1,1′-Biferrocenylenes-the more redox stable Ferrocenes! new derivatives, corrected NMR assignments, redox behavior, and spectroelectrochemistry

Article abstract of DOI:10.1021/om201215w

Following an improved protocol, several monosubstituted 1,1′-biferrocenylenes (BFDs) were prepared as a mixture of α and β constitutional isomers. The isomers were separated and their structures assigned from ¹H-¹H-COSY and ¹

Full text of DOI:10.1021/om201215w

Article
pubs.acs.org/Organometallics
1,1′-BiferrocenylenesThe More Redox Stable Ferrocenes! New
Derivatives, Corrected NMR Assignments, Redox Behavior, and
Spectroelectrochemistry
Rochus Breuer and Michael Schmittel*
Center of Micro and Nanochemistry and Engineering, Department of Chemistry and Biology, Organische Chemie I, Universitat
̈
Siegen, Adolf-Reichwein-Straße 2, D-57068 Siegen, Germany
S
* Supporting Information
ABSTRACT: Following an improved protocol, several monosubstituted 1,1′-
biferrocenylenes (BFDs) were prepared as a mixture of α and β constitutional isomers.
1
The isomers were separated and their structures assigned from H−1H-COSY and
1H−1H-ROESY NMR data, resulting in a correction of earlier erroneous assignments.
Both redox stages (BFD0/BFD+ and BFD+/BFD2+) were examined by cyclic
voltammetry. The reactivity of the parent BFD+ versus that of ferrocenium (Fc+) in
aqueous solution was evaluated by UV−vis spectroscopy, suggesting that ferrocene
should be replaced by BFD derivatives for redox applications in aqueous media due to
their more than 1000-fold higher kinetic stability. Electronic transitions of
monoalkylated BFD+ derivatives were measured by thin-layer spectroelectrochemistry,
revealing unperturbed mixed-valence class III systems independent of α or β
substitution.
INTRODUCTION
RESULTS AND DISCUSSION
Synthesis of New BFD Derivatives. As shown in Scheme
1, various monosubstituted 1,1′-biferrocenylenes (BFDs) were
Scheme 1. Synthetic Route to BFD Derivatives 2a,b−10a,b
■
■
1,1′-Biferrocenylene1 (BFD, bis(fulvalene)diiron) represents a
textbook example of a mixed-valence class III metallocene as
defined by Robin and Day,2 displaying two fully reversible
oxidation processes at 1E1/2 = −0.29 VFc for BFD/BFD+ and at
2E1/2 = +0.38 VFc for BFD+/BFD2+. Despite its interesting
redox chemistry, BFD has received almost no attention so far,
primarily due to problems with its solubility and its
functionalization. Its utility thus remains largely unrecognized,
quite in contrast to the situation with ferrocene3 and even
biferrocenes.4 A comprehensive literature search reveals that
altogether only six BFD derivatives have been reported up to
now5,6 and that in case of the five reported monosubstituted
BFDs even the assignment of the two possible constitutional
isomers is cumbersome.5
Herein, we present an improved synthetic protocol to
monofunctionalized BFDs and a corrected assignment of their
constitutional α,β isomers using 2D 1H NMR techniques.
Results of spectroelectrochemical investigations confirm the
mixed-valence class III character for alkylated BFD+ cations as
well. Furthermore, the current study establishes the outstanding
stability of BFD+ against aqueous basic media, exceeding that of
the widely used ferrocenium ion (Fc+) by more than 1000−
4000 times. The increased kinetic stability suggests the use of
the BFD/BFD+ redox pair in a multitude of aqueous media
applications and replacement of the commonly used ferrocene
in the fields of bioorganic chemistry,7 redox sensing,8,9 redox
actuation,10,11 charge storage,12,13 and medicinal applica-
tions.14,15
prepared by applying a modified Friedel−Crafts acylation
protocol. The problem of the limited solubility of the parent
BFD in organic solvents was overcome by using a solvent
mixture of carbon disulfide and dichloroethane at elevated
Received: December 7, 2011
Published: February 6, 2012
© 2012 American Chemical Society
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temperatures, improving the yield to ca. 60% and thus to more
than 6 times of what had been reported in the literature so far.5
All reactions employ an excess of several equivalents of AlCl3 to
achieve full conversion and yield a mixture of monosubstituted
BFDs in 2- (α isomers 2a−6a) and in 3-positions (β isomers
2b−6b) (Table 1). In general, the yield of the β isomer exceeds
Figure 2. Selected characteristic 1H NMR multiplets of four protons of
3a. This pattern is analogous for all α constitutional isomers.
Table 1. Yields of BFD Derivatives 2a,b−10a,b
9-H, 8′-H, 9′-H, 3′-H, 4′-H) appear as triplets of doublets (td, 3J
≅ 2 Hz, 4J ≅ 1 Hz) in the upfield region of the 1H NMR. The
introduction of a substituent leads to significant shifts of the
respective cyclopentadienyl ring protons and changes in their
multiplet character. In the case of the α isomers (Figures 1 and
2), proton 4-H now appears as a pseudotriplet (dd(t) = doublet
entry
α/β yield (%)
entry
α/β yield (%)
2a,b
3a,b
4a,b
5a,b
6a,b
18/40
20/43
13/45
11/33
18/49
7a,b
8a,b
9a,b
10a,b
70/68
75/79
75/73
71/75
3
of doublets appearing as triplet, with J ≅ 3 Hz) at 4.40 ppm
and proton 3-H as a doublet of doublets (dd) at 4.21 ppm, both
located within the set of upfield-shifted protons. In contrast, the
signal of proton 5-H shows up as a doublet of doublets (dd) in
the downfield region. Regarding the corresponding β isomers, it
that of the corresponding α isomer by more than double.
Separation of the two constitutional isomers is best achieved at
the stage of the acyl derivatives 2a,b−6a,b (X = CO) by
applying conventional flash chromatography on silica gel. The
separation is aided by the large differences of the corresponding
Rf values and by the higher solubility of the α-acyl derivatives
2a−6a in comparison to that of the less soluble β-acyl isomers
2b−6b. After separation of the isomers, the carbonyl
functionality of the acyl derivatives is reduced to −CH2− by
the borane reagent t-BuNH2·BH3, affording 7a−10a and 7b−
10b in good yields.
4
is proton 2-H that is split into a pseudotriplet (dd(t), J ≅ 2
Hz), appearing together with the signal of 5-H (dd) in the
1
downfield region of the H NMR. Reciprocally, the upfield-
3
shifted proton 4-H exhibits a doublet of doublets (dd, J = 3
Hz, 4J = 2 Hz). The correlation of the proton signals within the
1
cyclopentadienyl rings was fully confirmed by H−1H-COSY
measurements. In the 1H−1H-COSY NMRs of the BFD
derivatives 2a,b−6a,b (see the Supporting Information) with an
acyl functionality (X = CO), the correlations consistently
display the inner protons 2-H, 5-H, 7-H, 10-H, 2′-H, 5′-H, 7′-H,
10′-H shifted downfield, as can be rationalized by the added
deshielding effects of two neighboring cyclopentadienyl rings.
In contrast, all outer β protons of BFD (3-H, 4-H, 8-H, 9-H, 3′-
H, 4′-H, 8′-H, 9′-H) experience deshielding effects from only
one aromatic cyclopentadienyl ring and thus appear more
Structural Identification of α and β Constitutional
Isomers. Unambiguous structural identification of the two
monosubstituted BFD isomers is derived from characteristic
1
multiplets of their fulvalene ring protons in simple H NMR
1
spectra, which is further ascertained by results from H−1H-
COSY and 1H−1H-ROESY NMR measurements. Figure 1
1
upfield in the H NMR spectra.
In order to allow for an accurate assignment of all individual
protons in the BFD system, in particular also those at the
unsubstituted cyclopentadienyl rings, the 1H−1H-ROESY
technique was applied. As an example, Figures 3 and 4 display
1
the H−1H-ROESY NMRs of the α and β constitutional BFD
derivatives 3a,b. In the case of α isomer 3a intense cross signals
are detected between protons 5-H(dd) and 7-H(dt), 5′-H(dt)
and 7′-H(dt), and 2′-H(dt) and 10′-H(dt), which enabled a
reliable assignment of protons at the neighboring cyclo-
pentadienyl rings. In compliance with the expected doublet of
triplets, using the multiplicity of the inner protons 2′-H, 5′-H, 7-
H, 7′-H, 10′-H and cross-checking the 1H−1H-ROESY
Figure 1. Top view of the substituted fulvalene system of α and β
constitutional isomers 2a,b−10a,b. The different multiplet splittings
(dt, dd, dd(t), td) of the ring protons observed in the 1H NMR spectra
are indicated.
gives a top view of the substituted fulvalene system of 2a,b−
10a,b that describes the different multiplet splittings (dt, dd,
1
assignments with the respective H−1H-COSY correlations,
the individual proton positions can be assigned over the whole
BFD system. In the same manner, the proton assignments were
made for β isomer 3b. Corroborating the suggested structure of
3b, the multiplet of 4-H is now a doublet of doublets (dd, 3J ≅
1
dd(t), td) as observed in the H NMR. The multiplets are
characteristic for either of the two isomers, allowing us to
readily differentiate α and β constitutional isomers. For α
isomer 3a the characteristic NMR pattern is displayed in Figure
2.
In general, the 15 protons of the monosubstituted BFDs
show up as two discrete sets of signals in the 1H NMR. One set
is shifted downfield (range 6.1−5.1 ppm) and the other to the
upfield region (range 4.4−3.6 ppm). In the course of assigning
all of them, we realized that the inner protons of the
unsubstituted cyclopentadienyl rings (7-H, 10-H, 7′-H, 10′-H,
2′-H, 5′-H) show up as doublets of triplets (dt, 3J ≅ 2 Hz, 4J ≅ 1
Hz) in the downfield region, whereas the outer protons (8-H,
4
3 Hz, J ≅ 2 Hz). In addition, a strong cross-peak is detected
1
between 2-H(dd(t)) and 10-H(dt) by H−1H-ROESY. Addi-
tional cross-checking with corresponding 1H−1H-COSY
correlations confirmed the complete assignments of all protons.
As described in Synthesis of New BFD Derivatives, the
reduction of the carbonyl functionality in α derivatives 2a−5a
and β derivatives 2b−5b leads to the corresponding saturated α
and β isomers 7a−10a and 7b−10b. Equally for the latter, the
protons show up as two distinct sets of downfield- and upfield-
1
shifted H NMR signals. Unfortunately, due to strong signal
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1
Figure 3. H−1H-ROESY NMR of α isomer 3a (the region of the BFD proton signals is shown).
1
Figure 4. H−1H-ROESY NMR of β isomer 3b (the region of the BFD proton signals is shown).
overlap not all protons within the two different sets (see
1H−1H-COSY NMR of 8a,b and 7a,b in the Supporting
Information) are clearly resolved, making it difficult to
unambiguously assign all protons equally for alkyl-substituted
BFDs.
monosubstituted BFD isomers are assumed to display eight
upfield protons.
1
In contrast, we present herein convincing evidence from H
1
1
NMR, H−1H-COSY, and H−1H-ROESY NMR analysis that
1
the formerly reported H NMR assignments of α- and β-
substituted BFD isomers need to be corrected and reversed. On
Our assignment of the constitutional isomers is reversing that
used so far in the literature.5 Concerning the acetyl-substituted
BFDs 2a,b (X = CO, R = CH3) two references assume for
assignment that the inner α protons next to the bridge between
1
the basis of the presented H NMR multiplet assignments and
1
1H−1H-COSY as well as H−1H-ROESY NMR correlations,
any α-monosubstituted BFD may be identified rather easily by
the appearance of a set of seven downfield-shifted (δ 6.1−5.0
ppm) and a second set of eight upfield-shifted (δ 4.4−3.1 ppm)
1
the two cyclopentadienyl rings ought to appear upfield in H
NMR, because they “experience greater diamagnetic aniso-
tropy” in the vicinity of the two iron centers.5 In contrast, the
outer β protons were supposed to appear more downfield, due
to the reduced shielding by only one iron atom. It was
concluded that α-monosubstituted BFD systems should exhibit
1
BFD protons in the H NMR. In contrast, β monosubstitution
is recognized by a set of eight downfield-shifted (δ 6.9−5.3
ppm) and a second set of seven upfield-shifted proton (δ 4.4−
1
3.4 ppm) signals. This simple H NMR assignment protocol
will facilitate the exact identification and precise assignment of
the different BFD derivatives in upcoming applications.
1
seven protons shifted upfield in the H NMR, whereas the β-
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a
Table 2. Oxidation Potentials of BFD Derivatives 2a,b−10a,b
b
c
b
c
entry
1E1/2 (VFc)
2E1/2 (VFc)
ΔE (V)
Kc
entry
1E1/2 (VFc)
2E1/2 (VFc)
ΔE (V)
Kc
1
−0.29
−0.15
−0.13
−0.16
−0.14
−0.20
−0.14
−0.17
−0.10
−0.15
−0.10
0.38
0.51
0.54
0.51
0.52
0.49
0.51
0.51
0.55
0.56
0.56
0.67
0.66
0.67
0.67
0.66
0.69
0.65
0.68
0.65
0.71
0.66
2.3 × 1011
1.5 × 1011
2.3 × 1011
2.3 × 1011
1.5 × 1011
5.0 × 1011
1.0 × 1011
3.4 × 1011
1.0 × 1011
1.1 × 1012
1.5 × 1011
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
7a
−0.29
−0.32
−0.29
−0.32
−0.27
−0.30
−0.25
−0.28
0.39
0.35
0.38
0.35
0.40
0.36
0.41
0.37
0.68
0.67
0.67
0.67
0.67
0.66
0.66
0.65
3.4 × 1011
2.3 × 1011
2.3 × 1011
2.3 × 1011
2.3 × 1011
1.5 × 1011
1.5 × 1011
1.0 × 1011
7b
8a
8b
9a
9b
10a
10b
a
b
c
Conditions: CH2Cl2, 0.1 M NBu4PF6, scan rate 0.1 V s−1. ΔE = E1/2 − E1/2. Kc = 10ΔE/0.059 V
.
2
1
−
−
Electrochemical Investigations. The results of the cyclic
Table 3. Half-Life (t1/2, min) of BFD+PF6 vs Fc+PF6 in
voltammetry investigations on derivatives 2a,b−10a,b and the
parent BFD (1) in dichloromethane are summarized in Table 2.
As typical mixed-valence class III compounds, all BFD systems
display two well-separated redox waves. In the case of 1, the
monocationic state (BFD0/BFD+) at 1E1/2 = −0.29 VFc and the
Aqueous Buffer Solution
pH
c
d
e
e
d
f
entry
pH 7
pH 8
pH 9
pH 10 pH 11
12
a
BFD+PF6
168 000
120
72 000
50
42 000
9
7 200
2
660
<1
120
<1
−
b
Fc+PF6
−
2
dicationic state (BFD+/BFD2+) at E1/2 = +0.38 VFc are
a
b
1 mM in acetonitrile/buffer (50/50 v/v). 2 mM in acetonitrile/
separated by a potential difference of 670 mV, furnishing a large
comproportionation constant Kc of 2.3 × 1011, very typical for a
mixed-valence class III compound.16 The Kc values of all
derivatives 2a,b−10a,b are found in the same regime without
notable deviations. Thus, the pronounced mixed-valence
character of the parent BFD system remains intact upon
substitution. According to the criteria of Nicholson and Shain,17
2a,b−10a,b proved to be fully reversible redox systems as for
the parent BFD. The influence of a carbonyl group in 2a,b−
6a,b entails a distinct anodic shift of both redox waves: for
example, in the case of the alkanoyl derivatives 2a,b and 3a,b,
an anodic shift of ca. 140−150 mV. A slightly stronger anodic
shift is exerted by acyl substituents attached at the β position
(2b−6b) than by those at the α position (2a−6a). When the
carbonyl group was replaced by a methylene unit (7a,b−10a,b),
both redox waves were found at almost the same positions as
those of the parent BFD (1). However, as with all acyl BFDs,
equally in the alkyl derivatives, a β substituent exerts a greater
influence on the redox potential than an α substituent.
c
d
buffer (50/50 v/v). KH2PO4/Na2HPO4. H3BO3/NaOH/HCl.
e
f
Na2B4O7/NaOH. Na2HPO4/NaOH.
BFD+ exceeds that of Fc+ by 1400 times and at pH 10 by up to
3600 times. In previous literature reports addressing the low
stability of Fc+ in the presence of nucleophiles, the iron center
was identified as the primary target in the decomposition: e.g.,
the iron center is attacked by HO− with formation of Fe(OH)3,
in particular, in the case of an alkaline aqueous solution.18 One
can rationalize the significantly higher stability of BFD+ by two
contributors: (i) delocalization of the positive charge over two
iron centers in the mixed-valence class III system renders the
BFD+ less electrophilic with only 0.5 positive charge per iron
center, and (ii) the more extended fulvalene units in the BFD
system contribute to a more effective shielding of the iron
atoms against nucleophilic attack.
The relative stability gain of BFD+ vs Fc+ was determined at
different pH values: pH 7 (1400×), pH 8 (1440×), pH 9
(4670×), and pH 10 (3600×). While the error is considered to
be 10% at pH 7 and pH 8, the very rapid decay of Fc+ at pH 9
and pH 10 leads to an error of 30%. Accordingly, the different
relative stabilities at distinct pH values may be simply due to
the larger errors in the kinetic measurement at high pH.
It is important to note that there are other ways to stabilize
ferrocene-type cations in comparison to the parent system: e.g.,
by permethylation as well as by donor substituents such as in
biferrocene4 and oligoferrocenes. For example, decamethylfer-
rocenium showed an improved stability vs the ferrocenium
cation in neutral and acidic aqueous medium.19
Spectroelectrochemistry of 8a,b. UV−vis−near-IR
absorption spectra of the alkyl-substituted BFD derivatives
8a,b in dichloromethane at both the monocation and dication
oxidation state are shown in Figure 5. The band region at
5000−10 000 cm−1 is characteristic for the BFD monocation as
a typical class III mixed-valence system. Absorption maxima are
located at 6300 cm−1 (shoulder at 8020 cm−1) and at 6550
cm−1 (shoulder at 8140 cm−1) for 8a+ and 8b+, respectively,
and are attributed to intervalence charge resonance (IVCR)20,21
transitions,22 as supported by recent TD-DFT calculations
(Table 4).23 Observed differences in the IVCR bands of both
Stability of BFD+ vs Fc+ Ion in Aqueous Solution. To
provide a comparison with the reported rapid decomposition of
Fc+ (ferrocenium ion) in basic aqueous solution,18 we
investigated the stability of the BFD+ monocation under
identical conditions. The stability of BFD+PF6− and Fc+PF6− in
various aqueous buffer solutions at pH 7−12 was determined
by following the decrease of their characteristic UV−vis
absorptions at 596 and 617 nm, respectively. Table 2 shows
the half-life times (t1/2 = ln 2/k) at different pH values averaged
over a total duration of 3 half-lives. Pseudo-first-order kinetics
during the decomposition process was assumed, allowing us to
read out k as the slope in the absorbance plot of ln[(At − A∞)/
(A0 − A∞)] vs time. Due to the extremely large lifetime of
BFD+PF6 at pH 7 (t1/2 = 168 000 min = 117 days) data
−
acquisition was restricted to 1 half-life in this case. Initial
concentrations of BFD+PF6 and Fc+PF6 were adjusted to 1
and 2 mM in an acetonitrile/buffer mixture (50/50 v/v),
respectively, to obtain a reasonable absorbance at the
beginning. The results of the measurements are summarized
in Table 3 and attest to the superior stability of the BFD+ vs
that of the Fc+ ion at all pH values. At pH 7, the stability of
−
−
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Spectroelectrochemical investigations indicate that alkyl sub-
stitution at position 2 or 3 of BFD will not decrease the mixed-
valence class III character; thus, it is suggested to utilize BFD+
and its derivatives in known and future water-based applications
instead of Fc+. A fundamental prerequisite to any wide use of
BFD systems in practical applications, however, will be the
facile availability of not only mono- but even difunctionalized
BFD derivatives, a challenge that hopefully will find some
solution in the near future.
EXPERIMENTAL SECTION
■
General Remarks. The atom-numbering system used for the BFD
system was proposed by Goldberg and Matteson.24 11-Bromounde-
canoic acid chloride was prepared by reaction of the corresponding
acid with oxalyl chloride in dichloromethane (CH2Cl2) and was used
without distillation. p-Iodobenzoic acid chloride (Aldrich), p-
methoxybenzoic acid chloride, sym-trimethylbenzoic acid chloride,
acetyl chloride, and t-BuNH2·BH3 (Acros) were purchased and used
without further purification. Copper powder for synthesis (1−5 μm)
was received from Aldrich and used without activation. AlCl3 was
purified by sublimation. Carbon disulfide (CS2) was dried over P2O5,
dichloromethane (CH2Cl2) and 1,2-dichloroethane (C2H4Cl2) were
dried over CaH2. Cautionary warning on the handling of 1,2-
dichloroethane and carbon disulfide! 1,2-Dichloroethane (C2H4Cl2)
may cause cancer and kidney damage. Carbon disulfide (CS2) is toxic
to kidneys, the nervous system, and liver by all routes of exposure and
is very hazardous in case of skin contact (permeator). Wear impervious
protective clothing and eye protection and work only in well-ventilated
hoods. BFD+PF6− and Fc+PF6− were prepared according to a modified
literature procedure (see the Supporting Information).25,28
Figure 5. UV−vis−near-IR spectra of 8a (neutral, red −··−;
monocation, red ; dication, red - - -) and 8b (neutral, black −··−;
monocation, black ; dication, black - - -) in dichloromethane at 298
K.
isomeric derivatives 8a+ and 8b+ are very small. In both cases,
the position and the shape of the measured IVCR bands are in
full compliance with results in the literature on the parent
BFD+PF6 measured in acetonitrile.23 During anodic prepara-
−
tion of the dications 8a2+ and 8b2+, the IVCR bands vanish
completely while simultaneously a new band at 21 300 cm−1
(shoulder at 23 000 cm−1) appears. As expected for a BFD2+
dication, the mixed-valence class III character is lost. From a
comparison of the IVCR spectra of 8a+ and 8b+ and that of the
1
Instrumental Methods. H NMR and 13C NMR spectra were
recorded on a 400 MHz Bruker Avance spectrometer or on a 600
MHz Varian spectrometer. The chemical shifts (δ) are reported in
ppm and are referenced with regard to the residual protiated solvent:
tetrachloroethane-d2, δ 5.91 (1H) and δ 74.2 (13C); chloroform-d, δ
7.26 (1H) and δ 77.0 (13C); benzene-d6, δ 7.15 (1H) and δ 128.0
(13C). The following abbreviations were utilized to describe NMR
peak splitting: s, singlet; d, doublet; t, triplet; dd, doublet of doublets;
dt, doublet of triplets; dd(t), doublet of doublets with two identical
coupling constants; td, triplet of doublets.
parent BFD+PF6 in CH2Cl2, it can be concluded that IVCR
−
bands keep their position and shape almost invariant of alkyl vs
H substitution. Apparently, alkyl substitution in positions 2 or 3
of the BFD system does not affect the mixed-valence class III
character of the BFD+ cation. Thus, the mixed-valence class III
property should be a part of other alkyl-substituted BFD
derivatives as well, opening interesting venues for future
applications.
For all cyclic voltammetry measurements (EG&G 2273 potentio-
stat/galvanostat), a conventional three-electrode setup was used, with
a 1 mm platinum-disk working electrode, a platinum-wire counter
electrode, and a silver wire as pseudoreference electrode. Tetra-n-
CONCLUSIONS
■
−
butylammonium hexafluorophosphate (TBA+PF6 ) served as support-
The notoriously difficult functionalization of BFD was
improved by applying a modified Friedel−Crafts acylation
protocol, allowing us to access several new BFD derivatives in
reasonable yields. α and β constitutional isomers of various
monosubstituted BFD systems were separated by chromatog-
raphy and fully assigned by 1H−1H-COSY and 1H−1H-ROESY
NMR, leading to a correction of previous erroneous assign-
ments. In a kinetic study, the superior stability of the BFD+
monocation vs the ferrocenium ion (Fc+) in aqueous solution
becomes apparent, a feature that is related to the pronounced
mixed-valence class III property of BFD+-type monocations.
ing electrolyte, and decamethylferrocene (E1/2 = −0.54 VFc) was used
as the internal standard. Spectroelectrochemical measurements were
performed on a Perkin-Elmer Lambda 750 UV−vis−near-IR
spectrometer. Spectroelectrochemistry was carried out in transmission
mode by using a thin-layer cell that has been already described in
detail,26 with a transparent gold minigrid serving as the working
electrode. The molar extinction coefficients εM (M−1 cm−1) of the
−
neutral BFD derivatives 8a,b and of the BFD+PF6 salt in
dichloromethane were determined in a 1 cm cuvette and were
averaged over three measurements, leading to an accuracy of at least
0.7%.
Table 4. UV−Vis−Near-IR Absorption Bands of 8a,b and BFD+PF6− in Dichloromethane, As Measured in a Transparent Gold-
Minigrid Thin-Layer Cell
UV−vis−near-IR abs/cm−1 (εM/M−1·cm−1
)
monocation
entry
neutral
IVCR
band II
band III
LMCT
dication
BFD+PF6
6450 (2090)
6300 (2050)
6550 (2300)
16 670 (380)
16 560 (430)
16 560 (450)
21 370 (1120)
21 280 (1180)
21 280 (1260)
30 120 (5540)
30 200 (5670)
29 990 (6160)
−
8a
8b
21 645 (296)
21 550 (298)
21 280 (4500)
21 280 (4600)
1874
dx.doi.org/10.1021/om201215w | Organometallics 2012, 31, 1870−1878

Organometallics
Article
1,1′-Biferrocenylene (1). 1,1′-Biferrocenylene was prepared via
Ullmann coupling of 1,1′-diiodoferrocene27 according to a literature
procedure.28 A mixture of 17.2 g (39.3 mmol) of 1,1′-diiodoferrocene,
25.0 g (393 mmol) of copper powder, and 400 g of biphenyl was
heated at 180 °C for 18 h. The reaction mixture was filtered hot
9-H), 3.80 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8′-H), 3.60 (td, 3J = 2 Hz, 4J =
1 Hz, 1H, 3′-H), 2.25 (s, 3H, 2′′-H). 13C NMR (C2D2Cl4): δ 202.4
(CO), 100.9, 97.8, 93.2, 93.0, 77.7, 73.5, 70.19, 70.21, 69.8, 69.7 (2
C), 69.4, 69.4, 69.0, 67.9 (2 C), 67.4, 67.2, 67.0, 66.7, 27.7. Anal. Calcd
for C22H18Fe2O: C, 64.44; H, 4.42. Found: C, 64.72; H, 4.32.
2-(11″-Bromoundecanoyl)-1,1′-biferrocenylene (3a). Flash chro-
matography (silica: dichloromethane/n-hexane, 60/40 v/v; Rf = 0.32).
Yield: 0.61 g (20%). Mp: 117 °C. IR (KBr, cm−1): 3089 (C−HAr, w),
2921 (s), 2848 (m), 1679 (CO, s), 1466 (m), 1428 (m), 1409 (m),
1374 (w), 1342 (m), 1271 (m), 1249 (w), 1224 (m), 1087 (w), 1047
(m), 1029 (m), 1000 (m), 927 (m), 858 (m), 808 (s), 756 (w), 726
(m), 640 (m), 552 (w), 501 (s), 412 (w). 1H NMR (C2D2Cl4): δ 6.09
through a Buchner funnel into n-hexane (1.5 L). The reddish brown
̈
precipitate was filtered off and purified by sublimation (240 °C at 0.07
mbar). The yield ranged between 1.80 and 2.70 g (25−37%). 1H
NMR (400 MHz, C6D6): δ 5.23 (m, 8H), 3.75 (m, 8H). Anal. Calcd
for C20H16Fe2: C, 65.27; H, 4.38. Found: C, 65.45; H, 4.29.
Compounds 2a,b−6a,b. General Procedure A: Friedel−
Crafts Acylation of BFD (1). Under nitrogen, 1,1′-biferrocenylene
(1.80 g, 4.89 mmol) in 150 mL of dry CS2 was heated to 50 °C. A
solution of the respective acid chloride (4.89 mmol) and AlCl3 (1.50 g,
11.2 mmol, 2.3 equiv) in dry dichloroethane (120 mL) was added
rapidly to the reaction mixture. After 3 as well as 12 h an additional
portion of solid AlCl3 (1.50 g, 11.2 mmol) was added. After a further
12 h, the reaction mixture was cooled to room temperature and water
(100 mL) was added. The separated aqueous layer was acidified with
hydrochloric acid to pH 1 and extracted with 100 mL of CH2Cl2. The
combined organic layers were washed twice with saturated NaHCO3
solution and water and finally dried over Na2SO4. After evaporation of
the solvent under reduced pressure, the solid was purified by flash
column chromatography.
Compounds 7a,b−10a,b. General Procedure B: Carbonyl
Reduction of BFD Derivatives. To a suspension of AlCl3 (600 mg,
4.50 mmol) in CH2Cl2 (60 mL) was added t-BuNH2·BH3 (783 mg,
9.00 mmol) at 0 °C. After the mixture was stirred for 15 min, a
solution of 1.50 mmol of the respective carbonyl compound (2a,b−
5a,b) in CH2Cl2 (50 mL) was added dropwise to the mixture. After
completion of the addition, stirring was continued for 1 h at room
temperature. Finally, the reaction mixture was quenched carefully with
0.1 M hydrochloric acid (50 mL). After extraction of the aqueous layer
with 50 mL of CH2Cl2, the combined organic layers were washed
twice with 50 mL of brine and dried over Na2SO4. After solvent
evaporation under reduced pressure the residue was purified by flash
column chromatography over silica (n-hexane/CH2Cl2).
3
4
3
4
(dt, J = 2 Hz, J = 1 Hz, 1H, 10-H), 5.69 (dd, J = 3 Hz, J = 2 Hz,
1H, 5-H), 5.28 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7′-H), 5.24 (dt, 3J = 2 Hz,
4J = 1 Hz, 1H, 7-H), 5.21 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 2′-H), 5.12 (dt,
3J = 2 Hz, 4J = 1 Hz, 1H, 10′-H), 5.06 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 5′-
3
3
4
H), 4.40 (dd(t), J = 3 Hz, 1H, 4-H), 4.21 (dd, J = 3 Hz, J = 2 Hz,
1H, 3-H), 4.12 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 3′-H), 4.02 (m, 2H, 9-H,
8′-H), 3.83 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8-H), 3.81 (td, 3J = 2 Hz, 4J =
1 Hz, 1H, 4′-H), 3.78 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9′-H), 3.36 (t, 3J =
7 Hz, 2H, 11″-H), 3.10 (ddd, 2J = 16 Hz, 3J = 8 Hz, 3J = 6 Hz, 1H, 2″-
Ha), 2.80 (ddd, 2J = 16 Hz, 3J = 8 Hz, 3J = 6 Hz, 1H, 2″-Hb), 1.79 (m,
4H, 3″-H, 10″-H), 1.36 (m, 8H, 4″-H, 5″-H, 8″-H, 9″-H), 1.27 (m, 4H,
6″-H, 7″-H). 13C NMR (C2D2Cl4): δ 206.1 (CO), 98.1, 94.3, 92.3,
91.8, 80.6, 75.7, 74.1, 72.7, 72.3, 71.4, 71.1, 71.1, 70.0, 69.8, 69.1, 68.6,
68.2, 67.9, 66.4, 66.2, 41.4, 35.0, 33.1, 29.9 (2C), 29.8, 29.8, 29.1, 28.5,
25.4. Anal. Calcd for C31H55BrFe2O: C, 60.52; H, 5.73. Found: C,
60.59; H, 5.65.
3-(11″-Bromoundecanoyl)-1,1′-biferrocenylene (3b). Flash chro-
matography (silica: dichloromethane; Rf = 0.29). Yield: 1.28 g (43%).
Mp: 190 °C. IR (KBr, cm−1): 3100 (C−HAr, m), 2914 (s), 2851 (m),
1670 (CO, s), 1453 (m), 1409 (w), 1344 (w), 1292 (m), 1270 (m),
1225 (w), 1175 (w), 1089 (w), 1048 (m), 1030 (s), 900 (w), 851 (m),
1
823 (m), 806 (s), 714 (w), 644 (m), 551 (w), 509 (s), 483 (s). H
NMR (C2D2Cl4): δ 5.95 (dd(t), 4J = 2 Hz, 1H, 2-H), 5.67 (dd, 3J = 3
Hz, 4J = 2 Hz, 1H, 5-H), 5.50 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 2′-H), 5.47
(dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 10-H), 5.43 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H,
10′-H), 5.39 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7-H), 5.34 (dt, 3J = 2 Hz, 4J
= 1 Hz, 1H, 5′-H), 5.28 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7′-H), 4.40 (dd,
3J = 3 Hz, 4J = 2 Hz, 1H, 4-H), 4.03 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 4′-
H), 3.88 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9′-H), 3.87 (td, 3J = 2 Hz, 4J = 1
Hz, 1H, 8-H), 3.85 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9-H), 3.80 (td, 3J = 2
Hz, 4J = 1 Hz, 1H, 8′-H), 3.60 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 3′-H), 3.34
2-Acetyl-1,1′-biferrocenylene (2a). Flash chromatography (silica:
dichloromethane; Rf = 0.29). Yield: 0.36 g (18%). Mp: 222 °C. IR
(KBr, cm−1): 3088 (C−HAr, w), 1663 (CO, s), 1499 (w), 1431 (m),
1399 (m), 1352 (m), 1270 (w), 1245 (s), 1206 (w), 1157 (w), 1112
(w), 1051 (m), 1031 (s), 999 (m), 930 (w), 897 (w), 853 (m), 809
(s), 694 (w), 635 (w), 584 (w), 546 (m), 504 (s), 484 (s), 422 (w).
3
4
1H NMR (600 MHz, C2D2Cl4): δ 6.08 (dt, J = 2 Hz, J = 1 Hz, 1H,
10-H), 5.71 (dd, 3J = 3 Hz, 4J = 2 Hz, 1H, 5-H), 5.29 (dt, 3J = 2 Hz, 4J
= 1 Hz, 1H, 7′-H), 5.25 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7-H), 5.23 (dt, 3J
3
(t, J = 7 Hz, 2H, 11″-H), 2.55 (m, 2H, 2″-H), 1.77 (m, 2H, 10″-H),
1.56 (m, 2H, 3″-H), 1.33 (m, 2H, 9″-H), 1.22 (m, 10H, 4″-H, 5″-H, 6″-
H, 7″-H, 8″-H). 13C NMR (C2D2Cl4): δ 205.0 (CO), 100.6, 97.7,
93.3, 93.1, 77.6, 73.3, 70.1, 69.8, 69.7, 69.7, 69.6, 69.4, 69.4, 68.8, 67.8,
67.5, 67.3, 67.2, 67.0, 66.8, 39.8, 35.0, 33.1, 29.8, 29.8, 29.7 (2C), 29.1,
28.5, 24.9. Anal. Calcd for C31H55BrFe2O: C, 60.52; H, 5.73. Found:
C, 60.79; H, 5.69.
4
3
4
= 2 Hz, J = 1 Hz, 1H, 2′-H), 5.13 (dt, J = 2 Hz, J = 1 Hz, 1H, 10′-
3
4
3
H), 5.07 (dt, J = 2 Hz, J = 1 Hz, 1H, 5′-H), 4.41 (dd(t), J = 3 Hz,
1H, 4-H), 4.19 (dd, 3J = 3 Hz, 4J = 2 Hz, 1H, 3-H), 4.13 (td, 3J = 2 Hz,
4J = 1 Hz, 1H, 3′-H), 4.02 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9-H), 4.01 (td,
3J = 2 Hz, 4J = 1 Hz, 1H, 8′-H), 3.83 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8-
H), 3.82 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 4′-H), 3.78 (td, 3J = 2 Hz, 4J = 1
Hz, 1H, 9′-H), 2.65 (s, 3H, 2′′-H). 13C NMR (C2D2Cl4): δ 203.7 (C
O), 98.5, 94.5, 92.6, 92.2, 80.2, 75.7, 73.8, 72.4, 72.3, 72.0, 71.3, 71.1,
69.8, 69.7, 69.2, 68.6, 68.2, 68.1, 66.6, 66.3, 29.9. Anal. Calcd for
C22H18Fe2O: C, 64.44; H, 4.42. Found: C, 64.65; H, 4.26.
2-(p-Methoxybenzoyl)-1,1′-biferrocenylene (4a). Flash chroma-
tography (silica: dichloromethane; Rf = 0.39). Yield: 0.33 g (13%).
Mp: 156 °C. IR (KBr, cm−1): 3084 (C−HAr, w), 1642 (CO, s),
1599 (s), 1574 (m), 1508 (m), 1428 (s), 1332 (m), 1254 (s), 1162
(s), 1028 (s), 914 (m), 899 (m), 844 (s), 808 (s), 769 (m), 621 (m),
1
3
501 (s). H NMR (C2D2Cl4): δ 7.87 (d, J = 9 Hz, 2H, 3″-H, 7″-H),
6.81 (d, 3J = 9 Hz, 2H, 4″-H, 6″-H), 5.72 (dd, 3J = 3 Hz, 4J = 2 Hz, 1H,
5-H), 5.61 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 2′-H), 5.57 (dt, 3J = 2 Hz, 4J =
1 Hz, 1H, 10-H), 5.41 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7′-H), 5.32 (dt, 3J
= 2 Hz, 4J = 1 Hz, 1H, 10′-H), 5.27 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7-H),
5.10 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 5′-H), 4.34 (dd(t), 3J = 3 Hz, 1H, 4-
H), 4.23 (td, 3J = 3 Hz, 4J = 2 Hz, 1H, 3′-H), 4.02 (td, 3J = 2 Hz, 4J = 1
Hz, 1H, 8′-H), 3.99 (dd, 3J = 2 Hz, 4J = 1 Hz, 1H, 3-H), 3.91 (td, 3J =
3-Acetyl-1,1′-biferrocenylene (2b). Flash chromatography (silica:
dichloromethane/ethyl acetate, 95/5 v/v; Rf = 0.52). Yield: 0.80 g
(40%). Mp: 260 °C dec. IR (KBr, cm−1): 3098 (C−HAr, w), 2922 (w),
2856 (w), 1665 (CO, s), 1450 (s), 1409 (m), 1355 (m), 1295 (m),
1269 (m), 1237 (m), 1176(w), 1115 (w), 1047 (s), 1031 (s), 1008
(m), 966 (w), 901 (w), 850 (m), 808 (s), 630 (w), 551 (w), 524 (m),
506 (s), 484 (s). 1H NMR (C2D2Cl4): δ 5.96 (dd(t), 4J = 2 Hz, 1H, 2-
H), 5.68 (dd, 3J = 3 Hz, 4J = 2 Hz, 1H, 5-H), 5.51 (dt, 3J = 2 Hz, 4J = 1
Hz, 1H, 2′-H), 5.46 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 10-H), 5.44 (dt, 3J =
2 Hz, 4J = 1 Hz, 1H, 10′-H), 5.39 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7-H),
5.35 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 5′-H), 5.28 (dt, 3J = 2 Hz, 4J = 1 Hz,
4
3
4
2 Hz, J = 1 Hz, 1H, 9-H), 3.78 (td, J = 2 Hz, J = 1 Hz, 1H, 4′-H),
3.77 (s, 3H, 8″-H) 3.71 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8-H), 3.70 (td, 3J
= 2 Hz, 4J = 1 Hz, 1H, 9′-H). 13C NMR (C2D2Cl4): δ 198.0 (CO),
163.2, 132.4, 131.9, 113.7, 97.9, 94.8, 93.3, 93.2, 85.7, 73.4, 72.3, 71.8,
71.6, 71.3, 71.3, 69.9, 69.4, 69.4, 69.2, 68.3, 68.1, 67.0, 66.0, 65.5, 55.9.
Anal. Calcd for C28H22Fe2O2: C, 66.97; H, 4.42. Found: C, 67.18; H,
4.37.
3
4
3
1H, 7′-H), 4.38 (dd, J = 3 Hz, J = 2 Hz, 1H, 4-H), 4.06 (td, J = 2
Hz, 4J = 1 Hz, 1H, 4′-H), 3.89 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9′-H), 3.88
(td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8-H), 3.85 (td, 3J = 2 Hz, 4J = 1 Hz, 1H,
1875
dx.doi.org/10.1021/om201215w | Organometallics 2012, 31, 1870−1878

Organometallics
Article
3-(p-Methoxybenzoyl)-1,1′-biferrocenylene (4b). Flash chroma-
tography (silica: dichloromethane/ethyl acetate, 95/5 v/v; Rf = 0.63).
Yield: 1.10 g (45%). Mp: 300 °C dec. IR (KBr, cm−1): 3095 (C−HAr,
w), 1624 (CO, s), 1601 (s), 1510 (m), 1438 (m), 1406 (m), 1321
(m), 1271(s), 1253 (s), 1173 (m), 1155 (m), 1079 (w), 1030 (m),
5.37 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 2′-H), 5.33 (dt, 3J = 2 Hz, 4J = 1 Hz,
1H, 7-H), 4.95 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7′-H), 4.44 (dd(t), 3J = 3
Hz, 1H, 4-H), 4.20 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9′-H), 4.15 (td, 3J = 2
Hz, 4J = 1 Hz, 1H, 9-H), 4.14 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 4′-H), 3.76
(td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8-H), 3.75 (td, 3J = 2 Hz, 4J = 1 Hz, 1H,
3′-H),3.63 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8′-H), 3.58 (dd, 3J = 3 Hz, 4J =
2 Hz, 1H, 3-H), 2.26 (s, 9H, 8″-H, 9″-H, 10″-H). 13C NMR (C2D2Cl4):
δ 206.5 (CO), 139.9, 138.5, 134.3, 128.8, 98.8, 96.4, 93.3, 92.5, 82.3,
75.6, 73.4, 73.2, 73.1, 71.7, 71.6, 71.0, 69.6, 69.5, 69.0, 68.9, 68.7, 67.2,
65.7, 65.3, 21.5, 20.3. Anal. Calcd for C30H26Fe2O: C, 70.07; H, 5.10.
Found: C, 70.14; H, 5.04.
1
843 (m), 807 (m), 770 (m), 623 (m), 511 (s), 482 (s). H NMR
3
3
(C2D2Cl4): δ 7.82 (d, J = 9 Hz, 2H, 3″-H, 7″-H), 6.91 (d, J = 9 Hz,
2H, 4″-H, 6″-H), 6.11 (dd(t), 4J = 2 Hz, 1H, 2-H), 5.76 (dd, 3J = 3 Hz,
4J = 2 Hz, 1H, 5-H), 5.56 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 2′-H), 5.51 (dt,
3J = 2 Hz, 4J = 1 Hz, 1H, 10-H), 5.46 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 10′-
H), 5.43 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7-H), 5.36 (dt, 3J = 2 Hz, 4J = 1
Hz, 1H, 5′-H), 5.29 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7′-H), 4.48 (dd, 3J =
3-(sym-Trimethylbenzoyl)-1,1′-biferrocenylene (6b). Flash chro-
matography (silica: dichloromethane/n-hexane, 80/20 v/v; Rf = 0.55).
Yield: 1.23 g (49%). Mp: 264 °C dec. IR (KBr, cm−1): 3098 (C−HAr,
w), 2962 (w), 2918 (w), 2854 (w), 1644 (CO, s), 1611 (m), 1439
(s), 1380 (w), 1346 (w), 1308 (m), 1294 (m), 1272 (w), 1240 (m),
1172 (w), 1075 (w), 1031 (m), 1013 (m), 968 (w), 845 (s), 810 (s),
4
3
4
3 Hz, J = 2 Hz, 1H, 4-H), 4.06 (td, J = 2 Hz, J = 1 Hz, 1H, 4′-H),
3.89 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9′-H), 3.88 (td, 3J = 2 Hz, 4J = 1 Hz,
1H, 8-H), 3.86 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9-H), 3.82 (s, 3H, 8″-H),
3.80 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8′-H), 3.57 (td, 3J = 2 Hz, 4J = 1 Hz,
1H, 3′-H). 13C NMR (C2D2Cl4): δ 197.7 (CO), 162.6, 132.4, 130.7,
113.8, 100.9, 97.9, 93.3, 93.3, 77.0, 73.5, 71.1, 70.6, 70.5, 69.9, 69.8,
69.6, 69.5, 69.4, 69.3, 68.2, 67.4, 67.2, 67.0, 66.7, 55.9. Anal. Calcd for
C28H22Fe2O2: C, 66.97; H, 4.42. Found: C, 67.28; H, 4.32.
1
725 (w), 625 (w), 525 (w), 498 (s). H NMR (C2D2Cl4): δ 6.81 (s,
2H, 4″-H, 6″-H), 5.74 (dd(t), 4J = 2 Hz, 1H, 2-H), 5.68 (dd, 3J = 3 Hz,
3
4
4J = 2 Hz, 1H, 5-H), 5.54 (dt, J = 2 Hz, J = 1 Hz, 1H, 10′-H), 5.42
(dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 10-H), 5.30 (m, 2H, 7-H, 2′-H), 5.24 (dt,
3J = 2 Hz, 4J = 1 Hz, 1H, 5′-H), 5.21 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7′-
H), 4.29 (dd, 3J = 3 Hz, 4J = 2 Hz, 1H, 4-H), 4.04 (td, 3J = 2 Hz, 4J = 1
Hz, 1H, 8′-H), 4.00 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9′-H), 3.94 (td, 3J = 2
Hz, 4J = 1 Hz, 1H, 9-H), 3.88 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 4′-H), 3.85
(td, 3J = 2 Hz, 4J = 1 Hz, 1H, 3′-H), 3.84 (td, 3J = 2 Hz, 4J = 1 Hz, 1H,
8-H), 2.27 (s, 3H, 10″-H), 2.08 (s, 6H, 8″-H, 9″-H). 13C NMR
(C2D2Cl4): δ 205.6 (CO), 138.7, 138.2, 134.6, 128.9, 100.2, 96.9,
92.7, 92.4, 79.6, 73.1, 71.0, 70.5, 70.1 (4C), 69.8 (2C), 69.5, 67.8, 67.6,
67.4, 67.2, 67.1, 21.5, 20.3. Anal. Calcd for C30H26Fe2O: C, 70.07; H,
5.10. Found: C, 70.23; H, 5.02.
2-(p-Iodobenzoyl)-1,1′-biferrocenylene (5a). Flash chromatogra-
phy (silica: dichloromethane/n-hexane, 80/20 v/v; Rf = 0.60). Yield:
0.32 g (11%). Mp: 200 °C. IR (KBr, cm−1): 3082 (C−HAr, w), 1648
(CO, s), 1579 (m), 1480 (w), 1423 (m), 1383 (m), 1339 (m), 1255
(m), 1182 (w), 1105 (w), 1059 (m), 1031 (m), 1001 (m), 985 (m),
898 (w), 850 (s), 826 (m), 810 (s), 757 (m), 729 (w), 687 (w), 602
(w), 551 (w), 503 (s), 489 (m). 1H NMR (C2D2Cl4): δ 7.73 (d, 3J = 8
Hz, 2H, 3″-H, 7″-H), 7.61 (d, 3J = 8 Hz, 2H, 4″-H, 6″-H), 5.80 (dd, 3J =
3
3 Hz, 4J = 2 Hz, 1H, 5-H), 5.74 (dt, J = 2 Hz, 4J = 1 Hz, 1H, 10-H),
5.49 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 2′-H), 5.40 (dt, 3J = 2 Hz, 4J = 1 Hz,
1H, 7′-H), 5.29 (dt, 3J = 2 Hz, 4J = 1 Hz, 2H, 10′-H, 7-H), 5.07 (dt, 3J
4
3
= 2 Hz, J = 1 Hz, 1H, 5′-H), 4.41 (dd(t), J = 3 Hz, 1H, 4-H), 4.19
(td, 3J = 2 Hz, 4J = 1 Hz, 1H, 3′-H), 4.04 (td, 3J = 2 Hz, 4J = 1 Hz, 1H,
2-Ethyl-1,1′-biferrocenylene (7a). Flash chromatography (silica:
dichloromethane/n-hexane, 50/50 v/v; Rf = 0.81). Yield: 0.42 g
(70%). Mp: 175 °C. IR (KBr, cm−1): 3097 (C−HAr, w), 2965 (w),
2848 (w), 1460 (w), 1407 (w), 1381 (w), 1267 (m), 1140 (w), 1075
(m), 1048 (m), 1030 (m), 998 (m), 953 (w), 848 (m), 806 (m), 686
(w), 640 (w), 570 (w), 501 (s). 1H NMR (C2D2Cl4): δ 5.48 (dt, 3J = 2
8′-H), 3.96 (m, 2H, 9-H, 3-H), 3.77 (td, J = 2 Hz, 4J = 1 Hz, 1H, 4′-
3
H), 3.75 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8-H), 3.73 (td, 3J = 2 Hz, 4J = 1
Hz, 1H, 9′-H). 13C NMR (C2D2Cl4): δ 199.6 (CO), 139.3, 137.7,
130.8, 100.1, 98.6, 95.6, 92.8, 92.7, 82.7, 73.8, 73.6, 72.3, 72.3, 72.0,
71.5, 70.3, 69.0, 69.6, 69.4, 68.6, 68.3, 67.4, 66.1, 65.8. Anal. Calcd for
C27H19Fe2IO: C, 54.23; H, 3.20. Found: C, 54.31; H, 3.00.
4
3
4
Hz, J = 1 Hz, 1H, 10-H), 5.40 (dt, J = 2 Hz, J = 1 Hz, 1H, 7-H),
3
4
5.35 (m, 2H, 7′-H, 5-H), 5.30 (dt, J = 2 Hz, J = 1 Hz, 1H, 10′-H),
5.27 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 5′-H), 5.00 (dt, 3J = 2 Hz, 4J = 1 Hz,
1H, 2′-H), 3.95 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 3′-H), 3.90 (td, 3J = 2 Hz,
4J = 1 Hz, 1H, 8-H), 3.87 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8′-H), 3.85 (m,
2H, 9-H, 9′-H), 3.83 (dd(t), 3J = 2.4 Hz, 1H, 4-H), 3.78 (td, 3J = 2 Hz,
3-(p-Iodobenzoyl)-1,1′-biferrocenylene (5b). Flash chromatogra-
phy (silica: dichloromethane; Rf = 0.35). Yield: 0.98 g (33%). Mp: 235
°C dec. IR (KBr, cm−1): 3099 (C−HAr, w), 1628 (CO, s), 1578
(m), 1555 (w), 1443 (m), 1409 (m), 1385 (w), 1347 (w), 1312 (m),
1293 (m), 1271 (w), 1250 (m), 1177 (m), 1108 (w), 1080 (m), 1050
(m), 1033 (m), 1006 (s), 969 (m), 854 (s), 834 (s), 806 (s), 757 (s),
4J = 1 Hz, 1H, 4′-H), 3.73 (dd, J = 2 Hz, J = 1 Hz, 1H, 3-H), 3.48
(dq, 2J = 15 Hz, 3J = 8 Hz, 1H, 1″-Ha), 3.25 (dq, 2J = 15 Hz, 3J = 8 Hz,
1H, 1″-Hb), 1.40 (t, 3J = 8 Hz, 3H, 2″-H). 13C NMR (C2D2Cl4): δ 95.5,
95.2, 95.1, 92.4, 91.7, 72.5, 70.4, 70.3, 69.7, 69.5, 69.3, 68.8, 67.2, 66.9,
66.7, 66.6, 66.3, 66.2, 65.7, 65.1, 23.2, 15.5. Anal. Calcd for C22H20Fe2:
C, 66.71; H, 5.09. Found: C, 66.95; H, 5.03.
3
4
1
683 (w), 609 (w), 572 (w), 500 (s), 484 (s), 431 (w). H NMR
3
3
(C2D2Cl4): δ 7.78 (d, J = 8 Hz, 2H, 3″-H, 7″-H), 7.49 (d, J = 8 Hz,
2H, 4″-H, 6″-H), 6.07 (dd(t), 4J = 2 Hz, 1H, 2-H), 5.79 (dd, 3J = 3 Hz,
4J = 2 Hz, 1H, 5-H), 5.54 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 2′-H), 5.50 (dt,
3J = 2 Hz, 4J = 1 Hz, 1H, 10-H), 5.45 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 10′-
H), 5.42 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7-H), 5.35 (dt, 3J = 2 Hz, 4J = 1
Hz, 1H, 5′-H), 5.28 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7′-H), 4.45 (dd, 3J =
3-Ethyl-1,1′-biferrocenylene (7b). Flash chromatography (silica:
dichloromethane; Rf = 0.97). Yield: 0.40 g (68%). Mp: 210 °C. IR
(KBr, cm−1): 3098 (C−HAr, w), 2964 (w), 2845 (w), 1524 (w), 1469
(w), 1407 (w), 1378 (w), 1324 (w), 1300 (w), 1268 (m), 1108 (w),
1080 (w), 1027 (s), 918 (w), 847 (s), 807 (s), 638 (w), 607 (w), 508
4
3
4
3 Hz, J = 2 Hz, 1H, 4-H), 4.05 (td, J = 2 Hz, J = 1 Hz, 1H, 4′-H),
3.90 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9′-H), 3.89 (td, 3J = 2 Hz, 4J = 1 Hz,
1H, 8-H), 3.86 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9-H), 3.80 (td, 3J = 2 Hz,
1
3
4
(s). H NMR (C2D2Cl4): δ 5.41 (dt, J = 2 Hz, J = 1 Hz, 1H, 2′-H),
4J = 1 Hz, 1H, 8′-H), 3.58 (td, J = 2 Hz, J = 1 Hz, 1H, 3′-H). 13C
NMR (C2D2Cl4): δ 198.5 (CO), 139.1, 137.9, 129.8, 101.8, 99.1,
98.3, 93.0, 92.9, 76.0, 74.1, 71.1, 70.5, 70.3, 69.9, 69.8, 69.7, 69.7, 69.5,
69.4, 68.3, 67.5, 67.3, 67.1, 66.8. Anal. Calcd for C27H19Fe2IO: C,
54.23; H, 3.20. Found: C, 54.29; H, 3.02.
3
4
3
4
5.34 (dt, J = 2 Hz, J = 1 Hz, 1H, 10′-H), 5.32 (m, 2H, 2-H, 7′-H),
3
4
5.31 (m, 2H, 10-H, 7-H), 5.29 (dt, J = 2 Hz, J = 1 Hz, 1H, 5′-H),
5.24 (dd, 3J = 2 Hz, 4J = 1 Hz, 1H, 5-H), 3.87 (td, 3J = 2 Hz, 4J = 1 Hz,
1H, 4′-H), 3.81 (m, 4H, 8-H, 8′-H, 9-H, 9′-H), 3.75 (dd, 3J = 2 Hz, 4J =
1 Hz, 1H, 4-H), 3.58 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 3′-H), 2.14 (m, 2H,
1″-H), 1.07 (t, 3J = 8 Hz, 3H, 2″-H). 13C NMR (C2D2Cl4): not
recorded due to solubility problems. Anal. Calcd for C22H20Fe2: C,
66.71; H, 5.09. Found: C, 66.50; H, 4.91.
2-(sym-Trimethylbenzoyl)-1,1′-biferrocenylene (6a). Flash chro-
matography (silica: dichloromethane/n-hexane, 50/50 v/v; Rf = 0.37).
Yield: 0.45 g (18%). Mp: 225 °C. IR (KBr, cm−1): 3096 (C−HAr, w),
2952 (w), 2918 (w), 2854 (w), 1659 (CO, s), 1609 (m), 1428 (s),
1375 (w), 1339 (m), 1250 (m), 1188 (w), 1060 (m), 1030 (m), 999
(w), 888 (w), 839 (s), 810 (s), 734 (w), 629 (w), 549 (w), 502 (s). 1H
NMR (C2D2Cl4): δ 6.82 (s, 2H, 4″-H, 6″-H), 6.41 (dt, 3J = 2 Hz, 4J = 1
Hz, 1H, 10-H), 5.95 (dd, 3J = 3 Hz, 4J = 2 Hz, 1H, 5-H), 5.51 (dt, 3J =
2 Hz, 4J = 1 Hz, 1H, 10′-H), 5.47 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 5′-H),
2-(11″-Bromoundecyl)-1,1′-biferrocenylene (8a). Flash chroma-
tography (silica: dichloromethane/n-hexane, 50/50 v/v; Rf = 0.77).
Yield: 0.68 g (75%). Mp: 109 °C. IR (KBr, cm−1): 3082 (C−HAr, w),
2922 (m), 2847 (m), 1465 (m), 1268 (m), 1045 (m), 1027 (m), 996
(m), 850 (m), 831 (m), 807 (s), 724 (m), 699 (w), 646 (m), 566 (w),
500 (s). 1H NMR (C2D2Cl4): δ 5.46 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 10-
1876
dx.doi.org/10.1021/om201215w | Organometallics 2012, 31, 1870−1878

Organometallics
Article
H), 5.38 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7-H), 5.35 (dt, 3J = 2 Hz, 4J = 1
Hz, 1H, 7′-H), 5.34 (dd, 3J = 2 Hz, 4J = 1 Hz, 1H, 5-H), 5.30 (dt, 3J =
2 Hz, 4J = 1 Hz, 1H, 10′-H), 5.25 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 5′-H),
4.99 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 2′-H), 3.95 (td, 3J = 2 Hz, 4J = 1 Hz,
1H, 3′-H), 3.88 (m, 2H, 8-H, 8′-H), 3.86 (td, 3J = 2 Hz, 4J = 1 Hz, 1H,
2-(p-Iodobenzyl)-1,1′-biferrocenylene (10a). Flash chromatogra-
phy (silica: dichloromethane/n-hexane, 50/50 v/v; Rf = 0.74). Yield:
0.62 g (71%). Mp: 219 °C dec. IR (KBr, cm−1): 3078 (C−HAr, w),
1483 (m), 1434 (w), 1397 (m), 1267 (m), 1256 (m), 1101 (w), 1054
(m), 1031 (m), 1008 (m), 876 (w), 843 (s), 807 (s), 727 (w), 631
(w), 505 (s). 1H NMR (C2D2Cl4): δ 7.52 (d, 3J = 8 Hz, 2H, 3″-H, 7″-
H), 6.95 (d, 3J = 8 Hz, 2H, 4″-H, 6″-H), 5.41 (dt, 3J = 2 Hz, 4J = 1 Hz,
1H), 5.39 (dd, 3J = 2 Hz, 4J = 1 Hz, 1H, 5-H), 5.34 (m, 2H), 5.30 (m,
3
9-H), 3.83 (m, 2H, 9′-H, 4-H), 3.75 (td, J = 2 Hz, 4J = 1 Hz, 1H, 4′-
H), 3.69 (dd, 3J = 2 Hz, 4J = 1 Hz, 1H, 3-H), 3.39 (ddd, 2J = 15 Hz, 3J
3
3
= 10 Hz, J = 7 Hz, 1H, 1″-Ha), 3.37 (t, J = 7 Hz, 2H, 11″-H), 3.25
(ddd, 2J = 15 Hz, 3J = 10 Hz, 3J = 7 Hz, 1H, 1″-Hb), 1.80 (m, 2H, 10″-
H), 1.66 (m, 2H, 2″-H), 1.49 (m, 2H, 3″-H), 1.36 (m, 4H, 4″-H, 9″-H),
1.27 (m, 8H, 5″-H, 6″-H, 7″-H, 8″-H). 13C NMR (C2D2Cl4): δ 95.5,
95.2 (2C), 92.3, 90.3, 72.6, 70.4, 70.3, 69.6, 69.5, 69.2, 68.8, 67.4, 67.3,
67.0, 66.7, 66.2, 66.1, 65.7, 65.2, 35.0, 33.1, 31.4, 30.3, 30.3, 30.0, 30.0,
29.9, 29.8, 29.1, 28.5. Anal. Calcd for C31H57BrFe2: C, 61.93; H, 6.20.
Found: C, 62.29; H, 6.18.
2
2H), 5.08 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H), 4.93 (d, J = 16 Hz, 1H, 1″-
2
3
4
Ha), 4.52 (d, J = 16 Hz, 1H, 1″-Hb), 3.91 (td, J = 2 Hz, J = 1 Hz,
1H), 3.90 (td, 3J = 2 Hz, 4J = 1 Hz, 1H), 3.86 (m, 2H, 4-H), 3.85 (m,
1H), 3.79 (m, 2H), 3.58 (dd, 3J = 2 Hz, 4J = 1 Hz, 1H, 3-H). 13C NMR
(C2D2Cl4): δ 141.3, 137.7, 130.9, 95.5, 94.7 (2 C), 92.9, 91.6, 87.2,
72.6, 71.0, 70.6, 69.7, 69.7, 69.5, 69.1, 68.6, 67.3, 67.1, 66.8, 66.5 (2 C),
66.3, 65.8, 35.8. Anal. Calcd for C27H21Fe2I: C, 55.52; H, 3.62. Found:
C, 55.60; H, 3.42.
3-(11″-Bromoundecyl)-1,1′-biferrocenylene (8b). Flash chroma-
tography (silica: dichloromethane/n-hexane, 80/20 v/v; Rf = 0.76).
Yield: 0.71 g (79%). Mp: 185 °C. IR (KBr, cm−1): 3100 (C−HAr, w),
2925 (m), 2849 (m), 1523 (w), 1471 (m), 1269 (m), 1080 (w), 1027
3-(p-Iodobenzyl)-1,1′-biferrocenylene (10b). Flash chromatogra-
phy (silica: dichloromethane/n-hexane, 80/20 v/v; Rf = 0.94). Yield:
0.66 g (75%). Mp: 225 °C dec. IR (KBr, cm−1): 3082 (C−HAr, w),
1523 (w), 1482 (m), 1400 (w), 1378 (w), 1292 (w), 1268 (m), 1206
(w), 1195 (m), 1108 (w), 1079 (w), 1035 (s), 1006 (s), 944 (m), 845
(s), 802 (s), 739 (m), 678 (w), 634 (w), 528 (w), 506 (s), 484 (s),
1
(s), 939 (w), 847 (m), 806 (s), 713 (w), 506 (s), 485 (s). H NMR
(C2D2Cl4): δ 5.43 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 2′-H), 5.35 (dt, 3J = 2
4
Hz, J = 1 Hz, 1H, 10′-H), 5.32 (m, 4H, 10-H, 7′-H, 2-H, 7-H), 5.29
1
3
452 (w). H NMR (C2D2Cl4): δ 7.51 (d, J = 8 Hz, 2H, 3″-H, 7″-H),
(dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 5′-H), 5.24 (dd, 3J = 2 Hz, 4J = 1 Hz, 1H,
6.82 (d, 3J = 8 Hz, 2H, 4″-H, 6″-H), 5.41 (m, 1H), 5.32 (m, 2H), 5.31
5-H), 3.87 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 4′-H), 3.81 (m, 4H, 8-H, 8′-H,
3
4
(m, 1H), 5.29 (m, 4H), 3.86 (td, J = 2 Hz, J = 1 Hz, 1H), 3.82 (m,
2H), 3.80 (m, 2H), 3.75 (dd, 3J = 2 Hz, 4J = 1 Hz, 1H, 4-H), 3.59 (td,
3J = 2 Hz, 4J = 1 Hz, 1H), 3.56 (d, 2J = 16 Hz, 1H, 1″-Ha), 3.32 (d, 2J =
16 Hz, 1H, 1″-Hb). 13C NMR (C2D2Cl4): δ 141.4, 137.6, 130.8, 95.2,
95.0, 94.7, 94.4, 91.5, 86.1, 70.6, 69.9, 69.8, 69.4, 69.3 (2C), 69.2, 69.0,
68.7, 67.0 (2C), 66.7, 66.7, 66.7, 66.5, 35.2. Anal. Calcd for
C27H21Fe2I: C, 55.52; H, 3.62. Found: C, 55.58; H, 3.41.
3
4
3
9-H, 9′-H), 3.74 (dd, J = 2 Hz, J = 1 Hz, 1H, 4-H), 3.54 (td, J = 2
Hz, 4J = 1 Hz, 1H, 3′-H), 3.36 (t, 3J = 7 Hz, 2H, 11″-H), 2.20 (ddd, 2J
= 15 Hz, 3J = 9 Hz, 3J = 6 Hz, 1H, 1″-Ha), 2.04 (ddd, 2J = 15 Hz, 3J = 9
Hz, 3J = 6 Hz, 1H, 1″-Hb), 1.78 (m, 2H, 10″-H), 1.37 (m, 4H, 2″-H, 9″-
H), 1.21 (m, 12H, 3″-H, 4″-H, 5″-H, 6″-H, 7″-H, 8″-H). 13C NMR
(C2D2Cl4): δ 95.2, 95.1, 94.6, 94.1, 88.5, 70.4, 69.9, 69.6, 69.2 (2C),
69.1 (2C), 68.7, 68.1, 66.8, 66.5 (2C), 66.4, 66.4 (2C), 35.0, 33.1, 31.4,
29.9 (3C), 29.8 (2C), 29.2, 29.1, 28.5. Anal. Calcd for C31H57BrFe2: C,
61.93; H, 6.20. Found: C, 62.11; H, 6.21.
ASSOCIATED CONTENT
■
2-(p-Methoxybenzyl)-1,1′-biferrocenylene (9a). Flash chromatog-
raphy (silica: dichloromethane/n-hexane, 50/50 v/v; Rf = 0.42). Yield:
0.55 g (75%). Mp: 220 °C. IR (KBr, cm−1): 3098 (C−HAr, w), 1612
(w), 1582 (w), 1514 (m), 1465 (w), 1438 (w), 1381 (w), 1317 (w),
1300 (m), 1242 (m), 1175 (m), 1132 (w), 1107 (m), 1071 (w), 1027
(m), 998 (m), 967 (w), 932 (w), 875 (w), 847 (m), 808 (m), 759
(m), 730 (m), 583 (m), 531 (m), 510 (s), 449 (m). 1H NMR
S
* Supporting Information
Figures and text giving additional H−1H-COSY NMR and
1
1H−1H-ROESY NMR spectra of the BFD derivatives 2a,b−
8a,b and details of the preparation of BFD+PF6 and Fc+PF6 .
This material is available free of charge via the Internet at
http://pubs.acs.org.
−
−
3
3
(C2D2Cl4): δ 7.14 (d, J = 9 Hz, 2H, 3″-H, 7″-H), 6.77 (d, J = 9 Hz,
2H, 4″-H, 6″-H), 5.41 (dt, 3J = 2 Hz, 4J = 1 Hz, 1H, 7-H), 5.40 (m, 2H,
10-H, 5-H), 5.36 (m, 2H, 10′-H, 7′-H), 5.30 (dt, 3J = 2 Hz, 4J = 1 Hz,
AUTHOR INFORMATION
Corresponding Author
* E-mail: schmittel@chemie.uni-siegen.de. Fax: (int +49) 271
740 3270.
■
3
4
2
1H, 5′-H), 5.11 (dt, J = 2 Hz, J = 1 Hz, 1H, 2′-H), 4.90 (d, J = 16
Hz, 1H, 1″-Ha), 4.56 (d, 2J = 16 Hz, 1H, 1″-Hb), 3.94 (td, 3J = 2 Hz, 4J
= 1 Hz, 1H, 3′-H), 3.91 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 8-H), 3.87 (m,
3H, 8′-H, 4-H, 9′-H), 3.81 (td, 3J = 2 Hz, 4J = 1 Hz, 1H, 9-H), 3.79 (td,
3J = 2 Hz, 4J = 1 Hz, 1H, 4′-H), 3.70 (s, 3H, 8″-H), 3.61 (dd, 3J = 2 Hz,
4J = 1 Hz, 1H, 3-H). 13C NMR (C2D2Cl4): δ 158.0, 133.7, 129.7,
114.1, 95.3, 95.0, 94.9, 92.8, 88.5, 72.7, 70.8, 70.5, 69.8, 69.7, 69.4,
69.0, 68.6, 67.3, 67.1, 66.8, 66.4, 66.4, 66.2, 65.7, 55.6, 35.4. Anal.
Calcd for C28H24Fe2O: C, 68.89; H, 4.96. Found: C, 69.05; H, 4.88.
3-(p-Methoxybenzyl)-1,1′-biferrocenylene (9b). Flash chromatog-
raphy (silica: dichloromethane/n-hexane, 75/25 v/v; Rf = 0.74). Yield:
0.53 g (73%). Mp: 197 °C. IR (KBr, cm−1): 3098 (C−HAr, w), 1610
(m), 1583 (w), 1511 (s), 1462 (m), 1436 (w), 1319 (w), 1300 (m),
1269 (m), 1244 (s), 1175 (m), 1107 (w), 1078 (w), 1035 (s), 1012
(m), 943 (w), 847 (s), 808 (s), 762 (m), 635 (w), 684 (w), 609 (w),
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We thank the Deutsche Forschungsgemeinschaft (DFG) for
financial support (FOR 516) and Dr. Gilbert Noll for help with
the spectroelectrochemistry.
■
̈
REFERENCES
■
(1) (a) Rausch, M. D.; Kovar, R. F.; Kraihanzel, C. S. J. Am. Chem.
Soc. 1969, 91, 1259−1261. (b) Hedberg, F. L.; Rosenberg, H. J. Am.
Chem. Soc. 1969, 91, 1258−1259.
(2) Robin, M. B.; Day, P. Adv. Inorg. Chem. Radiochem. 1967, 10,
247−422.
1
3
555 (w), 505 (s), 488 (s). H NMR (C2D2Cl4): δ 6.99 (d, J = 9 Hz,
3
3
2H, 3″-H, 7″-H), 6.74 (d, J = 9 Hz, 2H, 4″-H, 6″-H), 5.41 (dt, J = 2
Hz, 4J = 1 Hz, 1H), 5.31 (m, 5H, 2-H), 5.28 (dt, 3J = 2 Hz, 4J = 1 Hz,
1H), 5.27 (dd, 3J = 2 Hz, 4J = 1 Hz, 1H, 5-H), 3.87 (td, 3J = 2 Hz, 4J =
(3) (a) Tropiano, M.; Kilah, N. L.; Morten, M.; Rahman, H.; Davis, J.
J.; Beer, P. D.; Faulkner, S. J. Am. Chem. Soc. 2011, 133, 11847−11849.
(b) Thakur, A.; Sardar, S.; Ghosh, S. Inorg. Chem. 2011, 50, 7066−
7073. (c) Martic, S.; Labib, M.; Shipman, P. O.; Kraatz, H. B. Dalton
Trans. 2011, 40, 7264−7290. (d) Kater, B.; Hunold, A.; Schmalz, H.
G.; Kater, L.; Bonitzki, B.; Jesse, P.; Prokop, A. J. Cancer Res. Clin.
Oncol. 2011, 137, 639−649. (e) Ornelas, C. New J. Chem. 2011, 35,
1973−1985. (f) Daeneke, T.; Kwon, T. H.; Holmes, A. B.; Duffy, N.
3
4
1 Hz, 1H), 3.81 (m, 4H), 3.76 (dd, J = 2 Hz, J = 1 Hz, 1H, 4-H),
3.70 (s, 3H, 8″-H), 3.61 (td, 3J = 2 Hz, 4J = 1 Hz, 1H), 3.55 (d, 2J = 15
Hz, 1H, 1″-Ha), 3.32 (d, 2J = 15 Hz, 1H, 1″-Hb). 13C NMR (C2D2Cl4):
δ 157.9, 133.9, 129.7, 114.0, 94.9, 94.8, 94.7, 94.6, 87.4, 70.7, 70.0,
69.8, 69.4, 69.3 (2C), 69.3, 69.0, 68.6, 66.9 (2C), 66.6 (2C), 66.6, 66.5,
55.6, 34.8. Anal. Calcd for C28H24Fe2O: C, 68.89; H, 4.96. Found: C,
68.71; H, 4.81.
1877
dx.doi.org/10.1021/om201215w | Organometallics 2012, 31, 1870−1878

Organometallics
Article
W.; Bach, U.; Spiccia, L. Nat. Chem. 2011, 3, 211−215. (g) Itoh, Y.;
Kim, B.; Gearba, R. I.; Tremblay, N. J.; Pindak, R.; Matsuo, Y.;
Nakamura, E.; Nuckolls, C. Chem. Mater. 2011, 23, 970−975.
(4) (a) Siebler, D.; Foster, C.; Gasi, T.; Heinze, K. Organometallics
2011, 30, 313−327. (b) Diallo, A. K.; Menuel, S.; Monflier, E.; Ruiz, J.;
Astruc, D. Tetrahedron Lett. 2010, 51, 4617−4619. (c) Ochi, Y.;
Suzuki, M.; Imaoka, T.; Murata, M.; Nishihara, H.; Einaga, Y.;
Yamamoto, K. J. Am. Chem. Soc. 2010, 132, 5061−5069. (d) Lohan,
M.; Justaud, F.; Roisnel, T.; Ecorchard, P.; Lang, H.; Lapinte, C.
Organometallics 2010, 29, 4804−4817. (e) Lohan, M.; Ecorchard, P.;
Ruffer, T.; Justaud, F.; Lapinte, C.; Lang, H. Organometallics 2009, 28,
1878−1890. (f) Chen, W.; Chen, S. W.; Ding, F. Z.; Wang, H. B.;
Brown, L. E.; Konopelski, J. P. J. Am. Chem. Soc. 2008, 130, 12156−
12162.
(28) LeVanda, C.; Bechgaard, K.; Cowan, D. O.; Mueller-Westerhoff,
U. T.; Eilbracht, P.; Candela, G. A.; Collins, R. L. J. Am. Chem. Soc.
1976, 98, 3181−3187.
(5) (a) Pittman, C. U. Jr.; Surynarayanan, B. J. Am. Chem. Soc. 1974,
96, 7916−7919. (b) Sakamoto, K.; Nishihara, H.; Aramaki, K. J. Chem.
Soc., Dalton Trans. 1992, 1877−1881.
(6) (a) Scott, P.; Rief, U.; Diebold, J.; Brintzinger, H. H.
Organometallics 1993, 12, 3094−3101. (b) Jaitner, P.;
Schottenberger, H.; Gamper, S.; Obendorf, D. J. Organomet. Chem.
1994, 475, 113−120.
(7) van Staveren, D. R.; Metzler-Nolte, N. Chem. Rev. 2004, 104,
5931−5985.
(8) Kang, D.; Zuo, X.; Yang, R.; Xia, F.; Plaxco, K. W.; White, R. J.
Anal. Chem. 2009, 81, 9109−9113.
(9) Ferapontova, E. E.; Gothelf, K. V. Langmuir 2009, 25, 4279−
4283.
(10) (a) Schmittel, M.; Langels, A. J. Chem. Soc., Perkin Trans. 2
1998, 565−572. (b) Schmittel, M.; He, B.; Kalsani, V.; Bats, J. W. Org.
Biomol. Chem. 2007, 5, 2395−2403.
(11) Norman, L. L.; Badia, A. J. Am. Chem. Soc. 2009, 131, 2328−
2337.
(12) Bochmann, M.; Lu, J.; Cannon, R. D. J. Organomet. Chem. 1996,
518, 97−103.
(13) (a) Ornelas, C.; Ruiz, J.; Belin, C.; Astruc, D. J. Am. Chem. Soc.
2009, 131, 590−601. (b) Fabre, B. Acc. Chem. Res. 2010, 43, 1509−
1518.
̀
(14) Hillard, E.; Vessieres, A.; Thouin, L.; Jaouen, G.; Amatore, C.
Angew. Chem., Int. Ed. 2006, 45, 285−290.
(15) Schatzschneider, U.; Metzler-Nolte, N. Angew. Chem., Int. Ed.
2006, 45, 1504−1507.
(16) (a) Creutz, C. Prog. Inorg. Chem. 1983, 30, 1−73. (b) Kaim, W.;
Klein, A.; Glockle, M. Acc. Chem. Res. 2000, 33, 755−763.
̈
(17) Nicholson, R. S.; Shain, I. Anal. Chem. 1964, 36, 706−723.
(18) (a) Prins, R.; Korswagen, A. R.; Kortbeek, A. G. T. G. J.
Organomet. Chem. 1972, 39, 335−344. (b) Holecek, J.; Handlir, K.;
Pavlik, I. Collect. Czech. Chem. Commun. 1972, 37, 1805−1815.
(c) Holecek, J.; Handlir, K.; Klikorka, J.; DinhBong, N. Collect. Czech.
Chem. Commun. 1979, 44, 1379−1387.
(19) Tabbì, G.; Cassino, C.; Cavigiolio, G.; Colangelo, D.; Ghiglia,
A.; Viano, I.; Osella, D. J. Med. Chem. 2002, 45, 5786−5796.
(20) Badger, B.; Brocklehurst, B. Trans. Faraday Soc. 1969, 65,
2576−2581.
(21) According to the proposal of Badger and Brocklehurst20 these
bands are labeled as IVCR transitions, owing to the fact that in a real
class III mixed-valence system no charge transfer is responsible for the
observed absorptions and the commonly used term IVCT transition
would not be correct.
(22) Talham, D. R.; Cowan, D. O. Organometallics 1984, 3, 1712−
1715.
(23) Warratz, R.; Aboulfadl, H.; Bally, T.; Tuczek, F. Chem. Eur. J.
2009, 15, 1604−1617.
(24) Goldberg, S. I.; Matteson, R. L. J. Org. Chem. 1964, 29, 323−
326.
(25) Jahn, U.; Hartmann, P.; Dix, I.; Jones, P. G. Eur. J. Org. Chem.
2001, 3333−3355.
(26) Salbeck, J. Anal. Chem. 1993, 65, 2169−2173.
(27) Kovar, R. F.; Rausch, M. D.; Rosenberg, H. Organomet. Chem.
Synth. 1970/1971, 1, 173−181.
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