Synthesis, characterization and electrochemical behaviour of dimethyleneamine-bridged methylated and non-methylated biferrocenyl derivatives

Article abstract of DOI:10.1016/j.jorganchem.2019.06.014

Two dimethyleneamine-bridged octamethylated and non-methylated biferrocenyl complexes, compounds 1 and 2, have been synthesized and characterized by ¹H, ²⁹Si{¹H} and ¹³C{¹H} NMR spectroscopy, and mass spectrometry. The redox activity of the ferrocenyl centers in 1 and 2 has been characterized by cyclic voltammetry in dichloromethane containing [n-Bu₄N][PF₆], [n-Bu₄N][B(C₆F₅)₄] or [n-Bu₄N]Cl as electrolyte support. Their electrochemistry is not only strongly dependent on the solvent/electrolyte medium but also on the substituents of the ferrocenyl moieties. Studies of the electrochemical oxidation of 1 provide evidence of the grafting of a ferrocene species onto platinum electrode surfaces.

Full text of DOI:10.1016/j.jorganchem.2019.06.014

Accepted Manuscript
Synthesis, characterization and electrochemical behaviour of dimethyleneamine-
bridged methylated and non-methylated biferrocenyl derivatives
Raquel Sevilla, Marta Herrero, Beatriz Alonso, M. Pilar García-Armada, Manuel
Algarra, Carmen M. Casado
PII:
S0022-328X(19)30253-0
DOI:
https://doi.org/10.1016/j.jorganchem.2019.06.014
JOM 20826
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 3 May 2019
Revised Date: 12 June 2019
Accepted Date: 13 June 2019
Please cite this article as: R. Sevilla, M. Herrero, B. Alonso, M.P. García-Armada, M. Algarra, C.M.
Casado, Synthesis, characterization and electrochemical behaviour of dimethyleneamine-bridged
methylated and non-methylated biferrocenyl derivatives, Journal of Organometallic Chemistry (2019),
doi: https://doi.org/10.1016/j.jorganchem.2019.06.014.
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ACCEPTED MANUSCRIPT
Synthesis,
characterization
and
electrochemical
behaviour
of
dimethyleneamine-bridged methylated and non-methylated biferrocenyl
derivatives
Raquel Sevilla,a Marta Herrero,a Beatriz Alonso,*a M. Pilar García-Armada,b Manuel
Algarra c and Carmen M. Casado*a
a Departamento de Química Inorgánica, Facultad de Ciencias, Universidad Autónoma de
Madrid, 28049-Madrid, Spain.
b Departamento de Ingeniería Química Industrial, Escuela Técnica Superior de Ingenieros
Industriales, Universidad Politécnica de Madrid, 28006-Madrid, Spain.
c Centro de Química da Madeira, Universidade da Madeira, Campus da Penteada, 9020-105
Funchal, Portugal.
KEYWORDS. Ferrocene; octamethylferrocene; electrochemistry; modified electrodes; electronic
communication.
Abstract
Two dimethyleneamine-bridged octamethylated and non-methylated biferrocenyl
1
complexes, compounds 1 and 2, have been synthesized and characterized by H,
13
29Si{1H} and C{1H} NMR spectroscopy, and mass spectrometry. The redox activity of
the ferrocenyl centers in 1 and 2 has been characterized by cyclic voltammetry in
dichloromethane containing [n-Bu4N][PF6], [n-Bu4N][B(C6F5)4] or [n-Bu4N]Cl as
electrolyte support. Their electrochemistry is not only strongly dependent on the
solvent/electrolyte medium but also on the substituents of the ferrocenyl moieties.
Studies of the electrochemical oxidation of 1 provide evidence of the grafting of a
ferrocene species onto platinum electrode surfaces.
1. Introduction
Organometallic mixed-valence species have long been the subject of a plethora
of studies.1-7 Among them, complexes bearing linked ferrocenyl units have
emerged as an important category of materials due to the high thermal stability
and interesting electrochemistry of ferrocene.8-19 However, complexes containing
chemically equivalent ferrocenyl centers bridged by a dimethyleneamine group
have been comparatively much less developed. In most of these studies,
modulation and control of the degree of electronic communication between the
ferrocene centers have been investigated by different means such as

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protonation or alkylation of the nitrogen bridge and by changing the solvent
polarity and electrolyte nature.20-23 Nevertheless, to the best of our knowledge,
no examples have been reported to date on alkylamine linked
bis(polymethylatedferrocenyl) complexes. In the present work, we report our
findings on the electrochemistry of two new dimethyleneamine-bridged
octamethylated and non-methylated biferrocenyl derivatives using three
electrolytes with anions of different coordinating properties. ∆E1/2 values and the
corresponding comproportionation constants, Kc, will be used as a guide to
compare the degree of the electronic interaction between the organometallic
centers. We will also examine the formation of a ferrocene derivative layer
persistently attached to the electrode surface.
2. Results and discussion
2.1.
Synthesis and characterization
N,N-bis((ferrocenyl)methyl)N-propyldiethoxymethylsilylamine, 1, has been synthesized
following a literature procedure,20,21 by refluxing (ferrocenylmethyl)trimethylammonium
iodide and 3-aminopropyldiethoxymethylsilane in acetonitrile (Scheme 1).
Scheme 1. Synthesis of 1.
The synthesis of the bis(octamethylatedferrocenyl) complex was not so straightforward
(Scheme 2). The key starting step in the preparation of the new compound is the
previous synthesis of the (octamethylferrocenyl)methyl carbocation.24 This
organometallic fragment was prepared by Vilsmeier reaction of octamethyl ferrocene to
give
octamethylferrocenyl
aldehyde,
which
was
then
reduced
to
(octamethylferrocenyl)methyl methanol by treatment with LiAlH4. Finally, it was
converted into (octamethylferrocenyl)methyl carbocation by treatment with acetic
anhydride and HBF4.Et2O.

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N,N-bis((octamethylferrocenyl)methyl)N-propyl diethoxymethylsilylamine, 2, was then
-
prepared via nucleophilic attack of 3-aminopropyldiethoxymethylsilane on the BF4 salt
of (octamethylferrocenyl)methyl carbocation in acetone.
Scheme 2. Synthesis of 2.
1
13
29
1
and
2
were characterized by H, C and Si NMR spectroscopy and FAB or
1
MALDI-TOF MS. H NMR spectra of
1 and 2 show key signals arising from the
organometallic moieties in the ranges 4.2−4.0 ppm and 1.9−1.6 ppm,
respectively, along with resonances corresponding to the adjacent methylene
group at around 3.3 ppm, and those of the protons of the propyl chain −(CH2)3−,
in the region 2.4−0.5 ppm, which have been unambiguously assigned. The
signals of the ethoxysilyl groups appear at around 3.7 and 1.2 ppm and that of
the Si-CH3 group at 0.1 ppm. The structures of
1 and 2 were also confirmed by
the 13C NMR spectra, which display exclusively the resonances expected for the
different carbon atoms (see the Experimental Section). The 29Si{1H} NMR
spectra display only the signal expected for the silicon atom in the molecules.
The FAB mass spectrum of
and the MALDI-TOF mass spectrum of
cases with isotopic patterns matching exactly the calculated values.
1
showed the protonated molecular ion at m/z 588.2,
2
, the molecular ion at m/z 811.5, in both

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2.2.
Electrochemistry
Cyclic voltammetry (CV) of
1
and 2 was recorded on Pt in CH2Cl2 solution,
between 0 and 0.9 V and -0.6 and 0.6 V, respectively, with [n-Bu4N][PF6]
(Figures 1A and 1C) and [n-Bu4N][B(C6F5)4] (Figures 1B and 1D) 0.1 M as
supporting electrolytes. In agreement with the results reported by Geiger and co-
workers, in a low polarity solvent such as dichloromethane, replacement of a
-
‘traditional’ anion such as hexafluorophosphate, PF6 , by the weakly coordinating
-
tetrakis(pentafluorophenyl) borate, B(C6F5)4 , minimizes ion-pairing interactions,
thus causing an important effect on the electrochemical properties.25-28 The
voltammetric behavior of
resembles that observed by Kaifer and co-workers for closely related
complexes.21 As shown in Figure 1A, oxidation of
occurs as a chemically
1 with [n-Bu4N][PF6] as supporting electrolyte,
1
reversible voltammetric composite wave, indicating that the two ferrocenyl
moieties are oxidized in two almost overlapped one-electron processes at 0.45
V, revealing that the electronic communication between the ferrocenyl units can
be considered essentially negligible. However, CVs of
Bu4N][B(C6F5)4] as supporting electrolyte (Figure 1B) show two well-separated
and reversible oxidation waves at E1/21 = 0.390 V and E1/22 = 0.570 V (
E1/2 = 180
1 recorded using [n-
∆
mV, Kc = 1106). This wave splitting, in the absence of electronic interactions, has
to be the result of a considerable through-space electrostatic effect between the
-
ferrocenium centers, in the presence of the weakly-coordinating B(C6F5)4 anion.
A
C
1 µA
B
D
0,0
0,3
0,6
0,9
-0,6
-0,3
0,0
0,3
0,6
E (V vs. SCE)
E (V vs. SCE)
Figure 1. CVs at a Pt-disk electrode in CH2Cl2/0.1 M supporting electrolyte of (A)
with [n-Bu4N][PF6], (B) with [n-Bu4N][B(C6F5)4], (C) with [n-Bu4N][PF6], (D)
with [n-Bu4N][B(C6F5)4]. Scan rate = 100 mV s-1.
1
1
2
2

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On the other hand, in the CVs of
electrolyte (Figure 1C) two partially overlapping waves are observed at E1/2 = -
0.029 V and E1/22 = 0.100 V (
E1/2 = 129 mV, Kc = 152). As expected, there is a
2 measured with [n-Bu4N][PF6] as supporting
1
∆
negative shift in the redox potentials due to the electron donating ability of the
methyl groups. When [n-Bu4N][B(C6F5)4] is used as supporting electrolyte, the
2
two redox waves for
2
appear completely resolved at E1/21 = -0.141 V and E1/2
=
0.043 V (∆E1/2 = 184 mV, Kc = 1293) (Figure 1D). This behavior contrasts with
that observed by Astruc and co-workers10,11 in rigid ferrocenyl-terminated redox
stars and dendrimers with and without methyl substituents on the ferrocenyl
groups, for which in all cases no splitting is observed in the presence of the
-
strongly ion-pairing PF6 , and overlapping waves are obtained with the weakly
-
coordinating anion, B[C6H3(CF3)2]4 .
With the aim of minimizing the electrostatic repulsion between the
electrogenerated charges, by increasing the ion pairing interactions between the
oxidized ferrocenes and the electrolyte anions, we decided to take advantage of
the strong ion-pairing ability of chloride27 and examine the electrochemical
properties of
2 using [n-Bu4N]Cl as supporting electrolyte. Surprisingly, two
overlapped, but clearly distinguishable waves were still observed (Figure 2).
2,0
1,5
1,0
0,5
0,0
-0,5
-1,0
-1,5
-0,4
-0,2
0,0
0,2
0,4
0,6
0,8
E (V vs SCE)
Figure 2. Cyclic voltammogram at a Pt-disk electrode of 2 in CH2Cl2 /[n-Bu4N]Cl 0.1M
solution. Scan rate 100 mV s-1.
The voltammograms of
2 in the three electrolytes show a progression of the
splitting from the smaller to the larger counter anion. This fact is most probably
the result of the electrostatic effect due to the increased steric bulk of the
methylated ligands. The octamethylation of the cyclopentadienyl ligands shields
and weakens the influence of the electrolyte counter anion in
2 compared to 1.

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We had envisaged taking advantage of the –Si(OEt)3 groups in
1 and 2 to
immobilize the complexes on platinum oxide surfaces. However, all our efforts to
obtain the corresponding derivatized electrodes following the procedure we have
previously used,29 were unsuccessful. On the other hand, unexpectedly, when
the potential was held fixed at 1 V vs SCE, for 5 min in a degassed solution of
1
in CH2Cl2/[n-Bu4N][PF6] 0.1 M, using a freshly polished platinum disk electrode,
this resulted in detectable electroactive material persistently attached to the
electrode surface. Figure 3 shows the voltammetric response of this electrode in
fresh CH2Cl2 containing only [n-Bu4N][PF6] 0.1 M. A single well-defined
oxidation-reduction wave is observed, with a formal potential value of +0.59 V vs
SCE and the expected linear relationship of peak current with potential sweep
rate, characteristic of a surface-confined redox species. The fact that no splitting
in the wave was detected, even in the presence of the non-coordinating
-
electrolyte B(C6F5)4 , was a surprising point. All our previous studies in CH2Cl2
solution, on compounds containing interacting ferrocenyl units confined onto
electrode surfaces, lead to two wave redox responses,15,29-31 which suggests that
in this case the rupture of the molecule has occurred.
0,1 µA
0,0
0,2
0,4
0,6
0,8
1,0
1,2
E (V vs SCE)
Figure 3. CV recorded in CH2Cl2 /[n-Bu4N][PF6] 0.1 M, of a Pt disk-electrode
previously modified by holding it at a fixed potential of 1 V for 5 min in a
degassed solution of
1
in CH2Cl2 /[n-Bu4N][PF6] 0.1 M. Scan rate = 100 mV s-1.
The electrochemical behaviour of
1 was then studied in a broader potential
range, up to 1.2 V vs SCE. In contrast to that observed when the potential scan
is reversed at a lower value, a CV characteristic of an ECE’ mechanism is
obtained. In the first scan an additional adsorption reduction peak appears at 0.6

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V (vs SCE),32 with an associate anodic wave that arises in the second scan
(Figure 4).
First scan
Second scan
1 µA
0,0
0,2
0,4
0,6
0,8
1,0
1,2
E (V vs. SCE)
Figure 4. CV of
1 at a Pt electrode in CH2Cl2 /[n-Bu4N][PF6] 0.1 M. Scan rate =
100 mV s-1.
The reduction potential of the new adsorbed system generated after the
oxidation of is very close to that observed for the species attached on the
1
electrode surface mentioned above (Figure 3), and so we have tried to find an
explanation to this fact. It is known that oxidation of aliphatic amines requires
rather positive potentials,33 however, as described by Torriero, Bond and co-
workers, the ferrocenium ion has shown to act as mediator in the catalytic
oxidation of aliphatic amines.34 On the other hand, in the early seventies, Mann
et al reported the cleavage of carbon-nitrogen bonds in tertiary aliphatic amines
upon electro-chemical oxidation.35 Therefore, it can be conceived that some of
the electrochemically generated ferrocenium ions in
1 trigger the electron-
transfer reaction with the amine group. This oxidation process could then be
followed by the cleavage of the carbon-nitrogen bond, to afford a new ferrocenyl
species that remains adsorbed on the electrode surface. The reduction potential
of the new reversible system generated after the oxidation of
1 is very close to
that observed for the species attached on the electrode surface mentioned
above (Figure 3).
In order to evaluate this surmise, we also performed an analogous
electrochemical
study
with
a
degassed
solution
of
N,N-
dimethylferrocenylmethylamine in CH2Cl2 /[n-Bu4N][PF6] 0.1 M. After holding the
potential fixed at 1 V vs SCE for 5 min, the platinum disk electrode was washed
thoroughly with CH2Cl2. A CV recorded in fresh CH2Cl2 containing only [n-

ACCEPTED MANUSCRIPT
Bu4N][PF6] 0.1 M shows a single well-defined oxidation-reduction wave, with a
formal potential value of +0.59 V vs SCE (Figure 5). This result sustains our
assumption of the intramolecular electron transfer process between the amine
group and the ferrocenium center followed by the rupture of the N-C bond,
leading to the formation of a ferrocenyl species that can derivatize electrode
surfaces.
1,0
0,5
0,0
-0,5
-1,0
0,0
0,2
0,4
0,6
0,8
1,0
1,2
E (V vs. SCE)
Figure 5. Voltammetric response of a Pt disk electrode modified with N,N-
dimethylferrocenylmethylamine in CH2Cl2 /[n-Bu4N][PF6] 0.1 M. Scan rate 100 mV s-1.
3. Experimental
3.1. Materials and methods
All reactions were performed under an inert atmosphere using Schlenk
techniques. Solvents were dried by standard procedures over the appropriate
drying agents and distilled immediately prior to use. Reagents were purchased
from Aldrich, Fluka, Panreac and Alfa Aesar and used as received without
further purification. Silica gel 60 silanized (0.063-0.200 mm) was used for column
chromatographic purifications. (Octamethylferrocenyl)methanol was prepared
according to literature procedures.24 NMR spectra were recorded on a FT
BRUKER AMX-300 spectrometer or on a FT BRUKER DRX-500 spectrometer.
Chemical shifts are reported in ppm (δ) relative to residual solvent resonances.
FAB mass spectrum was obtained using a VG AutoSpect mass spectrometer
and 3-Nitrobenzyl alcohol (m-NBA) as matrix. MALDI-TOF mass spectrum was
collected on a Reflex III (Bruker) mass spectrometer and trans-2-[3-(4-tert-
butylphenyl)-2-methyl-2-propenylidene] malononitrile (DCTB) was used as
matrix. Electrochemical experiments were performance using an Autolab
PGSTAT 128N potentiostat. Electrochemical measurements were carried out in

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freshly distilled CH2Cl2 from calcium hydride under argon. A conventional three-
electrode cell was used with a platinum-disk working electrode (A=0.020 cm2),
SCE as the reference electrode and a coiled platinum wire as a counter
electrode. Under our conditions the FcH/FcH+ couple was at 0.42 V vs SCE. The
supporting electrolytes used were tetra-n-butylammonium hexafluorophosphate
([n-Bu4N][PF6]), tetra-n-butylammonium chloride ([n-Bu4N]Cl), and tetra-n-
butylammonium tetrakis(pentafluorophenyl)borate ([n-Bu4N][B(C6F5)4]), which
was synthesised as described in the literature.36,37 The supporting electrolyte
concentration was typically 0.1 M. Solutions for cyclic voltammetry were
deoxygenated by purging with prepurified nitrogen and contained 0.5 mM in the
redox-active species.
3.2.
Synthetic procedures
3.2.1. Synthesis
of
(1).
(123
N,N-bis((ferrocenyl)methyl)N-
propyldiethoxymethylsilylamine
aminopropyldiethoxymethylsilane
In
a
Schlenk
0.59
flask,
mmol)
3-
µl,
and
(ferrocenyl)trimethylammonium iodide (0.50 g, 1.29 mmol) were dissolved in 12
mL of acetonitrile and stirred at 85º C for 24 h in the presence of potassium
carbonate K2CO3 (0.81 g, 5.86 mmol). After cooling to room temperature, the
potassium carbonate excess was removed by filtration and the solid was washed
with dichloromethane. The solvent of the filtrates was removed under vacuum to
give an orange residue, which was purified by silanized silica column
chromatography using hexane as eluent and triethylamine 2%.
1 was obtained
1
as a yellow oil (0.11 g, 32%). H NMR (CDCl3, 300 MHz): δ 4.16 (m, 4H, C5H4),
4.11 (m, 4H, C5H4), 4.08 (s, 10H, C5H5), 3.75 (q, 4H, J = 7, OCH2CH3), 3.40 (s,
4H, Fc-CH2), 2.28 (t, 2H, J = 7.5, NCH2CH2CH2Si), 1.48 (m, 2H,
NCH2CH2CH2Si), 1.22 (t, 6H, J = 7, OCH2CH3), 0.52 (m, 2H, NCH2CH2CH2Si),
0.10 (s, 3H, SiCH3). 13C{1H} NMR (CDCl3, 75 MHz): δ 83.80, 70.14 (C5H4), 68.47
(C5H5), 67.73 (C5H4), 58.07 (OCH2CH3), 55.46 (NCH2CH2CH2Si), 52.56 (Fc-
CH2), 20.59 (NCH2CH2CH2Si), 18.44 (OCH2CH3), 11.32 (NCH2CH2CH2Si), 4.77
(SiCH3). 29Si{1H} NMR (CDCl3, 60 MHz): δ -4.50. MS (FAB; m/z): 588.2 (M+H)+.
3.2.2. Synthesis
of
N,N-bis((octamethylferrocenyl)methyl)N-
propyldiethoxymethylsilyl amine (2). Acetic anhydride (215 µL, 2.28 mmol)
was added to a stirred solution of (octamethylferrocenyl)methanol (0.43 g, 1.30
mmol) in Et2O (40 mL) and then HBF4·Et2O (345 µL, 2.54 mmol) was added to
lead a precipitate. After removing the solvent by filtration, the solid was washed

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-
twice with pentane and dried under vacuum, affording the BF4 salt of
[(octamethylferrocenyl)methyl carbocation] as a reddish-orange solid. This solid
was
immediately
dissolved
in
acetone
(30
mL)
and
3-
aminopropyl(diethoxy)methylsilane (2.9 mL, 13.96 mmol) was then added. After
stirring for 45 minutes, the solvent was evaporated under vacuum and a
greenish yellow residue was obtained. This residue was subjected to column
chromatography on silanized silica using hexane/methanol (20:1) as eluents and
triethylamine 2%. After removal of the solvent, the compound
2 was obtained as
1
a yellow solid (0.24g, 45%). H NMR (C6D6, 500 MHz): δ 3.66 (q, 4H, J = 7,
OCH2CH3), 3.28 (s, 4H, Fc#-CH2), 3.20 (s, 2H, C5(CH3)4H), 2.44 (t, 2H, J = 7,
NCH2CH2CH2Si), 1.88 (s, 12H, C5(CH3)4), 1.74 (s, 12H, C5(CH3)4), 1.73 (s, 12H,
C5(CH3)4), 1.65 (s, 12H, C5(CH3)4), 1.16 (t, 6H, J = 7, OCH2CH3), 0.62 (m, 2H,
13
NCH2CH2CH2Si), 0.08 (s, 3H, SiCH3). C{1H} NMR (CDCl3, 125 MHz): δ 80.60
(C5(CH3)4), 58.07 (OCH2CH3), 56.71 (NCH2CH2CH2Si), 49.13 (Fc#-CH2), 20.51
(NCH2CH2CH2Si), 18.49 (OCH2CH3), 11.38 (NCH2CH2CH2Si), 11.04, 10.03,
29
9.75, 9.21 (C5(CH3)4), -4.90 (SiCH3). Si{1H} NMR (CDCl3, 100MHz): δ -3.68.
MS (MALDI-TOF; m/z): 811.5 (M)+.
4. Conclusions
Two dimethyleneamine-bridged octamethylated and non-methylated biferrocenyl
complexes,
know,
bis(polymethylatedferrocenyl) complex. The voltammetric behaviour of the non-
methylated with different supporting electrolytes, resembles that observed
1
and
2, have been synthesized and characterized. As far as we
2
constitutes the first example of an alkylamine linked
1
before for related complexes, with negligible electronic communication in the
-
presence of the strongly ion-pairing PF6 , and a significant through-space
electrostatic effect between the ferrocenium centers, when the anion is the
-
weakly-coordinating B(C6F5)4 . In contrast, the voltammetric behavior of
2
measured with [n-Bu4N][PF6] or even [n-Bu4N]Cl as supporting electrolytes
shows in both cases a noticeable through-space electrostatic effect between the
octamethylated ferrocenium centers, as a result of the steric bulk of the
methylated ligands, which shield the influence of the electrolyte counter anion.
A stable ferrocenyl specie that remains persistently attached to the electrode
surface upon electrochemical studies of the dimethyleneamine-bridged
biferrocenyl complex
1 is reported.

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Acknowledgements
This work was supported by the Spanish Ministerio de Ciencia e Innovación
(Project CTQ 2009-12332-C02) and Ministerio de Economía, Industria y
Competitividad, (Project MAT2016-77608-C3-1-P). M.H. acknowledges the
Ministerio de Ciencia e Innovación for a predoctoral fellowship (BES-2010-
031723). M.A. acknowledges ARDITI-Agência Regional para o Desenvolvimento
da Investigaçao Tecnologia e Inovaçao, through the Project M1420-01-0145-
FEDER-000005.
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ACCEPTED MANUSCRIPT
Synthesis, characterization and electrochemical behaviour of
dimethyleneamine-bridged methylated and non-methylated
biferrocenyl derivatives
Raquel Sevilla,a Marta Herrero,a Beatriz Alonso,*a M. Pilar García-Armada,b Manuel Algarra c and
Carmen M. Casado*a
a Departamento de Química Inorgánica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049-
Madrid, Spain.
b Departamento de Ingeniería Química Industrial, Escuela Técnica Superior de Ingenieros Industriales,
Universidad Politécnica de Madrid, 28006-Madrid, Spain.
c
Centro de Química da Madeira, Universidade da Madeira, Campus da Penteada, 9020-105 Funchal,
Portugal.
Corresponding Authors
* E-mail: carmenm.casado@uam.es (C.M.C.); beatriz.alonso@uam.es (B.A.)
To be considered for publication in the Special Issue of the Journal or
Organometallic Chemistry, Title “Organometallic Chemsitry in Spain” (in memoriam
to Pascual Royo).
HIGHLIGHTS
We report the synthesis and complete characterization of two dimethyleneamine-bridged
octamethylated and non-methylated biferrocenyl complexes:
1. As far as we know, this is the first example of an alkylamine linked
bis(polymethylatedferrocenyl) complex.
2. Its voltammetric behaviour differs from that of the non-methylated derivative due
to the steric bulk of the methylated ligands, which shield the influence of the
electrolyte counter anion.
3. A stable ferrocenyl species that remains persistently attached to the electrode
surface upon electrochemical studies of the dimethyleneamine-bridged
biferrocenyl complex is also reported.