Ferrocenylethenylsilatranes and a cymantrenylsilatrane

Article abstract of DOI:10.1016/S0022-328X(99)00440-4

The syntheses, properties and crystal structures of two isomeric ferrocenylethenylsilatranes and 1-(3-methylcymantrenyl)silatrane are reported. The organometallic moieties and the silatrane show little structural influence on each other. The Si-N distance

Full text of DOI:10.1016/S0022-328X(99)00440-4

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 590 (1999) 129–137
Ferrocenylethenylsilatranes and a cymantrenylsilatrane
Bjørn Pedersen a, Gabriele Wagner a,1, Rudolf Herrmann a,*, Wolfgang Scherer b,
Klaus Meerholz c, Elmar Schma¨lzlin c, Christoph Bra¨uchle c
a Institut fu¨r Organische Chemie und Biochemie der Technischen Uni6ersita¨t Mu¨nchen, Lichtenbergstrasse 4, D-85747 Garching, Germany
b Anorganisch-Chemisches Institut der Technischen Uni6ersita¨t Mu¨nchen, Lichtenbergstrasse 4, D-85747 Garching, Germany
c Institut fu¨r Physikalische Chemie der Ludwig-Maximilians-Uni6ersita¨t Mu¨nchen, Butenandtstrasse 5-13, Haus E, D-81377 Munich, Germany
Received 29 June 1999; accepted 14 July 1999
Abstract
The syntheses, properties and crystal structures of two isomeric ferrocenylethenylsilatranes and 1-(3-methylcy-
mantrenyl)silatrane are reported. The organometallic moieties and the silatrane show little structural influence on each other. The
,
SiꢀN distances remain in the expected range of 2.13–2.22 A, asserting the hypervalency of silicon. The electron-donating effect
of the silatrane group is transmitted through the CꢀC double bond to ferrocene, as shown by the redox potentials. The first
hyperpolarizability of the ferrocene derivatives was determined by hyper-Rayleigh scattering. © 1999 Elsevier Science S.A. All
rights reserved.
Keywords: Silatrane; Ferrocene; Cymantrene; Non-linear optics
1. Introduction
ferrocene derivatives, have been studied intensely with
respect to NLO properties [10,11], nothing is known
about silatranes.
In this article, we present the synthesis, structure and
properties of silatranes connected to ferrocene via a
double bond, and of the first silatrane containing a
cymantrene moiety.
Silatranes (5 - aza - 2,8,9 - trioxa - 1 - silabicyclo[3.3.3]-
undecanes) are cage compounds which contain a hyper-
valent silicon atom with a transannular (comparatively
,
weak) bond to nitrogen (bond length 2.0–2.4 A). This
bond is responsible for their chemical stability, e.g.
towards hydrolysis [1–4]. Although a great variety of
substituents at silicon were introduced, there are only a
few silatranes containing transition metals (e.g. [5–7]).
This is surprising, since interactions of the transition
metal with the silatrane moiety are conceivable, and
new applications can be envisaged. Thus, it was found
that a silatrane moiety acts as a net electron donor
towards a ferrocene directly connected to it [8,9]. We
therefore decided to investigate silatranes as potential
materials for applications in non-linear optics (NLO).
Although transition metal compounds, in particular
2. Syntheses
The synthesis of the ferrocene and cymantrene
derivatives is straightforward and shown in Fig. 1. We
first decided to use the Heck reaction [12] for the
synthesis of the ferrocenylethenylsilatranes (iodofer-
rocene and 1-ethenylsilatrane 1 under palladium cataly-
sis). The regioselectivity should be governed mainly by
the donor/acceptor properties of the substituents at the
olefinic double bond, where donor substituents (e.g.
alkoxy groups) give a higher amount of a-product [13].
Since the silatrane moiety can be considered as a strong
donor, as seen by its influence on the redox potentials
of ferrocenylsilatranes [9], one might expect a mixture
of a- and b-products with excess of the a-compound 2.
Surprisingly, we found exclusi6ely the a-product, re-
* Corresponding author. Tel.: +49-89-28913325; fax: +49-89-
28913329.
E-mail address: rherrman@nucleus.org.chemie.tu-muenchen.de (R.
Herrmann)
1 Present address: Centro de Qu´ımica Estrutural, Complexo I,
Instituto Superior Te´cnico, Avenida Rovisco Pais, P-1049-001 Lis-
bon, Portugal.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00440-4

130
B. Pedersen et al. / Journal of Organometallic Chemistry 590 (1999) 129–137
trimethoxysilane as hydrosilylation reagent gives an
almost 1:1-mixture of a- and b-product with the same
alkyne. Exactly the same tendency was observed for
ethinylbenzene as well [18]. For the ferrocene deriva-
tives, which are comparatively easy to oxidize,
trichlorosilane can be expected to give lower yields of
hydrosilylation products, and therefore trimethoxysi-
lane is more promising; only alkyl- and arylsilanes (no
chloro derivatives) were used for the hydrosilylation of
ethenylferrocene [19]. Fortunately, ethinylferrocene 3
behaves very differently from 1-ethinyl-4-nitrobenzene
and leads to the trans-b-product exclusively, even with
trimethoxysilane. The direct products of the hydrosilyl-
ation reaction, the trichlorosilyl- or trimethoxysilyl-
alkenes, were not isolated but converted directly to the
corresponding silatranes, either by the acetic anhydride
method [20] or by transesterification with boratrane
[21], respectively.
To obtain the cymantrenylsilatrane 6, we lithiated
methylcymantrene with butyl lithium. The site of the
lithiation of cymantrene is solvent dependent; in THF,
the cp ring is attacked [22], while the carbonyl groups
are preferred in diethyl ether [23]. We found also, that
for methylcymantrene, the lithiation occurs at the cp
ring when THF is used as solvent. Since the reaction
product with tetraethoxysilane is of comparatively low
stability, we converted it immediately to the silatrane
gardless which conditions, solvents, or additives we
used (see Section 4 for some variations). Considering
the proposed mechanism [12] for the Heck reaction
with oxidative addition of iodoferrocene to palladium,
followed by insertion of the double bond into the
ferroceneꢀpalladium bond, one can see that the regio-
selectivity is biased towards the a-product probably for
steric reasons, since both the ferrocene and the silatrane
are very bulky substituents, and the formation of a
s-bonded intermediate where a CH2-group is attached
to palladium should be highly favored over a CHꢀFc or
CHꢀsilatrane group in the same position.
To obtain the b-product 4, we therefore used the
hydrosilylation of ethinylferrocene 3 catalyzed by
Speier’s catalyst (H2PtCl6 in isopropanol). We found
that the most convenient access to ethinylsilatrane is by
the Corey–Fuchs procedure [14], starting with fer-
rocenecarboxaldehyde. This method has already been
used by others for the synthesis of 1,2-diethinylfer-
rocene [15]. The regioselectivity of the hydrosilylation
strongly depends on the catalyst and the reaction condi-
tions, as well as on properties of the substituent at the
double bond and on the silicon reagent applied [16,17].
Thus, trichlorosilane leads to the trans-b-product pref-
erentially, as exemplified by the reaction with 1-ethinyl-
4-nitrobenzene where no a-product can be detected (see
Section 4). On the other hand, the more convenient
Fig. 1. Synthesis of the ferrocenylethenylsilatranes 2 and 4 and 1-(3-methylcymantrenyl)silatrane 6.

B. Pedersen et al. / Journal of Organometallic Chemistry 590 (1999) 129–137
131
Table 1
Selected bond lengths (A) and angles (°) for compounds 2, 4 and 6
a
,
2
4
6
Bond lengths
SiꢀN
SiꢀC11
C11ꢀC12
C10ꢀC11
FeꢀC (cp, av.)
CꢀC (fc, av.)
CꢀC (sil, av.)
SiꢀO (av.)
OꢀC (av)
2.222(2)
1.901(2)
1.328(3)
1.484(3)
2.04(2)
SiꢀN
SiꢀC12
C11ꢀC12
C10ꢀC11
FeꢀC (cp, av.)
CꢀC (fc, av.)
CꢀC (sil, av.)
SiꢀO (av.)
OꢀC (av.)
NꢀC (av.)
2.198(2)
1.872(2)
1.340(3)
1.471(4)
2.04(1)
1.42(1)
1.51(1)
1.659(2)
1.416(4)
1.46(1)
SiꢀN
SiꢀC4
2.138(2)
1.888(3)
MnꢀC (cp, av.)
CꢀC (cp, av.)
CꢀC (sil, av.)
SiꢀO (av.)
OꢀC (sil, av.)
NꢀC (av.)
2.14(1)
1.43(1)
1.51(1)
1.663(2)
1.417(5)
1.474(5)
1.41(1)
1.515(4)
1.655(1)
1.42(1)
NꢀC (av)
1.47(1)
Bond angles
NꢀSiꢀC11
OꢀSiꢀO(av.)
CꢀNꢀC (av.)
SiꢀOꢀC (av.)
C10ꢀC11ꢀC12
SiꢀC11ꢀC12
179.6(1)
NꢀSiꢀC12
179.9(2)
118(2)
114.5(5)
123.8(1)
126.9(2)
126.8(2)
NꢀSiꢀC4
178.7(1)
118.1(1)
114.4(1)
123.5(1)
119.5(2)
120.1(2)
OꢀSiꢀO (av.)
CꢀNꢀC (av.)
SiꢀOꢀC (av.)
C10ꢀC11ꢀC12
SiꢀC12ꢀC11
OꢀSiꢀO (av.)
CꢀNꢀC (av.)
SiꢀOꢀC (av.)
119(2)
114(1)
122.6(7)
MnꢀC7
MnꢀC8
MnꢀC9
O1ꢀC7
02ꢀC8
03ꢀC9
C1ꢀC2
1.779(4)
1.794(4)
1.795(3)
1.155(5)
1.149(6)
1.146(4)
1.508(5)
a Abbreviations: fc, ferrocene; cp, cyclopentadienyl; sil, silatrane; av., average.
by transesterification with triethanolamine (TEA). Be-
cause of the low yield, we cannot say for certain if the
lithiation is site selective and produces 3-lithio-methyl-
cymantrene exclusively, or if some 2-lithiated com-
pound is formed as well. In the case of methylferrocene,
no 2-metallated products are observed with pentyl
sodium or pentyl potassium [24].
electron donor properties of ferrocene may be consid-
ered as an additional reason. However, one should keep
in mind that the weak SiꢀN bond is also strongly
influenced by crystal packing effects, as one can see
when comparing different modifications of 1-phenylsila-
,
trane (a-modification, 2.193(5) A [26]; g-modification,
,
2.132(4) A [27]). All other features of the silatranyl
moiety are very similar in 1-b-phenylethenylsilatrane 7
and its ferrocene counterpart 4. The olefinic double
bond which is directly connected to the different aro-
matic residues is slightly shortened in the phenyl com-
3. Properties of the compounds
The ferrocene derivatives 2 and 4 and the cy-
mantrenylsilatrane 6 were characterized by X-ray crys-
tallography. Details on data collection and refinement
are given in Section 4 and in Table 3, selected bond
lengths and angles in Table 1. The structures are shown
in Figs. 2–4.
The influence of the organometallic moiety and the
silatrane on each other’s structural features is limited.
Thus, the SiꢀN distances in 1-a-ferrocenylethenylsila-
,
trane 2 (2.222(2) A) and its 1-b counterpart 4 (2.198(2)
,
A) are close to the value in 1-ferrocenylsilatrane
(2.181(2) b) [9]. In 1-b-phenylethenylsilatrane 7, a SiꢀN
distance of 2.127(4) A was found [25]. The bulkiness of
,
the ferrocene group when compared with phenyl might
be responsible for the longer SiꢀN distance in 4 when
compared with 7, although an influence of the stronger
Fig. 2. PLATON plot of the molecular structure of 1-(1-ferro-
cenylethenyl)silatrane 2 (50% probability factor).

132
B. Pedersen et al. / Journal of Organometallic Chemistry 590 (1999) 129–137
the ferrocene derivatives, both the organometallic and
the silatrane moieties remain almost undisturbed, which
is reflected in very similar features for the silatrane
groups in all three compounds studied (e.g. average
,
NꢀC distance, 1.474(5) A, angle NꢀSiꢀC4, 178.7(1)°,
and average SiꢀOꢀC angle, 122.6(7)°). The organo-
metallic part closely resembles the unsubstituted
cymantrene [28], not only in the MnꢀC distances to the
cp ring, but also in the bonds to the carbonyl groups.
Two of the three bonds are longer (1.794(4) and
,
1.795(3) A), while the other is somewhat shorter
,
(1.779(4) A); a similar effect was observed in cy-
,
mantrene (1.795(3), 1.797(3), and 1.788(3) A). The dif-
ference in the carbonyl groups is not a mere crystal
packing effect, since a considerable broadening of the
13C-NMR signal is observed in solution, which points
to a hindered rotation of the cp ring with respect to the
positions of the CO groups in the Mn(CO)3 unit.
When a silatrane group is directly attached to fer-
rocene, the oxidation potential of the Fe(II)/Fe(III)
transition becomes considerably more negative when
compared with that of triethoxysilylferrocene (DE=
0.26 V). The effect is somewhat less pronounced when
comparing the dimethylaminomethyl derivative 9 with
its triethoxysilyl counterpart (DE=0.14 V), but still
obvious. The ease of reduction of the ferrocenylsila-
tranes has been traced back to a high antibonding
contribution of the SiꢀN bond to the HOMO [9]. In
compounds 2 and 4, the ferrocene and the silatrane are
not directly connected, but separated by one (in 2) or
two (in 4) carbon atoms. As expected for ferrocene
derivatives, they show reversible Fe(II)/Fe(III) oxida-
tions [29]. The oxidation potentials (quoted relative to
the ferrocene/ferrocinium redox couple with E1/2=0 V)
are very similar to that of 9, despite the separation of
the two groups (2, E1/2= −0.14 V; 4, E1/2= −0.08 V;
9, E1/2= −0.14 V). Thus, the transmission of the net
electron-donor effect of the silatrane correlates with the
spatial separation of silatrane and ferrocene, and even
when separated by two carbon atoms, the influence of
the silatrane is still visible in the Fe(II)/Fe(III) redox
potentials.
Fig. 3. PLATON plot of the molecular structure of 1-(2-ferro-
cenylethenyl)silatrane 4 (50% probability factor).
,
,
pound (CꢁC 1.312(6) A in 7 [25] vs. 1.340(3) A in 4).
The ferrocene groups adopt a rather unstrained geome-
try, since there is only a very small tilt of the two cp
rings: The angle between the planes defined by both
rings is 3.9(2)° in 2 and 2.2(2)° in 4 (and 3.1(1)° in
1-ferrocenylsilatrane [9]). In addition, the iron is well
centered in the sandwich structure, since the centers of
the cp rings form almost a straight line with the iron
atom (angle centroid–Fe–centroid 177.0(2) and
178.7(2)°). Only slight distortions of the cp rings away
from planarity and a narrow spread of the standard
deviations in the average values of the CꢀC distances in
the cp rings were found. In contrast to the observations
made in 1-b-phenylethenylsilatrane 7, no indication of
disorder was detected, neither in the silatrane group (as
in 1-b-phenylethenylsilatrane [25]), nor in any other
part of the molecules.
The SiꢀN distance in the cymantrenylsilatrane 6 is
,
shorter (2.138(2) A) than in the ferrocene derivatives, a
fact which might be due to the lower electron donating
ability of cymantrene compared with ferrocene. As for
The observation of electronic communication be-
tween the silatrane and the ferrocene by electrochem-
istry suggests a correlation with non-linear optical
(NLO) properties. Therefore, the first hyperpolarizabil-
ity i for frequency doubling of the compounds 2 and 4
was determined by hyper-Rayleigh scattering (MRS)
measurements [30], together with that of 7, 8, and 9, for
comparison. Experimental details have been described
in Refs. [31,32]. The external reference method has been
applied, using 4-nitroaniline (i1303634=6.2×10−50 C m3
V
−2, umax=348 nm (CHCl3), umax=350 nm (CH2Cl2)
[33]) as external reference compound for 7 and 8, and
1300
333
4-(N,N-dimethylamino)cinnamic aldehyde (i
=
Fig. 4. PLATON plot of the molecular structure of 1-(3-methylcy-
mantrenyl)silatrane 6 (40% probability factor).
15.2×10−50 C m3 V−2, umax=384 nm (CHCl3) [34])

B. Pedersen et al. / Journal of Organometallic Chemistry 590 (1999) 129–137
133
Table 2
sign is based on a different concept, since the silatrane
moiety does not contain p-bonds, and an extended
conducting bridge does not appear to increase the
hyperpolarizability. Instead, this is achieved by the
combination of both donor and acceptor groups with a
silatrane (compare 4 and 8 with 7). This unconventional
behavior is under theoretical investigation in our group.
The lack of extended p-systems also leads to an im-
proved transparency in the visible range; the standard
First hyperpolarizability i333 (in 10−50 C m3
V
−2) for compounds 2,
4, 7, 8, and 9, together with wavelength umax (in nm) and optical
density ‡ (in m2 mol−1) of the maximum absorption, and fundamen-
tal wavelength uex (in nm) a
Compound
umax
‡
uex
i333
2
4
7
8
9
446
446
257
320
400
23
28
1600
1300
12
1300
1300
1064
1064
1300
4.8
8.4
3.7
4.8
8.5
material 4-nitroaniline (i1330364=6.2×10−50 C m3 V−2
)
has a umax of 348 nm with an optical density ‡=1400
m2 mol−1 (in chloroform) [37], with an extension to the
visible range (yellow color), whereas the nitro-substi-
tuted silatrane 8 with almost the same b value, absorbs
with a similar intensity only at umax=320 nm and
appears almost colorless to the eye. The ferrocene
derivatives differ insofar as they all show the broad
metal-to-ligand charge transfer band between 400 and
500 nm, but with only very low optical densities (e.g. 12
m2 mol−1 at umax=400 nm for 9). Concluding, one can
say that silatranes show a better ‘nonlinearity/transpar-
ency tradeoff’ [38] than classical NLO materials with
similar structures.
a Compounds 2 and 4 were measured in dichloromethane, all other
compounds in chloroform as solvent.
for all other compounds. The dependence of the inten-
sity of the HRS signal on the concentration was linear
(range 0.6–6×10−2 mol l−1). No degradation of the
compounds during measurement was observed, as ver-
ified by NMR measurements afterwards. The results are
summarized in Table 2. The calculation of the diagonal
component i333 of the hyperpolarizability tensor as-
sumes a rod-like shape of the molecules. This is, how-
ever, only an approximation for 2 and 9, and therefore
the values should be considered with care [32,35].
Considering the silatrane as an electron donor, it is
not surprising that the i333 value increases when a nitro
group is introduced in the phenyl ring (compare 7 and
8), since the introduction of an acceptor in the position
opposite to a donor at a multiple bond makes the
material more similar to classical organic NLO materi-
als based on the familiar ‘donor-conducting bridge-ac-
ceptor’ model [10,11,36]. However, the silatrane is not a
p-system as generally assumed in this model, and there-
fore one cannot expect that the analogy holds for all
combinations with other groups. Thus, ferrocene is a
rather strong electron donor when compared with
phenyl, but the replacement of phenyl in 7 with ferro-
cenyl in 4 increases the i333 value instead of decreasing
it, as one would expect according to the model. Also in
contrast to the model, the introduction of the double
bond (as conducting bridge) does not increase the hy-
perpolarizability, but leads to a very similar value as
without it (compare 4 and 9; the NMe2 group of the
side chain in 9 does not come close to the ferrocene nor
to the silatrane [9] and should therefore be of negligible
importance for the optical properties). On the other
hand, the considerably lower value of the a-ferrocene
compound 2 relative to the b-derivative 4 suggests that
the relative orientation of the dipole moments of both
ferrocene and silatrane is essential for the enhancement
of the hyperpolarizability.
4. Experimental
NMR spectra were measured with a Bruker AM 360
1
instrument, operating at 360.13 MHz for H and 90.56
MHz for 13C. Hyper-Rayleigh scattering measurements
were performed with the equipment described [31,32].
Electrochemical studies were performed with an EG&G
PAR 173 potentiostat and an EG&G Parc 175 univer-
sal programmer, using a 0.2 M solution of NBu4BF4 in
THF, a platinum working electrode and a silver refer-
ence electrode. Potentials were determined relative to
the internal cyanoferrocene/cyanoferrocinium redox
ox
1/3
couple (E =0.89 V vs. SCE) [29]. They are quoted
ox
1/3
relative to ferrocene/ferrocinium (E =0 V).
Single-crystal data for 2, 4, and 6 were collected on a
kappa-CCD system from Nonius with a rotating anode
,
generator (Nonius FR591; Mo–Ka, u=0.71073 A) in
rotation mode (F-scans). Details on measurement and
processing are given in Table 3. All frames were scaled
using the Denzo-SMN program suite [39]. No crystal
decay was observed. The structures were solved by
direct methods [40] (all non-H atoms) and refined [41]
by full-matrix least-squares (F2) with all non-hydrogen
atoms assigned anisotropic displacement parameters.
For data analysis and visualization, the program PLA-
TON [42] was used. Full crystallographic details, exclud-
ing structure factor tables, have been deposited at the
Cambridge Crystallographic Data Center (CCDC).
Any request to the CCDC for this material should
quote the full literature citation and the reference num-
bers CCDC 133891–133893.
The absolute i333 values of the silatranes are not
exceedingly high when compared with standard materi-
als like 4-(N,N-dimethylamino)cinnamic aldehyde
(i1333030=15.2×10−50 C m3 V−2). However, their de-

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B. Pedersen et al. / Journal of Organometallic Chemistry 590 (1999) 129–137
Iodoferrocene [43], 1-ethenylsilatrane 1 [44,20], 1-(2-
phenylethenyl)silatrane [45], 1-[2-(N,N-dimethyl-
Found C, 56.5; H, 6.2; N, 3.3. C18H23FeNO3Si
7
Anal. Calc. C, 56.1; H, 6.0; N, 3.6. Crystals suitable
for X-ray crystal structure analysis were grown by
slow evaporation of a solution in dichloromethane.
2. Iodoferrocene (1000 mg, 3.2 mmol) and 1-ethenylsi-
latrane 1 (670 mg, 3.2 mmol) were dissolved in 25
ml of diisopropylamine, and the solution was de-
gassed. After addition of 220 mg of Pd(PPh3)2Cl2
(0.32 mmol, 10 mol%), the solution was heated to
reflux for 5 h. After removal of the solvent at 0.1
mm, the residue was chromatographed on silica to
give 620 mg of the product 2 (50%), together with
some ferrocene and decomposition products.
3. Palladium(II)acetate (6.7 mg, 0.03 mmol), PPh3
(15.7 mg, 0.06 mmol), AgNO3 (170 mg, 1.0 mmol),
iodoferrocene (312 mg, 1.0 mmol), triethylamine
(0.17 ml, 2.1 mmol), and 1-ethenylsilatrane 1 (241
mg, 1.2 mmol) were dissolved in 15 ml of degassed
acetonitrile and heated to 100°C for 24 h. The
solution was poured on a short (5 cm) column of
neutral alumina. Elution with dichloromethane
yielded the product 2 (290 mg, 75%)
aminomethyl)ferrocenyl]silatrane 9 [9], and boratrane
[21] were prepared as described. Commercial methylcy-
mantrene 5 was purified by filtration over neutral alu-
mina prior to use. Solvents were dried by standard
techniques. Other chemicals were used as supplied.
4.1. 1-(1-Ferrocenylethenyl)silatrane 2
1. 1-Ethenylsilatrane 1 (160 mg, 0.77 mmol) and iodo-
ferrocene (240 mg, 0.77 mmol) were dissolved in 5
ml of dry DMF, and 0.20 ml of triethylamine (2.5
mmol) were added. The solution was degassed by
three freeze–evacuate–thaw-cycles. After addition
of 35 mg (0.05 mmol) of Pd(PPh3)2Cl2, the mixture
was heated to reflux overnight. After removal of all
volatile components at 0.1 mm, the residue was
chromatographed (silica, dichloromethane). The
main yellow–orange band (Rf 0.70) contained the
product 2 (280 mg, 90%), m.p. 215–220°C (dec.).
1H-NMR (CDCl3): 5.91 and 5.76 (2×d, 1 H each,
4.1 Hz,=CH2), 4.47 (t, 2 H, 2.0 Hz, Fc-a), 4.11 (t,
2 H, 2.0 Hz, Fc-b), 4.09 (s, 5 H, unsubst. cp), 3.85
(t, 6 H, 5.7 Hz, OꢀCH2), 2.85 (t, 6 H, 5.7 Hz,
NꢀCH2). 13C-NMR (CDCl3): 147.0 (Cꢁ), 122.9
(ꢁCH2), 89.2 (Fc-ipso), 69.3 (unsubst. cp), 67.7, 67.4
(Fc-a, b), 58.1 (OꢀCH2), 51.5 (NꢀCH2). Anal.
4. 1-Ethenylsilatrane 1 (590 mg, 2.85 mmol) and iodo-
ferrocene (610 mg, 0.95 mmol) were dissolved in 15
ml of degassed dimethylacetamide, and sodium ac-
etate (320 mg, 3.5 mmol) and palladium(II)acetate
(63 mg, 0.28 mmol, 10 mol%) were added. After
heating to 100°C for 24 h, the solvent was removed
Table 3
Data collection and structure solution for compounds 2, 4 and 6
2
4
6
Formula
Crystal system
Space group
C18H23FeNO3Si
Monoclinic
P21/n (No. 14)
16.5091(4)
7.4072(1)
13.9988(3)
90
96.3130(10)
90
1701.48(6)
0.13×0.13×0.15
293
C18H23FeNO3Si
Monoclinic
P21/c (No. 14)
13.4286(2)
10.5069(2)
12.6195(2)
90
107.497(9)
90
1698.14(10)
0.15×0.17×0.20
293
C15H18MnNO6Si
Monoclinic
P21/n (No. 14)
10.2134(2)
13.1247(3)
13.3018(3)
90
110.7777(11)
90
1667.11(6)
0.10×0.18×0.20
193
,
a (A)
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Crystal size (mm)
Temperature (K)
U
min, Umax (°)
4.6, 26.4
0–360, 1
4.8, 30.5
0–360,1
4.5, 30.5
0–530,1
ƒ-scan, step (°)
Dataset
−19BhB19
−8BkB8
−17BlB17
22841, 3314
0.031
−18BhB18
−14BkB14
−16BlB16
23210, 4140
0.034
−9BhB9
−18BkB18
−17BlB18
24832, 4110
0.030
Total, unique data
Rint
Observed data
I\2.0|(I)
2820
3490
3976
Nref, Npar
R1, wR2
Goodness-of-fit
Min/max resd. dens. (e A
3314, 217
0.0318, 0.0877
1.06
4140, 217
0.0540, 0.1636
1.07
4110, 217
0.0541, 0.1535
1.06
a
−3
,
)
−0.39, 0.26
−0.57, 1.55
−0.68, 1.52
a R1=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ. wR2={ꢀ[w(F2o−Fc2)2]/ꢀ[w(Fo2)]2}1/2
.

B. Pedersen et al. / Journal of Organometallic Chemistry 590 (1999) 129–137
135
at 0.1 mm and the residue was chromatographed
(silica, dichloromethane) to give 95 mg of ferrocene
(20%) and 340 mg of the product 2 (30%).
140.5 (CH=(1)), 126.3 (ꢁCH(2)), 86.0 (Fe-ipso), 69.0
(unsubst. cp), 68.0, 66.8 (Fc-a, b), 57.7 (OꢀCH2), 51.0
(NꢀCH2). Anal. Found C, 56.3; H, 6.0; N, 3.8.
C18H23FeNO3Si Anal. Calc. C, 56.1; H, 6.0; N, 3.6.
Crystals suitable for X-ray crystal structure analysis
were grown by slow evaporation of a solution in
dichloromethane.
4.2. Ethinylferrocene 3
Tetrabromomethane (16.6 g, 50 mmol), zinc powder
(3.3 g, 50 mmol, activated by treatment with HCl) and
PPh3 (13.1g, 50 mmol) were suspended in 50 ml of
dichloromethane. After stirring for 1.5 h, ferrocenecar-
boxaldehyde (5.35 g, 25 mmol) in 25 ml of
dichloromethane was added dropwise. After 4 h stirring
at room temperature (r.t.), the formed triphenylphos-
phine oxide was precipitated by addition of 350 ml of
pentane. The precipitate (which includes much of the
product) was filtered off, dissolved in dichloromethane
and precipitated again with pentane. The procedure
was repeated until the extracts remained almost color-
less. The combined solutions were concentrated and
chromatographed on silica (hexane). Yield 7.08 g (76%)
of 2,2-dibromoethenylferrocene. By elution with hex-
ane/ether (2:1), 1.45 g of ferrocenecarboxaldehyde
(24%) could be recovered.
4.4. 1-(3-Methylcymantrenyl)silatrane 6
To a solution of methylcymantrene 5 (3.18g, 14.6
mmol) in 30 ml of THF, a 2.5 M solution of butyl
lithium in hexane (18.0 mmol) was added at −78°C.
After warming to r.t., the solution was stirred
overnight. Tetraethoxysilane (3.3 ml, 15.0 mmol) was
added and the mixture stirred for 6 h. Then, 2.34 g
(15.0 mmol) of boratrane were added and stirring con-
tinued overnight. After evaporation of the solvent, the
residue was rapidly chromatographed over a short
column (3 cm) of neutral alumina with pentane and
ether to remove unreacted starting materials, and then
with dichloromethane. This fraction was concentrated
and subjected to
a
second chromatography
To a solution of 20 ml of butyl lithium (2.5 M in
hexane, 50 mmol) in 20 ml of diethylether/THF (2:1) at
−78°C, a solution of 2,2-dibromoethenylferrocene
(7.08 g, 19 mmol) in the same solvent mixture (50 ml)
was added dropwise. After stirring for 2 h at −78°C,
the mixture was allowed to come to r.t. within 1 h.
Stirring was continued for 2 h. After cooling to
−78°C, 10 ml of saturated aqueous ammonium chlo-
ride solution were added. After coming to r.t. and
stirring for 10 min, the mixture was added to 20 ml of
saturated sodium carbonate solution. The organic layer
was separated, the aqueous layer extracted once with
hexane, and the combined organic solutions were dried
over sodium sulfate. Removal of the solvent yielded
3.91 g of ethinylferrocene 3 (98%), with properties
identical to the ones reported [46].
(dichloromethane) under the same conditions to yield
210 mg (4%) of the product 6. It is very unstable in
solution and precipitates paramagnetic material, but
can be stored as a solid under nitrogen at 0°C for
longer periods. Microanalytical data could not be ob-
tained because of its sensitivity. Crystals suitable for
X-ray crystal structure analysis were grown by slow
diffusion of a pentane layer to a dichloromethane solu-
1
tion at −30°C. H-NMR (C6D6): 1.61 (s, 3 H, Me),
1.80 (tr, 6 H, 5.9 Hz, CH2ꢀN), 3.35 (tr, 6 H, 5.9 Hz,
CH2ꢀO), 4.18, 4.95, 5.00 (3×s, 1 H each, cp). 13C-
NMR (C6D6): 13.3 (Me), 50.7 (CH2ꢀN), 57.4 (CH2ꢀO),
83.9, 90.9, 91.8 (CH (cp)), 92.5, 103.1 (Cq (cp)), 227.6
(CO).
4.5. 1-[2-(4-Nitrophenyl)ethenyl]silatrane 8
4.3. 1-(2-Ferrocenylethenyl)silatrane 4
1. To a solution of 1-ethinyl-4-nitrobenzene [47] (147
mg, 1.0 mmol) and trichlorosilane (163 mg, 1.2
mmol) in 1.0 ml of toluene, 1 drop of Speier’s
catalyst was added. The mixture was kept in a
closed vessel at 70°C for 16 h. The solvent was
evaporated in a vacuum, and to the residue was
added sodium acetate (20 mg, 0.25 mmol) and acetic
anhydride (310 mg, 3.0 mmol). The mixture was
kept at 60°C for 5 h. All volatile components of the
mixture were removed in a vacuum. The residue was
dissolved in 15 ml of chloroform, and a solution of
triethanolamine (150 mg, 1.0 mmol) in 10 ml of
chloroform was added at 0°C dropwise within 30
min. Stirring was continued for 2 h at 0°C and at
r.t. overnight. The solvent was removed in a vacuum
and the residue purified by chromatography (silica,
Ethinylferrocene 3 (440 mg, 2.1 mmol), trimethoxysi-
lane (300 mg, 2.5 mmol), and one drop of Speier’s
catalyst (0.1 M solution of H2PtCl6 in isopropanol)
were heated to 50°C in a closed Schlenk tube overnight.
Triethanolamine (300 mg, 2.0 mmol), 10 mg of KOH
and 10 ml of toluene were added, and the mixture was
heated to reflux for 24 h. After removal of the solvent
at 0.1 mm, the residue was chromatographed (silica,
dichloromethane), yielding 700 mg (90%) of the
product 4, Rf 0.7, m.p. 250–255°C (dec.). 1H-NMR
(CDCl3): 6.77 (d, 1 H, 18.0 Hz, ꢁCH(1)), 5.85 (d, 1 H,
18.0 Hz, ꢁCH(2)), 4.31 and 4.09 (2×s, 2 H each, Fc),
4.06 (s, 5 H, unsubst. cp), 3.81 (t, 6 H, 5.4 Hz, OꢀCH2),
2.81 (t, 6 H, 5.4 Hz, NꢀCH2). 13C-NMR (CDCl3):

136
B. Pedersen et al. / Journal of Organometallic Chemistry 590 (1999) 129–137
[8] G. Cerveau, C. Chuit, E. Colomer, R.J.P. Corriu, C. Reye´,
2:1 dichloromethane–ethyl acetate), to give the
Organometallics 9 (1990) 2415.
product 8, Rf 0.23, yield 120 mg (37%), m.p. 245–
246°C. 1H-NMR(CDCl3): 2.92 (t, 6 H, 5.9 Hz,
CH2ꢀN), 3.88 (t, 6 H, 5.9 Hz), 6.58 and 7.15 (2×d,
1 H each, 19.1 Hz, ꢁCH), 7.54 and 8.11 (2×d, 2 H
each, 8.8 Hz, arom.). 13C-NMR (CDCl3): 51.0
(CH2ꢀN), 57.4 (CH2ꢀO), 136.4, 139.8 (ꢁCH), 123.6,
126.8 (CH arom.), 145.9, 146.5 (Cq). Anal. Found
C, 52.4; H, 5.5; N, 8.4. C14H18N2O5Si. Anal. Calc.
C, 52.2; H, 5.6; N, 8.7.
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2. To a solution of 1-ethinyl-4-nitrobenzene [47] (147
mg, 1.0 mmol) and trimethoxysilane (122 mg, 1.0
mmol) in toluene (1 ml) was added 1 drop of
Speier’s catalyst, and the mixture was heated to
reflux overnight. The solvent was evaporated in a
vacuum and the residue dissolved in 1.0 ml of
xylene. Boratrane (160 mg, 1.0 mmol) and AlCl3
(10 mg) were added and the mixture was refluxed
for 1 day. After evaporation of the solvent, the
residue was chromatographed (silica gel, 2:1
dichloromethane–ethyl acetate). The product 8 (Rf
0.23, 30 mg, 9%) was preceded by the isomeric
1-[1-(4-nitrophenyl)ethenyl]silatrane (Rf 0.48, 40 mg,
13%), m.p. 210–213°C. 1H-NMR (CDCl3): 2.89 (t, 6
H, 5.9 Hz, CH2ꢀN), 3.85 (t, 6 H, 5.9 Hz, CH2O),
5.74 and 5.97 (2×d, 1 H each, 3.9 Hz, ꢁCH2), 7.57
and 8.09 (2×d, 2 H each, arom.). 13C-NMR
(CDCl3): 51.2 (CH2ꢀN), 57.6 (CH2ꢀO), 128.8
(ꢁCH2), 122.9, 128.0 (CH, arom.), 145.8, 152.8,
154.6 (Cq). Anal. Found C, 52.5; H, 5.8; N, 8.3.
C14H18N2O5Si. Anal. Calc. C, 52.2; H, 5.6; N, 8.7.
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Acknowledgements
We wish to thank Professor Dr Fernanda N.N. Car-
valho, Instituto Superior Te´cnico, Lisbon, Portugal, for
help with electrochemical measurements, and Professor
Dr Ivar Ugi, TU Mu¨nchen, for general support. Finan-
cial support by Fonds der Chemischen Industrie is
gratefully acknowledged.
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