The synthesis and structure of a thiobenzyl-functionalized dibenzoferrocene complex

Article abstract of DOI:10.1080/00958971003690447

3-(Thiobenzyl)indene (2) was prepared from lithium indenide and dibenzyl disulfide. Deprotonation with BuLi/TMEDA in THF and the addition of FeCl ₂ gave the expected 1: 1 mixture of rac-and meso-bis(1- thiobenzylindenyl)iron(II) (3). ¹³C-NMR studies in THF suggest that 3 undergoes a ring-flipping process to interconvert rac-and meso-3. Complex 3 exhibits a reversible cyclic voltammogram with an oxidation potential of-177 mV versus the Fc/Fc⁺ couple in dichloromethane. Indene (2) and ferrocene (3) were also characterised by X-ray crystallography.

Full text of DOI:10.1080/00958971003690447

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The synthesis and structure
of a thiobenzyl-functionalized
dibenzoferrocene complex
Owen J. Curnow a & Rong Shang a
a Department of Chemistry , University of Canterbury , Private
Bag 4800, Christchurch 8140, New Zealand
Published online: 09 Mar 2010.
To cite this article: Owen J. Curnow & Rong Shang (2010) The synthesis and structure of a
thiobenzyl-functionalized dibenzoferrocene complex, Journal of Coordination Chemistry, 63:14-16,
2790-2799, DOI: 10.1080/00958971003690447
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Journal of Coordination Chemistry
Vol. 63, Nos. 14–16, 20 July–20 August 2010, 2790–2799
The synthesis and structure of a thiobenzyl-functionalized
dibenzoferrocene complex
OWEN J. CURNOW* and RONG SHANG
Department of Chemistry, University of Canterbury, Private Bag 4800,
Christchurch 8140, New Zealand
(Received 10 December 2009; in final form 29 January 2010)
3-(Thiobenzyl)indene (2) was prepared from lithium indenide and dibenzyl disulfide.
Deprotonation with BuLi/TMEDA in THF and the addition of FeCl2 gave the expected 1 : 1
mixture of rac- and meso-bis(1-thiobenzylindenyl)iron(II) (3). 13C-NMR studies in THF
suggest that 3 undergoes a ring-flipping process to interconvert rac- and meso-3. Complex 3
exhibits a reversible cyclic voltammogram with an oxidation potential of –177 mV versus the
Fc/Fcþ couple in dichloromethane. Indene (2) and ferrocene (3) were also characterised by
X-ray crystallography.
Keywords: Ferrocene; Indenyl; Iron; Thioether
1. Introduction
Functionalized ferrocenes have been intensively investigated for a wide range of
properties and applications [1]. The stability and stereochemical rigidity of the
cyclopentadienyl–iron interaction is one of the reasons that ferrocenes are of such
interest. Stereochemical rigidity is particularly important for planar chiral ferrocenyl
phosphine complexes as any ring-flipping process would result in the racemization of
the planar chiral center. In 2002, we first reported the remarkably facile ring-flipping
process of bis(1-diphenylphosphinoindenyl)iron(II) (1) in which the rac and meso
isomers interconvert in THF solution at ambient temperatures (scheme 1) [2]. A number
of experiments indicated that the likely mechanism involves the reversible displacement
of indenide by THF with the continued coordination of the ligand via the phosphine [3].
Subsequent studies have attempted to elucidate the steric and electronic factors
involved in this process [4]. Although a number of thioether-functionalized ferrocenes
are known [5], analogous indenyl compounds are unknown for iron, while, in the
previously reported and well-characterized example, Rausch and coworkers [6]
described the synthesis and styrene-polymerization ability of (1-thiomethylindenyl)-
trichlorotitanium, although no structural study has been reported. Some
2-thioalkyl-substituted zirconocenes have been reported in the patent literature;
however, no characterization data were included [7].
*Corresponding author. Email: owen.curnow@canterbury.ac.nz
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2010 Taylor & Francis
DOI: 10.1080/00958971003690447

Thiobenzyl-functionalized dibenzoferrocene complex
2791
Scheme 1. Ring-flipping process for 1.
2. Experimental
All experimental work was carried out under the argon or dinitrogen atmosphere using
standard Schlenk techniques unless otherwise noted. THF and diethylether were
distilled from Na/benzophenone under argon prior to use. Hexane and dichloro-
methane were distilled from calcium hydride under argon. Ethanol was distilled over
1
magnesium turnings under argon. H- and 13C{1H}-NMR data were collected on a
Varian Unity-300 spectrometer operating at 300 and 75 MHz, respectively. Spectra were
measured at ambient temperature with the residual solvent as internal standard.
The numbering scheme for the NMR assignments is given in scheme 2. EI mass spectra
were collected on a Kratos MS80RFA mass spectrometer. Elemental analyses were
carried out by Campbell Microanalytical Services, University of Otago, Dunedin.
UV-Vis spectra were obtained on
a
VARIAN Cary 50 Probe UV-Vis
Spectrophotometer using 1 cm cuvettes. Electrochemical measurements were made in
CH2Cl2 with 0.1 mol [Bu4N]BF4 electrolyte and using a three-electrode cell comprising
of a platinum-disk working electrode (1 mm diameter), a platinum-wire auxiliary
electrode, and a Ag/Agþ pseudo reference electrode. Sample concentration was
1.3 mmol. Voltammetry was performed using an Autolab Eco Chemie (The
Netherlands) with the associated GPES software. All potentials are reported versus
the ferrocene/ferrocenium (Fc/Fcþ) couple after referencing to in situ ferrocene.
Electrochemical measurements were made at ambient temperature under an inert
atmosphere. All reagents were used as supplied commercially.
2.1. Synthesis of 3-(thiobenzyl)indene (2)
Freshly distilled indene (9.3 mL, 0.080 mol) was added dropwise via a syringe to a stirred
solution of n-BuLi (50 mL, 1.6 mol, 0.080 mol) in hexane (100 mL) on an ice-bath.
A pale yellow solution was formed with a white precipitate. The solution was allowed to
warm to the ambient temperature and then stirred overnight. Dibenzyldisulfide (19.7 g,
0.080 mol) was then added portion-wise and the reaction mixture was stirred vigorously
for a further 12 h. A pink solution with a white precipitate was formed. This mixture was
then filtered through a Celite column (10 ꢀ 3.5 cm). An orange solid was left after the
evaporation of the solution. The crude product was flash chromatographed through
alumina using diethylether : hexane (3 : 7). Recrystallization from hexane afforded 9.4 g
(46%) of colorless needle-like crystals of 2. 1H-NMR (CDCl3): ꢀ 7.42–7.20 (m, 9H, H4/7

2792
O.J. Curnow and R. Shang
Scheme 2. Numbering scheme for NMR assignments.
and Ph), 6.21 (t, 3JHH 2.4, 1H, H2), 4.17 (s, 2H, CH2Ph), 3.41 (d, 3JHH 2.4, 2H, indene
CH2). 13C{1H}-NMR (CDCl3): ꢀ 36.7 (C1), 38.5 (benzyl CH2), 119.3 (C4), 123.7 (C7),
125.3 (C6), 126.3 (C5), 127.3 (C2), 127.3 ( p-Ph), 128.5 (m-Ph), 128.8 (o-Ph), 137.1 (ipso-
Ph), 137.5 (C9/3), 143.3 (C8), 143.6 (C3/9). Quaternary carbon atom peaks could not be
assigned unambiguously. Mass spec. (EI, m/z(%)): 239.1 (100, Mþ). Anal. Calcd for
C16H14S (%): C, 80.62; H, 5.92; S, 13.45. Found (%): C, 80.14; H, 5.96; S, 13.41.
2.2. Synthesis of bis(1-benzylthioindenyl)iron(II) (3)
n-BuLi (4.30 mL, 6.88 mmol) was added dropwise to a solution of 2 (1.64 g, 6.88 mmol)
in freshly distilled THF (100 mL) and TMEDA (0.7 mL) at ꢁ78ꢂC. The solution
immediately turned yellow-brown. After 2.5 h at ꢁ78ꢂC, anhydrous FeCl2 ꢃ 1.5THF
(0.81 g, 3.4 mmol) was added to the light brown solution, which then quickly darkened
in color. Vigorous stirring at ꢁ78ꢂC for 50 min was carried out before removing the
cold bath and the solution was allowed to gradually warm to the ambient temperature.
The solution was filtered through a Celite column using diethylether and a dark green
solution was collected. The solvent was removed in vacuo and a black oily residue was
1
obtained. H- and 13C{1H}-NMR spectra of the crude product indicated that indene 2
and both ferrocene isomers are present. The rac/meso ratio in the 13C{1H}-NMR
spectrum was approximately 1 : 1. The crude product was then redissolved in freshly
distilled THF (20 mL) and stirred for 20 h. The solution was filtered through a Celite
column using diethylether and the solvent was removed in vacuo. The 13C{1H}-NMR
spectrum of the dark red oil showed a rac : meso ratio of approximately 1 : 0.6. Further
recrystallization from diethylether afforded 0.11 g (2.3%) of dark red rac-3. The
13C-NMR chemical shifts reported here are the values corrected for paramagnetic
impurities, as described in the ‘‘Supplementary material’’. Interestingly, the quaternary
C atoms are more strongly affected by the paramagnetic impurities than the tertiary C
atoms which are more strongly affected than the secondary C atoms, by averages of
1.96, 1.84, and 1.72 ppm, respectively, in the crude solution and by 4.53, 4.31, and
4.00 ppm, respectively, in the isomerized solution. rac-Isomer: 1H-NMR (CDCl3): ꢀ 3.60
(4H, s, CH2), 4.16 (2H, s, H2/3), 4.58 (2H, s, H2/3), 6.68–7.42 (18H, m). 13C{1H}-NMR
(CDCl3): ꢀ 41.8 (CH2), 64.6 (C3), 71.1 (C1), 77.2 (C2), 88.1 (C8/9), 89.0 (C9/8), 123.0
(C4), 123.4 (C7), 123.6 (C6), 125.1 (C5), 126.7 ( p-Ph), 128.2 (m-Ph), 128.7 (o-Ph), 138.4
(ipso-Ph). meso-Isomer: 13C{1H}-NMR (CDCl3): ꢀ 41.4 (CH2), 62.9 (C3), 71.7 (C1),
77.4 (C2), 87.6 (C8/9), 89.0 (C9/8), 123.6 (C4), 124.2 (C7), 124.9 (C6), 125.4 (C2), 126.6
( p-Ph), 128.1 (m-Ph), 128.8 (o-Ph), 128.4 (ipso-Ph). Anal. Calcd for C32H22FeS2
(%): C, 73.00; H, 4.21. Found (%): C, 70.17; H, 4.18. Values are low due to the
unavoidable decomposition of the product.

Thiobenzyl-functionalized dibenzoferrocene complex
2.3. X-ray crystallography
2793
Crystal data and experimental details are given in table 1. For each compound, a crystal
was mounted on a glass fiber. Data were collected using a Bruker–Nonius
diffractometer equipped with an APEX-II CCD area detector and the associated
software. Processing was carried out by the use of SAINT [8], which applied Lorentz
and polarization corrections to 3-D integrated diffraction spots. The program SADABS
[8] was utilized for the scaling of diffraction data, the application of decay corrections,
and empirical absorption corrections based on redundant reflections. The structures
were solved by direct methods [9]. Both structures were refined by least-squares
methods on F 2 with anisotropic thermal parameters for all non-hydrogen atoms.
Hydrogens were added as riding contributors at calculated positions with isotropic
thermal parameters based on the attached carbon.
3. Results and discussion
3.1. Synthesis of 3-(thiobenzyl)indene (2)
3-(Thiobenzyl)indene was prepared by a route analogous to that used by Rausch and
coworkers [6] for the preparation of 3-(thiomethyl)indene: dibenzyldisulfide was added
Table 1. Details of crystallographic collection and refinement data for 2 and rac-3.
2
rac-3
C16H13Fe0.50
Empirical formula
Formula weight
Temperature (K)
C16H14
238.33
293(2)
S
S
265.25
293(2)
˚
Wavelength (A)
0.71073
Monoclinic
P2(1)/c
0.71073
Monoclinic
C2/c
Crystal system
Space group
Unit cell dimensions (A,
ꢂ
˚
)
a
b
c
ꢁ
ꢂ
ꢃ
12.5484(4)
5.5266(2)
18.7392(6)
90
107.460(2)
90
1239.69(7), 4
1.277
0.234
10.9413(4)
14.6122(6)
15.7579(7)
90
90.9660(10)
90
2518.96(18), 8
3
˚
Volume (A ), Z
Calculated density (g cmꢁ3
)
1.399
0.784
Absorption coefficient (mmꢁ1
F(000)
)
504
0.60 ꢀ 0.45 ꢀ 0.26
1104
0.40 ꢀ 0.40 ꢀ 0.08
Crystal size (mm3)
ꢄ range for data collection (ꢂ)
Limiting indices
1.70–34.70
ꢁ18 ꢄ h ꢄ 19; ꢁ8 ꢄ k ꢄ 8;
ꢁ28 ꢄ l ꢄ 28
2.59–31.59
ꢁ15 ꢄ h ꢄ 11; ꢁ17 ꢄ k ꢄ 21;
ꢁ17 ꢄ l ꢄ 19
6932
Reflections collected
Independent reflections
Completeness to ꢄ ¼ 34.70 (%)
Absorption correction
Refinement method
Data/restraints/parameters
Goodness-of-fit on F 2
Final R indices [I 4 2ꢅ(I )]
R indices (all data)
22,355
4511 [R(int) ¼ 0.0277]
3428 [R(int) ¼ 0.0158]
84.7
None
94.1
None
Full-matrix least-squares on F 2
4511/0/155
1.193
3428/0/159
1.154
R1 ¼ 0.0307, wR2 ¼ 0.0838
R1 ¼ 0.0383, wR2 ¼ 0.0979
0.624 and ꢁ0.431
R1 ¼ 0.0355, wR2 ¼ 0.1300
R1 ¼ 0.0411, wR2 ¼ 0.1410
0.536 and ꢁ0.250
ꢁ3
˚
Largest difference peak and hole (e A
)

2794
O.J. Curnow and R. Shang
to a suspension of lithium indenide in hexane and the product was isolated via
chromatography (scheme 3). NMR spectra indicated that the 3-isomer had been
isolated; possibly as a result of the isomerization of the expected 1-isomer during the
alumina filtration step, as has been observed for analogous indenylphosphines [10].
However, it is also possible that the lithium benzylthiolate coproduct could have acted
as a catalyst for this isomerization via a deprotonation/protonation mechanism. The
structure of 2 was further confirmed by an X-ray crystallographic study that was
undertaken to compare the indene with the coordinated indenide.
3.2. Synthesis and characterization of rac- and meso-bis(1-thiobenzylindenyl)
iron(II) (3)
Treatment of indene 2 with n-BuLi in THF gave a precipitate of the indenide that reacts
poorly with FeCl2. Addition of TMEDA dissolves the lithium indenide which then
produces the expected ferrocene product 3 upon reaction with FeCl2 (scheme 4).
13C-NMR spectra indicated that both rac and meso isomers formed in approximately
equal amounts (figure 1a). After stirring the mixture of isomers for 20 h in THF, the
ratio changed to approximately 1 : 0.6 (figure 1b). Unfortunately, a significant amount
of decomposition/hydrolysis was observed with the formation of free indene and
paramagnetic materials. Thus, one cannot say unambiguously that the change in the
ratio is due to an isomerization process rather than a difference in the rate of
decomposition. Attempts to follow the reaction by NMR in THF-d8 proved futile due
to the extreme sensitivity of 3 to the traces of water. However, it should be noted that
Scheme 3. Synthesis of 3-(thiobenzyl)indene (2).
Scheme 4. Synthesis of 3.

Thiobenzyl-functionalized dibenzoferrocene complex
2795
Figure 1. (a) 13C-NMR spectrum of 3 in CDCl3 before isomerization. (b) 13C-NMR spectrum of 3 in CDCl3
after stirring for 20 h in THF. The differences in the chemical shift relative to solvent CDCl3 are due to the
presence of different amounts of paramagnetic decomposition products.
the mechanistic studies on the rate of hydrolysis for 1 [3] showed that the hydrolysis
mechanism involves the same intermediate as the isomerization process. Thus, the
intermediate responsible for isomerization is likely to be present suggesting that
ring-flipping is likely to be occurring.
Electrochemistry of 3 was investigated to compare the electronic effect of the
thiobenzyl substituent with other substituents. Cyclic voltammetry in CH2Cl2 gave a
single reversible (DEp ¼ 87 mV compared to 92 mV for the internal ferrocene standard)
redox process with E0 at ꢁ177 mV versus the Fc/Fcþ couple (figure 2). Any
difference between the two isomers, therefore, is likely to be insignificant. This
is a lower oxidation potential than the phosphino analogue 1 (ꢁ140 mV) [11],
but is higher than the unsubstituted dibenzoferrocene (ꢁ278 mV) [12],
1,10-dimethyl-substituted dibenzoferrocene (ꢁ375 mV) [12], and bis(1-trimethylsilyl)-
substituted dibenzoferrocene (ꢁ275 mV) [13]. Similar trends have been observed in the
analogous cyclopentadienyl systems [14]. Notably, 3 has a higher oxidation potential
than methyl- and trimethylsilyl-substituted bis(phosphinoindenyl)iron(II) complexes
(ꢁ220 to ꢁ350 mV) that have been reported to date and have not been observed to
undergo ring-flipping. This is consistent with the electrophilicity of the metal center
being an important factor in facilitating the attack by THF, the first step in the
ring-flipping process.
As with other dibenzoferrocenes, 3 exhibits two absorption bands in the UV-Vis
region (figure 3), a strong band at 415 nm (" ¼ 855 L molꢁ1 cmꢁ1) and a weaker band
at 545 nm (" ¼ 203 L molꢁ1 cmꢁ1). These are at slightly higher energy than the

2796
O.J. Curnow and R. Shang
Figure 2. Cyclic voltammogram of 3 (1.3 ꢀ 10ꢁ3 mol) in CH2Cl2 relative to Fc/Fcþ.
Figure 3. UV-Vis spectrum of 3 (1.6 ꢀ 10ꢁ3 mol) in CH2Cl2.
corresponding
bands
in
1:
420
(" ¼ 870 L molꢁ1 cmꢁ1
)
and
565 nm
(" ¼ 265 L molꢁ1 cmꢁ1), respectively. These bands have been attributed to d–d
transitions [13].
3.3. Crystallographic studies
The solid state structures of 2 and rac-3 were determined by X-ray crystallography.
Collection and refinement data are given in table 1 and selected bond distances
and angles are given in table 2. The structure of indene 2 (a thermal ellipsoid plot is
shown in figure 4) is consistent with the 3-isomer: C3 has a trigonal planar geometry
(sum of angles ¼ 360.0ꢂ) and the C2–C3 distance is significantly shorter than the C1–C2
˚
˚
˚
and C3–C9 distances (1.3531(12) A vs. 1.5075(12) A and 1.4698(12) A). The thiobenzyl
substituent lies in the plane of the indene with C2–C3–S–C10 ¼ 0.4ꢂ and a trans
configuration about S–C10 (C3–S–C10–C11 ¼ 173.3ꢂ). The phenyl group, however, lies

Thiobenzyl-functionalized dibenzoferrocene complex
2797
ꢂ
˚
Table 2. Selected bond distances (A) and angles ( ) for 2 and
rac-3.
2
rac-3
1.654
Fe–CNT
Fe–C1
Fe–C2
Fe–C3
Fe–C8
Fe–C9
S–C3
S–C10
C1–C2
C1–C8
C2–C3
C3–C9
C4–C5
C4–C9
C5–C6
C6–C7
C7–C8
C8–C9
C10–C11
2.0401(15)
2.0185(13)
2.0334(14)
2.0928(14)
2.0933(13)
1.7547(17)
1.8280(17)
1.425(2)
1.436(2)
1.436(2)
1.4394(19)
1.361(2)
1.423(2)
1.7440(9)
1.8170(9)
1.5075(12)
1.5061(13)
1.3531(12)
1.4698(12)
1.3934(13)
1.3924(12)
1.3951(14)
1.3968(14)
1.3895(13)
1.4045(11)
1.5062(12)
1.421(3)
1.361(2)
1.426(2)
1.440(2)
1.505(2)
CNT–Fe–CNT
CNT–C3–S
C3–S–C10
C2–C3–C9
C2–C3–S
179.11
174.86
101.04(4)
109.61(8)
130.70(7)
119.67(6)
108.63(6)
102.53(9)
107.35(14)
126.27(11)
126.15(12)
113.81(11)
C9–C3–S
C11–C10–S
Figure 4. ORTEP of indene 2.
approximately perpendicular to this plane (S–C10–C11–C12 ¼ 75.7ꢂ). Some steric
repulsion between the benzyl group and indene are apparent in the wide C2–C3–S angle
(130.70(7)ꢂ) compared to the C9–C3–S angle (119.67(6)ꢂ). Similar effects are apparent
in Ph2P(C9H7) (127.8(1)ꢂ and 123.2(1)ꢂ) [15] and 1 (130.3ꢂ and 123.8ꢂ) [4], whereas no
significant effect is observed in PhP(S)(C9H7)2 (124.2–126.8ꢂ) [10a].

2798
O.J. Curnow and R. Shang
Figure 5. ORTEP of rac-3 showing atomic labeling scheme and the view down the centroid–centroid axis of
the five-membered rings. Hydrogen atoms have been omitted for clarity.
Thermal ellipsoid plots of rac-3 are shown in figure 5. It was found to pack in
the monoclinic C2/c space group with the C2-symmetric molecules lying on the
crystallographic C2 axes. In complete contrast to the indene, the thiobenzyl group
in rac-3 is oriented out of the indenyl plane (C2–C3–S–C10 ¼ 94.1ꢂ) and adopts
a
twisted cis conformation about the S–C10 bond (C3–S–C10–C11 ¼ 65.8ꢂ).
Consequently, the C2–C3–S and C9–C3–S angles are very similar due to the lack of
steric repulsion: 126.15(12)ꢂ and 126.27(11)ꢂ, respectively. The indenyl rings show a
ꢆ-offset arrangement (figure 5) to maximize the ꢆ–ꢆ stacking interactions [16] with a
rotation angle, RA (the angle formed by two lines determined by the centroids of the
five- and six-membered rings), of 23.4ꢂ. This is similar to those exhibited by rac-1
(20.8ꢂ) and rac-bis(1-diphenylphosphino-4,7-dimethylindenyl)iron(II) (rac-4) (12.1ꢂ) [4];
however, the offset in those complexes was in the opposite direction: consequently, the
torsion angle C3–CNT–CNT00C30 is greater for rac-2 (167.5ꢂ) than for the phosphino
analogues (123.1ꢂ and 131.9ꢂ, respectively). The direction of offset in the phosphino
analogues was attributed to favorable CH–ꢆ-arene hydrogen bonding between the
diphenylphosphino groups [4]. Curiously, the fold angle (FA) of rac-3 (angle between
the planes defined by the five- and six-membered rings) is 4.1ꢂ with the six-membered
ring bent towards the Fe atom. In contrast, the 14 FA angles reported in [4, 12]
are all less than 2.8ꢂ (or have the six-membered ring pointed away from the Fe atom).
Similarly, the thiobenzyl
S
atom is bent towards the Fe atom by 5.1ꢂ
(CNT–C3–S ¼ 174.9ꢂ), whereas almost all other substituents on dibenzoferrocenes are
bent away [4, 12], the notable exceptions being rac-1 (bent in by 3.9ꢂ) and rac-4
(one phosphino group is bent in by 3.6ꢂ) [4]. There appears to be a general trend of
substituents bending towards the metal as the oxidation potential increases, and this
may facilitate ring-flipping in 1 and 3. These structural effects are also likely to be
˚
related to the short Fe–CNT distances in 3 of 1.654 A: The fourteen Fe–CNT distances
˚
reported in [4, 12] range from 1.666 to 1.707 A (average of 1.68 A).
˚
4. Conclusions
This article has described the synthesis of a thiobenzyl-functionalized dibenzoferrocene
that appears to undergo ring-flipping in THF. Cyclic voltammetry and X-ray

Thiobenzyl-functionalized dibenzoferrocene complex
2799
crystallographic studies are consistent with an electrophilic iron center that may
enhance the attack of THF to initiate the ring-flipping process. Unfortunately, the
system reported here does not allow us to discriminate between steric and elec-
tronic effects on the ring-flipping process, and further work will be required to separate
these factors.
Supplementary material
Crystallographic data for structural analyses reported in this article have been deposited
with the Cambridge Crystallographic Data Centre with the CCDC nos. 756465 (2) and
756466 (rac-3). Corrections required for 13C-NMR chemical shifts of 2 by the
comparison of the indene peaks in CDCl3 and in ferrocene solutions before and after
isomerization are given in table 1S. Observed and corrected 13C-NMR chemical shifts
for 3 are given in table 2S.
Acknowledgments
We are grateful to Prof. Ward T. Robinson for assistance with the X-ray
crystallographic studies and to Dr Paula Brooksby for the cyclic voltammetry studies.
References
ˇ
[1] (a) P. Stepnicka (Ed.). Ferrocenes: Ligands, Materials and Biomolecules, John Wiley and Sons, Ltd,
ˇ ˇ
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