Titanium(IV) isopropoxide-mediated dimerization of 2- (ferrocenylmethylidene)-1,3-dicarbonyl compounds

Article abstract of DOI:10.1016/j.jorganchem.2010.06.018

Diethyl 2-(ferrocenylmethylidene)malonate undergoes linear dimerization with formation of tetraethyl 2,3-diferrocenylbutane-1,1,4,4-tetracarboxylate when treated with EtMgBr in the presence of Ti(OⁱPr)₄. Under similar conditions, eth

Full text of DOI:10.1016/j.jorganchem.2010.06.018

Journal of Organometallic Chemistry 695 (2010) 2264e2272
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Titanium(IV) isopropoxide-mediated dimerization
of 2-(ferrocenylmethylidene)-1,3-dicarbonyl compounds
,
a
a
b
Elena Klimova a , Tatiana Klimova , Marcos Flores-Alamo , Leon V. Backinowsky ,
*
Miguel A. González-Fuentes c, Luis Ortiz-Frade c, Marcos Martínez García d
a Universidad Nacional Autónoma de México, Facultad de Química, Cd. Universitaria, Coyoacán, C.P. 04510, México D.F., Mexico
b N. D. Zelinsky Institute of Organic Chemisrty, Russian Academy of Sciences, 47, Leninsky prosp., 117913 Moscow, Russian Federation
c Electrochemistry Department, Centro de Investigación y Desarrollo Tecnológico en Electroquímica S.C. Parque Tecnológico Querétaro, Sanfandila, Pedro de Escobedo,
C.P. 76703, Querétaro, Mexico
d Universidad Nacional Autónoma de México, Instituto de Química, Cd. Universitaria, Coyoacán, C.P. 04510, México D.F., Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
Diethyl 2-(ferrocenylmethylidene)malonate undergoes linear dimerization with formation of tetraethyl
2,3-diferrocenylbutane-1,1,4,4-tetracarboxylate when treated with EtMgBr in the presence of Ti(OiPr)4.
Under similar conditions, ethyl (E)-2-(ferrocenylmethylidene)benzoylacetate and ethyl (E,Z)-2-(ferroce-
nylmethylidene)acetoacetate afford linear dimerization products (3,4-diferrocenyladipic acid derivatives)
and intramolecular cyclization products of the latter (3,4-diferrocenylcyclopentanol derivatives). No
products of the Kulinkovich reaction (hydroxycyclopropanation of the ester groups) were observed. The
structures of the compounds obtained were established based on data from IR, 1H and 13C NMR spec-
troscopy, mass spectrometry and X-ray diffraction analysis. The mechanistic aspects of these reactions
are discussed. Electrochemical properties of the compounds 7a, 10 and 12 were investigated using cyclic
voltammetry, one step potential chronoamperometry and square wave voltammetry. Two electro-
Received 26 February 2010
Received in revised form
15 June 2010
Accepted 16 June 2010
Available online 30 July 2010
Keywords:
Ferrocene
2-(Ferrocenylmethylidene)-1,3-dicarbonyl
compounds
Reductive dimerization
Titanium(IV) isopropoxide
Electrochemistry
chemical processes (IeII), attributed to the oxidations of the ferrocenes moieties, E00(I), E00(II),
and comproportionation constant Kcom are reported.
D
E00(IIeI)
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
mainly, starting from esters of saturated acids or unsaturated
nonconjugated acids [8].
Organometallic derivatives of the main group metals (organo-
As to esters of a,b-unsaturated acids, they have not virtually
lithium,
organomagnesium,
organozinc,
organoaluminum
been studied. The only publication known [9] is devoted to the
introduction of the hydroxycyclopropane ring into acrylates,
cyclohex-1-enecarboxylates, and cyclopent-1-enecarboxylates. No
studies on the behaviour of metallocene derivatives under the
conditions of the Kulinkovich reaction have been carried out so far.
As a continuation of our research into ferrocenylcyclopropanes
and ferrocenylcyclopropenes, it was of interest to investigate the
Kulinkovich reaction as a feasible route for the conversion of
alkoxycarbonyl derivatives of the ferrocene series into the
hydroxycyclopropane-containing compounds. In the present work,
we report the results of studies of reactions of 2-(ferrocenylme-
thylidene)-1,3-dicarbonyl compounds with EtMgBr/Ti(OiPr)4.
compounds) are widely used in synthetic organic chemistry as
monocarbanionic nucleophiles in reactions with electrophiles [1,2].
In the presence of stoichiometric or catalytic amounts of transition
metal complexes, structural transformations of monocarbanionic
equivalents can occur leading to new, e.g., bis-anionic intermedi-
ates [3,4]. The transformations pertaining to this type of reactions
include hydroxycyclopropanation of ester groups (the Kulinkovich
reaction) under the action of, formally, ethylene bis-anion derived
from ethylmagnesium bromide (ethyl monoanion) in the presence
of Ti(OiPr)4 [5e7] (Scheme 1).
In recent years, the Kulinkovich reaction in its diverse versions
has widely been used for the construction of the hydrox-
ycyclopropane ring in different types of organic compounds,
2. Results and discussion
Diethyl 2-(ferrocenylmethylidene)malonate (2), ethyl (E)-2-
(ferrocenylmethylidene)benzoylacetate (E-3), and ethyl (E,Z)-2-
(ferrocenylmethylidene)acetoacetates (E-4 and Z-5) were used as
* Corresponding author. Tel.: þ52 55 56225371.
E-mail address: klimova@servidor.unam.mx (E. Klimova).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.06.018

E. Klimova et al. / Journal of Organometallic Chemistry 695 (2010) 2264e2272
2265
H
H
H
H
H
H
iPrO
iPrO
iPrO
iPrO
iPrO
iPrO
Ti(OiPr)4
-
CH3CH3
2
Ti
Ti
Ti
MgBr
H
H
1
O
R
OR1
OR1
O
HO
R
iPrO
iPrO
iPrO
iPrO
OR1
H2O
Ti
Ti
HCl
O
R
R
Scheme 1.
O
C
O
The diastereomers 7a and 7b differ in physical parameters (m.p.,
Fc
H
R
Rf), and exhibit similar NMR spectral characteristics, which suggest
their symmetrical structures (Fig. 1a, b, respectively). Thus the
1H NMR spectra of the dimers 7a and 7b contain each two char-
acteristic triplets and two quadruplets for the protons of four CH3
and four CH2 groups of the four eCOOEt groups, one singlet for the
protons of two unsubstituted cyclopentadienyl rings of two ferro-
cene substituents, one doublet for the protons of two methyne
groups and one multiplet for the protons of two FcCH-fragments.
The spatial structure of the major diastereomer 7a (yield ca.
40%) was elucidated by X-ray diffraction analysis of a single crystal
obtained by crystallization from dichloromethane. The general
view of the molecule 7a is shown in Fig. 2. It follows from these data
that compound 7a is tetraethyl 2S*,3R*-2,3-diferrocenylbutane-
1,1,4,4-tetracarboxylate. The structure of tetraethyl 2R*,3R*-2,
3-diferrocenylbutane-1,1,4,4-tetracarb-oxylate was assigned to
diastereomer 7b.
R
C5H11
N
C
FcCHO
H2C
+
AcOH
OEt
OEt
6a-c
O
O
2, E-3, E-4, Z-5
R= OEt (2, 6a); R= Ph (E-3, 6b); R= CH3 (E-4, Z-5, 6c); Fc= C5H5FeC5H4
Scheme 2.
the starting compounds. They were prepared by coupling ferroce-
necarbaldehyde (1) with diethyl malonate (6a), ethyl benzoylace-
tate (6b), and ethyl acetoacetate (6c), respectively, in the presence
of piperidinium acetate [10,11] (Scheme 2).
We found that the reaction of diethyl 2-(ferrocenylmethylidene)
malonate 2 with EtMgBr in the presence of Ti(OiPr)4 afforded 68% of
linear dimer (7a,b) as a ca. 2:1 mixture of two diastereomers 7a and
7b (1H NMR data). In addition, the reduction product of the starting
compound, viz., diethyl 2-(ferrocenylmethyl)malonate (8), and the
1,4-adduct of EtMgBr to the conjugated system, viz., diethyl 2-(1-
ferrocenylpropyl)malonate (9), were also isolated (Scheme 3).
The structures of compounds 7a, 7b, 8, and 9 isolated by column
chromatography on alumina were established based on the data
from IR and NMR spectroscopy, mass spectrometry, and elemental
analysis. The dimeric nature of compounds 7a and 7b followed
from their mass spectra, which contain peaks (m/z ¼ 714) corre-
sponding to the doubled molecular weight of the starting ester
2 [2 ꢀ Mr(2) þ 2].
We found further that the reactions of ethyl (E)-2-(ferroce-
nylmethylidene)benzoylacetate (E-3) and ethyl (E,Z)-2-(ferroce-
nylmethylidene)acetoacetates (E-4 and Z-5) with EtMgBr in the
presence of Ti(OiPr)4 afford, in addition to linear (10, 11) dimers, the
corresponding cyclic products (12, 13) (ca. 1:2, 1H NMR data) in
a total yield of 65e71%. The stereochemistry of acetylacetates (E- or
Z-) did not virtually influence the ratio of cyclic and linear dimers.
As in the case of reaction with malonate 2, the reduction products
of the starting compounds (14, 15) and the 1,4-adducts of EtMgBr to
the system of conjugated double bonds (16a,b, 17a,b) (Scheme 4)
also represented minor components.
The structures of compounds 10e17 were established by spec-
troscopy. The 1H NMR spectra of dimers 10 and 12 are shown in
Fig. 1c, d. The spectroscopic data (1H NMR) suggest that compounds
COOEt Fc
COOEt
COOEt
EtMgBr (3 eq)
COOEt
FcCH2CH
+
FcCH
EtOOC
Ti(OiPr)4 (1 eq)
COOEt
COOEt
Fc
COOEt
8 (~7%)
2
7a,b (~69%)
COOEt
CH3CH2
FcCHCH
+
COOEt
9 (~10%)
Scheme 3.

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E. Klimova et al. / Journal of Organometallic Chemistry 695 (2010) 2264e2272
Fig. 1. 1H NMR spectrums: (a) of 7a; (b) of 7b; (c) of 10; (d) of 12.
10e13 represent each single diastereomer and compounds 16, 17
represent two diastereomers (16a,b and 17a,b).
(Fig. 1c). The presence in the 13C NMR spectrum of compound 10 of
one signal for two methyl groups, two ferrocenyl fragments, two
Cipso Fc carbon atoms, two Cipso carbon atoms, two C]O groups, and
The dimeric nature of compounds 10e13 followed from their
mass spectra, which contain peaks (m/z ¼ 778 for 10 and 12, 654 for
11 and 13) corresponding to the doubled molecular weight of the
starting esters E-3, E-4 and Z-5.
presence of two signals for two Ph(OH)]Ce fragments [d 106.40
(2C) and 171.75 (2CeOH) ppm] corroborates completely the sug-
gested symmetric structure.
The 1H NMR spectrum of the linear dimer 10 contains charac-
teristic signals for two protons of the enolic hydroxyl groups
The 1H NMR spectrum of the cyclodimer 12 contains signals for
the protons of two methyl groups (eCOOEt), two C5H5 fragments
of two ferrocenyl substituents, two doublets and one doublet of
doublets for the methine protons of the cyclopentane ring
(Fig. 1d).
(d 13.24), one triplet for six protons of two methyl groups (eCOOEt),
one singlet for the protons of unsubstituted C5H5 rings of two
ferrocenes, and a multiplet for the protons of two Ph groups

E. Klimova et al. / Journal of Organometallic Chemistry 695 (2010) 2264e2272
2267
ꢀ
Fig. 3. Molecular structure of 12. Selected bond lengths (A): C(14)eC(15) ¼ 1.577(4), C
(15)eC(16) ¼ 1.545(4), C(16)eC(17) ¼ 1.525(4), C(17)eC(18) ¼ 1.573(4), C(14)eC(13) ¼
1.558(4), C(14)eC(22) ¼ 1.526(4), C(13)eO(1) ¼ 1.213(3), C(22)eO(3) ¼ 1.203(4).
Selected bond angles (ꢁ): C(14)eC(15)eC(16) ¼ 105.5(2), C(15)eC(14)eC(18) ¼ 105.4
(2), C(22)eC(14)eC(13) ¼ 111.0(3), O(3)eC(22)eO(4) ¼ 123.8(3), O(2)eC(18)eC(7) ¼
106.0(2), C(22)eC(14)eC(15) ¼ 106.0(2), O(2)eC(18)eC(17) ¼ 111.4(2), C(14)eC(15)eC
(25) ¼ 112.0(2).
ꢀ
Fig. 2. Molecular structure of 7a. Selected bond lengths (A): C(11)eC(12) ¼ 1.567(3), C
(13)eO(4) ¼ 1.333(3), C(11)eC(11a) ¼ 1.544(4), C(12)eC(13) ¼ 1.515(3), C(16)eO(1) ¼
1.193(3), C(16)eO(2) ¼ 1.326(3), C(13)eO(3) ¼ 1.187(2). Selected bond angles (ꢁ):
C
(12)eC(11)eC(11a) ¼ 109.85(19), C(6)eC(11)eC(11a) ¼ 114.4(2), O(1)eC(16)eO(2) ¼
123.6(2), O(1)eC(16)eC(12) ¼ 126.3(2), O(2)eC(16)eC(12) ¼ 110.01(18), C(7)eC(6)eC
(10) ¼ 106.91(18), C(7)eC(6)eC(11) ¼ 123.85(19), C(7)eC(6)eFe(1) ¼ 68.19(12).
cyclodimer 13. Our attempts to obtain crystals of compounds 10
and 11 suitable for X-ray diffraction analysis failed, therefore we
could not unambiguously establish the spatial structures of these
linear dimers.
The formation of dimers with linear (7a,b, 10, 11) and cyclic
structures (12, 13) and reduction products (8, 14, 15) of 2-(ferroce-
nylmethylidene)-1,3-dicarbonyl compounds (2e5) upon treatment
with EtMgBr in the presence of Ti(OiPr)4 proceeds, in ouropinion, via
dialkoxytitanate 1 as in the Kulinkovich reaction [5e7]. This inter-
mediate generated in the first step plays the role of ethylene bis-
anion in the reactionwith a,b-unsaturated carbonyl compounds, but
then adds, unlike the Kulinkovich reaction, at positions 1,4 of the
C]CeC]O system of multiple bonds (Scheme 5).
The intermediate 5-membered oxatitanacycle 18 with a 4,5-
double bond is converted to the reduction product (8, 14, 15) or
The spatial structure of cyclodimer 12 could be elucidated by
X-ray diffraction analysis of a single crystal obtained by crystalli-
zation from chloroform. The general view of the molecule 12 is
shown in Fig. 3.
The key element of the structure is the central cyclopentane ring
in the envelope conformation. The ferrocenyl substituents are trans
oriented to each other as are the hydrogen atoms at C(15), C(16),
and C(17). The lengths of the bonds C(14)eC(18), C(14)eC(15), and
C(17)eC(18) of the cyclopentadiene ring are equal to 1.605(4), 1.574
ꢀ
(4), and 1.573(4) A, respectively, which exceed somewhat the
ꢀ
standard CeC
s
-bonds (cf. literature data [12,13]: d(CeC) ¼ 1.54 A).
The data from the X-ray diffraction analysis show that compound
12 is 2R*-benzoyl-2,5S*-diethoxycarbonyl-3R*,4S*-diferrocenyl-
1R*-phenylcyclopentanol. An analogous structure was assigned to
EtOOC
Fc
OH
R= Ph
Ph
Ph
Fc
Fc
HO
Fc
COOEt
O
Fc
H
R
COR
10
EtMgBr
Ti(OiPr)4
EtO
+
C
C
COOEt
O
OEt
OH
EtOOC
O
Fc
O
R
O
H3C
12, 13
R= Me
CH3
E-3, E-4, Z-5
Fc
COOEt
11
COR
CH3CH2
FcCHCH
COR
FcCH2CH
+
R= Ph (E-3, 10, 12, 14, 16a,b)
R= Me (E-4, Z-5, 11, 13, 15, 17a,b)
COOEt
14, 15
COOEt
16a,b; 17a,b
Scheme 4.

2268
E. Klimova et al. / Journal of Organometallic Chemistry 695 (2010) 2264e2272
H
H
iPrO
iPrO
O
R
Ti
Ti
FcCH
R
+
O
iPrO
iPrO
OEt
H
H2O
HCl
O
H
Ti
8, 14, 15
OEt
CH2
H C
-
H
2
H
H
iPrO
iPrO
Fc
O
18
H
1
Scheme 5.
R
O
iPrO
COOEt
R
Ti
Fc
OEt
O
iPrO
iPrO
H2O
HCl
Ti
O
linear dimers
7a,b; 10, 11
O
Fc
R
iPrO
O
Fc
CHFc
R
EtO
COOEt
O
19
R = EtO, Ph, Me
Scheme 6.
serves as a monoanionic equivalent in subsequent reactions with 2-
(ferrocenylmethylidene)-1,3-dicarbonyl compounds according to
Schemes 6 and 7:
These dimerization schemes are supported by the following
experimental facts: (1) the absence of hydroxycyclopropanation
products of the ethoxycarbonyl groups in neither of reactions
studied; (2) isolation of the reduction products of the starting 2-
(ferrocenylmethylidene)-1,3-dicarbonyl compounds; (3) identifi-
cation of linear dimers in the enol 10, ketone 7a,b, 11 and cyclic 12,
13 forms.
When the potential scan was initiated to a positive direction,
two oxidation signals (Ia and IIa) were observed. When the cycle
was completed, two complementary reduction signals (Ic and IIc)
were also detected. The anodic peak currents values for signals Ia
and IIa were independent of scan rate, which indicates that both
responses are diffusion-controlled. In order to obtain the number of
exchanged electrons in each process, one-step potential chro-
noamperometry experiments were performed at a potential step
corresponding to the potential peak values, Epa(I) and Epa(II)
(Fig. 5).
Particular attention should be paid to the diastereoselectivity of
the dimerization processes, i.e., the formation of two linear dia-
stereomers 7a and 7b (ca. 2:1) or linear (10, 11) and cyclic (12, 13)
products (ca.1.5:1).
For two consecutive electron transfer reactions controlled by
diffusion, the currents are established by the Cottrell equations (1)
and (2) [14]. These relationships indicate that when a potential is
held at the electrode surface with a constant value that promotes
either the first (Eq. (1)) or the second electrochemical reaction (Eq.
(2)), the current depends on the diffusion of the electroactive
species from a solution to the electrode surface and the number of
exchanged electrons. Under these conditions, the current I(t) is
a function of tꢂ1/2, due to the growth of a diffusion layer caused by
the electrolysis near the electrode.
3. Electrochemistry
Fig. 4 shows cyclic voltammetric response of compound 7a in
acetonitrile containing 0.1 M tetra-N-butylammonium tetrafluoro-
borate (TBABF4).
OEt
EtO
O
iPrO
O
Ti
Fc
R
iPrO
iPrO
Et
iPrO
R
H2O
HCl
EtMgBr
2
cyclodimers
12, 13
Ti
+
OH
Fc
O
Et
Fc
COOEt
COR
ROC
FcCH
COOEt
R = Ph, Me
Scheme 7.

E. Klimova et al. / Journal of Organometallic Chemistry 695 (2010) 2264e2272
2269
Table 1
ΙΙ
Formal electrode potential E0(I), E0(II) and
compounds 7a, 10 and 12.a
D
E0(IIeI), and constant Kcom for
a
12
8
Ι
a
Compound
E0(I)
E0(II)
D
E0(IIeI)
Kcom
7a
10
12
0.015
0.019
ꢂ0.017
0.120
0.073
0.093
0.105
0.054
0.110
60
8
73
4
a
Formal electrode potential (E00) vs ferrocene/ferrocenium in the presence of
0
0.1 M TBABF4-acetonitrile. Obtained by square wave voltammetry.
-4
-8
-12
ΙΙ
c
I(t) ¼ n1F ꢀ A ꢀ D10/2
ꢀ
pꢂ1/2 ꢀ Co*tꢂ1/2
(1)
(2)
Ι
c
I(t) ¼ (n1 þ n2)F ꢀ A ꢀ D10/2
ꢀ
pꢂ1/2 ꢀ Co*tꢂ1/2
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
For processes I and II, two linear relationships of current I(t) and
tꢂ1/2 were obtained, with the equations II(t) ¼ 3.9tꢂ1/2 þ 0.36
(r ¼ 0.999) and III(t) ¼ 8.1tꢂ1/2 þ 0.8 (r ¼ 0.999). Considering the
same values of diffusion coefficient, the ratio of the slopes from the
obtained relationships, allows us to estimate n1 ¼1 and n2 ¼1. This
evidence indicates that processes I and II are attributed to the two
consecutive one-electron transfers for ferrocene moieties. To obtain
the formal electrode potential for both processes, square wave
voltammetry experiments were carried out (Fig. 6).
E(V/Fc-Fc+)
Fig. 4. Cyclic voltammograms obtained for 7a in the presence of 0.1 M TBABF4 in
acetonitrile. The scan potential was initiated from Eocp to positive direction. The scan
rate 0.1 V sꢂ1. The working electrode used was platinum.
0
0
The obtained values for processes I and II, were E (I) ¼ 0.015 V/
160
120
0
þ
0
FceFcþ and E (II) ¼ 0.120 V/FceFc . The value of
D
E (IIeI) for
0
0
processes I and II was 0.105 V and the corresponding value of
comproportionation constant Kcom was 60 [14,15]. The electro-
chemical response of compounds 10 and 12 is very similar than the
presented in compound 7a. Table 1 shows a summary of the
obtained values of E (I), E (II), and Kcom for the compounds 7a, 10,
and 12. The estimated values of Kcom for all compounds suggest that
the electronic charge is slightly delocalized in the mixed valence
state generated electrochemically according to the Robin-Day
0
0
0
0
80
(B)
(A)
40
Table 2
Crystal data and structure refinement parameters for compounds 7a and 12.
0.02
0.04
0.06
0.08
Data
7a
12
t(s)
Molecular formula
Formula weight (g molꢂ1
Temperature (K)
Crystal system
C36H42Fe2O8
714.40
298 (2)
Monoclinic
P21/n
10.0544 (6)
18.9430 (6)
10.0633 (5)
90
118.258 (7)
90
1688.24 (18)
2
1.405
0.910
748
C44H42Fe2O6
778.48
293 (2)
Triclinic
P-1
8.2180 (2)
12.5620 (5)
17.6610 (6)
87.120 (3)
78.448 (3)
86.795 (3)
1782.08 (10)
2
1.451
0.865
812
Mo-Ka, 0.71073
Graphite
3.38e26.73
16187
7511
Fig. 5. One-step potential chronoamperometric experiments for 7a in the presence of
0.1 M TBABF4 in acetonitrile. The initial potential was the open circuit potential value
Eocp. The potential step (E1) was (A) Epa(I) and (B) Epa(II). Pulse width time of 0.1 s.
)
Space group
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
25
20
15
10
5
3
ꢀ
V (A )
Z
D calc. (mg mmꢂ3
)
Absorption coefficient (mmꢂ1
)
F(000)
Radiation,
ꢀ
l
(A)
Mo-K
a
, 0.71073
Monochromator
Graphite
3.15e29.48
6259
3460
0.0180
q
range (ꢁ)
Reflections collected
Reflections independent
Rint
0.0238
Final R indices [I > 2
s
(I)]
R1 ¼ 0.0357,
wR2 ¼ 0.0905
R1 ¼ 0.0566,
wR2 ¼ 0.0963
232
R1 ¼ 0.0506,
wR2 ¼ 0.1425
R1 ¼ 0.0788,
wR2 ¼ 0.1563
453
0
R indices (all data)
-0.2
0.0
0.2
0.4
Refinable parameters
Goodness-of-fit
E(V/Fc-Fc+)
0.985
1.086
Refinement method
Full-matrix-least-
squares on F2
ꢂ0.287/0.303
Full-matrix-least-
squares on F2
ꢂ0.930/1.246
Fig. 6. Square wave voltammetry obtained for 7a in the presence of 0.1 M TBABF4 in
acetonitrile. The amplitude was 50 mV with a frequency of 10 Hz. The working elec-
trode used was platinum.
Minimum/maximum residual
ꢀꢂ3
electron density (e A
)

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E. Klimova et al. / Journal of Organometallic Chemistry 695 (2010) 2264e2272
classification [15,16]. These values are in agreement with the
presence of ethylene group between the ferrocene moieties [17]. It
can be noticed that the presence of four COOEt groups in compound
7a enhances the electronic charge delocalization (Kcom ¼ 60)
compared with its analogue, compound 10 (Kcom ¼ 8), where there
are only two COOEt groups.
piperidinium acetate [10,11]. The physical and 1H NMR spectro-
scopic characteristics of compounds 2, E-3, E-4 and Z-5 were in
accord with the literature data [20e22].
5.1. Reactions of diethyl 2-(ferrocenylmethylidene)malonate (2)
with EtMgBr in the presence of Ti(OiPr)4
4. Conclusion
(a) A solution of EtMgBr in THF (1.0 M, 20 ml) was added dropwise
with stirring at 10e15 ꢁC to a solution of compound 2 (3.56 g,
10 mmol) and Ti(OiPr)4 (2.84 g, 10 mmol) in anhydrous THF
(50 ml) and ether (100 ml) in an inert dry atmosphere. The
mixture was stirred at this temperature for 2 h and quenched
with 10% HCl (100 ml). The organic layer was separated,
washed with water and 5% aqueous NaHCO3, and dried with
MgSO4. The solvent was evaporated in vacuo and the residue
was chromatographed on a column with Al2O3 (activity III) to
afford the following reaction products: diethyl 2-(ferroce-
nylmethyl)malonate (8) (0.29 g, 8%, eluted with hexane);
diethyl 2-(1-ferrocenylpropyl)malonate (9) (0.35 g, 9%, eluted
with hexane); dimer 7b (0.82 g, 23%, eluted with hexane-ethyl
acetate, 1:10) and dimer 7a (1.64 g, 46%, eluted with hex-
aneeethyl acetate, 1:2).
Thus, diethyl 2-(ferrocenylmethylidene)malonate (2), ethyl (E)-
2-(ferrocenylmethylidene)benzoylacetate (E-3) and ethyl (E,Z)-2-
(ferrocenylmethylidene)acetoacetate (E-4 and Z-5) produce no
hydroxycyclopropyl derivatives in reactions with EtMgBr in the
presence of Ti(OiPr)4 but rather undergo stereoselective dimeriza-
tion into linear and cyclic polyfunctional products.
5. Experimental
All the solvents were dried according to the standard procedures
and were freshly distilled before use. The 1H and 13C NMR spectra of
compounds 2e17 were recorded on a Unity Inova Varian spec-
trometer (300 and 75 MHz for 1H and 13C, respectively) of solutions
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 with an FTIR spectrophotometer
(Spectrum RXI PerkineElmer instruments). The mass spectra were
obtained on a Varian-MAT CH-6 instrument (EI, 70 eV). Elementar
Analysensysteme LECO CHNS-900 was used for elemental analyses.
Column chromatography was carried out on alumina (Brockmann
activity III).
The unit cell parameters and the X-ray diffraction intensities
were recorded on a Siemens P4 diffractometer. The crystallographic
data, the experimental conditions, and corrections are given in
Table 2.The structures of compounds 7a and 12 were solved by the
direct method (SHELXS-97 [18]) and refined using full-matrix least-
squares on F2.
(b) A solution of Ti(OiPr)4 (2.84 g, 10 mmol) in anhydrous THF
(50 ml) was added dropwise to a 1.0 M solution of EtMgBr in
THF (20 ml) in an inert dry atmosphere at 0e5 ꢁC. The resulting
dark-blue solution was stirred for an additional 30 min at 20 ꢁC
and a solution of 2 (3.56 g, 10 mmol) in THF (30 ml) was added
dropwise and 100 ml of ether. After 1 h, the reaction mixture
was quenched with HCl and worked up as described above. The
following products were isolated by column chromatography:
8 (0.25 g, 7%), 9 (0.39 g, 10%), 7b (0.75 g, 21%) and 7a (1.6 g,
45%).
Tetraethyl 2S*,3R*-2,3-diferrocenylbutane-1,1,4,4-tetracarbox-
ylate (7a), yellow crystals, m.p. 168e169 ꢁC. IR (KBr):
n 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,
All electrochemical studies were performed at sample concen-
trations of ca. 1 mM in acetonitrile containing 0.1 M tetra-N-buty-
lammonium tetrafluoroborate (TBABF4) using an Epsilon-BAS
potentiostat/galvanostat.
employed. The working electrode was a platinum disk (
2955, 3086 cmꢂ1. 1H NMR:
d
1.07 (6H, t, 2CH3, J ¼ 7.2 Hz), 1.35 (6H, t,
2CH3, J ¼ 7.11 Hz), 3.77 (4H, m, 2CH2), 4.09 (2H, m, C5H4), 4.14 (2H,
m, 2CH-Fc), 4.27 (10H, s, 2C5H5), 4.37(4H, m, 2CH2), 4.39 (4H, m,
C5H4), 4.59 (2H, m, C5H4), 4.33 (2H, d, 2CH, J ¼ 7.2 Hz). 13C NMR:
A
typical three-electrode array was
¼ 2 mm).
4
A platinum wire served as a counter-electrode. A silver wire
immersed in acetonitrile solution with 0.1 M tetra-N-butylammo-
nium chloride (TBACl), in a separate compartment connected to the
working cell through a BAS vycorÔ tip, was used as a pseudo
reference electrode. All solutions were bubbled with nitrogen prior
each measurement. Cyclic voltammetry experiments were initiated
from open circuit potential (Eocp) to a positive direction using
a range of scan rate from 0.1 to 0.5 V sꢂ1. One step potential chro-
noamperometry experiments with a pulse width time of 1s were
acquired from open circuit potential (Eocp) to different potential
values (E2) which correspond to anodic peak potential values.
Square wave voltammetry experiments with amplitude of 50 mV
and a frequency of 10 Hz were also performed. All potentials were
reported versus the couple Fc/Fcþ according to IUPAC convention
[19].
The following reagents were purchased from Aldrich: ferroce-
necarbaldehyde, 99%; diethyl malonate, 99%; ethyl acetoacetate,
99þ%; ethyl benzoylacetate, 90%; ethylmagnesium bromide, 3.0 M
solution in diethyl ether; titanium (IV) isopropoxide, 97%.
Diethyl 2-(ferrocenylmethylidene)malonate 2, ethyl 2-(ferroce-
nylmethylidene)benzoylacetate E-3 and ethyl 2-(ferrocenylmethy-
lidene)acetoacetates E-4 and Z-5 were prepared by condensation of
ferrocenecarbaldehyde with diethyl malonate, ethyl benzoylacetate
and ethyl acetoacetate, respectively, in benzene in the presence of
d 13.69, 14.18 (4CH3), 42.42, 54.16 (4CH), 61.21, 61.45 (4CH2), 68.88
(2C5H5), 66.36, 67.40, 69.05, 70.46 (2C5H4), 91.13 (2Cipso Fc), 168.64,
170.06 (4C]O). Anal. Calc. for C36H42Fe2O8: C, 60.52; H, 5.93; Fe,
15.64. Found: C, 60.41; H, 6.09; Fe, 15.59%. MS: m/z 714 [M]þ.
Tetraethyl 2R*,3R*-2,3-diferrocenylbutane-1,1,4,4-tetracarbox-
ylate (7b), yellow powder, m.p. 149e151 ꢁC. IR (KBr):
n 416, 477, 531,
587, 632, 698, 724, 754, 813, 946, 999, 1025, 1080, 1226, 1325, 1381,
1417, 1460, 1480, 1527, 1549, 1594, 1652, 1712, 1839, 2991,
3057 cmꢂ1. 1H NMR:
d
1.15 (6H, t, 2CH3, J ¼ 7.2 Hz), 1.36 (6H, t, 2CH3,
J ¼ 7.11 Hz), 3.75e3.93 (4H, m, 2CH2), 4.08 (4H, m, C5H4), 4.11 (2H,
m, 2CH-Fc), 4.17 (10H, s, 2C5H5), 4.15 (2H, m, 2CH2), 4.73 (2H, m,
C5H4), 4.31 (4H, q, 2CH2, J ¼ 7.2 Hz), 4.25 (2H, d, 2CH, J ¼ 6.0 Hz). 13
C
NMR:
d 13.81, 14.13 (4CH3), 40.71, 56.72 (4CH), 61.06, 61.20 (4CH2),
69.02 (2C5H5), 66.55, 66.98, 68.59, 69.47 (2C5H4), 90.66 (2Cipso Fc),
168.22, 169.52 (4C]O). Anal. Calc. for C36H42Fe2O8: C, 60.52;
H, 5.93; Fe, 15.64. Found: C, 60.68; H, 5.88; Fe, 15.55%. MS: m/z 714
[M]þ.
Diethyl 2-ferrocenylmethylmalonate (8), yellow oil. 1H NMR:
d
0.80 (6H, t, 2CH3, J ¼ 7.2 Hz), 3.02 (1H, dd, CH2, J ¼ 6.3, 10.2 Hz),
3.12 (1H, dd, CH2, J ¼ 4.2, 10.2 Hz), 3. 47 (1H, dd, CH, J ¼ 4.2, 6.3 Hz),
4.04 (4H, q, 2CH2, J ¼ 7.2 Hz), 4.05 (1H, m, C5H4), 4.09 (2H, m, C5H4),
4.12 (5H, s, C5H5), 4.16 (1H, m, C5H4). Anal. Calc. for C18H22FeO4: C,
60.35; H, 6.19; Fe, 15.60. Found: C, 60.41; H, 6.23; Fe, 15.50%. MS: m/
z 358 [M]þ.

E. Klimova et al. / Journal of Organometallic Chemistry 695 (2010) 2264e2272
2271
Diethyl 2-(1-ferrocenylpropyl)malonate (9), yellow oil. 1H NMR:
1.01 (3H, t, CH3, J ¼ 7.5 Hz), 1.17 (3H, t, CH3, J ¼ 7.65 Hz), 1.26 (3H, t,
Ethyl 2-(1-ferrocenylpropyl)benzoylacetate (16a,b) (w1:1),
yield 0.29 g (7%, hexane), yellow oil. 1H NMR:
0.95 (3H, t, CH3,
d
d
CH3, J ¼ 7.5 Hz), 1.82 (1H, m, CH2), 1.96 (1H, m, CH2), 3.10 (1H, m,
CH), 3.70 (1H, d, CH, J ¼ 4.8 Hz), 4.05 (2H, q, CH2, J ¼ 7.5 Hz), 4.17
(2H, q, CH2, J ¼ 7.65 Hz), 4.04 (4H, q, 2CH2, J ¼ 7.2 Hz), 4.07 (3H, m,
J ¼ 6.9 Hz), 0.99 (3H, t, CH3, J ¼ 6.9 Hz), 1.09 (3H, t, CH3, J ¼ 6.9 Hz),
1.15 (3H, t, CH3, J ¼ 7.2 Hz), 1.83e2.09 (4H, m, 2CH2, 2Et), 3.38e3.45
(2H, m, 2CHeFc), 3.88 (4H, q, 2CH2, J ¼ 6.9 Hz), 4.06 (5H, s, C5H5), 4.11
(5H, s, C5H5), 3.96 (2H, m, C5H4), 4.00 (2H, m, C5H4), 4.07 (2H, m,
C5H4), 4.14 (2H, m, C5H4), 4.44 (1H, d, CH, J ¼ 6.9 Hz), 4.71 (1H, d, CH,
J ¼ 6.9 Hz), 7.43 (3H, t, C6H5, J ¼ 8.1 Hz), 7.50 (3H, t, C6H5, J ¼ 7.2 Hz),
7.87 (2H, d, C6H5, J ¼ 8.1 Hz), 7.93 (2H, d, C6H5, J ¼ 7.2 Hz). 13C NMR:
C5H4), 4.15 (1H, m, C5H4), 4.12 (5H, s, C5H5). 13C NMR:
d 12.42 (CH3),
13.83 (2CH3), 25.91 (CH2), 40.14, 54.09 (2CH), 61.91 (2CH2), 68.37
(C5H5), 66.86, 67.03, 67.65, 67.68 (C5H4), 90.97 (Cipso Fc), 168.76
(2C]O). Anal. Calc. for C20H26FeO4: C, 62.19; H, 6.79; Fe, 14.46.
Found: C, 62.14; H, 6.64; Fe, 14.66%. MS: m/z 386 [M]þ.
d
12.38, 12.77, 13.73, 13.90 (4CH3), 26.51, 26.57 (2CH2), 39.54, 39.59
(2FcCH), 59.56, 59.61 (2CH), 61.06, 61.20 (OCH2), 68.48, 68.52
(2C5H5), 66.85, 66.89, 66.95, 67.05, 67.18, 67.67, 68.25, 68.93 (2C5H4),
91.14, 91.90 (2Cipso Fc), 128.20, 128.27, 128.48, 128.60, 133.08, 133.22
(2C6H5), 136.6, 136.94 (2Cipso), 168.80, 169.06 (2COOEt), 194.14,
194.67 (2PhC]O). Anal. Calc. for C24H26FeO3: C, 68.90; H, 6.27; Fe,
13.35. Found: C, 69.04; H, 6.21; Fe, 13.27%. MS: m/z 418 [M]þ.
5.2. Reactions of ethyl 2-ferrocenylmethylidenebenzoylacetate
(E-3) with EtMgBr in the presence of Ti(O Pr)4
i
This was carried out analogously using of E-3 (3.88 g, 10 mmol),
Ti(OiPr)4 (2.84 g, 10 mmol in 50 ml THF), 1.0 M solution of EtMgBr
(in 50 ml THF) and 100 ml of ether. The reaction mixture was
worked up as described above, subsequent chromatography on
Al2O3 gave compounds 10, 12, 14, and 16a,b.
5.3. Reactions of ethyl 2-ferrocenylmethylideneacetoacetates (E-4)
and (Z-5) with EtMgBr in the presence of Ti(OiPr)4
Diethyl 1,6-dihydroxy-3,4-diferrocenyl-1,6-diphenylhexa-1,5-
diene-2,5-dicarboxylate (10), yield 0.91 g (23.3%, hexaneeethyl
This was carried out analogously using of E-4 or Z-5 (3.26 g,
10 mmol), Ti(OiPr)4 (2.84 g, 10 mmol in 50 ml THF), 1.0 M solution
of EtMgBr (in 20 ml THF) and 100 ml of ether.
The reaction mixture was worked up as described above,
subsequent chromatography on Al2O3 gave compounds 11, 13 15,
and 17a,b.
Diethyl 4,5-diferrocenyloctan-2,7-dione-3,6-dicarboxylate (11),
yield 0.71 g (22% from E-4) and 0.65 g (20%, from Z-4) (hexane-
ethyl acetate, 3:1), yellow crystals, m.p. 143e144 ꢁC. IR (KBr):
acetate, 1:2), yellow crystals, m.p. 228e229 ꢁC. IR (KBr):
n
¼ 482,
706, 779, 823, 863, 918, 1002, 1022, 1045, 1105, 1126, 1182, 1236,
1263, 1285, 1348, 1381, 1398, 1412, 1446, 1491, 1574, 1590, 1625,
2736, 2938, 2977, 3095, 3430 cmꢂ1 1H NMR:
. d 1.02 (6H, t, 2CH3,
J ¼ 7.2 Hz), 3.76 (2H, d, 2CH, J ¼ 7.5 Hz),4.03 (4H, m, 2CH2), 3.88 (4H,
m, C5H4), 4.04 (2H, m, C5H4), 4.39 (2H, m, C5H4), 3.98 (10H, s,
2C5H5),7.53 (6H, m, 2C6H5), 7.72 (4H, m, 2C6H5), 13.24 (2H, s, 2OH).
13C NMR:
d 14.29 (2CH3), 40.98 (2CH), 60.32 (2CH2), 68.30 (2C5H5),
65.76, 67.09, 68.36, 69.63 (2C5H4), 93.88 (2Cipso Fc), 106.40 (2C),
127.01, 129.23, 129.34 (2C6H5), 136.79 (2Cipso), 171.75 (2CeOH),
173.87 (2C]O). Anal. Calc. for C44H42Fe2O6: C, 67.88; H, 5.44; Fe,
14.35. Found: C, 67.96; H, 5.51; Fe, 14.20%. MS: m/z 778 [M]þ.
2R*-Benzoyl-2,5S*-diethoxycarbonyl-3R*,4S*-diferrocenyl-1R*-
phenylcyclopentanol (12), yield 1.84 g (47%, hexane-ethyl acetate,
n
¼ 485, 709, 780, 820, 858, 920, 1001, 1021, 1043, 1106, 1120, 1184,
1231, 1259, 1284, 1347, 1399, 1421, 1445, 1489, 1575, 1592, 1627,
1724, 2730, 2979, 3090 cmꢂ1 1H NMR:
1.39 (6H, t, 2CH3,
.
d
J ¼ 7.2 Hz), 2.28 (6H, s, 2CH3), 3.87 (2H, m, 2FcCH), 4.13 (4H, q, 2CH2,
J ¼ 7.2 Hz), 4.33 (2H, d, 2CH, J ¼ 7.2 Hz), 3.93 (2H, m, C5H4), 4.02 (2H,
m, C5H4), 4.17 (2H, m, C5H4), 4.26 (2H, m, C5H4), 4.08 (10H, s,
3:1), yellow crystals, m.p. 183e184 ꢁC. IR (KBr):
n
¼ 431, 483, 707,
2C5H5). 13C NMR:
d 14.11 (2CH3), 20.87 (2CH3), 47.31, 62.19 (4CH),
782, 820, 863, 919, 1001, 1021, 1076, 1106, 1125, 1165, 1235, 1262,
1286, 1318, 1380, 1398, 1414, 1463, 1491, 1573, 1589, 1626, 1673,
60.35 (2CH2), 68.37 (2C5H5), 66.79, 67.23, 68.14, 68.62 (2C5H4),
90.81 (2Cipso Fc), 168.67 (2COOEt), 187.98 (2C]O). Anal. Calc. for
C34H38Fe2O6: C, 62.41; H, 5.85; Fe,17.07. Found: C, 62.56; H, 5.91; Fe,
16.86%. MS: m/z 654 [M]þ.
2735, 2904, 2938, 2977, 3060, 3095, 3433 cmꢂ1. 1H NMR:
d 0.49 (3H,
t, CH3, J ¼ 7.2 Hz), 0.82 (3H, t, CH3, J ¼ 7.2 Hz), 3.22 (1H, m, CH2),
3.46 (1H, m, CH2), 3.94 (2H, q, CH2, J ¼ 7.2 Hz), 3.81 (5H, s, C5H5),
4.28 (5H, s, C5H5), 3.90 (1H, m, C5H4), 3.98 (1H, m, C5H4), 4.09 (1H,
m, C5H4), 4.22 (1H, m, C5H4), 4.32 (1H, m, C5H4), 4.43 (1H, m, C5H4),
4.51 (1H, m, C5H4), 5.07 (1H, m, C5H4), 4.12 (1H, dd, CH, J ¼ 7.08,
11.1 Hz), 4.19(1H, d, CH, J ¼ 7.08 Hz), 4.38 (1H, d, CH, J ¼ 11.1 Hz),
2R*-Acetyl-2,5S*-diethoxycarbonyl-3R*,4S*-diferrocenyl-1R*-
methylcyclopentanol (13), yield 1.43 g (44% from E-4) and 1.50 g
(46%, from Z-4) (hexane-ethyl acetate, 3:1), yellow crystals, m.p.
132e133ꢁC. IR (KBr):
n
¼ 483, 704, 769, 822, 851, 916, 1002, 1020,
1041, 1105, 1121, 1182, 1230, 1262, 1282, 1345, 1400, 1422, 1446,
6.50 (1H, s, OH), 6.98e7.55 (10H, m, 2C6H5). 13C NMR:
d 12.62, 13.61
1492, 1578, 1591, 1631, 1727, 2737, 2979, 3096, 3432 cmꢂ1. 1H NMR:
(2CH3), 42.66, 53.64 (2CH), 60.23, 60.89 (2CH2), 65.21 (CH), 68.50,
68.69 (2C5H5), 66.27, 66.52, 67.02, 67.50, 68.28, 68.32, 70.72,71.45
(2C5H4), 87.12, 88.39 (2Cipso Fc), 95.92, 99.92 (2C), 127.24, 127.29,
127.32, 127.38, 127.45, 127.81 (2C6H5), 138.65, 140.65 (2Cipso),
170.90, 173.18 (2COOEt), 198.49 (PhC]O). Anal. Calc. for
C44H42Fe2O6: C, 67.88; H, 5.44; Fe, 14.35. Found: C, 67.76; H, 5.52;
Fe, 14.33%. MS: m/z 778 [M]þ.
d
1.29 (3H, t, CH3, J ¼ 7.2 Hz), 1.37 (3H, s, CH3), 1.39 (3H, t, CH3,
J ¼ 7.2 Hz), 2.53 (3H, s, CH3), 2.6 (1H, bs, OH), 3.82 (1H, m, C5H4),
3.96 (1H, m, C5H4), 4.20 (1H, m, C5H4), 4.23 (1H, m, C5H4), 4.32 (2H,
m, C5H4), 4.46 (2H, m, C5H4), 4.11 (5H, s, C5H5), 4.14 (5H, s, C5H5),
4.05 (1H, dd, CH, J ¼ 7.5, 10.5 Hz), 4.12 (1H, d, CH, J ¼ 7.5 Hz), 4.24
(2H, q, 2CH2, J ¼ 7.2 Hz), 4.27 (2H, q, 2CH2, J ¼ 7.2 Hz), 4.55 (1H, d,
CH, J ¼ 10.5 Hz). 13C NMR:
d 13.98, 14.05, 21.63, 31.89 (4CH3), 41.96,
Ethyl 2-ferrocenylmethyl(benzoyl)acetate (14), yield 0.35 g (9%,
47.01, 62.18 (3CH), 61.53 (2OCH2), 68.56, 68.82 (2C5H5), 66.61,
66.78, 67.99, 68.40, 68.78, 69.21, 69.66, 69.91 (2C5H4), 80.52, 82.56
(2C), 84.28, 90.19 (2Cipso Fc), 165.04, 168.10 (2COOEt), 189.13 (C]O).
Anal. Calc. for C34H38Fe2O6: C, 62.41; H, 5.85; Fe, 17.07. Found: C,
62.33; H, 5.74; Fe, 17.26%. MS: m/z 654 [M]þ.
hexane), yellow powder, m.p.107e109 ꢁC. 1H NMR:
d 0.86 (3H, t,
CH3, J ¼ 7.5 Hz), 3.14 (1H, dd, CH2, J ¼ 6.9,10.5 Hz), 3.23 (1H, dd, CH2,
J ¼ 5.1, 10.5 Hz), 3.51 (1H, dd, CH, J ¼ 5.1, 6.9 Hz), 4.07 (2H, q, CH2,
J ¼ 7.5 Hz), 4.10 (5H, s, C5H5), 4.0 (1H, m, C5H4), 4.04 (2H, m, C5H4),
4.12 (1H, m, C5H4), 7.45 (2H, t, C6H5, J ¼ 7.8 Hz), 7.52 (1H, t, C6H5,
Ethyl 2-ferrocenylmethyl(aceto)acetate (15), yield 0.27 g (8%
J ¼ 7.5 Hz), 7.97 (2H, d, C6H5, J ¼ 7.5 Hz). 13C NMR:
d 11.66 (CH3),
from E-4) and 0.3 g (9%, from Z-4) (hexane), yellow oil. 1H NMR:
d
29.16, 35.55 (2CH2), 44.17 (CH), 68.40 (C5H5), 66.46, 66.93, 67.04,
67.57 (C5H4), 93.94 (Cipso Fc), 128.04, 128.55, 132.91 (C6H5), 137.43
(Cipso), 169.09 (COOEt), 199.80 (PhC]O). Anal. Calc. for C22H22FeO3:
C, 67.71; H, 5.68; Fe, 14.31. Found: C, 67.89; H, 5.71; Fe, 14.10%. MS:
m/z 390 [M]þ.
0.84 (3H, t, CH3, J ¼ 7.2 Hz), 1.98 (3H, s, CH3), 3.03 (1H, dd, CH2,
J ¼ 6.6, 10.2 Hz), 3.17 (1H, dd, CH2, J ¼ 4.5, 10.2 Hz), 3.59 (1H, dd, CH,
J ¼ 4.5, 6.6 Hz), 4.15 (2H, q, CH2, J ¼ 7.2 Hz), 4.08 (5H, s, C5H5), 4.02
(1H, m, C5H4), 4.05 (2H, m, C5H4), 4.21 (1H, m, C5H4). 13C NMR:
d
11.81, 20.12 (2CH3), 29.87, 40.63 (2CH2), 46.34 (CH), 68.18 (C5H5),

2272
E. Klimova et al. / Journal of Organometallic Chemistry 695 (2010) 2264e2272
66.83, 67.64, 67.91, 68.27 (C5H4), 89.96 (Cipso Fc), 168.11 (COOEt),
189.93 (MeC]O). Anal. Calc. for C17H20FeO3: C, 62.21; H, 6.14; Fe,
17.02. Found: C, 62.17; H, 6.21; Fe, 16.99%. MS: m/z 328 [M]þ.
Ethyl 2-(1-ferrocenylpropyl)acetoacetate (17a,b) (w1:1), yield
0.25 g (7% from E-4) and 0.21 g (6%, from Z-4) (hexane), yellowoil.1H
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NMR:
d
1.05 (3H, t, CH3, J ¼ 7.2 Hz), 1.11 (3H, t, CH3, J ¼ 7.2 Hz), 1.21
(3H, t, CH3, J ¼ 6.9 Hz), 1.25 (3H, t, CH3, J ¼ 6.9 Hz), 1.95e2.18 (4H, m,
2CH2, 2Et), 2.31 (3H, s, CH3), 2.40 (3H, s, CH3), 3.59 (2H, m, 2CHeFc),
4.03 (4H, q, 2CH2, J ¼ 6.9 Hz), 4.07 (5H, s, C5H5), 4.10 (5H, s, C5H5),
4.12 (2H, m, C5H4), 4.15 (2H, m, C5H4), 4.21 (2H, m, C5H4), 4.29 (2H, m,
C5H4), 4.49 (1H, d, CH, J ¼ 6.9 Hz), 4.68 (1H, d, CH, J ¼ 6.9 Hz). 13
C
NMR:
d 12.13, 12.23, 13.79, 13.97, 20.23, 20.64 (6CH3), 26.69, 26.98
(2CH2), 41.42, 43.87 (2FcCH), 59.85, 60.06 (2CH), 61.29, 61.71 (OCH2),
68.52, 68.61 (2C5H5), 66.97, 67.09, 67.34, 67.58, 67.88, 68.37, 68.75,
68.89 (2C5H4), 90.03, 90.79 (2Cipso Fc), 167.81, 168.03 (2COOEt),
189.12, 189.26 (2MeC]O). Anal. Calc. for C19H24FeO3: C, 64.06; H,
6.79; Fe,15.68. Found: C, 64.12; H, 6.67; Fe,15.74%. MS: m/z 356 [M]þ.
Acknowledgements
[13] L.E. Sutton (Ed.), Tables of Interatomic Distances and Configuration in Mole-
cules and Ions, The Chemical Soiety, London, 1965.
This work was supported by the CONAyT (Mexico, grant
100970). Thanks are due to E.A. Vázquez López for his technical
assistance.
[14] A.J. Bard, L.R. Faulkner, in: Electrochemical Methods, Fundamentals and
Applications, second ed. John Wiley and Sons, New York, 2001 Chapter 5.
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Royal Society of Chemistry, Cambridge, UK, 2003.
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Appendix A. Supplementary material
[18] G.M. Sheldrick, SHELXL-97, Program for The Refinement of Crystal Structures.
University of Göttingen, Germany, 1994.
CCDC-761352 (for 7a) and CCDC-761353 (for 12) contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge at www.ccdc.cam.ac.uk/const/retrieving.
html [or from the Cambridge Crystallographic Data Centre, 12,
Union Road, Cambridge DB2 1EZ, UK; fax: (internat.) þ44 1223/336
033; E-mail: deposit@ccdc.cam.ac.uk].
[19] G. Gritzner, J. Küta, Pure Appl. Chem. 4 (1984) 461.
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R.A. Toscano, L.V. Backinowsky, Eur. J. Org. Chem. (2006) 4755.
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[22] V.N. Postnov, Yu.N. Polivin, V.A. Sazonova, Dokl. Akad. Nauk SSSR 271 (1983)
1399.