Trimethylsilyl-functionalised bis(indenyl)iron(II) complexes: Solid-state structure of [η5-1,3-(SiMe3) 2C9H5]2Fe

Article abstract of DOI:10.1016/j.jorganchem.2003.11.045

The synthesis of the bis(η⁵-indenyl)iron sandwich complexes (η⁵-1-SiMe₃-C₉ H₆)₂Fe (3a), (η⁵-2-SiMe₃ -C₉H₆)₂Fe (3b), [η⁵-1,2 -(SiMe₃)₂C₉H₅]₂Fe (4a) and [η⁵-1,3-(SiMe₃)₂ C₉H₅]₂Fe (4b), by the reaction of the appropriate lithium indenide salts [prepared from 1-SiMe₃ -C₉H₇ (2a), 2-SiMe₃-C₉ H₇ (2b), 1,2-(SiMe₃)₂C₉ H₆ (2c) or 1,3-(SiMe₃)₂C₉ H₆ (2d)] with ferrous chloride (1) in a 2:1 molar ratio is discussed. The solid-state structure of 4b was determined by single-crystal X-ray diffractometry. Complex 4b exists in a gauche conformation, showing that the indenyl ligands are sterically imposed by the bulk of the Me₃Si substituents. The average Fe-C distance is 2.091(3) A?. Cyclovoltammetric studies indicate that 3 and 4 are redox-active with one-electron oxidations [E^1/2= -270 to -360 mV versus Fc/Fc⁺, Fc=(η⁵ -C₅H₅)₂Fe].

Full text of DOI:10.1016/j.jorganchem.2003.11.045

Journal of Organometallic Chemistry 689 (2004) 1139–1144
www.elsevier.com/locate/jorganchem
Trimethylsilyl-functionalised bis(indenyl)iron(II) complexes:
solid-state structure of [g5-1,3-(SiMe3)2C9H5]2Fe
a
Glen M. Fern , Sami Klaib , Owen J. Curnow , Heinrich Lang
b
b
*
a
Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
Lehrstuhl Anorganische Chemie, Institut f€ur Chemie, Fakult€at f€ur Naturwissenschaften, Technische Universit€at Chemnitz,
Straße der Nationen 62, D-09111 Chemnitz, Germany
b
Received 1 August 2003; accepted 24 November 2003
Abstract
The synthesis of the bis(g5-indenyl)iron sandwich complexes (g5-1-SiMe3–C9H6)2Fe (3a), (g5-2-SiMe3–C9H6)2Fe (3b), [g5-1,2-
(SiMe3)2C9H5]2Fe (4a) and [g5-1,3-(SiMe3)2C9H5]2Fe (4b), by the reaction of the appropriate lithium indenide salts [prepared from
1-SiMe3–C9H7 (2a), 2-SiMe3–C9H7 (2b), 1,2-(SiMe3)2C9H6 (2c) or 1,3-(SiMe3)2C9H6 (2d)] with ferrous chloride (1) in a 2:1 molar
ratio is discussed. The solid-state structure of 4b was determined by single-crystal X-ray diffractometry. Complex 4b exists in a
gauche conformation, showing that the indenyl ligands are sterically imposed by the bulk of the Me3Si substituents. The average Fe–
1=2
ꢀ
C distance is 2.091(3) A. Cyclovoltammetric studies indicate that 3 and 4 are redox-active with one-electron oxidations [E ¼ ꢀ270
to )360 mV versus Fc/Fcþ, Fc ¼ (g5-C5H5)2Fe].
ꢀ 2003 Elsevier B.V. All rights reserved.
Keywords: Indenyl; Iron; Sandwich; X-ray structure
1. Introduction
attributed to, for example, the enhanced reactivity of the
transition metal indenyl complexes, when compared
with their cyclopentadienyl analogues [1–4]. This can be
explained by the relative ease of the slippage of the in-
denyl building block from g5 ! g3 ! g5 [4c].
In this paper, we report on the synthesis and char-
acterisation of a variety of Me3Si-substituted bis(inde-
nyl)iron sandwich complexes.
Cyclopentadienyl and indenyl ligands are two of the
most commonly used classes of building blocks in or-
ganometallic chemistry, because they are straightfor-
ward to tune and can also be readily functionalised
[1–4]. Depending on the nature of the substituents at the
p-annulene, complexes containing such ligands are of
particular interest, for example, as catalytic species in
homogeneous catalysis [1], and in the preparation of
multimetallic complexes in which the metal atoms may
exhibit synergistic and co-operative effects. While the
coordination chemistry of cyclopentadienyls with tran-
sition metals is well studied, investigations of their in-
denyl counterparts are not as extensive, which is
2. Results and discussion
The synthesis of the Me3Si-substituted indenes 1-
SiMe3–C9H7 (2a), 2-SiMe3–C9H7 (2b), 1,2-(SiMe3)2
C9H6 (2c) and 1,3-(SiMe3)2C9H6 (2d) have been re-
ported [5]. These species can easily be lithiated by the
addition of equimolar amounts of n-BuLi at low-tem-
perature in tetrahydrofuran. The lithium salts thus ob-
tained can be reacted further with ferrous chloride (1) to
produce the bis(indenyl)iron complexes 3 and 4 (Eq. 1)
(Table 1).
* Corresponding author.
E-mail addresses: o.curnow@chem.canterbury.ac.nz (O.J. Cur-
now), heinrich.lang@chemie.tu-chemnitz.de (H. Lang).
0022-328X/$ - see front matter ꢀ 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.11.045

1140
G.M. Fern et al. / Journal of Organometallic Chemistry 689 (2004) 1139–1144
1:1.2, indicating again that two isomers are present (vide
supra).
In the 13C{1H} NMR spectra of 3 and 4, well-re-
R
R´
R
solved signals are found, of which the signals for the
cyclopentadienyl ring carbon atoms appear at higher
field (62–90 ppm) than the ones for the benzo group
(124–131 ppm). The assignment of the Me3Si resonance
signals are readily made based on their chemical shift
(0.3–1.5 ppm).
R´´
1. nBuLi
Fe
R´
2. FeCl2 (1)
ð1Þ
R´´
R´´
´R
Reversible one-electron oxidations were observed for
each of the bis(indenyl)iron complexes using cyclic vol-
tammetry, with dichloromethane as a solvent (Fig. 1).
R
2a - 2d
3, 4
Filtration through Celite and removal of all volatile
materials provides 3 and 4 in yields of 35–75% (Table 1)
as green (3a), green-blue (3b) oils, or green solids (4a and
4b), which are only stable under inert gas atmosphere.
Compounds 3 and 4 have been characterised by IR-,
UV–Vis-, 1H- and 13C{1H} NMR spectroscopy, mi-
croanalysis, cyclovoltammetry and mass spectrometry
[6]. The X-ray structure analysis of 4b is also reported.
The infrared spectra of 3 and 4 are not very enlight-
ening, since only distinctive vibrations for the C@C, CH
and C–Si entities are found. More informative is NMR
1
spectroscopy. Thus, in the H NMR spectra of 3 and 4,
typical resonance signals for the Me3Si groups are ob-
served between 0.0 and 0.5 ppm. The indenyl ring pro-
tons appear in the range of 3.2–8.0 ppm of which the
benzo protons resonate at somewhat lower field than the
respective cyclopentadienyl ring protons. Nevertheless,
the hydrogen atoms of the latter ring show a very
characteristic pattern. In 3a, two sets of two resonance
signals are observed at 3.24 and 4.68 ppm as well as 3.99
and 4.94 ppm, which can be assigned to the protons in
positions 2 and 3 (high-field and low-field, respectively).
This indicates that 3a is obtained as a mixture of two
isomers, the rac and meso diastereomers, in a 1.6:1 ratio.
This is also evidenced by 13C{1H} NMR spectroscopic
studies, since two sets of resonance signals are found.
For 3b, due to the symmetric arrangement of the Me3Si
group in position 2, only one signal for the cyclopen-
tadienyl ring protons is observed at 3.86 ppm. The
proton present in 4b shows its resonance signal at 4.46
ppm, whereas in 4a, for the proton in position 3, two
signals (3.75 and 5.1 ppm) are observed in the ratio of
Fig. 1. Cyclic voltammogram of 3b in dichloromethane, 0.1 M
[nBu4N]PF6, scan rate ¼ 200 mV sꢀ1; potential in V vs. FcH/FcHþ
[Fc ¼ [g5-C5H5]2Fe].
Table 1
Synthesis of complexes 3 and 4
Compound
R
R0
R00
Yield
(%)a
3a
3b
4a
4b
SiMe3
H
H
H
74
63
35
39
SiMe3
SiMe3
H
H
SiMe3
SiMe3
H
SiMe3
Fig. 2. XP-plot (drawing at 50% probability level) of the molecular
structure and adopted atom-numbering scheme of 4b.
a Based on 1.

G.M. Fern et al. / Journal of Organometallic Chemistry 689 (2004) 1139–1144
1141
Table 2
a
ꢀ
Selected interatomic distances (A) and angles (ꢁ) of complex 4b
ꢀ
Bond distances (A)
Fe–C(1)
Fe–C(10)
Fe–C(2)
Fe–C(20)
Fe–C(3)
Fe–C(30)
Fe–C(8)
Fe–C(80)
Fe–C(9)
Fe–C(90)
Si(1)–C(1)
Si(10)–C(10)
Si(2)–C(3)
Si(20)–C(30)
2.075(3)
2.074(3)
2.043(3)
2.045(3)
2.080(3)
2.091(3)
2.130(3)
2.123(3)
2.125(3)
2.121(3)
1.859(4)
1.863(4)
1.867(4)
1.860(4)
C(1)–C(2)
C(1)–C(20)
C(2)–C(3)
C(20)–C(30)
C(3)–C(9)
C(30)–C(90)
C(8)–C(9)
C(80)–C(90)
C(1)–C(8)
C(10)–C(80)
Ind–Feb
1.435(5)
1.431(5)
1.424(5)
1.436(5)
1.458(5)
1.439(5)
1.434(5)
1.438(5)
1.449(5)
1.462(5)
1.695
Fe–Ind0
1.694
Bond angles (ꢁ)
Si(1)–C(1)–C(2)
Si(10)–C(10)–C(20)
Si(1)–C(1)–C(8)
Si(10)–C(10)–C(80)
Si(2)–C(3)–C(2)
Si(20)–C(30)–C(20)
Si(2)–C(3)–C(9)
Si(20)–C(30)–C(90)
Si(1)–C(1)–Fe
125.1(2)
C(1)–C(2)–C(3)
C(10)–C(20)–C(30)
C(2)–C(3)–C(9)
C(20)–C(30)–C(90)
C(9)–C(8)–C(1)
C(90)–C(80)–C(10)
C(8)–C(1)–C(2)
C(80)–C(10)–C(20)
Ind–Fe–Ind0b
112.2(3)
126.3(3)
126.7(3)
126.3(3)
125.9(3)
125.5(3)
126.1(3)
127.9(3)
139.2(2)
138.3(2)
139.3(2)
136.2(2)
112.3(3)
105.0(3)
105.0(3)
108.9(3)
108.4(3)
105.1(3)
104.7(3)
178.0
Si(10)–C(10-Fe
Si(2)–C(3)–Fe
Si(20)–C(30)–Fe
a The estimated standard deviations of the last significant digits are shown in parantheses.
b Midpoint of the cyclopentadienyl groups of the indenyl ligand.
The potentials [versus Fc/Fcþ, Fc ¼ (g5-C5H5)2Fe] for
Table 3
Crystal data and structure refinement parameters for complex 4b
these oxidations are E1=2 ¼ ꢀ275 mV (E ¼ 125 mV, 3a),
E1=2 ¼ ꢀ270 mV (DE ¼ 145 mV, 3b), E1=2 ¼ ꢀ291 mV
(DE ¼ 112 mV, 4a) and E1=2 ¼ ꢀ358 mV (DE ¼ 70 mV,
4b). These data indicate that the ease of oxidation in-
creases when one goes from ferrocene to bis(inde-
nyl)iron sandwich complexes {e.g. (g5-C5H5)2Fe: 0.0 V;
[7] (g5-C9H7)2Fe, )278 mV [8]}.
Formula weight
Chemical formula
Crystal system
Space group
574.88
C
30H46FeSi4
Monoclinic
P21=c
ꢀ
a (A)
19.56(1)
10.238(5)
18.634(9)
3283(3)
118.361(7)
1.163
ꢀ
b (A)
ꢀ
c (A)
3
ꢀ
V (A )
b (ꢁ)
High-resolution mass spectrometric studies confirm
the composition of 3 and 4.
Single crystals of 4b could be obtained by slowly
cooling a petroleum solution containing 4b to )20 ꢁC.
The molecular structure of 4b is depicted in Fig. 2. Se-
dcalc (g cmꢀ3
F ð000Þ
)
1232
Crystal dimensions (mm3)
0.43 · 0.30 · 0.03
4
0.71073
Z
ꢀ
Radiation, l (A)
ꢀ
lected interatomic bond distances (A) and angles (ꢁ) are
listed in Table 2 and crystal data and structure refine-
ment parameters are given in Table 3 (Section 4).
Maximum and minimum transmission
Total reflections
Unique reflections
1.000000 and 0.901477
41 643
6712
Compound 4b crystallises in the monoclinic space
group P21/c. The molecular structure of 4b shows the
iron atom Fe coordinated linearly by the centroids of
the indenyl five-membered rings (Fig. 2). The two in-
denyl ligands are orientated almost parallel to each
other (5.8ꢁ); the Ind–Fe–Ind0 angle (Ind ¼ centroid of
the five-membered ring) is 178.0ꢁ. Due to the steric
congestion of the four Me3Si units, the indenyl rings are
twisted by 94.3ꢁ [C(1)–Ind–Ind0–C(10); C(3)–Ind–Ind0–
C(30)] with respect to each other to give a gauche
conformation. The average bond distance of the 5-
Observed reflections [I P 2rðIÞ]
3897
316
Refined parameters
b
R1a, wR2 [I P 2rðIÞ]
0.0387, 0.1107
0.0936, 0.1515
0.0921
b
R1a, wR2 (all data)
Rint
Maximum and minimum peak (e A
ꢀ3
ꢀ
)
0.311 and )0.285
0.580
Goodness-of-fit on F 2
h
i.
P
2
P ¼ ½Fo2 þ 2Fc2ꢁ=3c; S ¼
wðFo2 ꢀ Fc2Þ
ðn ꢀ pÞ1=2; n is number
.h
i
P
2
2
of reflections, p is parameters used; w ¼ 1
ðFo2Þ þ ðaPÞ þ bP .
P
P
a R1 ¼ ½ ðjjFoj ꢀ jFcj= jFojÞꢁ:
h
.
i
1=2
P
P
2
b wR2 ¼
ðwðFo2 ꢀ Fc2Þ Þ
ðwFo4Þ
:

1142
G.M. Fern et al. / Journal of Organometallic Chemistry 689 (2004) 1139–1144
membered ring centroids (Ind) to the iron atom is 1.695
ꢀ
with a platinum disc electrode (0.125 cm2, EDI 101 T,
Radiometer), a platinum wire counter electrode and a
saturated calomel electrode filled with methylenedi-
chloride as solvent of the electrolyte solution at 25 ꢁC,
using a standard three-electrode cell in a Radiometer
Copenhagen DEA 101 Digital Electrochemical Analy-
ser with a IMT 102 (Radiometer) Electrochemical In-
terface. Experiments were run with VOLTALAB-3.1
software (V.2.0) at a scan rate dE=dt ¼ 200 mV sꢀ1. All
potentials were referenced to the ferrocene/ferrocenium
[ferrocene ¼ (g5-C5H5)2Fe] couple, which was used as
an internal standard with E0 ¼ 0:00 V. Electrolyte so-
lutions were prepared from [nBu4N][PF6] (Fluka, dried
in an oil pump vacuum at 120 ꢁC), 0.1 M in methy-
lenedichloride with 5.0 mg of the complex in 5.0 ml of
methylenedichloride. Microanalysis of 4a was per-
formed by the Organic Department, Chemnitz, Tech-
nical University.
A (Table 2), which is in agreement with such sandwich
complexes [for example: [(g5-C9H7)2Fe, 1.665 A;
ꢀ
5
ꢀ
(g -C9Me7)2Fe, 1.677 A] [9]]. The bond distances Fe
–C(1), –C(2), –C(3), –C(8), –C(9) and Fe–C(10), –C(20),
–C(30), –C(80), –C(90) are 2.043(3) [Fe–C(2)], 2.075(3)/
ꢀ
2.080(3) [Fe–C(1)/Fe–C(3)] and 2.125(3)/2.130(3) A
[Fe–C(9)/Fe–C(8)]. They point to the fact that the five-
membered ring of the indenyl group is somewhat un-
symmetrically bound to iron. This asymmetry can also
be found in the different C–C bond lengths in the 5-
membered indenyl ring. The C–C distances in the allylic
ꢀ
sub-unit [C(1) to C(3)] are 0.023 A shorter than the
distances to the aromatic benzene structure [C(1)–C(8);
C(3)–C(9)].
3. Conclusion
4.2. General remarks
We have isolated and characterised the Me3Si-func-
tionalised bis(indenyl)iron sandwiches [1-SiMe3–C9H6]2-
Fe (3a), [2-SiMe3–C9H6]2Fe (3b), [1,2-(SiMe3)2C9H5]2Fe
(4a) and (1,3)-(SiMe3)2C9H5]2Fe (4b). Complexes 3a and
4a exist in two isomeric forms: a rac form with C2 sym-
metry and a meso form with Cs symmetry. Cyclovoltam-
metric studies show no influence of the position, 1 or 2, of
the Me3Si group on the oxidation potential of 3a and 3b
in comparison with (g5-C9H7)2Fe. However, sandwiches
4a and 4b possess different potentials, depending on the
position of the Me3Si groups.
Indenes 2a–2d were prepared by published proce-
dures [5]. All other chemicals were purchased by com-
mercial suppliers and were used as received.
4.3. Preparation of bis[1-(trimethylsilyl)indenyl]iron(II)
(3a)
To a solution of 1-(trimethylsilyl)indene (1.208 g, 6.41
mmol) in tetrahydrofuran (50 ml) is added n-BuLi (4.00
ml, 1.6 M, 6.41 mmol) at )80 ꢁC. After stirring the re-
action mixture at ambient temperature for 2 h, FeCl2 (1)
(0.410 g, 3.21 mmol) is added and the reaction mixture is
stirred for further 3 h at ambient temperature. After-
wards, the solvent is removed by oil-pump vacuum to
leave a dark green oily residue, which is dissolved in
diethyl ether and filtered through Celite. Removal of the
solvent by oil-pump vacuum yielded 1.03 g (2.40 mmol,
74% based on 1) of 3a as a dark-green oily residue. The
product obtained is a mixture of rac and meso diaste-
reomers in a 1.6:1 ratio.
4. Experimental
4.1. General methods
All reactions were carried out in an atmosphere of
nitrogen or argon using standard Schlenk techniques.
Solvents were purified by distillation; petroleum ether
and dichloromethane: calcium hydride; tetrahydrofu-
ran, diethyl ether: sodium/benzophenone ketyl. FT-IR
spectra were obtained on a Perkin–Elmer FT-IR 1000
spectrometer as KBr pressings. NMR spectra were re-
corded on a Bruker Avance 250 spectrometer, operat-
Major isomer. 1H NMR (CDCl3): 0.49 (s, 18H,
SiMe3), 3.99 (s, 2H, H2), 4.94 (s, 2H, H3), 6.51–7.60 (m,
8H, H4–7). 13C{1H} NMR (C6D6): d 0.35 (SiMe3),
62.92 (C1), 65.19 (C3), 74.07 (C2), 90.20, 90.41 [C8(9)],
122.19, 122.35 [C5(6)], 124.36, 127.02 [C4(7)].
1
ing in the Fourier transform mode. H NMR spectra
were recorded at 250.130 MHz (internal standard rel-
ative to C6D6, d ¼ 7:24 or CDCl3, d ¼ 7:27). 13C{1H}
NMR spectra were recorded at 62.860 MHz (internal
standard relative to CDCl3, d ¼ 77:0). Chemical shifts
are reported in d units (ppm) downfield from SiMe4
with the solvent as reference signal. Melting points were
determined using analytically pure samples, sealed off
in nitrogen-purged capillaries on a Gallenkamp MFB
595 010 M melting point apparatus. Electrochemical
measurements were carried out by cyclic voltammetry
Minor isomer. 1H NMR (CDCl3): d 0.39 (s, 18H,
SiMe3), 3.24 (s, 2H, H2), 4.68 (s, 2H, H3), 6.51–7.60 (m,
8H, H4–7). 13C{1H} NMR (C6D6): d 0.44 (SiMe3),
62.79 (C1), 65.60 (C3), 78.04 (C2), 89.96, 90.09 [C8(9)],
123.94, 124.27 [C5(6)], 129.73, 130.55 [C4(7)].
EI-MS: [m=z (%)]: 430 (33, Mþ), 241 [25, C9H4
(SiMe3)Feþ], 187 (45, C9H6SiMeþ3 ), 112 (46, C9Hþ4 ), 73
(100, SiMeþ3 ). HR-MS: Mþ, Calc., 430.12345; Found:
430.12247. CV (CH2Cl2): E1=2 ¼ ꢀ275 mV, DEp ¼ 125
mV.

G.M. Fern et al. / Journal of Organometallic Chemistry 689 (2004) 1139–1144
1143
4.4. Preparation of bis[2-(trimethylsilyl)indenyl]iron(II)
(3b)
reaction mixture at ambient temperature for 12 h, FeCl2
(1) (0.260 g, 2.03 mmol) is added, and the reaction
mixture is stirred for a further 6 h at ambient tempera-
ture. The solvent is removed by oil-pump vacuum to
leave a green/blue oily residue. Chromatography on
silica gel (25 ꢁC) with petroleum ether gives green 4b,
which is crystallised from petroleum ether at )20 ꢁC to
afford 0.45 g (0.78 mmol, 39% based on 1) of 4b.
To a solution of 2-(trimethylsilyl)indene (1.266 g, 6.72
mmol) in tetrahydrofuran (50 ml) is added n-BuLi (4.20
ml, 1.6 M, 6.72 mmol) at )80 ꢁC. After stirring the re-
action mixture at ambient temperature for 6 h, FeCl2 (1)
(0.852 g, 3.36 mmol) is added and the reaction mixture is
stirred a further 16 h at ambient temperature. The sol-
vent is removed by oil-pump vacuum to leave a dark-
green oily residue, which is dissolved in petroleum ether
and filtered through Celite. Removal of solvent by oil-
pump vacuum yields 0.92 g (2.14 mmol, 63% based on 1)
of 1 as a dark blue oily residue.
1H NMR (C6D6): d 0.37 (s, 36H, SiMe3), 4.46 (s, 2H,
H2), 7.03 [AA0BB0, 4H, H5(6)], 7.57 [AA0BB0, 4H,
H4(7)]; H4–7 exhibit an AA0BB0 pattern with 3JH4H5 ¼ 3
Hz, JH4H6 ¼ 9 Hz and JH5H6 ¼ 3 Hz. 13C{1H} NMR
(C6D6): d 0.94 (SiMe3), 64.92 [C1(3)], 82.21 (C2), 95.78
[C8(9)], 124.87 [C5(6)], 130.94 [C4(7)]. EI-MS: [m=z (%)]:
574 (83, Mþ), 501 (7, Mþ–SiMe3) 259 [17,
C9H5(SiMe3)þ2 ], 244 [17, C9H5(SiMe3)(SiMe2)þ], 229
[24, C9H5(SiMe2)2þ], 187 (38, C9H6SiMeþ3 ), 172 (100,
C9H5SiMeþ2 ), 73 (65, SiMeþ3 ). HR-MS: Mþ Calc.,
4
3
1H NMR (C6D6): d 0.36 (s, 18H, SiMe3), 3.86 [s, 4H,
H1(3)], 7.00 [AA0BB0, 4H, H5(6)], 7.41 [AA0BB0, 4H,
H4(7)]; H4–7 exhibit an AA0BB0 pattern with 3JH4H5 ¼ 3
4
3
Hz, JH4H6 ¼ 9 Hz and JH5H6 ¼ 3 Hz. 13C{1H} NMR
(C6D6): d 0.35 (SiMe3), 66.76 [C1(3)], 77.21 (C2), 90.88
[C8(9)], 124.05 [C5(6)], 129.86 [C4(7)]. EI-MS: [m=z (%)]:
430 (100, Mþ), 358 (26, HMþ–SiMe3), 172 (14,
C9H6SiMeþ2 ), 115 (25, C9H7þ), 73 (47, SiMeþ3 ). HR-MS:
Mþ, Calc., 430.12345; Found: 430.12257. CV (CH2Cl2):
E1=2 ¼ ꢀ270 mV, DEp ¼ 145 mV.
574.20260; Found: 574.20464. CV (CH2Cl2): E1=2
¼
ꢀ358 mV, DEp ¼ 70 mV. Anal. Calc. for C30H46FeSi4:
C, 62.68; H, 8.07. Found: C, 63.01; H, 7.93%.
4.7. X-ray structure determination of 4b
The solid-state structure of the title compound was
determined by single-crystal X-ray diffraction. Data
collection was performed on a Siemens P4 Smart CCD
area detector using Mo Ka radiation. Crystallographic
data of 4b is listed in Table 3.
4.5. Preparation of bis[1,2-bis(trimethylsilyl)inde-
nyl]iron(II) (4a)
To 1,2-bis(trimethylsilyl)indene (1.00 g, 3.84 mmol) in
tetrahydrofuran (50 ml), n-BuLi (1.54 ml, 3.84 mmol,
2.5 M in hexane) is added at )78 ꢁC. After stirring the
reaction mixture at ambient temperature for 12 h, FeCl2
(1) (0.245 g, 1.92 mmol) is added, and the reaction mix-
ture is stirred for another 6 h. Afterwards, the solvent is
removed in oil-pump vacuum to leave a green-blue oily
residue. The remaining oil is purified by column chro-
matography (column size: 20 · 2.5 cm, petroleum ether,
silica gel). After the solvent is removed from the eluate by
oil-pump vacuum, 0.39 g (0.68 mmol, 35% based on 1) of
4b as a mixture of rac and meso isomers can be obtained
in a 1.2:1 ratio as a green solid.
The structure was solved by direct methods (G.M.
€
€
Sheldrick, SHELX-97; University of Gottingen: Gottin-
gen, Germany, 1997). An empirical absorption correc-
tion was applied. The structure was refined by the least
squares method based on F 2 with all reflections. All
non-hydrogen atoms were refined anisotropically; the
hydrogen atoms were placed in calculated positions. The
picture was drawn using XP in SHELXTL
.
5. Supplementary material
1H NMR (CDCl3): d 0.00 (s, 9H, SiMe3), 0.03 (s, 9H,
SiMe3), 0.12 (s, 9 H, SiMe3), 0.31 (s, 9H, SiMe3), 3.75
(m, 1H, C9H6), 5.1 (m, 1H, C9H6), 7.25 (m, 4H, C9H6),
7.5 (m, 2H, C9H6), 7.9 (m, 2H, C9H6). IR (KBr, cmꢀ1):
3054(w), 2985(m), 2685(m), 2410(w), 2305(w), 1422(s),
1264(s). Anal. Calc. for C30H46Fe2Si4: C, 62.68; H: 8.07.
Found: C, 63.05; H, 7.95%. CV (CH2Cl2): E1=2 ¼ ꢀ291
mV, DEp ¼ 112 mV.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 210352 for complex 4b.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ UK (fax: +44-1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk or http://www.ccdc.
cam.ac.uk).
4.6. Preparation of bis[1,3-bis(trimethylsilyl)inde-
nyl]iron(II) (4b)
Acknowledgement
To a solution of 1,3-bis(trimethylsilyl)indene (1.055 g,
4.05 mmol) in tetrahydrofuran (50 ml), n-BuLi (2.53 ml,
1.6 M, 4.05 mmol) is added at )80 ꢁC. After stirring the
The authors are grateful for financial support from
the Deutsche Forschungsgemeinschaft and the Fonds
der Chemischen Industrie.

1144
G.M. Fern et al. / Journal of Organometallic Chemistry 689 (2004) 1139–1144
(b) C. Cauletti, J.C. Green, M.R. Kelly, P. Powell, J. van Tilborg, J.
References
Robbins, J. Smart, J. Electron Spectrosc. Relat. Phenom. 19 (1980)
327;
[1] (a) For example: D. Morcos, W. Tikkanen, J. Organomet. Chem.
371 (1989) 15;
(c) M.E. Rerek, F. Basolo, J. Am. Chem. Soc. 106 (1984) 5908.
[5] (a) M. Rerk, L. Ji, F. Basolo, J. Chem. Soc., Chem. Commun.
(1983) 1208;
(b) K.S. Gan, T.S.A. Hor, in: A. Togni, T. Hayashi (Eds.),
Ferrocenes: Homogeneous Catalysis, Organic Synthesis, Materials
Science, VCH, Weinheim, 1995;
(b) P.E. Rakita, A. Davison, J. Organomet. Chem. 23 (1970)
407.
(c) R. Broussier, G. Delmas, P. Beron, B. Gautheron, J.L. Petersen,
J. Organomet. Chem. 511 (1996) 185;
[6] R. Holze, G.M. Fern, S. Klaib, O. Curnow, H. Lang, J. Electroanal.
Chem. (2003) in press.
(d) W.A. Schenk, T. Gutman, J. Organomet. Chem. 544 (1997) 69.
[2] (a) J. Adams, D.E. Berry, J. Browning, D. Burth, O.J. Curnow, J.
Organomet. Chem. 580 (1999) 245;
[7] (a) For example: H. Henning, O. Gurtler, J. Organomet. Chem. 11
(1968) 307;
(b) G.L.K. Hoh, W.E. McEwen, J. Kleinberg, J. Am. Chem. Soc.
83 (1961) 3949;
(b) O.J. Curnow, G.M. Fern, Organometallics 21 (2002) 2827.
€
[3] (a) R. Aumann, B. Jasper, R. Frohlich, Organometallics 14 (1995)
(c) W.F. Little, C.W. Reilley, J.D. Johnson, K.N. Lynn, A.P.
Sanders, J. Am. Chem. Soc. 86 (1964) 1376.
[8] (a) R.W Dessy, F.E. Stary, R.B. King, M. Waldrup, J. Am. Chem.
Soc. 88 (1966) 471;
231;
(b) K.H. Dotz, I. Pruskil, U. Schubert, K. Ackermann, Chem. Ber.
€
116 (1983) 2337;
(c) K.A. Fallis, G.K. Anderson, N.P. Rath, Organometallics 11
(1992) 885;
(b) J.H. Osiecki, C.J. Hoffmann, D.P. Hollis, J. Organomet. Chem.
3 (1965) 107;
(d) M. Stradiotto, C.M. Kozak, M.J. McGlinchey, J. Organomet.
Chem. 564 (1998) 101;
(c) P.M. Treichel, J.W. Johnson, K.P. Wagner, J. Organomet.
Chem. 88 (1975) 227.
(e) C.J. Schaverien, R. Ernst, W. Terlouw, P. Schut, O. Sudmeijer,
P.H.M. Budzelaar, J. Mol. Catal. A 128 (1998) 245;
(f) M. Riedel, G. Erker, B. Bosch, A. Bertuleit, DE 19632919
(1998); Chem. Abstr. 128, 205237;
[9] (a) J. Trotter, Acta Crystallogr. 11 (1958) 355;
(b) S.A. Westcott, A.K. Kakkar, G. Stringer, N.J. Taylor, T.B.
Marder, J. Organomet. Chem. 394 (1990) 777;
(c) E.D. Brady, J.S. Overby, M.B. Meredith, A.B. Mussman, M.A.
Cohn, T.B. Hanusa, G.T. Yee, M. Pink, J. Am. Chem. Soc. 124
(2002) 9556;
(g) J. Klosin, W.J. Kruper, P.N. Nickias, J.T. Patton, D.R. Wilson,
WO 9806727 (1998); Chem. Abstr. 128, 167818;
(h) K.H.A.O. Starzewski, W.M. Kelly, A. Stumpf, WO
9801487(1998); Chem. Abstr. 128, 141901;
(d) M.J. Chalhorda, L.F. Veiros, Coord. Chem. Rev. 185–186
(1999) 37;
€
(i) H. Bonnemann, Angew. Chem., Int. Ed. Engl. 24 (1985) 248.
(e) H. Schuhmann, O. Stenzel, S. Dechert, R.L. Halterman,
Organometallics 20 (2001) 1983.
[4] (a) For example: J.M. OÕConnor, C.P. Casey, Chem. Rev. 87 (1987)
307;