Intramolecular nitrogen ligand stabilization of phenyl-imidazolidine derived silicon species

Article abstract of DOI:10.1016/S0022-328X(98)00815-8

The synthesis of some new functional aminoarylsilanes with the aromatic ring substituted in the ortho-position by a 2-(1,3-dimethyl)imidazolidine ligand is presented. The donating properties of the imidazolidine fragment, in which the two coordinating nitrogen atoms are located on the same side of the silicon center induce a specific chemical behavior of the organosilicon species. Thus, only one Si-H bond of ArSiH₃ was found to react with an excess of organic acids and heterocumulenes. NMR studies showed that, if in imidazolidinylphenyldihydrosilanes containing a strong electronegative substituent, the silicon center is pentacoordinated by forming one additional N→Si bond, only a small activation energy is sufficient to exchange the two donating nitrogen atoms. The reason for this easy exchange is probably the small distance between the two donor centers and the rigidity caused by the bridging ethylene unit.

Full text of DOI:10.1016/S0022-328X(98)00815-8

Journal of Organometallic Chemistry 570 (1998) 183–193
Intramolecular nitrogen ligand stabilization of phenyl-imidazolidine
derived silicon species
Robert J.P. Corriu *, Andreas Mix, Ge´rard F. Lanneau 1
Laboratoire de Chimie Mole´culaire et Organisation du Solide, UMR 5637, Uni6ersite´ Montpellier II, Case 007, Place Euge`ne Bataillon,
34095 Montpellier Cedex 05, France
Received 5 March 1998; received in revised form 16 June 1998
Abstract
The synthesis of some new functional aminoarylsilanes with the aromatic ring substituted in the ortho-position by a
2-(1,3-dimethyl)imidazolidine ligand is presented. The donating properties of the imidazolidine fragment, in which the two
coordinating nitrogen atoms are located on the same side of the silicon center induce a specific chemical behavior of the
organosilicon species. Thus, only one Si–H bond of ArSiH3 was found to react with an excess of organic acids and
heterocumulenes. NMR studies showed that, if in imidazolidinylphenyldihydrosilanes containing a strong electronegative
substituent, the silicon center is pentacoordinated by forming one additional N“Si bond, only a small activation energy is
sufficient to exchange the two donating nitrogen atoms. The reason for this easy exchange is probably the small distance between
the two donor centers and the rigidity caused by the bridging ethylene unit. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Si-pentacoordination; 2-(1,3-Dimethylimidazolidine-2-yl)aryl ligand; Intramolecular nucleophilic activation
1. Introduction
There is continuing interest in the theoretical and
mechanistic aspects of the nucleophilic catalyzed substi-
tutions at silicon [1]. Hypercoordinated species with
mono or bidentate aminoaryl ligands have been synthe-
sized in order to mimic the different geometries of the
possible intermediates involved in these reactions [2].
Among them, the fused bis(aminonaphthyl) derivatives
A, with a formally hexacoordinated silicon atom, pre-
sented an unexpected chemical stability [3], whereas the
bis(dimethylaminophenyl) compound B was shown to
exist in solution as an equilibrium between pentacoordi-
More recently, we applied the approach of Van
Koten [5] to obtain some new nitrogen bis chelating
silicon species, starting from the 2,5-bis(dimethy-
lamino)phenyl lithium. We isolated a series of stabilized
nated species [4].
siliconium ionic derivatives C, in which the two nitro-
gen atoms occupy the trans-diaxial positions of a trigo-
nal bipyramidal geometric species [6]. The siliconium
ionic compound was supposed to be formed [7] through
the nucleophilic displacement of the halogen (as a good
leaving group) by the second NMe2 coordinating ligand
at silicon (Chart 2).
* Corresponding author. Tel.: +33 467 143971; fax: +33 467
143888; e-mail: lanneaug@univ-montp2.fr
1 Also corresponding author.
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00815-8

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In this context, it was of interest to study the struc-
ture and the chemical behavior of compounds in which
the two coordinating nitrogen centers are located on
the same side of the silicon atom [8]. For this purpose,
we choosed phenyl silanes substituted in ortho-position
by a 2-(1,3-dimethyl)imidazolidine ligand.
Scheme 1.
According to that method, we synthesized a series of
aromatic imidazolidines. The heterocyclic compounds
1–8 (Chart 3) are available in high yields as very
viscous colourless oils. To check the possibility of selec-
tive ortho (peri) lithiation for introducing a silicon side
chain in these positions, the imidazolidines 1–8 were
treated with one equivalent of n-butyl lithium in diethyl
ether. After some hours, a colourless precipitation of
2. Results and discussion
2.1. Synthesis and metalation of the ligands
The dimethylimidazolidine system can be easily built-
up by reaction of an aromatic aldehyde with N,N%-
dimethylethylenediamine in the presence of a catalytic
amount of acid (Eq. 1) [9].
the aryl lithium compound was observed, which was
trapped after 12
tetramethoxysilane.
h
with
a
slight excess of

R.J.P. Corriu et al. / Journal of Organometallic Chemistry 570 (1998) 183–193
185
The isolated silanes showed that the phenyl deriva-
tives 1–4 can be ortho-metalated selectively in good
yields. Double metalation of the dichloro compound 3
was not possible, even when an excess of the lithiating
agent was added. Compound 4 offered the possibility to
introduce a silicon side chain in the 6-position between
the two imidazolidine ligands. In fact, the metalation
takes place only in the sterically less hindered 2-posi-
tion, instead of the more activated 6-position. Surpris-
ingly, deprotonation of the peri position of the
naphthyl compound 7 presented some difficulties. Be-
sides the peri silylated compound 25, the ortho product
24 was formed simultaneously. A similar result was
obtained by metalation of the o-tolyllimidazolidine 5
with n-butyl lithium, in Et2O, followed by reaction with
tetramethoxysilane. The reaction leads only to the ortho
product 20, and the compound 21 with the silyl group
in benzylic position was not observed. However, such a
metalation of the less favorable benzylic position in 5 is
possible by complexing the n-butyl lithium with
TMEDA (Scheme 1).
Deprotonation of the anthracenyl compound 8 failed
completely. No silylated product was detectable after
refluxing a mixture of 8 with n-butyl lithium in DME
for several hours, followed by addition of Si(OMe)4.
The reason for this unusual behavior with compounds
5, 7 is probably steric in origin.
Scheme 2.
2.2. Synthesis of imidazolidinylphenyl substituted silanes
corresponding difluoro silane 31 is synthesized by react-
ing the aryl lithium compound 9 with the trifluorosilane
30. Difluorosilane 31 is more stable to air than com-
pound 30, a situation which is certainly an effect of a
better sterical protection of the SiF2 unit by the second
imidazolidinyl aryl system.
Besides the trimethoxysilane 17, both the chloro
compounds 26 and 27 are available by reaction of the
lithiated ligand 9 with one equivalent of the corre-
sponding chlorosilane (Scheme 2). Compounds 26 and
27 are isolated as air and moisture sensitive powders,
insoluble in apolar solvents like pentane or ether. Intro-
duction of the trimethylsilyl group can be carried out
by reaction of 9 with trimethylchlorosilane. Dihydrosi-
lane 29, bearing a second aryl substituent is directly
available by reaction of phenyl silane with the lithiated
ligand 9.
2.3. Reactions of imidazolidinylphenyl silane 33
Corresponding to comparable known systems,
the silane 33 itself should be also a good precursor
for the synthesis of
a wide range of aryl or
As already shown in the literature ([1]b, [2]c, [6–8]),
aryltrimethoxy silanes are good precursors for the syn-
thesis of other functionalized silanes. Thus, it should be
possible to modify the substitution pattern in 17 and in
27 by standard reactions (Scheme 3). Correspondingly,
treatment of 17 with boron trifluoride-diethyl ether
complex at r.t. lead to the trifluorosilane 30, isolated as
a very air sensitive and highly viscous yellow liquid.
The silane 33 was obtained as a colourless, air stable
liquid, either by stirring of 17 with lithium aluminium
hydride or by reduction of the trichlorosilyl derivative
27. Compounds containing two imidazolidinyl-aryl lig-
ands were available, for example, by reaction of te-
tramethoxysilane with two equivalents of the lithiated
ligand 9, which affords the dimethoxysilane 32. The
alkyl substituted silanes by reaction with nucleo-
philes like alkyl or aryl lithium compounds ([1], [3]c,
[6–8]).
Pentacoordinated organosilicon hydrides add to CꢀX
double bonds (X=O, S, N) in heterocumulenes like
carbodiimides, isocyanates, isothiocyanates, CO2 and
CS2 [10–12]. In some instances, the intermediates are
thermally unstable and decompose to products contain-
ing SiꢀX double bonds. Following that methodology, a
silanethione has been isolated [13] in the case of
dimethylaminomethylene naphthyl system (Scheme 4).
The imidazolidinylphenyl substituted silane 33 shows
a chemical behavior different to that of the analogous
arylmethyldimethylamino compounds (Scheme 5). In

186
R.J.P. Corriu et al. / Journal of Organometallic Chemistry 570 (1998) 183–193
Scheme 3.
33, only one hydrogen is activated and enabled to react,
for example with organic acids or with heterocumule-
nes. Thus, the silane 33 reacts with acetic acid giving
the silyl ester 36. Bis- or tris-substituted products are
not observed, even in the presence of an excess of acid.
Only the corresponding formic ester 35 is formed with
formic acid. Interestingly, this ester is also the only
product obtained by adding the silane 33 to CO2.
Reaction of 33 with phenylisothiocyanate yields the
thioamide 34, which is characterized as a mixture of
two isomers. Hydrogen–chlorine exchange in 33 is
observed with PCl5 [14].
Upfield shifts are obtained for the silanes 26, 27, 29,
30, 31, 33, and 34–37 which all contain electronegative
substituents. The imidazolidine system is supposed to
coordinate to the silicon center in these compounds,
since the l values correspond to those of the dimethy-
laminomethyl substituted derivatives (Table 1), for
which extension of coordination is well demonstrated
[4,6–8,17]. The question whether the silicon in the
silanes containing an electronegative substituent is pen-
tacoordinated or if the coordination sphere in these
silanes is extended to six can be answered by the results
of temperature dependent NMR spectroscopic investi-
gations (Table 2), which were typically carried out for
the silanes 30, 33, 36, 37.
2.4. Intramolecular coordination at silicon
The NMR data presented here prove that, in these
compounds, the silicon center is only pentacoordinated,
but the structure is highly dynamic. In other words, a
fast exchange occurs from one nitrogen to the other for
coordination to the central silicon, as shown in Scheme
6. This exchange can be stopped by cooling down the
mixture to low temperature.
Extension of coordination around a silicon atom
from four to five is normally accompanied by an upfield
shift in the position of the 29Si-NMR signal [6–8,15].
As expected, all the species described here show charac-
teristic 29Si-NmR upfield variations relative to their
tetracoordinated analogues Table 1. Some 2-(dimethy-
laminomethyl)phenylsilanes
and
2,6(bis-dimethy-
To better understand the fluxional behavior of our
models, we have first carried out variable temperature
19F-NMR investigation of compound 30, in d8-toluene.
The 19F-NMR spectrum presents at −90°C three
triplets, two broad signals respectively at −125.75
(J=36 Hz), −142.60 ppm (J=24 Hz) and a better
laminomethyl)phenylsilanes are also reported for
comparisons. As already observed in previous studies
previous studies [4,17], the smaller differences are noted
in the case of methoxy derivatives 17, 32 and trimethyl
moiety 28, which behave like tetravalent silanes.

R.J.P. Corriu et al. / Journal of Organometallic Chemistry 570 (1998) 183–193
187
Scheme 4. Insertion and decomposition of heterocumulenes.
resolved system at −138.15 ppm (J=35.8 Hz). When
the temperature is raised, the signals coalesce at 213 K
to give a single resonance at −135.55 ppm, allowing
the free energy of activation for the whole process to be
estimated as 8.7 kcal mol−1, applying the Eyring equa-
tion [16]. The 29Si-NMR spectrum gives a quartet at l
−101 ppm [J(19F–29Si)=232 Hz], with no important
modification of the shape from 223 to 343 K. Both, the
upfield chemical shift and the lower Si–F coupling
constant relative to PhSiF3 are indicative of an hyper-
groups give differentiated signals, the N–CH2 moieties
give broad multiplets and the Si–H2 protons appear as
AB systems. At r.t., one signal is observed for the
N–CH3 groups, two quartets for the N–CH2, and one
singlet for the SiH2 moiety. The more reasonable ge-
ometry of the stable form expected in pentacoordinated
trifunctional silanes bearing two hydrogen ligands is
this one in which the two hydrogen atoms occupy
equatorial positions of a trigonal bipyramidal structure
[17] with the third functional group and the nitrogen
coordinating ligand in apical positions.
1
coordinated species. Temperature dependent H-NMR
investigations for the trifluoro silane 30 show that the
N–Me groups are equivalent even at 203 K, whereas
the quartets corresponding to the N–CH2 groups (two
types of protons) are maintained when the solution is
cooled to 200 K. Such results can only be interpreted
through a decoordinating process of the imidazolidine
moiety, when the temperature is raised. The two N-
methyl groups are equivalent through the fast ex-
change, whereas the methylenic hydrogens keep their
different environment in the five-membered ring geome-
try with two hydrogen atoms in endo (exo) position
relative to the silicon atom. An extension of coordina-
tion to six ligands around the central silicon, which
could alternatively explain both the equivalence of the
N–Me groups and maintain the AB system of the CH2
groups, must be accompanied by the equivalence of
only two of the fluorine atoms, which is not observed.
The more reasonable explanation is fast decoordina-
tion, allowing free rotation of the non-coordinating
substituents, before reclosure.
The results are interpreted by a fast exchange be-
tween the two nitrogen coordinating ligands. The val-
ues for the energy of activation calculated [16] for this
process from the NMR data (Table 2) are lower than
the 9–13 kcal mol−1 obtained [18] for the dissociative
process
of
the
corresponding
2-[1-(dimethy-
lamino)ethyl]phenyl substituted analogues (Chart 4).
Obviously, the nearness of the second nitrogen in the
fused imidazolidine system facilitates a rapid change of
these atoms in their coordination to the silicon center.
3. Conclusion
1
Table 2 shows the H-NMR chemical shift values for
The synthetic and spectroscopic results presented
here show that the imidazolidinyl-phenyl substituent
bonded to a silicon center stretch out some unusual
properties in the resulting compounds. Starting from
the trimethoxy derivative 17, a large number of silicon
compounds with a wide range of different substituents
at the silicon center is available. The donating proper-
ties of the imidazolidine fragment are suitable to com-
pensate electron deficits at the silicon atom caused by a
strong electronegative substituent, by forming a donor
contact. The electronic properties also influence the
chemical behavior of the silicon center. This is exem-
plified by the reactions of the silane 33. Thus, only the
compounds 33, 35, 36, 37. In the trihydrosilane 33,
signals corresponding to only one type of imidazolidine
ring are observed at all temperatures from 183 K (in
CD2Cl2) to 400 K (in C6D5NO2). The 29Si-NMR (d8-
toluene) spectrum gives a quartet of doublets at l
−70.45 ppm (J1=198.8 Hz, J2=8.3 Hz), with no
important modification of the chemical shift and cou-
pling constant from 223 to 343 K. Apparently, the
nitrogen coordination is too weak and/or the nitrogen
exchanges are too fast in the pentacordinated species to
give rise to observable diastereotopy. Compounds 35,
36 and 37 present a more interesting behavior in their
1H-NMR spectra. At low temperature, the two N–CH3

188
R.J.P. Corriu et al. / Journal of Organometallic Chemistry 570 (1998) 183–193
Scheme 5.
axial hydrogen was found to be activated enough to give
reactions with organic acids and heterocumulenes.
NMR studies showed that, if in imidazo-
lidinylphenyldihydrosilanes containing a strong elec-
tronegative substituent the silicon center is pentaco-
ordinated by forming one additional N“Si bond, only
a small activation energy is necessary to exchange the
donating nitrogen atoms. The structure in solution is
highly dynamic, but base-coordinated silyl cations are
not evidenced ([6]c, [19]). The reason for this easy
exchange is probably the small distance between the two
donor centers and the rigidity caused by the bridging
ethylene unit.
handled by standard Schlenk techniques. Diethyl ether
was dried and distilled from a purple solution of sodium/
benzophenone ketyl. Toluene was distilled from sodium
under nitrogen. Chloroform and dichloromethane were
dried with CaH2 and distilled under nitrogen. Glassware
was dried in an oven at 110–120°C prior to use.
Commercially available chemicals were used as such
without any further purification. For a concern of
presentation, and since pertinent data are reported in the
text (Tables 1 and 2), the NMR data of the new
compounds have been placed in a supporting section.
The mass spectra were obtained on a Delsi Nermag
Automass [diphenyl (5%) dimethylsilicone as stationary
phase, electron impact mode, 70 eV] or a JEOL JMS
D100 apparatus by EI ionization at 30 or 70 eV. In some
cases, positive FAB mass spectra in m-nitrobenzyl alco-
hol (NBA) were also recorded. Elemental analyses were
carried out by the Service Central de Microanalyse du
CNRS in Lyon or in the ENSC Montpellier.
4. Experimental part
All reactions were carried out under an atmosphere of
dry argon. Air-sensitive products and reagents were

R.J.P. Corriu et al. / Journal of Organometallic Chemistry 570 (1998) 183–193
189
Table 1
29Si-NMR chemical shifts of some aminoaryl silanes versus tetravalent derivatives (coupling constants, in Hz, in parentheses)
Ar–SiF3
Ar–SiH3
Ar–Si(OMe)3
Ar–SiMe3
Ar–SiH2Ph
Ar2SiF2
−72.9 (267)
−61.5 (200)
−54.5
−101.0 (232)
−70.45 (199)
−54.0
−4.3
−44.4 (214)
−54.2 (269)
−102.2 (233)
−75.95 (198)
−54.0
−80.0 (200)
−53.8
−7.6
−4.1
−4.9
−33.8 (200)
−29.1 (302)
−33.8 (200)
−34.5
−44.6 (210)
−53.9 (270)
−45.01 (199)
−51.5 (194)
Ar2SiH2
Ar2Si(OMe)2
−29.4
4.1. Substituted dimethylimidazolidines
amount of p-toluene sulfonic acid, and refluxed in 300
ml of toluene. The water is collected in a Dean–Stark
trap. After usual work-up, the compound 6 is distilled
b.p. 106°C/1.6 mm Hg. Yield 21.7 g (46%). Anal. Calc.
for C12H18N2: C, 75.74; H, 9.53; N, 14.71. Found: C,
73.73; H, 9.39; N, 14.55. FAB-MS (m/e, relative inten-
sity%): 191 (M+ + H, 95), 190 (M+, 90), 146 (M+-
CH3NCH3, 50), 99 (Imid+; 100) 190 (M+, 90), 146
(M+-CH3NCH3, 50), 99 (Imid+, 100)
1,3-Dimethyl-2-(1-naphthyl)imidazolidine 7: same
procedure as above. Yield 73%. Colourless oily liquid.
b.p. 110°C/0.01 mmHg. Anal. Calc. for C15H18N2: C,
79.61; H, 8.02; N, 12.37. Found: C, 79.76; H, 7.97; N,
12.65. FAB-MS (m/e, relative intensity%): 226 (M+,
35), 225 (M+-H, 100), 182 (M+-CH3NCH2, 15), 168
(M+-CH3NCH2CH3, 15), 99 (imid+, 80).
1,3-Dimethyl [2-anthracen-9 yl] imidazolidine, 8:
same procedure as above. After removal of the solvent,
the brown residue is crystallized in Et2O/toluene (20/
80). The solid is collected by filtration and washed with
pentane. Yield 71%. m.p. 121°C. Yellow solid. Anal.
Calc. for C19H20N2: C, 82.57; H, 7.29; N, 10.13. Found:
C, 82.44; H, 7.27; N, 10.13. FAB-MS (m/e, relative
intensity%): 276 (M+ + H, 60), 275 (M+-H, 40), 274
(M+- H, 90), 232 (M+-CH2NCH3,30), 218 (M+-
CH3NCH2CH3, 28), 191 (M+-CH3NCH2CH2NCH3,
20), 178 (M+-imid, 15), 99 (imid.+-, 100).
Aryl substituted dimethylimidazolidines 1–8 have
been prepared according to literature [9]. In a typical
experiment, benzaldehyde (20 g, 0.19 mol) and N,N%-
dimethylethylenediamine (18 g, 0.2 mol) are dissolved
in 200 ml of toluene, with 0.5 ml of p-toluenesulfonic
acid as catalyst, and the mixture is refluxed for 6 h with
connection to a Dean–Stark trap in which water is
collected. The solvent is then removed and the residue
is distilled in vacuo. Colourless liquid, b.p. 65°C/0.1
mmHg:Yield 84%. The 1,3-dimethyl-2-phenylimidazo-
lidine, 1, has been identified by comparison of its
characteristics with those of an authentic sample [9].
The other dimethylimidazolidines 2–8 have been pre-
pared using the same procedure with the appropriate
aldehyde.
1,3-Dimethyl-2(2-bromophenyl) imidazolidine, 2:
Colourless liquid. Yield 93%. b.p. 85°C/0.5 mmHg.
Anal. Calc. for C11H15 Br N2: C, 51.79; H, 5.93; N,
10.98. Found: C, 51.88; H, 6.18; N, 10.89. FAB MS;
m/e (relative intensity%): 255 (M+ +H), 253 (M+-H),
99 (Imid+).
1,3-Dimethyl-2(2,6 dichlorophenyl) imidazolidine, 3:
Colourless liquid. Yield 73%. bp. 104°C/0.5 mmHg.
Anal. Calc. for C11H14Cl2N2: C, 53.89; H, 5.76; N,
11.43. Found: C, 54.05; H, 5.77; N, 11.29.
1,3-Bis(1,3-dimethyl imidazolidine-2-yl) benzene, 4:
Colourless oily liquid. Yield 74%. b.p. 110°C/5.10–2
Torr. Anal. Calc. for C16H26N4: C, 70.03; H, 9.55; N,
20.41. Found: C, 70.25; H, 9.64; N, 20.81. FAB-MS
(m/e, relative intensity ‰): 275 (M+ +H, 25) 274
(M+, 15), 273 (M+-H, 60, 216 (M+-CH3NCH2CH3,
25), 175 (M+-Imid-H, 30), 99 (Imid+, 100).
1,3-Dimethyl-2-benzyl imidazolidine, 6: 30.0 g (0.25
mol) of phenylacetaldehyde are mixed with 24.0 g (0.27
mol) of dimethylethylene diamine, plus a catalytic
2-(1,3-Dimethylimidazolidine-2-yl) phenyl trimeth-
oxysilane 17: 4.4 g (25.00 mmol) of 1,3-dimethyl-2-
phenylimidazolidine are dissolved in 40 ml of anhy-
drous ether. The solution is treated with 10 ml of a 2.5
M solution of n-Bu Li in hexane (25.0 mmol). After
stirring overnight, the mixture is added slowly to a
solution of 5.7 g (27.5 mmol) of tetramethoxysilane in
40 ml of Et2O at −10°C. The mixture is warmed to r.t.
and stirred for additional 12 h. The solvent is removed
in vacuo and hexane is added to precipitate MeOLi.

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Table 2
Selected 1H-NMR data of 29, 33, 35, 36, 37
No
Formula
Conditions
N–CH3
2.04
N–CH2
N–CH
3.42
Si–H
4.91
DGc (kcal mol−1
)
29
(Ip5)SiH2Ph
25°C
CDCl3
2.47
3.35
B8.0
−90°C
CD2Cl2
2.10
2.15
2.15
2.31
2.57
3.35
3.48
3.46
3.48
3.76
3.71
3.71
3.67
3.78
3.79
4.80
4.19
4.18
4.82
TcB
−90°C
33
35
36
37
(Ip5) SiH3
25°C
CDCl3
2.56
3.33
B7.5
−100°C
CD2Cl2
2.60
3.32
TcB
−100°C
(Ip5)SiH2OCOH
(Ip5)SiH2OCOCH3
(Ip5)SiH2Cl
25°C
CDCl3
2.73
3.50
10.1
−80°C
CD2Cl2
2.16
2.28
2.7
3.3–3.5
4.385
4.875
Tc
−45°C
25°C
CDCl3
2.27
2.69
3.47
4.78
9.9
−90°C
CD2Cl2
2.185
2.245
2.5
3.4–3.6
4.285
4.805
Tc
−65°C
25°C
CDCl3
2.28
2.72
3.45
5.18
11.0
−80°C
CD2Cl2
2.19
2.30
2.7
3.4–3.6
4.875
5.235
Tc
−40°C
After filtration and concentration, the compound 17 is
isolated by distillation, b.p. 95°C/5×10−2 mmHg. Yield
4.4 g (57%).
160°C/2 mmHg. Yield 2.3 g (58%). Anal. Calc..for
C14H23ClN2SiO3: C, 50.81; H, 7.01; N, 8.47. Found: C,
51.54; H, 7.18; N, 8.48.
Anal. Calc. for C14H24N2SiO3: C, 56.73; H, 8.16; N,
9.45. Found: C, 56.55; H, 8.62; N, 9.90. FAB-MS (m/e,
relative intensity%): 296 (M+, 6) 175 (M+-Si(OCH3)3,
25), 132 (M+-Si (OCH)3–CH3 NCH2, 20), 99 (imid.+ 100).
3-Chloro-2 (1,3-dimethylimidazolidine-2-yl) phenyl
trimethoxysilane, 18: 20.4 ml of a 2.5 M solution of
n-BuLi in hexane (48.8 mmol) are added dropwise to a
solution of 3.0 g (12.2 mmol) of 2 (1,3-dichlorophenyl)
1,3-dimethylimidazolidine in 70 ml of ether. After 6 days
the mixture is added to a solution of 8.0 g (52.6 mmol)
of Si (OMe)4, in 20 ml of ether. After 12 h, the solvent
is removed and the residue is suspended in 50 ml of
pentane. After filtration, the solvent is removed and the
compound 18 is isolated by distillation in vacuo. b.p.
Bis [2-(1,3-dimethylimidazolidine-2-yl)-phenyl] dime-
thoxysilane 19: using the same procedure as above, 20 ml
of n-BuLi/hexane (2.5 M) were treated with 8.8 g (50
mmol) of 1,3 dimethyl-2-phenylimidazolidine; after 60 h,
3.8 g (25.2 mmol) of tetramethoxysilane were added.
After usual work-up, distillation afforded 4.1 g (yield
36%) of pure dimethoxysilane 19 (b.p. 150°C/10−2
mmHg). Anal Calc.for C24H36N4SiO2: C, 65.43, H, 8.24;
N, 12.50. Found: C, 64.95; H, 12.48. FAB-MS (m/e) 441
(M+-H), 411 (M+-OCH3), 341 (M+-Imid), 99 (Imid+).
3-Methyl-2 (1,3-dimethylimidazolidine-2-yl) phenyl-
trimethoxysilane, 20: In the same conditions as above, 9.5
g (50 mmol) of 1,3-dimethyl-2-o-tolylimidazolidine 11
are treated with n-BuLi (50 mmol) and then 10 g (65
mmol) of tetramethoxysilane, in anhydrous ether. After
work-up, flash distillation of the crude material gave 2.7
g (17% yield) of compound 20. Anal Calc. for
C15H26N2SiO3: C, 58.03; H, 8.44; N, 9.02. Found: C,
58.67; H, 8.59; N, 8.81.
4.2. Miscellaneous reactions
Attempted synthesis of 2 (1,3-dimethylimidazolidine-
2-yl) dichlorosilane, 26. In 40 ml of Et2O are mixed 4.4
g (25 mmol) of 1,3-dimethyl-2-phenyl-imidazolidine
and 10 ml of n-BuLi (2.5 M) in hexane. After stirring
for 12 h, silicochloroform is added at −40°C. The
Scheme 6. Scheme 6

R.J.P. Corriu et al. / Journal of Organometallic Chemistry 570 (1998) 183–193
191
2-(1,3-Dimethylimidazolidine-2-yl) trifluorosilane, 30:
0.86 ml (7 mmol) of BF3–Et2O are added dropwise to
a solution of 2.0 g (6.8 mmol) of 1,3-dimethyl imidazo-
lidine-2-yl) trimethoxysilane, 17, in 30 ml of anhydrous
ether. After 3h, the solvent is removed in vacuo, and
the compound 30 is isolated by distillation: b.p. 139°C/
2 mmHg. Yield 59%. Anal. Calc..for C11H15F3N2Si: C,
50.76; H, 5.81; N, 10.76. Found: C, 51.06; H, 5.98; N,
10.74.
mixture is warmed up and stirred for 12 h. The solvent
is changed to hexane and the mixture is filtered. After
removal of the solvent under vacuum, attempted distil-
lation afforded an highly viscous residue.
13C{1H}-NMR (CDCl3): l 41.03 (NCH3), 52.75
(NCH2), 91.35 (CH), 127.07, 129.86, 131.26, 133.62,
138.58, 143.71 (aromatics). 29Si-NMR (CDCl3): l −
54.3 (J(SiH): 352 Hz. Only broad signals were observed
1
in the H-NMR spectrum.
Bis [2-(1,3-dimethylimidazolidine-2-yl-phenyl] difl-
uorosilane, 31: 4.33 g (16.7 mmol) of 1,3-dimethyl-2-(2-
bromophenyl) imidazolidine are dissolved in 70 ml of
Et2O. At −40°C, 6.7 ml (16.7 mmol) of n-butyl lithium
in n-hexane (2.5 M) are added. After 1 h, the mixture is
warmed up to 0°C and is added slowly to a solution of
2-(1,3-dimethylimidazolidine-2-yl) trifluorosilane, 30,
4.33 g (16.7 mmol). The mixture is stirred for 3 h at r.t.
After filtration and evaporation of the solvents, 31 is
isolated by distillation in vacuo, 2.35 g (yield 34%). b.p.
160°C/0.2 mm Hg. Anal. Calc. for C22H30F2N4Si: C,
63.43; H, 7.26; N, 13.44: Found: C, 63.97; H, 7.18; N,
13.61.
Bis [2-(1,3-dimethylimidazolidine-2-yl) pheny] dim-
ethoxysilane, 32: 20.0 ml of a 2.5 M solution of n-butyl-
lithium in n-hexane are added to a solution of 8.8 g (50
mmol) of 1,3-dimethyl-2-phenylimidazolidine, in 80 ml
of Et2O. After stirring for 48 h, 3.8 g (25 mmol) of
tetramethoxysilane are added. The mixture is refluxed
for 3 h and stirred overnight. After filtration, the
solvents are removed and the oily residue is distilled in
vacuo, giving 4.0 g of 32. Yield 36%, b.p. 150°C, 0.05
2-(1,3-Dimethylimidazolidine-2-yl) phenyltrichlorosi-
lane 27. To a solution of 5.0 g (19.6 mmol) of 1,3-
dimethyl-2-(o-bromophenyl) imidazolidine in 100 ml of
ether, was added a solution of 9.0 ml of n-butyl lithium
(2.2 M) in hexane at −30°C. After coming to 0°C, the
mixture was added to a solution of 4.0 g (23.5 mmol) of
silicon tetrachloride at −60°C. The mixture allowed to
come to r.t. and was stirred for 12 h. The solvent was
removed in vacuo, and the yellow residue dissolved in
50 ml of methylene chloride. After filtration, removal of
solvent left 27 as a yellow solid residue. Yield 91%.
Anal. Calc..for C11H15Cl3N2Si: C, 42.68; H, 4.88; N,
9.04. Found: C, 42.65; H, 4.91; N, 8.88. MS [EI, 30 eV;
m/e (relative intensity%)]: 175 (M+-SiCl3, 30, 132
(M+-SiCl3–CH3NCH2, 40) 99 (Imid+, 100).
2-(1,3-Dimethylimidazolidine-21-yl) phenyl trimethyl-
silane, 28: 5.0 g (19.6 mmol) of 2-(o-bromophenyl)
1,3-dimethylimidazolidine dissolved in 80 ml of anhy-
drous ether are metalated with 8.1 ml of a 2.4 M
solution of n-butyllithium in n-hexane (19.6 mmol) at
−20°C for 1.5 h. Then, 3.0 g (19.6 mmol) of
trimethylchlorosilane are added. After coming to r.t.,
the mixture is stirred for 12 h. The solvent is removed
and the residue is extracted with pentane. After re-
moval of the volatile products, the compound 28 is
purified by vacuum distillation. b.p. 102°C/1.5 mmHg.
Yield: 4.10 g (84%). Anal. Calc. for C14H24N2Si: C,
67.68; H, 9.74; N, 11.28. Found: C, 67.24; H, 10.03; N,
11.50. FAB-MS (m/e): 249 (M+ + 1, 80), 2.48 (M+,
50), 2.47 (M+-1, 70). 233 (40), 217 (20), 204 (15), 190
(20), 176 (40), 99 (100).
2-(1,3-Dimethylimidazolidine-2-yl) phenylsilane, 29:
3.1 g (17.6 mmol) of 1,3-dimethylimidazolidine are
dissolved in 60 ml of ether. To the solution, 8 ml of a
2.5 M solution of n-BuLi in hexane (17.6 mmol) are
added dropwise at r.t. and the mixture is stirred for
three days. Then, 1.9 g (18.6 mmol) of phenylsilane is
added. After 2 h, LiH is removed by filtration and the
solvent is eliminated in vacuo. Distillation affords 3.02
g (10.7 mmol) of compound 29 as a pale yellow liquid,
sensitive to air and moisture. Yield 61%. b.p. 116°C/
0.02 mmHg. Anal. Calc. for C17H22N2Si: C, 72.30; H,
7.85; N, 9.92. Found: C, 72.22; H, 7.79; N, 10.15 3.
FAB-MS (m/e, relative intensity%): 282 (M+, 15), 281
(M+-1, 90), 265 (10), 224 (30), 205 (25), 175 (10), 148
(10), 99 (100).
mmHg. FAB-MS (m/e relative intensity%): 441 (M+
+
1, 30), 411 (M+-OCH3, 15), 355 (M+-CH3NCH2
CH2CH3, 10), 341 (M+-Imid, 8) 250 (18), 209 (10), 174
(15) (6), 99 (100). Anal. Calc. for C24H36N4SiO2: C,
65.43; H, 8.24; N, 12.72. Found: C, 64.98; H, 8.19; N,
12.54.
Attempted fluoration of 32 with BF3–Et2O. In 15 ml
of Et2O were added dropwise 1.11 g (2.52 mmol) of 32
and 0.24 g (1.68 mmol) of BF3–Et2O, at r.t. A white
precipitate formed immediately. After 3 h, the liquid
phase was separated and the organic residue dried in
vacuo. Distillation afforded an untractable material.
No signal corresponding to 31 was observed, even if the
BF3-complex with 31 was observed in the wide
material.
2-(1,3-Dimethylimidazolidine-2-yl)silane 33: 2.0
g
(6.76 mmol) of 17 in 10 ml of Et2O is added to a
suspension of 0.38 g (10.1 mmol) of LiAlH4 in 20 ml of
Et2O at 0°C. The mixture is warmed up to r.t. and
stirred for 15 h. After changing the solvent to hexane,
the mixture is filtered and the solvent is removed.
Distillation in vacuo yields 1.22 g (70%) b.p. 70°C/2
mmHg. Characteristics of 33: Anal. Calc. for
C11H18N2Si: C, 64.01; H, 8.79; N, 13.57. Found: C,
62.92; H, 8.79; N, 14.09. FAB-MS (m/e, relative inten-

192
R.J.P. Corriu et al. / Journal of Organometallic Chemistry 570 (1998) 183–193
sity%): 206 (M+, 10), 205 (M+- 1, 60) 148 (M+-
The residue is washed with pentane: a yellow resinous
solid is obtained which decomposes by heating. The
characteristics correspond to 2-(1,3-dimethylimidazo-
lidine-2-yl) phenylchlorosilane, 37. Anal. Calc. for
C11H17N2SiCl: C, 54.87; H, 7.12; N, 11,63; Cl, 14.74.
Found: C, 53.27; H, 7.01; N, 10.99; Cl, 13.86. MS (EI,
30 eV; m/e, relative intensity%) 240 (M+, 16), 239
(M+-1, 65), 205 (M+-Cl, 18), 182 (M+-
CH3NCH2CH3, 37), 99 (Imid+, 100).
CHNCH2CH2), 25), 99 (Imid+, 100).
4.3. Reactions of 33
4.3.1. With PhNCS
In 20 ml of CDCl3, 500 mg (2.43 mmol) of 33 are
mixed with 328 mg (2.43 mol) of phenylisothiocyanate
at −20°C. After warming up to r.t., the mixture is
stirred for 3 h. Removal of the solvent affords an oily
residue which is analyzed as such. The product iden-
tified as thioformyl phenylamido-2-(1,3-dimethylimida-
zolidine-2-yl) silane 34. Anal. Calc. for C18H23N3SiS: C,
63.33; H, 6.71, N, 12.31; S, 9.37. Found: C, 63.27; H,
6.81; N, 11.7; S, 9.24. MS (EI, 30 eV; m/e) 341 (M+),
296 (M+-CHS), 205 (M+-CHSNPh) 137 (PhNCSH).
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4.3.3. With CH3COOH
A total of 41.0 mg (0.68 mmol) of acetic acid are
added to a solution of 140 mg (0.68 mmol) of 2-(1,3-
dimethyl imidazolidine-2-yl) phenylsilane 33 in 2.5 ml
of CDCl3 at r.t. After 12 h, spectroscopic investigations
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2-(1,3-dimethylimidazolidine-2-yl) phenyl acetoxysilane,
36.
Removal of the solvent left 179 mg of 36. Character-
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7.63; N, 10.59. Found: C, 59.37; H, 7.49; N, 10.64. MS
(EI, 30 eV; m/e, relative intensity%): 264 (M+, 7), 263
(M+-1, 28), 262 (M+ -2, 10), 221 (M+-CH3CO, 15),
205 (M+-CH3 COO, 42), 175 (M+-SiH2OAc, 93), 99
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1
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of dichloromethane (yellow solution). After the solution
was warmed up to r.t., the solvent is removed in vacuo.
.

192
R.J.P. Corriu et al. / Journal of Organometallic Chemistry 570 (1998) 183–193
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.