The [Cp(CO)2Fe] (Fp) group as a donor in donor/acceptor substituted disilanes: Synthesis, structure and electronic properties of

Article abstract of DOI:10.1016/S0022-328X(02)02113-7

UV-vis absorption spectroscopy and cyclic voltammetry are used to study electronic interactions in the donor/acceptor substituted disilane Fp-Si₂Me₄-C₆H₄CH=C(CN) ₂ (Fp = η⁵- C₅H₅Fe(CO) ₂) (1). The synthesis of 1 was achieved by a conventional chemical route, the model substances Fp-SiMe₃ (2), Fp-Si₂Me₅ (3) and Fp-Si₂ Me₄C₆H₅ (4) were obtained by the electrolysis of Fp₂ in the presence of the appropriate chlorosilane. The structure of 1, determined by X-ray diffraction, exhibits an all-trans-array of the Fe-Si-Si-C_aryl fragment, a basic requirement for optimal through-bond interaction. UV-vis and CV data indicate strong intramolecular donor/acceptor interaction in 1.

Full text of DOI:10.1016/S0022-328X(02)02113-7

Journal of Organometallic Chemistry 665 (2003) 186ꢀ195
/
www.elsevier.com/locate/jorganchem
The [Cp(CO)2Fe] (Fp) group as a donor in donor/acceptor substituted
disilanes: synthesis, structure and electronic properties of FpÃ
Si2Me4ÃC6H4CHÄC(CN)2
/
/
/
Christa Grogger a,*, Helmut Fallmann a, Gottfried Furpaß a, Harald Stuger a,
¨
¨
Guido Kickelbick b
a Institut fur Anorganische Chemie, Technische Universitat Graz, Stremayrgasse 16, A-8010 Graz, Austria
¨
¨
b Institut fur Anorganische Chemie, Technische Universitat Wien, Getreidemarkt 9, A-1060 Wien, Austria
¨
¨
Received 11 March 2002; accepted 2 October 2002
Abstract
UVꢀ
substituted disilane FpÃ
chemical route, the model substances FpÃ
Fp2 in the presence of the appropriate chlorosilane. The structure of 1, determined by X-ray diffraction, exhibits an all-trans-array
of the FeÃSiÃSiÃCaryl fragment, a basic requirement for optimal through-bond interaction. UVꢀvis and CV data indicate strong
/
vis absorption spectroscopy and cyclic voltammetry are used to study electronic interactions in the donor/acceptor
Si2Me4ÃC6H4CHÄC(CN)2 (Fpꢁ
h5-C5H5Fe(CO)2) (1). The synthesis of 1 was achieved by a conventional
SiMe3 (2), FpÃSi2Me5 (3) and FpÃSi2Me4C6H5 (4) were obtained by the electrolysis of
/
/
/
/
/
/
/
/
/
/
/
intramolecular donor/acceptor interaction in 1.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: FeÃSi bond; UV absorption; Cyclic voltammetry; Silyl bridge
/
1. Introduction
chromophores, corresponding to direct transitions to
highly dipolar Dꢂ-bridge-Aꢃ charge transfer states.
Intramolecular electron transfer between redox cen-
ters interconnected by various types of more or less
rigid, saturated hydrocarbon bridges has also been
reported [3] and it has been suggested, that through-
bond interaction of the donor and the acceptor moieties
via the bridge of s-orbitals is very likely involved in
mediating the electron transfer in such system. Thus, a
so called s-coupled transition with CT character and a
hypsochromic shift of the local acceptor absorption
band are observed in the UV absorption spectra of D/A-
substituted cyclohexanes, when the geometry favors
through-bond interaction between the chromophores
There is considerable interest in the development of
organic and organometallic materials showing pro-
nounced second-order nonlinear optical properties of
technological significance [1]. It is generally accepted
that molecules with both large differences between
ground state and excited state dipole moments and
large transition dipole moments will have large second-
order optical nonlinearities [2]. Pertinent studies re-
vealed that molecular assemblies of appropriate donor
and acceptor units joined together by p-bond conju-
gated bridges nearly perfectly fulfil these requirements.
p-Bond conjugated spacers facilitate donor-to-acceptor
charge transfer, their effectiveness at electronic coupling
can almost readily be seen in form of completely new
absorption bands, usually red shifted compared with the
absorption bands of the individual donor and acceptor
[4]. Polymethylene-linked anthraceneꢀdialkylaniline bi-
/
chromophores have also been studied extensively [5]. It
has been demonstrated by UV absorption and fluores-
cence spectroscopy, that strong electron-donorꢀaccep-
/
tor interaction exists in the ground state of these
molecules, when the energy level of the charge transfer
state is lowered below that of the localized excited state
by appropriate substituents. Under certain circum-
* Corresponding author. Tel.: ꢂ
873-8701.
E-mail address: grogger@anorg.tu-graz.ac.at (C. Grogger).
/
43-316-873-8217; fax: ꢂ43-316-
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 2 1 1 3 - 7

C. Grogger et al. / Journal of Organometallic Chemistry 665 (2003) 186ꢀ
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187
stances, therefore, s-bonded D-bridge-A compounds
might also be suitable candidates for the synthesis of
materials comprising nonlinear optical properties.
Fp substituted silyl compounds are most commonly
made from [h5-C5H5)Fe(CO)2]Na and the appropriate
chlorosilane simply by salt elimination [10a]. Based on a
work by Ruiz et al. [12], who synthesized FpÃ
/
SiMe3 by
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 activity [6].
Although it is well established, that the s-electrons in
polysilanes are delocalized rather effectively along the
silicon backbone resulting in unusual electronic proper-
ties like low ionization potentials of these polysilane
chains [7], silicon was found to be only a weak charge
transmitter when donor and acceptor moieties are
the electrolysis of [(h5-C5H5)Fe(CO)2]2 (Fp2) in the
presence of ClSiMe3, we found electrosynthesis to be a
convenient alternative avoiding the handling of rather
tedious materials like mercury or sodium amalgam.
Thus, we applied the electrochemical procedure devel-
oped by Ruiz et al. to mixtures of Fp2 with ClSiMe2-
SiMe3 or ClSiMe2SiMe2Cl in order to extend the scope
of the method to the synthesis of the Fp-functional
disilanyl derivatives 3 and 4 relevant in the course of the
current study.
connected by permethylated SiÃ
/
Si-chains and the result-
ing optical nonlinearities are just moderate. Quite
similar results independently have been obtained by
Pannell et al. [8] and in our laboratories [9] for disilanes
containing ferrocene as a donor and various organic
acceptor groups.
2. Results and discussion
2.1. Synthesis
The present paper describes a study on electron-
donorꢀ
acceptor interactions in 1-[dicarbonyl(h5-cyclo-
/
As shown in Table 1, electrolysis is excellently suitable
for the synthesis of disilanes containing the Fp sub-
stituent. High yields of the appropriate target molecules
3 and 4 were obtained using this simple method, which is
fast and easy to perform. As example the electrochemi-
cal preparation of 4 is outlined in Scheme 1. Compared
with the conventional multi-step chemical route de-
scribed in the literature for the synthesis of 4 [11b] the
procedure is simplified to a one pot reaction with an
overall yield of 62% based on ClSiMe2SiMe2Cl (com-
pare Scheme 1).
pentadienyl)iron]-2-[p-(2,2-dicyanoethenyl)phenyl]tetra-
methyldisilane (1) using UV absorption spectroscopy,
cyclic voltammetry and X-ray crystallography. Because
iron in 1 is bonded to silicon and, thus, directly
incorporated into the conjugation path, increased inter-
actions of the donor fragment with the polysilane chain
can be expected as compared with the corresponding
ferrocenyl derivative 1-ferrocenyl-2-[(2,2-dicyanoethe-
nyl)phenyl]tetramethyldisilane. The model compounds
[dicarbonyl(h5-cyclopentadienyl)iron]trimethylsilane
(2), [dicarbonyl(h5-cyclopentadienyl)iron]pentamethyl-
disilane (3), 1-[dicarbonyl(h5-cyclopentadienyl)iron]-2-
phenyltetramethyldisilane (4) and p-(2,2-dicyanoethe-
nyl)phenylpentamethyldisilane (5) are used to describe
the properties of the dicarbonylcyclopentadienyliron
(Fp) donor and the (2,2-dicyanoethenyl)phenyl acceptor
groups bonded to silicon in the absence of interaction.
Among many possible organometallic donors we
decided to use the Fp-group in this basic study mainly
The mechanism proposed by Ruiz et al. for the
electrochemical formation of the SiÃ/Fe bond is depicted
in Scheme 2. According to this mechanism primarily two
electron reduction of the Fp dimer takes place followed
by nucleophilic attack of the formed Fpꢃ species on the
chlorosilane.
Upon upscaling of the reaction in order to get
preparative amounts of products, however, we observed,
that far less than the stoichiometric amount of electrons
(2 F molꢃ1) is needed to achieve complete conversion.
Monitoring of the reaction by 29Si-NMR and IR
(disappearance of the band corresponding to the brid-
because of the stability of the FpÃ
/
Si-moiety and due to
its well established chemistry [10]. Fp-substituted short
chain polysilanes, however, previously have been shown
to be considerably photolabile [11], which strongly
impedes the investigation of the nonlinear optical
properties of 1 and related compounds addressed in
this study. Preliminary results mainly based on UV
absorption spectroscopy suggest that the photochemical
decay of 1 follows a similar pathway as already
described by Pannell for complexes FpSi2Me4C6H4X
where X is an electron withdrawing substituent [11c].
The synthesis of photolytically stable silicon-transition
metal based NLO chromophores containing alternative
organometallic donors currently is the matter of on-
going studies in our laboratories.
ging carbonyls in Fp2 at nCO
ꢁ
1784 cmꢃ1) showed, that
/
all of the starting material is already consumed after 5 h,
which means that only about 4% of the theoretically
necessary charge had to be passed through the solution.
Finally, we found that the reaction of chlorosilanes with
Fp2 in the presence of Mg in THFꢀBu4NBr proceeds
/
even without electricity, although the reaction rate is
very slow (several days to weeks, depending on the
chlorosilane). Obviously, the reaction is catalyzed by the
electrochemically induced activation of Mg. As a con-
sequence, a mechanism involving the formation of
Grignard type ‘FpÃ
/
Mg’ intermediates explains the

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/
Table 1
Electrochemical synthesis of Fp substituted silanes
Starting silane
Reduced species
Product
Number
Percentage isolated yield
66
51
Me3SiCl
Fp2
Fp2
PhBr
Fp2
FpSiMe3
2
3
Me3SiSiMe2Cl
ClSiMe2SiMe2Cl
ClSiMe2SiMe2Ph
FpSiMe2SiMe3
ClSiMe2SiMe2Ph
FpSiMe2SiMe2Ph
a
a
4
62
a
Based on ClSiMe2SiMe2Cl, ClSiMe2SiMe2Ph not isolated.
experimental results much better than controlled two
electron reduction of Fp2.
The difunctional derivative 1 could not be prepared
electrochemically. When Fp2 is electrolyzed together with
observed for FpÃ
/
Si-derivatives [14]. The geometry
around the silicon atoms is approximately tetrahedral.
The 2,2-(dicyanovinyl)phenyl group appears to be
nearly perfectly planar (compare e.g. the dihedral angle
ClSiMe2SiMe2Ã
/
C6H4Ã
/
CHÄ
/
C(CN)2, the activated dou-
of 1788 for C(32)Ã
exhibits an all-trans-array of the FeÃ
fragment and a roughly perpendicular arrangement of
the plane of the phenyl ring relative to the SiÃSi bond
with a torsional angle of 84.08 for Si(1)ÃSi(2)ÃC(30)Ã
C(31). The molecular structure adopted by compound 1
in the solid state, therefore, provides an excellent basis
for efficient through-bond interaction between the Fp-
and the 2,2-(dicyanovinyl)phenyl group via the central
/
C(33)Ã
/
C(40)Ã
/
C(41)). Compound 1
ble bond of the dicyanovinyl group reacts preferentially
and a complex mixture of products is obtained. There-
fore, 1 was made according to Scheme 3 starting from 1-
/
Si(1)ÃSi(2)ÃC(30)
/
/
/
chloro-2-(p-bromophenyl)tetramethyldisilane using
reaction sequence similar to the procedure already
applied successfully for the preparation of the ferroce-
a
/
/
/
nyldisilane FcÃ
/
SiMe2SiMe2Ã
/
PhÃ
/
CHÄ/C(CN)2 [8].
Moderately air-sensitive but extremely photolabile
yellow crystals of 1 are obtained in an overall yield of
42%. All products were characterized by standard
SiÃ/Si-bond, because optimal through-bond interaction
of functional groups via an array of s-bonds is only
feasible, when the corresponding orbitals and the s-
bonds have an all-trans relationship [15].
spectroscopic techniques (29Si-, 13C- and H-NMR, EI-
1
MS) and elemental analysis. The results (compare
Section 4) are in accordance with the proposed struc-
tures in all cases.
2.3. UV absorption spectra
2.2. X-ray structure of 1
UV absorption data of compound 1 are presented in
Table 3 together with data obtained for the reference
A drawing of the molecular structure of 1 with atom
labeling is depicted in Fig. 1. Selected bond lengths and
angles are summarized in Table 2.
compounds 2ꢀ7 which represent reasonable model
systems to estimate the properties of the donor and
the acceptor group in the absence of interaction.
/
Compound 1 crystallizes in the centrosymmetric point
group P21/n with four molecules in the unit cell. Most of
the bond lengths and bond angles are quite unexcep-
Ferrocenylpolysilanes of the general structure FcÃ
/
(Si)n Ã
/
A, where ferrocene as a donor is linked to the
(2,2-dicyanoethenyl)phenyl acceptor group, where
shown to exhibit only negligible intramolecular ground
tional. The observed SiÃ
larger than the common value of 234 pm for disilanes
bearing small substituents. The FeÃSi-distance of 232
pm appears to be significantly shorter than the value
predicted for a SiÃFe-single bond [13], which is usually
/Si-bond length is only slightly
state donorꢀ
/
acceptor interactions. Thus, the UVꢀvis
/
/
absorption spectrum of 1-ferrocenyl-2-[p-(2,2-dicya-
noethenyl)phenyl]tetramethyldisilane fulfills the classi-
cal expectation for nonconjugatively connected
/
Scheme 1. Electrochemical synthesis of compound 4.

C. Grogger et al. / Journal of Organometallic Chemistry 665 (2003) 186ꢀ
/195
189
Scheme 2. Mechanism for the electrochemical FeÃSi bond formation proposed by Ruiz et al. [12].
/
its most intense absorption, and (ii) the appearance of a
new absorption band at the long wavelength side of the
spectrum centered at 360 nm (Fig. 2B). These findings
strongly suggest, that 1 exhibits considerable ground
state electronic interaction between the Fp and the (2,2-
dicyanoethenyl)phenyl chromophores via the SiÃ
/Si-
bond, which is not present in the corresponding
ferrocenyl derivative or D/A substituted 1,2-diphenyldi-
silanes studied in the literature [6]. In order to consider
the possibility of intermolecular D/A interaction in
compound 1 we recorded the UV spectrum of a mixture
of 3 and 5. However, as the mixture comprises exactly
the same spectrum as 3 or 5 alone intermolecular
interaction is rather unlikely.
In view of the fact that intramolecular D/A-interac-
tions were also detected in donor-bridge-acceptor com-
pounds containing saturated hydrocarbon bridges [3]
and of the electron donor/acceptor character of the
substituents it seems logical to assign the 360 nm band
appearing in the absorption spectrum of 1 to a transition
with considerable charge-transfer character. Although a
tentative assignment cannot be given at present, in
particular without any fluorescence data, which are
not accessible due to the photolytic sensitivity of 1, we
are quite confident to observe direct ground state EDA
interaction in the absorption spectrum of the com-
pound. Further support for this assumption is given
by the cyclic voltammetry data discussed below.
Fig. 1. ORTEP plot of the molecular structure of 1 (hydrogens are
omitted for clarity).
chromophores, its absorption spectrum being identical
to the sum spectrum of the isolated donor and acceptor
model systems ferrocenylpentamethyldisilane and p-
(2,2-dicyanoethenyl)phenylpentamethyldisilane
2A).
(Fig.
This situation, however, is quite different for com-
pound 1 comprising two pronounced features in its
absorption spectrum: (i) a hypsochromic shift combined
with an intensity decrease of the band in the 320 nm
region, where the isolated acceptor chromophore shows
2.4. Cyclovoltammetric studies
Cyclic voltammetric data of compounds 1ꢀ
presented in Table 3. Within the scan rates of 10ꢀ
mV sꢃ1 all oxidation steps display electrochemical
/
7 are
/
200
Scheme 3. Synthesis of compound 1.

190
C. Grogger et al. / Journal of Organometallic Chemistry 665 (2003) 186ꢀ195
/
Table 2
Selected bond lengths, angles and dihedral angles for compound 1
irreversibility and can be related to the presence of the
FeÃSi-skeleton. Introduction of the Fp-group into
/
hexamethyldisilane gives rise to a tremendous decrease
of the first oxidation potential (compare the values of
Epa1 for 7 and 3 in Table 3). This finding is consistent
with He(I) and He(II) photoelectron spectroscopy
studies of compound 2 [16], showing the lowest valence
ionizations to occur from mainly metal based orbitals
and an unusually low value of the first ionization
potential (7.89 eV as compared with 8.39 eV in 7 [17]).
When going from 2 to 3 to 4 the observed cathodic shift
increases with extension of the conjugated system. The
120 mV anodic shift observed for the first oxidation
potential of 1 relative to 4 indicates the acceptor
properties of the 2,2-dicyano-ethenyl group as its
introduction leads to an increase of Epa.
Bond lengths
Si(1)Ã
FeÃSi(1)
Si(2)ÃC(30)
SiÃCmethyl (mean)
/
Si(2)
2.3543(9)
2.3256(8)
1.892(3)
1.884
/
/
/
Bond angles
FeÃSi(1)ÃSi(2)
Si(1)ÃSi(2)ÃC(30)
Cmethyl Cmethyl (mean)
SiÃ
SiÃSiÃCmethyl (mean)
Ccp Ccp (mean)
Cph Cph (mean)
/
/
113.34(3)
107.11(8)
106.89
/
/
Ã
/
/
/
/
109.63
Ccp
Cph
Ã
Ã
/
Ã
Ã
/
108.00
120.00
/
/
Dihedral angles
FeÃSi(1)ÃSi(2)Ã
Si(1)ÃSi(2)ÃC(30)Ã
C(32)ÃC(33)ÃC(40)Ã
C(33)ÃC(40)ÃC(41)Ã
/
/
/
C(30)
C(31)
C(41)
C(42)
ꢃ
/
176.90(8)
84.0(2)
/
/
/
/
/
/
178.0(3)
177.5(2)
/
/
/
Table 3
Electrochemical data and UV absorption maxima for compounds 1ꢀ
/7

C. Grogger et al. / Journal of Organometallic Chemistry 665 (2003) 186ꢀ
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191
Fig. 2. UV absorption spectra of 1-ferrocenyl-(2,2-dicyanoethenyl)phenylpentamethyldisilane (A) and compound 1 (B) compared with the
corresponding donor and acceptor model systems.
The irreversible wave at high cathodic potential (1, 5,
6) can be attributed to reduction processes of the
dicyanovinyl group [18]. Again, the extension of the
conjugated system is reflected by a shift of the redox
potential; increasing the conjugation from 6 to 5 to 1 the
reduction potential moves to more positive values. Thus,
1 exhibits a 80 mV anodic shift in the reduction potential
relative to 6. Intermolecular D/A interaction in 1 is also
unlikely on the basis of the electrochemical data, as a
mixture of 3 and 5 yielded exactly the same values for
Epa1 and Epc as 3 or 5 alone.
4. Experimental
4.1. 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. The water content
was checked by Karl Fischer titration to be below 20
ppm. Bu4NBr and Bu4NBF4 (Fluka ‘puriss. electro-
chem. grade’) was dried in vacuum at 50 8C for 2 days.
Me3SiCl and chlorobenzene were distilled prior to use.
Malononitrile and [(h5-C5H5)Fe(CO)2]2 were used as
purchased without further purification. N,N-Dimethyl-
˚
3. Conclusions
formamide was allowed to stand on 4 A molecular sieve
and distilled from CaH2. [(h5-C5H5)Fe(CO)2]Na [19], p-
(2,2-dicyanoethenyl)phenyl]pentamethyldisilane [20], 1-
chloro-2-(p-bromophenyl)tetramethyldisilane [6a] and
the starting silicon compounds ClMe2SiSiMe3 and
ClMe2SiSiMe2Cl [21] were synthesized as previously
The all-trans relationship along the FeÃ
/
SiÃ
/
SiÃ
/
C
fragment of compound 1 in the solid state provides the
basis for optimal through-bond interaction between the
Fp-donor and the 2,2-(dicyanovinyl)phenyl acceptor via
the central SiÃ
/
Si-bond. The UV absorption and cyclic
reported. UVꢀ
/
vis absorption spectra were recorded on
voltammetry data support this assumption for solutions
and indicate remarkable intramolecular electronic cou-
pling within the molecular framework of compound 1.
a PerkinꢀElmer Lambda 35 spectrometer in cyclohex-
/
ane solution. NMR spectra were recorded on a Bruker
300-MSL spectrometer; 1H-NMR: 300.13 MHz; 13C-
NMR: 75.47 MHz; 29Si-NMR: 59.62 MHz. Mass
They show a distinct decrease of the HOMOꢀ
/LUMO
gap upon introduction of the Fp group (ꢃEpcꢂ
/
/
Epa1
ꢁ
/
spectra were run either on a HP 5971/A/5890-II GCꢀ
/
2.96 V in 5 and 2.26 V in 1), which is consistent with the
30 nm bathochromic shift of the first UV absorption
band.
MS coupling (HP 1 capillary column, length 25 m,
diameter 0.2 mm, 0.33 mm polydimethylsiloxane) or on a
Kratos Profile mass spectrometer equipped with a solids

192
C. Grogger et al. / Journal of Organometallic Chemistry 665 (2003) 186ꢀ195
/
probe inlet. Elemental analyses were carried out on a
Hanau VARIO ELEMENTAR EL apparatus.
4.5. [Dicarbonyl(h5-cydopentadienyl)iron]-
pentamethyldisilane (3)
Me3SiSiMe2Cl (1.8 g, 10.8 mmol) and 1.9 g (5.4
mmol) of [(h5-C5H5)Fe(CO)2]2 were electrolyzed for 5 h
at 15 mA. Yield 1.7 g (51%). 29Si-NMR (THF/ext. lock
4.2. Cyclic voltammetry
D2O, ext. TMS, ppm): dꢁ
literature [24].
/
16.9, ꢃ11.3; consistent with
/
All voltammograms were run under an inert atmo-
sphere at room temperature with a Wenking LB 95M
potentiostat/Wenking POS 73 scan generator and re-
corded with a Kipp and Zonen BD8 flatbed recorder.
The three electrode system consisted of a platinum disk
microelectrode (500 mm), a Pt counter electrode and a
Ag/AgCl reference electrode. 25 ml of a 0.1 M solution
of Bu4NBF4 in CH2Cl2 were introduced into the cell and
the silane was added in a concentration of 10ꢃ3 M.
Ferrocene was added at the end of each experiment and
used as an internal standard. Thus, all potentials are
4.6. 1-[Dicarbonyl(h5-cyclopentadienyliron]-2-
phenyltetramethyldisilane (4)
ClMe2SiSiMe2Cl (2.5 g, 13.5 mmol) and 1.5 g (13.5
mmol) of chlorobenzene were electrolyzed at 25 mA.
After 24 h all of the chlorobenzene was consumed
(reaction control by GCꢀMS) and 2.4 g (6.8 mmol) of
/
[(h5-C5H5)Fe(CO)2]2 were added to the solution. After 5
h of further electrolysis the reaction was finished. Yield:
3.1 g (62%). Si-NMR (THF/ext. lock D2O, ext. TMS,
quoted relative to the ferroceneꢀ/ferrocenium redox
couple [22].
ppm): dꢁ
/
16.7, ꢃ15.2; consistent with literature [11b].
/
4.7. 1-[Dicarbonyl(cyclopentadienyl)iron]-2-
(p-bromophenyl)tetramethyldisilane
4.3. General procedure for electrolysis
ClSiMe2SiMe2(p-BrC6H4) (3.45 g, 11.2 mmol) were
dissolved in 50 ml of pentane and added dropwise to 200
ml of a THF solution of [(h5-C5H5)Fe(CO)2]Na (pre-
pared from 2.0 g (5.6 mmol) of [(h5-C5H5)Fe(CO)2]2,
0.34 g (14.8 mmol) of Na and 40 g of Hg) over a period
of 30 min at 0 8C. The reaction mixture was then
allowed to stir at room temperature for 2 h before the
solvents were stripped off in vacuum. After addition of
pentane the solution was filtered, concentrated and
subjected to column chromatography on a silica gel
column. Elution with toluene yielded an orange band,
which upon collection, removal of the solvent and
recrystallization from pentane gave 4.32 g (86%) of the
orange crystalline title complex.
Constant current supply was afforded by a Wenking
STP 84 potentiostat. Electrolysis was carried out in an
undivided cell equipped with a magnesium anode in the
center and a cylindrical cathode, made of stainless steel,
around it. Bu4NBr was dissolved in a concentration of
0.02 mol lꢃ1 in THF, and 50 ml of this solution were
introduced into the cell under a dry nitrogen atmo-
sphere. After addition of the silane and the
dicarbonyl(h5-cyclopentadienyl)iron dimer (Fp2), elec-
trolysis was carried out at a constant current density of
1 mA cmꢃ2. The reaction was monitored by 29Si-NMR
and IR (disappearance of the band corresponding to the
bridging carbonyls in Fp2 at nCO
ꢁ
1784 cmꢃ1). After
/
removal of all volatile compounds from the resulting
solution at reduced pressure, 60 ml of anhydrous
pentane were added to the dark red residue. The
precipitated salts were filtered off and washed with
pentane twice. Subsequently, the pentane was evapo-
rated and the crude product solved in 5 ml of toluene.
After elution with toluene on a silica gel column and
removal of excess toluene the pure products are
obtained.
Melting point (m.p.): 77ꢀ
45.73; H, 4.72. Calc. for C17H21BrFeO2Si2: C, 45.45; H,
4.71%. IR (heptane): nCO
1999, 1948 cmꢃ1 29Si-NMR
(C6D6, ext. TMS, ppm): 16.14 (FpÃSi(CH3)2); ꢃ14.83
(p-BrC6H4Ã
Si(CH3)2). 1H-NMR (C6D6, ext. TMS,
ppm, rel. Int.): 7.38ꢀ7.14 (AA?BB?, 4H, C6H4); 3.94 (s,
5H, C5H5); 0.47 (s, 6H, p-BrC6H4ÃSi(CH3)2); 0.36 (s,
6H, FpÃ
Si(CH3)2). 13C-NMR (C6D6, ext. TMS, ppm):
216.05 (CO); 140.80, 136.10, 131.75, 123.94 (C6H4);
83.44 (C5H5); 3.94 (FpÃSi(CH3)2); ꢃ2.19 (p-BrC6H4Ã
Si(CH3)2). MS (m/e (rel. Int.)): 448 [17, Mꢂ]; 420 [7,
Mꢂꢃ Mꢂꢃ
CO]; 392 [9, 2CO]; 313 (18,
CpFeSi2(CH3)4C6H4ꢂ); 271 (74, BrC6H4Si2(CH3)4ꢂ);
235 (100, 213 (27,
Cp(CO)2FeSi(CH3)2ꢂ);
/
78 8C. Anal. Found: C,
ꢁ
/
.
/
/
/
/
/
/
/
/
/
4.4. [Dicarbonyl(h5-cyclopentadienyl)iron]-
trimethylsilane (2) [12]
/
/
Me3SiCl (2.2 g, 20 mmol) and 3.5 g (10 mmol) of [(h5-
C5H5)Fe(CO)2]2 were electrolyzed for 5 h at 15 mA.
Yield 3.3 g (66%). 29Si-NMR (THF/ext. lock D2O, ext.
BrC6H4Si(CH3)2ꢂ); 207 (15, Cp(CO)FeSi(CH3)2ꢂ); 193
(62, C6H4Si2(CH3)4ꢂ); 179 (16, CpFeSi(CH3)2ꢂ); 177 (23,
Cp(CO)FeSiꢂ); 149 (21, CpFeSiꢂ); 121 (25, CpFeꢂ);
93 (17, CpSiꢂ); 73 (31, (CH3)3Siꢂ); 28 (9, COꢂ).
TMS, ppm): dꢁ41.6; consistent with literature [23].
/

C. Grogger et al. / Journal of Organometallic Chemistry 665 (2003) 186ꢀ
/195
193
4.8. 1-[Dicarbonyl(cyclopentadienyl)iron]-2-(p-
formylphenyl)tetramethyldisilane
(s, 6H, p-OHCC6H4Ã
/
Si(CH3)2); 0.38 (s, 6H, FpÃ
/
Si(CH3)2). 13C-NMR (C6D6, ext. TMS, ppm): 215.99
(CO); 150.61, 137.28, 134.83, 129.16 (C6H4); 83.41
(C5H5); 3.93 (FpÃ
Si(CH3)2). MS (m/e (rel. Int.)): 398 [44, Mꢂ]; 342 [12,
Mꢂꢃ2CO]; 313(11, CpFeSi2(CH3)4C6H4ꢂ); 235 (49,
Cp(CO)2FeSi(CH3)2ꢂ);
221 (100, OHCC6H4Si2-
(CH3)4ꢂ); 207 (12, Cp(CO)FeSi(CH3)2ꢂ); 193 (16,
C6H5Si2(CH3)4ꢂ); 186 (23, CpFeCpꢂ); 179 (12,
CpFeSi(CH3)2ꢂ); 163 (39, OHCC6H4Si(CH3)2ꢂ); 149
(24, CpFeSiꢂ); 121 (32, CpFeꢂ); 93 (14, CpSiꢂ); 73
(22, (CH3)3Siꢂ); 28 (31, COꢂ).
/
Si(CH3)2); ꢃ
/
2.37 (p-OHCC6H4Ã
/
To 120 ml of a cooled (ꢃ78 8C) THF solution of
/
4.32 g (9.6 mmol) of (h5-C5H5)Fe(CO)2SiMe2SiMe2(p-
BrC6H4) was added slowly a cyclohexane solution of 9.6
mmol of n-butyllithium. The mixture was stirred for
another 5 min followed by addition of 3.0 ml (38.9
mmol) of dry DMF. The reaction mixture was then
stirred overnight at room temperature and aqueously
worked up with saturated NH4Cl solution. After
extraction with diethylether the combined organic layers
were dried over Na2SO4 and concentrated. Column
chromatography (silica gel) with toluene as the mobile
/
4.9. 1-[Dicarbonyl(cyclopentadienyl)iron]-2-[p-(2,2-
dicyanoethenyl)phenyl]-tetramethyldisilane (1)
phase yielded 3.10 g (81%) of a yellowꢀ
/
brown solid.
M.p. (dec.): 39 8C. Anal. Found: C, 54.26; H, 5.55.
Calc. for C18H22FeO3Si2: C, 54.27; H, 5.57%. IR
To a solution of 3.10 g (7.8 mmol) of (h5-
C5H5)Fe(CO)2SiMe2SiMe2(p-OHCC6H4) in 100 ml of
diethylether was added 0.53 g (8.0 mmol) of solid
malonodinitrile and one drop of piperidine. In order
to guarantee total conversion the mixture was allowed
to stir overnight at room temperature (DC monitoring
recommended). The solvent was removed under reduced
pressure and the bright yellow residue purified by
column chromatography (silica gel) with toluene as the
mobile phase. Subsequent recrystallization from pen-
(heptane): nCO
ꢁ
/
2000, 1949 cmꢃ1, nCHO
ꢁ
/
1711 cmꢃ1
.
29Si-NMR (C6D6, ext. TMS, ppm): 16.40 (FpÃ
/
1
Si(CH3)2); ꢃ
(C6D6, ext. TMS, ppm, rel. Int.): 9.71 (s, 1H, CHO);
7.61ꢀ7.42 (AA?BB?, 4H, C6H4); 3.93 (s, 5H, C5H5); 0.47
/
14.52 (p-OHCC6H4Ã
/
Si(CH3)2). H-NMR
/
Table 4
Crystallographic data for compound 1
tane at ꢃ
crystalline title compound.
M.p.: 128ꢀ130 8C. Anal. Found: C, 56.81; H, 4.92.
Calc. for C21H22N2FeO2Si2: C, 56.50; H, 4.97%. IR
(Nujol): nCN
2228 cmꢃ1, nCO 1983, 1933 cmꢃ1 29Si-
NMR (C6D6, ext. TMS, ppm): 16.58 (FpÃSi(CH3)2);
14.06 (p-(NC)2CÄCHC6H4Ã
Si(CH3)2). 1H-NMR
(C6D6, ext. TMS, ppm, rel. Int.): 7.32ꢀ7.25 (AA?BB?,
4H, C6H4); 6.48 (s, 1H, CHÄC(CN)2); 3.95 (s, 5H,
C5H5); 0.43 (s, 6H, p-(NC)2CÄCHC6H4ÃSi(CH3)2);
0.36 (s, 6H, FpÃ
Si(CH3)2). 13C-NMR (C6D6, ext.
TMS, ppm): 215.86 (CO); 159.25 (CHÄC(CN)2);
151.70, 134.96, 131.30, 129.86 (C6H4); 114.59, 113.62
(CN); 83.52 (C5H5); 82.93 (CHÄC(CN)2); 3.94 (FpÃ
Si(CH3)2); ꢃ2.47 (p-(NC)2CÄCHC6H4ÃSi(CH3)2). MS
(m/e (rel. Int.)): 446 [35, Mꢂ]; 418 [15, Mꢂꢃ
CO]; 390
[23, Mꢂꢃ CHC6H4Si2(CH3)4ꢂ);
2CO]; 269 (49, (NC)2CÄ
/
30 8C gave 2.37 g (68%) of the yellow
Crystal parameters
Empirical formula
Formula weight
Crystal system
Space group
C21H22FeN2O2Si2
446.44
/
Monoclinic
P21/n
ꢁ
/
ꢁ
/
.
/
˚
a (A)
7.0656(1)
29.2685(1)
10.8184(2)
90
˚
ꢃ
/
/
/
b (A)
˚
c (A)
/
a (8)
b (8)
g (8)
/
98.619(1)
90
/
/
3
/
˚
Volume (A )
2211.97(5)
4
0.808
/
Z
Absorption coefficient (mmꢃ1
F(000)
)
928
/
/
Data collection
uRange (8)
Limiting indices
/
/
/
1.39ꢀ
8B
l B13
4513
/
26.38
/
ꢃ
/
/
h B8, 0B
/
/
k B
/
36, 0B
/
/
/
/
235 (100, Cp(CO)2FeSi(CH3)2ꢂ); 211 (21, (NC)2CÄ
/
Reflections collected
CHC6H4Si(CH3)2ꢂ); 207 (10, Cp(CO)FeSi(CH3)2ꢂ); 186
(28, CpFeCpꢂ); 179 (13, CpFeSi(CH3)2ꢂ); 121 (29,
CpFeꢂ); 93 (13, CpSiꢂ); 73 (24, (CH3)3Siꢂ); 28 (28,
COꢂ).
Independent reflections
4512 [Rint
99.6
ꢁ/0.0476]
Completeness to uꢁ
/
26.388 (%)
Max and min transmission
0.9092 and 0.7707
Refinement
Parameters
254
Final R indices
R indices (all data)
Weighting scheme
R1ꢁ
R1ꢁ
1/s2F2oꢂ
Pꢁ
(F2oꢂ
1.270
0.0022(3)
/
0.0414, wR2ꢁ
/
0.0893
/0.0494, wR2ꢁ
/
0.1026
2.28P;
4.10. X-ray crystallography
/
(0.0190P)2ꢂ
2F2c)/3
/
/
/
Suitable crystals of 1 were grown by slow diffusion of
pentane into a saturated solution of 1 in diethylether. A
Goodness-of-fit on F2
Extinction coefficient
yellow crystal of the dimensions 0.34ꢄ
was mounted on a glass fiber. Diffraction data were
/
0.28ꢄ0.12 mm
/
Max and min heights in final differ- 0.357 and ꢃ0.313
/
ꢃ3
˚
ence Fourier synthesis (e A
)

194
C. Grogger et al. / Journal of Organometallic Chemistry 665 (2003) 186ꢀ195
/
(c) A.W.J.D. Dekkers, J.W. Verhoven, W.N. Speckamp, Tetra-
hedron 29 (1973) 1691.
collected on a Siemens SMART CCD diffractometer at
293 K using graphite monochromated Moꢀ
/
Ka radiation
[5] S. Zhang, M.J. Lang, S. Goodman, C. Durnell, V. Fidlar, G.R.
Fleming, N. Yang, J. Am. Chem. Soc. 118 (1996) 9042.
[6] (a) G. Mignani, M. Barzoukas, J. Zyss, G. Soula, F. Balegroune,
D. Grandjean, D. Josse, Organometallics 10 (1991) 3660;
˚
0.71073 A), a nominal crystal-to-detector distance
(lꢁ
/
of 4.40 cm and 0.38 v-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 correction (SADABS
[25]) was applied. The structure was solved by direct
methods (SHELXS86 [26]). The structure refinement was
performed in a full-matrix least-squares method against
(b) G. Mignani, A. Kramer, G. Puccetti, I. Ledoux, G. Soula, J.
¨
Zyss, R. Meyrueix, Organometallics 9 (1990) 2640;
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¨
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F2
(SHELXL-93 [27]). All non-hydrogen atoms were
(e) D. Hissink, J. Brouwer, R. Flipse, G. Hadziioannou, Polym.
Pepr. 32 (1991) 136;
refined anisotropically, all hydrogen atoms were in-
serted in calculated positions.
(f) D. Hissink, H.J. Bolink, J.W. Eshuis, G.G. Malliaras, G.
Hadziioannou, Polym. Pepr. 34 (1993) 721.
[7] (a) R.D. Miller, J. Michl, Chem. Rev. 89 (1989) 1359;
(b) R. West, in: G. Wilkinson, F.G.A. Stone, E.W. Abel (Eds.),
Comparative Organometallic Chemistry II, vol. 2, Pergamon
Press, 1995, p. 77.
5. Supplementary material
[8] H.K. Sharma, K.H. Pannell, I. Ledoux, J. Zyss, A. Ceccanti, P.
Zanello, Organometallics 19 (2000) 770.
[9] C. Grogger, H. Siegl, H. Rautz, H. Stuger, in: N. Auner, J. Weis
¨
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 181002, for compound 1.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
(Eds.), Organosilicon Chemistry IV, Verlag Chemie, Weinheim,
2000, p. 384.
[10] (a) K.H. Pannell, H.K. Sharma, Chem. Rev. 95 (1995)
Cambridge, CB2 1EZ, UK (Fax: ꢂ44-1223-336033; e-
mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
/
1351;
(b) W. Malisch, H. Jehle, S. Moller, C.S. Moller, W. Adam, Eur.
¨ ¨
J. Inorg. Chem. (1998) 1585;
(c) W. Ries, W. Malisch, J. Organomet. Chem. 241 (1983)
321;
(d) W. Malisch, H. Jehle, M. Lager, M. Nieger, in: N. Auner, J.
Weis (Eds.), Organosilicon Chemistry IV, from Molecules to
Materials, Wiley-VCH, Weinheim, 2000, p. 437;
Acknowledgements
(e) W. Malisch, S. Moller, O. Fey, H.-U. Wekel, R. Pikl, U.
¨
We wish to thank the Fonds zur Forderung der
¨
Posset, W. Kiefer, J. Organomet. Chem. 507 (1996) 117.
[11] (a) K.H. Pannell, J.C. Cervantes, C. Hernandez, J. Cassias, S.
Vincenti, Organometallics 5 (1986) 1086;
wissenschaftlichen Forschung (Wien, Austria) for finan-
cial support and the Wacker Chemie GMBH (Burghau-
sen, Germany) for the donation of silane precursors.
(b) K.H. Pannell, J.M. Rozell, C. Hernandez, J. Am. Chem. Soc.
111 (1989) 4482;
(c) K.L. Jones, K.H. Pannell, J. Am. Chem. Soc. 115 (1993)
11336.
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