A new approach for ferrocenyl-cyclopentenone and ferrocenyl- cyclopentenedione compound synthesis

Article abstract of DOI:10.1021/om800246s

A simple and convenient route for the synthesis of the ferrocenyl- cyclopentenone compounds (3 and 7) and ferrocenyl-cyclopentenedione compounds (4 and 8) has been developed. Compounds 3 and 7 were obtained by a selective oxidating reaction of the ferrocenyl-cyclopenta[d]pyridazine species of 2 and 6 in CH₂Cl₂ in air, respectively. Compounds 4 and 8 were generated by a hydrolysis reaction of 3 and 7 in a H₂O/EtOH mixed solvent system in the presence of SnCl₂, respectively. The substituted ferrocenyl group plays a central role in the formation of the ferrocenyl-cyclopentenone (3 and 7) and ferrocenyl-cyclopentenedione (4 and 8) derivatives, which is demonstrated well by the current experimental data as well as the theoretical calculations. All the new ferrocene-containing complexes have been characterized by elemental analysis, IR spectra, and ¹H NMR spectroscopy, as well as for 3, 4, 5, 7, 8, and 9 by X-ray diffraction analysis. In addition, the luminescent properties of 1-4 were investigated preliminarily in CH₂Cl₂ at room temperature.

Full text of DOI:10.1021/om800246s

5446
Organometallics 2008, 27, 5446–5452
A New Approach for Ferrocenyl-Cyclopentenone and
Ferrocenyl-Cyclopentenedione Compound Synthesis
Jie Li, Jian-Ping Ma, Fengling Liu, Xiang-Wen Wu, Yu-Bin Dong,* and Ru-Qi Huang
College of Chemistry, Chemical Engineering and Materials Science, Key Laboratory of Molecular and
Nano Probe, Engineering Research Center of Pesticide and Medicine Intermediate Clean Production,
Ministry of Education, Shandong Normal UniVersity, Jinan, 250014, People’s Republic of China
ReceiVed March 16, 2008
A simple and convenient route for the synthesis of the ferrocenyl-cyclopentenone compounds (3 and
7) and ferrocenyl-cyclopentenedione compounds (4 and 8) has been developed. Compounds 3 and 7
were obtained by a selective oxidating reaction of the ferrocenyl-cyclopenta[d]pyridazine species of 2
and 6 in CH2Cl2 in air, respectively. Compounds 4 and 8 were generated by a hydrolysis reaction of 3
and 7 in a H2O/EtOH mixed solvent system in the presence of SnCl2, respectively. The substituted
ferrocenyl group plays a central role in the formation of the ferrocenyl-cyclopentenone (3 and 7) and
ferrocenyl-cyclopentenedione (4 and 8) derivatives, which is demonstrated well by the current experimental
data as well as the theoretical calculations. All the new ferrocene-containing complexes have been
1
characterized by elemental analysis, IR spectra, and H NMR spectroscopy, as well as for 3, 4, 5, 7, 8,
and 9 by X-ray diffraction analysis. In addition, the luminescent properties of 1-4 were investigated
preliminarily in CH2Cl2 at room temperature.
active molecules, which are potentially used as the electro-probe
to explore the biological activity and drug working mechanism.
In this contribution, we report a new and convenient approach
for the synthesis of ferrocene-containing cyclopentenone and
cyclopentenedione derivatives.
Introduction
The widespread importance of cyclopentyl compounds has
led to numerous methods for their synthesis.1 Cyclopentenone
and cyclopentenedione derivatives are particularly useful com-
pounds that have vast importance in biology, medicine, and
chemistry due to their versatility of functionality.2 For instance,
cyclopentenone prostaglandins exhibiting a characteristic bio-
logical activity and soft acid-type electrophilic cyclopentendione
moiety are good candidates for antitumor drug design.3 The
classical methods for their synthesis involve the intramolecular
aldol reaction of a selected 1,5-diketone and the metal-mediated
approach, which was developed by Pauson and Khand.2a,4 On
the other hand, conjugated ferrocene-containing organic mol-
ecules have emerged as an important class of materials with
numerous applications; for example, the Fe(II)/Fe(III) redox
couple has been widely used in redox-active sensing applications
because it is readily available and exhibits “well-behaved”
electrochemistry and photochromism.5 We wondered if the
electro-active moiety, ferrocene, could be combined with the
cyclopentenone or cyclopentenedione species to generate new
types of functional molecules, such as complex biologically
Results and Discussion
Synthesis and Characterization of 1-4. We have been
interested in the synthesis of new fulvene molecules by
aroylation of the substituted cyclopentadienyl anion and the
organometallic coordination polymers based on them.6 Moti-
vated by our interest, we have initiated a synthetic program for
the preparation of new organometallic fulvene molecules and
their reaction chemistry, in which FcCOCl and ferrocenyl-
substituted aroyl chloride are used instead of aroyl chloride to
perform the reactions. The aroylation of cyclohexyl-substituted
cyclopentadienyl anion by FcCOCl resulted in 1 as red-orange
crystalline solids in moderate yield.6h The same as its phenyl
or heterocycle terminal-substituted fulvene analogues,6a,b
1
readily reacted with hydrazine in EtOH at reflux to generate 2
as yellow-orange crystalline solids in quantitative yield. In the
1H NMR spectra, a single peak related to the imine group was
observed at 13.11 ppm, which is about 5 ppm shifted to higher
field compared to the proton resonance (18.20 ppm) of the
hydroxy hydrogen on its precursor 1. The IR spectrum of 2
showed a sharp -NH absorption band at 3379 cm-1. The strong
* Corresponding author. E-mail: yubindong@sdnu.edu.cn.
(1) (a) Trost, B. M.; Toste, F. D. J. Am. Chem. Soc. 2000, 122, 714. (b)
Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 7026.
(2) (a) Gibson, S. E.; Mainolfi, N. Angew. Chem., Int. Ed. 2005, 44,
3022. (b) Gibson, S. E.; Stevenazzi, A. Angew. Chem., Int. Ed. 2003, 42,
1800. (c) Hori, H.; Nagasawa, H.; Ishibashi, M.; Uto, Y.; Hirata, A.; Saijo,
K.; Ohkura, K.; Kirk, K. L.; Uehara, Y. Bioorg. Med. Chem. 2002, 10,
3257.
(3) (a) Straus, D. S.; Glass, C. K. Med. Res. ReV. 2001, 21, 185. (b)
Moos, P. J.; Edes, K.; Cassidy, P.; Massuda, E.; Fitzpatrick, F. A. J. Biol.
Chem. 2003, 278, 745.
(4) Khand, I. U.; Knox, G. R.; Pauson, P. L.; Watts, W. E. J. Chem.
Soc. D 1971, 36.
(6) (a) Dong, Y.-B.; Geng, Y.; Ma, J.-P.; Huang, R.-Q. Organometallics
2006, 25, 447. (b) Dong, Y.-B.; Geng, Y.; Ma, J.-P.; Huang, R.-Q. Inorg.
Chem. 2005, 44, 1693. (c) Wang, P.; Dong, Y.-B.; Ma, J.-P.; Huang, R.-
Q.; Smith, M. D. Crystal Growth Des. 2005, 5, 701. (d) Dong, Y.-B.; Wang,
P.; Huang, R.-Q.; Smith, M. D. Inorg. Chem. 2004, 43, 4727. (e) Dong,
Y.-B.; Jin, G.-X.; Zhao, X.; Huang, R.-Q.; Smith, M. D.; Stitzer, K. E.; zur
Loye, H.-C. Organometallics 2004, 23, 1604. (f) Dong, Y.-B.; Ma, J.-P.;
Jin, G.-X.; Huang, R.-Q.; Smith, M. D. Dalton Trans 2003, 22, 4324. (g)
Dong, Y.-B.; Jin, G.-X.; Smith, M. D.; Tang, B.; zur Loye, H.-C. Inorg.
Chem. 2002, 41, 4909. (h) Jiao, L.-J.; Liu, G.-H.; Ma, Y.-D.; Dong, Y.-B.
Chin. J. Org. Chem. 1995, 15, 259.
(5) (a) Wang, K.; Mun´oz, S.; Zhang, L.; Castro, R.; Kaifer, A. E.; Gokel,
G. W. J. Am. Chem. Soc. 1996, 118, 6707. (b) Hillard, E.; Vessie`res, A.;
Thouin, L.; Jaouen, G.; Amatore, C. Angew. Chem., Int. Ed. 2006, 45, 285.
(c) Sakamato, R.; Murata, M.; Nishihara, H. Angew. Chem., Int. Ed. 2006,
45, 4793.
10.1021/om800246s CCC: $40.75
2008 American Chemical Society
Publication on Web 10/10/2008

Ferrocenyl-Cyclopentenone Compound Synthesis
Organometallics, Vol. 27, No. 21, 2008 5447
Figure 1. Molecular structure of 3.
absorption bands at 1594 and 1369 cm-1 are consistent with
the >CdN and fulvene adsorptions, respectively, which are
comparable to the corresponding bands in known compounds.6
Thus, the H-bonded seven-membered ring of 1 was replaced
by a six-membered hydropyridazino moiety in 2.
Figure 2. Consecutive cyclic voltammogram from 2 (trace 1) to 3
(trace 5) in CH2Cl2.
We were delighted to find that, upon exposure to air for 12 h
at room temperature (monitored by TLC), solution of 2 in
CH2Cl2 reacted cleanly to form the novel ferrocenyl-cyclopen-
tenone 3 as deep-green crystalline solids in good yield. In
contrast to the 1H NMR spectra of 1 and 2, no proton resonance
was found in the downfield (>10 ppm) region with respect to
the loss of the active hydrogen on the N atom in 3. In addition,
the IR spectrum of 3 showed a 1713 cm-1 absorption derived
from the typical conjugated carbonyl, which is reflected in the
oxidation restricted to the C-H bond.
Figure 3. Molecular structure of 4.
The cyclopentadiene moiety in 2 was oxidized to cyclopen-
tadienone species 3, which was further confirmed by its X-ray
single-crystal structure. The single-crystal X-ray diffraction
analysis revealed that 2 was oxidated at the central fulvene ring
instead of ferrocene. As shown in Figure 1, the C(1)-H(1) bond
in 2 was oxidized to C(1)dO(1). The two ferrocenyl groups
attached to the pyridazino ring in 3 were located above and
below the cyclopentadienone- hydropyridazino plane in the solid
state. One of the two substituted ferrocenyl groups (Fe(1)) was
fixed by one set of intramolecular hydrogen bonds (dO(1) · · · H(34)
) 2.2 Å, dO(1) · · · C(34) ) 2.9 Å and O(1)-H(34)-C(34) )
135°), which might be the reason for the ferrocenyl proton
signals splitting up into four groups, which is compatible with
the assigned structure.
The whole oxidiation process of 2 in air was monitored by
CV (Figure 2). As expected, the cyclic voltammetric response
in methylene chloride solution in air indicated that the difer-
rocenyl complex 2 underwent two oxidation steps (E1/2 ) 487
and 675 mV). As time went on, the double redox waves of 2
overlapped gradually and the redox waves of 3 formed finally.
No long-lived intermediates are involved during the oxidation
process. Compared to ferrocene (E1/2 ) 0.41-0.42 V), the
voltammograms for 2 and 3 reveal an anodic shift due to the
adjacent electron-withdrawing imine units.
It is interesting that 3 is not prone to further oxidation in air
at room temperature. The Fc-cyclopentenedione 4, however,
could be obtained as purple crystalline solids by the hydrolysis
of 3 in the presence of SnCl2 at room temperature in good yield
(75%). When 3 was treated with several drops of water in EtOH
in the presence of SnCl2 under N2 atmosphere, compound 4
was obtained in the same yield; however, the reaction carried
out in anhydrous EtOH in the presence of SnCl2 in dry air did
not lead to the formation of 4. These parallel reactions confirmed
that the formation of 4 from 3 went through a hydrolytic process
instead of an oxidating process. X-ray single-crystal analysis
revealed that the hydrolysis happened on the other sp2 carbon
atom, C(17), of the central cyclopentenone ring (Figure 3).
Different from 3, two terminal ferrocenyl substituents of 4 are
fixed by two sets of intramolecular hydrogen bonds (dO(2) · · · H(34)
) 2.0 Å, dO(2) · · · C(34) ) 2.7 Å and O(2)-H(34)-C(34) ) 134°;
dO(1) · · · H(24) )2.0Å,dO(1) · · · C(24) )2.7Åand O(1)-H(24)-C(24)
) 137°), respectively, which gave rise to the ferrocenyl proton
Molecular oxygen is a highly desirable oxidant from chemical,
environmental, and economic standpoints. However, the effec-
tive utilization of O2 in selective C-H oxidation reactions still
remains a great challenge due to a very limited understanding
of how transition metal complexes activate either the C-H bond
or O2. Significant recent progress in the use of metal complex
catalysts for selective aerobic oxidations has emphasized the
importance of developing a thorough comprehension of reactions
between metal complexes, O2, and C-H substrates.7 Herein, it
is no doubt that such novel selective oxidation on the C-H
bond was promoted by the ferrocenyl substituents, which was
demonstrated well by our experiments. For example, when the
solutions of the analogues of 2 in CH2Cl2, such as phenyl or
heterocycle terminal-substituted fulvene molecules,6 were al-
lowed to stand in air for several days, no oxidated products
were detected. In addition, parallel reactions carried out under
ambient light and in the dark showed comparable rates for the
formation of 3, which strongly suggests that the oxidation of 2
to 3 did not proceed via a light-induced radical mechanism.
1
signals splitting up into five groups in its H NMR spectrum.
The side view of 4 indicated that both ferrocenyl groups are
symmetrically located on the same side of the cyclopentenedi-
one-hydropyridazino plane in the solid state (Figure 3).
The UV/vis spectra of 1-4 are characterized by a strong
absorption band at 303 nm (ꢀ ) 1.48 × 104 M-1 cm-1) (1),
306 nm (ꢀ ) 1.60 × 104 M-1 cm-1) (2), 303 nm (ꢀ ) 1.55 ×
(7) (a) Shilov, A. E.; Shteinman, A. A. Acc. Chem. Res. 1999, 32, 763.
(b) Merkx, M.; Kopp, D. A.; Sazinsky, M. H.; Blazyk, J. L.; Mu¨ller, J.;
Lippard, S. J. Angew. Chem., Int. Ed. 2001, 40, 2782. (c) Stahl, S. S. Angew.
Chem., Int. Ed. 2004, 43, 3400.
104 M-1 cm-1) (3), and 295 nm (ꢀ ) 9.49 × 103 M-1 cm-1
)
(4), respectively, which are assigned to a high-energy π-π*

5448 Organometallics, Vol. 27, No. 21, 2008
Li et al.
Scheme 1. Synthesis of Compounds 1 (red), 2 (yellow), 3
(green), and 4 (purple) in CH2Cl2
Scheme 2. Synthesis of Compounds 5 (red-orange), 6 (light
yellow), 7 (brown), and 8 (light brown) in CH2Cl2
electronic transition, and moderate absorption bands at 436 nm
(ꢀ ) 1.14 × 104 M-1 cm-1) (1), 442 nm (ꢀ ) 2.73 × 103 M-1
cm-1) (2), 367 nm (ꢀ ) 5.44 × 103 M-1 cm-1) (3), and 339
nm (ꢀ ) 1.24 × 104 M-1 cm-1) (4), which are attributed to a
n-π* electronic transition. The lower energy weaker bands at
518 nm (ꢀ ) 7.72 × 103 M-1 cm-1) (1), 521 nm (ꢀ ) 1.55 ×
103 M-1 cm-1) (3), and 527 nm (ꢀ ) 3.40 × 103 M-1 cm-1
)
took a longer time (72 h, monitored by TLC), which is probably
due to the effective electron delocalization caused by the larger
conjugated system in 6.
(4) correspond to the metal-to-ligand charge transfer process
(d-π*).8 Such spectral features confer a series of color changes
from 1 to 4 (Scheme 1), which enables us to easily monitor the
reactions by the naked eye. In addition, all four complexes are
strongly luminescent in CH2Cl2 at room temperature (λex/λem
(nm): 364/410 (1), 367/410 (2), 363/411 (3), and 367/411 (4));
they exhibit similar fluorescence spectra due to their similar
conjugated systems (Figure 4).
The single-crystal structure of 7 shows that one of the C-H
bonds on the central cyclopentadiene ring was activated and
oxidized to a >CdO group. It is different from 5 in that the
two terminal ferrocenyl groups are located on both sides of the
central plane and point in the opposite directions (Figure 6).
Again, in EtOH solution, 7 underwent clean hydrolysis reaction
to produce 8 at room temperature, which has been confirmed
Synthesis and Characterization of 5-9. In order to further
confirm this interesting chemical phenomenon related to fer-
rocene-substituted fulvene compounds, we designed and syn-
thesized compound 5, which is generated from ferrocenyl
benzoyl chloride. As shown in Scheme 2, compound 5 was
obtained as red-orange crystalline solids by the aroylation of
cyclohexyl-substituted cyclopentadienyl anion by 4-FcC6H4-
COCl in a relatively low yield (25%). The X-ray single-crystal
structural analysis revealed that 5 and 1 are isostructural but
with two longer side arms. The distance between the two Fe(II)
centers in 5 is 17.554 Å, and the two terminal ferrocenyl groups
are perpendicular to each other in the solid state (Figure 5). As
for 1, compound 5 could condense with hydrazine in dry ethanol
to generate a cyclopenta[d]pyridazine derivative as the yellow-
orange crystalline solid 6 in 93% yield. In comparison to 2,
compound 6 in methylene chloride could also be oxidized by
O2 to its cyclopentenone species 7 upon exposure to air, but it
1
by H NMR, elemental analysis, and X-ray diffraction. The
transformation rates of 7 to 8 and 3 to 4 are comparative. As
shown by the diagrams in Figure 7, the phenyl ring attached to
the quaternary carbon atom (C(21)) bends markedly to the
pyridazine plane and interacts with it through a weak π-π
stacking interaction. The two ferrocenyl groups in 8 are parallel
and point in the same direction.
As shown in Scheme 2, reaction of compound 6 with excess
FcCOCl in dry CH2Cl2 afforded the triferrocenyl compound 9.
The absorption band corresponding to the -NH group disap-
peared, whereas the new strong absorption band at 1710 cm-1
is in good agreement with the carbonyl attached to the nitrogen
1
atom. The H NMR spectrum of 9 displayed a multiplet at
4.02-4.81 ppm assigned to 27 Cp protons, which are attributed
to the three Fc groups. The molecular structure of 9 was
unambiguously confirmed by crystal X-ray diffraction analysis.
The ORTEP view of 9 is presented in Figure 8, and selected
bond lengths and angles are given in Table 2. Compared to 6,
one more Fc group was attached to the central cyclopenta[d]-
pyridazine moiety bridged by a carbonyl.
Similar to compounds 1-4, UV-vis spectra of 5-9 in
CH2Cl2 show strong absorption bands, which are assigned to a
high-energy π-π* electronic transition and a n-π* electronic
transition, respectively (Table 3). Compared to 1-4, compounds
5-9, however, do not show significant photoluminescence.
As shown in Table 4, the cyclic voltammogram data of 6-8
show one quasi-reversible redox wave, while 9 shows two quasi-
reversible redox waves, which corresponds to a [FeIII/FeII]
process. Compared to 2 and 3, the half-wave potentials (E1/2
of 6-9 are negatively shifted due to the weaker electron-
)
Figure 4. Photoinduced excitation (black line) and emission (gray
line) spectra of 1 in CH2Cl2.

Ferrocenyl-Cyclopentenone Compound Synthesis
Organometallics, Vol. 27, No. 21, 2008 5449
Figure 5. ORTEP drawing and stick representation of 5.
Figure 6. ORTEP drawing and stick representation of 7.
Figure 7. ORTEP drawing and stick representation of 8.
withdrawing effect of imine caused by the inserted phenyl group.
Different from 6-8, compound 9 shows two quasi-reversible
redox waves. The E1/2 value of 0.707 V is assigned to the Fc
attached to the >CdO, which is a strong electron-withdrawing
group. The other wave is assigned to the two terminal ferro-
cenyls attached to the phenyl groups. The inserted phenyl groups
significantly reduce the electron-withdrawing effect of the
central cyclopenta[d]pyridazine moiety, which results in the two
terminal ferrocenyl groups being in basically the same electro-
chemical environment and in a lower E value.
Preliminary Theoretical Calculations. To gain a deeper
insight into the novel oxidation and hydrolysis reactions, for
this study, DFT calculations with the B3LYP functional and
the 6-31G(d) basis set were used.9 Full geometry optimizations
without any symmetry constraints were carried out. The
calculations were performed with the Gaussian 98 software on

5450 Organometallics, Vol. 27, No. 21, 2008
Li et al.
Figure 8. ORTEP drawing and stick representation of 9.
Table 1. Crystallographic Data for 3-5 and 7-9
empirical formula
C39H34Fe2N2O
3
C39H34Fe2N2O2 C51H44 Fe2O2
C52H44Cl2Fe2N2O C53H46Cl4Fe2N2O2 C63H54Cl2Fe3N2O
4
5
7
8
9
fw
cryst syst
a (Å)
b (Å)
c (Å)
658.38
triclinic
674.38
orthorhombic
16.871(2)
9.3341(12)
37.956(5)
90
800.56
triclinic
895.49
triclinic
996.42
orthorhombic
28.871(7)
7.5729(17)
10.514(2)
90
90
90
2298.6(9)
Pmn2(1)
2
1.440
0.908
293(2)
4130
0.0886; 0.2112
1093.53
triclinic
12.865(2)
14.584(3)
14.693(3)
78.951(3)
72.719(3)
87.210(3)
2583.2(8)
Pmn2(1)
2
11.231(8)
12.606(9)
12.790(9)
114.550(12)
97.629(12)
108.532(12)
1486.3(17)
j
P1
2
1.471
1.012
293(2)
5053
10.140(2)
15.103(4)
15.293(4)
117.633(4)
91.536(5)
108.432(4)
1926.1(8)
j
P1
2
1.380
0.795
293(2)
6640
10.438(4)
14.746(5)
14.994(5)
83.396(5)
71.005(5)
73.007(5)
2086.4(13)
j
P1
2
1.425
0.866
293(2)
7184
R (deg)
ꢀ (deg)
90
90
γ (deg)
V (Å3)
5977.3(13)
Pbca
8
1.499
1.011
space group
Z value
F calc (g/cm3)
µ(Mo KR) (mm-1
temp (K)
1.406
0.980
293(2)
9063
)
293(2)
5265
no. of observations (I > 3σ)
final R indices [I > 2σ(I)]:a R; Rw 0.0833; 0.1408 0.0575; 0.1361 0.0691; 0.1116 0.0823; 0.2308
0.0935; 0.2302
2
2 2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) {∑[w(Fo - Fc ) ]/Σ[w(Fo2)2]}1/2
.
a Pentium computer. The calculated results are summarized in
Table 3. The highest occupied molecular orbital (HOMO) and
lowest unoccupied molecular orbital (LUMO) for 2 and 3 are
shown in Figure 9. It was found that the energy of the HOMO
of 3 (E ) 2.53 eV) is lower than that of 2 (E ) 2.66 eV);
moreover, the electron density on the atom B of 3 is low, which
indicates this carbon atom is not easy to oxidize. On the other
hand, the energy of the LUMO (E ) 4.12 eV) of 3 is much
lower than that of 2 (E ) 6.12 eV), which means that compound
3 prefers to accept electrons for nucleophilic reactions to take
place, such as hydrolyzing reactions. As expected, similar
calculated results on compounds 6 and 7 were obtained.
Compared to 2, the energy of the HOMO of 6 is clearly
decreased, which means 6 is more difficult to oxidize than 2
due to its large conjugated system. Thus, the theoretical
calculations herein provide a supportive trend for the current
results and discussion.
synthesized successively from the Fc-containing fulvene mol-
ecule based on a very simple approach. The current results
demonstrated that ferrocenyl groups play a central role in the
formation of the cyclopentenone and cyclopentenedione deriva-
tives. Their structures were further confirmed by X-ray single
crystal analysis. The oxidation and hydrolysis reactions based
on 2, 3, 6, and 7 are in good agreement with the theoretical
calculation. We are currently extending this result by preparing
new symmetric and unsymmetric ferrocenyl-containing cyclo-
pentenone and cyclopentenedione derivatives of this type, which
are potentially used as electronic microsensors for biological
and chemical processes.
Experimental Section
Materials and Methods. Compound 1 was prepared according
to literature methods.6 The inorganic metal salts and organic regents
were purchased from Acros and used without further purification.
Infrared (IR) samples were prepared as KBr pellets, and spectra
were obtained in the 400-4000 cm-1 range using a Perkin-Elmer
1600 FTIR spectrometer. 1H NMR data were collected using a
JEOL FX 90Q NMR or AM-300 spectrometer. Chemical shifts are
reported in δ relative to TMS. Element analyses were performed
on a Perkin-Elmer model 240C analyzer. All fluorescence measure-
ments were carried out on a Cary Eclipse spectrofluorimeter (Varian,
Australia) equipped with a xenon lamp and quartz carrier at room
temperature.
Conclusion
In conclusion, a series of Fc-containing cyclopentenone (3
and 7) and cyclopentenedione (4 and 8) derivatives were
(8) (a) Caballero, A.; Lloveras, V.; Ta´rraga, A.; Espinosa, A.; Velasco,
M. D.; Vidal-Gancedo, J.; Rovira, C.; Wurst, K.; Molina, P.; Veciana, J.
Angew. Chem., Int. Ed. 2005, 44, 1977. (b) Mart´ınez, R.; Ratera, I.; Ta´rraga,
A.; Molina, P.; Veciana, J. Chem. Commun. 2006, 3809.
(9) (a) Hohenberg, P.; Kohn, W. Phys. ReV. B 1964, 136, 864. (b) Kohn,
W.; Sham, L. J. Phys. ReV. A 1965, 140, 1133. (c) Becke, A. D. J. Chem.
Phys. 1992, 97, 9173. (d) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. B
1988, 37, 785.
Synthesis of 1. Compound 1 was prepared according to the
literature method.6h The characterization data of 1H NMR,

Ferrocenyl-Cyclopentenone Compound Synthesis
Organometallics, Vol. 27, No. 21, 2008 5451
Table 2. Interatomic Distances (Å) and Bond Angles (deg) with
-Fc), 2.46-1.68 (m, 10H, -C6H10). Anal. (%) Calcd for
C39H36N2Fe2: C 72.67, H 5.59, N 4.35. Found: C 72.86, H 5.60, N
4.24.
esd’s for 3-5 and 7-9
3
Synthesis of 3. A solution of 2 in CH2Cl2 was stirred at room
temperature for 24 h in air, and then the solvent was removed under
reduced pressure to give deep green solids. The product was purified
by column chromatography on Al2O3 (CH2Cl2) to afford deep green
crystalline solids. Yield: 88%. Mp ) 248-250 °C. IR (KBr pellet
cm-1): 3092(w), 2929(s), 2855(w), 1713(vs), 1640(m), 1555(vs),
1492(w), 1465(m), 1385(m), 1314(w), 1269(w), 1236(w), 1192(w),
1105(w), 1029(m), 1002(m), 966(w), 909(w), 874(w), 819(s),
729(s), 699(m), 648(w), 561(w), 438(s). 1H NMR (300 MHz,
CDCl3, 25 °C, TMS, ppm): 7.69 (s, 1H, -C5H), 7.48-7.22 (m,
5H, -C6H5), 5.55-4.03 (s, s, d, d, 18H, -Fc), 2.51-1.63 (m, 10H,
-C6H10). Anal. (%) Calcd for C39H34N2OFe2: C 71.12, H 5.17, N
4.26. Found: C 71.34, H 5.26, N 4.15.
Synthesis of 4. A catalytic amount of SnCl2 and several drops
of water were added to a solution of 3 (0.18 g, 0.27 mmol) in
anhydrous EtOH (100 mL), and the mixture was stirred at room
temperature for 12 h. Solvent was removed under reduced pressure
to give purple crystalline solids. The product was purified by column
chromatography on Al2O3 (CH2Cl2) to afford purple crystalline
solids. Yield: 75%. Mp ) 234-236 °C. IR (KBr pellet cm-1):
3090(w), 2925(vs), 2854(s), 1715(vs), 1635(m), 1537(s), 1495(w),
1467(s), 1385(s), 1341(m), 1318(w), 1249(w), 1197(w), 1160(w),
1127(w), 1104(m), 1056(w), 1026(m), 1002(m), 879(w), 866(w),
818(s), 761(w), 735(w), 704(s), 615(w), 555(w), 524(w), 502(s),
482(s). 1H NMR (300 MHz, CDCl3, 25 °C, TMS, ppm): 7.42-7.10
(m, 5H, -C6H5), 5.58-4.00 (s, s, s, d, d, 18H, -Fc), 3.17-1.44
(m, 10H, -C6H10). Anal. (%) Calcd for C39H33N2O2Fe2: C 69.54,
H 4.90, N 4.16. Found: C 69.65, H 4.78, N 4.24.
Synthesis of 5. The process was the same as that for 1 but used
FcC6H4COCl rather than FcCOCl as the starting material. Yield:
25.0%. Mp ) 198 °C (dec). IR (KBr pellet cm-1): 2928(m),
2854(w), 1625(s), 1603(vs), 1494(m), 1406(s), 1346(s), 1267(m),
1175(m), 1106(w), 882(w), 828(m), 670(s), 484(m). 1H NMR (300
MHz, CDCl3, 25 °C, TMS, ppm): 18.26 (s, 1H, -OH), 7.71-7.52
(m, 8H, -C6H4), 7.28-7.12 (m, 5H, -C6H5), 7.12 (s, 2H, -C5H2),
4.77-4.12 (m, 18H, -Cp), 2.17-1.57 (m, 10H, -C6H10). Anal.
(%) Calcd for C51H44O2Fe2: C 76.50, H 5.50. Found: C 76.56, H
5.28.
Synthesis of 6. The process was the same as that for 2 but used
5 rather than 1 as the starting material. Yield: 92.3%. Mp ) 270
°C (dec). IR (KBr pellet cm-1): 3414(s), 3091(s), 2930(vs),
2855(m), 1607(s), 1515(s), 1450(vs), 1369(vs), 1282(m), 1186(w),
1109(m), 1077(m), 1003(m), 947(w), 887(w), 833(s), 752(w),
698(s), 673(m), 534(w), 507(m), 462(w). 1H NMR (300 MHz,
CDCl3, 25 °C, TMS, ppm): 10.63 (s, 1H, -NH), 7.84-7.62 (m,
8H, -C6H4), 7.39-7.07 (m, 5H, -C6H5), 6.97 (s, 2H, -C5H2),
4.76-4.10 (m, 18H, -Cp), 2.50-1.64 (m, 10H, -C6H10). Anal.
(%) Calcd for C51H44N2Fe2: C 76.88, H 5.53, N 3.52. Found: C
76.78, H 5.40, N 3.38.
C(1)-O(1)
1.237(8)
1.346(8)
2.014(9)
105.7(7)
118.5(7)
C(1)-C(2)
1.505(10)
1.332(8)
2.046(8)
125.3(7)
120.0(6)
C(17)-N(1)
N(1)-N(2)
Fe(1)-C(31)
C(15)-C(2)-C(1)
N(1)-C(17)-C(16)
Fe(2)-C(19)
O(1)-C(1)-C(2)
N(1)-N(2)-C(29)
4
5
7
C(3)-O(2)
C(1)-N(1)
Fe(1)-C(26)
O(2)-C(3)-C(2)
N(2)-N(1)-C(1)
1.168(6)
1.349(5)
2.026(5)
127.4(4)
121.0(3)
C(17)-O(1)
1.212(7)
1.337(4)
2.025(4)
123.8(5)
121.8(3)
N(1)-N(2)
Fe(2)-C(30)
O(2)-C(3)-C(4)
N(1)-N(2)-C(19)
C(18)-O(1)
1.299(6)
1.407(7)
2.018(7)
122.5(5)
126.0(5)
C(33)-O(2)
1.279(6)
1.474(8)
2.022(6)
115.0(5)
129.1(7)
C(16)-C(17)
C(22)-C(23)
Fe(1)-C(50)
Fe(2)-C(23)
O(2)-C(33)-C(1)
C(2)-C(1)-C(33)
O(2)-C(33)-C(34)
C(24)-C(23)-C(22)
C(14)-O(1)
1.203(7)
1.343(6)
1.341(6)
120.4(4)
124.5(5)
N(1)-N(2)
1.329(5)
2.012(6)
2.022(11)
121.8(4)
121.3(5)
N(1)-C(16)
Fe(1)-C(46)
N(2)-C(34)
Fe(2)-C(28)
N(2)-N(1)-C(16)
O(1)-C(14)-C(2)
N(1)-N(2)-C(34)
C(19)-C(20)-C(23)
8
9
C(19)-O(1)
C(17)-N(1)
N(1)#1-N(1)-C(17)
O(1)-C(19)-C(18)
1.153(14)
1.345(10)
121.2(4)
N(1)-N(1)#1
Fe(1)-C(3)
O(1)-C(19)-C(18)
C(3)-Fe(1)-C(9)
1.335(11)
2.011(9)
127.7(11)
125.3(4)
127.7(11)
N(1)-N(2)
1.362(7)
1.325(8)
2.021(8)
126.6(5)
125.0(6)
C(45)-N(2)
1.325(8)
2.014(7)
1.210(8)
109.4(5)
118.6(6)
C(45)-N(2)
C(34)-Fe(3)
C(54)-Fe(2)
C(39)-O(1)
N(2)-N(1)-C(17)
O(1)-C(39)-C(38)
N(2)-N(1)-C(39)
O(1)-C(39)-N(1)
a
Table 3. UV/Vis Absorption Data for Compounds 5-9 in CH2Cl2
absorption maxima λmax
,
compound
nm (ꢀ, 104 M-1 cm-1
)
5
6
7
8
9
229 (8.47), 305 (7.07), 451 (5.36)
227 (5.09), 308 (6.20), 446 (0.50)
229 (6.47), 312 (5.47), 376 (1.97)
228 (3.83), 295 (2.59), 342 (2.45), 469 (0.59)
228 (5.42), 295 (5.02), 441 (0.59)
a From OTTLE spectroelectrochemistry in CH2Cl2/0.1 M n-Bu4NPF6.
Table 4. Cyclic Voltammogram Data of 6-9
compound
Ep,a
Ep,c
E1/2 (V)a
∆Ep (mV)b
Ipa/Ipc
6
7
8
9
0.524
0.524
0.496
0.742
0.546
0.438
0.456
0.430
0.672
0.454
0.481
0.490
0.463
0.707
0.500
86
68
66
70
92
1.09
0.97
0.97
0.94
0.86
a E1/2 ) Ep,a + Ep,c/2. b ∆Ep ) Ep,a - Ep,c
.
Synthesis of 7. The process was the same as that for 3 but used
6 rather than 2 as the starting material. In addition, the reaction
time is 72 h instead of 24 h. Yield: 64.6%. Mp ) 260 °C (dec). IR
(KBr pellet cm-1) 3090(w), 2928(s), 2855(m), 1719(vs), 1608(vs),
1572(w), 1520(m), 1494(w), 1445(w), 1414(w), 1358(s), 1280(w),
1230(w), 1187(w), 1106(m), 1032(m), 1015(m), 886(m), 820(s),
757(w), 698(m), 665(w), 488(m). 1H NMR (300 MHz, CDCl3, 25
°C, TMS, ppm): 7.94-7.54 (m, 8H, -C6H4), 7.63 (s, 1H, -C5H),
7.42-7.17 (m, 5H, -C6H5), 4.79-4.13 (m, 18H, -Cp), 2.37-1.59
(m, 10H, -C6H10). Anal. (%) Calcd for C51H42N2OFe2: C 75.56,
H 5.18, N 3.46. Found: C 75.48, H 5.07, N 3.35.
IR, and elemental analysis are consistent with the our previous
report.6h
Synthesis of 2. A solution of 1 (0.32 g, 0.49 mmol) in anhydrous
EtOH (20 mL) and a large excess N2H4 · H2O was heated to reflux
for about 24 h. After cooling to room temperature, the solvent was
removed under reduced pressure to give a yellow-orange solid. The
product was recrystallized from EtOH to give orange crystals of 2
(yield 96%). Mp ) 253 °C (dec). IR (KBr pellet cm-1): 3379(vs),
3090(w), 2933(vs), 2855(m), 1594(s), 1517(s), 1492(m), 1454(s),
1369(m), 1335(m), 1166(w), 1104(w), 1030(m), 1002(w), 877(w),
832(m), 752(w), 701(m), 669(w), 637(w), 501(vs). 1H NMR (300
MHz, CDCl3, 25 °C, TMS, ppm): 10.32 (s, 1H, -OH), 7.44-7.11
(m, 5H, -C6H5), 6.95 (s, 2H, -C5H2), 4.93-4.12 (s, s, s, 18H,
Synthesis of 8. The process was the same as that for 4 but used
7 rather than 3 as the starting material. Yield: 50.2%. Mp ) 220
°C (dec). IR (KBr pellet cm-1): 3090(w), 2930(m), 2857(w),
1721(vs), 1607(vs), 1517(w), 1452(w), 1417(m), 1383(vs), 1281(w),

5452 Organometallics, Vol. 27, No. 21, 2008
Li et al.
Figure 9. HOMO and LUMO of 2, 3, 6, and 7.
Table 5. Calculation Results for 2, 3, 6, and 7a
solution. Suitable single crystals of 3-5 and 7-9 were selected
and mounted in air onto thin glass fibers. X-ray intensity data were
measured at 293(2) K on a Bruker SMART APEX CCD-based
diffractometer (Mo KR radiation, λ ) 0.71073 Å). The raw frame
data for 3 and 4 were integrated into SHELX-format reflection files
and corrected for Lorentz and polarization effects using SAINT.10
Corrections for incident and diffracted beam absorption effects were
applied using SADABS.10 None of the crystals showed evidence
of crystal decay during data collection. The structure was solved
by a combination of direct methods and difference Fourier syntheses
and refined against F2 by the full-matrix least-squares technique.
Crystal data, data collection parameters, and refinement statistics
for 3-5 and 7-9 are listed in Tables 1 and 2.
2
3
6
7
HOMO (E/eV)
LUMO (E/eV)
2.66
6.12
2.53
4.12
1.22
3.53
1.00
2.00
0.322
-0.138
charge of atom A
charge of atom B
-0.316
-0.314
0.303
-0.143
-0.306
-0.304
a Charge ) -2; singlet. Atoms A and B are marked in Schemes1 and 2.
1188(m), 1137(w), 1103(s), 1083(m), 1030(m), 1015(m), 886(m),
840(s), 827(s), 765(w), 732(vs), 704(s), 645(w), 515(s), 482(m),
453(w). 1H NMR (300 MHz, CDCl3, 25 °C, TMS, ppm): 7.81-7.61
(m, 8H, -C6H4), 7.28-7.00 (m, 5H, -C6H5), 4.74-4.08 (m, 18H,
-Cp), 3.15-1.38 (m, 10H, -C6H10). Anal. (%) Calcd for
C51H41N2O2Fe2: C 74.18, H 4.97, N 3.39. Found: C 74.09, H 4.58,
N 3.41.
Synthesis of 9. FcC6H4COCl (0.14 g, 0.57 mmol) was added to
a solution of 6 (0.15 g, 0.19 mmol) in CH2Cl2 (30 mL). The mixture
was stirred for 24 h at room temperature. Solvent was removed
under vacuum to give orange crystalline solids. The product was
purified by column chromatography on silica gel (CH2Cl2) to afford
yellow-orange crystalline solids. Yield: 54.7%. IR (KBr pellet
cm-1): 2927(s), 2854(m), 1710(s), 1607(s), 1522(m), 1443(s),
1401(vs), 1321(s), 1258(vs), 1185(w), 1082(s), 1054(m), 1028(m),
1001(s), 868(m), 820(s), 754(s), 733(m), 699(m), 489(s). 1H NMR
(300 MHz, CDCl3, 25 °C, TMS, ppm): 7.97-7.08 (m, 13H, -C6H4,
-C6H5), 6.95, 6.69 (s, s, 2H, -C5H2), 4.81-4.02 (m, 27H, -Cp),
2.38-1.61 (m, 10H, -C6H10). Anal. (%) Calcd for C62H52N2OFe3:
C 73.81, H 5.16. Found: C 73.72, H 5.14.
Acknowledgment. We are grateful for financial support
from the National Natural Science Foundation of China
(Grant Nos. 20871076 and 20671060), National Basic
Research Program of China (973 Program, 2007CB936000),
and Shangdong Natural Science Foundation (Nos. J06D05,
2006BS04040, and 2007BS04002).
Supporting Information Available: Crystallographic informa-
tion files (CIF). This material is available free of charge via the
Internet at http://pubs.acs.org.
OM800246S
Single-Crystal Structure Determination. Single crystals of 3-5
and 7-9 were obtained by the slow evaporation of a CH2Cl2/EtOH
(10) SAINT; Bruker Analytical X-ray Systems, Inc.: Madison, WI, 1998.