Synthesis, structural characterization and 57Fe-M?ssbauer spectra of ferrocenylhexasilanes

Article abstract of DOI:10.1016/S0022-328X(01)00743-4

Linear and cyclic ferrocenylhexasilanes 1,6-Fc-Si₆Me₁₂-X [X=Me, -C₆H₄CH=C(CN)₂], 1,3- and 1,4-Fc-Si₆Me₁₀-X [X=Me, -C₆H₄CH=C(CN)₂], have been synthesized and their M?ssbauer spectra have been measured. All compounds possess localized electronic structures on the M?ssbauer timescale and partial Fe(III) character of the iron atom due to Cp→(Si_n) electron transfer. The M?ssbauer data obtained, furthermore, indicate considerable aryl-ferrocenyl interaction via the hexasilane moiety. The single crystal X-ray structures of 1,3- and 1,4-Fc-Si₆Me₁₀-C₆H₄CH=C(CN) ₂ exhibit the cyclohexasilane ring in chair conformation with the bulky Fc- and aryl substituents in equatorial positions.

Full text of DOI:10.1016/S0022-328X(01)00743-4

Journal of Organometallic Chemistry 627 (2001) 167–178
www.elsevier.nl/locate/jorganchem
57
Synthesis, structural characterization and Fe-Mo¨ssbauer spectra
of ferrocenylhexasilanes
Hermann Rautz a, Harald Stu¨ger a,*, Guido Kickelbick b, Claus Pietzsch c
a Institut fu¨r Anorganische Chemie, Technische Uni6ersita¨t Graz, Stremayrgasse 16, A-8010 Graz, Austria
b Institut fu¨r Anorganische Chemie, Technische Uni6ersita¨t Wien, Getreidemarkt 9, A-1060 Wien, Austria
c Institut fu¨r Angewandte Physik, TU Bergakademie Freiberg, Bernhard 6. Cottastrasse 4, D-09596 Freiberg, Germany
Received 15 December 2000; accepted 5 February 2001
Abstract
Linear and cyclic ferrocenylhexasilanes 1,6-Fc–Si6Me12–X [X=Me, –C6H4CHꢀC(CN)2], 1,3- and 1,4-Fc–Si6Me10–X [X=
Me, –C6H4CHꢀC(CN)2], have been synthesized and their Mo¨ssbauer spectra have been measured. All compounds possess
localized electronic structures on the Mo¨ssbauer timescale and partial Fe(III) character of the iron atom due to Cp“(Sin) electron
transfer. The Mo¨ssbauer data obtained, furthermore, indicate considerable aryl–ferrocenyl interaction via the hexasilane moiety.
The single crystal X-ray structures of 1,3- and 1,4-Fc–Si6Me10–C6H4CHꢀC(CN)2 exhibit the cyclohexasilane ring in chair
conformation with the bulky Fc- and aryl substituents in equatorial positions. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Polysilanes; Ferrocene; Crystal structures; Mo¨ssbauer spectroscopy
phenyl moieties are connected by linear Si–Si-chains
and the resulting optical nonlinearities are just moder-
ate. Quite similar results independently have been ob-
tained by Pannell et al. [3] and in our laboratories [4]
for disilanes containing ferrocene as a donor and vari-
ous organic acceptor groups. For the corresponding
cyclohexasilane derivatives, however, we observed sig-
nificantly increased values of the quadratic hyperpolar-
izabilities b and noticeable electron transmission effects
via the cyclohexasilane ring [5].
In cyclic polysilanes delocalization of s(Si–Si) elec-
trons over the ring silicon atoms gives these molecules a
variety of properties resembling those of aromatic hy-
drocarbons [6]. So far the chemistry and the properties
of cyclopolysilanes have been explored mainly by the
groups of Hengge [7] and West [8]. Here we report the
detailed synthesis, characterization and crystal struc-
tures of the donor/acceptor substituted cyclohexasilanes
1-ferrocenyl-4-[(2,2-dicyanoethenyl)phenyl]decamethyl-
cyclohexasilane (3) and 1-ferrocenyl-3-[(2,2-dicyano-
ethenyl)phenyl]decamethylcyclohexasilane (4). For
comparison we have also synthesized ferrocenylunde-
camethylcyclohexasilane (6) and the open chained
compounds 1-ferrocenyl-2-[(2,2-dicyanoethenyl)phenyl]-
disilane (1), 1-ferrocenyl-6-[(2,2-dicyanoethenyl)phenyl]-
1. Introduction
Quite recently organic and organometallic materials
with second order nonlinear optical properties have
been the subject of intense investigation what led to the
development of certain structure/NLO property rela-
tionships [1]. Pertinent studies revealed that large sec-
ond order nonlinearities are always associated with
chromophores comprised of electron donors and accep-
tors linked by a conjugated p system. In the class of
organometallic NLO compounds ferrocene based sys-
tems are prominent [1b,c], what is mainly due to attrac-
tive features like air- and thermal stability,
photochemical stability and synthetic versatility com-
bined with large optical nonlinearities.
Recently several reports appeared in the literature
concerning the synthesis and characterization of dipolar
silicon compounds showing an extended transparency
range combined with nonlinear optical activities [2].
Silicon, however, was found to be only a weak charge
transmitter when donor and acceptor phenyl–Si–
* Corresponding author. Tel.: +43-316-8738708; fax: +43-316-
8738701.
E-mail address: stueger@anorg.tu-graz.ac.at (H. Stu¨ger).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00743-4

168
H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
dodecamethylhexasilane (2) and 1-ferrocenyltrideca-
methylhexasilane (5). Detailed 57Fe-Mo¨ssbauer studies
have been performed on these compounds in order to
assess intramolecular donor/acceptor interactions.
ing mono- and bis-(p-bromophenyl)permethylcyclo-
hexasilane. Similar results were obtained starting from
1,6-dichlorododecamethylhexasilane. When both chlo-
rines, however, are replaced by p-bromophenyl groups
using two equivalents of p-BrPhLi in a primary step,
one of the Si–aryl bonds can be rechlorinated selec-
tively with triflic acid/LiCl and the desired (p-bro-
mophenyl)chloropermethylhexasilanes are formed. At
this stage the ferrocene moiety easily can be attached to
the hexasilane skeleton with monolithioferrocene. Fi-
nally the 2,2-dicyanoethylene group can be generated
by derivatization of the aryl–Br linkage with n-BuLi/
DMF followed by Knoevenagel condensation of the
resulting aromatic aldehyde with malononitrile. After
column chromatography 2, 3 and 4 are obtained as red
air stable solids.
2. Results and discussion
2.1. Synthesis
The hexasilane derivatives 2–6 addressed in this pa-
per were prepared employing standard organometallic
reactions (Scheme 1).
Attempts to react 1,3- or 1,4-dichlorodecamethylcy-
clohexasilane with one equivalent of p-BrPhLi only
resulted in the formation of mixtures of the correspond-
Scheme 1. Synthesis of compounds 1–6.

H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
169
Table 1
1H- and 29Si-NMR chemical shifts and assignment for compounds 2, 3 and 4a
l(1H) (ppm) a
l(29Si) (ppm) a
2
7.34, 7.31, 7.24, 7.21 (s, 1H)
Phenyl
Ferrocene
–Si(CH3)
−16.60(1) b
−17.69(1)
−38.61(1)
−39.01(1)
−42.65(1)
−43.24(1)
−39.94(1)
−40.68(2)
−41.00(2)
−41.64(1)
SiMe2Ph
SiMe2Fc
4.20 (t, 2H), 4.07 (s, 5H), 4.00 (t, 2H)
0.43 (s, 6H), 0.31 (s, 6H), 0.21 (s, 6H),
0.20 (s, 6H), 0.17 (s, 6H), 0.15 (s, 6H)
SiMe2
trans-3
cis-3
7.35 (s, 2H, 7.15 (s, 2H)
6.56 (s, 1H)
4.21 (t, 2H), 4.11 (s, 5H), 4.0 (t, 2H)
0.52 (s, 3H), 0.40 (s, 3H), 0.33 (s, 6H),
0.27 (s, 6H) 0.26 (s, 6H), 0.12 (s, 6H)
7.31 (s, 2H), 7.15 (s, 2H)
Phenyl
(Si4) c
(Si2/Si3)
(Si1)
–HCꢀC(CN)2
Ferrocene
–Si(CH3)
Phenyl
−39.45(1)
−41.44(2)
−41.76(2)
−41.92(1)
(Si4)
6.51 (s, 1H)
–HCꢀC(CN)2
Ferrocene
–Si(CH3)
4.22 (t, 2H), 4.11 (s, 5H), 4.0 (t, 2H)
0.53 (s, 3H), 0.43 (s, 3H), 0.30 (s, 6H),
0.29 (s, 6H), 0.15 (s, 6H), 0.13 (s, 6H)
7.35 (s, 2H), 7.15 (s, 2H)
(Si2/Si3)
(Si1)
cis-4
Phenyl
–HCꢀC(CN)2
Ferrocene
−38.93(1)
−40.99(1)
−41.08(2)
−41.19(1)
−41.81(1)
(Si3)
6.56 (s, 1H)
4.21 (t, 2H), 4.11 (s, 5H), 4.01 (t, 2H)
0.53 (s, 3H), 0.45 (s, 3H), 0.35 (s, 3H),
0.34 (s, 3H), 0.27 (s, 3H), 0.22 (s, 3H),
0.21 (s, 3H), 0.19 (s, 6H), 0.16 (s, 3H)
7.35–7.25 (m, 4H)
6.54 (s, 1H)
4.20 (m, 2H), 4.06 (s, 5H),
4.03–3.95 (m, 2H)
(Si2/Si4/Si5/Si6)
(Si1)
–Si(CH3)
trans-4
Phenyl
–HCꢀC(CN)2
Ferrocene
−39.09(1)
−41.43(1)
−41.46(1)
−41.53(1)
−41.61(1)
−42.24(1)
(Si3)
(Si2/Si4/Si5/Si6)
0.50, 0.36, 0.32, 0.29, 0.26, 0.24, 0.22,
0.17, 0.15, 0.11 (s, 3H)
–Si(CH3)
(Si1)
a Versus ext. Me4Si; hydrocarbon solution.
b Number of Si-atoms in brackets.
c Atom numbering according to Figs. 1 and 2.
Since the substituents can be attached to the cyclo-
hexasilane ring either cis or trans relative to each other,
isomeric mixtures of the disubstituted permethylcyclo-
hexasilanes 3 and 4 are obtained containing nearly
equal amounts of the cis- and trans-isomers. Separation
of the isomers easily can be achieved by recrystalliza-
tion. As confirmed by X-ray crystallography (compare
the following section) the stereoisomer with both bulky
substituents in equatorial positions (trans in the case of
3 and cis in the case of 4) crystallizes selectively from
hexane solutions of 3 and 4 at −80°C. The second
isomer can be enriched in the filtrate up to 85% by
removing the less soluble isomer by repeated crystalliza-
tion from hexane at −80°C.
[9]. While the NMR spectra of the open chained hexa-
silanes 2 and 5 can be interpreted rather straightfor-
ward, complicated NMR patterns are observed for the
cyclic compounds 3 and 4. Substitution of two of the
methyls in Si6Me12 with different groups R and R%
produces four nonequivalent silicons in the case of 3
and six nonequivalent silicons in the case of 4. The
stereoisomers of 3 and 4 additionally exhibit different
29Si chemical shift values. The methyl groups, further-
more, can be either cis or trans to the substituents what
leads to 6 nonequivalent methyls for each isomer of 3
(intensity ratio 1:2:2:2:2:1) and to ten nonequivalent
methyls for each isomer of 4. The resulting number of
resonance lines actually appears in the experimental 1H-
and 29Si-NMR spectra, though some are to close to
each other to be completely resolved.
The proposed structures are consistent with MS and
NMR data and with the results of C, H, N elemental
1
analyses. 29Si- and H-NMR data are given in Table 1.
Only weak electronic effects of the substituents on the
ring silicon atoms are apparent in the 29Si-NMR
spectra. Introduction of the electron withdrawing
–CHꢀC(CN)2 group into the phenyl ring, for instance,
causes a slight downfield shift of the a-Si resonances in
3 and 4 (Dl=0.8 and 1.4 ppm) relative to PhSi6Me11
2.2. X-ray Structures of 3 and 4
Drawings of the molecular structures of 3 and 4 with
atom labeling are depicted in Figs. 1 and 2. Selected
bond lengths and angles are summarized in Table 2.

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H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
Table 2
The cyclohexasilane rings in 3 and 4 adopt slightly
Selected bond lengths, angles and torsion angles for 3 and 4
distorted chair conformations. The bulky substituents
in the 1,3 or 1,4-positions, respectively, occupy equato-
rial sites in order to minimize non-bonding interactions.
The aromatic rings are arranged roughly perpendicular
to one of the adjacent Si–Si bonds as shown by the
torsional angles in Table 2. Deviations from perpendic-
3
4
Bond lengths
Si(1)–Si(2)
Si(2)–Si(3)
Si(3)–Si(4)
Si(4)–Si(5)
Si(5)–Si(6)
Si(6)–Si(1)
Si(1)–C(11)
Si(3)–C(41)
Si(4)–C(41)
Si–C(methyl) mean
2.353(4)
2.351(4)
2.343(4)
2.354(4)
2.347(4)
2.351(4)
1.879(9)
2.351(6)
2.342(7)
2.356(6)
2.341(7)
2.321(7)
2.353(6)
1.866(9)
1.898(10)
1.901(9)
1.890
1.884
Bond angles
Si(1)–Si(2)–Si(3)
Si(2)–Si(3)–Si(4)
Si(3)–Si(4)–Si(5)
Si(4)–Si(5)–Si(6)
Si(5)–Si(6)–Si(1)
Si(6)–Si(1)–Si(2)
Si(1)–Si(2)–C(11)
Si(6)–Si(1)–C(11)
Si(2)–Si(3)–C(41)
Si(3)–Si(4)–C(41)
Si(4)–Si(5)–C(41)
C–Si–C mean
116.31(13)
110.20(13)
108.50(14)
111.68(13)
108.19(13)
110.10(14)
103.7(3)
110.2(2)
110.6(2)
112.9(2)
108.9(2)
112.9(2)
108.9(2)
105.3(3)
112.2(3)
109.9(3)
108.8(3)
113.5(3)
107.2(3)
110.5(3)
108.0
108.1
C(cp)–C(cp) mean
C(ph)–C(ph) mean
N(1)–C(61)–C(52)
N(2)–C(62)–C(52)
108.1
119.9
178.7(11)
179.3(11)
108.0
120.0
177.3(14)
178.0(12)
Dihedral angles
Si(2)–Si(1)–C(11)–C(15)
Si(2)–Si(1)–C(11)–C(12)
Si(3)–Si(4)–C(41)–C(46)
Si(3)–Si(4)–C(41)–C(42)
Si(4)–Si(3)–C(41)–C(46)
Si(4)–Si(3)–C(41)–C(42)
C(44)–C(51)–C(52)–C(61)
C(45)–C(44)–C(51)–C(52)
C(42)–C(43)–C(44)–C(51)
−90.2(9)
84.5(8)
87.0(8)
−107.4(7)
72.2(6)
Fig. 1. ORTEP plot of the molecular structure of 3 (hydrogens are
omitted for clarity).
−91.3(8)
−75.7(7)
101.6(8)
−2.4(16)
−11.5(15)
−177.4(10)
1.5(17)
−5.6(17)
−175.0(9)
ularity are larger for compound 4 and amount to about
15°. The tilt between the phenyl and the cyclopentadi-
enyl ring is 62° for compound 3 and 89° for compound
4. Both compounds possess nearly eclipsed ferrocenyl
geometry with almost coplanar cyclopentadienyl rings.
,
The average Si–Si distances of 2.349 A in 3 and 2.344
,
in 4 are close to that in elemental silicon, 2.352 A [10],
,
,
1,4-Ph2Si6Me10, 2.350 A [11] and Si6Me12, 2.338 A [12].
These distances agree well with the Si–Si covalent bond
,
length of 2.34 A. The average Si–Si–Si bond angles
[110.8(3)° for 3 and 110.7(5)° for 4] and the average
Si–Si–Si–Si torsion angles [56.0(9)° for 3 and 56.6(7)
for 4] are close to the respective angles found in other
cyclohexasilane structures studies so far [11–13]. 3 and
4 crystallize in centrosymmetric point groups, where the
unit cell contains two, respectively four symmetry
equivalent molecules (compare Fig. 3). The molecules
Fig. 2. ORTEP plot of the molecular structure of 4 (hydrogens are
omitted for clarity).

H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
171
show a stacking behavior parallel to the silica rings
along the a axis in the case of 3 and along the b axis in
the case of 4.
As shown in Fig. 4 each spectrum displays a doublet
and a broad singlet with isomer shift (l) and quadru-
pole splitting (m) values characteristic of Fe(II) and
Fe(III) sites, what implies, that 1–6 have localized
electronic structures on the Mo¨ssbauer time scale (10−7
s) [14,15]. The singlet can be interpreted as a doublet
with small quadrupole splitting as well without any
significant impact on the results. In general, ferrocenyl
groups (Fe(II)) give spectra with large quadrupole split-
ting in the range of 2.0 to 2.2 mm s−1, while the spectra
2.3. Mo¨ssbauer spectra
57Fe-Mo¨ssbauer spectra of the ferrocenyl oligosilanes
1–6 were obtained in order to probe the nature of the
iron sites. The Mo¨ssbauer effect spectral parameters are
presented in Table 3.
Fig. 3. Stereo view of the unit cells of compounds 3 (top) and 4 (bottom).
Table 3
Mo¨ssbauer data for compounds 1–6
Doublet
Singlet
l (mm s−1
)
m (mm s−1
)
I (%)
Y (mm s−1
)
l (mm s−1
)
I (%)
Y (mm s−1
)
1
2
3
4
5
6
0.528(1)
0.53(4)
0.544(6)
0.532(4)
0.526(1)
0.529(3)
2.323(3)
2.313(8)
2.36(1)
2.332(9)
2.320(2)
2.335(2)
89(1)
67(2)
67(3)
60(3)
89(1)
90(1)
0.306(4)
0.30(1)
0.252(2)
0.251(8)
0.267(3)
0.275(3)
0.32(1)
0.31(2)
0.28(3)
0.30(2)
0.29(2)
0.27(3)
11(1)
33(3)
33(4)
40(3)
11(1)
10(1)
0.46(5)
0.65(8)
0.72(8)
0.80(6)
0.57(6)
0.75(1)

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H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
Fig. 4. Mo¨ssbauer spectra of compounds 1–6.

H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
173
of ferricinium cations (Fe(III)) are characterized by
small or vanishing quadrupole splitting [16].
standard TMS. Mass spectra were run either on a HP
5971/A/5890-II GC/MS coupling (HP capillary
1
The appearance of the Fe(III) signal in all spectra
clearly indicates the electron accepting character of the
polysilanyl groups attached to ferrocene. Electron
transfer in the direction Cp“(Sin) removes electron
density from the cyclopentadienyl ring, what is com-
pensated by the partial oxidation Fe(II)“Fe(III). The
relative intensities of the Fe(II) and Fe(III) signals
deserve particular attention, because the intensity of the
Fe(III) singlet in the spectra of the dipolar hexasilanes
2, 3 and 4 turns out to by significantly enhanced as
compared to the other compounds investigated in this
study. Two important conclusions may be drawn from
this observation: (i) When the dicyanoethylphenyl ac-
ceptor group is attached to the (Si6) moiety in 5 and 6,
Cp“(Sin) electron transfer is more pronounced, what
is a clear indication for the transmission of the electron
accepting properties of the –Ph–CHꢀC(CN)2 group via
the hexasilane framework. (ii) The magnitude of Cp“
(Sin) electron transfer is increased when going from
disilane 1 to the more extended Si–Si-skeletons in 2, 3
and 4, what may be related to the higher polarizability
of the larger hexasilane frameworks. Both findings are
consistent with recent cyclovoltammetric studies and
NLO measurements [5] also showing increased trans-
parency for electronic effects in particular for the cyclo-
hexasilane moiety.
column, length 25 m, diameter 0.2 mm, 0.33 mm poly-
dimethylsiloxane) or on a Kratos Profile mass spec-
trometer equipped with a solids probe inlet. Elemental
analyses were carried out on a Hanau Vario Elementar
EL apparatus. Mo¨ssbauer spectra were obtained at a
temperature of 80 K in transmission geometry using a
WISSEL system. The source material was 57Co/Rh with
an activity of 10 mCi. The spectrometer was calibrated
with a-Fe. All isomer shifts are relative to a-Fe. All
spectra were fit assuming Lorentz profiles.
3.2. Ferrocenyllithium
75 mmoles of tert-butyllithium in hexane were added
slowly to a solution of 21 g (113 mmol) of ferrocene in
150 ml of THF at 0°C. Subsequently ferrocenyllithium
was crystallized by cooling the solution to −30°C
overnight, filtered and washed with cold THF in order
to remove excess ferrocene and unreacted tert-butyl-
lithium. Further purification of the reaction product
can be achieved by recrystallization from THF at
−30°C.
3.3. 1-Ferrocenyl-6-[(2,2-dicyanoethenyl)phenyl]-
dodecamethylhexasilane (2)
In conclusion, the Mo¨ssbauer analysis performed in
this study further substantiates the assumption, that
especially the cyclohexasilane framework is able to act
as a good mediator for electronic effects.
3.3.1. 1,6-bis-(4-Bromophenyl)dodecamethyl-
cyclohexasilane
To a solution of 37.7 g (89.8 mmol) of 1,6-
dichlorododecamethylhexasilane in 100 ml diethylether,
a −70°C cold solution of 184 mmol of 4-bromophenyl-
lithium in 150 ml of diethylether was added dropwise.
The mixture was stirred for 2 h at room temperature
and subsequently refluxed for 1 h. After aqueous
workup with 50 ml of saturated NH4Cl solution the
combined organic layers were dried over Na2SO4 and
the solvent was stripped off in vacuum. Recrystalliza-
tion of the crude product from 1-propanol affords pure
white crystals of 1,6-bis-(4-bromophenyl)dodeca-
methylhexasilane in 75% yield. 29Si-NMR (Toluol/D2O,
ext. Me4Si, ppm): −16.80; −38.34; −42.55.
3. Experimental
3.1. General procedures
All reactions and other manipulations were carried
out using standard Schlenk techniques under an inert
atmosphere of nitrogen. All solvents were dried and
distilled under nitrogen prior to use. Malononitrile,
triflic acid and 1,4-dibromobenzene were used as pur-
chased without further purification. N,N-Dimethylfor-
,
mamide was allowed to stand on 4 A molecular sieve
and distilled from CaH2. Ferrocenyllithium [17], 4-bro-
mophenyllithium [18], 1-ferrocenyl-2-[(2,2-dicyano-
ethenyl)phenyl]disilane (1) [3], ferrocenylundecamethyl-
cyclohexasilane (6) [5] and the starting silicon com-
pounds 1,6-dichlorododecamethylhexasilane [19], 1,3-
dichlorodecamethylcyclohexasilane and 1,4-dichlorode-
camethylcyclohexasilane [20,21] were synthesized as
previously reported. NMR spectra were recorded on a
Bruker 300-MSL spectrometer; 1H-NMR (300.13
MHz): C6D6 solution, ext. standard Me4Si; 29Si-NMR
(59.62 MHz): toluene solution, ext. lock D2O, ext.
3.3.2. 1-Chloro-6-(4-bromophenyl)dodecamethyl-
hexasilane
A total of 5.9 ml (67.6 mmol) of triflic acid was
added to a solution of 42.6 g (64.4 mmol) of 1,6-bis(4-
bromophenyl)dodecamethylhexasilane in 1000 ml of
toluene at −20°C over a period of 7 h. The mixture
was stirred at room temperature (r.t.) overnight. Four
hundred milliliters of toluene were removed in vacuum
and replaced by diethylether. A total of 6.1 g (144.2
mmol) of anhydrous LiCl was added at 0°C and the
mixture was stirred for another 12 h at r.t. After

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H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
removal of the solvent in vacuum 200 ml of petroleum
ether was added and the solution was filtered. Finally
the solvent was stripped off again and the title com-
pound was isolated from the resulting solid residue by
Kugelrohr distillation at 160°C and 10−2 mbar fol-
lowed by recrystallization from petroleum ether. Yield
73% of colorless crystals. 29Si-NMR (Toluol/D2O, ext.
Me4Si, ppm): 25.70; −16.78; −38.42; −39.15;
−40.53; −42.52. MS (70 eV) m/e (rel. int.): 540 [M+,
9], 325 (6), 267 (100), 209 (33), 131 (15), 73 (47).
mixture of 15 ml of THF and 80 ml of ethanol was
added 0.51 g (7.8 mmol) of solid molononitrile and two
drops of piperidine. The mixture was stirred for 45 min
(DC monitoring recommended) and then the solvents
were removed in vacuum. After column chromatogra-
phy (silica gel) with toluene as the mobile phase and
subsequent recrystallization from hexane orange–red
crystals of the title compound were obtained in 62%
yield. M.p.: 135–137°C. Anal. Found: C, 55.48; H,
7.26; N, 3.97. C32H50FeN2Si6 (687.12) Calc.: C, 55.94;
1
H, 7.33; N, 4.07%. 29Si-NMR, H-NMR: Table 1. MS
3.3.3. 1-Ferrocenyl-6-(4-bromophenyl)dodecamethyl-
hexasilane
(70 eV) m/e (rel. int.): 686 [M+, 4], 243 (100), 186 (47),
121 (17), 73 (16).
A solution of ferrocenyllithium in 150 ml of THF
[prepared from 21 g (112.9 mmol) of ferrocene and 75
mmol of tert-butyllithium] was added slowly to a
stirred solution of 26.3 g (48.7 mmol) of 1-chloro-6-(4-
bromophenyl)dodecamethylhexasilane in 10 ml of THF
at r.t. The resulting mixture was refluxed overnight.
Subsequently the solvent was stripped off and residual
ferrocene was removed by sublimation at 50°C and
10−2 mbar. The resulting orange residue was dissolved
in 150 ml of diethylether. After aqueous workup with
saturated NH4Cl solution the combined organic layers
were dried over Na2SO4 and concentrated. Chromatog-
raphy on a silica gel column developed by a mixture of
heptane+toluene (95:5) affords 9.7 g (30%) of the
desired compound as an orange solid. 29Si-NMR
(Toluol/D2O, ext. Me4Si, ppm): −16.73; −16.92;
−38.40; −38.60; −42.65; −42.71. MS (EI, m/z, %):
690 [M+, 2], 610 (7), 243 (100), 186 (11), 135 (15), 73
(20).
3.4. 1-Ferrocenyl-4-[(2,2-dicyanoethenyl)phenyl]-
decamethylcyclohexasilane (3)
3.4.1. 1,4-bis(4-Bromophenyl)decamethylcyclohexasilane
(isomeric mixture)
The procedure followed was that used for 1,6-bis(4-
bromophenyl)dodecamethylcyclohexasilane with 35 g
(89.8 mmol) of 1,4-dichlorodecamethylcyclohexasilane
and 276 mmol of 4-bromophenyllithium. Yield: 41 g
(=67% based on 1,4-dichlorodecamethylcyclohexasi-
lane). 29Si-NMR (Toluol/D2O, ext. Me4Si, ppm):
−40.81/−39.86; −41.05/−42.00. MS (70 eV) m/e
(rel. int.): 630 [M+, 4], 551 (11), 341 (8), 207 (100), 72
(85).
3.4.2. 1-Chloro-4-(4-bromophenyl)decamethylcyclo-
hexasilane (isomeric mixture)
The procedure followed was that used for 1-chloro-6-
(4-bromophenyl)dodecamethylhexasilane with 40.6 g
(64.4 mmol) of 1,4-bis(4-bromophenyl)decamethyl-
cyclohexasilane, 5.9 ml (67.6 mmol) of triflic acid and
6.1 g (144.3 mmol) of lithium chloride. The reaction
product was isolated by sublimation at 120°C and 10−2
mbar to give colorless crystals in 73% yield. 29Si-NMR
(Toluol/D2O, ext. Me4Si, ppm): 16.72/15.50; −38.84/
−39.53; −40.52/−40.59; −41.61/−42.22. MS (70
eV) m/e (rel. int.): 510 [M+, 9], 429 (31), 341 (14), 215
(19), 73 (100).
3.3.4. 1-Ferrocenyl-6-(4-formylphenyl)dodecamethyl-
hexasilane
To a solution of 9.0 g (13.1 mmol) of 1-ferrocenyl-6-
(4-bromophenyl)dodecamethylhexasilane in 80 ml of
THF at −78°C, a pentane solution of 26.1 mmol of
n-butyllithium was added slowly. The mixture was
stirred for another 5 min and 10.5 ml (135 mmol) of dry
DMF was added. After stirring the mixture overnight
at r.t. aqueous workup with saturated NH4Cl solution
and recrystallization of the crude product from pentane
affords orange crystals of the desired compound in 67%
yield. 29Si-NMR (Toluol/D2O, ext. Me4Si, ppm):
−16.32; −17.02; −38.17; −38.48; −42.26; −42.71
1H-NMR (C6D6, ext. Me4Si, ppm, rel. int.): 10.02 (s,
1H, CHO); 7.84–7.62 (4H, phenyl); 4.32 (t, 2H, fer-
rocene); 4.16 (s, 5H, ferrocene); 4.02 (t, 2H, ferrocene);
0.44–0.06 (36H, Si(CH3)). MS (EI, m/z, %): 638 [M+,
22], 243 (100), 186 (13), 73 (26).
3.4.3. 1-Ferrocenyl-4-(4-bromophenyl)-
decamethylcyclohexasilane
The procedure followed was that used for 1-ferro-
cenyl-6-(4-bromophenyl)dodecamethylhexasilane with
25 g (48.7 mmol) of 1-chloro-4-(4-bromophenyl)deca-
methylcyclohexasilane, 21 g (112.9 mmol) of ferrocene
and 75 mmol of tert-butyllithium. Yield: 8.6 g (27%).
After crystallization from hexane at −80°C orange
crystals of the pure trans-isomer of the compound were
obtained. The cis-isomer can be enriched in the filtrate
up to 85% by removing the less soluble trans-isomer by
repeated crystallization from hexane and is obtained as
an orange oil after subsequent removal of the solvent in
vacuum. 29Si-NMR (Toluol/D2O, ext. Me4Si, ppm):
3.3.5. 1-Ferrocenyl-6-[(2,2-dicyanoethenyl)phenyl]-
dodecamethylhexasilane
To a solution of 4.5 g (7.1 mmol) of 1-ferrocenyl-6-
(4-formylphenyl)dodecamethylhexasilane dissolved in a

H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
175
trans-isomer: −40.84; −41.26; −41.34; −41.77. cis-
isomer: −40.40; −42.02; −42.13; −42.1. MS (70 eV)
m/e (rel. int.): 660 [M+, 8], 580 (100), 243 (85), 186
(50), 135 (37), 73 (56).
and 276 mmol of 4-bromophenyllithium. Yield: 45.2 g
(75%). 29Si-NMR (Toluol/D2O, ext. Me4Si, ppm):
−39.88/−40.33; −40.88/−40.99; −41.06/−41.26;
−41.44/−41.44; −41.90/−41.67; −42.32/−42.06.
MS (70 eV) m/e (rel. int.): 630 [M+, 5], 551 (7), 341 (9),
215 (40), 73 (100).
3.4.4. 1-Ferrocenyl-4-(4-formylphenyl)-
decamethylcyclohexasilane (isomeric mixture)
The procedure followed was that used for 1-ferro-
cenyl-6-(4-formylphenyl)dodecamethylhexasilane with
8.6 g (13.1 mmol) of 1-ferrocenyl-4-(4-bromophenyl)-
decamethylcyclohexasilane, 26.1 mmol of tert-butyl-
lithium and 10.4 ml of dry DMF. Due to the sensitivity
of the desired compound versus oxygen all solvents and
reagents need to be carefully deoxygenated prior to use.
Final purification of the reaction product was achieved
by column chromatography on a silica gel column
developed by a mixture of deoxygenated heptane+tol-
uene (95:5). Yield: 4.4 g (55%) of orange–red, light and
oxygen sensitive crystals. 29Si-NMR (Toluol/D2O, ext.
Me4Si, ppm): −39.66/−40.02; −40.68/−41.44;
−40.80/−41.39; −41.25/−41.63. 1H-NMR (C6D6,
ext. Me4Si, ppm, rel. int.): 9.72/9.69 (s, 1H, CHO);
7.62–7.47 (4H, phenyl); 4.21–4.00 (9H, ferrocene);
0.53–0.14 (30H, Si(CH3)). MS (70 eV) m/e (rel. int.):
608 [M+, 78], 460 (13), 243 (77), 186 (100), 121 (25), 73
(20).
3.5.2. 1-Chloro-3-(4-bromophenyl)decamethylcyclo-
hexasilane (isomeric mixture)
The procedure followed was that used for 1-chloro-4-
(4-bromophenyl)decamethylcyclohexasilane with 40.6 g
(64.4 mmol) of 1,3-bis(4-bromophenyl)decamethyl-
cyclohexasilane, 10.2 g (67.6 mmol) of triflic acid and
6.1 g (144.3 mmol) of lithium chloride. Yield: 24.1 g
(73%). 29Si-NMR (Toluol/D2O, ext. Me4Si, ppm):
16.95/15.50;
−38.39/−38.47;
−39.23/−39.43;
−40.51/−40.66; −40.88/−40.92; −41.20/−41.86.
MS (70 eV) m/e (rel. int.): 510 [M+, 6], 429 (15), 341
(11), 215 (38), 73 (100).
3.5.3. 1-Ferrocenyl-3-(4-bromophenyl)-
decamethylcyclohexasilane
The procedure followed was that used for 1-ferro-
cenyl-6-(4-bromophenyl)dodecamethylhexasilane with
25 g (48.7 mmol) of 1-chloro-3-(4-bromophenyl)deca-
methylcyclohexasilane, 21 g (112.9 mmol) of ferrocene
and 75 mmol of tert-butyllithium. Yield: 9.7 g (30%).
After crystallization from hexane at −80°C orange
crystals of the pure cis-isomer of the compound are
obtained. The trans-isomer can be enriched in the
filtrate up to 85% by removing the less soluble cis-iso-
mer by repeated crystallization from hexane and is
isolated as an orange oil after subsequent removal of
the solvent in vacuum. 29Si-NMR (Toluol/D2O, ext.
Me4Si, ppm): cis-isomer: −40.19; −41.37 (int. ×2);
−41.41; −41.69 (int. ×2). trans -isomer: −40.02;
−41.47; −41.74; −42.13; −42.37 (int. ×2). MS (70
eV) m/e (rel. int.): 660 [M+, 2], 385 (15), 243 (100), 213
(31), 73 (65).
3.4.5. 1-Ferrocenyl-4-[(2,2-dicyanoethenyl)phenyl]-
decamethylcyclohexasilane
The procedure followed was that used for 1-ferro-
cenyl - 6 - [(2,2 - dicyanoethenyl)phenyl]dodecamethyl-
hexasilane with 4.3 g (7.1 mmol) of 1-ferrocenyl-4-(4-
formylphenyl)decamethylcyclohexasilane, 0.52 g (7.8
mmol) of molononitrile and two drops of piperidine.
After column chromatography (silica gel) with toluene
as the mobile phase and subsequent recrystallization
from hexane at −80°C red crystals of the trans (e,e)-
isomer were obtained in 35% yield. The cis (e,a)-isomer
can be enriched in the filtrate up to 95% by removing
the less soluble trans-isomer by repeated crystallization
from hexane and is obtained as a red oil in 15% yield
after removal of the solvent in vacuum. M.p. (trans-iso-
mer): 152–153°C. Anal. Found: C, 54.92; H, 6.74; N,
4.22. C30H44FeN2Si6 (657.06) calcd.: C, 54.84; H, 6.75;
3.5.4. 1-Ferrocenyl-3-(4-formylphenyl)-
decamethylcyclohexasilane (isomeric mixture)
The procedure followed was that used for (4-
formylphenyl)undecamethylcyclohexasilane with 8.6 g
(13.1 mmol) of 1-ferrocenyl-4-(4-bromophenyl)deca-
methylcyclohexasilane, 26.1 mmol of tert-butyllithium
and 10.4 ml of dry DMF. Due to the sensitivity of the
desired compound versus oxygen all solvents and
reagents need to be carefully deoxygenated prior to use.
Final purification of the reaction product was achieved
by column chromatography on a silica gel column
developed by a mixture of deoxygenated heptane+tol-
uene (95:5). Yield: 4.8 g (60%) of orange–red, light and
oxygen sensitive crystals. 29Si-NMR (Toluol/D2O, ext.
Me4Si, ppm): −39.55; −39.98; −41.18; −41.26;
−41.38 (int. x2); −41.51; −41.62; −41.70; −41.73;
1
N, 4.21%. 29Si-NMR, H-NMR: Table 1. MS (70 eV)
m/e (rel. int.): 656 [M+, 3], 243 (4), 186 (100), 121 (24),
66 (12), 44 (22).
3.5. 1-Ferrocenyl-3-[(2,2-dicyanoethenyl)phenyl]-
decamethylcyclohexasilane (4)
3.5.1. 1,3-bis(4-Bromophenyl)decamethylcyclohexasilane
(isomeric mixture)
The procedure followed was that used for 1,6-bis(4-
bromophenyl)dodecamethylcyclohexasilane with 35 g
(89.8 mmol) of 1,3-dichlorodecamethylcyclohexasilane

176
H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
1
−41.91; −42.25. H-NMR (C6D6, ext. Me4Si, ppm,
rel. int.): 9.71/9.70 (s, 1H, CHO); 7.59–7.38 (4H,
phenyl); 4.18–3.96 (9H, ferrocene); 0.54–0.13 (30H,
Si(CH3)). MS (70 eV) m/e (rel. int.): 608 [M+, 36], 371
(7), 243 (100), 213 (13), 163 (20), 73 (69).
r.t. After aqueous workup with saturated NH4Cl solu-
tion the combined organic layers were dried over
Na2SO4 and concentrated. Chromatography on a silica
gel column developed by heptane affords 2.3 g (70%) of
the desired compound as an orange solid. M.p.: 84–
87°C. Anal. Found: C, 55.41; H, 8.91. C23H48FeSi6
(549.0) Calc.: C, 50.32; H, 8.81%. 29Si-NMR (Toluol/
D2O, ext. Me4Si, ppm): −15.01, −17.65, −39.15,
−39.17, −43.16, −43.27. 1H-NMR (C6D6, ext.
Me4Si, ppm, rel. int.): 4.20 (t, 2H, ferrocene), 4.07 (s,
5H, ferrocene), 4.00 (t, 2H, ferrocene); 0.43 (s, 6H),
0.31 (s, 6H), 0.21 (s, 6H), 0.20 (s, 6H), 0.17 (s, 6H), 0.15
(s, 6H): Si(CH3). MS (70 eV) m/e (rel. int.): 548 [M+,
3], 285 (4), 243 (100), 131 (5), 73 (21).
3.5.5. 1-Ferrocenyl-3-[(2,2-dicyanoethenyl)phenyl]-
decamethylcyclohexasilane
The procedure followed was that used for 1-ferro-
cenyl-6-[(2,2-dicyanoethenyl)phenyl]dodecamethylhexa-
silane with 4.3 g (7.1 mmol) of 1-ferrocenyl-4-(4-
formylphenyl)decamethylcyclohexasilane, 0.52 g (7.8
mmol) of molononitrile and 2 drops of piperidine. After
column chromatography (silica gel) with toluene as the
mobile phase and subsequent recrystallization from
hexane at −80°C red crystals of the cis (e,e)-isomer
were obtained in 35% yield. The trans (e,a)-isomer can
be enriched in the filtrate up to 95% by removing the
less soluble cis-isomer by repeated crystallization from
hexane and is obtained as a red oil in 15% yield after
removal of the solvent in vacuum. M.p. (cis-isomer):
152°C. Anal. Found: C, 55.02; H, 6.72; N, 4.18.
C30H44FeN2Si6 (657.06) Calc.: C, 54.84; H, 6.75; N,
3.7. X-ray crystallography
Suitable crystals of 3 and 4 were grown by cooling
hexane solutions slowly to −80°C. The crystals were
mounted on a glass fiber. Diffraction data were col-
lected on a Siemens SMART CCD diffractometer at
293 K using graphite monochromated Mo–Ka radia-
,
tion (u=0.71073 A), a nominal crystal-to-detector dis-
1
4.21%. 29Si-NMR, H-NMR: Table 1. MS (70 eV) m/e
tance of 4.40 cm and 0.3° ꢀ–scan frames. Crystal data
and the details of the structure determinations are given
in Table 4. The data were corrected for Lorentz and
polarization effects and an empirical absorption correc-
tion (SADABS [22]) was applied. Structure 3 was solved
by the Patterson method while 4 was solved by direct
methods (SHELXS-86 [23]). The structure refinement was
performed in a full-matrix least-squares against F2
(rel. int.): 656 [M+, 100], 243 (34), 186 (84), 121 (20), 73
(11).
3.6. 1-Ferrocenyltridecamethylhexasilane (5)
3.6.1. 1-(4-Bromophenyl)tridecamethylhexasilane
A total of 8.25 ml of a 1.6 M pentane solution of
methyllithium (15.13 mmol) was slowly added to a
solution of 8.2 g (15.13 mmol) of 1-chloro-6-(4-bro-
mophenyl)dodecamethylhexasilane in 100 ml of toluene
at −20°C. The resulting mixture was stirred overnight.
After removal of the solvent in vacuum 50 ml of
petroleum ether was added and the salts were removed
by filtration. Finally the solvent was stripped off again
and the title compound was isolated from the resulting
solid residue by Kugelrohr distillation at 150°C and
10−2 mbar. Yield 5.2 g (66%) of colorless crystals.
29Si-NMR (Toluol/D2O, ext. Me4Si, ppm): −15.07;
−17.42; −39.17; −39.29; −43.10; −43.28. MS (EI,
m/z, %): 519 [M+, 9], 389 (22), 331 (30), 215 (32), 73
(100).
(SHELXTL V5.03 [24]). All non-hydrogen atoms were
refined anisotropically, all hydrogen atoms were in-
serted in ideal positions. The crystals obtained were not
of very good quality, what is the reason for the quite
high internal R values of the data sets. In structure 3 a
strongly disordered solvent molecule, probably hexane,
could be partly refined. However only four carbon
atoms of this molecule were found and were refined
anisotropically without adding hydrogen atoms. The
other part of the solvent molecule is generated by the
symmetry operation.
4. Supplementary material
3.6.2. 1-Ferrocenyltridecamethylhexasilane
A total of 0.53 ml (6.0 mmol) of triflic acid was
added slowly to a solution of 3.1 g (6.0 mmol) of
1-(4-bromophenyl)tridecamethylhexasilane in 60 ml of
toluene at −20°C. The mixture was stirred at r.t.
overnight. After removal of the solvent in vacuum 10
ml of THF was added. The resulting solution was
treated dropwise with a THF solution of 1.2 g (6.0
mmol) of ferrocenyllithium and stirred for one hour at
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 152536 for compound 3 and
152537 for compound 4. Copies of this information
may be obtained from The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (fax: +44-1233-336-
033; e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).

H. Rautz et al. / Journal of Organometallic Chemistry 627 (2001) 167–178
177
Table 4
Crystallographic data for compounds 3 and 4a
3
4
Empirical formula
Formula weight
Color
C30H44FeN2Si6C6H14
657.06
Red
C30H44FeN2Si6
657.06
Red
Crystal size (mm)
Crystal system
Space group
0.36×0.12×0.10
Triclinic
0.40×0.14×0.10
Monoclinic
P21/c
14.04(4)
7.81(2)
33.92(11)
90.00
90.96
90.00
3718.(19)
4
0.620
44
(
P1
,
a (A)
8.9262(18)
13.652(4)
17.360(4)
98.19(2)
90.12(3)
105.00(2)
2020.8(9)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Absorption coefficient (mm−1
Detector distance (mm)
q Range (°)
)
0.575
44
2.10–20.81
1.20–20.90
Limiting indices
Reflections collected
Independent reflections
−8BhB8, −13BkB13, 0BlB17 −13BhB13, 0BkB7, 0BlB33
4201
3871
4201 [Rint=0.36]
3408
3871 [Rint=0.17]
3037
Observed reflections [I\4|(I)]
Parameters/restraints
389/0
353/0
Final R indices [I\4|(I)] a
R indices [all data]
R1=0.0380, wR2=0.0931
R1=0.0517, wR2=0.1010
1/|2Fo+(0.0524P)2+1.17P;
P=Fo+2F2c/3
1.023
R1=0.0668, wR2=0.1745
R1=0.0867, wR2=0.2031
1/|2Fo+(0.0885P)2+9.8161P;
P=Fo+2F2c/3
1.172
Weighting scheme
Goodness-of-fit on F2
Extinction coefficient
0.0011(5)
0.0003(4)
Max and min heights in final difference Fourier synthesis
0.314, −0.219
0.420, −0.366
−3
,
(e A
]
a R1=S ꢀꢀFoꢀ−ꢀFcꢀꢀ/S ꢀFoꢀ; wR2=[S w(ꢀFoꢀ−ꢀFcꢀ)2/S wF2o]0.5
.
lics 10 (1991) 3656. (d) D. Hissink, P.F. van Hutten, G. Hadzi-
ioannou, J. Organomet. Chem. 454 (1993) 25. (e) D. Hissink, J.
Brouwer, R. Flipse, G. Hadziioannou, Polymer Pepr. 32 (1991)
136. (f) D. Hissink, H.J. Bolink, J.W. Eshuis, G.G. Malliaras, G.
Hadziioannou, Polymer Pepr. 34 (1993) 721.
Acknowledgements
We wish to thank the Fonds zur Fo¨rderung der
wissenschaftlichen Forschung (Wien, Austria), for
financial support within the Spezialforschungsbereich
‘Elektroaktive Stoffe’ and the Wacker Chemie GmbH
(Burghausen, Germany) for the donation of silane
precursors.
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