Synthesis of 1,2-diferrocenyl-3-(diacylmethylidene)cyclopropenes and 1,1-diacyl-2,3-diferrocenyl-4-methylsulfanylbuta-1,3-dienes, their structures and electrochemical properties

Article abstract of DOI:10.1016/j.jorganchem.2008.01.015

2,3-Diferrocenyl-1-morpholinocyclopropenylium tetrafluoroborate reacts with 1,3-diketones in the presence of triethylamine to give 3-diacylmethylidene-1,2-diferrocenylcyclopropenes (8a-d). Under similar conditions, 2,3-diferrocenyl-1-methylsulfanylcyclopr

Full text of DOI:10.1016/j.jorganchem.2008.01.015

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1215–1224
www.elsevier.com/locate/jorganchem
Synthesis of 1,2-diferrocenyl-3-(diacylmethylidene)cyclopropenes
and 1,1-diacyl-2,3-diferrocenyl-4-methylsulfanylbuta-1,3-dienes,
their structures and electrochemical properties
a,
a
b
*
Elena Klimova , Tatiana Klimova Berestneva , Simon Hernandez-Ortega ,
c
d
b
´
´
Luis Ortiz-Frade , Leon V. Backinowsky , Marcos Martınez Garcıa
a Universidad Nacional Auto´noma de Me´xico, Facultad de Quı´mica, Cd. Universitaria, Coyoaca´n, C.P. 04510, Me´xico D.F., Mexico
b Universidad Nacional Auto´noma de Me´xico, Instituto de Quı´mica, Cd. Universitaria, Coyoaca´n, C.P. 04510, Me´xico D.F., Mexico
c Centro de Investigacio´n y Desarrollo Tecnolo´gico en Electroquı´mica S.C. Parque Tecnolo´gico Quere´taro, C.P. 76703, Quere´taro, Mexico
d N.D. Zelinsky Institute of Organic Chemisrty, Russian Academy of Sciences, 47 Leninsky Prosp., 117913 Moscow, Russian Federation
Received 16 November 2007; received in revised form 9 January 2008; accepted 9 January 2008
Available online 16 January 2008
Abstract
2,3-Diferrocenyl-1-morpholinocyclopropenylium tetrafluoroborate reacts with 1,3-diketones in the presence of triethylamine to give
3-diacylmethylidene-1,2-diferrocenylcyclopropenes (8a–d). Under similar conditions, 2,3-diferrocenyl-1-methylsulfanylcyclopropenylium
iodide affords 8a–c (ꢀ25–30%) and 1,1-diacyl-2,3-diferrocenyl-4-methylsulfanylbuta-1,3-dienes (10a–c) (ꢀ50–60%). The structures of the
1
products obtained were established based on the data from H (1D NOE) and 13C NMR spectra and X-ray diffraction analysis. Elec-
trochemical properties of several (diacylmethylidene)diferrocenylcyclopropenes (8a–c) and 1,1-diacyl-2,3-diferrocenyl-4-methylsulfanylb-
uta-1,3-dienes (10a–c) are studied.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Diferrocenyl(morpholino)cyclopropenylium tetrafluoroborate; Diacylmethylidene(diferrocenyl)cyclopropenes; Diferrocenyl(methylsulfanyl)
cyclopropenylium iodide; Diacyl(diferrocenyl)butadienes; Electrochemistry
1. Introduction
gous conditions, alkylsulfanyl(diphenyl)cyclopropenylium
iodides afford cyclopenta-2,4-dienol derivatives (2b) with
the alkylsulfanyl-substituent in position 2 of the five-mem-
bered ring [5] (Scheme 1).
Presumably [5], these reactions involve the initial attack
of the nucleophile (3) on the carbon atom of the three-
membered ring linked to a phenyl substituent to form tet-
rasubstituted cyclopropene intermediates 4a or 4b, which
undergo ring extension (see Scheme 1).
Diarylcyclopropenylium salts containing dialkylamino
and alkylsulfanyl groups in the small ring have successfully
been employed in organic synthesis as three-carbon-atom
building blocks [1]. The reactions of this kind of com-
pounds 1a,b with carbon- and nitrogen-centered nucleo-
philes were shown [1–7] to produce selectively five- and
six-membered carbo- and heterocycles.
Thus dialkylamino(diphenyl)cyclopropenylium tetra-
fluoroborates (1a) react with b-dicarbonyl compounds in
the presence of triethylamine to yield 3-dialkylaminocyclo-
penta-2,4-dienol derivatives 2a (Scheme 1). Under analo-
The behavior of diferrocenyl analogs [8–10] of dialkyla-
mino- or alkylsulfanyl-cyclopropenylium salts in reactions
with 1,3-diketones has not been studied so far. In the pres-
ent work, we studied the reactions of 2,3-diferrocenyl-1-
morpholinocyclopropenylium tetrafluoroborate (5a) and
2,3-diferrocenyl-1-methylsulfanylcyclopropenylium iodide
(5c) with 1,3-diketones and investigated some chemical
and electrochemical properties of the reaction products.
*
Corresponding author. Tel./fax: +52 55 56225371.
E-mail address: klimova@servidor.unam.mx (E. Klimova).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.01.015

1216
E. Klimova et al. / Journal of Organometallic Chemistry 693 (2008) 1215–1224
Their structures were established by 1H and 13C NMR
O
O
spectroscopy, mass spectrometry, and elemental analysis.
The formation of cyclopropenes 8a–d can obviously be
rationalized as the initial attack of a nucleophilic reagent
on the C(1) atom of the cyclopropenylium cation resulting
in cyclopropene intermediates (9a–d) followed by elimina-
tion of morpholine (Scheme 4).
We found further that, unlike diferrocenyl(morpho-
lino)cyclopropenylium tetrafluoroborate (5a), diferroce-
nyl(methylsulfanyl)cyclopropenylium iodide (5c) reacts
with 1,3-diketones 7a–c to give two products, viz., (diacy-
lmethylidene)diferrocenylcyclopropenes (8a–c) (ꢀ25–30%)
and 1,1-diacyl-2,3-diferrocenyl-4-methylsulfanylbuta-1,3-
dienes (10a–c) (ꢀ50–60%) separated by chromatography
on alumina (Scheme 5).
X
R
Y
+
H
O
O
Ph
Ph
1a,b
R
3
Et3N
X
X
O
Ph
O
R
Ph
The structures of compounds 10a–c were established by
mass spectrometry, 13C and 1H NMR (including 1D NOE)
Ph
O
Ph
4b
4a
1
spectroscopy, and elemental analysis. The H NMR spec-
O
tra of compounds 10a–c contain signals for the protons
of the acyl substituents, of two ferrocenyl fragments, a sin-
glet of protons of the methylsulfanyl group, and a singlet of
the olefinic proton. The 13C NMR spectra of compounds
10a–c contain signals for the carbon atoms of two carbonyl
groups, of two ferrocenyl fragments with two signals for
X
X
Ph
Ph
Ph
O
C
ipso, and the corresponding number of signals for other
1
R
H
R
carbon atoms of the molecules. The H NMR spectrum
of compound 10c suggests that this was isolated as a single
geometric isomer; its absolute configuration has not been
established. The position of a proton at the double bond
adjacent to the MeS group in compounds 10a–c was con-
firmed by NOE experiments: irradiation of the methyl pro-
tons gave a response at the vinylic proton.
O
H
O
O
X
X
Ph
Ph
A putative mechanism for the formation of compounds
10a–c is presented in Scheme 6.
Ph
OH
R
R
The results obtained in the present study demonstrate
that the nucleophilic attacks on the cation 5c with a meth-
ylsulfanyl substituent are directed, contrary to the cation
5a, on both the C(1) atom of the small ring and the C(2)
atom. In the former case, cyclopropenes (8a–c) are formed
according to Scheme 4. In the case of the attack on the C(2)
atom linked to a ferrocenyl substituent, 3-ferrocenylcyclo-
propenes (11a–c) are formed as unstable intermediates
[12–14]. These undergo spontaneous opening of the three-
membered ring to yield vinylcarbenes (12a–c). The trans-
formations of vinylcarbenes (12a–c) with intramolecular
proton shift affords ultimately the linear products 10a–c.
The intramolecular character of the transformation of
analogous vinylcarbenes was proved earlier for the reaction
of the cation 5c with diethyl [D2]malonate [15].
Ph
Ph
OH
O
2a
2b
O
R= CH3, OEt
X= NR21, Y- = BF-4 (a)
X= SR2, Y- = I- (b)
Scheme 1.
2. Results and discussion
The starting compounds, 2,3-diferrocenyl-1-morpholi-
nocyclopropenylium tetrafluoroborate (5a) and 2,3-diferr-
ocenyl-1-methylsulfanylcyclopropenylium iodide (5c),
were prepared [11] from 2,3-diferrocenylcyclopropenone
(6) according to Scheme 2.
We found that compound 5a reacts with b-diketones
(acetylacetone, dibenzoylmethane, dipivaloylmethane, and
benzoylacetone (7a–d)) in the presence of triethylamine to
afford high yields of 1,2-diferrocenyl-3-(diacylmethylid-
ene)cyclopropenes (8a–d) (Scheme 3).
The formation of diacylmethylidenecyclopropenes (8a–d)
as sole reaction products of morpholino(diferroce-
nyl)cyclopropenylium tetrafluoroborate (5a) with 1,3-dike-
tones should be stressed. This seems to be related to
different distribution of the electron density deficiency in
the three-membered rings of the amino 5a and thio 5c
d+
d+
derivatives: N–C1d+ > Fc–C2 for 5a, Fc–C2d+ > S–C1
The cyclopropenes 8a–d were isolated by column chro-
matography on alumina and recrystallized from ethanol.
for 5c.

E. Klimova et al. / Journal of Organometallic Chemistry 693 (2008) 1215–1224
1217
O
OEt
O
N
NH
O
Et3O BF4
BF4
BF4
Fc
Fc
Fc
Fc
6
5
Fc
Fc
5a
NaHS
Fc= C5H5FeC5H4
SMe
S
MeI
I
Fc
Fc
Fc
O
Fc
5b
5c
Scheme 2.
O
N
O
O
R1
R
R
Et3N
CH2
O
+
R1
BF4
Fc
Fc
Fc
Fc
8a-d
7a-d
5a
R= R1 = CH3 (a)
R= R1 = Ph (b)
R= CH3, R1 = Ph (c)
R= R1 = tBu (d)
Scheme 3.
O
N
R1
O
H
H
O
O
O
N
R
+
R
R1
BF4
Fc
O
Fc
Fc
Fc
5a
9a-d
O
-
N
H
8a-d
Scheme 4.
The structure of compound 8a was confirmed by X-ray
diffraction analysis. X-ray analysis of a single crystal pre-
pared by crystallization from dichloromethane proved its
structure as 1,2-diferrocenyl-3-(diacetylmethylidene)cyclo-
propene. The general view of the molecule 8a is shown in
Fig. 1, the main geometrical parameters are given in Table 1.

1218
E. Klimova et al. / Journal of Organometallic Chemistry 693 (2008) 1215–1224
Fc
O
CH2
O
SMe
R
Fc
SMe
Et3N
I
H
+
8a-c
+
R
R1
R1
Fc
Fc
5c
10a-c
O
O
Scheme 5.
SMe
R1
O
R
R1
H
O
SMe
H
O
R
+
I
Fc
O
Fc
Fc
Fc
5c
11a-d
Fc
Fc
SMe
R
10a-c
H
O
R1
12 a-c
O
Scheme 6.
Table 1
Selected bond lengths and bond angles for 8a
˚
Bond lengths, r (A)
Bond angles, x (°)
C(1)–C(2)
C(1)–C(3)
C(2)–C(3)
C(1)–C(28)
C(24)–C(28)
C(26)–C(28)
C(24)–O(2)
C(26)–O(1)
1.409(4)
1.404(4)
1.348(4)
1.377(4)
1.455(4)
1.466(40)
1.213(4)
1.223(4)
C(3)–C(1)–C(2)
C(1)–C(2)–C(3)
C(2)–C(3)–C(1)
C(1)–C(28)–C(26)
C(28)–C(1)–C(2)
C(28)–C(1)–C(3)
C(1)–C(28)–C(24)
C(26)–C(28)–C(24)
57.3(2)
61.1 (2)
61.6(2)
115.3(3)
155.3(3)
147.4(3)
122.3(3)
122.3(3)
˚
ring are somewhat shorter (r = 1.409(4) and 1.404(4) A,
˚
respectively) than the standard values of 1.483 A [16] and
the C(1)–C(28), C(24)–C(28) and C(26)–C(28) bonds are
˚
˚
somewhat longer [r = 1.377(4), 1.455(4) and 1.466(4) A,
respectively] than the standard values of 1.34 and 1.42 A
[17], indicating a small contribution of the dipolar form
and the pseudoaromatic character [18,19] of compound
8a, as well as of compounds 8b,c.
The lengths of the C–Fe and C–C bonds in the ferrocenyl
substituents as well as the geometrical parameters of the fer-
rocene sandwiches are close to the standard values [12].
The pseudoaromatic character of 3-diacylmethylidene-
1,2-diferrocenylcyclopropenes (8a–c) are manifested in
Fig. 1. Molecular structure of 8a.
The central fragment of the molecule 8a is a flat three-
membered ring. Data from the X-ray analysis show that
the C(1)–C(2) and C(1)–C(3) bonds in the cyclopropene

E. Klimova et al. / Journal of Organometallic Chemistry 693 (2008) 1215–1224
1219
theirs stability towards thermolysis (ꢀ200 °C) and upon
the action of acids (HCl, AcOH). These compounds do
not form Diels-Alder adducts with dienes such as cyclo-
hexa-1,3-diene, 1,3-diphenylisobenzofuran, tetraphenylcyclo-
pentadiene.
tively). Data from the 13C NMR spectrum corroborate
the structures of the salts 13a–c. They each contained three,
four, or five signals for carbon atoms bearing no hydrogen
atoms, one (13a,b) or two (13c) signals for the carbon
atoms of groups –C–Oꢁ ꢁ ꢁ, one or two carbon atoms CipsoFc
of the ferrocene units. The number of signals for the C5H5,
C5H4–, C6H5– and Me groups and their chemical shifts
correspond completely to the structures 13a–c.
Unlike aryl- and ferrocenylcyclopropenyl cations, which
give 3-substituted cyclopropenes upon the action of nucle-
ophiles [19], the cations 13a–c undergo deprotonation upon
treatment with bases (N,N-dimethylaniline, pyridine) with
the formation of the starting diacylmethylidene(diferroce-
nyl)cyclopropenes 8a–c (Scheme 7).
The compounds 8a–c are ferrocene-containing a,b-
enediones, which could be expected to react with hydra-
zines giving derivatives of the diferrocenylcyclopropenylid-
ene-4,5-dihydropyrazoles analogous to these obtained
from ferrocenyl-a,b-enones [20–22]. However, our studies
demonstrate that compounds 8a–c do not form heterocy-
cles of the type A (Scheme 8). The only reaction products
Treatment of the diacylmethylidene(diferrocenyl)cyclo-
propenes (8a–c) with tetrafluoroboric acid diethyl etherate
affords crystalline salts (13a–c), which can be stored in a
dry inert atmosphere (Scheme 7).
1
The structure of the salts 13a–c was confirmed by H
and 13C NMR spectroscopic data. The signals for the pro-
1
tons of the cyclopentadienyl rings of ferrocene in the H
NMR spectrum of the salts 13a–c are noticeably shifted
to lower fields (dC H ¼ 4:37; 4.45; 4.26 and 4.41 ppm;
5
5
dC H ¼ 4:85, 5.36; 4.91, 5.37; 4.49, 4.63, 4.98, 5.59 ppm,
5
4
respectively) relative to those of the original cyclopropenes
(8a–c) (dC H ¼ 4:24; 4.23; 4.15 and 4.27 ppm; dC H ¼ 4:71,
5
5
5
4
5.20; 4.65, 5.08; 4.32, 4.48, 4.72, 5.37 ppm). In addition, the
1H NMR spectra of compounds 13a–c contain signals for
the protons of the acyl substituents and broad signals for
the one proton (dH = 5.43, 5.66 and 5.74 ppm, respec-
O
O
O
O
O
O
O
O
R1
Fc
R
R1
Fc
R
R1
Fc
R
R1
Fc
R
Fc
Fc
Fc
Fc
8a-c
HBF4
H
O
O
R
R1
Fc
Base
8a-c
BF4
Fc
13a-c
Scheme 7.
N
NHR2
R1
O
O
O
O
R1
R
R
R1
R
NH2NHR2
NH2NHR2
Fc
N
N
Fc
Fc
R2
Fc
Fc
Fc
R2= H (14a-c)
R2= CH3 (15a)
A
Scheme 8.

1220
E. Klimova et al. / Journal of Organometallic Chemistry 693 (2008) 1215–1224
are monohydrazones 14a–c and 15a obtained in high yields
(Scheme 8).
The structures of compounds 14a–c and 15a were estab-
lished based on their 1H (including 1D NOE) and 13C
NMR spectroscopic and elemental analysis data.
15
10
5
ΙΙ
a
Ι
a
E
+λ
3. Electrochemistry
E
-λ
0
Fig. 2 shows the voltammetry of compound 8a in ace-
tonitrile solution containing 0.1 M Bu4N+BF4ꢂ. When the
potential scan was initiated in positive direction and when
the cycle was completed two oxidation signals (Ia and IIa)
and two reduction signals (Ic and IIc) were observed. The
obtained values of anodic and cathodic peak potentials
Epa(I) and Epc(I) for signal Ia and Ic were 0.280 V/Fc–
Fc+ and 0.221 V/Fc–Fc+, respectively. The DEp was
0.059 V and independent of the scan rate (0.1–1 V sꢂ1).
A reversible electrochemical behavior is presented [23].
The anodic and cathodic peak potential values for signals
IIa and IIc Epa(II) and Epc(II) are 0.398 and 0.338 V/Fc–
Fc+, respectively. The DEp was also independent of the
scan rate (0.1–1 V sꢂ1). It can be suggested a two-step
reversible oxidation of ferrocene moieties for process is I
and II.
ΙΙ
c
-5
Ι
c
-10
-1.2
-0.8
-0.4
0.0
0.4
0.8
E(V/Fc-Fc+)
Fig. 3. Cyclic voltammogram for a 2.0 ꢃ 10ꢂ3 mol dmꢂ3 solution of
compound 10b in acetonitrile in the presence of 0.1 M Bu4N+BF4ꢂ. The
scan potential was initiated from Eocp to positive direction. Scan rate
0.1 V sꢂ1. The working electrode used was platinum.
Table 2
Formal electrode potentials E0(I), E0(II) and DE0(II–I), and constant Kcom
for compounds 8a–c and 10a–c
Compound
E° (I)
E°(II)
DE°(II–I)
Kcom
The formal electrode potential was evaluated with the
8a
8b
0.250
0.249
0.250
0.006
0.007
0.011
0.368
0.362
0.362
0.241
0.240
0.239
0.118
0.113
0.112
0.235
0.233
0.228
100
82
80
9617
8895
7318
half sum of the anodic and cathodic peak potentials,
0
E0 = (Epa + Epc). The values for processes I and II, were
8c
0
+
0
+
0
0
E (I) = 0.250 V/Fc–Fc
and E (II) = 0.368 V/Fc–Fc .
10a
10b
10c
0
0
The value of DE (II–I) for processes I and II was
0.118 V and the corresponding value of comproportiona-
tion constant Kcom was 100 [23,24]. The electrochemical
response of compounds 8b and 8c is very similar than the
presented in compound 8a.
E0 = (Epa + Epc)/2, reported vs. ferrocene in 0.1 M Bu4N+BF4ꢂ-aceto-
nitrile. Scan rate 0.10 V sꢂ1
0
.
0
0
0
0
Cyclic voltammetry experiment of compound 10b also
indicates a two consecutive electron transfer mechanism
EE, Fig. 3.
A summary of the obtained values of E (I), E (II) and
Kcom for all the compounds studied by cyclic voltammetry
is presented in Table 2.
The calculated values of Kcom for all compounds sug-
gests that the electron charge is slightly delocalized in the
mixed valence state generated electrochemically, according
to the Robin-Day classification (class II) [24,25]. The sim-
ilar values of Kcom for compounds 8a and 8b, 8c suggest
no effect of the substituent in the mixed valence state.
The values obtained for compounds 10a–c suggest no
differences in the electronic communication between ferro-
cene moieties in these compounds. The largest values of
Kcom for compounds 10a–c compared with 8a–c can be
attributed to the presence of a sulfur atom close to one fer-
rocene moiety. The electronic communication in com-
pounds 10a–c cannot be neglected but probably with a
minor effect compared with the presence of sulfur, which
increases the value of DE°(II–I).
ΙΙ
15
12
9
a
Ι
a
E
+λ
6
3
E
-λ
0
-3
-6
-9
ΙΙ
c
Ι
c
-0.8 -0.6 -0.4 -0.2 0.0
0.2
0.4
0.6
0.8
E(V/Fc-Fc+)
4. Conclusion
Fig. 2. Cyclic voltammogram for a 2.0 ꢃ 10ꢂ3 mol dmꢂ3 solution of
compound 8a in acetonitrile in the presence of 0.1 M Bu4N+BF4ꢂ. The
scan potential was initiated from Eocp to positive direction. Scan rate
0.1 V sꢂ1. The working electrode used was platinum.
Thus, the results of the present study support our previ-
ous conclusion [8–10], that, depending on whether the
nucleophile attacks C(1) or C(2) of the cations 5a or 5c,

E. Klimova et al. / Journal of Organometallic Chemistry 693 (2008) 1215–1224
1221
Table 3
the initially formed intermediates 9a–d or 11a–c (see
Crystal data and structure refinement parameters for compound 8a
Schemes 4 and 6) usually form the products that retain
the original three-membered ring or undergo C–C bond
cleavage to give ring-opened products. Diferrocenyl(mor-
pholino)cyclopropenylium tetrafluoroborate (5a) reacts with
1,3-diketones to afford solely the products with retention
Data
8a
Molecular formula
Formula weight (g molꢂ1
Temperature (K)
Crystal system
C28H24Fe2O2
504.17
291(2)
Monoclinic
P21=n
10.6648(6)
11.0139(6)
18.3080(10)
90
94.7870(10)
90
2143.0(2)
4
1.563
1.378
)
of the three-membered ring
– 3-diacylmethylidene-
Space group
1,2-diferrocenylcyclopropenes (8a–d), while diferrocenyl-
(methylsulfanyl)cyclopropenylium iodide (5c) affords
preferentially linear products (1,1-diacyl-2,3-diferrocenyl-
4-methylsulfanylbuta-1,3-dienes (10a-c)) resulted from the
opening of the small ring. This behavior of 5c is substan-
tially different from its morpholino analog 5a. No cyclic
products similar to cyclopentadienols 2a and 2b were
observed in the reactions of compounds 5a and 5c with
1,3-diketones, which distinguishes diferrocenylcycloprope-
nylium salts from their diaryl-substituted analogs.
At the same time, it is known [26] that the presence of
ferrocenyl substituents in molecules of organic compounds
imparts new properties to these compounds that are
absent, as a rule, in their alkyl/aryl analogs. This statement
seems to concern also diferrocenylcyclopropenylium salts,
which may prove to be appropriate synthons for the prep-
aration of various classes of functionalized compounds
with ferrocenyl substituents in molecules, of substances
with valuable properties such as electrical conductivity,
nonlinear optical effects, pharmacological activity, mag-
netic behavior, thermal stability, etc.
˚
a (A)
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
Dcalc (Mg mmꢂ3
)
Absorption coefficient (mmꢂ1
)
F(000)
Radiation, k (A)
Monochromator
h range (°)
Reflections collected
Reflections independent
Rint
1040
˚
Mo Ka, 0.71073
Graphite
2.16–25.00
17171
3779
0.0606
Final R indices [I > 2r(I)]
R1 = 0.0444,
wR2 = 0.0849
R1 = 0.0617,
wR2 = 0.0908
291
R indices (all data)
Refinable parameters
Goodness-of-fit
1.000
Refinement method
Full-matrix-least-squares
on F2
Minimum/maxꢂim3 um residual electron
ꢂ0.275/0.389
˚
density (e A
)
5. Experimental
All the solvents were dried according to the standard
inum wire as counter-electrode. A pseudo reference elec-
trode of silver wire immersed in a 0.1 M tetra-N-
butylammonium chloride (Bu4N+Clꢂ) in acetonitrile was
also employed. All solutions were bubbled with nitrogen
prior each measurement. In all experiments, a 2.0 ꢃ
10ꢂ3 mol dmꢂ3 solution of each compound in supporting
electrolyte was used. All voltammograms were initiated
from open circuit potential (Eocp) and the scan potential
was obtained in both positive and negative directions. All
potentials were reported versus the couple Fc/Fc+ accord-
ing to IUPAC convention [28].
The following reagents were purchased from Aldrich:
ferrocene, 98%; aluminum chloride, 99.99%; tetrachlorocy-
clopropene, 98%; triethyloxonium tetrafluoroborate, 1.0 M
solution in dichloromethane; morpholine, 99+%; sodium
hydrosulfide hydrate NaHS ꢁ xH2O; triethylamine, 99+%;
2,4-pentanedione, 99+%; dibenzoylmethane, 98%; 1-ben-
zoylacetone, 99%; 2,2,6,6-tetramethyl-3,5-heptanedione,
98+%; iodomethane, 99.5%; hydrazine monohydrate,
98%; methylhydrazine, 98%. Tetrafluoroboric acid ether-
ate, 50–52%, was purchased from Alfa AESAR.
1
procedures and were freshly distilled before use. The H
and 13C NMR spectra of compounds 8a–d and 10a–c were
recorded on a Unity Inova Varian spectrometer (300 and
1
75 MHz for H and 13C, respectively) of solns in CDCl3
with Me4Si as the internal standard. Chemical shifts are
given in ppm and J values in Hz. The IR spectra of samples
prepared as KBr pellets were measured on a Specord IR-75
instrument. The mass spectrum were obtained on a Varian-
MAT CH-6 instrument (EI, 70 eV). An elemental analysis
System GmbH was used for elemental analyses. Columns
chromatography was carried out on alumina (Brockmann
activity III).
The unit cell parameters and the X-ray diffraction
intensities were recorded on a Bruker Smart Apex CCD
area detector/x diffractometer. The crystallographic data,
the experimental conditions, and corrections are given in
Table 3. The structure of compound 8a was solved by
direct method (SHELXS-97 [27]) and refined using full-
matrix least-squares on F2.
All electrochemical measurements were performed in
acetonitrile solution containing 0.1 M tetra-N-butylammo-
nium tetrafluoroborate (tBu4N+BF4ꢂ). A potentiostat/gal-
vanostat EG&G PAR model 263A controlled by a PC
software was used. A three-electrode array was employed.
A platinum disk was used as working electrode, and a plat-
2,3-Diferrocenylcyclopropenone (6) was obtained from
the ferrocene and tetrachlorocyclopropene in the presence
of AlCl3 according to the standard procedure [29]. Eth-
oxy(diferrocenyl)cyclopropenylium tetrafluoroborate (5)
was obtained from the 2,3-diferrocenylcyclopropenone (6)

1222
E. Klimova et al. / Journal of Organometallic Chemistry 693 (2008) 1215–1224
in the presence of triethyloxonium tetrafluoroborate (1.0 M
solution in dichloromethane) [8]. Differocenyl(morpho-
lino)cyclopropenylium tetrafluoroborate (5a) was obtained
from ethoxy(diferrocenyl)cyclopropenylium tetrafluorobo-
rate and morpholine in dichloromethane [8,9]. 2,3-Diferr-
ocenylcyclopropenethione (5b) was obtained by treating
ethanolic differocenyl(morpholino)cyclopropenylium tetra-
fluoroborate [10] with an aqueous solution of NaSH [10],
yield 91%, m.p. 208–209 °C. 2,3-Diferrocenyl(methylsulfa-
nyl)cyclopropenylium iodide (5c) was obtained from the
2,3-diferrocenylcyclopropenethione and iodomethane [10].
(2CipsoFc), 128.55, 129.26, 131.45 (C6H5), 137.45, 138.70,
140.10, 142.13 (4C), 186.20, 195.32 (2C@O). Anal. Calc.
for C33H36Fe2O2: C, 70.00; H, 4.63; Fe, 19.73. Found: C,
69.84; H, 4.80; Fe, 19.59%. MS: m/z 566 [M]+.
3-Dipivaloylmethylidene-1,2-diferrocenylcyclopropene
(8d), yield 1.28 g (72%), orange powder, m.p. 238–239 °C.
IR (KBr): m = 414, 465, 542, 580, 626, 698, 729, 753, 854,
952, 999, 1003, 1032, 1057, 1100, 1174, 1221, 1266, 1321,
1354, 1443, 1462, 1574, 1653, 1679, 1711, 1843, 2955,
1
3087 cmꢂ1. H NMR: d 1.07 (18H, s, 6CH3), 4.20 (10H,
s, 2C5H5), 4.45 (4H, m, C5H4), 4.73 (4H, m, C5H4). 13C
NMR: d 27.84 (6CH3), 44.59 (2C), 64.48 (C), 70.31
(2C5H5), 72.21, 72.93 (2C5H4), 99.87, 101.70 (2CipsoFc),
139.31(C), 140.83 (2C), 190.32, 195.04 (2C@O). Anal. Calc.
for C34H36Fe2O2: C, 69.40; H, 6.17; Fe, 19.00. Found: C,
69.52; H, 6.04; Fe, 18.87%. MS: m/z 588 [M]+.
5.1. Reaction of diferrocenyl(morpholino)cyclopropenylium
tetrafluoroborate (5a) with b-diketones (7a–d)
b-Diketones 7a–d (6 mmol) and Et3N (10 ml) were
added with stirring in a mixture of salt 5a (1.75 g, 3 mmol)
in dry benzene (50 ml). After stirring for 6 h at ambient
temperature, the volatiles were removed in vacuo; chroma-
tography of the residue on Al2O3 (hexane-ether, 10:1) gave
compounds 8a–d.
5.2. Reaction of diferrocenyl(methylsulfanyl)-
cyclopropenylium iodide (5c) with b-diketones (7a–c)
This was carried out analogously using salt 5c (1.74 g,
3.0 mmol), b-diketones (7a–c) (5 mmol), Et3N (10 ml) and
benzene (50 ml). The reaction mixture was worked up as
described above, subsequent chromatography on Al2O3
(hexane-diethyl ether, 4:1) gave compounds 8a–c and
10a–c.
3-Diacetylmethylidene-1,2-diferrocenylcyclopropene (8a),
yield 1.07 g (71%), orange crystals, m.p. 168–169 °C. IR
(KBr): m = 486, 574, 661, 730, 818, 948, 1001, 1027, 1057,
1105, 1171, 1268, 1291, 1331, 1356, 1392, 1452, 1479,
1510, 1549, 1594, 1649, 1709, 1851, 2920, 2955,
1
3086 cmꢂ1. H NMR: d 2.59 (6H, s, 2CH3), 4.25 (10H, s,
1,1-Diacetyl-2,3-diferrocenyl-4-methylthio-1,3-butadiene
(10a), yield 0.90 g (54%), orange crystals, m.p.182–183 °C.
IR (KBr): m 764, 807, 887, 971, 1018, 1047, 1079, 1121,
1147, 1228, 1285, 1380, 1421, 1442, 1614, 1661, 1691,
2C5H5), 4.71 (4H, m, C5H4), 5.20 (4H, m, C5H4).13C
NMR: d 30.61 (2CH3), 64.61 (C), 70.42 (2C5H5), 72.53,
73.00 (2C5H4), 100.99, 105.08 (2CipsoFc), 139.34(C),
140.89 (2C), 191.30, 195.65 (2C@O). Anal. Calc. for
C28H24Fe2O2: C, 66.70; H, 4.80; Fe, 22.15. Found: C,
66.49; H, 4.91; Fe, 21.97%. MS: m/z 504 [M]+.
1813, 2926, 2987, 3095 cmꢂ1 1H NMR: d 2.22 (3H, s,
.
CH3), 2.24 (3H, s, CH3), 2.35 (3H, s, CH3S), 4.09 (5H, s,
C5H5), 4.24 (5H, s, C5H5), 4.31 (1H, m, C5H4), 4.33 (3H,
m, C5H4), 4.34 (1H, m, C5H4), 4.48 (1H, m, C5H4), 4.61
(1H, m, C5H4), 4.63 (1H, m, C5H4), 6.54 (1H, s, CH=).
13C NMR: d 16.49 (CH3S), 29.85, 30.59 (2CH3), 70.16,
70.54 (2C5H5), 68.70, 69.05, 69.33, 70.63 (1C5H4), 70.00,
70.75 (1C5H4), 83.33, 85.33 (2CipsoFc), 126.12 (CH@),
133.19, 138.20, 155.80 (3C), 197.69, 200.34 (2C@O). Anal.
Calc. for C29H28Fe2O2S: C, 63.07; H, 5.11; Fe, 20.23; S,
5.79. Found: C, 63.18; H, 5.012; Fe, 20.37; S, 5.64%. MS:
m/z 552 [M]+.
3-Dibenzoylmethylidene-1,2-diferrocenylcyclopropene
(8b), yield 1.29 g (68%), orange powder, m.p. 299–301 °C.
IR (KBr): m = 416, 477, 531, 587, 632, 698, 724, 754, 813,
946, 999, 1025, 1080, 1226, 1325, 1381, 1417, 1460, 1480,
1
1527, 1549, 1594, 1652, 1712, 1839, 2991, 3057 cmꢂ1. H
NMR: d 4.23 (10H, s, 2C5H5), 4.65 (4H, m, C5H4), 5.08
(4H, m, C5H4), 7.15–7.24 (6H, m, C6H5), 7.61– 7.65 (4H,
m, C6H5).13C NMR: d 64.73 (C), 70.25 (2C5H5), 72.73,
73.11 (2C5H4), 94.15, 101.51 (2CipsoFc), 127.79, 127.87,
128.18, 128.82, 130.51, 131.53 (2C6H5), 138.48, 138.93,
139.46 (3C), 142.04 (2C), 184.77, 195.03 (2C@O). Anal.
Calc. for C38H28Fe2O2: C, 72.64; H, 4.49; Fe, 17.78.
Found: C, 72.73; H, 4.32; Fe, 17.91%. MS: m/z 628 [M]+.
3-Acetyl(benzoyl)methylidene-1,2-diferrocenylcyclopro-
pene (8c), yield 1.19 g (70%), orange powder, m.p. 206–
208 °C. IR (KBr): m = 412, 488, 552, 631, 697, 746, 821,
946, 989, 1000, 1027, 1048, 1109, 1173, 1237, 1290, 1331,
1381, 1406, 1453, 1522, 1594, 1638, 1679, 1700, 1823,
Compound 8a, yield 0.31 g (20%), orange crystals, m.p.
168–169 °C. MS: m/z 504 [M]+.
1,1-Dibenzoyl-2,3-diferrocenyl-4-methylthio-1,3-butadi-
ene (10b), yield 1.24 g (61%), orange crystals, m.p. 314–
316 °C. IR (KBr): m 772, 821, 892, 948, 987, 1007, 1024,
1053, 1080, 1124, 1147, 1231, 1289, 1386, 1431, 1447,
1
1634, 1668, 1696, 1811, 2928, 2979, 3058 cmꢂ1. H NMR:
d 2.11 (3H, s, CH3S), 4.11 (5H, s, C5H5), 4.28 (5H, s,
C5H5), 4.26 (1H, m, C5H4), 4.32 (1H, m, C5H4), 4.38
(2H, m, C5H4), 4.46 (1H, m, C5H4), 4.55 (1H, m, C5H4),
4.59 (1H, m, C5H4), 4.79 (1H, m, C5H4), 7.06(1H, s,
CH@), 7.10–7.93 (10H, m, 2C6H5). 13C NMR: d 16.02
(CH3S), 69.80, 70.19 (2C5H5), 68.05, 68.30, 69.27, 69.64,
69.74, 69.87, 70.63, 71.48 (2C5H4), 84.18, 85.58 (2CipsoFc),
121.48 (CH@), 127.76, 128.03, 128.09, 129.70, 131.82,
2904, 3056 cmꢂ1 1H NMR: d 2.33 (3H, s, CH3), 4.15
.
(5H, s, C5H5), 4.27 (5H, s, C5H5), 4.32 (2H, m, C5H4),
4.48 (2H, m, C5H4), 4.72 (2H, m, C5H4), 5.37 (2H, m,
C5H4), 7.39–7.52 (3H, m, C6H5), 7.77–7.80 (2H, m,
C6H5).13C NMR: d 30.04 (CH3), 64.05 (C), 70.07, 70.24
(2C5H5), 71.70, 72.71, 73.08, 73.17 (2C5H4), 99.84, 102.90

E. Klimova et al. / Journal of Organometallic Chemistry 693 (2008) 1215–1224
1223
132.93 (2C6H5), 128.82, 135.95, 138.15, 139.11, 158.08
(5C), 188.48, 192.50 (2 C@O). Anal. Calc. for C39H32-
Fe2O2S: C, 69.25; H, 4.77; Fe, 16.52; S, 4.73. Found: C,
69.34; H, 4.89; Fe, 16.39; S, 4.95%. MS: m/z 676 [M]+.
Compound 8b, yield 0.34 g(18%), orange powder, m.p.
298–300 °C. MS: m/z 628 [M]+.
Tetrafluoroborate 13c, yield 0.27 g (84%), m.p. ca.
224 °C (decomp.). H NMR: d 4.26 (5H, s, C5H5), 4.41
1
(5H, s, C5H5), 4.49 (2H, m, C5H4), 4.63 (2H, m, C5H4),
4.98 (2H, m, C5H4), 5.59 (2H, m, C5H4), 5.74 (1H, bs),
7.47–7.71 (5H, m, C6H5).13C NMR: d 27.64 (CH3), 66.43
(C), 70.79, 71.38 (2C5H5), 71.92, 73.12, 73.56, 73.89
(2C5H4), 108.03, 111.15 (2CipsoFc), 129.42, 129.69, 132.83
(C6H5), 138.81, 139.64, 142.16, 144.06 (4C), 171.02
(2C@O. . .1H). Anal. Calc. for C33H27 BF4Fe2O2: C,
60.60; H, 4.16; B 1.65; F, 11.62; Fe, 17.08. Found: C,
60.72; H, 4.06; F, 11.51; Fe, 16.93%.
1-Acetyl-1-benzoyl-2,3-diferrocenyl-4-methylthio-1,3-
butadiene (10c), yield 1.05 g (57%), orange crystals, m.p.
211–212 °C. IR (KBr): m 769, 819, 890, 946, 991, 1004,
1022, 1051, 1078, 1125, 1147, 1228, 1283, 1377, 1430,
1
1444, 1635, 1663, 1691, 1802, 2929, 2969, 3041 cmꢂ1. H
NMR: d 2.13 (3H, s, CH3), 2.21 (3H, s, CH3S), 3.89 (5H,
s, C5H5), 4.31 (5H, s, C5H5), 4.15 (3H, m, C5H4), 4.21
(1H, m, C5H4), 4.36 (2H, m, C5H4), 4.62 (1H, m, C5H4),
4.73 (1H, m, C5H4), 6.30(1H, s, CH@), 7.30–7.35 (2H, m,
C6H5), 7.47 (1H, m, C6H5), 7.88 (2H, m, C6H5).13C
NMR: d 16.26 (CH3S), 70.34, 70.57 (2C5H5), 68.21,
68.34, 69.35, 69.53, 69.78, 69.79, 70.60, 71.42 (2C5H4),
83.26, 85.32 (2CipsoFc), 120.96 (CH@), 128.34, 129.38,
131.79 (C6H5), 128.88, 136.06, 139.03, 154.12 (4C),
192.67, 198.84 (2 C@O). Anal. Calc. for C34H30Fe2O2S:
C, 66.48; H, 4.92; Fe, 18.18; S, 5.21. Found: C, 66.63; H,
5.08; Fe, 18.3; S, 5.29%. MS: m/z 614 [M]+.
5.4. Reaction of 3-diacylmethylidene-1,2-
diferrocenylcyclopropenes (8a–c) with hydrazines (16a,b)
A solution of compounds 8a–c (0.5 mmol) and hydra-
zine hydrate or methylhydrazine (1.5 ml) in ethanol
(20 ml) was stirred for 3 h at 20 °C. The reaction mixture
was evaporated in vacuo, and residue was chromato-
graphed (Al2O3; hexane/ether, 4:1) to give hydrazones
14a–c and 15a–c.
Hydrazone 14a, yield 0.16 g (62%), orange powder, p.m.
218–219 °C. IR (KBr): m 495, 555, 691, 820, 879, 920, 958,
1001, 1025, 1081, 1106, 1159, 1234, 1269, 1332, 1355, 1373,
1389, 1412, 1446, 1518, 1584, 1672, 1703, 1725, 2889, 2924,
Compound 8c, yield 0.37 g(22%), orange powder, m.p.
206–207 °C. MS: m/z 566 [M]+.
1
3090, 3430 cmꢂ1. H NMR: d 2.11 (3H, s, CH3), 2.54 (3H,
5.3. The action of tetrafluoroboric acid diethyl etherate on
3-diacylmethylidene-1,2-diferrocenylcyclopropenes (8a–c)
s, CH3), 3.97 (2H, bs, NH2), 4.14 (5H, s, C5H5), 4.22 (5H,
s, C5H5), 4.00 (2H, m, C5H4), 4.06 (2H, m, C5H4), 4.51
(2H, m, C5H4), 5.03 (2H, m, C5H4). Anal. Calc. for
C28H26Fe2N2O: C, 64.90; H, 5.06; Fe, 21.55; N, 5.40. Found:
C, 64.78; H, 4.98; Fe, 21.64; N, 5.17%. MS: m/z 518 [M]+.
Hydrazone 14b, yield 0.20 g (60%), orange powder, p.m.
305–307 °C. IR (KBr): m 492, 561, 690, 819, 864, 926, 963,
1001, 1022, 1085, 1105, 1157, 1242, 1267, 1334, 1357, 1384,
1412, 1448, 1521, 1588, 1643, 1664, 1700, 1723, 2887, 2918,
3087, 3425 cmꢂ1. 1H NMR: d 4.04 (2H, bs, NH2), 4.21 (5H,
s, C5H5), 4.29 (5H, s, C5H5), 4.11 (2H, m, C5H4), 4.18 (2H,
m, C5H4), 4.59 (2H, m, C5H4), 5.11 (2H, m, C5H4), 7.20–
7.56 (10H, m, 2C6H5). Anal. Calc. for C38H30Fe2N2O: C,
71.05; H, 4.71; Fe, 17.39; N, 4.36. Found: C, 70.96; H,
4.83; Fe, 17.48; N, 4.28%. MS: m/z 642 [M]+.
Tetrafluoroboric acid diethyl etherate (0.5 ml) was
added dropwise with stirring at 20 °C in an atmosphere
of dry nitrogen to a solution of compounds 8a–c
(0.5 mmol) in dry dichloromethane (30 ml). The mixture
was stirred for 1 h at 20 °C and then dry diethyl ether
(150 ml) was added. The crystals that formed were filtered
off, washed on a filter with several portions of dry diethyl
ether, and then dried in a vacuum desiccator over CaCl2.
The yield of tetrafluoroborates (13a–c) were 80–87%,
brown crystals.
Tetrafluoroborate (13a), yield 0.24 g (81%), m.p. ca.
1
237 °C (decomp.). H NMR: d 2.67 (6H, s, 2CH3), 4.37
(10H, s, 2C5H5), 4.85 (4H, m, C5H4), 5.36 (4H, m,
C5H4), 5.43 (1H, bs). 13C NMR: d 31.06 (2CH3), 65.47
(C), 70.82 (2C5H5), 73.21, 73.70 (2C5H4), 109.03 (2CipsoFc),
142.41(2C), 149,02 (C), 168.47 (2C@O. . .1H). Anal. Calc.
for C28H25 BF4Fe2O2: C, 56.80; H, 4.26; B 1.83; F, 12.84;
Fe, 18.87. Found: C, 56.62; H, 4.31; F, 12.98; Fe, 18.73%.
Tetrafluoroborate (13b), yield 0.31 g (87%), m.p. ca.
Hydrazone 14c, yield 0.18g (63%), orange powder, p.m.
227–228°C. IR (KBr): m 489, 557, 689, 821, 863, 924, 962,
1002, 1021, 1082, 1103, 1155, 1241, 1264, 1336, 1356,
1383, 1412, 1446, 1520, 1587, 1640, 1663, 1703, 1720,
2883, 2921, 3090, 3430 cmꢂ1 1H NMR: d 2.40 (3H, s,
.
CH3), 3.88 (2H, bs, NH2), 4.00 (5H, s, C5H5), 4.20 (5H,
s, C5H5), 3.99 (2H, m, C5H4), 4.19 (2H, m, C5H4), 4.48
(2H, m, C5H4), 5.06 (2H, m, C5H4), 7.23–7.62 (5H, m,
C6H5). Anal. Calc. for C33H28Fe2N2O: C, 68.30; H, 4.86;
Fe, 19.25; N, 4.83. Found: C, 68.42; H, 4.93; Fe, 19.32;
N, 4.75%. MS: m/z 580 [M]+.
1
261 °C (decomp.). H NMR: d 4.45 (10H, s, 2C5H5), 4.91
(4H, m, C5H4), 5.37 (4H, m, C5H4), 5.66 (1H, bs), 7.34–
7.51 (6H, m, C6H5), 7.76–7.89 (4H, m, C6H5). 13C NMR:
d 66.52 (C), 71.04 (2C5H5), 72.98, 73.76 (2C5H4), 109.43
(2CipsoFc), 128.03, 128.16, 128.45, 128.91, 131.19, 133.37
(2C6H5), 139.61, 139.72, 139.93 (3C), 144.87(2C), 174.14
(2C@O. . .1H). Anal. Calc. for C38H29BF4Fe2O2: C, 63.73;
H, 4.08; B 1.51; F, 10.61; Fe, 15.60. Found: C, 63.56; H,
4.11; F, 10.72; Fe, 15.43%.
Hydrazone 15a, yield 0.17 g (62%), orange powder, p.m.
207–209 °C. IR (KBr): m 491, 557, 691, 818, 880, 921, 959,
1001, 1022, 1079, 1104, 1161, 1234, 1267, 1333, 1355, 1374,
1386, 1410, 1447, 1521, 1585, 1671, 1705, 1721, 2880, 2920,
1
3087, 3424 cmꢂ1. H NMR: d 1.84 (3H, s, CH3), 2.44 (3H,

1224
E. Klimova et al. / Journal of Organometallic Chemistry 693 (2008) 1215–1224
[10] T. Klimova Berestneva, E.I. Klimova, A.R. Toscano, C. Alvarez
s, CH3), 3,59 (3H, s, CH3), 4.17 (1H, s, NH), 4.09 (5H, s,
C5H5), 4.28 (5H, s, C5H5), 4.24 (2H, m, C5H4), 4.30 (2H,
m, C5H4), 4.44 (2H, m, C5H4), 4.83 (2H, m, C5H4). Anal.
Calc. for C29H28Fe2N2O: C, 65.43; H, 5.30; Fe, 21.00; N,
5.26. Found: C, 65.29; H, 5.41; Fe, 21.10; N, 5.32%. MS:
m/z 532 [M]+.
´
´
´
Toledano, S. Hernandez Ortega, M. Martınez Garcıa, Eur. J. Org.
Chem. (2005) 4406.
´
´
´
[11] E.I. Klimova, M. Martınez Garcıa, T. Klimova, J.M. Mendez
´
Stivalet, S. Hernandez Ortega, L. Ruız Ramirez, J. Organomet.
Chem. 659 (2002) 56.
[12] V.N. Postnov, E.I. Klimova, A.N. Pushin, N.N. Meleshonkova,
Metalloorg. Khim. 5 (1992) 564.
[13] E.I. Klimova, T. Klimova, S. Hernandez Ortega, R.M. Esquivelzeta,
6. Supplementary material
´
´
´
L. Ruız Ramirez, M. Martınez Garcıa, J. Organomet. Chem. 689
(2004) 2395.
CCDC 665728 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[14] I. Agranat, E. Aharon-Shalom, J. Am. Chem. Soc. 35 (1975) 3829.
´
´
[15] E.I. Klimova, M. Martınez Garcıa, T. Klimova Berestneva, C.
Alvarez Toledano, R.A. Toscano, L.V. Backinowsky, Eur. J. Org.
Chem. (2006) 4755.
[16] C.H. Chang, R.F. Porter, S.H. Bauer, J. Am. Chem. Soc. 92 (1970)
5313.
Acknowledgements
[17] L.E. Sutton (Ed.), Tables of Interatomic Distances and Configuration
in Molecules and Ions, The Chemical Society, London, 1965.
[18] K. Komatsu, T. Kitagawa, Chem. Rev. 103 (2003) 1371.
[19] A.J. Fry, P.S. Jain, R.L. Krieger, J. Organomet. Chem. 214 (1981)
381.
This work was supported by the DGAPA-UNAM
(Mexico, Grant IN 207606). Thanks are due to E.A. Vaz-
´
´
`
quez Lopez and Juan Manuel Martınez Mendoza for their
[20] Kh.M. Hassan, M.M. Aly, G.M. El-Nagkar, J. Chem. Tech.
Biotechnol. 29 (1979) 515.
technical assistance.
[21] A.N. Nesmeyanov, V.N. Postnov, A.M. Baran, V.A. Sazonova, Izv.
Akad. Nauk SSSR. Ser. Khim. (1981) 222 [Bull. Acad. Sci. USSR.
Div. Chem. Sci. 30 (1981) (Engl. Transl.)].
References
[22] M.A. El-Maghraby, Kh. M. Hassan, J. Indian Chem. Soc. 53 (1976)
1030.
[1] K. Kamatsu, T. Kitagawa, Chem. Rev. 103 (2003) 1371.
[2] E.A. Chandross, G. Smolinsky, Tetrahedron Lett. (1960) 19.
[3] T. Eicher, D. Lerch, Tetrahedron Lett. 21 (1980) 3751.
[4] S. Yoneda, H. Hirai, Z. Yoshida, Heterocycles 15 (1981) 865.
[5] H. Yoshida, Y. Takahashi, H. Kinoshida, S. Ukishima, T. Ogata, K.
Matsumoto, Bull. Chem. Soc. Jpn. 64 (1991) 3565.
[6] H. Yoshida, F. Utsumi, H. Suzuki, S. Ito, S. Sakashita, T. Ogata, K.
Matsumoto, Bull. Chem. Soc. Jpn. 65 (1992) 698.
[7] Z. Yoshida, H. Hirai, S. Miki, S. Yoneda, Tetrahedron 45 (1989) 3217.
[23] A. J Bard, L.R. Faulkner, Electrochemical Methods, Fundamentals
and Applications, John Wiley and Sons, NY, 1980.
[24] P. Zanello, Inorganic Electrochemistry, Theory, Practice and Appli-
cation, The Royal Society of Chemistry, Cambridge, UK, 2003.
[25] M.B. Robinson, P. Day, Inorg. Chem. Radiochem. 10 (1967) 247.
[26] A. Togni, R.L. Halterman, Metallocenes, 2, VCH, Weinheim, 1998;
A. Togni, T. Hayashi (Eds.), Ferrocenes, VCH, Weinheim, 1995, pp.
497–530.
´
[8] E.I. Klimova, T. Klimova Berestneva, S. Hernandez Ortega, D.
[27] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal
Structures, University of Go¨ttingen, Germany, 1997.
´
´
´
´
Mendez Iturbide, A. Garcıa Marquez, M. Martınez Garcıa, J.
Organomet. Chem. 690 (2005) 3333.
[28] G. Gritzner, J. Kuta, Pure Appl. Chem. 4 (1984) 461.
¨
´
´
[9] T. Klimova Berestneva, M. Martınez Garcıa, L. Ortiz-Frade, S.
Hernandez Ortega, A.R. Toscano, E. Klimova, J. Organomet. Chem.
691 (2006) 2872.
[29] E.I. Klimova, T. Klimova Berestneva, A. Cinquantini, M. Corsini,
´
´
P. Zanello, A.R. Toscano, S. Hernandez Ortega, M. Martınez
´
Garcıa, Org. Biomol.Chem. 1 (2003) 4458.