Reaction of the (dichloromethyl)oligosilanes R(Me3Si)2Si - CHCl2 (R = Me, Ph, Me3Si) with organolithium reagents and the synthesis of novel kinetically stabilized silenes

Article abstract of DOI:10.1002/1099-0682(200102)2001:2<481::AID-EJIC481>3.0.CO;2-6

The dichloromethyloligosilanes R¹(Me₃Si)₂Si - CHCl₂ (1a,b) (1a: R¹ = Me; 1b: R¹ = Ph), prepared by treatment of methylbis(trimethylsilyl)silane or phenylbis(trimethylsilyl)silane respective

Full text of DOI:10.1002/1099-0682(200102)2001:2<481::AID-EJIC481>3.0.CO;2-6

FULL PAPER
Reaction of the (Dichloromethyl)oligosilanes R(Me3Si)2Si؊CHCl2 (R ؍ Me,
Ph, Me3Si) with Organolithium Reagents and the Synthesis of Novel
Kinetically Stabilized Silenes
Kathleen Schmohl,[a] Helmut Reinke,[a] and Hartmut Oehme*[a]
Keywords: Lithium / Silaethene / Silanes / Silenes / Silicon
The dichloromethyloligosilanes R1(Me3Si)2Si−CHCl2 (1a,b)
(1a: R1 = Me; 1b: R1 = Ph), prepared by treatment of methyl-
bis(trimethylsilyl)silane or phenylbis(trimethylsilyl)silane re-
of 1b with 2,4,6-triisopropylphenyllithium (molar ratio 1:2).
Similarly, (Me3Si)(2,4,6-iPr3C6H2)Si=C(SiMe3)2 (8c) and
(Me3Si)(2-tBu-4,5,6-Me3C6H)Si=C(SiMe3)2 (9c) were pre-
spectively, with chloroform and potassium tert-butoxide, pared from (dichloromethyl)tris(trimethylsilyl)silane (1c) and
treated with the organolithium reagents R2Li (R2 = Me, Ph)
to produce the intermediate organolithium derivatives
2,4,6-triisopropylphenyllithium or 1c and 2-tert-butyl-4,5,6-
trimethylphenyllithium (1:2), respectively, but due to diffi-
R1R22Si−CLi(SiMe3)2 (10). Hydrolysis of 10 during the aque- culties in the separation of starting material and side prod-
ous workup afforded the [bis(trimethylsilyl)methyl]silanes
R1R22Si−CH(SiMe3)2 (2); quenching of the reaction mixture
with chlorotrimethylsilane gave the [tris(trimethylsilyl)me-
ucts, 8b, 8c, and 9c were obtained in impure form only. De-
spite the steric congestion, the compounds are reactive and
exhibit the usual behavior of silenes. Thus 8b, 8c, and 9c
thyl]silanes R1R22Si−C(SiMe3)3 (11). The formation of 10 is dis- were chemically characterized by the reaction with water to
cussed as proceeding through a remarkable series of iso- give silanols, by the addition of methanol to give methoxy-
merization processes involving the transient silenes R1R2Si=
C(SiMe3)2 (7), which in the presence of an effective excess
of R2Li are immediately trapped to give 10. By the use of
silanes and by formal [2+2] cycloadditions with benzaldehyde
to afford stable 1,2-oxasiletanes. 1-Methyl-1-(2,4,6-triisopro-
pylphenyl)-2,2-bis(trimethylsilyl)silene (8a), produced as in-
sterically congested organolithium derivatives, the nucleo- termediate from 1a and 2,4,6-triisopropylphenyllithium (1:2),
philic addition of R2Li to the Si=C bond of 7 can be prevented
and kinetically stabilized silenes obtained. Thus, Ph(2,4,6-
iPr3C6H2)Si=C(SiMe3)2 (8b) was synthesized by the reaction
proved to be unstable in the presence of excess aryllithium
compound. Thus, only the addition product Me(2,4,6-
iPr3C6H2)2SiCH(SiMe3)2 (14) was isolated (after hydrolysis).
Introduction
2-neopentylsilene.[4] A further method, which has proved to
be an efficient general route to silenes, is the sila Peterson
reaction. We were able to contribute to the development of
the process and generated a number of transient silenes and
studied their mode of dimerization,[5] and in 1996 Apeloig
and co-workers succeeded in preparing the stable derivative
(tBuMe2Si)2SiϭCAdЈ (AdЈ ϭ 2-adamantylidene) by this
method.[6] A few further stable silenes have been isolated by
the groups mentioned.[1] Of course, the structures of these
compounds are related to their methods of preparation, and
extension of the substitution pattern by introducing new
synthetic pathways is desirable.
Recently we reported the reaction of (dichloromethyl)-
tris(trimethylsilyl)silane (1c) with organolithium reagents
RLi (R ϭ Me, nBu, Ph, Mes).[7] As the result of a remark-
able sequence of isomerization and addition steps, and a
complete reorganization of the substitution pattern of the
starting compound, [bis(trimethylsilyl)methyl]silanes 2 were
formed as end products [Equation (1)].
Silenes are known to be extremely labile compounds
which can be isolated and handled under normal conditions
only in those cases where structural influences cause an effi-
cient stabilization of the SiϭC system.[1] In numerous reac-
tions transient silenes occur as reactive intermediates, but
until now the number of synthetic methods affording stable,
isolable silenes is rather limited. Brook and co-workers in-
troduced the photochemical isomerization of acyloligo-
silanes as a versatile method for the generation of silenes,
and in 1982 they were the first to isolate a stable silene,
(Me3Si)2SiϭC(OSiMe3)Ad (Ad ϭ 1-adamantyl), and to
perform an X-ray analysis of the compound.[2] In 1983
Wiberg and his group succeeded in applying the classical
1,2 salt elimination to the synthesis of the stable silene
Me2SiϭC(SiMetBu2)SiMe3 and provided the results of its
X-ray analysis.[3] Elimination of lithium chloride after addi-
tion of tert-butyllithium to the carbonϪcarbon double
bond of chloro(vinyl)silanes is also the crucial step in estab-
lishing SiϭC bonds in a method developed by the groups
of Jones and Auner, which was successfully used by Couret
et al. in 1994 in the preparation of the stable 1,1-dimesityl-
[a]
Fachbereich Chemie der Universität Rostock,
18051 Rostock, Germany
Fax: (internat.) ϩ 49-(0)381/498-1765
E-mail: hartmut.oehme@chemie.uni-rostock.de
Eur. J. Inorg. Chem. 2001, 481Ϫ489
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/0202Ϫ0481 $ 17.50ϩ.50/0
481

K. Schmohl, H. Reinke, H. Oehme
FULL PAPER
As outlined in Scheme 1 for the behavior of the (dichloro- lithium derivatives occupy the former positions of the two
methyl)oligosilanes 1aϪc towards methyllithium or trimethylsilyl substituents. Despite the unexpected outcome
phenyllithium respectively, in the course of this reaction of the reaction, the conversion can be rationalized as a clear
transient silenes occurred as intermediates, which in the sequence of known steps. Our proposal for the reaction
presence of excess organolithium reagent were trapped to mechanism is outlined in Scheme 1, which also includes the
give the products mentioned. Increasing the bulkiness of the formerly described conversion of 1c.[7]
substituents of the organolithium derivatives used in this
The dichloromethylsilanes 1aϪc are deprotonated by the
reaction is expected to afford kinetically stabilized silenes, organolithium reagents with generation of the silylcarbeno-
sufficiently protected against the attack of excess lithium ids 3. Elimination of lithium chloride and migration of one
compound and stable with respect to dimerization. Thus, trimethylsilyl group from the central silicon atom to the car-
this paper describes the extension of the conversion de- bene carbon atom affords the intermediate silene 5.
picted in Equation (1) for 1c to (dichloromethyl)methylbis-
Rearrangements of silylcarbenes to silenes involving the
(trimethylsilyl)silane (1a) and (dichloromethyl)phenylbis- shift of one substituent from the silicon atom to the neigh-
(trimethylsilyl)silane (1b), as well as the generation of novel boring carbene carbon atom are well-documented reactions
stable silenes along this new synthetic pathway.
and a standard method for the generation of transient sil-
enes.[10] Hydrogen, alkyl, aryl, and silyl groups have been
found to be suitable migrating substituents in this isomer-
ization process; the migrating ability of the silyl groups ex-
ceeds that of the other groups mentioned.[11] In the presence
of excess organolithium reagent the silenes 5 are immedi-
ately trapped to give the new carbenoids 6. Repeated elim-
ination of LiCl and a further 1,2-Si,C shift of one trimethyl-
silyl group affords the silenes 7, which again undergo nucle-
ophilic addition of a third equivalent of R2Li, producing
10. Hydrolysis during the aqueous workup affords 2.
The intermediate existence of the chlorosilylcarbene 4
could not be proved and an intramolecular Me3Si/Li ex-
change in 3, followed by a 1,2 lithium chloride elimination,
might be an alternative route to the silene 5. Trapping ex-
periments of the carbene 4 were abandoned, since it is well
known that silylcarbenes, generated photochemically or
thermally from the corresponding diazo compounds, very
rapidly rearrange to the respective silenes, and in numerous
experiments with different scavenger reagents only the sil-
enes were detected.[11,12] The carbenoids 6 proved to be
moderately stable at low temperatures. As described previ-
ously, we succeeded in trapping 6cy, generated from 1c and
phenyllithium, with chlorotrimethylsilane to give
Ph(Me3Si)2SiϪCCl(SiMe3)2 and by quenching with water,
affording Ph(Me3Si)2SiϪCHClSiMe3.[7] The intermediate
organolithium compounds 10, formed by addition of
Results and Discussion
Reaction of (Dichloromethyl)methylbis(trimethylsilyl)silane
(1a) and (Dichloromethyl)phenylbis(trimethylsilyl)silane (1b)
with Organolithium Derivatives
The dichloromethylsilanes 1a and 1b were prepared ad-
apting a procedure reported by Weidenbruch et al. for the
preparation of (dichloromethyl)tri-tert-butylsilane.[8] Thus,
treatment of methylbis(trimethylsilyl)silane with chloroform
in the presence of potassium tert-butoxide afforded 1a in a
yield of 36%. Compound 1b was similarly obtained from
phenylbis(trimethylsilyl)silane, HCCl3 and KOtBu (yield
41%) [Equation (2)]. The dichloromethylsilane 1a has al-
ready been described by Sakurai et al., who obtained the
compound from 2-chloroheptamethyltrisilane and dichloro-
methyllithium.[9]
In agreement with the described reaction of 1c with or- methyllithium or phenyllithium to the silene double bond
ganolithium compounds,[7] 1a reacted with methyllithium at of 7, are suitable precursors for highly congested tris(silyl)-
room temperature (molar ratio 1:3) to give, after hydrolytic methyl-substituted silanes. Thus, addition of chlorotrime-
workup, tris(trimethylsilyl)methane (2ax). Under the same thylsilane to the product mixture obtained after the reaction
conditions 1a and phenyllithium afforded methyldi- of 1a,b with MeLi or PhLi produced the [tris(trimethyl-
phenyl[bis(trimethylsilyl)methyl]silane (2ay). Similarly, reac- silyl)methyl]silanes 11. Similarly, quenching of 10 with
tion of 1b with the same organolithium derivatives gave di- Me2SiHCl gave the [dimethylsilylbis(trimethylsilyl)-
methylphenyl[bis(trimethylsilyl)methyl]silane (2bx) and tri- methyl]silanes 12.
phenyl[bis(trimethylsilyl)methyl]silane (2by), respectively
Independent of the molar ratio 1aϪc/RLi, we found the
(Scheme 1). The structures of the compounds obtained reaction to proceed through all intermediates outlined in
were elucidated on the basis of NMR and MS data (see Scheme 1 to give the final products 2, 11, or 12, respectively.
Experimental Section).
Attempts to isolate dimers of the silenes 5 or 7 by reducing
The conversion of 1aϪc to 2 by the means of organoli- the ratio of the reactants to 1:2 or 1:1 were unsuccessful.
thium compounds is a complex process. Two trimethylsilyl We assume that the deprotonation of 1aϪc, producing the
groups migrate from the central silicon atom to the neigh- carbenoids 3, is a slow process compared with the sub-
boring carbon atom, formally replacing the two chlorine sequent steps, and the transient silenes 5 and 7, formed dur-
substituents, and the two organic groups introduced by the ing the course of the reaction, always meet an effective ex-
482
Eur. J. Inorg. Chem. 2001, 481Ϫ489

Reaction of (Dichloromethyl)oligosilanes with Organolithium Reagents
FULL PAPER
Scheme 1. Reaction of the dichloromethyloligosilanes 1a؊c with organolithium reagents R2Li
cess of the organolithium reagent, finally producing the tivity of silenes of type 5 also allows the addition of ex-
congested silanes.
tremely congested organolithium derivatives to produce
carbenoids 6, which after loss of LiCl and subsequent iso-
merization may result in the formation of kinetically stabi-
lized SiϭC systems. Thus, we consider (dichloromethyl)oli-
gosilanes and their reaction with organometallic bases as a
promising tool in the synthesis of stable silenes.
Reaction of the Dichloromethylsilanes 1a؊c with 2,4,6-
Triisopropylphenyllithium and of 1c with 2-tert-Butyl-4,5,6-
trimethylphenyllithium ؊ Synthesis and Behavior of the
Stable Silenes 8b, 8c, and 9c
As discussed above, in the course of the reaction of the
Following this concept we studied the reaction of 1c with
dichloromethylsilanes 1aϪc with methyllithium or phenylli- 8-dimethylamino-1-naphthyllithium and obtained 13 in a
thium, the transient silenes 5 and 7 occur as intermediates. straightforward one-pot reaction as a yellow, crystalline
As expected, in the presence of excess organolithium re- compound in a yield of 79% [Equation (3)].[13] The X-ray
agent, the almost unprotected, reactive silenes are immedi- analysis of 13 confirmed the expected picture of an intra-
ately trapped to give the addition products 6 or 10, respec- molecularly donor-stabilized silene with fourfold coordina-
tively. However, if organolithium reagents are chosen with tion at the silene silicon atom. Obviously, the 8-dimethyl-
groups R2, which, when introduced to the silene Si atom of aminonaphthyl substituent dramatically decreases the elec-
7, provide sufficient stabilization of the silaethene by means trophilic character of the silicon center and prevents further
of their steric bulk or by intramolecular donor-acceptor in- attack of organolithium reagent at the silene double bond.
teractions, the reaction may stop at this stage and the re- Thus, 13 is stable and can be isolated, and the reaction is
sulting silenes may be expected to be stable. The high reac- highly recommended as an efficient and versatile method
Eur. J. Inorg. Chem. 2001, 481Ϫ489
483

K. Schmohl, H. Reinke, H. Oehme
FULL PAPER
for the synthesis of further intramolecularly donor-stabi- the compounds are given. The silene 8c was obtained as a
lized silenes.
pale yellow oil, only slightly contaminated with 1,3,5-triiso-
propylbenzene, after reaction of the components, removal
of the solvent and extraction of the residue with pentane.
Triisopropylbenzene, formed as by-product, was separated
by repeated concentration of the pentane solution in vacuo,
finally at 100 °C. Furthermore, under these conditions no
silene dimerization or uncontrolled decomposition was ob-
served. Compound 8c could be characterized by its NMR
and MS data (see Experimental Section). Indicative of the
proposed structure is the 29Si chemical shift of the silene
silicon atom of 8c (δ ϭ 79.6). Silenes with comparable sub-
stitution patterns are unknown, but similarly structured de-
rivatives, such as (E)-(Me3Si)TipSiϭC(OSiMe3)Ad (δ29Si ϭ
40.3; Ad ϭ 1-adamantyl),[14] Mes2SiϭCHCH2tBu (δ29Si ϭ
77.6)[4] or (Me3Si)(tBuMe2Si)SiϭAdЈ (δ29Si ϭ 51.7, AdЈ ϭ
2-adamantylidene)[6] also show characteristic downfield
shifts of the SiϭC signals in their 29Si NMR spectra. Unfor-
tunately, the 13C NMR signal of the silene carbon atom of
8c, which is expected to appear with very low intensity,
could not be assigned unambiguously.
For the synthesis of kinetically stabilized silenes of type
7 two options were taken into consideration. Firstly, bulky
groups R1 may be introduced at the silene Si atom by start-
ing with appropriately substituted (dichloromethyl)silanes
1, or secondly, space-demanding substituents R2 may be in-
troduced by the respective organolithium derivatives R2Li
in the reaction with 1aϪc. Concerning the first alternative,
we tried to synthesize (dichloromethyl)mesitylbis(trimethyl-
silyl)silane following the standard method described above.
Unfortunately, mesitylbis(trimethylsilyl)silane was reco-
vered unchanged after treatment with chloroform and pot-
assium tert-butoxide. No reaction between the H-silane and
CCl2 occurred, probably due to steric reasons. On the other
hand, 1b and 1c, which were chosen for some preliminary
experiments, reacted with mesityllithium (1:2) to give after
hydrolysis the ‘‘normal‘‘ silene addition products
To our surprise, the reaction of 1a with 2,4,6-triisoprop-
ylphenyllithium (molar ratio 1:2) did not give the stable si-
lene 8a, but led after aqueous workup to methylbis(2,4,6-
triisopropylphenyl)[bis(trimethylsilyl)methyl]silane
(14)
[Equation (4)]. Obviously, replacement of a phenyl group or
a trimethylsilyl group in 8b or 8c, respectively, by the
smaller methyl substituent, decreases the steric protection
of the SiϭC system and in the presence of excess organoli-
thium reagent a second 2,4,6-triisopropylphenyl substituent
is introduced at the silene silicon atom. Compound 14 is an
extremely congested silane and structural data would be of
particular interest. However, due to the poor crystal quality,
the accuracy of the X-ray structural analysis was not very
high. Thus, the connectivity of the structure proposed was
PhMes2SiϪCH(SiMe3)2
(2bz)
and
Me3SiMes2-
SiϪCH(SiMe3)2 (2cz),[7] respectively, (Scheme 1). Obvi-
ously, one Si-mesityl substituent and one Si-phenyl or Si-
trimethylsilyl group at the silene silicon atom of 7 provides
insufficient protection to the SiϭC system against the at-
tack of mesityllithium. Replacement of the mesityl group in
7 by a 2,4,6-tri-tert-butylphenyl substituent is expected to
increase the kinetic stability of the silene. But 2,4,6-tri-tert-
butylphenyllithium did not react with the (dichloromethyl)-
silane 1c. The components remained unchanged, i.e. no de-
protonation of 1c occurred, very likely due to the steric con-
gestion in both the dichloromethylsilane and the organoli-
thium compound. Also, the reaction of 1c with tert-butylli-
thium in pentane gave unsatisfactory results. We obtained
a complex mixture of products. Neither a silene, nor any
product resulting from a silene, could identified.
However, treatment of 1b and 1c with 2,4,6-triisopropyl-
phenyllithium (molar ratio 1:2) afforded in a clean reaction
the indefinitely stable silenes 8b and 8c, respectively. Sim-
ilarly, 1c and 2-tert-butyl-4,5,6-trimethylphenyllithium (1:2)
gave the silene 9c (Scheme 1). The compounds were ob-
tained by a straightforward one-pot reaction of the com-
ponents in ether at room temperature. Unfortunately, we
did not succeed in crystallizing the compounds, and in all
cases complete separation of starting materials or side prod-
ucts from the oily silenes failed. In particular the quality of
8b and 9c did not allow an unambiguous assignment of e.g.
Figure 1. Molecular structure of 19b in the crystal (H atoms omit-
˚
ted); selected bond lengths [A] and angles [°]: Si1ϪO1 1.679(2), O1-
C2 1.461(4), C2ϪC1 1.607(5), C1ϪSi1 1.924(3), Si1ϪC15 1.900(3),
Si1ϪC9 1.890(3), C1ϪSi2 1.912(3), C1ϪSi3 1.915(4), C2ϪC3
1.495(5); Si1ϪO1ϪC2 112.6(2), O1ϪC2ϪC1 99.3(2), C2ϪC1ϪSi1
79.11(18), C1ϪSi1ϪO1 80.72(13), C9ϪSi1ϪC15 107.71(14),
their NMR signals, and therefore no spectroscopic data of Si2ϪC1ϪSi3 111.86(17), torsion angle C1ϪC2ϪO1ϪSi1 25.9(2)
484 Eur. J. Inorg. Chem. 2001, 481Ϫ489

Reaction of (Dichloromethyl)oligosilanes with Organolithium Reagents
FULL PAPER
confirmed unambiguously, but a detailed discussion of
bond parameters is excluded.
Benzaldehyde adds to the SiϭC functionality of 8b, 8c,
and 9c in a formal [2ϩ2] reaction to afford the 1,2-oxasilet-
anes 19b, 19c, and 20c (Scheme 2). 1,2-Oxasiletanes, gener-
ated as intermediates in the reaction of transient silenes
with carbonyl compounds in most cases undergo rapid de-
cyclizations to give oligomers of the respective silanones
and an olefin.[16] But in case of relatively stable silenes of
the ‘‘Brook-type’’,[1b] the formation of stable 1,2-oxasilet-
anes is common.[17] Compounds 19b, 19c, and 20c were
formed in low yields (besides large quantities of unidenti-
fied material), but could be isolated in crystalline form, and
for all three compounds X-ray structural analyses were per-
formed. The molecular structure of 19b, which was chosen
as an example of the comparable 1,2-oxasiletane systems, is
shown in Figure 1. In all three structures the ring bonds
are slightly longer than the usual acyclic values [SiϪC: 19b:
1.924(3), 19c: 1.944(3), 20c: 1.939(3); CϪC: 19b: 1.607(5),
19c: 1.603(4), 20c: 1.600(5); CϪO: 19b: 1.461(4), 19c:
1.440(4), 20c: 1.446(4); SiϪO: 19b: 1.679(2), 19c: 1.684(2),
Despite the steric congestion, which prevents the dimer-
ization of 8b, 8c, and 9c, the compounds are reactive and
exhibit the typical behavior of silenes. Thus, treatment with
water led to the expected formation of the silanols 15b, 15c,
and 16c (Scheme 2). Similarly, methanol was added to the
silene group to afford the methoxysilanes 17b, 17c, and 18c.
The results of the nucleophilic addition of methyllithium or
phenyllithium to the SiϭC unit, a reaction which we gener-
ally used for the characterization of transient silenes,[15]
were unclear in case of 8b, 8c, and 9c. We obtained complex
mixtures of products, from which no compounds could be
isolated. Further, reactions with 2,3-dimethyl-1,3-butadiene,
which were intended to give [2ϩ2] or [2ϩ4] cycloadducts,[1]
produced unsatisfactory results. The components were reco-
vered unchanged. Both unsuccessful attempts at character-
ization are interpreted as an indication of the extreme steric
shielding of the silene group.
˚
20c: 1.680(2) A]. These data are comparable with those re-
ported for 1,2-oxasiletanes.[17] The four-membered rings in
19c and 20c are nearly planar, in 19b the ring is folded, the
torsion angle C1ϪC2ϪO1ϪSi1 being 25.9°.
Experimental Section
General: All reactions involving organometallic reagents were car-
ried out under purified argon. Ϫ NMR: Bruker AC 250 or Bruker
ARX 300, tetramethylsilane as internal standard. Ϫ IR: Nicolet
205 FT-IR. Ϫ MS: Intectra AMD 402. Ϫ Me(Me3Si)2SiH, Ph(Me3-
Si)2SiH, and (Me3Si)3SiH were prepared using the method de-
scribed by Marschner.[18] Ϫ The syntheses and structures of 1c,
2cx, 2cy, and 2cz were described previously.[7] Ϫ Due to the forma-
tion of SiC, the results of the elemental analyses of some com-
pounds were unsatisfactory. In these cases HRMS data are given.
(Dichloromethyl)methylbis(trimethylsilyl)silane (1a):[9] At room
temperature, KOtBu (1.42 g, 12.6 mmol) and chloroform (1.51 g,
12.6 mmol) were added gradually to a solution of methylbis(trime-
thylsilyl)silane (2.2 g, 11.5 mmol) in pentane (30 mL). After stirring
for 12 h, water was added, the organic layer separated and the
aqueous phase extracted with pentane. The collected extracts were
dried and concentrated and the residue purified by kugelrohr distil-
lation (50 °C/1.4·10Ϫ2 mbar) to give 1.14 g (36%) of 1a. Colorless
1
oil. Ϫ H NMR ([D6]benzene): δ ϭ 0.16 [s, Si(CH3)3; 18 H], 0.20
(s, SiCH3; 3 H), 5.28 (s, CH; 1 H). Ϫ 13C NMR ([D6]benzene): δ ϭ
Ϫ0.7 [Si(CH3)3], Ϫ8.4 (SiCH3), 64.8 (CH). Ϫ 29Si NMR ([D6]ben-
zene): δ ϭ Ϫ23.2 (SiSiMe3), Ϫ15.8 (SiMe3). Ϫ C8H22Cl2Si3 (273.4):
calcd. C 35.14, H 8.11, Cl 25.93; found C 35.35, H 8.39, Cl 24.94.
(Dichloromethyl)phenylbis(trimethylsilyl)silane (1b): As described
for 1a, phenylbis(trimethylsilyl)silane (2.2 g, 8.71 mmol), KOtBu
(1.1 g, 9.81 mmol) and chloroform (1.17 g, 9.81 mmol) afforded
after kugelrohr distillation at 110 °C/2.2·10Ϫ1 mbar 1.2 g (41%) of
1
a colorless oil. Ϫ H NMR ([D6]benzene): δ ϭ 0.24 (s, SiCH3; 18
H), 5.63 (s, CH; 1 H), 7.11Ϫ7.45 (m, arom. CH; 5 H). Ϫ 13C NMR
([D6]benzene): δ ϭ Ϫ0.0 (SiCH3), 63.6 (CH), 128.3, 129.2, and
135.3 (arom. CH), 133.8 (arom. C). Ϫ 29Si NMR ([D6]benzene):
δ ϭ Ϫ24.2 (SiSiMe3), Ϫ15.2 (SiSiMe3). Ϫ MS (70 eV); m/z (%):
334 (1) [M]ϩ, 319 (3) [M Ϫ CH3]ϩ, 299 (100) [M Ϫ Cl]ϩ. Ϫ
C13H24Cl2Si3 (335.5): calcd. C 46.54, H 7.20, Cl 21.13; found C
46.79, H 7.13, Cl 21.38.
Scheme 2. Conversion of the stable silenes 8b, 8c, and 9c with water
into the silanols 15b, 15c, and 16c, with methanol into the methoxy-
silanes 17b, 17c, and 18c, and with benzaldehyde into the 1,2-oxa-
siletanes 19b, 19c, and 20c
Eur. J. Inorg. Chem. 2001, 481Ϫ489
485

K. Schmohl, H. Reinke, H. Oehme
FULL PAPER
Tris(trimethylsilyl)methane (2ax): To a solution of 1a (0.5 g,
1.83 mmol) in ether (30 mL), a threefold molar quantity of methyl-
room temperature. After stirring for 12 h, the mixture was concen-
trated and the residue extracted with pentane. After filtration, the
lithium was gradually added at room temperature. After stirring solution was repeatedly concentrated (with further addition of
for 12 h, the mixture was hydrolyzed and the organic layer sepa-
rated, dried and concentrated. Compound 2ax was separated by
column chromatography (silica gel, heptane) as a colorless oil, yield
0.3 g (70%). The spectral data measured for 2ax agree with those
described in the literature.[19]
pentane) in vacuo, finally at 100 °C/10Ϫ2 mbar, to give 0.4 g (58%)
of a pale yellow oil, which proved to be a mixture of 8c and 1,3,5-
triisopropylbenzene. Ϫ 8c: 1H NMR ([D6]benzene): δ ϭ 0.17, 0.24,
and 0.49 (3 s, SiCH3, 3 ϫ 9 H), 1.17, 1.25, and 1.38 (3 d, 3J ϭ
3
6.7 Hz, iPr-CH3, 3 ϫ 6 H), 2.72 (sept, J ϭ 6.7 Hz, iPr-CH, 1 H),
3
3.33 (sept, J ϭ 6.7 Hz, iPr-CH, 2 H), 7.00 (s, arom. CH, 2 H). Ϫ
Methyldiphenyl[bis(trimethylsilyl)methyl]silane (2ay): Similarly, 1a
(0.5 g, 1.83 mmol) and ethereal phenyllithium solution (5.5 mmol)
afforded 0.45 g (68%) of 2ay. Colorless crystals, m.p. 66Ϫ69 °C. Ϫ
1H NMR ([D6]benzene): δ ϭ 0.02 [s, Si(CH3)3, 18 H], 0.04 (s, CH,
1 H), 0.74 (s, SiCH3, 3 H), 7.13Ϫ7.52 (m, arom. CH, 10 H). Ϫ 13C
NMR ([D6]benzene): δ ϭ Ϫ2.2 (CH), 1.3 (SiCH3), 3.4 [Si(CH3)3],
128.3, 129.0, and 134.8 (arom. CH), 140.4 (arom. C). Ϫ 29Si NMR
([D6]benzene): δ ϭ Ϫ9.6 (SiMe3), Ϫ0.1. Ϫ(SiMe). Ϫ MS (70 eV);
m/z (%): 356 (2) [M]ϩ, 341 (100) [M Ϫ CH3]ϩ, 279 (5) [M Ϫ Ph]ϩ.
Ϫ C20H32Si3 (356.7): calcd. C 67.34, H 9.04; found C 67.04, H 9.07.
13C NMR ([D6]benzene): δ ϭ 1.3, 4.8, and 6.3 (SiCH3), 24.1, 24.2,
and 24.7 (iPr-CH3), 34.7 and 38.1 (iPr-CH), 121.0 (arom. CH),
136.0, 151.7, and 152.4 (arom. C), the signal of the SiϭC atom
could not be assigned unambiguously. Ϫ 29Si NMR ([D6]benzene):
δ ϭ Ϫ15.4 (SiSiMe3), Ϫ6.8 and Ϫ5.7 (CSiMe3), 79.6 (SiϭC). Ϫ
MS (70 eV); m/z (%): 463 (88) [M ϩ H]ϩ, 390 (5) [M Ϫ SiMe3]ϩ;
HRMS calcd. for C25H50Si4 462.29285, found 462.29895. Ϫ 1,3,5-
iPr3C6H3: 1H NMR ([D6]benzene): δ ϭ 1.24 (d, 3J ϭ 7.5 Hz,
CCH3, 18 H), 2.82 (sept, 3J ϭ 7.5 Hz, CHMe2, 3 H), 6.99 (s, arom.
CH, 3 H). Ϫ 13C NMR ([D6]benzene): δ ϭ 24.4 (CH3), 34.8 (CH),
122.4 (arom. CH), 149.1 (arom. C).
Dimethylphenyl[bis(trimethylsilyl)methyl]silane (2bx): As described
for 2ax, 1b (0.5 g, 1.49 mmol), and MeLi (4.50 mmol) gave after
chromatographic separation (silica gel, heptane) 0.73 g (84%) of
Tetrakis(trimethylsilyl)methane (11ax): To a solution of 1a (0.5 g,
1.83 mmol) in ether (30 mL), MeLi (5.5 mol) was added at room
temperature. The mixture was stirred for 12 h and subsequently
chlorotrimethylsilane (0.5 g, 4.5 mmol) was added. Stirring was
continued for further 12 h. After the addition of water, separation
of the organic layer and concentration, the residue was purified by
column chromatography (silica gel, heptane). Colorless crystals,
yield 0.46 g (82%), m.p. 129Ϫ135 °C. The spectral data obtained
for 11ax are identical with those of authentic material.[20]
1
2bx. Colorless oil. Ϫ H NMR ([D6]benzene): δ ϭ Ϫ0.38 (s, CH,
1 H), 0.08 [s, Si(CH3)3, 18 H], 0.38 [s, Si(CH3)2, 6 H], 7.18Ϫ7.49
(m, arom. CH, 5 H). Ϫ 13C NMR ([D6]benzene): δ ϭ Ϫ1.0 (CH),
1.8 [Si(CH3)3], 3.4 [Si(CH3)2], 128.8, 133.7, and 134.7 (arom. CH),
142.5 (arom. C). Ϫ 29Si NMR ([D6]benzene): δ ϭ Ϫ 16.2 (Si-
Me2Ph), Ϫ 0.3 (SiMe3). Ϫ MS (70 eV); m/z (%): 279 (100) [M Ϫ
CH3]ϩ. Ϫ C15H30Si3 (294.7): calcd. C 61.14, H 10.26; found C
61.16, H 10.26.
Methyldiphenyl[tris(trimethylsilyl)methyl]silane (11ay): Following
the procedure for the synthesis of 11ax, 1a (0.5 g, 1.83 mmol), PhLi
(5.5 mmol) and chlorotrimethylsilane (0.5 g, 4.5 mmol) gave after
chromatography (silica gel, heptane) and recrystallization from eth-
anol gave colorless crystals (0.44 g), which proved to be a mixture
of 11ay and approx. 10% of 2ay. The two compounds could not be
cleanly separated, therefore only the NMR and MS data of 11ay
Triphenyl[bis(trimethylsilyl)methyl]silane (2by): As described for
2ax, 1b (0.5 g, 1.49 mmol), and PhLi (4.50 mmol) gave after chro-
matographic separation (silica gel, heptane) and recrystallization
from methanol 0.44 g (70%) of 2by. Colorless crystals, m.p. 82Ϫ84
1
°C. Ϫ H NMR ([D6]benzene): δ ϭ 0.07 (s, SiCH3, 18 H), 0.31 (s,
CH, 1 H), 7.15Ϫ7.71 (m, arom. CH, 15 H). Ϫ 13C NMR ([D6]ben-
zene): δ ϭ 1.3 (CH), 3.8 (SiCH3), 127.9, 129.4, and 136.7 (arom.
CH), 137.9 (arom. C). Ϫ 29Si NMR ([D6]benzene): δ ϭ Ϫ10.0
(SiPh3), Ϫ0.0 (SiMe3). Ϫ MS (70 eV); m/z (%): 419 (2) [M ϩ H]ϩ,
403 (48) [M Ϫ CH3]ϩ, 341 (100) [M Ϫ Ph]ϩ, 264 (6) [M Ϫ Ph2]ϩ,
259 (11) [M Ϫ CH(SiMe3)2]ϩ. Ϫ C25H34Si3 (418.8): calcd. C 71.70,
H 8.18; found 70.84, 8.05. HRMS calcd. for C24H31Si3 (M Ϫ CH3):
403.17337; found 403.17013.
1
are given. Ϫ H NMR ([D6]benzene): δ ϭ 0.10 (s, SiCH3, 27 H),
0.32 (s, SiCH3, 3 H), 7.13Ϫ7.79 (m, arom. H). Ϫ 13C NMR
([D6]benzene): δ ϭ 0.8 (SiCH3), 3.5 [Si(CH3)3], Si4C could not be
assigned unambiguously, 128.3, 128.9, and 136.3 (m, arom. CH),
140.1 (arom. C). Ϫ 29Si NMR ([D6]benzene): δ ϭ Ϫ13.1 (Si-
MePh2), 2.2 (SiMe3). Ϫ MS (70 eV); m/z (%): 413 (2) [M Ϫ CH3]ϩ,
351 (1) [M Ϫ Ph]ϩ, 192 (100) [M Ϫ C(SiMe3)3]ϩ.
Dimesitylphenyl[bis(trimethylsilyl)methyl]silane (2bz): At room tem-
perature, a twofold molar excess of mesityllithium was added to a
solution of 1b (0.56 g, 1.65 mmol) in ether (30 mL). After stirring
for 12 h, water was added and the organic phase was separated,
dried and concentrated. Column chromatography of the residue
(silica gel, heptane) and recrystallization of the product from meth-
anol gave 0.1 g (12%) colorless crystals, m.p. 45Ϫ50 °C. Ϫ 1H
NMR ([D6]benzene): δ ϭ Ϫ0.07 and 0.05 (2 s, SiCH3, 2 ϫ 9 H),
0.33 (s, CH, 1 H), 2.09 and 2.22 (2 s, Mes-CH3, 2 ϫ 6 H), 2.33 and
2.34 (2 s, Mes-CH3, 2 ϫ 3 H), 6.70Ϫ7.86 (m, arom. CH, 9 H). Ϫ
13C NMR ([D6]benzene): δ ϭ Ϫ0.4 and 4.7 (SiMe3), 4.7 (CH), 20.9,
21.0, 21.1, 25.8, and 26.1 (aryl-CH3), 127.4, 128.2, 128.9, 129.2,
130.0, 130.6, 136.3, 138.1, 138.5, 143.8, and 144.5 (arom. C). Ϫ 29Si
NMR ([D6]benzene): δ ϭ Ϫ16.0 (aryl3Si), 0.3 and 1.1 (SiMe3). Ϫ
MS (70 eV); m/z (%): 502 (1) [M]ϩ, 487 (5) [M Ϫ CH3]ϩ; HRMS
calcd. for C31H46Si3 502.25965, found 502.29074.
Dimethyl[tris(trimethylsilyl)methyl]silane (12ax): The preparation
of 12ax followed the procedure given for 11ax, but chlorodimethyl-
silane was used instead of chlorotrimethylsilane. Thus, 1a (0.5 g,
1.83 mmol), MeLi (5.5 mmol) and Me2SiHCl (0.5 g, 5.5 mmol)
gave after purification by column chromatography (silica gel, hept-
ane) colorless crystals, yield 0.43 g (82%), m.p. 97Ϫ103 °C. Ϫ IR
1
(KBr): ν˜ ϭ 2099 cmϪ1 (SiH). Ϫ H NMR ([D6]benzene): δ ϭ 0.25
3
3
(s, SiCH3, 27 H), 0.21 (d, J ϭ 3.0 Hz, SiCH3, 3 H), 0.30 (d, J ϭ
3.0 Hz, SiCH3, 3 H), 4.31 (br. q, 3J ϭ 3.0 Hz, SiH, 1 H). Ϫ 13C
NMR ([D6]benzene): δ ϭ Ϫ4.1 (quat. C), 1.6 (HSiCH3), 4.5
[Si(CH3)3]. Ϫ 29Si NMR ([D6]benzene): δ ϭ Ϫ16.9 (SiH), Ϫ1.3
(SiMe3). Ϫ MS (70 eV): m/z (%): 289 (1) [M Ϫ H]ϩ, 275 (100) [M
Ϫ CH3]ϩ. Ϫ C12H34Si4 (290.7): calcd. C 49.57, H 11.79; found C
49.50, H 11.58.
Methyldiphenyl[(dimethylsilyl)bis(trimethylsilyl)methyl]silane
(12ay): Similarly, 1a (0.5 g, 1.83 mmol), PhLi (5.5 mmol), and Me2-
SiHCl (0.5 g, 5.5 mmol) afforded 0.3 g (40%) of 12ay. Colorless
1-(2,4,6-Triisopropylphenyl)-1,2,2-tris(trimethylsilyl)silene (8c): To a
solution of 1c (0.5 g, 1.5 mmol) in ether (30 mL) a twofold molar
excess of 2,4,6-triisopropylphenyllithium was gradually added at
1
crystals, m.p. 93Ϫ97 °C. Ϫ IR (KBr): ν˜ ϭ 2122 cmϪ1 (SiH). Ϫ H
486
Eur. J. Inorg. Chem. 2001, 481Ϫ489

Reaction of (Dichloromethyl)oligosilanes with Organolithium Reagents
FULL PAPER
NMR ([D6]benzene): δ ϭ 0.18 [d, 3J ϭ 3.8 Hz, Si(CH3)2, 6 H], 0.22 (arom. CH), 134.9, 149.9, and 154.5 (arom. C). Ϫ 29Si NMR
[s, Si(CH3)3, 18 H], 0.91 (s, PhSiCH3, 3 H), 5.08 (sept, 3J ϭ 3.8 Hz, ([D6]benzene): δ ϭ Ϫ19.3 (SiSiMe3), Ϫ0.6 and 1.8 (CSiMe3), 7.6
SiH, 1 H), 7.14Ϫ8.01 (m, arom. CH, 10 H). Ϫ 13C NMR ([D6]ben-
(SiOH). Ϫ MS (70 eV); m/z (%): 465 (3) [M Ϫ CH3]ϩ, 390 (1) [M
zene): δ ϭ Ϫ1.8 (quat. C), 1.8 [Si(CH3)2], 5.6 [Si(CH3)3], 127.5, Ϫ SiMe3, Ϫ OH, Ϫ H]ϩ, 203 (100) [M Ϫ Tip, Ϫ SiMe3, Ϫ H]ϩ.
129.2, and 136.8 (arom. CH), 139.6 (arom. C). Ϫ 29Si NMR
([D6]benzene): δ ϭ Ϫ16.0 and Ϫ15.5 (SiPh2 and SiH), Ϫ0.8
(SiMe3). Ϫ MS (70 eV); m/z (%): 399 (1) [M Ϫ H]ϩ, 336 (50) [M
Ϫ C6H5, Ϫ H]ϩ, 321 (100) [M Ϫ C6H5, Ϫ CH3, Ϫ H]ϩ, 264 (10)
[M Ϫ C6H5, Ϫ SiMe3]ϩ. Ϫ C22H38Si4 (414.9): calcd. C 63.69, H
9.23; found C 63.65, H 9.13.
Ϫ C25H52OSi4 (481.6): calcd. C 62.42, H 10.89; found C 62.14,
H 10.87.
16c: Compound 1c (0.5 g, 1.5 mmol) and 2-tert-butyl-4,5,6-trime-
thylphenyllithium (3.3 mmol) gave 0.3 g (44%) 16c, colorless crys-
tals, m.p. 50Ϫ56 °C. Ϫ IR (nujol): ν˜ ϭ 3695 cmϪ1 (OH). Ϫ 1H
NMR ([D6]benzene): δ ϭ Ϫ0.03, 0.19, and 0.38 (3 s, SiCH3, 3 ϫ 9
H), 0.32 (s, CH, 1 H), 1.48 (s, tBu-CH3, 9 H), 1.62 (s, OH, 1 H),
1.93, 2.12, and 2.16 (3 s, aryl-CH3, 3 ϫ 3 H), 7.23 (s, arom. CH, 1
H). Ϫ 13C NMR ([D6]benzene): δ ϭ 0.2, 3.6, and 4.4 (SiCH3), 6.1
(CH), 15.1, 21.1, and 24.0 (aryl-CH3), 34.2 (tBu-CH3), 36.6 (tBu-
C), 127.0 (arom. CH), 132.4, 135.9, 136.3, 141.2, and 153.7 (arom.
C). Ϫ 29Si NMR ([D6]benzene): δ ϭ Ϫ18.2 (SiSiMe3), 0.5
(CSiMe3), 1.5 (SiOH). Ϫ MS (70 eV); m/z (%): 437 (5) [M Ϫ
CH3]ϩ, 379 (37) [M Ϫ SiMe3]ϩ; HRMS calcd. for C23H48OSi4
437.24907, found 437.25476.
Methylbis(2,4,6-triisopropylphenyl)[bis(trimethylsilyl)methyl]silane
(14): At room temperature a threefold molar excess of 2,4,6-triiso-
propylphenyllithium was added to 1a (0.5 g, 1.8 mmol) in ether
(30 mL). After stirring for 12 h, water was added and the organic
layer separated, dried and concentrated. Chromatographic separa-
tion of the residue (silica gel, heptane) gave 0.42 g (44%) of 14.
Single crystals were obtained by recrystallization from heptane,
m.p. 151Ϫ156 °C. Ϫ 1H NMR ([D6]benzene): δ ϭ 0.11 and 0.38
(2 s, SiCH3, 2 ϫ 9 H), 0.22 (br. s, SiCH3, 3 H), 0.46 (s, CH, 1 H),
1.40 (br. signal) and 1.12Ϫ1.23 (m, iPr-CH3, 36 H), 2.73 (m, iPr-
CH, 2 H), 3.23, 3.32, 3.59, and 3.73 (4 br. signals, iPr-CH, 4 ϫ 1
H), 6.90Ϫ7.20 (2 m, arom. CH, 4 H). Ϫ 13C NMR ([D6]benzene):
δ ϭ 4.3 and 5.7 [Si(CH3)3], 8.2 (CH), 9.2 (SiCH3), 22.3, 23.0, 23.7,
23.9, 24.9, 25.7, 26.5, and 27.0 (iPr-CH3), 31.7, 32.4, 33.2, 34.1,
and 35.3 (iPr-CH), 122.7 (arom. CH), 138.1, 148.8, and 149.4
(arom. C). Ϫ 29Si NMR ([D6]benzene): δ ϭ Ϫ13.0 (SiMe), Ϫ1.4
and 0.6 (SiMe3). Ϫ MS (70 eV); m/z (%): 608 (1) [M]ϩ, 593 (16)
[M Ϫ CH3]ϩ, 535 (1) [M Ϫ SiMe3]ϩ, 449 (9) [M Ϫ CH(SiMe3)2]ϩ,
404 (89) [M Ϫ Tip, Ϫ H]ϩ, 201 (100) [M Ϫ 2 Tip, Ϫ H]ϩ. Ϫ
C38H68Si3 (609.2): calcd. C 74.92, H 11.25; found C 74.10, H 11.01.
General Procedure for the Preparation of the Methoxysilanes 17b,
17c, and 18c: At room temperature a 2.2-fold molar excess of the
respective organolithium reagent was added to the ethereal solution
of 1b or 1c, respectively After stirring for 12 h, excess methanol
was added and stirring was continued for 2 h. The ethereal phases
were separated and concentrated, and the residues were purified by
chromatography (silica gel, heptane).
17b: Compound 1b (0.5 g, 1.5 mmol) and 2,4,6-triisopropylphenyl-
lithium (3.3 mmol) gave 0.45 g (60%) of 17b, colorless oil. Ϫ IR
(cap.): ν˜ ϭ 1103 cmϪ1 (SiOC). Ϫ 1H NMR ([D6]benzene): δ ϭ 0.05
and 0.12 (2 s, SiCH3, 2 ϫ 9 H), 0.15 (s, CH, 1 H), 1.04, 1.07 and
General Procedure for the Preparation of the Silanols 15b, 15c, and
16c: To an ethereal solution of the dichloromethylsilane 1b or 1c a
2.2-fold molar excess of the respective organolithium compound
was added at room temperature. After stirring for 12 h, the product
was hydrolyzed by addition of water. The resulting silanols were
extracted with ether and the solutions dried and concentrated. The
residues were purified by chromatography (silica gel, heptane).
3
1.13 (3 d, J ϭ 6.7 Hz, iPr-CH3, 3 ϫ 6 H), 2.63 (sept, iPr-CH, 1
H), 3.18 (s, OCH3, 3 H), 3.45 (sept, iPr-CH, 2 H), 7.04 (s, Tip-CH,
2 H), 6.95 and 7.54 (2 m, Ph-CH, 5 H). Ϫ 13C NMR ([D6]benzene):
δ ϭ 3.6 and 4.2 (SiCH3), 8.4 (CH), 24.4, 24.6, and 26.3 (iPr-CH3),
32.3 and 34.5 (iPrCH), 51.8 (OCH3), 121.9, 127.5, 129.6, and 132.3
(arom. CH), 136.5, 138.3, 150.5, and 155.6 (arom. C). Ϫ 29Si NMR
([D6]benzene): δ ϭ Ϫ0.8 and Ϫ0.7 (SiMe3), 0.9 (SiOMe). Ϫ MS
(70 eV): m/z (%): 497 (4) [M Ϫ H]ϩ, 483 (25) [M Ϫ CH3]ϩ, 425 (8)
[M Ϫ SiMe3]ϩ, 295 (100) [M Ϫ Tip]ϩ. Ϫ C29H50OSi3 (499.1): calcd.
C 69.81, H 10.10; found C 70.09, H 10.11.
15b: Compound 1b (0.5 g, 1.5 mmol) and 2,4,6-triisopropylphenyl-
lithium (3.3 mmol) gave 0.4 g (55%) of silanol 15b. Colorless oil. Ϫ
IR (cap.): ν˜ ϭ 3682 cmϪ1(OH). Ϫ 1H NMR ([D6]benzene): δ ϭ
0.17 and 0.20 (2 s, SiCH3, 2 ϫ 9 H), 0.31 (s, CH, 1 H), 1.20 (d,
17c: Compound 1c (0.5 g, 1.5 mmol) and 2,4,6-triisopropylphenyl-
lithium (3.3 mmol) gave 0.3 g (40%) of 17c, colorless crystals, m.p.
58Ϫ65 °C. Ϫ IR (nujol): ν˜ ϭ 1114 cmϪ1 (SiOC). Ϫ 1H NMR
([D6]benzene): δ ϭ 0.02 (s, SiCH3, 9 H), 0.10 (s, CH, 1 H), 0.33 (s,
SiCH3, 18 H),1.23 (d, 3J ϭ 6.7 Hz, iPr-CH3, 6 H), 1.36 (d, 3J ϭ
6.7 Hz, iPr-CH3, 12 H), 2.80 (sept, 3J ϭ 6.7 Hz, iPr-CH, 1 H), 3.18
(sept, 3J ϭ 6.7 Hz, iPr-CH, 2 H), 3.47 (s, OCH3, 3 H), 7.09 (s,
arom. CH), 2 H). Ϫ 13C NMR ([D6]benzene): δ ϭ 2.1, 3.3, and 3.8
(SiCH3), 9.9 (CH), 24.1, 25.9, and 26.2 (iPr-CH3), 33.3 and 34.4
(iPr-CH), 52.2 (OCH3), 121.9 (arom. CH), 135.9, 149.9, and 155.1
(arom. C). Ϫ 29Si NMR ([D6]benzene): δ ϭ Ϫ21.7 (SiSiMe3), Ϫ0.2
and 1.8 (CSiMe3), 10.4 (SiOMe). Ϫ MS (70 eV); m/z (%): 494 (8)
[M]ϩ, 479 (59) [M Ϫ CH3]ϩ, 291 (100) [M Ϫ Tip]ϩ; HRMS calcd.
for C26H54OSi4 479.29319, found 479.30170. Ϫ C26H54OSi4 (495.1):
calcd. C 63.08, H 10.99; found C 63.00, H 10.85.
3
3J ϭ 6.7 Hz, iPr-CH3, 12 H), 1.23 (d, J ϭ 6.7 Hz, iPr-CH3, 6 H),
1.89 (s, OH, 1 H), 2.75 (sept, 3J ϭ 6.7 Hz, iPr-CH, 1 H), 3.65 (sept,
3J ϭ 6.7 Hz, iPr-CH, 2 H), 7.10Ϫ7.70 (m, arom. CH, 7 H). Ϫ 13C
NMR ([D6]benzene): δ ϭ 3.5 and 3.7 (SiCH3), 7.8 (CH), 24.0, 24.8,
and 25.7 (iPr-CH3), 33.3 and 34.5 (iPr-CH), 121.9, 127.4, 129.4,
and 133.1 (arom. CH), 135.1, 142.5, 150.5, and 155.3 (arom. C). Ϫ
29Si NMR ([D6]benzene): δ ϭ Ϫ2.8 (SiOH), Ϫ0.4 and 0.7 (SiMe3).
Ϫ MS (70 eV); m/z (%): 469 (70) [M Ϫ CH3]ϩ, 467 (100) [M Ϫ
OH]ϩ, 407 (20) [M Ϫ SiMe3]ϩ. Ϫ C28H48Si3O (484.9): calcd. C
69.35, H 9.98; found C 66.87, H 9.80; HRMS calcd. for C27H45OSi3
[M Ϫ CH3] 469.26051, found 469.27783.
15c: Compound 1c (0.5 g, 1.5 mmol) and 2,4,6-triisopropylphenyl-
lithium (3.3 mmol) afforded 0.35 g (49%) of 15c, colorless crystals,
m.p. 54Ϫ57 °C (heptane). Ϫ IR (KBr): ν˜ ϭ 3681 cmϪ1 (OH). Ϫ
1H NMR ([D6]benzene): δ ϭ 0.02 (s, CH, 1 H), 0.06, 0.20 and 0.30
(3 s, SiCH3, 3 ϫ 9 H), 1.35 (s, OH, 1 H), 1.21, 1.32 and 1.37 (3 d,
18c: Compound 1c (0.5 g 1.5 mmol) and 2-tert-butyl-4,5,6-trime-
thylphenyllithium (3.3 mmol) afforded 0.3 g (43%) of 18c, colorless
crystals, m.p. 86Ϫ89 °C. Ϫ IR (nujol): ν˜ ϭ 1124 cmϪ1 (SiOC). Ϫ
3
3J ϭ 6.7 Hz, iPr-CH3, 3 ϫ 6 H), 2.77 (sept, J ϭ 6.7 Hz, iPr-CH,
3
1 H), 3.50 (sept, J ϭ 6.7 Hz, iPr-CH, 2 H), 7.09 (s, arom. CH, 2 1H NMR ([D6]benzene): δ ϭ Ϫ0.05, 0.28, and 0.35 (3 s, SiCH3, 3
H). Ϫ 13C NMR ([D6]benzene): δ ϭ 0.7, 3.4, and 3.7 (SiCH3), 9.2
(CH), 24.1, 25.6, and 26.0 (iPr-CH3), 32.5 and 32.4 (iPr-CH), 121.7 2.17 (3 s, aryl-CH3, 3 ϫ 3 H), 3.55 (s, OCH3, 3 H), 7.26 (s, arom.
ϫ 9 H), 0.05 (s, CH, 1 H), 1.54 (s, tBu-CH3, 9 H), 1.92, 2.14, and
Eur. J. Inorg. Chem. 2001, 481Ϫ489
487

K. Schmohl, H. Reinke, H. Oehme
FULL PAPER
CH, 1 H). Ϫ 13C NMR ([D6]benzene): δ ϭ 2.1, 3.5, and 4.3 MS (70 eV); m/z (%): 572 (4) [M]ϩ, 557 (5) [M Ϫ CH3]ϩ, 495 (2)
(SiCH3), 7.1 (CH), 15.1, 21.0, and 25.3 (aryl-CH3), 33.5 (tBu-CH3), [M Ϫ Ph]ϩ, 325 (100) [M Ϫ PhCC(SiMe3)2]ϩ; HRMS calcd. for
37.4 (tBu-CH), 52.8 (OCH3), 127.3 (arom. CH), 128.3, 132.3, C35H52OSi3 572.31011, found 572.33258.
135.8, 140.8, and 154.3 (arom. C). Ϫ 29Si NMR ([D6]benzene): δ ϭ
19c: Compound 1c (0.5 g, 1.5 mmol), 2,4,6-triisopropylphenylli-
Ϫ18.6 (SiSiMe3), Ϫ0.3 and 0.6 (CSiMe3), 3.8 (SiOMe). Ϫ MS
thium (3.3 mmol) and benzaldehyde (0.16 g, 1.5 mmol) afforded
(70 eV); m/z (%): 466 (1) [M]ϩ, 451 (10) [M Ϫ CH3]ϩ, 393 (100)
0.3 g (35%) of 19c, colorless crystals, m.p. 153Ϫ155 °C. Ϫ IR (nu-
[M Ϫ SiMe3]ϩ; HRMS calcd. for C23H47OSi4 [M Ϫ CH3]
1
jol): ν˜ ϭ 1009 cmϪ1 (SiOC). Ϫ H NMR ([D6]benzene): δ ϭ 0.04,
451.27550, found 451.27042. Ϫ C24H50OSi4 (467.0): calcd. C 61.73,
0.20, and 0.29 (3 s, SiCH3, 3 ϫ 9 H), 1.22 (d, 3J ϭ 6.7 Hz, iPr-
H 10.79; found C 61.90, H 10.58.
3
CH3, 6 H), 1.25, 1.39, 1.44, and 1.52 (4 d, J ϭ 6.7 Hz, iPr-CH3,
3
3
General Procedure for the Preparation of the 1,2-Oxasiletanes 19b, 4 ϫ 3 H), 2.75 (sept, J ϭ 6.7 Hz, iPr-CH, 2 H), 4.13 (sept, J ϭ
19c, and 20c: At room temperature a 2.2-fold molar excess of the 6.7 Hz, iPr-CH, 1 H), 6.26 (s, PhCH, 1 H), 7.03 and 7.24 (2 s, Tip-
respective organolithium reagent was added to the ethereal solution CH, 2 ϫ 1 H), 7.11Ϫ7.82 (m, arom. CH). Ϫ 13C NMR ([D6]ben-
of 1b or 1c, respectively. After stirring for 12 h, an equimolar zene): δ ϭ 1.1, 2.6, and 3.4 (SiCH3), 31.4 [C(SiMe3)2], 82.5 (PhCH),
quantity of benzaldehyde was added, stirring was continued for 24.1, 25.3, 25.9, 26.2, and 26.8 (iPr-CH3), 31.8, 34.5, and 35.0 (iPr-
2 h and the reaction quenched with water. The organic layer was CH), 120.3, 122.7, 126.6, and 127.1 (arom. CH), 135.9, 145.6,
separated, dried and concentrated and the residue was purified by 150.8, 151.8, and 155.6 (arom. C). Ϫ 29Si NMR ([D6]benzene): δ ϭ
chromatography (silica gel, heptane). Single crystals of the oxasilet- Ϫ15.0 (SiSiMe3), Ϫ2.6 and 0.9 (CSiMe3), 36.5 (ring-Si). Ϫ MS
anes were obtained by recrystallization from acetone.
(70 eV); m/z (%): 553 (10) [M Ϫ CH3]ϩ, 495 (69) [M Ϫ SiMe3]ϩ;
HRMS calcd. for C31H53OSi4 [M Ϫ CH3] 553.30991, found
553.31738.
19b: Compound 1b (0.5 g, 1.5 mmol), 2,4,6-triisopropylphenylli-
thium (3.3 mmol) and benzaldehyde (0.16 g, 1.5 mmol) gave 0.1 g
(12%) of 19b, colorless crystals, m.p. 114Ϫ119 °C. Ϫ IR (cap.): ν˜ ϭ 20c: Compound 1c (0.5 g, 1.5 mmol), 2-tert-butyl-4,5,6-trimethyl-
1101 cmϪ1 (SiOC). Ϫ 1H NMR ([D6]benzene): δ ϭ Ϫ0.07 and 0.17 phenyllithium (3.3 mmol), and benzaldehyde (0.16 g, 1.5 mmol) af-
3
(2 s, SiCH3, 2 ϫ 9 H), 1.17 (d, J ϭ 6.5 Hz, iPr-CH3, 6 H), 1.08, forded 0.1 g (12%) of 20c, colorless crystals, m.p. 170Ϫ175 °C. Ϫ
1
1.37, 1.49, and 1.69 (4 d, 3J ϭ 6.5 Hz, iPr-CH3, 4 ϫ 3 H), 2.84, IR (nujol): ν˜ ϭ 999 cmϪ1 (SiOC). Ϫ H NMR ([D6]benzene): δ ϭ
3.26, and 4.37 (3 sept, 3J ϭ 6.5 Hz, iPr-CH, 3 ϫ 1 H), 6.28 (s, 0.04, 0.08, and 0.34 (3 s, SiCH3, 3 ϫ 9 H), 1.60 (s, tBu-CH3, 9 H),
PhCH, 1 H), 7.00Ϫ8.07 (m, arom. CH, 12 H). Ϫ 13C NMR 1.93, 2.14, and 2.34 (3 s, aryl-CH3, 3 ϫ 3 H), 6.21 (s, PhCH, 1 H),
([D6]benzene): δ ϭ 2.8 and 4.0 (SiCH3), 23.9, 25.3, 25.5, 25.9, and 7.08Ϫ7.84 (m, arom. CH, 6 H). Ϫ 13C NMR ([D6]benzene): δ ϭ
28.1 (iPr-CH3), 31.2, 34.5, and 36.5 (iPr-CH), 36.2 (C(SiMe3)2), 1.2, 2.9, and 4.7 (SiCH3), 14.7, 21.1, and 23.3 (aryl-CH3), 29.9
81.3 (CH), 121.0, 123.3, 126.9, 128.2, 129.7, 132.4, and 134.5 [C(SiMe3)2], 33.4 (tBu-CH3), 37.1 (tBu-C), 79.8 (PhCH), 126.9,
(arom. CH), 134.8, 139.8, 151.4, 153.0, and 157.0 (arom. C). Ϫ 29Si 127.3, 127.7, and 127.8 (arom. CH), 128.3, 131.6, 136.5, 137.2,
NMR ([D6]benzene): δ ϭ Ϫ2.2 and Ϫ0.4 (SiMe3), 8.4 (ring-Si). Ϫ 138.6, and 144.9 (arom. C). Ϫ 29Si NMR ([D6]benzene): δ ϭ Ϫ16.2
Table 1. Crystal data and structure refinement data for compounds 19b, 19c, and 20c
Compound
19b
19c
20c
Empirical formula
Molecular mass
Crystal system
C35H52OSi3
573.04
C32H56OSi4
569.13
C30H52OSi4
541.08
triclinic
monoclinic
P21/c
monoclinic
P21/c
¯
P1
Space group
˚
˚
˚
Unit cell dimensions
a ϭ 9.440(2) A
a ϭ 20.740(4) A
a ϭ 21.048(4) A
˚
˚
˚
˚
b ϭ 11.112(3) A
b ϭ 9.7790(10) A
b ϭ 9.516(2) A
˚
˚
c ϭ 18.440(6) A
c ϭ 18.695(2) A
c ϭ 16.667(6) A
α ϭ 83.47(3)°
β ϭ 81.43(3)°
γ ϭ65.600(10)°
1738.9(8)
α ϭ 90°
α ϭ 90°
β ϭ 109.260(10)°
γ ϭ 90°
β ϭ 100.31(2)°
γ ϭ 90°
3
˚
Volume [A ]
3579.4(9)
4
3284.4(15)
4
Z
2
Density (calcd.) [Mg/m3]
Absorption coeff. [mmϪ1
F(000)
1.094
1.056
1.094
]
0.161
0.187
0.201
624
1248
1184
Crystal size [mm3 ]
Θ range for data coll.[°]
Index ranges
0.82ϫ0.52ϫ0.36
2.02 to 22.00
Ϫ9 Յ h Յ 1,
Ϫ11 Յ k Յ 11,
Ϫ19 Յ l Յ 19
5219
0.66ϫ0.46ϫ0.32
2.20 to 22.00
Ϫ21 Յ h Յ 20,
Ϫ10 Յ k Յ 1,
Ϫ1 Յ l Յ 19
5578
0.80ϫ0.40ϫ0.35
1.97 to 22.00
Ϫ22 Յ h Յ 22,
Ϫ10 Յ k Յ 1,
Ϫ1 Յ l Յ 17
5170
Reflections collected
Independent reflections
[R(int)]
4261
4395
4018
0.0322
0.0362
0.0400
Completeness to Θ ϭ 22.00°
Data/restraints/param.
99.9%
99.9%
99.9%
4261/0/352
1.020
4395/0/334
1.021
4018/0/318
1.011
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)]
R1 ϭ 0.0565
wR2 ϭ 0.1512
R1 ϭ 0.0691
wR2 ϭ 0.1615
0.390/Ϫ0.267
R1 ϭ 0.0493
wR2 ϭ 0.1227
R1 ϭ 0.0694
wR2 ϭ 0.1354
0.220/Ϫ0.174
R1 ϭ 0.0484
wR2 ϭ 0.1225
R1 ϭ 0.0679
wR2 ϭ 0.1348
0.226/Ϫ0.193
R indices (all data)
Ϫ3
˚
Largest diff. peak/hole [e·A
]
488
Eur. J. Inorg. Chem. 2001, 481Ϫ489

Reaction of (Dichloromethyl)oligosilanes with Organolithium Reagents
FULL PAPER
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X-ray Structure Determinations of 19b, 19c, and 20c: Suitable crys-
tals of the compounds were selected under a microscope and sealed
onto a glass fiber. Afterwards rotational photos were taken and
13 reflections chosen to find reasonable reduced cells for the data
collections. These data collections were done with a Siemens P4
four-circle diffractometer equipped with a graphite monochroma-
tor and using Mo-Kα radiation in a routine ω-scan. The structures
were solved by direct methods (SHELXTL, Siemens Analytical X-
ray Inst. Inc., 1990) and refined by the full-matrix least-squares
method of SHELXL-97 (G. M. Sheldrick, Universität Göttingen,
1997). All non-hydrogen atoms were refined anisotropically . The
H atoms were put into theoretical positions and refined using the
riding model. Further details see Table 1. Crystallographic data (ex-
cluding structure factors) for the structures in this paper have been
deposited with the Cambridge Crystallographic Data Centre as
supplementary publication no. CCDC-143201 (19b), -143202 (19c),
and -143203 (20c). Copies of the data can be obtained, free
of charge, on application to CCDC, 12 Union Road, Cambridge
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Acknowledgments
We gratefully acknowledge the support of our work by the
Deutsche Forschungsgemeinschaft and the Fonds der Chemischen
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[I00188]
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489