.1002/1099-0682(200203)2002:3<597::AID-EJIC597>3.0.CO;2-3

(3-Hydroxy-1-propenyl)tris (trimethylsilyl)silanes (Me₃Si)₃-SiCH=CHCR₂OH (8b,c) (b: R = Me; c: R = Ph) undergo a rapid rearrangement involving a 1,2-Si,C migration of one trimethylsilyl group from the central silicon atom to a cationic neighboring carbon atom and a shift of the olefinic double bond, in the presence of acid, to afford (1-trimethylsilyl-2-propenyl)bis(trimethylsilyl)silanols (Me₃Si)₂Si(OH)CH-(SiMe₃)CH=CR₂ (13b,c). Treatment of 8b,c with sulfuric acid in methanol gives the methoxysilanes (Me₃Si)₂Si(OMe)CH-(SiMe₃)CH=CR₂ (14b,c). In a related reaction, 8b,c are converted by boron trifluoride into the fluorosilanes (Me₃Si)₂-SiFCH(SiMe₃)CH=CR₂ (15b,c). A possible mechanism of the isomerization reaction, involving the rearrangement of the silylcarbenium ions [(Me₃Si)₃SiCH=CHCR₂]⁺ into the silylium ions [(Me₃Si)₂SiCH (SiMe₃)CH=CR₂]⁺, is proposed. This is supported by calculations, which indicate the higher stability of the silylium ion 10b compared with the isomeric silylcarbenium cation 9b. For 14c the results of an X-ray structural analysis are given.

Full text of DOI:10.1002/1099-0682(200203)2002:3<597::AID-EJIC597>3.0.CO;2-3

FULL PAPER
The Cationic Rearrangement of (3-Hydroxy-1-propenyl)tris(trimethylsilyl)-
silanes into (1-Trimethylsilyl-2-propenyl)bis(trimethylsilyl)silanols ؊
Experimental and Theoretical Studies
Kathleen Schmohl,[a] Dirk Wandschneider,[a][‡] Helmut Reinke,[a] Andreas Heintz,*[a] and
Hartmut Oehme*[a]
Keywords: Alcohols / Rearrangements / Silanes / Silicon
(3-Hydroxy-1-propenyl)tris(trimethylsilyl)silanes (Me3Si)3-
verted by boron trifluoride into the fluorosilanes (Me3Si)2-
SiCH=CHCR2OH (8b,c) (b: R = Me; c: R = Ph) undergo a
SiFCH(SiMe3)CH=CR2 (15b,c). A possible mechanism of the
rapid rearrangement involving a 1,2-Si,C migration of one isomerization reaction, involving the rearrangement of the
trimethylsilyl group from the central silicon atom to a cationic
neighboring carbon atom and a shift of the olefinic double
bond, in the presence of acid, to afford (1-trimethylsilyl-2-
silylcarbenium ions [(Me3Si)3SiCH=CHCR2]+ into the silyl-
ium ions [(Me3Si)2SiCH(SiMe3)CH=CR2]+, is proposed. This
is supported by calculations, which indicate the higher
stability of the silylium ion 10b compared with the isomeric
silylcarbenium cation 9b. For 14c the results of an X-ray
propenyl)bis(trimethylsilyl)silanols
(Me3Si)2Si(OH)CH-
(SiMe3)CH=CR2 (13b,c). Treatment of 8b,c with sulfuric acid
in methanol gives the methoxysilanes (Me3Si)2Si(OMe)CH- structural analysis are given.
(SiMe3)CH=CR2 (14b,c). In a related reaction, 8b,c are con-
Introduction
silicon center to the neighboring carbon atom. Some reac-
tions of this type have recently been described,[2,3] and con-
firm expectations from theoretical work, according to
which α-silyl carbenium ions should generally be less stable
than the isomeric silylium ions.[4]
Recently we found that 1-hydroxyalkyltris(trimethylsilyl)-
silanes (1) undergo a rapid isomerization in the presence of
strong acids into 1-trimethylsilylalkylbis(trimethylsilyl)sil-
anols (6) (Scheme 1).[1] The reaction path was interpreted
in terms of a cationic rearrangement initiated by an acid-
catalyzed elimination of water from the alcohol 1 and
formation of the carbenium ion 2. The subsequent 1,2-Si,C
migration of one trimethylsilyl group, and attack of XϪ, the
conjugate base of the acid used as the catalyst, at the central
silicon atom produces the intermediate 5, which after hy-
drolytic workup affords the silanol 6. A decision as to
whether the reaction involves a synchronous nucleophilic
attack by XϪ on the central silicon atom and migration of
one trimethylsilyl group from silicon to carbon (3) or, al-
ternatively, proceeds through a silylium ion intermediate 4,
could not be made. It is very likely that the isomerization
is facilitated by the greater stability of the silylium ion 4
than the carbenium cation 2, and we consider the crucial
step of the conversion 1Ǟ6 to be the isomerization of the
silyl-substituted carbenium ion into the silylium ion by 1,2-
migration of one SiMe3 group from the tetracoordinated
Continuing these studies we extended our experiments to
vinylogous derivatives of the alcohols 1, and in the present
paper we report on the related behavior of (3-hydroxy-1-
propenyl)tris(trimethylsilyl)silanes 8, which rearrange in the
presence of acid to give the (1-trimethylsilyl-2-propenyl)bis-
(trimethylsilyl)silanols 13.
Results and Discussion
The aim of the studies described in this paper was to
examine whether tris(trimethylsilyl)silyl-substituted carben-
ium ions with a delocalized positive charge also undergo
1,2-Si,C trimethylsilyl migrations as discussed above for the
isomerization of 2 into 5. As model compounds we have
chosen tris(trimethylsilyl)silylcarbocations, which were in-
tended to be generated by the acid-induced elimination of
water from the respective 3-hydroxy-1-propenylsilanes. For
that purpose we prepared the alcohols 8a؊c by addition of
tris(trimethylsilyl)silane (7) across the triple bonds of pro-
pargylic alcohol, 2-methyl-3-butyn-2-ol and 1,1-diphenyl-2-
propyn-1-ol (Scheme 2). This method, and its application
to the synthesis of 8a, has already been described,[5] and
proved to be suitable also for the reaction of 7 with the
above-mentioned propynols.
[‡]
Theoretical calculations
[a]
Fachbereich Chemie der Universität Rostock
18051 Rostock, Germany
Fax: (internat.) ϩ49-(0)381/498-6382
E-mail: hartmut.oehme@chemie.uni-rostock.de
andreas.heintz@chemie.uni-rostock.de
Eur. J. Inorg. Chem. 2002, 597Ϫ601
WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ1948/02/0303Ϫ0597 $ 17.50ϩ.50/0
597

K. Schmohl, D. Wandschneider, H. Reinke, A. Heintz, H. Oehme
FULL PAPER
ways recovered unchanged. Under the same conditions,
however, 8b and 8c underwent rapid rearrangements and
after aqueous workup of the reaction mixtures we obtained
the silanols 13b and 13c, respectively. Sulfuric acid proved
to be most effective for the acid-catalyzed isomerization of
1-hydroxyalkyl-tris(trimethylsilyl)silanes (1).[1] Therefore —
and also because of the convenient experimental proced-
ure — we used only this catalyst in all the studies de-
scribed below.
The suggested mechanism of the reaction is outlined in
Scheme 3. Protonation of 8b,c and elimination of water
leads to the carbenium ions 9b,c. (3-Hydroxy-1-propenyl)-
tris(trimethylsilyl)silane (8a) is reluctant to undergo the re-
arrangement. Obviously, elimination of water from the
primary alcohol failed under our conditions and therefore
no reaction occurs. Despite delocalization of the positive
charge in 9b,c, which is expected to enhance the stability of
the carbocations, one trimethylsilyl group migrates from the
central silicon atom to the adjacent carbon atom generating
the transient silylium ions 10b,c. As already mentioned,
Apeloig et al. found that α-silyl-substituted carbenium ions
are generally less stable than the isomeric silylium ions.[3,4]
This is confirmed by ab initio calculations, described below,
which indicate a significantly higher stability of the silylium
ion 10b than the carbenium ion 9b; this energy difference
is supposed to be the driving force of the rearrangement
9b,cǞ10b,c. Addition of XϪ to the silylium silicon atoms
results in formation of the silanes 12b,c, which during the
aqueous workup hydrolyse to give the silanols 13b,c. Of
course, a synchronous process involving an attack of XϪ at
the central silicon atom of 9b,c and a simultaneous shift of
one Me3Si group to the α-carbon atom of the alkyl substitu-
ent affording 12b,c cannot be excluded.
Scheme 1. The acid-induced rearrangement of 1-hydroxyalkyltris-
(trimethylsilyl)silanes 1 into bis(trimethylsilyl)-1-trimethylsilylalkyl-
silanols 6
For the reaction of 8c with ethereal HCl the intermediate
chlorosilane 12c (R ϭ Cl) was isolated; this compound can
easily be converted into the silanol 13c by addition of water.
Attempts to isolate the silyl sulfates 12b,c (R ϭ OSO3H)
after reaction of 8b,c with sulfuric acid failed. Due to rapid
hydrolysis, the products obtained always contained consid-
erable amounts of the silanols 13b,c. When the isomeri-
zation of 8b,c was carried out with sulfuric acid in meth-
anol, solvolysis of the silylsulfates 12b,c (X ϭ OSO3H)
afforded the methoxysilanes 14b,c (Scheme 3).
Of course, a 1,4-migration of one trimethylsilyl group of
9b,c producing the silylium ions 11b,c may be possible
(Scheme 3), although products originating from conver-
sions of 11b,c were not observed. This is in agreement with
the results of the calculations described below.
Scheme 2
In agreement with the literature data, the addition of 7
to the triple bond of propargylic alcohol led to the Z-olefin
8a.[5] In contrast, the coupling constants of the olefinic pro-
tons in 8b and 8c unambiguously revealed an E-configura-
tion for both olefins. This difference is due to the different
space filling properties of the C(OH)R2 substituents (R ϭ
Me, Ph) in 8b,c.
According to a related mechanism, treatment of 8b,c with
boron trifluoride produced the fluorosilanes 15b,c
(Scheme 4).
The structures of 8b,c and 13b,c؊15b,c were elucidated
by a full spectral analysis (1H, 13C and 29Si NMR spectro-
scopy, IR spectroscopy, MS and elemental analysis). For
The Acid-Induced Isomerization of the (3-Hydroxy-1-
propenyl)tris(trimethylsilyl)silanes into (1-Trimethylsilyl-2-
propenyl)bis(trimethylsilyl)silanols
The alcohols 8a؊c, dissolved in ether, were treated with the methoxysilane 14c an X-ray structural analysis was per-
hydrochloric acid or, alternatively, pentane solutions of formed, which confirmed the compound as a crowded sil-
8a؊c were stirred with a few drops of sulfuric acid at room ane (Figure 1). Thus, the Si1ϪC1 bond in 14c is slightly
˚
temperature. In all experiments with 8a the alcohol was al- elongated (1.906 A) and the angle C1ϪSi1ϪSi3 (112.53 °)
598
Eur. J. Inorg. Chem. 2002, 597Ϫ601

The Rearrangement of Hydroxysilanes into Silanols
FULL PAPER
Figure 1. Molecular structure of 14c in the crystal (H atoms omit-
ted, except C1H and C2H, ORTEP plot with 30% probability of
˚
the thermal ellipsoids); selected bond lengths [A] and angles [°]:
Si1ϪC1 1.906(4), Si1ϪSi2 2.3621(19), Si1ϪSi3 2.3630(18), Si1ϪO1
1.645(4), C1ϪSi4 1.898(4), C1ϪC2 1.496(5), C2ϪC3 1.338(5);
Si2ϪSi1ϪSi3 111.27(7), Si1ϪC1ϪSi4 114.60(19), Si1ϪO1ϪC19
131.6(5), Si3ϪSi1ϪC1 112.53(13), Si2ϪSi1ϪC1 109.54(13),
O1ϪSi1ϪC1 105.74(19)
ity of a 1,4-trimethylsilyl migration in 9b, we also included
the silylium ion 11b in these studies (Scheme 3). The calcu-
lations were performed for isolated species using the
Gaussian 98 program package.[6] The following procedure
was applied. First, we made a geometry optimization of 9b,
10b and 11b at the HF/6-31G(d) level. Based on these geo-
metric structures single point energy calculations were per-
formed at the HF/6-31G(d) and MP2/6-31G(d) levels. Sec-
ondly, geometry optimizations with single point energy cal-
culations were performed at the HF/6-31ϩϩG(d,p) level.[7]
The values of the absolute energies obtained by these pro-
cedures are shown in Table 1. Table 2 shows the energy dif-
ferences in kcal/mol. The differences of the absolute ener-
gies obtained at the different levels indicate a stabilization
of 10b of between 9.9 and 22.7 kcal·molϪ1 compared with
9b depending on the method indicated in Table 2. The
values obtained are close to the stabilization energies of
other silylium ions over their isomeric α-silyl-substituted
carbenium ions reported by Apeloig.[4] The other possible
intermediate 11b is energetically disfavoured by between 3.6
Scheme 3. The acid-induced conversion of the 3-hydroxy-1-propen-
yltris(trimethylsilyl)silanes 8b,c into the silanols 13b,c or the me-
thoxysilanes 14b,c
Scheme 4
is widened. The other bond lengths and angles are in the
expected range.
The reaction sequence 8Ǟ10 can be considered to be
Table 1. Sum of electronic energies and nuclear repulsion energies
possibly a useful method for the generation of sterically E [Hartrees][a] of isomers 9b, 10b and 11b, without corrections due
to zero-point energies, thermal energies and solute-solvent interac-
tions
congested silylium ions just by operating in the unprotected
periphery of the molecule.
Method
E(9b)
E(10b)
E(11b)
Theoretical Studies
HF/6-31G(d)
Ϫ1706.05509 Ϫ1706.07197 Ϫ1706.06543
Ϫ1708.20490 Ϫ1708.24102 Ϫ1708.22252
Since there is no direct experimental evidence that the
rearrangement of 8b,c Ǟ 13b,c proceeds through the inter-
mediates 9b,c and 10b,c, we have used ab initio calculations
to predict the relative stabilities of the carbenium ion 9b
MP2/6-31G(d)[b]
HF/6-31ϩϩG(d,p) Ϫ1706.12505 Ϫ1706.14087 Ϫ1706.13510
[a] 1 Hartree ϭ 627.5095 kcal·molϪ1 [b] Single point energy calcula-
and the isomeric silylium ion 10b. To estimate the probabil- tion based on an HF/6-31G(d) geometry optimization.
.
Eur. J. Inorg. Chem. 2002, 597Ϫ601
599

K. Schmohl, D. Wandschneider, H. Reinke, A. Heintz, H. Oehme
FULL PAPER
kcal·molϪ1 [HF/6-31ϩϩG(d,p)] and 11.6 kcal·molϪ1 [MP2/
6-31G(d)] compared with 10b. These results clearly indicate
a higher stability of 10b compared with 9b and 11b, sup-
porting the reaction mechanism suggested in Scheme 3.
30 mL of ether containing excess hydrogen chloride, and the solu-
tion was stirred at room temperature for 8 h. After addition of solid
NaHCO3 and filtration, the solution was evaporated. Chromato-
graphic separation of the residue (silica gel, heptane/ethyl acetate
20:1) gave 0.14 g (26%) of the chlorosilane 12c and 0.15 g (30%) of
the silanol 13c.
12c: Colorless oil. 1H NMR ([D6]benzene): δ ϭ 0.18, 0.22 and 0.27
Table 2. Differences in the total energies [kcal·molϪ1] of the three
isomeric cations 9b, 10b and 11b
3
(3s, 3 ϫ 9 H, SiCH3). 2.51 (d, J ϭ 13.4 Hz, 1 H, SiCH), 6.43 (d,
3J ϭ 13.4 Hz, 1 H, olef. CH), 6.98Ϫ7.48 (m, arom. 10 H, CH). 13
C
NMR ([D6]benzene): δ ϭ Ϫ0.9, Ϫ0.6 and 0.3 (SiCH3), 22.8 (CH),
126.9, 127.1, 127.2, 127.4, 128.6, 128.7, 130.7, 139.4, 140.3 and
143.5 (arom. and olef. C). 29Si NMR ([D6]benzene): δ ϭ Ϫ14.3 and
Ϫ13.7 (SiSiMe3), 3.3 (CSiMe3), 9.6 (SiCl). MS (70 eV): m/z (%) ϭ
474 (5) [M]ϩ, 459 (4) [M Ϫ CH3]ϩ, 439 (1) [M Ϫ Cl]ϩ, 401 (2) [M
Ϫ SiMe3]ϩ, 73 (100) [SiMe3]ϩ. C24H39ClSi4 (475.4): calcd. C 60.64,
H 8.27, Cl 7.46; found C 61.18, H 8.24, Cl 8.07. HRMS: calcd.
474.18173; found 474.18510.
Method
E(9b) Ϫ E(10b)
E(11b) Ϫ E(10b)
HF/6-31G(d)
10.6
22.7
9.9
4.1
11.6
3.6
MP2/6-31G(d)[a]
HF/6-31ϩϩG(d,p)
[a]
Single point energy calculation based on a HF/6-31G(d) geo-
metry optimization.
(3-Methyl-1-trimethylsilyl-2-butenyl)bis(trimethylsilyl)silanol (13b):
Concentrated sulfuric acid (0.15 g, 1.5 mmol) was added gradually
to a solution of 8b (0.5 g, 1.5 mmol) in pentane (30 mL) and the
mixture was stirred at room temperature for 8 h. After neutraliza-
tion with aqueous NaHCO3 solution, washing with water and dry-
ing, the solvent was removed in vacuo and the residue purified by
column chromatography (silica gel, heptane/ethyl acetate 20:1) to
give 0.09 g (18%) of 13b. Colorless oil. IR (nujol): ν˜ ϭ 3454 cmϪ1
(SiOHass.), 3649 cmϪ1 and 3677 cmϪ1 (SiOHfree). 1H NMR
([D6]benzene): δ ϭ 0.19 (s, 18 H, SiSiCH3), 0.24 (s, 9 H, SCSiCH3),
0.52 (s, 1 H, OH), 1.54 and 1.70 (2d, 4J ϭ 1.2 Hz, 2 ϫ 3 H, CCH3),
1.97 (d, J ϭ 12.8 Hz, 1 H, SiCH), 5.24 (dpseudoquart, J ϭ 12.8,
4J ϭ 1.2 Hz, 1 H, olef.CH). 13C NMR ([D6]benzene): δ ϭ Ϫ1.1,
Ϫ0.3 and Ϫ0.1 (SiCH3), 17.9 and 26.0 (CCH3), 22.8 (CH), 121.6
and 127.8 (olef. C). 29Si NMR ([D6]benzene): δ ϭ Ϫ19.4 and Ϫ19.6
(SiSiMe3), 2.0 (CSiMe3), 8.4 (SiSiMe3). MS (70 eV): m/z (%) ϭ 332
(2) [M]ϩ, 317 (4) [M Ϫ CH3]ϩ, 259 (19) [M Ϫ SiMe3]ϩ, 73 (100)
[SiMe3]ϩ. HRMS: calcd. 332.18433; found 332.18365.
Experimental Section
General: All reactions involving organometallic reagents were car-
ried out under purified argon. NMR: Bruker AC 250 or Bruker
ARX 300, tetramethylsilane as internal standard. IR: Nicolet 205
FT-IR. MS: Intectra AMD 402. (Me3Si)3SiH (7) was prepared us-
ing the method described by Marschner;[8] 8a was synthesized fol-
lowing the procedure given by Utimoto,[5] but the reaction was in-
duced by AIBN instead of triethylborane. Due to the formation of
SiC, the results of the elemental analyses of some compounds were
unsatisfactory. In these cases HRMS data are given.
3
3
(3-Hydroxy-3-methyl-1-butenyl)tris(trimethylsilyl)silane (8b): 2-
Methyl-3-butyn-2-ol (1.2 g, 14.0 mmol) and AIBN (0.2 g) were
gradually added at room temperature to a solution of 7 (3.0 g,
12.1 mmol) in toluene (30 mL). The mixture was heated under re-
flux for 5 h, and then water was added and the organic phase separ-
ated, dried and the solvents evaporated. The residue was purified
by kugelrohr distillation at 75Ϫ100 °C/7·10Ϫ3 mbar to afford 3.0 g
(74.7%) of 8b. Colorless crystals, m.p. 58Ϫ63 °C. IR (nujol): ν˜ ϭ
3407 cmϪ1 (OH). 1H NMR ([D6]benzene): δ ϭ 0.27 (s, 27 H,
SiCH3), 0.98 (s, 1 H, OH), 1.15 (s, 6 H, CCH3), 5.92 (d, 3J ϭ
18.6 Hz, 1 H, CH), 6.29 (d, 3J ϭ 18.6 Hz, 1 H, CH). 13C NMR
([D6]benzene): δ ϭ 0.9 (SiCH3), 29.7 (CCH3), 71.9 (COH), 115.4
and 156.9 (olef. C). 29Si NMR ([D6]benzene): δ ϭ Ϫ85.5 (SiSiMe3),
Ϫ13.1 (SiMe3). MS (70 eV): m/z (%) ϭ 317 (3) [M Ϫ CH3]ϩ, 315
(3) [M Ϫ OH]ϩ, 259 (12) [M Ϫ SiMe3]ϩ, 73 (100) [SiMe3]ϩ.
C14H36OSi4 (332.8): calcd. C 50.53, H 10.90; found C 50.79, H
10.85.
(3,3-Diphenyl-1-trimethylsilyl-2-propenyl)bis(trimethylsilyl)silanol
(13c): Following the procedure described above but using ether in-
stead of pentane as the solvent, 0.5 g (1.1 mmol) of 8c and 0.3 g
(0.3 mmol) of sulfuric acid afforded 0.22 g (45%) of 13c. Colorless
crystals from heptane/ethyl acetate, m.p 96Ϫ98 °C. IR (nujol): ν˜ ϭ
3463 cmϪ1 (SiOHass.), 3646 and 3677 cmϪ1 (SiOHfree). 1H NMR
([D6]benzene): δ ϭ 0.12, 0.21 and 0.23 (3s, 3 ϫ 9 H, SiCH3), 0.57 (s,
1 H, OH), 2.47 (d, 3J ϭ 13.4 Hz, 1 H, CH), 6.52 (d, 3J ϭ 13.4 Hz, 1
H, CH), 6.98Ϫ7.41 (m, arom. 10 H, CH). 13C NMR ([D6]acetone):
δ ϭ Ϫ1.0, Ϫ0.5 and 0.0 (SiCH3), 25.8 (CH), 126.5, 127.0, 127.2,
128.6, 128.8, 129.7, 130.9, 137.2, 140.8 and 144.0 (arom. and olef.
C). 29Si NMR ([D6]benzene): δ ϭ Ϫ19.1 and Ϫ18.8 (SiSiMe3), 2.1
(CSiMe3), 8.8 (SiSiMe3). MS (70 eV): m/z (%) ϭ 456 (2) [M]ϩ, 441
(5) [M Ϫ CH3]ϩ, 338 (20) [M Ϫ SiMe3]ϩ, 73 (100) [SiMe3]ϩ.
C24H40OSi4 (456.9): calcd. C 63.09, H 8.82; found C 62.92, H 8.88.
(3-Hydroxy-3,3-diphenyl-1-propenyl)tris(trimethylsilyl)silane (8c):
Following the procedure given for 8b, 3.0 g (12.1 mmol) of 7, 2.50 g
(12.1 mmol) of 1,1-diphenyl-2-propyn-1-ol and 0.2 g of AIBN gave
2.7 g (49%) of 8c after kugelrohr distillation (200 °C/3·10Ϫ2 mbar).
Ϫ1
˜
Colorless oil. IR (cap.): ν ϭ 3462 cm (OHass.), 3556 and 3601
Methoxy(3-methyl-1-trimethylsilyl-2-butenyl)bis(trimethylsilyl)-
silane (14b): Compound 8b (0.5 g, 1.5 mmol) and sulfuric acid
(0.4 g, 3.6 mmol) were dissolved in 30 mL of methanol. The solu-
tion was stirred at room temperature for 8 h, neutralized with solid
NaHCO3 and washed with cold water. The product was extracted
with ether, the solution evaporated and the residue purified by
chromatography (silica gel, heptane/ethyl acetate 20:1) to afford
1
cmϪ1 (OHfree). H NMR ([D6]benzene): δ ϭ 0.23 (s, 27 H, SiCH3),
3
3
1.84 (s, 1 H, OH), 6.12 (d, J ϭ 18.6 Hz, 1 H, CH), 6.82 (d, J ϭ
18.6 Hz, 1 H, CH), 7.03Ϫ7.49 (m, arom. 10 H, CH). 13C NMR
([D6]benzene): δ ϭ 1.0 (SiCH3), 81.0 (COH), 119.6 and 153.3 (olef.
C), 127.3, 127.5 and 128.3 (arom. CH), 146.8 (arom. C). 29Si NMR
([D6]benzene): δ ϭ Ϫ85.0 (SiSiMe3), Ϫ12.8 (SiMe3). MS (70 eV):
m/z (%) ϭ 456 (2) [M]ϩ, 441 (2) [M Ϫ CH3]ϩ, 439 (2) [M Ϫ OH]ϩ,
383 (7) [M Ϫ SiMe3], 73 (100) [SiMe3]ϩ. C24H40OSi4 (456.9): calcd.
C 63.09, H 8.82; found 63.47, H 8.86.
0.21 g (40%) of 14b. Colorless crystals, m.p. 54Ϫ58 °C. IR (nujol):
Ϫ1
ν ϭ 1087 cm (SiOC). 1H NMR ([D6]benzene): δ ϭ 0.22, 0.24
˜
4
and 0.29 (3s, 3 ϫ 9 H, SiCH3), 1.56 and 1.70 (2d, J ϭ 1.2 Hz, 2
Chloro(3,3-diphenyl-2-propenyl-1-trimethylsilyl)bis(trimethylsilyl)- ϫ 3 H, CCH3), 2.01 (d, 3J ϭ 12.8 Hz, 1 H, SiCH), 3.31 (s, 3 H,
silane (12c): Compound 8c (0.5 g, 1.1 mmol) was dissolved in OCH3), 5.25 (dpseudoquart, 3J ϭ 12.8, 4J ϭ 1.2 Hz, 1 H, olef.
600
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The Rearrangement of Hydroxysilanes into Silanols
FULL PAPER
CH). 13C NMR ([D6]benzene): δ ϭ Ϫ0.2, Ϫ0.1 and 0.6 (SiCH3),
17.9 and 26.0 (CCH3), 21.3 (CH), 53.6 (OCH3), 121.7 and 127.7
X-ray Structure Determination of 14c: X-ray diffraction data were
collected with a Bruker P4 four-circle diffractometer, Mo-Ka radi-
(olef. C). 29Si NMR ([D6]benzene): δ ϭ Ϫ19.6 and Ϫ19.8 (SiS- ation, graphite monochromator, crystal size 0.48 ϫ 0.44 ϫ 0.41
iMe3), 2.4 (CSiMe3), 12.2 (SiOMe). MS (70 eV): m/z (%) ϭ 346 (2) mm3, T ϭ 293(2)K, C25H42OSi4, M ϭ 470.95, colorless prism,
[M]ϩ, 331 (7) [M Ϫ CH3]ϩ, 273 (15) [M Ϫ SiMe3]ϩ, 73 (100)
monoclinic, a ϭ 9.205(2), b ϭ 12.684(7), c ϭ 13.226(4) A, β ϭ
˚
3
[SiMe3]ϩ. C15H38OSi4 (346.8): calcd. C 51.95, H 11.04; found C 94.78(3)°, V ϭ 1538.8(10) A , Z ϭ 2, space group Pn, ρber ϭ 1.016
˚
51.82, H 10.89. HRMS: calcd. 346.19998; found 346.19792.
Mg mϪ3, µ ϭ 0.206 mmϪ1, F(000) ϭ 512, data collection range:
4.46Յ 2Θ Յ 44.00, Ϫ9 Յ h Յ 9, Ϫ13 Յ k Յ 13, Ϫ13 Յ l Յ 13,
4054 reflections collected, 3776 independent and 3156 observed [I
Ͼ 2σ (I)], R1 ϭ 0.0452 (obs.), wR2 ϭ 0.1073 (obs.), GOF(F2) ϭ
Methoxy(3,3-diphenyl-1-trimethylsilyl-2-propenyl)bis(trimethyl-
silyl)silane (14c): As described for 14b, 0.5 g (1.1 mmol) of 8c gave
0.4 g (78%) of 14c after treatment with H2SO4 in methanol. The
purification was performed by chromatography (silica gel, hept-
ane); single crystals were obtained by recrystallization from hept-
Ϫ3
˚
1.033; max./min. residual electron density: ϩ0.122/Ϫ0.105 e·A
.
The weighting scheme was calculated according to wϪ1 ϭ σ2 (F02)ϩ
(0.0485P)2 ϩ 0.000 P with P ϭ (F02 ϩ 2 F2c)/3. The structure was
solved by direct methods (Bruker SHELXTL). All non-hydrogen
atoms were refined anisotropically, with the hydrogen atoms
introduced into theoretical positions and refined using a riding
model.
Ϫ1
1
˜
ane, m.p. 83Ϫ87 °C. IR (nujol): ν ϭ 1090 cm (SiOC). H NMR
([D6]benzene): δ ϭ 0.17, 0.24 and 0.29 (3s, 3 ϫ 9 H, SiCH3), 2.52
3
3
(d, J ϭ 13.4 Hz, 1 H, SiCH), 3.28 (s, OCH3, 1 H), 6.54 (d, J ϭ
13.4 Hz, 1 H, olef. CH), 7.01Ϫ7.42 (m, 10 H, arom. CH). 13C
NMR ([D6]benzene): δ ϭ 0.1, 0.2 and 0.7 (SiCH3), 24.9 (CH), 53.6
(OCH3), 126.6, 127.0, 127.2, 128.5, 128.6, 128.9, 130.9, 137.9, 140.6
and 144.0 (arom. and olef. C). 29Si NMR ([D6]benzene): δ ϭ
Ϫ19.26 and Ϫ19.31 (SiSiMe3), 2.7 (CSiMe3), 13.2 (SiOMe). MS
(70 eV): m/z (%) ϭ 470 (2) [M]ϩ, 450 (10) [M Ϫ CH3]ϩ, 397 (15)
[M Ϫ SiMe3]ϩ, 73 (100) [SiMe3]ϩ. C25H42OSi4 (471.0): calcd. C
63.76, H 8.99; found C 63.75, H 8.78.
Crystallographic data (excluding structure factors) for the
structure in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no.
CCDC-156379. Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK [Fax: (internat.) ϩ44-1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk].
Fluoro(3-methyl-1-trimethylsilyl-2-butenyl)bis(trimethylsilyl)silane
(15b): Boron trifluoride diethyl ether complex (0.22 g, 1.6 mmol)
was added gradually at Ϫ78 °C to a solution of 8b (0.50 g,
1.5 mmol) in diethyl ether (30 mL) and the mixture was stirred for
2 h. After warming to room temperature stirring was continued for
4 h, water was added and the organic phase was separated, dried
and the solvents evaporated. Column chromatography (silica gel,
heptane) of the residue gave 0.40 g (79.5%) of 15b. Colorless oil.
Acknowledgments
We gratefully acknowledge the support of our work by the
Deutsche Forschungsgemeinschaft and the Fonds der Chemischen
Industrie. We thank Prof. M. Michalik, Dr. W. Baumann and Prof.
N. Stoll for recording the NMR and mass spectra.
[1]
˜
Ϫ1 (SiF). 1H NMR ([D6]benzene): δ ϭ 0.21
K. Sternberg, H. Oehme, Eur. J. Inorg. Chem. 1998, 177Ϫ181.
P. D. Lickiss, J. Chem. Soc., Dalton Trans. 1992, 1333Ϫ1338; J.
IR (nujol): ν ϭ 1011 cm
[2]
4
(s, 18 H, SiSiMe3), 0.25 (s, 9 H, CSiMe3), 1.51 and 1.67 (2d, J ϭ
Chojnovski, W. Stancsyk, Main Group Met. Chem. 1994, 2,
6Ϫ15; J. B. Lambert, L. Kania, S. Zhang, Chem. Rev. 1995, 95,
1191Ϫ1201; R. Bakhtiar, C. M. Holznagel, D. B. Jacobson, J.
Am. Chem. Soc. 1992, 114, 3227Ϫ3235 and references cited
therein.
3
3
1.53 Hz, 2 ϫ 3 H, CCH3), 2.18 (dd, J ϭ 5.8, J ϭ 12.8 Hz, 1 H,
CH), 5.27 (dpseudoquart, 3J ϭ 12.8, 4J ϭ 1.53 Hz, olef. CH, 1 H).
13C NMR ([D6]benzene): δ ϭ Ϫ1.5, Ϫ0.6 and Ϫ0.5 (SiCH3), 17.8
and 25.9 (CCH3), 22.9 (d, 2J ϭ 15.0 Hz, SiCH), 120.3 (d, 3J ϭ
4.7 Hz, olef. CH), 128.3 (olef. C). 29Si NMR ([D6]benzene): δ ϭ
[3]
Y. Apeloig, A. Stanger, J. Am. Chem. Soc. 1987, 109, 272Ϫ273.
1
[4]
Ϫ19.0 and Ϫ19.4 (SiSiMe3), 2.6 (CSiMe3), 33.5 (d, J ϭ 334 Hz,
Y. Apeloig, A. Stanger, J. Am. Chem. Soc. 1985, 107,
SiF). 19F NMR ([D6]benzene): δ ϭ Ϫ198.1 (SiF). MS (70 eV): m/z
(%) ϭ 335 (5) [M ϩ H]ϩ, 319 (5) [M Ϫ CH3]ϩ, 261 (15) [M Ϫ
SiMe3]ϩ, 73 (100) [SiMe3]ϩ. Due to the ease of fragmentation an
HRMS could not be obtained.
2806Ϫ2807.
[5]
K. Miura, K. Oshima, K. Utimoto, Bull. Chem. Soc. Jpn. 1993,
66, 2356Ϫ2364.
Gaussian 98, Revision A.9; M. J. Frisch, G. W. Trucks, H. B.
[6]
Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G.
Zakrzewski, J. A. Montgomery, Jr., R. E. Stratmann, J. C. Bur-
ant, S. Dapprich, J. M. Millam, A. D. Daniels, K. N. Kudin,
M. C. Strain, O. Farkas, J. Tomasi, V. Barone, M. Cossi, R.
Cammi, B. Mennucci, C. Pomelli, C. Adamo, S. Clifford, J.
Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, K. Morokuma,
D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman,
J. Cioslowski, J. V. Ortiz, A. G. Baboul, B. B. Stefanov, G. Liu,
A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A.
Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.
Chen, M. W. Wong, J. L. Andres, C. Gonzalez, M. Head-Gor-
don, E. S. Replogle, and J. A. Pople, Gaussian, Inc., Pittsburgh
PA, 1998.
Fluoro(3,3-diphenyl-1-trimethylsilyl-2-propenyl)bis(trimethylsilyl)-
silane (15c): As described above, treatment of 0.50 g (1.1 mmol) of
8c with 0.16 g (1.1 mmol) of boron trifluoride diethyl ether complex
in ether (30 mL) afforded 0.22 g (43%) of colorless crystals, m.p.
Ϫ1
76Ϫ79 °C. IR (nujol): ν ϭ 1021 cm (SiF). 1H NMR ([D6]ben-
˜
zene): δ ϭ 0.13, 0.23 and 0.27 (3s, 3 ϫ 9 H, SiCH3), 2.57 (dd, 3J ϭ
3
3
8.8, J ϭ 13.4 Hz, 1 H, SiCH), 6.57 (d, J ϭ 13.4 Hz, 1 H, olef.
CH), 7.01Ϫ7.39 (m, 10 H, arom. CH). 13C NMR ([D6]benzene):
δ ϭ Ϫ1.3, Ϫ0.7 and Ϫ0.3 (SiCH3), 26.2 (d, 2J ϭ 15.9 Hz, CH),
126.8, 126.9, 127.2, 128.3, 128.7, 130.6, 138.8, 140.6, 143.3 and
148.7 (arom. and olef. C). 29Si NMR ([D6]benzene): δ ϭ Ϫ18.6
(SiSiMe3), 3.0 (CSiMe3), 34.7 (d, 1J ϭ 334 Hz, SiF). 19F NMR
([D6]benzene): δ ϭ Ϫ197.5 (SiF). MS (70 eV): m/z (%) ϭ 458 (5)
[M]ϩ, 443 (2) [M Ϫ CH3]ϩ, 385 (2) [M Ϫ SiMe3]ϩ, 73 (100)
[SiMe3]ϩ. C24H39FSi4 (458.9): calcd. C 62.81, H 8.57; found C
62.82, H 8.50.
[7]
Geometric data of the calculated structures are available on re-
quest.
[8]
C. Marschner, Eur. J. Inorg. Chem. 1998, 221Ϫ226.
Received May 7, 2001
[I01158]
Eur. J. Inorg. Chem. 2002, 597Ϫ601
601