Reaction studies on hypervalent silicon hydride compounds

Article abstract of DOI:10.1016/S0022-328X(98)00553-1

The versatile reaction chemistry of penta-coordinated silanes of type [C₆H₄CH₂N(CH₃)₂-2](H ₂C=CH)(CH₃)SiH (1a) and [C₆H₄CH₂N(CH₃)

Full text of DOI:10.1016/S0022-328X(98)00553-1

Journal of Organometallic Chemistry 561 (1998) 131–141
Reaction studies on hypervalent silicon hydride compounds
Markus Weinmann a, Olaf Walter b, Gottfried Huttner b, Heinrich Lang c,*
a Max-Planck-Institut fu¨r Materialforschung, Institut fu¨r Werkstoffwissenschaft, Pul6ermetallurgisches Laboratorium, Heisenbergstr. 5,
D-70569 Stuttgart, Germany
b Ruprecht-Karls-Uni6ersita¨t, Anorganisch-Chemisches Institut, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
c Technische Uni6ersita¨t Chemnitz, Institut fu¨r Chemie, Lehrstuhl Anorganische Chemie, Straße der Nationen 62, D-09111 Chemnitz, Germany
Received 16 December 1997; received in revised form 5 February 1998
Abstract
The versatile reaction chemistry of penta-coordinated silanes of type [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)SiH (1a) and
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiH2 (1b) with different substrates is described. The reaction behavior along with the structure and
bonding of the compounds obtained is compared with tetravalent silicon molecules. Hypervalent 1a and 1b react, without added
catalysts, with alcohols, water and benzoylic acid to produce alcoxysilanes, siloxanes and carboxysilanes, respectively. Compounds
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)Si(OCH3) (3), [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)Si(OR)2 (4a: R=CH3, 4b: R=C2H5, 4c:
R=iC3H7, 4d: R=CH2CꢂCH), {[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)Si}2O (5a), {[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiO}n (5b) as
well as [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)Si(H)[OC(O)C6H5] (8) are formed in quantitative yields. The carboxysilane 8 reacts with
C6H5CO2H (7) further to give the polymeric siloxane 5b and benzoylic anhydride. Moreover, H2PtCl6-catalyzed head–tail
polymerization of 1b yields the oligomeric carbosilane {[C6H4CH2N(CH3)2ꢀ2](H)SiꢀCH2CH2ꢀ}n (6). Due to the intramolecular
nitrogen–silicon interaction in hypervalent 1a as well as 1b, the hydrosilylation reaction with C6H5NꢁCꢁX (11a: X=S, 11b: X=O)
takes place without a catalyst added, whereas hydrosilylation of isocyanates and isothiocyanates does not occur with tetravalent
silanes. The obtained products [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(R)Si(C6H5NCHX) (12a: R=CH3, X=S; 12b: R=H, X=S; 12c:
R=H, X=O) are suitable catalysts for the cyclooligomerization of isocyanates and isothiocyanates. While compounds 12a–12c
are stable in the solid state, 12c starts to rearrange in solution to afford oligomeric 5b along with 1,3,5-triphenylhexahydro-1,3,5-tri-
azine (13). A possible mechanism for the formation of the latter compounds is discussed. An example for an insertion–elimination
process of compound 1b is given by the insertion of sulfur into the silicon–hydrogen bonds, yielding
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)Si(SH)2 (15) as an intermediate first; elimination of H2S affords the intermolecular donor-stabilized
silanethion [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiꢁS (16). The X-ray structure analysis of compound 12b is reported. Crystals of 12b
˚
are monoclinic, space group P21/n with the cell constants a=9.356(3), b=10.890(4), c=17.236(6) A, i=99.80(3)°, V=1730(1)
A and Z=4. © 1998 Elsevier Science S.A. All rights reserved.
3
˚
Keywords: Silicon; Silicon hydride; Hypervalent silicon
1. Introduction
the preparation of a variety of different organosilicon
compounds [1].
Silicon compounds with a coordination number
larger than 4 are the object of many studies with respect
to their application as catalysts in organic as well as
organometallic synthesis, and as starting materials for
Moreover, their use as model compounds to study
the mechanism of nucleophilic substitution reactions is
of wide interest, as the silicon atom possesses the
possibility of extending its coordination number effort-
lessly [1,2].
In this respect, we discuss the reaction chemistry of
penta-coordinated silicon hydrides towards different
substrates.
* Corresponding author. Fax: +49 371 5311833; E-mail: hein-
rich.lang@chemie.tu-chemnitz.de
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00553-1

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M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
2. Results and discussion
hydrolysis of 1b yields oligomeric {[C6H4CH2N(CH3)2ꢀ
2](H2CꢁCH)SiO}n (5b). However, the formation of hy-
pervalent silanols of type {[C6H4CH2N(CH3)2ꢀ2]
(H2CꢁCH)(R)SiOH as intermediates could not be de-
tected.
The preparation of the penta-coordinated silanes
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)SiH (1a) and
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiH2 (1b) succeeded by
treatment of LiC6H4CH2N(CH3)2ꢀ2 with the corre-
sponding chloro, dichloro or alcoxy silanes, followed by
the reaction with LiAlH4 in diethylether solutions [3].
Due to the intramolecular coordination of the nitro-
gen atom of the dimethylaminomethylene group to the
central silicon atom, an enhanced reactivity, as com-
pared with tetravalent silicon compounds, is observed
[3,4]. This increased reactivity accompanied by the in-
tramolecular N–Si coordination can be explained by
the coordinative expansion of the silicon atom [1,2]. We
describe the manifold reaction chemistry of the hyper-
valent silanes 1a and 1b.
2.1. Nucleophilic substitution reactions
The highly reactive penta-coordinated silanes
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)SiH (1a) and
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiH2 (1b) react with al-
cohols ROH (2a: R=CH3; 2b: R=C2H5; 2c: R=
iC3H7; 2d: R=CH2CꢂCH) in strongly exothermic
reactions to produce the mono- or all-substituted com-
pounds 3 or 4a–4d. The alcoxysilanes 3 and 4a–4d are
obtained as colorless oils in high yields and can best be
purified by vacuum distillation.
After appropriate work-up, the disiloxane 5a is ob-
tained as a colorless powder, whereas oligomeric 5b
could be isolated as a very viscous colorless oil in
quantitative yields. Both the disiloxane 5a and the
oligosiloxane 5b are stable to air.
A further possibility to synthesize oligomeric pen-
tavalent silicon compounds is given by heating 1b in the
presence of catalytic amounts of H2PtCl6. In a head-to-
tail addition reaction, the oligomeric carbosilane
{[C6H4CH2N(CH3)2ꢀ2)(H)SiꢀCH2CH2ꢀ}n (6) is ob-
tained as a pale-yellow liquid (for a detailed discussion
of compound 6 see below).
Changing from weaker Bro¨nsted acids, e.g. alcohols
and water, to stronger acidic carboxylic acids, the sub-
stitution of the hydrogen atoms in compound 1b pro-
ceeds more rapidly and at lower temperatures, when
compared with the above mentioned substrates for the
synthesis of compounds 3–5. The reaction of 1b with
benzoylic acid is described exemplary. Without added
catalyst, 1b reacts spontaneously with C6H5CO2H (7) in
chloroform at 0°C with evolution of dihydrogen. The
benzoyloxysilane
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)Si-
(H)[OC(O)C6H5] (8) is obtained as a colorless oil in
98% yield after appropriate work-up. By heating the
latter compound to above 120°C, elimination of ben-
zaldehyde (10a) is observed and the formation of
oligomeric 5b takes place. Similar observations were
made by Corriu and coworkers; a possible reaction
mechanism is discussed ([1]a,b, [5]).
While hydrolysis of compound 1a affords the silox-
ane {[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)Si}2O (5a),

M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
133
Moreover, we found that on addition of further
benzoic acid to compound 8, the formation of benzan-
hydride (10b) along with oligomeric 5b is observed.
These products are formed in quantitative yields. 10b
could be separated from 5b by column chromatography.
The formation of compounds 5b and 10b by reacting
7 with 8 can best be explained by the intermediate
formation of [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)Si[OC-
(O)C6H5]2 (9a), from which benzanhydride (10b) is elim-
inated, thus forming the silanone 9b as an intermediate.
The latter molecule oligomerizes under the reaction
conditions applied to produce 5b. However, isostruc-
tural compounds to 9a could be isolated for penta-coor-
dinated [C6H4CH2N(CH3)2ꢀ2](C10H7ꢀ8)Si[OC(O)C6H5]2
([4]a).
From the results obtained, it can be concluded that
the hydrogen atoms in neutral pentavalent silicon com-
pounds show an enhanced reactivity towards different
Bro¨nsted acids, as compared with tetravalent silanes.
This points to a stronger hydridic character of the
hydrogen atoms in hypervalent silicon compounds,
when compared with their tetravalent analogs. The
stronger hydridic character can be explained with a
charge transfer from the dative-bonded nitrogen atom
of the N,N-benzyldimethylamino ligand to the silicon
center, and results in a higher electron density on the
silicon atom.
The penta-coordinated silane 1a reacts, as compared
with the corresponding tetravalent silane, much faster
and without the requirement of any added catalyst. The
same observations are made by the hydrosilylation
reactions of the penta-coordinated vinyl-substituted di-
hydridosilane [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiH2 (1b)
with stoichiometric amounts of the heterocumulenes
C6H5NꢁCꢁX (11a: X=S; 11b: X=O) in chloroform
solutions at 25°C. The mono-substituted silyl-thiofor-
mamide and -formamide compounds [C6H4CH2N-
(CH3)2ꢀ2](H2CꢁCH)Si(H)(C6H5NCHX) (12b: X=S;
12c: X=O) are obtained in 94% (12b) or 83% (12c)
yield.
2.2. Hydrosilylation reactions
Compounds 12a–12c are soluble in most common
polar organic solvents, but insoluble in nonpolar ones,
such as n-pentane or toluene. They can best be purified
by distillation (12c) or crystallization (12a, 12b) from
saturated methylenechloride/n-pentane solutions at
−30°C. While solutions, containing isothiocyanate
building blocks, as given in molecules 12a and 12b, are
stable even at 25°C for a long period of time, it is found
that when the silyl isocyanate 12c is kept in solution for
a number of weeks, trimeric 1,3,5-triphenyl-1,3,5-
hexahydrotriazine (13) along with oligomeric
{[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiO}n (5b) is formed.
One possible explanation for the formation of com-
pounds 5b and 13 by starting out from pentavalent silyl
isocyanate 12c is presented in Scheme 1.
There are not many reactions known for the synthesis
of N-acyl formamides and N-acyl thioformamides
([1]a,b, [6]). The high reactivity of penta-coordinated
silanes should provide an easy access to these type of
compounds. For this reason, the silanes 1a and 1b were
reacted with C6H5NꢁCꢁX (11a: X=S; 11b: X=O).
The reaction of [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)-
(CH3)SiH (1a) with C6H5NꢁCꢁS (11a) yields, by means
of a hydrosilylation-type reaction, the hypervalent thio-
formamide compound [C6H4CH2N(CH3)2ꢀ2](H2Cꢁ
CH)(CH3)Si[C6H5NC(S)H] (12a). Compound 12a is
obtained as a pale-yellow solid by crystallization from
saturated dichloromethane/n-pentane solutions at
−30°C.

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M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
Scheme 1. Possible mechanism for the formation of compounds 5b and 13 from 12c.
The trimerization of the isocyanates and isothio-
Presumably in the first step an intramolecular hy-
cyanates relies upon a repeated insertion of 11a or
11b into the silicon–nitrogen bond of the
SiꢀN(C6H5)(CHX) moiety in 12b or 12c ([6]b). After
two insertions of PhNꢁCꢁX molecules, the elimination
of trimeric 14a (X=S) or 14b (X=O) occurs with
reformation of the hypervalent dihydrosilane 1b.
A further hydrosilylation-type reaction, which finally
leads to an oligomeric hypervalent carbosilane, is given
in the head-to-tail oligomerization of compound 1b in
the presence of catalytic amounts of Speier’s catalyst.
This hydrosilylation reaction is performed by slowly
heating neat 1b to 200°C and keeping the reaction
mixture at this temperature for 2 h. Oligomeric
{[C6H4CH2N(CH3)2ꢀ2](H)SiꢀCH2CH2ꢀ}n (6) is ob-
tained as a pale-yellow oil, which hydrolysis slowly on
exposure to air and which is soluble in most common
organic solvents. Cryoscopic molecular weight determi-
nation in benzene [7] denotes that compound 6 is
oligomeric with n=3.6.
drosilylation process takes place to afford the 1-sila-2-
aza-4-oxetane intermediate A (Scheme 1). In means of a
[2+2] retrocycloaddition reaction of postulated cyclic
A, the two intermediates phenylimine (Type
B
molecule) and the base-stabilized silanone of structural
type C are built. Both species are not stable under the
conditions used, and by trimerization of the
phenylimine B, compound 13 is formed, while
oligomerization of the silanone C affords the oligosilox-
ane 5b (Scheme 1).
Attempts to induce a desirable second insertion of a
formamide or thioformamide entity into the remaining
silicon–hydrogen bond in compounds 12b and 12c
failed. However, it was found that upon treatment of
the silylthioformamide 12b, as well as the silylfor-
mamide 12c with a 10-fold excess of C6H5NꢁCꢁX (11a:
X=S; 11b: X=O) produces the trimers of phenyl
isothiocyanate (compound 14a) and phenyl isocyanate
(compound 14b) in chloroform solutions at 25°C.
2.3. Insertion–elimination reaction
Pentavalent dihydridosilanes can also be used suc-
cessfully for the preparation of donor-stabilized low-co-
ordinated silicon compounds ([1]a, [8,9]). We describe
an access to 1-thia-2-sila-l,3-dienes by treatment of 1b
with sulfur in chloroform as solvent at 25°C. The
Additionally, the latter compounds can be obtained
in much better yields by the direct reaction of the
dihydridosilane 1b with an 10-fold excess of 11a or 11b
in chloroform solutions at 25°C.

M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
135
heterobutadiene [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiꢁS
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(H)Si[OC(O)Ph]
(8)
(16) is obtained in 93% yield as a colorless solid with a
putrid smell. It appears that compound 16 is extremely
sensitive to moisture and by elimination of H2S
oligomeric 5b is formed.
and
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(H)Si(C6H5NC-
HX) (12b: R=H, X=S; 12c: R=H, X=O) only one
wSiꢀH absorption band in the region of 2125–2140 cm−1
The formation of compound 16 can best be explained
by the insertion reaction of sulfur into the silicon–hy-
drogen bonds in 1b, yielding [C6H4CH2N(CH3)2ꢀ2]-
(H2CꢁCH)Si(SH)2 (15) first. From this intermediate, the
elimination of H2S occurs. A similar reaction sequence
has been postulated for the synthesis of oligomeric 5b,
but it could not be infallibly found out, whether the
condensation step proceeds inter- or intramoleculary.
However, the intermediate formation of isostructural
oxygen containing compounds could not be perceived.
For the silanethione structure of 16 a ylidic character
is reasonable, which possibly can be expressed by a
mesomeric structure shown in Scheme 2. ([1]a).
is recognized, which is typical for tetravalent silanes
[10]. This indicates that the hydrogen atoms in these
compounds are located exclusively in equatorial posi-
tions of the penta-coordinated silicon center, whereas
the apical position of the coordination polyeder is
occupied by the hydrogen atom in 1a as well. However,
the introduced groups OC(O)Ph and PhNCHX (X=O,
S) in the products formed are orientated in the apical
position, which can be explained by the increased ease
of stretching the oxygenꢀsilicon bond or the nitrogen–
silicon bond, and the increased ability in delocalizing
electron density as compared with the silicon–carbon
bonds of the vinyl or the methyl group and the silicon–
hydrogen bond.
2.4. Structure and bonding
1
In the H-NMR spectra of compounds 12a, 12b and
16 intramolecular nitrogen coordination to the silicon
atom can be observed by the appearance of
All synthesized compounds could be unequivocally
characterized by elemental analysis and spectroscopic
1
methods (IR, H-, 13C{1H}-, 29Si{1H}-NMR, MS). It
diastereotopic
methylene
protons
of
the
C6H4CH2N(CH3)2 unit with coupling constants of
2JHH=12.4 Hz for 12a, 14.3 Hz for 12b or 8.0 Hz for
16. Additionally, the 1H-NMR spectrum of the in-
tramolecular base-stabilized low-valent silanethion 16
also represents diastereotopic methyl groups at 2.26
and 2.44 ppm, respectively.
appeared that the IR technique is the most suitable one
for the surveillance of the reactions performed, as well
as for a rapid characterization of the products ob-
tained. In general, it is observed that the two SiꢀH
stretching frequencies at 2131 and 2088 cm−1 in
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)SiH (1a), due to
different conformations in which the hydrogen atom is
located in an apical or equatorial position in the trigo-
nal-bipyramidal coordination sphere of the silicon
atom, disappear by alcoholysis, hydrolysis or hydrosily-
lation of the latter compound. New characteristic IR
absorptions are found for the appropriate groups OR
or PhNCHS introduced. Similar observations are made
when the dihydridosilane [C6H4CH2N(CH3)2ꢀ2](H2Cꢁ
CH)SiH2 (1b) is reacted with water or alcohols. While
in the monohydrogen-substituted silane 1a, two SiꢀH
stretching frequencies are found, in compounds
The molecule ion peaks M+ of the new synthesized
compounds, with the exception of silanes 5a and 12, are
found in EI-MS experiments. As typical fragments M+
-CH3, M+-C2H3, CH2N(CH3)2 +as well as N(CH3)3
+
are observed. Similar fragmentation is found for
compounds 5a and 12 under FAB conditions.
The result of the X-ray structure analysis, which was
carried out exemplary for [C6H4CH2N(CH3)2–
2](H2CꢁCH)(H)Si(C6H5NCHS) (12b) is in agreement
with the spectroscopic findings (Fig. 1). Crystallo-
graphic parameters are given in Table 1, selected inter-
atomic distances and angles are presented in Table 2
and atomic coordinates are listed in Table 3.
Compound 12b crystallizes in the monoclinic space
group P21/n and is characterized by a trigonal-bipyra-
midal coordinated silicon atom. The vinyl group (C17,
C18), the aryl entity of the built-in ligand
C6H4CH2N(CH3)2ꢀ2 (C1–C6), as well as the silicon-
Scheme 2. Mesomeric formula of the silanethione 16.

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M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
ꢀ2](H2CꢁCH)(H)Si[OC(O)C6H5] (8) and [C6H4CH2N-
(CH3)2ꢀ2](H2CꢁCH)Si[OC(O)(C6H5)]2 (9a) can be
achieved. On heating these compounds they show dif-
ferent types of reactions: while 8 is suitable for the
preparation of benzaldehyde, 9a yields benzanhydride
by means of a dehydration-type reaction. The high
reactivity of the penta-coordinated dihydrosilane 1b can
also be used for the preparation of oligomeric carbosi-
lanes, as well as for the synthesis of N-functionalized
formamide and thioformamide compounds. While in a
one-to-one reaction of 1b with PhNꢁCꢁX (X=O, S)
the hydrosilylation product [C6H4CH2N(CH3)2ꢀ2]-
(H2CꢁCH)(H)Si(C6H5NCHX) (12b: X=S; 12c: X=O)
is formed, the latter compounds are suitable as catalysts
for the cyclotrimerization of the heterocumulenes
PhNꢁCꢁX, respectively. In addition, the formamide 12c
affords the synthesis of the oligomeric siloxane 5b and
the 1,3,5-triphenyl-1,3,5-hexahydrotriazine 13 by means
of a redox reaction. The synthesis of the novel in-
tramolecular donor-stabilized 1-thia-2-sila-l,3-diene
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiꢁS (16) by an inser-
tion–elimination mechanism is discussed.
Fig. 1. ZOPTEP drawing (drawn at 50% probability level) of com-
pound 12b with the atom numbering scheme (hydrogen labels, except
H(1), omitted for better clarity).
Table 1
Crystallograhic parameters for compound 12b
bonded hydrogen atom H1 are located in equatorial
positions; whereas the nitrogen atoms of the dimethy-
lamino group N1 and the N-acyl thioformamide unit N2
occupy the axial positions of the coordination polyeder
[angle N1ꢀSi1ꢀN2 174.5(1)°]. The internal comparison of
Empirical formula
Formula weight
Temperature (K)
C18H22N2SSi
326.53
205
˚
Radiation (u, A)
Mo–Kh, u=0.71069
Crystal system
Space group
monoclinic
P21/n
9.356(3)
10.890(4)
˚
˚
the Si1ꢀN1 [2.225(3) A] and the Si1ꢀN2 [1.898(3) A] bond
lengths confirm that a covalent silicon–nitrogen bonding
(Si1ꢀN2) is present next to a coordinative-bonded nitro-
gen atom (N1). One discernable feature of compound 12b
is the trigonal planar environment around the nitrogen
atom N2 (sum of angles: 359.68°). In accord with this is
˚
a (A)
˚
b (A)
˚
c (A)
17.236(6)
i (°)
V (A )
99.80(3)
1730(1)
3
˚
Z
4
˚
the interatomic bond distance N2ꢀC10 at 1.322(5) A,
Dcalc. (g cm−3
)
1.253
0.255
Absorption coefficient, v (mm−1
Crystal size (mm)
Diffractometer model
2q range (°)
)
which is typical for CꢁN bond lengths in imines [11].
0.20×0.30×0.10
Siemens (Nicolet) R3m/V
4.4–42.1
˚
Moreover, the S1ꢀC10 bond length at 1.646(4) A is
specific for carbon–sulfur single bond lengths in thiols
and mercaptals [11]. These findings indicate that the
N-acyl thioformamide unit in compound 12b can best be
described as a zwitterionic moiety with a 1-imminum-2-
thiolate component (Scheme 3).
Index ranges
−95h59, −15k510,
−175l517
v-scan
0.75
5.8–29.3
2012
Scan mode
Scan range (°)
Scan speed (° min−1
Unique reflections
)
Observed reflections [I52|(I)]
1871
3. Conclusion
Refined parameters
212
Min/max residual electron density 0.432/−0.180
−3
˚
(eA
)
In general, it could be shown that the penta-coordi-
nated silicon hydrides [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)-
(CH3)SiH (1a) and [C6H4CH2N(CH3)2ꢀ2](H2Cꢁ
CH)SiH2 (1b), as compared with their tetravalent
analogs, show an enhanced reactivity towards different
substrates. This is well-documented in the alcoholysis
or hydrolysis of compounds 1a and 1b without added
catalyst. In a similar manner, the synthesis of penta-co-
ordinated silyl carboxylates, such as [C6H4CH2N(CH3)2
R1/wRa2 [I\2|(I)]
R1/wRa2 (all)
0.0421/0.0957
0.0600/0.1049
1.067
S (goodness-of-fit)b on F2
1/2
ꢀ
n ꢀ
n
a R1=% (ꢁꢁFoꢁ−ꢁFcꢁꢁ)/%ꢁFoꢁ , wR2=% (w(Fo2−Fc2)2)/%(wFo
)
.
4
ꢀ
n
2 2
b S= %w(Fo2−Fc
)
/(n−p)1/2, n, number of reflections, p, parame-
ters used. Definition of w [where P=(Fo2+2Fc2)/3]: 12b, w=1/
[|2(Fo2)+(0.0482)2+1.23P].

M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
137
Table 2
Selected bond lengths (A) and angles (°) of compound 12b
a
˚
˚
Bond lengths (A)
Si1ꢀN1
Si1ꢀN2
Si1ꢀC1
Si1ꢀC17
Si1ꢀH1
N2ꢀC10
2.225(3)
1.898(3)
1.872(4)
1.853(4)
1.390(3)
1.322(5)
N2ꢀC11
N1ꢀC7
N1ꢀC8
N1ꢀC9
C10ꢀS1
C17ꢀC18
1.442(5)
1.463(5)
1.480(5)
1.474(5)
1.646(4)
1.320(6)
Scheme 3. Mesomeric formula of compound 12b.
Angles (°)
ethylether and tetrahydrofuran were purified by
distillation from sodium/benzophenone ketyl; n-pen-
tane and n-hexane were purified by distillation from
calcium hydride. Dichloromethane and chloroform
were distilled from P2O5. IR spectra were obtained
with a Perkin-Elmer 983G spectrometer (KBr pellets
or as film between NaCl plates). 1H-NMR spectra
were recorded on a Bruker AC 200 spectrometer oper-
ating at 200.132 MHz in the Fourier transform mode;
13C{1H}-NMR spectra were recorded at 50.323 MHz
and 29Si{1H}-NMR spectra were recorded at 39.763
MHz. Chemical shifts are reported in l units (ppm)
downfield from tetramethylsilane (l=0) with the sol-
vent as the reference signal; 1H-NMR: CDCl3 l=
7.27, 13C-NMR: CDCl3 l=77.0. EI- or FAB-MS
were recorded on a Finnigan 8400 mass spectrometer,
operating in the positive ion mode. Melting points
were determined using analytically pure samples,
sealed off in nitrogen-purged capillaries on a Gal-
lenkamp MFB 595 010 M melting point apparatus.
Microanalyses were performed by the Organisch-
Chemisches Institut der Universita¨t Heidelberg. The
molecular weights of oligomeric compounds were de-
termined by cryoscopic methods in benzene as solvent
[7].
N1ꢀSi1ꢀN2
C1ꢀSi1ꢀH1
C1ꢀSi1ꢀC17
C17ꢀSi1ꢀH1
N1ꢀSi1ꢀH1
N1ꢀSi1ꢀC1
N1ꢀSi1ꢀC17
N2ꢀSi1ꢀH1
N2ꢀSi1ꢀC1
N2ꢀSi1ꢀC17
174.5(1)
C7ꢀN1ꢀC8
C7ꢀN1ꢀC9
C7ꢀN1ꢀSi1
C8ꢀN1ꢀC9
C8ꢀN1ꢀSi1
C9ꢀN1ꢀSi1
Si1ꢀN2ꢀC10
Si1ꢀN2ꢀC11
C10ꢀN2ꢀC11
C10ꢀN2ꢀC11
108.7(3)
115.4(1)
124.7(1)
115.6(1)
81.9(1)
80.3(1)
87.0(1)
95.0(1)
97.0(1)
98.5(2)
110.7(3)
101.6(2)
108.9(3)
113.9(2)
112.8(2)
122.8(2)
118.8(2)
118.1(3)
130.4(3)
a Numbers in parentheses are estimated S.D. in the least significant
digits.
4. Experimental
4.1. General comments
All reactions were carried out under a nitrogen at-
mosphere using standard Schlenk techniques. Di-
Table 3
Atomic coordinates (×104) and equivalent isotropic thermal parame-
ters (×103 A ) for compound 12b
2
a
˚
Atom
x/a
y/b
z/c
8685(1)
Ueq
Si1
N2
S1
N1
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
840(1)
6413(1)
7940(3)
10333(1)
4595(3)
6729(3)
7884(3)
8011(4)
6985(4)
5834(4)
5702(3)
4483(3)
4544(4)
3581(4)
8918(4)
8080(3)
8649(3)
8747(4)
8281(4)
7694(4)
7600(4)
6413(4)
5956(4)
27(1)
27(1)
45(1)
32(1)
24(1)
29(1)
35(1)
34(1)
31(1)
25(1)
31(1)
45(1)
47(1)
33(1)
29(1)
37(1)
46(1)
53(1)
51(1)
37(1)
43(1)
61(1)
−146(3)
−193(1)
1886(3)
1839(4)
2154(4)
2828(4)
3197(4)
2901(4)
2229(4)
1837(4)
3419(4)
1083(5)
422(4)
−1506(4)
−1574(4)
−2877(5)
−4118(5)
−4059(5)
−2757(4)
1676(5)
992(6)
8532(2)
8127(1)
8963(2)
9702(2)
10036(2)
10806(2)
11266(2)
10953(2)
10178(2)
9804(2)
8852(2)
8519(3)
8248(2)
8811(2)
9520(2)
9783(3)
9349(3)
8644(3)
8376(2)
7785(2)
7114(3)
4.2. Synthesis of
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)SiH (1a) and
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiH2 (1b) [3]
A solution of 30.0 g (124.0 mmol) [C6H4CH2-
N(CH3)2ꢀ2](H2CꢁCH)(CH3)SiCl [3] in 500 ml of di-
ethylether or 16.0 g (62.0 mmol) [C6H4CH2N(CH3)2ꢀ2]
(H2CꢁCH)SiCl2 [3,12] in 300 ml of diethylether is
added dropwise to a suspension of 2.6 g (68.4 mmol)
LiAlH4 in 500 ml diethylether under vigorous stirring
at 0°C. The reaction mixture is allowed to warm
slowly to 25°C and then refluxed for 1 h. All volatile
materials are removed at 0°C and the grey residue is
extracted with 500 ml of n-pentane. Following filtra-
tion through a pad of Celite and distillation of the
eluate obtained in vacuum, produces 14.3 g (70 mmol,
54%) of [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)SiH (1a)
or 6.7 g (35.3 mmol, 57%) of [C6H4CH2N(CH3)2ꢀ2]
(H2CꢁCH)SiH2 (1b) as colorless oils.
a
Estimated S.D. in units of the last significant digit in parentheses;
Ueq is defined as one third of the trace of the orthogonalized Uij
tensor.

138
M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
4.2.1. Data for compound 1a
purification by distillation in vacuum, compounds 3 (48
mmol, 95%), 4a (48 mmol, 95%), 4b (45 mmol, 90%)
and 4c (35 mmol, 70%) are obtained as colorless oils.
Analytical pure 4d (50 mmol, 100%) is obtained by
distilling off all volatile components from the reaction
mixture at 25°C.
Boiling point 63°C/10−1 mbar. Anal. Calc. for
C12H19NSi (205.37): C, 70.16; H, 9.32. Found: C, 70.23;
1
3
H, 9.24. H-NMR (CDCl3): l 0.55 (d, JHH=3.6 Hz,
3H, SiCH3), 2.29 (s, 6H, NCH3), 3.59 (s, 1H, CH2),
3
3J
3.61 (s, 1H, CH2), 4.75 (dq, JHH=2.6 Hz, HH=3.6
2
3
Hz, 1H, SiH), 5.96 (dd, JHH=4.2 Hz, JHH=19.9 Hz,
2
3
4.3.1. Data for compound 3
1H, C2H3), 6.19 (dd, JHH=4.2 Hz, JHH=14.4 Hz,
Boiling point 107°C/10−1 mbar. Anal. Calc. for
C13H21NOSi (235.40): C, 66.33; H, 8.99. Found: C,
66.13; H, 8.78. 1H-NMR (CDCl3): l 0.59 (s, 3H,
3
3
1H, C2H3), 6.49 (ddd, JHH=2.6 Hz, JHH=14.4 Hz,
3JHH=19.9 Hz, 1H, C2H3), 7.3–7.4 (m, 3H, C6H4),
7.7–7.8 (m, 1H, C6H4). 13C{1H}-NMR (CDCl3): l 4.4
(SiCH3), 44.5 (NCH3), 64.6 (CH2), 126.5 (C6H4), 128.3
(C6H4), 129.1 (C6H4), 132.4 (C6H4), 136.0 (C6H4), 136.2
(C2H3), 137.8 (C6H4), 145.8 (C2H3). 29Si{1H}-NMR
(CDCl3): l −31.9. EI-MS [m/z (rel. intensity)] M+ 205
(13), M+-CH3 190 (53), M+-C2H3 178 (14), M+-
CH3ꢀC2H4 162 (100), M+-3CH3 160 (61),
(C6H4CH2)Si(C2H3)+ 145 (77). IR (NaCl): wCH=3043
(s), 2997 (s), 2965 (s), 2937 (s), 2851 (s), 2817 (vs), 2773
2
SiCH3), 2.10 (s, 6H, NCH3), 3.36 (d, JHH=13.1 Hz,
2
1H, CH2), 3.46 (s, 3H, OCH3), 3.53 (d, JHH=13.1 Hz,
1H, CH2), 5.79 (dd, 2JHH=4.3 Hz, 3JHH=19.7 Hz,
2
3
C2H3), 5.98 (dd, JHH=4.3 Hz, JHH=15.4 Hz, C2H3),
3
3
6.27 (dd, JHH=15.4 Hz, JHH=19.7 Hz, 1H, C2H3),
7.2–7.3 (m, 3H, C6H4), 7.7–7.8 (m, 1H, C6H4).
13C{1H}-NMR (CDCl3):
l
−0.8 (SiCH3), 44.8
(NCH3), 50.4 (OCH3), 64.1 (CH2), 126.3 (C6H4), 128.2
(C6H4), 129.3 (C6H4), 139.4 (C6H4), 132.5 (C6H4), 135.7
(C2H3), 136.3 (C6H4), 145.7 (C2H3). 29Si{1H}-NMR
(CDCl3): l −12.4. EI-MS [m/z (rel. intensity)] M+ 235
(6), M+-CH3 220 (17), M+-CH3ꢀC2H4 192 (43), M+-
2CH3ꢀC2H3 178 (100). IR (NaCl): wCH=3044 (s), 2965
(vs), 2938 (vs), 2897 (s), 2851 (vs), 2811 (vs), 2771 (s);
(vs); wSiH=2133 (vs), 2094 (m); wCꢁC=1586 (m) cm−1
.
4.2.2. Data for compound 1b
Boiling point 64–68°C/10−1 mbar. Anal. Calc. for
C11H17NSi (191.34): C, 69.05; H, 8.95. Found: C, 68.28;
1
H, 9.04. H-NMR (CDCl3): l 2.35 (s, 6H, CH3), 3.67
wCꢁC=1587 (m); wSiO=1076 (vs) cm−1
.
3
(s, 2H, CH2), 4.73 (d, JHH=3.2 Hz, 2H, SiH), 6.13
2
3
(dd, JHH=4.4 Hz, JHH=19.5 Hz, 1H, C2H3), 6.28
(dd, 2JHH=4.4 Hz, 3JHH=14.1 Hz, 1H, C2H3), 6.5–6.7
(m, 1H, C2H3), 7.3–7.4 (m, 1H, C6H4), 7.4–7.5 (m, 2H,
C6H4), 7.8–7.9 (m, 1H, C6H4). 13C{1H}-NMR (CDCl3):
l 46.1 (CH3), 61.9 (CH2), 126.6 (C6H4), 126.9 (C6H4),
129.4 (C6H4), 133.2 (C6H4), 133.5 (C2H3), 136.9 (C6H4),
139.5 (C6H4), 145.7 (C2H3). 29Si{1H}-NMR (CDCl3): l
−46.2. EI-MS [m/z (rel. intensity)] M+ 191 (36), M+-
H 190 (55), M+-CH3 176 (57), M+-C2H3 164 (64),
M+-CH3ꢀC2H4 148 (98), (C6H4CH2)Si(C2H3)+ 145
(100). IR (NaCl): wCH=3045 (s), 2969 (s), 2937 (s),
2852 (s), 2817 (s), 2781 (s); wSiH=2135 (vs), 2081 (s);
4.3.2. Data for compound 4a
Boiling point 118°C/10−1 mbar. Anal. Calc. for
C13H21NO2Si (251.40): C, 62.11; H, 8.42. Found: C,
62.48; H, 8.89. 1H-NMR (CDCl3): l 2.16 (s, 6H,
NCH3), 3.51 (s, 2H, CH2), 3.59 (s, 6H, OCH3), 5.8–5.9
(m, 1H, C2H3), 6.0–6.2 (m, 2H, C2H3), 7.3–7.4 (m, 3H,
C6H4), 7.8–7.9 (m, 1H, C6H4). 13C{1H}-NMR (CDCl3):
l 44.7 (NCH3), 50.1 (OCH3), 63.8 (CH2), 126.1 (C6H4),
128.0 (C6H4), 129.9 (C6H4), 131.7 (C6H4), 133.4 (C6H4),
133.7 (C2H3), 136.5 (C6H4), 146.5 (C2H3). 29Si{1H}-
NMR (CDCl3): l −32.7. EI-MS [m/z (rel. intensity)]
M+ 251 (24), M+-CH3 236 (50), M+-C2H3ꢀCH4 208
(100). IR (NaCl): wCH=3047 (s), 2967 (s), 2933 (vs),
2948 (m), 2827 (s), 2811 (s), 2771 (s); wCꢁC=1588 (m);
wCꢁC=1586 (s) cm−1
.
4.3. Synthesis of
wSiO=1084 (vs) cm−1
.
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)Si(OCH3) (3)
and [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)Si(OR)2 (4a:
R=CH3, 4b: R=C2H5, 4c: R=iC3H7, 4d:
R=CH2CꢂCH)
4.3.3. Data for compound 4b
Boiling point 110°C/1.5×10−2 mbar. Anal. Calc.
for C15H25NO2Si (279.46): C, 64.47; H, 9.02. Found: C,
1
3
Under
vigorous
stirring,
50
mmol
of
63.99; H, 9.60. H-NMR (CDCl3): l 1.20 (t, JHH=7.0
Hz, 6H, OCH2CH3), 2.16 (s, 6H, NCH3), 3.48 (s, 2H,
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(R)SiH (1a: R=CH3
10.0 g, 1b: R=H 9.5 g) are added to 50 ml ROH (2a:
R=CH3, 2b: R=C2H5, 2c: R=iC3H7, 2d: R=
CH2CꢂCH). When 1a and 1b are reacted with the
alcohols 2a, 2b or 2d, an exothermic reaction takes
3
NCH2), 3.77 (q, JHH=7.0 Hz, 4H, OCH2CH3), 5.6–
5.9 (m, 1H, C2H3), 6.0–6.1 (m, 2H, C2H3), 7.2 (m, 1H,
C6H4), 7.3 (m, 2H, C6H4), 7.6–7.8 (m, 1H, C6H4).
13C{1H}-NMR (CDCl3): l 18.2 (OCH2CH3), 45.0
(NCH3), 58.3 (OCH2CH3), 63.8 (CH2), 126.0 (C6H4),
128.2 (C6H4), 129.9 (C6H4), 132.6 (C6H4), 133.9 (C2H3),
134.2 (C6H4), 136.4 (C6H4), 146.4 (C2H3). 29Si{1H}-
place.
However,
for
the
synthesis
of
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)Si(OiC3H7)2 (4c), the
reaction mixture has to be refluxed for 12 h. After

M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
139
NMR (CDCl3): l −40.0. EI-MS [m/z (rel. intensity)]
M+ 279 (20), M+-CH3 264 (52), M+-CH3ꢀC2H4 236
(100), M+-OCH2CH3 234 (37). IR (NaCl): wCH=3048
(s), 2966 (s), 2937 (vs), 2873 (m), 2810 (s), 2768 (s);
dichloromethane and the colorless solution is dried over
MgSO4. After evaporation of dichloromethane, the
product is dried for 3 h at 25°C/10−3 mbar. While 5a is
a colorless solid, 5b is obtained as a colorless oil.
wCꢁC=1588 (m); wSiO=1079 (vs) cm−1
.
4.4.1. Data for compound 5a
4.3.4. Data for compound 4c
Yield: 4.24 g (10.0 mmol, 100%). Anal. Calc. for
C24H36N2OSi2 (424.73): C, 65.11; H, 8.65. Found: C,
65.65; H, 7.99. 1H-NMR (CDCl3): l 0.53 (s, 6H,
Boiling point 153°C/10−2 mbar. Anal. Calc. for
C17H29NO2Si (307.51): C, 66.40; H, 9.50. Found: C,
1
2
64.61; H, 9.16. H-NMR (CDCl3): l 1.27 [m*, 12H,
SiCH3), 2.26 (s, 12H, NCH3), 3.33 (d, JHH=12.2 Hz,
2
OCH(CH3)2], 2.25 (s, 6H, NCH3), 3.66 (s, 2H, NCH2),
4.28 [m*, 2H, OCH(CH3)2], 6.0–6.2 (m, 3H, C2H3),
7.3–7.6 (m, 3H, C6H4), 7.9 (m, 1H, C6H4). * At 25°C a
free rotation of the isopropoxy groups is sterically
hindered. This leads to the observation of a multiplet
structure for the methyl protons of these entities.
13C{1H}-NMR (CDCl3): l 25.0 [OCH(CH3)2], 25.6
[OCH(CH3)2]**, 45.2 (NCH3), 63.5 (NCH2), 65.2
[OCH(CH3)2], 125.8 (C6H4), 128.1 (C6H4), 129.9
(C6H4), 133.2 (C6H4), 134.5 (C6H4), 134.9 (C2H3), 136.2
(C6H4), 146.0 (C2H3). ** Due to the hindered rotation
of the isopropoxy groups at 25°C, two resonance sig-
nals for the methyl carbon atoms are observed.
29Si{1H}-NMR (CDCl3): l −42.3. EI-MS [m/z (rel.
intensity)] M+ 307 (33), M+-CH3 292 (64), M+-
CH(CH3)2 264 (100), M+-OCH(CH3)2 248 (58). IR
(NaCl): wCH=3049 (m), 2965 (vs), 2936 (vs), 2882 (m),
2810 (s), 2767 (s); wCꢁC=1588 (m); wSiO=1029 (vs)
2H, NCH2), 3.83 (d, JHH=12.2 Hz, 2H, NCH2), 5.8–
6.5 (m, 6H, C2H3), 7.2–7.6 (m, 6H, C6H4), 7.8–7.9 (m,
2H, C6H4). 13C{1H}-NMR (CDCl3): l −1.5 (SiCH3),
45.0 (NCH3), 64.2 (NCH2), 126.0–145.0 (m, C2H3 and
C6H5). 29Si{1H}-NMR (CDCl3): l −20.3. FAB-MS
[m/z (rel. intensity)] M+ 425 (9), M+-CH3 410 (19),
M+-C2H3 398 (10), M+-N(CH3)2ꢀC2H3ꢀCH4 338 (79),
[C6H4CH2N(CH3)2ꢀ2](C2H3)(CH3)Si}+-H 204 (60). IR
(NaCl): wCꢀH=2944 (vs), 2817 (vs), 2777 (vs); wCꢁC
=
1588 (w); wSiO=1044 (vs) cm−1
.
4.4.2. Data for compound 5b
Yield: 4.1 g (20.0 mmol, 100%). Anal. Calc. for
[C11H15ONSi]n: C, 64.35; H, 7.36. Found: C, 64.98; H,
1
7.01. H-NMR (CDCl3): 2.0–2.3 (m, 6H, NCH3), 3.4–
3.7 (br, 2H, NCH2), 5.6–6.4 (m, 3H, C2H3), 7.0–8.0
(m, 4H, C6H4). IR (NaCl): wCꢁC=1594 (w); wSiO=1080
(vs) cm−1. M: 600 g mol−1 (n: 2.9).
cm−1
.
4.5. Synthesis of
4.3.5. Data for compound 4d
{[C6H4CH2N(CH3)2ꢀ2](H)SiꢀCH2CH2ꢀ}n (6)
Boiling point 25°C/10−3 mbar. Anal. Calc. for
C17H21NO2Si (299.45): C, 68.19; H, 7.07. Found: C,
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiH2 (1b) (600 mg,
3.13 mmol) and 0.1 ml of H2PtCl6 (5% solution in
isopropanol), are heated for 8 h to 200°C. The oily
product is extracted in three stages each with 30 ml of
n-pentane and filtered through a pad of Celite. After
removal of the solvent in vacuum, 540 mg (2.8 mmol,
90%) of compound 6 are obtained as a pale-yellow oil.
Anal Calc. for [C11H17NSi]n: C, 69.05; H, 8.95.
1
68.29; H, 7.14. H-NMR (CDCl3): l 2.14 (s, 6H, CH3),
4
2.43 (t, JHH=2.5 Hz, 2H, ꢂCH), 3.53 (s, 2H, NCH2),
4
4.46 (d, JHH=2.5 Hz, 4H, OCH2), 5.89–5.92 (m, 1H,
C2H3), 6.0–6.1 (m, 2H, C2H3), 7.2–7.4 (m, 3H, C6H4),
7.9–8.0 (m, 1H, C6H4). 29Si{1H}-NMR (CDCl3): l
−35.4. EI-MS [m/z (rel. intensity)] M+ 299 (13), M+-
CH3 284 (37), M+-C2H3 272 (20), M+-CH3ꢀC2H3 257
(42), M+-OCH2CCH 244 (63), M+ꢀN(CH3)2ꢀC2H3
Found: C, 70.13; H, 8.31. H-NMR (CDCl3) 0.8–1.3
1
+
228 (47), CH2N(CH3)2 58 (100). IR (NaCl): wCH
=
(m, 4H, SiCH2), 1.7–2.5 (m, 6H, CH3), 3.3–3.7 (m, 2H,
NCH2), 4.0–4.5 (m, 1H, SiH), 6.9–7.8 (m, 4H, C6H4).
IR (NaCl): wSiH=2136 (vs, br) cm−1. M: 680 g mol−1
(n: 3.6).
3047 (m), 3001 (s), 2972 (vs), 2940 (vs), 2855 (vs), 2815
(vs), 2775 (vs); wCꢂC=2119 (m); wCꢁC=1588 (s); wSiO
1083 (vs) cm−1
=
.
4.4. Synthesis of
4.6. Synthesis of
{[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)Si}2O (5a) and
{[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiO}n (5b)
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(H)Si[OC(O)C6H5] (8)
At 25°C, 780 mg (4.08 mmol) [C6H4CH2N(CH3)2ꢀ2]-
(H2CꢁCH)SiH2 (1b) are dissolved in 30 ml of chloro-
form and 500 mg (4.08 mmol) of benzoic acid are
added in one portion. Evolution of H2 is observed.
After removal of all volatile materials in vacuum, 1.25
g (4.01 mmol, 98%) of analytically pure 8 are obtained
as a colorless oil.
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(R)SiH (1a: R=
CH3, 4.1 g; 1b: R=H, 3.8 g) (20 mmol) in 100 ml of
tetrahydrofuran is reacted with 1.0 ml (55.0 mmol) of
water at 25°C. The reaction mixture is refluxed for 3 h
and all volatile materials are removed in vacuum. The
resulting oil is extracted with 100 ml of

140
M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
4.7.2. Data for compound 12b
Yield: 740 mg (2.26 mmol, 83%). M.p. 96–99°C.
Anal. Calc. for C18H21NO2Si (311.46): C, 69.41; H,
6.80. Found: C, 69.70; H, 7.01. H-NMR (CDCl3): l
1
Anal. Calc. for C18H22N2SSi (326.53): C, 66.21; H, 6.79.
2.30 (s, 6H, CH3), 3.66 (s, 2H, CH2), 5.15 (br, 1H,
1
SiH), 5.82 (dd, 2JHH=4.8 Hz, 3JHH=20.1 Hz, 1H,
Found: C, 64.95; H, 6.98. H-NMR (CDCl3): l 2.22 (s,
6H, NCH3), 3.57 (d, 2JHH=14.3 Hz, 1H, CH2), 3.77 (d,
2
3
C2H3), 6.03 (dd, JHH=4.8 Hz, JHH=14.8 Hz, 1H,
3
2JHH=14.3 Hz, 1H, CH2), 4.70 (d, JHH=1.8 Hz, 1H,
C2H3), 6.47 (ddd, JHH =2.2 Hz, 3JHH=14.8 Hz,
3
Si
3JHH=20.1 Hz, 1H, C2H3), 7.2–7.3 (m, 2H, C6H4 and
C6H5), 7.4–7.7 (m, 5H, C6H4 and C6H5), 8.1–8.3 (m,
2H, C6H4 and C6H5). 13C{1H}-NMR (CDCl3): l 44.8
(CH3), 62.7 (CH2), 125.2, 127.1, 127.9, 129.7, 129.8,
131.1, 131.9, 132.8, 133.8, 134.5, 136.9, 144.4 (C2H3,
C6H4 and C6H5), 167.9 (CꢁO). 29Si{1H}-NMR (CDCl3)
l −61.9. EI-MS [m/z (rel. intensity)] M+ 311 (5),
M+-CH3 296 (31), M+-C6H5CO2 190 (46) M+-
SiH), 5.6–5.7 (m, 1H, C2H3), 6.0–6.4 (m, 2H, C2H3),
7.1–7.4 (m, 8H, C6H4 and C6H5), 7.8–7.9 (m, 1H,
C6H4), 9.85 (s, 1H, HCS). 13C{1H}-NMR (CDCl3): l
44.6 (CH3), 62.2 (CH2), 125.6, 125.9, 126.6, 127.6,
128.5, 128.7, 130.6, 132.0, 132.6, 137.5, 144.6, 145.1
(C2H3, C6H4 and C6H5), 196.6 (HCS). 29Si{1H}-NMR
(CDCl3): l 55.3. FAB-MS [m/z (rel. intensity)] M+ 326
(8), M+-C2H3 299 (6), M+-C6H5NCHS 190 (100). IR
(KBr): wSiH=2136 (s); wCꢁC=1561 (m) cm−1
.
C6H5CO2ꢀCH3 165 (35), M+-C6H5CO2ꢀC2H3 163 (15),
C6H5CO+ 105 (100), C6H5 77 (58). IR (NaCl): wSiH
=
+
4.7.3. X-ray structure determination of compound 12b
[13]
2127 (vs); wCꢁO=1655 (vs); wCꢁC=1595 (m) cm−1
.
The molecular structure of compound 12b (Fig. 1)
was determined from single crystal X-ray diffraction
data, which were collected using a Siemens R3m/V
(Nicolet Syntex) diffractometer. Crystallographic data
for compound 12b are given in Table 1, interatomic
distances in Table 2 and atomic coordinates in Table 3.
The structure of 12b was solved by direct methods
(SHELXTL PLUS; Sheldrick, University of Go¨ttingen,
1988) and refined by the least-squares method based on
F2 with all reflections (SHELXL 93; Sheldrick, Univer-
sity of Go¨ttingen, 1993). All non-hydrogen atoms, as
well as the silicon-bonded hydrogen atom H(1) were
refined anisotropically; the hydrogen atoms were placed
in calculated positions. An empirical absorption correc-
tion was applied. The structure plots have been made
using ZORTEP (Zsolnai and Huttner, University of
Heidelberg, Germany, 1994).
4.7. Synthesis of
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(CH3)Si(C6H5NCHS)
(12a) and
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(H)Si(C6H5NCHX)
(12b: X=S, 12c: X=O)
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)(R)SiH (2.73 mmol)
(1a: R=CH3, 560 mg; 1b R=H 520 mg) are dissolved
in 30 ml of chloroform and 2.73 mmol of PhNꢁCꢁX
(11a: X=S 370 mg; 11b: X=O, 330 mg) are added
dropwise at 25°C. The reaction mixture is stirred for 3
h at 25°C and then all volatile materials are removed in
vacuum. Purification of the products is carried out by
crystallization of the residues from 20 ml
methylenechloride/n-pentane (3:1) (12a, 12b) or by ex-
traction with diethylether/n-pentane (1:1) followed by
vacuum distillation (12c). 12a and 12b are obtained as
pale-yellow solids, while 12c is obtained as a colorless
oil.
4.7.4. Data for compound 12c
Yield: 800 mg (2.57 mmol, 94%). Anal. Calc. for
C18H22N2OSi (310.46): C, 69.64; H, 7.14. Found: C,
1
69.23; H, 7.33. H-NMR (CDCl3): l 2.27 (s, 6H, CH3),
4.7.1. Data for compound 12a
Yield: 390 mg (1.13 mmol, 42%). M.p. 116°C. Anal.
Calc. for C19H24N2SSi (340.56): C, 67.01; H, 7.10.
2
3.65 (s, 2H, CH2), 4.76 (br, 1H, SiH), 5.82 (dd, JHH
=
3.7 Hz, 3JHH=20.0 Hz, 1H, C2H3), 6.03 (dd, 2JHH=3.7
Hz, JHH=14.7 Hz, 1H, C2H3), 6.33 (dd, JHH=14.7
Hz, JHH=20.0 Hz, 1H, C2H3), 7.0–7.4 (m, 8H, C6H4
3
3
1
Product rapidly decomposes in air. H-NMR (CDCl3,):
3
l 0.49 (s, 3H, SiCH3), 2.24 (s, 6H, NCH3), 3.32 (d,
and C6H5), 8.0–8.1 (m, 1H, C6H4), 8.15 (br, 1H, HCO).
13C{1H}-NMR (CDCl3): l 45.0 (CH3), 63.1 (CH2),
123.0, 123.4, 124.2, 125.2, 127.4, 129.1, 130.2, 132.1,
132.7, 134.2, 138.0, 144.7 (C2H3, C6H4 and C6H5), 167.4
(HCO). 29Si{1H}-NMR (CDCl3): l −26.9. IR (KBr):
2JHH=12.4 Hz, 1H, CH2), 3.80 (d, JHH=12.4 Hz, 1H,
2
CH2), 6.30 (dd, 2JHH=4.5 Hz, 3JHH=19.7 Hz, 1H,
2
3
C2H3), 6.05 (dd, JHH=4.5 Hz, JHH=14.7 Hz, 1H,
3
3
C2H3), 6.30 (dd, JHH=14.7 Hz, JHH=19.7 Hz, 1H,
C2H3), 7.1–7.4 (m, 8H, C6H4 and C6H5), 7.5–7.6 (m,
1H, C6H4), 9.81 (s, 1 H, HCS). 13C{1H}-NMR
(CDCl3): l −1.2 (SiCH3), 45.0 (NCH3), 61.8 (CH2),
125.6, 126.0, 126.5, 127.2, 128.1, 128.7, 132.9, 133.1,
133.4, 139.2, 144.4, 145.4 (C2H3, C6H4 and C6H5), 198.0
(HCS). 29Si{1H}-NMR (CDCl3): l −10.5. FAB-MS
[m/z (rel. intensity)] M+-C6H5NCHS 204 (100).
wSiH: 2132 (br) cm−1
.
4.8. Synthesis of [C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiꢁS
(16)
[C6H4CH2N(CH3)2ꢀ2](H2CꢁCH)SiH2 1b (200 mg, 1.0
mmol) and 64.0 mg (2.0 mmol) of 1/8 S8 are suspended

M. Weinmann et al. / Journal of Organometallic Chemistry 561 (1998) 131–141
141
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in 30 ml of chloroform and reacted in an ultrasonic
bath. The sulfur completely dissolves during 30 min.
Under evolution of H2S, 205 mg (0.93 mmol, 93%) of
16 precipitate as a colorless solid, which is extremely
sensitive to oxygen and moisture.
Anal. Calc. for C11H15NSSi (221.40): C, 59.67; H,
6.83: Found: C, 57.34; H, 7.02. Product rapidly decom-
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1
poses in air. H-NMR (CDCl3): l 2.26 (s, 3H, CH3),
2
2.44 (s, 3H, CH3), 3.50 (d, JHH=8.0 Hz, 1H, CH2),
3.72 (d, 2JHH=8.0 Hz, 1H, CH2), 5.8–6.1 (m, 2H,
C2H3), 6.2–6.4 (m, 1H, C2H3), 7.1–7.4 (m, 3H, C6H4),
7.7–7.9 (m, 1H, C6H4). EI-MS [m/z (rel. intensity)]:
M+ 221 (21), M+-CH3 206 (62), M+-CH3ꢀC2H3 179
+
(19), N(CH3)3 59 (100).
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Acknowledgements
We are grateful to the Deutsche Forschungsgemein-
schaft (SFB 247) and the Fonds der Chemischen Indus-
trie for financial support. We thank Thomas Jannack
for carrying out the MS measurements, Wacker Com-
pany (Burghausen) for supplying us with a generous
gift of silicon compounds, S. Ahrens for many discus-
sions and K. Do¨rr for assistance in drawing up the
manuscript.
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˚
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˚
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.